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Nature Ecology & Evolution Manuscript Title: Palaeoecological data indicates land- use changes across Europe linked to spatial heterogeneity in mortality during the Black Death pandemic Corresponding author name(s): Alessia Masi + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +2nd August 2021 + +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +Dear Dr Masi, + +Your manuscript entitled "Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe" has now been seen by four reviewers, whose comments are attached. The reviewers have raised a number of concerns which will need to be addressed before we can offer publication in Nature Ecology & Evolution. We will therefore need to see your responses to the criticisms raised and to some editorial concerns, along with a revised manuscript, before we can reach a final decision regarding publication. + +In particular, you will see that the reviewers emphasise the need to tone down the degree to which the narrative presented is a surprise from a historical perspective- - I don't think this compromises novelty since as reviewer 1 argues, it is valuable to show the palaeoecological dimension on land use change during the period. And as reviewer 4 comments, there is also a need to shore up the linkage between mortality and land use changes- - bringing more historical perspective in here could help. + +We therefore invite you to revise your manuscript taking into account all reviewer and editor comments. Please highlight all changes in the manuscript text file [OPTIONAL: in Microsoft Word format]. + +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<--- Page Split ---> + +# natureresearch + +When revising your manuscript: + +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each reviewer comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the reviewers along with the revised manuscript. + +\* If you have not done so already please begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +Please use the link below to submit your revised manuscript and related files: + +## [REDACTED] + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We hope to receive your revised manuscript within four to eight weeks. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. + +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +## [REDACTED] + +Reviewer expertise: + +Reviewer #1: medieval economic history + +<--- Page Split ---> + +# natureresearch + +Reviewer #2: Black Death archaeology + +Reviewer #3: palaeoecology and palynology + +Reviewer #4: palaeoecology and palynology + +Reviewers' comments: + +Reviewer #1 (Remarks to the Author): + +This is an interesting article about the regional variation of agrarian changes in Europe during the late middle ages. Probably for the first time such a large amount of data based on pollen analysis has been brought together to study the regional variation and changes of rural cultivation activity during that period. + +It confirms the existing knowledge (already since Biraben's publication of 1975 and many others after that) that the influence of the late medieval crisis hit Europe with a huge regional variation. However one of the most important merits of the article is that it is the first time that a study like this is done on the basis a large scale dataset out of the positive sciences. + +However, contrary to what the title and some parts of the article are suggesting, the data do not exclusively reveal the impact of the pest epidemic of 1347- 1352. They are on the contrary revealing also other changes in the late medieval society that are due to other factors as well. Indeed other demographic catastrophes were typical for the (later) middle ages as well and certainly also are reflected in pollen analyses. We think about famines (e.g. a° 1315- 1317), wars (that became much more devastating in the late middle ages and also caused epidemic diseases) but especially other epidemics and most importantly the s.c. 'echo- (pest- )epidemics' after the first plague epidemic (e.g. 1357- 9, 1373, 1400- 1401...). However also these epidemics occurred with huge regional variations. Moreover during that period structural changes of the rural society took place that were only partly linked to the black death (e.g. land concentration and the occurrence of new elites). + +To conclude: Interesting article but before publication we advise that the content should be changed as mentioned and that a new title should be formulated that is more conform to its content. + +Reviewer #2 (Remarks to the Author): + +This interesting study uses changes in the type of pollen in sediment cores to investigate the consequences of the black death upon the types of plant growing. The study uses a logical approach, and the illustrations explain the data convincingly. + +Estimating Black Death Mortality section (lines 131- 165). You write that until now texts have been the best way to study the impact of the Black Death on population size, although it is good that you do mention papers about changing pollution levels. However, other techniques are available. One study looked at the number of fragments of pottery in test pits to show that there was a significant drop in + +<--- Page Split ---> + +# natureresearch + +pottery use and production in England following the Black Death, likely a result of the smaller population size. I would encourage you to read this and give a couple of sentences on its approach (it is not my paper): Lewis, C. (2016) Disaster recovery: new archaeological evidence for the long- term impact of the 'calamitous' fourteenth century. Antiquity 90(351): 777- 797. + +Minor point: Abstract first sentence: 'reknown' should read 'renown'. + +Reviewer #3 (Remarks to the Author): + +This is a very interesting and topical paper. In principle, I was surprised by the methodological approach, but after studying it repeatedly, I find that the idea is provocative and has great explanatory power. The conclusion about the spatial and social heterogeneity of the epidemic is common sense regardless of conventional historicist approaches based on inevitably biased sources. + +Obviously, pollen analysis also entails its spatial sampling, analysis and interpretation biases, in addition to the biases derived from the resolution in the identification of palynological types. Not even close to all the pollen analyses published in the studied territory are presented here either. Naturally, all these limitations are unapproachable in the current state of collaboration with Big Data. + +That said, the epistemological and methodological approach of this study seems fresh and healthy to me as a pioneering study on the frontiers of knowledge. A much needed consilience between the natural sciences and the social sciences. A brilliant work in my opinion, which will be a must- read for the general public and which I predict a considerable media success. + +My enthusiasm cannot but lead to the belief that the paper can be published in its current form. The language is accessible, the information well collected and the message clear and direct, without frills. Congratulations to the authors. + +Reviewer #4 (Remarks to the Author): + +In "Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe" the authors evaluate palaeorecord of series of sedimentary sequences from 19 European countries to evaluate whether landscape changes could be linked with the hypothesis that half of the population died within a single year. This is a very interesting paper with an interesting approach and I have enjoyed reading it. It is really exciting seeing how fossil pollen time- series are answering big and relevant questions of concern to society as pandemics are. However, I have some concerns I would like the authors to consider. + +Main points: + +1) Mortality and landscape change: After reading the paper with interest and SI (lines 445 474) the + +<--- Page Split ---> + +# natureresearch + +"direct" link between population decline or mortality and landscape change that I think is the main hypothesis of the paper is not clear to me. The authors used \(>1600\) palynological time- series to evaluate the demographic impact of the Black Death on a regional scale across Europe. I think that the results of the paper are not strictly quantifying mortality (e.g. what magnitude?) but responses of local/regional vegetation/landscapes to changes on land- use, and other factors including mortality. However, I think the results are still relevant. + +I also found that the manuscript requires an improved discussion on demographic changes- how the authors interpret demographic changes in their results? It is mortality quantified "only" with th increase and decrease of cereals, etc? In Lines 191- 198 there are more discussion on validation. And I thank the authors for including this but I keep struggling in understanding what is the actual quantification of mortality. Also, why Poland experienced growth? More is required in here. + +2) Time period: It requires more detail on why the analysis are focusing on the period between 1250 and 1450 CE. I think this detail should be explored in-depth to better discuss the otherwise relevant results. + +3) Regional selection: Another issues I think it requires more description/discussion is why the authors included and excluded sites (Fig 1). I understand the limitation on finding good quality datasets for the time period of interest but I think that comparing sites located in mountain areas vs coastal areas and/or with different population densities, etc. probably impacted the findings. + +Minor points + +Line 113: I think it is missing the years that the pandemic was active. Please add the years. + +Ecological indices: It is missing a line with the relevance of these indices to help linking landscape change and the scale of the Black Death mortality. Why are these indices important to answer the question? I read the detail in SI but still not clear to me why the authors are using them. Not suggesting that the approach is not relevant but there are so many analysis to quantify how cereals and different vegetation types change over time that it require a better justification. + +Lines 171- 172: The authors suggested that "Pollen data can be used to assess past demographic dynamics as human pressure on the landscape in the preindustrial period was directly dependent on the availability of rural labour." I think this line is a bit confusing as it is mixing up to rural vs city demographics with the main point of the paper that is mortality. + +Line 261: This is a very strong sentence "The significant variability of Black Death mortality that our BDP approach identifies remains..." I'm struggling to accept that the results are showing differences in mortality rates. I think that it is an interesting hypothesis but it could well be that the landscape change found may respond to differences in vegetation resilience, different baseline population densities and cultures, land- use, culture differences, etc. + +Lines 286- 295 probably could be placed at the beginning of the manuscript to help integrating the spatial distribution of the Black Death and to better justify the time- period. + +Lines 487- 494: Depth age models- have the authors re- calibrated them using the new calibration curves? + +<--- Page Split ---> + +# natureresearch + +I hope my comments are helpful to improve the manuscript. + +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*END\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\* + +# Author Rebuttal to Initial comments + +## Response to reviewers + +## Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe + +Izdebski et al. + +Editor: In particular, you will see that the reviewers emphasise the need to tone down the degree to which the narrative presented is a surprise from a historical perspective- - I don't think this compromises novelty since as reviewer 1 argues, it is valuable to show the palaeoecological dimension on land use change during the period. + +- > We toned down the first section of the article and took into account the non-Anglophone historiography, which contrary to the recent English-speaking consensus on the Black Death as a universal catastrophic event, noticed some regional variation during the initial phases of the second plague pandemic. + +And as reviewer 4 comments, there is also a need to shore up the linkage between mortality and land use changes- - bringing more historical perspective in here could help. + +- > We rewrote the relevant (first) section of the Methods, providing it with additional references. In particular, we divided this section into two clearly distinguished main points: (1) the close connection between landscape changes as revealed by palynology and population dynamics as revealed by historical sources, as proved by several recent historical-palynological studies; (2) + +<--- Page Split ---> + +# natureresearch + +the landscape changes to be expected in plague- struck areas during the Black Death, based on the current consensus on estimated population decline among the historians of the Black Death. + +Reviewer expertise: + +Reviewer #1: medieval economic history + +Reviewer #2: Black Death archaeology + +Reviewer #3: palaeoecology and palynology + +Reviewer #4: palaeoecology and palynology + +Reviewer #1 (Remarks to the Author): + +This is an interesting article about the regional variation of agrarian changes in Europe during the late middle ages. Probably for the first time such a large amount of data based on pollen analysis has been brought together to study the regional variation and changes of rural cultivation activity during that period. + +It confirms the existing knowledge (already since Biraben's publication of 1975 and many others after that) that the influence of the late medieval crisis hit Europe with a huge regional variation. However one of the most important merits of the article is that it is the first time that a study like this is done on the basis a large scale dataset out of the positive sciences. + +However, contrary to what the title and some parts of the article are suggesting, the data do not exclusively reveal the impact of the pest epidemic of 1347- 1352. They are on the contrary revealing also other changes in the late medieval society that are due to other factors as well. Indeed other demographic catastrophes were typical for the (later) middle ages as well and certainly also are reflected in pollen analyses. We think about famines (e.g. a° 1315- 1317), wars (that became much more devastating in the late middle ages and also caused epidemic + +<--- Page Split ---> + +# natureresearch + +diseases) but especially other epidemics and most importantly the s.c. 'echo- (pest- )epidemics' after the first plague epidemic (e.g. 1357- 9, 1373, 1400- 1401...). However also these epidemics occurred with huge regional variations. Moreover during that period structural changes of the rural society took place that were only partly linked to the black death (e.g. land concentration and the occurrence of new elites). + +- > We are grateful for these careful and constructive comments. We had long discussions among the historians who co-authored this paper about the extent to which our results are connected with phenomena other than the Black Death itself. Our conclusion is that our method produces results that actually are connected directly to the Black Death understood as the initial introduction of Y. pestis to Europe during the second pandemic. Of course, the later echo-epidemics (later outbreaks) amplified the consequences of the Black Death, but the role of the outbreak of the Black Death was crucial for whether a population collapse - leading to significant landscape changes - occurred in a particular region or not. It is the Black Death itself, the pandemic of the mid-fourteenth-century, that is attributed with killing half of the population of Europe in a few years, not the subsequent outbreaks, which only added, albeit in a regionalized way, to the mortality of the Black Death decades after the Black Death. As such, it is the Black Death that we focus on. It was the major demographic moment of change in fourteenth-century European history and, in fact, in late medieval history more generally. Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century. + +To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well- constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death. + +Hence, the results presented in our article concern 100- year periods before and after the Black Death, that is 4 human generations (the minimum time to overcome a sudden population loss in the range of 30- 50%). Additionally, in the Supplementary Material, we already showed the results for 50 and 25 year periods before and after the Black Death: they + +<--- Page Split ---> + +# natureresearch + +are very similar to the results of the 100 year periods, as we discussed in the main text. To emphasise this fact, and further demonstrate the focus of our analysis on the Black Death in particular, we now added additional figures to the text and commented on them. Based on the consistency between these different periods of analysis, we are convinced that the landscape changes we analyse across Europe are related directly to the Black Death, and not - as the reviewer suggests - to the 'Dantean Anomaly' and the Great Famine of the 1310s or to the late fourteenth or early fifteenth century- plague outbreaks. The impact of these phenomena is not captured by the 25 year or even 50 year periods of analysis). Thus, given the current consensus hypothesis we want to test (universal mass mortality), we are able to demonstrate that whereas it did occur in some areas (e.g. Greece, Sweden or Italy), it did not occur elsewhere (e.g. Poland or Spain). We believe this is the main merit of our article, and to some extent it is indeed confirmation of historical works of Biraben, Malwost or Gottfried, who emphasised regional differentiation of the late medieval crisis in Europe, a minority perspective today which we now make clear reference to in the article). + +To conclude: Interesting article but before publication we advise that the content should be changed as mentioned and that a new title should be formulated that is more conform to its content. + +- > We have suggested a new title, clearly focused on the vision of the Black Death that dominates plague studies and the public imagination - the vision which we falsify in our study. + +Reviewer #2 (Remarks to the Author): + +This interesting study uses changes in the type of pollen in sediment cores to investigate the consequences of the black death upon the types of plant growing. The study uses a logical approach, and the illustrations explain the data convincingly. + +Estimating Black Death Mortality section (lines 131- 165). You write that until now texts have been the best way to study the impact of the Black Death on population size, although it is good that you do mention papers about changing pollution levels. However, other techniques are available. One study looked at the number of fragments of pottery in test pits to show that there was a significant drop in pottery use and production in England following the Black Death, likely a result of the smaller population size. I would encourage you to read this and give a couple of sentences on its approach (it is not my paper): Lewis, C. (2016) Disaster recovery: new archaeological evidence for the long- term impact of the 'calamitous' fourteenth century. Antiquity 90(351): 777- 797. + +<--- Page Split ---> + +# natureresearch + +- > We have now included this study in our method section. We also would like to thank the reviewer 2 for the positive comments on our paper and for expanding even further our interdisciplinarity. + +Minor point: Abstract first sentence: 'reknown' should read 'renown'. + +- > Corrected, thank you. + +Reviewer #3 (Remarks to the Author): + +This is a very interesting and topical paper. In principle, I was surprised by the methodological approach, but after studying it repeatedly, I find that the idea is provocative and has great explanatory power. The conclusion about the spatial and social heterogeneity of the epidemic is common sense regardless of conventional historicist approaches based on inevitably biased sources. + +Obviously, pollen analysis also entails its spatial sampling, analysis and interpretation biases, in addition to the biases derived from the resolution in the identification of palynological types. Not even close to all the pollen analyses published in the studied territory are presented here either. Naturally, all these limitations are unapproachable in the current state of collaboration with Big Data. + +That said, the epistemological and methodological approach of this study seems fresh and healthy to me as a pioneering study on the frontiers of knowledge. A much needed consilience between the natural sciences and the social sciences. A brilliant work in my opinion, which will be a must- read for the general public and which I predict a considerable media success. + +My enthusiasm cannot but lead to the belief that the paper can be published in its current form. The language is accessible, the information well collected and the message clear and direct, without frills. Congratulations to the authors. + +- > Thank you very much for such an encouraging review! + +Reviewer #4 (Remarks to the Author): + +<--- Page Split ---> + +# natureresearch + +In "Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe" the authors evaluate paleorecord of series of sedimentary sequences from 19 European countries to evaluate whether landscape changes could be linked with the hypothesis that half of the population died within a single year. This is a very interesting paper with an interesting approach and I have enjoyed reading it. It is really exciting seeing how fossil pollen time- series are answering big and relevant questions of concern to society as pandemics are. However, I have some concerns I would like the authors to consider. + +Main points: + +1) Mortality and landscape change: After reading the paper with interest and SI (lines 445 474) the "direct" link between population decline or mortality and landscape change that I think is the main hypothesis of the paper is not clear to me. The authors used >1600 palynological time-series to evaluate the demographic impact of the Black Death on a regional scale across Europe. I think that the results of the paper are not strictly quantifying mortality (e.g. what magnitude?) but responses of local/regional vegetation/landscapes to changes on land-use, and other factors including mortality. However, I think the results are still relevant. + +-> Yes, indeed. In agreement with the comments of R1, and by changing the title, we now tried to make clear that while we do study landscape changes (or lack thereof), we do so entirely in order to test the currently dominant view that the Black Death led to universal mortality within the range of 30-50%. We now make clear in the methods section why this is important to us: such a truly significant mortality would lead to profound and sudden landscape change, which we indeed observe in some of our study regions. + +I also found that the manuscript requires an improved discussion on demographic changes- how the authors interpret demographic changes in their results? It is mortality quantified "only" with th increase and decrease of cereals, etc? In Lines 191- 198 there are more discussion on validation. And I thank the authors for including this but I keep struggling in understanding what is the actual quantification of mortality. + +-> Entirely understood. We have now improved our discussion of the connection to plague mortality in the relevant sections of the Methods section and in the main text. As we explain, we do not provide direct, concrete estimates of mortality, as the state of the research on palynology and historical demography has not yet reached this stage, despite some major + +<--- Page Split ---> + +# natureresearch + +recent advances in this respect. Our aim instead is to use pollen data to verify the popular vision of the Black Death as a universal mortality catastrophe in Europe, leading to \(30 - 50\%\) of the population dying in a few mere years. As we now try to explain more clearly, such a scenario would result in major landscape changes following the sudden and profound reduction of human pressure on the landscape. We observe significant population erosion in some parts of Europe (consistently with the limited written evidence available for Black Death mortality), while not in others (for which we provide explanation in the concluding section of the main text). + +Also, why Poland experienced growth? More is required in here. + +- > We now explain this fact. + +2) Time period: It requires more detail on why the analysis are focusing on the period between 1250 and 1450 CE. I think this detail should be explored in-depth to better discuss the otherwise relevant results. + +- > We now discuss our choice of 100 year slices of time on either side of 1350 as our main period of analysis in the first section of the Methods. We now also discuss the results we obtained for shorter time periods in the main text. + +3) Regional selection: Another issues I think it requires more description/discussion is why the authors included and excluded sites (Fig 1). I understand the limitation on finding good quality datasets for the time period of interest but I think that comparing sites located in mountain areas vs coastal areas and/or with different population densities, etc. probably impacted the findings. + +- > We now provide two additional supplementary figures that show the geographical setting (lowland vs highland) of our sites as well as the population densities around our sites in the fourteenth century. These variables are not linked to the results we obtained for our BDP pollen indicators, however. Please note that we undertook as well a comparative study of change in the landscape over periods of 200, 100 and 50 years. We assume that over such short time scales physical geographical characteristics of each site remain stable and do not impact our results and conclusions. + +<--- Page Split ---> + +# natureresearch + +Minor points + +Line 113: I think it is missing the years that the pandemic was active. Please add the years. + +- > This Black Death pandemic probably began in the 1330s in Central Asia and in many parts of Eurasia and Africa - outside of Europe - continued until the late 1350s. For this reason, we believe providing an approximate chronological range of the "mid-14th c." is most correct. For the entire Eurasia and Africa, providing set years would be difficult to substantiate and there is no consensus (contrary to the dates for Europe only). + +Ecological indices: It is missing a line with the relevance of these indices to help linking landscape change and the scale of the Black Death mortality. Why are these indices important to answer the question? I read the detail in SI but still not clear to me why the authors are using them. Not suggesting that the approach is not relevant but there are so many analysis to quantify how cereals and different vegetation types change over time that it require a better justification. + +- > We have now provided more explanation in the main text and in the Methods. + +Lines 171- 172: The authors suggested that "Pollen data can be used to assess past demographic dynamics as human pressure on the landscape in the preindustrial period was directly dependent on the availability of rural labour." I think this line is a bit confusing as it is mixing up to rural vs city demographics with the main point of the paper that is mortality. + +- > As we explain in the Methods, \(\sim 90\%\) of the late medieval European population lived in the countryside, so in order to understand overall mortality levels during the Black Death, our primary focus should be the rural populations. + +Line 261: This is a very strong sentence "The significant variability of Black Death mortality that our BDP approach identifies remains..." I'm struggling to accept that the results are showing differences in mortality rates. I think that it is an interesting hypothesis but it could well be that + +<--- Page Split ---> + +# natureresearch + +the landscape change found may respond to differences in vegetation resilience, different baseline population densities and cultures, land- use, culture differences, etc. + +- > Duly noted. As we argue in the Methods, though, the changes we observe are related to human pressure on the landscape, which in turn was dependent on population levels. We also focus primarily on cultivated plants, cereals, whose presence in the landscape diminishes dramatically and over very short time scales without human activity/pressure that supports these plants, as we explain in the Methods. Moreover, thanks to our strict chronological focus, also as now explained further in response to the comments of R1, we are in the position to argue that these landscape changes (or lack thereof) were directly related to the Black Death, that is, the commonly supposed most important demographic event of the fourteenth century. At the same time, we agree with R4 that the factors s/he mentions were important as moderating the Black Death's impact at the regional and local level - and we discuss this point in the concluding section of the main text. + +Lines 286- 295 probably could be placed at the beginning of the manuscript to help integrating the spatial distribution of the Black Death and to better justify the time- period. + +- > We now focus more on explaining the temporal and spatial focus we have adopted throughout the text. + +Lines 487- 494: Depth age models- have the authors re- calibrated them using the new calibration curves? + +- > Yes, absolutely: as we explain in the Methods, we re- calculated age-depth models for a large portion of our sites: especially for those that were using the older calibration curves. + +I hope my comments are helpful to improve the manuscript. + +- > Yes, indeed, thank you very much! + +<--- Page Split ---> + +# natureresearch + +## Decision Letter, first revision: + +8th October 2021 + +Dear Dr. Masi, + +Thank you for submitting your revised manuscript "The Black Death Killed Far Fewer Europeans than Commonly Thought, Big Data Paleoecology Reveals" (NATECoLEVEL- 210614034A). It has now been seen again by the original reviewers and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Ecology & Evolution, pending revisions to satisfy the reviewers' final requests and to comply with our editorial and formatting guidelines. As explained below, our full recommendations will be sent in a later email, but for now, please note that both reviewers recommend that considerable nuance be brought into the discussion--your main text is on the short side by my rough calculation, so I estimate that you should be able to incorporate up to about 500 words of additional discussion which should address the remaining reviewer concerns. + +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)-- we can not proceed with PDFs at this stage. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +## [REDACTED] + +Reviewer #1 (Remarks to the Author): + +## GENERAL COMMENT: + +The article has been upgraded a lot: the amount of relevant literature has been increased and the text is more nuanced. + +A few remarks anyway (put in the reply- text of the authors) + +## DETAILS: + +Reply text of the authors to the first remarks: + +"Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century." + +Reply of the reviewer: Anyway there were important regions where the later outbreaks had much more influence that the first outbreak. Moreover if there would not have been 'echo- epidemics', the economy (and the landscapes) probably would + +<--- Page Split ---> + +# natureresearch + +have recovered early. + +Reply text of the authors to the review + +"To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death." + +Reply of the reviewer: + +My remark remains...Why should the data reveal more the influence of the black dead than other elements of the rural economy that were changing in the later middle ages? Of course it is logic that one cannot deal with these other elements but at least it could be mentioned. + +Reviewer #4 (Remarks to the Author): + +This version of the manuscript reads very well and I thank the authors for taking into consideration my comments. This paper is interesting, well written, with fantastic figures, and can bring good discussion on how to integrate data from different paleo- sciences. I agree that population changes may result in major landscape changes (accounted using pollen) following the sudden and profound reduction of human pressure on the landscape that the BD produced- we have a good example with COVID- 19. However, I keep struggling with the concept that the land- use changes found are reflecting differences in mortality rates or the magnitude of the severity of BD, only (line 313, title, etc). + +Overall, the authors should tone down a bit more the narrative around novelty (e.g. pioneering). Using pollen data (or Big- data palaeoecology as the authors refers too) to infer land- use changes or landscape changes is not novel as it is not the link between land- use change and population dynamics. What is novel and exciting of this paper is the integration of historical and paleoecological sources to answer a current important research question: what happen to the landscape when there is a global pandemic with all the associated factors (economical crisis, rates of mortality, duration of the pandemic, type of vegetation, etc...)? + +Interesting paper! + +<--- Page Split ---> + +# natureresearch + +13th October 2021 + +Dear Dr. Masi, + +Thank you for your patience as we've prepared the guidelines for final submission of your Nature Ecology & Evolution manuscript, "The Black Death Killed Far Fewer Europeans than Commonly Thought, Big Data Paleoecology Reveals" (NATECOLEVOL- 210614034A). Please carefully follow the step- by- step instructions provided in the attached file, and add a response in each row of the table to indicate the changes that you have made. Please also check and comment on any additional marked- up edits we have proposed within the text. 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Moreover if there would not have been 'echoepidemics', the economy (and the landscapes) probably would have recovered early. + +Reply text of the authors to the review + +"To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death." + +Reply of the reviewer: + +My remark remains...Why should the data reveal more the influence of the black dead than other elements of the rural economy that were changing in the later middle ages? Of course it is logic that one cannot deal with these other elements but at least it could be mentioned. + +Reviewer #4: Remarks to the Author: + +<--- Page Split ---> + +# natureresearch + +This version of the manuscript reads very well and I thank the authors for taking into consideration my comments. This paper is interesting, well written, with fantastic figures, and can bring good discussion on how to integrate data from different paleo- sciences. I agree that population changes may result in major landscape changes (accounted using pollen) following the sudden and profound reduction of human pressure on the landscape that the BD produced- we have a good example with COVID- 19. However, I keep struggling with the concept that the land- use changes found are reflecting differences in mortality rates or the magnitude of the severity of BD, only (line 313, title, etc). + +Overall, the authors should tone down a bit more the narrative around novelty (e.g. pioneering). Using pollen data (or Big- data palaeoecology as the authors refers too) to infer land- use changes or landscape changes is not novel as it is not the link between land- use change and population dynamics. What is novel and exciting of this paper is the integration of historical and paleoecological sources to answer a current important research question: what happen to the landscape when there is a global pandemic with all the associated factors (economical crisis, rates of mortality, duration of the pandemic, type of vegetation, etc...)? + +Interesting paper! + +Author Rebuttal, first revision: + +## Response to the reviewers' comments (second revision) + +Reviewer #1: Remarks to the Author: GENERAL COMMENT: The article has been upgraded a lot: the amount of relevant literature has been increased and the text is more nuanced. + +- > Thank you! + +A few remarks anyway (put in the reply- text of the authors) + +DETAILS: + +Reply text of the authors to the first remarks: + +"Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century." + +Reply of the reviewer: Anyway there were important regions where the later outbreaks had much more influence that the first outbreak. Moreover if there would not have been 'echo + +<--- Page Split ---> + +# natureresearch + +epidemics', the economy (and the landscapes) probably would have recovered early. + +- > We took account of this point in the discussion. + +Reply text of the authors to the review + +"To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death." + +Reply of the reviewer: + +My remark remains...Why should the data reveal more the influence of the black dead than other elements of the rural economy that were changing in the later middle ages? Of course it is logic that one cannot deal with these other elements but at least it could be mentioned. + +- > As suggested, we now discuss these elements. + +Reviewer #4: + +Remarks to the Author: + +This version of the manuscript reads very well and I thank the authors for taking into consideration my comments. This paper is interesting, well written, with fantastic figures, and can bring good discussion on how to integrate data from different paleo- sciences. I agree that population changes may result in major landscape changes (accounted using pollen) following the sudden and profound reduction of human pressure on the landscape that the BD produced- we have a good example with COVID- 19. However, I keep struggling with the concept that the land- use changes found are reflecting differences in mortality rates or the magnitude of the severity of BD, only (line 313, title, etc). + +- > We modified the text in order to account for the context-dependent complexities involved in this potential link. + +Overall, the authors should tone down a bit more the narrative around novelty (e.g. pioneering). Using pollen data (or Big- data palaeoecology as the authors refers too) to infer land- use changes or landscape changes is not novel as it is not the link between land- use change and population dynamics. What is novel and exciting of this paper is the integration of historical and paleoecological sources to answer a current important research question: what + +<--- Page Split ---> + +# natureresearch + +happen to the landscape when there is a global pandemic with all the associated factors (economical crisis, rates of mortality, duration of the pandemic, type of vegetation, etc...)? + +- > Thank you. We now try to make it clear – and the narrative has been toned down. + +Interesting paper! + +- > Thank you! + +## Final Decision Letter: + +Dear Alessia, + +We are pleased to inform you that your Article entitled "Palaeoecological data indicates land- use changes across Europe linked to spatial heterogeneity in mortality during the Black Death pandemic", has now been accepted for publication in Nature Ecology & Evolution. + +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Ecology and Evolution style. Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required + +After the grant of rights is completed, you will receive a link to your electronic proof via email with a request to make any corrections within 48 hours. 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The reviewers have raised a number of concerns which will need to be addressed before we can offer publication in Nature Ecology & Evolution. We will therefore need to see your responses to the criticisms raised and to some editorial concerns, along with a revised manuscript, before we can reach a final decision regarding publication. + +<|ref|>text<|/ref|><|det|>[[115, 662, 868, 738]]<|/det|> +In particular, you will see that the reviewers emphasise the need to tone down the degree to which the narrative presented is a surprise from a historical perspective- - I don't think this compromises novelty since as reviewer 1 argues, it is valuable to show the palaeoecological dimension on land use change during the period. And as reviewer 4 comments, there is also a need to shore up the linkage between mortality and land use changes- - bringing more historical perspective in here could help. + +<|ref|>text<|/ref|><|det|>[[116, 752, 837, 798]]<|/det|> +We therefore invite you to revise your manuscript taking into account all reviewer and editor comments. Please highlight all changes in the manuscript text file [OPTIONAL: in Microsoft Word format]. + +<|ref|>text<|/ref|><|det|>[[116, 811, 876, 857]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 158, 353, 173]]<|/det|> +When revising your manuscript: + +<|ref|>text<|/ref|><|det|>[[116, 187, 845, 232]]<|/det|> +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each reviewer comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the reviewers along with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 247, 866, 291]]<|/det|> +\* If you have not done so already please begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +<|ref|>text<|/ref|><|det|>[[116, 306, 855, 351]]<|/det|> +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +<|ref|>text<|/ref|><|det|>[[116, 366, 692, 381]]<|/det|> +Please use the link below to submit your revised manuscript and related files: + +<|ref|>sub_title<|/ref|><|det|>[[116, 396, 221, 411]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[116, 425, 866, 470]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[116, 484, 880, 529]]<|/det|> +We hope to receive your revised manuscript within four to eight weeks. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[115, 544, 872, 660]]<|/det|> +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[115, 676, 875, 706]]<|/det|> +Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. + +<|ref|>text<|/ref|><|det|>[[115, 722, 857, 752]]<|/det|> +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +<|ref|>sub_title<|/ref|><|det|>[[116, 767, 221, 782]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[116, 813, 262, 827]]<|/det|> +Reviewer expertise: + +<|ref|>text<|/ref|><|det|>[[116, 842, 420, 857]]<|/det|> +Reviewer #1: medieval economic history + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 157, 407, 172]]<|/det|> +Reviewer #2: Black Death archaeology + +<|ref|>text<|/ref|><|det|>[[116, 187, 446, 201]]<|/det|> +Reviewer #3: palaeoecology and palynology + +<|ref|>text<|/ref|><|det|>[[116, 216, 446, 231]]<|/det|> +Reviewer #4: palaeoecology and palynology + +<|ref|>text<|/ref|><|det|>[[116, 261, 283, 276]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[116, 291, 405, 306]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 320, 879, 380]]<|/det|> +This is an interesting article about the regional variation of agrarian changes in Europe during the late middle ages. Probably for the first time such a large amount of data based on pollen analysis has been brought together to study the regional variation and changes of rural cultivation activity during that period. + +<|ref|>text<|/ref|><|det|>[[116, 395, 874, 455]]<|/det|> +It confirms the existing knowledge (already since Biraben's publication of 1975 and many others after that) that the influence of the late medieval crisis hit Europe with a huge regional variation. However one of the most important merits of the article is that it is the first time that a study like this is done on the basis a large scale dataset out of the positive sciences. + +<|ref|>text<|/ref|><|det|>[[115, 470, 865, 619]]<|/det|> +However, contrary to what the title and some parts of the article are suggesting, the data do not exclusively reveal the impact of the pest epidemic of 1347- 1352. They are on the contrary revealing also other changes in the late medieval society that are due to other factors as well. Indeed other demographic catastrophes were typical for the (later) middle ages as well and certainly also are reflected in pollen analyses. We think about famines (e.g. a° 1315- 1317), wars (that became much more devastating in the late middle ages and also caused epidemic diseases) but especially other epidemics and most importantly the s.c. 'echo- (pest- )epidemics' after the first plague epidemic (e.g. 1357- 9, 1373, 1400- 1401...). However also these epidemics occurred with huge regional variations. Moreover during that period structural changes of the rural society took place that were only partly linked to the black death (e.g. land concentration and the occurrence of new elites). + +<|ref|>text<|/ref|><|det|>[[115, 634, 865, 664]]<|/det|> +To conclude: Interesting article but before publication we advise that the content should be changed as mentioned and that a new title should be formulated that is more conform to its content. + +<|ref|>text<|/ref|><|det|>[[116, 708, 404, 723]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 738, 869, 783]]<|/det|> +This interesting study uses changes in the type of pollen in sediment cores to investigate the consequences of the black death upon the types of plant growing. The study uses a logical approach, and the illustrations explain the data convincingly. + +<|ref|>text<|/ref|><|det|>[[116, 798, 877, 857]]<|/det|> +Estimating Black Death Mortality section (lines 131- 165). You write that until now texts have been the best way to study the impact of the Black Death on population size, although it is good that you do mention papers about changing pollution levels. However, other techniques are available. One study looked at the number of fragments of pottery in test pits to show that there was a significant drop in + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 874, 207]]<|/det|> +pottery use and production in England following the Black Death, likely a result of the smaller population size. I would encourage you to read this and give a couple of sentences on its approach (it is not my paper): Lewis, C. (2016) Disaster recovery: new archaeological evidence for the long- term impact of the 'calamitous' fourteenth century. Antiquity 90(351): 777- 797. + +<|ref|>text<|/ref|><|det|>[[115, 230, 530, 261]]<|/det|> +Minor point: Abstract first sentence: 'reknown' should read 'renown'. + +<|ref|>text<|/ref|><|det|>[[116, 305, 404, 321]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 336, 864, 397]]<|/det|> +This is a very interesting and topical paper. In principle, I was surprised by the methodological approach, but after studying it repeatedly, I find that the idea is provocative and has great explanatory power. The conclusion about the spatial and social heterogeneity of the epidemic is common sense regardless of conventional historicist approaches based on inevitably biased sources. + +<|ref|>text<|/ref|><|det|>[[116, 410, 874, 471]]<|/det|> +Obviously, pollen analysis also entails its spatial sampling, analysis and interpretation biases, in addition to the biases derived from the resolution in the identification of palynological types. Not even close to all the pollen analyses published in the studied territory are presented here either. Naturally, all these limitations are unapproachable in the current state of collaboration with Big Data. + +<|ref|>text<|/ref|><|det|>[[116, 484, 868, 545]]<|/det|> +That said, the epistemological and methodological approach of this study seems fresh and healthy to me as a pioneering study on the frontiers of knowledge. A much needed consilience between the natural sciences and the social sciences. A brilliant work in my opinion, which will be a must- read for the general public and which I predict a considerable media success. + +<|ref|>text<|/ref|><|det|>[[116, 559, 868, 605]]<|/det|> +My enthusiasm cannot but lead to the belief that the paper can be published in its current form. The language is accessible, the information well collected and the message clear and direct, without frills. Congratulations to the authors. + +<|ref|>text<|/ref|><|det|>[[116, 664, 404, 679]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 693, 860, 800]]<|/det|> +In "Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe" the authors evaluate palaeorecord of series of sedimentary sequences from 19 European countries to evaluate whether landscape changes could be linked with the hypothesis that half of the population died within a single year. This is a very interesting paper with an interesting approach and I have enjoyed reading it. It is really exciting seeing how fossil pollen time- series are answering big and relevant questions of concern to society as pandemics are. However, I have some concerns I would like the authors to consider. + +<|ref|>text<|/ref|><|det|>[[116, 814, 208, 829]]<|/det|> +Main points: + +<|ref|>text<|/ref|><|det|>[[115, 842, 860, 858]]<|/det|> +1) Mortality and landscape change: After reading the paper with interest and SI (lines 445 474) the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 875, 232]]<|/det|> +"direct" link between population decline or mortality and landscape change that I think is the main hypothesis of the paper is not clear to me. The authors used \(>1600\) palynological time- series to evaluate the demographic impact of the Black Death on a regional scale across Europe. I think that the results of the paper are not strictly quantifying mortality (e.g. what magnitude?) but responses of local/regional vegetation/landscapes to changes on land- use, and other factors including mortality. However, I think the results are still relevant. + +<|ref|>text<|/ref|><|det|>[[115, 247, 880, 322]]<|/det|> +I also found that the manuscript requires an improved discussion on demographic changes- how the authors interpret demographic changes in their results? It is mortality quantified "only" with th increase and decrease of cereals, etc? In Lines 191- 198 there are more discussion on validation. And I thank the authors for including this but I keep struggling in understanding what is the actual quantification of mortality. Also, why Poland experienced growth? More is required in here. + +<|ref|>text<|/ref|><|det|>[[115, 336, 870, 382]]<|/det|> +2) Time period: It requires more detail on why the analysis are focusing on the period between 1250 and 1450 CE. I think this detail should be explored in-depth to better discuss the otherwise relevant results. + +<|ref|>text<|/ref|><|det|>[[115, 396, 881, 457]]<|/det|> +3) Regional selection: Another issues I think it requires more description/discussion is why the authors included and excluded sites (Fig 1). I understand the limitation on finding good quality datasets for the time period of interest but I think that comparing sites located in mountain areas vs coastal areas and/or with different population densities, etc. probably impacted the findings. + +<|ref|>text<|/ref|><|det|>[[115, 472, 208, 486]]<|/det|> +Minor points + +<|ref|>text<|/ref|><|det|>[[115, 500, 800, 516]]<|/det|> +Line 113: I think it is missing the years that the pandemic was active. Please add the years. + +<|ref|>text<|/ref|><|det|>[[115, 530, 861, 606]]<|/det|> +Ecological indices: It is missing a line with the relevance of these indices to help linking landscape change and the scale of the Black Death mortality. Why are these indices important to answer the question? I read the detail in SI but still not clear to me why the authors are using them. Not suggesting that the approach is not relevant but there are so many analysis to quantify how cereals and different vegetation types change over time that it require a better justification. + +<|ref|>text<|/ref|><|det|>[[115, 619, 864, 680]]<|/det|> +Lines 171- 172: The authors suggested that "Pollen data can be used to assess past demographic dynamics as human pressure on the landscape in the preindustrial period was directly dependent on the availability of rural labour." I think this line is a bit confusing as it is mixing up to rural vs city demographics with the main point of the paper that is mortality. + +<|ref|>text<|/ref|><|det|>[[115, 694, 880, 769]]<|/det|> +Line 261: This is a very strong sentence "The significant variability of Black Death mortality that our BDP approach identifies remains..." I'm struggling to accept that the results are showing differences in mortality rates. I think that it is an interesting hypothesis but it could well be that the landscape change found may respond to differences in vegetation resilience, different baseline population densities and cultures, land- use, culture differences, etc. + +<|ref|>text<|/ref|><|det|>[[115, 784, 848, 814]]<|/det|> +Lines 286- 295 probably could be placed at the beginning of the manuscript to help integrating the spatial distribution of the Black Death and to better justify the time- period. + +<|ref|>text<|/ref|><|det|>[[115, 828, 841, 858]]<|/det|> +Lines 487- 494: Depth age models- have the authors re- calibrated them using the new calibration curves? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 157, 565, 173]]<|/det|> +I hope my comments are helpful to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 231, 523, 245]]<|/det|> +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*END\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\* + +<|ref|>title<|/ref|><|det|>[[120, 268, 395, 283]]<|/det|> +# Author Rebuttal to Initial comments + +<|ref|>sub_title<|/ref|><|det|>[[115, 305, 333, 324]]<|/det|> +## Response to reviewers + +<|ref|>sub_title<|/ref|><|det|>[[115, 370, 864, 414]]<|/det|> +## Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe + +<|ref|>text<|/ref|><|det|>[[115, 426, 226, 443]]<|/det|> +Izdebski et al. + +<|ref|>text<|/ref|><|det|>[[115, 485, 863, 535]]<|/det|> +Editor: In particular, you will see that the reviewers emphasise the need to tone down the degree to which the narrative presented is a surprise from a historical perspective- - I don't think this compromises novelty since as reviewer 1 argues, it is valuable to show the palaeoecological dimension on land use change during the period. + +<|ref|>text<|/ref|><|det|>[[115, 572, 878, 648]]<|/det|> +- > We toned down the first section of the article and took into account the non-Anglophone historiography, which contrary to the recent English-speaking consensus on the Black Death as a universal catastrophic event, noticed some regional variation during the initial phases of the second plague pandemic. + +<|ref|>text<|/ref|><|det|>[[115, 684, 880, 717]]<|/det|> +And as reviewer 4 comments, there is also a need to shore up the linkage between mortality and land use changes- - bringing more historical perspective in here could help. + +<|ref|>text<|/ref|><|det|>[[115, 756, 876, 831]]<|/det|> +- > We rewrote the relevant (first) section of the Methods, providing it with additional references. In particular, we divided this section into two clearly distinguished main points: (1) the close connection between landscape changes as revealed by palynology and population dynamics as revealed by historical sources, as proved by several recent historical-palynological studies; (2) + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 883, 180]]<|/det|> +the landscape changes to be expected in plague- struck areas during the Black Death, based on the current consensus on estimated population decline among the historians of the Black Death. + +<|ref|>text<|/ref|><|det|>[[115, 220, 248, 235]]<|/det|> +Reviewer expertise: + +<|ref|>text<|/ref|><|det|>[[115, 276, 386, 291]]<|/det|> +Reviewer #1: medieval economic history + +<|ref|>text<|/ref|><|det|>[[115, 331, 371, 346]]<|/det|> +Reviewer #2: Black Death archaeology + +<|ref|>text<|/ref|><|det|>[[115, 386, 409, 401]]<|/det|> +Reviewer #3: palaeoecology and palynology + +<|ref|>text<|/ref|><|det|>[[115, 441, 409, 456]]<|/det|> +Reviewer #4: palaeoecology and palynology + +<|ref|>text<|/ref|><|det|>[[115, 527, 419, 544]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 563, 861, 637]]<|/det|> +This is an interesting article about the regional variation of agrarian changes in Europe during the late middle ages. Probably for the first time such a large amount of data based on pollen analysis has been brought together to study the regional variation and changes of rural cultivation activity during that period. + +<|ref|>text<|/ref|><|det|>[[115, 656, 881, 730]]<|/det|> +It confirms the existing knowledge (already since Biraben's publication of 1975 and many others after that) that the influence of the late medieval crisis hit Europe with a huge regional variation. However one of the most important merits of the article is that it is the first time that a study like this is done on the basis a large scale dataset out of the positive sciences. + +<|ref|>text<|/ref|><|det|>[[115, 749, 880, 858]]<|/det|> +However, contrary to what the title and some parts of the article are suggesting, the data do not exclusively reveal the impact of the pest epidemic of 1347- 1352. They are on the contrary revealing also other changes in the late medieval society that are due to other factors as well. Indeed other demographic catastrophes were typical for the (later) middle ages as well and certainly also are reflected in pollen analyses. We think about famines (e.g. a° 1315- 1317), wars (that became much more devastating in the late middle ages and also caused epidemic + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 874, 237]]<|/det|> +diseases) but especially other epidemics and most importantly the s.c. 'echo- (pest- )epidemics' after the first plague epidemic (e.g. 1357- 9, 1373, 1400- 1401...). However also these epidemics occurred with huge regional variations. Moreover during that period structural changes of the rural society took place that were only partly linked to the black death (e.g. land concentration and the occurrence of new elites). + +<|ref|>text<|/ref|><|det|>[[114, 274, 880, 571]]<|/det|> +- > We are grateful for these careful and constructive comments. We had long discussions among the historians who co-authored this paper about the extent to which our results are connected with phenomena other than the Black Death itself. Our conclusion is that our method produces results that actually are connected directly to the Black Death understood as the initial introduction of Y. pestis to Europe during the second pandemic. Of course, the later echo-epidemics (later outbreaks) amplified the consequences of the Black Death, but the role of the outbreak of the Black Death was crucial for whether a population collapse - leading to significant landscape changes - occurred in a particular region or not. It is the Black Death itself, the pandemic of the mid-fourteenth-century, that is attributed with killing half of the population of Europe in a few years, not the subsequent outbreaks, which only added, albeit in a regionalized way, to the mortality of the Black Death decades after the Black Death. As such, it is the Black Death that we focus on. It was the major demographic moment of change in fourteenth-century European history and, in fact, in late medieval history more generally. Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century. + +<|ref|>text<|/ref|><|det|>[[114, 580, 884, 765]]<|/det|> +To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well- constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death. + +<|ref|>text<|/ref|><|det|>[[115, 775, 857, 849]]<|/det|> +Hence, the results presented in our article concern 100- year periods before and after the Black Death, that is 4 human generations (the minimum time to overcome a sudden population loss in the range of 30- 50%). Additionally, in the Supplementary Material, we already showed the results for 50 and 25 year periods before and after the Black Death: they + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 878, 403]]<|/det|> +are very similar to the results of the 100 year periods, as we discussed in the main text. To emphasise this fact, and further demonstrate the focus of our analysis on the Black Death in particular, we now added additional figures to the text and commented on them. Based on the consistency between these different periods of analysis, we are convinced that the landscape changes we analyse across Europe are related directly to the Black Death, and not - as the reviewer suggests - to the 'Dantean Anomaly' and the Great Famine of the 1310s or to the late fourteenth or early fifteenth century- plague outbreaks. The impact of these phenomena is not captured by the 25 year or even 50 year periods of analysis). Thus, given the current consensus hypothesis we want to test (universal mass mortality), we are able to demonstrate that whereas it did occur in some areas (e.g. Greece, Sweden or Italy), it did not occur elsewhere (e.g. Poland or Spain). We believe this is the main merit of our article, and to some extent it is indeed confirmation of historical works of Biraben, Malwost or Gottfried, who emphasised regional differentiation of the late medieval crisis in Europe, a minority perspective today which we now make clear reference to in the article). + +<|ref|>text<|/ref|><|det|>[[116, 420, 857, 476]]<|/det|> +To conclude: Interesting article but before publication we advise that the content should be changed as mentioned and that a new title should be formulated that is more conform to its content. + +<|ref|>text<|/ref|><|det|>[[116, 494, 866, 531]]<|/det|> +- > We have suggested a new title, clearly focused on the vision of the Black Death that dominates plague studies and the public imagination - the vision which we falsify in our study. + +<|ref|>text<|/ref|><|det|>[[116, 550, 418, 567]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 586, 855, 642]]<|/det|> +This interesting study uses changes in the type of pollen in sediment cores to investigate the consequences of the black death upon the types of plant growing. The study uses a logical approach, and the illustrations explain the data convincingly. + +<|ref|>text<|/ref|><|det|>[[114, 660, 883, 825]]<|/det|> +Estimating Black Death Mortality section (lines 131- 165). You write that until now texts have been the best way to study the impact of the Black Death on population size, although it is good that you do mention papers about changing pollution levels. However, other techniques are available. One study looked at the number of fragments of pottery in test pits to show that there was a significant drop in pottery use and production in England following the Black Death, likely a result of the smaller population size. I would encourage you to read this and give a couple of sentences on its approach (it is not my paper): Lewis, C. (2016) Disaster recovery: new archaeological evidence for the long- term impact of the 'calamitous' fourteenth century. Antiquity 90(351): 777- 797. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 844, 200]]<|/det|> +- > We have now included this study in our method section. We also would like to thank the reviewer 2 for the positive comments on our paper and for expanding even further our interdisciplinarity. + +<|ref|>text<|/ref|><|det|>[[115, 228, 566, 264]]<|/det|> +Minor point: Abstract first sentence: 'reknown' should read 'renown'. + +<|ref|>text<|/ref|><|det|>[[116, 293, 309, 310]]<|/det|> +- > Corrected, thank you. + +<|ref|>text<|/ref|><|det|>[[115, 348, 418, 366]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 385, 882, 477]]<|/det|> +This is a very interesting and topical paper. In principle, I was surprised by the methodological approach, but after studying it repeatedly, I find that the idea is provocative and has great explanatory power. The conclusion about the spatial and social heterogeneity of the epidemic is common sense regardless of conventional historicist approaches based on inevitably biased sources. + +<|ref|>text<|/ref|><|det|>[[115, 496, 874, 589]]<|/det|> +Obviously, pollen analysis also entails its spatial sampling, analysis and interpretation biases, in addition to the biases derived from the resolution in the identification of palynological types. Not even close to all the pollen analyses published in the studied territory are presented here either. Naturally, all these limitations are unapproachable in the current state of collaboration with Big Data. + +<|ref|>text<|/ref|><|det|>[[115, 607, 872, 682]]<|/det|> +That said, the epistemological and methodological approach of this study seems fresh and healthy to me as a pioneering study on the frontiers of knowledge. A much needed consilience between the natural sciences and the social sciences. A brilliant work in my opinion, which will be a must- read for the general public and which I predict a considerable media success. + +<|ref|>text<|/ref|><|det|>[[115, 700, 840, 755]]<|/det|> +My enthusiasm cannot but lead to the belief that the paper can be published in its current form. The language is accessible, the information well collected and the message clear and direct, without frills. Congratulations to the authors. + +<|ref|>text<|/ref|><|det|>[[115, 774, 568, 792]]<|/det|> +- > Thank you very much for such an encouraging review! + +<|ref|>text<|/ref|><|det|>[[115, 830, 418, 848]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 161, 870, 292]]<|/det|> +In "Big Data Palaeoecology reveals significant variation in Black Death mortality in Europe" the authors evaluate paleorecord of series of sedimentary sequences from 19 European countries to evaluate whether landscape changes could be linked with the hypothesis that half of the population died within a single year. This is a very interesting paper with an interesting approach and I have enjoyed reading it. It is really exciting seeing how fossil pollen time- series are answering big and relevant questions of concern to society as pandemics are. However, I have some concerns I would like the authors to consider. + +<|ref|>text<|/ref|><|det|>[[115, 312, 217, 328]]<|/det|> +Main points: + +<|ref|>text<|/ref|><|det|>[[115, 346, 881, 476]]<|/det|> +1) Mortality and landscape change: After reading the paper with interest and SI (lines 445 474) the "direct" link between population decline or mortality and landscape change that I think is the main hypothesis of the paper is not clear to me. The authors used >1600 palynological time-series to evaluate the demographic impact of the Black Death on a regional scale across Europe. I think that the results of the paper are not strictly quantifying mortality (e.g. what magnitude?) but responses of local/regional vegetation/landscapes to changes on land-use, and other factors including mortality. However, I think the results are still relevant. + +<|ref|>text<|/ref|><|det|>[[115, 515, 876, 625]]<|/det|> +-> Yes, indeed. In agreement with the comments of R1, and by changing the title, we now tried to make clear that while we do study landscape changes (or lack thereof), we do so entirely in order to test the currently dominant view that the Black Death led to universal mortality within the range of 30-50%. We now make clear in the methods section why this is important to us: such a truly significant mortality would lead to profound and sudden landscape change, which we indeed observe in some of our study regions. + +<|ref|>text<|/ref|><|det|>[[115, 644, 878, 737]]<|/det|> +I also found that the manuscript requires an improved discussion on demographic changes- how the authors interpret demographic changes in their results? It is mortality quantified "only" with th increase and decrease of cereals, etc? In Lines 191- 198 there are more discussion on validation. And I thank the authors for including this but I keep struggling in understanding what is the actual quantification of mortality. + +<|ref|>text<|/ref|><|det|>[[115, 776, 860, 849]]<|/det|> +-> Entirely understood. We have now improved our discussion of the connection to plague mortality in the relevant sections of the Methods section and in the main text. As we explain, we do not provide direct, concrete estimates of mortality, as the state of the research on palynology and historical demography has not yet reached this stage, despite some major + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 880, 291]]<|/det|> +recent advances in this respect. Our aim instead is to use pollen data to verify the popular vision of the Black Death as a universal mortality catastrophe in Europe, leading to \(30 - 50\%\) of the population dying in a few mere years. As we now try to explain more clearly, such a scenario would result in major landscape changes following the sudden and profound reduction of human pressure on the landscape. We observe significant population erosion in some parts of Europe (consistently with the limited written evidence available for Black Death mortality), while not in others (for which we provide explanation in the concluding section of the main text). + +<|ref|>text<|/ref|><|det|>[[116, 330, 628, 348]]<|/det|> +Also, why Poland experienced growth? More is required in here. + +<|ref|>text<|/ref|><|det|>[[117, 387, 337, 404]]<|/det|> +- > We now explain this fact. + +<|ref|>text<|/ref|><|det|>[[116, 424, 872, 478]]<|/det|> +2) Time period: It requires more detail on why the analysis are focusing on the period between 1250 and 1450 CE. I think this detail should be explored in-depth to better discuss the otherwise relevant results. + +<|ref|>text<|/ref|><|det|>[[116, 517, 833, 572]]<|/det|> +- > We now discuss our choice of 100 year slices of time on either side of 1350 as our main period of analysis in the first section of the Methods. We now also discuss the results we obtained for shorter time periods in the main text. + +<|ref|>text<|/ref|><|det|>[[115, 591, 870, 683]]<|/det|> +3) Regional selection: Another issues I think it requires more description/discussion is why the authors included and excluded sites (Fig 1). I understand the limitation on finding good quality datasets for the time period of interest but I think that comparing sites located in mountain areas vs coastal areas and/or with different population densities, etc. probably impacted the findings. + +<|ref|>text<|/ref|><|det|>[[115, 712, 881, 842]]<|/det|> +- > We now provide two additional supplementary figures that show the geographical setting (lowland vs highland) of our sites as well as the population densities around our sites in the fourteenth century. These variables are not linked to the results we obtained for our BDP pollen indicators, however. Please note that we undertook as well a comparative study of change in the landscape over periods of 200, 100 and 50 years. We assume that over such short time scales physical geographical characteristics of each site remain stable and do not impact our results and conclusions. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 202, 220, 218]]<|/det|> +Minor points + +<|ref|>text<|/ref|><|det|>[[115, 238, 835, 256]]<|/det|> +Line 113: I think it is missing the years that the pandemic was active. Please add the years. + +<|ref|>text<|/ref|><|det|>[[115, 285, 872, 378]]<|/det|> +- > This Black Death pandemic probably began in the 1330s in Central Asia and in many parts of Eurasia and Africa - outside of Europe - continued until the late 1350s. For this reason, we believe providing an approximate chronological range of the "mid-14th c." is most correct. For the entire Eurasia and Africa, providing set years would be difficult to substantiate and there is no consensus (contrary to the dates for Europe only). + +<|ref|>text<|/ref|><|det|>[[115, 406, 881, 516]]<|/det|> +Ecological indices: It is missing a line with the relevance of these indices to help linking landscape change and the scale of the Black Death mortality. Why are these indices important to answer the question? I read the detail in SI but still not clear to me why the authors are using them. Not suggesting that the approach is not relevant but there are so many analysis to quantify how cereals and different vegetation types change over time that it require a better justification. + +<|ref|>text<|/ref|><|det|>[[115, 556, 761, 573]]<|/det|> +- > We have now provided more explanation in the main text and in the Methods. + +<|ref|>text<|/ref|><|det|>[[115, 592, 881, 666]]<|/det|> +Lines 171- 172: The authors suggested that "Pollen data can be used to assess past demographic dynamics as human pressure on the landscape in the preindustrial period was directly dependent on the availability of rural labour." I think this line is a bit confusing as it is mixing up to rural vs city demographics with the main point of the paper that is mortality. + +<|ref|>text<|/ref|><|det|>[[115, 705, 857, 760]]<|/det|> +- > As we explain in the Methods, \(\sim 90\%\) of the late medieval European population lived in the countryside, so in order to understand overall mortality levels during the Black Death, our primary focus should be the rural populations. + +<|ref|>text<|/ref|><|det|>[[115, 789, 877, 844]]<|/det|> +Line 261: This is a very strong sentence "The significant variability of Black Death mortality that our BDP approach identifies remains..." I'm struggling to accept that the results are showing differences in mortality rates. I think that it is an interesting hypothesis but it could well be that + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 836, 180]]<|/det|> +the landscape change found may respond to differences in vegetation resilience, different baseline population densities and cultures, land- use, culture differences, etc. + +<|ref|>text<|/ref|><|det|>[[114, 209, 872, 412]]<|/det|> +- > Duly noted. As we argue in the Methods, though, the changes we observe are related to human pressure on the landscape, which in turn was dependent on population levels. We also focus primarily on cultivated plants, cereals, whose presence in the landscape diminishes dramatically and over very short time scales without human activity/pressure that supports these plants, as we explain in the Methods. Moreover, thanks to our strict chronological focus, also as now explained further in response to the comments of R1, we are in the position to argue that these landscape changes (or lack thereof) were directly related to the Black Death, that is, the commonly supposed most important demographic event of the fourteenth century. At the same time, we agree with R4 that the factors s/he mentions were important as moderating the Black Death's impact at the regional and local level - and we discuss this point in the concluding section of the main text. + +<|ref|>text<|/ref|><|det|>[[115, 440, 867, 478]]<|/det|> +Lines 286- 295 probably could be placed at the beginning of the manuscript to help integrating the spatial distribution of the Black Death and to better justify the time- period. + +<|ref|>text<|/ref|><|det|>[[115, 506, 800, 543]]<|/det|> +- > We now focus more on explaining the temporal and spatial focus we have adopted throughout the text. + +<|ref|>text<|/ref|><|det|>[[115, 572, 800, 608]]<|/det|> +Lines 487- 494: Depth age models- have the authors re- calibrated them using the new calibration curves? + +<|ref|>text<|/ref|><|det|>[[115, 648, 875, 684]]<|/det|> +- > Yes, absolutely: as we explain in the Methods, we re- calculated age-depth models for a large portion of our sites: especially for those that were using the older calibration curves. + +<|ref|>text<|/ref|><|det|>[[115, 704, 597, 722]]<|/det|> +I hope my comments are helpful to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 752, 412, 769]]<|/det|> +- > Yes, indeed, thank you very much! + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[123, 181, 345, 197]]<|/det|> +## Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[120, 216, 250, 231]]<|/det|> +8th October 2021 + +<|ref|>text<|/ref|><|det|>[[116, 245, 223, 260]]<|/det|> +Dear Dr. Masi, + +<|ref|>text<|/ref|><|det|>[[115, 274, 879, 425]]<|/det|> +Thank you for submitting your revised manuscript "The Black Death Killed Far Fewer Europeans than Commonly Thought, Big Data Paleoecology Reveals" (NATECoLEVEL- 210614034A). It has now been seen again by the original reviewers and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Ecology & Evolution, pending revisions to satisfy the reviewers' final requests and to comply with our editorial and formatting guidelines. As explained below, our full recommendations will be sent in a later email, but for now, please note that both reviewers recommend that considerable nuance be brought into the discussion--your main text is on the short side by my rough calculation, so I estimate that you should be able to incorporate up to about 500 words of additional discussion which should address the remaining reviewer concerns. + +<|ref|>text<|/ref|><|det|>[[115, 438, 857, 470]]<|/det|> +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)-- we can not proceed with PDFs at this stage. + +<|ref|>text<|/ref|><|det|>[[116, 483, 860, 529]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[115, 543, 870, 574]]<|/det|> +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +<|ref|>sub_title<|/ref|><|det|>[[116, 587, 221, 603]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[116, 618, 404, 633]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[116, 648, 273, 662]]<|/det|> +## GENERAL COMMENT: + +<|ref|>text<|/ref|><|det|>[[115, 663, 877, 693]]<|/det|> +The article has been upgraded a lot: the amount of relevant literature has been increased and the text is more nuanced. + +<|ref|>text<|/ref|><|det|>[[115, 694, 564, 709]]<|/det|> +A few remarks anyway (put in the reply- text of the authors) + +<|ref|>sub_title<|/ref|><|det|>[[115, 723, 188, 737]]<|/det|> +## DETAILS: + +<|ref|>text<|/ref|><|det|>[[115, 739, 457, 753]]<|/det|> +Reply text of the authors to the first remarks: + +<|ref|>text<|/ref|><|det|>[[115, 753, 876, 797]]<|/det|> +"Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century." + +<|ref|>text<|/ref|><|det|>[[115, 798, 585, 858]]<|/det|> +Reply of the reviewer: Anyway there were important regions where the later outbreaks had much more influence that the first outbreak. Moreover if there would not have been 'echo- epidemics', the economy (and the landscapes) probably would + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 143, 277, 157]]<|/det|> +have recovered early. + +<|ref|>text<|/ref|><|det|>[[116, 173, 405, 187]]<|/det|> +Reply text of the authors to the review + +<|ref|>text<|/ref|><|det|>[[115, 188, 879, 321]]<|/det|> +"To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death." + +<|ref|>text<|/ref|><|det|>[[116, 337, 280, 351]]<|/det|> +Reply of the reviewer: + +<|ref|>text<|/ref|><|det|>[[116, 352, 560, 425]]<|/det|> +My remark remains...Why should the data reveal more the influence of the black dead than other elements of the rural economy that were changing in the later middle ages? Of course it is logic that one cannot deal with these other elements but at least it could be mentioned. + +<|ref|>text<|/ref|><|det|>[[116, 470, 404, 485]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 500, 880, 604]]<|/det|> +This version of the manuscript reads very well and I thank the authors for taking into consideration my comments. This paper is interesting, well written, with fantastic figures, and can bring good discussion on how to integrate data from different paleo- sciences. I agree that population changes may result in major landscape changes (accounted using pollen) following the sudden and profound reduction of human pressure on the landscape that the BD produced- we have a good example with COVID- 19. However, I keep struggling with the concept that the land- use changes found are reflecting differences in mortality rates or the magnitude of the severity of BD, only (line 313, title, etc). + +<|ref|>text<|/ref|><|det|>[[115, 619, 882, 724]]<|/det|> +Overall, the authors should tone down a bit more the narrative around novelty (e.g. pioneering). Using pollen data (or Big- data palaeoecology as the authors refers too) to infer land- use changes or landscape changes is not novel as it is not the link between land- use change and population dynamics. What is novel and exciting of this paper is the integration of historical and paleoecological sources to answer a current important research question: what happen to the landscape when there is a global pandemic with all the associated factors (economical crisis, rates of mortality, duration of the pandemic, type of vegetation, etc...)? + +<|ref|>text<|/ref|><|det|>[[116, 739, 250, 753]]<|/det|> +Interesting paper! + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 160, 255, 174]]<|/det|> +13th October 2021 + +<|ref|>text<|/ref|><|det|>[[116, 203, 223, 217]]<|/det|> +Dear Dr. Masi, + +<|ref|>text<|/ref|><|det|>[[115, 232, 872, 337]]<|/det|> +Thank you for your patience as we've prepared the guidelines for final submission of your Nature Ecology & Evolution manuscript, "The Black Death Killed Far Fewer Europeans than Commonly Thought, Big Data Paleoecology Reveals" (NATECOLEVOL- 210614034A). 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Authors will not be required to make a final decision about access to their article until it has been accepted. Find out more about Transformative Journals + +<|ref|>text<|/ref|><|det|>[[115, 515, 876, 679]]<|/det|> +Authors may need to take specific actions to achieve compliance with funder and institutional open access mandates. For submissions from January 2021, if your research is supported by a funder that requires immediate open access (e.g. according to Plan S principles) then you should select the gold OA route, and we will direct you to the compliant route where possible. For authors selecting the subscription publication route our standard licensing terms will need to be accepted, including our self- archiving policies. Those standard licensing terms will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 694, 848, 724]]<|/det|> +Please note that you will not receive your proofs until the publishing agreement has been received through our system. + +<|ref|>text<|/ref|><|det|>[[115, 739, 866, 799]]<|/det|> +For information regarding our different publishing models please see our Transformative Journals page. If you have any questions about costs, Open Access requirements, or our legal forms, please contact ASJournals@springernature.com. + +<|ref|>text<|/ref|><|det|>[[115, 843, 553, 858]]<|/det|> +Please use the following link for uploading these materials: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[115, 142, 222, 159]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[115, 173, 601, 189]]<|/det|> +If you have any further questions, please feel free to contact me. + +<|ref|>sub_title<|/ref|><|det|>[[115, 217, 222, 233]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[115, 262, 293, 309]]<|/det|> +Reviewer #1: Remarks to the Author: GENERAL COMMENT: + +<|ref|>text<|/ref|><|det|>[[115, 309, 880, 339]]<|/det|> +The article has been upgraded a lot: the amount of relevant literature has been increased and the text is more nuanced. + +<|ref|>text<|/ref|><|det|>[[115, 339, 564, 354]]<|/det|> +A few remarks anyway (put in the reply- text of the authors) + +<|ref|>text<|/ref|><|det|>[[115, 368, 188, 381]]<|/det|> +DETAILS: + +<|ref|>text<|/ref|><|det|>[[115, 382, 457, 396]]<|/det|> +Reply text of the authors to the first remarks: + +<|ref|>text<|/ref|><|det|>[[115, 397, 875, 440]]<|/det|> +"Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century." + +<|ref|>text<|/ref|><|det|>[[115, 441, 585, 516]]<|/det|> +Reply of the reviewer: Anyway there were important regions where the later outbreaks had much more influence that the first outbreak. Moreover if there would not have been 'echoepidemics', the economy (and the landscapes) probably would have recovered early. + +<|ref|>text<|/ref|><|det|>[[115, 530, 405, 545]]<|/det|> +Reply text of the authors to the review + +<|ref|>text<|/ref|><|det|>[[115, 546, 877, 679]]<|/det|> +"To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death." + +<|ref|>text<|/ref|><|det|>[[115, 694, 280, 708]]<|/det|> +Reply of the reviewer: + +<|ref|>text<|/ref|><|det|>[[115, 709, 560, 783]]<|/det|> +My remark remains...Why should the data reveal more the influence of the black dead than other elements of the rural economy that were changing in the later middle ages? Of course it is logic that one cannot deal with these other elements but at least it could be mentioned. + +<|ref|>text<|/ref|><|det|>[[115, 828, 291, 858]]<|/det|> +Reviewer #4: Remarks to the Author: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 880, 248]]<|/det|> +This version of the manuscript reads very well and I thank the authors for taking into consideration my comments. This paper is interesting, well written, with fantastic figures, and can bring good discussion on how to integrate data from different paleo- sciences. I agree that population changes may result in major landscape changes (accounted using pollen) following the sudden and profound reduction of human pressure on the landscape that the BD produced- we have a good example with COVID- 19. However, I keep struggling with the concept that the land- use changes found are reflecting differences in mortality rates or the magnitude of the severity of BD, only (line 313, title, etc). + +<|ref|>text<|/ref|><|det|>[[115, 261, 881, 367]]<|/det|> +Overall, the authors should tone down a bit more the narrative around novelty (e.g. pioneering). Using pollen data (or Big- data palaeoecology as the authors refers too) to infer land- use changes or landscape changes is not novel as it is not the link between land- use change and population dynamics. What is novel and exciting of this paper is the integration of historical and paleoecological sources to answer a current important research question: what happen to the landscape when there is a global pandemic with all the associated factors (economical crisis, rates of mortality, duration of the pandemic, type of vegetation, etc...)? + +<|ref|>text<|/ref|><|det|>[[116, 381, 250, 396]]<|/det|> +Interesting paper! + +<|ref|>text<|/ref|><|det|>[[120, 415, 354, 431]]<|/det|> +Author Rebuttal, first revision: + +<|ref|>sub_title<|/ref|><|det|>[[120, 476, 805, 501]]<|/det|> +## Response to the reviewers' comments (second revision) + +<|ref|>text<|/ref|><|det|>[[115, 510, 850, 590]]<|/det|> +Reviewer #1: Remarks to the Author: GENERAL COMMENT: The article has been upgraded a lot: the amount of relevant literature has been increased and the text is more nuanced. + +<|ref|>text<|/ref|><|det|>[[115, 630, 208, 644]]<|/det|> +- > Thank you! + +<|ref|>text<|/ref|><|det|>[[115, 673, 512, 688]]<|/det|> +A few remarks anyway (put in the reply- text of the authors) + +<|ref|>text<|/ref|><|det|>[[115, 706, 175, 720]]<|/det|> +DETAILS: + +<|ref|>text<|/ref|><|det|>[[115, 723, 419, 738]]<|/det|> +Reply text of the authors to the first remarks: + +<|ref|>text<|/ref|><|det|>[[115, 740, 875, 787]]<|/det|> +"Very few historians would expect the landscape of a region to have been altered significantly if it was not struck by the Black Death, but only by secondary and tertiary outbreaks of plague after the Black Death in the fourteenth century." + +<|ref|>text<|/ref|><|det|>[[115, 789, 521, 837]]<|/det|> +Reply of the reviewer: Anyway there were important regions where the later outbreaks had much more influence that the first outbreak. Moreover if there would not have been 'echo + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 536, 176]]<|/det|> +epidemics', the economy (and the landscapes) probably would have recovered early. + +<|ref|>text<|/ref|><|det|>[[116, 214, 448, 228]]<|/det|> +- > We took account of this point in the discussion. + +<|ref|>text<|/ref|><|det|>[[116, 247, 375, 262]]<|/det|> +Reply text of the authors to the review + +<|ref|>text<|/ref|><|det|>[[115, 263, 877, 396]]<|/det|> +"To these remark, we should add that our method is not focused on showing the different trajectories of the late medieval crisis (as was, for instance, Izdebski et al. 2016, https://doi.org/10.1016/j.eeh.2015.10.003); instead of focusing on time series and trend analysis, we focus on the extent to which a single event, well constrained in time - the Black Death - can be associated with landscape changes across Europe. It may well be that all the other phenomena that are collectively known as the late medieval crisis left their imprint on the landscape as well (for instance, our data show the impact of the Great Famine of 1315- 1317 in Devon/England, for which we have no significant impact of the Black Death), but our method in this particular article is set up in such a way that it does not reveal them: it is very clearly focused on the Black Death." + +<|ref|>text<|/ref|><|det|>[[115, 414, 264, 428]]<|/det|> +Reply of the reviewer: + +<|ref|>text<|/ref|><|det|>[[115, 430, 516, 512]]<|/det|> +My remark remains...Why should the data reveal more the influence of the black dead than other elements of the rural economy that were changing in the later middle ages? Of course it is logic that one cannot deal with these other elements but at least it could be mentioned. + +<|ref|>text<|/ref|><|det|>[[116, 530, 440, 545]]<|/det|> +- > As suggested, we now discuss these elements. + +<|ref|>text<|/ref|><|det|>[[115, 564, 203, 577]]<|/det|> +Reviewer #4: + +<|ref|>text<|/ref|><|det|>[[116, 581, 273, 594]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 596, 872, 713]]<|/det|> +This version of the manuscript reads very well and I thank the authors for taking into consideration my comments. This paper is interesting, well written, with fantastic figures, and can bring good discussion on how to integrate data from different paleo- sciences. I agree that population changes may result in major landscape changes (accounted using pollen) following the sudden and profound reduction of human pressure on the landscape that the BD produced- we have a good example with COVID- 19. However, I keep struggling with the concept that the land- use changes found are reflecting differences in mortality rates or the magnitude of the severity of BD, only (line 313, title, etc). + +<|ref|>text<|/ref|><|det|>[[115, 748, 871, 764]]<|/det|> +- > We modified the text in order to account for the context-dependent complexities involved in this potential link. + +<|ref|>text<|/ref|><|det|>[[115, 782, 876, 849]]<|/det|> +Overall, the authors should tone down a bit more the narrative around novelty (e.g. pioneering). Using pollen data (or Big- data palaeoecology as the authors refers too) to infer land- use changes or landscape changes is not novel as it is not the link between land- use change and population dynamics. What is novel and exciting of this paper is the integration of historical and paleoecological sources to answer a current important research question: what + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 882, 177]]<|/det|> +happen to the landscape when there is a global pandemic with all the associated factors (economical crisis, rates of mortality, duration of the pandemic, type of vegetation, etc...)? + +<|ref|>text<|/ref|><|det|>[[115, 203, 677, 218]]<|/det|> +- > Thank you. We now try to make it clear – and the narrative has been toned down. + +<|ref|>text<|/ref|><|det|>[[115, 247, 237, 262]]<|/det|> +Interesting paper! + +<|ref|>text<|/ref|><|det|>[[115, 300, 208, 315]]<|/det|> +- > Thank you! + +<|ref|>sub_title<|/ref|><|det|>[[120, 365, 282, 380]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[115, 399, 213, 414]]<|/det|> +Dear Alessia, + +<|ref|>text<|/ref|><|det|>[[115, 428, 872, 473]]<|/det|> +We are pleased to inform you that your Article entitled "Palaeoecological data indicates land- use changes across Europe linked to spatial heterogeneity in mortality during the Black Death pandemic", has now been accepted for publication in Nature Ecology & Evolution. + +<|ref|>text<|/ref|><|det|>[[115, 488, 874, 548]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Ecology and Evolution style. Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required + +<|ref|>text<|/ref|><|det|>[[115, 563, 865, 608]]<|/det|> +After the grant of rights is completed, you will receive a link to your electronic proof via email with a request to make any corrections within 48 hours. If, when you receive your proof, you cannot meet this deadline, please inform us at rjsproduction@springernature.com immediately. + +<|ref|>text<|/ref|><|det|>[[115, 622, 872, 638]]<|/det|> +You will not receive your proofs until the publishing agreement has been received through our system + +<|ref|>text<|/ref|><|det|>[[115, 652, 880, 728]]<|/det|> +Due to the importance of these deadlines, we ask you please us know now whether you will be difficult to contact over the next month. 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Authors may publish their research with us through the traditional subscription access route or make their paper immediately open access through payment of an article- processing charge (APC). Authors will not be + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 860, 188]]<|/det|> +required to make a final decision about access to their article until it has been accepted. Find out more about Transformative Journals + +<|ref|>text<|/ref|><|det|>[[115, 203, 878, 368]]<|/det|> +Authors may need to take specific actions to achieve compliance with funder and institutional open access mandates. For submissions from January 2021, if your research is supported by a funder that requires immediate open access (e.g. according to Plan S principles) then you should select the gold OA route, and we will direct you to the compliant route where possible. For authors selecting the subscription publication route our standard licensing terms will need to be accepted, including our self- archiving policies. Those standard licensing terms will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 381, 843, 427]]<|/det|> +In approximately 10 business days you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. + +<|ref|>text<|/ref|><|det|>[[115, 441, 875, 457]]<|/det|> +You will not receive your proofs until the publishing agreement has been received through our system. + +<|ref|>text<|/ref|><|det|>[[115, 470, 875, 501]]<|/det|> +If you have any questions about our publishing options, costs, Open Access requirements, or our legal forms, please contact ASJournals@springernature.com + +<|ref|>text<|/ref|><|det|>[[115, 515, 596, 530]]<|/det|> +An online order form for reprints of your paper is available at text<|/ref|><|det|>[[115, 531, 870, 592]]<|/det|> +href="https://www.nature.com/reprints/author- reprints.html">https://www.nature.com/reprints/author- reprints.html. All co- authors, authors' institutions and authors' funding agencies can order reprints using the form appropriate to their geographical region. + +<|ref|>text<|/ref|><|det|>[[115, 604, 880, 725]]<|/det|> +We welcome the submission of potential cover material (including a short caption of around 40 words) related to your manuscript; suggestions should be sent to Nature Ecology & Evolution as electronic files (the image should be 300 dpi at \(210 \times 297 \text{mm}\) in either TIFF or JPEG format). Please note that such pictures should be selected more for their aesthetic appeal than for their scientific content, and that colour images work better than black and white or grayscale images. Please do not try to design a cover with the Nature Ecology & Evolution logo etc., and please do not submit composites of images related to your work. I am sure you will understand that we cannot make any promise as to whether any of your suggestions might be selected for the cover of the journal. + +<|ref|>text<|/ref|><|det|>[[115, 739, 872, 784]]<|/det|> +You can now use a single sign- on for all your accounts, view the status of all your manuscript submissions and reviews, access usage statistics for your published articles and download a record of your refereeing activity for the Nature journals. + +<|ref|>text<|/ref|><|det|>[[115, 798, 878, 858]]<|/det|> +To assist our authors in disseminating their research to the broader community, our SharedIt initiative provides you with a unique shareable link that will allow anyone (with or without a subscription) to read the published article. Recipients of the link with a subscription will also be able to download and print the PDF. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 157, 833, 188]]<|/det|> +You can generate the link yourself when you receive your article DOI by entering it here: http://authors.springernature.com/share. + +<|ref|>text<|/ref|><|det|>[[115, 204, 234, 219]]<|/det|> +Yours sincerely, + +<|ref|>text<|/ref|><|det|>[[115, 248, 216, 263]]<|/det|> +{REDACTED} + +<--- Page Split ---> diff --git a/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..5898f9ac42c97dcd9a3a2ea309242c2896a36e83 --- /dev/null +++ b/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,221 @@ + +# Sex difference in BAT thermogenesis depends on PGC-1α- mediated phospholipid synthesis in mice + +Corresponding Author: Dr Kazutaka Tsujimoto + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In this manuscript, the authors determined the role of transcriptional coactivator PGC- 1α in sex- specific regulation of brown adipose tissue (BAT) thermogenic activity by investigating adipocyte- specific PGC- 1α knockout (AKO) male and female mice. They found that PGC- 1α AKO females exhibit less cold tolerance along with reduced BAT temperature and lower response to norepinephrine compared to males. This reduction in BAT thermogenesis was associated with altered mitochondrial membrane structure and lipid profiles, and decreased TCA cycle metabolites. In addition, expression of genes involved in ChREBPβ- mediated de novo lipogenesis (DNL) pathway was reduced in PGC- 1α AKO females but not in PGC- 1α AKO males. Based on these findings, the authors conclude that PGC- 1α plays a unique, sex- specific role in BAT of female mice through activation of ChREBPβ- mediated DNL, which contributes to the maintenance of mitochondrial membrane structure. However, it is not clear how PGC- 1α promotes ChREBPβ- mediated DNL. In addition, although the authors concluded that estrogen signaling also regulates ChREBPβ/DNL- related gene expression in female BAT, the relative contribution of direct estrogen signaling vs increased sympathetic nervous system (SNS) output to enhancing this pathway in BAT remains unclear. It is likely that PGC- 1α is one of many downstream factors activated in BAT of female mice due to BAT activation via enhanced SNS output. + +1. It is not clear how PGC-1α promotes ChREBPβ-mediated DNL. Does PGC-1α interact with and coactivate ChREBPβ? PGC-1β has been shown to coactivate ChREBPβ and promote DNL gene expression. Does PGC-1α deletion alter PGC-1β expression? + +2. It is not clear whether AAV-shChrebp targets specifically Chrebpb without altering Chrebpa expression. What is the effect of ChREBPβ knockdown on mitochondrial membrane structure and lipid profiles in male BAT? + +3. Estrogen has been shown to enhance BAT function by increasing sympathetic nervous system (SNS) output to BAT (PMC4082097). In addition, mild cold (room temp)-induced AKT2 signaling has been shown to stimulate ChREBP-mediated DNL (PMC5762420). These findings indicate that increased SNS output to BAT in female mice can stimulate PGC-1α expression and ChRRBP-mediated DNL. Estrogen receptor antagonist TMX is likely to suppress SNS output to BAT. Thus, it is not clear whether TMX-mediated effect on BAT function is directly due to impaired estrogen signaling in BAT or due to reduced SNS output to BAT. Immunolabeling of tyrosine hydroxylase, a marker for sympathetic neurons, in male and female BAT may be considered. + +## Reviewer #2 + +(Remarks to the Author) + +In this study, the authors investigate the role mechanism(s) of PGC- 1α in sexual dimorphism. Inducible adipocyte- specific PGC- 1α knockout (KO) mice displayed decreased BAT thermogenesis only in females. Expression of Chrebpβ and downstream de novo lipogenesis (DNL) related genes were both reduced only in female KO mice. BAT- specific knockdown of Chrebpβ reduced the DNL- related gene expression and BAT thermogenesis in female wild- type mice. Furthermore, PGC- 1α enhanced the sensitivity of female BAT estrogen signaling, thereby increasing Chrebpβ and its downstream DNL- related gene expression. These findings suggest that PGC- 1α- ChREBPβ mediated DNL plays a pivotal role in BAT thermogenesis in a sex- dependent manner. + +Major points + +1- The stage of the estrus cycle is critical for Interpretation of the date obtained in female mice. + +<--- Page Split ---> + +2- Is UCP1 expression more elevated in BAT from females than from males ?3- In Figure 3 and in Figure 7, the expression of ChREBPa (RT- qPCR) as well as ChREBP protein content should be measured (actually in males and in females)4- What are the functional consequences of the OVX- treatment on mitochondrial shape, /structure/function ?5- FGF21, a key actor of BAT function, known to be regulated in a sexual dimorphic manner should be measured in all the experiments presented. + +## Reviewer #3 + +(Remarks to the Author) + +The manuscript by Takeuchi et al found a female- specific effect of BAT thermogenesis most likely depending on PGC- 1a- CHREBPb mediated de novo lipogenesis. Overall, this study is well designed and executed and the findings are quite interesting. The major concern for this study is that lack of functional study on the DNL with only gene expressions of some DNL related genes, such as Acss2, FASN etc. It remains unknown why DNL in BAT is important for thermogenesis. Although the authors attempted to show the lipidomic profiles in BAT, especially cardiolipins. However, tetra linoleoyl CL is the major functional cardiolipins, and it is NOT dependent on DNL, since linoleic acid is an essential acid and can only be taken up from dietary sources. It is recommended to show some data that DNL is in fact important in the proposed mechanism using isotope tracing experiments, such as 3H labeled glucose, or 3H H2O. Below are some minor concerns: + +1. Please indicate the weights/mass of BAT in different mice. + +2. Figure 1d and 1f, Male KO mice also showed similar trends with female mice although it is not statistically significant. Is it because of the larger individual variation? + +3. How to explain the difference of GTT in male and female mice in Fig.s1f + +4. IN Figure 4A, please justify why they only focused on polar metabolites using CE-MS methods. IN the heatmap, how do they normalize the different metabolites? + +5. In Figure 5e and 5f, why the patterns of CL(18:2) are different in these two figures? + +6. In line 644, what does "10 uL brown adipose tissue samples" mean? + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Reviewer #2 + +(Remarks to the Author) + +No more comments + +My queries were addressed, congratulations on the mice work ! + +Reviewer #3 + +(Remarks to the Author) + +The authors satisfactorily addressed my concerns + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Reviewer #1 + +## It is not clear how PGC-1α promotes ChREBPβ-mediated DNL. Does PGC-1α interact with and coactivate ChREBPβ? + +It is not clear how PGC- 1α promotes ChREBPβ- mediated DNL. Does PGC- 1α interact with and coactivate ChREBPβ?We appreciate the insightful comments provided by Reviewer #1 and the editor, which have highlighted the critical importance of elucidating the role of PGC- 1α in ChREBPβ- mediated DNL. We fully recognize the significance of addressing this question and have conducted additional analyses to characterize the potential interaction between PGC- 1α and ChREBPβ. We showed that PGC- 1α KO reduced Chrebβ expression at the transcriptional level in female BAT. Although the direct regulation of Chrebβ transcription by PGC- 1α has not been reported, PGC- 1α is known to influence the transcription of target genes through various histone modifications (PMID: 19008463). Therefore, we performed ATAC- seq analysis to assess chromatin accessibility at the relevant regulatory regions. Our results showed that the female BAT exhibited greater chromatin accessibility near the transcription start site (TSS) of Chrebβ than the male BAT (Fig. 3g), suggesting a sex- specific regulatory mechanism. Notably, this sex difference in chromatin accessibility was abolished only in female PGC- 1α knockout (KO) mice. These results indicate that PGC- 1α in female BAT regulates ChREBPβ expression at the transcriptional level through the modulation of chromatin accessibility in a female- specific manner, rather than through direct interaction. Although further examinations are required to clarify the mechanism by which PGC- 1α modulates chromatin accessibility near the TSS of Chrebβ only in female mice, we will be committed to addressing this important question in our future studies. These results have been added to the Results section (Lines 171–189, Figure 3d–g). + +These results have been added to the Results section (Lines 171- 189, Figure 3d- g). + +## PGC-1β has been shown to coactivate ChREBPβ and promote DNL gene expression. + +## Does PGC-1α deletion alter PGC-1β expression? + +To answer this question, we additionally examined Pgc1β expression levels in BAT. No significant difference in Pgc1β expression was observed between male and female BAT. Moreover, Pgc1β expression levels were not affected by PGC- 1α knockout (Fig. S1g). These results indicate that PGC- 1α regulates expression of ChREBPβ and DNL- related genes in a PGC- 1β- independent manner. + +These results have been added to the Results section of the revised manuscript (Lines 104- 105, Supplementary Figure 1g). + +It is not clear whether AAV- shChrebp targets specifically Chrebpb without altering Chrebpa expression. What is the effect of ChREBPβ knockdown on mitochondrial membrane structure and lipid profiles in male BAT? + +<--- Page Split ---> + +We evaluated the knockdown (KD) efficiency of AAV- shChrebp on Chrebpβ and Chrebpa expression in the BAT of both sexes. Our results demonstrated that AAV- shChrebp administration almost completely suppressed Chrebpβ expression while having no significant effect on Chrebpa expression in both male and female BAT (Fig. 6a, Fig. S5a, Fig. S6a- b). These results indicate that AAV- shChrebp selectively targets Chrebpβ expression in the BAT of male and female mice. + +These results have been added to the Results section of the revised manuscript (Lines 252- 254: Figure 6a; Supplementary Figure 5a, and Lines 273- 274: Supplementary Figures 6a- b). + +The reviewer requested examination of the effects of ChREBPβ KD on mitochondrial membrane structure and lipid profiles in male BAT. Furthermore, it appears that investigating the effects of ChREBPβ KD on lipid profiles in female BAT is necessary to assess its effect on the mitochondrial membrane structure. Therefore, we additionally analyzed the lipid profile in the BAT of female ChREBPβ KD mice. + +We first examined the effect of ChREBPβ KD on mitochondrial membrane structure and lipid profiles in male BAT. In male mice, ChREBPβ KD did not affect the mitochondrial membrane structure (Fig. S6c- e). Therefore, we focused on the levels of cardiolipin (CL) and ether- linked phosphatidylethanolamines (PEs), which are known to maintain mitochondrial morphology and function (PMID: 29034233, 37069167, 38129691). Notably, CL(18:2)4 and ether- linked PEs were found to be reduced only in female Pgc- 1α KO mice (Fig. 5f- g, Fig. S5e). Interestingly, these lipid levels were not reduced in the BAT of male ChREBPβ KD mice (Fig. S6f- g). + +Next, we examined the effects of ChREBPβ KD on CL(18:2)4 and ether- linked PE levels in female BAT. In female BAT, ChREBPβ KD reduced ether- linked PE levels but did not affect CL(18:2)4 levels (Fig. 6f- g). These results indicate that a female- specific ChREBPβ- dependent mechanism may enhance ether- linked PE levels in BAT, which could play a critical role in maintaining mitochondrial morphology and function. In contrast, ChREBPβ did not appear to be involved in PGC- 1α- mediated CL(18:2)4 production in female BAT. + +In addition, we observed that PGC- 1α KO did not affect Chrebpa expression in the BAT of either sex (Fig. S3a). Overall, these findings indicate that PGC- 1α may regulate mitochondrial membrane structure through ChREBPβ- dependent ether- linked PE production and ChREBPβ- independent CL(18:2)4 production in a female- specific manner. These results have been added to the Results section of the revised manuscript (Lines 273- 279: Supplementary Figure 6a- g, and Lines 263- 266: Figure 6f- g) and discussed in the Discussion section of the revised manuscript (Lines 370- 373 and Lines 379- 386). + +<--- Page Split ---> + +Estrogen has been shown to enhance BAT function by increasing sympathetic nervous system (SNS) output to BAT (PMC4082097). In addition, mild cold (room temp)- induced AKT2 signaling has been shown to stimulate ChREBP- mediated DNL (PMC5762420). These findings indicate that increased SNS output to BAT in female mice can stimulate PGC- 1α expression and ChREBP- mediated DNL. Estrogen receptor antagonist TMX is likely to suppress SNS output to BAT. Thus, it is not clear whether TMX- mediated effect on BAT function is directly due to impaired estrogen signaling in BAT or due to reduced SNS output to BAT. Immunolabeling of tyrosine hydroxylase, a marker for sympathetic neurons, in male and female BAT may be considered. + +We appreciate the reviewer's insightful comment regarding the potential role of estrogen signaling and SNS output in regulating BAT function. To address this concern, we performed the immunolabeling of tyrosine hydroxylase (TH) and examined the mRNA levels of TH in the BAT of male and female wild- type mice treated with either TMX or vehicle for 5 days. Our results showed no significant differences in TH expression between the sexes or between the TMX and vehicle groups (Fig. S8a- b). These findings suggest that TMX- induced estrogen antagonism does not significantly affect SNS output to BAT in females. Furthermore, as shown in Figure 7g, TMX administration did not alter BAT Pgc1α gene expression, further supporting the conclusion that TMX does not influence SNS output. These results have been added to the Results section of the revised manuscript (Lines 307- 312: Supplementary Figure 8a- b). + +## Reviewer #2 + +## The stage of the estrus cycle is critical for Interpretation of the date obtained in female mice. + +As the reviewer pointed out, the estrus cycle might influence the interpretation of the experimental results. However, in our study, consistent phenotypes—including suppressed thermogenesis and mitochondrial structural deficits in female BAT, induced by either PGC- 1α KO or TMX treatment—were observed across all experiments conducted on a single experimental day (Fig. 1- 7), without any special consideration of the estrus cycle. To determine why this consistency was achieved, we collected blood samples from wild- type female mice during a single experimental day, as in our previous experiments, and measured serum estrogen levels. As shown in the figure below, we observed variability in serum estrogen levels among individual mice, which likely reflects the different stages of the estrus cycle on a single experimental day. Importantly, all experiments (Fig. 1- 7) were performed under these conditions, where female mice had varying serum estrogen levels. + +<--- Page Split ---> + +Despite this variability, consistent phenotypes were obtained, suggesting that the observed effects are not dependent on the estrus cycle stage. Furthermore, serum estrogen levels in male mice were found to be below the detection limit, consistent with a previous report (PMID: 25856427). These findings collectively suggest that even the lowest levels of estrogen in female mice are sufficient to account for the observed sex differences in BAT thermogenesis. Therefore, the estrus cycle stage may not be critical for interpreting the results obtained from female mice. + +![PLACEHOLDER_6_0] + + +## Is UCP1 expression more elevated in BAT from females than from males? + +We measured the expression levels of Ucp1 in BAT. The expression levels of Ucp1 in BAT were higher in females than in males (Fig. S1a), consistent with the enhancement of BAT thermogenesis in female mice. + +These results have been added to the Results section of the revised manuscript (Lines 88- 89: Supplementary Figure 1a). + +## In Figure 3 and in Figure 7, the expression of ChREBPa (RT-qPCR) as well as ChREBP protein content should be measured (actually in males and in females) + +We measured Chrebpa gene expression levels and ChREBP protein levels in the BAT of both PGC- 1α KO mice and TMX- , an estrogen receptor antagonist, administered mice. Neither PGC- 1α KO (Fig. S3a) nor TMX administration (Fig. S7b) resulted in any changes in the expression levels of Chrebpa in either sex. Moreover, the expression levels of the ChREBP protein in BAT were higher in females than in males. In females, both PGC- 1α KO (Fig. S3b) and TMX administration (Fig. S7c) reduced BAT ChREBP protein expression levels, whereas in males, neither PGC- 1α KO nor TMX treatment induced such reductions. + +These results have been added to the Results section of the revised manuscript (Lines 162- 166: Supplementary Figure 3a- b, and Lines 294- 296: Supplementary Figure 7b- c). + +What are the functional consequences of the OVX- treatment on mitochondrial shape, + +<--- Page Split ---> + +## /structure/function ? + +In the BAT of ovariectomized mice, the mitochondrial area was smaller, and the total length of the cristae was also reduced compared with that in the sham- operated female mice (Fig. S7g- i). In addition, VO2 after NE administration was reduced in ovariectomized mice compared with that in sham- operated female mice (Fig. S7f). These results were similar to those observed in the TMX- administered female mice in this study. Overall, these results suggest that estrogen signaling plays an important role in BAT thermogenesis in female mice. + +These results have been added to the Results section of the revised manuscript (Lines 302- 306: Supplementary Figure 7f- i). + +## FGF21, a key actor of BAT function, known to be regulated in a sexual dimorphic manner should be measured in all the experiments presented. + +We measured the expression levels of Fgf21 in BAT in all experiments. No significant differences were observed in the expression levels of Fgf21 between the control and intervention groups as well as between males and females (Fig. S3c, and as shown in the figure below). These results suggest that FGF21 did not play an important role in the sex difference in BAT thermogenesis in this model. + +These results have been added to the Results section of the revised manuscript (Lines 166- 168: Supplementary Figure 3c). + +![PLACEHOLDER_7_0] + + +Reviewer #3 + +However, tetra linoleoyl CL is the major functional cardiolipins, and it is NOT dependent on DNL, since linoleic acid is an essential acid and can only be taken up from dietary sources. It is recommended to show some data that DNL is in fact important in the proposed mechanism using isotope tracing experiments, such as 3H labeled glucose, or 3H H2O. + +We deeply appreciate your valuable advice and suggestions. As suggested, we performed + +<--- Page Split ---> + +lipidomics after \(\mathsf{D}_2\mathsf{O}\) administration and found that the labeled components of CL(18:2)4 were not detected in the PGC- 1α KO and Control mice of both sexes.. This result clearly indicates that PGC- 1α does not enhance CL(18:2)4 production through DNL in the BAT of female mice. In addition, we found that ChREBPβ knockdown did not affect CL(18:2)4 levels in female BAT (Fig. 6f). Overall, these results suggest that PGC- 1α increases CL(18:2)4 levels through molecular mechanism(s) other than ChREBPβ- mediated DNL in female BAT. In addition, we found that several molecular species of ether- linked phosphatidylethanolamine (PE), which were decreased in the female BAT of PGC- 1α KO mice (Fig. S5e), were commonly reduced following BAT ChREBPβ knockdown in female mice (Fig. 6g). The labeled components of ether- linked PE(O- 16:1_18:1) showed a significant decrease in lipidomics after \(\mathsf{D}_2\mathsf{O}\) administration in female Pgc- 1α KO mice (Fig. 6h). These results suggest that ether- linked PE is synthesized via PGC- 1α- ChREBPβ- mediated DNL. Recent studies have highlighted that ether- linked phospholipids play a crucial role in maintaining the morphology and function of the mitochondria (PMID: 37069167, 38129691). + +In summary, PGC- 1α may play a pivotal role in the mitochondrial function of female BAT through both ChREBPβ- dependent de novo ether- linked PE production and ChREBPβ- independent CL(18:2)4 production. + +These observations have been added to the Results section of the revised manuscript (Lines 263- 272: Figure 6f- h, Supplementary Figure 5e) and discussed in the Discussion section of the revised manuscript (Lines 370- 373 and Lines 379- 386). + +## Below are some minor concerns: + +## 1. Please indicate the weights/mass of BAT in different mice. + +We measured the BAT mass in PGC- 1α KO or TMX-, an estrogen receptor antagonist, administered mice. As shown in the figure below, neither PGC- 1α KO nor TMX administration resulted in any change in BAT weight in either sex. + +![PLACEHOLDER_8_0] + + +<--- Page Split ---> + +## 2. Figure 1d and 1f, Male KO mice also showed similar trends with female mice although it is not statistically significant. Is it because of the larger individual variation? + +We agree that body temperature during cold exposure tended to be lower in Male KO mice than in Male Control mice. However, as the reviewer pointed out, these differences were not statistically significant. Moreover, the effects of PGC- 1α KO on BAT, such as energy expenditure (Figure 1g), gene expression (Figure 3a- c), metabolite profile (Figure 4a- e), lipid profile (Figure 5a- i), and mitochondrial structure (Figure 2a- c) and activity (Figure 2d and Figure 4e), were all observed only in female BAT, which is completely consistent with the fact that cold tolerance was significantly reduced only in female mice (Figure 1d, f). Therefore, the lack of a significant reduction in cold tolerance in male mice may be due to sex differences in BAT function. + +## 3. How to explain the difference of GTT in male and female mice in Fig.s1f + +A previous study (PMID: 22645355) reported that male adipocyte- specific PGC- 1α KO mice were systemic glucose intolerant. Our results are compatible with those of this previous report. Given that male mice have poorer glucose tolerance than female mice, impaired glucose tolerance may be more pronounced in male mice than in female mice, although further studies are required to clarify the mechanisms underlying this sex difference. + +## 4. IN Figure 4A, please justify why they only focused on polar metabolites using CEMS methods. IN the heatmap, how do they normalize the different metabolites? + +We focused only on polar metabolites because most molecules produced when the mitochondrial TCA cycle and electron transport chain are activated during BAT thermogenesis are water- soluble and easily ionized molecules. CE- MS methods were used because they are suitable for analyzing polar metabolites. In the heatmap analysis, we used the following formula for normalization: \(Z = (X - \mu) / \sigma\) (Z: standardized value of each metabolite, X: Relative area of each metabolite, \(\mu\) : mean of each metabolite, \(\sigma\) : SD of each metabolite) + +## 5. In Figure 5e and 5f, why the patterns of CL(18:2) are different in these two figures? + +Figure 5e shows the proportion of each CL molecular species, including CL(18:2)4, relative to the total lipid content in BAT. In contrast, Figure 5f presents the proportion of the CL(18:2)4 molecular species normalized to the total CL content in BAT. The proportions of CL among + +<--- Page Split ---> + +all lipids are very small, and those of individual CL species are greatly influenced not only by changes in the absolute amount of individual CL species but also by changes in the absolute amount of total lipids excluding CL. Therefore, to evaluate the changes in CL(18:2)4 within CL, we measured the proportion of CL(18:2)4 among CL as previously reported (PMID: 16855048) and found that CL(18:2)4 was actually reduced only in female knockout mice, as shown in Figure 5f. + +## 6. In line 644, what does "10 uL brown adipose tissue samples" mean? + +We thank the reviewer for this comment. This is a typographical error; the correct notation should be "1 mg brown adipose tissue." We have corrected this error in the text. + +<--- Page Split ---> diff --git a/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0d3c4a98591ab3f3883315d91c9c0eb1c2587ade --- /dev/null +++ b/peer_reviews/122b72a9723a3c9132ec90ab7bdc0cbef880f2e545ab1ae7ee8a6ffcabe67710/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,302 @@ +<|ref|>title<|/ref|><|det|>[[73, 161, 891, 211]]<|/det|> +# Sex difference in BAT thermogenesis depends on PGC-1α- mediated phospholipid synthesis in mice + +<|ref|>text<|/ref|><|det|>[[73, 224, 471, 241]]<|/det|> +Corresponding Author: Dr Kazutaka Tsujimoto + +<|ref|>text<|/ref|><|det|>[[72, 275, 864, 290]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 327, 145, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 354, 220, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 418, 920, 589]]<|/det|> +In this manuscript, the authors determined the role of transcriptional coactivator PGC- 1α in sex- specific regulation of brown adipose tissue (BAT) thermogenic activity by investigating adipocyte- specific PGC- 1α knockout (AKO) male and female mice. They found that PGC- 1α AKO females exhibit less cold tolerance along with reduced BAT temperature and lower response to norepinephrine compared to males. This reduction in BAT thermogenesis was associated with altered mitochondrial membrane structure and lipid profiles, and decreased TCA cycle metabolites. In addition, expression of genes involved in ChREBPβ- mediated de novo lipogenesis (DNL) pathway was reduced in PGC- 1α AKO females but not in PGC- 1α AKO males. Based on these findings, the authors conclude that PGC- 1α plays a unique, sex- specific role in BAT of female mice through activation of ChREBPβ- mediated DNL, which contributes to the maintenance of mitochondrial membrane structure. However, it is not clear how PGC- 1α promotes ChREBPβ- mediated DNL. In addition, although the authors concluded that estrogen signaling also regulates ChREBPβ/DNL- related gene expression in female BAT, the relative contribution of direct estrogen signaling vs increased sympathetic nervous system (SNS) output to enhancing this pathway in BAT remains unclear. It is likely that PGC- 1α is one of many downstream factors activated in BAT of female mice due to BAT activation via enhanced SNS output. + +<|ref|>text<|/ref|><|det|>[[72, 600, 920, 640]]<|/det|> +1. It is not clear how PGC-1α promotes ChREBPβ-mediated DNL. Does PGC-1α interact with and coactivate ChREBPβ? PGC-1β has been shown to coactivate ChREBPβ and promote DNL gene expression. Does PGC-1α deletion alter PGC-1β expression? + +<|ref|>text<|/ref|><|det|>[[72, 640, 920, 667]]<|/det|> +2. It is not clear whether AAV-shChrebp targets specifically Chrebpb without altering Chrebpa expression. What is the effect of ChREBPβ knockdown on mitochondrial membrane structure and lipid profiles in male BAT? + +<|ref|>text<|/ref|><|det|>[[72, 667, 923, 758]]<|/det|> +3. Estrogen has been shown to enhance BAT function by increasing sympathetic nervous system (SNS) output to BAT (PMC4082097). In addition, mild cold (room temp)-induced AKT2 signaling has been shown to stimulate ChREBP-mediated DNL (PMC5762420). These findings indicate that increased SNS output to BAT in female mice can stimulate PGC-1α expression and ChRRBP-mediated DNL. Estrogen receptor antagonist TMX is likely to suppress SNS output to BAT. Thus, it is not clear whether TMX-mediated effect on BAT function is directly due to impaired estrogen signaling in BAT or due to reduced SNS output to BAT. Immunolabeling of tyrosine hydroxylase, a marker for sympathetic neurons, in male and female BAT may be considered. + +<|ref|>sub_title<|/ref|><|det|>[[73, 783, 161, 795]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 810, 238, 822]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 823, 920, 913]]<|/det|> +In this study, the authors investigate the role mechanism(s) of PGC- 1α in sexual dimorphism. Inducible adipocyte- specific PGC- 1α knockout (KO) mice displayed decreased BAT thermogenesis only in females. Expression of Chrebpβ and downstream de novo lipogenesis (DNL) related genes were both reduced only in female KO mice. BAT- specific knockdown of Chrebpβ reduced the DNL- related gene expression and BAT thermogenesis in female wild- type mice. Furthermore, PGC- 1α enhanced the sensitivity of female BAT estrogen signaling, thereby increasing Chrebpβ and its downstream DNL- related gene expression. These findings suggest that PGC- 1α- ChREBPβ mediated DNL plays a pivotal role in BAT thermogenesis in a sex- dependent manner. + +<|ref|>text<|/ref|><|det|>[[73, 914, 160, 925]]<|/det|> +Major points + +<|ref|>text<|/ref|><|det|>[[72, 926, 713, 939]]<|/det|> +1- The stage of the estrus cycle is critical for Interpretation of the date obtained in female mice. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 901, 125]]<|/det|> +2- Is UCP1 expression more elevated in BAT from females than from males ?3- In Figure 3 and in Figure 7, the expression of ChREBPa (RT- qPCR) as well as ChREBP protein content should be measured (actually in males and in females)4- What are the functional consequences of the OVX- treatment on mitochondrial shape, /structure/function ?5- FGF21, a key actor of BAT function, known to be regulated in a sexual dimorphic manner should be measured in all the experiments presented. + +<|ref|>sub_title<|/ref|><|det|>[[73, 164, 162, 177]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 189, 238, 202]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 202, 912, 288]]<|/det|> +The manuscript by Takeuchi et al found a female- specific effect of BAT thermogenesis most likely depending on PGC- 1a- CHREBPb mediated de novo lipogenesis. Overall, this study is well designed and executed and the findings are quite interesting. The major concern for this study is that lack of functional study on the DNL with only gene expressions of some DNL related genes, such as Acss2, FASN etc. It remains unknown why DNL in BAT is important for thermogenesis. Although the authors attempted to show the lipidomic profiles in BAT, especially cardiolipins. However, tetra linoleoyl CL is the major functional cardiolipins, and it is NOT dependent on DNL, since linoleic acid is an essential acid and can only be taken up from dietary sources. It is recommended to show some data that DNL is in fact important in the proposed mechanism using isotope tracing experiments, such as 3H labeled glucose, or 3H H2O. Below are some minor concerns: + +<|ref|>text<|/ref|><|det|>[[72, 288, 910, 312]]<|/det|> +1. Please indicate the weights/mass of BAT in different mice. + +<|ref|>text<|/ref|><|det|>[[72, 312, 912, 339]]<|/det|> +2. Figure 1d and 1f, Male KO mice also showed similar trends with female mice although it is not statistically significant. Is it because of the larger individual variation? + +<|ref|>text<|/ref|><|det|>[[72, 339, 581, 353]]<|/det|> +3. How to explain the difference of GTT in male and female mice in Fig.s1f + +<|ref|>text<|/ref|><|det|>[[72, 353, 904, 380]]<|/det|> +4. IN Figure 4A, please justify why they only focused on polar metabolites using CE-MS methods. IN the heatmap, how do they normalize the different metabolites? + +<|ref|>text<|/ref|><|det|>[[72, 380, 652, 395]]<|/det|> +5. In Figure 5e and 5f, why the patterns of CL(18:2) are different in these two figures? + +<|ref|>text<|/ref|><|det|>[[72, 395, 559, 409]]<|/det|> +6. In line 644, what does "10 uL brown adipose tissue samples" mean? + +<|ref|>text<|/ref|><|det|>[[73, 433, 144, 447]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 460, 220, 474]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 486, 161, 500]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 512, 238, 527]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 551, 162, 565]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 578, 238, 591]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 592, 199, 604]]<|/det|> +No more comments + +<|ref|>text<|/ref|><|det|>[[73, 604, 506, 618]]<|/det|> +My queries were addressed, congratulations on the mice work ! + +<|ref|>text<|/ref|><|det|>[[73, 631, 162, 644]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 657, 238, 670]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 671, 415, 685]]<|/det|> +The authors satisfactorily addressed my concerns + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[140, 120, 236, 135]]<|/det|> +Reviewer #1 + +<|ref|>sub_title<|/ref|><|det|>[[140, 140, 839, 179]]<|/det|> +## It is not clear how PGC-1α promotes ChREBPβ-mediated DNL. Does PGC-1α interact with and coactivate ChREBPβ? + +<|ref|>text<|/ref|><|det|>[[139, 183, 855, 580]]<|/det|> +It is not clear how PGC- 1α promotes ChREBPβ- mediated DNL. Does PGC- 1α interact with and coactivate ChREBPβ?We appreciate the insightful comments provided by Reviewer #1 and the editor, which have highlighted the critical importance of elucidating the role of PGC- 1α in ChREBPβ- mediated DNL. We fully recognize the significance of addressing this question and have conducted additional analyses to characterize the potential interaction between PGC- 1α and ChREBPβ. We showed that PGC- 1α KO reduced Chrebβ expression at the transcriptional level in female BAT. Although the direct regulation of Chrebβ transcription by PGC- 1α has not been reported, PGC- 1α is known to influence the transcription of target genes through various histone modifications (PMID: 19008463). Therefore, we performed ATAC- seq analysis to assess chromatin accessibility at the relevant regulatory regions. Our results showed that the female BAT exhibited greater chromatin accessibility near the transcription start site (TSS) of Chrebβ than the male BAT (Fig. 3g), suggesting a sex- specific regulatory mechanism. Notably, this sex difference in chromatin accessibility was abolished only in female PGC- 1α knockout (KO) mice. These results indicate that PGC- 1α in female BAT regulates ChREBPβ expression at the transcriptional level through the modulation of chromatin accessibility in a female- specific manner, rather than through direct interaction. Although further examinations are required to clarify the mechanism by which PGC- 1α modulates chromatin accessibility near the TSS of Chrebβ only in female mice, we will be committed to addressing this important question in our future studies. These results have been added to the Results section (Lines 171–189, Figure 3d–g). + +<|ref|>text<|/ref|><|det|>[[140, 576, 784, 594]]<|/det|> +These results have been added to the Results section (Lines 171- 189, Figure 3d- g). + +<|ref|>sub_title<|/ref|><|det|>[[140, 614, 833, 632]]<|/det|> +## PGC-1β has been shown to coactivate ChREBPβ and promote DNL gene expression. + +<|ref|>sub_title<|/ref|><|det|>[[140, 635, 537, 651]]<|/det|> +## Does PGC-1α deletion alter PGC-1β expression? + +<|ref|>text<|/ref|><|det|>[[140, 655, 850, 757]]<|/det|> +To answer this question, we additionally examined Pgc1β expression levels in BAT. No significant difference in Pgc1β expression was observed between male and female BAT. Moreover, Pgc1β expression levels were not affected by PGC- 1α knockout (Fig. S1g). These results indicate that PGC- 1α regulates expression of ChREBPβ and DNL- related genes in a PGC- 1β- independent manner. + +<|ref|>text<|/ref|><|det|>[[140, 760, 848, 800]]<|/det|> +These results have been added to the Results section of the revised manuscript (Lines 104- 105, Supplementary Figure 1g). + +<|ref|>text<|/ref|><|det|>[[140, 823, 825, 884]]<|/det|> +It is not clear whether AAV- shChrebp targets specifically Chrebpb without altering Chrebpa expression. What is the effect of ChREBPβ knockdown on mitochondrial membrane structure and lipid profiles in male BAT? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[139, 118, 850, 243]]<|/det|> +We evaluated the knockdown (KD) efficiency of AAV- shChrebp on Chrebpβ and Chrebpa expression in the BAT of both sexes. Our results demonstrated that AAV- shChrebp administration almost completely suppressed Chrebpβ expression while having no significant effect on Chrebpa expression in both male and female BAT (Fig. 6a, Fig. S5a, Fig. S6a- b). These results indicate that AAV- shChrebp selectively targets Chrebpβ expression in the BAT of male and female mice. + +<|ref|>text<|/ref|><|det|>[[140, 247, 848, 287]]<|/det|> +These results have been added to the Results section of the revised manuscript (Lines 252- 254: Figure 6a; Supplementary Figure 5a, and Lines 273- 274: Supplementary Figures 6a- b). + +<|ref|>text<|/ref|><|det|>[[139, 310, 850, 415]]<|/det|> +The reviewer requested examination of the effects of ChREBPβ KD on mitochondrial membrane structure and lipid profiles in male BAT. Furthermore, it appears that investigating the effects of ChREBPβ KD on lipid profiles in female BAT is necessary to assess its effect on the mitochondrial membrane structure. Therefore, we additionally analyzed the lipid profile in the BAT of female ChREBPβ KD mice. + +<|ref|>text<|/ref|><|det|>[[139, 418, 855, 586]]<|/det|> +We first examined the effect of ChREBPβ KD on mitochondrial membrane structure and lipid profiles in male BAT. In male mice, ChREBPβ KD did not affect the mitochondrial membrane structure (Fig. S6c- e). Therefore, we focused on the levels of cardiolipin (CL) and ether- linked phosphatidylethanolamines (PEs), which are known to maintain mitochondrial morphology and function (PMID: 29034233, 37069167, 38129691). Notably, CL(18:2)4 and ether- linked PEs were found to be reduced only in female Pgc- 1α KO mice (Fig. 5f- g, Fig. S5e). Interestingly, these lipid levels were not reduced in the BAT of male ChREBPβ KD mice (Fig. S6f- g). + +<|ref|>text<|/ref|><|det|>[[139, 589, 855, 712]]<|/det|> +Next, we examined the effects of ChREBPβ KD on CL(18:2)4 and ether- linked PE levels in female BAT. In female BAT, ChREBPβ KD reduced ether- linked PE levels but did not affect CL(18:2)4 levels (Fig. 6f- g). These results indicate that a female- specific ChREBPβ- dependent mechanism may enhance ether- linked PE levels in BAT, which could play a critical role in maintaining mitochondrial morphology and function. In contrast, ChREBPβ did not appear to be involved in PGC- 1α- mediated CL(18:2)4 production in female BAT. + +<|ref|>text<|/ref|><|det|>[[139, 716, 850, 862]]<|/det|> +In addition, we observed that PGC- 1α KO did not affect Chrebpa expression in the BAT of either sex (Fig. S3a). Overall, these findings indicate that PGC- 1α may regulate mitochondrial membrane structure through ChREBPβ- dependent ether- linked PE production and ChREBPβ- independent CL(18:2)4 production in a female- specific manner. These results have been added to the Results section of the revised manuscript (Lines 273- 279: Supplementary Figure 6a- g, and Lines 263- 266: Figure 6f- g) and discussed in the Discussion section of the revised manuscript (Lines 370- 373 and Lines 379- 386). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[137, 118, 856, 303]]<|/det|> +Estrogen has been shown to enhance BAT function by increasing sympathetic nervous system (SNS) output to BAT (PMC4082097). In addition, mild cold (room temp)- induced AKT2 signaling has been shown to stimulate ChREBP- mediated DNL (PMC5762420). These findings indicate that increased SNS output to BAT in female mice can stimulate PGC- 1α expression and ChREBP- mediated DNL. Estrogen receptor antagonist TMX is likely to suppress SNS output to BAT. Thus, it is not clear whether TMX- mediated effect on BAT function is directly due to impaired estrogen signaling in BAT or due to reduced SNS output to BAT. Immunolabeling of tyrosine hydroxylase, a marker for sympathetic neurons, in male and female BAT may be considered. + +<|ref|>text<|/ref|><|det|>[[138, 305, 857, 567]]<|/det|> +We appreciate the reviewer's insightful comment regarding the potential role of estrogen signaling and SNS output in regulating BAT function. To address this concern, we performed the immunolabeling of tyrosine hydroxylase (TH) and examined the mRNA levels of TH in the BAT of male and female wild- type mice treated with either TMX or vehicle for 5 days. Our results showed no significant differences in TH expression between the sexes or between the TMX and vehicle groups (Fig. S8a- b). These findings suggest that TMX- induced estrogen antagonism does not significantly affect SNS output to BAT in females. Furthermore, as shown in Figure 7g, TMX administration did not alter BAT Pgc1α gene expression, further supporting the conclusion that TMX does not influence SNS output. These results have been added to the Results section of the revised manuscript (Lines 307- 312: Supplementary Figure 8a- b). + +<|ref|>sub_title<|/ref|><|det|>[[140, 592, 238, 606]]<|/det|> +## Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[140, 611, 802, 649]]<|/det|> +## The stage of the estrus cycle is critical for Interpretation of the date obtained in female mice. + +<|ref|>text<|/ref|><|det|>[[139, 653, 848, 884]]<|/det|> +As the reviewer pointed out, the estrus cycle might influence the interpretation of the experimental results. However, in our study, consistent phenotypes—including suppressed thermogenesis and mitochondrial structural deficits in female BAT, induced by either PGC- 1α KO or TMX treatment—were observed across all experiments conducted on a single experimental day (Fig. 1- 7), without any special consideration of the estrus cycle. To determine why this consistency was achieved, we collected blood samples from wild- type female mice during a single experimental day, as in our previous experiments, and measured serum estrogen levels. As shown in the figure below, we observed variability in serum estrogen levels among individual mice, which likely reflects the different stages of the estrus cycle on a single experimental day. Importantly, all experiments (Fig. 1- 7) were performed under these conditions, where female mice had varying serum estrogen levels. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[139, 119, 852, 265]]<|/det|> +Despite this variability, consistent phenotypes were obtained, suggesting that the observed effects are not dependent on the estrus cycle stage. Furthermore, serum estrogen levels in male mice were found to be below the detection limit, consistent with a previous report (PMID: 25856427). These findings collectively suggest that even the lowest levels of estrogen in female mice are sufficient to account for the observed sex differences in BAT thermogenesis. Therefore, the estrus cycle stage may not be critical for interpreting the results obtained from female mice. + +<|ref|>image<|/ref|><|det|>[[145, 297, 283, 430]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[140, 461, 750, 479]]<|/det|> +## Is UCP1 expression more elevated in BAT from females than from males? + +<|ref|>text<|/ref|><|det|>[[140, 483, 828, 542]]<|/det|> +We measured the expression levels of Ucp1 in BAT. The expression levels of Ucp1 in BAT were higher in females than in males (Fig. S1a), consistent with the enhancement of BAT thermogenesis in female mice. + +<|ref|>text<|/ref|><|det|>[[140, 546, 839, 586]]<|/det|> +These results have been added to the Results section of the revised manuscript (Lines 88- 89: Supplementary Figure 1a). + +<|ref|>sub_title<|/ref|><|det|>[[140, 610, 835, 648]]<|/det|> +## In Figure 3 and in Figure 7, the expression of ChREBPa (RT-qPCR) as well as ChREBP protein content should be measured (actually in males and in females) + +<|ref|>text<|/ref|><|det|>[[139, 652, 853, 800]]<|/det|> +We measured Chrebpa gene expression levels and ChREBP protein levels in the BAT of both PGC- 1α KO mice and TMX- , an estrogen receptor antagonist, administered mice. Neither PGC- 1α KO (Fig. S3a) nor TMX administration (Fig. S7b) resulted in any changes in the expression levels of Chrebpa in either sex. Moreover, the expression levels of the ChREBP protein in BAT were higher in females than in males. In females, both PGC- 1α KO (Fig. S3b) and TMX administration (Fig. S7c) reduced BAT ChREBP protein expression levels, whereas in males, neither PGC- 1α KO nor TMX treatment induced such reductions. + +<|ref|>text<|/ref|><|det|>[[140, 803, 848, 842]]<|/det|> +These results have been added to the Results section of the revised manuscript (Lines 162- 166: Supplementary Figure 3a- b, and Lines 294- 296: Supplementary Figure 7b- c). + +<|ref|>text<|/ref|><|det|>[[137, 867, 850, 885]]<|/det|> +What are the functional consequences of the OVX- treatment on mitochondrial shape, + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[140, 120, 316, 136]]<|/det|> +## /structure/function ? + +<|ref|>text<|/ref|><|det|>[[139, 141, 852, 285]]<|/det|> +In the BAT of ovariectomized mice, the mitochondrial area was smaller, and the total length of the cristae was also reduced compared with that in the sham- operated female mice (Fig. S7g- i). In addition, VO2 after NE administration was reduced in ovariectomized mice compared with that in sham- operated female mice (Fig. S7f). These results were similar to those observed in the TMX- administered female mice in this study. Overall, these results suggest that estrogen signaling plays an important role in BAT thermogenesis in female mice. + +<|ref|>text<|/ref|><|det|>[[140, 290, 848, 329]]<|/det|> +These results have been added to the Results section of the revised manuscript (Lines 302- 306: Supplementary Figure 7f- i). + +<|ref|>sub_title<|/ref|><|det|>[[140, 354, 810, 393]]<|/det|> +## FGF21, a key actor of BAT function, known to be regulated in a sexual dimorphic manner should be measured in all the experiments presented. + +<|ref|>text<|/ref|><|det|>[[140, 397, 833, 500]]<|/det|> +We measured the expression levels of Fgf21 in BAT in all experiments. No significant differences were observed in the expression levels of Fgf21 between the control and intervention groups as well as between males and females (Fig. S3c, and as shown in the figure below). These results suggest that FGF21 did not play an important role in the sex difference in BAT thermogenesis in this model. + +<|ref|>text<|/ref|><|det|>[[140, 504, 848, 543]]<|/det|> +These results have been added to the Results section of the revised manuscript (Lines 166- 168: Supplementary Figure 3c). + +<|ref|>image<|/ref|><|det|>[[147, 572, 600, 710]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[140, 740, 238, 755]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[139, 760, 849, 864]]<|/det|> +However, tetra linoleoyl CL is the major functional cardiolipins, and it is NOT dependent on DNL, since linoleic acid is an essential acid and can only be taken up from dietary sources. It is recommended to show some data that DNL is in fact important in the proposed mechanism using isotope tracing experiments, such as 3H labeled glucose, or 3H H2O. + +<|ref|>text<|/ref|><|det|>[[137, 867, 839, 885]]<|/det|> +We deeply appreciate your valuable advice and suggestions. As suggested, we performed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[137, 118, 856, 435]]<|/det|> +lipidomics after \(\mathsf{D}_2\mathsf{O}\) administration and found that the labeled components of CL(18:2)4 were not detected in the PGC- 1α KO and Control mice of both sexes.. This result clearly indicates that PGC- 1α does not enhance CL(18:2)4 production through DNL in the BAT of female mice. In addition, we found that ChREBPβ knockdown did not affect CL(18:2)4 levels in female BAT (Fig. 6f). Overall, these results suggest that PGC- 1α increases CL(18:2)4 levels through molecular mechanism(s) other than ChREBPβ- mediated DNL in female BAT. In addition, we found that several molecular species of ether- linked phosphatidylethanolamine (PE), which were decreased in the female BAT of PGC- 1α KO mice (Fig. S5e), were commonly reduced following BAT ChREBPβ knockdown in female mice (Fig. 6g). The labeled components of ether- linked PE(O- 16:1_18:1) showed a significant decrease in lipidomics after \(\mathsf{D}_2\mathsf{O}\) administration in female Pgc- 1α KO mice (Fig. 6h). These results suggest that ether- linked PE is synthesized via PGC- 1α- ChREBPβ- mediated DNL. Recent studies have highlighted that ether- linked phospholipids play a crucial role in maintaining the morphology and function of the mitochondria (PMID: 37069167, 38129691). + +<|ref|>text<|/ref|><|det|>[[140, 439, 830, 499]]<|/det|> +In summary, PGC- 1α may play a pivotal role in the mitochondrial function of female BAT through both ChREBPβ- dependent de novo ether- linked PE production and ChREBPβ- independent CL(18:2)4 production. + +<|ref|>text<|/ref|><|det|>[[140, 504, 855, 564]]<|/det|> +These observations have been added to the Results section of the revised manuscript (Lines 263- 272: Figure 6f- h, Supplementary Figure 5e) and discussed in the Discussion section of the revised manuscript (Lines 370- 373 and Lines 379- 386). + +<|ref|>sub_title<|/ref|><|det|>[[141, 590, 411, 605]]<|/det|> +## Below are some minor concerns: + +<|ref|>sub_title<|/ref|><|det|>[[140, 610, 653, 627]]<|/det|> +## 1. Please indicate the weights/mass of BAT in different mice. + +<|ref|>text<|/ref|><|det|>[[140, 632, 802, 692]]<|/det|> +We measured the BAT mass in PGC- 1α KO or TMX-, an estrogen receptor antagonist, administered mice. As shown in the figure below, neither PGC- 1α KO nor TMX administration resulted in any change in BAT weight in either sex. + +<|ref|>image<|/ref|><|det|>[[147, 709, 660, 850]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[139, 140, 794, 200]]<|/det|> +## 2. Figure 1d and 1f, Male KO mice also showed similar trends with female mice although it is not statistically significant. Is it because of the larger individual variation? + +<|ref|>text<|/ref|><|det|>[[139, 204, 852, 393]]<|/det|> +We agree that body temperature during cold exposure tended to be lower in Male KO mice than in Male Control mice. However, as the reviewer pointed out, these differences were not statistically significant. Moreover, the effects of PGC- 1α KO on BAT, such as energy expenditure (Figure 1g), gene expression (Figure 3a- c), metabolite profile (Figure 4a- e), lipid profile (Figure 5a- i), and mitochondrial structure (Figure 2a- c) and activity (Figure 2d and Figure 4e), were all observed only in female BAT, which is completely consistent with the fact that cold tolerance was significantly reduced only in female mice (Figure 1d, f). Therefore, the lack of a significant reduction in cold tolerance in male mice may be due to sex differences in BAT function. + +<|ref|>sub_title<|/ref|><|det|>[[140, 418, 758, 435]]<|/det|> +## 3. How to explain the difference of GTT in male and female mice in Fig.s1f + +<|ref|>text<|/ref|><|det|>[[139, 440, 848, 544]]<|/det|> +A previous study (PMID: 22645355) reported that male adipocyte- specific PGC- 1α KO mice were systemic glucose intolerant. Our results are compatible with those of this previous report. Given that male mice have poorer glucose tolerance than female mice, impaired glucose tolerance may be more pronounced in male mice than in female mice, although further studies are required to clarify the mechanisms underlying this sex difference. + +<|ref|>sub_title<|/ref|><|det|>[[140, 568, 835, 606]]<|/det|> +## 4. IN Figure 4A, please justify why they only focused on polar metabolites using CEMS methods. IN the heatmap, how do they normalize the different metabolites? + +<|ref|>text<|/ref|><|det|>[[139, 610, 844, 778]]<|/det|> +We focused only on polar metabolites because most molecules produced when the mitochondrial TCA cycle and electron transport chain are activated during BAT thermogenesis are water- soluble and easily ionized molecules. CE- MS methods were used because they are suitable for analyzing polar metabolites. In the heatmap analysis, we used the following formula for normalization: \(Z = (X - \mu) / \sigma\) (Z: standardized value of each metabolite, X: Relative area of each metabolite, \(\mu\) : mean of each metabolite, \(\sigma\) : SD of each metabolite) + +<|ref|>sub_title<|/ref|><|det|>[[140, 803, 848, 821]]<|/det|> +## 5. In Figure 5e and 5f, why the patterns of CL(18:2) are different in these two figures? + +<|ref|>text<|/ref|><|det|>[[140, 825, 856, 884]]<|/det|> +Figure 5e shows the proportion of each CL molecular species, including CL(18:2)4, relative to the total lipid content in BAT. In contrast, Figure 5f presents the proportion of the CL(18:2)4 molecular species normalized to the total CL content in BAT. The proportions of CL among + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[139, 118, 858, 244]]<|/det|> +all lipids are very small, and those of individual CL species are greatly influenced not only by changes in the absolute amount of individual CL species but also by changes in the absolute amount of total lipids excluding CL. Therefore, to evaluate the changes in CL(18:2)4 within CL, we measured the proportion of CL(18:2)4 among CL as previously reported (PMID: 16855048) and found that CL(18:2)4 was actually reduced only in female knockout mice, as shown in Figure 5f. + +<|ref|>sub_title<|/ref|><|det|>[[140, 269, 722, 286]]<|/det|> +## 6. In line 644, what does "10 uL brown adipose tissue samples" mean? + +<|ref|>text<|/ref|><|det|>[[140, 291, 844, 328]]<|/det|> +We thank the reviewer for this comment. This is a typographical error; the correct notation should be "1 mg brown adipose tissue." We have corrected this error in the text. + +<--- Page Split ---> diff --git a/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/images_list.json b/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..3c89d4f7df2151e71eee5fdb5ee1d48ad76e1c67 --- /dev/null +++ b/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "From Fig. 2. (A-E) Acute nociceptive effects of \\(\\mathsf{PGE}_2\\) in IL6-treated mice. Note the persistence of the effects at the 1-h time point even in mice treated with NAAA inhibitor ARN19702 (please see Fig. 2 for details). #P < 0.05, #P < 0.01, and #P < 0.001 compared to veh/veh (n = 10). See Figure S9 for details.", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..62d0cea82f806a98a5ccb14132f1c5c47d53f1d4 --- /dev/null +++ b/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,283 @@ + +# nature portfolio + +Peer Review File + +NAAA- regulated lipid signaling in monocytes controls the induction of hyperalgesic priming in mice + +![](images/Figure_2.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +N- acylethanolamine- hydrolyzing acid amidase (NAAA) is a lysosomal enzyme abundant in monocytes and macrophages. NAAA hydrolyzes N- acylethanolamines, including palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Over the years, the authors have studied the anti- inflammatory and analgesic actions of N- acylethanolamines in vivo and have developed specific NAAA inhibitors which exhibit anti- inflammatory and analgesic effects. In the present study the authors extended their interests to the involvement of NAAA in hyperalgesic priming. They used specific NAAA inhibitors and plural kinds of NAAA- deficient mice to provide the evidence that NAAA- regulated signaling at PPAR- alpha directs monocytes and macrophages to initiate hyperalgesic priming in mice exposed to an inflammatory stimulus. This is the first report clearly showing that NAAA- regulated signaling is involved in hyperalgesic priming. Thus, the work is of significance to the field and rich in originality. The work sufficiently supports the conclusions. There are no flaws in the data analysis, interpretation and conclusions. The methodology is also sound. I think that the work meets the expected standards in our field. + +I just have some minor comments. + +1. In Fig. 4E, the symbols for significance should be placed near the line of CD11b-/-. + +2. In Fig. 4F1, the asterisks should be explained in the legend. + +3. In Fig. 4G1, the symbols may be asterisks. + +Reviewer #2 (Remarks to the Author): + +This study shows that the induction of hyperalgesic priming by intraplantar IL- 6 to intraplantar PGE2 involves monocytes and macrophages. These immune cells are the source for hydrolase NAAA that acts on two lipids (PEA and OEA) which are agonists for intracellular PPAR- alpha signalling. The interruption of this pathway in monocytes and macrophages by a peripheralized NAAA inhibitor blocks the induction of IL- 6- mediated hyperalgesic priming in male and female mice. + +In addition, HP induction is impaired in global NAAA knockout and following silencing of NAAA in CD11b cells and by clotronate liposome and CSF1 receptor antagonist treatments. + +These data suggest that monocyte/macrophages are critical for the induction of hyperalgesic priming and in such cells lipid signalling regulated by NAAA plays a mechanistic role. + +This is an interesting possibility for a novel neuro- immune interaction- mediated mechanisms in the induction of persistent pain. However, the current behavioural data in transgenic mice should be paired with characterization of monocytes/macrophages in the injected paw before and after intraplantar injections of IL- 6 and PGE2. + +<--- Page Split ---> + +More specifically some of the following points should be addressed: + +1. Do hind paw macrophages express and regulate expression of IL-6 receptor? What levels of NAAA, PEA, OEA and palmitic acid do they contain before, 6 hours and 3 days after IL-6 injections? + +2. What is the level of NAAA, PEA, OEA and PA in macrophages isolated from the hind paw of NAAACD11b-/- and PparaCD11b-/- mice? + +3. Which phenotypes do monocytes and macrophages acquire at 6 h and 3 days after intrapalantar IL-6 and after PGE2? Are they more likely to release pro-nociceptive chemicals? (Figure 6). + +4. How do the authors explain IL-6 and PGE2 pro-nociceptive effects at 1 h after injections in NAAACD11b-/- in figure 3? + +Reviewer #3 (Remarks to the Author): + +In this manuscript, the authors aim to identify molecular mechanism of acute to chronic pain transition. They concluded a critical role of NAAA on monocyte- derived cells and PPAR- a receptors in the event by using a mouse model of hyperalgesic priming. The study is carefully designed, with various experimental approaches. While a large amount of data supported most of their conclusion, I have several major concerns on the limitation of the study. + +- Model of hyperalgesic priming: I greatly appreciate the model provides us an evidence that prior priming nociceptors could lead increased sensitivity to subsequent stimulation. The authors in this study demonstrated potential underlying mechanism mediated by monocyte-derived cells-associated NAAA. However, this is a very restricted model, only limited to inflammatory triggers, with specific agents and specific doses. I am sure not if the agent or the dose changed, whether the 72hour-interval is still valid, not saying if this is valid with a non-inflammatory trigger. It may mislead knowledge users by generalize the findings. + +- Pain behavioral testing methods: Only heat sensitivity was assessed in the study. Whether such priming is also effective in mechanical and cold sensitivity is unknown. Whether NAAA mediates other pain modalities following the priming was not assessed either in the study. + +- Skin macrophages: Two experimental approaches to deplete monocytes used in the study are indeed not ideal. Both are more effective and suitable in depleting macrophages/microglia than monocytes. The authors repeatedly indicated that observed effects are derived from monocytes/macrophages. They + +<--- Page Split ---> + +excluded CNS microglia effect, but they didn't touch anything on skin macrophages, which is essential. If we believe there is a crucial peripheral contribution of NAAA in inflammatory mediator induced priming, detailed changes of macrophages in affected paw are indispensable, as they are direct players. Such data may also help to understand why it works not before or not after 72hr interval. + +- Clinical implications: It is difficult for me to imagine in what clinical setting where the findings from the current study can apply. What does this 72 hr interval, not before or not after, mean for patients who come to see a physician for an acute pain? + +Thus, in general, I recognize the value and the quality of the study in identifying molecular mechanism of hypersensitivity priming in a specific setting, I feel the conclusion, including the title of the study was overstated. Chronic pain is complex, I believe we need to develop precision medicine for each specific type of chronic pain. + +Reviewer #4 (Remarks to the Author): + +The manuscript "NAAA- regulated lipid signaling in monocyte- derived cells controls the induction of hyperalgesic priming", by Fotio et al, provides additional mechanistic information regarding a model of the transition from acute to chronic pain, hyperalgesic priming (HP). This is an interesting study, with the experiments appropriately conducted, clearly exemplifying the involvement of the immune system in the development of persistent nociceptive sensitization. The conclusions certainly add to the characterization of such phenomenon, previously shown to play a role in the persistence of pain observed in some clinical conditions. Although I do not see a reason preventing its publication, I would appreciate if the authors could clarify or include some minor comments in the final version of the manuscript: + +- Experimentally, HP is defined by the potentiation (prolongation) of the mechanical hyperalgesia induced by PGE2 (>4h) in the paw when compared to a non-primed paw (<2h), indicating the hyper-responsive state triggered by the inflammation in the primary neuron. In the current study the authors evaluate the effect of PGE2 on the thermal nociceptive threshold in primed paws. What is the time course of the response produced by PGE2 on the thermal sensitivity in a normal, non-primed paw? Including this information would help the reader to visualize the increased sensitivity of the nociceptor produced by the priming stimulus, for comparison. + +- Induction of HP by carrageenan is, in rats, sexually dimorphic, modulated by estrogen at the level of PKCepsilon. In mice, HP is also sexually dimorphic. However, instead of being an "all or nothing" phenomenon as in rats, this difference in mice seems to be more complex. Can the authors include a comment about these differences in the Discussion? Since the development of HP in mice of both sexes is suggested to occur at the level of NAAA, the upstream differential mechanism could be mentioned (or speculated), specifically considering that NAAA is important only during the incubation phase, when protein translation is happening. + +- Why did the authors use the tail flick method to determine nociceptive thresholds if all the relevant behavior experiments were performed using the Hargreaves plantar test in the paw? + +<--- Page Split ---> + +- Were the compounds injected in the paw intradermally or subcutaneously? + +The information provided by this study contribute to the knowledge about the mechanisms involved in the transition from acute to chronic pain, which is of utmost importance. I look forward to receiving the authors' response and comments added to the revised version of this article. + +<--- Page Split ---> + +## RESPONSE TO REVIEWER COMMENTS + +We are grateful to the Reviewers for their constructive and stimulating comments. We addressed them with several new experiments and substantive text edits, highlighted in red in this resubmission. + +## Reviewer #1 + +N- acylethanolamine- hydrolyzing acid amidase (NAAA) is a lysosomal enzyme abundant in monocytes and macrophages. NAAA hydrolyzes N- acylethanolamines, including palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Over the years, the authors have studied the anti- inflammatory and analgesic actions of N- acylethanolamines in vivo and have developed specific NAAA inhibitors which exhibit anti- inflammatory and analgesic effects. In the present study the authors extended their interests to the involvement of NAAA in hyperalgesic priming. They used specific NAAA inhibitors and plural kinds of NAAA- deficient mice to provide the evidence that NAAA- regulated signaling at PPAR- alpha directs monocytes and macrophages to initiate hyperalgesic priming in mice exposed to an inflammatory stimulus. This is the first report clearly showing that NAAA- regulated signaling is involved in hyperalgesic priming. Thus, the work is of significance to the field and rich in originality. The work sufficiently supports the conclusions. There are no flaws in the data analysis, interpretation and conclusions. The methodology is also sound. I think that the work meets the expected standards in our field. I just have some minor comments. + +We are grateful for this positive evaluation of our work. + +1. In Fig. 4E, the symbols for significance should be placed near the line of CD11b-/-. + +2. In Fig. 4F1, the asterisks should be explained in the legend. + +3. In Fig. 4G1, the symbols may be asterisks. + +Done. + +## Reviewer #2 + +This study shows that the induction of hyperalgesic priming by intraplantar IL- 6 to intraplantar PGE2 involves monocytes and macrophages. These immune cells are the source for hydrolase NAAA that acts on two lipids (PEA and OEA) which are agonists for intracellular PPAR- alpha signalling. The interruption of this pathway in monocytes and macrophages by a peripheralized NAAA inhibitor blocks the induction of IL- 6- mediated hyperalgesic priming in male and female mice. In addition, HP induction is impaired in global NAAA knockout and following silencing of NAAA in CD11b cells and by clodronate liposome and CSF1 receptor antagonist treatments. + +These data suggest that monocyte/macrophages are critical for the induction of hyperalgesic priming and in such cells lipid signalling regulated by NAAA plays a mechanistic role. This is an interesting possibility for a novel neuro- immune interaction- mediated mechanisms in the induction of persistent pain. However, the current behavioural data in transgenic mice should be paired with characterization of monocytes/macrophages in the injected paw before and after + +<--- Page Split ---> + +intraplantar injections of IL- 6 and PGE2. More specifically some of the following points should be addressed: 1. Do hind paw macrophages express and regulate expression of IL- 6 receptor? What levels of NAAA, PEA, OEA and palmitic acid do they contain before, 6 hours and 3 days after IL- 6 injections? 2. What is the level of NAAA, PEA, OEA and PA in macrophages isolated from the hind paw of NAAACD11b-/- and PparaCD11b-/- mice? + +We thank the Reviewer for this important comment, which was echoed by a similar one made by Reviewer 3. Prompted by these suggestions, we conducted a new experiment to assess whether resident macrophages contribute to the initiation of hyperalgesic priming. We removed macrophages from the hind paws of mice with two intraplantar injections of clodronate liposomes (PBS liposomes were injected as control) and examined the effects of IL- 6 administration in the same paws. The results, which are reported in new Figure S9, show that clodronate treatment substantially reduced the number of \(\mathrm{CD68^{+}}\) macrophages in paw tissue (Fig. S9B) but did not prevent IL- 6- induced hyperalgesic priming (new Fig. S9E). + +![PLACEHOLDER_6_0] + + +From Fig. S9. (B) Effect of PBS- containing liposomes (left) and clodronate- containing liposomes (right) on \(\mathrm{CD68 + }\) cells (resident macrophages) in mouse paw skin. (C) Effect of PBS- or clodronate- containing liposomes on the induction of hyperalgesic priming (response to PGE2 six days after IL- 6). See Figure S9 for additional details. + +By contrast, clodronate delayed the acute response to IL- 6, suggesting that local macrophages contribute in part to such response. + +![PLACEHOLDER_6_1] + + +From Fig. S9. (E) Effect of PBS- or clodronate- containing liposomes on the acute nociceptive response to IL- 6. # \(P < 0.05\) compared to PBS ( \(n = 8\) ). See Figure S9 for details. + +Along with the data shown in Figure 5 (effects of systemic clodronate and PLX- 5622) these findings indicate that blood- borne monocytes, rather than resident macrophages, are required for priming initiation. We modified our hypothetical model (and the title of the study) to reflect these new results (please see new Fig. 7). + +<--- Page Split ---> + +Which phenotypes do monocytes and macrophages acquire at 6 h and 3 days after intraplantar IL- 6 and after PGE2? Are they more likely to release pro- nociceptive chemicals? (Figure 6). + +Based on our results showing that monocytes, not resident macrophages, are involved in priming, we addressed this question by examining the molecular phenotype of circulating immune cells by high- resolution mass cytometry by time of flight (CyTOF). Mice received intraplantar IL- 6 injections and, 72 hours later (i.e., at the tail end of the incubation phase of priming), cardiac blood was collected for CyTOF analyses. The results, which are illustrated in new Figure 6, indicate that the incubation phase of hyperalgesic priming coincides with the emergence of one or more subpopulation(s) of activated circulating monocytes. For example: + +![PLACEHOLDER_7_0] + + +From Fig. 6. (B) Optimized Stochastic Neighbor Embedding (opt- SNE) plots depicting density heatmaps of cells expressing the markers of monocyte activation CCR2 (top), CD43 (middle), and CX3CR1 (bottom) in vehicle- (left) and IL- 6- treated (right) mice. See new Figure 6 for details. + +4. How do the authors explain IL-6 and PGE2 pro-nociceptive effects at 1 h after injections in NAAACD11b-/- in figure 3? + +As pointed out by the Reviewer, Figure 3E shows that, one h after injection, PGE2 exerts a nociceptive effect in both control Naaa f/l and Naaa CD11b-/- mice: + +![PLACEHOLDER_7_1] + + +From Fig. 3. (E) Acute nociceptive effects of PGE2 in Naaa CD11b-/- mice (green symbols) and control Naaa f/l mice (magenta symbols) #P < 0.001 (n = 8). See Figure 3 for details. + +<--- Page Split ---> + +This effect is expected because the 1h time point measures the acute nociceptive response to \(\mathsf{PGE}_2\) , which is generally not affected by pharmacological or genetic interventions targeting NAAA. See, for example: + +![PLACEHOLDER_8_0] + +
From Fig. 2. (A-E) Acute nociceptive effects of \(\mathsf{PGE}_2\) in IL6-treated mice. Note the persistence of the effects at the 1-h time point even in mice treated with NAAA inhibitor ARN19702 (please see Fig. 2 for details). #P < 0.05, #P < 0.01, and #P < 0.001 compared to veh/veh (n = 10). See Figure S9 for details.
+ +One exception is represented by global Naaa ko mice, which exhibited a weaker response to \(\mathsf{PGE}_2\) at the 1- h time point (Fig. 3). This could be due to NAAA deletion in as- yet- unidentified cells that are not readily accessible to the NAAA inhibitors used in our study. + +## Reviewer #3 + +In this manuscript, the authors aim to identify molecular mechanism of acute to chronic pain transition. They concluded a critical role of NAAA on monocyte- derived cells and PPAR- a receptors in the event by using a mouse model of hyperalgesic priming. The study is carefully designed, with various experimental approaches. While a large amount of data supported most of their conclusion, I have several major concerns on the limitation of the study. + +Model of hyperalgesic priming: I greatly appreciate the model provides us an evidence that prior priming nociceptors could lead increased sensitivity to subsequent stimulation. The authors in this study demonstrated potential underlying mechanism mediated by monocyte- derived cells- associated NAAA. However, this is a very restricted model, only limited to inflammatory triggers, with specific agents and specific doses. I am sure not if the agent or the dose changed, whether the 72hour- interval is still valid, not saying if this is valid with a non- inflammatory trigger. It may mislead knowledge users by generalize the findings. + +Hyperalgesic priming can be induced by a variety of stimuli, including proinflammatory cytokines (e.g., IL- 6, TNF- \(\alpha\) ), growth factors (e.g., NGF, CSF- 1), inflammatory triggers (e.g., carrageenan), and tissue damage (e.g., surgical paw incision). Its clinical relevance has been convincingly argued by various investigators (Levine, Price, etc.) who pointed out that "... the experimental framework of the hyperalgesic priming model provides important insight into clinical chronic pain because it captures the recurrent nature of some of the most common pathological pain conditions." (Kandasamy R, Price TJ. The pharmacology of nociceptor priming. Handb Exp Pharmacol. 2015; 227:15- 37. PMID: 25846612) Our previous submission described the results of experiments with three distinct proinflammatory stimuli – IL- 6, TNF- \(\alpha\) , and carrageenan. Nevertheless, to address the spirit of the Reviewer's concern, we have included new data using a fourth stimulus, paw incision, which has a strong nociceptive component. The results, reported in new Figure S7, show + +<--- Page Split ---> + +that administration of a NAAA inhibitor in the first 72h after the incision fully prevents priming initiation, lending further support to the general validity of our findings. + +Pain behavioral testing methods: Only heat sensitivity was assessed in the study. Whether such priming is also effective in mechanical and cold sensitivity is unknown. Whether NAAA mediates other pain modalities following the priming was not assessed either in the study. + +We assessed both heat and mechanical hypersensitivity, with similar results. Representative sets of mechanical hypersensitivity data are included in new Figure S2 and S4. + +Skin macrophages: Two experimental approaches to deplete monocytes used in the study are indeed not ideal. Both are more effective and suitable in depleting macrophages/microglia than monocytes. + +We direct the Reviewer's attention to the results reported in Figure 5, which show that both approaches (clodronate and PLX- 5622) substantially reduced monocyte numbers in the bloodstream. + +The authors repeatedly indicated that observed effects are derived from monocytes/macrophages. They excluded CNS microglia effect, but they didn't touch anything on skin macrophages, which is essential. If we believe there is a crucial peripheral contribution of NAAA in inflammatory mediator induced priming, detailed changes of macrophages in affected paw are indispensable, as they are direct players. Such data may also help to understand why it works not before or not after 72hr interval. + +We thank the Reviewer for this suggestion, which we have addressed with the new experiment described in our response to Reviewer 2. Please see above. + +Clinical implications: It is difficult for me to imagine in what clinical setting where the findings from the current study can apply. What does this 72 hr interval, not before or not after, mean for patients who come to see a physician for an acute pain? + +This basic science study is not meant to have immediate repercussions on clinical practice. It does have, however, potential clinical significance in that it suggests that postsurgical NAAA inhibition (but not postsurgical treatment with standard analgesics) may prevent the transition to pain chronicity, a significant problem for patients who undergo thoracotomy, knee arthroplasty, mastectomy, and other invasive surgeries. + +Thus, in general, I recognize the value and the quality of the study in identifying molecular mechanism of hypersensitivity priming in a specific setting, I feel the conclusion, including the title of the study was overstated. Chronic pain is complex, I believe we need to develop precision medicine for each specific type of chronic pain. + +Our views about the complexity of chronic pain are very similar to the Reviewer's, as affirmed in the Discussion section of the manuscript: + +"Chronic pain states are widely heterogeneous in causes, symptoms, impact on function, and temporal development3. This diversity justifies skepticism toward a simplistic view of the progression to pain chronicity as transformation of one mechanistic type of pain (e.g., acute pain associated with injury) into another (e.g., neuropathic pain)99." + +<--- Page Split ---> + +Thus, we are surprised by the Reviewer's statement that "the conclusion, including the title of the study was overstated." The title of our manuscript (NAAA- regulated lipid signaling in monocytes controls the induction of hyperalgesic priming) accurately reflects the findings presented. Our conclusion is equally cautious and, we believe, fully warranted by the data: "Clinical studies should determine whether algostatic agents might offer a strategy to prevent chronic pain after invasive surgery and other kinds of physical trauma." However, when interpretation could have been ambiguous, we replaced 'chronic pain' with 'persistent pathological nociception' (see, for example, Abstract, line 38). + +## Reviewer #4 + +The manuscript "NAAA- regulated lipid signaling in monocyte- derived cells controls the induction of hyperalgesic priming", by Fotio et al, provides additional mechanical information regarding a model of the transition from acute to chronic pain, hyperalgesic priming (HP). This is an interesting study, with the experiments appropriately conducted, clearly exemplifying the involvement of the immune system in the development of persistent nociceptive sensitization. The conclusions certainly add to the characterization of such phenomenon, previously shown to play a role in the persistence of pain observed in some clinical conditions. + +We appreciate the positive comments. + +Although I do not see a reason preventing its publication, I would appreciate if the authors could clarify or include some minor comments in the final version of the manuscript: + +Experimentally, HP is defined by the potentiation (prolongation) of the mechanical hyperalgesia induced by PGE2 (>4h) in the paw when compared to a non- primed paw (<2h), indicating the hyper- responsive state triggered by the inflammation in the primary neuron. In the current study the authors evaluate the effect of PGE2 on the thermal nociceptive threshold in primed paws. What is the time course of the response produced by PGE2 on the thermal sensitivity in a normal, non- primed paw? Including this information would help the reader to visualize the increased sensitivity of the nociceptor produced by the priming stimulus, for comparison. + +We have added a new supplemental figure (Fig. S2) that contains the requested information. + +Induction of HP by carrageenan is, in rats, sexually dimorphic, modulated by estrogen at the level of PKCepsilon. In mice, HP is also sexually dimorphic. However, instead of being an "all or nothing" phenomenon as in rats, this difference in mice seems to be more complex. Can the authors include a comment about these differences in the Discussion? Since the development of HP in mice of both sexes is suggested to occur at the level of NAAA, the upstream differential mechanism could be mentioned (or speculated), specifically considering that NAAA is important only during the incubation phase, when protein translation is happening. + +We do not know how inflammatory challenges trigger NAAA activation and whether this process might be sexually dimorphic. But we appreciate the point raised by the Reviewer and addressed its spirit by adding the following comment to the Discussion section of the manuscript (p. 17): + +"In this context, an important question that remains to be answered pertains to the mechanisms through which inflammatory stimuli lead to the suppression of NAPE- PLD + +<--- Page Split ---> + +transcription and the enhancement of NAAA activity. Elucidating such mechanisms might shed light on aspects of HP – such as the existence of sexual dimorphisms in rats88- 90 and mice91 – which are presently unclear." + +Why did the authors use the tail flick method to determine nociceptive thresholds if all the relevant behavior experiments were performed using the Hargreaves plantar test in the paw? + +We routinely use the tail- flick method to identify potential alterations in baseline nociceptive threshold in newly developed mouse lines such as those introduced in the present study. Here, we combined tail- flick (Fig. S9) and Hargreaves plantar tests (Fig. 3D and Fig. 4G1) to obtain a more complete view of the lines' nociceptive phenotype. + +Were the compounds injected in the paw intradermally or subcutaneously? + +Compounds were injected subcutaneously, between skin and muscular fascia/tendon, as customary in this model. We clarified this point in the Materials and Methods section of the manuscript. + +The information provided by this study contribute to the knowledge about the mechanisms involved in the transition from acute to chronic pain, which is of utmost importance. I look forward to receiving the authors' response and comments added to the revised version of this article. + +Thank you. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors appropriately revised the manuscript in response to my comments. + +Reviewer #2 (Remarks to the Author): + +My points have been partially addressed. + +Specifically, whilst I suggested to characterise monocytes/macrophages at the site of IL- 6 injection (hind paw) the authors have looked at blood monocytes. They provide evidence that intraplantar injection of IL- 6 is associated with more CCR2+ monocytes circulating in blood. However, classical monocytes will have to infiltrate tissue to come in the vicinity of primary afferent terminals and promote nociceptive signalling. + +Whether CCR2+ monocytes infiltrate the site of injection remains to be established and Figure 7 schematic should indicate that this study does not provide direct evidence that "monocytes migrate to target tissue". + +New Figure 6: How do the authors explain presence of F4/80 positive cells (macrophages) in blood? + +Discussion: It is possible that CCL2 is upregulated in endothelial cells, and sensory neurons and accumulates in primary afferent terminals. However, the authors provide no direct evidence that this happens in their experimental conditions. + +Other points. Ref 12 line 57: This is an early observation and more recent evidence indicates no infiltration of monocytes in the spinal cord following peripheral nerve injury. The authors could rephrase their statement. + +Line 167: replace "deleted" with "depleted". + +Reviewer #3 (Remarks to the Author): + +The authors addressed the reviewer's concerns. I don't have further comments. + +Reviewer #4 (Remarks to the Author): + +I am satisfied with the revision provided by the authors. I recommend this study for publication. + +<--- Page Split ---> + +Specifically, whilst I suggested to characterise monocytes/macrophages at the site of IL- 6 injection (hind paw) the authors have looked at blood monocytes. They provide evidence that intraplantar injection of IL- 6 is associated with more CCR2+ monocytes circulating in blood. However, classical monocytes will have to infiltrate tissue to come in the vicinity of primary afferent terminals and promote nociceptive signalling. Whether CCR2+ monocytes infiltrate the site of injection remains to be established and Figure 7 schematic should indicate that this study does not provide direct evidence that "monocytes migrate to target tissue". + +We clarified that Figure 7 provides a hypothetical model which summarizes the data presented in our study and suggests a roadmap for future experiments. Please see Figure 7 legend. + +New Figure 6: How do the authors explain presence of F4/80 positive cells (macrophages) in blood? + +Though unlikely, it is possible that the antibody we used cross- reacted with a different monocyte antigen. Owing to this uncertainty, we removed F4/80 data from Figure 6C. + +Discussion: It is possible that CCL2 is upregulated in endothelial cells, and sensory neurons and accumulates in primary afferent terminals. However, the authors provide no direct evidence that this happens in their experimental conditions. + +There is substantial evidence that peripheral nerve injury upregulates CCL2 in DRG neurons, but future experiments will have to address this question as it pertains to the model used here. + +Other points. Ref 12 line 57: This is an early observation and more recent evidence indicates no infiltration of monocytes in the spinal cord following peripheral nerve injury. The authors could rephrase their statement. + +Evidence indicates that spinal nerve resection does not stimulate monocytes migration toward the spinal cord (PMID 27373153, presumably the study the reviewer had in mind). The hyperalgesic priming model we used, however, is quite different and, possibly, mechanistically closer to the one used in Ref 12 (partial sciatic nerve ligation). Indeed, both hyperalgesic priming and sciatic nerve ligation exhibit a rather strong inflammatory component that is not observed after spinal nerve resection. + +Line 167: replace "deleted" with "depleted". + +Done. + +<--- Page Split ---> diff --git a/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..103e6d194ddd1d4e7e08cd8650109a679b2a58e1 --- /dev/null +++ b/peer_reviews/123bd0ee09c9429721618645aa9aeb915f306f1aae5c4eccbeaf12f98f492aec/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,382 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 852, 212]]<|/det|> +NAAA- regulated lipid signaling in monocytes controls the induction of hyperalgesic priming in mice + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 147, 392, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 175, 884, 394]]<|/det|> +N- acylethanolamine- hydrolyzing acid amidase (NAAA) is a lysosomal enzyme abundant in monocytes and macrophages. NAAA hydrolyzes N- acylethanolamines, including palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Over the years, the authors have studied the anti- inflammatory and analgesic actions of N- acylethanolamines in vivo and have developed specific NAAA inhibitors which exhibit anti- inflammatory and analgesic effects. In the present study the authors extended their interests to the involvement of NAAA in hyperalgesic priming. They used specific NAAA inhibitors and plural kinds of NAAA- deficient mice to provide the evidence that NAAA- regulated signaling at PPAR- alpha directs monocytes and macrophages to initiate hyperalgesic priming in mice exposed to an inflammatory stimulus. This is the first report clearly showing that NAAA- regulated signaling is involved in hyperalgesic priming. Thus, the work is of significance to the field and rich in originality. The work sufficiently supports the conclusions. There are no flaws in the data analysis, interpretation and conclusions. The methodology is also sound. I think that the work meets the expected standards in our field. + +<|ref|>text<|/ref|><|det|>[[116, 405, 367, 421]]<|/det|> +I just have some minor comments. + +<|ref|>text<|/ref|><|det|>[[114, 460, 728, 479]]<|/det|> +1. In Fig. 4E, the symbols for significance should be placed near the line of CD11b-/-. + +<|ref|>text<|/ref|><|det|>[[114, 490, 562, 506]]<|/det|> +2. In Fig. 4F1, the asterisks should be explained in the legend. + +<|ref|>text<|/ref|><|det|>[[115, 518, 437, 534]]<|/det|> +3. In Fig. 4G1, the symbols may be asterisks. + +<|ref|>text<|/ref|><|det|>[[116, 574, 392, 590]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 602, 872, 694]]<|/det|> +This study shows that the induction of hyperalgesic priming by intraplantar IL- 6 to intraplantar PGE2 involves monocytes and macrophages. These immune cells are the source for hydrolase NAAA that acts on two lipids (PEA and OEA) which are agonists for intracellular PPAR- alpha signalling. The interruption of this pathway in monocytes and macrophages by a peripheralized NAAA inhibitor blocks the induction of IL- 6- mediated hyperalgesic priming in male and female mice. + +<|ref|>text<|/ref|><|det|>[[114, 704, 872, 740]]<|/det|> +In addition, HP induction is impaired in global NAAA knockout and following silencing of NAAA in CD11b cells and by clotronate liposome and CSF1 receptor antagonist treatments. + +<|ref|>text<|/ref|><|det|>[[114, 779, 856, 815]]<|/det|> +These data suggest that monocyte/macrophages are critical for the induction of hyperalgesic priming and in such cells lipid signalling regulated by NAAA plays a mechanistic role. + +<|ref|>text<|/ref|><|det|>[[114, 825, 870, 898]]<|/det|> +This is an interesting possibility for a novel neuro- immune interaction- mediated mechanisms in the induction of persistent pain. However, the current behavioural data in transgenic mice should be paired with characterization of monocytes/macrophages in the injected paw before and after intraplantar injections of IL- 6 and PGE2. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 611, 135]]<|/det|> +More specifically some of the following points should be addressed: + +<|ref|>text<|/ref|><|det|>[[115, 174, 852, 211]]<|/det|> +1. Do hind paw macrophages express and regulate expression of IL-6 receptor? What levels of NAAA, PEA, OEA and palmitic acid do they contain before, 6 hours and 3 days after IL-6 injections? + +<|ref|>text<|/ref|><|det|>[[115, 250, 789, 286]]<|/det|> +2. What is the level of NAAA, PEA, OEA and PA in macrophages isolated from the hind paw of NAAACD11b-/- and PparaCD11b-/- mice? + +<|ref|>text<|/ref|><|det|>[[115, 324, 864, 361]]<|/det|> +3. Which phenotypes do monocytes and macrophages acquire at 6 h and 3 days after intrapalantar IL-6 and after PGE2? Are they more likely to release pro-nociceptive chemicals? (Figure 6). + +<|ref|>text<|/ref|><|det|>[[115, 399, 789, 435]]<|/det|> +4. How do the authors explain IL-6 and PGE2 pro-nociceptive effects at 1 h after injections in NAAACD11b-/- in figure 3? + +<|ref|>text<|/ref|><|det|>[[116, 474, 392, 491]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 503, 876, 594]]<|/det|> +In this manuscript, the authors aim to identify molecular mechanism of acute to chronic pain transition. They concluded a critical role of NAAA on monocyte- derived cells and PPAR- a receptors in the event by using a mouse model of hyperalgesic priming. The study is carefully designed, with various experimental approaches. While a large amount of data supported most of their conclusion, I have several major concerns on the limitation of the study. + +<|ref|>text<|/ref|><|det|>[[115, 632, 877, 761]]<|/det|> +- Model of hyperalgesic priming: I greatly appreciate the model provides us an evidence that prior priming nociceptors could lead increased sensitivity to subsequent stimulation. The authors in this study demonstrated potential underlying mechanism mediated by monocyte-derived cells-associated NAAA. However, this is a very restricted model, only limited to inflammatory triggers, with specific agents and specific doses. I am sure not if the agent or the dose changed, whether the 72hour-interval is still valid, not saying if this is valid with a non-inflammatory trigger. It may mislead knowledge users by generalize the findings. + +<|ref|>text<|/ref|><|det|>[[115, 771, 875, 825]]<|/det|> +- Pain behavioral testing methods: Only heat sensitivity was assessed in the study. Whether such priming is also effective in mechanical and cold sensitivity is unknown. Whether NAAA mediates other pain modalities following the priming was not assessed either in the study. + +<|ref|>text<|/ref|><|det|>[[115, 836, 879, 890]]<|/det|> +- Skin macrophages: Two experimental approaches to deplete monocytes used in the study are indeed not ideal. Both are more effective and suitable in depleting macrophages/microglia than monocytes. The authors repeatedly indicated that observed effects are derived from monocytes/macrophages. They + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 880, 162]]<|/det|> +excluded CNS microglia effect, but they didn't touch anything on skin macrophages, which is essential. If we believe there is a crucial peripheral contribution of NAAA in inflammatory mediator induced priming, detailed changes of macrophages in affected paw are indispensable, as they are direct players. Such data may also help to understand why it works not before or not after 72hr interval. + +<|ref|>text<|/ref|><|det|>[[115, 173, 872, 227]]<|/det|> +- Clinical implications: It is difficult for me to imagine in what clinical setting where the findings from the current study can apply. What does this 72 hr interval, not before or not after, mean for patients who come to see a physician for an acute pain? + +<|ref|>text<|/ref|><|det|>[[115, 266, 881, 338]]<|/det|> +Thus, in general, I recognize the value and the quality of the study in identifying molecular mechanism of hypersensitivity priming in a specific setting, I feel the conclusion, including the title of the study was overstated. Chronic pain is complex, I believe we need to develop precision medicine for each specific type of chronic pain. + +<|ref|>text<|/ref|><|det|>[[117, 378, 392, 394]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 406, 881, 570]]<|/det|> +The manuscript "NAAA- regulated lipid signaling in monocyte- derived cells controls the induction of hyperalgesic priming", by Fotio et al, provides additional mechanistic information regarding a model of the transition from acute to chronic pain, hyperalgesic priming (HP). This is an interesting study, with the experiments appropriately conducted, clearly exemplifying the involvement of the immune system in the development of persistent nociceptive sensitization. The conclusions certainly add to the characterization of such phenomenon, previously shown to play a role in the persistence of pain observed in some clinical conditions. Although I do not see a reason preventing its publication, I would appreciate if the authors could clarify or include some minor comments in the final version of the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 581, 868, 709]]<|/det|> +- Experimentally, HP is defined by the potentiation (prolongation) of the mechanical hyperalgesia induced by PGE2 (>4h) in the paw when compared to a non-primed paw (<2h), indicating the hyper-responsive state triggered by the inflammation in the primary neuron. In the current study the authors evaluate the effect of PGE2 on the thermal nociceptive threshold in primed paws. What is the time course of the response produced by PGE2 on the thermal sensitivity in a normal, non-primed paw? Including this information would help the reader to visualize the increased sensitivity of the nociceptor produced by the priming stimulus, for comparison. + +<|ref|>text<|/ref|><|det|>[[114, 719, 876, 846]]<|/det|> +- Induction of HP by carrageenan is, in rats, sexually dimorphic, modulated by estrogen at the level of PKCepsilon. In mice, HP is also sexually dimorphic. However, instead of being an "all or nothing" phenomenon as in rats, this difference in mice seems to be more complex. Can the authors include a comment about these differences in the Discussion? Since the development of HP in mice of both sexes is suggested to occur at the level of NAAA, the upstream differential mechanism could be mentioned (or speculated), specifically considering that NAAA is important only during the incubation phase, when protein translation is happening. + +<|ref|>text<|/ref|><|det|>[[113, 857, 852, 893]]<|/det|> +- Why did the authors use the tail flick method to determine nociceptive thresholds if all the relevant behavior experiments were performed using the Hargreaves plantar test in the paw? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 676, 107]]<|/det|> +- Were the compounds injected in the paw intradermally or subcutaneously? + +<|ref|>text<|/ref|><|det|>[[115, 118, 872, 172]]<|/det|> +The information provided by this study contribute to the knowledge about the mechanisms involved in the transition from acute to chronic pain, which is of utmost importance. I look forward to receiving the authors' response and comments added to the revised version of this article. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[327, 89, 670, 107]]<|/det|> +## RESPONSE TO REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 121, 882, 170]]<|/det|> +We are grateful to the Reviewers for their constructive and stimulating comments. We addressed them with several new experiments and substantive text edits, highlighted in red in this resubmission. + +<|ref|>sub_title<|/ref|><|det|>[[115, 209, 219, 225]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[115, 240, 882, 466]]<|/det|> +N- acylethanolamine- hydrolyzing acid amidase (NAAA) is a lysosomal enzyme abundant in monocytes and macrophages. NAAA hydrolyzes N- acylethanolamines, including palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Over the years, the authors have studied the anti- inflammatory and analgesic actions of N- acylethanolamines in vivo and have developed specific NAAA inhibitors which exhibit anti- inflammatory and analgesic effects. In the present study the authors extended their interests to the involvement of NAAA in hyperalgesic priming. They used specific NAAA inhibitors and plural kinds of NAAA- deficient mice to provide the evidence that NAAA- regulated signaling at PPAR- alpha directs monocytes and macrophages to initiate hyperalgesic priming in mice exposed to an inflammatory stimulus. This is the first report clearly showing that NAAA- regulated signaling is involved in hyperalgesic priming. Thus, the work is of significance to the field and rich in originality. The work sufficiently supports the conclusions. There are no flaws in the data analysis, interpretation and conclusions. The methodology is also sound. I think that the work meets the expected standards in our field. I just have some minor comments. + +<|ref|>text<|/ref|><|det|>[[173, 480, 608, 497]]<|/det|> +We are grateful for this positive evaluation of our work. + +<|ref|>text<|/ref|><|det|>[[115, 511, 792, 529]]<|/det|> +1. In Fig. 4E, the symbols for significance should be placed near the line of CD11b-/-. + +<|ref|>text<|/ref|><|det|>[[115, 544, 610, 561]]<|/det|> +2. In Fig. 4F1, the asterisks should be explained in the legend. + +<|ref|>text<|/ref|><|det|>[[115, 576, 476, 593]]<|/det|> +3. In Fig. 4G1, the symbols may be asterisks. + +<|ref|>text<|/ref|><|det|>[[174, 608, 222, 624]]<|/det|> +Done. + +<|ref|>sub_title<|/ref|><|det|>[[115, 656, 221, 673]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[116, 688, 882, 800]]<|/det|> +This study shows that the induction of hyperalgesic priming by intraplantar IL- 6 to intraplantar PGE2 involves monocytes and macrophages. These immune cells are the source for hydrolase NAAA that acts on two lipids (PEA and OEA) which are agonists for intracellular PPAR- alpha signalling. The interruption of this pathway in monocytes and macrophages by a peripheralized NAAA inhibitor blocks the induction of IL- 6- mediated hyperalgesic priming in male and female mice. In addition, HP induction is impaired in global NAAA knockout and following silencing of NAAA in CD11b cells and by clodronate liposome and CSF1 receptor antagonist treatments. + +<|ref|>text<|/ref|><|det|>[[116, 815, 882, 896]]<|/det|> +These data suggest that monocyte/macrophages are critical for the induction of hyperalgesic priming and in such cells lipid signalling regulated by NAAA plays a mechanistic role. This is an interesting possibility for a novel neuro- immune interaction- mediated mechanisms in the induction of persistent pain. However, the current behavioural data in transgenic mice should be paired with characterization of monocytes/macrophages in the injected paw before and after + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 170]]<|/det|> +intraplantar injections of IL- 6 and PGE2. More specifically some of the following points should be addressed: 1. Do hind paw macrophages express and regulate expression of IL- 6 receptor? What levels of NAAA, PEA, OEA and palmitic acid do they contain before, 6 hours and 3 days after IL- 6 injections? 2. What is the level of NAAA, PEA, OEA and PA in macrophages isolated from the hind paw of NAAACD11b-/- and PparaCD11b-/- mice? + +<|ref|>text<|/ref|><|det|>[[165, 200, 883, 345]]<|/det|> +We thank the Reviewer for this important comment, which was echoed by a similar one made by Reviewer 3. Prompted by these suggestions, we conducted a new experiment to assess whether resident macrophages contribute to the initiation of hyperalgesic priming. We removed macrophages from the hind paws of mice with two intraplantar injections of clodronate liposomes (PBS liposomes were injected as control) and examined the effects of IL- 6 administration in the same paws. The results, which are reported in new Figure S9, show that clodronate treatment substantially reduced the number of \(\mathrm{CD68^{+}}\) macrophages in paw tissue (Fig. S9B) but did not prevent IL- 6- induced hyperalgesic priming (new Fig. S9E). + +<|ref|>image<|/ref|><|det|>[[333, 350, 723, 500]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[180, 510, 870, 567]]<|/det|> +From Fig. S9. (B) Effect of PBS- containing liposomes (left) and clodronate- containing liposomes (right) on \(\mathrm{CD68 + }\) cells (resident macrophages) in mouse paw skin. (C) Effect of PBS- or clodronate- containing liposomes on the induction of hyperalgesic priming (response to PGE2 six days after IL- 6). See Figure S9 for additional details. + +<|ref|>text<|/ref|><|det|>[[166, 589, 881, 623]]<|/det|> +By contrast, clodronate delayed the acute response to IL- 6, suggesting that local macrophages contribute in part to such response. + +<|ref|>image<|/ref|><|det|>[[413, 640, 627, 772]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[180, 782, 866, 812]]<|/det|> +From Fig. S9. (E) Effect of PBS- or clodronate- containing liposomes on the acute nociceptive response to IL- 6. # \(P < 0.05\) compared to PBS ( \(n = 8\) ). See Figure S9 for details. + +<|ref|>text<|/ref|><|det|>[[166, 835, 882, 901]]<|/det|> +Along with the data shown in Figure 5 (effects of systemic clodronate and PLX- 5622) these findings indicate that blood- borne monocytes, rather than resident macrophages, are required for priming initiation. We modified our hypothetical model (and the title of the study) to reflect these new results (please see new Fig. 7). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 883, 139]]<|/det|> +Which phenotypes do monocytes and macrophages acquire at 6 h and 3 days after intraplantar IL- 6 and after PGE2? Are they more likely to release pro- nociceptive chemicals? (Figure 6). + +<|ref|>text<|/ref|><|det|>[[165, 153, 883, 281]]<|/det|> +Based on our results showing that monocytes, not resident macrophages, are involved in priming, we addressed this question by examining the molecular phenotype of circulating immune cells by high- resolution mass cytometry by time of flight (CyTOF). Mice received intraplantar IL- 6 injections and, 72 hours later (i.e., at the tail end of the incubation phase of priming), cardiac blood was collected for CyTOF analyses. The results, which are illustrated in new Figure 6, indicate that the incubation phase of hyperalgesic priming coincides with the emergence of one or more subpopulation(s) of activated circulating monocytes. For example: + +<|ref|>image<|/ref|><|det|>[[384, 297, 603, 550]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[212, 574, 901, 617]]<|/det|> +From Fig. 6. (B) Optimized Stochastic Neighbor Embedding (opt- SNE) plots depicting density heatmaps of cells expressing the markers of monocyte activation CCR2 (top), CD43 (middle), and CX3CR1 (bottom) in vehicle- (left) and IL- 6- treated (right) mice. See new Figure 6 for details. + +<|ref|>text<|/ref|><|det|>[[115, 658, 884, 691]]<|/det|> +4. How do the authors explain IL-6 and PGE2 pro-nociceptive effects at 1 h after injections in NAAACD11b-/- in figure 3? + +<|ref|>text<|/ref|><|det|>[[163, 705, 883, 737]]<|/det|> +As pointed out by the Reviewer, Figure 3E shows that, one h after injection, PGE2 exerts a nociceptive effect in both control Naaa f/l and Naaa CD11b-/- mice: + +<|ref|>image<|/ref|><|det|>[[425, 752, 549, 870]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[127, 872, 870, 901]]<|/det|> +From Fig. 3. (E) Acute nociceptive effects of PGE2 in Naaa CD11b-/- mice (green symbols) and control Naaa f/l mice (magenta symbols) #P < 0.001 (n = 8). See Figure 3 for details. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[165, 105, 882, 155]]<|/det|> +This effect is expected because the 1h time point measures the acute nociceptive response to \(\mathsf{PGE}_2\) , which is generally not affected by pharmacological or genetic interventions targeting NAAA. See, for example: + +<|ref|>image<|/ref|><|det|>[[123, 171, 880, 305]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[125, 314, 864, 358]]<|/det|> +
From Fig. 2. (A-E) Acute nociceptive effects of \(\mathsf{PGE}_2\) in IL6-treated mice. Note the persistence of the effects at the 1-h time point even in mice treated with NAAA inhibitor ARN19702 (please see Fig. 2 for details). #P < 0.05, #P < 0.01, and #P < 0.001 compared to veh/veh (n = 10). See Figure S9 for details.
+ +<|ref|>text<|/ref|><|det|>[[165, 379, 882, 428]]<|/det|> +One exception is represented by global Naaa ko mice, which exhibited a weaker response to \(\mathsf{PGE}_2\) at the 1- h time point (Fig. 3). This could be due to NAAA deletion in as- yet- unidentified cells that are not readily accessible to the NAAA inhibitors used in our study. + +<|ref|>sub_title<|/ref|><|det|>[[116, 443, 221, 460]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[115, 474, 882, 556]]<|/det|> +In this manuscript, the authors aim to identify molecular mechanism of acute to chronic pain transition. They concluded a critical role of NAAA on monocyte- derived cells and PPAR- a receptors in the event by using a mouse model of hyperalgesic priming. The study is carefully designed, with various experimental approaches. While a large amount of data supported most of their conclusion, I have several major concerns on the limitation of the study. + +<|ref|>text<|/ref|><|det|>[[115, 570, 882, 684]]<|/det|> +Model of hyperalgesic priming: I greatly appreciate the model provides us an evidence that prior priming nociceptors could lead increased sensitivity to subsequent stimulation. The authors in this study demonstrated potential underlying mechanism mediated by monocyte- derived cells- associated NAAA. However, this is a very restricted model, only limited to inflammatory triggers, with specific agents and specific doses. I am sure not if the agent or the dose changed, whether the 72hour- interval is still valid, not saying if this is valid with a non- inflammatory trigger. It may mislead knowledge users by generalize the findings. + +<|ref|>text<|/ref|><|det|>[[157, 698, 882, 884]]<|/det|> +Hyperalgesic priming can be induced by a variety of stimuli, including proinflammatory cytokines (e.g., IL- 6, TNF- \(\alpha\) ), growth factors (e.g., NGF, CSF- 1), inflammatory triggers (e.g., carrageenan), and tissue damage (e.g., surgical paw incision). Its clinical relevance has been convincingly argued by various investigators (Levine, Price, etc.) who pointed out that "... the experimental framework of the hyperalgesic priming model provides important insight into clinical chronic pain because it captures the recurrent nature of some of the most common pathological pain conditions." (Kandasamy R, Price TJ. The pharmacology of nociceptor priming. Handb Exp Pharmacol. 2015; 227:15- 37. PMID: 25846612) Our previous submission described the results of experiments with three distinct proinflammatory stimuli – IL- 6, TNF- \(\alpha\) , and carrageenan. Nevertheless, to address the spirit of the Reviewer's concern, we have included new data using a fourth stimulus, paw incision, which has a strong nociceptive component. The results, reported in new Figure S7, show + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[156, 88, 882, 123]]<|/det|> +that administration of a NAAA inhibitor in the first 72h after the incision fully prevents priming initiation, lending further support to the general validity of our findings. + +<|ref|>text<|/ref|><|det|>[[117, 136, 882, 186]]<|/det|> +Pain behavioral testing methods: Only heat sensitivity was assessed in the study. Whether such priming is also effective in mechanical and cold sensitivity is unknown. Whether NAAA mediates other pain modalities following the priming was not assessed either in the study. + +<|ref|>text<|/ref|><|det|>[[150, 201, 882, 234]]<|/det|> +We assessed both heat and mechanical hypersensitivity, with similar results. Representative sets of mechanical hypersensitivity data are included in new Figure S2 and S4. + +<|ref|>text<|/ref|><|det|>[[117, 249, 882, 298]]<|/det|> +Skin macrophages: Two experimental approaches to deplete monocytes used in the study are indeed not ideal. Both are more effective and suitable in depleting macrophages/microglia than monocytes. + +<|ref|>text<|/ref|><|det|>[[152, 313, 882, 361]]<|/det|> +We direct the Reviewer's attention to the results reported in Figure 5, which show that both approaches (clodronate and PLX- 5622) substantially reduced monocyte numbers in the bloodstream. + +<|ref|>text<|/ref|><|det|>[[116, 376, 883, 473]]<|/det|> +The authors repeatedly indicated that observed effects are derived from monocytes/macrophages. They excluded CNS microglia effect, but they didn't touch anything on skin macrophages, which is essential. If we believe there is a crucial peripheral contribution of NAAA in inflammatory mediator induced priming, detailed changes of macrophages in affected paw are indispensable, as they are direct players. Such data may also help to understand why it works not before or not after 72hr interval. + +<|ref|>text<|/ref|><|det|>[[152, 489, 882, 521]]<|/det|> +We thank the Reviewer for this suggestion, which we have addressed with the new experiment described in our response to Reviewer 2. Please see above. + +<|ref|>text<|/ref|><|det|>[[116, 536, 882, 585]]<|/det|> +Clinical implications: It is difficult for me to imagine in what clinical setting where the findings from the current study can apply. What does this 72 hr interval, not before or not after, mean for patients who come to see a physician for an acute pain? + +<|ref|>text<|/ref|><|det|>[[152, 600, 882, 681]]<|/det|> +This basic science study is not meant to have immediate repercussions on clinical practice. It does have, however, potential clinical significance in that it suggests that postsurgical NAAA inhibition (but not postsurgical treatment with standard analgesics) may prevent the transition to pain chronicity, a significant problem for patients who undergo thoracotomy, knee arthroplasty, mastectomy, and other invasive surgeries. + +<|ref|>text<|/ref|><|det|>[[116, 696, 882, 760]]<|/det|> +Thus, in general, I recognize the value and the quality of the study in identifying molecular mechanism of hypersensitivity priming in a specific setting, I feel the conclusion, including the title of the study was overstated. Chronic pain is complex, I believe we need to develop precision medicine for each specific type of chronic pain. + +<|ref|>text<|/ref|><|det|>[[150, 775, 882, 808]]<|/det|> +Our views about the complexity of chronic pain are very similar to the Reviewer's, as affirmed in the Discussion section of the manuscript: + +<|ref|>text<|/ref|><|det|>[[152, 823, 882, 888]]<|/det|> +"Chronic pain states are widely heterogeneous in causes, symptoms, impact on function, and temporal development3. This diversity justifies skepticism toward a simplistic view of the progression to pain chronicity as transformation of one mechanistic type of pain (e.g., acute pain associated with injury) into another (e.g., neuropathic pain)99." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[151, 89, 883, 218]]<|/det|> +Thus, we are surprised by the Reviewer's statement that "the conclusion, including the title of the study was overstated." The title of our manuscript (NAAA- regulated lipid signaling in monocytes controls the induction of hyperalgesic priming) accurately reflects the findings presented. Our conclusion is equally cautious and, we believe, fully warranted by the data: "Clinical studies should determine whether algostatic agents might offer a strategy to prevent chronic pain after invasive surgery and other kinds of physical trauma." However, when interpretation could have been ambiguous, we replaced 'chronic pain' with 'persistent pathological nociception' (see, for example, Abstract, line 38). + +<|ref|>sub_title<|/ref|><|det|>[[116, 256, 220, 273]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[116, 288, 883, 401]]<|/det|> +The manuscript "NAAA- regulated lipid signaling in monocyte- derived cells controls the induction of hyperalgesic priming", by Fotio et al, provides additional mechanical information regarding a model of the transition from acute to chronic pain, hyperalgesic priming (HP). This is an interesting study, with the experiments appropriately conducted, clearly exemplifying the involvement of the immune system in the development of persistent nociceptive sensitization. The conclusions certainly add to the characterization of such phenomenon, previously shown to play a role in the persistence of pain observed in some clinical conditions. + +<|ref|>text<|/ref|><|det|>[[160, 416, 464, 433]]<|/det|> +We appreciate the positive comments. + +<|ref|>text<|/ref|><|det|>[[116, 447, 883, 481]]<|/det|> +Although I do not see a reason preventing its publication, I would appreciate if the authors could clarify or include some minor comments in the final version of the manuscript: + +<|ref|>text<|/ref|><|det|>[[116, 495, 883, 609]]<|/det|> +Experimentally, HP is defined by the potentiation (prolongation) of the mechanical hyperalgesia induced by PGE2 (>4h) in the paw when compared to a non- primed paw (<2h), indicating the hyper- responsive state triggered by the inflammation in the primary neuron. In the current study the authors evaluate the effect of PGE2 on the thermal nociceptive threshold in primed paws. What is the time course of the response produced by PGE2 on the thermal sensitivity in a normal, non- primed paw? Including this information would help the reader to visualize the increased sensitivity of the nociceptor produced by the priming stimulus, for comparison. + +<|ref|>text<|/ref|><|det|>[[156, 623, 882, 657]]<|/det|> +We have added a new supplemental figure (Fig. S2) that contains the requested information. + +<|ref|>text<|/ref|><|det|>[[116, 671, 883, 785]]<|/det|> +Induction of HP by carrageenan is, in rats, sexually dimorphic, modulated by estrogen at the level of PKCepsilon. In mice, HP is also sexually dimorphic. However, instead of being an "all or nothing" phenomenon as in rats, this difference in mice seems to be more complex. Can the authors include a comment about these differences in the Discussion? Since the development of HP in mice of both sexes is suggested to occur at the level of NAAA, the upstream differential mechanism could be mentioned (or speculated), specifically considering that NAAA is important only during the incubation phase, when protein translation is happening. + +<|ref|>text<|/ref|><|det|>[[160, 800, 882, 865]]<|/det|> +We do not know how inflammatory challenges trigger NAAA activation and whether this process might be sexually dimorphic. But we appreciate the point raised by the Reviewer and addressed its spirit by adding the following comment to the Discussion section of the manuscript (p. 17): + +<|ref|>text<|/ref|><|det|>[[157, 871, 882, 904]]<|/det|> +"In this context, an important question that remains to be answered pertains to the mechanisms through which inflammatory stimuli lead to the suppression of NAPE- PLD + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[160, 89, 882, 138]]<|/det|> +transcription and the enhancement of NAAA activity. Elucidating such mechanisms might shed light on aspects of HP – such as the existence of sexual dimorphisms in rats88- 90 and mice91 – which are presently unclear." + +<|ref|>text<|/ref|><|det|>[[118, 160, 883, 194]]<|/det|> +Why did the authors use the tail flick method to determine nociceptive thresholds if all the relevant behavior experiments were performed using the Hargreaves plantar test in the paw? + +<|ref|>text<|/ref|><|det|>[[159, 208, 882, 273]]<|/det|> +We routinely use the tail- flick method to identify potential alterations in baseline nociceptive threshold in newly developed mouse lines such as those introduced in the present study. Here, we combined tail- flick (Fig. S9) and Hargreaves plantar tests (Fig. 3D and Fig. 4G1) to obtain a more complete view of the lines' nociceptive phenotype. + +<|ref|>text<|/ref|><|det|>[[118, 288, 712, 305]]<|/det|> +Were the compounds injected in the paw intradermally or subcutaneously? + +<|ref|>text<|/ref|><|det|>[[159, 320, 882, 369]]<|/det|> +Compounds were injected subcutaneously, between skin and muscular fascia/tendon, as customary in this model. We clarified this point in the Materials and Methods section of the manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 383, 883, 431]]<|/det|> +The information provided by this study contribute to the knowledge about the mechanisms involved in the transition from acute to chronic pain, which is of utmost importance. I look forward to receiving the authors' response and comments added to the revised version of this article. + +<|ref|>text<|/ref|><|det|>[[159, 447, 249, 464]]<|/det|> +Thank you. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 174, 697, 192]]<|/det|> +The authors appropriately revised the manuscript in response to my comments. + +<|ref|>text<|/ref|><|det|>[[115, 230, 393, 248]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 259, 416, 277]]<|/det|> +My points have been partially addressed. + +<|ref|>text<|/ref|><|det|>[[115, 287, 872, 380]]<|/det|> +Specifically, whilst I suggested to characterise monocytes/macrophages at the site of IL- 6 injection (hind paw) the authors have looked at blood monocytes. They provide evidence that intraplantar injection of IL- 6 is associated with more CCR2+ monocytes circulating in blood. However, classical monocytes will have to infiltrate tissue to come in the vicinity of primary afferent terminals and promote nociceptive signalling. + +<|ref|>text<|/ref|><|det|>[[115, 389, 864, 444]]<|/det|> +Whether CCR2+ monocytes infiltrate the site of injection remains to be established and Figure 7 schematic should indicate that this study does not provide direct evidence that "monocytes migrate to target tissue". + +<|ref|>text<|/ref|><|det|>[[115, 454, 842, 472]]<|/det|> +New Figure 6: How do the authors explain presence of F4/80 positive cells (macrophages) in blood? + +<|ref|>text<|/ref|><|det|>[[115, 482, 854, 537]]<|/det|> +Discussion: It is possible that CCL2 is upregulated in endothelial cells, and sensory neurons and accumulates in primary afferent terminals. However, the authors provide no direct evidence that this happens in their experimental conditions. + +<|ref|>text<|/ref|><|det|>[[115, 547, 875, 602]]<|/det|> +Other points. Ref 12 line 57: This is an early observation and more recent evidence indicates no infiltration of monocytes in the spinal cord following peripheral nerve injury. The authors could rephrase their statement. + +<|ref|>text<|/ref|><|det|>[[115, 612, 438, 630]]<|/det|> +Line 167: replace "deleted" with "depleted". + +<|ref|>text<|/ref|><|det|>[[115, 668, 393, 686]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 697, 696, 715]]<|/det|> +The authors addressed the reviewer's concerns. I don't have further comments. + +<|ref|>text<|/ref|><|det|>[[115, 754, 393, 772]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[112, 783, 813, 801]]<|/det|> +I am satisfied with the revision provided by the authors. I recommend this study for publication. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[85, 88, 934, 187]]<|/det|> +Specifically, whilst I suggested to characterise monocytes/macrophages at the site of IL- 6 injection (hind paw) the authors have looked at blood monocytes. They provide evidence that intraplantar injection of IL- 6 is associated with more CCR2+ monocytes circulating in blood. However, classical monocytes will have to infiltrate tissue to come in the vicinity of primary afferent terminals and promote nociceptive signalling. Whether CCR2+ monocytes infiltrate the site of injection remains to be established and Figure 7 schematic should indicate that this study does not provide direct evidence that "monocytes migrate to target tissue". + +<|ref|>text<|/ref|><|det|>[[85, 201, 933, 235]]<|/det|> +We clarified that Figure 7 provides a hypothetical model which summarizes the data presented in our study and suggests a roadmap for future experiments. Please see Figure 7 legend. + +<|ref|>text<|/ref|><|det|>[[88, 248, 930, 266]]<|/det|> +New Figure 6: How do the authors explain presence of F4/80 positive cells (macrophages) in blood? + +<|ref|>text<|/ref|><|det|>[[85, 280, 930, 314]]<|/det|> +Though unlikely, it is possible that the antibody we used cross- reacted with a different monocyte antigen. Owing to this uncertainty, we removed F4/80 data from Figure 6C. + +<|ref|>text<|/ref|><|det|>[[85, 328, 933, 378]]<|/det|> +Discussion: It is possible that CCL2 is upregulated in endothelial cells, and sensory neurons and accumulates in primary afferent terminals. However, the authors provide no direct evidence that this happens in their experimental conditions. + +<|ref|>text<|/ref|><|det|>[[85, 392, 930, 425]]<|/det|> +There is substantial evidence that peripheral nerve injury upregulates CCL2 in DRG neurons, but future experiments will have to address this question as it pertains to the model used here. + +<|ref|>text<|/ref|><|det|>[[85, 440, 930, 473]]<|/det|> +Other points. Ref 12 line 57: This is an early observation and more recent evidence indicates no infiltration of monocytes in the spinal cord following peripheral nerve injury. The authors could rephrase their statement. + +<|ref|>text<|/ref|><|det|>[[85, 488, 933, 568]]<|/det|> +Evidence indicates that spinal nerve resection does not stimulate monocytes migration toward the spinal cord (PMID 27373153, presumably the study the reviewer had in mind). The hyperalgesic priming model we used, however, is quite different and, possibly, mechanistically closer to the one used in Ref 12 (partial sciatic nerve ligation). Indeed, both hyperalgesic priming and sciatic nerve ligation exhibit a rather strong inflammatory component that is not observed after spinal nerve resection. + +<|ref|>text<|/ref|><|det|>[[86, 583, 429, 600]]<|/det|> +Line 167: replace "deleted" with "depleted". + +<|ref|>text<|/ref|><|det|>[[86, 616, 135, 631]]<|/det|> +Done. + +<--- Page Split ---> diff --git a/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/images_list.json b/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..75842702ccf4eeca3224aaa84c3d749f0adeb262 --- /dev/null +++ b/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,41 @@ +[ + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4 | Total Cr(VI) in wind-dispersible soil and ash particles. a. \\(\\mu\\) -XRF image (pixel resolution: \\(1 \\mu m\\) ) showing the relative intensity of Cr(VI) (green; estimated as the intensity ratio at 5993 and 6010 eV) and total Cr (blue; measured at 6010 eV) within the \\(< 53 - \\mu m\\) size fraction of Cr-bearing soil-ash particulates from a serpentine chaparral that experienced high fire severity (A7). b. Normalized \\(\\mu\\) -XANES spectra (Cr K-edge) from numbered locations on Cr-bearing particles in a. Dashed lines indicate energies characteristic of Cr(VI) (5993 eV), Cr(III) (6003 eV), and total Cr (6010 eV), at which \\(\\mu\\) -XRF images were also collected.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure S9 | Total Cr(VI) in wind-dispersible soil and ash particles. a. \\(\\mu\\) -XRF image (pixel resolution: \\(1\\mu \\mathrm{m}\\) ) showing the relative intensity of \\(\\mathrm{Cr(VI)}\\) (green; estimated as the intensity ratio at 5993 and \\(6010\\mathrm{eV}\\) ) and total Cr (blue; measured at \\(6010\\mathrm{eV}\\) ) within the \\(< 53 - \\mu \\mathrm{m}\\) size fraction of Cr-bearing soil-ash particulates from a serpentine chaparral that experienced high fire severity (A7). b. Normalized \\(\\mu\\) -XANES spectra (Cr K-edge) from numbered locations on Cr-bearing particles in a. Dashed lines indicate energies characteristic of \\(\\mathrm{Cr(VI)}\\) (5993 eV), \\(\\mathrm{Cr(III)}\\) (6003 eV), and total Cr (6010 eV).", + "footnote": [], + "bbox": [ + [ + 128, + 182, + 777, + 444 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure S7: Legend : ... from a serpentine chaparral soil...", + "footnote": [], + "bbox": [], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4: Change A and B in Figure plot panels to a and b reflected in the figure caption", + "footnote": [], + "bbox": [], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..63286da9b6707443c44b48900791e2b88519664f --- /dev/null +++ b/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,389 @@ + +# nature portfolio + +# Peer Review File + +# Metal Toxin Threat in Wildland Fires Determined by Geology and Fire Severity + +![](images/Figure_4.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +# REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +# Review of manuscript 395109 submitted to Nature Communication + +# Metal toxin threat in wildland fires determined by geology and fire severity + +Alandra Marie Lopez, Juan Lezama Pacheco and Scott Fendorf + +This manuscript presents the results of a study aimed at emphasizing the health threat potentially arising from chromium transformation to its most harmful \(\mathrm{Cr(VI)}\) form in soils and ashes upon wildfires. To reach their objective, the authors analyzed 38 cores drilled in more or less severely burned soils at four Preserves that experienced large wildfires in the North Coast Range of California (USA). The results obtained confirm the catalytic effect of high temperatures generated by wildfires on chromium oxidation in soil, and they point to control of soil geology and fire severity on this effect. They also interestingly indicate that reactive \(\mathrm{Cr(VI)}\) can reach dangerous levels in wind- dispersible particulates found in the surficial layers of the soil at ultramafic settings, and that this harmful form of chromium can persist in the soil/ash system up to one year after the wildfire if rainfalls are not significant. These results yield to the conclusion that more work is required to further evaluate this potential risk around the world. + +I found this paper very pleasant to read. The subject is well introduced, the sites and samples are well described and fit with the objective of the study, the results are well presented and they support the discussion that gives proper attention to the existing literature on the topic and yield to the novel conclusions that geology and fire intensity are important drivers of harmful hexavalent chromium in soils and wind- dispersible soil/ash surface particles, and that the associated health risk can persist up to one year after fire. + +Although the scale of the study (North Coast Range of California, USA) could at first be considered too short to extend its findings at the global scale, I agree with the authors that the number and diversity of sites studied can be considered enough to address this issue. I also agree with the concluding remark on the importance of further evaluating the potential risk of wildfire- induced harmful hexavalent chromium in wind- dispersible soil/ash particles at the global scale. Finally, I agree with the authors that the results provided in this study deserve to be shared with a large audience, ranging from scientists working on the topic to policy makers, public administrators and nature managers. + +For all these reasons, I consider that this manuscript deserves to be published in Nature Communications. I have listed below few issues that I would be interested to see addressed, although only few of them are mandatory for publication. + +## Figure 1 + +I agree that a large fraction of ultramafic/mafic areas are concerned by wildfires at the global scale. Figure 1 shows that these areas are mainly located in the tropical region where most soils are deeply weathered (Utilisols and Oxisols, according to the USDA classification). However, the Fe contents reported in Table S6 suggest that the soils studied in this work do not correspond to these soil types. This raises the question of the actual representativeness of the results regarding tropical areas. I would + +<--- Page Split ---> + +recommend that the authors comment on that point, and maybe further consider it in their concluding remarks. + +## Figure 3 + +Maybe, the authors could add the results of comparative statistics tests on barplots and boxplots (either directly report the p- values or show corresponding labels as \*\*\* or \*\*\*)? + +Do they have any hypothesis to explain the much higher concentration in reactive C(VI) measured in the A7 surface soil- ash sample from the serpentine chaparral landscape ? The data provided in Table S6 indicate about twice more total Cr in this sample compared to sample A6 (for instance), but the concentration in reactive Cr(VI) is more than 3 times higher in the bulk fraction and more than 25 three times higher in the \(< 53\mu m\) fraction. Are there any mineralogical differences with the other moderatelyhighly burned serpentine soil- ash samples (A3- A6) that could help to explain that ? + +## Figure 4 + +I wonder if this figure should be maintained in the main text. First, I am not convince that it really supports the assumption that 'total Cr(VI) was most abundant in wind- dispersible soils and ash particulates after high fire severity conditions compared to a low severity sample'. Second, I do not understand why the two figures are plotted on different sizes (A is larger than B). + +It could maybe be replaced by a figure similar to Figure S7 (maybe use only panels A and B or panels C and D from Figure S7 and add two similar panels from a low fire severity burn sample from a serpentine chaparral soil)? + +Whatever, if Figure 4 is maintained in the main text, I would recommend that the authors add some histograms with the estimated number of Cr(VI) and total Cr particles on the two figures, in order to help the reader to better assess the relative proportion of both types of particles. At least, I would recommend that they change for more contrasted colors, in order to help the reader to better visually decipher between Cr(VI) and total Cr particles. + +## Figure S6 + +I would recommend to change the letters for A, B and C in the legend to fit with the letters reported on the figure. + +## Table S6 + +Total concentrations in bulk surface soil- ash samples (and some \(< 53\mu m\) fractions) are displayed, but total concentration in bulk soil samples across the whole soil cores are not provided. I would recommend that the authors provide these data (at least those for Cr) as mean total concentration for rhyolite, melange and serpentine soils in SI, either in the form of a Table or as a figure similar to Figure 2. Such a figure would better show that the fractions of reactive Cr(VI) is very low compared to total Cr concentration. In the same way, I would have been interested to see a figure similar to Figure 2 that would have depicted the fraction of reactive Cr(VI) as a function of the total Cr concentration. Indeed, such a figure would have helped to check if the fraction of reactive Cr(VI) is really higher in serpentine soils. Even if I agree with the authors that the concentration of reactive Cr(VI) is the most relevant parameter to assess a potential environmental and/or health risk, the fraction of reactive Cr(VI) could further inform on the actual mechanism(s) and/or soil characteristic(s) that favor Cr(III) to + +<--- Page Split ---> + +Cr(VI) oxidation in burned soils. But, maybe this question is beyond the scope of the paper... + +## Figure S7 + +Figure S7Legend : ... from a serpentine chaparral soil...Why did the authors not tried to analyze more some Cr(VI) areas on panel A ?The XANES spectrum at point 1 on panel C shows a well-marked Cr(VI) pre-edge peak but the color code indicate rather low amounts of Cr(VI) at this point. Could the authors explain that ? + +## Suggested additional references + +Suggested additional referencesRascio et al., 2022. Evidence of hexavalent chromium formation and changes of Cr speciation after laboratory- simulated fires of composted tannery sludges long- term amended agricultural soils. Journal of Hazardous Materials, 436, 129117. https://doi.org/10.1016/j.jhazmat.2022.129117Terzano et al., 2021. Fire effects on the distribution and bioavailability of potentially toxic elements (PTEs) in agricultural soils. Chemosphere, 130752. https://doi.org/10.1016/j.chemosphere.2021.130752Ré et al., 2021. Cytotoxic effects of wildfires ashes : In- vitro responses of skin cells. Environmental Pollution, 285, 117279. https://doi.org/10.1016/j.envpol.2021.117279Jahn et al., 2021. Metallic and crustal elements in biomass- burning aerosols and ash: Prevalence, significance, and similarities to soil particles. ACS Earth and Space Chemistry, 5, 136- 148. https://dx.doi.org/10.1021/acsearthspacechem.0c00191Xu et al., 2020. Wildfires, global climate change, and human health. The New England Journal of Medicine, 383, 2173- 2181. https://doi.org/10.1056/NEJMsr2028985 + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +The authors have to highlight the novelty of their manuscript. The abstract should be revised to attract the reader's attention. The Introduction section should be improved by adding references dealing soil contamination issues. However, the problem is that the English and the whole organisation of the present version are definitely below an acceptable standard for an international scientific journal. Analytical quality control is missing. Detection limits of the applied methods should be reported. The main problem for this manuscript is its structure. Major parts are missing from the manuscript. My suggestion is to reject this manuscript and encourage the authors to submit a more mature manuscript. + +<--- Page Split ---> + +## Response to Review Comments + +## Reviewer #1 + +This manuscript presents the results of a study aimed at emphasizing the health threat potentially arising from chromium transformation to its most harmful \(\mathrm{Cr(VI)}\) form in soils and ashes upon wildfires. To reach their objective, the authors analyzed 38 cores drilled in more or less severely burned soils at four Preserves that experienced large wildfires in the North Coast Range of California (USA). The results obtained confirm the catalytic effect of high temperatures generated by wildfires on chromium oxidation in soil, and they point to control of soil geology and fire severity on this effect. They also interestingly indicate that reactive \(\mathrm{Cr(VI)}\) can reach dangerous levels in wind- dispersible particulates found in the surficial layers of the soil at ultramafic settings, and that this harmful form of chromium can persist in the soil/ash system up to one year after the wildfire if rainfalls are not significant. These results yield to the conclusion that more work is required to further evaluate this potential risk around the world. + +I found this paper very pleasant to read. The subject is well introduced, the sites and samples are well described and fit with the objective of the study, the results are well presented and they support the discussion that gives proper attention to the existing literature on the topic and yield to the novel conclusions that geology and fire intensity are important drivers of harmful hexavalent chromium in soils and wind- dispersible soil/ash surface particles, and that the associated health risk can persist up to one year after fire. + +Although the scale of the study (North Coast Range of California, USA) could at first be considered too short to extend its findings at the global scale, I agree with the authors that the number and diversity of sites studied can be considered enough to address this issue. I also agree with the concluding remark on the importance of further evaluating the potential risk of wildfire- induced harmful hexavalent chromium in wind- dispersible soil/ash particles at the global scale. Finally, I agree with the authors that the results provided in this study deserve to be shared with a large audience, ranging from scientists working on the topic to policy makers, public administrators and nature managers. + +For all these reasons, I consider that this manuscript deserves to be published in Nature Communications. I have listed below few issues that I would be interested to see addressed, although only few of them are mandatory for publication. + +Response: We thank the reviewer for their constructive feedback and review of the manuscript's findings and implications. We have reviewed and addressed in detail below the reviewer's suggestions. + +Changes: Please see our specific changes to the reviewer's suggestions below. + +Figure 1: I agree that a large fraction of ultramafic/mafic areas are concerned by wildfires at the global scale. Figure 1 shows that these areas are mainly located in the tropical region where most soils are deeply weathered (Ultisols and Oxisols, according to the USDA classification). However, the Fe contents reported in Table S6 suggest that the soils studied in this work do not + +<--- Page Split ---> + +correspond to these soil types. This raises the question of the actual representativeness of the results regarding tropical areas. I would recommend that the authors comment on that point, and maybe further consider it in their concluding remarks. + +Response: We agree with the reviewer that the soils in this study are not as deeply weathered as Oxisols and Ultisols, like lateritic soils, common across tropical climate regions (e.g., New Caledonia, Cuba, Brazil, Malaysia, Indonesia, Madagascar, northern Australia). In our study, the average Fe concentration across burned and unburned bulk ultramafic (serpentine) soil was 8.71 wt. \(\%\) , while lateritic soils can contain more than 5x more Fe, typically in the form of crystalline Fe oxides (e.g., hematite, goethite). Chromium is predominantly found within these crystalline Fe oxides. Additionally, lateritic soils are often depleted in Ca, Mg, and Si. The Fe concentrations of our study soils are representative of serpentine soils in Mediterranean or temperate climates (e.g., California, Oregon, Washington, Turkey, Balkans) with moderate Fe oxide content and neutral to alkaline pH. We have added a paragraph within the Discussion section that addresses the characterization of ultramafic soils globally and the limitations of soil types within our study site when considering mechanisms in lateritic and highly weathered metal- rich soils in the tropical regions. Furthermore, we place our findings from field analysis in the context of laboratory studies that examine Cr(VI) generation from Cr(III) solids common to lateritic soils. + +Changes: Within the Discussion we now state: + +"While recognized for urban fires, threats from metal exposure in smoke and dust need to be recognized within wildland fires arising on metal- rich geologies. Across tropical climate regions, deeply weathered lateritic soils are common, in which Cr is predominantly found within crystalline Fe oxides (e.g., hematite, goethite), and soil Fe content may exceed 50 wt. \(\%\) . Past work has quantified the Cr oxidation capacity of Cr- bearing Fe oxides and lateritic soils during heating simulations \(^{35,62}\) . For example, the greatest Cr(VI) formation (more than 40% of total Cr) upon heating hematite occurred at temperatures less than \(400^{\circ}\mathrm{C}\) , while up to 100% of total Cr in goethite transformed to Cr(VI) at \(800^{\circ}\mathrm{C}\) . In Mediterranean or temperate climates (similar to this study's region), ultramafic soils are relatively more enriched in Cr- bearing phyllosilicate minerals (e.g., serpentine), Fe oxide content is moderate (typically less than 10 wt. \(\%\) ) with more amorphous secondary phases, and soil pH is neutral to alkaline pH. In our study, and under natural wildfire conditions, we observed that up to about 0.015% of total Cr was reactive Cr(VI) in burned serpentine soils. Chromium(VI) generation during wildfires depend on fire conditions and host mineralogy; thus, the extent of Cr(VI) formation in lateritic soils may differ from temperate serpentine soils, but field observations of Cr(VI) in burned lateritic soils following wildfires are currently lacking." + +Figure 3: Maybe, the authors could add the results of comparative statistics tests on barplots and boxplots (either directly report the \(p\) - values or show corresponding labels as \(***\) or \(**\) )? + +Response: We performed a one- way ANOVA for Figure 3c and found no statistically significant difference between the three groups (p- value = 0.164). In Figure 3b, we are illustrate reactive concentrations within surface soil- ash based on fire severity (low + +<--- Page Split ---> + +versus moderate- high) and particle size (bulk soil less than \(2\mathrm{mm}\) versus the silt and clay- sized fraction less than \(53\mu \mathrm{m}\) ). We are unable to run a two- way ANOVA because burn severity sample sizes are not equal. + +Changes: For Figure 3, we now state "Reactive \(\mathrm{Cr(VI)}\) concentrations ranged from 64 to \(1,060\mu \mathrm{g / kg}\) , with a median concentration of \(257\mu \mathrm{g / kg}\) , and remained elevated compared to concentrations (5- 64 \(\mu \mathrm{g / kg}\) ) within the near surface depths (0- 2 cm) of unburned serpentine soil (Figure 3c); however, these differences were not statistically significant (p- value \(= 0.164\) )." + +Do they have any hypothesis to explain the much higher concentration in reactive \(\mathrm{C(VI)}\) measured in the A7 surface soil- ash sample from the serpentine chaparral landscape? The data provided in Table S6 indicate about twice more total \(\mathrm{Cr}\) in this sample compared to sample A6 (for instance), but the concentration in reactive \(\mathrm{Cr(VI)}\) is more than 3 times higher in the bulk fraction and more than 25 three times higher in the \(< 53\mu \mathrm{m}\) fraction. Are there any mineralogical differences with the other moderately- highly burned serpentine soil- ash samples (A3- A6) that could help to explain that? + +Response: At site A7, the soil experienced longer burning duration and fire intensities with greater biomass combustion that may further contribute to the high- levels of \(\mathrm{Cr(VI)}\) . Unlike A7 (original Figure S9; revised Figure S11), we did not observe mineralogical changes in bulk composition for samples A3- A6 in the surface soil and ash compared to underlying burned soil. We suspect that high temperatures did not persist for sufficient time to alter bulk mineralogy in the latter samples. + +Changes: Within the Results we state: "At site A7, the average reactive \(\mathrm{Cr(VI)}\) concentration was more than three times greater than other moderate- high fire severity sites (Figure 3b). We suspect that longer burning duration and fire intensities with greater biomass combustion contributed to the relatively high- levels of \(\mathrm{Cr(VI)}\) , as this was a severely burned forested area. Importantly, ash from severely burned areas concentrate alkali (Na, K) and alkaline earth (Ca, Mg) metals (often from biomass combustion) that are key for the thermal oxidation of \(\mathrm{Cr(III)}\) \(^{13,43}\) . For example, \(\mathrm{CaCrO_4}\) was noted after agricultural soil amended with composted \(\mathrm{Cr(III)}\) - rich tannery sludge was heated at \(500^{\circ}\mathrm{C}\) \(^{55}\) ." + +Figure 4: I wonder if this figure should be maintained in the main text. First, I am not convince that it really supports the assumption that "total \(\mathrm{Cr(VI)}\) was most abundant in wind- dispersible soils and ash particulates after high fire severity conditions compared to a low severity sample". Second, I do not understand why the two figures are plotted on different sizes (A is larger than B). + +It could maybe be replaced by a figure similar to Figure S7 (maybe use only panels A and B or panels C and D from Figure S7 and add two similar panels from a low fire severity burn sample from a serpentine chaparral soil)? + +<--- Page Split ---> + +Whatever, if Figure 4 is maintained in the main text, I would recommend that the authors add some histograms with the estimated number of Cr(VI) and total Cr particles on the two figures, in order to help the reader to better assess the relative proportion of both types of particles. At least, I would recommend that they change for more contrasted colors, in order to help the reader to better visually decipher between Cr(VI) and total Cr particles. + +Response: We appreciate the reviewer's feedback regarding Figure 4. We agree that our results of greater Cr(VI)- bearing particles in high severity soil- ash versus low- severity conditions can be clearer, especially by including a histogram of particles containing Cr(VI). Regarding the reviewer's concern about the different size plots, the sample area for large- scale micro- XRF maps of each thin section were not held constant during data collection, resulting in different mapped areas. Due to limitations of the analysis software, we are unable to change for more contrasted colors, but we can update the min/max values for color brightness. + +We have revised Figure 4 to focus on a \(1 - \mu \mathrm{m}\) resolution XRF image containing particles from a high fire severity sample with and without measurable Cr(VI) by XANES analysis. We then moved the original Figure 4 to the Supplementary Information as Figure S8, and added another example of Cr(VI)- containing particles in a \(1 - \mu \mathrm{m}\) resolution XRF image as Figure S9. We also revised the main text related to the figures to highlight the presence of Cr(VI)- containing particles within the high fire severity samples, which was not apparent in low fire severity samples. + +Changes: See revised Figure 4, Figure S8, and Figure S9 below. + +"Using micro- scale X- ray techniques, Cr(VI)- containing soil and ash particulates were identified in a high fire severity sample as opposed to a low fire severity sample (Figure 4; Figure S8). Here, Cr(VI) was associated with mineral surfaces (e.g., adsorbed) or enriched in relatively low- Cr particles with Ca and K (Figure 4, Figure S9). Consistent with particle analysis, reactive Cr(VI) concentrations spanned from 326 to \(13,000 \mu \mathrm{g / kg}\) (Figure 3b)." + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Figure 4 | Total Cr(VI) in wind-dispersible soil and ash particles. a. \(\mu\) -XRF image (pixel resolution: \(1 \mu m\) ) showing the relative intensity of Cr(VI) (green; estimated as the intensity ratio at 5993 and 6010 eV) and total Cr (blue; measured at 6010 eV) within the \(< 53 - \mu m\) size fraction of Cr-bearing soil-ash particulates from a serpentine chaparral that experienced high fire severity (A7). b. Normalized \(\mu\) -XANES spectra (Cr K-edge) from numbered locations on Cr-bearing particles in a. Dashed lines indicate energies characteristic of Cr(VI) (5993 eV), Cr(III) (6003 eV), and total Cr (6010 eV), at which \(\mu\) -XRF images were also collected.
+ +<--- Page Split ---> + +Figure S8 | Total Cr(VI) in wind-dispersible soil and ash particles. \(\mu\) - XRF image showing particle distribution of total Cr(VI) (green; estimated as the intensity ratio at 5993 and 6010 eV) and total Cr (blue; measured at 6010 eV) within the \(< 53 - \mu \mathrm{m}\) size fraction of Cr-bearing soil- ash particulates from a. high fire severity site (A7) and b. low fire severity site (A1) in a serpentine chaparral. + +![](images/Figure_unknown_1.jpg) + +
Figure S9 | Total Cr(VI) in wind-dispersible soil and ash particles. a. \(\mu\) -XRF image (pixel resolution: \(1\mu \mathrm{m}\) ) showing the relative intensity of \(\mathrm{Cr(VI)}\) (green; estimated as the intensity ratio at 5993 and \(6010\mathrm{eV}\) ) and total Cr (blue; measured at \(6010\mathrm{eV}\) ) within the \(< 53 - \mu \mathrm{m}\) size fraction of Cr-bearing soil-ash particulates from a serpentine chaparral that experienced high fire severity (A7). b. Normalized \(\mu\) -XANES spectra (Cr K-edge) from numbered locations on Cr-bearing particles in a. Dashed lines indicate energies characteristic of \(\mathrm{Cr(VI)}\) (5993 eV), \(\mathrm{Cr(III)}\) (6003 eV), and total Cr (6010 eV).
+ +![](images/Figure_4.jpg) + + +<--- Page Split ---> + +Figure S6: I would recommend to change the letters for A, B and C in the legend to fit with the letters reported on the figure. + +Response: Based on the reviewer's recommendation, we have revised the figure, accordingly, by changing uppercase letters to lowercase, in addition to the other figures with sub- panels (similarly identified by Reviewer #2). + +Changes: We changed the letters to lowercase, as requested. + +Table S6: Total concentrations in bulk surface soil- ash samples (and some \(< 53 \mu \mathrm{m}\) fractions) are displayed, but total concentration in bulk soil samples across the whole soil cores are not provided. I would recommend that the authors provide these data (at least those for Cr) as mean total concentration for rhyolite, mélange and serpentine soils in SI, either in the form of a Table or as a figure similar to Figure 2. Such a figure would better show that the fractions of reactive \(\mathrm{Cr(VI)}\) is very low compared to total Cr concentration. + +Response: We thank the reviewer for their recommendation, which we have addressed in the revision. Please refer to our response and changes to the reviewer's next comment related to including a figure showing the fraction of reactive \(\mathrm{Cr(VI)}\) to total Cr concentrations. + +Changes: Using total Cr concentrations reported for soil cores in Table S1, we have revised Table S6 to include the mean total element concentrations for Cr, Fe, Mn, Ni, Ca, Mg, Na, and K in addition to the surface soil- ash sample data so that the reader can compare elemental concentrations in surface soil and ash to bulk soil from different geologies. + +<--- Page Split ---> + +Table S6 | Physicochemical characteristics of bulk soil and ash (up to 2 mm), and selected fine size fractions less than 53 μm, collected from surface layers of the burned serpentine chaparral, and mean elemental concentrations from bulk underlying soil based on geology type (rhyolitic, mélange, and serpentine). + +
IDFire
Severitya
% Sandb
(2-0.05 mm)
% Siltc
(53-2 μm)
% ClaycCr
mg/kg
Fe
mg/g
Mn
mg/kg
Ni
mg/kg
Ca
mg/g
Mg
mg/g
Na
mg/g
K
mg/g
Surface Soil-Ash
A1L114764.71351152815.577.34.633.76
A2L153269.11203253010.2158<0.11.65
A3M/H160684.2148031179.3148<0.11.54
A4M/H87.511.70.8225678.9143833808.7159<0.10.90
A5M/H99957.71022184910.21252.102.48
A6M/H78.220.21.6197079.21555272629.9174<0.12.86
A7M/H85.712.91.448291021543264317.9211<0.12.29
Less than 53 μm size fraction
A4M/H113394.71975304241.5124<0.13.38
A6M/H94682.71910229444.2133<0.14.41
A7M/H16431052547348934.01892.023.91
Bulk Soild
Rhyolitic \((n=7)\)16234.57968810.77.913.69.70
Melange \((n=16)\)31450.085525910.737.38.1713.2
Serpentine \((n=10)\)237387.1151129294.41503.611.69
+ +a L = Low severity, M = Moderate severity, H = High severity + +b Determined by sieve analysis + +c Determined by laser diffraction particle size counter + +d Bulk soil concentrations are mean values using all soil cores (fire-affected and unburned) for each geology type:rhyolitic \((n=7)\) , mélange \((n=16)\) , and serpentine \((n=10)\) . + +<--- Page Split ---> + +In the same way, I would have been interested to see a figure similar to Figure 2 that would have depicted the fraction of reactive \(\mathrm{Cr(VI)}\) as a function of the total \(\mathrm{Cr}\) concentration. Indeed, such a figure would have helped to check if the fraction of reactive \(\mathrm{Cr(VI)}\) is really higher in serpentine soils. Even if I agree with the authors that the concentration of reactive \(\mathrm{Cr(VI)}\) is the most relevant parameter to assess a potential environmental and/or health risk, the fraction of reactive \(\mathrm{Cr(VI)}\) could further inform on the actual mechanism(s) and/or soil characteristic(s) that favor \(\mathrm{Cr(III)}\) to \(\mathrm{Cr(VI)}\) oxidation in burned soils. But, maybe this question is beyond the scope of the paper... + +Response: We thank the reviewer for their recommendation. We agree that the reactive \(\mathrm{Cr(VI)}\) fraction of total \(\mathrm{Cr}\) in soil and soil- ash is low; however, the fraction is relatively higher in near surface soil depths compared to past studies quantifying natural \(\mathrm{Cr(III)}\) oxidation in unburned soils, including a 2017 study at McLaughlin Natural Reserve. Moreover, as the reviewer notes, the hazard imposed by the particulates is related to the reactive \(\mathrm{Cr(VI)}\) . The percentage of total \(\mathrm{Cr}\) that was reactive \(\mathrm{Cr(VI)}\) in unburned serpentine soil was consistent with previous measurements (McClain et al., 2017). Interestingly, the reactive \(\mathrm{Cr(VI)}\) fraction differs based on geology (rhyolite, mélange, and serpentinite). The reactive \(\mathrm{Cr(VI)}\) fraction in rhyolitic and mélange soils composed more of the total \(\mathrm{Cr}\) content than the relative fraction within serpentine soils. In order to highlight these variations across soil depth in fire- affected and unburned sites, we added a figure to the supplementary information. + +Changes: Figure S6 (below) was added to the Supplementary Information. Succeeding figure numbers were updated based on this addition. Within the Results and Discussion sections, we now state: + +"Average \(\mathrm{Cr(VI)}\) concentrations generated in soils derived from mélange (Figure 2b) were more than double the respective levels in rhyolitic soil (Figure 2a) regardless of overlapping ranges in total \(\mathrm{Cr}\) content, 152- 954 and 102- 338 mg/kg, respectively, reflecting the potential contribution of differing mineralogy to \(\mathrm{Cr(VI)}\) generation (Figure S6) 35. " + +"In our study, and under natural wildfire conditions, we observed that up to about \(0.015\%\) of total \(\mathrm{Cr}\) was reactive \(\mathrm{Cr(VI)}\) in burned serpentine soils (Figure S6)." + +<--- Page Split ---> + +Figure S6 | Fraction of total Cr that is reactive \(\mathrm{Cr(VI)}\) in burned and unburned soils. The ratio of reactive \(\mathrm{Cr(VI)}\) to total Cr concentrations (as a percentage) within a. rhyolite- , b. mélange- , c. serpentinite- derived soil profiles (0- 16 cm) that were not burned (gray; rhyolite, \(n =\) 3; mélange, \(n = 7\) ; serpentinite, \(n = 3\) ) or were fire- affected (colored; rhyolite, \(n = 4\) ; mélange, \(n\) \(= 9\) ; serpentinite, \(n = 7\) ). Percentages were also plotted for serpentinite- derived soil (0- 20 cm) from McClain et al. (2017) in c. for comparison. Each point represents the average percentage for a soil core based on triplicate measurements. + +![PLACEHOLDER_14_0] + +
Figure S7: Legend : ... from a serpentine chaparral soil...
+ +Response: We agree with the reviewer's recommendation and have made the appropriate changes. Based on the reviewer's previous recommendations, this figure has revised as Figure 4 and Figure S9. + +Changes: (Figure 4 and Figure S9 caption) "... particles ( \(< 53 \mu \mathrm{m}\) ) from a serpentine chaparral that experienced high fire severity ..." + +Why did the authors not tried to analyze more some \(\mathrm{Cr(VI)}\) areas on panel A? The XANES spectrum at point 1 on panel C shows a well- marked \(\mathrm{Cr(VI)}\) pre- edge peak but the color code indicate rather low amounts of \(\mathrm{Cr(VI)}\) at this point. Could the authors explain that? + +Response: Our XANES analysis was used to corroborate our bulk measurements of reactive \(\mathrm{Cr(VI)}\) . Particles within the XRF map were used to denote the presence and abundance of \(\mathrm{Cr(VI)}\) , corroborating (and visualizing) the reactive fraction measurements. + +Changes: "To corroborate bulk measurements of reactive \(\mathrm{Cr(VI)}\) , we combined multi- energy mapping with \(\mu\) - XANES of select spots on particles to confirm the presence of \(\mathrm{Cr(VI)}\) ." + +## Suggested additional references + +Rascio et al., 2022. Evidence of hexavalent chromium formation and changes of \(\mathrm{Cr}\) speciation after laboratory- simulated fires of composted tannery sludges long- term amended agricultural + +<--- Page Split ---> + +soils. Journal of Hazardous Materials, 436, 129117. https://doi.org/10.1016/j.jhazmat.2022.129117 Terzano et al., 2021. Fire effects on the distribution and bioavailability of potentially toxic elements (PTEs) in agricultural soils. Chemosphere, 130752. https://doi.org/10.1016/j.chemosphere.2021.130752 Ré et al., 2021. Cytotoxic effects of wildfires ashes : In- vitro responses of skin cells. Environmental Pollution, 285, 117279. https://doi.org/10.1016/j.envpol.2021.117279 Jahn et al., 2021. Metallic and crustal elements in biomass- burning aerosols and ash: Prevalence, significance, and similarities to soil particles. ACS Earth and Space Chemistry, 5, 136- 148. https://dx.doi.org/10.1021/acsearthspacechem.0c00191 Xu et al., 2020. Wildfires, global climate change, and human health. The New England Journal of Medicine, 383, 2173- 2181. https://doi.org/10.1056/NEJMsr2028985 + +Response: We thank the reviewer for sharing additional references. We agree that these references are relevant to the study. + +Changes: We have added these references suggested above, in addition to a few other recently published and relevant studies, to discussions within the main text. + +"Global wildfire activity represents a rising distributed health risk from smoke and dust inhalation \(^{5 - 10}\) ." + +10. Xu, R. et al. Wildfires, Global Climate Change, and Human Health. N. Engl. J. Med. 383, 2173-2181 (2020). + +"Increased heavy metals in PM have been documented during wildfire episodes and may induce cytotoxicity, increase lung cancer risks, and greatly contribute to oxidative stress \(^{19 - 30}\) ." + +"Suburban fires illustrates the impacts of inhaling Cr(VI)- containing ash within the respiratory tract by measuring Cr(VI) leached with a simulated lung fluid \(^{36,37}\) and discerning Cr mineralogy within nano- sized particulates (< 100 nm) \(^{22,30}\) ." + +21. Boaggio, K. et al. Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California. Environ. Sci. Technol. 56, 14272-14283 (2022). + +22. Alshehri, T. et al. Wildland-urban interface fire ashes as a major source of incidental nanomaterials. J. Hazard. Mater. 443, 130311 (2023). + +28. Jahn, L. G. et al. Metallic and crustal elements in biomass-burning aerosol and ash: Prevalence, significance, and similarity to soil particles. ACS Earth Sp. Chem. 5, 136-148 (2021). + +29. Ré, A. et al. Cytotoxic effects of wildfire ashes: In-vitro responses of skin cells. Environ. Pollut. 285, 117279 (2021). + +<--- Page Split ---> + +"Metals in soils and ash are commonly linked to structural burning within wildland- urban interfaces (WUI) \(^{1,31 - 33}\) , with negligible awareness of wildland landscapes (soils and ash) as an alternative and highly distributed source \(^{1}\) ." + +32. Alexakis, D. E. Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environ. Res. 183, 109153 (2020). + +33. Alam, M. et al. Identification and quantification of Cr, Cu, and As incidental nanomaterials derived from CCA-treated wood in wildland-urban interface fire ashes. J. Hazard. Mater. 445, 130608 (2023). + +"Following wildfires, severely burned areas are often barren and blanketed with ash and loose, rough topsoil leading to enhanced post-fire wind and water erosion \(^{8,39 - 42}\) ." + +41. Yu, Y. & Ginoux, P. Enhanced dust emission following large wildfires due to vegetation disturbance. Nat. Geosci. 2022 1511 15, 878-884 (2022). + +42. Shakesby, R. A. & Doerr, S. H. Wildfire as a hydrological and geomorphological agent. Earth-Science Rev. 74, 269-307 (2006). + +"For example, CaCrO4 was noted after agricultural soil amended with composted Cr(III)- rich tannery sludge was heated at \(500^{\circ}\mathrm{C}^{55}\) ." + +55. Rascio, I. et al. Evidence of hexavalent chromium formation and changes of Cr speciation after laboratory-simulated fires of composted tannery sludges long-term amended agricultural soils. J. Hazard. Mater. 436, 129117 (2022). + +<--- Page Split ---> + +## Reviewer 2 + +The authors have to highlight the novelty of their manuscript. The abstract should be revised to attract the reader's attention. The Introduction section should be improved by adding references dealing soil contamination issues. However, the problem is that the English and the whole organisation of the present version are definitely below an acceptable standard for an international scientific journal. Analytical quality control is missing. Detection limits of the applied methods should be reported. The main problem for this manuscript is its structure. Major parts are missing from the manuscript. My suggestion is to reject this manuscript and encourage the authors to submit a more mature manuscript. + +Response: We appreciate the reviewer's feedback and have sought to make the abstract, and the manuscript, have more pizzazz. With that said, the manuscript was formatted specifically to the Nature guidelines. Further, the authors are all native speakers, and the senior author has published several hundred articles, including ones in Nature and Science. The present manuscript holds to those same standards. It is also worth noting that counter to Reviewer 2, Reviewer 1 stated "I found this paper very pleasant to read. The subject is well introduced, the sites and samples are well described and fit with the objective of the study, the results are well presented and they support the discussion...". Further, several established authors at Stanford have read the manuscript and all support the writing and presentation. Thus, while we don't want to dismiss the comments of the Reviewer, we do see them as anonymous in comparison to others. + +Based on the reviewer's feedback, we have revised our Methods section to include more information regarding our analyses. We have added detection limits for \(\mathrm{Cr(VI)}\) and \(\mathrm{NH_4}\) measurements, and have revised related Figures and Tables to reflect these changes. With the exception of Na (detection limit of \(0.1\mathrm{mg / g}\) ), total concentrations for all elements reported using XRF were significantly greater than respective detection limits. We periodically analyzed certified reference material, NIST 2711a, with bulk soil samples to confirm accuracy of the XRF instrument. For aqueous extractions and associated instrument analyses, we tracked quality assurance in multiple ways. For each round of aqueous extractions using \(10\mathrm{mM}\mathrm{K_2HPO_4 / KH_2PO_4}\) solution, we included at least two centrifuge tubes containing the phosphate buffer solution and no soil/ash that were analyzed similar to samples for \(\mathrm{Cr(VI)}\) and \(\mathrm{NH_4}\) . Unless soil mass was limited, extractions were conducted in triplicate to assess sample heterogeneity. On the UV- Vis and ICP- MS, we analyzed instrument blanks every 15- 20 samples and multiple quality control standard solutions prepared with certified Cr reference solutions throughout each analysis. + +Changes: We have modified the Abstract, added references to the Introduction section, and have sought to ensure the format and writing are consistent with the expected quality of the Nature journals. We have also revised the Methods to include detection limits, where relevant, and have similarly revised Figures and Tables to reflect non- detectable sample concentrations throughout the manuscript. + +Within the Methods section, we now state: + +<--- Page Split ---> + +"Aqueous Extractions and Chemical AnalysisReactive \(\mathrm{Cr(VI)}\) concentrations (most available fraction, including dissolved and adsorbed \(\mathrm{Cr(VI)}\) ) in bulk soil ash samples (bulk and particle size fraction \(< 53 \mu \mathrm{m}\) ) and within soil cores were extracted with \(10 \mathrm{mM} \mathrm{K}_2\mathrm{HPO}_4 / \mathrm{KH}_2\mathrm{PO}_4\) (buffered at \(\mathrm{pH} 7.2\) ) \(^{79,80}\) . Phosphate effectively competes with \(\mathrm{Cr(VI)}\) ions for surface adsorption sites. At circumnatural to alkaline pH ranges in natural soils, it's expected that nearly all aqueous \(\mathrm{Cr}\) is present in the hexavalent form, and that \(\mathrm{Cr(VI)}\) concentrations will be primarily limited by adsorption \(^{81}\) . The clay size fraction (less than \(2 - \mu \mathrm{m}\) diameter) typically has a dominant influence on species retention given their high surface areas and greater number of adsorption sites; therefore, it is likely that the reactive \(\mathrm{Cr(VI)}\) concentrations measured here largely represent the fraction of \(\mathrm{Cr(VI)}\) associated with clay particles. Triplicate samples were agitated in a 1:4 soil/solution ratio for \(24 \mathrm{h}\) , centrifuged (30 min, \(4000 \mathrm{rpm}\) , \(4^{\circ}\mathrm{C}\) ), and filtered through \(0.22 - \mu \mathrm{m}\) filters. A subsample of unacidified filtrate was used to quantify aqueous \(\mathrm{Cr(VI)}\) concentrations using the diphenylcarbazide (DPC) method on a UV- Vis spectrophotometer (Shimadzu UV- 1601) \(^{79,82}\) . The detection limit was \(3 \mu \mathrm{g / L}\) (approximately \(12 \mu \mathrm{g / kg}\) ) \(^{82}\) . Total \(\mathrm{Cr}\) concentrations were determined with inductively coupled plasma mass spectrometry (ICP- MS, Thermo Scientific XSERIES 2), and confirmed that approximately all aqueous \(\mathrm{Cr}\) was in the form of \(\mathrm{Cr(VI)}\) in unburned soil and burned soil and ash, similarly observed in previous studies \(^{36,37}\) . An aliquot of each soil extract was immediately acidified post- filtration and stored in \(2\%\) nitric acid at \(4^{\circ}\mathrm{C}\) until ICP- MS analysis. + +To determine relative differences in \(\mathrm{K}^+\) - extractable \(\mathrm{NH_4^+}\) concentrations (mg \(\mathrm{NH_4^+ - N / kg)}\) within burned and unburned soils (Figure S10), additional unacidified samples (after \(\mathrm{K_2HPO_4 / KH_2PO_4}\) extraction) from 30 of the 38 total soil cores (21 fire- affected and 9 unburned soil cores) were frozen at \(- 20^{\circ}\mathrm{C}\) until chemical analysis. Ammonium is a direct combustion product and will be elevated in the near surface soil after wildfires depending on burn severity \(^{40}\) . Ammonium concentrations in the top 6- cm were measured in triplicate (when sample volume allowed) using a flow injection analyzer (Westco SmartChem 200 Discrete Analyzer), with a detection limit of \(0.05 \mathrm{mg / L}\) \(^{82}\) . + +## Statistical Analyses + +Means and standard errors were calculated for aqueous and solid- phase chemical measurements in all cores using replicates described below. Half the detection limit was used when measured concentrations were below detection limits. Total elemental concentrations were measured in 3- 4 solid- phase aliquots from each soil core (Table S1). At each soil depth interval (1- cm from 0- 6 cm; 2- cm from 6- 16 cm), triplicate aqueous extractions were conducted to evaluate reactive \(\mathrm{Cr(VI)}\) and exchangeable \(\mathrm{NH_4^+}\) concentrations (Figure 2, Figure 3a, Figure S10). In select soil depths within cores, replicates were limited (less than 3) due to solid mass or post- extraction aqueous volume. + +To assess data normality, we applied the Shapiro- Wilk test and reported \(W\) statistics and p- values (Table S7). If data met normality assumptions at the \(95\%\) confidence interval (p- value \(= 0.05\) ), we used two- sided parametric tests; otherwise, we utilized two- sided nonparametric tests. Likewise, we used the f- test to determine equal variance. Unpaired \(t\) + +<--- Page Split ---> + +tests were used to compare mean reactive Cr(VI) concentrations at the \(95\%\) confidence interval in near surface soil (0- 2 cm) of fire- affected and unburned sites based on geology. If one or both datasets were not normally distributed, such as in burned and unburned soils at control depths (10- 16 cm), Mann- Whitney U test was used. Within a soil core, we compared mean reactive Cr(VI) concentrations in surface soil (0- 2 cm) versus control depths (10- 16 cm) using either paired \(t\) test or Wilcoxon signed rank test. Detailed information about and results for each statistical analysis is provided in Tables S2- S5 and Table S7 the Supplementary Information. All statistical analyses were executed using the stats package in R (v. 4.1.3)." + +## From comments made on the manuscript pdf + +Introduction section needs a short paragraph at the beginning to discuss elements distribution issues in wildfire impacted areas worldwide. More papers related to this paragraph will be beneficial for the paper. + +May I suggest, among others, the following articles, e.g.: + +1) Wildfire effects on soil quality. Application on a suburban area of West Attica (Greece). + +Geosciences Journal, 25 (2), 243- 253 (https://doi.org/10.1007/s12303- 020- 0011- 1). + +2) Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environmental Research, 183, 109153, https://doi.org/10.1016/j.envres.2020.109153. + +Research, 183, 109153, https://doi.org/10.1016/j.envres.2020.109153. + +3) Elements' Content in Stream Sediment and Wildfire Ash of Suburban Areas in West Attica (Greece). Water 2022, 14, 310. https://doi.org/10.3390/w14030310 + +Response: We thank the reviewer for the suggestion to add a paragraph discussing elemental concentrations of soil and ash after wildfires. We address past work that has quantified elemental concentrations in soils and ash in the first two paragraphs of the Introduction. We have added the second reference the reviewer suggested to our main text, in addition to a few recent studies on metals and their prevalence as a function of structural burning. References 1 and 3 address elemental concentrations within stream sediments of WUIs, and are ancillary to the introduction on metals within airborne particulate matter, and soil and ash, which are the focus of our study. + +Changes: Based on both reviewers' recommendations, we have added the following references within the main text: + +10. Xu, R. et al. Wildfires, Global Climate Change, and Human Health. N. Engl. J. Med. 383, 2173-2181 (2020). + +26. Jahn, L. G. et al. Metallic and crustal elements in biomass-burning aerosol and ash: Prevalence, significance, and similarity to soil particles. ACS Earth Sp. Chem. 5, 136-148 (2021). + +<--- Page Split ---> + +27. Ré, A. et al. Cytotoxic effects of wildfire ashes: In-vitro responses of skin cells. Environ. Pollut. 285, 117279 (2021). + +29. Boaggio, K. et al. Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California. Environ. Sci. Technol. 56, 14272-14283 (2022). + +30. Alshehri, T. et al. Wildland-urban interface fire ashes as a major source of incidental nanomaterials. J. Hazard. Mater. 443, 130311 (2023). + +32. Alexakis, D. E. Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environ. Res. 183, 109153 (2020). + +33. Alam, M. et al. Identification and quantification of Cr, Cu, and As incidental nanomaterials derived from CCA-treated wood in wildland-urban interface fire ashes. J. Hazard. Mater. 445, 130608 (2023). + +41. Yu, Y. & Ginoux, P. Enhanced dust emission following large wildfires due to vegetation disturbance. Nat. Geosci. 2022 1511 15, 878-884 (2022). + +42. Shakesby, R. A. & Doerr, S. H. Wildfire as a hydrological and geomorphological agent. Earth-Science Rev. 74, 269-307 (2006). + +55. Rascio, I. et al. Evidence of hexavalent chromium formation and changes of Cr speciation after laboratory-simulated fires of composted tannery sludges long-term amended agricultural soils. J. Hazard. Mater. 436, 129117 (2022). + +80. James, B. R. & Bartlett, R. J. Behavior of Chromium in Soils: VII. Adsorption and Reduction of Hexavalent Forms1. J. Environ. Qual. 12, 177 (1983). + +81. Rai, D., Eary, L. E. & Zachara, J. M. Environmental chemistry of chromium. Sci. Total Environ. 86, 15-23 (1989). + +82. McClain, C. N., Fendorf, S., Johnson, S. T., Menendez, A. & Maher, K. Lithologic and redox controls on hexavalent chromium in vadose zone sediments of California's Central Valley. Geochim. Cosmochim. Acta 265, 478-494 (2019). + +Figure 2: Change A, B, and C in Figure plot panels to a, b, and c, reflected in the figure caption + +Response: We appreciate the reviewer's feedback and have made the salient changes. + +Changes: We have revised the figure panels (see below) in addition to references to the figure throughout the main text. + +<--- Page Split ---> +![PLACEHOLDER_21_0] + + +Please avoid using "we". Apply this type of revision all over the manuscript. + +Response: We appreciate the reviewer's concern for the use of "we" within the manuscript. According to the editor and style guidelines for Nature Communications, the use of "we" is allowed and in some places encouraged. + +Changes: No changes were made. + +Please avoid using "we". + +Response: Please refer to previous response. + +Changes: No changes were made. + +Figure 3: Change A, B, and C in Figure plot panels to a, b, and c, reflected in the figure caption + +Response: We appreciate the reviewer's feedback agree with the suggestions. + +Changes: We have revised the figure panels (see below) in addition to references to the figure throughout the main text. + +<--- Page Split ---> +![PLACEHOLDER_22_0] + +
Figure 4: Change A and B in Figure plot panels to a and b reflected in the figure caption
+ +Response: We appreciate the reviewer's feedback and agree with the suggestions. + +Changes: We have revised the figure panels (see below) in addition to references to the figure throughout the main text. Please note that this figure was moved to the Supplementary Information (revised Figure S8), based on the recommendation of Reviewer 1. + +![PLACEHOLDER_22_1] + + +Where are the sections "Results and Discussion" and "Conclusions"? + +<--- Page Split ---> + +Response: We have followed the format for Nature, which often do not have specific sections denoted as "Results and Discussion" nor "Conclusions". Further, within the author guidelines for Nature Communication submissions: "Nature Communications is flexible with regard to the format of initial submissions. Within reason, style and length will not directly influence consideration of a manuscript. We also do not require a particular structure or format at first submission. If and when revisions are required, the editor will provide detailed formatting instructions at that time." Based on the editor's instructions for manuscript revisions, we have defined "Introduction" and "Results" sections in the manuscript according to the Nature Communications formatting instructions. + +Changes: Based on the editor's instructions for manuscript revisions, we have defined "Introduction" and "Results" sections in the manuscript according to the Nature Communications formatting instructions. + +<--- Page Split ---> diff --git a/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c09412c798f03d683eb7f6e18613003f723a640b --- /dev/null +++ b/peer_reviews/12438c2ece72c0a7ec2a093dc88eaba15e637ea325a5525049bbab0bfceb822d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,523 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[68, 110, 361, 139]]<|/det|> +# Peer Review File + +<|ref|>title<|/ref|><|det|>[[83, 154, 914, 210]]<|/det|> +# Metal Toxin Threat in Wildland Fires Determined by Geology and Fire Severity + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 783]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[401, 10, 599, 25]]<|/det|> +# REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[373, 37, 629, 51]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>title<|/ref|><|det|>[[179, 82, 817, 100]]<|/det|> +# Review of manuscript 395109 submitted to Nature Communication + +<|ref|>title<|/ref|><|det|>[[140, 115, 856, 133]]<|/det|> +# Metal toxin threat in wildland fires determined by geology and fire severity + +<|ref|>text<|/ref|><|det|>[[241, 147, 815, 164]]<|/det|> +Alandra Marie Lopez, Juan Lezama Pacheco and Scott Fendorf + +<|ref|>text<|/ref|><|det|>[[117, 196, 881, 394]]<|/det|> +This manuscript presents the results of a study aimed at emphasizing the health threat potentially arising from chromium transformation to its most harmful \(\mathrm{Cr(VI)}\) form in soils and ashes upon wildfires. To reach their objective, the authors analyzed 38 cores drilled in more or less severely burned soils at four Preserves that experienced large wildfires in the North Coast Range of California (USA). The results obtained confirm the catalytic effect of high temperatures generated by wildfires on chromium oxidation in soil, and they point to control of soil geology and fire severity on this effect. They also interestingly indicate that reactive \(\mathrm{Cr(VI)}\) can reach dangerous levels in wind- dispersible particulates found in the surficial layers of the soil at ultramafic settings, and that this harmful form of chromium can persist in the soil/ash system up to one year after the wildfire if rainfalls are not significant. These results yield to the conclusion that more work is required to further evaluate this potential risk around the world. + +<|ref|>text<|/ref|><|det|>[[117, 410, 881, 526]]<|/det|> +I found this paper very pleasant to read. The subject is well introduced, the sites and samples are well described and fit with the objective of the study, the results are well presented and they support the discussion that gives proper attention to the existing literature on the topic and yield to the novel conclusions that geology and fire intensity are important drivers of harmful hexavalent chromium in soils and wind- dispersible soil/ash surface particles, and that the associated health risk can persist up to one year after fire. + +<|ref|>text<|/ref|><|det|>[[117, 542, 881, 689]]<|/det|> +Although the scale of the study (North Coast Range of California, USA) could at first be considered too short to extend its findings at the global scale, I agree with the authors that the number and diversity of sites studied can be considered enough to address this issue. I also agree with the concluding remark on the importance of further evaluating the potential risk of wildfire- induced harmful hexavalent chromium in wind- dispersible soil/ash particles at the global scale. Finally, I agree with the authors that the results provided in this study deserve to be shared with a large audience, ranging from scientists working on the topic to policy makers, public administrators and nature managers. + +<|ref|>text<|/ref|><|det|>[[117, 704, 880, 772]]<|/det|> +For all these reasons, I consider that this manuscript deserves to be published in Nature Communications. I have listed below few issues that I would be interested to see addressed, although only few of them are mandatory for publication. + +<|ref|>sub_title<|/ref|><|det|>[[118, 788, 192, 803]]<|/det|> +## Figure 1 + +<|ref|>text<|/ref|><|det|>[[117, 807, 881, 906]]<|/det|> +I agree that a large fraction of ultramafic/mafic areas are concerned by wildfires at the global scale. Figure 1 shows that these areas are mainly located in the tropical region where most soils are deeply weathered (Utilisols and Oxisols, according to the USDA classification). However, the Fe contents reported in Table S6 suggest that the soils studied in this work do not correspond to these soil types. This raises the question of the actual representativeness of the results regarding tropical areas. I would + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 83, 880, 116]]<|/det|> +recommend that the authors comment on that point, and maybe further consider it in their concluding remarks. + +<|ref|>sub_title<|/ref|><|det|>[[117, 133, 195, 149]]<|/det|> +## Figure 3 + +<|ref|>text<|/ref|><|det|>[[116, 153, 880, 201]]<|/det|> +Maybe, the authors could add the results of comparative statistics tests on barplots and boxplots (either directly report the p- values or show corresponding labels as \*\*\* or \*\*\*)? + +<|ref|>text<|/ref|><|det|>[[116, 202, 880, 317]]<|/det|> +Do they have any hypothesis to explain the much higher concentration in reactive C(VI) measured in the A7 surface soil- ash sample from the serpentine chaparral landscape ? The data provided in Table S6 indicate about twice more total Cr in this sample compared to sample A6 (for instance), but the concentration in reactive Cr(VI) is more than 3 times higher in the bulk fraction and more than 25 three times higher in the \(< 53\mu m\) fraction. Are there any mineralogical differences with the other moderatelyhighly burned serpentine soil- ash samples (A3- A6) that could help to explain that ? + +<|ref|>sub_title<|/ref|><|det|>[[117, 334, 194, 350]]<|/det|> +## Figure 4 + +<|ref|>text<|/ref|><|det|>[[116, 353, 880, 435]]<|/det|> +I wonder if this figure should be maintained in the main text. First, I am not convince that it really supports the assumption that 'total Cr(VI) was most abundant in wind- dispersible soils and ash particulates after high fire severity conditions compared to a low severity sample'. Second, I do not understand why the two figures are plotted on different sizes (A is larger than B). + +<|ref|>text<|/ref|><|det|>[[116, 435, 880, 484]]<|/det|> +It could maybe be replaced by a figure similar to Figure S7 (maybe use only panels A and B or panels C and D from Figure S7 and add two similar panels from a low fire severity burn sample from a serpentine chaparral soil)? + +<|ref|>text<|/ref|><|det|>[[116, 484, 880, 581]]<|/det|> +Whatever, if Figure 4 is maintained in the main text, I would recommend that the authors add some histograms with the estimated number of Cr(VI) and total Cr particles on the two figures, in order to help the reader to better assess the relative proportion of both types of particles. At least, I would recommend that they change for more contrasted colors, in order to help the reader to better visually decipher between Cr(VI) and total Cr particles. + +<|ref|>sub_title<|/ref|><|det|>[[117, 598, 208, 614]]<|/det|> +## Figure S6 + +<|ref|>text<|/ref|><|det|>[[116, 617, 880, 650]]<|/det|> +I would recommend to change the letters for A, B and C in the legend to fit with the letters reported on the figure. + +<|ref|>sub_title<|/ref|><|det|>[[117, 667, 201, 682]]<|/det|> +## Table S6 + +<|ref|>text<|/ref|><|det|>[[116, 686, 880, 899]]<|/det|> +Total concentrations in bulk surface soil- ash samples (and some \(< 53\mu m\) fractions) are displayed, but total concentration in bulk soil samples across the whole soil cores are not provided. I would recommend that the authors provide these data (at least those for Cr) as mean total concentration for rhyolite, melange and serpentine soils in SI, either in the form of a Table or as a figure similar to Figure 2. Such a figure would better show that the fractions of reactive Cr(VI) is very low compared to total Cr concentration. In the same way, I would have been interested to see a figure similar to Figure 2 that would have depicted the fraction of reactive Cr(VI) as a function of the total Cr concentration. Indeed, such a figure would have helped to check if the fraction of reactive Cr(VI) is really higher in serpentine soils. Even if I agree with the authors that the concentration of reactive Cr(VI) is the most relevant parameter to assess a potential environmental and/or health risk, the fraction of reactive Cr(VI) could further inform on the actual mechanism(s) and/or soil characteristic(s) that favor Cr(III) to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 880, 117]]<|/det|> +Cr(VI) oxidation in burned soils. But, maybe this question is beyond the scope of the paper... + +<|ref|>sub_title<|/ref|><|det|>[[117, 132, 208, 149]]<|/det|> +## Figure S7 + +<|ref|>text<|/ref|><|det|>[[117, 152, 880, 234]]<|/det|> +Figure S7Legend : ... from a serpentine chaparral soil...Why did the authors not tried to analyze more some Cr(VI) areas on panel A ?The XANES spectrum at point 1 on panel C shows a well-marked Cr(VI) pre-edge peak but the color code indicate rather low amounts of Cr(VI) at this point. Could the authors explain that ? + +<|ref|>sub_title<|/ref|><|det|>[[118, 250, 410, 267]]<|/det|> +## Suggested additional references + +<|ref|>text<|/ref|><|det|>[[115, 270, 883, 530]]<|/det|> +Suggested additional referencesRascio et al., 2022. Evidence of hexavalent chromium formation and changes of Cr speciation after laboratory- simulated fires of composted tannery sludges long- term amended agricultural soils. Journal of Hazardous Materials, 436, 129117. https://doi.org/10.1016/j.jhazmat.2022.129117Terzano et al., 2021. Fire effects on the distribution and bioavailability of potentially toxic elements (PTEs) in agricultural soils. Chemosphere, 130752. https://doi.org/10.1016/j.chemosphere.2021.130752Ré et al., 2021. Cytotoxic effects of wildfires ashes : In- vitro responses of skin cells. Environmental Pollution, 285, 117279. https://doi.org/10.1016/j.envpol.2021.117279Jahn et al., 2021. Metallic and crustal elements in biomass- burning aerosols and ash: Prevalence, significance, and similarities to soil particles. ACS Earth and Space Chemistry, 5, 136- 148. https://dx.doi.org/10.1021/acsearthspacechem.0c00191Xu et al., 2020. Wildfires, global climate change, and human health. The New England Journal of Medicine, 383, 2173- 2181. https://doi.org/10.1056/NEJMsr2028985 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 85, 437, 101]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 103, 880, 252]]<|/det|> +The authors have to highlight the novelty of their manuscript. The abstract should be revised to attract the reader's attention. The Introduction section should be improved by adding references dealing soil contamination issues. However, the problem is that the English and the whole organisation of the present version are definitely below an acceptable standard for an international scientific journal. Analytical quality control is missing. Detection limits of the applied methods should be reported. The main problem for this manuscript is its structure. Major parts are missing from the manuscript. My suggestion is to reject this manuscript and encourage the authors to submit a more mature manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[345, 91, 651, 111]]<|/det|> +## Response to Review Comments + +<|ref|>sub_title<|/ref|><|det|>[[115, 128, 220, 146]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[115, 162, 880, 355]]<|/det|> +This manuscript presents the results of a study aimed at emphasizing the health threat potentially arising from chromium transformation to its most harmful \(\mathrm{Cr(VI)}\) form in soils and ashes upon wildfires. To reach their objective, the authors analyzed 38 cores drilled in more or less severely burned soils at four Preserves that experienced large wildfires in the North Coast Range of California (USA). The results obtained confirm the catalytic effect of high temperatures generated by wildfires on chromium oxidation in soil, and they point to control of soil geology and fire severity on this effect. They also interestingly indicate that reactive \(\mathrm{Cr(VI)}\) can reach dangerous levels in wind- dispersible particulates found in the surficial layers of the soil at ultramafic settings, and that this harmful form of chromium can persist in the soil/ash system up to one year after the wildfire if rainfalls are not significant. These results yield to the conclusion that more work is required to further evaluate this potential risk around the world. + +<|ref|>text<|/ref|><|det|>[[115, 371, 880, 477]]<|/det|> +I found this paper very pleasant to read. The subject is well introduced, the sites and samples are well described and fit with the objective of the study, the results are well presented and they support the discussion that gives proper attention to the existing literature on the topic and yield to the novel conclusions that geology and fire intensity are important drivers of harmful hexavalent chromium in soils and wind- dispersible soil/ash surface particles, and that the associated health risk can persist up to one year after fire. + +<|ref|>text<|/ref|><|det|>[[115, 493, 881, 633]]<|/det|> +Although the scale of the study (North Coast Range of California, USA) could at first be considered too short to extend its findings at the global scale, I agree with the authors that the number and diversity of sites studied can be considered enough to address this issue. I also agree with the concluding remark on the importance of further evaluating the potential risk of wildfire- induced harmful hexavalent chromium in wind- dispersible soil/ash particles at the global scale. Finally, I agree with the authors that the results provided in this study deserve to be shared with a large audience, ranging from scientists working on the topic to policy makers, public administrators and nature managers. + +<|ref|>text<|/ref|><|det|>[[116, 650, 837, 703]]<|/det|> +For all these reasons, I consider that this manuscript deserves to be published in Nature Communications. I have listed below few issues that I would be interested to see addressed, although only few of them are mandatory for publication. + +<|ref|>text<|/ref|><|det|>[[173, 719, 872, 771]]<|/det|> +Response: We thank the reviewer for their constructive feedback and review of the manuscript's findings and implications. We have reviewed and addressed in detail below the reviewer's suggestions. + +<|ref|>text<|/ref|><|det|>[[171, 788, 790, 807]]<|/det|> +Changes: Please see our specific changes to the reviewer's suggestions below. + +<|ref|>text<|/ref|><|det|>[[115, 823, 879, 894]]<|/det|> +Figure 1: I agree that a large fraction of ultramafic/mafic areas are concerned by wildfires at the global scale. Figure 1 shows that these areas are mainly located in the tropical region where most soils are deeply weathered (Ultisols and Oxisols, according to the USDA classification). However, the Fe contents reported in Table S6 suggest that the soils studied in this work do not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 850, 143]]<|/det|> +correspond to these soil types. This raises the question of the actual representativeness of the results regarding tropical areas. I would recommend that the authors comment on that point, and maybe further consider it in their concluding remarks. + +<|ref|>text<|/ref|><|det|>[[172, 160, 880, 440]]<|/det|> +Response: We agree with the reviewer that the soils in this study are not as deeply weathered as Oxisols and Ultisols, like lateritic soils, common across tropical climate regions (e.g., New Caledonia, Cuba, Brazil, Malaysia, Indonesia, Madagascar, northern Australia). In our study, the average Fe concentration across burned and unburned bulk ultramafic (serpentine) soil was 8.71 wt. \(\%\) , while lateritic soils can contain more than 5x more Fe, typically in the form of crystalline Fe oxides (e.g., hematite, goethite). Chromium is predominantly found within these crystalline Fe oxides. Additionally, lateritic soils are often depleted in Ca, Mg, and Si. The Fe concentrations of our study soils are representative of serpentine soils in Mediterranean or temperate climates (e.g., California, Oregon, Washington, Turkey, Balkans) with moderate Fe oxide content and neutral to alkaline pH. We have added a paragraph within the Discussion section that addresses the characterization of ultramafic soils globally and the limitations of soil types within our study site when considering mechanisms in lateritic and highly weathered metal- rich soils in the tropical regions. Furthermore, we place our findings from field analysis in the context of laboratory studies that examine Cr(VI) generation from Cr(III) solids common to lateritic soils. + +<|ref|>text<|/ref|><|det|>[[173, 456, 546, 473]]<|/det|> +Changes: Within the Discussion we now state: + +<|ref|>text<|/ref|><|det|>[[173, 473, 877, 769]]<|/det|> +"While recognized for urban fires, threats from metal exposure in smoke and dust need to be recognized within wildland fires arising on metal- rich geologies. Across tropical climate regions, deeply weathered lateritic soils are common, in which Cr is predominantly found within crystalline Fe oxides (e.g., hematite, goethite), and soil Fe content may exceed 50 wt. \(\%\) . Past work has quantified the Cr oxidation capacity of Cr- bearing Fe oxides and lateritic soils during heating simulations \(^{35,62}\) . For example, the greatest Cr(VI) formation (more than 40% of total Cr) upon heating hematite occurred at temperatures less than \(400^{\circ}\mathrm{C}\) , while up to 100% of total Cr in goethite transformed to Cr(VI) at \(800^{\circ}\mathrm{C}\) . In Mediterranean or temperate climates (similar to this study's region), ultramafic soils are relatively more enriched in Cr- bearing phyllosilicate minerals (e.g., serpentine), Fe oxide content is moderate (typically less than 10 wt. \(\%\) ) with more amorphous secondary phases, and soil pH is neutral to alkaline pH. In our study, and under natural wildfire conditions, we observed that up to about 0.015% of total Cr was reactive Cr(VI) in burned serpentine soils. Chromium(VI) generation during wildfires depend on fire conditions and host mineralogy; thus, the extent of Cr(VI) formation in lateritic soils may differ from temperate serpentine soils, but field observations of Cr(VI) in burned lateritic soils following wildfires are currently lacking." + +<|ref|>text<|/ref|><|det|>[[115, 785, 857, 821]]<|/det|> +Figure 3: Maybe, the authors could add the results of comparative statistics tests on barplots and boxplots (either directly report the \(p\) - values or show corresponding labels as \(***\) or \(**\) )? + +<|ref|>text<|/ref|><|det|>[[174, 838, 856, 890]]<|/det|> +Response: We performed a one- way ANOVA for Figure 3c and found no statistically significant difference between the three groups (p- value = 0.164). In Figure 3b, we are illustrate reactive concentrations within surface soil- ash based on fire severity (low + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[174, 90, 877, 143]]<|/det|> +versus moderate- high) and particle size (bulk soil less than \(2\mathrm{mm}\) versus the silt and clay- sized fraction less than \(53\mu \mathrm{m}\) ). We are unable to run a two- way ANOVA because burn severity sample sizes are not equal. + +<|ref|>text<|/ref|><|det|>[[173, 160, 879, 247]]<|/det|> +Changes: For Figure 3, we now state "Reactive \(\mathrm{Cr(VI)}\) concentrations ranged from 64 to \(1,060\mu \mathrm{g / kg}\) , with a median concentration of \(257\mu \mathrm{g / kg}\) , and remained elevated compared to concentrations (5- 64 \(\mu \mathrm{g / kg}\) ) within the near surface depths (0- 2 cm) of unburned serpentine soil (Figure 3c); however, these differences were not statistically significant (p- value \(= 0.164\) )." + +<|ref|>text<|/ref|><|det|>[[113, 263, 880, 387]]<|/det|> +Do they have any hypothesis to explain the much higher concentration in reactive \(\mathrm{C(VI)}\) measured in the A7 surface soil- ash sample from the serpentine chaparral landscape? The data provided in Table S6 indicate about twice more total \(\mathrm{Cr}\) in this sample compared to sample A6 (for instance), but the concentration in reactive \(\mathrm{Cr(VI)}\) is more than 3 times higher in the bulk fraction and more than 25 three times higher in the \(< 53\mu \mathrm{m}\) fraction. Are there any mineralogical differences with the other moderately- highly burned serpentine soil- ash samples (A3- A6) that could help to explain that? + +<|ref|>text<|/ref|><|det|>[[173, 403, 877, 508]]<|/det|> +Response: At site A7, the soil experienced longer burning duration and fire intensities with greater biomass combustion that may further contribute to the high- levels of \(\mathrm{Cr(VI)}\) . Unlike A7 (original Figure S9; revised Figure S11), we did not observe mineralogical changes in bulk composition for samples A3- A6 in the surface soil and ash compared to underlying burned soil. We suspect that high temperatures did not persist for sufficient time to alter bulk mineralogy in the latter samples. + +<|ref|>text<|/ref|><|det|>[[173, 525, 877, 682]]<|/det|> +Changes: Within the Results we state: "At site A7, the average reactive \(\mathrm{Cr(VI)}\) concentration was more than three times greater than other moderate- high fire severity sites (Figure 3b). We suspect that longer burning duration and fire intensities with greater biomass combustion contributed to the relatively high- levels of \(\mathrm{Cr(VI)}\) , as this was a severely burned forested area. Importantly, ash from severely burned areas concentrate alkali (Na, K) and alkaline earth (Ca, Mg) metals (often from biomass combustion) that are key for the thermal oxidation of \(\mathrm{Cr(III)}\) \(^{13,43}\) . For example, \(\mathrm{CaCrO_4}\) was noted after agricultural soil amended with composted \(\mathrm{Cr(III)}\) - rich tannery sludge was heated at \(500^{\circ}\mathrm{C}\) \(^{55}\) ." + +<|ref|>text<|/ref|><|det|>[[114, 698, 880, 787]]<|/det|> +Figure 4: I wonder if this figure should be maintained in the main text. First, I am not convince that it really supports the assumption that "total \(\mathrm{Cr(VI)}\) was most abundant in wind- dispersible soils and ash particulates after high fire severity conditions compared to a low severity sample". Second, I do not understand why the two figures are plotted on different sizes (A is larger than B). + +<|ref|>text<|/ref|><|det|>[[113, 803, 875, 857]]<|/det|> +It could maybe be replaced by a figure similar to Figure S7 (maybe use only panels A and B or panels C and D from Figure S7 and add two similar panels from a low fire severity burn sample from a serpentine chaparral soil)? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 865, 178]]<|/det|> +Whatever, if Figure 4 is maintained in the main text, I would recommend that the authors add some histograms with the estimated number of Cr(VI) and total Cr particles on the two figures, in order to help the reader to better assess the relative proportion of both types of particles. At least, I would recommend that they change for more contrasted colors, in order to help the reader to better visually decipher between Cr(VI) and total Cr particles. + +<|ref|>text<|/ref|><|det|>[[173, 194, 870, 334]]<|/det|> +Response: We appreciate the reviewer's feedback regarding Figure 4. We agree that our results of greater Cr(VI)- bearing particles in high severity soil- ash versus low- severity conditions can be clearer, especially by including a histogram of particles containing Cr(VI). Regarding the reviewer's concern about the different size plots, the sample area for large- scale micro- XRF maps of each thin section were not held constant during data collection, resulting in different mapped areas. Due to limitations of the analysis software, we are unable to change for more contrasted colors, but we can update the min/max values for color brightness. + +<|ref|>text<|/ref|><|det|>[[173, 350, 870, 473]]<|/det|> +We have revised Figure 4 to focus on a \(1 - \mu \mathrm{m}\) resolution XRF image containing particles from a high fire severity sample with and without measurable Cr(VI) by XANES analysis. We then moved the original Figure 4 to the Supplementary Information as Figure S8, and added another example of Cr(VI)- containing particles in a \(1 - \mu \mathrm{m}\) resolution XRF image as Figure S9. We also revised the main text related to the figures to highlight the presence of Cr(VI)- containing particles within the high fire severity samples, which was not apparent in low fire severity samples. + +<|ref|>text<|/ref|><|det|>[[174, 490, 682, 508]]<|/det|> +Changes: See revised Figure 4, Figure S8, and Figure S9 below. + +<|ref|>text<|/ref|><|det|>[[173, 524, 872, 630]]<|/det|> +"Using micro- scale X- ray techniques, Cr(VI)- containing soil and ash particulates were identified in a high fire severity sample as opposed to a low fire severity sample (Figure 4; Figure S8). Here, Cr(VI) was associated with mineral surfaces (e.g., adsorbed) or enriched in relatively low- Cr particles with Ca and K (Figure 4, Figure S9). Consistent with particle analysis, reactive Cr(VI) concentrations spanned from 326 to \(13,000 \mu \mathrm{g / kg}\) (Figure 3b)." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[216, 156, 753, 740]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[125, 750, 864, 891]]<|/det|> +
Figure 4 | Total Cr(VI) in wind-dispersible soil and ash particles. a. \(\mu\) -XRF image (pixel resolution: \(1 \mu m\) ) showing the relative intensity of Cr(VI) (green; estimated as the intensity ratio at 5993 and 6010 eV) and total Cr (blue; measured at 6010 eV) within the \(< 53 - \mu m\) size fraction of Cr-bearing soil-ash particulates from a serpentine chaparral that experienced high fire severity (A7). b. Normalized \(\mu\) -XANES spectra (Cr K-edge) from numbered locations on Cr-bearing particles in a. Dashed lines indicate energies characteristic of Cr(VI) (5993 eV), Cr(III) (6003 eV), and total Cr (6010 eV), at which \(\mu\) -XRF images were also collected.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 875, 179]]<|/det|> +Figure S8 | Total Cr(VI) in wind-dispersible soil and ash particles. \(\mu\) - XRF image showing particle distribution of total Cr(VI) (green; estimated as the intensity ratio at 5993 and 6010 eV) and total Cr (blue; measured at 6010 eV) within the \(< 53 - \mu \mathrm{m}\) size fraction of Cr-bearing soil- ash particulates from a. high fire severity site (A7) and b. low fire severity site (A1) in a serpentine chaparral. + +<|ref|>image<|/ref|><|det|>[[128, 182, 777, 444]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 466, 878, 590]]<|/det|> +
Figure S9 | Total Cr(VI) in wind-dispersible soil and ash particles. a. \(\mu\) -XRF image (pixel resolution: \(1\mu \mathrm{m}\) ) showing the relative intensity of \(\mathrm{Cr(VI)}\) (green; estimated as the intensity ratio at 5993 and \(6010\mathrm{eV}\) ) and total Cr (blue; measured at \(6010\mathrm{eV}\) ) within the \(< 53 - \mu \mathrm{m}\) size fraction of Cr-bearing soil-ash particulates from a serpentine chaparral that experienced high fire severity (A7). b. Normalized \(\mu\) -XANES spectra (Cr K-edge) from numbered locations on Cr-bearing particles in a. Dashed lines indicate energies characteristic of \(\mathrm{Cr(VI)}\) (5993 eV), \(\mathrm{Cr(III)}\) (6003 eV), and total Cr (6010 eV).
+ +<|ref|>image<|/ref|><|det|>[[128, 599, 644, 875]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 866, 125]]<|/det|> +Figure S6: I would recommend to change the letters for A, B and C in the legend to fit with the letters reported on the figure. + +<|ref|>text<|/ref|><|det|>[[173, 142, 864, 194]]<|/det|> +Response: Based on the reviewer's recommendation, we have revised the figure, accordingly, by changing uppercase letters to lowercase, in addition to the other figures with sub- panels (similarly identified by Reviewer #2). + +<|ref|>text<|/ref|><|det|>[[173, 212, 652, 229]]<|/det|> +Changes: We changed the letters to lowercase, as requested. + +<|ref|>text<|/ref|><|det|>[[115, 246, 877, 352]]<|/det|> +Table S6: Total concentrations in bulk surface soil- ash samples (and some \(< 53 \mu \mathrm{m}\) fractions) are displayed, but total concentration in bulk soil samples across the whole soil cores are not provided. I would recommend that the authors provide these data (at least those for Cr) as mean total concentration for rhyolite, mélange and serpentine soils in SI, either in the form of a Table or as a figure similar to Figure 2. Such a figure would better show that the fractions of reactive \(\mathrm{Cr(VI)}\) is very low compared to total Cr concentration. + +<|ref|>text<|/ref|><|det|>[[173, 368, 880, 437]]<|/det|> +Response: We thank the reviewer for their recommendation, which we have addressed in the revision. Please refer to our response and changes to the reviewer's next comment related to including a figure showing the fraction of reactive \(\mathrm{Cr(VI)}\) to total Cr concentrations. + +<|ref|>text<|/ref|><|det|>[[173, 455, 881, 542]]<|/det|> +Changes: Using total Cr concentrations reported for soil cores in Table S1, we have revised Table S6 to include the mean total element concentrations for Cr, Fe, Mn, Ni, Ca, Mg, Na, and K in addition to the surface soil- ash sample data so that the reader can compare elemental concentrations in surface soil and ash to bulk soil from different geologies. + +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[114, 91, 875, 160]]<|/det|> +Table S6 | Physicochemical characteristics of bulk soil and ash (up to 2 mm), and selected fine size fractions less than 53 μm, collected from surface layers of the burned serpentine chaparral, and mean elemental concentrations from bulk underlying soil based on geology type (rhyolitic, mélange, and serpentine). + +<|ref|>table<|/ref|><|det|>[[117, 193, 892, 530]]<|/det|> + +
IDFire
Severitya
% Sandb
(2-0.05 mm)
% Siltc
(53-2 μm)
% ClaycCr
mg/kg
Fe
mg/g
Mn
mg/kg
Ni
mg/kg
Ca
mg/g
Mg
mg/g
Na
mg/g
K
mg/g
Surface Soil-Ash
A1L114764.71351152815.577.34.633.76
A2L153269.11203253010.2158<0.11.65
A3M/H160684.2148031179.3148<0.11.54
A4M/H87.511.70.8225678.9143833808.7159<0.10.90
A5M/H99957.71022184910.21252.102.48
A6M/H78.220.21.6197079.21555272629.9174<0.12.86
A7M/H85.712.91.448291021543264317.9211<0.12.29
Less than 53 μm size fraction
A4M/H113394.71975304241.5124<0.13.38
A6M/H94682.71910229444.2133<0.14.41
A7M/H16431052547348934.01892.023.91
Bulk Soild
Rhyolitic \((n=7)\)16234.57968810.77.913.69.70
Melange \((n=16)\)31450.085525910.737.38.1713.2
Serpentine \((n=10)\)237387.1151129294.41503.611.69
+ +<|ref|>text<|/ref|><|det|>[[114, 537, 511, 550]]<|/det|> +a L = Low severity, M = Moderate severity, H = High severity + +<|ref|>text<|/ref|><|det|>[[114, 552, 325, 564]]<|/det|> +b Determined by sieve analysis + +<|ref|>text<|/ref|><|det|>[[114, 567, 464, 580]]<|/det|> +c Determined by laser diffraction particle size counter + +<|ref|>text<|/ref|><|det|>[[114, 580, 854, 606]]<|/det|> +d Bulk soil concentrations are mean values using all soil cores (fire-affected and unburned) for each geology type:rhyolitic \((n=7)\) , mélange \((n=16)\) , and serpentine \((n=10)\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 878, 232]]<|/det|> +In the same way, I would have been interested to see a figure similar to Figure 2 that would have depicted the fraction of reactive \(\mathrm{Cr(VI)}\) as a function of the total \(\mathrm{Cr}\) concentration. Indeed, such a figure would have helped to check if the fraction of reactive \(\mathrm{Cr(VI)}\) is really higher in serpentine soils. Even if I agree with the authors that the concentration of reactive \(\mathrm{Cr(VI)}\) is the most relevant parameter to assess a potential environmental and/or health risk, the fraction of reactive \(\mathrm{Cr(VI)}\) could further inform on the actual mechanism(s) and/or soil characteristic(s) that favor \(\mathrm{Cr(III)}\) to \(\mathrm{Cr(VI)}\) oxidation in burned soils. But, maybe this question is beyond the scope of the paper... + +<|ref|>text<|/ref|><|det|>[[172, 247, 880, 456]]<|/det|> +Response: We thank the reviewer for their recommendation. We agree that the reactive \(\mathrm{Cr(VI)}\) fraction of total \(\mathrm{Cr}\) in soil and soil- ash is low; however, the fraction is relatively higher in near surface soil depths compared to past studies quantifying natural \(\mathrm{Cr(III)}\) oxidation in unburned soils, including a 2017 study at McLaughlin Natural Reserve. Moreover, as the reviewer notes, the hazard imposed by the particulates is related to the reactive \(\mathrm{Cr(VI)}\) . The percentage of total \(\mathrm{Cr}\) that was reactive \(\mathrm{Cr(VI)}\) in unburned serpentine soil was consistent with previous measurements (McClain et al., 2017). Interestingly, the reactive \(\mathrm{Cr(VI)}\) fraction differs based on geology (rhyolite, mélange, and serpentinite). The reactive \(\mathrm{Cr(VI)}\) fraction in rhyolitic and mélange soils composed more of the total \(\mathrm{Cr}\) content than the relative fraction within serpentine soils. In order to highlight these variations across soil depth in fire- affected and unburned sites, we added a figure to the supplementary information. + +<|ref|>text<|/ref|><|det|>[[174, 473, 866, 526]]<|/det|> +Changes: Figure S6 (below) was added to the Supplementary Information. Succeeding figure numbers were updated based on this addition. Within the Results and Discussion sections, we now state: + +<|ref|>text<|/ref|><|det|>[[174, 542, 877, 629]]<|/det|> +"Average \(\mathrm{Cr(VI)}\) concentrations generated in soils derived from mélange (Figure 2b) were more than double the respective levels in rhyolitic soil (Figure 2a) regardless of overlapping ranges in total \(\mathrm{Cr}\) content, 152- 954 and 102- 338 mg/kg, respectively, reflecting the potential contribution of differing mineralogy to \(\mathrm{Cr(VI)}\) generation (Figure S6) 35. " + +<|ref|>text<|/ref|><|det|>[[172, 647, 881, 682]]<|/det|> +"In our study, and under natural wildfire conditions, we observed that up to about \(0.015\%\) of total \(\mathrm{Cr}\) was reactive \(\mathrm{Cr(VI)}\) in burned serpentine soils (Figure S6)." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 875, 211]]<|/det|> +Figure S6 | Fraction of total Cr that is reactive \(\mathrm{Cr(VI)}\) in burned and unburned soils. The ratio of reactive \(\mathrm{Cr(VI)}\) to total Cr concentrations (as a percentage) within a. rhyolite- , b. mélange- , c. serpentinite- derived soil profiles (0- 16 cm) that were not burned (gray; rhyolite, \(n =\) 3; mélange, \(n = 7\) ; serpentinite, \(n = 3\) ) or were fire- affected (colored; rhyolite, \(n = 4\) ; mélange, \(n\) \(= 9\) ; serpentinite, \(n = 7\) ). Percentages were also plotted for serpentinite- derived soil (0- 20 cm) from McClain et al. (2017) in c. for comparison. Each point represents the average percentage for a soil core based on triplicate measurements. + +<|ref|>image<|/ref|><|det|>[[125, 222, 870, 461]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 480, 572, 500]]<|/det|> +
Figure S7: Legend : ... from a serpentine chaparral soil...
+ +<|ref|>text<|/ref|><|det|>[[172, 515, 880, 569]]<|/det|> +Response: We agree with the reviewer's recommendation and have made the appropriate changes. Based on the reviewer's previous recommendations, this figure has revised as Figure 4 and Figure S9. + +<|ref|>text<|/ref|><|det|>[[172, 585, 852, 621]]<|/det|> +Changes: (Figure 4 and Figure S9 caption) "... particles ( \(< 53 \mu \mathrm{m}\) ) from a serpentine chaparral that experienced high fire severity ..." + +<|ref|>text<|/ref|><|det|>[[115, 638, 870, 691]]<|/det|> +Why did the authors not tried to analyze more some \(\mathrm{Cr(VI)}\) areas on panel A? The XANES spectrum at point 1 on panel C shows a well- marked \(\mathrm{Cr(VI)}\) pre- edge peak but the color code indicate rather low amounts of \(\mathrm{Cr(VI)}\) at this point. Could the authors explain that? + +<|ref|>text<|/ref|><|det|>[[172, 708, 875, 760]]<|/det|> +Response: Our XANES analysis was used to corroborate our bulk measurements of reactive \(\mathrm{Cr(VI)}\) . Particles within the XRF map were used to denote the presence and abundance of \(\mathrm{Cr(VI)}\) , corroborating (and visualizing) the reactive fraction measurements. + +<|ref|>text<|/ref|><|det|>[[172, 777, 857, 830]]<|/det|> +Changes: "To corroborate bulk measurements of reactive \(\mathrm{Cr(VI)}\) , we combined multi- energy mapping with \(\mu\) - XANES of select spots on particles to confirm the presence of \(\mathrm{Cr(VI)}\) ." + +<|ref|>sub_title<|/ref|><|det|>[[115, 848, 375, 865]]<|/det|> +## Suggested additional references + +<|ref|>text<|/ref|><|det|>[[115, 866, 861, 901]]<|/det|> +Rascio et al., 2022. Evidence of hexavalent chromium formation and changes of \(\mathrm{Cr}\) speciation after laboratory- simulated fires of composted tannery sludges long- term amended agricultural + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 868, 300]]<|/det|> +soils. Journal of Hazardous Materials, 436, 129117. https://doi.org/10.1016/j.jhazmat.2022.129117 Terzano et al., 2021. Fire effects on the distribution and bioavailability of potentially toxic elements (PTEs) in agricultural soils. Chemosphere, 130752. https://doi.org/10.1016/j.chemosphere.2021.130752 Ré et al., 2021. Cytotoxic effects of wildfires ashes : In- vitro responses of skin cells. Environmental Pollution, 285, 117279. https://doi.org/10.1016/j.envpol.2021.117279 Jahn et al., 2021. Metallic and crustal elements in biomass- burning aerosols and ash: Prevalence, significance, and similarities to soil particles. ACS Earth and Space Chemistry, 5, 136- 148. https://dx.doi.org/10.1021/acsearthspacechem.0c00191 Xu et al., 2020. Wildfires, global climate change, and human health. The New England Journal of Medicine, 383, 2173- 2181. https://doi.org/10.1056/NEJMsr2028985 + +<|ref|>text<|/ref|><|det|>[[172, 315, 868, 352]]<|/det|> +Response: We thank the reviewer for sharing additional references. We agree that these references are relevant to the study. + +<|ref|>text<|/ref|><|det|>[[173, 368, 857, 404]]<|/det|> +Changes: We have added these references suggested above, in addition to a few other recently published and relevant studies, to discussions within the main text. + +<|ref|>text<|/ref|><|det|>[[173, 420, 866, 455]]<|/det|> +"Global wildfire activity represents a rising distributed health risk from smoke and dust inhalation \(^{5 - 10}\) ." + +<|ref|>text<|/ref|><|det|>[[173, 472, 870, 508]]<|/det|> +10. Xu, R. et al. Wildfires, Global Climate Change, and Human Health. N. Engl. J. Med. 383, 2173-2181 (2020). + +<|ref|>text<|/ref|><|det|>[[173, 524, 872, 575]]<|/det|> +"Increased heavy metals in PM have been documented during wildfire episodes and may induce cytotoxicity, increase lung cancer risks, and greatly contribute to oxidative stress \(^{19 - 30}\) ." + +<|ref|>text<|/ref|><|det|>[[174, 593, 830, 648]]<|/det|> +"Suburban fires illustrates the impacts of inhaling Cr(VI)- containing ash within the respiratory tract by measuring Cr(VI) leached with a simulated lung fluid \(^{36,37}\) and discerning Cr mineralogy within nano- sized particulates (< 100 nm) \(^{22,30}\) ." + +<|ref|>text<|/ref|><|det|>[[174, 664, 861, 717]]<|/det|> +21. Boaggio, K. et al. Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California. Environ. Sci. Technol. 56, 14272-14283 (2022). + +<|ref|>text<|/ref|><|det|>[[173, 733, 870, 769]]<|/det|> +22. Alshehri, T. et al. Wildland-urban interface fire ashes as a major source of incidental nanomaterials. J. Hazard. Mater. 443, 130311 (2023). + +<|ref|>text<|/ref|><|det|>[[174, 785, 860, 838]]<|/det|> +28. Jahn, L. G. et al. Metallic and crustal elements in biomass-burning aerosol and ash: Prevalence, significance, and similarity to soil particles. ACS Earth Sp. Chem. 5, 136-148 (2021). + +<|ref|>text<|/ref|><|det|>[[173, 855, 830, 890]]<|/det|> +29. Ré, A. et al. Cytotoxic effects of wildfire ashes: In-vitro responses of skin cells. Environ. Pollut. 285, 117279 (2021). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[174, 106, 880, 160]]<|/det|> +"Metals in soils and ash are commonly linked to structural burning within wildland- urban interfaces (WUI) \(^{1,31 - 33}\) , with negligible awareness of wildland landscapes (soils and ash) as an alternative and highly distributed source \(^{1}\) ." + +<|ref|>text<|/ref|><|det|>[[174, 177, 880, 230]]<|/det|> +32. Alexakis, D. E. Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environ. Res. 183, 109153 (2020). + +<|ref|>text<|/ref|><|det|>[[174, 246, 867, 299]]<|/det|> +33. Alam, M. et al. Identification and quantification of Cr, Cu, and As incidental nanomaterials derived from CCA-treated wood in wildland-urban interface fire ashes. J. Hazard. Mater. 445, 130608 (2023). + +<|ref|>text<|/ref|><|det|>[[174, 333, 870, 369]]<|/det|> +"Following wildfires, severely burned areas are often barren and blanketed with ash and loose, rough topsoil leading to enhanced post-fire wind and water erosion \(^{8,39 - 42}\) ." + +<|ref|>text<|/ref|><|det|>[[174, 385, 816, 421]]<|/det|> +41. Yu, Y. & Ginoux, P. Enhanced dust emission following large wildfires due to vegetation disturbance. Nat. Geosci. 2022 1511 15, 878-884 (2022). + +<|ref|>text<|/ref|><|det|>[[174, 437, 844, 473]]<|/det|> +42. Shakesby, R. A. & Doerr, S. H. Wildfire as a hydrological and geomorphological agent. Earth-Science Rev. 74, 269-307 (2006). + +<|ref|>text<|/ref|><|det|>[[174, 508, 876, 543]]<|/det|> +"For example, CaCrO4 was noted after agricultural soil amended with composted Cr(III)- rich tannery sludge was heated at \(500^{\circ}\mathrm{C}^{55}\) ." + +<|ref|>text<|/ref|><|det|>[[174, 560, 828, 612]]<|/det|> +55. Rascio, I. et al. Evidence of hexavalent chromium formation and changes of Cr speciation after laboratory-simulated fires of composted tannery sludges long-term amended agricultural soils. J. Hazard. Mater. 436, 129117 (2022). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 210, 108]]<|/det|> +## Reviewer 2 + +<|ref|>text<|/ref|><|det|>[[115, 124, 876, 265]]<|/det|> +The authors have to highlight the novelty of their manuscript. The abstract should be revised to attract the reader's attention. The Introduction section should be improved by adding references dealing soil contamination issues. However, the problem is that the English and the whole organisation of the present version are definitely below an acceptable standard for an international scientific journal. Analytical quality control is missing. Detection limits of the applied methods should be reported. The main problem for this manuscript is its structure. Major parts are missing from the manuscript. My suggestion is to reject this manuscript and encourage the authors to submit a more mature manuscript. + +<|ref|>text<|/ref|><|det|>[[173, 281, 870, 473]]<|/det|> +Response: We appreciate the reviewer's feedback and have sought to make the abstract, and the manuscript, have more pizzazz. With that said, the manuscript was formatted specifically to the Nature guidelines. Further, the authors are all native speakers, and the senior author has published several hundred articles, including ones in Nature and Science. The present manuscript holds to those same standards. It is also worth noting that counter to Reviewer 2, Reviewer 1 stated "I found this paper very pleasant to read. The subject is well introduced, the sites and samples are well described and fit with the objective of the study, the results are well presented and they support the discussion...". Further, several established authors at Stanford have read the manuscript and all support the writing and presentation. Thus, while we don't want to dismiss the comments of the Reviewer, we do see them as anonymous in comparison to others. + +<|ref|>text<|/ref|><|det|>[[173, 490, 877, 752]]<|/det|> +Based on the reviewer's feedback, we have revised our Methods section to include more information regarding our analyses. We have added detection limits for \(\mathrm{Cr(VI)}\) and \(\mathrm{NH_4}\) measurements, and have revised related Figures and Tables to reflect these changes. With the exception of Na (detection limit of \(0.1\mathrm{mg / g}\) ), total concentrations for all elements reported using XRF were significantly greater than respective detection limits. We periodically analyzed certified reference material, NIST 2711a, with bulk soil samples to confirm accuracy of the XRF instrument. For aqueous extractions and associated instrument analyses, we tracked quality assurance in multiple ways. For each round of aqueous extractions using \(10\mathrm{mM}\mathrm{K_2HPO_4 / KH_2PO_4}\) solution, we included at least two centrifuge tubes containing the phosphate buffer solution and no soil/ash that were analyzed similar to samples for \(\mathrm{Cr(VI)}\) and \(\mathrm{NH_4}\) . Unless soil mass was limited, extractions were conducted in triplicate to assess sample heterogeneity. On the UV- Vis and ICP- MS, we analyzed instrument blanks every 15- 20 samples and multiple quality control standard solutions prepared with certified Cr reference solutions throughout each analysis. + +<|ref|>text<|/ref|><|det|>[[174, 768, 875, 856]]<|/det|> +Changes: We have modified the Abstract, added references to the Introduction section, and have sought to ensure the format and writing are consistent with the expected quality of the Nature journals. We have also revised the Methods to include detection limits, where relevant, and have similarly revised Figures and Tables to reflect non- detectable sample concentrations throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[175, 873, 510, 890]]<|/det|> +Within the Methods section, we now state: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 90, 881, 457]]<|/det|> +"Aqueous Extractions and Chemical AnalysisReactive \(\mathrm{Cr(VI)}\) concentrations (most available fraction, including dissolved and adsorbed \(\mathrm{Cr(VI)}\) ) in bulk soil ash samples (bulk and particle size fraction \(< 53 \mu \mathrm{m}\) ) and within soil cores were extracted with \(10 \mathrm{mM} \mathrm{K}_2\mathrm{HPO}_4 / \mathrm{KH}_2\mathrm{PO}_4\) (buffered at \(\mathrm{pH} 7.2\) ) \(^{79,80}\) . Phosphate effectively competes with \(\mathrm{Cr(VI)}\) ions for surface adsorption sites. At circumnatural to alkaline pH ranges in natural soils, it's expected that nearly all aqueous \(\mathrm{Cr}\) is present in the hexavalent form, and that \(\mathrm{Cr(VI)}\) concentrations will be primarily limited by adsorption \(^{81}\) . The clay size fraction (less than \(2 - \mu \mathrm{m}\) diameter) typically has a dominant influence on species retention given their high surface areas and greater number of adsorption sites; therefore, it is likely that the reactive \(\mathrm{Cr(VI)}\) concentrations measured here largely represent the fraction of \(\mathrm{Cr(VI)}\) associated with clay particles. Triplicate samples were agitated in a 1:4 soil/solution ratio for \(24 \mathrm{h}\) , centrifuged (30 min, \(4000 \mathrm{rpm}\) , \(4^{\circ}\mathrm{C}\) ), and filtered through \(0.22 - \mu \mathrm{m}\) filters. A subsample of unacidified filtrate was used to quantify aqueous \(\mathrm{Cr(VI)}\) concentrations using the diphenylcarbazide (DPC) method on a UV- Vis spectrophotometer (Shimadzu UV- 1601) \(^{79,82}\) . The detection limit was \(3 \mu \mathrm{g / L}\) (approximately \(12 \mu \mathrm{g / kg}\) ) \(^{82}\) . Total \(\mathrm{Cr}\) concentrations were determined with inductively coupled plasma mass spectrometry (ICP- MS, Thermo Scientific XSERIES 2), and confirmed that approximately all aqueous \(\mathrm{Cr}\) was in the form of \(\mathrm{Cr(VI)}\) in unburned soil and burned soil and ash, similarly observed in previous studies \(^{36,37}\) . An aliquot of each soil extract was immediately acidified post- filtration and stored in \(2\%\) nitric acid at \(4^{\circ}\mathrm{C}\) until ICP- MS analysis. + +<|ref|>text<|/ref|><|det|>[[174, 472, 880, 613]]<|/det|> +To determine relative differences in \(\mathrm{K}^+\) - extractable \(\mathrm{NH_4^+}\) concentrations (mg \(\mathrm{NH_4^+ - N / kg)}\) within burned and unburned soils (Figure S10), additional unacidified samples (after \(\mathrm{K_2HPO_4 / KH_2PO_4}\) extraction) from 30 of the 38 total soil cores (21 fire- affected and 9 unburned soil cores) were frozen at \(- 20^{\circ}\mathrm{C}\) until chemical analysis. Ammonium is a direct combustion product and will be elevated in the near surface soil after wildfires depending on burn severity \(^{40}\) . Ammonium concentrations in the top 6- cm were measured in triplicate (when sample volume allowed) using a flow injection analyzer (Westco SmartChem 200 Discrete Analyzer), with a detection limit of \(0.05 \mathrm{mg / L}\) \(^{82}\) . + +<|ref|>sub_title<|/ref|><|det|>[[175, 630, 328, 647]]<|/det|> +## Statistical Analyses + +<|ref|>text<|/ref|><|det|>[[174, 664, 877, 805]]<|/det|> +Means and standard errors were calculated for aqueous and solid- phase chemical measurements in all cores using replicates described below. Half the detection limit was used when measured concentrations were below detection limits. Total elemental concentrations were measured in 3- 4 solid- phase aliquots from each soil core (Table S1). At each soil depth interval (1- cm from 0- 6 cm; 2- cm from 6- 16 cm), triplicate aqueous extractions were conducted to evaluate reactive \(\mathrm{Cr(VI)}\) and exchangeable \(\mathrm{NH_4^+}\) concentrations (Figure 2, Figure 3a, Figure S10). In select soil depths within cores, replicates were limited (less than 3) due to solid mass or post- extraction aqueous volume. + +<|ref|>text<|/ref|><|det|>[[174, 821, 875, 891]]<|/det|> +To assess data normality, we applied the Shapiro- Wilk test and reported \(W\) statistics and p- values (Table S7). If data met normality assumptions at the \(95\%\) confidence interval (p- value \(= 0.05\) ), we used two- sided parametric tests; otherwise, we utilized two- sided nonparametric tests. Likewise, we used the f- test to determine equal variance. Unpaired \(t\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 90, 867, 247]]<|/det|> +tests were used to compare mean reactive Cr(VI) concentrations at the \(95\%\) confidence interval in near surface soil (0- 2 cm) of fire- affected and unburned sites based on geology. If one or both datasets were not normally distributed, such as in burned and unburned soils at control depths (10- 16 cm), Mann- Whitney U test was used. Within a soil core, we compared mean reactive Cr(VI) concentrations in surface soil (0- 2 cm) versus control depths (10- 16 cm) using either paired \(t\) test or Wilcoxon signed rank test. Detailed information about and results for each statistical analysis is provided in Tables S2- S5 and Table S7 the Supplementary Information. All statistical analyses were executed using the stats package in R (v. 4.1.3)." + +<|ref|>sub_title<|/ref|><|det|>[[115, 281, 483, 300]]<|/det|> +## From comments made on the manuscript pdf + +<|ref|>text<|/ref|><|det|>[[115, 315, 866, 368]]<|/det|> +Introduction section needs a short paragraph at the beginning to discuss elements distribution issues in wildfire impacted areas worldwide. More papers related to this paragraph will be beneficial for the paper. + +<|ref|>text<|/ref|><|det|>[[115, 385, 566, 403]]<|/det|> +May I suggest, among others, the following articles, e.g.: + +<|ref|>text<|/ref|><|det|>[[115, 403, 850, 427]]<|/det|> +1) Wildfire effects on soil quality. Application on a suburban area of West Attica (Greece). + +<|ref|>text<|/ref|><|det|>[[115, 427, 780, 444]]<|/det|> +Geosciences Journal, 25 (2), 243- 253 (https://doi.org/10.1007/s12303- 020- 0011- 1). + +<|ref|>text<|/ref|><|det|>[[115, 444, 852, 477]]<|/det|> +2) Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environmental Research, 183, 109153, https://doi.org/10.1016/j.envres.2020.109153. + +<|ref|>text<|/ref|><|det|>[[115, 478, 850, 493]]<|/det|> +Research, 183, 109153, https://doi.org/10.1016/j.envres.2020.109153. + +<|ref|>text<|/ref|><|det|>[[115, 494, 850, 528]]<|/det|> +3) Elements' Content in Stream Sediment and Wildfire Ash of Suburban Areas in West Attica (Greece). Water 2022, 14, 310. https://doi.org/10.3390/w14030310 + +<|ref|>text<|/ref|><|det|>[[173, 544, 855, 682]]<|/det|> +Response: We thank the reviewer for the suggestion to add a paragraph discussing elemental concentrations of soil and ash after wildfires. We address past work that has quantified elemental concentrations in soils and ash in the first two paragraphs of the Introduction. We have added the second reference the reviewer suggested to our main text, in addition to a few recent studies on metals and their prevalence as a function of structural burning. References 1 and 3 address elemental concentrations within stream sediments of WUIs, and are ancillary to the introduction on metals within airborne particulate matter, and soil and ash, which are the focus of our study. + +<|ref|>text<|/ref|><|det|>[[173, 699, 839, 733]]<|/det|> +Changes: Based on both reviewers' recommendations, we have added the following references within the main text: + +<|ref|>text<|/ref|><|det|>[[173, 750, 869, 785]]<|/det|> +10. Xu, R. et al. Wildfires, Global Climate Change, and Human Health. N. Engl. J. Med. 383, 2173-2181 (2020). + +<|ref|>text<|/ref|><|det|>[[173, 803, 860, 855]]<|/det|> +26. Jahn, L. G. et al. Metallic and crustal elements in biomass-burning aerosol and ash: Prevalence, significance, and similarity to soil particles. ACS Earth Sp. Chem. 5, 136-148 (2021). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 90, 830, 126]]<|/det|> +27. Ré, A. et al. Cytotoxic effects of wildfire ashes: In-vitro responses of skin cells. Environ. Pollut. 285, 117279 (2021). + +<|ref|>text<|/ref|><|det|>[[173, 142, 861, 195]]<|/det|> +29. Boaggio, K. et al. Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California. Environ. Sci. Technol. 56, 14272-14283 (2022). + +<|ref|>text<|/ref|><|det|>[[173, 212, 870, 247]]<|/det|> +30. Alshehri, T. et al. Wildland-urban interface fire ashes as a major source of incidental nanomaterials. J. Hazard. Mater. 443, 130311 (2023). + +<|ref|>text<|/ref|><|det|>[[173, 264, 878, 316]]<|/det|> +32. Alexakis, D. E. Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environ. Res. 183, 109153 (2020). + +<|ref|>text<|/ref|><|det|>[[173, 333, 866, 386]]<|/det|> +33. Alam, M. et al. Identification and quantification of Cr, Cu, and As incidental nanomaterials derived from CCA-treated wood in wildland-urban interface fire ashes. J. Hazard. Mater. 445, 130608 (2023). + +<|ref|>text<|/ref|><|det|>[[173, 402, 818, 438]]<|/det|> +41. Yu, Y. & Ginoux, P. Enhanced dust emission following large wildfires due to vegetation disturbance. Nat. Geosci. 2022 1511 15, 878-884 (2022). + +<|ref|>text<|/ref|><|det|>[[173, 454, 844, 490]]<|/det|> +42. Shakesby, R. A. & Doerr, S. H. Wildfire as a hydrological and geomorphological agent. Earth-Science Rev. 74, 269-307 (2006). + +<|ref|>text<|/ref|><|det|>[[173, 507, 828, 560]]<|/det|> +55. Rascio, I. et al. Evidence of hexavalent chromium formation and changes of Cr speciation after laboratory-simulated fires of composted tannery sludges long-term amended agricultural soils. J. Hazard. Mater. 436, 129117 (2022). + +<|ref|>text<|/ref|><|det|>[[173, 576, 856, 612]]<|/det|> +80. James, B. R. & Bartlett, R. J. Behavior of Chromium in Soils: VII. Adsorption and Reduction of Hexavalent Forms1. J. Environ. Qual. 12, 177 (1983). + +<|ref|>text<|/ref|><|det|>[[173, 628, 841, 664]]<|/det|> +81. Rai, D., Eary, L. E. & Zachara, J. M. Environmental chemistry of chromium. Sci. Total Environ. 86, 15-23 (1989). + +<|ref|>text<|/ref|><|det|>[[173, 680, 857, 733]]<|/det|> +82. McClain, C. N., Fendorf, S., Johnson, S. T., Menendez, A. & Maher, K. Lithologic and redox controls on hexavalent chromium in vadose zone sediments of California's Central Valley. Geochim. Cosmochim. Acta 265, 478-494 (2019). + +<|ref|>text<|/ref|><|det|>[[116, 785, 875, 806]]<|/det|> +Figure 2: Change A, B, and C in Figure plot panels to a, b, and c, reflected in the figure caption + +<|ref|>text<|/ref|><|det|>[[171, 821, 848, 840]]<|/det|> +Response: We appreciate the reviewer's feedback and have made the salient changes. + +<|ref|>text<|/ref|><|det|>[[173, 856, 867, 891]]<|/det|> +Changes: We have revised the figure panels (see below) in addition to references to the figure throughout the main text. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 110, 872, 360]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 398, 714, 417]]<|/det|> +Please avoid using "we". Apply this type of revision all over the manuscript. + +<|ref|>text<|/ref|><|det|>[[173, 433, 875, 486]]<|/det|> +Response: We appreciate the reviewer's concern for the use of "we" within the manuscript. According to the editor and style guidelines for Nature Communications, the use of "we" is allowed and in some places encouraged. + +<|ref|>text<|/ref|><|det|>[[173, 503, 447, 521]]<|/det|> +Changes: No changes were made. + +<|ref|>text<|/ref|><|det|>[[115, 538, 312, 555]]<|/det|> +Please avoid using "we". + +<|ref|>text<|/ref|><|det|>[[173, 572, 529, 590]]<|/det|> +Response: Please refer to previous response. + +<|ref|>text<|/ref|><|det|>[[173, 608, 447, 625]]<|/det|> +Changes: No changes were made. + +<|ref|>text<|/ref|><|det|>[[115, 642, 875, 661]]<|/det|> +Figure 3: Change A, B, and C in Figure plot panels to a, b, and c, reflected in the figure caption + +<|ref|>text<|/ref|><|det|>[[172, 677, 784, 696]]<|/det|> +Response: We appreciate the reviewer's feedback agree with the suggestions. + +<|ref|>text<|/ref|><|det|>[[172, 712, 867, 747]]<|/det|> +Changes: We have revised the figure panels (see below) in addition to references to the figure throughout the main text. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[122, 117, 868, 325]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 373, 820, 393]]<|/det|> +
Figure 4: Change A and B in Figure plot panels to a and b reflected in the figure caption
+ +<|ref|>text<|/ref|><|det|>[[171, 408, 818, 428]]<|/det|> +Response: We appreciate the reviewer's feedback and agree with the suggestions. + +<|ref|>text<|/ref|><|det|>[[173, 444, 867, 514]]<|/det|> +Changes: We have revised the figure panels (see below) in addition to references to the figure throughout the main text. Please note that this figure was moved to the Supplementary Information (revised Figure S8), based on the recommendation of Reviewer 1. + +<|ref|>image<|/ref|><|det|>[[130, 535, 867, 835]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 860, 662, 878]]<|/det|> +Where are the sections "Results and Discussion" and "Conclusions"? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 89, 866, 265]]<|/det|> +Response: We have followed the format for Nature, which often do not have specific sections denoted as "Results and Discussion" nor "Conclusions". Further, within the author guidelines for Nature Communication submissions: "Nature Communications is flexible with regard to the format of initial submissions. Within reason, style and length will not directly influence consideration of a manuscript. We also do not require a particular structure or format at first submission. If and when revisions are required, the editor will provide detailed formatting instructions at that time." Based on the editor's instructions for manuscript revisions, we have defined "Introduction" and "Results" sections in the manuscript according to the Nature Communications formatting instructions. + +<|ref|>text<|/ref|><|det|>[[174, 281, 855, 334]]<|/det|> +Changes: Based on the editor's instructions for manuscript revisions, we have defined "Introduction" and "Results" sections in the manuscript according to the Nature Communications formatting instructions. + +<--- Page Split ---> diff --git a/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1f5a0cd12523f9984e8cf93f88530bca2d3f0da4 --- /dev/null +++ b/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,231 @@ + +# nature portfolio + +Peer Review File + +# Temperate forests can deliver future wood demand and climate-change mitigation dependent on afforestation and circularity + +Corresponding Author: Ms Eilidh Forster + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The manuscript "Can temperate forests deliver both future wood demand and climate- change mitigation?" by Forster et al. presents the results of the lifecycle assessments of the global warming potential of wood supply under the growing wood demand scenarios. The analysis is fairly clear and thorough, however I have several reservations outlined below: + +1. There are no uncertainty estimates around the wood supply and demand as well as GWP. Incorporating the uncertainty analysis into the study would provide insight into where the future research efforts should be directed in order to reduce the uncertainty, as well as help evaluate the confidence in the reported estimates. For an example of uncertainty analysis using CBM-CFS please refer to J.M. Metsaranta, C.H. Shaw, W.A. Kurz, C. Boisvenue, and S. Morken. 2017. Uncertainty of inventory-based estimates of the carbon dynamics of Canada's managed forest (1990-2014). Canadian Journal of Forest Research. 47(8): 1082-1094. https://doi.org/10.1139/cjfr-2017-0088 + +2. Although authors did state in the methods section that risks of pests disease, wind, fire, warming and other climate change effects would not significantly alter the study findings because the risks are highly uncertain and would apply similarly across the study, I don't think it is the case. Fire, drought, changing productivity due to climate change would not change the wood demand, however they could profoundly affect the wood supply. Given the length of the projections in the study, warming would substantially increase heterotrophic respiration, and therefore would alter GWP projections. Drought events could substantially and repeatedly reduce forest yield due via inhibition of the photosynthetic rate and increasing mortality rate. Warming temperatures and changing precipitation regimes are also likely to affect forest net primary production. Increasing fire frequency and severity could profoundly affect the wood supply. I don't think these effects are negligible for GWP and wood supply estimates, and therefore should be considered in the study, especially given the 100-year projection time. + +3. The study results are generalized for a "temperate country", however most of the data used in the study are for the UK, why not make the study focused on the UK? It would make it easier to assess the feasibility of the proposed scenarios and allow to avoid generalized statements (as a reader, I had a little trouble with those). + +Reviewer #2 + +(Remarks to the Author) + +Summary: In this manuscript, authors present a combined application of forest carbon models and life cycle assessment (LCA) to estimate global warming (GW) impacts (+/-) of harvested wood products' (HWPs) value chain in a temperate country (appears to be UK). For projected high and low wood demands, the GW impacts are assessed for different scenarios within the country (changing rotation length of forests, increasing rate of production, and expansion of forest area) and overseas imports from non-temperate forests (tropical country). This kind of study is an interesting attempt to integrate two areas of the forest products value chain (forestry and HWPs) for policy implications. The results indicate that increased wood use is not a climate-change solution unless afforestation, increasing forest productivity under sustainable forest management, and mitigating demand increases through enhanced circularity and cascading of wood use are also integrated + +<--- Page Split ---> + +into the strategy. I am offering below some comments/suggestions to improve the manuscript. + +Major comments + +103- 104: The current production and consumption levels of this temperate country should have been characterized to visualize the gap between demand and supply for the reference year 2023, and the how different scenarios or intended decisions might close this gap and influence GW impacts. + +107- 108: What was the reason for selection of Sitka spruce forest in afforestation? The authors might discuss whether the results would be different if the forests were Douglas- fir or Western hemlock. + +Figure 2: Please change y- axis units to Tg CO2e. + +234: More interpretations could be added in 'high wood demand projection' results. + +264- 267: Not clearly explained how GWP impact of alternative increased due to increase in overseas wood supply. Prolonged use of non- wood product and fuel alternatives? + +278- 279: Please add explanation to this sentence, it seems confusing that more imports from tropical afforestation is better. 295: Clarity is needed on what type of non- wood product is considered substituted by HWPs. Because substitution credits for two type of non- wood products can be different for same HWP. + +340: BECCS is associated with 'energy substitution' like non- wood products avoided is associated with 'product substitution'. There aren't a lot of interpretations in the results and discussion that focused on energy substitution. 600: there is no 'ix' in the components of LCA system boundary. Including via ...? + +724- 740: This whole paragraph does not seem to be fit for methodology. Its more suitable for introduction. + +747- 748: What is the per capita timber consumption in UK, which translates to \(30\%\) increase in demand by 2050? 754: In this paragraph, it would be good if authors give a brief about the different HWP end- uses (primary and cascading + +uses) considered and maybe a justification for selecting HWP uses. + +766: More clarity on defining the overseas forest type and carbon storage. Also, was the transportation distance and mode of transport included in the analysis? + +785: Why 'GWP (forest C) impact...'? Forest carbon can be stored, emitted, or removed but cannot be equated directly to GWP. + +Overall, the methods section appears weak to me and needs a thorough revision to ensure that work can be reproduced. Minor comments + +325 and 330: should it be trip or tip? + +723: why question marks in middle of the sentence? + +Double numbering in references + +Some of the links in supplementary excel file are broken. Please check. + +## Reviewer #3 + +(Remarks to the Author) + +The aim of this case study is to quantify the GHG mitigation potential of different measures or forest management options (in particular afforestation) in terms of meeting an increasing demand for wood, assuming that existing models for the forest sector tend to "underestimate" forest carbon fluxes. + +In fact, in addition to the development of forest carbon stocks, the delayed release of biogenic carbon through the use of wood as material as well as potential shifting effects of the GHG emission balances associated with the life cycle of these wood- containing product systems and their potential product alternatives do also have an impact on the overall GHG balance. + +However, the implementation of the presented approach to estimate the total GHG impact of different management scenarios compared to the defined reference, in our view appears to be completely inadequate in this study. It does not comply with applicable international standards and existing state- of- the- art knowledge. + +While the modeling of carbon storage development in the forest using the internationally recognized Carbon Budget Model for the Canadian Forestry Service appears adequate, the methodological inadequacies relate in particular to the life cycle assessment methodology, on the basis of whose standard- compliant, consistent and transparent implementation avoided emissions through "product substitution" can be estimated in the first place. In order to adequately consider process chain emissions and based on those also "avoided emissions from product substitution", it is crucial to meet the internationally standardized requirements for life cycle assessment (including ISO 14040/44 and ISO 21930). The mere summation of unrelated LCA process information from a background database (here: Ecolnvent) is inadequate - at least for the processes outside the forest along the processing and value chain. The data used for calculating "primary avoided emissions (FF/product substitution)" are also completely unsuitable. + +Furthermore, the simplified calculation of assumed carbon storage effects through the use of wood as a material (harvested wood products) contradicts central core requirements in the calculation as set out in the methodological guidelines and requirements provided by IPCC (incl. e.g. the consideration of inherited emissions). In consequence, the HWP contribution trough biogenic carbon storage as well as potential "avoided emissions" appear to be massively overestimated. + +While it seems undisputed, even without the present study, that "the expansion of the (industrial) bioeconomy should be linked to the availability of raw materials in order to avoid unrealistic supply expectations," statements to the effect that "considerable HWP- C storage and product substitution credits can be achieved simultaneously" are not at all tenable on the basis of this simple and, in our view, completely methodologically inadequate implementation. + +<--- Page Split ---> + +The simple comparison of a changing supply of forest wood with a modeled demand for this raw material (including potential gaps) can also be carried out without balancing all GHG emissions relevant to the forestry and wood sector. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors provided fairly comprehensive responses to the reviewers' comments. Yet, after reading the revised paper there is a dissonance between the level of detail in the manuscript and practical applicability of the findings. In the response to reviewers authors noted that this manuscript implements a framework laid out in an earlier paper published in Nature Communications, however the implementation is rather abstract, an interested party (e.g. government of a temperate country) would have to re- do the analyses (i.e. implement the framework to their specific country) and may get substantially different results. This makes me question the value of this particular manuscript, given lack of connection to any specific country, for which the feasibility of the generated estimates could be evaluated. + +In my opinion, the treatment of the uncertainties associated with the effects of climate change and disturbances on productivity and GWP was fairly simplistic, not illustrated in all figures and not illustrated for GWP estimates. Lastly, please correct the following: CBM- CFS stands for "Carbon Budget Model of the Canadian Forest Sector". + +Reviewer #2 + +(Remarks to the Author) + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +# Author Responses to Reviewer Comments + +We are grateful to and thank the reviewers for taking time to consider our manuscript. + +
Remarks to AuthorAuthor Responses
Reviewer #1:
The manuscript "Can temperate forests deliver both
future wood demand and climate-change mitigation?" by Forster et al. presents the results of the lifecycle
assessments of the global warming potential of wood
supply under the growing wood demand scenarios. The analysis is fairly clear and thorough, however I have
several reservations outlined below:
We thank the reviewer for the positive comments and valuable specific suggestions to
further enhance the paper.
1There are no uncertainty estimates around the wood
supply and demand as well as GWP. Incorporating the
uncertainty analysis into the study would provide
insight into where the future research efforts should be directed in order to reduce the uncertainty, as well as
help evaluate the confidence in the reported estimates. For an example of uncertainty analysis using CBM-CFS
please refer to J.M. Metsaranta, C.H. Shaw, W.A. Kurz,
C. Boisvenue, and S. Morken. 2017. Uncertainty of
inventory-based estimates of the carbon dynamics of
Canada's managed forest (1990-2014). Canadian
Journal of Forest Research. 47(8): 1082-1094.
https://doi.org/10.1139/cjfr-2017-0088
The demand profiles modelled are based on the outcome of an extensive literature
review of wood demand modelling studies. We recognise and account for the significant
uncertainty sourrounding future wood demand projections (indicated by the wide range
of demand projections published in the literature) by modelling two different demand
profiles in the present study. These two demand profiles capture the range in the
published literature. LCA of forest management scenarios under each of these demand
profile senarios indicates the degree of uncertainty and sensitivity of results to future
demand projection assumptions. In dealing with uncertainties for the supply side, we
have taken the simple and clear approach of testing multiple scenarios of variation in
future forest productivity (yield). We believe that this is an efficient way of integrating all of these causes of uncertainty listed by the reviewer 1 comment 2. We have also added
the following text to the 'Discussion section' lines 375-379: "There is an urgent need for
more integrated evidence that incorporates holistic assessment of prospective forestry
value chains alongside landscape dynamics (including forest management and
expansion), at both national and global scales, including improved estimates of the
potential impacts of climate change-linked threats to the future productivity of both
temperate forests and the other forest biomes providing wood production."
See continuation of this response in response to reviewer 1 comment 2 below.
+ +<--- Page Split ---> + + +
Remarks to AuthorAuthor Responses
2Although authors did state in the methods section that risks of pests disease, wind, fire, warming and other climate change effects would not significantly alter the study findings because the risks are highly uncertain and would apply similarly across the study, I don't think it is the case. Fire, drought, changing productivity due to climate change would not change the wood demand, however they could profoundly affect the wood supply. Given the length of the projections in the study, warming would substantially increase heterotrophic respiration, and therefore would alter GWP projections. Drought events could substantially and repeatedly reduce forest yield due via inhibition of the photosynthetic rate and increasing mortality rate. Warming temperatures and changing precipitation regimes are also likely to affect forest net primary production. Increasing fire frequency and severity could profoundly affect the wood supply. I don't think these effects are negligible for GWP and wood supply estimates, and therefore should be considered in the study, especially given the 100-year projection time.As described in response to the previous comment, we believe that the approach to test multiple scenarios of variation in future forest productivity (yield) is an efficient way of integrating many of the causes of uncertainty listed by the reviewer. It is the approach that is most compatible with the LCA methodology of our study. Therefore, to address this specific reviewer requirement we have introduced a further pair of scenarios ('lower productivity' than the reference scenario) to model impact of possible ecosystem shocks (leading to yield reduction) that could arise from natural disturbance such as pests, disease, wind, drought and fire. These new scenarios are a modification of the 'reference rotation' existing forest (YC18, 50-yr rotation) + afforestation combination. The new scenarios are a transition of a) 15% and b) 30% of the existing forest from YC18 to YC12 ramping up over a 15 year period (remaining as a 50-yr harvest rotation), followed by recovery back to YC18 after one harvest rotation, ramping back down over a 15-yr period. (The afforestation assumptions were unchanged). Essentially the scenario represents a rapid shock of -two different intensities (affect on 15% &amp; 30% of the total area), followed by recovery after harvest (at 50-yrs old). A detailed description of the basis for the parameterisation of these two scenarios (two and a half pages of text) based on a substantial new literature review (32 references cited) is provided in the new Supplementary Information file "Modelling of natural disturbances - 'reduced productivity'". We recognise that natural disturbances, the intensity and rate of impact, and management responses to these are complex and therefore the modelling options available are vast. We believe the new scenarios selected correspond to contrasting realistic disturbance patterns presented in the reviewed literature and therefore offer additional insights to the other scenarios already modelled. We have included the new results in an updated version of 'Supplementary Data 3', alongside the results of all the other scenarios modelled in this paper.
We modelled these two new scenarios under high and low demand projections and for the variation in afforestation rates and planting periods. We found that the new 'lower productivity' scenarios in this set led to higher net forest carbon loss (domestic and overseas) than the 'reference rotation' scenarios, as well as other changes, yet these disturbances do not change the overall results or findings of the study. We have added text on this to the methodology (lines 701-708) and results section of the manuscript
+ +<--- Page Split ---> + + +
Remarks to AuthorAuthor Responses
(lines 114-118; 169-172; and 201-204) and have included a more comprehensive description in the new Supplementary Information file (Supplementary Methods 1) in order to minimise additional word count.
+ +<--- Page Split ---> + + +
Remarks to AuthorAuthor Responses
3The study results are generalized for a “temperate country”, however most of the data used in the study are for the UK, why not make the study focused on the UK? It would make it easier to assess the feasibility of the proposed scenarios and allow to avoid generalized statements (as a reader, I had a little trouble with those).We intentionally kept the analysis generic for a hypothetical temperate country rather than a UK-specific case study in order to provide evidence that has broad relevance. (The UK is not 'typical' in that it has a high baseline of imports and low domestic wood production.) This study is prospective in nature and focuses on the impacts of change, based on transparent assumptions for future changes (e.g. rate of decarbonisation, projected wood demand increase, shifts in forest management, different afforestation rates) that are not unique to the UK (or any other country) or dependant on historic conditions that may be unique to the UK.
In order to perform the LCA we needed to make assumptions on typical product breakouts at the forest gate and at a sawmill and a representative wood product flow. Given limitations on public availability of this kind of data, we used data available for the UK as the basis for these assumptions. These assumptions are broadly representative across temperate countries beyond the UK given the similarities in technology and wood value chains. For example, typical rates of conversion of softwood to sawtimber at sawmills is similar across temperate regions. We have edited the Methodology 'Scope of LCA' section (e.g. lines 622-628) to try and improve the reconciliation between our use of UK data and generalised statements.
+ +<--- Page Split ---> + + +
Remarks to AuthorAuthor Responses
Reviewer #2
Summary: In this manuscript, authors present a combined application of forest carbon models and life cycle assessment (LCA) to estimate global warming (GW) impacts (+/-) of harvested wood products' (HWPs) value chain in a temperate country (appears to be UK). For projected high and low wood demands, the GW impacts are assessed for different
scenarios within the country (changing rotation length of forests, increasing rate of production, and expansion of forest area) and overseas imports from non-temperate forests (tropical country). This kind of study is an interesting attempt to integrate two areas of the forest products value chain (forestry and HWPs) for policy implications. The results indicate that increased wood use is not a climate-change solution unless afforestation, increasing forest productivity under sustainable forest management, and mitigating
demand increases through enhanced circularity and
cascading of wood use are also integrated into the strategy. I am offering below some comments/suggestions to improve the manuscript.
We thank the reviewer for the positive comments and endorsement of the important findings of the paper.
Major comments
1103-104: The current production and consumption levels of this temperate country should have been characterized to visualize the gap between demand and supply for the
reference year 2023, and the how different scenarios or
intended decisions might close this gap and influence GW
impacts.
We intentionally defined a hypothetical scenario in which domestic production equals domestic consumption in the reference year 2023, as indicated in Figure 1. As described in our response to reviewer 1 comment 3 above, we have taken this hypothetical approach rather than characterising the actual production and
consumption levels of a specific country in order to provide evidence that has
broad relevance. (For example, the UK is not 'typical' in that it has a high baseline of imports and low domestic wood production.) It makes sense for a
counterfactual lifecycle assessment (which is concerned with change from a
baseline) to start the scenario with production = consumption rather that starting
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with a deficit or surplus, which would make interpretation of results more challenging.
We then visualise how the different scenarios close the gap between future (increasing) demand and supply in Figure 1 by colour coding the supply deficit in red (and the supply surplus in pink). We have also added some additional text in the Figure 1 title to improve this description.
2107-108: What was the reason for selection of Sitka spruce forest in afforestation? The authors might discuss whether the results would be different if the forests were Douglas-fir or Western hemlock.Sitka spruce was selected as it grows widely (native to west coast of Canada and the United States; now planted in 16 countries worldwide, including as the predominant plantation species in the UK, Ireland and Denmark - all countries with low forest cover). Sitka spruce also grows well in degraded upland sites where land is most economically viable for afforestation, unlike productive Douglas fir or western hemlock, which require lower altitude land that is of higher value for food production. LCA results would not be different if different species (or species mixes) were modelled unless a significantly different yield class (growth curve) was also assumed. It is the yield rather than the species choice that drives the GWP impact results (which of course would be related in specific geographic contexts but in a hypothetical forest study such as this, the yield class is specified independently by the modeller as a representative average across contexts). In this way, the choice of Sitka spruce is simply a proxy for commercial conifer species. However, we believe that the clarity of the manuscript benefits from naming the case species, which links to the UK sawmill and-representative wood product flow data used in the study.
3Figure 2: Please change y-axis units to Tg CO2e.We have made this change.
4234: More interpretations could be added in 'high wood demand projection' results.We are pleased that Reviewer 2 sees further possible interpretations that we could include. We would welcome the opportunity to add more interpretations, however because of the journal's strict word limits this would necessitate making significant cuts to other parts of the text, which would sacrifice their clarity and content. Given the importance of these other components of the paper that would have to be cut, with regret we have concluded that adding more
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interpretations to the 'high wood demand projection' results would be of net cost to the value of the paper.
5264-267: Not clearly explained how GWP impact of alternative increased due to increase in overseas wood supply. Prolonged use of non-wood product and fuel alternatives?We have added words in this sentence (line 290) to clarify that the GWP impact of the alternative is "curtailed HWP supply" i.e. prolonged use of non-wood product and fuel alternatives. We have also added further description to indicate the relative impact of the specific overseas scenarios ('Boreal 1,2&3, Tropical CVL and Tropical (afforestation)' in Fig. 4) in which emissions associated with supplying the wood shortfall are higher or lower that the emissions from 'curtailed HWP supply' (prolonged use of non-wood and fuel alternatives).
6278-279: Please add explanation to this sentence, it seems confusing that more imports from tropical afforestation is better.It is unclear to us why this is confusing as it seems to be clearly shown in the results reported in Fig. 4. We do acknowledge the potential disbenefits of new tropical afforestation in lines 363-364 ("numerous socio-economic51 and biodiversity conservation20 caveats". In essence, increasing demand for fast-growing tropical tree species, which could be established on the large areas of degraded land in the tropics (if local socio-economic conditions make them available), could actually enhance terrestrial carbon stocks.
7295: Clarity is needed on what type of non-wood product is considered substituted by HWPs. Because substitution credits for two type of non-wood products can be different for same HWP.In response to this point, to avoid adding significant additional word count, we have added text to the methodology (line 616-617) and in the Fig. 5 title to direct readers to supplementary information for more detail on the substitution credits assumptions (supplementary figure 1 and supplementary Table 1). We also direct readers to Forster et al. (2021) where the methodology was originally published. We have also improved figure 5 in the present paper to convey, among other things, the product substitution assumptions more clearly.
8340: BECCS is associated with 'energy substitution' like non-wood products avoided is associated with 'product substitution'. There aren't a lot of interpretations in the results and discussion that focused on energy substitution.We have expanded the sentence referring to BECCS to mention product substitution and emphasise the permanent geological storage of biogenic carbon that contributes a carbon sink. Lines 368-369.
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9600: there is no ‘ix’ in the components of LCA system boundary. Including via ...?We have checked the numbering of components of the LCA system boundary in figure 5 and in the text and cannot find anything missing.
10724-740: This whole paragraph does not seem to be fit for methodology. Its more suitable for introduction.We believe that the paragraph is important for justifying the important selection of assumptions for the projected rate of demand increase used in the study, which is a core aspect of the study's methodology. We have edited and changed the order of the text to make the inclusion of this text in the methodology more fluent and justified. E.g. lines 779-785 have been moved from earlier in the section.
11747-748: What is the per capita timber consumption in UK, which translates to 30% increase in demand by 2050?We do not believe that including per capita timber consumption in the UK is relevant to the study. The 30% increase by 2050 statistic was included as this is a date that many published projections focus on, because it is an important date for many 'net zero' targets as mandated by the 2015 Paris Agreement of UNFCCC, and therefore a statistic that readers are likely to be interested in. As stated in our response to reviewer 2 comment 1, we have prioritised assumptions that are non-country-specific and forward looking wherever possible, to maximise the transferability of results. In essence, the critical (and transferable) mathematical/biophysical dynamic is the rate of demand increase from the baseline relative to the expansion rate of baseline forest area (through afforestation) and the (change in) productivity of existing (and new) forest.
12754: In this paragraph, it would be good if authors give a brief about the different HWP end-uses (primary and cascading uses) considered and maybe a justification for selecting HWP uses.The primary HWP end-uses are described in the methodology and further in the SI, including in a revised system diagram (Figure 5) indicating major processes and products. Details of cascading uses and also justification for the assumptions used are provided in Forster et al. (2021), which we cite in the methodology. We believe there is insufficient justification to repeat all of this detail here, especially on account of the word count restrictions.
13766: More clarity on defining the overseas forest type and carbon storage. Also, was the transportation distance and mode of transport included in the analysis?Description of the overseas forest types is provided in the following paragraphs (lines 827-856).
We did not include assumed differences in transport distances between overseas and domestic HWPs because, in a previous study (Forster et al., 2023), we found that these differences made a very small contribution (less than 0.01%) relative to the net GWP impact of the value chain.
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14785: Why 'GWP (forest C) impact...'? Forest carbon can be stored, emitted, or removed but cannot be equated directly to GWP.GWP (forest C) impact is defined in the previous paragraph as the 'GWP impact of fluxes in forest carbon stocks'. We have added '(GWP (forest C))' after this definition to add clarity. It refers to the GWP impact associated with net CO2e fluxes to/from the forest. Line 828.
15Overall, the methods section appears weak to me and needs a thorough revision to ensure that work can be reproduced.We have carefully addressed each of the reviewers specific comments and assume that in doing so we have met the need expressed here.
Minor comments
16325 and 330: should it be trip or tip?Tip means to tilt, tumble or topple. In this context, 'the balance... can tip from sink to source', means the balance can tilt or shift from sink to source.
17723: why question marks in middle of the sentence?We have removed these.
18Double numbering in referencesWe have removed these.
19Some of the links in supplementary excel file are broken. Please check.We have checked the supplementary Excel files and assume that the reviewer is referring to the 'HWP calculation module' (Supplementary Data 2). The broken links are the emissions factors cells that link to the original LCA worksheet (Supplementary Data 1) that generated them. These links do not work once the workbook is resaved in a different location. However, in the final version of these supplementary data files, which will be stored in a permanent repository or in the publisher's website, we will endeavour to ensure the links all work.
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Reviewer #3:
1The aim of this case study is to quantify the GHG mitigation potential of different measures or forest management
options (in particular afforestation) in terms of meeting an
increasing demand for wood, assuming that existing models for the forest sector tend to "underestimate" forest carbon fluxes.
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2In fact, in addition to the development of forest carbon stocks, the delayed release of biogenic carbon through the use of wood as material as well as potential shifting effects of the GHG emission balances associated with the life cycle of these wood-containing product systems and their potential product alternatives do also have an impact on the overall GHG balance.We are not clear on whether this forms part of the reviewer's summary of the paper or is a comment requiring our response. In case it is the latter, we provide the following clarification. We agree with the reviewer about the importance of impacts throughout the wood products life cycle. Yet, the full climate mitigation effects of forestry are often under-represented because: (i) LCA approaches that (sometimes) better represent substitution and possible end-of-life carbon storage effects are usually only applied to specific products (partial wood flows out of forests); (ii) inventory approaches that attempt to represent all wood products, typically neglect short-lived wood products used for energy, and don't attribute substitution effects back to the forest sector; (iii) both LCA and inventory approaches often disregard cascading uses of wood, and associated second (and possible further) substitutions, along with extended carbon storage effects; (iv) only very prospective analyses consider future BECCS deployment that could lock up biogenic carbon indefinitely.
3However, the implementation of the presented approach to estimate the total GHG impact of different management scenarios compared to the defined reference, in our view appears to be completely inadequate in this study. It does not comply with applicable international standards and existing state-of-the-art knowledge.We are surprised by this comment, which we strongly believe does not reflect the content and rigour of our study or its compliance with the highest international standards. International standards apply to specific types of accounting, such as Environmental Product Declarations for (LCA of) wood products or UNFCCC guidelines for national GHG inventory accounting. In contrast, there are no such "standards" for the prospective consequential LCA of entire forest and multiple downstream product systems, which is the innovative methodological approach of our study. That is precisely what makes this approach so valuable - it transcends the accounting rules that are applied to deal with truncated system boundaries (e.g. how to allocate forest effects to specific downstream products). This paper builds on the state-of-the-art approach applied in our earlier, highly-cited manuscript published in Nature Communications (Forster et al., 2021), and applies it to a temperate forest system under different management and expansion regimes; this is highly novel. To reiterate, we are not attempting to calculate product footprints as per various international standards, but instead (as is befitting for a submission to Nature Communications) to provide a novel, holistic and rigorous analysis of the climate mitigation efficacy of different forest
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management strategies, providing key new evidence for policy makers and an innovative novel approach for researchers.
4While the modeling of carbon storage development in the forest using the internationally recognized Carbon Budget Model for the Canadian Forestry Service appears adequate, the methodological inadequacies relate in particular to the life cycle assessment methodology, on the basis of whose standard-compliant, consistent and transparent implementation avoided emissions through "product substitution" can be estimated in the first place. In order to adequately consider process chain emissions and based on those also "avoided emissions from product substitution", it is crucial to meet the internationally standardized requirements for life cycle assessment (including ISO 14040/44 and ISO 21930). The mere summation of unrelated LCA process information from a background database (here: Ecolnvent) is inadequate - at least for the processes outside the forest along the processing and value chain. The data used for calculating "primary avoided emissions (FF/product substitution)" are also completely unsuitable.As explained in our previous response, our study is categorically not an attributional LCA, which seems to have been the assumption of the reviewer. Instead it is a consequential LCA. That said, this study does fully comply with ISO 14040 and 14044 standards (which in reality are a basic framework to structure LCA), insofar as it: provides a clear goal and scope of the study; calculates an inventory that accounts for relevant changes within the expanded system boundary; applies GWP100 characterisation factors for the life cycle impact assessment phase; interprets results with clear regard for the question and methods used (now including important sensitivity analyses). Furthermore, this study uses system expansion in preference to allocation, as recommended in the allocation hierarchy advocated by the ISO standards. The study categorically does not sum "unrelated" LCA process information - incurred or avoided processes are clearly indicated in the system boundary (Supplementary Fig. 1 and in Fig. 5, also now improved), based on a consequential LCA approach that incorporates all changes associated with the scenarios vs the baseline counterfactual situation.
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5Furthermore, the simplified calculation of assumed carbon storage effects through the use of wood as a material (harvested wood products) contradicts central core requirements in the calculation as set out in the methodological guidelines and requirements provided by IPCC (incl. e.g. the consideration of inherited emissions). In consequence, the HWP contribution trough biogenic carbon storage as well as potential “avoided emissions” appear to be massively overestimated.Our methodology does not contradict core requirements of the IPCC and from this comment we do not understand how the reviewer considers that it does so. The IPCC provide guidelines for a number of approaches to deal with HWP C storage at a national scale. All of them are based on the fact that biogenic carbon harvested from the forest is "lost" from the terrestrial system, but some of this carbon "reappears" in longer-lived HWPs (with a large deficit reflecting biomass assumed to be immediately oxidised via combustion for bioenergy or for kiln drying of wood in sawmills). Our approach fully respects the biogenic carbon balance - in fact much more explicitly than typical national inventory accounting (with which we are fully familiar), because flows into all main products, both short- and long-lived, are accounted for, and the duration of carbon storage in each of these products, and any subsequent products, is explicitly accounted for in our methodology. Again, this is the benefit of our expanded boundary approach (across products and through time) - it minimises the influence of "cut-off" rules and associated value judgements, which often profoundly influence carbon footprints at the wood product level.
6While it seems undisputed, even without the present study, that "the expansion of the (industrial) bioeconomy should be linked to the availability of raw materials in order to avoid unrealistic supply expectations, " statements to the effect that "considerable HWP-C storage and product substitution credits can be achieved simultaneously" are not at all tenable on the basis of this simple and, in our view, completely methodologically inadequate implementation.Without any further insight from the reviewer as to where our methodology is inadequate, it is difficult to address this comment. We acknowledge that our original system diagram did not fully represent the scope of our methodology (although it was described fully in the text and illustrated in Supplementary Fig.1). Therefore, we hope that the improved system diagram in the resubmitted manuscript helps understanding of precisely how we have linked forest C storage with HWP-C storage and substitution, and long-term CCS C-storage effects in a coherent manner. As previously mentioned, this builds on the methodology of Forster et al. (2021) published in Nature Communications.
7The simple comparison of a changing supply of forest wood with a modeled demand for this raw material (including potential gaps) can also be carried out without balancing all GHG emissions relevant to the forestry and wood sector.It is true that a simple comparison of changing supply of forest wood with demand could be carried out in isolation. However, that would not address the important policy question of what the climate mitigation effect would be of alternative forest strategies that aim to minimise the gap between future supply and demand. That is where this paper provides a unique and robust contribution to the scientific literature, for which its rigorous methodological consequential LCA approach is essential.
+ +<--- Page Split ---> + +# 1.1.1.1.1.1.1.1.1.1.1 + +<--- Page Split ---> + +## Author response to reviewer comments + +We are once again grateful for the opportunity to respond to Reviewer comments. We have addressed the comments below and in doing so believe we have further enhanced the article, as outlined in our response. All changes to the manuscript are highlighted in 'tracked- changes'. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +## Comment 1 + +The authors provided fairly comprehensive responses to the reviewers' comments. Yet, after reading the revised paper there is a dissonance between the level of detail in the manuscript and practical applicability of the findings. In the response to reviewers authors noted that this manuscript implements a framework laid out in an earlier paper published in Nature Communications, however the implementation is rather abstract, an interested party (e.g. government of a temperate country) would have to re- do the analyses (i.e. implement the framework to their specific country) and may get substantially different results. This makes me question the value of this particular manuscript, given lack of connection to any specific country, for which the feasibility of the generated estimates could be evaluated. + +## Response to Comment 1 + +We thank Reviewer 1 for their further comments, to which we have given careful consideration. The main point raised here is that the methodology remains abstract, such that others would need to perform their own analysis. We fully agree that researchers and other interested parties should perform context- specific analysis, and not rely solely on the results of a generic country case study (of the kind we use here to demonstrate the rigour, power and applicability of the framework that we have developed in this paper). We have subtly revised framing to reflect this, with additional clarity and emphasis on the novel methodological framework we have developed. In a new SI, we outline the framework in diagram, table and text form, highlighting its substantial novel components not previously published, and describe its implementation with reference to important parameters and examples of datasets and models of the kind that are available to generate context- specific results. However, we maintain that using a generic temperate country with an even- aged forest as an illustrative case study provides important insights that do have broad relevance for readers, whereas using the context of a specific country would not, owing to the unique nature of its forest- age deviations. We have made small edits throughout the manuscript to further emphasise to readers the importance of tailoring studies to specific contexts, especially where the results of such studies are intended to inform policy. + +The framework sets out our exploratory approach for identifying 'low regrets' climate solutions for the forestry value chain by evaluating a range of plausible future scenarios, using powerful integrated forest modelling and lifecycle assessment (LCA) (Supplementary Fig. 1 & Supplementary Methods 1). + +The present study builds substantially on the detailed prospective dynamic LCA modelling of entire forest- wood value chains developed and explained in Forster et al. (2021). Crucially, in the present study the full downstream greenhouse gas (GHG) mitigation consequences of wood use and end- of + +<--- Page Split ---> + +life management are considered - including carbon storage and material and energy substitution within a decarbonising future economy. Novel aspects to the present study (shown in pink in the new Supplementary Fig. 1) include calculating potential future wood supply deficit by comparing projected wood demand curves to wood supply from a range of modelled (expanded) temperate forest management scenarios, and linking the supply deficit to marginal expansion of supply from other regions. + +Elaboration of the framework within the SI will facilitate interested parties to follow our approach for a relevant study context (Supplementary Table 1). We signpost readers to this SI at multiple points in the manuscript. + +## Comment 2 + +In my opinion, the treatment of the uncertainties associated with the effects of climate change and disturbances on productivity and GWP was fairly simplistic, not illustrated in all figures and not illustrated for GWP estimates. + +## Response to Comment 2 + +We acknowledge the simple treatment of climate change and disturbances (which we note can vary considerably, geographically) for our generic temperate country study. However, we maintain that this approach is appropriate to illustrate the magnitude of effect associated with highly uncertain future events. Recent articles pertaining to climate mitigation modelling highlight the need for "robust" rather than optimised decision making in the face of deep uncertainty and high complexity (Workman et al. (2021) and Workman et al. (2024)). We now cite these articles to further justify our approach, and propose natural disturbance events as a key parameter to represent (where possible) this impact within the proposed framework when tailoring scenarios in future studies for specific context. + +## Comment 3 + +Lastly, please correct the following: CBM- CFS stands for "Carbon Budget Model of the Canadian Forest Sector". + +## Response to Comment 3 + +Corrections made. + +<--- Page Split ---> diff --git a/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..06963a3a62a9361833e5aa23ecd5615d62d2311a --- /dev/null +++ b/peer_reviews/1254719c0acba0418d8fd83238729cf53dbf1fdc706c2f360fa1b3b6652b884b/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,307 @@ +<|ref|>title<|/ref|><|det|>[[73, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 97, 296, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 874, 235]]<|/det|> +# Temperate forests can deliver future wood demand and climate-change mitigation dependent on afforestation and circularity + +<|ref|>text<|/ref|><|det|>[[73, 249, 420, 266]]<|/det|> +Corresponding Author: Ms Eilidh Forster + +<|ref|>text<|/ref|><|det|>[[70, 299, 864, 314]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 351, 144, 364]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 377, 219, 390]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 403, 160, 416]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 430, 238, 443]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 443, 904, 482]]<|/det|> +The manuscript "Can temperate forests deliver both future wood demand and climate- change mitigation?" by Forster et al. presents the results of the lifecycle assessments of the global warming potential of wood supply under the growing wood demand scenarios. The analysis is fairly clear and thorough, however I have several reservations outlined below: + +<|ref|>text<|/ref|><|det|>[[72, 494, 916, 574]]<|/det|> +1. There are no uncertainty estimates around the wood supply and demand as well as GWP. Incorporating the uncertainty analysis into the study would provide insight into where the future research efforts should be directed in order to reduce the uncertainty, as well as help evaluate the confidence in the reported estimates. For an example of uncertainty analysis using CBM-CFS please refer to J.M. Metsaranta, C.H. Shaw, W.A. Kurz, C. Boisvenue, and S. Morken. 2017. Uncertainty of inventory-based estimates of the carbon dynamics of Canada's managed forest (1990-2014). Canadian Journal of Forest Research. 47(8): 1082-1094. https://doi.org/10.1139/cjfr-2017-0088 + +<|ref|>text<|/ref|><|det|>[[71, 586, 920, 716]]<|/det|> +2. Although authors did state in the methods section that risks of pests disease, wind, fire, warming and other climate change effects would not significantly alter the study findings because the risks are highly uncertain and would apply similarly across the study, I don't think it is the case. Fire, drought, changing productivity due to climate change would not change the wood demand, however they could profoundly affect the wood supply. Given the length of the projections in the study, warming would substantially increase heterotrophic respiration, and therefore would alter GWP projections. Drought events could substantially and repeatedly reduce forest yield due via inhibition of the photosynthetic rate and increasing mortality rate. Warming temperatures and changing precipitation regimes are also likely to affect forest net primary production. Increasing fire frequency and severity could profoundly affect the wood supply. I don't think these effects are negligible for GWP and wood supply estimates, and therefore should be considered in the study, especially given the 100-year projection time. + +<|ref|>text<|/ref|><|det|>[[72, 728, 909, 768]]<|/det|> +3. The study results are generalized for a "temperate country", however most of the data used in the study are for the UK, why not make the study focused on the UK? It would make it easier to assess the feasibility of the proposed scenarios and allow to avoid generalized statements (as a reader, I had a little trouble with those). + +<|ref|>text<|/ref|><|det|>[[73, 794, 161, 806]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 820, 238, 833]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 833, 923, 938]]<|/det|> +Summary: In this manuscript, authors present a combined application of forest carbon models and life cycle assessment (LCA) to estimate global warming (GW) impacts (+/-) of harvested wood products' (HWPs) value chain in a temperate country (appears to be UK). For projected high and low wood demands, the GW impacts are assessed for different scenarios within the country (changing rotation length of forests, increasing rate of production, and expansion of forest area) and overseas imports from non-temperate forests (tropical country). This kind of study is an interesting attempt to integrate two areas of the forest products value chain (forestry and HWPs) for policy implications. The results indicate that increased wood use is not a climate-change solution unless afforestation, increasing forest productivity under sustainable forest management, and mitigating demand increases through enhanced circularity and cascading of wood use are also integrated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 707, 61]]<|/det|> +into the strategy. I am offering below some comments/suggestions to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 61, 188, 72]]<|/det|> +Major comments + +<|ref|>text<|/ref|><|det|>[[72, 73, 895, 112]]<|/det|> +103- 104: The current production and consumption levels of this temperate country should have been characterized to visualize the gap between demand and supply for the reference year 2023, and the how different scenarios or intended decisions might close this gap and influence GW impacts. + +<|ref|>text<|/ref|><|det|>[[72, 112, 900, 138]]<|/det|> +107- 108: What was the reason for selection of Sitka spruce forest in afforestation? The authors might discuss whether the results would be different if the forests were Douglas- fir or Western hemlock. + +<|ref|>text<|/ref|><|det|>[[73, 139, 409, 152]]<|/det|> +Figure 2: Please change y- axis units to Tg CO2e. + +<|ref|>text<|/ref|><|det|>[[72, 152, 641, 165]]<|/det|> +234: More interpretations could be added in 'high wood demand projection' results. + +<|ref|>text<|/ref|><|det|>[[72, 165, 860, 191]]<|/det|> +264- 267: Not clearly explained how GWP impact of alternative increased due to increase in overseas wood supply. Prolonged use of non- wood product and fuel alternatives? + +<|ref|>text<|/ref|><|det|>[[72, 191, 910, 229]]<|/det|> +278- 279: Please add explanation to this sentence, it seems confusing that more imports from tropical afforestation is better. 295: Clarity is needed on what type of non- wood product is considered substituted by HWPs. Because substitution credits for two type of non- wood products can be different for same HWP. + +<|ref|>text<|/ref|><|det|>[[72, 229, 846, 268]]<|/det|> +340: BECCS is associated with 'energy substitution' like non- wood products avoided is associated with 'product substitution'. There aren't a lot of interpretations in the results and discussion that focused on energy substitution. 600: there is no 'ix' in the components of LCA system boundary. Including via ...? + +<|ref|>text<|/ref|><|det|>[[72, 268, 792, 281]]<|/det|> +724- 740: This whole paragraph does not seem to be fit for methodology. Its more suitable for introduction. + +<|ref|>text<|/ref|><|det|>[[72, 281, 850, 308]]<|/det|> +747- 748: What is the per capita timber consumption in UK, which translates to \(30\%\) increase in demand by 2050? 754: In this paragraph, it would be good if authors give a brief about the different HWP end- uses (primary and cascading + +<|ref|>text<|/ref|><|det|>[[72, 308, 540, 320]]<|/det|> +uses) considered and maybe a justification for selecting HWP uses. + +<|ref|>text<|/ref|><|det|>[[72, 321, 920, 346]]<|/det|> +766: More clarity on defining the overseas forest type and carbon storage. Also, was the transportation distance and mode of transport included in the analysis? + +<|ref|>text<|/ref|><|det|>[[72, 347, 899, 373]]<|/det|> +785: Why 'GWP (forest C) impact...'? Forest carbon can be stored, emitted, or removed but cannot be equated directly to GWP. + +<|ref|>text<|/ref|><|det|>[[72, 373, 899, 399]]<|/det|> +Overall, the methods section appears weak to me and needs a thorough revision to ensure that work can be reproduced. Minor comments + +<|ref|>text<|/ref|><|det|>[[72, 399, 320, 412]]<|/det|> +325 and 330: should it be trip or tip? + +<|ref|>text<|/ref|><|det|>[[72, 413, 430, 425]]<|/det|> +723: why question marks in middle of the sentence? + +<|ref|>text<|/ref|><|det|>[[72, 426, 297, 437]]<|/det|> +Double numbering in references + +<|ref|>text<|/ref|><|det|>[[72, 438, 560, 451]]<|/det|> +Some of the links in supplementary excel file are broken. Please check. + +<|ref|>sub_title<|/ref|><|det|>[[72, 476, 162, 490]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 503, 237, 515]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 515, 916, 555]]<|/det|> +The aim of this case study is to quantify the GHG mitigation potential of different measures or forest management options (in particular afforestation) in terms of meeting an increasing demand for wood, assuming that existing models for the forest sector tend to "underestimate" forest carbon fluxes. + +<|ref|>text<|/ref|><|det|>[[72, 567, 901, 620]]<|/det|> +In fact, in addition to the development of forest carbon stocks, the delayed release of biogenic carbon through the use of wood as material as well as potential shifting effects of the GHG emission balances associated with the life cycle of these wood- containing product systems and their potential product alternatives do also have an impact on the overall GHG balance. + +<|ref|>text<|/ref|><|det|>[[72, 632, 921, 673]]<|/det|> +However, the implementation of the presented approach to estimate the total GHG impact of different management scenarios compared to the defined reference, in our view appears to be completely inadequate in this study. It does not comply with applicable international standards and existing state- of- the- art knowledge. + +<|ref|>text<|/ref|><|det|>[[72, 685, 914, 803]]<|/det|> +While the modeling of carbon storage development in the forest using the internationally recognized Carbon Budget Model for the Canadian Forestry Service appears adequate, the methodological inadequacies relate in particular to the life cycle assessment methodology, on the basis of whose standard- compliant, consistent and transparent implementation avoided emissions through "product substitution" can be estimated in the first place. In order to adequately consider process chain emissions and based on those also "avoided emissions from product substitution", it is crucial to meet the internationally standardized requirements for life cycle assessment (including ISO 14040/44 and ISO 21930). The mere summation of unrelated LCA process information from a background database (here: Ecolnvent) is inadequate - at least for the processes outside the forest along the processing and value chain. The data used for calculating "primary avoided emissions (FF/product substitution)" are also completely unsuitable. + +<|ref|>text<|/ref|><|det|>[[72, 815, 913, 867]]<|/det|> +Furthermore, the simplified calculation of assumed carbon storage effects through the use of wood as a material (harvested wood products) contradicts central core requirements in the calculation as set out in the methodological guidelines and requirements provided by IPCC (incl. e.g. the consideration of inherited emissions). In consequence, the HWP contribution trough biogenic carbon storage as well as potential "avoided emissions" appear to be massively overestimated. + +<|ref|>text<|/ref|><|det|>[[72, 879, 919, 932]]<|/det|> +While it seems undisputed, even without the present study, that "the expansion of the (industrial) bioeconomy should be linked to the availability of raw materials in order to avoid unrealistic supply expectations," statements to the effect that "considerable HWP- C storage and product substitution credits can be achieved simultaneously" are not at all tenable on the basis of this simple and, in our view, completely methodologically inadequate implementation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 923, 75]]<|/det|> +The simple comparison of a changing supply of forest wood with a modeled demand for this raw material (including potential gaps) can also be carried out without balancing all GHG emissions relevant to the forestry and wood sector. + +<|ref|>text<|/ref|><|det|>[[73, 99, 144, 112]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 125, 219, 138]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 151, 160, 164]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 177, 238, 190]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 190, 920, 280]]<|/det|> +The authors provided fairly comprehensive responses to the reviewers' comments. Yet, after reading the revised paper there is a dissonance between the level of detail in the manuscript and practical applicability of the findings. In the response to reviewers authors noted that this manuscript implements a framework laid out in an earlier paper published in Nature Communications, however the implementation is rather abstract, an interested party (e.g. government of a temperate country) would have to re- do the analyses (i.e. implement the framework to their specific country) and may get substantially different results. This makes me question the value of this particular manuscript, given lack of connection to any specific country, for which the feasibility of the generated estimates could be evaluated. + +<|ref|>text<|/ref|><|det|>[[72, 280, 852, 320]]<|/det|> +In my opinion, the treatment of the uncertainties associated with the effects of climate change and disturbances on productivity and GWP was fairly simplistic, not illustrated in all figures and not illustrated for GWP estimates. Lastly, please correct the following: CBM- CFS stands for "Carbon Budget Model of the Canadian Forest Sector". + +<|ref|>text<|/ref|><|det|>[[73, 333, 161, 346]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 359, 238, 372]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 740, 916, 793]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 793, 797, 806]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 806, 911, 858]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 858, 618, 871]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[83, 124, 314, 140]]<|/det|> +# Author Responses to Reviewer Comments + +<|ref|>text<|/ref|><|det|>[[83, 162, 545, 178]]<|/det|> +We are grateful to and thank the reviewers for taking time to consider our manuscript. + +<|ref|>table<|/ref|><|det|>[[81, 195, 911, 810]]<|/det|> + +
Remarks to AuthorAuthor Responses
Reviewer #1:
The manuscript "Can temperate forests deliver both
future wood demand and climate-change mitigation?" by Forster et al. presents the results of the lifecycle
assessments of the global warming potential of wood
supply under the growing wood demand scenarios. The analysis is fairly clear and thorough, however I have
several reservations outlined below:
We thank the reviewer for the positive comments and valuable specific suggestions to
further enhance the paper.
1There are no uncertainty estimates around the wood
supply and demand as well as GWP. Incorporating the
uncertainty analysis into the study would provide
insight into where the future research efforts should be directed in order to reduce the uncertainty, as well as
help evaluate the confidence in the reported estimates. For an example of uncertainty analysis using CBM-CFS
please refer to J.M. Metsaranta, C.H. Shaw, W.A. Kurz,
C. Boisvenue, and S. Morken. 2017. Uncertainty of
inventory-based estimates of the carbon dynamics of
Canada's managed forest (1990-2014). Canadian
Journal of Forest Research. 47(8): 1082-1094.
https://doi.org/10.1139/cjfr-2017-0088
The demand profiles modelled are based on the outcome of an extensive literature
review of wood demand modelling studies. We recognise and account for the significant
uncertainty sourrounding future wood demand projections (indicated by the wide range
of demand projections published in the literature) by modelling two different demand
profiles in the present study. These two demand profiles capture the range in the
published literature. LCA of forest management scenarios under each of these demand
profile senarios indicates the degree of uncertainty and sensitivity of results to future
demand projection assumptions. In dealing with uncertainties for the supply side, we
have taken the simple and clear approach of testing multiple scenarios of variation in
future forest productivity (yield). We believe that this is an efficient way of integrating all of these causes of uncertainty listed by the reviewer 1 comment 2. We have also added
the following text to the 'Discussion section' lines 375-379: "There is an urgent need for
more integrated evidence that incorporates holistic assessment of prospective forestry
value chains alongside landscape dynamics (including forest management and
expansion), at both national and global scales, including improved estimates of the
potential impacts of climate change-linked threats to the future productivity of both
temperate forests and the other forest biomes providing wood production."
See continuation of this response in response to reviewer 1 comment 2 below.
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2Although authors did state in the methods section that risks of pests disease, wind, fire, warming and other climate change effects would not significantly alter the study findings because the risks are highly uncertain and would apply similarly across the study, I don't think it is the case. Fire, drought, changing productivity due to climate change would not change the wood demand, however they could profoundly affect the wood supply. Given the length of the projections in the study, warming would substantially increase heterotrophic respiration, and therefore would alter GWP projections. Drought events could substantially and repeatedly reduce forest yield due via inhibition of the photosynthetic rate and increasing mortality rate. Warming temperatures and changing precipitation regimes are also likely to affect forest net primary production. Increasing fire frequency and severity could profoundly affect the wood supply. I don't think these effects are negligible for GWP and wood supply estimates, and therefore should be considered in the study, especially given the 100-year projection time.As described in response to the previous comment, we believe that the approach to test multiple scenarios of variation in future forest productivity (yield) is an efficient way of integrating many of the causes of uncertainty listed by the reviewer. It is the approach that is most compatible with the LCA methodology of our study. Therefore, to address this specific reviewer requirement we have introduced a further pair of scenarios ('lower productivity' than the reference scenario) to model impact of possible ecosystem shocks (leading to yield reduction) that could arise from natural disturbance such as pests, disease, wind, drought and fire. These new scenarios are a modification of the 'reference rotation' existing forest (YC18, 50-yr rotation) + afforestation combination. The new scenarios are a transition of a) 15% and b) 30% of the existing forest from YC18 to YC12 ramping up over a 15 year period (remaining as a 50-yr harvest rotation), followed by recovery back to YC18 after one harvest rotation, ramping back down over a 15-yr period. (The afforestation assumptions were unchanged). Essentially the scenario represents a rapid shock of -two different intensities (affect on 15% &amp; 30% of the total area), followed by recovery after harvest (at 50-yrs old). A detailed description of the basis for the parameterisation of these two scenarios (two and a half pages of text) based on a substantial new literature review (32 references cited) is provided in the new Supplementary Information file "Modelling of natural disturbances - 'reduced productivity'". We recognise that natural disturbances, the intensity and rate of impact, and management responses to these are complex and therefore the modelling options available are vast. We believe the new scenarios selected correspond to contrasting realistic disturbance patterns presented in the reviewed literature and therefore offer additional insights to the other scenarios already modelled. We have included the new results in an updated version of 'Supplementary Data 3', alongside the results of all the other scenarios modelled in this paper.
We modelled these two new scenarios under high and low demand projections and for the variation in afforestation rates and planting periods. We found that the new 'lower productivity' scenarios in this set led to higher net forest carbon loss (domestic and overseas) than the 'reference rotation' scenarios, as well as other changes, yet these disturbances do not change the overall results or findings of the study. We have added text on this to the methodology (lines 701-708) and results section of the manuscript
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(lines 114-118; 169-172; and 201-204) and have included a more comprehensive description in the new Supplementary Information file (Supplementary Methods 1) in order to minimise additional word count.
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3The study results are generalized for a “temperate country”, however most of the data used in the study are for the UK, why not make the study focused on the UK? It would make it easier to assess the feasibility of the proposed scenarios and allow to avoid generalized statements (as a reader, I had a little trouble with those).We intentionally kept the analysis generic for a hypothetical temperate country rather than a UK-specific case study in order to provide evidence that has broad relevance. (The UK is not 'typical' in that it has a high baseline of imports and low domestic wood production.) This study is prospective in nature and focuses on the impacts of change, based on transparent assumptions for future changes (e.g. rate of decarbonisation, projected wood demand increase, shifts in forest management, different afforestation rates) that are not unique to the UK (or any other country) or dependant on historic conditions that may be unique to the UK.
In order to perform the LCA we needed to make assumptions on typical product breakouts at the forest gate and at a sawmill and a representative wood product flow. Given limitations on public availability of this kind of data, we used data available for the UK as the basis for these assumptions. These assumptions are broadly representative across temperate countries beyond the UK given the similarities in technology and wood value chains. For example, typical rates of conversion of softwood to sawtimber at sawmills is similar across temperate regions. We have edited the Methodology 'Scope of LCA' section (e.g. lines 622-628) to try and improve the reconciliation between our use of UK data and generalised statements.
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Reviewer #2
Summary: In this manuscript, authors present a combined application of forest carbon models and life cycle assessment (LCA) to estimate global warming (GW) impacts (+/-) of harvested wood products' (HWPs) value chain in a temperate country (appears to be UK). For projected high and low wood demands, the GW impacts are assessed for different
scenarios within the country (changing rotation length of forests, increasing rate of production, and expansion of forest area) and overseas imports from non-temperate forests (tropical country). This kind of study is an interesting attempt to integrate two areas of the forest products value chain (forestry and HWPs) for policy implications. The results indicate that increased wood use is not a climate-change solution unless afforestation, increasing forest productivity under sustainable forest management, and mitigating
demand increases through enhanced circularity and
cascading of wood use are also integrated into the strategy. I am offering below some comments/suggestions to improve the manuscript.
We thank the reviewer for the positive comments and endorsement of the important findings of the paper.
Major comments
1103-104: The current production and consumption levels of this temperate country should have been characterized to visualize the gap between demand and supply for the
reference year 2023, and the how different scenarios or
intended decisions might close this gap and influence GW
impacts.
We intentionally defined a hypothetical scenario in which domestic production equals domestic consumption in the reference year 2023, as indicated in Figure 1. As described in our response to reviewer 1 comment 3 above, we have taken this hypothetical approach rather than characterising the actual production and
consumption levels of a specific country in order to provide evidence that has
broad relevance. (For example, the UK is not 'typical' in that it has a high baseline of imports and low domestic wood production.) It makes sense for a
counterfactual lifecycle assessment (which is concerned with change from a
baseline) to start the scenario with production = consumption rather that starting
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with a deficit or surplus, which would make interpretation of results more challenging.
We then visualise how the different scenarios close the gap between future (increasing) demand and supply in Figure 1 by colour coding the supply deficit in red (and the supply surplus in pink). We have also added some additional text in the Figure 1 title to improve this description.
2107-108: What was the reason for selection of Sitka spruce forest in afforestation? The authors might discuss whether the results would be different if the forests were Douglas-fir or Western hemlock.Sitka spruce was selected as it grows widely (native to west coast of Canada and the United States; now planted in 16 countries worldwide, including as the predominant plantation species in the UK, Ireland and Denmark - all countries with low forest cover). Sitka spruce also grows well in degraded upland sites where land is most economically viable for afforestation, unlike productive Douglas fir or western hemlock, which require lower altitude land that is of higher value for food production. LCA results would not be different if different species (or species mixes) were modelled unless a significantly different yield class (growth curve) was also assumed. It is the yield rather than the species choice that drives the GWP impact results (which of course would be related in specific geographic contexts but in a hypothetical forest study such as this, the yield class is specified independently by the modeller as a representative average across contexts). In this way, the choice of Sitka spruce is simply a proxy for commercial conifer species. However, we believe that the clarity of the manuscript benefits from naming the case species, which links to the UK sawmill and-representative wood product flow data used in the study.
3Figure 2: Please change y-axis units to Tg CO2e.We have made this change.
4234: More interpretations could be added in 'high wood demand projection' results.We are pleased that Reviewer 2 sees further possible interpretations that we could include. We would welcome the opportunity to add more interpretations, however because of the journal's strict word limits this would necessitate making significant cuts to other parts of the text, which would sacrifice their clarity and content. Given the importance of these other components of the paper that would have to be cut, with regret we have concluded that adding more
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interpretations to the 'high wood demand projection' results would be of net cost to the value of the paper.
5264-267: Not clearly explained how GWP impact of alternative increased due to increase in overseas wood supply. Prolonged use of non-wood product and fuel alternatives?We have added words in this sentence (line 290) to clarify that the GWP impact of the alternative is "curtailed HWP supply" i.e. prolonged use of non-wood product and fuel alternatives. We have also added further description to indicate the relative impact of the specific overseas scenarios ('Boreal 1,2&3, Tropical CVL and Tropical (afforestation)' in Fig. 4) in which emissions associated with supplying the wood shortfall are higher or lower that the emissions from 'curtailed HWP supply' (prolonged use of non-wood and fuel alternatives).
6278-279: Please add explanation to this sentence, it seems confusing that more imports from tropical afforestation is better.It is unclear to us why this is confusing as it seems to be clearly shown in the results reported in Fig. 4. We do acknowledge the potential disbenefits of new tropical afforestation in lines 363-364 ("numerous socio-economic51 and biodiversity conservation20 caveats". In essence, increasing demand for fast-growing tropical tree species, which could be established on the large areas of degraded land in the tropics (if local socio-economic conditions make them available), could actually enhance terrestrial carbon stocks.
7295: Clarity is needed on what type of non-wood product is considered substituted by HWPs. Because substitution credits for two type of non-wood products can be different for same HWP.In response to this point, to avoid adding significant additional word count, we have added text to the methodology (line 616-617) and in the Fig. 5 title to direct readers to supplementary information for more detail on the substitution credits assumptions (supplementary figure 1 and supplementary Table 1). We also direct readers to Forster et al. (2021) where the methodology was originally published. We have also improved figure 5 in the present paper to convey, among other things, the product substitution assumptions more clearly.
8340: BECCS is associated with 'energy substitution' like non-wood products avoided is associated with 'product substitution'. There aren't a lot of interpretations in the results and discussion that focused on energy substitution.We have expanded the sentence referring to BECCS to mention product substitution and emphasise the permanent geological storage of biogenic carbon that contributes a carbon sink. Lines 368-369.
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9600: there is no ‘ix’ in the components of LCA system boundary. Including via ...?We have checked the numbering of components of the LCA system boundary in figure 5 and in the text and cannot find anything missing.
10724-740: This whole paragraph does not seem to be fit for methodology. Its more suitable for introduction.We believe that the paragraph is important for justifying the important selection of assumptions for the projected rate of demand increase used in the study, which is a core aspect of the study's methodology. We have edited and changed the order of the text to make the inclusion of this text in the methodology more fluent and justified. E.g. lines 779-785 have been moved from earlier in the section.
11747-748: What is the per capita timber consumption in UK, which translates to 30% increase in demand by 2050?We do not believe that including per capita timber consumption in the UK is relevant to the study. The 30% increase by 2050 statistic was included as this is a date that many published projections focus on, because it is an important date for many 'net zero' targets as mandated by the 2015 Paris Agreement of UNFCCC, and therefore a statistic that readers are likely to be interested in. As stated in our response to reviewer 2 comment 1, we have prioritised assumptions that are non-country-specific and forward looking wherever possible, to maximise the transferability of results. In essence, the critical (and transferable) mathematical/biophysical dynamic is the rate of demand increase from the baseline relative to the expansion rate of baseline forest area (through afforestation) and the (change in) productivity of existing (and new) forest.
12754: In this paragraph, it would be good if authors give a brief about the different HWP end-uses (primary and cascading uses) considered and maybe a justification for selecting HWP uses.The primary HWP end-uses are described in the methodology and further in the SI, including in a revised system diagram (Figure 5) indicating major processes and products. Details of cascading uses and also justification for the assumptions used are provided in Forster et al. (2021), which we cite in the methodology. We believe there is insufficient justification to repeat all of this detail here, especially on account of the word count restrictions.
13766: More clarity on defining the overseas forest type and carbon storage. Also, was the transportation distance and mode of transport included in the analysis?Description of the overseas forest types is provided in the following paragraphs (lines 827-856).
We did not include assumed differences in transport distances between overseas and domestic HWPs because, in a previous study (Forster et al., 2023), we found that these differences made a very small contribution (less than 0.01%) relative to the net GWP impact of the value chain.
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14785: Why 'GWP (forest C) impact...'? Forest carbon can be stored, emitted, or removed but cannot be equated directly to GWP.GWP (forest C) impact is defined in the previous paragraph as the 'GWP impact of fluxes in forest carbon stocks'. We have added '(GWP (forest C))' after this definition to add clarity. It refers to the GWP impact associated with net CO2e fluxes to/from the forest. Line 828.
15Overall, the methods section appears weak to me and needs a thorough revision to ensure that work can be reproduced.We have carefully addressed each of the reviewers specific comments and assume that in doing so we have met the need expressed here.
Minor comments
16325 and 330: should it be trip or tip?Tip means to tilt, tumble or topple. In this context, 'the balance... can tip from sink to source', means the balance can tilt or shift from sink to source.
17723: why question marks in middle of the sentence?We have removed these.
18Double numbering in referencesWe have removed these.
19Some of the links in supplementary excel file are broken. Please check.We have checked the supplementary Excel files and assume that the reviewer is referring to the 'HWP calculation module' (Supplementary Data 2). The broken links are the emissions factors cells that link to the original LCA worksheet (Supplementary Data 1) that generated them. These links do not work once the workbook is resaved in a different location. However, in the final version of these supplementary data files, which will be stored in a permanent repository or in the publisher's website, we will endeavour to ensure the links all work.
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Reviewer #3:
1The aim of this case study is to quantify the GHG mitigation potential of different measures or forest management
options (in particular afforestation) in terms of meeting an
increasing demand for wood, assuming that existing models for the forest sector tend to "underestimate" forest carbon fluxes.
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2In fact, in addition to the development of forest carbon stocks, the delayed release of biogenic carbon through the use of wood as material as well as potential shifting effects of the GHG emission balances associated with the life cycle of these wood-containing product systems and their potential product alternatives do also have an impact on the overall GHG balance.We are not clear on whether this forms part of the reviewer's summary of the paper or is a comment requiring our response. In case it is the latter, we provide the following clarification. We agree with the reviewer about the importance of impacts throughout the wood products life cycle. Yet, the full climate mitigation effects of forestry are often under-represented because: (i) LCA approaches that (sometimes) better represent substitution and possible end-of-life carbon storage effects are usually only applied to specific products (partial wood flows out of forests); (ii) inventory approaches that attempt to represent all wood products, typically neglect short-lived wood products used for energy, and don't attribute substitution effects back to the forest sector; (iii) both LCA and inventory approaches often disregard cascading uses of wood, and associated second (and possible further) substitutions, along with extended carbon storage effects; (iv) only very prospective analyses consider future BECCS deployment that could lock up biogenic carbon indefinitely.
3However, the implementation of the presented approach to estimate the total GHG impact of different management scenarios compared to the defined reference, in our view appears to be completely inadequate in this study. It does not comply with applicable international standards and existing state-of-the-art knowledge.We are surprised by this comment, which we strongly believe does not reflect the content and rigour of our study or its compliance with the highest international standards. International standards apply to specific types of accounting, such as Environmental Product Declarations for (LCA of) wood products or UNFCCC guidelines for national GHG inventory accounting. In contrast, there are no such "standards" for the prospective consequential LCA of entire forest and multiple downstream product systems, which is the innovative methodological approach of our study. That is precisely what makes this approach so valuable - it transcends the accounting rules that are applied to deal with truncated system boundaries (e.g. how to allocate forest effects to specific downstream products). This paper builds on the state-of-the-art approach applied in our earlier, highly-cited manuscript published in Nature Communications (Forster et al., 2021), and applies it to a temperate forest system under different management and expansion regimes; this is highly novel. To reiterate, we are not attempting to calculate product footprints as per various international standards, but instead (as is befitting for a submission to Nature Communications) to provide a novel, holistic and rigorous analysis of the climate mitigation efficacy of different forest
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management strategies, providing key new evidence for policy makers and an innovative novel approach for researchers.
4While the modeling of carbon storage development in the forest using the internationally recognized Carbon Budget Model for the Canadian Forestry Service appears adequate, the methodological inadequacies relate in particular to the life cycle assessment methodology, on the basis of whose standard-compliant, consistent and transparent implementation avoided emissions through "product substitution" can be estimated in the first place. In order to adequately consider process chain emissions and based on those also "avoided emissions from product substitution", it is crucial to meet the internationally standardized requirements for life cycle assessment (including ISO 14040/44 and ISO 21930). The mere summation of unrelated LCA process information from a background database (here: Ecolnvent) is inadequate - at least for the processes outside the forest along the processing and value chain. The data used for calculating "primary avoided emissions (FF/product substitution)" are also completely unsuitable.As explained in our previous response, our study is categorically not an attributional LCA, which seems to have been the assumption of the reviewer. Instead it is a consequential LCA. That said, this study does fully comply with ISO 14040 and 14044 standards (which in reality are a basic framework to structure LCA), insofar as it: provides a clear goal and scope of the study; calculates an inventory that accounts for relevant changes within the expanded system boundary; applies GWP100 characterisation factors for the life cycle impact assessment phase; interprets results with clear regard for the question and methods used (now including important sensitivity analyses). Furthermore, this study uses system expansion in preference to allocation, as recommended in the allocation hierarchy advocated by the ISO standards. The study categorically does not sum "unrelated" LCA process information - incurred or avoided processes are clearly indicated in the system boundary (Supplementary Fig. 1 and in Fig. 5, also now improved), based on a consequential LCA approach that incorporates all changes associated with the scenarios vs the baseline counterfactual situation.
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[80, 113, 905, 870]]<|/det|> + +
Remarks to AuthorAuthor Responses
5Furthermore, the simplified calculation of assumed carbon storage effects through the use of wood as a material (harvested wood products) contradicts central core requirements in the calculation as set out in the methodological guidelines and requirements provided by IPCC (incl. e.g. the consideration of inherited emissions). In consequence, the HWP contribution trough biogenic carbon storage as well as potential “avoided emissions” appear to be massively overestimated.Our methodology does not contradict core requirements of the IPCC and from this comment we do not understand how the reviewer considers that it does so. The IPCC provide guidelines for a number of approaches to deal with HWP C storage at a national scale. All of them are based on the fact that biogenic carbon harvested from the forest is "lost" from the terrestrial system, but some of this carbon "reappears" in longer-lived HWPs (with a large deficit reflecting biomass assumed to be immediately oxidised via combustion for bioenergy or for kiln drying of wood in sawmills). Our approach fully respects the biogenic carbon balance - in fact much more explicitly than typical national inventory accounting (with which we are fully familiar), because flows into all main products, both short- and long-lived, are accounted for, and the duration of carbon storage in each of these products, and any subsequent products, is explicitly accounted for in our methodology. Again, this is the benefit of our expanded boundary approach (across products and through time) - it minimises the influence of "cut-off" rules and associated value judgements, which often profoundly influence carbon footprints at the wood product level.
6While it seems undisputed, even without the present study, that "the expansion of the (industrial) bioeconomy should be linked to the availability of raw materials in order to avoid unrealistic supply expectations, " statements to the effect that "considerable HWP-C storage and product substitution credits can be achieved simultaneously" are not at all tenable on the basis of this simple and, in our view, completely methodologically inadequate implementation.Without any further insight from the reviewer as to where our methodology is inadequate, it is difficult to address this comment. We acknowledge that our original system diagram did not fully represent the scope of our methodology (although it was described fully in the text and illustrated in Supplementary Fig.1). Therefore, we hope that the improved system diagram in the resubmitted manuscript helps understanding of precisely how we have linked forest C storage with HWP-C storage and substitution, and long-term CCS C-storage effects in a coherent manner. As previously mentioned, this builds on the methodology of Forster et al. (2021) published in Nature Communications.
7The simple comparison of a changing supply of forest wood with a modeled demand for this raw material (including potential gaps) can also be carried out without balancing all GHG emissions relevant to the forestry and wood sector.It is true that a simple comparison of changing supply of forest wood with demand could be carried out in isolation. However, that would not address the important policy question of what the climate mitigation effect would be of alternative forest strategies that aim to minimise the gap between future supply and demand. That is where this paper provides a unique and robust contribution to the scientific literature, for which its rigorous methodological consequential LCA approach is essential.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[0, 0, 997, 997]]<|/det|> +# 1.1.1.1.1.1.1.1.1.1.1 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[120, 85, 426, 100]]<|/det|> +## Author response to reviewer comments + +<|ref|>text<|/ref|><|det|>[[119, 111, 848, 162]]<|/det|> +We are once again grateful for the opportunity to respond to Reviewer comments. We have addressed the comments below and in doing so believe we have further enhanced the article, as outlined in our response. All changes to the manuscript are highlighted in 'tracked- changes'. + +<|ref|>sub_title<|/ref|><|det|>[[119, 199, 298, 214]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 233, 404, 248]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[119, 268, 210, 283]]<|/det|> +## Comment 1 + +<|ref|>text<|/ref|><|det|>[[118, 293, 879, 448]]<|/det|> +The authors provided fairly comprehensive responses to the reviewers' comments. Yet, after reading the revised paper there is a dissonance between the level of detail in the manuscript and practical applicability of the findings. In the response to reviewers authors noted that this manuscript implements a framework laid out in an earlier paper published in Nature Communications, however the implementation is rather abstract, an interested party (e.g. government of a temperate country) would have to re- do the analyses (i.e. implement the framework to their specific country) and may get substantially different results. This makes me question the value of this particular manuscript, given lack of connection to any specific country, for which the feasibility of the generated estimates could be evaluated. + +<|ref|>sub_title<|/ref|><|det|>[[119, 460, 308, 475]]<|/det|> +## Response to Comment 1 + +<|ref|>text<|/ref|><|det|>[[117, 485, 876, 760]]<|/det|> +We thank Reviewer 1 for their further comments, to which we have given careful consideration. The main point raised here is that the methodology remains abstract, such that others would need to perform their own analysis. We fully agree that researchers and other interested parties should perform context- specific analysis, and not rely solely on the results of a generic country case study (of the kind we use here to demonstrate the rigour, power and applicability of the framework that we have developed in this paper). We have subtly revised framing to reflect this, with additional clarity and emphasis on the novel methodological framework we have developed. In a new SI, we outline the framework in diagram, table and text form, highlighting its substantial novel components not previously published, and describe its implementation with reference to important parameters and examples of datasets and models of the kind that are available to generate context- specific results. However, we maintain that using a generic temperate country with an even- aged forest as an illustrative case study provides important insights that do have broad relevance for readers, whereas using the context of a specific country would not, owing to the unique nature of its forest- age deviations. We have made small edits throughout the manuscript to further emphasise to readers the importance of tailoring studies to specific contexts, especially where the results of such studies are intended to inform policy. + +<|ref|>text<|/ref|><|det|>[[118, 770, 864, 838]]<|/det|> +The framework sets out our exploratory approach for identifying 'low regrets' climate solutions for the forestry value chain by evaluating a range of plausible future scenarios, using powerful integrated forest modelling and lifecycle assessment (LCA) (Supplementary Fig. 1 & Supplementary Methods 1). + +<|ref|>text<|/ref|><|det|>[[118, 848, 870, 900]]<|/det|> +The present study builds substantially on the detailed prospective dynamic LCA modelling of entire forest- wood value chains developed and explained in Forster et al. (2021). Crucially, in the present study the full downstream greenhouse gas (GHG) mitigation consequences of wood use and end- of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 853, 186]]<|/det|> +life management are considered - including carbon storage and material and energy substitution within a decarbonising future economy. Novel aspects to the present study (shown in pink in the new Supplementary Fig. 1) include calculating potential future wood supply deficit by comparing projected wood demand curves to wood supply from a range of modelled (expanded) temperate forest management scenarios, and linking the supply deficit to marginal expansion of supply from other regions. + +<|ref|>text<|/ref|><|det|>[[118, 196, 857, 248]]<|/det|> +Elaboration of the framework within the SI will facilitate interested parties to follow our approach for a relevant study context (Supplementary Table 1). We signpost readers to this SI at multiple points in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[118, 276, 210, 291]]<|/det|> +## Comment 2 + +<|ref|>text<|/ref|><|det|>[[118, 302, 866, 352]]<|/det|> +In my opinion, the treatment of the uncertainties associated with the effects of climate change and disturbances on productivity and GWP was fairly simplistic, not illustrated in all figures and not illustrated for GWP estimates. + +<|ref|>sub_title<|/ref|><|det|>[[118, 364, 308, 379]]<|/det|> +## Response to Comment 2 + +<|ref|>text<|/ref|><|det|>[[117, 390, 875, 544]]<|/det|> +We acknowledge the simple treatment of climate change and disturbances (which we note can vary considerably, geographically) for our generic temperate country study. However, we maintain that this approach is appropriate to illustrate the magnitude of effect associated with highly uncertain future events. Recent articles pertaining to climate mitigation modelling highlight the need for "robust" rather than optimised decision making in the face of deep uncertainty and high complexity (Workman et al. (2021) and Workman et al. (2024)). We now cite these articles to further justify our approach, and propose natural disturbance events as a key parameter to represent (where possible) this impact within the proposed framework when tailoring scenarios in future studies for specific context. + +<|ref|>sub_title<|/ref|><|det|>[[118, 555, 210, 569]]<|/det|> +## Comment 3 + +<|ref|>text<|/ref|><|det|>[[118, 581, 839, 613]]<|/det|> +Lastly, please correct the following: CBM- CFS stands for "Carbon Budget Model of the Canadian Forest Sector". + +<|ref|>sub_title<|/ref|><|det|>[[118, 625, 308, 640]]<|/det|> +## Response to Comment 3 + +<|ref|>text<|/ref|><|det|>[[118, 653, 258, 667]]<|/det|> +Corrections made. + +<--- Page Split ---> diff --git a/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/images_list.json b/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..3057394b9b43f4fbb352d9a48c42c5af263f51b2 --- /dev/null +++ b/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,123 @@ + +# nature portfolio + +Peer Review File + +Systematic Review and Meta- Analysis for a Global Patient co- Owned Cloud (GPOC) + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The article systematically reviews sharing of electronic health records in a cloud. The text is original, follows PRISMA protocol, and presents exciting insights to the scientific community. The authors considered the most significant articles on the subject. The protocol is adequately done and gives a discussion pointing out the main challenges and issues. + +Following, I list some suggestions to improve the article: + +- GPOC is not a universally accepts term. It is a term that the authors have used in previous publications. Although I do not see a problem using this term in the article, the authors could better define what it means and why it could not use just PHR to represent this idea. Another doubt is what is a co-owned cloud. Is it a public cloud? Is it co-owned by the patient and its health providers? + +- Pg. 3, line 45: The authors discuss centralized approaches. It would be interesting to mention fog-based and peer-to-peer/hierarchical methods for completeness. + +- Pg. 3, line 63: How to deal with the language barrier among cross-border travel? I would appreciate a discussion on this subject. + +- When discussing security and privacy, one of the focuses of the article, you could analyze the implications of HIPAA and GDPR. There are many aspects that these kinds of legislation affect privacy regarding health records and their relation to cross-border travel. + +- Security is mainly discussed in terms of encryption and decryption of data. A more comprehensive analysis is needed, including the three main aspects of confidentiality, integrity, and availability. + +- The method is well-defined and based on PRISMA. I did not find the range period for the search, the bases used, and the specific terms (on page 5, line 94, you only mention some keywords). + +- Interoperability is an important issue that is not discussed at all. What is the rationale, and why was it not considered in the article? A global trend of adopting HL7 FHIR and other standards could influence the field. + +- Security-based parameters are based on times in ms: time for encryption, time for decryption, and the ratio of means. These times depend on the infrastructure: CPU, memory, network bandwidth, etc. Just showing the number of effective time adds little value since it depends on the infrastructure used. + +- I missed a big picture of the main issues in the discussion section. The discussion is based on the more traditional "Author X studied that; Author Y discusses." You could start with a big picture presenting the main topics and then more implicitly bringing the related studies. + +- You cite types of encryptions on lines 281-282 (page 14). A discussion could be added because it could influence many essential aspects of the study. + +- Blockchain is cited throughout the article, and I consider it a trend. You could discuss this technology further and its impact with more emphasis. Other crucial subjects still need to be explored, including Federated Learning, Fog Computing, and the Internet of Things (how to combine data from wearables from patient EHR, for instance). + +- On page 19 you discuss machine learning and the use of data for decision, preserving privacy, and not disclosing patients' details. Anonymization and obfuscation, among other methods, could be commented on here. Although machine learning is not a focus of the article, it could influence GPOC in the services provided and organization/storage of data. + +<--- Page Split ---> + +- Line 386, Pg. 20, you cite "four main areas," but it seems to be five. It would be nice to see some future directions. + +Reviewer #2: + +Remarks to the Author: + +I appreciate and congratulate all authors for adding knowledge to the Global Patient co- Owned Cloud (GPOC) a Cloud- based infrastructure that shares information in the Personal Health Records (PHRs) space. This topic is timely and requires significant effort to establish particularly the concern on data security and privacy. I believe the meta- analysis and results presented cover the area to some extent however the term "use- ubiquity globally" that appears in the abstract does not take any advantages and/or support to the claims (refer to the conclusion). + +Some areas to improve based on the Electronic Health Records (EHRs) use are: + +(1) Validity and Bias: This is very critical to explain how the risk minimisation was managed. + +(2) Perhaps, the language tome could be lower to support the general audience and/or readers (since this is Open Access Forum); + +(3) In addition, Blockchain protocol-embedded PHRs might be another approach that did not dominate the claim hence expanding such idea and thinking would be an added advantage to the paper. + +(4) The conclusion section: + +I believe there are standards when sharing EHRs. Such standards are depending on the Geographical locations, the Country's data protection, and/or breaches of legislation and their maturity (this is a very challenging area indeed). + +## ADDITIONAL COMMENTS: + +The manuscripts share some form of information from the literature search. While they are interconnected, scientifically it is appropriate and valid to share the information however, the merit of the research contributions is somewhat diluted. Hence, it would be advisable to realign the findings specifically to the papers titled, for the readers' comfort and benefits. + +In general, the body of work completed was commendable. At the same time, the written language may not be palatable to a wider audience and readers. It would be advisable to make it simple where possible since there are several paragraphs confounded with each other. + +One of the classic examples in the paper titled "Systematic Review and Meta- Analysis for a Global Patient co- Owned Cloud (GPOC)" uses the term "use- ubiquity globally" in the abstract. This term is misleading based on the conclusion. + +<--- Page Split ---> + +Please see the below answers and actions to all the 30 points of the major revision. + +(1) The manuscript **GPOC SYS-META Clean** does not contain comments, it is a revised clean manuscript. + +(2) The manuscript **GPOC SYS-META Comms** - you find the actions labelled with comments #1-30. + +(3) The manuscript **GPOC SYS-META Highlighted** - you find all the changes underlined and highlighted. + +(4) For convenience, the manuscript **GPOC SYS-META Trace** (Word-tracked) is fully traceable from the previous version that you reviewed. + +
Comments#PartPoint by Point Answers & Actions
Editor comments found in the
separate cover letter.
1-8AllSee author cover letter.
REVIEWER COMMENTS
Reviewer #1 (Remarks to the
Author)
The article systematically
reviews sharing of electronic
health records in a cloud. The
text is original, follows
PRISMA protocol, and presents
exciting insights to the
scientific community. The
authors considered the most
significant articles on the
subject. The protocol is
adequately done and gives a
discussion pointing out the
main challenges and issues.
9AllWe thank the reviewer for constructive and helpful comments that has ameliorated the manuscript.
Following, I list some
suggestions to improve the
article: GPOC is not a
universally accepts term. It is a term that the authors have used
in previous publications.
Although I do not see a
problem using this term in the
article, the authors could better
define what it means and why it could not use just PHR to
represent this idea. Another
doubt is what is a co-owned
cloud. Is it a public cloud? Is it
co-owned by the patient and its
health providers?
10Abst.
&
Intro.
It is important to define the unicity of the GPOC concept. This has now been implemented into the abstract and introduction. Hence, now there is a better definition of GPOC, what the co-ownership is, and why it is trisected for legal reasons. It has also been highlighted why a just PHR cannot be used - the
unicity of the GPOC concept of cloud, ownership, AI
integration, blockchain, foundation, globality, sharing,
independence, interaction, legal foundation status and
substrate for development of ML and its global dissemination has been elaborated.
- Pg. 3, line 45: The authors
discuss centralized approaches.
It would be interesting to
mention fog-based and peer-to-peer/hierarchical methods for
completeness.
11Disc.These have now been implemented as valuable new angles.
Now the fog-based and peer-to-peer/hierarchical methods are mentioned.
+ +<--- Page Split ---> + + +
- Pg. 3, line 63: How to deal with the language barrier among cross-border travel? I would appreciate a discussion on this subject.12Disc.This is now included in the discussion among the challenges and importance of AI integration into GPOC. We exemplify how inbuilt AI in the GPOC can solve language barriers.
- When discussing security and privacy, one of the focuses of the article, you could analyze the implications of HIPAA and GDPR. There are many aspects that these kinds of legislation affect privacy regarding health records and their relation to cross-border travel.13Disc.Thank you, we have now added a comment about and discuss this. After this comment we refer to the GPOC Ethics article 4 in the reference list. This article focuses entirely on ethics, policy, legal, regulation, etc. This is a self-contained article within the GPOC series. GDPR &amp; HIPAA now mentioned (without infringing into the Ethics' article), but now highlighted. Indeed, we cross reference to the article that focuses in this area.
- Security is mainly discussed in terms of encryption and decryption of data. A more comprehensive analysis is needed, including the three main aspects of confidentiality, integrity, and availability.14Disc.Now included and analysed articles of the systematic review elaborating these main aspects of confidentiality (19), integrity (11), and availability (12). Within parenthesis the number of articles bringing this up.
- The method is well-defined and based on PRISMA. I did not find the range period for the search, the bases used, and the specific terms (on page 5, line 94, you only mention some keywords).15Meth. &amp; Supp.The PRISMA form and other search documents have now all been included as supplements and referred to as supplementary files S1 and S3. In S1 the full search strategy is visible, with search strings etc. In S3 the PRISMA checklist is presented.
- Interoperability is an important issue that is not discussed at all. What is the rationale, and why was it not considered in the article? A global trend of adopting HL7 FHIR and other standards could influence the field.16Disc.Now interoperability has been implemented into the discussion. Now also HL7 FHIR is mentioned. Also, as cross referencing here has been made to the technical EcoTech Article.2
- Security-based parameters are based on times in ms: time for encryption, time for decryption, and the ratio of means. These times depend on the infrastructure: CPU, memory, network bandwidth, etc. Just showing the number of effective time adds little value since it depends on the infrastructure used.17Disc.Now this point has been added to the big picture of the results, as a decisive factor to consider and weigh in. The infrastructure for GPOC is further elaborated in the technical EcoTech Article.2 It is cross referenced to this now too.
- I missed a big picture of the main issues in the discussion section. The discussion is based on the more traditional "Author X studied that; Author Y discusses." You could start with a big picture presenting the main topics and then more implicitly bringing the related studies.18Disc.Now the big picture has been added in an initial overview, but also in the discussion. Al the places with the traditionally mention "author X studied Y", etc, have been altered and the result is a much better flow. Now, with an accompanying big picture before and after, it is more readable. As advised the big picture is presented mainly first. Also, the traditional author mentioning has been partly altered where possible now, so that the sentences are more neutral as flow better for the reader.
- You cite types of encryptions on lines 281-282 (page 14). A19Disc.A discussion has now been added on encryption. Also, referring further the technical EcoTech Article.2
+ +<--- Page Split ---> + + +
discussion could be added
because it could influence many
essential aspects of the study.
- Blockchain is cited throughout the article, and I consider it a
trend. You could discuss this
technology further and its
impact with more emphasis.
Other crucial subjects still need
to be explored, including
Federated Learning, Fog
Computing, and the Internet of
Things (how to combine data
from wearables from patient
EHR, for instance).
20Disc.Now a discussion on blockchain has been added. Federated Learning, Fog Computing, and the Internet of Things are mentioned, but also a refence for further reading of the technical EcoTech Article.2
- On page 19 you discuss
machine learning and the use of
data for decision, preserving
privacy, and not disclosing
patients' details. Anonymization and obfuscation, among other
methods, could be commented
on here. Although machine
learning is not a focus of the
article, it could influence GPOC in the services provided and
organization/storage of data.
21Disc.Now anonymization and obfuscation and also fully
homomorphic encryption is mentioned. There is now also a refence for further reading, where this is elaborated, in the technical EcoTech Article.2
- Line 386, Pg. 20, you cite
"four main areas," but it seems
to be five. It would be nice to
see some future directions.
22Disc.It has now been changed to eight (8) areas. Moreover, the initial keywords of each numbered paragraph have been italicised for increased clarity and readability. Also, the
number of directions has been expanded and are now also synched with the six problems statements mentioned before and also referred to in the GPOC series. Again, without any overlap.
Reviewer #2 (Remarks to the
Author)
I appreciate and congratulate all
authors for adding knowledge
to the Global Patient co-Owned Cloud (GPOC) a Cloud-based
infrastructure that shares
information in the Personal
Health Records (PHRs) space.
This topic is timely and requires significant effort to establish
particularly the concern on data security and privacy. I believe
the meta-analysis and results
presented cover the area to
some extent however the term
"use-ubiquity globally" that
appears in the abstract does not
take any advantages and/or
support to the claims (refer to
the conclusion).
23Abst.Many thanks. And yes, the term "use-ubiquity globally" that appears in the abstract, has been deleted and the whole
abstract has been completely rewritten. It is now within the
required limits of <150 words. Decreased from 244 words.
The abstract now starts to explain GPOC, present the series to get a context for the reader, and then focuses on the article and what it shows.
Some areas to improve based
on the Electronic Health
Records (EHRs) use are: 1)
Validity and Bias: This is very
24Res.Now under the headline "Validity and Bias" it has now been
explained how the risk minimisation was managed.
+ +<--- Page Split ---> + + +
critical to explain how the risk minimisation was managed.
(2) Perhaps, the language tone could be lower to support the general audience and/or readers (since this is Open Access Forum)25AllAs the editor also requested (and referred to reviewer 2) above in comment #1, very sentence of the whole manuscript has been put under revision and all paragraphs and nearly all sentences have been altered or polished. Hence, the language is now more suitable to a general audience and the sentences are shorter.
(3) In addition, Blockchain protocol-embedded PHRs might be another approach that did not dominate the claim hence expanding such idea and thinking would be an added advantage to the paper.26Disc.Now the approach with Blockchain protocol-embedded PHRs have been mentioned. Reference added for further reading of the technical EcoTech Article.²
(4) The conclusion section: I believe there are standards when sharing EHRs. Such standards are depending on the Geographical locations, the Country's data protection, and/or breaches of legislation and their maturity (this is a very challenging area indeed).27Disc. & Con.Now a hint about this is added. This is the full subject and ranger of the Ethics Article⁴. This article fully delves into geographical variations of ethics, legislation, regulations and policies. It is an additional combinatory literature review and interview series on this subject. It could not have been included into the present systematic review and meta-analysis and is self-contained and stands on its own legs. But a cross referencing has been added with the mentioned hint that this is important, and worth an independent article. See also the last point 8 of the discussion summary.
ADDITIONAL COMMENTS
The manuscripts share some form of information from the literature search. While they are interconnected, scientifically it is appropriate and valid to share the information however, the merit of the research contributions is somewhat diluted. Hence, it would be advisable to realign the findings specifically to the papers titled, for the readers' comfort and benefits.28Abst. & IntroAbsolutely. The overlaps have now been minimised. Hopefully eradicated. For instance, it is requested in the revision to delve into a technical or regulatory area, and these have now been added, but only very brief and with a reference to the article which has this area as its main subject. It is hence important that the required technical additions to the systematic review do not infringe or dilute other manuscripts. Note: all mentioning of subjects belonging to another manuscript has been deleted. Similarly other subjects belonging to other self-contained parts of the series have been deleted and referred to only once for information to the reader (ref 1,2,3,4). Hence, a total realignment has been carried out.
In general, the body of work completed was commendable. At the same time, the written language may not be palatable to a wider audience and readers. It would be advisable to make it simple where possible since there are several paragraphs confounded with each other.29AllThe whole text has now been rewritten. The language has been improved and the text flows better. It is adapted to the general audience. The sentences are less complex and shorter. Easier terminology has been used, whenever possible. When comparing the previous version and the present article manuscript all paragraphs and a majority of sentences have been rewritten to ease the flow for the general audience, which is very important. The paragraphing has been changed to eradicate any confusion. Note that now both the abstract (in two short sentences) and the introduction's first paragraph briefly mention the GPOC concept and the context of the GPOC series. Hence, the reader will immediately know what to expect from the articles regarding scope and contents. At the onset the reader will be aware that the five GPOC series entities will display distinct and non-overlapping foci. Hence, this sets the tone and contributes to the realignment of the articles. Several paragraphs hence became superfluous and have been deleted.
+ +<--- Page Split ---> + + +
One of the classic examples in the paper titled "Systematic Review and Meta-Analysis for a Global Patient co-Owned Cloud (GPOC)" uses the term "use-ubiquity globally" in the abstract. This term is misleading based on the conclusion.30Abst.This term has been deleted. The abstract has been completely rewritten. It has also been shortened from 244 to the required 150 words maximum. All intricate sentences with complex syntax and prosody have been altered. The message is clearer. Sentences shorter. Language simpler.
+ +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The authors have conducted all the modifications asked for in the previous review. The article is now ready to be accepted. + +<--- Page Split ---> diff --git a/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6a53e32a80933620d6da8d42ab3b7ed9d842a1f9 --- /dev/null +++ b/peer_reviews/1265f8b06778239434bb4b6e3d1588d191708414dc2de58cfdb2da9350869262/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,163 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 912, 211]]<|/det|> +Systematic Review and Meta- Analysis for a Global Patient co- Owned Cloud (GPOC) + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 223, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 140, 860, 197]]<|/det|> +The article systematically reviews sharing of electronic health records in a cloud. The text is original, follows PRISMA protocol, and presents exciting insights to the scientific community. The authors considered the most significant articles on the subject. The protocol is adequately done and gives a discussion pointing out the main challenges and issues. + +<|ref|>text<|/ref|><|det|>[[119, 210, 551, 224]]<|/det|> +Following, I list some suggestions to improve the article: + +<|ref|>text<|/ref|><|det|>[[119, 238, 874, 309]]<|/det|> +- GPOC is not a universally accepts term. It is a term that the authors have used in previous publications. Although I do not see a problem using this term in the article, the authors could better define what it means and why it could not use just PHR to represent this idea. Another doubt is what is a co-owned cloud. Is it a public cloud? Is it co-owned by the patient and its health providers? + +<|ref|>text<|/ref|><|det|>[[118, 322, 848, 351]]<|/det|> +- Pg. 3, line 45: The authors discuss centralized approaches. It would be interesting to mention fog-based and peer-to-peer/hierarchical methods for completeness. + +<|ref|>text<|/ref|><|det|>[[118, 364, 812, 393]]<|/det|> +- Pg. 3, line 63: How to deal with the language barrier among cross-border travel? I would appreciate a discussion on this subject. + +<|ref|>text<|/ref|><|det|>[[119, 406, 847, 448]]<|/det|> +- When discussing security and privacy, one of the focuses of the article, you could analyze the implications of HIPAA and GDPR. There are many aspects that these kinds of legislation affect privacy regarding health records and their relation to cross-border travel. + +<|ref|>text<|/ref|><|det|>[[119, 461, 848, 504]]<|/det|> +- Security is mainly discussed in terms of encryption and decryption of data. A more comprehensive analysis is needed, including the three main aspects of confidentiality, integrity, and availability. + +<|ref|>text<|/ref|><|det|>[[118, 517, 870, 547]]<|/det|> +- The method is well-defined and based on PRISMA. I did not find the range period for the search, the bases used, and the specific terms (on page 5, line 94, you only mention some keywords). + +<|ref|>text<|/ref|><|det|>[[118, 560, 875, 602]]<|/det|> +- Interoperability is an important issue that is not discussed at all. What is the rationale, and why was it not considered in the article? A global trend of adopting HL7 FHIR and other standards could influence the field. + +<|ref|>text<|/ref|><|det|>[[119, 616, 874, 672]]<|/det|> +- Security-based parameters are based on times in ms: time for encryption, time for decryption, and the ratio of means. These times depend on the infrastructure: CPU, memory, network bandwidth, etc. Just showing the number of effective time adds little value since it depends on the infrastructure used. + +<|ref|>text<|/ref|><|det|>[[118, 686, 875, 728]]<|/det|> +- I missed a big picture of the main issues in the discussion section. The discussion is based on the more traditional "Author X studied that; Author Y discusses." You could start with a big picture presenting the main topics and then more implicitly bringing the related studies. + +<|ref|>text<|/ref|><|det|>[[118, 742, 875, 771]]<|/det|> +- You cite types of encryptions on lines 281-282 (page 14). A discussion could be added because it could influence many essential aspects of the study. + +<|ref|>text<|/ref|><|det|>[[119, 785, 830, 841]]<|/det|> +- Blockchain is cited throughout the article, and I consider it a trend. You could discuss this technology further and its impact with more emphasis. Other crucial subjects still need to be explored, including Federated Learning, Fog Computing, and the Internet of Things (how to combine data from wearables from patient EHR, for instance). + +<|ref|>text<|/ref|><|det|>[[119, 855, 863, 911]]<|/det|> +- On page 19 you discuss machine learning and the use of data for decision, preserving privacy, and not disclosing patients' details. Anonymization and obfuscation, among other methods, could be commented on here. Although machine learning is not a focus of the article, it could influence GPOC in the services provided and organization/storage of data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 97, 835, 125]]<|/det|> +- Line 386, Pg. 20, you cite "four main areas," but it seems to be five. It would be nice to see some future directions. + +<|ref|>text<|/ref|><|det|>[[118, 167, 222, 180]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 181, 298, 194]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 195, 870, 281]]<|/det|> +I appreciate and congratulate all authors for adding knowledge to the Global Patient co- Owned Cloud (GPOC) a Cloud- based infrastructure that shares information in the Personal Health Records (PHRs) space. This topic is timely and requires significant effort to establish particularly the concern on data security and privacy. I believe the meta- analysis and results presented cover the area to some extent however the term "use- ubiquity globally" that appears in the abstract does not take any advantages and/or support to the claims (refer to the conclusion). + +<|ref|>text<|/ref|><|det|>[[118, 293, 725, 308]]<|/det|> +Some areas to improve based on the Electronic Health Records (EHRs) use are: + +<|ref|>text<|/ref|><|det|>[[118, 308, 660, 336]]<|/det|> +(1) Validity and Bias: This is very critical to explain how the risk minimisation was managed. + +<|ref|>text<|/ref|><|det|>[[118, 363, 848, 392]]<|/det|> +(2) Perhaps, the language tome could be lower to support the general audience and/or readers (since this is Open Access Forum); + +<|ref|>text<|/ref|><|det|>[[118, 404, 864, 447]]<|/det|> +(3) In addition, Blockchain protocol-embedded PHRs might be another approach that did not dominate the claim hence expanding such idea and thinking would be an added advantage to the paper. + +<|ref|>text<|/ref|><|det|>[[118, 461, 325, 475]]<|/det|> +(4) The conclusion section: + +<|ref|>text<|/ref|><|det|>[[118, 476, 837, 519]]<|/det|> +I believe there are standards when sharing EHRs. Such standards are depending on the Geographical locations, the Country's data protection, and/or breaches of legislation and their maturity (this is a very challenging area indeed). + +<|ref|>sub_title<|/ref|><|det|>[[118, 533, 316, 546]]<|/det|> +## ADDITIONAL COMMENTS: + +<|ref|>text<|/ref|><|det|>[[118, 547, 876, 603]]<|/det|> +The manuscripts share some form of information from the literature search. While they are interconnected, scientifically it is appropriate and valid to share the information however, the merit of the research contributions is somewhat diluted. Hence, it would be advisable to realign the findings specifically to the papers titled, for the readers' comfort and benefits. + +<|ref|>text<|/ref|><|det|>[[118, 616, 878, 659]]<|/det|> +In general, the body of work completed was commendable. At the same time, the written language may not be palatable to a wider audience and readers. It would be advisable to make it simple where possible since there are several paragraphs confounded with each other. + +<|ref|>text<|/ref|><|det|>[[118, 671, 876, 714]]<|/det|> +One of the classic examples in the paper titled "Systematic Review and Meta- Analysis for a Global Patient co- Owned Cloud (GPOC)" uses the term "use- ubiquity globally" in the abstract. This term is misleading based on the conclusion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 131, 786, 147]]<|/det|> +Please see the below answers and actions to all the 30 points of the major revision. + +<|ref|>text<|/ref|><|det|>[[147, 150, 866, 180]]<|/det|> +(1) The manuscript **GPOC SYS-META Clean** does not contain comments, it is a revised clean manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 183, 824, 212]]<|/det|> +(2) The manuscript **GPOC SYS-META Comms** - you find the actions labelled with comments #1-30. + +<|ref|>text<|/ref|><|det|>[[147, 215, 880, 245]]<|/det|> +(3) The manuscript **GPOC SYS-META Highlighted** - you find all the changes underlined and highlighted. + +<|ref|>text<|/ref|><|det|>[[147, 247, 850, 278]]<|/det|> +(4) For convenience, the manuscript **GPOC SYS-META Trace** (Word-tracked) is fully traceable from the previous version that you reviewed. + +<|ref|>table<|/ref|><|det|>[[108, 304, 895, 875]]<|/det|> + +
Comments#PartPoint by Point Answers & Actions
Editor comments found in the
separate cover letter.
1-8AllSee author cover letter.
REVIEWER COMMENTS
Reviewer #1 (Remarks to the
Author)
The article systematically
reviews sharing of electronic
health records in a cloud. The
text is original, follows
PRISMA protocol, and presents
exciting insights to the
scientific community. The
authors considered the most
significant articles on the
subject. The protocol is
adequately done and gives a
discussion pointing out the
main challenges and issues.
9AllWe thank the reviewer for constructive and helpful comments that has ameliorated the manuscript.
Following, I list some
suggestions to improve the
article: GPOC is not a
universally accepts term. It is a term that the authors have used
in previous publications.
Although I do not see a
problem using this term in the
article, the authors could better
define what it means and why it could not use just PHR to
represent this idea. Another
doubt is what is a co-owned
cloud. Is it a public cloud? Is it
co-owned by the patient and its
health providers?
10Abst.
&
Intro.
It is important to define the unicity of the GPOC concept. This has now been implemented into the abstract and introduction. Hence, now there is a better definition of GPOC, what the co-ownership is, and why it is trisected for legal reasons. It has also been highlighted why a just PHR cannot be used - the
unicity of the GPOC concept of cloud, ownership, AI
integration, blockchain, foundation, globality, sharing,
independence, interaction, legal foundation status and
substrate for development of ML and its global dissemination has been elaborated.
- Pg. 3, line 45: The authors
discuss centralized approaches.
It would be interesting to
mention fog-based and peer-to-peer/hierarchical methods for
completeness.
11Disc.These have now been implemented as valuable new angles.
Now the fog-based and peer-to-peer/hierarchical methods are mentioned.
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[108, 80, 895, 900]]<|/det|> + +
- Pg. 3, line 63: How to deal with the language barrier among cross-border travel? I would appreciate a discussion on this subject.12Disc.This is now included in the discussion among the challenges and importance of AI integration into GPOC. We exemplify how inbuilt AI in the GPOC can solve language barriers.
- When discussing security and privacy, one of the focuses of the article, you could analyze the implications of HIPAA and GDPR. There are many aspects that these kinds of legislation affect privacy regarding health records and their relation to cross-border travel.13Disc.Thank you, we have now added a comment about and discuss this. After this comment we refer to the GPOC Ethics article 4 in the reference list. This article focuses entirely on ethics, policy, legal, regulation, etc. This is a self-contained article within the GPOC series. GDPR &amp; HIPAA now mentioned (without infringing into the Ethics' article), but now highlighted. Indeed, we cross reference to the article that focuses in this area.
- Security is mainly discussed in terms of encryption and decryption of data. A more comprehensive analysis is needed, including the three main aspects of confidentiality, integrity, and availability.14Disc.Now included and analysed articles of the systematic review elaborating these main aspects of confidentiality (19), integrity (11), and availability (12). Within parenthesis the number of articles bringing this up.
- The method is well-defined and based on PRISMA. I did not find the range period for the search, the bases used, and the specific terms (on page 5, line 94, you only mention some keywords).15Meth. &amp; Supp.The PRISMA form and other search documents have now all been included as supplements and referred to as supplementary files S1 and S3. In S1 the full search strategy is visible, with search strings etc. In S3 the PRISMA checklist is presented.
- Interoperability is an important issue that is not discussed at all. What is the rationale, and why was it not considered in the article? A global trend of adopting HL7 FHIR and other standards could influence the field.16Disc.Now interoperability has been implemented into the discussion. Now also HL7 FHIR is mentioned. Also, as cross referencing here has been made to the technical EcoTech Article.2
- Security-based parameters are based on times in ms: time for encryption, time for decryption, and the ratio of means. These times depend on the infrastructure: CPU, memory, network bandwidth, etc. Just showing the number of effective time adds little value since it depends on the infrastructure used.17Disc.Now this point has been added to the big picture of the results, as a decisive factor to consider and weigh in. The infrastructure for GPOC is further elaborated in the technical EcoTech Article.2 It is cross referenced to this now too.
- I missed a big picture of the main issues in the discussion section. The discussion is based on the more traditional "Author X studied that; Author Y discusses." You could start with a big picture presenting the main topics and then more implicitly bringing the related studies.18Disc.Now the big picture has been added in an initial overview, but also in the discussion. Al the places with the traditionally mention "author X studied Y", etc, have been altered and the result is a much better flow. Now, with an accompanying big picture before and after, it is more readable. As advised the big picture is presented mainly first. Also, the traditional author mentioning has been partly altered where possible now, so that the sentences are more neutral as flow better for the reader.
- You cite types of encryptions on lines 281-282 (page 14). A19Disc.A discussion has now been added on encryption. Also, referring further the technical EcoTech Article.2
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[108, 80, 895, 900]]<|/det|> + +
discussion could be added
because it could influence many
essential aspects of the study.
- Blockchain is cited throughout the article, and I consider it a
trend. You could discuss this
technology further and its
impact with more emphasis.
Other crucial subjects still need
to be explored, including
Federated Learning, Fog
Computing, and the Internet of
Things (how to combine data
from wearables from patient
EHR, for instance).
20Disc.Now a discussion on blockchain has been added. Federated Learning, Fog Computing, and the Internet of Things are mentioned, but also a refence for further reading of the technical EcoTech Article.2
- On page 19 you discuss
machine learning and the use of
data for decision, preserving
privacy, and not disclosing
patients' details. Anonymization and obfuscation, among other
methods, could be commented
on here. Although machine
learning is not a focus of the
article, it could influence GPOC in the services provided and
organization/storage of data.
21Disc.Now anonymization and obfuscation and also fully
homomorphic encryption is mentioned. There is now also a refence for further reading, where this is elaborated, in the technical EcoTech Article.2
- Line 386, Pg. 20, you cite
"four main areas," but it seems
to be five. It would be nice to
see some future directions.
22Disc.It has now been changed to eight (8) areas. Moreover, the initial keywords of each numbered paragraph have been italicised for increased clarity and readability. Also, the
number of directions has been expanded and are now also synched with the six problems statements mentioned before and also referred to in the GPOC series. Again, without any overlap.
Reviewer #2 (Remarks to the
Author)
I appreciate and congratulate all
authors for adding knowledge
to the Global Patient co-Owned Cloud (GPOC) a Cloud-based
infrastructure that shares
information in the Personal
Health Records (PHRs) space.
This topic is timely and requires significant effort to establish
particularly the concern on data security and privacy. I believe
the meta-analysis and results
presented cover the area to
some extent however the term
"use-ubiquity globally" that
appears in the abstract does not
take any advantages and/or
support to the claims (refer to
the conclusion).
23Abst.Many thanks. And yes, the term "use-ubiquity globally" that appears in the abstract, has been deleted and the whole
abstract has been completely rewritten. It is now within the
required limits of <150 words. Decreased from 244 words.
The abstract now starts to explain GPOC, present the series to get a context for the reader, and then focuses on the article and what it shows.
Some areas to improve based
on the Electronic Health
Records (EHRs) use are: 1)
Validity and Bias: This is very
24Res.Now under the headline "Validity and Bias" it has now been
explained how the risk minimisation was managed.
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[108, 80, 895, 900]]<|/det|> + +
critical to explain how the risk minimisation was managed.
(2) Perhaps, the language tone could be lower to support the general audience and/or readers (since this is Open Access Forum)25AllAs the editor also requested (and referred to reviewer 2) above in comment #1, very sentence of the whole manuscript has been put under revision and all paragraphs and nearly all sentences have been altered or polished. Hence, the language is now more suitable to a general audience and the sentences are shorter.
(3) In addition, Blockchain protocol-embedded PHRs might be another approach that did not dominate the claim hence expanding such idea and thinking would be an added advantage to the paper.26Disc.Now the approach with Blockchain protocol-embedded PHRs have been mentioned. Reference added for further reading of the technical EcoTech Article.²
(4) The conclusion section: I believe there are standards when sharing EHRs. Such standards are depending on the Geographical locations, the Country's data protection, and/or breaches of legislation and their maturity (this is a very challenging area indeed).27Disc. & Con.Now a hint about this is added. This is the full subject and ranger of the Ethics Article⁴. This article fully delves into geographical variations of ethics, legislation, regulations and policies. It is an additional combinatory literature review and interview series on this subject. It could not have been included into the present systematic review and meta-analysis and is self-contained and stands on its own legs. But a cross referencing has been added with the mentioned hint that this is important, and worth an independent article. See also the last point 8 of the discussion summary.
ADDITIONAL COMMENTS
The manuscripts share some form of information from the literature search. While they are interconnected, scientifically it is appropriate and valid to share the information however, the merit of the research contributions is somewhat diluted. Hence, it would be advisable to realign the findings specifically to the papers titled, for the readers' comfort and benefits.28Abst. & IntroAbsolutely. The overlaps have now been minimised. Hopefully eradicated. For instance, it is requested in the revision to delve into a technical or regulatory area, and these have now been added, but only very brief and with a reference to the article which has this area as its main subject. It is hence important that the required technical additions to the systematic review do not infringe or dilute other manuscripts. Note: all mentioning of subjects belonging to another manuscript has been deleted. Similarly other subjects belonging to other self-contained parts of the series have been deleted and referred to only once for information to the reader (ref 1,2,3,4). Hence, a total realignment has been carried out.
In general, the body of work completed was commendable. At the same time, the written language may not be palatable to a wider audience and readers. It would be advisable to make it simple where possible since there are several paragraphs confounded with each other.29AllThe whole text has now been rewritten. The language has been improved and the text flows better. It is adapted to the general audience. The sentences are less complex and shorter. Easier terminology has been used, whenever possible. When comparing the previous version and the present article manuscript all paragraphs and a majority of sentences have been rewritten to ease the flow for the general audience, which is very important. The paragraphing has been changed to eradicate any confusion. Note that now both the abstract (in two short sentences) and the introduction's first paragraph briefly mention the GPOC concept and the context of the GPOC series. Hence, the reader will immediately know what to expect from the articles regarding scope and contents. At the onset the reader will be aware that the five GPOC series entities will display distinct and non-overlapping foci. Hence, this sets the tone and contributes to the realignment of the articles. Several paragraphs hence became superfluous and have been deleted.
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[108, 82, 890, 210]]<|/det|> + +
One of the classic examples in the paper titled "Systematic Review and Meta-Analysis for a Global Patient co-Owned Cloud (GPOC)" uses the term "use-ubiquity globally" in the abstract. This term is misleading based on the conclusion.30Abst.This term has been deleted. The abstract has been completely rewritten. It has also been shortened from 244 to the required 150 words maximum. All intricate sentences with complex syntax and prosody have been altered. The message is clearer. Sentences shorter. Language simpler.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 293, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[118, 113, 222, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[118, 127, 298, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 141, 853, 169]]<|/det|> +The authors have conducted all the modifications asked for in the previous review. The article is now ready to be accepted. + +<--- Page Split ---> diff --git a/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/images_list.json b/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..070a3e17a5d2f5a9f25afc511525b212615c3fcd --- /dev/null +++ b/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,188 @@ + +# nature portfolio + +Peer Review File + +Supertorical light pulses as electromagnetic skyrmions propagating in free space + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The topology of electromagnetic beams and pulses is at the focus of growing research efforts currently, in particular with respect to the possibility of studying and exploiting topological phenomena typically observed in condensed matter (e.g. skyrmions). Whereas a number of works have studied such phenomena in electromagnetic beams, not much is known about the topological properties of pulses. Thus, the presented results are important and will be of considerable interest to the community. Overall, the paper is well written, and I recommend it for publication. I also suggest the following optional improvement to the manuscript: + +1. The authors may want to discuss in more detail the importance of their findings, in particular in the context of the recent stream of works (e.g. refs. [19,20,24]) on "skyrmion-like" electromagnetic field configurations. +2. The authors may want to qualitatively discuss the dependence of the topological structure on the q1 & q2 parameters. +3. The authors may want to suggest methods to generate the "supertoroidal pulses". Can they be generated in principle and what are the practical challenges? +4. The singularity structures presented in the Fig. 1 are not well explained. For instance, in the inset to Fig. 1a, what is annotated as line singularity appears to be a saddle point singularity. + +Finally, there is a typo in the beginning of the Discussion section (line 4): "maagnetic". + +Reviewer #2 (Remarks to the Author): + +The authors introduce a complete theoretical work of a new family of structured light pulses, which possess many attractive topological properties, including the general toroidal topology, skyrmions, fractal patterns. Both the toroidal electrodynamics and optical skyrmions are increasingly hot topics in recent years, and I am pleased to see the presented modeling in this manuscript manage to find an intersection of these two subjects. Also, the pulse family refers to the structuring of few- cycle ultrafast pulses, thus it shows importance to open new research direction of ultrafast nonlinear optics. To me it is also the first demonstration of optical quasiparticle, i.e. the skyrmions in propagating freespace light pulses, bring new topological states of light. Therefore, this article has enough novelty that deserved to be published, after some revisions as suggested below. + +(1) In my opinion, the work delivers two main novelties, the toroidal and the skyrmion. However, the backgrounds for both subjects are not included in the Introduction section. What is the importance of exploring new toroidal topology? What is the motivation of optical skyrmion? Besides, the authors have a paragraph introducing THz wave, which is confusing to me, since I don't get how THz motivate this work. Anyway, the article is well written except the Introduction section. Please reconsider the logic to give a more convincing introduction. + +(2) There is a misleading citation in the last sentence of first paragraph, that reference [25] has nothing to do with spin-orbit optical forces, while it is a work on nucleon interaction. I suggest this citation being replaced or removed. I understand skyrmion is a very hot topic, but please be careful that many works are not in optics, and what discussed here is optical skyrmion. + +(3) The "Results" part is very good, except a few expressions in the last subsection. For "fine-scale", how fine is the scale? Nanoscale or microscale? The author indeed explained this that it is sub-q1 scale, and q1 is effective wavelength, but one should avoid any ambiguous adjective in academic papers. Moreover, I found the sub-"wavelength' feature of skyrmion discussed here is extremely similar to a prior important work "Deep-subwavelength features of photonic skyrmions in a confined electromagnetic field with orbital angular momentum. Nat. Phys. 15, 650-654 (2019)." The similarity of two works should be discussed. + +(4) The supplemental material includes a very clear and detailed derivation of supertoroidal pulses, but no basic theoretical framework on skyrmion. The Methods include a part introducing the skyrmion background, + +<--- Page Split ---> + +but, as a reader, I am looking for a clearer theoretical background showing what is the ideal state of topological skyrmions. It helps if some simulation result can be provided so that one can compare the skyrmions in supertoroidal pulses with the ideal models. I suggest authors add some results in the supplemental material. + +Reviewer #3 (Remarks to the Author): + +The manuscript reports a family of few- cycle toroidal light pulses. The groundwork to this description was set in 1989, when Zielkowsky derived exact solution to Maxwell's equations in free space that combine properties of electromagnetic bullets and transient beams, including the defining equation of toroidal beams. Several properties of the simplest toroidal beams with azimuthal electric or magnetic fields were described soon after in 1996 by Hellwarth and Nouchi. The current manuscript extends this description to include higher order modes of toroidal light pulses, and describes phenomenologically several of their properties, including the spatial distribution of their vector fields, some considerations of the skyrmion character and energy backflow. + +This is in principle an interesting development, and, without following the mathematical derivation in detail, I have no doubt that the work is correct. + +What the manuscript lacks, in my opinion, is an explanation of why the described properties are important, and a motivation that goes beyond superficial hints at potential applications in information transfer or microscopy. + +Where are the higher order modes superior? + +What is the role of the defining parameter alpha, is there a fundamental difference between integer and fractal values of alpha, how does it impact on the skyrmion number or the energy backflow? What are general considerations beyond describing features of the specific examples? Are there experimental considerations for generating the more sophisticated modes? + +I note that the "growing attention" that toroidal light pulses are apparently attracting is demonstrated with 10 papers sharing the final author with the current manuscript - a more balanced view would strengthen this point. + +Finally, I suggest to replace the term "supertoroidal" with the more neutral "generalised toroidal light pulses". + +<--- Page Split ---> + +## Reviewer #1: + +"The topology of electromagnetic beams and pulses is at the focus of growing research efforts currently, in particular with respect to the possibility of studying and exploiting topological phenomena typically observed in condensed matter (e.g. skyrmions). Whereas a number of works have studied such phenomena in electromagnetic beams, not much is known about the topological properties of pulses. Thus, the presented results are important and will be of considerable interest to the community. Overall, the paper is well written, and I recommend it for publication. I also suggest the following optional improvement to the manuscript:" + +We thank the reviewer for their positive comments and recommendation for publication. + +"1. The authors may want to discuss in more detail the importance of their findings, in particular in the context of the recent stream of works (e.g. refs. [19,20,24]) on "skyrmion-like" electromagnetic field configurations." + +We now include a comprehensive discussion of recent advances in the field of electromagnetic skyrmions in the Introduction, see page 1, left column, first paragraph. + +"2. The authors may want to qualitatively discuss the dependence of the topological structure on the \(q1\) & \(q2\) parameters." + +In response to the reviewer's comment, we discuss the dependence of the topological structure on the \(q_{1}\) and \(q_{2}\) parameters in page 7, right column, end of first paragraph. We have also added two videos in the supplementary material to illustrate this dependence (see Supplementary Videos 3 & 6). + +"3. The authors may want to suggest methods to generate the "supertoroidal pulses". Can they be generated in principle and what are the practical challenges?" + +The main challenges for the generation of supertoroidal pulses involve its toroidal topology, broad bandwidth (single- cycle duration), and complex spatially- dependent spectral structure (see Supplementary Information E). We argue that supertoroidal pulses can be generated similarly to the generation of fundamental toroidal pulses [30,31], i.e. by conversion of ultrashort linearly polarized pulses in a two- stage process. This process shall involve the linear- to- radial polarization conversion of an ultrashort laser pulse, followed by the spatio- spectral modification of the pulse in a multi- layered gradient metasurface. We anticipate that the requirement for the single- cycle temporal profile will be possible to be met if we use attosecond laser pulses as input. Alternatively, in the THz range, single- cycle pulses can be routinely generated by optical rectification of femtosecond optical pulses. + +We discuss the generation of supertoroidal pulses in page 7, right column, \(2^{\mathrm{nd}}\) paragraph of the Discussion section. + +<--- Page Split ---> + +“4. The singularity structures presented in the Fig. 1 are not well explained. For instance, in the inset to Fig. 1a, what is annotated as line singularity appears to be a saddle point singularity.” + +We thank the reviewer for pointing out this error. In the revised manuscript, we have corrected and expanded the description of singularities in Fig. 1: grey lines represent vortex- type singularities, solid circles indicate saddle- type singularities, and the colored vectors represent skyrmionic structures in selected transverse planes (see page 2, last paragraph before section “Electric field singularity”). + +“Finally, there is a typo in the beginning of the Discussion section (line 4): "maagnetic".” + +We have corrected this typo. + +## Reviewer #2: + +“The authors introduce a complete theoretical work of a new family of structured light pulses, which possess many attractive topological properties, including the general toroidal topology, skyrmions, fractal patterns. Both the toroidal electrodynamics and optical skyrmions are increasingly hot topics in recent years, and I am pleased to see the presented modeling in this manuscript manage to find an intersection of these two subjects. Also, the pulse family refers to the structuring of few- cycle ultrafast pulses, thus it shows importance to open new research direction of ultrafast nonlinear optics. To me it is also the first demonstration of optical quasiparticle, i.e. the skyrmions in propagating freespace light pulses, bring new topological states of light. Therefore, this article has enough novelty that deserved to be published, after some revisions as suggested below.” + +We thank the reviewer for their supportive comments. + +“(1) In my opinion, the work delivers two main novelties, the toroidal and the skyrmion. However, the backgrounds for both subjects are not included in the Introduction section. What is the importance of exploring new toroidal topology? What is the motivation of optical skyrmion? Besides, the authors have a paragraph introducing THz wave, which is confusing to me, since I don’t get how THz motivate this work. Anyway, the article is well written except the Introduction section. Please reconsider the logic to give a more convincing introduction.” + +We thank the reviewer for their suggestion. We have expanded our Introduction section to include a discussion of earlier work on the “toroidal” and “skyrmion” aspects of our work and have removed the paragraph on THz waves (see page 1, paragraphs 1 & 2). + +“(2) There is a misleading citation in the last sentence of first paragraph, that reference [25] has nothing to do with spin-orbit optical forces, while it is a work on nucleon interaction. I suggest this citation being replaced or removed. I understand skyrmion is a very hot topic, but please be careful that many works are not in optics, and what discussed here is optical skyrmion.” + +We thank the reviewer for pointing out this error, which has been corrected in the revised manuscript. + +<--- Page Split ---> + +"(3) The "Results" part is very good, except a few expressions in the last subsection. For "fine-scale", how fine is the scale? Nanoscale or microscale? The author indeed explained this that it is sub- q1 scale, and q1 is effective wavelength, but one should avoid any ambiguous adjective in academic papers. Moreover, I found the sub-'wavelength' feature of skyrmion discussed here is extremely similar to a prior important work "Deep-subwavelength features of photonic skyrmions in a confined electromagnetic field with orbital angular momentum. Nat. Phys. 15, 650-654 (2019)." The similarity of two works should be discussed." + +In response to the reviewer's comment, we have replaced the phrase "fine- scale" with "subwavelength" and clearly state that the "wavelength" here refers to \(\mathrm{q}_1\) , the effective wavelength (cycle- length) of the pulse. + +There is a dramatic difference between the subwavelength features presented in our work and that of Du et al., as our results involve free- space propagating waves rather than evanescent plasmonic fields. This is discussed in the Section "Subwavelength features of skyrmionic structures". + +"(4) The supplemental material includes a very clear and detailed derivation of supertoroidal pulses, but no basic theoretical framework on skyrmion. The Methods include a part introducing the skyrmion background, but, as a reader, I am looking for a clearer theoretical background showing what is the ideal state of topological skyrmions. It helps if some simulation result can be provided so that one can compare the skyrmions in supertoroidal pulses with the ideal models. I suggest authors add some results in the supplemental material." + +We thank the reviewer for their suggestion. We have added a discussion of the theoretical framework of skyrmions in Supplementary Information F. + +## Reviewer #3: + +"The manuscript reports a family of few- cycle toroidal light pulses. The groundwork to this description was set in 1989, when Zielkowsky derived exact solution to Maxwell's equations in free space that combine properties of electromagnetic bullets and transient beams, including the defining equation of toroidal beams. Several properties of the simplest toroidal beams with azimuthal electric or magnetic fields were described soon after in 1996 by Hellwarth and Nouchi. The current manuscript extends this description to include higher order modes of toroidal light pulses, and describes phenomenologically several of their properties, including the spatial distribution of their vector fields, some considerations of the skyrmion character and energy backflow. This is in principle an interesting development, and, without following the mathematical derivation in detail, I have no doubt that the work is correct. What the manuscript lacks, in my opinion, is an explanation of why the described properties are important, and a motivation that goes beyond superficial hints at potential applications in information transfer or microscopy." + +We thank the reviewer for their positive comments. + +"Where are the higher order modes superior?" + +<--- Page Split ---> + +Supertoroidal pulses exhibit a number of advantages with respect to the fundamental Flying Doughnuts. Firstly, higher order toroidal pulses exhibit a range of different skyrmionic field configurations, which will be of interest for probing the topology of excitations in matter. Secondly, information can be encoded in the increasingly complex topological structure of the propagating pulses, which could be of interest for optical communications. Finally, the subwavelength features of the singular structures of the pulses may lead to new approaches to superresolution imaging and nanoscale metrology. + +We include now this discussion in the final paragraph of the Discussion section, in page 7, right column. + +"What is the role of the defining parameter alpha, is there a fundamental difference between integer and fractal values of alpha, how does it impact on the skyrmion number or the energy backflow?" + +The parameter \(\alpha\) prescribes the degree of energy confinement in the pulse and is directly related to the finite energy requirement for the description of physical pulses. In particular, \(\alpha < 1\) results in pulses of infinite energy, such as planar waves and cylindrical waves, while \(\alpha \geq 1\) leads to finite- energy pulses. The parameter \(\alpha\) is also related to the topology of the pulse. Indeed, given the few- cycle nature of the supertoroidal pulses, the increasing localization of energy for high values of \(\alpha\) results in increasingly complex topological structures. Finally, in our study we found no evidence of a qualitative difference between integer and fractional values of \(\alpha\) (see Supplementary Video 4). + +We now include this discussion in page 1, first paragraph of the Results section. + +"What are general considerations beyond describing features of the specific examples?" + +We added general considerations, especially in (1) Light- matter interactions; (2) Information transfer; (3) Imaging and metrology. See more details same as the response to the first comment. + +"Are there experimental considerations for generating the more sophisticated modes?" + +Please see our response to point 3 by reviewer #1. + +"I note that the "growing attention" that toroidal light pulses are apparently attracting is demonstrated with 10 papers sharing the final author with the current manuscript - a more balanced view would strengthen this point." + +In the revised manuscript, we provide a more comprehensive introduction on toroidal light with balanced citations (see added Refs. [34,35,38- 42]). + +"Finally, I suggest to replace the term "supertoroidal" with the more neutral "generalised toroidal light pulses"." + +<--- Page Split ---> + +We respectfully disagree with the reviewer. In the electrodynamics community, the term “supertoroidal” refers to generalizations of toroidal excitations (see for example Photonics 6, 43 (2019), PRA 98, 023858 (2018)). We now motivate the use of the term “supertoroidal” in the second paragraph of the Introduction section. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +I am satisfied with author corrections and replies related to my comments. I recommend this paper for publication in Nature Communications. + +Reviewer #2: + +Remarks to the Author: + +The authors have made a good revision work and well addressed all the concerns. Thus I recommend its publication in Nature Communications. + +Reviewer #3: None + +<--- Page Split ---> + +## Response to Reviewer #1: + +"I am satisfied with author corrections and replies related to my comments. I recommend this paper for publication in Nature Communications." + +We thank the reviewer for their positive comments and recommendation for publication. + +## Response to Reviewer #2: + +"The authors have made a good revision work and well addressed all the concerns. Thus I recommend its publication in Nature Communications." + +We thank the reviewer for their positive comments and recommendation for publication. + +<--- Page Split ---> diff --git a/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f7f249ff50babd7fc538df699df36626d09c8eb9 --- /dev/null +++ b/peer_reviews/126886759851d7ab006726a2a5b4c6ce9d24ee1c0468e8a9a6cfd9c1f1293206/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,258 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[69, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 836, 212]]<|/det|> +Supertorical light pulses as electromagnetic skyrmions propagating in free space + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[105, 84, 281, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[105, 113, 401, 128]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[105, 143, 936, 248]]<|/det|> +The topology of electromagnetic beams and pulses is at the focus of growing research efforts currently, in particular with respect to the possibility of studying and exploiting topological phenomena typically observed in condensed matter (e.g. skyrmions). Whereas a number of works have studied such phenomena in electromagnetic beams, not much is known about the topological properties of pulses. Thus, the presented results are important and will be of considerable interest to the community. Overall, the paper is well written, and I recommend it for publication. I also suggest the following optional improvement to the manuscript: + +<|ref|>text<|/ref|><|det|>[[102, 262, 936, 396]]<|/det|> +1. The authors may want to discuss in more detail the importance of their findings, in particular in the context of the recent stream of works (e.g. refs. [19,20,24]) on "skyrmion-like" electromagnetic field configurations. +2. The authors may want to qualitatively discuss the dependence of the topological structure on the q1 & q2 parameters. +3. The authors may want to suggest methods to generate the "supertoroidal pulses". Can they be generated in principle and what are the practical challenges? +4. The singularity structures presented in the Fig. 1 are not well explained. For instance, in the inset to Fig. 1a, what is annotated as line singularity appears to be a saddle point singularity. + +<|ref|>text<|/ref|><|det|>[[104, 411, 768, 426]]<|/det|> +Finally, there is a typo in the beginning of the Discussion section (line 4): "maagnetic". + +<|ref|>text<|/ref|><|det|>[[105, 471, 401, 485]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[104, 501, 939, 635]]<|/det|> +The authors introduce a complete theoretical work of a new family of structured light pulses, which possess many attractive topological properties, including the general toroidal topology, skyrmions, fractal patterns. Both the toroidal electrodynamics and optical skyrmions are increasingly hot topics in recent years, and I am pleased to see the presented modeling in this manuscript manage to find an intersection of these two subjects. Also, the pulse family refers to the structuring of few- cycle ultrafast pulses, thus it shows importance to open new research direction of ultrafast nonlinear optics. To me it is also the first demonstration of optical quasiparticle, i.e. the skyrmions in propagating freespace light pulses, bring new topological states of light. Therefore, this article has enough novelty that deserved to be published, after some revisions as suggested below. + +<|ref|>text<|/ref|><|det|>[[104, 636, 937, 725]]<|/det|> +(1) In my opinion, the work delivers two main novelties, the toroidal and the skyrmion. However, the backgrounds for both subjects are not included in the Introduction section. What is the importance of exploring new toroidal topology? What is the motivation of optical skyrmion? Besides, the authors have a paragraph introducing THz wave, which is confusing to me, since I don't get how THz motivate this work. Anyway, the article is well written except the Introduction section. Please reconsider the logic to give a more convincing introduction. + +<|ref|>text<|/ref|><|det|>[[104, 726, 930, 785]]<|/det|> +(2) There is a misleading citation in the last sentence of first paragraph, that reference [25] has nothing to do with spin-orbit optical forces, while it is a work on nucleon interaction. I suggest this citation being replaced or removed. I understand skyrmion is a very hot topic, but please be careful that many works are not in optics, and what discussed here is optical skyrmion. + +<|ref|>text<|/ref|><|det|>[[104, 786, 937, 875]]<|/det|> +(3) The "Results" part is very good, except a few expressions in the last subsection. For "fine-scale", how fine is the scale? Nanoscale or microscale? The author indeed explained this that it is sub-q1 scale, and q1 is effective wavelength, but one should avoid any ambiguous adjective in academic papers. Moreover, I found the sub-"wavelength' feature of skyrmion discussed here is extremely similar to a prior important work "Deep-subwavelength features of photonic skyrmions in a confined electromagnetic field with orbital angular momentum. Nat. Phys. 15, 650-654 (2019)." The similarity of two works should be discussed. + +<|ref|>text<|/ref|><|det|>[[101, 875, 930, 905]]<|/det|> +(4) The supplemental material includes a very clear and detailed derivation of supertoroidal pulses, but no basic theoretical framework on skyrmion. The Methods include a part introducing the skyrmion background, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 83, 885, 142]]<|/det|> +but, as a reader, I am looking for a clearer theoretical background showing what is the ideal state of topological skyrmions. It helps if some simulation result can be provided so that one can compare the skyrmions in supertoroidal pulses with the ideal models. I suggest authors add some results in the supplemental material. + +<|ref|>text<|/ref|><|det|>[[106, 188, 401, 202]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[104, 217, 936, 338]]<|/det|> +The manuscript reports a family of few- cycle toroidal light pulses. The groundwork to this description was set in 1989, when Zielkowsky derived exact solution to Maxwell's equations in free space that combine properties of electromagnetic bullets and transient beams, including the defining equation of toroidal beams. Several properties of the simplest toroidal beams with azimuthal electric or magnetic fields were described soon after in 1996 by Hellwarth and Nouchi. The current manuscript extends this description to include higher order modes of toroidal light pulses, and describes phenomenologically several of their properties, including the spatial distribution of their vector fields, some considerations of the skyrmion character and energy backflow. + +<|ref|>text<|/ref|><|det|>[[101, 338, 937, 361]]<|/det|> +This is in principle an interesting development, and, without following the mathematical derivation in detail, I have no doubt that the work is correct. + +<|ref|>text<|/ref|><|det|>[[105, 363, 928, 410]]<|/det|> +What the manuscript lacks, in my opinion, is an explanation of why the described properties are important, and a motivation that goes beyond superficial hints at potential applications in information transfer or microscopy. + +<|ref|>text<|/ref|><|det|>[[105, 425, 446, 440]]<|/det|> +Where are the higher order modes superior? + +<|ref|>text<|/ref|><|det|>[[105, 441, 900, 503]]<|/det|> +What is the role of the defining parameter alpha, is there a fundamental difference between integer and fractal values of alpha, how does it impact on the skyrmion number or the energy backflow? What are general considerations beyond describing features of the specific examples? Are there experimental considerations for generating the more sophisticated modes? + +<|ref|>text<|/ref|><|det|>[[105, 517, 939, 562]]<|/det|> +I note that the "growing attention" that toroidal light pulses are apparently attracting is demonstrated with 10 papers sharing the final author with the current manuscript - a more balanced view would strengthen this point. + +<|ref|>text<|/ref|><|det|>[[100, 576, 884, 607]]<|/det|> +Finally, I suggest to replace the term "supertoroidal" with the more neutral "generalised toroidal light pulses". + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[144, 90, 246, 105]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[144, 116, 854, 237]]<|/det|> +"The topology of electromagnetic beams and pulses is at the focus of growing research efforts currently, in particular with respect to the possibility of studying and exploiting topological phenomena typically observed in condensed matter (e.g. skyrmions). Whereas a number of works have studied such phenomena in electromagnetic beams, not much is known about the topological properties of pulses. Thus, the presented results are important and will be of considerable interest to the community. Overall, the paper is well written, and I recommend it for publication. I also suggest the following optional improvement to the manuscript:" + +<|ref|>text<|/ref|><|det|>[[144, 247, 781, 264]]<|/det|> +We thank the reviewer for their positive comments and recommendation for publication. + +<|ref|>text<|/ref|><|det|>[[144, 302, 854, 353]]<|/det|> +"1. The authors may want to discuss in more detail the importance of their findings, in particular in the context of the recent stream of works (e.g. refs. [19,20,24]) on "skyrmion-like" electromagnetic field configurations." + +<|ref|>text<|/ref|><|det|>[[144, 364, 830, 398]]<|/det|> +We now include a comprehensive discussion of recent advances in the field of electromagnetic skyrmions in the Introduction, see page 1, left column, first paragraph. + +<|ref|>text<|/ref|><|det|>[[144, 435, 853, 470]]<|/det|> +"2. The authors may want to qualitatively discuss the dependence of the topological structure on the \(q1\) & \(q2\) parameters." + +<|ref|>text<|/ref|><|det|>[[144, 480, 853, 548]]<|/det|> +In response to the reviewer's comment, we discuss the dependence of the topological structure on the \(q_{1}\) and \(q_{2}\) parameters in page 7, right column, end of first paragraph. We have also added two videos in the supplementary material to illustrate this dependence (see Supplementary Videos 3 & 6). + +<|ref|>text<|/ref|><|det|>[[144, 578, 853, 611]]<|/det|> +"3. The authors may want to suggest methods to generate the "supertoroidal pulses". Can they be generated in principle and what are the practical challenges?" + +<|ref|>text<|/ref|><|det|>[[144, 621, 853, 793]]<|/det|> +The main challenges for the generation of supertoroidal pulses involve its toroidal topology, broad bandwidth (single- cycle duration), and complex spatially- dependent spectral structure (see Supplementary Information E). We argue that supertoroidal pulses can be generated similarly to the generation of fundamental toroidal pulses [30,31], i.e. by conversion of ultrashort linearly polarized pulses in a two- stage process. This process shall involve the linear- to- radial polarization conversion of an ultrashort laser pulse, followed by the spatio- spectral modification of the pulse in a multi- layered gradient metasurface. We anticipate that the requirement for the single- cycle temporal profile will be possible to be met if we use attosecond laser pulses as input. Alternatively, in the THz range, single- cycle pulses can be routinely generated by optical rectification of femtosecond optical pulses. + +<|ref|>text<|/ref|><|det|>[[144, 804, 853, 837]]<|/det|> +We discuss the generation of supertoroidal pulses in page 7, right column, \(2^{\mathrm{nd}}\) paragraph of the Discussion section. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 89, 843, 124]]<|/det|> +“4. The singularity structures presented in the Fig. 1 are not well explained. For instance, in the inset to Fig. 1a, what is annotated as line singularity appears to be a saddle point singularity.” + +<|ref|>text<|/ref|><|det|>[[145, 134, 853, 220]]<|/det|> +We thank the reviewer for pointing out this error. In the revised manuscript, we have corrected and expanded the description of singularities in Fig. 1: grey lines represent vortex- type singularities, solid circles indicate saddle- type singularities, and the colored vectors represent skyrmionic structures in selected transverse planes (see page 2, last paragraph before section “Electric field singularity”). + +<|ref|>text<|/ref|><|det|>[[145, 258, 796, 275]]<|/det|> +“Finally, there is a typo in the beginning of the Discussion section (line 4): "maagnetic".” + +<|ref|>text<|/ref|><|det|>[[145, 285, 352, 301]]<|/det|> +We have corrected this typo. + +<|ref|>sub_title<|/ref|><|det|>[[145, 335, 246, 351]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[144, 362, 853, 533]]<|/det|> +“The authors introduce a complete theoretical work of a new family of structured light pulses, which possess many attractive topological properties, including the general toroidal topology, skyrmions, fractal patterns. Both the toroidal electrodynamics and optical skyrmions are increasingly hot topics in recent years, and I am pleased to see the presented modeling in this manuscript manage to find an intersection of these two subjects. Also, the pulse family refers to the structuring of few- cycle ultrafast pulses, thus it shows importance to open new research direction of ultrafast nonlinear optics. To me it is also the first demonstration of optical quasiparticle, i.e. the skyrmions in propagating freespace light pulses, bring new topological states of light. Therefore, this article has enough novelty that deserved to be published, after some revisions as suggested below.” + +<|ref|>text<|/ref|><|det|>[[145, 545, 535, 561]]<|/det|> +We thank the reviewer for their supportive comments. + +<|ref|>text<|/ref|><|det|>[[144, 588, 853, 693]]<|/det|> +“(1) In my opinion, the work delivers two main novelties, the toroidal and the skyrmion. However, the backgrounds for both subjects are not included in the Introduction section. What is the importance of exploring new toroidal topology? What is the motivation of optical skyrmion? Besides, the authors have a paragraph introducing THz wave, which is confusing to me, since I don’t get how THz motivate this work. Anyway, the article is well written except the Introduction section. Please reconsider the logic to give a more convincing introduction.” + +<|ref|>text<|/ref|><|det|>[[145, 703, 853, 755]]<|/det|> +We thank the reviewer for their suggestion. We have expanded our Introduction section to include a discussion of earlier work on the “toroidal” and “skyrmion” aspects of our work and have removed the paragraph on THz waves (see page 1, paragraphs 1 & 2). + +<|ref|>text<|/ref|><|det|>[[145, 782, 853, 850]]<|/det|> +“(2) There is a misleading citation in the last sentence of first paragraph, that reference [25] has nothing to do with spin-orbit optical forces, while it is a work on nucleon interaction. I suggest this citation being replaced or removed. I understand skyrmion is a very hot topic, but please be careful that many works are not in optics, and what discussed here is optical skyrmion.” + +<|ref|>text<|/ref|><|det|>[[144, 860, 853, 895]]<|/det|> +We thank the reviewer for pointing out this error, which has been corrected in the revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 116, 854, 237]]<|/det|> +"(3) The "Results" part is very good, except a few expressions in the last subsection. For "fine-scale", how fine is the scale? Nanoscale or microscale? The author indeed explained this that it is sub- q1 scale, and q1 is effective wavelength, but one should avoid any ambiguous adjective in academic papers. Moreover, I found the sub-'wavelength' feature of skyrmion discussed here is extremely similar to a prior important work "Deep-subwavelength features of photonic skyrmions in a confined electromagnetic field with orbital angular momentum. Nat. Phys. 15, 650-654 (2019)." The similarity of two works should be discussed." + +<|ref|>text<|/ref|><|det|>[[145, 247, 853, 299]]<|/det|> +In response to the reviewer's comment, we have replaced the phrase "fine- scale" with "subwavelength" and clearly state that the "wavelength" here refers to \(\mathrm{q}_1\) , the effective wavelength (cycle- length) of the pulse. + +<|ref|>text<|/ref|><|det|>[[145, 309, 853, 360]]<|/det|> +There is a dramatic difference between the subwavelength features presented in our work and that of Du et al., as our results involve free- space propagating waves rather than evanescent plasmonic fields. This is discussed in the Section "Subwavelength features of skyrmionic structures". + +<|ref|>text<|/ref|><|det|>[[144, 387, 854, 491]]<|/det|> +"(4) The supplemental material includes a very clear and detailed derivation of supertoroidal pulses, but no basic theoretical framework on skyrmion. The Methods include a part introducing the skyrmion background, but, as a reader, I am looking for a clearer theoretical background showing what is the ideal state of topological skyrmions. It helps if some simulation result can be provided so that one can compare the skyrmions in supertoroidal pulses with the ideal models. I suggest authors add some results in the supplemental material." + +<|ref|>text<|/ref|><|det|>[[145, 501, 852, 536]]<|/det|> +We thank the reviewer for their suggestion. We have added a discussion of the theoretical framework of skyrmions in Supplementary Information F. + +<|ref|>sub_title<|/ref|><|det|>[[145, 564, 246, 580]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[144, 589, 854, 814]]<|/det|> +"The manuscript reports a family of few- cycle toroidal light pulses. The groundwork to this description was set in 1989, when Zielkowsky derived exact solution to Maxwell's equations in free space that combine properties of electromagnetic bullets and transient beams, including the defining equation of toroidal beams. Several properties of the simplest toroidal beams with azimuthal electric or magnetic fields were described soon after in 1996 by Hellwarth and Nouchi. The current manuscript extends this description to include higher order modes of toroidal light pulses, and describes phenomenologically several of their properties, including the spatial distribution of their vector fields, some considerations of the skyrmion character and energy backflow. This is in principle an interesting development, and, without following the mathematical derivation in detail, I have no doubt that the work is correct. What the manuscript lacks, in my opinion, is an explanation of why the described properties are important, and a motivation that goes beyond superficial hints at potential applications in information transfer or microscopy." + +<|ref|>text<|/ref|><|det|>[[145, 824, 515, 840]]<|/det|> +We thank the reviewer for their positive comments. + +<|ref|>text<|/ref|><|det|>[[147, 859, 494, 875]]<|/det|> +"Where are the higher order modes superior?" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 89, 854, 210]]<|/det|> +Supertoroidal pulses exhibit a number of advantages with respect to the fundamental Flying Doughnuts. Firstly, higher order toroidal pulses exhibit a range of different skyrmionic field configurations, which will be of interest for probing the topology of excitations in matter. Secondly, information can be encoded in the increasingly complex topological structure of the propagating pulses, which could be of interest for optical communications. Finally, the subwavelength features of the singular structures of the pulses may lead to new approaches to superresolution imaging and nanoscale metrology. + +<|ref|>text<|/ref|><|det|>[[144, 219, 839, 253]]<|/det|> +We include now this discussion in the final paragraph of the Discussion section, in page 7, right column. + +<|ref|>text<|/ref|><|det|>[[144, 291, 820, 343]]<|/det|> +"What is the role of the defining parameter alpha, is there a fundamental difference between integer and fractal values of alpha, how does it impact on the skyrmion number or the energy backflow?" + +<|ref|>text<|/ref|><|det|>[[144, 353, 854, 492]]<|/det|> +The parameter \(\alpha\) prescribes the degree of energy confinement in the pulse and is directly related to the finite energy requirement for the description of physical pulses. In particular, \(\alpha < 1\) results in pulses of infinite energy, such as planar waves and cylindrical waves, while \(\alpha \geq 1\) leads to finite- energy pulses. The parameter \(\alpha\) is also related to the topology of the pulse. Indeed, given the few- cycle nature of the supertoroidal pulses, the increasing localization of energy for high values of \(\alpha\) results in increasingly complex topological structures. Finally, in our study we found no evidence of a qualitative difference between integer and fractional values of \(\alpha\) (see Supplementary Video 4). + +<|ref|>text<|/ref|><|det|>[[144, 502, 721, 519]]<|/det|> +We now include this discussion in page 1, first paragraph of the Results section. + +<|ref|>text<|/ref|><|det|>[[145, 545, 790, 563]]<|/det|> +"What are general considerations beyond describing features of the specific examples?" + +<|ref|>text<|/ref|><|det|>[[144, 573, 842, 608]]<|/det|> +We added general considerations, especially in (1) Light- matter interactions; (2) Information transfer; (3) Imaging and metrology. See more details same as the response to the first comment. + +<|ref|>text<|/ref|><|det|>[[144, 635, 775, 652]]<|/det|> +"Are there experimental considerations for generating the more sophisticated modes?" + +<|ref|>text<|/ref|><|det|>[[144, 662, 505, 679]]<|/det|> +Please see our response to point 3 by reviewer #1. + +<|ref|>text<|/ref|><|det|>[[144, 707, 854, 758]]<|/det|> +"I note that the "growing attention" that toroidal light pulses are apparently attracting is demonstrated with 10 papers sharing the final author with the current manuscript - a more balanced view would strengthen this point." + +<|ref|>text<|/ref|><|det|>[[144, 769, 836, 802]]<|/det|> +In the revised manuscript, we provide a more comprehensive introduction on toroidal light with balanced citations (see added Refs. [34,35,38- 42]). + +<|ref|>text<|/ref|><|det|>[[144, 831, 797, 866]]<|/det|> +"Finally, I suggest to replace the term "supertoroidal" with the more neutral "generalised toroidal light pulses"." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 853, 158]]<|/det|> +We respectfully disagree with the reviewer. In the electrodynamics community, the term “supertoroidal” refers to generalizations of toroidal excitations (see for example Photonics 6, 43 (2019), PRA 98, 023858 (2018)). We now motivate the use of the term “supertoroidal” in the second paragraph of the Introduction section. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 84, 280, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[105, 114, 210, 127]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[105, 130, 285, 142]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[103, 144, 895, 174]]<|/det|> +I am satisfied with author corrections and replies related to my comments. I recommend this paper for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[105, 218, 210, 231]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[105, 234, 285, 247]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[103, 248, 904, 277]]<|/det|> +The authors have made a good revision work and well addressed all the concerns. Thus I recommend its publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[105, 323, 210, 352]]<|/det|> +Reviewer #3: None + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[144, 90, 343, 106]]<|/det|> +## Response to Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[144, 117, 853, 151]]<|/det|> +"I am satisfied with author corrections and replies related to my comments. I recommend this paper for publication in Nature Communications." + +<|ref|>text<|/ref|><|det|>[[144, 160, 840, 179]]<|/det|> +We thank the reviewer for their positive comments and recommendation for publication. + +<|ref|>sub_title<|/ref|><|det|>[[144, 206, 343, 223]]<|/det|> +## Response to Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[144, 233, 800, 267]]<|/det|> +"The authors have made a good revision work and well addressed all the concerns. Thus I recommend its publication in Nature Communications." + +<|ref|>text<|/ref|><|det|>[[142, 276, 840, 295]]<|/det|> +We thank the reviewer for their positive comments and recommendation for publication. + +<--- Page Split ---> diff --git a/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/images_list.json b/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..025e0c340d7dcc32580ee9785c44f992f3f0d2da --- /dev/null +++ b/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1 Schematic of the experimental setup used to characterize the linewidths of individual comb lines.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure R2 a) Frequency noise spectrum of a single-mode lasing state, single-lobe comb state (Comb 1), and bifurcated two-lobe comb state (Comb 2). For the combs, the frequency noise is for the entire combs, similar to Fig.2 in the paper. b) Optical spectrum (blue) and recorded linewidth (red dot) for the single-mode lasing state. c) Optical spectrum (blue) and recorded linewidths (red dots) of individual comb lines, for the single-lobe comb state (Comb 1). d) Same as c) but for the bifurcated two-lobe comb state (Comb 2). In b)-d), the small spectral gap on the noise floor is due to the spectral filtering by the FBG filter.", + "footnote": [], + "bbox": [ + [ + 171, + 92, + 826, + 466 + ] + ], + "page_idx": 7 + } +] \ No newline at end of file diff --git a/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..bee419113ff34e8b17822e14b78d286252162d72 --- /dev/null +++ b/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,224 @@ + +# nature portfolio + +Peer Review File + +Electrically empowered microcomb laser + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In the paper titled "Electrically empowered microcomb laser", the authors demonstrated an external cavity laser that can generate combs due to the combination of Kerr nonlinearity and EO modulation. This concept is novel, and the experimental results are solid. I think this paper can be accepted by Nature Communications after addressing the following issue: + +1. I think some claims of the paper can be modified. Personally, I don't think this work addresses all the problems of "complex soliton initialization, high threshold, low power efficiency, and limited comb reconfigurability" for microcombs. It might be better to focus more on the dynamics of this unique laser configuration. + +2. When calculating the wall-plug efficiency, I think the RF power applied to the cavity needs to be counted. One major problem for people using EO combs is the large RF power required. I think discussions regarding this problem should be added. + +3. Can the author discuss more about the power of individual comb lines? What really matters in most of the applications is the comb line power, so a more detailed discussion could be helpful. + +4. I feel that the statement "100% utilization of optical power fully contributing to comb generation" is strange. How to define which potion of power contribute to comb generation? For traditional microcomb this can be defined by the soliton state power/pump power, but I don't think it applies here. + +5. What is the time domain pattern of this mode locked state? Is it more like a soliton or dark pulse? What is the pulse width? + +6. Can the author add discussions about the tuning range of the FSR? + +Reviewer #2 (Remarks to the Author): + +This paper introduces a novel method of microcomb laser by hybridizing Kerr nonlinearity, EO modulation and the gain/lasing process in an EO modulated LN microresonator. The proposed scheme is novel and elegant in terms of the underlying concept, and exhibits significant performance advantages including high efficiency and a straightforward triggering process. While I do have some questions regarding the theoretical analysis detailed below, I believe a properly revised version could be considered for publication in Nature Communications. + +1. Although the combination of Kerr nonlinearity, EO modulation and laser is intriguing, the concept of microcomb laser has previously been demonstrated using Kerr nonlinearity and lasing process [18,21]. Compared with these previous works, this comb spectra in this work show bifurcated spectral shapes + +<--- Page Split ---> + +and narrower optical bandwidths. It would be great if the authors could provide more explanations and insights, from physics point of view, on the difference between these two microcomb laser schemes. + +2. This method eliminates the need for pre-configuration compared with self-injection locking for microcomb stimulation. However, the proposed method require precise alignment of multiple resonances within a wideband between the two cavities, which seems quite challenging. The authors also mentioned, "this problem can be resolved by further optimization of the roundtrip length of the main laser cavity and introducing tunability". Compared with self-injection locking, which involves tuning the optical phase - an easy task in integrated photonics, this method requires tuning the cavity length or group index, which is actually highly challenging for on-chip photonics? Please comment on these problems and potential solutions, if any. + +3. The authors identified three limitations in previous microcomb works, including complex initialization process, low power efficiency and limited reconfigurability. The proposed scheme does solve the first two problems quite obviously, but I'm not too sure what the authors refer to when mentioning "reconfigurability". Does this refer to the fast chirping depicted in Fig. 4, or the comb spacing tuning shown in Fig. 3? Since controlling comb spacing and spectral shape is well known technique in Kerr-based microcombs, I hope the authors could be more specific when mentioning "reconfigurability" and provide more explanations if possible. + +4. The linewidth testing shown in Fig. 2e, which is obtained from a heterodyne measurement of the entire comb, is quite confusing to me. The authors claim that the tested linewidth is "the upper limit of the intrinsic linewidth of individual comb lines" (Page 4, line 222)? In my understanding, the noises of comb lines with higher signal powers would overwhelm those of low-power comb lines. As a result when normalizing the noise spectrum of the entire comb, one is probably seeing a larger noise contribution from higher-power lines, which are not necessarily better or worse than the lower-power lines. Please provide more references or proof to support this claim. + +5. Following up on the above question, it would be really nice if the authors could characterize the linewidths of each comb lines. The intrinsic linewidth variation among different comb lines could assist the understanding of the microcomb dynamics. For Kerr microcombs and EO combs, they both show the increasing linewidths when moving from the center to sides (Ref. [1, 2] below). I am curious about the linewidth variation trend of the proposed microcomb under different states as shown in Fig. 2b and Fig. 5d. Specifically, for the 'clustered' comb state shown in Fig. 2b, Fig. S3b and d, would the linewidth increase from respective centers of different clusters? + +[1] Lei, F., Ye, Z., Helgason, Ö. B., Fülöp, A., Girardi, M., & Torres- Company, V. (2022). Optical linewidth of soliton microcombs. Nature Communications, 13(1), 3161. [2] Skehan, J. C., Naveau, C., Schroder, J., & Andrekson, P. (2021). Widely tunable, low linewidth, and high power laser source using an electro-optic comb and injection-locked slave laser array. Optics Express, 29(11), 17077-17086. + +6. The optical spectra presented in the experiment and simulation exhibit notable differences. Could the authors comment on the main reasons for the difference? Would the mismatch between the main laser + +<--- Page Split ---> + +cavity and the racetrack resonator influence the comb state? Will the comb power keeping increasing with higher RF power as claimed in Page 4 line 234? As the authors emphasize that the cavities are dispersion- engineered, what is the influence of the dispersion of different cavities (the racetrack cavity and the main laser cavity) on the comb states? Comprehensive analyses are needed to get a better understanding of the proposed microcomb. + +7. In Fig.2, the hybrid microcomb produces clustered microcombs, which are also shown in Fig. S3, while the spectral shapes in Fig. 5 are quite different. Could the authors comment on the possible origins of this difference. Is this due to the use of an optoelectronic feedback loop? + +8. In Fig. 5, the authors show the feedback mode-locking of the comb laser. The concept is similar to the combination of EO combs and optoelectronic oscillators as demonstrated in previous works, such as Ref. [3-4] below. It is recommended to reference these works. + +[3] Peng, H., Lei, P., Xie, X., & Chen, Z. (2021). Dynamics and timing-jitter of regenerative RF feedback assisted resonant electro-optic frequency comb. Optics Express, 29(26), 42435-42456. [4] Sakamoto, T., Kawanishi, T., & Izutsu, M. (2006). Optoelectronic oscillator using a LiNbO3 phase modulator for self-oscillating frequency comb generation. Optics letters, 31(6), 811-813. + +9. There are several typos in describing Fig. 4: + +Page 5, line 290-291: "Fig. 4f-h show the temporal variation of the 15-GHz beating signal..." While the temporal variations are presented in Fig. 4b- d. + +Page 5, line 307- 309: "The frequency tuning range of 1.2 GHz at the modulation speed of 100 MHz (Fig. 4h) corresponds to a frequency tuning rate..." The fast-chirping results are given in Fig. 4d. + +Page 5, line 314- 315: "As shown in Fig. 4e, the device exhibits a frequency tuning efficiency..." The efficiency is shown in Fig. 4h. + +<--- Page Split ---> + +## Author's response to Manuscript NCOMMS-23-59501-T: + +Dear Editors and Reviewers of Nature Communications, + +We greatly appreciate your thorough editing of our manuscript and we thank the reviewers for their critical reading of our manuscript and making suggestions that have improved the manuscript. We have revised the manuscript wherever necessary. We list reviewers' comments in blue and our responses in black. + +## Response to Reviewer 1's comments: + +In the paper titled "Electrically empowered micro comb laser", the authors demonstrated an external cavity laser that can generate combs due to the combination of Kerr nonlinearity and EO modulation. This concept is novel, and the experimental results are solid. I think this paper can be accepted by Nature Communications after addressing the following issue. + +RE: We thank the reviewer for the positive comments. + +1. I think some claims of the paper can be modified. Personally, I don't think this work addresses all the problems of "complex soliton initialization, high threshold, low power efficiency, and limited comb reconfigurability" for microcombs. It might be better to focus more on the dynamics of this unique laser configuration. + +RE: We thank the reviewer for the comment. We have revised the related sentences in the Abstract to make it clear. The analysis of the dynamics of our system is provided in detail in the supplementary information. + +2. When calculating the wall-plug efficiency, I think the RF power applied to the cavity needs to be counted. One major problem for people using EO combs is the large RF power required. I think discussions regarding this problem should be added. + +RE: We thank the reviewer for the comment. We understand that, for a commercial laser product, the overall wall-plug efficiency should include all power consumptions of the whole laser system to quantify its overall energy efficiency. However, such a metric does not provide insight into the essential performance of the semiconductor laser itself since a laser system always requires certain but different peripheral control circuits for proper operation that do not contribute to the final laser output power. This will make it difficult for readers to tell the fundamental laser performance and compare one with another. As such, the term of "wall-plug efficiency" is generally used to characterize the fundamental power efficiency of the diode laser itself, defined as the laser optical power compared with the electric power used to drive the laser diode. One typical example is that nearly all semiconductor lasers require temperature control, but the related power consumption is not included in the calculation of "wall-plug efficiency" in the literature. + +We follow this convention in our paper. But to make it clear, we have added a sentence in the section of Comb Laser Performance to describe how the wall- plug efficiency is measured. Moreover, the detailed RF power applied to the device is provided in Fig.S3 of the supplementary information. + +3. Can the author discuss more about the power of individual comb lines? What really matters in most of the applications is the comb line power, so a more detailed discussion could be helpful. + +RE: We thank the reviewer for raising this question. The power of individual comb lines is in the range of 0.25—2mW. We have added this information in the section of Comb Laser Performance. + +4. I feel that the statement "100% utilization of optical power fully contributing to comb generation" is strange. How to define which potion of power contributes to comb generation? For traditional microcomb this can be defined by the soliton state power/pump power, but I don't think it applies here. + +<--- Page Split ---> + +RE: We thank the reviewer for the comment. We used this sentence to show the fact that, in our laser, all power of the optical wave stays in the form of comb output, in contrast to traditional microcomb in which only a small portion of the optical power is transferred to the comb from the pump laser. To make it clear, we have added a sentence to explain this in the Introduction section. + +5. What is the time domain pattern of this mode-locked state? Is it more like a soliton or dark pulse? What is the pulse width? + +RE: It is soliton-like pulses, as evident by the auto-correlation traces shown in the insets of Fig. 2b and Fig. 3b&c. The pulse width is estimated from the autocorrelation trace to be around 7 ps. + +6. Can the author add discussions about the tuning range of the FSR? + +RE: We thank the reviewer for the suggestion. The FSR of the comb can be tuned by about 1GHz. The details are provided in Fig.S3 of the supplementary information and are discussed in Section II.B. + +## Response to Reviewer 2's comments: + +This paper introduces a novel method of microcomb laser by hybridizing Kerr nonlinearity, EO modulation and the gain/lasing process in an EO modulated LN microresonator. The proposed scheme is novel and elegant in terms of the underlying concept, and exhibits significant performance advantages including high efficiency and a straightforward triggering process. While I do have some questions regarding the theoretical analysis detailed below, I believe a properly revised version could be considered for publication in Nature Communications. This paper introduces a novel method of microcomb laser by hybridizing Kerr nonlinearity, EO modulation and the gain/lasing process in an EO modulated LN microresonator. The proposed scheme is novel and elegant in terms of the underlying concept, and exhibits significant performance advantages including high efficiency and a straightforward triggering process. While I do have some questions regarding the theoretical analysis detailed below, I believe a properly revised version could be considered for publication in Nature Communications. + +RE: We thank the reviewer for the positive comments. + +1. Although the combination of Kerr nonlinearity, EO modulation and laser is intriguing, the concept of microcomb laser has previously been demonstrated using Kerr nonlinearity and lasing process [18,21]. Compared with these previous works, this comb spectra in this work show bifurcated spectral shapes and narrower optical bandwidths. It would be great if the authors could provide more explanations and insights, from physics point of view, on the difference between these two microcomb laser schemes. + +RE: We thank the reviewer for the comment. + +The fundamental mechanism of comb generation in our laser is very different from that in Ref.[18,21] where the self- emergence of the soliton- state relies crucially on the thermal- optic nonlinearity of the erbium- doped fiber amplifier (EDFA) to compensate for that in the nested microresonator. In contrast, our laser uses EO modulation to initiate the comb generation, Kerr nonlinearity to broaden the comb spectrum and phase lock comb lines, and the laser gain to sustain the comb operation. We have explained this point clearly in the sections of Introduction and Comb laser performance. To make it clearer, we have added a sentence in the section of Comb laser performance. + +The narrower comb spectral bandwidth in our laser is simply due to the lower pump power available in our gain chip compared with an EDFA. We have provided a discussion about comb spectral bandwidth in the Discussion section. As to the bifurcated comb spectrum, its exact physical nature is not clear at this moment, which requires future exploration. We speculate that it could be likely related to the dispersion and mismatched group delay. Note that our laser can also produce single- lobe comb spectrum. The details are shown in Fig.S3 of the supplementary information, as well as Fig.5d of the main text. + +<--- Page Split ---> + +2. This method eliminates the need for pre-configuration compared with self-injection locking for microcomb stimulation. However, the proposed method require precise alignment of multiple resonances within a wideband between the two cavities, which seems quite challenging. The authors also mentioned, "this problem can be resolved by further optimization of the roundtrip length of the main laser cavity and introducing tunability". Compared with self-injection locking, which involves tuning the optical phase - an easy task in integrated photonics, this method requires tuning the cavity length or group index, which is actually highly challenging for on-chip photonics? Please comment on these problems and potential solutions, if any. + +RE: We thank the reviewer for raising this point. Controlling the cavity length can be realized by multiple approaches. Two examples are given below: + +I) Heterogenous integration approach where the gain element is bonded on the top of the external laser cavity. In this approach, the cavity length is purely determined by the external laser cavity, which can be precisely controlled by the fabrication process.II) Tuning approach to add a group-delay tuning element into the external laser cavity. One example is Ref.[1] given below.[1] Y. Liu, et al, "Continuously tunable silicon optical true-time delay lines with a large delay tuning range and a low delay fluctuation," Opt. Express 32, 7848 (2024). + +We have added these points in the section of Discussion. + +3. The authors identified three limitations in previous microcomb works, including complex initialization process, low power efficiency and limited reconfigurability. The proposed scheme does solve the first two problems quite obviously, but I'm not too sure what the authors refer to when mentioning "reconfigurability". Does this refer to the fast chirping depicted in Fig. 4, or the comb spacing tuning shown in Fig. 3? Since controlling comb spacing and spectral shape is well known technique in Kerr-based microcombs, I hope the authors could be more specific when mentioning "reconfigurability" and provide more explanations if possible. + +RE: We thank the reviewer for the comment. The reconfigurability refers both the fast chirping and comb spacing switching and tuning. For fast chirping, we have demonstrated unprecedented chirping rate up to \(2.4 \times 10^{17} \mathrm{~Hz} / \mathrm{s}\) orders of magnitude faster than other approaches. For comb spacing switching and tuning, we achieved it with high-speed EO modulation without involving complex tuning dynamics, which, again, is significantly faster than conventional Kerr microcombs. To make it clear, we have revised the related sentences in Abstract and Introduction. + +4. The linewidth testing shown in Fig. 2e, which is obtained from a heterodyne measurement of the entire comb, is quite confusing to me. The authors claim that the tested linewidth is "the upper limit of the intrinsic linewidth of individual comb lines" (Page 4, line 222)? In my understanding, the noises of comb lines with higher signal powers would overwhelm those of low-power comb lines. As a result when normalizing the noise spectrum of the entire comb, one is probably seeing a larger noise contribution from higher-power lines, which are not necessarily better or worse than the lower-power lines. Please provide more references or proof to support this claim. + +RE: We thank the reviewer for raising this point. The reviewer is correct and we have revised the relevant sentences in the paper. We provide more detailed linewidth characterizations in the following. + +5. Following up on the above question, it would be really nice if the authors could characterize the linewidths of each comb line. The intrinsic linewidth variation among different comb lines could assist the understanding of the microcomb dynamics. For Kerr microcombs and EO combs, they both show the increasing linewidths when moving from the center to sides (Ref. [1, 2] below). I am curious about the linewidth variation trend of the proposed microcomb under different states as shown in Fig. 2b and + +<--- Page Split ---> + +Fig. 5d. Specifically, for the ‘clustered’ comb state shown in Fig. 2b, Fig. S3b and d, would the linewidth increase from respective centers of different clusters? + +[1] Lei, F., Ye, Z., Helgason, Ó. B., Fülöp, A., Girardi, M., & Torres- Company, V. (2022). Optical linewidth of soliton microcombs. Nature Communications, 13(1), 3161. + +[2] Skehan, J. C., Naveau, C., Schroder, J., & Andrekson, P. (2021). Widely tunable, low linewidth, and high power laser source using an electro-optic comb and injection- locked slave laser array. Optics Express, 29(11), 17077- 17086. + +RE: We thank the reviewer for the suggestion. We have performed detailed characterizations on the linewidths of individual comb lines. We used the setup shown in Fig. R1 below for the measurements, in which an individual comb line is separated from the rest of the comb by a tunable narrow- band fiber Bragg grating (FBG) filter and its linewidth is measured by the self- heterodyning method. + +![](images/Figure_2.jpg) + +
Figure R1 Schematic of the experimental setup used to characterize the linewidths of individual comb lines.
+ +Figure R2a shows the overall frequency noise spectra for different lasing states. For the comb states, the linewidth measurement was performed on the entire combs similar to Fig. 2 in the paper. It shows an overall linewidth of about \(7\mathrm{kHz}\) , \(7\mathrm{kHz}\) , and \(1.5\mathrm{kHz}\) , respectively, for the single- mode lasing state, the single- lobe comb state, and the bifurcated two- lobe comb state. These values are slightly worse than those shown in the paper simply due to the slight degradation of the LN device and the RSOA in the past four months. + +The recorded linewidths for individual comb lines are shown in Fig. R2c and d for the two comb states. Due to the limited powers of the individual comb lines, we can only perform linewidth characterizations for the central portion of the combs. Figure R2c shows that, for the single- lobe comb state, the individual comb lines exhibit linewidths in the range of \(1 - 3\mathrm{kHz}\) . Figure R2d shows that one lobe of the comb exhibits individual comb linewidths in the range of \(0.8 - 2\mathrm{kHz}\) , while the other lobe exhibits slightly larger linewidths in the range of \(5 - 8\mathrm{kHz}\) . The exact physical reason for this difference is not clear at this moment, which requires further exploration. + +Overall, the linewidths of individual comb lines do not show a certain deterministic trend across the comb spectrum, distinctive to the ones shown in Ref. [1,2] pointed out by the reviewer. This is understandable since the linewidth feature shown in Ref.[1] is due to the recoil effect between Raman- induced self- frequency shift and dispersive wave generation, and that shown in Ref.[2] is due to the noise multiplication during the cascaded sideband creation in a pure EO comb. The mechanism of comb generation is fundamentally different in our comb laser which could lead to different linewidth behaviors. + +<--- Page Split ---> +![PLACEHOLDER_8_0] + +
Figure R2 a) Frequency noise spectrum of a single-mode lasing state, single-lobe comb state (Comb 1), and bifurcated two-lobe comb state (Comb 2). For the combs, the frequency noise is for the entire combs, similar to Fig.2 in the paper. b) Optical spectrum (blue) and recorded linewidth (red dot) for the single-mode lasing state. c) Optical spectrum (blue) and recorded linewidths (red dots) of individual comb lines, for the single-lobe comb state (Comb 1). d) Same as c) but for the bifurcated two-lobe comb state (Comb 2). In b)-d), the small spectral gap on the noise floor is due to the spectral filtering by the FBG filter.
+ +6. The optical spectra presented in the experiment and simulation exhibit notable differences. Could the authors comment on the main reasons for the difference? Would the mismatch between the main laser cavity and the racetrack resonator influence the comb state? Will the comb power keeping increasing with higher RF power as claimed in Page 4 line 234? As the authors emphasize that the cavities are dispersion-engineered, what is the influence of the dispersion of different cavities (the racetrack cavity and the main laser cavity) on the comb states? Comprehensive analyses are needed to get a better understanding of the proposed microcomb. + +RE: We thank the reviewer for the detailed questions. We answer the questions separately in the following: + +I) Could the authors comment on the main reasons for the difference? + +In fact, we are able to generate a comb from Laser \(\beta\) similar to the simulation, as we showed in Fig.S2 of the supplementary information. The mechanism underlying the bifurcated comb produced by Laser \(\alpha\) is currently still under investigation, which may result from complex physics not included in the simplified model. We have added one sentence in Section III.B of the supplementary information to make this point clear. + +II) Would the mismatch between the main laser cavity and the racetrack resonator influence the comb state? + +<--- Page Split ---> + +Yes, the mismatch has strong impact on the stability and shape of the comb state. Chaotic comb may occur in a mismatched laser. We are currently still investigating the dynamics of the laser at different cavity length offset. + +III) Will the comb power keeping increasing with higher RF power as claimed in Page 4 line 234? + +The detailed relationship between the produced comb laser power and the RF driving power is shown in Fig. S3 a,c,f,h of the supplementary information for the two lasers. We observed comb power saturation in Laser \(\beta\) . In Laser \(\alpha\) , however, we haven't observed saturation within the applicable RF power range. + +IV) As the authors emphasize that the cavities are dispersion-engineered, what is the influence of the dispersion of different cavities (the racetrack cavity and the main laser cavity) on the comb states? + +Dispersion of the racetrack microresonator is crucial for the comb generation and mode locking. A slight anomalous dispersion is required, as we showed in the numerical modeling. The dispersion of the main laser cavity plays a minor role. We engineered it to be close to zero. + +7. In Fig.2, the hybrid microcomb produces clustered microcombs, which are also shown in Fig. S3, while the spectral shapes in Fig. 5 are quite different. Could the authors comment on the possible origins of this difference. Is this due to the use of an optoelectronic feedback loop? + +RE: We thank the reviewer for the question. We do observe different comb spectra for RF driven comb and feedback lock comb. Currently, the feedback locked comb is wider in spectrum. This could be related to that the dynamically adjusted feedbacked RF modulation assist in the generation of broader comb, but the detailed mechanism require further investigation in future works. + +8. In Fig. 5, the authors show the feedback mode-locking of the comb laser. The concept is similar to the combination of EO combs and optoelectronic oscillators as demonstrated in previous works, such as Ref. [3-4] below. It is recommended to reference these works. + +[3] Peng, H., Lei, P., Xie, X., & Chen, Z. (2021). Dynamics and timing-jitter of regenerative RF feedback assisted resonant electro-optic frequency comb. Optics Express, 29(26), 42435-42456. + +[4] Sakamoto, T., Kawanishi, T., & Izutsu, M. (2006). Optoelectronic oscillator using a LiNbO3 phase modulator for self-oscillating frequency comb generation. Optics letters, 31(6), 811-813. + +RE: We thank the reviewer for the suggestion. We have added these two references as Ref.[47, 48] in the paper. + +9. There are several typos in describing Fig. 4: Page 5, line 290-291: "Fig. 4f-h show the temporal variation of the 15-GHz beating signal..." While the temporal variations are presented in Fig. 4b-d. Page 5, line 307-309: "The frequency tuning range of 1.2 GHz at the modulation speed of 100 MHz (Fig. 4h) corresponds to a frequency tuning rate..." The fast-chirping results are given in Fig. 4d. Page 5, line 314-315: "As shown in Fig. 4e, the device exhibits a frequency tuning efficiency..." The efficiency is shown in Fig. 4h. + +RE: We thank the reviewer for finding these typos. We have corrected them in the paper. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have addressed all my comments and I suggest publication for this paper. + +Reviewer #2 (Remarks to the Author): + +The authors have addressed most of my comments. There is still a lot of physics here unexplored and not yet fully understood but I think it is reasonable to leave them to future studies as the results here are quite interesting and deserve to be published. There is one typo though: The unit of the phase noise in Fig. 5g should be "dBc/Hz". + +<--- Page Split ---> diff --git a/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e6ee3cbb97de5a9ea3f35b9aea9ac640a79c253a --- /dev/null +++ b/peer_reviews/12696181428465838111cfb9bc03699d1113262f9765d95778f49019f4af4f2b/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,309 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 630, 180]]<|/det|> +Electrically empowered microcomb laser + +<|ref|>image<|/ref|><|det|>[[57, 732, 239, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 291, 107]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 392, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 163, 856, 236]]<|/det|> +In the paper titled "Electrically empowered microcomb laser", the authors demonstrated an external cavity laser that can generate combs due to the combination of Kerr nonlinearity and EO modulation. This concept is novel, and the experimental results are solid. I think this paper can be accepted by Nature Communications after addressing the following issue: + +<|ref|>text<|/ref|><|det|>[[115, 254, 872, 327]]<|/det|> +1. I think some claims of the paper can be modified. Personally, I don't think this work addresses all the problems of "complex soliton initialization, high threshold, low power efficiency, and limited comb reconfigurability" for microcombs. It might be better to focus more on the dynamics of this unique laser configuration. + +<|ref|>text<|/ref|><|det|>[[115, 346, 833, 400]]<|/det|> +2. When calculating the wall-plug efficiency, I think the RF power applied to the cavity needs to be counted. One major problem for people using EO combs is the large RF power required. I think discussions regarding this problem should be added. + +<|ref|>text<|/ref|><|det|>[[115, 419, 880, 455]]<|/det|> +3. Can the author discuss more about the power of individual comb lines? What really matters in most of the applications is the comb line power, so a more detailed discussion could be helpful. + +<|ref|>text<|/ref|><|det|>[[115, 474, 874, 528]]<|/det|> +4. I feel that the statement "100% utilization of optical power fully contributing to comb generation" is strange. How to define which potion of power contribute to comb generation? For traditional microcomb this can be defined by the soliton state power/pump power, but I don't think it applies here. + +<|ref|>text<|/ref|><|det|>[[115, 547, 848, 582]]<|/det|> +5. What is the time domain pattern of this mode locked state? Is it more like a soliton or dark pulse? What is the pulse width? + +<|ref|>text<|/ref|><|det|>[[115, 602, 620, 619]]<|/det|> +6. Can the author add discussions about the tuning range of the FSR? + +<|ref|>text<|/ref|><|det|>[[116, 675, 392, 691]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 711, 875, 820]]<|/det|> +This paper introduces a novel method of microcomb laser by hybridizing Kerr nonlinearity, EO modulation and the gain/lasing process in an EO modulated LN microresonator. The proposed scheme is novel and elegant in terms of the underlying concept, and exhibits significant performance advantages including high efficiency and a straightforward triggering process. While I do have some questions regarding the theoretical analysis detailed below, I believe a properly revised version could be considered for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 840, 864, 894]]<|/det|> +1. Although the combination of Kerr nonlinearity, EO modulation and laser is intriguing, the concept of microcomb laser has previously been demonstrated using Kerr nonlinearity and lasing process [18,21]. Compared with these previous works, this comb spectra in this work show bifurcated spectral shapes + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 870, 126]]<|/det|> +and narrower optical bandwidths. It would be great if the authors could provide more explanations and insights, from physics point of view, on the difference between these two microcomb laser schemes. + +<|ref|>text<|/ref|><|det|>[[114, 144, 881, 291]]<|/det|> +2. This method eliminates the need for pre-configuration compared with self-injection locking for microcomb stimulation. However, the proposed method require precise alignment of multiple resonances within a wideband between the two cavities, which seems quite challenging. The authors also mentioned, "this problem can be resolved by further optimization of the roundtrip length of the main laser cavity and introducing tunability". Compared with self-injection locking, which involves tuning the optical phase - an easy task in integrated photonics, this method requires tuning the cavity length or group index, which is actually highly challenging for on-chip photonics? Please comment on these problems and potential solutions, if any. + +<|ref|>text<|/ref|><|det|>[[114, 309, 872, 438]]<|/det|> +3. The authors identified three limitations in previous microcomb works, including complex initialization process, low power efficiency and limited reconfigurability. The proposed scheme does solve the first two problems quite obviously, but I'm not too sure what the authors refer to when mentioning "reconfigurability". Does this refer to the fast chirping depicted in Fig. 4, or the comb spacing tuning shown in Fig. 3? Since controlling comb spacing and spectral shape is well known technique in Kerr-based microcombs, I hope the authors could be more specific when mentioning "reconfigurability" and provide more explanations if possible. + +<|ref|>text<|/ref|><|det|>[[114, 456, 881, 584]]<|/det|> +4. The linewidth testing shown in Fig. 2e, which is obtained from a heterodyne measurement of the entire comb, is quite confusing to me. The authors claim that the tested linewidth is "the upper limit of the intrinsic linewidth of individual comb lines" (Page 4, line 222)? In my understanding, the noises of comb lines with higher signal powers would overwhelm those of low-power comb lines. As a result when normalizing the noise spectrum of the entire comb, one is probably seeing a larger noise contribution from higher-power lines, which are not necessarily better or worse than the lower-power lines. Please provide more references or proof to support this claim. + +<|ref|>text<|/ref|><|det|>[[114, 601, 878, 729]]<|/det|> +5. Following up on the above question, it would be really nice if the authors could characterize the linewidths of each comb lines. The intrinsic linewidth variation among different comb lines could assist the understanding of the microcomb dynamics. For Kerr microcombs and EO combs, they both show the increasing linewidths when moving from the center to sides (Ref. [1, 2] below). I am curious about the linewidth variation trend of the proposed microcomb under different states as shown in Fig. 2b and Fig. 5d. Specifically, for the 'clustered' comb state shown in Fig. 2b, Fig. S3b and d, would the linewidth increase from respective centers of different clusters? + +<|ref|>text<|/ref|><|det|>[[114, 747, 880, 840]]<|/det|> +[1] Lei, F., Ye, Z., Helgason, Ö. B., Fülöp, A., Girardi, M., & Torres- Company, V. (2022). Optical linewidth of soliton microcombs. Nature Communications, 13(1), 3161. [2] Skehan, J. C., Naveau, C., Schroder, J., & Andrekson, P. (2021). Widely tunable, low linewidth, and high power laser source using an electro-optic comb and injection-locked slave laser array. Optics Express, 29(11), 17077-17086. + +<|ref|>text<|/ref|><|det|>[[114, 858, 875, 894]]<|/det|> +6. The optical spectra presented in the experiment and simulation exhibit notable differences. Could the authors comment on the main reasons for the difference? Would the mismatch between the main laser + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 866, 180]]<|/det|> +cavity and the racetrack resonator influence the comb state? Will the comb power keeping increasing with higher RF power as claimed in Page 4 line 234? As the authors emphasize that the cavities are dispersion- engineered, what is the influence of the dispersion of different cavities (the racetrack cavity and the main laser cavity) on the comb states? Comprehensive analyses are needed to get a better understanding of the proposed microcomb. + +<|ref|>text<|/ref|><|det|>[[115, 200, 876, 253]]<|/det|> +7. In Fig.2, the hybrid microcomb produces clustered microcombs, which are also shown in Fig. S3, while the spectral shapes in Fig. 5 are quite different. Could the authors comment on the possible origins of this difference. Is this due to the use of an optoelectronic feedback loop? + +<|ref|>text<|/ref|><|det|>[[115, 273, 876, 326]]<|/det|> +8. In Fig. 5, the authors show the feedback mode-locking of the comb laser. The concept is similar to the combination of EO combs and optoelectronic oscillators as demonstrated in previous works, such as Ref. [3-4] below. It is recommended to reference these works. + +<|ref|>text<|/ref|><|det|>[[115, 345, 852, 417]]<|/det|> +[3] Peng, H., Lei, P., Xie, X., & Chen, Z. (2021). Dynamics and timing-jitter of regenerative RF feedback assisted resonant electro-optic frequency comb. Optics Express, 29(26), 42435-42456. [4] Sakamoto, T., Kawanishi, T., & Izutsu, M. (2006). Optoelectronic oscillator using a LiNbO3 phase modulator for self-oscillating frequency comb generation. Optics letters, 31(6), 811-813. + +<|ref|>text<|/ref|><|det|>[[115, 437, 448, 453]]<|/det|> +9. There are several typos in describing Fig. 4: + +<|ref|>text<|/ref|><|det|>[[115, 456, 860, 490]]<|/det|> +Page 5, line 290-291: "Fig. 4f-h show the temporal variation of the 15-GHz beating signal..." While the temporal variations are presented in Fig. 4b- d. + +<|ref|>text<|/ref|><|det|>[[115, 492, 867, 526]]<|/det|> +Page 5, line 307- 309: "The frequency tuning range of 1.2 GHz at the modulation speed of 100 MHz (Fig. 4h) corresponds to a frequency tuning rate..." The fast-chirping results are given in Fig. 4d. + +<|ref|>text<|/ref|><|det|>[[115, 528, 833, 562]]<|/det|> +Page 5, line 314- 315: "As shown in Fig. 4e, the device exhibits a frequency tuning efficiency..." The efficiency is shown in Fig. 4h. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 678, 112]]<|/det|> +## Author's response to Manuscript NCOMMS-23-59501-T: + +<|ref|>text<|/ref|><|det|>[[115, 128, 524, 144]]<|/det|> +Dear Editors and Reviewers of Nature Communications, + +<|ref|>text<|/ref|><|det|>[[115, 161, 882, 214]]<|/det|> +We greatly appreciate your thorough editing of our manuscript and we thank the reviewers for their critical reading of our manuscript and making suggestions that have improved the manuscript. We have revised the manuscript wherever necessary. We list reviewers' comments in blue and our responses in black. + +<|ref|>sub_title<|/ref|><|det|>[[116, 236, 424, 254]]<|/det|> +## Response to Reviewer 1's comments: + +<|ref|>text<|/ref|><|det|>[[115, 261, 882, 325]]<|/det|> +In the paper titled "Electrically empowered micro comb laser", the authors demonstrated an external cavity laser that can generate combs due to the combination of Kerr nonlinearity and EO modulation. This concept is novel, and the experimental results are solid. I think this paper can be accepted by Nature Communications after addressing the following issue. + +<|ref|>text<|/ref|><|det|>[[115, 332, 505, 349]]<|/det|> +RE: We thank the reviewer for the positive comments. + +<|ref|>text<|/ref|><|det|>[[115, 355, 882, 420]]<|/det|> +1. I think some claims of the paper can be modified. Personally, I don't think this work addresses all the problems of "complex soliton initialization, high threshold, low power efficiency, and limited comb reconfigurability" for microcombs. It might be better to focus more on the dynamics of this unique laser configuration. + +<|ref|>text<|/ref|><|det|>[[115, 426, 882, 460]]<|/det|> +RE: We thank the reviewer for the comment. We have revised the related sentences in the Abstract to make it clear. The analysis of the dynamics of our system is provided in detail in the supplementary information. + +<|ref|>text<|/ref|><|det|>[[115, 466, 882, 515]]<|/det|> +2. When calculating the wall-plug efficiency, I think the RF power applied to the cavity needs to be counted. One major problem for people using EO combs is the large RF power required. I think discussions regarding this problem should be added. + +<|ref|>text<|/ref|><|det|>[[115, 521, 882, 682]]<|/det|> +RE: We thank the reviewer for the comment. We understand that, for a commercial laser product, the overall wall-plug efficiency should include all power consumptions of the whole laser system to quantify its overall energy efficiency. However, such a metric does not provide insight into the essential performance of the semiconductor laser itself since a laser system always requires certain but different peripheral control circuits for proper operation that do not contribute to the final laser output power. This will make it difficult for readers to tell the fundamental laser performance and compare one with another. As such, the term of "wall-plug efficiency" is generally used to characterize the fundamental power efficiency of the diode laser itself, defined as the laser optical power compared with the electric power used to drive the laser diode. One typical example is that nearly all semiconductor lasers require temperature control, but the related power consumption is not included in the calculation of "wall-plug efficiency" in the literature. + +<|ref|>text<|/ref|><|det|>[[115, 689, 882, 738]]<|/det|> +We follow this convention in our paper. But to make it clear, we have added a sentence in the section of Comb Laser Performance to describe how the wall- plug efficiency is measured. Moreover, the detailed RF power applied to the device is provided in Fig.S3 of the supplementary information. + +<|ref|>text<|/ref|><|det|>[[115, 745, 882, 777]]<|/det|> +3. Can the author discuss more about the power of individual comb lines? What really matters in most of the applications is the comb line power, so a more detailed discussion could be helpful. + +<|ref|>text<|/ref|><|det|>[[115, 784, 881, 816]]<|/det|> +RE: We thank the reviewer for raising this question. The power of individual comb lines is in the range of 0.25—2mW. We have added this information in the section of Comb Laser Performance. + +<|ref|>text<|/ref|><|det|>[[115, 823, 882, 872]]<|/det|> +4. I feel that the statement "100% utilization of optical power fully contributing to comb generation" is strange. How to define which potion of power contributes to comb generation? For traditional microcomb this can be defined by the soliton state power/pump power, but I don't think it applies here. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 154]]<|/det|> +RE: We thank the reviewer for the comment. We used this sentence to show the fact that, in our laser, all power of the optical wave stays in the form of comb output, in contrast to traditional microcomb in which only a small portion of the optical power is transferred to the comb from the pump laser. To make it clear, we have added a sentence to explain this in the Introduction section. + +<|ref|>text<|/ref|><|det|>[[115, 161, 881, 194]]<|/det|> +5. What is the time domain pattern of this mode-locked state? Is it more like a soliton or dark pulse? What is the pulse width? + +<|ref|>text<|/ref|><|det|>[[115, 201, 881, 233]]<|/det|> +RE: It is soliton-like pulses, as evident by the auto-correlation traces shown in the insets of Fig. 2b and Fig. 3b&c. The pulse width is estimated from the autocorrelation trace to be around 7 ps. + +<|ref|>text<|/ref|><|det|>[[115, 241, 625, 257]]<|/det|> +6. Can the author add discussions about the tuning range of the FSR? + +<|ref|>text<|/ref|><|det|>[[115, 264, 882, 297]]<|/det|> +RE: We thank the reviewer for the suggestion. The FSR of the comb can be tuned by about 1GHz. The details are provided in Fig.S3 of the supplementary information and are discussed in Section II.B. + +<|ref|>sub_title<|/ref|><|det|>[[115, 348, 424, 365]]<|/det|> +## Response to Reviewer 2's comments: + +<|ref|>text<|/ref|><|det|>[[115, 372, 882, 548]]<|/det|> +This paper introduces a novel method of microcomb laser by hybridizing Kerr nonlinearity, EO modulation and the gain/lasing process in an EO modulated LN microresonator. The proposed scheme is novel and elegant in terms of the underlying concept, and exhibits significant performance advantages including high efficiency and a straightforward triggering process. While I do have some questions regarding the theoretical analysis detailed below, I believe a properly revised version could be considered for publication in Nature Communications. This paper introduces a novel method of microcomb laser by hybridizing Kerr nonlinearity, EO modulation and the gain/lasing process in an EO modulated LN microresonator. The proposed scheme is novel and elegant in terms of the underlying concept, and exhibits significant performance advantages including high efficiency and a straightforward triggering process. While I do have some questions regarding the theoretical analysis detailed below, I believe a properly revised version could be considered for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 556, 508, 571]]<|/det|> +RE: We thank the reviewer for the positive comments. + +<|ref|>text<|/ref|><|det|>[[117, 579, 882, 658]]<|/det|> +1. Although the combination of Kerr nonlinearity, EO modulation and laser is intriguing, the concept of microcomb laser has previously been demonstrated using Kerr nonlinearity and lasing process [18,21]. Compared with these previous works, this comb spectra in this work show bifurcated spectral shapes and narrower optical bandwidths. It would be great if the authors could provide more explanations and insights, from physics point of view, on the difference between these two microcomb laser schemes. + +<|ref|>text<|/ref|><|det|>[[115, 666, 440, 681]]<|/det|> +RE: We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[115, 690, 882, 802]]<|/det|> +The fundamental mechanism of comb generation in our laser is very different from that in Ref.[18,21] where the self- emergence of the soliton- state relies crucially on the thermal- optic nonlinearity of the erbium- doped fiber amplifier (EDFA) to compensate for that in the nested microresonator. In contrast, our laser uses EO modulation to initiate the comb generation, Kerr nonlinearity to broaden the comb spectrum and phase lock comb lines, and the laser gain to sustain the comb operation. We have explained this point clearly in the sections of Introduction and Comb laser performance. To make it clearer, we have added a sentence in the section of Comb laser performance. + +<|ref|>text<|/ref|><|det|>[[115, 810, 883, 904]]<|/det|> +The narrower comb spectral bandwidth in our laser is simply due to the lower pump power available in our gain chip compared with an EDFA. We have provided a discussion about comb spectral bandwidth in the Discussion section. As to the bifurcated comb spectrum, its exact physical nature is not clear at this moment, which requires future exploration. We speculate that it could be likely related to the dispersion and mismatched group delay. Note that our laser can also produce single- lobe comb spectrum. The details are shown in Fig.S3 of the supplementary information, as well as Fig.5d of the main text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 219]]<|/det|> +2. This method eliminates the need for pre-configuration compared with self-injection locking for microcomb stimulation. However, the proposed method require precise alignment of multiple resonances within a wideband between the two cavities, which seems quite challenging. The authors also mentioned, "this problem can be resolved by further optimization of the roundtrip length of the main laser cavity and introducing tunability". Compared with self-injection locking, which involves tuning the optical phase - an easy task in integrated photonics, this method requires tuning the cavity length or group index, which is actually highly challenging for on-chip photonics? Please comment on these problems and potential solutions, if any. + +<|ref|>text<|/ref|><|det|>[[115, 225, 881, 258]]<|/det|> +RE: We thank the reviewer for raising this point. Controlling the cavity length can be realized by multiple approaches. Two examples are given below: + +<|ref|>text<|/ref|><|det|>[[142, 264, 882, 396]]<|/det|> +I) Heterogenous integration approach where the gain element is bonded on the top of the external laser cavity. In this approach, the cavity length is purely determined by the external laser cavity, which can be precisely controlled by the fabrication process.II) Tuning approach to add a group-delay tuning element into the external laser cavity. One example is Ref.[1] given below.[1] Y. Liu, et al, "Continuously tunable silicon optical true-time delay lines with a large delay tuning range and a low delay fluctuation," Opt. Express 32, 7848 (2024). + +<|ref|>text<|/ref|><|det|>[[115, 400, 525, 416]]<|/det|> +We have added these points in the section of Discussion. + +<|ref|>text<|/ref|><|det|>[[115, 423, 882, 536]]<|/det|> +3. The authors identified three limitations in previous microcomb works, including complex initialization process, low power efficiency and limited reconfigurability. The proposed scheme does solve the first two problems quite obviously, but I'm not too sure what the authors refer to when mentioning "reconfigurability". Does this refer to the fast chirping depicted in Fig. 4, or the comb spacing tuning shown in Fig. 3? Since controlling comb spacing and spectral shape is well known technique in Kerr-based microcombs, I hope the authors could be more specific when mentioning "reconfigurability" and provide more explanations if possible. + +<|ref|>text<|/ref|><|det|>[[115, 541, 882, 639]]<|/det|> +RE: We thank the reviewer for the comment. The reconfigurability refers both the fast chirping and comb spacing switching and tuning. For fast chirping, we have demonstrated unprecedented chirping rate up to \(2.4 \times 10^{17} \mathrm{~Hz} / \mathrm{s}\) orders of magnitude faster than other approaches. For comb spacing switching and tuning, we achieved it with high-speed EO modulation without involving complex tuning dynamics, which, again, is significantly faster than conventional Kerr microcombs. To make it clear, we have revised the related sentences in Abstract and Introduction. + +<|ref|>text<|/ref|><|det|>[[115, 646, 882, 760]]<|/det|> +4. The linewidth testing shown in Fig. 2e, which is obtained from a heterodyne measurement of the entire comb, is quite confusing to me. The authors claim that the tested linewidth is "the upper limit of the intrinsic linewidth of individual comb lines" (Page 4, line 222)? In my understanding, the noises of comb lines with higher signal powers would overwhelm those of low-power comb lines. As a result when normalizing the noise spectrum of the entire comb, one is probably seeing a larger noise contribution from higher-power lines, which are not necessarily better or worse than the lower-power lines. Please provide more references or proof to support this claim. + +<|ref|>text<|/ref|><|det|>[[115, 766, 881, 799]]<|/det|> +RE: We thank the reviewer for raising this point. The reviewer is correct and we have revised the relevant sentences in the paper. We provide more detailed linewidth characterizations in the following. + +<|ref|>text<|/ref|><|det|>[[115, 805, 882, 886]]<|/det|> +5. Following up on the above question, it would be really nice if the authors could characterize the linewidths of each comb line. The intrinsic linewidth variation among different comb lines could assist the understanding of the microcomb dynamics. For Kerr microcombs and EO combs, they both show the increasing linewidths when moving from the center to sides (Ref. [1, 2] below). I am curious about the linewidth variation trend of the proposed microcomb under different states as shown in Fig. 2b and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 883, 123]]<|/det|> +Fig. 5d. Specifically, for the ‘clustered’ comb state shown in Fig. 2b, Fig. S3b and d, would the linewidth increase from respective centers of different clusters? + +<|ref|>text<|/ref|><|det|>[[143, 129, 883, 163]]<|/det|> +[1] Lei, F., Ye, Z., Helgason, Ó. B., Fülöp, A., Girardi, M., & Torres- Company, V. (2022). Optical linewidth of soliton microcombs. Nature Communications, 13(1), 3161. + +<|ref|>text<|/ref|><|det|>[[144, 168, 882, 217]]<|/det|> +[2] Skehan, J. C., Naveau, C., Schroder, J., & Andrekson, P. (2021). Widely tunable, low linewidth, and high power laser source using an electro-optic comb and injection- locked slave laser array. Optics Express, 29(11), 17077- 17086. + +<|ref|>text<|/ref|><|det|>[[115, 224, 882, 289]]<|/det|> +RE: We thank the reviewer for the suggestion. We have performed detailed characterizations on the linewidths of individual comb lines. We used the setup shown in Fig. R1 below for the measurements, in which an individual comb line is separated from the rest of the comb by a tunable narrow- band fiber Bragg grating (FBG) filter and its linewidth is measured by the self- heterodyning method. + +<|ref|>image<|/ref|><|det|>[[300, 319, 712, 456]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[130, 469, 866, 501]]<|/det|> +
Figure R1 Schematic of the experimental setup used to characterize the linewidths of individual comb lines.
+ +<|ref|>text<|/ref|><|det|>[[115, 507, 882, 589]]<|/det|> +Figure R2a shows the overall frequency noise spectra for different lasing states. For the comb states, the linewidth measurement was performed on the entire combs similar to Fig. 2 in the paper. It shows an overall linewidth of about \(7\mathrm{kHz}\) , \(7\mathrm{kHz}\) , and \(1.5\mathrm{kHz}\) , respectively, for the single- mode lasing state, the single- lobe comb state, and the bifurcated two- lobe comb state. These values are slightly worse than those shown in the paper simply due to the slight degradation of the LN device and the RSOA in the past four months. + +<|ref|>text<|/ref|><|det|>[[115, 595, 882, 708]]<|/det|> +The recorded linewidths for individual comb lines are shown in Fig. R2c and d for the two comb states. Due to the limited powers of the individual comb lines, we can only perform linewidth characterizations for the central portion of the combs. Figure R2c shows that, for the single- lobe comb state, the individual comb lines exhibit linewidths in the range of \(1 - 3\mathrm{kHz}\) . Figure R2d shows that one lobe of the comb exhibits individual comb linewidths in the range of \(0.8 - 2\mathrm{kHz}\) , while the other lobe exhibits slightly larger linewidths in the range of \(5 - 8\mathrm{kHz}\) . The exact physical reason for this difference is not clear at this moment, which requires further exploration. + +<|ref|>text<|/ref|><|det|>[[115, 715, 882, 812]]<|/det|> +Overall, the linewidths of individual comb lines do not show a certain deterministic trend across the comb spectrum, distinctive to the ones shown in Ref. [1,2] pointed out by the reviewer. This is understandable since the linewidth feature shown in Ref.[1] is due to the recoil effect between Raman- induced self- frequency shift and dispersive wave generation, and that shown in Ref.[2] is due to the noise multiplication during the cascaded sideband creation in a pure EO comb. The mechanism of comb generation is fundamentally different in our comb laser which could lead to different linewidth behaviors. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[171, 92, 826, 466]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 475, 883, 574]]<|/det|> +
Figure R2 a) Frequency noise spectrum of a single-mode lasing state, single-lobe comb state (Comb 1), and bifurcated two-lobe comb state (Comb 2). For the combs, the frequency noise is for the entire combs, similar to Fig.2 in the paper. b) Optical spectrum (blue) and recorded linewidth (red dot) for the single-mode lasing state. c) Optical spectrum (blue) and recorded linewidths (red dots) of individual comb lines, for the single-lobe comb state (Comb 1). d) Same as c) but for the bifurcated two-lobe comb state (Comb 2). In b)-d), the small spectral gap on the noise floor is due to the spectral filtering by the FBG filter.
+ +<|ref|>text<|/ref|><|det|>[[115, 600, 882, 715]]<|/det|> +6. The optical spectra presented in the experiment and simulation exhibit notable differences. Could the authors comment on the main reasons for the difference? Would the mismatch between the main laser cavity and the racetrack resonator influence the comb state? Will the comb power keeping increasing with higher RF power as claimed in Page 4 line 234? As the authors emphasize that the cavities are dispersion-engineered, what is the influence of the dispersion of different cavities (the racetrack cavity and the main laser cavity) on the comb states? Comprehensive analyses are needed to get a better understanding of the proposed microcomb. + +<|ref|>text<|/ref|><|det|>[[115, 720, 880, 739]]<|/det|> +RE: We thank the reviewer for the detailed questions. We answer the questions separately in the following: + +<|ref|>text<|/ref|><|det|>[[115, 745, 618, 762]]<|/det|> +I) Could the authors comment on the main reasons for the difference? + +<|ref|>text<|/ref|><|det|>[[115, 769, 882, 850]]<|/det|> +In fact, we are able to generate a comb from Laser \(\beta\) similar to the simulation, as we showed in Fig.S2 of the supplementary information. The mechanism underlying the bifurcated comb produced by Laser \(\alpha\) is currently still under investigation, which may result from complex physics not included in the simplified model. We have added one sentence in Section III.B of the supplementary information to make this point clear. + +<|ref|>text<|/ref|><|det|>[[113, 857, 880, 875]]<|/det|> +II) Would the mismatch between the main laser cavity and the racetrack resonator influence the comb state? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 138]]<|/det|> +Yes, the mismatch has strong impact on the stability and shape of the comb state. Chaotic comb may occur in a mismatched laser. We are currently still investigating the dynamics of the laser at different cavity length offset. + +<|ref|>text<|/ref|><|det|>[[115, 144, 825, 162]]<|/det|> +III) Will the comb power keeping increasing with higher RF power as claimed in Page 4 line 234? + +<|ref|>text<|/ref|><|det|>[[115, 168, 883, 218]]<|/det|> +The detailed relationship between the produced comb laser power and the RF driving power is shown in Fig. S3 a,c,f,h of the supplementary information for the two lasers. We observed comb power saturation in Laser \(\beta\) . In Laser \(\alpha\) , however, we haven't observed saturation within the applicable RF power range. + +<|ref|>text<|/ref|><|det|>[[115, 225, 883, 257]]<|/det|> +IV) As the authors emphasize that the cavities are dispersion-engineered, what is the influence of the dispersion of different cavities (the racetrack cavity and the main laser cavity) on the comb states? + +<|ref|>text<|/ref|><|det|>[[115, 264, 883, 313]]<|/det|> +Dispersion of the racetrack microresonator is crucial for the comb generation and mode locking. A slight anomalous dispersion is required, as we showed in the numerical modeling. The dispersion of the main laser cavity plays a minor role. We engineered it to be close to zero. + +<|ref|>text<|/ref|><|det|>[[115, 320, 883, 368]]<|/det|> +7. In Fig.2, the hybrid microcomb produces clustered microcombs, which are also shown in Fig. S3, while the spectral shapes in Fig. 5 are quite different. Could the authors comment on the possible origins of this difference. Is this due to the use of an optoelectronic feedback loop? + +<|ref|>text<|/ref|><|det|>[[115, 374, 883, 439]]<|/det|> +RE: We thank the reviewer for the question. We do observe different comb spectra for RF driven comb and feedback lock comb. Currently, the feedback locked comb is wider in spectrum. This could be related to that the dynamically adjusted feedbacked RF modulation assist in the generation of broader comb, but the detailed mechanism require further investigation in future works. + +<|ref|>text<|/ref|><|det|>[[115, 446, 883, 495]]<|/det|> +8. In Fig. 5, the authors show the feedback mode-locking of the comb laser. The concept is similar to the combination of EO combs and optoelectronic oscillators as demonstrated in previous works, such as Ref. [3-4] below. It is recommended to reference these works. + +<|ref|>text<|/ref|><|det|>[[140, 502, 883, 535]]<|/det|> +[3] Peng, H., Lei, P., Xie, X., & Chen, Z. (2021). Dynamics and timing-jitter of regenerative RF feedback assisted resonant electro-optic frequency comb. Optics Express, 29(26), 42435-42456. + +<|ref|>text<|/ref|><|det|>[[140, 541, 883, 574]]<|/det|> +[4] Sakamoto, T., Kawanishi, T., & Izutsu, M. (2006). Optoelectronic oscillator using a LiNbO3 phase modulator for self-oscillating frequency comb generation. Optics letters, 31(6), 811-813. + +<|ref|>text<|/ref|><|det|>[[115, 581, 883, 614]]<|/det|> +RE: We thank the reviewer for the suggestion. We have added these two references as Ref.[47, 48] in the paper. + +<|ref|>text<|/ref|><|det|>[[115, 620, 883, 717]]<|/det|> +9. There are several typos in describing Fig. 4: Page 5, line 290-291: "Fig. 4f-h show the temporal variation of the 15-GHz beating signal..." While the temporal variations are presented in Fig. 4b-d. Page 5, line 307-309: "The frequency tuning range of 1.2 GHz at the modulation speed of 100 MHz (Fig. 4h) corresponds to a frequency tuning rate..." The fast-chirping results are given in Fig. 4d. Page 5, line 314-315: "As shown in Fig. 4e, the device exhibits a frequency tuning efficiency..." The efficiency is shown in Fig. 4h. + +<|ref|>text<|/ref|><|det|>[[115, 723, 757, 740]]<|/det|> +RE: We thank the reviewer for finding these typos. We have corrected them in the paper. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 303, 106]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 127, 393, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 163, 740, 180]]<|/det|> +The authors have addressed all my comments and I suggest publication for this paper. + +<|ref|>text<|/ref|><|det|>[[115, 218, 393, 234]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 254, 882, 326]]<|/det|> +The authors have addressed most of my comments. There is still a lot of physics here unexplored and not yet fully understood but I think it is reasonable to leave them to future studies as the results here are quite interesting and deserve to be published. There is one typo though: The unit of the phase noise in Fig. 5g should be "dBc/Hz". + +<--- Page Split ---> diff --git a/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/images_list.json b/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c335f535855cb1f48100b1c1e43b77d2ee19376e --- /dev/null +++ b/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,429 @@ + +# nature portfolio + +# Peer Review File + +T- Cell Dysfunction in the Glioblastoma Microenvironment is Mediated by Myeloid Cells Releasing Interleukin- 10 + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +This manuscript studies the crosstalk between infiltrating microglia/macrophages and T- cells in the immunosuppressive microenvironment of glioblastoma. This is an important topic that can offer further insights into the mechanisms of resistance to anti- PD1 immunotherapy (Zhao et al. Nat. Medicine 25 (2019)). This work is a continuation of previously published work (Herik Heiland et al., Nat. Commun. 10 (2019)), where the authors found that the crosstalk between microglia cells and reactive astrocytes is responsible for upregulating IL- 10 release in glioblastoma through JAK/STAT signaling. In this manuscript, the authors show that IL- 10 secreted by HMOX1+ myeloid cells is responsible for inducing a dysfunctional state in T cells infiltrating mesenchymal regions of the tumor. + +There are several aspects that in my opinion need to be addressed before publication: + +1. Some of the statements in the Abstract, Introduction, and Discussion do not seem to have clear support in the data and analyses that are presented in the manuscript. Either those statements need to be more carefully crafted or the data and analyses supporting them need to be more clearly presented: + +1a. Lines 375-378: the authors state that their analysis indicates that the dysfunctional state of T cells appears to be a transient state. However, this reviewer was unable to find any data or analyses supporting the transitory character of dysfunctional T cell states in subsection "Dysfunctional State of T cells is Driven by IL-10 Signaling". + +1b. Lines 58, 117-119, and 394-396: the authors mention that HMOX1+ myeloid cells co-localize spatially with the mesenchymal signature of glioblastoma. However, Figs. 3f,g only show the spotwise correlation between dysfunctional T cell gene expression markers (HAVCR2 and LAG3) and the mesenchymal gene expression signature, but as far as I see they do not present any analysis of the spot-wise correlation between HMOX1+ myeloid cell markers and the mesenchymal gene expression signature. Similarly, in subsection "T cell Activation and Exhaustion Reveals Spatial Heterogeneity and Association with Glioblastoma Subtypes" there seem to be no results about the spatial pattern of HMOX1+ myeloid cells. + +1c. Lines 403-405. The authors state that their experiments with the ex vivo neocortical GBM model confirm that HMOX1+ myeloid cells cause a reduction of effector T cells. However, in these experiments both HMOX1+ and HMOX1- myeloid cells are depleted using clodronate. In absence of other data, these experiments only show that myeloid cells cause a reduction of effector T cells. + +1d. Lines 352-356 and 414-418, and Fig 4q-r. It is unclear what comparison was performed here. How did the authors determine that there is a significant enrichment for activated T cells and B cells upon JAK/STAT inhibition in the patient? A more detailed explanation of the comparison and the assumptions that were made would be useful here. + +2. The authors introduce the "nearest functionally connected neighbor" algorithm to infer candidate paracrine interactions from the single-cell RNA-seq data. Since the performance of this algorithm has not been rigorously evaluated, it is hard to know how reliable the results of this method are in general. In Supplementary Fig. 5, the authors show that the more conventional and established algorithm NicheNet (Browaeys et al. Nat. Methods 17 (2020)) also finds the candidate interaction between myeloid cells (expressing IL10) and T-cells (expressing IL10RA). However, NicheNet does not show that this interaction is specific to HOMX1+ myeloid cells. Can the authors present any other evidence from the single-cell RNA-seq data to support their statement that HOMX1+ cells are mostly responsible for this interaction (e.g. correlation between HOMX1+ and IL10 expression within myeloid cells)? It would be also useful to show the UMAP representation labeled by HMOX1 expression. + +3. The description of the "nearest functionally connected neighbor" algorithm in the Methods section + +<--- Page Split ---> + +lacks much technical detail. It would be useful to include details about the models, fitting methods, etc., and rewrite the description of the algorithm more carefully. + +4. I found the main figures to be unnecessarily complex with 10-18 panels each. The authors might consider keeping the panels that convey the main results and moving the rest of the panels to supplementary figures. There are also several typos that need to be corrected. For example, the panels in Fig. 3 are mismatched with the figure legend (e.g. 3c and 3d seem to be exchanged) and with the main text (lines 283-310). Supplementary Fig. 6 includes a caption "Supplementary Fig. 5" which should be removed. The legend of Supplementary Fig. 3 says "Dimensional reduction (UMAP) of gene expression of the different simulation experiments". However, what is shown in the figure seems to be the UMAP of the single-cell RNA-seq data from the patients colored by the imputed stimulation signatures. + +Reviewer #2 (Remarks to the Author): + +NCOMMS- 21- 07876- T Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling + +In their manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators leveraged single- cell and spatial transcriptomics to infer cellular crosstalk between macrophages/microglia and T cells within human GBM samples. From eight GBM samples, 21 clusters were identified, where many of these clusters represented macrophages and microglia. Sub- clustering of the T cell cluster revealed different activation states that were then mapped with pseudo- time and RNA velocity analyses. This provided a differentiation map from naive to terminally exhausted, with an intermediate highly proliferative state. Additionally, by combining these techniques, authors identified an association between the mesenchymal GBM subtype and T cell exhaustion. Furthermore, authors developed a new model, nearest functional connected neighbor, to identify ligand/receptor interactions from scRNAseq data. Computational analyses are thorough and novel; however, the follow- up mechanistic studies, using an in vitro neocortical model, were limited in their support of computational findings. Primary concerns are related to the impact of the mechanistic studies. These concerns are detailed below: + +1. A major limitation is the in vitro neocortical model used in Figure 4. Authors state that this model replicates the tumor microenvironment because it is derived from brain tissue; however, during tumorigenesis the TME is largely shaped by the infiltrating immune cells (1), which are absent in this model. Authors should comment on the "myeloid" cells that exist within the neocortical tissue that are being evaluated in figure 4, which should primarily be microglia and not the HMOX1+ macrophages from the computational studies. Along these lines, a quantification of tumor growth in the myeloid depleted condition is important, as myeloid cells generally promote tumor growth, so their absence alone may have an effect on tumor growth independent of T cells or IL10 inhibition. + +2. Additionally, the short incubation time (3 days) from tumor injection and subsequent T cell transfer may not provide sufficient time for meaningful interactions and subsequent functional outputs to occur, for example T cell exhaustion. Regarding the transferred T cells, it was not clearly stated whether there is selection for tumor-specific T cells from patient blood, therefore T cells that are injected into the neocortical model may or may not react to the tumor. Evidence of T cell recognition of tumor cells through killing or activation is necessary to increase the impact of this model. Much of T cell exhaustion biology is ignored in this model, such as the conditions and locations under which priming occur and trafficking to the tumor site. Therefore, conclusions that can be drawn from this model are limited. Furthermore, authors should address potential allogeneic reactivity to the cell line BTSC#233 by patient T cells. + +3. Although important for spatial information, the immunofluorescence images shown without + +<--- Page Split ---> + +quantifications in figure 4 are not sufficient to validate the computational studies. For example, in figure 4g, TIM3 is used to identify "exhausted T cells", but it has been shown that TIM3 can also be a marker of terminal effector differentiation. Therefore, this would be more convincing if other parameters were used to identify this population, such as PD1 or other functional studies showing T cell activity. + +4. When looking at the contribution of different patients to the final clusters, it is apparent that many clusters are specific to single patients. In particular, \(80\%\) of the HMOX1+ group is made up of a single patient. What impact does this have on the broader applicability of these findings? Would this bias for a single patient carry over into the downstream analyses? Is this to be expected whenever pooling human samples? + +5. The approval for the use of an un-licensed drug in a GBM patient needs to be specifically addressed within the ethics section. + +## 6. Minor concerns: + +a. The conclusion that myeloid and lymphoid interactions lead to T cell dysfunction through IL10 is vague and not unoriginal. Secretion of IL10 by myeloid cells is not a novel finding, nor is the role of IL10 in T cell dysfunction(2,3). +b. Using in vitro stimulated T cells to compare with in vivo T cells coming from a tumor ignores much of the complexity in signals that is occurring intratumorally. +c. Using a second cell line in the in vitro neocortical studies would increase the impact of related findings. + +In general, authors show novel and interesting computational analyses from cutting edge techniques, however they lack substance in their follow up mechanistic studies. The use of pseudotime and RNA velocity to interrogate T cell activation states and pair them with GBM subtypes and spatial information are intriguing. Additionally, the nearest functionally connected neighbor algorithm will add to the expanding pool of resources for inferring intercellular communication from scRNAseq data. Follow-up studies are limited in their support of computational findings (IL- 10 mediated T cell exhaustion); therefore, additional validation studies are required, or the focus of the story should shift to highlight the novel bioinformatic analyses. + +## Reference: + +1. Salmon, H., Remark, R., Gnjatic, S. and Merad, M., 2019. Host tissue determinants of tumour immunity. Nature Reviews Cancer, 19(4), pp.215-227. +2. McLane, L.M., Abdel-Hakeem, M.S. and Wherry, E.J., 2019. CD8 T cell exhaustion during chronic viral infection and cancer. Annual review of immunology, 37, pp.457-495. +3. Quail, D.F. and Joyce, J.A., 2017. The microenvironmental landscape of brain tumors. Cancer cell, 31(3), pp.326-341. + +Reviewer #3 (Remarks to the Author): + +Ravi, Neidert, Will et al present a single- cell RNA- sequencing study of tumor- infiltrating lymphocytes of patients with GBM. The profile 8 patients and additionally show data for 3 additional patients using spatial profiling, all using 10x platforms. Using established and novel analytical tools to infer trajectories of cell differentiation, they identify variability among T cells; among other, they find subclusters of CD8+ T cells with high expression of dysfunction marker TIM3 (HAVCR2) and cells with a hypoxia signature with distinct trajectories. They correlate these signatures with signatures of T cells collected following in vitro stimulation with different cytokines, including IL2, IFNG and IL10, arguing that IL10 stimulated cells have a lower activation score compared to other cells identified as effector cells. Using spatial RNA- seq of three tumors, they find an association of tumor- mesenchymal niches + +<--- Page Split ---> + +and infiltration of exhausted T cells (TIM3/LAG3), suggesting that niches of dysfunctional T cells may be in part explained by cancer cell intrinsic features. In order to understand the origin of IL10 and to solidify the role of T cells as IL10 recipients, they present a analytical framework that infers ligandreceptor interactions using several constraints, and demonstrate that myeloid cells (CD163+, HMOX1+) are a main source of IL10. To begin validating this finding, they use slice cultures that they deplete of myeloid cells and show that depletion of myeloid cells results in reduction of IL10 (in the presence of tumor cells); in these models, they then co- culture autologous T cells and show that depletion of myeloid cells in slice cultures results in increased IL2, but not IFNG protein abundance. Incubation of T cells with an IL10R- inhibitor prior to co- culture with tissues results in increased IL2 production in T cells. Because the JAK/STAT pathway is downstream of IL10 signaling, they use ruxolitinib (a selective JAK1/2 inhibitor) first i slice model showing increased IL2, and then use this drug in the neo- adjuvant therapy of a patient with GBM, followed by analysis of the surgical specimen, which shows activation of T cells. + +GBM is a disease with extremely poor prognosis, and therapeutic development has in part been hampered by limited understanding of the tumor microenvironment; as such, the study of potentially high importance. However, several aspects raised significant concerns and reduced enthusiasm for this study, and need to be addressed, + +Major points: + +1. Nowhere in the manuscript do the authors describe the characteristics of the patient tumors used for either single-cell sequencing of spatial sequencing. Are these all treatment naive tumors? where they exposed to different therapies (radiation, chemotherapy, immunotherapy, investigational drugs) - this will have a dramatic impact on the measured T cell phenotypes and in and of itself could describe variability seen in the data set. The authors should describe basic demographics and treatment history; it is not reasonable to request from the authors to attempt to account for variability based on basic demographics (this, and virtually any single-cell study would be underpowered), but they should show major analyses/findings in the context of different therapies received to exclude the possibility noted above. + +2. Technical quality: it is somewhat surprising that the authors only recover \(\sim 1000\) unique genes per cell with only \(\sim 2300\) unique molecular identifiers - this is not on par with the quality described and raises concerns regarding data quality; this is particularly surprising as they used the 3.1 chemistry which performs better than prior chemistries; in fact recent studies performing profiling from frozen tissues even achieved similar or better quality compared to this present study (Slyper, Nature Medicine, 2020). Furthermore, some of the clusters described might be artifactual due to tissue processing (e.g. "hypoxia cluster")- this possibility should be addressed using available data sets systematically investigating such artifacts (e.g. Ido Amit laboratory). Furthermore, the authors should comment on the technical quality. An additional embedding showing the UML count for major analyses should be shown in the supplement to exclude the possibility of technical artifacts as drivers of clustering. + +3. There is no statistical evaluation of the inference made in Figure 3f - the authors should provide this; in this same figure, they also show that CCL2 myeloid cells are scoring highly, which is a gene considered to be an immunostimulatory gene/protein - how do they reconcile this? This brings up the question about a more nuanced annotation of the myeloid cells beyond monocytes, macrophages and microglia. The effect size of the gene set enrichment analysis in 3h is very underwhelming. In fact, throughout this section and the studies shown in Figure 4, the effect sizes are very small with in part borderline significance, raising the question of biological significance of these findings. + +4. The experiments in slice cultures should be described in more detail in the main text. Here, they state that they performed "myeloid depletion" when in fact they performed microglia depletion (as stated as header in the methods section). The effect size of myeloid/microglia depletion on IL10 production is rather modest. One missing control is depletion of other cell types within the slice culture and measurement of the effect on IL10 to exclude the possibility that there are other major sources of + +<--- Page Split ---> + +IL10 production (which is likely). Furthermore, it is surprising that IL2 production, but not IFNG production increases during T cell depletion - the authors should offer potential explanations as this argues against reinvigoration of T cell poly- functionality. The results shown in 4j confirm that IL10 is an immunosuppressive cytokine, but do not substantiate claims that this is medicated by myeloid cells. Again, perplexing that no change in interferon gamma is seen. The single patient study is encouraging - was this pre- /post- comparison performed after single- agent therapy with ruxolitinib or was there a combination used? If the latter, it is possible that observed effects are due to other treatment constituents (see comment 1). + +<--- Page Split ---> + +## Point - by - Point + +D. H. Heiland + +We thank all reviewers for their time and effort in evaluating our manuscript and appreciate the positive feedback on our project. We have tried to mitigate the issues highlighted by the reviewers, which has led to a significant improvement in the quality of our manuscript. The following main changes have been made in this context: + +## 1. Quality of the scRNA-seq experiments. + +By resequencing the libraries, the quality of the entire dataset was significantly improved and the number of detected genes as well as the UMIs per cell were significantly increased. + +## 2. Analysis and data integration + +By applying more advanced algorithms for horizonal and vertical data integration as well as cell type alignment, we were able to present a clearer picture of T cell diversity in the tumors. We separated CD4 and CD8 positive T cells for all downstream analysis. + +## 3. Avoid overfitting in the NFCN algorithm + +Our cell communication algorithm has been optimized to reduce potential overfitting and improve prediction. For this purpose, we integrated multiple prediction/validation layers and external algorithms. The new version is also compatible with the conventional scRNA- seq tools (Seurat) and available as an R package (NFCN2). + +## 4. Structure of the manuscript and presentation + +We restructured our manuscript to present clear hypothesis- driven argumentation and pointed out limitations and ambiguities. The illustrations have been simplified to improve general understanding. + +## 5. Validation model + +Our experimental model is not without limitations, which are discussed in detail. We performed new experiments and analysis to improve the experimental validation. + +## 6. Clinical Dataset + +Our in- vivo dataset is now described in detail, and we were able to generate further data to strengthen our hypothesis. + +In order to discuss the reviewer comments in detail, we provide a point- by- point discussion. + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +This manuscript studies the crosstalk between infiltrating microglia/macrophages and T- cells in the immunosuppressive microenvironment of glioblastoma. This is an important topic that can offer further insights into the mechanisms of resistance to anti- PD1 immunotherapy (Zhao et al. Nat. Medicine 25 (2019)). This work is a continuation of previously published work (Henrik Heiland et al., Nat. Commun. 10 (2019)), where the authors found that the crosstalk between microglia cells and reactive astrocytes is responsible for upregulating IL- 10 release in glioblastoma through JAK/STAT signaling. In this manuscript, the authors show that IL- 10 secreted by HMOX1+ myeloid cells is responsible for inducing a dysfunctional state in T cells infiltrating mesenchymal regions of the tumor. + +We would like to thank the reviewer for his time and comments leading to an improvement of the manuscript. + +There are several aspects that in my opinion need to be addressed before publication: + +1. Some of the statements in the Abstract, Introduction, and Discussion do not seem to have clear support in the data and analyses that are presented in the manuscript. Either those statements need to be more carefully crafted or the data and analyses supporting them need to be more clearly presented: + +We have substantially revised our argumentation to better support the data presented and to clearly define our hypotheses. By improving the scRNA-seq datasets and analysis approaches, some of our previously stated hypotheses have been relativized. The major difference compared to our previous manuscript is a separation of CD8 and CD4 positive T cells for all further sub analysis. Our new data incorporated novel aspects of the underlying mechanism of tumor-associated T cell response. + +1a. Lines 375- 378: the authors state that their analysis indicates that the dysfunctional state of T cells appears to be a transient state. However, this reviewer was unable to find any data or analyses supporting the transitory character of dysfunctional T cell states in subsection "Dysfunctional State of T cells is Driven by IL- 10 Signaling". + +In our revised version, we performed model integration of RNA- velocity and lineage tree reconstruction to improve the exploration of state specific pathway activation. We found that IL10 response was highly correlated with the expression of exhaustion programs in two T cell clusters. We rewrote this part of the manuscript to improve understanding and removed statements that are no longer supported or have caused confusion. + +1b. Lines 58, 117- 119, and 394- 396: the authors mention that HMOX1+ myeloid cells co- localize spatially with the mesenchymal signature of glioblastoma. However, Figs. 3f,g only show the spot- wise correlation between dysfunctional T cell gene expression markers (HAVCR2 and LAG3) and the mesenchymal gene expression signature, but as far as I see they do not present any analysis of the + +<--- Page Split ---> + +spot- wise correlation between HMOX1+ myeloid cell markers and the mesenchymal gene expression signature. Similarly, in subsection "T cell Activation and Exhaustion Reveals Spatial Heterogeneity and Association with Glioblastoma Subtypes" there seem to be no results about the spatial pattern of HMOX1+ myeloid cells. + +We thank the reviewer for picking up on this lack of clarity in presentation. We have improved the text and figure legends for clarity. In our revised version of the manuscript, we added spot- wise correlations to support our hypothesis as well as spatial data analysis of the model. + +1c. Lines 403- 405. The authors state that their experiments with the ex vivo neocortical GBM model confirm that HMOX1+ myeloid cells cause a reduction of effector T cells. However, in these experiments both HMOX1+ and HMOX1- myeloid cells are depleted using clotronate. In absence of other data, these experiments only show that myeloid cells cause a reduction of effector T cells. + +Thank you for this helpful comment. It is indeed the case that we remove all myeloid cells and therefore are unable to differentiate HMOX1 pos/neg myeloid cells individually. Using our human model, we are currently not able to specifically target HMOX1 positive cells. We have described these limitations. To approach this limitation, we quantified the spatial distance of HMOX1- positive and - negative cells in our model and concluded that HMOX- positive cells are mainly localized in the proximity of the tumor. Thus, we assumed that HMOX1- negative cells were only present to a small extent within the tumor. However, in our more detailed analysis of the slice model, we discuss limitations and cofounders more detailed. + +1d. Lines 352- 356 and 414- 418, and Fig 4q- r. It is unclear what comparison was performed here. How did the authors determine that there is a significant enrichment for activated T cells and B cells upon JAK/STAT inhibition in the patient? A more detailed explanation of the comparison and the assumptions that were made would be useful here. + +This part was fully rewritten for an improved presentation of our hypothesis. The data are re- analyzed in accordance with our new findings. + +2. The authors introduce the "nearest functionally connected neighbor" algorithm to infer candidate paracrine interactions from the single-cell RNA-seq data. Since the performance of this algorithm has not been rigorously evaluated, it is hard to know how reliable the results of this method are in general. In Supplementary Fig. 5, the authors show that the more conventional and established algorithm NicheNet (Browaeys et al. Nat. Methods 17 (2020)) also finds the candidate interaction between myeloid cells (expressing IL10) and T-cells (expressing IL10RA). However, NicheNet does not show that this interaction is specific to HOMX1+ myeloid cells. Can the authors present any other evidence from the single-cell RNA-seq data to support their statement that HOMX1+ cells are mostly responsible + +<--- Page Split ---> + +for this interaction (e.g. correlation between HOMX1+ and IL10 expression within myeloid cells)? It would be also useful to show the UMAP representation labeled by HMOX1 expression. + +In the new version of our "nearest functionally connected neighbor" (NFCN) algorithm, we implemented various new functions. In general, NFCN is built to quantify cellular interactions of a defined pathway (in our case the IL10- IL10R interaction). In comparison to NicheNet and CellChat, we inferred cellular connections based on the likelihood of cell pairs from the scRNA- seq dataset. Indeed, this quantification leads to overfitting as long as the ground truth is unknown. In order to overcome this problem, we redesigned the algorithm to integrate 3 data layers for improved prediction of cellular interactions. + +1. Prediction of the cell-pair likelihood based on scRNA-seq data. + +2. Deconvolution of Cell-Cell signaling from doublets + +3. Integration of spatial resolved transcriptomics to confirm spatial juxta positioning of cell pairs. + +We further integrated an unsupervised model using CellChat to infer the most common Cell- Cell interaction across clusters. Through our optimization, we tailored the model to predict cellular communication and reduced bias. We have added a supplementary result part to explain this model in detail. + +3. The description of the "nearest functionally connected neighbor" algorithm in the Methods section lacks much technical detail. It would be useful to include details about the models, fitting methods, etc., and rewrite the description of the algorithm more carefully. + +As mentioned in the answer above, we added supplementary results with detailed information. + +4. I found the main figures to be unnecessarily complex with 10-18 panels each. The authors might consider keeping the panels that convey the main results and moving the rest of the panels to supplementary figures. There are also several typos that need to be corrected. For example, the panels in Fig. 3 are mismatched with the figure legend (e.g. 3c and 3d seem to be exchanged) and with the main text (lines 283-310). Supplementary Fig. 6 includes a caption "Supplementary Fig. 5" which should be removed. The legend of Supplementary Fig. 3 says "Dimensional reduction (UMAP) of gene expression of the different simulation experiments". However, what is shown in the figure seems to be the UMAP of the single-cell RNA-seq data from the patients colored by the imputed stimulation signatures. + +Thanks for pointing out the typos and complexity of the figures. We have adapted the figures to facilitate ease of understanding. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling. In their manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators leveraged single- cell and spatial transcriptomics to infer cellular crosstalk between macrophages/microglia and T cells within human GBM samples. From eight GBM samples, 21 clusters were identified, where many of these clusters represented macrophages and microglia. Sub- clustering of the T cell cluster revealed different activation states that were then mapped with pseudo- time and RNA velocity analyses. This provided a differentiation map from naive to terminally exhausted, with an intermediate highly proliferative state. Additionally, by combining these techniques, authors identified an association between the mesenchymal GBM subtype and T cell exhaustion. Furthermore, authors developed a new model, nearest functional connected neighbor, to identify ligand/receptor interactions from scRNAseq data. Computational analyses are thorough and novel; however, the follow- up mechanistic studies, using an in vitro neocortical model, were limited in their support of computational findings. Primary concerns are related to the impact of the mechanistic studies. These concerns are detailed below: + +We would like to thank the reviewer for his time and comments leading to an improvement of the manuscript. + +1. A major limitation is the in vitro neocortical model used in Figure 4. Authors state that this model replicates the tumor microenvironment because it is derived from brain tissue; however, during tumorigenesis the TME is largely shaped by the infiltrating immune cells (1), which are absent in this model. Authors should comment on the "myeloid" cells that exist within the neocortical tissue that are being evaluated in figure 4, which should primarily be microglia and not the HMOX1+ macrophages from the computational studies. Along these lines, a quantification of tumor growth in the myeloid depleted condition is important, as myeloid cells generally promote tumor growth, so their absence alone may have an effect on tumor growth independent of T cells or IL10 inhibition. + +Thank you for this valuable comment. We have addressed and discussed this limitation in detail. There is no doubt that the myeloid cells within the presented model are predominantly composed of microglial cells. However, these cells can also transform reactively and consequently become HMOX1 positive. HMOX1 positive microglial cells also play a crucial role in other pathologies such as traumatic brain injury and subarachnoid hemorrhage. Therefore, it would be safe to assume that although the model is limited, the specific role associated with HMOX1 expression can be associated with activated microglial cells. We have discussed this limitation in detail. + +Regarding the quantification of tumor growth in myeloid depletion condition: This question is of high interest and our laboratory is currently working on this interaction. At the moment, we feel that the addition of this data will result in a loss of focus of the results presented in this manuscript. + +<--- Page Split ---> + +2. Additionally, the short incubation time (3 days) from tumor injection and subsequent T cell transfer may not provide sufficient time for meaningful interactions and subsequent functional outputs to occur, for example T cell exhaustion. Regarding the transferred T cells, it was not clearly stated whether there is selection for tumor-specific T cells from patient blood, therefore T cells that are injected into the neocortical model may or may not react to the tumor. Evidence of T cell recognition of tumor cells through killing or activation is necessary to increase the impact of this model. Much of T cell exhaustion biology is ignored in this model, such as the conditions and locations under which priming occur and trafficking to the tumor site. Therefore, conclusions that can be drawn from this model are limited. Furthermore, authors should address potential allogeneic reactivity to the cell line BTSC#233 by patient T cells. + +Thank you for the detailed review of the model, which aids illustrating the various aspects, functionalities and limitations. Indeed, we are limited in the interpretation of our results. However, the following points deserve to be considered: + +1. Regarding the first part of the question: We did not isolate tumor-specific T cells (mutation-associated neoantigens (MANA) associated TILs) from blood. In the context of brain tumors, to purify MANA-TILs is extremely challenging and only insufficiently possible using current methods. The aim of our model was to generate a T cell response and investigate the role of the tumor-associated microenvironment. Injection of a primary cell line which causes an allogeneic response is part of the model. Without this stimulus, a T cell response, as you mentioned above, is limited. This allogeneic reactivity should therefore be considered as intentional. + +2) Regarding the second part of the question: Our data show that T cell activity (GZMB) in the tumor region becomes detectable after 3 days. (See data presented). The temporal dimensions of our slice model span a few days because the tumor infiltrates a large portion of the slice within 7 days. We have already reported tumor growth times in our previous publications1,2. + +3. Although important for spatial information, the immunofluorescence images shown without quantifications in figure 4 are not sufficient to validate the computational studies. For example, in figure 4g, TIM3 is used to identify "exhausted T cells", but it has been shown that TIM3 can also be a marker of terminal effector differentiation. Therefore, this would be more convincing if other parameters were used to identify this population, such as PD1 or other functional studies showing T cell activity. + +We added a more sophisticated validation of the imaging results. We choose Tim3 to confirm the results from the computational studies, in which the tissue resident memory cluster revealed the strongest enrichment of exhaustion markers. + +<--- Page Split ---> + +4. When looking at the contribution of different patients to the final clusters, it is apparent that many clusters are specific to single patients. In particular, \(80\%\) of the HMOX1+ group is made up of a single patient. What impact does this have on the broader applicability of these findings? Would this bias for a single patient carry over into the downstream analyses? Is this to be expected whenever pooling human samples? + +This problem was based on the vertical integration algorithm which has been fully revised. + +5. The approval for the use of an un-licensed drug in a GBM patient needs to be specifically addressed within the ethics section. + +The treatment was performed as part of the "Compassionate Use" program (RL 2001/83/EG VO 726/2004). We added explanations in the manuscript. + +6. Minor concerns: a. The conclusion that myeloid and lymphoid interactions lead to T cell dysfunction through IL10 is vague and not unoriginal. Secretion of IL10 by myeloid cells is not a novel finding, nor is the role of IL10 in T cell dysfunction(2,3). + +Indeed, this mechanism is reported in other cancer types but not for brain malignancy so far. Other cancer types can also be treated with checkpoint inhibitors, which is not possible for GBM. We think that investigating this special environment expands our comprehension. The fact that we found similar mechanism that can be also observed in other cancer types is not unexpected. + +b. Using in vitro stimulated T cells to compare with in vivo T cells coming from a tumor ignores much of the complexity in signals that is occurring intratumorally. + +The stimulation experiments are used to detect downstream pathway activation based on an isolated cytokine. We remove all other interpretations. + +c. Using a second cell line in the in vitro neocortical studies would increase the impact of related findings. + +Since this work does not focus on the tumor directly, using multiple donors to investigate the variance across patients was our main focus. + +In general, authors show novel and interesting computational analyses from cutting edge techniques, however they lack substance in their follow up mechanistic studies. The use of pseudotime and RNA velocity to interrogate T cell activation states and pair them with GBM subtypes and spatial information are intriguing. Additionally, the nearest functionally connected neighbor algorithm will add to the expanding pool of resources for inferring intercellular communication from scRNAseq data. Follow- up + +<--- Page Split ---> + +studies are limited in their support of computational findings (IL- 10 mediated T cell exhaustion); therefore, additional validation studies are required, or the focus of the story should shift to highlight the novel bioinformatic analyses. + +Thank you for the appreciation of the computational results and tools. However, we think that biological validation, even if limited, supports the computational analysis. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +Reviewer #3 (Remarks to the Author):Ravi, Neidert, Will et al present a single- cell RNA- sequencing study of tumor- infiltrating lymphocytes of patients with GBM. The profile 8 patients and additionally show data for 3 additional patients using spatial profiling, all using 10x platforms. Using established and novel analytical tools to infer trajectories of cell differentiation, they identify variability among T cells; among other, they find sub- clusters of CD8+ T cells with high expression of dysfunction marker TIM3 (HAVCR2) and cells with a hypoxia signature with distinct trajectories. They correlate these signatures with signatures of T cells collected following in vitro stimulation with different cytokines, including IL2, IFNG and IL10, arguing that IL10 stimulated cells have a lower activation sore compared to other cells identified as effector cells. Using spatial RNA- seq of three tumors, they find an association of tumor- mesenchymal niches and infiltration of exhausted T cells (TIM3/LAG3), suggesting that niches of dysfunctional T cells may be in part explained by cancer cell intrinsic features. In order to understand the origin of IL10 and to solidify the role of T cells as IL10 recipients, they present a analytical framework that infers ligand- receptor interactions using several constraints, and demonstrate that myeloid cells (CD163+, HMOX1+) are a main source of IL10. To begin validating this finding, they use slice cultures that they deplete of myeloid cells and show that depletion of myeloid cells results in reduction of IL10 (in the presence of tumor cells); in these models, they then co- culture autologous T cells and show that depletion of myeloid cells in slice cultures results in increased IL2, but not IFNG protein abundance. Incubation of T cells with an IL10R- inhibitor prior to co- culture with tissues results in increased IL2 production in T cells. Because the JAK/STAT pathway is downstream of IL10 signaling, they use ruxolitinib (a selective JAK1/2 inhibitor) first slice model showing increased IL2, and then use this drug in the neo- adjuvant therapy of a patient with GBM, followed by analysis of the surgical specimen, which shows activation of T cells. + +GBM is a disease with extremely poor prognosis, and therapeutic development has in part been hampered by limited understanding of the tumor microenvironment; as such, the study of potentially high importance. However, several aspects raised significant concerns and reduced enthusiasm for this study, and need to be addressed, + +We would like to thank the reviewer for his time and comments leading to an improvement of the manuscript. + +Major points: + +1. Nowhere in the manuscript do the authors describe the characteristics of the patient tumors used for either single-cell sequencing of spatial sequencing. Are these all treatment naive tumors? where they exposed to different therapies (radiation, chemotherapy, immunotherapy, investigational drugs) - this will have a dramatic impact on the measured T cell phenotypes and in and of itself could describe variability seen in the data set. + +All samples used for the dataset are naive non-treated primary GBM samples except the JAK-inhibitor treated samples as described in the last section on the manuscript. + +<--- Page Split ---> + +The authors should describe basic demographics and treatment history; it is not reasonable to request from the authors to attempt to account for variability based on basic demographics (this, and virtually any single- cell study would be underpowered), but they should show major analyses/findings in the context of different therapies received to exclude the possibility noted above. + +Indeed, prior treatment can strongly affect the immune compartment. Here, only primary non- treated samples are included. We have added a supplementary table for demographic details. + +2. Technical quality: it is somewhat surprising that the authors only recover \(\sim 1000\) unique genes per cell with only \(\sim 2300\) unique molecular identifiers - this is not on par with the quality described and raises concerns regarding data quality; this is particularly surprising as they used the 3.1 chemistry which performs better than prior chemistries; in fact recent studies performing profiling from frozen tissues even achieved similar or better quality compared to this present study (Slyper, Nature Medicine, 2020). Indeed, the sequencing depth of the samples was only moderate (Sequencing Saturation \(\sim 10\% - 15\%\) ) and we decided to re-sequence all our libraries. We gained an improvement in quality to approximately \(\sim 2400\) genes per cell and \(\sim 10k\) unique molecular identifiers. To provide an overview of the dataset quality, we have added some comparisons to recent published datasets, Supplementary Figure 2. + +Furthermore, some of the clusters described might be artifactual due to tissue processing (e.g. "hypoxia cluster")- this possibility should be addressed using available data sets systematically investigating such artifacts (e.g. Ido Amit laboratory). Furthermore, the authors should comment on the technical quality. An additional embedding showing the UMI count for major analyses should be shown in the supplement to exclude the possibility of technical artifacts as drivers of clustering. + +We added a scRNA- seq quality check in the supplementary results. Using a recently reported cell- type alignment algorithm (WNN3), we redesigned the first part and specifically investigated CD8 and CD4 T cells separately. As recommended, we have opted for alignment to reference datasets. The stress cluster within the T cell population has already been confirmed in the meantime in another cohort4. + +3. There is no statistical evaluation of the inference made in Figure 3f - the authors should provide this; in this same figure, they also show that CCL2 myeloid cells are scoring highly, which is a gene considered to be an immunostimulatory gene/protein - how do they reconcile this? This brings up the question about a more nuanced annotation of the myeloid cells beyond monocytes, macrophages and microglia. The effect size of the gene set enrichment analysis in 3h is very underwhelming. In fact, throughout this section and the studies shown in Figure 4, the effect sizes are very small with in part borderline significance, raising the question of biological significance of these findings. + +We have revised large parts of the results presented formerly in Figure 4. This was done by resequencing and improving the vertical integration, have eliminated the previously seen myeloid cell populations. As already mentioned above, the myeloid populations seem to have been an artefact of + +<--- Page Split ---> + +insufficient vertical integration. Retrospectively, the integration used at that time by means of the cell ranger pipeline was not a sufficient approach. The MNN integration used now offers a much better approach to data integration. + +4. The experiments in slice cultures should be described in more detail in the main text. Here, they state that they performed "myeloid depletion" when in fact they performed microglia depletion (as stated as header in the methods section). + +We have tried to discuss the experimental part, especially the limitations, in detail. Our new data and analyses better support the reported results. The chemical depletion of microglia used here, the myeloid population in the human brain slice, has already been described in detail our previous work1,2. + +The effect size of myeloid/microglia depletion on IL10 production is rather modest. One missing control is depletion of other cell types within the slice culture and measurement of the effect on IL10 to exclude the possibility that there are other major sources of IL10 production (which is likely). + +Indeed, we agree that there are other sources of IL10 release in the tumor microenvironment. Neurons, astrocytes, and oligodendrocytes are potential candidates for IL10 release, but protocols for depletion of these cell types have not yet been established. To address this question, we attempted to establish cell- specific depletion for astrocytes. Unfortunately, we failed with this because the toxicity of astrocyte depletion is too high. Our results with IL10 inhibition confirm the downstream mechanism but cannot conclusively resolve the question of which cell type should also be considered as an IL10 source. At least our data suggest that a large fraction of IL10 is derived from HMOX1- positive myeloid cells. + +Furthermore, it is surprising that IL2 production, but not IFNG production increases during T cell depletion - the authors should offer potential explanations as this argues against reinvigoration of T cell poly- functionality. + +We agree with the reviewer that the IFNG signal is difficult to explain. When we examined the raw signal, we found generally high levels (including the negative control) of IFNG and other cytokines in the ELISA, suggesting a potential technical problem. We fully reviewed the ELISA data and re- ran the assay. The new data provided a clearer picture. Also in the new data, we see only a small baseline effect on IL10 after depletion of microglia. We assume that within our slice model the reactive transformation of microglia is necessary to upregulate IL10 release. Therefore, differences in the "no- tumor" slices were not observed. + +The results shown in 4j confirm that IL10 is an immunosuppressive cytokine, but do not substantiate claims that this is mediated by myeloid cells. Again, perplexing that no change in interferon gamma is seen. + +As mentioned above, we are limited within our model to elucidate all potential sources of IL10 release. Our data confirms that a significant part originates from myeloid cells. + +<--- Page Split ---> + +The single patient study is encouraging - was this pre-/post- comparison performed after single- agent therapy with ruxolitinib or was there a combination used? If the latter, it is possible that observed effects are due to other treatment constituents (see comment 1). + +We used monotherapy in a neoadjuvant setting. However, the patient was pretreated with RT+TMZ +CCNU (CeTeG protocol) and received TTF (not in parallel to ruxolitinib). Resection of the tumor was subsequently performed after 6 weeks of ruxolitinib monotherapy. For analysis, we were able to perform staining for direct pre/post- treatment. Unfortunately, single cell sequencing could not be performed from the very small biopsy sample (before therapy), but only from the surgery sample (after treatment). We added a more detailed description and illustrations in the updated manuscript. + +<--- Page Split ---> + +## Bibliography + +1. Ravi, V. M. et al. Human organotypic brain slice culture: a novel framework for environmental research in neuro-oncology. Life Sci. Alliance 2, (2019). +2. Henrik Heiland, D. et al. Tumor-associated reactive astrocytes aid the evolution of immunosuppressive environment in glioblastoma. Nat. Commun. 10, 2541 (2019). +3. Hao, Y., Hao, S. & Andersen, E. Integrated analysis of multimodal single-cell data. Nissen +4. Mathewson, N. D. et al. Inhibitory CD161 receptor identified in glioma-infiltrating T cells by single-cell analysis. Cell 184, 1281–1298.e26 (2021). + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have substantially improved the presentation of the hypotheses, analyses, and data in the revised manuscript, and have incorporated several new analyses that fill some of the gaps in the previous version. In my opinion, the revised manuscript is suited for publication. + +I would only like to point some typos and small suggestions to improve the clarity of some parts: + +- Line 123: "reference datasets" -> "reference dataset" +- Line 137: "Supplementary Figure 1b-c" -> "Figure 1b-c" +- Line 189: "Figure 2b" -> "Figure 2c" +- Line 223: "Figure 3d" -> "Figure 3f" +- Line 309: "Figure 5b" -> "Figure 5c" +- Line 389: "Benjamini-Hochberger" -> "Benjamini-Hochberg" + +- Line 316: the notation used for the two clusters of myeloid cells (aM\Phi and bM\Phi) does not match with the notation used in Supplementary Fig. 5. + +- In figure 1d,e it is unclear what the authors mean by "z-scored Gene Expression". z-scores are not bounded between 0 and 1, so I suspect the authors refer to something else or they have rescaled the z-scores in some way to lie between 0 and 1. I would suggest clarifying the normalization used in the figure legend and in the methods section. + +- The specific gene sets from MSigDB v7 that were used should be specified in the methods section. + +- I find the notation used in Fig. 5c and other figures (circle color + size) to be confusing. For example, in Fig. 5c the Mes-like correlation of #URK_S3 seems larger than the Mes-like correlation of #UKF_S2 based on the color of the circle, but smaller or equal based on the size of the circle. + +- It would be helpful to add more details in the legend of Fig. 5b. For example, what does each of the colors in the figure denotes? + +Reviewer #2 (Remarks to the Author): + +In their revised manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators coupled scRNAseq and stRNAseq to query the tumor microenvironment of 8 treatment naive glioblastoma patients. Ligand/receptor interactions were identified using a novel algorithm, nearest functionally connected neighbors (NFCN), ultimately identifying HMOX1+ myeloid cells as a major source of IL- 10. A T cell exhaustion phenotype was linked to the HMOX1+ myeloid cells and validated with both stRNAseq and an ex vivo neocortical system. In this revision, authors addressed concerns regarding the limitations of ex vivo experiments in validation of in silico findings. Additionally, authors increased the detail in many of the results sections to clarify relevant findings. These revisions greatly improve the quality and impact of the manuscript. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The authors have done a very good job revising the manuscript and addressing my comments and suggestions. + +I would strongly encourage them to highlight some of the technical and experimental challenges they had in their revision, as this might be of importance for future studies by their and other groups. + +Benjamin Izar + +<--- Page Split ---> + +## Point - by - Point Revision 2 + +D. H. Heiland + +We thank all reviewers for their time and effort in evaluating our manuscript and appreciate the positive feedback on our project. + +Reviewer #1 (Remarks to the Author): + +The authors have substantially improved the presentation of the hypotheses, analyses, and data in the revised manuscript, and have incorporated several new analyses that fill some of the gaps in the previous version. In my opinion, the revised manuscript is suited for publication. + +I would only like to point some typos and small suggestions to improve the clarity of some parts: + +- Line 123: "reference datasets" -> "reference dataset" + +Changed + +- Line 137: "Supplementary Figure 1b-c" -> "Figure 1b-c" + +Changed + +- Line 189: "Figure 2b" -> "Figure 2c" + +Changed + +- Line 223: "Figure 3d" -> "Figure 3f" + +Changed + +- Line 309: "Figure 5b" -> "Figure 5c" + +Changed + +- Line 389: "Benjamini- Hochberger" -> "Benjamini-Hochberg" + +Changed + +- Line 316: the notation used for the two clusters of myeloid cells (aM\Phi and bM\Phi) does not match with the notation used in Supplementary Fig. 5. + +Changed in the new supplementary file + +- In figure 1d,e it is unclear what the authors mean by "z-scored Gene Expression". z-scores are not bounded between 0 and 1, so I suspect the authors refer to something else or they have rescaled the z-scores in some way to lie between 0 and 1. I would suggest clarifying the normalization used in the figure legend and in the methods section. + +It is normalized gene expression, we changed the figure description + +- The specific gene sets from MSigDB v7 that were used should be specified in the methods section. + +The gene sets are implemented in the method part. + +- I find the notation used in Fig. 5c and other figures (circle color + size) to be confusing. For example, in Fig. 5c the Mes-like correlation of #URK_S3 seems larger than the Mes-like correlation of #UKF_S2 based on the color of the circle, but smaller or equal based on the size of the circle. + +<--- Page Split ---> + +It was based on the fact that plots were created individually, we changed this. + +- It would be helpful to add more details in the legend of Fig. 5b. For example, what does each of the colors in the figure denotes? + +We added a description in the figure. + +Reviewer #2 (Remarks to the Author): + +In their revised manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators coupled scRNAseq and stRNAseq to query the tumor microenvironment of 8 treatment naive glioblastoma patients. Ligand/receptor interactions were identified using a novel algorithm, nearest functionally connected neighbors (NFCN), ultimately identifying HMOX1+ myeloid cells as a major source of IL- 10. A T cell exhaustion phenotype was linked to the HMOX1+ myeloid cells and validated with both stRNAseq and an ex vivo neocortical system. In this revision, authors addressed concerns regarding the limitations of ex vivo experiments in validation of in silico findings. Additionally, authors increased the detail in many of the results sections to clarify relevant findings. These revisions greatly improve the quality and impact of the manuscript. + +Reviewer #3 (Remarks to the Author): + +The authors have done a very good job revising the manuscript and addressing my comments and suggestions. I would strongly encourage them to highlight some of the technical and experimental challenges they had in their revision, as this might be of importance for future studies by their and other groups. + +R2 & R3: Thank you for the positive response. We are pleased that the reviewers appreciated the considerable effort and the change during the revision process. In our opinion, a description of these changes in the discussion clearly hampers the red- thread and takes the focus away from the scientific results. In our opinion, the detailed process can be reconstructed very well from published reviewers' comments, so we have refrained from making a statement in the discussion part. + +<--- Page Split ---> diff --git a/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..5efc6c49b7773b0ef5127109f0ce243a9c99f4d0 --- /dev/null +++ b/peer_reviews/126b45d3c59304c8cdcaeff2fb15da92849086ba5d613f1f0d668d95576aa34f/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,589 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[66, 110, 362, 139]]<|/det|> +# Peer Review File + +<|ref|>text<|/ref|><|det|>[[88, 154, 910, 210]]<|/det|> +T- Cell Dysfunction in the Glioblastoma Microenvironment is Mediated by Myeloid Cells Releasing Interleukin- 10 + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 312, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 112, 402, 128]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 142, 879, 262]]<|/det|> +This manuscript studies the crosstalk between infiltrating microglia/macrophages and T- cells in the immunosuppressive microenvironment of glioblastoma. This is an important topic that can offer further insights into the mechanisms of resistance to anti- PD1 immunotherapy (Zhao et al. Nat. Medicine 25 (2019)). This work is a continuation of previously published work (Herik Heiland et al., Nat. Commun. 10 (2019)), where the authors found that the crosstalk between microglia cells and reactive astrocytes is responsible for upregulating IL- 10 release in glioblastoma through JAK/STAT signaling. In this manuscript, the authors show that IL- 10 secreted by HMOX1+ myeloid cells is responsible for inducing a dysfunctional state in T cells infiltrating mesenchymal regions of the tumor. + +<|ref|>text<|/ref|><|det|>[[120, 275, 759, 290]]<|/det|> +There are several aspects that in my opinion need to be addressed before publication: + +<|ref|>text<|/ref|><|det|>[[119, 304, 868, 364]]<|/det|> +1. Some of the statements in the Abstract, Introduction, and Discussion do not seem to have clear support in the data and analyses that are presented in the manuscript. Either those statements need to be more carefully crafted or the data and analyses supporting them need to be more clearly presented: + +<|ref|>text<|/ref|><|det|>[[119, 377, 872, 437]]<|/det|> +1a. Lines 375-378: the authors state that their analysis indicates that the dysfunctional state of T cells appears to be a transient state. However, this reviewer was unable to find any data or analyses supporting the transitory character of dysfunctional T cell states in subsection "Dysfunctional State of T cells is Driven by IL-10 Signaling". + +<|ref|>text<|/ref|><|det|>[[118, 450, 873, 570]]<|/det|> +1b. Lines 58, 117-119, and 394-396: the authors mention that HMOX1+ myeloid cells co-localize spatially with the mesenchymal signature of glioblastoma. However, Figs. 3f,g only show the spotwise correlation between dysfunctional T cell gene expression markers (HAVCR2 and LAG3) and the mesenchymal gene expression signature, but as far as I see they do not present any analysis of the spot-wise correlation between HMOX1+ myeloid cell markers and the mesenchymal gene expression signature. Similarly, in subsection "T cell Activation and Exhaustion Reveals Spatial Heterogeneity and Association with Glioblastoma Subtypes" there seem to be no results about the spatial pattern of HMOX1+ myeloid cells. + +<|ref|>text<|/ref|><|det|>[[118, 583, 864, 644]]<|/det|> +1c. Lines 403-405. The authors state that their experiments with the ex vivo neocortical GBM model confirm that HMOX1+ myeloid cells cause a reduction of effector T cells. However, in these experiments both HMOX1+ and HMOX1- myeloid cells are depleted using clodronate. In absence of other data, these experiments only show that myeloid cells cause a reduction of effector T cells. + +<|ref|>text<|/ref|><|det|>[[118, 656, 878, 717]]<|/det|> +1d. Lines 352-356 and 414-418, and Fig 4q-r. It is unclear what comparison was performed here. How did the authors determine that there is a significant enrichment for activated T cells and B cells upon JAK/STAT inhibition in the patient? A more detailed explanation of the comparison and the assumptions that were made would be useful here. + +<|ref|>text<|/ref|><|det|>[[117, 730, 875, 880]]<|/det|> +2. The authors introduce the "nearest functionally connected neighbor" algorithm to infer candidate paracrine interactions from the single-cell RNA-seq data. Since the performance of this algorithm has not been rigorously evaluated, it is hard to know how reliable the results of this method are in general. In Supplementary Fig. 5, the authors show that the more conventional and established algorithm NicheNet (Browaeys et al. Nat. Methods 17 (2020)) also finds the candidate interaction between myeloid cells (expressing IL10) and T-cells (expressing IL10RA). However, NicheNet does not show that this interaction is specific to HOMX1+ myeloid cells. Can the authors present any other evidence from the single-cell RNA-seq data to support their statement that HOMX1+ cells are mostly responsible for this interaction (e.g. correlation between HOMX1+ and IL10 expression within myeloid cells)? It would be also useful to show the UMAP representation labeled by HMOX1 expression. + +<|ref|>text<|/ref|><|det|>[[115, 893, 860, 909]]<|/det|> +3. The description of the "nearest functionally connected neighbor" algorithm in the Methods section + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 848, 112]]<|/det|> +lacks much technical detail. It would be useful to include details about the models, fitting methods, etc., and rewrite the description of the algorithm more carefully. + +<|ref|>text<|/ref|><|det|>[[118, 127, 868, 262]]<|/det|> +4. I found the main figures to be unnecessarily complex with 10-18 panels each. The authors might consider keeping the panels that convey the main results and moving the rest of the panels to supplementary figures. There are also several typos that need to be corrected. For example, the panels in Fig. 3 are mismatched with the figure legend (e.g. 3c and 3d seem to be exchanged) and with the main text (lines 283-310). Supplementary Fig. 6 includes a caption "Supplementary Fig. 5" which should be removed. The legend of Supplementary Fig. 3 says "Dimensional reduction (UMAP) of gene expression of the different simulation experiments". However, what is shown in the figure seems to be the UMAP of the single-cell RNA-seq data from the patients colored by the imputed stimulation signatures. + +<|ref|>text<|/ref|><|det|>[[120, 305, 401, 320]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 334, 880, 380]]<|/det|> +NCOMMS- 21- 07876- T Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling + +<|ref|>text<|/ref|><|det|>[[118, 393, 878, 585]]<|/det|> +In their manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators leveraged single- cell and spatial transcriptomics to infer cellular crosstalk between macrophages/microglia and T cells within human GBM samples. From eight GBM samples, 21 clusters were identified, where many of these clusters represented macrophages and microglia. Sub- clustering of the T cell cluster revealed different activation states that were then mapped with pseudo- time and RNA velocity analyses. This provided a differentiation map from naive to terminally exhausted, with an intermediate highly proliferative state. Additionally, by combining these techniques, authors identified an association between the mesenchymal GBM subtype and T cell exhaustion. Furthermore, authors developed a new model, nearest functional connected neighbor, to identify ligand/receptor interactions from scRNAseq data. Computational analyses are thorough and novel; however, the follow- up mechanistic studies, using an in vitro neocortical model, were limited in their support of computational findings. Primary concerns are related to the impact of the mechanistic studies. These concerns are detailed below: + +<|ref|>text<|/ref|><|det|>[[118, 599, 870, 717]]<|/det|> +1. A major limitation is the in vitro neocortical model used in Figure 4. Authors state that this model replicates the tumor microenvironment because it is derived from brain tissue; however, during tumorigenesis the TME is largely shaped by the infiltrating immune cells (1), which are absent in this model. Authors should comment on the "myeloid" cells that exist within the neocortical tissue that are being evaluated in figure 4, which should primarily be microglia and not the HMOX1+ macrophages from the computational studies. Along these lines, a quantification of tumor growth in the myeloid depleted condition is important, as myeloid cells generally promote tumor growth, so their absence alone may have an effect on tumor growth independent of T cells or IL10 inhibition. + +<|ref|>text<|/ref|><|det|>[[118, 731, 875, 880]]<|/det|> +2. Additionally, the short incubation time (3 days) from tumor injection and subsequent T cell transfer may not provide sufficient time for meaningful interactions and subsequent functional outputs to occur, for example T cell exhaustion. Regarding the transferred T cells, it was not clearly stated whether there is selection for tumor-specific T cells from patient blood, therefore T cells that are injected into the neocortical model may or may not react to the tumor. Evidence of T cell recognition of tumor cells through killing or activation is necessary to increase the impact of this model. Much of T cell exhaustion biology is ignored in this model, such as the conditions and locations under which priming occur and trafficking to the tumor site. Therefore, conclusions that can be drawn from this model are limited. Furthermore, authors should address potential allogeneic reactivity to the cell line BTSC#233 by patient T cells. + +<|ref|>text<|/ref|><|det|>[[118, 895, 808, 910]]<|/det|> +3. Although important for spatial information, the immunofluorescence images shown without + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 868, 158]]<|/det|> +quantifications in figure 4 are not sufficient to validate the computational studies. For example, in figure 4g, TIM3 is used to identify "exhausted T cells", but it has been shown that TIM3 can also be a marker of terminal effector differentiation. Therefore, this would be more convincing if other parameters were used to identify this population, such as PD1 or other functional studies showing T cell activity. + +<|ref|>text<|/ref|><|det|>[[118, 171, 875, 247]]<|/det|> +4. When looking at the contribution of different patients to the final clusters, it is apparent that many clusters are specific to single patients. In particular, \(80\%\) of the HMOX1+ group is made up of a single patient. What impact does this have on the broader applicability of these findings? Would this bias for a single patient carry over into the downstream analyses? Is this to be expected whenever pooling human samples? + +<|ref|>text<|/ref|><|det|>[[118, 260, 800, 290]]<|/det|> +5. The approval for the use of an un-licensed drug in a GBM patient needs to be specifically addressed within the ethics section. + +<|ref|>sub_title<|/ref|><|det|>[[118, 305, 258, 318]]<|/det|> +## 6. Minor concerns: + +<|ref|>text<|/ref|><|det|>[[118, 319, 860, 420]]<|/det|> +a. The conclusion that myeloid and lymphoid interactions lead to T cell dysfunction through IL10 is vague and not unoriginal. Secretion of IL10 by myeloid cells is not a novel finding, nor is the role of IL10 in T cell dysfunction(2,3). +b. Using in vitro stimulated T cells to compare with in vivo T cells coming from a tumor ignores much of the complexity in signals that is occurring intratumorally. +c. Using a second cell line in the in vitro neocortical studies would increase the impact of related findings. + +<|ref|>text<|/ref|><|det|>[[118, 435, 872, 555]]<|/det|> +In general, authors show novel and interesting computational analyses from cutting edge techniques, however they lack substance in their follow up mechanistic studies. The use of pseudotime and RNA velocity to interrogate T cell activation states and pair them with GBM subtypes and spatial information are intriguing. Additionally, the nearest functionally connected neighbor algorithm will add to the expanding pool of resources for inferring intercellular communication from scRNAseq data. Follow-up studies are limited in their support of computational findings (IL- 10 mediated T cell exhaustion); therefore, additional validation studies are required, or the focus of the story should shift to highlight the novel bioinformatic analyses. + +<|ref|>sub_title<|/ref|><|det|>[[118, 585, 202, 598]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[117, 599, 870, 689]]<|/det|> +1. Salmon, H., Remark, R., Gnjatic, S. and Merad, M., 2019. Host tissue determinants of tumour immunity. Nature Reviews Cancer, 19(4), pp.215-227. +2. McLane, L.M., Abdel-Hakeem, M.S. and Wherry, E.J., 2019. CD8 T cell exhaustion during chronic viral infection and cancer. Annual review of immunology, 37, pp.457-495. +3. Quail, D.F. and Joyce, J.A., 2017. The microenvironmental landscape of brain tumors. Cancer cell, 31(3), pp.326-341. + +<|ref|>text<|/ref|><|det|>[[119, 747, 402, 761]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 775, 870, 910]]<|/det|> +Ravi, Neidert, Will et al present a single- cell RNA- sequencing study of tumor- infiltrating lymphocytes of patients with GBM. The profile 8 patients and additionally show data for 3 additional patients using spatial profiling, all using 10x platforms. Using established and novel analytical tools to infer trajectories of cell differentiation, they identify variability among T cells; among other, they find subclusters of CD8+ T cells with high expression of dysfunction marker TIM3 (HAVCR2) and cells with a hypoxia signature with distinct trajectories. They correlate these signatures with signatures of T cells collected following in vitro stimulation with different cytokines, including IL2, IFNG and IL10, arguing that IL10 stimulated cells have a lower activation score compared to other cells identified as effector cells. Using spatial RNA- seq of three tumors, they find an association of tumor- mesenchymal niches + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 875, 275]]<|/det|> +and infiltration of exhausted T cells (TIM3/LAG3), suggesting that niches of dysfunctional T cells may be in part explained by cancer cell intrinsic features. In order to understand the origin of IL10 and to solidify the role of T cells as IL10 recipients, they present a analytical framework that infers ligandreceptor interactions using several constraints, and demonstrate that myeloid cells (CD163+, HMOX1+) are a main source of IL10. To begin validating this finding, they use slice cultures that they deplete of myeloid cells and show that depletion of myeloid cells results in reduction of IL10 (in the presence of tumor cells); in these models, they then co- culture autologous T cells and show that depletion of myeloid cells in slice cultures results in increased IL2, but not IFNG protein abundance. Incubation of T cells with an IL10R- inhibitor prior to co- culture with tissues results in increased IL2 production in T cells. Because the JAK/STAT pathway is downstream of IL10 signaling, they use ruxolitinib (a selective JAK1/2 inhibitor) first i slice model showing increased IL2, and then use this drug in the neo- adjuvant therapy of a patient with GBM, followed by analysis of the surgical specimen, which shows activation of T cells. + +<|ref|>text<|/ref|><|det|>[[119, 289, 860, 349]]<|/det|> +GBM is a disease with extremely poor prognosis, and therapeutic development has in part been hampered by limited understanding of the tumor microenvironment; as such, the study of potentially high importance. However, several aspects raised significant concerns and reduced enthusiasm for this study, and need to be addressed, + +<|ref|>text<|/ref|><|det|>[[119, 364, 216, 378]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[118, 393, 876, 525]]<|/det|> +1. Nowhere in the manuscript do the authors describe the characteristics of the patient tumors used for either single-cell sequencing of spatial sequencing. Are these all treatment naive tumors? where they exposed to different therapies (radiation, chemotherapy, immunotherapy, investigational drugs) - this will have a dramatic impact on the measured T cell phenotypes and in and of itself could describe variability seen in the data set. The authors should describe basic demographics and treatment history; it is not reasonable to request from the authors to attempt to account for variability based on basic demographics (this, and virtually any single-cell study would be underpowered), but they should show major analyses/findings in the context of different therapies received to exclude the possibility noted above. + +<|ref|>text<|/ref|><|det|>[[118, 540, 876, 701]]<|/det|> +2. Technical quality: it is somewhat surprising that the authors only recover \(\sim 1000\) unique genes per cell with only \(\sim 2300\) unique molecular identifiers - this is not on par with the quality described and raises concerns regarding data quality; this is particularly surprising as they used the 3.1 chemistry which performs better than prior chemistries; in fact recent studies performing profiling from frozen tissues even achieved similar or better quality compared to this present study (Slyper, Nature Medicine, 2020). Furthermore, some of the clusters described might be artifactual due to tissue processing (e.g. "hypoxia cluster")- this possibility should be addressed using available data sets systematically investigating such artifacts (e.g. Ido Amit laboratory). Furthermore, the authors should comment on the technical quality. An additional embedding showing the UML count for major analyses should be shown in the supplement to exclude the possibility of technical artifacts as drivers of clustering. + +<|ref|>text<|/ref|><|det|>[[118, 716, 878, 820]]<|/det|> +3. There is no statistical evaluation of the inference made in Figure 3f - the authors should provide this; in this same figure, they also show that CCL2 myeloid cells are scoring highly, which is a gene considered to be an immunostimulatory gene/protein - how do they reconcile this? This brings up the question about a more nuanced annotation of the myeloid cells beyond monocytes, macrophages and microglia. The effect size of the gene set enrichment analysis in 3h is very underwhelming. In fact, throughout this section and the studies shown in Figure 4, the effect sizes are very small with in part borderline significance, raising the question of biological significance of these findings. + +<|ref|>text<|/ref|><|det|>[[118, 834, 878, 909]]<|/det|> +4. The experiments in slice cultures should be described in more detail in the main text. Here, they state that they performed "myeloid depletion" when in fact they performed microglia depletion (as stated as header in the methods section). The effect size of myeloid/microglia depletion on IL10 production is rather modest. One missing control is depletion of other cell types within the slice culture and measurement of the effect on IL10 to exclude the possibility that there are other major sources of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 860, 201]]<|/det|> +IL10 production (which is likely). Furthermore, it is surprising that IL2 production, but not IFNG production increases during T cell depletion - the authors should offer potential explanations as this argues against reinvigoration of T cell poly- functionality. The results shown in 4j confirm that IL10 is an immunosuppressive cytokine, but do not substantiate claims that this is medicated by myeloid cells. Again, perplexing that no change in interferon gamma is seen. The single patient study is encouraging - was this pre- /post- comparison performed after single- agent therapy with ruxolitinib or was there a combination used? If the latter, it is possible that observed effects are due to other treatment constituents (see comment 1). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[120, 86, 395, 112]]<|/det|> +## Point - by - Point + +<|ref|>text<|/ref|><|det|>[[120, 124, 222, 138]]<|/det|> +D. H. Heiland + +<|ref|>text<|/ref|><|det|>[[118, 164, 881, 243]]<|/det|> +We thank all reviewers for their time and effort in evaluating our manuscript and appreciate the positive feedback on our project. We have tried to mitigate the issues highlighted by the reviewers, which has led to a significant improvement in the quality of our manuscript. The following main changes have been made in this context: + +<|ref|>sub_title<|/ref|><|det|>[[120, 268, 448, 283]]<|/det|> +## 1. Quality of the scRNA-seq experiments. + +<|ref|>text<|/ref|><|det|>[[118, 288, 880, 325]]<|/det|> +By resequencing the libraries, the quality of the entire dataset was significantly improved and the number of detected genes as well as the UMIs per cell were significantly increased. + +<|ref|>sub_title<|/ref|><|det|>[[119, 350, 374, 365]]<|/det|> +## 2. Analysis and data integration + +<|ref|>text<|/ref|><|det|>[[118, 370, 880, 427]]<|/det|> +By applying more advanced algorithms for horizonal and vertical data integration as well as cell type alignment, we were able to present a clearer picture of T cell diversity in the tumors. We separated CD4 and CD8 positive T cells for all downstream analysis. + +<|ref|>sub_title<|/ref|><|det|>[[118, 452, 456, 467]]<|/det|> +## 3. Avoid overfitting in the NFCN algorithm + +<|ref|>text<|/ref|><|det|>[[118, 472, 881, 550]]<|/det|> +Our cell communication algorithm has been optimized to reduce potential overfitting and improve prediction. For this purpose, we integrated multiple prediction/validation layers and external algorithms. The new version is also compatible with the conventional scRNA- seq tools (Seurat) and available as an R package (NFCN2). + +<|ref|>sub_title<|/ref|><|det|>[[118, 575, 500, 590]]<|/det|> +## 4. Structure of the manuscript and presentation + +<|ref|>text<|/ref|><|det|>[[118, 595, 880, 632]]<|/det|> +We restructured our manuscript to present clear hypothesis- driven argumentation and pointed out limitations and ambiguities. The illustrations have been simplified to improve general understanding. + +<|ref|>sub_title<|/ref|><|det|>[[118, 656, 274, 670]]<|/det|> +## 5. Validation model + +<|ref|>text<|/ref|><|det|>[[118, 676, 880, 713]]<|/det|> +Our experimental model is not without limitations, which are discussed in detail. We performed new experiments and analysis to improve the experimental validation. + +<|ref|>sub_title<|/ref|><|det|>[[118, 738, 265, 752]]<|/det|> +## 6. Clinical Dataset + +<|ref|>text<|/ref|><|det|>[[118, 758, 880, 795]]<|/det|> +Our in- vivo dataset is now described in detail, and we were able to generate further data to strengthen our hypothesis. + +<|ref|>text<|/ref|><|det|>[[115, 820, 797, 836]]<|/det|> +In order to discuss the reviewer comments in detail, we provide a point- by- point discussion. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 82, 420, 98]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 123, 882, 284]]<|/det|> +This manuscript studies the crosstalk between infiltrating microglia/macrophages and T- cells in the immunosuppressive microenvironment of glioblastoma. This is an important topic that can offer further insights into the mechanisms of resistance to anti- PD1 immunotherapy (Zhao et al. Nat. Medicine 25 (2019)). This work is a continuation of previously published work (Henrik Heiland et al., Nat. Commun. 10 (2019)), where the authors found that the crosstalk between microglia cells and reactive astrocytes is responsible for upregulating IL- 10 release in glioblastoma through JAK/STAT signaling. In this manuscript, the authors show that IL- 10 secreted by HMOX1+ myeloid cells is responsible for inducing a dysfunctional state in T cells infiltrating mesenchymal regions of the tumor. + +<|ref|>text<|/ref|><|det|>[[118, 308, 880, 345]]<|/det|> +We would like to thank the reviewer for his time and comments leading to an improvement of the manuscript. + +<|ref|>text<|/ref|><|det|>[[119, 370, 760, 386]]<|/det|> +There are several aspects that in my opinion need to be addressed before publication: + +<|ref|>text<|/ref|><|det|>[[118, 410, 881, 469]]<|/det|> +1. Some of the statements in the Abstract, Introduction, and Discussion do not seem to have clear support in the data and analyses that are presented in the manuscript. Either those statements need to be more carefully crafted or the data and analyses supporting them need to be more clearly presented: + +<|ref|>text<|/ref|><|det|>[[118, 492, 881, 591]]<|/det|> +We have substantially revised our argumentation to better support the data presented and to clearly define our hypotheses. By improving the scRNA-seq datasets and analysis approaches, some of our previously stated hypotheses have been relativized. The major difference compared to our previous manuscript is a separation of CD8 and CD4 positive T cells for all further sub analysis. Our new data incorporated novel aspects of the underlying mechanism of tumor-associated T cell response. + +<|ref|>text<|/ref|><|det|>[[118, 615, 881, 692]]<|/det|> +1a. Lines 375- 378: the authors state that their analysis indicates that the dysfunctional state of T cells appears to be a transient state. However, this reviewer was unable to find any data or analyses supporting the transitory character of dysfunctional T cell states in subsection "Dysfunctional State of T cells is Driven by IL- 10 Signaling". + +<|ref|>text<|/ref|><|det|>[[118, 697, 881, 795]]<|/det|> +In our revised version, we performed model integration of RNA- velocity and lineage tree reconstruction to improve the exploration of state specific pathway activation. We found that IL10 response was highly correlated with the expression of exhaustion programs in two T cell clusters. We rewrote this part of the manuscript to improve understanding and removed statements that are no longer supported or have caused confusion. + +<|ref|>text<|/ref|><|det|>[[118, 820, 881, 898]]<|/det|> +1b. Lines 58, 117- 119, and 394- 396: the authors mention that HMOX1+ myeloid cells co- localize spatially with the mesenchymal signature of glioblastoma. However, Figs. 3f,g only show the spot- wise correlation between dysfunctional T cell gene expression markers (HAVCR2 and LAG3) and the mesenchymal gene expression signature, but as far as I see they do not present any analysis of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 881, 161]]<|/det|> +spot- wise correlation between HMOX1+ myeloid cell markers and the mesenchymal gene expression signature. Similarly, in subsection "T cell Activation and Exhaustion Reveals Spatial Heterogeneity and Association with Glioblastoma Subtypes" there seem to be no results about the spatial pattern of HMOX1+ myeloid cells. + +<|ref|>text<|/ref|><|det|>[[118, 185, 881, 243]]<|/det|> +We thank the reviewer for picking up on this lack of clarity in presentation. We have improved the text and figure legends for clarity. In our revised version of the manuscript, we added spot- wise correlations to support our hypothesis as well as spatial data analysis of the model. + +<|ref|>text<|/ref|><|det|>[[118, 266, 881, 345]]<|/det|> +1c. Lines 403- 405. The authors state that their experiments with the ex vivo neocortical GBM model confirm that HMOX1+ myeloid cells cause a reduction of effector T cells. However, in these experiments both HMOX1+ and HMOX1- myeloid cells are depleted using clotronate. In absence of other data, these experiments only show that myeloid cells cause a reduction of effector T cells. + +<|ref|>text<|/ref|><|det|>[[117, 368, 882, 530]]<|/det|> +Thank you for this helpful comment. It is indeed the case that we remove all myeloid cells and therefore are unable to differentiate HMOX1 pos/neg myeloid cells individually. Using our human model, we are currently not able to specifically target HMOX1 positive cells. We have described these limitations. To approach this limitation, we quantified the spatial distance of HMOX1- positive and - negative cells in our model and concluded that HMOX- positive cells are mainly localized in the proximity of the tumor. Thus, we assumed that HMOX1- negative cells were only present to a small extent within the tumor. However, in our more detailed analysis of the slice model, we discuss limitations and cofounders more detailed. + +<|ref|>text<|/ref|><|det|>[[118, 553, 881, 632]]<|/det|> +1d. Lines 352- 356 and 414- 418, and Fig 4q- r. It is unclear what comparison was performed here. How did the authors determine that there is a significant enrichment for activated T cells and B cells upon JAK/STAT inhibition in the patient? A more detailed explanation of the comparison and the assumptions that were made would be useful here. + +<|ref|>text<|/ref|><|det|>[[118, 656, 880, 693]]<|/det|> +This part was fully rewritten for an improved presentation of our hypothesis. The data are re- analyzed in accordance with our new findings. + +<|ref|>text<|/ref|><|det|>[[117, 717, 882, 878]]<|/det|> +2. The authors introduce the "nearest functionally connected neighbor" algorithm to infer candidate paracrine interactions from the single-cell RNA-seq data. Since the performance of this algorithm has not been rigorously evaluated, it is hard to know how reliable the results of this method are in general. In Supplementary Fig. 5, the authors show that the more conventional and established algorithm NicheNet (Browaeys et al. Nat. Methods 17 (2020)) also finds the candidate interaction between myeloid cells (expressing IL10) and T-cells (expressing IL10RA). However, NicheNet does not show that this interaction is specific to HOMX1+ myeloid cells. Can the authors present any other evidence from the single-cell RNA-seq data to support their statement that HOMX1+ cells are mostly responsible + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 880, 120]]<|/det|> +for this interaction (e.g. correlation between HOMX1+ and IL10 expression within myeloid cells)? It would be also useful to show the UMAP representation labeled by HMOX1 expression. + +<|ref|>text<|/ref|><|det|>[[117, 144, 882, 265]]<|/det|> +In the new version of our "nearest functionally connected neighbor" (NFCN) algorithm, we implemented various new functions. In general, NFCN is built to quantify cellular interactions of a defined pathway (in our case the IL10- IL10R interaction). In comparison to NicheNet and CellChat, we inferred cellular connections based on the likelihood of cell pairs from the scRNA- seq dataset. Indeed, this quantification leads to overfitting as long as the ground truth is unknown. In order to overcome this problem, we redesigned the algorithm to integrate 3 data layers for improved prediction of cellular interactions. + +<|ref|>text<|/ref|><|det|>[[118, 268, 603, 284]]<|/det|> +1. Prediction of the cell-pair likelihood based on scRNA-seq data. + +<|ref|>text<|/ref|><|det|>[[118, 289, 510, 304]]<|/det|> +2. Deconvolution of Cell-Cell signaling from doublets + +<|ref|>text<|/ref|><|det|>[[118, 309, 826, 325]]<|/det|> +3. Integration of spatial resolved transcriptomics to confirm spatial juxta positioning of cell pairs. + +<|ref|>text<|/ref|><|det|>[[117, 329, 881, 406]]<|/det|> +We further integrated an unsupervised model using CellChat to infer the most common Cell- Cell interaction across clusters. Through our optimization, we tailored the model to predict cellular communication and reduced bias. We have added a supplementary result part to explain this model in detail. + +<|ref|>text<|/ref|><|det|>[[118, 431, 880, 489]]<|/det|> +3. The description of the "nearest functionally connected neighbor" algorithm in the Methods section lacks much technical detail. It would be useful to include details about the models, fitting methods, etc., and rewrite the description of the algorithm more carefully. + +<|ref|>text<|/ref|><|det|>[[118, 513, 818, 529]]<|/det|> +As mentioned in the answer above, we added supplementary results with detailed information. + +<|ref|>text<|/ref|><|det|>[[117, 553, 882, 733]]<|/det|> +4. I found the main figures to be unnecessarily complex with 10-18 panels each. The authors might consider keeping the panels that convey the main results and moving the rest of the panels to supplementary figures. There are also several typos that need to be corrected. For example, the panels in Fig. 3 are mismatched with the figure legend (e.g. 3c and 3d seem to be exchanged) and with the main text (lines 283-310). Supplementary Fig. 6 includes a caption "Supplementary Fig. 5" which should be removed. The legend of Supplementary Fig. 3 says "Dimensional reduction (UMAP) of gene expression of the different simulation experiments". However, what is shown in the figure seems to be the UMAP of the single-cell RNA-seq data from the patients colored by the imputed stimulation signatures. + +<|ref|>text<|/ref|><|det|>[[118, 758, 880, 795]]<|/det|> +Thanks for pointing out the typos and complexity of the figures. We have adapted the figures to facilitate ease of understanding. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 420, 98]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 123, 882, 407]]<|/det|> +Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling. In their manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators leveraged single- cell and spatial transcriptomics to infer cellular crosstalk between macrophages/microglia and T cells within human GBM samples. From eight GBM samples, 21 clusters were identified, where many of these clusters represented macrophages and microglia. Sub- clustering of the T cell cluster revealed different activation states that were then mapped with pseudo- time and RNA velocity analyses. This provided a differentiation map from naive to terminally exhausted, with an intermediate highly proliferative state. Additionally, by combining these techniques, authors identified an association between the mesenchymal GBM subtype and T cell exhaustion. Furthermore, authors developed a new model, nearest functional connected neighbor, to identify ligand/receptor interactions from scRNAseq data. Computational analyses are thorough and novel; however, the follow- up mechanistic studies, using an in vitro neocortical model, were limited in their support of computational findings. Primary concerns are related to the impact of the mechanistic studies. These concerns are detailed below: + +<|ref|>text<|/ref|><|det|>[[118, 430, 880, 468]]<|/det|> +We would like to thank the reviewer for his time and comments leading to an improvement of the manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 492, 882, 653]]<|/det|> +1. A major limitation is the in vitro neocortical model used in Figure 4. Authors state that this model replicates the tumor microenvironment because it is derived from brain tissue; however, during tumorigenesis the TME is largely shaped by the infiltrating immune cells (1), which are absent in this model. Authors should comment on the "myeloid" cells that exist within the neocortical tissue that are being evaluated in figure 4, which should primarily be microglia and not the HMOX1+ macrophages from the computational studies. Along these lines, a quantification of tumor growth in the myeloid depleted condition is important, as myeloid cells generally promote tumor growth, so their absence alone may have an effect on tumor growth independent of T cells or IL10 inhibition. + +<|ref|>text<|/ref|><|det|>[[117, 676, 882, 816]]<|/det|> +Thank you for this valuable comment. We have addressed and discussed this limitation in detail. There is no doubt that the myeloid cells within the presented model are predominantly composed of microglial cells. However, these cells can also transform reactively and consequently become HMOX1 positive. HMOX1 positive microglial cells also play a crucial role in other pathologies such as traumatic brain injury and subarachnoid hemorrhage. Therefore, it would be safe to assume that although the model is limited, the specific role associated with HMOX1 expression can be associated with activated microglial cells. We have discussed this limitation in detail. + +<|ref|>text<|/ref|><|det|>[[118, 840, 880, 899]]<|/det|> +Regarding the quantification of tumor growth in myeloid depletion condition: This question is of high interest and our laboratory is currently working on this interaction. At the moment, we feel that the addition of this data will result in a loss of focus of the results presented in this manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 882, 284]]<|/det|> +2. Additionally, the short incubation time (3 days) from tumor injection and subsequent T cell transfer may not provide sufficient time for meaningful interactions and subsequent functional outputs to occur, for example T cell exhaustion. Regarding the transferred T cells, it was not clearly stated whether there is selection for tumor-specific T cells from patient blood, therefore T cells that are injected into the neocortical model may or may not react to the tumor. Evidence of T cell recognition of tumor cells through killing or activation is necessary to increase the impact of this model. Much of T cell exhaustion biology is ignored in this model, such as the conditions and locations under which priming occur and trafficking to the tumor site. Therefore, conclusions that can be drawn from this model are limited. Furthermore, authors should address potential allogeneic reactivity to the cell line BTSC#233 by patient T cells. + +<|ref|>text<|/ref|><|det|>[[118, 308, 880, 365]]<|/det|> +Thank you for the detailed review of the model, which aids illustrating the various aspects, functionalities and limitations. Indeed, we are limited in the interpretation of our results. However, the following points deserve to be considered: + +<|ref|>text<|/ref|><|det|>[[117, 389, 882, 530]]<|/det|> +1. Regarding the first part of the question: We did not isolate tumor-specific T cells (mutation-associated neoantigens (MANA) associated TILs) from blood. In the context of brain tumors, to purify MANA-TILs is extremely challenging and only insufficiently possible using current methods. The aim of our model was to generate a T cell response and investigate the role of the tumor-associated microenvironment. Injection of a primary cell line which causes an allogeneic response is part of the model. Without this stimulus, a T cell response, as you mentioned above, is limited. This allogeneic reactivity should therefore be considered as intentional. + +<|ref|>text<|/ref|><|det|>[[118, 554, 881, 632]]<|/det|> +2) Regarding the second part of the question: Our data show that T cell activity (GZMB) in the tumor region becomes detectable after 3 days. (See data presented). The temporal dimensions of our slice model span a few days because the tumor infiltrates a large portion of the slice within 7 days. We have already reported tumor growth times in our previous publications1,2. + +<|ref|>text<|/ref|><|det|>[[117, 656, 881, 755]]<|/det|> +3. Although important for spatial information, the immunofluorescence images shown without quantifications in figure 4 are not sufficient to validate the computational studies. For example, in figure 4g, TIM3 is used to identify "exhausted T cells", but it has been shown that TIM3 can also be a marker of terminal effector differentiation. Therefore, this would be more convincing if other parameters were used to identify this population, such as PD1 or other functional studies showing T cell activity. + +<|ref|>text<|/ref|><|det|>[[118, 779, 880, 836]]<|/det|> +We added a more sophisticated validation of the imaging results. We choose Tim3 to confirm the results from the computational studies, in which the tissue resident memory cluster revealed the strongest enrichment of exhaustion markers. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 102, 881, 202]]<|/det|> +4. When looking at the contribution of different patients to the final clusters, it is apparent that many clusters are specific to single patients. In particular, \(80\%\) of the HMOX1+ group is made up of a single patient. What impact does this have on the broader applicability of these findings? Would this bias for a single patient carry over into the downstream analyses? Is this to be expected whenever pooling human samples? + +<|ref|>text<|/ref|><|det|>[[118, 225, 787, 243]]<|/det|> +This problem was based on the vertical integration algorithm which has been fully revised. + +<|ref|>text<|/ref|><|det|>[[118, 266, 880, 305]]<|/det|> +5. The approval for the use of an un-licensed drug in a GBM patient needs to be specifically addressed within the ethics section. + +<|ref|>text<|/ref|><|det|>[[118, 328, 880, 366]]<|/det|> +The treatment was performed as part of the "Compassionate Use" program (RL 2001/83/EG VO 726/2004). We added explanations in the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 389, 880, 448]]<|/det|> +6. Minor concerns: a. The conclusion that myeloid and lymphoid interactions lead to T cell dysfunction through IL10 is vague and not unoriginal. Secretion of IL10 by myeloid cells is not a novel finding, nor is the role of IL10 in T cell dysfunction(2,3). + +<|ref|>text<|/ref|><|det|>[[118, 471, 881, 551]]<|/det|> +Indeed, this mechanism is reported in other cancer types but not for brain malignancy so far. Other cancer types can also be treated with checkpoint inhibitors, which is not possible for GBM. We think that investigating this special environment expands our comprehension. The fact that we found similar mechanism that can be also observed in other cancer types is not unexpected. + +<|ref|>text<|/ref|><|det|>[[118, 574, 880, 612]]<|/det|> +b. Using in vitro stimulated T cells to compare with in vivo T cells coming from a tumor ignores much of the complexity in signals that is occurring intratumorally. + +<|ref|>text<|/ref|><|det|>[[118, 635, 880, 673]]<|/det|> +The stimulation experiments are used to detect downstream pathway activation based on an isolated cytokine. We remove all other interpretations. + +<|ref|>text<|/ref|><|det|>[[115, 696, 877, 714]]<|/det|> +c. Using a second cell line in the in vitro neocortical studies would increase the impact of related findings. + +<|ref|>text<|/ref|><|det|>[[118, 737, 880, 775]]<|/det|> +Since this work does not focus on the tumor directly, using multiple donors to investigate the variance across patients was our main focus. + +<|ref|>text<|/ref|><|det|>[[118, 799, 881, 899]]<|/det|> +In general, authors show novel and interesting computational analyses from cutting edge techniques, however they lack substance in their follow up mechanistic studies. The use of pseudotime and RNA velocity to interrogate T cell activation states and pair them with GBM subtypes and spatial information are intriguing. Additionally, the nearest functionally connected neighbor algorithm will add to the expanding pool of resources for inferring intercellular communication from scRNAseq data. Follow- up + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 880, 140]]<|/det|> +studies are limited in their support of computational findings (IL- 10 mediated T cell exhaustion); therefore, additional validation studies are required, or the focus of the story should shift to highlight the novel bioinformatic analyses. + +<|ref|>text<|/ref|><|det|>[[117, 144, 880, 182]]<|/det|> +Thank you for the appreciation of the computational results and tools. However, we think that biological validation, even if limited, supports the computational analysis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 83, 404, 99]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 103, 882, 530]]<|/det|> +Reviewer #3 (Remarks to the Author):Ravi, Neidert, Will et al present a single- cell RNA- sequencing study of tumor- infiltrating lymphocytes of patients with GBM. The profile 8 patients and additionally show data for 3 additional patients using spatial profiling, all using 10x platforms. Using established and novel analytical tools to infer trajectories of cell differentiation, they identify variability among T cells; among other, they find sub- clusters of CD8+ T cells with high expression of dysfunction marker TIM3 (HAVCR2) and cells with a hypoxia signature with distinct trajectories. They correlate these signatures with signatures of T cells collected following in vitro stimulation with different cytokines, including IL2, IFNG and IL10, arguing that IL10 stimulated cells have a lower activation sore compared to other cells identified as effector cells. Using spatial RNA- seq of three tumors, they find an association of tumor- mesenchymal niches and infiltration of exhausted T cells (TIM3/LAG3), suggesting that niches of dysfunctional T cells may be in part explained by cancer cell intrinsic features. In order to understand the origin of IL10 and to solidify the role of T cells as IL10 recipients, they present a analytical framework that infers ligand- receptor interactions using several constraints, and demonstrate that myeloid cells (CD163+, HMOX1+) are a main source of IL10. To begin validating this finding, they use slice cultures that they deplete of myeloid cells and show that depletion of myeloid cells results in reduction of IL10 (in the presence of tumor cells); in these models, they then co- culture autologous T cells and show that depletion of myeloid cells in slice cultures results in increased IL2, but not IFNG protein abundance. Incubation of T cells with an IL10R- inhibitor prior to co- culture with tissues results in increased IL2 production in T cells. Because the JAK/STAT pathway is downstream of IL10 signaling, they use ruxolitinib (a selective JAK1/2 inhibitor) first slice model showing increased IL2, and then use this drug in the neo- adjuvant therapy of a patient with GBM, followed by analysis of the surgical specimen, which shows activation of T cells. + +<|ref|>text<|/ref|><|det|>[[118, 553, 881, 631]]<|/det|> +GBM is a disease with extremely poor prognosis, and therapeutic development has in part been hampered by limited understanding of the tumor microenvironment; as such, the study of potentially high importance. However, several aspects raised significant concerns and reduced enthusiasm for this study, and need to be addressed, + +<|ref|>text<|/ref|><|det|>[[118, 656, 880, 692]]<|/det|> +We would like to thank the reviewer for his time and comments leading to an improvement of the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 718, 216, 733]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[117, 758, 881, 855]]<|/det|> +1. Nowhere in the manuscript do the authors describe the characteristics of the patient tumors used for either single-cell sequencing of spatial sequencing. Are these all treatment naive tumors? where they exposed to different therapies (radiation, chemotherapy, immunotherapy, investigational drugs) - this will have a dramatic impact on the measured T cell phenotypes and in and of itself could describe variability seen in the data set. + +<|ref|>text<|/ref|><|det|>[[118, 860, 880, 897]]<|/det|> +All samples used for the dataset are naive non-treated primary GBM samples except the JAK-inhibitor treated samples as described in the last section on the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 881, 161]]<|/det|> +The authors should describe basic demographics and treatment history; it is not reasonable to request from the authors to attempt to account for variability based on basic demographics (this, and virtually any single- cell study would be underpowered), but they should show major analyses/findings in the context of different therapies received to exclude the possibility noted above. + +<|ref|>text<|/ref|><|det|>[[118, 185, 880, 223]]<|/det|> +Indeed, prior treatment can strongly affect the immune compartment. Here, only primary non- treated samples are included. We have added a supplementary table for demographic details. + +<|ref|>text<|/ref|><|det|>[[117, 247, 882, 427]]<|/det|> +2. Technical quality: it is somewhat surprising that the authors only recover \(\sim 1000\) unique genes per cell with only \(\sim 2300\) unique molecular identifiers - this is not on par with the quality described and raises concerns regarding data quality; this is particularly surprising as they used the 3.1 chemistry which performs better than prior chemistries; in fact recent studies performing profiling from frozen tissues even achieved similar or better quality compared to this present study (Slyper, Nature Medicine, 2020). Indeed, the sequencing depth of the samples was only moderate (Sequencing Saturation \(\sim 10\% - 15\%\) ) and we decided to re-sequence all our libraries. We gained an improvement in quality to approximately \(\sim 2400\) genes per cell and \(\sim 10k\) unique molecular identifiers. To provide an overview of the dataset quality, we have added some comparisons to recent published datasets, Supplementary Figure 2. + +<|ref|>text<|/ref|><|det|>[[117, 451, 881, 550]]<|/det|> +Furthermore, some of the clusters described might be artifactual due to tissue processing (e.g. "hypoxia cluster")- this possibility should be addressed using available data sets systematically investigating such artifacts (e.g. Ido Amit laboratory). Furthermore, the authors should comment on the technical quality. An additional embedding showing the UMI count for major analyses should be shown in the supplement to exclude the possibility of technical artifacts as drivers of clustering. + +<|ref|>text<|/ref|><|det|>[[117, 574, 881, 652]]<|/det|> +We added a scRNA- seq quality check in the supplementary results. Using a recently reported cell- type alignment algorithm (WNN3), we redesigned the first part and specifically investigated CD8 and CD4 T cells separately. As recommended, we have opted for alignment to reference datasets. The stress cluster within the T cell population has already been confirmed in the meantime in another cohort4. + +<|ref|>text<|/ref|><|det|>[[117, 676, 882, 816]]<|/det|> +3. There is no statistical evaluation of the inference made in Figure 3f - the authors should provide this; in this same figure, they also show that CCL2 myeloid cells are scoring highly, which is a gene considered to be an immunostimulatory gene/protein - how do they reconcile this? This brings up the question about a more nuanced annotation of the myeloid cells beyond monocytes, macrophages and microglia. The effect size of the gene set enrichment analysis in 3h is very underwhelming. In fact, throughout this section and the studies shown in Figure 4, the effect sizes are very small with in part borderline significance, raising the question of biological significance of these findings. + +<|ref|>text<|/ref|><|det|>[[118, 840, 881, 899]]<|/det|> +We have revised large parts of the results presented formerly in Figure 4. This was done by resequencing and improving the vertical integration, have eliminated the previously seen myeloid cell populations. As already mentioned above, the myeloid populations seem to have been an artefact of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 880, 140]]<|/det|> +insufficient vertical integration. Retrospectively, the integration used at that time by means of the cell ranger pipeline was not a sufficient approach. The MNN integration used now offers a much better approach to data integration. + +<|ref|>text<|/ref|><|det|>[[118, 164, 881, 222]]<|/det|> +4. The experiments in slice cultures should be described in more detail in the main text. Here, they state that they performed "myeloid depletion" when in fact they performed microglia depletion (as stated as header in the methods section). + +<|ref|>text<|/ref|><|det|>[[118, 226, 881, 285]]<|/det|> +We have tried to discuss the experimental part, especially the limitations, in detail. Our new data and analyses better support the reported results. The chemical depletion of microglia used here, the myeloid population in the human brain slice, has already been described in detail our previous work1,2. + +<|ref|>text<|/ref|><|det|>[[118, 308, 881, 366]]<|/det|> +The effect size of myeloid/microglia depletion on IL10 production is rather modest. One missing control is depletion of other cell types within the slice culture and measurement of the effect on IL10 to exclude the possibility that there are other major sources of IL10 production (which is likely). + +<|ref|>text<|/ref|><|det|>[[117, 370, 882, 510]]<|/det|> +Indeed, we agree that there are other sources of IL10 release in the tumor microenvironment. Neurons, astrocytes, and oligodendrocytes are potential candidates for IL10 release, but protocols for depletion of these cell types have not yet been established. To address this question, we attempted to establish cell- specific depletion for astrocytes. Unfortunately, we failed with this because the toxicity of astrocyte depletion is too high. Our results with IL10 inhibition confirm the downstream mechanism but cannot conclusively resolve the question of which cell type should also be considered as an IL10 source. At least our data suggest that a large fraction of IL10 is derived from HMOX1- positive myeloid cells. + +<|ref|>text<|/ref|><|det|>[[118, 533, 881, 591]]<|/det|> +Furthermore, it is surprising that IL2 production, but not IFNG production increases during T cell depletion - the authors should offer potential explanations as this argues against reinvigoration of T cell poly- functionality. + +<|ref|>text<|/ref|><|det|>[[117, 595, 882, 734]]<|/det|> +We agree with the reviewer that the IFNG signal is difficult to explain. When we examined the raw signal, we found generally high levels (including the negative control) of IFNG and other cytokines in the ELISA, suggesting a potential technical problem. We fully reviewed the ELISA data and re- ran the assay. The new data provided a clearer picture. Also in the new data, we see only a small baseline effect on IL10 after depletion of microglia. We assume that within our slice model the reactive transformation of microglia is necessary to upregulate IL10 release. Therefore, differences in the "no- tumor" slices were not observed. + +<|ref|>text<|/ref|><|det|>[[118, 758, 881, 816]]<|/det|> +The results shown in 4j confirm that IL10 is an immunosuppressive cytokine, but do not substantiate claims that this is mediated by myeloid cells. Again, perplexing that no change in interferon gamma is seen. + +<|ref|>text<|/ref|><|det|>[[118, 820, 880, 858]]<|/det|> +As mentioned above, we are limited within our model to elucidate all potential sources of IL10 release. Our data confirms that a significant part originates from myeloid cells. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 881, 140]]<|/det|> +The single patient study is encouraging - was this pre-/post- comparison performed after single- agent therapy with ruxolitinib or was there a combination used? If the latter, it is possible that observed effects are due to other treatment constituents (see comment 1). + +<|ref|>text<|/ref|><|det|>[[117, 144, 882, 264]]<|/det|> +We used monotherapy in a neoadjuvant setting. However, the patient was pretreated with RT+TMZ +CCNU (CeTeG protocol) and received TTF (not in parallel to ruxolitinib). Resection of the tumor was subsequently performed after 6 weeks of ruxolitinib monotherapy. For analysis, we were able to perform staining for direct pre/post- treatment. Unfortunately, single cell sequencing could not be performed from the very small biopsy sample (before therapy), but only from the surgery sample (after treatment). We added a more detailed description and illustrations in the updated manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 84, 213, 99]]<|/det|> +## Bibliography + +<|ref|>text<|/ref|><|det|>[[117, 117, 868, 214]]<|/det|> +1. Ravi, V. M. et al. Human organotypic brain slice culture: a novel framework for environmental research in neuro-oncology. Life Sci. Alliance 2, (2019). +2. Henrik Heiland, D. et al. Tumor-associated reactive astrocytes aid the evolution of immunosuppressive environment in glioblastoma. Nat. Commun. 10, 2541 (2019). +3. Hao, Y., Hao, S. & Andersen, E. Integrated analysis of multimodal single-cell data. Nissen +4. Mathewson, N. D. et al. Inhibitory CD161 receptor identified in glioma-infiltrating T cells by single-cell analysis. Cell 184, 1281–1298.e26 (2021). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 312, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 113, 402, 128]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 142, 865, 187]]<|/det|> +The authors have substantially improved the presentation of the hypotheses, analyses, and data in the revised manuscript, and have incorporated several new analyses that fill some of the gaps in the previous version. In my opinion, the revised manuscript is suited for publication. + +<|ref|>text<|/ref|><|det|>[[117, 201, 832, 216]]<|/det|> +I would only like to point some typos and small suggestions to improve the clarity of some parts: + +<|ref|>text<|/ref|><|det|>[[117, 230, 580, 394]]<|/det|> +- Line 123: "reference datasets" -> "reference dataset" +- Line 137: "Supplementary Figure 1b-c" -> "Figure 1b-c" +- Line 189: "Figure 2b" -> "Figure 2c" +- Line 223: "Figure 3d" -> "Figure 3f" +- Line 309: "Figure 5b" -> "Figure 5c" +- Line 389: "Benjamini-Hochberger" -> "Benjamini-Hochberg" + +<|ref|>text<|/ref|><|det|>[[118, 407, 875, 437]]<|/det|> +- Line 316: the notation used for the two clusters of myeloid cells (aM\Phi and bM\Phi) does not match with the notation used in Supplementary Fig. 5. + +<|ref|>text<|/ref|><|det|>[[118, 451, 872, 511]]<|/det|> +- In figure 1d,e it is unclear what the authors mean by "z-scored Gene Expression". z-scores are not bounded between 0 and 1, so I suspect the authors refer to something else or they have rescaled the z-scores in some way to lie between 0 and 1. I would suggest clarifying the normalization used in the figure legend and in the methods section. + +<|ref|>text<|/ref|><|det|>[[118, 525, 866, 540]]<|/det|> +- The specific gene sets from MSigDB v7 that were used should be specified in the methods section. + +<|ref|>text<|/ref|><|det|>[[118, 555, 875, 599]]<|/det|> +- I find the notation used in Fig. 5c and other figures (circle color + size) to be confusing. For example, in Fig. 5c the Mes-like correlation of #URK_S3 seems larger than the Mes-like correlation of #UKF_S2 based on the color of the circle, but smaller or equal based on the size of the circle. + +<|ref|>text<|/ref|><|det|>[[118, 614, 866, 644]]<|/det|> +- It would be helpful to add more details in the legend of Fig. 5b. For example, what does each of the colors in the figure denotes? + +<|ref|>text<|/ref|><|det|>[[120, 673, 402, 687]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 702, 868, 850]]<|/det|> +In their revised manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators coupled scRNAseq and stRNAseq to query the tumor microenvironment of 8 treatment naive glioblastoma patients. Ligand/receptor interactions were identified using a novel algorithm, nearest functionally connected neighbors (NFCN), ultimately identifying HMOX1+ myeloid cells as a major source of IL- 10. A T cell exhaustion phenotype was linked to the HMOX1+ myeloid cells and validated with both stRNAseq and an ex vivo neocortical system. In this revision, authors addressed concerns regarding the limitations of ex vivo experiments in validation of in silico findings. Additionally, authors increased the detail in many of the results sections to clarify relevant findings. These revisions greatly improve the quality and impact of the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 98, 402, 113]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 127, 855, 158]]<|/det|> +The authors have done a very good job revising the manuscript and addressing my comments and suggestions. + +<|ref|>text<|/ref|><|det|>[[118, 171, 867, 202]]<|/det|> +I would strongly encourage them to highlight some of the technical and experimental challenges they had in their revision, as this might be of importance for future studies by their and other groups. + +<|ref|>text<|/ref|><|det|>[[118, 216, 223, 231]]<|/det|> +Benjamin Izar + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 85, 580, 112]]<|/det|> +## Point - by - Point Revision 2 + +<|ref|>text<|/ref|><|det|>[[119, 124, 222, 139]]<|/det|> +D. H. Heiland + +<|ref|>text<|/ref|><|det|>[[118, 165, 880, 202]]<|/det|> +We thank all reviewers for their time and effort in evaluating our manuscript and appreciate the positive feedback on our project. + +<|ref|>text<|/ref|><|det|>[[119, 226, 402, 242]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 266, 881, 325]]<|/det|> +The authors have substantially improved the presentation of the hypotheses, analyses, and data in the revised manuscript, and have incorporated several new analyses that fill some of the gaps in the previous version. In my opinion, the revised manuscript is suited for publication. + +<|ref|>text<|/ref|><|det|>[[118, 348, 832, 366]]<|/det|> +I would only like to point some typos and small suggestions to improve the clarity of some parts: + +<|ref|>text<|/ref|><|det|>[[118, 388, 525, 405]]<|/det|> +- Line 123: "reference datasets" -> "reference dataset" + +<|ref|>text<|/ref|><|det|>[[118, 410, 191, 425]]<|/det|> +Changed + +<|ref|>text<|/ref|><|det|>[[118, 430, 540, 446]]<|/det|> +- Line 137: "Supplementary Figure 1b-c" -> "Figure 1b-c" + +<|ref|>text<|/ref|><|det|>[[118, 452, 191, 466]]<|/det|> +Changed + +<|ref|>text<|/ref|><|det|>[[118, 471, 392, 487]]<|/det|> +- Line 189: "Figure 2b" -> "Figure 2c" + +<|ref|>text<|/ref|><|det|>[[118, 492, 191, 507]]<|/det|> +Changed + +<|ref|>text<|/ref|><|det|>[[118, 512, 390, 528]]<|/det|> +- Line 223: "Figure 3d" -> "Figure 3f" + +<|ref|>text<|/ref|><|det|>[[118, 533, 191, 548]]<|/det|> +Changed + +<|ref|>text<|/ref|><|det|>[[118, 553, 392, 568]]<|/det|> +- Line 309: "Figure 5b" -> "Figure 5c" + +<|ref|>text<|/ref|><|det|>[[118, 574, 191, 589]]<|/det|> +Changed + +<|ref|>text<|/ref|><|det|>[[118, 593, 576, 610]]<|/det|> +- Line 389: "Benjamini- Hochberger" -> "Benjamini-Hochberg" + +<|ref|>text<|/ref|><|det|>[[118, 615, 191, 630]]<|/det|> +Changed + +<|ref|>text<|/ref|><|det|>[[118, 635, 880, 672]]<|/det|> +- Line 316: the notation used for the two clusters of myeloid cells (aM\Phi and bM\Phi) does not match with the notation used in Supplementary Fig. 5. + +<|ref|>text<|/ref|><|det|>[[118, 676, 412, 692]]<|/det|> +Changed in the new supplementary file + +<|ref|>text<|/ref|><|det|>[[117, 696, 881, 775]]<|/det|> +- In figure 1d,e it is unclear what the authors mean by "z-scored Gene Expression". z-scores are not bounded between 0 and 1, so I suspect the authors refer to something else or they have rescaled the z-scores in some way to lie between 0 and 1. I would suggest clarifying the normalization used in the figure legend and in the methods section. + +<|ref|>text<|/ref|><|det|>[[118, 779, 624, 796]]<|/det|> +It is normalized gene expression, we changed the figure description + +<|ref|>text<|/ref|><|det|>[[118, 799, 866, 816]]<|/det|> +- The specific gene sets from MSigDB v7 that were used should be specified in the methods section. + +<|ref|>text<|/ref|><|det|>[[118, 821, 500, 836]]<|/det|> +The gene sets are implemented in the method part. + +<|ref|>text<|/ref|><|det|>[[117, 840, 881, 898]]<|/det|> +- I find the notation used in Fig. 5c and other figures (circle color + size) to be confusing. For example, in Fig. 5c the Mes-like correlation of #URK_S3 seems larger than the Mes-like correlation of #UKF_S2 based on the color of the circle, but smaller or equal based on the size of the circle. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 694, 98]]<|/det|> +It was based on the fact that plots were created individually, we changed this. + +<|ref|>text<|/ref|><|det|>[[117, 103, 880, 140]]<|/det|> +- It would be helpful to add more details in the legend of Fig. 5b. For example, what does each of the colors in the figure denotes? + +<|ref|>text<|/ref|><|det|>[[118, 145, 394, 160]]<|/det|> +We added a description in the figure. + +<|ref|>text<|/ref|><|det|>[[118, 186, 404, 201]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 225, 882, 427]]<|/det|> +In their revised manuscript titled "Crosstalk between lymphoid and myeloid cells orchestrates glioblastoma immunity through Interleukin 10 signaling", investigators coupled scRNAseq and stRNAseq to query the tumor microenvironment of 8 treatment naive glioblastoma patients. Ligand/receptor interactions were identified using a novel algorithm, nearest functionally connected neighbors (NFCN), ultimately identifying HMOX1+ myeloid cells as a major source of IL- 10. A T cell exhaustion phenotype was linked to the HMOX1+ myeloid cells and validated with both stRNAseq and an ex vivo neocortical system. In this revision, authors addressed concerns regarding the limitations of ex vivo experiments in validation of in silico findings. Additionally, authors increased the detail in many of the results sections to clarify relevant findings. These revisions greatly improve the quality and impact of the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 472, 404, 488]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 512, 881, 591]]<|/det|> +The authors have done a very good job revising the manuscript and addressing my comments and suggestions. I would strongly encourage them to highlight some of the technical and experimental challenges they had in their revision, as this might be of importance for future studies by their and other groups. + +<|ref|>text<|/ref|><|det|>[[117, 615, 881, 714]]<|/det|> +R2 & R3: Thank you for the positive response. We are pleased that the reviewers appreciated the considerable effort and the change during the revision process. In our opinion, a description of these changes in the discussion clearly hampers the red- thread and takes the focus away from the scientific results. In our opinion, the detailed process can be reconstructed very well from published reviewers' comments, so we have refrained from making a statement in the discussion part. + +<--- Page Split ---> diff --git a/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f9f920f537d386005063c854d73dde481269e808 --- /dev/null +++ b/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,56 @@ + +# nature portfolio + +Peer Review File + +# Mechanistic evaluation of enhanced graphene toxicity to Bacillus induced by humic acid adsorption + +Corresponding Author: Professor Qing Zhao + +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Communications. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The authors have made proper revisions. + +Reviewer #2 + +(Remarks to the Author) + +The manuscript by Zhao et al. describes a comprehensive investigation of the effect of the humic acid corona on the toxicity of graphene nanosheets (GNSs) to Bacillus tropicus. I previously reviewed this manuscript and my initial impressions were that the study was thorough and the results were interesting and had potential for high impact. Following several rounds of revision, I believe the authors have addressed the major and minor concerns raised by the reviewers and significantly improved the clarity of the manuscript. I have no further suggestions for revision and believe the manuscript is now publishable in its present form. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +We are delighted with the generally positive feedback regarding the manuscript. Please find below a list of our detailed responses to all comments. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have made proper revisions. + +Thank you for providing us so many insightful comments and suggestions, which have significantly enhanced the quality of our manuscript. + +Reviewer #2 (Remarks to the Author): + +The manuscript by Zhao et al. describes a comprehensive investigation of the effect of the humic acid corona on the toxicity of graphene nanosheets (GNSs) to Bacillus tropicus. I previously reviewed this manuscript and my initial impressions were that the study was thorough and the results were interesting and had potential for high impact. Following several rounds of revision, I believe the authors have addressed the major and minor concerns raised by the reviewers and significantly improved the clarity of the manuscript. I have no further suggestions for revision and believe the manuscript is now publishable in its present form. + +Thank you for the positive feedback. Your expert insights and suggestions are immensely valuable in enhancing the quality of the manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..99a33895f039e3a1b6a413a580e2f8a13693214e --- /dev/null +++ b/peer_reviews/126ed42b3fd6d9a339d2cd64a17c61348e2a1fa4df128380a49ace31df8377ca/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,78 @@ +<|ref|>title<|/ref|><|det|>[[73, 50, 295, 79]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[74, 160, 855, 211]]<|/det|> +# Mechanistic evaluation of enhanced graphene toxicity to Bacillus induced by humic acid adsorption + +<|ref|>text<|/ref|><|det|>[[74, 224, 455, 241]]<|/det|> +Corresponding Author: Professor Qing Zhao + +<|ref|>text<|/ref|><|det|>[[73, 275, 874, 302]]<|/det|> +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[70, 313, 866, 329]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 366, 145, 379]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 392, 219, 405]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 418, 160, 431]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 444, 355, 471]]<|/det|> +(Remarks to the Author) The authors have made proper revisions. + +<|ref|>text<|/ref|><|det|>[[73, 483, 162, 496]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 509, 238, 522]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 521, 914, 602]]<|/det|> +The manuscript by Zhao et al. describes a comprehensive investigation of the effect of the humic acid corona on the toxicity of graphene nanosheets (GNSs) to Bacillus tropicus. I previously reviewed this manuscript and my initial impressions were that the study was thorough and the results were interesting and had potential for high impact. Following several rounds of revision, I believe the authors have addressed the major and minor concerns raised by the reviewers and significantly improved the clarity of the manuscript. I have no further suggestions for revision and believe the manuscript is now publishable in its present form. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 848, 135]]<|/det|> +We are delighted with the generally positive feedback regarding the manuscript. Please find below a list of our detailed responses to all comments. + +<|ref|>sub_title<|/ref|><|det|>[[149, 247, 390, 265]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 303, 460, 320]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 358, 479, 375]]<|/det|> +The authors have made proper revisions. + +<|ref|>text<|/ref|><|det|>[[148, 386, 850, 432]]<|/det|> +Thank you for providing us so many insightful comments and suggestions, which have significantly enhanced the quality of our manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 469, 460, 486]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 523, 852, 738]]<|/det|> +The manuscript by Zhao et al. describes a comprehensive investigation of the effect of the humic acid corona on the toxicity of graphene nanosheets (GNSs) to Bacillus tropicus. I previously reviewed this manuscript and my initial impressions were that the study was thorough and the results were interesting and had potential for high impact. Following several rounds of revision, I believe the authors have addressed the major and minor concerns raised by the reviewers and significantly improved the clarity of the manuscript. I have no further suggestions for revision and believe the manuscript is now publishable in its present form. + +<|ref|>text<|/ref|><|det|>[[148, 756, 850, 802]]<|/det|> +Thank you for the positive feedback. Your expert insights and suggestions are immensely valuable in enhancing the quality of the manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/images_list.json b/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..45dfc98430383a6eae851a64efa08086fe4ff7ab --- /dev/null +++ b/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Dynamic compression of liquid water at a compression rate (10 GPa/ms). The sample pressure over time is measured using simultaneously the \\(S\\vert \\mathrm{text}(SrB)_2[4]\\vert \\mathrm{text}(O)_2[7]\\vert \\mathrm{text}(Sm)^\\wedge (2 + )S\\) and the ruby fluorescence", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Dynamic compression of liquid water at a compression rate (10 GPa/ms). The sample pressure over time is measured using simultaneously the S(Text(Si6)_[4]/text(O)_[7]/text(Sm)^(2+)/S and the ruby fluorescence", + "footnote": [], + "bbox": [ + [ + 100, + 90, + 410, + 280 + ] + ], + "page_idx": 14 + } +] \ No newline at end of file diff --git a/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..974e623a3ff17460700a4d294903ccc34a445f2d --- /dev/null +++ b/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,459 @@ + +# nature portfolio + +Peer Review File + +Metastable water at several compression rates and its freezing kinetics into ice VII + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial note: Parts of this Peer Review File have been redacted as indicated to remove third- party material where no permission to publish could be obtained. + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +This work shows in situ, time resolved x- ray diffraction data on the H2O system subjected to a wide range of compression rates. The diffraction data show real- time structural response of the system and allow unambiguous identification of solid phases of ice. I think the presented data provide interesting and important insight into the freezing dynamics and help to resolve discrepancies from other measurements. + +I had several thoughts on how the manuscript could be made clearer but, beyond these, would like to recommend publication. + +1. Page 2 introduction: "having the simplest ice structure with..." I think the work "simplest" is subjective. Since the structure of ice VII is highly disordered, one could say an ordered phase, such as ice VIII is structurally simpler. More appropriate would be a specific statement like "simplest crystallographic unit cell". + +2. Page 2 introduction: "is a topic of current focus" when stating this, I think citations should be provided. + +3. Page 5 instrumentation: It is mentioned that the pressure is measured via multiple approaches. Hence, how does the reader know which is refered to when pressures are quoted throughout the manuscript. E.g. what is shown in Figure 1? + +4. Page 5 pressure response of...compression ramps": "the convolution with" I'm not sure this effect is a convolution in the mathematical sense. + +5. Page 5 pressure response of...compression ramps": "1.56 GPa" No quantified uncertainty is given for this number and, on the basis of Figure 2 where error bar are shown to be ±0.05 this number is stated too precisely. Assuming the error bars indicate the magnitude of a standard deviation, quoting the pressure to one decimal place is sufficient. + +6. Page 8 Freezing pressure of...compression rate: "0.056, which matches...0.069" Use of the + +<--- Page Split ---> + +word 'matches' requires some information on experimental uncertainty, which is not provided. + +7. Page 8 Freezing pressure of..compression rate: "When metastable water freeze under a compression rate of 110 GPa/ms, it corresponds to a cooling rate of \(10^{\wedge}7 \text{K / s}\) ". I have no idea how this equivalence was derived, can the authors explain their argument? + +8. Figure 2: I was confused by the meaning of the coloured horizontal bands indicating phase regions. Are these taken from other work? Or if they are they guides to the eye to indicate behaviour observed in this study, I found it confusing that they are horizontal and not vertical as each phase is only present for bounded periods of time. + +9. Figure 4: How can pressure be inferred from this plot? Is it possible to show in some way? 10. Figure 4: Out of curiosity, is some interpolation or smoothing applied to the 2d 2theta vs time data? + +11. Figure 4: "A mixture of ice VI and ice VII is still observed" I wondered if it is possible by Rietveld analysis (likely with a highly constrained model) to determine the phase fraction of VI and VII? From the 2d image, it indeed looks like the intensity of the ice VII 110 decreases as the ice VI forms. If it could be quantitatively shown that this change is due to direct transformation of the volume of ice VII in the x-ray beam, that would strengthen the interpretation given. + +## Reviewer #2 (Remarks to the Author): + +This manuscript describes the effects of rapid compression of liquid water to its crystalline phases using dynamic- piezo- Diamond- Anvil- Cell. The main goal of this study was to provide experimental details and perhaps a physical understanding the structural changes of water undergoing rapid temperature and/or pressure variation. + +Although there have been many studies of phase transitions in both water and ice, this study focused on one particular phase transition where there have been different previously reported results and interpretations. This is a transition between metastable liquid water and particular dense crystalline phases. The authors of this study employed additional an experimental technique of time- resolved X- ray diffraction with a dynamic- piezo- Diamond- Anvil- Cell. The employment of this technique provided sufficient new data to resolve the + +<--- Page Split ---> + +contradictions that are in the literature. + +This is a very well written manuscript and I therefore have only a small list of comments that should be addressed in more detail.1) On page 3 the authors indicate that they are investigating whether ice VII is still the freezing state of metastable water?? Under what, P conditions are they referring to?2) On page 5 the authors give a value of 1.56 GPa? How accurate is this number? T, P effects?3) On page 6: It was stated and suggested that crystallization occurs into ice VII, although without time-resolved XRD measurements this proposition remains to be proven. Ref?4) Pg. 6: excellent agreement between the different pressure determinations. Can the authors be clearer on this point? Perhaps by simply referring to the figures.5) On Pg. 7, it is stated that there was a e previous domain of investigation in d- DAC experiments. A reference. is needed here.6) without time-resolved XRD measurements this proposition remains to be proven. A reference should be made here.7) On page. 9 the authors state "Since water and ice are quite incompressible" Here a comparison with other triatomic molecules would strengthen this statement.8) It is important to emphasize that the model employed to fit the data is a classical nucleation theory description of the experimental results. It fits the data very well and provides a very good physical picture and interpretation of the experimental results but this depends on parameters used for fitting the data so small changes in the parameters employed could have a significant effect on the model used. This could be mentioned by the authors. + +This report follows up on the previous domain of investigation in d- DAC experiments focusing on the solidification of metastable water. This is the key goal reached in this study. The authors clearly state that support the hypothesis that metastable water, within the pressure range of 1.5 GPa to 2.1 GPa, nucleates into ice VII first, despite this range being the stability field of ice VI. results offer a clarification to the apparent contradiction of the + +<--- Page Split ---> + +previous findings. + +previous findings.In summary, this manuscript clearly addresses and presents a solution to the phase transition discrepancies in the literature. A key improvement in the measurement technique was time- resolved X- ray diffraction. This technique is very well described in the manuscript All figures were clearly presented and definitely provided added clarity to the report. Acceptance is therefore suggested after the minor comments listed above are addressed. + +## Reviewer #3 (Remarks to the Author): + +The authors investigated the interesting behaviour of water ice under dynamic compression with various compression rates using d- DAC by time- resolved x- ray diffraction method and found that ice VII crystallise under the conditions where ice VI should be stable. They also interpret the excess pressure and growth time during the crystallization of ice VII using a phenomenological model based on the classical nucleation theory, succeeding in a comprehensive explanation for the growth rate of ice VII grown under various compression rates. The investigated technique, x- ray diffraction with ruby fluorescence observations at micro- to milli- second order, is somehow remarkable, and the overall achievements of this study would be worth recognising for the ice community. Thus, I do not doubt that this manuscript should be eventually published in at least some specific journal, but I am not sure whether this manuscript will be published by Nature Communication. + +Two key points in assessing the value of this study would be 1) how new the observed results are and 2) how much their interpretation will influence other related studies. First, concerning the observed results, it should be stated that no truly new phenomena have been reported in this study. It has long been known among ice researchers that ice VII nucleates in the stable region of ice VI even under static compression (e.g. K. Yamamoto, Jpn J Appl Phys, 19, 1841, 1980, doi: 10.1143/JJAP.19.1841). A recent study using d- DAC has also reported ice VII nucleation in the stability region of ice VI [18]. Therefore, what is new in this manuscript are the results of quantitative experiments on how the growth rate of ice VII changes when the compression rate is varied. The experimental results in this study are novel in the sense that they are quantitative, but the observed phenomena themselves are not particularly novel. The manuscript also does not elaborate on how the quantitative growth rates obtained might affect other related studies. It is therefore difficult to assess, at + +<--- Page Split ---> + +least at the moment, how important these results are. + +Even if the importance of this manuscript is recognised by other reviewers and considered for publication in Nat. Commun., the following concerns remain and should be fully considered before potential publication. + +- The authors assume that the sample temperature should not be increased by the rapid compression, but it should be more carefully evaluated and explained in the manuscript. I also believe that temperature might be quickly stable at room temperature owing to the high thermal conductivity of the diamond. However, if the sample size is enough large, this might not be the case since the thermal conductivity of ice VII would not be such high, so the temperature could temporally increase in a very short time. This issue should be quantitatively assessed, for example, by FEM simulation. + +- In the adopted phenomenological model for the nucleation rate, authors ignore the effect of crystal growth, but only take the nucleation rate into account. However, I recognized that the grown ice VII may be somehow coarse crystalline size because the observed diffraction patterns are not like smooth lines but spotty. In particular, I found 111 spots of ice VII, which should be very very weak (generally invisible) if the specimen is fine powder, showing the specimen should be somehow coarse aggregates of many single crystals. The actual rate of ice VII growth may be expressed as the combination of nucleation and growth rates. In fact, the results obtained in this study could be interpreted by different phenomenological models, such as the simple JMAK model. The point would be 'which model is the best' to describe the observed phenomena. Even if one model fits well, this does not necessarily mean that this is the only correct model. + +Plus, I am also concerned about the lack of temperature terms in the adopted model. I suppose the temperature term should appear since the classical nucleation theory generally has it. Authors should discuss this point (why temperature term could be ignored), if they stick to this model only. + +- Previous studies using d-DAC reported that ice VI and HDA coexist [19,20] as mentioned in the manuscript, but HDA was not observed in this study. The authors should describe the difference from the previous study. + +<--- Page Split ---> + +## Minor points + +1. The precise wavelength should be described in Method section. I found the x-ray energy is 19 keV, but the number of significant figures is only two in this case. +2. The reflection indices should not be in parenthesis. Index in parenthesis, (hkl) means Miller index that is used for corresponding Miller plane in real space. But reflection index, hkl, in reciprocal space should not have any parenthesis (see International Tables for crystallography, for this criterion). +3. Effective digit and/or the error should be considered throughout the whole manuscript, in particular, in Table I + +<--- Page Split ---> + +## Detailed answer to reviewers' comments. + +## Reviewer #1 + +This work shows in situ, time resolved \(x\) - ray diffraction data on the H2O system subjected to a wide range of compression rates. The diffraction data show real- time structural response of the system and allow unambiguous identification of solid phases of ice. I think the presented data provide interesting and important insight into the freezing dynamics and help to resolve discrepancies from other measurements. + +I had several thoughts on how the manuscript could be made clearer but, beyond these, would like to recommend publication. + +1. Page 2 introduction: "having the simplest ice structure with..." I think the work "simplest" is subjective. Since the structure of ice VII is highly disordered, one could say an ordered phase, such as ice VIII is structurally simpler. More appropriate would be a specific statement like "simplest crystallographic unit cell". + +The sentence was modified accordingly. + +2. Page 2 introduction: "is a topic of current focus" when stating this, I think citations should be provided. + +We have added citations. + +3. Page 5 instrumentation: It is mentioned that the pressure is measured via multiple approaches. Hence, how does the reader know which is referred to when pressures are quoted throughout the manuscript. E.g. what is shown in Figure 1? + +As mentioned in the manuscript, the imaging and X- ray diffraction (XRD) processes could not be conducted simultaneously. The pressure was measured using luminescence during imaging and by determining the volume of copper during XRD. + +An essential aspect to highlight, as illustrated in Figure 3, is the high degree of repeatability and reproducibility of the compression ramps using the different diagnostic techniques. To enhance clarity, we have included the following sentence: + +"The pressure was determined using a luminescence gauge during imaging and by utilizing XRD equation- of- state (EOS) data during XRD. The results from the different pressure measurement methods were found to be highly consistent with each other." + +4. Page 5 pressure response of...compression ramps": "the convolution with" I'm not sure this effect is a convolution in the mathematical sense. + +The sentence now reads: "However, if a phase transition occurs, the pressure rise is disrupted by the pressure drop associated to the negative volume discontinuity at the transition, resulting in an apparent negative compressibility." + +<--- Page Split ---> + +5. Page 5 pressure response of...compression ramps": "1.56 GPa" No quantified uncertainty is given for this number and, on the basis of Figure 2 where error bar are shown to be \(\pm 0.05\) this number is stated too precisely. Assuming the error bars indicate the magnitude of a standard deviation, quoting the pressure to one decimal place is sufficient. + +The pressure was modified to 1.6 GPa to take into account the \(\pm 0.05\) GPa uncertainty. + +6. Page 8 Freezing pressure of...compression rate: "0.056, which matches...0.069" Use of the word 'matches' requires some information on experimental uncertainty, which is not provided. + +The sentence now reads: "Remarkably, the exponent 'c' obtained from the fit is 0.056, which closely aligns with the value of 0.069 predicted by Myint's scaling law." + +7. Page 8 Freezing pressure of compression rate: "When metastable water freeze under a compression rate of 110 GPa/ms, it corresponds to a cooling rate of \(10^{7} \mathrm{~K} / \mathrm{s}\) ". I have no idea how this equivalence was derived, can the authors explain their argument. + +At a compression rate of 110 GPa/ms at 300 K, the freezing process occurs at 2.9 GPa after an over-compression duration of 18 us in the metastable water state. To achieve the same state through a 18 us cooling at 2.9 GPa from the liquid state, considering the melting point of water at 2.9 GPa is 423 K (Datchi et al., PRB 61, 6535 (2000)), the required cooling rate would have to be \(7 \times 10^{6} \mathrm{~K} / \mathrm{s}\) , approximately \(10^{7} \mathrm{~K} / \mathrm{s}\) . This calculation has been included in the supplementary material. + +8. Figure 2: I was confused by the meaning of the coloured horizontal bands indicating phase regions. Are these taken from other work? Or if they are they guides to the eye to indicate behaviour observed in this study, I found it confusing that they are horizontal and not vertical as each phase is only present for bounded periods of time. + +The colored regions in the figure represent the (meta)stability pressure domains at 300 K for the various phases. These domains are inferred from the static phase diagram and the newly measured metastable melting of liquid- ice VII in this study. They are included as a visual aid to guide the interpretation of the data. + +9. Figure 4: How can pressure be inferred from this plot? Is it possible to show in some way? + +Pressure is inferred from the measured volumes of Sn, ice VII and ice VI. A reference to the Sn EoS has been added and a clarification has been added in the text which now reads: "Here, the ice sample remaining as a mixture of ice VI and ice VII is observed at 1.8 GPa, as inferred from the measured volumes of Sn, ice VII and VI". + +10. Figure 4: Out of curiosity, is some interpolation or smoothing applied to the 2d 2theta vs time data? + +<--- Page Split ---> + +A gourdash shading is indeed applied to the data. + +11. Figure 4: "A mixture of ice VI and ice VII is still observed" I wondered if it is possible by Rietveld analysis (likely with a highly constrained model) to determine the phase fraction of VI and VII? From the 2d image, it indeed looks like the intensity of the ice VII 110 decreases as the ice VI forms. If it could be quantitatively shown that this change is due to direct transformation of the volume of ice VII in the x-ray beam, that would strengthen the interpretation given. + +Although the presence of a mixture of ice VI and ice VII is undeniable, conducting a Rietveld analysis to determine the exact phase fractions of ice VI and ice VII appears impracticable here. This is mainly due to the fact that ice VI and ice VII exhibit different textures and the detector angle-coverage is only partial. + +## Reviewer #2 + +This manuscript describes the effects of rapid compression of liquid water to its crystalline phases using dynamic- piezo- Diamond- Anvil- Cell. The main goal of this study was to provide experimental details and perhaps a physical understanding the structural changes of water undergoing rapid temperature and/or pressure variation. + +Although there have been many studies of phase transitions in both water and ice, this study focused on one particular phase transition where there have been different previously reported results and interpretations. This is a transition between metastable liquid water and particular dense crystalline phases. The authors of this study employed additional an experimental technique of time- resolved X- ray diffraction with a dynamic- piezo- Diamond- Anvil- Cell. The employment of this technique provided sufficient new data to resolve the contradictions that are in the literature. + +This is a very well written manuscript and I therefore have only a small list of comments that should be addressed in more detail. + +1) On page 3 the authors indicate that they are investigating whether ice VII is still the freezing state of metastable water?? Under what, P conditions are they referring to? + +The previous speculations about the transformation of water into ice VII during shock compression experiments have been uncertain due to the lack of X- ray diffraction diagnostic. In this study, we aim to clarify this phenomenon by investigating the crystallization of metastable water under high compression rates within the stability field of ice VII. Specifically, we seek to determine whether the freezing state of metastable water under these conditions is indeed ice VII or another metastable structure. The text has been slightly modified to make it clearer: 'In particular, we are investigating whether the freezing state of metastable water at high compression rates above 2 GPa is indeed ice VII or a metastable structure....' + +<--- Page Split ---> + +2) On page 5 the authors give a value of1.56 GPa? How accurate is this number? T, P effects? + +Referee #1 has also brought up a similar point. To address this, we have adjusted the pressure to 1.6 GPa, which accounts for the uncertainty of \(\pm 0.05\) GPa. + +3) On page 6: It was stated and suggested that crystallization occurs into ice VII, although without time-resolved XRD measurements this proposition remains to be proven. Ref? + +The relevant references (14- 17) have already been cited a few lines earlier. To avoid redundancy and maintain the flow of the text, we have chosen not to repeat them in this instance. + +4) Pg. 6: excellent agreement between the different pressure determinations. Can the authors be clearer on this point? Perhaps by simply referring to the figures. + +A reference to Figure 3 was added accordingly, showing that the pressure determination from the different gauges (Cu, Ice VII and SrB4O7 : Sm2+) are consistent with each other. + +5) On Pg. 7, it is stated that there was a e previous domain of investigation in d-DAC experiments. A reference. is needed here. + +The corresponding references (18- 20) have been added. + +6) without time-resolved XRD measurements this proposition remains to be proven. A reference should be made here. + +This point has been answered in point #3. + +7) On page. 9 the authors state "Since water and ice are quite incompressible" Here a comparison with other triatomic molecules would strengthen this statement. + +The bulk modulus of water ice is approximately 20 GPa, which is relatively high compared to other molecular systems, such as NH3 (4.2 GPa). However, the focus of this analysis is not on the incompressibility of the system, but rather on the assumption of constant compressibility. By using a first- order Birch equation of state (EoS), assuming constant compressibility, which is a reasonable approximation over the 10 GPa pressure range considered, we can derive a phenomenological model fit function with three free parameters (Equation 4). This function provides a good fit for the data obtained from diamond anvil cell (d- DAC), laser, and gas gun experiments, as shown in Figure 6. + +We have removed the assertion: ' since water and ice are incompressible'. + +<--- Page Split ---> + +8) It is important to emphasize that the model employed to fit the data is a classical nucleation theory description of the experimental results. It fits the data very well and provides a very good physical picture and interpretation of the experimental results but this depends on parameters used for fitting the data so small changes in the parameters employed could have a significant effect on the model used. This could be mentioned by the authors. + +We have explicitly stated in the text that the phenomenological model used serves as a fitting function. To further clarify this, we have slightly modified the caption of Figure 6 to read: 'Fitted using the CNT- based phenomenological model given in Equation 4, with the three free parameters equal to ... + +This report follows up on the previous domain of investigation in d- DAC experiments focusing on the solidification of metastable water. This is the key goal reached in this study. The authors clearly state that support the hypothesis that metastable water, within the pressure range of 1.5 GPa to 2.1 GPa, nucleates into ice VII first, despite this range being the stability field of ice VI. results offer a clarification to the apparent contradiction of the previous findings. + +In summary, this manuscript clearly addresses and presents a solution to the phase transition discrepancies in the literature. A key improvement in the measurement technique was time- resolved X- ray diffraction. This technique is very well described in the manuscript All figures were clearly presented and definitely provided added clarity to the report. Acceptance is therefore suggested after the minor comments listed above are addressed. + +## Reviewer #3 + +The authors investigated the interesting behaviour of water ice under dynamic compression with various compression rates using d- DAC by time- resolved x- ray diffraction method and found that ice VII crystallise under the conditions where ice VI should be stable. They also interpret the excess pressure and growth time during the crystallization of ice VII using a phenomenological model based on the classical nucleation theory, succeeding in a comprehensive explanation for the growth rate of ice VII grown under various compression rates. The investigated technique, x- ray diffraction with ruby fluorescence observations at micro- to milli- second order, is somehow remarkable, and the overall achievements of this study would be worth recognising for the ice community. Thus, I do not doubt that this manuscript should be eventually published in at least some specific journal, but I am not sure whether this manuscript will be published by Nature Communication. Two key points in assessing the value of this study would be 1) how new the observed results are and 2) how much their interpretation will influence other related studies. First, concerning the observed results, it should be stated that no truly new phenomena have been reported in this study. It has long been known among ice researchers that ice VII nucleates in the stable region of ice VI even under static compression (e.g. K. Yamamoto, Jpn J Appl Phys, + +<--- Page Split ---> + +19, 1841, 1980, doi: 10.1143/JJAP.19.1841). A recent study using d- DAC has also reported ice VII nucleation in the stability region of ice VI [18]. Therefore, what is new in this manuscript are the results of quantitative experiments on how the growth rate of ice VII changes when the compression rate is varied. The experimental results in this study are novel in the sense that they are quantitative, but the observed phenomena themselves are not particularly novel. The manuscript also does not elaborate on how the quantitative growth rates obtained might affect other related studies. It is therefore difficult to assess, at least at the moment, how important these results are. + +It is true that the nucleation of ice VII in the stability field of ice VI and the increase in the pressure of overcompressed metastable water with the compression rate were previously known phenomena. But being able to provide an explanation of phenomena through quantitative measurement is the ultimate goal of the physical science research. + +As acknowledged by reviewer #3, the possibility to control the compression rate over 4 orders of magnitude and to perform time resolved XRD and imaging with the appropriate time- frame from microsecond to millisecond is a significant accomplishment. The quantitative measurements obtained through this approach have enabled us to clarify and unify all previous measurements of the freezing of overcompressed water in a coherent interpretation. Metastable water overcompression under dynamical compression has been the subject of many studies over the past 20 years, many published in high impact journals, as a textbook case of phase transition occurring under far- from- equilibrium conditions. In the present case of water solidification at extreme overcompression, we were able to test a universal scaling law, recently proposed. The Classical Nucleation Theory was shown to unify all previous measurements which lacked the microscopic XRD information. + +Regarding the solidification of ice VII in the stability domain of ice VI, we thank reviewer#3 for providing this Jp. J. Appl. Phys. reference. However, in it, the reported observation of ice VII in the stability field of ice VI is not exactly what is reported in our study. The nucleation of ice VII was obtained at the metastable extension of the melting line of ice VII in the stability field of ice VI by heating the sample so that the overcompression of water that can be obtained under quasi- static compression could reach the metastable melting line of ice VII. Nucleation of ice VII is stated then to occasionally form and a facetted single crystal of ice VII can bestabilized in equilibrium with the liquid. However, ice VII is kept metastable only if facetted in equilibrium with the liquid. That is exactly what we observed and used in the experiment reported in our supplementary material to precisely extend the ice VII melting line in the stability domain of ice VI. We now have cited the reference in our supplementary information. However, out of this liquid- solid phase equilibrium, by slightly increasing pressure ice VII transforms into ice VI. We are reported a different story here. Under dynamical compression, metastable water always freeze into ice VII in the metastability domain of ice VII and then ice VII transforms to ice VI over a ms time scale and a mixture ice VI - ice VII then exists, which should eventually evolve to an amorphous - ice VI mixture. This resolves all previous contradictions of the literature between reports of amorphous HAD, HAD- ice VI mixture or ice VII. + +<--- Page Split ---> + +Even if the importance of this manuscript is recognised by other reviewers and considered for publication in Nat. Commun., the following concerns remain and should be fully considered before potential publication. + +- The authors assume that the sample temperature should not be increased by the rapid compression, but it should be more carefully evaluated and explained in the manuscript. I also believe that temperature might be quickly stable at room temperature owing to the high thermal conductivity of the diamond. However, if the sample size is enough large, this might not be the case since the thermal conductivity of ice VII would not be such high, so the temperature could temporally increase in a very short time. This issue should be quantitatively assessed, for example, by FEM simulation. + +The temperature increase in the sample could be an issue. A recent d- DAC measurement leveraged this effect to measure the Gruneisen parameter but for doing that they had to put a layer of zirconia powder on the anvil tip to prevent heat loss from the diamond (ref. 25). We have taken steps to quantify the heating associated to rapid compression by using two pressure luminescence gauges, specifically ruby and SrB40.7:Sm2+, positioned inside the sample chamber, as detailed in ref. 29. The luminescence line of ruby depends on pressure and temperature, whereas that of Samarium depends only on pressure. This method has been previously used to accurately measure melting lines (Datchi et al, PRB 61, 6535). We thus could show that the heating of the sample is negligible. That is illustrated in the figure below showing that, no discernible heating was detected within the measurement's sensitivity, approximately \(\pm 3 \mathrm{~K}\) . Therefore, we can confidently assert that there is no heating occurring. We have now included this quantification of the absence of heating in the supplementary material. + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Dynamic compression of liquid water at a compression rate (10 GPa/ms). The sample pressure over time is measured using simultaneously the \(S\vert \mathrm{text}(SrB)_2[4]\vert \mathrm{text}(O)_2[7]\vert \mathrm{text}(Sm)^\wedge (2 + )S\) and the ruby fluorescence
+ +- In the adopted phenomenological model for the nucleation rate, authors ignore the effect of crystal growth, but only take the nucleation rate into account. However, I recognized that the grown ice VII may be somehow coarse crystalline size because the observed diffraction patterns are not like smooth lines but spotty. In particular, I found 111 spots of ice VII, which should be very very weak (generally invisible) if the specimen is fine powder, showing the specimen should be somehow coarse aggregates of many single crystals. The actual rate of ice VII growth may be expressed as the combination of nucleation and growth rates. In fact, the results obtained in this study could be interpreted by different phenomenological models, such as the simple JMAK model. The point would be 'which model is the best' to describe the observed phenomena. Even if one model fits well, this does not necessarily mean that this is the only correct model. + +Plus, I am also concerned about the lack of temperature terms in the adopted model. I suppose the temperature term should appear since the classical nucleation theory generally has it. Authors should discuss this point (why temperature term could be ignored), if they stick to this model only. + +First, it is important to note that there is no temperature term involved, as explained above. In the discussion, we begin with the JMAK model and make the assumption that the nucleation rate is predominant over the growth rate. This assumption has been previously utilized in the analysis of overcompression studies of water (ref. 15 and Ref. 16). + +We have explicitly stated in the text that, for compression rates exceeding a few GPa/ms, this assumption appears reasonable. This conclusion is drawn from the imaging observation of instantaneous nucleation throughout the entire sample chamber, as well + +<--- Page Split ---> + +as the absence of a plateau in the pressure - time evolution during compression. This pertains to the data points presented in figure 6. Conversely, for data points obtained below 1 GPa/ms, a plateau is observed and the growth of the crystallites is imaged, as shown in figure 2. So + +<--- Page Split ---> + +, we believe we correctly explain the framework of our analysis. + +- Previous studies using d-DAC reported that ice VI and HDA coexist [19,20] as mentioned in the manuscript, but HDA was not observed in this study. The authors should describe the difference from the previous study. + +At the end of the section on crystallization of ice VII in the stability domain of ice VI, we explicitly mention that ice VII transforming into ice VI could evolve to a mixture of ice VI and HDA. We have no experimental evidence for a more ascertain statement. + +Minor points + +1. The precise wavelength should be described in Method section. I found the \(x\) -ray energy is \(19 \mathrm{keV}\) , but the number of significant figures is only two in this case. +2. The reflection indices should not be in parenthesis. Index in parenthesis, (hkl) means Miller index that is used for corresponding Miller plane in real space. But reflection index, hkl, in reciprocal space should not have any parenthesis (see International Tables for crystallography, for this criterion). + +The manuscript was modified accordingly. + +3. Effective digit and/or the error should be considered throughout the whole manuscript, in particular, in Table I. + +This comment was taken into account throughout the whole manuscript. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The authors have adequately responded to my comments on their first submission. I'm happy to recommend publication. + +## Reviewer #2 (Remarks to the Author): + +This manuscript has clarified the occurrence of crystallization into ice VII occurs in between19 + +1.6 GPa and 2.0 GPa, that is in the stability field of ice VI. This was achieved by employing time-resolved X-ray diffraction and a Diamond-Annil-Cell, with pressure rise times from 0.1 ms to 100 ms. + +The authors have added appropriate references as suggested by the reviewers. The authors have also added appropriate clarifying sentences in response to reviewer's remarks and questions. + +An important exception to this is an incorrect comment made by the authors regarding an important reference to an article by cited by a reviewer. The authors state in their rebuttal comments "We now have cited the Yamamoto reference in our supplementary information" This is not seen in the revised manuscript and supplementary information copy submitted by the authors. + +In summary, this revised manuscript describes in more detail than previously published studies the results of a re- examination of the phase transition of water to ice VII. It is not clear however that providing additional details of a known phase transition qualifies for acceptance in Nature. + +## Reviewer #3 (Remarks to the Author): + +Please find the attached comments. + +[editorial note: please see the next page(s) for reviewer #3's comments.] + +<--- Page Split ---> + +Comments on the manuscript entitled 'Metastable water at several compression rates and its freezing kinetics into ice VII" by Pepin et al., + +I noticed other two reviewers appreciated the importance of this study, which is in itself pleasing as a researcher in ice study. Although I understand most of authors rebuttal comments, authors replies to my comments raised the following further concerns. I point out my concerns as replies (bold) following to the rebuttal comments from the authors (italic). + +1. + +Regarding the solidification of ice VII in the stability domain of ice VI, we thank reviewer#3 for providing this Jp. J. Appl. Phys. reference. However, in it, the reported observation of ice VII in the stability field of ice VI is not exactly what is reported in our study. The nucleation of ice VII was obtained at the metastable extension of the melting line of ice VII in the stability field of ice VI by heating the sample so that the overcompression of water that can be obtained under quasi- static compression could reach the metastable melting line of ice VII. Nucleation of ice VII is stated then to occasionally form and a facetted single crystal of ice VII can bestabilized in equilibrium with the liquid. However, ice VII is kept metastable only if facetted in equilibrium with the liquid. That is exactly what we observed and used in the experiment reported in our supplementary material to precisely extend the ice VII melting line in the stability domain of ice VI. We now have cited the reference in our supplementary information. + +However, out of this liquid- solid phase equilibrium, by slightly increasing pressure ice VII transforms into ice VI. We are reported a different story here. Under dynamical compression, metastable water always freeze into ice VII in the metastability domain of ice VII and then ice VII transforms to ice VI over a ms time scale and a mixture ice VI - ice VII then exists, which should eventually evolve to an amorphous - ice VI mixture. This resolves all previous contradictions of the literature between reports of amorphous HAD (could be HDA?), HAD- ice VI mixture or ice VII. + +and the reply to the last comment. + +- Previous studies using d-DAC reported that ice VI and HDA coexist [19,20] as mentioned in the manuscript, but HDA was not observed in this study. The authors should describe the difference from the previous study. At the end of the section on crystallization of ice VII in the stability domain of ice VI, we explicitly mention that ice VII transforming into ice VI could evolve to a mixture of ice VI and HDA. We have no experimental + +<--- Page Split ---> + +I agree the dynamic compression may be somehow different to the static compression, but one point I would indicate is that the metastable ice VII made by the static compression in ice VI stability region also eventually convert to ice VI, since it is metastable. The difference to the static compression would be the degree of over- compression (AG between liquid and ice VII). Facet morphology found in ice VII by the static compression could also be found in that made by the dynamic compression in sub- micrometer scale, which could be just the difference of size. In that sense, the phenomenological difference between static and dynamic compression may be still unclear. + +In this study, the HDA- ice VI mixture was not observed, and may not be explained the clear reason why HDA was observed in the previous study as stated in the reply to the last comment. It is briefly mentioned in the line 190- 197, as 'This difference could be explained by the fact that at 1.8 GPa, ice VII is approaching its thermodynamic stability, allowing for the stabilization of a mixture of ice VI and ice VII, whereas at 1.7 GPa, ice VII is gradually transforming, leading to the stabilization of a mixture of ice VI and amorphous ice.' But I could not satisfy this description resolves all previous contractions. The present results would show even another contradiction in the sense that they could not observe amorphous state. + +2. + +We thus could show that the heating of the sample is negligible. That is illustrated in the figure below showing that, no discernible heating was detected within the measurement's sensitivity, approximately \(\pm 3 \text{K}\) . Therefore, we can confidently assert that there is no heating occurring. We have now included this quantification of the absence of heating in the supplementary material. + +<--- Page Split ---> +![PLACEHOLDER_20_0] + +
Dynamic compression of liquid water at a compression rate (10 GPa/ms). The sample pressure over time is measured using simultaneously the S(Text(Si6)_[4]/text(O)_[7]/text(Sm)^(2+)/S and the ruby fluorescence
+ +From the above figure, I could see significant increases in temperatures, exceeding 315 K (42 °C), it does not look like \(\pm 3\) K. Plus, the plot in Fig. 9 shows the temperature \(\sim 21\) °C (294 K), it contradicts with the above figure. If the temperature changes over 10 K, the story might change since the experimental conditions are close to the melting line. + +![PLACEHOLDER_20_1] + + +Finally one minor question for the above figure, what is the blue atom in ice VI structure? + +<--- Page Split ---> + +## Detailed answer to reviewers' comments. + +## Reviewer #1: + +The authors have adequately responded to my comments on their first submission. I'm happy to recommend publication. + +We thank reviewer #1 for his recommendation. + +## Reviewer #2: + +This manuscript has clarified the occurrence of crystallization into ice VII occurs in between 1.6 GPa and 2.0 GPa, that is in the stability field of ice VI. This was achieved by employing time- resolved X- ray diffraction and a Diamond- Anvil- Cell, with pressure rise times from 0.1 ms to 100 ms. + +The authors have added appropriate references as suggested by the reviewers. The authors have also added appropriate clarifying sentences in response to reviewer's remarks and questions. An important exception to this is an incorrect comment made by the authors regarding an important reference to an article by cited by a reviewer. The authors state in their rebuttal comments "We now have cited the Yamamoto reference in our supplementary information" This is not seen in the revised manuscript and supplementary information copy submitted by the authors. + +In summary, this revised manuscript describes in more detail than previously published studies the results of a re- examination of the phase transition of water to ice VII. It is not clear however that providing additional details of a known phase transition qualifies for acceptance in Nature. + +We thank reviewer #2 for his feedback on our revised manuscript. We acknowledge the oversight regarding the the Yamamoto reference and have now included it in the revised supplementary information. + +However, we are surprised by the change in Reviewer #2's appreciation of our manuscript. Initially, the reviewer suggested acceptance after minor comments were addressed, but he/she is now questioning the suitability of our work for publication in Nature. This change in stance is unexpected and lacks clarification. + +## Reviewer #3: + +I noticed other two reviewers appreciated the importance of this study, which is in itself pleasing as a researcher in ice study. Although I understand most of authors rebuttal comments, authors replies to my comments raised the following further concerns + +I agree the dynamic compression may be somehow different to the static compression, but one point I would indicate is that the metastable ice VII made by the static compression in ice VI + +<--- Page Split ---> + +stability region also eventually convert to ice VI, since it is metastable. The difference to the static compression would be the degree of over- compression (AG between liquid and ice VII). Facet morphology found in ice VII by the static compression could also be found in that made by the dynamic compression in sub- micrometer scale, which could be just the difference of size. In that sense, the phenomenological difference between static and dynamic compression may be still unclear. In this study, the HDA- ice VI mixture was not observed, and may not be explained the clear reason why HDA was observed in the previous study as stated in the reply to the last comment. It is briefly mentioned in the line 190- 197, as 'This difference could be explained by the fact that at 1.8 GPa, ice VII is approaching its thermodynamic stability, allowing for the stabilization of a mixture of ice VI and ice VII, whereas at 1.7 GPa, ice VII is gradually transforming, leading to the stabilization of a mixture of ice VI and amorphous ice.' But I could not satisfy this description resolves all previous contractions. The present results would show even another contradiction in the sense that they could not observe amorphous state. + +We respectfully disagree with reviewer #3. There is a phenomenological difference between static and dynamic compressions concerning the observation of stable ice VII in the stability field of ice VI. In the static experiment, ice VII was brought into the stability field of ice VI by following the metastable melting line of ice VII down to 300K. If the melting equilibrium is lost and complete solidification occurs, ice VII transforms to ice VI. In dynamical compression, the over- compression pressure of metastable water is increasing with the compression rate. For compression rates in between 0.15 GPa/ms sans 0.9 GPa/ms, the freezing of metastable water falls in the stability domain of ice VI and in the metastability domain of ice VII, as determined by the extension of the melting line of ice VII. Our study shows that metastable water under such conditions always freezes in ice VII and then transforms into ice VI over a few milliseconds. Using time resolved XRD we could thus show a preferred nucleation mechanism into ice VII which was not shown by static measurements. + +Regarding the formation of amorphous ice, HDA, as reported by previous studies based on Raman measurements, we are unable to observe it because it is a too weak signal by X- ray diffraction. It should also be noted that a mixture of fine powder of ice VI and ice VII would have a Raman signal that looks like the one of HDA ice. The important points of our study are the preferred nucleation of water into ice VII and then the time- scale of the transformation into ice VI. Whether there is complete transformation into ice VI, a mixture of ice VI and ice VII, a mixture of ice VI and HDA could depend of the final pressure of the rapid compression. We have modified the manuscript to make this point clearer. The sentence now reads: "This difference could be explained by the fact that at 1.8 GPa, ice VII is approaching its thermodynamic stability, allowing for the stabilization of a mixture of ice VI and ice VII (and a possible amorphous state, which could not be observed in our case due to its very low diffraction power), whereas at 1.7 GPa, ice VII has been reported to gradually transform in a mixture of ice VI and amorphous ice." + +From the above figure, I could see significant increases in temperatures, exceeding 315 K (42 °C), it does not look like \(\pm 3\) K. Plus, the plot in Fig. 9 shows the temperature \(\sim 21\) °C (294 K), it contradicts with the above figure. If the temperature changes over 10 K, the story might change since the experimental conditions are close to the melting line. + +<--- Page Split ---> +![PLACEHOLDER_23_0] + + +We apologize for any confusion caused by the previous error bars in our temperature measurements. The \(\pm 3 \mathrm{K}\) error bar was taken from the reference article based on the luminescence gauges, but we have since re- estimated the error bars to be \(\pm 10 \mathrm{K}\) . + +We would like to point out that the temperature relation in our study was obtained in non- hydrostatic pressure conditions, whereas in ref. 29, the error bar estimation was obtained in a hydrostatic pressure medium. This impacts the fluorescence of the ruby by broadening the peaks and making them asymmetrical, which slightly skews the pressure measurements. This is evidenced in the bottom graph of the figure provided. If a temperature increase were to take place during the fast compression, the temperature should be an increasing function of time throughout the entire compression sequence. However, this is not the case here, as we observed the temperature oscillating around the initial temperature of \(294 \mathrm{K}\) , within a \(\pm 10 \mathrm{K}\) error bar. + +Furthermore, if we consider a temperature increase of \(10 \mathrm{K}\) for our point under 14.82 GPa/ms, the figure below shows that it corresponds to a pressure difference in the overcompression of metastable water of \(\sim 0.06 \mathrm{GPa}\) , which is within the error bars that we considered in our models of figures 5 and 6. + +In conclusion, the temperature increase during compression is very small and if any, of the order of \(10 \mathrm{K}\) , does not affect the overall results and conclusions of our study. + +We have slightly modified the manuscript to reflect this and the figure as shown above. The sentence now reads: "That is illustrated by the figure below showing that, no discernible heating was detected within the measurement's sensitivity, approximately \(\pm 10 \mathrm{K}\) ". + +<--- Page Split ---> +![PLACEHOLDER_24_0] + + +Finally one minor question for the above figure, what is the blue atom in ice VI structure? + +This is just a visual representation of the oxygen atoms occupying two different positions (Wycoff site 2b in blue and 8g in red). + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #3 (Remarks to the Author): Please find the attached comments. + +[editorial note: please see the next page(s) for reviewer #3's comments.] + +<--- Page Split ---> + +1. I acknowledge the author's comments on my previous concerns regarding the phenomenological difference between static and dynamic compression. First, I would indicate one fact that ice VII could also nucleate into the stability field of ice VI as written by Yamamoto et al., described as + +"...it was discovered in the present experiment that ice VII occasionally formed directly from water at point B in Fig. 1 without the formation of ice VI at point A." (see below) + +[figure redacted] + +Therefore, the author's indication in their rebuttal comments, + +"In the static experiment, ice VII was brought into the stability field of ice VI by following the metastable melting line of ice VII down to 300K. If the melting equilibrium is lost and complete solidification occurs, ice VII transforms to ice VI." + +is misunderstanding. + +But, if in the dynamic compression ice VII "always" preferably nucleates rather than ice VI, this is the phenomenological difference since in the static compression ice VII could only "occasionally" nucleate. Authors could emphasize this point with the reference to Yamamoto et al. + +<--- Page Split ---> + +2. As for the description of (non)appearance of HDA, the added sentence "(and a possible amorphous state, which could not be observed in our case due to its very low diffraction power)" is a bit inaccurate since the diffraction power ("scattering power" may be more appropriate term in the case of amorphous, though "diffraction power" is also correct) itself is comparable to the crystalline material if all integrated through whole reciprocal space. I suggest this sentence would be "...in our case since the scattering from amorphous may be hidden in the Bragg peaks even it exists" or so. In any case, the last sentence of this paragraph, "These results offer a clarification to the apparent contradiction of the previous findings." seems a bit overstatement to me. + +3. I consider, repeatedly saying, that the difference to static compression would be the degree of overcompression. The over-compression as large as a few GPa could not be achieved by the static compression. The strong point of this study would be the quantitative analysis of the nucleation time as a function of the over-compression. This is the reason why I repeatedly indicate the quantitative considerations for the temperature effect since I suppose the \(10\mathrm{K}\) difference is huge for water molecules at a few GPa regions. I suggest some comments on the temperature effect, as written in the rebuttal comments, may be included in the main text as well. + +4. Regarding the qualitative analysis, I pointed out in the first comment, + +"Effective digit and/or the error should be considered throughout the whole manuscript, in particular, in Table I." + +and authors replied, + +"This comment was taken into account throughout the whole manuscript." + +I did not carefully check in the second round (since I believed this reply), but I realized that Table I was not modified yet. For example, the rate of compression in the first raw is written as '870787.5 (GPa/ms)". I could not believe the effective digit could reach 7 digits, such very precise pressure control would not be possible. Similarly, in the caption of Figure 6, the parameter b is written like "b=245293534.93", which is also unrealistic effective digit considering the fitting result shown in Figure 6. Such representations without care of effective digits led readers to the question of the whole results of this study. Authors should carefully check again this point. + +<--- Page Split ---> + +## Detailed answer to reviewers' comments. + +1- I acknowledge the author's comments on my previous concerns regarding the phenomenological difference between static and dynamic compression. First, I would like to point out that ice VII could also nucleate within the stability field of ice VI, as written by Yamamoto et al., described as: + +"...it was discovered in the present experiment that ice VII occasionally formed directly from water at point B in Fig. I without the formation of ice VI at point A." (see below) Therefore, the author's statement in their rebuttal comments, "In the static experiment, ice VII was brought into the stability field of ice VI by following the metastable melting line of ice VII down to 300K. If the melting equilibrium is lost and complete solidification occurs, ice VII transforms to ice VI." is a misunderstanding. However, if under dynamic compression ice VII "always" nucleates preferentially rather than ice VI, this would be the phenomenological difference, since under static compression ice VII could only "occasionally" nucleate. The authors could emphasize this point with reference to Yamamoto et al. + +Following the reviewer's advice, we have added a sentence that reads: "It was also shown that ice VII could occasionally nucleate in the stability domain of ice VI above the metastable melting line [41]". + +2- Regarding the description of the (non)appearance of HDA, the added sentence "(and a possible amorphous state, which could not be observed in our case due to its very low diffraction power)" is somewhat inaccurate, as the diffraction power ("scattering power" might be a more appropriate term in the case of amorphous materials, although "diffraction power" is also correct) itself is comparable to that of crystalline material if integrated over the whole reciprocal space. I suggest rephrasing this sentence as "...in our case since the scattering from amorphous material may be hidden in the Bragg peaks even if it exists," or something similar. In any case, the last sentence of this paragraph, "These results offer a clarification to the apparent contradiction of the previous findings," seems a bit of an overstatement to me. + +We have modified the main text accordingly. + +3- I believe, and have repeatedly stated, that the difference with static compression lies in the degree of over-compression. Over-compression as large as a few GPa could not be achieved by static compression. The strength of this study lies in the quantitative analysis of nucleation time as a function of over-compression. This is why I repeatedly emphasize the importance of quantitative considerations regarding the temperature effect, as I believe the 10 K difference is significant for water molecules under a few GPa. I suggest that some comments on the temperature effect, as written in the rebuttal comments, be included in the main text as well. + +We have added a statement in the supplementary information. It reads: "We would like to point out that the temperature relation in our study was obtained in non- hydrostatic pressure conditions, whereas in Ref.\cite{Datchi97}, the error bar estimation was obtained in a hydrostatic pressure medium. This impacts the fluorescence of the ruby by broadening the peaks and making them asymmetrical, which slightly skews the pressure measurements. This is evidenced in the bottom graph of Supplementary Figure \ref{fig:figureS4}. If a temperature increase were to take place during the fast compression, the temperature should be an + +<--- Page Split ---> + +increasing function of time throughout the entire compression sequence. However, this is not the case here, as we observed the temperature oscillating around the initial temperature of 294 K, within a \(\pm 10 \mathrm{K}\) error bar. + +Furthermore, if we consider a temperature increase of \(10 \mathrm{K}\) for the point at \(14.82 \mathrm{GPa / ms}\) , it would correspond to a pressure difference in the overcompression of metastable water of \(- 0.06 \mathrm{GPa}\) , which is within the error bars that we considered in our models of figures 5 and 6. ” + +4- Regarding the qualitative analysis, I pointed out in my first comment, "Effective digits and/or errors should be considered throughout the entire manuscript, particularly in Table I," and the authors replied, "This comment was taken into account throughout the entire manuscript." I did not carefully check this during the second round (as I trusted their reply), but I later realized that Table I had not yet been modified. For example, the rate of compression in the first row is written as '870787.5 (GPa/ms).' I cannot believe the effective digits could reach seven digits; such precise pressure control would not be possible. Similarly, in the caption of Figure 6, the parameter \(b\) is written as " \(b = 245293534.93\) ," which is also an unrealistic number of significant digits considering the fitting result shown in Figure 6. Such representations without careful attention to significant digits lead readers to question the overall results of this study. The authors should carefully check this point again. + +We have modified the main text accordingly, carefully checking for effective digits. However, some number have not been modified because they are derived from data from references cited in our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b47b1c14c4f58085e40e7dcafec3c9bd5e06a509 --- /dev/null +++ b/peer_reviews/127b4a1df348ee954b5fefb88eeed0676c975caa5b61439cfcd7368eac65b846/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,619 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 934, 210]]<|/det|> +Metastable water at several compression rates and its freezing kinetics into ice VII + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 784]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 843, 129]]<|/det|> +Editorial note: Parts of this Peer Review File have been redacted as indicated to remove third- party material where no permission to publish could be obtained. + +<|ref|>sub_title<|/ref|><|det|>[[118, 182, 315, 199]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[118, 234, 437, 252]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 259, 877, 383]]<|/det|> +This work shows in situ, time resolved x- ray diffraction data on the H2O system subjected to a wide range of compression rates. The diffraction data show real- time structural response of the system and allow unambiguous identification of solid phases of ice. I think the presented data provide interesting and important insight into the freezing dynamics and help to resolve discrepancies from other measurements. + +<|ref|>text<|/ref|><|det|>[[118, 415, 844, 460]]<|/det|> +I had several thoughts on how the manuscript could be made clearer but, beyond these, would like to recommend publication. + +<|ref|>text<|/ref|><|det|>[[115, 493, 875, 588]]<|/det|> +1. Page 2 introduction: "having the simplest ice structure with..." I think the work "simplest" is subjective. Since the structure of ice VII is highly disordered, one could say an ordered phase, such as ice VIII is structurally simpler. More appropriate would be a specific statement like "simplest crystallographic unit cell". + +<|ref|>text<|/ref|><|det|>[[117, 597, 877, 642]]<|/det|> +2. Page 2 introduction: "is a topic of current focus" when stating this, I think citations should be provided. + +<|ref|>text<|/ref|><|det|>[[117, 651, 833, 722]]<|/det|> +3. Page 5 instrumentation: It is mentioned that the pressure is measured via multiple approaches. Hence, how does the reader know which is refered to when pressures are quoted throughout the manuscript. E.g. what is shown in Figure 1? + +<|ref|>text<|/ref|><|det|>[[117, 730, 860, 774]]<|/det|> +4. Page 5 pressure response of...compression ramps": "the convolution with" I'm not sure this effect is a convolution in the mathematical sense. + +<|ref|>text<|/ref|><|det|>[[117, 782, 874, 878]]<|/det|> +5. Page 5 pressure response of...compression ramps": "1.56 GPa" No quantified uncertainty is given for this number and, on the basis of Figure 2 where error bar are shown to be ±0.05 this number is stated too precisely. Assuming the error bars indicate the magnitude of a standard deviation, quoting the pressure to one decimal place is sufficient. + +<|ref|>text<|/ref|><|det|>[[115, 886, 872, 905]]<|/det|> +6. Page 8 Freezing pressure of...compression rate: "0.056, which matches...0.069" Use of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 820, 128]]<|/det|> +word 'matches' requires some information on experimental uncertainty, which is not provided. + +<|ref|>text<|/ref|><|det|>[[117, 137, 860, 207]]<|/det|> +7. Page 8 Freezing pressure of..compression rate: "When metastable water freeze under a compression rate of 110 GPa/ms, it corresponds to a cooling rate of \(10^{\wedge}7 \text{K / s}\) ". I have no idea how this equivalence was derived, can the authors explain their argument? + +<|ref|>text<|/ref|><|det|>[[117, 215, 861, 310]]<|/det|> +8. Figure 2: I was confused by the meaning of the coloured horizontal bands indicating phase regions. Are these taken from other work? Or if they are they guides to the eye to indicate behaviour observed in this study, I found it confusing that they are horizontal and not vertical as each phase is only present for bounded periods of time. + +<|ref|>text<|/ref|><|det|>[[117, 318, 876, 386]]<|/det|> +9. Figure 4: How can pressure be inferred from this plot? Is it possible to show in some way? 10. Figure 4: Out of curiosity, is some interpolation or smoothing applied to the 2d 2theta vs time data? + +<|ref|>text<|/ref|><|det|>[[117, 396, 872, 546]]<|/det|> +11. Figure 4: "A mixture of ice VI and ice VII is still observed" I wondered if it is possible by Rietveld analysis (likely with a highly constrained model) to determine the phase fraction of VI and VII? From the 2d image, it indeed looks like the intensity of the ice VII 110 decreases as the ice VI forms. If it could be quantitatively shown that this change is due to direct transformation of the volume of ice VII in the x-ray beam, that would strengthen the interpretation given. + +<|ref|>sub_title<|/ref|><|det|>[[120, 606, 438, 623]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 632, 870, 728]]<|/det|> +This manuscript describes the effects of rapid compression of liquid water to its crystalline phases using dynamic- piezo- Diamond- Anvil- Cell. The main goal of this study was to provide experimental details and perhaps a physical understanding the structural changes of water undergoing rapid temperature and/or pressure variation. + +<|ref|>text<|/ref|><|det|>[[117, 761, 880, 910]]<|/det|> +Although there have been many studies of phase transitions in both water and ice, this study focused on one particular phase transition where there have been different previously reported results and interpretations. This is a transition between metastable liquid water and particular dense crystalline phases. The authors of this study employed additional an experimental technique of time- resolved X- ray diffraction with a dynamic- piezo- Diamond- Anvil- Cell. The employment of this technique provided sufficient new data to resolve the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 446, 101]]<|/det|> +contradictions that are in the literature. + +<|ref|>text<|/ref|><|det|>[[115, 135, 880, 707]]<|/det|> +This is a very well written manuscript and I therefore have only a small list of comments that should be addressed in more detail.1) On page 3 the authors indicate that they are investigating whether ice VII is still the freezing state of metastable water?? Under what, P conditions are they referring to?2) On page 5 the authors give a value of 1.56 GPa? How accurate is this number? T, P effects?3) On page 6: It was stated and suggested that crystallization occurs into ice VII, although without time-resolved XRD measurements this proposition remains to be proven. Ref?4) Pg. 6: excellent agreement between the different pressure determinations. Can the authors be clearer on this point? Perhaps by simply referring to the figures.5) On Pg. 7, it is stated that there was a e previous domain of investigation in d- DAC experiments. A reference. is needed here.6) without time-resolved XRD measurements this proposition remains to be proven. A reference should be made here.7) On page. 9 the authors state "Since water and ice are quite incompressible" Here a comparison with other triatomic molecules would strengthen this statement.8) It is important to emphasize that the model employed to fit the data is a classical nucleation theory description of the experimental results. It fits the data very well and provides a very good physical picture and interpretation of the experimental results but this depends on parameters used for fitting the data so small changes in the parameters employed could have a significant effect on the model used. This could be mentioned by the authors. + +<|ref|>text<|/ref|><|det|>[[117, 787, 878, 911]]<|/det|> +This report follows up on the previous domain of investigation in d- DAC experiments focusing on the solidification of metastable water. This is the key goal reached in this study. The authors clearly state that support the hypothesis that metastable water, within the pressure range of 1.5 GPa to 2.1 GPa, nucleates into ice VII first, despite this range being the stability field of ice VI. results offer a clarification to the apparent contradiction of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 265, 101]]<|/det|> +previous findings. + +<|ref|>text<|/ref|><|det|>[[117, 110, 880, 234]]<|/det|> +previous findings.In summary, this manuscript clearly addresses and presents a solution to the phase transition discrepancies in the literature. A key improvement in the measurement technique was time- resolved X- ray diffraction. This technique is very well described in the manuscript All figures were clearly presented and definitely provided added clarity to the report. Acceptance is therefore suggested after the minor comments listed above are addressed. + +<|ref|>sub_title<|/ref|><|det|>[[118, 292, 438, 310]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 317, 875, 600]]<|/det|> +The authors investigated the interesting behaviour of water ice under dynamic compression with various compression rates using d- DAC by time- resolved x- ray diffraction method and found that ice VII crystallise under the conditions where ice VI should be stable. They also interpret the excess pressure and growth time during the crystallization of ice VII using a phenomenological model based on the classical nucleation theory, succeeding in a comprehensive explanation for the growth rate of ice VII grown under various compression rates. The investigated technique, x- ray diffraction with ruby fluorescence observations at micro- to milli- second order, is somehow remarkable, and the overall achievements of this study would be worth recognising for the ice community. Thus, I do not doubt that this manuscript should be eventually published in at least some specific journal, but I am not sure whether this manuscript will be published by Nature Communication. + +<|ref|>text<|/ref|><|det|>[[115, 606, 877, 912]]<|/det|> +Two key points in assessing the value of this study would be 1) how new the observed results are and 2) how much their interpretation will influence other related studies. First, concerning the observed results, it should be stated that no truly new phenomena have been reported in this study. It has long been known among ice researchers that ice VII nucleates in the stable region of ice VI even under static compression (e.g. K. Yamamoto, Jpn J Appl Phys, 19, 1841, 1980, doi: 10.1143/JJAP.19.1841). A recent study using d- DAC has also reported ice VII nucleation in the stability region of ice VI [18]. Therefore, what is new in this manuscript are the results of quantitative experiments on how the growth rate of ice VII changes when the compression rate is varied. The experimental results in this study are novel in the sense that they are quantitative, but the observed phenomena themselves are not particularly novel. The manuscript also does not elaborate on how the quantitative growth rates obtained might affect other related studies. It is therefore difficult to assess, at + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 85, 565, 101]]<|/det|> +least at the moment, how important these results are. + +<|ref|>text<|/ref|><|det|>[[117, 110, 861, 181]]<|/det|> +Even if the importance of this manuscript is recognised by other reviewers and considered for publication in Nat. Commun., the following concerns remain and should be fully considered before potential publication. + +<|ref|>text<|/ref|><|det|>[[116, 188, 866, 365]]<|/det|> +- The authors assume that the sample temperature should not be increased by the rapid compression, but it should be more carefully evaluated and explained in the manuscript. I also believe that temperature might be quickly stable at room temperature owing to the high thermal conductivity of the diamond. However, if the sample size is enough large, this might not be the case since the thermal conductivity of ice VII would not be such high, so the temperature could temporally increase in a very short time. This issue should be quantitatively assessed, for example, by FEM simulation. + +<|ref|>text<|/ref|><|det|>[[115, 396, 879, 677]]<|/det|> +- In the adopted phenomenological model for the nucleation rate, authors ignore the effect of crystal growth, but only take the nucleation rate into account. However, I recognized that the grown ice VII may be somehow coarse crystalline size because the observed diffraction patterns are not like smooth lines but spotty. In particular, I found 111 spots of ice VII, which should be very very weak (generally invisible) if the specimen is fine powder, showing the specimen should be somehow coarse aggregates of many single crystals. The actual rate of ice VII growth may be expressed as the combination of nucleation and growth rates. In fact, the results obtained in this study could be interpreted by different phenomenological models, such as the simple JMAK model. The point would be 'which model is the best' to describe the observed phenomena. Even if one model fits well, this does not necessarily mean that this is the only correct model. + +<|ref|>text<|/ref|><|det|>[[117, 684, 877, 782]]<|/det|> +Plus, I am also concerned about the lack of temperature terms in the adopted model. I suppose the temperature term should appear since the classical nucleation theory generally has it. Authors should discuss this point (why temperature term could be ignored), if they stick to this model only. + +<|ref|>text<|/ref|><|det|>[[117, 814, 872, 885]]<|/det|> +- Previous studies using d-DAC reported that ice VI and HDA coexist [19,20] as mentioned in the manuscript, but HDA was not observed in this study. The authors should describe the difference from the previous study. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 86, 227, 101]]<|/det|> +## Minor points + +<|ref|>text<|/ref|><|det|>[[115, 110, 870, 315]]<|/det|> +1. The precise wavelength should be described in Method section. I found the x-ray energy is 19 keV, but the number of significant figures is only two in this case. +2. The reflection indices should not be in parenthesis. Index in parenthesis, (hkl) means Miller index that is used for corresponding Miller plane in real space. But reflection index, hkl, in reciprocal space should not have any parenthesis (see International Tables for crystallography, for this criterion). +3. Effective digit and/or the error should be considered throughout the whole manuscript, in particular, in Table I + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 84, 528, 102]]<|/det|> +## Detailed answer to reviewers' comments. + +<|ref|>sub_title<|/ref|><|det|>[[115, 121, 222, 138]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[115, 155, 880, 244]]<|/det|> +This work shows in situ, time resolved \(x\) - ray diffraction data on the H2O system subjected to a wide range of compression rates. The diffraction data show real- time structural response of the system and allow unambiguous identification of solid phases of ice. I think the presented data provide interesting and important insight into the freezing dynamics and help to resolve discrepancies from other measurements. + +<|ref|>text<|/ref|><|det|>[[115, 261, 880, 296]]<|/det|> +I had several thoughts on how the manuscript could be made clearer but, beyond these, would like to recommend publication. + +<|ref|>text<|/ref|><|det|>[[115, 314, 880, 385]]<|/det|> +1. Page 2 introduction: "having the simplest ice structure with..." I think the work "simplest" is subjective. Since the structure of ice VII is highly disordered, one could say an ordered phase, such as ice VIII is structurally simpler. More appropriate would be a specific statement like "simplest crystallographic unit cell". + +<|ref|>text<|/ref|><|det|>[[117, 394, 459, 412]]<|/det|> +The sentence was modified accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 439, 880, 474]]<|/det|> +2. Page 2 introduction: "is a topic of current focus" when stating this, I think citations should be provided. + +<|ref|>text<|/ref|><|det|>[[117, 484, 333, 501]]<|/det|> +We have added citations. + +<|ref|>text<|/ref|><|det|>[[115, 529, 822, 582]]<|/det|> +3. Page 5 instrumentation: It is mentioned that the pressure is measured via multiple approaches. Hence, how does the reader know which is referred to when pressures are quoted throughout the manuscript. E.g. what is shown in Figure 1? + +<|ref|>text<|/ref|><|det|>[[115, 599, 870, 652]]<|/det|> +As mentioned in the manuscript, the imaging and X- ray diffraction (XRD) processes could not be conducted simultaneously. The pressure was measured using luminescence during imaging and by determining the volume of copper during XRD. + +<|ref|>text<|/ref|><|det|>[[115, 666, 833, 717]]<|/det|> +An essential aspect to highlight, as illustrated in Figure 3, is the high degree of repeatability and reproducibility of the compression ramps using the different diagnostic techniques. To enhance clarity, we have included the following sentence: + +<|ref|>text<|/ref|><|det|>[[115, 731, 868, 782]]<|/det|> +"The pressure was determined using a luminescence gauge during imaging and by utilizing XRD equation- of- state (EOS) data during XRD. The results from the different pressure measurement methods were found to be highly consistent with each other." + +<|ref|>text<|/ref|><|det|>[[115, 815, 857, 850]]<|/det|> +4. Page 5 pressure response of...compression ramps": "the convolution with" I'm not sure this effect is a convolution in the mathematical sense. + +<|ref|>text<|/ref|><|det|>[[115, 860, 848, 913]]<|/det|> +The sentence now reads: "However, if a phase transition occurs, the pressure rise is disrupted by the pressure drop associated to the negative volume discontinuity at the transition, resulting in an apparent negative compressibility." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 100, 877, 171]]<|/det|> +5. Page 5 pressure response of...compression ramps": "1.56 GPa" No quantified uncertainty is given for this number and, on the basis of Figure 2 where error bar are shown to be \(\pm 0.05\) this number is stated too precisely. Assuming the error bars indicate the magnitude of a standard deviation, quoting the pressure to one decimal place is sufficient. + +<|ref|>text<|/ref|><|det|>[[116, 181, 861, 199]]<|/det|> +The pressure was modified to 1.6 GPa to take into account the \(\pm 0.05\) GPa uncertainty. + +<|ref|>text<|/ref|><|det|>[[116, 226, 875, 278]]<|/det|> +6. Page 8 Freezing pressure of...compression rate: "0.056, which matches...0.069" Use of the word 'matches' requires some information on experimental uncertainty, which is not provided. + +<|ref|>text<|/ref|><|det|>[[116, 288, 860, 323]]<|/det|> +The sentence now reads: "Remarkably, the exponent 'c' obtained from the fit is 0.056, which closely aligns with the value of 0.069 predicted by Myint's scaling law." + +<|ref|>text<|/ref|><|det|>[[116, 351, 846, 402]]<|/det|> +7. Page 8 Freezing pressure of compression rate: "When metastable water freeze under a compression rate of 110 GPa/ms, it corresponds to a cooling rate of \(10^{7} \mathrm{~K} / \mathrm{s}\) ". I have no idea how this equivalence was derived, can the authors explain their argument. + +<|ref|>text<|/ref|><|det|>[[115, 413, 880, 519]]<|/det|> +At a compression rate of 110 GPa/ms at 300 K, the freezing process occurs at 2.9 GPa after an over-compression duration of 18 us in the metastable water state. To achieve the same state through a 18 us cooling at 2.9 GPa from the liquid state, considering the melting point of water at 2.9 GPa is 423 K (Datchi et al., PRB 61, 6535 (2000)), the required cooling rate would have to be \(7 \times 10^{6} \mathrm{~K} / \mathrm{s}\) , approximately \(10^{7} \mathrm{~K} / \mathrm{s}\) . This calculation has been included in the supplementary material. + +<|ref|>text<|/ref|><|det|>[[115, 547, 877, 616]]<|/det|> +8. Figure 2: I was confused by the meaning of the coloured horizontal bands indicating phase regions. Are these taken from other work? Or if they are they guides to the eye to indicate behaviour observed in this study, I found it confusing that they are horizontal and not vertical as each phase is only present for bounded periods of time. + +<|ref|>text<|/ref|><|det|>[[115, 634, 877, 700]]<|/det|> +The colored regions in the figure represent the (meta)stability pressure domains at 300 K for the various phases. These domains are inferred from the static phase diagram and the newly measured metastable melting of liquid- ice VII in this study. They are included as a visual aid to guide the interpretation of the data. + +<|ref|>text<|/ref|><|det|>[[115, 733, 872, 750]]<|/det|> +9. Figure 4: How can pressure be inferred from this plot? Is it possible to show in some way? + +<|ref|>text<|/ref|><|det|>[[115, 760, 875, 830]]<|/det|> +Pressure is inferred from the measured volumes of Sn, ice VII and ice VI. A reference to the Sn EoS has been added and a clarification has been added in the text which now reads: "Here, the ice sample remaining as a mixture of ice VI and ice VII is observed at 1.8 GPa, as inferred from the measured volumes of Sn, ice VII and VI". + +<|ref|>text<|/ref|><|det|>[[115, 859, 869, 892]]<|/det|> +10. Figure 4: Out of curiosity, is some interpolation or smoothing applied to the 2d 2theta vs time data? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 533, 100]]<|/det|> +A gourdash shading is indeed applied to the data. + +<|ref|>text<|/ref|><|det|>[[115, 126, 875, 234]]<|/det|> +11. Figure 4: "A mixture of ice VI and ice VII is still observed" I wondered if it is possible by Rietveld analysis (likely with a highly constrained model) to determine the phase fraction of VI and VII? From the 2d image, it indeed looks like the intensity of the ice VII 110 decreases as the ice VI forms. If it could be quantitatively shown that this change is due to direct transformation of the volume of ice VII in the x-ray beam, that would strengthen the interpretation given. + +<|ref|>text<|/ref|><|det|>[[116, 240, 849, 312]]<|/det|> +Although the presence of a mixture of ice VI and ice VII is undeniable, conducting a Rietveld analysis to determine the exact phase fractions of ice VI and ice VII appears impracticable here. This is mainly due to the fact that ice VI and ice VII exhibit different textures and the detector angle-coverage is only partial. + +<|ref|>sub_title<|/ref|><|det|>[[116, 343, 224, 360]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[116, 378, 870, 450]]<|/det|> +This manuscript describes the effects of rapid compression of liquid water to its crystalline phases using dynamic- piezo- Diamond- Anvil- Cell. The main goal of this study was to provide experimental details and perhaps a physical understanding the structural changes of water undergoing rapid temperature and/or pressure variation. + +<|ref|>text<|/ref|><|det|>[[115, 466, 872, 590]]<|/det|> +Although there have been many studies of phase transitions in both water and ice, this study focused on one particular phase transition where there have been different previously reported results and interpretations. This is a transition between metastable liquid water and particular dense crystalline phases. The authors of this study employed additional an experimental technique of time- resolved X- ray diffraction with a dynamic- piezo- Diamond- Anvil- Cell. The employment of this technique provided sufficient new data to resolve the contradictions that are in the literature. + +<|ref|>text<|/ref|><|det|>[[115, 608, 868, 642]]<|/det|> +This is a very well written manuscript and I therefore have only a small list of comments that should be addressed in more detail. + +<|ref|>text<|/ref|><|det|>[[115, 679, 820, 714]]<|/det|> +1) On page 3 the authors indicate that they are investigating whether ice VII is still the freezing state of metastable water?? Under what, P conditions are they referring to? + +<|ref|>text<|/ref|><|det|>[[115, 723, 864, 884]]<|/det|> +The previous speculations about the transformation of water into ice VII during shock compression experiments have been uncertain due to the lack of X- ray diffraction diagnostic. In this study, we aim to clarify this phenomenon by investigating the crystallization of metastable water under high compression rates within the stability field of ice VII. Specifically, we seek to determine whether the freezing state of metastable water under these conditions is indeed ice VII or another metastable structure. The text has been slightly modified to make it clearer: 'In particular, we are investigating whether the freezing state of metastable water at high compression rates above 2 GPa is indeed ice VII or a metastable structure....' + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 100, 820, 135]]<|/det|> +2) On page 5 the authors give a value of1.56 GPa? How accurate is this number? T, P effects? + +<|ref|>text<|/ref|><|det|>[[115, 144, 848, 181]]<|/det|> +Referee #1 has also brought up a similar point. To address this, we have adjusted the pressure to 1.6 GPa, which accounts for the uncertainty of \(\pm 0.05\) GPa. + +<|ref|>text<|/ref|><|det|>[[115, 207, 853, 243]]<|/det|> +3) On page 6: It was stated and suggested that crystallization occurs into ice VII, although without time-resolved XRD measurements this proposition remains to be proven. Ref? + +<|ref|>text<|/ref|><|det|>[[115, 252, 870, 305]]<|/det|> +The relevant references (14- 17) have already been cited a few lines earlier. To avoid redundancy and maintain the flow of the text, we have chosen not to repeat them in this instance. + +<|ref|>text<|/ref|><|det|>[[115, 333, 872, 368]]<|/det|> +4) Pg. 6: excellent agreement between the different pressure determinations. Can the authors be clearer on this point? Perhaps by simply referring to the figures. + +<|ref|>text<|/ref|><|det|>[[115, 377, 876, 430]]<|/det|> +A reference to Figure 3 was added accordingly, showing that the pressure determination from the different gauges (Cu, Ice VII and SrB4O7 : Sm2+) are consistent with each other. + +<|ref|>text<|/ref|><|det|>[[115, 457, 808, 492]]<|/det|> +5) On Pg. 7, it is stated that there was a e previous domain of investigation in d-DAC experiments. A reference. is needed here. + +<|ref|>text<|/ref|><|det|>[[115, 502, 594, 520]]<|/det|> +The corresponding references (18- 20) have been added. + +<|ref|>text<|/ref|><|det|>[[115, 547, 810, 582]]<|/det|> +6) without time-resolved XRD measurements this proposition remains to be proven. A reference should be made here. + +<|ref|>text<|/ref|><|det|>[[115, 592, 474, 610]]<|/det|> +This point has been answered in point #3. + +<|ref|>text<|/ref|><|det|>[[115, 636, 821, 672]]<|/det|> +7) On page. 9 the authors state "Since water and ice are quite incompressible" Here a comparison with other triatomic molecules would strengthen this statement. + +<|ref|>text<|/ref|><|det|>[[115, 681, 878, 824]]<|/det|> +The bulk modulus of water ice is approximately 20 GPa, which is relatively high compared to other molecular systems, such as NH3 (4.2 GPa). However, the focus of this analysis is not on the incompressibility of the system, but rather on the assumption of constant compressibility. By using a first- order Birch equation of state (EoS), assuming constant compressibility, which is a reasonable approximation over the 10 GPa pressure range considered, we can derive a phenomenological model fit function with three free parameters (Equation 4). This function provides a good fit for the data obtained from diamond anvil cell (d- DAC), laser, and gas gun experiments, as shown in Figure 6. + +<|ref|>text<|/ref|><|det|>[[115, 833, 751, 850]]<|/det|> +We have removed the assertion: ' since water and ice are incompressible'. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 100, 875, 189]]<|/det|> +8) It is important to emphasize that the model employed to fit the data is a classical nucleation theory description of the experimental results. It fits the data very well and provides a very good physical picture and interpretation of the experimental results but this depends on parameters used for fitting the data so small changes in the parameters employed could have a significant effect on the model used. This could be mentioned by the authors. + +<|ref|>text<|/ref|><|det|>[[115, 198, 875, 270]]<|/det|> +We have explicitly stated in the text that the phenomenological model used serves as a fitting function. To further clarify this, we have slightly modified the caption of Figure 6 to read: 'Fitted using the CNT- based phenomenological model given in Equation 4, with the three free parameters equal to ... + +<|ref|>text<|/ref|><|det|>[[115, 303, 878, 410]]<|/det|> +This report follows up on the previous domain of investigation in d- DAC experiments focusing on the solidification of metastable water. This is the key goal reached in this study. The authors clearly state that support the hypothesis that metastable water, within the pressure range of 1.5 GPa to 2.1 GPa, nucleates into ice VII first, despite this range being the stability field of ice VI. results offer a clarification to the apparent contradiction of the previous findings. + +<|ref|>text<|/ref|><|det|>[[115, 411, 875, 500]]<|/det|> +In summary, this manuscript clearly addresses and presents a solution to the phase transition discrepancies in the literature. A key improvement in the measurement technique was time- resolved X- ray diffraction. This technique is very well described in the manuscript All figures were clearly presented and definitely provided added clarity to the report. Acceptance is therefore suggested after the minor comments listed above are addressed. + +<|ref|>sub_title<|/ref|><|det|>[[116, 588, 224, 604]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[115, 622, 870, 890]]<|/det|> +The authors investigated the interesting behaviour of water ice under dynamic compression with various compression rates using d- DAC by time- resolved x- ray diffraction method and found that ice VII crystallise under the conditions where ice VI should be stable. They also interpret the excess pressure and growth time during the crystallization of ice VII using a phenomenological model based on the classical nucleation theory, succeeding in a comprehensive explanation for the growth rate of ice VII grown under various compression rates. The investigated technique, x- ray diffraction with ruby fluorescence observations at micro- to milli- second order, is somehow remarkable, and the overall achievements of this study would be worth recognising for the ice community. Thus, I do not doubt that this manuscript should be eventually published in at least some specific journal, but I am not sure whether this manuscript will be published by Nature Communication. Two key points in assessing the value of this study would be 1) how new the observed results are and 2) how much their interpretation will influence other related studies. First, concerning the observed results, it should be stated that no truly new phenomena have been reported in this study. It has long been known among ice researchers that ice VII nucleates in the stable region of ice VI even under static compression (e.g. K. Yamamoto, Jpn J Appl Phys, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 874, 224]]<|/det|> +19, 1841, 1980, doi: 10.1143/JJAP.19.1841). A recent study using d- DAC has also reported ice VII nucleation in the stability region of ice VI [18]. Therefore, what is new in this manuscript are the results of quantitative experiments on how the growth rate of ice VII changes when the compression rate is varied. The experimental results in this study are novel in the sense that they are quantitative, but the observed phenomena themselves are not particularly novel. The manuscript also does not elaborate on how the quantitative growth rates obtained might affect other related studies. It is therefore difficult to assess, at least at the moment, how important these results are. + +<|ref|>text<|/ref|><|det|>[[115, 233, 866, 305]]<|/det|> +It is true that the nucleation of ice VII in the stability field of ice VI and the increase in the pressure of overcompressed metastable water with the compression rate were previously known phenomena. But being able to provide an explanation of phenomena through quantitative measurement is the ultimate goal of the physical science research. + +<|ref|>text<|/ref|><|det|>[[115, 313, 864, 525]]<|/det|> +As acknowledged by reviewer #3, the possibility to control the compression rate over 4 orders of magnitude and to perform time resolved XRD and imaging with the appropriate time- frame from microsecond to millisecond is a significant accomplishment. The quantitative measurements obtained through this approach have enabled us to clarify and unify all previous measurements of the freezing of overcompressed water in a coherent interpretation. Metastable water overcompression under dynamical compression has been the subject of many studies over the past 20 years, many published in high impact journals, as a textbook case of phase transition occurring under far- from- equilibrium conditions. In the present case of water solidification at extreme overcompression, we were able to test a universal scaling law, recently proposed. The Classical Nucleation Theory was shown to unify all previous measurements which lacked the microscopic XRD information. + +<|ref|>text<|/ref|><|det|>[[115, 535, 874, 871]]<|/det|> +Regarding the solidification of ice VII in the stability domain of ice VI, we thank reviewer#3 for providing this Jp. J. Appl. Phys. reference. However, in it, the reported observation of ice VII in the stability field of ice VI is not exactly what is reported in our study. The nucleation of ice VII was obtained at the metastable extension of the melting line of ice VII in the stability field of ice VI by heating the sample so that the overcompression of water that can be obtained under quasi- static compression could reach the metastable melting line of ice VII. Nucleation of ice VII is stated then to occasionally form and a facetted single crystal of ice VII can bestabilized in equilibrium with the liquid. However, ice VII is kept metastable only if facetted in equilibrium with the liquid. That is exactly what we observed and used in the experiment reported in our supplementary material to precisely extend the ice VII melting line in the stability domain of ice VI. We now have cited the reference in our supplementary information. However, out of this liquid- solid phase equilibrium, by slightly increasing pressure ice VII transforms into ice VI. We are reported a different story here. Under dynamical compression, metastable water always freeze into ice VII in the metastability domain of ice VII and then ice VII transforms to ice VI over a ms time scale and a mixture ice VI - ice VII then exists, which should eventually evolve to an amorphous - ice VI mixture. This resolves all previous contradictions of the literature between reports of amorphous HAD, HAD- ice VI mixture or ice VII. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 100, 877, 152]]<|/det|> +Even if the importance of this manuscript is recognised by other reviewers and considered for publication in Nat. Commun., the following concerns remain and should be fully considered before potential publication. + +<|ref|>text<|/ref|><|det|>[[115, 170, 866, 294]]<|/det|> +- The authors assume that the sample temperature should not be increased by the rapid compression, but it should be more carefully evaluated and explained in the manuscript. I also believe that temperature might be quickly stable at room temperature owing to the high thermal conductivity of the diamond. However, if the sample size is enough large, this might not be the case since the thermal conductivity of ice VII would not be such high, so the temperature could temporally increase in a very short time. This issue should be quantitatively assessed, for example, by FEM simulation. + +<|ref|>text<|/ref|><|det|>[[114, 304, 877, 535]]<|/det|> +The temperature increase in the sample could be an issue. A recent d- DAC measurement leveraged this effect to measure the Gruneisen parameter but for doing that they had to put a layer of zirconia powder on the anvil tip to prevent heat loss from the diamond (ref. 25). We have taken steps to quantify the heating associated to rapid compression by using two pressure luminescence gauges, specifically ruby and SrB40.7:Sm2+, positioned inside the sample chamber, as detailed in ref. 29. The luminescence line of ruby depends on pressure and temperature, whereas that of Samarium depends only on pressure. This method has been previously used to accurately measure melting lines (Datchi et al, PRB 61, 6535). We thus could show that the heating of the sample is negligible. That is illustrated in the figure below showing that, no discernible heating was detected within the measurement's sensitivity, approximately \(\pm 3 \mathrm{~K}\) . Therefore, we can confidently assert that there is no heating occurring. We have now included this quantification of the absence of heating in the supplementary material. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[240, 82, 753, 448]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 453, 875, 480]]<|/det|> +
Dynamic compression of liquid water at a compression rate (10 GPa/ms). The sample pressure over time is measured using simultaneously the \(S\vert \mathrm{text}(SrB)_2[4]\vert \mathrm{text}(O)_2[7]\vert \mathrm{text}(Sm)^\wedge (2 + )S\) and the ruby fluorescence
+ +<|ref|>text<|/ref|><|det|>[[115, 506, 875, 686]]<|/det|> +- In the adopted phenomenological model for the nucleation rate, authors ignore the effect of crystal growth, but only take the nucleation rate into account. However, I recognized that the grown ice VII may be somehow coarse crystalline size because the observed diffraction patterns are not like smooth lines but spotty. In particular, I found 111 spots of ice VII, which should be very very weak (generally invisible) if the specimen is fine powder, showing the specimen should be somehow coarse aggregates of many single crystals. The actual rate of ice VII growth may be expressed as the combination of nucleation and growth rates. In fact, the results obtained in this study could be interpreted by different phenomenological models, such as the simple JMAK model. The point would be 'which model is the best' to describe the observed phenomena. Even if one model fits well, this does not necessarily mean that this is the only correct model. + +<|ref|>text<|/ref|><|det|>[[115, 686, 880, 753]]<|/det|> +Plus, I am also concerned about the lack of temperature terms in the adopted model. I suppose the temperature term should appear since the classical nucleation theory generally has it. Authors should discuss this point (why temperature term could be ignored), if they stick to this model only. + +<|ref|>text<|/ref|><|det|>[[115, 753, 872, 840]]<|/det|> +First, it is important to note that there is no temperature term involved, as explained above. In the discussion, we begin with the JMAK model and make the assumption that the nucleation rate is predominant over the growth rate. This assumption has been previously utilized in the analysis of overcompression studies of water (ref. 15 and Ref. 16). + +<|ref|>text<|/ref|><|det|>[[115, 850, 877, 904]]<|/det|> +We have explicitly stated in the text that, for compression rates exceeding a few GPa/ms, this assumption appears reasonable. This conclusion is drawn from the imaging observation of instantaneous nucleation throughout the entire sample chamber, as well + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 850, 152]]<|/det|> +as the absence of a plateau in the pressure - time evolution during compression. This pertains to the data points presented in figure 6. Conversely, for data points obtained below 1 GPa/ms, a plateau is observed and the growth of the crystallites is imaged, as shown in figure 2. So + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[225, 83, 771, 100]]<|/det|> +, we believe we correctly explain the framework of our analysis. + +<|ref|>text<|/ref|><|det|>[[115, 126, 880, 181]]<|/det|> +- Previous studies using d-DAC reported that ice VI and HDA coexist [19,20] as mentioned in the manuscript, but HDA was not observed in this study. The authors should describe the difference from the previous study. + +<|ref|>text<|/ref|><|det|>[[115, 190, 876, 243]]<|/det|> +At the end of the section on crystallization of ice VII in the stability domain of ice VI, we explicitly mention that ice VII transforming into ice VI could evolve to a mixture of ice VI and HDA. We have no experimental evidence for a more ascertain statement. + +<|ref|>text<|/ref|><|det|>[[115, 262, 223, 278]]<|/det|> +Minor points + +<|ref|>text<|/ref|><|det|>[[115, 279, 876, 384]]<|/det|> +1. The precise wavelength should be described in Method section. I found the \(x\) -ray energy is \(19 \mathrm{keV}\) , but the number of significant figures is only two in this case. +2. The reflection indices should not be in parenthesis. Index in parenthesis, (hkl) means Miller index that is used for corresponding Miller plane in real space. But reflection index, hkl, in reciprocal space should not have any parenthesis (see International Tables for crystallography, for this criterion). + +<|ref|>text<|/ref|><|det|>[[115, 394, 483, 411]]<|/det|> +The manuscript was modified accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 439, 864, 474]]<|/det|> +3. Effective digit and/or the error should be considered throughout the whole manuscript, in particular, in Table I. + +<|ref|>text<|/ref|><|det|>[[115, 484, 740, 502]]<|/det|> +This comment was taken into account throughout the whole manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 316, 101]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[118, 137, 437, 154]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 163, 834, 206]]<|/det|> +The authors have adequately responded to my comments on their first submission. I'm happy to recommend publication. + +<|ref|>sub_title<|/ref|><|det|>[[118, 266, 437, 284]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 292, 792, 336]]<|/det|> +This manuscript has clarified the occurrence of crystallization into ice VII occurs in between19 + +<|ref|>text<|/ref|><|det|>[[118, 344, 866, 414]]<|/det|> +1.6 GPa and 2.0 GPa, that is in the stability field of ice VI. This was achieved by employing time-resolved X-ray diffraction and a Diamond-Annil-Cell, with pressure rise times from 0.1 ms to 100 ms. + +<|ref|>text<|/ref|><|det|>[[117, 422, 872, 492]]<|/det|> +The authors have added appropriate references as suggested by the reviewers. The authors have also added appropriate clarifying sentences in response to reviewer's remarks and questions. + +<|ref|>text<|/ref|><|det|>[[117, 500, 878, 623]]<|/det|> +An important exception to this is an incorrect comment made by the authors regarding an important reference to an article by cited by a reviewer. The authors state in their rebuttal comments "We now have cited the Yamamoto reference in our supplementary information" This is not seen in the revised manuscript and supplementary information copy submitted by the authors. + +<|ref|>text<|/ref|><|det|>[[117, 631, 850, 728]]<|/det|> +In summary, this revised manuscript describes in more detail than previously published studies the results of a re- examination of the phase transition of water to ice VII. It is not clear however that providing additional details of a known phase transition qualifies for acceptance in Nature. + +<|ref|>sub_title<|/ref|><|det|>[[118, 789, 437, 805]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 815, 415, 831]]<|/det|> +Please find the attached comments. + +<|ref|>text<|/ref|><|det|>[[118, 850, 719, 868]]<|/det|> +[editorial note: please see the next page(s) for reviewer #3's comments.] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 87, 900, 128]]<|/det|> +Comments on the manuscript entitled 'Metastable water at several compression rates and its freezing kinetics into ice VII" by Pepin et al., + +<|ref|>text<|/ref|><|det|>[[87, 175, 880, 263]]<|/det|> +I noticed other two reviewers appreciated the importance of this study, which is in itself pleasing as a researcher in ice study. Although I understand most of authors rebuttal comments, authors replies to my comments raised the following further concerns. I point out my concerns as replies (bold) following to the rebuttal comments from the authors (italic). + +<|ref|>text<|/ref|><|det|>[[88, 311, 104, 325]]<|/det|> +1. + +<|ref|>text<|/ref|><|det|>[[85, 342, 911, 568]]<|/det|> +Regarding the solidification of ice VII in the stability domain of ice VI, we thank reviewer#3 for providing this Jp. J. Appl. Phys. reference. However, in it, the reported observation of ice VII in the stability field of ice VI is not exactly what is reported in our study. The nucleation of ice VII was obtained at the metastable extension of the melting line of ice VII in the stability field of ice VI by heating the sample so that the overcompression of water that can be obtained under quasi- static compression could reach the metastable melting line of ice VII. Nucleation of ice VII is stated then to occasionally form and a facetted single crystal of ice VII can bestabilized in equilibrium with the liquid. However, ice VII is kept metastable only if facetted in equilibrium with the liquid. That is exactly what we observed and used in the experiment reported in our supplementary material to precisely extend the ice VII melting line in the stability domain of ice VI. We now have cited the reference in our supplementary information. + +<|ref|>text<|/ref|><|det|>[[86, 581, 902, 715]]<|/det|> +However, out of this liquid- solid phase equilibrium, by slightly increasing pressure ice VII transforms into ice VI. We are reported a different story here. Under dynamical compression, metastable water always freeze into ice VII in the metastability domain of ice VII and then ice VII transforms to ice VI over a ms time scale and a mixture ice VI - ice VII then exists, which should eventually evolve to an amorphous - ice VI mixture. This resolves all previous contradictions of the literature between reports of amorphous HAD (could be HDA?), HAD- ice VI mixture or ice VII. + +<|ref|>text<|/ref|><|det|>[[88, 763, 340, 779]]<|/det|> +and the reply to the last comment. + +<|ref|>text<|/ref|><|det|>[[85, 794, 905, 890]]<|/det|> +- Previous studies using d-DAC reported that ice VI and HDA coexist [19,20] as mentioned in the manuscript, but HDA was not observed in this study. The authors should describe the difference from the previous study. At the end of the section on crystallization of ice VII in the stability domain of ice VI, we explicitly mention that ice VII transforming into ice VI could evolve to a mixture of ice VI and HDA. We have no experimental + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 186, 896, 342]]<|/det|> +I agree the dynamic compression may be somehow different to the static compression, but one point I would indicate is that the metastable ice VII made by the static compression in ice VI stability region also eventually convert to ice VI, since it is metastable. The difference to the static compression would be the degree of over- compression (AG between liquid and ice VII). Facet morphology found in ice VII by the static compression could also be found in that made by the dynamic compression in sub- micrometer scale, which could be just the difference of size. In that sense, the phenomenological difference between static and dynamic compression may be still unclear. + +<|ref|>text<|/ref|><|det|>[[86, 355, 907, 536]]<|/det|> +In this study, the HDA- ice VI mixture was not observed, and may not be explained the clear reason why HDA was observed in the previous study as stated in the reply to the last comment. It is briefly mentioned in the line 190- 197, as 'This difference could be explained by the fact that at 1.8 GPa, ice VII is approaching its thermodynamic stability, allowing for the stabilization of a mixture of ice VI and ice VII, whereas at 1.7 GPa, ice VII is gradually transforming, leading to the stabilization of a mixture of ice VI and amorphous ice.' But I could not satisfy this description resolves all previous contractions. The present results would show even another contradiction in the sense that they could not observe amorphous state. + +<|ref|>text<|/ref|><|det|>[[87, 583, 104, 598]]<|/det|> +2. + +<|ref|>text<|/ref|><|det|>[[87, 614, 907, 702]]<|/det|> +We thus could show that the heating of the sample is negligible. That is illustrated in the figure below showing that, no discernible heating was detected within the measurement's sensitivity, approximately \(\pm 3 \text{K}\) . Therefore, we can confidently assert that there is no heating occurring. We have now included this quantification of the absence of heating in the supplementary material. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[100, 90, 410, 280]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[92, 281, 464, 295]]<|/det|> +
Dynamic compression of liquid water at a compression rate (10 GPa/ms). The sample pressure over time is measured using simultaneously the S(Text(Si6)_[4]/text(O)_[7]/text(Sm)^(2+)/S and the ruby fluorescence
+ +<|ref|>text<|/ref|><|det|>[[87, 342, 901, 430]]<|/det|> +From the above figure, I could see significant increases in temperatures, exceeding 315 K (42 °C), it does not look like \(\pm 3\) K. Plus, the plot in Fig. 9 shows the temperature \(\sim 21\) °C (294 K), it contradicts with the above figure. If the temperature changes over 10 K, the story might change since the experimental conditions are close to the melting line. + +<|ref|>image<|/ref|><|det|>[[108, 455, 603, 792]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[87, 852, 755, 869]]<|/det|> +Finally one minor question for the above figure, what is the blue atom in ice VI structure? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 84, 528, 102]]<|/det|> +## Detailed answer to reviewers' comments. + +<|ref|>sub_title<|/ref|><|det|>[[115, 130, 248, 148]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 167, 856, 199]]<|/det|> +The authors have adequately responded to my comments on their first submission. I'm happy to recommend publication. + +<|ref|>text<|/ref|><|det|>[[115, 227, 505, 243]]<|/det|> +We thank reviewer #1 for his recommendation. + +<|ref|>sub_title<|/ref|><|det|>[[115, 288, 248, 306]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 324, 875, 390]]<|/det|> +This manuscript has clarified the occurrence of crystallization into ice VII occurs in between 1.6 GPa and 2.0 GPa, that is in the stability field of ice VI. This was achieved by employing time- resolved X- ray diffraction and a Diamond- Anvil- Cell, with pressure rise times from 0.1 ms to 100 ms. + +<|ref|>text<|/ref|><|det|>[[115, 392, 876, 492]]<|/det|> +The authors have added appropriate references as suggested by the reviewers. The authors have also added appropriate clarifying sentences in response to reviewer's remarks and questions. An important exception to this is an incorrect comment made by the authors regarding an important reference to an article by cited by a reviewer. The authors state in their rebuttal comments "We now have cited the Yamamoto reference in our supplementary information" This is not seen in the revised manuscript and supplementary information copy submitted by the authors. + +<|ref|>text<|/ref|><|det|>[[115, 493, 866, 544]]<|/det|> +In summary, this revised manuscript describes in more detail than previously published studies the results of a re- examination of the phase transition of water to ice VII. It is not clear however that providing additional details of a known phase transition qualifies for acceptance in Nature. + +<|ref|>text<|/ref|><|det|>[[115, 562, 848, 612]]<|/det|> +We thank reviewer #2 for his feedback on our revised manuscript. We acknowledge the oversight regarding the the Yamamoto reference and have now included it in the revised supplementary information. + +<|ref|>text<|/ref|><|det|>[[115, 629, 876, 694]]<|/det|> +However, we are surprised by the change in Reviewer #2's appreciation of our manuscript. Initially, the reviewer suggested acceptance after minor comments were addressed, but he/she is now questioning the suitability of our work for publication in Nature. This change in stance is unexpected and lacks clarification. + +<|ref|>sub_title<|/ref|><|det|>[[115, 763, 248, 781]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 820, 866, 870]]<|/det|> +I noticed other two reviewers appreciated the importance of this study, which is in itself pleasing as a researcher in ice study. Although I understand most of authors rebuttal comments, authors replies to my comments raised the following further concerns + +<|ref|>text<|/ref|><|det|>[[115, 881, 845, 914]]<|/det|> +I agree the dynamic compression may be somehow different to the static compression, but one point I would indicate is that the metastable ice VII made by the static compression in ice VI + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 877, 301]]<|/det|> +stability region also eventually convert to ice VI, since it is metastable. The difference to the static compression would be the degree of over- compression (AG between liquid and ice VII). Facet morphology found in ice VII by the static compression could also be found in that made by the dynamic compression in sub- micrometer scale, which could be just the difference of size. In that sense, the phenomenological difference between static and dynamic compression may be still unclear. In this study, the HDA- ice VI mixture was not observed, and may not be explained the clear reason why HDA was observed in the previous study as stated in the reply to the last comment. It is briefly mentioned in the line 190- 197, as 'This difference could be explained by the fact that at 1.8 GPa, ice VII is approaching its thermodynamic stability, allowing for the stabilization of a mixture of ice VI and ice VII, whereas at 1.7 GPa, ice VII is gradually transforming, leading to the stabilization of a mixture of ice VI and amorphous ice.' But I could not satisfy this description resolves all previous contractions. The present results would show even another contradiction in the sense that they could not observe amorphous state. + +<|ref|>text<|/ref|><|det|>[[115, 311, 878, 532]]<|/det|> +We respectfully disagree with reviewer #3. There is a phenomenological difference between static and dynamic compressions concerning the observation of stable ice VII in the stability field of ice VI. In the static experiment, ice VII was brought into the stability field of ice VI by following the metastable melting line of ice VII down to 300K. If the melting equilibrium is lost and complete solidification occurs, ice VII transforms to ice VI. In dynamical compression, the over- compression pressure of metastable water is increasing with the compression rate. For compression rates in between 0.15 GPa/ms sans 0.9 GPa/ms, the freezing of metastable water falls in the stability domain of ice VI and in the metastability domain of ice VII, as determined by the extension of the melting line of ice VII. Our study shows that metastable water under such conditions always freezes in ice VII and then transforms into ice VI over a few milliseconds. Using time resolved XRD we could thus show a preferred nucleation mechanism into ice VII which was not shown by static measurements. + +<|ref|>text<|/ref|><|det|>[[115, 541, 878, 763]]<|/det|> +Regarding the formation of amorphous ice, HDA, as reported by previous studies based on Raman measurements, we are unable to observe it because it is a too weak signal by X- ray diffraction. It should also be noted that a mixture of fine powder of ice VI and ice VII would have a Raman signal that looks like the one of HDA ice. The important points of our study are the preferred nucleation of water into ice VII and then the time- scale of the transformation into ice VI. Whether there is complete transformation into ice VI, a mixture of ice VI and ice VII, a mixture of ice VI and HDA could depend of the final pressure of the rapid compression. We have modified the manuscript to make this point clearer. The sentence now reads: "This difference could be explained by the fact that at 1.8 GPa, ice VII is approaching its thermodynamic stability, allowing for the stabilization of a mixture of ice VI and ice VII (and a possible amorphous state, which could not be observed in our case due to its very low diffraction power), whereas at 1.7 GPa, ice VII has been reported to gradually transform in a mixture of ice VI and amorphous ice." + +<|ref|>text<|/ref|><|det|>[[116, 799, 864, 866]]<|/det|> +From the above figure, I could see significant increases in temperatures, exceeding 315 K (42 °C), it does not look like \(\pm 3\) K. Plus, the plot in Fig. 9 shows the temperature \(\sim 21\) °C (294 K), it contradicts with the above figure. If the temperature changes over 10 K, the story might change since the experimental conditions are close to the melting line. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[228, 82, 765, 460]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 475, 822, 527]]<|/det|> +We apologize for any confusion caused by the previous error bars in our temperature measurements. The \(\pm 3 \mathrm{K}\) error bar was taken from the reference article based on the luminescence gauges, but we have since re- estimated the error bars to be \(\pm 10 \mathrm{K}\) . + +<|ref|>text<|/ref|><|det|>[[115, 536, 880, 688]]<|/det|> +We would like to point out that the temperature relation in our study was obtained in non- hydrostatic pressure conditions, whereas in ref. 29, the error bar estimation was obtained in a hydrostatic pressure medium. This impacts the fluorescence of the ruby by broadening the peaks and making them asymmetrical, which slightly skews the pressure measurements. This is evidenced in the bottom graph of the figure provided. If a temperature increase were to take place during the fast compression, the temperature should be an increasing function of time throughout the entire compression sequence. However, this is not the case here, as we observed the temperature oscillating around the initial temperature of \(294 \mathrm{K}\) , within a \(\pm 10 \mathrm{K}\) error bar. + +<|ref|>text<|/ref|><|det|>[[115, 699, 863, 766]]<|/det|> +Furthermore, if we consider a temperature increase of \(10 \mathrm{K}\) for our point under 14.82 GPa/ms, the figure below shows that it corresponds to a pressure difference in the overcompression of metastable water of \(\sim 0.06 \mathrm{GPa}\) , which is within the error bars that we considered in our models of figures 5 and 6. + +<|ref|>text<|/ref|><|det|>[[115, 777, 866, 810]]<|/det|> +In conclusion, the temperature increase during compression is very small and if any, of the order of \(10 \mathrm{K}\) , does not affect the overall results and conclusions of our study. + +<|ref|>text<|/ref|><|det|>[[115, 820, 875, 871]]<|/det|> +We have slightly modified the manuscript to reflect this and the figure as shown above. The sentence now reads: "That is illustrated by the figure below showing that, no discernible heating was detected within the measurement's sensitivity, approximately \(\pm 10 \mathrm{K}\) ". + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[212, 85, 780, 475]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 536, 816, 553]]<|/det|> +Finally one minor question for the above figure, what is the blue atom in ice VI structure? + +<|ref|>text<|/ref|><|det|>[[115, 562, 848, 597]]<|/det|> +This is just a visual representation of the oxygen atoms occupying two different positions (Wycoff site 2b in blue and 8g in red). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 85, 330, 101]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 137, 439, 180]]<|/det|> +Reviewer #3 (Remarks to the Author): Please find the attached comments. + +<|ref|>text<|/ref|><|det|>[[118, 224, 720, 241]]<|/det|> +[editorial note: please see the next page(s) for reviewer #3's comments.] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[88, 84, 909, 133]]<|/det|> +1. I acknowledge the author's comments on my previous concerns regarding the phenomenological difference between static and dynamic compression. First, I would indicate one fact that ice VII could also nucleate into the stability field of ice VI as written by Yamamoto et al., described as + +<|ref|>text<|/ref|><|det|>[[87, 142, 904, 176]]<|/det|> +"...it was discovered in the present experiment that ice VII occasionally formed directly from water at point B in Fig. 1 without the formation of ice VI at point A." (see below) + +<|ref|>text<|/ref|><|det|>[[295, 330, 439, 347]]<|/det|> +[figure redacted] + +<|ref|>text<|/ref|><|det|>[[88, 686, 543, 703]]<|/det|> +Therefore, the author's indication in their rebuttal comments, + +<|ref|>text<|/ref|><|det|>[[88, 711, 899, 760]]<|/det|> +"In the static experiment, ice VII was brought into the stability field of ice VI by following the metastable melting line of ice VII down to 300K. If the melting equilibrium is lost and complete solidification occurs, ice VII transforms to ice VI." + +<|ref|>text<|/ref|><|det|>[[88, 770, 243, 785]]<|/det|> +is misunderstanding. + +<|ref|>text<|/ref|><|det|>[[88, 794, 861, 844]]<|/det|> +But, if in the dynamic compression ice VII "always" preferably nucleates rather than ice VI, this is the phenomenological difference since in the static compression ice VII could only "occasionally" nucleate. Authors could emphasize this point with the reference to Yamamoto et al. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 83, 907, 215]]<|/det|> +2. As for the description of (non)appearance of HDA, the added sentence "(and a possible amorphous state, which could not be observed in our case due to its very low diffraction power)" is a bit inaccurate since the diffraction power ("scattering power" may be more appropriate term in the case of amorphous, though "diffraction power" is also correct) itself is comparable to the crystalline material if all integrated through whole reciprocal space. I suggest this sentence would be "...in our case since the scattering from amorphous may be hidden in the Bragg peaks even it exists" or so. In any case, the last sentence of this paragraph, "These results offer a clarification to the apparent contradiction of the previous findings." seems a bit overstatement to me. + +<|ref|>text<|/ref|><|det|>[[87, 224, 907, 338]]<|/det|> +3. I consider, repeatedly saying, that the difference to static compression would be the degree of overcompression. The over-compression as large as a few GPa could not be achieved by the static compression. The strong point of this study would be the quantitative analysis of the nucleation time as a function of the over-compression. This is the reason why I repeatedly indicate the quantitative considerations for the temperature effect since I suppose the \(10\mathrm{K}\) difference is huge for water molecules at a few GPa regions. I suggest some comments on the temperature effect, as written in the rebuttal comments, may be included in the main text as well. + +<|ref|>text<|/ref|><|det|>[[88, 346, 622, 363]]<|/det|> +4. Regarding the qualitative analysis, I pointed out in the first comment, + +<|ref|>text<|/ref|><|det|>[[87, 371, 902, 404]]<|/det|> +"Effective digit and/or the error should be considered throughout the whole manuscript, in particular, in Table I." + +<|ref|>text<|/ref|><|det|>[[88, 414, 235, 430]]<|/det|> +and authors replied, + +<|ref|>text<|/ref|><|det|>[[88, 439, 640, 456]]<|/det|> +"This comment was taken into account throughout the whole manuscript." + +<|ref|>text<|/ref|><|det|>[[87, 464, 910, 580]]<|/det|> +I did not carefully check in the second round (since I believed this reply), but I realized that Table I was not modified yet. For example, the rate of compression in the first raw is written as '870787.5 (GPa/ms)". I could not believe the effective digit could reach 7 digits, such very precise pressure control would not be possible. Similarly, in the caption of Figure 6, the parameter b is written like "b=245293534.93", which is also unrealistic effective digit considering the fitting result shown in Figure 6. Such representations without care of effective digits led readers to the question of the whole results of this study. Authors should carefully check again this point. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 84, 528, 103]]<|/det|> +## Detailed answer to reviewers' comments. + +<|ref|>text<|/ref|><|det|>[[115, 136, 870, 201]]<|/det|> +1- I acknowledge the author's comments on my previous concerns regarding the phenomenological difference between static and dynamic compression. First, I would like to point out that ice VII could also nucleate within the stability field of ice VI, as written by Yamamoto et al., described as: + +<|ref|>text<|/ref|><|det|>[[115, 202, 876, 366]]<|/det|> +"...it was discovered in the present experiment that ice VII occasionally formed directly from water at point B in Fig. I without the formation of ice VI at point A." (see below) Therefore, the author's statement in their rebuttal comments, "In the static experiment, ice VII was brought into the stability field of ice VI by following the metastable melting line of ice VII down to 300K. If the melting equilibrium is lost and complete solidification occurs, ice VII transforms to ice VI." is a misunderstanding. However, if under dynamic compression ice VII "always" nucleates preferentially rather than ice VI, this would be the phenomenological difference, since under static compression ice VII could only "occasionally" nucleate. The authors could emphasize this point with reference to Yamamoto et al. + +<|ref|>text<|/ref|><|det|>[[116, 382, 879, 434]]<|/det|> +Following the reviewer's advice, we have added a sentence that reads: "It was also shown that ice VII could occasionally nucleate in the stability domain of ice VI above the metastable melting line [41]". + +<|ref|>text<|/ref|><|det|>[[115, 448, 867, 614]]<|/det|> +2- Regarding the description of the (non)appearance of HDA, the added sentence "(and a possible amorphous state, which could not be observed in our case due to its very low diffraction power)" is somewhat inaccurate, as the diffraction power ("scattering power" might be a more appropriate term in the case of amorphous materials, although "diffraction power" is also correct) itself is comparable to that of crystalline material if integrated over the whole reciprocal space. I suggest rephrasing this sentence as "...in our case since the scattering from amorphous material may be hidden in the Bragg peaks even if it exists," or something similar. In any case, the last sentence of this paragraph, "These results offer a clarification to the apparent contradiction of the previous findings," seems a bit of an overstatement to me. + +<|ref|>text<|/ref|><|det|>[[116, 629, 480, 646]]<|/det|> +We have modified the main text accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 661, 876, 778]]<|/det|> +3- I believe, and have repeatedly stated, that the difference with static compression lies in the degree of over-compression. Over-compression as large as a few GPa could not be achieved by static compression. The strength of this study lies in the quantitative analysis of nucleation time as a function of over-compression. This is why I repeatedly emphasize the importance of quantitative considerations regarding the temperature effect, as I believe the 10 K difference is significant for water molecules under a few GPa. I suggest that some comments on the temperature effect, as written in the rebuttal comments, be included in the main text as well. + +<|ref|>text<|/ref|><|det|>[[115, 792, 878, 910]]<|/det|> +We have added a statement in the supplementary information. It reads: "We would like to point out that the temperature relation in our study was obtained in non- hydrostatic pressure conditions, whereas in Ref.\cite{Datchi97}, the error bar estimation was obtained in a hydrostatic pressure medium. This impacts the fluorescence of the ruby by broadening the peaks and making them asymmetrical, which slightly skews the pressure measurements. This is evidenced in the bottom graph of Supplementary Figure \ref{fig:figureS4}. If a temperature increase were to take place during the fast compression, the temperature should be an + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 876, 132]]<|/det|> +increasing function of time throughout the entire compression sequence. However, this is not the case here, as we observed the temperature oscillating around the initial temperature of 294 K, within a \(\pm 10 \mathrm{K}\) error bar. + +<|ref|>text<|/ref|><|det|>[[115, 148, 872, 214]]<|/det|> +Furthermore, if we consider a temperature increase of \(10 \mathrm{K}\) for the point at \(14.82 \mathrm{GPa / ms}\) , it would correspond to a pressure difference in the overcompression of metastable water of \(- 0.06 \mathrm{GPa}\) , which is within the error bars that we considered in our models of figures 5 and 6. ” + +<|ref|>text<|/ref|><|det|>[[115, 231, 870, 428]]<|/det|> +4- Regarding the qualitative analysis, I pointed out in my first comment, "Effective digits and/or errors should be considered throughout the entire manuscript, particularly in Table I," and the authors replied, "This comment was taken into account throughout the entire manuscript." I did not carefully check this during the second round (as I trusted their reply), but I later realized that Table I had not yet been modified. For example, the rate of compression in the first row is written as '870787.5 (GPa/ms).' I cannot believe the effective digits could reach seven digits; such precise pressure control would not be possible. Similarly, in the caption of Figure 6, the parameter \(b\) is written as " \(b = 245293534.93\) ," which is also an unrealistic number of significant digits considering the fitting result shown in Figure 6. Such representations without careful attention to significant digits lead readers to question the overall results of this study. The authors should carefully check this point again. + +<|ref|>text<|/ref|><|det|>[[115, 444, 880, 494]]<|/det|> +We have modified the main text accordingly, carefully checking for effective digits. However, some number have not been modified because they are derived from data from references cited in our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/images_list.json b/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2372b5d0c3963cb8befffe3ac9666dccf48621da --- /dev/null +++ b/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_12.jpg", + "caption": "Rebuttal Figure 1 Posterior probability functions of the inverted source parameters from Event 2. Notations are the same as Supplementary Figure 12 in the manuscript.", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..ab10ad0baa9da53afd691ce35e0552db3112b5a6 --- /dev/null +++ b/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,947 @@ + +# nature portfolio + +Peer Review File + +Episodic transport of discrete magma batches beneath Aso volcano + +![](images/Supplementary_Figure_12.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +## Overall impression + +Overall impressionThe article written by Niu and Song shows an exciting interpretation of tons of tilt and seismic signals that repeatedly occurred at Aso volcano, Japan, with precise analysis procedures and its results. It sheds light on the new concept of the magma plumbing system at the volcano, adding a magma storage zone located between the magma chamber and the conduit. It identifies that this zone's inflation and deflation are associated with episodic magma discharge from below and are indeed relating to the surficial phenomena. After calculating the 1- D conduit flow, it improves the public image of magma ascent dynamics from the magma chamber to the surface. It also provides a future direction of geophysical research to real- time evaluate upcoming eruptions. This article seems to be well- organized, and the methods and results are detailed and very interesting for the scientific community widely. I would recommend their article for publishing in the journal after minor revisions of some comments below I pointed out. + +## Specific comments + +P3 L13 - The authors use the term "long- period tremor (LPT)" for the objected seismic signal in the whole in this article because they respect the nomenclature that had been established in previous papers. However, this term seems to be a local vernacular or jargon only at Aso volcano. I am also suspect that that signal is not a "tremor?" I suggest using the more widely used term VLP or ultra- long- period (ULP) signals in the volcanological field instead of LPT for readers of this journal from more wide backgrounds. + +P4 L4 - Were the VLP signals the authors checked from the catalog associated individually with any surficial eruption activities at the crater during the erupted periods? A paper reported that the occurrence of the VLP seismic signal preceded by few seconds from the onset of Strombolian eruption (Ishii et al., 2019, EPS). What the meaning of a difference of such elapsed time (2 min for Oct. 2016 phreatomagmatic eruption and 2- 3 s for Strombolian explosions), as well as the meaning of a difference with or without eruptions? I think such a time difference may not relate to the patterns of the tilt source. Are there several types of VLPs with similar waveforms, but specific properties are different? Can the author comment on this topic at any part of this article? + +P4 L20 - Can the authors show a result of the same method using another template (Event 2) in the supplementary? I could not find validity to use Event 1 (not 2) as a reference signal in this article. I am convincing that the conclusion will be the same as this article if Event 2 is used. However, curious about the time evolution of the VLPs for the case of 2. + +P5 L15 - The authors should explain the excitation mechanism of the SPT concerning the occurrence of VLP as well as the series of phenomena starting from a deeper place (top of the magma chamber; the authors argue). I could not imagine why the SPT starts at the top portion of the conduit (VLP source) at first, and 10 s later, the VLP occurs (it is the same time as the SPT peak), whenever the events are inflation or deflation. + +P6 L10 - The authors cited Hata et al. (2018, JGR) in this article; however, it seems inappropriate. At least another paper of Hata et al. (2018, JGR, 10.1029/2018JB015951), or much preferable Matsushima et al. (2020, EPS) showing the revised model of the Hata et al.'s result should be cited. + +P6 L20 - Add any comment on how to make seismicity around the roof of the magma chamber if gas- dominant materials transport upward. + +P7 L1 - Can the authors show other evidence of inflation and deflation during these periods? It would be enough to cite some papers of InSAR or GNSS that can strengthen their argument. + +P7 L14 - I could not understand the concept relating to SO2 gas emission. Could the author explain more carefully? The authors describe the prominence of inflation events equivalent to pressurization and lowering SO2 emission. The relation between inflation and pressurization is readily accepted because both are relative + +<--- Page Split ---> + +changes of the SMSZ condition. However, in my understanding, SO2 emission does not seem to this relative change; but relates to the absolute volume of magma transported to a shallow depth. Is this wrong? I could not see a significant correlation between Fig 4b and 4c. + +P9 L11 - Probably the wrong citation; did not Miyabuchi & Hara (2019, EPS) treat the 2016 phreatomagmatic explosion? I guess Ishii (2018, EPS), Ishii et al. (2018, EPS) and Sato et al. (2018, EPS) are more suitable for the mass of ejected materials. + +P11 L 13 - Unclear to me. + +References - It is not good to cite several papers written in Japanese, which most of the readers cannot probably reach and read. Other accessible papers should be referred to in this article as far as possible. The author also should discuss the proposed plumbing system with the result of Tsutsui & Sudo (2004, JVGR). + +Fig. 2 - I guess the exact time of the onset in longer signals is quite tricky. How about the reading error? + +P37 L 14 - need a reference for assumption (or evaluation) + +Reviewer #2 (Remarks to the Author): + +This paper provides interesting new observations of coupled seismic and ground deformation of repeated magma transport events observed at Aso volcano, Japan that are at least sometimes associated with eruptions. These types of high spatial and temporal resolution observations combining these datasets are rare (to my knowledge) and provide a unique perspective on the timing, location, and volume change of magma movements within a volcano. It would be good to get the perspective of an expert on the Aso system, but as far as I can tell, this paper provides new insight into the plumbing system at this volcano and is possibly applicable (in terms of the conceptual model and technique) to other volcanic systems. + +I recommend publication after moderate revision. There are several steps in the analysis that are not well documented (see detailed comments below). Further, the paper is unclear in some locations or the discussion is incomplete (again documented below). + +Page 1: + +Line 10 and Page 1 lines 6- 9: How do we know that Aso has a crystal rich mush and that it is relevant for this study? Maybe the magma batches are coming from a crystal poor reservoir? Maybe the crystal rich mush is deeper? + +Line 14: "individual" should be "an individual" + +Lines 16- 24: I found the following sentences unclear and confusing - - can the authors be more specific? What do you mean by "composition dependent"? Is the composition of each magma batch different? Does the last sentence mean that you can forecast the eruption style, plume height, etc. based on the tilt/seismic data described above? If so provide some more details as to how. + +"whereas their recurrences, potentially composition dependent, are regulated by the brittle- to- ductile transition rheology under low differential stress and high strain rate due to the surge of magma from below, regulating long- term volcanic output rate. The magma ascent velocity, decompression rates, and cumulative magma output deduced from the episodic deformation events before recent eruptions in Aso volcano are compatible with retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real- time evaluation of upcoming eruptions." + +Further, the results shown in Figures 4- 6 aren't really described in the abstract. + +<--- Page Split ---> + +Page 2: + +Line 5: the ambient stress state also matters + +Line 16: Also the ambient stress state matters - - seismicity will only occur where the rocks are near to failure. Magma can move aseismically if the stress state is not close to failure. + +Page 3: + +Line 8: "signal" should be "signals" + +Line 10: How do we know this is a "shallow hydrothermal reservoir"? + +Line 11: use "on" instead of "against" + +Line 12 (and Page 1 line 12): Mentioning the source is near sea level is confusing, how far is this below the surface? It would be better to tell us the depth of the source beneath the surface (or at least tell us both pieces of information). + +Line 16: Need some introduction to the eruptive cycle - - why was the time period 2011- 2016 chosen? Why not a longer time period? Is the LPT only seen in this time period? Is this the only time period when the patterns described below occur? Or some other reason? + +Line 17: "waveform" should be "waveforms" + +Line 21: How do you know these LPT events are "anomalous"? Where do you define normal or background LPT activity? + +Page 4: + +Line 4: where do the displacement waveforms come from? Integration of the seismograms? If so, how? + +Line 5: are these events associated with eruptions? + +Line 6: What does "east- down" mean? Doe that mean tilt toward the east? + +Line 8- 9: This phrase could be more precise: "between the signal of LPT and the tilt offset". Perhaps: "between the LPT signal and the tilt offset at different stations and in the different components at the same station." + +Line 17: Are all the LPT events associated with eruptions? Are there LPT events that aren't found by the matched filter? If so, what type of events do they represent? + +The sections entitled "LPT and synchronous tilt/displacement offset" and "Discovery of the inflation/deflation event beneath Aso volcano" could be better organized. + +It seems to organized in a chronological manner instead of a logical description of what was discovered - - the first paragraph talks about the 2016 eruption, the next paragraph is about a manual search and the next paragraph is about a matched filter. Instead, why not just discuss the procedure (pointing to the Materials and Methods as needed) and then describe what you found? Maybe organize: this is what we analyzed, describe the 2016 events (including the variation in signals between stations) and then the global stack. + +Page 5, + +<--- Page Split ---> + +line 4: How many events are in the stack? Do the number of events vary in time in a systematic manner? What do the unstacked events look like? + +Line 5: what does volcanic unrest mean here? Are there eruptions in 2011- 2014 or are these events occurring without eruption? If so, that is strange - - why do these similar events occur sometimes with eruption and sometimes without? + +Page 6: + +Line 4: Make clear from the source what your forward model is in terms of source characteristics and elastic structure. + +Line 15: What is the composition of the magma batch based on the eruption? One hypothesis is that this portion of magma is ascending because it has accumulated enough gas to become buoyant, so what is known about the gas compositions in the eruptions? + +Line 16: How do we know that this is a crystal rich magma? Is this just a guess or is there some evidence from petrology about the source region? + +Line 20: An alternative is that the magma is that there is no new injection of magma and it is cooling/crystallizing, accumulating gas at the top of the reservoir and then episodically having sufficient buoyancy to cause brittle failure. (This is a top- down instead of a bottom- up trigger for eruptions, see for example Girona, T., Costa, F., & Schubert, G. (2015). Degassing during quiescence as a trigger of magma ascent and volcanic eruptions. Scientific reports, 5(1), 1- 7. + +Page 7: + +Line 18: This conceptual model is reasonable, but what is the evidence that there is a crystal- rich or crystal- poor mush? What is the petrological evidence for the percentage of crystals? Is it really \(>50\%\) in one reservoir and \(< 50\%\) in the other? + +Page 8: + +Line 2: You should be clear that you have demonstrated this for a particular volcano during a particular time period and not imply this is a universal process: "the upward transport of magma/gas from the magma chamber toward the surface is a stepwise process in an episodic fashion" + +Page 9: I'm glad to see the discussion of gas (finally), but what are the observations on degassing rate measured on the ground or by satellite? Is it really likely that some events have a high gas proportion and over events a few months later have a low gas proportion? Further, the volume discrepancy might not have anything to do with gas, but could be due to additional reservoirs being tapped that were filled long before the current eruption (that may not have a tilt/trémor signature). A volume difference of 6- 8 is at the high range considered by Rivalta and Segall (2008) but maybe appropriate for this arc volcano? What do the authors think this ratio implies? The question of gas in the magma could be uniquely addressed with this dataset. + +Page 11: + +Line4: This sentence is filled with either assumptions or claims that aren't yet supported in the manuscript such as the existence of a "crystal- rich mush and crystal- poor pool" + +Line 6: Is this claim discussed further somewhere? If so, I missed it: "The duration of each deformation event ( \(\sim 50\) s) is much longer than what is expected for crustal earthquakes of similar size and such a slow deformation" + +<--- Page Split ---> + +The perspective could be improved with adding a paragraph or two about how the lessons here could be applied to specific other volcanoes (if possible). Applying the techniques to other volcanoes is mentioned, but what other volcanoes have a similar eruptive style and might be the best targets to investigate? Also, there are many types of eruptions or plumbing systems for which these types of analysis would not work and should be mentioned as well. If additional space is needed, I suggest dropped Figs. 5 and 6 below. + +The data availability statement is not clear: Are the tilt and seismic waveforms available from the link provided? Also the statement that data products are available by request is no longer considered a best practice (for example, it is not allowed by AGU). These data products are not required to be made available in a public repository, but it would add great value if they were. Does UCL have such a repository? + +Fig.1: What are BCU and BYA chambers? They are not mentioned in the caption. Also, what is the depth of the low velocity zone, and other features listed in the legend (maybe refer to Fig. 3)? + +Fig. 2: Some more details are needed in the caption. How many events are stacked together here? How were events horizontally aligned? + +Fig. 3: Where do the horizontal and vertical displacements in a and b come from? GNSS? Or integrated from seismometer? I could be helpful in d to show the depths of the features shown in a, b, and c: where are the low velocity zone, BYA and BCA chambers, inverted source location (Red Cross) and new Mogi (black circle)? Why is there an aquifer labeled in d? I don't think the aquifer is mentioned in the caption or the text. I'm also confused about what is happening in e, f, and g. What are the red and blue dotted lines at the line labeled LPT? What are the arrow at the SPT line? What are the arrows in- between the LPT and SPT lines? What physical processes do these arrows/features represent? + +Fig. 4a: where does the accumulative net volume change come from? The data used to calculate this should be mentioned in the caption. I do not user stand the labels that say, for example, delta V magma \(< <\) delta V gas during time period 1. It looks like the volume change is basically flat during this time period, so shouldn't these two volume changes be in approximate balance instead of orders of magnitude different (as implied by using \(< <\) )? + +Fig. 4b: What is "outgassing potential"? I haven't heard this term before and the phrase used in the caption is still confusing: "the moment ratio between pressurization and 10 depressurization LPTs" + +Fig. 4d: Where is the volume change rate being measured? SMSZ? The caption says the black crosses are the "inflation event" but I think this should be "inflation events." What is the geodetic data used to estimate the green cross? Is this the same tilt data described in this paper or something else, like GNSS? What is the time period of the geodetic data? In general, it should be noted that these volume change rates are being measured over vastly different time periods and the time periods should be mentioned in the caption. + +Fig. 4e: Considering there are only 2 data points, it does not seem wise to draw a line between them. + +Figures 5 and 6 have minimal discussion in the text and do not seem to factor into the key conclusions mentioned in the abstract - - could they be removed? They probably deserve further discussion in a separate paper. Fig. 5 has a huge amount of information that isn't discussed in the main text. In particular, I think Fig. 6 is confusing and possibly misleading. It seems to take a single volcanic system and wildly extrapolate it to all systems worldwide. This figure seems to imply that the magma plumbing system of Aso is relevant to all types of eruptions from Rhylites to flood basalts which is clearly not true - - we have enough information to know that the plumbing of Aso is not widely applicable to all volcanoes. The authors should consider what is the point this figure is trying to make and if it is already made successfully in the text. If the point is that "Composition, viscosity, rheology and tectonic settings govern the recurrences of episodic + +<--- Page Split ---> + +deformation" then this point can be made adequately in the text without confusing the reader. + +Fig. 6: "providing the glue" is a confusing phrase here + +Reviewer #3 (Remarks to the Author): + +Review comments on Episodic transport of discrete magma batches beneath Aso volcano By Jieming Niu, Teh- Ru Alex Song + +This manuscript is quite interesting and is sufficiently valuable to publish on Nature Communications. + +Major comments + +1) Source of tilt offset is discussed in the relation of crystal rich and crystal poor zones. I cannot well understand how to relate the source of tilt off set with the rate of crystal. The reference 48 investigate volatile from the viewpoint of petrology. If source of tilt offset is related with volatile-rich and volatile-poor zones, this might be better understood. + +2) Source of tilt offset is also discussed on brittle-ductile transition zone. However, the authors assumes that tilt offset is induced by volume change of a combination model of tensile crack and explosive source in elastic medium and this model does not include fracture. Brittle and ductile are manners of fracture. Regarding to the model of elastic deformation, source of tilt offset should be discussed on difference in elastic constants along the magma plumbing system. + +3) The significance of comparison of 2011-2016 eruptivity of Aso with basaltic eruptivity is not well understood. As mentioned in the text, long-term eruption rate of andesitic volcanoes is lower than basaltic volcanoes. I cannot find a significance of comparison of eruption rate between andesitic and basaltic volcanoes in this manuscript. The eruption 2011-2016 is an eruptive activity of Aso, however it does not cover all the eruptivity of Aso. If compared, the eruption 2011-2016 should be compared with past eruptivity of Aso or long-term eruptivity of the volcano. + +Minor comments + +P3L20 + +"natural period" -> band width + +P4L12 + +LP signal east- west is much weaker, but north- south is stronger than N.ASIV. + +P4L13 "These observations strongly indicate that the source of the tilt offset is spatially separated from the LPT source" + +It is possible, but is it necessary to examine source difference between tilt offset and LPT? + +P4L14 "which is near the active Naka- dake first crater" + +Show references or see Method. + +P5L3 global waveform stacks + +What do you mean "global"? How many LPTs were stacked? + +P5L9 relatively steady + +Almost the same? + +P5L21 Fig. S4 + +Fig. S4 is "Synthetic amplitude- distance decay against static and filtered waveforms". Inserting Fig. S4 explains why you choose 100- 200s ULP band? + +P7L2 "SMSZ" + +"SMSZ" firstly appeared here. This should be explained. + +P7L5 intense + +Is this word necessary? What do you mean "intense unrest"? + +P7L18 "a deeper reservoir (i.e., a crystal- rich mush) and temporarily stalled in the SMSZ (i.e., a crystal- poor pool)" + +The reference 48 investigate volatile. How does it relate to crystal? Are there any evidence for crystal- poor in the SMSZ? + +<--- Page Split ---> + +P8L1- L7 + +For estimation of volume increase, Method should be referred. + +P8L13- L22 + +This hypothesis is true. As the authors show clearly, LPT is a short- lived phenomenon. What does the author mention, comparing short- lived volume change with long- term eruptivity? + +P10L11- L13 "While the estimated mass flow rate in Aso is lower than those estimated in basaltic eruptions by an order of magnitude (Fig. 5), such a difference is consistent with the disparity in the average volcanic output rate between basaltic eruptions and andesitic eruptions" + +In this case, Aso means activity 2011- 2016? Which eruption does "basaltic eruption" indicate? The first half is comparison of short term activity. Second half is long- term comparison. Long- term comparison may be true. But short- term comparison is case- by- case. It is not necessary to be consistent. + +P22L11Takahiro -> Takahiro + +FiguresP24L9 October 8, 2016Need time of onset of the eruption.(b) N.ASHV.LE is tilt of east- side down at station N.ASHV? + +Is Figure 6 needed? + +<--- Page Split ---> + +In the following response, the comments by the reviewers are shown in italic, our responses are shown in bold. The page and line numbers in the original manuscript are noted as P?L??. The page and line numbers In the revised manuscript are noted as nP?L??. The responses discussed in the rebuttal letter are also highlighted in yellow in the revised manuscript. + +Reviewer #1 (Remarks to the Author): + +Overall impression + +The article written by Niu and Song shows an exciting interpretation of tons of tilt and seismic signals that repeatedly occurred at Aso volcano, Japan, with precise analysis procedures and its results. It sheds light on the new concept of the magma plumbing system at the volcano, adding a magma storage zone located between the magma chamber and the conduit. It identifies that this zone's inflation and deflation are associated with episodic magma discharge from below and are indeed relating to the surficial phenomena. After calculating the 1- D conduit flow, it improves the public image of magma ascent dynamics from the magma chamber to the surface. It also provides a future direction of geophysical research to real- time evaluate upcoming eruptions. This article seems to be well- organized, and the methods and results are detailed and very interesting for the scientific community widely. I would recommend their article for publishing in the journal after minor revisions of some comments below I pointed out. + +We thank the reviewer for the positive comments and support for the publication. + +Specific comments + +P3 L13 - The authors use the term "long- period tremor (LPT)" for the objected seismic signal in the whole in this article because they respect the nomenclature that had been established in previous papers. However, this term seems to be a local vernacular or jargon only at Aso volcano. I am also suspect that that signal is not a "tremor?" I suggest using the more widely used term VLP or ultra- long- period (ULP) signals in the volcanological field instead of LPT for readers of this journal from more wide backgrounds. + +We thank the reviewer for the suggestion. + +Indeed, the LPT is associated with event- like signal, and it does not resemble typical tremors. We have replaced LPT with the more widely recognized term VLP in the revised manuscript. We also replaced the term SPT with the more widely recognized term LP to represent the long- period signal above the crack- like conduit in Aso volcano. + +P4 L4 - Were the VLP signals the authors checked from the catalog associated individually with any surficial eruption activities at the crater during the erupted periods? + +We thank the reviewer for the comment. + +Some VLPs are indeed associated with individual surficial eruption during the erupted periods. This corroborates the observation by Ishii et al. (2019, EPS). We briefly noted this in the revised manuscript (nP11L6). + +A paper reported that the occurrence of the VLP seismic signal preceded by few seconds from the onset of Strombolian eruption (Ishii et al., 2019, EPS). What the meaning of a difference of such elapsed time (2 min for Oct. 2016 phreatomagmatic eruption and 2- 3 s for Strombolian explosions), as well as the meaning of a difference with or without eruptions? I think such a time difference may not relate to the patterns of the tilt source. + +We thank the reviewer's comment. + +Motivated by the discussions by Ishii et al. (2019), we have added two paragraphs and highlighted the implications of these differences against the inferred magma ascent velocity + +<--- Page Split ---> + +in the SMSZ (nP11L3- L13). We conceive that the time delay between VLP and the onset of Strombolian eruption can be reasonably attributed to gas ascent in the shallow conduit under slow magma ascent (e.g., 0.01- 0.1 m/s). On the other hand, the 120 s time delay between Event 2 and the onset of 2016 phreatomagmatic eruption can be reconciled with the relatively magma ascent in the SMSZ (e.g., \(\sim 7 \mathrm{m / s}\) ). + +On the other hand, VLP and synchronous inflation/deflation event does occur with or without eruption. It implies that the occurrence of VLP is likely a necessary condition for surface eruption. As discussed by Niu & Song (2020), conduit/plug permeability and overpressure also play a key role in facilitating surface eruptive activities. We have added a short note in the revised manuscript (nP8L20- L24). + +Are there several types of VLPs with similar waveforms, but specific properties are different? Can the author comment on this topic at any part of this article? + +We thank the reviewer's comment. + +We have commented their differences (e.g., resonance period, initial polarity) in the revised manuscript (nP3L10- L14). + +P4 L20 - Can the authors show a result of the same method using another template (Event 2) in the supplementary? I could not find validity to use Event 1 (not 2) as a reference signal in this article. I am convincing that the conclusion will be the same as this article if Event 2 is used. + +We thank the reviewer for the comments. + +Choosing Event 1 as the template has one advantage in that it potentially minimises the interference from the eruption signal at long period (i.e., 50- 250 sec). However, the waveforms from Event 1 and Event 2 are highly correlated, using Event 2 as the reference event does not result in noticeable difference in the detection of inflation or deflation events. The inverted source location and mechanism from Event 2 are practically the same as those inverted from Event 1 (see figure below). We do not include the inversion result from Event 2 in this paper to avoid redundancy. We emphasized the high correlation between Event 1 and Event 2 in the revised manuscript (nP3L24- P4L1). + +![PLACEHOLDER_9_0] + +
Rebuttal Figure 1 Posterior probability functions of the inverted source parameters from Event 2. Notations are the same as Supplementary Figure 12 in the manuscript.
+ +<--- Page Split ---> + +However, curious about the time evolution of the VLPs for the case of 2. + +We thank the reviewer's comment. + +Perhaps there is a misunderstanding here. We emphasize that waveforms from Event 1 and Event 2 are practical identical in the period of our interest (i.e., 50- 250 sec). Therefore, VLP signal of 10 sec period is not the focus of our detection. Rather, the timing of VLP was used to detect inflation or deflation events. + +In a separate note, the evolution of VLPs has been thoroughly documented by Niu & Song (2020, JVGR) and we refer the reader to this article for details. + +P5 L15 - The authors should explain the excitation mechanism of the SPT concerning the occurrence of VLP as well as the series of phenomena starting from a deeper place (top of the magma chamber; the authors argue). I could not imagine why the SPT starts at the top portion of the conduit (VLP source) at first, and 10 s later, the VLP occurs (it is the same time as the SPT peak), whenever the events are inflation or deflation. + +We thank the reviewer for this comment. + +Following the discussions by Kaneshima et al. (1996) and Kawakatsu et al. (2000), we have added a paragraph to note the possible processes associated with VLP and LP. We emphasize the stress perturbation induced during the initial stage of the inflation/deflation event results in fractures in the conduit plug above the shallow crack- like conduit, promoting LP and VLP (nP6L7- L12). + +We have appended additional paragraphs in the revised manuscript and elaborated the series of phenomena starting from the deep source near the chamber roof (nP7L3- L28). We caution that this is a tentative interpretation at this point and a more elaborated discussion is beyond the main scope of this manuscript. + +P6 L10 - The authors cited Hata et al. (2018, JGR) in this article; however, it seems inappropriate. At least another paper of Hata et al. (2018, JGR, 10.1029/2018JB015951), or much preferable Matsushima et al. (2020, EPS) showing the revised model of the Hata et al.'s result should be cited. + +We thank the reviewer for pointing out this issue. + +We have cited Hata et al. (2018, JGR, 10.1029/2018JB015951) and Matsushima et al. (2020, EPS) in the revised manuscript (nP6L23). + +P6 L20 - Add any comment on how to make seismicity around the roof of the magma chamber if gas- dominant materials transport upward. + +We thank the reviewer for this comment. + +As also included in the reply earlier, we noted the role of gassed magma in the inflation/deflation events in the revised manuscript (nP7L7- L13). The discussions are in line with the suggestion by the reviewer3 that gas near at the top of the magma chamber may facilitate episodic brittle failure due to increasing magma buoyancy. + +P7 L1 - Can the authors show other evidence of inflation and deflation during these periods? It would be enough to cite some papers of InSAR or GNSS that can strengthen their argument. + +We thank the reviewer for the comment. + +As noted in the original manuscript, the signals associated with the inflation or deflation events are on the order of \(1 \mu \mathrm{m}\) in displacement, which is much smaller than the detection threshold of InSAR and GNSS (i.e., mm to cm). We have emphasized the limitation in the revised manuscript (nP2L22- L28). + +<--- Page Split ---> + +Furthermore, as readily discussed in the Methods sections, to identify the displacement or tilt offset, we remove the mean of the background trend before the LPT arrival. As suggested in the original manuscript, these detected events likely represent episodic transport of discrete magma from the roof of the magma chamber to the storage zone directly above, i.e., the source and sink are probably too close to be deciphered from GNSS or InSAR. + +On the other hand, we note that GNSS displacement from JMA show a notable inflation of the magma chamber in mid- July 2014, May 2015 and July 2016, suggesting magma ascent from a deep reservoir \((> - 10\mathrm{km})\) toward the magma chamber. These episodes coincide with a substantial increase in the number of inflation events and magma transport toward the SMSZ. We have briefly discussed this in the revised manuscript (nP8L12- L14). + +P7 L14 - I could not understand the concept relating to SO2 gas emission. Could the author explain more carefully? The authors describe the prominence of inflation events equivalent to pressurization and lowering SO2 emission. The relation between inflation and pressurization is readily accepted because both are relative changes of the SMSZ condition. However, in my understanding, SO2 emission does not seem to this relative change; but relates to the absolute volume of magma transported to a shallow depth. Is this wrong? I could not see a significant correlation between Fig 4b and 4c. + +We thank the reviewer for this comment. + +In the original manuscript, we refer to the observation that the prominence of inflation (deflation) events coincides with a higher proportion of the pressurization (depressurization) VLP event in the crack like conduit and a lower (higher) \(\mathrm{SO}_2\) emission. We do not mean to suggest that there is causal relationship between \(\mathrm{SO}_2\) emission and the prominence of inflation events. As discussed in Niu & Song (2020), the outgassing potential shown in Fig. 4b in the original manuscript was meant to infer conduit/plug permeability. Therefore, we do not necessarily expect a high correlation between Fig. 4b and Fig. 4c in the original manuscript. + +On the other hand, we do observe a clear correlation between rising \(\mathrm{SO}_2\) emission, the accumulative volume of magma transport in the SMSZ and crater bottom temperature before the 2014 Strombolian eruption. We have replaced Fig 4b with the crater bottom temperature (now Fig. 5b in the revised manuscript) highlight these observations in the revised manuscript (nP8L14- L18). + +P9 L11 - Probably the wrong citation; did not Miyabuchi & Hara (2019, EPS) treat the 2016 phreatomagmatic explosion? I guess Ishii (2018, EPS), Ishii et al. (2018, EPS) and Sato et al. (2018, EPS) are more suitable for the mass of ejected materials. + +We thank the reviewer's comment. + +Miyabushi & Hara (2019, EPS) concerned about the eruptive mass of the 2014 strombulian eruption, which is not a suitable citation. On the other hand, the reference cited in the original manuscript was Miyabuchi et al. (2017, JpGU abstract), which reported the eruptive mass from the field survey. We note the result of field survey by Miyabuchi et al., (2017) has also been cited by Ishii (2018), Ishii et al. (2018) and Sato et al. (2018). To keep the reference list not too long, we have cited Ishii (2018, EPS) in the revised manuscript (nP9L27). + +P11 L 13 - Unclear to me. + +<--- Page Split ---> + +We thank the reviewer for the comment. + +We have rephrased and clarified how one may use the amplitude scaling between VLP and the inflation (or deflation) event derived in recent eruptions to evaluate pre- eruptive volume change in the SMSZ that is otherwise inaccessible for historical eruptions without modern data (nP12L11- L16). + +References - It is not good to cite several papers written in Japanese, which most of the readers cannot probably reach and read. Other accessible papers should be referred to in this article as far as possible. + +We thank the reviewer's comment. + +There are four cited papers written in Japanese. The reference (54,69) in the original manuscript have been removed. However, the results in references (40,49) are essential and there is no alternative literature published in English. Therefore, we retain the two references (40, 49) (reference 46, 45 in the revised manuscript). + +40. Ohkura et al. (2009). + +49. Sudo et al. (2006). + +54. Yokoo & Miyabuchi (2015). + +69. Sakaguchi et al. (2008). + +The author also should discuss the proposed plumbing system with the result of Tsutsui & Sudo (2004, JVGR). + +We thank the reviewer's comment. + +We have cited Tsutsui & Sudo (2004) in the proposed plumbing system in the revised manuscript (nP6L20). + +Fig. 2 - I guess the exact time of the onset in longer signals is quite tricky. How about the reading error? + +We thank the reviewer for this comment. + +The onset of the long- period signal is identified when the velocity exceeds the peak- to- peak amplitude of the background noise (Fig. 2). We estimate the picking error of \(\sim 5\) sec or less. + +P37 L 14 - need a reference for assumption (or evaluation) + +We thank the reviewer for the suggestion. + +There was a typo in the Lame's constant in the original manuscript (P37L14). The correct Lame's constant \(\lambda\) is 1.649 GPa. Following Legrand (2000), we assume \(\nu_{p} = 1500 m / s\) , \(\nu_{s} = 800 m / s\) and \(\rho = 1700 kg / m^{3}\) . We have cited this reference in the supplementary. Since the period of interest is 50 sec and longer, as detailed in the reply to the reviewer 3, the absolute value of the elastic constant does not change the source characteristics or the estimated volume change. We noted this in the revised manuscript (nP5L26- L29). + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +This paper provides interesting new observations of coupled seismic and ground deformation of repeated magma transport events observed at Aso volcano, Japan that are at least sometimes associated with eruptions. These types of high spatial and temporal resolution observations combining these datasets are rare (to my knowledge) and provide a unique perspective on the timing, location, and volume change of magma movements within a volcano. It would be good to get the perspective of an expert on the Aso system, but as far as I can tell, this paper provides new insight into the plumbing system at this volcano and is possibly applicable (in terms of the conceptual model and technique) to other volcanic systems. + +We thank the reviewer for the positive comments and support for the publication. + +I recommend publication after moderate revision. There are several steps in the analysis that are not well documented (see detailed comments below). Further, the paper is unclear in some locations or the discussion is incomplete (again documented below). + +Page 1: + +Line 10 and Page 1 lines 6- 9: How do we know that Aso has a crystal rich mush and that it is relevant for this study? Maybe the magma batches are coming from a crystal poor reservoir? Maybe the crystal rich mush is deeper? + +We thank the reviewer for the comment, which help improve the interpretation. + +We largely agree with the reviewer's suggestion. In the revised manuscript, the abstract has been modified. We note that the crystal- rich mush domain likely remains at a deeper depth (i.e., \(>10\mathrm{km}\) ) after the most recent Aso- 4 caldera forming eruption (e.g., Ishibashi et al., 2018) (nP6L13- L18). + +Line 14: "individual" should be "an individual" + +We thank the reviewer for the comment. + +It has been removed in the abstract in the revised manuscript. + +Lines 16- 24: I found the following sentences unclear and confusing - - can the authors be more specific? What do you mean by "composition dependent"? Is the composition of each magma batch different? Does the last sentence mean that you can forecast the eruption style, plume height, etc. based on the tilt/seismic data described above? If so provide some more details as to how. + +"whereas their recurrences, potentially composition dependent, are regulated by the brittle- to- ductile transition rheology under low differential stress and high strain rate due to the surge of magma from below, regulating long- term volcanic output rate. The magma ascent velocity, decompression rates, and cumulative magma output deduced from the episodic deformation events before recent eruptions in Aso volcano are compatible with retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real- time evaluation of upcoming eruptions." + +We thank the reviewer's comment. + +First, we clarify the misunderstanding that the composition of each magma batch is different. Rather, "composition- dependent" was referred to the hypothesis that the recurrence interval of magma transport in a more silici magma may occur much less frequently than that in a basaltic or andesitic magma. We have removed this sentence in the revised manuscript to avoid confusion. + +<--- Page Split ---> + +The last sentence in the abstract in the original manuscript does imply the possibility of assessing the eruption size and style through the estimated mass flow rate and magma ascent velocity before the upcoming eruption. While the abstract has been rewritten, we simply note the effect of magma composition on the recurrence interval of episodic deformation events (nP10L12- L14). + +Further, the results shown in Figures 4- 6 aren't really described in the abstract. + +We thank the reviewer for the comment. + +As suggested by the reviewers, we removed Figure 6 in the original manuscript. The results in Figs. 4- 5 (Figs. 5- 7 in the revised manuscript) are honoured in the abstract in the revised manuscript. + +Page 2: + +Line 5: the ambient stress state also matters + +We thank the reviewer for this comment. + +We have modified the sentence accordingly in the revised manuscript (nP2L4). + +Line 16: Also the ambient stress state matters - - seismicity will only occur where the rocks are near to failure. Magma can move aseismically if the stress state is not close to failure. + +We thank the reviewer for this comment. + +We agree with the reviewer and have stressed this point in the revised manuscript (nP2L18- L19). + +Page 3: + +Line 8: "signal" should be "signals" + +We thank the reviewer for this comment. + +We have modified the phrase accordingly (nP3L4). + +Line 10: How do we know this is a "shallow hydrothermal reservoir"? + +We thank the reviewer for the comment. + +The presence of a shallow hydrothermal reservoir was inferred from a high electrical conductivity channel in several literatures (Hase et al., 2005; Hata et al., 2016; 2018; Kanda et al., 2008, 2019). We have cited relevant references in the revised manuscript (nP3L7- L9). + +Line 11: use "on" instead of "against" + +We thank the reviewer for this comment. + +This phrase has been modified accordingly (nP3L7). + +Line 12 (and Page 1 line 12): Mentioning the source is near sea level is confusing, how far is this below the surface? It would be better to tell us the depth of the source beneath the surface (or at least tell us both pieces of information). + +We thank the reviewer for the comment. + +We have appended the source depth in the revised manuscript (nP3L9). + +Line 16: Need some introduction to the eruptive cycle - - why was the time period 2011- 2016 chosen? Why not a longer time period? + +We thank the reviewer for this comment. + +The typical eruption cycle in Aso volcano has been summarized previously (e.g., Sudo et al., 2006, Kawakatsu et al., 2000). We have added some details in the introduction (nP3L15- L20). + +<--- Page Split ---> + +Analysis of a larger dataset including activities after 2016 is currently undertaking and will be reported in the future. + +Is the LPT only seen in this time period? + +We thank the reviewer's comment. + +As stated in the original manuscript, LPT can be observed regardless of surface activity and it has also been observed in the past (e.g., Sassa, 1933; Kaneshima et al., 1996; Kawakatsu et al., 2000; Niu & Song, 2020). As noted above, the analysis includes a relatively complete Aso eruption cycle in 2011- 2016. + +Is this the only time period when the patterns described below occur? Or some other reason? As noted above, the analysis and detection of inflation/deflation events includes a relatively complete Aso eruption cycle in 2011- 2016. Analysis of a larger dataset beyond 2016 is currently undertaking and will be reported in the future. + +Line 17: "waveform" should be "waveforms" We thank the reviewer for this comment. We have modified accordingly in the revised manuscript (nP3L23). + +Line 21: How do you know these LPT events are "anomalous"? Where do you define normal or background LPT activity? + +We thank the reviewer for this comment. + +The LPT catalog has been detailed in Niu & Song (2020, JVGR). The amplitude of the two LPT events prior to the 2016 eruption is at least 2 orders magnitude larger than any LPTs we identified in 2011- 2016. We add a brief note in the revised manuscript (nP3L28- nP4L1). + +Page 4: + +Line 4: where do the displacement waveforms come from? Integration of the seismograms? If so, how? + +We thank the reviewer for the comment. + +The vertical and horizontal displacement are integrated from the seismograms. This signal processing has been described in Methods in the original manuscript and in the revised manuscript. + +Line 5: are these events associated with eruptions? + +We thank the reviewer for this comment. + +As shown in Fig S1, these events are not necessarily associated with eruptions. We have noted this in the revised manuscript (nP4L16). + +line 6: What does "east- down" mean? Does that mean tilt toward the east? + +We thank the reviewer for the comment. + +Yes, "east- down" tilt means that tilt toward the east. We have rephrased the sentence in the revised manuscript (nP4L13- L14). + +Line 8- 9: This phrase could be more precise: "between the signal of LPT and the tilt offset". Perhaps: "between the LPT signal and the tilt offset at different stations and in the different components at the same station." + +We thank the reviewer for the suggestion. + +We have rephrased accordingly in the revised manuscript (nP4L17- L21). + +<--- Page Split ---> + +Line 17: Are all the LPT events associated with eruptions? + +We thank the reviewer for this comment. + +As detailed in P3L16 in the original manuscript, LPT is repetitive regardless of surface activity. Hence, they are not necessarily associated with eruptions. + +Are there LPT events that aren't found by the matched filter? If so, what type of events do they represent? + +The detection capability of the matched filter has been detailed in Niu & Song (2020, JVGR) and they have shown a nominal missed pick rate \(\sim 0.1\%\) . When the signal- to- noise ratio is low, the matched filter will not be able to detect or characterize very small LPT events. + +The sections entitled "LPT and synchronous tilt/displacement offset" and "Discovery of the inflation/deflation event beneath Aso volcano" could be better organized. It seems to organized in a chronological manner instead of a logical description of what was discovered - - the first paragraph talks about the 2016 eruption, the next paragraph is about a manual search and the next paragraph is about a matched filter. Instead, why not just discuss the procedure (pointing to the Materials and Methods as needed) and then describe what you found? Maybe organize: this is what we analyzed, describe the 2016 events (including the variation in signals between stations) and then the global stack. + +We thank the reviewer for this comment. + +We have reorganized this section in the revised manuscript (nP3L22- P5L21). Fig. S4 in the original manuscript has now been moved to Fig. S1 in the revised manuscript. + +Page 5, + +line 4: How many events are in the stack? + +We thank the reviewer for this missing information. + +There are 671 and 967 events for the global inflation and deflation stacks, respectively. This is appended in the caption of the revised manuscript. + +Do the number of events vary in time in a systematic manner? + +The number of events is relatively low in 2011- 2013. The activity increases notably in early 2014 and substantially since July 2014. The monthly event numbers are included in the Fig. S5- 10. + +What do the unstacked events look like? + +Waveforms of the unstacked events have been shown in Fig. S1 in the original manuscript and in the revised manuscript. + +Line 5: what does volcanic unrest mean here? + +We thank the reviewer for this comment. + +The volcanic unrest includes surface volcanic activities such as the dried- up of the crater- late, minor phreatic and ash eruptions and incandescent phenomena. We have appended a sentence in the revised manuscript (nP4L27- L28). + +Are there eruptions in 2011- 2014 or are these events occurring without eruption? If so, that is strange - - why do these similar events occur sometimes with eruption and sometimes without? As noted in Fig. 4, there are isolated minor phreatic eruption and ash eruptions in 2011- 2014, but the detected events are generally not associated with eruptions. As noted by Niu & Song (2020), surface eruptions are not only dictated by the overpressure (i.e., magma + +<--- Page Split ---> + +supply), but also the strength/permeability of the conduit plug. We have appended a brief note in the revised manuscript (nP8L20- L24). + +Page 6: + +Line 4: Make clear from the source what your forward model is in terms of source characteristics and elastic structure. + +We thank the reviewer for this comment. + +While the details of the forward model are described in Method of the initial submission, we add a sentence in the revised manuscript to clarify the source characteristics and elastic structure (nP5L26- L27). + +Line 15: What is the composition of the magma batch based on the eruption? One hypothesis is that this portion of magma is ascending because it has accumulated enough gas to become buoyant, so what is known about the gas compositions in the eruptions? + +We thank the reviewer for the comment. + +The composition of the magma batch is basalt- andesitic, and the detailed analysis has been performed by Saito et al. (2018). They estimated that the buoyancy associated with the gassed magma is up to \(\sim 150 - 350 \mathrm{g / cm^3}\) , facilitating magma ascent. We have noted the role of magma buoyancy in the revised manuscript (nP7L7- L12). + +Line 16: How do we know that this is a crystal rich magma? Is this just a guess or is there some evidence from petrology about the source region? + +We thank the reviewer for this comment. + +We refer to earlier response in the rebuttal letter. We also briefly note the crystal- rich mush region in the revised manuscript (nP6L13- L18). + +Line 20: An alternative is that the magma is that there is no new injection of magma and it is cooling/crystallizing, accumulating gas at the top of the reservoir and then episodically having sufficient buoyancy to cause brittle failure. (This is a top- down instead of a bottom- up trigger for eruptions, see for example Girona, T., Costa, F., & Schubert, G. (2015). Degassing during quiescence as a trigger of magma ascent and volcanic eruptions. Scientific reports, 5(1), 1- 7. + +We thank the reviewer for the comment. + +We agree that accumulating gas at the top of the reservoir may facilitate episodic brittle failure and we have included this mechanism in the revised manuscript (nP7L7- L19). + +As noted in the rebuttal letter earlier, GNSS data reported by JMA indicate a slowdown of deflation in the magma chamber in July 2014, May 2015 and July 2016, suggesting a notable injection of magma from a deeper reservoir below toward the bottom of the magma chamber. These episodes correspond to increasing activities of inflation events and rising crater bottom temperature and SO2 emission (Fig. 5). The discussions are added in the revised manuscript (nP8L12- L18). + +Page 7: + +Line 18: This conceptual model is reasonable, but what is the evidence that there is a crystal- rich or crystal- poor mush? What is the petrological evidence for the percentage of crystals? Is it really \(>50\%\) in one reservoir and \(< 50\%\) in the other? + +We thank the reviewer for this comment. + +We note that the crystal- rich mush domain likely remains at a deeper depth (i.e., \(>10 \mathrm{km}\) ) after the most recent Aso- 4 caldera forming eruption (Ishibashi et al., 2018). On the other hand, we have revisited the magma plumbing system recently summarised by Kawaguchi et al. (2021) and modified the interpretation in the revised manuscript. Specifically, we noted + +<--- Page Split ---> + +the process of magma mixing for post- caldera volcanisms beneath Aso volcano (Miyoshi et al. 2011; Miyoshi et al., 2012; Kawaguchi et al., 2021) and inferred discrete magma transport between a chamber with volatile- poor silicic magma and a storage zone of mixed- magma (i.e., SMSZ) (nP6L13- L19). + +Page 8: + +Line 2: You should be clear that you have demonstrated this for a particular volcano during a particular time period and not imply this is a universal process: "the upward transport of magma/gas from the magma chamber toward the surface is a stepwise process in an episodic fashion" + +We thank the reviewer's comment. We have rephrased the sentence in the revised manuscript (nP8L20- L22). + +Page 9: I'm glad to see the discussion of gas (finally), but what are the observations on degassing rate measured on the ground or by satellite? + +We thank the reviewer's comment. + +The observations of \(\mathrm{SO}_2\) emission were from the campaign ground- based sensor and it is noted in the Fig. 5 caption in the revised manuscript. + +Is it really likely that some events have a high gas proportion and over events a few months later have a low gas proportion? + +We thank the reviewer's comment. + +As detailed later in the rebuttal letter, we stress that the tilt- offset in some of the deflation events during the eruption may decay beyond the time scale of our analysis (i.e., \(\sim 1\) hr) and the volume change of these events is likely associated with the transport of gas, rather than magma. We suspect that such deflation events are likely of a small magnitude and lower signal- to- noise ratio. + +We have appended the net volume change estimated from events with a high signal- to- noise ratio (i.e., subset I+II) (Fig. 5a). While the estimated net volume change before the eruption remains the same, the net volume change in the SMSZ during the eruption is more compatible with the net volume change before the eruption. We have expanded and clarified the discussions in the revised manuscript (nP9L11- L24). + +Further, the volume discrepancy might not have anything to do with gas, but could be due to additional reservoirs being tapped that were filled long before the current eruption (that may not have a tilt/tremor signature). A volume difference of 6- 8 is at the high range considered by Rivalta and Segall (2008) but maybe appropriate for this arc volcano? + +What do the authors think this ratio implies? The question of gas in the magma could be uniquely addressed with this dataset. + +We thank the reviewer's comment. + +First, we followed Rivalta & Segall (2008) and included the effect of magma compressibility, on the estimate of volume change in SMSZ (Fig. 6a in the revised manuscript). The details are included in the Methods section. In short, we obtain \(R_{\nu} = 1.1 - 2.3\) , which means that the eruption output (i.e., mass of tephra fallout) is 1.1- 2.3 times of the estimated volume change in the SMSZ. As discussed by Rivalta & Segall (2008), \(R_{\nu}\) is always greater than 1. However, in the original manuscript, we have shown that the estimated volume change in the SMSZ is 6- 8 times of the DRE of tephra fallout, or equivalently \(R_{\nu} \sim 0.12 - 0.14 < 1\) . Therefore, we think the volume difference is not a result of magma compressibility. + +<--- Page Split ---> + +We again refer to the discussion in the revised manuscript (nP9L11- L24). + +Page 11: + +Line4: This sentence is filled with either assumptions or claims that aren't yet supported in the manuscript such as the existence of a "crystal- rich mush and crystal- poor pool" + +We thank the reviewer for the comment. + +As noted earlier in the rebuttal letter, we have revisited the magma plumbing system recently summarised by Kawaguchi et al. (2021) and slightly modified the interpretation in the revised manuscript (nP6L13- L18). Specifically, we noted the process of magma mixing for post- caldera volcanisms beneath Aso (Miyoshi et al. 2011; Miyoshi et al., 2012; Kawaguchi et al., 2021) and inferred discrete magma transport between a chamber with volatile- poor silicic magma and a storage zone of mixed- magma (i.e., SMSZ). + +On the other hand, we note that the crystal- rich mush domain likely remains at a deeper depth (i.e., \(>10\mathrm{km}\) ) after the most recent Aso- 4 caldera forming eruption (Ishibashi et al., 2018). This is briefly noted in the revised manuscript (nP6L13- L19). We also append a short paragraph in the introduction to lay out the background on the transition of magma plumbing system from caldera- forming eruptions to post- caldera volcanisms (nP2L7- L13). + +Line 6: Is this claim discussed further somewhere? If so, I missed it: "The duration of each deformation event ( \(\sim 50\) s) is much longer than what is expected for crustal earthquakes of similar size and such a slow deformation" + +We thank the reviewer for this comment. + +To put the discussion in a proper context, we have rearranged the paragraph in the revised manuscript (nP7L24- L28). + +The perspective could be improved with adding a paragraph or two about how the lessons here could be applied to specific other volcanoes (if possible). Applying the techniques to other volcanoes is mentioned, but what other volcanoes have a similar eruptive style and might be the best targets to investigate? Also, there are many types of eruptions or plumbing systems for which these types of analysis would not work and should be mentioned as well. If additional space is needed, I suggest dropped Figs. 5 and 6 below. + +We thank the reviewer's comment. + +We have added a paragraph to discuss the applicability of the detection and identified volcanoes where the inference may be possible (nP12L17- L24). Following the suggestion by the review 2 and reviewer 3, we have removed Fig. 6 in the original manuscript. + +The data availability statement is not clear: Are the tilt and seismic waveforms available from the link provided? Also the statement that data products are available by request is no longer considered a best practice (for example, it is not allowed by AGU). These data products are not required to be made available in a public repository, but it would add great value if they were. Does UCL have such a repository? + +We thank the reviewer for the comment. + +The data availability and code availability have been restructured according to Nature Communications requirement. The broadband and tilt waveforms are available from the provided link. The catalogue and code can be obtained upon request. + +Fig.1: What are BCU and BYA chambers? They are not mentioned in the caption. Also, what is the depth of the low velocity zone, and other features listed in the legend (maybe refer to Fig. 3)? We thank the reviewer for this comment. + +<--- Page Split ---> + +We refer the depths info to Fig. 3c. + +Fig. 2: Some more details are needed in the caption. How many events are stacked together here? We thank the reviewer for the comment. We have revised the caption. The number of events used for the inflation and deflation stacks is 671 and 967, respectively. + +How were events horizontally aligned? We clarified in the caption that the traces are aligned with respect to the onset of LP. + +Fig. 3: Where do the horizontal and vertical displacements in a and b come from? GNSS? Or integrated from seismometer? + +We thank the reviewer for this comment. + +The horizontal and vertical displacement are obtained from the broadband seismograms and the data processing has been detailed in the Method section (Estimate the static displacement offset from broadband seismograms). + +I could be helpful in d to show the depths of the features shown in a, b, and c: where are the low velocity zone, BYA and BCA chambers, inverted source location (Red Cross) and new Mogi (black circle)? + +We thank the reviewer's comment. We show the depths of all features in Fig. 3c with a legend. + +Why is there an aquifer labeled in d? I don't think the aquifer is mentioned in the caption or the text. + +The aquifer near the crack- like conduit has been widely discussed in the literature. We have noted the aquifer in the revised manuscript (nP6L6- L12) + +I'm also confused about what is happening in e, f, and g. What are the red and blue dotted lines at the line labeled LPT? What are the arrow at the SPT line? What are the arrows in- between the LPT and SPT lines? What physical processes do these arrows/features represent? + +We thank the reviewer's comment. + +We have modified the caption and append the details (Fig 4 in the revised manuscript). + +Fig. 4a: where does the accumulative net volume change come from? The data used to calculate this should be mentioned in the caption. + +We thank the reviewer for the comment. + +As already noted in the original manuscript (P8L8- L12), the accumulative net volume change is calculated from the monthly volume change associated with the monthly inflation/deflation event stacks. We also mentioned this information in the revised manuscript (nP9L1- L5). + +I do not user stand the labels that say, for example, delta \(V\) magma \(< <\) delta \(V\) gas during time period 1. It looks like the volume change is basically flat during this time period, so shouldn't these two volume changes be in approximate balance instead of orders of magnitude different (as implied by using \(< <\) )? + +We thank the reviewer for this suggestion. + +The volume change during episode 1 is not flat. As noted in earlier reply, we have modified the text to clarify the discussion in the revised manuscript (nP9L11- L17). In particular, we have appended the net volume change from events with a high signal- to- noise ratio (i.e., subset I+II) (Fig. 5a in the revised manuscript) to facilitate the discussion. + +<--- Page Split ---> + +Fig. 4b: What is "outgassing potential"? I haven't heard this term before and the phrase used in the caption is still confusing: "the moment ratio between pressurization and 10 depressurization LPTs" + +We thank the reviewer for the comment. + +To avoid confusion and focus on the observations, we replace Fig. 5b with crater bottom (wall) temperature and append discussions in the revised manuscript (nP8L14- L18). + +Fig. 4d: Where is the volume change rate being measured? SMSZ? The caption says the black crosses are the "inflation event" but I think this should be "inflation events. + +We thank the reviewer for this comment. + +Yes, the volume change rates refer to the SMSZ. We have used circle and cross to indicate the averaged rate and single- event rate, respectively. Fig. 4d has now been rearranged as Fig. 6b in the revised manuscript. + +" What is the geodetic data used to estimate the green cross? Is this the same tilt data described in this paper or something else, like GNSS? What is the time period of the geodetic data? The geodetic data corresponding to the green cross is levelling data. The time period of the geodetic data is from 1958 to 2004. This has been clarified in the revised manuscript (Fig. 6b). + +In general, it should be noted that these volume change rates are being measured over vastly different time periods and the time periods should be mentioned in the caption. + +We thank the comment by the reviewer. + +We have modified the figure and the caption to highlight the difference. In addition, we use a different symbol to highlight the volume change rate for a single event (i.e., time scale of \(\sim\) 100 s). + +Fig. 4e: Considering there are only 2 data points, it does not seem wise to draw a line between them. + +The line is not a fitting line. It simply indicates a 1- to- 1 relationship between the estimated mass change in SMSZ and the mass of tephra fallout. If the estimated mass change in SMSZ is equal to the mass of tephra fallout, the data point will fall on the line. + +Figures 5 and 6 have minimal discussion in the text and do not seem to factor into the key conclusions mentioned in the abstract - - could they be removed? They probably deserve further discussion in a separate paper. Fig. 5 has a huge amount of information that isn't discussed in the main text. + +We thank the review for the suggestion. + +We have removed Fig. 6 in the original manuscript. On the other hand, we have expanded the discussions for Fig. 5 (now Fig. 7) in the revised manuscript (nP11L26- nP12L5). + +In particular, I think Fig. 6 is confusing and possibly misleading. It seems to take a single volcanic system and wildly extrapolate it to all systems worldwide. This figure seems to imply that the magma plumbing system of Aso is relevant to all types of eruptions from Rhyolites to flood basalts which is clearly not true - - we have enough information to know that the plumbing of Aso is not widely applicable to all volcanoes. The authors should consider what is the point this figure is trying to make and if it is already made successfully in the text. If the point is that "Composition, viscosity, rheology and tectonic settings govern the recurrences of episodic deformation" then this point can be made adequately in the text without confusing the reader. + +<--- Page Split ---> + +Following the suggestion by the reviewer 3 and another reviewer, we remove Fig. 6 in the original manuscript since the main point has been discussed in the text. Instead, we add a sentence in the revised manuscript to emphasize that magma composition, viscosity, rheology and tectonic settings govern the recurrences of episodic deformation (nP10L12- L14). + +Fig. 6: "providing the glue" is a confusing phrase herePlease see above reply and Fig. 6 in the original manuscript has been removed. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +Review comments on Episodic transport of discrete magma batches beneath Aso volcano By Jieming Niu, Teh- Ru Alex Song + +This manuscript is quite interesting and is sufficiently valuable to publish on Nature Communications. + +Major comments + +1) Source of tilt offset is discussed in the relation of crystal rich and crystal poor zones. I cannot well understand how to relate the source of tilt off set with the rate of crystal. The reference 48 investigate volatile from the viewpoint of petrology. If source of tilt offset is related with volatile-rich and volatile-poor zones, this might be better understood. + +We thank the reviewer for the comments. As pointed out by the reviewer, the reference 48 (Kawaguchi et al., 2021) did not directly address crystal-rich or crystal-poor zone in the magmatic system beneath Aso caldera. + +As noted earlier in the rebuttal letter, following latest petrological studies (e.g., Kawaguchi et al., 2021), we note magma mixing between volatile-poor silicic magma at the magma chamber ( \(\sim 4 - 10 \mathrm{km}\) ) and volatile-rich basaltic magma coming from a deeper reservoir ( \(>10 \mathrm{km}\) ). Furthermore, the storage depth of mixed-magma is determined at \(\sim 2 - 4 \mathrm{km}\) depth (or \(\sim 1 - 3 \mathrm{km}\) BSL). The source of tilt is interpreted as a transport of magma batch between the top of magma chamber and the storage zone of mixed magma (SMSZ discussed in the manuscript). We have modified the interpretation in the revised manuscript (nP6L13- L18, nP6L23- L28). The transport process is also elaborated in the revised manuscript (nP7L3- L28). + +2) Source of tilt offset is also discussed on brittle-ductile transition zone. However, the authors assumes that tilt offset is induced by volume change of a combination model of tensile crack and explosive source in elastic medium and this model does not include fracture. Brittle and ductile are manners of fracture. + +We thank the comment by the reviewer. + +Here we disagree with the reviewer's comment. As noted by Aki & Richard (2002, Quantitative Seismology, chapter 3) and many other seismology textbooks, seismic moment tensor is a general force- equivalent representation of internal sources, including fracture, explosion and tensile- crack inside the earth. On the other hand, to reiterate, our seismic moment tensor inversion shows that the source of the tilt- offset has a predominant volumetric component and \((\sim 80\%)\) and a minor normal- fault component \((\sim 20\%)\) . + +Regarding to the model of elastic deformation, source of tilt offset should be discussed on difference in elastic constants along the magma plumbing system. + +As noted by Aki & Richard (2002, Quantitative Seismology, chapter 3), the elastic moduli used in the force- equivalent representation of internal sources are constants appropriate for the wall rock (or unaltered rock). While it is likely that the elastic constant within the magma plumbing system may vary, it does not change seismic wave excitation in the frequency band of our interest (i.e., \(>50\) sec). We have briefly discussed the effect of elastic constant on source inversion and the volume change in the revised manuscript (nP5L26- L29). + +The inverted source location and geometry only depends on the displacement or tilt ratio among different stations or/and different components. We also inverted the source with a different velocity structure and the effect of elastic constant on the solution is minimal. + +<--- Page Split ---> + +3) The significance of comparison of 2011-2016 eruptivity of Aso with basaltic eruptivity is not well understood. As mentioned in the text, long-term eruption rate of andesitic volcanoes is lower than basaltic volcanoes. I cannot find a significance of comparison of eruption rate between andesitic and basaltic volcanoes in this manuscript. + +We thank the reviewer for the comment. + +We have added a paragraph and noted the relevance of the comparison in the revised manuscript (nP11L26-nP12L5). Comparing mass discharge rate between basaltic and basalt-andesitic volcanoes help elucidate the regime where the mass discharge rate can be approximated by the mass flow rate. + +The eruption 2011- 2016 is an eruptive activity of Aso, however it does not cover all the eruptivity of Aso. If compared, the eruption 2011- 2016 should be compared with past eruptivity of Aso or long- term eruptivity of the volcano. + +We largely agree with the reviewer's comment. In Fig. 4d in the original manuscript, we did compare the averaged eruption output rate in 2011- 2016 against the output rate in historical eruptions and long- term eruption output rate over the geological time scale. These comparisons have been noted in P8L8- L18 in the original manuscript. In the revised manuscript, we also appended the magma discharge rates of the 1979 and 1989 eruptions in the Fig. 6 for comparisons. We have modified the text accordingly (nP11L16- L20). + +Minor comments P3L20 + +"natural period" -> band width + +The use of natural period was correct. It is used to describe the resonant period of a seismometer (pp.175, Lay and Wallace, 1995). + +P4L12 + +LP signal east- west is much weaker, but north- south is stronger than N.ASIV. + +We thank the reviewer for the comment. The change has been made in the revised manuscript (nP4L17- L21). + +P4L13 "These observations strongly indicate that the source of the tilt offset is spatially separated from the LPT source" + +It is possible, but is it necessary to examine source difference between tilt offset and LPT? + +We thank the reviewer for the comment. + +As discussed in P4L8- L13 in the original manuscript, the difference in the amplitude between LPT and tilt offset among different seismic station or/and channels is a direct indication that the source of tilt offset must differ from the source of LPT, either in location or mechanism. We have rephrased the sentence to clarify this conjecture (nP4L23- L25). + +P4L14 "which is near the active Naka- dake first crater" + +Show references or see Method. + +We thank the reviewer's comment and have cited relevant references in the revised manuscript (nP4L25). + +P5L3 global waveform stacks + +What do you mean "global"? How many LPTs were stacked? + +We thank the reviewer for the comment. The term "global" is used to highlight waveform stacks over the period of unrest (2011- 2014 August) and Strombolian eruption (Nov. 2014- + +<--- Page Split ---> + +Apr 2015). The number of LPT events used for stacking is shown in Fig. 2 and noted in the caption. + +P5L9 relatively steady Almost the same? + +We thank the reviewer's comment. We have rephrased the sentence in the revised manuscript (nP5L4). + +P5L21 Fig. S4 + +Fig. S4 is "Synthetic amplitude- distance decay against static and filtered waveforms". Inserting Fig. S4 explains why you choose 100- 200s ULP band? + +We thank the reviewer for the comment. + +We have modified the sentences accordingly in the revised manuscript (nP4L3- L6). + +P7L2 "SMSZ" + +"SMSZ" firstly appeared here. This should be explained. + +We thank the reviewer for the comment. The SMSZ is first defined and noted in the revised manuscript (nP6L21). + +P7L5 intense + +Is this word necessary? What do you mean "intense unrest"? + +We thank the reviewer for the comment. + +We have added a brief note to define specific activities in the revised manuscript (nP8L2- L4). + +P7L18 "a deeper reservoir (i.e., a crystal- rich mush) and temporarily stalled in the SMSZ (i.e., a crystal- poor pool)" + +The reference 48 investigate volatile. How does it relate to crystal? Are there any evidence for crystal- poor in the SMSZ? + +We thank the reviewer for the comment. + +As noted earlier in the rebuttal letter, we have modified the interpretation and the discussions in the revised manuscript (nP6L13- L19). + +P8L1- L7 + +For estimation of volume increase, Method should be referred. + +We thank the reviewer for the comment. This statement has been referred to the Method in the revised manuscript (nP9L1- L5). + +P8L13- L22 + +This hypothesis is true. As the authors show clearly, LPT is a short- lived phenomenon. What does the author mention, comparing short- lived volume change with long- term eruptivity? + +We thank the reviewer for the comment. + +As noted in the original manuscript LPT (termed VLP in the revised manuscript) has been observed over multiple eruption cycles since 1920s (Sassa, 1935; Sakaguchi et al., 2008). This provides a means to detect synchronous VLP and inflation/deflation event and evaluate single- event volume change for historical eruptions. This point has been addressed in the revised manuscript (nP12L11- L16). + +P10L11- L13 "While the estimated mass flow rate in Aso is lower than those estimated in basaltic eruptions by an order of magnitude (Fig. 5), such a difference is consistent with the disparity in the average volcanic output rate between basaltic eruptions and andesitic eruptions" + +<--- Page Split ---> + +In this case, Aso means activity 2011- 2016? Which eruption does "basaltic eruption" indicate? + +We thank the reviewer for the comment. + +Yes, the mass discharge rate was referred to Aso activity 2011- 2016. In the original manuscript, the basaltic eruptions refer to data shown in Fig 5 (solid diamonds in Fig. 7 in the revised manuscript) where both the decompression rate and the mass discharge rate are available (Barth et al., 2019). On the other hand, the relevant discussion has been revised in the revised manuscript (nP11L26- nP12L5). + +The first half is comparison of short term activity. Second half is long- term comparison. Long- term comparison may be true. But short- term comparison is case- by- case. It is not necessary to be consistent. + +As noted above in the rebuttal letter, the relevant discussion can be referred to the revised manuscript (nP11L26- nP12L5). + +P22L11Takahiro -> TakahiroWe thank the reviewer for the comment. This has been modified accordingly. + +FiguresP24L9 October 8, 2016Need time of onset of the eruption.The onset of the eruption is marked by the red line. We have modified the caption of Fig. 1b accordingly. + +(b) N.ASHV.LE is tilt of east-side down at station N.ASHV?Yes, we have also clarified this in the caption. + +Is Figure 6 needed?We thank the reviewer for the comment.As suggested by the reviewers, this figure has been removed. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #2 (Remarks to the Author): + +I thank the authors for addressing my comments in the first round of review. I think they have adequately modified their manuscript and I recommend publication in its present form. + +Reviewer #3 (Remarks to the Author): + +I think the manuscript is well revised according to the comments by the reviewers. This manuscript documents magma plumbing system of Aso volcano from the deep chamber to the shallow conduit and reveals SMSZ to connect the two magmas. The two stages; pre- eruptive and Strombolian eruption are well separated by extracting minor offset of the tilt and seismic events. This attains at a level to publish on nature communications, supporting high- precision data. + +The followings may be mistyped. P2 L27 sthe- >the Fig1 L6 NewMogi - > New Mogi Fig2 L8 acasual - > casual + +<--- Page Split ---> + +In the following response, the comments by the reviewers are shown in italic, our responses are shown in bold. The page and line numbers in the original manuscript are noted as P?L??. The responses discussed in the rebuttal letter are also highlighted in yellow in the revised manuscript. + +Reviewer #2 (Remarks to the Author): + +I thank the authors for addressing my comments in the first round of review. I think they have adequately modified their manuscript and I recommend publication in its present form. We thank the reviewer for the positive comments and support for the publication. + +Reviewer #3 (Remarks to the Author): + +I think the manuscript is well revised according to the comments by the reviewers. This manuscript documents magma plumbing system of Aso volcano from the deep chamber to the shallow conduit and reveals SMSZ to connect the two magmas. The two stages; pre-eruptive and Strombolian eruption are well separated by extracting minor offset of the tilt and seismic events. This attains at a level to publish on nature communications, supporting high- precision data. We thank the reviewer for the positive comments and support for the publication. + +The followings may be mistyped. + +P2 L27 sthe- >the This has been corrected as P2L27 in the revised manuscript. + +Fig1 L6 NewMogi - > New Mogi This has been corrected as P30L8 in the revised manuscript. "NewMogi" in the figure has also been replaced by "New Mogi". + +Fig2 L8 acasual - > casual This has been corrected as P31L8 in the revised manuscript. + +Note we slightly revise Fig. 5b and append the temperature data from ground- based thermal camera (Cigolini et al., 2018), filling the data gap between late 2014 and 2016. We append two references summarizing latest efforts on deep low- frequency earthquakes (P12L25). We slightly refine and make a more precise description of source mechanism (P6L3- 5) and append uncertainty estimates in the supplementary Table 2. + +Finally, we have also followed the checklist and slightly reformat the manuscript. As suggested by the editorial team, we include an image to be featured in Nature Communications. We believe the image vividly illustrates the background crater- lake and diverse eruption styles in Aso volcano. The original images are credited to Dr. Akihiko Yokoo in Aso Volcano Observatory. + +<--- Page Split ---> diff --git a/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..152ef31f683b43148fc8729ecde82ab514bd277f --- /dev/null +++ b/peer_reviews/1287b0275a1ceb77692926e47e4cb244d3ebcdcf9220bb8cc464a7bb7c810ed0/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1358 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 880, 209]]<|/det|> +Episodic transport of discrete magma batches beneath Aso volcano + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[105, 84, 281, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[105, 113, 401, 128]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[105, 144, 250, 157]]<|/det|> +## Overall impression + +<|ref|>text<|/ref|><|det|>[[104, 158, 934, 308]]<|/det|> +Overall impressionThe article written by Niu and Song shows an exciting interpretation of tons of tilt and seismic signals that repeatedly occurred at Aso volcano, Japan, with precise analysis procedures and its results. It sheds light on the new concept of the magma plumbing system at the volcano, adding a magma storage zone located between the magma chamber and the conduit. It identifies that this zone's inflation and deflation are associated with episodic magma discharge from below and are indeed relating to the surficial phenomena. After calculating the 1- D conduit flow, it improves the public image of magma ascent dynamics from the magma chamber to the surface. It also provides a future direction of geophysical research to real- time evaluate upcoming eruptions. This article seems to be well- organized, and the methods and results are detailed and very interesting for the scientific community widely. I would recommend their article for publishing in the journal after minor revisions of some comments below I pointed out. + +<|ref|>sub_title<|/ref|><|det|>[[104, 325, 250, 338]]<|/det|> +## Specific comments + +<|ref|>text<|/ref|><|det|>[[104, 339, 934, 413]]<|/det|> +P3 L13 - The authors use the term "long- period tremor (LPT)" for the objected seismic signal in the whole in this article because they respect the nomenclature that had been established in previous papers. However, this term seems to be a local vernacular or jargon only at Aso volcano. I am also suspect that that signal is not a "tremor?" I suggest using the more widely used term VLP or ultra- long- period (ULP) signals in the volcanological field instead of LPT for readers of this journal from more wide backgrounds. + +<|ref|>text<|/ref|><|det|>[[103, 427, 936, 547]]<|/det|> +P4 L4 - Were the VLP signals the authors checked from the catalog associated individually with any surficial eruption activities at the crater during the erupted periods? A paper reported that the occurrence of the VLP seismic signal preceded by few seconds from the onset of Strombolian eruption (Ishii et al., 2019, EPS). What the meaning of a difference of such elapsed time (2 min for Oct. 2016 phreatomagmatic eruption and 2- 3 s for Strombolian explosions), as well as the meaning of a difference with or without eruptions? I think such a time difference may not relate to the patterns of the tilt source. Are there several types of VLPs with similar waveforms, but specific properties are different? Can the author comment on this topic at any part of this article? + +<|ref|>text<|/ref|><|det|>[[104, 562, 933, 621]]<|/det|> +P4 L20 - Can the authors show a result of the same method using another template (Event 2) in the supplementary? I could not find validity to use Event 1 (not 2) as a reference signal in this article. I am convincing that the conclusion will be the same as this article if Event 2 is used. However, curious about the time evolution of the VLPs for the case of 2. + +<|ref|>text<|/ref|><|det|>[[104, 636, 934, 696]]<|/det|> +P5 L15 - The authors should explain the excitation mechanism of the SPT concerning the occurrence of VLP as well as the series of phenomena starting from a deeper place (top of the magma chamber; the authors argue). I could not imagine why the SPT starts at the top portion of the conduit (VLP source) at first, and 10 s later, the VLP occurs (it is the same time as the SPT peak), whenever the events are inflation or deflation. + +<|ref|>text<|/ref|><|det|>[[104, 711, 925, 755]]<|/det|> +P6 L10 - The authors cited Hata et al. (2018, JGR) in this article; however, it seems inappropriate. At least another paper of Hata et al. (2018, JGR, 10.1029/2018JB015951), or much preferable Matsushima et al. (2020, EPS) showing the revised model of the Hata et al.'s result should be cited. + +<|ref|>text<|/ref|><|det|>[[102, 770, 884, 800]]<|/det|> +P6 L20 - Add any comment on how to make seismicity around the roof of the magma chamber if gas- dominant materials transport upward. + +<|ref|>text<|/ref|><|det|>[[102, 816, 904, 846]]<|/det|> +P7 L1 - Can the authors show other evidence of inflation and deflation during these periods? It would be enough to cite some papers of InSAR or GNSS that can strengthen their argument. + +<|ref|>text<|/ref|><|det|>[[104, 861, 937, 905]]<|/det|> +P7 L14 - I could not understand the concept relating to SO2 gas emission. Could the author explain more carefully? The authors describe the prominence of inflation events equivalent to pressurization and lowering SO2 emission. The relation between inflation and pressurization is readily accepted because both are relative + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 83, 935, 127]]<|/det|> +changes of the SMSZ condition. However, in my understanding, SO2 emission does not seem to this relative change; but relates to the absolute volume of magma transported to a shallow depth. Is this wrong? I could not see a significant correlation between Fig 4b and 4c. + +<|ref|>text<|/ref|><|det|>[[105, 143, 923, 188]]<|/det|> +P9 L11 - Probably the wrong citation; did not Miyabuchi & Hara (2019, EPS) treat the 2016 phreatomagmatic explosion? I guess Ishii (2018, EPS), Ishii et al. (2018, EPS) and Sato et al. (2018, EPS) are more suitable for the mass of ejected materials. + +<|ref|>text<|/ref|><|det|>[[105, 204, 301, 217]]<|/det|> +P11 L 13 - Unclear to me. + +<|ref|>text<|/ref|><|det|>[[105, 234, 932, 278]]<|/det|> +References - It is not good to cite several papers written in Japanese, which most of the readers cannot probably reach and read. Other accessible papers should be referred to in this article as far as possible. The author also should discuss the proposed plumbing system with the result of Tsutsui & Sudo (2004, JVGR). + +<|ref|>text<|/ref|><|det|>[[103, 293, 909, 308]]<|/det|> +Fig. 2 - I guess the exact time of the onset in longer signals is quite tricky. How about the reading error? + +<|ref|>text<|/ref|><|det|>[[105, 323, 557, 337]]<|/det|> +P37 L 14 - need a reference for assumption (or evaluation) + +<|ref|>text<|/ref|><|det|>[[105, 381, 401, 396]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[105, 411, 939, 517]]<|/det|> +This paper provides interesting new observations of coupled seismic and ground deformation of repeated magma transport events observed at Aso volcano, Japan that are at least sometimes associated with eruptions. These types of high spatial and temporal resolution observations combining these datasets are rare (to my knowledge) and provide a unique perspective on the timing, location, and volume change of magma movements within a volcano. It would be good to get the perspective of an expert on the Aso system, but as far as I can tell, this paper provides new insight into the plumbing system at this volcano and is possibly applicable (in terms of the conceptual model and technique) to other volcanic systems. + +<|ref|>text<|/ref|><|det|>[[105, 532, 916, 576]]<|/det|> +I recommend publication after moderate revision. There are several steps in the analysis that are not well documented (see detailed comments below). Further, the paper is unclear in some locations or the discussion is incomplete (again documented below). + +<|ref|>text<|/ref|><|det|>[[105, 592, 164, 605]]<|/det|> +Page 1: + +<|ref|>text<|/ref|><|det|>[[105, 621, 914, 665]]<|/det|> +Line 10 and Page 1 lines 6- 9: How do we know that Aso has a crystal rich mush and that it is relevant for this study? Maybe the magma batches are coming from a crystal poor reservoir? Maybe the crystal rich mush is deeper? + +<|ref|>text<|/ref|><|det|>[[105, 681, 456, 695]]<|/det|> +Line 14: "individual" should be "an individual" + +<|ref|>text<|/ref|><|det|>[[105, 711, 936, 770]]<|/det|> +Lines 16- 24: I found the following sentences unclear and confusing - - can the authors be more specific? What do you mean by "composition dependent"? Is the composition of each magma batch different? Does the last sentence mean that you can forecast the eruption style, plume height, etc. based on the tilt/seismic data described above? If so provide some more details as to how. + +<|ref|>text<|/ref|><|det|>[[105, 786, 936, 874]]<|/det|> +"whereas their recurrences, potentially composition dependent, are regulated by the brittle- to- ductile transition rheology under low differential stress and high strain rate due to the surge of magma from below, regulating long- term volcanic output rate. The magma ascent velocity, decompression rates, and cumulative magma output deduced from the episodic deformation events before recent eruptions in Aso volcano are compatible with retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real- time evaluation of upcoming eruptions." + +<|ref|>text<|/ref|><|det|>[[105, 890, 713, 904]]<|/det|> +Further, the results shown in Figures 4- 6 aren't really described in the abstract. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 100, 164, 113]]<|/det|> +Page 2: + +<|ref|>text<|/ref|><|det|>[[105, 129, 451, 143]]<|/det|> +Line 5: the ambient stress state also matters + +<|ref|>text<|/ref|><|det|>[[100, 159, 891, 188]]<|/det|> +Line 16: Also the ambient stress state matters - - seismicity will only occur where the rocks are near to failure. Magma can move aseismically if the stress state is not close to failure. + +<|ref|>text<|/ref|><|det|>[[105, 218, 164, 232]]<|/det|> +Page 3: + +<|ref|>text<|/ref|><|det|>[[105, 248, 374, 262]]<|/det|> +Line 8: "signal" should be "signals" + +<|ref|>text<|/ref|><|det|>[[105, 277, 633, 291]]<|/det|> +Line 10: How do we know this is a "shallow hydrothermal reservoir"? + +<|ref|>text<|/ref|><|det|>[[105, 307, 394, 321]]<|/det|> +Line 11: use "on" instead of "against" + +<|ref|>text<|/ref|><|det|>[[105, 337, 925, 381]]<|/det|> +Line 12 (and Page 1 line 12): Mentioning the source is near sea level is confusing, how far is this below the surface? It would be better to tell us the depth of the source beneath the surface (or at least tell us both pieces of information). + +<|ref|>text<|/ref|><|det|>[[105, 397, 924, 441]]<|/det|> +Line 16: Need some introduction to the eruptive cycle - - why was the time period 2011- 2016 chosen? Why not a longer time period? Is the LPT only seen in this time period? Is this the only time period when the patterns described below occur? Or some other reason? + +<|ref|>text<|/ref|><|det|>[[105, 456, 444, 470]]<|/det|> +Line 17: "waveform" should be "waveforms" + +<|ref|>text<|/ref|><|det|>[[100, 486, 922, 515]]<|/det|> +Line 21: How do you know these LPT events are "anomalous"? Where do you define normal or background LPT activity? + +<|ref|>text<|/ref|><|det|>[[105, 532, 164, 545]]<|/det|> +Page 4: + +<|ref|>text<|/ref|><|det|>[[100, 561, 899, 576]]<|/det|> +Line 4: where do the displacement waveforms come from? Integration of the seismograms? If so, how? + +<|ref|>text<|/ref|><|det|>[[105, 591, 500, 605]]<|/det|> +Line 5: are these events associated with eruptions? + +<|ref|>text<|/ref|><|det|>[[105, 621, 674, 635]]<|/det|> +Line 6: What does "east- down" mean? Doe that mean tilt toward the east? + +<|ref|>text<|/ref|><|det|>[[105, 651, 928, 695]]<|/det|> +Line 8- 9: This phrase could be more precise: "between the signal of LPT and the tilt offset". Perhaps: "between the LPT signal and the tilt offset at different stations and in the different components at the same station." + +<|ref|>text<|/ref|><|det|>[[105, 711, 900, 740]]<|/det|> +Line 17: Are all the LPT events associated with eruptions? Are there LPT events that aren't found by the matched filter? If so, what type of events do they represent? + +<|ref|>text<|/ref|><|det|>[[105, 755, 931, 784]]<|/det|> +The sections entitled "LPT and synchronous tilt/displacement offset" and "Discovery of the inflation/deflation event beneath Aso volcano" could be better organized. + +<|ref|>text<|/ref|><|det|>[[105, 785, 937, 858]]<|/det|> +It seems to organized in a chronological manner instead of a logical description of what was discovered - - the first paragraph talks about the 2016 eruption, the next paragraph is about a manual search and the next paragraph is about a matched filter. Instead, why not just discuss the procedure (pointing to the Materials and Methods as needed) and then describe what you found? Maybe organize: this is what we analyzed, describe the 2016 events (including the variation in signals between stations) and then the global stack. + +<|ref|>text<|/ref|><|det|>[[105, 875, 163, 889]]<|/det|> +Page 5, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 83, 912, 112]]<|/det|> +line 4: How many events are in the stack? Do the number of events vary in time in a systematic manner? What do the unstacked events look like? + +<|ref|>text<|/ref|><|det|>[[105, 128, 889, 172]]<|/det|> +Line 5: what does volcanic unrest mean here? Are there eruptions in 2011- 2014 or are these events occurring without eruption? If so, that is strange - - why do these similar events occur sometimes with eruption and sometimes without? + +<|ref|>text<|/ref|><|det|>[[105, 189, 164, 202]]<|/det|> +Page 6: + +<|ref|>text<|/ref|><|det|>[[100, 218, 932, 247]]<|/det|> +Line 4: Make clear from the source what your forward model is in terms of source characteristics and elastic structure. + +<|ref|>text<|/ref|><|det|>[[105, 263, 911, 307]]<|/det|> +Line 15: What is the composition of the magma batch based on the eruption? One hypothesis is that this portion of magma is ascending because it has accumulated enough gas to become buoyant, so what is known about the gas compositions in the eruptions? + +<|ref|>text<|/ref|><|det|>[[101, 323, 914, 352]]<|/det|> +Line 16: How do we know that this is a crystal rich magma? Is this just a guess or is there some evidence from petrology about the source region? + +<|ref|>text<|/ref|><|det|>[[105, 367, 920, 441]]<|/det|> +Line 20: An alternative is that the magma is that there is no new injection of magma and it is cooling/crystallizing, accumulating gas at the top of the reservoir and then episodically having sufficient buoyancy to cause brittle failure. (This is a top- down instead of a bottom- up trigger for eruptions, see for example Girona, T., Costa, F., & Schubert, G. (2015). Degassing during quiescence as a trigger of magma ascent and volcanic eruptions. Scientific reports, 5(1), 1- 7. + +<|ref|>text<|/ref|><|det|>[[105, 457, 164, 470]]<|/det|> +Page 7: + +<|ref|>text<|/ref|><|det|>[[105, 487, 934, 530]]<|/det|> +Line 18: This conceptual model is reasonable, but what is the evidence that there is a crystal- rich or crystal- poor mush? What is the petrological evidence for the percentage of crystals? Is it really \(>50\%\) in one reservoir and \(< 50\%\) in the other? + +<|ref|>text<|/ref|><|det|>[[105, 561, 164, 575]]<|/det|> +Page 8: + +<|ref|>text<|/ref|><|det|>[[105, 591, 936, 635]]<|/det|> +Line 2: You should be clear that you have demonstrated this for a particular volcano during a particular time period and not imply this is a universal process: "the upward transport of magma/gas from the magma chamber toward the surface is a stepwise process in an episodic fashion" + +<|ref|>text<|/ref|><|det|>[[105, 666, 931, 785]]<|/det|> +Page 9: I'm glad to see the discussion of gas (finally), but what are the observations on degassing rate measured on the ground or by satellite? Is it really likely that some events have a high gas proportion and over events a few months later have a low gas proportion? Further, the volume discrepancy might not have anything to do with gas, but could be due to additional reservoirs being tapped that were filled long before the current eruption (that may not have a tilt/trémor signature). A volume difference of 6- 8 is at the high range considered by Rivalta and Segall (2008) but maybe appropriate for this arc volcano? What do the authors think this ratio implies? The question of gas in the magma could be uniquely addressed with this dataset. + +<|ref|>text<|/ref|><|det|>[[105, 802, 174, 815]]<|/det|> +Page 11: + +<|ref|>text<|/ref|><|det|>[[100, 817, 920, 845]]<|/det|> +Line4: This sentence is filled with either assumptions or claims that aren't yet supported in the manuscript such as the existence of a "crystal- rich mush and crystal- poor pool" + +<|ref|>text<|/ref|><|det|>[[105, 860, 929, 904]]<|/det|> +Line 6: Is this claim discussed further somewhere? If so, I missed it: "The duration of each deformation event ( \(\sim 50\) s) is much longer than what is expected for crustal earthquakes of similar size and such a slow deformation" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 97, 915, 173]]<|/det|> +The perspective could be improved with adding a paragraph or two about how the lessons here could be applied to specific other volcanoes (if possible). Applying the techniques to other volcanoes is mentioned, but what other volcanoes have a similar eruptive style and might be the best targets to investigate? Also, there are many types of eruptions or plumbing systems for which these types of analysis would not work and should be mentioned as well. If additional space is needed, I suggest dropped Figs. 5 and 6 below. + +<|ref|>text<|/ref|><|det|>[[105, 202, 930, 262]]<|/det|> +The data availability statement is not clear: Are the tilt and seismic waveforms available from the link provided? Also the statement that data products are available by request is no longer considered a best practice (for example, it is not allowed by AGU). These data products are not required to be made available in a public repository, but it would add great value if they were. Does UCL have such a repository? + +<|ref|>text<|/ref|><|det|>[[102, 277, 925, 307]]<|/det|> +Fig.1: What are BCU and BYA chambers? They are not mentioned in the caption. Also, what is the depth of the low velocity zone, and other features listed in the legend (maybe refer to Fig. 3)? + +<|ref|>text<|/ref|><|det|>[[102, 322, 904, 352]]<|/det|> +Fig. 2: Some more details are needed in the caption. How many events are stacked together here? How were events horizontally aligned? + +<|ref|>text<|/ref|><|det|>[[104, 366, 937, 472]]<|/det|> +Fig. 3: Where do the horizontal and vertical displacements in a and b come from? GNSS? Or integrated from seismometer? I could be helpful in d to show the depths of the features shown in a, b, and c: where are the low velocity zone, BYA and BCA chambers, inverted source location (Red Cross) and new Mogi (black circle)? Why is there an aquifer labeled in d? I don't think the aquifer is mentioned in the caption or the text. I'm also confused about what is happening in e, f, and g. What are the red and blue dotted lines at the line labeled LPT? What are the arrow at the SPT line? What are the arrows in- between the LPT and SPT lines? What physical processes do these arrows/features represent? + +<|ref|>text<|/ref|><|det|>[[104, 501, 939, 576]]<|/det|> +Fig. 4a: where does the accumulative net volume change come from? The data used to calculate this should be mentioned in the caption. I do not user stand the labels that say, for example, delta V magma \(< <\) delta V gas during time period 1. It looks like the volume change is basically flat during this time period, so shouldn't these two volume changes be in approximate balance instead of orders of magnitude different (as implied by using \(< <\) )? + +<|ref|>text<|/ref|><|det|>[[104, 590, 932, 635]]<|/det|> +Fig. 4b: What is "outgassing potential"? I haven't heard this term before and the phrase used in the caption is still confusing: "the moment ratio between pressurization and 10 depressurization LPTs" + +<|ref|>text<|/ref|><|det|>[[104, 650, 935, 725]]<|/det|> +Fig. 4d: Where is the volume change rate being measured? SMSZ? The caption says the black crosses are the "inflation event" but I think this should be "inflation events." What is the geodetic data used to estimate the green cross? Is this the same tilt data described in this paper or something else, like GNSS? What is the time period of the geodetic data? In general, it should be noted that these volume change rates are being measured over vastly different time periods and the time periods should be mentioned in the caption. + +<|ref|>text<|/ref|><|det|>[[102, 740, 881, 755]]<|/det|> +Fig. 4e: Considering there are only 2 data points, it does not seem wise to draw a line between them. + +<|ref|>text<|/ref|><|det|>[[104, 770, 936, 905]]<|/det|> +Figures 5 and 6 have minimal discussion in the text and do not seem to factor into the key conclusions mentioned in the abstract - - could they be removed? They probably deserve further discussion in a separate paper. Fig. 5 has a huge amount of information that isn't discussed in the main text. In particular, I think Fig. 6 is confusing and possibly misleading. It seems to take a single volcanic system and wildly extrapolate it to all systems worldwide. This figure seems to imply that the magma plumbing system of Aso is relevant to all types of eruptions from Rhylites to flood basalts which is clearly not true - - we have enough information to know that the plumbing of Aso is not widely applicable to all volcanoes. The authors should consider what is the point this figure is trying to make and if it is already made successfully in the text. If the point is that "Composition, viscosity, rheology and tectonic settings govern the recurrences of episodic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[103, 83, 827, 99]]<|/det|> +deformation" then this point can be made adequately in the text without confusing the reader. + +<|ref|>text<|/ref|><|det|>[[104, 114, 520, 129]]<|/det|> +Fig. 6: "providing the glue" is a confusing phrase here + +<|ref|>text<|/ref|><|det|>[[105, 158, 401, 173]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[104, 188, 787, 218]]<|/det|> +Review comments on Episodic transport of discrete magma batches beneath Aso volcano By Jieming Niu, Teh- Ru Alex Song + +<|ref|>text<|/ref|><|det|>[[103, 233, 878, 248]]<|/det|> +This manuscript is quite interesting and is sufficiently valuable to publish on Nature Communications. + +<|ref|>text<|/ref|><|det|>[[104, 264, 234, 277]]<|/det|> +Major comments + +<|ref|>text<|/ref|><|det|>[[103, 278, 925, 339]]<|/det|> +1) Source of tilt offset is discussed in the relation of crystal rich and crystal poor zones. I cannot well understand how to relate the source of tilt off set with the rate of crystal. The reference 48 investigate volatile from the viewpoint of petrology. If source of tilt offset is related with volatile-rich and volatile-poor zones, this might be better understood. + +<|ref|>text<|/ref|><|det|>[[103, 339, 936, 411]]<|/det|> +2) Source of tilt offset is also discussed on brittle-ductile transition zone. However, the authors assumes that tilt offset is induced by volume change of a combination model of tensile crack and explosive source in elastic medium and this model does not include fracture. Brittle and ductile are manners of fracture. Regarding to the model of elastic deformation, source of tilt offset should be discussed on difference in elastic constants along the magma plumbing system. + +<|ref|>text<|/ref|><|det|>[[103, 412, 940, 501]]<|/det|> +3) The significance of comparison of 2011-2016 eruptivity of Aso with basaltic eruptivity is not well understood. As mentioned in the text, long-term eruption rate of andesitic volcanoes is lower than basaltic volcanoes. I cannot find a significance of comparison of eruption rate between andesitic and basaltic volcanoes in this manuscript. The eruption 2011-2016 is an eruptive activity of Aso, however it does not cover all the eruptivity of Aso. If compared, the eruption 2011-2016 should be compared with past eruptivity of Aso or long-term eruptivity of the volcano. + +<|ref|>text<|/ref|><|det|>[[104, 517, 234, 530]]<|/det|> +Minor comments + +<|ref|>text<|/ref|><|det|>[[104, 533, 154, 545]]<|/det|> +P3L20 + +<|ref|>text<|/ref|><|det|>[[104, 548, 343, 562]]<|/det|> +"natural period" -> band width + +<|ref|>text<|/ref|><|det|>[[104, 564, 153, 575]]<|/det|> +P4L12 + +<|ref|>text<|/ref|><|det|>[[103, 577, 700, 591]]<|/det|> +LP signal east- west is much weaker, but north- south is stronger than N.ASIV. + +<|ref|>text<|/ref|><|det|>[[103, 592, 926, 621]]<|/det|> +P4L13 "These observations strongly indicate that the source of the tilt offset is spatially separated from the LPT source" + +<|ref|>text<|/ref|><|det|>[[103, 622, 795, 636]]<|/det|> +It is possible, but is it necessary to examine source difference between tilt offset and LPT? + +<|ref|>text<|/ref|><|det|>[[104, 637, 530, 651]]<|/det|> +P4L14 "which is near the active Naka- dake first crater" + +<|ref|>text<|/ref|><|det|>[[104, 653, 350, 666]]<|/det|> +Show references or see Method. + +<|ref|>text<|/ref|><|det|>[[104, 668, 328, 681]]<|/det|> +P5L3 global waveform stacks + +<|ref|>text<|/ref|><|det|>[[104, 683, 562, 697]]<|/det|> +What do you mean "global"? How many LPTs were stacked? + +<|ref|>text<|/ref|><|det|>[[104, 699, 274, 712]]<|/det|> +P5L9 relatively steady + +<|ref|>text<|/ref|><|det|>[[104, 714, 245, 727]]<|/det|> +Almost the same? + +<|ref|>text<|/ref|><|det|>[[104, 729, 211, 742]]<|/det|> +P5L21 Fig. S4 + +<|ref|>text<|/ref|><|det|>[[103, 743, 891, 772]]<|/det|> +Fig. S4 is "Synthetic amplitude- distance decay against static and filtered waveforms". Inserting Fig. S4 explains why you choose 100- 200s ULP band? + +<|ref|>text<|/ref|><|det|>[[104, 787, 207, 800]]<|/det|> +P7L2 "SMSZ" + +<|ref|>text<|/ref|><|det|>[[104, 802, 530, 816]]<|/det|> +"SMSZ" firstly appeared here. This should be explained. + +<|ref|>text<|/ref|><|det|>[[104, 818, 207, 830]]<|/det|> +P7L5 intense + +<|ref|>text<|/ref|><|det|>[[104, 832, 572, 846]]<|/det|> +Is this word necessary? What do you mean "intense unrest"? + +<|ref|>text<|/ref|><|det|>[[103, 847, 936, 876]]<|/det|> +P7L18 "a deeper reservoir (i.e., a crystal- rich mush) and temporarily stalled in the SMSZ (i.e., a crystal- poor pool)" + +<|ref|>text<|/ref|><|det|>[[103, 877, 924, 906]]<|/det|> +The reference 48 investigate volatile. How does it relate to crystal? Are there any evidence for crystal- poor in the SMSZ? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 99, 169, 111]]<|/det|> +P8L1- L7 + +<|ref|>text<|/ref|><|det|>[[104, 114, 580, 128]]<|/det|> +For estimation of volume increase, Method should be referred. + +<|ref|>text<|/ref|><|det|>[[104, 130, 188, 142]]<|/det|> +P8L13- L22 + +<|ref|>text<|/ref|><|det|>[[103, 145, 936, 174]]<|/det|> +This hypothesis is true. As the authors show clearly, LPT is a short- lived phenomenon. What does the author mention, comparing short- lived volume change with long- term eruptivity? + +<|ref|>text<|/ref|><|det|>[[103, 189, 925, 234]]<|/det|> +P10L11- L13 "While the estimated mass flow rate in Aso is lower than those estimated in basaltic eruptions by an order of magnitude (Fig. 5), such a difference is consistent with the disparity in the average volcanic output rate between basaltic eruptions and andesitic eruptions" + +<|ref|>text<|/ref|><|det|>[[103, 235, 920, 278]]<|/det|> +In this case, Aso means activity 2011- 2016? Which eruption does "basaltic eruption" indicate? The first half is comparison of short term activity. Second half is long- term comparison. Long- term comparison may be true. But short- term comparison is case- by- case. It is not necessary to be consistent. + +<|ref|>text<|/ref|><|det|>[[104, 294, 264, 323]]<|/det|> +P22L11Takahiro -> Takahiro + +<|ref|>text<|/ref|><|det|>[[104, 339, 550, 396]]<|/det|> +FiguresP24L9 October 8, 2016Need time of onset of the eruption.(b) N.ASHV.LE is tilt of east- side down at station N.ASHV? + +<|ref|>text<|/ref|><|det|>[[104, 412, 258, 426]]<|/det|> +Is Figure 6 needed? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 883, 151]]<|/det|> +In the following response, the comments by the reviewers are shown in italic, our responses are shown in bold. The page and line numbers in the original manuscript are noted as P?L??. The page and line numbers In the revised manuscript are noted as nP?L??. The responses discussed in the rebuttal letter are also highlighted in yellow in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[120, 166, 413, 182]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 199, 270, 214]]<|/det|> +Overall impression + +<|ref|>text<|/ref|><|det|>[[117, 214, 880, 388]]<|/det|> +The article written by Niu and Song shows an exciting interpretation of tons of tilt and seismic signals that repeatedly occurred at Aso volcano, Japan, with precise analysis procedures and its results. It sheds light on the new concept of the magma plumbing system at the volcano, adding a magma storage zone located between the magma chamber and the conduit. It identifies that this zone's inflation and deflation are associated with episodic magma discharge from below and are indeed relating to the surficial phenomena. After calculating the 1- D conduit flow, it improves the public image of magma ascent dynamics from the magma chamber to the surface. It also provides a future direction of geophysical research to real- time evaluate upcoming eruptions. This article seems to be well- organized, and the methods and results are detailed and very interesting for the scientific community widely. I would recommend their article for publishing in the journal after minor revisions of some comments below I pointed out. + +<|ref|>text<|/ref|><|det|>[[118, 402, 793, 419]]<|/det|> +We thank the reviewer for the positive comments and support for the publication. + +<|ref|>text<|/ref|><|det|>[[118, 434, 263, 449]]<|/det|> +Specific comments + +<|ref|>text<|/ref|><|det|>[[117, 450, 872, 545]]<|/det|> +P3 L13 - The authors use the term "long- period tremor (LPT)" for the objected seismic signal in the whole in this article because they respect the nomenclature that had been established in previous papers. However, this term seems to be a local vernacular or jargon only at Aso volcano. I am also suspect that that signal is not a "tremor?" I suggest using the more widely used term VLP or ultra- long- period (ULP) signals in the volcanological field instead of LPT for readers of this journal from more wide backgrounds. + +<|ref|>text<|/ref|><|det|>[[118, 560, 463, 575]]<|/det|> +We thank the reviewer for the suggestion. + +<|ref|>text<|/ref|><|det|>[[117, 575, 880, 637]]<|/det|> +Indeed, the LPT is associated with event- like signal, and it does not resemble typical tremors. We have replaced LPT with the more widely recognized term VLP in the revised manuscript. We also replaced the term SPT with the more widely recognized term LP to represent the long- period signal above the crack- like conduit in Aso volcano. + +<|ref|>text<|/ref|><|det|>[[117, 652, 870, 684]]<|/det|> +P4 L4 - Were the VLP signals the authors checked from the catalog associated individually with any surficial eruption activities at the crater during the erupted periods? + +<|ref|>text<|/ref|><|det|>[[118, 684, 455, 699]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[117, 700, 880, 747]]<|/det|> +Some VLPs are indeed associated with individual surficial eruption during the erupted periods. This corroborates the observation by Ishii et al. (2019, EPS). We briefly noted this in the revised manuscript (nP11L6). + +<|ref|>text<|/ref|><|det|>[[117, 762, 877, 842]]<|/det|> +A paper reported that the occurrence of the VLP seismic signal preceded by few seconds from the onset of Strombolian eruption (Ishii et al., 2019, EPS). What the meaning of a difference of such elapsed time (2 min for Oct. 2016 phreatomagmatic eruption and 2- 3 s for Strombolian explosions), as well as the meaning of a difference with or without eruptions? I think such a time difference may not relate to the patterns of the tilt source. + +<|ref|>text<|/ref|><|det|>[[118, 857, 407, 872]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[117, 873, 880, 905]]<|/det|> +Motivated by the discussions by Ishii et al. (2019), we have added two paragraphs and highlighted the implications of these differences against the inferred magma ascent velocity + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 164]]<|/det|> +in the SMSZ (nP11L3- L13). We conceive that the time delay between VLP and the onset of Strombolian eruption can be reasonably attributed to gas ascent in the shallow conduit under slow magma ascent (e.g., 0.01- 0.1 m/s). On the other hand, the 120 s time delay between Event 2 and the onset of 2016 phreatomagmatic eruption can be reconciled with the relatively magma ascent in the SMSZ (e.g., \(\sim 7 \mathrm{m / s}\) ). + +<|ref|>text<|/ref|><|det|>[[118, 178, 880, 258]]<|/det|> +On the other hand, VLP and synchronous inflation/deflation event does occur with or without eruption. It implies that the occurrence of VLP is likely a necessary condition for surface eruption. As discussed by Niu & Song (2020), conduit/plug permeability and overpressure also play a key role in facilitating surface eruptive activities. We have added a short note in the revised manuscript (nP8L20- L24). + +<|ref|>text<|/ref|><|det|>[[118, 273, 844, 305]]<|/det|> +Are there several types of VLPs with similar waveforms, but specific properties are different? Can the author comment on this topic at any part of this article? + +<|ref|>text<|/ref|><|det|>[[120, 306, 408, 320]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 320, 880, 352]]<|/det|> +We have commented their differences (e.g., resonance period, initial polarity) in the revised manuscript (nP3L10- L14). + +<|ref|>text<|/ref|><|det|>[[118, 367, 860, 414]]<|/det|> +P4 L20 - Can the authors show a result of the same method using another template (Event 2) in the supplementary? I could not find validity to use Event 1 (not 2) as a reference signal in this article. I am convincing that the conclusion will be the same as this article if Event 2 is used. + +<|ref|>text<|/ref|><|det|>[[120, 415, 463, 429]]<|/det|> +We thank the reviewer for the comments. + +<|ref|>text<|/ref|><|det|>[[118, 430, 880, 556]]<|/det|> +Choosing Event 1 as the template has one advantage in that it potentially minimises the interference from the eruption signal at long period (i.e., 50- 250 sec). However, the waveforms from Event 1 and Event 2 are highly correlated, using Event 2 as the reference event does not result in noticeable difference in the detection of inflation or deflation events. The inverted source location and mechanism from Event 2 are practically the same as those inverted from Event 1 (see figure below). We do not include the inversion result from Event 2 in this paper to avoid redundancy. We emphasized the high correlation between Event 1 and Event 2 in the revised manuscript (nP3L24- P4L1). + +<|ref|>image<|/ref|><|det|>[[118, 567, 880, 870]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 870, 880, 895]]<|/det|> +
Rebuttal Figure 1 Posterior probability functions of the inverted source parameters from Event 2. Notations are the same as Supplementary Figure 12 in the manuscript.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 678, 115]]<|/det|> +However, curious about the time evolution of the VLPs for the case of 2. + +<|ref|>text<|/ref|><|det|>[[120, 116, 409, 131]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 132, 875, 195]]<|/det|> +Perhaps there is a misunderstanding here. We emphasize that waveforms from Event 1 and Event 2 are practical identical in the period of our interest (i.e., 50- 250 sec). Therefore, VLP signal of 10 sec period is not the focus of our detection. Rather, the timing of VLP was used to detect inflation or deflation events. + +<|ref|>text<|/ref|><|det|>[[118, 210, 864, 242]]<|/det|> +In a separate note, the evolution of VLPs has been thoroughly documented by Niu & Song (2020, JVGR) and we refer the reader to this article for details. + +<|ref|>text<|/ref|><|det|>[[118, 256, 877, 337]]<|/det|> +P5 L15 - The authors should explain the excitation mechanism of the SPT concerning the occurrence of VLP as well as the series of phenomena starting from a deeper place (top of the magma chamber; the authors argue). I could not imagine why the SPT starts at the top portion of the conduit (VLP source) at first, and 10 s later, the VLP occurs (it is the same time as the SPT peak), whenever the events are inflation or deflation. + +<|ref|>text<|/ref|><|det|>[[120, 352, 457, 367]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 368, 879, 445]]<|/det|> +Following the discussions by Kaneshima et al. (1996) and Kawakatsu et al. (2000), we have added a paragraph to note the possible processes associated with VLP and LP. We emphasize the stress perturbation induced during the initial stage of the inflation/deflation event results in fractures in the conduit plug above the shallow crack- like conduit, promoting LP and VLP (nP6L7- L12). + +<|ref|>text<|/ref|><|det|>[[118, 460, 879, 525]]<|/det|> +We have appended additional paragraphs in the revised manuscript and elaborated the series of phenomena starting from the deep source near the chamber roof (nP7L3- L28). We caution that this is a tentative interpretation at this point and a more elaborated discussion is beyond the main scope of this manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 540, 852, 602]]<|/det|> +P6 L10 - The authors cited Hata et al. (2018, JGR) in this article; however, it seems inappropriate. At least another paper of Hata et al. (2018, JGR, 10.1029/2018JB015951), or much preferable Matsushima et al. (2020, EPS) showing the revised model of the Hata et al.'s result should be cited. + +<|ref|>text<|/ref|><|det|>[[118, 603, 528, 618]]<|/det|> +We thank the reviewer for pointing out this issue. + +<|ref|>text<|/ref|><|det|>[[118, 619, 870, 650]]<|/det|> +We have cited Hata et al. (2018, JGR, 10.1029/2018JB015951) and Matsushima et al. (2020, EPS) in the revised manuscript (nP6L23). + +<|ref|>text<|/ref|><|det|>[[118, 665, 868, 697]]<|/det|> +P6 L20 - Add any comment on how to make seismicity around the roof of the magma chamber if gas- dominant materials transport upward. + +<|ref|>text<|/ref|><|det|>[[120, 697, 457, 712]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 713, 879, 775]]<|/det|> +As also included in the reply earlier, we noted the role of gassed magma in the inflation/deflation events in the revised manuscript (nP7L7- L13). The discussions are in line with the suggestion by the reviewer3 that gas near at the top of the magma chamber may facilitate episodic brittle failure due to increasing magma buoyancy. + +<|ref|>text<|/ref|><|det|>[[118, 790, 879, 822]]<|/det|> +P7 L1 - Can the authors show other evidence of inflation and deflation during these periods? It would be enough to cite some papers of InSAR or GNSS that can strengthen their argument. + +<|ref|>text<|/ref|><|det|>[[120, 823, 456, 837]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 838, 879, 902]]<|/det|> +As noted in the original manuscript, the signals associated with the inflation or deflation events are on the order of \(1 \mu \mathrm{m}\) in displacement, which is much smaller than the detection threshold of InSAR and GNSS (i.e., mm to cm). We have emphasized the limitation in the revised manuscript (nP2L22- L28). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 880, 195]]<|/det|> +Furthermore, as readily discussed in the Methods sections, to identify the displacement or tilt offset, we remove the mean of the background trend before the LPT arrival. As suggested in the original manuscript, these detected events likely represent episodic transport of discrete magma from the roof of the magma chamber to the storage zone directly above, i.e., the source and sink are probably too close to be deciphered from GNSS or InSAR. + +<|ref|>text<|/ref|><|det|>[[118, 210, 880, 290]]<|/det|> +On the other hand, we note that GNSS displacement from JMA show a notable inflation of the magma chamber in mid- July 2014, May 2015 and July 2016, suggesting magma ascent from a deep reservoir \((> - 10\mathrm{km})\) toward the magma chamber. These episodes coincide with a substantial increase in the number of inflation events and magma transport toward the SMSZ. We have briefly discussed this in the revised manuscript (nP8L12- L14). + +<|ref|>text<|/ref|><|det|>[[118, 305, 860, 415]]<|/det|> +P7 L14 - I could not understand the concept relating to SO2 gas emission. Could the author explain more carefully? The authors describe the prominence of inflation events equivalent to pressurization and lowering SO2 emission. The relation between inflation and pressurization is readily accepted because both are relative changes of the SMSZ condition. However, in my understanding, SO2 emission does not seem to this relative change; but relates to the absolute volume of magma transported to a shallow depth. Is this wrong? I could not see a significant correlation between Fig 4b and 4c. + +<|ref|>text<|/ref|><|det|>[[120, 430, 457, 445]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 446, 884, 572]]<|/det|> +In the original manuscript, we refer to the observation that the prominence of inflation (deflation) events coincides with a higher proportion of the pressurization (depressurization) VLP event in the crack like conduit and a lower (higher) \(\mathrm{SO}_2\) emission. We do not mean to suggest that there is causal relationship between \(\mathrm{SO}_2\) emission and the prominence of inflation events. As discussed in Niu & Song (2020), the outgassing potential shown in Fig. 4b in the original manuscript was meant to infer conduit/plug permeability. Therefore, we do not necessarily expect a high correlation between Fig. 4b and Fig. 4c in the original manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 587, 880, 667]]<|/det|> +On the other hand, we do observe a clear correlation between rising \(\mathrm{SO}_2\) emission, the accumulative volume of magma transport in the SMSZ and crater bottom temperature before the 2014 Strombolian eruption. We have replaced Fig 4b with the crater bottom temperature (now Fig. 5b in the revised manuscript) highlight these observations in the revised manuscript (nP8L14- L18). + +<|ref|>text<|/ref|><|det|>[[118, 697, 848, 744]]<|/det|> +P9 L11 - Probably the wrong citation; did not Miyabuchi & Hara (2019, EPS) treat the 2016 phreatomagmatic explosion? I guess Ishii (2018, EPS), Ishii et al. (2018, EPS) and Sato et al. (2018, EPS) are more suitable for the mass of ejected materials. + +<|ref|>text<|/ref|><|det|>[[120, 745, 408, 759]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 760, 880, 869]]<|/det|> +Miyabushi & Hara (2019, EPS) concerned about the eruptive mass of the 2014 strombulian eruption, which is not a suitable citation. On the other hand, the reference cited in the original manuscript was Miyabuchi et al. (2017, JpGU abstract), which reported the eruptive mass from the field survey. We note the result of field survey by Miyabuchi et al., (2017) has also been cited by Ishii (2018), Ishii et al. (2018) and Sato et al. (2018). To keep the reference list not too long, we have cited Ishii (2018, EPS) in the revised manuscript (nP9L27). + +<|ref|>text<|/ref|><|det|>[[120, 885, 320, 899]]<|/det|> +P11 L 13 - Unclear to me. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 455, 100]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 101, 880, 164]]<|/det|> +We have rephrased and clarified how one may use the amplitude scaling between VLP and the inflation (or deflation) event derived in recent eruptions to evaluate pre- eruptive volume change in the SMSZ that is otherwise inaccessible for historical eruptions without modern data (nP12L11- L16). + +<|ref|>text<|/ref|><|det|>[[118, 179, 880, 227]]<|/det|> +References - It is not good to cite several papers written in Japanese, which most of the readers cannot probably reach and read. Other accessible papers should be referred to in this article as far as possible. + +<|ref|>text<|/ref|><|det|>[[120, 228, 408, 243]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 243, 880, 306]]<|/det|> +There are four cited papers written in Japanese. The reference (54,69) in the original manuscript have been removed. However, the results in references (40,49) are essential and there is no alternative literature published in English. Therefore, we retain the two references (40, 49) (reference 46, 45 in the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[118, 306, 330, 320]]<|/det|> +40. Ohkura et al. (2009). + +<|ref|>text<|/ref|><|det|>[[118, 321, 301, 335]]<|/det|> +49. Sudo et al. (2006). + +<|ref|>text<|/ref|><|det|>[[118, 337, 378, 351]]<|/det|> +54. Yokoo & Miyabuchi (2015). + +<|ref|>text<|/ref|><|det|>[[118, 353, 340, 367]]<|/det|> +69. Sakaguchi et al. (2008). + +<|ref|>text<|/ref|><|det|>[[118, 383, 860, 415]]<|/det|> +The author also should discuss the proposed plumbing system with the result of Tsutsui & Sudo (2004, JVGR). + +<|ref|>text<|/ref|><|det|>[[118, 416, 408, 430]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 431, 880, 462]]<|/det|> +We have cited Tsutsui & Sudo (2004) in the proposed plumbing system in the revised manuscript (nP6L20). + +<|ref|>text<|/ref|><|det|>[[118, 478, 880, 509]]<|/det|> +Fig. 2 - I guess the exact time of the onset in longer signals is quite tricky. How about the reading error? + +<|ref|>text<|/ref|><|det|>[[118, 510, 457, 525]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 525, 870, 557]]<|/det|> +The onset of the long- period signal is identified when the velocity exceeds the peak- to- peak amplitude of the background noise (Fig. 2). We estimate the picking error of \(\sim 5\) sec or less. + +<|ref|>text<|/ref|><|det|>[[118, 572, 578, 587]]<|/det|> +P37 L 14 - need a reference for assumption (or evaluation) + +<|ref|>text<|/ref|><|det|>[[118, 588, 465, 603]]<|/det|> +We thank the reviewer for the suggestion. + +<|ref|>text<|/ref|><|det|>[[117, 618, 861, 717]]<|/det|> +There was a typo in the Lame's constant in the original manuscript (P37L14). The correct Lame's constant \(\lambda\) is 1.649 GPa. Following Legrand (2000), we assume \(\nu_{p} = 1500 m / s\) , \(\nu_{s} = 800 m / s\) and \(\rho = 1700 kg / m^{3}\) . We have cited this reference in the supplementary. Since the period of interest is 50 sec and longer, as detailed in the reply to the reviewer 3, the absolute value of the elastic constant does not change the source characteristics or the estimated volume change. We noted this in the revised manuscript (nP5L26- L29). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 413, 100]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 115, 870, 243]]<|/det|> +This paper provides interesting new observations of coupled seismic and ground deformation of repeated magma transport events observed at Aso volcano, Japan that are at least sometimes associated with eruptions. These types of high spatial and temporal resolution observations combining these datasets are rare (to my knowledge) and provide a unique perspective on the timing, location, and volume change of magma movements within a volcano. It would be good to get the perspective of an expert on the Aso system, but as far as I can tell, this paper provides new insight into the plumbing system at this volcano and is possibly applicable (in terms of the conceptual model and technique) to other volcanic systems. + +<|ref|>text<|/ref|><|det|>[[120, 242, 794, 259]]<|/det|> +We thank the reviewer for the positive comments and support for the publication. + +<|ref|>text<|/ref|><|det|>[[118, 273, 875, 321]]<|/det|> +I recommend publication after moderate revision. There are several steps in the analysis that are not well documented (see detailed comments below). Further, the paper is unclear in some locations or the discussion is incomplete (again documented below). + +<|ref|>text<|/ref|><|det|>[[118, 336, 180, 352]]<|/det|> +Page 1: + +<|ref|>text<|/ref|><|det|>[[118, 367, 846, 414]]<|/det|> +Line 10 and Page 1 lines 6- 9: How do we know that Aso has a crystal rich mush and that it is relevant for this study? Maybe the magma batches are coming from a crystal poor reservoir? Maybe the crystal rich mush is deeper? + +<|ref|>text<|/ref|><|det|>[[118, 414, 780, 430]]<|/det|> +We thank the reviewer for the comment, which help improve the interpretation. + +<|ref|>text<|/ref|><|det|>[[118, 430, 880, 494]]<|/det|> +We largely agree with the reviewer's suggestion. In the revised manuscript, the abstract has been modified. We note that the crystal- rich mush domain likely remains at a deeper depth (i.e., \(>10\mathrm{km}\) ) after the most recent Aso- 4 caldera forming eruption (e.g., Ishibashi et al., 2018) (nP6L13- L18). + +<|ref|>text<|/ref|><|det|>[[118, 508, 490, 524]]<|/det|> +Line 14: "individual" should be "an individual" + +<|ref|>text<|/ref|><|det|>[[118, 525, 455, 540]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 541, 630, 557]]<|/det|> +It has been removed in the abstract in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 571, 868, 650]]<|/det|> +Lines 16- 24: I found the following sentences unclear and confusing - - can the authors be more specific? What do you mean by "composition dependent"? Is the composition of each magma batch different? Does the last sentence mean that you can forecast the eruption style, plume height, etc. based on the tilt/seismic data described above? If so provide some more details as to how. + +<|ref|>text<|/ref|><|det|>[[118, 665, 866, 777]]<|/det|> +"whereas their recurrences, potentially composition dependent, are regulated by the brittle- to- ductile transition rheology under low differential stress and high strain rate due to the surge of magma from below, regulating long- term volcanic output rate. The magma ascent velocity, decompression rates, and cumulative magma output deduced from the episodic deformation events before recent eruptions in Aso volcano are compatible with retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real- time evaluation of upcoming eruptions." + +<|ref|>text<|/ref|><|det|>[[118, 777, 408, 792]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 792, 880, 870]]<|/det|> +First, we clarify the misunderstanding that the composition of each magma batch is different. Rather, "composition- dependent" was referred to the hypothesis that the recurrence interval of magma transport in a more silici magma may occur much less frequently than that in a basaltic or andesitic magma. We have removed this sentence in the revised manuscript to avoid confusion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 844, 164]]<|/det|> +The last sentence in the abstract in the original manuscript does imply the possibility of assessing the eruption size and style through the estimated mass flow rate and magma ascent velocity before the upcoming eruption. While the abstract has been rewritten, we simply note the effect of magma composition on the recurrence interval of episodic deformation events (nP10L12- L14). + +<|ref|>text<|/ref|><|det|>[[118, 179, 740, 195]]<|/det|> +Further, the results shown in Figures 4- 6 aren't really described in the abstract. + +<|ref|>text<|/ref|><|det|>[[118, 196, 450, 211]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 211, 870, 258]]<|/det|> +As suggested by the reviewers, we removed Figure 6 in the original manuscript. The results in Figs. 4- 5 (Figs. 5- 7 in the revised manuscript) are honoured in the abstract in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 274, 179, 290]]<|/det|> +Page 2: + +<|ref|>text<|/ref|><|det|>[[118, 305, 461, 320]]<|/det|> +Line 5: the ambient stress state also matters + +<|ref|>text<|/ref|><|det|>[[118, 321, 460, 336]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 337, 768, 353]]<|/det|> +We have modified the sentence accordingly in the revised manuscript (nP2L4). + +<|ref|>text<|/ref|><|det|>[[118, 368, 855, 400]]<|/det|> +Line 16: Also the ambient stress state matters - - seismicity will only occur where the rocks are near to failure. Magma can move aseismically if the stress state is not close to failure. + +<|ref|>text<|/ref|><|det|>[[118, 400, 460, 415]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 415, 875, 446]]<|/det|> +We agree with the reviewer and have stressed this point in the revised manuscript (nP2L18- L19). + +<|ref|>text<|/ref|><|det|>[[118, 462, 179, 478]]<|/det|> +Page 3: + +<|ref|>text<|/ref|><|det|>[[118, 493, 400, 508]]<|/det|> +Line 8: "signal" should be "signals" + +<|ref|>text<|/ref|><|det|>[[118, 509, 460, 524]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 525, 540, 541]]<|/det|> +We have modified the phrase accordingly (nP3L4). + +<|ref|>text<|/ref|><|det|>[[118, 556, 664, 571]]<|/det|> +Line 10: How do we know this is a "shallow hydrothermal reservoir"? + +<|ref|>text<|/ref|><|det|>[[118, 572, 450, 586]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 587, 879, 635]]<|/det|> +The presence of a shallow hydrothermal reservoir was inferred from a high electrical conductivity channel in several literatures (Hase et al., 2005; Hata et al., 2016; 2018; Kanda et al., 2008, 2019). We have cited relevant references in the revised manuscript (nP3L7- L9). + +<|ref|>text<|/ref|><|det|>[[118, 650, 416, 665]]<|/det|> +Line 11: use "on" instead of "against" + +<|ref|>text<|/ref|><|det|>[[118, 666, 460, 680]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 682, 550, 697]]<|/det|> +This phrase has been modified accordingly (nP3L7). + +<|ref|>text<|/ref|><|det|>[[118, 712, 875, 759]]<|/det|> +Line 12 (and Page 1 line 12): Mentioning the source is near sea level is confusing, how far is this below the surface? It would be better to tell us the depth of the source beneath the surface (or at least tell us both pieces of information). + +<|ref|>text<|/ref|><|det|>[[118, 760, 460, 775]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 776, 710, 792]]<|/det|> +We have appended the source depth in the revised manuscript (nP3L9). + +<|ref|>text<|/ref|><|det|>[[118, 807, 836, 839]]<|/det|> +Line 16: Need some introduction to the eruptive cycle - - why was the time period 2011- 2016 chosen? Why not a longer time period? + +<|ref|>text<|/ref|><|det|>[[118, 840, 460, 854]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 855, 879, 901]]<|/det|> +The typical eruption cycle in Aso volcano has been summarized previously (e.g., Sudo et al., 2006, Kawakatsu et al., 2000). We have added some details in the introduction (nP3L15- L20). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 872, 132]]<|/det|> +Analysis of a larger dataset including activities after 2016 is currently undertaking and will be reported in the future. + +<|ref|>text<|/ref|><|det|>[[119, 147, 434, 163]]<|/det|> +Is the LPT only seen in this time period? + +<|ref|>text<|/ref|><|det|>[[119, 164, 408, 178]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 179, 880, 242]]<|/det|> +As stated in the original manuscript, LPT can be observed regardless of surface activity and it has also been observed in the past (e.g., Sassa, 1933; Kaneshima et al., 1996; Kawakatsu et al., 2000; Niu & Song, 2020). As noted above, the analysis includes a relatively complete Aso eruption cycle in 2011- 2016. + +<|ref|>text<|/ref|><|det|>[[118, 257, 870, 321]]<|/det|> +Is this the only time period when the patterns described below occur? Or some other reason? As noted above, the analysis and detection of inflation/deflation events includes a relatively complete Aso eruption cycle in 2011- 2016. Analysis of a larger dataset beyond 2016 is currently undertaking and will be reported in the future. + +<|ref|>text<|/ref|><|det|>[[118, 336, 672, 383]]<|/det|> +Line 17: "waveform" should be "waveforms" We thank the reviewer for this comment. We have modified accordingly in the revised manuscript (nP3L23). + +<|ref|>text<|/ref|><|det|>[[118, 398, 860, 430]]<|/det|> +Line 21: How do you know these LPT events are "anomalous"? Where do you define normal or background LPT activity? + +<|ref|>text<|/ref|><|det|>[[118, 430, 460, 445]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 445, 876, 493]]<|/det|> +The LPT catalog has been detailed in Niu & Song (2020, JVGR). The amplitude of the two LPT events prior to the 2016 eruption is at least 2 orders magnitude larger than any LPTs we identified in 2011- 2016. We add a brief note in the revised manuscript (nP3L28- nP4L1). + +<|ref|>text<|/ref|><|det|>[[118, 508, 180, 523]]<|/det|> +Page 4: + +<|ref|>text<|/ref|><|det|>[[118, 540, 870, 571]]<|/det|> +Line 4: where do the displacement waveforms come from? Integration of the seismograms? If so, how? + +<|ref|>text<|/ref|><|det|>[[118, 572, 456, 587]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 588, 880, 635]]<|/det|> +The vertical and horizontal displacement are integrated from the seismograms. This signal processing has been described in Methods in the original manuscript and in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 651, 518, 666]]<|/det|> +Line 5: are these events associated with eruptions? + +<|ref|>text<|/ref|><|det|>[[118, 667, 460, 681]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 682, 880, 714]]<|/det|> +As shown in Fig S1, these events are not necessarily associated with eruptions. We have noted this in the revised manuscript (nP4L16). + +<|ref|>text<|/ref|><|det|>[[118, 729, 692, 745]]<|/det|> +line 6: What does "east- down" mean? Does that mean tilt toward the east? + +<|ref|>text<|/ref|><|det|>[[118, 745, 456, 759]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 760, 875, 791]]<|/det|> +Yes, "east- down" tilt means that tilt toward the east. We have rephrased the sentence in the revised manuscript (nP4L13- L14). + +<|ref|>text<|/ref|><|det|>[[118, 806, 834, 853]]<|/det|> +Line 8- 9: This phrase could be more precise: "between the signal of LPT and the tilt offset". Perhaps: "between the LPT signal and the tilt offset at different stations and in the different components at the same station." + +<|ref|>text<|/ref|><|det|>[[118, 854, 465, 869]]<|/det|> +We thank the reviewer for the suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 870, 722, 885]]<|/det|> +We have rephrased accordingly in the revised manuscript (nP4L17- L21). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 575, 115]]<|/det|> +Line 17: Are all the LPT events associated with eruptions? + +<|ref|>text<|/ref|><|det|>[[120, 116, 460, 131]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 131, 880, 164]]<|/det|> +As detailed in P3L16 in the original manuscript, LPT is repetitive regardless of surface activity. Hence, they are not necessarily associated with eruptions. + +<|ref|>text<|/ref|><|det|>[[118, 178, 852, 210]]<|/det|> +Are there LPT events that aren't found by the matched filter? If so, what type of events do they represent? + +<|ref|>text<|/ref|><|det|>[[118, 210, 886, 258]]<|/det|> +The detection capability of the matched filter has been detailed in Niu & Song (2020, JVGR) and they have shown a nominal missed pick rate \(\sim 0.1\%\) . When the signal- to- noise ratio is low, the matched filter will not be able to detect or characterize very small LPT events. + +<|ref|>text<|/ref|><|det|>[[118, 273, 880, 400]]<|/det|> +The sections entitled "LPT and synchronous tilt/displacement offset" and "Discovery of the inflation/deflation event beneath Aso volcano" could be better organized. It seems to organized in a chronological manner instead of a logical description of what was discovered - - the first paragraph talks about the 2016 eruption, the next paragraph is about a manual search and the next paragraph is about a matched filter. Instead, why not just discuss the procedure (pointing to the Materials and Methods as needed) and then describe what you found? Maybe organize: this is what we analyzed, describe the 2016 events (including the variation in signals between stations) and then the global stack. + +<|ref|>text<|/ref|><|det|>[[118, 414, 460, 429]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 430, 870, 462]]<|/det|> +We have reorganized this section in the revised manuscript (nP3L22- P5L21). Fig. S4 in the original manuscript has now been moved to Fig. S1 in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 477, 178, 493]]<|/det|> +Page 5, + +<|ref|>text<|/ref|><|det|>[[118, 508, 445, 524]]<|/det|> +line 4: How many events are in the stack? + +<|ref|>text<|/ref|><|det|>[[118, 525, 550, 540]]<|/det|> +We thank the reviewer for this missing information. + +<|ref|>text<|/ref|><|det|>[[118, 540, 875, 572]]<|/det|> +There are 671 and 967 events for the global inflation and deflation stacks, respectively. This is appended in the caption of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 587, 600, 602]]<|/det|> +Do the number of events vary in time in a systematic manner? + +<|ref|>text<|/ref|><|det|>[[118, 603, 872, 650]]<|/det|> +The number of events is relatively low in 2011- 2013. The activity increases notably in early 2014 and substantially since July 2014. The monthly event numbers are included in the Fig. S5- 10. + +<|ref|>text<|/ref|><|det|>[[118, 666, 430, 681]]<|/det|> +What do the unstacked events look like? + +<|ref|>text<|/ref|><|det|>[[118, 682, 861, 713]]<|/det|> +Waveforms of the unstacked events have been shown in Fig. S1 in the original manuscript and in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 729, 478, 744]]<|/det|> +Line 5: what does volcanic unrest mean here? + +<|ref|>text<|/ref|><|det|>[[118, 745, 460, 759]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 760, 866, 807]]<|/det|> +The volcanic unrest includes surface volcanic activities such as the dried- up of the crater- late, minor phreatic and ash eruptions and incandescent phenomena. We have appended a sentence in the revised manuscript (nP4L27- L28). + +<|ref|>text<|/ref|><|det|>[[118, 822, 878, 902]]<|/det|> +Are there eruptions in 2011- 2014 or are these events occurring without eruption? If so, that is strange - - why do these similar events occur sometimes with eruption and sometimes without? As noted in Fig. 4, there are isolated minor phreatic eruption and ash eruptions in 2011- 2014, but the detected events are generally not associated with eruptions. As noted by Niu & Song (2020), surface eruptions are not only dictated by the overpressure (i.e., magma + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 860, 119]]<|/det|> +supply), but also the strength/permeability of the conduit plug. We have appended a brief note in the revised manuscript (nP8L20- L24). + +<|ref|>text<|/ref|><|det|>[[118, 118, 180, 133]]<|/det|> +Page 6: + +<|ref|>text<|/ref|><|det|>[[118, 147, 876, 179]]<|/det|> +Line 4: Make clear from the source what your forward model is in terms of source characteristics and elastic structure. + +<|ref|>text<|/ref|><|det|>[[118, 179, 460, 195]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 195, 878, 243]]<|/det|> +While the details of the forward model are described in Method of the initial submission, we add a sentence in the revised manuscript to clarify the source characteristics and elastic structure (nP5L26- L27). + +<|ref|>text<|/ref|><|det|>[[118, 257, 860, 305]]<|/det|> +Line 15: What is the composition of the magma batch based on the eruption? One hypothesis is that this portion of magma is ascending because it has accumulated enough gas to become buoyant, so what is known about the gas compositions in the eruptions? + +<|ref|>text<|/ref|><|det|>[[118, 305, 460, 320]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 320, 880, 384]]<|/det|> +The composition of the magma batch is basalt- andesitic, and the detailed analysis has been performed by Saito et al. (2018). They estimated that the buoyancy associated with the gassed magma is up to \(\sim 150 - 350 \mathrm{g / cm^3}\) , facilitating magma ascent. We have noted the role of magma buoyancy in the revised manuscript (nP7L7- L12). + +<|ref|>text<|/ref|><|det|>[[118, 398, 866, 430]]<|/det|> +Line 16: How do we know that this is a crystal rich magma? Is this just a guess or is there some evidence from petrology about the source region? + +<|ref|>text<|/ref|><|det|>[[118, 430, 460, 445]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 445, 878, 478]]<|/det|> +We refer to earlier response in the rebuttal letter. We also briefly note the crystal- rich mush region in the revised manuscript (nP6L13- L18). + +<|ref|>text<|/ref|><|det|>[[118, 492, 875, 570]]<|/det|> +Line 20: An alternative is that the magma is that there is no new injection of magma and it is cooling/crystallizing, accumulating gas at the top of the reservoir and then episodically having sufficient buoyancy to cause brittle failure. (This is a top- down instead of a bottom- up trigger for eruptions, see for example Girona, T., Costa, F., & Schubert, G. (2015). Degassing during quiescence as a trigger of magma ascent and volcanic eruptions. Scientific reports, 5(1), 1- 7. + +<|ref|>text<|/ref|><|det|>[[118, 570, 460, 585]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 585, 880, 617]]<|/det|> +We agree that accumulating gas at the top of the reservoir may facilitate episodic brittle failure and we have included this mechanism in the revised manuscript (nP7L7- L19). + +<|ref|>text<|/ref|><|det|>[[118, 632, 880, 729]]<|/det|> +As noted in the rebuttal letter earlier, GNSS data reported by JMA indicate a slowdown of deflation in the magma chamber in July 2014, May 2015 and July 2016, suggesting a notable injection of magma from a deeper reservoir below toward the bottom of the magma chamber. These episodes correspond to increasing activities of inflation events and rising crater bottom temperature and SO2 emission (Fig. 5). The discussions are added in the revised manuscript (nP8L12- L18). + +<|ref|>text<|/ref|><|det|>[[118, 744, 180, 759]]<|/det|> +Page 7: + +<|ref|>text<|/ref|><|det|>[[118, 774, 878, 822]]<|/det|> +Line 18: This conceptual model is reasonable, but what is the evidence that there is a crystal- rich or crystal- poor mush? What is the petrological evidence for the percentage of crystals? Is it really \(>50\%\) in one reservoir and \(< 50\%\) in the other? + +<|ref|>text<|/ref|><|det|>[[118, 822, 460, 838]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 838, 880, 901]]<|/det|> +We note that the crystal- rich mush domain likely remains at a deeper depth (i.e., \(>10 \mathrm{km}\) ) after the most recent Aso- 4 caldera forming eruption (Ishibashi et al., 2018). On the other hand, we have revisited the magma plumbing system recently summarised by Kawaguchi et al. (2021) and modified the interpretation in the revised manuscript. Specifically, we noted + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 150]]<|/det|> +the process of magma mixing for post- caldera volcanisms beneath Aso volcano (Miyoshi et al. 2011; Miyoshi et al., 2012; Kawaguchi et al., 2021) and inferred discrete magma transport between a chamber with volatile- poor silicic magma and a storage zone of mixed- magma (i.e., SMSZ) (nP6L13- L19). + +<|ref|>text<|/ref|><|det|>[[118, 163, 180, 180]]<|/det|> +Page 8: + +<|ref|>text<|/ref|><|det|>[[118, 194, 850, 258]]<|/det|> +Line 2: You should be clear that you have demonstrated this for a particular volcano during a particular time period and not imply this is a universal process: "the upward transport of magma/gas from the magma chamber toward the surface is a stepwise process in an episodic fashion" + +<|ref|>text<|/ref|><|det|>[[118, 258, 880, 290]]<|/det|> +We thank the reviewer's comment. We have rephrased the sentence in the revised manuscript (nP8L20- L22). + +<|ref|>text<|/ref|><|det|>[[118, 304, 880, 336]]<|/det|> +Page 9: I'm glad to see the discussion of gas (finally), but what are the observations on degassing rate measured on the ground or by satellite? + +<|ref|>text<|/ref|><|det|>[[120, 336, 408, 351]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 351, 880, 384]]<|/det|> +The observations of \(\mathrm{SO}_2\) emission were from the campaign ground- based sensor and it is noted in the Fig. 5 caption in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 398, 871, 430]]<|/det|> +Is it really likely that some events have a high gas proportion and over events a few months later have a low gas proportion? + +<|ref|>text<|/ref|><|det|>[[120, 430, 408, 445]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 460, 880, 541]]<|/det|> +As detailed later in the rebuttal letter, we stress that the tilt- offset in some of the deflation events during the eruption may decay beyond the time scale of our analysis (i.e., \(\sim 1\) hr) and the volume change of these events is likely associated with the transport of gas, rather than magma. We suspect that such deflation events are likely of a small magnitude and lower signal- to- noise ratio. + +<|ref|>text<|/ref|><|det|>[[118, 555, 880, 635]]<|/det|> +We have appended the net volume change estimated from events with a high signal- to- noise ratio (i.e., subset I+II) (Fig. 5a). While the estimated net volume change before the eruption remains the same, the net volume change in the SMSZ during the eruption is more compatible with the net volume change before the eruption. We have expanded and clarified the discussions in the revised manuscript (nP9L11- L24). + +<|ref|>text<|/ref|><|det|>[[118, 649, 880, 712]]<|/det|> +Further, the volume discrepancy might not have anything to do with gas, but could be due to additional reservoirs being tapped that were filled long before the current eruption (that may not have a tilt/tremor signature). A volume difference of 6- 8 is at the high range considered by Rivalta and Segall (2008) but maybe appropriate for this arc volcano? + +<|ref|>text<|/ref|><|det|>[[118, 713, 875, 744]]<|/det|> +What do the authors think this ratio implies? The question of gas in the magma could be uniquely addressed with this dataset. + +<|ref|>text<|/ref|><|det|>[[120, 744, 408, 759]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 759, 881, 886]]<|/det|> +First, we followed Rivalta & Segall (2008) and included the effect of magma compressibility, on the estimate of volume change in SMSZ (Fig. 6a in the revised manuscript). The details are included in the Methods section. In short, we obtain \(R_{\nu} = 1.1 - 2.3\) , which means that the eruption output (i.e., mass of tephra fallout) is 1.1- 2.3 times of the estimated volume change in the SMSZ. As discussed by Rivalta & Segall (2008), \(R_{\nu}\) is always greater than 1. However, in the original manuscript, we have shown that the estimated volume change in the SMSZ is 6- 8 times of the DRE of tephra fallout, or equivalently \(R_{\nu} \sim 0.12 - 0.14 < 1\) . Therefore, we think the volume difference is not a result of magma compressibility. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 723, 101]]<|/det|> +We again refer to the discussion in the revised manuscript (nP9L11- L24). + +<|ref|>text<|/ref|><|det|>[[118, 133, 191, 147]]<|/det|> +Page 11: + +<|ref|>text<|/ref|><|det|>[[118, 148, 853, 180]]<|/det|> +Line4: This sentence is filled with either assumptions or claims that aren't yet supported in the manuscript such as the existence of a "crystal- rich mush and crystal- poor pool" + +<|ref|>text<|/ref|><|det|>[[120, 180, 456, 194]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 195, 880, 290]]<|/det|> +As noted earlier in the rebuttal letter, we have revisited the magma plumbing system recently summarised by Kawaguchi et al. (2021) and slightly modified the interpretation in the revised manuscript (nP6L13- L18). Specifically, we noted the process of magma mixing for post- caldera volcanisms beneath Aso (Miyoshi et al. 2011; Miyoshi et al., 2012; Kawaguchi et al., 2021) and inferred discrete magma transport between a chamber with volatile- poor silicic magma and a storage zone of mixed- magma (i.e., SMSZ). + +<|ref|>text<|/ref|><|det|>[[118, 304, 880, 384]]<|/det|> +On the other hand, we note that the crystal- rich mush domain likely remains at a deeper depth (i.e., \(>10\mathrm{km}\) ) after the most recent Aso- 4 caldera forming eruption (Ishibashi et al., 2018). This is briefly noted in the revised manuscript (nP6L13- L19). We also append a short paragraph in the introduction to lay out the background on the transition of magma plumbing system from caldera- forming eruptions to post- caldera volcanisms (nP2L7- L13). + +<|ref|>text<|/ref|><|det|>[[118, 398, 825, 445]]<|/det|> +Line 6: Is this claim discussed further somewhere? If so, I missed it: "The duration of each deformation event ( \(\sim 50\) s) is much longer than what is expected for crustal earthquakes of similar size and such a slow deformation" + +<|ref|>text<|/ref|><|det|>[[118, 446, 460, 461]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 462, 870, 494]]<|/det|> +To put the discussion in a proper context, we have rearranged the paragraph in the revised manuscript (nP7L24- L28). + +<|ref|>text<|/ref|><|det|>[[118, 508, 880, 602]]<|/det|> +The perspective could be improved with adding a paragraph or two about how the lessons here could be applied to specific other volcanoes (if possible). Applying the techniques to other volcanoes is mentioned, but what other volcanoes have a similar eruptive style and might be the best targets to investigate? Also, there are many types of eruptions or plumbing systems for which these types of analysis would not work and should be mentioned as well. If additional space is needed, I suggest dropped Figs. 5 and 6 below. + +<|ref|>text<|/ref|><|det|>[[120, 603, 408, 617]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 618, 880, 666]]<|/det|> +We have added a paragraph to discuss the applicability of the detection and identified volcanoes where the inference may be possible (nP12L17- L24). Following the suggestion by the review 2 and reviewer 3, we have removed Fig. 6 in the original manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 697, 880, 777]]<|/det|> +The data availability statement is not clear: Are the tilt and seismic waveforms available from the link provided? Also the statement that data products are available by request is no longer considered a best practice (for example, it is not allowed by AGU). These data products are not required to be made available in a public repository, but it would add great value if they were. Does UCL have such a repository? + +<|ref|>text<|/ref|><|det|>[[120, 777, 456, 791]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 792, 880, 839]]<|/det|> +The data availability and code availability have been restructured according to Nature Communications requirement. The broadband and tilt waveforms are available from the provided link. The catalogue and code can be obtained upon request. + +<|ref|>text<|/ref|><|det|>[[118, 854, 880, 900]]<|/det|> +Fig.1: What are BCU and BYA chambers? They are not mentioned in the caption. Also, what is the depth of the low velocity zone, and other features listed in the legend (maybe refer to Fig. 3)? We thank the reviewer for this comment. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[120, 85, 406, 101]]<|/det|> +We refer the depths info to Fig. 3c. + +<|ref|>text<|/ref|><|det|>[[117, 131, 888, 197]]<|/det|> +Fig. 2: Some more details are needed in the caption. How many events are stacked together here? We thank the reviewer for the comment. We have revised the caption. The number of events used for the inflation and deflation stacks is 671 and 967, respectively. + +<|ref|>text<|/ref|><|det|>[[120, 210, 825, 244]]<|/det|> +How were events horizontally aligned? We clarified in the caption that the traces are aligned with respect to the onset of LP. + +<|ref|>text<|/ref|><|det|>[[118, 257, 845, 290]]<|/det|> +Fig. 3: Where do the horizontal and vertical displacements in a and b come from? GNSS? Or integrated from seismometer? + +<|ref|>text<|/ref|><|det|>[[120, 290, 460, 305]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[118, 306, 852, 354]]<|/det|> +The horizontal and vertical displacement are obtained from the broadband seismograms and the data processing has been detailed in the Method section (Estimate the static displacement offset from broadband seismograms). + +<|ref|>text<|/ref|><|det|>[[118, 368, 866, 415]]<|/det|> +I could be helpful in d to show the depths of the features shown in a, b, and c: where are the low velocity zone, BYA and BCA chambers, inverted source location (Red Cross) and new Mogi (black circle)? + +<|ref|>text<|/ref|><|det|>[[118, 415, 602, 446]]<|/det|> +We thank the reviewer's comment. We show the depths of all features in Fig. 3c with a legend. + +<|ref|>text<|/ref|><|det|>[[118, 461, 864, 494]]<|/det|> +Why is there an aquifer labeled in d? I don't think the aquifer is mentioned in the caption or the text. + +<|ref|>text<|/ref|><|det|>[[118, 494, 878, 526]]<|/det|> +The aquifer near the crack- like conduit has been widely discussed in the literature. We have noted the aquifer in the revised manuscript (nP6L6- L12) + +<|ref|>text<|/ref|><|det|>[[118, 541, 881, 589]]<|/det|> +I'm also confused about what is happening in e, f, and g. What are the red and blue dotted lines at the line labeled LPT? What are the arrow at the SPT line? What are the arrows in- between the LPT and SPT lines? What physical processes do these arrows/features represent? + +<|ref|>text<|/ref|><|det|>[[118, 589, 408, 603]]<|/det|> +We thank the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[118, 603, 835, 620]]<|/det|> +We have modified the caption and append the details (Fig 4 in the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[118, 634, 868, 666]]<|/det|> +Fig. 4a: where does the accumulative net volume change come from? The data used to calculate this should be mentioned in the caption. + +<|ref|>text<|/ref|><|det|>[[118, 666, 456, 681]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 682, 880, 745]]<|/det|> +As already noted in the original manuscript (P8L8- L12), the accumulative net volume change is calculated from the monthly volume change associated with the monthly inflation/deflation event stacks. We also mentioned this information in the revised manuscript (nP9L1- L5). + +<|ref|>text<|/ref|><|det|>[[118, 760, 876, 824]]<|/det|> +I do not user stand the labels that say, for example, delta \(V\) magma \(< <\) delta \(V\) gas during time period 1. It looks like the volume change is basically flat during this time period, so shouldn't these two volume changes be in approximate balance instead of orders of magnitude different (as implied by using \(< <\) )? + +<|ref|>text<|/ref|><|det|>[[118, 825, 469, 840]]<|/det|> +We thank the reviewer for this suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 840, 880, 902]]<|/det|> +The volume change during episode 1 is not flat. As noted in earlier reply, we have modified the text to clarify the discussion in the revised manuscript (nP9L11- L17). In particular, we have appended the net volume change from events with a high signal- to- noise ratio (i.e., subset I+II) (Fig. 5a in the revised manuscript) to facilitate the discussion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 100, 865, 148]]<|/det|> +Fig. 4b: What is "outgassing potential"? I haven't heard this term before and the phrase used in the caption is still confusing: "the moment ratio between pressurization and 10 depressurization LPTs" + +<|ref|>text<|/ref|><|det|>[[119, 149, 455, 164]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[117, 164, 880, 196]]<|/det|> +To avoid confusion and focus on the observations, we replace Fig. 5b with crater bottom (wall) temperature and append discussions in the revised manuscript (nP8L14- L18). + +<|ref|>text<|/ref|><|det|>[[117, 210, 852, 243]]<|/det|> +Fig. 4d: Where is the volume change rate being measured? SMSZ? The caption says the black crosses are the "inflation event" but I think this should be "inflation events. + +<|ref|>text<|/ref|><|det|>[[119, 243, 460, 258]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[117, 258, 880, 306]]<|/det|> +Yes, the volume change rates refer to the SMSZ. We have used circle and cross to indicate the averaged rate and single- event rate, respectively. Fig. 4d has now been rearranged as Fig. 6b in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 320, 880, 400]]<|/det|> +" What is the geodetic data used to estimate the green cross? Is this the same tilt data described in this paper or something else, like GNSS? What is the time period of the geodetic data? The geodetic data corresponding to the green cross is levelling data. The time period of the geodetic data is from 1958 to 2004. This has been clarified in the revised manuscript (Fig. 6b). + +<|ref|>text<|/ref|><|det|>[[117, 414, 840, 446]]<|/det|> +In general, it should be noted that these volume change rates are being measured over vastly different time periods and the time periods should be mentioned in the caption. + +<|ref|>text<|/ref|><|det|>[[119, 446, 456, 461]]<|/det|> +We thank the comment by the reviewer. + +<|ref|>text<|/ref|><|det|>[[117, 461, 880, 508]]<|/det|> +We have modified the figure and the caption to highlight the difference. In addition, we use a different symbol to highlight the volume change rate for a single event (i.e., time scale of \(\sim\) 100 s). + +<|ref|>text<|/ref|><|det|>[[117, 524, 857, 555]]<|/det|> +Fig. 4e: Considering there are only 2 data points, it does not seem wise to draw a line between them. + +<|ref|>text<|/ref|><|det|>[[117, 556, 880, 603]]<|/det|> +The line is not a fitting line. It simply indicates a 1- to- 1 relationship between the estimated mass change in SMSZ and the mass of tephra fallout. If the estimated mass change in SMSZ is equal to the mass of tephra fallout, the data point will fall on the line. + +<|ref|>text<|/ref|><|det|>[[117, 618, 880, 681]]<|/det|> +Figures 5 and 6 have minimal discussion in the text and do not seem to factor into the key conclusions mentioned in the abstract - - could they be removed? They probably deserve further discussion in a separate paper. Fig. 5 has a huge amount of information that isn't discussed in the main text. + +<|ref|>text<|/ref|><|det|>[[119, 682, 447, 697]]<|/det|> +We thank the review for the suggestion. + +<|ref|>text<|/ref|><|det|>[[117, 697, 880, 729]]<|/det|> +We have removed Fig. 6 in the original manuscript. On the other hand, we have expanded the discussions for Fig. 5 (now Fig. 7) in the revised manuscript (nP11L26- nP12L5). + +<|ref|>text<|/ref|><|det|>[[117, 743, 864, 880]]<|/det|> +In particular, I think Fig. 6 is confusing and possibly misleading. It seems to take a single volcanic system and wildly extrapolate it to all systems worldwide. This figure seems to imply that the magma plumbing system of Aso is relevant to all types of eruptions from Rhyolites to flood basalts which is clearly not true - - we have enough information to know that the plumbing of Aso is not widely applicable to all volcanoes. The authors should consider what is the point this figure is trying to make and if it is already made successfully in the text. If the point is that "Composition, viscosity, rheology and tectonic settings govern the recurrences of episodic deformation" then this point can be made adequately in the text without confusing the reader. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 856, 163]]<|/det|> +Following the suggestion by the reviewer 3 and another reviewer, we remove Fig. 6 in the original manuscript since the main point has been discussed in the text. Instead, we add a sentence in the revised manuscript to emphasize that magma composition, viscosity, rheology and tectonic settings govern the recurrences of episodic deformation (nP10L12- L14). + +<|ref|>text<|/ref|><|det|>[[118, 179, 768, 212]]<|/det|> +Fig. 6: "providing the glue" is a confusing phrase herePlease see above reply and Fig. 6 in the original manuscript has been removed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[120, 85, 413, 100]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 115, 810, 148]]<|/det|> +Review comments on Episodic transport of discrete magma batches beneath Aso volcano By Jieming Niu, Teh- Ru Alex Song + +<|ref|>text<|/ref|><|det|>[[118, 162, 772, 194]]<|/det|> +This manuscript is quite interesting and is sufficiently valuable to publish on Nature Communications. + +<|ref|>text<|/ref|><|det|>[[118, 211, 251, 225]]<|/det|> +Major comments + +<|ref|>text<|/ref|><|det|>[[118, 226, 872, 288]]<|/det|> +1) Source of tilt offset is discussed in the relation of crystal rich and crystal poor zones. I cannot well understand how to relate the source of tilt off set with the rate of crystal. The reference 48 investigate volatile from the viewpoint of petrology. If source of tilt offset is related with volatile-rich and volatile-poor zones, this might be better understood. + +<|ref|>text<|/ref|><|det|>[[118, 289, 880, 336]]<|/det|> +We thank the reviewer for the comments. As pointed out by the reviewer, the reference 48 (Kawaguchi et al., 2021) did not directly address crystal-rich or crystal-poor zone in the magmatic system beneath Aso caldera. + +<|ref|>text<|/ref|><|det|>[[118, 351, 880, 494]]<|/det|> +As noted earlier in the rebuttal letter, following latest petrological studies (e.g., Kawaguchi et al., 2021), we note magma mixing between volatile-poor silicic magma at the magma chamber ( \(\sim 4 - 10 \mathrm{km}\) ) and volatile-rich basaltic magma coming from a deeper reservoir ( \(>10 \mathrm{km}\) ). Furthermore, the storage depth of mixed-magma is determined at \(\sim 2 - 4 \mathrm{km}\) depth (or \(\sim 1 - 3 \mathrm{km}\) BSL). The source of tilt is interpreted as a transport of magma batch between the top of magma chamber and the storage zone of mixed magma (SMSZ discussed in the manuscript). We have modified the interpretation in the revised manuscript (nP6L13- L18, nP6L23- L28). The transport process is also elaborated in the revised manuscript (nP7L3- L28). + +<|ref|>text<|/ref|><|det|>[[118, 508, 868, 572]]<|/det|> +2) Source of tilt offset is also discussed on brittle-ductile transition zone. However, the authors assumes that tilt offset is induced by volume change of a combination model of tensile crack and explosive source in elastic medium and this model does not include fracture. Brittle and ductile are manners of fracture. + +<|ref|>text<|/ref|><|det|>[[120, 572, 450, 587]]<|/det|> +We thank the comment by the reviewer. + +<|ref|>text<|/ref|><|det|>[[118, 588, 880, 682]]<|/det|> +Here we disagree with the reviewer's comment. As noted by Aki & Richard (2002, Quantitative Seismology, chapter 3) and many other seismology textbooks, seismic moment tensor is a general force- equivalent representation of internal sources, including fracture, explosion and tensile- crack inside the earth. On the other hand, to reiterate, our seismic moment tensor inversion shows that the source of the tilt- offset has a predominant volumetric component and \((\sim 80\%)\) and a minor normal- fault component \((\sim 20\%)\) . + +<|ref|>text<|/ref|><|det|>[[118, 697, 812, 729]]<|/det|> +Regarding to the model of elastic deformation, source of tilt offset should be discussed on difference in elastic constants along the magma plumbing system. + +<|ref|>text<|/ref|><|det|>[[118, 729, 880, 840]]<|/det|> +As noted by Aki & Richard (2002, Quantitative Seismology, chapter 3), the elastic moduli used in the force- equivalent representation of internal sources are constants appropriate for the wall rock (or unaltered rock). While it is likely that the elastic constant within the magma plumbing system may vary, it does not change seismic wave excitation in the frequency band of our interest (i.e., \(>50\) sec). We have briefly discussed the effect of elastic constant on source inversion and the volume change in the revised manuscript (nP5L26- L29). + +<|ref|>text<|/ref|><|det|>[[118, 855, 856, 902]]<|/det|> +The inverted source location and geometry only depends on the displacement or tilt ratio among different stations or/and different components. We also inverted the source with a different velocity structure and the effect of elastic constant on the solution is minimal. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 878, 163]]<|/det|> +3) The significance of comparison of 2011-2016 eruptivity of Aso with basaltic eruptivity is not well understood. As mentioned in the text, long-term eruption rate of andesitic volcanoes is lower than basaltic volcanoes. I cannot find a significance of comparison of eruption rate between andesitic and basaltic volcanoes in this manuscript. + +<|ref|>text<|/ref|><|det|>[[120, 164, 455, 179]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 180, 880, 242]]<|/det|> +We have added a paragraph and noted the relevance of the comparison in the revised manuscript (nP11L26-nP12L5). Comparing mass discharge rate between basaltic and basalt-andesitic volcanoes help elucidate the regime where the mass discharge rate can be approximated by the mass flow rate. + +<|ref|>text<|/ref|><|det|>[[118, 256, 876, 304]]<|/det|> +The eruption 2011- 2016 is an eruptive activity of Aso, however it does not cover all the eruptivity of Aso. If compared, the eruption 2011- 2016 should be compared with past eruptivity of Aso or long- term eruptivity of the volcano. + +<|ref|>text<|/ref|><|det|>[[118, 322, 878, 432]]<|/det|> +We largely agree with the reviewer's comment. In Fig. 4d in the original manuscript, we did compare the averaged eruption output rate in 2011- 2016 against the output rate in historical eruptions and long- term eruption output rate over the geological time scale. These comparisons have been noted in P8L8- L18 in the original manuscript. In the revised manuscript, we also appended the magma discharge rates of the 1979 and 1989 eruptions in the Fig. 6 for comparisons. We have modified the text accordingly (nP11L16- L20). + +<|ref|>text<|/ref|><|det|>[[118, 450, 258, 479]]<|/det|> +Minor comments P3L20 + +<|ref|>text<|/ref|><|det|>[[120, 481, 370, 496]]<|/det|> +"natural period" -> band width + +<|ref|>text<|/ref|><|det|>[[118, 497, 810, 529]]<|/det|> +The use of natural period was correct. It is used to describe the resonant period of a seismometer (pp.175, Lay and Wallace, 1995). + +<|ref|>text<|/ref|><|det|>[[118, 544, 171, 557]]<|/det|> +P4L12 + +<|ref|>text<|/ref|><|det|>[[118, 560, 720, 575]]<|/det|> +LP signal east- west is much weaker, but north- south is stronger than N.ASIV. + +<|ref|>text<|/ref|><|det|>[[118, 576, 797, 607]]<|/det|> +We thank the reviewer for the comment. The change has been made in the revised manuscript (nP4L17- L21). + +<|ref|>text<|/ref|><|det|>[[118, 622, 802, 653]]<|/det|> +P4L13 "These observations strongly indicate that the source of the tilt offset is spatially separated from the LPT source" + +<|ref|>text<|/ref|><|det|>[[118, 654, 816, 670]]<|/det|> +It is possible, but is it necessary to examine source difference between tilt offset and LPT? + +<|ref|>text<|/ref|><|det|>[[118, 670, 455, 684]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 685, 880, 749]]<|/det|> +As discussed in P4L8- L13 in the original manuscript, the difference in the amplitude between LPT and tilt offset among different seismic station or/and channels is a direct indication that the source of tilt offset must differ from the source of LPT, either in location or mechanism. We have rephrased the sentence to clarify this conjecture (nP4L23- L25). + +<|ref|>text<|/ref|><|det|>[[118, 764, 559, 779]]<|/det|> +P4L14 "which is near the active Naka- dake first crater" + +<|ref|>text<|/ref|><|det|>[[118, 780, 365, 794]]<|/det|> +Show references or see Method. + +<|ref|>text<|/ref|><|det|>[[118, 796, 806, 827]]<|/det|> +We thank the reviewer's comment and have cited relevant references in the revised manuscript (nP4L25). + +<|ref|>text<|/ref|><|det|>[[118, 842, 350, 857]]<|/det|> +P5L3 global waveform stacks + +<|ref|>text<|/ref|><|det|>[[118, 858, 598, 873]]<|/det|> +What do you mean "global"? How many LPTs were stacked? + +<|ref|>text<|/ref|><|det|>[[118, 874, 864, 906]]<|/det|> +We thank the reviewer for the comment. The term "global" is used to highlight waveform stacks over the period of unrest (2011- 2014 August) and Strombolian eruption (Nov. 2014- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 870, 117]]<|/det|> +Apr 2015). The number of LPT events used for stacking is shown in Fig. 2 and noted in the caption. + +<|ref|>text<|/ref|><|det|>[[118, 132, 295, 163]]<|/det|> +P5L9 relatively steady Almost the same? + +<|ref|>text<|/ref|><|det|>[[118, 164, 800, 196]]<|/det|> +We thank the reviewer's comment. We have rephrased the sentence in the revised manuscript (nP5L4). + +<|ref|>text<|/ref|><|det|>[[118, 211, 234, 225]]<|/det|> +P5L21 Fig. S4 + +<|ref|>text<|/ref|><|det|>[[118, 227, 866, 258]]<|/det|> +Fig. S4 is "Synthetic amplitude- distance decay against static and filtered waveforms". Inserting Fig. S4 explains why you choose 100- 200s ULP band? + +<|ref|>text<|/ref|><|det|>[[118, 258, 455, 272]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 273, 805, 289]]<|/det|> +We have modified the sentences accordingly in the revised manuscript (nP4L3- L6). + +<|ref|>text<|/ref|><|det|>[[118, 304, 235, 318]]<|/det|> +P7L2 "SMSZ" + +<|ref|>text<|/ref|><|det|>[[118, 320, 560, 335]]<|/det|> +"SMSZ" firstly appeared here. This should be explained. + +<|ref|>text<|/ref|><|det|>[[118, 336, 875, 368]]<|/det|> +We thank the reviewer for the comment. The SMSZ is first defined and noted in the revised manuscript (nP6L21). + +<|ref|>text<|/ref|><|det|>[[118, 383, 222, 398]]<|/det|> +P7L5 intense + +<|ref|>text<|/ref|><|det|>[[118, 400, 595, 415]]<|/det|> +Is this word necessary? What do you mean "intense unrest"? + +<|ref|>text<|/ref|><|det|>[[118, 415, 456, 430]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 431, 878, 462]]<|/det|> +We have added a brief note to define specific activities in the revised manuscript (nP8L2- L4). + +<|ref|>text<|/ref|><|det|>[[118, 478, 872, 509]]<|/det|> +P7L18 "a deeper reservoir (i.e., a crystal- rich mush) and temporarily stalled in the SMSZ (i.e., a crystal- poor pool)" + +<|ref|>text<|/ref|><|det|>[[118, 510, 856, 540]]<|/det|> +The reference 48 investigate volatile. How does it relate to crystal? Are there any evidence for crystal- poor in the SMSZ? + +<|ref|>text<|/ref|><|det|>[[118, 541, 455, 555]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 556, 880, 587]]<|/det|> +As noted earlier in the rebuttal letter, we have modified the interpretation and the discussions in the revised manuscript (nP6L13- L19). + +<|ref|>text<|/ref|><|det|>[[118, 602, 191, 616]]<|/det|> +P8L1- L7 + +<|ref|>text<|/ref|><|det|>[[118, 619, 606, 634]]<|/det|> +For estimation of volume increase, Method should be referred. + +<|ref|>text<|/ref|><|det|>[[118, 635, 872, 666]]<|/det|> +We thank the reviewer for the comment. This statement has been referred to the Method in the revised manuscript (nP9L1- L5). + +<|ref|>text<|/ref|><|det|>[[118, 682, 210, 696]]<|/det|> +P8L13- L22 + +<|ref|>text<|/ref|><|det|>[[118, 698, 875, 728]]<|/det|> +This hypothesis is true. As the authors show clearly, LPT is a short- lived phenomenon. What does the author mention, comparing short- lived volume change with long- term eruptivity? + +<|ref|>text<|/ref|><|det|>[[118, 729, 456, 743]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 744, 880, 822]]<|/det|> +As noted in the original manuscript LPT (termed VLP in the revised manuscript) has been observed over multiple eruption cycles since 1920s (Sassa, 1935; Sakaguchi et al., 2008). This provides a means to detect synchronous VLP and inflation/deflation event and evaluate single- event volume change for historical eruptions. This point has been addressed in the revised manuscript (nP12L11- L16). + +<|ref|>text<|/ref|><|det|>[[118, 838, 875, 885]]<|/det|> +P10L11- L13 "While the estimated mass flow rate in Aso is lower than those estimated in basaltic eruptions by an order of magnitude (Fig. 5), such a difference is consistent with the disparity in the average volcanic output rate between basaltic eruptions and andesitic eruptions" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 863, 100]]<|/det|> +In this case, Aso means activity 2011- 2016? Which eruption does "basaltic eruption" indicate? + +<|ref|>text<|/ref|><|det|>[[120, 100, 460, 115]]<|/det|> +We thank the reviewer for the comment. + +<|ref|>text<|/ref|><|det|>[[118, 115, 880, 196]]<|/det|> +Yes, the mass discharge rate was referred to Aso activity 2011- 2016. In the original manuscript, the basaltic eruptions refer to data shown in Fig 5 (solid diamonds in Fig. 7 in the revised manuscript) where both the decompression rate and the mass discharge rate are available (Barth et al., 2019). On the other hand, the relevant discussion has been revised in the revised manuscript (nP11L26- nP12L5). + +<|ref|>text<|/ref|><|det|>[[118, 210, 860, 257]]<|/det|> +The first half is comparison of short term activity. Second half is long- term comparison. Long- term comparison may be true. But short- term comparison is case- by- case. It is not necessary to be consistent. + +<|ref|>text<|/ref|><|det|>[[118, 257, 880, 289]]<|/det|> +As noted above in the rebuttal letter, the relevant discussion can be referred to the revised manuscript (nP11L26- nP12L5). + +<|ref|>text<|/ref|><|det|>[[118, 304, 456, 368]]<|/det|> +P22L11Takahiro -> TakahiroWe thank the reviewer for the comment. This has been modified accordingly. + +<|ref|>text<|/ref|><|det|>[[118, 383, 880, 462]]<|/det|> +FiguresP24L9 October 8, 2016Need time of onset of the eruption.The onset of the eruption is marked by the red line. We have modified the caption of Fig. 1b accordingly. + +<|ref|>text<|/ref|><|det|>[[118, 477, 582, 508]]<|/det|> +(b) N.ASHV.LE is tilt of east-side down at station N.ASHV?Yes, we have also clarified this in the caption. + +<|ref|>text<|/ref|><|det|>[[118, 524, 640, 572]]<|/det|> +Is Figure 6 needed?We thank the reviewer for the comment.As suggested by the reviewers, this figure has been removed. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[105, 84, 296, 98]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[105, 113, 401, 128]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[103, 143, 920, 173]]<|/det|> +I thank the authors for addressing my comments in the first round of review. I think they have adequately modified their manuscript and I recommend publication in its present form. + +<|ref|>text<|/ref|><|det|>[[105, 203, 401, 217]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[105, 233, 926, 307]]<|/det|> +I think the manuscript is well revised according to the comments by the reviewers. This manuscript documents magma plumbing system of Aso volcano from the deep chamber to the shallow conduit and reveals SMSZ to connect the two magmas. The two stages; pre- eruptive and Strombolian eruption are well separated by extracting minor offset of the tilt and seismic events. This attains at a level to publish on nature communications, supporting high- precision data. + +<|ref|>text<|/ref|><|det|>[[105, 322, 356, 381]]<|/det|> +The followings may be mistyped. P2 L27 sthe- >the Fig1 L6 NewMogi - > New Mogi Fig2 L8 acasual - > casual + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 884, 152]]<|/det|> +In the following response, the comments by the reviewers are shown in italic, our responses are shown in bold. The page and line numbers in the original manuscript are noted as P?L??. The responses discussed in the rebuttal letter are also highlighted in yellow in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[120, 166, 415, 182]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 198, 845, 247]]<|/det|> +I thank the authors for addressing my comments in the first round of review. I think they have adequately modified their manuscript and I recommend publication in its present form. We thank the reviewer for the positive comments and support for the publication. + +<|ref|>text<|/ref|><|det|>[[120, 261, 415, 277]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 292, 872, 386]]<|/det|> +I think the manuscript is well revised according to the comments by the reviewers. This manuscript documents magma plumbing system of Aso volcano from the deep chamber to the shallow conduit and reveals SMSZ to connect the two magmas. The two stages; pre-eruptive and Strombolian eruption are well separated by extracting minor offset of the tilt and seismic events. This attains at a level to publish on nature communications, supporting high- precision data. We thank the reviewer for the positive comments and support for the publication. + +<|ref|>text<|/ref|><|det|>[[120, 401, 372, 417]]<|/det|> +The followings may be mistyped. + +<|ref|>text<|/ref|><|det|>[[118, 418, 616, 450]]<|/det|> +P2 L27 sthe- >the This has been corrected as P2L27 in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 464, 860, 514]]<|/det|> +Fig1 L6 NewMogi - > New Mogi This has been corrected as P30L8 in the revised manuscript. "NewMogi" in the figure has also been replaced by "New Mogi". + +<|ref|>text<|/ref|><|det|>[[118, 528, 616, 560]]<|/det|> +Fig2 L8 acasual - > casual This has been corrected as P31L8 in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 574, 880, 656]]<|/det|> +Note we slightly revise Fig. 5b and append the temperature data from ground- based thermal camera (Cigolini et al., 2018), filling the data gap between late 2014 and 2016. We append two references summarizing latest efforts on deep low- frequency earthquakes (P12L25). We slightly refine and make a more precise description of source mechanism (P6L3- 5) and append uncertainty estimates in the supplementary Table 2. + +<|ref|>text<|/ref|><|det|>[[118, 671, 861, 754]]<|/det|> +Finally, we have also followed the checklist and slightly reformat the manuscript. As suggested by the editorial team, we include an image to be featured in Nature Communications. We believe the image vividly illustrates the background crater- lake and diverse eruption styles in Aso volcano. The original images are credited to Dr. Akihiko Yokoo in Aso Volcano Observatory. + +<--- Page Split ---> diff --git a/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/images_list.json b/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..40d4bcaacc70c4de1ab6ab449a2104f8620a7f70 --- /dev/null +++ b/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,167 @@ + +# nature portfolio + +Peer Review File + +Activator- blocker model of transcriptional regulation by pioneer- like factors + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Riesle and Gao et al. analyzed ATAC- seq, H3K27ac ChIP- seq, and transcriptome of zebrafish mutants of ZGA regulator TFs. They found the existence of synergistic and antagonistic enhancer types, and Pou5f3 and Nanog can function as activator or blocker in antagonistic enhancers. The topic is unquestionably important for the field, but this reviewer feels that the novelty of the study seems weak. I have several major concerns as described below. + +Regarding the novelty, the fact that the pioneer factors (Pou5f3 and Sox19b) is preventing premature expression for some of the genes during ZGA has already been reported by the same group (Gao et al., 2022). The idea that Pou5f3 and Nanog is competing at a same binding site and may function as a blocker is indeed interesting and advancing our knowledge, but molecular experimental evidence is lacking. How Pou5f3 and Nanog function as a non- pioneer blocker is also completely a blackbox. To address underlying molecular mechanisms, at least the authors should do experiments such as gel- shift assay to enhancer sequences of specific group of genes. + +The authors claim the presence of additional genome activators, but the evidence is not enough. First, in Fig. 2a, why did not the authors use the MZsox19b for the classification? Second, the results show that \(\sim 50\%\) or \(\sim 80\%\) of group 4. - TdARs can be rescued by Sox19b alone, or by Sox19b and Nanog, respectively (Fig S3). From these data, it is likely that SoxB, or SoxB and Nanog is required on chromatin accessibility of most of group 4. - TdARs. + +Characterization of antagonistic enhancers is not enough. They show GC content for 1. PN, 2. P, 3. N, and 4. -, but comparison between p- n+, p+ n- and others is required. Furthermore, they mention that exact match to the motif is important for Pou5f3 and Nanog to function as pioneer TFs, but this does not explain the difference between synergistic and antagonistic enhancers. Why do Pou5f3 and Nanog function as blocker only in antagonistic enhancers, but not in synergistic enhancers? The author also need to have additional experimental data as stated above. + +Regarding the mathematical modelling; in Figure 5c, expressions of 3b. P- N+ genes do not seem to be upregulated in MZps. They even seems down regulated at stages before 6 hpf. Furthermore, gene ontology analyses are not enough to evaluate the model accuracy, and validation in other method is required. For example, is there any differences in sequence feature between enhancers of the six groups sorted by the model? + +Reviewer #2 (Remarks to the Author): + +The manuscript "Activator- blocker model of transcriptional regulation by pioneer- like factors," by Riesle et al takes a deep dive into functions for the transcription factors Pou5f3, Sox19b and Nanog during zebrafish zygotic genome activation. Their analysis uses a combination of elegant genetic and genomic approaches. The results reveal surprising complexities in the ways in which Pou5f3, Sox19b and Nanog work both together and antagonistically to regulate early transcription. + +<--- Page Split ---> + +Overall this is a rigorous study which produces useful data sets and shifts the way we need to think about how these transcription factors act during zebrafish ZGA. I have only minor comments. + +The authors do a very nice job of detailing the crosses performed to generate the various mutant lines in the methods, and the original alleles are cited. However, given the importance of the mutants it might be worth reviewing the nature of the alleles in the start of the results section. For example, do any of them produce proteins that could still have some DNA binding capacity? + +Figure 2b, not clear exactly what control genomic regions are. + +With respect to figure 2, it could be more helpful to include a little more detail on the binning of up down and unchanged groups in the text or figure legend (what were the cutoffs/criteria for including). I similarly struggled to find this information in the methods, if it is there it is not easy to find. + +Figure 3 panel 1 is a little confusing. Is purple color code also needed? + +With respect to figure 3 F, it isn't entirely clear to me why this group couldn't reflect a requirement for all three TFs together, rather than any one plus GC binding factor- Fig 3b seems to suggests binding motifs for all three are detected in this group, although the so: pou motif is underrepresented. The GC enrichment could still represent a hypothetical GC binding factor required in addition to the three factors? Alternatively, is it possible that there is simply a structural property of these GC rich regions that is keeping them more open? I believe there is reasonable data to support a relationship between GC content and nucleosome occupancy + +The rescue experiments in Fig S3 are quite nice. I almost wonder if they might be better in the main text of the manuscript. + +Figure 4, Panel C in particular is really important and very difficult to interpret, not at all intuitive. Is there any other way to present this data more clearly? I had to sit with the browser shots in panel H a good while to understand what was going on holistically in figure 4. + +I think a prediction of the model in 4f is that you should never be able to IP A and B from chromatin together at these types of sites. Is it possible to do sequential IPs to explore that possibility? This could be interesting additional support, but if this is technically too challenging, could be viewed as beyond the current paper's scope. + +<--- Page Split ---> + +Dear reviewers #1 and #2, + +We are grateful that you professionally spotted the weak points in our manuscript, which helped us to improve it. We performed additional experiments, added new sub- chapter in the results section with new main Fig. 5 and Fig. S6, performed additional analysis and made changes in most of the figures. We numbered your comments and linked them as comments to the yellow- marked text in the PDF file "Riesle_main_and SUPPL_marked for reviewers", which contains main text and figures, supplementary figures and legends and also additional supplementary Figure for Reviewer 1, at the end of the supplementary material. Please find detailed answers to your criticisms below. Sincerely, the authors. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Riesle and Gao et al. analyzed ATAC- seq, H3K27ac ChIP- seq, and transcriptome of zebrafish mutants of ZGA regulator TFs. They found the existence of synergistic and antagonistic enhancer types, and Pou5f3 and Nanog can function as activator or blocker in antagonistic enhancers. The topic is unquestionably important for the field, but this reviewer feels that the novelty of the study seems weak. I have several major concerns as described below. + +R1- 1. Regarding the novelty, the fact that the pioneer factors (Pou5f3 and Sox19b) is preventing premature expression for some of the genes during ZGA has already been reported by the same group (Gao et al., 2022). The idea that Pou5f3 and Nanog is competing at a same binding site and may function as a blocker is indeed interesting and advancing our knowledge, but molecular experimental evidence is lacking. How Pou5f3 and Nanog function as a non- pioneer blocker is also completely a blackbox. To address underlying molecular mechanisms, at least the authors should do experiments such as gel- shift assay to enhancer sequences of specific group of genes. + +A 1- 1. We agree with the comment and provide requested evidence. We performed series of the gel- shift assays with the oligos from different enhancers, added the new figures 5 and S6 and a chapter "Pou5f3 and Nanog bind to the common binding sites in a mutually exclusive way". We also show that in most cases TdARs have only one match to either Pou5f3 or Nanog motif (new panel Fig. S5f). + +R1- 2. The authors claim the presence of additional genome activators, but the evidence is not enough. First, in Fig. 2a, why did not the authors use the MZsox19b for the classification? Second, the results show that \(\sim 50\%\) or \(\sim 80\%\) of group 4- TdARs can be rescued by Sox19b alone, or by Sox19b and Nanog, respectively (Fig S3). From these data, it is likely that SoxB, or SoxB and Nanog is required on chromatin accessibility of most of group 4- TdARs. + +A1- 2. We agree with both points. In response to this criticism we - made additional analysis of 4- group, using ATAC- seq in MZsox19b and three double mutants (new panel c in the Fig. S3). - removed "hypothetical GC protein" from the scheme in Fig.3; and speculations about "hypothetical GC protein" from the corresponding text in the results. + +R1- 3. Characterization of antagonistic enhancers is not enough. They show GC content for 1. PN, 2. P, 3. N, and 4. -, but comparison between p- n+, p+ n- and others is required. + +A1- 3. Done (Fig. S4). Conclusion: overall GC content of enhancers activated by Pou5f3 is lower than of the enhancers activated by Nanog. This is seen in both ATAC- seq (Fig.3e, Fig. S4b) and H3K27ac comparisons between TdARs (Fig. S4b). + +R1- 4. Furthermore, they mention that exact match to the motif is important for Pou5f3 and Nanog to function as pioneer TFs, but this does not explain the difference between synergistic and antagonistic enhancers. Why do Pou5f3 and Nanog function as blocker only in antagonistic enhancers, but not in synergistic enhancers? The author also need to have additional experimental data as stated above. + +A1- 4. There are two parts of the answer to this criticism: + +1) Yes, we provided additional experimental data and confirmed now with gel-shifts, that the factor which binds stronger in-vitro works as an activator in-vivo (9 out of 9 oligos with single motif, where the binding worked for any of the two TFs, see the new Fig. 5 panel e). We also show that GC content is important: Pou5f3 activates the enhancers with lower GC content range, than Nanog, as judged by pioneer activity (Fig.3e) and H3K27ac change (Fig.S4). + +<--- Page Split ---> + +2) No, we can not explain the mechanistic difference between synergistic and antagonistic enhancers from gel-shifts and bulk genomic data. We assume that cell-specific cofactors are involved (see discussion). Single-cell analysis is required to answer this question; as far as we know ChIP-seq technique for single cells is not yet developed. We hope that our manuscript is novel enough to be published without it. + +R1- 5. Regarding the mathematical modelling; in Figure 5c, expressions of 3b. P- N+ genes do not seem to be upregulated in MZps. They even seems down regulated at stages before 6 hpf.f + +This is because most of 3b. P- N+ genes are coactivated by SOXB1 sum, and SOXB1 sum is decreased in MZps. ( see the supplementary Figure for Reviewer 1 included in the file for reviewers). 3b. P- N+ model group consists of three mini- models: of three mini- models: S+P- N+ (best fit to 398 transcripts), SOP- N+ (best fit to 24 transcripts) and S- P- N+ (best fit to 6 transcripts). In response to this criticism we changed the summatory figure S8, which shows now the example fits to all mini- models ( and not to the groups as before). + +R1- 6. Furthermore, gene ontology analyses are not enough to evaluate the model accuracy, and validation in other method is required. + +We did not intent to validate the modeling with GO analysis. In response to this criticism we completly removed this GO analysis from the paper, not to distract the reader attention. We renamed the sub- chapters and put the cross- validation part (the synergistically and antagonistically regulated transcripts are linked to synergistically and antagonistically regulated enhancers) just after the description of the modeling results (see the marking of the text for reviewers). + +R1- 7. For example, is there any differences in sequence feature between enhancers of the six groups sorted by the model? + +Yes, there is a difference in both sequence features: motif frequency and in GC content. We show it now in Fig. S9 c,d, as additional validation. + +Reviewer #2 (Remarks to the Author): + +The manuscript "Activator- blocker model of transcriptional regulation by pioneer- like factors," by Riesle et al takes a deep dive into functions for the transcription factors Pou53, Sox19b and Nanog during zebrafish zygotic genome activation. Their analysis uses a combination of elegant genetic and genomic approaches. The results reveal surprising complexities in the ways in which Pou53, Sox19b and Nanog work both together and antagonistically to regulate early transcription. + +Overall this is a rigorous study which produces useful data sets and shifts the way we need to think about how these transcription factors act during zebrafish ZGA. I have only minor comments. + +R2- 1. The authors do a very nice job of detailing the crosses performed to generate the various mutant lines in the methods, and the original alleles are cited. However, given the importance of the mutants it might be worth reviewing the nature of the alleles in the start of the results section. For example, do any of them produce proteins that could still have some DNA binding capacity? + +A2- 1. All the mutants are genetic nulls: Pou53 mutant has a point- mutation before DNA- binding domain, Sox19b and Nanog have TALEN- induced frameshifts before the DNA- binding domains. We mention it in the results and give the references to the original publications where it was characterized after each mutant name. + +R2- 2. Figure 2b, not clear exactly what control genomic regions are. + +A2- 2. Included in the legend for Figure 2b: "To obtain control genomic regions (co, dotted line), genomic coordinates of all ARs were shifted 1 kb downstream". + +R2- 3. With respect to figure 2, it could be more helpful to include a little more detail on the binning of up down and unchanged groups in the text or figure legend (what were the cutoffs/criteria for including). I similarly struggled to find this information in the methods, if it is there it is not easy to find. + +<--- Page Split ---> + +A2- 3. We agree (it is only in "Methods" and in too detailed). We included in the figure legend for Fig. 2a: "Three groups of accessible regions (ARs) were selected as follows: in "down" and "up" regions, ATAC- signal was reduced or increased, respectively, in six MZtriple biological replicates compared to seven wild- type biological replicates with false discovery rate \(< 5\%\) . "same" - the remaining ARs which were considered unchanged". R2- 4. Figure 3 panel 1 is a little confusing. Is purple color code also needed? + +A2- 4. Yes! We included it to Fig 3a and to Fig S3a. + +R2- 5. With respect to figure 3 F, it isn't entirely clear to me why this group couldn't reflect a requirement for all three TFs together, rather than any one plus GC binding factor- Fig 3b seems to suggests binding motifs for all three are detected in this group, although the sox: pou motif is underrepresented. The GC enrichment could still represent a hypothetical GC binding factor required in addition to the three factors? Alternatively, is it possible that there is simply a structural property of these GC rich regions that is keeping them more open? I believe there is reasonable data to support a relationship between GC content and nucleosome occupancy + +A2- 5. We agree, we do not really need the GC factor in the scheme. We replaced it, removed the speculations about GC protein from the text, and included additional analysis of the 4. - group to the Figure S3c. + +R2- 6. The rescue experiments in Fig S3 are quite nice. I almost wonder if they might be better in the main text of the manuscript. + +A2- 6. We agree. We moved the experiments from the Fig.S3 to Fig. 3, panels f,g. + +R2- 7. Figure 4, Panel C in particular is really important and very difficult to interpret, not at all intuitive. Is there any other way to present this data more clearly? I had to sit with the browser shots in panel H a good while to understand what was going on holistically in figure 4. + +A2- 7. We tried our best to make the things simpler to precept. As a result, we expanded the analysis, the panel C is now moved from Fig. 4 to the new Supplementary Fig.4 which is completely filled with analysis. The order of remaining panels in the main Fig. 4 is reorganized. + +R2- 8. I think a prediction of the model in 4f is that you should never be able to IP A and B from chromatin together at these types of sites. Is it possible to do sequential IPs to explore that possibility? This could be interesting additional support, but if this is technically too challenging, could be viewed as beyond the current paper's scope. + +A2- 8. Thank you for 1) the clear formulation of this very important message, and 2) for putting this request in the minor comments. We show now in the new panel of the supplementary Fig. 5f that most of the open regions bound by TFs have only one site, either for Pou5f3 or for Nanog. We have also done a set of gel retardation assays with tagged Pou5f3 and Nanog and supershifts, showing that Pou5f3 and Nanog do not bind together to the same DNA motifs in- vitro. We included the new Fig 5, Fig. S5 and new sub- chapter of the results: "Pou5f3 and Nanog bind to the common binding sites in a mutually exclusive way". + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Reviewer #1 (Remarks to the Author):The reviewer appreciates the authors' efforts in incorporating new data into the revised manuscript. However, I still have a concern. The authors have made an attempt to demonstrate the mutually exclusive binding of Pou5f3 and Nanog using gel- shift assays (Figure 5). Nevertheless, the data only indicate that either Pou5f3 or Nanog strongly binds, while the other protein binds weakly to the same oligo. It does not clearly show the blocking of one protein by the other. It would be valuable for the authors to provide evidence by demonstrating the actual replacement of Pou5f3 binding with Nanog binding as the concentration of Nanog increases and vice versa, using the gel- shift assay the authors established. The reviewer is sure that the authors would easily perform this kind of experiments. Given that the activator- blocker model is one of the most crucial assertions of this paper, the reviewer thinks, it is essential to experimentally validate the molecular mechanism. + +Reviewer #2 (Remarks to the Author): + +All of my concerns regarding this manuscript have been addressed. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +R1- 1 + +The reviewer appreciates the authors' efforts in incorporating new data into the revised manuscript. However, I still have a concern. The authors have made an attempt to demonstrate the mutually exclusive binding of Pou5f3 and Nanog using gel- shift assays (Figure 5). Nevertheless, the data only indicate that either Pou5f3 or Nanog strongly binds, while the other protein binds weakly to the same oligo. It does not clearly show the blocking of one protein by the other. It would be valuable for the authors to provide evidence by demonstrating the actual replacement of Pou5f3 binding with Nanog binding as the concentration of Nanog increases and vice versa, using the gel- shift assay the authors established. The reviewer is sure that the authors would easily perform this kind of experiments. Given that the activator- blocker model is one of the most crucial assertions of this paper, the reviewer thinks, it is essential to experimentally validate the molecular mechanism. + +I performed the requested EMSA experiments, included them as a new Supplementary Fig.7 and referred them in the text (please see the yellow marking in the PDF file for reviewers). + +Sincerely, Dr.Daria Onichtchouk. + +Reviewer #2 (Remarks to the Author): + +All of my concerns regarding this manuscript have been addressed. + +<--- Page Split ---> diff --git a/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7f22169fbb97233c6f012ed125272d4bf9f8ecdb --- /dev/null +++ b/peer_reviews/129058fcec31e99c0819f8921d0245dbb3bd7403d48f93401d336635a4c8ebb2/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,232 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[108, 162, 808, 219]]<|/det|> +Activator- blocker model of transcriptional regulation by pioneer- like factors + +<|ref|>image<|/ref|><|det|>[[95, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 88, 305, 104]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 118, 404, 134]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 148, 880, 224]]<|/det|> +In this manuscript, Riesle and Gao et al. analyzed ATAC- seq, H3K27ac ChIP- seq, and transcriptome of zebrafish mutants of ZGA regulator TFs. They found the existence of synergistic and antagonistic enhancer types, and Pou5f3 and Nanog can function as activator or blocker in antagonistic enhancers. The topic is unquestionably important for the field, but this reviewer feels that the novelty of the study seems weak. I have several major concerns as described below. + +<|ref|>text<|/ref|><|det|>[[115, 252, 879, 358]]<|/det|> +Regarding the novelty, the fact that the pioneer factors (Pou5f3 and Sox19b) is preventing premature expression for some of the genes during ZGA has already been reported by the same group (Gao et al., 2022). The idea that Pou5f3 and Nanog is competing at a same binding site and may function as a blocker is indeed interesting and advancing our knowledge, but molecular experimental evidence is lacking. How Pou5f3 and Nanog function as a non- pioneer blocker is also completely a blackbox. To address underlying molecular mechanisms, at least the authors should do experiments such as gel- shift assay to enhancer sequences of specific group of genes. + +<|ref|>text<|/ref|><|det|>[[115, 386, 877, 462]]<|/det|> +The authors claim the presence of additional genome activators, but the evidence is not enough. First, in Fig. 2a, why did not the authors use the MZsox19b for the classification? Second, the results show that \(\sim 50\%\) or \(\sim 80\%\) of group 4. - TdARs can be rescued by Sox19b alone, or by Sox19b and Nanog, respectively (Fig S3). From these data, it is likely that SoxB, or SoxB and Nanog is required on chromatin accessibility of most of group 4. - TdARs. + +<|ref|>text<|/ref|><|det|>[[115, 490, 875, 581]]<|/det|> +Characterization of antagonistic enhancers is not enough. They show GC content for 1. PN, 2. P, 3. N, and 4. -, but comparison between p- n+, p+ n- and others is required. Furthermore, they mention that exact match to the motif is important for Pou5f3 and Nanog to function as pioneer TFs, but this does not explain the difference between synergistic and antagonistic enhancers. Why do Pou5f3 and Nanog function as blocker only in antagonistic enhancers, but not in synergistic enhancers? The author also need to have additional experimental data as stated above. + +<|ref|>text<|/ref|><|det|>[[115, 609, 880, 685]]<|/det|> +Regarding the mathematical modelling; in Figure 5c, expressions of 3b. P- N+ genes do not seem to be upregulated in MZps. They even seems down regulated at stages before 6 hpf. Furthermore, gene ontology analyses are not enough to evaluate the model accuracy, and validation in other method is required. For example, is there any differences in sequence feature between enhancers of the six groups sorted by the model? + +<|ref|>text<|/ref|><|det|>[[116, 744, 404, 759]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 789, 867, 864]]<|/det|> +The manuscript "Activator- blocker model of transcriptional regulation by pioneer- like factors," by Riesle et al takes a deep dive into functions for the transcription factors Pou5f3, Sox19b and Nanog during zebrafish zygotic genome activation. Their analysis uses a combination of elegant genetic and genomic approaches. The results reveal surprising complexities in the ways in which Pou5f3, Sox19b and Nanog work both together and antagonistically to regulate early transcription. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 857, 119]]<|/det|> +Overall this is a rigorous study which produces useful data sets and shifts the way we need to think about how these transcription factors act during zebrafish ZGA. I have only minor comments. + +<|ref|>text<|/ref|><|det|>[[115, 148, 878, 209]]<|/det|> +The authors do a very nice job of detailing the crosses performed to generate the various mutant lines in the methods, and the original alleles are cited. However, given the importance of the mutants it might be worth reviewing the nature of the alleles in the start of the results section. For example, do any of them produce proteins that could still have some DNA binding capacity? + +<|ref|>text<|/ref|><|det|>[[115, 223, 576, 238]]<|/det|> +Figure 2b, not clear exactly what control genomic regions are. + +<|ref|>text<|/ref|><|det|>[[115, 253, 875, 298]]<|/det|> +With respect to figure 2, it could be more helpful to include a little more detail on the binning of up down and unchanged groups in the text or figure legend (what were the cutoffs/criteria for including). I similarly struggled to find this information in the methods, if it is there it is not easy to find. + +<|ref|>text<|/ref|><|det|>[[115, 312, 640, 327]]<|/det|> +Figure 3 panel 1 is a little confusing. Is purple color code also needed? + +<|ref|>text<|/ref|><|det|>[[115, 342, 881, 448]]<|/det|> +With respect to figure 3 F, it isn't entirely clear to me why this group couldn't reflect a requirement for all three TFs together, rather than any one plus GC binding factor- Fig 3b seems to suggests binding motifs for all three are detected in this group, although the so: pou motif is underrepresented. The GC enrichment could still represent a hypothetical GC binding factor required in addition to the three factors? Alternatively, is it possible that there is simply a structural property of these GC rich regions that is keeping them more open? I believe there is reasonable data to support a relationship between GC content and nucleosome occupancy + +<|ref|>text<|/ref|><|det|>[[115, 462, 866, 492]]<|/det|> +The rescue experiments in Fig S3 are quite nice. I almost wonder if they might be better in the main text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 506, 877, 551]]<|/det|> +Figure 4, Panel C in particular is really important and very difficult to interpret, not at all intuitive. Is there any other way to present this data more clearly? I had to sit with the browser shots in panel H a good while to understand what was going on holistically in figure 4. + +<|ref|>text<|/ref|><|det|>[[115, 566, 861, 625]]<|/det|> +I think a prediction of the model in 4f is that you should never be able to IP A and B from chromatin together at these types of sites. Is it possible to do sequential IPs to explore that possibility? This could be interesting additional support, but if this is technically too challenging, could be viewed as beyond the current paper's scope. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 81, 295, 95]]<|/det|> +Dear reviewers #1 and #2, + +<|ref|>text<|/ref|><|det|>[[116, 105, 866, 205]]<|/det|> +We are grateful that you professionally spotted the weak points in our manuscript, which helped us to improve it. We performed additional experiments, added new sub- chapter in the results section with new main Fig. 5 and Fig. S6, performed additional analysis and made changes in most of the figures. We numbered your comments and linked them as comments to the yellow- marked text in the PDF file "Riesle_main_and SUPPL_marked for reviewers", which contains main text and figures, supplementary figures and legends and also additional supplementary Figure for Reviewer 1, at the end of the supplementary material. Please find detailed answers to your criticisms below. Sincerely, the authors. + +<|ref|>sub_title<|/ref|><|det|>[[117, 216, 291, 230]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 241, 372, 255]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 265, 876, 329]]<|/det|> +In this manuscript, Riesle and Gao et al. analyzed ATAC- seq, H3K27ac ChIP- seq, and transcriptome of zebrafish mutants of ZGA regulator TFs. They found the existence of synergistic and antagonistic enhancer types, and Pou5f3 and Nanog can function as activator or blocker in antagonistic enhancers. The topic is unquestionably important for the field, but this reviewer feels that the novelty of the study seems weak. I have several major concerns as described below. + +<|ref|>text<|/ref|><|det|>[[117, 351, 860, 439]]<|/det|> +R1- 1. Regarding the novelty, the fact that the pioneer factors (Pou5f3 and Sox19b) is preventing premature expression for some of the genes during ZGA has already been reported by the same group (Gao et al., 2022). The idea that Pou5f3 and Nanog is competing at a same binding site and may function as a blocker is indeed interesting and advancing our knowledge, but molecular experimental evidence is lacking. How Pou5f3 and Nanog function as a non- pioneer blocker is also completely a blackbox. To address underlying molecular mechanisms, at least the authors should do experiments such as gel- shift assay to enhancer sequences of specific group of genes. + +<|ref|>text<|/ref|><|det|>[[117, 449, 880, 502]]<|/det|> +A 1- 1. We agree with the comment and provide requested evidence. We performed series of the gel- shift assays with the oligos from different enhancers, added the new figures 5 and S6 and a chapter "Pou5f3 and Nanog bind to the common binding sites in a mutually exclusive way". We also show that in most cases TdARs have only one match to either Pou5f3 or Nanog motif (new panel Fig. S5f). + +<|ref|>text<|/ref|><|det|>[[117, 526, 880, 591]]<|/det|> +R1- 2. The authors claim the presence of additional genome activators, but the evidence is not enough. First, in Fig. 2a, why did not the authors use the MZsox19b for the classification? Second, the results show that \(\sim 50\%\) or \(\sim 80\%\) of group 4- TdARs can be rescued by Sox19b alone, or by Sox19b and Nanog, respectively (Fig S3). From these data, it is likely that SoxB, or SoxB and Nanog is required on chromatin accessibility of most of group 4- TdARs. + +<|ref|>text<|/ref|><|det|>[[116, 601, 870, 666]]<|/det|> +A1- 2. We agree with both points. In response to this criticism we - made additional analysis of 4- group, using ATAC- seq in MZsox19b and three double mutants (new panel c in the Fig. S3). - removed "hypothetical GC protein" from the scheme in Fig.3; and speculations about "hypothetical GC protein" from the corresponding text in the results. + +<|ref|>text<|/ref|><|det|>[[116, 686, 863, 714]]<|/det|> +R1- 3. Characterization of antagonistic enhancers is not enough. They show GC content for 1. PN, 2. P, 3. N, and 4. -, but comparison between p- n+, p+ n- and others is required. + +<|ref|>text<|/ref|><|det|>[[116, 724, 848, 763]]<|/det|> +A1- 3. Done (Fig. S4). Conclusion: overall GC content of enhancers activated by Pou5f3 is lower than of the enhancers activated by Nanog. This is seen in both ATAC- seq (Fig.3e, Fig. S4b) and H3K27ac comparisons between TdARs (Fig. S4b). + +<|ref|>text<|/ref|><|det|>[[116, 773, 863, 825]]<|/det|> +R1- 4. Furthermore, they mention that exact match to the motif is important for Pou5f3 and Nanog to function as pioneer TFs, but this does not explain the difference between synergistic and antagonistic enhancers. Why do Pou5f3 and Nanog function as blocker only in antagonistic enhancers, but not in synergistic enhancers? The author also need to have additional experimental data as stated above. + +<|ref|>text<|/ref|><|det|>[[116, 835, 491, 849]]<|/det|> +A1- 4. There are two parts of the answer to this criticism: + +<|ref|>text<|/ref|><|det|>[[145, 849, 874, 912]]<|/det|> +1) Yes, we provided additional experimental data and confirmed now with gel-shifts, that the factor which binds stronger in-vitro works as an activator in-vivo (9 out of 9 oligos with single motif, where the binding worked for any of the two TFs, see the new Fig. 5 panel e). We also show that GC content is important: Pou5f3 activates the enhancers with lower GC content range, than Nanog, as judged by pioneer activity (Fig.3e) and H3K27ac change (Fig.S4). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 81, 877, 134]]<|/det|> +2) No, we can not explain the mechanistic difference between synergistic and antagonistic enhancers from gel-shifts and bulk genomic data. We assume that cell-specific cofactors are involved (see discussion). Single-cell analysis is required to answer this question; as far as we know ChIP-seq technique for single cells is not yet developed. We hope that our manuscript is novel enough to be published without it. + +<|ref|>text<|/ref|><|det|>[[118, 155, 850, 182]]<|/det|> +R1- 5. Regarding the mathematical modelling; in Figure 5c, expressions of 3b. P- N+ genes do not seem to be upregulated in MZps. They even seems down regulated at stages before 6 hpf.f + +<|ref|>text<|/ref|><|det|>[[117, 192, 880, 260]]<|/det|> +This is because most of 3b. P- N+ genes are coactivated by SOXB1 sum, and SOXB1 sum is decreased in MZps. ( see the supplementary Figure for Reviewer 1 included in the file for reviewers). 3b. P- N+ model group consists of three mini- models: of three mini- models: S+P- N+ (best fit to 398 transcripts), SOP- N+ (best fit to 24 transcripts) and S- P- N+ (best fit to 6 transcripts). In response to this criticism we changed the summatory figure S8, which shows now the example fits to all mini- models ( and not to the groups as before). + +<|ref|>text<|/ref|><|det|>[[118, 290, 850, 316]]<|/det|> +R1- 6. Furthermore, gene ontology analyses are not enough to evaluate the model accuracy, and validation in other method is required. + +<|ref|>text<|/ref|><|det|>[[117, 326, 880, 391]]<|/det|> +We did not intent to validate the modeling with GO analysis. In response to this criticism we completly removed this GO analysis from the paper, not to distract the reader attention. We renamed the sub- chapters and put the cross- validation part (the synergistically and antagonistically regulated transcripts are linked to synergistically and antagonistically regulated enhancers) just after the description of the modeling results (see the marking of the text for reviewers). + +<|ref|>text<|/ref|><|det|>[[117, 412, 861, 439]]<|/det|> +R1- 7. For example, is there any differences in sequence feature between enhancers of the six groups sorted by the model? + +<|ref|>text<|/ref|><|det|>[[116, 450, 863, 477]]<|/det|> +Yes, there is a difference in both sequence features: motif frequency and in GC content. We show it now in Fig. S9 c,d, as additional validation. + +<|ref|>text<|/ref|><|det|>[[118, 535, 372, 549]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 572, 877, 636]]<|/det|> +The manuscript "Activator- blocker model of transcriptional regulation by pioneer- like factors," by Riesle et al takes a deep dive into functions for the transcription factors Pou53, Sox19b and Nanog during zebrafish zygotic genome activation. Their analysis uses a combination of elegant genetic and genomic approaches. The results reveal surprising complexities in the ways in which Pou53, Sox19b and Nanog work both together and antagonistically to regulate early transcription. + +<|ref|>text<|/ref|><|det|>[[118, 658, 857, 685]]<|/det|> +Overall this is a rigorous study which produces useful data sets and shifts the way we need to think about how these transcription factors act during zebrafish ZGA. I have only minor comments. + +<|ref|>text<|/ref|><|det|>[[117, 707, 880, 759]]<|/det|> +R2- 1. The authors do a very nice job of detailing the crosses performed to generate the various mutant lines in the methods, and the original alleles are cited. However, given the importance of the mutants it might be worth reviewing the nature of the alleles in the start of the results section. For example, do any of them produce proteins that could still have some DNA binding capacity? + +<|ref|>text<|/ref|><|det|>[[117, 770, 873, 809]]<|/det|> +A2- 1. All the mutants are genetic nulls: Pou53 mutant has a point- mutation before DNA- binding domain, Sox19b and Nanog have TALEN- induced frameshifts before the DNA- binding domains. We mention it in the results and give the references to the original publications where it was characterized after each mutant name. + +<|ref|>text<|/ref|><|det|>[[118, 819, 572, 832]]<|/det|> +R2- 2. Figure 2b, not clear exactly what control genomic regions are. + +<|ref|>text<|/ref|><|det|>[[117, 843, 812, 869]]<|/det|> +A2- 2. Included in the legend for Figure 2b: "To obtain control genomic regions (co, dotted line), genomic coordinates of all ARs were shifted 1 kb downstream". + +<|ref|>text<|/ref|><|det|>[[117, 880, 880, 918]]<|/det|> +R2- 3. With respect to figure 2, it could be more helpful to include a little more detail on the binning of up down and unchanged groups in the text or figure legend (what were the cutoffs/criteria for including). I similarly struggled to find this information in the methods, if it is there it is not easy to find. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 81, 866, 147]]<|/det|> +A2- 3. We agree (it is only in "Methods" and in too detailed). We included in the figure legend for Fig. 2a: "Three groups of accessible regions (ARs) were selected as follows: in "down" and "up" regions, ATAC- signal was reduced or increased, respectively, in six MZtriple biological replicates compared to seven wild- type biological replicates with false discovery rate \(< 5\%\) . "same" - the remaining ARs which were considered unchanged". R2- 4. Figure 3 panel 1 is a little confusing. Is purple color code also needed? + +<|ref|>text<|/ref|><|det|>[[118, 147, 580, 160]]<|/det|> +A2- 4. Yes! We included it to Fig 3a and to Fig S3a. + +<|ref|>text<|/ref|><|det|>[[116, 168, 883, 244]]<|/det|> +R2- 5. With respect to figure 3 F, it isn't entirely clear to me why this group couldn't reflect a requirement for all three TFs together, rather than any one plus GC binding factor- Fig 3b seems to suggests binding motifs for all three are detected in this group, although the sox: pou motif is underrepresented. The GC enrichment could still represent a hypothetical GC binding factor required in addition to the three factors? Alternatively, is it possible that there is simply a structural property of these GC rich regions that is keeping them more open? I believe there is reasonable data to support a relationship between GC content and nucleosome occupancy + +<|ref|>text<|/ref|><|det|>[[116, 253, 860, 280]]<|/det|> +A2- 5. We agree, we do not really need the GC factor in the scheme. We replaced it, removed the speculations about GC protein from the text, and included additional analysis of the 4. - group to the Figure S3c. + +<|ref|>text<|/ref|><|det|>[[116, 290, 868, 317]]<|/det|> +R2- 6. The rescue experiments in Fig S3 are quite nice. I almost wonder if they might be better in the main text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 327, 661, 341]]<|/det|> +A2- 6. We agree. We moved the experiments from the Fig.S3 to Fig. 3, panels f,g. + +<|ref|>text<|/ref|><|det|>[[116, 352, 857, 390]]<|/det|> +R2- 7. Figure 4, Panel C in particular is really important and very difficult to interpret, not at all intuitive. Is there any other way to present this data more clearly? I had to sit with the browser shots in panel H a good while to understand what was going on holistically in figure 4. + +<|ref|>text<|/ref|><|det|>[[116, 401, 875, 440]]<|/det|> +A2- 7. We tried our best to make the things simpler to precept. As a result, we expanded the analysis, the panel C is now moved from Fig. 4 to the new Supplementary Fig.4 which is completely filled with analysis. The order of remaining panels in the main Fig. 4 is reorganized. + +<|ref|>text<|/ref|><|det|>[[116, 450, 878, 488]]<|/det|> +R2- 8. I think a prediction of the model in 4f is that you should never be able to IP A and B from chromatin together at these types of sites. Is it possible to do sequential IPs to explore that possibility? This could be interesting additional support, but if this is technically too challenging, could be viewed as beyond the current paper's scope. + +<|ref|>text<|/ref|><|det|>[[116, 498, 870, 574]]<|/det|> +A2- 8. Thank you for 1) the clear formulation of this very important message, and 2) for putting this request in the minor comments. We show now in the new panel of the supplementary Fig. 5f that most of the open regions bound by TFs have only one site, either for Pou5f3 or for Nanog. We have also done a set of gel retardation assays with tagged Pou5f3 and Nanog and supershifts, showing that Pou5f3 and Nanog do not bind together to the same DNA motifs in- vitro. We included the new Fig 5, Fig. S5 and new sub- chapter of the results: "Pou5f3 and Nanog bind to the common binding sites in a mutually exclusive way". + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 89, 305, 104]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 119, 404, 134]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 148, 877, 298]]<|/det|> +Reviewer #1 (Remarks to the Author):The reviewer appreciates the authors' efforts in incorporating new data into the revised manuscript. However, I still have a concern. The authors have made an attempt to demonstrate the mutually exclusive binding of Pou5f3 and Nanog using gel- shift assays (Figure 5). Nevertheless, the data only indicate that either Pou5f3 or Nanog strongly binds, while the other protein binds weakly to the same oligo. It does not clearly show the blocking of one protein by the other. It would be valuable for the authors to provide evidence by demonstrating the actual replacement of Pou5f3 binding with Nanog binding as the concentration of Nanog increases and vice versa, using the gel- shift assay the authors established. The reviewer is sure that the authors would easily perform this kind of experiments. Given that the activator- blocker model is one of the most crucial assertions of this paper, the reviewer thinks, it is essential to experimentally validate the molecular mechanism. + +<|ref|>text<|/ref|><|det|>[[116, 327, 404, 342]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 357, 616, 372]]<|/det|> +All of my concerns regarding this manuscript have been addressed. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 105, 291, 119]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 131, 373, 145]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 156, 152, 168]]<|/det|> +R1- 1 + +<|ref|>text<|/ref|><|det|>[[117, 168, 878, 280]]<|/det|> +The reviewer appreciates the authors' efforts in incorporating new data into the revised manuscript. However, I still have a concern. The authors have made an attempt to demonstrate the mutually exclusive binding of Pou5f3 and Nanog using gel- shift assays (Figure 5). Nevertheless, the data only indicate that either Pou5f3 or Nanog strongly binds, while the other protein binds weakly to the same oligo. It does not clearly show the blocking of one protein by the other. It would be valuable for the authors to provide evidence by demonstrating the actual replacement of Pou5f3 binding with Nanog binding as the concentration of Nanog increases and vice versa, using the gel- shift assay the authors established. The reviewer is sure that the authors would easily perform this kind of experiments. Given that the activator- blocker model is one of the most crucial assertions of this paper, the reviewer thinks, it is essential to experimentally validate the molecular mechanism. + +<|ref|>text<|/ref|><|det|>[[117, 304, 875, 342]]<|/det|> +I performed the requested EMSA experiments, included them as a new Supplementary Fig.7 and referred them in the text (please see the yellow marking in the PDF file for reviewers). + +<|ref|>text<|/ref|><|det|>[[117, 353, 266, 378]]<|/det|> +Sincerely, Dr.Daria Onichtchouk. + +<|ref|>text<|/ref|><|det|>[[118, 400, 373, 414]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 425, 570, 439]]<|/det|> +All of my concerns regarding this manuscript have been addressed. + +<--- Page Split ---> diff --git a/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d6c182b27031913f0032c6c00c60940fa077eac6 --- /dev/null +++ b/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,451 @@ + +# nature portfolio + +Peer Review File + +# The role of cytochrome bc1 inhibitors in future tuberculosis treatment regimens + +Corresponding Author: Dr Clara Aguilar Pérez + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The manuscript by Perez and colleagues present data on the effects of cytochrome bc1 inhibitors and their potential efficacy in drug regimens against multidrug resistant TB as well as its role in reducing the duration of chemotherapy in drug susceptible TB. The work is important and timely considered the burden of drug- resistant TB and the prolonged treatment protocols for both drug resistant and susceptible cases of TB. The experimental approach is solid and data presented are robust to support their hypotheses. + +One of the main interesting points in the manuscript is the fact that cytochrome bc1 inhibitors are more potent against clinical isolates than the lab strains. A further investigation into this would have increased the impact of the work as well as our understanding of the mechanisms of action of these inhibitors. Especially as these are claimed to be validated inhibitors, it would also be nice to see more of their characterisation and target engagement in vitro. + +In addition, would this variability on strain efficacy mean that there are potential other targets being inhibited by the same compounds or is it the secondary effects of inhibiting the cytochrome bc1 and the respiratory chain of Mtb? + +For the present study, authors can expand the discussion regarding the efficacy of their compound in the background of bd and how this could affect the outcome. More importantly, the authors can use these compounds to further interrogate this hypothesis. In addition, having another look at their data, I could see that if you calculate the MBC/MIC ratio for the reference lab strain (H37Rv) and the cytochrome deleted mutant (H37Rv_CytBd- KO) on supplementary table S2 one can see that their inhibitor is bacteriostatic on H37Rv whereas it is bactericidal on cytochrome bd deleted mutant (H37Rv_CytBd- KO). That further adds to the argument that the expression levels of cytochrome bd is an important factor in their compound efficacy. + +Furthermore, the authors did not include if these compounds are active against MDR and XDR Mtb strains. Taking into account that the main use of these inhibitors would be towards a drug regimen for treating MDR- TB, it would be nice to see that the compounds maintain their activity against a panel of multiple drug- resistant strains including MDR and XDR clinical isolates. + +Obviously a series of experiments where one looks at the levels of expression of these genes under treatment or not in a series of lab and clinical strains of Mtb would shed light on this question. But I don't think these experiments need to be part of this work. + +Lastly, in the Figure S3, I cannot see the control line as well as the figure legend need a bit more explanation. + +## Reviewer #2 + +(Remarks to the Author) The authors have done an excellent job of identifying cytochrome bc1 as an important component of the Mtb electron transport chain and a potentially sterilizing target in for TB regimen development. Using a relapsing mouse model, they have attempted to demonstrate that cytochrome bc1 inhibitors could be effective partner drugs in TB regimen development that could enhance sterilization. They report on several novel regimens + +<--- Page Split ---> + +as examples of this role for bc1 inhibitors in regimens for both multidrug- resistant TB (MDR- TB) and drug- sensitive TB (DSTB), where cytochrome bc1 inhibitors could contribute to sterilization and treatment shortening. importantly, they have shown that clinical isolates exhibit heightened susceptibility to cytochrome bc1 inhibitors compared to laboratory- adapted strains, further supporting their potential usefulness in a clinical setting even as their contribution may be low or undetectable against a lab adapted strain. They take these findings as confirmation that cytochrome bc1 inhibitors have significant potential to improve TB treatment outcomes and highlight the need for further studies to evaluate their clinical contribution to novel treatment regimens. + +What are the noteworthy results? The authors have done an excellent job of identifying and advancing highly potent inhibitors against their chosen target, cytochrome bc1. There is enough evidence to demonstrate that this is a sound choice of target, especially with the excellent success of bedaquiline, the flagship ATP synthase developed by the same group that has literally changed the paradigm in TB treatment shortening and highlighted the electron transport chain as a highly valuable and sterilizing target, at the same level or better than the rifamycin of prior years. It is therefore sound and admirable to hit this pathway as hard as possible, at multiple points and potentially achieve better cure. The problem seems to be that the interplay between cytochrome bc and cytochrome bd seems complicated and makes it difficult to determine with available data, including the data reported here, if just inhibiting bc, but not bd will be enough to realize the expected benefits. It seems that high expression of bd is able to reverse or nullify the effects of inhibiting bc. This is potentially the reason why there is strain difference between lab adapted versus clinical isolates. Further proof is gleaned from the excellent performance of Q203, the lead asset in this target space, versus mycobacterial species that do not express bd like M. leprae and M. ulcerans. This leaves the potential for a bc inhibitor uncertain against tuberculosis. Having said that, the team has identified a tool compound that together with Q203 will be useful in further investigating this target + +Will the work be of significance to the field and related fields? While the actual developability of this asset in future TB drug regimens is in doubt until more work is done to fully appreciate contribution against all TB strains, publication of this work will be of great significance to the field and specifically to the grand idea of targeting the electron transport chain of Mtb at multiple nodes to achieve better cure for TB. Furthermore, the compound reported here could also be expanded to the NTM space as is being done for Q203 which is currently being evaluated against leprosy and buruli ulcer, arguably important and neglected diseases as well. But for use in tuberculosis, more work needs to be done to understand the importance of targeting bc1 in a background with high expression of bd. And to determine if the site of infection and location in a lesion affects the usefulness of this asset. And if the mouse model as used today is the best model for this particular asset + +How does it compare to the established literature? The work reported here is of a high level, similar to other novel drug development programs. Importantly, this was not just a random shot in the dark, instead it was a highly impressive hypothesis driven mission that actually delivered a high- quality compound that is available for further evaluation to prove the hypothesis and potentially deliver a developable asset. It could be argued that in some of the regimen development, drug combination studies in mice, a more factorial approach that builds from 2, to 3 and then perhaps four drugs, with the ability to clearly demonstrate the sterilizing contribution of the asset being evaluated could have been more rigorous than reported here. This leaves this reviewer unable in some cases to confirm that the J bc1 inhibitor contributed anything at all in some of the reported combinations. This could be cleaned up on a re- submission, or in future studies that would attempt to demonstrate the full potential of this asset. + +If the work is not original, please provide relevant references. The work is original and very well done + +Does the work support the conclusions and claims, or is additional evidence needed? The work supports some of the claims, but as stated above, the usefulness of developing a bc1 inhibitors and that inhibitor demonstrating a real contribution to treatment shortening against a tuberculosis infection still needs more work. + +Are there any flaws in the data analysis, interpretation and conclusions? Target validation for bc1 in a highly expressed bd background needs special attention. Contribution of the asset to significant treatment shortening in a developable regimen could be improved + +Do these prohibit publication or require revision? I recommend publication of this work with a more substantive discussion of the strain difference and usefulness of bc1 inhibitors vs bd expression and a better demonstration of contribution to treatment shortening + +Is the methodology sound? The methods used are sound except for the identified shortcomings + +Does the work meet the expected standards in your field? The work is high quality from a highly experienced group working in a target pathway with which they are clearly experts. The regimen development work, especially with this challenging target, relative to bd expression could be improved + +Is there enough detail provided in the methods for the work to be reproduced? Yes + +Recommendation: Accept for publication with some revision of the highlighted aspects, above + +Reviewer #3 + +(Remarks to the Author) + +<--- Page Split ---> + +## General Comments + +The manuscript presents valuable findings on the role of cytochrome bc1 inhibitors in tuberculosis treatment. However, it currently lacks a clear and well- organized structure, which makes it challenging to follow. To be considered suitable for publication, we strongly recommend rewriting the whole manuscript to include distinct and complete sections—specifically, Introduction, Materials & Methods, Results, Discussion, and Conclusion. The current format hinders readability and clarity and omits critical information necessary to fully assess the study's findings. Additionally, the manuscript would benefit from enhanced experimental justification and a more thorough discussion of the results. + +The experimental design, including details on mice strains and compound combinations and its rationale, should be consistently presented across all sections (Introduction, Results, Materials & Methods) and thoroughly discussed. Introduction + +The manuscript provides a well- articulated description of the problem and effectively highlights the potential of the electron transport chain inhibitors in tuberculosis treatment. However, we miss a proper introduction and a clear justification of the two new drug candidates (JNJ- 2901 and JNJ- 4052) that the authors test (according to the figures), and the differences and their potential benefits when compared to the cytochrome bc1 inhibitor Q203 (Telacebec) already being evaluated in clinical trials. This would provide proof of the manuscript's novelty. + +Hypothesis, aim and objectives are not well presented, and clearly insufficiently described. Moreover, supplementary information and figures should not be included in the Introduction but rather integrated and discussed in the results section. Results + +The results demonstrate promising data on JNJ- 2901's efficacy in reducing bacterial burden and preventing relapse in mice models. The findings suggest a potential shortening of TB treatment regimens, particularly with BPaCJ, which showed the highest efficacy and lowest relapse rates compared to BPaL, BPaM, BPaC, and BPaJ. + +However, we have major concerns regarding the description and structure of this section: + +- Global experimental plan should first be presented to help understand what the authors did, and then each set of results should be clearly introduced with a summary of the main conclusion before presenting the data of each experimental study. +- The experimental design (mice strain, infection mode, treatment duration, and rationale for each study) and must be clearly stated at the beginning of each results subsection. We here wanted to point out that the naming convention of studies (e.g., Study A, B, C, etc.) does not provide enough information to the reader. We suggest their replacement throughout the manuscript with descriptive terms reflecting the experimental model. For example, instead of "In an additional study (Study C)," we suggest "We additionally investigated drug combination efficacy and relapse in intravenously infected mice." +- Why a second compound – JNJ-4052- is tested in Study F? Why to test another candidate? + +Discussion + +Although a very small discussion comments are integrated into the manuscript (e.g., L136- 143, L156- 161, L171- 177), a dedicated Discussion section is necessary. We suggest moving the relevant lines into a standalone Discussion section and expanding on several key topics: + +- Comparison of JNJ-2901 and JNJ-4052 with Telacebec (Q203): The manuscript should provide a comparative analysis of the new candidates with existing inhibitors in terms of efficacy, safety, and pharmacokinetics as well as treatment efficacy and relapsing rates. What is the novelty? Why these compounds are better? Why they test 2 different compounds? And if everything is done with JNJ-2901, why to include JNJ-4052 in one of the studies? + +- Differences in mice models and infection routes: The study utilizes different infection models, and these differences should be considered to discuss the results. In addition, the authors should also discuss the gender bias in the experiments (only female mice are used) and how this could impact clinical translation. + +- Comparison between clinical isolates and wild-type (WT) strains: Authors should also discuss the observed differences in drug efficacy between clinical isolates and WT strains. The reasons behind these differences need to be explained and appropriately discussed. + +- Experimental limitations: The mention of limitations in L119 is too vague. The authors should explicitly outline the limitations of their experimental design. + +- The potential of cytochrome bc1 inhibitors: The claim that these inhibitors could significantly impact TB treatment is overstated for the level of preclinical data presented. Further discussion on the limitations of the preclinical findings hereby presented and next steps for clinical translation is needed, including challenges, barriers and further work to be done before undergoing clinical evaluation. + +## Materials and Methods + +The Materials & Methods section is well- detailed and allows for experimental reproducibility. However, there we have some comments: + +- As in the Results section, avoid referring only to different experiments as Study A, B, etc. Instead, add descriptive headings such as "Intranasal Mice Challenge", "Intravenous Mice Challenge", or "High-Dose Aerosol Challenge." + +- Each experimental model should consistently include the following information: Mouse strain, sex, and age; inoculum + +preparation, infection route, and dose; treatment duration and euthanasia time points. + +- Authors should provide in the ethical statement the end-point criteria. + +- Supplementary tables and results should not be included in the Methods section but should be properly cited in the Results section. + +- There are several experimental methods referenced in the supplementary material but not appearing in the main text (e.g. PK and tolerability in mouse, ADME assays, HepG2 cytotoxicity assay, mitochondrial toxicity assay Glu/Gal, Ames II Mutagenicity assay, mutant isolation and WGS). These should be briefly mentioned in the main text, such as: "Both JNJ-2901 and JNJ-4052 were evaluated for ADME and toxicity. All parameters supported further use of these compounds in subsequent experiments (Supplementary Table S2)". + +Additionally, we suggest to address the following minor comments: + +- L62: we would suggest classifying tuberculosis as a global pandemic. +- L79: MoA abbreviation is not needed. + +<--- Page Split ---> + +- L87: the word "validated" to describe the inhibitor compound JNJ-2901 is confusing as the presented manuscript seems to be the validation of the compound as an effective treatment adjuvant. If this is not the case, please provide the reference where the compound is validated for its inhibition of the cytochrome bc1. + +- L91-96: we suggest to relocate this in the line 76, as the TB-PRACTECAL trial results are a good justification of linezolid-associated adverse effects when treating MDR-TB. + +- L116-122: please contextualize the results from this part. + +- L127: move the figure citation to line 133. After the results are explained. + +- L146: please provide the justification of why using Telacobec in this study and not JNJ-2901 and provide rationale about the drug regimen used for this experimental design. + +- L164: as far as we understood, JNJ-2901 and Telacobec were also assessed for its bactericidal activity against clinical isolates in comparison to the H37Rv strain (Figure 2 B,C,D and E). Please provide a proper description of the compound used for this experiment and further discussion of this results in the main text. + +- Figure 1: If the mice strain and experimental design are the same, consider re-structure Figure 1B and 1C in a unique figure. + +- Figure 2: Please, consider a figure rearrangement. We suggest dividing Figure 2 in two. Section A on one side (resulting in Figure 2) and sections B, C, D, E and F on the other (resulting in Figure 3 A, B, C, D and E). Since the results represented refer to different experimental questions and require a results section for each one. + +## Final Recommendation + +This study presents valuable preclinical data on cytochrome bc1 inhibitors in TB treatment. However, we have significant concerns regarding the manuscript as it currently stands. It lacks a proper structure, clarity, and experimental justification, and the discussion is entirely insufficient. The manuscript needs to be totally rewritten to address these issues, ensuring that it achieves the required readability, scientific rigor, and overall impact to be considered suitable for publication. + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The revised manuscript of Clara Aguilar Pérez and colleagues has addressed all of my previous concerns and I am happy to see some of the recommendation on the revised discussion section as well as extended new data. The study represents an important progress on inhibition of respiration machinery in Mtb and has potential for the development of future therapeutics. + +Reviewer #3 + +(Remarks to the Author) + +We would like to thank the authors for thoughtfully addressing our major suggestions regarding the manuscript. Our feedback primarily focused on improving its structure, clarity, and the discussion surrounding the experimental procedures and results. In particular, the authors have now effectively justified the differences observed when treating laboratory strains with different cytochrome bc1 inhibitors versus clinical strains. With these revisions, the manuscript now clearly highlights the significance of this investigation in advancing our understanding of tuberculosis treatment strategies. + +This work underscores the potential of bc1 inhibitors as viable alternatives to fluoroquinolones and linezolid, which are often associated with adverse effects in current regimens for drug- resistant tuberculosis. Moreover, it contributes to the possibility of treatment shortening for drug- sensitive tuberculosis, with added potential against clinical strains. The experiments were performed using different, well- justified preclinical mouse models, which strengthens the translational relevance of the findings and supports further investigation of this promising asset. Based on these improvements and the scientific merit of the study, we believe the manuscript is now better suited for publication. + +However, we would like the authors to address the following remaining issue: + +Please add a paragraph on limitations to the discussion section. For example, the sample size of mice used in the experiments could be acknowledged as a limitation (even though we recognize that this is already mentioned on page 7). Additionally, regarding the authors' response that "no differences between sexes have been reported in relation to drug efficacy in TB mouse models," we would like to stress that, even if ethical requirements do not mandate the inclusion of both biological sexes, doing so is strongly advisable. There is robust evidence from both clinical and preclinical studies that biological sex influences TB epidemiology and treatment outcomes (for example, see: Idris, R., Infection 2025, https://doi.org/10.1007/s15010-024-02424-5; Dutta NK, Front Immunol, 2020, doi: 10.3389/fimmu.2020.01465; Tannenbaum, + +<--- Page Split ---> + +C., Nature, 2019, https://doi.org/10.1038/s41586-019-1657-6). These differences are driven by a combination of hormonal, genetic, and immunological factors, as well as potential differences in treatment adherence and broader social determinants of health. While we acknowledge that using female mice can be more practical in terms of logistics and animal management- since males often display more aggressive behavior that can complicate experiments- there is now ample evidence showing that men and women often have different disease trajectories (not only for TB!) and responses to treatment. One persistent issue in drug development is that preclinical and clinical studies frequently fail to reflect the biological diversity found in real- world populations. Including both sexes in preclinical experiments wherever feasible would help improve the generalizability of the findings and ensure that results more accurately inform treatment strategies for all patients. + +In summary, we encourage the authors to carefully consider any additional limitations of their study and clearly state them, as this will add valuable context and transparency. Once this is done, the manuscript can be endorsed for publication. + +## Reviewer #4 + +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Reviewers' comments + +We thank the reviewers for providing useful comments and suggestions that have greatly improved this manuscript. We have addressed each comment below (red). + +## Reviewer #1 (Remarks to the Author): + +The manuscript by Perez and colleagues present data on the effects of cytochrome bc1 inhibitors and their potential efficacy in drug regimens against multidrug resistant TB as well as its role in reducing the duration of chemotherapy in drug susceptible TB. The work is important and timely considered the burden of drug- resistant TB and the prolonged treatment protocols for both drug resistant and susceptible cases of TB. The experimental approach is solid and data presented are robust to support their hypotheses. + +One of the main interesting points in the manuscript is the fact that cytochrome bc1 inhibitors are more potent against clinical isolates than the lab strains. A further investigation into this would have increased the impact of the work as well as our understanding of the mechanisms of action of these inhibitors. Especially as these are claimed to be validated inhibitors, it would also be nice to see more of their characterisation and target engagement in vitro. + +A second paper has recently been published which describes the characterisation, validation and target engagement of the JNJ- 2901 inhibitor (PMID:40191462). We have provided validation of JNJ- 4052, which comes from the same chemical series as JNJ- 2901, in Supplementary Tables S1- 3. + +In addition, would this variability on strain efficacy mean that there are potential other targets being inhibited by the same compounds or is it the secondary effects of inhibiting the cytochrome bc1 and the respiratory chain of Mtb? + +We do not believe that there are any genuine secondary targets for these compounds. Our resistance data demonstrates that a single nucleotide polymorphism in qcrB can provide high level resistance (for example T313A leads to \(>2000\) - fold resistance to JNJ- 4052; Supplementary Table S1). As discussed below, we believe the differences are most likely due to the increased expression of cytochrome bd, an alternative oxidase that can compensate for cytochrome bc1 inhibition. This is now outlined in the Discussion section (pg 9- 10). + +For the present study, authors can expand the discussion regarding the efficacy of their compound in the background of bd and how this could affect the outcome. More importantly, the authors can use these compounds to further interrogate this hypothesis. In addition, having another look at their data, I could see that if you calculate the MBC/MIC ratio for the reference lab strain (H37Rv) and the cytochrome deleted mutant (H37Rv_CytBd- KO) on supplementary table S2 one can see that their inhibitor is bacteriostatic on H37Rv whereas it is bactericidal on cytochrome bd deleted mutant (H37Rv_CytBd- KO). That further adds to the argument that the expression levels of cytochrome bd is an important factor in their compound efficacy. + +We agree that this is an important point and have now provided discussion of the difference in bactericidality between H37Rv and H37Rv_CytBd- KO strains in the Discussion section (pg 9- 10). + +Furthermore, the authors did not include if these compounds are active against MDR and XDR Mtb strains. Taking into account that the main use of these inhibitors would be towards a drug regimen for treating MDR- TB, it would be nice to see that the compounds maintain their activity against a panel of multiple drug- resistant strains including MDR and XDR clinical isolates. + +<--- Page Split ---> + +Activity of JNJ- 2901 against a panel of 18 MDR- TB strains has now been published showing that the inhibitor is more active compared to lab- adapted strains (PMID:40191462). + +Obviously a series of experiments where one looks at the levels of expression of these genes under treatment or not in a series of lab and clinical strains of Mtb would shed light on this question. But I don't think these experiments need to be part of this work. + +Lastly, in the Figure S3, I cannot see the control line as well as the figure legend need a bit more explanation. + +We have updated the figure legend to indicate that moxifloxacin is hidden by BDQ (Supplementary Figure S3). We have added more detail of the experimental conditions in the figure legend. + +## Reviewer #2 (Remarks to the Author): + +The authors have done an excellent job of identifying cytochrome bc1 as an important component of the Mtb electron transport chain and a potentially sterilizing target in for TB regimen development. Using a relapsing mouse model, they have attempted to demonstrate that cytochrome bc1 inhibitors could be effective partner drugs in TB regimen development that could enhance sterilization. They report on several novel regimens as examples of this role for bc1 inhibitors in regimens for both multidrug- resistant TB (MDR- TB) and drug- sensitive TB (DS- TB), where cytochrome bc1 inhibitors could contribute to sterilization and treatment shortening. importantly, they have shown that clinical isolates exhibit heightened susceptibility to cytochrome bc1 inhibitors compared to laboratory- adapted strains, further supporting their potential usefulness in a clinical setting even as their contribution may be low or undetectable against a lab adapted strain. They take these findings as confirmation that cytochrome bc1 inhibitors have significant potential to improve TB treatment outcomes and highlight the need for further studies to evaluate their clinical contribution to novel treatment regimens. + +What are the noteworthy results? The authors have done an excellent job of identifying and advancing highly potent inhibitors against their chosen target, cytochrome bc1. There is enough evidence to demonstrate that this is a sound choice of target, especially with the excellent success of bedaquiline, the flagship ATP synthase developed by the same group that has literally changed the paradigm in TB treatment shortening and highlighted the electron transport chain as a highly valuable and sterilizing target, at the same level or better than the rifamycins of prior years. It is therefore sound and admirable to hit this pathway as hard as possible, at multiple points and potentially achieve better cure. The problem seems to be that the interplay between cytochrome bc and cytochrome bd seems complicated and makes it difficult to determine with available data, including the data reported here, if just inhibiting bc, but not bd will be enough to realize the expected benefits. It seems that high expression of bd is able to reverse or nullify the effects of inhibiting bc. This is potentially the reason why there is strain difference between lab adapted versus clinical isolates. Further proof is gleaned from the excellent performance of Q203, the lead asset in this target space, versus mycobacterial species that do not express bd like M. leprae and M. ulcerans. This leaves the potential for a bc inhibitor uncertain against tuberculosis. Having said that, the team has identified a tool compound that together with Q203 will be useful in further investigating this target + +Will the work be of significance to the field and related fields? While the actual developability of this asset in future TB drug regimens is in doubt until more work is done to fully appreciate contribution + +<--- Page Split ---> + +against all TB strains, publication of this work will be of great significance to the field and specifically to the grand idea of targeting the electron transport chain of Mtb at multiple nodes to achieve better cure for TB. Furthermore, the compound reported here could also be expanded to the NTM space as is being done for Q203 which is currently being evaluated against leprosy and buruli ulcer, arguably important and neglected diseases as well. But for use in tuberculosis, more work needs to be done to understand the importance of targeting bc1 in a background with high expression of bd. And to determine if the site of infection and location in a lesion affects the usefulness of this asset. And if the mouse model as used today is the best model for this particular asset + +How does it compare to the established literature? The work reported here is of a high level, similar to other novel drug development programs. Importantly, this was not just a random shot in the dark, instead it was a highly impressive hypothesis driven mission that actually delivered a high- quality compound that is available for further evaluation to prove the hypothesis and potentially deliver a developable asset. It could be argued that in some of the regimen development, drug combination studies in mice, a more factorial approach that builds from 2, to 3 and then perhaps four drugs, with the ability to clearly demonstrate the sterilizing contribution of the asset being evaluated could have been more rigorous than reported here. This leaves this reviewer unable in some cases to confirm that the J bc1 inhibitor contributed anything at all in some of the reported combinations. This could be cleaned up on a re- submission, or in future studies that would attempt to demonstrate the full potential of this asset. + +A more stepwise factorial approach (building from two- to three- and then four- drug combinations) could have further clarified the sterilising contribution of a cytochrome \(bc_{1}\) inhibitor. However, the aim of these studies was not to develop an entirely new regimen but rather to replace moxifloxacin and linezolid with a potentially superior compound while maintaining the existing backbone. Therefore, we prioritised evaluating the \(bc_{1}\) inhibitor in combination with a clinically relevant regimen to reflect a realistic therapeutic setting. + +Additionally, we were mindful of the ethical considerations regarding animal use. Expanding the study design to include a larger number of combinations/conditions would have significantly increased the number of animals required. + +In several of our studies, the addition of a cytochrome \(bc_{1}\) inhibitor led to a statistical improvement in relapse rates (e.g. Figure 2; CZ vs CZT). Nevertheless, we agree that future investigations could employ a more granular factorial design to better define the specific contribution of the \(bc_{1}\) inhibitor. These follow- up studies would help further demonstrate the full potential of cytochrome \(bc_{1}\) inhibitors and strengthen its case for clinical development. + +If the work is not original, please provide relevant references. The work is original and very well done + +Does the work support the conclusions and claims, or is additional evidence needed? The work supports some of the claims, but as stated above, the usefulness of developing a bc1 inhibitors and that inhibitor demonstrating a real contribution to treatment shortening against a tuberculosis infection still needs more work. + +While we acknowledge that additional studies are needed to fully establish the potential of cytochrome \(bc_{1}\) inhibitors to shorten treatment duration, particularly in the context of multidrug- resistant tuberculosis (MDR- TB), the data presented here clearly demonstrate that the inclusion of a cytochrome \(bc_{1}\) inhibitor reduces the treatment time required. For example, the addition of telacebec to CZ reduces the treatment by at least 2 months (Figure 2). This is the starting point for further work to investigate this in more detail. + +<--- Page Split ---> + +Are there any flaws in the data analysis, interpretation and conclusions? Target validation for bc1 in a highly expressed bd background needs special attention. + +We have recently published the validation of JNJ- 2901 (PMID: 40191462) and have expanded our discussion on bd expression (pg 9- 10). + +Contribution of the asset to significant treatment shortening in a developable regimen could be improved + +As discussed above, we view this work as an important starting point for investigating the potential contribution of cytochrome \(bc_{1}\) inhibitors to future treatment- shortening regimens. We agree that further work is required beyond the current study. However, one challenge in addressing this more definitively is the lack of consensus on what constitutes a 'developable' regimen, as different organisations often have varying perspectives on which drugs should be prioritised; clofazimine being a notable example here. + +Do these prohibit publication or require revision? I recommend publication of this work with a more substantive discussion of the strain difference and usefulness of bc1 inhibitors vs bd expression and a better demonstration of contribution to treatment shortening + +We have now re- formatted the manuscript and expanded the discussion on the clinical isolate differences we observed. + +Is the methodology sound? The methods used are sound except for the identified shortcomings + +Does the work meet the expected standards in your field? The work is high quality from a highly experienced group working in a target pathway with which they are clearly experts. The regimen development work, especially with this challenging target, relative to bd expression could be improved + +Is there enough detail provided in the methods for the work to be reproduced? Yes Recommendation: Accept for publication with some revision of the highlighted aspects, above + +## Reviewer #3 and #4 (Remarks to the Author): + +General Comments + +The manuscript presents valuable findings on the role of cytochrome bc1 inhibitors in tuberculosis treatment. However, it currently lacks a clear and well- organized structure, which makes it challenging to follow. To be considered suitable for publication, we strongly recommend rewriting the whole manuscript to include distinct and complete sections—specifically, Introduction, Materials & Methods, Results, Discussion, and Conclusion. The current format hinders readability and clarity and omits critical information necessary to fully assess the study's findings. Additionally, the manuscript would benefit from enhanced experimental justification and a more thorough discussion of the results. + +We have now re- formatted the manuscript for Nature Communications as suggested and expanded on the Discussion section. + +The experimental design, including details on mice strains and compound combinations and its + +<--- Page Split ---> + +rationale, should be consistently presented across all sections (Introduction, Results, Materials & Methods) and thoroughly discussed. + +## Introduction + +The manuscript provides a well- articulated description of the problem and effectively highlights the potential of the electron transport chain inhibitors in tuberculosis treatment. However, we miss a proper introduction and a clear justification of the two new drug candidates (JNJ- 2901 and JNJ- 4052) that the authors test (according to the figures), and the differences and their potential benefits when compared to the cytochrome bc1 inhibitor Q203 (Telacebec) already being evaluated in clinical trials. This would provide proof of the manuscript's novelty. + +The primary focus of this manuscript is to understand the contribution of a cytochrome bc1- targeting inhibitor to TB treatment regimens, rather than specifically focusing on JNJ- 2091 or suggesting it is a superior molecule. We consider all the compounds discussed in this work as tool compounds used to increase our understanding of how this mode of action could complement existing drug regimens. In parallel, we have published a separate validation of JNJ- 2901 (PMID:40191462) and have added additional justification here (pg 5- 6). + +Hypothesis, aim and objectives are not well presented, and clearly insufficiently described. + +We have clarified and expanded the objectives of each section as requested. + +Moreover, supplementary information and figures should not be included in the Introduction but rather integrated and discussed in the results section. + +Reference to the figures and supplementary information has been removed from the introduction following re- formatting. + +## Results + +The results demonstrate promising data on JNJ- 2901's efficacy in reducing bacterial burden and preventing relapse in mice models. The findings suggest a potential shortening of TB treatment regimens, particularly with BPaCJ, which showed the highest efficacy and lowest relapse rates compared to BPaL, BPaM, BPaC, and BPaJ. + +However, we have major concerns regarding the description and structure of this section: + +- Global experimental plan should first be presented to help understand what the authors did, and then each set of results should be clearly introduced with a summary of the main conclusion before presenting the data of each experimental study. + +We agree, and have now divided this section more clearly with Figures 1b- c now discussed sequentially. An overview of the first set of experiments is provided in Figure 1a. + +- The experimental design (mice strain, infection mode, treatment duration, and rationale for each study) and must be clearly stated at the beginning of each results subsection. We here wanted to point out that the naming convention of studies (e.g., Study A, B, C, etc.) does not provide enough information to the reader. We suggest their replacement throughout the manuscript with descriptive terms reflecting the experimental model. For example, instead of “In an additional study (Study C),” we suggest “We additionally investigated drug combination efficacy and relapse in intravenously infected mice.” + +<--- Page Split ---> + +We respectfully disagree, as the experimental design is indicated in the Materials and Methods section. We do not believe it is necessary to repeat this information in the Results section or figure legends. We have named them A, B, C etc. because the studies were performed by different institutions rather than because they are different type of studies. + +- Why a second compound – JNJ-4052- is tested in Study F? Why to test another candidate? + +JNJ- 2901 and JNJ- 4052 belong to the same chemical series and exhibit very similar activity and safety profiles. Our cytochrome \(bc_{1}\) drug discovery programme has been ongoing for 7 years, during which time we have progressed a number of lead compounds including JNJ- 4052 and JNJ- 2901. The in vivo clinical isolate study (Study F) was performed using the earlier lead, JNJ- 4052. While we acknowledge that repeating this experiment with JNJ- 2901 would have been ideal, given the comparable profiles of both compounds, we do not anticipate a change in the outcome. Therefore, we believe repeating this study would not represent a justifiable use of mice. + +## Discussion + +Although a very small discussion comments are integrated into the manuscript (e.g., L136- 143, L156- 161, L171- 177), a dedicated Discussion section is necessary. We suggest moving the relevant lines into a standalone Discussion section and expanding on several key topics: + +- Comparison of JNJ-2901 and JNJ-4052 with Telacebec (Q203): The manuscript should provide a comparative analysis of the new candidates with existing inhibitors in terms of efficacy, safety, and pharmacokinetics as well as treatment efficacy and relapsing rates. What is the novelty? Why these compounds are better? Why they test 2 different compounds? And if everything is done with JNJ-2901, why to include JNJ-4052 in one of the studies? + +The aim of the project was to investigate the role of cytochrome \(bc_{1}\) inhibitors in future treatment regimens rather than suggest that JNJ- 2901 is superior to telacebec. We selected three inhibitors with related chemical structure, mode of binding and efficacy to achieve these aims; we have made this clearer in the text (pg 5- 6). + +- Differences in mice models and infection routes: The study utilizes different infection models, and these differences should be considered to discuss the results. In addition, the authors should also discuss the gender bias in the experiments (only female mice are used) and how this could impact clinical translation. + +In this study, two different infection models were used: nasal (via aerosol or intranasal instillation) and intravenous. As noted in the text, we acknowledge that the intravenous model exhibits a higher severity of the disease since this infection route confers a systemic infection, whereas the nasal route mainly leads to a pulmonary infection. The intention of this study was not to characterise the treatment response at the pathology level, but rather to have a broad knowledge of the activity of cytochrome \(bc_{1}\) - containing regimens in multiple potential scenarios. + +Regarding the use of only female mice, we acknowledge recommendations for including both sexes in animal studies. However, in line with our institutional policies focused on the 3Rs, we used only female mice to minimise stress and harm. Relapse studies are very long and involve repeated daily handling and dosing, which can lead to a higher risk of aggres behaviour in males. Clinical translation would take place when human exposures are known in a Phase I trial. Additionally, no differences between sex have been reported in relation to drug efficacy in TB mouse models. + +- Comparison between clinical isolates and wild-type (WT) strains: Authors should also discuss the + +<--- Page Split ---> + +observed differences in drug efficacy between clinical isolates and WT strains. The reasons behind these differences need to be explained and appropriately discussed. + +We have now added discussion on the comparison of WT vs. clinical isolate (pg 9- 10). + +- Experimental limitations: The mention of limitations in L119 is too vague. The authors should explicitly outline the limitations of their experimental design. + +The main limitation of this study was the number of animals used did not provide enough statistical power to differentiate the different conditions. We have mentioned this in the text (pg 7). + +- The potential of cytochrome bc1 inhibitors: The claim that these inhibitors could significantly impact TB treatment is overstated for the level of preclinical data presented. Further discussion on the limitations of the preclinical findings hereby presented and next steps for clinical translation is needed, including challenges, barriers and further work to be done before undergoing clinical evaluation. + +As discussed above, we wish to make it clear that JNJ- 2901 is a tool compound that we have used to demonstrate how, inhibitors of cytochrome bc1, a novel mode of action, would interact with existing treatments. Our conclusions refer to 'cytochrome bc1 inhibitors' rather than to a specific compound in development. + +## Materials and Methods + +The Materials & Methods section is well- detailed and allows for experimental reproducibility. However, there we have some comments: + +- As in the Results section, avoid referring only to different experiments as Study A, B, etc. Instead, add descriptive headings such as "Intranasal Mice Challenge", "Intravenous Mice Challenge", or "High-Dose Aerosol Challenge." + +- Each experimental model should consistently include the following information: Mouse strain, sex, and age; inoculum preparation, infection route, and dose; treatment duration and euthanasia time points. + +We respectfully disagree with this suggestion. The experimental details for each study are already included in the Methods section, and adding them to the Results and figure legends would lead to unnecessary repetition. We have intentionally used this naming strategy to clearly distinguish studies from different institutions. Furthermore, many of the models have similar experimental parameters, making it difficult to differentiate them by name alone. + +- Authors should provide in the ethical statement the end-point criteria. + +We have now included the humane end points for the in vivo studies (pg 18). + +- Supplementary tables and results should not be included in the Methods section but should be properly cited in the Results section. + +Where possible, we have discussed supplementary tables and results in the Results section, however we disagree that these elements cannot be cited in the methods. + +- There are several experimental methods referenced in the supplementary material but not appearing in the main text (e.g PK and tolerability in mouse, ADME assays, HepG2 cytotoxicity assay, mitochondrial toxicity assay Glu/Gal, Ames II Mutagenicity assay, mutant isolation and WGS). These should be briefly mentioned in the main text, such as: "Both JNJ-2901 and JNJ-4052 + +<--- Page Split ---> + +were evaluated for ADME and toxicity. All parameters supported further use of these compounds in subsequent experiments (Supplementary Table S2)". + +We have now included this information in the Results section (pg 5- 6). + +Additionally, we suggest to address the following minor comments: - L62: we would suggest classifying tuberculosis as a global pandemic. + +We have updated this as suggested. + +- L79: MoA abbreviation is not needed. + +'MoA' is used elsewhere in the manuscript. + +- L87: the word "validated" to describe the inhibitor compound JNJ-2901 is confusing as the presented manuscript seems to be the validation of the compound as an effective treatment adjuvant. If this is not the case, please provide the reference where the compound is validated for its inhibition of the cytochrome bc1. + +We have kept 'validated' as we can now present an additional manuscript (PMID:40191462), which outlines this validation. + +- L91-96: we suggest to relocate this in the line 76, as the TB-PRACTECAL trial results are a good justification of linezolid-associated adverse effects when treating MDR-TB. + +We have now moved this section to the Introduction as suggested. + +- L116-122: please contextualize the results from this part. + +We have expanded the results as requested. + +- L127: move the figure citation to line 133. After the results are explained. + +This has been moved as requested. + +- L146: please provide the justification of why using Telacebec in this study and not JNJ-2901 and provide rationale about the drug regimen used for this experimental design. + +This study was inspired by previous in vitro work demonstrating that the combination of bedaquiline, clofazimine, and telacebec resulted in rapid killing (PMID:27506290). We aimed to evaluate the in vivo efficacy of treatment regimens containing these compounds in combination with pyrazinamide, which has also been shown to enhance efficacy, potentially supporting treatment shortening (PMID:25622149). To allow comparison with previous work, we continued to use telacebec in this study rather than JNJ-2901. We have now clarified this justification in the results (pg 7) and discussion (pg 9). + +- L164: as far as we understood, JNJ-2901 and Telacebec were also assessed for its bactericidal activity against clinical isolates in comparison to the H37Rv strain (Figure 2 B,C,D and E). Please provide a proper description of the compound used for this experiment and further discussion of this results in the main text. + +At the time that this experiment was initiated, JNJ- 4052 was our lead molecule from our cytochrome bc1 drug discovery programme. This was the main reason it was chosen for the in vivo study outlined in Figure 3e. This compound provides a proof-of-principle for inhibition of cytochrome bc1, with other compounds with this MoA expected to have the same response as suggested by Figure 3b-d. + +<--- Page Split ---> + +- Figure 1: If the mice strain and experimental design are the same, consider re-structure Figure 1B and 1C in a unique figure. + +We would prefer to keep these studies separate, enabling the reader to discriminate between the individual experiments. + +- Figure 2: Please, consider a figure rearrangement. We suggest dividing Figure 2 in two. Section A on one side (resulting in Figure 2) and sections B, C, D, E and F on the other (resulting in Figure 3 A, B, C, D and E). Since the results represented refer to different experimental questions and require a results section for each one. + +We agree, and have now split Figure 2 into two new figures as suggested. + +## Final Recommendation + +This study presents valuable preclinical data on cytochrome bc1 inhibitors in TB treatment. However, we have significant concerns regarding the manuscript as it currently stands. It lacks a proper structure, clarity, and experimental justification, and the discussion is entirely insufficient. The manuscript needs to be totally rewritten to address these issues, ensuring that it achieves the required readability, scientific rigor, and overall impact to be considered suitable for publication. + +<--- Page Split ---> + +## Response to reviewer's comments + +We have addressed the final reviewer's comment in red below. We once again thank the reviewer's for their valuable comments. + +Reviewer #1 (Remarks to the Author): + +The revised manuscript of Clara Aguilar Pérez and colleagues has addressed all of my previous concerns and I am happy to see some of the recommendation on the revised discussion section as well as extended new data. The study represents an important progress on inhibition of respiration machinery in Mtb and has potential for the development of future therapeutics. + +Reviewer #3 (Remarks to the Author): + +We would like to thank the authors for thoughtfully addressing our major suggestions regarding the manuscript. Our feedback primarily focused on improving its structure, clarity, and the discussion surrounding the experimental procedures and results. In particular, the authors have now effectively justified the differences observed when treating laboratory strains with different cytochrome bc1 inhibitors versus clinical strains. With these revisions, the manuscript now clearly highlights the significance of this investigation in advancing our understanding of tuberculosis treatment strategies. + +This work underscores the potential of bc1 inhibitors as viable alternatives to fluoroquinolones and linezolid, which are often associated with adverse effects in current regimens for drug- resistant tuberculosis. Moreover, it contributes to the possibility of treatment shortening for drug- sensitive tuberculosis, with added potential against clinical strains. The experiments were performed using different, well- justified preclinical mouse models, which strengthens the translational relevance of the findings and supports further investigation of this promising asset. Based on these improvements and the scientific merit of the study, we believe the manuscript is now better suited for publication. + +However, we would like the authors to address the following remaining issue: + +Please add a paragraph on limitations to the discussion section. For example, the sample size of mice used in the experiments could be acknowledged as a limitation (even though we recognize that this is already mentioned on page 7). Additionally, regarding the authors' response that "no differences between sexes have been reported in relation to drug efficacy in TB mouse models," we would like to stress that, even if ethical requirements do not mandate the inclusion of both biological sexes, doing so is strongly advisable. There is robust evidence from both clinical and preclinical studies that biological sex influences TB epidemiology and treatment outcomes(for example, see: Idris, R., Infection 2025, https://doi.org/10.1007/s15010-024-02424-5; Dutta NK, Front Immunol, 2020, doi: 10.3389/fimmu.2020.01465; Tannenbaum, C., Nature, 2019, https://doi.org/10.1038/s41586-019-1657-6). These differences are driven by a combination of hormonal, genetic, and immunological factors, as well as potential differences in treatment adherence and broader social determinants of health. While we acknowledge that using female mice can be more + +<--- Page Split ---> + +practical in terms of logistics and animal management- since males often display more aggressive behavior that can complicate experiments- there is now ample evidence showing that men and women often have different disease trajectories (not only for TB!) and responses to treatment. One persistent issue in drug development is that preclinical and clinical studies frequently fail to reflect the biological diversity found in real- world populations. Including both sexes in preclinical experiments wherever feasible would help improve the generalizability of the findings and ensure that results more accurately inform treatment strategies for all patients. + +We thank the reviewer for their helpful suggestion. We have now added a paragraph to the discussion (pg. 10) outlining the limitations of our study and lessons for future work. Specifically, we address the use of female mice, as suggested, and also note the following points for improvement of future studies: (i) increasing statistical power by using larger animal group sizes, (ii) incorporating monotherapy arms to enable regimen deconvolution, and (iii) including clinical isolates to better reflect the diversity and relevance of circulating M. tuberculosis strains. + +In summary, we encourage the authors to carefully consider any additional limitations of their study and clearly state them, as this will add valuable context and transparency. Once this is done, the manuscript can be endorsed for publication. + +Reviewer #4 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> diff --git a/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c98d571baf13a00024cc0cbfe57a8f8b07d78175 --- /dev/null +++ b/peer_reviews/1292826cb041fd67ca20b49f8643de61f387627c09dfbb550f24e651c23d0208/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,643 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 161, 896, 210]]<|/det|> +# The role of cytochrome bc1 inhibitors in future tuberculosis treatment regimens + +<|ref|>text<|/ref|><|det|>[[73, 224, 468, 241]]<|/det|> +Corresponding Author: Dr Clara Aguilar Pérez + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 219, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 418, 919, 485]]<|/det|> +The manuscript by Perez and colleagues present data on the effects of cytochrome bc1 inhibitors and their potential efficacy in drug regimens against multidrug resistant TB as well as its role in reducing the duration of chemotherapy in drug susceptible TB. The work is important and timely considered the burden of drug- resistant TB and the prolonged treatment protocols for both drug resistant and susceptible cases of TB. The experimental approach is solid and data presented are robust to support their hypotheses. + +<|ref|>text<|/ref|><|det|>[[72, 496, 920, 550]]<|/det|> +One of the main interesting points in the manuscript is the fact that cytochrome bc1 inhibitors are more potent against clinical isolates than the lab strains. A further investigation into this would have increased the impact of the work as well as our understanding of the mechanisms of action of these inhibitors. Especially as these are claimed to be validated inhibitors, it would also be nice to see more of their characterisation and target engagement in vitro. + +<|ref|>text<|/ref|><|det|>[[72, 561, 899, 589]]<|/det|> +In addition, would this variability on strain efficacy mean that there are potential other targets being inhibited by the same compounds or is it the secondary effects of inhibiting the cytochrome bc1 and the respiratory chain of Mtb? + +<|ref|>text<|/ref|><|det|>[[72, 600, 923, 680]]<|/det|> +For the present study, authors can expand the discussion regarding the efficacy of their compound in the background of bd and how this could affect the outcome. More importantly, the authors can use these compounds to further interrogate this hypothesis. In addition, having another look at their data, I could see that if you calculate the MBC/MIC ratio for the reference lab strain (H37Rv) and the cytochrome deleted mutant (H37Rv_CytBd- KO) on supplementary table S2 one can see that their inhibitor is bacteriostatic on H37Rv whereas it is bactericidal on cytochrome bd deleted mutant (H37Rv_CytBd- KO). That further adds to the argument that the expression levels of cytochrome bd is an important factor in their compound efficacy. + +<|ref|>text<|/ref|><|det|>[[72, 691, 916, 745]]<|/det|> +Furthermore, the authors did not include if these compounds are active against MDR and XDR Mtb strains. Taking into account that the main use of these inhibitors would be towards a drug regimen for treating MDR- TB, it would be nice to see that the compounds maintain their activity against a panel of multiple drug- resistant strains including MDR and XDR clinical isolates. + +<|ref|>text<|/ref|><|det|>[[72, 757, 916, 796]]<|/det|> +Obviously a series of experiments where one looks at the levels of expression of these genes under treatment or not in a series of lab and clinical strains of Mtb would shed light on this question. But I don't think these experiments need to be part of this work. + +<|ref|>text<|/ref|><|det|>[[70, 807, 818, 822]]<|/det|> +Lastly, in the Figure S3, I cannot see the control line as well as the figure legend need a bit more explanation. + +<|ref|>sub_title<|/ref|><|det|>[[72, 847, 161, 861]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 874, 922, 940]]<|/det|> +(Remarks to the Author) The authors have done an excellent job of identifying cytochrome bc1 as an important component of the Mtb electron transport chain and a potentially sterilizing target in for TB regimen development. Using a relapsing mouse model, they have attempted to demonstrate that cytochrome bc1 inhibitors could be effective partner drugs in TB regimen development that could enhance sterilization. They report on several novel regimens + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 921, 140]]<|/det|> +as examples of this role for bc1 inhibitors in regimens for both multidrug- resistant TB (MDR- TB) and drug- sensitive TB (DSTB), where cytochrome bc1 inhibitors could contribute to sterilization and treatment shortening. importantly, they have shown that clinical isolates exhibit heightened susceptibility to cytochrome bc1 inhibitors compared to laboratory- adapted strains, further supporting their potential usefulness in a clinical setting even as their contribution may be low or undetectable against a lab adapted strain. They take these findings as confirmation that cytochrome bc1 inhibitors have significant potential to improve TB treatment outcomes and highlight the need for further studies to evaluate their clinical contribution to novel treatment regimens. + +<|ref|>text<|/ref|><|det|>[[71, 151, 919, 321]]<|/det|> +What are the noteworthy results? The authors have done an excellent job of identifying and advancing highly potent inhibitors against their chosen target, cytochrome bc1. There is enough evidence to demonstrate that this is a sound choice of target, especially with the excellent success of bedaquiline, the flagship ATP synthase developed by the same group that has literally changed the paradigm in TB treatment shortening and highlighted the electron transport chain as a highly valuable and sterilizing target, at the same level or better than the rifamycin of prior years. It is therefore sound and admirable to hit this pathway as hard as possible, at multiple points and potentially achieve better cure. The problem seems to be that the interplay between cytochrome bc and cytochrome bd seems complicated and makes it difficult to determine with available data, including the data reported here, if just inhibiting bc, but not bd will be enough to realize the expected benefits. It seems that high expression of bd is able to reverse or nullify the effects of inhibiting bc. This is potentially the reason why there is strain difference between lab adapted versus clinical isolates. Further proof is gleaned from the excellent performance of Q203, the lead asset in this target space, versus mycobacterial species that do not express bd like M. leprae and M. ulcerans. This leaves the potential for a bc inhibitor uncertain against tuberculosis. Having said that, the team has identified a tool compound that together with Q203 will be useful in further investigating this target + +<|ref|>text<|/ref|><|det|>[[72, 332, 920, 439]]<|/det|> +Will the work be of significance to the field and related fields? While the actual developability of this asset in future TB drug regimens is in doubt until more work is done to fully appreciate contribution against all TB strains, publication of this work will be of great significance to the field and specifically to the grand idea of targeting the electron transport chain of Mtb at multiple nodes to achieve better cure for TB. Furthermore, the compound reported here could also be expanded to the NTM space as is being done for Q203 which is currently being evaluated against leprosy and buruli ulcer, arguably important and neglected diseases as well. But for use in tuberculosis, more work needs to be done to understand the importance of targeting bc1 in a background with high expression of bd. And to determine if the site of infection and location in a lesion affects the usefulness of this asset. And if the mouse model as used today is the best model for this particular asset + +<|ref|>text<|/ref|><|det|>[[72, 449, 921, 568]]<|/det|> +How does it compare to the established literature? The work reported here is of a high level, similar to other novel drug development programs. Importantly, this was not just a random shot in the dark, instead it was a highly impressive hypothesis driven mission that actually delivered a high- quality compound that is available for further evaluation to prove the hypothesis and potentially deliver a developable asset. It could be argued that in some of the regimen development, drug combination studies in mice, a more factorial approach that builds from 2, to 3 and then perhaps four drugs, with the ability to clearly demonstrate the sterilizing contribution of the asset being evaluated could have been more rigorous than reported here. This leaves this reviewer unable in some cases to confirm that the J bc1 inhibitor contributed anything at all in some of the reported combinations. This could be cleaned up on a re- submission, or in future studies that would attempt to demonstrate the full potential of this asset. + +<|ref|>text<|/ref|><|det|>[[72, 580, 761, 595]]<|/det|> +If the work is not original, please provide relevant references. The work is original and very well done + +<|ref|>text<|/ref|><|det|>[[72, 606, 921, 648]]<|/det|> +Does the work support the conclusions and claims, or is additional evidence needed? The work supports some of the claims, but as stated above, the usefulness of developing a bc1 inhibitors and that inhibitor demonstrating a real contribution to treatment shortening against a tuberculosis infection still needs more work. + +<|ref|>text<|/ref|><|det|>[[72, 658, 911, 700]]<|/det|> +Are there any flaws in the data analysis, interpretation and conclusions? Target validation for bc1 in a highly expressed bd background needs special attention. Contribution of the asset to significant treatment shortening in a developable regimen could be improved + +<|ref|>text<|/ref|><|det|>[[72, 710, 923, 752]]<|/det|> +Do these prohibit publication or require revision? I recommend publication of this work with a more substantive discussion of the strain difference and usefulness of bc1 inhibitors vs bd expression and a better demonstration of contribution to treatment shortening + +<|ref|>text<|/ref|><|det|>[[72, 762, 723, 778]]<|/det|> +Is the methodology sound? The methods used are sound except for the identified shortcomings + +<|ref|>text<|/ref|><|det|>[[72, 788, 917, 830]]<|/det|> +Does the work meet the expected standards in your field? The work is high quality from a highly experienced group working in a target pathway with which they are clearly experts. The regimen development work, especially with this challenging target, relative to bd expression could be improved + +<|ref|>text<|/ref|><|det|>[[72, 840, 635, 855]]<|/det|> +Is there enough detail provided in the methods for the work to be reproduced? Yes + +<|ref|>text<|/ref|><|det|>[[72, 866, 714, 881]]<|/det|> +Recommendation: Accept for publication with some revision of the highlighted aspects, above + +<|ref|>text<|/ref|><|det|>[[72, 906, 161, 919]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 931, 238, 945]]<|/det|> +(Remarks to the Author) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[73, 48, 208, 60]]<|/det|> +## General Comments + +<|ref|>text<|/ref|><|det|>[[72, 60, 914, 140]]<|/det|> +The manuscript presents valuable findings on the role of cytochrome bc1 inhibitors in tuberculosis treatment. However, it currently lacks a clear and well- organized structure, which makes it challenging to follow. To be considered suitable for publication, we strongly recommend rewriting the whole manuscript to include distinct and complete sections—specifically, Introduction, Materials & Methods, Results, Discussion, and Conclusion. The current format hinders readability and clarity and omits critical information necessary to fully assess the study's findings. Additionally, the manuscript would benefit from enhanced experimental justification and a more thorough discussion of the results. + +<|ref|>text<|/ref|><|det|>[[72, 139, 870, 180]]<|/det|> +The experimental design, including details on mice strains and compound combinations and its rationale, should be consistently presented across all sections (Introduction, Results, Materials & Methods) and thoroughly discussed. Introduction + +<|ref|>text<|/ref|><|det|>[[72, 178, 920, 245]]<|/det|> +The manuscript provides a well- articulated description of the problem and effectively highlights the potential of the electron transport chain inhibitors in tuberculosis treatment. However, we miss a proper introduction and a clear justification of the two new drug candidates (JNJ- 2901 and JNJ- 4052) that the authors test (according to the figures), and the differences and their potential benefits when compared to the cytochrome bc1 inhibitor Q203 (Telacebec) already being evaluated in clinical trials. This would provide proof of the manuscript's novelty. + +<|ref|>text<|/ref|><|det|>[[72, 243, 912, 283]]<|/det|> +Hypothesis, aim and objectives are not well presented, and clearly insufficiently described. Moreover, supplementary information and figures should not be included in the Introduction but rather integrated and discussed in the results section. Results + +<|ref|>text<|/ref|><|det|>[[72, 281, 916, 323]]<|/det|> +The results demonstrate promising data on JNJ- 2901's efficacy in reducing bacterial burden and preventing relapse in mice models. The findings suggest a potential shortening of TB treatment regimens, particularly with BPaCJ, which showed the highest efficacy and lowest relapse rates compared to BPaL, BPaM, BPaC, and BPaJ. + +<|ref|>text<|/ref|><|det|>[[72, 322, 683, 336]]<|/det|> +However, we have major concerns regarding the description and structure of this section: + +<|ref|>text<|/ref|><|det|>[[72, 335, 920, 440]]<|/det|> +- Global experimental plan should first be presented to help understand what the authors did, and then each set of results should be clearly introduced with a summary of the main conclusion before presenting the data of each experimental study. +- The experimental design (mice strain, infection mode, treatment duration, and rationale for each study) and must be clearly stated at the beginning of each results subsection. We here wanted to point out that the naming convention of studies (e.g., Study A, B, C, etc.) does not provide enough information to the reader. We suggest their replacement throughout the manuscript with descriptive terms reflecting the experimental model. For example, instead of "In an additional study (Study C)," we suggest "We additionally investigated drug combination efficacy and relapse in intravenously infected mice." +- Why a second compound – JNJ-4052- is tested in Study F? Why to test another candidate? + +<|ref|>text<|/ref|><|det|>[[72, 439, 152, 451]]<|/det|> +Discussion + +<|ref|>text<|/ref|><|det|>[[72, 451, 918, 491]]<|/det|> +Although a very small discussion comments are integrated into the manuscript (e.g., L136- 143, L156- 161, L171- 177), a dedicated Discussion section is necessary. We suggest moving the relevant lines into a standalone Discussion section and expanding on several key topics: + +<|ref|>text<|/ref|><|det|>[[72, 490, 916, 544]]<|/det|> +- Comparison of JNJ-2901 and JNJ-4052 with Telacebec (Q203): The manuscript should provide a comparative analysis of the new candidates with existing inhibitors in terms of efficacy, safety, and pharmacokinetics as well as treatment efficacy and relapsing rates. What is the novelty? Why these compounds are better? Why they test 2 different compounds? And if everything is done with JNJ-2901, why to include JNJ-4052 in one of the studies? + +<|ref|>text<|/ref|><|det|>[[72, 543, 916, 583]]<|/det|> +- Differences in mice models and infection routes: The study utilizes different infection models, and these differences should be considered to discuss the results. In addition, the authors should also discuss the gender bias in the experiments (only female mice are used) and how this could impact clinical translation. + +<|ref|>text<|/ref|><|det|>[[72, 582, 916, 622]]<|/det|> +- Comparison between clinical isolates and wild-type (WT) strains: Authors should also discuss the observed differences in drug efficacy between clinical isolates and WT strains. The reasons behind these differences need to be explained and appropriately discussed. + +<|ref|>text<|/ref|><|det|>[[72, 620, 860, 648]]<|/det|> +- Experimental limitations: The mention of limitations in L119 is too vague. The authors should explicitly outline the limitations of their experimental design. + +<|ref|>text<|/ref|><|det|>[[72, 647, 916, 700]]<|/det|> +- The potential of cytochrome bc1 inhibitors: The claim that these inhibitors could significantly impact TB treatment is overstated for the level of preclinical data presented. Further discussion on the limitations of the preclinical findings hereby presented and next steps for clinical translation is needed, including challenges, barriers and further work to be done before undergoing clinical evaluation. + +<|ref|>sub_title<|/ref|><|det|>[[72, 712, 231, 724]]<|/det|> +## Materials and Methods + +<|ref|>text<|/ref|><|det|>[[72, 724, 916, 750]]<|/det|> +The Materials & Methods section is well- detailed and allows for experimental reproducibility. However, there we have some comments: + +<|ref|>text<|/ref|><|det|>[[72, 750, 920, 790]]<|/det|> +- As in the Results section, avoid referring only to different experiments as Study A, B, etc. Instead, add descriptive headings such as "Intranasal Mice Challenge", "Intravenous Mice Challenge", or "High-Dose Aerosol Challenge." + +<|ref|>text<|/ref|><|det|>[[72, 789, 800, 803]]<|/det|> +- Each experimental model should consistently include the following information: Mouse strain, sex, and age; inoculum + +<|ref|>text<|/ref|><|det|>[[72, 802, 655, 815]]<|/det|> +preparation, infection route, and dose; treatment duration and euthanasia time points. + +<|ref|>text<|/ref|><|det|>[[72, 814, 551, 827]]<|/det|> +- Authors should provide in the ethical statement the end-point criteria. + +<|ref|>text<|/ref|><|det|>[[72, 826, 920, 852]]<|/det|> +- Supplementary tables and results should not be included in the Methods section but should be properly cited in the Results section. + +<|ref|>text<|/ref|><|det|>[[72, 850, 910, 910]]<|/det|> +- There are several experimental methods referenced in the supplementary material but not appearing in the main text (e.g. PK and tolerability in mouse, ADME assays, HepG2 cytotoxicity assay, mitochondrial toxicity assay Glu/Gal, Ames II Mutagenicity assay, mutant isolation and WGS). These should be briefly mentioned in the main text, such as: "Both JNJ-2901 and JNJ-4052 were evaluated for ADME and toxicity. All parameters supported further use of these compounds in subsequent experiments (Supplementary Table S2)". + +<|ref|>text<|/ref|><|det|>[[72, 909, 530, 922]]<|/det|> +Additionally, we suggest to address the following minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 922, 560, 948]]<|/det|> +- L62: we would suggest classifying tuberculosis as a global pandemic. +- L79: MoA abbreviation is not needed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 914, 87]]<|/det|> +- L87: the word "validated" to describe the inhibitor compound JNJ-2901 is confusing as the presented manuscript seems to be the validation of the compound as an effective treatment adjuvant. If this is not the case, please provide the reference where the compound is validated for its inhibition of the cytochrome bc1. + +<|ref|>text<|/ref|><|det|>[[70, 87, 910, 113]]<|/det|> +- L91-96: we suggest to relocate this in the line 76, as the TB-PRACTECAL trial results are a good justification of linezolid-associated adverse effects when treating MDR-TB. + +<|ref|>text<|/ref|><|det|>[[73, 113, 465, 126]]<|/det|> +- L116-122: please contextualize the results from this part. + +<|ref|>text<|/ref|><|det|>[[73, 126, 576, 139]]<|/det|> +- L127: move the figure citation to line 133. After the results are explained. + +<|ref|>text<|/ref|><|det|>[[70, 140, 905, 166]]<|/det|> +- L146: please provide the justification of why using Telacobec in this study and not JNJ-2901 and provide rationale about the drug regimen used for this experimental design. + +<|ref|>text<|/ref|><|det|>[[70, 166, 900, 205]]<|/det|> +- L164: as far as we understood, JNJ-2901 and Telacobec were also assessed for its bactericidal activity against clinical isolates in comparison to the H37Rv strain (Figure 2 B,C,D and E). Please provide a proper description of the compound used for this experiment and further discussion of this results in the main text. + +<|ref|>text<|/ref|><|det|>[[70, 204, 884, 230]]<|/det|> +- Figure 1: If the mice strain and experimental design are the same, consider re-structure Figure 1B and 1C in a unique figure. + +<|ref|>text<|/ref|><|det|>[[70, 230, 918, 270]]<|/det|> +- Figure 2: Please, consider a figure rearrangement. We suggest dividing Figure 2 in two. Section A on one side (resulting in Figure 2) and sections B, C, D, E and F on the other (resulting in Figure 3 A, B, C, D and E). Since the results represented refer to different experimental questions and require a results section for each one. + +<|ref|>sub_title<|/ref|><|det|>[[72, 283, 235, 295]]<|/det|> +## Final Recommendation + +<|ref|>text<|/ref|><|det|>[[72, 296, 920, 348]]<|/det|> +This study presents valuable preclinical data on cytochrome bc1 inhibitors in TB treatment. However, we have significant concerns regarding the manuscript as it currently stands. It lacks a proper structure, clarity, and experimental justification, and the discussion is entirely insufficient. The manuscript needs to be totally rewritten to address these issues, ensuring that it achieves the required readability, scientific rigor, and overall impact to be considered suitable for publication. + +<|ref|>sub_title<|/ref|><|det|>[[72, 373, 161, 386]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 399, 238, 411]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 412, 864, 451]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 464, 144, 476]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 490, 219, 503]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 515, 160, 528]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 542, 238, 554]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 555, 923, 595]]<|/det|> +The revised manuscript of Clara Aguilar Pérez and colleagues has addressed all of my previous concerns and I am happy to see some of the recommendation on the revised discussion section as well as extended new data. The study represents an important progress on inhibition of respiration machinery in Mtb and has potential for the development of future therapeutics. + +<|ref|>text<|/ref|><|det|>[[72, 607, 160, 620]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 634, 238, 646]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 647, 915, 712]]<|/det|> +We would like to thank the authors for thoughtfully addressing our major suggestions regarding the manuscript. Our feedback primarily focused on improving its structure, clarity, and the discussion surrounding the experimental procedures and results. In particular, the authors have now effectively justified the differences observed when treating laboratory strains with different cytochrome bc1 inhibitors versus clinical strains. With these revisions, the manuscript now clearly highlights the significance of this investigation in advancing our understanding of tuberculosis treatment strategies. + +<|ref|>text<|/ref|><|det|>[[72, 724, 920, 802]]<|/det|> +This work underscores the potential of bc1 inhibitors as viable alternatives to fluoroquinolones and linezolid, which are often associated with adverse effects in current regimens for drug- resistant tuberculosis. Moreover, it contributes to the possibility of treatment shortening for drug- sensitive tuberculosis, with added potential against clinical strains. The experiments were performed using different, well- justified preclinical mouse models, which strengthens the translational relevance of the findings and supports further investigation of this promising asset. Based on these improvements and the scientific merit of the study, we believe the manuscript is now better suited for publication. + +<|ref|>text<|/ref|><|det|>[[72, 826, 602, 840]]<|/det|> +However, we would like the authors to address the following remaining issue: + +<|ref|>text<|/ref|><|det|>[[72, 853, 920, 945]]<|/det|> +Please add a paragraph on limitations to the discussion section. For example, the sample size of mice used in the experiments could be acknowledged as a limitation (even though we recognize that this is already mentioned on page 7). Additionally, regarding the authors' response that "no differences between sexes have been reported in relation to drug efficacy in TB mouse models," we would like to stress that, even if ethical requirements do not mandate the inclusion of both biological sexes, doing so is strongly advisable. There is robust evidence from both clinical and preclinical studies that biological sex influences TB epidemiology and treatment outcomes (for example, see: Idris, R., Infection 2025, https://doi.org/10.1007/s15010-024-02424-5; Dutta NK, Front Immunol, 2020, doi: 10.3389/fimmu.2020.01465; Tannenbaum, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 921, 166]]<|/det|> +C., Nature, 2019, https://doi.org/10.1038/s41586-019-1657-6). These differences are driven by a combination of hormonal, genetic, and immunological factors, as well as potential differences in treatment adherence and broader social determinants of health. While we acknowledge that using female mice can be more practical in terms of logistics and animal management- since males often display more aggressive behavior that can complicate experiments- there is now ample evidence showing that men and women often have different disease trajectories (not only for TB!) and responses to treatment. One persistent issue in drug development is that preclinical and clinical studies frequently fail to reflect the biological diversity found in real- world populations. Including both sexes in preclinical experiments wherever feasible would help improve the generalizability of the findings and ensure that results more accurately inform treatment strategies for all patients. + +<|ref|>text<|/ref|><|det|>[[70, 177, 905, 206]]<|/det|> +In summary, we encourage the authors to carefully consider any additional limitations of their study and clearly state them, as this will add valuable context and transparency. Once this is done, the manuscript can be endorsed for publication. + +<|ref|>sub_title<|/ref|><|det|>[[73, 216, 162, 230]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 243, 863, 296]]<|/det|> +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 650, 916, 702]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 702, 915, 768]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[73, 767, 618, 780]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[105, 81, 294, 98]]<|/det|> +## Reviewers' comments + +<|ref|>text<|/ref|><|det|>[[102, 107, 894, 143]]<|/det|> +We thank the reviewers for providing useful comments and suggestions that have greatly improved this manuscript. We have addressed each comment below (red). + +<|ref|>sub_title<|/ref|><|det|>[[105, 180, 425, 198]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[104, 206, 894, 311]]<|/det|> +The manuscript by Perez and colleagues present data on the effects of cytochrome bc1 inhibitors and their potential efficacy in drug regimens against multidrug resistant TB as well as its role in reducing the duration of chemotherapy in drug susceptible TB. The work is important and timely considered the burden of drug- resistant TB and the prolonged treatment protocols for both drug resistant and susceptible cases of TB. The experimental approach is solid and data presented are robust to support their hypotheses. + +<|ref|>text<|/ref|><|det|>[[104, 319, 894, 406]]<|/det|> +One of the main interesting points in the manuscript is the fact that cytochrome bc1 inhibitors are more potent against clinical isolates than the lab strains. A further investigation into this would have increased the impact of the work as well as our understanding of the mechanisms of action of these inhibitors. Especially as these are claimed to be validated inhibitors, it would also be nice to see more of their characterisation and target engagement in vitro. + +<|ref|>text<|/ref|><|det|>[[104, 415, 894, 467]]<|/det|> +A second paper has recently been published which describes the characterisation, validation and target engagement of the JNJ- 2901 inhibitor (PMID:40191462). We have provided validation of JNJ- 4052, which comes from the same chemical series as JNJ- 2901, in Supplementary Tables S1- 3. + +<|ref|>text<|/ref|><|det|>[[104, 478, 894, 530]]<|/det|> +In addition, would this variability on strain efficacy mean that there are potential other targets being inhibited by the same compounds or is it the secondary effects of inhibiting the cytochrome bc1 and the respiratory chain of Mtb? + +<|ref|>text<|/ref|><|det|>[[104, 539, 894, 643]]<|/det|> +We do not believe that there are any genuine secondary targets for these compounds. Our resistance data demonstrates that a single nucleotide polymorphism in qcrB can provide high level resistance (for example T313A leads to \(>2000\) - fold resistance to JNJ- 4052; Supplementary Table S1). As discussed below, we believe the differences are most likely due to the increased expression of cytochrome bd, an alternative oxidase that can compensate for cytochrome bc1 inhibition. This is now outlined in the Discussion section (pg 9- 10). + +<|ref|>text<|/ref|><|det|>[[104, 652, 894, 790]]<|/det|> +For the present study, authors can expand the discussion regarding the efficacy of their compound in the background of bd and how this could affect the outcome. More importantly, the authors can use these compounds to further interrogate this hypothesis. In addition, having another look at their data, I could see that if you calculate the MBC/MIC ratio for the reference lab strain (H37Rv) and the cytochrome deleted mutant (H37Rv_CytBd- KO) on supplementary table S2 one can see that their inhibitor is bacteriostatic on H37Rv whereas it is bactericidal on cytochrome bd deleted mutant (H37Rv_CytBd- KO). That further adds to the argument that the expression levels of cytochrome bd is an important factor in their compound efficacy. + +<|ref|>text<|/ref|><|det|>[[104, 800, 894, 835]]<|/det|> +We agree that this is an important point and have now provided discussion of the difference in bactericidality between H37Rv and H37Rv_CytBd- KO strains in the Discussion section (pg 9- 10). + +<|ref|>text<|/ref|><|det|>[[104, 844, 894, 914]]<|/det|> +Furthermore, the authors did not include if these compounds are active against MDR and XDR Mtb strains. Taking into account that the main use of these inhibitors would be towards a drug regimen for treating MDR- TB, it would be nice to see that the compounds maintain their activity against a panel of multiple drug- resistant strains including MDR and XDR clinical isolates. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 80, 894, 115]]<|/det|> +Activity of JNJ- 2901 against a panel of 18 MDR- TB strains has now been published showing that the inhibitor is more active compared to lab- adapted strains (PMID:40191462). + +<|ref|>text<|/ref|><|det|>[[104, 124, 894, 177]]<|/det|> +Obviously a series of experiments where one looks at the levels of expression of these genes under treatment or not in a series of lab and clinical strains of Mtb would shed light on this question. But I don't think these experiments need to be part of this work. + +<|ref|>text<|/ref|><|det|>[[104, 186, 894, 221]]<|/det|> +Lastly, in the Figure S3, I cannot see the control line as well as the figure legend need a bit more explanation. + +<|ref|>text<|/ref|><|det|>[[104, 231, 894, 266]]<|/det|> +We have updated the figure legend to indicate that moxifloxacin is hidden by BDQ (Supplementary Figure S3). We have added more detail of the experimental conditions in the figure legend. + +<|ref|>sub_title<|/ref|><|det|>[[105, 310, 425, 328]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[103, 337, 894, 562]]<|/det|> +The authors have done an excellent job of identifying cytochrome bc1 as an important component of the Mtb electron transport chain and a potentially sterilizing target in for TB regimen development. Using a relapsing mouse model, they have attempted to demonstrate that cytochrome bc1 inhibitors could be effective partner drugs in TB regimen development that could enhance sterilization. They report on several novel regimens as examples of this role for bc1 inhibitors in regimens for both multidrug- resistant TB (MDR- TB) and drug- sensitive TB (DS- TB), where cytochrome bc1 inhibitors could contribute to sterilization and treatment shortening. importantly, they have shown that clinical isolates exhibit heightened susceptibility to cytochrome bc1 inhibitors compared to laboratory- adapted strains, further supporting their potential usefulness in a clinical setting even as their contribution may be low or undetectable against a lab adapted strain. They take these findings as confirmation that cytochrome bc1 inhibitors have significant potential to improve TB treatment outcomes and highlight the need for further studies to evaluate their clinical contribution to novel treatment regimens. + +<|ref|>text<|/ref|><|det|>[[103, 571, 894, 866]]<|/det|> +What are the noteworthy results? The authors have done an excellent job of identifying and advancing highly potent inhibitors against their chosen target, cytochrome bc1. There is enough evidence to demonstrate that this is a sound choice of target, especially with the excellent success of bedaquiline, the flagship ATP synthase developed by the same group that has literally changed the paradigm in TB treatment shortening and highlighted the electron transport chain as a highly valuable and sterilizing target, at the same level or better than the rifamycins of prior years. It is therefore sound and admirable to hit this pathway as hard as possible, at multiple points and potentially achieve better cure. The problem seems to be that the interplay between cytochrome bc and cytochrome bd seems complicated and makes it difficult to determine with available data, including the data reported here, if just inhibiting bc, but not bd will be enough to realize the expected benefits. It seems that high expression of bd is able to reverse or nullify the effects of inhibiting bc. This is potentially the reason why there is strain difference between lab adapted versus clinical isolates. Further proof is gleaned from the excellent performance of Q203, the lead asset in this target space, versus mycobacterial species that do not express bd like M. leprae and M. ulcerans. This leaves the potential for a bc inhibitor uncertain against tuberculosis. Having said that, the team has identified a tool compound that together with Q203 will be useful in further investigating this target + +<|ref|>text<|/ref|><|det|>[[103, 875, 894, 910]]<|/det|> +Will the work be of significance to the field and related fields? While the actual developability of this asset in future TB drug regimens is in doubt until more work is done to fully appreciate contribution + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 80, 893, 219]]<|/det|> +against all TB strains, publication of this work will be of great significance to the field and specifically to the grand idea of targeting the electron transport chain of Mtb at multiple nodes to achieve better cure for TB. Furthermore, the compound reported here could also be expanded to the NTM space as is being done for Q203 which is currently being evaluated against leprosy and buruli ulcer, arguably important and neglected diseases as well. But for use in tuberculosis, more work needs to be done to understand the importance of targeting bc1 in a background with high expression of bd. And to determine if the site of infection and location in a lesion affects the usefulness of this asset. And if the mouse model as used today is the best model for this particular asset + +<|ref|>text<|/ref|><|det|>[[104, 228, 894, 418]]<|/det|> +How does it compare to the established literature? The work reported here is of a high level, similar to other novel drug development programs. Importantly, this was not just a random shot in the dark, instead it was a highly impressive hypothesis driven mission that actually delivered a high- quality compound that is available for further evaluation to prove the hypothesis and potentially deliver a developable asset. It could be argued that in some of the regimen development, drug combination studies in mice, a more factorial approach that builds from 2, to 3 and then perhaps four drugs, with the ability to clearly demonstrate the sterilizing contribution of the asset being evaluated could have been more rigorous than reported here. This leaves this reviewer unable in some cases to confirm that the J bc1 inhibitor contributed anything at all in some of the reported combinations. This could be cleaned up on a re- submission, or in future studies that would attempt to demonstrate the full potential of this asset. + +<|ref|>text<|/ref|><|det|>[[104, 428, 894, 531]]<|/det|> +A more stepwise factorial approach (building from two- to three- and then four- drug combinations) could have further clarified the sterilising contribution of a cytochrome \(bc_{1}\) inhibitor. However, the aim of these studies was not to develop an entirely new regimen but rather to replace moxifloxacin and linezolid with a potentially superior compound while maintaining the existing backbone. Therefore, we prioritised evaluating the \(bc_{1}\) inhibitor in combination with a clinically relevant regimen to reflect a realistic therapeutic setting. + +<|ref|>text<|/ref|><|det|>[[105, 541, 893, 592]]<|/det|> +Additionally, we were mindful of the ethical considerations regarding animal use. Expanding the study design to include a larger number of combinations/conditions would have significantly increased the number of animals required. + +<|ref|>text<|/ref|><|det|>[[105, 602, 893, 688]]<|/det|> +In several of our studies, the addition of a cytochrome \(bc_{1}\) inhibitor led to a statistical improvement in relapse rates (e.g. Figure 2; CZ vs CZT). Nevertheless, we agree that future investigations could employ a more granular factorial design to better define the specific contribution of the \(bc_{1}\) inhibitor. These follow- up studies would help further demonstrate the full potential of cytochrome \(bc_{1}\) inhibitors and strengthen its case for clinical development. + +<|ref|>text<|/ref|><|det|>[[105, 699, 892, 716]]<|/det|> +If the work is not original, please provide relevant references. The work is original and very well done + +<|ref|>text<|/ref|><|det|>[[105, 726, 893, 794]]<|/det|> +Does the work support the conclusions and claims, or is additional evidence needed? The work supports some of the claims, but as stated above, the usefulness of developing a bc1 inhibitors and that inhibitor demonstrating a real contribution to treatment shortening against a tuberculosis infection still needs more work. + +<|ref|>text<|/ref|><|det|>[[105, 806, 893, 908]]<|/det|> +While we acknowledge that additional studies are needed to fully establish the potential of cytochrome \(bc_{1}\) inhibitors to shorten treatment duration, particularly in the context of multidrug- resistant tuberculosis (MDR- TB), the data presented here clearly demonstrate that the inclusion of a cytochrome \(bc_{1}\) inhibitor reduces the treatment time required. For example, the addition of telacebec to CZ reduces the treatment by at least 2 months (Figure 2). This is the starting point for further work to investigate this in more detail. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 97, 895, 132]]<|/det|> +Are there any flaws in the data analysis, interpretation and conclusions? Target validation for bc1 in a highly expressed bd background needs special attention. + +<|ref|>text<|/ref|><|det|>[[102, 141, 895, 177]]<|/det|> +We have recently published the validation of JNJ- 2901 (PMID: 40191462) and have expanded our discussion on bd expression (pg 9- 10). + +<|ref|>text<|/ref|><|det|>[[102, 186, 895, 221]]<|/det|> +Contribution of the asset to significant treatment shortening in a developable regimen could be improved + +<|ref|>text<|/ref|><|det|>[[104, 231, 895, 334]]<|/det|> +As discussed above, we view this work as an important starting point for investigating the potential contribution of cytochrome \(bc_{1}\) inhibitors to future treatment- shortening regimens. We agree that further work is required beyond the current study. However, one challenge in addressing this more definitively is the lack of consensus on what constitutes a 'developable' regimen, as different organisations often have varying perspectives on which drugs should be prioritised; clofazimine being a notable example here. + +<|ref|>text<|/ref|><|det|>[[104, 344, 895, 397]]<|/det|> +Do these prohibit publication or require revision? I recommend publication of this work with a more substantive discussion of the strain difference and usefulness of bc1 inhibitors vs bd expression and a better demonstration of contribution to treatment shortening + +<|ref|>text<|/ref|><|det|>[[104, 407, 850, 441]]<|/det|> +We have now re- formatted the manuscript and expanded the discussion on the clinical isolate differences we observed. + +<|ref|>text<|/ref|><|det|>[[102, 468, 864, 486]]<|/det|> +Is the methodology sound? The methods used are sound except for the identified shortcomings + +<|ref|>text<|/ref|><|det|>[[104, 495, 870, 565]]<|/det|> +Does the work meet the expected standards in your field? The work is high quality from a highly experienced group working in a target pathway with which they are clearly experts. The regimen development work, especially with this challenging target, relative to bd expression could be improved + +<|ref|>text<|/ref|><|det|>[[104, 565, 850, 600]]<|/det|> +Is there enough detail provided in the methods for the work to be reproduced? Yes Recommendation: Accept for publication with some revision of the highlighted aspects, above + +<|ref|>sub_title<|/ref|><|det|>[[104, 643, 487, 660]]<|/det|> +## Reviewer #3 and #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[105, 661, 263, 676]]<|/det|> +General Comments + +<|ref|>text<|/ref|><|det|>[[104, 678, 895, 816]]<|/det|> +The manuscript presents valuable findings on the role of cytochrome bc1 inhibitors in tuberculosis treatment. However, it currently lacks a clear and well- organized structure, which makes it challenging to follow. To be considered suitable for publication, we strongly recommend rewriting the whole manuscript to include distinct and complete sections—specifically, Introduction, Materials & Methods, Results, Discussion, and Conclusion. The current format hinders readability and clarity and omits critical information necessary to fully assess the study's findings. Additionally, the manuscript would benefit from enhanced experimental justification and a more thorough discussion of the results. + +<|ref|>text<|/ref|><|det|>[[104, 825, 895, 860]]<|/det|> +We have now re- formatted the manuscript for Nature Communications as suggested and expanded on the Discussion section. + +<|ref|>text<|/ref|><|det|>[[102, 887, 860, 904]]<|/det|> +The experimental design, including details on mice strains and compound combinations and its + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 80, 875, 115]]<|/det|> +rationale, should be consistently presented across all sections (Introduction, Results, Materials & Methods) and thoroughly discussed. + +<|ref|>sub_title<|/ref|><|det|>[[104, 143, 201, 159]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[104, 160, 888, 264]]<|/det|> +The manuscript provides a well- articulated description of the problem and effectively highlights the potential of the electron transport chain inhibitors in tuberculosis treatment. However, we miss a proper introduction and a clear justification of the two new drug candidates (JNJ- 2901 and JNJ- 4052) that the authors test (according to the figures), and the differences and their potential benefits when compared to the cytochrome bc1 inhibitor Q203 (Telacebec) already being evaluated in clinical trials. This would provide proof of the manuscript's novelty. + +<|ref|>text<|/ref|><|det|>[[104, 273, 895, 378]]<|/det|> +The primary focus of this manuscript is to understand the contribution of a cytochrome bc1- targeting inhibitor to TB treatment regimens, rather than specifically focusing on JNJ- 2091 or suggesting it is a superior molecule. We consider all the compounds discussed in this work as tool compounds used to increase our understanding of how this mode of action could complement existing drug regimens. In parallel, we have published a separate validation of JNJ- 2901 (PMID:40191462) and have added additional justification here (pg 5- 6). + +<|ref|>text<|/ref|><|det|>[[104, 386, 822, 404]]<|/det|> +Hypothesis, aim and objectives are not well presented, and clearly insufficiently described. + +<|ref|>text<|/ref|><|det|>[[105, 413, 715, 431]]<|/det|> +We have clarified and expanded the objectives of each section as requested. + +<|ref|>text<|/ref|><|det|>[[104, 440, 864, 476]]<|/det|> +Moreover, supplementary information and figures should not be included in the Introduction but rather integrated and discussed in the results section. + +<|ref|>text<|/ref|><|det|>[[104, 485, 894, 520]]<|/det|> +Reference to the figures and supplementary information has been removed from the introduction following re- formatting. + +<|ref|>sub_title<|/ref|><|det|>[[104, 549, 167, 564]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[104, 565, 872, 633]]<|/det|> +The results demonstrate promising data on JNJ- 2901's efficacy in reducing bacterial burden and preventing relapse in mice models. The findings suggest a potential shortening of TB treatment regimens, particularly with BPaCJ, which showed the highest efficacy and lowest relapse rates compared to BPaL, BPaM, BPaC, and BPaJ. + +<|ref|>text<|/ref|><|det|>[[105, 633, 812, 650]]<|/det|> +However, we have major concerns regarding the description and structure of this section: + +<|ref|>text<|/ref|><|det|>[[104, 651, 892, 703]]<|/det|> +- Global experimental plan should first be presented to help understand what the authors did, and then each set of results should be clearly introduced with a summary of the main conclusion before presenting the data of each experimental study. + +<|ref|>text<|/ref|><|det|>[[104, 712, 893, 747]]<|/det|> +We agree, and have now divided this section more clearly with Figures 1b- c now discussed sequentially. An overview of the first set of experiments is provided in Figure 1a. + +<|ref|>text<|/ref|><|det|>[[104, 756, 895, 877]]<|/det|> +- The experimental design (mice strain, infection mode, treatment duration, and rationale for each study) and must be clearly stated at the beginning of each results subsection. We here wanted to point out that the naming convention of studies (e.g., Study A, B, C, etc.) does not provide enough information to the reader. We suggest their replacement throughout the manuscript with descriptive terms reflecting the experimental model. For example, instead of “In an additional study (Study C),” we suggest “We additionally investigated drug combination efficacy and relapse in intravenously infected mice.” + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 80, 894, 150]]<|/det|> +We respectfully disagree, as the experimental design is indicated in the Materials and Methods section. We do not believe it is necessary to repeat this information in the Results section or figure legends. We have named them A, B, C etc. because the studies were performed by different institutions rather than because they are different type of studies. + +<|ref|>text<|/ref|><|det|>[[104, 159, 840, 177]]<|/det|> +- Why a second compound – JNJ-4052- is tested in Study F? Why to test another candidate? + +<|ref|>text<|/ref|><|det|>[[104, 186, 894, 308]]<|/det|> +JNJ- 2901 and JNJ- 4052 belong to the same chemical series and exhibit very similar activity and safety profiles. Our cytochrome \(bc_{1}\) drug discovery programme has been ongoing for 7 years, during which time we have progressed a number of lead compounds including JNJ- 4052 and JNJ- 2901. The in vivo clinical isolate study (Study F) was performed using the earlier lead, JNJ- 4052. While we acknowledge that repeating this experiment with JNJ- 2901 would have been ideal, given the comparable profiles of both compounds, we do not anticipate a change in the outcome. Therefore, we believe repeating this study would not represent a justifiable use of mice. + +<|ref|>sub_title<|/ref|><|det|>[[104, 318, 194, 334]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[104, 336, 888, 400]]<|/det|> +Although a very small discussion comments are integrated into the manuscript (e.g., L136- 143, L156- 161, L171- 177), a dedicated Discussion section is necessary. We suggest moving the relevant lines into a standalone Discussion section and expanding on several key topics: + +<|ref|>text<|/ref|><|det|>[[104, 389, 888, 473]]<|/det|> +- Comparison of JNJ-2901 and JNJ-4052 with Telacebec (Q203): The manuscript should provide a comparative analysis of the new candidates with existing inhibitors in terms of efficacy, safety, and pharmacokinetics as well as treatment efficacy and relapsing rates. What is the novelty? Why these compounds are better? Why they test 2 different compounds? And if everything is done with JNJ-2901, why to include JNJ-4052 in one of the studies? + +<|ref|>text<|/ref|><|det|>[[104, 483, 894, 552]]<|/det|> +The aim of the project was to investigate the role of cytochrome \(bc_{1}\) inhibitors in future treatment regimens rather than suggest that JNJ- 2901 is superior to telacebec. We selected three inhibitors with related chemical structure, mode of binding and efficacy to achieve these aims; we have made this clearer in the text (pg 5- 6). + +<|ref|>text<|/ref|><|det|>[[104, 561, 894, 630]]<|/det|> +- Differences in mice models and infection routes: The study utilizes different infection models, and these differences should be considered to discuss the results. In addition, the authors should also discuss the gender bias in the experiments (only female mice are used) and how this could impact clinical translation. + +<|ref|>text<|/ref|><|det|>[[104, 641, 894, 744]]<|/det|> +In this study, two different infection models were used: nasal (via aerosol or intranasal instillation) and intravenous. As noted in the text, we acknowledge that the intravenous model exhibits a higher severity of the disease since this infection route confers a systemic infection, whereas the nasal route mainly leads to a pulmonary infection. The intention of this study was not to characterise the treatment response at the pathology level, but rather to have a broad knowledge of the activity of cytochrome \(bc_{1}\) - containing regimens in multiple potential scenarios. + +<|ref|>text<|/ref|><|det|>[[104, 753, 894, 857]]<|/det|> +Regarding the use of only female mice, we acknowledge recommendations for including both sexes in animal studies. However, in line with our institutional policies focused on the 3Rs, we used only female mice to minimise stress and harm. Relapse studies are very long and involve repeated daily handling and dosing, which can lead to a higher risk of aggres behaviour in males. Clinical translation would take place when human exposures are known in a Phase I trial. Additionally, no differences between sex have been reported in relation to drug efficacy in TB mouse models. + +<|ref|>text<|/ref|><|det|>[[104, 885, 888, 902]]<|/det|> +- Comparison between clinical isolates and wild-type (WT) strains: Authors should also discuss the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 80, 890, 115]]<|/det|> +observed differences in drug efficacy between clinical isolates and WT strains. The reasons behind these differences need to be explained and appropriately discussed. + +<|ref|>text<|/ref|><|det|>[[102, 124, 790, 142]]<|/det|> +We have now added discussion on the comparison of WT vs. clinical isolate (pg 9- 10). + +<|ref|>text<|/ref|><|det|>[[102, 152, 856, 187]]<|/det|> +- Experimental limitations: The mention of limitations in L119 is too vague. The authors should explicitly outline the limitations of their experimental design. + +<|ref|>text<|/ref|><|det|>[[102, 196, 890, 232]]<|/det|> +The main limitation of this study was the number of animals used did not provide enough statistical power to differentiate the different conditions. We have mentioned this in the text (pg 7). + +<|ref|>text<|/ref|><|det|>[[102, 241, 888, 328]]<|/det|> +- The potential of cytochrome bc1 inhibitors: The claim that these inhibitors could significantly impact TB treatment is overstated for the level of preclinical data presented. Further discussion on the limitations of the preclinical findings hereby presented and next steps for clinical translation is needed, including challenges, barriers and further work to be done before undergoing clinical evaluation. + +<|ref|>text<|/ref|><|det|>[[102, 337, 894, 407]]<|/det|> +As discussed above, we wish to make it clear that JNJ- 2901 is a tool compound that we have used to demonstrate how, inhibitors of cytochrome bc1, a novel mode of action, would interact with existing treatments. Our conclusions refer to 'cytochrome bc1 inhibitors' rather than to a specific compound in development. + +<|ref|>sub_title<|/ref|><|det|>[[104, 417, 288, 433]]<|/det|> +## Materials and Methods + +<|ref|>text<|/ref|><|det|>[[102, 434, 835, 469]]<|/det|> +The Materials & Methods section is well- detailed and allows for experimental reproducibility. However, there we have some comments: + +<|ref|>text<|/ref|><|det|>[[102, 469, 890, 520]]<|/det|> +- As in the Results section, avoid referring only to different experiments as Study A, B, etc. Instead, add descriptive headings such as "Intranasal Mice Challenge", "Intravenous Mice Challenge", or "High-Dose Aerosol Challenge." + +<|ref|>text<|/ref|><|det|>[[102, 521, 880, 572]]<|/det|> +- Each experimental model should consistently include the following information: Mouse strain, sex, and age; inoculum preparation, infection route, and dose; treatment duration and euthanasia time points. + +<|ref|>text<|/ref|><|det|>[[102, 581, 895, 668]]<|/det|> +We respectfully disagree with this suggestion. The experimental details for each study are already included in the Methods section, and adding them to the Results and figure legends would lead to unnecessary repetition. We have intentionally used this naming strategy to clearly distinguish studies from different institutions. Furthermore, many of the models have similar experimental parameters, making it difficult to differentiate them by name alone. + +<|ref|>text<|/ref|><|det|>[[104, 678, 661, 695]]<|/det|> +- Authors should provide in the ethical statement the end-point criteria. + +<|ref|>text<|/ref|><|det|>[[104, 705, 714, 722]]<|/det|> +We have now included the humane end points for the in vivo studies (pg 18). + +<|ref|>text<|/ref|><|det|>[[102, 732, 870, 767]]<|/det|> +- Supplementary tables and results should not be included in the Methods section but should be properly cited in the Results section. + +<|ref|>text<|/ref|><|det|>[[102, 777, 892, 811]]<|/det|> +Where possible, we have discussed supplementary tables and results in the Results section, however we disagree that these elements cannot be cited in the methods. + +<|ref|>text<|/ref|><|det|>[[102, 821, 890, 891]]<|/det|> +- There are several experimental methods referenced in the supplementary material but not appearing in the main text (e.g PK and tolerability in mouse, ADME assays, HepG2 cytotoxicity assay, mitochondrial toxicity assay Glu/Gal, Ames II Mutagenicity assay, mutant isolation and WGS). These should be briefly mentioned in the main text, such as: "Both JNJ-2901 and JNJ-4052 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 80, 890, 115]]<|/det|> +were evaluated for ADME and toxicity. All parameters supported further use of these compounds in subsequent experiments (Supplementary Table S2)". + +<|ref|>text<|/ref|><|det|>[[104, 125, 661, 142]]<|/det|> +We have now included this information in the Results section (pg 5- 6). + +<|ref|>text<|/ref|><|det|>[[104, 153, 666, 187]]<|/det|> +Additionally, we suggest to address the following minor comments: - L62: we would suggest classifying tuberculosis as a global pandemic. + +<|ref|>text<|/ref|><|det|>[[105, 197, 395, 214]]<|/det|> +We have updated this as suggested. + +<|ref|>text<|/ref|><|det|>[[105, 225, 412, 241]]<|/det|> +- L79: MoA abbreviation is not needed. + +<|ref|>text<|/ref|><|det|>[[105, 252, 445, 268]]<|/det|> +'MoA' is used elsewhere in the manuscript. + +<|ref|>text<|/ref|><|det|>[[104, 279, 881, 348]]<|/det|> +- L87: the word "validated" to describe the inhibitor compound JNJ-2901 is confusing as the presented manuscript seems to be the validation of the compound as an effective treatment adjuvant. If this is not the case, please provide the reference where the compound is validated for its inhibition of the cytochrome bc1. + +<|ref|>text<|/ref|><|det|>[[102, 358, 891, 392]]<|/det|> +We have kept 'validated' as we can now present an additional manuscript (PMID:40191462), which outlines this validation. + +<|ref|>text<|/ref|><|det|>[[102, 402, 888, 437]]<|/det|> +- L91-96: we suggest to relocate this in the line 76, as the TB-PRACTECAL trial results are a good justification of linezolid-associated adverse effects when treating MDR-TB. + +<|ref|>text<|/ref|><|det|>[[104, 448, 633, 464]]<|/det|> +We have now moved this section to the Introduction as suggested. + +<|ref|>text<|/ref|><|det|>[[104, 475, 567, 491]]<|/det|> +- L116-122: please contextualize the results from this part. + +<|ref|>text<|/ref|><|det|>[[104, 502, 461, 518]]<|/det|> +We have expanded the results as requested. + +<|ref|>text<|/ref|><|det|>[[104, 529, 692, 546]]<|/det|> +- L127: move the figure citation to line 133. After the results are explained. + +<|ref|>text<|/ref|><|det|>[[105, 557, 390, 572]]<|/det|> +This has been moved as requested. + +<|ref|>text<|/ref|><|det|>[[104, 583, 884, 617]]<|/det|> +- L146: please provide the justification of why using Telacebec in this study and not JNJ-2901 and provide rationale about the drug regimen used for this experimental design. + +<|ref|>text<|/ref|><|det|>[[104, 628, 894, 749]]<|/det|> +This study was inspired by previous in vitro work demonstrating that the combination of bedaquiline, clofazimine, and telacebec resulted in rapid killing (PMID:27506290). We aimed to evaluate the in vivo efficacy of treatment regimens containing these compounds in combination with pyrazinamide, which has also been shown to enhance efficacy, potentially supporting treatment shortening (PMID:25622149). To allow comparison with previous work, we continued to use telacebec in this study rather than JNJ-2901. We have now clarified this justification in the results (pg 7) and discussion (pg 9). + +<|ref|>text<|/ref|><|det|>[[104, 759, 879, 826]]<|/det|> +- L164: as far as we understood, JNJ-2901 and Telacebec were also assessed for its bactericidal activity against clinical isolates in comparison to the H37Rv strain (Figure 2 B,C,D and E). Please provide a proper description of the compound used for this experiment and further discussion of this results in the main text. + +<|ref|>text<|/ref|><|det|>[[104, 837, 894, 906]]<|/det|> +At the time that this experiment was initiated, JNJ- 4052 was our lead molecule from our cytochrome bc1 drug discovery programme. This was the main reason it was chosen for the in vivo study outlined in Figure 3e. This compound provides a proof-of-principle for inhibition of cytochrome bc1, with other compounds with this MoA expected to have the same response as suggested by Figure 3b-d. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 80, 870, 115]]<|/det|> +- Figure 1: If the mice strain and experimental design are the same, consider re-structure Figure 1B and 1C in a unique figure. + +<|ref|>text<|/ref|><|det|>[[102, 124, 875, 160]]<|/det|> +We would prefer to keep these studies separate, enabling the reader to discriminate between the individual experiments. + +<|ref|>text<|/ref|><|det|>[[102, 169, 893, 239]]<|/det|> +- Figure 2: Please, consider a figure rearrangement. We suggest dividing Figure 2 in two. Section A on one side (resulting in Figure 2) and sections B, C, D, E and F on the other (resulting in Figure 3 A, B, C, D and E). Since the results represented refer to different experimental questions and require a results section for each one. + +<|ref|>text<|/ref|><|det|>[[104, 248, 696, 266]]<|/det|> +We agree, and have now split Figure 2 into two new figures as suggested. + +<|ref|>sub_title<|/ref|><|det|>[[104, 276, 292, 292]]<|/det|> +## Final Recommendation + +<|ref|>text<|/ref|><|det|>[[104, 293, 883, 380]]<|/det|> +This study presents valuable preclinical data on cytochrome bc1 inhibitors in TB treatment. However, we have significant concerns regarding the manuscript as it currently stands. It lacks a proper structure, clarity, and experimental justification, and the discussion is entirely insufficient. The manuscript needs to be totally rewritten to address these issues, ensuring that it achieves the required readability, scientific rigor, and overall impact to be considered suitable for publication. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[120, 85, 424, 100]]<|/det|> +## Response to reviewer's comments + +<|ref|>text<|/ref|><|det|>[[118, 112, 844, 146]]<|/det|> +We have addressed the final reviewer's comment in red below. We once again thank the reviewer's for their valuable comments. + +<|ref|>text<|/ref|><|det|>[[120, 159, 430, 175]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 193, 870, 279]]<|/det|> +The revised manuscript of Clara Aguilar Pérez and colleagues has addressed all of my previous concerns and I am happy to see some of the recommendation on the revised discussion section as well as extended new data. The study represents an important progress on inhibition of respiration machinery in Mtb and has potential for the development of future therapeutics. + +<|ref|>text<|/ref|><|det|>[[119, 314, 430, 330]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 348, 866, 469]]<|/det|> +We would like to thank the authors for thoughtfully addressing our major suggestions regarding the manuscript. Our feedback primarily focused on improving its structure, clarity, and the discussion surrounding the experimental procedures and results. In particular, the authors have now effectively justified the differences observed when treating laboratory strains with different cytochrome bc1 inhibitors versus clinical strains. With these revisions, the manuscript now clearly highlights the significance of this investigation in advancing our understanding of tuberculosis treatment strategies. + +<|ref|>text<|/ref|><|det|>[[117, 487, 861, 625]]<|/det|> +This work underscores the potential of bc1 inhibitors as viable alternatives to fluoroquinolones and linezolid, which are often associated with adverse effects in current regimens for drug- resistant tuberculosis. Moreover, it contributes to the possibility of treatment shortening for drug- sensitive tuberculosis, with added potential against clinical strains. The experiments were performed using different, well- justified preclinical mouse models, which strengthens the translational relevance of the findings and supports further investigation of this promising asset. Based on these improvements and the scientific merit of the study, we believe the manuscript is now better suited for publication. + +<|ref|>text<|/ref|><|det|>[[118, 643, 749, 659]]<|/det|> +However, we would like the authors to address the following remaining issue: + +<|ref|>text<|/ref|><|det|>[[116, 677, 877, 901]]<|/det|> +Please add a paragraph on limitations to the discussion section. For example, the sample size of mice used in the experiments could be acknowledged as a limitation (even though we recognize that this is already mentioned on page 7). Additionally, regarding the authors' response that "no differences between sexes have been reported in relation to drug efficacy in TB mouse models," we would like to stress that, even if ethical requirements do not mandate the inclusion of both biological sexes, doing so is strongly advisable. There is robust evidence from both clinical and preclinical studies that biological sex influences TB epidemiology and treatment outcomes(for example, see: Idris, R., Infection 2025, https://doi.org/10.1007/s15010-024-02424-5; Dutta NK, Front Immunol, 2020, doi: 10.3389/fimmu.2020.01465; Tannenbaum, C., Nature, 2019, https://doi.org/10.1038/s41586-019-1657-6). These differences are driven by a combination of hormonal, genetic, and immunological factors, as well as potential differences in treatment adherence and broader social determinants of health. While we acknowledge that using female mice can be more + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 878, 222]]<|/det|> +practical in terms of logistics and animal management- since males often display more aggressive behavior that can complicate experiments- there is now ample evidence showing that men and women often have different disease trajectories (not only for TB!) and responses to treatment. One persistent issue in drug development is that preclinical and clinical studies frequently fail to reflect the biological diversity found in real- world populations. Including both sexes in preclinical experiments wherever feasible would help improve the generalizability of the findings and ensure that results more accurately inform treatment strategies for all patients. + +<|ref|>text<|/ref|><|det|>[[118, 234, 880, 354]]<|/det|> +We thank the reviewer for their helpful suggestion. We have now added a paragraph to the discussion (pg. 10) outlining the limitations of our study and lessons for future work. Specifically, we address the use of female mice, as suggested, and also note the following points for improvement of future studies: (i) increasing statistical power by using larger animal group sizes, (ii) incorporating monotherapy arms to enable regimen deconvolution, and (iii) including clinical isolates to better reflect the diversity and relevance of circulating M. tuberculosis strains. + +<|ref|>text<|/ref|><|det|>[[119, 383, 880, 435]]<|/det|> +In summary, we encourage the authors to carefully consider any additional limitations of their study and clearly state them, as this will add valuable context and transparency. Once this is done, the manuscript can be endorsed for publication. + +<|ref|>text<|/ref|><|det|>[[120, 465, 430, 481]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 494, 880, 545]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> diff --git a/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/images_list.json b/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..298f96e7840f3ff160972bfd8b37705de2a3c12a --- /dev/null +++ b/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,40 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure L1: Comparison of biological triplicates for the 43 validation variants grown in SD-\\(Ura + 2\\%\\) glucose. Experiments show a strong a correlation between all 3 repeats.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure L2: Fitness analysis for yeast cells expressing the 43-variant validation set grown in YPD. (a) The 43 validation variants were grown in YPD in duplicates and tracked for OD as a function of time (circles). For each variant the growth data are fitted (blue lines) by a classic growth curve (see Supplementary Information). (b) The rates of growth for each variant are plotted as a scatter plot pair for both repeats.", + "footnote": [], + "bbox": [ + [ + 123, + 298, + 861, + 581 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure L3:Cross correlation data for 43-variant validation experiments plotted with error-bars. (a) yeast cross-correlation data. (b-c) The \\(2\\%\\) glucose yeast expression data plotted as a function of CHO (b) and HeLa (c) expression data. Error-bars were computed using standard-error analysis carried out on mean flow cytometry fluorescence measurements obtained from three or four biological repeats – depending on data set.", + "footnote": [], + "bbox": [ + [ + 123, + 383, + 863, + 607 + ] + ], + "page_idx": 7 + } +] \ No newline at end of file diff --git a/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8e36124360df1c804e553132a969709657927db6 --- /dev/null +++ b/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,460 @@ + +# nature portfolio + +Peer Review File + +A universal system for boosting gene expression in Eukaryotic cell- lines + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +In this study, the authors introduce an algorithm designed to predict regulatory sequences that modulate gene expression in eukaryotic cells. To achieve this, they identified 41 Transcription Factor Binding Sites (TFBS) from various organisms, including S. cerevisiae, S. pombe, D. melanogaster S2 cells, and murine ES cells. These TFBS (or motifs) were used to construct a library of nearly 190,000 variants, each containing up to three different motifs and their variants. Using a combination of machine learning and oligo library analysis in yeast, the authors aimed to identify specific motifs capable of enhancing or attenuating gene expression. These motifs were then assessed in two mammalian cell lines. + +Overall, the study addresses a topic of general interest: fine tunability of gene expression for optimal output production. However, the manuscript suffers from issues related to clarity, methodology transparency, and validation, ultimately raising concerns about the rigour and robustness of the study. Detailed comments and suggestions are provided below. + +1. The TFBS used in this study are for endogenous TFs, and some correlate with both activation and repression activity. This may depend on different cell types, cell states and growth conditions, potentially generating high variability in the promoter's behavior. The authors should validate the identified sequences with a significant number of biological replicates (at least 3), at different cell passages and possibly different culturing conditions (e.g. different cell densities, different media composition, etc). + +2. The authors should ensure that the cells carrying a specific barcode indeed harbour the intended promoter variant, especially considering the complexity of the designed library. Thus, one significant gap in the methodology is the absence of verification steps after sorting, ideally conducted after the final PCR step just before Next-Generation Sequencing (NGS). This validation step could take various forms, even only Sanger sequencing of a select subset of variants (not only 1!). This additional verification would provide confidence in the accuracy of the cell content and the presence of the intended promoter variants. + +3. Figure 2c should ideally show a relatively tight cluster of data points resembling a straight line with some expected noise and a few outliers, reflecting the inherent variability in biological systems and NGS data. However, the observed data points in this plot appear scattered, indicating a significant divergence from expected behavior. To mitigate this concern and validate the Sort-Seq values, it is advisable to conduct an extensive validation experiment. This experiment could involve the measurement of fluorescence or RNA-seq for individual variants, followed by a correlation analysis with the NGS-based fluorescence (FL mean) values. If this validation does not yield a strong correlation, it could raise doubts about the reliability of the entire experimental approach and data interpretation. Therefore, addressing these issues through thorough verification and validation steps is crucial to enhance the study's credibility and confidence in the results. + +4. Increased gene expression, can correlate with reduced host organism fitness (DOI: https://doi.org/10.1038/nmeth.3339) and unwanted competition for intracellular resources (DOI: https://doi.org/10.1038/s41467-020-18392-x). If the final goal is to characterize new promoters for bioproduction, the authors should show that they do not impact the fitness of the host cells. + +5. Both introduction and discussion need more supporting citations. Please add evidences to support all claims. Additionally, some claims seem only partially true or imprecise: + +a. Line 47: there are studies that addressed the same problem (e.g. DOI: https://doi.org/10.1128/aem.00939-22). These should be cited and discussed. +b. Lines 81-85: these claims should be either supported by citations or toned down. There are many well characterized constitutive promoters active across eukaryotic species (CMV, EF1a, PGK, etc). The authors should motivate why their design is superior to existing solutions. + +6. Some experimental choices and pipeline steps are unclear: + +a. How were the 41 TFBS selected, especially since many are not common across the 4 eukaryotic cell types evaluated? + +b. Line 128: how was the threshold of \(>73\%\) determined and why? + +c. In the method section, describe how the total of 1600 million NGS reads mentioned is processed and the steps involved. Why only \(25\%\) of NGS reads were selected? What is the potential impact on the results? + +7. Some of the conclusions drawn by the authors in the results section are questionable. Can the + +<--- Page Split ---> + +authors comment on the following points? + +a. In Fig. 2a the authors claim that there is a clear correlation between the median of the mean fluorescence and the motif: this is not clear from this graphic and it could be pure randomness. +b. Line 236: the observed correlation indicates that the distribution is mainly not described by the model. +c. Line 269-271 and Fig. 3d: there is no clear correlation between an increase in mixed letters and increase in model performance. The values of 10, 26, 36, 16, 23, 18% of correlation could be more or less random numbers. +8. The manuscript presentation is unclear in some parts, especially in the results and discussion sections preventing full understanding of the study: +a. The term "mean FL" is a function of the NGS reads. This is confusing as "mean FL" should intuitively be the mean of the measured fluorescence only. +b. Is "mean fluorescence" (Fig. 2a) same as "mean FL" (Fig. 2c and others)? +c. Large parts of the results section suffer from a lack of clarity, for example lines 168-190. Please work on improving the clarity of the entire section. +d. The structure of the discussion is confusing: start with a brief summary of the work, then draw a conclusion and hypothesize the next steps, only to return to the summary in the middle of the second paragraph. Consider restructuring. +9. There are several overstatements in the manuscript that should be toned down. E.g.: +a. Line 106 "pan-organism": the study focuses on one yeast strain and two mammalian cell lines only. +b. Line 112 "different murine tissues": this is inconsistent with the caption of Supplementary Figure 1 where only mouse embryonic stem cells are mentioned. +10. Some scientific basics are lacking: +a. space between number and units +b. organism in italic +c. missing descriptions in the methods (see comment 6c) +d. missing code and data online: will these be provided after publication? +e. the unit of fluorescence is never stated, is it arbitrary units (au)? +f. number of biological replicates should be specified. Especially Figure 6 does not have error bars: was validation run on one biological replicate only? If this is the case, it is scientifically inaccurate to draw any conclusion. + +Minor comments: + +1. Line 49: "whose promoter is capable of transcribing" is wrong. A promoter does not transcribe, the polymerase does. +2. Line 102: "reliable prediction" +3. Line 106: "constitutive" instead of non-inducible +4. Line 156: "Fig. 1f" +5. Line 802: what is a PPM? +6. Line 140: Fig. 1c? +7. Line 185: which type of correlation is it? +8. Line 422: "for a weak and a strong promoter", only one variant tested for each +9. Line 430: "circuits" (Remove "bio-") +10. Line 869: "of" "s"? +11. Lines 780-781: lasers wavelength? +12. Discussion: The name UNILIB is introduced only at this point, why? +13. Figures: +a. Increase the font size in all figures, as they appear too small for easy readability +b. 1f: the vertical line should be at 40, it is at 30 though +c. 2d: no error bars +d. 3e: labels can be put under x axis instead of colors +e. 3d: if a linear correlation (Pearson) is assumed, add the line to the plot +f. 4a: error bars are at null level? +g. 4b (and following): no tick marks in the right plots +h. 5f: error bars +i. 6: add axis label, what type of data is shown? + +<--- Page Split ---> + +Reviewer #2: + +Remarks to the Author: + +In this manuscript from Vaknin et al, the authors develop a library of synthetic promoters by merging a target core promoter and upstream TF binding sites, to enhance protein expression in eukaryotic cells. This is not the first time synthetic promoters are designed by this approach and previous work has shown that is possible to engineer mammalian cells based on mining of TFBS and core promoter engineering (e.g. Johari et al. 2019 and others). + +The manuscript tries to go beyond the state of art by building a system functional in more than one chassis. + +I have a few questions, mainly on the experimental side, as I am not a computational person. It is not fully clear to me what the authors mean with the term "motif" and it could be useful to define this. + +It is not fully clear also how the 41 motifs were identified and if this was validated by using more than one TF data base. + +In figure 1e it is not fully clear why authors have not taken population 2 and re- bin it in order to capture more variants and potentially more interesting candidates with higher expression. It could have been beneficial to do so here. + +In figure 6, for CHO cell experiments, the authors mentioned they used a BFP for fluorescence normalisation. However, it is known from literature that resource competition can impact normalisation (see Frei et al, 2020. Jones et al, 2020). + +Can the authors shown the expression levels of the CHO library but with no normalisation and check if that improves the results? Caption of figure 6 should also more clearly describe what the figures shows. + +Minor comments pertain to several typos present in the manuscript like Eukaryotic that should be lower case; + +Figures are called at time with capital letter and at times with lower case. + +In conclusion I suggest the work to be published once these questions have been addressed. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +In this study, the authors introduce an algorithm designed to predict regulatory sequences that modulate gene expression in eukaryotic cells. To achieve this, they identified 41 Transcription Factor Binding Sites (TFBS) from various organisms, including S. cerevisiae, S. pombe, D. melanogaster S2 cells, and murine ES cells. These TFBS (or motifs) were used to construct a library of nearly 190,000 variants, each containing up to three different motifs and their variants. Using a combination of machine learning and oligo library analysis in yeast, the authors aimed to identify specific motifs capable of enhancing or attenuating gene expression. These motifs were then assessed in two mammalian cell lines. Overall, the study addresses a topic of general interest: fine tunability of gene expression for optimal output production. However, the manuscript suffers from issues related to clarity, methodology transparency, and validation, ultimately raising concerns about the rigour and robustness of the study. Detailed comments and suggestions are provided below. + +1. The TFBS used in this study are for endogenous TFs, and some correlate with both activation and repression activity. This may depend on different cell types, cell states and growth conditions, potentially generating high variability in the promoter's behavior. The authors should validate the identified sequences with a significant number of biological replicates (at least 3), at different cell passages and possibly different culturing conditions (e.g. different cell densities, different media composition, etc). + +We thank the reviewer for this comment, and the opportunity to improve our work. First, we would like to note that only 27 of the 41 motifs were validated transcription-factor binding sites. The rest of the motifs were unknown, and not attributed to a particular regulatory process. The motifs were found to be conserved across various Eukaryotic lineages in a HT-SELEX assay carried out by Jussi Taipale's group (published in DOI: 10.1038/nbt.4138). As a result of the UNILIB experiment, we were able to characterize 5 of the unknown motifs as either up- or down-regulating. Some of these motifs are weak and require multiple sites or combinations of sites to show a measurable regulatory effect. + +Second, with regards to the function of the motifs in different cell- growth conditions or cell types, there indeed could be a variation. Consequently, we created 43 unseen synthetic URS variants. We used 32 variants, which sampled 23 of the motifs for which a significant up or down- regulatory behavior was identified, for the results depicted in Fig. 5, and an additional 11 variants were used for the validation of the machine- learning model in Fig. 3. Altogether the 43 validation variants sample 31 of the 42 motifs including all the motifs that were found to be significant. + +However, given the reviewer's critical comment, we decided to use these variants to expand our validation set to further strengthen our conclusions. The revised manuscript now includes two new figures: Fig. 6 and Fig. 7, which replace the original Fig. 6. New Fig. 6 details the results of 7 separate experimental measurements carried out in biological triplicates as follows: + +1. Yeast: SD-Ura+2% glucose, \(30^{\circ}\mathrm{C}\) , weak core promoter (mCore), no additives, 43 variants. +2. Yeast: SD-Ura+2% glycerol, \(30^{\circ}\mathrm{C}\) , weak core promoter (mCore), no additives, 43 variants. +3. Yeast: SD-Ura+2% glucose, \(39^{\circ}\mathrm{C}\) , weak core promoter (mCore), no additives, 43 variants. +4. Yeast: SD-Ura+2% glucose, \(30^{\circ}\mathrm{C}\) , weak core promoter (mCore), 1M NaCl, 43 variants. +5. Yeast: SD-Ura+2% glucose, \(30^{\circ}\mathrm{C}\) , strong core promoter (FEC-mCore), no additives, 20 variants. +6. CHO/K1 cells grown in F12 medium, 32 variants. +7. HeLa cells grown in DMEM high glucose medium, 32 variants. + +The results for all the yeast experiments, whether as biological replicates or in different culturing conditions, correlate strongly with one another in a statistically significant fashion (see below Figs. L1 in addition to Fig. 6 and Supplemental Fig. 6 in the revised manuscript). These results support a conserved function in yeast independent of growth conditions. This is consistent with the previous findings of (Keren et al., Mol. + +<--- Page Split ---> + +Sys. Biol., 9:701 (2013)) who tested the activities of \(\sim 900\) S. cerevisiae promoters in 10 different conditions and found no significant difference in activities across the panel of growth conditions used. In addition, the experimental data also shows a statistically significant correlation between the mammalian cell measurements and the yeast measurements, which we showed also in the original manuscript. Finally, we also improved our modelling scheme by extending the machine- learning model developed in Fig. 3 using the additive model described in Fig. 5 to create a hybrid model, which improved performance on all datasets. The new hybrid model now predicts HeLa and CHO cells regulatory activity in a statistically significant fashion (see new Fig. 7). + +The revised validation segment of our manuscript now allows us to make an improved argument that the synthetic URS sequences that we created can generate a regulatory function that is, for the most- part, independent of cell- type and growth conditions, making these sequences a potentially widely applicable tool. + +![](images/Figure_unknown_1.jpg) + +
Figure L1: Comparison of biological triplicates for the 43 validation variants grown in SD-\(Ura + 2\%\) glucose. Experiments show a strong a correlation between all 3 repeats.
+ +2. The authors should ensure that the cells carrying a specific barcode indeed harbour the intended promoter variant, especially considering the complexity of the designed library. Thus, one significant gap in the methodology is the absence of verification steps after sorting, ideally conducted after the final PCR step just before Next-Generation Sequencing (NGS). This validation step could take various forms, even only Sanger sequencing of a select subset of variants (not only 1!). This additional verification would provide confidence in the accuracy of the cell content and the presence of the intended promoter variants. + +In brief, due to their short length (bc+sURS+core- promoter) our variants were fully sequenced in the NGS. While we apologize for not including this data in the manuscript, as part of our validation, we screened for all full- length reads in the library (i.e. reads that yielded a full length of over 200 bp that include the barcodes, sURS, and primer regions). We found approx. 400M such reads, and they all perfectly matched the barcodes, motifs, and primer regions. We then quantified the correctness of the downstream sequence to the barcode with the intended design and found that per position \(>99\%\) match the design. In addition, we designed the barcodes, such that the Hamming distance between each two is at least 3, which maximized our ability to identify variants. We thank the reviewer for this important comment. In response to the comment, we have added a comment under the Methods sub- section "NGS data processing and read normalization" to clarify this issue. + +3. Figure 2c should ideally show a relatively tight cluster of data points resembling a straight line with some expected noise and a few outliers, reflecting the inherent variability in biological systems and NGS data. + +<--- Page Split ---> + +However, the observed data points in this plot appear scattered, indicating a significant divergence from expected behavior. To mitigate this concern and validate the Sort- Seq values, it is advisable to conduct an extensive validation experiment. This experiment could involve the measurement of fluorescence or RNA- seq for individual variants, followed by a correlation analysis with the NGS- based fluorescence (FL mean) values. If this validation does not yield a strong correlation, it could raise doubts about the reliability of the entire experimental approach and data interpretation. Therefore, addressing these issues through thorough verification and validation steps is crucial to enhance the study's credibility and confidence in the results. + +We are aware of the lack of correlation observed in our OL measurements, which we view as a feature of the methodology rather than an artefact. The data used to compose panel 2c consisted of OL variants that were encoded with two barcodes. The lack of correlation observed for most variant pairs was due to three main reasons: + +1. In SORT-seq experiments, it is impossible to tell how many reads came from a single sorted cell. For example, one cell can yield several hundred reads or a single read in the final count. This can lead to a lack of correlation if the number of cells sorted per a particular variant is small as in this case. We remind the reviewer that our library was unprecedented in size ( \(\sim 200\mathrm{K}\) mixed-base variants), and thus the number of cells collected for each variant was small. +2. In SORT-seq experiments, it is impossible to tell whether cells die after sorting or divide. In such a case, a single cell may also yield more read events in comparison to another cell, though the original sort had them at an equal weight. +3. Variants which do not encode a particular regulatory function are more susceptible to transcriptional variation. The strongly up- and down-regulating variants (top and bottom corners of the plot respectively) are strongly correlated as expected from a fully functional regulatory element. + +The analysis shown in Figure 2 and referred to by the reviewer was, therefore, used as impetus for the quantitative analysis that was done on the 2,435- variant subset that were encoded with 22 barcodes. We reasoned that the sources for the lack of correlation discussed in the points above will be minimized by analyzing multiple barcodes on the same variants. For example, identifying all 22 barcodes immediately implies that at the very least we screened 22 separate fluorescent yeast cells. Consequently, we reasoned that such a subset will lead to a more robust statistical analysis, even though a given pair of barcodes may not be as correlated as we would like. + +The analysis carried out in Figure 3 shows that the choice of unifying the 22 barcodes is statistically robust as evident by the agreement with the de Boer machine- learning model that was trained using independent experimental data. In addition, the validation set of Figures 5- 7 and the agreement with the models that were derived from the experimental data obtained from the 2,435- variant subset essentially shows that both the SORT- seq experiment and the analysis were robust. Consequently, we believe that we have provided sufficient proof in the manuscript both computationally and experimentally that our analysis and experimental approach were robust, and no additional validation is necessary. + +4. Increased gene expression, can correlate with reduced host organism fitness (DOI: https://doi.org/10.1038/nmeth.3339) and unwanted competition for intracellular resources (DOI: https://doi.org/10.1038/s41467-020-18392-x). If the final goal is to characterize new promoters for bioproduction, the authors should show that they do not impact the fitness of the host cells. + +We thank the reviewer for this comment. In response to the comment, we carried out fitness analysis on the 32 validation variants. The results are shown in Figure L2 and have been added to the Supplementary Information as Supplementary Fig. 6. In our experiments, we did not detect any effect on fitness as a result of our synthetic upstream regulatory sequences and mentioned that in the "Boosted expression level translates from yeast and mammalian cells" Results subsection of the revised manuscript. Specifically, we grew the 43 validation variants in YPD and tracked their growth via OD measurement as function of time + +<--- Page Split ---> + +(Fig. L2a - circles). For each strain we then fitted the OD measurements (Fig. L2a - blue line) with the following model for exponential growth: + +\[OD_{600}(t) = C + \frac{L}{(1 + e^{-k(t - t_0)})}\] + +Where \(C\) is background OD levels, \(L\) is the max OD, \(k\) is the growth rate, and \(t_0\) corresponds to the lag time (i.e. time at which the culture reaches OD of L/2). Using this model, we extracted the growth rate for each strain and for both repeats. We plotted in Fig. L2b the different fitted growth rates \((k)\) for both repeats that were measured for each variant. The results show that the growth rates for all experiments was found to be within a narrow range of \(\sim 0.4 - 1.3\) (1/hr) without any significant correlation between duplicates. The lack of correlation between duplicates and narrow range of growth rates provides strong evidence that our variants do not affect the fitness of the yeast cells. + +![](images/Figure_unknown_2.jpg) + +
Figure L2: Fitness analysis for yeast cells expressing the 43-variant validation set grown in YPD. (a) The 43 validation variants were grown in YPD in duplicates and tracked for OD as a function of time (circles). For each variant the growth data are fitted (blue lines) by a classic growth curve (see Supplementary Information). (b) The rates of growth for each variant are plotted as a scatter plot pair for both repeats.
+ +5. Both introduction and discussion need more supporting citations. Please add evidences to support all claims. Additionally, some claims seem only partially true or imprecise: a. Line 47: there are studies that addressed the same problem (e.g. DOI: https://doi.org/10.1128/aem.00939-22). These should be cited and discussed. b. Lines 81-85: these claims should be either supported by citations or toned down. There are many well characterized constitutive promoters active across eukaryotic species (CMV, EF1a, PGK, etc). The authors should motivate why their design is superior to existing solutions. + +We thank the reviewer for providing the additional reference, and for pointing out misstatements in the Introduction. In response to the comment, we added this and other references and rephrased the text in the Introduction and Discussion sections accordingly. Please see the marked up version of the revised manuscript for the details. + +6. Some experimental choices and pipeline steps are unclear: + +<--- Page Split ---> + +a. How were the 41 TFBS selected, especially since many are not common across the 4 eukaryotic cell types evaluated? + +We apologize that these choices were unclear. In brief, the motifs were chosen as part of a past collaboration with Jussi Taipale's group. At the time, the Taipale group had a study (later published in DOI: 10.1038/nbt.4138) that was focused on developing a protein activity assay specifically for DNA- binding TFs in cell and tissue extracts. His team was able to identify strong and enriched TFBS motifs using this assay, including the 41 TFBSs that we selected for our research. Those and other motifs were discovered in numerous organisms, including two types of yeast, different tissues from mice, bacteria, and Drosophila S2 cells. Even though some of the motifs were not found to be common/conserved across these organisms, we nevertheless chose to characterize them due to similarities to well- characterized protein families in higher eukaryotes (e.g. the bHLH motif). For a detailed explanation as to how and why we chose these 41 motifs, please see the new Methods subsection titled "Motif selection and encoding into OL. Based on the study's data, we selected the 41 enriched motifs according to the following criteria: + +1. Different motif types: 8 organism-shared motifs, 5 mice tissue-shared motifs, 14 unshared motifs (unique to an organism), and 14 unknown motifs (with unknown regulatory function). +2. Known/unknown regulatory function: 27 of the selected motifs have known regulatory function, and those were anticipated to be the control motifs. Characterizing the regulatory function of the 14 unknown motifs in yeast was one of the stated goals of the study. + +b. Line 128: how was the threshold of \(>73\%\) determined and why? + +We thank the reviewer for this question and apologize for not including the rationale for our choice in the original manuscript. In response to the comment, we have added a new Methods subsection entitled "Motif selection and encoding into OL", where the rationale is now described. In brief, K and M substitutions were based on the percentage calculation of the respective G/T and A/C occurrences, in each position of the motif according to the PFM data given to us by the Taipale group (later published in DOI: 10.1038/nbt.4138). Positions within the motif, with dominant percentages, were replaced by either K or M in the final design. \(70\%\) threshold was set to determine the K/M substitution, but the actual calculated threshold was higher at \(73\%\) , as specified in the Results section. + +c. In the method section, describe how the total of 1600 million NGS reads mentioned is processed and the steps involved. Why only \(25\%\) of NGS reads were selected? What is the potential impact on the results? + +We thank the reviewer for this question. In response to the comment, we have expanded the Methods subsection titled "NGS data processing and read normalization", specifying the processing steps accordingly. Given the size of the UNILIB library, we opted to use Illumina's NovaSeq for its ability to generate as much as 1B reads per run. We used Illumina's S1 kit, and despite Illumina's reliability claims, indeed only \(25\%\) of the reads were found to be correct in both the NovaSeq runs that were made. Neither we nor the Genomics Center at the Weizmann Institute are certain about the underlying cause for this low fidelity, which may have been due to the choice of primers. Irrespective of that, the center offered to re- sequence the library, ultimately allowing us to extract 400M correct reads. This number of reads proved to be sufficient for the analysis in our study, which was based on the machine- learning modelling. + +As discussed above, our analysis showed that the use of two barcodes per variant was insufficient for proper quantitative analysis, as such a low number introduced a large statistical uncertainty regarding the actual number of sorted cells. On the flip side, the same analysis showed that 22 barcodes per variant significantly reduced this uncertainty. In the former case, increasing the number of reads would not have affected the cell number uncertainty, while in the latter the 22 barcodes ensured that we have a sufficient amount of reads for every one of the variants of the 2,435- variant subset even with only 400M correct reads extracted in total. Consequently, the \(25\%\) extraction rate did not impact our conclusions or results of the downstream analysis. + +<--- Page Split ---> + +7. Some of the conclusions drawn by the authors in the results section are questionable. Can the authors comment on the following points? + +a. In Fig. 2a the authors claim that there is a clear correlation between the median of the mean fluorescence and the motif: this is not clear from this graphic and it could be pure randomness. + +We thank the reviewer for this comment and apologize for not assessing the correlation in the original manuscript. In response to the comment, to assess the correlation between the median of mean fluorescent expression levels and motifs, we conducted a Wilcoxon rank-sum test by comparing the mean fluorescent expression levels of the group of variants containing each motif to the group of variants containing motifs ranked at least 5 motifs away. To correct for multiple tests, we applied the Benjamini-Hochberg procedure with an FDR threshold of 0.1. This new analysis revealed significant differences for 36 out of 42 motifs (p- value<0.05), where the 6 non- significant motifs are in motifs ordered 15- 20 in decreasing order, which is expected since their values are distributed around the center of the mean- fluorescence distribution. We added this new statistical significance analysis to the Results section. + +b. Line 236: the observed correlation indicates that the distribution is mainly not described by the model. + +We thank the reviewer for this comment. In various biological problems, such as inference of protein- DNA binding preferences based on protein- binding- microarray data, correlation values are within 0.4- 0.6 (10.1109/TCBB.2019.2947461). Moreover, the correlation of 0.45 was achieved by the all- data model (ADM), which we showed is inferior to the AMM and MBO models. In addition, this value is calculated on a test set of variants, where most have only 2 barcodes, which implies the lower quality of their mean- fluorescence measurements compared to variants with 22 barcodes. One of the key insights from our study was that variants supported by 22 barcodes, as opposed to 2 barcodes, yielded more accurate mean- fluorescence measurements (due to the inclusion of more cells carrying the variant). When the MBO model was exclusively trained and tested on datasets of variants with 22 barcodes, the obtained Pearson correlation was 0.61. This suggests that using more accurate training and test sets results in a higher observed correlation, which better explains the variability in the data. + +c. Line 269-271 and Fig. 3d: there is no clear correlation between an increase in mixed letters and increase in model performance. The values of 10, 26, 36, 16, 23, 18% of correlation could be more or less random numbers. + +We thank the reviewer for pointing this unclear part of our manuscript. We acknowledge that the reported correlation values may not achieve statistical significance. In response to this comment, we removed Fig. 3d and the corresponding text describing the analyses and results from the Results section. + +8. The manuscript presentation is unclear in some parts, especially in the results and discussion sections preventing full understanding of the study: + +a. The term "mean FL" is a function of the NGS reads. This is confusing as "mean FL" should intuitively be the mean of the measured fluorescence only. + +We thank the reviewer for this comment and have changed all "mean FL" labels for the NGS data to the one used by (Sharon, E. et al. Nat Biotechnol 30, 521-530 (2012)) in a similar oligo library experiment: "Expression (A.U.)". All relevant labels in the figures and text have been changed to Expression (A.U.) in the revised manuscript. + +b. Is "mean fluorescence" (Fig. 2a) same as "mean FL" (Fig. 2c and others)? We thank the reviewer for finding this minor error, and changed to Expression (A.U.). + +<--- Page Split ---> + +c. Large parts of the results section suffer from a lack of clarity, for example lines 168-190. Please work on improving the clarity of the entire section. + +We thank the reviewer for this comment and have clarified the Results, including the subsection titled "Variants manifest a broad range of regulatory behavior". Please see the marked-up version of the revised manuscript for the changes. + +d. The structure of the discussion is confusing: start with a brief summary of the work, then draw a conclusion and hypothesize the next steps, only to return to the summary in the middle of the second paragraph. Consider restructuring. + +We thank the reviewer for this comment. We decided to leave the structure of the Discussion as is with minor modifications. We opted for this option so we can highlight at the beginning of the section the design algorithm that was developed, which we believe is the most important achievement of this work. + +9. There are several overstatements in the manuscript that should be toned down. E.g.: a. Line 106 "pan-organism": the study focuses on one yeast strain and two mammalian cell lines only. + +In response to the comment, we deleted the term pan-organism from the Introduction. + +b. Line 112 "different murine tissues": this is inconsistent with the caption of Supplementary Figure 1 where only mouse embryonic stem cells are mentioned. + +In response to the comment, we corrected the error and replaced the term "different murine tissues" by mouse (ES cells and different tissues). + +10. Some scientific basics are lacking: + +a. space between number and units + +Errors were corrected. + +b. organism in italic + +Errors were corrected. + +c. missing descriptions in the methods (see comment 6c) + +All missing methods were added. Please see responses above. + +d. missing code and data online: will these be provided after publication? + +All data and code were uploaded. Please see data and code availability statements in the revised manuscript. + +e. the unit of fluorescence is never stated, is it arbitrary units (au)? + +The mean FL was replaced by the consensus Expression (A.U.) for all mean level expression level measurements. + +f. number of biological replicates should be specified. Especially Figure 6 does not have error bars: was validation run on one biological replicate only? If this is the case, it is scientifically inaccurate to draw any conclusion. + +We thank the reviewer for this comment and would like to clarify our choice of plotting. All validation experiments were conducted in (at least) biological triplicates as discussed above (see Fig. L1 for example). In response to Comment 1, we have substantially increased the volume of the validation experiments, and consequently split the original Fig. 6 in the original manuscript to a new Fig. 6 depicting only experimental data, and a new Figure 7 depicting the modelling analysis. Given the quantity of data, we opted to omit the error-bars from some of the plots for aesthetic reasons (see for example Fig. L3 which depicts Fig. 6a-c + +<--- Page Split ---> + +with error bars). Since we recognize the need to visually and numerically report the variance in the validation measurements, we have done the following: + +- The variation for the various validation datasets across the repeats can be assessed using new Supplementary Figure 6, and via the correlation heatmap plots of new Fig. 6 (panels d and e). Note, that the autocorrelation between the various repeats of the yeast experiments does not yield a higher Pearson correlation coefficient, as compared with the cross-correlation of the mean fluorescent expression levels of the various conditions. This result provides statistically significant experimental evidence that the different yeast growth conditions do not alter the expression of our variants, and in our opinion is depicted more convincingly via the mode of plotting that we chose to use in the revised manuscript.- We plotted Fig.6a with error bars to convey directly the variance in the cross-correlation analysis. This panel is identical to the one shown in Fig. L3a.- Fig. 6b-c are depicted without error-bars. Here, the purpose is to highlight the fact that out of the dataset 24 variants behaved similarly to yeast (blue), while 8 were uncorrelated in CHO (red). We have added the panel b and c to supplementary fig.6 as panel g and h.- We plotted the error-bars for the both the yeast-glucose \(2\%\) and HeLa-blue variants in panel b and c of Fig. 7. + +![PLACEHOLDER_11_0] + +
Figure L3:Cross correlation data for 43-variant validation experiments plotted with error-bars. (a) yeast cross-correlation data. (b-c) The \(2\%\) glucose yeast expression data plotted as a function of CHO (b) and HeLa (c) expression data. Error-bars were computed using standard-error analysis carried out on mean flow cytometry fluorescence measurements obtained from three or four biological repeats – depending on data set.
+ +Minor comments: + +1. Line 49: "whose promoter is capable of transcribing" is wrong. A promoter does not transcribe, the polymerase does. + +We changed the statement to "whose promoter is capable of initiating transcription" + +2. Line 102: "reliable prediction" + +We removed the word prediction. + +3. Line 106: "constitutive" instead of non-inducible + +We retrained the word non-inducible. + +4. Line 156: "Fig. 1f" + +<--- Page Split ---> + +We corrected the typo. + +5. Line 802: what is a PPM? + +We corrected PPM to PWM - position weighted matrix. + +6. Line 140: Fig. 1c? + +We corrected the typo. + +7. Line 185: which type of correlation is it? + +We added the word "Pearson". + +8. Line 422: "for a weak and a strong promoter", only one variant tested for each + +We changed the phrase in accordance with the reviewer's suggestion. + +9. Line 430: "circuits" (Remove "bio- ") + +We removed the word bio. + +10. Line 869: "of""s"?! + +We corrected the typo. + +11. Lines 780-781: lasers wavelength? + +We added MacsQuant laser wavelength. + +12. Discussion: The name UNILIB is introduced only at this point, why? + +We chose to name the completed design algorithm UNILIB, and name it only after we demonstrated that it worked via the validation experiments. + +13. Figures: + +a. Increase the font size in all figures, as they appear too small for easy readability + +We corrected where possible. + +b. 1f: the vertical line should be at 40, it is at 30 though + +We corrected this error. + +c. 2d: no error bars + +There are no error bars for the medians of the mean fluorescent expression level distributions. + +d. 3e: labels can be put under x axis instead of colors + +We improved the figure accordingly. + +e. 3d: if a linear correlation (Pearson) is assumed, add the line to the plot + +We removed old Fig. 3d. + +f. 4a: error bars are at null level? + +There are no error bars for the large colored bars as they represent the p- value estimate from comparing two distributions as shown in the inset. + +g. 4b (and following): no tick marks in the right plots + +We corrected this error. + +h. 5f: error bars + +We opted to present the actual measurements as circles instead of error bars to convey the distribution of the measured data. + +i. 6: add axis label, what type of data is shown? + +Old Fig. 6 was replaced by new Fig. 6 and Fig. 7. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +In this manuscript from Vaknin et al, the authors develop a library of synthetic promoters by merging a target core promoter and upstream TF binding sites, to enhance protein expression in eukaryotic cells. This is not the first time synthetic promoters are designed by this approach and previous work has shown that is possible to engineer mammalian cells based on mining of TFBS and core promoter engineering (e.g. Johari et al. 2019 and others). + +The manuscript tries to go beyond the state of art by building a system functional in more than one chassis. I have a few questions, mainly on the experimental side, as I am not a computational person. It is not fully clear to me what the authors mean with the term "motif" and it could be useful to define this. + +We thank the reviewer for this very important comment and apologize for not specifying our rationale for choosing the motifs. In response to the comment, we have added a Methods subsection titled "Motif selection and encoding into OL", where our motif selection process and definition are described. In brief, motifs were based on short conserved sequence segments obtained by Jussi Taipale's group, and provided to us prior to their publication as position weight matrices (DOI: 10.1038/nbt.4138). The Taipale motifs were created by an empirical assay that was designed to test protein activity in a broad swath of organisms. + +It is not fully clear also how the 41 motifs were identified and if this was validated by using more than one TF data base. + +In brief, the Taipale study focused on developing a protein activity assay specifically for DNA- binding TFs in cell and tissue extracts. Based on the study's data, we selected 41 enriched motifs from various organisms and tissue cells (e.g., yeast, fly, and mice tissue cells), according to the following criteria: + +3. Different motif types: 8 organism-shared motifs, 5 mice tissue-shared motifs, 14 unshared motifs (unique to an organism), and 14 unknown motifs (with unknown regulatory function). +4. Known/unknown regulatory function: 27 of the selected motifs have known regulatory function, and those were anticipated to be the control motifs. Characterizing the regulatory function of the 14 unknown motifs in yeast was one of the stated goals of the study. + +With regards to validation by an additional database, this was not done for two major reasons. First, we chose the motifs based on the Taipale group experimental findings to show that our approach can be used as a validation exercise to similar experimental findings. Second, 14 of the motifs were uncharacterized and thus would not appear in any database. In fact, our assay enabled us to characterize the regulatory function of 5 of the 14 unknown motifs, and thus validated our approach. + +In figure 1e it is not fully clear why authors have not taken population 2 and re- bin it in order to capture more variants and potentially more interesting candidates with higher expression. It could have been beneficial to do so here. + +We fully agree with the reviewer's sentiment. Unfortunately, in this case, hindsight is 20/20. At the time of the actual SORT- seq experiment, we chose not to re- bin as we were worried about how the increased sorting time may affect the re- binned yeast cells. In addition, in preliminary tests we did not expect to find many variants in this upper bin, and as a result we opted not to risk adding expression noise to the re- binned variants at the expanse of losing expression resolution. Since we were able to identify several strong up- regulating motifs, and train a machine- learning model which provided robust predictions for the unseen validation set, we are confident that whatever information was lost in our decision to not re- bin would not have affected our results or conclusions profoundly. + +In figure 6, for CHO cell experiments, the authors mentioned they used a BFP for fluorescence normalisation. However, it is known from literature that resource competition can impact normalisation (see Frei et al, 2020. Jones et al, 2020). + +<--- Page Split ---> + +We thank the reviewer for this comment and would like to clarify. The use of BFP in the CHO and HeLa cell experiments was done to ensure that cells that were identified as “red” (i.e. mCherry expressing) were indeed transfected by a plasmid and not false positives. In addition, for each variant we compared the mean mCherry expression levels measured to the ratio of the mCherry and BFP channels. The results (see the revised Supplementary Figure 6e) show that BFP does not impact the results or their interpretation. + +Can the authors shown the expression levels of the CHO library but with no normalisation and check if that improves the results? + +We thank the reviewer for this comment. In the revised manuscript, all mammalian data (see new Figs. 6 and 7) is presented without normalization by BFP. + +Caption of figure 6 should also more clearly describe what the figures shows. + +We thank the reviewer for this comment. The captions for revised Fig. 6 and 7 provide additional details about the data presented as compared with the captions in the original manuscript. + +Minor comments pertain to several typos present in the manuscript like Eukaryotic that should be lower case; Figures are called at time with capital letter and at times with lower case. + +We corrected the typos. + +In conclusion I suggest the work to be published once these questions have been addressed. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The authors addressed all major and minor comments listed in the first round of reviews. The manuscript is greatly improved – I would recommend publication. + +Reviewer #2: + +Remarks to the Author: + +First of all, I would like to thank the authors for addressing my comments and questions. I am generally satisfied with their revision but I would need to ask clarification on two points. Supplementary figure 6. The authors state that they are confirming that the expression of BFP does not impact mCherry expression. However, it is not very clear from the figure caption and response in the rebuttal, nor from the methods section, if they actually performed the experiments in presence and absence of competition or if they simply compared the mCherry signal alone with mCherry normalised on BFP but from the same experiment peformed in presence of competition. Can the authors clarify? + +I would like also to ask the authors if they can comment on the large error bars present for HeLa cell expression experiments. + +<--- Page Split ---> + +## Reviewer #2 + +First of all, I would like to thank the authors for addressing my comments and questions. I am generally satisfied with their revision but I would need to ask clarification on two points. + +Reviewer comment: Supplementary figure 6. The authors state that they are confirming that the expression of BFP does not impact mCherry expression. However, it is not very clear from the figure caption and response in the rebuttal, nor from the methods section, if they actually performed the experiments in presence and absence of competition or if they simply compared the mCherry signal alone with mCherry normalised on BFP but from the same experiment performed in presence of competition. Can the authors clarify? + +Author response: We thank the reviewer for the opportunity to clarify. We did not create a separate set of clones lacking the BFP gene. The plot presented in Supplementary Fig. 5e (note the renumbering of the supplementary figures) depicts the mCherry channel compared with the mCherry normalized by the BFP channel as measured on the same cells. The purpose of this plot is to show that normalizing by a synthetic house- keeping gene did not affect the trends observed in the data. We remind the reviewer that the utilization of this house- keeping gene was for us to ensure that sorted cells were transfected by the sURS plasmid. In our opinion an experiment lacking this form of "house- keeping" may not be as reliable, since "false- positive" cells may enter the analysis particularly for weakly expressing strains. We have added a statement regarding this experimental strategy to the Figure caption of supplementary figure 6 to alleviate any further confusion. + +Reviewer comment: I would like also to ask the authors if they can comment on the large error bars present for HeLa cell expression experiments. + +Author response: The error bar observed for the HeLa cells (i.e. Supplementary Fig. 5h) reflect the actual natural deviation in the expression data observed over the triplicates. The unusual variation may be due to the fact that the intensity of expression was not as strong as compared with the expression measured for the CHO cells, which may have led to increased noise. Fortunately, this expression level was sufficiently strong to differentiate between the different boosts enabled by the sURS variants, which correlated well with both the CHO cell measurements and the revised model. + +<--- Page Split ---> diff --git a/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c689143524a2bd07b361b8a02800eb4ec02cfdf1 --- /dev/null +++ b/peer_reviews/12bee38be00ca6148fc0c8a69c26bf2450d3af9d3ae7dfb34f177755640c2e32/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,623 @@ +<|ref|>title<|/ref|><|det|>[[61, 41, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 111, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 918, 211]]<|/det|> +A universal system for boosting gene expression in Eukaryotic cell- lines + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 783]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 293, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 223, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 140, 864, 255]]<|/det|> +In this study, the authors introduce an algorithm designed to predict regulatory sequences that modulate gene expression in eukaryotic cells. To achieve this, they identified 41 Transcription Factor Binding Sites (TFBS) from various organisms, including S. cerevisiae, S. pombe, D. melanogaster S2 cells, and murine ES cells. These TFBS (or motifs) were used to construct a library of nearly 190,000 variants, each containing up to three different motifs and their variants. Using a combination of machine learning and oligo library analysis in yeast, the authors aimed to identify specific motifs capable of enhancing or attenuating gene expression. These motifs were then assessed in two mammalian cell lines. + +<|ref|>text<|/ref|><|det|>[[119, 254, 833, 308]]<|/det|> +Overall, the study addresses a topic of general interest: fine tunability of gene expression for optimal output production. However, the manuscript suffers from issues related to clarity, methodology transparency, and validation, ultimately raising concerns about the rigour and robustness of the study. Detailed comments and suggestions are provided below. + +<|ref|>text<|/ref|><|det|>[[118, 321, 876, 405]]<|/det|> +1. The TFBS used in this study are for endogenous TFs, and some correlate with both activation and repression activity. This may depend on different cell types, cell states and growth conditions, potentially generating high variability in the promoter's behavior. The authors should validate the identified sequences with a significant number of biological replicates (at least 3), at different cell passages and possibly different culturing conditions (e.g. different cell densities, different media composition, etc). + +<|ref|>text<|/ref|><|det|>[[118, 405, 880, 504]]<|/det|> +2. The authors should ensure that the cells carrying a specific barcode indeed harbour the intended promoter variant, especially considering the complexity of the designed library. Thus, one significant gap in the methodology is the absence of verification steps after sorting, ideally conducted after the final PCR step just before Next-Generation Sequencing (NGS). This validation step could take various forms, even only Sanger sequencing of a select subset of variants (not only 1!). This additional verification would provide confidence in the accuracy of the cell content and the presence of the intended promoter variants. + +<|ref|>text<|/ref|><|det|>[[118, 504, 880, 644]]<|/det|> +3. Figure 2c should ideally show a relatively tight cluster of data points resembling a straight line with some expected noise and a few outliers, reflecting the inherent variability in biological systems and NGS data. However, the observed data points in this plot appear scattered, indicating a significant divergence from expected behavior. To mitigate this concern and validate the Sort-Seq values, it is advisable to conduct an extensive validation experiment. This experiment could involve the measurement of fluorescence or RNA-seq for individual variants, followed by a correlation analysis with the NGS-based fluorescence (FL mean) values. If this validation does not yield a strong correlation, it could raise doubts about the reliability of the entire experimental approach and data interpretation. Therefore, addressing these issues through thorough verification and validation steps is crucial to enhance the study's credibility and confidence in the results. + +<|ref|>text<|/ref|><|det|>[[118, 644, 864, 685]]<|/det|> +4. Increased gene expression, can correlate with reduced host organism fitness (DOI: https://doi.org/10.1038/nmeth.3339) and unwanted competition for intracellular resources (DOI: https://doi.org/10.1038/s41467-020-18392-x). If the final goal is to characterize new promoters for bioproduction, the authors should show that they do not impact the fitness of the host cells. + +<|ref|>text<|/ref|><|det|>[[118, 685, 860, 725]]<|/det|> +5. Both introduction and discussion need more supporting citations. Please add evidences to support all claims. Additionally, some claims seem only partially true or imprecise: + +<|ref|>text<|/ref|><|det|>[[118, 725, 880, 800]]<|/det|> +a. Line 47: there are studies that addressed the same problem (e.g. DOI: https://doi.org/10.1128/aem.00939-22). These should be cited and discussed. +b. Lines 81-85: these claims should be either supported by citations or toned down. There are many well characterized constitutive promoters active across eukaryotic species (CMV, EF1a, PGK, etc). The authors should motivate why their design is superior to existing solutions. + +<|ref|>text<|/ref|><|det|>[[118, 800, 590, 813]]<|/det|> +6. Some experimental choices and pipeline steps are unclear: + +<|ref|>text<|/ref|><|det|>[[118, 813, 870, 840]]<|/det|> +a. How were the 41 TFBS selected, especially since many are not common across the 4 eukaryotic cell types evaluated? + +<|ref|>text<|/ref|><|det|>[[118, 840, 632, 854]]<|/det|> +b. Line 128: how was the threshold of \(>73\%\) determined and why? + +<|ref|>text<|/ref|><|det|>[[118, 854, 875, 895]]<|/det|> +c. In the method section, describe how the total of 1600 million NGS reads mentioned is processed and the steps involved. Why only \(25\%\) of NGS reads were selected? What is the potential impact on the results? + +<|ref|>text<|/ref|><|det|>[[118, 896, 860, 910]]<|/det|> +7. Some of the conclusions drawn by the authors in the results section are questionable. Can the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[120, 84, 441, 98]]<|/det|> +authors comment on the following points? + +<|ref|>text<|/ref|><|det|>[[116, 98, 872, 530]]<|/det|> +a. In Fig. 2a the authors claim that there is a clear correlation between the median of the mean fluorescence and the motif: this is not clear from this graphic and it could be pure randomness. +b. Line 236: the observed correlation indicates that the distribution is mainly not described by the model. +c. Line 269-271 and Fig. 3d: there is no clear correlation between an increase in mixed letters and increase in model performance. The values of 10, 26, 36, 16, 23, 18% of correlation could be more or less random numbers. +8. The manuscript presentation is unclear in some parts, especially in the results and discussion sections preventing full understanding of the study: +a. The term "mean FL" is a function of the NGS reads. This is confusing as "mean FL" should intuitively be the mean of the measured fluorescence only. +b. Is "mean fluorescence" (Fig. 2a) same as "mean FL" (Fig. 2c and others)? +c. Large parts of the results section suffer from a lack of clarity, for example lines 168-190. Please work on improving the clarity of the entire section. +d. The structure of the discussion is confusing: start with a brief summary of the work, then draw a conclusion and hypothesize the next steps, only to return to the summary in the middle of the second paragraph. Consider restructuring. +9. There are several overstatements in the manuscript that should be toned down. E.g.: +a. Line 106 "pan-organism": the study focuses on one yeast strain and two mammalian cell lines only. +b. Line 112 "different murine tissues": this is inconsistent with the caption of Supplementary Figure 1 where only mouse embryonic stem cells are mentioned. +10. Some scientific basics are lacking: +a. space between number and units +b. organism in italic +c. missing descriptions in the methods (see comment 6c) +d. missing code and data online: will these be provided after publication? +e. the unit of fluorescence is never stated, is it arbitrary units (au)? +f. number of biological replicates should be specified. Especially Figure 6 does not have error bars: was validation run on one biological replicate only? If this is the case, it is scientifically inaccurate to draw any conclusion. + +<|ref|>text<|/ref|><|det|>[[118, 545, 252, 558]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 559, 868, 884]]<|/det|> +1. Line 49: "whose promoter is capable of transcribing" is wrong. A promoter does not transcribe, the polymerase does. +2. Line 102: "reliable prediction" +3. Line 106: "constitutive" instead of non-inducible +4. Line 156: "Fig. 1f" +5. Line 802: what is a PPM? +6. Line 140: Fig. 1c? +7. Line 185: which type of correlation is it? +8. Line 422: "for a weak and a strong promoter", only one variant tested for each +9. Line 430: "circuits" (Remove "bio-") +10. Line 869: "of" "s"? +11. Lines 780-781: lasers wavelength? +12. Discussion: The name UNILIB is introduced only at this point, why? +13. Figures: +a. Increase the font size in all figures, as they appear too small for easy readability +b. 1f: the vertical line should be at 40, it is at 30 though +c. 2d: no error bars +d. 3e: labels can be put under x axis instead of colors +e. 3d: if a linear correlation (Pearson) is assumed, add the line to the plot +f. 4a: error bars are at null level? +g. 4b (and following): no tick marks in the right plots +h. 5f: error bars +i. 6: add axis label, what type of data is shown? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 99, 222, 111]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 113, 298, 125]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 127, 858, 197]]<|/det|> +In this manuscript from Vaknin et al, the authors develop a library of synthetic promoters by merging a target core promoter and upstream TF binding sites, to enhance protein expression in eukaryotic cells. This is not the first time synthetic promoters are designed by this approach and previous work has shown that is possible to engineer mammalian cells based on mining of TFBS and core promoter engineering (e.g. Johari et al. 2019 and others). + +<|ref|>text<|/ref|><|det|>[[118, 197, 850, 225]]<|/det|> +The manuscript tries to go beyond the state of art by building a system functional in more than one chassis. + +<|ref|>text<|/ref|><|det|>[[118, 225, 850, 266]]<|/det|> +I have a few questions, mainly on the experimental side, as I am not a computational person. It is not fully clear to me what the authors mean with the term "motif" and it could be useful to define this. + +<|ref|>text<|/ref|><|det|>[[118, 266, 860, 294]]<|/det|> +It is not fully clear also how the 41 motifs were identified and if this was validated by using more than one TF data base. + +<|ref|>text<|/ref|><|det|>[[118, 294, 870, 335]]<|/det|> +In figure 1e it is not fully clear why authors have not taken population 2 and re- bin it in order to capture more variants and potentially more interesting candidates with higher expression. It could have been beneficial to do so here. + +<|ref|>text<|/ref|><|det|>[[118, 335, 844, 377]]<|/det|> +In figure 6, for CHO cell experiments, the authors mentioned they used a BFP for fluorescence normalisation. However, it is known from literature that resource competition can impact normalisation (see Frei et al, 2020. Jones et al, 2020). + +<|ref|>text<|/ref|><|det|>[[118, 377, 864, 418]]<|/det|> +Can the authors shown the expression levels of the CHO library but with no normalisation and check if that improves the results? Caption of figure 6 should also more clearly describe what the figures shows. + +<|ref|>text<|/ref|><|det|>[[118, 419, 866, 446]]<|/det|> +Minor comments pertain to several typos present in the manuscript like Eukaryotic that should be lower case; + +<|ref|>text<|/ref|><|det|>[[118, 447, 680, 461]]<|/det|> +Figures are called at time with capital letter and at times with lower case. + +<|ref|>text<|/ref|><|det|>[[118, 475, 828, 490]]<|/det|> +In conclusion I suggest the work to be published once these questions have been addressed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 392, 106]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 128, 882, 305]]<|/det|> +In this study, the authors introduce an algorithm designed to predict regulatory sequences that modulate gene expression in eukaryotic cells. To achieve this, they identified 41 Transcription Factor Binding Sites (TFBS) from various organisms, including S. cerevisiae, S. pombe, D. melanogaster S2 cells, and murine ES cells. These TFBS (or motifs) were used to construct a library of nearly 190,000 variants, each containing up to three different motifs and their variants. Using a combination of machine learning and oligo library analysis in yeast, the authors aimed to identify specific motifs capable of enhancing or attenuating gene expression. These motifs were then assessed in two mammalian cell lines. Overall, the study addresses a topic of general interest: fine tunability of gene expression for optimal output production. However, the manuscript suffers from issues related to clarity, methodology transparency, and validation, ultimately raising concerns about the rigour and robustness of the study. Detailed comments and suggestions are provided below. + +<|ref|>text<|/ref|><|det|>[[115, 328, 882, 410]]<|/det|> +1. The TFBS used in this study are for endogenous TFs, and some correlate with both activation and repression activity. This may depend on different cell types, cell states and growth conditions, potentially generating high variability in the promoter's behavior. The authors should validate the identified sequences with a significant number of biological replicates (at least 3), at different cell passages and possibly different culturing conditions (e.g. different cell densities, different media composition, etc). + +<|ref|>text<|/ref|><|det|>[[115, 414, 882, 529]]<|/det|> +We thank the reviewer for this comment, and the opportunity to improve our work. First, we would like to note that only 27 of the 41 motifs were validated transcription-factor binding sites. The rest of the motifs were unknown, and not attributed to a particular regulatory process. The motifs were found to be conserved across various Eukaryotic lineages in a HT-SELEX assay carried out by Jussi Taipale's group (published in DOI: 10.1038/nbt.4138). As a result of the UNILIB experiment, we were able to characterize 5 of the unknown motifs as either up- or down-regulating. Some of these motifs are weak and require multiple sites or combinations of sites to show a measurable regulatory effect. + +<|ref|>text<|/ref|><|det|>[[115, 534, 882, 631]]<|/det|> +Second, with regards to the function of the motifs in different cell- growth conditions or cell types, there indeed could be a variation. Consequently, we created 43 unseen synthetic URS variants. We used 32 variants, which sampled 23 of the motifs for which a significant up or down- regulatory behavior was identified, for the results depicted in Fig. 5, and an additional 11 variants were used for the validation of the machine- learning model in Fig. 3. Altogether the 43 validation variants sample 31 of the 42 motifs including all the motifs that were found to be significant. + +<|ref|>text<|/ref|><|det|>[[115, 637, 882, 703]]<|/det|> +However, given the reviewer's critical comment, we decided to use these variants to expand our validation set to further strengthen our conclusions. The revised manuscript now includes two new figures: Fig. 6 and Fig. 7, which replace the original Fig. 6. New Fig. 6 details the results of 7 separate experimental measurements carried out in biological triplicates as follows: + +<|ref|>text<|/ref|><|det|>[[142, 710, 875, 829]]<|/det|> +1. Yeast: SD-Ura+2% glucose, \(30^{\circ}\mathrm{C}\) , weak core promoter (mCore), no additives, 43 variants. +2. Yeast: SD-Ura+2% glycerol, \(30^{\circ}\mathrm{C}\) , weak core promoter (mCore), no additives, 43 variants. +3. Yeast: SD-Ura+2% glucose, \(39^{\circ}\mathrm{C}\) , weak core promoter (mCore), no additives, 43 variants. +4. Yeast: SD-Ura+2% glucose, \(30^{\circ}\mathrm{C}\) , weak core promoter (mCore), 1M NaCl, 43 variants. +5. Yeast: SD-Ura+2% glucose, \(30^{\circ}\mathrm{C}\) , strong core promoter (FEC-mCore), no additives, 20 variants. +6. CHO/K1 cells grown in F12 medium, 32 variants. +7. HeLa cells grown in DMEM high glucose medium, 32 variants. + +<|ref|>text<|/ref|><|det|>[[115, 835, 882, 900]]<|/det|> +The results for all the yeast experiments, whether as biological replicates or in different culturing conditions, correlate strongly with one another in a statistically significant fashion (see below Figs. L1 in addition to Fig. 6 and Supplemental Fig. 6 in the revised manuscript). These results support a conserved function in yeast independent of growth conditions. This is consistent with the previous findings of (Keren et al., Mol. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 882, 219]]<|/det|> +Sys. Biol., 9:701 (2013)) who tested the activities of \(\sim 900\) S. cerevisiae promoters in 10 different conditions and found no significant difference in activities across the panel of growth conditions used. In addition, the experimental data also shows a statistically significant correlation between the mammalian cell measurements and the yeast measurements, which we showed also in the original manuscript. Finally, we also improved our modelling scheme by extending the machine- learning model developed in Fig. 3 using the additive model described in Fig. 5 to create a hybrid model, which improved performance on all datasets. The new hybrid model now predicts HeLa and CHO cells regulatory activity in a statistically significant fashion (see new Fig. 7). + +<|ref|>text<|/ref|><|det|>[[114, 226, 882, 290]]<|/det|> +The revised validation segment of our manuscript now allows us to make an improved argument that the synthetic URS sequences that we created can generate a regulatory function that is, for the most- part, independent of cell- type and growth conditions, making these sequences a potentially widely applicable tool. + +<|ref|>image<|/ref|><|det|>[[123, 308, 876, 504]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 533, 844, 566]]<|/det|> +
Figure L1: Comparison of biological triplicates for the 43 validation variants grown in SD-\(Ura + 2\%\) glucose. Experiments show a strong a correlation between all 3 repeats.
+ +<|ref|>text<|/ref|><|det|>[[114, 580, 882, 677]]<|/det|> +2. The authors should ensure that the cells carrying a specific barcode indeed harbour the intended promoter variant, especially considering the complexity of the designed library. Thus, one significant gap in the methodology is the absence of verification steps after sorting, ideally conducted after the final PCR step just before Next-Generation Sequencing (NGS). This validation step could take various forms, even only Sanger sequencing of a select subset of variants (not only 1!). This additional verification would provide confidence in the accuracy of the cell content and the presence of the intended promoter variants. + +<|ref|>text<|/ref|><|det|>[[114, 692, 882, 853]]<|/det|> +In brief, due to their short length (bc+sURS+core- promoter) our variants were fully sequenced in the NGS. While we apologize for not including this data in the manuscript, as part of our validation, we screened for all full- length reads in the library (i.e. reads that yielded a full length of over 200 bp that include the barcodes, sURS, and primer regions). We found approx. 400M such reads, and they all perfectly matched the barcodes, motifs, and primer regions. We then quantified the correctness of the downstream sequence to the barcode with the intended design and found that per position \(>99\%\) match the design. In addition, we designed the barcodes, such that the Hamming distance between each two is at least 3, which maximized our ability to identify variants. We thank the reviewer for this important comment. In response to the comment, we have added a comment under the Methods sub- section "NGS data processing and read normalization" to clarify this issue. + +<|ref|>text<|/ref|><|det|>[[113, 869, 881, 902]]<|/det|> +3. Figure 2c should ideally show a relatively tight cluster of data points resembling a straight line with some expected noise and a few outliers, reflecting the inherent variability in biological systems and NGS data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 202]]<|/det|> +However, the observed data points in this plot appear scattered, indicating a significant divergence from expected behavior. To mitigate this concern and validate the Sort- Seq values, it is advisable to conduct an extensive validation experiment. This experiment could involve the measurement of fluorescence or RNA- seq for individual variants, followed by a correlation analysis with the NGS- based fluorescence (FL mean) values. If this validation does not yield a strong correlation, it could raise doubts about the reliability of the entire experimental approach and data interpretation. Therefore, addressing these issues through thorough verification and validation steps is crucial to enhance the study's credibility and confidence in the results. + +<|ref|>text<|/ref|><|det|>[[115, 209, 882, 272]]<|/det|> +We are aware of the lack of correlation observed in our OL measurements, which we view as a feature of the methodology rather than an artefact. The data used to compose panel 2c consisted of OL variants that were encoded with two barcodes. The lack of correlation observed for most variant pairs was due to three main reasons: + +<|ref|>text<|/ref|><|det|>[[144, 273, 883, 449]]<|/det|> +1. In SORT-seq experiments, it is impossible to tell how many reads came from a single sorted cell. For example, one cell can yield several hundred reads or a single read in the final count. This can lead to a lack of correlation if the number of cells sorted per a particular variant is small as in this case. We remind the reviewer that our library was unprecedented in size ( \(\sim 200\mathrm{K}\) mixed-base variants), and thus the number of cells collected for each variant was small. +2. In SORT-seq experiments, it is impossible to tell whether cells die after sorting or divide. In such a case, a single cell may also yield more read events in comparison to another cell, though the original sort had them at an equal weight. +3. Variants which do not encode a particular regulatory function are more susceptible to transcriptional variation. The strongly up- and down-regulating variants (top and bottom corners of the plot respectively) are strongly correlated as expected from a fully functional regulatory element. + +<|ref|>text<|/ref|><|det|>[[115, 464, 882, 576]]<|/det|> +The analysis shown in Figure 2 and referred to by the reviewer was, therefore, used as impetus for the quantitative analysis that was done on the 2,435- variant subset that were encoded with 22 barcodes. We reasoned that the sources for the lack of correlation discussed in the points above will be minimized by analyzing multiple barcodes on the same variants. For example, identifying all 22 barcodes immediately implies that at the very least we screened 22 separate fluorescent yeast cells. Consequently, we reasoned that such a subset will lead to a more robust statistical analysis, even though a given pair of barcodes may not be as correlated as we would like. + +<|ref|>text<|/ref|><|det|>[[115, 592, 882, 704]]<|/det|> +The analysis carried out in Figure 3 shows that the choice of unifying the 22 barcodes is statistically robust as evident by the agreement with the de Boer machine- learning model that was trained using independent experimental data. In addition, the validation set of Figures 5- 7 and the agreement with the models that were derived from the experimental data obtained from the 2,435- variant subset essentially shows that both the SORT- seq experiment and the analysis were robust. Consequently, we believe that we have provided sufficient proof in the manuscript both computationally and experimentally that our analysis and experimental approach were robust, and no additional validation is necessary. + +<|ref|>text<|/ref|><|det|>[[115, 720, 882, 785]]<|/det|> +4. Increased gene expression, can correlate with reduced host organism fitness (DOI: https://doi.org/10.1038/nmeth.3339) and unwanted competition for intracellular resources (DOI: https://doi.org/10.1038/s41467-020-18392-x). If the final goal is to characterize new promoters for bioproduction, the authors should show that they do not impact the fitness of the host cells. + +<|ref|>text<|/ref|><|det|>[[115, 791, 882, 888]]<|/det|> +We thank the reviewer for this comment. In response to the comment, we carried out fitness analysis on the 32 validation variants. The results are shown in Figure L2 and have been added to the Supplementary Information as Supplementary Fig. 6. In our experiments, we did not detect any effect on fitness as a result of our synthetic upstream regulatory sequences and mentioned that in the "Boosted expression level translates from yeast and mammalian cells" Results subsection of the revised manuscript. Specifically, we grew the 43 validation variants in YPD and tracked their growth via OD measurement as function of time + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 883, 123]]<|/det|> +(Fig. L2a - circles). For each strain we then fitted the OD measurements (Fig. L2a - blue line) with the following model for exponential growth: + +<|ref|>equation<|/ref|><|det|>[[374, 123, 621, 160]]<|/det|> +\[OD_{600}(t) = C + \frac{L}{(1 + e^{-k(t - t_0)})}\] + +<|ref|>text<|/ref|><|det|>[[114, 172, 883, 285]]<|/det|> +Where \(C\) is background OD levels, \(L\) is the max OD, \(k\) is the growth rate, and \(t_0\) corresponds to the lag time (i.e. time at which the culture reaches OD of L/2). Using this model, we extracted the growth rate for each strain and for both repeats. We plotted in Fig. L2b the different fitted growth rates \((k)\) for both repeats that were measured for each variant. The results show that the growth rates for all experiments was found to be within a narrow range of \(\sim 0.4 - 1.3\) (1/hr) without any significant correlation between duplicates. The lack of correlation between duplicates and narrow range of growth rates provides strong evidence that our variants do not affect the fitness of the yeast cells. + +<|ref|>image<|/ref|><|det|>[[123, 298, 861, 581]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 584, 883, 649]]<|/det|> +
Figure L2: Fitness analysis for yeast cells expressing the 43-variant validation set grown in YPD. (a) The 43 validation variants were grown in YPD in duplicates and tracked for OD as a function of time (circles). For each variant the growth data are fitted (blue lines) by a classic growth curve (see Supplementary Information). (b) The rates of growth for each variant are plotted as a scatter plot pair for both repeats.
+ +<|ref|>text<|/ref|><|det|>[[113, 662, 865, 775]]<|/det|> +5. Both introduction and discussion need more supporting citations. Please add evidences to support all claims. Additionally, some claims seem only partially true or imprecise: a. Line 47: there are studies that addressed the same problem (e.g. DOI: https://doi.org/10.1128/aem.00939-22). These should be cited and discussed. b. Lines 81-85: these claims should be either supported by citations or toned down. There are many well characterized constitutive promoters active across eukaryotic species (CMV, EF1a, PGK, etc). The authors should motivate why their design is superior to existing solutions. + +<|ref|>text<|/ref|><|det|>[[115, 790, 883, 855]]<|/det|> +We thank the reviewer for providing the additional reference, and for pointing out misstatements in the Introduction. In response to the comment, we added this and other references and rephrased the text in the Introduction and Discussion sections accordingly. Please see the marked up version of the revised manuscript for the details. + +<|ref|>text<|/ref|><|det|>[[114, 871, 555, 888]]<|/det|> +6. Some experimental choices and pipeline steps are unclear: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 123]]<|/det|> +a. How were the 41 TFBS selected, especially since many are not common across the 4 eukaryotic cell types evaluated? + +<|ref|>text<|/ref|><|det|>[[115, 129, 882, 305]]<|/det|> +We apologize that these choices were unclear. In brief, the motifs were chosen as part of a past collaboration with Jussi Taipale's group. At the time, the Taipale group had a study (later published in DOI: 10.1038/nbt.4138) that was focused on developing a protein activity assay specifically for DNA- binding TFs in cell and tissue extracts. His team was able to identify strong and enriched TFBS motifs using this assay, including the 41 TFBSs that we selected for our research. Those and other motifs were discovered in numerous organisms, including two types of yeast, different tissues from mice, bacteria, and Drosophila S2 cells. Even though some of the motifs were not found to be common/conserved across these organisms, we nevertheless chose to characterize them due to similarities to well- characterized protein families in higher eukaryotes (e.g. the bHLH motif). For a detailed explanation as to how and why we chose these 41 motifs, please see the new Methods subsection titled "Motif selection and encoding into OL. Based on the study's data, we selected the 41 enriched motifs according to the following criteria: + +<|ref|>text<|/ref|><|det|>[[144, 311, 882, 393]]<|/det|> +1. Different motif types: 8 organism-shared motifs, 5 mice tissue-shared motifs, 14 unshared motifs (unique to an organism), and 14 unknown motifs (with unknown regulatory function). +2. Known/unknown regulatory function: 27 of the selected motifs have known regulatory function, and those were anticipated to be the control motifs. Characterizing the regulatory function of the 14 unknown motifs in yeast was one of the stated goals of the study. + +<|ref|>text<|/ref|><|det|>[[115, 399, 596, 416]]<|/det|> +b. Line 128: how was the threshold of \(>73\%\) determined and why? + +<|ref|>text<|/ref|><|det|>[[115, 422, 883, 552]]<|/det|> +We thank the reviewer for this question and apologize for not including the rationale for our choice in the original manuscript. In response to the comment, we have added a new Methods subsection entitled "Motif selection and encoding into OL", where the rationale is now described. In brief, K and M substitutions were based on the percentage calculation of the respective G/T and A/C occurrences, in each position of the motif according to the PFM data given to us by the Taipale group (later published in DOI: 10.1038/nbt.4138). Positions within the motif, with dominant percentages, were replaced by either K or M in the final design. \(70\%\) threshold was set to determine the K/M substitution, but the actual calculated threshold was higher at \(73\%\) , as specified in the Results section. + +<|ref|>text<|/ref|><|det|>[[115, 566, 882, 599]]<|/det|> +c. In the method section, describe how the total of 1600 million NGS reads mentioned is processed and the steps involved. Why only \(25\%\) of NGS reads were selected? What is the potential impact on the results? + +<|ref|>text<|/ref|><|det|>[[115, 606, 882, 750]]<|/det|> +We thank the reviewer for this question. In response to the comment, we have expanded the Methods subsection titled "NGS data processing and read normalization", specifying the processing steps accordingly. Given the size of the UNILIB library, we opted to use Illumina's NovaSeq for its ability to generate as much as 1B reads per run. We used Illumina's S1 kit, and despite Illumina's reliability claims, indeed only \(25\%\) of the reads were found to be correct in both the NovaSeq runs that were made. Neither we nor the Genomics Center at the Weizmann Institute are certain about the underlying cause for this low fidelity, which may have been due to the choice of primers. Irrespective of that, the center offered to re- sequence the library, ultimately allowing us to extract 400M correct reads. This number of reads proved to be sufficient for the analysis in our study, which was based on the machine- learning modelling. + +<|ref|>text<|/ref|><|det|>[[115, 765, 882, 895]]<|/det|> +As discussed above, our analysis showed that the use of two barcodes per variant was insufficient for proper quantitative analysis, as such a low number introduced a large statistical uncertainty regarding the actual number of sorted cells. On the flip side, the same analysis showed that 22 barcodes per variant significantly reduced this uncertainty. In the former case, increasing the number of reads would not have affected the cell number uncertainty, while in the latter the 22 barcodes ensured that we have a sufficient amount of reads for every one of the variants of the 2,435- variant subset even with only 400M correct reads extracted in total. Consequently, the \(25\%\) extraction rate did not impact our conclusions or results of the downstream analysis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 883, 139]]<|/det|> +7. Some of the conclusions drawn by the authors in the results section are questionable. Can the authors comment on the following points? + +<|ref|>text<|/ref|><|det|>[[115, 145, 883, 179]]<|/det|> +a. In Fig. 2a the authors claim that there is a clear correlation between the median of the mean fluorescence and the motif: this is not clear from this graphic and it could be pure randomness. + +<|ref|>text<|/ref|><|det|>[[115, 185, 882, 329]]<|/det|> +We thank the reviewer for this comment and apologize for not assessing the correlation in the original manuscript. In response to the comment, to assess the correlation between the median of mean fluorescent expression levels and motifs, we conducted a Wilcoxon rank-sum test by comparing the mean fluorescent expression levels of the group of variants containing each motif to the group of variants containing motifs ranked at least 5 motifs away. To correct for multiple tests, we applied the Benjamini-Hochberg procedure with an FDR threshold of 0.1. This new analysis revealed significant differences for 36 out of 42 motifs (p- value<0.05), where the 6 non- significant motifs are in motifs ordered 15- 20 in decreasing order, which is expected since their values are distributed around the center of the mean- fluorescence distribution. We added this new statistical significance analysis to the Results section. + +<|ref|>text<|/ref|><|det|>[[115, 344, 870, 361]]<|/det|> +b. Line 236: the observed correlation indicates that the distribution is mainly not described by the model. + +<|ref|>text<|/ref|><|det|>[[115, 367, 882, 544]]<|/det|> +We thank the reviewer for this comment. In various biological problems, such as inference of protein- DNA binding preferences based on protein- binding- microarray data, correlation values are within 0.4- 0.6 (10.1109/TCBB.2019.2947461). Moreover, the correlation of 0.45 was achieved by the all- data model (ADM), which we showed is inferior to the AMM and MBO models. In addition, this value is calculated on a test set of variants, where most have only 2 barcodes, which implies the lower quality of their mean- fluorescence measurements compared to variants with 22 barcodes. One of the key insights from our study was that variants supported by 22 barcodes, as opposed to 2 barcodes, yielded more accurate mean- fluorescence measurements (due to the inclusion of more cells carrying the variant). When the MBO model was exclusively trained and tested on datasets of variants with 22 barcodes, the obtained Pearson correlation was 0.61. This suggests that using more accurate training and test sets results in a higher observed correlation, which better explains the variability in the data. + +<|ref|>text<|/ref|><|det|>[[115, 559, 882, 608]]<|/det|> +c. Line 269-271 and Fig. 3d: there is no clear correlation between an increase in mixed letters and increase in model performance. The values of 10, 26, 36, 16, 23, 18% of correlation could be more or less random numbers. + +<|ref|>text<|/ref|><|det|>[[115, 614, 882, 663]]<|/det|> +We thank the reviewer for pointing this unclear part of our manuscript. We acknowledge that the reported correlation values may not achieve statistical significance. In response to this comment, we removed Fig. 3d and the corresponding text describing the analyses and results from the Results section. + +<|ref|>text<|/ref|><|det|>[[115, 679, 882, 712]]<|/det|> +8. The manuscript presentation is unclear in some parts, especially in the results and discussion sections preventing full understanding of the study: + +<|ref|>text<|/ref|><|det|>[[115, 712, 882, 744]]<|/det|> +a. The term "mean FL" is a function of the NGS reads. This is confusing as "mean FL" should intuitively be the mean of the measured fluorescence only. + +<|ref|>text<|/ref|><|det|>[[115, 750, 882, 815]]<|/det|> +We thank the reviewer for this comment and have changed all "mean FL" labels for the NGS data to the one used by (Sharon, E. et al. Nat Biotechnol 30, 521-530 (2012)) in a similar oligo library experiment: "Expression (A.U.)". All relevant labels in the figures and text have been changed to Expression (A.U.) in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 831, 736, 864]]<|/det|> +b. Is "mean fluorescence" (Fig. 2a) same as "mean FL" (Fig. 2c and others)? We thank the reviewer for finding this minor error, and changed to Expression (A.U.). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 105, 870, 139]]<|/det|> +c. Large parts of the results section suffer from a lack of clarity, for example lines 168-190. Please work on improving the clarity of the entire section. + +<|ref|>text<|/ref|><|det|>[[115, 138, 878, 187]]<|/det|> +We thank the reviewer for this comment and have clarified the Results, including the subsection titled "Variants manifest a broad range of regulatory behavior". Please see the marked-up version of the revised manuscript for the changes. + +<|ref|>text<|/ref|><|det|>[[115, 201, 882, 251]]<|/det|> +d. The structure of the discussion is confusing: start with a brief summary of the work, then draw a conclusion and hypothesize the next steps, only to return to the summary in the middle of the second paragraph. Consider restructuring. + +<|ref|>text<|/ref|><|det|>[[115, 256, 882, 306]]<|/det|> +We thank the reviewer for this comment. We decided to leave the structure of the Discussion as is with minor modifications. We opted for this option so we can highlight at the beginning of the section the design algorithm that was developed, which we believe is the most important achievement of this work. + +<|ref|>text<|/ref|><|det|>[[115, 320, 882, 355]]<|/det|> +9. There are several overstatements in the manuscript that should be toned down. E.g.: a. Line 106 "pan-organism": the study focuses on one yeast strain and two mammalian cell lines only. + +<|ref|>text<|/ref|><|det|>[[115, 359, 732, 377]]<|/det|> +In response to the comment, we deleted the term pan-organism from the Introduction. + +<|ref|>text<|/ref|><|det|>[[115, 391, 882, 425]]<|/det|> +b. Line 112 "different murine tissues": this is inconsistent with the caption of Supplementary Figure 1 where only mouse embryonic stem cells are mentioned. + +<|ref|>text<|/ref|><|det|>[[115, 431, 882, 465]]<|/det|> +In response to the comment, we corrected the error and replaced the term "different murine tissues" by mouse (ES cells and different tissues). + +<|ref|>text<|/ref|><|det|>[[116, 480, 393, 497]]<|/det|> +10. Some scientific basics are lacking: + +<|ref|>text<|/ref|><|det|>[[115, 504, 370, 520]]<|/det|> +a. space between number and units + +<|ref|>text<|/ref|><|det|>[[115, 528, 277, 543]]<|/det|> +Errors were corrected. + +<|ref|>text<|/ref|><|det|>[[115, 551, 262, 567]]<|/det|> +b. organism in italic + +<|ref|>text<|/ref|><|det|>[[115, 575, 277, 590]]<|/det|> +Errors were corrected. + +<|ref|>text<|/ref|><|det|>[[115, 597, 525, 614]]<|/det|> +c. missing descriptions in the methods (see comment 6c) + +<|ref|>text<|/ref|><|det|>[[115, 620, 561, 637]]<|/det|> +All missing methods were added. Please see responses above. + +<|ref|>text<|/ref|><|det|>[[115, 644, 644, 661]]<|/det|> +d. missing code and data online: will these be provided after publication? + +<|ref|>text<|/ref|><|det|>[[115, 667, 880, 685]]<|/det|> +All data and code were uploaded. Please see data and code availability statements in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 691, 595, 708]]<|/det|> +e. the unit of fluorescence is never stated, is it arbitrary units (au)? + +<|ref|>text<|/ref|><|det|>[[115, 714, 882, 747]]<|/det|> +The mean FL was replaced by the consensus Expression (A.U.) for all mean level expression level measurements. + +<|ref|>text<|/ref|><|det|>[[115, 753, 882, 803]]<|/det|> +f. number of biological replicates should be specified. Especially Figure 6 does not have error bars: was validation run on one biological replicate only? If this is the case, it is scientifically inaccurate to draw any conclusion. + +<|ref|>text<|/ref|><|det|>[[115, 809, 882, 906]]<|/det|> +We thank the reviewer for this comment and would like to clarify our choice of plotting. All validation experiments were conducted in (at least) biological triplicates as discussed above (see Fig. L1 for example). In response to Comment 1, we have substantially increased the volume of the validation experiments, and consequently split the original Fig. 6 in the original manuscript to a new Fig. 6 depicting only experimental data, and a new Figure 7 depicting the modelling analysis. Given the quantity of data, we opted to omit the error-bars from some of the plots for aesthetic reasons (see for example Fig. L3 which depicts Fig. 6a-c + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 123]]<|/det|> +with error bars). Since we recognize the need to visually and numerically report the variance in the validation measurements, we have done the following: + +<|ref|>text<|/ref|><|det|>[[142, 130, 884, 373]]<|/det|> +- The variation for the various validation datasets across the repeats can be assessed using new Supplementary Figure 6, and via the correlation heatmap plots of new Fig. 6 (panels d and e). Note, that the autocorrelation between the various repeats of the yeast experiments does not yield a higher Pearson correlation coefficient, as compared with the cross-correlation of the mean fluorescent expression levels of the various conditions. This result provides statistically significant experimental evidence that the different yeast growth conditions do not alter the expression of our variants, and in our opinion is depicted more convincingly via the mode of plotting that we chose to use in the revised manuscript.- We plotted Fig.6a with error bars to convey directly the variance in the cross-correlation analysis. This panel is identical to the one shown in Fig. L3a.- Fig. 6b-c are depicted without error-bars. Here, the purpose is to highlight the fact that out of the dataset 24 variants behaved similarly to yeast (blue), while 8 were uncorrelated in CHO (red). We have added the panel b and c to supplementary fig.6 as panel g and h.- We plotted the error-bars for the both the yeast-glucose \(2\%\) and HeLa-blue variants in panel b and c of Fig. 7. + +<|ref|>image<|/ref|><|det|>[[123, 383, 863, 607]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 621, 883, 703]]<|/det|> +
Figure L3:Cross correlation data for 43-variant validation experiments plotted with error-bars. (a) yeast cross-correlation data. (b-c) The \(2\%\) glucose yeast expression data plotted as a function of CHO (b) and HeLa (c) expression data. Error-bars were computed using standard-error analysis carried out on mean flow cytometry fluorescence measurements obtained from three or four biological repeats – depending on data set.
+ +<|ref|>text<|/ref|><|det|>[[115, 727, 245, 742]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[112, 749, 884, 784]]<|/det|> +1. Line 49: "whose promoter is capable of transcribing" is wrong. A promoter does not transcribe, the polymerase does. + +<|ref|>text<|/ref|><|det|>[[115, 789, 720, 806]]<|/det|> +We changed the statement to "whose promoter is capable of initiating transcription" + +<|ref|>text<|/ref|><|det|>[[115, 806, 355, 821]]<|/det|> +2. Line 102: "reliable prediction" + +<|ref|>text<|/ref|><|det|>[[115, 822, 356, 836]]<|/det|> +We removed the word prediction. + +<|ref|>text<|/ref|><|det|>[[115, 837, 489, 852]]<|/det|> +3. Line 106: "constitutive" instead of non-inducible + +<|ref|>text<|/ref|><|det|>[[115, 853, 384, 868]]<|/det|> +We retrained the word non-inducible. + +<|ref|>text<|/ref|><|det|>[[115, 870, 273, 884]]<|/det|> +4. Line 156: "Fig. 1f" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 279, 106]]<|/det|> +We corrected the typo. + +<|ref|>text<|/ref|><|det|>[[115, 107, 322, 122]]<|/det|> +5. Line 802: what is a PPM? + +<|ref|>text<|/ref|><|det|>[[115, 123, 520, 139]]<|/det|> +We corrected PPM to PWM - position weighted matrix. + +<|ref|>text<|/ref|><|det|>[[115, 140, 272, 155]]<|/det|> +6. Line 140: Fig. 1c? + +<|ref|>text<|/ref|><|det|>[[115, 156, 279, 170]]<|/det|> +We corrected the typo. + +<|ref|>text<|/ref|><|det|>[[115, 171, 430, 186]]<|/det|> +7. Line 185: which type of correlation is it? + +<|ref|>text<|/ref|><|det|>[[115, 187, 339, 201]]<|/det|> +We added the word "Pearson". + +<|ref|>text<|/ref|><|det|>[[115, 202, 700, 218]]<|/det|> +8. Line 422: "for a weak and a strong promoter", only one variant tested for each + +<|ref|>text<|/ref|><|det|>[[115, 219, 615, 234]]<|/det|> +We changed the phrase in accordance with the reviewer's suggestion. + +<|ref|>text<|/ref|><|det|>[[115, 235, 409, 250]]<|/det|> +9. Line 430: "circuits" (Remove "bio- ") + +<|ref|>text<|/ref|><|det|>[[115, 251, 304, 265]]<|/det|> +We removed the word bio. + +<|ref|>text<|/ref|><|det|>[[115, 266, 293, 281]]<|/det|> +10. Line 869: "of""s"?! + +<|ref|>text<|/ref|><|det|>[[115, 283, 279, 297]]<|/det|> +We corrected the typo. + +<|ref|>text<|/ref|><|det|>[[115, 298, 395, 313]]<|/det|> +11. Lines 780-781: lasers wavelength? + +<|ref|>text<|/ref|><|det|>[[115, 315, 405, 329]]<|/det|> +We added MacsQuant laser wavelength. + +<|ref|>text<|/ref|><|det|>[[115, 330, 642, 346]]<|/det|> +12. Discussion: The name UNILIB is introduced only at this point, why? + +<|ref|>text<|/ref|><|det|>[[115, 346, 870, 377]]<|/det|> +We chose to name the completed design algorithm UNILIB, and name it only after we demonstrated that it worked via the validation experiments. + +<|ref|>text<|/ref|><|det|>[[115, 378, 201, 393]]<|/det|> +13. Figures: + +<|ref|>text<|/ref|><|det|>[[115, 394, 707, 410]]<|/det|> +a. Increase the font size in all figures, as they appear too small for easy readability + +<|ref|>text<|/ref|><|det|>[[115, 411, 325, 425]]<|/det|> +We corrected where possible. + +<|ref|>text<|/ref|><|det|>[[115, 426, 515, 441]]<|/det|> +b. 1f: the vertical line should be at 40, it is at 30 though + +<|ref|>text<|/ref|><|det|>[[115, 442, 280, 456]]<|/det|> +We corrected this error. + +<|ref|>text<|/ref|><|det|>[[115, 458, 253, 472]]<|/det|> +c. 2d: no error bars + +<|ref|>text<|/ref|><|det|>[[115, 473, 790, 489]]<|/det|> +There are no error bars for the medians of the mean fluorescent expression level distributions. + +<|ref|>text<|/ref|><|det|>[[115, 490, 500, 505]]<|/det|> +d. 3e: labels can be put under x axis instead of colors + +<|ref|>text<|/ref|><|det|>[[115, 506, 380, 521]]<|/det|> +We improved the figure accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 522, 640, 538]]<|/det|> +e. 3d: if a linear correlation (Pearson) is assumed, add the line to the plot + +<|ref|>text<|/ref|><|det|>[[115, 539, 295, 553]]<|/det|> +We removed old Fig. 3d. + +<|ref|>text<|/ref|><|det|>[[115, 554, 352, 569]]<|/det|> +f. 4a: error bars are at null level? + +<|ref|>text<|/ref|><|det|>[[115, 570, 863, 600]]<|/det|> +There are no error bars for the large colored bars as they represent the p- value estimate from comparing two distributions as shown in the inset. + +<|ref|>text<|/ref|><|det|>[[115, 601, 504, 616]]<|/det|> +g. 4b (and following): no tick marks in the right plots + +<|ref|>text<|/ref|><|det|>[[115, 617, 285, 631]]<|/det|> +We corrected this error. + +<|ref|>text<|/ref|><|det|>[[115, 633, 230, 647]]<|/det|> +h. 5f: error bars + +<|ref|>text<|/ref|><|det|>[[115, 648, 870, 679]]<|/det|> +We opted to present the actual measurements as circles instead of error bars to convey the distribution of the measured data. + +<|ref|>text<|/ref|><|det|>[[115, 680, 459, 696]]<|/det|> +i. 6: add axis label, what type of data is shown? + +<|ref|>text<|/ref|><|det|>[[115, 697, 472, 712]]<|/det|> +Old Fig. 6 was replaced by new Fig. 6 and Fig. 7. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 392, 107]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 113, 882, 194]]<|/det|> +In this manuscript from Vaknin et al, the authors develop a library of synthetic promoters by merging a target core promoter and upstream TF binding sites, to enhance protein expression in eukaryotic cells. This is not the first time synthetic promoters are designed by this approach and previous work has shown that is possible to engineer mammalian cells based on mining of TFBS and core promoter engineering (e.g. Johari et al. 2019 and others). + +<|ref|>text<|/ref|><|det|>[[115, 200, 882, 249]]<|/det|> +The manuscript tries to go beyond the state of art by building a system functional in more than one chassis. I have a few questions, mainly on the experimental side, as I am not a computational person. It is not fully clear to me what the authors mean with the term "motif" and it could be useful to define this. + +<|ref|>text<|/ref|><|det|>[[115, 255, 882, 353]]<|/det|> +We thank the reviewer for this very important comment and apologize for not specifying our rationale for choosing the motifs. In response to the comment, we have added a Methods subsection titled "Motif selection and encoding into OL", where our motif selection process and definition are described. In brief, motifs were based on short conserved sequence segments obtained by Jussi Taipale's group, and provided to us prior to their publication as position weight matrices (DOI: 10.1038/nbt.4138). The Taipale motifs were created by an empirical assay that was designed to test protein activity in a broad swath of organisms. + +<|ref|>text<|/ref|><|det|>[[115, 359, 882, 391]]<|/det|> +It is not fully clear also how the 41 motifs were identified and if this was validated by using more than one TF data base. + +<|ref|>text<|/ref|><|det|>[[115, 398, 882, 447]]<|/det|> +In brief, the Taipale study focused on developing a protein activity assay specifically for DNA- binding TFs in cell and tissue extracts. Based on the study's data, we selected 41 enriched motifs from various organisms and tissue cells (e.g., yeast, fly, and mice tissue cells), according to the following criteria: + +<|ref|>text<|/ref|><|det|>[[143, 454, 882, 536]]<|/det|> +3. Different motif types: 8 organism-shared motifs, 5 mice tissue-shared motifs, 14 unshared motifs (unique to an organism), and 14 unknown motifs (with unknown regulatory function). +4. Known/unknown regulatory function: 27 of the selected motifs have known regulatory function, and those were anticipated to be the control motifs. Characterizing the regulatory function of the 14 unknown motifs in yeast was one of the stated goals of the study. + +<|ref|>text<|/ref|><|det|>[[115, 541, 882, 621]]<|/det|> +With regards to validation by an additional database, this was not done for two major reasons. First, we chose the motifs based on the Taipale group experimental findings to show that our approach can be used as a validation exercise to similar experimental findings. Second, 14 of the motifs were uncharacterized and thus would not appear in any database. In fact, our assay enabled us to characterize the regulatory function of 5 of the 14 unknown motifs, and thus validated our approach. + +<|ref|>text<|/ref|><|det|>[[115, 628, 882, 677]]<|/det|> +In figure 1e it is not fully clear why authors have not taken population 2 and re- bin it in order to capture more variants and potentially more interesting candidates with higher expression. It could have been beneficial to do so here. + +<|ref|>text<|/ref|><|det|>[[115, 684, 882, 813]]<|/det|> +We fully agree with the reviewer's sentiment. Unfortunately, in this case, hindsight is 20/20. At the time of the actual SORT- seq experiment, we chose not to re- bin as we were worried about how the increased sorting time may affect the re- binned yeast cells. In addition, in preliminary tests we did not expect to find many variants in this upper bin, and as a result we opted not to risk adding expression noise to the re- binned variants at the expanse of losing expression resolution. Since we were able to identify several strong up- regulating motifs, and train a machine- learning model which provided robust predictions for the unseen validation set, we are confident that whatever information was lost in our decision to not re- bin would not have affected our results or conclusions profoundly. + +<|ref|>text<|/ref|><|det|>[[115, 828, 861, 877]]<|/det|> +In figure 6, for CHO cell experiments, the authors mentioned they used a BFP for fluorescence normalisation. However, it is known from literature that resource competition can impact normalisation (see Frei et al, 2020. Jones et al, 2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 170]]<|/det|> +We thank the reviewer for this comment and would like to clarify. The use of BFP in the CHO and HeLa cell experiments was done to ensure that cells that were identified as “red” (i.e. mCherry expressing) were indeed transfected by a plasmid and not false positives. In addition, for each variant we compared the mean mCherry expression levels measured to the ratio of the mCherry and BFP channels. The results (see the revised Supplementary Figure 6e) show that BFP does not impact the results or their interpretation. + +<|ref|>text<|/ref|><|det|>[[115, 185, 882, 218]]<|/det|> +Can the authors shown the expression levels of the CHO library but with no normalisation and check if that improves the results? + +<|ref|>text<|/ref|><|det|>[[115, 225, 881, 258]]<|/det|> +We thank the reviewer for this comment. In the revised manuscript, all mammalian data (see new Figs. 6 and 7) is presented without normalization by BFP. + +<|ref|>text<|/ref|><|det|>[[115, 273, 673, 290]]<|/det|> +Caption of figure 6 should also more clearly describe what the figures shows. + +<|ref|>text<|/ref|><|det|>[[115, 296, 870, 329]]<|/det|> +We thank the reviewer for this comment. The captions for revised Fig. 6 and 7 provide additional details about the data presented as compared with the captions in the original manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 344, 866, 377]]<|/det|> +Minor comments pertain to several typos present in the manuscript like Eukaryotic that should be lower case; Figures are called at time with capital letter and at times with lower case. + +<|ref|>text<|/ref|><|det|>[[116, 384, 285, 400]]<|/det|> +We corrected the typos. + +<|ref|>text<|/ref|><|det|>[[115, 415, 772, 432]]<|/det|> +In conclusion I suggest the work to be published once these questions have been addressed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 228, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 298, 139]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 140, 835, 168]]<|/det|> +The authors addressed all major and minor comments listed in the first round of reviews. The manuscript is greatly improved – I would recommend publication. + +<|ref|>text<|/ref|><|det|>[[119, 210, 222, 222]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 225, 298, 237]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 238, 877, 350]]<|/det|> +First of all, I would like to thank the authors for addressing my comments and questions. I am generally satisfied with their revision but I would need to ask clarification on two points. Supplementary figure 6. The authors state that they are confirming that the expression of BFP does not impact mCherry expression. However, it is not very clear from the figure caption and response in the rebuttal, nor from the methods section, if they actually performed the experiments in presence and absence of competition or if they simply compared the mCherry signal alone with mCherry normalised on BFP but from the same experiment peformed in presence of competition. Can the authors clarify? + +<|ref|>text<|/ref|><|det|>[[118, 350, 860, 378]]<|/det|> +I would like also to ask the authors if they can comment on the large error bars present for HeLa cell expression experiments. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 200, 102]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[115, 103, 710, 131]]<|/det|> +First of all, I would like to thank the authors for addressing my comments and questions. I am generally satisfied with their revision but I would need to ask clarification on two points. + +<|ref|>text<|/ref|><|det|>[[115, 144, 882, 214]]<|/det|> +Reviewer comment: Supplementary figure 6. The authors state that they are confirming that the expression of BFP does not impact mCherry expression. However, it is not very clear from the figure caption and response in the rebuttal, nor from the methods section, if they actually performed the experiments in presence and absence of competition or if they simply compared the mCherry signal alone with mCherry normalised on BFP but from the same experiment performed in presence of competition. Can the authors clarify? + +<|ref|>text<|/ref|><|det|>[[115, 214, 882, 336]]<|/det|> +Author response: We thank the reviewer for the opportunity to clarify. We did not create a separate set of clones lacking the BFP gene. The plot presented in Supplementary Fig. 5e (note the renumbering of the supplementary figures) depicts the mCherry channel compared with the mCherry normalized by the BFP channel as measured on the same cells. The purpose of this plot is to show that normalizing by a synthetic house- keeping gene did not affect the trends observed in the data. We remind the reviewer that the utilization of this house- keeping gene was for us to ensure that sorted cells were transfected by the sURS plasmid. In our opinion an experiment lacking this form of "house- keeping" may not be as reliable, since "false- positive" cells may enter the analysis particularly for weakly expressing strains. We have added a statement regarding this experimental strategy to the Figure caption of supplementary figure 6 to alleviate any further confusion. + +<|ref|>text<|/ref|><|det|>[[115, 348, 881, 377]]<|/det|> +Reviewer comment: I would like also to ask the authors if they can comment on the large error bars present for HeLa cell expression experiments. + +<|ref|>text<|/ref|><|det|>[[115, 376, 882, 459]]<|/det|> +Author response: The error bar observed for the HeLa cells (i.e. Supplementary Fig. 5h) reflect the actual natural deviation in the expression data observed over the triplicates. The unusual variation may be due to the fact that the intensity of expression was not as strong as compared with the expression measured for the CHO cells, which may have led to increased noise. Fortunately, this expression level was sufficiently strong to differentiate between the different boosts enabled by the sURS variants, which correlated well with both the CHO cell measurements and the revised model. + +<--- Page Split ---> diff --git a/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..1d8eb8a819893f8b589ecbf537390ca5fb4c7675 --- /dev/null +++ b/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,430 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and 72 h FBS preservation.", + "footnote": [], + "bbox": [ + [ + 152, + 108, + 850, + 400 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. S31. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b-g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for 12 h.", + "footnote": [], + "bbox": [ + [ + 157, + 495, + 848, + 768 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S27. The emission wavelength analysis of the LED light.", + "footnote": [], + "bbox": [ + [ + 350, + 664, + 644, + 878 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Changes in the Supporting Information: Fig. S35. The anticancer activity ( \\(\\mathrm{IC}_{50}\\) , \\(\\mu \\mathrm{M}\\) ) of TBmA-Glu against GGT overexpressing OVCAR5 and 4T1, and GGT normally expressing HLF1 cells.", + "footnote": [], + "bbox": [ + [ + 150, + 357, + 866, + 696 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation (b) and 72h FBS preservation (c).", + "footnote": [], + "bbox": [ + [ + 150, + 492, + 864, + 793 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. S34. The HepG2 cells were imaged after incubation with TBmA-Glu (5 \\(\\mu \\mathrm{M}\\) ) for 12 hours. Subsequently, the cells were exposed to a \\(465\\mathrm{nm}\\) laser for 10 minutes, and images were captured every minute. \\(\\lambda_{\\mathrm{ex}} = 465\\mathrm{nm}\\) ; \\(\\lambda_{\\mathrm{em}} = 700\\pm 20\\mathrm{nm}\\) , Scale bar, \\(20\\mu \\mathrm{m}\\) .", + "footnote": [], + "bbox": [ + [ + 157, + 88, + 864, + 244 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Changes in the Supporting Information:", + "footnote": [], + "bbox": [ + [ + 152, + 359, + 866, + 639 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. S32. Fluorescence emission changes of DCFH (10 \\(\\mu \\mathrm{M}\\) ) in the presence of \\(5\\mu \\mathrm{M}\\) photosensitizers in DMSO-PBS \\((v:v = 1 / 99)\\) after irradiation \\((20\\mathrm{mW}\\cdot \\mathrm{cm}^{-2})\\) for different time. (a) TBmA aggregates in PBS, (b) TBmA aggregates produced in GGT catalytic reaction, DCHF, \\(\\lambda_{\\mathrm{ex}} = 488 \\mathrm{nm}\\) . (c) Plot of the relative emission intensity \\((II_{0})\\) of DCF (10 \\(\\mu \\mathrm{M}\\) ) in presence of TBmA (5 \\(\\mu \\mathrm{M}\\) ), TBmA aggregates produced in GGT reaction (5 \\(\\mu \\mathrm{M}\\) ) or Rose Bengal (RB, \\(5\\mu \\mathrm{M}\\) ) versus the irradiation \\((20\\mathrm{mW}\\cdot \\mathrm{cm}^{-2})\\) time, where \\(I_{0} = \\mathrm{PL}\\) intensity of DCFH in solutions with different water fraction \\((f_{\\mathrm{w}})\\) without light irradiation. \\(\\lambda_{\\mathrm{ex}} = 488 \\mathrm{nm}\\) .", + "footnote": [], + "bbox": [ + [ + 157, + 88, + 866, + 249 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. S33. The time-dependent uptake process of TBmA-Glu (a) / TBmA (b) in HepG2 cells. (c) The time-dependent uptake process of TBmA-Glu in LO2 cells. All the cells were incubated with \\(5\\mu \\mathrm{M}\\) TBmA-Glu / TBmA and imaged at the indicated time. \\(\\lambda_{\\mathrm{ex}} = 465 \\mathrm{nm}\\) ; \\(\\lambda_{\\mathrm{em}} = 700 \\pm 20 \\mathrm{nm}\\) , Scale bar, \\(20\\mu \\mathrm{m}\\) .", + "footnote": [], + "bbox": [ + [ + 160, + 87, + 866, + 585 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and 72h FBS preservation.", + "footnote": [], + "bbox": [], + "page_idx": 26 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Fig. S34. The HepG2 cells were imaged after incubation with TBmA-Glu (5 \\(\\mu \\mathrm{M}\\) ) for 12 hours. Subsequently, the cells were exposed to a \\(465 \\mathrm{nm}\\) laser for 10 minutes, and images were captured every minute. \\(\\lambda_{\\mathrm{ex}} = 465 \\mathrm{nm}\\) ; \\(\\lambda_{\\mathrm{em}} = 700 \\pm 20 \\mathrm{nm}\\) , Scale bar, \\(20 \\mu \\mathrm{m}\\) .", + "footnote": [], + "bbox": [ + [ + 155, + 490, + 864, + 648 + ] + ], + "page_idx": 27 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Fig. S39. Malondialdehyde (MDA) levels in HepG2 cells after treated with the TBmA-Glu (2 \\(\\mu \\mathrm{M}\\) ) for \\(12\\mathrm{h}\\) . Then, the cells were irradiated with a white laser array \\((12\\mathrm{J}\\cdot \\mathrm{cm}^{-2})\\) and the MDA levels were detected using a Lipid Peroxidation MDA Assay Kit. Data expressed as average \\(\\pm\\) standard error, \\(\\mathrm{n} = 3\\) . Statistical significance: P values, \\(\\mathrm{***P}< 0.001\\) , calculated with the Student's T-test.", + "footnote": [], + "bbox": [ + [ + 355, + 421, + 641, + 612 + ] + ], + "page_idx": 27 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Fig. S36. The effects of hypoxia (2% \\(O_2\\) ) and normoxia (20% \\(O_2\\) ) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells.", + "footnote": [], + "bbox": [ + [ + 333, + 83, + 660, + 303 + ] + ], + "page_idx": 28 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Fig. R1. The long-term stability of TBmA aggregates in \\(30\\%\\) BSA solutions.", + "footnote": [], + "bbox": [ + [ + 286, + 388, + 707, + 707 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_14.jpg", + "caption": "Fig. R2. The ROS generation capacity of \\(\\mathrm{TBmA}\\) aggregates after dispersed in \\(30\\%\\) BSA solution for \\(0\\mathrm{h}\\) (a) and \\(72\\mathrm{h}\\) (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity \\((I / I_0)\\) of DC versus the irradiation \\((20\\mathrm{mW}\\cdot \\mathrm{cm}^{-2})\\) time, where \\(I_0 = \\mathrm{PL}\\) intensity of DCFH in solutions without light irradiation.", + "footnote": [], + "bbox": [ + [ + 160, + 87, + 845, + 250 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_15.jpg", + "caption": "Fig. R3 The impact of white light and \\(450\\mathrm{nm}\\) light exposure \\((12\\mathrm{J / cm^2})\\) on the cellular viability of HepG2 cells.", + "footnote": [], + "bbox": [ + [ + 365, + 141, + 627, + 302 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_16.jpg", + "caption": "Fig. R4 Scheme of the photochemical reactions for type I and type II PDT. \\(^{9}\\)", + "footnote": [], + "bbox": [ + [ + 147, + 195, + 788, + 375 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_17.jpg", + "caption": "Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \\(10 \\mu \\mathrm{M}\\) ) in the presence of \\(5 \\mu \\mathrm{M}\\) photosensitizers in DMSO-PBS \\((v:v = 1:99)\\) after irradiation (20 \\(\\mathrm{mW}\\cdot \\mathrm{cm}^{-2}\\) ) for a different time under anoxia conditions. (b) \\(\\mathrm{TBmA}\\) , (c) Rose Bengal (RB). DCHF, \\(\\lambda_{\\mathrm{ex}} = 488 \\mathrm{nm}\\) .", + "footnote": [], + "bbox": [ + [ + 155, + 426, + 863, + 595 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_18.jpg", + "caption": "Fig. R6 Schematic illustration of the \\(^{1}\\mathrm{O}_{2}\\) generation mechanisms by conventional PDT agents (left) and GQDs (right).", + "footnote": [], + "bbox": [ + [ + 198, + 621, + 789, + 821 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_19.jpg", + "caption": "Changes in the Supporting Information:", + "footnote": [], + "bbox": [ + [ + 150, + 599, + 850, + 891 + ] + ], + "page_idx": 38 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_20.jpg", + "caption": "Fig. S31. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b-g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for \\(12\\mathrm{h}\\) .", + "footnote": [], + "bbox": [ + [ + 156, + 153, + 850, + 428 + ] + ], + "page_idx": 44 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_21.jpg", + "caption": "Fig. S27. The emission wavelength analysis of the LED light.", + "footnote": [], + "bbox": [ + [ + 348, + 621, + 647, + 834 + ] + ], + "page_idx": 45 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_22.jpg", + "caption": "Fig. S36. The effects of hypoxia (2% O2) and normoxia (20% O2) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells.", + "footnote": [], + "bbox": [ + [ + 333, + 340, + 660, + 562 + ] + ], + "page_idx": 47 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_23.jpg", + "caption": "Fig. R1. The long-term stability of TBmA aggregates in \\(30\\%\\) BSA solutions.", + "footnote": [], + "bbox": [ + [ + 286, + 92, + 707, + 410 + ] + ], + "page_idx": 52 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_24.jpg", + "caption": "Fig. R2. The ROS generation capacity of TBmA aggregates after dispersed in \\(30\\%\\) BSA solution for \\(0 \\mathrm{~h}\\) (a) and \\(72 \\mathrm{~h}\\) (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity \\((I / I_0)\\) of DC versus the irradiation \\((20 \\mathrm{mW} \\cdot \\mathrm{cm}^{-2})\\) time, where \\(I_0 = \\mathrm{PL}\\) intensity of DCFH in solutions without light irradiation.", + "footnote": [], + "bbox": [ + [ + 156, + 456, + 848, + 620 + ] + ], + "page_idx": 54 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_25.jpg", + "caption": "Fig. R3 The impact of white light and \\(450 \\mathrm{nm}\\) light exposure ( \\(12 \\mathrm{J / cm^2}\\) ) on the cellular viability of HepG2 cells.", + "footnote": [], + "bbox": [ + [ + 366, + 554, + 627, + 714 + ] + ], + "page_idx": 54 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_26.jpg", + "caption": "Fig. R4 Scheme of the photochemical reactions for type I and type II PDT. \\(^{9}\\)", + "footnote": [], + "bbox": [ + [ + 148, + 675, + 789, + 857 + ] + ], + "page_idx": 56 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_27.jpg", + "caption": "Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \\(10~\\mu \\mathrm{M}\\) ) in the presence of \\(5~\\mu \\mathrm{M}\\) photosensitizers in DMSO-PBS \\((v:v = 1:99)\\) after irradiation ( \\(20\\mathrm{mW}\\cdot \\mathrm{cm}^{-2}\\) ) for a different time under anoxia conditions. (b) \\(\\mathrm{TBmA}\\) , (c) Rose Bengal (RB). DCHF, \\(\\lambda_{\\mathrm{ex}} = 488 \\mathrm{nm}\\) .", + "footnote": [], + "bbox": [ + [ + 155, + 93, + 864, + 262 + ] + ], + "page_idx": 58 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_28.jpg", + "caption": "Fig. R6 Schematic illustration of the \\(^{1}\\mathrm{O}_{2}\\) generation mechanisms by conventional PDT agents (left) and GQDs (right).", + "footnote": [], + "bbox": [ + [ + 199, + 345, + 789, + 544 + ] + ], + "page_idx": 59 + } +] \ No newline at end of file diff --git a/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9738eadac80afd544709487eec4af9e686b091db --- /dev/null +++ b/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,1294 @@ + +# nature portfolio + +# Peer Review File + +# Enzymatically Catalyzed Molecular Aggregation + +Corresponding Author: Professor Ben Zhong Tang + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Attachments originally included by the reviewers as part of their assessment can be found at the end of this file. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". + +This referee finds important design flaws and problems with the implementation of the work. + +Here are the major issues: + +Problem with Aggregates: + +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +Excitation wavelength: + +The absorption peak of the monomeric compounds and the aggregates in this work is around 450 nm. This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +Confusion about the Type- I and Type- II PDT: + +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; it is not and it is not easy to separate these two processes (I/II). + +Enhancement of emission "AND" PDT efficiency. + +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +Reviewer #2 + +(Remarks to the Author) + +Tang and colleagues reported a \(\gamma\) - glutamyl transferase (GGT) activatable aggregation- induced emission photosensitizer (AIE- PS) named TBmA- Glu. TBmA- Glu is designed to specifically target and aggregate cancer cells through the catalytic action of tumor- overexpression GGT. Selective tumor cell aggregation not only enhances AIE- PS emission and + +<--- Page Split ---> + +photodynamic activity but also induces ferroptosis in cancer cells by depleting GSH and promoting lipid peroxidation. Both in vitro cell assays and in vivo animal models were used to validate the phototoxicity and antitumor effects of TBmA- Glu, providing a comprehensive assessment of its potential as a therapeutic agent. The aggregation strategies in this paper allow a controlled release of the photodynamic effect, which is critical for therapies such as PDT. AIE- PS remains dormant until it reaches the cancerous environment where GGT is present, ensuring minimal impact on healthy cells and maximizing the therapeutic effect on cancer cells. This study highlights the significance of targeting activation of AIE- PSs for targeting and enhanced cancer photodynamic therapy. It is also a sophisticated strategy for targeted delivery and activation of a photodynamic therapeutic agent for disease. I suggest this article be published with minor revisions. + +1. The authors claimed that TBmA-Glu could be activated by GGT. Is there evidence to suggest that TBmA-Glu could be effective against other types of cancer that overexpress GGT, or is its application currently limited to the cancer types studied? + +2. How photostable is TBmA-Glu under the conditions used for PDT, and does its aggregation state affect its photostability? + +3. The author claimed the aggregate size has a great impression on the PDT efficiency of AIE-PSs, What are the typical sizes and shapes of the TBmA-Glu aggregates formed in the presence of GGT? How do these properties affect the emission properties and PDT efficacy? + +4. Can aggregated TBmA be expelled from cancer cells via exocytosis, potentially reducing its therapeutic efficacy? Long-term (48 h) cellular imaging results should be provided by the author. + +5. The abbreviations, such as DCF, DCFH-DA, HPF, ABDA, CLSM, et al., should be defined at the first time they are used. + +Reviewer #3 + +(Remarks to the Author) + +This work present a novel approach to targeted cancer therapy by leveraging the tumor- overexpressed enzyme \(\gamma\) - Glutamyl Transferase (GGT) to induce aggregation of an aggregation- induced emission photosensitizer (AIE- PS), TBmA- Glu. This innovative strategy not only enhances the photosensitivity of the AIE- PS but also results in the degradation of GGT and the accumulation of lipid peroxides, leading to cancer cell ferroptosis. The study is significant for its potential to advance targeted photodynamic therapy (PDT) and the development of smart therapeutics that exploit enzyme activity for controlled molecular aggregation within cancer cells. The authors have demonstrated a clear understanding of the complex interactions between molecular aggregation and biological environments, and the manuscript is well- structured, presenting a logical flow of information from synthesis and characterization to in vivo efficacy. The results are compelling, showing the selective activation of TBmA- Glu by GGT, its enhanced photodynamic activity, and the subsequent therapeutic effects on cancer cells. The manuscript is well- written and provides a solid foundation for further research in the field of nanomedicine and targeted drug delivery. I recommend publication following minor modifications, my concerns are outlined below: + +1. The author could incorporate a concise, visual representation of key discoveries and TBmA-Glu's proposed mechanism of action through a mechanistic cartoon or schematic. + +2. The stability of the aggregates of TBmA, especially the photostability of it in physiological conditions should be discussed. + +3. The author acclaimed the lipid peroxides (LPOs) resulting from the photodynamic process of activated AIE-PS induce the ferroptosis of cancer cells, the changes in the level of LPOs in cancer cells after photodynamic therapy should be quantified. + +4. Detailed experimental procedures for minimally invasive PDT should be provided. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Reviewer 1 responses to the authors' comments is highlighted in red. + +REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". This referee finds important design flaws and problems with the implementation of the work. Response: We thank the reviewer for the constructive comments on our paper. In this manuscript, we actually did not intend to compare the Type I and Type II PDT processes, and the efficiency of type I and type II photosensitizers is not the key point of this work. We just want to present the objective performance of the developed photosensitizers based on their ROS generation capability. As clearly stated in the manuscript: "It was found that TBmA and TBpA produced significantly higher ROS compared to TBmA- Glu and TBpA- Glu, even surpassing the commercial photosensitizer, Rose Bengal (RB). Moreover, TBmA was identified as the most potent photosensitizer among the four compounds. Further analysis revealed + +<--- Page Split ---> + +that TBmA and TBpA functioned as strong type I photosensitizers (Fig. 1c and Fig. S25), while TBmA- Glu and TBpA- Glu acted as very weak type II photosensitizers (Fig. 1c and Fig. S26)." + +\*\*\*The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +251. "only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA- Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." + +Here are the major issues: + +Problem with Aggregates: + +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +Response and revision: Thank you for your thoughtful comments regarding AIE compounds. We appreciate your concerns and would like to address them point by point: + +(i) Stability and standardization: we acknowledge that stability is crucial for bio-application. Our recent studies have shown promising results regarding the stability of TBmA aggregates in high-protein environments, specifically: (a) Long-term stability: TBmA aggregates showed no significant degradation when dispersed in FBS for 72 hours (Fig. S28a and S28c). \*\*\* Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +(ii) (b) Photostability: The aggregates remained stable under continuous light irradiation for 30 minutes (Fig. S28a and S28b). These findings collectively highlight the exceptional stability exhibited by TBmA. These findings demonstrate the exceptional stability of TBmA aggregates in biologically relevant conditions. + +Moreover, numerous AIEgens, including small molecules or AIE nanoparticles, have been extensively reported for their long- term monitoring and therapeutic applications.1, 2, 3 These pieces of evidence underscore the remarkable stability of AIEgens, making them highly promising candidates for therapeutic applications. + +(iii) Aggregate structure: To address concerns about ill- defined aggregate structures, we extensively investigated the aggregate size of TBmA using Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). The results suggest that the TBmA forms spherical particles with 140 nm in 99% PBS and 150 nm diameter after the GGT catalysis reaction (12 h, Fig. S31). These results indicate that TBmA consistently forms nanoparticles of definite shape and size in aqueous environments, regardless of the specific conditions. Numerous works have been reported to show the definite shape and size, as well as the excellent stability and biocompatibility of the AIE aggregates.4, 5, 6 + +\*\*\* References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +(iv) A comparative analysis of small molecular drugs and AIE materials: Although molecular drugs and traditional photosensitizers have their advantages, AIE compounds offer unique benefits such as enhanced emission upon aggregation, responsiveness to stimuli, and multifunctional potential. Revealing reports increasingly indicate that small molecular photosensitizers, such as CE6, exhibit low solubility and undergo aggregation in solution, resulting in the deactivation of their photosensitizing activity and hindering their biopallcation.7, 8, 9, 10 We believe that AIE compounds can serve as complementary agents, rather than substitutes, for small molecule drugs. Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring. 4, 11, 12, 13 + +We believe that AIE compounds, including TBmA- Glu, offer valuable and unique properties that complement existing molecular drugs and photosensitizers. While challenges remain, the growing body of research on AIE materials suggests significant potential for advancing biomedical imaging and therapeutic applications. We appreciate the reviewer's perspective and believe that continued research and development in this field will address current limitations and unlock new possibilities in biomedical science. + +\*\*\* While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +Changes in the Revised Manuscript: + +Moreover, the TBmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS (fetal bovine serum) solution for 72 h or light irradiated for 30 min. Changes in the Supporting Information: + +Fig. S28. (a) The average hydrodynamic diameter (Z- average) of TBmA aggregates measured by Dynamic Light Scattering + +<--- Page Split ---> + +(DLS). The distribution of TBM a aggregates during 30 min light irradiation and 72 h FBS preservation. + +Fig. S31. (a) The average hydrodynamic diameter (Z- average) of TBM a aggregates produced in GGT catalytic reaction measured by DLS. (b- g) Distribution of TBM a aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBM a aggregates formed after the GGT catalytic reaction for 12 h. + +## References + +1. Zuo J, et al. Long-term spatiotemporal and highly specific imaging of the plasma membrane of diverse plant cells using a near-infrared AIE probe. Angew. Chem. Int. Ed. 14, 2139-2148 (2023). +2. Wang Z, et al. Long-term fluorescent cellular tracing by the aggregates of aie bioconjugates. J. Am. Chem. Soc. 135, 8238-8245 (2013). +3. Li K, et al. Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing. Sci. Rep. 3, 1150 (2013). +4. Wang J, et al. Nanolab in a cell: Crystallization-induced in situ self-assembly for cancer theranostic amplification. J. Am. Chem. Soc. 144, 14388-14395 (2022). +5. Li Y, et al. Trojan Horse-Like Nano-AIE Aggregates Based on Homologous Targeting Strategy and Their Photodynamic Therapy in Anticancer Application. Adv. Sci. 8, 2102561 (2021). +6. Yan Z, et al. Preparation of ultrasmall AIE nanoparticles with tunable molecular packing via freeze assembly. Nano Lett. 23, 1030-1035 (2023). +7. Li Y, et al. Near-infrared light and redox dual-activatable nanosystems for synergistically cascaded cancer phototherapy with reduced skin photosensitization. Biomaterials 288, 121700 (2022). +8. Tian S, He J, Lyu D, Li S, Xu Q-H. Aggregation enhanced photocativity of photosensitizer conjugated metal nanoparticles for multimodal imaging and synergistic phototherapy below skin tolerance threshold. Nano Today 45, 101534 (2022). +9. Wang H, Xue K-F, Yang Y, Hu H, Xu J-F, Zhang X. In Situ Hypoxia-Induced Supramolecular Perylene Diimide Radical Anions in Tumors for Photothermal Therapy with Improved Specificity. J. Am. Chem. Soc. 144, 2360-2367 (2022). +10. Li X, et al. Nanostructured Phthalocyanine Assemblies with Protein-Driven Switchable Photoactivities for Biophotonic Imaging and Therapy. J. Am. Chem. Soc. 139, 10880-10886 (2017). +11. Chen C, Zhang X, Gao Z, Feng G, Ding D. Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection. Nat. Protoc., in press (2024). +12. Liu Z, Wang Q, Zhu Z, Liu M, Zhao X, Zhu W-H. AIE-based nanoaggregate tracker: high-fidelity visualization of lysosomal movement and drug-escaping processes. Chem. Sci. 11, 12755-12763 (2020). +13. Yu Y, et al. Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking. Adv. Mater. 23, 3298-3302 (2011). + +## Excitation wavelength: + +The absorption peak of the monomeric compounds and the aggregates in this work is around 450 nm. This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +Response and revision: We appreciate the reviewer's concern regarding light penetration and the effects of our light source. Our analysis of the white LED light shows predominant peaks at 450 and 570 nm, with no detectable UV peak, which could address the concerns of the reviewers about unintended UV- induced effects (Fig. S27). Furthermore, all anticancer IC50 values of tested compounds were detected using the MTT assays, and no significant effect on cell viability was detected in the control group after exposure to LED irradiation. MTT assays and control experiments demonstrate that the observed cell death is due to TBMa- Glu's photodynamic properties, not the LED light itself. + +\*\*\* May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to 450 nm peak. There are literature reports of blue (450 nm) light causing cellular damage. + +Depth of Penetration in Tissues: While it is true that the penetration depth of light at 450 nm is limited, this wavelength is still within the range where some penetration can occur in biological tissues. The actual penetration depth can be influenced by factors such as tissue type, pigmentation, and the optical properties of the tissue. Furthermore, we employed a minimally invasive approach for PDT to optimize the efficiency of photodynamic therapy and minimize the impact of light penetration. + +\*\*\* One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as 450 nm is less than 1 mm, which is significantly less than needed for an effective "photo"- driven process. + +Changes in the Revised Manuscript: The generation of total ROS generation (2',7'- dichlorodihydrofroourescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10- anthracenediy1- bis(methylene)dinamionic Acid, ABDA) by photosensitizers (5 \(\mu \mathrm{M}\) ) after white LED light (predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation (20 mW- cm- 2) for 15 min using the corresponding ROS indicator in PBS/DMSO (v/v = 99:1). DCF, \(\lambda \mathrm{ex} = 488 \mathrm{nm}\) . Changes in the Supporting Information: + +Fig. S27. The emission wavelength analysis of the LED light. + +<--- Page Split ---> + +Confusion about the Type- I and Type- II PDT: + +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; and it is not easy to separate these two processes (I/II). + +Response: We appreciate the reviewer's insightful comments on the Type- I and Type- II PDT processes. We agree that PDT often involves a combination of both processes and that ROS species can undergo interconversion through various enzymatic processes in vivo. Our study focused on characterizing the predominant mechanism of TBM a under specific conditions, not comparing the superiority of Type- I vs Type- II processes. We found that the cleaved TBM- Glu (TBM a) primarily exerts its anticancer effects through the type I PDT process. And aligning with this finding, we observed the oxygen independence of TBM a's photodynamic activity in the hypoxia condition, which is potentially advantageous in hypoxic tumor environments. + +We acknowledge the complexity of PDT processes in biological systems, which may reflect both directly generated species and enzymatic interconversions. However, the ROS we detected in cells are coordinating with the results we detected in vitro, which validates the validity of our conclusion. + +\*\*\* First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919.) So, instead of 1 O2 % hypoxia, if the authors were to switch to 0.5 % O2 hypoxia, or anoxia, the effectiveness would be much more different. + +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Esbelsen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide (N3- ) is a singlet oxygen quencher + +Enhancement of emission "AND" PDT efficiency. + +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +Response: We appreciate the reviewer's insights regarding the competitive nature of fluorescence and reactive oxygen species (ROS) generation in AIE- PDT systems. While both processes utilize energy from the excited state, our findings on the simultaneous enhancement of aggregate luminescence and photodynamic activity are not contradictory. Here is some reported literature. + +(i) Aggregation-induced intermolecular intersystem crossing (AI-ISC): Jiang et al. proposed a new mechanism called aggregation-induced intersystem crossing (AI-ISC) to understand the effect of aggregation on increasing ISC efficiency.1, 2 According to the AI-ISC theory, more excitonic couplings cause excited-state energy splitting and overlapping of singlet and triplet in aggregate. The energy splitting and overlapping significantly produce many ISC channels with very small \(\Delta \mathrm{EST}\) in aggregates, which is available for ISC processes. Therefore, the formation of aggregates can facilitate the production of triplet excitons. In addition to emitting phosphorescent radiation, these triplet excitons can also undergo a non-radiative pathway known as the aggregation-enhanced photodynamic effect to return to their ground state. 3, 4, 5 + +\*\*\* Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +(ii) Restriction of intramolecular motion (RIM): The aggregation of AIE molecules results in a restriction of intramolecular rotations and vibrations, effectively suppressing molecular motions, which is also beneficial for the ISC process.6, 7 All the evidence highlights the potential of AIE materials in PDT. The aggregation-induced changes in the molecular environment can optimize both the imaging and therapeutic aspects of the treatment.8, 9, 10 \*\*\*Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +## References: + +1. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +2. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +3. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). +4. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). +5. Ji C, Lai L, Li P, Wu Z, Cheng W, Yin M. Organic dye assemblies with aggregation-induced photophysical changes and their bio-applications. Aggregate 2, e39 (2021). +6. Kwok RTK, Leung CWT, Lam JWY, Tang BZ. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 44, 4228-4238 (2015). +7. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +8. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +9. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). + +<--- Page Split ---> + +10. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +## Reviewer #2 + +(Remarks to the Author) The authors have addressed all the concerns in the revisions. And the manuscript is ready to be published. + +## Reviewer #3 + +(Remarks to the Author) The paper's focus is the enzymatically catalyzed molecular aggregation for improving the response and PDT treatment. The paper has been revised accordingly, and ready for publication. + +Version 2: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) Response + +General opinion + +The present manuscript claims to achieve a better targeting of a proposed photosensitizer (PS) which can activated by GGT and be excited at short wavelengths. + +Also, activated (aggregate structure) may have a better cytotoxic effect, compared its non-activated form, which is another example of activated- PS + +There have been countless photosensitizers which can be targeted one way of or another. Many reviews exist about activatable photosensitizers. Some enzymatically, some by hypoxia, by higher H2O2 or GSH concentrations, or acidic pH. + +The main, may be the only reason why PDT did not develop significantly since 70's is that fact that light, even at the socalled "therapeutic window" does not go through tissues. And of course, there is no real justification for a 450 nm chromophore to be proposed as a novelty. There are very specific, niche cases, where a single cell layer penetration may be useful. But citing these, is missing the point of all PDT- work. + +Type- I processes being less oxygen dependent has been proposed without real evidence. The new data provided by the authors is also not a fair comparison (see below). + +Thus the manuscript does not bring any novelty to the field. The requirement for aggregation, if anything, complicates the picture very unnecessarily. + +Reviewer #1 (Remarks to the Author): + +Q1: The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +251. "only marginal variation was observed in the phototoxicity of TBmA-Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA-Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." Response and revision: We appreciate the valuable suggestions provided by the reviewer. To enhance the accuracy of our study, we conducted additional experiments using Rose Bengal (RB), a well-established type II photosensitizer1, as a control. These experiments revealed that RB's photodynamic efficiency decreased significantly under hypoxia conditions (2% O2) compared to normoxia conditions, while TBmA maintained relatively consistent activity across both environments (Fig. R1). + +To discuss this result more accurately, we have revised our manuscript by replacing the statement "This suggests that oxygen content has negligible influence on its photodynamic activity." with "This suggests that TBmA exhibits tolerance towards hypoxic conditions." + +<--- Page Split ---> + +Fig. S36. The effects of hypoxia (2% O2) and normoxia (20% O2) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells. + +Revised in manuscript: + +Additionally, only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d), while the type- II PS, RB, showed a significant decrease in photodynamic efficiency under hypoxia conditions (2% O2) compared to normoxia conditions (Fig. S36). This suggests that TBmA exhibits tolerance towards hypoxic conditions. + +## Reference: + +1. Fischer BB, Krieger-Liszkay A, Eggen RIL. Oxidative stress induced by the photosensitizers neutral red (type I) or rose bengal (type II) in the light causes different molecular responses in Chlamydomonas reinhardtii. Plant Sci. 168, 747-759 (2005). + +response + ++++ Light source in Fig S36 was not given, if it is white LED, it is not a fair comparison, because LED emission profile fits TBmA/aggregate better. + +Q2: Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +Response: We appreciate the reviewer's insightful comments regarding the nature of supramolecular aggregation and the potential for de-aggregation in biological media. We would like to clarify several key points that address these concerns. + +Firstly, it's crucial to emphasize that TBmA- Glu is a water- soluble prodrug. The aggregation process only occurs after the Glu moiety is cleaved by GGT in HepG2 cells. This design ensures that TBmA- Glu remains soluble in the blood, avoiding premature aggregation. Aggregation is triggered specifically in the intracellular environment of GGT- overexpressing tumor cells. + +We acknowledge that FBS is not an ideal model for the intracellular environment. To address this issue, we further conducted stability studies using a 30% BSA (Bovine Serum Albumin) solution, which is a better model for the protein- rich intracellular milieu. The intracellular protein concentration typically ranges from 50- 400 mg/mL, and our 30% BSA solution ( \(\sim 300 \text{mg / mL}\) ) falls within this range. TBmA aggregates showed remarkable stability in this environment, with no significant degradation observed over 72 hours (Fig. R1). + +We also agree that pharmacokinetics studies would be valuable. However, our system presents unique challenges for such studies, as the aggregates form intracellularly rather than in circulation. Collecting and analyzing intracellular aggregates from tumor sections poses significant technical difficulties. Our approach using a highly concentrated protein solution provides valuable insights into aggregate stability in a physiologically relevant environment. + +Importantly, beyond structural stability, we have observed that the aggregates maintain their photodynamic properties in the 30% BSA solution for 72 h (Fig. R2). This functional stability is crucial for the compound's theranostic applications. + +Fig. R1. The long- term stability of TBmA aggregates in 30% BSA solutions. + +Fig. R2. The ROS generation capacity of TBmA aggregates after dispersed in 30% BSA solution for 0 h (a) and 72 h (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity (I/I0) of DC versus the irradiation (20 mW · cm- 2) time, where I0 = PL intensity of DCFH in solutions without light irradiation. + +Q3: References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +Response: We thank the reviewer for the critical feedback. The unique photophysical properties of AIE compounds stem from the restriction of intramolecular motion (RIM) mechanism, where aggregation limits molecular rotations and vibrations, leading to enhanced fluorescence. Therefore, the fluorescence behavior of AIE materials does provide valuable insights into their molecular state and environment. + +This interpretation is supported by several factors. First of all, TBmA- Glu is engineered to aggregate specifically in response to GGT activity, which is overexpressed in certain tumor cells. This targeted approach minimizes premature aggregation in circulation. Secondly, the crowded, protein- rich cytoplasmic environment of tumor cells likely provides conditions that favor aggregate stability once formed. Additionally, we observed that the photosensitivity of TBmA was maintained in our 30% BSA studies, suggesting a preservation of the aggregate structure. + +Q4: While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to + +<--- Page Split ---> + +avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +Response: We appreciate the reviewer's thoughtful comments regarding the therapeutic relevance of AIE compounds and the importance of careful characterization of their behavior in biological systems. + +Regarding the stability and behavior of TBmA, we emphasize that TBmA- Glu is designed as a water- soluble prodrug that only forms aggregates within tumor cells following enzymatic reaction. This targeted approach minimizes potential issues related to premature aggregation or size changes in circulation. Furthermore, we have demonstrated the stability of TBmA aggregates in a \(30\%\) BSA solution for 72 hours, providing initial evidence of their potential stability in protein- rich environments. + +About "personalized medicine and real- time treatment monitoring." in the previous response letter: The full sentence is "Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring." We agree that such terminology should be used judiciously, especially in early- stage research, however, our intention here is to highlight the potential of AIE materials to contribute to these fields in the future, rather than to claim immediate clinical applicability. The unique properties of AIE materials, including their AIE and potential for stimuli- responsive behavior, do offer intriguing possibilities for both imaging and therapeutic applications. However, we agree that rigorous investigation is needed to establish their efficacy and safety for PDT or other therapeutic schemes. Moving forward, we will focus on providing concrete evidence for the specific advantages of AIE compounds in relevant biological contexts, rather than speculating on broad future applications. We believe this approach will better serve the scientific community and responsibly advance the field. + +Q5: May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to 450 nm peak. There are literature reports of blue (450 nm) light causing cellular damage. + +Response: We acknowledge that there are indeed literature reports of blue light (450 nm) causing cellular damage. This is an important consideration in photodynamic therapy and other light- based treatments. However, we would like to emphasize that the biological effects of light exposure are highly dependent on both wavelength and dosage. + +In our experiments, we carefully controlled the light dosage to minimize potential phototoxicity while maintaining therapeutic efficacy. Under the experimental conditions described in our manuscript, we did not observe any significant effects on cell viability following LED light irradiation (Fig. R3). + +To address the reviewer's concern, we also conducted a blue light irradiation (450 nm, 12 J/cm2) PDT assay. In this experiment, we also found no significant effect on cellular viability. This suggests that at the dosages used in our study, the blue light alone does not cause substantial cellular damage. + +However, we agree that the potential for phototoxicity is an important consideration in developing light- based therapies. In future studies, we plan to conduct a more comprehensive dose- response analysis to determine the threshold at which blue light exposure may begin to affect cell viability. We also intend to investigate the potential long- term effects of repeated light exposure and compare the effects of our AIE- based approach with traditional photosensitizers at equivalent light doses. + +Fig. R3 The impact of white light and 450 nm light exposure (12 J/cm2) on the cellular viability of HepG2 cells. + +Q6: One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as 450 nm is less than 1 mm, which is significantly less than needed for an effective "photo"- driven process. + +Response: It is correct that the typical penetration depth of 450 nm light is less than 1 mm in tissue, which is indeed less than ideal for treating deep- seated tumors. However, we would like to highlight several important considerations: First, though direct light penetration is restricted, the effective depth of PDT damage may increase due to light reflection and scattering within tissues. This occurrence can expand the scope of the photodynamic impact beyond the initial penetration depth. + +Secondly, several clinical scenarios exist where shallow light penetration is sufficient or even advantageous. For instance, PDT with blue light excitation could be particularly useful for superficial skin cancers and precancerous lesions, intraoperative treatment of residual tumor cells after surgical resection, treatment of early- stage mucosal cancers in inaccessible areas (e.g., oral cavity, bladder), and endoscopic applications for gastrointestinal tumors. Finally, numerous published studies demonstrate the successful use of 450 nm light and white light (including the blue spectrum) for PDT when the photosensitizers have maximum absorption around 450 nm. 2, 3, 4, 5, 6, 7 Nevertheless, we fully agree that blue light's limited tissue penetration restricts the broader applicability of our current system for treating deep- seated tumors. Given this limitation, our future research directions include exploring two- photon excitation to achieve deeper tissue penetration, investigating upconversion nanoparticles to convert longer- wavelength light to blue light locally, and developing new AIE photosensitizers with red- shifted absorption for improved tissue penetration. We believe that addressing these challenges will expand the potential applications of our AIE- based PDT system while utilizing its unique properties. + +## References: + +2. Fan L, et al. A Bioactive Photosensitizer for Hypoxia-Tolerant Molecular Targeting-Photo-Immunotherapy of Malignant Tumor. Adv. Funct. Mater. 34, 2313755 (2023). +3. Li X, et al. A novel 450-nm laser-mediated sinoporphyrin sodium-based photodynamic therapy induces autophagic cell death in gastric cancer through regulation of the ROS/PI3K/Akt/mTOR signaling pathway. BMC Med. 20, 475 (2022). +4. Mei Y, et al. A Novel Photosensitizer Based 450-nm Blue Laser-Mediated Photodynamic Therapy Induces Apoptosis in Colorectal Cancer - in Vitro and in Vivo Study. Front. Biosci. (Landmark Ed) 29, 199 (2024). + +<--- Page Split ---> + +5. Chen Y, et al. Photoactivatable metal organic framework for synergistic ferroptosis and photodynamic therapy using 450 nm laser. Chem. Eng. J. 454, 140438 (2023). +6. Sun P, et al. A water-soluble phosphorescent conjugated polymer brush for tumor-targeted photodynamic therapy. Polym. Chem. 8, 5836-5844 (2017). +7. An J, et al. An unexpected strategy to alleviate hypoxia limitation of photodynamic therapy by biotinylation of photosensitizers. Nat. Commun. 13, 2225 (2022). + +Q7: First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to 0.5 % O2 hypoxia, or anoxia, the effectiveness would be much more different. + +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Esbelsen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide (N3- ) is a singlet oxygen quencher. + +Response and revision: We agree with the reviewer that oxygen plays a pivotal role in the Type I and Type II PDT processes. However, from the PDT mechanism, we know that the type I photosensitizers could directly transfer electrons to the substrate, forming a radical cation or neutral radical. These radicals could immediately react with O2 or H2O to generate hydrogen peroxide (H2O2), hydroxyl radicals (- OH), or superoxide anions (- O2- ) (Fig. R4).1, 2 + +We have tried but could not finish the antitumor PDT assays in the anaerobic conditions, because the anoxia condition resulted in death of the tumor cells (Fig. R5a). So, we re- evaluated the photodynamic efficiency of TBMa and RB using a deoxidized PBS solution. The results showed that TBMa could also induce the oxidation of DFCH under the anoxia condition (Fig. R5b), while the photodynamic efficiency of RB showed significant degradation. Hence, type- I photosensitizers exhibit relatively higher tolerance towards oxygen concentrations, which implies that, even under low oxygen conditions, they can still engage in substrate reactions through electron transfer. + +We are sorry for the mistake in the figure legend in Figure 4b. "Esbelsen" has been revised as "Trolox." However, it should be noted that Trolox is not only a 1O2 scavenger but also a scavenger of peroxy and alkoxy groups.3 The type- I designation is mainly based on the ROS species we detected in vitro (Fig. R5c). + +Fig. R4 Scheme of the photochemical reactions for type I and type II PDT.9 + +Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \(10\mu \mathrm{M}\) ) in the presence of \(5\mu \mathrm{M}\) photosensitizers in DMSO- PBS ( \(\mathrm{v}:\mathrm{v} = 1:99\) ) after irradiation (20 mW·cm- 2) for a different time under anoxia conditions. (b) TBMa, (c) Rose Bengal (RB). DCHF, \(\lambda \mathrm{ex} = 488 \mathrm{nm}\) . + +Revised in manuscript: Trolox: \(50\mu \mathrm{M}\) (ROO- scavenger and 1O2 scavenger); D- mannitol: \(50\mathrm{mM}\) (- OH scavenger); Tiron: \(10\mathrm{mM}\) (- O2- scavenger); NaN3: \(5\mathrm{mM}\) (1O2 scavenger) + +References: + +1. Zhao X, Liu J, Fan J, Chao H, Peng X. Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application. Chem. Soc. Rev. 50, 4185-4219 (2021). +2. Fan W, Huang P, Chen X. Overcoming the Achilles' heel of photodynamic therapy. Chem. Soc. Rev. 45, 6488-6519 (2016). +3. Lúcio M, Nunes C, Gaspar D, Ferreira H, Lima JLFC, Reis S. Antioxidant Activity of Vitamin E and Trolox: Understanding of the Factors that Govern Lipid Peroxidation Studies In Vitro. Food Biophys. 4, 312-320 (2009). + +\(+++0.5\) or \(1\%\) hypoxia may be better. + +Q8: Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +Response: Indeed, the total quantum yield of all radiative and non- radiative processes cannot exceed 1. However, the energy consumption in no radiative processes contains both the energy for ISC processes and the molecular motion as well. Molecular aggregation could induce the restriction of intramolecular motions (RIM) and, as a result, reduce energy loss through non- radiative molecular motion, potentially increasing the energy available for emission and ISC processes. So, the energy efficiency of both emission and ISC can be enhanced in aggregated structure due to RIM. + +However, in specific cases, such as the graphene quantum dots reported by Zhang et al., the apparent quantum yield could be larger than 1.1 This occurs when the energy gaps between \(\Delta \mathrm{EST}\) and \(\Delta \mathrm{ETG}\) (the energy gap between T1 and Ground state) are larger than the formation energy of 1O2 (22.5 kcal mol 1). In such cases, 1O2 generation happens through multiple pathways: energy transfer from T1 (ET(1) in Fig. R6), but also the energy transfer from S1 to 3O2 during the S1- T1 intersystem crossing transition (ET(2) in Figure R6). This multi- pathway mechanism can lead to an overall 1O2 quantum + +<--- Page Split ---> + +yield greater than 1.0, as more than one 1O2 molecule can be produced per absorbed photon.2 + +Fig. R6 Schematic illustration of the 1O2 generation mechanisms by conventional PDT agents (left) and GQDs (right). + +## References + +1. Ge J, et al. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation. Nat. Commun. 5, 4596 (2014). +2. Kanner RC, Foote CS. Singlet oxygen production from singlet and triplet states of 9,10-dicyanoanthracene. J. Am. Chem. Soc. 114, 678-681 (1992). + +\(^{+ + + }\) Both of these articles while interesting, hardly relevant to PDT considering the absorption peaks of the proposed sensitizers are in blue, and the fact that they are very unique cases. The first one reached to a suprizing conclusion without doing any photophysical work. Vibrational (or rotational) relaxation and their control by micro- or molecular environments, by molecular steric hinderence is well known. However, only accurate quantum yield determinations would prove simultaneous increases in emission and singlet oxygen quantum yields. This is not done in Ref 1. + +Q9: Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +Response: As previously discussed, TBmA- Glu is a water- soluble molecule that forms aggregates within tumor cells upon activation by GGT to produce TBmA. Consequently, most of these aggregates are localized in the tumor cells. Furthermore, we have demonstrated the stability of TBmA aggregates for 72 hours in a \(30\%\) BSA solution. Additionally, considering that PDT processes were conducted 12 hours after administration of TBmA- Glu, it can be inferred that the TBmA aggregates exhibit sufficient stability to complete the PDT processes. + +\(^{+ + + }\) The problem is that now "activated" aggregates, will not stay forever in tumor cells, as these cells disintegrate. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<--- Page Split ---> + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Point-by-Point Responses + +We are very grateful to the reviewers for their insightful comments, which have significantly enhanced the quality of our paper. Following their valuable feedback and suggestions, we have carefully revised the manuscript. Our responses and revisions are presented in a blue font for easy reference. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". + +This referee finds important design flaws and problems with the implementation of the work. Response: We thank the reviewer for the constructive comments on our paper. In this manuscript, we actually did not intend to compare the Type I and Type II PDT processes, and the efficiency of type I and type II photosensitizers is not the key point of this work. We just want to present the objective performance of the developed photosensitizers based on their ROS generation capability. As clearly stated in the manuscript: "It was found that TBmA and TBpA produced significantly higher ROS compared to TBmA- Glu and TBpA- Glu, even surpassing the commercial photosensitizer, Rose Bengal (RB). Moreover, TBmA was identified as the most potent photosensitizer among the four compounds. Further analysis revealed that TBmA and TBpA functioned as strong type I photosensitizers (Fig. 1c and Fig. S25), while TBmA- Glu and TBpA- Glu acted as very weak type II photosensitizers (Fig. 1c and Fig. S26)." + +Here are the major issues: + +Problem with Aggregates: + +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +Response and revision: Thank you for your thoughtful comments regarding AIE compounds. We appreciate your concerns and would like to address them point by point: + +(i) Stability and standardization: we acknowledge that stability is crucial for bio- application. Our recent studies have shown promising results regarding the stability of TBmA aggregates in high-protein environments, specifically: (a) Long-term stability: TBmA aggregates showed no significant degradation when dispersed in FBS for 72 hours (Fig. S28a and S28c). (b) Photostability: The aggregates remained stable under continuous light irradiation for 30 minutes (Fig. S28a and S28b). These findings collectively highlight the exceptional + +<--- Page Split ---> + +stability exhibited by TBmA. These findings demonstrate the exceptional stability of TBmA aggregates in biologically relevant conditions. + +Moreover, numerous AIEgens, including small molecules or AIE nanoparticles, have been extensively reported for their long- term monitoring and theranostic applications. \(^{1,2,3}\) These pieces of evidence underscore the remarkable stability of AIEgens, making them highly promising candidates for theranostic applications. + +(ii) Aggregate structure: To address concerns about ill- defined aggregate structures, we extensively investigated the aggregate size of TBmA using Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). The results suggest that the TBmA forms spherical particles with \(140 \mathrm{nm}\) in \(99\%\) PBS and \(150 \mathrm{nm}\) diameter after the GGT catalysis reaction (12 h, Fig. S31). These results indicate that TBmA consistently forms nanoparticles of definite shape and size in aqueous environments, regardless of the specific conditions. Numerous works have been reported to show the definite shape and size, as well as the excellent stability and biocompatibility of the AIE aggregates. \(^{4,5,6}\) + +(iii) A comparative analysis of small molecular drugs and AIE materials: Although molecular drugs and traditional photosensitizers have their advantages, AIE compounds offer unique benefits such as enhanced emission upon aggregation, responsiveness to stimuli, and multifunctional potential. Revealing reports increasingly indicate that small molecular photosensitizers, such as CE6, exhibit low solubility and undergo aggregation in solution, resulting in the deactivation of their photosensitizing activity and hindering their bioapplication. \(^{7,8,9,10}\) We believe that AIE compounds can serve as complementary agents, rather than substitutes, for small molecule drugs. Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring. \(^{4,11,12,13}\) + +We believe that AIE compounds, including TBmA- Glu, offer valuable and unique properties that complement existing molecular drugs and photosensitizers. While challenges remain, the growing body of research on AIE materials suggests significant potential for advancing biomedical imaging and therapeutic applications. We appreciate the reviewer's perspective and believe that continued research and development in this field will address current limitations and unlock new possibilities in biomedical science. + +## Changes in the Revised Manuscript: + +Moreover, the TBmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS (fetal bovine serum) solution for \(72 \mathrm{h}\) or light irradiated for \(30 \mathrm{min}\) . + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and 72 h FBS preservation.
+ +![](images/Figure_unknown_1.jpg) + +
Fig. S31. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b-g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for 12 h.
+ +## References + +<--- Page Split ---> + +1. Zuo J, et al. Long-term spatiotemporal and highly specific imaging of the plasma membrane of diverse plant cells using a near-infrared AIE probe. Angew. Chem. Int. Ed. 14, 2139-2148 (2023). + +2. Wang Z, et al. Long-term fluorescent cellular tracing by the aggregates of aie bioconjugates. J. Am. Chem. Soc. 135, 8238-8245 (2013). + +3. Li K, et al. Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing. Sci. Rep. 3, 1150 (2013). + +4. Wang J, et al. Nanolab in a cell: Crystallization-induced in situ self-assembly for cancer theranostic amplification. J. Am. Chem. Soc. 144, 14388-14395 (2022). + +5. Li Y, et al. Trojan Horse-Like Nano-AIE Aggregates Based on Homologous Targeting Strategy and Their Photodynamic Therapy in Anticancer Application. Adv. Sci. 8, 2102561 (2021). + +6. Yan Z, et al. Preparation of ultrasmall AIE nanoparticles with tunable molecular packing via freeze assembly. Nano Lett. 23, 1030-1035 (2023). + +7. Li Y, et al. Near-infrared light and redox dual-activatable nanosystems for synergistically cascaded cancer phototherapy with reduced skin photosensitization. Biomaterials 288, 121700 (2022). + +8. Tian S, He J, Lyu D, Li S, Xu Q-H. Aggregation enhanced photoactivity of photosensitizer conjugated metal nanoparticles for multimodal imaging and synergistic phototherapy below skin tolerance threshold. Nano Today 45, 101534 (2022). + +9. Wang H, Xue K-F, Yang Y, Hu H, Xu J-F, Zhang X. In Situ Hypoxia-Induced Supramolecular Perylene Diimide Radical Anions in Tumors for Photothermal Therapy with Improved Specificity. J. Am. Chem. Soc. 144, 2360-2367 (2022). + +10. Li X, et al. Nanostructured Phthalocyanine Assemblies with Protein-Driven Switchable Photoactivities for Biophotonic Imaging and Therapy. J. Am. Chem. Soc. 139, 10880-10886 (2017). + +11. Chen C, Zhang X, Gao Z, Feng G, Ding D. Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection. Nat. Protoc., in press (2024). + +12. Liu Z, Wang Q, Zhu Z, Liu M, Zhao X, Zhu W-H. AIE-based nanoaggregate tracker: high-fidelity visualization of lysosomal movement and drug-escaping processes. Chem. Sci. 11, 12755-12763 (2020). + +13. Yu Y, et al. Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking. Adv. Mater. 23, 3298-3302 (2011). + +Excitation wavelength: + +The absorption peak of the monomeric compounds and the aggregates in this work is around + +<--- Page Split ---> + +450 nm. This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +Response and revision: We appreciate the reviewer's concern regarding light penetration and the effects of our light source. Our analysis of the white LED light shows predominant peaks at 450 and 570 nm, with no detectable UV peak, which could address the concerns of the reviewers about unintended UV- induced effects (Fig. S27). Furthermore, all anticancer \(\mathrm{IC}_{50}\) values of tested compounds were detected using the MTT assays, and no significant effect on cell viability was detected in the control group after exposure to LED irradiation. MTT assays and control experiments demonstrate that the observed cell death is due to \(\mathrm{TBmA}\) - Glu's photodynamic properties, not the LED light itself. + +Depth of Penetration in Tissues: While it is true that the penetration depth of light at \(450\mathrm{nm}\) is limited, this wavelength is still within the range where some penetration can occur in biological tissues. The actual penetration depth can be influenced by factors such as tissue type, pigmentation, and the optical properties of the tissue. Furthermore, we employed a minimally invasive approach for PDT to optimize the efficiency of photodynamic therapy and minimize the impact of light penetration. + +## Changes in the Revised Manuscript: + +The generation of total ROS generation (2,7'- dichlorodihydrofluorescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10- anthracenediylbis(methylene)dimalonic Acid, ABDA) by photosensitizers (5 \(\mu \mathrm{M}\) ) after white LED light (predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation ( \(20\mathrm{mW}\cdot \mathrm{cm}^{- 2}\) ) for 15 min using the corresponding ROS indicator in PBS/DMSO (v/v = 99:1). DCF, \(\lambda_{\mathrm{ex}} = 488\mathrm{nm}\) . + +## Changes in the Supporting Information: + +![](images/Figure_unknown_2.jpg) + +
Fig. S27. The emission wavelength analysis of the LED light.
+ +<--- Page Split ---> + +Confusion about the Type- I and Type- II PDT: + +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; and it is not easy to separate these two processes (I/II). + +Response: We appreciate the reviewer's insightful comments on the Type- I and Type- II PDT processes. We agree that PDT often involves a combination of both processes and that ROS species can undergo interconversion through various enzymatic processes in vivo. Our study focused on characterizing the predominant mechanism of \(\mathrm{TBmA}\) under specific conditions, not comparing the superiority of Type- I vs Type- II processes. We found that the cleaved \(\mathrm{TBmA}\) - Glu ( \(\mathrm{TBmA}\) ) primarily exerts its anticancer effects through the type I PDT process. And aligning with this finding, we observed the oxygen independence of \(\mathrm{TBmA}\) 's photodynamic activity in the hypoxia condition, which is potentially advantageous in hypoxic tumor environments. + +We acknowledge the complexity of PDT processes in biological systems, which may reflect both directly generated species and enzymatic interconversions. However, the ROS we detected in cells are coordinating with the results we detected in vitro, which validates the validity of our conclusion. + +Enhancement of emission "AND" PDT efficiency. + +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +Response: We appreciate the reviewer's insights regarding the competitive nature of fluorescence and reactive oxygen species (ROS) generation in AIE- PDT systems. While both processes utilize energy from the excited state, our findings on the simultaneous enhancement of aggregate luminescence and photodynamic activity are not contradictory. Here is some reported literature. + +(i) Aggregation-induced intermolecular intersystem crossing (AI-ISC): Jiang et al. proposed a new mechanism called aggregation-induced intersystem crossing (AI-ISC) to understand the effect of aggregation on increasing ISC efficiency. \(^{1,2}\) According to the AI-ISC theory, more excitonic couplings cause excited-state energy splitting and overlapping of singlet and triplet in aggregate. The energy splitting and overlapping significantly produce many ISC channels with very small \(\Delta E_{\mathrm{ST}}\) in aggregates, which is available for ISC processes. Therefore, the formation of aggregates can facilitate the production of triplet excitons. In addition to + +<--- Page Split ---> + +emitting phosphorescent radiation, these triplet excitons can also undergo a non- radiative pathway known as the aggregation- enhanced photodynamic effect to return to their ground state. 3, 4, 5 + +(ii) Restriction of intramolecular motion (RIM): The aggregation of AIE molecules results in a restriction of intramolecular rotations and vibrations, effectively suppressing molecular motions, which is also beneficial for the ISC process.6, 7 + +All the evidence highlights the potential of AIE materials in PDT. The aggregation- induced changes in the molecular environment can optimize both the imaging and therapeutic aspects of the treatment.8, 9, 10 + +We hope that these clarifications address the reviewer's concerns and reinforce the validity of our findings. We are grateful for the opportunity to discuss these important aspects of AIE- PDT and hope that our response provides a clearer understanding of the complex interplay between fluorescence and photodynamic activity in our study. + +## References: + +1. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +2. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +3. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). +4. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). +5. Ji C, Lai L, Li P, Wu Z, Cheng W, Yin M. Organic dye assemblies with aggregation-induced photophysical changes and their bio-applications. Aggregate 2, e39 (2021). +6. Kwok RTK, Leung CWT, Lam JWY, Tang BZ. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 44, 4228-4238 (2015). +7. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +8. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +9. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 + +<--- Page Split ---> + +(2020). + +10. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +Reviewer #2 (Remarks to the Author): + +Tang and colleagues reported a \(\gamma\) - glutamyl transferase (GGT) activatable aggregation- induced emission photosensitizer (AIE- PS) named TBmA- Glu. TBmA- Glu is designed to specifically target and aggregate cancer cells through the catalytic action of tumor- overexpression GGT. Selective tumor cell aggregation not only enhances AIE- PS emission and photodynamic activity but also induces ferroptosis in cancer cells by depleting GSH and promoting lipid peroxidation. Both in vitro cell assays and in vivo animal models were used to validate the phototoxicity and antitumor effects of TBmA- Glu, providing a comprehensive assessment of its potential as a therapeutic agent. The aggregation strategies in this paper allow a controlled release of the photodynamic effect, which is critical for therapies such as PDT. AIE- PS remains dormant until it reaches the cancerous environment where GGT is present, ensuring minimal impact on healthy cells and maximizing the therapeutic effect on cancer cells. This study highlights the significance of targeting activation of AIE- PSs for targeting and enhanced cancer photodynamic therapy. It is also a sophisticated strategy for targeted delivery and activation of a photodynamic therapeutic agent for disease. I suggest this article be published with minor revisions. + +Response: We would like to express our gratitude for the favorable remarks provided by the reviewer regarding our manuscript. + +1. The authors claimed that TBmA-Glu could be activated by GGT. Is there evidence to suggest that TBmA-Glu could be effective against other types of cancer that overexpress GGT, or is its application currently limited to the cancer types studied? + +Response and revision: We appreciate the reviewer's suggestion and subsequently conducted further investigations into the anticancer efficacy of TBmA-Glu on additional cancer cell lines overexpressing GGT, including OVCAR-5 cells and 4T1 cells (mouse breast cancer cells), as well as HLF-1 cells with regular GGT expression, using MTT assays. The \(\mathrm{IC}_{50}\) values for photodynamic therapy were determined to be \(5.13 \pm 0.69 \mu \mathrm{M}\) (OVCAR-5) and \(5.28 \pm 1.56 \mu \mathrm{M}\) (4T1, Fig. S35), respectively. Moreover, no significant photocytotoxicity was observed in HLF-1 cells with regular GGT expression, nor any significant dark cytotoxicity. These results demonstrate the broad-spectrum anticancer potential of TBmA-Glu against GGT- overexpressing cancer cells, and the rationale for the broader application of TBmA-Glu lies in the overexpression of GGT in various cancerous conditions. Therefore, the potential + +<--- Page Split ---> + +effectiveness of TBmA- Glu could extend to other cancers that exhibit elevated GGT levels. + +## Changes in the Revised Manuscript: + +The broad- spectrum anticancer potential of TBmA- Glu against GGT- overexpressing cancer cells was further demonstrated through subsequent investigations, including OVCAR- 5 and murine 4T1 cancer cells (Fig. S35). The \(\mathrm{IC}_{50}\) values for photodynamic therapy were determined to be \(5.13 \pm 0.69 \mu \mathrm{M}\) (OVCAR- 5) and \(5.28 \pm 1.56 \mu \mathrm{M}\) (4T1), respectively. Moreover, no significant photocytotoxicity was observed in HLF- 1 cells with regular GGT expression, nor any significant dark cytotoxicity. Therefore, the potential effectiveness of TBmA- Glu could extend to other cancers that exhibit elevated GGT levels. + +![](images/Figure_unknown_3.jpg) + +
Changes in the Supporting Information: Fig. S35. The anticancer activity ( \(\mathrm{IC}_{50}\) , \(\mu \mathrm{M}\) ) of TBmA-Glu against GGT overexpressing OVCAR5 and 4T1, and GGT normally expressing HLF1 cells.
+ +2. How photostable is TBmA-Glu under the conditions used for PDT, and does its aggregation state affect its photostability? + +Response and revision: We appreciate the reviewer's question regarding the photostability of TBmA- Glu. To address this, we conducted comprehensive stability studies on TBmA- Glu and its active form, TBmA, produced in cancer cells. We extensively investigated the long- term stability and photostability of TBmA aggregates in FBS (Fig. S28c). The results demonstrate + +<--- Page Split ---> + +that no significant degradation or aggregation was observed after TBmA aggregates were dispersed in PBS for \(72\mathrm{h}\) or subjected to continuous light irradiation for 30 minutes. Then, we monitored the photostability of TBmA- Glu in HepG2 cells during light irradiation (Fig. S28b). The results show no significant decrease in fluorescence intensity during the light exposure period (Fig. S34). All these findings, along with the stability studies in PBS, collectively demonstrate the high photostability of TBmA- Glu and its active form TBmA under PDT conditions, both in solution and in the cellular environment. + +## Changes in the Revised Manuscript: + +Moreover, the TbmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS solution for \(72\mathrm{h}\) or light irradiated for \(30\mathrm{min}\) . Additionally, TBmA- Glu showed remarkable specific accumulation in HepG2 cells compared to TBmA (Fig. 3b and Fig. S33c), along with exceptional photostability within living cells (Fig. S34a), as evidenced by the absence of significant bleaching even after continuous light irradiation (Fig. S34b). + +## Changes in the Supporting Information: + +![](images/Figure_unknown_4.jpg) + +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation (b) and 72h FBS preservation (c).
+ +<--- Page Split ---> +![](images/Figure_unknown_5.jpg) + +
Fig. S34. The HepG2 cells were imaged after incubation with TBmA-Glu (5 \(\mu \mathrm{M}\) ) for 12 hours. Subsequently, the cells were exposed to a \(465\mathrm{nm}\) laser for 10 minutes, and images were captured every minute. \(\lambda_{\mathrm{ex}} = 465\mathrm{nm}\) ; \(\lambda_{\mathrm{em}} = 700\pm 20\mathrm{nm}\) , Scale bar, \(20\mu \mathrm{m}\) .
+ +3. The author claimed the aggregate size has a great impression on the PDT efficiency of AIE-PSs. What are the typical sizes and shapes of the TBmA-Glu aggregates formed in the presence of GGT? How do these properties affect the emission properties and PDT efficacy? + +Response and revision: We monitored the aggregate sizes of TBmA produced from the GGT- catalyzed reaction using DLS (Fig. S31). The sizes of TBmA aggregates increase from \(66.7\mathrm{nm}\) (1 h, Fig. S31b) to \(158.0\mathrm{nm}\) (4 h, Fig. S31e). Subsequently, no further changes in size were observed as the incubation time was extended. The morphology of the aggregate in \(12\mathrm{h}\) was further analyzed using the transmission electron microscope (TEM, Fig. S34h). The aggregate size measured by TEM is about \(100\mathrm{nm}\) , which is in accord with the size detected by DLS. The stable aggregates produced by GGT catalysis were found to be slightly larger than those detected in \(99\%\) PBS ( \(156.8\mathrm{nm}\) vs \(139.5\mathrm{nm}\) ). + +Additionally, we evaluated the total ROS generation properties of stable TBmA aggregates generated through a GGT- catalyzed reaction (12 h) using DCFH (Fig. S32). Upon 15 minutes of white LED light exposure ( \(20\mathrm{mW}\cdot \mathrm{cm}^{- 2}\) ), GGT- catalyzed TBmA aggregates exhibited an approximately 164- fold (Fig. S32c) increase in fluorescent intensity. While this enhancement was slightly lower than the aggregates formed in \(99\%\) PBS (188- fold), it was significantly higher than Rose Bengal (67.0- fold). These findings are consistent with previous observations that smaller aggregate size tends to enhance photodynamic efficiency. Our results demonstrate that TBmA aggregates generated by GGT possess potent photodynamic activity. + +## Changes in the Revised Manuscript: + +Furthermore, we investigated the morphology of TBmA aggregates formed at the endpoint GGT catalytic reaction (12 h) and its ROS generation capability by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). The DLS results revealed a gradual increase in the size of aggregates to approximately \(158.0\mathrm{nm}\) over the initial 4- hour period. + +<--- Page Split ---> + +Subsequently, a steady state size was attained after 4 hours of incubation, with no further changes observed even when extending the incubation time to 12 hours (Fig. S31). The TEM analysis revealed that GGT facilitated the formation of spherical TBmA aggregates, exhibiting an average diameter of approximately \(100\mathrm{nm}\) (Fig. S31h). Additionally, evaluation of the total ROS generation properties of stable TBmA aggregates showed that it induced an approximately 164- fold increase in the intensity of DCFH after 15 min light irradiation (Fig. S32). While this enhancement was slightly lower than the aggregates formed in \(99\%\) PBS (188- fold), it was significantly higher than Rose Bengal (67.0- fold). These findings are consistent with previous observations that smaller aggregate size tends to enhance photodynamic efficiency. Our results demonstrate that TBmA aggregates generated by GGT possess potent photodynamic activity. + +![](images/Figure_unknown_6.jpg) + +
Changes in the Supporting Information:
+ +Fig. S31. (a) The average hydrodynamic diameter (Z- average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b- g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for \(12\mathrm{h}\) . + +<--- Page Split ---> +![](images/Figure_unknown_7.jpg) + +
Fig. S32. Fluorescence emission changes of DCFH (10 \(\mu \mathrm{M}\) ) in the presence of \(5\mu \mathrm{M}\) photosensitizers in DMSO-PBS \((v:v = 1 / 99)\) after irradiation \((20\mathrm{mW}\cdot \mathrm{cm}^{-2})\) for different time. (a) TBmA aggregates in PBS, (b) TBmA aggregates produced in GGT catalytic reaction, DCHF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) . (c) Plot of the relative emission intensity \((II_{0})\) of DCF (10 \(\mu \mathrm{M}\) ) in presence of TBmA (5 \(\mu \mathrm{M}\) ), TBmA aggregates produced in GGT reaction (5 \(\mu \mathrm{M}\) ) or Rose Bengal (RB, \(5\mu \mathrm{M}\) ) versus the irradiation \((20\mathrm{mW}\cdot \mathrm{cm}^{-2})\) time, where \(I_{0} = \mathrm{PL}\) intensity of DCFH in solutions with different water fraction \((f_{\mathrm{w}})\) without light irradiation. \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) .
+ +4. Can aggregated TBmA be expelled from cancer cells via exocytosis, potentially reducing its therapeutic efficacy? Long-term (48 h) cellular imaging results should be provided by the author. Response and revision: We conducted confocal imaging to investigate the intracellular retention of TBmA-Glu. Compared with the short treatment groups, no significant decrease in the imaging fluorescent intensity was detected after 48 h of incubation (Fig. S33a). + +## Changes in the Revised Manuscript: + +The results demonstrated that TBmA- Glu has excellent selectivity towards HepG2 cells compared to LO2 cells (Fig. S33a and S33b) and long- term retention ability in HepG2 cells (Fig. S33a). + +Changes in the Supporting Information: + +<--- Page Split ---> +![](images/Figure_unknown_8.jpg) + +
Fig. S33. The time-dependent uptake process of TBmA-Glu (a) / TBmA (b) in HepG2 cells. (c) The time-dependent uptake process of TBmA-Glu in LO2 cells. All the cells were incubated with \(5\mu \mathrm{M}\) TBmA-Glu / TBmA and imaged at the indicated time. \(\lambda_{\mathrm{ex}} = 465 \mathrm{nm}\) ; \(\lambda_{\mathrm{em}} = 700 \pm 20 \mathrm{nm}\) , Scale bar, \(20\mu \mathrm{m}\) .
+ +5. The abbreviations, such as DCF, DCFH-DA, HPF, ABDA, CLSM, et al., should be defined the first time they are used. + +Response and revision: we have ensured that all the abbreviations are defined when they first appear in the revised manuscript. + +## Changes in the Revised Manuscript: + +"(c) The generation of total ROS generation (2,7'-dichlorodihydrofluorescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10-anthracenediy1- bis(methylene)dimalonic Acid, ABDA) by photosensitizers (5 \(\mu \mathrm{M}\) ) after white LED light + +<--- Page Split ---> + +(predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation (20 mW·cm \(^{- 2}\) ) for 15 min using the corresponding ROS indicator in PBS/DMSO (v/v = 99:1).” + +“Fig. 3 (a) Confocal laser scanning microscope (CLSM) images of co- incubated cancer (HepG2; luciferase- transfected) and normal (LO2) cells after treatment with TBmA- Glu (5 μM, 12 h).” + +## Reviewer #3 (Remarks to the Author): + +This work present a novel approach to targeted cancer therapy by leveraging the tumor- overexpressed enzyme \(\gamma\) - Glutamyl Transferase (GGT) to induce aggregation of an aggregation- induced emission photosensitizer (AIE- PS), TBmA- Glu. This innovative strategy not only enhances the photosensitivity of the AIE- PS but also results in the degradation of GGT and the accumulation of lipid peroxides, leading to cancer cell ferroptosis. The study is significant for its potential to advance targeted photodynamic therapy (PDT) and the development of smart therapeutics that exploit enzyme activity for controlled molecular aggregation within cancer cells. The authors have demonstrated a clear understanding of the complex interactions between molecular aggregation and biological environments, and the manuscript is well- structured, presenting a logical flow of information from synthesis and characterization to in vivo efficacy. The results are compelling, showing the selective activation of TBmA- Glu by GGT, its enhanced photodynamic activity, and the subsequent therapeutic effects on cancer cells. The manuscript is well- written and provides a solid foundation for further research in the field of nanomedicine and targeted drug delivery. I recommend publication following minor modifications, my concerns are outlined below: + +Response: Firstly, we appreciate the reviewer's positive comments on our manuscript. + +1. The author could incorporate a concise, visual representation of key discoveries and TBmA- Glu's proposed mechanism of action through a mechanistic cartoon or schematic. + +Response and revision: As suggested by the reviewer, we supplemented a schematic diagram of the mechanism of TBmA- Glu's anticancer activities (Scheme 1). + +Changes in the Revised Manuscript: + +<--- Page Split ---> +![](images/Figure_unknown_9.jpg) + + +Scheme 1: Schematic illumination of the aggregation- enhanced photodynamic therapeutic mechanism mediated by TBmA- Glu. + +2. The stability of the aggregates of TBmA, especially the photostability of it in physiological conditions should be discussed. + +Response and revision: The long- term stability and photostability of the TBmA aggregates were investigated through DLS. The results suggested no significant degradation was observed when TBmA aggregates were dispersed in FBS for 72 hours or subjected to continuous light irradiation for 30 minutes (Fig. S28). TBmA- Glu also exhibited well anti- bleaching properties in living cells (Fig. S34). + +## Changes in the Revised Manuscript: + +Moreover, the TbmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS solution for 72 h or light irradiated for 30 min. + +Additionally, TBmA- Glu showed remarkable specific accumulation in HepG2 cells compared to TBmA (Fig. 3b and Fig. S33c), along with exceptional photostability within living cells (Fig. S34a), as evidenced by the absence of significant bleaching even after continuous light irradiation (Fig. S34b). + +Changes in the Supporting Information: + +<--- Page Split ---> +![](images/Figure_unknown_10.jpg) + +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and 72h FBS preservation.
+ +![](images/Figure_unknown_11.jpg) + +
Fig. S34. The HepG2 cells were imaged after incubation with TBmA-Glu (5 \(\mu \mathrm{M}\) ) for 12 hours. Subsequently, the cells were exposed to a \(465 \mathrm{nm}\) laser for 10 minutes, and images were captured every minute. \(\lambda_{\mathrm{ex}} = 465 \mathrm{nm}\) ; \(\lambda_{\mathrm{em}} = 700 \pm 20 \mathrm{nm}\) , Scale bar, \(20 \mu \mathrm{m}\) .
+ +3. The author acclaimed the lipid peroxides (LPOs) resulting from the photodynamic process of activated AIE-PS induce the ferroptosis of cancer cells, the changes in the level of LPOs in cancer cells after photodynamic therapy should be quantified. + +Response and revision: The amounts of oxidative products of lipids in HepG2 cells after the photodynamic therapy are quantified using the Lipid Peroxidation MDA (malondialdehyde) Assay Kit. It can be seen from the results that, compared with the control group and dark- treatment groups, TBmA-Glu induced a significant accumulation of the LPOs in HepG2 cells + +<--- Page Split ---> + +after light irradiation treatment (Fig. S39), which corresponds with the previous ROS species and lipids oxidation in our results. + +## Changes in the Revised Manuscript: + +The peroxidation products of DOPE and the lipid peroxidation products, malondialdehyde (MDA), were also detected in the DOPE/TBmA mixture (Fig. S38) and the cells after light irradiation (Fig. S39). + +Measurement of MDA levels. HepG2 cells were cultured in \(6\mathrm{cm}\) dishes until they reached approximately \(80\%\) confluency, followed by treatment with TBmA- Glu \((2\mu \mathrm{M})\) for \(12\mathrm{h}\) . The cells were then harvested, counted, and lysed with RAPI lysis buffer at \(4^{\circ}\mathrm{C}\) for \(15\mathrm{min}\) . MDA levels in each group were determined using the Lipid Peroxidation MDA Assay Kit (Beyotime, China), according to the manufacturer's instructions. + +## Changes in the Supporting Information: + +![](images/Figure_unknown_12.jpg) + +
Fig. S39. Malondialdehyde (MDA) levels in HepG2 cells after treated with the TBmA-Glu (2 \(\mu \mathrm{M}\) ) for \(12\mathrm{h}\) . Then, the cells were irradiated with a white laser array \((12\mathrm{J}\cdot \mathrm{cm}^{-2})\) and the MDA levels were detected using a Lipid Peroxidation MDA Assay Kit. Data expressed as average \(\pm\) standard error, \(\mathrm{n} = 3\) . Statistical significance: P values, \(\mathrm{***P}< 0.001\) , calculated with the Student's T-test.
+ +4. Detailed experimental procedures for minimally invasive PDT should be provided. Response and revision: The experimental procedure for minimally invasive PDT assay has been incorporated into the "In vivo antitumor assay" section in the "Methods" of the manuscript. + +## Changes in the Revised Manuscript: + +For the minimally invasive photodynamic therapy, the mice were initially anesthetized using an isoflurane inhalant anesthesia apparatus. The TBmA fluorescence was utilized to precisely + +<--- Page Split ---> + +locate the tumor section in the liver, and a small incision (2 mm) was meticulously made with a scalpel at the localized region. Subsequently, the laser probe was carefully inserted into the incision to execute the photodynamic therapy. Finally, the wound was sutured and disinfected. + +Finally, we would like to reiterate our sincere gratitude to all the reviewers and the editorial office for their invaluable suggestions and diligent efforts, which have significantly enhanced the quality of this manuscript. + +<--- Page Split ---> + +## Point-by-point Response + +We express our sincere gratitude to the reviewers for their insightful comments, which have significantly enhanced the scholarly quality of our paper. In response to their valuable feedback and suggestions, we have carefully revised the manuscript. Our responses and revisions are presented in a distinguishable blue font for convenient reference. + +## Reviewer #1 (Remarks to the Author): + +Q1: The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +251. "only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA- Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." + +Response and revision: We appreciate the valuable suggestions provided by the reviewer. To enhance the accuracy of our study, we conducted additional experiments using Rose Bengal (RB), a well- established type II photosensitizer1, as a control. These experiments revealed that RB's photodynamic efficiency decreased significantly under hypoxia conditions (2% O2) compared to normoxia conditions, while TBmA maintained relatively consistent activity across both environments (Fig. R1). + +To discuss this result more accurately, we have revised our manuscript by replacing the statement "This suggests that oxygen content has negligible influence on its photodynamic activity." with "This suggests that TBmA exhibits tolerance towards hypoxic conditions." + +<--- Page Split ---> +![](images/Figure_unknown_13.jpg) + +
Fig. S36. The effects of hypoxia (2% \(O_2\) ) and normoxia (20% \(O_2\) ) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells.
+ +## Revised in manuscript: + +Additionally, only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d), while the type- II PS, RB, showed a significant decrease in photodynamic efficiency under hypoxia conditions (2% \(O_2\) ) compared to normoxia conditions (Fig. S36). This suggests that TBmA exhibits tolerance towards hypoxic conditions. + +## Reference: + +1. Fischer BB, Krieger-Liszkay A, Eggen RIL. Oxidative stress induced by the photosensitizers neutral red (type I) or rose bengal (type II) in the light causes different molecular responses in Chlamydomonas reinhardtii. Plant Sci. 168, 747-759 (2005). + +Q2: Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +Response: We appreciate the reviewer's insightful comments regarding the nature of supramolecular aggregation and the potential for de- aggregation in biological media. We would like to clarify several key points that address these concerns. + +Firstly, it's crucial to emphasize that TBmA- Glu is a water- soluble prodrug. The aggregation process only occurs after the Glu moiety is cleaved by GGT in HepG2 cells. This design ensures that TBmA- Glu remains soluble in the blood, avoiding premature aggregation. Aggregation is triggered specifically in the intracellular environment of GGT- overexpressing tumor cells. + +We acknowledge that FBS is not an ideal model for the intracellular environment. To address this issue, we further conducted stability studies using a 30% BSA (Bovine Serum Albumin) solution, which is a better model for the protein- rich intracellular + +<--- Page Split ---> + +milieu. The intracellular protein concentration typically ranges from 50- 400 mg/mL, and our \(30\%\) BSA solution ( \(\sim 300 \mathrm{mg / mL}\) ) falls within this range. TBmA aggregates showed remarkable stability in this environment, with no significant degradation observed over 72 hours (Fig. R1). + +We also agree that pharmacokinetics studies would be valuable. However, our system presents unique challenges for such studies, as the aggregates form intracellularly rather than in circulation. Collecting and analyzing intracellular aggregates from tumor sections poses significant technical difficulties. Our approach using a highly concentrated protein solution provides valuable insights into aggregate stability in a physiologically relevant environment. + +Importantly, beyond structural stability, we have observed that the aggregates maintain their photodynamic properties in the \(30\%\) BSA solution for \(72 \mathrm{h}\) (Fig. R2). This functional stability is crucial for the compound's theranostic applications. + +![](images/Figure_unknown_14.jpg) + +
Fig. R1. The long-term stability of TBmA aggregates in \(30\%\) BSA solutions.
+ +<--- Page Split ---> +![](images/Figure_unknown_15.jpg) + +
Fig. R2. The ROS generation capacity of \(\mathrm{TBmA}\) aggregates after dispersed in \(30\%\) BSA solution for \(0\mathrm{h}\) (a) and \(72\mathrm{h}\) (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity \((I / I_0)\) of DC versus the irradiation \((20\mathrm{mW}\cdot \mathrm{cm}^{-2})\) time, where \(I_0 = \mathrm{PL}\) intensity of DCFH in solutions without light irradiation.
+ +Q3: References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +Response: We thank the reviewer for the critical feedback. The unique photophysical properties of AIE compounds stem from the restriction of intramolecular motion (RIM) mechanism, where aggregation limits molecular rotations and vibrations, leading to enhanced fluorescence. Therefore, the fluorescence behavior of AIE materials does provide valuable insights into their molecular state and environment. + +This interpretation is supported by several factors. First of all, \(\mathrm{TBmA - Glu}\) is engineered to aggregate specifically in response to GGT activity, which is overexpressed in certain tumor cells. This targeted approach minimizes premature aggregation in circulation. Secondly, the crowded, protein- rich cytoplasmic environment of tumor cells likely provides conditions that favor aggregate stability once formed. Additionally, we observed that the photosensitivity of \(\mathrm{TBmA}\) was maintained in our \(30\%\) BSA studies, suggesting a preservation of the aggregate structure. + +Q4: While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +Response: We appreciate the reviewer's thoughtful comments regarding the therapeutic relevance of AIE compounds and the importance of careful characterization of their behavior in biological systems. + +Regarding the stability and behavior of \(\mathrm{TBmA}\) , we emphasize that \(\mathrm{TBmA - Glu}\) is designed as a water- soluble prodrug that only forms aggregates within tumor cells following enzymatic reaction. This targeted approach minimizes potential issues related + +<--- Page Split ---> + +to premature aggregation or size changes in circulation. Furthermore, we have demonstrated the stability of TBmA aggregates in a \(30\%\) BSA solution for 72 hours, providing initial evidence of their potential stability in protein- rich environments. + +About "personalized medicine and real- time treatment monitoring." in the previous response letter: The full sentence is "Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring." We agree that such terminology should be used judiciously, especially in early- stage research, however, our intention here is to highlight the potential of AIE materials to contribute to these fields in the future, rather than to claim immediate clinical applicability. + +The unique properties of AIE materials, including their AIE and potential for stimuli- responsive behavior, do offer intriguing possibilities for both imaging and therapeutic applications. However, we agree that rigorous investigation is needed to establish their efficacy and safety for PDT or other therapeutic schemes. Moving forward, we will focus on providing concrete evidence for the specific advantages of AIE compounds in relevant biological contexts, rather than speculating on broad future applications. We believe this approach will better serve the scientific community and responsibly advance the field. + +Q5: May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to \(450\mathrm{nm}\) peak. There are literature reports of blue (450 nm) light causing cellular damage. + +Response: We acknowledge that there are indeed literature reports of blue light (450 nm) causing cellular damage. This is an important consideration in photodynamic therapy and other light- based treatments. However, we would like to emphasize that the biological effects of light exposure are highly dependent on both wavelength and dosage. + +In our experiments, we carefully controlled the light dosage to minimize potential phototoxicity while maintaining therapeutic efficacy. Under the experimental conditions described in our manuscript, we did not observe any significant effects on cell viability following LED light irradiation (Fig. R3). + +To address the reviewer's concern, we also conducted a blue light irradiation (450 nm, \(12\mathrm{J / cm^2}\) ) PDT assay. In this experiment, we also found no significant effect on cellular viability. This suggests that at the dosages used in our study, the blue light alone does not cause substantial cellular damage. + +However, we agree that the potential for phototoxicity is an important consideration in developing light- based therapies. In future studies, we plan to conduct a more comprehensive dose- response analysis to determine the threshold at which blue light exposure may begin to affect cell viability. We also intend to investigate the potential + +<--- Page Split ---> + +long- term effects of repeated light exposure and compare the effects of our AIE- based approach with traditional photosensitizers at equivalent light doses. + +![](images/Figure_unknown_16.jpg) + +
Fig. R3 The impact of white light and \(450\mathrm{nm}\) light exposure \((12\mathrm{J / cm^2})\) on the cellular viability of HepG2 cells.
+ +Q6: One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as \(450\mathrm{nm}\) is less than 1 mm, which is significantly less than needed for an effective "photo"- driven process. + +Response: It is correct that the typical penetration depth of \(450\mathrm{nm}\) light is less than 1 mm in tissue, which is indeed less than ideal for treating deep- seated tumors. However, we would like to highlight several important considerations: + +First, though direct light penetration is restricted, the effective depth of PDT damage may increase due to light reflection and scattering within tissues. This occurrence can expand the scope of the photodynamic impact beyond the initial penetration depth. + +Secondly, several clinical scenarios exist where shallow light penetration is sufficient or even advantageous. For instance, PDT with blue light excitation could be particularly useful for superficial skin cancers and precancerous lesions, intraoperative treatment of residual tumor cells after surgical resection, treatment of early- stage mucosal cancers in inaccessible areas (e.g., oral cavity, bladder), and endoscopic applications for gastrointestinal tumors. + +Finally, numerous published studies demonstrate the successful use of \(450\mathrm{nm}\) light and white light (including the blue spectrum) for PDT when the photosensitizers have maximum absorption around \(450\mathrm{nm}\) . 2, 3, 4, 5, 6, 7 + +Nevertheless, we fully agree that blue light's limited tissue penetration restricts the broader applicability of our current system for treating deep- seated tumors. Given this limitation, our future research directions include exploring two- photon excitation to achieve deeper tissue penetration, investigating upconversion nanoparticles to convert longer- wavelength light to blue light locally, and developing new AIE photosensitizers with red- shifted absorption for improved tissue penetration. We believe that addressing + +<--- Page Split ---> + +these challenges will expand the potential applications of our AIE- based PDT system while utilizing its unique properties. + +## References: + +2. Fan L, et al. A Bioactive Photosensitizer for Hypoxia-Tolerant Molecular Targeting-Photo-Immunotherapy of Malignant Tumor. Adv. Funct. Mater. 34, 2313755 (2023). +3. Li X, et al. A novel 450-nm laser-mediated sinoporphyrin sodium-based photodynamic therapy induces autophagic cell death in gastric cancer through regulation of the ROS/PI3K/Akt/mTOR signaling pathway. BMC Med. 20, 475 (2022). +4. Mei Y, et al. A Novel Photosensitizer Based 450-nm Blue Laser-Mediated Photodynamic Therapy Induces Apoptosis in Colorectal Cancer - in Vitro and in Vivo Study. Front. Biosci. (Landmark Ed) 29, 199 (2024). +5. Chen Y, et al. Photoactivatable metal organic framework for synergistic ferroptosis and photodynamic therapy using 450 nm laser. Chem. Eng. J. 454, 140438 (2023). +6. Sun P, et al. A water-soluble phosphorescent conjugated polymer brush for tumor-targeted photodynamic therapy. Polym. Chem. 8, 5836-5844 (2017). +7. An J, et al. An unexpected strategy to alleviate hypoxia limitation of photodynamic therapy by biotinylation of photosensitizers. Nat. Commun. 13, 2225 (2022). + +Q7: First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to \(0.5\%\) O2 hypoxia, or anoxia, the effectiveness would be much more different. + +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Ebselen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide \(\mathrm{(N_3)}\) - is a singlet oxygen quencher. + +Response and revision: We agree with the reviewer that oxygen plays a pivotal role in the Type I and Type II PDT processes. However, from the PDT mechanism, we know that the type I photosensitizers could directly transfer electrons to the substrate, forming a radical cation or neutral radical. These radicals could immediately react with \(\mathrm{O_2}\) or \(\mathrm{H_2O}\) to generate hydrogen peroxide \(\mathrm{(H_2O_2)}\) , hydroxyl radicals (- OH), or superoxide anions (- \(\mathrm{O_2}\) - ) (Fig. R4).1, 2 + +We have tried but could not finish the antitumor PDT assays in the anaerobic conditions, because the anoxia condition resulted in death of the tumor cells (Fig. R5a). So, we re- evaluated the photodynamic efficiency of TBmA and RB using a deoxidized PBS solution. The results showed that TBmA could also induce the oxidation of DFCH under the anoxia condition (Fig. R5b), while the photodynamic efficiency of RB showed significant degradation. Hence, type- I photosensitizers exhibit relatively higher tolerance towards oxygen concentrations, which implies that, even under low oxygen conditions, they can still engage in substrate reactions through electron transfer. + +<--- Page Split ---> + +We are sorry for the mistake in the figure legend in Figure 4b. “Ebselen” has been revised as “Trolox.” However, it should be noted that Trolox is not only a \(^{1}\mathrm{O}_{2}\) scavenger but also a scavenger of peroxy and alkoxy groups. \(^{3}\) The type-I designation is mainly based on the ROS species we detected in vitro (Fig. R5c). + +![](images/Figure_unknown_17.jpg) + +
Fig. R4 Scheme of the photochemical reactions for type I and type II PDT. \(^{9}\)
+ +![](images/Figure_unknown_18.jpg) + +
Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \(10 \mu \mathrm{M}\) ) in the presence of \(5 \mu \mathrm{M}\) photosensitizers in DMSO-PBS \((v:v = 1:99)\) after irradiation (20 \(\mathrm{mW}\cdot \mathrm{cm}^{-2}\) ) for a different time under anoxia conditions. (b) \(\mathrm{TBmA}\) , (c) Rose Bengal (RB). DCHF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) .
+ +## Revised in manuscript: + +Trolox: \(50 \mu \mathrm{M}\) (ROO. scavenger and \(^{1}\mathrm{O}_{2}\) scavenger); D- mannitol: \(50 \mathrm{mM}\) (- OH scavenger); Tiron: \(10 \mathrm{mM}\) (- \(\mathrm{O}_{2}\) scavenger); \(\mathrm{NaN}_{3}\) : \(5 \mathrm{mM}\) ( \(^{1}\mathrm{O}_{2}\) scavenger) + +## References: + +1. Zhao X, Liu J, Fan J, Chao H, Peng X. Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application. Chem. Soc. Rev. 50, 4185-4219 (2021). +2. Fan W, Huang P, Chen X. Overcoming the Achilles' heel of photodynamic therapy. Chem. Soc. Rev. 45, 6488-6519 (2016). + +<--- Page Split ---> + +3. Lúcio M, Nunes C, Gaspar D, Ferreira H, Lima JLFC, Reis S. Antioxidant Activity of Vitamin E and Trolox: Understanding of the Factors that Govern Lipid Peroxidation Studies In Vitro. Food Biophys. 4, 312-320 (2009). + +Q8: Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +Response: Indeed, the total quantum yield of all radiative and non- radiative processes cannot exceed 1. However, the energy consumption in no radiative processes contains both the energy for ISC processes and the molecular motion as well. Molecular aggregation could induce the restriction of intramolecular motions (RIM) and, as a result, reduce energy loss through non- radiative molecular motion, potentially increasing the energy available for emission and ISC processes. So, the energy efficiency of both emission and ISC can be enhanced in aggregated structure due to RIM. + +However, in specific cases, such as the graphene quantum dots reported by Zhang et al., the apparent quantum yield could be larger than \(1. ^{1}\) This occurs when the energy gaps between \(\Delta E_{\mathrm{ST}}\) and \(\Delta E_{\mathrm{TG}}\) (the energy gap between \(\mathrm{T_1}\) and Ground state) are larger than the formation energy of \(^{1}\mathrm{O}_{2}\) (22.5 kcal mol \(^{- 1}\) ). In such cases, \(^{1}\mathrm{O}_{2}\) generation happens through multiple pathways: energy transfer from \(\mathrm{T_1}\) (ET(1) in Fig. R6), but also the energy transfer from \(\mathrm{S_1}\) to \(^{3}\mathrm{O}_{2}\) during the \(\mathrm{S_1 - T_1}\) intersystem crossing transition (ET(2) in Figure R6). This multi- pathway mechanism can lead to an overall \(^{1}\mathrm{O}_{2}\) quantum yield greater than 1.0, as more than one \(^{1}\mathrm{O}_{2}\) molecule can be produced per absorbed photon. \(^{2}\) + +![](images/Figure_unknown_19.jpg) + +
Fig. R6 Schematic illustration of the \(^{1}\mathrm{O}_{2}\) generation mechanisms by conventional PDT agents (left) and GQDs (right).
+ +## References + +<--- Page Split ---> + +1. Ge J, et al. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation. Nat. Commun. 5, 4596 (2014). +2. Kanner RC, Foote CS. Singlet oxygen production from singlet and triplet states of 9,10-dicyanoanthracene. J. Am. Chem. Soc. 114, 678-681 (1992). + +Q9: Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +Response: As previously discussed, TBmA- Glu is a water- soluble molecule that forms aggregates within tumor cells upon activation by GGT to produce TBmA. Consequently, most of these aggregates are localized in the tumor cells. Furthermore, we have demonstrated the stability of TBmA aggregates for 72 hours in a 30% BSA solution. Additionally, considering that PDT processes were conducted 12 hours after administration of TBmA- Glu, it can be inferred that the TBmA aggregates exhibit sufficient stability to complete the PDT processes. + +Reviewer #2 (Remarks to the Author): + +Q1: The authors have addressed all the concerns in the revisions. And the manuscript is ready to be published. + +Response: We would like to express our sincere gratitude to the reviewer again for their invaluable suggestions, which have significantly enhanced the comprehensiveness and rigor of this paper. + +Reviewer #3 (Remarks to the Author): + +Q1: The paper's focus is the enzymatically catalyzed molecular aggregation for improving the response and PDT treatment. The paper has been revised accordingly, and ready for publication. + +Response: We would like to thank the reviewer for their invaluable suggestions, which have significantly improved the comprehensiveness and rigor of this paper. + +<--- Page Split ---> + +## Point-by-point Response + +We express our sincere gratitude to the reviewers, which have significantly enhanced the scholarly quality of our paper. In response to your valuable feedback and suggestions, we have carefully revised the manuscript. Our responses and revisions are presented in a distinguishable blue font for convenient reference. + +## Reviewer #1 (Remarks to the Author) + +General opinion + +The present manuscript claims to achieve a better targeting of a proposed photosensitizer (PS) which can activated by GGT and be excited at short wavelengths. + +Also, activated (aggregate structure) may have a better cytotoxic effect, compared its non- activated form, which is another example of activated- PS + +There have been countless photosensitizers which can be targeted one way of or another. Many reviews exist about activatable photosensitizers. Some enzymatically, some by hypoxia, by higher \(\mathrm{H}_2\mathrm{O}_2\) or GSH concentrations, or acidic pH. + +The main, may be the only reason why PDT did not develop significantly since 70's is that fact that light, even at the so- called "therapeutic window" does not go through tissues. And of course, there is no real justification for a \(450\mathrm{nm}\) chromophore to be proposed as a novelty. There are very specific, niche cases, where a single cell layer penetration may be useful. But citing these, is missing the point of all PDT- work. + +Type- I processes being less oxygen dependent has been proposed without real evidence. The new data provided by the authors is also not a fair comparison (see below). + +Thus the manuscript does not bring any novelty to the field. The requirement for aggregation, if anything, complicates the picture very unnecessarily. + +Response: We would like to thank the reviewer for the insightful comments, which have significantly enhanced the quality of our paper. + +## Reviewer #1 (Remarks to the Author): + +Q1: Light source in Fig S36 was not given, if it is white LED, it is not a fair comparison, because LED emission profile fits TbmA/aggregate better. + +Response: Rose Bengal (RB) has its maximum absorption at \(558\mathrm{nm}\) . We can see from the emission spectrum of the LED light (Fig. S28) that the LED has a broad maximum emission at \(550 - 600\mathrm{nm}\) . It means that LED emission also fits the absorption of RB. + +<--- Page Split ---> + +Q2: 0.5 or \(1\%\) hypoxia may be better. + +Response and revision: In previous experiments, we have proved that TBmA has more potent PDT efficiency than Rose Bengal (RB) even under anoxia conditions. So, we think the 0.5 or \(1\%\) hypoxia would not lead to the different PDT efficiency of TBmA and RB. Furthermore, to address your concerns about the hypoxia PDT efficiency, we decided to remove the discussion of the hypoxia photosensitization of AIE photosensitizers in our manuscript. + +Q3: Both of these articles while interesting, hardly relevant to PDT considering the absorption peaks of the proposed sensitizers are in blue, and the fact that they are very unique cases. The first one reached to a suprizing conclusion without doing any photophysical work. Vibrational (or rotational) relaxation and their control by micro- or molecular environments, by molecular steric hinderence is well known. However, only accurate quantum yield determinations would prove simulataneous increases in emission and singlet oxygen quantum yields. This is not done in Ref 1. + +Response and revision: I would like to clarify that our discussion here is indeed focused on the quantum yield during the photodynamic therapy (PDT) process. It is important for you to know that, regardless of the light source used to excite the photosensitizer, all photodynamic processes share the same underlying photophysical mechanisms. + +In the first reference, the authors demonstrated the quantum yield of graphene quantum dots (GQDs) using electron paramagnetic resonance (EPR) assays, which is a critical aspect of validating the multistate sensitization (MSS) mechanism. The authors also focused on the fluorescence intensity at \(680 \mathrm{nm}\) and the singlet oxygen ( \(^{1}\mathrm{O}_{2}\) ) quantum yield of GQDs in solutions with varying oxygen concentrations. All the results are in agreement with the proposed MSS mechanism, which suggests that an overall \(^{1}\mathrm{O}_{2}\) quantum yield greater than 1.0 can be achieved under specific conditions. However, we fully concur with your assessment that more work is necessary before any definitive conclusions. + +Q4: The problem is that now "activated" aggregates, will not stay forever in tumor cells, as these cells disintegrate. + +Response and revision: It is important to point out that we do not want the aggregates to stay in cells forever. What we need to make sure is that the "activated" aggregates work properly during treatment. The stability and photodynamic efficiency assays have proved that the activated aggregates could meet the therapeutic requirement in the study. + +<--- Page Split ---> + +Reviewer 1 responses to the authors' comments is highlighted in red. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". + +This referee finds important design flaws and problems with the implementation of the work. Response: We thank the reviewer for the constructive comments on our paper. In this manuscript, we actually did not intend to compare the Type I and Type II PDT processes, and the efficiency of type I and type II photosensitizers is not the key point of this work. We just want to present the objective performance of the developed photosensitizers based on their ROS generation capability. As clearly stated in the manuscript: "It was found that TBMa and + +ROS generation capability. As clearly stated in the manuscript: "It was found that TBMa and TBPa produced significantly higher ROS compared to TBMa- Glu and TBPa- Glu, even surpassing the commercial photosensitizer, Rose Bengal (RB). Moreover, TBMa was identified as the most potent photosensitizer among the four compounds. Further analysis revealed that TBMa and TBPa functioned as strong type I photosensitizers (Fig. 1c and Fig. S25), while TBMa- Glu and TBPa- Glu acted as very weak type II photosensitizers (Fig. 1c and Fig. S26)." + +\*\*\*The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +21. "only marginal variation was observed in the phototoxicity of TBMa-Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBMa-Glu (TBMa) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." + +Here are the major issues: + +Problem with Aggregates: + +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +Response and revision: Thank you for your thoughtful comments regarding AIE compounds. We appreciate your concerns and would like to address them point by point: + +<--- Page Split ---> + +(i) Stability and standardization: we acknowledge that stability is crucial for bio- application. Our recent studies have shown promising results regarding the stability of TBmA aggregates in high-protein environments, specifically: (a) Long-term stability: TBmA aggregates showed no significant degradation when dispersed in FBS for 72 hours (Fig. S28a and S28c). + +\*\*\* Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +(ii) (b) Photostability: The aggregates remained stable under continuous light irradiation for 30 minutes (Fig. S28a and S28b). These findings collectively highlight the exceptional stability exhibited by TBmA. These findings demonstrate the exceptional stability of TBmA aggregates in biologically relevant conditions. + +Moreover, numerous AIEggens, including small molecules or AIE nanoparticles, have been extensively reported for their long- term monitoring and theranostic applications. \(^{1,2,3}\) These pieces of evidence underscore the remarkable stability of AIEggens, making them highly promising candidates for theranostic applications. + +(iii) Aggregate structure: To address concerns about ill- defined aggregate structures, we extensively investigated the aggregate size of TBmA using Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). The results suggest that the TBmA forms spherical particles with 140 nm in 99% PBS and 150 nm diameter after the GGT catalysis reaction (12 h, Fig. S31). These results indicate that TBmA consistently forms nanoparticles of definite shape and size in aqueous environments, regardless of the specific conditions. Numerous works have been reported to show the definite shape and size, as well as the excellent stability and biocompatibility of the AIE aggregates. \(^{4,5,6}\) + +\*\*\* References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +(iv) A comparative analysis of small molecular drugs and AIE materials: Although molecular drugs and traditional photosensitizers have their advantages, AIE compounds offer unique benefits such as enhanced emission upon aggregation, responsiveness to stimuli, and multifunctional potential. Revealing reports increasingly indicate that small molecular photosensitizers, such as CE6, exhibit low solubility and undergo aggregation in solution, resulting in the deactivation of their photosensitizing activity and hindering their bioapplication. \(^{7,8,9,10}\) We believe that AIE compounds can serve as complementary agents, + +<--- Page Split ---> + +rather than substitutes, for small molecule drugs. Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring. \(^{4, 11, 12, 13}\) + +We believe that AIE compounds, including TBM- A- Glu, offer valuable and unique properties that complement existing molecular drugs and photosensitizers. While challenges remain, the growing body of research on AIE materials suggests significant potential for advancing biomedical imaging and therapeutic applications. We appreciate the reviewer's perspective and believe that continued research and development in this field will address current limitations and unlock new possibilities in biomedical science. + +\*\*\* While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +## Changes in the Revised Manuscript: + +Moreover, the TBM- A aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS (fetal bovine serum) solution for 72 h or light irradiated for 30 min. + +![](images/Figure_unknown_20.jpg) + +
Changes in the Supporting Information:
+ +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBM-A aggregates measured
+ +<--- Page Split ---> + +by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and \(72\mathrm{h}\) FBS preservation. + +![](images/Figure_unknown_21.jpg) + +
Fig. S31. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b-g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for \(12\mathrm{h}\) .
+ +## References + +1. Zuo J, et al. Long-term spatiotemporal and highly specific imaging of the plasma membrane of diverse plant cells using a near-infrared AIE probe. Angew. Chem. Int. Ed. 14, 2139-2148 (2023). +2. Wang Z, et al. Long-term fluorescent cellular tracing by the aggregates of aie bioconjugates. J. Am. Chem. Soc. 135, 8238-8245 (2013). +3. Li K, et al. Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing. Sci. Rep. 3, 1150 (2013). +4. Wang J, et al. Nanolab in a cell: Crystallization-induced in situ self-assembly for cancer theranostic amplification. J. Am. Chem. Soc. 144, 14388-14395 (2022). +5. Li Y, et al. Trojan Horse-Like Nano-AIE Aggregates Based on Homologous Targeting Strategy and Their Photodynamic Therapy in Anticancer Application. Adv. Sci. 8, 2102561 (2021). +6. Yan Z, et al. Preparation of ultrasmall AIE nanoparticles with tunable molecular packing via freeze assembly. Nano Lett. 23, 1030-1035 (2023). +7. Li Y, et al. Near-infrared light and redox dual-activatable nanosystems for synergistically + +<--- Page Split ---> + +cascaded cancer phototherapy with reduced skin photosensitization. Biomaterials 288, 121700 (2022). + +8. Tian S, He J, Lyu D, Li S, Xu Q-H. Aggregation enhanced photoactivity of photosensitizer conjugated metal nanoparticles for multimodal imaging and synergistic phototherapy below skin tolerance threshold. Nano Today 45, 101534 (2022). + +9. Wang H, Xue K-F, Yang Y, Hu H, Xu J-F, Zhang X. In Situ Hypoxia-Induced Supramolecular Perylene Diimide Radical Anions in Tumors for Photothermal Therapy with Improved Specificity. J. Am. Chem. Soc. 144, 2360-2367 (2022). + +10. Li X, et al. Nanostructured Phthalocyanine Assemblies with Protein-Driven Switchable Photoactivities for Biophotonic Imaging and Therapy. J. Am. Chem. Soc. 139, 10880-10886 (2017). + +11. Chen C, Zhang X, Gao Z, Feng G, Ding D. Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection. Nat. Protoc., in press (2024). + +12. Liu Z, Wang Q, Zhu Z, Liu M, Zhao X, Zhu W-H. AIE-based nanoaggregate tracker: high-fidelity visualization of lysosomal movement and drug-escaping processes. Chem. Sci. 11, 12755-12763 (2020). + +13. Yu Y, et al. Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking. Adv. Mater. 23, 3298-3302 (2011). + +Excitation wavelength: + +The absorption peak of the monomeric compounds and the aggregates in this work is around \(450~\mathrm{nm}\) . This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +Response and revision: We appreciate the reviewer's concern regarding light penetration and the effects of our light source. Our analysis of the white LED light shows predominant peaks at \(450~\mathrm{nm}\) , with no detectable UV peak, which could address the concerns of the reviewers about unintended UV- induced effects (Fig. S27). Furthermore, all anticancer \(\mathrm{IC}_{50}\) values of tested compounds were detected using the MTT assays, and no significant effect on cell viability was detected in the control group after exposure to LED irradiation. MTT assays and control experiments demonstrate that the observed cell death is due to \(\mathrm{TBmA}\) - Glu's photodynamic properties, not the LED light itself. + +\*\*\* May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to \(450~\mathrm{nm}\) peak. There are literature reports of blue (450 nm) light + +<--- Page Split ---> + +causing cellular damage. + +Depth of Penetration in Tissues: While it is true that the penetration depth of light at 450 nm is limited, this wavelength is still within the range where some penetration can occur in biological tissues. The actual penetration depth can be influenced by factors such as tissue type, pigmentation, and the optical properties of the tissue. Furthermore, we employed a minimally invasive approach for PDT to optimize the efficiency of photodynamic therapy and minimize the impact of light penetration. + +\*\*\* One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. \(450 \mathrm{nm}\) is not compatible with PDT. The typical penetration length as \(450 \mathrm{nm}\) is less than \(1 \mathrm{mm}\) , which is significantly less than needed for an effective "photo"- driven process. + +## Changes in the Revised Manuscript: + +The generation of total ROS generation (2,7'- dichlorodihydrofluorescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10- anthracenediy1- bis(methylene)dimalonic Acid, ABDA) by photosensitizers ( \(5 \mu \mathrm{M}\) ) after white LED light (predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation (20 \(\mathrm{mW}\cdot \mathrm{cm}^{- 2}\) ) for 15 min using the corresponding ROS indicator in PBS/DMSO ( \(\mathrm{v} / \mathrm{v} = 99:1\) ). DCF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) . + +# Changes in the Supporting Information: + +![](images/Figure_unknown_22.jpg) + +
Fig. S27. The emission wavelength analysis of the LED light.
+ +Confusion about the Type- I and Type- II PDT: + +<--- Page Split ---> + +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; and it is not easy to separate these two processes (I/II). + +Response: We appreciate the reviewer's insightful comments on the Type- I and Type- II PDT processes. We agree that PDT often involves a combination of both processes and that ROS species can undergo interconversion through various enzymatic processes in vivo. Our study focused on characterizing the predominant mechanism of \(\mathrm{TBmA}\) under specific conditions, not comparing the superiority of Type- I vs Type- II processes. We found that the cleaved \(\mathrm{TBmA}\) - Glu ( \(\mathrm{TBmA}\) ) primarily exerts its anticancer effects through the type I PDT process. And aligning with this finding, we observed the oxygen independence of \(\mathrm{TBmA}\) 's photodynamic activity in the hypoxia condition, which is potentially advantageous in hypoxic tumor environments. + +We acknowledge the complexity of PDT processes in biological systems, which may reflect both directly generated species and enzymatic interconversions. However, the ROS we detected in cells are coordinating with the results we detected in vitro, which validates the validity of our conclusion. + +\*\*\* First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to 0.5 % O2 hypoxia, or anoxia, the effectiveness would be much more different. + +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Ebselen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide (N3- ) is a singlet oxygen quencher + +Enhancement of emission "AND" PDT efficiency. + +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +Response: We appreciate the reviewer's insights regarding the competitive nature of fluorescence and reactive oxygen species (ROS) generation in AIE- PDT systems. While both processes utilize energy from the excited state, our findings on the simultaneous enhancement of aggregate luminescence and photodynamic activity are not contradictory. Here is some reported literature. + +(i) Aggregation-induced intermolecular intersystem crossing (AI-ISC): Jiang et al. proposed a new mechanism called aggregation-induced intersystem crossing (AI-ISC) to + +<--- Page Split ---> + +understand the effect of aggregation on increasing ISC efficiency. \(^{1,2}\) According to the AI- ISC theory, more excitonic couplings cause excited- state energy splitting and overlapping of singlet and triplet in aggregate. The energy splitting and overlapping significantly produce many ISC channels with very small \(\Delta E_{\mathrm{ST}}\) in aggregates, which is available for ISC processes. Therefore, the formation of aggregates can facilitate the production of triplet excitons. In addition to emitting phosphorescent radiation, these triplet excitons can also undergo a non- radiative pathway known as the aggregation- enhanced photodynamic effect to return to their ground state. \(^{3,4,5}\) + +\*\*\* Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +(ii) Restriction of intramolecular motion (RIM): The aggregation of AIE molecules results in a restriction of intramolecular rotations and vibrations, effectively suppressing molecular motions, which is also beneficial for the ISC process. \(^{6,7}\) + +All the evidence highlights the potential of AIE materials in PDT. The aggregation- induced changes in the molecular environment can optimize both the imaging and therapeutic aspects of the treatment. \(^{8,9,10}\) + +\*\*\*Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +## References: + +1. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +2. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +3. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). +4. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +<--- Page Split ---> + +5. Ji C, Lai L, Li P, Wu Z, Cheng W, Yin M. Organic dye assemblies with aggregation-induced photophysical changes and their bio-applications. Aggregate 2, e39 (2021).6. Kwok RTK, Leung CWT, Lam JWY, Tang BZ. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 44, 4228-4238 (2015).7. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020).8. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019).9. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020).10. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +<--- Page Split ---> + +## Response + +## General opinion + +The present manuscript claims to achieve a better targeting of a proposed photosensitizer (PS) which can activated by GGT and be excited at short wavelengths. + +Also, activated (aggregate structure) may have a better cytotoxic effect, compared its non- activated form, which is another example of activated- PS + +There have been countless photosensitizers which can be targeted one way of or another. Many reviews exist about activatable photosensitizers. Some enzymatically, some by hypoxia, by higher \(\mathrm{H}_2\mathrm{O}_2\) or GSH concentrations, or acidic pH. + +The main, may be the only reason why PDT did not develop significantly since 70's is that fact that light, even at the so- called "therapeutic window" does not go through tissues. And of course, there is no real justification for a \(450~\mathrm{nm}\) chromophore to be proposed as a novelty. There are very specific, niche cases, where a single cell layer penetration may be useful. But citing these, is missing the point of all PDT- work. + +Type- I processes being less oxygen dependent has been proposed without real evidence. The new data provided by the authors is also not a fair comparison (see below). + +Thus the manuscript does not bring any novelty to the field. The requirement for aggregation, if anything, complicates the picture very unnecessarily. + +## Reviewer #1 (Remarks to the Author): + +Q1: The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +251. "only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA- Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which + +<--- Page Split ---> + +is consistent with the prior findings." + +Response and revision: We appreciate the valuable suggestions provided by the reviewer. To enhance the accuracy of our study, we conducted additional experiments using Rose Bengal (RB), a well- established type II photosensitizer1, as a control. These experiments revealed that RB's photodynamic efficiency decreased significantly under hypoxia conditions (2% O2) compared to normoxia conditions, while TBmA maintained relatively consistent activity across both environments (Fig. R1). + +To discuss this result more accurately, we have revised our manuscript by replacing the statement "This suggests that oxygen content has negligible influence on its photodynamic activity." with "This suggests that TBmA exhibits tolerance towards hypoxic conditions." + +![](images/Figure_unknown_23.jpg) + +
Fig. S36. The effects of hypoxia (2% O2) and normoxia (20% O2) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells.
+ +## Revised in manuscript: + +Additionally, only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d), while the type- II PS, RB, showed a significant decrease in photodynamic efficiency under hypoxia conditions (2% O2) compared to normoxia conditions (Fig. S36). This suggests that TBmA exhibits tolerance towards hypoxic conditions. + +## Reference: + +1. Fischer BB, Krieger-Liszkay A, Eggen RIL. Oxidative stress induced by the photosensitizers neutral red (type I) or rose bengal (type II) in the light causes different molecular responses in Chlamydomonas reinhardtii. Plant Sci. 168, 747-759 (2005). + +## response + +\(+++\) Light source in Fig S36 was not given, if it is white LED, it is not a fair comparison, because LED emission profile fits TbmA/aggregate better. + +<--- Page Split ---> + +Q2: Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +Response: We appreciate the reviewer's insightful comments regarding the nature of supramolecular aggregation and the potential for de- aggregation in biological media. We would like to clarify several key points that address these concerns. + +Firstly, it's crucial to emphasize that TBmA- Glu is a water- soluble prodrug. The aggregation process only occurs after the Glu moiety is cleaved by GGT in HepG2 cells. This design ensures that TBmA- Glu remains soluble in the blood, avoiding premature aggregation. Aggregation is triggered specifically in the intracellular environment of GGT- overexpressing tumor cells. + +We acknowledge that FBS is not an ideal model for the intracellular environment. To address this issue, we further conducted stability studies using a \(30\%\) BSA (Bovine Serum Albumin) solution, which is a better model for the protein- rich intracellular milieu. The intracellular protein concentration typically ranges from 50- 400 mg/mL, and our \(30\%\) BSA solution ( \(\sim 300 \mathrm{mg / mL}\) ) falls within this range. TBmA aggregates showed remarkable stability in this environment, with no significant degradation observed over 72 hours (Fig. R1). + +We also agree that pharmacokinetics studies would be valuable. However, our system presents unique challenges for such studies, as the aggregates form intracellularly rather than in circulation. Collecting and analyzing intracellular aggregates from tumor sections poses significant technical difficulties. Our approach using a highly concentrated protein solution provides valuable insights into aggregate stability in a physiologically relevant environment. + +Importantly, beyond structural stability, we have observed that the aggregates maintain their photodynamic properties in the \(30\%\) BSA solution for \(72 \mathrm{~h}\) (Fig. R2). This functional stability is crucial for the compound's theranostic applications. + +<--- Page Split ---> +![](images/Figure_unknown_24.jpg) + +
Fig. R1. The long-term stability of TBmA aggregates in \(30\%\) BSA solutions.
+ +![](images/Figure_unknown_25.jpg) + +
Fig. R2. The ROS generation capacity of TBmA aggregates after dispersed in \(30\%\) BSA solution for \(0 \mathrm{~h}\) (a) and \(72 \mathrm{~h}\) (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity \((I / I_0)\) of DC versus the irradiation \((20 \mathrm{mW} \cdot \mathrm{cm}^{-2})\) time, where \(I_0 = \mathrm{PL}\) intensity of DCFH in solutions without light irradiation.
+ +Q3: References 4, 5 and 6 were carefully checked. Stability of the aggregates “in vivo” was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +Response: We thank the reviewer for the critical feedback. The unique photophysical properties of AIE compounds stem from the restriction of intramolecular motion (RIM) mechanism, where aggregation limits molecular rotations and vibrations, leading to enhanced fluorescence. Therefore, the fluorescence behavior of AIE materials does provide valuable insights into their molecular state and environment. + +This interpretation is supported by several factors. First of all, TBmA- Glu is + +<--- Page Split ---> + +engineered to aggregate specifically in response to GGT activity, which is overexpressed in certain tumor cells. This targeted approach minimizes premature aggregation in circulation. Secondly, the crowded, protein- rich cytoplasmic environment of tumor cells likely provides conditions that favor aggregate stability once formed. Additionally, we observed that the photosensitivity of TBmA was maintained in our \(30\%\) BSA studies, suggesting a preservation of the aggregate structure. + +Q4: While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +Response: We appreciate the reviewer's thoughtful comments regarding the therapeutic relevance of AIE compounds and the importance of careful characterization of their behavior in biological systems. + +Regarding the stability and behavior of TBmA, we emphasize that TBmA- Glu is designed as a water- soluble prodrug that only forms aggregates within tumor cells following enzymatic reaction. This targeted approach minimizes potential issues related to premature aggregation or size changes in circulation. Furthermore, we have demonstrated the stability of TBmA aggregates in a \(30\%\) BSA solution for 72 hours, providing initial evidence of their potential stability in protein- rich environments. + +About "personalized medicine and real- time treatment monitoring." in the previous response letter: The full sentence is "Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring." We agree that such terminology should be used judiciously, especially in early- stage research, however, our intention here is to highlight the potential of AIE materials to contribute to these fields in the future, rather than to claim immediate clinical applicability. + +The unique properties of AIE materials, including their AIE and potential for stimuli- responsive behavior, do offer intriguing possibilities for both imaging and therapeutic applications. However, we agree that rigorous investigation is needed to establish their efficacy and safety for PDT or other therapeutic schemes. Moving forward, we will focus on providing concrete evidence for the specific advantages of AIE compounds in relevant biological contexts, rather than speculating on broad future applications. We believe this approach will better serve the scientific community and responsibly advance the field. + +Q5: May be it wasn't clear in my earlier statement of concern, I did say near UV, + +<--- Page Split ---> + +but I was specifically referring to \(450 \mathrm{nm}\) peak. There are literature reports of blue (450 nm) light causing cellular damage. + +Response: We acknowledge that there are indeed literature reports of blue light (450 nm) causing cellular damage. This is an important consideration in photodynamic therapy and other light- based treatments. However, we would like to emphasize that the biological effects of light exposure are highly dependent on both wavelength and dosage. + +In our experiments, we carefully controlled the light dosage to minimize potential phototoxicity while maintaining therapeutic efficacy. Under the experimental conditions described in our manuscript, we did not observe any significant effects on cell viability following LED light irradiation (Fig. R3). + +To address the reviewer's concern, we also conducted a blue light irradiation (450 nm, \(12 \mathrm{J / cm^2}\) ) PDT assay. In this experiment, we also found no significant effect on cellular viability. This suggests that at the dosages used in our study, the blue light alone does not cause substantial cellular damage. + +However, we agree that the potential for phototoxicity is an important consideration in developing light- based therapies. In future studies, we plan to conduct a more comprehensive dose- response analysis to determine the threshold at which blue light exposure may begin to affect cell viability. We also intend to investigate the potential long- term effects of repeated light exposure and compare the effects of our AIE- based approach with traditional photosensitizers at equivalent light doses. + +![](images/Figure_unknown_26.jpg) + +
Fig. R3 The impact of white light and \(450 \mathrm{nm}\) light exposure ( \(12 \mathrm{J / cm^2}\) ) on the cellular viability of HepG2 cells.
+ +Q6: One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as \(450 \mathrm{nm}\) is less than \(1 \mathrm{mm}\) , which is significantly less than needed for an effective "photo"- driven process. + +Response: It is correct that the typical penetration depth of \(450 \mathrm{nm}\) light is less than \(1 \mathrm{mm}\) in tissue, which is indeed less than ideal for treating deep- seated tumors. + +<--- Page Split ---> + +However, we would like to highlight several important considerations: + +First, though direct light penetration is restricted, the effective depth of PDT damage may increase due to light reflection and scattering within tissues. This occurrence can expand the scope of the photodynamic impact beyond the initial penetration depth. + +Secondly, several clinical scenarios exist where shallow light penetration is sufficient or even advantageous. For instance, PDT with blue light excitation could be particularly useful for superficial skin cancers and precancerous lesions, intraoperative treatment of residual tumor cells after surgical resection, treatment of early- stage mucosal cancers in inaccessible areas (e.g., oral cavity, bladder), and endoscopic applications for gastrointestinal tumors. + +Finally, numerous published studies demonstrate the successful use of \(450 \mathrm{nm}\) light and white light (including the blue spectrum) for PDT when the photosensitizers have maximum absorption around \(450 \mathrm{nm}\) . 2, 3, 4, 5, 6, 7 + +Nevertheless, we fully agree that blue light's limited tissue penetration restricts the broader applicability of our current system for treating deep- seated tumors. Given this limitation, our future research directions include exploring two- photon excitation to achieve deeper tissue penetration, investigating upconversion nanoparticles to convert longer- wavelength light to blue light locally, and developing new AIE photosensitizers with red- shifted absorption for improved tissue penetration. We believe that addressing these challenges will expand the potential applications of our AIE- based PDT system while utilizing its unique properties. + +## References: + +2. Fan L, et al. A Bioactive Photosensitizer for Hypoxia-Tolerant Molecular Targeting-Photo-Immunotherapy of Malignant Tumor. Adv. Funct. Mater. 34, 2313755 (2023). +3. Li X, et al. A novel 450-nm laser-mediated sinoporphyrin sodium-based photodynamic therapy induces autophagic cell death in gastric cancer through regulation of the ROS/PI3K/Akt/mTOR signaling pathway. BMC Med. 20, 475 (2022). +4. Mei Y, et al. A Novel Photosensitizer Based 450-nm Blue Laser-Mediated Photodynamic Therapy Induces Apoptosis in Colorectal Cancer - in Vitro and in Vivo Study. Front. Biosci. (Landmark Ed) 29, 199 (2024). +5. Chen Y, et al. Photoactivatable metal organic framework for synergistic ferroptosis and photodynamic therapy using 450 nm laser. Chem. Eng. J. 454, 140438 (2023). +6. Sun P, et al. A water-soluble phosphorescent conjugated polymer brush for tumor-targeted photodynamic therapy. Polym. Chem. 8, 5836-5844 (2017). +7. An J, et al. An unexpected strategy to alleviate hypoxia limitation of photodynamic therapy by biotinylation of photosensitizers. Nat. Commun. 13, 2225 (2022). + +<--- Page Split ---> + +Q7: First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to \(0.5\%\) O2 hypoxia, or anoxia, the effectiveness would be much more different. + +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Esbelsen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide \(\mathrm{(N_3)}\) is a singlet oxygen quencher. + +Response and revision: We agree with the reviewer that oxygen plays a pivotal role in the Type I and Type II PDT processes. However, from the PDT mechanism, we know that the type I photosensitizers could directly transfer electrons to the substrate, forming a radical cation or neutral radical. These radicals could immediately react with \(\mathrm{O_2}\) or \(\mathrm{H_2O}\) to generate hydrogen peroxide \(\mathrm{(H_2O_2)}\) , hydroxyl radicals (- OH), or superoxide anions (- \(\mathrm{O_2}\) - ) (Fig. R4). \(^{1,2}\) + +We have tried but could not finish the antitumor PDT assays in the anaerobic conditions, because the anoxia condition resulted in death of the tumor cells (Fig. R5a). So, we re- evaluated the photodynamic efficiency of \(\mathrm{TBmA}\) and RB using a deoxidized PBS solution. The results showed that \(\mathrm{TBmA}\) could also induce the oxidation of DFCH under the anoxia condition (Fig. R5b), while the photodynamic efficiency of RB showed significant degradation. Hence, type- I photosensitizers exhibit relatively higher tolerance towards oxygen concentrations, which implies that, even under low oxygen conditions, they can still engage in substrate reactions through electron transfer. + +We are sorry for the mistake in the figure legend in Figure 4b. "Esbelsen" has been revised as "Trolox." However, it should be noted that Trolox is not only a \(^{1}\mathrm{O_2}\) scavenger but also a scavenger of peroxy and alkoxy groups. \(^{3}\) The type- I designation is mainly based on the ROS species we detected in vitro (Fig. R5c). + +![](images/Figure_unknown_27.jpg) + +
Fig. R4 Scheme of the photochemical reactions for type I and type II PDT. \(^{9}\)
+ +<--- Page Split ---> +![](images/Figure_unknown_28.jpg) + +
Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \(10~\mu \mathrm{M}\) ) in the presence of \(5~\mu \mathrm{M}\) photosensitizers in DMSO-PBS \((v:v = 1:99)\) after irradiation ( \(20\mathrm{mW}\cdot \mathrm{cm}^{-2}\) ) for a different time under anoxia conditions. (b) \(\mathrm{TBmA}\) , (c) Rose Bengal (RB). DCHF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) .
+ +## Revised in manuscript: + +Trolox: \(50~\mu \mathrm{M}\) (ROO- scavenger and \(^{1}\mathrm{O}_{2}\) scavenger); D- mannitol: \(50~\mathrm{mM}\) (OH scavenger); Tiron: \(10\mathrm{mM}\) ( \(\cdot \mathrm{O}_{2}\) scavenger); \(\mathrm{NaN}_3\) : \(5\mathrm{mM}\) ( \(\mathrm{O}_2\) scavenger) + +## References: + +1. Zhao X, Liu J, Fan J, Chao H, Peng X. Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application. Chem. Soc. Rev. 50, 4185-4219 (2021). +2. Fan W, Huang P, Chen X. Overcoming the Achilles' heel of photodynamic therapy. Chem. Soc. Rev. 45, 6488-6519 (2016). +3. Lúcio M, Nunes C, Gaspar D, Ferreira H, Lima JLFC, Reis S. Antioxidant Activity of Vitamin E and Trolox: Understanding of the Factors that Govern Lipid Peroxidation Studies In Vitro. Food Biophys. 4, 312-320 (2009). + +\(+ + + 0.5\) or \(1\%\) hypoxia may be better. + +Q8: Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +Response: Indeed, the total quantum yield of all radiative and non- radiative processes cannot exceed 1. However, the energy consumption in no radiative processes contains both the energy for ISC processes and the molecular motion as well. Molecular aggregation could induce the restriction of intramolecular motions (RIM) and, as a result, reduce energy loss through non- radiative molecular motion, potentially + +<--- Page Split ---> + +increasing the energy available for emission and ISC processes. So, the energy efficiency of both emission and ISC can be enhanced in aggregated structure due to RIM. + +However, in specific cases, such as the graphene quantum dots reported by Zhang et al., the apparent quantum yield could be larger than \(1. ^{1}\) This occurs when the energy gaps between \(\Delta E_{\mathrm{ST}}\) and \(\Delta E_{\mathrm{TG}}\) (the energy gap between \(\mathrm{T_1}\) and Ground state) are larger than the formation energy of \(^{1}\mathrm{O}_{2}\) (22.5 kcal mol \(^{- 1}\) ). In such cases, \(^{1}\mathrm{O}_{2}\) generation happens through multiple pathways: energy transfer from \(\mathrm{T_1}\) (ET(1) in Fig. R6), but also the energy transfer from \(\mathrm{S_1}\) to \(^{3}\mathrm{O}_{2}\) during the \(\mathrm{S_1 - T_1}\) intersystem crossing transition (ET(2) in Figure R6). This multi- pathway mechanism can lead to an overall \(^{1}\mathrm{O}_{2}\) quantum yield greater than 1.0, as more than one \(^{1}\mathrm{O}_{2}\) molecule can be produced per absorbed photon. \(^{2}\) + +![PLACEHOLDER_60_0] + +
Fig. R6 Schematic illustration of the \(^{1}\mathrm{O}_{2}\) generation mechanisms by conventional PDT agents (left) and GQDs (right).
+ +## References + +1. Ge J, et al. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation. Nat. Commun. 5, 4596 (2014). +2. Kanner RC, Foote CS. Singlet oxygen production from singlet and triplet states of 9,10-dicyanoanthracene. J. Am. Chem. Soc. 114, 678-681 (1992). + ++++ Both of these articles while interesting, hardly relevant to PDT considering the absorption peaks of the proposed sensitizers are in blue, and the fact that they are very unique cases. The first one reached to a suprizing conclusion without doing any photophysical work. Vibrational (or rotational) relaxation and their control by micro- or molecular environments, by molecular steric hinderence is well known. However, only accurate quantum yield determinations would prove simulataneous increases in emission and singlet oxygen quantum yields. This is not done in Ref 1. + +Q9: Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short + +<--- Page Split ---> + +wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +Response: As previously discussed, TBmA- Glu is a water- soluble molecule that forms aggregates within tumor cells upon activation by GGT to produce TBmA. Consequently, most of these aggregates are localized in the tumor cells. Furthermore, we have demonstrated the stability of TBmA aggregates for 72 hours in a \(30\%\) BSA solution. Additionally, considering that PDT processes were conducted 12 hours after administration of TBmA- Glu, it can be inferred that the TBmA aggregates exhibit sufficient stability to complete the PDT processes. + ++++ The problem is that now "activated" aggregates, will not stay forever in tumor cells, as these cells disintegrate. + +<--- Page Split ---> diff --git a/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0f2295df213985a5fe9ec079986e86f8acafd717 --- /dev/null +++ b/peer_reviews/12c8cd2ab4e7cfd26a2e2ccf93098324824525e6e4e9cfa53534dc8d649ac45f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1741 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[75, 96, 296, 119]]<|/det|> +# Peer Review File + +<|ref|>title<|/ref|><|det|>[[75, 160, 733, 187]]<|/det|> +# Enzymatically Catalyzed Molecular Aggregation + +<|ref|>text<|/ref|><|det|>[[73, 199, 509, 217]]<|/det|> +Corresponding Author: Professor Ben Zhong Tang + +<|ref|>text<|/ref|><|det|>[[72, 249, 870, 265]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[72, 276, 890, 291]]<|/det|> +Attachments originally included by the reviewers as part of their assessment can be found at the end of this file. + +<|ref|>text<|/ref|><|det|>[[73, 328, 144, 342]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 354, 219, 368]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 160, 394]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 406, 238, 420]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 420, 911, 447]]<|/det|> +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". + +<|ref|>text<|/ref|><|det|>[[73, 459, 697, 473]]<|/det|> +This referee finds important design flaws and problems with the implementation of the work. + +<|ref|>text<|/ref|><|det|>[[73, 485, 253, 499]]<|/det|> +Here are the major issues: + +<|ref|>text<|/ref|><|det|>[[73, 511, 252, 525]]<|/det|> +Problem with Aggregates: + +<|ref|>text<|/ref|><|det|>[[72, 536, 916, 603]]<|/det|> +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +<|ref|>text<|/ref|><|det|>[[73, 615, 230, 628]]<|/det|> +Excitation wavelength: + +<|ref|>text<|/ref|><|det|>[[72, 641, 920, 694]]<|/det|> +The absorption peak of the monomeric compounds and the aggregates in this work is around 450 nm. This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +<|ref|>text<|/ref|><|det|>[[73, 705, 382, 719]]<|/det|> +Confusion about the Type- I and Type- II PDT: + +<|ref|>text<|/ref|><|det|>[[72, 731, 915, 785]]<|/det|> +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; it is not and it is not easy to separate these two processes (I/II). + +<|ref|>text<|/ref|><|det|>[[73, 797, 410, 811]]<|/det|> +Enhancement of emission "AND" PDT efficiency. + +<|ref|>text<|/ref|><|det|>[[72, 822, 895, 850]]<|/det|> +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +<|ref|>text<|/ref|><|det|>[[73, 862, 161, 875]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 889, 238, 902]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 902, 900, 942]]<|/det|> +Tang and colleagues reported a \(\gamma\) - glutamyl transferase (GGT) activatable aggregation- induced emission photosensitizer (AIE- PS) named TBmA- Glu. TBmA- Glu is designed to specifically target and aggregate cancer cells through the catalytic action of tumor- overexpression GGT. Selective tumor cell aggregation not only enhances AIE- PS emission and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 922, 151]]<|/det|> +photodynamic activity but also induces ferroptosis in cancer cells by depleting GSH and promoting lipid peroxidation. Both in vitro cell assays and in vivo animal models were used to validate the phototoxicity and antitumor effects of TBmA- Glu, providing a comprehensive assessment of its potential as a therapeutic agent. The aggregation strategies in this paper allow a controlled release of the photodynamic effect, which is critical for therapies such as PDT. AIE- PS remains dormant until it reaches the cancerous environment where GGT is present, ensuring minimal impact on healthy cells and maximizing the therapeutic effect on cancer cells. This study highlights the significance of targeting activation of AIE- PSs for targeting and enhanced cancer photodynamic therapy. It is also a sophisticated strategy for targeted delivery and activation of a photodynamic therapeutic agent for disease. I suggest this article be published with minor revisions. + +<|ref|>text<|/ref|><|det|>[[72, 163, 897, 203]]<|/det|> +1. The authors claimed that TBmA-Glu could be activated by GGT. Is there evidence to suggest that TBmA-Glu could be effective against other types of cancer that overexpress GGT, or is its application currently limited to the cancer types studied? + +<|ref|>text<|/ref|><|det|>[[70, 214, 916, 230]]<|/det|> +2. How photostable is TBmA-Glu under the conditions used for PDT, and does its aggregation state affect its photostability? + +<|ref|>text<|/ref|><|det|>[[72, 241, 920, 282]]<|/det|> +3. The author claimed the aggregate size has a great impression on the PDT efficiency of AIE-PSs, What are the typical sizes and shapes of the TBmA-Glu aggregates formed in the presence of GGT? How do these properties affect the emission properties and PDT efficacy? + +<|ref|>text<|/ref|><|det|>[[70, 293, 907, 322]]<|/det|> +4. Can aggregated TBmA be expelled from cancer cells via exocytosis, potentially reducing its therapeutic efficacy? Long-term (48 h) cellular imaging results should be provided by the author. + +<|ref|>text<|/ref|><|det|>[[70, 332, 910, 348]]<|/det|> +5. The abbreviations, such as DCF, DCFH-DA, HPF, ABDA, CLSM, et al., should be defined at the first time they are used. + +<|ref|>text<|/ref|><|det|>[[73, 359, 163, 372]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 384, 238, 398]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 397, 915, 543]]<|/det|> +This work present a novel approach to targeted cancer therapy by leveraging the tumor- overexpressed enzyme \(\gamma\) - Glutamyl Transferase (GGT) to induce aggregation of an aggregation- induced emission photosensitizer (AIE- PS), TBmA- Glu. This innovative strategy not only enhances the photosensitivity of the AIE- PS but also results in the degradation of GGT and the accumulation of lipid peroxides, leading to cancer cell ferroptosis. The study is significant for its potential to advance targeted photodynamic therapy (PDT) and the development of smart therapeutics that exploit enzyme activity for controlled molecular aggregation within cancer cells. The authors have demonstrated a clear understanding of the complex interactions between molecular aggregation and biological environments, and the manuscript is well- structured, presenting a logical flow of information from synthesis and characterization to in vivo efficacy. The results are compelling, showing the selective activation of TBmA- Glu by GGT, its enhanced photodynamic activity, and the subsequent therapeutic effects on cancer cells. The manuscript is well- written and provides a solid foundation for further research in the field of nanomedicine and targeted drug delivery. I recommend publication following minor modifications, my concerns are outlined below: + +<|ref|>text<|/ref|><|det|>[[70, 553, 923, 581]]<|/det|> +1. The author could incorporate a concise, visual representation of key discoveries and TBmA-Glu's proposed mechanism of action through a mechanistic cartoon or schematic. + +<|ref|>text<|/ref|><|det|>[[70, 592, 920, 608]]<|/det|> +2. The stability of the aggregates of TBmA, especially the photostability of it in physiological conditions should be discussed. + +<|ref|>text<|/ref|><|det|>[[70, 618, 920, 647]]<|/det|> +3. The author acclaimed the lipid peroxides (LPOs) resulting from the photodynamic process of activated AIE-PS induce the ferroptosis of cancer cells, the changes in the level of LPOs in cancer cells after photodynamic therapy should be quantified. + +<|ref|>text<|/ref|><|det|>[[72, 657, 652, 672]]<|/det|> +4. Detailed experimental procedures for minimally invasive PDT should be provided. + +<|ref|>text<|/ref|><|det|>[[73, 697, 144, 710]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 723, 219, 736]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 749, 160, 762]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 775, 238, 789]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 789, 545, 803]]<|/det|> +Reviewer 1 responses to the authors' comments is highlighted in red. + +<|ref|>text<|/ref|><|det|>[[73, 803, 253, 815]]<|/det|> +REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[73, 816, 333, 829]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 828, 920, 945]]<|/det|> +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". This referee finds important design flaws and problems with the implementation of the work. Response: We thank the reviewer for the constructive comments on our paper. In this manuscript, we actually did not intend to compare the Type I and Type II PDT processes, and the efficiency of type I and type II photosensitizers is not the key point of this work. We just want to present the objective performance of the developed photosensitizers based on their ROS generation capability. As clearly stated in the manuscript: "It was found that TBmA and TBpA produced significantly higher ROS compared to TBmA- Glu and TBpA- Glu, even surpassing the commercial photosensitizer, Rose Bengal (RB). Moreover, TBmA was identified as the most potent photosensitizer among the four compounds. Further analysis revealed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 900, 75]]<|/det|> +that TBmA and TBpA functioned as strong type I photosensitizers (Fig. 1c and Fig. S25), while TBmA- Glu and TBpA- Glu acted as very weak type II photosensitizers (Fig. 1c and Fig. S26)." + +<|ref|>text<|/ref|><|det|>[[72, 85, 914, 140]]<|/det|> +\*\*\*The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +<|ref|>text<|/ref|><|det|>[[72, 140, 920, 181]]<|/det|> +251. "only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA- Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." + +<|ref|>text<|/ref|><|det|>[[72, 192, 254, 204]]<|/det|> +Here are the major issues: + +<|ref|>text<|/ref|><|det|>[[72, 205, 254, 218]]<|/det|> +Problem with Aggregates: + +<|ref|>text<|/ref|><|det|>[[72, 217, 915, 281]]<|/det|> +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +<|ref|>text<|/ref|><|det|>[[72, 281, 910, 308]]<|/det|> +Response and revision: Thank you for your thoughtful comments regarding AIE compounds. We appreciate your concerns and would like to address them point by point: + +<|ref|>text<|/ref|><|det|>[[72, 308, 910, 399]]<|/det|> +(i) Stability and standardization: we acknowledge that stability is crucial for bio-application. Our recent studies have shown promising results regarding the stability of TBmA aggregates in high-protein environments, specifically: (a) Long-term stability: TBmA aggregates showed no significant degradation when dispersed in FBS for 72 hours (Fig. S28a and S28c). \*\*\* Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +<|ref|>text<|/ref|><|det|>[[72, 411, 900, 451]]<|/det|> +(ii) (b) Photostability: The aggregates remained stable under continuous light irradiation for 30 minutes (Fig. S28a and S28b). These findings collectively highlight the exceptional stability exhibited by TBmA. These findings demonstrate the exceptional stability of TBmA aggregates in biologically relevant conditions. + +<|ref|>text<|/ref|><|det|>[[72, 451, 904, 490]]<|/det|> +Moreover, numerous AIEgens, including small molecules or AIE nanoparticles, have been extensively reported for their long- term monitoring and therapeutic applications.1, 2, 3 These pieces of evidence underscore the remarkable stability of AIEgens, making them highly promising candidates for therapeutic applications. + +<|ref|>text<|/ref|><|det|>[[72, 490, 905, 568]]<|/det|> +(iii) Aggregate structure: To address concerns about ill- defined aggregate structures, we extensively investigated the aggregate size of TBmA using Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). The results suggest that the TBmA forms spherical particles with 140 nm in 99% PBS and 150 nm diameter after the GGT catalysis reaction (12 h, Fig. S31). These results indicate that TBmA consistently forms nanoparticles of definite shape and size in aqueous environments, regardless of the specific conditions. Numerous works have been reported to show the definite shape and size, as well as the excellent stability and biocompatibility of the AIE aggregates.4, 5, 6 + +<|ref|>text<|/ref|><|det|>[[72, 568, 880, 595]]<|/det|> +\*\*\* References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +<|ref|>text<|/ref|><|det|>[[72, 607, 905, 710]]<|/det|> +(iv) A comparative analysis of small molecular drugs and AIE materials: Although molecular drugs and traditional photosensitizers have their advantages, AIE compounds offer unique benefits such as enhanced emission upon aggregation, responsiveness to stimuli, and multifunctional potential. Revealing reports increasingly indicate that small molecular photosensitizers, such as CE6, exhibit low solubility and undergo aggregation in solution, resulting in the deactivation of their photosensitizing activity and hindering their biopallcation.7, 8, 9, 10 We believe that AIE compounds can serve as complementary agents, rather than substitutes, for small molecule drugs. Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring. 4, 11, 12, 13 + +<|ref|>text<|/ref|><|det|>[[72, 710, 900, 775]]<|/det|> +We believe that AIE compounds, including TBmA- Glu, offer valuable and unique properties that complement existing molecular drugs and photosensitizers. While challenges remain, the growing body of research on AIE materials suggests significant potential for advancing biomedical imaging and therapeutic applications. We appreciate the reviewer's perspective and believe that continued research and development in this field will address current limitations and unlock new possibilities in biomedical science. + +<|ref|>text<|/ref|><|det|>[[72, 788, 899, 840]]<|/det|> +\*\*\* While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +<|ref|>text<|/ref|><|det|>[[72, 852, 323, 866]]<|/det|> +Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[72, 866, 895, 920]]<|/det|> +Moreover, the TBmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS (fetal bovine serum) solution for 72 h or light irradiated for 30 min. Changes in the Supporting Information: + +<|ref|>text<|/ref|><|det|>[[70, 931, 912, 947]]<|/det|> +Fig. S28. (a) The average hydrodynamic diameter (Z- average) of TBmA aggregates measured by Dynamic Light Scattering + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 770, 61]]<|/det|> +(DLS). The distribution of TBM a aggregates during 30 min light irradiation and 72 h FBS preservation. + +<|ref|>text<|/ref|><|det|>[[72, 85, 889, 126]]<|/det|> +Fig. S31. (a) The average hydrodynamic diameter (Z- average) of TBM a aggregates produced in GGT catalytic reaction measured by DLS. (b- g) Distribution of TBM a aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBM a aggregates formed after the GGT catalytic reaction for 12 h. + +<|ref|>sub_title<|/ref|><|det|>[[72, 139, 155, 151]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[70, 152, 914, 476]]<|/det|> +1. Zuo J, et al. Long-term spatiotemporal and highly specific imaging of the plasma membrane of diverse plant cells using a near-infrared AIE probe. Angew. Chem. Int. Ed. 14, 2139-2148 (2023). +2. Wang Z, et al. Long-term fluorescent cellular tracing by the aggregates of aie bioconjugates. J. Am. Chem. Soc. 135, 8238-8245 (2013). +3. Li K, et al. Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing. Sci. Rep. 3, 1150 (2013). +4. Wang J, et al. Nanolab in a cell: Crystallization-induced in situ self-assembly for cancer theranostic amplification. J. Am. Chem. Soc. 144, 14388-14395 (2022). +5. Li Y, et al. Trojan Horse-Like Nano-AIE Aggregates Based on Homologous Targeting Strategy and Their Photodynamic Therapy in Anticancer Application. Adv. Sci. 8, 2102561 (2021). +6. Yan Z, et al. Preparation of ultrasmall AIE nanoparticles with tunable molecular packing via freeze assembly. Nano Lett. 23, 1030-1035 (2023). +7. Li Y, et al. Near-infrared light and redox dual-activatable nanosystems for synergistically cascaded cancer phototherapy with reduced skin photosensitization. Biomaterials 288, 121700 (2022). +8. Tian S, He J, Lyu D, Li S, Xu Q-H. Aggregation enhanced photocativity of photosensitizer conjugated metal nanoparticles for multimodal imaging and synergistic phototherapy below skin tolerance threshold. Nano Today 45, 101534 (2022). +9. Wang H, Xue K-F, Yang Y, Hu H, Xu J-F, Zhang X. In Situ Hypoxia-Induced Supramolecular Perylene Diimide Radical Anions in Tumors for Photothermal Therapy with Improved Specificity. J. Am. Chem. Soc. 144, 2360-2367 (2022). +10. Li X, et al. Nanostructured Phthalocyanine Assemblies with Protein-Driven Switchable Photoactivities for Biophotonic Imaging and Therapy. J. Am. Chem. Soc. 139, 10880-10886 (2017). +11. Chen C, Zhang X, Gao Z, Feng G, Ding D. Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection. Nat. Protoc., in press (2024). +12. Liu Z, Wang Q, Zhu Z, Liu M, Zhao X, Zhu W-H. AIE-based nanoaggregate tracker: high-fidelity visualization of lysosomal movement and drug-escaping processes. Chem. Sci. 11, 12755-12763 (2020). +13. Yu Y, et al. Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking. Adv. Mater. 23, 3298-3302 (2011). + +<|ref|>sub_title<|/ref|><|det|>[[72, 489, 230, 501]]<|/det|> +## Excitation wavelength: + +<|ref|>text<|/ref|><|det|>[[72, 502, 920, 555]]<|/det|> +The absorption peak of the monomeric compounds and the aggregates in this work is around 450 nm. This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +<|ref|>text<|/ref|><|det|>[[72, 555, 917, 634]]<|/det|> +Response and revision: We appreciate the reviewer's concern regarding light penetration and the effects of our light source. Our analysis of the white LED light shows predominant peaks at 450 and 570 nm, with no detectable UV peak, which could address the concerns of the reviewers about unintended UV- induced effects (Fig. S27). Furthermore, all anticancer IC50 values of tested compounds were detected using the MTT assays, and no significant effect on cell viability was detected in the control group after exposure to LED irradiation. MTT assays and control experiments demonstrate that the observed cell death is due to TBMa- Glu's photodynamic properties, not the LED light itself. + +<|ref|>text<|/ref|><|det|>[[72, 645, 920, 673]]<|/det|> +\*\*\* May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to 450 nm peak. There are literature reports of blue (450 nm) light causing cellular damage. + +<|ref|>text<|/ref|><|det|>[[72, 684, 917, 738]]<|/det|> +Depth of Penetration in Tissues: While it is true that the penetration depth of light at 450 nm is limited, this wavelength is still within the range where some penetration can occur in biological tissues. The actual penetration depth can be influenced by factors such as tissue type, pigmentation, and the optical properties of the tissue. Furthermore, we employed a minimally invasive approach for PDT to optimize the efficiency of photodynamic therapy and minimize the impact of light penetration. + +<|ref|>text<|/ref|><|det|>[[72, 750, 912, 790]]<|/det|> +\*\*\* One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as 450 nm is less than 1 mm, which is significantly less than needed for an effective "photo"- driven process. + +<|ref|>text<|/ref|><|det|>[[72, 828, 922, 899]]<|/det|> +Changes in the Revised Manuscript: The generation of total ROS generation (2',7'- dichlorodihydrofroourescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10- anthracenediy1- bis(methylene)dinamionic Acid, ABDA) by photosensitizers (5 \(\mu \mathrm{M}\) ) after white LED light (predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation (20 mW- cm- 2) for 15 min using the corresponding ROS indicator in PBS/DMSO (v/v = 99:1). DCF, \(\lambda \mathrm{ex} = 488 \mathrm{nm}\) . Changes in the Supporting Information: + +<|ref|>text<|/ref|><|det|>[[72, 919, 490, 933]]<|/det|> +Fig. S27. The emission wavelength analysis of the LED light. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 382, 60]]<|/det|> +Confusion about the Type- I and Type- II PDT: + +<|ref|>text<|/ref|><|det|>[[72, 60, 920, 112]]<|/det|> +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; and it is not easy to separate these two processes (I/II). + +<|ref|>text<|/ref|><|det|>[[72, 111, 923, 202]]<|/det|> +Response: We appreciate the reviewer's insightful comments on the Type- I and Type- II PDT processes. We agree that PDT often involves a combination of both processes and that ROS species can undergo interconversion through various enzymatic processes in vivo. Our study focused on characterizing the predominant mechanism of TBM a under specific conditions, not comparing the superiority of Type- I vs Type- II processes. We found that the cleaved TBM- Glu (TBM a) primarily exerts its anticancer effects through the type I PDT process. And aligning with this finding, we observed the oxygen independence of TBM a's photodynamic activity in the hypoxia condition, which is potentially advantageous in hypoxic tumor environments. + +<|ref|>text<|/ref|><|det|>[[72, 202, 920, 243]]<|/det|> +We acknowledge the complexity of PDT processes in biological systems, which may reflect both directly generated species and enzymatic interconversions. However, the ROS we detected in cells are coordinating with the results we detected in vitro, which validates the validity of our conclusion. + +<|ref|>text<|/ref|><|det|>[[72, 242, 917, 281]]<|/det|> +\*\*\* First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919.) So, instead of 1 O2 % hypoxia, if the authors were to switch to 0.5 % O2 hypoxia, or anoxia, the effectiveness would be much more different. + +<|ref|>text<|/ref|><|det|>[[72, 281, 914, 321]]<|/det|> +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Esbelsen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide (N3- ) is a singlet oxygen quencher + +<|ref|>text<|/ref|><|det|>[[73, 333, 410, 346]]<|/det|> +Enhancement of emission "AND" PDT efficiency. + +<|ref|>text<|/ref|><|det|>[[72, 346, 897, 372]]<|/det|> +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +<|ref|>text<|/ref|><|det|>[[72, 372, 912, 424]]<|/det|> +Response: We appreciate the reviewer's insights regarding the competitive nature of fluorescence and reactive oxygen species (ROS) generation in AIE- PDT systems. While both processes utilize energy from the excited state, our findings on the simultaneous enhancement of aggregate luminescence and photodynamic activity are not contradictory. Here is some reported literature. + +<|ref|>text<|/ref|><|det|>[[72, 424, 919, 515]]<|/det|> +(i) Aggregation-induced intermolecular intersystem crossing (AI-ISC): Jiang et al. proposed a new mechanism called aggregation-induced intersystem crossing (AI-ISC) to understand the effect of aggregation on increasing ISC efficiency.1, 2 According to the AI-ISC theory, more excitonic couplings cause excited-state energy splitting and overlapping of singlet and triplet in aggregate. The energy splitting and overlapping significantly produce many ISC channels with very small \(\Delta \mathrm{EST}\) in aggregates, which is available for ISC processes. Therefore, the formation of aggregates can facilitate the production of triplet excitons. In addition to emitting phosphorescent radiation, these triplet excitons can also undergo a non-radiative pathway known as the aggregation-enhanced photodynamic effect to return to their ground state. 3, 4, 5 + +<|ref|>text<|/ref|><|det|>[[72, 515, 920, 567]]<|/det|> +\*\*\* Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +<|ref|>text<|/ref|><|det|>[[72, 579, 894, 671]]<|/det|> +(ii) Restriction of intramolecular motion (RIM): The aggregation of AIE molecules results in a restriction of intramolecular rotations and vibrations, effectively suppressing molecular motions, which is also beneficial for the ISC process.6, 7 All the evidence highlights the potential of AIE materials in PDT. The aggregation-induced changes in the molecular environment can optimize both the imaging and therapeutic aspects of the treatment.8, 9, 10 \*\*\*Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +<|ref|>sub_title<|/ref|><|det|>[[72, 698, 156, 710]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[68, 710, 925, 945]]<|/det|> +1. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +2. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +3. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). +4. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). +5. Ji C, Lai L, Li P, Wu Z, Cheng W, Yin M. Organic dye assemblies with aggregation-induced photophysical changes and their bio-applications. Aggregate 2, e39 (2021). +6. Kwok RTK, Leung CWT, Lam JWY, Tang BZ. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 44, 4228-4238 (2015). +7. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +8. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +9. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 877, 75]]<|/det|> +10. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +<|ref|>sub_title<|/ref|><|det|>[[73, 112, 162, 125]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 139, 803, 166]]<|/det|> +(Remarks to the Author) The authors have addressed all the concerns in the revisions. And the manuscript is ready to be published. + +<|ref|>sub_title<|/ref|><|det|>[[73, 177, 162, 191]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 204, 920, 245]]<|/det|> +(Remarks to the Author) The paper's focus is the enzymatically catalyzed molecular aggregation for improving the response and PDT treatment. The paper has been revised accordingly, and ready for publication. + +<|ref|>text<|/ref|><|det|>[[73, 255, 144, 269]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 281, 220, 295]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 307, 161, 320]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 333, 238, 360]]<|/det|> +(Remarks to the Author) Response + +<|ref|>text<|/ref|><|det|>[[73, 372, 186, 386]]<|/det|> +General opinion + +<|ref|>text<|/ref|><|det|>[[70, 397, 907, 425]]<|/det|> +The present manuscript claims to achieve a better targeting of a proposed photosensitizer (PS) which can activated by GGT and be excited at short wavelengths. + +<|ref|>text<|/ref|><|det|>[[70, 435, 902, 463]]<|/det|> +Also, activated (aggregate structure) may have a better cytotoxic effect, compared its non-activated form, which is another example of activated- PS + +<|ref|>text<|/ref|><|det|>[[70, 475, 904, 503]]<|/det|> +There have been countless photosensitizers which can be targeted one way of or another. Many reviews exist about activatable photosensitizers. Some enzymatically, some by hypoxia, by higher H2O2 or GSH concentrations, or acidic pH. + +<|ref|>text<|/ref|><|det|>[[72, 513, 921, 568]]<|/det|> +The main, may be the only reason why PDT did not develop significantly since 70's is that fact that light, even at the socalled "therapeutic window" does not go through tissues. And of course, there is no real justification for a 450 nm chromophore to be proposed as a novelty. There are very specific, niche cases, where a single cell layer penetration may be useful. But citing these, is missing the point of all PDT- work. + +<|ref|>text<|/ref|><|det|>[[70, 579, 900, 607]]<|/det|> +Type- I processes being less oxygen dependent has been proposed without real evidence. The new data provided by the authors is also not a fair comparison (see below). + +<|ref|>text<|/ref|><|det|>[[70, 618, 900, 647]]<|/det|> +Thus the manuscript does not bring any novelty to the field. The requirement for aggregation, if anything, complicates the picture very unnecessarily. + +<|ref|>text<|/ref|><|det|>[[73, 722, 332, 736]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 748, 916, 802]]<|/det|> +Q1: The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +<|ref|>text<|/ref|><|det|>[[72, 802, 920, 906]]<|/det|> +251. "only marginal variation was observed in the phototoxicity of TBmA-Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA-Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." Response and revision: We appreciate the valuable suggestions provided by the reviewer. To enhance the accuracy of our study, we conducted additional experiments using Rose Bengal (RB), a well-established type II photosensitizer1, as a control. These experiments revealed that RB's photodynamic efficiency decreased significantly under hypoxia conditions (2% O2) compared to normoxia conditions, while TBmA maintained relatively consistent activity across both environments (Fig. R1). + +<|ref|>text<|/ref|><|det|>[[72, 905, 888, 946]]<|/det|> +To discuss this result more accurately, we have revised our manuscript by replacing the statement "This suggests that oxygen content has negligible influence on its photodynamic activity." with "This suggests that TBmA exhibits tolerance towards hypoxic conditions." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 85, 901, 113]]<|/det|> +Fig. S36. The effects of hypoxia (2% O2) and normoxia (20% O2) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells. + +<|ref|>text<|/ref|><|det|>[[73, 126, 232, 139]]<|/det|> +Revised in manuscript: + +<|ref|>text<|/ref|><|det|>[[73, 139, 883, 191]]<|/det|> +Additionally, only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d), while the type- II PS, RB, showed a significant decrease in photodynamic efficiency under hypoxia conditions (2% O2) compared to normoxia conditions (Fig. S36). This suggests that TBmA exhibits tolerance towards hypoxic conditions. + +<|ref|>sub_title<|/ref|><|det|>[[73, 204, 150, 216]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[73, 216, 899, 255]]<|/det|> +1. Fischer BB, Krieger-Liszkay A, Eggen RIL. Oxidative stress induced by the photosensitizers neutral red (type I) or rose bengal (type II) in the light causes different molecular responses in Chlamydomonas reinhardtii. Plant Sci. 168, 747-759 (2005). + +<|ref|>text<|/ref|><|det|>[[73, 256, 140, 268]]<|/det|> +response + +<|ref|>text<|/ref|><|det|>[[72, 268, 900, 295]]<|/det|> ++++ Light source in Fig S36 was not given, if it is white LED, it is not a fair comparison, because LED emission profile fits TBmA/aggregate better. + +<|ref|>text<|/ref|><|det|>[[73, 307, 909, 359]]<|/det|> +Q2: Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +<|ref|>text<|/ref|><|det|>[[72, 359, 901, 386]]<|/det|> +Response: We appreciate the reviewer's insightful comments regarding the nature of supramolecular aggregation and the potential for de-aggregation in biological media. We would like to clarify several key points that address these concerns. + +<|ref|>text<|/ref|><|det|>[[73, 397, 907, 450]]<|/det|> +Firstly, it's crucial to emphasize that TBmA- Glu is a water- soluble prodrug. The aggregation process only occurs after the Glu moiety is cleaved by GGT in HepG2 cells. This design ensures that TBmA- Glu remains soluble in the blood, avoiding premature aggregation. Aggregation is triggered specifically in the intracellular environment of GGT- overexpressing tumor cells. + +<|ref|>text<|/ref|><|det|>[[73, 463, 911, 529]]<|/det|> +We acknowledge that FBS is not an ideal model for the intracellular environment. To address this issue, we further conducted stability studies using a 30% BSA (Bovine Serum Albumin) solution, which is a better model for the protein- rich intracellular milieu. The intracellular protein concentration typically ranges from 50- 400 mg/mL, and our 30% BSA solution ( \(\sim 300 \text{mg / mL}\) ) falls within this range. TBmA aggregates showed remarkable stability in this environment, with no significant degradation observed over 72 hours (Fig. R1). + +<|ref|>text<|/ref|><|det|>[[73, 541, 914, 594]]<|/det|> +We also agree that pharmacokinetics studies would be valuable. However, our system presents unique challenges for such studies, as the aggregates form intracellularly rather than in circulation. Collecting and analyzing intracellular aggregates from tumor sections poses significant technical difficulties. Our approach using a highly concentrated protein solution provides valuable insights into aggregate stability in a physiologically relevant environment. + +<|ref|>text<|/ref|><|det|>[[72, 606, 911, 633]]<|/det|> +Importantly, beyond structural stability, we have observed that the aggregates maintain their photodynamic properties in the 30% BSA solution for 72 h (Fig. R2). This functional stability is crucial for the compound's theranostic applications. + +<|ref|>text<|/ref|><|det|>[[73, 657, 585, 672]]<|/det|> +Fig. R1. The long- term stability of TBmA aggregates in 30% BSA solutions. + +<|ref|>text<|/ref|><|det|>[[72, 697, 920, 737]]<|/det|> +Fig. R2. The ROS generation capacity of TBmA aggregates after dispersed in 30% BSA solution for 0 h (a) and 72 h (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity (I/I0) of DC versus the irradiation (20 mW · cm- 2) time, where I0 = PL intensity of DCFH in solutions without light irradiation. + +<|ref|>text<|/ref|><|det|>[[72, 749, 890, 777]]<|/det|> +Q3: References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +<|ref|>text<|/ref|><|det|>[[72, 777, 921, 829]]<|/det|> +Response: We thank the reviewer for the critical feedback. The unique photophysical properties of AIE compounds stem from the restriction of intramolecular motion (RIM) mechanism, where aggregation limits molecular rotations and vibrations, leading to enhanced fluorescence. Therefore, the fluorescence behavior of AIE materials does provide valuable insights into their molecular state and environment. + +<|ref|>text<|/ref|><|det|>[[72, 828, 919, 894]]<|/det|> +This interpretation is supported by several factors. First of all, TBmA- Glu is engineered to aggregate specifically in response to GGT activity, which is overexpressed in certain tumor cells. This targeted approach minimizes premature aggregation in circulation. Secondly, the crowded, protein- rich cytoplasmic environment of tumor cells likely provides conditions that favor aggregate stability once formed. Additionally, we observed that the photosensitivity of TBmA was maintained in our 30% BSA studies, suggesting a preservation of the aggregate structure. + +<|ref|>text<|/ref|><|det|>[[72, 905, 897, 947]]<|/det|> +Q4: While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 703, 62]]<|/det|> +avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +<|ref|>text<|/ref|><|det|>[[72, 60, 905, 88]]<|/det|> +Response: We appreciate the reviewer's thoughtful comments regarding the therapeutic relevance of AIE compounds and the importance of careful characterization of their behavior in biological systems. + +<|ref|>text<|/ref|><|det|>[[72, 87, 905, 152]]<|/det|> +Regarding the stability and behavior of TBmA, we emphasize that TBmA- Glu is designed as a water- soluble prodrug that only forms aggregates within tumor cells following enzymatic reaction. This targeted approach minimizes potential issues related to premature aggregation or size changes in circulation. Furthermore, we have demonstrated the stability of TBmA aggregates in a \(30\%\) BSA solution for 72 hours, providing initial evidence of their potential stability in protein- rich environments. + +<|ref|>text<|/ref|><|det|>[[72, 152, 923, 285]]<|/det|> +About "personalized medicine and real- time treatment monitoring." in the previous response letter: The full sentence is "Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring." We agree that such terminology should be used judiciously, especially in early- stage research, however, our intention here is to highlight the potential of AIE materials to contribute to these fields in the future, rather than to claim immediate clinical applicability. The unique properties of AIE materials, including their AIE and potential for stimuli- responsive behavior, do offer intriguing possibilities for both imaging and therapeutic applications. However, we agree that rigorous investigation is needed to establish their efficacy and safety for PDT or other therapeutic schemes. Moving forward, we will focus on providing concrete evidence for the specific advantages of AIE compounds in relevant biological contexts, rather than speculating on broad future applications. We believe this approach will better serve the scientific community and responsibly advance the field. + +<|ref|>text<|/ref|><|det|>[[72, 295, 895, 323]]<|/det|> +Q5: May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to 450 nm peak. There are literature reports of blue (450 nm) light causing cellular damage. + +<|ref|>text<|/ref|><|det|>[[72, 333, 920, 373]]<|/det|> +Response: We acknowledge that there are indeed literature reports of blue light (450 nm) causing cellular damage. This is an important consideration in photodynamic therapy and other light- based treatments. However, we would like to emphasize that the biological effects of light exposure are highly dependent on both wavelength and dosage. + +<|ref|>text<|/ref|><|det|>[[72, 372, 920, 411]]<|/det|> +In our experiments, we carefully controlled the light dosage to minimize potential phototoxicity while maintaining therapeutic efficacy. Under the experimental conditions described in our manuscript, we did not observe any significant effects on cell viability following LED light irradiation (Fig. R3). + +<|ref|>text<|/ref|><|det|>[[72, 410, 914, 450]]<|/det|> +To address the reviewer's concern, we also conducted a blue light irradiation (450 nm, 12 J/cm2) PDT assay. In this experiment, we also found no significant effect on cellular viability. This suggests that at the dosages used in our study, the blue light alone does not cause substantial cellular damage. + +<|ref|>text<|/ref|><|det|>[[72, 449, 916, 503]]<|/det|> +However, we agree that the potential for phototoxicity is an important consideration in developing light- based therapies. In future studies, we plan to conduct a more comprehensive dose- response analysis to determine the threshold at which blue light exposure may begin to affect cell viability. We also intend to investigate the potential long- term effects of repeated light exposure and compare the effects of our AIE- based approach with traditional photosensitizers at equivalent light doses. + +<|ref|>text<|/ref|><|det|>[[70, 526, 822, 543]]<|/det|> +Fig. R3 The impact of white light and 450 nm light exposure (12 J/cm2) on the cellular viability of HepG2 cells. + +<|ref|>text<|/ref|><|det|>[[72, 554, 916, 595]]<|/det|> +Q6: One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as 450 nm is less than 1 mm, which is significantly less than needed for an effective "photo"- driven process. + +<|ref|>text<|/ref|><|det|>[[72, 605, 923, 671]]<|/det|> +Response: It is correct that the typical penetration depth of 450 nm light is less than 1 mm in tissue, which is indeed less than ideal for treating deep- seated tumors. However, we would like to highlight several important considerations: First, though direct light penetration is restricted, the effective depth of PDT damage may increase due to light reflection and scattering within tissues. This occurrence can expand the scope of the photodynamic impact beyond the initial penetration depth. + +<|ref|>text<|/ref|><|det|>[[72, 683, 916, 844]]<|/det|> +Secondly, several clinical scenarios exist where shallow light penetration is sufficient or even advantageous. For instance, PDT with blue light excitation could be particularly useful for superficial skin cancers and precancerous lesions, intraoperative treatment of residual tumor cells after surgical resection, treatment of early- stage mucosal cancers in inaccessible areas (e.g., oral cavity, bladder), and endoscopic applications for gastrointestinal tumors. Finally, numerous published studies demonstrate the successful use of 450 nm light and white light (including the blue spectrum) for PDT when the photosensitizers have maximum absorption around 450 nm. 2, 3, 4, 5, 6, 7 Nevertheless, we fully agree that blue light's limited tissue penetration restricts the broader applicability of our current system for treating deep- seated tumors. Given this limitation, our future research directions include exploring two- photon excitation to achieve deeper tissue penetration, investigating upconversion nanoparticles to convert longer- wavelength light to blue light locally, and developing new AIE photosensitizers with red- shifted absorption for improved tissue penetration. We believe that addressing these challenges will expand the potential applications of our AIE- based PDT system while utilizing its unique properties. + +<|ref|>sub_title<|/ref|><|det|>[[72, 855, 157, 867]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[70, 867, 904, 944]]<|/det|> +2. Fan L, et al. A Bioactive Photosensitizer for Hypoxia-Tolerant Molecular Targeting-Photo-Immunotherapy of Malignant Tumor. Adv. Funct. Mater. 34, 2313755 (2023). +3. Li X, et al. A novel 450-nm laser-mediated sinoporphyrin sodium-based photodynamic therapy induces autophagic cell death in gastric cancer through regulation of the ROS/PI3K/Akt/mTOR signaling pathway. BMC Med. 20, 475 (2022). +4. Mei Y, et al. A Novel Photosensitizer Based 450-nm Blue Laser-Mediated Photodynamic Therapy Induces Apoptosis in Colorectal Cancer - in Vitro and in Vivo Study. Front. Biosci. (Landmark Ed) 29, 199 (2024). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 918, 125]]<|/det|> +5. Chen Y, et al. Photoactivatable metal organic framework for synergistic ferroptosis and photodynamic therapy using 450 nm laser. Chem. Eng. J. 454, 140438 (2023). +6. Sun P, et al. A water-soluble phosphorescent conjugated polymer brush for tumor-targeted photodynamic therapy. Polym. Chem. 8, 5836-5844 (2017). +7. An J, et al. An unexpected strategy to alleviate hypoxia limitation of photodynamic therapy by biotinylation of photosensitizers. Nat. Commun. 13, 2225 (2022). + +<|ref|>text<|/ref|><|det|>[[72, 150, 920, 191]]<|/det|> +Q7: First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to 0.5 % O2 hypoxia, or anoxia, the effectiveness would be much more different. + +<|ref|>text<|/ref|><|det|>[[72, 191, 914, 231]]<|/det|> +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Esbelsen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide (N3- ) is a singlet oxygen quencher. + +<|ref|>text<|/ref|><|det|>[[72, 242, 917, 296]]<|/det|> +Response and revision: We agree with the reviewer that oxygen plays a pivotal role in the Type I and Type II PDT processes. However, from the PDT mechanism, we know that the type I photosensitizers could directly transfer electrons to the substrate, forming a radical cation or neutral radical. These radicals could immediately react with O2 or H2O to generate hydrogen peroxide (H2O2), hydroxyl radicals (- OH), or superoxide anions (- O2- ) (Fig. R4).1, 2 + +<|ref|>text<|/ref|><|det|>[[72, 307, 884, 388]]<|/det|> +We have tried but could not finish the antitumor PDT assays in the anaerobic conditions, because the anoxia condition resulted in death of the tumor cells (Fig. R5a). So, we re- evaluated the photodynamic efficiency of TBMa and RB using a deoxidized PBS solution. The results showed that TBMa could also induce the oxidation of DFCH under the anoxia condition (Fig. R5b), while the photodynamic efficiency of RB showed significant degradation. Hence, type- I photosensitizers exhibit relatively higher tolerance towards oxygen concentrations, which implies that, even under low oxygen conditions, they can still engage in substrate reactions through electron transfer. + +<|ref|>text<|/ref|><|det|>[[72, 398, 920, 439]]<|/det|> +We are sorry for the mistake in the figure legend in Figure 4b. "Esbelsen" has been revised as "Trolox." However, it should be noted that Trolox is not only a 1O2 scavenger but also a scavenger of peroxy and alkoxy groups.3 The type- I designation is mainly based on the ROS species we detected in vitro (Fig. R5c). + +<|ref|>text<|/ref|><|det|>[[72, 463, 584, 478]]<|/det|> +Fig. R4 Scheme of the photochemical reactions for type I and type II PDT.9 + +<|ref|>text<|/ref|><|det|>[[72, 502, 923, 544]]<|/det|> +Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \(10\mu \mathrm{M}\) ) in the presence of \(5\mu \mathrm{M}\) photosensitizers in DMSO- PBS ( \(\mathrm{v}:\mathrm{v} = 1:99\) ) after irradiation (20 mW·cm- 2) for a different time under anoxia conditions. (b) TBMa, (c) Rose Bengal (RB). DCHF, \(\lambda \mathrm{ex} = 488 \mathrm{nm}\) . + +<|ref|>text<|/ref|><|det|>[[72, 555, 919, 595]]<|/det|> +Revised in manuscript: Trolox: \(50\mu \mathrm{M}\) (ROO- scavenger and 1O2 scavenger); D- mannitol: \(50\mathrm{mM}\) (- OH scavenger); Tiron: \(10\mathrm{mM}\) (- O2- scavenger); NaN3: \(5\mathrm{mM}\) (1O2 scavenger) + +<|ref|>text<|/ref|><|det|>[[72, 607, 158, 620]]<|/det|> +References: + +<|ref|>text<|/ref|><|det|>[[72, 620, 916, 696]]<|/det|> +1. Zhao X, Liu J, Fan J, Chao H, Peng X. Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application. Chem. Soc. Rev. 50, 4185-4219 (2021). +2. Fan W, Huang P, Chen X. Overcoming the Achilles' heel of photodynamic therapy. Chem. Soc. Rev. 45, 6488-6519 (2016). +3. Lúcio M, Nunes C, Gaspar D, Ferreira H, Lima JLFC, Reis S. Antioxidant Activity of Vitamin E and Trolox: Understanding of the Factors that Govern Lipid Peroxidation Studies In Vitro. Food Biophys. 4, 312-320 (2009). + +<|ref|>text<|/ref|><|det|>[[73, 709, 331, 723]]<|/det|> +\(+++0.5\) or \(1\%\) hypoxia may be better. + +<|ref|>text<|/ref|><|det|>[[72, 735, 886, 789]]<|/det|> +Q8: Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +<|ref|>text<|/ref|><|det|>[[72, 802, 920, 868]]<|/det|> +Response: Indeed, the total quantum yield of all radiative and non- radiative processes cannot exceed 1. However, the energy consumption in no radiative processes contains both the energy for ISC processes and the molecular motion as well. Molecular aggregation could induce the restriction of intramolecular motions (RIM) and, as a result, reduce energy loss through non- radiative molecular motion, potentially increasing the energy available for emission and ISC processes. So, the energy efficiency of both emission and ISC can be enhanced in aggregated structure due to RIM. + +<|ref|>text<|/ref|><|det|>[[72, 879, 920, 946]]<|/det|> +However, in specific cases, such as the graphene quantum dots reported by Zhang et al., the apparent quantum yield could be larger than 1.1 This occurs when the energy gaps between \(\Delta \mathrm{EST}\) and \(\Delta \mathrm{ETG}\) (the energy gap between T1 and Ground state) are larger than the formation energy of 1O2 (22.5 kcal mol 1). In such cases, 1O2 generation happens through multiple pathways: energy transfer from T1 (ET(1) in Fig. R6), but also the energy transfer from S1 to 3O2 during the S1- T1 intersystem crossing transition (ET(2) in Figure R6). This multi- pathway mechanism can lead to an overall 1O2 quantum + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 725, 61]]<|/det|> +yield greater than 1.0, as more than one 1O2 molecule can be produced per absorbed photon.2 + +<|ref|>text<|/ref|><|det|>[[72, 86, 875, 101]]<|/det|> +Fig. R6 Schematic illustration of the 1O2 generation mechanisms by conventional PDT agents (left) and GQDs (right). + +<|ref|>sub_title<|/ref|><|det|>[[73, 114, 155, 126]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[72, 127, 915, 180]]<|/det|> +1. Ge J, et al. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation. Nat. Commun. 5, 4596 (2014). +2. Kanner RC, Foote CS. Singlet oxygen production from singlet and triplet states of 9,10-dicyanoanthracene. J. Am. Chem. Soc. 114, 678-681 (1992). + +<|ref|>text<|/ref|><|det|>[[73, 203, 920, 270]]<|/det|> +\(^{+ + + }\) Both of these articles while interesting, hardly relevant to PDT considering the absorption peaks of the proposed sensitizers are in blue, and the fact that they are very unique cases. The first one reached to a suprizing conclusion without doing any photophysical work. Vibrational (or rotational) relaxation and their control by micro- or molecular environments, by molecular steric hinderence is well known. However, only accurate quantum yield determinations would prove simultaneous increases in emission and singlet oxygen quantum yields. This is not done in Ref 1. + +<|ref|>text<|/ref|><|det|>[[73, 282, 904, 322]]<|/det|> +Q9: Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +<|ref|>text<|/ref|><|det|>[[73, 333, 915, 399]]<|/det|> +Response: As previously discussed, TBmA- Glu is a water- soluble molecule that forms aggregates within tumor cells upon activation by GGT to produce TBmA. Consequently, most of these aggregates are localized in the tumor cells. Furthermore, we have demonstrated the stability of TBmA aggregates for 72 hours in a \(30\%\) BSA solution. Additionally, considering that PDT processes were conducted 12 hours after administration of TBmA- Glu, it can be inferred that the TBmA aggregates exhibit sufficient stability to complete the PDT processes. + +<|ref|>text<|/ref|><|det|>[[72, 411, 850, 425]]<|/det|> +\(^{+ + + }\) The problem is that now "activated" aggregates, will not stay forever in tumor cells, as these cells disintegrate. + +<|ref|>text<|/ref|><|det|>[[72, 817, 916, 870]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 871, 915, 938]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 618, 61]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[351, 86, 646, 108]]<|/det|> +## Point-by-Point Responses + +<|ref|>text<|/ref|><|det|>[[148, 128, 850, 199]]<|/det|> +We are very grateful to the reviewers for their insightful comments, which have significantly enhanced the quality of our paper. Following their valuable feedback and suggestions, we have carefully revised the manuscript. Our responses and revisions are presented in a blue font for easy reference. + +<|ref|>sub_title<|/ref|><|det|>[[148, 226, 356, 242]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 248, 437, 264]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 270, 850, 331]]<|/det|> +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". + +<|ref|>text<|/ref|><|det|>[[147, 336, 850, 535]]<|/det|> +This referee finds important design flaws and problems with the implementation of the work. Response: We thank the reviewer for the constructive comments on our paper. In this manuscript, we actually did not intend to compare the Type I and Type II PDT processes, and the efficiency of type I and type II photosensitizers is not the key point of this work. We just want to present the objective performance of the developed photosensitizers based on their ROS generation capability. As clearly stated in the manuscript: "It was found that TBmA and TBpA produced significantly higher ROS compared to TBmA- Glu and TBpA- Glu, even surpassing the commercial photosensitizer, Rose Bengal (RB). Moreover, TBmA was identified as the most potent photosensitizer among the four compounds. Further analysis revealed that TBmA and TBpA functioned as strong type I photosensitizers (Fig. 1c and Fig. S25), while TBmA- Glu and TBpA- Glu acted as very weak type II photosensitizers (Fig. 1c and Fig. S26)." + +<|ref|>text<|/ref|><|det|>[[149, 559, 343, 574]]<|/det|> +Here are the major issues: + +<|ref|>text<|/ref|><|det|>[[149, 580, 344, 596]]<|/det|> +Problem with Aggregates: + +<|ref|>text<|/ref|><|det|>[[148, 602, 851, 729]]<|/det|> +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +<|ref|>text<|/ref|><|det|>[[148, 735, 848, 774]]<|/det|> +Response and revision: Thank you for your thoughtful comments regarding AIE compounds. We appreciate your concerns and would like to address them point by point: + +<|ref|>text<|/ref|><|det|>[[147, 779, 851, 907]]<|/det|> +(i) Stability and standardization: we acknowledge that stability is crucial for bio- application. Our recent studies have shown promising results regarding the stability of TBmA aggregates in high-protein environments, specifically: (a) Long-term stability: TBmA aggregates showed no significant degradation when dispersed in FBS for 72 hours (Fig. S28a and S28c). (b) Photostability: The aggregates remained stable under continuous light irradiation for 30 minutes (Fig. S28a and S28b). These findings collectively highlight the exceptional + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 850, 127]]<|/det|> +stability exhibited by TBmA. These findings demonstrate the exceptional stability of TBmA aggregates in biologically relevant conditions. + +<|ref|>text<|/ref|><|det|>[[148, 131, 851, 216]]<|/det|> +Moreover, numerous AIEgens, including small molecules or AIE nanoparticles, have been extensively reported for their long- term monitoring and theranostic applications. \(^{1,2,3}\) These pieces of evidence underscore the remarkable stability of AIEgens, making them highly promising candidates for theranostic applications. + +<|ref|>text<|/ref|><|det|>[[147, 220, 852, 393]]<|/det|> +(ii) Aggregate structure: To address concerns about ill- defined aggregate structures, we extensively investigated the aggregate size of TBmA using Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). The results suggest that the TBmA forms spherical particles with \(140 \mathrm{nm}\) in \(99\%\) PBS and \(150 \mathrm{nm}\) diameter after the GGT catalysis reaction (12 h, Fig. S31). These results indicate that TBmA consistently forms nanoparticles of definite shape and size in aqueous environments, regardless of the specific conditions. Numerous works have been reported to show the definite shape and size, as well as the excellent stability and biocompatibility of the AIE aggregates. \(^{4,5,6}\) + +<|ref|>text<|/ref|><|det|>[[147, 398, 852, 630]]<|/det|> +(iii) A comparative analysis of small molecular drugs and AIE materials: Although molecular drugs and traditional photosensitizers have their advantages, AIE compounds offer unique benefits such as enhanced emission upon aggregation, responsiveness to stimuli, and multifunctional potential. Revealing reports increasingly indicate that small molecular photosensitizers, such as CE6, exhibit low solubility and undergo aggregation in solution, resulting in the deactivation of their photosensitizing activity and hindering their bioapplication. \(^{7,8,9,10}\) We believe that AIE compounds can serve as complementary agents, rather than substitutes, for small molecule drugs. Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring. \(^{4,11,12,13}\) + +<|ref|>text<|/ref|><|det|>[[148, 643, 852, 771]]<|/det|> +We believe that AIE compounds, including TBmA- Glu, offer valuable and unique properties that complement existing molecular drugs and photosensitizers. While challenges remain, the growing body of research on AIE materials suggests significant potential for advancing biomedical imaging and therapeutic applications. We appreciate the reviewer's perspective and believe that continued research and development in this field will address current limitations and unlock new possibilities in biomedical science. + +<|ref|>sub_title<|/ref|><|det|>[[150, 798, 437, 815]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 820, 851, 903]]<|/det|> +Moreover, the TBmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS (fetal bovine serum) solution for \(72 \mathrm{h}\) or light irradiated for \(30 \mathrm{min}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 108, 850, 400]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 405, 850, 468]]<|/det|> +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and 72 h FBS preservation.
+ +<|ref|>image<|/ref|><|det|>[[157, 495, 848, 768]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 772, 852, 857]]<|/det|> +
Fig. S31. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b-g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for 12 h.
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 884, 237, 899]]<|/det|> +## References + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 87, 852, 145]]<|/det|> +1. Zuo J, et al. Long-term spatiotemporal and highly specific imaging of the plasma membrane of diverse plant cells using a near-infrared AIE probe. Angew. Chem. Int. Ed. 14, 2139-2148 (2023). + +<|ref|>text<|/ref|><|det|>[[145, 152, 850, 191]]<|/det|> +2. Wang Z, et al. Long-term fluorescent cellular tracing by the aggregates of aie bioconjugates. J. Am. Chem. Soc. 135, 8238-8245 (2013). + +<|ref|>text<|/ref|><|det|>[[145, 198, 850, 237]]<|/det|> +3. Li K, et al. Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing. Sci. Rep. 3, 1150 (2013). + +<|ref|>text<|/ref|><|det|>[[145, 243, 850, 281]]<|/det|> +4. Wang J, et al. Nanolab in a cell: Crystallization-induced in situ self-assembly for cancer theranostic amplification. J. Am. Chem. Soc. 144, 14388-14395 (2022). + +<|ref|>text<|/ref|><|det|>[[145, 287, 850, 347]]<|/det|> +5. Li Y, et al. Trojan Horse-Like Nano-AIE Aggregates Based on Homologous Targeting Strategy and Their Photodynamic Therapy in Anticancer Application. Adv. Sci. 8, 2102561 (2021). + +<|ref|>text<|/ref|><|det|>[[145, 354, 850, 393]]<|/det|> +6. Yan Z, et al. Preparation of ultrasmall AIE nanoparticles with tunable molecular packing via freeze assembly. Nano Lett. 23, 1030-1035 (2023). + +<|ref|>text<|/ref|><|det|>[[145, 399, 850, 459]]<|/det|> +7. Li Y, et al. Near-infrared light and redox dual-activatable nanosystems for synergistically cascaded cancer phototherapy with reduced skin photosensitization. Biomaterials 288, 121700 (2022). + +<|ref|>text<|/ref|><|det|>[[145, 465, 850, 526]]<|/det|> +8. Tian S, He J, Lyu D, Li S, Xu Q-H. Aggregation enhanced photoactivity of photosensitizer conjugated metal nanoparticles for multimodal imaging and synergistic phototherapy below skin tolerance threshold. Nano Today 45, 101534 (2022). + +<|ref|>text<|/ref|><|det|>[[145, 532, 850, 592]]<|/det|> +9. Wang H, Xue K-F, Yang Y, Hu H, Xu J-F, Zhang X. In Situ Hypoxia-Induced Supramolecular Perylene Diimide Radical Anions in Tumors for Photothermal Therapy with Improved Specificity. J. Am. Chem. Soc. 144, 2360-2367 (2022). + +<|ref|>text<|/ref|><|det|>[[145, 598, 850, 658]]<|/det|> +10. Li X, et al. Nanostructured Phthalocyanine Assemblies with Protein-Driven Switchable Photoactivities for Biophotonic Imaging and Therapy. J. Am. Chem. Soc. 139, 10880-10886 (2017). + +<|ref|>text<|/ref|><|det|>[[145, 665, 850, 725]]<|/det|> +11. Chen C, Zhang X, Gao Z, Feng G, Ding D. Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection. Nat. Protoc., in press (2024). + +<|ref|>text<|/ref|><|det|>[[145, 731, 850, 792]]<|/det|> +12. Liu Z, Wang Q, Zhu Z, Liu M, Zhao X, Zhu W-H. AIE-based nanoaggregate tracker: high-fidelity visualization of lysosomal movement and drug-escaping processes. Chem. Sci. 11, 12755-12763 (2020). + +<|ref|>text<|/ref|><|det|>[[145, 799, 850, 837]]<|/det|> +13. Yu Y, et al. Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking. Adv. Mater. 23, 3298-3302 (2011). + +<|ref|>text<|/ref|><|det|>[[147, 866, 321, 881]]<|/det|> +Excitation wavelength: + +<|ref|>text<|/ref|><|det|>[[145, 888, 850, 905]]<|/det|> +The absorption peak of the monomeric compounds and the aggregates in this work is around + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 852, 170]]<|/det|> +450 nm. This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +<|ref|>text<|/ref|><|det|>[[147, 176, 852, 349]]<|/det|> +Response and revision: We appreciate the reviewer's concern regarding light penetration and the effects of our light source. Our analysis of the white LED light shows predominant peaks at 450 and 570 nm, with no detectable UV peak, which could address the concerns of the reviewers about unintended UV- induced effects (Fig. S27). Furthermore, all anticancer \(\mathrm{IC}_{50}\) values of tested compounds were detected using the MTT assays, and no significant effect on cell viability was detected in the control group after exposure to LED irradiation. MTT assays and control experiments demonstrate that the observed cell death is due to \(\mathrm{TBmA}\) - Glu's photodynamic properties, not the LED light itself. + +<|ref|>text<|/ref|><|det|>[[147, 354, 852, 483]]<|/det|> +Depth of Penetration in Tissues: While it is true that the penetration depth of light at \(450\mathrm{nm}\) is limited, this wavelength is still within the range where some penetration can occur in biological tissues. The actual penetration depth can be influenced by factors such as tissue type, pigmentation, and the optical properties of the tissue. Furthermore, we employed a minimally invasive approach for PDT to optimize the efficiency of photodynamic therapy and minimize the impact of light penetration. + +<|ref|>sub_title<|/ref|><|det|>[[150, 510, 437, 526]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 531, 852, 640]]<|/det|> +The generation of total ROS generation (2,7'- dichlorodihydrofluorescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10- anthracenediylbis(methylene)dimalonic Acid, ABDA) by photosensitizers (5 \(\mu \mathrm{M}\) ) after white LED light (predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation ( \(20\mathrm{mW}\cdot \mathrm{cm}^{- 2}\) ) for 15 min using the corresponding ROS indicator in PBS/DMSO (v/v = 99:1). DCF, \(\lambda_{\mathrm{ex}} = 488\mathrm{nm}\) . + +<|ref|>sub_title<|/ref|><|det|>[[149, 644, 468, 661]]<|/det|> +## Changes in the Supporting Information: + +<|ref|>image<|/ref|><|det|>[[350, 664, 644, 878]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 888, 607, 905]]<|/det|> +
Fig. S27. The emission wavelength analysis of the LED light.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 109, 488, 126]]<|/det|> +Confusion about the Type- I and Type- II PDT: + +<|ref|>text<|/ref|><|det|>[[147, 131, 851, 260]]<|/det|> +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; and it is not easy to separate these two processes (I/II). + +<|ref|>text<|/ref|><|det|>[[147, 265, 851, 459]]<|/det|> +Response: We appreciate the reviewer's insightful comments on the Type- I and Type- II PDT processes. We agree that PDT often involves a combination of both processes and that ROS species can undergo interconversion through various enzymatic processes in vivo. Our study focused on characterizing the predominant mechanism of \(\mathrm{TBmA}\) under specific conditions, not comparing the superiority of Type- I vs Type- II processes. We found that the cleaved \(\mathrm{TBmA}\) - Glu ( \(\mathrm{TBmA}\) ) primarily exerts its anticancer effects through the type I PDT process. And aligning with this finding, we observed the oxygen independence of \(\mathrm{TBmA}\) 's photodynamic activity in the hypoxia condition, which is potentially advantageous in hypoxic tumor environments. + +<|ref|>text<|/ref|><|det|>[[147, 464, 851, 548]]<|/det|> +We acknowledge the complexity of PDT processes in biological systems, which may reflect both directly generated species and enzymatic interconversions. However, the ROS we detected in cells are coordinating with the results we detected in vitro, which validates the validity of our conclusion. + +<|ref|>text<|/ref|><|det|>[[148, 575, 523, 592]]<|/det|> +Enhancement of emission "AND" PDT efficiency. + +<|ref|>text<|/ref|><|det|>[[148, 598, 850, 637]]<|/det|> +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +<|ref|>text<|/ref|><|det|>[[147, 642, 851, 748]]<|/det|> +Response: We appreciate the reviewer's insights regarding the competitive nature of fluorescence and reactive oxygen species (ROS) generation in AIE- PDT systems. While both processes utilize energy from the excited state, our findings on the simultaneous enhancement of aggregate luminescence and photodynamic activity are not contradictory. Here is some reported literature. + +<|ref|>text<|/ref|><|det|>[[147, 754, 851, 904]]<|/det|> +(i) Aggregation-induced intermolecular intersystem crossing (AI-ISC): Jiang et al. proposed a new mechanism called aggregation-induced intersystem crossing (AI-ISC) to understand the effect of aggregation on increasing ISC efficiency. \(^{1,2}\) According to the AI-ISC theory, more excitonic couplings cause excited-state energy splitting and overlapping of singlet and triplet in aggregate. The energy splitting and overlapping significantly produce many ISC channels with very small \(\Delta E_{\mathrm{ST}}\) in aggregates, which is available for ISC processes. Therefore, the formation of aggregates can facilitate the production of triplet excitons. In addition to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 853, 145]]<|/det|> +emitting phosphorescent radiation, these triplet excitons can also undergo a non- radiative pathway known as the aggregation- enhanced photodynamic effect to return to their ground state. 3, 4, 5 + +<|ref|>text<|/ref|><|det|>[[147, 153, 852, 214]]<|/det|> +(ii) Restriction of intramolecular motion (RIM): The aggregation of AIE molecules results in a restriction of intramolecular rotations and vibrations, effectively suppressing molecular motions, which is also beneficial for the ISC process.6, 7 + +<|ref|>text<|/ref|><|det|>[[147, 220, 852, 280]]<|/det|> +All the evidence highlights the potential of AIE materials in PDT. The aggregation- induced changes in the molecular environment can optimize both the imaging and therapeutic aspects of the treatment.8, 9, 10 + +<|ref|>text<|/ref|><|det|>[[147, 287, 852, 370]]<|/det|> +We hope that these clarifications address the reviewer's concerns and reinforce the validity of our findings. We are grateful for the opportunity to discuss these important aspects of AIE- PDT and hope that our response provides a clearer understanding of the complex interplay between fluorescence and photodynamic activity in our study. + +<|ref|>sub_title<|/ref|><|det|>[[148, 399, 243, 414]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 420, 852, 903]]<|/det|> +1. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +2. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +3. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). +4. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). +5. Ji C, Lai L, Li P, Wu Z, Cheng W, Yin M. Organic dye assemblies with aggregation-induced photophysical changes and their bio-applications. Aggregate 2, e39 (2021). +6. Kwok RTK, Leung CWT, Lam JWY, Tang BZ. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 44, 4228-4238 (2015). +7. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +8. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +9. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[185, 88, 241, 103]]<|/det|> +(2020). + +<|ref|>text<|/ref|><|det|>[[150, 108, 850, 170]]<|/det|> +10. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +<|ref|>text<|/ref|><|det|>[[150, 199, 437, 215]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 220, 852, 549]]<|/det|> +Tang and colleagues reported a \(\gamma\) - glutamyl transferase (GGT) activatable aggregation- induced emission photosensitizer (AIE- PS) named TBmA- Glu. TBmA- Glu is designed to specifically target and aggregate cancer cells through the catalytic action of tumor- overexpression GGT. Selective tumor cell aggregation not only enhances AIE- PS emission and photodynamic activity but also induces ferroptosis in cancer cells by depleting GSH and promoting lipid peroxidation. Both in vitro cell assays and in vivo animal models were used to validate the phototoxicity and antitumor effects of TBmA- Glu, providing a comprehensive assessment of its potential as a therapeutic agent. The aggregation strategies in this paper allow a controlled release of the photodynamic effect, which is critical for therapies such as PDT. AIE- PS remains dormant until it reaches the cancerous environment where GGT is present, ensuring minimal impact on healthy cells and maximizing the therapeutic effect on cancer cells. This study highlights the significance of targeting activation of AIE- PSs for targeting and enhanced cancer photodynamic therapy. It is also a sophisticated strategy for targeted delivery and activation of a photodynamic therapeutic agent for disease. I suggest this article be published with minor revisions. + +<|ref|>text<|/ref|><|det|>[[148, 555, 849, 594]]<|/det|> +Response: We would like to express our gratitude for the favorable remarks provided by the reviewer regarding our manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 620, 850, 683]]<|/det|> +1. The authors claimed that TBmA-Glu could be activated by GGT. Is there evidence to suggest that TBmA-Glu could be effective against other types of cancer that overexpress GGT, or is its application currently limited to the cancer types studied? + +<|ref|>text<|/ref|><|det|>[[147, 688, 852, 904]]<|/det|> +Response and revision: We appreciate the reviewer's suggestion and subsequently conducted further investigations into the anticancer efficacy of TBmA-Glu on additional cancer cell lines overexpressing GGT, including OVCAR-5 cells and 4T1 cells (mouse breast cancer cells), as well as HLF-1 cells with regular GGT expression, using MTT assays. The \(\mathrm{IC}_{50}\) values for photodynamic therapy were determined to be \(5.13 \pm 0.69 \mu \mathrm{M}\) (OVCAR-5) and \(5.28 \pm 1.56 \mu \mathrm{M}\) (4T1, Fig. S35), respectively. Moreover, no significant photocytotoxicity was observed in HLF-1 cells with regular GGT expression, nor any significant dark cytotoxicity. These results demonstrate the broad-spectrum anticancer potential of TBmA-Glu against GGT- overexpressing cancer cells, and the rationale for the broader application of TBmA-Glu lies in the overexpression of GGT in various cancerous conditions. Therefore, the potential + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 88, 825, 104]]<|/det|> +effectiveness of TBmA- Glu could extend to other cancers that exhibit elevated GGT levels. + +<|ref|>sub_title<|/ref|><|det|>[[150, 133, 437, 149]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 154, 852, 305]]<|/det|> +The broad- spectrum anticancer potential of TBmA- Glu against GGT- overexpressing cancer cells was further demonstrated through subsequent investigations, including OVCAR- 5 and murine 4T1 cancer cells (Fig. S35). The \(\mathrm{IC}_{50}\) values for photodynamic therapy were determined to be \(5.13 \pm 0.69 \mu \mathrm{M}\) (OVCAR- 5) and \(5.28 \pm 1.56 \mu \mathrm{M}\) (4T1), respectively. Moreover, no significant photocytotoxicity was observed in HLF- 1 cells with regular GGT expression, nor any significant dark cytotoxicity. Therefore, the potential effectiveness of TBmA- Glu could extend to other cancers that exhibit elevated GGT levels. + +<|ref|>image<|/ref|><|det|>[[150, 357, 866, 696]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 333, 469, 349]]<|/det|> +
Changes in the Supporting Information: Fig. S35. The anticancer activity ( \(\mathrm{IC}_{50}\) , \(\mu \mathrm{M}\) ) of TBmA-Glu against GGT overexpressing OVCAR5 and 4T1, and GGT normally expressing HLF1 cells.
+ +<|ref|>text<|/ref|><|det|>[[148, 774, 850, 812]]<|/det|> +2. How photostable is TBmA-Glu under the conditions used for PDT, and does its aggregation state affect its photostability? + +<|ref|>text<|/ref|><|det|>[[147, 818, 852, 901]]<|/det|> +Response and revision: We appreciate the reviewer's question regarding the photostability of TBmA- Glu. To address this, we conducted comprehensive stability studies on TBmA- Glu and its active form, TBmA, produced in cancer cells. We extensively investigated the long- term stability and photostability of TBmA aggregates in FBS (Fig. S28c). The results demonstrate + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 852, 238]]<|/det|> +that no significant degradation or aggregation was observed after TBmA aggregates were dispersed in PBS for \(72\mathrm{h}\) or subjected to continuous light irradiation for 30 minutes. Then, we monitored the photostability of TBmA- Glu in HepG2 cells during light irradiation (Fig. S28b). The results show no significant decrease in fluorescence intensity during the light exposure period (Fig. S34). All these findings, along with the stability studies in PBS, collectively demonstrate the high photostability of TBmA- Glu and its active form TBmA under PDT conditions, both in solution and in the cellular environment. + +<|ref|>sub_title<|/ref|><|det|>[[150, 265, 437, 281]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 287, 852, 437]]<|/det|> +Moreover, the TbmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS solution for \(72\mathrm{h}\) or light irradiated for \(30\mathrm{min}\) . Additionally, TBmA- Glu showed remarkable specific accumulation in HepG2 cells compared to TBmA (Fig. 3b and Fig. S33c), along with exceptional photostability within living cells (Fig. S34a), as evidenced by the absence of significant bleaching even after continuous light irradiation (Fig. S34b). + +<|ref|>sub_title<|/ref|><|det|>[[149, 465, 468, 481]]<|/det|> +## Changes in the Supporting Information: + +<|ref|>image<|/ref|><|det|>[[150, 492, 864, 793]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 803, 852, 864]]<|/det|> +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation (b) and 72h FBS preservation (c).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[157, 88, 864, 244]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 253, 852, 315]]<|/det|> +
Fig. S34. The HepG2 cells were imaged after incubation with TBmA-Glu (5 \(\mu \mathrm{M}\) ) for 12 hours. Subsequently, the cells were exposed to a \(465\mathrm{nm}\) laser for 10 minutes, and images were captured every minute. \(\lambda_{\mathrm{ex}} = 465\mathrm{nm}\) ; \(\lambda_{\mathrm{em}} = 700\pm 20\mathrm{nm}\) , Scale bar, \(20\mu \mathrm{m}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 342, 851, 404]]<|/det|> +3. The author claimed the aggregate size has a great impression on the PDT efficiency of AIE-PSs. What are the typical sizes and shapes of the TBmA-Glu aggregates formed in the presence of GGT? How do these properties affect the emission properties and PDT efficacy? + +<|ref|>text<|/ref|><|det|>[[147, 409, 852, 583]]<|/det|> +Response and revision: We monitored the aggregate sizes of TBmA produced from the GGT- catalyzed reaction using DLS (Fig. S31). The sizes of TBmA aggregates increase from \(66.7\mathrm{nm}\) (1 h, Fig. S31b) to \(158.0\mathrm{nm}\) (4 h, Fig. S31e). Subsequently, no further changes in size were observed as the incubation time was extended. The morphology of the aggregate in \(12\mathrm{h}\) was further analyzed using the transmission electron microscope (TEM, Fig. S34h). The aggregate size measured by TEM is about \(100\mathrm{nm}\) , which is in accord with the size detected by DLS. The stable aggregates produced by GGT catalysis were found to be slightly larger than those detected in \(99\%\) PBS ( \(156.8\mathrm{nm}\) vs \(139.5\mathrm{nm}\) ). + +<|ref|>text<|/ref|><|det|>[[147, 588, 852, 760]]<|/det|> +Additionally, we evaluated the total ROS generation properties of stable TBmA aggregates generated through a GGT- catalyzed reaction (12 h) using DCFH (Fig. S32). Upon 15 minutes of white LED light exposure ( \(20\mathrm{mW}\cdot \mathrm{cm}^{- 2}\) ), GGT- catalyzed TBmA aggregates exhibited an approximately 164- fold (Fig. S32c) increase in fluorescent intensity. While this enhancement was slightly lower than the aggregates formed in \(99\%\) PBS (188- fold), it was significantly higher than Rose Bengal (67.0- fold). These findings are consistent with previous observations that smaller aggregate size tends to enhance photodynamic efficiency. Our results demonstrate that TBmA aggregates generated by GGT possess potent photodynamic activity. + +<|ref|>sub_title<|/ref|><|det|>[[150, 787, 437, 803]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 809, 851, 893]]<|/det|> +Furthermore, we investigated the morphology of TBmA aggregates formed at the endpoint GGT catalytic reaction (12 h) and its ROS generation capability by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). The DLS results revealed a gradual increase in the size of aggregates to approximately \(158.0\mathrm{nm}\) over the initial 4- hour period. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 852, 304]]<|/det|> +Subsequently, a steady state size was attained after 4 hours of incubation, with no further changes observed even when extending the incubation time to 12 hours (Fig. S31). The TEM analysis revealed that GGT facilitated the formation of spherical TBmA aggregates, exhibiting an average diameter of approximately \(100\mathrm{nm}\) (Fig. S31h). Additionally, evaluation of the total ROS generation properties of stable TBmA aggregates showed that it induced an approximately 164- fold increase in the intensity of DCFH after 15 min light irradiation (Fig. S32). While this enhancement was slightly lower than the aggregates formed in \(99\%\) PBS (188- fold), it was significantly higher than Rose Bengal (67.0- fold). These findings are consistent with previous observations that smaller aggregate size tends to enhance photodynamic efficiency. Our results demonstrate that TBmA aggregates generated by GGT possess potent photodynamic activity. + +<|ref|>image<|/ref|><|det|>[[152, 359, 866, 639]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 333, 468, 349]]<|/det|> +
Changes in the Supporting Information:
+ +<|ref|>text<|/ref|><|det|>[[147, 650, 852, 735]]<|/det|> +Fig. S31. (a) The average hydrodynamic diameter (Z- average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b- g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for \(12\mathrm{h}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[157, 88, 866, 249]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 253, 852, 404]]<|/det|> +
Fig. S32. Fluorescence emission changes of DCFH (10 \(\mu \mathrm{M}\) ) in the presence of \(5\mu \mathrm{M}\) photosensitizers in DMSO-PBS \((v:v = 1 / 99)\) after irradiation \((20\mathrm{mW}\cdot \mathrm{cm}^{-2})\) for different time. (a) TBmA aggregates in PBS, (b) TBmA aggregates produced in GGT catalytic reaction, DCHF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) . (c) Plot of the relative emission intensity \((II_{0})\) of DCF (10 \(\mu \mathrm{M}\) ) in presence of TBmA (5 \(\mu \mathrm{M}\) ), TBmA aggregates produced in GGT reaction (5 \(\mu \mathrm{M}\) ) or Rose Bengal (RB, \(5\mu \mathrm{M}\) ) versus the irradiation \((20\mathrm{mW}\cdot \mathrm{cm}^{-2})\) time, where \(I_{0} = \mathrm{PL}\) intensity of DCFH in solutions with different water fraction \((f_{\mathrm{w}})\) without light irradiation. \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 430, 853, 537]]<|/det|> +4. Can aggregated TBmA be expelled from cancer cells via exocytosis, potentially reducing its therapeutic efficacy? Long-term (48 h) cellular imaging results should be provided by the author. Response and revision: We conducted confocal imaging to investigate the intracellular retention of TBmA-Glu. Compared with the short treatment groups, no significant decrease in the imaging fluorescent intensity was detected after 48 h of incubation (Fig. S33a). + +<|ref|>sub_title<|/ref|><|det|>[[150, 565, 437, 581]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 587, 850, 650]]<|/det|> +The results demonstrated that TBmA- Glu has excellent selectivity towards HepG2 cells compared to LO2 cells (Fig. S33a and S33b) and long- term retention ability in HepG2 cells (Fig. S33a). + +<|ref|>text<|/ref|><|det|>[[149, 677, 469, 694]]<|/det|> +Changes in the Supporting Information: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[160, 87, 866, 585]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 588, 852, 671]]<|/det|> +
Fig. S33. The time-dependent uptake process of TBmA-Glu (a) / TBmA (b) in HepG2 cells. (c) The time-dependent uptake process of TBmA-Glu in LO2 cells. All the cells were incubated with \(5\mu \mathrm{M}\) TBmA-Glu / TBmA and imaged at the indicated time. \(\lambda_{\mathrm{ex}} = 465 \mathrm{nm}\) ; \(\lambda_{\mathrm{em}} = 700 \pm 20 \mathrm{nm}\) , Scale bar, \(20\mu \mathrm{m}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 699, 850, 738]]<|/det|> +5. The abbreviations, such as DCF, DCFH-DA, HPF, ABDA, CLSM, et al., should be defined the first time they are used. + +<|ref|>text<|/ref|><|det|>[[147, 744, 850, 783]]<|/det|> +Response and revision: we have ensured that all the abbreviations are defined when they first appear in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 810, 437, 826]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 832, 850, 894]]<|/det|> +"(c) The generation of total ROS generation (2,7'-dichlorodihydrofluorescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10-anthracenediy1- bis(methylene)dimalonic Acid, ABDA) by photosensitizers (5 \(\mu \mathrm{M}\) ) after white LED light + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 852, 128]]<|/det|> +(predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation (20 mW·cm \(^{- 2}\) ) for 15 min using the corresponding ROS indicator in PBS/DMSO (v/v = 99:1).” + +<|ref|>text<|/ref|><|det|>[[148, 133, 853, 173]]<|/det|> +“Fig. 3 (a) Confocal laser scanning microscope (CLSM) images of co- incubated cancer (HepG2; luciferase- transfected) and normal (LO2) cells after treatment with TBmA- Glu (5 μM, 12 h).” + +<|ref|>sub_title<|/ref|><|det|>[[148, 200, 437, 216]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 222, 852, 549]]<|/det|> +This work present a novel approach to targeted cancer therapy by leveraging the tumor- overexpressed enzyme \(\gamma\) - Glutamyl Transferase (GGT) to induce aggregation of an aggregation- induced emission photosensitizer (AIE- PS), TBmA- Glu. This innovative strategy not only enhances the photosensitivity of the AIE- PS but also results in the degradation of GGT and the accumulation of lipid peroxides, leading to cancer cell ferroptosis. The study is significant for its potential to advance targeted photodynamic therapy (PDT) and the development of smart therapeutics that exploit enzyme activity for controlled molecular aggregation within cancer cells. The authors have demonstrated a clear understanding of the complex interactions between molecular aggregation and biological environments, and the manuscript is well- structured, presenting a logical flow of information from synthesis and characterization to in vivo efficacy. The results are compelling, showing the selective activation of TBmA- Glu by GGT, its enhanced photodynamic activity, and the subsequent therapeutic effects on cancer cells. The manuscript is well- written and provides a solid foundation for further research in the field of nanomedicine and targeted drug delivery. I recommend publication following minor modifications, my concerns are outlined below: + +<|ref|>text<|/ref|><|det|>[[148, 555, 785, 571]]<|/det|> +Response: Firstly, we appreciate the reviewer's positive comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 598, 849, 637]]<|/det|> +1. The author could incorporate a concise, visual representation of key discoveries and TBmA- Glu's proposed mechanism of action through a mechanistic cartoon or schematic. + +<|ref|>text<|/ref|><|det|>[[148, 644, 849, 682]]<|/det|> +Response and revision: As suggested by the reviewer, we supplemented a schematic diagram of the mechanism of TBmA- Glu's anticancer activities (Scheme 1). + +<|ref|>text<|/ref|><|det|>[[149, 709, 437, 725]]<|/det|> +Changes in the Revised Manuscript: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[145, 85, 866, 360]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 365, 850, 404]]<|/det|> +Scheme 1: Schematic illumination of the aggregation- enhanced photodynamic therapeutic mechanism mediated by TBmA- Glu. + +<|ref|>text<|/ref|><|det|>[[147, 431, 850, 470]]<|/det|> +2. The stability of the aggregates of TBmA, especially the photostability of it in physiological conditions should be discussed. + +<|ref|>text<|/ref|><|det|>[[147, 476, 851, 583]]<|/det|> +Response and revision: The long- term stability and photostability of the TBmA aggregates were investigated through DLS. The results suggested no significant degradation was observed when TBmA aggregates were dispersed in FBS for 72 hours or subjected to continuous light irradiation for 30 minutes (Fig. S28). TBmA- Glu also exhibited well anti- bleaching properties in living cells (Fig. S34). + +<|ref|>sub_title<|/ref|><|det|>[[149, 608, 437, 625]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 630, 850, 693]]<|/det|> +Moreover, the TbmA aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS solution for 72 h or light irradiated for 30 min. + +<|ref|>text<|/ref|><|det|>[[147, 720, 851, 805]]<|/det|> +Additionally, TBmA- Glu showed remarkable specific accumulation in HepG2 cells compared to TBmA (Fig. 3b and Fig. S33c), along with exceptional photostability within living cells (Fig. S34a), as evidenced by the absence of significant bleaching even after continuous light irradiation (Fig. S34b). + +<|ref|>text<|/ref|><|det|>[[149, 810, 469, 827]]<|/det|> +Changes in the Supporting Information: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[155, 92, 864, 393]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 402, 852, 465]]<|/det|> +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates measured by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and 72h FBS preservation.
+ +<|ref|>image<|/ref|><|det|>[[155, 490, 864, 648]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 657, 851, 720]]<|/det|> +
Fig. S34. The HepG2 cells were imaged after incubation with TBmA-Glu (5 \(\mu \mathrm{M}\) ) for 12 hours. Subsequently, the cells were exposed to a \(465 \mathrm{nm}\) laser for 10 minutes, and images were captured every minute. \(\lambda_{\mathrm{ex}} = 465 \mathrm{nm}\) ; \(\lambda_{\mathrm{em}} = 700 \pm 20 \mathrm{nm}\) , Scale bar, \(20 \mu \mathrm{m}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 745, 851, 808]]<|/det|> +3. The author acclaimed the lipid peroxides (LPOs) resulting from the photodynamic process of activated AIE-PS induce the ferroptosis of cancer cells, the changes in the level of LPOs in cancer cells after photodynamic therapy should be quantified. + +<|ref|>text<|/ref|><|det|>[[147, 813, 851, 898]]<|/det|> +Response and revision: The amounts of oxidative products of lipids in HepG2 cells after the photodynamic therapy are quantified using the Lipid Peroxidation MDA (malondialdehyde) Assay Kit. It can be seen from the results that, compared with the control group and dark- treatment groups, TBmA-Glu induced a significant accumulation of the LPOs in HepG2 cells + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 850, 126]]<|/det|> +after light irradiation treatment (Fig. S39), which corresponds with the previous ROS species and lipids oxidation in our results. + +<|ref|>sub_title<|/ref|><|det|>[[150, 154, 437, 170]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 176, 850, 238]]<|/det|> +The peroxidation products of DOPE and the lipid peroxidation products, malondialdehyde (MDA), were also detected in the DOPE/TBmA mixture (Fig. S38) and the cells after light irradiation (Fig. S39). + +<|ref|>text<|/ref|><|det|>[[148, 243, 851, 350]]<|/det|> +Measurement of MDA levels. HepG2 cells were cultured in \(6\mathrm{cm}\) dishes until they reached approximately \(80\%\) confluency, followed by treatment with TBmA- Glu \((2\mu \mathrm{M})\) for \(12\mathrm{h}\) . The cells were then harvested, counted, and lysed with RAPI lysis buffer at \(4^{\circ}\mathrm{C}\) for \(15\mathrm{min}\) . MDA levels in each group were determined using the Lipid Peroxidation MDA Assay Kit (Beyotime, China), according to the manufacturer's instructions. + +<|ref|>sub_title<|/ref|><|det|>[[149, 376, 468, 393]]<|/det|> +## Changes in the Supporting Information: + +<|ref|>image<|/ref|><|det|>[[355, 421, 641, 612]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 623, 851, 730]]<|/det|> +
Fig. S39. Malondialdehyde (MDA) levels in HepG2 cells after treated with the TBmA-Glu (2 \(\mu \mathrm{M}\) ) for \(12\mathrm{h}\) . Then, the cells were irradiated with a white laser array \((12\mathrm{J}\cdot \mathrm{cm}^{-2})\) and the MDA levels were detected using a Lipid Peroxidation MDA Assay Kit. Data expressed as average \(\pm\) standard error, \(\mathrm{n} = 3\) . Statistical significance: P values, \(\mathrm{***P}< 0.001\) , calculated with the Student's T-test.
+ +<|ref|>text<|/ref|><|det|>[[147, 757, 850, 820]]<|/det|> +4. Detailed experimental procedures for minimally invasive PDT should be provided. Response and revision: The experimental procedure for minimally invasive PDT assay has been incorporated into the "In vivo antitumor assay" section in the "Methods" of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[150, 847, 437, 863]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 869, 850, 908]]<|/det|> +For the minimally invasive photodynamic therapy, the mice were initially anesthetized using an isoflurane inhalant anesthesia apparatus. The TBmA fluorescence was utilized to precisely + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 850, 150]]<|/det|> +locate the tumor section in the liver, and a small incision (2 mm) was meticulously made with a scalpel at the localized region. Subsequently, the laser probe was carefully inserted into the incision to execute the photodynamic therapy. Finally, the wound was sutured and disinfected. + +<|ref|>text<|/ref|><|det|>[[148, 176, 850, 239]]<|/det|> +Finally, we would like to reiterate our sincere gratitude to all the reviewers and the editorial office for their invaluable suggestions and diligent efforts, which have significantly enhanced the quality of this manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[320, 91, 675, 118]]<|/det|> +## Point-by-point Response + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 232]]<|/det|> +We express our sincere gratitude to the reviewers for their insightful comments, which have significantly enhanced the scholarly quality of our paper. In response to their valuable feedback and suggestions, we have carefully revised the manuscript. Our responses and revisions are presented in a distinguishable blue font for convenient reference. + +<|ref|>sub_title<|/ref|><|det|>[[149, 252, 479, 269]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 289, 850, 380]]<|/det|> +Q1: The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +<|ref|>text<|/ref|><|det|>[[148, 381, 850, 472]]<|/det|> +251. "only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA- Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." + +<|ref|>text<|/ref|><|det|>[[147, 474, 850, 585]]<|/det|> +Response and revision: We appreciate the valuable suggestions provided by the reviewer. To enhance the accuracy of our study, we conducted additional experiments using Rose Bengal (RB), a well- established type II photosensitizer1, as a control. These experiments revealed that RB's photodynamic efficiency decreased significantly under hypoxia conditions (2% O2) compared to normoxia conditions, while TBmA maintained relatively consistent activity across both environments (Fig. R1). + +<|ref|>text<|/ref|><|det|>[[148, 586, 850, 659]]<|/det|> +To discuss this result more accurately, we have revised our manuscript by replacing the statement "This suggests that oxygen content has negligible influence on its photodynamic activity." with "This suggests that TBmA exhibits tolerance towards hypoxic conditions." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[333, 83, 660, 303]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 308, 850, 344]]<|/det|> +
Fig. S36. The effects of hypoxia (2% \(O_2\) ) and normoxia (20% \(O_2\) ) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells.
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 364, 350, 380]]<|/det|> +## Revised in manuscript: + +<|ref|>text<|/ref|><|det|>[[149, 382, 850, 455]]<|/det|> +Additionally, only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d), while the type- II PS, RB, showed a significant decrease in photodynamic efficiency under hypoxia conditions (2% \(O_2\) ) compared to normoxia conditions (Fig. S36). This suggests that TBmA exhibits tolerance towards hypoxic conditions. + +<|ref|>sub_title<|/ref|><|det|>[[149, 475, 244, 490]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 493, 850, 547]]<|/det|> +1. Fischer BB, Krieger-Liszkay A, Eggen RIL. Oxidative stress induced by the photosensitizers neutral red (type I) or rose bengal (type II) in the light causes different molecular responses in Chlamydomonas reinhardtii. Plant Sci. 168, 747-759 (2005). + +<|ref|>text<|/ref|><|det|>[[148, 566, 850, 658]]<|/det|> +Q2: Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +<|ref|>text<|/ref|><|det|>[[149, 660, 850, 714]]<|/det|> +Response: We appreciate the reviewer's insightful comments regarding the nature of supramolecular aggregation and the potential for de- aggregation in biological media. We would like to clarify several key points that address these concerns. + +<|ref|>text<|/ref|><|det|>[[148, 733, 850, 824]]<|/det|> +Firstly, it's crucial to emphasize that TBmA- Glu is a water- soluble prodrug. The aggregation process only occurs after the Glu moiety is cleaved by GGT in HepG2 cells. This design ensures that TBmA- Glu remains soluble in the blood, avoiding premature aggregation. Aggregation is triggered specifically in the intracellular environment of GGT- overexpressing tumor cells. + +<|ref|>text<|/ref|><|det|>[[149, 844, 850, 898]]<|/det|> +We acknowledge that FBS is not an ideal model for the intracellular environment. To address this issue, we further conducted stability studies using a 30% BSA (Bovine Serum Albumin) solution, which is a better model for the protein- rich intracellular + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 159]]<|/det|> +milieu. The intracellular protein concentration typically ranges from 50- 400 mg/mL, and our \(30\%\) BSA solution ( \(\sim 300 \mathrm{mg / mL}\) ) falls within this range. TBmA aggregates showed remarkable stability in this environment, with no significant degradation observed over 72 hours (Fig. R1). + +<|ref|>text<|/ref|><|det|>[[148, 177, 850, 288]]<|/det|> +We also agree that pharmacokinetics studies would be valuable. However, our system presents unique challenges for such studies, as the aggregates form intracellularly rather than in circulation. Collecting and analyzing intracellular aggregates from tumor sections poses significant technical difficulties. Our approach using a highly concentrated protein solution provides valuable insights into aggregate stability in a physiologically relevant environment. + +<|ref|>text<|/ref|><|det|>[[148, 307, 850, 362]]<|/det|> +Importantly, beyond structural stability, we have observed that the aggregates maintain their photodynamic properties in the \(30\%\) BSA solution for \(72 \mathrm{h}\) (Fig. R2). This functional stability is crucial for the compound's theranostic applications. + +<|ref|>image<|/ref|><|det|>[[286, 388, 707, 707]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 715, 770, 733]]<|/det|> +
Fig. R1. The long-term stability of TBmA aggregates in \(30\%\) BSA solutions.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[160, 87, 845, 250]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 252, 850, 326]]<|/det|> +
Fig. R2. The ROS generation capacity of \(\mathrm{TBmA}\) aggregates after dispersed in \(30\%\) BSA solution for \(0\mathrm{h}\) (a) and \(72\mathrm{h}\) (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity \((I / I_0)\) of DC versus the irradiation \((20\mathrm{mW}\cdot \mathrm{cm}^{-2})\) time, where \(I_0 = \mathrm{PL}\) intensity of DCFH in solutions without light irradiation.
+ +<|ref|>text<|/ref|><|det|>[[149, 344, 850, 400]]<|/det|> +Q3: References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +<|ref|>text<|/ref|><|det|>[[148, 400, 850, 493]]<|/det|> +Response: We thank the reviewer for the critical feedback. The unique photophysical properties of AIE compounds stem from the restriction of intramolecular motion (RIM) mechanism, where aggregation limits molecular rotations and vibrations, leading to enhanced fluorescence. Therefore, the fluorescence behavior of AIE materials does provide valuable insights into their molecular state and environment. + +<|ref|>text<|/ref|><|det|>[[148, 507, 850, 636]]<|/det|> +This interpretation is supported by several factors. First of all, \(\mathrm{TBmA - Glu}\) is engineered to aggregate specifically in response to GGT activity, which is overexpressed in certain tumor cells. This targeted approach minimizes premature aggregation in circulation. Secondly, the crowded, protein- rich cytoplasmic environment of tumor cells likely provides conditions that favor aggregate stability once formed. Additionally, we observed that the photosensitivity of \(\mathrm{TBmA}\) was maintained in our \(30\%\) BSA studies, suggesting a preservation of the aggregate structure. + +<|ref|>text<|/ref|><|det|>[[148, 668, 850, 780]]<|/det|> +Q4: While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +<|ref|>text<|/ref|><|det|>[[149, 781, 849, 836]]<|/det|> +Response: We appreciate the reviewer's thoughtful comments regarding the therapeutic relevance of AIE compounds and the importance of careful characterization of their behavior in biological systems. + +<|ref|>text<|/ref|><|det|>[[149, 850, 850, 905]]<|/det|> +Regarding the stability and behavior of \(\mathrm{TBmA}\) , we emphasize that \(\mathrm{TBmA - Glu}\) is designed as a water- soluble prodrug that only forms aggregates within tumor cells following enzymatic reaction. This targeted approach minimizes potential issues related + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 139]]<|/det|> +to premature aggregation or size changes in circulation. Furthermore, we have demonstrated the stability of TBmA aggregates in a \(30\%\) BSA solution for 72 hours, providing initial evidence of their potential stability in protein- rich environments. + +<|ref|>text<|/ref|><|det|>[[148, 155, 850, 283]]<|/det|> +About "personalized medicine and real- time treatment monitoring." in the previous response letter: The full sentence is "Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring." We agree that such terminology should be used judiciously, especially in early- stage research, however, our intention here is to highlight the potential of AIE materials to contribute to these fields in the future, rather than to claim immediate clinical applicability. + +<|ref|>text<|/ref|><|det|>[[148, 298, 850, 446]]<|/det|> +The unique properties of AIE materials, including their AIE and potential for stimuli- responsive behavior, do offer intriguing possibilities for both imaging and therapeutic applications. However, we agree that rigorous investigation is needed to establish their efficacy and safety for PDT or other therapeutic schemes. Moving forward, we will focus on providing concrete evidence for the specific advantages of AIE compounds in relevant biological contexts, rather than speculating on broad future applications. We believe this approach will better serve the scientific community and responsibly advance the field. + +<|ref|>text<|/ref|><|det|>[[148, 465, 850, 519]]<|/det|> +Q5: May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to \(450\mathrm{nm}\) peak. There are literature reports of blue (450 nm) light causing cellular damage. + +<|ref|>text<|/ref|><|det|>[[148, 539, 850, 630]]<|/det|> +Response: We acknowledge that there are indeed literature reports of blue light (450 nm) causing cellular damage. This is an important consideration in photodynamic therapy and other light- based treatments. However, we would like to emphasize that the biological effects of light exposure are highly dependent on both wavelength and dosage. + +<|ref|>text<|/ref|><|det|>[[148, 646, 849, 719]]<|/det|> +In our experiments, we carefully controlled the light dosage to minimize potential phototoxicity while maintaining therapeutic efficacy. Under the experimental conditions described in our manuscript, we did not observe any significant effects on cell viability following LED light irradiation (Fig. R3). + +<|ref|>text<|/ref|><|det|>[[148, 735, 849, 806]]<|/det|> +To address the reviewer's concern, we also conducted a blue light irradiation (450 nm, \(12\mathrm{J / cm^2}\) ) PDT assay. In this experiment, we also found no significant effect on cellular viability. This suggests that at the dosages used in our study, the blue light alone does not cause substantial cellular damage. + +<|ref|>text<|/ref|><|det|>[[148, 823, 849, 895]]<|/det|> +However, we agree that the potential for phototoxicity is an important consideration in developing light- based therapies. In future studies, we plan to conduct a more comprehensive dose- response analysis to determine the threshold at which blue light exposure may begin to affect cell viability. We also intend to investigate the potential + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 848, 121]]<|/det|> +long- term effects of repeated light exposure and compare the effects of our AIE- based approach with traditional photosensitizers at equivalent light doses. + +<|ref|>image<|/ref|><|det|>[[365, 141, 627, 302]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 307, 848, 343]]<|/det|> +
Fig. R3 The impact of white light and \(450\mathrm{nm}\) light exposure \((12\mathrm{J / cm^2})\) on the cellular viability of HepG2 cells.
+ +<|ref|>text<|/ref|><|det|>[[148, 362, 850, 436]]<|/det|> +Q6: One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as \(450\mathrm{nm}\) is less than 1 mm, which is significantly less than needed for an effective "photo"- driven process. + +<|ref|>text<|/ref|><|det|>[[148, 454, 849, 510]]<|/det|> +Response: It is correct that the typical penetration depth of \(450\mathrm{nm}\) light is less than 1 mm in tissue, which is indeed less than ideal for treating deep- seated tumors. However, we would like to highlight several important considerations: + +<|ref|>text<|/ref|><|det|>[[148, 525, 850, 580]]<|/det|> +First, though direct light penetration is restricted, the effective depth of PDT damage may increase due to light reflection and scattering within tissues. This occurrence can expand the scope of the photodynamic impact beyond the initial penetration depth. + +<|ref|>text<|/ref|><|det|>[[148, 598, 850, 709]]<|/det|> +Secondly, several clinical scenarios exist where shallow light penetration is sufficient or even advantageous. For instance, PDT with blue light excitation could be particularly useful for superficial skin cancers and precancerous lesions, intraoperative treatment of residual tumor cells after surgical resection, treatment of early- stage mucosal cancers in inaccessible areas (e.g., oral cavity, bladder), and endoscopic applications for gastrointestinal tumors. + +<|ref|>text<|/ref|><|det|>[[148, 725, 850, 779]]<|/det|> +Finally, numerous published studies demonstrate the successful use of \(450\mathrm{nm}\) light and white light (including the blue spectrum) for PDT when the photosensitizers have maximum absorption around \(450\mathrm{nm}\) . 2, 3, 4, 5, 6, 7 + +<|ref|>text<|/ref|><|det|>[[148, 794, 850, 904]]<|/det|> +Nevertheless, we fully agree that blue light's limited tissue penetration restricts the broader applicability of our current system for treating deep- seated tumors. Given this limitation, our future research directions include exploring two- photon excitation to achieve deeper tissue penetration, investigating upconversion nanoparticles to convert longer- wavelength light to blue light locally, and developing new AIE photosensitizers with red- shifted absorption for improved tissue penetration. We believe that addressing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 848, 120]]<|/det|> +these challenges will expand the potential applications of our AIE- based PDT system while utilizing its unique properties. + +<|ref|>sub_title<|/ref|><|det|>[[149, 142, 250, 157]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 160, 850, 418]]<|/det|> +2. Fan L, et al. A Bioactive Photosensitizer for Hypoxia-Tolerant Molecular Targeting-Photo-Immunotherapy of Malignant Tumor. Adv. Funct. Mater. 34, 2313755 (2023). +3. Li X, et al. A novel 450-nm laser-mediated sinoporphyrin sodium-based photodynamic therapy induces autophagic cell death in gastric cancer through regulation of the ROS/PI3K/Akt/mTOR signaling pathway. BMC Med. 20, 475 (2022). +4. Mei Y, et al. A Novel Photosensitizer Based 450-nm Blue Laser-Mediated Photodynamic Therapy Induces Apoptosis in Colorectal Cancer - in Vitro and in Vivo Study. Front. Biosci. (Landmark Ed) 29, 199 (2024). +5. Chen Y, et al. Photoactivatable metal organic framework for synergistic ferroptosis and photodynamic therapy using 450 nm laser. Chem. Eng. J. 454, 140438 (2023). +6. Sun P, et al. A water-soluble phosphorescent conjugated polymer brush for tumor-targeted photodynamic therapy. Polym. Chem. 8, 5836-5844 (2017). +7. An J, et al. An unexpected strategy to alleviate hypoxia limitation of photodynamic therapy by biotinylation of photosensitizers. Nat. Commun. 13, 2225 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 455, 850, 528]]<|/det|> +Q7: First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to \(0.5\%\) O2 hypoxia, or anoxia, the effectiveness would be much more different. + +<|ref|>text<|/ref|><|det|>[[148, 530, 850, 603]]<|/det|> +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Ebselen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide \(\mathrm{(N_3)}\) - is a singlet oxygen quencher. + +<|ref|>text<|/ref|><|det|>[[148, 621, 850, 731]]<|/det|> +Response and revision: We agree with the reviewer that oxygen plays a pivotal role in the Type I and Type II PDT processes. However, from the PDT mechanism, we know that the type I photosensitizers could directly transfer electrons to the substrate, forming a radical cation or neutral radical. These radicals could immediately react with \(\mathrm{O_2}\) or \(\mathrm{H_2O}\) to generate hydrogen peroxide \(\mathrm{(H_2O_2)}\) , hydroxyl radicals (- OH), or superoxide anions (- \(\mathrm{O_2}\) - ) (Fig. R4).1, 2 + +<|ref|>text<|/ref|><|det|>[[148, 750, 850, 899]]<|/det|> +We have tried but could not finish the antitumor PDT assays in the anaerobic conditions, because the anoxia condition resulted in death of the tumor cells (Fig. R5a). So, we re- evaluated the photodynamic efficiency of TBmA and RB using a deoxidized PBS solution. The results showed that TBmA could also induce the oxidation of DFCH under the anoxia condition (Fig. R5b), while the photodynamic efficiency of RB showed significant degradation. Hence, type- I photosensitizers exhibit relatively higher tolerance towards oxygen concentrations, which implies that, even under low oxygen conditions, they can still engage in substrate reactions through electron transfer. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 103, 850, 177]]<|/det|> +We are sorry for the mistake in the figure legend in Figure 4b. “Ebselen” has been revised as “Trolox.” However, it should be noted that Trolox is not only a \(^{1}\mathrm{O}_{2}\) scavenger but also a scavenger of peroxy and alkoxy groups. \(^{3}\) The type-I designation is mainly based on the ROS species we detected in vitro (Fig. R5c). + +<|ref|>image<|/ref|><|det|>[[147, 195, 788, 375]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 380, 761, 399]]<|/det|> +
Fig. R4 Scheme of the photochemical reactions for type I and type II PDT. \(^{9}\)
+ +<|ref|>image<|/ref|><|det|>[[155, 426, 863, 595]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 604, 850, 696]]<|/det|> +
Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \(10 \mu \mathrm{M}\) ) in the presence of \(5 \mu \mathrm{M}\) photosensitizers in DMSO-PBS \((v:v = 1:99)\) after irradiation (20 \(\mathrm{mW}\cdot \mathrm{cm}^{-2}\) ) for a different time under anoxia conditions. (b) \(\mathrm{TBmA}\) , (c) Rose Bengal (RB). DCHF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) .
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 716, 350, 731]]<|/det|> +## Revised in manuscript: + +<|ref|>text<|/ref|><|det|>[[149, 733, 850, 770]]<|/det|> +Trolox: \(50 \mu \mathrm{M}\) (ROO. scavenger and \(^{1}\mathrm{O}_{2}\) scavenger); D- mannitol: \(50 \mathrm{mM}\) (- OH scavenger); Tiron: \(10 \mathrm{mM}\) (- \(\mathrm{O}_{2}\) scavenger); \(\mathrm{NaN}_{3}\) : \(5 \mathrm{mM}\) ( \(^{1}\mathrm{O}_{2}\) scavenger) + +<|ref|>sub_title<|/ref|><|det|>[[149, 790, 250, 805]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 808, 850, 899]]<|/det|> +1. Zhao X, Liu J, Fan J, Chao H, Peng X. Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application. Chem. Soc. Rev. 50, 4185-4219 (2021). +2. Fan W, Huang P, Chen X. Overcoming the Achilles' heel of photodynamic therapy. Chem. Soc. Rev. 45, 6488-6519 (2016). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 849, 140]]<|/det|> +3. Lúcio M, Nunes C, Gaspar D, Ferreira H, Lima JLFC, Reis S. Antioxidant Activity of Vitamin E and Trolox: Understanding of the Factors that Govern Lipid Peroxidation Studies In Vitro. Food Biophys. 4, 312-320 (2009). + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 269]]<|/det|> +Q8: Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +<|ref|>text<|/ref|><|det|>[[148, 288, 850, 436]]<|/det|> +Response: Indeed, the total quantum yield of all radiative and non- radiative processes cannot exceed 1. However, the energy consumption in no radiative processes contains both the energy for ISC processes and the molecular motion as well. Molecular aggregation could induce the restriction of intramolecular motions (RIM) and, as a result, reduce energy loss through non- radiative molecular motion, potentially increasing the energy available for emission and ISC processes. So, the energy efficiency of both emission and ISC can be enhanced in aggregated structure due to RIM. + +<|ref|>text<|/ref|><|det|>[[148, 455, 850, 602]]<|/det|> +However, in specific cases, such as the graphene quantum dots reported by Zhang et al., the apparent quantum yield could be larger than \(1. ^{1}\) This occurs when the energy gaps between \(\Delta E_{\mathrm{ST}}\) and \(\Delta E_{\mathrm{TG}}\) (the energy gap between \(\mathrm{T_1}\) and Ground state) are larger than the formation energy of \(^{1}\mathrm{O}_{2}\) (22.5 kcal mol \(^{- 1}\) ). In such cases, \(^{1}\mathrm{O}_{2}\) generation happens through multiple pathways: energy transfer from \(\mathrm{T_1}\) (ET(1) in Fig. R6), but also the energy transfer from \(\mathrm{S_1}\) to \(^{3}\mathrm{O}_{2}\) during the \(\mathrm{S_1 - T_1}\) intersystem crossing transition (ET(2) in Figure R6). This multi- pathway mechanism can lead to an overall \(^{1}\mathrm{O}_{2}\) quantum yield greater than 1.0, as more than one \(^{1}\mathrm{O}_{2}\) molecule can be produced per absorbed photon. \(^{2}\) + +<|ref|>image<|/ref|><|det|>[[198, 621, 789, 821]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 825, 850, 861]]<|/det|> +
Fig. R6 Schematic illustration of the \(^{1}\mathrm{O}_{2}\) generation mechanisms by conventional PDT agents (left) and GQDs (right).
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 882, 245, 898]]<|/det|> +## References + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 159]]<|/det|> +1. Ge J, et al. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation. Nat. Commun. 5, 4596 (2014). +2. Kanner RC, Foote CS. Singlet oxygen production from singlet and triplet states of 9,10-dicyanoanthracene. J. Am. Chem. Soc. 114, 678-681 (1992). + +<|ref|>text<|/ref|><|det|>[[148, 178, 850, 251]]<|/det|> +Q9: Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +<|ref|>text<|/ref|><|det|>[[148, 270, 853, 399]]<|/det|> +Response: As previously discussed, TBmA- Glu is a water- soluble molecule that forms aggregates within tumor cells upon activation by GGT to produce TBmA. Consequently, most of these aggregates are localized in the tumor cells. Furthermore, we have demonstrated the stability of TBmA aggregates for 72 hours in a 30% BSA solution. Additionally, considering that PDT processes were conducted 12 hours after administration of TBmA- Glu, it can be inferred that the TBmA aggregates exhibit sufficient stability to complete the PDT processes. + +<|ref|>text<|/ref|><|det|>[[149, 418, 460, 435]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 455, 850, 491]]<|/det|> +Q1: The authors have addressed all the concerns in the revisions. And the manuscript is ready to be published. + +<|ref|>text<|/ref|><|det|>[[148, 510, 850, 565]]<|/det|> +Response: We would like to express our sincere gratitude to the reviewer again for their invaluable suggestions, which have significantly enhanced the comprehensiveness and rigor of this paper. + +<|ref|>text<|/ref|><|det|>[[149, 585, 460, 602]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 621, 850, 676]]<|/det|> +Q1: The paper's focus is the enzymatically catalyzed molecular aggregation for improving the response and PDT treatment. The paper has been revised accordingly, and ready for publication. + +<|ref|>text<|/ref|><|det|>[[148, 696, 850, 732]]<|/det|> +Response: We would like to thank the reviewer for their invaluable suggestions, which have significantly improved the comprehensiveness and rigor of this paper. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[320, 92, 677, 119]]<|/det|> +## Point-by-point Response + +<|ref|>text<|/ref|><|det|>[[148, 125, 852, 208]]<|/det|> +We express our sincere gratitude to the reviewers, which have significantly enhanced the scholarly quality of our paper. In response to your valuable feedback and suggestions, we have carefully revised the manuscript. Our responses and revisions are presented in a distinguishable blue font for convenient reference. + +<|ref|>sub_title<|/ref|><|det|>[[150, 258, 434, 274]]<|/det|> +## Reviewer #1 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[149, 304, 265, 319]]<|/det|> +General opinion + +<|ref|>text<|/ref|><|det|>[[148, 325, 850, 363]]<|/det|> +The present manuscript claims to achieve a better targeting of a proposed photosensitizer (PS) which can activated by GGT and be excited at short wavelengths. + +<|ref|>text<|/ref|><|det|>[[148, 370, 850, 408]]<|/det|> +Also, activated (aggregate structure) may have a better cytotoxic effect, compared its non- activated form, which is another example of activated- PS + +<|ref|>text<|/ref|><|det|>[[148, 414, 850, 475]]<|/det|> +There have been countless photosensitizers which can be targeted one way of or another. Many reviews exist about activatable photosensitizers. Some enzymatically, some by hypoxia, by higher \(\mathrm{H}_2\mathrm{O}_2\) or GSH concentrations, or acidic pH. + +<|ref|>text<|/ref|><|det|>[[148, 480, 853, 586]]<|/det|> +The main, may be the only reason why PDT did not develop significantly since 70's is that fact that light, even at the so- called "therapeutic window" does not go through tissues. And of course, there is no real justification for a \(450\mathrm{nm}\) chromophore to be proposed as a novelty. There are very specific, niche cases, where a single cell layer penetration may be useful. But citing these, is missing the point of all PDT- work. + +<|ref|>text<|/ref|><|det|>[[148, 592, 850, 630]]<|/det|> +Type- I processes being less oxygen dependent has been proposed without real evidence. The new data provided by the authors is also not a fair comparison (see below). + +<|ref|>text<|/ref|><|det|>[[148, 636, 850, 675]]<|/det|> +Thus the manuscript does not bring any novelty to the field. The requirement for aggregation, if anything, complicates the picture very unnecessarily. + +<|ref|>text<|/ref|><|det|>[[148, 681, 850, 719]]<|/det|> +Response: We would like to thank the reviewer for the insightful comments, which have significantly enhanced the quality of our paper. + +<|ref|>sub_title<|/ref|><|det|>[[149, 747, 440, 763]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 770, 850, 808]]<|/det|> +Q1: Light source in Fig S36 was not given, if it is white LED, it is not a fair comparison, because LED emission profile fits TbmA/aggregate better. + +<|ref|>text<|/ref|><|det|>[[148, 814, 850, 875]]<|/det|> +Response: Rose Bengal (RB) has its maximum absorption at \(558\mathrm{nm}\) . We can see from the emission spectrum of the LED light (Fig. S28) that the LED has a broad maximum emission at \(550 - 600\mathrm{nm}\) . It means that LED emission also fits the absorption of RB. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 421, 103]]<|/det|> +Q2: 0.5 or \(1\%\) hypoxia may be better. + +<|ref|>text<|/ref|><|det|>[[147, 110, 852, 216]]<|/det|> +Response and revision: In previous experiments, we have proved that TBmA has more potent PDT efficiency than Rose Bengal (RB) even under anoxia conditions. So, we think the 0.5 or \(1\%\) hypoxia would not lead to the different PDT efficiency of TBmA and RB. Furthermore, to address your concerns about the hypoxia PDT efficiency, we decided to remove the discussion of the hypoxia photosensitization of AIE photosensitizers in our manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 242, 852, 372]]<|/det|> +Q3: Both of these articles while interesting, hardly relevant to PDT considering the absorption peaks of the proposed sensitizers are in blue, and the fact that they are very unique cases. The first one reached to a suprizing conclusion without doing any photophysical work. Vibrational (or rotational) relaxation and their control by micro- or molecular environments, by molecular steric hinderence is well known. However, only accurate quantum yield determinations would prove simulataneous increases in emission and singlet oxygen quantum yields. This is not done in Ref 1. + +<|ref|>text<|/ref|><|det|>[[147, 376, 852, 460]]<|/det|> +Response and revision: I would like to clarify that our discussion here is indeed focused on the quantum yield during the photodynamic therapy (PDT) process. It is important for you to know that, regardless of the light source used to excite the photosensitizer, all photodynamic processes share the same underlying photophysical mechanisms. + +<|ref|>text<|/ref|><|det|>[[147, 465, 853, 638]]<|/det|> +In the first reference, the authors demonstrated the quantum yield of graphene quantum dots (GQDs) using electron paramagnetic resonance (EPR) assays, which is a critical aspect of validating the multistate sensitization (MSS) mechanism. The authors also focused on the fluorescence intensity at \(680 \mathrm{nm}\) and the singlet oxygen ( \(^{1}\mathrm{O}_{2}\) ) quantum yield of GQDs in solutions with varying oxygen concentrations. All the results are in agreement with the proposed MSS mechanism, which suggests that an overall \(^{1}\mathrm{O}_{2}\) quantum yield greater than 1.0 can be achieved under specific conditions. However, we fully concur with your assessment that more work is necessary before any definitive conclusions. + +<|ref|>text<|/ref|><|det|>[[147, 665, 850, 703]]<|/det|> +Q4: The problem is that now "activated" aggregates, will not stay forever in tumor cells, as these cells disintegrate. + +<|ref|>text<|/ref|><|det|>[[147, 710, 852, 793]]<|/det|> +Response and revision: It is important to point out that we do not want the aggregates to stay in cells forever. What we need to make sure is that the "activated" aggregates work properly during treatment. The stability and photodynamic efficiency assays have proved that the activated aggregates could meet the therapeutic requirement in the study. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 88, 660, 104]]<|/det|> +Reviewer 1 responses to the authors' comments is highlighted in red. + +<|ref|>sub_title<|/ref|><|det|>[[149, 110, 356, 125]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 132, 437, 148]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 154, 850, 215]]<|/det|> +The authors report two compounds that they claim to undergo enzyme triggered aggregation (both in vitro and vivo) leading to effective PDT outcomes, partly due to a "type- I PDT" process they claim to be better than "type II". + +<|ref|>text<|/ref|><|det|>[[148, 220, 850, 309]]<|/det|> +This referee finds important design flaws and problems with the implementation of the work. Response: We thank the reviewer for the constructive comments on our paper. In this manuscript, we actually did not intend to compare the Type I and Type II PDT processes, and the efficiency of type I and type II photosensitizers is not the key point of this work. We just want to present the objective performance of the developed photosensitizers based on their ROS generation capability. As clearly stated in the manuscript: "It was found that TBMa and + +<|ref|>text<|/ref|><|det|>[[148, 310, 850, 436]]<|/det|> +ROS generation capability. As clearly stated in the manuscript: "It was found that TBMa and TBPa produced significantly higher ROS compared to TBMa- Glu and TBPa- Glu, even surpassing the commercial photosensitizer, Rose Bengal (RB). Moreover, TBMa was identified as the most potent photosensitizer among the four compounds. Further analysis revealed that TBMa and TBPa functioned as strong type I photosensitizers (Fig. 1c and Fig. S25), while TBMa- Glu and TBPa- Glu acted as very weak type II photosensitizers (Fig. 1c and Fig. S26)." + +<|ref|>text<|/ref|><|det|>[[148, 455, 850, 545]]<|/det|> +\*\*\*The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +<|ref|>text<|/ref|><|det|>[[178, 564, 833, 656]]<|/det|> +21. "only marginal variation was observed in the phototoxicity of TBMa-Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBMa-Glu (TBMa) primarily exerts its anticancer effects through the type I PDT process, which is consistent with the prior findings." + +<|ref|>text<|/ref|><|det|>[[149, 694, 343, 710]]<|/det|> +Here are the major issues: + +<|ref|>text<|/ref|><|det|>[[149, 716, 344, 732]]<|/det|> +Problem with Aggregates: + +<|ref|>text<|/ref|><|det|>[[148, 737, 850, 865]]<|/det|> +While AIE compounds may be interesting for imaging perhaps mostly in cell culture and mice models (considering limited light penetration) as a therapeutic agent, aggregate structures are ill- defined and especially in high protein milieus, not very stable and difficult to standardize. More to the point, there is really no real justification for the use of aggregates, considering the fact molecular drugs or photosensitizers are better than the aggregates in many aspects, and nothing new is offered or even suggested by these compounds. + +<|ref|>text<|/ref|><|det|>[[148, 870, 848, 910]]<|/det|> +Response and revision: Thank you for your thoughtful comments regarding AIE compounds. We appreciate your concerns and would like to address them point by point: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 852, 193]]<|/det|> +(i) Stability and standardization: we acknowledge that stability is crucial for bio- application. Our recent studies have shown promising results regarding the stability of TBmA aggregates in high-protein environments, specifically: (a) Long-term stability: TBmA aggregates showed no significant degradation when dispersed in FBS for 72 hours (Fig. S28a and S28c). + +<|ref|>text<|/ref|><|det|>[[147, 198, 852, 306]]<|/det|> +\*\*\* Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +<|ref|>text<|/ref|><|det|>[[147, 330, 852, 416]]<|/det|> +(ii) (b) Photostability: The aggregates remained stable under continuous light irradiation for 30 minutes (Fig. S28a and S28b). These findings collectively highlight the exceptional stability exhibited by TBmA. These findings demonstrate the exceptional stability of TBmA aggregates in biologically relevant conditions. + +<|ref|>text<|/ref|><|det|>[[147, 420, 852, 504]]<|/det|> +Moreover, numerous AIEggens, including small molecules or AIE nanoparticles, have been extensively reported for their long- term monitoring and theranostic applications. \(^{1,2,3}\) These pieces of evidence underscore the remarkable stability of AIEggens, making them highly promising candidates for theranostic applications. + +<|ref|>text<|/ref|><|det|>[[147, 508, 852, 681]]<|/det|> +(iii) Aggregate structure: To address concerns about ill- defined aggregate structures, we extensively investigated the aggregate size of TBmA using Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). The results suggest that the TBmA forms spherical particles with 140 nm in 99% PBS and 150 nm diameter after the GGT catalysis reaction (12 h, Fig. S31). These results indicate that TBmA consistently forms nanoparticles of definite shape and size in aqueous environments, regardless of the specific conditions. Numerous works have been reported to show the definite shape and size, as well as the excellent stability and biocompatibility of the AIE aggregates. \(^{4,5,6}\) + +<|ref|>text<|/ref|><|det|>[[148, 686, 850, 726]]<|/det|> +\*\*\* References 4, 5 and 6 were carefully checked. Stability of the aggregates "in vivo" was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +<|ref|>text<|/ref|><|det|>[[147, 754, 852, 904]]<|/det|> +(iv) A comparative analysis of small molecular drugs and AIE materials: Although molecular drugs and traditional photosensitizers have their advantages, AIE compounds offer unique benefits such as enhanced emission upon aggregation, responsiveness to stimuli, and multifunctional potential. Revealing reports increasingly indicate that small molecular photosensitizers, such as CE6, exhibit low solubility and undergo aggregation in solution, resulting in the deactivation of their photosensitizing activity and hindering their bioapplication. \(^{7,8,9,10}\) We believe that AIE compounds can serve as complementary agents, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 851, 170]]<|/det|> +rather than substitutes, for small molecule drugs. Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring. \(^{4, 11, 12, 13}\) + +<|ref|>text<|/ref|><|det|>[[148, 175, 851, 305]]<|/det|> +We believe that AIE compounds, including TBM- A- Glu, offer valuable and unique properties that complement existing molecular drugs and photosensitizers. While challenges remain, the growing body of research on AIE materials suggests significant potential for advancing biomedical imaging and therapeutic applications. We appreciate the reviewer's perspective and believe that continued research and development in this field will address current limitations and unlock new possibilities in biomedical science. + +<|ref|>text<|/ref|><|det|>[[148, 330, 851, 440]]<|/det|> +\*\*\* While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +<|ref|>sub_title<|/ref|><|det|>[[150, 465, 437, 481]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 486, 851, 569]]<|/det|> +Moreover, the TBM- A aggregates exhibited excellent long- term stability (Fig. S28a and S28c) and photodynamic stability (Fig. S28a and S28b), no significant aggregation or degradation was found after dispersed in FBS (fetal bovine serum) solution for 72 h or light irradiated for 30 min. + +<|ref|>image<|/ref|><|det|>[[150, 599, 850, 891]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 575, 469, 592]]<|/det|> +
Changes in the Supporting Information:
+<|ref|>image_caption<|/ref|><|det|>[[145, 895, 850, 912]]<|/det|> +
Fig. S28. (a) The average hydrodynamic diameter (Z-average) of TBM-A aggregates measured
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 850, 126]]<|/det|> +by Dynamic Light Scattering (DLS). The distribution of TBmA aggregates during 30 min light irradiation and \(72\mathrm{h}\) FBS preservation. + +<|ref|>image<|/ref|><|det|>[[156, 153, 850, 428]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 432, 851, 516]]<|/det|> +
Fig. S31. (a) The average hydrodynamic diameter (Z-average) of TBmA aggregates produced in GGT catalytic reaction measured by DLS. (b-g) Distribution of TBmA aggregates formed at different times of GGT catalytic reaction. (h) The transmission electron microscope (TEM) of the TBmA aggregates formed after the GGT catalytic reaction for \(12\mathrm{h}\) .
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 544, 237, 559]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[147, 565, 852, 895]]<|/det|> +1. Zuo J, et al. Long-term spatiotemporal and highly specific imaging of the plasma membrane of diverse plant cells using a near-infrared AIE probe. Angew. Chem. Int. Ed. 14, 2139-2148 (2023). +2. Wang Z, et al. Long-term fluorescent cellular tracing by the aggregates of aie bioconjugates. J. Am. Chem. Soc. 135, 8238-8245 (2013). +3. Li K, et al. Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing. Sci. Rep. 3, 1150 (2013). +4. Wang J, et al. Nanolab in a cell: Crystallization-induced in situ self-assembly for cancer theranostic amplification. J. Am. Chem. Soc. 144, 14388-14395 (2022). +5. Li Y, et al. Trojan Horse-Like Nano-AIE Aggregates Based on Homologous Targeting Strategy and Their Photodynamic Therapy in Anticancer Application. Adv. Sci. 8, 2102561 (2021). +6. Yan Z, et al. Preparation of ultrasmall AIE nanoparticles with tunable molecular packing via freeze assembly. Nano Lett. 23, 1030-1035 (2023). +7. Li Y, et al. Near-infrared light and redox dual-activatable nanosystems for synergistically + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[183, 87, 850, 127]]<|/det|> +cascaded cancer phototherapy with reduced skin photosensitization. Biomaterials 288, 121700 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 131, 851, 194]]<|/det|> +8. Tian S, He J, Lyu D, Li S, Xu Q-H. Aggregation enhanced photoactivity of photosensitizer conjugated metal nanoparticles for multimodal imaging and synergistic phototherapy below skin tolerance threshold. Nano Today 45, 101534 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 198, 851, 261]]<|/det|> +9. Wang H, Xue K-F, Yang Y, Hu H, Xu J-F, Zhang X. In Situ Hypoxia-Induced Supramolecular Perylene Diimide Radical Anions in Tumors for Photothermal Therapy with Improved Specificity. J. Am. Chem. Soc. 144, 2360-2367 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 265, 851, 327]]<|/det|> +10. Li X, et al. Nanostructured Phthalocyanine Assemblies with Protein-Driven Switchable Photoactivities for Biophotonic Imaging and Therapy. J. Am. Chem. Soc. 139, 10880-10886 (2017). + +<|ref|>text<|/ref|><|det|>[[148, 331, 851, 394]]<|/det|> +11. Chen C, Zhang X, Gao Z, Feng G, Ding D. Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection. Nat. Protoc., in press (2024). + +<|ref|>text<|/ref|><|det|>[[148, 398, 850, 460]]<|/det|> +12. Liu Z, Wang Q, Zhu Z, Liu M, Zhao X, Zhu W-H. AIE-based nanoaggregate tracker: high-fidelity visualization of lysosomal movement and drug-escaping processes. Chem. Sci. 11, 12755-12763 (2020). + +<|ref|>text<|/ref|><|det|>[[148, 465, 850, 505]]<|/det|> +13. Yu Y, et al. Cytophilic Fluorescent Bioprobes for Long-Term Cell Tracking. Adv. Mater. 23, 3298-3302 (2011). + +<|ref|>text<|/ref|><|det|>[[148, 532, 322, 548]]<|/det|> +Excitation wavelength: + +<|ref|>text<|/ref|><|det|>[[147, 554, 851, 660]]<|/det|> +The absorption peak of the monomeric compounds and the aggregates in this work is around \(450~\mathrm{nm}\) . This means essentially no penetration in tissues (just single cell width). This is the reason why the authors use a White LED light source, which is a non- descript identification of a light source, but is known that LEDs of this type have a very strong near UV peak. Part of the cell death in cell cultures is clearly due to white LED. + +<|ref|>text<|/ref|><|det|>[[147, 665, 852, 837]]<|/det|> +Response and revision: We appreciate the reviewer's concern regarding light penetration and the effects of our light source. Our analysis of the white LED light shows predominant peaks at \(450~\mathrm{nm}\) , with no detectable UV peak, which could address the concerns of the reviewers about unintended UV- induced effects (Fig. S27). Furthermore, all anticancer \(\mathrm{IC}_{50}\) values of tested compounds were detected using the MTT assays, and no significant effect on cell viability was detected in the control group after exposure to LED irradiation. MTT assays and control experiments demonstrate that the observed cell death is due to \(\mathrm{TBmA}\) - Glu's photodynamic properties, not the LED light itself. + +<|ref|>text<|/ref|><|det|>[[148, 864, 850, 904]]<|/det|> +\*\*\* May be it wasn't clear in my earlier statement of concern, I did say near UV, but I was specifically referring to \(450~\mathrm{nm}\) peak. There are literature reports of blue (450 nm) light + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 89, 333, 104]]<|/det|> +causing cellular damage. + +<|ref|>text<|/ref|><|det|>[[147, 131, 852, 261]]<|/det|> +Depth of Penetration in Tissues: While it is true that the penetration depth of light at 450 nm is limited, this wavelength is still within the range where some penetration can occur in biological tissues. The actual penetration depth can be influenced by factors such as tissue type, pigmentation, and the optical properties of the tissue. Furthermore, we employed a minimally invasive approach for PDT to optimize the efficiency of photodynamic therapy and minimize the impact of light penetration. + +<|ref|>text<|/ref|><|det|>[[147, 287, 851, 372]]<|/det|> +\*\*\* One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. \(450 \mathrm{nm}\) is not compatible with PDT. The typical penetration length as \(450 \mathrm{nm}\) is less than \(1 \mathrm{mm}\) , which is significantly less than needed for an effective "photo"- driven process. + +<|ref|>sub_title<|/ref|><|det|>[[149, 444, 437, 460]]<|/det|> +## Changes in the Revised Manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 464, 852, 594]]<|/det|> +The generation of total ROS generation (2,7'- dichlorodihydrofluorescein, DCF), hydroxyl radical (hydroxyphenyl fluorescein, HPF) and singlet oxygen (9,10- anthracenediy1- bis(methylene)dimalonic Acid, ABDA) by photosensitizers ( \(5 \mu \mathrm{M}\) ) after white LED light (predominant emission peaks at 450 and 570 nm, Fig. S27) irradiation (20 \(\mathrm{mW}\cdot \mathrm{cm}^{- 2}\) ) for 15 min using the corresponding ROS indicator in PBS/DMSO ( \(\mathrm{v} / \mathrm{v} = 99:1\) ). DCF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) . + +<|ref|>title<|/ref|><|det|>[[148, 600, 469, 616]]<|/det|> +# Changes in the Supporting Information: + +<|ref|>image<|/ref|><|det|>[[348, 621, 647, 834]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 844, 607, 861]]<|/det|> +
Fig. S27. The emission wavelength analysis of the LED light.
+ +<|ref|>text<|/ref|><|det|>[[148, 888, 488, 904]]<|/det|> +Confusion about the Type- I and Type- II PDT: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 851, 216]]<|/det|> +In recent articles regarding PDT, it seems like a misreading of PDT processes getting entrenched. PDT is a combination of both of these processes. Most ROS species are interconvertible by various enzymatic processes in vivo. Same articles also push the misconception that Type- I process (which are partly based on the degradation of the photosensitizers) are better, because it is less oxygen dependent; and it is not easy to separate these two processes (I/II). + +<|ref|>text<|/ref|><|det|>[[147, 220, 852, 415]]<|/det|> +Response: We appreciate the reviewer's insightful comments on the Type- I and Type- II PDT processes. We agree that PDT often involves a combination of both processes and that ROS species can undergo interconversion through various enzymatic processes in vivo. Our study focused on characterizing the predominant mechanism of \(\mathrm{TBmA}\) under specific conditions, not comparing the superiority of Type- I vs Type- II processes. We found that the cleaved \(\mathrm{TBmA}\) - Glu ( \(\mathrm{TBmA}\) ) primarily exerts its anticancer effects through the type I PDT process. And aligning with this finding, we observed the oxygen independence of \(\mathrm{TBmA}\) 's photodynamic activity in the hypoxia condition, which is potentially advantageous in hypoxic tumor environments. + +<|ref|>text<|/ref|><|det|>[[147, 420, 851, 504]]<|/det|> +We acknowledge the complexity of PDT processes in biological systems, which may reflect both directly generated species and enzymatic interconversions. However, the ROS we detected in cells are coordinating with the results we detected in vitro, which validates the validity of our conclusion. + +<|ref|>text<|/ref|><|det|>[[147, 507, 851, 580]]<|/det|> +\*\*\* First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to 0.5 % O2 hypoxia, or anoxia, the effectiveness would be much more different. + +<|ref|>text<|/ref|><|det|>[[147, 584, 856, 668]]<|/det|> +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Ebselen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide (N3- ) is a singlet oxygen quencher + +<|ref|>text<|/ref|><|det|>[[148, 695, 523, 711]]<|/det|> +Enhancement of emission "AND" PDT efficiency. + +<|ref|>text<|/ref|><|det|>[[148, 716, 850, 756]]<|/det|> +The authors should also keep in mind that any emission from the aggregates, is a loss in ROS generation efficiency. So, AIE- PDT carries a certain self- contradictory character. + +<|ref|>text<|/ref|><|det|>[[147, 761, 851, 867]]<|/det|> +Response: We appreciate the reviewer's insights regarding the competitive nature of fluorescence and reactive oxygen species (ROS) generation in AIE- PDT systems. While both processes utilize energy from the excited state, our findings on the simultaneous enhancement of aggregate luminescence and photodynamic activity are not contradictory. Here is some reported literature. + +<|ref|>text<|/ref|><|det|>[[147, 872, 850, 911]]<|/det|> +(i) Aggregation-induced intermolecular intersystem crossing (AI-ISC): Jiang et al. proposed a new mechanism called aggregation-induced intersystem crossing (AI-ISC) to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 86, 852, 260]]<|/det|> +understand the effect of aggregation on increasing ISC efficiency. \(^{1,2}\) According to the AI- ISC theory, more excitonic couplings cause excited- state energy splitting and overlapping of singlet and triplet in aggregate. The energy splitting and overlapping significantly produce many ISC channels with very small \(\Delta E_{\mathrm{ST}}\) in aggregates, which is available for ISC processes. Therefore, the formation of aggregates can facilitate the production of triplet excitons. In addition to emitting phosphorescent radiation, these triplet excitons can also undergo a non- radiative pathway known as the aggregation- enhanced photodynamic effect to return to their ground state. \(^{3,4,5}\) + +<|ref|>text<|/ref|><|det|>[[147, 265, 852, 372]]<|/det|> +\*\*\* Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +<|ref|>text<|/ref|><|det|>[[147, 398, 852, 460]]<|/det|> +(ii) Restriction of intramolecular motion (RIM): The aggregation of AIE molecules results in a restriction of intramolecular rotations and vibrations, effectively suppressing molecular motions, which is also beneficial for the ISC process. \(^{6,7}\) + +<|ref|>text<|/ref|><|det|>[[147, 465, 851, 526]]<|/det|> +All the evidence highlights the potential of AIE materials in PDT. The aggregation- induced changes in the molecular environment can optimize both the imaging and therapeutic aspects of the treatment. \(^{8,9,10}\) + +<|ref|>text<|/ref|><|det|>[[147, 532, 850, 593]]<|/det|> +\*\*\*Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +<|ref|>sub_title<|/ref|><|det|>[[148, 644, 242, 659]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 665, 851, 905]]<|/det|> +1. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020). +2. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019). +3. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020). +4. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 85, 852, 437]]<|/det|> +5. Ji C, Lai L, Li P, Wu Z, Cheng W, Yin M. Organic dye assemblies with aggregation-induced photophysical changes and their bio-applications. Aggregate 2, e39 (2021).6. Kwok RTK, Leung CWT, Lam JWY, Tang BZ. Biosensing by luminogens with aggregation-induced emission characteristics. Chem. Soc. Rev. 44, 4228-4238 (2015).7. Li Q, et al. Time-dependent photodynamic therapy for multiple targets: A highly efficient aie-active photosensitizer for selective bacterial elimination and cancer cell ablation. Angew. Chem. Int. Ed. 59, 9470-9477 (2020).8. Liu Z, et al. Tuning organelle specificity and photodynamic therapy efficiency by molecular function design. ACS Nano 13, 11283-11293 (2019).9. Lee E, et al. A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria. Chem. Sci. 11, 5735-5739 (2020).10. Wan Q, et al. Molecular engineering to boost aie-active free radical photogenerators and enable high-performance photodynamic therapy under hypoxia. Adv. Func. Mater. 30, 2002057 (2020). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[430, 93, 567, 118]]<|/det|> +## Response + +<|ref|>sub_title<|/ref|><|det|>[[149, 141, 289, 158]]<|/det|> +## General opinion + +<|ref|>text<|/ref|><|det|>[[149, 178, 849, 214]]<|/det|> +The present manuscript claims to achieve a better targeting of a proposed photosensitizer (PS) which can activated by GGT and be excited at short wavelengths. + +<|ref|>text<|/ref|><|det|>[[149, 233, 849, 269]]<|/det|> +Also, activated (aggregate structure) may have a better cytotoxic effect, compared its non- activated form, which is another example of activated- PS + +<|ref|>text<|/ref|><|det|>[[149, 288, 849, 344]]<|/det|> +There have been countless photosensitizers which can be targeted one way of or another. Many reviews exist about activatable photosensitizers. Some enzymatically, some by hypoxia, by higher \(\mathrm{H}_2\mathrm{O}_2\) or GSH concentrations, or acidic pH. + +<|ref|>text<|/ref|><|det|>[[149, 362, 850, 455]]<|/det|> +The main, may be the only reason why PDT did not develop significantly since 70's is that fact that light, even at the so- called "therapeutic window" does not go through tissues. And of course, there is no real justification for a \(450~\mathrm{nm}\) chromophore to be proposed as a novelty. There are very specific, niche cases, where a single cell layer penetration may be useful. But citing these, is missing the point of all PDT- work. + +<|ref|>text<|/ref|><|det|>[[149, 474, 849, 529]]<|/det|> +Type- I processes being less oxygen dependent has been proposed without real evidence. The new data provided by the authors is also not a fair comparison (see below). + +<|ref|>text<|/ref|><|det|>[[149, 548, 848, 584]]<|/det|> +Thus the manuscript does not bring any novelty to the field. The requirement for aggregation, if anything, complicates the picture very unnecessarily. + +<|ref|>sub_title<|/ref|><|det|>[[149, 697, 479, 714]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 732, 850, 825]]<|/det|> +Q1: The authors are accurate in stating that a comparison was not made (see the green text below from the manuscript). However, they claim that oxygen content has a negligible influence on the observed activity under hypoxia, which is linked to Type- I process, based on previous claims. These claims were not supported by "negative controls" with standart PDT photosensitizers, in a fair comparison. + +<|ref|>text<|/ref|><|det|>[[149, 826, 849, 900]]<|/det|> +251. "only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d). This suggests that oxygen content has negligible influence on its photodynamic activity. The cleaved TBmA- Glu (TBmA) primarily exerts its anticancer effects through the type I PDT process, which + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 450, 101]]<|/det|> +is consistent with the prior findings." + +<|ref|>text<|/ref|><|det|>[[148, 104, 850, 232]]<|/det|> +Response and revision: We appreciate the valuable suggestions provided by the reviewer. To enhance the accuracy of our study, we conducted additional experiments using Rose Bengal (RB), a well- established type II photosensitizer1, as a control. These experiments revealed that RB's photodynamic efficiency decreased significantly under hypoxia conditions (2% O2) compared to normoxia conditions, while TBmA maintained relatively consistent activity across both environments (Fig. R1). + +<|ref|>text<|/ref|><|det|>[[148, 233, 850, 306]]<|/det|> +To discuss this result more accurately, we have revised our manuscript by replacing the statement "This suggests that oxygen content has negligible influence on its photodynamic activity." with "This suggests that TBmA exhibits tolerance towards hypoxic conditions." + +<|ref|>image<|/ref|><|det|>[[333, 340, 660, 562]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 567, 850, 603]]<|/det|> +
Fig. S36. The effects of hypoxia (2% O2) and normoxia (20% O2) conditions on the anticancer photodynamic efficiency of Rose Bengal against HepG2 cells.
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 623, 350, 639]]<|/det|> +## Revised in manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 641, 850, 731]]<|/det|> +Additionally, only marginal variation was observed in the phototoxicity of TBmA- Glu between normoxic and hypoxic conditions (Fig. 3d), while the type- II PS, RB, showed a significant decrease in photodynamic efficiency under hypoxia conditions (2% O2) compared to normoxia conditions (Fig. S36). This suggests that TBmA exhibits tolerance towards hypoxic conditions. + +<|ref|>sub_title<|/ref|><|det|>[[148, 753, 243, 768]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 770, 850, 842]]<|/det|> +1. Fischer BB, Krieger-Liszkay A, Eggen RIL. Oxidative stress induced by the photosensitizers neutral red (type I) or rose bengal (type II) in the light causes different molecular responses in Chlamydomonas reinhardtii. Plant Sci. 168, 747-759 (2005). + +<|ref|>sub_title<|/ref|><|det|>[[148, 848, 226, 862]]<|/det|> +## response + +<|ref|>text<|/ref|><|det|>[[148, 864, 849, 900]]<|/det|> +\(+++\) Light source in Fig S36 was not given, if it is white LED, it is not a fair comparison, because LED emission profile fits TbmA/aggregate better. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 103, 850, 196]]<|/det|> +Q2: Aggregation is a type of supramolecular association which is perfectly reversible. It is only natural to expect deaggregation in the biological media with so many different gradients of hydrophobicity. FBS is not a good approximation for intracellular medium as its protein content is very low. Of course, a simple pharmacokinetics study would reveal how stable is those aggregates are in vivo. + +<|ref|>text<|/ref|><|det|>[[149, 197, 850, 251]]<|/det|> +Response: We appreciate the reviewer's insightful comments regarding the nature of supramolecular aggregation and the potential for de- aggregation in biological media. We would like to clarify several key points that address these concerns. + +<|ref|>text<|/ref|><|det|>[[149, 270, 850, 362]]<|/det|> +Firstly, it's crucial to emphasize that TBmA- Glu is a water- soluble prodrug. The aggregation process only occurs after the Glu moiety is cleaved by GGT in HepG2 cells. This design ensures that TBmA- Glu remains soluble in the blood, avoiding premature aggregation. Aggregation is triggered specifically in the intracellular environment of GGT- overexpressing tumor cells. + +<|ref|>text<|/ref|><|det|>[[149, 380, 850, 511]]<|/det|> +We acknowledge that FBS is not an ideal model for the intracellular environment. To address this issue, we further conducted stability studies using a \(30\%\) BSA (Bovine Serum Albumin) solution, which is a better model for the protein- rich intracellular milieu. The intracellular protein concentration typically ranges from 50- 400 mg/mL, and our \(30\%\) BSA solution ( \(\sim 300 \mathrm{mg / mL}\) ) falls within this range. TBmA aggregates showed remarkable stability in this environment, with no significant degradation observed over 72 hours (Fig. R1). + +<|ref|>text<|/ref|><|det|>[[149, 530, 850, 639]]<|/det|> +We also agree that pharmacokinetics studies would be valuable. However, our system presents unique challenges for such studies, as the aggregates form intracellularly rather than in circulation. Collecting and analyzing intracellular aggregates from tumor sections poses significant technical difficulties. Our approach using a highly concentrated protein solution provides valuable insights into aggregate stability in a physiologically relevant environment. + +<|ref|>text<|/ref|><|det|>[[149, 658, 849, 713]]<|/det|> +Importantly, beyond structural stability, we have observed that the aggregates maintain their photodynamic properties in the \(30\%\) BSA solution for \(72 \mathrm{~h}\) (Fig. R2). This functional stability is crucial for the compound's theranostic applications. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[286, 92, 707, 410]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 419, 770, 437]]<|/det|> +
Fig. R1. The long-term stability of TBmA aggregates in \(30\%\) BSA solutions.
+ +<|ref|>image<|/ref|><|det|>[[156, 456, 848, 620]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 621, 851, 713]]<|/det|> +
Fig. R2. The ROS generation capacity of TBmA aggregates after dispersed in \(30\%\) BSA solution for \(0 \mathrm{~h}\) (a) and \(72 \mathrm{~h}\) (b). The ROS was identified using DCFH as an indicator. (c) The plot of the relative emission intensity \((I / I_0)\) of DC versus the irradiation \((20 \mathrm{mW} \cdot \mathrm{cm}^{-2})\) time, where \(I_0 = \mathrm{PL}\) intensity of DCFH in solutions without light irradiation.
+ +<|ref|>text<|/ref|><|det|>[[148, 732, 857, 787]]<|/det|> +Q3: References 4, 5 and 6 were carefully checked. Stability of the aggregates “in vivo” was not studied in these articles. Retention of fluorescence is not necessarily a sign of stability. + +<|ref|>text<|/ref|><|det|>[[148, 789, 851, 880]]<|/det|> +Response: We thank the reviewer for the critical feedback. The unique photophysical properties of AIE compounds stem from the restriction of intramolecular motion (RIM) mechanism, where aggregation limits molecular rotations and vibrations, leading to enhanced fluorescence. Therefore, the fluorescence behavior of AIE materials does provide valuable insights into their molecular state and environment. + +<|ref|>text<|/ref|><|det|>[[148, 895, 850, 913]]<|/det|> +This interpretation is supported by several factors. First of all, TBmA- Glu is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 214]]<|/det|> +engineered to aggregate specifically in response to GGT activity, which is overexpressed in certain tumor cells. This targeted approach minimizes premature aggregation in circulation. Secondly, the crowded, protein- rich cytoplasmic environment of tumor cells likely provides conditions that favor aggregate stability once formed. Additionally, we observed that the photosensitivity of TBmA was maintained in our \(30\%\) BSA studies, suggesting a preservation of the aggregate structure. + +<|ref|>text<|/ref|><|det|>[[148, 247, 850, 358]]<|/det|> +Q4: While AIE compounds seem to provide potentially useful imaging opportunities, their relevance in PDT or other therapeutic schemes remain questionable. A therapeutic agent which would change size on meeting hydrophobic membranes or proteins, which could lead to different properties has to be handled very carefully. It would be advisable to avoid hype terminology such as "personalized medicine and real- time treatment monitoring". + +<|ref|>text<|/ref|><|det|>[[149, 360, 849, 413]]<|/det|> +Response: We appreciate the reviewer's thoughtful comments regarding the therapeutic relevance of AIE compounds and the importance of careful characterization of their behavior in biological systems. + +<|ref|>text<|/ref|><|det|>[[148, 428, 850, 539]]<|/det|> +Regarding the stability and behavior of TBmA, we emphasize that TBmA- Glu is designed as a water- soluble prodrug that only forms aggregates within tumor cells following enzymatic reaction. This targeted approach minimizes potential issues related to premature aggregation or size changes in circulation. Furthermore, we have demonstrated the stability of TBmA aggregates in a \(30\%\) BSA solution for 72 hours, providing initial evidence of their potential stability in protein- rich environments. + +<|ref|>text<|/ref|><|det|>[[148, 554, 850, 700]]<|/det|> +About "personalized medicine and real- time treatment monitoring." in the previous response letter: The full sentence is "Recent literature has demonstrated the potential of AIE compounds for combining imaging and therapeutic functions in a single entity opening up new possibilities for personalized medicine and real- time treatment monitoring." We agree that such terminology should be used judiciously, especially in early- stage research, however, our intention here is to highlight the potential of AIE materials to contribute to these fields in the future, rather than to claim immediate clinical applicability. + +<|ref|>text<|/ref|><|det|>[[148, 716, 850, 862]]<|/det|> +The unique properties of AIE materials, including their AIE and potential for stimuli- responsive behavior, do offer intriguing possibilities for both imaging and therapeutic applications. However, we agree that rigorous investigation is needed to establish their efficacy and safety for PDT or other therapeutic schemes. Moving forward, we will focus on providing concrete evidence for the specific advantages of AIE compounds in relevant biological contexts, rather than speculating on broad future applications. We believe this approach will better serve the scientific community and responsibly advance the field. + +<|ref|>text<|/ref|><|det|>[[146, 882, 848, 900]]<|/det|> +Q5: May be it wasn't clear in my earlier statement of concern, I did say near UV, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 848, 121]]<|/det|> +but I was specifically referring to \(450 \mathrm{nm}\) peak. There are literature reports of blue (450 nm) light causing cellular damage. + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 232]]<|/det|> +Response: We acknowledge that there are indeed literature reports of blue light (450 nm) causing cellular damage. This is an important consideration in photodynamic therapy and other light- based treatments. However, we would like to emphasize that the biological effects of light exposure are highly dependent on both wavelength and dosage. + +<|ref|>text<|/ref|><|det|>[[148, 247, 850, 321]]<|/det|> +In our experiments, we carefully controlled the light dosage to minimize potential phototoxicity while maintaining therapeutic efficacy. Under the experimental conditions described in our manuscript, we did not observe any significant effects on cell viability following LED light irradiation (Fig. R3). + +<|ref|>text<|/ref|><|det|>[[148, 336, 850, 409]]<|/det|> +To address the reviewer's concern, we also conducted a blue light irradiation (450 nm, \(12 \mathrm{J / cm^2}\) ) PDT assay. In this experiment, we also found no significant effect on cellular viability. This suggests that at the dosages used in our study, the blue light alone does not cause substantial cellular damage. + +<|ref|>text<|/ref|><|det|>[[148, 423, 850, 534]]<|/det|> +However, we agree that the potential for phototoxicity is an important consideration in developing light- based therapies. In future studies, we plan to conduct a more comprehensive dose- response analysis to determine the threshold at which blue light exposure may begin to affect cell viability. We also intend to investigate the potential long- term effects of repeated light exposure and compare the effects of our AIE- based approach with traditional photosensitizers at equivalent light doses. + +<|ref|>image<|/ref|><|det|>[[366, 554, 627, 714]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 720, 850, 756]]<|/det|> +
Fig. R3 The impact of white light and \(450 \mathrm{nm}\) light exposure ( \(12 \mathrm{J / cm^2}\) ) on the cellular viability of HepG2 cells.
+ +<|ref|>text<|/ref|><|det|>[[148, 775, 850, 849]]<|/det|> +Q6: One of the most important issues here is the fact that short wavelength irradiation is required to excite the chromophore, whether it is in organic or aqueous medium. 450 nm is not compatible with PDT. The typical penetration length as \(450 \mathrm{nm}\) is less than \(1 \mathrm{mm}\) , which is significantly less than needed for an effective "photo"- driven process. + +<|ref|>text<|/ref|><|det|>[[148, 868, 848, 904]]<|/det|> +Response: It is correct that the typical penetration depth of \(450 \mathrm{nm}\) light is less than \(1 \mathrm{mm}\) in tissue, which is indeed less than ideal for treating deep- seated tumors. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 719, 102]]<|/det|> +However, we would like to highlight several important considerations: + +<|ref|>text<|/ref|><|det|>[[149, 117, 850, 172]]<|/det|> +First, though direct light penetration is restricted, the effective depth of PDT damage may increase due to light reflection and scattering within tissues. This occurrence can expand the scope of the photodynamic impact beyond the initial penetration depth. + +<|ref|>text<|/ref|><|det|>[[149, 192, 850, 302]]<|/det|> +Secondly, several clinical scenarios exist where shallow light penetration is sufficient or even advantageous. For instance, PDT with blue light excitation could be particularly useful for superficial skin cancers and precancerous lesions, intraoperative treatment of residual tumor cells after surgical resection, treatment of early- stage mucosal cancers in inaccessible areas (e.g., oral cavity, bladder), and endoscopic applications for gastrointestinal tumors. + +<|ref|>text<|/ref|><|det|>[[149, 317, 850, 371]]<|/det|> +Finally, numerous published studies demonstrate the successful use of \(450 \mathrm{nm}\) light and white light (including the blue spectrum) for PDT when the photosensitizers have maximum absorption around \(450 \mathrm{nm}\) . 2, 3, 4, 5, 6, 7 + +<|ref|>text<|/ref|><|det|>[[148, 387, 850, 534]]<|/det|> +Nevertheless, we fully agree that blue light's limited tissue penetration restricts the broader applicability of our current system for treating deep- seated tumors. Given this limitation, our future research directions include exploring two- photon excitation to achieve deeper tissue penetration, investigating upconversion nanoparticles to convert longer- wavelength light to blue light locally, and developing new AIE photosensitizers with red- shifted absorption for improved tissue penetration. We believe that addressing these challenges will expand the potential applications of our AIE- based PDT system while utilizing its unique properties. + +<|ref|>sub_title<|/ref|><|det|>[[149, 555, 250, 570]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 574, 850, 884]]<|/det|> +2. Fan L, et al. A Bioactive Photosensitizer for Hypoxia-Tolerant Molecular Targeting-Photo-Immunotherapy of Malignant Tumor. Adv. Funct. Mater. 34, 2313755 (2023). +3. Li X, et al. A novel 450-nm laser-mediated sinoporphyrin sodium-based photodynamic therapy induces autophagic cell death in gastric cancer through regulation of the ROS/PI3K/Akt/mTOR signaling pathway. BMC Med. 20, 475 (2022). +4. Mei Y, et al. A Novel Photosensitizer Based 450-nm Blue Laser-Mediated Photodynamic Therapy Induces Apoptosis in Colorectal Cancer - in Vitro and in Vivo Study. Front. Biosci. (Landmark Ed) 29, 199 (2024). +5. Chen Y, et al. Photoactivatable metal organic framework for synergistic ferroptosis and photodynamic therapy using 450 nm laser. Chem. Eng. J. 454, 140438 (2023). +6. Sun P, et al. A water-soluble phosphorescent conjugated polymer brush for tumor-targeted photodynamic therapy. Polym. Chem. 8, 5836-5844 (2017). +7. An J, et al. An unexpected strategy to alleviate hypoxia limitation of photodynamic therapy by biotinylation of photosensitizers. Nat. Commun. 13, 2225 (2022). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 102, 850, 177]]<|/det|> +Q7: First of all, no PDT is independent of oxygen (please refer to Baptista, et al., Photochemistry and Photobiology, 2017, 93 (4) 912- 919. ) So, instead of 1 O2 % hypoxia, if the authors were to switch to \(0.5\%\) O2 hypoxia, or anoxia, the effectiveness would be much more different. + +<|ref|>text<|/ref|><|det|>[[148, 178, 850, 251]]<|/det|> +I am also worried about the fact that the type- I designation is partly based on Figure 4b, there is some inconsistencies between the legend and the plot. Esbelsen found in the legend, is not found on the plot, which is a singlet oxygen quencher. Also, Trolox, just like azide \(\mathrm{(N_3)}\) is a singlet oxygen quencher. + +<|ref|>text<|/ref|><|det|>[[148, 270, 850, 380]]<|/det|> +Response and revision: We agree with the reviewer that oxygen plays a pivotal role in the Type I and Type II PDT processes. However, from the PDT mechanism, we know that the type I photosensitizers could directly transfer electrons to the substrate, forming a radical cation or neutral radical. These radicals could immediately react with \(\mathrm{O_2}\) or \(\mathrm{H_2O}\) to generate hydrogen peroxide \(\mathrm{(H_2O_2)}\) , hydroxyl radicals (- OH), or superoxide anions (- \(\mathrm{O_2}\) - ) (Fig. R4). \(^{1,2}\) + +<|ref|>text<|/ref|><|det|>[[148, 399, 850, 565]]<|/det|> +We have tried but could not finish the antitumor PDT assays in the anaerobic conditions, because the anoxia condition resulted in death of the tumor cells (Fig. R5a). So, we re- evaluated the photodynamic efficiency of \(\mathrm{TBmA}\) and RB using a deoxidized PBS solution. The results showed that \(\mathrm{TBmA}\) could also induce the oxidation of DFCH under the anoxia condition (Fig. R5b), while the photodynamic efficiency of RB showed significant degradation. Hence, type- I photosensitizers exhibit relatively higher tolerance towards oxygen concentrations, which implies that, even under low oxygen conditions, they can still engage in substrate reactions through electron transfer. + +<|ref|>text<|/ref|><|det|>[[148, 584, 850, 658]]<|/det|> +We are sorry for the mistake in the figure legend in Figure 4b. "Esbelsen" has been revised as "Trolox." However, it should be noted that Trolox is not only a \(^{1}\mathrm{O_2}\) scavenger but also a scavenger of peroxy and alkoxy groups. \(^{3}\) The type- I designation is mainly based on the ROS species we detected in vitro (Fig. R5c). + +<|ref|>image<|/ref|><|det|>[[148, 675, 789, 857]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 862, 761, 880]]<|/det|> +
Fig. R4 Scheme of the photochemical reactions for type I and type II PDT. \(^{9}\)
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[155, 93, 864, 262]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 270, 852, 363]]<|/det|> +
Fig. R5 (a) Cellular viability of HepG2 cells in normoxia and anoxia conditions. (b) Fluorescence emission changes of DCFH (Dichlorodihydrofluorescein, \(10~\mu \mathrm{M}\) ) in the presence of \(5~\mu \mathrm{M}\) photosensitizers in DMSO-PBS \((v:v = 1:99)\) after irradiation ( \(20\mathrm{mW}\cdot \mathrm{cm}^{-2}\) ) for a different time under anoxia conditions. (b) \(\mathrm{TBmA}\) , (c) Rose Bengal (RB). DCHF, \(\lambda_{\mathrm{ex}} = 488 \mathrm{nm}\) .
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 382, 350, 399]]<|/det|> +## Revised in manuscript: + +<|ref|>text<|/ref|><|det|>[[149, 400, 850, 437]]<|/det|> +Trolox: \(50~\mu \mathrm{M}\) (ROO- scavenger and \(^{1}\mathrm{O}_{2}\) scavenger); D- mannitol: \(50~\mathrm{mM}\) (OH scavenger); Tiron: \(10\mathrm{mM}\) ( \(\cdot \mathrm{O}_{2}\) scavenger); \(\mathrm{NaN}_3\) : \(5\mathrm{mM}\) ( \(\mathrm{O}_2\) scavenger) + +<|ref|>sub_title<|/ref|><|det|>[[149, 457, 250, 472]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 473, 850, 621]]<|/det|> +1. Zhao X, Liu J, Fan J, Chao H, Peng X. Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application. Chem. Soc. Rev. 50, 4185-4219 (2021). +2. Fan W, Huang P, Chen X. Overcoming the Achilles' heel of photodynamic therapy. Chem. Soc. Rev. 45, 6488-6519 (2016). +3. Lúcio M, Nunes C, Gaspar D, Ferreira H, Lima JLFC, Reis S. Antioxidant Activity of Vitamin E and Trolox: Understanding of the Factors that Govern Lipid Peroxidation Studies In Vitro. Food Biophys. 4, 312-320 (2009). + +<|ref|>text<|/ref|><|det|>[[149, 641, 461, 658]]<|/det|> +\(+ + + 0.5\) or \(1\%\) hypoxia may be better. + +<|ref|>text<|/ref|><|det|>[[148, 678, 850, 788]]<|/det|> +Q8: Regardless of the mechanism, the total quantum yield of all radiative and not radiative processes is not going to be larger than 1. So far, I did not come across a quantum yield of ROS formation, or emission quantum yield reported with aggregated structures. However, that should be the first thing to be studied when reporting a novel photosensitizer, but especially so, when both emission and ISC is claimed to be enhanced. + +<|ref|>text<|/ref|><|det|>[[148, 808, 850, 900]]<|/det|> +Response: Indeed, the total quantum yield of all radiative and non- radiative processes cannot exceed 1. However, the energy consumption in no radiative processes contains both the energy for ISC processes and the molecular motion as well. Molecular aggregation could induce the restriction of intramolecular motions (RIM) and, as a result, reduce energy loss through non- radiative molecular motion, potentially + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 84, 850, 139]]<|/det|> +increasing the energy available for emission and ISC processes. So, the energy efficiency of both emission and ISC can be enhanced in aggregated structure due to RIM. + +<|ref|>text<|/ref|><|det|>[[148, 159, 851, 325]]<|/det|> +However, in specific cases, such as the graphene quantum dots reported by Zhang et al., the apparent quantum yield could be larger than \(1. ^{1}\) This occurs when the energy gaps between \(\Delta E_{\mathrm{ST}}\) and \(\Delta E_{\mathrm{TG}}\) (the energy gap between \(\mathrm{T_1}\) and Ground state) are larger than the formation energy of \(^{1}\mathrm{O}_{2}\) (22.5 kcal mol \(^{- 1}\) ). In such cases, \(^{1}\mathrm{O}_{2}\) generation happens through multiple pathways: energy transfer from \(\mathrm{T_1}\) (ET(1) in Fig. R6), but also the energy transfer from \(\mathrm{S_1}\) to \(^{3}\mathrm{O}_{2}\) during the \(\mathrm{S_1 - T_1}\) intersystem crossing transition (ET(2) in Figure R6). This multi- pathway mechanism can lead to an overall \(^{1}\mathrm{O}_{2}\) quantum yield greater than 1.0, as more than one \(^{1}\mathrm{O}_{2}\) molecule can be produced per absorbed photon. \(^{2}\) + +<|ref|>image<|/ref|><|det|>[[199, 345, 789, 544]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 548, 848, 584]]<|/det|> +
Fig. R6 Schematic illustration of the \(^{1}\mathrm{O}_{2}\) generation mechanisms by conventional PDT agents (left) and GQDs (right).
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 605, 245, 620]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[148, 623, 850, 696]]<|/det|> +1. Ge J, et al. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation. Nat. Commun. 5, 4596 (2014). +2. Kanner RC, Foote CS. Singlet oxygen production from singlet and triplet states of 9,10-dicyanoanthracene. J. Am. Chem. Soc. 114, 678-681 (1992). + +<|ref|>text<|/ref|><|det|>[[148, 733, 850, 861]]<|/det|> ++++ Both of these articles while interesting, hardly relevant to PDT considering the absorption peaks of the proposed sensitizers are in blue, and the fact that they are very unique cases. The first one reached to a suprizing conclusion without doing any photophysical work. Vibrational (or rotational) relaxation and their control by micro- or molecular environments, by molecular steric hinderence is well known. However, only accurate quantum yield determinations would prove simulataneous increases in emission and singlet oxygen quantum yields. This is not done in Ref 1. + +<|ref|>text<|/ref|><|det|>[[147, 881, 848, 899]]<|/det|> +Q9: Imaging on surface tumors or in mice, perhaps; but not therapeutics. Short + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 139]]<|/det|> +wavelength excitation, and their aggregate structure, which would most likely disintegrate as it travels through the body into different sized nanoparticles would limit their potential. + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 287]]<|/det|> +Response: As previously discussed, TBmA- Glu is a water- soluble molecule that forms aggregates within tumor cells upon activation by GGT to produce TBmA. Consequently, most of these aggregates are localized in the tumor cells. Furthermore, we have demonstrated the stability of TBmA aggregates for 72 hours in a \(30\%\) BSA solution. Additionally, considering that PDT processes were conducted 12 hours after administration of TBmA- Glu, it can be inferred that the TBmA aggregates exhibit sufficient stability to complete the PDT processes. + +<|ref|>text<|/ref|><|det|>[[148, 308, 848, 343]]<|/det|> ++++ The problem is that now "activated" aggregates, will not stay forever in tumor cells, as these cells disintegrate. + +<--- Page Split ---> diff --git a/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/images_list.json b/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..10836344f7b3c840587661cbadd16d0a2e5b5d2e --- /dev/null +++ b/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,79 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "a: Venn diagram shows the shared protein between PrE genes and SALL4 up-regulated proteins after BMP4 treatment; b: Line chart shows Slc9a3r1 expression pattern in BMP4+ and BMP4- condition; c: Line chart shows Slc9a3r1 expression pattern in WT-SALL4 and delN12-SALL4; d, e, f, g: Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two-sided, unpaired t test; n = 3 independent experiments, \\(*p < 0.05\\) , \\(**p < 0.01\\) , \\(***p < 0.001\\) .", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "a, Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean \\(\\pm\\) s.d., two-sided, unpaired t test; \\(n = 3\\) independent experiments, \\(^{*}p< 0.05\\) , \\(^{**}p< 0.01\\) , \\(^{**}p< 0.001\\) ; b: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar \\(= 5mm\\)", + "footnote": [], + "bbox": [], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "a, b : Histograms show the qPCR results of PrE gene relative expression level of every group, \\(n = 3\\) independent experiments.", + "footnote": [], + "bbox": [ + [ + 220, + 95, + 714, + 404 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "a: UMAP shows the cells distribution of BMP4+ and BMP4- conditions; b: Stacked barplot shows the cell proportion in each cell type.", + "footnote": [], + "bbox": [ + [ + 210, + 630, + 785, + 784 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "a: Heatmap shows the common and different features between MEF and BMP4+ cells in cluster 2; b: Bar plots show the top 5 GO terms of gene sets; c: UMAP shows the expression of selected marker genes", + "footnote": [], + "bbox": [ + [ + 183, + 512, + 792, + 864 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "a, b: UMAP shows the integration of PrECLCs/Pluripotent cells' data in this study and Epiblast/PrE data of Sala2019 in vivo; c, d, e, f: UMAP shows the expression of marker genes at single cell level; g: Correlation heatmap of reprogramming cells and developmental cells.", + "footnote": [], + "bbox": [], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "a, b: Histograms show the qPCR results of PrE gene relative expression level of every group, \\(n = 3\\) independent experiments.", + "footnote": [], + "bbox": [], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..515578b6cbb18bd24dd812470066ee456ad8f800 --- /dev/null +++ b/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,378 @@ + +# nature portfolio + +Peer Review File + +Cell fate decision by a morphogen- transcription factor- chromatin modifier axis + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +In this study, Ming et al. presented a hypothesis positing that BMP4 signaling impedes the induction of pluripotency by impairing the NURD- SALL4 interaction complex during JGES- mediated reprogramming. Intriguingly, the authors demonstrated that the introduction of BMP4 redirects reprogramming towards a more primitive endoderm (PrE)- like fate. The authors have provided compelling evidence to support these findings, particularly in their immunoprecipitation (IP) experiments, which exhibit a dissociation between SALL4 and NURD upon BMP4 administration. Furthermore, the authors bolstered their hypothesis by rescuing reprogramming through the covalent binding of SALL4 to various NuRD components. Finally, the authors demonstrate that SALL4 overexpression instructs the PrE fate. + +However, the paper could benefit from the following suggestions: + +1. Elaboration of the BMP4 mechanism: The paper lacks a detailed mechanism explaining how BMP4 guides reprogramming cells towards a more PrE-like fate. Considering that SALL4 itself can induce PrE fates, it suggests potential competitive binding between SALL4 and PrE-related proteins versus SALL4 and NuRD. The exact mechanism by which BMP4 promotes a PrE fate remains unclear beyond the inability to interact with NuRD, which is necessary for pluripotency. It may be beneficial to explore the upregulated proteins identified in the IP-MS experiments to gain deeper insights into the shift toward PrE. Again, this is particularly relevant since SALL4 alone can reprogram cells to a PrE fate. + +2. The blastocyst injection experiments require refinement. It is challenging to discern whether the GFP-labeled cells are contributing to the embryo or primitive endoderm since there is no co-staining with specific markers for PrE. Furthermore, the paper lacks essential statistical analysis, information regarding the number of embryos injected, and other pertinent details. It would be beneficial to include a parallel experiment utilizing pluripotent cells for comparison. Additionally, it is unclear how these experiments are performed. Specifically, are purified PrE cells injected? Or is this a heterogeneous population containing both PrE and pluripotent cells? + +3. Inhibition of BMP4 signaling: Considering that BMP4 addition was shown to slow down JGES reprogramming, it raises the question of whether inhibiting BMP4 or downstream targets of BMP4 signaling could enhance the efficiency of reprogramming. Investigating this aspect would strengthen and broaden the author's conclusions. + +4. Drop-out screen logic: The rationale behind the drop-out screen is somewhat unclear. Instead of a drop-out to identify factors necessary for pluripotent cells, it might be more informative to perform a drop-out screen to pinpoint the factors required for PrE cell formation. This would focus on understanding the specific components necessary for the observed phenotype rather than pluripotency. + +5. Exploration of BMP4's effects on reprogramming: The paper briefly touches on the dichotomy between BMP4's effects on OCT4-based and SALL4-based reprogramming, which could offer a novel aspect to the study. Expanding on this aspect might provide additional insights. + +6. Methods: The Methods section requires improvement, with several crucial details missing and certain portions being misplaced. Additionally, it is essential to include statistical analysis for the figures, display individual replicates, and provide the Western blot membranes as supplementary figures. + +Reviewer #2 (Remarks to the Author): + +Reviewer Comments (Round 1: 20210720) In this manuscript by Ming and colleagues, the authors explore the role of BMP4 in cell fate switching, when reprogrammed using their previous JGES (Jdp2, Glis1, Esrrb and Sall4) over expression system. Using number of Oct4- GFP positive cells as readout, the authors observe that + +<--- Page Split ---> + +BMP4 addition reduces the reprogrammed cells both in a dosage and time- dependent manner. Performing scRNA- seq upon JGES induction, BMP4- cells give rise to intermediate state, endothelial and pluripotent cells, while BMP4+ gives rise to intermediate, endothelial and PrECLCs (primitive endoderm- like cells), with both reprogramming yielding \(\sim 20\%\) of total single- cell pool. These PrECLCs transcriptomically are show to be similar to published primitive endoderm (PrE) cells from E4.5- 5.5embryos. The authors subsequently perform a JGES dropout reprogramming screen with and without BMP4, ascertaining ability of BMP4 with Oct4 to reprogram MEFs, and with Sall4 acting antagonistically to BMP4. Using IP- MS, the authors observe perturbed SALL4- NuRD interaction when treating with BMP, an find that BMP4 blocks iPSC reprogramming via disruption of Sall4- NuRD cooperation (N- terminal 12AAs of SALL4). Lastly, the authors show that Sall4DeIN12 alone can reset MEFs to induced extra- embryonic state, faster than Sall4WT; and perform blastocyst injections for iPRe- GFP for extra- embryonic intergration. + +The study and results are indeed interesting, the ms is very well written and supported by suitable experiments and analysis. However, the insights from the paper provide marginal gains and mainly improve on authors previous findings. + +The reviewer shares a few major and minor concerns stated below. + +## Comments + +- In figure 2A, it was unclear why the authors chose the BMP4 induction after 2 days? Figure 1d, highlights that number of Oct4-GFP+ve colonies are same as un-induced (row 1 vs row 3). Figure 1D-E suggest that BMP4 induction in Days0-3 may not be quite consequential. +- In Figure 2B-C, It is unclear whether there no no pluripotent cells from BMP4+ population. +- Additionally a subset of BMP4+ are shared with MEF cluster (Pink cells in yellow cluster, Fig2B) even after 7 days, are these non-reprogrammed cells or different state (similar cells are not observed in BMP4+ population). +o Also look very diff from ESCs. +- The authors report that PrECLCs are PrE cells based on bulk markers and single-cell comparison. The PrE markers are non-zero in BMP4-ve cells? What is the explanation for this? It would be useful to visualise other PrE markers at single-cell level in Fig S2D, to see if the distinction between BMP4+ to PrE/PrCLC and BMP4- to pluripotent. The reviewer feels that correlation values could be plotted (instead of high low) to appreciate magnitude of similarity. +- In Fig 3b (-sall4) and 3d (oct4, -sall4), the authors should comment on the target gene sets and their activitation (cooperativity vs exclusivity), during Oct4 and BMP4 mediated reprogramming. Which sites are unique vs co-bound with Sall4, and regulated? +- In Fig5, the authors should describe number/percentage of PrECLC cells between WT and Sall4DeIN12. Which other cell types emerge during reprogramming (pluripotent, endoderm, intermediate and percentages)? Since the FPKM/counts are non-zero; the cell-fate switch is likely to be non-binary decision. +- Similarly, statistics of Fig5DF and EG could be provided. What percentage of cells of the total were GFP positive. + +## Minor + +- The introduction seems brief and generalised. +- In the discussion, the authors do not comment whether BMP4 mediated cell fate changes are due to JGES TF cooperativity vs exclusivity in action? +- The authors could double check the scalebar between both panels in in Fig5c scale. In the print/web version, lower panel seems more magnified. +- What duration and timing of BMP4 induction is most crucial to fate specification in JGES reprogramming? The authors perform a titration and dosage curve, but choose 1 condition for all experiments. + +<--- Page Split ---> + +Point- by- point response to the reviewers: + +Dear editor and reviewers, + +We sincerely thank you for considering and reviewing our work. We especially appreciate the constructive comments that helped us to improve the manuscript through experiments. As suggested by all the reviewers, we performed the relevant experiments and performed literature research to answer all the questions. As such, we sincerely believe that the manuscript has been improved through careful revision as detailed by point- by- point responses below. We hope that your comments have been addressed in full and we obviously welcome any additional ones as well. Please note that the responses are marked with blue color in the text, the references are list at the end of the text, all Figures mentioned in this text have been up- dated in the new version. + +Main changes and additions made to Figures. + +1: Figure 1d: Day 7 to Day 0 is changed to Day 0 to Day 7 from left to right; +2: Supplement Figure 1a, 1b, Supplement Figure 2a, 2b, Figure 3i, 3j, Figure 4g, 4h, 4i are added; +3: Supplement Figure 2e, 2f, 2g are updated; +4: Figure 3a, 3b, 3d, 3e are re- organized; +5: Supplement Figure 3a, 3b, 3c, 3d are added; +6: Figure 5 and Supplement Figure 5 are new data, previous figure 5 and Supplement Figure 5 are change to Figure 6 and Supplement Figure 6; +7: Previous Figure 5i is deleted; +8: Previous Figure 5h is changed to Figure 6l; +9: Previous Figure 5d, 5e, 5f, 5g are changed to Supplement Figure 6e, 6f, 6g, 6h; +10: Figure 6c, 6d, 6e, 6f, 6g, 6h, 6i, 6j, 6k, Supplement Figure 6i, 6j are added. + +Reviewer #1 (Remarks to the Author): + +In this study, Ming et al. presented a hypothesis positing that BMP4 signaling impedes the induction of pluripotency by impairing the NURD- SALL4 interaction complex during JGES- mediated reprogramming. Intriguingly, the authors demonstrated that the introduction of BMP4 redirects reprogramming towards a more primitive endoderm (PrE)- like fate. The authors have provided compelling evidence to support these findings, particularly in their immunoprecipitation (IP) experiments, which exhibit a dissociation between SALL4 and NURD upon BMP4 administration. Furthermore, the authors bolstered their hypothesis by rescuing reprogramming through the covalent binding of SALL4 to various NuRD components. Finally, the authors demonstrate that SALL4 overexpression instructs the PrE fate. + +## Response: + +We appreciate the reviewer's insightful comments for our work. As reprogramming as a technology has become rather routine and so many nice works have been published over the past 15 years, we branched out into areas far less popular, but perhaps more interesting. One of such areas is the BMP4- Sall4- NuRD axis as detailed in this paper. Beyond the pathways we delineated, we also find, with a bit surprise, that we can generate PrE or PE, the sister fate of epiblasts. So, we decided to look into this further with results we written up for this manuscript. Much needs to be done as pointed out by the reviewer, but we + +<--- Page Split ---> + +were encouraged that we have made a good start. So, we especially appreciate the encouraging comments from the reviewer. + +However, the paper could benefit from the following suggestions: + +1. Elaboration of the BMP4 mechanism: The paper lacks a detailed mechanism explaining how BMP4 guides reprogramming cells towards a more PrE-like fate. Considering that SALL4 itself can induce PrE fates, it suggests potential competitive binding between SALL4 and PrE-related proteins versus SALL4 and NuRD. The exact mechanism by which BMP4 promotes a PrE fate remains unclear beyond the inability to interact with NuRD, which is necessary for pluripotency. It may be beneficial to explore the upregulated proteins identified in the IP-MS experiments to gain deeper insights into the shift toward PrE. Again, this is particularly relevant since SALL4 alone can reprogram cells to a PrE fate. + +## Response: + +We would like to thank the reviewer for pointing out our deficiencies concerning PrE fate control. As we pointed out above, we are perhaps a few labs in the world remaining interested in reprogramming. This is our second paper on the JGES reprogramming system following our initial 7F system paper. Unfortunately, we have yet to see the rest of the field paying attention to this reprogramming system, so the value of this system to the entire stem cell field remains near zero. We thought that we can improve this by showing interesting mechanisms and previously unknown paths. So, we devoted most of our energy to the BMP4- Sall4- NuRD axis, neglected to our detriment the PrE aspect. + +As we have learnt since we realised that PrE is the fate diverted by BMPs, PrE is fascinating, but not well described in the literature, to our knowledge, there are only a handful papers describing its derivation, not on the mechanism aspect1. So, we appreciate the comments from the reviewer and performed experiments to address them as detailed below. + +First, we appreciate the insightful suggestion to explore the IP- MS experiments for "potential competitive binding between SALL4 and PrE- related proteins versus SALL4 and NuRD" on BMP4 mechanism study, we look into our IP- MS data and PrE related proteins, the upregulated proteins identified in the SALL4 IP- MS experiments after BMP4 treatment, \(\mathrm{FC} = 1.5\) , pValue=0.05, the same as Fig 4b in the manuscript, 67 proteins appear, at the meantime, We plotted a Venn diagram between the 67 proteins and 142 genes specific expressed in the PrECLCs cluster in our scRNA- seq dataSlc9a3r1 turns out to be the only overlapped protein(a, b, c), unfortunately, Slc9a3r1 overexpression can't mimic BMP4's inhibition effect on JGES reprogramming under BMP4- (d, e), Slc9a3r1 KD can't rescue BMP4 induced reprogramming decreasing either(f, g), thus, Slc9a3r1 may not be the critical protein based on these results. Slc9a3r1 is reported to be a HDAC responsive gene, it is a solute- carrier protein and activated upon inhibition or complete loss of HDAC function2, this is in agreement with our main conclusion that BMP4 signals to dissociate SALL4- NuRD interaction. Slc9a3r1 is also reported to be required for optimal bone density and bone homeostasis3,4 which could be another explanation for the Slc9a3r1 activation by bone morphogenetic protein 4, BMP4. + +<--- Page Split ---> + +To gain deeper insights into the shift toward PrE, we look into PrE related and BMP4 induced transcriptome regulation, for SALL4- NuRD axis is to remodel transcriptional profile by altering H3K27ac level, by regulon analyzing on scRNA- sequencing data and additional experiments, Gata4 turns out to be the key regulon to guide JGES reprogramming to PrE cell fate, BMP4 and SALL4delN12 can also elevate Gata4 expression level. BMP4 mechanism on PrE cell fate induction can be explained as below: BMP4 dissociates SALL4- NuRD interaction leads to PrE cell fate formation by up regulate PrE key regulon Gata4 expression. We also add these data into Figure 5. + +![](images/Figure_unknown_1.jpg) + +
a: Venn diagram shows the shared protein between PrE genes and SALL4 up-regulated proteins after BMP4 treatment; b: Line chart shows Slc9a3r1 expression pattern in BMP4+ and BMP4- condition; c: Line chart shows Slc9a3r1 expression pattern in WT-SALL4 and delN12-SALL4; d, e, f, g: Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two-sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) .
+ +We then discussed if BMP4 inhibits pluripotent cell fate by dissociating SALL4- NuRD interaction. The function of SALL4- NuRD axis is transcriptional regulation by altering H3K27ac level of the target genes which has been clarified in detail in our last paper4, so we look into the transcription regulation of the PrE- like cell fate, so as to explain how this cell fate appears and the underlying mechanism of BMP4. We apply regulon analysis by SCENIC method on the PrECLCs cluster with our scRNA- sequence data to identify the main transcription regulons of PrE related genes; the top 5 regulon factors are Sox17, Pitx1, Klf4, Gata4 and Foxa2 (a), UMAP shows the regulon scores calculated by SCENIC (top panel) and the expression level (lower panel) of transcription factors(b), network plot shows the transcription factors and their target genes (c), Gata4 regulated the largest PrE gene number among the top 5 regulons and it is more restricted to PrECLCs than the other four regulons(b). Over- expression (OE) experiments shows Gata4 has the strongest inhibition effect on pluripotency induction(d) and promotion effect on PrE formation(e), Supplementary Figure 2b indicates BMP4 can elevate Gata4 expression, and Knocking- + +<--- Page Split ---> + +down Gata4 in JGES reprogramming with BMP4 treatment can also inhibit PrE fate formation by qPCR experiments (f, g). These data indicate BMP4 guides reprogramming cells towards a more PrE- like fate through activating Gata4. + +![](images/Figure_unknown_2.jpg) + + +Besides this, we also want to know the relationship between BMP4 activating PrE regulon genes expression and dissociating SALL4- NuRD interaction. We apply SALL4deN12 and SALL4WT with JGE without BMP4 treatment, and show that SALL4deN12 could mimic BMP4 function both on pluripotency inhibition(h, i) and PrE promotion(j). Previous study has indicated Gata4 and other PrE related markers are absent in homozygous mutant Sall4 cell cultures derived from ICM5. In conclusion, BMP4 dissociates SALL4- NuRD interaction leading to PrE cell fate formation by upregulating PrE key regulon Gata4 expression. We add these data to Figure 5 in the new version. + +![](images/Figure_unknown_3.jpg) + + +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + + +a: Plot shows the top 5 regulons of PrE; b: UMAP shows the regulon scores calculated by SCENIC (top panel) and the expression level (lower panel) of transcription factors; c: Network plot shows the transcription factors and their target genes; d: Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two- sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) ; e, f, g: Histograms show the qPCR results of PrE gene relative expression level of every group; h, Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two- sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) ; i: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar= 5mm; j: Histograms show the qPCR results of PrE gene relative expression level of every group, data are mean ± s.d., two- sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) . + +2. The blastocyst injection experiments require refinement. It is challenging to discern whether the GFP- labeled cells are contributing to the embryo or primitive endoderm since there is no co- staining with specific markers for PrE. Furthermore, the paper lacks essential statistical analysis, information regarding the number of embryos injected, and other pertinent details. It would be beneficial to include a parallel experiment utilizing pluripotent cells for comparison. Additionally, it is unclear how these experiments are performed. Specifically, are purified PrE cells injected? Or is this a heterogeneous population containing both PrE and pluripotent cells? + +## Response: + +As stated above, we really appreciate these suggestions and added "The iPrE clones induced by SALL4WT alone are picked by pipette at day 11, after 3 days, the patches are digested into single cells or smaller patches by 0.25% trypsin. After one or two extra- passages to deplete the non- induced cells, the iPrE cells + +<--- Page Split ---> + +are ready to be labeled by GFP." to the method part. iPrEs- GFP we used to perform the blastocyst injection experiments should be a heterogeneous population containing both iPrE cells and very rare non- iPrE cells but no pluripotent cells. For iPrE shaped clones are all Oct4- GFP negative, there is no comparability between iPrEs and pluripotent cells. Indeed we applied MEF cells marked by GFP as a parallel experiment for the iPrE cells are derived from MEFs, and the results indicate iPrE could incorporate into PrE upon blastocyst injection but not MEFs (Supplementary Figure 6e, 6f). + +As previously described in the Figure legend 5g, "g. Pictures show iPrE- GFP emerge at embryo yolk sac after transplantation. 8 embryos were obtained at E12.5, 5 of which have GFP+ cells in their yolk sac, no GFP+ cells were found in embryo yolk sac of MEFs- GFP group, data not shown." 5/8 embryos we obtained have GFP+ cells in their yolk sac, and we showed two of them in the previous Figure 5 (Batch 1). In order to replenish the essential statistical analysis, we did the blastocyst injection experiment four more times. Statistical data are shown in the table below, and we also added this table to Supplementary Figure 6i: + +
BatchSurrogate MiceiPrEs Injected BlastocystsEmbryos at E12.5Embryos With GFP Labeled
122885
21722
32120/
411422
522273
SUM8831912
+ +PrE cells arise around E4.5- E5.5 in the embryo development in vivo, and these cells are PrE markers positive. However, when they take part in the formation of extra- embryonic yolk sac at E12.5, they become multiple cell types, so when we inject our GFP+ iPrE cells into E3.5 embryo cavity, it is difficult to trace which kind of cells they are in the extra- embryonic yolk sac, as it is very difficult to co- stain extra- embryonic yolk sac markers with GFP labeled iPrE cells. This blastocyst injection experiments we performed was used to test the in vivo developmental ability of the iPrE cells, like the previous study tests the in vivo developmental potential of PrESCs (primitive endoderm stem cells) separated from blastocyst. However, the chimeric efficiency of iPrEs is far below PrESCs (Supplementary Figure 6g, 6h), we are still trying to enhance the induction and chimeric efficiency of iPrE cells. + +To further determine the cell identity of iPrE, we also performed IF (Fig 6a) to test the PrE markers expression in iPrE clones, and detected retrovirus silencing, a characteristic of mouse stem cells (Supplementary Figure 6b), iPrE cells show strong proliferation capacity as well(Supplementary Figure 6c). Unlike ESCs, PrESCs can form a single layer cavity under suspension culture, exhibiting polarity characteristics and condensed extracellular matrix, iPrE cells are also capable of this feature(Supplementary Figure 6d). Together, these iPrE cells have primitive endoderm like characteristics. + +3. Inhibition of BMP4 signaling: Considering that BMP4 addition was shown to slow down JGES reprogramming, it raises the question of whether inhibiting BMP4 or downstream targets of BMP4 signaling could enhance the efficiency of reprogramming. Investigating this aspect would strengthen and broaden the author's conclusions. + +<--- Page Split ---> + +## Response: + +We again appreciate very much this insight, BMP4 signaling pathway belongs to the TGF- b super family, of which the SMADs proteins are downstream effectors, Smad6 and Samd7 are inhibitory SMADs of TGF- b signaling9, Smad6 is more specific to BMP4 signaling than Smad710,11. We over- expressed Smad6 and Smad7 individually in JGES reprogramming with or without BMP4 treatment, and show that both SMADs could markedly rescue the inhibition effect caused by BMP4, the rescue efficiency of Smad6 is higher than that of Smad7 which is in accord with the inhibition preference between the two genes. We also add these results into Supplementary figure 1. + +![](images/Figure_unknown_5.jpg) + +
a, Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean \(\pm\) s.d., two-sided, unpaired t test; \(n = 3\) independent experiments, \(^{*}p< 0.05\) , \(^{**}p< 0.01\) , \(^{**}p< 0.001\) ; b: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar \(= 5mm\)
+ +4. Drop-out screen logic: The rationale behind the drop-out screen is somewhat unclear. Instead of a dropout to identify factors necessary for pluripotent cells, it might be more informative to perform a drop-out screen to pinpoint the factors required for PrE cell formation. This would focus on understanding the specific components necessary for the observed phenotype rather than pluripotency. + +## Response: + +We welcome the opportunity to clarify the logic for the drop-out screen experiments. We clarified this part in the manuscript and reorganized the Figures to a better reflect of our drop-out logic. + +We also performed extra experiments to pinpoint the requirement of factors for PrE cell formation. When we dropout every single factor of JGES under BMP4+ condition, the qPCR results show that except for Jdp2's dropout which shows a strong promotion of PrE genes, We hypothesized that the other three factor Glis1, Esrrb and Sall4 may form an interaction network for PrE formation, To overcome this confounding effect and identify which factor is essential for PrE cell formation, we added the four factors individually into OS reprogramming with BMP4 treatment, ad show that that Sall4 is the only factor to increase PrE gene expression level, consistent with notion that BMP4 functions to divert cell fate from pluripotency to PrE. We also add this data into Figure 3i, 3j. + +<--- Page Split ---> +![](images/Figure_unknown_6.jpg) + +
a, b : Histograms show the qPCR results of PrE gene relative expression level of every group, \(n = 3\) independent experiments.
+ +5. Exploration of BMP4's effects on reprogramming: The paper briefly touches on the dichotomy between BMP4's effects on OCT4-based and SALL4-based reprogramming, which could offer a novel aspect to the study. Expanding on this aspect might provide additional insights. + +## Response: + +Indeed, the most surprising result is the opposing effect of BMP4 on Oct4- and Sall4- centered reprogramming. We have shown, in our view quite convincingly, that BMP4 can either be a positive or negative factor in reprogramming depending on the factors used, perhaps reflecting the diversity of paths towards pluripotency at present12. Given the complexity of BMP4 mediated pathways, it remains quite surprising that it can exert this unexpected role in cell fate control in vitro13. + +Apart from BMP4 being a reprogramming enhancer, in Oct4- based reprogramming14- 16, NuRD in general has been regarded as a reprogramming barrier in reprogramming system reported so far17,18. However, it is indeed surprising as described above that both BMP4 and NuRD behave quite differently in JGES reprogramming system. As we reported in our last paper, Sall4 is important to drive JGES reprogramming, and that NuRD is the most important interaction partner of SALL4. In this paper, we reveal further surprise that BMP4 is inhibitory for JGES reprogramming. The BMP4- Sall4- NuRD axis remains functional even in the context of Oct4- based reprogramming as shown in Figure 3e, 3g, 3h, which strongly suggests that this axis is a robust pathway not recognized until our work. + +However, we feel that our results are clear enough that we do not need to expand excessively. However, the implication remains quite clearly that cell fate control is context dependent and should be examined as carefully as possible as we demonstrated here. + +<--- Page Split ---> + +6. Methods: The Methods section requires improvement, with several crucial details missing and certain portions being misplaced. Additionally, it is essential to include statistical analysis for the figures, display individual replicates, and provide the Western blot membranes as supplementary figures. + +## Response: + +We really appreciate this suggestion. We have tried to improved our method details and appended statistical analysis of the figures and manuscript, also added the Western blot membranes into the Statistics Source Data. + +Reviewer #2 (Remarks to the Author): + +Reviewer Comments (Round 1: 20210720) + +In this manuscript by Ming and colleagues, the authors explore the role of BMP4 in cell fate switching, when reprogrammed using their previous JGES (Jdp2, Glis1, Esrrb and Sall4) over expression system. Using number of Oct4- GFP positive cells as readout, the authors observe that BMP4 addition reduces the reprogrammed cells both in a dosage and time- dependent manner. Performing scRNA- seq upon JGES induction, BMP4- cells give rise to intermediate state, endothelial and pluripotent cells, while BMP4+ gives rise to intermediate, endothelial and PrECLCs (primitive endoderm- like cells), with both reprogramming yielding \(\sim 20\%\) of total single- cell pool. These PrECLCs transcriptomically are show to be similar to published primitive endoderm (PrE) cells from E4.5- 5.5embryos. The authors subsequently perform a JGES dropout reprogramming screen with and without BMP4, ascertaining ability of BMP4 with Oct4 to reprogram MEFs, and with Sall4 acting antagonistically to BMP4. Using IP- MS, the authors observe perturbed SALL4- NuRD interaction when treating with BMP, an find that BMP4 blocks iPSC reprogramming via disruption of Sall4- NuRD cooperation (N- terminal 12AAs of SALL4). Lastly, the authors show that Sall4DelN12 alone can reset MEFs to induced extra- embryonic state, faster than Sall4WT; and perform blastocyst injections for iPRe- GFP for extra- embryonic intergration. + +The study and results are indeed interesting, the ms is very well written and supported by suitable experiments and analysis. However, the insights from the paper provide marginal gains and mainly improve on authors previous findings. + +The reviewer shares a few major and minor concerns stated below. + +## Comments + +- In figure 2A, it was unclear why the authors chose the BMP4 induction after 2 days? + +## Response: + +We apologize for this confusion. We normally allowed the cells to be infected with the reprogramming factors for 2 days based on our previous optimizations.. In figure 2A, the "day 2" means 2 days post transfection, when we start the induction process under BMP4+ or BMP4- , "day 7" means 7 days post transfection we start the scRNA- sequencing process, we have changed "day 2" into "transfection for 2 days" in Figure 2a. + +<--- Page Split ---> + +Figure 1d, highlights that number of Oct4- GFP+ve colonies are same as un- induced (row 1 vs row 3). Figure 1D- E suggest that BMP4 induction in Days0- 3 may not be quite consequential. + +## Response: + +Again, we appreciate this opportunity to clarify this confusion. The schema chart in Figure 1d shows the number of Oct4- GFP+ clones at different time windows. The condition with BMP4 treatment are colored in blue, and without BMP4 treatment are colored in gray. Row 1 is without BMP4 treatment and row 3 means with BMP4 treatment from day 4 to day 7. Based on these results, we show that BMP4 doesn't inhibit JGES reprogramming efficiency from day 4- day 7. Figure 1d exhibits that BMP4's inhibition effect only occurs in the first three days. We changed Day 7 to Day 0 labels to Day 0 to Day 7 from left to right to make the figure more intuitive. + +In our previously paper, SALL4- NuRD axis is important to silence somatic- related genes which is necessary in the early stage in reprogramming19, Figure 1d also shows that BMP4 dissociates SALL4- NuRD interaction. Figure 1e and f show that the reprogramming efficiency of JGES under different BMP4 dosages from day 0 to day 7. In order to eliminate the high dosage inhibition effect, we applied different BMP4 dosage in JGES, the results show that 1ng/ml BMP4 is able to inhibit half of Oct4- GFP+ clones, demonstrating that BMP4's inhibition function on JGES reprogramming is dosage dependent. + +- In Figure 2B-C, It is unclear whether there no no pluripotent cells from BMP4+ population. + +## Response: + +Indeed, these is no pluripotent cells in BMP+ population with JGES reprogramming. In Figure 2b- c, BMP4+ populations are colored in red in Figure 2b, pluripotent cell group is colored in red in Figure 2c. When align together carefully, we can find there are very rare BMP4+ populations located in pluripotent group. To make this clear, we added new charts to show BMP4+ and BMP4- populations in different cell types in Figure 2c. We added these charts to Supplementary Figure 2a- c. + +![PLACEHOLDER_12_0] + +
a: UMAP shows the cells distribution of BMP4+ and BMP4- conditions; b: Stacked barplot shows the cell proportion in each cell type.
+ +<--- Page Split ---> + +- Additionally a subset of BMP4+ are shared with MEF cluster (Pink cells in yellow cluster, Fig2B) even after 7 days, are these non-reprogrammed cells or different state (similar cells are not observed in BMP4+ population). Also look very diff from ESCs. + +## Response: + +We indeed noticed the subset of BMP4+ which shared the same cluster with MEF in Fig 2b. However, we don't think they are non- reprogrammed MEF cells, but at a different state from MEF cells as well as ESCs, based on the following reason. + +Firstly, we analysed the gene expression pattern between the two subsets, there are 90 genes commonly expressed in both subsets, and 51 genes specific expressed in MEFs, 157 genes specifically in BMP4+ (a). GO analysis show the genes commonly expressed are related to wound healing, collagen fibril organization, positive regulation of cell- substrate adhesion and extracellular structure organization. Genes, specifically expressed in MEF are related to extracellular matrix assembly, ossification, bone mineralization and biomineral tissue development. Finally, genes, specifically expressed in BMP4+ are related to regulation of protein stability, regulation of epithelial cell migration, Wnt signaling pathway and cell- cell signaling by Wnt (b). MEF subset specific express Atp5o, Srp54b, Aspn etc, but BMP4+ subset specific express Ins2, Pgk1, Apoe etc (c). In terms of gene quantity, 52.7% genes expressed in BMP4+ subset are different from MEF cells, in terms of gene function, BMP4+ subset is also very different from MEF cells, and so BMP4+ subset within the MEF cluster should be a different state from MEF cells. So, based on these results, we believe that these cells are different from MEFs, but at different stages as described. + +![PLACEHOLDER_13_0] + +
a: Heatmap shows the common and different features between MEF and BMP4+ cells in cluster 2; b: Bar plots show the top 5 GO terms of gene sets; c: UMAP shows the expression of selected marker genes
+ +<--- Page Split ---> + +- The authors report that PrECLCs are PrE cells based on bulk markers and single-cell comparison. The PrE markers are non-zero in BMP4-ve cells? What is the explanation for this? + +## Response: + +Based on single- cell comparison, bulk markers, IF experiments, indeed we have detected a subset of cells from JGES reprogramming with BMP4 treatment are PrE cell- like cells. The non- zero PrE markers in the BMP4- group is because there are a background level \(\sim 0.16\%\) PrECLCs in BMP4- cluster from our scRNA- seq data shown in Figure 2f colored in green. This is because SALL4 alone could reset MEF cells to PrECLCs state at very low efficiency without BMP4 treatment as shown in Figure 6a. We think PrECLCs arise from JGES reprogramming as an alternative fate and indeed over- expressing PrE marker genes in JGES could decrease Oct4- GFP+ clone number as shown in Figure 2h. Therefore, JGES reprogramming generates a background level of PrE, making up markers as non- zero in BMP4- group. + +- It would be useful to visualise other PrE markers at single-cell level in Fig S2D, to see if the distinction between BMP4+ to PrE/PrCLC and BMP4- to pluripotent.The reviewer feels that correlation values could be plotted (instead of high low) to appreciate magnitude of similarity + +## Response: + +We appreciate this advice.To better compare the states of BMP4+ to PrE/PrECLC and BMP4- to pluripotent cells, we used a new dataset20 whose quality is superior to the one previously used21, PrECLCs of BMP4+ can co- localize with E4.5- 5.5 PrE, pluripotency cells of BMP4- can co- localize with E4.5- 5.5 epiblast (a, b).We also visualized additional pluripotency and PrE markers among the two clusters at single cell level, and observed shared gene expression as well as differential gene expression between reprogramming cells and in vivo cells(c, d, e, f). We also used the CCA algorithm to integrate reprogramming data with mouse embryo data of E4.5- E5.522. The results show that PrECLCs are similar to in vivo PrE cells, with a Pearson correlation coefficient of 0.88, while Pluripotent cells are similar to in vivo Epiblast cells, with a correlation coefficient of 0.86 (g). We updated it to Supplementary Figure 2e, 2f, 2g in the new manuscript version. + +![PLACEHOLDER_14_0] + + +<--- Page Split ---> +![PLACEHOLDER_15_0] + +
a, b: UMAP shows the integration of PrECLCs/Pluripotent cells' data in this study and Epiblast/PrE data of Sala2019 in vivo; c, d, e, f: UMAP shows the expression of marker genes at single cell level; g: Correlation heatmap of reprogramming cells and developmental cells.
+ +- In Fig 3b (-sall4) and 3d (oct4, -sall4), the authors should comment on the target gene sets and their activation (cooperativity vs exclusivity), during Oct4 and BMP4 mediated reprogramming. Which sites are unique vs co-bound with Sall4, and regulated? + +## Response: + +We appreciate this insightful suggestion. To answer this question, we performed bulk RNA- sequence on JGE vs JGES and, JGEO vs JGESO under BMP4+ and BMP4- condition, and evaluated BMP4's function on pluripotency gene sites and PrE related gene sites with or without Sall4. The results show that BMP4 can decrease pluripotency genes expression dramatically when Sall4 exists both in JGE vs JGES and JGEO vs JGESO (a b); BMP4 can decrease pluripotency genes expression dramatically when Sall4 exists both in JGE vs JGES and JGEO vs JGESO, BMP4 can also increase PrE genes expression dramatically when Sall4 presents in JGE vs JGES, in JGEO vs JGESO, BMP4 could also upgrade PrE genes expression slightly(c, d). All these data indicate that BMP4 functions to inhibit pluripotency gene and promote PrE gene sites when Sall4 present. We added the results to Supplementary Figure 3a, 3b, 3c, 3d. + +<--- Page Split ---> +![PLACEHOLDER_16_0] + + +a. Box plot shows the expression levels of pluripotency genes between conditions with and without BMP4 treatment at day 7 during JGE, JGES, JGEO, JGESO reprogramming; b, Box plot shows the fold changes in the expression of pluripotency genes between conditions with and without BMP4 treatment at day 7, during the JGE, JGES, JGEO, JGESO reprogramming, represented on a logarithmic scale; c, Box plot shows the expression levels of PrE related genes between conditions with and without BMP4 treatment at day 7 during JGE, JGES, JGEO, JGESO reprogramming; d, Box plot shows the fold changes in the expression of PrE related genes between conditions with and without BMP4 treatment at day 7, during the JGE, JGES, JGEO, JGESO reprogramming, represented on a logarithmic scale. + +- In Fig5, the authors should describe number/percentage of PrECLC cells between WT and Sall4DelN12. Which other cell types emerge during reprogramming (pluripotent, endoderm, intermediate and percentages. Since the FPKM counts are non-zero; the cell-fate switch is likely to be non-binary decision. + +## Response: + +Indeed, we agree with the reviewer's suggestion. Here we show the IF results of GATA4+ clone number (a) and whole well screening pictures (b) between WT and delN12- SALL4 PrE induction at day 11, delN12- SALL4 group is much higher than WT- SALL4. We agree with the opinion, the cell- fate switch is not a binary decision between BMP4+ and BMP4- group of JGES reprogramming, not even in WT- SALL4 and delN12- SALL4 single factor induced reprogramming, PrECLCs cluster is not the only cell group which obtain a proportion increase after BMP4 treatment, however, PrECLCs is a result of BMP4 induced SALL4- NuRD dissociation in JGES reprogramming, SALL4- NuRD (delN12- SALL4) dissociation leads to pluripotency inhibition (c, d) and PrE cell fate promotion (e). + +<--- Page Split ---> + +In the single factor induced reprogramming, we checked the expression pattern of pluripotency, endoderm and intermediate related marker genes, based on bulk RNA- sequence data, unlike the expression pattern of PrE genes, delN12- SALL4 doesn't show an improvement effect on these cell lineage (f, g, h). Although PrE cell fate may not be the only direction of delN12- induced MEF cells, additional function will be discussed further in our subsequent research. + +![PLACEHOLDER_17_0] + + +a, Histogram shows IF results of GATA4 positive iPRE colonies number in different group, data are mean \(\pm\) s.d., two- sided, unpaired t test; \(\bar{\mathsf{n}} = 3\) independent experiments, \(^{*}\mathsf{p}< 0.05\) , \(^{**}p< 0.01\) , \(^{***}p< 0.001\) ; b: Pictures show the in situ whole well screening of GATA4 positive iPRE colonies number of different group, scale bar \(= 10\mathsf{mm}\) c, Histogram shows Oct4 GFP positive iPSE colonies number in different group, data are mean \(\pm\) s.d., two- sided, unpaired t test; \(\bar{\mathsf{n}} = 3\) independent experiments, \(^{*}\mathsf{p}< 0.05\) , \(^{**}p< 0.01\) , \(^{***}p< 0.001\) ; d: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar \(= 5\mathsf{mm}\) ; e, Histograms show the qPCR results of PrE gene relative expression level of every group, \(\bar{\mathsf{n}} = 3\) independent experiments; f, g, h: Line charts show the expression pattern of different cell lineage markers between SALL4WT and SALL4delN12. + +- Similarly, statistics of Fig5DF and EG could be provided. What percentage of cells of the total were GFP positive. + +# Response: + +<--- Page Split ---> + +We again appreciate this suggestion. However it is really hard to quantify the exact GFP positive cell percentage in the whole yolk sac at E12.5 chimeric embryos. We performed the blastocyst injection experiments to test iPrE's in vivo developmental ability. In previous studies, in vivo developmental potential of PrESCs (primitive endoderm stem cells) separated from blastocyst are also tested by this way 6. However, the chimeric efficiency of iPrEs is indeed lower than PrESCs (Supplementary Figure 6g, 6h). Additionally, it is very hard to digest the GFP positive cells from the yolk sac for it has very condense extra- cellular matrix and complicated tissue structure, our previous study also didn't show the exact cell percentage of the chimerism cells, because of these limitations. This technological difficulties are formidable enough to provide a more exact assessment. Nevertheless, we are trying to enhance the induction and chimeric efficiency of iPrE cells. + +Minor + +- The introduction seems brief and generalised. + +## Response: + +Highly appreciate your suggestion, we improved the introduction part of this manuscript. By providing more relevant background on PrE, BMP and also early cell fate decisions. + +- In the discussion, the authors do not comment whether BMP4 mediated cell fate changes are due to JGES TF cooperativity vs exclusivity in action? + +## Response: + +Reviewer #1 also asked a similar question. We performed the JGES TF dropout experiments and added the TF one by one into OS- derived reprogramming with BMP4 treatment again, after that we check the PrE genes expression among them by qPCR, the results indicate that except Jdp2 dropout has a strong promotion of PrE genes expression, the other three factor dropout all inhibit PrE cell fate, Glis1, Esrrb and Sal/4 may form an cooperativity interaction network for PrE formation and Jdp2 is a antagonists in PrE cell fate formation (a), however, in OS reprogramming, Sal/4 is the only factor to increase PrE gene expression level (b), Sal/4 is important in PrE cell fate formation both in JGES and OS system under BMP4 treatment. We revised the discussion by focusing more on the effect of SALL4 more and its impact with BMP4 treatment. We are not sure about cooperativity or exclusivity. It is clear that BMP4 is targeting Sal/4- NuRD for the cell fate decisions. + +![PLACEHOLDER_18_0] + + +<--- Page Split ---> +![PLACEHOLDER_19_0] + +
a, b: Histograms show the qPCR results of PrE gene relative expression level of every group, \(n = 3\) independent experiments.
+ +- The authors could double check the scalebar between both panels in in Fig5c scale. In the print/web version, lower panel seems more magnified + +## Response: + +Thanks for this suggestion and sorry for the mistake we made, we change the picture we used in Figure 6a. + +- What duration and timing of BMP4 induction is most crucial to fate specification in JGES reprogramming? The authors perform a titration and dosage curve, but choose 1 condition for all experiments. + +## Response: + +According to Figure 1d, e, f, the first three days is the most crucial time window for BMP4 pluripotency inhibition. However, BMP4 has the strongest inhibition on JGES under day0- day7, so we chose this condition. The reason why we perform a titration and dosage curve is to confirm BMP4's inhibition on JGES reprogramming is not due to nonspecific effect. Since \(10 \text{ng / ml}\) BMP4 has been proved to be a reprogramming promoter in previously studies14,23, is also an effective inhibition dosage in Figure 1e, so we choose \(10 \text{ng / ml}\) . + +<--- Page Split ---> + +1 Graham, S. J. et al. BMP signalling regulates the pre-implantation development of extraembryonic cell lineages in the mouse embryo. Nat Commun 5, 5667, doi:10.1038/ncomms6667 (2014).2 Dudakovic, A. et al. Histone deacetylase inhibition destabilizes the multi-potent state of uncommitted adipose-derived mesenchymal stromal cells. J Cell Physiol 230, 52- 62, doi:10.1002/jcp.24680 (2015).3 Dudakovic, A. et al. Histone deacetylase inhibition promotes osteoblast maturation by altering the histone H4 epigenome and reduces Akt phosphorylation. J Biol Chem 288, 28783- 28791, doi:10.1074/jbc.M113.489732 (2013).4 Schroeder, T. M., Nair, A. K., Staggs, R., Lamblin, A. F. & Westendorf, J. J. 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The Role of the TGF- \(\beta\) Superfamily in Myocardial Infarction. Front Cardiovasc Med 6, 140, doi:10.3389/fcvm.2019.00140 (2019).10 Choi, K. C. et al. Smad6 negatively regulates interleukin 1- receptor- Toll- like receptor signaling through direct interaction with the adaptor Pellino- 1. Nat Immunol 7, 1057- 1065, doi:10.1038/nl1383 (2006).11 Estrada, K. D., Retting, K. N., Chin, A. M. & Lyons, K. M. Smad6 is essential to limit BMP signaling during cartilage development. J Bone Miner Res 26, 2498- 2510, doi:10.1002/jbrmr.443 (2011).12 Hanna, J. et al. Direct cell reprogramming is a stochastic process amenable to acceleration. Nature 462, 595- 601, doi:10.1038/nature08592 (2009).13 Sadlon, T. J., Lewis, I. D. & D'Andrea, R. J. BMP4: its role in development of the hematopoietic system and potential as a hematopoietic growth factor. Stem Cells 22, 457- 474, doi:10.1634/stemcells.22- 4- 457 (2004).14 Chen, J. et al. BMPs functionally replace Klf4 and support efficient reprogramming of mouse fibroblasts by Oct4 alone. Cell Res 21, 205- 212, doi:10.1038/cr.2010.172 (2011).15 Hayashi, Y. et al. BMP- SMAD- ID promotes reprogramming to pluripotency by inhibiting p16/INK4A- dependent senescence. Proc Natl Acad Sci U S A 113, 13057- 13062, doi:10.1073/pnas.1603668113 (2016).16 Yu, S. et al. BMP4 resets mouse epiblast stem cells to naive pluripotency through ZBTB7A/B- mediated chromatin remodelling. Nat Cell Biol 22, 651- 662, doi:10.1038/s41556- 020- 0516- x (2020).17 Luo, M. et al. NuRD blocks reprogramming of mouse somatic cells into pluripotent stem + +<--- Page Split ---> + +cells. Stem Cells 31, 1278- 1286, doi:10.1002/stem.1374 (2013). 18 Rais, Y. et al. Deterministic direct reprogramming of somatic cells to pluripotency. Nature 502, 65- 70, doi:10.1038/nature12587 (2013). 19 Wang, B. et al. The NuRD complex cooperates with SALL4 to orchestrate reprogramming. Nat Commun 14, 2846, doi:10.1038/s41467- 023- 38543- 0 (2023). 20 Pijuan- Sala, B. et al. A single- cell molecular map of mouse gastrulation and early organogenesis. Nature 566, 490- 495, doi:10.1038/s41586- 019- 0933- 9 (2019). 21 Nowotschin, S. et al. The emergent landscape of the mouse gut endoderm at single- cell resolution. Nature 569, 361- 367, doi:10.1038/s41586- 019- 1127- 1 (2019). 22 Butler, A., Hoffman, P., Smibert, P., Papalexi, E. & Satija, R. Integrating single- cell transcriptomic data across different conditions, technologies, and species. Nat Biotechnol 36, 411- 420, doi:10.1038/nbt.4096 (2018). 23 Lin, L. et al. The homeobox transcription factor MSX2 partially mediates the effects of bone morphogenetic protein 4 (BMP4) on somatic cell reprogramming. J Biol Chem 293, 14905- 14915, doi:10.1074/jbc.RA118.003913 (2018). + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors have satisfactorily responded to all my comments. A final minor point: the authors should carefully check the text for typos, particularly throughout the methods section. + +Reviewer #2 (Remarks to the Author): + +In this revised manuscript by Ming and colleagues, the authors have provided answers to most of the raised comments. + +<--- Page Split ---> + +Point- by- point response to the reviewers: + +Reviewer #1: + +Dear reviewer, + +We sincerely appreciate your efforts for considering and reviewing our work again. We have checked and corrected them in the final version. We would like to express our gratitude for your insightful comments and suggestions which have significantly contributed to improve the quality of our work. + +Reviewer #1: + +Dear reviewer, + +Thank you for your invaluable time and efforts dedicated to reviewing our manuscript. We are so happy that our previous revised manuscript has provided answers to most of your comments. We sincerely acknowledge your rigorous evaluation and comments, which have immensely improved our work. + +Sincerely, + +Duanqing + +<--- Page Split ---> diff --git a/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b1e7d6f966e350de16f07b5b5768e74675565825 --- /dev/null +++ b/peer_reviews/12d14f46911ac862fa0888c9a21b38d01db99f055a47f952b75adc66b6066d87/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,484 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[67, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[125, 154, 878, 210]]<|/det|> +Cell fate decision by a morphogen- transcription factor- chromatin modifier axis + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 414, 98]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 111, 875, 238]]<|/det|> +In this study, Ming et al. presented a hypothesis positing that BMP4 signaling impedes the induction of pluripotency by impairing the NURD- SALL4 interaction complex during JGES- mediated reprogramming. Intriguingly, the authors demonstrated that the introduction of BMP4 redirects reprogramming towards a more primitive endoderm (PrE)- like fate. The authors have provided compelling evidence to support these findings, particularly in their immunoprecipitation (IP) experiments, which exhibit a dissociation between SALL4 and NURD upon BMP4 administration. Furthermore, the authors bolstered their hypothesis by rescuing reprogramming through the covalent binding of SALL4 to various NuRD components. Finally, the authors demonstrate that SALL4 overexpression instructs the PrE fate. + +<|ref|>text<|/ref|><|det|>[[119, 251, 616, 266]]<|/det|> +However, the paper could benefit from the following suggestions: + +<|ref|>text<|/ref|><|det|>[[118, 279, 877, 392]]<|/det|> +1. Elaboration of the BMP4 mechanism: The paper lacks a detailed mechanism explaining how BMP4 guides reprogramming cells towards a more PrE-like fate. Considering that SALL4 itself can induce PrE fates, it suggests potential competitive binding between SALL4 and PrE-related proteins versus SALL4 and NuRD. The exact mechanism by which BMP4 promotes a PrE fate remains unclear beyond the inability to interact with NuRD, which is necessary for pluripotency. It may be beneficial to explore the upregulated proteins identified in the IP-MS experiments to gain deeper insights into the shift toward PrE. Again, this is particularly relevant since SALL4 alone can reprogram cells to a PrE fate. + +<|ref|>text<|/ref|><|det|>[[118, 405, 875, 504]]<|/det|> +2. The blastocyst injection experiments require refinement. It is challenging to discern whether the GFP-labeled cells are contributing to the embryo or primitive endoderm since there is no co-staining with specific markers for PrE. Furthermore, the paper lacks essential statistical analysis, information regarding the number of embryos injected, and other pertinent details. It would be beneficial to include a parallel experiment utilizing pluripotent cells for comparison. Additionally, it is unclear how these experiments are performed. Specifically, are purified PrE cells injected? Or is this a heterogeneous population containing both PrE and pluripotent cells? + +<|ref|>text<|/ref|><|det|>[[118, 517, 866, 574]]<|/det|> +3. Inhibition of BMP4 signaling: Considering that BMP4 addition was shown to slow down JGES reprogramming, it raises the question of whether inhibiting BMP4 or downstream targets of BMP4 signaling could enhance the efficiency of reprogramming. Investigating this aspect would strengthen and broaden the author's conclusions. + +<|ref|>text<|/ref|><|det|>[[118, 588, 877, 658]]<|/det|> +4. Drop-out screen logic: The rationale behind the drop-out screen is somewhat unclear. Instead of a drop-out to identify factors necessary for pluripotent cells, it might be more informative to perform a drop-out screen to pinpoint the factors required for PrE cell formation. This would focus on understanding the specific components necessary for the observed phenotype rather than pluripotency. + +<|ref|>text<|/ref|><|det|>[[118, 672, 855, 715]]<|/det|> +5. Exploration of BMP4's effects on reprogramming: The paper briefly touches on the dichotomy between BMP4's effects on OCT4-based and SALL4-based reprogramming, which could offer a novel aspect to the study. Expanding on this aspect might provide additional insights. + +<|ref|>text<|/ref|><|det|>[[118, 728, 861, 785]]<|/det|> +6. Methods: The Methods section requires improvement, with several crucial details missing and certain portions being misplaced. Additionally, it is essential to include statistical analysis for the figures, display individual replicates, and provide the Western blot membranes as supplementary figures. + +<|ref|>text<|/ref|><|det|>[[119, 825, 414, 840]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 853, 867, 910]]<|/det|> +Reviewer Comments (Round 1: 20210720) In this manuscript by Ming and colleagues, the authors explore the role of BMP4 in cell fate switching, when reprogrammed using their previous JGES (Jdp2, Glis1, Esrrb and Sall4) over expression system. Using number of Oct4- GFP positive cells as readout, the authors observe that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 877, 252]]<|/det|> +BMP4 addition reduces the reprogrammed cells both in a dosage and time- dependent manner. Performing scRNA- seq upon JGES induction, BMP4- cells give rise to intermediate state, endothelial and pluripotent cells, while BMP4+ gives rise to intermediate, endothelial and PrECLCs (primitive endoderm- like cells), with both reprogramming yielding \(\sim 20\%\) of total single- cell pool. These PrECLCs transcriptomically are show to be similar to published primitive endoderm (PrE) cells from E4.5- 5.5embryos. The authors subsequently perform a JGES dropout reprogramming screen with and without BMP4, ascertaining ability of BMP4 with Oct4 to reprogram MEFs, and with Sall4 acting antagonistically to BMP4. Using IP- MS, the authors observe perturbed SALL4- NuRD interaction when treating with BMP, an find that BMP4 blocks iPSC reprogramming via disruption of Sall4- NuRD cooperation (N- terminal 12AAs of SALL4). Lastly, the authors show that Sall4DeIN12 alone can reset MEFs to induced extra- embryonic state, faster than Sall4WT; and perform blastocyst injections for iPRe- GFP for extra- embryonic intergration. + +<|ref|>text<|/ref|><|det|>[[118, 252, 875, 293]]<|/det|> +The study and results are indeed interesting, the ms is very well written and supported by suitable experiments and analysis. However, the insights from the paper provide marginal gains and mainly improve on authors previous findings. + +<|ref|>text<|/ref|><|det|>[[120, 293, 632, 308]]<|/det|> +The reviewer shares a few major and minor concerns stated below. + +<|ref|>sub_title<|/ref|><|det|>[[118, 323, 202, 335]]<|/det|> +## Comments + +<|ref|>text<|/ref|><|det|>[[116, 336, 870, 660]]<|/det|> +- In figure 2A, it was unclear why the authors chose the BMP4 induction after 2 days? Figure 1d, highlights that number of Oct4-GFP+ve colonies are same as un-induced (row 1 vs row 3). Figure 1D-E suggest that BMP4 induction in Days0-3 may not be quite consequential. +- In Figure 2B-C, It is unclear whether there no no pluripotent cells from BMP4+ population. +- Additionally a subset of BMP4+ are shared with MEF cluster (Pink cells in yellow cluster, Fig2B) even after 7 days, are these non-reprogrammed cells or different state (similar cells are not observed in BMP4+ population). +o Also look very diff from ESCs. +- The authors report that PrECLCs are PrE cells based on bulk markers and single-cell comparison. The PrE markers are non-zero in BMP4-ve cells? What is the explanation for this? It would be useful to visualise other PrE markers at single-cell level in Fig S2D, to see if the distinction between BMP4+ to PrE/PrCLC and BMP4- to pluripotent. The reviewer feels that correlation values could be plotted (instead of high low) to appreciate magnitude of similarity. +- In Fig 3b (-sall4) and 3d (oct4, -sall4), the authors should comment on the target gene sets and their activitation (cooperativity vs exclusivity), during Oct4 and BMP4 mediated reprogramming. Which sites are unique vs co-bound with Sall4, and regulated? +- In Fig5, the authors should describe number/percentage of PrECLC cells between WT and Sall4DeIN12. Which other cell types emerge during reprogramming (pluripotent, endoderm, intermediate and percentages)? Since the FPKM/counts are non-zero; the cell-fate switch is likely to be non-binary decision. +- Similarly, statistics of Fig5DF and EG could be provided. What percentage of cells of the total were GFP positive. + +<|ref|>sub_title<|/ref|><|det|>[[118, 688, 163, 700]]<|/det|> +## Minor + +<|ref|>text<|/ref|><|det|>[[116, 701, 875, 814]]<|/det|> +- The introduction seems brief and generalised. +- In the discussion, the authors do not comment whether BMP4 mediated cell fate changes are due to JGES TF cooperativity vs exclusivity in action? +- The authors could double check the scalebar between both panels in in Fig5c scale. In the print/web version, lower panel seems more magnified. +- What duration and timing of BMP4 induction is most crucial to fate specification in JGES reprogramming? The authors perform a titration and dosage curve, but choose 1 condition for all experiments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 87, 425, 100]]<|/det|> +Point- by- point response to the reviewers: + +<|ref|>text<|/ref|><|det|>[[149, 142, 328, 155]]<|/det|> +Dear editor and reviewers, + +<|ref|>text<|/ref|><|det|>[[147, 178, 851, 323]]<|/det|> +We sincerely thank you for considering and reviewing our work. We especially appreciate the constructive comments that helped us to improve the manuscript through experiments. As suggested by all the reviewers, we performed the relevant experiments and performed literature research to answer all the questions. As such, we sincerely believe that the manuscript has been improved through careful revision as detailed by point- by- point responses below. We hope that your comments have been addressed in full and we obviously welcome any additional ones as well. Please note that the responses are marked with blue color in the text, the references are list at the end of the text, all Figures mentioned in this text have been up- dated in the new version. + +<|ref|>text<|/ref|><|det|>[[149, 346, 456, 360]]<|/det|> +Main changes and additions made to Figures. + +<|ref|>text<|/ref|><|det|>[[147, 364, 850, 565]]<|/det|> +1: Figure 1d: Day 7 to Day 0 is changed to Day 0 to Day 7 from left to right; +2: Supplement Figure 1a, 1b, Supplement Figure 2a, 2b, Figure 3i, 3j, Figure 4g, 4h, 4i are added; +3: Supplement Figure 2e, 2f, 2g are updated; +4: Figure 3a, 3b, 3d, 3e are re- organized; +5: Supplement Figure 3a, 3b, 3c, 3d are added; +6: Figure 5 and Supplement Figure 5 are new data, previous figure 5 and Supplement Figure 5 are change to Figure 6 and Supplement Figure 6; +7: Previous Figure 5i is deleted; +8: Previous Figure 5h is changed to Figure 6l; +9: Previous Figure 5d, 5e, 5f, 5g are changed to Supplement Figure 6e, 6f, 6g, 6h; +10: Figure 6c, 6d, 6e, 6f, 6g, 6h, 6i, 6j, 6k, Supplement Figure 6i, 6j are added. + +<|ref|>text<|/ref|><|det|>[[149, 586, 404, 600]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 622, 851, 768]]<|/det|> +In this study, Ming et al. presented a hypothesis positing that BMP4 signaling impedes the induction of pluripotency by impairing the NURD- SALL4 interaction complex during JGES- mediated reprogramming. Intriguingly, the authors demonstrated that the introduction of BMP4 redirects reprogramming towards a more primitive endoderm (PrE)- like fate. The authors have provided compelling evidence to support these findings, particularly in their immunoprecipitation (IP) experiments, which exhibit a dissociation between SALL4 and NURD upon BMP4 administration. Furthermore, the authors bolstered their hypothesis by rescuing reprogramming through the covalent binding of SALL4 to various NuRD components. Finally, the authors demonstrate that SALL4 overexpression instructs the PrE fate. + +<|ref|>sub_title<|/ref|><|det|>[[149, 772, 228, 785]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 804, 851, 912]]<|/det|> +We appreciate the reviewer's insightful comments for our work. As reprogramming as a technology has become rather routine and so many nice works have been published over the past 15 years, we branched out into areas far less popular, but perhaps more interesting. One of such areas is the BMP4- Sall4- NuRD axis as detailed in this paper. Beyond the pathways we delineated, we also find, with a bit surprise, that we can generate PrE or PE, the sister fate of epiblasts. So, we decided to look into this further with results we written up for this manuscript. Much needs to be done as pointed out by the reviewer, but we + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 848, 119]]<|/det|> +were encouraged that we have made a good start. So, we especially appreciate the encouraging comments from the reviewer. + +<|ref|>text<|/ref|><|det|>[[148, 156, 584, 171]]<|/det|> +However, the paper could benefit from the following suggestions: + +<|ref|>text<|/ref|><|det|>[[148, 192, 851, 320]]<|/det|> +1. Elaboration of the BMP4 mechanism: The paper lacks a detailed mechanism explaining how BMP4 guides reprogramming cells towards a more PrE-like fate. Considering that SALL4 itself can induce PrE fates, it suggests potential competitive binding between SALL4 and PrE-related proteins versus SALL4 and NuRD. The exact mechanism by which BMP4 promotes a PrE fate remains unclear beyond the inability to interact with NuRD, which is necessary for pluripotency. It may be beneficial to explore the upregulated proteins identified in the IP-MS experiments to gain deeper insights into the shift toward PrE. Again, this is particularly relevant since SALL4 alone can reprogram cells to a PrE fate. + +<|ref|>sub_title<|/ref|><|det|>[[149, 370, 228, 384]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 402, 851, 529]]<|/det|> +We would like to thank the reviewer for pointing out our deficiencies concerning PrE fate control. As we pointed out above, we are perhaps a few labs in the world remaining interested in reprogramming. This is our second paper on the JGES reprogramming system following our initial 7F system paper. Unfortunately, we have yet to see the rest of the field paying attention to this reprogramming system, so the value of this system to the entire stem cell field remains near zero. We thought that we can improve this by showing interesting mechanisms and previously unknown paths. So, we devoted most of our energy to the BMP4- Sall4- NuRD axis, neglected to our detriment the PrE aspect. + +<|ref|>text<|/ref|><|det|>[[148, 546, 851, 616]]<|/det|> +As we have learnt since we realised that PrE is the fate diverted by BMPs, PrE is fascinating, but not well described in the literature, to our knowledge, there are only a handful papers describing its derivation, not on the mechanism aspect1. So, we appreciate the comments from the reviewer and performed experiments to address them as detailed below. + +<|ref|>text<|/ref|><|det|>[[147, 634, 851, 890]]<|/det|> +First, we appreciate the insightful suggestion to explore the IP- MS experiments for "potential competitive binding between SALL4 and PrE- related proteins versus SALL4 and NuRD" on BMP4 mechanism study, we look into our IP- MS data and PrE related proteins, the upregulated proteins identified in the SALL4 IP- MS experiments after BMP4 treatment, \(\mathrm{FC} = 1.5\) , pValue=0.05, the same as Fig 4b in the manuscript, 67 proteins appear, at the meantime, We plotted a Venn diagram between the 67 proteins and 142 genes specific expressed in the PrECLCs cluster in our scRNA- seq dataSlc9a3r1 turns out to be the only overlapped protein(a, b, c), unfortunately, Slc9a3r1 overexpression can't mimic BMP4's inhibition effect on JGES reprogramming under BMP4- (d, e), Slc9a3r1 KD can't rescue BMP4 induced reprogramming decreasing either(f, g), thus, Slc9a3r1 may not be the critical protein based on these results. Slc9a3r1 is reported to be a HDAC responsive gene, it is a solute- carrier protein and activated upon inhibition or complete loss of HDAC function2, this is in agreement with our main conclusion that BMP4 signals to dissociate SALL4- NuRD interaction. Slc9a3r1 is also reported to be required for optimal bone density and bone homeostasis3,4 which could be another explanation for the Slc9a3r1 activation by bone morphogenetic protein 4, BMP4. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 212]]<|/det|> +To gain deeper insights into the shift toward PrE, we look into PrE related and BMP4 induced transcriptome regulation, for SALL4- NuRD axis is to remodel transcriptional profile by altering H3K27ac level, by regulon analyzing on scRNA- sequencing data and additional experiments, Gata4 turns out to be the key regulon to guide JGES reprogramming to PrE cell fate, BMP4 and SALL4delN12 can also elevate Gata4 expression level. BMP4 mechanism on PrE cell fate induction can be explained as below: BMP4 dissociates SALL4- NuRD interaction leads to PrE cell fate formation by up regulate PrE key regulon Gata4 expression. We also add these data into Figure 5. + +<|ref|>image<|/ref|><|det|>[[155, 229, 858, 565]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 591, 852, 660]]<|/det|> +
a: Venn diagram shows the shared protein between PrE genes and SALL4 up-regulated proteins after BMP4 treatment; b: Line chart shows Slc9a3r1 expression pattern in BMP4+ and BMP4- condition; c: Line chart shows Slc9a3r1 expression pattern in WT-SALL4 and delN12-SALL4; d, e, f, g: Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two-sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 677, 852, 899]]<|/det|> +We then discussed if BMP4 inhibits pluripotent cell fate by dissociating SALL4- NuRD interaction. The function of SALL4- NuRD axis is transcriptional regulation by altering H3K27ac level of the target genes which has been clarified in detail in our last paper4, so we look into the transcription regulation of the PrE- like cell fate, so as to explain how this cell fate appears and the underlying mechanism of BMP4. We apply regulon analysis by SCENIC method on the PrECLCs cluster with our scRNA- sequence data to identify the main transcription regulons of PrE related genes; the top 5 regulon factors are Sox17, Pitx1, Klf4, Gata4 and Foxa2 (a), UMAP shows the regulon scores calculated by SCENIC (top panel) and the expression level (lower panel) of transcription factors(b), network plot shows the transcription factors and their target genes (c), Gata4 regulated the largest PrE gene number among the top 5 regulons and it is more restricted to PrECLCs than the other four regulons(b). Over- expression (OE) experiments shows Gata4 has the strongest inhibition effect on pluripotency induction(d) and promotion effect on PrE formation(e), Supplementary Figure 2b indicates BMP4 can elevate Gata4 expression, and Knocking- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 138]]<|/det|> +down Gata4 in JGES reprogramming with BMP4 treatment can also inhibit PrE fate formation by qPCR experiments (f, g). These data indicate BMP4 guides reprogramming cells towards a more PrE- like fate through activating Gata4. + +<|ref|>image<|/ref|><|det|>[[145, 155, 863, 592]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 612, 853, 740]]<|/det|> +Besides this, we also want to know the relationship between BMP4 activating PrE regulon genes expression and dissociating SALL4- NuRD interaction. We apply SALL4deN12 and SALL4WT with JGE without BMP4 treatment, and show that SALL4deN12 could mimic BMP4 function both on pluripotency inhibition(h, i) and PrE promotion(j). Previous study has indicated Gata4 and other PrE related markers are absent in homozygous mutant Sall4 cell cultures derived from ICM5. In conclusion, BMP4 dissociates SALL4- NuRD interaction leading to PrE cell fate formation by upregulating PrE key regulon Gata4 expression. We add these data to Figure 5 in the new version. + +<|ref|>image<|/ref|><|det|>[[207, 754, 781, 900]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[192, 85, 830, 468]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 479, 852, 641]]<|/det|> +a: Plot shows the top 5 regulons of PrE; b: UMAP shows the regulon scores calculated by SCENIC (top panel) and the expression level (lower panel) of transcription factors; c: Network plot shows the transcription factors and their target genes; d: Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two- sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) ; e, f, g: Histograms show the qPCR results of PrE gene relative expression level of every group; h, Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean ± s.d., two- sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) ; i: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar= 5mm; j: Histograms show the qPCR results of PrE gene relative expression level of every group, data are mean ± s.d., two- sided, unpaired t test; n = 3 independent experiments, \(*p < 0.05\) , \(**p < 0.01\) , \(***p < 0.001\) . + +<|ref|>text<|/ref|><|det|>[[147, 677, 851, 806]]<|/det|> +2. The blastocyst injection experiments require refinement. It is challenging to discern whether the GFP- labeled cells are contributing to the embryo or primitive endoderm since there is no co- staining with specific markers for PrE. Furthermore, the paper lacks essential statistical analysis, information regarding the number of embryos injected, and other pertinent details. It would be beneficial to include a parallel experiment utilizing pluripotent cells for comparison. Additionally, it is unclear how these experiments are performed. Specifically, are purified PrE cells injected? Or is this a heterogeneous population containing both PrE and pluripotent cells? + +<|ref|>sub_title<|/ref|><|det|>[[148, 823, 228, 837]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 854, 850, 907]]<|/det|> +As stated above, we really appreciate these suggestions and added "The iPrE clones induced by SALL4WT alone are picked by pipette at day 11, after 3 days, the patches are digested into single cells or smaller patches by 0.25% trypsin. After one or two extra- passages to deplete the non- induced cells, the iPrE cells + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 194]]<|/det|> +are ready to be labeled by GFP." to the method part. iPrEs- GFP we used to perform the blastocyst injection experiments should be a heterogeneous population containing both iPrE cells and very rare non- iPrE cells but no pluripotent cells. For iPrE shaped clones are all Oct4- GFP negative, there is no comparability between iPrEs and pluripotent cells. Indeed we applied MEF cells marked by GFP as a parallel experiment for the iPrE cells are derived from MEFs, and the results indicate iPrE could incorporate into PrE upon blastocyst injection but not MEFs (Supplementary Figure 6e, 6f). + +<|ref|>text<|/ref|><|det|>[[147, 210, 852, 336]]<|/det|> +As previously described in the Figure legend 5g, "g. Pictures show iPrE- GFP emerge at embryo yolk sac after transplantation. 8 embryos were obtained at E12.5, 5 of which have GFP+ cells in their yolk sac, no GFP+ cells were found in embryo yolk sac of MEFs- GFP group, data not shown." 5/8 embryos we obtained have GFP+ cells in their yolk sac, and we showed two of them in the previous Figure 5 (Batch 1). In order to replenish the essential statistical analysis, we did the blastocyst injection experiment four more times. Statistical data are shown in the table below, and we also added this table to Supplementary Figure 6i: + +<|ref|>table<|/ref|><|det|>[[148, 350, 848, 437]]<|/det|> + +
BatchSurrogate MiceiPrEs Injected BlastocystsEmbryos at E12.5Embryos With GFP Labeled
122885
21722
32120/
411422
522273
SUM8831912
+ +<|ref|>text<|/ref|><|det|>[[147, 452, 852, 617]]<|/det|> +PrE cells arise around E4.5- E5.5 in the embryo development in vivo, and these cells are PrE markers positive. However, when they take part in the formation of extra- embryonic yolk sac at E12.5, they become multiple cell types, so when we inject our GFP+ iPrE cells into E3.5 embryo cavity, it is difficult to trace which kind of cells they are in the extra- embryonic yolk sac, as it is very difficult to co- stain extra- embryonic yolk sac markers with GFP labeled iPrE cells. This blastocyst injection experiments we performed was used to test the in vivo developmental ability of the iPrE cells, like the previous study tests the in vivo developmental potential of PrESCs (primitive endoderm stem cells) separated from blastocyst. However, the chimeric efficiency of iPrEs is far below PrESCs (Supplementary Figure 6g, 6h), we are still trying to enhance the induction and chimeric efficiency of iPrE cells. + +<|ref|>text<|/ref|><|det|>[[147, 634, 852, 760]]<|/det|> +To further determine the cell identity of iPrE, we also performed IF (Fig 6a) to test the PrE markers expression in iPrE clones, and detected retrovirus silencing, a characteristic of mouse stem cells (Supplementary Figure 6b), iPrE cells show strong proliferation capacity as well(Supplementary Figure 6c). Unlike ESCs, PrESCs can form a single layer cavity under suspension culture, exhibiting polarity characteristics and condensed extracellular matrix, iPrE cells are also capable of this feature(Supplementary Figure 6d). Together, these iPrE cells have primitive endoderm like characteristics. + +<|ref|>text<|/ref|><|det|>[[147, 796, 850, 867]]<|/det|> +3. Inhibition of BMP4 signaling: Considering that BMP4 addition was shown to slow down JGES reprogramming, it raises the question of whether inhibiting BMP4 or downstream targets of BMP4 signaling could enhance the efficiency of reprogramming. Investigating this aspect would strengthen and broaden the author's conclusions. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 87, 228, 100]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 117, 852, 246]]<|/det|> +We again appreciate very much this insight, BMP4 signaling pathway belongs to the TGF- b super family, of which the SMADs proteins are downstream effectors, Smad6 and Samd7 are inhibitory SMADs of TGF- b signaling9, Smad6 is more specific to BMP4 signaling than Smad710,11. We over- expressed Smad6 and Smad7 individually in JGES reprogramming with or without BMP4 treatment, and show that both SMADs could markedly rescue the inhibition effect caused by BMP4, the rescue efficiency of Smad6 is higher than that of Smad7 which is in accord with the inhibition preference between the two genes. We also add these results into Supplementary figure 1. + +<|ref|>image<|/ref|><|det|>[[207, 263, 730, 421]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 427, 850, 478]]<|/det|> +
a, Histogram shows Oct4 GFP positive iPS colonies numbers in different group, data are mean \(\pm\) s.d., two-sided, unpaired t test; \(n = 3\) independent experiments, \(^{*}p< 0.05\) , \(^{**}p< 0.01\) , \(^{**}p< 0.001\) ; b: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar \(= 5mm\)
+ +<|ref|>text<|/ref|><|det|>[[147, 513, 851, 586]]<|/det|> +4. Drop-out screen logic: The rationale behind the drop-out screen is somewhat unclear. Instead of a dropout to identify factors necessary for pluripotent cells, it might be more informative to perform a drop-out screen to pinpoint the factors required for PrE cell formation. This would focus on understanding the specific components necessary for the observed phenotype rather than pluripotency. + +<|ref|>sub_title<|/ref|><|det|>[[148, 603, 228, 617]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 635, 850, 670]]<|/det|> +We welcome the opportunity to clarify the logic for the drop-out screen experiments. We clarified this part in the manuscript and reorganized the Figures to a better reflect of our drop-out logic. + +<|ref|>text<|/ref|><|det|>[[147, 686, 852, 832]]<|/det|> +We also performed extra experiments to pinpoint the requirement of factors for PrE cell formation. When we dropout every single factor of JGES under BMP4+ condition, the qPCR results show that except for Jdp2's dropout which shows a strong promotion of PrE genes, We hypothesized that the other three factor Glis1, Esrrb and Sall4 may form an interaction network for PrE formation, To overcome this confounding effect and identify which factor is essential for PrE cell formation, we added the four factors individually into OS reprogramming with BMP4 treatment, ad show that that Sall4 is the only factor to increase PrE gene expression level, consistent with notion that BMP4 functions to divert cell fate from pluripotency to PrE. We also add this data into Figure 3i, 3j. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[220, 95, 714, 404]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[145, 415, 847, 428]]<|/det|> +
a, b : Histograms show the qPCR results of PrE gene relative expression level of every group, \(n = 3\) independent experiments.
+ +<|ref|>text<|/ref|><|det|>[[148, 464, 850, 518]]<|/det|> +5. Exploration of BMP4's effects on reprogramming: The paper briefly touches on the dichotomy between BMP4's effects on OCT4-based and SALL4-based reprogramming, which could offer a novel aspect to the study. Expanding on this aspect might provide additional insights. + +<|ref|>sub_title<|/ref|><|det|>[[149, 536, 228, 550]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 567, 851, 658]]<|/det|> +Indeed, the most surprising result is the opposing effect of BMP4 on Oct4- and Sall4- centered reprogramming. We have shown, in our view quite convincingly, that BMP4 can either be a positive or negative factor in reprogramming depending on the factors used, perhaps reflecting the diversity of paths towards pluripotency at present12. Given the complexity of BMP4 mediated pathways, it remains quite surprising that it can exert this unexpected role in cell fate control in vitro13. + +<|ref|>text<|/ref|><|det|>[[148, 674, 851, 819]]<|/det|> +Apart from BMP4 being a reprogramming enhancer, in Oct4- based reprogramming14- 16, NuRD in general has been regarded as a reprogramming barrier in reprogramming system reported so far17,18. However, it is indeed surprising as described above that both BMP4 and NuRD behave quite differently in JGES reprogramming system. As we reported in our last paper, Sall4 is important to drive JGES reprogramming, and that NuRD is the most important interaction partner of SALL4. In this paper, we reveal further surprise that BMP4 is inhibitory for JGES reprogramming. The BMP4- Sall4- NuRD axis remains functional even in the context of Oct4- based reprogramming as shown in Figure 3e, 3g, 3h, which strongly suggests that this axis is a robust pathway not recognized until our work. + +<|ref|>text<|/ref|><|det|>[[149, 836, 850, 889]]<|/det|> +However, we feel that our results are clear enough that we do not need to expand excessively. However, the implication remains quite clearly that cell fate control is context dependent and should be examined as carefully as possible as we demonstrated here. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 103, 850, 157]]<|/det|> +6. Methods: The Methods section requires improvement, with several crucial details missing and certain portions being misplaced. Additionally, it is essential to include statistical analysis for the figures, display individual replicates, and provide the Western blot membranes as supplementary figures. + +<|ref|>sub_title<|/ref|><|det|>[[148, 175, 228, 189]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 193, 850, 245]]<|/det|> +We really appreciate this suggestion. We have tried to improved our method details and appended statistical analysis of the figures and manuscript, also added the Western blot membranes into the Statistics Source Data. + +<|ref|>text<|/ref|><|det|>[[149, 318, 404, 332]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 355, 439, 370]]<|/det|> +Reviewer Comments (Round 1: 20210720) + +<|ref|>text<|/ref|><|det|>[[147, 373, 852, 630]]<|/det|> +In this manuscript by Ming and colleagues, the authors explore the role of BMP4 in cell fate switching, when reprogrammed using their previous JGES (Jdp2, Glis1, Esrrb and Sall4) over expression system. Using number of Oct4- GFP positive cells as readout, the authors observe that BMP4 addition reduces the reprogrammed cells both in a dosage and time- dependent manner. Performing scRNA- seq upon JGES induction, BMP4- cells give rise to intermediate state, endothelial and pluripotent cells, while BMP4+ gives rise to intermediate, endothelial and PrECLCs (primitive endoderm- like cells), with both reprogramming yielding \(\sim 20\%\) of total single- cell pool. These PrECLCs transcriptomically are show to be similar to published primitive endoderm (PrE) cells from E4.5- 5.5embryos. The authors subsequently perform a JGES dropout reprogramming screen with and without BMP4, ascertaining ability of BMP4 with Oct4 to reprogram MEFs, and with Sall4 acting antagonistically to BMP4. Using IP- MS, the authors observe perturbed SALL4- NuRD interaction when treating with BMP, an find that BMP4 blocks iPSC reprogramming via disruption of Sall4- NuRD cooperation (N- terminal 12AAs of SALL4). Lastly, the authors show that Sall4DelN12 alone can reset MEFs to induced extra- embryonic state, faster than Sall4WT; and perform blastocyst injections for iPRe- GFP for extra- embryonic intergration. + +<|ref|>text<|/ref|><|det|>[[149, 633, 850, 686]]<|/det|> +The study and results are indeed interesting, the ms is very well written and supported by suitable experiments and analysis. However, the insights from the paper provide marginal gains and mainly improve on authors previous findings. + +<|ref|>text<|/ref|><|det|>[[149, 689, 600, 703]]<|/det|> +The reviewer shares a few major and minor concerns stated below. + +<|ref|>sub_title<|/ref|><|det|>[[149, 727, 225, 740]]<|/det|> +## Comments + +<|ref|>text<|/ref|><|det|>[[149, 744, 720, 759]]<|/det|> +- In figure 2A, it was unclear why the authors chose the BMP4 induction after 2 days? + +<|ref|>sub_title<|/ref|><|det|>[[149, 777, 228, 791]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 809, 851, 900]]<|/det|> +We apologize for this confusion. We normally allowed the cells to be infected with the reprogramming factors for 2 days based on our previous optimizations.. In figure 2A, the "day 2" means 2 days post transfection, when we start the induction process under BMP4+ or BMP4- , "day 7" means 7 days post transfection we start the scRNA- sequencing process, we have changed "day 2" into "transfection for 2 days" in Figure 2a. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 86, 848, 120]]<|/det|> +Figure 1d, highlights that number of Oct4- GFP+ve colonies are same as un- induced (row 1 vs row 3). Figure 1D- E suggest that BMP4 induction in Days0- 3 may not be quite consequential. + +<|ref|>sub_title<|/ref|><|det|>[[148, 138, 228, 152]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 170, 852, 297]]<|/det|> +Again, we appreciate this opportunity to clarify this confusion. The schema chart in Figure 1d shows the number of Oct4- GFP+ clones at different time windows. The condition with BMP4 treatment are colored in blue, and without BMP4 treatment are colored in gray. Row 1 is without BMP4 treatment and row 3 means with BMP4 treatment from day 4 to day 7. Based on these results, we show that BMP4 doesn't inhibit JGES reprogramming efficiency from day 4- day 7. Figure 1d exhibits that BMP4's inhibition effect only occurs in the first three days. We changed Day 7 to Day 0 labels to Day 0 to Day 7 from left to right to make the figure more intuitive. + +<|ref|>text<|/ref|><|det|>[[147, 332, 852, 440]]<|/det|> +In our previously paper, SALL4- NuRD axis is important to silence somatic- related genes which is necessary in the early stage in reprogramming19, Figure 1d also shows that BMP4 dissociates SALL4- NuRD interaction. Figure 1e and f show that the reprogramming efficiency of JGES under different BMP4 dosages from day 0 to day 7. In order to eliminate the high dosage inhibition effect, we applied different BMP4 dosage in JGES, the results show that 1ng/ml BMP4 is able to inhibit half of Oct4- GFP+ clones, demonstrating that BMP4's inhibition function on JGES reprogramming is dosage dependent. + +<|ref|>text<|/ref|><|det|>[[148, 457, 758, 472]]<|/det|> +- In Figure 2B-C, It is unclear whether there no no pluripotent cells from BMP4+ population. + +<|ref|>sub_title<|/ref|><|det|>[[148, 491, 228, 504]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 522, 852, 612]]<|/det|> +Indeed, these is no pluripotent cells in BMP+ population with JGES reprogramming. In Figure 2b- c, BMP4+ populations are colored in red in Figure 2b, pluripotent cell group is colored in red in Figure 2c. When align together carefully, we can find there are very rare BMP4+ populations located in pluripotent group. To make this clear, we added new charts to show BMP4+ and BMP4- populations in different cell types in Figure 2c. We added these charts to Supplementary Figure 2a- c. + +<|ref|>image<|/ref|><|det|>[[210, 630, 785, 784]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 795, 839, 827]]<|/det|> +
a: UMAP shows the cells distribution of BMP4+ and BMP4- conditions; b: Stacked barplot shows the cell proportion in each cell type.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 138]]<|/det|> +- Additionally a subset of BMP4+ are shared with MEF cluster (Pink cells in yellow cluster, Fig2B) even after 7 days, are these non-reprogrammed cells or different state (similar cells are not observed in BMP4+ population). Also look very diff from ESCs. + +<|ref|>sub_title<|/ref|><|det|>[[148, 157, 228, 170]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 188, 850, 241]]<|/det|> +We indeed noticed the subset of BMP4+ which shared the same cluster with MEF in Fig 2b. However, we don't think they are non- reprogrammed MEF cells, but at a different state from MEF cells as well as ESCs, based on the following reason. + +<|ref|>text<|/ref|><|det|>[[147, 258, 852, 496]]<|/det|> +Firstly, we analysed the gene expression pattern between the two subsets, there are 90 genes commonly expressed in both subsets, and 51 genes specific expressed in MEFs, 157 genes specifically in BMP4+ (a). GO analysis show the genes commonly expressed are related to wound healing, collagen fibril organization, positive regulation of cell- substrate adhesion and extracellular structure organization. Genes, specifically expressed in MEF are related to extracellular matrix assembly, ossification, bone mineralization and biomineral tissue development. Finally, genes, specifically expressed in BMP4+ are related to regulation of protein stability, regulation of epithelial cell migration, Wnt signaling pathway and cell- cell signaling by Wnt (b). MEF subset specific express Atp5o, Srp54b, Aspn etc, but BMP4+ subset specific express Ins2, Pgk1, Apoe etc (c). In terms of gene quantity, 52.7% genes expressed in BMP4+ subset are different from MEF cells, in terms of gene function, BMP4+ subset is also very different from MEF cells, and so BMP4+ subset within the MEF cluster should be a different state from MEF cells. So, based on these results, we believe that these cells are different from MEFs, but at different stages as described. + +<|ref|>image<|/ref|><|det|>[[183, 512, 792, 864]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 873, 850, 906]]<|/det|> +
a: Heatmap shows the common and different features between MEF and BMP4+ cells in cluster 2; b: Bar plots show the top 5 GO terms of gene sets; c: UMAP shows the expression of selected marker genes
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 103, 850, 138]]<|/det|> +- The authors report that PrECLCs are PrE cells based on bulk markers and single-cell comparison. The PrE markers are non-zero in BMP4-ve cells? What is the explanation for this? + +<|ref|>sub_title<|/ref|><|det|>[[149, 156, 228, 170]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 187, 852, 334]]<|/det|> +Based on single- cell comparison, bulk markers, IF experiments, indeed we have detected a subset of cells from JGES reprogramming with BMP4 treatment are PrE cell- like cells. The non- zero PrE markers in the BMP4- group is because there are a background level \(\sim 0.16\%\) PrECLCs in BMP4- cluster from our scRNA- seq data shown in Figure 2f colored in green. This is because SALL4 alone could reset MEF cells to PrECLCs state at very low efficiency without BMP4 treatment as shown in Figure 6a. We think PrECLCs arise from JGES reprogramming as an alternative fate and indeed over- expressing PrE marker genes in JGES could decrease Oct4- GFP+ clone number as shown in Figure 2h. Therefore, JGES reprogramming generates a background level of PrE, making up markers as non- zero in BMP4- group. + +<|ref|>text<|/ref|><|det|>[[148, 350, 850, 404]]<|/det|> +- It would be useful to visualise other PrE markers at single-cell level in Fig S2D, to see if the distinction between BMP4+ to PrE/PrCLC and BMP4- to pluripotent.The reviewer feels that correlation values could be plotted (instead of high low) to appreciate magnitude of similarity + +<|ref|>sub_title<|/ref|><|det|>[[149, 421, 228, 435]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 452, 852, 636]]<|/det|> +We appreciate this advice.To better compare the states of BMP4+ to PrE/PrECLC and BMP4- to pluripotent cells, we used a new dataset20 whose quality is superior to the one previously used21, PrECLCs of BMP4+ can co- localize with E4.5- 5.5 PrE, pluripotency cells of BMP4- can co- localize with E4.5- 5.5 epiblast (a, b).We also visualized additional pluripotency and PrE markers among the two clusters at single cell level, and observed shared gene expression as well as differential gene expression between reprogramming cells and in vivo cells(c, d, e, f). We also used the CCA algorithm to integrate reprogramming data with mouse embryo data of E4.5- E5.522. The results show that PrECLCs are similar to in vivo PrE cells, with a Pearson correlation coefficient of 0.88, while Pluripotent cells are similar to in vivo Epiblast cells, with a correlation coefficient of 0.86 (g). We updated it to Supplementary Figure 2e, 2f, 2g in the new manuscript version. + +<|ref|>image<|/ref|><|det|>[[175, 653, 820, 790]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[205, 88, 711, 440]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 480, 850, 532]]<|/det|> +
a, b: UMAP shows the integration of PrECLCs/Pluripotent cells' data in this study and Epiblast/PrE data of Sala2019 in vivo; c, d, e, f: UMAP shows the expression of marker genes at single cell level; g: Correlation heatmap of reprogramming cells and developmental cells.
+ +<|ref|>text<|/ref|><|det|>[[148, 600, 850, 654]]<|/det|> +- In Fig 3b (-sall4) and 3d (oct4, -sall4), the authors should comment on the target gene sets and their activation (cooperativity vs exclusivity), during Oct4 and BMP4 mediated reprogramming. Which sites are unique vs co-bound with Sall4, and regulated? + +<|ref|>sub_title<|/ref|><|det|>[[149, 672, 228, 685]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 702, 852, 885]]<|/det|> +We appreciate this insightful suggestion. To answer this question, we performed bulk RNA- sequence on JGE vs JGES and, JGEO vs JGESO under BMP4+ and BMP4- condition, and evaluated BMP4's function on pluripotency gene sites and PrE related gene sites with or without Sall4. The results show that BMP4 can decrease pluripotency genes expression dramatically when Sall4 exists both in JGE vs JGES and JGEO vs JGESO (a b); BMP4 can decrease pluripotency genes expression dramatically when Sall4 exists both in JGE vs JGES and JGEO vs JGESO, BMP4 can also increase PrE genes expression dramatically when Sall4 presents in JGE vs JGES, in JGEO vs JGESO, BMP4 could also upgrade PrE genes expression slightly(c, d). All these data indicate that BMP4 functions to inhibit pluripotency gene and promote PrE gene sites when Sall4 present. We added the results to Supplementary Figure 3a, 3b, 3c, 3d. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[275, 88, 720, 475]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 480, 852, 604]]<|/det|> +a. Box plot shows the expression levels of pluripotency genes between conditions with and without BMP4 treatment at day 7 during JGE, JGES, JGEO, JGESO reprogramming; b, Box plot shows the fold changes in the expression of pluripotency genes between conditions with and without BMP4 treatment at day 7, during the JGE, JGES, JGEO, JGESO reprogramming, represented on a logarithmic scale; c, Box plot shows the expression levels of PrE related genes between conditions with and without BMP4 treatment at day 7 during JGE, JGES, JGEO, JGESO reprogramming; d, Box plot shows the fold changes in the expression of PrE related genes between conditions with and without BMP4 treatment at day 7, during the JGE, JGES, JGEO, JGESO reprogramming, represented on a logarithmic scale. + +<|ref|>text<|/ref|><|det|>[[148, 622, 851, 675]]<|/det|> +- In Fig5, the authors should describe number/percentage of PrECLC cells between WT and Sall4DelN12. Which other cell types emerge during reprogramming (pluripotent, endoderm, intermediate and percentages. Since the FPKM counts are non-zero; the cell-fate switch is likely to be non-binary decision. + +<|ref|>sub_title<|/ref|><|det|>[[149, 693, 228, 706]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 725, 852, 871]]<|/det|> +Indeed, we agree with the reviewer's suggestion. Here we show the IF results of GATA4+ clone number (a) and whole well screening pictures (b) between WT and delN12- SALL4 PrE induction at day 11, delN12- SALL4 group is much higher than WT- SALL4. We agree with the opinion, the cell- fate switch is not a binary decision between BMP4+ and BMP4- group of JGES reprogramming, not even in WT- SALL4 and delN12- SALL4 single factor induced reprogramming, PrECLCs cluster is not the only cell group which obtain a proportion increase after BMP4 treatment, however, PrECLCs is a result of BMP4 induced SALL4- NuRD dissociation in JGES reprogramming, SALL4- NuRD (delN12- SALL4) dissociation leads to pluripotency inhibition (c, d) and PrE cell fate promotion (e). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 175]]<|/det|> +In the single factor induced reprogramming, we checked the expression pattern of pluripotency, endoderm and intermediate related marker genes, based on bulk RNA- sequence data, unlike the expression pattern of PrE genes, delN12- SALL4 doesn't show an improvement effect on these cell lineage (f, g, h). Although PrE cell fate may not be the only direction of delN12- induced MEF cells, additional function will be discussed further in our subsequent research. + +<|ref|>image<|/ref|><|det|>[[156, 191, 825, 644]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 652, 852, 795]]<|/det|> +a, Histogram shows IF results of GATA4 positive iPRE colonies number in different group, data are mean \(\pm\) s.d., two- sided, unpaired t test; \(\bar{\mathsf{n}} = 3\) independent experiments, \(^{*}\mathsf{p}< 0.05\) , \(^{**}p< 0.01\) , \(^{***}p< 0.001\) ; b: Pictures show the in situ whole well screening of GATA4 positive iPRE colonies number of different group, scale bar \(= 10\mathsf{mm}\) c, Histogram shows Oct4 GFP positive iPSE colonies number in different group, data are mean \(\pm\) s.d., two- sided, unpaired t test; \(\bar{\mathsf{n}} = 3\) independent experiments, \(^{*}\mathsf{p}< 0.05\) , \(^{**}p< 0.01\) , \(^{***}p< 0.001\) ; d: Pictures show the in situ whole well screening of Oct4 GFP positive clone number of different group, scale bar \(= 5\mathsf{mm}\) ; e, Histograms show the qPCR results of PrE gene relative expression level of every group, \(\bar{\mathsf{n}} = 3\) independent experiments; f, g, h: Line charts show the expression pattern of different cell lineage markers between SALL4WT and SALL4delN12. + +<|ref|>text<|/ref|><|det|>[[147, 832, 848, 866]]<|/det|> +- Similarly, statistics of Fig5DF and EG could be provided. What percentage of cells of the total were GFP positive. + +<|ref|>title<|/ref|><|det|>[[148, 871, 228, 884]]<|/det|> +# Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 268]]<|/det|> +We again appreciate this suggestion. However it is really hard to quantify the exact GFP positive cell percentage in the whole yolk sac at E12.5 chimeric embryos. We performed the blastocyst injection experiments to test iPrE's in vivo developmental ability. In previous studies, in vivo developmental potential of PrESCs (primitive endoderm stem cells) separated from blastocyst are also tested by this way 6. However, the chimeric efficiency of iPrEs is indeed lower than PrESCs (Supplementary Figure 6g, 6h). Additionally, it is very hard to digest the GFP positive cells from the yolk sac for it has very condense extra- cellular matrix and complicated tissue structure, our previous study also didn't show the exact cell percentage of the chimerism cells, because of these limitations. This technological difficulties are formidable enough to provide a more exact assessment. Nevertheless, we are trying to enhance the induction and chimeric efficiency of iPrE cells. + +<|ref|>text<|/ref|><|det|>[[148, 286, 191, 299]]<|/det|> +Minor + +<|ref|>text<|/ref|><|det|>[[150, 304, 466, 318]]<|/det|> +- The introduction seems brief and generalised. + +<|ref|>sub_title<|/ref|><|det|>[[149, 337, 228, 351]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 369, 850, 403]]<|/det|> +Highly appreciate your suggestion, we improved the introduction part of this manuscript. By providing more relevant background on PrE, BMP and also early cell fate decisions. + +<|ref|>text<|/ref|><|det|>[[149, 438, 850, 472]]<|/det|> +- In the discussion, the authors do not comment whether BMP4 mediated cell fate changes are due to JGES TF cooperativity vs exclusivity in action? + +<|ref|>sub_title<|/ref|><|det|>[[149, 491, 228, 504]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 522, 852, 705]]<|/det|> +Reviewer #1 also asked a similar question. We performed the JGES TF dropout experiments and added the TF one by one into OS- derived reprogramming with BMP4 treatment again, after that we check the PrE genes expression among them by qPCR, the results indicate that except Jdp2 dropout has a strong promotion of PrE genes expression, the other three factor dropout all inhibit PrE cell fate, Glis1, Esrrb and Sal/4 may form an cooperativity interaction network for PrE formation and Jdp2 is a antagonists in PrE cell fate formation (a), however, in OS reprogramming, Sal/4 is the only factor to increase PrE gene expression level (b), Sal/4 is important in PrE cell fate formation both in JGES and OS system under BMP4 treatment. We revised the discussion by focusing more on the effect of SALL4 more and its impact with BMP4 treatment. We are not sure about cooperativity or exclusivity. It is clear that BMP4 is targeting Sal/4- NuRD for the cell fate decisions. + +<|ref|>image<|/ref|><|det|>[[266, 721, 714, 857]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[264, 87, 731, 230]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[145, 250, 848, 264]]<|/det|> +
a, b: Histograms show the qPCR results of PrE gene relative expression level of every group, \(n = 3\) independent experiments.
+ +<|ref|>text<|/ref|><|det|>[[148, 300, 850, 336]]<|/det|> +- The authors could double check the scalebar between both panels in in Fig5c scale. In the print/web version, lower panel seems more magnified + +<|ref|>sub_title<|/ref|><|det|>[[149, 353, 228, 367]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 385, 849, 419]]<|/det|> +Thanks for this suggestion and sorry for the mistake we made, we change the picture we used in Figure 6a. + +<|ref|>text<|/ref|><|det|>[[149, 454, 849, 490]]<|/det|> +- What duration and timing of BMP4 induction is most crucial to fate specification in JGES reprogramming? The authors perform a titration and dosage curve, but choose 1 condition for all experiments. + +<|ref|>sub_title<|/ref|><|det|>[[149, 507, 228, 521]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 538, 852, 648]]<|/det|> +According to Figure 1d, e, f, the first three days is the most crucial time window for BMP4 pluripotency inhibition. However, BMP4 has the strongest inhibition on JGES under day0- day7, so we chose this condition. The reason why we perform a titration and dosage curve is to confirm BMP4's inhibition on JGES reprogramming is not due to nonspecific effect. Since \(10 \text{ng / ml}\) BMP4 has been proved to be a reprogramming promoter in previously studies14,23, is also an effective inhibition dosage in Figure 1e, so we choose \(10 \text{ng / ml}\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 87, 852, 900]]<|/det|> +1 Graham, S. J. et al. BMP signalling regulates the pre-implantation development of extraembryonic cell lineages in the mouse embryo. Nat Commun 5, 5667, doi:10.1038/ncomms6667 (2014).2 Dudakovic, A. et al. Histone deacetylase inhibition destabilizes the multi-potent state of uncommitted adipose-derived mesenchymal stromal cells. J Cell Physiol 230, 52- 62, doi:10.1002/jcp.24680 (2015).3 Dudakovic, A. et al. Histone deacetylase inhibition promotes osteoblast maturation by altering the histone H4 epigenome and reduces Akt phosphorylation. J Biol Chem 288, 28783- 28791, doi:10.1074/jbc.M113.489732 (2013).4 Schroeder, T. M., Nair, A. K., Staggs, R., Lamblin, A. F. & Westendorf, J. J. Gene profile analysis of osteoblast genes differentially regulated by histone deacetylase inhibitors. BMC Genomics 8, 362, doi:10.1186/1471- 2164- 8- 362 (2007).5 Elling, U., Klasen, C., Eisenberger, T., Anlag, K. & Treier, M. Murine inner cell mass- derived lineages depend on SalI4 function. Proc Natl Acad Sci U S A 103, 16319- 16324, doi:10.1073/pnas.0607884103 (2006).6 Ohinata, Y. et al. Establishment of mouse stem cells that can recapitulate the developmental potential of primitive endoderm. Science 375, 574- 578, doi:10.1126/science.aay3325 (2022).7 Schorn, A. J., Gutbrod, M. J., LeBlanc, C. & Martienssen, R. LTR- Retrotransposon Control by tRNA- Derived Small RNAs. Cell 170, 61- 71.e11, doi:10.1016/j.cell.2017.06.013 (2017).8 Tosenberger, A. et al. A multiscale model of early cell lineage specification including cell division. NPJ Syst Biol Appl 3, 16, doi:10.1038/s41540- 017- 0017- 0 (2017).9 Hanna, A. & Frangogiannis, N. G. The Role of the TGF- \(\beta\) Superfamily in Myocardial Infarction. Front Cardiovasc Med 6, 140, doi:10.3389/fcvm.2019.00140 (2019).10 Choi, K. C. et al. Smad6 negatively regulates interleukin 1- receptor- Toll- like receptor signaling through direct interaction with the adaptor Pellino- 1. Nat Immunol 7, 1057- 1065, doi:10.1038/nl1383 (2006).11 Estrada, K. D., Retting, K. N., Chin, A. M. & Lyons, K. M. Smad6 is essential to limit BMP signaling during cartilage development. J Bone Miner Res 26, 2498- 2510, doi:10.1002/jbrmr.443 (2011).12 Hanna, J. et al. Direct cell reprogramming is a stochastic process amenable to acceleration. Nature 462, 595- 601, doi:10.1038/nature08592 (2009).13 Sadlon, T. J., Lewis, I. D. & D'Andrea, R. J. BMP4: its role in development of the hematopoietic system and potential as a hematopoietic growth factor. Stem Cells 22, 457- 474, doi:10.1634/stemcells.22- 4- 457 (2004).14 Chen, J. et al. BMPs functionally replace Klf4 and support efficient reprogramming of mouse fibroblasts by Oct4 alone. Cell Res 21, 205- 212, doi:10.1038/cr.2010.172 (2011).15 Hayashi, Y. et al. BMP- SMAD- ID promotes reprogramming to pluripotency by inhibiting p16/INK4A- dependent senescence. Proc Natl Acad Sci U S A 113, 13057- 13062, doi:10.1073/pnas.1603668113 (2016).16 Yu, S. et al. BMP4 resets mouse epiblast stem cells to naive pluripotency through ZBTB7A/B- mediated chromatin remodelling. Nat Cell Biol 22, 651- 662, doi:10.1038/s41556- 020- 0516- x (2020).17 Luo, M. et al. NuRD blocks reprogramming of mouse somatic cells into pluripotent stem + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 84, 852, 360]]<|/det|> +cells. Stem Cells 31, 1278- 1286, doi:10.1002/stem.1374 (2013). 18 Rais, Y. et al. Deterministic direct reprogramming of somatic cells to pluripotency. Nature 502, 65- 70, doi:10.1038/nature12587 (2013). 19 Wang, B. et al. The NuRD complex cooperates with SALL4 to orchestrate reprogramming. Nat Commun 14, 2846, doi:10.1038/s41467- 023- 38543- 0 (2023). 20 Pijuan- Sala, B. et al. A single- cell molecular map of mouse gastrulation and early organogenesis. Nature 566, 490- 495, doi:10.1038/s41586- 019- 0933- 9 (2019). 21 Nowotschin, S. et al. The emergent landscape of the mouse gut endoderm at single- cell resolution. Nature 569, 361- 367, doi:10.1038/s41586- 019- 1127- 1 (2019). 22 Butler, A., Hoffman, P., Smibert, P., Papalexi, E. & Satija, R. Integrating single- cell transcriptomic data across different conditions, technologies, and species. Nat Biotechnol 36, 411- 420, doi:10.1038/nbt.4096 (2018). 23 Lin, L. et al. The homeobox transcription factor MSX2 partially mediates the effects of bone morphogenetic protein 4 (BMP4) on somatic cell reprogramming. J Biol Chem 293, 14905- 14915, doi:10.1074/jbc.RA118.003913 (2018). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 415, 98]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 112, 857, 154]]<|/det|> +The authors have satisfactorily responded to all my comments. A final minor point: the authors should carefully check the text for typos, particularly throughout the methods section. + +<|ref|>text<|/ref|><|det|>[[119, 182, 415, 196]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 210, 866, 239]]<|/det|> +In this revised manuscript by Ming and colleagues, the authors have provided answers to most of the raised comments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 87, 425, 100]]<|/det|> +Point- by- point response to the reviewers: + +<|ref|>text<|/ref|><|det|>[[149, 142, 240, 155]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[149, 180, 249, 192]]<|/det|> +Dear reviewer, + +<|ref|>text<|/ref|><|det|>[[149, 198, 850, 249]]<|/det|> +We sincerely appreciate your efforts for considering and reviewing our work again. We have checked and corrected them in the final version. We would like to express our gratitude for your insightful comments and suggestions which have significantly contributed to improve the quality of our work. + +<|ref|>text<|/ref|><|det|>[[149, 273, 240, 286]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[149, 310, 249, 322]]<|/det|> +Dear reviewer, + +<|ref|>text<|/ref|><|det|>[[149, 328, 850, 379]]<|/det|> +Thank you for your invaluable time and efforts dedicated to reviewing our manuscript. We are so happy that our previous revised manuscript has provided answers to most of your comments. We sincerely acknowledge your rigorous evaluation and comments, which have immensely improved our work. + +<|ref|>text<|/ref|><|det|>[[149, 402, 216, 415]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[149, 439, 216, 453]]<|/det|> +Duanqing + +<--- Page Split ---> diff --git a/peer_reviews/13bf6458fcf02e570f84c76bf84696729113a9f983cbf367b27e04ad99d1e068/supplementary_1_Peer Review Information/images_list.json b/peer_reviews/13bf6458fcf02e570f84c76bf84696729113a9f983cbf367b27e04ad99d1e068/supplementary_1_Peer Review Information/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/13bf6458fcf02e570f84c76bf84696729113a9f983cbf367b27e04ad99d1e068/supplementary_1_Peer Review Information/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/13bf6458fcf02e570f84c76bf84696729113a9f983cbf367b27e04ad99d1e068/supplementary_1_Peer Review Information/supplementary_1_Peer Review Information.mmd b/peer_reviews/13bf6458fcf02e570f84c76bf84696729113a9f983cbf367b27e04ad99d1e068/supplementary_1_Peer Review Information/supplementary_1_Peer Review Information.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7957923b60c43cdd3755002401e3fd46b339c985 --- /dev/null +++ b/peer_reviews/13bf6458fcf02e570f84c76bf84696729113a9f983cbf367b27e04ad99d1e068/supplementary_1_Peer Review Information/supplementary_1_Peer Review Information.mmd @@ -0,0 +1,257 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Structural and Molecular Biology Manuscript Title: GPCR activation mechanisms across classes and macro/microscales Corresponding author name(s): David Gloriam + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +2nd Jun 2021 + +Dear David, + +Thank you again for submitting your manuscript "GPCR activation mechanisms across classes and macro/microscales". I apologize for the delay in responding, which, as you already know, resulted from the difficulty in obtaining suitable referee reports. Nevertheless, we now have comments (below) from the 2 reviewers who evaluated your paper. In light of those reports, we remain interested in your study and would like to see your response to the comments of the referees, in the form of a revised manuscript. + +You will see that the reviewers (both experts in GPCR structure/function) are positive about the interest and quality of the study, and reviewer 2 recommends publication as is. However, reviewer 1 made several useful suggestions to improve the presentation of the findings and requested experimental validation of key results, which we agree would greatly strengthen the manuscript. + +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +Please be sure to address all concerns of the referees in full in a point- by- point response and highlight all changes in the revised manuscript text file. If you have comments that are intended for editors only, please include those in a separate cover letter. + +We expect to see your revised manuscript within 12 weeks. If you cannot send it within this time, please contact us to discuss an extension; we would still consider your revision, provided that no similar work has been accepted for publication at NSMB or published elsewhere. + +<--- Page Split ---> + +# natureresearch + +As you already know, we put great emphasis on ensuring that the methods and statistics reported in our papers are correct and accurate. As such, if there are any changes that should be reported, please submit an updated version of the Reporting Summary along with your revision. + +Please follow the links below to download these files: + +Reporting Summary: https://www.nature.com/documents/nr- reporting- summary.pdf + +Please note that the form is a dynamic 'smart pdf' and must therefore be downloaded and completed in Adobe Reader. + +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- research/editorial- policies/image- integrity">Digital Image Integrity Guidelines.
+ +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +SOURCE DATA: we urge authors to provide, in tabular form, the data underlying the graphical representations used in figures. This is to further increase transparency in data reporting, as detailed in this editorial (http://www.nature.com/nsmb/journal/v22/n10/full/nsmb.3110. html). Spreadsheets can be submitted in excel format. Only one (1) file per figure is permitted; thus, for multi- paneled figures, the source data for each panel should be clearly labeled in the Excel file; alternately the data can be provided as multiple, clearly labeled sheets in an Excel file. When submitting files, the title field should indicate which figure the source data pertains to. We encourage our authors to provide source data at the revision stage, so that they are part of the peer- review process. + +Data availability: this journal strongly supports public availability of data. All data used in accepted papers should be available via a public data repository, or alternatively, as Supplementary Information. If data can only be shared on request, please explain why in your Data Availability Statement, and also in the correspondence with your editor. Please note that for some data types, deposition in a public repository is mandatory - more information on our data deposition policies and available repositories can be found below: + +https://www.nature.com/nature- research/editorial- policies/reporting- standards#availability- of- data + +While we encourage the use of color in preparing figures, please note that this will incur a charge to partially defray the cost of printing. Information about color charges can be found at http://www.nature.com/nsmb/authors/submit/index.html#costs + +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by + +<--- Page Split ---> + +# natureresearch + +clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please use the link below to submit your revised manuscript and related files: + +## [READACTED] + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +Kind regards, Florian + +Florian Ullrich, Ph.D. Associate Editor Nature Structural & Molecular Biology ORCID 0000- 0002- 1153- 2040 + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: + +Hauser et al. used a newly developed online GPCR structure analysis platform to investigate the GPCR activation mechanisms. The authors analyzed all available 488 structures from different GPCR classes and presented a molecular map for GPCR activation, ligand binding, and G protein coupling. The newly developed online GPCR structure analysis platform is useful and easy to navigate. Using this platform, the authors provided macro and micro switches for GPCR activation. The results suggested new activation switches along with activation switches that have been suggested by other studies. Overall, the manuscript suggests novel findings that would provide valuable information for the structural mechanism of GPCR activation. There are, however, a few issues that should be addressed to improve the manuscript. + +## Major comments + +1. Although they have provided the detailed information as supplementary data, It would be nice if the authors provide more detailed information about activation structures (agonist-bound or G protein-bound or arrestin-bound states) analyzed in the manuscript text. + +2. Would the analysis results provide different macro or micro switches that discern the G protein binding and arrestin binding or selectivity for G protein subtypes? + +3. It has been suggested that there are sequential conformational changes during GPCR activation and G protein coupling, and the complex structures are final stage structures (DOI: 10.1016/j.cell.2019.04.022, 10.1016/j.cell.2019.04.021). Please consider discussing this issue along + +<--- Page Split ---> + +# natureresearch + +with the analysis results of the manuscript. + +4. Please provide experimental evidence for the newly suggested GPCR activation switches. + +Minor comments + +1. On page 4 and Fig. 3a class F, should it be \(52\%\) and \(48\%\) , not \(62\%\) (line 25) and \(38\%\) ? +2. Please consider rewriting a sentence on page 5 line 15, "We next ... pairs confirms." + +Reviewer #2: + +Remarks to the Author: + +This manuscript by Kooistra et al., Babu and Gloriam provides an integrated and comprehensive analysis of the movements and transduction pathways shared and different among the four major GPCR families as they transit from inactivated to activated states. A great strength of the work is their use of distance pairs, rather than more traditional superposition of structures and RMSDs, to find conserved interactions and switches among inactive- and active- stabilizing residue pairs, and switch residues implicated in both. A key contribution will be the reduction to groups of these residues that define the states among each of the GPCR families. From these studies both granular analyses of transduction pathways emerge, as do more general features (e.g., that residue rotomer switches are rare, the centrality of TM Helix 3, the ubiquitousness of helix rotation, often over rotomer changes, and the greater similarities of among receptors within families than within active vs inactive states). Many of these will provide guidance to the community to drive specific research questions (e.g., what state is my receptor in, how to I drive that/interrupt that by mutation, what is such- and- so ligand doing...?). I thus find this a strong manuscript that will interest the community, and I support publication. As I have seen it previously (and liked it then), and since most of my key critiques have been addressed, I think the manuscript can be published as is. + +## Author Rebuttal to Initial comments + +We thank all Reviewers for the insightful and positive comments which have improved the manuscript and online resources. We respond to each comment below. In addition, we have also incorporated recent structural templates for classes C and F (class A and B1 already had strong coverage) and updated all associated figures and text accordingly. We look forward to your opinion on the revised manuscript. + +Reviewer #1: + +<--- Page Split ---> + +# natureresearch + +Hauser et al. used a newly developed online GPCR structure analysis platform to investigate the GPCR activation mechanisms. The authors analyzed all available 488 structures from different GPCR classes and presented a molecular map for GPCR activation, ligand binding, and G protein coupling. + +The newly developed online GPCR structure analysis platform is useful and easy to navigate. Using this platform, the authors provided macro and micro switches for GPCR activation. The results suggested new activation switches along with activation switches that have been suggested by other studies. Overall, the manuscript suggests novel findings that would provide valuable information for the structural mechanism of GPCR activation. There are, however, a few issues that should be addressed to improve the manuscript. + +We thank the reviewer for the nice summary of the paper and its scope providing both macro and micro switches for GPCR activation, including many new activation switches (not reported for classes B1, C and F before). Furthermore, we highly appreciate the confirmation of that the novel findings provide valuable information about the structural mechanism of GPCR activation, and of the utility of the online structure analysis platform. + +## Major comments + +1. Although they have provided the detailed information as supplementary data, It would be nice if the authors provide more detailed information about activation structures (agonist-bound or G proteinbound or arrestin-bound states) analyzed in the manuscript text. + +We have added more detailed information about active structures in all places where specific receptors are discussed or where the type of complex could be expected to affect the conclusions. As it is not possible to list all complexed proteins and ligands for all active state receptors investigated, for the other places of the text we have added additional references to the relevant supplementary data. All representative active state structures used for the analyses are in the G protein- bound active state. No arrestin- bound states have gone into the analysis of the activation state comparisons. + +2. Would the analysis results provide different macro or micro switches that discern the G protein binding and arrestin binding or selectivity for G protein subtypes? + +This particular paper focuses on the common activation mechanisms that govern the stabilization of an inactive and active state, respectively. It solely uses G protein- bound templates, as these are at the top of the signaling cascade and have a shared structural scaffold allowing comparable active receptor + +<--- Page Split ---> + +# natureresearch + +states, which is a prerequisite of our comparative structure analysis approach. Other studies have described molecular mechanisms (DOI: 10.1038/s41586- 018- 0077- 3, 10.1038/s41594- 018- 0071- 3) and motifs (DOI: 10.1038/s41467- 019- 09204- y, DOI: 10.1016/j.cell.2017.07.002) involved in GPCR- mediated arrestin activation. + +It would indeed be intriguing to investigate G protein family specific determinants of binding and activation. However, there are not sufficient templates yet to do that in a comprehensive comparative fashion across the GPCR classes and G protein families. Such an analysis would, conversely to this, not identify common activation determinants for a given GPCR class but those unique to a G protein family. Such an analysis would therefore have a larger focus on determinants of G protein binding selectivity, which has also been studied previously (e.g. DOI: 10.1038/nature22070) using a sequence- based approach. We suggest that structure- based comparisons across GPCR classes and G protein families are revisited when the coverage by structural templates is improved. + +3. It has been suggested that there are sequential conformational changes during GPCR activation and G protein coupling, and the complex structures are final stage structures (DOI: 10.1016/j.cell.2019.04.022, 10.1016/j.cell.2019.04.021). Please consider discussing this issue along with the analysis results of the manuscript. + +Indeed, during GPCR activation more transient intermediate states can form and the complex structures in our analysis represent the stable nucleotide- free GPCR- G protein "final stage" complexes. To reflect this, we have added the following text to the Discussion: + +It has furthermore been suggested that there are sequential conformational changes during GPCR activation and G protein coupling with transient intermediate states facilitating the transition of the extensive conformational rearrangement, which is not captured by currently available complex structures. (10.1016/j.cell.2019.04.022, 10.1016/j.cell.2019.04.021). The proposed intermediate state complexes may require additional state determinants beyond the ones identified herein. Hence, going forward, it will be important to combine structural studies with biophysical investigations such as FRET- based systems (https://doi.org/10.1038/nature22354), DEER- (10.1073/pnas.2013904117), NMR (10.1073/pnas.2009786117) or even mass spectroscopy (10.1016/j.sbi.2021.03.014) for monitoring specific interactions in more infrequent conformations. + +<--- Page Split ---> + +# natureresearch + +4. Please provide experimental evidence for the newly suggested GPCR activation switches. + +We have added mutagenesis data generated by Franziska M. Heydenreich, Dmitry B. Veprintsev and Michel Bouvier. This confirms that mutations of predicted state-changing residues have a larger effect on potency (but not on efficacy) than do predicted non-state changing residues. We also provide a structural mapping of the tested mutations showing a clustering in the transduction pathway bridging the ligand and G protein sites. + +## Minor comments + +1. On page 4 and Fig. 3a class F, should it be \(52\%\) and \(48\%\) , not \(62\%\) (line 25) and \(38\%\) ? + +We thank the Reviewer for spotting this error. It has now been corrected. + +2. Please consider rewriting a sentence on page 5 line 15, "We next ... pairs confirms." + +This sentence has been corrected to "We next investigated single helix rearrangements across 13 receptor inactive/active state structure pairs.". + +## Reviewer #2: + +## Remarks to the Author: + +This manuscript by Kooistra et al., Babu and Gloriam provides an integrated and comprehensive analysis of the movements and transduction pathways shared and different among the four major GPCR families as they transit from inactivated to activated states. A great strength of the work is their use of distance pairs, rather than more traditional superposition of structures and RMSDs, to find conserved interactions and switches among inactive- and active- stabilizing residue pairs, and switch residues implicated in both. A key contribution will be the reduction to groups of these residues that define the states among each of the GPCR families. From these studies both granular analyses of transduction pathways emerge, as do more general features (e.g., that residue rotomer switches are rare, the centrality of TM Helix 3, the ubiquitousness of helix rotation, often over rotomer changes, and the + +<--- Page Split ---> + +# natureresearch + +greater similarities of among receptors within families than within active vs inactive states). Many of these will provide guidance to the community to drive specific research questions (e.g., what state is my receptor in, how to I drive that/interrupt that by mutation, what is such- and- so ligand doing...?). I thus find this a strong manuscript that will interest the community, and I support publication. As I have seen it previously (and liked it then), and since most of my key critiques have been addressed, I think the manuscript can be published as is. + +We thank Reviewer 2 for reviewing this manuscript again, which has indeed been revised after review by another journal. We are very pleased to get the solid confirmation of the value of the new approaches, and that the analysis will be able to guide future studies seeking to answer yet unsolved questions about receptor activation. + +## Decision Letter, first revision: + +12th Aug 2021 + +Dear David, + +Thank you for submitting your revised manuscript "GPCR activation mechanisms across classes and macro/microscales" (NSMB- A44783A). It has now been seen by one of the original referees and their comments are below. The reviewer finds that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Structural & Molecular Biology, pending minor revisions to comply with our editorial and formatting guidelines. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +\(< b>\) To facilitate our work at this stage, we would appreciate if you could send us the main text as a word file. Please make sure to copy the NSMB account (cc'ed above). \(< /b>\) + +Thank you again for your interest in Nature Structural & Molecular Biology Please do not hesitate to contact me if you have any questions. + +Kind regards, Florian + +Florian Ullrich, Ph.D. Associate Editor Nature Structural & Molecular Biology ORCID 0000- 0002- 1153- 2040 + +<--- Page Split ---> + +# natureresearch + +Reviewer #1 (Remarks to the Author): + +The authors resolved all the concerns that I raised. + +## Final Decision Letter: + +22nd Sep 2021 + +Dear David, + +We are now happy to accept your revised paper "GPCR activation mechanisms across classes and macro/microscales" for publication as a Article in Nature Structural & Molecular Biology. + +Acceptance is conditional on the manuscript's not being published elsewhere and on there being no announcement of this work to the newspapers, magazines, radio or television until the publication date in Nature Structural & Molecular Biology. + +Before the manuscript is sent to the printers, we shall make any detailed changes in the text that may be necessary either to make it conform with house style or to make it intelligible to a wider readership. 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I apologize for the delay in responding, which, as you already know, resulted from the difficulty in obtaining suitable referee reports. Nevertheless, we now have comments (below) from the 2 reviewers who evaluated your paper. In light of those reports, we remain interested in your study and would like to see your response to the comments of the referees, in the form of a revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 604, 864, 666]]<|/det|> +You will see that the reviewers (both experts in GPCR structure/function) are positive about the interest and quality of the study, and reviewer 2 recommends publication as is. However, reviewer 1 made several useful suggestions to improve the presentation of the findings and requested experimental validation of key results, which we agree would greatly strengthen the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 679, 877, 725]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[115, 738, 877, 784]]<|/det|> +Please be sure to address all concerns of the referees in full in a point- by- point response and highlight all changes in the revised manuscript text file. If you have comments that are intended for editors only, please include those in a separate cover letter. + +<|ref|>text<|/ref|><|det|>[[115, 798, 843, 844]]<|/det|> +We expect to see your revised manuscript within 12 weeks. If you cannot send it within this time, please contact us to discuss an extension; we would still consider your revision, provided that no similar work has been accepted for publication at NSMB or published elsewhere. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 879, 188]]<|/det|> +As you already know, we put great emphasis on ensuring that the methods and statistics reported in our papers are correct and accurate. As such, if there are any changes that should be reported, please submit an updated version of the Reporting Summary along with your revision. + +<|ref|>text<|/ref|><|det|>[[115, 202, 510, 217]]<|/det|> +Please follow the links below to download these files: + +<|ref|>text<|/ref|><|det|>[[115, 233, 591, 263]]<|/det|> +Reporting Summary: https://www.nature.com/documents/nr- reporting- summary.pdf + +<|ref|>text<|/ref|><|det|>[[115, 277, 870, 308]]<|/det|> +Please note that the form is a dynamic 'smart pdf' and must therefore be downloaded and completed in Adobe Reader. + +<|ref|>text<|/ref|><|det|>[[115, 337, 845, 383]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- research/editorial- policies/image- integrity">Digital Image Integrity Guidelines. + +<|ref|>text<|/ref|><|det|>[[115, 396, 857, 442]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[115, 455, 879, 576]]<|/det|> +SOURCE DATA: we urge authors to provide, in tabular form, the data underlying the graphical representations used in figures. This is to further increase transparency in data reporting, as detailed in this editorial (http://www.nature.com/nsmb/journal/v22/n10/full/nsmb.3110. html). Spreadsheets can be submitted in excel format. Only one (1) file per figure is permitted; thus, for multi- paneled figures, the source data for each panel should be clearly labeled in the Excel file; alternately the data can be provided as multiple, clearly labeled sheets in an Excel file. When submitting files, the title field should indicate which figure the source data pertains to. We encourage our authors to provide source data at the revision stage, so that they are part of the peer- review process. + +<|ref|>text<|/ref|><|det|>[[115, 589, 864, 680]]<|/det|> +Data availability: this journal strongly supports public availability of data. All data used in accepted papers should be available via a public data repository, or alternatively, as Supplementary Information. If data can only be shared on request, please explain why in your Data Availability Statement, and also in the correspondence with your editor. Please note that for some data types, deposition in a public repository is mandatory - more information on our data deposition policies and available repositories can be found below: + +<|ref|>text<|/ref|><|det|>[[115, 680, 861, 695]]<|/det|> +https://www.nature.com/nature- research/editorial- policies/reporting- standards#availability- of- data + +<|ref|>text<|/ref|><|det|>[[115, 710, 861, 755]]<|/det|> +While we encourage the use of color in preparing figures, please note that this will incur a charge to partially defray the cost of printing. Information about color charges can be found at http://www.nature.com/nsmb/authors/submit/index.html#costs + +<|ref|>text<|/ref|><|det|>[[115, 769, 874, 858]]<|/det|> +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 841, 174]]<|/det|> +clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[115, 187, 692, 202]]<|/det|> +Please use the link below to submit your revised manuscript and related files: + +<|ref|>sub_title<|/ref|><|det|>[[116, 217, 220, 232]]<|/det|> +## [READACTED] + +<|ref|>text<|/ref|><|det|>[[116, 246, 864, 291]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[115, 306, 857, 336]]<|/det|> +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +<|ref|>text<|/ref|><|det|>[[115, 351, 216, 380]]<|/det|> +Kind regards, Florian + +<|ref|>text<|/ref|><|det|>[[115, 396, 396, 455]]<|/det|> +Florian Ullrich, Ph.D. Associate Editor Nature Structural & Molecular Biology ORCID 0000- 0002- 1153- 2040 + +<|ref|>text<|/ref|><|det|>[[116, 486, 286, 500]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 515, 291, 544]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 545, 875, 679]]<|/det|> +Hauser et al. used a newly developed online GPCR structure analysis platform to investigate the GPCR activation mechanisms. The authors analyzed all available 488 structures from different GPCR classes and presented a molecular map for GPCR activation, ligand binding, and G protein coupling. The newly developed online GPCR structure analysis platform is useful and easy to navigate. Using this platform, the authors provided macro and micro switches for GPCR activation. The results suggested new activation switches along with activation switches that have been suggested by other studies. Overall, the manuscript suggests novel findings that would provide valuable information for the structural mechanism of GPCR activation. There are, however, a few issues that should be addressed to improve the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 695, 241, 708]]<|/det|> +## Major comments + +<|ref|>text<|/ref|><|det|>[[116, 709, 880, 753]]<|/det|> +1. Although they have provided the detailed information as supplementary data, It would be nice if the authors provide more detailed information about activation structures (agonist-bound or G protein-bound or arrestin-bound states) analyzed in the manuscript text. + +<|ref|>text<|/ref|><|det|>[[115, 769, 842, 799]]<|/det|> +2. Would the analysis results provide different macro or micro switches that discern the G protein binding and arrestin binding or selectivity for G protein subtypes? + +<|ref|>text<|/ref|><|det|>[[115, 813, 880, 857]]<|/det|> +3. It has been suggested that there are sequential conformational changes during GPCR activation and G protein coupling, and the complex structures are final stage structures (DOI: 10.1016/j.cell.2019.04.022, 10.1016/j.cell.2019.04.021). Please consider discussing this issue along + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 437, 158]]<|/det|> +with the analysis results of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 172, 795, 189]]<|/det|> +4. Please provide experimental evidence for the newly suggested GPCR activation switches. + +<|ref|>text<|/ref|><|det|>[[115, 203, 241, 217]]<|/det|> +Minor comments + +<|ref|>text<|/ref|><|det|>[[115, 218, 790, 249]]<|/det|> +1. On page 4 and Fig. 3a class F, should it be \(52\%\) and \(48\%\) , not \(62\%\) (line 25) and \(38\%\) ? +2. Please consider rewriting a sentence on page 5 line 15, "We next ... pairs confirms." + +<|ref|>text<|/ref|><|det|>[[115, 291, 217, 306]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 307, 293, 321]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[113, 321, 878, 548]]<|/det|> +This manuscript by Kooistra et al., Babu and Gloriam provides an integrated and comprehensive analysis of the movements and transduction pathways shared and different among the four major GPCR families as they transit from inactivated to activated states. A great strength of the work is their use of distance pairs, rather than more traditional superposition of structures and RMSDs, to find conserved interactions and switches among inactive- and active- stabilizing residue pairs, and switch residues implicated in both. A key contribution will be the reduction to groups of these residues that define the states among each of the GPCR families. From these studies both granular analyses of transduction pathways emerge, as do more general features (e.g., that residue rotomer switches are rare, the centrality of TM Helix 3, the ubiquitousness of helix rotation, often over rotomer changes, and the greater similarities of among receptors within families than within active vs inactive states). Many of these will provide guidance to the community to drive specific research questions (e.g., what state is my receptor in, how to I drive that/interrupt that by mutation, what is such- and- so ligand doing...?). I thus find this a strong manuscript that will interest the community, and I support publication. As I have seen it previously (and liked it then), and since most of my key critiques have been addressed, I think the manuscript can be published as is. + +<|ref|>sub_title<|/ref|><|det|>[[120, 565, 396, 581]]<|/det|> +## Author Rebuttal to Initial comments + +<|ref|>text<|/ref|><|det|>[[115, 600, 881, 672]]<|/det|> +We thank all Reviewers for the insightful and positive comments which have improved the manuscript and online resources. We respond to each comment below. In addition, we have also incorporated recent structural templates for classes C and F (class A and B1 already had strong coverage) and updated all associated figures and text accordingly. We look forward to your opinion on the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 752, 240, 770]]<|/det|> +Reviewer #1: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 863, 198]]<|/det|> +Hauser et al. used a newly developed online GPCR structure analysis platform to investigate the GPCR activation mechanisms. The authors analyzed all available 488 structures from different GPCR classes and presented a molecular map for GPCR activation, ligand binding, and G protein coupling. + +<|ref|>text<|/ref|><|det|>[[115, 207, 872, 318]]<|/det|> +The newly developed online GPCR structure analysis platform is useful and easy to navigate. Using this platform, the authors provided macro and micro switches for GPCR activation. The results suggested new activation switches along with activation switches that have been suggested by other studies. Overall, the manuscript suggests novel findings that would provide valuable information for the structural mechanism of GPCR activation. There are, however, a few issues that should be addressed to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 327, 880, 419]]<|/det|> +We thank the reviewer for the nice summary of the paper and its scope providing both macro and micro switches for GPCR activation, including many new activation switches (not reported for classes B1, C and F before). Furthermore, we highly appreciate the confirmation of that the novel findings provide valuable information about the structural mechanism of GPCR activation, and of the utility of the online structure analysis platform. + +<|ref|>sub_title<|/ref|><|det|>[[115, 488, 245, 503]]<|/det|> +## Major comments + +<|ref|>text<|/ref|><|det|>[[115, 514, 870, 569]]<|/det|> +1. Although they have provided the detailed information as supplementary data, It would be nice if the authors provide more detailed information about activation structures (agonist-bound or G proteinbound or arrestin-bound states) analyzed in the manuscript text. + +<|ref|>text<|/ref|><|det|>[[115, 580, 874, 689]]<|/det|> +We have added more detailed information about active structures in all places where specific receptors are discussed or where the type of complex could be expected to affect the conclusions. As it is not possible to list all complexed proteins and ligands for all active state receptors investigated, for the other places of the text we have added additional references to the relevant supplementary data. All representative active state structures used for the analyses are in the G protein- bound active state. No arrestin- bound states have gone into the analysis of the activation state comparisons. + +<|ref|>text<|/ref|><|det|>[[115, 757, 833, 792]]<|/det|> +2. Would the analysis results provide different macro or micro switches that discern the G protein binding and arrestin binding or selectivity for G protein subtypes? + +<|ref|>text<|/ref|><|det|>[[115, 804, 870, 858]]<|/det|> +This particular paper focuses on the common activation mechanisms that govern the stabilization of an inactive and active state, respectively. It solely uses G protein- bound templates, as these are at the top of the signaling cascade and have a shared structural scaffold allowing comparable active receptor + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 875, 215]]<|/det|> +states, which is a prerequisite of our comparative structure analysis approach. Other studies have described molecular mechanisms (DOI: 10.1038/s41586- 018- 0077- 3, 10.1038/s41594- 018- 0071- 3) and motifs (DOI: 10.1038/s41467- 019- 09204- y, DOI: 10.1016/j.cell.2017.07.002) involved in GPCR- mediated arrestin activation. + +<|ref|>text<|/ref|><|det|>[[114, 254, 874, 401]]<|/det|> +It would indeed be intriguing to investigate G protein family specific determinants of binding and activation. However, there are not sufficient templates yet to do that in a comprehensive comparative fashion across the GPCR classes and G protein families. Such an analysis would, conversely to this, not identify common activation determinants for a given GPCR class but those unique to a G protein family. Such an analysis would therefore have a larger focus on determinants of G protein binding selectivity, which has also been studied previously (e.g. DOI: 10.1038/nature22070) using a sequence- based approach. We suggest that structure- based comparisons across GPCR classes and G protein families are revisited when the coverage by structural templates is improved. + +<|ref|>text<|/ref|><|det|>[[114, 467, 879, 540]]<|/det|> +3. It has been suggested that there are sequential conformational changes during GPCR activation and G protein coupling, and the complex structures are final stage structures (DOI: 10.1016/j.cell.2019.04.022, 10.1016/j.cell.2019.04.021). Please consider discussing this issue along with the analysis results of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 551, 878, 605]]<|/det|> +Indeed, during GPCR activation more transient intermediate states can form and the complex structures in our analysis represent the stable nucleotide- free GPCR- G protein "final stage" complexes. To reflect this, we have added the following text to the Discussion: + +<|ref|>text<|/ref|><|det|>[[114, 644, 868, 808]]<|/det|> +It has furthermore been suggested that there are sequential conformational changes during GPCR activation and G protein coupling with transient intermediate states facilitating the transition of the extensive conformational rearrangement, which is not captured by currently available complex structures. (10.1016/j.cell.2019.04.022, 10.1016/j.cell.2019.04.021). The proposed intermediate state complexes may require additional state determinants beyond the ones identified herein. Hence, going forward, it will be important to combine structural studies with biophysical investigations such as FRET- based systems (https://doi.org/10.1038/nature22354), DEER- (10.1073/pnas.2013904117), NMR (10.1073/pnas.2009786117) or even mass spectroscopy (10.1016/j.sbi.2021.03.014) for monitoring specific interactions in more infrequent conformations. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 172, 783, 189]]<|/det|> +4. Please provide experimental evidence for the newly suggested GPCR activation switches. + +<|ref|>text<|/ref|><|det|>[[115, 200, 864, 291]]<|/det|> +We have added mutagenesis data generated by Franziska M. Heydenreich, Dmitry B. Veprintsev and Michel Bouvier. This confirms that mutations of predicted state-changing residues have a larger effect on potency (but not on efficacy) than do predicted non-state changing residues. We also provide a structural mapping of the tested mutations showing a clustering in the transduction pathway bridging the ligand and G protein sites. + +<|ref|>sub_title<|/ref|><|det|>[[115, 360, 246, 375]]<|/det|> +## Minor comments + +<|ref|>text<|/ref|><|det|>[[115, 387, 747, 404]]<|/det|> +1. On page 4 and Fig. 3a class F, should it be \(52\%\) and \(48\%\) , not \(62\%\) (line 25) and \(38\%\) ? + +<|ref|>text<|/ref|><|det|>[[115, 415, 655, 432]]<|/det|> +We thank the Reviewer for spotting this error. It has now been corrected. + +<|ref|>text<|/ref|><|det|>[[115, 472, 745, 489]]<|/det|> +2. Please consider rewriting a sentence on page 5 line 15, "We next ... pairs confirms." + +<|ref|>text<|/ref|><|det|>[[115, 500, 827, 535]]<|/det|> +This sentence has been corrected to "We next investigated single helix rearrangements across 13 receptor inactive/active state structure pairs.". + +<|ref|>sub_title<|/ref|><|det|>[[115, 635, 240, 653]]<|/det|> +## Reviewer #2: + +<|ref|>sub_title<|/ref|><|det|>[[115, 667, 293, 682]]<|/det|> +## Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[114, 694, 879, 857]]<|/det|> +This manuscript by Kooistra et al., Babu and Gloriam provides an integrated and comprehensive analysis of the movements and transduction pathways shared and different among the four major GPCR families as they transit from inactivated to activated states. A great strength of the work is their use of distance pairs, rather than more traditional superposition of structures and RMSDs, to find conserved interactions and switches among inactive- and active- stabilizing residue pairs, and switch residues implicated in both. A key contribution will be the reduction to groups of these residues that define the states among each of the GPCR families. From these studies both granular analyses of transduction pathways emerge, as do more general features (e.g., that residue rotomer switches are rare, the centrality of TM Helix 3, the ubiquitousness of helix rotation, often over rotomer changes, and the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 879, 252]]<|/det|> +greater similarities of among receptors within families than within active vs inactive states). Many of these will provide guidance to the community to drive specific research questions (e.g., what state is my receptor in, how to I drive that/interrupt that by mutation, what is such- and- so ligand doing...?). I thus find this a strong manuscript that will interest the community, and I support publication. As I have seen it previously (and liked it then), and since most of my key critiques have been addressed, I think the manuscript can be published as is. + +<|ref|>text<|/ref|><|det|>[[114, 263, 883, 335]]<|/det|> +We thank Reviewer 2 for reviewing this manuscript again, which has indeed been revised after review by another journal. We are very pleased to get the solid confirmation of the value of the new approaches, and that the analysis will be able to guide future studies seeking to answer yet unsolved questions about receptor activation. + +<|ref|>sub_title<|/ref|><|det|>[[122, 384, 344, 400]]<|/det|> +## Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[120, 419, 231, 434]]<|/det|> +12th Aug 2021 + +<|ref|>text<|/ref|><|det|>[[115, 448, 204, 463]]<|/det|> +Dear David, + +<|ref|>text<|/ref|><|det|>[[115, 477, 875, 555]]<|/det|> +Thank you for submitting your revised manuscript "GPCR activation mechanisms across classes and macro/microscales" (NSMB- A44783A). It has now been seen by one of the original referees and their comments are below. The reviewer finds that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Structural & Molecular Biology, pending minor revisions to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[115, 567, 860, 614]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[115, 627, 861, 659]]<|/det|> +\(< b>\) To facilitate our work at this stage, we would appreciate if you could send us the main text as a word file. 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The absolute error distributions of the proton configuration distribution fittings. a-b. The absolute error distributions for fitting the proton configuration distribution with two and four 2D Gaussian functions, respectively. The unit of RMSE and AE is \\(\\hat{\\mathrm{A}}^{-2}\\) .", + "footnote": [], + "bbox": [ + [ + 152, + 94, + 829, + 275 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_3a.jpg", + "caption": "Fig. R2. 2D probability density distribution of proton configurations in 0.01 M HCl. a. Distribution of the chosen trajectory segments. b. Distribution for the entire trajectory (the same as Manuscript Fig. 3a).", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R3. Variation of the average proton stretching frequencies for the three configurations as a function of the assignment criterion. The blue, yellow, and orange lines represent the frequency differences for the Zundel-like, Intermediate, and Eigen-like configurations, respectively.", + "footnote": [], + "bbox": [ + [ + 295, + 243, + 700, + 457 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_10.jpg", + "caption": "Supplementary Fig. 10. The conditional ensemble average distributions of the local electric field for the two 2D Gaussian distributions. a. The local electric field distributions along the collective coordinate \\(q_{1}\\) of the two 2D Gaussian distributions, respectively. b. The local electric field distributions along the collective coordinate \\(q_{s}\\) of the two 2D Gaussian distributions, respectively. The color bar of the scatter points signifies the structural probability densities in units of \\(\\mathring{\\mathrm{A}}^{-1}\\) .", + "footnote": [], + "bbox": [], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Initial Manuscript Fig. 5", + "footnote": [], + "bbox": [ + [ + 150, + 402, + 848, + 651 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_10.jpg", + "caption": "Initial Supplementary Fig. 10", + "footnote": [], + "bbox": [ + [ + 150, + 85, + 844, + 451 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. R1. Schematic illustration of the vibrational vectors of \\(\\mathrm{H}_3\\mathrm{O}_2^+\\) with its first solvation shell in water. a-c. The vibrational vectors for three proton-stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively.", + "footnote": [], + "bbox": [ + [ + 150, + 142, + 825, + 392 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. R1. Schematic illustration of the vibrational vectors of \\(\\mathrm{H}_5\\mathrm{O}_2^+\\) with its first solvation shell in water. a-c. The vibrational vectors for three proton-stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively.", + "footnote": [], + "bbox": [], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the \"proton continuum\". From a to c, the vibrational vectors for three proton-stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d),", + "footnote": [], + "bbox": [ + [ + 149, + 552, + 828, + 797 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. R4. Proton VDOS spectrum. The dark blue line represents the non-stretching vibrational spectrum of the proton, the light blue line represents the Gaussian peaks used to fit the dark blue line, and the red dashed line represents the sum of the Gaussian peaks.", + "footnote": [], + "bbox": [ + [ + 293, + 181, + 702, + 393 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. R5. Proton stretching band fitting from the reference. The dark blue line represents the proton stretching band from the reference (J. Phys. Chem. B, 2019, 123, 33, 7214-7224), the light blue line represents the Gaussian peaks used to fit the dark blue line, and the red dashed line represents the sum of the Gaussian peaks.", + "footnote": [], + "bbox": [ + [ + 293, + 98, + 700, + 309 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. R6. RDFs of the ANNFF MD trajectory for the 0.9 M HCl solution. Panels a-e display the RDFs for H-H, O-H, O-O, Cl-H, and Cl-O pairs. The dark blue lines correspond to the RDFs from the RPBE-D3 classical MD trajectory, while the red dashed lines represent the RDFs from the revPBE0-D3 TRPMD trajectory.", + "footnote": [], + "bbox": [ + [ + 150, + 145, + 844, + 389 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. R7. VDOS for the 0.1 M HCl solution and pure water. The orange and cyan lines represent the VDOS from the RPBE-D3 classical MD and revPBE0-D3 TRPMD trajectories for pure water, respectively. The dark blue and yellow dashed lines represent the VDOS from the RPBE-D3 classical MD and revPBE0-D3 TRPMD trajectories for the 0.1 M HCl solution, respectively.", + "footnote": [], + "bbox": [ + [ + 300, + 503, + 692, + 700 + ] + ], + "page_idx": 26 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. R1. Schematic illustration of the criterion for configuration assignment of vibration periods. a-c. The boundaries for the three configuration types at thresholds of \\(50\\%\\) (a), \\(60\\%\\) (b), and \\(70\\%\\) (c). The red, light blue, and dark blue dashed lines represent the boundaries for Zundel-like, Intermediate, and Eigen-like configurations, respectively.", + "footnote": [], + "bbox": [ + [ + 149, + 641, + 848, + 764 + ] + ], + "page_idx": 26 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. R2. Proton VDOS spectra for \\(\\mathrm{H_5O_2^+}\\) and \\(\\mathrm{H_9O_4^+}\\) . a. Proton VDOS spectra. The blue line corresponds to the proton in \\(\\mathrm{H_5O_2^+}\\) , and the red line corresponds to the protons in \\(\\mathrm{H_9O_4^+}\\) . b. Proton stretch spectra.", + "footnote": [], + "bbox": [ + [ + 151, + 390, + 841, + 572 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_16.jpg", + "caption": "Supplementary Fig. 16. 2D probability density distribution of proton configurations in 0.01 M HCl. a. Distribution of the chosen trajectory segments. b. Distribution for the entire trajectory.", + "footnote": [], + "bbox": [ + [ + 153, + 92, + 839, + 275 + ] + ], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. R3. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along the collective coordinate \\(\\mathfrak{q}_{\\mathrm{l}}\\) of the intermediate state, for Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations, respectively. b. The local electric field distributions along the collective coordinate \\(\\mathfrak{q}_{\\mathrm{s}}\\) of the intermediate state, for Zundel-like, Intermediate and Eigen-like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \\(\\mathring{\\mathrm{A}}^{-1}\\)", + "footnote": [], + "bbox": [ + [ + 149, + 258, + 830, + 440 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Fig. R4. VDOS difference spectra between 0.1 M HCl solution and pure water. The blue line represents the difference spectrum from the RPBE-D3 classical MD trajectory, and the red line represents the difference spectrum from the revPBE0-D3 TRPMD trajectory.", + "footnote": [], + "bbox": [], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_8a.jpg", + "caption": "Fig. R5. The 2D configurational probability density distributions of proton in 0.1 M HCl solution. a. The 2D probability density distribution from the revPBE0-D3 TRPMD trajectory. b. The three 2D Gaussian-type fitting functions for the distribution in (a) are assigned to Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations. The black lines illustrate the contour plot of the sum of the three types. c. The 2D probability density distribution from the RPBE-D3 classical MD trajectory. d. The three 2D Gaussian-type fitting functions for the distribution in (c). c-d are identical to Supplementary Fig. 8a-b.", + "footnote": [], + "bbox": [ + [ + 152, + 85, + 842, + 450 + ] + ], + "page_idx": 34 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Fig. R6. Theoretical and experimental IR spectra of HCl solutions and water. The cyan and orange curves represent the theoretical IR spectra of \\(0.9\\mathrm{M}\\) HCl solution and pure water, respectively. The blue curve corresponds to the theoretical IR difference spectrum between \\(0.9\\mathrm{M}\\) HCl solution and water. The yellow curve shows the experimental IR difference spectrum between \\(0.1\\mathrm{M}\\) HCl solution and water. The horizontal dashed line is the zero line for the difference spectra.", + "footnote": [], + "bbox": [ + [ + 295, + 144, + 702, + 355 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Fig. R1. The distributions of the HB number difference \\((\\Delta)\\) computed with conditional ensemble average. Scatter plots depict \\(\\Delta\\) versus the proton transfer coordinate \\(\\delta\\) for Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations. The color bar represents structural probability densities in units of \\(\\mathrm{\\AA}^{-1}\\) .", + "footnote": [], + "bbox": [ + [ + 287, + 81, + 684, + 300 + ] + ], + "page_idx": 38 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Fig. R2. The distribution of the local electric field computed with conditional ensemble average. Scatter plots depict the local electric field versus \\(\\Delta\\) for all configurations. The color bar signifies structural probability densities in units of \\(\\mathrm{\\AA}^{-1}\\) .", + "footnote": [], + "bbox": [ + [ + 293, + 87, + 702, + 297 + ] + ], + "page_idx": 39 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \\(q_{1}\\) , for Zundel-like (0-0.13 V/Å, blue), Intermediate (0.13-0.28 V/Å, yellow) and Eigen-like (0.28-0.40 V/Å, green) configurations, respectively. b. The local electric field distributions along collective coordinate \\(q_{s}\\) , for Zundel-like, Intermediate and Eigen-like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \\(\\mathrm{\\AA}^{-1}\\) .", + "footnote": [], + "bbox": [ + [ + 149, + 371, + 833, + 555 + ] + ], + "page_idx": 39 + } +] \ No newline at end of file diff --git a/peer_reviews/13c45b352f4324e58c719da7d35b03718b9e3bcac141fff9c42f5e1328c7150c/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd b/peer_reviews/13c45b352f4324e58c719da7d35b03718b9e3bcac141fff9c42f5e1328c7150c/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..952efa6f4ff4de700cc14233f84301a32e80b15d --- /dev/null +++ b/peer_reviews/13c45b352f4324e58c719da7d35b03718b9e3bcac141fff9c42f5e1328c7150c/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd @@ -0,0 +1,827 @@ + +# nature portfolio + +Peer Review File + +# Unveiling the Intermediate Hydrated Proton in water: Resolving the \(1,750 \text{cm}^{-1}\) Signature via Vibrational Spectrum Assignment + +Corresponding Author: Professor Chungen Liu + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The manuscript is well written and presents an important topic within the scientific society. Methodology is novel, results are well presented with good data analysis made by the authors. The description is detailed enough for a reader to be able to reproduce their work. + +As it is known in the literature, the structure of proton excess in acidic solutions is an actual theme of debate. And as has been pointed out by the authors, there is a dilemma between structural diversity and solvent fluctuations. The significance of this work arises from the assignment of infrared signature at \(1750 \text{cm}^{- 1}\) to an intermediate structure that is obtained from the combination of theoretical molecular dynamics simulations and experimental infrared spectroscopy. However, there are some questions regarding this assignment, such as: + +1- The structural definition of this intermediate specie is defined by the 2D Gaussian- type fitting of the "special pair" moiety of proton, employing the distances between the excess proton (H\\*) and its two adjacent oxygen atoms (O1 and O2) of flanking water molecules. Therefore they defined this new species from this fitting, without considering other water molecules beyond them. As has been pointed out before [J. Phys. Chem. B 2023, 127, 45, 9822- 9832, J. Am. Chem. Soc. 2021, 143, 18672], it should be necessary to define at least the first solvation shell of the proposed structure to fully understand it. In this line, we also would like to ask, what are the main differences between this structure and a distorted Eigen or even a distorted Zundel structure. + +2- Authors claim this novel species as a result of a 2D Gaussian type fitting, in this respect we would like to know the results of fitting this with two, four or more 2D Gaussian type functions. Why do the authors consider only the case of 3 Gaussian type functions? + +3- Figure 4 only shows two water molecules, but for item b) it should take into account at least the first solvation shell. + +On the other hand, authors used a novel methodology that combines theory and experiment, in this line it would be nice to point out the steps I, II and III that are explicitly on the figure caption also in the Figure 1. + +Although the methodology is novel, in line 274 it is said that only \(60\%\) of the proton excess configurations are considered. In this regard: what could be the consequence of disregarding this \(40\%\) of the configurations on the analyzed results? + +Considering the determination of the intermediate structure (line 134 main and 138 SI), there are some concerns: - Regarding the determination of the vibrations to assign them to each configuration, are they well chosen? Is there no bias in choosing them so specifically? + +- In line with previous concern: in the assignment of a vibration to a configuration that dominates it \(50\%\) of the time, isn't there too much overlap in the configurations then? + +<--- Page Split ---> + +Authors find an explanation based on the electric field originating on the HB network (lines 223 and 72 of SI) to the existence of the intermediate structure. In this respect, it is not clear how the first solvation shell is defined and it should be addressed. Also, to be clearer Figure 5 of the main text could be just two panels (one for ql and one for qs) with the three types of configurations together with different colors or something like that. + +As minor concerns: + +Regarding this methodology, the employment of the IFFT method is novel and it could be more emphasized. + +On lines 368, 369 and 370, authors describe three simulation boxes, it does not remain clear which one is used along the work. + +In line 64 of SI, it is said that Zundel structure is preferential in concentrated solution but the difference in Zundel population with HCl concentration is too low. + +## Reviewer #2 + +(Remarks to the Author) In this work, the authors categorize important configurational motifs for aqueous acids. The indication of the "intermediate" configuration is demonstrated using Gaussian fitting of the vibrational density of states (VDOS) and the 2D configurational probability density distribution. This is further characterized by frequency- specific vibrational vectors, obtained through the inverse Fourier transformation of the VDOS. The target of the work seems intriguing; however, the following points need to be addressed before suggesting publication: + +(1) The theoretical spectra are computed using VDOS; however, this method cannot capture polarization and charge transfer effects, which may be crucial for systems like excess protons in water. Indeed, there are ML methods (e.g., Zhang, L., Chen, M., Wu, X., Wang, H., E, W., and Car, R. (2020) Physical Review B, 102(4), 041121.) that can train the position of Wannier centers as well, allowing access to dipole moment-derived spectra that can be more directly comparable with experiments. + +(2) The authors calculate local electric field from the SPC/E point charge. However, this provides only partial information, where any contribution from polarization/charge transfer is completely missing. Again, the Wannier center representation would likely to work better to reveal the influence of surrounding water. + +(3) The authors consider \(\mathrm{H5O2^{\wedge}(+)}\) moiety to devise the vibrational vector corresponding to the spectral signature of Eigen, Zundel or Intemediate-like configurations (Fig. 4). However, it is known that \(\mathrm{H5O2^{\wedge}(+)}\) is a candidate for Zundel-like and \(\mathrm{H9O4^{\wedge}(+)}\) is a candidate for Eigen-like picture. Additionally, proton transfer event is directly associated with the charge of the H-bond coordination of the proton-donating and proton-accepting water. Thus, in the spectral signature (at least for intermediate and Eigen configurations), other water molecules in the coordination shell are likely to be involved. + +(4) The authors schematically illustrate the extraction of vibrational vectors using inverse Fourier transformation in Figure 1. However, they should elaborate on the numerical quality of each step leading to the final vibrational vectors shown in Figure 4. + +(5) Diagonalizing the velocity covariance or cross-correlation matrix produces a normal mode-like picture that naturally includes the effects of temperature and anharmonicities in the dynamics (e.g., (i) Strachan A. J Chem Phys. 2004, 120(1), or (ii) Sun J, Niehues G, Forbert H, Decka D, Schwaab G, Marx D, Havenith M. J Am Chem Soc. 2014, 136(13)). The author should discuss the relevance and accuracy of the proposed methodology in relation to the existing methods mentioned above. + +(6) How is the box length determined in all the simulations? Ideally, it should be based on the experimental density or from an NPT equilibration. + +## Reviewer #3 + +(Remarks to the Author) The manuscript from Xuanye Yang and coworkers deals with a long- standing challenge in solution science, proton + +<--- Page Split ---> + +hydration and transport in water, and the associated spectroscopic signatures. The authors propose an approach to interpret the spectroscopic signatures of the hydrated proton in water in terms of frequency- specific vibrational vectors that are constructed from MD simulations at the DFT- GGA level, therefore, without neglecting anharmonicity and the dynamics of the liquid system. These vibrational vectors are defined based on the smallest unit composed of the excess proton and the two closest water molecules. With this approach, the authors identify an intermediate, long- lived structure between the limiting Zundel- like and Eigen- like conformations and predict its spectroscopic fingerprint at 1770 cm- 1. This is certainly a hot topic of broad interest in solution science, with many implications in acid- base chemistry and redox processes. However, in the present state, I am not fully convinced that this work advances our understanding to a level that justifies publication in Nature Communication. The possibility of intermediate states has already been reported in several works; it would make a difference if the authors could show how their findings substantially alter our understanding of the proton transport mechanism. + +I also have some concerns about the results and methodology that must be solved before considering publication. + +In Fig. 2a, the theoretical VDOS spectrum shows poor agreement with the experimental data around the proton continuum region, which is worrying for the reliability of the results of this work. This is even more worrying considering the authors then dissect the VODS spectrum in the proton continuum and discuss small differences, which look smaller in magnitude than the differences to the experimental spectra. Can the authors elaborate on this? + +As a general comment, VDOS should not be directly compared to IR spectra, as they are substantially different spectra due to the selection rules. Theoretical IR spectra instead of VDOS would make the work much more convincing. + +The authors define vibrational vectors based on the smallest unit composed of the excess proton and the two closest water molecules. Isn't the unit too small? For instance, water molecules in the 1st coordination shell of the two waters sharing the proton are also important for properly defining the excess proton environment. Moreover, the selection is based on spatial coordinates, which have recently been suggested to be not suitable for properly characterizing excess proton configurations; see, e.g., ref.[Nat. Chem. (2024). https://doi.org/10.1038/s41557-024-01593- y]. Please elaborate. + +In their analysis, the authors divide the MD trajectory into 3ps blocks. A block is defined to contain an excess proton if the same excess proton remains as such for \(60\%\) of the 3ps. This definition adds arbitrary noise to all the subsequent analyses due to the remaining \(40\%\) . Please elaborate. + +The authors introduce the need to search for intermediate proton configurations based on their choice to dissect the VDOS spectrum with Gaussian functions. However, the authors do not show if intermediate proton configurations identified from structural criteria reproduce the deconvolved Gaussian signature. I doubt it since their spectroscopic signature will hardly be Gaussian. Moreover, the authors need 6 Gaussians to fit the VDOS spectrum, this may suggest that a Gaussian fit of that complex frequency range may not be a physically meaningful choice. This can be checked with theoretical spectroscopy by computing theoretical spectra for each identified proton configuration. + +In general, I'm not convinced of the physical insights that the definition of local vibrational modes can bring in a collective and strongly correlated system such as water, where vibrational modes couple between many water molecules, for sure within the 1st shell of both the water molecules around the excess proton. + +As regards the simulation method, it would be nice if the authors could justify the choice of RPBE for AIMD for a subtle problem such as excess proton characterization. Taking advantage of ML techniques, recent MD studies have been conducted at a higher level of theory, e.g., hybrid DFT. + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have responded in detail to the reviewer's comments 1- 5 and 8- 12 and have addressed them adequately. However, responses 6 and 7 (which are related) are not entirely convincing. + +In particular, MD simulations were performed to determine the possible structure of the excess proton in solvation and its correspondence to its frequency in the solvation vibrational spectrum. Since the system has intrinsically high fluctuations, the correspondence between the vibrational frequency and the structure of the "special pair" could be fuzzy and, consequently, the assignment of a vibration is made to a configuration that dominates it \(50\%\) of the time. As the authors showed in their response, considering a stricter criterion implies obtaining higher frequencies that do not match the experiment and also discarding about \(50\%\) of the data. However, this criterion seems a bit arbitrary. In this sense, is it + +<--- Page Split ---> + +possible to run longer simulations to reach a criterion higher than \(50\%\) that explains the experimental results? + +## Reviewer #2 + +(Remarks to the Author) + +In the revised manuscript, the authors have addressed most of my comments. However, after reviewing their responses and the revisions, I find that the following points still need to be addressed regarding the assignment of the structural motif - the novel/central analysis in this manuscript - before it can be published. + +(1) Special pair dance refers to a hydrated central core hydronium structure that continually switches (O-H...O) special pair hydrogen-bond partners with the three closest water molecules. This means that the identity of the second water molecule (which is away from the unpaired H+) in the flanking partner (O2H5+) continuously changes. The author should calculate the survival probability of a particular O2H5+ complex as well as a particular O4H9+ to validate (a) the chosen 3 ps segment for spectral analysis and (b) O2H5+ is better compared to O4H9+ for the vibrational assignment. + +(2) In Figure 5, 'the ranges of intensities are distinctly different and essentially non-overlapping' seems to be due to the fact that the collective variable (CV) for different motifs represents different variable (despite using the same notations, q_s or q_l). I wonder if the same variable were used, the intensities would not differ much across the three motifs. In that case, the observed difference would be attributed to the choice of the variable, rather than to a true difference in the structural parameter. + +(3) Finally, the structural motifs (Eigen, Zundel and Intermediate) extracted here should be aligned with recent findings by Gomez et al. (Gomez, A., Thompson, W.H. & Laage, D. Nat. Chem. 16, 1838-1844 (2024)), who used a more accurate description of electrons and nuclei in their simulations and identified the same three motifs but using a different set of CVs. The authors should verify whether applying the same type of CVs (as used by Gomez et al.) to the extracted motifs presented herein aligns with the microscopic structure of the proton in water, as described by the recent work of Gemoz et al. + +## Reviewer #3 + +(Remarks to the Author) + +The authors made substantial efforts to address reviewers' concerns, which I find convincing regarding the significance of the work, the simulation approach used, and the data analysis. + +However, the concern about the use of VDOS instead of IR theoretical spectra to compare to experiments remains unanswered. + +The authors correctly state in their answer that the band position doesn't shift significantly from VDOS to IR. However, the lineshape is significantly altered by the magnitude of the transient dipole, which is not taken into account in the VODS spectrum, as also noted by reviewer 2. Since the authors discuss small differences in the shape of broad bands underlying several vibrational motions (as revealed by their decomposition and Gaussian fit), this problem can potentially affect their conclusion and assignment. I still believe this is a serious issue, which deserves to be better addressed by computing IR spectra instead of VDOS, which is doable in several ways, even from ML approaches, as also noted by another reviewer. + +However, I don't want to stand in the way of this otherwise interesting manuscript, and I leave the choice on this matter to the editor. + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 2: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have responded convincingly and in detail to the reviewer's comment, and also modified the SI and the main paper to address it. As far as this reviewer is concerned, the paper could be accepted as it is. + +## Reviewer #2 + +(Remarks to the Author) + +The authors have satisfactorily addressed almost all of the comments. Regarding the final point, they have conducted an additional comparison with quantum hybrid simulations, which is convincing. However, to complete the picture, I suggest + +<--- Page Split ---> + +that the authors should consider computing the donor and acceptor hydrogen bond numbers of the flanking/special pair water molecules, as well as the proton transfer coordinate. + +According to the study by Gemoz et al., in a perfect Zundel complex, both water molecules donate two hydrogen bonds, with the proton symmetrically located between them. In contrast, in the perfect Eigen structure, the water molecule on the side where the proton resides donates two hydrogen bonds, while the water molecule on the opposite side (farther from the proton) donates two hydrogen bonds and also accepts one. The "Zundel- like" species exhibits hydrogen- bonding features similar to those of the perfect Zundel, while the proton is localized to one side, akin to the Eigen configuration. I presume this corresponds to the "intermediate" species discussed in the present study — hence, an explicit analysis would be valuable. + +Therefore, an additional analysis of the hydrogen bonding and the proton transfer coordinate would provide a more comprehensive and insightful picture. That said, the presented work is otherwise well suited for publication without further revision. + +Reviewer #3 + +(Remarks to the Author) The authors addressed my concerns, therefore I can recommend publication. + +Reviewer #4 + +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 3: + +Reviewer comments: + +Reviewer #2 + +(Remarks to the Author) The authors have addressed all the points raised in a convincing manner and have revised the manuscript accordingly. I therefore recommend the manuscript for publication. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, + +<--- Page Split ---> + +unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## - - - Answers to Reviewer #1- - - - + +General Comments: The manuscript is well written and presents an important topic within the scientific society. Methodology is novel, results are well presented with good data analysis made by the authors. The description is detailed enough for a reader to be able to reproduce their work. + +As it is known in the literature, the structure of proton excess in acidic solutions is an actual theme of debate. And as has been pointed out by the authors, there is a dilemma between structural diversity and solvent fluctuations. The significance of this work arises from the assignment of infrared signature at \(1750\mathrm{cm^{- 1}}\) to an intermediate structure that is obtained from the combination of theoretical molecular dynamics simulations and experimental infrared spectroscopy. However, there are some questions regarding this assignment, such as: + +Response: We thank the reviewer for the insightful comments and recognition of our work on deciphering the vibrational features of hydrated protons in water. We are grateful for the valuable suggestions and are pleased to incorporate them into our revised manuscript. Below is our point- by- point response to the reviewer's feedback. The page and line numbers mentioned hereafter refer to those found in the highlighted manuscript and Supplementary Information. + +Comment 1- 1: The structural definition of this intermediate specie is defined by the 2D Gaussian type fitting of the "special pair" moiety of proton, employing the distances between the excess proton (H\\*) and its two adjacent oxygen atoms (O1 and O2) of flanking water molecules. Therefore they defined this new species from this fitting, without considering other water molecules beyond them. As has been pointed out before [J. Phys. Chem. B 2023, 127, 45, 9822- 9832, J. Am. Chem. Soc. 2021, 143, 18672], it should be necessary to define at least the first solvation shell of the proposed structure to fully understand it. In this line, we also would like to ask, what are the main differences between this structure and a distorted Eigen or even a distorted Zundel structure. + +Response: We thank the reviewer for highlighting the structural definition of the intermediate species and for raising the question regarding its distinction from previously proposed configurations. We have defined the intermediate species based on the local coordinates of the "special pair", as they are strongly correlated with the proton stretching mode, which is the primary focus of this work. Our results strongly support the intermediate configuration should be treated as a distinct species due to its unique proton stretching peak at \(1770\mathrm{cm^{- 1}}\) . Regarding the first solvation shell does not change the identification of the stretching mode at \(1770\mathrm{cm^{- 1}}\) and its corresponding intermediate structure, more details are provided in our response to Comment 1- 3. + +In addition, the primary focus of this work is to investigate the structural + +<--- Page Split ---> + +assignments of the proton stretching mode and to interpret the "proton continuum" observed in the linear infrared spectrum as well as the cross peaks in the 2D infrared spectrum. Thus, we choose to define the intermediate species based on the local coordinates of the "special pair", which are strongly correlated with the proton stretch, as demonstrated in prior studies (Nat. Chem., 2013, 5, 1, 29- 35, J. Phys. Chem. B, 2019, 123, 33, 7214- 7224, J. Chem. Phys., 2020, 153, 12, 124506). This discussion is placed in the manuscript on page 8, lines 204- 206. + +Moreover, we observe substantial overlap between adjacent configuration distributions, with the overall distribution exhibiting a single peak. This finding is consistent with results from the global free energy surface analysis (J. Phys. Chem. B, 2023, 127, 45, 9822- 9832). Therefore, simplifying the configuration definition to spatial coordinates of the "special pair" does not undermine the validity of our conclusions. This discussion can be found in the manuscript on page 8, lines 208- 210 and line 212. + +From a structural standpoint, categorizing the intermediate species as a distorted Eigen or distorted Zundel configuration as previous literature (J. Am. Chem. Soc., 2021, 143, 18672, Nat. Chem., 2018, 10, 9, 932- 937) does not fully represent its unique spectroscopic characteristics, particularly the proton stretching peak at \(1770 \mathrm{cm}^{- 1}\) , which is clearly different from the peaks associated with Zundel- like (1250 \(\mathrm{cm}^{- 1}\) ) and Eigen- like (2530 \(\mathrm{cm}^{- 1}\) ) configurations. Moreover, simply classifying the intermediate structures as distorted Eigen or Zundel does not adequately explain the presence of three proton stretching peaks in the VODS spectrum, nor does it account for the fact that the \(1750 \mathrm{cm}^{- 1}\) signal in the 2D IR spectrum exhibits vibrational relaxation decay that follows a biexponential function (J. Phys. Chem. B, 2018, 122, 10, 2792- 2802). + +Comment 1- 2: Authors claim this novel species as a result of a 2D Gaussian type fitting, in this respect we would like to know the results of fitting this with two, four or more 2D Gaussian type functions. Why do the authors consider only the case of 3 Gaussian type functions? + +Response: We thank the reviewer for raising concerns regarding the reliability of the fitting approach used for the configuration distribution. This issue is briefly discussed in the caption of Manuscript Fig. 3, where we note that reducing the number of Gaussian functions results in a significant increase in the fitting error, whereas adding additional Gaussian functions does not lead to notable improvements (see Supplementary Fig. 8). Furthermore, Supplementary Fig. 8 presents the error distributions obtained when fitting with two or four 2D Gaussian functions. + +<--- Page Split ---> +![](images/Supplementary_Figure_8.jpg) + +
Supplementary Fig. 8. The absolute error distributions of the proton configuration distribution fittings. a-b. The absolute error distributions for fitting the proton configuration distribution with two and four 2D Gaussian functions, respectively. The unit of RMSE and AE is \(\hat{\mathrm{A}}^{-2}\) .
+ +Since the figure caption may be overlooked, we have decided to incorporate this explanation into the manuscript, now found on page 8, lines 213- 215. + +Comment 1- 3: Figure 4 only shows two water molecules, but for item b) it should take into account at least the first solvation shell. + +Response: We thank the reviewer for the suggestion regarding the range of vibrational vector calculations. To evaluate the influence of cluster size on vibrational vector calculations, we present in Fig. R1 the vibrational vectors for the clusters including the first solvation shell of \(\mathrm{H}_5\mathrm{O}_2^+\) . A comparison with Manuscript Fig. 4 reveals that the vibrational vectors of the central \(\mathrm{H}_5\mathrm{O}_2^+\) remain unchanged. Moreover, at the frequencies corresponding to the proton stretching peaks (Fig. R1a- c), the contribution from the first solvation shell is negligible. + +![](images/Figure_3a.jpg) + + +<--- Page Split ---> + +Fig. R1. Schematic illustration of the vibrational vectors of \(\mathrm{H_5O_2^+}\) with its first solvation shell in water. a-c. The vibrational vectors for three proton- stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively. + +![](images/Figure_unknown_0.jpg) + + +Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the "proton continuum". From a to c, the vibrational vectors for three proton- stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d), umbrella (e), and bending (f), respectively. + +Since we used MD trajectory segments to compute the vibrational vectors, rather than static structures, the motions of \(\mathrm{H_5O_2^+}\) inherently preserve the dynamical impact of the surrounding water molecules. Consequently, expanding the range of calculations would not modify the intrinsic vibrational vectors of \(\mathrm{H_5O_2^+}\) , but would only incorporate additional vibrational information from the surrounding water molecules. This underscores one of the advantages of our approach: the chosen cluster size does not affect the vibrational vectors of the concerned motifs. + +The discussions are provided in the manuscript on page 9, lines 251- 255 and in the Supplementary Information on page 7, lines 175- 181. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 13. + +Comment 1- 4: On the other hand, authors used a novel methodology that combines theory and experiment, in this line it would be nice to point out the steps I, II and III that are explicitly on the figure caption also in the Figure 1. + +Response: We sincerely appreciate the reviewer's valuable suggestion. In accordance with the recommendation, we have explicitly labeled steps I, II, III, and IV in + +<--- Page Split ---> + +Manuscript Fig. 1 to ensure consistency with the figure caption, as shown below. + +![](images/Supplementary_Figure_10.jpg) + + +Manuscript Fig. 1. An integrated approach for assigning vibrational spectrum derived from molecular dynamics simulations. A "special pair", consisting of the excess proton and its two flanking water molecules, is employed as the fundamental moiety for interpreting the solvated proton's vibrational spectrum (Nat. Commun., 2022, 13, 1, 6170). For an arbitrary frequency in the vibrational spectrum, the vibrational vectors of all atoms in the moiety can be derived via the four distinct steps illustrated in the flowchart. + +Comment 1- 5: Although the methodology is novel, in line 274 it is said that only \(60\%\) of the proton excess configurations are considered. In this regard: what could be the consequence of disregarding this \(40\%\) of the configurations on the analyzed results? + +Response: We thank the reviewer for raising the issue regarding the selection of trajectory segments. To address this, we would like to emphasize that the chosen segments are representative of the entire trajectory. Additionally, in remaining \(40\%\) of the configurations, the proton undergoes rapid exchange through "special pair dance". We have found that the impact of this proton exchange phenomenon on the vibrational spectrum assignment is minimal. + +In our study, the MD trajectory was divided into 3 ps segments, with a segment being classified as containing an excess proton if the same proton in the \(\mathrm{H_2O\cdots H^+\cdots H_2O}\) configuration was present for more than \(60\%\) of the 3 ps. Based on this criterion, we selected 26 segments for further analysis, which collectively account for \(6.5\%\) of the entire trajectory. + +To validate the representativeness of the chosen segments, we computed the 2D probability density distribution of proton configurations for the chosen trajectory segments (see Fig. R2a) and compared it with the distribution obtained from the entire trajectory (Fig. R2b). The results reveal good agreement between the two distributions, confirming the adequacy of the segment selection scheme. + +<--- Page Split ---> +![](images/Figure_5.jpg) + +
Fig. R2. 2D probability density distribution of proton configurations in 0.01 M HCl. a. Distribution of the chosen trajectory segments. b. Distribution for the entire trajectory (the same as Manuscript Fig. 3a).
+ +Furthermore, a comprehensive analysis of the chosen trajectory segments revealed that the proton remains within the identified \(\mathrm{H}_3\mathrm{O}_2^+\) cluster with a probability of \(99.7\%\) and with the probability of \(89.8\%\) it dwells on a single \(\mathrm{H}_3\mathrm{O}^+\) motif. This indicates that in the remaining less than \(40\%\) configurations, the excess proton stays in the \(\mathrm{H}_3\mathrm{O}_2^+\) species but rapidly exchanges with hydrogen atoms on the two flanking waters through "special pair dance". Therefore, the \(\mathrm{H}_3\mathrm{O}_2^+\) moiety is essentially effective for characterizing the excess proton in water. + +It is crucial to highlight that the excess proton exists in a state of ultrafast special pair dance predominantly in the Eigen- like configuration, which results in the three hydrogen atoms within the \(\mathrm{H}_3\mathrm{O}^+\) core of an Eigen- like cation continuously exchanging their identities, shifting between being the excess proton and hydrogen atoms of the flanking water molecules. Importantly, the excess proton remains confined within the \(\mathrm{H}_3\mathrm{O}_2^+\) moiety, and since our analysis identifies the proton based on the longest O- H bond, the two exchanged hydrogen atoms in Eigen- like configurations exhibit similar O- H bond lengths, thus corresponding to similar proton stretching frequencies (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). Consequently, the overall configuration as well as the identity of the proton should not be considered altered. + +Due to the current limitations in criteria for identifying the excess proton, the special pair dance undergone by the excess proton is often misinterpreted as instances of identity shifting, leading to an underestimation of the probability of the sustained configuration. If the \(\mathrm{H}_3\mathrm{O}_4^+\) model were adopted, the probability of the proton remaining unchanged in trajectory segments would be \(89.8\%\) . However, because of the significant difference in stretching frequencies between the proton and the hydrogens of the flanking water molecules in intermediate and Zundel- like configurations, we prefer to retain the \(\mathrm{H}_2\mathrm{O}\dots \mathrm{H}^+\dots \mathrm{H}_2\mathrm{O}\) configuration for vibrational analysis. Despite this, we believe segmenting the trajectory into 3 ps blocks to identify the same proton within the \(\mathrm{H}_2\mathrm{O}\dots \mathrm{H}^+\dots \mathrm{H}_2\mathrm{O}\) configuration, which remains consistent for over \(60\%\) of the time, constitutes a reasonable and reliable methodology. + +To avoid potential misunderstandings, we have revised the description of the segment selection process in the Methods section on page 14, lines 358- 369. The + +<--- Page Split ---> + +analyses of the chosen trajectory segments are added to the Supplementary Information on page 7, lines 182- 192. Fig. R2 has been added to the Supplementary Information as Supplementary Fig. 14. + +Comment 1- 6: Considering the determination of the intermediate structure (line 134 main and 138 SI), there are some concerns: + +- Regarding the determination of the vibrations to assign them to each configuration, are they well chosen? Is there no bias in choosing them so specifically? + +Response: We thank the reviewer for pointing out the key point of our work. Due to the significant dynamical effects exhibited by protons in acidic solutions, the direct one- to- one correspondence between proton configurations and their stretching frequencies is inaccessible. Therefore, we circumvent this obstacle to explore the statistical correlation between proton configurations and proton stretching frequencies, rather than focusing on the specific behavior of proton configurations in individual snapshots. + +The statistical results of the average proton stretching frequencies across the three configuration distributions reveal a clear correlation between the configuration distributions and the stretching peak positions. However, this does not imply that, in each snapshot of the trajectory, the proton configuration and its corresponding stretching frequency strictly follow this correlation. As shown in Fig. 2d and Fig. 3b of the manuscript, there is some overlap between the three proton stretching peaks, and the distributions of the three configurations also exhibit overlap. For detailed data, please refer to Response 1- 7. + +In response to the reviewer's comment, we have revised the Supplementary Information on page 6, lines 145- 149 and lines 169- 171. + +Comment 1- 7: In line with previous concern: in the assignment of a vibration to a configuration that dominates it \(50\%\) of the time, isn't there too much overlap in the configurations then? + +Response: Thanks for your comment. Given the typically large amplitude of proton stretching, protons are prone to crossing configuration boundaries in vibrational motions. Thus, setting a very strict assignment criterion may result in the exclusion of a significant amount of valuable data. For instance, increasing the criterion from \(50\%\) to \(70\%\) would result in the discard of \(52\%\) of the data. + +The impact of adjusting the criterion on the average proton stretching frequencies is illustrated in Fig. R3. The average frequencies for each configuration type at a \(50\%\) criterion are used as the reference, and the frequency differences for other criteria are computed relative to this reference. Notably, for the Zundel- like and Eigen- like configurations, the frequency variation remains relatively small between the \(50\%\) and \(60\%\) criteria. However, a more significant shift occurs when the criterion is increased from \(60\%\) to \(70\%\) . A stricter criterion tends to filter out instances with longer periods, + +<--- Page Split ---> + +resulting in an overestimation of the average frequency. Specifically, increasing the criterion to \(70\%\) would shift the average proton stretching frequencies for the Zundel- like, intermediate, and Eigen- like configurations to \(1430\mathrm{cm}^{- 1}\) , \(2010\mathrm{cm}^{- 1}\) , and \(2530\mathrm{cm}^{- 1}\) , respectively, leading to a substantial deviation from the experimental IR spectrum. Therefore, we find the \(50\% - 60\%\) range to be the most appropriate for defining the assignment criterion, as it strikes a balance between configuration uncertainty and the utilization rate of the MD trajectory. + +![](images/Supplementary_Figure_10.jpg) + +
Fig. R3. Variation of the average proton stretching frequencies for the three configurations as a function of the assignment criterion. The blue, yellow, and orange lines represent the frequency differences for the Zundel-like, Intermediate, and Eigen-like configurations, respectively.
+ +The \(50 - 60\%\) criterion is, in fact, a rough estimate. Due to the dynamic effects within the solution, the periodic motion of atoms is often disrupted, which introduces some uncertainty in the average frequencies derived from the MD trajectory. Nevertheless, our statistical analysis reveals significant differences in the average frequencies of proton stretching across the three configurations, with a progressive increase from Zundel- like to Eigen- like configurations. Specifically, when the assignment criterion is set at \(50\%\) , configurations with a vibrational frequency near \(1770\mathrm{cm}^{- 1}\) are attributed predominantly to the intermediate configuration, comprising up to \(70\%\) . + +In response to the reviewer's comment, we have revised the manuscript (page 9, lines 231- 233) and the Supplementary Information (page 6, lines 156- 168 and lines 171- 174). + +Comment 1- 8: Authors find an explanation based on the electric field originating on the HB network (lines 223 and 72 of SI) to the existence of the intermediate structure. In this respect, it is not clear how the first solvation shell is defined and it should be addressed. + +<--- Page Split ---> + +Response: We thank the reviewer for pointing out the need for clarification regarding the definition of the first solvation shell. To clarify, our definition of the first solvation shell is added to the Supplementary Information on pages 3- 4, lines 81- 84, as detailed below: + +"For hydrogen atoms surrounding the proton, if either of the closest or second- closest oxygen atoms originates from the \(\mathrm{H}_3\mathrm{O}_2^+\) moiety, we classify the water molecule containing the other oxygen atom as part of the first solvation shell of \(\mathrm{H}_3\mathrm{O}_2^+\) ." + +Comment 1- 9: Also, to be clearer Figure 5 of the main text could be just two panels (one for ql and one for qs) with the three types of configurations together with different colors or something like that. + +Response: We thank the reviewer for the valuable suggestion. In response, we have revised Manuscript Fig. 5 to feature two panels. Similar modifications have also been applied to Supplementary Fig. 10. The original figures are provided for comparison, as shown below. + +![](images/Figure_unknown_1.jpg) + + +Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \(\mathfrak{q}_1\) , for Zundel- like (0- 0.13 V/A, blue), Intermediate (0.13- 0.28 V/A, yellow) and Eigen- like (0.28- 0.40 V/A, green) configurations, respectively. b. The local electric field distributions along collective coordinate \(\mathfrak{q}_s\) , for Zundel- like, Intermediate and Eigen- like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathrm{\AA}^{- 1}\) . + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Supplementary Fig. 10. The conditional ensemble average distributions of the local electric field for the two 2D Gaussian distributions. a. The local electric field distributions along the collective coordinate \(q_{1}\) of the two 2D Gaussian distributions, respectively. b. The local electric field distributions along the collective coordinate \(q_{s}\) of the two 2D Gaussian distributions, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathring{\mathrm{A}}^{-1}\) .
+ +![](images/Figure_4.jpg) + +
Initial Manuscript Fig. 5
+ +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Initial Supplementary Fig. 10
+ +Comment 1- 10: As minor concerns: Regarding this methodology, the employment of the IFFT method is novel and it could be more emphasized. + +Response: We thank the reviewer for the valuable suggestion regarding the IFFT method. In response, we have revised the detailed description of our approach, originally in the caption of Manuscript Fig. 1, and incorporated it into the manuscript on page 3, lines 79- 99. Additionally, we have emphasized its significance on page 3, lines 100- 104, stating: + +"The core of this integrated approach lies in utilizing the IFFT to determine, for any given frequency, the vibrational amplitudes and phases associated with all atoms within a specified structural motif of interest. Through a carefully designed strategy that involves averaging the vibrational vectors over different segments, this method offers a feasible framework for assigning vibrational spectra in highly flexible structures, such as liquids." + +Comment 1- 11: On lines 368, 369 and 370, authors describe three simulation boxes, it does not remain clear which one is used along the work. + +Response: We appreciate the reviewer for addressing the issue concerning the + +<--- Page Split ---> + +simulation boxes used in the study. As stated in lines 108- 110 of the manuscript, we have clarified that all subsequent analyses are based on a 0.01 M HCl solution, comprising 4095 H₂O molecules, a proton, and a Cl⁻ ion, in order to minimize the influence of chloride ions. + +To enhance clarity, we have incorporated additional details in the Methods section (page 18, lines 484- 490), as outlined below. + +"For comparison, a system comprising 63 water molecules, a proton, and a chloride ion pair (equivalent to 0.9 M HCl) is presented in the Supplementary Information. Additionally, a system containing 511 water molecules, a proton, and a chloride ion pair (0.1 M HCl), as well as a system with 512 water molecules, were utilized to generate the theoretical difference VDOS spectrum shown in Fig. 2a. These systems are also included in the Supplementary Information for comparison. All other analyses presented in the manuscript are based on a 0.01 M HCl solution, which consists of 4,095 water molecules, a proton, and a chloride ion pair." + +Comment 1- 12: In line 64 of SI, it is said that Zundel structure is preferential in concentrated solution but the difference in Zundel population with HCl concentration is too low. + +Response: We thank the reviewer for pointing out the limited variation in the Zundel- like population with respect to HCl concentration. We agree with this observation. Previous studies have shown that at higher proton concentrations, the population of Zundel- like configurations increases significantly (Science, 2017, 357, 6350, 491- 495). However, within the concentration range considered in our study, the proportion of Zundel- like configurations remains relatively stable. + +In response, we have revised the description of Supplementary Table 2 (Supplementary Information page 3, lines 65- 68) to more accurately reflect our findings. The updated description is provided below: + +"As the HCl concentration increases, the proportions of these three configurations exhibit minimal variation, as detailed in Supplementary Table 2. This observation suggests that the intermediate configuration remains stable under dilute HCl solutions." + +<--- Page Split ---> + +## -Answers to Reviewer #2- + +**General Comments:** In this work, the authors categorize important configurational motifs for aqueous acids. The indication of the "intermediate" configuration is demonstrated using Gaussian fitting of the vibrational density of states (VDOS) and the 2D configurational probability density distribution. This is further characterized by frequency-specific vibrational vectors, obtained through the inverse Fourier transformation of the VDOS. The target of the work seems intriguing; however, the following points need to be addressed before suggesting publication: + +**Response:** We sincerely thank the reviewer for their thorough evaluation of our manuscript and for the insightful comments provided. We have carefully considered each point raised and addressed them in detail. Based on these responses, we have made substantial revisions to the manuscript to enhance its clarity and overall quality. We hope that the following clarifications and revisions will address the concerns raised by the reviewer. The page and line numbers mentioned hereafter refer to those found in the highlighted manuscript and Supplementary Information. + +**Comment 2-1:** The theoretical spectra are computed using VDOS; however, this method cannot capture polarization and charge transfer effects, which may be crucial for systems like excess protons in water. Indeed, there are ML methods (e.g., Zhang, L., Chen, M., Wu, X., Wang, H., E, W., and Car, R. (2020) Physical Review B, 102(4), 041121.) that can train the position of Wannier centers as well, allowing access to dipole moment-derived spectra that can be more directly comparable with experiments. + +**Response:** We thank the reviewer for the insightful suggestion regarding the use of machine learning methods to compute infrared spectra. We would like to emphasize that our analysis reveals a strong consistency between the structural features of VDOS and IR spectra, with differences primarily in intensity. This suggests that vibrational analysis based on VDOS can effectively capture the features of the IR spectrum. + +The work referenced by the reviewer (Zhang, L., Chen, M., Wu, X., Wang, H., E, W., and Car, R. (2020) Physical Review B, 102(4), 041121.) offers a promising approach to calculating theoretical IR spectra based on machine learning force fields. However, it is important to note that infrared spectra derived from the dipole moment autocorrelation function cannot directly provide the atomic velocities necessary for calculating vibrational vectors. Furthermore, the calculation of IR spectra does not influence the results of our vibrational vector analysis. For the purposes of this study and subsequent analysis, we have chosen to focus on the VDOS based on atomic velocities. While we acknowledge the limitations of this approach, we intend to explore more advanced machine learning methods in future work to gain a more comprehensive understanding of vibrational properties. + +Additionally, Markland’s work (J. Chem. Phys., 2018, 148, 22, 222833) provides + +<--- Page Split ---> + +VDOS and IR spectra of HCl solutions and water, calculated from AIMD trajectories using the revPBE- D3 functional, along with difference spectra. This study shows that theoretical VDOS and IR spectra exhibit the same structural features, differing primarily in intensity, and that the peak positions align with experimental IR spectra. This consistency indicates that vibrational analysis based on VDOS can effectively capture the characteristic features of the IR spectrum. + +In response to the reviewer's suggestion, we have included the relevant clarification in the manuscript on page 6, lines 158- 166. + +Comment 2- 2: The authors calculate local electric field from the SPC/E point charge. However, this provides only partial information, where any contribution from polarization/charge transfer is completely missing. Again, the Wannier center representation would likely to work better to reveal the influence of surrounding water. + +Response: We thank the reviewer for highlighting the limitation of using the SPC/E point charge model in the calculation of the local electric field, as it does not capture polarization or charge transfer effects. + +In our prior work (Phys. Rev. Lett., 2023, 131, 15, 158001), we compared the use of SPC/E and DFT charges for calculating the local electric field. Specifically, 3,000 structures were randomly selected from metadynamics trajectories, and the iterative Hirshfeld method was employed to analyze atomic charge distributions. The results indicated that the local electric field distributions derived from both charge schemes were highly similar. Consequently, employing SPC/E point charges for local electric field calculations is a valid and efficient approximation that does not impact significantly the solidity of the conclusions. + +In response to this concern, we have included a brief clarification in the caption of Manuscript Fig. 5. + +Comment 2- 3: The authors consider \(\mathrm{H5O2}^{\wedge}\{+\}\) moiety to devise the vibrational vector corresponding to the spectral signature of Eigen, Zundel or Intemediate- like configurations (Fig. 4). However, it is known that \(\mathrm{H5O2}^{\wedge}\{+\}\) is a candidate for Zundel- like and \(\mathrm{H9O4}^{\wedge}\{+\}\) is a candidate for Eigen- like picture. Additionally, proton transfer event is directly associated with the change of the H- bond coordination of the proton- donating and proton- accepting water. Thus, in the spectral signature (at least for intermediate and Eigen configurations), other water molecules in the coordination shell are likely to be involved. + +Response: We thank the reviewer for the constructive comment regarding the scope of the vibrational vector calculations. To evaluate the influence of cluster size on vibrational vector calculations, we present Fig. R1, which displays the vibrational vectors for the first solvation shell of \(\mathrm{H_5O_2}^+\) . A comparison with Manuscript Fig. 4 reveals that the vibrational vectors of the central \(\mathrm{H_5O_2}^+\) remain consistent. Moreover, at + +<--- Page Split ---> + +the frequencies corresponding to the proton stretching peaks (Fig. R1a- c), the contribution from the first solvation shell is negligible. + +![](images/Figure_unknown_4.jpg) + +
Fig. R1. Schematic illustration of the vibrational vectors of \(\mathrm{H}_3\mathrm{O}_2^+\) with its first solvation shell in water. a-c. The vibrational vectors for three proton-stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively.
+ +![](images/Figure_unknown_5.jpg) + + +Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the "proton continuum". From a to c, the vibrational vectors for three proton- stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d), umbrella (e), and bending (f), respectively. + +In our study, we used MD trajectory segments to compute the vibrational vectors, + +<--- Page Split ---> + +rather than relying on static structures. This approach inherently preserves the dynamic impact of the surrounding water molecules on the \(\mathrm{H_3O_2}^+\) moiety. As a result, expanding the range of the calculation would not alter the intrinsic vibrational vectors of \(\mathrm{H_3O_2}^+\) itself but would instead incorporate additional vibrational contributions from the surrounding water molecules. This feature of our methodology highlights one of its advantages: the chosen cluster size does not affect the vibrational vector on atoms of concerned moieties. + +We have included relative discussions in the manuscript on page 9, lines 251- 255 and in the Supplementary Information on page 7, lines 175- 181. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 13. + +Comment 2- 4: The authors schematically illustrate the extraction of vibrational vectors using inverse Fourier transformation in Figure 1. However, they should elaborate on the numerical quality of each step leading to the final vibrational vectors shown in Figure 4. + +Response: We thank the reviewer for highlighting the numerical quality of the vibrational vector extraction process. To provide further clarity, we would like to elaborate on the steps involved: + +For each degree of freedom, we compute the IFFT on the VDOS or cross spectrum to derive the amplitude and phase information at specific frequencies within each segment, which are then used to construct the final vibrational vectors by statistical averaging. This approach avoids reliance on the total VDOS of the chosen cluster, thereby avoiding potential numerical issues that might arise from spectral decomposition. In our calculations, the numerical precision of the vibrational vectors obtained via IFFT is on the order of \(10^{- 5}\) , and the precision of the averaged vibrational vectors also reaches \(10^{- 5}\) . Furthermore, the configuration averaging and vibrational vector projection processes do not affect the numerical accuracy. + +In response to the reviewer's suggestion, we have revised the description of our approach in the manuscript on page 3, lines 79- 99. + +Comment 2- 5: Diagonalizing the velocity covariance or cross- correlation matrix produces a normal mode- like picture that naturally includes the effects of temperature and anharmonicities in the dynamics (e.g., (i) Strachan A. J Chem Phys. 2004, 120(1), or (ii) Sun J, Niehues G, Forbert H, Decka D, Schwaab G, Marx D, Havenith M. J Am Chem Soc. 2014, 136(13)). The author should discuss the relevance and accuracy of the proposed methodology in relation to the existing methods mentioned above. + +Response: We sincerely thank the reviewer for providing the valuable references: (i) Strachan A. J Chem Phys. 2004, 120(1) and (ii) Sun J, Niehues G, Forbert H, Decka D, Schwaab G, Marx D, Havenith M. J Am Chem Soc. 2014, 136(13). Below, we present a detailed analysis and comparison of our approach with the methods outlined in these + +<--- Page Split ---> + +references. + +Both our approach and the methods discussed in these references utilize velocities from MD simulations to extract vibrational features, naturally incorporating the effects of temperature and anharmonicities. However, there are key differences in the methodologies employed to obtain the vibrational vectors. The approaches described in references involve diagonalizing the velocity covariance or cross- correlation matrix to determine vibrational frequencies and vectors, whereas our method employs IFFT to extract vibrational vectors at specific frequencies. + +Concerning the method in reference (i), the assumption underlying the diagonalization of the velocity covariance matrix is that the velocities of different vibrational modes are uncorrelated. This assumption is valid for systems with well- separated vibrational peaks, such as gas- phase molecules or solid- state crystals. However, in liquid systems, particularly in HCl solutions that exhibit broad absorption bands in the \(1000–3000\mathrm{cm}^{- 1}\) range, where vibrational modes are strongly coupled, this assumption does not hold. In contrast, our approach, which uses IFFT to extract vibrational vectors at distinct frequencies, imposes no such correlation constraints on vibrational modes, allowing them to mix. This makes our method more suitable for the analysis of complex liquid systems. Furthermore, our method is applicable to gas- phase and solid- state systems, offering greater versatility. + +The method outlined in reference (ii) incorporates contributions from off- diagonal terms in the diagonalized dipole velocity cross- correlation matrix. This approach has proven successful in analyzing THz spectra of glycine in water. However, due to the frequent proton hopping in HCl solutions, the MD trajectories must be divided into shorter segments for analysis. If the method from reference (ii) was applied, each segment would exhibit different vibrational modes and corresponding frequency distributions, complicating the extraction of comprehensive vibrational features for the entire trajectory. In contrast, our method, which analyzes specific frequencies in the vibrational spectrum, enables averaging of vibrational vectors at the same frequency across different segments, facilitating the calculation of statistical vibrational features. + +In response to the reviewer's comment, we have included this discussion in the manuscript (page 2, lines 65- 69) and the Methods section (page 16, lines 405- 418). + +Comment 2- 6: How is the box length determined in all the simulations? Ideally, it should be based on the experimental density or from an NPT equilibration. + +Response: We appreciate the reviewer for raising the question regarding the determination of cell length in the simulations. As stated in lines 341- 342 of the Methods section, the cell length in the AIMD simulations was set based on an experimental density of \(1\mathrm{g / cm^3}\) . This approach is widely adopted in DFT- level calculations (Nature, 1999, 397, 6720, 601- 604, J. Am. Chem. Soc., 2021, 143, 44, 18672- 18683). The same methodology was employed to determine the cell length in the ANNFF MD simulations. + +In response to the reviewer's comment, we have added the relevant clarification + +<--- Page Split ---> + +in the Methods section (page 17, line 450 and page 18, lines 480- 481). + +<--- Page Split ---> + +## - - - Answers to Reviewer #3- - - - + +General Comments: The manuscript from Xuanye Yang and coworkers deals with a long- standing challenge in solution science, proton hydration and transport in water, and the associated spectroscopic signatures. The authors propose an approach to interpret the spectroscopic signatures of the hydrated proton in water in terms of frequency- specific vibrational vectors that are constructed from MD simulations at the DFT- GGA level, therefore, without neglecting anharmonicity and the dynamics of the liquid system. These vibrational vectors are defined based on the smallest unit composed of the excess proton and the two closest water molecules. With this approach, the authors identify an intermediate, long- lived structure between the limiting Zundellike and Eigen- like conformations and predict its spectroscopic fingerprint at 1770 cm- 1. This is certainly a hot topic of broad interest in solution science, with many implications in acid- base chemistry and redox processes. However, in the present state, I am not fully convinced that this work advances our understanding to a level that justifies publication in Nature Communication. The possibility of intermediate states has already been reported in several works; it would make a difference if the authors could show how their findings substantially alter our understanding of the proton transport mechanism. + +I also have some concerns about the results and methodology that must be solved before considering publication. + +Response: We sincerely thank the reviewer for their thorough evaluation of our manuscript. We have carefully considered each comment and addressed them individually. Based on this feedback, we have made substantial revisions to the manuscript to address the issues raised, thereby enhancing its clarity and overall quality. The page and line numbers mentioned hereafter refer to those found in the highlighted manuscript and Supplementary Information. + +Regarding the reviewer's comment on the reported existence of intermediate states, we would like to offer further clarification. While previous studies (Chin. Phys. B, 2020, 29, 8, 083101, J. Chem. Phys., 2020, 153, 12, 124506) have suggested the potential presence of such intermediate states based on structural classifications, they did not fully substantiate these claims, particularly in terms of definitive vibrational signatures. The vibrational signal at 1770 cm- 1 has long been a subject of intense research, but its corresponding proton configuration assignment remains controversial, and it has never been assigned to an intermediate state. + +Our work successfully identifies the 1770 cm- 1 peak as a unique proton stretching vibration corresponding to the intermediate state. This finding contributes to a deeper understanding of linear infrared spectra in acid solutions and prompts a re- evaluation of existing interpretations in 2D infrared spectroscopy for such systems. + +The relevant additions have been incorporated into the manuscript, specifically on page 9, lines 235- 243. + +<--- Page Split ---> + +Moreover, we would like to emphasize that the identification of the intermediate state significantly enriches our comprehension of proton dynamics. For example, by precisely measuring the lifetimes of the three configuration types, we provide new insights into the timescales of proton transport. These contributions are important to reshaping the understanding of proton transport mechanisms, and we intend to further investigate this topic in future studies. We hope this clarification underscores the importance of our work. + +Comment 3- 1: In Fig. 2a, the theoretical VDOS spectrum shows poor agreement with the experimental data around the proton continuum region, which is worrying for the reliability of the results of this work. This is even more worrying considering the authors then dissect the VODS spectrum in the proton continuum and discuss small differences, which look smaller in magnitude than the differences to the experimental spectra. Can the authors elaborate on this? + +As a general comment, VDOS should not be directly compared to IR spectra, as they are substantially different spectra due to the selection rules. Theoretical IR spectra instead of VDOS would make the work much more convincing. + +Response: We sincerely thank the reviewer for raising concerns about the reliability of directly comparing the VDOS spectrum with experimental IR data, particularly in the proton continuum region. Many previous studies have demonstrated that the vibrational peak positions of the VDOS are consistent with those of the IR spectrum (J. Chem. Phys., 2018, 148, 22, 222833, J. Chem. Phys., 2017, 146, 2, 024505). In particular, Markland's work (J. Chem. Phys., 2018, 148, 22, 222833) provides both VDOS and IR spectra for HCl solutions and water, and explicitly states, "The absolute and difference VDOS spectra exhibit the same structural features as the IR, albeit with different intensities." This agreement suggests that vibrational analysis based on VDOS can effectively capture the essential features of the IR spectrum. + +In response to the reviewer's suggestion, we have incorporated these clarifications into the manuscript on page 6, lines 158- 166. + +Comment 3- 2: The authors define vibrational vectors based on the smallest unit composed of the excess proton and the two closest water molecules. Isn't the unit too small? For instance, water molecules in the 1st coordination shell of the two waters sharing the proton are also important for properly defining the excess proton environment. Moreover, the selection is based on spatial coordinates, which have recently been suggested to be not suitable for properly characterizing excess proton configurations; see, e.g., ref.[Nat. Chem. (2024). https://doi.org/10.1038/s41557- 024- 01593- y]. Please elaborate. + +Response: We thank the reviewer for raising the important issue regarding the size of the unit used for defining vibrational vectors and the selection of spatial coordinates for + +<--- Page Split ---> + +characterizing proton configurations. To address the issue of cluster size, we present Fig. R1 to demonstrate the vibrational vectors for the first solvation shell of \(\mathrm{H}_5\mathrm{O}_2^+\) . A comparison with Fig. 4 in the manuscript reveals that the vibrational vectors of the central \(\mathrm{H}_5\mathrm{O}_2^+\) remain unchanged, and the contribution from the first solvation shell is negligible at the frequencies corresponding to the proton stretching peaks (Fig. R1a- c). + +![](images/Figure_unknown_6.jpg) + +
Fig. R1. Schematic illustration of the vibrational vectors of \(\mathrm{H}_5\mathrm{O}_2^+\) with its first solvation shell in water. a-c. The vibrational vectors for three proton-stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively.
+ +![](images/Figure_unknown_7.jpg) + +
Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the "proton continuum". From a to c, the vibrational vectors for three proton-stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d),
+ +<--- Page Split ---> + +umbrella (e), and bending (f), respectively. + +In our study, we compute vibrational vectors using MD trajectory segments, rather than static structures. This dynamic approach allows the motions of \(\mathrm{H_5O_2^+}\) to inherently preserve the impact of the surrounding water molecules. Therefore, expanding the size of the defined unit would not alter the intrinsic vibrational vectors of \(\mathrm{H_5O_2^+}\) but would instead incorporate additional vibrational information from the surrounding water molecules. + +This dynamic representation contributed to one of the advantages of our approach: the chosen cluster size does not affect the vibrational vector on atoms of concerned moieties, as it inherently accounts for the contributions from neighboring molecules in the environment. + +These points are discussed in the manuscript on page 9, lines 251- 255 and further elaborated in the Supplementary Information on page 7, lines 175- 181. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 13. + +Regarding the choice of coordinates for proton configurations, the coordinate system discussed in ref. [Nat. Chem. (2024). https://doi.org/10.1038/s41557- 024- 01593- y] indeed offers significant advantages in studying proton environment rearrangements on the picosecond timescale. However, the primary objective of our study is to assign specific vibrational modes in the IR spectrum, correlate them with proton configurations, and, based on which to interpret the "proton continuum" in the linear IR spectrum as well as the cross- peaks in 2D infrared spectra. Given the closer relationship between spatial coordinates and vibrational features (Nat. Chem., 2013, 5, 1, 29- 35, J. Phys. Chem. B, 2019, 123, 33, 7214- 7224, J. Chem. Phys., 2020, 153, 12, 124506), we opted to use spatial coordinates to characterize proton configurations. + +In response to the reviewer's comment, we have made revisions to the manuscript on pages 7- 8, lines 199- 206. + +Comment 3- 3: In their analysis, the authors divide the MD trajectory into 3ps blocks. A block is defined to contain an excess proton if the same excess proton remains as such for \(60\%\) of the 3ps. This definition adds arbitrary noise to all the subsequent analyses due to the remaining \(40\%\) . Please elaborate. + +Response: Thanks for your comment. To clarify, we emphasize that in less than \(40\%\) of the configurations, the proton does not significantly dislocate from its initial position but instead engages in rapid proton exchange through the "special pair dance" with hydrogen atoms from flanking water molecules. We have found that this proton exchange has a minimal impact on the overall analysis. + +Our comprehensive analysis of the chosen trajectory segments has shown that the proton remains within the identified \(\mathrm{H_5O_2^+}\) cluster with a high probability of \(99.7\%\) , and on one side of the \(\mathrm{H_5O_2^+}\) cluster (within one \(\mathrm{H_3O^+}\) ) with a probability of \(89.8\%\) . This indicates in remaining less than \(40\%\) of the configurations, the proton is + +<--- Page Split ---> + +predominantly in an Eigen- like configuration, and exchange with other two hydrogen atoms via "special pair dance", where three hydrogen atoms exhibit similar vibrational characteristics. + +It is worth noting that our method for identifying the proton is based on the longest O- H bond. Consequently, it is hard to identify the same hydrogen atom as a proton throughout the entire segment. During "special pair dance" process, the two exchanged hydrogen atoms (the proton and a hydrogen from a flanking water molecule) have nearly identical O- H bond lengths, thus corresponding to similar proton stretching frequencies in Eigen- like configurations (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). + +If the \(\mathrm{H}_9\mathrm{O}_4^+\) model were adopted, the proton would remain unchanged in the trajectory segments with a probability of \(89.8\%\) . However, due to the significant difference in stretching frequencies between the proton and the hydrogens of the flanking water molecules in intermediate and Zundel- like configurations, we prefer to retain the \(\mathrm{H}_2\mathrm{O}\cdots \mathrm{H}^+\cdots \mathrm{H}_2\mathrm{O}\) configuration for vibrational analysis. + +In light of these findings, we believe segmenting the trajectory into 3 ps blocks and selecting those in which the \(\mathrm{H}_2\mathrm{O}\cdots \mathrm{H}^+\cdots \mathrm{H}_2\mathrm{O}\) configuration remains consistent for over \(60\%\) of the time is a reasonable and valid approach. + +For further reference, the analysis of the chosen trajectory segments has been included in the Supplementary Information on page 7, lines 187- 192. + +Comment 3- 4: The authors introduce the need to search for intermediate proton configurations based on their choice to dissect the VDOS spectrum with Gaussian functions. However, the authors do not show if intermediate proton configurations identified from structural criteria reproduce the deconvolved Gaussian signature. I doubt it since their spectroscopic signature will hardly be Gaussian. Moreover, the authors need 6 Gaussians to fit the VDOS spectrum, this may suggest that a Gaussian fit of that complex frequency range may not be a physically meaningful choice. This can be checked with theoretical spectroscopy by computing theoretical spectra for each identified proton configuration. + +Response: Thanks for the comment. In lines 128- 133 of the manuscript, we clarify that we did not directly fit the proton VDOS with six Gaussian functions. Instead, we employed three Gaussians to fit the proton stretching band and another three for the non- stretching components of the proton VDOS. Furthermore, we would like to emphasize that the proton stretching band exhibits characteristics that align well with Gaussian modeling, as confirmed by the high coefficients of determination obtained from the Gaussian fittings in both our work and in Bowman's study (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). + +The non- stretching components exhibit three distinct vibrational peaks (Fig. R4), and irrespective of whether a Gaussian fit is applied, the identification of these peaks' number and positions remains unaffected. Additionally, the proton stretching band also follows a trend of three peaks, with their positions obtained from the Gaussian fit aligning with frequencies derived from the average proton stretching periods in the MD + +<--- Page Split ---> + +trajectory. This supports the reliability of using Gaussian functions to fit the proton stretching band. Furthermore, the high coefficient of determination ( \(\mathrm{R}^2 = 0.990\) ) further validates the reliability and accuracy of applying the 3+3 Gaussian fitting approach to the proton VDOS spectrum. + +![](images/Figure_unknown_8.jpg) + +
Fig. R4. Proton VDOS spectrum. The dark blue line represents the non-stretching vibrational spectrum of the proton, the light blue line represents the Gaussian peaks used to fit the dark blue line, and the red dashed line represents the sum of the Gaussian peaks.
+ +We also recognize that various methods have been employed to compute the vibrational spectra of static protonated water clusters extracted from MD trajectories of aqueous solutions (J. Chem. Phys., 2017, 146, 15, 154507, J. Am. Chem. Soc., 2021, 143, 18672, J. Phys. Chem. Lett., 2017, 8, 21, 5246- 5252, Nat. Chem., 2024, 16, 1838- 1844, J. Phys. Chem. B, 2019, 123, 33, 7214- 7224, J. Chem. Phys., 2020, 153, 12, 124506). To further validate the effectiveness and appropriateness of our Gaussian fitting approach, we utilized vibrational spectral data from these studies. For instance, we applied three Gaussian functions to fit the proton stretching band data from Fig. S6b in the Supporting Information of Bowman's work (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224), with a resulting coefficient of determination of \(\mathrm{R}^2 = 0.889\) , as shown in Fig. R5. Additional proton stretching band data also exhibited high coefficients of determination when fitted with three Gaussian functions, further confirming that Gaussian fitting is a robust and appropriate approach for modeling the vibrational spectra. + +<--- Page Split ---> +![](images/Supplementary_Figure_16.jpg) + +
Fig. R5. Proton stretching band fitting from the reference. The dark blue line represents the proton stretching band from the reference (J. Phys. Chem. B, 2019, 123, 33, 7214-7224), the light blue line represents the Gaussian peaks used to fit the dark blue line, and the red dashed line represents the sum of the Gaussian peaks.
+ +Comment 3- 5: In general, I'm not convinced of the physical insights that the definition of local vibrational modes can bring in a collective and strongly correlated system such as water, where vibrational modes couple between many water molecules, for sure within the 1st shell of both the water molecules around the excess proton. + +Response: We appreciate the reviewer's insightful comment regarding the definition of local vibrational modes in strongly correlated systems such as water, where vibrational modes exhibit significant coupling between multiple water molecules, especially within the first hydration shell surrounding the excess proton. + +As outlined in our response to Comment 3- 2, we compute vibrational vectors from MD trajectory segments rather than static structures. This dynamic approach inherently preserves the impact of surrounding water molecules on the motion of \(\mathrm{H_5O_2^+}\) . Expanding the defined unit would not change the intrinsic vibrational vectors of \(\mathrm{H_5O_2^+}\) ; rather, it would incorporate additional vibrational contributions from the neighboring water molecules. This dynamic perspective contributed to the advantage of our method: the chosen cluster size does not affect the vibrational vector on atoms of concerned moieties, as it naturally accounts for the coupling of vibrational modes with surrounding molecules in the hydration shell. + +Comment 3- 6: As regards the simulation method, it would be nice if the authors could justify the choice of RPBE for AIMD for a subtle problem such as excess proton characterization. Taking advantage of ML techniques, recent MD studies have been conducted at a higher level of theory, e.g., hybrid DFT. + +<--- Page Split ---> + +Response: We thank the reviewer for raising the question regarding the MD simulations utilizing the GGA level of DFT method. As noted in Markland's studies (J. Chem. Phys., 2018, 148, 22, 222833, J. Chem. Phys., 2023, 159, 7), classical simulation with GGA density functionals can reasonably reproduce most fundamental features of the experimental IR spectrum of HCl solutions and the proton diffusion coefficient due to the mutual cancellation of the nuclear quantum effect and the insufficient account of the electronic correlation. This is the reason why we prefer to implementing the classical simulations using a GGA functional. It is also important to note that classical hybrid trajectories tend to significantly underestimate the proton diffusion coefficient (J. Chem. Phys., 2023, 159, 7). In response to the reviewer's concern, we further conducted a comparative analysis by performing thermostatted ring- polymer molecular dynamics (TRPMD) simulations using the hybrid functional revPBE0- D3, implemented through the ANNFF model. This theoretical scheme further enhances the account of the electronic correlation effect as well as incorporates the nuclear quantum effect. The consistency observed in both the RDF and VDOS between the RPBE- D3 classical MD and revPBE0- D3 quantum MD simulations confirms that transitioning from a GGA functional to a hybrid functional does not alter the key conclusions of our study. + +Initially, we calculated the energies and forces at the revPBE0- D3 level using a training set that consisted of 3,259 configurations derived from the RPBE- D3 level. This initial set was then used to train a neural network with the same descriptors in the Methods section. We subsequently performed 6- beads PIGLET MD simulations (Phys. Rev. Lett., 2012, 109, 100604) using the I- PI software (Comp. Phys. Commun., 2014, 185, 1019- 1026). During these simulations, we identified structures exhibiting extrapolation warnings, which were recalculated at the revPBE0- D3 level and incorporated into the training set. After several iterations of training and configuration selection, the ANNFF model was ready for 50 ps PIGLET MD simulations with few extrapolation warnings. The final training set comprised 4,212 configurations, with an energy RMSE of 0.231 meV/atom and a force RMSE of 53.3 meV/Å, reflecting promising accuracy. + +Subsequently, we utilized the trained ANNFF model to perform TRPMD simulations (J. Chem. Phys., 2014, 140, 234116) for three systems: one containing 63 \(\mathrm{H_2O}\) molecules, a proton, and a Cl- (0.9 M HCl); another with 511 \(\mathrm{H_2O}\) molecules, a proton, and a Cl- (0.1 M HCl); and a third system consisting of 512 \(\mathrm{H_2O}\) molecules. Using the I- PI software, we set 32 beads per atom, a 60 ps trajectory length, 298 K temperature, 1 atm pressure, and a 0.3 fs time step. + +The results demonstrate that for the 0.9 M HCl system, the RDF derived from the revPBE0- D3 TRPMD trajectory closely matches that obtained from the RPBE- D3 classical MD trajectory in our study (see Fig. R6). Similarly, for both the 0.1 M HCl and water systems, the VDOS from the revPBE0- D3 TRPMD trajectory is in agreement with the features from the RPBE- D3 classical MD simulations (see Fig. R7). This consistency in both RDF and VDOS supports the conclusion that transitioning from classical MD simulations using a GGA functional (RPBE- D3) to TRPMD with a hybrid functional (revPBE0- D3) does not affect the principal conclusions of our study. These + +<--- Page Split ---> + +results further validate the appropriateness and reliability of employing RPBE- D3 for AIMD simulations. + +![](images/Figure_unknown_9.jpg) + +
Fig. R6. RDFs of the ANNFF MD trajectory for the 0.9 M HCl solution. Panels a-e display the RDFs for H-H, O-H, O-O, Cl-H, and Cl-O pairs. The dark blue lines correspond to the RDFs from the RPBE-D3 classical MD trajectory, while the red dashed lines represent the RDFs from the revPBE0-D3 TRPMD trajectory.
+ +![](images/Figure_unknown_10.jpg) + +
Fig. R7. VDOS for the 0.1 M HCl solution and pure water. The orange and cyan lines represent the VDOS from the RPBE-D3 classical MD and revPBE0-D3 TRPMD trajectories for pure water, respectively. The dark blue and yellow dashed lines represent the VDOS from the RPBE-D3 classical MD and revPBE0-D3 TRPMD trajectories for the 0.1 M HCl solution, respectively.
+ +<--- Page Split ---> + +## Answers to Reviewer #1 + +General Comments: The authors have responded in detail to the reviewer's comments 1- 5 and 8- 12 and have addressed them adequately. However, responses 6 and 7 (which are related) are not entirely convincing. + +Response: We sincerely appreciate the reviewer's overall positive assessment of our responses to comments 1- 5 and 8- 12. Regarding the concerns raised about responses 6 and 7, we acknowledge that further clarification and additional analyses are necessary to fully address the reviewer's points. Below, we provide a more detailed explanation and supplementary results to address these concerns and incorporate them into our revised manuscript and Supplementary Information. The page and line numbers mentioned hereafter refer to those found in the highlighted version. + +Comment 1- 1: In particular, MD simulations were performed to determine the possible structure of the excess proton in solvation and its correspondence to its frequency in the solvation vibrational spectrum. Since the system has intrinsically high fluctuations, the correspondence between the vibrational frequency and the structure of the "special pair" could be fuzzy and, consequently, the assignment of a vibration is made to a configuration that dominates it \(50\%\) of the time. As the authors showed in their response, considering a stricter criterion implies obtaining higher frequencies that do not match the experiment and also discarding about \(50\%\) of the data. However, this criterion seems a bit arbitrary. In this sense, is it possible to run longer simulations to reach a criterion higher than \(50\%\) that explains the experimental results? + +Response: We sincerely thank the reviewer for their insightful comments and constructive feedback. In response to the concerns raised regarding the criterion for configuration assignment, we have conducted a comprehensive re- evaluation and refined our approach to address the limitations of the previously adopted criterion. + +The initial criterion, which assigned a vibration period to a configuration if it dominated more than \(50\%\) of the period, has certain limitations. This is primarily due to the periodic variation of atomic velocities during vibration, leading to a non- uniform distribution of configurations over time. Specifically, configurations are more likely to occur near the vibration extrema and less likely near the equilibrium positions. Since the equilibrium positions of different vibration periods tend to distribute in lower- energy regions, the overall configuration distribution still favors lower- energy configurations. Furthermore, as mentioned in our response to the first round of review comments, the large amplitude of proton stretch often results in crossing configuration boundaries, making it challenging to apply a stricter criterion. + +To address these issues, we have redefined the criterion based on the equilibrium configuration of proton stretch, since the expected values of the hydrated proton configuration parameters have been shown to effectively correlate configurations with + +<--- Page Split ---> + +proton stretching frequencies (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). The new criterion is implemented as follows: + +1. Equilibrium Configuration Determination. For each vibration period, the equilibrium configuration is determined by calculating the average configuration. + +2. Probability Density Calculation. The probability densities of the equilibrium configuration \((R_{O_1\mathrm{H}^*}, R_{O_2\mathrm{H}^*})\) for the three configuration types (Zundel-like, Intermediate, and Eigen-like) are computed using their respective 2D Gaussian distribution functions. The probability density for each configuration type \(i\) is expressed as: + +\[P_{i} = A_{i}\exp \left\{-\left[(R_{O_{1}\mathrm{H}^{*}} - R_{1i})^{2} / 2\sigma_{1i}^{2} + (R_{O_{2}\mathrm{H}^{*}} - R_{2i})^{2} / 2\sigma_{2i}^{2} + c_{i}(R_{O_{1}\mathrm{H}^{*}} - R_{1i})(R_{O_{2}\mathrm{H}^{*}} - R_{2i})\right]\right\},\] + +where \(A_{i}, R_{1i}, R_{2i}, \sigma_{1i}, \sigma_{2i}\) and \(c_{i}\) are the parameters of the corresponding Gaussian distribution. + +3. Normalization and Assignment. The calculated probability densities are normalized to obtain the normalized probability, + +\[P_{i}^{N} = P_{i} / \sum_{i}P_{i}.\] + +A vibration period is assigned to a configuration type if the normalized probability of its equilibrium configuration \(P_{i}^{N} > 60\%\) . + +This refined criterion, as shown in Fig. R1b, offers several advantages: (1) it effectively distinguishes between Zundel- like, Intermediate, and Eigen- like configurations; (2) it preserves data in the central regions of the configuration distributions. To validate the criterion, we examined the effects of varying the threshold: lowering the threshold to \(50\%\) resulted in overlapping boundaries between configuration types (Fig. R1a), while raising it to \(70\%\) led to the exclusion of some data in the central regions of distributions (Fig. R1c). The \(60\%\) threshold strikes an optimal balance between configuration discrimination and data retention. + +![](images/Supplementary_Figure_8a.jpg) + +
Fig. R1. Schematic illustration of the criterion for configuration assignment of vibration periods. a-c. The boundaries for the three configuration types at thresholds of \(50\%\) (a), \(60\%\) (b), and \(70\%\) (c). The red, light blue, and dark blue dashed lines represent the boundaries for Zundel-like, Intermediate, and Eigen-like configurations, respectively.
+ +Applying this new criterion, we recalculated the average proton stretching periods + +<--- Page Split ---> + +for Zundel- like, Intermediate, and Eigen- like configurations, obtaining 25.3 fs, 18.7 fs, and 13.7 fs, respectively. These correspond to vibrational frequencies of \(1320 \mathrm{cm}^{- 1}\) , \(1780 \mathrm{cm}^{- 1}\) , and \(2430 \mathrm{cm}^{- 1}\) , which exhibit improved consistency with experimental data compared to our previous results. Importantly, the criterion's robustness is further demonstrated by the minimal impact of threshold adjustments: increasing the threshold to \(70\%\) yields frequencies of \(1280 \mathrm{cm}^{- 1}\) , \(1700 \mathrm{cm}^{- 1}\) , and \(2490 \mathrm{cm}^{- 1}\) , which remain in good agreement with experimental observations. + +The discussions are provided in the manuscript on page 8, lines 218- 221 and in the Supplementary Information on pages 4- 5, lines 97- 135. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 10. These revisions enhance the methodological rigor and reliability of our findings, ensuring a more robust interpretation of the relationship between proton configurations and their vibrational spectra. + +<--- Page Split ---> + +## Answers to Reviewer #2 + +General Comments: In the revised manuscript, the authors have addressed most of my comments. However, after reviewing their responses and the revisions, I find that the following points still need to be addressed regarding the assignment of the structural motif - the novel/central analysis in this manuscript - before it can be published. + +Response: We sincerely appreciate the reviewer's acknowledgment of the revisions made to address most of the comments, as well as their constructive feedback on the remaining points related to the assignment of structural motifs. Below, we provide a detailed response to the specific comments, along with additional clarifications and revisions to further strengthen our methodology and interpretation. These revisions have been incorporated into the manuscript and Supplementary Information to ensure clarity and rigor. We hope that the following explanations and modifications will fully address the reviewer's concerns. The page and line numbers mentioned hereafter refer to those found in the highlighted version. + +Comment 2- 1: Special pair dance refers to a hydrated central core hydronium structure that continually switches \((\mathrm{O - H}\dots \mathrm{O})\) special pair hydrogen- bond partners with the three closest water molecules. This means that the identity of the second water molecule (which is away from the unpaired \(\mathrm{H + }\) ) in the flanking partner \((\mathrm{O2H5 + })\) continuously changes. The author should calculate the survival probability of a particular \(\mathrm{O2H5 + }\) complex as well as a particular \(\mathrm{O4H9 + }\) to validate (a) the chosen 3 ps segment for spectral analysis and (b) \(\mathrm{O2H5 + }\) is better compared to \(\mathrm{O4H9 + }\) for the vibrational assignment. + +Response: We sincerely thank the reviewer for their insightful comments regarding the survival probability of particular \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) complexes and their implications for vibrational spectral analysis. Below, we provide a detailed response to address the reviewer's concerns and clarify the rationale behind our methodological choices. + +The primary rationale for selecting the \(\mathrm{H_5O_2^+}\) motif as the focus of our study lies in its ability to more accurately reflect the vibrational characteristics of the excess proton. In a particular \(\mathrm{H_5O_2^+}\) motif, the proton remains localized between two flanking water molecules, while the oxygen atom bonded to the proton can dynamically switch within the motif. This stability in proton identity makes the \(\mathrm{H_5O_2^+}\) motif particularly suitable for calculating proton vibrational spectra. In contrast, in a particular \(\mathrm{H_9O_4^+}\) motif, the oxygen atom of the \(\mathrm{H_5O^+}\) core remains constant, while the proton rapidly exchanges among the three hydrogen atoms bonded to it. Although the \(\mathrm{H_9O_4^+}\) motif is well- suited for characterizing the dynamic behavior of the Eigen cation (i.e., the "special pair dance"), it introduces complications in the assignment and interpretation of proton vibrational spectra, as discussed below. Therefore, we argue that the \(\mathrm{H_5O_2^+}\) motif offers significant advantages for analyzing proton vibrational features. However, + +<--- Page Split ---> + +for studies focusing on hydrogen- bond vibrational modes in the terahertz frequency range, the \(\mathrm{H_9O_4^+}\) motif may be more appropriate. + +In response to the reviewer's suggestion, we calculated the survival probabilities of particular \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) complexes over the chosen 3 ps segments used for spectral analysis. The results indicate that the survival probabilities of \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) are comparable, at \(65.3\%\) and \(62.1\%\) , respectively. From the perspective of survival probability alone, either motif could be considered a valid choice for analysis. However, when using the \(\mathrm{H_9O_4^+}\) motif, all three hydrogen atoms of the central \(\mathrm{H_3O^+}\) should be treated as protons. The resulting proton VDOS spectra are shown in Fig. R2. Compared to the \(\mathrm{H_5O_2^+}\) motif, the proton vibrational features in \(\mathrm{H_9O_4^+}\) are significantly averaged, particularly for the configuration- sensitive proton stretch mode (Fig. R2b). This averaging leads to a flattening of the VDOS intensity in the \(1000 - 2500\mathrm{cm}^{- 1}\) range and introduces a prominent peak near \(3000\mathrm{cm}^{- 1}\) , corresponding to the flanking water stretching. These features complicate the fitting and assignment of the proton stretch mode, further supporting the rationale for selecting the \(\mathrm{H_5O_2^+}\) motif. + +![](images/Figure_unknown_11.jpg) + +
Fig. R2. Proton VDOS spectra for \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) . a. Proton VDOS spectra. The blue line corresponds to the proton in \(\mathrm{H_5O_2^+}\) , and the red line corresponds to the protons in \(\mathrm{H_9O_4^+}\) . b. Proton stretch spectra.
+ +Regarding the reliability of the chosen 3 ps segments, we have demonstrated in Supplementary Fig. 16 that the configuration distribution within these segments is highly consistent with that of the entire trajectory. This consistency confirms that the 3 ps segments are representative of the overall dynamical behavior of the proton. We emphasize that the selection of trajectory segments does not follow a unique standard; as long as the segments are reasonably chosen, the resulting vibrational spectra will exhibit qualitative consistency, with only minor quantitative differences in peak intensities. These differences do not significantly affect the overall spectral features or the assignment of vibrational modes, and thus do not impact the validity of our conclusions. + +<--- Page Split ---> +![](images/Figure_unknown_12.jpg) + +
Supplementary Fig. 16. 2D probability density distribution of proton configurations in 0.01 M HCl. a. Distribution of the chosen trajectory segments. b. Distribution for the entire trajectory.
+ +The reviewer may note that the survival probability of the particular \(\mathrm{H_9O_4^+}\) complex \((62.1\%)\) is lower than the probability of the proton remaining on one side of the \(\mathrm{H_5O_2^+}\) motif \((89.8\%)\) reported in the Supplementary Information. This discrepancy arises from differences in the statistical criteria used in the two analyses. In the previous calculation, we focused on whether the proton deviated from the chosen \(\mathrm{H_5O_2^+}\) motif during 3 ps, calculating the probability that the proton belongs to one of the three hydrogen atoms in the \(\mathrm{H_3O^+}\) core without imposing constraints on the oxygen atom bonded to the proton. This approach included cases where the proton shifted closer to the special pair partners. In the current analysis, to reflect the survival probability of the particular \(\mathrm{H_9O_4^+}\) complex, we imposed stricter criteria by requiring the oxygen atom bonded to the proton to remain constant, resulting in a survival probability of \(62.1\%\) . This value reflects the dynamic evolution of the proton motif in the solution. + +We emphasize that the choice between the \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) motifs does not affect the calculation of vibrational vectors, as detailed in our response to the first round of review comments. Our selection of the \(\mathrm{H_5O_2^+}\) motif is based on its ability to more precisely capture proton vibrational features rather than any inherent differences in the calculation of vibrational vectors. + +In response to the reviewer's comment, we have revised the Supplementary Information (pages 8- 9, lines 234- 244) to provide a more detailed justification for selecting the \(\mathrm{H_5O_2^+}\) motif and to highlight its advantages for vibrational spectral analysis. These revisions further strengthen the clarity and rigor of our methodology. + +Comment 2- 2: In Figure 5, 'the ranges of intensities are distinctly different and essentially non- overlapping' seems to be due to the fact that the collective variable (CV) for different motifs represents different variable (despite using the same notations, q_s or q_l). I wonder if the same variable were used, the intensities would not differ much across the three motifs. In that case, the observed difference would be attributed to the choice of the variable, rather than to a true difference in the structural parameter. + +<--- Page Split ---> + +**Response:** We sincerely thank the reviewer for their insightful comments regarding the influence of collective variable (CV) selection on the distribution of local electric field intensities. Below, we provide a detailed response to address the reviewer's concerns. + +In response to the reviewer's suggestion, we calculated the conditional ensemble averages of the local electric field for Zundel- like, Intermediate, and Eigen- like configurations using the same collective coordinates \(\mathfrak{q}_{\mathrm{l}}\) and \(\mathfrak{q}_{\mathrm{s}}\) of the Intermediate state. The results are presented in Fig. R3. + +![](images/Figure_unknown_13.jpg) + +
Fig. R3. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along the collective coordinate \(\mathfrak{q}_{\mathrm{l}}\) of the intermediate state, for Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations, respectively. b. The local electric field distributions along the collective coordinate \(\mathfrak{q}_{\mathrm{s}}\) of the intermediate state, for Zundel-like, Intermediate and Eigen-like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathring{\mathrm{A}}^{-1}\)
+ +![](images/Figure_5.jpg) + + +Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \(\mathfrak{q}_{\mathrm{l}}\) , for Zundel- like (0- 0.13 V/Å, blue), Intermediate (0.13- 0.28 V/Å, yellow) and Eigen- like (0.28- 0.40 V/Å, green) configurations, respectively. b. The local electric field distributions along collective coordinate \(\mathfrak{q}_{\mathrm{s}}\) , for Zundel- like, Intermediate and Eigen- like configurations, respectively. The color bar of the scatter points signifies the + +<--- Page Split ---> + +structural probability densities in units of \(\hat{A}^{- 1}\) . + +As shown in Fig. R3a, even when using the same collective coordinate \(\mathfrak{q}\) to compute the conditional ensemble averages of the local electric field for all three configurations, the intensity ranges of the local electric field remain "distinctly different and essentially non- overlapping." This result demonstrates that the observed differences in the local electric field distributions are not due to the choice of collective variables but rather reflect intrinsic differences in the structural parameters of the three configurations. Therefore, as long as the chosen collective variables reasonably capture the structural features of the configurations, the differences in local electric field distributions among the three configurations can be clearly resolved. + +As shown in Fig. R3b, compared to Manuscript Fig. 5b, the local electric fields of Zundel- like and Eigen- like configurations exhibit some correlation with the collective coordinate \(\mathfrak{q}_5\) of the Intermediate state. This suggests that for Zundel- like and Eigen- like configurations, relying solely on the collective coordinate \(\mathfrak{q}\) of the Intermediate state is insufficient to fully describe their properties. Instead, \(\mathfrak{q}_5\) serves as a complementary coordinate that better captures their structural features. Thus, for these two configurations, using the collective coordinate \(\mathfrak{q}\) of the Intermediate state is less accurate and complete than using their respective collective coordinate \(\mathfrak{q}_5\) . + +In response to the reviewer's comments, we have included relative discussions in the manuscript on page 11, lines 292- 296 and in the Supplementary Information on page 7, lines 187- 204 to provide a more detailed justification for the choice of collective variables and to highlight their impact on the analysis of local electric field distributions. Fig. R3 has been added to the Supplementary Information as Supplementary Fig. 14 to further support our findings. These revisions enhance the rigor and reliability of our study. + +Comment 2- 3: Finally, the structural motifs (Eigen, Zundel and Intermediate) extracted here should be aligned with recent findings by Gomez et al. (Gomez, A., Thompson, W.H. & Laage, D. Nat. Chem. 16, 1838- 1844 (2024)), who used a more accurate description of electrons and nuclei in their simulations and identified the same three motifs but using a different set of CVs. The authors should verify whether applying the same type of CVs (as used by Gomez et al.) to the extracted motifs presented herein aligns with the microscopic structure of the proton in water, as described by the recent work of Gemoz et al. + +Response: We sincerely thank the reviewer for their insightful comments regarding the alignment of our structural motifs (Eigen- like, Zundel- like, and Intermediate) with the recent findings by Gomez et al. (Gomez, A., Thompson, W.H., & Laage, D. Nat. Chem. 16, 1838- 1844 (2024)), who employed a more accurate description of electrons and nuclei in their simulations and identified the same three motifs using a different set of CVs. Below, we provide a detailed response to address the reviewer's concerns and clarify the consistency between our results and those of Gomez et al. + +<--- Page Split ---> + +The core issue raised by the reviewer pertains to the reliability of our RPBE- D3 classical MD trajectories and their consistency with the revPBE0- D3 TRPMD trajectories used by Gomez et al. We acknowledge that the research objectives of Gomez et al. and our study differ significantly, which directly influences the choice of CVs and the definition of proton motifs. Gomez et al. focused on proton transfer processes, defining the three motifs primarily based on the asymmetry and coordination number of the two flanking water molecules of the proton, which are closely related to the microscopic mechanisms of proton transfer dynamics. In contrast, our study emphasizes the characterization of proton vibrational features, and our definition of the three configurations (Eigen- like, Intermediate, and Zundel- like) is based on the differences in the O- H bond lengths and hydrogen bond lengths of the protons, which are directly related to proton vibrations. Due to these differences in research objectives and definition criteria, the three motifs extracted in our study do not have a one- to- one correspondence with those of Gomez et al., making direct comparisons inappropriate. + +Nevertheless, we fully understand the reviewer's concerns regarding the reliability of the RPBE- D3 classical MD trajectories. In response, we have supplemented our analysis with revPBE0- D3 TRPMD trajectory calculations, as detailed in our response to the first round of review comments. By comparing the RDFs and overall VDOS between the RPBE- D3 classical MD and revPBE0- D3 TRPMD trajectories, we have demonstrated their consistency in overall structural features and vibrational behavior. To further validate the microscopic consistency of proton characteristics between the two trajectories, we have conducted additional analyses, including VDOS difference spectra and proton configuration distribution comparisons, as shown in Figs. R4, R5, and Table R1. + +![PLACEHOLDER_41_0] + +
Fig. R4. VDOS difference spectra between 0.1 M HCl solution and pure water. The blue line represents the difference spectrum from the RPBE-D3 classical MD trajectory, and the red line represents the difference spectrum from the revPBE0-D3 TRPMD trajectory.
+ +<--- Page Split ---> +![PLACEHOLDER_42_0] + +
Fig. R5. The 2D configurational probability density distributions of proton in 0.1 M HCl solution. a. The 2D probability density distribution from the revPBE0-D3 TRPMD trajectory. b. The three 2D Gaussian-type fitting functions for the distribution in (a) are assigned to Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations. The black lines illustrate the contour plot of the sum of the three types. c. The 2D probability density distribution from the RPBE-D3 classical MD trajectory. d. The three 2D Gaussian-type fitting functions for the distribution in (c). c-d are identical to Supplementary Fig. 8a-b.
+ +Table R1. The proportions of configurations in 0.1 M HCl solution. + +
MD trajectoryZundel-likeIntermediateEigen-like
Classical GGA0.310.420.27
Quantum hybrid0.330.420.25
+ +As shown in Fig. R4, the VDOS difference spectra from the RPBE- D3 classical MD and revPBE0- D3 TRPMD trajectories are consistent, indicating that both trajectories capture similar vibrational features of hydrated proton complex. From Fig. R5 and Table R1, it is evident that the proton configuration distributions and the proportions of the three configurations (Zundel- like, Intermediate, and Eigen- like) are highly consistent between the RPBE- D3 classical MD and revPBE0- D3 TRPMD trajectories. Specifically, compared to the RPBE- D3 classical MD trajectory, the proton configuration distribution in the revPBE0- D3 TRPMD trajectory is slightly flatter, with + +<--- Page Split ---> + +a small increase in the proportion of Zundel- like configurations and a slight decrease in the proportion of Eigen- like configurations, while the proportion of Intermediate configurations remains nearly unchanged. These minor differences do not affect the overall consistency of the configuration distributions. + +The above analyses demonstrate that, despite differences in the accuracy of electron and nuclear descriptions between the two trajectories, they exhibit high consistency in capturing proton configurations and their vibrational features. Therefore, the use of more accurate descriptions of electrons and nuclei does not compromise the reliability of our conclusions. + +<--- Page Split ---> + +## Answers to Reviewer #3 + +General Comments: The authors made substantial efforts to address reviewers' concerns, which I find convincing regarding the significance of the work, the simulation approach used, and the data analysis. + +Response: We sincerely thank the reviewer for their overall positive assessment of our work and for acknowledging the significance of our findings, the robustness of our simulation approach, and the rigor of our data analysis. We also appreciate the reviewer's constructive feedback regarding the use of VDOS instead of IR theoretical spectra for comparison with experimental data. In response to this comment, we have conducted additional analyses and implemented substantial revisions to the manuscript and Supplementary Information to address this concern. The page and line numbers mentioned hereafter refer to those found in the highlighted version. + +Comment 3- 1: However, the concern about the use of VDOS instead of IR theoretical spectra to compare to experiments remains unanswered. + +The authors correctly state in their answer that the band position doesn't shift significantly from VDOS to IR. However, the lineshape is significantly altered by the magnitude of the transient dipole, which is not taken into account in the VODS spectrum, as also noted by reviewer 2. Since the authors discuss small differences in the shape of broad bands underlying several vibrational motions (as revealed by their decomposition and Gaussian fit), this problem can potentially affect their conclusion and assignment. I still believe this is a serious issue, which deserves to be better addressed by computing IR spectra instead of VDOS, which is doable in several ways, even from ML approaches, as also noted by another reviewer. + +However, I don't want to stand in the way of this otherwise interesting manuscript, and I leave the choice on this matter to the editor. + +Response: We sincerely thank the reviewer for their valuable comments regarding the use of VDOS instead of theoretical IR spectra for comparison with experimental data. In response to the reviewer's concerns, we have conducted additional theoretical calculations to address this issue. Below, we provide a detailed response. + +Following the reviewer's suggestion, we calculated the IR spectra and their difference spectra for a \(0.9\mathrm{MHCl}\) solution and pure water. Specifically, we extracted a \(30\mathrm{ps}\) trajectory from our ANNFF MD simulations of two systems, respectively: one containing 63 water molecules, one proton, and one \(\mathrm{Cl}^-\) ion ( \(0.9\mathrm{MHCl}\) ), and the other containing 64 water molecules. Using the CP2K package (version 2024.1), we computed the Wannier centers for each structure and derived the dipole moments based on these centers. By performing Fourier transforms on the autocorrelation functions of the dipole moment derivatives, we obtained the IR spectra for \(0.9\mathrm{MHCl}\) solution and + +<--- Page Split ---> + +pure water, as well as the corresponding difference spectrum. The results are shown in Fig. R6. + +![PLACEHOLDER_45_0] + +
Fig. R6. Theoretical and experimental IR spectra of HCl solutions and water. The cyan and orange curves represent the theoretical IR spectra of \(0.9\mathrm{M}\) HCl solution and pure water, respectively. The blue curve corresponds to the theoretical IR difference spectrum between \(0.9\mathrm{M}\) HCl solution and water. The yellow curve shows the experimental IR difference spectrum between \(0.1\mathrm{M}\) HCl solution and water. The horizontal dashed line is the zero line for the difference spectra.
+ +The results demonstrate that our theoretical IR difference spectrum exhibits excellent agreement with our experimental IR difference spectrum in terms of lineshape. This finding not only confirms the reliability of our ANFFF MD trajectories but also validates the accuracy of our trajectory- based vibrational spectral analysis. Importantly, the agreement between the theoretical and experimental IR difference spectra supports the robustness of our conclusions regarding the assignment of vibrational features. + +In response to the reviewer's comments, we have revised the manuscript (page 5, lines 146- 150) and Supplementary Information (page 3, lines 65- 78) to include these additional calculations and discussions. Fig. R6 has been added to the Supplementary Information as Supplementary Fig. 6 to further support our findings. These revisions enhance the rigor and reliability of our study. + +<--- Page Split ---> + +## Answers to Reviewer #2 + +General Comments: The authors have satisfactorily addressed almost all of the comments. Regarding the final point, they have conducted an additional comparison with quantum hybrid simulations, which is convincing. However, to complete the picture, I suggest that the authors should consider computing the donor and acceptor hydrogen bond numbers of the flanking/special pair water molecules, as well as the proton transfer coordinate. + +Response: We sincerely appreciate the reviewer's positive assessment of our revisions and the constructive suggestion regarding additional hydrogen bonding analysis. Below, we provide a comprehensive response to address the remaining concern, with corresponding revisions incorporated into the manuscript and Supplementary Information. The page and line numbers mentioned hereafter refer to the highlighted version. + +Comment 2- 1: According to the study by Gemoz et al., in a perfect Zundel complex, both water molecules donate two hydrogen bonds, with the proton symmetrically located between them. In contrast, in the perfect Eigen structure, the water molecule on the side where the proton resides donates two hydrogen bonds, while the water molecule on the opposite side (farther from the proton) donates two hydrogen bonds and also accepts one. The "Zundel- like" species exhibits hydrogen- bonding features similar to those of the perfect Zundel, while the proton is localized to one side, akin to the Eigen configuration. I presume this corresponds to the "intermediate" species discussed in the present study — hence, an explicit analysis would be valuable. + +Therefore, an additional analysis of the hydrogen bonding and the proton transfer coordinate would provide a more comprehensive and insightful picture. That said, the presented work is otherwise well suited for publication without further revision. + +Response: We sincerely thank the reviewer for their valuable suggestion. Following the reviewer's recommendation, we have supplemented our analysis by computing the donor and acceptor hydrogen bond (HB) numbers for the flanking water molecules and examining their correlation with the proton transfer coordinate. Our results indicate that the HB characteristics of the "intermediate" species in our study differ significantly from those of the "Zundel- like" species proposed by Gomez et al., suggesting no direct correspondence. Below, we provide a detailed response. + +Consistent with our previous work (Phys. Rev. Lett., 2023, 131, 15, 158001), we calculated the donor and acceptor HB coordination numbers ( \(\mathrm{CN_D}\) and \(\mathrm{CN_A}\) ) for the oxygen atoms ( \(\mathrm{O_1}\) and \(\mathrm{O_2}\) ) of the flanking water molecules using the expression: + +\[\mathrm{CN_{D / A}(O_{i}) = \sum_{k = 1}^{1}\frac{[1 - (R_{i k} / R_{1})^{16}]}{[1 - (R_{i k} / R_{1})^{56}]}\cdot \frac{[1 - (\theta_{i k} / \theta_{1})^{16}]}{[1 - (\theta_{i k} / \theta_{1})^{56}]}},\] + +where the cutoff \(R_{1}\) and \(\theta_{1}\) were set as \(3.3\mathrm{\AA}\) and \(\pi /4\) , respectively. \(R_{ik}\) denotes the distance between \(\mathrm{O_i}\) and \(\mathrm{O}_k\) , and \(\theta_{ik}\) represents the supplementary angle of the \(\mathrm{O}_i\) - \(\mathrm{H - O}_k\) hydrogen bond. We statistically analyzed the average donor/acceptor HB numbers for \(\mathrm{O_1}\) (nearest to the proton) and \(\mathrm{O_2}\) (next- nearest) across three configuration types (Eigen- like, Intermediate, and Zundel- like), as summarized in + +<--- Page Split ---> + + +Table R1. The average HB numbers for Eigen-like configurations. + +
CNDCNACND - CNA
O11.940.041.90
O21.650.451.20
Difference0.29-0.410.70
+ +Table R2. The average HB numbers for Intermediate configurations. + +
CNDCNACND - CNA
O11.930.071.86
O21.750.301.45
Difference0.18-0.230.41
+ +Table R3. The average HB numbers for Zundel-like configurations. + +
CNDCNACND - CNA
O11.900.131.77
O21.840.191.65
Difference0.06-0.060.12
+ +The results demonstrate that the hydrogen bond number difference, defined as \(\Delta = [\mathrm{CN}_{\mathrm{D}}(\mathrm{O}_{1}) - \mathrm{CN}_{\mathrm{A}}(\mathrm{O}_{1})] - [\mathrm{CN}_{\mathrm{D}}(\mathrm{O}_{2}) - \mathrm{CN}_{\mathrm{A}}(\mathrm{O}_{2})]\) , is an effective indicator for distinguishing the HB network environments among the three configuration types. This observation suggests that each hydrogen bond contributed by the flanking water molecules significantly influences the overall difference in the HB network, consistent with the results of the bond- order analysis in prior literature (J. Chem. Phys., 2005, 122, 014506). Leveraging this definition, we conducted an analysis of the correlation between \(\Delta\) and the proton transfer coordinate \(\delta = R_{\mathrm{O}_2\mathrm{H}^*} - R_{\mathrm{O}_1\mathrm{H}^*}\) , as illustrated in Fig. R1. + +The results presented in Fig. R1 elucidate a clear linear correlation between \(\Delta\) and \(\delta\) , with essentially non- overlapping ranges of \(\Delta\) among the three configuration types. Specifically, Zundel- like configurations exhibit the smallest \(\Delta\) values, indicative of nearly symmetric HB environments surrounding the two flanking water molecules. In contrast, Eigen- like configurations display the largest \(\Delta\) values, reflecting pronounced asymmetry in the HB networks. Intermediate configurations demonstrate medium \(\Delta\) values, suggesting a moderate degree of HB network asymmetry between the Zundel- like and Eigen- like configurations. Consequently, the intermediate configurations markedly differ from the "Zundel- like" species characterized by a symmetric HB network proposed by Gomez et al., thereby emphasizing that our "intermediate" species are not equated with their "Zundel- like" species. + +<--- Page Split ---> +![PLACEHOLDER_48_0] + +
Fig. R1. The distributions of the HB number difference \((\Delta)\) computed with conditional ensemble average. Scatter plots depict \(\Delta\) versus the proton transfer coordinate \(\delta\) for Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations. The color bar represents structural probability densities in units of \(\mathrm{\AA}^{-1}\) .
+ +Additionally, the expression for the local electric field provided in the Supplementary Information, + +\[E_{1} = \frac{1}{4\pi\epsilon_{0}}\left(\sum_{i}\frac{q_{i}\vec{R}_{i\mathrm{H}^{*}}}{R_{i\mathrm{H}^{*}}^{3}}\right)\cdot \frac{\vec{R}_{O_{1}\mathrm{H}^{*}}}{R_{O_{1}\mathrm{H}^{*}}},\] + +reveals two key characteristics: + +1. Opposite signs for \(\mathbf{O}_{1}\) and \(\mathbf{O}_{2}\) : For a given coordinating type (donor/acceptor), the local electric field contributions from \(\mathbf{O}_{1}\) and \(\mathbf{O}_{2}\) exhibit opposite signs. +2. Opposite signs for donors and acceptors: For a given \(\mathbf{O}_{1}\) or \(\mathbf{O}_{2}\) , the local electric fields from HB donors and acceptors also possess opposite signs. + +These characteristics are consistent with the physical interpretation of the HB number difference \(\Delta\) , suggesting that the local electric field and \(\Delta\) encode similar structural information. + +To validate this hypothesis, we calculated the local electric field within the first coordination shell (defined by a HB distance criterion of \(< 3.5\mathrm{\AA}\) and an angle criterion of \(>3\pi /4\) ) and examined its correlation with \(\Delta\) . The results are presented in Fig. R2. This figure confirms a strong correlation between the local electric field and the HB number difference \(\Delta\) . This relationship underscores the efficacy of the local electric field as a descriptor for quantifying the asymmetry in the HB networks surrounding the two flanking water molecules. Specifically, the intermediate configurations exhibit a characteristic local electric field intensity that falls within a moderate range, which corresponds to a medium degree of HB network asymmetry, as illustrated in Manuscript Fig. 5. + +The rationale for prioritizing local electric field analysis over hydrogen- bond number analysis in the manuscript stems from the latter has some subjectivity—different HB criteria may yield varying results. In contrast, the local electric field serves as an objective descriptor with clear physical significance. + +<--- Page Split ---> +![PLACEHOLDER_49_0] + +
Fig. R2. The distribution of the local electric field computed with conditional ensemble average. Scatter plots depict the local electric field versus \(\Delta\) for all configurations. The color bar signifies structural probability densities in units of \(\mathrm{\AA}^{-1}\) .
+ +![PLACEHOLDER_49_1] + +
Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \(q_{1}\) , for Zundel-like (0-0.13 V/Å, blue), Intermediate (0.13-0.28 V/Å, yellow) and Eigen-like (0.28-0.40 V/Å, green) configurations, respectively. b. The local electric field distributions along collective coordinate \(q_{s}\) , for Zundel-like, Intermediate and Eigen-like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathrm{\AA}^{-1}\) .
+ +The revised analysis has been integrated into the manuscript on page 11, lines 304- 311 and in the Supplementary Information on pages 7- 8, lines 193- 236. Figs. R1- R2 have been added to the Supplementary Information as Supplementary Figs. 15- 16, and Tables R1- R3 have been included as Supplementary Tables 7- 9. These revisions enhance the rigor and reliability of our study. + +<--- Page Split ---> diff --git a/peer_reviews/13c45b352f4324e58c719da7d35b03718b9e3bcac141fff9c42f5e1328c7150c/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd b/peer_reviews/13c45b352f4324e58c719da7d35b03718b9e3bcac141fff9c42f5e1328c7150c/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7eac0063fbfd90189a2bc88ccb4696851f896389 --- /dev/null +++ b/peer_reviews/13c45b352f4324e58c719da7d35b03718b9e3bcac141fff9c42f5e1328c7150c/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd @@ -0,0 +1,1091 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 296, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 97, 296, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 914, 240]]<|/det|> +# Unveiling the Intermediate Hydrated Proton in water: Resolving the \(1,750 \text{cm}^{-1}\) Signature via Vibrational Spectrum Assignment + +<|ref|>text<|/ref|><|det|>[[73, 254, 473, 271]]<|/det|> +Corresponding Author: Professor Chungen Liu + +<|ref|>text<|/ref|><|det|>[[72, 305, 865, 320]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 357, 144, 370]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 383, 219, 396]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 409, 160, 422]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 436, 238, 449]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 449, 916, 488]]<|/det|> +The manuscript is well written and presents an important topic within the scientific society. Methodology is novel, results are well presented with good data analysis made by the authors. The description is detailed enough for a reader to be able to reproduce their work. + +<|ref|>text<|/ref|><|det|>[[72, 500, 905, 566]]<|/det|> +As it is known in the literature, the structure of proton excess in acidic solutions is an actual theme of debate. And as has been pointed out by the authors, there is a dilemma between structural diversity and solvent fluctuations. The significance of this work arises from the assignment of infrared signature at \(1750 \text{cm}^{- 1}\) to an intermediate structure that is obtained from the combination of theoretical molecular dynamics simulations and experimental infrared spectroscopy. However, there are some questions regarding this assignment, such as: + +<|ref|>text<|/ref|><|det|>[[72, 578, 921, 669]]<|/det|> +1- The structural definition of this intermediate specie is defined by the 2D Gaussian- type fitting of the "special pair" moiety of proton, employing the distances between the excess proton (H\\*) and its two adjacent oxygen atoms (O1 and O2) of flanking water molecules. Therefore they defined this new species from this fitting, without considering other water molecules beyond them. As has been pointed out before [J. Phys. Chem. B 2023, 127, 45, 9822- 9832, J. Am. Chem. Soc. 2021, 143, 18672], it should be necessary to define at least the first solvation shell of the proposed structure to fully understand it. In this line, we also would like to ask, what are the main differences between this structure and a distorted Eigen or even a distorted Zundel structure. + +<|ref|>text<|/ref|><|det|>[[72, 682, 914, 722]]<|/det|> +2- Authors claim this novel species as a result of a 2D Gaussian type fitting, in this respect we would like to know the results of fitting this with two, four or more 2D Gaussian type functions. Why do the authors consider only the case of 3 Gaussian type functions? + +<|ref|>text<|/ref|><|det|>[[70, 734, 870, 748]]<|/det|> +3- Figure 4 only shows two water molecules, but for item b) it should take into account at least the first solvation shell. + +<|ref|>text<|/ref|><|det|>[[70, 760, 905, 787]]<|/det|> +On the other hand, authors used a novel methodology that combines theory and experiment, in this line it would be nice to point out the steps I, II and III that are explicitly on the figure caption also in the Figure 1. + +<|ref|>text<|/ref|><|det|>[[70, 799, 916, 825]]<|/det|> +Although the methodology is novel, in line 274 it is said that only \(60\%\) of the proton excess configurations are considered. In this regard: what could be the consequence of disregarding this \(40\%\) of the configurations on the analyzed results? + +<|ref|>text<|/ref|><|det|>[[72, 851, 920, 890]]<|/det|> +Considering the determination of the intermediate structure (line 134 main and 138 SI), there are some concerns: - Regarding the determination of the vibrations to assign them to each configuration, are they well chosen? Is there no bias in choosing them so specifically? + +<|ref|>text<|/ref|><|det|>[[70, 890, 920, 916]]<|/det|> +- In line with previous concern: in the assignment of a vibration to a configuration that dominates it \(50\%\) of the time, isn't there too much overlap in the configurations then? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 923, 100]]<|/det|> +Authors find an explanation based on the electric field originating on the HB network (lines 223 and 72 of SI) to the existence of the intermediate structure. In this respect, it is not clear how the first solvation shell is defined and it should be addressed. Also, to be clearer Figure 5 of the main text could be just two panels (one for ql and one for qs) with the three types of configurations together with different colors or something like that. + +<|ref|>text<|/ref|><|det|>[[73, 112, 207, 125]]<|/det|> +As minor concerns: + +<|ref|>text<|/ref|><|det|>[[73, 138, 812, 153]]<|/det|> +Regarding this methodology, the employment of the IFFT method is novel and it could be more emphasized. + +<|ref|>text<|/ref|><|det|>[[73, 164, 904, 192]]<|/det|> +On lines 368, 369 and 370, authors describe three simulation boxes, it does not remain clear which one is used along the work. + +<|ref|>text<|/ref|><|det|>[[73, 203, 911, 230]]<|/det|> +In line 64 of SI, it is said that Zundel structure is preferential in concentrated solution but the difference in Zundel population with HCl concentration is too low. + +<|ref|>sub_title<|/ref|><|det|>[[73, 269, 162, 282]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 295, 610, 411]]<|/det|> +(Remarks to the Author) In this work, the authors categorize important configurational motifs for aqueous acids. The indication of the "intermediate" configuration is demonstrated using Gaussian fitting of the vibrational density of states (VDOS) and the 2D configurational probability density distribution. This is further characterized by frequency- specific vibrational vectors, obtained through the inverse Fourier transformation of the VDOS. The target of the work seems intriguing; however, the following points need to be addressed before suggesting publication: + +<|ref|>text<|/ref|><|det|>[[72, 436, 808, 528]]<|/det|> +(1) The theoretical spectra are computed using VDOS; however, this method cannot capture polarization and charge transfer effects, which may be crucial for systems like excess protons in water. Indeed, there are ML methods (e.g., Zhang, L., Chen, M., Wu, X., Wang, H., E, W., and Car, R. (2020) Physical Review B, 102(4), 041121.) that can train the position of Wannier centers as well, allowing access to dipole moment-derived spectra that can be more directly comparable with experiments. + +<|ref|>text<|/ref|><|det|>[[72, 541, 664, 594]]<|/det|> +(2) The authors calculate local electric field from the SPC/E point charge. However, this provides only partial information, where any contribution from polarization/charge transfer is completely missing. Again, the Wannier center representation would likely to work better to reveal the influence of surrounding water. + +<|ref|>text<|/ref|><|det|>[[72, 606, 710, 698]]<|/det|> +(3) The authors consider \(\mathrm{H5O2^{\wedge}(+)}\) moiety to devise the vibrational vector corresponding to the spectral signature of Eigen, Zundel or Intemediate-like configurations (Fig. 4). However, it is known that \(\mathrm{H5O2^{\wedge}(+)}\) is a candidate for Zundel-like and \(\mathrm{H9O4^{\wedge}(+)}\) is a candidate for Eigen-like picture. Additionally, proton transfer event is directly associated with the charge of the H-bond coordination of the proton-donating and proton-accepting water. Thus, in the spectral signature (at least for intermediate and Eigen configurations), other water molecules in the coordination shell are likely to be involved. + +<|ref|>text<|/ref|><|det|>[[72, 710, 697, 750]]<|/det|> +(4) The authors schematically illustrate the extraction of vibrational vectors using inverse Fourier transformation in Figure 1. However, they should elaborate on the numerical quality of each step leading to the final vibrational vectors shown in Figure 4. + +<|ref|>text<|/ref|><|det|>[[72, 763, 820, 841]]<|/det|> +(5) Diagonalizing the velocity covariance or cross-correlation matrix produces a normal mode-like picture that naturally includes the effects of temperature and anharmonicities in the dynamics (e.g., (i) Strachan A. J Chem Phys. 2004, 120(1), or (ii) Sun J, Niehues G, Forbert H, Decka D, Schwaab G, Marx D, Havenith M. J Am Chem Soc. 2014, 136(13)). The author should discuss the relevance and accuracy of the proposed methodology in relation to the existing methods mentioned above. + +<|ref|>text<|/ref|><|det|>[[72, 854, 616, 881]]<|/det|> +(6) How is the box length determined in all the simulations? Ideally, it should be based on the experimental density or from an NPT equilibration. + +<|ref|>sub_title<|/ref|><|det|>[[73, 894, 162, 906]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 920, 857, 947]]<|/det|> +(Remarks to the Author) The manuscript from Xuanye Yang and coworkers deals with a long- standing challenge in solution science, proton + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 923, 191]]<|/det|> +hydration and transport in water, and the associated spectroscopic signatures. The authors propose an approach to interpret the spectroscopic signatures of the hydrated proton in water in terms of frequency- specific vibrational vectors that are constructed from MD simulations at the DFT- GGA level, therefore, without neglecting anharmonicity and the dynamics of the liquid system. These vibrational vectors are defined based on the smallest unit composed of the excess proton and the two closest water molecules. With this approach, the authors identify an intermediate, long- lived structure between the limiting Zundel- like and Eigen- like conformations and predict its spectroscopic fingerprint at 1770 cm- 1. This is certainly a hot topic of broad interest in solution science, with many implications in acid- base chemistry and redox processes. However, in the present state, I am not fully convinced that this work advances our understanding to a level that justifies publication in Nature Communication. The possibility of intermediate states has already been reported in several works; it would make a difference if the authors could show how their findings substantially alter our understanding of the proton transport mechanism. + +<|ref|>text<|/ref|><|det|>[[72, 203, 850, 217]]<|/det|> +I also have some concerns about the results and methodology that must be solved before considering publication. + +<|ref|>text<|/ref|><|det|>[[72, 229, 923, 281]]<|/det|> +In Fig. 2a, the theoretical VDOS spectrum shows poor agreement with the experimental data around the proton continuum region, which is worrying for the reliability of the results of this work. This is even more worrying considering the authors then dissect the VODS spectrum in the proton continuum and discuss small differences, which look smaller in magnitude than the differences to the experimental spectra. Can the authors elaborate on this? + +<|ref|>text<|/ref|><|det|>[[72, 293, 911, 320]]<|/det|> +As a general comment, VDOS should not be directly compared to IR spectra, as they are substantially different spectra due to the selection rules. Theoretical IR spectra instead of VDOS would make the work much more convincing. + +<|ref|>text<|/ref|><|det|>[[72, 332, 921, 399]]<|/det|> +The authors define vibrational vectors based on the smallest unit composed of the excess proton and the two closest water molecules. Isn't the unit too small? For instance, water molecules in the 1st coordination shell of the two waters sharing the proton are also important for properly defining the excess proton environment. Moreover, the selection is based on spatial coordinates, which have recently been suggested to be not suitable for properly characterizing excess proton configurations; see, e.g., ref.[Nat. Chem. (2024). https://doi.org/10.1038/s41557-024-01593- y]. Please elaborate. + +<|ref|>text<|/ref|><|det|>[[72, 411, 915, 450]]<|/det|> +In their analysis, the authors divide the MD trajectory into 3ps blocks. A block is defined to contain an excess proton if the same excess proton remains as such for \(60\%\) of the 3ps. This definition adds arbitrary noise to all the subsequent analyses due to the remaining \(40\%\) . Please elaborate. + +<|ref|>text<|/ref|><|det|>[[72, 462, 918, 543]]<|/det|> +The authors introduce the need to search for intermediate proton configurations based on their choice to dissect the VDOS spectrum with Gaussian functions. However, the authors do not show if intermediate proton configurations identified from structural criteria reproduce the deconvolved Gaussian signature. I doubt it since their spectroscopic signature will hardly be Gaussian. Moreover, the authors need 6 Gaussians to fit the VDOS spectrum, this may suggest that a Gaussian fit of that complex frequency range may not be a physically meaningful choice. This can be checked with theoretical spectroscopy by computing theoretical spectra for each identified proton configuration. + +<|ref|>text<|/ref|><|det|>[[72, 555, 900, 595]]<|/det|> +In general, I'm not convinced of the physical insights that the definition of local vibrational modes can bring in a collective and strongly correlated system such as water, where vibrational modes couple between many water molecules, for sure within the 1st shell of both the water molecules around the excess proton. + +<|ref|>text<|/ref|><|det|>[[72, 606, 881, 647]]<|/det|> +As regards the simulation method, it would be nice if the authors could justify the choice of RPBE for AIMD for a subtle problem such as excess proton characterization. Taking advantage of ML techniques, recent MD studies have been conducted at a higher level of theory, e.g., hybrid DFT. + +<|ref|>sub_title<|/ref|><|det|>[[72, 658, 161, 671]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 685, 238, 697]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 697, 864, 737]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 750, 144, 762]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 775, 218, 788]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 802, 160, 815]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 828, 238, 841]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 841, 881, 870]]<|/det|> +The authors have responded in detail to the reviewer's comments 1- 5 and 8- 12 and have addressed them adequately. However, responses 6 and 7 (which are related) are not entirely convincing. + +<|ref|>text<|/ref|><|det|>[[72, 870, 900, 947]]<|/det|> +In particular, MD simulations were performed to determine the possible structure of the excess proton in solvation and its correspondence to its frequency in the solvation vibrational spectrum. Since the system has intrinsically high fluctuations, the correspondence between the vibrational frequency and the structure of the "special pair" could be fuzzy and, consequently, the assignment of a vibration is made to a configuration that dominates it \(50\%\) of the time. As the authors showed in their response, considering a stricter criterion implies obtaining higher frequencies that do not match the experiment and also discarding about \(50\%\) of the data. However, this criterion seems a bit arbitrary. In this sense, is it + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 820, 61]]<|/det|> +possible to run longer simulations to reach a criterion higher than \(50\%\) that explains the experimental results? + +<|ref|>sub_title<|/ref|><|det|>[[73, 86, 161, 99]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 112, 238, 125]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 125, 916, 166]]<|/det|> +In the revised manuscript, the authors have addressed most of my comments. However, after reviewing their responses and the revisions, I find that the following points still need to be addressed regarding the assignment of the structural motif - the novel/central analysis in this manuscript - before it can be published. + +<|ref|>text<|/ref|><|det|>[[72, 177, 923, 256]]<|/det|> +(1) Special pair dance refers to a hydrated central core hydronium structure that continually switches (O-H...O) special pair hydrogen-bond partners with the three closest water molecules. This means that the identity of the second water molecule (which is away from the unpaired H+) in the flanking partner (O2H5+) continuously changes. The author should calculate the survival probability of a particular O2H5+ complex as well as a particular O4H9+ to validate (a) the chosen 3 ps segment for spectral analysis and (b) O2H5+ is better compared to O4H9+ for the vibrational assignment. + +<|ref|>text<|/ref|><|det|>[[72, 267, 911, 333]]<|/det|> +(2) In Figure 5, 'the ranges of intensities are distinctly different and essentially non-overlapping' seems to be due to the fact that the collective variable (CV) for different motifs represents different variable (despite using the same notations, q_s or q_l). I wonder if the same variable were used, the intensities would not differ much across the three motifs. In that case, the observed difference would be attributed to the choice of the variable, rather than to a true difference in the structural parameter. + +<|ref|>text<|/ref|><|det|>[[72, 345, 920, 412]]<|/det|> +(3) Finally, the structural motifs (Eigen, Zundel and Intermediate) extracted here should be aligned with recent findings by Gomez et al. (Gomez, A., Thompson, W.H. & Laage, D. Nat. Chem. 16, 1838-1844 (2024)), who used a more accurate description of electrons and nuclei in their simulations and identified the same three motifs but using a different set of CVs. The authors should verify whether applying the same type of CVs (as used by Gomez et al.) to the extracted motifs presented herein aligns with the microscopic structure of the proton in water, as described by the recent work of Gemoz et al. + +<|ref|>sub_title<|/ref|><|det|>[[73, 424, 161, 437]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 450, 238, 463]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 463, 904, 490]]<|/det|> +The authors made substantial efforts to address reviewers' concerns, which I find convincing regarding the significance of the work, the simulation approach used, and the data analysis. + +<|ref|>text<|/ref|><|det|>[[72, 502, 852, 529]]<|/det|> +However, the concern about the use of VDOS instead of IR theoretical spectra to compare to experiments remains unanswered. + +<|ref|>text<|/ref|><|det|>[[72, 529, 911, 609]]<|/det|> +The authors correctly state in their answer that the band position doesn't shift significantly from VDOS to IR. However, the lineshape is significantly altered by the magnitude of the transient dipole, which is not taken into account in the VODS spectrum, as also noted by reviewer 2. Since the authors discuss small differences in the shape of broad bands underlying several vibrational motions (as revealed by their decomposition and Gaussian fit), this problem can potentially affect their conclusion and assignment. I still believe this is a serious issue, which deserves to be better addressed by computing IR spectra instead of VDOS, which is doable in several ways, even from ML approaches, as also noted by another reviewer. + +<|ref|>text<|/ref|><|det|>[[70, 620, 920, 647]]<|/det|> +However, I don't want to stand in the way of this otherwise interesting manuscript, and I leave the choice on this matter to the editor. + +<|ref|>sub_title<|/ref|><|det|>[[73, 659, 161, 672]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 686, 238, 698]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 699, 864, 737]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 750, 145, 762]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 775, 219, 789]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 802, 160, 815]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 828, 238, 841]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 841, 900, 868]]<|/det|> +The authors have responded convincingly and in detail to the reviewer's comment, and also modified the SI and the main paper to address it. As far as this reviewer is concerned, the paper could be accepted as it is. + +<|ref|>sub_title<|/ref|><|det|>[[73, 880, 161, 893]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 907, 238, 920]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 920, 899, 947]]<|/det|> +The authors have satisfactorily addressed almost all of the comments. Regarding the final point, they have conducted an additional comparison with quantum hybrid simulations, which is convincing. However, to complete the picture, I suggest + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 888, 74]]<|/det|> +that the authors should consider computing the donor and acceptor hydrogen bond numbers of the flanking/special pair water molecules, as well as the proton transfer coordinate. + +<|ref|>text<|/ref|><|det|>[[72, 86, 921, 166]]<|/det|> +According to the study by Gemoz et al., in a perfect Zundel complex, both water molecules donate two hydrogen bonds, with the proton symmetrically located between them. In contrast, in the perfect Eigen structure, the water molecule on the side where the proton resides donates two hydrogen bonds, while the water molecule on the opposite side (farther from the proton) donates two hydrogen bonds and also accepts one. The "Zundel- like" species exhibits hydrogen- bonding features similar to those of the perfect Zundel, while the proton is localized to one side, akin to the Eigen configuration. I presume this corresponds to the "intermediate" species discussed in the present study — hence, an explicit analysis would be valuable. + +<|ref|>text<|/ref|><|det|>[[72, 177, 904, 218]]<|/det|> +Therefore, an additional analysis of the hydrogen bonding and the proton transfer coordinate would provide a more comprehensive and insightful picture. That said, the presented work is otherwise well suited for publication without further revision. + +<|ref|>text<|/ref|><|det|>[[72, 230, 161, 244]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 256, 598, 283]]<|/det|> +(Remarks to the Author) The authors addressed my concerns, therefore I can recommend publication. + +<|ref|>text<|/ref|><|det|>[[72, 294, 161, 308]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 320, 863, 373]]<|/det|> +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 385, 144, 398]]<|/det|> +Version 3: + +<|ref|>text<|/ref|><|det|>[[72, 411, 219, 424]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 436, 161, 450]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 463, 891, 504]]<|/det|> +(Remarks to the Author) The authors have addressed all the points raised in a convincing manner and have revised the manuscript accordingly. I therefore recommend the manuscript for publication. + +<|ref|>text<|/ref|><|det|>[[72, 857, 916, 910]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 910, 896, 938]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 910, 88]]<|/det|> +unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[336, 95, 658, 113]]<|/det|> +## - - - Answers to Reviewer #1- - - - + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 212]]<|/det|> +General Comments: The manuscript is well written and presents an important topic within the scientific society. Methodology is novel, results are well presented with good data analysis made by the authors. The description is detailed enough for a reader to be able to reproduce their work. + +<|ref|>text<|/ref|><|det|>[[148, 214, 850, 343]]<|/det|> +As it is known in the literature, the structure of proton excess in acidic solutions is an actual theme of debate. And as has been pointed out by the authors, there is a dilemma between structural diversity and solvent fluctuations. The significance of this work arises from the assignment of infrared signature at \(1750\mathrm{cm^{- 1}}\) to an intermediate structure that is obtained from the combination of theoretical molecular dynamics simulations and experimental infrared spectroscopy. However, there are some questions regarding this assignment, such as: + +<|ref|>text<|/ref|><|det|>[[148, 362, 850, 473]]<|/det|> +Response: We thank the reviewer for the insightful comments and recognition of our work on deciphering the vibrational features of hydrated protons in water. We are grateful for the valuable suggestions and are pleased to incorporate them into our revised manuscript. Below is our point- by- point response to the reviewer's feedback. The page and line numbers mentioned hereafter refer to those found in the highlighted manuscript and Supplementary Information. + +<|ref|>text<|/ref|><|det|>[[147, 510, 851, 695]]<|/det|> +Comment 1- 1: The structural definition of this intermediate specie is defined by the 2D Gaussian type fitting of the "special pair" moiety of proton, employing the distances between the excess proton (H\\*) and its two adjacent oxygen atoms (O1 and O2) of flanking water molecules. Therefore they defined this new species from this fitting, without considering other water molecules beyond them. As has been pointed out before [J. Phys. Chem. B 2023, 127, 45, 9822- 9832, J. Am. Chem. Soc. 2021, 143, 18672], it should be necessary to define at least the first solvation shell of the proposed structure to fully understand it. In this line, we also would like to ask, what are the main differences between this structure and a distorted Eigen or even a distorted Zundel structure. + +<|ref|>text<|/ref|><|det|>[[148, 715, 851, 880]]<|/det|> +Response: We thank the reviewer for highlighting the structural definition of the intermediate species and for raising the question regarding its distinction from previously proposed configurations. We have defined the intermediate species based on the local coordinates of the "special pair", as they are strongly correlated with the proton stretching mode, which is the primary focus of this work. Our results strongly support the intermediate configuration should be treated as a distinct species due to its unique proton stretching peak at \(1770\mathrm{cm^{- 1}}\) . Regarding the first solvation shell does not change the identification of the stretching mode at \(1770\mathrm{cm^{- 1}}\) and its corresponding intermediate structure, more details are provided in our response to Comment 1- 3. + +<|ref|>text<|/ref|><|det|>[[180, 883, 848, 900]]<|/det|> +In addition, the primary focus of this work is to investigate the structural + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 213]]<|/det|> +assignments of the proton stretching mode and to interpret the "proton continuum" observed in the linear infrared spectrum as well as the cross peaks in the 2D infrared spectrum. Thus, we choose to define the intermediate species based on the local coordinates of the "special pair", which are strongly correlated with the proton stretch, as demonstrated in prior studies (Nat. Chem., 2013, 5, 1, 29- 35, J. Phys. Chem. B, 2019, 123, 33, 7214- 7224, J. Chem. Phys., 2020, 153, 12, 124506). This discussion is placed in the manuscript on page 8, lines 204- 206. + +<|ref|>text<|/ref|><|det|>[[148, 215, 851, 343]]<|/det|> +Moreover, we observe substantial overlap between adjacent configuration distributions, with the overall distribution exhibiting a single peak. This finding is consistent with results from the global free energy surface analysis (J. Phys. Chem. B, 2023, 127, 45, 9822- 9832). Therefore, simplifying the configuration definition to spatial coordinates of the "special pair" does not undermine the validity of our conclusions. This discussion can be found in the manuscript on page 8, lines 208- 210 and line 212. + +<|ref|>text<|/ref|><|det|>[[148, 363, 851, 547]]<|/det|> +From a structural standpoint, categorizing the intermediate species as a distorted Eigen or distorted Zundel configuration as previous literature (J. Am. Chem. Soc., 2021, 143, 18672, Nat. Chem., 2018, 10, 9, 932- 937) does not fully represent its unique spectroscopic characteristics, particularly the proton stretching peak at \(1770 \mathrm{cm}^{- 1}\) , which is clearly different from the peaks associated with Zundel- like (1250 \(\mathrm{cm}^{- 1}\) ) and Eigen- like (2530 \(\mathrm{cm}^{- 1}\) ) configurations. Moreover, simply classifying the intermediate structures as distorted Eigen or Zundel does not adequately explain the presence of three proton stretching peaks in the VODS spectrum, nor does it account for the fact that the \(1750 \mathrm{cm}^{- 1}\) signal in the 2D IR spectrum exhibits vibrational relaxation decay that follows a biexponential function (J. Phys. Chem. B, 2018, 122, 10, 2792- 2802). + +<|ref|>text<|/ref|><|det|>[[148, 585, 853, 658]]<|/det|> +Comment 1- 2: Authors claim this novel species as a result of a 2D Gaussian type fitting, in this respect we would like to know the results of fitting this with two, four or more 2D Gaussian type functions. Why do the authors consider only the case of 3 Gaussian type functions? + +<|ref|>text<|/ref|><|det|>[[148, 678, 851, 806]]<|/det|> +Response: We thank the reviewer for raising concerns regarding the reliability of the fitting approach used for the configuration distribution. This issue is briefly discussed in the caption of Manuscript Fig. 3, where we note that reducing the number of Gaussian functions results in a significant increase in the fitting error, whereas adding additional Gaussian functions does not lead to notable improvements (see Supplementary Fig. 8). Furthermore, Supplementary Fig. 8 presents the error distributions obtained when fitting with two or four 2D Gaussian functions. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 94, 829, 275]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 288, 850, 364]]<|/det|> +
Supplementary Fig. 8. The absolute error distributions of the proton configuration distribution fittings. a-b. The absolute error distributions for fitting the proton configuration distribution with two and four 2D Gaussian functions, respectively. The unit of RMSE and AE is \(\hat{\mathrm{A}}^{-2}\) .
+ +<|ref|>text<|/ref|><|det|>[[148, 381, 849, 419]]<|/det|> +Since the figure caption may be overlooked, we have decided to incorporate this explanation into the manuscript, now found on page 8, lines 213- 215. + +<|ref|>text<|/ref|><|det|>[[148, 455, 849, 492]]<|/det|> +Comment 1- 3: Figure 4 only shows two water molecules, but for item b) it should take into account at least the first solvation shell. + +<|ref|>text<|/ref|><|det|>[[147, 511, 851, 641]]<|/det|> +Response: We thank the reviewer for the suggestion regarding the range of vibrational vector calculations. To evaluate the influence of cluster size on vibrational vector calculations, we present in Fig. R1 the vibrational vectors for the clusters including the first solvation shell of \(\mathrm{H}_5\mathrm{O}_2^+\) . A comparison with Manuscript Fig. 4 reveals that the vibrational vectors of the central \(\mathrm{H}_5\mathrm{O}_2^+\) remain unchanged. Moreover, at the frequencies corresponding to the proton stretching peaks (Fig. R1a- c), the contribution from the first solvation shell is negligible. + +<|ref|>image<|/ref|><|det|>[[150, 661, 815, 914]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 852, 159]]<|/det|> +Fig. R1. Schematic illustration of the vibrational vectors of \(\mathrm{H_5O_2^+}\) with its first solvation shell in water. a-c. The vibrational vectors for three proton- stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively. + +<|ref|>image<|/ref|><|det|>[[149, 181, 827, 425]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 436, 852, 549]]<|/det|> +Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the "proton continuum". From a to c, the vibrational vectors for three proton- stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d), umbrella (e), and bending (f), respectively. + +<|ref|>text<|/ref|><|det|>[[147, 566, 852, 696]]<|/det|> +Since we used MD trajectory segments to compute the vibrational vectors, rather than static structures, the motions of \(\mathrm{H_5O_2^+}\) inherently preserve the dynamical impact of the surrounding water molecules. Consequently, expanding the range of calculations would not modify the intrinsic vibrational vectors of \(\mathrm{H_5O_2^+}\) , but would only incorporate additional vibrational information from the surrounding water molecules. This underscores one of the advantages of our approach: the chosen cluster size does not affect the vibrational vectors of the concerned motifs. + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 752]]<|/det|> +The discussions are provided in the manuscript on page 9, lines 251- 255 and in the Supplementary Information on page 7, lines 175- 181. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 13. + +<|ref|>text<|/ref|><|det|>[[148, 789, 850, 844]]<|/det|> +Comment 1- 4: On the other hand, authors used a novel methodology that combines theory and experiment, in this line it would be nice to point out the steps I, II and III that are explicitly on the figure caption also in the Figure 1. + +<|ref|>text<|/ref|><|det|>[[148, 863, 850, 900]]<|/det|> +Response: We sincerely appreciate the reviewer's valuable suggestion. In accordance with the recommendation, we have explicitly labeled steps I, II, III, and IV in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 812, 103]]<|/det|> +Manuscript Fig. 1 to ensure consistency with the figure caption, as shown below. + +<|ref|>image<|/ref|><|det|>[[152, 123, 844, 318]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 325, 855, 455]]<|/det|> +Manuscript Fig. 1. An integrated approach for assigning vibrational spectrum derived from molecular dynamics simulations. A "special pair", consisting of the excess proton and its two flanking water molecules, is employed as the fundamental moiety for interpreting the solvated proton's vibrational spectrum (Nat. Commun., 2022, 13, 1, 6170). For an arbitrary frequency in the vibrational spectrum, the vibrational vectors of all atoms in the moiety can be derived via the four distinct steps illustrated in the flowchart. + +<|ref|>text<|/ref|><|det|>[[148, 491, 851, 548]]<|/det|> +Comment 1- 5: Although the methodology is novel, in line 274 it is said that only \(60\%\) of the proton excess configurations are considered. In this regard: what could be the consequence of disregarding this \(40\%\) of the configurations on the analyzed results? + +<|ref|>text<|/ref|><|det|>[[148, 566, 852, 678]]<|/det|> +Response: We thank the reviewer for raising the issue regarding the selection of trajectory segments. To address this, we would like to emphasize that the chosen segments are representative of the entire trajectory. Additionally, in remaining \(40\%\) of the configurations, the proton undergoes rapid exchange through "special pair dance". We have found that the impact of this proton exchange phenomenon on the vibrational spectrum assignment is minimal. + +<|ref|>text<|/ref|><|det|>[[148, 679, 851, 771]]<|/det|> +In our study, the MD trajectory was divided into 3 ps segments, with a segment being classified as containing an excess proton if the same proton in the \(\mathrm{H_2O\cdots H^+\cdots H_2O}\) configuration was present for more than \(60\%\) of the 3 ps. Based on this criterion, we selected 26 segments for further analysis, which collectively account for \(6.5\%\) of the entire trajectory. + +<|ref|>text<|/ref|><|det|>[[148, 771, 851, 864]]<|/det|> +To validate the representativeness of the chosen segments, we computed the 2D probability density distribution of proton configurations for the chosen trajectory segments (see Fig. R2a) and compared it with the distribution obtained from the entire trajectory (Fig. R2b). The results reveal good agreement between the two distributions, confirming the adequacy of the segment selection scheme. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[153, 85, 833, 263]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 270, 850, 325]]<|/det|> +
Fig. R2. 2D probability density distribution of proton configurations in 0.01 M HCl. a. Distribution of the chosen trajectory segments. b. Distribution for the entire trajectory (the same as Manuscript Fig. 3a).
+ +<|ref|>text<|/ref|><|det|>[[148, 344, 851, 473]]<|/det|> +Furthermore, a comprehensive analysis of the chosen trajectory segments revealed that the proton remains within the identified \(\mathrm{H}_3\mathrm{O}_2^+\) cluster with a probability of \(99.7\%\) and with the probability of \(89.8\%\) it dwells on a single \(\mathrm{H}_3\mathrm{O}^+\) motif. This indicates that in the remaining less than \(40\%\) configurations, the excess proton stays in the \(\mathrm{H}_3\mathrm{O}_2^+\) species but rapidly exchanges with hydrogen atoms on the two flanking waters through "special pair dance". Therefore, the \(\mathrm{H}_3\mathrm{O}_2^+\) moiety is essentially effective for characterizing the excess proton in water. + +<|ref|>text<|/ref|><|det|>[[148, 474, 851, 658]]<|/det|> +It is crucial to highlight that the excess proton exists in a state of ultrafast special pair dance predominantly in the Eigen- like configuration, which results in the three hydrogen atoms within the \(\mathrm{H}_3\mathrm{O}^+\) core of an Eigen- like cation continuously exchanging their identities, shifting between being the excess proton and hydrogen atoms of the flanking water molecules. Importantly, the excess proton remains confined within the \(\mathrm{H}_3\mathrm{O}_2^+\) moiety, and since our analysis identifies the proton based on the longest O- H bond, the two exchanged hydrogen atoms in Eigen- like configurations exhibit similar O- H bond lengths, thus corresponding to similar proton stretching frequencies (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). Consequently, the overall configuration as well as the identity of the proton should not be considered altered. + +<|ref|>text<|/ref|><|det|>[[148, 660, 851, 861]]<|/det|> +Due to the current limitations in criteria for identifying the excess proton, the special pair dance undergone by the excess proton is often misinterpreted as instances of identity shifting, leading to an underestimation of the probability of the sustained configuration. If the \(\mathrm{H}_3\mathrm{O}_4^+\) model were adopted, the probability of the proton remaining unchanged in trajectory segments would be \(89.8\%\) . However, because of the significant difference in stretching frequencies between the proton and the hydrogens of the flanking water molecules in intermediate and Zundel- like configurations, we prefer to retain the \(\mathrm{H}_2\mathrm{O}\dots \mathrm{H}^+\dots \mathrm{H}_2\mathrm{O}\) configuration for vibrational analysis. Despite this, we believe segmenting the trajectory into 3 ps blocks to identify the same proton within the \(\mathrm{H}_2\mathrm{O}\dots \mathrm{H}^+\dots \mathrm{H}_2\mathrm{O}\) configuration, which remains consistent for over \(60\%\) of the time, constitutes a reasonable and reliable methodology. + +<|ref|>text<|/ref|><|det|>[[148, 863, 850, 899]]<|/det|> +To avoid potential misunderstandings, we have revised the description of the segment selection process in the Methods section on page 14, lines 358- 369. The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +analyses of the chosen trajectory segments are added to the Supplementary Information on page 7, lines 182- 192. Fig. R2 has been added to the Supplementary Information as Supplementary Fig. 14. + +<|ref|>text<|/ref|><|det|>[[148, 177, 850, 212]]<|/det|> +Comment 1- 6: Considering the determination of the intermediate structure (line 134 main and 138 SI), there are some concerns: + +<|ref|>text<|/ref|><|det|>[[148, 214, 850, 250]]<|/det|> +- Regarding the determination of the vibrations to assign them to each configuration, are they well chosen? Is there no bias in choosing them so specifically? + +<|ref|>text<|/ref|><|det|>[[148, 270, 850, 380]]<|/det|> +Response: We thank the reviewer for pointing out the key point of our work. Due to the significant dynamical effects exhibited by protons in acidic solutions, the direct one- to- one correspondence between proton configurations and their stretching frequencies is inaccessible. Therefore, we circumvent this obstacle to explore the statistical correlation between proton configurations and proton stretching frequencies, rather than focusing on the specific behavior of proton configurations in individual snapshots. + +<|ref|>text<|/ref|><|det|>[[148, 382, 851, 529]]<|/det|> +The statistical results of the average proton stretching frequencies across the three configuration distributions reveal a clear correlation between the configuration distributions and the stretching peak positions. However, this does not imply that, in each snapshot of the trajectory, the proton configuration and its corresponding stretching frequency strictly follow this correlation. As shown in Fig. 2d and Fig. 3b of the manuscript, there is some overlap between the three proton stretching peaks, and the distributions of the three configurations also exhibit overlap. For detailed data, please refer to Response 1- 7. + +<|ref|>text<|/ref|><|det|>[[148, 531, 850, 566]]<|/det|> +In response to the reviewer's comment, we have revised the Supplementary Information on page 6, lines 145- 149 and lines 169- 171. + +<|ref|>text<|/ref|><|det|>[[148, 604, 850, 658]]<|/det|> +Comment 1- 7: In line with previous concern: in the assignment of a vibration to a configuration that dominates it \(50\%\) of the time, isn't there too much overlap in the configurations then? + +<|ref|>text<|/ref|><|det|>[[148, 678, 851, 769]]<|/det|> +Response: Thanks for your comment. Given the typically large amplitude of proton stretching, protons are prone to crossing configuration boundaries in vibrational motions. Thus, setting a very strict assignment criterion may result in the exclusion of a significant amount of valuable data. For instance, increasing the criterion from \(50\%\) to \(70\%\) would result in the discard of \(52\%\) of the data. + +<|ref|>text<|/ref|><|det|>[[148, 771, 851, 899]]<|/det|> +The impact of adjusting the criterion on the average proton stretching frequencies is illustrated in Fig. R3. The average frequencies for each configuration type at a \(50\%\) criterion are used as the reference, and the frequency differences for other criteria are computed relative to this reference. Notably, for the Zundel- like and Eigen- like configurations, the frequency variation remains relatively small between the \(50\%\) and \(60\%\) criteria. However, a more significant shift occurs when the criterion is increased from \(60\%\) to \(70\%\) . A stricter criterion tends to filter out instances with longer periods, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 852, 214]]<|/det|> +resulting in an overestimation of the average frequency. Specifically, increasing the criterion to \(70\%\) would shift the average proton stretching frequencies for the Zundel- like, intermediate, and Eigen- like configurations to \(1430\mathrm{cm}^{- 1}\) , \(2010\mathrm{cm}^{- 1}\) , and \(2530\mathrm{cm}^{- 1}\) , respectively, leading to a substantial deviation from the experimental IR spectrum. Therefore, we find the \(50\% - 60\%\) range to be the most appropriate for defining the assignment criterion, as it strikes a balance between configuration uncertainty and the utilization rate of the MD trajectory. + +<|ref|>image<|/ref|><|det|>[[295, 243, 700, 457]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 474, 852, 549]]<|/det|> +
Fig. R3. Variation of the average proton stretching frequencies for the three configurations as a function of the assignment criterion. The blue, yellow, and orange lines represent the frequency differences for the Zundel-like, Intermediate, and Eigen-like configurations, respectively.
+ +<|ref|>text<|/ref|><|det|>[[147, 567, 851, 732]]<|/det|> +The \(50 - 60\%\) criterion is, in fact, a rough estimate. Due to the dynamic effects within the solution, the periodic motion of atoms is often disrupted, which introduces some uncertainty in the average frequencies derived from the MD trajectory. Nevertheless, our statistical analysis reveals significant differences in the average frequencies of proton stretching across the three configurations, with a progressive increase from Zundel- like to Eigen- like configurations. Specifically, when the assignment criterion is set at \(50\%\) , configurations with a vibrational frequency near \(1770\mathrm{cm}^{- 1}\) are attributed predominantly to the intermediate configuration, comprising up to \(70\%\) . + +<|ref|>text<|/ref|><|det|>[[148, 734, 850, 788]]<|/det|> +In response to the reviewer's comment, we have revised the manuscript (page 9, lines 231- 233) and the Supplementary Information (page 6, lines 156- 168 and lines 171- 174). + +<|ref|>text<|/ref|><|det|>[[148, 825, 850, 899]]<|/det|> +Comment 1- 8: Authors find an explanation based on the electric field originating on the HB network (lines 223 and 72 of SI) to the existence of the intermediate structure. In this respect, it is not clear how the first solvation shell is defined and it should be addressed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 102, 852, 177]]<|/det|> +Response: We thank the reviewer for pointing out the need for clarification regarding the definition of the first solvation shell. To clarify, our definition of the first solvation shell is added to the Supplementary Information on pages 3- 4, lines 81- 84, as detailed below: + +<|ref|>text<|/ref|><|det|>[[148, 178, 850, 234]]<|/det|> +"For hydrogen atoms surrounding the proton, if either of the closest or second- closest oxygen atoms originates from the \(\mathrm{H}_3\mathrm{O}_2^+\) moiety, we classify the water molecule containing the other oxygen atom as part of the first solvation shell of \(\mathrm{H}_3\mathrm{O}_2^+\) ." + +<|ref|>text<|/ref|><|det|>[[148, 269, 850, 325]]<|/det|> +Comment 1- 9: Also, to be clearer Figure 5 of the main text could be just two panels (one for ql and one for qs) with the three types of configurations together with different colors or something like that. + +<|ref|>text<|/ref|><|det|>[[148, 344, 850, 417]]<|/det|> +Response: We thank the reviewer for the valuable suggestion. In response, we have revised Manuscript Fig. 5 to feature two panels. Similar modifications have also been applied to Supplementary Fig. 10. The original figures are provided for comparison, as shown below. + +<|ref|>image<|/ref|><|det|>[[150, 435, 830, 617]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 622, 852, 753]]<|/det|> +Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \(\mathfrak{q}_1\) , for Zundel- like (0- 0.13 V/A, blue), Intermediate (0.13- 0.28 V/A, yellow) and Eigen- like (0.28- 0.40 V/A, green) configurations, respectively. b. The local electric field distributions along collective coordinate \(\mathfrak{q}_s\) , for Zundel- like, Intermediate and Eigen- like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathrm{\AA}^{- 1}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 85, 828, 265]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 270, 852, 382]]<|/det|> +
Supplementary Fig. 10. The conditional ensemble average distributions of the local electric field for the two 2D Gaussian distributions. a. The local electric field distributions along the collective coordinate \(q_{1}\) of the two 2D Gaussian distributions, respectively. b. The local electric field distributions along the collective coordinate \(q_{s}\) of the two 2D Gaussian distributions, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathring{\mathrm{A}}^{-1}\) .
+ +<|ref|>image<|/ref|><|det|>[[150, 402, 848, 651]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 660, 365, 678]]<|/det|> +
Initial Manuscript Fig. 5
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 85, 844, 451]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 456, 406, 474]]<|/det|> +
Initial Supplementary Fig. 10
+ +<|ref|>text<|/ref|><|det|>[[148, 511, 851, 566]]<|/det|> +Comment 1- 10: As minor concerns: Regarding this methodology, the employment of the IFFT method is novel and it could be more emphasized. + +<|ref|>text<|/ref|><|det|>[[147, 585, 851, 677]]<|/det|> +Response: We thank the reviewer for the valuable suggestion regarding the IFFT method. In response, we have revised the detailed description of our approach, originally in the caption of Manuscript Fig. 1, and incorporated it into the manuscript on page 3, lines 79- 99. Additionally, we have emphasized its significance on page 3, lines 100- 104, stating: + +<|ref|>text<|/ref|><|det|>[[147, 678, 851, 789]]<|/det|> +"The core of this integrated approach lies in utilizing the IFFT to determine, for any given frequency, the vibrational amplitudes and phases associated with all atoms within a specified structural motif of interest. Through a carefully designed strategy that involves averaging the vibrational vectors over different segments, this method offers a feasible framework for assigning vibrational spectra in highly flexible structures, such as liquids." + +<|ref|>text<|/ref|><|det|>[[147, 826, 850, 862]]<|/det|> +Comment 1- 11: On lines 368, 369 and 370, authors describe three simulation boxes, it does not remain clear which one is used along the work. + +<|ref|>text<|/ref|><|det|>[[147, 881, 850, 900]]<|/det|> +Response: We appreciate the reviewer for addressing the issue concerning the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 158]]<|/det|> +simulation boxes used in the study. As stated in lines 108- 110 of the manuscript, we have clarified that all subsequent analyses are based on a 0.01 M HCl solution, comprising 4095 H₂O molecules, a proton, and a Cl⁻ ion, in order to minimize the influence of chloride ions. + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 195]]<|/det|> +To enhance clarity, we have incorporated additional details in the Methods section (page 18, lines 484- 490), as outlined below. + +<|ref|>text<|/ref|><|det|>[[148, 196, 851, 344]]<|/det|> +"For comparison, a system comprising 63 water molecules, a proton, and a chloride ion pair (equivalent to 0.9 M HCl) is presented in the Supplementary Information. Additionally, a system containing 511 water molecules, a proton, and a chloride ion pair (0.1 M HCl), as well as a system with 512 water molecules, were utilized to generate the theoretical difference VDOS spectrum shown in Fig. 2a. These systems are also included in the Supplementary Information for comparison. All other analyses presented in the manuscript are based on a 0.01 M HCl solution, which consists of 4,095 water molecules, a proton, and a chloride ion pair." + +<|ref|>text<|/ref|><|det|>[[148, 380, 850, 435]]<|/det|> +Comment 1- 12: In line 64 of SI, it is said that Zundel structure is preferential in concentrated solution but the difference in Zundel population with HCl concentration is too low. + +<|ref|>text<|/ref|><|det|>[[148, 455, 852, 565]]<|/det|> +Response: We thank the reviewer for pointing out the limited variation in the Zundel- like population with respect to HCl concentration. We agree with this observation. Previous studies have shown that at higher proton concentrations, the population of Zundel- like configurations increases significantly (Science, 2017, 357, 6350, 491- 495). However, within the concentration range considered in our study, the proportion of Zundel- like configurations remains relatively stable. + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 621]]<|/det|> +In response, we have revised the description of Supplementary Table 2 (Supplementary Information page 3, lines 65- 68) to more accurately reflect our findings. The updated description is provided below: + +<|ref|>text<|/ref|><|det|>[[148, 623, 850, 677]]<|/det|> +"As the HCl concentration increases, the proportions of these three configurations exhibit minimal variation, as detailed in Supplementary Table 2. This observation suggests that the intermediate configuration remains stable under dilute HCl solutions." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[336, 95, 658, 113]]<|/det|> +## -Answers to Reviewer #2- + +<|ref|>text<|/ref|><|det|>[[148, 142, 850, 270]]<|/det|> +**General Comments:** In this work, the authors categorize important configurational motifs for aqueous acids. The indication of the "intermediate" configuration is demonstrated using Gaussian fitting of the vibrational density of states (VDOS) and the 2D configurational probability density distribution. This is further characterized by frequency-specific vibrational vectors, obtained through the inverse Fourier transformation of the VDOS. The target of the work seems intriguing; however, the following points need to be addressed before suggesting publication: + +<|ref|>text<|/ref|><|det|>[[148, 290, 850, 418]]<|/det|> +**Response:** We sincerely thank the reviewer for their thorough evaluation of our manuscript and for the insightful comments provided. We have carefully considered each point raised and addressed them in detail. Based on these responses, we have made substantial revisions to the manuscript to enhance its clarity and overall quality. We hope that the following clarifications and revisions will address the concerns raised by the reviewer. The page and line numbers mentioned hereafter refer to those found in the highlighted manuscript and Supplementary Information. + +<|ref|>text<|/ref|><|det|>[[148, 457, 850, 567]]<|/det|> +**Comment 2-1:** The theoretical spectra are computed using VDOS; however, this method cannot capture polarization and charge transfer effects, which may be crucial for systems like excess protons in water. Indeed, there are ML methods (e.g., Zhang, L., Chen, M., Wu, X., Wang, H., E, W., and Car, R. (2020) Physical Review B, 102(4), 041121.) that can train the position of Wannier centers as well, allowing access to dipole moment-derived spectra that can be more directly comparable with experiments. + +<|ref|>text<|/ref|><|det|>[[148, 587, 850, 678]]<|/det|> +**Response:** We thank the reviewer for the insightful suggestion regarding the use of machine learning methods to compute infrared spectra. We would like to emphasize that our analysis reveals a strong consistency between the structural features of VDOS and IR spectra, with differences primarily in intensity. This suggests that vibrational analysis based on VDOS can effectively capture the features of the IR spectrum. + +<|ref|>text<|/ref|><|det|>[[148, 681, 850, 880]]<|/det|> +The work referenced by the reviewer (Zhang, L., Chen, M., Wu, X., Wang, H., E, W., and Car, R. (2020) Physical Review B, 102(4), 041121.) offers a promising approach to calculating theoretical IR spectra based on machine learning force fields. However, it is important to note that infrared spectra derived from the dipole moment autocorrelation function cannot directly provide the atomic velocities necessary for calculating vibrational vectors. Furthermore, the calculation of IR spectra does not influence the results of our vibrational vector analysis. For the purposes of this study and subsequent analysis, we have chosen to focus on the VDOS based on atomic velocities. While we acknowledge the limitations of this approach, we intend to explore more advanced machine learning methods in future work to gain a more comprehensive understanding of vibrational properties. + +<|ref|>text<|/ref|><|det|>[[188, 884, 848, 900]]<|/det|> +Additionally, Markland’s work (J. Chem. Phys., 2018, 148, 22, 222833) provides + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 195]]<|/det|> +VDOS and IR spectra of HCl solutions and water, calculated from AIMD trajectories using the revPBE- D3 functional, along with difference spectra. This study shows that theoretical VDOS and IR spectra exhibit the same structural features, differing primarily in intensity, and that the peak positions align with experimental IR spectra. This consistency indicates that vibrational analysis based on VDOS can effectively capture the characteristic features of the IR spectrum. + +<|ref|>text<|/ref|><|det|>[[148, 197, 850, 232]]<|/det|> +In response to the reviewer's suggestion, we have included the relevant clarification in the manuscript on page 6, lines 158- 166. + +<|ref|>text<|/ref|><|det|>[[148, 270, 850, 343]]<|/det|> +Comment 2- 2: The authors calculate local electric field from the SPC/E point charge. However, this provides only partial information, where any contribution from polarization/charge transfer is completely missing. Again, the Wannier center representation would likely to work better to reveal the influence of surrounding water. + +<|ref|>text<|/ref|><|det|>[[148, 363, 850, 416]]<|/det|> +Response: We thank the reviewer for highlighting the limitation of using the SPC/E point charge model in the calculation of the local electric field, as it does not capture polarization or charge transfer effects. + +<|ref|>text<|/ref|><|det|>[[148, 418, 850, 565]]<|/det|> +In our prior work (Phys. Rev. Lett., 2023, 131, 15, 158001), we compared the use of SPC/E and DFT charges for calculating the local electric field. Specifically, 3,000 structures were randomly selected from metadynamics trajectories, and the iterative Hirshfeld method was employed to analyze atomic charge distributions. The results indicated that the local electric field distributions derived from both charge schemes were highly similar. Consequently, employing SPC/E point charges for local electric field calculations is a valid and efficient approximation that does not impact significantly the solidity of the conclusions. + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 602]]<|/det|> +In response to this concern, we have included a brief clarification in the caption of Manuscript Fig. 5. + +<|ref|>text<|/ref|><|det|>[[148, 640, 850, 787]]<|/det|> +Comment 2- 3: The authors consider \(\mathrm{H5O2}^{\wedge}\{+\}\) moiety to devise the vibrational vector corresponding to the spectral signature of Eigen, Zundel or Intemediate- like configurations (Fig. 4). However, it is known that \(\mathrm{H5O2}^{\wedge}\{+\}\) is a candidate for Zundel- like and \(\mathrm{H9O4}^{\wedge}\{+\}\) is a candidate for Eigen- like picture. Additionally, proton transfer event is directly associated with the change of the H- bond coordination of the proton- donating and proton- accepting water. Thus, in the spectral signature (at least for intermediate and Eigen configurations), other water molecules in the coordination shell are likely to be involved. + +<|ref|>text<|/ref|><|det|>[[148, 808, 850, 899]]<|/det|> +Response: We thank the reviewer for the constructive comment regarding the scope of the vibrational vector calculations. To evaluate the influence of cluster size on vibrational vector calculations, we present Fig. R1, which displays the vibrational vectors for the first solvation shell of \(\mathrm{H_5O_2}^+\) . A comparison with Manuscript Fig. 4 reveals that the vibrational vectors of the central \(\mathrm{H_5O_2}^+\) remain consistent. Moreover, at + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +the frequencies corresponding to the proton stretching peaks (Fig. R1a- c), the contribution from the first solvation shell is negligible. + +<|ref|>image<|/ref|><|det|>[[150, 142, 825, 392]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 399, 851, 474]]<|/det|> +
Fig. R1. Schematic illustration of the vibrational vectors of \(\mathrm{H}_3\mathrm{O}_2^+\) with its first solvation shell in water. a-c. The vibrational vectors for three proton-stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively.
+ +<|ref|>image<|/ref|><|det|>[[150, 496, 828, 742]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 752, 851, 863]]<|/det|> +Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the "proton continuum". From a to c, the vibrational vectors for three proton- stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d), umbrella (e), and bending (f), respectively. + +<|ref|>text<|/ref|><|det|>[[185, 882, 848, 900]]<|/det|> +In our study, we used MD trajectory segments to compute the vibrational vectors, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 213]]<|/det|> +rather than relying on static structures. This approach inherently preserves the dynamic impact of the surrounding water molecules on the \(\mathrm{H_3O_2}^+\) moiety. As a result, expanding the range of the calculation would not alter the intrinsic vibrational vectors of \(\mathrm{H_3O_2}^+\) itself but would instead incorporate additional vibrational contributions from the surrounding water molecules. This feature of our methodology highlights one of its advantages: the chosen cluster size does not affect the vibrational vector on atoms of concerned moieties. + +<|ref|>text<|/ref|><|det|>[[149, 215, 850, 269]]<|/det|> +We have included relative discussions in the manuscript on page 9, lines 251- 255 and in the Supplementary Information on page 7, lines 175- 181. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 13. + +<|ref|>text<|/ref|><|det|>[[148, 306, 850, 379]]<|/det|> +Comment 2- 4: The authors schematically illustrate the extraction of vibrational vectors using inverse Fourier transformation in Figure 1. However, they should elaborate on the numerical quality of each step leading to the final vibrational vectors shown in Figure 4. + +<|ref|>text<|/ref|><|det|>[[148, 399, 850, 453]]<|/det|> +Response: We thank the reviewer for highlighting the numerical quality of the vibrational vector extraction process. To provide further clarity, we would like to elaborate on the steps involved: + +<|ref|>text<|/ref|><|det|>[[148, 456, 850, 621]]<|/det|> +For each degree of freedom, we compute the IFFT on the VDOS or cross spectrum to derive the amplitude and phase information at specific frequencies within each segment, which are then used to construct the final vibrational vectors by statistical averaging. This approach avoids reliance on the total VDOS of the chosen cluster, thereby avoiding potential numerical issues that might arise from spectral decomposition. In our calculations, the numerical precision of the vibrational vectors obtained via IFFT is on the order of \(10^{- 5}\) , and the precision of the averaged vibrational vectors also reaches \(10^{- 5}\) . Furthermore, the configuration averaging and vibrational vector projection processes do not affect the numerical accuracy. + +<|ref|>text<|/ref|><|det|>[[148, 624, 850, 659]]<|/det|> +In response to the reviewer's suggestion, we have revised the description of our approach in the manuscript on page 3, lines 79- 99. + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 806]]<|/det|> +Comment 2- 5: Diagonalizing the velocity covariance or cross- correlation matrix produces a normal mode- like picture that naturally includes the effects of temperature and anharmonicities in the dynamics (e.g., (i) Strachan A. J Chem Phys. 2004, 120(1), or (ii) Sun J, Niehues G, Forbert H, Decka D, Schwaab G, Marx D, Havenith M. J Am Chem Soc. 2014, 136(13)). The author should discuss the relevance and accuracy of the proposed methodology in relation to the existing methods mentioned above. + +<|ref|>text<|/ref|><|det|>[[148, 826, 850, 899]]<|/det|> +Response: We sincerely thank the reviewer for providing the valuable references: (i) Strachan A. J Chem Phys. 2004, 120(1) and (ii) Sun J, Niehues G, Forbert H, Decka D, Schwaab G, Marx D, Havenith M. J Am Chem Soc. 2014, 136(13). Below, we present a detailed analysis and comparison of our approach with the methods outlined in these + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 238, 100]]<|/det|> +references. + +<|ref|>text<|/ref|><|det|>[[148, 104, 850, 231]]<|/det|> +Both our approach and the methods discussed in these references utilize velocities from MD simulations to extract vibrational features, naturally incorporating the effects of temperature and anharmonicities. However, there are key differences in the methodologies employed to obtain the vibrational vectors. The approaches described in references involve diagonalizing the velocity covariance or cross- correlation matrix to determine vibrational frequencies and vectors, whereas our method employs IFFT to extract vibrational vectors at specific frequencies. + +<|ref|>text<|/ref|><|det|>[[148, 234, 850, 435]]<|/det|> +Concerning the method in reference (i), the assumption underlying the diagonalization of the velocity covariance matrix is that the velocities of different vibrational modes are uncorrelated. This assumption is valid for systems with well- separated vibrational peaks, such as gas- phase molecules or solid- state crystals. However, in liquid systems, particularly in HCl solutions that exhibit broad absorption bands in the \(1000–3000\mathrm{cm}^{- 1}\) range, where vibrational modes are strongly coupled, this assumption does not hold. In contrast, our approach, which uses IFFT to extract vibrational vectors at distinct frequencies, imposes no such correlation constraints on vibrational modes, allowing them to mix. This makes our method more suitable for the analysis of complex liquid systems. Furthermore, our method is applicable to gas- phase and solid- state systems, offering greater versatility. + +<|ref|>text<|/ref|><|det|>[[148, 437, 850, 620]]<|/det|> +The method outlined in reference (ii) incorporates contributions from off- diagonal terms in the diagonalized dipole velocity cross- correlation matrix. This approach has proven successful in analyzing THz spectra of glycine in water. However, due to the frequent proton hopping in HCl solutions, the MD trajectories must be divided into shorter segments for analysis. If the method from reference (ii) was applied, each segment would exhibit different vibrational modes and corresponding frequency distributions, complicating the extraction of comprehensive vibrational features for the entire trajectory. In contrast, our method, which analyzes specific frequencies in the vibrational spectrum, enables averaging of vibrational vectors at the same frequency across different segments, facilitating the calculation of statistical vibrational features. + +<|ref|>text<|/ref|><|det|>[[148, 622, 850, 657]]<|/det|> +In response to the reviewer's comment, we have included this discussion in the manuscript (page 2, lines 65- 69) and the Methods section (page 16, lines 405- 418). + +<|ref|>text<|/ref|><|det|>[[148, 696, 850, 731]]<|/det|> +Comment 2- 6: How is the box length determined in all the simulations? Ideally, it should be based on the experimental density or from an NPT equilibration. + +<|ref|>text<|/ref|><|det|>[[148, 752, 850, 878]]<|/det|> +Response: We appreciate the reviewer for raising the question regarding the determination of cell length in the simulations. As stated in lines 341- 342 of the Methods section, the cell length in the AIMD simulations was set based on an experimental density of \(1\mathrm{g / cm^3}\) . This approach is widely adopted in DFT- level calculations (Nature, 1999, 397, 6720, 601- 604, J. Am. Chem. Soc., 2021, 143, 44, 18672- 18683). The same methodology was employed to determine the cell length in the ANNFF MD simulations. + +<|ref|>text<|/ref|><|det|>[[180, 882, 848, 898]]<|/det|> +In response to the reviewer's comment, we have added the relevant clarification + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 725, 103]]<|/det|> +in the Methods section (page 17, line 450 and page 18, lines 480- 481). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[336, 95, 657, 112]]<|/det|> +## - - - Answers to Reviewer #3- - - - + +<|ref|>text<|/ref|><|det|>[[147, 140, 851, 455]]<|/det|> +General Comments: The manuscript from Xuanye Yang and coworkers deals with a long- standing challenge in solution science, proton hydration and transport in water, and the associated spectroscopic signatures. The authors propose an approach to interpret the spectroscopic signatures of the hydrated proton in water in terms of frequency- specific vibrational vectors that are constructed from MD simulations at the DFT- GGA level, therefore, without neglecting anharmonicity and the dynamics of the liquid system. These vibrational vectors are defined based on the smallest unit composed of the excess proton and the two closest water molecules. With this approach, the authors identify an intermediate, long- lived structure between the limiting Zundellike and Eigen- like conformations and predict its spectroscopic fingerprint at 1770 cm- 1. This is certainly a hot topic of broad interest in solution science, with many implications in acid- base chemistry and redox processes. However, in the present state, I am not fully convinced that this work advances our understanding to a level that justifies publication in Nature Communication. The possibility of intermediate states has already been reported in several works; it would make a difference if the authors could show how their findings substantially alter our understanding of the proton transport mechanism. + +<|ref|>text<|/ref|><|det|>[[149, 456, 848, 492]]<|/det|> +I also have some concerns about the results and methodology that must be solved before considering publication. + +<|ref|>text<|/ref|><|det|>[[148, 511, 851, 621]]<|/det|> +Response: We sincerely thank the reviewer for their thorough evaluation of our manuscript. We have carefully considered each comment and addressed them individually. Based on this feedback, we have made substantial revisions to the manuscript to address the issues raised, thereby enhancing its clarity and overall quality. The page and line numbers mentioned hereafter refer to those found in the highlighted manuscript and Supplementary Information. + +<|ref|>text<|/ref|><|det|>[[148, 622, 852, 769]]<|/det|> +Regarding the reviewer's comment on the reported existence of intermediate states, we would like to offer further clarification. While previous studies (Chin. Phys. B, 2020, 29, 8, 083101, J. Chem. Phys., 2020, 153, 12, 124506) have suggested the potential presence of such intermediate states based on structural classifications, they did not fully substantiate these claims, particularly in terms of definitive vibrational signatures. The vibrational signal at 1770 cm- 1 has long been a subject of intense research, but its corresponding proton configuration assignment remains controversial, and it has never been assigned to an intermediate state. + +<|ref|>text<|/ref|><|det|>[[149, 770, 851, 844]]<|/det|> +Our work successfully identifies the 1770 cm- 1 peak as a unique proton stretching vibration corresponding to the intermediate state. This finding contributes to a deeper understanding of linear infrared spectra in acid solutions and prompts a re- evaluation of existing interpretations in 2D infrared spectroscopy for such systems. + +<|ref|>text<|/ref|><|det|>[[149, 844, 850, 881]]<|/det|> +The relevant additions have been incorporated into the manuscript, specifically on page 9, lines 235- 243. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 214]]<|/det|> +Moreover, we would like to emphasize that the identification of the intermediate state significantly enriches our comprehension of proton dynamics. For example, by precisely measuring the lifetimes of the three configuration types, we provide new insights into the timescales of proton transport. These contributions are important to reshaping the understanding of proton transport mechanisms, and we intend to further investigate this topic in future studies. We hope this clarification underscores the importance of our work. + +<|ref|>text<|/ref|><|det|>[[148, 251, 851, 377]]<|/det|> +Comment 3- 1: In Fig. 2a, the theoretical VDOS spectrum shows poor agreement with the experimental data around the proton continuum region, which is worrying for the reliability of the results of this work. This is even more worrying considering the authors then dissect the VODS spectrum in the proton continuum and discuss small differences, which look smaller in magnitude than the differences to the experimental spectra. Can the authors elaborate on this? + +<|ref|>text<|/ref|><|det|>[[149, 360, 850, 416]]<|/det|> +As a general comment, VDOS should not be directly compared to IR spectra, as they are substantially different spectra due to the selection rules. Theoretical IR spectra instead of VDOS would make the work much more convincing. + +<|ref|>text<|/ref|><|det|>[[148, 437, 851, 622]]<|/det|> +Response: We sincerely thank the reviewer for raising concerns about the reliability of directly comparing the VDOS spectrum with experimental IR data, particularly in the proton continuum region. Many previous studies have demonstrated that the vibrational peak positions of the VDOS are consistent with those of the IR spectrum (J. Chem. Phys., 2018, 148, 22, 222833, J. Chem. Phys., 2017, 146, 2, 024505). In particular, Markland's work (J. Chem. Phys., 2018, 148, 22, 222833) provides both VDOS and IR spectra for HCl solutions and water, and explicitly states, "The absolute and difference VDOS spectra exhibit the same structural features as the IR, albeit with different intensities." This agreement suggests that vibrational analysis based on VDOS can effectively capture the essential features of the IR spectrum. + +<|ref|>text<|/ref|><|det|>[[149, 624, 850, 660]]<|/det|> +In response to the reviewer's suggestion, we have incorporated these clarifications into the manuscript on page 6, lines 158- 166. + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 844]]<|/det|> +Comment 3- 2: The authors define vibrational vectors based on the smallest unit composed of the excess proton and the two closest water molecules. Isn't the unit too small? For instance, water molecules in the 1st coordination shell of the two waters sharing the proton are also important for properly defining the excess proton environment. Moreover, the selection is based on spatial coordinates, which have recently been suggested to be not suitable for properly characterizing excess proton configurations; see, e.g., ref.[Nat. Chem. (2024). https://doi.org/10.1038/s41557- 024- 01593- y]. Please elaborate. + +<|ref|>text<|/ref|><|det|>[[148, 864, 851, 900]]<|/det|> +Response: We thank the reviewer for raising the important issue regarding the size of the unit used for defining vibrational vectors and the selection of spatial coordinates for + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 852, 177]]<|/det|> +characterizing proton configurations. To address the issue of cluster size, we present Fig. R1 to demonstrate the vibrational vectors for the first solvation shell of \(\mathrm{H}_5\mathrm{O}_2^+\) . A comparison with Fig. 4 in the manuscript reveals that the vibrational vectors of the central \(\mathrm{H}_5\mathrm{O}_2^+\) remain unchanged, and the contribution from the first solvation shell is negligible at the frequencies corresponding to the proton stretching peaks (Fig. R1a- c). + +<|ref|>image<|/ref|><|det|>[[149, 200, 825, 448]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 455, 852, 531]]<|/det|> +
Fig. R1. Schematic illustration of the vibrational vectors of \(\mathrm{H}_5\mathrm{O}_2^+\) with its first solvation shell in water. a-c. The vibrational vectors for three proton-stretch signatures located in different frequency regions. d-f. The vibrational vectors for libration (d), umbrella (e), and bending (f), respectively.
+ +<|ref|>image<|/ref|><|det|>[[149, 552, 828, 797]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 808, 852, 901]]<|/det|> +
Manuscript Fig. 4. Schematic illustration of the vibrational vectors of the hydrated proton moiety in water, which are computed for six spectral signatures in the "proton continuum". From a to c, the vibrational vectors for three proton-stretch signatures located in different frequency regions, which are casted onto their corresponding configuration types. From d to f, the vibrational vectors for libration (d),
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 496, 102]]<|/det|> +umbrella (e), and bending (f), respectively. + +<|ref|>text<|/ref|><|det|>[[148, 121, 851, 232]]<|/det|> +In our study, we compute vibrational vectors using MD trajectory segments, rather than static structures. This dynamic approach allows the motions of \(\mathrm{H_5O_2^+}\) to inherently preserve the impact of the surrounding water molecules. Therefore, expanding the size of the defined unit would not alter the intrinsic vibrational vectors of \(\mathrm{H_5O_2^+}\) but would instead incorporate additional vibrational information from the surrounding water molecules. + +<|ref|>text<|/ref|><|det|>[[148, 234, 851, 306]]<|/det|> +This dynamic representation contributed to one of the advantages of our approach: the chosen cluster size does not affect the vibrational vector on atoms of concerned moieties, as it inherently accounts for the contributions from neighboring molecules in the environment. + +<|ref|>text<|/ref|><|det|>[[148, 307, 851, 362]]<|/det|> +These points are discussed in the manuscript on page 9, lines 251- 255 and further elaborated in the Supplementary Information on page 7, lines 175- 181. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 13. + +<|ref|>text<|/ref|><|det|>[[147, 380, 851, 566]]<|/det|> +Regarding the choice of coordinates for proton configurations, the coordinate system discussed in ref. [Nat. Chem. (2024). https://doi.org/10.1038/s41557- 024- 01593- y] indeed offers significant advantages in studying proton environment rearrangements on the picosecond timescale. However, the primary objective of our study is to assign specific vibrational modes in the IR spectrum, correlate them with proton configurations, and, based on which to interpret the "proton continuum" in the linear IR spectrum as well as the cross- peaks in 2D infrared spectra. Given the closer relationship between spatial coordinates and vibrational features (Nat. Chem., 2013, 5, 1, 29- 35, J. Phys. Chem. B, 2019, 123, 33, 7214- 7224, J. Chem. Phys., 2020, 153, 12, 124506), we opted to use spatial coordinates to characterize proton configurations. + +<|ref|>text<|/ref|><|det|>[[148, 568, 850, 603]]<|/det|> +In response to the reviewer's comment, we have made revisions to the manuscript on pages 7- 8, lines 199- 206. + +<|ref|>text<|/ref|><|det|>[[148, 640, 850, 714]]<|/det|> +Comment 3- 3: In their analysis, the authors divide the MD trajectory into 3ps blocks. A block is defined to contain an excess proton if the same excess proton remains as such for \(60\%\) of the 3ps. This definition adds arbitrary noise to all the subsequent analyses due to the remaining \(40\%\) . Please elaborate. + +<|ref|>text<|/ref|><|det|>[[148, 733, 850, 825]]<|/det|> +Response: Thanks for your comment. To clarify, we emphasize that in less than \(40\%\) of the configurations, the proton does not significantly dislocate from its initial position but instead engages in rapid proton exchange through the "special pair dance" with hydrogen atoms from flanking water molecules. We have found that this proton exchange has a minimal impact on the overall analysis. + +<|ref|>text<|/ref|><|det|>[[148, 827, 850, 900]]<|/det|> +Our comprehensive analysis of the chosen trajectory segments has shown that the proton remains within the identified \(\mathrm{H_5O_2^+}\) cluster with a high probability of \(99.7\%\) , and on one side of the \(\mathrm{H_5O_2^+}\) cluster (within one \(\mathrm{H_3O^+}\) ) with a probability of \(89.8\%\) . This indicates in remaining less than \(40\%\) of the configurations, the proton is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +predominantly in an Eigen- like configuration, and exchange with other two hydrogen atoms via "special pair dance", where three hydrogen atoms exhibit similar vibrational characteristics. + +<|ref|>text<|/ref|><|det|>[[148, 141, 851, 251]]<|/det|> +It is worth noting that our method for identifying the proton is based on the longest O- H bond. Consequently, it is hard to identify the same hydrogen atom as a proton throughout the entire segment. During "special pair dance" process, the two exchanged hydrogen atoms (the proton and a hydrogen from a flanking water molecule) have nearly identical O- H bond lengths, thus corresponding to similar proton stretching frequencies in Eigen- like configurations (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). + +<|ref|>text<|/ref|><|det|>[[148, 252, 851, 343]]<|/det|> +If the \(\mathrm{H}_9\mathrm{O}_4^+\) model were adopted, the proton would remain unchanged in the trajectory segments with a probability of \(89.8\%\) . However, due to the significant difference in stretching frequencies between the proton and the hydrogens of the flanking water molecules in intermediate and Zundel- like configurations, we prefer to retain the \(\mathrm{H}_2\mathrm{O}\cdots \mathrm{H}^+\cdots \mathrm{H}_2\mathrm{O}\) configuration for vibrational analysis. + +<|ref|>text<|/ref|><|det|>[[148, 344, 850, 397]]<|/det|> +In light of these findings, we believe segmenting the trajectory into 3 ps blocks and selecting those in which the \(\mathrm{H}_2\mathrm{O}\cdots \mathrm{H}^+\cdots \mathrm{H}_2\mathrm{O}\) configuration remains consistent for over \(60\%\) of the time is a reasonable and valid approach. + +<|ref|>text<|/ref|><|det|>[[148, 399, 850, 435]]<|/det|> +For further reference, the analysis of the chosen trajectory segments has been included in the Supplementary Information on page 7, lines 187- 192. + +<|ref|>text<|/ref|><|det|>[[148, 474, 851, 639]]<|/det|> +Comment 3- 4: The authors introduce the need to search for intermediate proton configurations based on their choice to dissect the VDOS spectrum with Gaussian functions. However, the authors do not show if intermediate proton configurations identified from structural criteria reproduce the deconvolved Gaussian signature. I doubt it since their spectroscopic signature will hardly be Gaussian. Moreover, the authors need 6 Gaussians to fit the VDOS spectrum, this may suggest that a Gaussian fit of that complex frequency range may not be a physically meaningful choice. This can be checked with theoretical spectroscopy by computing theoretical spectra for each identified proton configuration. + +<|ref|>text<|/ref|><|det|>[[148, 658, 851, 805]]<|/det|> +Response: Thanks for the comment. In lines 128- 133 of the manuscript, we clarify that we did not directly fit the proton VDOS with six Gaussian functions. Instead, we employed three Gaussians to fit the proton stretching band and another three for the non- stretching components of the proton VDOS. Furthermore, we would like to emphasize that the proton stretching band exhibits characteristics that align well with Gaussian modeling, as confirmed by the high coefficients of determination obtained from the Gaussian fittings in both our work and in Bowman's study (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). + +<|ref|>text<|/ref|><|det|>[[148, 808, 850, 899]]<|/det|> +The non- stretching components exhibit three distinct vibrational peaks (Fig. R4), and irrespective of whether a Gaussian fit is applied, the identification of these peaks' number and positions remains unaffected. Additionally, the proton stretching band also follows a trend of three peaks, with their positions obtained from the Gaussian fit aligning with frequencies derived from the average proton stretching periods in the MD + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 852, 159]]<|/det|> +trajectory. This supports the reliability of using Gaussian functions to fit the proton stretching band. Furthermore, the high coefficient of determination ( \(\mathrm{R}^2 = 0.990\) ) further validates the reliability and accuracy of applying the 3+3 Gaussian fitting approach to the proton VDOS spectrum. + +<|ref|>image<|/ref|><|det|>[[293, 181, 702, 393]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 400, 852, 473]]<|/det|> +
Fig. R4. Proton VDOS spectrum. The dark blue line represents the non-stretching vibrational spectrum of the proton, the light blue line represents the Gaussian peaks used to fit the dark blue line, and the red dashed line represents the sum of the Gaussian peaks.
+ +<|ref|>text<|/ref|><|det|>[[147, 492, 852, 753]]<|/det|> +We also recognize that various methods have been employed to compute the vibrational spectra of static protonated water clusters extracted from MD trajectories of aqueous solutions (J. Chem. Phys., 2017, 146, 15, 154507, J. Am. Chem. Soc., 2021, 143, 18672, J. Phys. Chem. Lett., 2017, 8, 21, 5246- 5252, Nat. Chem., 2024, 16, 1838- 1844, J. Phys. Chem. B, 2019, 123, 33, 7214- 7224, J. Chem. Phys., 2020, 153, 12, 124506). To further validate the effectiveness and appropriateness of our Gaussian fitting approach, we utilized vibrational spectral data from these studies. For instance, we applied three Gaussian functions to fit the proton stretching band data from Fig. S6b in the Supporting Information of Bowman's work (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224), with a resulting coefficient of determination of \(\mathrm{R}^2 = 0.889\) , as shown in Fig. R5. Additional proton stretching band data also exhibited high coefficients of determination when fitted with three Gaussian functions, further confirming that Gaussian fitting is a robust and appropriate approach for modeling the vibrational spectra. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[293, 98, 700, 309]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 325, 850, 399]]<|/det|> +
Fig. R5. Proton stretching band fitting from the reference. The dark blue line represents the proton stretching band from the reference (J. Phys. Chem. B, 2019, 123, 33, 7214-7224), the light blue line represents the Gaussian peaks used to fit the dark blue line, and the red dashed line represents the sum of the Gaussian peaks.
+ +<|ref|>text<|/ref|><|det|>[[148, 435, 850, 510]]<|/det|> +Comment 3- 5: In general, I'm not convinced of the physical insights that the definition of local vibrational modes can bring in a collective and strongly correlated system such as water, where vibrational modes couple between many water molecules, for sure within the 1st shell of both the water molecules around the excess proton. + +<|ref|>text<|/ref|><|det|>[[148, 529, 850, 603]]<|/det|> +Response: We appreciate the reviewer's insightful comment regarding the definition of local vibrational modes in strongly correlated systems such as water, where vibrational modes exhibit significant coupling between multiple water molecules, especially within the first hydration shell surrounding the excess proton. + +<|ref|>text<|/ref|><|det|>[[148, 604, 851, 770]]<|/det|> +As outlined in our response to Comment 3- 2, we compute vibrational vectors from MD trajectory segments rather than static structures. This dynamic approach inherently preserves the impact of surrounding water molecules on the motion of \(\mathrm{H_5O_2^+}\) . Expanding the defined unit would not change the intrinsic vibrational vectors of \(\mathrm{H_5O_2^+}\) ; rather, it would incorporate additional vibrational contributions from the neighboring water molecules. This dynamic perspective contributed to the advantage of our method: the chosen cluster size does not affect the vibrational vector on atoms of concerned moieties, as it naturally accounts for the coupling of vibrational modes with surrounding molecules in the hydration shell. + +<|ref|>text<|/ref|><|det|>[[148, 808, 850, 881]]<|/det|> +Comment 3- 6: As regards the simulation method, it would be nice if the authors could justify the choice of RPBE for AIMD for a subtle problem such as excess proton characterization. Taking advantage of ML techniques, recent MD studies have been conducted at a higher level of theory, e.g., hybrid DFT. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 416]]<|/det|> +Response: We thank the reviewer for raising the question regarding the MD simulations utilizing the GGA level of DFT method. As noted in Markland's studies (J. Chem. Phys., 2018, 148, 22, 222833, J. Chem. Phys., 2023, 159, 7), classical simulation with GGA density functionals can reasonably reproduce most fundamental features of the experimental IR spectrum of HCl solutions and the proton diffusion coefficient due to the mutual cancellation of the nuclear quantum effect and the insufficient account of the electronic correlation. This is the reason why we prefer to implementing the classical simulations using a GGA functional. It is also important to note that classical hybrid trajectories tend to significantly underestimate the proton diffusion coefficient (J. Chem. Phys., 2023, 159, 7). In response to the reviewer's concern, we further conducted a comparative analysis by performing thermostatted ring- polymer molecular dynamics (TRPMD) simulations using the hybrid functional revPBE0- D3, implemented through the ANNFF model. This theoretical scheme further enhances the account of the electronic correlation effect as well as incorporates the nuclear quantum effect. The consistency observed in both the RDF and VDOS between the RPBE- D3 classical MD and revPBE0- D3 quantum MD simulations confirms that transitioning from a GGA functional to a hybrid functional does not alter the key conclusions of our study. + +<|ref|>text<|/ref|><|det|>[[148, 418, 851, 640]]<|/det|> +Initially, we calculated the energies and forces at the revPBE0- D3 level using a training set that consisted of 3,259 configurations derived from the RPBE- D3 level. This initial set was then used to train a neural network with the same descriptors in the Methods section. We subsequently performed 6- beads PIGLET MD simulations (Phys. Rev. Lett., 2012, 109, 100604) using the I- PI software (Comp. Phys. Commun., 2014, 185, 1019- 1026). During these simulations, we identified structures exhibiting extrapolation warnings, which were recalculated at the revPBE0- D3 level and incorporated into the training set. After several iterations of training and configuration selection, the ANNFF model was ready for 50 ps PIGLET MD simulations with few extrapolation warnings. The final training set comprised 4,212 configurations, with an energy RMSE of 0.231 meV/atom and a force RMSE of 53.3 meV/Å, reflecting promising accuracy. + +<|ref|>text<|/ref|><|det|>[[148, 641, 851, 751]]<|/det|> +Subsequently, we utilized the trained ANNFF model to perform TRPMD simulations (J. Chem. Phys., 2014, 140, 234116) for three systems: one containing 63 \(\mathrm{H_2O}\) molecules, a proton, and a Cl- (0.9 M HCl); another with 511 \(\mathrm{H_2O}\) molecules, a proton, and a Cl- (0.1 M HCl); and a third system consisting of 512 \(\mathrm{H_2O}\) molecules. Using the I- PI software, we set 32 beads per atom, a 60 ps trajectory length, 298 K temperature, 1 atm pressure, and a 0.3 fs time step. + +<|ref|>text<|/ref|><|det|>[[148, 753, 851, 899]]<|/det|> +The results demonstrate that for the 0.9 M HCl system, the RDF derived from the revPBE0- D3 TRPMD trajectory closely matches that obtained from the RPBE- D3 classical MD trajectory in our study (see Fig. R6). Similarly, for both the 0.1 M HCl and water systems, the VDOS from the revPBE0- D3 TRPMD trajectory is in agreement with the features from the RPBE- D3 classical MD simulations (see Fig. R7). This consistency in both RDF and VDOS supports the conclusion that transitioning from classical MD simulations using a GGA functional (RPBE- D3) to TRPMD with a hybrid functional (revPBE0- D3) does not affect the principal conclusions of our study. These + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +results further validate the appropriateness and reliability of employing RPBE- D3 for AIMD simulations. + +<|ref|>image<|/ref|><|det|>[[150, 145, 844, 389]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 399, 851, 473]]<|/det|> +
Fig. R6. RDFs of the ANNFF MD trajectory for the 0.9 M HCl solution. Panels a-e display the RDFs for H-H, O-H, O-O, Cl-H, and Cl-O pairs. The dark blue lines correspond to the RDFs from the RPBE-D3 classical MD trajectory, while the red dashed lines represent the RDFs from the revPBE0-D3 TRPMD trajectory.
+ +<|ref|>image<|/ref|><|det|>[[300, 503, 692, 700]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 714, 851, 806]]<|/det|> +
Fig. R7. VDOS for the 0.1 M HCl solution and pure water. The orange and cyan lines represent the VDOS from the RPBE-D3 classical MD and revPBE0-D3 TRPMD trajectories for pure water, respectively. The dark blue and yellow dashed lines represent the VDOS from the RPBE-D3 classical MD and revPBE0-D3 TRPMD trajectories for the 0.1 M HCl solution, respectively.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[336, 95, 658, 113]]<|/det|> +## Answers to Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[149, 140, 849, 195]]<|/det|> +General Comments: The authors have responded in detail to the reviewer's comments 1- 5 and 8- 12 and have addressed them adequately. However, responses 6 and 7 (which are related) are not entirely convincing. + +<|ref|>text<|/ref|><|det|>[[148, 215, 850, 344]]<|/det|> +Response: We sincerely appreciate the reviewer's overall positive assessment of our responses to comments 1- 5 and 8- 12. Regarding the concerns raised about responses 6 and 7, we acknowledge that further clarification and additional analyses are necessary to fully address the reviewer's points. Below, we provide a more detailed explanation and supplementary results to address these concerns and incorporate them into our revised manuscript and Supplementary Information. The page and line numbers mentioned hereafter refer to those found in the highlighted version. + +<|ref|>text<|/ref|><|det|>[[148, 380, 857, 566]]<|/det|> +Comment 1- 1: In particular, MD simulations were performed to determine the possible structure of the excess proton in solvation and its correspondence to its frequency in the solvation vibrational spectrum. Since the system has intrinsically high fluctuations, the correspondence between the vibrational frequency and the structure of the "special pair" could be fuzzy and, consequently, the assignment of a vibration is made to a configuration that dominates it \(50\%\) of the time. As the authors showed in their response, considering a stricter criterion implies obtaining higher frequencies that do not match the experiment and also discarding about \(50\%\) of the data. However, this criterion seems a bit arbitrary. In this sense, is it possible to run longer simulations to reach a criterion higher than \(50\%\) that explains the experimental results? + +<|ref|>text<|/ref|><|det|>[[148, 585, 850, 657]]<|/det|> +Response: We sincerely thank the reviewer for their insightful comments and constructive feedback. In response to the concerns raised regarding the criterion for configuration assignment, we have conducted a comprehensive re- evaluation and refined our approach to address the limitations of the previously adopted criterion. + +<|ref|>text<|/ref|><|det|>[[148, 660, 850, 842]]<|/det|> +The initial criterion, which assigned a vibration period to a configuration if it dominated more than \(50\%\) of the period, has certain limitations. This is primarily due to the periodic variation of atomic velocities during vibration, leading to a non- uniform distribution of configurations over time. Specifically, configurations are more likely to occur near the vibration extrema and less likely near the equilibrium positions. Since the equilibrium positions of different vibration periods tend to distribute in lower- energy regions, the overall configuration distribution still favors lower- energy configurations. Furthermore, as mentioned in our response to the first round of review comments, the large amplitude of proton stretch often results in crossing configuration boundaries, making it challenging to apply a stricter criterion. + +<|ref|>text<|/ref|><|det|>[[149, 844, 849, 899]]<|/det|> +To address these issues, we have redefined the criterion based on the equilibrium configuration of proton stretch, since the expected values of the hydrated proton configuration parameters have been shown to effectively correlate configurations with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 849, 120]]<|/det|> +proton stretching frequencies (J. Phys. Chem. B, 2019, 123, 33, 7214- 7224). The new criterion is implemented as follows: + +<|ref|>text<|/ref|><|det|>[[147, 122, 850, 158]]<|/det|> +1. Equilibrium Configuration Determination. For each vibration period, the equilibrium configuration is determined by calculating the average configuration. + +<|ref|>text<|/ref|><|det|>[[147, 159, 850, 250]]<|/det|> +2. Probability Density Calculation. The probability densities of the equilibrium configuration \((R_{O_1\mathrm{H}^*}, R_{O_2\mathrm{H}^*})\) for the three configuration types (Zundel-like, Intermediate, and Eigen-like) are computed using their respective 2D Gaussian distribution functions. The probability density for each configuration type \(i\) is expressed as: + +<|ref|>equation<|/ref|><|det|>[[155, 255, 840, 284]]<|/det|> +\[P_{i} = A_{i}\exp \left\{-\left[(R_{O_{1}\mathrm{H}^{*}} - R_{1i})^{2} / 2\sigma_{1i}^{2} + (R_{O_{2}\mathrm{H}^{*}} - R_{2i})^{2} / 2\sigma_{2i}^{2} + c_{i}(R_{O_{1}\mathrm{H}^{*}} - R_{1i})(R_{O_{2}\mathrm{H}^{*}} - R_{2i})\right]\right\},\] + +<|ref|>text<|/ref|><|det|>[[147, 299, 849, 343]]<|/det|> +where \(A_{i}, R_{1i}, R_{2i}, \sigma_{1i}, \sigma_{2i}\) and \(c_{i}\) are the parameters of the corresponding Gaussian distribution. + +<|ref|>text<|/ref|><|det|>[[147, 345, 849, 381]]<|/det|> +3. Normalization and Assignment. The calculated probability densities are normalized to obtain the normalized probability, + +<|ref|>equation<|/ref|><|det|>[[430, 388, 567, 430]]<|/det|> +\[P_{i}^{N} = P_{i} / \sum_{i}P_{i}.\] + +<|ref|>text<|/ref|><|det|>[[147, 436, 850, 473]]<|/det|> +A vibration period is assigned to a configuration type if the normalized probability of its equilibrium configuration \(P_{i}^{N} > 60\%\) . + +<|ref|>text<|/ref|><|det|>[[147, 474, 850, 621]]<|/det|> +This refined criterion, as shown in Fig. R1b, offers several advantages: (1) it effectively distinguishes between Zundel- like, Intermediate, and Eigen- like configurations; (2) it preserves data in the central regions of the configuration distributions. To validate the criterion, we examined the effects of varying the threshold: lowering the threshold to \(50\%\) resulted in overlapping boundaries between configuration types (Fig. R1a), while raising it to \(70\%\) led to the exclusion of some data in the central regions of distributions (Fig. R1c). The \(60\%\) threshold strikes an optimal balance between configuration discrimination and data retention. + +<|ref|>image<|/ref|><|det|>[[149, 641, 848, 764]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 771, 850, 862]]<|/det|> +
Fig. R1. Schematic illustration of the criterion for configuration assignment of vibration periods. a-c. The boundaries for the three configuration types at thresholds of \(50\%\) (a), \(60\%\) (b), and \(70\%\) (c). The red, light blue, and dark blue dashed lines represent the boundaries for Zundel-like, Intermediate, and Eigen-like configurations, respectively.
+ +<|ref|>text<|/ref|><|det|>[[186, 881, 849, 899]]<|/det|> +Applying this new criterion, we recalculated the average proton stretching periods + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 213]]<|/det|> +for Zundel- like, Intermediate, and Eigen- like configurations, obtaining 25.3 fs, 18.7 fs, and 13.7 fs, respectively. These correspond to vibrational frequencies of \(1320 \mathrm{cm}^{- 1}\) , \(1780 \mathrm{cm}^{- 1}\) , and \(2430 \mathrm{cm}^{- 1}\) , which exhibit improved consistency with experimental data compared to our previous results. Importantly, the criterion's robustness is further demonstrated by the minimal impact of threshold adjustments: increasing the threshold to \(70\%\) yields frequencies of \(1280 \mathrm{cm}^{- 1}\) , \(1700 \mathrm{cm}^{- 1}\) , and \(2490 \mathrm{cm}^{- 1}\) , which remain in good agreement with experimental observations. + +<|ref|>text<|/ref|><|det|>[[148, 215, 850, 325]]<|/det|> +The discussions are provided in the manuscript on page 8, lines 218- 221 and in the Supplementary Information on pages 4- 5, lines 97- 135. Fig. R1 has been added to the Supplementary Information as Supplementary Fig. 10. These revisions enhance the methodological rigor and reliability of our findings, ensuring a more robust interpretation of the relationship between proton configurations and their vibrational spectra. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[336, 95, 658, 112]]<|/det|> +## Answers to Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 213]]<|/det|> +General Comments: In the revised manuscript, the authors have addressed most of my comments. However, after reviewing their responses and the revisions, I find that the following points still need to be addressed regarding the assignment of the structural motif - the novel/central analysis in this manuscript - before it can be published. + +<|ref|>text<|/ref|><|det|>[[148, 233, 851, 399]]<|/det|> +Response: We sincerely appreciate the reviewer's acknowledgment of the revisions made to address most of the comments, as well as their constructive feedback on the remaining points related to the assignment of structural motifs. Below, we provide a detailed response to the specific comments, along with additional clarifications and revisions to further strengthen our methodology and interpretation. These revisions have been incorporated into the manuscript and Supplementary Information to ensure clarity and rigor. We hope that the following explanations and modifications will fully address the reviewer's concerns. The page and line numbers mentioned hereafter refer to those found in the highlighted version. + +<|ref|>text<|/ref|><|det|>[[148, 436, 850, 583]]<|/det|> +Comment 2- 1: Special pair dance refers to a hydrated central core hydronium structure that continually switches \((\mathrm{O - H}\dots \mathrm{O})\) special pair hydrogen- bond partners with the three closest water molecules. This means that the identity of the second water molecule (which is away from the unpaired \(\mathrm{H + }\) ) in the flanking partner \((\mathrm{O2H5 + })\) continuously changes. The author should calculate the survival probability of a particular \(\mathrm{O2H5 + }\) complex as well as a particular \(\mathrm{O4H9 + }\) to validate (a) the chosen 3 ps segment for spectral analysis and (b) \(\mathrm{O2H5 + }\) is better compared to \(\mathrm{O4H9 + }\) for the vibrational assignment. + +<|ref|>text<|/ref|><|det|>[[148, 602, 850, 676]]<|/det|> +Response: We sincerely thank the reviewer for their insightful comments regarding the survival probability of particular \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) complexes and their implications for vibrational spectral analysis. Below, we provide a detailed response to address the reviewer's concerns and clarify the rationale behind our methodological choices. + +<|ref|>text<|/ref|><|det|>[[148, 678, 850, 899]]<|/det|> +The primary rationale for selecting the \(\mathrm{H_5O_2^+}\) motif as the focus of our study lies in its ability to more accurately reflect the vibrational characteristics of the excess proton. In a particular \(\mathrm{H_5O_2^+}\) motif, the proton remains localized between two flanking water molecules, while the oxygen atom bonded to the proton can dynamically switch within the motif. This stability in proton identity makes the \(\mathrm{H_5O_2^+}\) motif particularly suitable for calculating proton vibrational spectra. In contrast, in a particular \(\mathrm{H_9O_4^+}\) motif, the oxygen atom of the \(\mathrm{H_5O^+}\) core remains constant, while the proton rapidly exchanges among the three hydrogen atoms bonded to it. Although the \(\mathrm{H_9O_4^+}\) motif is well- suited for characterizing the dynamic behavior of the Eigen cation (i.e., the "special pair dance"), it introduces complications in the assignment and interpretation of proton vibrational spectra, as discussed below. Therefore, we argue that the \(\mathrm{H_5O_2^+}\) motif offers significant advantages for analyzing proton vibrational features. However, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 848, 120]]<|/det|> +for studies focusing on hydrogen- bond vibrational modes in the terahertz frequency range, the \(\mathrm{H_9O_4^+}\) motif may be more appropriate. + +<|ref|>text<|/ref|><|det|>[[147, 123, 850, 362]]<|/det|> +In response to the reviewer's suggestion, we calculated the survival probabilities of particular \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) complexes over the chosen 3 ps segments used for spectral analysis. The results indicate that the survival probabilities of \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) are comparable, at \(65.3\%\) and \(62.1\%\) , respectively. From the perspective of survival probability alone, either motif could be considered a valid choice for analysis. However, when using the \(\mathrm{H_9O_4^+}\) motif, all three hydrogen atoms of the central \(\mathrm{H_3O^+}\) should be treated as protons. The resulting proton VDOS spectra are shown in Fig. R2. Compared to the \(\mathrm{H_5O_2^+}\) motif, the proton vibrational features in \(\mathrm{H_9O_4^+}\) are significantly averaged, particularly for the configuration- sensitive proton stretch mode (Fig. R2b). This averaging leads to a flattening of the VDOS intensity in the \(1000 - 2500\mathrm{cm}^{- 1}\) range and introduces a prominent peak near \(3000\mathrm{cm}^{- 1}\) , corresponding to the flanking water stretching. These features complicate the fitting and assignment of the proton stretch mode, further supporting the rationale for selecting the \(\mathrm{H_5O_2^+}\) motif. + +<|ref|>image<|/ref|><|det|>[[151, 390, 841, 572]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 586, 841, 640]]<|/det|> +
Fig. R2. Proton VDOS spectra for \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) . a. Proton VDOS spectra. The blue line corresponds to the proton in \(\mathrm{H_5O_2^+}\) , and the red line corresponds to the protons in \(\mathrm{H_9O_4^+}\) . b. Proton stretch spectra.
+ +<|ref|>text<|/ref|><|det|>[[147, 660, 850, 844]]<|/det|> +Regarding the reliability of the chosen 3 ps segments, we have demonstrated in Supplementary Fig. 16 that the configuration distribution within these segments is highly consistent with that of the entire trajectory. This consistency confirms that the 3 ps segments are representative of the overall dynamical behavior of the proton. We emphasize that the selection of trajectory segments does not follow a unique standard; as long as the segments are reasonably chosen, the resulting vibrational spectra will exhibit qualitative consistency, with only minor quantitative differences in peak intensities. These differences do not significantly affect the overall spectral features or the assignment of vibrational modes, and thus do not impact the validity of our conclusions. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[153, 92, 839, 275]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 288, 849, 344]]<|/det|> +
Supplementary Fig. 16. 2D probability density distribution of proton configurations in 0.01 M HCl. a. Distribution of the chosen trajectory segments. b. Distribution for the entire trajectory.
+ +<|ref|>text<|/ref|><|det|>[[147, 362, 851, 583]]<|/det|> +The reviewer may note that the survival probability of the particular \(\mathrm{H_9O_4^+}\) complex \((62.1\%)\) is lower than the probability of the proton remaining on one side of the \(\mathrm{H_5O_2^+}\) motif \((89.8\%)\) reported in the Supplementary Information. This discrepancy arises from differences in the statistical criteria used in the two analyses. In the previous calculation, we focused on whether the proton deviated from the chosen \(\mathrm{H_5O_2^+}\) motif during 3 ps, calculating the probability that the proton belongs to one of the three hydrogen atoms in the \(\mathrm{H_3O^+}\) core without imposing constraints on the oxygen atom bonded to the proton. This approach included cases where the proton shifted closer to the special pair partners. In the current analysis, to reflect the survival probability of the particular \(\mathrm{H_9O_4^+}\) complex, we imposed stricter criteria by requiring the oxygen atom bonded to the proton to remain constant, resulting in a survival probability of \(62.1\%\) . This value reflects the dynamic evolution of the proton motif in the solution. + +<|ref|>text<|/ref|><|det|>[[148, 585, 850, 676]]<|/det|> +We emphasize that the choice between the \(\mathrm{H_5O_2^+}\) and \(\mathrm{H_9O_4^+}\) motifs does not affect the calculation of vibrational vectors, as detailed in our response to the first round of review comments. Our selection of the \(\mathrm{H_5O_2^+}\) motif is based on its ability to more precisely capture proton vibrational features rather than any inherent differences in the calculation of vibrational vectors. + +<|ref|>text<|/ref|><|det|>[[148, 679, 849, 751]]<|/det|> +In response to the reviewer's comment, we have revised the Supplementary Information (pages 8- 9, lines 234- 244) to provide a more detailed justification for selecting the \(\mathrm{H_5O_2^+}\) motif and to highlight its advantages for vibrational spectral analysis. These revisions further strengthen the clarity and rigor of our methodology. + +<|ref|>text<|/ref|><|det|>[[148, 789, 850, 899]]<|/det|> +Comment 2- 2: In Figure 5, 'the ranges of intensities are distinctly different and essentially non- overlapping' seems to be due to the fact that the collective variable (CV) for different motifs represents different variable (despite using the same notations, q_s or q_l). I wonder if the same variable were used, the intensities would not differ much across the three motifs. In that case, the observed difference would be attributed to the choice of the variable, rather than to a true difference in the structural parameter. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 102, 850, 158]]<|/det|> +**Response:** We sincerely thank the reviewer for their insightful comments regarding the influence of collective variable (CV) selection on the distribution of local electric field intensities. Below, we provide a detailed response to address the reviewer's concerns. + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 233]]<|/det|> +In response to the reviewer's suggestion, we calculated the conditional ensemble averages of the local electric field for Zundel- like, Intermediate, and Eigen- like configurations using the same collective coordinates \(\mathfrak{q}_{\mathrm{l}}\) and \(\mathfrak{q}_{\mathrm{s}}\) of the Intermediate state. The results are presented in Fig. R3. + +<|ref|>image<|/ref|><|det|>[[149, 258, 830, 440]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 454, 850, 585]]<|/det|> +
Fig. R3. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along the collective coordinate \(\mathfrak{q}_{\mathrm{l}}\) of the intermediate state, for Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations, respectively. b. The local electric field distributions along the collective coordinate \(\mathfrak{q}_{\mathrm{s}}\) of the intermediate state, for Zundel-like, Intermediate and Eigen-like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathring{\mathrm{A}}^{-1}\)
+ +<|ref|>image<|/ref|><|det|>[[149, 602, 830, 784]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 789, 850, 899]]<|/det|> +Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \(\mathfrak{q}_{\mathrm{l}}\) , for Zundel- like (0- 0.13 V/Å, blue), Intermediate (0.13- 0.28 V/Å, yellow) and Eigen- like (0.28- 0.40 V/Å, green) configurations, respectively. b. The local electric field distributions along collective coordinate \(\mathfrak{q}_{\mathrm{s}}\) , for Zundel- like, Intermediate and Eigen- like configurations, respectively. The color bar of the scatter points signifies the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 528, 102]]<|/det|> +structural probability densities in units of \(\hat{A}^{- 1}\) . + +<|ref|>text<|/ref|><|det|>[[148, 122, 850, 288]]<|/det|> +As shown in Fig. R3a, even when using the same collective coordinate \(\mathfrak{q}\) to compute the conditional ensemble averages of the local electric field for all three configurations, the intensity ranges of the local electric field remain "distinctly different and essentially non- overlapping." This result demonstrates that the observed differences in the local electric field distributions are not due to the choice of collective variables but rather reflect intrinsic differences in the structural parameters of the three configurations. Therefore, as long as the chosen collective variables reasonably capture the structural features of the configurations, the differences in local electric field distributions among the three configurations can be clearly resolved. + +<|ref|>text<|/ref|><|det|>[[148, 289, 850, 436]]<|/det|> +As shown in Fig. R3b, compared to Manuscript Fig. 5b, the local electric fields of Zundel- like and Eigen- like configurations exhibit some correlation with the collective coordinate \(\mathfrak{q}_5\) of the Intermediate state. This suggests that for Zundel- like and Eigen- like configurations, relying solely on the collective coordinate \(\mathfrak{q}\) of the Intermediate state is insufficient to fully describe their properties. Instead, \(\mathfrak{q}_5\) serves as a complementary coordinate that better captures their structural features. Thus, for these two configurations, using the collective coordinate \(\mathfrak{q}\) of the Intermediate state is less accurate and complete than using their respective collective coordinate \(\mathfrak{q}_5\) . + +<|ref|>text<|/ref|><|det|>[[148, 437, 850, 565]]<|/det|> +In response to the reviewer's comments, we have included relative discussions in the manuscript on page 11, lines 292- 296 and in the Supplementary Information on page 7, lines 187- 204 to provide a more detailed justification for the choice of collective variables and to highlight their impact on the analysis of local electric field distributions. Fig. R3 has been added to the Supplementary Information as Supplementary Fig. 14 to further support our findings. These revisions enhance the rigor and reliability of our study. + +<|ref|>text<|/ref|><|det|>[[148, 603, 850, 750]]<|/det|> +Comment 2- 3: Finally, the structural motifs (Eigen, Zundel and Intermediate) extracted here should be aligned with recent findings by Gomez et al. (Gomez, A., Thompson, W.H. & Laage, D. Nat. Chem. 16, 1838- 1844 (2024)), who used a more accurate description of electrons and nuclei in their simulations and identified the same three motifs but using a different set of CVs. The authors should verify whether applying the same type of CVs (as used by Gomez et al.) to the extracted motifs presented herein aligns with the microscopic structure of the proton in water, as described by the recent work of Gemoz et al. + +<|ref|>text<|/ref|><|det|>[[148, 770, 850, 899]]<|/det|> +Response: We sincerely thank the reviewer for their insightful comments regarding the alignment of our structural motifs (Eigen- like, Zundel- like, and Intermediate) with the recent findings by Gomez et al. (Gomez, A., Thompson, W.H., & Laage, D. Nat. Chem. 16, 1838- 1844 (2024)), who employed a more accurate description of electrons and nuclei in their simulations and identified the same three motifs using a different set of CVs. Below, we provide a detailed response to address the reviewer's concerns and clarify the consistency between our results and those of Gomez et al. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 344]]<|/det|> +The core issue raised by the reviewer pertains to the reliability of our RPBE- D3 classical MD trajectories and their consistency with the revPBE0- D3 TRPMD trajectories used by Gomez et al. We acknowledge that the research objectives of Gomez et al. and our study differ significantly, which directly influences the choice of CVs and the definition of proton motifs. Gomez et al. focused on proton transfer processes, defining the three motifs primarily based on the asymmetry and coordination number of the two flanking water molecules of the proton, which are closely related to the microscopic mechanisms of proton transfer dynamics. In contrast, our study emphasizes the characterization of proton vibrational features, and our definition of the three configurations (Eigen- like, Intermediate, and Zundel- like) is based on the differences in the O- H bond lengths and hydrogen bond lengths of the protons, which are directly related to proton vibrations. Due to these differences in research objectives and definition criteria, the three motifs extracted in our study do not have a one- to- one correspondence with those of Gomez et al., making direct comparisons inappropriate. + +<|ref|>text<|/ref|><|det|>[[148, 345, 851, 529]]<|/det|> +Nevertheless, we fully understand the reviewer's concerns regarding the reliability of the RPBE- D3 classical MD trajectories. In response, we have supplemented our analysis with revPBE0- D3 TRPMD trajectory calculations, as detailed in our response to the first round of review comments. By comparing the RDFs and overall VDOS between the RPBE- D3 classical MD and revPBE0- D3 TRPMD trajectories, we have demonstrated their consistency in overall structural features and vibrational behavior. To further validate the microscopic consistency of proton characteristics between the two trajectories, we have conducted additional analyses, including VDOS difference spectra and proton configuration distribution comparisons, as shown in Figs. R4, R5, and Table R1. + +<|ref|>image<|/ref|><|det|>[[306, 558, 690, 757]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 771, 850, 844]]<|/det|> +
Fig. R4. VDOS difference spectra between 0.1 M HCl solution and pure water. The blue line represents the difference spectrum from the RPBE-D3 classical MD trajectory, and the red line represents the difference spectrum from the revPBE0-D3 TRPMD trajectory.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 85, 842, 450]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 455, 850, 602]]<|/det|> +
Fig. R5. The 2D configurational probability density distributions of proton in 0.1 M HCl solution. a. The 2D probability density distribution from the revPBE0-D3 TRPMD trajectory. b. The three 2D Gaussian-type fitting functions for the distribution in (a) are assigned to Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations. The black lines illustrate the contour plot of the sum of the three types. c. The 2D probability density distribution from the RPBE-D3 classical MD trajectory. d. The three 2D Gaussian-type fitting functions for the distribution in (c). c-d are identical to Supplementary Fig. 8a-b.
+ +<|ref|>table<|/ref|><|det|>[[210, 646, 784, 732]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[210, 621, 785, 639]]<|/det|> +Table R1. The proportions of configurations in 0.1 M HCl solution. + +
MD trajectoryZundel-likeIntermediateEigen-like
Classical GGA0.310.420.27
Quantum hybrid0.330.420.25
+ +<|ref|>text<|/ref|><|det|>[[147, 750, 850, 899]]<|/det|> +As shown in Fig. R4, the VDOS difference spectra from the RPBE- D3 classical MD and revPBE0- D3 TRPMD trajectories are consistent, indicating that both trajectories capture similar vibrational features of hydrated proton complex. From Fig. R5 and Table R1, it is evident that the proton configuration distributions and the proportions of the three configurations (Zundel- like, Intermediate, and Eigen- like) are highly consistent between the RPBE- D3 classical MD and revPBE0- D3 TRPMD trajectories. Specifically, compared to the RPBE- D3 classical MD trajectory, the proton configuration distribution in the revPBE0- D3 TRPMD trajectory is slightly flatter, with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 157]]<|/det|> +a small increase in the proportion of Zundel- like configurations and a slight decrease in the proportion of Eigen- like configurations, while the proportion of Intermediate configurations remains nearly unchanged. These minor differences do not affect the overall consistency of the configuration distributions. + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 250]]<|/det|> +The above analyses demonstrate that, despite differences in the accuracy of electron and nuclear descriptions between the two trajectories, they exhibit high consistency in capturing proton configurations and their vibrational features. Therefore, the use of more accurate descriptions of electrons and nuclei does not compromise the reliability of our conclusions. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[338, 95, 658, 112]]<|/det|> +## Answers to Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[149, 140, 850, 195]]<|/det|> +General Comments: The authors made substantial efforts to address reviewers' concerns, which I find convincing regarding the significance of the work, the simulation approach used, and the data analysis. + +<|ref|>text<|/ref|><|det|>[[148, 215, 850, 362]]<|/det|> +Response: We sincerely thank the reviewer for their overall positive assessment of our work and for acknowledging the significance of our findings, the robustness of our simulation approach, and the rigor of our data analysis. We also appreciate the reviewer's constructive feedback regarding the use of VDOS instead of IR theoretical spectra for comparison with experimental data. In response to this comment, we have conducted additional analyses and implemented substantial revisions to the manuscript and Supplementary Information to address this concern. The page and line numbers mentioned hereafter refer to those found in the highlighted version. + +<|ref|>text<|/ref|><|det|>[[148, 400, 850, 437]]<|/det|> +Comment 3- 1: However, the concern about the use of VDOS instead of IR theoretical spectra to compare to experiments remains unanswered. + +<|ref|>text<|/ref|><|det|>[[148, 437, 850, 602]]<|/det|> +The authors correctly state in their answer that the band position doesn't shift significantly from VDOS to IR. However, the lineshape is significantly altered by the magnitude of the transient dipole, which is not taken into account in the VODS spectrum, as also noted by reviewer 2. Since the authors discuss small differences in the shape of broad bands underlying several vibrational motions (as revealed by their decomposition and Gaussian fit), this problem can potentially affect their conclusion and assignment. I still believe this is a serious issue, which deserves to be better addressed by computing IR spectra instead of VDOS, which is doable in several ways, even from ML approaches, as also noted by another reviewer. + +<|ref|>text<|/ref|><|det|>[[149, 621, 849, 657]]<|/det|> +However, I don't want to stand in the way of this otherwise interesting manuscript, and I leave the choice on this matter to the editor. + +<|ref|>text<|/ref|><|det|>[[148, 677, 850, 750]]<|/det|> +Response: We sincerely thank the reviewer for their valuable comments regarding the use of VDOS instead of theoretical IR spectra for comparison with experimental data. In response to the reviewer's concerns, we have conducted additional theoretical calculations to address this issue. Below, we provide a detailed response. + +<|ref|>text<|/ref|><|det|>[[148, 752, 850, 900]]<|/det|> +Following the reviewer's suggestion, we calculated the IR spectra and their difference spectra for a \(0.9\mathrm{MHCl}\) solution and pure water. Specifically, we extracted a \(30\mathrm{ps}\) trajectory from our ANNFF MD simulations of two systems, respectively: one containing 63 water molecules, one proton, and one \(\mathrm{Cl}^-\) ion ( \(0.9\mathrm{MHCl}\) ), and the other containing 64 water molecules. Using the CP2K package (version 2024.1), we computed the Wannier centers for each structure and derived the dipole moments based on these centers. By performing Fourier transforms on the autocorrelation functions of the dipole moment derivatives, we obtained the IR spectra for \(0.9\mathrm{MHCl}\) solution and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +pure water, as well as the corresponding difference spectrum. The results are shown in Fig. R6. + +<|ref|>image<|/ref|><|det|>[[295, 144, 702, 355]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 363, 851, 473]]<|/det|> +
Fig. R6. Theoretical and experimental IR spectra of HCl solutions and water. The cyan and orange curves represent the theoretical IR spectra of \(0.9\mathrm{M}\) HCl solution and pure water, respectively. The blue curve corresponds to the theoretical IR difference spectrum between \(0.9\mathrm{M}\) HCl solution and water. The yellow curve shows the experimental IR difference spectrum between \(0.1\mathrm{M}\) HCl solution and water. The horizontal dashed line is the zero line for the difference spectra.
+ +<|ref|>text<|/ref|><|det|>[[148, 493, 852, 602]]<|/det|> +The results demonstrate that our theoretical IR difference spectrum exhibits excellent agreement with our experimental IR difference spectrum in terms of lineshape. This finding not only confirms the reliability of our ANFFF MD trajectories but also validates the accuracy of our trajectory- based vibrational spectral analysis. Importantly, the agreement between the theoretical and experimental IR difference spectra supports the robustness of our conclusions regarding the assignment of vibrational features. + +<|ref|>text<|/ref|><|det|>[[148, 603, 850, 696]]<|/det|> +In response to the reviewer's comments, we have revised the manuscript (page 5, lines 146- 150) and Supplementary Information (page 3, lines 65- 78) to include these additional calculations and discussions. Fig. R6 has been added to the Supplementary Information as Supplementary Fig. 6 to further support our findings. These revisions enhance the rigor and reliability of our study. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[338, 85, 658, 103]]<|/det|> +## Answers to Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[148, 119, 850, 219]]<|/det|> +General Comments: The authors have satisfactorily addressed almost all of the comments. Regarding the final point, they have conducted an additional comparison with quantum hybrid simulations, which is convincing. However, to complete the picture, I suggest that the authors should consider computing the donor and acceptor hydrogen bond numbers of the flanking/special pair water molecules, as well as the proton transfer coordinate. + +<|ref|>text<|/ref|><|det|>[[148, 234, 852, 334]]<|/det|> +Response: We sincerely appreciate the reviewer's positive assessment of our revisions and the constructive suggestion regarding additional hydrogen bonding analysis. Below, we provide a comprehensive response to address the remaining concern, with corresponding revisions incorporated into the manuscript and Supplementary Information. The page and line numbers mentioned hereafter refer to the highlighted version. + +<|ref|>text<|/ref|><|det|>[[148, 365, 850, 514]]<|/det|> +Comment 2- 1: According to the study by Gemoz et al., in a perfect Zundel complex, both water molecules donate two hydrogen bonds, with the proton symmetrically located between them. In contrast, in the perfect Eigen structure, the water molecule on the side where the proton resides donates two hydrogen bonds, while the water molecule on the opposite side (farther from the proton) donates two hydrogen bonds and also accepts one. The "Zundel- like" species exhibits hydrogen- bonding features similar to those of the perfect Zundel, while the proton is localized to one side, akin to the Eigen configuration. I presume this corresponds to the "intermediate" species discussed in the present study — hence, an explicit analysis would be valuable. + +<|ref|>text<|/ref|><|det|>[[149, 529, 850, 579]]<|/det|> +Therefore, an additional analysis of the hydrogen bonding and the proton transfer coordinate would provide a more comprehensive and insightful picture. That said, the presented work is otherwise well suited for publication without further revision. + +<|ref|>text<|/ref|><|det|>[[148, 594, 850, 710]]<|/det|> +Response: We sincerely thank the reviewer for their valuable suggestion. Following the reviewer's recommendation, we have supplemented our analysis by computing the donor and acceptor hydrogen bond (HB) numbers for the flanking water molecules and examining their correlation with the proton transfer coordinate. Our results indicate that the HB characteristics of the "intermediate" species in our study differ significantly from those of the "Zundel- like" species proposed by Gomez et al., suggesting no direct correspondence. Below, we provide a detailed response. + +<|ref|>text<|/ref|><|det|>[[149, 710, 850, 760]]<|/det|> +Consistent with our previous work (Phys. Rev. Lett., 2023, 131, 15, 158001), we calculated the donor and acceptor HB coordination numbers ( \(\mathrm{CN_D}\) and \(\mathrm{CN_A}\) ) for the oxygen atoms ( \(\mathrm{O_1}\) and \(\mathrm{O_2}\) ) of the flanking water molecules using the expression: + +<|ref|>equation<|/ref|><|det|>[[272, 765, 725, 813]]<|/det|> +\[\mathrm{CN_{D / A}(O_{i}) = \sum_{k = 1}^{1}\frac{[1 - (R_{i k} / R_{1})^{16}]}{[1 - (R_{i k} / R_{1})^{56}]}\cdot \frac{[1 - (\theta_{i k} / \theta_{1})^{16}]}{[1 - (\theta_{i k} / \theta_{1})^{56}]}},\] + +<|ref|>text<|/ref|><|det|>[[148, 820, 850, 906]]<|/det|> +where the cutoff \(R_{1}\) and \(\theta_{1}\) were set as \(3.3\mathrm{\AA}\) and \(\pi /4\) , respectively. \(R_{ik}\) denotes the distance between \(\mathrm{O_i}\) and \(\mathrm{O}_k\) , and \(\theta_{ik}\) represents the supplementary angle of the \(\mathrm{O}_i\) - \(\mathrm{H - O}_k\) hydrogen bond. We statistically analyzed the average donor/acceptor HB numbers for \(\mathrm{O_1}\) (nearest to the proton) and \(\mathrm{O_2}\) (next- nearest) across three configuration types (Eigen- like, Intermediate, and Zundel- like), as summarized in + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[238, 139, 758, 245]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[214, 117, 781, 135]]<|/det|> +Table R1. The average HB numbers for Eigen-like configurations. + +
CNDCNACND - CNA
O11.940.041.90
O21.650.451.20
Difference0.29-0.410.70
+ +<|ref|>table<|/ref|><|det|>[[238, 281, 758, 389]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[201, 260, 794, 279]]<|/det|> +Table R2. The average HB numbers for Intermediate configurations. + +
CNDCNACND - CNA
O11.930.071.86
O21.750.301.45
Difference0.18-0.230.41
+ +<|ref|>table<|/ref|><|det|>[[238, 425, 758, 532]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[208, 403, 787, 422]]<|/det|> +Table R3. The average HB numbers for Zundel-like configurations. + +
CNDCNACND - CNA
O11.900.131.77
O21.840.191.65
Difference0.06-0.060.12
+ +<|ref|>text<|/ref|><|det|>[[147, 547, 850, 698]]<|/det|> +The results demonstrate that the hydrogen bond number difference, defined as \(\Delta = [\mathrm{CN}_{\mathrm{D}}(\mathrm{O}_{1}) - \mathrm{CN}_{\mathrm{A}}(\mathrm{O}_{1})] - [\mathrm{CN}_{\mathrm{D}}(\mathrm{O}_{2}) - \mathrm{CN}_{\mathrm{A}}(\mathrm{O}_{2})]\) , is an effective indicator for distinguishing the HB network environments among the three configuration types. This observation suggests that each hydrogen bond contributed by the flanking water molecules significantly influences the overall difference in the HB network, consistent with the results of the bond- order analysis in prior literature (J. Chem. Phys., 2005, 122, 014506). Leveraging this definition, we conducted an analysis of the correlation between \(\Delta\) and the proton transfer coordinate \(\delta = R_{\mathrm{O}_2\mathrm{H}^*} - R_{\mathrm{O}_1\mathrm{H}^*}\) , as illustrated in Fig. R1. + +<|ref|>text<|/ref|><|det|>[[147, 698, 850, 880]]<|/det|> +The results presented in Fig. R1 elucidate a clear linear correlation between \(\Delta\) and \(\delta\) , with essentially non- overlapping ranges of \(\Delta\) among the three configuration types. Specifically, Zundel- like configurations exhibit the smallest \(\Delta\) values, indicative of nearly symmetric HB environments surrounding the two flanking water molecules. In contrast, Eigen- like configurations display the largest \(\Delta\) values, reflecting pronounced asymmetry in the HB networks. Intermediate configurations demonstrate medium \(\Delta\) values, suggesting a moderate degree of HB network asymmetry between the Zundel- like and Eigen- like configurations. Consequently, the intermediate configurations markedly differ from the "Zundel- like" species characterized by a symmetric HB network proposed by Gomez et al., thereby emphasizing that our "intermediate" species are not equated with their "Zundel- like" species. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[287, 81, 684, 300]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 305, 850, 375]]<|/det|> +
Fig. R1. The distributions of the HB number difference \((\Delta)\) computed with conditional ensemble average. Scatter plots depict \(\Delta\) versus the proton transfer coordinate \(\delta\) for Zundel-like (blue), Intermediate (yellow) and Eigen-like (green) configurations. The color bar represents structural probability densities in units of \(\mathrm{\AA}^{-1}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 389, 848, 424]]<|/det|> +Additionally, the expression for the local electric field provided in the Supplementary Information, + +<|ref|>equation<|/ref|><|det|>[[362, 430, 634, 479]]<|/det|> +\[E_{1} = \frac{1}{4\pi\epsilon_{0}}\left(\sum_{i}\frac{q_{i}\vec{R}_{i\mathrm{H}^{*}}}{R_{i\mathrm{H}^{*}}^{3}}\right)\cdot \frac{\vec{R}_{O_{1}\mathrm{H}^{*}}}{R_{O_{1}\mathrm{H}^{*}}},\] + +<|ref|>text<|/ref|><|det|>[[148, 487, 404, 503]]<|/det|> +reveals two key characteristics: + +<|ref|>text<|/ref|><|det|>[[147, 503, 850, 570]]<|/det|> +1. Opposite signs for \(\mathbf{O}_{1}\) and \(\mathbf{O}_{2}\) : For a given coordinating type (donor/acceptor), the local electric field contributions from \(\mathbf{O}_{1}\) and \(\mathbf{O}_{2}\) exhibit opposite signs. +2. Opposite signs for donors and acceptors: For a given \(\mathbf{O}_{1}\) or \(\mathbf{O}_{2}\) , the local electric fields from HB donors and acceptors also possess opposite signs. + +<|ref|>text<|/ref|><|det|>[[148, 570, 850, 620]]<|/det|> +These characteristics are consistent with the physical interpretation of the HB number difference \(\Delta\) , suggesting that the local electric field and \(\Delta\) encode similar structural information. + +<|ref|>text<|/ref|><|det|>[[147, 620, 850, 785]]<|/det|> +To validate this hypothesis, we calculated the local electric field within the first coordination shell (defined by a HB distance criterion of \(< 3.5\mathrm{\AA}\) and an angle criterion of \(>3\pi /4\) ) and examined its correlation with \(\Delta\) . The results are presented in Fig. R2. This figure confirms a strong correlation between the local electric field and the HB number difference \(\Delta\) . This relationship underscores the efficacy of the local electric field as a descriptor for quantifying the asymmetry in the HB networks surrounding the two flanking water molecules. Specifically, the intermediate configurations exhibit a characteristic local electric field intensity that falls within a moderate range, which corresponds to a medium degree of HB network asymmetry, as illustrated in Manuscript Fig. 5. + +<|ref|>text<|/ref|><|det|>[[148, 785, 850, 852]]<|/det|> +The rationale for prioritizing local electric field analysis over hydrogen- bond number analysis in the manuscript stems from the latter has some subjectivity—different HB criteria may yield varying results. In contrast, the local electric field serves as an objective descriptor with clear physical significance. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[293, 87, 702, 297]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 305, 850, 358]]<|/det|> +
Fig. R2. The distribution of the local electric field computed with conditional ensemble average. Scatter plots depict the local electric field versus \(\Delta\) for all configurations. The color bar signifies structural probability densities in units of \(\mathrm{\AA}^{-1}\) .
+ +<|ref|>image<|/ref|><|det|>[[149, 371, 833, 555]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 558, 850, 679]]<|/det|> +
Manuscript Fig. 5. The distributions of the local electric field computed with conditional ensemble average. a. The local electric field distributions along collective coordinate \(q_{1}\) , for Zundel-like (0-0.13 V/Å, blue), Intermediate (0.13-0.28 V/Å, yellow) and Eigen-like (0.28-0.40 V/Å, green) configurations, respectively. b. The local electric field distributions along collective coordinate \(q_{s}\) , for Zundel-like, Intermediate and Eigen-like configurations, respectively. The color bar of the scatter points signifies the structural probability densities in units of \(\mathrm{\AA}^{-1}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 694, 850, 778]]<|/det|> +The revised analysis has been integrated into the manuscript on page 11, lines 304- 311 and in the Supplementary Information on pages 7- 8, lines 193- 236. Figs. R1- R2 have been added to the Supplementary Information as Supplementary Figs. 15- 16, and Tables R1- R3 have been included as Supplementary Tables 7- 9. These revisions enhance the rigor and reliability of our study. + +<--- Page Split ---> diff --git a/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/images_list.json b/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..1b75278326e050979bd26f45bfd7fc2239ff720c --- /dev/null +++ b/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1,47 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Reviewer Figure 1. IL-33-ST2 signaling is not required for CTL expansion and SLEC differentiation in LCMV re-challenged mice. Wildtype, \\(IIIr1I^{- / - }\\) , \\(IIIr1I\\) -ExAB \\(^{- / - }\\) , and \\(IIIr1I\\) -ExC \\(^{- / - }\\) mice were primed with 200 plaque-forming units (PFU) of LCMV-WE. Mice were re-challenged with \\(2 \\times 10^{6}\\) PFU LCMV-CI13 on day 30 p.i. and splenic T cells were analyzed 7 days after re-challenge (WT: \\(n = 6\\) , \\(IIIr1I^{- / - }\\) : \\(n = 6\\) , \\(IIIr1I\\) -ExAB \\(^{- / - }\\) : \\(n = 6\\) , \\(IIIr1I\\) ExC \\(^{- / - }\\) : \\(n = 5\\) ). a, Experimental outline. b, Representative staining of CD8 on lymphocytes. c, Frequencies and absolute cell counts of CTLs. d, Frequencies of activated CD44 \\(^+\\) CD62L \\(^+\\) CTLs. e, Absolute cell counts of LCMV NP396-404-specific CTLs. f, Representative FACS plots showing KLRG1 and CD127 expression by CD8 \\(^+\\) T cells. g, Frequencies and absolute cell counts of KLRG1 \\(^+\\) CD127- CTLs. Data are presented as mean \\(\\pm\\) SD with each dot representing one mouse. P was determined using One- way ANOVA with Tukey's post- hoc tests.", + "footnote": [], + "bbox": [ + [ + 117, + 315, + 884, + 525 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Reviewer Figure 2. ST2 expression on bone-marrow-derived macrophages. Bone marrow cells were isolated from femurs and tibias of wildtype, llrl1- , or llrl1-ExAB- mice and differentiated in the", + "footnote": [], + "bbox": [ + [ + 115, + 556, + 884, + 904 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Reviewer Figure 3. ST2 expression on neutrophils stimulated in vitro. a, Pre-gating strategy for the analysis of Ly6G+ CD11b+ neutrophils. b, c, Bone-marrow neutrophils of wildtype, Il1rl1-/- and Il1rl1-ExAB-/- mice were isolated and stimulated with IL-33 (50 ng/ml), IL-12 (10 ng/ml), IL-4 (10 ng/ml), or combinations thereof, for 24 h. Representative FACS plots (b) and quantification (c) showing no detectable expression of ST2 on Ly6G+ CD11b+ neutrophils after ex vivo stimulation (n = 3 per genotype and condition, data represent one of two independent experiments). Data are presented as mean ± SD with each dot representing one mouse.", + "footnote": [], + "bbox": [ + [ + 115, + 85, + 880, + 404 + ] + ], + "page_idx": 14 + } +] \ No newline at end of file diff --git a/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f5b1b066d7176719eed17aecebeb7d91f82504ce --- /dev/null +++ b/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,517 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Immunology Manuscript Title: A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses Corresponding author name(s): Professor Max Loehning, Dr Tobias Brunner + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +23rd Feb 2023 + +Dear Professor Löhning, + +Thank you for sharing your point- by- point reply to referees comments on your manuscript "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses". We would be interested in considering a revised version as outlined in your response. + +We hope you will find the referees' comments useful as you decide how to proceed. If you wish to submit a substantially revised manuscript, please bear in mind that we will be reluctant to approach the referees again in the absence of major revisions. Please do not hesitate to get in touch if you would like to discuss these issues further + +If you choose to revise your manuscript taking into account all reviewer and editor comments, please highlight all changes in the manuscript text file [OPTIONAL: in Microsoft Word format]. + +We are committed to providing a fair and constructive peer- review process. 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If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Immunology or published elsewhere. + +Nature Immunology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +href="http://www.springernature.com/orcid">www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +Thank you for the opportunity to review your work. + +Sincerely, + +<--- Page Split ---> + +# natureresearch + +Stephanie Houston Editor Nature Immunology + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The authors identified a novel alternative TSS for Il1rl1 gene that is specifically utilized by Th1 and CTL cells. Loss of this promoter region significantly impaired CTL differentiation in to SLEC resulting in deficient response to LCMV. The study is elegantly designed and conducted, and only a few minor issues need to be addressed. + +1. In figure 2, the authors examined the conservation of type I Il1rl1 promoter in humans and mice. Based on figure 2a, only the Tbet and STAT4 binding motifs in CNS5 are conserved and the conservation score for the actual promoter region is low. Therefore, only the usage of this promoter is conserved, but not the promoter itself. The section title "The type-1 Il1rl1 promoter is conserved between mice and humans" is thus misleading and needs to be revised. + +2. There seem to be an enhancer located very close to, but downstream of, the promoter region. This enhancer is also bound by T-bet and STAT4 in Th1 cells and could potentially be important for ST2 expression driven by T-bet and STAT4. Thus, the authors should demonstrate whether this enhancer is impacted by the ExAB deletion. In fact, the sequence alignment of this promoter region and surrounding area between mouse and human should be provided, and the area of deletion indicated. +3. In Figure 3k, loss of Type 1 promoter region seems to result only in partial loss of ST2 expression in Th1 cells. What is the explanation of this phenotype? Is there another yet undiscovered TSS for ST2 that is specific for Th1? Or are Th1 cells capable of utilizing GATA3-dependent type II promoters? The authors should comment on this. + +4. In figure 4k and o. There seems to be a CD45.2+ CD45.1+ population. Yet, according to the method section, CD45.1+/- and CD45.2+/- BM/T cells were used. Where did this double positive fraction is coming from? Or is there an error in the method section? + +5. Figure 4f showed reduced Ki67+ cells in ExAB-/- mice, however, there seems to be a larger fraction of cycling cells in ExAB-/- mice by scRNA-seq as shown in figure 5b. What's causing this discrepancy? +6. Instead of a simple lack of SLEC expansion induced by the loss of type I promoter region, there seems to be a diversion from SLEC fate to MPEC fate in ExAB-/- mice, as evidenced by the significantly increased MPEC cluster shown in Figure 5b. The authors should conduct a LCMV re- + +challenge experiment to explore whether there is a memory-related phenotype in these mice. +7. A heatmap of differential gene expression between WT and ExAB-/- cells from each cluster should be shown to demonstrate the transcriptional impact resulting from loss of the type I promoter. The merged heatmap showing all only the top 10 marker for each cluster is not sufficient. + +8. According to Figure 6b IL-33 induces Zeb2 expression in all T cell subsets examined. Zeb2 expression is required for SLEC differentiation. The phenotype of T cells specific loss of Zeb2 during LCMV infection (Dominguez et all JEM 2015 and Omulisik et al JEM 2015) strongly resembles the phenotype observed in ExAB-/- mice. The authors should examine whether the effect on CD8 T cells during LCMV infection after the loss of Type I promoter is mediated by Zeb2. + +<--- Page Split ---> + +# natureresearch + +Reviewer #2: + +Remarks to the Author: + +In this manuscript, Brunner et al. report the discovery and functional characterization of a type- 1- immunity- restricted promoter of the gene Il1rl1, encoding the ST2 receptor for interleukin- 33 (IL- 33), a critical regulator of type- 1, type- 2 and regulatory immune responses. The authors demonstrate that this novel promoter is located \(40\mathrm{kb}\) upstream of the annotated Il1rl1 gene and conserved between mice and humans. In previous work, the authors reported that ST2 expression is upregulated on CD8 T cells (CTLs) and CD4 T cells (Th1s) during viral infection (LCMV model). Now, they demonstrate that this upregulation of ST2 on CTLs and Th1s does not occur during viral infection in mice with deletion of the type- 1 Il1rl1 promoter. They convincingly show that the expression of ST2 driven by the type- 1 promoter is critical for clonal expansion of short- lived effector T cells during antiviral responses. They propose that IL- 33/ST2 signalling provides a strong costimulatory signal for amplification of antiviral responses mediated by CTLs. + +The authors performed a significant number of experiments and the results are novel, interesting and potentially important. Recent results in a Phase 2 clinical trial of COPD revealed promising efficacy of anti- IL- 33 therapeutic antibodies, indicating that IL- 33 plays important roles in type- 1 inflammatory diseases in humans. A better understanding of the mechanisms implicated in the activation of type- 1 immune responses by IL- 33 is thus urgent. + +However, at this point, the data are not sufficient to support the title and conclusions of the manuscript: "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene...'. The authors analysed Th1s and CTLs but did not analyse the potential role of the type- 1 promoter in other immune cells that express ST2 during type- 1 immune responses. These include NK and iNKT cells, macrophages, dendritic cells and neutrophils. To increase the significance of their findings, it is thus essential that the authors analyse the potential role of the type 1- promoter in the regulation of ST2 expression in other immune cell types, associated with type- 1 immune responses. + +Is there a general role of the type 1- promoter in all type- 1 immune cells or a specific role in T cells ? This is an important question because the identification of the type- 1 immunity- restricted promoter of Il1rl1 is the main message of the paper. + +The authors have all the tools in hands, including mice knock- out for the type- 1 Il1rl1 promoter (or immune cells derived from these mice) and a validated flow cytometry assay for ST2 (with DJ8 mAb), to answer this critical question using ex vivo or in vivo assays (see Major Points). + +## MAJOR POINTS + +1) Role of the type-1 promoter in NK and iNKT cells: both human and mouse iNKT and NK cells are direct targets of IL-33, and produce high levels of IFNg after co-stimulation with IL-33 and IL-12 (1-3). NK cells are an important source of IFNg in viral infection and cancer. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in NK cells and iNKT cells (ex vivo or in vivo assays). + +2) Role of the type-1 promoter in macrophages: myeloid-derived antigen-presenting cells, including macrophages and DCs, can respond to IL-33. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in macrophages. For instance, they could use ex vivo assays with bone marrow-derived macrophages, as previously described (3, 4). + +3) Role of the type-1 promoter in neutrophils: resting bone marrow neutrophils express low levels of + +<--- Page Split ---> + +# natureresearch + +ST2 mRNA, and ST2 protein is upregulated at the cell surface after IL- 33 treatment (5). The authors should determine whether the type- 1 promoter controls ST2 expression and/or IL- 33 responsiveness in neutrophils. + +4) Detection of ST2 in immune cells and differences in expression levels: quantification of ST2 by flow cytometry is a critical method for this study. However, the authors used different mAb clones for the detection of ST2 in Th1 cells/CTLs (clone DJ8, with PE- or APC-FASER amplification; Fig 1b, 3e) and ILC2s/mast cells (clone DIH9, ST2-BV421; Ext Fig 4c, f). Commercial ST2 antibodies exhibit significant background staining and are best for highly expressing cells. Could it be that the background with clone DIH9 (ST2-BV421 direct fluorescent conjugate) was too high and the specific signal without amplification too low for detection of ST2 expression in Th1/CTLs? The authors should comment about the differences in ST2 expression levels in different immune cells and explain why they developed a more sensitive assay with DJ8 mAb for Th1/CTLs. In the extended data figures, they should compare the different ST2 mAbs on the same cell types (both type-1 and type-2 immune cells) using Ilrl1 KO cells as controls for gating. RMST2-2 is another widely used mAb clone. The authors have all the tools in hands (various Il1rl1 KO cells) to perform a careful comparison of ST2 detection with the three clones (DJ8, DIH9, RMST2-2) on different type-1 and type-2 immune cells. This will be very useful for the scientific community and will increase the interest and impact of the article, beyond the field of T cells. + +## OTHER POINTS + +5) Fig. 2a and p6: it is not clear why the authors do not comment the T-bet/STAT4 ChIP-Seq and CD8+ SLEC (abbreviation not defined in the legend) ATAC-seq signals downstream of exons A + B ? No T-bet or STAT4 binding sites ? Sites not conserved in humans ? + +6) Fig 2c: the position of the CNS-5 in the human gene is not clear. ChIP-seq data/binding sites for STAT4 ? + +7) p7 'However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, blockade of IL-33 or ST2 using therapeutic antibodies has shown conflicting results in preclinical disease models47'. This sentence is outdated. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in Phase 2 clinical trials of asthma and COPD, as recently reviewed (6). A more appropriate sentence/paragraph could be 'Modulation of the IL-33-ST2 axis could represent a promising approach in treating inflammatory diseases. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in clinical trials of asthma and COPD (6). However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, fine-tuned treatment approaches might offer a critical advantage.' + +## References + +1. Smithgall MD, et al. (2008) IL-33 amplifies both Th1- and Th2-type responses through its activity on human basophils, allergen-reactive Th2 cells, iNKT and NK cells. Int Immunol 20(8):1019-1030. +2. Bourgeois E, et al. (2009) The pro-Th2 cytokine IL-33 directly interacts with invariant NKT and NK cells to induce IFN-gamma production. Eur J Immunol 39:1046-1055. +3. Kearley J, et al. (2015) Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection. Immunity 42(3):566-579. + +<--- Page Split ---> + +# natureresearch + +4. Dagher R, et al. (2020) IL-33-ST2 axis regulates myeloid cell differentiation and activation enabling effective club cell regeneration. Nat Commun 11(1):4786. +5. Alves-Filho JC, et al. (2010) Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection. Nat Med 16(6):708-712. +6. Cayrol C & Girard JP (2022) Interleukin-33 (IL-33): A critical review of its biology and the mechanisms involved in its release as a potent extracellular cytokine. Cytokine 156:155891. + +Reviewer #3: + +Remarks to the Author: + +The authors characterize a distinct transcriptional process for expression of the gene (Il1rl1) encoding ST2 (the IL- 33 receptor) in type- 1 (CTL, Th1) compared to type- 2 (Th2) T cells. They go on to show that ablation of the exons used in the "type- 1" transcripts of Il1rl1 leads to selective loss of ST2 on those cells and impairs the generation of type- 1 effector cells following viral infection. They also find that IL- 33 promotes expression of genes which support TCR and costimulatory stimulation, and which are associated with effector cell differentiation. + +The report carefully lays out the methodical way in which the authors identify different upstream noncoding exons that are selectively used for Il1rl1 transcripts in CTL/Th1 vs Th2 cells, and present strong evidence that this accurately distinguishes the basis for ST2 expression by type- 1 vs type- 2 T cells (with Treg aligning with Th2, in this case). Their generation of mice lacking the "type- 1" related exons confirmed this, with selective loss of ST2 on Th1 and CTL, and their evidence is compelling that the impact of this mutation almost phenocopies the impact of complete Il1rl1 gene ablation, with respect to type- 1 responses. + +The data are convincing, and - as the authors point out - this appears to be a rare (if not unique) example in which genes that are expressed by both type- 1 and - 2 polarized T cells involve distinct transcriptional start sites (regulated by distinct transcription factors). At the same time, once the authors find that loss of exons A/B (ExA/B) leads to almost complete loss of ST2 on type- 1 cells, much of the subsequent data corresponds with earlier work, showing a cell- intrinsic role for ST2 in the antiviral response of these cells. This limitation is somewhat balanced by the authors going deeper than previous studies with respect to the gene expression changes driven by IL- 33 in type- 1 and - 2 T cells (Fig. 6), and by their data indicating that IL- 33 stimulation specifically enhances effector cell differentiation (Fig. 5). Nevertheless, there are remaining concerns. + +1) The studies on impaired generation of short-lived effector cells (SLEC) by CD8+ T cells lacking ExA/B are convincing but the consequences for memory differentiation are underdeveloped. Numerous panels in Figs. 4 and 5 present the frequencies and numbers of SLEC phenotype cells, but do not show the corresponding data for the MPEC (KLRG1- CD127+) cells - based on panels such Fig. 5e, one would presume these cells are increased in frequency. It is unclear whether MPEC are unchanged (or, perhaps more likely, modestly reduced) in absolute numbers. These data are needed for a more complete picture of how defective ST2 regulation (ExA/B knockout) or expression (Il1rl1 knockout) affects CD8+ T cells differentiating along the effector vs memory pathways. + +2) Along the same lines, the authors' analysis of the anti-viral response of ExA/B and Il1rl1 deficient T cells appears to be limited to the first \(\sim 10\) days following infection, and exclusively (as far as this reviewer can ascertain) focuses on cells in the spleen. It would be important to know how mutation of + +<--- Page Split ---> + +# natureresearch + +ExA/B impacts generation of the various subsets of circulating memory CD8+ and CD4+ T cells during these responses, and to extend the scope of the work to analysis of at least some non- lymphoid tissues to determine the effect on generation of resident memory T cells. As it stands, it is unclear whether the loss of normal ST2 regulation leads to a selective loss of type- 1 effector differentiation – with, perhaps, minimal effect on establishment of long- lived memory – or a more generalized defect that is magnified in but not exclusive to the effector pool. + +# Author Rebuttal to Initial comments + +See inserted PDF + +<--- Page Split ---> + +## Point-by-point Reply to Reviewers' Comments: + +## A type-1 immunity-restricted promoter of the IL-33 receptor gene directs antiviral T cell responses (NI-A35288-T) + +We are grateful for the valuable input and feedback provided by the reviewers regarding our work. We have thoroughly addressed each of these comments and suggestions. Below, please will find our responses to the reviewer comments (Blue text), presenting the additional experiments performed and outlining the specific changes we have implemented in our manuscript. + +Within the manuscript text, we have used Blue underlined text to indicate changes made to the original version as a result of the reviewer comments. + +## Reviewer #1 + +(Remarks to the Author) + +The authors identified a novel alternative TSS for Il1rl1 gene that is specifically utilized by Th1 and CTL cells. Loss of this promoter region significantly impaired CTL differentiation in to SLEC resulting in deficient response to LCMV. The study is elegantly designed and conducted, and only a few minor issues need to be addressed. + +We thank the reviewer for this very favorable feedback and the helpful comments. We have addressed all the minor points raised as outlined below. + +1. In figure 2, the authors examined the conservation of type I Il1rl1 promoter in humans and mice. Based on figure 2a, only the T-bet and STAT4 binding motifs in CNS5 are conserved and the conservation score for the actual promoter region is low. Therefore, only the usage of this promoter is conserved, but not the promoter itself. The section title "The type-1 Il1rl1 promoter is conserved between mice and humans" is thus misleading and needs to be revised. + +We fully agree with the reviewer and have amended the section title as follows: "Usage of the type- 1 Il1rl1 promoter is conserved between mice and humans." (p. 6, I. 148) + +2. There seem to be an enhancer located very close to, but downstream of, the promoter region. This enhancer is also bound by T-bet and STAT4 in Th1 cells and could potentially be important for ST2 expression driven by T-bet and STAT4. Thus, the authors should demonstrate whether this enhancer is impacted by the ExAB deletion. In fact, the sequence alignment of this promoter region and surrounding area between mouse and human should be provided, and the area of deletion indicated. + +We concur that there is a region downstream of the identified exons A and B, which is bound by STAT4 and T- bet, and is marked by an ATAC- Seq peak in activated but not naive CD8 \(^+\) T cells. Importantly, this putative enhancer specified by the reviewer is not deleted in the generated Il1rl1- ExAB- \(^+\) mice. We have provided a new subpanel (Extended Data Fig. 3b) to indicate the area of deletions in Il1rl1- ExAB- \(^+\) and Il1rl1- ExC- \(^+\) mice in relation to the ATAC- and ChIP- Seq peaks. An interpretable single- nucleotide sequence alignment of the promoter region, including all important sites, would exceed by far the size limit of a figure (multiple thousand base- pairs). To offer the reviewer and the readership a readily accessible way to investigate the data presented in the manuscript, we have provided access to the RNA- Seq, ATAC- Seq, and ChIP- Seq tracks in a UCSC Genome browser session. Using the following link: https://genome.ucsc.edu/s/agloehning/BrunnerServeatal2023, reviewers and readers can inspect the data in detail and compare the conservation of all positions at the desired resolution. We hope that these measures support the claims made in our study by enhancing the data transparency of our manuscript. + +<--- Page Split ---> + +3. In Figure 3k, loss of Type 1 promoter region seems to result only in partial loss of ST2 expression in Th1 cells. What is the explanation of this phenotype? Is there another yet undiscovered TSS for ST2 that is specific for Th1? Or are Th1 cells capable of utilizing GATA3-dependent type II promoters? The authors should comment on this. + +We thank the reviewer for addressing this highly interesting point. Indeed, while the loss of exons A and B largely abrogates ST2 expression of CTLs in vitro and in vivo, Th1 cells appear to be able to partially compensate for the loss of the type- 1 promoter in vivo, as we observed a mere \(\sim 50\%\) reduction in frequency of ST2+ Th1 cells in Il1rl1- ExAB- mice. To address the question which promoter is utilized by ExonAB- deficient Th1 cells, we adaptively transferred naive Smarta or Smarta Il1rl1- ExAB- cells into wildtype (WT) recipients, which were subsequently infected with LCMV (Extended Data Fig. 6s). Like the polyclonal Th1 population in Il1rl1- ExAB- mice, also Smarta T cells displayed a \(\sim 50 - 60\%\) reduction in frequencies of ST2- expressing cells at the peak of the acute T cell response (Extended Data Fig. 6t,u). Congenitally marked Th1 cells were flow- cytometrically sorted from spleens of infected animals, and RNA was isolated to assess their ST2 promoter usage. Interestingly, ExonAB- deficient, but not wildtype Smarta cells utilized the proximal promoter (reported to be used by e.g. fibroblasts) to express ST2, and thus incorporated exon 1b into their 5' untranslated regions (Extended Data Fig. 6v). Neither WT, nor Il1rl1- ExAB- Smarta cells expressed significant amounts of exon 1a. Importantly, exon 1b was barely detectable in 2 out of 4 recipients of WT Smarta cells, indicating that it does not critically contribute to ST2 expression if the type- 1 promoter is intact. We have incorporated these data into the manuscript (Extended Data Fig. 6s- v) (p. 10 l. 260- 262). The molecular mechanisms underlying this finding will be addressed in future studies using the appropriate gene- targeted mice. + +4. In figure 4k and o. There seems to be a \(\mathrm{CD45.2 + }\) CD45.1+ population. Yet, according to the method section, \(\mathrm{CD45.1 + / - }\) and \(\mathrm{CD45.2 + / + }\) BM/T cells were used. Where did this double positive fraction is coming from? Or is there an error in the method section? + +Indeed, in the experiment presented in Fig. 4j- m, irradiated \(\mathrm{CD45.1^{+ / + }}\) recipients were reconstituted with bone marrow from \(\mathrm{CD45.1^{+ / - }}\) (WT) mice and \(\mathrm{CD45.2^{+ / + }}\) (Il1rl1- ExAB- , or Il1rl1- ExC- ) mice. In Fig. 4n- r, \(\mathrm{CD45.1^{+ / - }}\) P14 cells were transferred together with \(\mathrm{CD45.1^{+ / + }}\) Il1rl1- ExAB- or Il1rl1- P14 cells into \(\mathrm{CD45.2^{+ / + }}\) WT recipients. Importantly, \(\mathrm{CD45.1}\) and \(\mathrm{CD45.2}\) are two variants of the \(\mathrm{CD45}\) gene differing in only few amino acids. Thus \(\mathrm{CD45.1^{+ / - }}\) cells express \(\mathrm{CD45.1}\) from one allele and \(\mathrm{CD45.2}\) from the second allele, which results in a double positive population if co- stained with \(\mathrm{CD45.1}\) - and \(\mathrm{CD45.2}\) - specific antibodies. Thus, the double positive fraction represents the reconstituted WT donor cells in Fig. 4k and the transferred P14 cells in Fig. 4o. To make it easier to follow these experimental layouts, we amended the figure legends to indicate the expression of both variants (e.g. \(\mathrm{CD45.1^{+}}\) \(\mathrm{CD45.2^{+}}\) instead of \(\mathrm{CD45.1^{+ / - }}\) ). + +5. Figure 4f showed reduced Ki67+ cells in ExAB-/- mice, however, there seems to be a larger fraction of cycling cells in ExAB-/- mice by scRNA-seq as shown in figure 5b. What's causing this discrepancy? + +In Fig. 4f, the frequency of Ki67- expressing cells among all \(\mathrm{CD8^{+}}\) T cells is depicted. The reduced frequency of Ki67+ cells among \(\mathrm{CD8^{+}}\) T cells in Il1rl1- ExAB- mice is a result of the impaired expansion of activated CTLs, a large fraction of which is positive for Ki67. In contrast, in Fig. 5b, activated \(\mathrm{CD44^{+}}\) CTLs were sorted and equal amounts of these CTLs per genotype were compared, thus reflecting the amount of cycling cells relative to an equal number of activated \(\mathrm{CD44^{+}}\) CTLs. However, as Fig. 5n illustrates, there is still a drastic difference in the numbers of \(\mathrm{CD44^{+}}\) CTLs per spleen in the scRNA- Seq experiment. When taking this into account, the absolute number of Ki67+ CTLs in WT mice far exceeds the number of Ki67+ CTLs in Il1rl1- ExAB- mice. + +6. Instead of a simple lack of SLEC expansion induced by the loss of type I promoter region, there seems to be a diversion from SLEC fate to MPEC fate in ExAB-/- mice, as evidenced by the significantly increased MPEC cluster shown in Figure 5b. The authors should conduct a LCMV re- challenge experiment to explore whether there is a memory-related phenotype in these mice. + +As pointed out in the answer to the previous question, in Fig. 5b equal numbers of activated CTLs per genotype were compared, irrespective of the differences in CTL expansion between the two + +<--- Page Split ---> + +genotypes. Consequently, the large relative increase in MPECs is in part due to a \(>10\) - fold decrease in the amount of SLECs per organ. However, in absolute terms, the amount of MPECs per spleen is even slightly decreased in \(IIIr1I\) - ExAB \(^{- / - }\) and \(IIIr1I^{- / - }\) mice. We have amended the text and have added the absolute numbers of MPECs to address this point (Fig. 5h, I; Fig. 6j, k and Extended Data Fig. 6m)(p. 10- 11, I. 290- 306; p. 13, I. 368- 370; p. 16, I. 450- 454). + +To address the reviewers' question whether \(IIIr1I\) - ExAB \(^{- / - }\) or \(IIIr1I^{- / - }\) mice display a memory- related phenotype, we have conducted a re- challenge experiment. We first infected WT, \(IIIr1I^{- / - }\) , \(IIIr1I\) - ExAB \(^{- / - }\) , or \(IIIr1I\) - ExC \(^{- / - }\) mice with 200 PFU of LCMV- WE. Then, 30 days after primary infection, mice were challenged with \(2 \times 10^{6}\) PFU of LCMV- CI13 and analyzed 7 days after secondary infection (Reviewer Fig. 1a). We have found no significant differences in frequencies or absolute numbers of CD8 \(^+\) T cells in spleens of re- challenged animals (Reviewer Fig. 1b, c). Further, no differences in frequencies of activated CD44 \(^+\) CD62L \(^+\) CTLs or counts of LCMV- specific NP396- Tetramer \(^+\) CTLs were observed (Reviewer Fig. 1d, e). Lastly, in this recall setting the proportion of short- lived effector cells amongst CTLs of \(IIIr1I^{- / - }\) , \(IIIr1I\) - ExAB \(^{- / - }\) and \(IIIr1I\) - ExC \(^{- / - }\) as well as their number was comparable to WT mice (Reviewer Fig. 1f, g). + +![](images/Figure_1.jpg) + +
Reviewer Figure 1. IL-33-ST2 signaling is not required for CTL expansion and SLEC differentiation in LCMV re-challenged mice. Wildtype, \(IIIr1I^{- / - }\) , \(IIIr1I\) -ExAB \(^{- / - }\) , and \(IIIr1I\) -ExC \(^{- / - }\) mice were primed with 200 plaque-forming units (PFU) of LCMV-WE. Mice were re-challenged with \(2 \times 10^{6}\) PFU LCMV-CI13 on day 30 p.i. and splenic T cells were analyzed 7 days after re-challenge (WT: \(n = 6\) , \(IIIr1I^{- / - }\) : \(n = 6\) , \(IIIr1I\) -ExAB \(^{- / - }\) : \(n = 6\) , \(IIIr1I\) ExC \(^{- / - }\) : \(n = 5\) ). a, Experimental outline. b, Representative staining of CD8 on lymphocytes. c, Frequencies and absolute cell counts of CTLs. d, Frequencies of activated CD44 \(^+\) CD62L \(^+\) CTLs. e, Absolute cell counts of LCMV NP396-404-specific CTLs. f, Representative FACS plots showing KLRG1 and CD127 expression by CD8 \(^+\) T cells. g, Frequencies and absolute cell counts of KLRG1 \(^+\) CD127- CTLs. Data are presented as mean \(\pm\) SD with each dot representing one mouse. P was determined using One- way ANOVA with Tukey's post- hoc tests.
+ +In our opinion, this experiment nicely reflects the role of IL- 33 as an alarmin. Secondary LCMV infections are rapidly controlled by highly potent memory CD8 \(^+\) T cells and additional antibody- dependent antiviral mechanisms \(^{1 - 3}\) . The data presented here show that ST2 signaling is not required for antiviral CD8 \(^+\) T cell expansion and SLEC differentiation when previously infected mice are re- challenged. A similar phenotype was observed in MyD88- deficient mice, which is an adaptor protein essential for ST2 signaling \(^{4,5}\) . However, we have addressed the role of IL- 33- ST2 signaling in memory T cell formation, maintenance, and recall responses in Baumann et al. \(^{6}\) . In the latter study, we found that a lack of IL- 33 signaling in primary infections did not affect recall responses in an IL- 33- competent environment. Yet, IL- 33 signals were essential for efficient expansion and reactivation of CD8 \(^+\) memory T cells when rechallenged in naive secondary WT recipients. These experiments have shown that also fully differentiated memory CTLs can (re-)express ST2 and can benefit from IL- 33 signals, likely depending on the inflammatory context. Together, these findings raise interesting questions. For instance, it remains unknown whether IL- 33 release differs between LCMV- primed and naive mice. Neither do we know whether the interval between priming and re- challenge affects the IL- 33/ST2- dependence of secondary CTL responses. + +<--- Page Split ---> + +The entirely novel finding of a type- 1 immunity- restricted promoter that regulates ST2 expression in antiviral T cells remains the focus of the current manuscript. As we would like to address the abovementioned questions in future studies, we decided to present the results of the re- infection experiment to the reviewer without adding it to the manuscript. + +7. A heatmap of differential gene expression between WT and ExAB-/- cells from each cluster should be shown to demonstrate the transcriptional impact resulting from loss of the type I promoter. The merged heatmap showing all only the top 10 marker for each cluster is not sufficient. + +We have performed a differential gene expression analysis of each cluster to demonstrate the impact of the type- 1 llrl1 promoter deletion on the transcriptome of individual subsets. The results are now displayed in the new Extended Data Fig. 8. + +8. According to Figure 6b IL-33 induces Zeb2 expression in all T cell subsets examined. Zeb2 expression is required for SLEC differentiation. The phenotype of T cells specific loss of Zeb2 during LCMV infection (Dominguez et all JEM 2015 and Omilusik et al JEM 2015) strongly resembles the phenotype observed in ExAB-/- mice. The authors should examine whether the effect on CD8 T cells during LCMV infection after the loss of Type I promoter is mediated by Zeb2. + +We fully agree with the reviewer that the phenotype of Zeb2-deficient CD8+ T cells in LCMV infections is very similar to the one observed in ExonAB- or ST2-deficient mice and that this resemblance is of considerable interest. + +Besides Zeb2, IL- 33 stimulation of CTLs also induced expression of T- bet and Blimp1, both of which are critical for expansion and SLEC differentiation of LCMV- specific CTLs7. Thus, impaired SLEC differentiation observed in ExAB- and llrl1- deficient mice is probably a combination of multiple factors and can possibly not be exclusively attributed to a reduction in Zeb2 expression alone. Interestingly however, analysis of scRNA- Seq data, as suggested by the reviewer in point 7, revealed a higher expression of Zeb2 transcripts in ExAB- deficient SLECs as compared to WT SLECs (Extended Data Fig. 8). This might reflect a compensatory mechanism, which could allow very few cells to differentiate into SLECs without IL- 33/ST2 signals, and further indicate an important link between ST2- signaling and Zeb2 expression in vivo. + +A putative experiment to assess this question in more detail, would be to overexpress Zeb2 in ST2- deficient T cells using transgenic mice or retro/entiviral constructs and to study the T cell response after LCMV infections. We regret that we don't have the necessary tools at hand to perform these elaborate experiments and we hope that the reviewer agrees that establishment of these tools would exceed the timeframe available for this revision. + +All things considered, we are very grateful for the reviewer's suggestions and believe that addressing the minor issues raised by the reviewer significantly improved the quality of our study. + +<--- Page Split ---> + +## Reviewer #2 + +(Remarks to the Author) + +In this manuscript, Brunner et al. report the discovery and functional characterization of a type- 1- immunity- restricted promoter of the gene ll1rl1, encoding the ST2 receptor for interleukin- 33 (IL- 33), a critical regulator of type- 1, type- 2 and regulatory immune responses. The authors demonstrate that this novel promoter is located 40 kb upstream of the annotated ll1rl1 gene and conserved between mice and humans. In previous work, the authors reported that ST2 expression is upregulated on CD8 T cells (CTLs) and CD4 T cells (Th1s) during viral infection (LCMV model). Now, they demonstrate that this upregulation of ST2 on CTLs and Th1s does not occur during viral infection in mice with deletion of the type- 1 ll1rl1 promoter. They convincingly show that the expression of ST2 driven by the type- 1 promoter is critical for clonal expansion of short- lived effector T cells during antiviral responses. They propose that IL- 33/ST2 signaling provides a strong costimulatory signal for amplification of antiviral responses mediated by CTLs. + +The authors performed a significant number of experiments and the results are novel, interesting and potentially important. Recent results in a Phase 2 clinical trial of COPD revealed promising efficacy of anti- IL- 33 therapeutic antibodies, indicating that IL- 33 plays important roles in type- 1 inflammatory diseases in humans. A better understanding of the mechanisms implicated in the activation of type- 1 immune responses by IL- 33 is thus urgent. + +However, at this point, the data are not sufficient to support the title and conclusions of the manuscript: "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene...". The authors analysed Th1s and CTLs but did not analyse the potential role of the type- 1 promoter in other immune cells that express ST2 during type- 1 immune responses. These include NK and iNKT cells, macrophages, dendritic cells and neutrophils. To increase the significance of their findings, it is thus essential that the authors analyse the potential role of the type 1- promoter in the regulation of ST2 expression in other immune cell types, associated with type- 1 immune responses. + +Is there a general role of the type 1- promoter in all type- 1 immune cells or a specific role in T cells? This is an important question because the identification of the type- 1 immunity- restricted promoter of ll1rl1 is the main message of the paper. + +The authors have all the tools in hands, including mice knock- out for the type- 1 ll1rl1 promoter (or immune cells derived from these mice) and a validated flow cytometry assay for ST2 (with DJ8 mAb), to answer this critical question using ex vivo or in vivo assays (see Major Points). + +We thank the reviewer for this positive feedback and are delighted to hear that the reviewer appreciates the impact of our findings. We certainly agree that a better understanding of type- 1 immunity- related aspects of IL- 33 biology is of utmost importance. + +We would like to emphasize that by using the wording "type- 1 immunity- restricted", we do not want to imply that the promoter is used by all IL- 33- responsive immune cells that contribute to type- 1 immune responses. Rather, we use this description to highlight that we have not found any evidence of this promoter being active in type- 2 immunity- associated T cells and innate cells, including ILC2s and mast cells nor in Treg cells. We have amended the text at two positions to communicate this more precisely (p. 2, l. 35; p. 14, l. 392). + +In addition, we have performed a significant number of experiments and made use of our highly sensitive ST2 staining protocol, to assess if the type- 1 ll1rl1 promoter is of importance for ST2 expression by NK cells, NKT cells, neutrophils and BMDMs (see below). + +## MAJOR POINTS + +1) Role of the type-1 promoter in NK and iNKT cells: both human and mouse iNKT and NK cells are direct targets of IL-33, and produce high levels of IFNg after co-stimulation with IL-33 and IL-12 (1-3). NK cells are an important source of IFNg in viral infection and cancer. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in NK cells and iNKT cells (ex vivo or in vivo assays). + +Indeed, NK cells are crucial players in the cellular immunity against infections and cancer. As cited, others have shown that NK cells can produce IFN- \(\gamma\) in response to combined stimulation with IL- 12 and IL- 33. To assess if the deletion of the type- 1 ll1rl1 promoter controls ST2 expression in NK cells, we thus have flow- cytometrically sorted NKp46+ TCR \(\beta\) NK cells from spleens of WT, ll1rl1- ExAB- \(\gamma\) , + +<--- Page Split ---> + +and llrl1- mice and cultured them in IL- 33- and IL- 12- containing medium. We found that after 2 days of stimulation, a fraction of WT NK cells expressed ST2, while no ST2 expression was found on llrl1- ExAB- or llrl1- NK cells (Extended Data Fig. 4d- f). + +In addition, NKT cells were sort purified from thymocytes by utilizing \(\alpha\) - Galactosylceramide- loaded CD1d tetramers. FACS- sorted NKT cells were then activated and expanded ex vivo in type- 1 conditions. After 6 days of culture, \(\sim 60\%\) of WT NKT cells expressed ST2 at considerable levels. In contrast, llrl1- ExAB- NKT cells were unable to express ST2 as it was the case in llrl1- NKT cells (Extended Data Fig. 4a- c). + +Together, these results clearly demonstrate that usage of the type- 1 llrl1 promoter is not restricted to T cells, but also directs ST2 expression in type- 1 polarized innate immune cells. We thank the reviewer for the excellent recommendation to perform these exciting experiments. We have added the results to the manuscript in Extended Data Fig. 4 and modified the text accordingly (p. 4, l. 87; p. 8, l. 206- 208; p. 14, l. 392). + +2) Role of the type-1 promoter in macrophages: myeloid-derived antigen-presenting cells, including macrophages and DCs, can respond to IL-33. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in macrophages. For instance, they could use ex vivo assays with bone marrow-derived macrophages, as previously described (3, 4). + +To address this question, we have cultured bone- marrow cells (BMDMs) from wildtype, llrl1- ExAB- , and llrl1- mice in the presence of recombinant M- CSF for 7 days as described in Kearley et al.8. As shown in Reviewer Fig. 2a, we achieved a high purity of BMDMs expressing F4/80 and CD11b. After 7 days, BMDMs were stimulated with IL- 33, IL- 4, IL- 12 + IL- 18, IFNα + IFNγ, Poly(I:C), or Poly(I:C) + IL- 33. We stained ST2 using our amplified staining protocol, as this provides a more direct readout as compared to e.g. ELISAs of the cell culture supernatant. + +Unfortunately, we were not able to detect ST2 on the surface of BMDMs irrespective of the genotype and the nature of stimulation (Reviewer Fig. 2b). Analysis of mRNA expression verified that ST2 transcript expression was very low in all culture conditions and substantially lower than in CTLs or Th2 cells (Reviewer Fig. 2c). In line with these results, IL- 33 stimulation of BMDMs did not upregulate TNF expression or enhance Poly(I:C)- induced expression of TNF (Reviewer Fig. 2d). + +![](images/Figure_2.jpg) + +
Reviewer Figure 2. ST2 expression on bone-marrow-derived macrophages. Bone marrow cells were isolated from femurs and tibias of wildtype, llrl1- , or llrl1-ExAB- mice and differentiated in the
+ +<--- Page Split ---> + +presence of recombinant M- CSF (20 ng/ml) for 7 days. a, Pre- gating strategy and representative FACS plot showing F4/80 and CD11b expression by differentiated BMDMs. b, Representative FACS plots showing no detectable expression of ST2 on BMDMs ( \(n = 3\) per genotype, experiment was performed twice). c, d, mRNA expression of ST2 (c) or TNF (d) by BMDMs after 24 h of stimulation with IL- 33 (10 ng/ml), IL- 4 (10 ng/ml), IL- 12 + IL- 18 (10 ng/ml each), IFNα (250 U/ml) + IFN- γ (10 ng/ml), Poly(I:C) (10 μg/ml), or Poly(I:C) (10 μg/ml) + IL- 33 (10 ng/ml). e, Representative FACS plots showing ST2 expression when BMDMs were differentiated for 7 days in the presence of M- CSF (20 ng/ml) and IL- 4 (10 ng/ml). f, Quantification of ST2 expression on BMDMs (WT: \(n = 5\) , \(II1r1^{- / - }\) : \(n = 4\) , \(II1r1^{- / - }\) ExAB \(^{- / - }\) : \(n = 4\) , data of independent experiments were pooled). Data are presented as mean ± SD with each dot representing one culture with bone marrow cells from individual mice. \(P\) was determined using two- tailed t- test (f, right panel) and One- way (f) or Two- way ANOVA (c, d) with Tukey's post- hoc tests. + +The addition of IL- 4 during BMDM culture was shown to promote differentiation into alternatively activated macrophages with higher expression of ST29. Indeed, we detected ST2 on the surface of WT macrophages when IL- 4 was added one day after plating bone marrow cells, albeit still at low levels (Reviewer Fig. 2e,f). As expected, \(II1r1^{- / - }\) ExAB \(^{- / - }\) macrophages did not exhibit a reduction in ST2 surface expression. + +At this point, we cannot explain the discrepancies between our results and the data published by Kearley et al.8 Thus, we refrain from including the data in the manuscript and hope the reviewer concurs with this decision. + +3) Role of the type-1 promoter in neutrophils: resting bone marrow neutrophils express low levels of ST2 mRNA, and ST2 protein is upregulated at the cell surface after IL-33 treatment (5). The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in neutrophils. + +To study whether the type- 1 promoter controls ST2 expression in neutrophils, we have assessed ST2 expression of bone- marrow neutrophils in wildtype, \(II1r1^{- / - }\) ExAB \(^{- / - }\) , and \(II1r1^{- / - }\) mice (Extended Data Fig. 5h,k,l). Supporting data published by Alves- Filho et al.10, we found that a small but obvious population of resting neutrophils expressed ST2 protein (Extended Data Fig. 5k). Importantly, this population was still evident in \(II1r1^{- / - }\) ExAB \(^{- / - }\) mice even though in slightly lower frequency, and ST2 expression intensity within this population was largely comparable to WT mice (Extended Data Fig. 5l). Of note, using the same staining, we have determined ST2 expression by bone- marrow eosinophils, which worked remarkably well. We thus have included these data in Extended Data Fig. 5i,j, to extend our analysis of ST2 expression by innate type- 2 immune cells. + +Next, we have purified bone- marrow neutrophils using a three- step Ficoll gradient11 followed by 24 h of stimulation with IL- 33, IL12, IL- 4, or combinations of IL- 33 and IL12 or IL- 4. To our surprise, using \(II1r1^{- / - }\) neutrophils as controls, no ST2 expression could be detected on stimulated CD11b+ Ly6G+ neutrophils isolated from wildtype or \(II1r1^{- / - }\) ExAB+ mice (Reviewer Fig. 3a- c). + +<--- Page Split ---> +![](images/Figure_3.jpg) + +
Reviewer Figure 3. ST2 expression on neutrophils stimulated in vitro. a, Pre-gating strategy for the analysis of Ly6G+ CD11b+ neutrophils. b, c, Bone-marrow neutrophils of wildtype, Il1rl1-/- and Il1rl1-ExAB-/- mice were isolated and stimulated with IL-33 (50 ng/ml), IL-12 (10 ng/ml), IL-4 (10 ng/ml), or combinations thereof, for 24 h. Representative FACS plots (b) and quantification (c) showing no detectable expression of ST2 on Ly6G+ CD11b+ neutrophils after ex vivo stimulation (n = 3 per genotype and condition, data represent one of two independent experiments). Data are presented as mean ± SD with each dot representing one mouse.
+ +We regret that the data shown in Reviewer Fig. 3b,c are not in line with results published by Alves- Filho et al. \(^{10}\) . As it is unclear what accounts for these inconsistencies (e.g. mouse background or experimental procedures), we prefer not to include these results in the manuscript. + +4) Detection of ST2 in immune cells and differences in expression levels: quantification of ST2 by flow cytometry is a critical method for this study. However, the authors used different mAb clones for the detection of ST2 in Th1 cells/CTLs (clone DJ8, with PE- or APC-FASER amplification; Fig 1b, 3e) and ILC2s/mast cells (clone DIH9, ST2-BV421; Ext Fig 4c, f). Commercial ST2 antibodies exhibit significant background staining and are best for highly expressing cells. Could it be that the background with clone DIH9 (ST2-BV421 direct fluorescent conjugate) was too high and the specific signal without amplification too low for detection of ST2 expression in Th1/CTLs? The authors should comment about the differences in ST2 expression levels in different immune cells and explain why they developed a more sensitive assay with DJ8 mAb for Th1/CTLs. In the extended data figures, they should compare the different ST2 mAbs on the same cell types (both type-1 and type-2 immune cells) using Ilrl1 KO cells as controls for gating. RMST2-2 is another widely used mAb clone. The authors have all the tools in hands (various Il1rl1 KO cells) to perform a careful comparison of ST2 detection with the three clones (DJ8, DIH9, RMST2-2) on different type-1 and type-2 immune cells. This will be very useful for the scientific community and will increase the interest and impact of the article, beyond the field of T cells. + +Indeed, as the reviewer points out, a conventional single- step staining of ST2 is insufficient to achieve a good staining resolution on CTLs or Th1- polarized T cells, as the surface expression of ST2 on these cells is much lower than on Th2- polarized T cells, ILC2s, or mast cells \(^{12}\) . Thus, we have established a staining protocol utilizing a digoxigenin- conjugated primary ST2 antibody, an APC- or PE- conjugated secondary Fab fragment, and two- rounds of FASER- amplification to determine ST2 expression on CTLs or Th1 cells in a highly sensitive manner. However, for assessment of ST2 on mast cells and ILC2s ex vivo, we still utilize the commercially available, directly conjugated clone DIH9, as this staining takes less time and is much more cost effective. Further, using unamplified + +<--- Page Split ---> + +stainings allows for higher flexibility in the flow- cytometry panel design, as the Faser amplification cannot be used when a staining with biotin- labelled antibodies or specific tandem- conjugates (e.g. APC- Cy7 or PE- Cy7) is required. + +To report on this technical aspect in more detail, we have directly compared our highly sensitive staining with a single- step staining using the clones DIH9 and RMST2- 2 on high and low ST2 expressing cells (Th2 and Th1 cells), as well as on ST2- deficient T cells as requested by the reviewer (Extended Data Fig. 1d,e)(p. 5, I. 101- 105). Of note, prior to this experiment, the directly PE- conjugated antibodies (DIH9 and RMST2- 2) were titrated to assure optimal staining quality. Our comparison shows nicely that stainings with directly conjugated DIH9 or RMST2- 2 antibodies were sufficient to discriminate ST2+ and ST2- cells when cells express high levels of ST2 (e.g. Th2 cells). However, only by using our established highly sensitive staining protocol, we can achieve a good ST2 staining on ST2 low- expressing cells (e.g. Th1 cells) (Extended Data Fig. 1d,e). + +We thank the reviewer for the suggestion to specifically explain and elaborate the rationale behind using this enhanced staining procedure to visualize ST2 on antiviral T cells. We think that this comparison illustrates why ST2 expression and the impact of IL- 33/ST2- signaling on type- 1 polarized T cells, has been underestimated in so many studies. + +## OTHER POINTS + +5) Fig. 2a and p6: it is not clear why the authors do not comment the T-bet/STAT4 ChIP-Seq and CD8+ SLEC (abbreviation not defined in the legend) ATAC-seq signals downstream of exons A + B ? No T-bet or STAT4 binding sites ? Sites not conserved in humans? + +Indeed, we focused on the ATAC-Seq signal 5kb upstream of exons A and B, as the position of the ATAC-peak downstream of the promoter did not coincide with a conserved DNA element. We have now explained this rationale in the text (p. 6, I. 155- 157). + +6) Fig 2c: the position of the CNS-5 in the human gene is not clear. ChIP-seq data/binding sites for STAT4 ? + +Due to additional DNA elements between this CNS and the first exon A, which are present in humans but not in mice, the distance of the CNS in relation to the first exon is different in humans and should thus not be termed CNS-5 in this context. Nevertheless, we have indicated the position of this particular CNS (CNS-5 in mice) in Fig. 2c with a red arrow and added a description to the figure legend (p. 28, I. 770- 773). Further, as pointed out in question 2 of Reviewer 1, we now provide easy access to data used in our manuscript via the following link: + +https://genome.ucsc.edu/s/agloehning/BrunnerServeetal2023. By uploading the RNA- Seq, ChIP- Seq, and ATAC- Seq data to the web- based UCSC genome browser, we offer reviewers and readers a tool to investigate the data in detail and to assess the conservation of all regions. We regret that we have not found suitable STAT4 ChIP- Seq data for human type- 1- polarized T cells to complement the mouse T- bet ChIP data. + +7) p7 'However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, blockade of IL-33 or ST2 using therapeutic antibodies has shown conflicting results in preclinical disease models47. This sentence is outdated. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in Phase 2 clinical trials of asthma and COPD, as recently reviewed (6). A more appropriate sentence/paragraph could be 'Modulation of the IL-33-ST2 axis could represent a promising approach in treating inflammatory diseases. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in clinical trials of asthma and COPD (6). However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, fine-tuned treatment approaches might offer a critical advantage.' + +We thank the reviewer for this suggestion and have amended the text accordingly (p. 7, I. 177- 180). + +<--- Page Split ---> + +1. Smithgall MD, et al. (2008) IL-33 amplifies both Th1- and Th2-type responses through its activity on human basophils, allergen-reactive Th2 cells, iNKT and NK cells. Int Immunol 20(8):1019-1030. +2. Bourgeois E, et al. (2009) The pro-Th2 cytokine IL-33 directly interacts with invariant NKT and NK cells to induce IFN-gamma production. Eur J Immunol 39:1046-1055. +3. Kearley J, et al. (2015) Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection. Immunity 42(3):566-579. +4. Dagher R, et al. (2020) IL-33-ST2 axis regulates myeloid cell differentiation and activation enabling effective club cell regeneration. Nat Commun 11(1):4786. +5. Alves-Filho JC, et al. (2010) Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection. Nat Med 16(6):708-712. +6. Cayrol C & Girard JP (2022) Interleukin-33 (IL-33): A critical review of its biology and the mechanisms involved in its release as a potent extracellular cytokine. Cytokine 156:155891. + +<--- Page Split ---> + +## Reviewer #3 + +(Remarks to the Author) + +The authors characterize a distinct transcriptional process for expression of the gene (ll1rl1) encoding ST2 (the IL- 33 receptor) in type- 1 (CTL, Th1) compared to type- 2 (Th2) T cells. They go on to show that ablation of the exons used in the "type- 1" transcripts of ll1rl1 leads to selective loss of ST2 on those cells and impairs the generation of type- 1 effector cells following viral infection. They also find that IL- 33 promotes expression of genes which support TCR and costimulatory stimulation, and which are associated with effector cell differentiation. + +The report carefully lays out the methodical way in which the authors identify different upstream noncoding exons that are selectively used for ll1rl1 transcripts in CTL/Th1 vs Th2 cells, and present strong evidence that this accurately distinguishes the basis for ST2 expression by type- 1 vs type- 2 T cells (with Treg aligning with Th2, in this case). Their generation of mice lacking the "type- 1" related exons confirmed this, with selective loss of ST2 on Th1 and CTL, and their evidence is compelling that the impact of this mutation almost phenocopies the impact of complete ll1rl1 gene ablation, with respect to type- 1 responses. + +The data are convincing, and - as the authors point out - this appears to be a rare (if not unique) example in which genes that are expressed by both type- 1 and - 2 polarized T cells involve distinct transcriptional start sites (regulated by distinct transcription factors). At the same time, once the authors find that loss of exons A/B (ExA/B) leads to almost complete loss of ST2 on type- 1 cells, much of the subsequent data corresponds with earlier work, showing a cell- intrinsic role for ST2 in the antiviral response of these cells. This limitation is somewhat balanced by the authors going deeper than previous studies with respect to the gene expression changes driven by IL- 33 in type- 1 and - 2 T cells (Fig. 6), and by their data indicating that IL- 33 stimulation specifically enhances effector cell differentiation (Fig. 5). Nevertheless, there are remaining concerns. + +We thank the reviewer for the very positive feedback on our study. In particular, we are pleased to hear that our evidence for a dedicated type- 1 promoter of the ll1rl1 gene is very convincing. Using the LCMV infection model in vivo in conjunction with our newly generated ExAB- or ExC- deficient mice allowed us to test precisely to which extend the type- 1 promoter- deficient T cells recapitulate the reported phenotype of ST2- deficient T cells, while the data presented in Fig. 5 and Fig. 6 shed new light on IL- 33/ST2 signaling and its functions in antiviral T cell responses. In addition, as shown in Fig. 3 our findings of alternative ll1rl1 promoters for the first time allow T cell lineage- selective targeting of ST2 expression even in WT T cells. + +1) The studies on impaired generation of short-lived effector cells (SLEC) by CD8+ T cells lacking ExA/B are convincing but the consequences for memory differentiation are underdeveloped. Numerous panels in Figs. 4 and 5 present the frequencies and numbers of SLEC phenotype cells, but do not show the corresponding data for the MPEC (KLRG1-CD127+) cells - based on panels such Fig. 5e, one would presume these cells are increased in frequency. It is unclear whether MPEC are unchanged (or, perhaps more likely, modestly reduced) in absolute numbers. These data are needed for a more complete picture of how defective ST2 regulation (ExA/B knockout) or expression (ll1rl1 knockout) affects CD8+ T cells differentiating along the effector vs memory pathways. + +We thank the reviewer for the recommendation to present the data for KLRG1: CD127+ MPECs to further elaborate the impact of IL- 33/ST2 signaling on these cells. The reviewer correctly assumes that, in contrast to SLECs, absolute counts of MPECs per organ are only modestly decreased in ll1rl1- ExAB- and ll1rl1- mice compared to wildtype mice. As suggested, we have added frequencies and absolute numbers of MPECs to all figures were SLEC frequencies were shown and amended the text accordingly (Fig. 5h,1, Fig. 6j,k, and Extended Data Fig. 6m) (p. 10- 11, I. 290- 299; p. 13, I. 368- 370; p. 16, I. 450- 454). + +2) Along the same lines, the authors' analysis of the anti-viral response of ExA/B and ll1rl1 deficient T cells appears to be limited to the first \(\sim 10\) days following infection, and exclusively (as far as this reviewer can ascertain) focuses on cells in the spleen. It would be important to know how mutation of ExA/B impacts generation of the various subsets of circulating memory CD8+ and CD4+ T cells during these responses, and to extend the scope of the work to analysis of at least some non-lymphoid tissues to determine the effect on generation of resident memory T cells. As it stands, it is unclear + +<--- Page Split ---> + +whether the loss of normal ST2 regulation leads to a selective loss of type- 1 effector differentiation – with, perhaps, minimal effect on establishment of long- lived memory – or a more generalized defect that is magnified in but not exclusive to the effector pool. + +Indeed, we have focused our analyses to the first \~10 days after LCMV infection and primarily analyzed spleens, as well as in some cases livers, of infected animals (Extended Data Fig. 6a- f, n- r). ST2 expression on antiviral T cells and phenotypic differences between ST2- competent and ST2- deficient T cells are most pronounced in the acute phase of the infection6,12. Thus, this time frame seemed optimal to accurately compare the response of Il1rl1- ExAB- /- T cells with Il1rl1- /- T cells and WT T cells. As mentioned in our reply to point 1) of this reviewer, the impact of IL- 33–ST2 signaling does not selectively affect short- lived effector cells, yet the effect on MPEC numbers is less pronounced. + +To assess the role of the type- 1 promoter and the impact of ST2 signaling on memory T cell formation, we have adoptively transferred naive P14, P14 Il1rl1- /- , or P14 Il1rl1- ExAB- /- T cells into WT recipients, which were subsequently infected with LCMV. After 30 days, we have labeled T cells in circulation by intravenous injection of CD90.2 antibody and sacrificed the mice afterwards (Extended Data Fig. 9a). Analysis of spleens, lungs, salivary glands, and kidneys showed that a lack of ST2 or of the type- 1 ST2 promoter reduced the amount of P14 memory cells found in these organs (Extended Data Fig. 9b- d). P14 cells of all genotypes predominantly formed effector memory cells (Tem) and no major impact on frequencies of central memory cells (Tcm) was observed (Extended Data Fig. 9e- g). Likewise, we have found that both circulating and tissue- resident memory T cells were formed, even in the absence of ST2 or the type- 1 promoter (Extended Data Fig. 9h- j). Lastly, quantification of in vivo labeled and non- labeled P14 cells showed that numerical differences between P14 memory and P14 Il1rl1- /- memory or P14 Il1rl1- ExAB- /- memory cells were more pronounced in the intravascular compartment (Extended Data Fig. 9k). + +We greatly appreciate the suggestion of the reviewer to investigate the impact of defective ST2 regulation on MPEC/SLEC fate decision and memory cell formation. We have complemented our study with these newly acquired in vivo data and amended our manuscript at several positions (p. 10- 11, I. 299- 306; p. 16, I. 450- 454). We now report that deletion of the type- 1 ST2 promoter or ST2 largely impairs SLEC expansion, but to a lesser extent, also affects MPEC numbers and consequently the number of antiviral memory CTLs generated. In our opinion, these changes made in response to the reviewer's comments have substantially improved the overall quality of our study. + +<--- Page Split ---> + +References1. Thomsen, A. R. & Marker, O. The complementary roles of cellular and humoral immunity in resistance to re-infection with LCM virus. \*Immunology\* 65, 9-15 (1988).2. Tebo, A. E. et al. Rapid recruitment of virus-specific CD8 T cells restructures immunodominance during protective secondary responses. \*J Virol\* 79, 12703-12713, doi:10.1128/JVI.79.20.12703-12713.2005 (2005).3. Cerny, A., Sutter, S., Bazin, H., Hengartner, H. & Zinkernagel, R. M. Clearance of lymphocytic choriomeningitis virus in antibody- and B-cell-deprived mice. \*J Virol\* 62, 1803-1807, doi:10.1128/JVI.62.5.1803-1807.1988 (1988).4. Rahman, A. H. et al. Antiviral memory CD8 T-cell differentiation, maintenance, and secondary expansion occur independently of MyD88. \*Blood\* 117, 3123-3130, doi:10.1182/blood-2010-11-318485 (2011).5. Schmitz, J. et al. IL-33, an interleukin-1-like cytokine that signals via the IL-1 receptor-related protein ST2 and induces T helper type 2-associated cytokines. \*Immunity\* 23, 479-490, doi:10.1016/j.immuni.2005.09.015 (2005).6. Baumann, C. et al. Memory CD8(+) T Cell Protection From Viral Reinfection Depends on Interleukin-33 Alarmin Signals. \*Front Immunol\* 10, 1833, doi:10.3389/fimmu.2019.01833 (2019).7. Joshi, N. S. et al. Inflammation directs memory precursor and short-lived effector CD8(+) T cell fates via the graded expression of T-bet transcription factor. \*Immunity\* 27, 281-295, doi:10.1016/j.immuni.2007.07.010 (2007).8. Kearley, J. et al. Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection. \*Immunity\* 42, 566-579, doi:10.1016/j.immuni.2015.02.011 (2015).9. Faas, M. et al. IL-33-induced metabolic reprogramming controls the differentiation of alternatively activated macrophages and the resolution of inflammation. \*Immunity\* 54, 2531-2546 e2535, doi:10.1016/j.immuni.2021.09.010 (2021).10. Alves-Filho, J. C. et al. Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection. \*Nat Med\* 16, 708-712, doi:10.1038/nm.2156 (2010).11. Ubags, N. D. J. & Suratt, B. T. Isolation and Characterization of Mouse Neutrophils. \*Methods Mol Biol\* 1809, 45-57, doi:10.1007/978-1-4939-8570-8_4 (2018).12. Baumann, C. et al. T-bet- and STAT4-dependent IL-33 receptor expression directly promotes antiviral Th1 cell responses. \*Proc Natl Acad Sci U S A\* 112, 4056-4061, doi:10.1073/pnas.1418549112 (2015). + +<--- Page Split ---> + +# natureresearch + +## Decision Letter, first revision: + +28th Sep 2023 + +Dear Dr. Löhning, + +Thank you for submitting your revised manuscript "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses" (NI- A35288A). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Immunology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +We will now perform detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +If you had not uploaded a Word file for the current version of the manuscript, we will need one before beginning the editing process; please email that to immunology@us.nature.com at your earliest convenience. + +Thank you again for your interest in Nature Immunology Please do not hesitate to contact me if you have any questions. + +Sincerely, + +Stephanie Houston, PhD Senior Editor Nature Immunology + +Reviewer #2 (Remarks to the Author): + +The authors have satisfactorily addressed my previous concerns. The manuscript has been greatly improved thanks to the addition of new data, and modifications in the text of the manuscript. + +The comparison of the different anti- ST2 mAbs in the flow cytometry assays (Extended data Fig 1d, e) will be very useful for the scientific community. The sensitivity of the enhanced staining procedure with clone DJ8 + FASER amplification is impressive. + +The revised manuscript will be an important contribution to the field. + +Reviewer #3 (Remarks to the Author): + +The authors have responded well to the concerns raised previously, by both including requested data + +<--- Page Split ---> + +# natureresearch + +(which involved several additional studies) and revising the text. + +Regarding the authors' findings on the generation of memory ST2- /- or ExA/B- /- CD8 T cells in lymphoid and non- lymphoid tissues, it might be worth highlighting (e.g., in the discussion) that impaired ST2 expression had minimal (if any) statistically significant effect on likely resident memory T cells (i.e., those cells that are not stained by intravenous antibody labeling). + +Since some effector- like \(\mathsf{CD8 + }\) T cells persist in the circulation well past d30 in the response to acute LCMV infection, it is therefore possible that failure of \(\mathsf{CD8 + }\) T cells to express ST2 is quite selective for effector/effector- like cell generation, while generation of bona fide memory \(\mathsf{CD8 + }\) T cells is, perhaps, completely unaffected. While further work would be needed to thoroughly test this interpretation, it would be an interesting hypothesis to raise since it suggests a quite focused role for IL- 33 sensitivity in generation of effector (but not memory) \(\mathsf{CD8 + }\) T cells, during an acute LCMV infection. + +# Author Rebuttal, first revision: + +Point- by- point Reply to Reviewers' Comments: + +## A type-1 immunity-restricted promoter of the IL-33 receptor gene directs antiviral T cell responses (NI-A35288A) + +We are thankful for the reviewers' feedback concerning our revised work and are grateful that in principle the manuscript has been deemed suitable for publication in Nature Immunology. Below, please find our responses to the reviewer's final requests (Blue text), outlining the specific changes we have implemented in our manuscript. Within the manuscript text, we have used blue underlined text to indicate changes made to the original version. + +## Reviewer #2 + +The authors have satisfactorily addressed my previous concerns. The manuscript has been greatly improved thanks to the addition of new data, and modifications in the text of the manuscript. + +The comparison of the different anti- ST2 mAbs in the flow cytometry assays (Extended data Fig 1d, e) will be very useful for the scientific community. The sensitivity of the enhanced staining procedure with clone DJ8 + FASER amplification is impressive. + +The revised manuscript will be an important contribution to the field. + +We thank the reviewer for this very supportive assessment. + +## Reviewer #3 + +The authors have responded well to the concerns raised previously, by both including requested data (which involved several additional studies) and revising the text. + +<--- Page Split ---> + +# natureresearch + +Regarding the authors' findings on the generation of memory ST2- /- or ExA/B- /- CD8 T cells in lymphoid and non- lymphoid tissues, it might be worth highlighting (e.g., in the discussion) that impaired ST2 expression had minimal (if any) statistically significant effect on likely resident memory T cells (i.e., those cells that are not stained by intravenous antibody labeling). + +Since some effector- like CD8+ T cells persist in the circulation well past d30 in the response to acute LCMV infection, it is therefore possible that failure of CD8+ T cells to express ST2 is quite selective for effector/effector- like cell generation, while generation of bona fide memory CD8+ T cells is, perhaps, completely unaffected. While further work would be needed to thoroughly test this interpretation, it would be an interesting hypothesis to raise since it suggests a quite focused role for IL- 33 sensitivity in generation of effector (but not memory) CD8+ T cells, during an acute LCMV infection. + +We thank the reviewer for this suggestion. Now we have included a statement addressing the apparently limited role for ST2 signals in the formation of antiviral tissue- resident CD8+ memory T cells in the Results section (p.10, I.255- 257) and have added the resulting hypothesis to the Discussion section (p.14- 15, I.387- 391). + +## Final Decision Letter: + +Dear Dr. Löhning, + +I am delighted to accept your manuscript entitled "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses" for publication in an upcoming issue of Nature Immunology. + +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Immunology style. 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Please let your coauthors and your institutions' public affairs office know that they are also welcome to order reprints by this method. + +Sincerely, + +Stephanie Houston, PhD Senior Editor Nature Immunology + +<--- Page Split ---> diff --git a/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6f8bda8f003cc154df424effcb7a305f936fbf6d --- /dev/null +++ b/peer_reviews/1445e32614f54f9a7288176ca18ac26ee6579e1e6ad6957074eada650ebe3b12/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,715 @@ +<|ref|>title<|/ref|><|det|>[[549, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>title<|/ref|><|det|>[[115, 188, 570, 219]]<|/det|> +# Peer Review Information + +<|ref|>text<|/ref|><|det|>[[115, 246, 825, 315]]<|/det|> +Journal: Nature Immunology Manuscript Title: A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses Corresponding author name(s): Professor Max Loehning, Dr Tobias Brunner + +<|ref|>sub_title<|/ref|><|det|>[[115, 343, 568, 368]]<|/det|> +## Reviewer Comments & Decisions: + +<|ref|>title<|/ref|><|det|>[[123, 419, 353, 434]]<|/det|> +# Decision Letter, initial version: + +<|ref|>text<|/ref|><|det|>[[116, 435, 226, 448]]<|/det|> +23rd Feb 2023 + +<|ref|>text<|/ref|><|det|>[[116, 464, 294, 479]]<|/det|> +Dear Professor Löhning, + +<|ref|>text<|/ref|><|det|>[[115, 493, 872, 539]]<|/det|> +Thank you for sharing your point- by- point reply to referees comments on your manuscript "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses". 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Refer also to any + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 142, 360, 157]]<|/det|> +guidelines provided in this letter. + +<|ref|>text<|/ref|><|det|>[[116, 173, 853, 218]]<|/det|> +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +<|ref|>text<|/ref|><|det|>[[115, 233, 592, 263]]<|/det|> +The Reporting Summary can be found here: https://www.nature.com/documents/nr- reporting- summary.pdf + +<|ref|>text<|/ref|><|det|>[[116, 277, 840, 322]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +<|ref|>text<|/ref|><|det|>[[115, 336, 840, 361]]<|/det|> +-- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. + +<|ref|>text<|/ref|><|det|>[[115, 363, 844, 394]]<|/det|> +-- that control panels for gels and western blots are appropriately described as loading on sample processing controls + +<|ref|>text<|/ref|><|det|>[[115, 395, 797, 411]]<|/det|> +-- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +<|ref|>text<|/ref|><|det|>[[116, 425, 857, 470]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[116, 499, 710, 515]]<|/det|> +You may use the link below to submit your revised manuscript and related files: + +<|ref|>sub_title<|/ref|><|det|>[[116, 529, 211, 545]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[116, 559, 870, 618]]<|/det|> +If you wish to submit a suitably revised manuscript we would hope to receive it within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Immunology or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[115, 633, 878, 740]]<|/det|> +Nature Immunology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[115, 740, 737, 755]]<|/det|> +href="http://www.springernature.com/orcid">www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[115, 769, 860, 799]]<|/det|> +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +<|ref|>text<|/ref|><|det|>[[115, 814, 497, 829]]<|/det|> +Thank you for the opportunity to review your work. + +<|ref|>text<|/ref|><|det|>[[116, 844, 189, 858]]<|/det|> +Sincerely, + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 158, 266, 203]]<|/det|> +Stephanie Houston Editor Nature Immunology + +<|ref|>text<|/ref|><|det|>[[116, 247, 285, 262]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 277, 220, 291]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[116, 293, 291, 307]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 307, 876, 367]]<|/det|> +The authors identified a novel alternative TSS for Il1rl1 gene that is specifically utilized by Th1 and CTL cells. Loss of this promoter region significantly impaired CTL differentiation in to SLEC resulting in deficient response to LCMV. The study is elegantly designed and conducted, and only a few minor issues need to be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 380, 876, 456]]<|/det|> +1. In figure 2, the authors examined the conservation of type I Il1rl1 promoter in humans and mice. Based on figure 2a, only the Tbet and STAT4 binding motifs in CNS5 are conserved and the conservation score for the actual promoter region is low. Therefore, only the usage of this promoter is conserved, but not the promoter itself. The section title "The type-1 Il1rl1 promoter is conserved between mice and humans" is thus misleading and needs to be revised. + +<|ref|>text<|/ref|><|det|>[[115, 456, 876, 590]]<|/det|> +2. There seem to be an enhancer located very close to, but downstream of, the promoter region. This enhancer is also bound by T-bet and STAT4 in Th1 cells and could potentially be important for ST2 expression driven by T-bet and STAT4. Thus, the authors should demonstrate whether this enhancer is impacted by the ExAB deletion. In fact, the sequence alignment of this promoter region and surrounding area between mouse and human should be provided, and the area of deletion indicated. +3. In Figure 3k, loss of Type 1 promoter region seems to result only in partial loss of ST2 expression in Th1 cells. What is the explanation of this phenotype? Is there another yet undiscovered TSS for ST2 that is specific for Th1? Or are Th1 cells capable of utilizing GATA3-dependent type II promoters? The authors should comment on this. + +<|ref|>text<|/ref|><|det|>[[115, 590, 844, 634]]<|/det|> +4. In figure 4k and o. There seems to be a CD45.2+ CD45.1+ population. Yet, according to the method section, CD45.1+/- and CD45.2+/- BM/T cells were used. Where did this double positive fraction is coming from? Or is there an error in the method section? + +<|ref|>text<|/ref|><|det|>[[115, 635, 877, 740]]<|/det|> +5. Figure 4f showed reduced Ki67+ cells in ExAB-/- mice, however, there seems to be a larger fraction of cycling cells in ExAB-/- mice by scRNA-seq as shown in figure 5b. What's causing this discrepancy? +6. Instead of a simple lack of SLEC expansion induced by the loss of type I promoter region, there seems to be a diversion from SLEC fate to MPEC fate in ExAB-/- mice, as evidenced by the significantly increased MPEC cluster shown in Figure 5b. The authors should conduct a LCMV re- + +<|ref|>text<|/ref|><|det|>[[115, 730, 866, 771]]<|/det|> +challenge experiment to explore whether there is a memory-related phenotype in these mice. +7. A heatmap of differential gene expression between WT and ExAB-/- cells from each cluster should be shown to demonstrate the transcriptional impact resulting from loss of the type I promoter. The merged heatmap showing all only the top 10 marker for each cluster is not sufficient. + +<|ref|>text<|/ref|><|det|>[[115, 771, 864, 844]]<|/det|> +8. According to Figure 6b IL-33 induces Zeb2 expression in all T cell subsets examined. Zeb2 expression is required for SLEC differentiation. The phenotype of T cells specific loss of Zeb2 during LCMV infection (Dominguez et all JEM 2015 and Omulisik et al JEM 2015) strongly resembles the phenotype observed in ExAB-/- mice. The authors should examine whether the effect on CD8 T cells during LCMV infection after the loss of Type I promoter is mediated by Zeb2. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 174, 216, 187]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 189, 291, 202]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 204, 881, 366]]<|/det|> +In this manuscript, Brunner et al. report the discovery and functional characterization of a type- 1- immunity- restricted promoter of the gene Il1rl1, encoding the ST2 receptor for interleukin- 33 (IL- 33), a critical regulator of type- 1, type- 2 and regulatory immune responses. The authors demonstrate that this novel promoter is located \(40\mathrm{kb}\) upstream of the annotated Il1rl1 gene and conserved between mice and humans. In previous work, the authors reported that ST2 expression is upregulated on CD8 T cells (CTLs) and CD4 T cells (Th1s) during viral infection (LCMV model). Now, they demonstrate that this upregulation of ST2 on CTLs and Th1s does not occur during viral infection in mice with deletion of the type- 1 Il1rl1 promoter. They convincingly show that the expression of ST2 driven by the type- 1 promoter is critical for clonal expansion of short- lived effector T cells during antiviral responses. They propose that IL- 33/ST2 signalling provides a strong costimulatory signal for amplification of antiviral responses mediated by CTLs. + +<|ref|>text<|/ref|><|det|>[[115, 380, 874, 456]]<|/det|> +The authors performed a significant number of experiments and the results are novel, interesting and potentially important. Recent results in a Phase 2 clinical trial of COPD revealed promising efficacy of anti- IL- 33 therapeutic antibodies, indicating that IL- 33 plays important roles in type- 1 inflammatory diseases in humans. A better understanding of the mechanisms implicated in the activation of type- 1 immune responses by IL- 33 is thus urgent. + +<|ref|>text<|/ref|><|det|>[[115, 456, 880, 560]]<|/det|> +However, at this point, the data are not sufficient to support the title and conclusions of the manuscript: "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene...'. The authors analysed Th1s and CTLs but did not analyse the potential role of the type- 1 promoter in other immune cells that express ST2 during type- 1 immune responses. These include NK and iNKT cells, macrophages, dendritic cells and neutrophils. To increase the significance of their findings, it is thus essential that the authors analyse the potential role of the type 1- promoter in the regulation of ST2 expression in other immune cell types, associated with type- 1 immune responses. + +<|ref|>text<|/ref|><|det|>[[115, 560, 875, 604]]<|/det|> +Is there a general role of the type 1- promoter in all type- 1 immune cells or a specific role in T cells ? This is an important question because the identification of the type- 1 immunity- restricted promoter of Il1rl1 is the main message of the paper. + +<|ref|>text<|/ref|><|det|>[[115, 605, 875, 650]]<|/det|> +The authors have all the tools in hands, including mice knock- out for the type- 1 Il1rl1 promoter (or immune cells derived from these mice) and a validated flow cytometry assay for ST2 (with DJ8 mAb), to answer this critical question using ex vivo or in vivo assays (see Major Points). + +<|ref|>sub_title<|/ref|><|det|>[[115, 665, 230, 678]]<|/det|> +## MAJOR POINTS + +<|ref|>text<|/ref|><|det|>[[115, 680, 863, 754]]<|/det|> +1) Role of the type-1 promoter in NK and iNKT cells: both human and mouse iNKT and NK cells are direct targets of IL-33, and produce high levels of IFNg after co-stimulation with IL-33 and IL-12 (1-3). NK cells are an important source of IFNg in viral infection and cancer. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in NK cells and iNKT cells (ex vivo or in vivo assays). + +<|ref|>text<|/ref|><|det|>[[115, 769, 861, 828]]<|/det|> +2) Role of the type-1 promoter in macrophages: myeloid-derived antigen-presenting cells, including macrophages and DCs, can respond to IL-33. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in macrophages. For instance, they could use ex vivo assays with bone marrow-derived macrophages, as previously described (3, 4). + +<|ref|>text<|/ref|><|det|>[[112, 842, 868, 858]]<|/det|> +3) Role of the type-1 promoter in neutrophils: resting bone marrow neutrophils express low levels of + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 868, 188]]<|/det|> +ST2 mRNA, and ST2 protein is upregulated at the cell surface after IL- 33 treatment (5). The authors should determine whether the type- 1 promoter controls ST2 expression and/or IL- 33 responsiveness in neutrophils. + +<|ref|>text<|/ref|><|det|>[[114, 202, 881, 425]]<|/det|> +4) Detection of ST2 in immune cells and differences in expression levels: quantification of ST2 by flow cytometry is a critical method for this study. However, the authors used different mAb clones for the detection of ST2 in Th1 cells/CTLs (clone DJ8, with PE- or APC-FASER amplification; Fig 1b, 3e) and ILC2s/mast cells (clone DIH9, ST2-BV421; Ext Fig 4c, f). Commercial ST2 antibodies exhibit significant background staining and are best for highly expressing cells. Could it be that the background with clone DIH9 (ST2-BV421 direct fluorescent conjugate) was too high and the specific signal without amplification too low for detection of ST2 expression in Th1/CTLs? The authors should comment about the differences in ST2 expression levels in different immune cells and explain why they developed a more sensitive assay with DJ8 mAb for Th1/CTLs. In the extended data figures, they should compare the different ST2 mAbs on the same cell types (both type-1 and type-2 immune cells) using Ilrl1 KO cells as controls for gating. RMST2-2 is another widely used mAb clone. The authors have all the tools in hands (various Il1rl1 KO cells) to perform a careful comparison of ST2 detection with the three clones (DJ8, DIH9, RMST2-2) on different type-1 and type-2 immune cells. This will be very useful for the scientific community and will increase the interest and impact of the article, beyond the field of T cells. + +<|ref|>sub_title<|/ref|><|det|>[[115, 440, 230, 455]]<|/det|> +## OTHER POINTS + +<|ref|>text<|/ref|><|det|>[[115, 470, 864, 515]]<|/det|> +5) Fig. 2a and p6: it is not clear why the authors do not comment the T-bet/STAT4 ChIP-Seq and CD8+ SLEC (abbreviation not defined in the legend) ATAC-seq signals downstream of exons A + B ? No T-bet or STAT4 binding sites ? Sites not conserved in humans ? + +<|ref|>text<|/ref|><|det|>[[115, 515, 857, 545]]<|/det|> +6) Fig 2c: the position of the CNS-5 in the human gene is not clear. ChIP-seq data/binding sites for STAT4 ? + +<|ref|>text<|/ref|><|det|>[[115, 559, 867, 694]]<|/det|> +7) p7 'However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, blockade of IL-33 or ST2 using therapeutic antibodies has shown conflicting results in preclinical disease models47'. This sentence is outdated. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in Phase 2 clinical trials of asthma and COPD, as recently reviewed (6). A more appropriate sentence/paragraph could be 'Modulation of the IL-33-ST2 axis could represent a promising approach in treating inflammatory diseases. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in clinical trials of asthma and COPD (6). However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, fine-tuned treatment approaches might offer a critical advantage.' + +<|ref|>sub_title<|/ref|><|det|>[[115, 739, 198, 753]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 768, 867, 858]]<|/det|> +1. Smithgall MD, et al. (2008) IL-33 amplifies both Th1- and Th2-type responses through its activity on human basophils, allergen-reactive Th2 cells, iNKT and NK cells. Int Immunol 20(8):1019-1030. +2. Bourgeois E, et al. (2009) The pro-Th2 cytokine IL-33 directly interacts with invariant NKT and NK cells to induce IFN-gamma production. Eur J Immunol 39:1046-1055. +3. Kearley J, et al. (2015) Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection. Immunity 42(3):566-579. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 141, 876, 233]]<|/det|> +4. Dagher R, et al. (2020) IL-33-ST2 axis regulates myeloid cell differentiation and activation enabling effective club cell regeneration. Nat Commun 11(1):4786. +5. Alves-Filho JC, et al. (2010) Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection. Nat Med 16(6):708-712. +6. Cayrol C & Girard JP (2022) Interleukin-33 (IL-33): A critical review of its biology and the mechanisms involved in its release as a potent extracellular cytokine. Cytokine 156:155891. + +<|ref|>text<|/ref|><|det|>[[115, 277, 216, 291]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 293, 291, 307]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 307, 875, 397]]<|/det|> +The authors characterize a distinct transcriptional process for expression of the gene (Il1rl1) encoding ST2 (the IL- 33 receptor) in type- 1 (CTL, Th1) compared to type- 2 (Th2) T cells. They go on to show that ablation of the exons used in the "type- 1" transcripts of Il1rl1 leads to selective loss of ST2 on those cells and impairs the generation of type- 1 effector cells following viral infection. They also find that IL- 33 promotes expression of genes which support TCR and costimulatory stimulation, and which are associated with effector cell differentiation. + +<|ref|>text<|/ref|><|det|>[[115, 410, 875, 516]]<|/det|> +The report carefully lays out the methodical way in which the authors identify different upstream noncoding exons that are selectively used for Il1rl1 transcripts in CTL/Th1 vs Th2 cells, and present strong evidence that this accurately distinguishes the basis for ST2 expression by type- 1 vs type- 2 T cells (with Treg aligning with Th2, in this case). Their generation of mice lacking the "type- 1" related exons confirmed this, with selective loss of ST2 on Th1 and CTL, and their evidence is compelling that the impact of this mutation almost phenocopies the impact of complete Il1rl1 gene ablation, with respect to type- 1 responses. + +<|ref|>text<|/ref|><|det|>[[115, 529, 880, 664]]<|/det|> +The data are convincing, and - as the authors point out - this appears to be a rare (if not unique) example in which genes that are expressed by both type- 1 and - 2 polarized T cells involve distinct transcriptional start sites (regulated by distinct transcription factors). At the same time, once the authors find that loss of exons A/B (ExA/B) leads to almost complete loss of ST2 on type- 1 cells, much of the subsequent data corresponds with earlier work, showing a cell- intrinsic role for ST2 in the antiviral response of these cells. This limitation is somewhat balanced by the authors going deeper than previous studies with respect to the gene expression changes driven by IL- 33 in type- 1 and - 2 T cells (Fig. 6), and by their data indicating that IL- 33 stimulation specifically enhances effector cell differentiation (Fig. 5). Nevertheless, there are remaining concerns. + +<|ref|>text<|/ref|><|det|>[[115, 677, 880, 800]]<|/det|> +1) The studies on impaired generation of short-lived effector cells (SLEC) by CD8+ T cells lacking ExA/B are convincing but the consequences for memory differentiation are underdeveloped. Numerous panels in Figs. 4 and 5 present the frequencies and numbers of SLEC phenotype cells, but do not show the corresponding data for the MPEC (KLRG1- CD127+) cells - based on panels such Fig. 5e, one would presume these cells are increased in frequency. It is unclear whether MPEC are unchanged (or, perhaps more likely, modestly reduced) in absolute numbers. These data are needed for a more complete picture of how defective ST2 regulation (ExA/B knockout) or expression (Il1rl1 knockout) affects CD8+ T cells differentiating along the effector vs memory pathways. + +<|ref|>text<|/ref|><|det|>[[115, 813, 879, 858]]<|/det|> +2) Along the same lines, the authors' analysis of the anti-viral response of ExA/B and Il1rl1 deficient T cells appears to be limited to the first \(\sim 10\) days following infection, and exclusively (as far as this reviewer can ascertain) focuses on cells in the spleen. It would be important to know how mutation of + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 877, 232]]<|/det|> +ExA/B impacts generation of the various subsets of circulating memory CD8+ and CD4+ T cells during these responses, and to extend the scope of the work to analysis of at least some non- lymphoid tissues to determine the effect on generation of resident memory T cells. As it stands, it is unclear whether the loss of normal ST2 regulation leads to a selective loss of type- 1 effector differentiation – with, perhaps, minimal effect on establishment of long- lived memory – or a more generalized defect that is magnified in but not exclusive to the effector pool. + +<|ref|>title<|/ref|><|det|>[[120, 290, 395, 304]]<|/det|> +# Author Rebuttal to Initial comments + +<|ref|>text<|/ref|><|det|>[[115, 308, 240, 321]]<|/det|> +See inserted PDF + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 82, 494, 97]]<|/det|> +## Point-by-point Reply to Reviewers' Comments: + +<|ref|>sub_title<|/ref|><|det|>[[117, 110, 812, 139]]<|/det|> +## A type-1 immunity-restricted promoter of the IL-33 receptor gene directs antiviral T cell responses (NI-A35288-T) + +<|ref|>text<|/ref|><|det|>[[117, 151, 880, 207]]<|/det|> +We are grateful for the valuable input and feedback provided by the reviewers regarding our work. We have thoroughly addressed each of these comments and suggestions. Below, please will find our responses to the reviewer comments (Blue text), presenting the additional experiments performed and outlining the specific changes we have implemented in our manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 219, 880, 248]]<|/det|> +Within the manuscript text, we have used Blue underlined text to indicate changes made to the original version as a result of the reviewer comments. + +<|ref|>sub_title<|/ref|><|det|>[[117, 274, 215, 288]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[117, 302, 298, 315]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[117, 316, 881, 370]]<|/det|> +The authors identified a novel alternative TSS for Il1rl1 gene that is specifically utilized by Th1 and CTL cells. Loss of this promoter region significantly impaired CTL differentiation in to SLEC resulting in deficient response to LCMV. The study is elegantly designed and conducted, and only a few minor issues need to be addressed. + +<|ref|>text<|/ref|><|det|>[[117, 383, 880, 411]]<|/det|> +We thank the reviewer for this very favorable feedback and the helpful comments. We have addressed all the minor points raised as outlined below. + +<|ref|>text<|/ref|><|det|>[[117, 437, 873, 507]]<|/det|> +1. In figure 2, the authors examined the conservation of type I Il1rl1 promoter in humans and mice. Based on figure 2a, only the T-bet and STAT4 binding motifs in CNS5 are conserved and the conservation score for the actual promoter region is low. Therefore, only the usage of this promoter is conserved, but not the promoter itself. The section title "The type-1 Il1rl1 promoter is conserved between mice and humans" is thus misleading and needs to be revised. + +<|ref|>text<|/ref|><|det|>[[117, 520, 863, 549]]<|/det|> +We fully agree with the reviewer and have amended the section title as follows: "Usage of the type- 1 Il1rl1 promoter is conserved between mice and humans." (p. 6, I. 148) + +<|ref|>text<|/ref|><|det|>[[117, 574, 870, 644]]<|/det|> +2. There seem to be an enhancer located very close to, but downstream of, the promoter region. This enhancer is also bound by T-bet and STAT4 in Th1 cells and could potentially be important for ST2 expression driven by T-bet and STAT4. Thus, the authors should demonstrate whether this enhancer is impacted by the ExAB deletion. In fact, the sequence alignment of this promoter region and surrounding area between mouse and human should be provided, and the area of deletion indicated. + +<|ref|>text<|/ref|><|det|>[[115, 657, 870, 850]]<|/det|> +We concur that there is a region downstream of the identified exons A and B, which is bound by STAT4 and T- bet, and is marked by an ATAC- Seq peak in activated but not naive CD8 \(^+\) T cells. Importantly, this putative enhancer specified by the reviewer is not deleted in the generated Il1rl1- ExAB- \(^+\) mice. We have provided a new subpanel (Extended Data Fig. 3b) to indicate the area of deletions in Il1rl1- ExAB- \(^+\) and Il1rl1- ExC- \(^+\) mice in relation to the ATAC- and ChIP- Seq peaks. An interpretable single- nucleotide sequence alignment of the promoter region, including all important sites, would exceed by far the size limit of a figure (multiple thousand base- pairs). To offer the reviewer and the readership a readily accessible way to investigate the data presented in the manuscript, we have provided access to the RNA- Seq, ATAC- Seq, and ChIP- Seq tracks in a UCSC Genome browser session. Using the following link: https://genome.ucsc.edu/s/agloehning/BrunnerServeatal2023, reviewers and readers can inspect the data in detail and compare the conservation of all positions at the desired resolution. We hope that these measures support the claims made in our study by enhancing the data transparency of our manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 880, 138]]<|/det|> +3. In Figure 3k, loss of Type 1 promoter region seems to result only in partial loss of ST2 expression in Th1 cells. What is the explanation of this phenotype? Is there another yet undiscovered TSS for ST2 that is specific for Th1? Or are Th1 cells capable of utilizing GATA3-dependent type II promoters? The authors should comment on this. + +<|ref|>text<|/ref|><|det|>[[115, 150, 880, 397]]<|/det|> +We thank the reviewer for addressing this highly interesting point. Indeed, while the loss of exons A and B largely abrogates ST2 expression of CTLs in vitro and in vivo, Th1 cells appear to be able to partially compensate for the loss of the type- 1 promoter in vivo, as we observed a mere \(\sim 50\%\) reduction in frequency of ST2+ Th1 cells in Il1rl1- ExAB- mice. To address the question which promoter is utilized by ExonAB- deficient Th1 cells, we adaptively transferred naive Smarta or Smarta Il1rl1- ExAB- cells into wildtype (WT) recipients, which were subsequently infected with LCMV (Extended Data Fig. 6s). Like the polyclonal Th1 population in Il1rl1- ExAB- mice, also Smarta T cells displayed a \(\sim 50 - 60\%\) reduction in frequencies of ST2- expressing cells at the peak of the acute T cell response (Extended Data Fig. 6t,u). Congenitally marked Th1 cells were flow- cytometrically sorted from spleens of infected animals, and RNA was isolated to assess their ST2 promoter usage. Interestingly, ExonAB- deficient, but not wildtype Smarta cells utilized the proximal promoter (reported to be used by e.g. fibroblasts) to express ST2, and thus incorporated exon 1b into their 5' untranslated regions (Extended Data Fig. 6v). Neither WT, nor Il1rl1- ExAB- Smarta cells expressed significant amounts of exon 1a. Importantly, exon 1b was barely detectable in 2 out of 4 recipients of WT Smarta cells, indicating that it does not critically contribute to ST2 expression if the type- 1 promoter is intact. We have incorporated these data into the manuscript (Extended Data Fig. 6s- v) (p. 10 l. 260- 262). The molecular mechanisms underlying this finding will be addressed in future studies using the appropriate gene- targeted mice. + +<|ref|>text<|/ref|><|det|>[[117, 422, 880, 465]]<|/det|> +4. In figure 4k and o. There seems to be a \(\mathrm{CD45.2 + }\) CD45.1+ population. Yet, according to the method section, \(\mathrm{CD45.1 + / - }\) and \(\mathrm{CD45.2 + / + }\) BM/T cells were used. Where did this double positive fraction is coming from? Or is there an error in the method section? + +<|ref|>text<|/ref|><|det|>[[117, 478, 880, 610]]<|/det|> +Indeed, in the experiment presented in Fig. 4j- m, irradiated \(\mathrm{CD45.1^{+ / + }}\) recipients were reconstituted with bone marrow from \(\mathrm{CD45.1^{+ / - }}\) (WT) mice and \(\mathrm{CD45.2^{+ / + }}\) (Il1rl1- ExAB- , or Il1rl1- ExC- ) mice. In Fig. 4n- r, \(\mathrm{CD45.1^{+ / - }}\) P14 cells were transferred together with \(\mathrm{CD45.1^{+ / + }}\) Il1rl1- ExAB- or Il1rl1- P14 cells into \(\mathrm{CD45.2^{+ / + }}\) WT recipients. Importantly, \(\mathrm{CD45.1}\) and \(\mathrm{CD45.2}\) are two variants of the \(\mathrm{CD45}\) gene differing in only few amino acids. Thus \(\mathrm{CD45.1^{+ / - }}\) cells express \(\mathrm{CD45.1}\) from one allele and \(\mathrm{CD45.2}\) from the second allele, which results in a double positive population if co- stained with \(\mathrm{CD45.1}\) - and \(\mathrm{CD45.2}\) - specific antibodies. Thus, the double positive fraction represents the reconstituted WT donor cells in Fig. 4k and the transferred P14 cells in Fig. 4o. To make it easier to follow these experimental layouts, we amended the figure legends to indicate the expression of both variants (e.g. \(\mathrm{CD45.1^{+}}\) \(\mathrm{CD45.2^{+}}\) instead of \(\mathrm{CD45.1^{+ / - }}\) ). + +<|ref|>text<|/ref|><|det|>[[117, 640, 877, 683]]<|/det|> +5. Figure 4f showed reduced Ki67+ cells in ExAB-/- mice, however, there seems to be a larger fraction of cycling cells in ExAB-/- mice by scRNA-seq as shown in figure 5b. What's causing this discrepancy? + +<|ref|>text<|/ref|><|det|>[[117, 695, 880, 807]]<|/det|> +In Fig. 4f, the frequency of Ki67- expressing cells among all \(\mathrm{CD8^{+}}\) T cells is depicted. The reduced frequency of Ki67+ cells among \(\mathrm{CD8^{+}}\) T cells in Il1rl1- ExAB- mice is a result of the impaired expansion of activated CTLs, a large fraction of which is positive for Ki67. In contrast, in Fig. 5b, activated \(\mathrm{CD44^{+}}\) CTLs were sorted and equal amounts of these CTLs per genotype were compared, thus reflecting the amount of cycling cells relative to an equal number of activated \(\mathrm{CD44^{+}}\) CTLs. However, as Fig. 5n illustrates, there is still a drastic difference in the numbers of \(\mathrm{CD44^{+}}\) CTLs per spleen in the scRNA- Seq experiment. When taking this into account, the absolute number of Ki67+ CTLs in WT mice far exceeds the number of Ki67+ CTLs in Il1rl1- ExAB- mice. + +<|ref|>text<|/ref|><|det|>[[117, 832, 848, 889]]<|/det|> +6. Instead of a simple lack of SLEC expansion induced by the loss of type I promoter region, there seems to be a diversion from SLEC fate to MPEC fate in ExAB-/- mice, as evidenced by the significantly increased MPEC cluster shown in Figure 5b. The authors should conduct a LCMV re- challenge experiment to explore whether there is a memory-related phenotype in these mice. + +<|ref|>text<|/ref|><|det|>[[115, 901, 874, 930]]<|/det|> +As pointed out in the answer to the previous question, in Fig. 5b equal numbers of activated CTLs per genotype were compared, irrespective of the differences in CTL expansion between the two + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 880, 152]]<|/det|> +genotypes. Consequently, the large relative increase in MPECs is in part due to a \(>10\) - fold decrease in the amount of SLECs per organ. However, in absolute terms, the amount of MPECs per spleen is even slightly decreased in \(IIIr1I\) - ExAB \(^{- / - }\) and \(IIIr1I^{- / - }\) mice. We have amended the text and have added the absolute numbers of MPECs to address this point (Fig. 5h, I; Fig. 6j, k and Extended Data Fig. 6m)(p. 10- 11, I. 290- 306; p. 13, I. 368- 370; p. 16, I. 450- 454). + +<|ref|>text<|/ref|><|det|>[[117, 163, 876, 303]]<|/det|> +To address the reviewers' question whether \(IIIr1I\) - ExAB \(^{- / - }\) or \(IIIr1I^{- / - }\) mice display a memory- related phenotype, we have conducted a re- challenge experiment. We first infected WT, \(IIIr1I^{- / - }\) , \(IIIr1I\) - ExAB \(^{- / - }\) , or \(IIIr1I\) - ExC \(^{- / - }\) mice with 200 PFU of LCMV- WE. Then, 30 days after primary infection, mice were challenged with \(2 \times 10^{6}\) PFU of LCMV- CI13 and analyzed 7 days after secondary infection (Reviewer Fig. 1a). We have found no significant differences in frequencies or absolute numbers of CD8 \(^+\) T cells in spleens of re- challenged animals (Reviewer Fig. 1b, c). Further, no differences in frequencies of activated CD44 \(^+\) CD62L \(^+\) CTLs or counts of LCMV- specific NP396- Tetramer \(^+\) CTLs were observed (Reviewer Fig. 1d, e). Lastly, in this recall setting the proportion of short- lived effector cells amongst CTLs of \(IIIr1I^{- / - }\) , \(IIIr1I\) - ExAB \(^{- / - }\) and \(IIIr1I\) - ExC \(^{- / - }\) as well as their number was comparable to WT mice (Reviewer Fig. 1f, g). + +<|ref|>image<|/ref|><|det|>[[117, 315, 884, 525]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 526, 880, 664]]<|/det|> +
Reviewer Figure 1. IL-33-ST2 signaling is not required for CTL expansion and SLEC differentiation in LCMV re-challenged mice. Wildtype, \(IIIr1I^{- / - }\) , \(IIIr1I\) -ExAB \(^{- / - }\) , and \(IIIr1I\) -ExC \(^{- / - }\) mice were primed with 200 plaque-forming units (PFU) of LCMV-WE. Mice were re-challenged with \(2 \times 10^{6}\) PFU LCMV-CI13 on day 30 p.i. and splenic T cells were analyzed 7 days after re-challenge (WT: \(n = 6\) , \(IIIr1I^{- / - }\) : \(n = 6\) , \(IIIr1I\) -ExAB \(^{- / - }\) : \(n = 6\) , \(IIIr1I\) ExC \(^{- / - }\) : \(n = 5\) ). a, Experimental outline. b, Representative staining of CD8 on lymphocytes. c, Frequencies and absolute cell counts of CTLs. d, Frequencies of activated CD44 \(^+\) CD62L \(^+\) CTLs. e, Absolute cell counts of LCMV NP396-404-specific CTLs. f, Representative FACS plots showing KLRG1 and CD127 expression by CD8 \(^+\) T cells. g, Frequencies and absolute cell counts of KLRG1 \(^+\) CD127- CTLs. Data are presented as mean \(\pm\) SD with each dot representing one mouse. P was determined using One- way ANOVA with Tukey's post- hoc tests.
+ +<|ref|>text<|/ref|><|det|>[[117, 690, 880, 905]]<|/det|> +In our opinion, this experiment nicely reflects the role of IL- 33 as an alarmin. Secondary LCMV infections are rapidly controlled by highly potent memory CD8 \(^+\) T cells and additional antibody- dependent antiviral mechanisms \(^{1 - 3}\) . The data presented here show that ST2 signaling is not required for antiviral CD8 \(^+\) T cell expansion and SLEC differentiation when previously infected mice are re- challenged. A similar phenotype was observed in MyD88- deficient mice, which is an adaptor protein essential for ST2 signaling \(^{4,5}\) . However, we have addressed the role of IL- 33- ST2 signaling in memory T cell formation, maintenance, and recall responses in Baumann et al. \(^{6}\) . In the latter study, we found that a lack of IL- 33 signaling in primary infections did not affect recall responses in an IL- 33- competent environment. Yet, IL- 33 signals were essential for efficient expansion and reactivation of CD8 \(^+\) memory T cells when rechallenged in naive secondary WT recipients. These experiments have shown that also fully differentiated memory CTLs can (re-)express ST2 and can benefit from IL- 33 signals, likely depending on the inflammatory context. Together, these findings raise interesting questions. For instance, it remains unknown whether IL- 33 release differs between LCMV- primed and naive mice. Neither do we know whether the interval between priming and re- challenge affects the IL- 33/ST2- dependence of secondary CTL responses. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 875, 138]]<|/det|> +The entirely novel finding of a type- 1 immunity- restricted promoter that regulates ST2 expression in antiviral T cells remains the focus of the current manuscript. As we would like to address the abovementioned questions in future studies, we decided to present the results of the re- infection experiment to the reviewer without adding it to the manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 164, 870, 207]]<|/det|> +7. A heatmap of differential gene expression between WT and ExAB-/- cells from each cluster should be shown to demonstrate the transcriptional impact resulting from loss of the type I promoter. The merged heatmap showing all only the top 10 marker for each cluster is not sufficient. + +<|ref|>text<|/ref|><|det|>[[117, 219, 870, 261]]<|/det|> +We have performed a differential gene expression analysis of each cluster to demonstrate the impact of the type- 1 llrl1 promoter deletion on the transcriptome of individual subsets. The results are now displayed in the new Extended Data Fig. 8. + +<|ref|>text<|/ref|><|det|>[[117, 286, 867, 356]]<|/det|> +8. According to Figure 6b IL-33 induces Zeb2 expression in all T cell subsets examined. Zeb2 expression is required for SLEC differentiation. The phenotype of T cells specific loss of Zeb2 during LCMV infection (Dominguez et all JEM 2015 and Omilusik et al JEM 2015) strongly resembles the phenotype observed in ExAB-/- mice. The authors should examine whether the effect on CD8 T cells during LCMV infection after the loss of Type I promoter is mediated by Zeb2. + +<|ref|>text<|/ref|><|det|>[[117, 368, 875, 410]]<|/det|> +We fully agree with the reviewer that the phenotype of Zeb2-deficient CD8+ T cells in LCMV infections is very similar to the one observed in ExonAB- or ST2-deficient mice and that this resemblance is of considerable interest. + +<|ref|>text<|/ref|><|det|>[[117, 410, 877, 533]]<|/det|> +Besides Zeb2, IL- 33 stimulation of CTLs also induced expression of T- bet and Blimp1, both of which are critical for expansion and SLEC differentiation of LCMV- specific CTLs7. Thus, impaired SLEC differentiation observed in ExAB- and llrl1- deficient mice is probably a combination of multiple factors and can possibly not be exclusively attributed to a reduction in Zeb2 expression alone. Interestingly however, analysis of scRNA- Seq data, as suggested by the reviewer in point 7, revealed a higher expression of Zeb2 transcripts in ExAB- deficient SLECs as compared to WT SLECs (Extended Data Fig. 8). This might reflect a compensatory mechanism, which could allow very few cells to differentiate into SLECs without IL- 33/ST2 signals, and further indicate an important link between ST2- signaling and Zeb2 expression in vivo. + +<|ref|>text<|/ref|><|det|>[[117, 533, 867, 602]]<|/det|> +A putative experiment to assess this question in more detail, would be to overexpress Zeb2 in ST2- deficient T cells using transgenic mice or retro/entiviral constructs and to study the T cell response after LCMV infections. We regret that we don't have the necessary tools at hand to perform these elaborate experiments and we hope that the reviewer agrees that establishment of these tools would exceed the timeframe available for this revision. + +<|ref|>text<|/ref|><|det|>[[117, 615, 867, 643]]<|/det|> +All things considered, we are very grateful for the reviewer's suggestions and believe that addressing the minor issues raised by the reviewer significantly improved the quality of our study. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 82, 216, 96]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[118, 109, 300, 123]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[117, 123, 878, 275]]<|/det|> +In this manuscript, Brunner et al. report the discovery and functional characterization of a type- 1- immunity- restricted promoter of the gene ll1rl1, encoding the ST2 receptor for interleukin- 33 (IL- 33), a critical regulator of type- 1, type- 2 and regulatory immune responses. The authors demonstrate that this novel promoter is located 40 kb upstream of the annotated ll1rl1 gene and conserved between mice and humans. In previous work, the authors reported that ST2 expression is upregulated on CD8 T cells (CTLs) and CD4 T cells (Th1s) during viral infection (LCMV model). Now, they demonstrate that this upregulation of ST2 on CTLs and Th1s does not occur during viral infection in mice with deletion of the type- 1 ll1rl1 promoter. They convincingly show that the expression of ST2 driven by the type- 1 promoter is critical for clonal expansion of short- lived effector T cells during antiviral responses. They propose that IL- 33/ST2 signaling provides a strong costimulatory signal for amplification of antiviral responses mediated by CTLs. + +<|ref|>text<|/ref|><|det|>[[117, 287, 875, 356]]<|/det|> +The authors performed a significant number of experiments and the results are novel, interesting and potentially important. Recent results in a Phase 2 clinical trial of COPD revealed promising efficacy of anti- IL- 33 therapeutic antibodies, indicating that IL- 33 plays important roles in type- 1 inflammatory diseases in humans. A better understanding of the mechanisms implicated in the activation of type- 1 immune responses by IL- 33 is thus urgent. + +<|ref|>text<|/ref|><|det|>[[117, 355, 879, 455]]<|/det|> +However, at this point, the data are not sufficient to support the title and conclusions of the manuscript: "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene...". The authors analysed Th1s and CTLs but did not analyse the potential role of the type- 1 promoter in other immune cells that express ST2 during type- 1 immune responses. These include NK and iNKT cells, macrophages, dendritic cells and neutrophils. To increase the significance of their findings, it is thus essential that the authors analyse the potential role of the type 1- promoter in the regulation of ST2 expression in other immune cell types, associated with type- 1 immune responses. + +<|ref|>text<|/ref|><|det|>[[117, 453, 870, 495]]<|/det|> +Is there a general role of the type 1- promoter in all type- 1 immune cells or a specific role in T cells? This is an important question because the identification of the type- 1 immunity- restricted promoter of ll1rl1 is the main message of the paper. + +<|ref|>text<|/ref|><|det|>[[117, 494, 870, 535]]<|/det|> +The authors have all the tools in hands, including mice knock- out for the type- 1 ll1rl1 promoter (or immune cells derived from these mice) and a validated flow cytometry assay for ST2 (with DJ8 mAb), to answer this critical question using ex vivo or in vivo assays (see Major Points). + +<|ref|>text<|/ref|><|det|>[[117, 547, 825, 589]]<|/det|> +We thank the reviewer for this positive feedback and are delighted to hear that the reviewer appreciates the impact of our findings. We certainly agree that a better understanding of type- 1 immunity- related aspects of IL- 33 biology is of utmost importance. + +<|ref|>text<|/ref|><|det|>[[117, 603, 880, 688]]<|/det|> +We would like to emphasize that by using the wording "type- 1 immunity- restricted", we do not want to imply that the promoter is used by all IL- 33- responsive immune cells that contribute to type- 1 immune responses. Rather, we use this description to highlight that we have not found any evidence of this promoter being active in type- 2 immunity- associated T cells and innate cells, including ILC2s and mast cells nor in Treg cells. We have amended the text at two positions to communicate this more precisely (p. 2, l. 35; p. 14, l. 392). + +<|ref|>text<|/ref|><|det|>[[117, 702, 828, 744]]<|/det|> +In addition, we have performed a significant number of experiments and made use of our highly sensitive ST2 staining protocol, to assess if the type- 1 ll1rl1 promoter is of importance for ST2 expression by NK cells, NKT cells, neutrophils and BMDMs (see below). + +<|ref|>sub_title<|/ref|><|det|>[[117, 770, 247, 783]]<|/det|> +## MAJOR POINTS + +<|ref|>text<|/ref|><|det|>[[117, 784, 868, 855]]<|/det|> +1) Role of the type-1 promoter in NK and iNKT cells: both human and mouse iNKT and NK cells are direct targets of IL-33, and produce high levels of IFNg after co-stimulation with IL-33 and IL-12 (1-3). NK cells are an important source of IFNg in viral infection and cancer. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in NK cells and iNKT cells (ex vivo or in vivo assays). + +<|ref|>text<|/ref|><|det|>[[117, 867, 866, 923]]<|/det|> +Indeed, NK cells are crucial players in the cellular immunity against infections and cancer. As cited, others have shown that NK cells can produce IFN- \(\gamma\) in response to combined stimulation with IL- 12 and IL- 33. To assess if the deletion of the type- 1 ll1rl1 promoter controls ST2 expression in NK cells, we thus have flow- cytometrically sorted NKp46+ TCR \(\beta\) NK cells from spleens of WT, ll1rl1- ExAB- \(\gamma\) , + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 875, 125]]<|/det|> +and llrl1- mice and cultured them in IL- 33- and IL- 12- containing medium. We found that after 2 days of stimulation, a fraction of WT NK cells expressed ST2, while no ST2 expression was found on llrl1- ExAB- or llrl1- NK cells (Extended Data Fig. 4d- f). + +<|ref|>text<|/ref|><|det|>[[117, 138, 860, 208]]<|/det|> +In addition, NKT cells were sort purified from thymocytes by utilizing \(\alpha\) - Galactosylceramide- loaded CD1d tetramers. FACS- sorted NKT cells were then activated and expanded ex vivo in type- 1 conditions. After 6 days of culture, \(\sim 60\%\) of WT NKT cells expressed ST2 at considerable levels. In contrast, llrl1- ExAB- NKT cells were unable to express ST2 as it was the case in llrl1- NKT cells (Extended Data Fig. 4a- c). + +<|ref|>text<|/ref|><|det|>[[117, 219, 875, 290]]<|/det|> +Together, these results clearly demonstrate that usage of the type- 1 llrl1 promoter is not restricted to T cells, but also directs ST2 expression in type- 1 polarized innate immune cells. We thank the reviewer for the excellent recommendation to perform these exciting experiments. We have added the results to the manuscript in Extended Data Fig. 4 and modified the text accordingly (p. 4, l. 87; p. 8, l. 206- 208; p. 14, l. 392). + +<|ref|>text<|/ref|><|det|>[[117, 315, 858, 372]]<|/det|> +2) Role of the type-1 promoter in macrophages: myeloid-derived antigen-presenting cells, including macrophages and DCs, can respond to IL-33. The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in macrophages. For instance, they could use ex vivo assays with bone marrow-derived macrophages, as previously described (3, 4). + +<|ref|>text<|/ref|><|det|>[[117, 385, 880, 467]]<|/det|> +To address this question, we have cultured bone- marrow cells (BMDMs) from wildtype, llrl1- ExAB- , and llrl1- mice in the presence of recombinant M- CSF for 7 days as described in Kearley et al.8. As shown in Reviewer Fig. 2a, we achieved a high purity of BMDMs expressing F4/80 and CD11b. After 7 days, BMDMs were stimulated with IL- 33, IL- 4, IL- 12 + IL- 18, IFNα + IFNγ, Poly(I:C), or Poly(I:C) + IL- 33. We stained ST2 using our amplified staining protocol, as this provides a more direct readout as compared to e.g. ELISAs of the cell culture supernatant. + +<|ref|>text<|/ref|><|det|>[[117, 470, 877, 540]]<|/det|> +Unfortunately, we were not able to detect ST2 on the surface of BMDMs irrespective of the genotype and the nature of stimulation (Reviewer Fig. 2b). Analysis of mRNA expression verified that ST2 transcript expression was very low in all culture conditions and substantially lower than in CTLs or Th2 cells (Reviewer Fig. 2c). In line with these results, IL- 33 stimulation of BMDMs did not upregulate TNF expression or enhance Poly(I:C)- induced expression of TNF (Reviewer Fig. 2d). + +<|ref|>image<|/ref|><|det|>[[115, 556, 884, 904]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 902, 881, 930]]<|/det|> +
Reviewer Figure 2. ST2 expression on bone-marrow-derived macrophages. Bone marrow cells were isolated from femurs and tibias of wildtype, llrl1- , or llrl1-ExAB- mice and differentiated in the
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 81, 883, 235]]<|/det|> +presence of recombinant M- CSF (20 ng/ml) for 7 days. a, Pre- gating strategy and representative FACS plot showing F4/80 and CD11b expression by differentiated BMDMs. b, Representative FACS plots showing no detectable expression of ST2 on BMDMs ( \(n = 3\) per genotype, experiment was performed twice). c, d, mRNA expression of ST2 (c) or TNF (d) by BMDMs after 24 h of stimulation with IL- 33 (10 ng/ml), IL- 4 (10 ng/ml), IL- 12 + IL- 18 (10 ng/ml each), IFNα (250 U/ml) + IFN- γ (10 ng/ml), Poly(I:C) (10 μg/ml), or Poly(I:C) (10 μg/ml) + IL- 33 (10 ng/ml). e, Representative FACS plots showing ST2 expression when BMDMs were differentiated for 7 days in the presence of M- CSF (20 ng/ml) and IL- 4 (10 ng/ml). f, Quantification of ST2 expression on BMDMs (WT: \(n = 5\) , \(II1r1^{- / - }\) : \(n = 4\) , \(II1r1^{- / - }\) ExAB \(^{- / - }\) : \(n = 4\) , data of independent experiments were pooled). Data are presented as mean ± SD with each dot representing one culture with bone marrow cells from individual mice. \(P\) was determined using two- tailed t- test (f, right panel) and One- way (f) or Two- way ANOVA (c, d) with Tukey's post- hoc tests. + +<|ref|>text<|/ref|><|det|>[[117, 270, 880, 341]]<|/det|> +The addition of IL- 4 during BMDM culture was shown to promote differentiation into alternatively activated macrophages with higher expression of ST29. Indeed, we detected ST2 on the surface of WT macrophages when IL- 4 was added one day after plating bone marrow cells, albeit still at low levels (Reviewer Fig. 2e,f). As expected, \(II1r1^{- / - }\) ExAB \(^{- / - }\) macrophages did not exhibit a reduction in ST2 surface expression. + +<|ref|>text<|/ref|><|det|>[[118, 342, 835, 384]]<|/det|> +At this point, we cannot explain the discrepancies between our results and the data published by Kearley et al.8 Thus, we refrain from including the data in the manuscript and hope the reviewer concurs with this decision. + +<|ref|>text<|/ref|><|det|>[[117, 412, 867, 470]]<|/det|> +3) Role of the type-1 promoter in neutrophils: resting bone marrow neutrophils express low levels of ST2 mRNA, and ST2 protein is upregulated at the cell surface after IL-33 treatment (5). The authors should determine whether the type-1 promoter controls ST2 expression and/or IL-33 responsiveness in neutrophils. + +<|ref|>text<|/ref|><|det|>[[117, 481, 880, 606]]<|/det|> +To study whether the type- 1 promoter controls ST2 expression in neutrophils, we have assessed ST2 expression of bone- marrow neutrophils in wildtype, \(II1r1^{- / - }\) ExAB \(^{- / - }\) , and \(II1r1^{- / - }\) mice (Extended Data Fig. 5h,k,l). Supporting data published by Alves- Filho et al.10, we found that a small but obvious population of resting neutrophils expressed ST2 protein (Extended Data Fig. 5k). Importantly, this population was still evident in \(II1r1^{- / - }\) ExAB \(^{- / - }\) mice even though in slightly lower frequency, and ST2 expression intensity within this population was largely comparable to WT mice (Extended Data Fig. 5l). Of note, using the same staining, we have determined ST2 expression by bone- marrow eosinophils, which worked remarkably well. We thus have included these data in Extended Data Fig. 5i,j, to extend our analysis of ST2 expression by innate type- 2 immune cells. + +<|ref|>text<|/ref|><|det|>[[117, 618, 884, 675]]<|/det|> +Next, we have purified bone- marrow neutrophils using a three- step Ficoll gradient11 followed by 24 h of stimulation with IL- 33, IL12, IL- 4, or combinations of IL- 33 and IL12 or IL- 4. To our surprise, using \(II1r1^{- / - }\) neutrophils as controls, no ST2 expression could be detected on stimulated CD11b+ Ly6G+ neutrophils isolated from wildtype or \(II1r1^{- / - }\) ExAB+ mice (Reviewer Fig. 3a- c). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 85, 880, 404]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 409, 884, 506]]<|/det|> +
Reviewer Figure 3. ST2 expression on neutrophils stimulated in vitro. a, Pre-gating strategy for the analysis of Ly6G+ CD11b+ neutrophils. b, c, Bone-marrow neutrophils of wildtype, Il1rl1-/- and Il1rl1-ExAB-/- mice were isolated and stimulated with IL-33 (50 ng/ml), IL-12 (10 ng/ml), IL-4 (10 ng/ml), or combinations thereof, for 24 h. Representative FACS plots (b) and quantification (c) showing no detectable expression of ST2 on Ly6G+ CD11b+ neutrophils after ex vivo stimulation (n = 3 per genotype and condition, data represent one of two independent experiments). Data are presented as mean ± SD with each dot representing one mouse.
+ +<|ref|>text<|/ref|><|det|>[[118, 531, 852, 574]]<|/det|> +We regret that the data shown in Reviewer Fig. 3b,c are not in line with results published by Alves- Filho et al. \(^{10}\) . As it is unclear what accounts for these inconsistencies (e.g. mouse background or experimental procedures), we prefer not to include these results in the manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 599, 880, 806]]<|/det|> +4) Detection of ST2 in immune cells and differences in expression levels: quantification of ST2 by flow cytometry is a critical method for this study. However, the authors used different mAb clones for the detection of ST2 in Th1 cells/CTLs (clone DJ8, with PE- or APC-FASER amplification; Fig 1b, 3e) and ILC2s/mast cells (clone DIH9, ST2-BV421; Ext Fig 4c, f). Commercial ST2 antibodies exhibit significant background staining and are best for highly expressing cells. Could it be that the background with clone DIH9 (ST2-BV421 direct fluorescent conjugate) was too high and the specific signal without amplification too low for detection of ST2 expression in Th1/CTLs? The authors should comment about the differences in ST2 expression levels in different immune cells and explain why they developed a more sensitive assay with DJ8 mAb for Th1/CTLs. In the extended data figures, they should compare the different ST2 mAbs on the same cell types (both type-1 and type-2 immune cells) using Ilrl1 KO cells as controls for gating. RMST2-2 is another widely used mAb clone. The authors have all the tools in hands (various Il1rl1 KO cells) to perform a careful comparison of ST2 detection with the three clones (DJ8, DIH9, RMST2-2) on different type-1 and type-2 immune cells. This will be very useful for the scientific community and will increase the interest and impact of the article, beyond the field of T cells. + +<|ref|>text<|/ref|><|det|>[[117, 819, 875, 930]]<|/det|> +Indeed, as the reviewer points out, a conventional single- step staining of ST2 is insufficient to achieve a good staining resolution on CTLs or Th1- polarized T cells, as the surface expression of ST2 on these cells is much lower than on Th2- polarized T cells, ILC2s, or mast cells \(^{12}\) . Thus, we have established a staining protocol utilizing a digoxigenin- conjugated primary ST2 antibody, an APC- or PE- conjugated secondary Fab fragment, and two- rounds of FASER- amplification to determine ST2 expression on CTLs or Th1 cells in a highly sensitive manner. However, for assessment of ST2 on mast cells and ILC2s ex vivo, we still utilize the commercially available, directly conjugated clone DIH9, as this staining takes less time and is much more cost effective. Further, using unamplified + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 850, 125]]<|/det|> +stainings allows for higher flexibility in the flow- cytometry panel design, as the Faser amplification cannot be used when a staining with biotin- labelled antibodies or specific tandem- conjugates (e.g. APC- Cy7 or PE- Cy7) is required. + +<|ref|>text<|/ref|><|det|>[[117, 124, 872, 249]]<|/det|> +To report on this technical aspect in more detail, we have directly compared our highly sensitive staining with a single- step staining using the clones DIH9 and RMST2- 2 on high and low ST2 expressing cells (Th2 and Th1 cells), as well as on ST2- deficient T cells as requested by the reviewer (Extended Data Fig. 1d,e)(p. 5, I. 101- 105). Of note, prior to this experiment, the directly PE- conjugated antibodies (DIH9 and RMST2- 2) were titrated to assure optimal staining quality. Our comparison shows nicely that stainings with directly conjugated DIH9 or RMST2- 2 antibodies were sufficient to discriminate ST2+ and ST2- cells when cells express high levels of ST2 (e.g. Th2 cells). However, only by using our established highly sensitive staining protocol, we can achieve a good ST2 staining on ST2 low- expressing cells (e.g. Th1 cells) (Extended Data Fig. 1d,e). + +<|ref|>text<|/ref|><|det|>[[117, 260, 870, 316]]<|/det|> +We thank the reviewer for the suggestion to specifically explain and elaborate the rationale behind using this enhanced staining procedure to visualize ST2 on antiviral T cells. We think that this comparison illustrates why ST2 expression and the impact of IL- 33/ST2- signaling on type- 1 polarized T cells, has been underestimated in so many studies. + +<|ref|>sub_title<|/ref|><|det|>[[118, 342, 245, 357]]<|/det|> +## OTHER POINTS + +<|ref|>text<|/ref|><|det|>[[117, 369, 871, 412]]<|/det|> +5) Fig. 2a and p6: it is not clear why the authors do not comment the T-bet/STAT4 ChIP-Seq and CD8+ SLEC (abbreviation not defined in the legend) ATAC-seq signals downstream of exons A + B ? No T-bet or STAT4 binding sites ? Sites not conserved in humans? + +<|ref|>text<|/ref|><|det|>[[118, 423, 857, 466]]<|/det|> +Indeed, we focused on the ATAC-Seq signal 5kb upstream of exons A and B, as the position of the ATAC-peak downstream of the promoter did not coincide with a conserved DNA element. We have now explained this rationale in the text (p. 6, I. 155- 157). + +<|ref|>text<|/ref|><|det|>[[116, 492, 853, 520]]<|/det|> +6) Fig 2c: the position of the CNS-5 in the human gene is not clear. ChIP-seq data/binding sites for STAT4 ? + +<|ref|>text<|/ref|><|det|>[[117, 533, 873, 606]]<|/det|> +Due to additional DNA elements between this CNS and the first exon A, which are present in humans but not in mice, the distance of the CNS in relation to the first exon is different in humans and should thus not be termed CNS-5 in this context. Nevertheless, we have indicated the position of this particular CNS (CNS-5 in mice) in Fig. 2c with a red arrow and added a description to the figure legend (p. 28, I. 770- 773). Further, as pointed out in question 2 of Reviewer 1, we now provide easy access to data used in our manuscript via the following link: + +<|ref|>text<|/ref|><|det|>[[117, 616, 880, 684]]<|/det|> +https://genome.ucsc.edu/s/agloehning/BrunnerServeetal2023. By uploading the RNA- Seq, ChIP- Seq, and ATAC- Seq data to the web- based UCSC genome browser, we offer reviewers and readers a tool to investigate the data in detail and to assess the conservation of all regions. We regret that we have not found suitable STAT4 ChIP- Seq data for human type- 1- polarized T cells to complement the mouse T- bet ChIP data. + +<|ref|>text<|/ref|><|det|>[[117, 710, 875, 835]]<|/det|> +7) p7 'However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, blockade of IL-33 or ST2 using therapeutic antibodies has shown conflicting results in preclinical disease models47. This sentence is outdated. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in Phase 2 clinical trials of asthma and COPD, as recently reviewed (6). A more appropriate sentence/paragraph could be 'Modulation of the IL-33-ST2 axis could represent a promising approach in treating inflammatory diseases. Blockade of IL-33 using therapeutic antibodies has shown encouraging efficacy in clinical trials of asthma and COPD (6). However, due to hard-to-predict effects on the balance between IL-33-mediated inflammation and tissue repair, fine-tuned treatment approaches might offer a critical advantage.' + +<|ref|>text<|/ref|><|det|>[[117, 847, 857, 862]]<|/det|> +We thank the reviewer for this suggestion and have amended the text accordingly (p. 7, I. 177- 180). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 111, 875, 275]]<|/det|> +1. Smithgall MD, et al. (2008) IL-33 amplifies both Th1- and Th2-type responses through its activity on human basophils, allergen-reactive Th2 cells, iNKT and NK cells. Int Immunol 20(8):1019-1030. +2. Bourgeois E, et al. (2009) The pro-Th2 cytokine IL-33 directly interacts with invariant NKT and NK cells to induce IFN-gamma production. Eur J Immunol 39:1046-1055. +3. Kearley J, et al. (2015) Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection. Immunity 42(3):566-579. +4. Dagher R, et al. (2020) IL-33-ST2 axis regulates myeloid cell differentiation and activation enabling effective club cell regeneration. Nat Commun 11(1):4786. +5. Alves-Filho JC, et al. (2010) Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection. Nat Med 16(6):708-712. +6. Cayrol C & Girard JP (2022) Interleukin-33 (IL-33): A critical review of its biology and the mechanisms involved in its release as a potent extracellular cytokine. Cytokine 156:155891. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 83, 216, 97]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[118, 110, 300, 124]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[118, 124, 875, 206]]<|/det|> +The authors characterize a distinct transcriptional process for expression of the gene (ll1rl1) encoding ST2 (the IL- 33 receptor) in type- 1 (CTL, Th1) compared to type- 2 (Th2) T cells. They go on to show that ablation of the exons used in the "type- 1" transcripts of ll1rl1 leads to selective loss of ST2 on those cells and impairs the generation of type- 1 effector cells following viral infection. They also find that IL- 33 promotes expression of genes which support TCR and costimulatory stimulation, and which are associated with effector cell differentiation. + +<|ref|>text<|/ref|><|det|>[[118, 218, 881, 317]]<|/det|> +The report carefully lays out the methodical way in which the authors identify different upstream noncoding exons that are selectively used for ll1rl1 transcripts in CTL/Th1 vs Th2 cells, and present strong evidence that this accurately distinguishes the basis for ST2 expression by type- 1 vs type- 2 T cells (with Treg aligning with Th2, in this case). Their generation of mice lacking the "type- 1" related exons confirmed this, with selective loss of ST2 on Th1 and CTL, and their evidence is compelling that the impact of this mutation almost phenocopies the impact of complete ll1rl1 gene ablation, with respect to type- 1 responses. + +<|ref|>text<|/ref|><|det|>[[118, 328, 880, 452]]<|/det|> +The data are convincing, and - as the authors point out - this appears to be a rare (if not unique) example in which genes that are expressed by both type- 1 and - 2 polarized T cells involve distinct transcriptional start sites (regulated by distinct transcription factors). At the same time, once the authors find that loss of exons A/B (ExA/B) leads to almost complete loss of ST2 on type- 1 cells, much of the subsequent data corresponds with earlier work, showing a cell- intrinsic role for ST2 in the antiviral response of these cells. This limitation is somewhat balanced by the authors going deeper than previous studies with respect to the gene expression changes driven by IL- 33 in type- 1 and - 2 T cells (Fig. 6), and by their data indicating that IL- 33 stimulation specifically enhances effector cell differentiation (Fig. 5). Nevertheless, there are remaining concerns. + +<|ref|>text<|/ref|><|det|>[[118, 464, 875, 575]]<|/det|> +We thank the reviewer for the very positive feedback on our study. In particular, we are pleased to hear that our evidence for a dedicated type- 1 promoter of the ll1rl1 gene is very convincing. Using the LCMV infection model in vivo in conjunction with our newly generated ExAB- or ExC- deficient mice allowed us to test precisely to which extend the type- 1 promoter- deficient T cells recapitulate the reported phenotype of ST2- deficient T cells, while the data presented in Fig. 5 and Fig. 6 shed new light on IL- 33/ST2 signaling and its functions in antiviral T cell responses. In addition, as shown in Fig. 3 our findings of alternative ll1rl1 promoters for the first time allow T cell lineage- selective targeting of ST2 expression even in WT T cells. + +<|ref|>text<|/ref|><|det|>[[118, 600, 876, 712]]<|/det|> +1) The studies on impaired generation of short-lived effector cells (SLEC) by CD8+ T cells lacking ExA/B are convincing but the consequences for memory differentiation are underdeveloped. Numerous panels in Figs. 4 and 5 present the frequencies and numbers of SLEC phenotype cells, but do not show the corresponding data for the MPEC (KLRG1-CD127+) cells - based on panels such Fig. 5e, one would presume these cells are increased in frequency. It is unclear whether MPEC are unchanged (or, perhaps more likely, modestly reduced) in absolute numbers. These data are needed for a more complete picture of how defective ST2 regulation (ExA/B knockout) or expression (ll1rl1 knockout) affects CD8+ T cells differentiating along the effector vs memory pathways. + +<|ref|>text<|/ref|><|det|>[[118, 724, 878, 820]]<|/det|> +We thank the reviewer for the recommendation to present the data for KLRG1: CD127+ MPECs to further elaborate the impact of IL- 33/ST2 signaling on these cells. The reviewer correctly assumes that, in contrast to SLECs, absolute counts of MPECs per organ are only modestly decreased in ll1rl1- ExAB- and ll1rl1- mice compared to wildtype mice. As suggested, we have added frequencies and absolute numbers of MPECs to all figures were SLEC frequencies were shown and amended the text accordingly (Fig. 5h,1, Fig. 6j,k, and Extended Data Fig. 6m) (p. 10- 11, I. 290- 299; p. 13, I. 368- 370; p. 16, I. 450- 454). + +<|ref|>text<|/ref|><|det|>[[118, 846, 878, 930]]<|/det|> +2) Along the same lines, the authors' analysis of the anti-viral response of ExA/B and ll1rl1 deficient T cells appears to be limited to the first \(\sim 10\) days following infection, and exclusively (as far as this reviewer can ascertain) focuses on cells in the spleen. It would be important to know how mutation of ExA/B impacts generation of the various subsets of circulating memory CD8+ and CD4+ T cells during these responses, and to extend the scope of the work to analysis of at least some non-lymphoid tissues to determine the effect on generation of resident memory T cells. As it stands, it is unclear + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 864, 125]]<|/det|> +whether the loss of normal ST2 regulation leads to a selective loss of type- 1 effector differentiation – with, perhaps, minimal effect on establishment of long- lived memory – or a more generalized defect that is magnified in but not exclusive to the effector pool. + +<|ref|>text<|/ref|><|det|>[[117, 137, 866, 248]]<|/det|> +Indeed, we have focused our analyses to the first \~10 days after LCMV infection and primarily analyzed spleens, as well as in some cases livers, of infected animals (Extended Data Fig. 6a- f, n- r). ST2 expression on antiviral T cells and phenotypic differences between ST2- competent and ST2- deficient T cells are most pronounced in the acute phase of the infection6,12. Thus, this time frame seemed optimal to accurately compare the response of Il1rl1- ExAB- /- T cells with Il1rl1- /- T cells and WT T cells. As mentioned in our reply to point 1) of this reviewer, the impact of IL- 33–ST2 signaling does not selectively affect short- lived effector cells, yet the effect on MPEC numbers is less pronounced. + +<|ref|>text<|/ref|><|det|>[[117, 247, 880, 425]]<|/det|> +To assess the role of the type- 1 promoter and the impact of ST2 signaling on memory T cell formation, we have adoptively transferred naive P14, P14 Il1rl1- /- , or P14 Il1rl1- ExAB- /- T cells into WT recipients, which were subsequently infected with LCMV. After 30 days, we have labeled T cells in circulation by intravenous injection of CD90.2 antibody and sacrificed the mice afterwards (Extended Data Fig. 9a). Analysis of spleens, lungs, salivary glands, and kidneys showed that a lack of ST2 or of the type- 1 ST2 promoter reduced the amount of P14 memory cells found in these organs (Extended Data Fig. 9b- d). P14 cells of all genotypes predominantly formed effector memory cells (Tem) and no major impact on frequencies of central memory cells (Tcm) was observed (Extended Data Fig. 9e- g). Likewise, we have found that both circulating and tissue- resident memory T cells were formed, even in the absence of ST2 or the type- 1 promoter (Extended Data Fig. 9h- j). Lastly, quantification of in vivo labeled and non- labeled P14 cells showed that numerical differences between P14 memory and P14 Il1rl1- /- memory or P14 Il1rl1- ExAB- /- memory cells were more pronounced in the intravascular compartment (Extended Data Fig. 9k). + +<|ref|>text<|/ref|><|det|>[[117, 437, 878, 533]]<|/det|> +We greatly appreciate the suggestion of the reviewer to investigate the impact of defective ST2 regulation on MPEC/SLEC fate decision and memory cell formation. We have complemented our study with these newly acquired in vivo data and amended our manuscript at several positions (p. 10- 11, I. 299- 306; p. 16, I. 450- 454). We now report that deletion of the type- 1 ST2 promoter or ST2 largely impairs SLEC expansion, but to a lesser extent, also affects MPEC numbers and consequently the number of antiviral memory CTLs generated. In our opinion, these changes made in response to the reviewer's comments have substantially improved the overall quality of our study. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 860, 724]]<|/det|> +References1. Thomsen, A. R. & Marker, O. The complementary roles of cellular and humoral immunity in resistance to re-infection with LCM virus. \*Immunology\* 65, 9-15 (1988).2. Tebo, A. E. et al. Rapid recruitment of virus-specific CD8 T cells restructures immunodominance during protective secondary responses. \*J Virol\* 79, 12703-12713, doi:10.1128/JVI.79.20.12703-12713.2005 (2005).3. Cerny, A., Sutter, S., Bazin, H., Hengartner, H. & Zinkernagel, R. M. Clearance of lymphocytic choriomeningitis virus in antibody- and B-cell-deprived mice. \*J Virol\* 62, 1803-1807, doi:10.1128/JVI.62.5.1803-1807.1988 (1988).4. Rahman, A. H. et al. Antiviral memory CD8 T-cell differentiation, maintenance, and secondary expansion occur independently of MyD88. \*Blood\* 117, 3123-3130, doi:10.1182/blood-2010-11-318485 (2011).5. Schmitz, J. et al. IL-33, an interleukin-1-like cytokine that signals via the IL-1 receptor-related protein ST2 and induces T helper type 2-associated cytokines. \*Immunity\* 23, 479-490, doi:10.1016/j.immuni.2005.09.015 (2005).6. Baumann, C. et al. Memory CD8(+) T Cell Protection From Viral Reinfection Depends on Interleukin-33 Alarmin Signals. \*Front Immunol\* 10, 1833, doi:10.3389/fimmu.2019.01833 (2019).7. Joshi, N. S. et al. Inflammation directs memory precursor and short-lived effector CD8(+) T cell fates via the graded expression of T-bet transcription factor. \*Immunity\* 27, 281-295, doi:10.1016/j.immuni.2007.07.010 (2007).8. Kearley, J. et al. Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection. \*Immunity\* 42, 566-579, doi:10.1016/j.immuni.2015.02.011 (2015).9. Faas, M. et al. IL-33-induced metabolic reprogramming controls the differentiation of alternatively activated macrophages and the resolution of inflammation. \*Immunity\* 54, 2531-2546 e2535, doi:10.1016/j.immuni.2021.09.010 (2021).10. Alves-Filho, J. C. et al. Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection. \*Nat Med\* 16, 708-712, doi:10.1038/nm.2156 (2010).11. Ubags, N. D. J. & Suratt, B. T. Isolation and Characterization of Mouse Neutrophils. \*Methods Mol Biol\* 1809, 45-57, doi:10.1007/978-1-4939-8570-8_4 (2018).12. Baumann, C. et al. T-bet- and STAT4-dependent IL-33 receptor expression directly promotes antiviral Th1 cell responses. \*Proc Natl Acad Sci U S A\* 112, 4056-4061, doi:10.1073/pnas.1418549112 (2015). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[121, 164, 345, 179]]<|/det|> +## Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[116, 181, 228, 195]]<|/det|> +28th Sep 2023 + +<|ref|>text<|/ref|><|det|>[[116, 210, 248, 225]]<|/det|> +Dear Dr. Löhning, + +<|ref|>text<|/ref|><|det|>[[115, 239, 867, 329]]<|/det|> +Thank you for submitting your revised manuscript "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses" (NI- A35288A). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Immunology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[115, 343, 875, 389]]<|/det|> +We will now perform detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[115, 402, 874, 448]]<|/det|> +If you had not uploaded a Word file for the current version of the manuscript, we will need one before beginning the editing process; please email that to immunology@us.nature.com at your earliest convenience. + +<|ref|>text<|/ref|><|det|>[[115, 462, 861, 492]]<|/det|> +Thank you again for your interest in Nature Immunology Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[115, 507, 189, 522]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[115, 536, 298, 582]]<|/det|> +Stephanie Houston, PhD Senior Editor Nature Immunology + +<|ref|>text<|/ref|><|det|>[[116, 610, 404, 625]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 640, 848, 671]]<|/det|> +The authors have satisfactorily addressed my previous concerns. The manuscript has been greatly improved thanks to the addition of new data, and modifications in the text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 685, 877, 731]]<|/det|> +The comparison of the different anti- ST2 mAbs in the flow cytometry assays (Extended data Fig 1d, e) will be very useful for the scientific community. The sensitivity of the enhanced staining procedure with clone DJ8 + FASER amplification is impressive. + +<|ref|>text<|/ref|><|det|>[[115, 745, 627, 760]]<|/det|> +The revised manuscript will be an important contribution to the field. + +<|ref|>text<|/ref|><|det|>[[116, 805, 404, 820]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 834, 868, 850]]<|/det|> +The authors have responded well to the concerns raised previously, by both including requested data + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 595, 158]]<|/det|> +(which involved several additional studies) and revising the text. + +<|ref|>text<|/ref|><|det|>[[115, 172, 870, 234]]<|/det|> +Regarding the authors' findings on the generation of memory ST2- /- or ExA/B- /- CD8 T cells in lymphoid and non- lymphoid tissues, it might be worth highlighting (e.g., in the discussion) that impaired ST2 expression had minimal (if any) statistically significant effect on likely resident memory T cells (i.e., those cells that are not stained by intravenous antibody labeling). + +<|ref|>text<|/ref|><|det|>[[115, 246, 876, 338]]<|/det|> +Since some effector- like \(\mathsf{CD8 + }\) T cells persist in the circulation well past d30 in the response to acute LCMV infection, it is therefore possible that failure of \(\mathsf{CD8 + }\) T cells to express ST2 is quite selective for effector/effector- like cell generation, while generation of bona fide memory \(\mathsf{CD8 + }\) T cells is, perhaps, completely unaffected. While further work would be needed to thoroughly test this interpretation, it would be an interesting hypothesis to raise since it suggests a quite focused role for IL- 33 sensitivity in generation of effector (but not memory) \(\mathsf{CD8 + }\) T cells, during an acute LCMV infection. + +<|ref|>title<|/ref|><|det|>[[117, 390, 352, 405]]<|/det|> +# Author Rebuttal, first revision: + +<|ref|>text<|/ref|><|det|>[[115, 406, 480, 421]]<|/det|> +Point- by- point Reply to Reviewers' Comments: + +<|ref|>sub_title<|/ref|><|det|>[[115, 434, 875, 466]]<|/det|> +## A type-1 immunity-restricted promoter of the IL-33 receptor gene directs antiviral T cell responses (NI-A35288A) + +<|ref|>text<|/ref|><|det|>[[115, 478, 875, 555]]<|/det|> +We are thankful for the reviewers' feedback concerning our revised work and are grateful that in principle the manuscript has been deemed suitable for publication in Nature Immunology. Below, please find our responses to the reviewer's final requests (Blue text), outlining the specific changes we have implemented in our manuscript. Within the manuscript text, we have used blue underlined text to indicate changes made to the original version. + +<|ref|>sub_title<|/ref|><|det|>[[115, 566, 212, 581]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[115, 594, 833, 625]]<|/det|> +The authors have satisfactorily addressed my previous concerns. The manuscript has been greatly improved thanks to the addition of new data, and modifications in the text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 637, 880, 683]]<|/det|> +The comparison of the different anti- ST2 mAbs in the flow cytometry assays (Extended data Fig 1d, e) will be very useful for the scientific community. The sensitivity of the enhanced staining procedure with clone DJ8 + FASER amplification is impressive. + +<|ref|>text<|/ref|><|det|>[[115, 696, 605, 712]]<|/det|> +The revised manuscript will be an important contribution to the field. + +<|ref|>text<|/ref|><|det|>[[115, 725, 544, 740]]<|/det|> +We thank the reviewer for this very supportive assessment. + +<|ref|>sub_title<|/ref|><|det|>[[115, 768, 212, 784]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[115, 797, 848, 828]]<|/det|> +The authors have responded well to the concerns raised previously, by both including requested data (which involved several additional studies) and revising the text. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 872, 202]]<|/det|> +Regarding the authors' findings on the generation of memory ST2- /- or ExA/B- /- CD8 T cells in lymphoid and non- lymphoid tissues, it might be worth highlighting (e.g., in the discussion) that impaired ST2 expression had minimal (if any) statistically significant effect on likely resident memory T cells (i.e., those cells that are not stained by intravenous antibody labeling). + +<|ref|>text<|/ref|><|det|>[[115, 215, 872, 304]]<|/det|> +Since some effector- like CD8+ T cells persist in the circulation well past d30 in the response to acute LCMV infection, it is therefore possible that failure of CD8+ T cells to express ST2 is quite selective for effector/effector- like cell generation, while generation of bona fide memory CD8+ T cells is, perhaps, completely unaffected. While further work would be needed to thoroughly test this interpretation, it would be an interesting hypothesis to raise since it suggests a quite focused role for IL- 33 sensitivity in generation of effector (but not memory) CD8+ T cells, during an acute LCMV infection. + +<|ref|>text<|/ref|><|det|>[[115, 316, 877, 377]]<|/det|> +We thank the reviewer for this suggestion. Now we have included a statement addressing the apparently limited role for ST2 signals in the formation of antiviral tissue- resident CD8+ memory T cells in the Results section (p.10, I.255- 257) and have added the resulting hypothesis to the Discussion section (p.14- 15, I.387- 391). + +<|ref|>sub_title<|/ref|><|det|>[[120, 432, 281, 447]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[116, 450, 249, 464]]<|/det|> +Dear Dr. Löhning, + +<|ref|>text<|/ref|><|det|>[[115, 478, 878, 524]]<|/det|> +I am delighted to accept your manuscript entitled "A type- 1 immunity- restricted promoter of the IL- 33 receptor gene directs antiviral T cell responses" for publication in an upcoming issue of Nature Immunology. + +<|ref|>text<|/ref|><|det|>[[115, 537, 875, 598]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Immunology style. 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The communities experience the extinction of species and loss of stability when crossing the dashed gray line (surviving boundary) and solid gray line (stability boundary), respectively. The color maps depict the mean value over 1000 simulations.", + "footnote": [], + "bbox": [], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_4c.jpg", + "caption": "Fig. 4c, Increasing species pool size and interaction strength leads to the emergence of priority effect, where the invasion probability of resident communities is smaller than their species survival fraction. The communities experience the extinction of species and loss of stability when crossing the dashed gray line (surviving boundary) and solid gray line (stability boundary), respectively.", + "footnote": [], + "bbox": [ + [ + 330, + 117, + 670, + 345 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig 4. The Lotka-Volterra model predicts a universal correspondence between invasion probability and survival fraction. a, The dependence of invasion probability on final richness of resident communities is qualitatively different depending upon how the richness is changed. Invasion probability positively correlates with richness when varying interaction strength or when randomly sampling communities with a fixed species pool size and interaction strength distribution. Invasion probability can decrease with community diversity when varying species pool size. b,", + "footnote": [], + "bbox": [ + [ + 180, + 532, + 825, + 761 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure. Microbial communities can exhibit fluctuations in biomass without corresponding fluctuations in pH in our experiment. The biomass (OD) of a microbial community fluctuates between days 6 and 10, while the pH time series stabilize during the same period (between days 6 and 10). The three curves represent three replicates of the same community.", + "footnote": [], + "bbox": [ + [ + 137, + 174, + 857, + 391 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure. The presence of pH-mediated interactions increases the mean and standard deviation of effective gLV-type interactions. a, The gLV-type interaction \\(\\alpha_{ij}\\) follows a uniform distribution \\(U[0,1]\\) , with a mean and standard deviation of 0.5 and 0.29, respectively. b, Under the influence of pH, the effective interaction \\(\\alpha_{ij}^{*} = \\frac{(\\alpha_{ij} - \\beta^{*}g_{i}k_{j})}{(1 - \\beta^{*}g_{i}k_{i})}\\) shows a larger mean interaction strength of 0.52 and a standard deviation of 0.37 compared to the pure gLV model. In this scenario, \\(\\alpha_{ij}\\) still follows \\(U[0,1]\\) , while the pH modification parameters \\(g_{i}\\) and \\(k_{i}\\) are sampled from a uniform distribution \\(U[-1,1]\\) . The environmental coupling strength \\(\\beta^{*}\\) is set to 0.5. c, The pure pH model without gLV-type interactions produces a distribution of effective \\(\\alpha_{ij}^{*}\\) with a standard deviation of 0.18.", + "footnote": [], + "bbox": [ + [ + 200, + 88, + 796, + 450 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_23.jpg", + "caption": "Supplementary Fig. 23. The invasion probability decreases with increasing pH-mediated interaction strength and gLV-type interaction strength, while the survival fraction remains approximately equal to the invasion probability. a, The pure pH model, without gLV-type interactions, predicts that invasion probability decreases with increasing pH interaction strength (mean of \\(\\beta^{*}g_{i}k_{i}\\) ) and species pool size. b, In the pure pH model, the survival fraction is approximately equal to the invasion probability, even without gLV-type interactions. c, When both pH interaction strength (mean of \\(\\beta^{*}g_{i}k_{i}\\) ) and gLV-type interaction strength (mean of \\(\\alpha_{ij}\\) ) increase simultaneously, the invasion probability decreases. d, The survival fraction remains approximately equal to the invasion probability when combining the pH model with the gLV model. The points and color maps depict the mean value over 100 simulations.", + "footnote": [], + "bbox": [ + [ + 115, + 87, + 875, + 538 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_25.jpg", + "caption": "Supplementary Fig. 25. Zero dispersal leads to stable communities under high nutrient conditions (strong interactions) in the experiment. The biomass of eight distinct microbial communities ( \\(S = 24\\) ) consistently reaches stable states when exposed to high nutrient concentrations (strong interactions) in the absence of species dispersal from the species pool to the community. In contrast, when dispersal is present, a significant proportion of communities exhibit fluctuations under the same high nutrient conditions and species pool size, as previously reported in Fig. 1d and in our previous paper (Hu et al. 2022) (Fig. 2C).", + "footnote": [], + "bbox": [], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_26.jpg", + "caption": "Supplementary Fig. 26. The survival threshold efficiently separates surviving species from extinct species, where the species abundances display a bimodal distribution in the simulations. a, The extinction threshold of \\(8 \\times 10^{-4}\\) (horizontal dashed line) clearly separates the high-abundant, surviving species from the low-abundant \"extinct\" species \\((S = 50, < \\alpha_{ij} > = 0.2)\\) . Such \"extinct\" species would reach zero abundance if dispersal is interrupted (c). b, The extinction threshold of \\(8 \\times 10^{-4}\\) (horizontal dashed line) similarly separates the high-abundant, surviving species from the low-abundant \"extinct\" species under different interaction strength \\((S = 50, < \\alpha_{ij} > = 0.6)\\) . c, After stopping dispersal at \\(t = 1000\\) , only species above the extinction threshold survive with stable abundances, while the others undergo extinction \\((S = 50, < \\alpha_{ij} > = 0.6)\\) . This demonstrates that the extinction threshold of \\(8 \\times 10^{-4}\\) efficiently classifies surviving species versus those that would go extinct without dispersal. d, The histogram shows the number of species exhibiting the indicated abundances at steady state. The dataset was generated from 10 in silico communities randomly sampled \\((S = 50, < \\alpha_{ij} > = 0.2)\\) .", + "footnote": [], + "bbox": [ + [ + 174, + 206, + 825, + 563 + ] + ], + "page_idx": 28 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_27.jpg", + "caption": "Supplementary Fig. 27. The mean fold change in biomass under high nutrient conditions is greater than under low nutrient conditions, which is robust to the choice of time points. a, Invasions into resident communities under low nutrient conditions (weak interactions) result in a statistically lower fold change in biomass compared to communities under high nutrient conditions (strong interactions) \\((p< 0.001)\\) . The number of successful invasions is \\(n = 51\\) (low nutrient) and \\(n = 11\\) (high nutrient). The fold change in biomass was calculated by comparing the biomass on day 6 (before invasion) with that on day 12 (after invasion colonization was fully established) across all communities. b, Similarly, invasions into resident communities under low nutrient conditions (weak interactions) cause a statistically lower fold change in biomass than those under high nutrient conditions (strong interactions) \\((p< 0.001)\\) . The fold change was calculated by comparing the biomass on day 6 (before invasion) with the average biomass of days 10, 11, and 12 (after invader colonization) across all communities.", + "footnote": [], + "bbox": [], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_28.jpg", + "caption": "Supplementary Fig. 28. Under serial dilutions in the gLV model, the invasion probability decreases with increasing interaction strength and species pool size, the survival fraction remains approximately equal to the invasion probability. a, Invasion probability decreases with increasing interaction strength and species pool size under serial dilutions. b, The survival fraction is approximately equal to the invasion probability under serial dilutions in the gLV model. The points and color maps depict the mean value over 100 simulations.", + "footnote": [], + "bbox": [ + [ + 120, + 88, + 860, + 313 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_29.jpg", + "caption": "Supplementary Fig. 29. The invasion probability decreases with increasing interaction strength and species pool size across different time windows, with the survival fraction remaining approximately equal to the invasion probability. a, The invasion probability decreases as interaction strength and species pool size increase. b, The survival fraction closely mirrors the invasion probability. To assess whether invader or resident species survived, we identified species whose abundance exceeded the extinction threshold at any point during the last 24 time units of the simulation. This approach yielded invasion probability patterns consistent with those observed in a 100-unit time window. The points and color maps depict the mean value over 100 simulations.", + "footnote": [], + "bbox": [ + [ + 120, + 90, + 881, + 315 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_31.jpg", + "caption": "Supplementary Fig. 31. The threshold of \\(10^{-3}\\) for the maximal CV of species abundance effectively separates fluctuating communities from stable ones, where the maximal CV of species abundance exhibits a bimodal distribution in the simulations. The histogram displays the number of communities with the indicated maximal CV of species abundance at steady state. The dataset was generated from 2000 in silico communities, randomly sampled with \\(< \\alpha_{ij} > \\in [0.02, 1.1]\\) and \\(S \\in [2, 60]\\) .", + "footnote": [], + "bbox": [ + [ + 305, + 99, + 661, + 315 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_33.jpg", + "caption": "Supplementary Fig. 33. The Invasion effect positively correlates with the final abundance of invaders in the invaded communities after colonization. a, Simulating \\(S = 32\\) communities with gLV shows positive correlations between invasion effect and final invader abundance under various average interaction strengths including \\(< \\alpha_{ij} > = 0.3\\) (correlation coefficient \\(= 0.23\\) , \\(\\mathrm{p} = 4.3 \\times 10^{- 13}\\) , \\(< \\alpha_{ij} > = 0.6\\) (correlation coefficient \\(= 0.75\\) , \\(\\mathrm{p} = 1.4 \\times 10^{- 126}\\) ), \\(< \\alpha_{ij} > = 1.0\\) (correlation coefficient \\(= 0.55\\) , \\(\\mathrm{p} = 2.6 \\times 10^{- 25}\\) ). \\(\\mathrm{n} = 1000\\) simulations for each interaction strength. b, In the experiment, there is a weak positive correlation between the invasion effect and final invader abundance under low nutrient conditions (weak interaction) (correlation coefficient \\(= 0.35\\) , \\(\\mathrm{p} = 0.013\\) , \\(\\mathrm{n} = 51\\) ). There is no statistically significant correlation under high nutrient conditions (strong interaction) (correlation coefficient \\(= 0.37\\) , \\(\\mathrm{p} = 0.23\\) , \\(\\mathrm{n} = 12\\) ).", + "footnote": [], + "bbox": [], + "page_idx": 37 + } +] \ No newline at end of file diff --git a/peer_reviews/144ec508aea22ca35925a350bcae1059143047006ce8602195d0a58feaa8e6c2/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/144ec508aea22ca35925a350bcae1059143047006ce8602195d0a58feaa8e6c2/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..ec983ed3ff09f3b08a0551637b8483c08ef42600 --- /dev/null +++ b/peer_reviews/144ec508aea22ca35925a350bcae1059143047006ce8602195d0a58feaa8e6c2/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,1368 @@ + +# nature portfolio + +# Peer Review File + +# Collective dynamical regimes predict invasion success and impacts in microbial communities + +Corresponding Author: Professor Jeff Gore + +Version 0: + +Decision Letter: + +17th April 2024 + +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +Dear Professor Gore, + +Thank you for your patience while your Article "Collective dynamical regimes predict invasion success and impacts in microbial communities" was under review. We have now received three reports. As you will see from the comments copied below, the reviewers find your work of considerable potential interest but have raised quite substantial concerns. In light of these comments, we cannot accept the manuscript for publication but would be very interested in considering a revised version that addresses these concerns. + +We hope you will find the reviewers' comments useful as you decide how to proceed. Please bear in mind that we will be reluctant to approach the reviewers again in the absence of major revisions. In particular, while we do not expect additional experimental work, addressing the concerns raised to the reviewers' satisfactions will likely require additional modelling work, as well as further information on the methodology. Regarding the latter, if you are concerned about space limitations in the main manuscript file, feel free to use the supplementary files to provide all the information required by the reviewers (with clear guidance as to where find a specific piece of information). + +If you choose to revise your manuscript taking into account all reviewer and editor comments, please highlight all changes in the manuscript text file, preferably in Microsoft Word format. + +We are committed to providing a fair and constructive peer- review process. Please do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +If revising your manuscript: + +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the referees along with the revised manuscript. + +\* If you have not done so already we suggest that you begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecove/ino/final- submission. Refer also to any guidelines provided in this letter. + +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +Please use the link below to submit a revised paper: + +Link Redacted + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +If you wish to submit a suitably revised manuscript we would hope to receive it within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are + +<--- Page Split ---> + +now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +Thank you for the opportunity to review your work. + +[redacted] + +Reviewers' comments: + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Hu et al. combine experiments and theory to elucidate the factors determining community invasions. They find that while diversity- invasibility relationships can be both positive and negative depending on the factors regulating diversity, the fraction of surviving species directly predicts invasibility. This manuscript leverages their recent insights on the dynamical phases of microbial ecosystems to provide a timely and relevant exploration of invasions. The results are interesting and the research is carried out soundly. My comments are primarily aimed at making the manuscript easier to follow. + +My first main comment concerns the exposition of the different diversity- invasibility relationships between Fig. 1 and Fig. 2/3, which on a first read was not immediately obvious. In Fig 1, more species and higher interaction strength makes for fluctuations and greater diversity, and fluctuating communities are more likely to be invaded; but both theory and Fig. 3 show a negative correlation between invasion probability and pool size/interaction strength. I naively expected increased pool size and stronger interactions to translate to a higher change of fluctuations (as in their recent paper), and thus greater richness and higher invasion probability. It is later revealed where this apparent contradiction comes from, but I believe it would be immensely helpful if this contradiction was highlighted early on. This issue is made more severe by the use of three different terms to describe the probability of successful invasions (invasion probability and invasion resistance, also invasibility) - especially because these have opposite meanings, I had to read this section of the manuscript carefully to understand its meaning. A single term would be easier to understand. + +My second main comment concerns the notion of priority effects. Here, as I understand it, the authors use this term basically to mean that a community of strongly interacting species has established itself, which makes invasions less likely (e.g., because all niches are filled or because antagonistic interactions are balanced out) but I am not convinced that this is the sense in which most ecologists tend to use that term; to me, the more common use appears to be referring to particular species whose presence or absence steers the community into different alternative stable states. Here, however, the community is already in a stable state and a new species is trying to invade, and thus "priority effect" does not apply in my view. I suggest a different way of describing this effect here, or, at the very least, the sentence in line 244- 246 needs more explanation. Similarly, I find the use of "alternative stable states" (I251) to be unclear since that is not really the subject of this paper. + +Minor comments: + +L110: "The lower probability" - compared to what? L174: "including species interaction strength" - is it clear that different synthetic communities can be characterized by the same average interaction strength? Perhaps some initial compositions have strong antibiotic producers or very similar metabolic profiles L227: correlation on -> with L239: Why should we expect a 1:1 correspondence between survival fraction and invasion probability? This only becomes clear in Fig 4b L280: ergodicity likely needs a bit more explanation to be clear L285: definition of invasion effect is slightly unclear. Is this the same definition as in L296? L317: SI Fig 17 does not show an Allee effect for invaders 2/3 Fig 2f/4c: Legend missing for the gray lines Fig 4a: it is very hard to parse the different colors + +Reviewer #2 (Remarks to the Author): + +Summary + +Overall, I found that the study addressed interesting questions and the choice to connect experiments with minimal models of community dynamics seemed like the appropriate choice. However, several decisions made and details about the experiment seem unclear. For example, it is unclear to me how 1) a generalized Lotka- Volterra (gLV) serves as an appropriate model for pH- mediated effects, how fluctuating/stable communities were classified, whether their experimentally- imposed migration rate was sufficient to induce deterministic fluctuations. + +<--- Page Split ---> + +The visualizations are effective and thorough. However, the authors often make claims about the interpretation of visualizations that need to be backed up by statistical tests. I have attempted to identify reasonable statistical tests when a test is lacking. There are also several instances where further clarification could help a broad readership understand the study. These instances are pointed out under both Major and Minor Comments. + +## Major Comments + +There is no explicit consideration of resources in their model. This makes sense in some respects, as the gLV can be derived in the adiabatic limit of certain consumer- resource models. Furthermore, their experimental manipulations of invasion are demographic rather than environmental, so it makes sense that a phenomenological model that does not explicitly consider microscopic interactions of resource consumption is sufficient. Progress has recently been made using phenomenological models to investigate the macroecological consequences of demographic manipulations (Shoemaker et al., 2023), which may provide outside support for the authors' modeling decisions. At a minimum the authors should provide additional justification for their modelling choices and why they are appropriate for their mode. + +However, the authors also manipulate resource concentration as a means to manipulate the strength of competitive interactions. This manipulation is done by increasing resource concentration, changing the pH, which is a feature of the environment that does not appear in the model and does not appear to be measured. So, while their invasion manipulations are demographic, it reads as though the difference in invasion outcomes between high and low nutrient treatments is driven by the environment. In the manuscript's current form, I imagine that it would be difficult for the reader to understand how the manipulation of resource concentration can be modeled as an increase in the strength of competitive interactions in a phenomenological gLV. + +The connection between interaction coefficients and growth- mediated pH is difficult to see given that pH tends to be incorporated into terms related to growth, both for models such as Monod growth (e.g., Houtsma et al., 1996) as well as Michaelis- Menten kinetics (chapter 10 of Cornish- Bowden, 2012). I suppose that pH- dependent competition coefficients could be derived if one started with a consumer- resource model where growth terms were pH dependent and took the adiabatic limit. At minimum a form of the gLV needs to be derived so the reader can see the connection between increased resource concentration change in pH increase in the strength of competitive interactions. However, it is also unclear that a phenomenological gLV is appropriate since the pH changes within a transfer cycle due to the growth of the community. Since the change in pH within a transfer cycle is on the same timescale of the growth rate, I do not see how a phenomenological gLV can serve as an appropriate model. + +My understanding is that the term "fluctuations" in the context of this study means fluctuations induced by chaotic dynamics. I understand that these are not meant to be viewed as stochastic fluctuations, but in my experience, I have found that only a fraction of eco/evo readers understand the distinction between fluctuations induced by deterministic vs. stochastic effects. It would aid the typical reader if the authors clarified what form of fluctuations they are focused on in the Introduction, specified the type of fluctuation whenever the term is used in the manuscript (e.g., "fluctuations" "deterministic fluctuations"), and briefly addressed in the Discussion how the consideration of stochastic fluctuations might factor into their subsequent research efforts. + +It is worth briefly mentioning in the supplement why continued migration from the regional pool was a necessarily experimental detail for this study. Specifically, how the absence of experimentally- imposed migration would correspond to a gLV with zero migration, the analytic results of which would be decidedly less rich (e.g., no chaos, etc.). Broad readership may not pick up on this detail. + +Related, did the authors perform any experiments without daily migration from the regional pool? Contrasting the results of this study with that type of experiment would strengthen their claims and provide further opportunities to test the utility of the gLV. Alternatively, if there are there any published experiments on invasion analysis using a similar experimental setting without imposing migration, then such results could be verbally compared to the results of their experiment. + +Is the experimentally- imposed migration rate sufficient to induce chaotic dynamics in the context of their gLV model? I searched for this detail in the supplement but did not find it. + +I would also encourage the authors to make both their code and raw data available on public repositories to ensure transparency and reproducibility. + +Lines 148- 149: It would help the reader if justification for the extinction threshold was provided in the main text. In lines 81- 82 of the supplement the authors describe the lower bound on detection due to sequencing, but it is not clear how they arrived at this particular value. It would also help if there was a comparison between the chosen threshold and the inverse of the typical total abundance of the community (all cells), the threshold for true extinction, to provide context for the detection limitation. + +Lines 208- 211: I am unaware of models where the competition coefficients between species can be examined as a function of media modification. If such a model exists, could the authors briefly describe it in their supplement to help the reader understand how environmental variables (e.g., pH) map onto competition coefficients in a gLV model? + +Lines 275- 280: How are alternative stable states determined here? + +Fig. 1d: Why are all but two of the "fluctuating" communities decreasing in biomass from day four to five. Could this simultaneous decrease in biomass be driven by experimental details rather than by the intrinsic dynamics of the communities? + +Fig. 1g; lines 380- 382: What statistical test was performed here? + +<--- Page Split ---> + +Fig. 2f: What do the dashed and solid grey lines represent? Could the authors include a legend in the figure? + +Fig. 4c: Could the authors add an axis label for the colorbar in the revision? + +Fig. 4d: "Effect on resident community" is a nice term for those unfamiliar with these types of experiments, but it still reads as somewhat vague. Could the authors describe what this term means in the figure legend and provide an equation for how the quantity was estimated in the supplement? + +Fig. 5: What timepoints are used to calculate the fold change? Are the same timepoints used for each community? Is the outcome of the statistical test robust to the choice of timepoints? + +Supplement line 52: The sampling detection limit is \(\sim 10^{\wedge}[-4]\) but the chosen dilution rate was \(10^{\wedge}[-5]\) . How does the difference between dilution rates and detection limit shape the observed outcomes of the experiment? If it does, it may be worth describing the outcomes in different parameter limits to the reader (i.e., sampling limit much greater than dilution rate and vice-versa). + +Supplement: Lines 52, 63: I am unfamiliar with the term "dispersal rate" used to describe the process of diluting cultures in a serial transfer experiment. The method used by the authors is different from the standard process of serial dilution, so I think some justification of the term as well as an explanation of how it connects to the mathematical definition of dispersal (Eq. S1) in the supplement is warranted. + +Supplement lines 100- 119: Does the absence of serial dilution being explicitly encoded into the simulation impact the results? Serial dilutions have been explicitly incorporated into mechanistic (Marsland et al., 2020) and phenomenological (Shoemaker et al., 2023) models of community dynamics in an experimental context. Could the authors provide justification of why serial dilution does not need to be explicitly encoded into their simulation? + +Supplement lines 109- 111: What are the units of time and how do they compare to the timescales of the experiments? Is the timescale of the simulation informed by the timescale of the experiment? + +Supplement lines 147- 148: It's unclear what the CV represents. My understanding is that each CV is calculated over time for each species for a given simulation iteration. Since the dynamics are deterministic and the interaction coefficients are a form of quenched disorder, what random variable is the CV calculated over? Does the distribution of CVs demonstrate a clear bimodality with the \(10^{\wedge}[-3]\) cutoff representing the valley between the two peaks? It would help the reader if 1) additional context was provided for the CV and what it represents as well as 2) distributions of simulated CVs plotted to demonstrate the intuition behind classifying communities into stable/fluctuating classes. + +Supplement lines 160- 163, Fig. S12c, d: Is some degree of correlation expected since biomass was used to calculate the abundance of each species? This seems similar to the case presented in. Garud et al., where the same parameter factors into both sides of the relationship (pg. 16 and 17 of supplement; 2019). Here the authors partitioned synonymous sites into two categories, providing two estimates of the quantities of interest. These two quantities are conditionally independent of the parameter that factors into both sides of the proposed relationship due to the Poisson thinning property. One quantity is then used to calculate the left side of the relationship while the other is used to calculate the right side. Is a similar analysis appropriate in this case given that total biomass factors into both sides of the quantities examined in Fig. S12c, d? + +An alternative option could be to examine the relationship between the CV of biomass (OD) and the CV of relative abundances for each ASV, allowing for the identification of community members that disproportionately contribute to the fluctuations in biomass. + +Fig. S2: Is there any phylogenetic structure to these results? Does the placement of a species on the phylogeny relative to the phylogenetic composition of a given community determine species invariability? + +Fig. S12: "The standard deviation of community biomass over day 5, day 6 and day 7" this detail is confusing since the timeseries represented in Fig. 1d ends at day six. What was the rational behind using only these three timepoints? Some justification of using these three timepoints is needed in the Supplement. + +Fig. S13: The figure is a useful visualization, but in its current form it is difficult to validate the claims made in the legend. + +- "Invisibility positively correlates with richness when varying interaction strength" Is a claim being made here about the direction in which the correlation changes with a change in interaction strength? It's not clear to me whether this claim is about the existence of positive correlations among treatments or the difference in positive correlations between treatments. + +- "Invisibility positively correlates with richness when randomly sample \(S = 20\) communities under high nutrient, due to fluctuating communities display larger richness and larger invasion probability." I am having a hard time parsing this statement. Is a claim being made about correlation being higher in high nutrient \(S = 20\) fluctuating communities relative to high nutrient \(S = 20\) stable communities? + +- The legend could use some retooling for clarity. Furthermore, if the claims are about the increase in correlation in one treatment vs. another, then additional statistical analyses are necessary. It seems like the authors are making three claims, which would require three tests. The question is what statistical model to use. A full regression analysis to examine the increase in slope between two treatments while controlling for potential cofounders could be seen as necessary. Alternatively, the authors could test for the difference between two correlation coefficients using Fisher's Z statistic with a null distribution obtained by permuting + +<--- Page Split ---> + +community identity for a given pair of treatments (Snedecor & Cochran, 1989). This statistic was recently used to test for the change in correlation coefficients in experimental microbial communities (Eq. 21 in Shoemaker et al., 2023). + +Fig. S15, 16: Some type of statistical test is necessary to establish the claim that invasions lead to changes in community composition. There are multiple ways to accomplish this task and the authors may have their own idea. One immediate option strikes me: calculate a paired t- statistic for each community between the control and successfully invaded community, demonstrating that absolute value of the t- statistics is significantly greater than zero. Null distributions could be obtained by permuting control/invade labels of each species within each community. + +Fig. S17, S18: Similar to Fig. S15 and S16, but now there are different invader species for each community. The authors could perform a paired t- test for each invader species, pooling observations across communities. A null could be generated for each invader species by permuting control/invade labels within each species within each community. + +Figs. S15- S18: Is there any relationship between the relative abundance of the invading species and the change in relative abundance of the remaining species between the control/invade treatments? This may not be the most appropriate analysis for compositional data, but you plot the relative abundance of the invading species vs. the mean difference in relative abundance between treatments for the remaining species, do you see a clear relationship? + +Fig. S19- S21: The authors' claims about the lack of correlations appear correct but I think the correlation coefficient should be provided along with the non- significant P- value. Statistical significance can be assessed by permuting x and y vectors. Permutations should be constrained on species identity for Fig. S19. + +## Minor Comments + +Both passive voice and active voice are used throughout the main manuscript and supplement. Consult the journal style guide and use the appropriate voice throughout the manuscript. + +Line 76: Should "occupy all available niches and resources" be "occupy all available niches by consuming all resources"? + +Line 85- 86: Given the experiment performed, would be more apt to say that the question is whether the dynamics are stationary with respect to deterministic fluctuations? + +Line 192: Should "effect" be plural? + +Line 235: Is "niches and resources" redundant here? My understanding that the niche is resource niche in the context of this study. + +Lines 304- 305: "stronger secondary effect" "stronger secondary effects" + +Lines 378- 379: Grammar. + +Lines 379- 380: "invasion probability to" "invasion probability of" + +Line 389: "invaders successfully invade" or "an invader successfully invades"? + +Line 437: "high nutrient" "high nutrient conditions" or something similar. + +Supplement lines 75- 76: Please summarize the DADA2 parameters used in your script and make your DADA2 pipeline available in a public code repository. + +Supplement lines 79- 81: Please make your raxml code available in a public repository. + +Supplement lines 123- 125: This sentence reads as if steady state is defined as the state where community properties change with time. Is this supposed to be the case? + +Supplement lines 144- 145: How is a window of time of 100 units analogous to a timescale of 24 hours in the experiment? Were growth rates in the simulation parameterized to correspond to growth rates in the experiment? + +Supplement lines 167- 168: Can you plot the results from varying the choice of time window? + +Supplement lines 174: "Algorithm" should be plural. + +Fig S1: Would an alternative color scale help the reader? It does not appear that colors are assigned based on taxonomy. Assigning different shades of a given color to the species belonging to a given phylum may help with visualization (e.g., Firmicutes get different shades of blue, etc.). + +Figs. S8- S11: Can you plot the extinction threshold as a dashed/dotted horizontal line? + +Fig. S12: Consider plotting the cutoff of 0.05 as a horizontal dashed line for reference in subplots a and b and as a vertical dashed line in subplots c and d. + +<--- Page Split ---> + +Fig. S14: How were priority effects quantified? What does the y-axis of the priority effect plot represent? + +## References + +Cornish- Bowden, A. (2012). Fundamentals of enzyme kinetics (4th, completely revised and greatly enlarged edition ed.). Wiley- Blackwell. Garud, N. R., Good, B. H., Hallatschek, O., & Pollard, K. S. (2019). Evolutionary dynamics of bacteria in the gut microbiome within and across hosts. PLOS Biology, 17(1), e3000102. https://doi.org/10.1371/journal.pbio.3000102 Houtsma, P. C., Kant- Muermans, M. L., Rombouts, F. M., & Zwietering, M. H. (1996). Model for the combined effects of temperature, pH, and sodium lactate on growth rates of Listeria innocua in broth and Bologna- type sausages. Applied and Environmental Microbiology, 62(5), 1616- 1622. Marsland, R., Cui, W., Goldford, J., & Mehta, P. (2020). The Community Simulator: A Python package for microbial ecology. PLOS ONE, 15(3), e0230430. https://doi.org/10.1371/journal.pone.0230430 Shoemaker, W. R., Sánchez, A., & Grilli, J. (2023). Macroecological laws in experimental microbial systems (p. 2023.07.24.550281). bioRxiv. https://doi.org/10.1101/2023.07.24.550281 Snedecor, G. W., & Cochran, W. G. (1989). Statistical methods (8th ed). Iowa State University Press. + +Reviewer #3 (Remarks to the Author): + +In this manuscript, Hu et al. aim to identify characteristics of microbial communities that determine their invasibility. They first carried out experimental invasions with assembled communities, finding that more diverse communities are more invasive. To further explore this positive invasibility- diversity relationship, a Loka- Volterra model was used to predict the effect of changing interspecies interaction strength and species pool size on invasibility. This showed that decreasing interaction strength and pool size increased invasibility. This was confirmed experimentally by changing the concentration of glucose and urea to tune interaction strength, and by changing species pool size. These three key determinants of invasibility (interaction strength, pool size, dynamical regime) determine the survival fraction, defined as the fraction of the initial species pool that survives the assembly process. The survival fraction correlates positively with community invasibility, serving as a unifying predictor. They find that under strong interaction strength, the invasion probability is lower than the survival fraction, indicating a priority effect. The strength of interactions is also shown to determine the impact of invasion on the resident community. Finally, the properties of invaders were briefly discussed. + +I see this as a valuable and novel contribution to the field. While the long- standing biotic resistance hypothesis predicts that more diverse communities should be less invasive due to niche filling, empirical evidence for this is mixed. By considering how diversity is achieved, the authors show that invasibility can be predicted from community features, which has not been done previously. A particular strength of the manuscript is the integration of modelling and experiments to gain mechanistic insight into relationships observed experimentally. + +I have two major comments regarding the tuning of interspecies interactions and determining the impact of invasion. In both cases, limitations of the findings of the manuscript need to be made more explicit. + +The authors state that increasing interaction strength decreases invasion probability. This is done experimentally by increasing the strength of competitive interactions. However, previous work (ref 30) has demonstrated that the type of interaction between the invader/residents, or between residents, impacts the invasion outcome. For example, positive interactions (e.g. facilitation) between the invader and resident community increases invasion probability (as posited by the diversity begets diversity hypothesis). Increasing interaction strength in this case could increase community invasibility, which is a possibility not considered by this study. While I recognise that experimental manipulation of interaction strength is difficult, I would recommend running the model with a distribution of interactions that considers positive interactions, to show the generality of their conclusions. If this has already been done (this is not clear) this should be included in the supplement. + +The limitations of the study in determining the impact of successful invasions on the structure of the resident community should be more explicit. The impact of successful invasions on the structure of the resident community was measured experimentally by the fold change in biomass, and the invasion effect on the community using 16s sequencing data. However, the fold change in biomass provides little insight on invasion impact. It is not possible to distinguish between the change in biomass of the resident community, and the increase in biomass of the successful invader. Thus, a lower change in biomass in the low nutrient regime may be due to the fact that the invader has less nutrients to grow on, and the converse for the high nutrient regime. Moreover, while species abundance data shows a statistically significant difference in community composition in the higher nutrient regime, it is important that the authors provide information about the effect size. For example, as a 95% confidence interval for the difference between the invasion success under high nutrient conditions and the invasion success under low nutrient conditions Finally, it is hard to conclude what the actual effect of invasion is using the selected measures. For example, though species composition may have changed, the invader could be functionally redundant with the species that were excluded, resulting in no change to community functioning. While a comprehensive assessment of invasion impact is out of the scope of this paper, I would recommend for these limitations to be discussed explicitly in the manuscript. + +## Minor points: + +- I strongly recommend including explicit definitions of key terms, which would improve clarity of the manuscript. For example, the definition of community diversity as the number of species that survive the assembly process is not made explicit in line 152. What 'rich dynamics' (line 191) or richness (line 195, 222 and others) refers to is also unclear to me. +- The findings of this study could be embedded more explicitly into existing concepts in invasion ecology, which is dominated by + +<--- Page Split ---> + +niche theory and resource competition. For example, in lines 175- 176 the authors state that fluctuating communities are more invisible. The basis of this relationship is not made clear to the reader - I assumed that this means more niches are open at any given point in time. Moreover, why strong interspecies interactions and a larger species pool decrease invasibility is not discussed. It would also be helpful to discuss this more in the conclusion. + +- I think that for those unfamiliar with previous work from this group, how interaction strength, species pool size and dynamical regime combine to determine survival fraction is difficult to understand. More explanation about how these features interface is necessary for clarity of the manuscript, since they are not independent. For example, it is not immediately clear why there are stable/fluctuating regimes for communities under high nutrient conditions, and not for low nutrient conditions + +- The measure of dispersion used is not included in the text of the manuscript (i.e., on line 148, 153, 154, 172 and more, parameter estimates are given as mean +/- X, where X is a measure of dispersion, but which measure it is is not defined). Defining the measure of dispersion is crucial to allow for interpretation of the findings. Some figure legends mention that error bars represent the standard error of the mean, which I assume is the measure used by the authors, but this should be clearly stated in the text of the manuscript. + +- State how invaders were chosen (line 146) - I assume they were chosen at random? + +- In the section discussing the model (lines 178-190), explicitly state at what relative abundance the invader is introduced relative to the community + +- In the representative time series of fig 2a, invasions are shown to cause a weak effect on the community when the invader grows to a low abundance relative to the rest of the community, whereas the invader causes a strong effect when it grows to high abundance. Is this true across other simulations, or in experiments? If this is the case, it would suggest that there is another factor that influences invasion effect aside from interaction strength. + +- I would include (strong interaction) or (weak interaction) every time high/low nutrient conditions are mentioned for clarity. This is missing now in line 240 and others + +- Remove "while resident community ... determining invasion outcome" from line 322-323. Invader properties have not been sufficiently explored in this manuscript to claim they don't play an important role in determining invasion outcome. + +Version 1: + +Decision Letter: + +Dear Jeff, + +As per my previous email, we received the reviewers' comments on your revised manuscript "Collective dynamical regimes predict invasion success and impacts in microbial communities" (NATECoLEVEL- 24020551A) and we decided in principle to publish it in Nature Ecology & Evolution, pending minor revisions and compliance with our editorial and formatting guidelines. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials until you receive this additional information from us. + +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +[redacted] + +Reviewer #1 (Remarks to the Author): + +The authors have addressed all my concerns, and added useful new analyses and discussions that clarify the manuscript and the modeling choices they made. I have no more concerns that would need to be resolved before publication. + +As an extremely minor point, I found the spread of the points in Fig. 5c and d to be a bit large, to the point where my eye didn't immediately parse the two clouds as separate categories - but that's presumably a matter of taste. + +Reviewer #1 (Remarks on code availability): + +No readme files, but the data looks complete. Both the sequencing data analysis code and the simulation code is clear and well- documented. I did not attempt to run the code, but as far as I can tell, the provided code only gives the backbone of the simulations and does not include code needed to reproduce the figures directly. + +Reviewer #2 (Remarks to the Author): + +Review #2 + +This is an impressive revision, and the quality reflects a high level of effort from the authors. The authors addressed all my comments and gave thoughtful, much appreciated answers. I believe the manuscript should be published. + +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. + +<--- Page Split ---> + +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +The Dryad repository looks good. + +Below are some minor comments that do not require a response. + +- The discussion of how pH mediated interactions can shape the strength of interaction in gLV is helpful. In general, I think a derivation of pH mediated interactions from the starting point of a consumer-resource model is needed, even if it's just for pedagogical reasons and all the heavy modeling is ultimately done using gLV, but such modeling efforts lie outside the scope of the paper. All-in-all the additions to the supplement make it a valuable resource. + +- The elaboration on the connection to ergodicity in response to R1 was very helpful. + +- The new color scheme should aid readers. + +- "In our group, we have been investigating the dependence of community diversity and dynamics on resource concentration across various consumer-resource models (e.g., linear growth or Monod growth)." Very much looking forward to reading this. + +- The added analyses for the survival threshold are rigorous. The sequencing depth justification is particularly useful since my group has encountered studies where the order of magnitude of demographic manipulations is not justified given the depth of sampling (i.e., # reads). + +Reviewer #2 (Remarks on code availability): + +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +I was unable to run the code as-is. + +Reviewer #3 (Remarks to the Author): + +I would like to thank the authors for their thorough revision of this manuscript. All my concerns have been addressed and I have no further comments. + +Reviewer #3 (Remarks on code availability): + +The code is usable but needs a README file for further clarity. + +Version 2: + +Decision Letter: + +25th November 2024 + +Dear Professor Gore, + +We are pleased to inform you that your Article entitled "Collective dynamical regimes predict invasion success and impacts in microbial communities", has now been accepted for publication in Nature Ecology & Evolution. + +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Ecology and Evolution style. 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They find that while diversity- invasibility relationships can be both positive and negative depending on the factors regulating diversity, the fraction of surviving species directly predicts invasibility. This manuscript leverages their recent insights on the dynamical phases of microbial ecosystems to provide a timely and relevant exploration of invasions. + +The results are interesting and the research is carried out soundly. My comments are primarily aimed at making the manuscript easier to follow. + +My first main comment concerns the exposition of the different diversity- invasibility relationships between Fig. 1 and Fig. 2/3, which on a first read was not immediately obvious. In Fig 1, more species and higher interaction strength makes for fluctuations and greater diversity, and fluctuating communities are more likely to be invaded; but both theory and Fig. 3 show a negative correlation between invasion probability and pool size/interaction strength. I naively expected increased pool size and stronger interactions to translate to a higher chance of fluctuations (as in their recent paper), and thus greater richness and higher invasion probability. It is later revealed where this apparent contradiction comes from, but I believe it would be immensely helpful if this contradiction was highlighted early on. This issue is made more severe by the use of three different terms to describe the probability of successful invasions (invasion probability and invasion resistance, also invasibility) - especially because these have opposite meanings, I had to read this section of the manuscript carefully to understand its meaning. A single term would be easier to understand. + +We thank the reviewer for this helpful comment to improve the readability of the manuscript. When we sample many communities under the same species pool size and the same nutrient concentration (interaction strength), we found the fluctuating communities are more diverse and invasive than the stable ones. However, if the species pool size or nutrient concentration (interaction strength) varies in the experiment or simulation, then fluctuating communities may not be more diverse and invasive than stable ones, as shown in Fig. 3. A more accurate statement should be: The average community invasibility decreases with species pool size and interaction strength (Fig. 2f and Fig. 3). Fluctuating communities are on average more diverse and invasive than stable communities under the same nutrient condition and species pool size. We now clarify in the caption of Fig. 1 and 2 that the fluctuating communities are more invasive than stable ones under the same species pool size and nutrient conditions (average interactions), rather than a universal statement across different conditions. We follow the reviewer's comment and avoid using any "invasion resistance" in the manuscript, which has opposite meanings to "invasibility" and "invasion probability". We further clarify this point in the early text on page 4 of the main text to avoid confusion: + +Our experimental tests of invasion demonstrate that, for fixed environment and species pool size, more diverse communities are more invasive because fluctuating communities are both more diverse and more susceptible to invasion. However, we will show later that when species pool size or nutrient concentration is varied, this relationship does not always hold. + +We also highlight this point on page 5 of the main text: + +<--- Page Split ---> + +It is important to note that although fluctuating communities exhibit larger invasion probability than stable communities under the same conditions, stable communities can still yield larger invasion probability under weaker interaction strength \(< a_{ij}>\) or smaller species pool size \(S\) (Fig. 2d- f). + +My second main comment concerns the notion of priority effects. Here, as I understand it, the authors use this term basically to mean that a community of strongly interacting species has established itself, which makes invasions less likely (e.g., because all niches are filled or because antagonistic interactions are balanced out) but I am not convinced that this is the sense in which most ecologists tend to use that term; to me, the more common use appears to be referring to particular species whose presence or absence steers the community into different alternative stable states. Here, however, the community is already in a stable state and a new species is trying to invade, and thus "priority effect" does not apply in my view. I suggest a different way of describing this effect here, or, at the very least, the sentence in line 244- 246 needs more explanation. Similarly, I find the use of "alternative stable states" to be unclear since that is not really the subject of this paper. + +We appreciate the reviewer for highlighting this important point. Our interpretation and use of the priority effect are in line with the reviewer's comments. In ecology, the "priority effect" refers to the phenomenon where the order and timing of species arrival in a community influence the subsequent structure and dynamics of that community. Specifically, the species that establish themselves first can significantly affect the community's composition and the success of later- arriving species. In our case we claim priority effect emergent under strong interaction because our model and experiment show that the later- arriving species (invader species) display lower surviving probability (invasion probability) than surviving probability of initial species assemble from the pool (early- arriving species) (as shown in Fig. 3c and Fig. 4c). Under low nutrient (weak interaction), the later- arriving species (invader species) display similar surviving probability (invasion probability) with surviving probability of initial species assemble from the pool (early- arriving species) (as shown in Fig. 3c and Fig. 4c), which indicate there is no priority effect under low nutrient (weak interaction). + +Based on our experiments and simulations, we found that the existence of alternative stable states is closely related to the presence of priority effects. As demonstrated in previous theories (Fried, Shnerb, and Kessler 2017; Bunin 2017) and in our experiment (new Supplementary Fig. 22), we observed that the same set of species can reach different alternative stable states when starting from different initial compositions under high nutrient concentrations (strong interactions). In contrast, under low nutrient concentrations (weak interactions), the species consistently converge to a single stable state, meaning that the order of species arrival does not affect the final community structure, indicating the absence of a priority effect. In this context, we consider the priority effect to be equivalent to the presence of alternative stable states. The existence of alternative stable states implies that different initial compositions or the order of species arrival can lead to different final community compositions, which aligns with the definition of the priority effect. Conversely, when no alternative stable state exists, different initial compositions or the order of species arrival result in the same final community composition, which corresponds to the absence of a priority effect. + +<--- Page Split ---> + +We therefore propose that the alternative stable states observed under high nutrient conditions exhibit a priority effect, which explains why invasion probability is generally lower than the survival fraction in these conditions (bottom left points in Fig. 3c). These stable communities strongly resist invasion due to their established alternative stable states. As the reviewer suggested, we've revised the manuscript to clarify the use of the terms "priority effect" and "alternative stable state". + +![](images/Figure_2f.jpg) + + +Supplementary Fig. 22. Communities reach global stable states under low nutrient conditions (weak interaction) but reach alternative stable states under high nutrient conditions (strong interaction) when starting from different initial species compositions. Each bar represents a final community stable state after 7 daily dilution cycles starting from a particular initial condition. The communities assemble from the same species in the original pool ( \(S = 12\) for the left and middle communities, \(S = 24\) for the right communities), under low- nutrient (weak interaction) and high- nutrient (strong interaction) conditions, respectively. For each initial condition, one of the species occupies \(99\%\) volume of the initial inoculum, while the other species in the pool together occupy only \(1\%\) volume of the initial inoculum. The results show that these very different initial species compositions lead to the same global stable state under low nutrient conditions (weak interaction) but result in alternative stable states under high nutrient conditions (strong interaction). This indicates the presence of alternative stable states and priority effect under high nutrient (strong interaction), where the initial composition influences the final community structure. + +We revised the paragraph on page 6 ang 7 with an additional explanation as the reviewer suggested: + +Despite the experimentally observed correspondence between invasion probability and survival fraction, we note that the invasion probability for communities under high nutrient (strong interaction) conditions is usually lower than their survival fraction (i.e. the majority of points on the bottom left are below the diagonal line on Fig. 3c). We now discuss how this can be interpreted in terms of priority effects or alternative stable states. If the assembly of species in the community does not depend on the order of species arrival (i.e., no effect of history), the survival fraction of species assembled from the initial pool should be statistically equal to the survival probability of + +<--- Page Split ---> + +the species that invade the communities later. In ecology, a "priority effect" refers to a situation in which the community structure is influenced by the order and timing of species' arrival(Sprockett, Fukami, and Relman 2018; Debray et al. 2022). We thus interpret the mismatch between invasion probability and survival fraction under high nutrient concentrations (strong interactions) as evidence of priority effects in the community assembly under strong interactions in our experiment. Early- arriving species can dominate by making it more challenging for subsequent invaders to establish, leading to a lower invasion probability than the survival fraction of species in the original pool. Under weak interactions, however, the colonization probability of invader species is similar to the probability of a species in the initial pool surviving the process of community assembly(Fig. 3c)(Case 1990). An emergent priority effect in communities composed of strongly interacting species can be explained by the presence of alternative stable states with different species compositions, which we observe in additional experiments (Supplementary Fig. 22). Early- arriving species establish dominance, making it more difficult for later- arriving invaders to successfully establish themselves, by inhibiting their growth at low abundance. These alternate stable states thus explain why the invasion probability is generally lower than the survival fraction from the initial pool under high nutrient (strong interaction) conditions(Case 1990; Hu et al. 2022). + +Minor comments: + +1) L110: "The lower probability" - compared to what? + +We appreciate the reviewer for pointing out the need for clarification. The text should specify that the lower invasion probability is compared to the survival fraction. We have revised the manuscript to make this comparison explicit. The revised Text is: + +"The lower invasion probability compared to the survival fraction suggests a priority effect, whereby earlier invaders preclude later ones from growing from small abundances." + +2) L174: "including species interaction strength" - is it clear that different synthetic communities can be characterized by the same average interaction strength? Perhaps some initial compositions have strong antibiotic producers or very similar metabolic profiles + +We thank the reviewer for this valuable question. We have clarified this point by specifying "for fixed species pool size and species interaction strength regime (nutrient concentrations)." We describe community conditions based on sampling species interactions from a given distribution. For example, in Fig. 2b, communities were sampled from the same species pool size ( \(S = 20\) ) and a uniform distribution of interaction \(\alpha_{ij}\) with a mean interaction of 1.8. Each sampled community has a unique but similarly distributed mean interaction. Our previous work shows that average pairwise interactions increase from low to high nutrient concentrations (Fig. 2B of Hu et al. Science 2022). Although the statistical distribution may vary with limited species sampling, species cultured in the same high nutrient concentration are in a strong interaction strength regime compared to those in a weak interaction strength regime under low nutrient concentrations. We have updated the manuscript on page 4 to reflect this clarification: + +Our experimental tests of invasion demonstrate that, for fixed species pool size and species interaction strength regime (nutrient concentrations), more diverse communities are more invisible because fluctuating communities are both more diverse and more susceptible to invasion. However, when species pool size or nutrient concentration is varied, this relationship does not always hold (Fig 2 and 3). + +<--- Page Split ---> + +## 3) L227: correlation on \(\rightarrow\) with + +We thank the reviewer for this point. We have edited the text to read "positive correlation of invasibility with survival fraction" in the main text. The revised Text is: + +"The results show a strongly positive correlation of invasibility with survival fraction." + +4) L239: Why should we expect a 1:1 correspondence between survival fraction and invasion probability? This only becomes clear in Fig 4b + +We thank the reviewer for this insightful question. If the assembly of species in the community does not depend on the order of species arrival (i.e., no history effect and priority effect), the survival fraction of species assembled from the initial pool should be statistically equal to the survival probability of the species that invade the communities later. If there is no priority effect and the order of species arrival does not matter, then the survival fraction is expected to approximately correspond with invasion probability, as shown in Fig. 4b. We have added this explanation to page 6 and 7 of the main text to clarify this point: + +Despite our experimentally observed correspondence between invasion probability and survival fraction, we noted that the invasion probability for communities under high nutrient is usually lower than their survival fraction (majority of points on the bottom left (high nutrient) are below the diagonal line on Fig. 3c). If the assembly of species in the community does not depend on the order of species arrival (i.e., no history effect and priority effect), the survival fraction of species assembled from the initial pool should be statistically equal to the survival probability of the species that invade the communities later. + +## 5) L280: ergodicity likely needs a bit more explanation to be clear + +We follow the reviewer's suggestion and have further clarified the concept of ergodicity in the supplementary materials and mentioned in the main text. As studied and shown in previous theoretical studies (Altieri et al. 2021; Pearce et al. 2020; Bunin 2017), ergodicity in the context of chaotic fluctuations means that the community's state is memoryless. The dynamical trajectories of species composition do not depend on the community's history and do not reach alternative stable states or alternative dynamical attractors. Therefore, different orders of species arrival or different initial species compositions do not lead to different community states in the chaotic fluctuation regime. We have added this explanation to improve clarity. The revised text in the supplementary materials is: + +"As studied and shown in previous theoretical studies (Altieri et al. 2021; Pearce et al. 2020; Bunin 2017), ergodicity in the context of chaotic fluctuations means that the community's state is memoryless. The dynamical trajectories of species composition do not depend on the community's history and do not reach alternative stable states or alternative dynamical attractors. Therefore, different orders of species arrival or different initial species compositions do not lead to different community states in the chaotic fluctuation regime." + +We refereed to this explanation in the main text on page 8: + +which can be explained by its ergodicity (Bunin 2017; Pearce et al. 2020; Altieri et al. 2021) (see a technical discussion in Supplementary Materials). + +6) L285: definition of invasion effect is slightly unclear. Is this the same definition as in L296? + +<--- Page Split ---> + +We further clarify the definition of invasion effect in the text. The definition of invasion effect in L285 is the same as the definition in L296. The invasion effect is measured as the proportion of change in surviving species before the invasion \((t = 10^{3})\) and after the invasion \((t = 2\times 10^{3})\) , calculated as 1 minus the ratio of the number of overlapping species (number of species surviving both at \(t = 2\times 10^{3}\) and \(t = 2\times 10^{3}\) ) to the total number of species (number of species surviving at \(t = 10^{3}\) or \(t = 2\times 10^{3}\) ). Mathematically the invasion effect is calculated through: 1 - (number of overlapping species / total number of species). We have revised the text to ensure this definition is clear and consistent throughout. The revised text on page 8 of the main text is: + +the invasion effect is quantified as the proportion of change in surviving species before the invasion \((t = 10^{3})\) and after the invasion \((t = 2\times 10^{3})\) (invasion effect \(= 1\) - (number of overlapping species / total number of species)) (Fig. 4d) + +7) L317: SI Fig 17 does not show an Allee effect for invaders 2/3 + +We thank the reviewer for pointing out this issue. To see the Allee effect for invaders 2 and 3, we need to look at the monoculture growth curve for these invaders, which is shown in SI Fig. 19. The growth curves of invaders 2 and 3 (blue and purple curves) indicate that they do not grow to a well- detectable signal on the OD reader over 20 hours, demonstrating an Allee effect. We have revised the main text to reference SI Fig. 19 for clarity. The revised text in the Supplement is: + +"To see the Allee effect for invaders 2 and 3, notice that the growth curves of invaders 2 and 3 (blue and purple curves) indicate that they do not grow to a well- detectable signal on the OD reader over 20 hours, demonstrating an Allee effect of these two species." + +## 8) Fig 2f/4c: Legend missing for the gray lines + +We thank the reviewer for raising this important point. We have added legends to Fig. 2f and Fig. 4c to explain the gray lines as shown below and in the main text figures. The solid lines represent the stability boundary, and the dashed lines represent the surviving boundary, which is further explained in the new caption of the figures. + +![](images/Figure_4c.jpg) + +
Fig. 2f, Increasing species pool size and interaction strength leads to a decrease in invasion probability. The communities experience the extinction of species and loss of stability when crossing the dashed gray line (surviving boundary) and solid gray line (stability boundary), respectively. The color maps depict the mean value over 1000 simulations.
+ +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Fig. 4c, Increasing species pool size and interaction strength leads to the emergence of priority effect, where the invasion probability of resident communities is smaller than their species survival fraction. The communities experience the extinction of species and loss of stability when crossing the dashed gray line (surviving boundary) and solid gray line (stability boundary), respectively.
+ +9) Fig 4a: it is very hard to parse the different colors + +We appreciate the reviewer for pointing this out. We have chosen a different set of colors to make the different lines easier to distinguish as shown below. + +![](images/Figure_unknown_0.jpg) + +
Fig 4. The Lotka-Volterra model predicts a universal correspondence between invasion probability and survival fraction. a, The dependence of invasion probability on final richness of resident communities is qualitatively different depending upon how the richness is changed. Invasion probability positively correlates with richness when varying interaction strength or when randomly sampling communities with a fixed species pool size and interaction strength distribution. Invasion probability can decrease with community diversity when varying species pool size. b,
+ +<--- Page Split ---> + +Invasion probability is approximately equal to the survival fraction of species in the resident communities, no matter how we change richness, species pool or interaction strength. + +Reviewer #2 (Remarks to the Author): + +## Summary + +Overall, I found that the study addressed interesting questions and the choice to connect experiments with minimal models of community dynamics seemed like the appropriate choice. However, several decisions made and details about the experiment seem unclear. For example, it is unclear to me how 1) a generalized Lotka- Volterra (gLV) serves as an appropriate model for pH- mediated effects, 2) how fluctuating/stable communities were classified, 3) whether their experimentally- imposed migration rate was sufficient to induce deterministic fluctuations. + +We appreciate the reviewer's feedback and suggestions on our manuscript. In our response letter, we provide a point- by- point answer to all the questions and suggestions from the referees. For convenience, the original comments from the reviewers appear in blue- color font and new text that now appears in either the main text or supplement is included in red. + +Below is a brief discussion regarding these three major points. More detailed responses can be found in our specific responses to the reviewer's comments. + +1) Generalized Lotka-Volterra (gLV) Model for pH-Mediated Effects: + +As a phenomenological model, the generalized Lotka- Volterra (gLV) framework describes the interaction between species through a pair- wise interaction matrix, capturing how the abundance of one species influences the growth of others. The gLV interaction matrix can incorporate various mechanisms, such as resource competition, cross- protection, cross- feeding, and pH- mediated interactions, if the interaction parameters are chosen based on experimental data. + +The gLV model provides a coarse- grained description of interaction signs and strength without delving into specific mechanisms, which is useful when interaction mechanisms are not fully known or when the focus is on collective community behaviors (e.g., fluctuations). + +In our study, pH- mediated interaction is one of several interaction mechanisms. A model solely based on pH- mediated interactions cannot explain some experimental observations. However, a model combining pH- mediated effects and gLV- type interactions can capture key experimental observations, with pH- mediated effects reducing to gLV- type interactions in the adiabatic limit. + +2) Classification of Fluctuating/Stable Communities: + +Communities were classified as fluctuating or stable based on the time series of total biomass and species composition. A community is classified as fluctuating if the variation in its total biomass and species composition over time exceeds a critical threshold. Detailed criteria and thresholds used for classification will be discussed in the following responses to specific comments. + +3) Experimentally-Imposed Migration Rate and Deterministic Fluctuations: + +We have included additional experimental and simulation results to demonstrate that our imposed migration rate leads to deterministic fluctuating or stable states. This point will be elaborated upon in detail in the following responses to specific comments. + +<--- Page Split ---> + +The visualizations are effective and thorough. However, the authors often make claims about the interpretation of visualizations that need to be backed up by statistical tests. I have attempted to identify reasonable statistical tests when a test is lacking. There are also several instances where further clarification could help a broad readership understand the study. These instances are pointed out under both Major and Minor Comments. + +We have now clarified the results of statistical tests when making claims about the interpretation of visualizations throughout the manuscript. We have conducted and reported appropriate statistical tests to support our visual interpretations, ensuring that our claims are robust and well- substantiated. Additionally, we have followed the reviewer's advice and added further clarification to points that may not be clear to a broad audience. These clarifications will be discussed in detail in our responses to the specific major and minor comments provided by the reviewer. + +## Major comments: + +1. There is no explicit consideration of resources in their model. This makes sense in some respects, as the gLV can be derived in the adiabatic limit of certain consumer-resource models. Furthermore, their experimental manipulations of invasion are demographic rather than environmental, so it makes sense that a phenomenological model that does not explicitly consider microscopic interactions of resource consumption is sufficient. Progress has recently been made using phenomenological models to investigate the macroecological consequences of demographic manipulations (Shoemaker et al., 2023), which may provide outside support for the authors' modeling decisions. At a minimum the authors should provide additional justification for their modelling choices and why they are appropriate for their mode. + +We thank the reviewer for this insightful comment on justifying our choice of the generalized Lotka- Volterra (gLV) model in this work. As a phenomenological model, gLV describes species interactions through a pair- wise interaction matrix, capturing how the abundance of one species influences the growth of others. The interaction matrix in the gLV framework is a high- level description that can incorporate various mechanisms, including resource competition, cross- protection, cross- feeding, and pH- mediated interactions. + +As the reviewer pointed out, the gLV model can be derived in the adiabatic limit of certain consumer- resource models. We found that a pH- explicit model can also be reduced to gLV in the adiabatic limit, where the gLV interaction matrix is a function of the pH effect. We would like to emphasize the following points: + +1) Multiple Interaction Mechanisms: pH-mediated interaction is not the only mechanism in our experiment. Some communities show fluctuating biomass while maintaining stable pH levels, indicating other mechanisms, such as cross-toxin interactions, are at play, particularly under high nutrient concentrations. + +2) Limitations of Solely pH-Mediated Models: + +Our model considering only pH- mediated interactions cannot explain all experimental observations. For instance, our experiments and gLV simulations show fluctuating communities with higher diversity and invasibility (Hu et al. 2022), while our pH- only models predict lower diversity and invasibility (Supplementary Fig. 10-11 of Hu et al. 2022) (Hu et al. 2022), contrary to our experimental findings. + +<--- Page Split ---> + +## 3) Combined Model Approach: + +We developed a model that integrates pH- mediated environmental effects with gLV- type species interactions. This combined framework successfully explains key experimental observations and, crucially, can be reduced to a pure gLV interaction matrix in the adiabatic limit- - where the pH dynamics evolve much faster than species growth, or when pH reaches stable state. This reduction explicitly demonstrates how pH influences the structure of the gLV interaction matrix + +These justifications support our use of the gLV model and align with recent progress in using phenomenological models for demographic manipulations (Shoemaker et al., 2023). We have added this explanation to the manuscript to provide additional justification for our modeling choices. + +2. However, the authors also manipulate resource concentration as a means to manipulate the strength of competitive interactions. This manipulation is done by increasing resource concentration, changing the pH, which is a feature of the environment that does not appear in the model and does not appear to be measured. So, while their invasion manipulations are demographic, it reads as though the difference in invasion outcomes between high and low nutrient treatments is driven by the environment. In the manuscript's current form, I imagine that it would be difficult for the reader to understand how the manipulation of resource concentration can be modeled as an increase in the strength of competitive interactions in a phenomenological gLV. + +We appreciate the reviewer for this insightful comment. We have performed pair- wise coculture experiments among the species in the pool and found that the fraction of coexistence between pairs of species decreased, while the fraction of competitive exclusion (only one species survives) increased when nutrient concentration was increased (Hu et al. 2022). We now cite these pair- wise coculture results in the manuscript to demonstrate more clearly that the average interaction between species increases with nutrient concentration. + +Previous work from our group (Ratzke, Barrere, and Gore 2020) has shown that increasing glucose and urea concentrations in the culture medium increases inter- species interaction strength among different soil bacterial species. Specifically, some species consume glucose and produce organic acids, leading to a decrease in pH, while others consume organic acids and increase the pH. Additionally, some species consume urea and produce ammonium, which also increases pH. These interactions modify the pH in different directions and affect species' growth and death rates, explaining the pH- mediated interaction under high nutrient concentrations. + +Our experiments show that without glucose and urea, pH does not significantly change, indicating weak pH- mediated interactions. However, we also observed that communities can fluctuate in biomass without corresponding pH fluctuations (see figure below), suggesting that pH is not the sole driver of strong interactions under high nutrient concentrations. Our ongoing spent- medium culture experiments show that other types of inter- species interactions, such as cross- toxin effects, also increase with nutrient concentration, contributing to the overall interaction strength. + +In our experiments, increasing nutrient concentration led to increased interaction strength and decreased community diversity. While existing resource- consumer models often display independence between resource concentration and interaction strength, our new pH model combines pH- mediated effects with gLV- type interactions, directly considering the quantitative interdependence between pH modification by species and pH effects on species growth, which can be measured experimentally. + +<--- Page Split ---> + +We agree with the reviewer that directly relating nutrient concentration to interaction strength is an important research direction, and we are actively working on relevant projects. We have added these explanations to the manuscript to clarify how manipulation of resource concentration can be modeled as an increase in competitive interaction strength in a phenomenological gLV framework. + +![](images/Figure_unknown_1.jpg) + +
Figure. Microbial communities can exhibit fluctuations in biomass without corresponding fluctuations in pH in our experiment. The biomass (OD) of a microbial community fluctuates between days 6 and 10, while the pH time series stabilize during the same period (between days 6 and 10). The three curves represent three replicates of the same community.
+ +3. The connection between interaction coefficients and growth-mediated pH is difficult to see given that pH tends to be incorporated into terms related to growth, both for models such as Monod growth (e.g., Houtsma et al., 1996) as well as Michaelis-Menten kinetics (chapter 10 of Cornish-Bowden, 2012). I suppose that pH-dependent competition coefficients could be derived if one started with a consumer-resource model where growth terms were pH-dependent and took the adiabatic limit. At minimum a form of the gLV needs to be derived so the reader can see the connection between increased resource concentration, change in pH, and increase in the strength of competitive interactions. However, it is also unclear that a phenomenological gLV is appropriate since the pH changes within a transfer cycle due to the growth of the community. Since the change in pH within a transfer cycle is on the same timescale of the growth rate, I do not see how a phenomenological gLV can serve as an appropriate model. + +We thank the reviewer for this insightful comment. As explained in our response to major comment, we have found that existing resource- consumer models do not explicitly relate resource concentration to pH changes and interactions. Recognizing the importance of incorporating pH- dependent growth into the model, we developed a model combining pH effects with gLV- type interactions to explain our experimental observations, which are consistent with gLV predictions. + +This pH model accounts for species' modifications of environmental pH and the pH- dependent growth of species. As the reviewer suggested, we found that this model can be reduced to a pure gLV- type interaction matrix in the adiabatic limit, allowing us to explicitly demonstrate how pH effects influence the phenomenological interaction matrix in the gLV model. In our approach, we considered linear functions for both species' modifications of environmental pH and the impact of environmental pH on species growth. This choice was made to capture the key features of community dynamics in a minimal model and because the linear form facilitates the reduction of + +<--- Page Split ---> + +\(\mathrm{pH}\) - mediated interactions into gLV- type interactions in the adiabatic limit. The results indicate that the presence of \(\mathrm{pH}\) effects increases both the mean and standard deviation of the distribution of effective inter- species interaction strengths \(\alpha_{ij}^{*}\) (see figure below). In the limit where gLV interaction strength is set to zero and only \(\mathrm{pH}\) - mediated interactions exist, we still observe a distribution of effective inter- species interaction strengths \((\alpha_{ij}^{*})\) (see figure below). These findings suggest that the presence of \(\mathrm{pH}\) effects in the model leads to an increase in the mean and standard deviation of gLV- type interaction strengths \((\alpha_{ij}^{*})\) . + +Furthermore, we found that as we increased the \(\mathrm{pH}\) - mediated interaction strength and species pool size in the model, the invasion probability decreased (new Supplementary Fig. 23). When both \(\mathrm{pH}\) - mediated and gLV- type interaction strengths were increased simultaneously, the invasion probability decreased in a manner similar to that observed when only the gLV- type interaction strength was increased (new Supplementary Fig. 23). In the presence of \(\mathrm{pH}\) - mediated interaction strength in the model, we observed that the survival fraction was approximately equal to the invasion probability under various conditions (new Supplementary Fig. 23). These results suggest that our conclusion—that invasion probability decreases with interaction strength and species pool size—is robust to the presence of \(\mathrm{pH}\) effects in the model. Meanwhile, the survival fraction serves as a good predictor of invasion probability in both the gLV and \(\mathrm{pH}\) models. Our results support the idea that the gLV model phenomenologically describes species interactions within the community and predicts robust patterns in community invasion outcomes, which can be qualitatively reproduced in a \(\mathrm{pH}\) model or a combined \(\mathrm{pH}\) and gLV model. + +Our previous measurements of \(\mathrm{pH}\) and biomass dynamics within one transfer cycle (24 hours) show that \(\mathrm{pH}\) dynamics are faster than population dynamics (Ratzke, Denk, and Gore 2018). Furthermore, the reduction of our \(\mathrm{pH}\) model to gLV does not require time- scale separation when the \(\mathrm{pH}\) and population dynamics reach stable states. More importantly, gLV provides a phenomenological and coarse- grained description of inter- species interactions averaged across different mechanisms and time scales, helping us characterize collective community dynamical regimes qualitatively. + +In summary, we agree with the reviewer that incorporating a \(\mathrm{pH}\) - explicit model is crucial for understanding how increasing nutrients and \(\mathrm{pH}\) can enhance inter- species interactions. We have revised the manuscript to include this explanation, showing the derivation of the gLV form and its connection to \(\mathrm{pH}\) - mediated interactions. In our group, we have been investigating the dependence of community diversity and dynamics on resource concentration across various consumer- resource models (e.g., linear growth or Monod growth). However, we have not observed that increasing resource concentration leads to a decrease in diversity and stability within these models, as seen in our experiments. We also explored a consumer- resource model with \(\mathrm{pH}\) - dependent growth terms, but similarly, we did not observe a decrease in diversity and stability with increased resource concentration in any of the models we tested. We agree with the reviewer that it is both interesting and important to explicitly relate resource concentration to changes in \(\mathrm{pH}\) and the subsequent increase in the strength of competitive interactions, this remains an open question in our ongoing projects. We have included a discussion of our new model, which combines \(\mathrm{pH}\) - mediated interactions and gLV- type interactions, in the supplementary materials: + +Theoretical alternatives to the Lotka- Volterra model + +<--- Page Split ---> + +To directly model the pH- mediated interactions in our framework, we consider a minimal model where the pH value \((p\) in the model) influences the species' per capita growth rates linearly, and, reciprocally, the species modify the environmental pH in a linear manner. This approach serves as a straightforward extension of the generalized Lotka- Volterra (gLV) model, which traditionally handles species interactions without considering environmental feedbacks such as pH. + +In this extended model, the interaction between species and pH is twofold: species can alter the pH of their environment, and this altered pH, in turn, affects their growth rates. This dual influence allows the model to capture more complex ecological dynamics, where pH acts as a mediating factor that can shift the balance between competition, cooperation, and exploitation among species. Depending on the specific parameters chosen—such as the sensitivity of growth rates to pH changes and the extent to which species modify pH—the model can simulate a variety of interaction scenarios. + +For instance, a species that raises the environmental pH could either inhibit or promote the growth of other species, depending on whether those species thrive in higher or lower pH conditions. Similarly, species that lower the pH could create environments that are hostile or favorable to others, depending on their pH preferences. This dynamic allows the model to represent competitive interactions (where species indirectly harm each other by altering pH), cooperative interactions (where species create favorable conditions for each other), and exploitative interactions (where one species benefits at the expense of another by altering the pH). + +By incorporating pH- mediated interactions, this model adds a layer of realism to the gLV framework, making it more applicable to ecosystems where environmental factors like pH play a critical role in shaping species interactions. The linear relationships assumed in this model are not just mathematically convenient; they also provide a minimal yet powerful way to explore how environmental feedbacks can influence community dynamics. This extension allows for the modeling of a broader range of ecological scenarios, potentially offering new insights into how species coexist and compete in pH- sensitive environments. + +\[\begin{array}{l}{\frac{dN_{i}}{d t} = N_{i}\left(1 - N_{i} - \sum_{j}\alpha_{i j}N_{j} + g_{i}p\right)}\\ {\dot{p} = -\delta p + \beta \sum_{j}k_{j}N_{j}} \end{array} \quad (2)\] + +In the adiabatic limit, where the rate of pH change is much faster than the species' growth rates (time scale separation), or at steady state, we can assume \(\dot{p} = - \delta p + \beta \sum_{j} k_{j} N_{j} = 0\) . This implies that \(p \equiv \beta^{*} \sum k_{j} N_{j}\) , where \(\beta^{*} = \beta / \delta\) . Substituting \(p \equiv \beta^{*} \sum k_{j} N_{j}\) into equation (2), we obtained: + +\[\frac{dN_{i}}{dt} = N_{i}\left(1 - \frac{N_{i} + \sum\alpha_{i j}^{*}N_{j}}{K_{i}^{*}}\right) \quad (4)\] + +where the effective gLV- type interaction strength is given by \(\alpha_{i j}^{*} = \frac{(\alpha_{i j} - \beta^{*}g_{i}k_{j})}{(1 - \beta^{*}g_{i}k_{i})}\) , and the effective carrying capacity can be calculated through \(\frac{1}{K_{i}^{*}} = (1 - \beta^{*}g_{i}k_{i})\) . Here, \(g_{i}\) quantifies how pH influences species growth, while \(k_{j}\) quantifies how species alter the environmental pH. The parameter \(\delta\) represents the recovery rate of pH due to the addition of fresh medium at the end of + +<--- Page Split ---> + +each serial dilution cycle (with pH being neutral, or 7, after each addition). In the model, \(p = 0\) corresponds to neutral \(\mathrm{pH} = 7\) in the experiment, \(p > 0\) and \(p< 0\) represents alkaline and acidic \(\mathrm{pH}\) respectively. The parameter \(\beta\) represents the environmental coupling strength, which quantifies the impact of species on environmental \(\mathrm{pH}\) and reflects the phosphate buffering concentration in the experiment. The normalized environmental coupling strength, considering the competing effects of \(\mathrm{pH}\) recovery \((\delta)\) and species- induced \(\mathrm{pH}\) changes (determined by \(\beta\) ), is given by \(\beta^{*} = \beta /\delta\) . + +We found that the mean and standard deviation of the effective interaction strength under \(\mathrm{pH}\) influence, \(\alpha_{ij}^{*}\) , are larger than the original gLV interaction strength, \(\alpha_{ij}\) (see figure below). Even when gLV interactions are set to zero, \(\mathrm{pH}\) - mediated interactions alone produce a non- zero distribution of \(\alpha_{ij}^{*}\) (see figure below). These results demonstrate that \(\mathrm{pH}\) - mediated interactions can be effectively incorporated into the gLV framework. The compatibility of the gLV model with pH- mediated interactions justifies our choice, as it allows us to account for environmental factors like \(\mathrm{pH}\) without sacrificing the simplicity and analytical power of the gLV model. + +To further explore the pH model's predictions on invasion outcomes, we simulated the model combining both \(\mathrm{pH}\) and gLV interaction effects across various parameter spaces. We found that even when considering only the \(\mathrm{pH}\) effect, the model predicts a decrease in invasion probability with increasing \(\mathrm{pH}\) interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) and species pool size (Supplementary Fig. 23), which qualitatively aligns with the predictions of the pure gLV model (Fig. 2f). In this purely pH- mediated interaction regime, the survival fraction is approximately equal to the invasion probability (Supplementary Fig. 23). + +Moreover, when both gLV interaction strength (mean of \(\alpha_{ij}\) ) and pH- mediated interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) are increased simultaneously, the invasion probability decreases (Supplementary Fig. 23) in a manner similar to that predicted by the gLV model alone (Fig. 2f). In all conditions, the survival fraction remains an efficient predictor of invasion probability (Supplementary Fig. 23), as observed in the pure gLV model (Fig. 4). + +These results demonstrate that the dependence of invasion probability on interaction strength, species pool size, and survival fraction is robust across both pure \(\mathrm{pH}\) and combined \(\mathrm{pH}\) - gLV models. This further justifies our choice of the gLV model, as it successfully predicts key features of invasion behavior in communities. By incorporating \(\mathrm{pH}\) - mediated interactions into the gLV framework, we capture the added complexity of \(\mathrm{pH}\) effects while retaining the simplicity and analytical power of the gLV model. + +<--- Page Split ---> +![](images/Supplementary_Figure_23.jpg) + +
Figure. The presence of pH-mediated interactions increases the mean and standard deviation of effective gLV-type interactions. a, The gLV-type interaction \(\alpha_{ij}\) follows a uniform distribution \(U[0,1]\) , with a mean and standard deviation of 0.5 and 0.29, respectively. b, Under the influence of pH, the effective interaction \(\alpha_{ij}^{*} = \frac{(\alpha_{ij} - \beta^{*}g_{i}k_{j})}{(1 - \beta^{*}g_{i}k_{i})}\) shows a larger mean interaction strength of 0.52 and a standard deviation of 0.37 compared to the pure gLV model. In this scenario, \(\alpha_{ij}\) still follows \(U[0,1]\) , while the pH modification parameters \(g_{i}\) and \(k_{i}\) are sampled from a uniform distribution \(U[-1,1]\) . The environmental coupling strength \(\beta^{*}\) is set to 0.5. c, The pure pH model without gLV-type interactions produces a distribution of effective \(\alpha_{ij}^{*}\) with a standard deviation of 0.18.
+ +<--- Page Split ---> +![](images/Supplementary_Figure_25.jpg) + +
Supplementary Fig. 23. The invasion probability decreases with increasing pH-mediated interaction strength and gLV-type interaction strength, while the survival fraction remains approximately equal to the invasion probability. a, The pure pH model, without gLV-type interactions, predicts that invasion probability decreases with increasing pH interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) and species pool size. b, In the pure pH model, the survival fraction is approximately equal to the invasion probability, even without gLV-type interactions. c, When both pH interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) and gLV-type interaction strength (mean of \(\alpha_{ij}\) ) increase simultaneously, the invasion probability decreases. d, The survival fraction remains approximately equal to the invasion probability when combining the pH model with the gLV model. The points and color maps depict the mean value over 100 simulations.
+ +The discussion on the pH model is referenced in the main text on page 5 and 6: + +We also developed a model that directly incorporates pH- mediated growth within the Lotka- Volterra framework, allowing interactions to be expressed as a function of pH modifications. This new model suggests that the presence of pH effects increases the effective inter- species interaction + +<--- Page Split ---> + +strengths and yields predictions similar to those of the canonical Lotka- Volterra model (Supplementary Fig. 23). + +As the reviewer suggested, we now add justification for the choice of Lotka- Volterra model in the Supplement: + +Justification for the choice of the Lotka- Volterra model + +As a phenomenological model, generalized Lotka- Volterra (gLV) model describes species interactions through a pair- wise interaction matrix, capturing how the abundance of one species influences the growth of others. The interaction matrix in the gLV framework is a high- level description that can incorporate various mechanisms, including resource competition, cross- protection, cross- toxin, cross- feeding, and pH- mediated interactions. + +It is important to emphasize that the pH- mediated interaction is not the only sole mechanism in our experiment. Some communities show fluctuating biomass while maintaining stable pH levels, indicating other mechanisms, such as cross- toxin interactions, are at play, particularly under high nutrient concentrations. Furthermore, our model considering only pH- mediated interactions cannot explain all experimental observations. For instance, our experiments and gLV simulations show fluctuating communities with higher diversity and invasibility (Hu et al. 2022), while our pH- only models predict lower diversity and invasibility (Supplementary Fig. 10- 11 of Hu et al. 2022) (Hu et al. 2022), contrary to our experimental findings. These justifications support our use of the gLV model and align with recent progress in using phenomenological models for demographic manipulations (Shoemaker, Sánchez, and Grilli 2023). + +To further justify our modelling approach, where increasing nutrient levels in the experiment correspond to corresponds to amplifying average interaction strength in the gLV model, we conducted pairwise coculture experiments. These experiments revealed that as nutrient concentration increased, the fraction of species pairs that coexisted decreased, while the fraction of competitive exclusions (where only one species survives) increased (Hu et al. 2022), reflecting the increase in interspecies interaction strength within the framework of the gLV model. + +4. My understanding is that the term "fluctuations" in the context of this study means fluctuations induced by chaotic dynamics. I understand that these are not meant to be viewed as stochastic fluctuations, but in my experience, I have found that only a fraction of eco/evo readers understand the distinction between fluctuations induced by deterministic vs. stochastic effects. It would aid the typical reader if the authors clarified what form of fluctuations they are focused on in the Introduction, specified the type of fluctuation whenever the term is used in the manuscript (e.g., "fluctuations" and "deterministic fluctuations"), and briefly addressed in the Discussion how the consideration of stochastic fluctuations might factor into their subsequent research efforts. + +We appreciate the reviewer for raising this important point. In this study, all fluctuations are referred to as deterministic fluctuations (chaos or limit cycle oscillations) driven by inter- species interactions, rather than stochastic fluctuations driven by demographic noise. + +The reason we believe our experiment is in the deterministic population dynamics regime, rather than the stochastic regime, is due to the large population size in our experimental communities. Colony plating and counting in our experiment indicate that the CFU is on the order of \(10^{9}\) per mL. We cultured each community in a \(300~\mu \mathrm{L}\) medium, consisting of around \(3\times 10^{8}\) cells, and transferred \(10~\mu \mathrm{L}\) of the community cultures into a new plate with \(300~\mu \mathrm{L}\) of fresh media in each + +<--- Page Split ---> + +dilution cycle, transferring about \(10^{7}\) cells. The relative ratio of deterministic population growth to stochastic birth and death is on the order of \(1 / \sqrt{n}\) , which is very low given the total population size of \(10^{7}\) to \(3 \times 10^{8}\) cells in our experiment. + +Additionally, our communities display stable species composition in stable communities, with sequencing results showing that species composition does not exhibit significant stochastic fluctuations (Hu et al. 2022). This suggests that stochastic fluctuations play a less important role in our experiment. We are indeed very interested in how demographic noise drives stochastic fluctuations in communities, and working on a subsequent research project on this topic. + +We have followed the reviewer's suggestion and clarified the distinction between deterministic and stochastic fluctuations in the manuscript. We have specified the type of fluctuation whenever the term is used in the manuscript (e.g., "deterministic fluctuations"). We have also added a brief discussion on how consideration of stochastic fluctuations might factor into future research. + +We revised the Introduction on page 3 of the main text: + +These deterministic fluctuations in communities are chaotic dynamics or limit cycle oscillations driven by inter- species interactions, rather than stochastic fluctuations driven by demographic noise, because of the large population size regime in this study (see Supplement). + +We addressed how the consideration of stochastic fluctuations might factor into their subsequent research efforts in the Discussion, on page 10 of the main text: + +Beyond the deterministic fluctuations observed under large population sizes in this work, it is important to study invasions under stochastic dynamics driven by demographic noise in subsequent research. Theory shows that demographic noise can drive stochastic transitions between alternative stable states, leading to another type of community fluctuations (Kessler and Shnerb 2015). + +We also added relevant discussion in supplementary materials to make this point clear: + +In this study, all fluctuations are referred to as deterministic fluctuations (chaos or limit cycle oscillations) driven by inter- species interactions, rather than stochastic fluctuations driven by demographic noise. The reason we believe our experiment is in the deterministic population dynamics regime, rather than the stochastic regime, is due to the large population size in our experimental communities. Colony plating and counting in our experiment indicate that the CFU is on the order of \(10^{9}\) per mL. We cultured each community in a \(300~\mu \mathrm{L}\) medium, consisting of around \(3 \times 10^{8}\) cells, and transferred \(10~\mu \mathrm{L}\) of the community cultures into a new plate with \(300~\mu \mathrm{L}\) of fresh media in each dilution cycle, transferring about \(10^{7}\) cells. The relative ratio of deterministic population growth to stochastic birth and death is on the order of \(1 / \sqrt{n}\) , which is very low given the total population size of \(10^{7}\) to \(3 \times 10^{8}\) cells in our experiment. Additionally, our communities display stable species composition in stable communities, with sequencing results showing that species composition does not exhibit significant stochastic fluctuations (Hu et al. 2022). This suggests that stochastic fluctuations play a less important role in our experiment. + +5. It is worth briefly mentioning in the supplement why continued migration from the regional pool was a necessarily experimental detail for this study. Specifically, how the absence of experimentally-imposed migration would correspond to a gLV with zero migration, the analytic + +<--- Page Split ---> + +results of which would be decidedly less rich (e.g., no chaos, etc.). Broad readership may not pick up on this detail. + +We have followed the reviewer's suggestion and discussed the importance of dispersal in the supplement to emphasize how dispersal from the regional pool contributes to maintaining community diversity and enabling persistent fluctuations: + +We introduced a dispersal rate of \(10^{- 5}\) in both of our experiments and gLV simulations. The dispersal from the species pool to the local community is important for maintaining persistent fluctuations in both gLV simulation and our experiment. We found that the lack of dispersal in the gLV model leads to a significantly lower fraction of fluctuating communities (Supplementary Fig. 24). Similarly, the fraction of fluctuating communities is much lower in our experimental communities without daily dispersal (Supplementary Fig. 25). Without dispersal from the species pool, some species reach the extinction boundary due to dramatic fluctuations and cannot recover. This results in a continuous decrease in community fluctuations in both the model and the experiment. + +![](images/Supplementary_Figure_26.jpg) + + +Supplementary Fig. 24. Non- zero dispersal sustains persistent community fluctuations in gLV model. The panels show the theoretical phase diagrams of community fluctuation fraction under different dispersal rates ( \(D = 0\) , \(D = 10^{- 7}\) , \(D = 10^{- 6}\) ). Communities under no dispersal ( \(D = 0\) , left panels) exhibit a low fluctuation fraction in the persistent fluctuation phase. The patterns of ecological diversity and dynamics do not significantly change as the dispersal rate varies from \(D = 10^{- 7}\) (middle panels) to \(D = 10^{- 6}\) (right panels). The dashed line and solid line in the figures represent survival boundary and stability boundary, respectively. The color maps depict the mean value over 1000 simulations. + +<--- Page Split ---> +![](images/Supplementary_Figure_27.jpg) + +
Supplementary Fig. 25. Zero dispersal leads to stable communities under high nutrient conditions (strong interactions) in the experiment. The biomass of eight distinct microbial communities ( \(S = 24\) ) consistently reaches stable states when exposed to high nutrient concentrations (strong interactions) in the absence of species dispersal from the species pool to the community. In contrast, when dispersal is present, a significant proportion of communities exhibit fluctuations under the same high nutrient conditions and species pool size, as previously reported in Fig. 1d and in our previous paper (Hu et al. 2022) (Fig. 2C).
+ +6. Related, did the authors perform any experiments without daily migration from the regional pool? Contrasting the results of this study with that type of experiment would strengthen their claims and provide further opportunities to test the utility of the gLV. Alternatively, if there are there any published experiments on invasion analysis using a similar experimental setting without imposing migration, then such results could be verbally compared to the results of their experiment. + +We conducted experiments without daily migration from the regional pool and observed that the fraction of fluctuating communities was significantly lower compared to experiments with daily dispersal. In the absence of dispersal, some species reached the extinction threshold due to dramatic fluctuations and were unable to recover, resulting in a continuous decrease in community diversity and the eventual disappearance of persistent fluctuations. These findings are consistent with the predictions of the gLV model without migration, which also shows a lower fraction of fluctuating communities. While we have not yet performed invasion experiments without dispersal, we agree with the reviewer that this would be an important and interesting experiment to pursue in our ongoing research. We have incorporated this comparison and discussion into the manuscript to emphasize the importance of dispersal in maintaining community diversity and enabling persistent fluctuations. + +7. Is the experimentally-imposed migration rate sufficient to induce chaotic dynamics in the context of their gLV model? I searched for this detail in the supplement but did not find it. + +The dispersal rate in our experiments and gLV simulations is \(10^{- 5}\) . We found that different levels of dispersal rates can sustain persistent fluctuations (chaos or limit cycle oscillations) in the gLV model. As long as the extinction-prone species can come back and bloom through dispersal, the persistent fluctuation is not influenced by specific values of the dispersal rate. Only a zero- dispersal rate leads to a significantly lower fraction of fluctuating communities in the model. Without dispersal from the species pool, some species hit the extinction boundary due to dramatic fluctuations and cannot recover, resulting in a continuous decrease in community fluctuations. We + +<--- Page Split ---> + +have discussed the consistency between dispersal rates in the experimental and simulation settings in the supplement to clarify this point. + +8. I would also encourage the authors to make both their code and raw data available on public repositories to ensure transparency and reproducibility. + +We thank the reviewer for raising this important point. We planned to make the code and raw data available in public repositories before publication. We have now uploaded our raw data and code to public repositories to ensure transparency and reproducibility: + +Data and materials availability: Isolates and communities are available upon request. All data are available in the supplementary materials and deposited on Dryad (https://datadryad.org/stash/share/Mi09U1xtHkQ8_0D4DPuVDzoSp0-hcIT8oG76h8edCdM). All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +9. Lines 148-149: It would help the reader if justification for the extinction threshold was provided in the main text. In lines 81-82 of the supplement the authors describe the lower bound on detection due to sequencing, but it is not clear how they arrived at this particular value. It would also help if there was a comparison between the chosen threshold and the inverse of the typical total abundance of the community (all cells), the threshold for true extinction, to provide context for the detection limitation. + +We appreciate the reviewer for this important comment, and have added the justification of the choice of extinction threshold in the supplement and refer it in the main text to provide context for the detection limitation and comparison with the typical total abundance of the community: + +We chose the survival threshold for three main reasons: + +1. Distinction from dispersal rate: The survival threshold should be significantly higher than the dispersal rate to distinguish truly surviving species from those whose low abundance is only sustained by dispersal. Since we used a dispersal rate of \(10^{-5}\) , the threshold should be high enough to be separated from the dispersal floor but not too high to falsely classify surviving species as extinct. Simulation results of gLV suggest that a threshold of \(8 \times 10^{-4}\) efficiently separates surviving species from extinct ones (Supplementary Fig. 26). + +2. Sequencing depth: The sequencing depth is on the order of \(10^{4}\) . The number of cells transferred in each dilution cycle is on the order of \(10^{7}\) cells, and the number of cells used in DNA extraction and amplicon sequencing is on the order of \(10^{6}\) cells. Therefore, the detection limit in our sequencing data is primarily determined by the sequencing depth of each community. Any threshold below the order of \(10^{-4}\) would be inconsistent with the detection limit of our sequencing depth. We chose \(8 \times 10^{-4}\) , which is sufficiently above the detection limit but not too high to exclude low-abundance surviving species. + +3. Robustness of conclusion: We found that varying the survival threshold between \(10^{-4}\) and \(10^{-3}\) does not alter our key conclusions. Specifically, a survival threshold of \(10^{-4}\) yielded exactly the same number of successful invasions as a threshold of \(8 \times 10^{-4}\) in our experiment. The survival threshold of \(10^{-3}\) resulted in 61 successful invasions out of 244 total invasion tests, compared to 63 successful invasions out of 244 total invasion tests + +<--- Page Split ---> + +under the \(8 \times 10^{- 4}\) threshold. There were only two cases where the invader abundance fell between \(8 \times 10^{- 4}\) and \(10^{- 3}\) , leading to a minor quantitative difference in the number of successful invasions. We further verified that this small difference does not affect our major conclusions, including (1) that fluctuating communities are more invisible than stable communities, and (2) that invasion probability decreases with increasing species pool and interaction strength. + +![](images/Supplementary_Figure_28.jpg) + +
Supplementary Fig. 26. The survival threshold efficiently separates surviving species from extinct species, where the species abundances display a bimodal distribution in the simulations. a, The extinction threshold of \(8 \times 10^{-4}\) (horizontal dashed line) clearly separates the high-abundant, surviving species from the low-abundant "extinct" species \((S = 50, < \alpha_{ij} > = 0.2)\) . Such "extinct" species would reach zero abundance if dispersal is interrupted (c). b, The extinction threshold of \(8 \times 10^{-4}\) (horizontal dashed line) similarly separates the high-abundant, surviving species from the low-abundant "extinct" species under different interaction strength \((S = 50, < \alpha_{ij} > = 0.6)\) . c, After stopping dispersal at \(t = 1000\) , only species above the extinction threshold survive with stable abundances, while the others undergo extinction \((S = 50, < \alpha_{ij} > = 0.6)\) . This demonstrates that the extinction threshold of \(8 \times 10^{-4}\) efficiently classifies surviving species versus those that would go extinct without dispersal. d, The histogram shows the number of species exhibiting the indicated abundances at steady state. The dataset was generated from 10 in silico communities randomly sampled \((S = 50, < \alpha_{ij} > = 0.2)\) .
+ +We have referred to the justification of the choice of extinction threshold in in the main text on page 4: + +relative invader abundance exceed extinction threshold \(8 \times 10^{- 4}\) on the last day 12; the rationale behind this choice of extinction threshold is explained in the Supplement. + +<--- Page Split ---> + +10. Lines 208-211: I am unaware of models where the competition coefficients between species can be examined as a function of media modification. If such a model exists, could the authors briefly describe it in their supplement to help the reader understand how environmental variables (e.g., pH) map onto competition coefficients in a gLV model? + +We have developed a model that combines the pH effect with gLV- type interactions to explain our experimental observations, consistent with gLV predictions. This pH model considers species' modifications of environmental pH and the pH- dependent growth of species. In our model, the interaction matrix in the gLV framework is influenced by pH changes induced by species interactions. This combined pH- gLV model can be reduced to a pure gLV- type interaction matrix in the adiabatic limit, allowing us to explicitly show how the pH effect influences the phenomenological interaction matrix in the gLV model. We have added a detailed description of this pH model in the supplement to help readers understand how environmental variables, such as pH, map onto competition coefficients in a gLV model. + +In our group, we have been investigating how community diversity and dynamics depend on resource concentration across various consumer- resource models (e.g., linear growth and Monod growth). However, unlike our experimental observations, we did not find that increasing resource concentration leads to a decrease in diversity and stability within these models. We also tested a consumer- resource model with pH- dependent growth terms, but similarly, we did not observe a decrease in diversity and stability with increased resource concentration in any of the models. We agree with the reviewer that explicitly relating resource concentration to changes in pH and the resulting increase in the strength of competitive interactions is both interesting and important; however, this remains an open question in our ongoing research. + +## 11. Lines 275-280: How are alternative stable states determined here? + +We thank the reviewer for this important question. As proved in previous theoretical work (Fried, Shnerb, and Kessler 2017; Bunin 2017) and shown in our experiments (new supplementary Fig. 22), we found that the same set of species starting from different initial species compositions can reach different alternative stable states under high nutrient concentration (strong interaction). In contrast, they reach a single global stable state under low nutrient concentration (weak interaction), with all communities receiving daily dispersal of species from the pool. + +The observed alternative stable states under high nutrient concentration (strong interaction) exhibit a priority effect, which helps explain why invasion probability is generally lower than the survival fraction under these conditions (bottom left points in Fig. 3c). We have added a detailed description of the determination of alternative stable states in the supplement to clarify this point. + +<--- Page Split ---> +![](images/Supplementary_Figure_29.jpg) + + +Supplementary Fig. 22. Communities reach global stable states under low nutrient conditions (weak interaction) but reach alternative stable states under high nutrient conditions (strong interaction) when starting from different initial species compositions. Each bar represents a final community stable state after 7 daily dilution cycles starting from a particular initial condition. The communities assemble from the same species in the original pool ( \(S = 12\) for the left and middle communities, \(S = 24\) for the right communities), under low- nutrient (weak interaction) and high- nutrient (strong interaction) conditions, respectively. For each initial condition, one of the species occupies \(99\%\) volume of the initial inoculum, while the other species in the pool together occupy only \(1\%\) volume of the initial inoculum. The results show that these very different initial species compositions lead to the same global stable state under low nutrient conditions (weak interaction) but result in alternative stable states under high nutrient conditions (strong interaction). This indicates the presence of alternative stable states and priority effect under high nutrient (strong interaction), where the initial composition influences the final community structure. + +12. Fig. 1d: Why are all but two of the "fluctuating" communities decreasing in biomass from day four to five. Could this simultaneous decrease in biomass be driven by experimental details rather than by the intrinsic dynamics of the communities? + +We thank the reviewer for raising this important point. We cultured both stable and fluctuating communities in a mixed manner on the same 96- well deep plates and subjected them to the same experimental processes, including daily dilution and dispersal. The total biomass and sequencing results of stable communities do not show any different behaviors from day 4 to day 5, suggesting that the behaviors of fluctuating communities were not driven by experimental details. Additionally, control wells containing only fresh medium on the same deep- well plates showed no contamination. + +While six of the fluctuating communities decrease in biomass from day four to day five and two of them increase, this pattern is likely due to the small sample size, as we only have eight time series, each spanning just six days. Although this synchrony is not the focus of our current work, it could potentially be explained by the alternating growth cycles of fermentation species and respiration species in our species pool. According to previous studies (Estrela et al. 2022), when fermentation species dominate and grow rapidly, they produce significant amounts of organic acid + +<--- Page Split ---> + +by consuming glucose, leading to highly acidic conditions. This acidity inhibits the growth of respiration species and can even result in the self- destruction of the fermentation species (Ratzke, Denk, and Gore 2018). During these cycles, nutrients are not efficiently utilized, resulting in low biomass and pH. In the subsequent cycle, respiration species may become dominant as the acidic conditions from the previous cycle have reduced the fermentation species population. This shift can lead to a higher pH environment where fermentation species do not self- destruct, allowing them to dominate in the next cycle. This alternating dominance between fermentation and respiration species could potentially explain why six of our communities fluctuate in a seemingly synchronized manner. We are currently working on a project to study the mechanism of these intrinsic fermentation and respiration cycles in our communities but do not yet have sufficient data to draw definitive conclusions. + +13. Fig. 1g; lines 380-382: What statistical test was performed here? + +We performed a two independent samples Student's t- test to compare the groups. We have now clarified this point in the figure caption and manuscript. + +14. Fig. 2f: What do the dashed and solid grey lines represent? Could the authors include a legend in the figure? + +We have added legends to Fig. 2f to explain the solid and dashed lines. The solid grey lines represent the stability boundary, and the dashed grey lines represent the surviving boundary. + +15. Fig. 4c: Could the authors add an axis label for the colorbar in the revision? + +We have added the axis label "priority effect" for the colorbar in Fig. 4c, as suggested. + +16. Fig. 4d: "Effect on resident community" is a nice term for those unfamiliar with these types of experiments, but it still reads as somewhat vague. Could the authors describe what this term means in the figure legend and provide an equation for how the quantity was estimated in the supplement? + +We thank the reviewer for this suggestion. The invasion effect on the resident community is measured as the proportion of change in surviving species before and after the invasion, calculated as 1 minus the ratio of overlapping species to total species (1 - (number of overlapping species / total number of species)). We have added the mathematical definition of "Effect on resident community" in Fig. 4d and its figure caption. We have also included the equations for how this quantity was calculated in the manuscript and the supplement. + +17. Fig. 5: What timepoints are used to calculate the fold change? Are the same timepoints used for each community? Is the outcome of the statistical test robust to the choice of timepoints? + +We thank the reviewer for this important question. We have clarified in the manuscript that the fold change of biomass was calculated using the biomass on day 6 (before the invasion) and day 12 (after the invasion colonization was well completed) across all communities. + +As the reviewer suggested, we further examined the robustness of the statistical test to the choice of timepoints. We found that the same statistical difference was observed when calculating the fold change using biomass on day 6 (before the invasion) and the average biomass of day 10, day 11, day 12 (after the invader colonization). This indicates that the outcome of the statistical test is robust to the choice of timepoints. We have included this additional analysis in the manuscript to ensure clarity and robustness. + +<--- Page Split ---> +![](images/Supplementary_Figure_31.jpg) + +
Supplementary Fig. 27. The mean fold change in biomass under high nutrient conditions is greater than under low nutrient conditions, which is robust to the choice of time points. a, Invasions into resident communities under low nutrient conditions (weak interactions) result in a statistically lower fold change in biomass compared to communities under high nutrient conditions (strong interactions) \((p< 0.001)\) . The number of successful invasions is \(n = 51\) (low nutrient) and \(n = 11\) (high nutrient). The fold change in biomass was calculated by comparing the biomass on day 6 (before invasion) with that on day 12 (after invasion colonization was fully established) across all communities. b, Similarly, invasions into resident communities under low nutrient conditions (weak interactions) cause a statistically lower fold change in biomass than those under high nutrient conditions (strong interactions) \((p< 0.001)\) . The fold change was calculated by comparing the biomass on day 6 (before invasion) with the average biomass of days 10, 11, and 12 (after invader colonization) across all communities.
+ +18. Supplement line 52: The sampling detection limit is \(\sim 10^{\wedge}\{-4\}\) but the chosen dilution rate was \(10^{\wedge}\{-5\}\) . How does the difference between dilution rates and detection limit shape the observed outcomes of the experiment? If it does, it may be worth describing the outcomes in different parameter limits to the reader (i.e., sampling limit much greater than dilution rate and vice-versa). + +We thank the reviewer for this important comment. As shown in the simulation results with gLV, the abundance of surviving species and successful invaders are all well above the surviving threshold \((8\times 10^{- 4})\) and the sampling detection limit \((10^{- 4})\) . Therefore, the measured diversity and invasion success in this work are not influenced by the existence of the sampling detection limit \((10^{- 4})\) . In other words, a better sampling detection limit (e.g., \(10^{- 5}\) or even higher depth) would not change the measured diversity and invasion probability in our work, and thus would not change our observations and conclusions. + +With a detection limit of \(10^{- 4}\) , we indeed cannot detect species whose low abundance is only sustained by the dispersal rate \((10^{- 5})\) . However, this does not impact our study because we focus on the invasion of surviving species whose abundances are high. We have added a description of these outcomes in different parameter limits to the supplement to provide further clarity. + +19. Supplement: Lines 52, 63: I am unfamiliar with the term “dispersal rate” used to describe the process of diluting cultures in a serial transfer experiment. The method used by the authors is different from the standard process of serial dilution, so I think some justification of the term as + +<--- Page Split ---> + +well as an explanation of how it connects to the mathematical definition of dispersal (Eq. S1) in the supplement is warranted. + +Daily dilution and daily dispersal are two different steps in our experiment. We performed a 30- fold daily dilution by transferring \(10 \mu \mathrm{L}\) of the community cultures into a new plate with \(300 \mu \mathrm{L}\) of fresh media. To apply a \(10^{- 5}\) daily dispersal, we diluted the monoculture of each species in the community by a \(10^{5}\) factor before inoculating \(10 \mu \mathrm{L}\) of diluted monoculture into the wells containing the corresponding experimental community matching each species pool. Therefore, the volume ratio between the dispersal from each species monoculture in the pool and the transfer of each community is \(10^{- 5}\) . + +We chose the term "dispersal rate" according to the ecology literature that studies the migration of species from the mainland or an outside habitat to a local community (Handel 2014). This low dispersal rate is sufficient to avoid the complete extinction of species due to occasional low abundance in persistent fluctuations. In our gLV simulation and experiment, some species hit the extinction boundary due to persistent fluctuation and cannot recover without dispersal, leading to the eventual disappearance of fluctuations due to the decrease in diversity over time. Therefore, the small dispersal rate is important to sustain persistent fluctuations in our community. + +The dispersal rate for each species in our model is also chosen to be \(10^{- 5}\) to match the experiment, and we found that the results do not vary significantly with specific values of the dispersal rate in the gLV model. + +We have followed the reviewer's suggestion and added more comments on the dispersal rate in the supplementary materials to clarify its connection to the mathematical definition of dispersal (Eq. S1). + +20. Supplement lines 100-119: Does the absence of serial dilution being explicitly encoded into the simulation impact the results? Serial dilutions have been explicitly incorporated into mechanistic (Marsland et al., 2020) and phenomenological (Shoemaker et al., 2023) models of community dynamics in an experimental context. Could the authors provide justification of why serial dilution does not need to be explicitly encoded into their simulation? + +We thank the reviewer for this important question. In our previous work (Hu et al. 2022) and other studies in our group, we found that continuous simulation of gLV yields similar qualitative outcomes as simulations incorporating serial dilutions. Specifically, we observed similar dynamical phases in simulations with or without serial dilutions. + +We agree with the reviewer that it is important to show how our results change if we consider a 30- fold daily dilution in our model. We have now added these results to the supplementary materials, demonstrating that the consideration of serial dilution does not change the pattern of invasion outcomes in our simulations. + +<--- Page Split ---> +![](images/Supplementary_Figure_33.jpg) + +
Supplementary Fig. 28. Under serial dilutions in the gLV model, the invasion probability decreases with increasing interaction strength and species pool size, the survival fraction remains approximately equal to the invasion probability. a, Invasion probability decreases with increasing interaction strength and species pool size under serial dilutions. b, The survival fraction is approximately equal to the invasion probability under serial dilutions in the gLV model. The points and color maps depict the mean value over 100 simulations.
+ +21. Supplement lines 109-111: What are the units of time and how do they compare to the timescales of the experiments? Is the timescale of the simulation informed by the timescale of the experiment? + +We thank the reviewer for this important question. The unit of time in the simulation is \(1 / r\) , where \(r\) is the growth rate of species in the gLV model, which is set to be unit 1 in our simulations. We are interested in the steady-state behaviors of invasion rather than the effects of transient dynamics. Our simulation results show that \(t = 10^{3}\) is long enough for the communities to complete their transient dynamics from initial conditions to their final fluctuating or stable state. In the steady-state regime, the results do not vary with the time window. As shown in our previous work, the fraction of fluctuations and survival fraction do not vary with time after reaching the steady state. + +We further demonstrate that invasion probability results remain consistent when introducing the invader at \(t = 2 \times 10^{3}\) compared to \(t = 10^{3}\) . Our experimental communities typically reach steady states by day 6, according to species composition and community biomass time series (Supplementary Fig. 3- 11). We found that stable communities' species compositions usually do not significantly vary after day 4, while fluctuating communities' species compositions continue to fluctuate on days 6 and 10 (Hu et al. 2022). Therefore, both our simulation and experiment characterize invasion behavior under community steady states. + +According to the growth curves of the isolates in our experiments (Supplementary Fig. 19), the characteristic growth rate of the isolates is around 1 \((1 / h)\) . Therefore, each daily dilution cycle approximately corresponds to 24 unit simulation time when the growth rate in the model is set to unit 1. This means that the one cycle timescale is on the order of 100 unit times based on this estimation. We have added a discussion of this point in the supplementary materials to clarify the relationship between the timescales of the simulation and the experiments. + +<--- Page Split ---> +![PLACEHOLDER_38_0] + +
Supplementary Fig. 29. The invasion probability decreases with increasing interaction strength and species pool size across different time windows, with the survival fraction remaining approximately equal to the invasion probability. a, The invasion probability decreases as interaction strength and species pool size increase. b, The survival fraction closely mirrors the invasion probability. To assess whether invader or resident species survived, we identified species whose abundance exceeded the extinction threshold at any point during the last 24 time units of the simulation. This approach yielded invasion probability patterns consistent with those observed in a 100-unit time window. The points and color maps depict the mean value over 100 simulations.
+ +22. Supplement lines 147-148: It's unclear what the CV represents. My understanding is that each CV is calculated over time for each species for a given simulation iteration. Since the dynamics are deterministic and the interaction coefficients are a form of quenched disorder, what random variable is the CV calculated over? Does the distribution of CVs demonstrate a clear bimodality with the \(10^{\wedge}\{-3\}\) cutoff representing the valley between the two peaks? It would help the reader if 1) additional context was provided for the CV and what it represents as well as 2) distributions of simulated CVs plotted to demonstrate the intuition behind classifying communities into stable/fluctuating classes. + +We thank the reviewer for this important comment. The CV represents the coefficient of variation of species abundance. We first calculate the CV of each species' abundance \(N_{i}\) over the time window between \(t = 10^{3} - 100\) and \(t = 10^{3}\) , then pick the maximal one among the species abundance CVs across all species in the community. We then identify the maximum CV among all species in the community. A community is considered fluctuating if this maximum CV exceeds a threshold, as stable communities are characterized by all species abundances that have reached stable states. + +As the reviewer correctly noted, steady- state communities exhibit small maximum CV values for species abundances, while fluctuating communities show relatively large maximum CV values, resulting in a bimodal distribution. The threshold of \(10^{- 3}\) serves as an efficient valley threshold to separate the two peaks. We have added the figure and a detailed discussion in the supplementary materials to clarify this point. + +<--- Page Split ---> +![PLACEHOLDER_39_0] + +
Supplementary Fig. 31. The threshold of \(10^{-3}\) for the maximal CV of species abundance effectively separates fluctuating communities from stable ones, where the maximal CV of species abundance exhibits a bimodal distribution in the simulations. The histogram displays the number of communities with the indicated maximal CV of species abundance at steady state. The dataset was generated from 2000 in silico communities, randomly sampled with \(< \alpha_{ij} > \in [0.02, 1.1]\) and \(S \in [2, 60]\) .
+ +23. Supplement lines 160-163, Fig. S12c, d: Is some degree of correlation expected since biomass was used to calculate the abundance of each species? This seems similar to the case presented in. Garud et al., where the same parameter factors into both sides of the relationship (pg. 16 and 17 of supplement; 2019). Here the authors partitioned synonymous sites into two categories, providing two estimates of the quantities of interest. These two quantities are conditionally independent of the parameter that factors into both sides of the proposed relationship due to the Poisson thinning property. One quantity is then used to calculate the left side of the relationship while the other is used to calculate the right side. Is a similar analysis appropriate in this case given that total biomass factors into both sides of the quantities examined in Fig. S12c, d? + +We appreciate the reviewer's insightful question. We found that the CV of community biomass is an effective indicator for classifying fluctuating and stable communities in our experiment (as shown in panels a and b of the figure below). Additionally, we demonstrate that both the normalized variation of absolute species abundance (the product of total biomass and species relative abundance by sequencing) and the normalized variation of relative species abundance (relative species composition by sequencing) show a significant positive correlation with biomass CV (correlation=0.91, \(\mathrm{p} = 4.67 \times 10^{- 10}\) ; correlation=0.76, \(\mathrm{p} = 1.06 \times 10^{- 5}\) ). As the reviewer noted, the normalized variation of absolute species abundance is indeed coupled with biomass CV because biomass is used in calculating absolute species abundance. However, the normalized variation of relative species abundance, derived from sequencing data, is independent of biomass. + +To further validate our classification approach, we applied the \(K\) - means clustering classification algorithm to biomass CV alone, normalized variation of absolute species abundance versus biomass CV (panel c), and normalized variation of relative species abundance versus biomass CV (panel d). All analyses yielded the same classification outcome for fluctuating and stable communities. We have now added these discussions to the supplementary materials to provide a clearer understanding of our methodology and results. + +<--- Page Split ---> +![PLACEHOLDER_40_0] + + +Supplementary Fig. 12. Classification of fluctuating and stable resident communities in experiment. a, The standard deviation of community biomass over day 4, day 5 and day 6 show that the stability threshold of 0.05 can separate the communities into stable ones (purple points) with small biomass deviation and fluctuating ones (orange points) with relatively large biomass deviation under high nutrient. b, The standard deviation of community biomass under low nutrient are small (all below the stability threshold of 0.05), which were naturally classified into stable communities. c, Similarly, the standard deviation of community biomass over days 3, 4, 5, and 6 under high nutrient conditions confirms that the stability threshold of 0.05 can distinguish between + +<--- Page Split ---> + +stable communities (purple points) with low biomass deviation and fluctuating communities (orange points) with higher biomass deviation. d, Under low nutrient conditions, the standard deviation of community biomass over days 3, 4, 5, and 6 remains below the stability threshold of 0.05, consistently classifying the communities as stable. e, The average coefficient of (temporal) variation for absolute species abundances \((N_{i}\) , computed as the product of total biomass and species relative abundance) exhibit a strong positive correlation with standard deviation of biomass in the experimental communities (correlation \(= 0.91\) , \(p = 4.67 \times 10^{- 10}\) ). \(K\) - means clustering method classifies the points into two clusters where fluctuating communities locate on top right region and stable communities locate on bottom left region. f, The average coefficient of (temporal) variation for relative species abundances \((N_{i}^{*}\) , relative species abundance through 16s sequencing) also exhibits a strong positive correlation with standard deviation of biomass in the experimental communities (correlation \(= 0.76\) , \(p = 1.06 \times 10^{- 5}\) ). \(K\) - means clustering method classifies the communities into stable ones (purple and gray points) and fluctuating ones (orange points). The results suggest that fluctuation in community biomass cooccurs with fluctuation in relative species abundances. + +24. An alternative option could be to examine the relationship between the CV of biomass (OD) and the CV of relative abundances for each ASV, allowing for the identification of community members that disproportionately contribute to the fluctuations in biomass. + +We thank the reviewer for this suggestion. The reason we do not calculate the CV of relative abundance for each ASV is that the read number of low abundance ASVs is small and significantly influenced by limited sequencing depth and variation in amplification efficiency for different sequences. While highly abundant ASVs can reach stable states in some stable communities (as shown in the figure below), low abundance ASVs often display fluctuations due to large noise effects from sampling a small number of reads and other amplification and sequencing noise. Calculating the average CV across all ASVs, including those with small numbers of reads, would amplify the detection variation caused by these small numbers and noise, potentially skewing the classification of community dynamics as fluctuating or stable. To mitigate these issues, we focus on community-level metrics that are less influenced by the noise associated with low abundance ASVs. This approach ensures a more robust classification of community dynamics. + +25. Fig. S2: Is there any phylogenetic structure to these results? Does the placement of a species on the phylogeny relative to the phylogenetic composition of a given community determine species invasibility? + +We thank the reviewer for this insightful question. To study the effect of phylogenetic overlap between invaders and resident species on invasion outcomes, we calculated the overlap fraction of resident species that share the same phylogeny with the invaders across different phylogenetic levels, weighted by the abundance of the resident species. Our analysis revealed a statistically significant positive correlation between this overlap fraction and invasion success, as measured by the final abundance of the invader after colonization. Specifically, invaders that are phylogenetically closer to the resident species tend to achieve higher post-invasion abundances. + +Our interpretation of this positive correlation aligns with our finding that the survival fraction is approximately equal to the invasion probability. A higher fraction of resident species sharing the same phylogeny as the invader indicates that this phylogenetic type is advantageous within the resident community, thereby increasing the likelihood of the invader's survival and success in this environment. We have included these findings on page 9 of the main text and in the supplementary + +<--- Page Split ---> + +materials to provide a more comprehensive understanding of how phylogenetic structure influences invasion outcome: + +Interestingly, invaders that are phylogenetically closer to resident species tend to achieve higher post- invasion abundances (Supplementary Fig. 32). + +![PLACEHOLDER_42_0] + + +Supplementary Fig. 32. Invaders that are phylogenetically closer to resident species tend to achieve higher post- invasion abundances. The overlap fraction of resident species sharing the same phylogeny with invaders shows a statistically significant positive correlation with invader abundance after colonization, across different phylogenetic levels, including phylum, class, order, family, and genus. The overlap fraction at the kingdom level is always 1, as all resident species and invaders in the experiment belong to the same kingdom, Bacteria. + +26. Fig. S12: "The standard deviation of community biomass over day 5, day 6 and day 7" this detail is confusing since the timeseries represented in Fig. 1d ends at day six. What was the rational behind using only these three timepoints? Some justification of using these three timepoints is needed in the Supplement. + +We thank the reviewer for this important comment. We apologize for the typo. The correct sentence should read "The standard deviation of community biomass over day 4, day 5, and day 6," + +<--- Page Split ---> + +consistent with the text in the supplementary materials: "We also calculated the average coefficient of variation (CV) for species abundances from day 4, day 5, to day 6." We aimed to classify the steady- state dynamical behavior of communities and therefore tried to avoid transient dynamics influencing our classification of fluctuation and stability. The reason we chose days 4, 5, and 6 to calculate the CV for classifying fluctuating and stable communities is that some communities had not reached steady- state dynamics before day 3 (as shown in the Fig. 1d, Supplementary Fig. 4- 11, showing transient dynamics occur before day 3). We found that most communities typically reach steady- state by day 4, so we used this as the starting point for calculating the CV of dynamics. + +We further checked that the CV calculated using data from days 3, 4, 5, and 6 alone yields the same classification results, demonstrating that our classification is not sensitive to the choice of time windows. We have added these new results and figures to the supplementary materials. + +![PLACEHOLDER_43_0] + + +Supplementary Fig. 12. Classification of fluctuating and stable resident communities in experiment is robust to choice of time window. a, The standard deviation of community biomass over days 4, 5, and 6 under high nutrient conditions shows that a stability threshold of 0.05 effectively separates the communities into stable (purple points) with low biomass deviation and fluctuating (orange points) with relatively high biomass deviation. b, Under low nutrient conditions, the standard deviation of community biomass over days 4, 5, and 6 is consistently below the stability threshold of 0.05, classifying all communities as stable. c, Similarly, the standard deviation of community biomass over days 3, 4, 5, and 6 under high nutrient conditions + +<--- Page Split ---> + +confirms that the stability threshold of 0.05 can distinguish between stable communities (purple points) with low biomass deviation and fluctuating communities (orange points) with higher biomass deviation. d, Under low nutrient conditions, the standard deviation of community biomass over days 3, 4, 5, and 6 remains below the stability threshold of 0.05, consistently classifying the communities as stable. + +27. Fig. S13: The figure is a useful visualization, but in its current form it is difficult to validate the claims made in the legend. + +- "Invisibility positively correlates with richness when varying interaction strength" Is a claim being made here about the direction in which the correlation changes with a change in interaction strength? It's not clear to me whether this claim is about the existence of positive correlations among treatments or the difference in positive correlations between treatments. + +We thank the reviewer for this comment. When we fixed the species pool size at \(S = 20\) , we found that the data points for \(S = 20\) under low nutrient and high nutrient conditions display a significant positive correlation between invasibility and richness. This finding is consistent with the gLV simulation results shown in Fig. 4a. + +To clarify this point, we have plotted the data in a separate new figure and tested the statistical significance of the positive correlation (correlation coefficient \(= 0.7\) , \(\mathrm{p} = 1.06 \times 10^{- 4}\) ). This approach makes it clearer that the claim is about the existence of positive correlations within treatments rather than differences between treatments. + +- "Invisibility positively correlates with richness when randomly sample \(S = 20\) communities under high nutrient, due to fluctuating communities display larger richness and larger invasion probability." I am having a hard time parsing this statement. Is a claim being made about correlation being higher in high nutrient \(S = 20\) fluctuating communities relative to high nutrient \(S = 20\) stable communities? + +When analyzing the data points under high nutrient conditions with \(S = 20\) , we found a significant positive correlation between invasibility and richness (correlation coefficient \(= 0.5\) , \(\mathrm{p} = 0.047\) ), as shown in the figure below. This positive correlation arises because fluctuating communities (orange points) are more diverse and more invisible than stable communities (purple points). As a result, fluctuating communities are located in the top right region while stable communities are located in the bottom left region of the figure below. + +To clarify this point, we further examined the correlation within stable (purple points) and fluctuating (orange points) communities separately. We confirmed that neither stable nor fluctuating communities displayed a statistically significant correlation between diversity and invasibility ( \(\mathrm{p} = 0.16\) for stable and \(\mathrm{p} = 0.15\) for fluctuating). Therefore, the overall positive correlation when combining the data points is due to the higher invasibility and diversity of fluctuating communities compared to stable ones. We have added a new figure and detailed discussion in the supplementary materials to elucidate this finding. + +- The legend could use some retooling for clarity. Furthermore, if the claims are about the increase in correlation in one treatment vs. another, then additional statistical analyses are necessary. It seems like the authors are making three claims, which would require three tests. The question is what statistical model to use. A full regression analysis to examine the increase in slope between two treatments while controlling for potential cofounders could be seen as necessary. Alternatively, + +<--- Page Split ---> + +the authors could test for the difference between two correlation coefficients using Fisher's Z statistic with a null distribution obtained by permuting community identity for a given pair of treatments (Snedecor & Cochran, 1989). This statistic was recently used to test for the change in correlation coefficients in experimental microbial communities (Eq. 21 in Shoemaker et al., 2023). + +We thank the reviewer for this comment. To clearly clarify our statements, we have added three new figures and performed additional statistical tests to show the following: + +1. Invisibility positively correlates with richness when varying interaction strength: We observe a positive correlation between invasibility and richness for \(\mathrm{S} = 20\) communities under low and high nutrient conditions (correlation coefficient \(= 0.7\) , \(\mathrm{p} = 1.06 \times 10^{-4}\) ). +2. Invisibility positively correlates with richness when randomly sampling \(\mathrm{S} = 20\) communities under high nutrient: This is due to fluctuating communities displaying larger richness and larger invasion probability (correlation coefficient \(= 0.5\) , \(\mathrm{p} = 0.047\) ). +3. Invisibility negatively correlates with richness when increasing species pool size from \(\mathrm{S} = 12\) to \(\mathrm{S} = 20\) under low nutrients: This correlation is statistically significant (correlation coefficient \(= -0.62\) , \(\mathrm{p} = 0.014\) ). + +Additionally, we show that under high nutrient conditions with \(\mathrm{S} = 20\) , neither stable communities (purple points) nor fluctuating communities (orange points) display any statistically significant correlation between diversity and invasibility ( \(\mathrm{p} = 0.16\) for stable and \(\mathrm{p} = 0.15\) for fluctuating). We have revised the legend and added these new analyses and figures to the supplementary materials. + +<--- Page Split ---> +![PLACEHOLDER_46_0] + + +Supplementary Fig. 13. Different invasibility- richness relationships in experiment depending upon how the richness is changed (a). b, Invasibility positively correlates with richness when varying interaction strength under fixed species pool (positive correlation between \(S = 20\) communities under low and high nutrient, correlation is calculated across all data points in panel b, correlation coefficient \(= 0.7\) , \(p = 1.06 \times 10^{- 4}\) ). c, Invasibility positively correlates with richness when randomly sample \(S = 20\) communities under high nutrient, due to fluctuating communities display larger richness and larger invasion probability (correlation is calculated across all data points in panel c, correlation coefficient \(= 0.5\) , \(p = 0.047\) ). Neither stable communities (purple points in panel c) nor fluctuating communities (orange points in panel c) display any statistically significant correlation between diversity and invasibility ( \(p = 0.16\) for stable and \(p = 0.15\) for fluctuating). d, Invasibility negatively correlates with richness when increasing species pool size from \(S = 12\) to \(S = 20\) under low nutrient (correlation is calculated across all data points in panel d, correlation coefficient \(= -0.62\) , \(p = 0.014\) ). + +28. Fig. S15, 16: Some type of statistical test is necessary to establish the claim that invasions lead to changes in community composition. There are multiple ways to accomplish this task and the + +<--- Page Split ---> + +authors may have their own idea. One immediate option strikes me: calculate a paired t- statistic for each community between the control and successfully invaded community, demonstrating that absolute value of the t- statistics is significantly greater than zero. Null distributions could be obtained by permuting control/invade labels of each species within each community. + +We thank the reviewer for the thoughtful suggestions regarding the statistical analysis of invasion effects on community composition. We followed the reviewer's recommendation to calculate the t- statistic for each community by comparing the control and successfully invaded communities, and to compare these values against a Null Distribution obtained by permuting the control/invade labels within each community. Upon conducting this analysis, we observed that the t- statistics for all communities did not show significant differences when compared to the Null Distributions. While this might seem unexpected, it is actually consistent with the underlying assumptions of our experimental and modeling framework. + +The reviewer's suggestion appears to be based on the assumption that invasion would cause significant changes in community composition, implying non- random effects—where the invasion typically has consistent and predictable impacts on the community, whether by increasing diversity, decreasing it, or causing other changes. However, in our study, this assumption does not hold true. Both the invader and resident species were chosen randomly, reflecting the inherent randomness of the ecological network (modeled using a generalized Lotka- Volterra (gLV) model). Given this random selection, the interactions between species are also random. As a result, the impact of an invader on the resident community is not deterministic but rather stochastic—an invader may cause the appearance of new species or lead to the extinction of some existing species. This stochastic nature of species interactions means that the effect of invasion does not necessarily result in a t- statistic that significantly deviates from the Null Distribution. + +In essence, the lack of significant differences between the t- statistic and the Null Distribution in our experimental data aligns with the random nature of species interactions in the gLV model. It suggests that in such a random ecological network, invasions do not consistently lead to systematic changes in community composition that would be detectable as a significant t- statistic. + +We revised the Supplement to clarify the significance of invasion effect: + +To demonstrate that the invasion causes a statistically significant effect on community structure under high nutrient conditions, we performed a one- sample t- test on the invasion effect data shown in Fig. 5d (right panel, under high nutrient conditions). The results indicate that the invasion effect is significantly greater than zero \((\mathrm{p} = 1.11 \times 10^{- 6})\) . The invasion effect is measured as the proportion of change in surviving species before the invasion (on day 6) and after the invasion (on day 12), calculated through: 1 - (number of overlapping species / total number of species). + +29. Fig. S17, S18: Similar to Fig. S15 and S16, but now there are different invader species for each community. The authors could perform a paired t-test for each invader species, pooling observations across communities. A null could be generated for each invader species by permuting control/invade labels within each species within each community. + +We thank the reviewer for the suggestion regarding the analysis of Figures S17 and S18. We followed the reviewer's suggestion and conducted the paired t- tests as recommended. However, similar to the findings in Figures S15 and S16, the results showed no significant differences + +<--- Page Split ---> + +between the t- statistics and the corresponding null distributions for each invader species. This outcome aligns with the inherent stochasticity in our experimental and modeling framework. + +In our study, different invader species were randomly assigned to each community, and the interactions between species within these communities were also random. This randomness reflects the stochastic nature of the ecological networks in our experiment and the generalized Lotka- Volterra (gLV) framework. Consequently, the impact of each invader on the communities varied randomly, without a consistent or predictable pattern of change in community composition. + +The reviewer's suggestion seems to assume that the invasion by different species would lead to systematic and significant changes in community composition across different communities, which would be detectable by the paired t- tests. However, given the random selection and interactions of species in our study, such systematic effects are not expected. The random nature of species interactions means that the effects of different invaders on community composition are likely to be random, leading to t- statistics that do not significantly deviate from the null distributions generated by permuting control/invade labels. + +We revised the Supplement to clarify the significance of invasion effect: + +To demonstrate that the invasion causes a statistically significant effect on community structure under low nutrient conditions, we performed a one- sample t- test on the invasion effect data shown in Fig. 5d (left panel, under low nutrient conditions). The results indicate that the invasion effect is significantly greater than zero ( \(\mathrm{p} = 2.07 \times 10^{- 25}\) ). The invasion effect is measured as the proportion of change in surviving species before the invasion (on day 6) and after the invasion (on day 12), calculated through: 1 - (number of overlapping species / total number of species). + +30. Figs. S15-S18: Is there any relationship between the relative abundance of the invading species and the change in relative abundance of the remaining species between the control/invade treatments? This may not be the most appropriate analysis for compositional data, but you plot the relative abundance of the invading species vs. the mean difference in relative abundance between treatments for the remaining species, do you see a clear relationship? + +We thank the reviewer for the insightful comments and suggestions on our manuscript. We have followed the reviewer's recommendation regarding Supplementary Figures 15- 18 to investigate the relationship between the relative abundance of the invading species and the change in relative abundance of the remaining species between the control/invasion treatments. Specifically, we plotted the relative abundance of the invading species against the mean difference in relative abundance between treatments for the remaining species. We conducted this analysis and found a clear relationship. The results and corresponding plots have been included in the supplementary materials for your review. + +<--- Page Split ---> +![PLACEHOLDER_49_0] + + +Supplementary Fig. 33. The Invasion effect positively correlates with the final abundance of invaders in the invaded communities after colonization. a, Simulating \(S = 32\) communities with gLV shows positive correlations between invasion effect and final invader abundance under various average interaction strengths including \(< \alpha_{ij} > = 0.3\) (correlation coefficient \(= 0.23\) , \(p = 4.3 \times 10^{- 13}\) ), \(< \alpha_{ij} > = 0.6\) (correlation coefficient \(= 0.75\) , \(p = 1.4 \times 10^{- 126}\) ), \(< \alpha_{ij} > = 1.0\) (correlation coefficient \(= 0.55\) , \(p = 2.6 \times 10^{- 25}\) ). \(n = 1000\) simulations for each interaction strength. b, In the experiment, there is a weak positive correlation between the invasion effect and final invader abundance under low nutrient conditions (weak interaction) (correlation coefficient \(= 0.35\) , \(p = 0.013\) , \(n = 51\) ). There is no statistically significant correlation under high nutrient conditions (strong interaction) (correlation coefficient \(= 0.37\) , \(p = 0.23\) , \(n = 12\) ). + +31. Fig. S19-S21: The authors' claims about the lack of correlations appear correct but I think the correlation coefficient should be provided along with the non-significant P-value. Statistical significance can be assessed by permuting x and y vectors. Permutations should be constrained on species identity for Fig. S19. + +We thank the reviewer for this important suggestion. We have followed the reviewer's comment and added the correlation coefficient and non- significant P- value (obtained by permuting x and y vectors, constrained on species identity for Fig. S19) to the supplementary materials: + +The correlation coefficient between invasion probability and invader growth rates is 0.212, p- value \(= 0.584\) under high nutrient; correlation coefficient \(= - 0.334\) , p- value \(= 0.380\) under low nutrient. The correlation coefficient between invasion probability and invader carrying capacities is 0.076, p- value \(= 0.846\) under high nutrient; correlation coefficient \(= - 0.324\) , p- value \(= 0.394\) under low nutrient. + +Supplementary Fig. 20. There is no statistically significant correlation between invasion effect and invader properties. Under high nutrient, invasion effect does not show statistically significant correlation with carrying capacity (a) (correlation coefficient \(= 0.281\) , p- value \(= 0.377\) ) + +<--- Page Split ---> + +and growth rate (b) (correlation coefficient=0.023, p- value=0.944). Under low nutrient, invasion effect does not show statistically significant correlation with carrying capacity (c) (correlation coefficient=0.208, p- value=0.143) and growth rate (d) (correlation coefficient=0.200, p- value=0.160). + +Supplementary Fig. 21. There is no statistically significant correlation between invasion effect and invasion probability. Under high nutrient, invasion effect does not show statistically significant correlation with invasion probability of invaders (a) (correlation coefficient=0.127, p- value=0.694) and invasion probability of resident communities (b) (correlation coefficient=0.105, p- value=0.745). Under low nutrient, invasion effect does not show statistically significant correlation with invasion probability of invaders (c) (correlation coefficient=- 0.086, p- value=0.550) and invasion probability of resident communities (d) (correlation coefficient=318, p- value=276). + +## Minor Comments + +1) Both passive voice and active voice are used throughout the main manuscript and supplement. Consult the journal style guide and use the appropriate voice throughout the manuscript. + +We have revised the manuscript to consistently use the active voice throughout, based on the journal style guide. + +2) Line 76: Should "occupy all available niches and resources" be "occupy all available niches by consuming all resources"? + +We have revised the text to: "occupy all available niches by consuming all resources". + +3) Line 85-86: Given the experiment performed, would be more apt to say that the question is whether the dynamics are stationary with respect to deterministic fluctuations? + +We have revised the text to: "A rarely emphasized property is the residents' dynamics: are the species abundances constant over time, consistent with a stable state, or are they deterministically fluctuating?" + +4) Line 192: Should "effect" be plural? + +We have revised the text to: "effects." + +5) Line 235: Is "niches and resources" redundant here? My understanding that the niche is resource niche in the context of this study. + +We have revised the text to only use "niches" to avoid redundancy. + +6) Lines 304-305: "stronger secondary effect" & "stronger secondary effects" + +We have revised the text to: "stronger secondary effects". + +7) Lines 378-379: Grammar. + +We have revised the text to: "The representative time course of relative species abundance shows that the invader successfully invades and grows in the fluctuating community." + +<--- Page Split ---> + +8) Lines 379-380: "invasion probability to" \(\hat{\mathbf{e}}\) "invasion probability of" + +We have revised the text to: "invasion probability of". + +9) Line 389: "invaders successfully invade" or "an invader successfully invades"? + +We have revised the text to: "an invader successfully invades". + +10) Line 437: "high nutrient" \(\hat{\mathbf{e}}\) "high nutrient conditions" or something similar. + +We have revised the text to: "high nutrient conditions". + +11) Supplement lines 75-76: Please summarize the DADA2 parameters used in your script and make your DADA2 pipeline available in a public code repository. + +We have summarized the DADA2 parameters used in our script and made the DADA2 pipeline available in a public code repository: + +https://github.com/Jiliang-Hu/Collective-dynamical-regimes-predict-invasion + +12) Supplement lines 79-81: Please make your raxml code available in a public repository. + +We have made all code, including the raxml code, available in a public repository: + +https://github.com/Jiliang-Hu/Collective-dynamical-regimes-predict-invasion + +13) Supplement lines 123-125: This sentence reads as if steady state is defined as the state where community properties change with time. Is this supposed to be the case? + +We thank the reviewer for raising this point. We have revised the sentence to: "We define the steady state of simulated communities as the community state in which community properties (e.g., survival fraction, fluctuation fraction, and invasion probability) do not significantly change as time goes on." + +14) Supplement lines 144-145: How is a window of time of 100 units analogous to a timescale of 24 hours in the experiment? Were growth rates in the simulation parameterized to correspond to growth rates in the experiment? + +According to the growth curves of the isolates in our experiments (see figure below), the characteristic growth rate of the isolates is around 1 (1/h). Therefore, each daily dilution cycle approximately corresponds to 24 unit simulation time when the growth rate in the model is unit 1. This means the one cycle timescale is on the order of 100 unit times based on this estimation. We found the results with a time window of 24 units of simulation time are not qualitatively different from the time window of 100 that we chose, demonstrating the robustness of our findings. We have added this discussion to the supplementary materials for clarity. + +<--- Page Split ---> +![PLACEHOLDER_52_0] + + +Supplementary Fig. 29. The invasion probability decreases with increasing interaction strength and species pool size across different time windows, with the survival fraction remaining approximately equal to the invasion probability. a, The invasion probability decreases as interaction strength and species pool size increase. b, The survival fraction closely mirrors the invasion probability. To assess whether invader or resident species survived, we identified species whose abundance exceeded the extinction threshold at any point during the last 24 time units of the simulation. This approach yielded invasion probability patterns consistent with those observed in a 100- unit time window. The points and color maps depict the mean value over 100 simulations. + +15) Supplement lines 167-168: Can you plot the results from varying the choice of time window? We have added figures of the results from varying the choice of time window in the supplementary materials. + +<--- Page Split ---> +![PLACEHOLDER_53_0] + + +Supplementary Fig. 12. Classification of fluctuating and stable resident communities in experiment is robust to choice of time window. a, The standard deviation of community biomass over days 4, 5, and 6 under high nutrient conditions shows that a stability threshold of 0.05 effectively separates the communities into stable (purple points) with low biomass deviation and fluctuating (orange points) with relatively high biomass deviation. b, Under low nutrient conditions, the standard deviation of community biomass over days 4, 5, and 6 is consistently below the stability threshold of 0.05, classifying all communities as stable. c, Similarly, the standard deviation of community biomass over days 3, 4, 5, and 6 under high nutrient conditions confirms that the stability threshold of 0.05 can distinguish between stable communities (purple points) with low biomass deviation and fluctuating communities (orange points) with higher biomass deviation. d, Under low nutrient conditions, the standard deviation of community biomass over days 3, 4, 5, and 6 remains below the stability threshold of 0.05, consistently classifying the communities as stable. + +16) Supplement lines 174: "Algorithm" should be plural. + +We have revised the text to: "algorithms". + +17) Fig S1: Would an alternative color scale help the reader? It does not appear that colors are assigned based on taxonomy. Assigning different shades of a given color to the species belonging to a given phylum may help with visualization (e.g., Firmicutes get different shades of blue, etc.). We have assigned the same type of color to the species that belong to the same phylum to help + +<--- Page Split ---> + +visualize the phylogeny, as suggested. The new color vectors span different shades of colors based on the phylum classification, as requested by the reviewer. Species belonging to the Firmicutes phylum are assigned different shades of blue, Proteobacteria species are assigned different shades of green, Bacteroidota species are assigned different shades of red, Actinobacteriota species are assigned different shades of purple, Cyanobacteria species are assigned different shades of yellow. + +<--- Page Split ---> + +Bacteria-Firmicutes-Bacilli-Lactobacillales-Streptococcaceae-Lactococcus Bacteria-Firmicutes-Bacilli-Lactobacillales-Leuconostocaceae-Leuconostoc Bacteria-Firmicutes-Bacilli-Lactobacillales-Leuconostocaeae-Leuconostoc Bacteria-Firmicutes-Bacilli-Exiguobacteriales-Exiguobacteriaceae-Exiguobacterium Bacteria-Firmicutes-Bacilli-Bacillales-Planococcaceae-Lysinibacillus Bacteria-Firmicutes-Bacilli-Staphylococcales-Staphylococcaceae-Staphylococcus Bacteria-Firmicutes-Bacilli-Bacillales-Bacillaceae-Bacillus Bacteria-Firmicutes-Bacilli-Lactobacillales-Streptococcaceae-Lactococcus Bacteria-Firmicutes-Bacilli-Bacillales-Planococcaceae-NA 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+ +<--- Page Split ---> + +Supplementary Fig. 1. Taxonomic identity of the bacterial isolates. The identities have been inferred from the ASV (Methods) of 16S sequencing, which allow the classification of the 80 isolates down to the genus level. Colors are consistent with those in the main text and other supplementary figures. Species belonging to the Firmicutes phylum are assigned different shades of blue, Proteobacteria species are assigned different shades of green, Bacteroidota species are assigned different shades of red, Actinobacteriota species are assigned different shades of purple, Cyanobacteria species are assigned different shades of yellow. + +18) Figs. S8-S11: Can you plot the extinction threshold as a dashed/dotted horizontal line? + +The current Figs. S8-S11 y-axis starts from the extinction threshold. The bottom boundary of the plot is the extinction threshold. We have clarified this point in the figure caption. + +19) Fig. S12: Consider plotting the cutoff of 0.05 as a horizontal dashed line for reference in subplots a and b and as a vertical dashed line in subplots c and d. + +We have added the cutoff of 0.05 in the figures as a horizontal dashed line in subplots a and b, and as a vertical dashed line in subplots c and d, to help illustrate the classification boundary. + +20) Fig. S14: How were priority effects quantified? What does the y-axis of the priority effect plot represent? + +The priority effect in Fig. S14 follows the same definition of the priority effect in the main text, which is quantified by calculating the difference between the survival fraction of resident species and the invasion probability of species that invade after the resident communities have assembled, where the difference was normalized by the survival fraction. The priority effect is defined as: (survival fraction – invasion probability)/(survival fraction). We have added this definition in the caption of the figure. + +## References + +Cornish- Bowden, A. (2012). Fundamentals of enzyme kinetics (4th, completely revised and greatly enlarged edition ed.). Wiley- Blackwell. + +Garud, N. R., Good, B. H., Hallatschek, O., & Pollard, K. S. (2019). Evolutionary dynamics of bacteria in the gut microbiome within and across hosts. PLOS Biology, 17(1), e3000102. https://doi.org/10.1371/journal.pbio.3000102 + +Houtsma, P. C., Kant- Muermans, M. L., Rombouts, F. M., & Zwietering, M. H. (1996). Model for the combined effects of temperature, pH, and sodium lactate on growth rates of Listeria innocua in broth and Bologna- type sausages. Applied and Environmental Microbiology, 62(5), 1616–1622. Marsland, R., Cui, W., Goldford, J., & Mehta, P. (2020). The Community Simulator: A Python package for microbial ecology. PLOS ONE, 15(3), e0230430. https://doi.org/10.1371/journal.pone.0230430 + +Shoemaker, W. R., Sánchez, Á., & Grilli, J. (2023). Macroecological laws in experimental microbial systems (p. 2023.07.24.550281). bioRxiv. https://doi.org/10.1101/2023.07.24.550281 Snedecor, G. W., & Cochran, W. G. (1989). Statistical methods (8th ed). Iowa State University Press. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +In this manuscript, Hu et al. aim to identify characteristics of microbial communities that determine their invasibility. They first carried out experimental invasions with assembled communities, finding that more diverse communities are more invasive. To further explore this positive invasibility- diversity relationship, a Lotka- Volterra model was used to predict the effect of changing interspecies interaction strength and species pool size on invasibility. This showed that decreasing interaction strength and pool size increased invasibility. This was confirmed experimentally by changing the concentration of glucose and urea to tune interaction strength, and by changing species pool size. These three key determinants of invasibility (interaction strength, pool size, dynamical regime) determine the survival fraction, defined as the fraction of the initial species pool that survives the assembly process. The survival fraction correlates positively with community invasibility, serving as a unifying predictor. They find that under strong interaction strength, the invasion probability is lower than the survival fraction, indicating a priority effect. The strength of interactions is also shown to determine the impact of invasion on the resident community. Finally, the properties of invaders were briefly discussed. + +I see this as a valuable and novel contribution to the field. While the long- standing biotic resistance hypothesis predicts that more diverse communities should be less invasive due to niche filling, empirical evidence for this is mixed. By considering how diversity is achieved, the authors show that invasibility can be predicted from community features, which has not been done previously. A particular strength of the manuscript is the integration of modelling and experiments to gain mechanistic insight into relationships observed experimentally. + +I have two major comments regarding the tuning of interspecies interactions and determining the impact of invasion. In both cases, limitations of the findings of the manuscript need to be made more explicit. + +The authors state that increasing interaction strength decreases invasion probability. This is done experimentally by increasing the strength of competitive interactions. However, previous work (ref 30) has demonstrated that the type of interaction between the invader/residents, or between residents, impacts the invasion outcome. For example, positive interactions (e.g. facilitation) between the invader and resident community increases invasion probability (as posited by the diversity begets diversity hypothesis). Increasing interaction strength in this case could increase community invasibility, which is a possibility not considered by this study. While I recognize that experimental manipulation of interaction strength is difficult, I would recommend running the model with a distribution of interactions that considers positive interactions, to show the generality of their conclusions. If this has already been done (this is not clear) this should be included in the supplement. + +We thank the reviewer for this insightful comment. We agree that stronger facilitative interactions between invaders and resident species can increase invasion probability. Our pair- wise coculture experiments show that competitive interactions dominate in our experiment, so our modeling has primarily focused on competitive interactions. + +To address the reviewer's suggestion, we have extended our model to include a distribution of interactions that consider both positive and negative interactions. We found that the invasion probability displays similar qualitative patterns with species pool size, interaction strength, and + +<--- Page Split ---> + +dynamical regimes. Specifically, we observed that invasion probability decreases with increasing species pool size and interaction strength. + +These new results demonstrate that our conclusions are robust across different interaction regimes. We have included these results and the corresponding discussion in the supplementary material. To make this point clear, we now clarify on page 5 of the main text when we introduce the simulation setup: + +We simulated the dynamics of communities with different species pool sizes \(S\) and competitive interaction matrices because competition is the dominant interaction type in our experiments (Hu et al. 2022). + +![PLACEHOLDER_58_0] + + +Supplementary Fig. 30. The invasion probability decreases with interaction strength and species pool size in presence of positive interactions. To test whether the existence of positive (facilitative) interactions in the ecological network could change our conclusions, we sampled values of \(\alpha_{ij}\) from a uniform distribution \([- \alpha_0, \alpha_0]\) , where \(\alpha_0\) varies between [0, 1.4] on the phase diagram. The invasion probability decreases with interaction strength and species pool size, analogous to those exhibited by communities with exclusively negative interactions (Fig. 2f). Note that the strength of interactions coincides with \(\mathrm{Std}(\alpha_{ij})\) in this case, since the mean of \(\alpha_{ij}\) is zero (both moments factor into the interaction strength metric \(\mathrm{std}(\alpha_{ij}) / (1 - < \alpha_{ij} > )\) that determines stability (Allesina and Tang 2012)). In these simulations, the linear interaction function in the gLV \((\alpha_{ij}N_j)\) was replaced with Monod function \((\alpha_{ij}N_j / (N_j + 1))\) to avoid unbounded growth due to positive interactions (Qian and Akçay 2020; Bunin 2017). The points and color maps depict the mean value over 100 simulations. + +This new supplementary Fig. 30 is now referenced in the main text on page 5 as follows: + +"In addition, we found that neither serial dilutions nor the existence of positive (facilitative) interspecies interactions qualitatively affects this result (Supplementary Fig. 28- 30)." + +The limitations of the study in determining the impact of successful invasions on the structure of the resident community should be more explicit. The impact of successful invasions on the + +<--- Page Split ---> + +structure of the resident community was measured experimentally by the fold change in biomass, and the invasion effect on the community using 16s sequencing data. However, the fold change in biomass provides little insight on invasion impact. It is not possible to distinguish between the change in biomass of the resident community, and the increase in biomass of the successful invader. Thus, a lower change in biomass in the low nutrient regime may be due to the fact that the invader has less nutrients to grow on, and the converse for the high nutrient regime. Moreover, while species abundance data shows a statistically significant difference in community composition in the higher nutrient regime, it is important that the authors provide information about the effect size. For example, as a \(95\%\) confidence interval for the difference between the invasion success under high nutrient conditions and the invasion success under low nutrient conditions. Finally, it is hard to conclude what the actual effect of invasion is using the selected measures. For example, though species composition may have changed, the invader could be functionally redundant with the species that were excluded, resulting in no change to community functioning. While a comprehensive assessment of invasion impact is out of the scope of this paper, I would recommend for these limitations to be discussed explicitly in the manuscript. + +We thank the reviewer for raising these important points. We agree that the fold change of biomass increases more under high nutrients than low nutrients, which might be due to the more available resources for the invader under high nutrients. However, the reason we found this increase to be noteworthy is for several reasons: + +1. Community and species biomass variability: We found that communities and single species can display both high and low total biomass under high nutrients (Supplementary Figs. 4-5, Fig. 19), indicating that species in the community may or may not grow to high biomass even under high nutrient supply. Interestingly, we did not observe any invader successfully invading those high biomass communities (OD \(>0.4\) ). Invaders only succeeded in invading low biomass communities (OD \(< 0.4\) ), increasing the community biomass after successful invasions under high nutrients (Figs. S4-S5). + +2. Lack of correlation with invader growth: We found no statistically significant correlation between invasion probability and the growth rate or carrying capacity of invaders (Supplementary Fig. 19). This indicates that high biomass invaders under high nutrients are not necessarily the most successful invaders, suggesting that the increase in total biomass after invasion under high nutrients may not be solely due to invader growth. + +However, we acknowledge that the comparison of the fold change of biomass between two different nutrient regimes may not be highly informative and could confuse the reader. We have therefore added comments on this limitation in the manuscript. + +To better demonstrate the invasion effect on community composition, we have followed the reviewer's suggestion and calculated the effect size and the \(95\%\) confidence interval for the difference in invasion success under high nutrient conditions versus low nutrient conditions. These results are now included on page 8 of the main text: + +The effect size on community composition caused by increasing from low nutrient (weak interaction) to high nutrient (strong interaction) conditions is 0.14, with a \(95\%\) confidence interval of [0.021, 0.259]. + +<--- Page Split ---> + +We agree that though species composition may have changed, the invader could be functionally redundant with the species that were excluded, resulting in no change to community functioning. We have added a discussion in the manuscript acknowledging that our definition of invasion effect in this work is limited to the impact on total biomass and community composition. We do not study the invasion effect on community function and cannot rule out the possibility that the community remains functionally unchanged due to functional redundancy between the invader and resident species replaced by the invader. + +We added a comment in the conclusion part on page 10 of the main text to discuss this important limitation: + +Our definition of the invasion effect in this work focuses on the impact on total biomass and community composition. We do not study the invasion effect on community function and cannot rule out the possibility that the community remains functionally unchanged due to functional redundancy between the invader and resident species replaced by the invader. Future research needs to include analysis of functional traits and ecosystem processes to fully understand the functional impact of invasions. + +Minor points: + +1) - I strongly recommend including explicit definitions of key terms, which would improve clarity of the manuscript. For example, the definition of community diversity as the number of species that survive the assembly process is not made explicit in line 152. What 'rich dynamics' (line 191) or richness (line 195, 222 and others) refers to is also unclear to me. + +We thank the reviewer for this comment. We have now explicitly clarified the definitions of key terms, including "diversity," "richness," and "rich dynamics," in the manuscript to improve clarity. We revised the text on page 4 of the main text: + +our experimental results display a significant \((p = 0.036)\) positive correlation between invasion probability and community diversity, where the diversity is defined as the number of species that survive the assembly process over 6 days (correlation coefficient \(= 0.51\) , Fig. 1c). + +We revised the text on page 5 of the main text to clarify the term "richness": + +we found a positive correlation between invasion probability and richness (the number of resident species coexisting before invasion) + +We replaced "rich dynamics and invasion outcomes" with "various dynamics and invasion outcomes" on page 5 of the main text to make it clear. In this sentence, we want to express that we observed various behaviors including invasion success or failure in communities with stable or fluctuating dynamics. + +Our simulations revealed a wide range of dynamics and invasion outcomes under strong interaction strength between species (Fig. 2a, Supplementary Fig. 31). + +2) - The findings of this study could be embedded more explicitly into existing concepts in invasion ecology, which is dominated by niche theory and resource competition. For example, in lines 175-176 the authors state that fluctuating communities are more invisible. The basis of this relationship is not made clear to the reader - I assumed that this means more niches are open at any given point + +<--- Page Split ---> + +in time. Moreover, why strong interspecies interactions and a larger species pool decrease invasibility is not discussed. It would also be helpful to discuss this more in the conclusion. + +We thank the reviewer for raising this point. We have added more discussion and citations to clarify the basis of the relationship between community fluctuation and increased invasibility, interpreting that fluctuating communities can create more temporal niches for invader species. There are two reasons we did not make a strong statement on this point: 1) It might need further experiment and study, such as temporal metabolome screening, are required to clearly illustrate the mechanism of higher invasibility in fluctuating communities due to time- varying niches, resources, and available metabolites. While this is beyond the scope of this work, it is an interesting direction for our future research. 2) there is some debate in the literature on the explanatory power of the niche concept in predicting invasion outcomes. Even species that have already occupied a niche can be invaded and outcompeted by another species that consumes the resource more efficiently. Therefore, the absence of available niches may not necessarily lead to failed invasions, as invaders can encroach on currently occupied niches. + +We have added a discussion of these points in the manuscript, as recommended by the reviewer. Regarding the observation that invasion probability decreases with species pool size and interaction strength, we have added more discussion in the conclusion section of the manuscript. In the generalized Lotka- Volterra (gLV) framework, interactions can be mathematically expressed in terms of niche overlap and resource competition, similar to the linear resource- consumer model. Therefore, stronger interaction strength corresponds to larger niche overlap and greater resource consumption. Similarly, a larger species pool leads to increased total interaction (more niche overlap) between community species and invader species, thereby inhibiting invasion more strongly. We have included these discussions and cited relevant literature in the conclusion, as recommended by the reviewer. + +We revised the main text on page 4 and 5 to relate our results to the framework of niche theory and resource consumption in invasion ecology: + +Our experimental tests of invasion demonstrate that, for fixed species pool size and species interaction strength regime (nutrient concentrations), more diverse communities are more invisible because fluctuating communities are both more diverse and more susceptible to invasion. However, when species pool size or nutrient concentration is varied, this relationship does not always hold (Fig. 2 and 3). This increased invasibility under fluctuation can be interpreted through the lens of niche theory, where fluctuating communities create fluctuating niche availability for invader species (Li and Stevens 2012). Temporal fluctuations in resource availability and environmental conditions allow invaders to exploit niches that may not be consistently available in stable communities (Li and Stevens 2012; Warner and Chesson 1985; Levin and Paine 1974). + +We add a discussion on page 5 of the main text on why strong interspecies interactions and a larger species pool decrease invasibility is not discussed: + +In the generalized Lotka- Volterra (gLV) framework, interactions can be mathematically expressed in terms of niche overlap and resource competition (Dalmedigos and Bunin 2020). Stronger interaction strength corresponds to larger niche overlap and greater resource consumption, making it harder for invaders to establish. Similarly, a larger species pool increases the total interaction (more niche overlap) between community species and invader species, thereby inhibiting invasion more strongly (Dalmedigos and Bunin 2020). + +<--- Page Split ---> + +3) - I think that for those unfamiliar with previous work from this group, how interaction strength, species pool size and dynamical regime combine to determine survival fraction is difficult to understand. More explanation about how these features interface is necessary for clarity of the manuscript, since they are not independent. For example, it is not immediately clear why there are stable/fluctuating regimes for communities under high nutrient conditions, and not for low nutrient conditions + +We appreciate this important point raised by the reviewer and agree it is crucial to introduce how species pool size, interaction strength, and collective dynamical regimes combine to determine survival fraction. We have added a discussion on this point in the manuscript to provide more clarity. + +We add a discussion on page 9 of the main text to clarify this point: + +Our previous findings indicate that, on average, increasing species pool size and interaction strength both decrease the overall survival fraction(Hu et al. 2022). We also observed that increasing species pool size and interaction strength led to the emergence of some fluctuating communities(Hu et al. 2022). These fluctuating communities, despite the general trend, exhibit a higher survival fraction compared to stable communities assembled from the same species pool size and nutrient concentrations (interaction strength)(Hu et al. 2022). This suggests that while stronger interactions and larger species pools typically reduce survival, the dynamic nature of fluctuating communities allows them to maintain higher survival fractions. + +We added text in the discussion and results part of the main text on page 6: + +We only observed stable communities under low nutrients (weak interaction) because fluctuation only emerges when species pool size and interaction strength are large enough to cross the stability boundary (Hu et al. 2022). + +We also more clearly introduced our previous work in the introduction part on page 3: + +As species pool size and strength of interactions increase, we found that microbial ecosystems transition between three distinct dynamical phases, from a stable equilibrium in which all species coexist to partial coexistence to the emergence of persistent fluctuations in species abundances (Hu et al. 2022). + +4) - The measure of dispersion used is not included in the text of the manuscript (i.e., on line 148, 153, 154, 172 and more, parameter estimates are given as mean +/- X, where X is a measure of dispersion, but which measure it is is not defined). Defining the measure of dispersion is crucial to allow for interpretation of the findings. Some figure legends mention that error bars represent the standard error of the mean, which I assume is the measure used by the authors, but this should be clearly stated in the text of the manuscript. + +We thank the reviewer for pointing this out. We used the standard error of the mean (SEM) as the measure of dispersion across the manuscript. We now state this point clearly in the manuscript where the measure of dispersion appears for the first time. + +We revised the main text on page 4 to clarify the use of SEM as the measure of dispersion: + +Throughout the manuscript, we used the standard error of the mean (SEM) as the measure of dispersion. + +<--- Page Split ---> + +5) - State how invaders were chosen (line 146) - I assume they were chosen at random? + +Yes, the invader species and resident species were both randomly chosen to study the invasion outcome from the perspective of the random ensemble. We have clarified this point in the manuscript. + +We revised the text on page 4 of the main text: + +For each resident community, we performed 7- 9 independent invasion tests with different randomly chosen invader species on day 6 + +6) - In the section discussing the model (lines 178-190), explicitly state at what relative abundance the invader is introduced relative to the community + +We followed the reviewer's suggestion and explicitly stated that the dispersal rate \(D = 10^{- 5}\) in the simulations, which is the same as in the experiment. + +We revised the text on page 5 of the main text: + +\(D\) is the dispersal rate, which is set to \(D = 10^{- 5}\) + +7) - In the representative time series of fig 2a, invasions are shown to cause a weak effect on the community when the invader grows to a low abundance relative to the rest of the community, whereas the invader causes a strong effect when it grows to high abundance. Is this true across other simulations, or in experiments? If this is the case, it would suggest that there is another factor that influences invasion effect aside from interaction strength. + +We thank the reviewer for this question. In the simulation and experiment, we did observe that there are many cases where the invader grows to high abundance while leading to a weak effect on the community structure, and also cases where the invader grows to low abundance while causing a strong effect on the community structure. To systematically study the dependence of invader abundance on the invasion effect, we analyzed the experimental data and performed simulations. We found a statistically significant weak positive correlation between final invader abundance and invasion effect on community structure under various average interaction strengths (figure below). Furthermore, we also found a statistically significant weak positive correlation between final invader abundance and invasion effect in the experiment under low nutrient conditions (weak interaction), while no statistically significant correlation under high nutrient conditions (strong interaction) in the experiment (figure below). + +We added these results in the supplementary materials and referred to the results in the main text on page 8: + +We also observed a weak positive correlation between the invasion effect and the final abundance of invaders in the experiment and simulation (Supplementary Fig. 33). + +<--- Page Split ---> +![PLACEHOLDER_64_0] + +
Supplementary Fig. 33. The Invasion effect positively correlates with the final abundance of invaders in the invaded communities after colonization. a, Simulating \(S = 32\) communities with gLV shows positive correlations between invasion effect and final invader abundance under various average interaction strengths including \(< \alpha_{ij} > = 0.3\) (correlation coefficient \(= 0.23\) , \(\mathrm{p} = 4.3 \times 10^{- 13}\) , \(< \alpha_{ij} > = 0.6\) (correlation coefficient \(= 0.75\) , \(\mathrm{p} = 1.4 \times 10^{- 126}\) ), \(< \alpha_{ij} > = 1.0\) (correlation coefficient \(= 0.55\) , \(\mathrm{p} = 2.6 \times 10^{- 25}\) ). \(\mathrm{n} = 1000\) simulations for each interaction strength. b, In the experiment, there is a weak positive correlation between the invasion effect and final invader abundance under low nutrient conditions (weak interaction) (correlation coefficient \(= 0.35\) , \(\mathrm{p} = 0.013\) , \(\mathrm{n} = 51\) ). There is no statistically significant correlation under high nutrient conditions (strong interaction) (correlation coefficient \(= 0.37\) , \(\mathrm{p} = 0.23\) , \(\mathrm{n} = 12\) ).
+ +8) - I would include (strong interaction) or (weak interaction) every time high/low nutrient conditions are mentioned for clarity. This is missing now in line 240 and others + +We thank the reviewer for this suggestion. We have revised the manuscript to use "high nutrient (strong interaction)" and "low nutrient (weak interaction)" throughout to provide clarity. + +9) - Remove "while resident community .... determining invasion outcome" from line 322-323. Invader properties have not been sufficiently explored in this manuscript to claim they don't play an important role in determining invasion outcome. + +We thank the reviewer for raising this point. Although we found no statistically significant correlation between the invasion probability of invaders and the growth rate/carrying capacity of invaders in our experiments (Supplementary Fig. 19), we agree that the invader properties affecting invasion outcomes have not been sufficiently explored in this work. We have therefore deleted the sentence as recommended by the reviewer. + +<--- Page Split ---> + +## Reference + +Allesina, Stefano, and Si Tang. 2012. “Stability Criteria for Complex Ecosystems.” Nature. https://doi.org/10.1038/nature10832. Altieri, Ada, Felix Roy, Chiara Cammarota, and Giulio Biroli. 2021. “Properties of Equilibria and Glassy Phases of the Random Lotka- Volterra Model with Demographic Noise.” Physical Review Letters. https://doi.org/10.1103/PhysRevLett.126.258301. Bunin, Guy. 2017. “Ecological Communities with Lotka- Volterra Dynamics.” Physical Review E 95 (4): 042414. https://doi.org/10.1103/PhysRevE.95.042414. Case, T. J. 1990. “Invasion Resistance Arises in Strongly Interacting Species- Rich Model Competition Communities.” Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.87.24.9610. Dalmedigos, Itay, and Guy Bunin. 2020. “Dynamical Persistence in High- Diversity Resource- Consumer Communities.” PLoS Computational Biology. https://doi.org/10.1371/journal.pcbi.1008189. Debray, Reena, Robin A. Herbert, Alexander L. Jaffe, Alexander Crits- Christoph, Mary E. Power, and Britt Koskella. 2022. “Priority Effects in Microbiome Assembly.” Nature Reviews Microbiology. https://doi.org/10.1038/s41579- 021- 00604- w. Estrela, Sylvie, Jean C.C. Vila, Nanxi Lu, Djordje Bajic, Maria Rebolleda- Gomez, Chang Yu Chang, Joshua E. Goldford, Alicia Sanchez- Gorostiaga, and Alvaro Sanchez. 2022. “Functional Attractors in Microbial Community Assembly.” Cell Systems. https://doi.org/10.1016/j.cells.2021.09.011. Fried, Yael, Nadav M. Shnerb, and David A. Kessler. 2017. “Alternative Steady States in Ecological Networks.” Physical Review E. https://doi.org/10.1103/PhysRevE.96.012412. Handel, S. N. 2014. “Dispersal Ecology and Evolution.” Ecological Restoration. https://doi.org/10.3368/er.32.4.464. Hu, Jiliang, Daniel R. Amor, Matthieu Barbier, Guy Bunin, and Jeff Gore. 2022. “Emergent Phases of Ecological Diversity and Dynamics Mapped in Microcosms.” Science. https://doi.org/10.1126/science.abm7841. Kessler, David A., and Nadav M. Shnerb. 2015. “Generalized Model of Island Biodiversity.” Physical Review E - Statistical, Nonlinear, and Soft Matter Physics. https://doi.org/10.1103/PhysRevE.91.042705. Levin, S. A., and R. T. Paine. 1974. “Disturbance, Patch Formation, and Community Structure.” Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.71.7.2744. Li, Wei, and M. Henry H. Stevens. 2012. “Fluctuating Resource Availability Increases Invasibility in Microbial Microcosms.” Oikos. https://doi.org/10.1111/j.1600- 0706.2011.19762. x. Pearce, Michael T., Atish Agarwala, Atish Agarwala, and Daniel S. Fisher. 2020. “Stabilization + +<--- Page Split ---> + +of Extensive Fine- Scale Diversity by Ecologically Driven Spatiotemporal Chaos." Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.1915313117. + +Qian, Jimmy J., and Erol Akçay. 2020. "The Balance of Interaction Types Determines the Assembly and Stability of Ecological Communities." Nature Ecology and Evolution. https://doi.org/10.1038/s41559- 020- 1121- x. + +Ratzke, Christoph, Julien Barrere, and Jeff Gore. 2020. "Strength of Species Interactions Determines Biodiversity and Stability in Microbial Communities." Nature Ecology and Evolution. https://doi.org/10.1038/s41559- 020- 1099- 4. + +Ratzke, Christoph, Jonas Denk, and Jeff Gore. 2018. "Ecological Suicide in Microbes." Nature Ecology and Evolution. https://doi.org/10.1038/s41559- 018- 0535- 1. + +Shoemaker, William R, Álvaro Sánchez, and Jacopo Grilli. 2023. "Macroecological Laws in Experimental Microbial Communities." BioRxiv. + +Sprockett, Daniel, Tadashi Fukami, and David A. Relman. 2018. "Role of Priority Effects in the Early- Life Assembly of the Gut Microbiota." Nature Reviews Gastroenterology and Hepatology. https://doi.org/10.1038/nrgastro.2017.173. + +Warner, R. R., and P. L. Chesson. 1985. "Coexistence Mediated by Recruitment Fluctuations: A Field Guide to the Storage Effect." American Naturalist. https://doi.org/10.1086/284379. + +<--- Page Split ---> + +Reviewer #1: + +Remarks to the Author: + +The authors have addressed all my concerns, and added useful new analyses and discussions that clarify the manuscript and the modeling choices they made. I have no more concerns that would need to be resolved before publication. + +We thank the reviewer for the encouraging feedback on our manuscript and for the valuable suggestions provided during the revision process. + +As an extremely minor point, I found the spread of the points in Fig. 5c and d to be a bit large, to the point where my eye didn't immediately parse the two clouds as separate categories - but that's presumably a matter of taste. + +We have retained the original spread of the points in Fig. 5c and d, as reducing it would increase overlap among low nutrient data points (gray ones), making them harder to distinguish. We used different colors for data points under low and high nutrient conditions to help readers differentiate the two clusters more clearly. + +Remarks on code availability: + +No readme files, but the data looks complete. Both the sequencing data analysis code and the simulation code is clear and well- documented. I did not attempt to run the code, but as far as I can tell, the provided code only gives the backbone of the simulations and does not include code needed to reproduce the figures directly. + +We have added detailed README files on GitHub to assist readers in understanding and running the code. + +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +Reviewer #2: Remarks to the Author: Review #2 + +This is an impressive revision, and the quality reflects a high level of effort from the authors. The authors addressed all my comments and gave thoughtful, much appreciated answers. I believe the manuscript should be published. + +<--- Page Split ---> + +We thank the reviewer for the encouraging feedback on our manuscript and for the valuable suggestions that contributed to the revision process. + +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. + +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. + +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +We have added file extensions to ensure compatibility, allowing readers to run the code directly in MATLAB. Additionally, we have included a detailed README file on GitHub to assist readers with setup, required packages, and instructions on how to run the code, as well as a link to the Dryad repository. The function LV_compute_invasion is defined within LV_Invade.m, so no additional files are needed. + +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +The Dryad repository looks good. + +Below are some minor comments that do not require a response. + +- The discussion of how pH mediated interactions can shape the strength of interaction in gLV is helpful. In general, I think a derivation of pH mediated interactions from the starting point of a consumer-resource model is needed, even if it's just for pedagogical reasons and all the heavy modeling is ultimately done using gLV, but such modeling efforts lie outside the scope of the paper. All-in-all the additions to the supplement make it a valuable resource. + +- The elaboration on the connection to ergodicity in response to R1 was very helpful. + +- The new color scheme should aid readers. + +- "In our group, we have been investigating the dependence of community diversity and dynamics on resource concentration across various consumer-resource models (e.g., linear growth or Monod growth)." Very much looking forward to reading this. + +<--- Page Split ---> + +- The added analyses for the survival threshold are rigorous. The sequencing depth justification is particularly useful since my group has encountered studies where the order of magnitude of demographic manipulations is not justified given the depth of sampling (i.e., # reads). + +Remarks on code availability: + +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. + +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. + +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +I was unable to run the code as- is. + +We have added file extensions to ensure compatibility, allowing readers to run the code directly in MATLAB. Additionally, we have included a detailed README file on GitHub to assist readers with setup, required packages, and instructions on how to run the code, as well as a link to the Dryad repository. The function LV_compute_invasion is defined within LV_Invade.m, so no additional files are needed. + +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +Reviewer #3: + +Remarks to the Author: + +I would like to thank the authors for their thorough revision of this manuscript. All my concerns have been addressed and I have no further comments. + +We thank the reviewer for their positive feedback and thoughtful suggestions, which were instrumental in improving our manuscript through the revision process. + +Remarks on code availability: + +The code is usable but needs a README file for further clarity. + +We have added detailed README files on GitHub to assist readers in understanding and running the code. + +<--- Page Split ---> + +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +<--- Page Split ---> diff --git a/peer_reviews/144ec508aea22ca35925a350bcae1059143047006ce8602195d0a58feaa8e6c2/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/144ec508aea22ca35925a350bcae1059143047006ce8602195d0a58feaa8e6c2/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..3e828f5f1516574511292bd683875ff24d35b407 --- /dev/null +++ b/peer_reviews/144ec508aea22ca35925a350bcae1059143047006ce8602195d0a58feaa8e6c2/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,1876 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 288, 79]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[73, 95, 290, 118]]<|/det|> +# Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 157, 870, 205]]<|/det|> +# Collective dynamical regimes predict invasion success and impacts in microbial communities + +<|ref|>text<|/ref|><|det|>[[72, 219, 434, 235]]<|/det|> +Corresponding Author: Professor Jeff Gore + +<|ref|>text<|/ref|><|det|>[[72, 268, 142, 281]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[72, 294, 179, 307]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 319, 177, 332]]<|/det|> +17th April 2024 + +<|ref|>text<|/ref|><|det|>[[72, 344, 840, 358]]<|/det|> +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +<|ref|>text<|/ref|><|det|>[[72, 369, 214, 382]]<|/det|> +Dear Professor Gore, + +<|ref|>text<|/ref|><|det|>[[72, 394, 923, 458]]<|/det|> +Thank you for your patience while your Article "Collective dynamical regimes predict invasion success and impacts in microbial communities" was under review. We have now received three reports. As you will see from the comments copied below, the reviewers find your work of considerable potential interest but have raised quite substantial concerns. In light of these comments, we cannot accept the manuscript for publication but would be very interested in considering a revised version that addresses these concerns. + +<|ref|>text<|/ref|><|det|>[[71, 469, 925, 548]]<|/det|> +We hope you will find the reviewers' comments useful as you decide how to proceed. Please bear in mind that we will be reluctant to approach the reviewers again in the absence of major revisions. In particular, while we do not expect additional experimental work, addressing the concerns raised to the reviewers' satisfactions will likely require additional modelling work, as well as further information on the methodology. Regarding the latter, if you are concerned about space limitations in the main manuscript file, feel free to use the supplementary files to provide all the information required by the reviewers (with clear guidance as to where find a specific piece of information). + +<|ref|>text<|/ref|><|det|>[[70, 559, 920, 586]]<|/det|> +If you choose to revise your manuscript taking into account all reviewer and editor comments, please highlight all changes in the manuscript text file, preferably in Microsoft Word format. + +<|ref|>text<|/ref|><|det|>[[70, 596, 884, 624]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Please do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[72, 635, 251, 648]]<|/det|> +If revising your manuscript: + +<|ref|>text<|/ref|><|det|>[[72, 660, 912, 699]]<|/det|> +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the referees along with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[70, 710, 900, 737]]<|/det|> +\* If you have not done so already we suggest that you begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecove/ino/final- submission. Refer also to any guidelines provided in this letter. + +<|ref|>text<|/ref|><|det|>[[70, 748, 920, 774]]<|/det|> +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +<|ref|>text<|/ref|><|det|>[[72, 785, 420, 799]]<|/det|> +Please use the link below to submit a revised paper: + +<|ref|>text<|/ref|><|det|>[[72, 811, 171, 824]]<|/det|> +Link Redacted + +<|ref|>text<|/ref|><|det|>[[70, 836, 920, 862]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[70, 873, 925, 912]]<|/det|> +If you wish to submit a suitably revised manuscript we would hope to receive it within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[70, 923, 910, 938]]<|/det|> +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 917, 120]]<|/det|> +now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[72, 133, 843, 148]]<|/det|> +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +<|ref|>text<|/ref|><|det|>[[73, 160, 404, 174]]<|/det|> +Thank you for the opportunity to review your work. + +<|ref|>text<|/ref|><|det|>[[72, 186, 140, 200]]<|/det|> +[redacted] + +<|ref|>text<|/ref|><|det|>[[72, 236, 225, 250]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[73, 261, 323, 275]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 287, 923, 364]]<|/det|> +In this manuscript, Hu et al. combine experiments and theory to elucidate the factors determining community invasions. They find that while diversity- invasibility relationships can be both positive and negative depending on the factors regulating diversity, the fraction of surviving species directly predicts invasibility. This manuscript leverages their recent insights on the dynamical phases of microbial ecosystems to provide a timely and relevant exploration of invasions. The results are interesting and the research is carried out soundly. My comments are primarily aimed at making the manuscript easier to follow. + +<|ref|>text<|/ref|><|det|>[[71, 374, 923, 503]]<|/det|> +My first main comment concerns the exposition of the different diversity- invasibility relationships between Fig. 1 and Fig. 2/3, which on a first read was not immediately obvious. In Fig 1, more species and higher interaction strength makes for fluctuations and greater diversity, and fluctuating communities are more likely to be invaded; but both theory and Fig. 3 show a negative correlation between invasion probability and pool size/interaction strength. I naively expected increased pool size and stronger interactions to translate to a higher change of fluctuations (as in their recent paper), and thus greater richness and higher invasion probability. It is later revealed where this apparent contradiction comes from, but I believe it would be immensely helpful if this contradiction was highlighted early on. This issue is made more severe by the use of three different terms to describe the probability of successful invasions (invasion probability and invasion resistance, also invasibility) - especially because these have opposite meanings, I had to read this section of the manuscript carefully to understand its meaning. A single term would be easier to understand. + +<|ref|>text<|/ref|><|det|>[[71, 514, 921, 616]]<|/det|> +My second main comment concerns the notion of priority effects. Here, as I understand it, the authors use this term basically to mean that a community of strongly interacting species has established itself, which makes invasions less likely (e.g., because all niches are filled or because antagonistic interactions are balanced out) but I am not convinced that this is the sense in which most ecologists tend to use that term; to me, the more common use appears to be referring to particular species whose presence or absence steers the community into different alternative stable states. Here, however, the community is already in a stable state and a new species is trying to invade, and thus "priority effect" does not apply in my view. I suggest a different way of describing this effect here, or, at the very least, the sentence in line 244- 246 needs more explanation. Similarly, I find the use of "alternative stable states" (I251) to be unclear since that is not really the subject of this paper. + +<|ref|>text<|/ref|><|det|>[[71, 628, 191, 640]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[71, 640, 916, 792]]<|/det|> +L110: "The lower probability" - compared to what? L174: "including species interaction strength" - is it clear that different synthetic communities can be characterized by the same average interaction strength? Perhaps some initial compositions have strong antibiotic producers or very similar metabolic profiles L227: correlation on -> with L239: Why should we expect a 1:1 correspondence between survival fraction and invasion probability? This only becomes clear in Fig 4b L280: ergodicity likely needs a bit more explanation to be clear L285: definition of invasion effect is slightly unclear. Is this the same definition as in L296? L317: SI Fig 17 does not show an Allee effect for invaders 2/3 Fig 2f/4c: Legend missing for the gray lines Fig 4a: it is very hard to parse the different colors + +<|ref|>text<|/ref|><|det|>[[72, 828, 323, 842]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 854, 137, 868]]<|/det|> +Summary + +<|ref|>text<|/ref|><|det|>[[71, 879, 923, 943]]<|/det|> +Overall, I found that the study addressed interesting questions and the choice to connect experiments with minimal models of community dynamics seemed like the appropriate choice. However, several decisions made and details about the experiment seem unclear. For example, it is unclear to me how 1) a generalized Lotka- Volterra (gLV) serves as an appropriate model for pH- mediated effects, how fluctuating/stable communities were classified, whether their experimentally- imposed migration rate was sufficient to induce deterministic fluctuations. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 59, 924, 111]]<|/det|> +The visualizations are effective and thorough. However, the authors often make claims about the interpretation of visualizations that need to be backed up by statistical tests. I have attempted to identify reasonable statistical tests when a test is lacking. There are also several instances where further clarification could help a broad readership understand the study. These instances are pointed out under both Major and Minor Comments. + +<|ref|>sub_title<|/ref|><|det|>[[72, 123, 187, 136]]<|/det|> +## Major Comments + +<|ref|>text<|/ref|><|det|>[[72, 148, 916, 238]]<|/det|> +There is no explicit consideration of resources in their model. This makes sense in some respects, as the gLV can be derived in the adiabatic limit of certain consumer- resource models. Furthermore, their experimental manipulations of invasion are demographic rather than environmental, so it makes sense that a phenomenological model that does not explicitly consider microscopic interactions of resource consumption is sufficient. Progress has recently been made using phenomenological models to investigate the macroecological consequences of demographic manipulations (Shoemaker et al., 2023), which may provide outside support for the authors' modeling decisions. At a minimum the authors should provide additional justification for their modelling choices and why they are appropriate for their mode. + +<|ref|>text<|/ref|><|det|>[[72, 249, 916, 327]]<|/det|> +However, the authors also manipulate resource concentration as a means to manipulate the strength of competitive interactions. This manipulation is done by increasing resource concentration, changing the pH, which is a feature of the environment that does not appear in the model and does not appear to be measured. So, while their invasion manipulations are demographic, it reads as though the difference in invasion outcomes between high and low nutrient treatments is driven by the environment. In the manuscript's current form, I imagine that it would be difficult for the reader to understand how the manipulation of resource concentration can be modeled as an increase in the strength of competitive interactions in a phenomenological gLV. + +<|ref|>text<|/ref|><|det|>[[72, 338, 912, 453]]<|/det|> +The connection between interaction coefficients and growth- mediated pH is difficult to see given that pH tends to be incorporated into terms related to growth, both for models such as Monod growth (e.g., Houtsma et al., 1996) as well as Michaelis- Menten kinetics (chapter 10 of Cornish- Bowden, 2012). I suppose that pH- dependent competition coefficients could be derived if one started with a consumer- resource model where growth terms were pH dependent and took the adiabatic limit. At minimum a form of the gLV needs to be derived so the reader can see the connection between increased resource concentration change in pH increase in the strength of competitive interactions. However, it is also unclear that a phenomenological gLV is appropriate since the pH changes within a transfer cycle due to the growth of the community. Since the change in pH within a transfer cycle is on the same timescale of the growth rate, I do not see how a phenomenological gLV can serve as an appropriate model. + +<|ref|>text<|/ref|><|det|>[[72, 463, 916, 541]]<|/det|> +My understanding is that the term "fluctuations" in the context of this study means fluctuations induced by chaotic dynamics. I understand that these are not meant to be viewed as stochastic fluctuations, but in my experience, I have found that only a fraction of eco/evo readers understand the distinction between fluctuations induced by deterministic vs. stochastic effects. It would aid the typical reader if the authors clarified what form of fluctuations they are focused on in the Introduction, specified the type of fluctuation whenever the term is used in the manuscript (e.g., "fluctuations" "deterministic fluctuations"), and briefly addressed in the Discussion how the consideration of stochastic fluctuations might factor into their subsequent research efforts. + +<|ref|>text<|/ref|><|det|>[[72, 552, 911, 603]]<|/det|> +It is worth briefly mentioning in the supplement why continued migration from the regional pool was a necessarily experimental detail for this study. Specifically, how the absence of experimentally- imposed migration would correspond to a gLV with zero migration, the analytic results of which would be decidedly less rich (e.g., no chaos, etc.). Broad readership may not pick up on this detail. + +<|ref|>text<|/ref|><|det|>[[72, 614, 911, 666]]<|/det|> +Related, did the authors perform any experiments without daily migration from the regional pool? Contrasting the results of this study with that type of experiment would strengthen their claims and provide further opportunities to test the utility of the gLV. Alternatively, if there are there any published experiments on invasion analysis using a similar experimental setting without imposing migration, then such results could be verbally compared to the results of their experiment. + +<|ref|>text<|/ref|><|det|>[[72, 677, 911, 704]]<|/det|> +Is the experimentally- imposed migration rate sufficient to induce chaotic dynamics in the context of their gLV model? I searched for this detail in the supplement but did not find it. + +<|ref|>text<|/ref|><|det|>[[70, 716, 920, 743]]<|/det|> +I would also encourage the authors to make both their code and raw data available on public repositories to ensure transparency and reproducibility. + +<|ref|>text<|/ref|><|det|>[[72, 753, 916, 805]]<|/det|> +Lines 148- 149: It would help the reader if justification for the extinction threshold was provided in the main text. In lines 81- 82 of the supplement the authors describe the lower bound on detection due to sequencing, but it is not clear how they arrived at this particular value. It would also help if there was a comparison between the chosen threshold and the inverse of the typical total abundance of the community (all cells), the threshold for true extinction, to provide context for the detection limitation. + +<|ref|>text<|/ref|><|det|>[[72, 816, 920, 855]]<|/det|> +Lines 208- 211: I am unaware of models where the competition coefficients between species can be examined as a function of media modification. If such a model exists, could the authors briefly describe it in their supplement to help the reader understand how environmental variables (e.g., pH) map onto competition coefficients in a gLV model? + +<|ref|>text<|/ref|><|det|>[[72, 867, 515, 880]]<|/det|> +Lines 275- 280: How are alternative stable states determined here? + +<|ref|>text<|/ref|><|det|>[[70, 892, 920, 919]]<|/det|> +Fig. 1d: Why are all but two of the "fluctuating" communities decreasing in biomass from day four to five. Could this simultaneous decrease in biomass be driven by experimental details rather than by the intrinsic dynamics of the communities? + +<|ref|>text<|/ref|><|det|>[[72, 930, 500, 944]]<|/det|> +Fig. 1g; lines 380- 382: What statistical test was performed here? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 60, 792, 74]]<|/det|> +Fig. 2f: What do the dashed and solid grey lines represent? Could the authors include a legend in the figure? + +<|ref|>text<|/ref|><|det|>[[70, 85, 571, 99]]<|/det|> +Fig. 4c: Could the authors add an axis label for the colorbar in the revision? + +<|ref|>text<|/ref|><|det|>[[70, 110, 896, 150]]<|/det|> +Fig. 4d: "Effect on resident community" is a nice term for those unfamiliar with these types of experiments, but it still reads as somewhat vague. Could the authors describe what this term means in the figure legend and provide an equation for how the quantity was estimated in the supplement? + +<|ref|>text<|/ref|><|det|>[[70, 161, 866, 187]]<|/det|> +Fig. 5: What timepoints are used to calculate the fold change? Are the same timepoints used for each community? Is the outcome of the statistical test robust to the choice of timepoints? + +<|ref|>text<|/ref|><|det|>[[70, 199, 916, 238]]<|/det|> +Supplement line 52: The sampling detection limit is \(\sim 10^{\wedge}[-4]\) but the chosen dilution rate was \(10^{\wedge}[-5]\) . How does the difference between dilution rates and detection limit shape the observed outcomes of the experiment? If it does, it may be worth describing the outcomes in different parameter limits to the reader (i.e., sampling limit much greater than dilution rate and vice-versa). + +<|ref|>text<|/ref|><|det|>[[70, 249, 915, 300]]<|/det|> +Supplement: Lines 52, 63: I am unfamiliar with the term "dispersal rate" used to describe the process of diluting cultures in a serial transfer experiment. The method used by the authors is different from the standard process of serial dilution, so I think some justification of the term as well as an explanation of how it connects to the mathematical definition of dispersal (Eq. S1) in the supplement is warranted. + +<|ref|>text<|/ref|><|det|>[[70, 312, 920, 365]]<|/det|> +Supplement lines 100- 119: Does the absence of serial dilution being explicitly encoded into the simulation impact the results? Serial dilutions have been explicitly incorporated into mechanistic (Marsland et al., 2020) and phenomenological (Shoemaker et al., 2023) models of community dynamics in an experimental context. Could the authors provide justification of why serial dilution does not need to be explicitly encoded into their simulation? + +<|ref|>text<|/ref|><|det|>[[70, 375, 884, 402]]<|/det|> +Supplement lines 109- 111: What are the units of time and how do they compare to the timescales of the experiments? Is the timescale of the simulation informed by the timescale of the experiment? + +<|ref|>text<|/ref|><|det|>[[70, 413, 918, 491]]<|/det|> +Supplement lines 147- 148: It's unclear what the CV represents. My understanding is that each CV is calculated over time for each species for a given simulation iteration. Since the dynamics are deterministic and the interaction coefficients are a form of quenched disorder, what random variable is the CV calculated over? Does the distribution of CVs demonstrate a clear bimodality with the \(10^{\wedge}[-3]\) cutoff representing the valley between the two peaks? It would help the reader if 1) additional context was provided for the CV and what it represents as well as 2) distributions of simulated CVs plotted to demonstrate the intuition behind classifying communities into stable/fluctuating classes. + +<|ref|>text<|/ref|><|det|>[[70, 502, 905, 592]]<|/det|> +Supplement lines 160- 163, Fig. S12c, d: Is some degree of correlation expected since biomass was used to calculate the abundance of each species? This seems similar to the case presented in. Garud et al., where the same parameter factors into both sides of the relationship (pg. 16 and 17 of supplement; 2019). Here the authors partitioned synonymous sites into two categories, providing two estimates of the quantities of interest. These two quantities are conditionally independent of the parameter that factors into both sides of the proposed relationship due to the Poisson thinning property. One quantity is then used to calculate the left side of the relationship while the other is used to calculate the right side. Is a similar analysis appropriate in this case given that total biomass factors into both sides of the quantities examined in Fig. S12c, d? + +<|ref|>text<|/ref|><|det|>[[70, 603, 911, 642]]<|/det|> +An alternative option could be to examine the relationship between the CV of biomass (OD) and the CV of relative abundances for each ASV, allowing for the identification of community members that disproportionately contribute to the fluctuations in biomass. + +<|ref|>text<|/ref|><|det|>[[70, 653, 900, 680]]<|/det|> +Fig. S2: Is there any phylogenetic structure to these results? Does the placement of a species on the phylogeny relative to the phylogenetic composition of a given community determine species invariability? + +<|ref|>text<|/ref|><|det|>[[70, 691, 872, 731]]<|/det|> +Fig. S12: "The standard deviation of community biomass over day 5, day 6 and day 7" this detail is confusing since the timeseries represented in Fig. 1d ends at day six. What was the rational behind using only these three timepoints? Some justification of using these three timepoints is needed in the Supplement. + +<|ref|>text<|/ref|><|det|>[[70, 741, 866, 755]]<|/det|> +Fig. S13: The figure is a useful visualization, but in its current form it is difficult to validate the claims made in the legend. + +<|ref|>text<|/ref|><|det|>[[70, 767, 918, 806]]<|/det|> +- "Invisibility positively correlates with richness when varying interaction strength" Is a claim being made here about the direction in which the correlation changes with a change in interaction strength? It's not clear to me whether this claim is about the existence of positive correlations among treatments or the difference in positive correlations between treatments. + +<|ref|>text<|/ref|><|det|>[[70, 817, 917, 869]]<|/det|> +- "Invisibility positively correlates with richness when randomly sample \(S = 20\) communities under high nutrient, due to fluctuating communities display larger richness and larger invasion probability." I am having a hard time parsing this statement. Is a claim being made about correlation being higher in high nutrient \(S = 20\) fluctuating communities relative to high nutrient \(S = 20\) stable communities? + +<|ref|>text<|/ref|><|det|>[[70, 880, 923, 945]]<|/det|> +- The legend could use some retooling for clarity. Furthermore, if the claims are about the increase in correlation in one treatment vs. another, then additional statistical analyses are necessary. It seems like the authors are making three claims, which would require three tests. The question is what statistical model to use. A full regression analysis to examine the increase in slope between two treatments while controlling for potential cofounders could be seen as necessary. Alternatively, the authors could test for the difference between two correlation coefficients using Fisher's Z statistic with a null distribution obtained by permuting + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 888, 73]]<|/det|> +community identity for a given pair of treatments (Snedecor & Cochran, 1989). This statistic was recently used to test for the change in correlation coefficients in experimental microbial communities (Eq. 21 in Shoemaker et al., 2023). + +<|ref|>text<|/ref|><|det|>[[72, 85, 905, 150]]<|/det|> +Fig. S15, 16: Some type of statistical test is necessary to establish the claim that invasions lead to changes in community composition. There are multiple ways to accomplish this task and the authors may have their own idea. One immediate option strikes me: calculate a paired t- statistic for each community between the control and successfully invaded community, demonstrating that absolute value of the t- statistics is significantly greater than zero. Null distributions could be obtained by permuting control/invade labels of each species within each community. + +<|ref|>text<|/ref|><|det|>[[72, 161, 905, 201]]<|/det|> +Fig. S17, S18: Similar to Fig. S15 and S16, but now there are different invader species for each community. The authors could perform a paired t- test for each invader species, pooling observations across communities. A null could be generated for each invader species by permuting control/invade labels within each species within each community. + +<|ref|>text<|/ref|><|det|>[[72, 212, 910, 265]]<|/det|> +Figs. S15- S18: Is there any relationship between the relative abundance of the invading species and the change in relative abundance of the remaining species between the control/invade treatments? This may not be the most appropriate analysis for compositional data, but you plot the relative abundance of the invading species vs. the mean difference in relative abundance between treatments for the remaining species, do you see a clear relationship? + +<|ref|>text<|/ref|><|det|>[[72, 274, 905, 315]]<|/det|> +Fig. S19- S21: The authors' claims about the lack of correlations appear correct but I think the correlation coefficient should be provided along with the non- significant P- value. Statistical significance can be assessed by permuting x and y vectors. Permutations should be constrained on species identity for Fig. S19. + +<|ref|>sub_title<|/ref|><|det|>[[72, 326, 188, 339]]<|/det|> +## Minor Comments + +<|ref|>text<|/ref|><|det|>[[70, 350, 905, 377]]<|/det|> +Both passive voice and active voice are used throughout the main manuscript and supplement. Consult the journal style guide and use the appropriate voice throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[70, 387, 884, 402]]<|/det|> +Line 76: Should "occupy all available niches and resources" be "occupy all available niches by consuming all resources"? + +<|ref|>text<|/ref|><|det|>[[70, 412, 910, 439]]<|/det|> +Line 85- 86: Given the experiment performed, would be more apt to say that the question is whether the dynamics are stationary with respect to deterministic fluctuations? + +<|ref|>text<|/ref|><|det|>[[72, 451, 306, 465]]<|/det|> +Line 192: Should "effect" be plural? + +<|ref|>text<|/ref|><|det|>[[70, 476, 891, 504]]<|/det|> +Line 235: Is "niches and resources" redundant here? My understanding that the niche is resource niche in the context of this study. + +<|ref|>text<|/ref|><|det|>[[72, 514, 550, 528]]<|/det|> +Lines 304- 305: "stronger secondary effect" "stronger secondary effects" + +<|ref|>text<|/ref|><|det|>[[72, 540, 243, 553]]<|/det|> +Lines 378- 379: Grammar. + +<|ref|>text<|/ref|><|det|>[[72, 564, 500, 578]]<|/det|> +Lines 379- 380: "invasion probability to" "invasion probability of" + +<|ref|>text<|/ref|><|det|>[[72, 589, 596, 603]]<|/det|> +Line 389: "invaders successfully invade" or "an invader successfully invades"? + +<|ref|>text<|/ref|><|det|>[[72, 615, 550, 629]]<|/det|> +Line 437: "high nutrient" "high nutrient conditions" or something similar. + +<|ref|>text<|/ref|><|det|>[[70, 640, 866, 667]]<|/det|> +Supplement lines 75- 76: Please summarize the DADA2 parameters used in your script and make your DADA2 pipeline available in a public code repository. + +<|ref|>text<|/ref|><|det|>[[72, 678, 648, 692]]<|/det|> +Supplement lines 79- 81: Please make your raxml code available in a public repository. + +<|ref|>text<|/ref|><|det|>[[70, 703, 900, 730]]<|/det|> +Supplement lines 123- 125: This sentence reads as if steady state is defined as the state where community properties change with time. Is this supposed to be the case? + +<|ref|>text<|/ref|><|det|>[[70, 741, 910, 768]]<|/det|> +Supplement lines 144- 145: How is a window of time of 100 units analogous to a timescale of 24 hours in the experiment? Were growth rates in the simulation parameterized to correspond to growth rates in the experiment? + +<|ref|>text<|/ref|><|det|>[[72, 779, 684, 793]]<|/det|> +Supplement lines 167- 168: Can you plot the results from varying the choice of time window? + +<|ref|>text<|/ref|><|det|>[[72, 804, 415, 818]]<|/det|> +Supplement lines 174: "Algorithm" should be plural. + +<|ref|>text<|/ref|><|det|>[[72, 829, 875, 869]]<|/det|> +Fig S1: Would an alternative color scale help the reader? It does not appear that colors are assigned based on taxonomy. Assigning different shades of a given color to the species belonging to a given phylum may help with visualization (e.g., Firmicutes get different shades of blue, etc.). + +<|ref|>text<|/ref|><|det|>[[72, 880, 648, 894]]<|/det|> +Figs. S8- S11: Can you plot the extinction threshold as a dashed/dotted horizontal line? + +<|ref|>text<|/ref|><|det|>[[70, 905, 875, 932]]<|/det|> +Fig. S12: Consider plotting the cutoff of 0.05 as a horizontal dashed line for reference in subplots a and b and as a vertical dashed line in subplots c and d. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 754, 60]]<|/det|> +Fig. S14: How were priority effects quantified? What does the y-axis of the priority effect plot represent? + +<|ref|>sub_title<|/ref|><|det|>[[72, 85, 150, 98]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[70, 108, 916, 265]]<|/det|> +Cornish- Bowden, A. (2012). Fundamentals of enzyme kinetics (4th, completely revised and greatly enlarged edition ed.). Wiley- Blackwell. Garud, N. R., Good, B. H., Hallatschek, O., & Pollard, K. S. (2019). Evolutionary dynamics of bacteria in the gut microbiome within and across hosts. PLOS Biology, 17(1), e3000102. https://doi.org/10.1371/journal.pbio.3000102 Houtsma, P. C., Kant- Muermans, M. L., Rombouts, F. M., & Zwietering, M. H. (1996). Model for the combined effects of temperature, pH, and sodium lactate on growth rates of Listeria innocua in broth and Bologna- type sausages. Applied and Environmental Microbiology, 62(5), 1616- 1622. Marsland, R., Cui, W., Goldford, J., & Mehta, P. (2020). The Community Simulator: A Python package for microbial ecology. PLOS ONE, 15(3), e0230430. https://doi.org/10.1371/journal.pone.0230430 Shoemaker, W. R., Sánchez, A., & Grilli, J. (2023). Macroecological laws in experimental microbial systems (p. 2023.07.24.550281). bioRxiv. https://doi.org/10.1101/2023.07.24.550281 Snedecor, G. W., & Cochran, W. G. (1989). Statistical methods (8th ed). Iowa State University Press. + +<|ref|>text<|/ref|><|det|>[[72, 299, 323, 312]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[71, 323, 920, 465]]<|/det|> +In this manuscript, Hu et al. aim to identify characteristics of microbial communities that determine their invasibility. They first carried out experimental invasions with assembled communities, finding that more diverse communities are more invasive. To further explore this positive invasibility- diversity relationship, a Loka- Volterra model was used to predict the effect of changing interspecies interaction strength and species pool size on invasibility. This showed that decreasing interaction strength and pool size increased invasibility. This was confirmed experimentally by changing the concentration of glucose and urea to tune interaction strength, and by changing species pool size. These three key determinants of invasibility (interaction strength, pool size, dynamical regime) determine the survival fraction, defined as the fraction of the initial species pool that survives the assembly process. The survival fraction correlates positively with community invasibility, serving as a unifying predictor. They find that under strong interaction strength, the invasion probability is lower than the survival fraction, indicating a priority effect. The strength of interactions is also shown to determine the impact of invasion on the resident community. Finally, the properties of invaders were briefly discussed. + +<|ref|>text<|/ref|><|det|>[[72, 475, 921, 540]]<|/det|> +I see this as a valuable and novel contribution to the field. While the long- standing biotic resistance hypothesis predicts that more diverse communities should be less invasive due to niche filling, empirical evidence for this is mixed. By considering how diversity is achieved, the authors show that invasibility can be predicted from community features, which has not been done previously. A particular strength of the manuscript is the integration of modelling and experiments to gain mechanistic insight into relationships observed experimentally. + +<|ref|>text<|/ref|><|det|>[[72, 551, 888, 578]]<|/det|> +I have two major comments regarding the tuning of interspecies interactions and determining the impact of invasion. In both cases, limitations of the findings of the manuscript need to be made more explicit. + +<|ref|>text<|/ref|><|det|>[[72, 588, 917, 691]]<|/det|> +The authors state that increasing interaction strength decreases invasion probability. This is done experimentally by increasing the strength of competitive interactions. However, previous work (ref 30) has demonstrated that the type of interaction between the invader/residents, or between residents, impacts the invasion outcome. For example, positive interactions (e.g. facilitation) between the invader and resident community increases invasion probability (as posited by the diversity begets diversity hypothesis). Increasing interaction strength in this case could increase community invasibility, which is a possibility not considered by this study. While I recognise that experimental manipulation of interaction strength is difficult, I would recommend running the model with a distribution of interactions that considers positive interactions, to show the generality of their conclusions. If this has already been done (this is not clear) this should be included in the supplement. + +<|ref|>text<|/ref|><|det|>[[72, 702, 925, 867]]<|/det|> +The limitations of the study in determining the impact of successful invasions on the structure of the resident community should be more explicit. The impact of successful invasions on the structure of the resident community was measured experimentally by the fold change in biomass, and the invasion effect on the community using 16s sequencing data. However, the fold change in biomass provides little insight on invasion impact. It is not possible to distinguish between the change in biomass of the resident community, and the increase in biomass of the successful invader. Thus, a lower change in biomass in the low nutrient regime may be due to the fact that the invader has less nutrients to grow on, and the converse for the high nutrient regime. Moreover, while species abundance data shows a statistically significant difference in community composition in the higher nutrient regime, it is important that the authors provide information about the effect size. For example, as a 95% confidence interval for the difference between the invasion success under high nutrient conditions and the invasion success under low nutrient conditions Finally, it is hard to conclude what the actual effect of invasion is using the selected measures. For example, though species composition may have changed, the invader could be functionally redundant with the species that were excluded, resulting in no change to community functioning. While a comprehensive assessment of invasion impact is out of the scope of this paper, I would recommend for these limitations to be discussed explicitly in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[72, 880, 160, 892]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[72, 892, 920, 942]]<|/det|> +- I strongly recommend including explicit definitions of key terms, which would improve clarity of the manuscript. For example, the definition of community diversity as the number of species that survive the assembly process is not made explicit in line 152. What 'rich dynamics' (line 191) or richness (line 195, 222 and others) refers to is also unclear to me. +- The findings of this study could be embedded more explicitly into existing concepts in invasion ecology, which is dominated by + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 920, 99]]<|/det|> +niche theory and resource competition. For example, in lines 175- 176 the authors state that fluctuating communities are more invisible. The basis of this relationship is not made clear to the reader - I assumed that this means more niches are open at any given point in time. Moreover, why strong interspecies interactions and a larger species pool decrease invasibility is not discussed. It would also be helpful to discuss this more in the conclusion. + +<|ref|>text<|/ref|><|det|>[[70, 99, 912, 150]]<|/det|> +- I think that for those unfamiliar with previous work from this group, how interaction strength, species pool size and dynamical regime combine to determine survival fraction is difficult to understand. More explanation about how these features interface is necessary for clarity of the manuscript, since they are not independent. For example, it is not immediately clear why there are stable/fluctuating regimes for communities under high nutrient conditions, and not for low nutrient conditions + +<|ref|>text<|/ref|><|det|>[[70, 150, 904, 213]]<|/det|> +- The measure of dispersion used is not included in the text of the manuscript (i.e., on line 148, 153, 154, 172 and more, parameter estimates are given as mean +/- X, where X is a measure of dispersion, but which measure it is is not defined). Defining the measure of dispersion is crucial to allow for interpretation of the findings. Some figure legends mention that error bars represent the standard error of the mean, which I assume is the measure used by the authors, but this should be clearly stated in the text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[70, 213, 640, 226]]<|/det|> +- State how invaders were chosen (line 146) - I assume they were chosen at random? + +<|ref|>text<|/ref|><|det|>[[70, 226, 923, 252]]<|/det|> +- In the section discussing the model (lines 178-190), explicitly state at what relative abundance the invader is introduced relative to the community + +<|ref|>text<|/ref|><|det|>[[70, 252, 925, 304]]<|/det|> +- In the representative time series of fig 2a, invasions are shown to cause a weak effect on the community when the invader grows to a low abundance relative to the rest of the community, whereas the invader causes a strong effect when it grows to high abundance. Is this true across other simulations, or in experiments? If this is the case, it would suggest that there is another factor that influences invasion effect aside from interaction strength. + +<|ref|>text<|/ref|><|det|>[[70, 303, 925, 330]]<|/det|> +- I would include (strong interaction) or (weak interaction) every time high/low nutrient conditions are mentioned for clarity. This is missing now in line 240 and others + +<|ref|>text<|/ref|><|det|>[[70, 330, 900, 356]]<|/det|> +- Remove "while resident community ... determining invasion outcome" from line 322-323. Invader properties have not been sufficiently explored in this manuscript to claim they don't play an important role in determining invasion outcome. + +<|ref|>text<|/ref|><|det|>[[72, 366, 142, 378]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 390, 178, 402]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 415, 137, 427]]<|/det|> +Dear Jeff, + +<|ref|>text<|/ref|><|det|>[[72, 439, 911, 478]]<|/det|> +As per my previous email, we received the reviewers' comments on your revised manuscript "Collective dynamical regimes predict invasion success and impacts in microbial communities" (NATECoLEVEL- 24020551A) and we decided in principle to publish it in Nature Ecology & Evolution, pending minor revisions and compliance with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[70, 488, 890, 515]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[70, 526, 920, 541]]<|/det|> +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[72, 552, 140, 565]]<|/det|> +[redacted] + +<|ref|>text<|/ref|><|det|>[[72, 589, 323, 602]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 615, 905, 641]]<|/det|> +The authors have addressed all my concerns, and added useful new analyses and discussions that clarify the manuscript and the modeling choices they made. I have no more concerns that would need to be resolved before publication. + +<|ref|>text<|/ref|><|det|>[[70, 652, 904, 679]]<|/det|> +As an extremely minor point, I found the spread of the points in Fig. 5c and d to be a bit large, to the point where my eye didn't immediately parse the two clouds as separate categories - but that's presumably a matter of taste. + +<|ref|>text<|/ref|><|det|>[[72, 690, 368, 704]]<|/det|> +Reviewer #1 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[70, 716, 920, 755]]<|/det|> +No readme files, but the data looks complete. Both the sequencing data analysis code and the simulation code is clear and well- documented. I did not attempt to run the code, but as far as I can tell, the provided code only gives the backbone of the simulations and does not include code needed to reproduce the figures directly. + +<|ref|>text<|/ref|><|det|>[[72, 780, 323, 792]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 805, 145, 817]]<|/det|> +Review #2 + +<|ref|>text<|/ref|><|det|>[[70, 830, 878, 856]]<|/det|> +This is an impressive revision, and the quality reflects a high level of effort from the authors. The authors addressed all my comments and gave thoughtful, much appreciated answers. I believe the manuscript should be published. + +<|ref|>text<|/ref|><|det|>[[72, 867, 668, 881]]<|/det|> +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +<|ref|>text<|/ref|><|det|>[[70, 892, 920, 945]]<|/det|> +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 891, 75]]<|/det|> +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +<|ref|>text<|/ref|><|det|>[[73, 98, 293, 112]]<|/det|> +The Dryad repository looks good. + +<|ref|>text<|/ref|><|det|>[[72, 135, 501, 149]]<|/det|> +Below are some minor comments that do not require a response. + +<|ref|>text<|/ref|><|det|>[[72, 160, 920, 213]]<|/det|> +- The discussion of how pH mediated interactions can shape the strength of interaction in gLV is helpful. In general, I think a derivation of pH mediated interactions from the starting point of a consumer-resource model is needed, even if it's just for pedagogical reasons and all the heavy modeling is ultimately done using gLV, but such modeling efforts lie outside the scope of the paper. All-in-all the additions to the supplement make it a valuable resource. + +<|ref|>text<|/ref|><|det|>[[72, 223, 630, 238]]<|/det|> +- The elaboration on the connection to ergodicity in response to R1 was very helpful. + +<|ref|>text<|/ref|><|det|>[[73, 249, 364, 263]]<|/det|> +- The new color scheme should aid readers. + +<|ref|>text<|/ref|><|det|>[[70, 274, 896, 302]]<|/det|> +- "In our group, we have been investigating the dependence of community diversity and dynamics on resource concentration across various consumer-resource models (e.g., linear growth or Monod growth)." Very much looking forward to reading this. + +<|ref|>text<|/ref|><|det|>[[72, 312, 904, 353]]<|/det|> +- The added analyses for the survival threshold are rigorous. The sequencing depth justification is particularly useful since my group has encountered studies where the order of magnitude of demographic manipulations is not justified given the depth of sampling (i.e., # reads). + +<|ref|>text<|/ref|><|det|>[[72, 400, 368, 415]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[72, 425, 668, 440]]<|/det|> +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +<|ref|>text<|/ref|><|det|>[[70, 450, 920, 528]]<|/det|> +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +<|ref|>text<|/ref|><|det|>[[72, 551, 300, 565]]<|/det|> +I was unable to run the code as-is. + +<|ref|>text<|/ref|><|det|>[[72, 588, 324, 602]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 613, 911, 641]]<|/det|> +I would like to thank the authors for their thorough revision of this manuscript. All my concerns have been addressed and I have no further comments. + +<|ref|>text<|/ref|><|det|>[[72, 652, 368, 666]]<|/det|> +Reviewer #3 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[72, 677, 489, 691]]<|/det|> +The code is usable but needs a README file for further clarity. + +<|ref|>text<|/ref|><|det|>[[72, 754, 141, 767]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[72, 779, 179, 792]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 804, 214, 817]]<|/det|> +25th November 2024 + +<|ref|>text<|/ref|><|det|>[[72, 830, 214, 843]]<|/det|> +Dear Professor Gore, + +<|ref|>text<|/ref|><|det|>[[70, 854, 904, 882]]<|/det|> +We are pleased to inform you that your Article entitled "Collective dynamical regimes predict invasion success and impacts in microbial communities", has now been accepted for publication in Nature Ecology & Evolution. + +<|ref|>text<|/ref|><|det|>[[70, 892, 907, 933]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Ecology and Evolution style. 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If you have any questions please click here.\*\* + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 922, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[70, 98, 917, 150]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[70, 149, 600, 163]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 295, 108]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[115, 117, 413, 135]]<|/det|> +Reviewer#1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 144, 883, 233]]<|/det|> +In this manuscript, Hu et al. combine experiments and theory to elucidate the factors determining community invasions. They find that while diversity- invasibility relationships can be both positive and negative depending on the factors regulating diversity, the fraction of surviving species directly predicts invasibility. This manuscript leverages their recent insights on the dynamical phases of microbial ecosystems to provide a timely and relevant exploration of invasions. + +<|ref|>text<|/ref|><|det|>[[115, 241, 883, 277]]<|/det|> +The results are interesting and the research is carried out soundly. My comments are primarily aimed at making the manuscript easier to follow. + +<|ref|>text<|/ref|><|det|>[[114, 285, 883, 514]]<|/det|> +My first main comment concerns the exposition of the different diversity- invasibility relationships between Fig. 1 and Fig. 2/3, which on a first read was not immediately obvious. In Fig 1, more species and higher interaction strength makes for fluctuations and greater diversity, and fluctuating communities are more likely to be invaded; but both theory and Fig. 3 show a negative correlation between invasion probability and pool size/interaction strength. I naively expected increased pool size and stronger interactions to translate to a higher chance of fluctuations (as in their recent paper), and thus greater richness and higher invasion probability. It is later revealed where this apparent contradiction comes from, but I believe it would be immensely helpful if this contradiction was highlighted early on. This issue is made more severe by the use of three different terms to describe the probability of successful invasions (invasion probability and invasion resistance, also invasibility) - especially because these have opposite meanings, I had to read this section of the manuscript carefully to understand its meaning. A single term would be easier to understand. + +<|ref|>text<|/ref|><|det|>[[114, 522, 883, 785]]<|/det|> +We thank the reviewer for this helpful comment to improve the readability of the manuscript. When we sample many communities under the same species pool size and the same nutrient concentration (interaction strength), we found the fluctuating communities are more diverse and invasive than the stable ones. However, if the species pool size or nutrient concentration (interaction strength) varies in the experiment or simulation, then fluctuating communities may not be more diverse and invasive than stable ones, as shown in Fig. 3. A more accurate statement should be: The average community invasibility decreases with species pool size and interaction strength (Fig. 2f and Fig. 3). Fluctuating communities are on average more diverse and invasive than stable communities under the same nutrient condition and species pool size. We now clarify in the caption of Fig. 1 and 2 that the fluctuating communities are more invasive than stable ones under the same species pool size and nutrient conditions (average interactions), rather than a universal statement across different conditions. We follow the reviewer's comment and avoid using any "invasion resistance" in the manuscript, which has opposite meanings to "invasibility" and "invasion probability". We further clarify this point in the early text on page 4 of the main text to avoid confusion: + +<|ref|>text<|/ref|><|det|>[[115, 794, 882, 865]]<|/det|> +Our experimental tests of invasion demonstrate that, for fixed environment and species pool size, more diverse communities are more invasive because fluctuating communities are both more diverse and more susceptible to invasion. However, we will show later that when species pool size or nutrient concentration is varied, this relationship does not always hold. + +<|ref|>text<|/ref|><|det|>[[115, 874, 549, 892]]<|/det|> +We also highlight this point on page 5 of the main text: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 160]]<|/det|> +It is important to note that although fluctuating communities exhibit larger invasion probability than stable communities under the same conditions, stable communities can still yield larger invasion probability under weaker interaction strength \(< a_{ij}>\) or smaller species pool size \(S\) (Fig. 2d- f). + +<|ref|>text<|/ref|><|det|>[[115, 169, 882, 363]]<|/det|> +My second main comment concerns the notion of priority effects. Here, as I understand it, the authors use this term basically to mean that a community of strongly interacting species has established itself, which makes invasions less likely (e.g., because all niches are filled or because antagonistic interactions are balanced out) but I am not convinced that this is the sense in which most ecologists tend to use that term; to me, the more common use appears to be referring to particular species whose presence or absence steers the community into different alternative stable states. Here, however, the community is already in a stable state and a new species is trying to invade, and thus "priority effect" does not apply in my view. I suggest a different way of describing this effect here, or, at the very least, the sentence in line 244- 246 needs more explanation. Similarly, I find the use of "alternative stable states" to be unclear since that is not really the subject of this paper. + +<|ref|>text<|/ref|><|det|>[[115, 378, 882, 606]]<|/det|> +We appreciate the reviewer for highlighting this important point. Our interpretation and use of the priority effect are in line with the reviewer's comments. In ecology, the "priority effect" refers to the phenomenon where the order and timing of species arrival in a community influence the subsequent structure and dynamics of that community. Specifically, the species that establish themselves first can significantly affect the community's composition and the success of later- arriving species. In our case we claim priority effect emergent under strong interaction because our model and experiment show that the later- arriving species (invader species) display lower surviving probability (invasion probability) than surviving probability of initial species assemble from the pool (early- arriving species) (as shown in Fig. 3c and Fig. 4c). Under low nutrient (weak interaction), the later- arriving species (invader species) display similar surviving probability (invasion probability) with surviving probability of initial species assemble from the pool (early- arriving species) (as shown in Fig. 3c and Fig. 4c), which indicate there is no priority effect under low nutrient (weak interaction). + +<|ref|>text<|/ref|><|det|>[[115, 622, 882, 865]]<|/det|> +Based on our experiments and simulations, we found that the existence of alternative stable states is closely related to the presence of priority effects. As demonstrated in previous theories (Fried, Shnerb, and Kessler 2017; Bunin 2017) and in our experiment (new Supplementary Fig. 22), we observed that the same set of species can reach different alternative stable states when starting from different initial compositions under high nutrient concentrations (strong interactions). In contrast, under low nutrient concentrations (weak interactions), the species consistently converge to a single stable state, meaning that the order of species arrival does not affect the final community structure, indicating the absence of a priority effect. In this context, we consider the priority effect to be equivalent to the presence of alternative stable states. The existence of alternative stable states implies that different initial compositions or the order of species arrival can lead to different final community compositions, which aligns with the definition of the priority effect. Conversely, when no alternative stable state exists, different initial compositions or the order of species arrival result in the same final community composition, which corresponds to the absence of a priority effect. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 195]]<|/det|> +We therefore propose that the alternative stable states observed under high nutrient conditions exhibit a priority effect, which explains why invasion probability is generally lower than the survival fraction in these conditions (bottom left points in Fig. 3c). These stable communities strongly resist invasion due to their established alternative stable states. As the reviewer suggested, we've revised the manuscript to clarify the use of the terms "priority effect" and "alternative stable state". + +<|ref|>image<|/ref|><|det|>[[163, 216, 787, 475]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 490, 883, 736]]<|/det|> +Supplementary Fig. 22. Communities reach global stable states under low nutrient conditions (weak interaction) but reach alternative stable states under high nutrient conditions (strong interaction) when starting from different initial species compositions. Each bar represents a final community stable state after 7 daily dilution cycles starting from a particular initial condition. The communities assemble from the same species in the original pool ( \(S = 12\) for the left and middle communities, \(S = 24\) for the right communities), under low- nutrient (weak interaction) and high- nutrient (strong interaction) conditions, respectively. For each initial condition, one of the species occupies \(99\%\) volume of the initial inoculum, while the other species in the pool together occupy only \(1\%\) volume of the initial inoculum. The results show that these very different initial species compositions lead to the same global stable state under low nutrient conditions (weak interaction) but result in alternative stable states under high nutrient conditions (strong interaction). This indicates the presence of alternative stable states and priority effect under high nutrient (strong interaction), where the initial composition influences the final community structure. + +<|ref|>text<|/ref|><|det|>[[116, 744, 880, 764]]<|/det|> +We revised the paragraph on page 6 ang 7 with an additional explanation as the reviewer suggested: + +<|ref|>text<|/ref|><|det|>[[115, 772, 883, 896]]<|/det|> +Despite the experimentally observed correspondence between invasion probability and survival fraction, we note that the invasion probability for communities under high nutrient (strong interaction) conditions is usually lower than their survival fraction (i.e. the majority of points on the bottom left are below the diagonal line on Fig. 3c). We now discuss how this can be interpreted in terms of priority effects or alternative stable states. If the assembly of species in the community does not depend on the order of species arrival (i.e., no effect of history), the survival fraction of species assembled from the initial pool should be statistically equal to the survival probability of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 387]]<|/det|> +the species that invade the communities later. In ecology, a "priority effect" refers to a situation in which the community structure is influenced by the order and timing of species' arrival(Sprockett, Fukami, and Relman 2018; Debray et al. 2022). We thus interpret the mismatch between invasion probability and survival fraction under high nutrient concentrations (strong interactions) as evidence of priority effects in the community assembly under strong interactions in our experiment. Early- arriving species can dominate by making it more challenging for subsequent invaders to establish, leading to a lower invasion probability than the survival fraction of species in the original pool. Under weak interactions, however, the colonization probability of invader species is similar to the probability of a species in the initial pool surviving the process of community assembly(Fig. 3c)(Case 1990). An emergent priority effect in communities composed of strongly interacting species can be explained by the presence of alternative stable states with different species compositions, which we observe in additional experiments (Supplementary Fig. 22). Early- arriving species establish dominance, making it more difficult for later- arriving invaders to successfully establish themselves, by inhibiting their growth at low abundance. These alternate stable states thus explain why the invasion probability is generally lower than the survival fraction from the initial pool under high nutrient (strong interaction) conditions(Case 1990; Hu et al. 2022). + +<|ref|>text<|/ref|><|det|>[[116, 395, 256, 411]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[116, 421, 547, 439]]<|/det|> +1) L110: "The lower probability" - compared to what? + +<|ref|>text<|/ref|><|det|>[[115, 448, 883, 502]]<|/det|> +We appreciate the reviewer for pointing out the need for clarification. The text should specify that the lower invasion probability is compared to the survival fraction. We have revised the manuscript to make this comparison explicit. The revised Text is: + +<|ref|>text<|/ref|><|det|>[[115, 510, 882, 547]]<|/det|> +"The lower invasion probability compared to the survival fraction suggests a priority effect, whereby earlier invaders preclude later ones from growing from small abundances." + +<|ref|>text<|/ref|><|det|>[[115, 555, 882, 609]]<|/det|> +2) L174: "including species interaction strength" - is it clear that different synthetic communities can be characterized by the same average interaction strength? Perhaps some initial compositions have strong antibiotic producers or very similar metabolic profiles + +<|ref|>text<|/ref|><|det|>[[114, 617, 882, 810]]<|/det|> +We thank the reviewer for this valuable question. We have clarified this point by specifying "for fixed species pool size and species interaction strength regime (nutrient concentrations)." We describe community conditions based on sampling species interactions from a given distribution. For example, in Fig. 2b, communities were sampled from the same species pool size ( \(S = 20\) ) and a uniform distribution of interaction \(\alpha_{ij}\) with a mean interaction of 1.8. Each sampled community has a unique but similarly distributed mean interaction. Our previous work shows that average pairwise interactions increase from low to high nutrient concentrations (Fig. 2B of Hu et al. Science 2022). Although the statistical distribution may vary with limited species sampling, species cultured in the same high nutrient concentration are in a strong interaction strength regime compared to those in a weak interaction strength regime under low nutrient concentrations. We have updated the manuscript on page 4 to reflect this clarification: + +<|ref|>text<|/ref|><|det|>[[115, 819, 882, 908]]<|/det|> +Our experimental tests of invasion demonstrate that, for fixed species pool size and species interaction strength regime (nutrient concentrations), more diverse communities are more invisible because fluctuating communities are both more diverse and more susceptible to invasion. However, when species pool size or nutrient concentration is varied, this relationship does not always hold (Fig 2 and 3). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 363, 108]]<|/det|> +## 3) L227: correlation on \(\rightarrow\) with + +<|ref|>text<|/ref|><|det|>[[115, 117, 884, 153]]<|/det|> +We thank the reviewer for this point. We have edited the text to read "positive correlation of invasibility with survival fraction" in the main text. The revised Text is: + +<|ref|>text<|/ref|><|det|>[[115, 161, 800, 181]]<|/det|> +"The results show a strongly positive correlation of invasibility with survival fraction." + +<|ref|>text<|/ref|><|det|>[[115, 189, 883, 225]]<|/det|> +4) L239: Why should we expect a 1:1 correspondence between survival fraction and invasion probability? This only becomes clear in Fig 4b + +<|ref|>text<|/ref|><|det|>[[115, 234, 882, 358]]<|/det|> +We thank the reviewer for this insightful question. If the assembly of species in the community does not depend on the order of species arrival (i.e., no history effect and priority effect), the survival fraction of species assembled from the initial pool should be statistically equal to the survival probability of the species that invade the communities later. If there is no priority effect and the order of species arrival does not matter, then the survival fraction is expected to approximately correspond with invasion probability, as shown in Fig. 4b. We have added this explanation to page 6 and 7 of the main text to clarify this point: + +<|ref|>text<|/ref|><|det|>[[115, 366, 882, 490]]<|/det|> +Despite our experimentally observed correspondence between invasion probability and survival fraction, we noted that the invasion probability for communities under high nutrient is usually lower than their survival fraction (majority of points on the bottom left (high nutrient) are below the diagonal line on Fig. 3c). If the assembly of species in the community does not depend on the order of species arrival (i.e., no history effect and priority effect), the survival fraction of species assembled from the initial pool should be statistically equal to the survival probability of the species that invade the communities later. + +<|ref|>sub_title<|/ref|><|det|>[[115, 499, 635, 518]]<|/det|> +## 5) L280: ergodicity likely needs a bit more explanation to be clear + +<|ref|>text<|/ref|><|det|>[[115, 526, 882, 684]]<|/det|> +We follow the reviewer's suggestion and have further clarified the concept of ergodicity in the supplementary materials and mentioned in the main text. As studied and shown in previous theoretical studies (Altieri et al. 2021; Pearce et al. 2020; Bunin 2017), ergodicity in the context of chaotic fluctuations means that the community's state is memoryless. The dynamical trajectories of species composition do not depend on the community's history and do not reach alternative stable states or alternative dynamical attractors. Therefore, different orders of species arrival or different initial species compositions do not lead to different community states in the chaotic fluctuation regime. We have added this explanation to improve clarity. The revised text in the supplementary materials is: + +<|ref|>text<|/ref|><|det|>[[115, 692, 882, 799]]<|/det|> +"As studied and shown in previous theoretical studies (Altieri et al. 2021; Pearce et al. 2020; Bunin 2017), ergodicity in the context of chaotic fluctuations means that the community's state is memoryless. The dynamical trajectories of species composition do not depend on the community's history and do not reach alternative stable states or alternative dynamical attractors. Therefore, different orders of species arrival or different initial species compositions do not lead to different community states in the chaotic fluctuation regime." + +<|ref|>text<|/ref|><|det|>[[115, 808, 576, 826]]<|/det|> +We refereed to this explanation in the main text on page 8: + +<|ref|>text<|/ref|><|det|>[[115, 835, 882, 871]]<|/det|> +which can be explained by its ergodicity (Bunin 2017; Pearce et al. 2020; Altieri et al. 2021) (see a technical discussion in Supplementary Materials). + +<|ref|>text<|/ref|><|det|>[[112, 877, 860, 897]]<|/det|> +6) L285: definition of invasion effect is slightly unclear. Is this the same definition as in L296? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 230]]<|/det|> +We further clarify the definition of invasion effect in the text. The definition of invasion effect in L285 is the same as the definition in L296. The invasion effect is measured as the proportion of change in surviving species before the invasion \((t = 10^{3})\) and after the invasion \((t = 2\times 10^{3})\) , calculated as 1 minus the ratio of the number of overlapping species (number of species surviving both at \(t = 2\times 10^{3}\) and \(t = 2\times 10^{3}\) ) to the total number of species (number of species surviving at \(t = 10^{3}\) or \(t = 2\times 10^{3}\) ). Mathematically the invasion effect is calculated through: 1 - (number of overlapping species / total number of species). We have revised the text to ensure this definition is clear and consistent throughout. The revised text on page 8 of the main text is: + +<|ref|>text<|/ref|><|det|>[[115, 239, 883, 293]]<|/det|> +the invasion effect is quantified as the proportion of change in surviving species before the invasion \((t = 10^{3})\) and after the invasion \((t = 2\times 10^{3})\) (invasion effect \(= 1\) - (number of overlapping species / total number of species)) (Fig. 4d) + +<|ref|>text<|/ref|><|det|>[[115, 302, 628, 320]]<|/det|> +7) L317: SI Fig 17 does not show an Allee effect for invaders 2/3 + +<|ref|>text<|/ref|><|det|>[[115, 329, 883, 417]]<|/det|> +We thank the reviewer for pointing out this issue. To see the Allee effect for invaders 2 and 3, we need to look at the monoculture growth curve for these invaders, which is shown in SI Fig. 19. The growth curves of invaders 2 and 3 (blue and purple curves) indicate that they do not grow to a well- detectable signal on the OD reader over 20 hours, demonstrating an Allee effect. We have revised the main text to reference SI Fig. 19 for clarity. The revised text in the Supplement is: + +<|ref|>text<|/ref|><|det|>[[115, 425, 882, 480]]<|/det|> +"To see the Allee effect for invaders 2 and 3, notice that the growth curves of invaders 2 and 3 (blue and purple curves) indicate that they do not grow to a well- detectable signal on the OD reader over 20 hours, demonstrating an Allee effect of these two species." + +<|ref|>sub_title<|/ref|><|det|>[[115, 489, 483, 508]]<|/det|> +## 8) Fig 2f/4c: Legend missing for the gray lines + +<|ref|>text<|/ref|><|det|>[[115, 515, 882, 587]]<|/det|> +We thank the reviewer for raising this important point. We have added legends to Fig. 2f and Fig. 4c to explain the gray lines as shown below and in the main text figures. The solid lines represent the stability boundary, and the dashed lines represent the surviving boundary, which is further explained in the new caption of the figures. + +<|ref|>image<|/ref|><|det|>[[325, 600, 670, 816]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 832, 882, 904]]<|/det|> +
Fig. 2f, Increasing species pool size and interaction strength leads to a decrease in invasion probability. The communities experience the extinction of species and loss of stability when crossing the dashed gray line (surviving boundary) and solid gray line (stability boundary), respectively. The color maps depict the mean value over 1000 simulations.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[330, 117, 670, 345]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 354, 883, 427]]<|/det|> +
Fig. 4c, Increasing species pool size and interaction strength leads to the emergence of priority effect, where the invasion probability of resident communities is smaller than their species survival fraction. The communities experience the extinction of species and loss of stability when crossing the dashed gray line (surviving boundary) and solid gray line (stability boundary), respectively.
+ +<|ref|>text<|/ref|><|det|>[[114, 433, 528, 452]]<|/det|> +9) Fig 4a: it is very hard to parse the different colors + +<|ref|>text<|/ref|><|det|>[[114, 461, 883, 498]]<|/det|> +We appreciate the reviewer for pointing this out. We have chosen a different set of colors to make the different lines easier to distinguish as shown below. + +<|ref|>image<|/ref|><|det|>[[180, 532, 825, 761]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 771, 884, 877]]<|/det|> +
Fig 4. The Lotka-Volterra model predicts a universal correspondence between invasion probability and survival fraction. a, The dependence of invasion probability on final richness of resident communities is qualitatively different depending upon how the richness is changed. Invasion probability positively correlates with richness when varying interaction strength or when randomly sampling communities with a fixed species pool size and interaction strength distribution. Invasion probability can decrease with community diversity when varying species pool size. b,
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 125]]<|/det|> +Invasion probability is approximately equal to the survival fraction of species in the resident communities, no matter how we change richness, species pool or interaction strength. + +<|ref|>text<|/ref|><|det|>[[115, 163, 417, 180]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[115, 191, 194, 207]]<|/det|> +## Summary + +<|ref|>text<|/ref|><|det|>[[115, 208, 882, 313]]<|/det|> +Overall, I found that the study addressed interesting questions and the choice to connect experiments with minimal models of community dynamics seemed like the appropriate choice. However, several decisions made and details about the experiment seem unclear. For example, it is unclear to me how 1) a generalized Lotka- Volterra (gLV) serves as an appropriate model for pH- mediated effects, 2) how fluctuating/stable communities were classified, 3) whether their experimentally- imposed migration rate was sufficient to induce deterministic fluctuations. + +<|ref|>text<|/ref|><|det|>[[115, 322, 882, 392]]<|/det|> +We appreciate the reviewer's feedback and suggestions on our manuscript. In our response letter, we provide a point- by- point answer to all the questions and suggestions from the referees. For convenience, the original comments from the reviewers appear in blue- color font and new text that now appears in either the main text or supplement is included in red. + +<|ref|>text<|/ref|><|det|>[[115, 401, 882, 437]]<|/det|> +Below is a brief discussion regarding these three major points. More detailed responses can be found in our specific responses to the reviewer's comments. + +<|ref|>text<|/ref|><|det|>[[115, 446, 671, 465]]<|/det|> +1) Generalized Lotka-Volterra (gLV) Model for pH-Mediated Effects: + +<|ref|>text<|/ref|><|det|>[[115, 473, 882, 562]]<|/det|> +As a phenomenological model, the generalized Lotka- Volterra (gLV) framework describes the interaction between species through a pair- wise interaction matrix, capturing how the abundance of one species influences the growth of others. The gLV interaction matrix can incorporate various mechanisms, such as resource competition, cross- protection, cross- feeding, and pH- mediated interactions, if the interaction parameters are chosen based on experimental data. + +<|ref|>text<|/ref|><|det|>[[115, 572, 882, 624]]<|/det|> +The gLV model provides a coarse- grained description of interaction signs and strength without delving into specific mechanisms, which is useful when interaction mechanisms are not fully known or when the focus is on collective community behaviors (e.g., fluctuations). + +<|ref|>text<|/ref|><|det|>[[115, 633, 882, 704]]<|/det|> +In our study, pH- mediated interaction is one of several interaction mechanisms. A model solely based on pH- mediated interactions cannot explain some experimental observations. However, a model combining pH- mediated effects and gLV- type interactions can capture key experimental observations, with pH- mediated effects reducing to gLV- type interactions in the adiabatic limit. + +<|ref|>text<|/ref|><|det|>[[115, 712, 540, 730]]<|/det|> +2) Classification of Fluctuating/Stable Communities: + +<|ref|>text<|/ref|><|det|>[[115, 740, 882, 810]]<|/det|> +Communities were classified as fluctuating or stable based on the time series of total biomass and species composition. A community is classified as fluctuating if the variation in its total biomass and species composition over time exceeds a critical threshold. Detailed criteria and thresholds used for classification will be discussed in the following responses to specific comments. + +<|ref|>text<|/ref|><|det|>[[115, 820, 717, 838]]<|/det|> +3) Experimentally-Imposed Migration Rate and Deterministic Fluctuations: + +<|ref|>text<|/ref|><|det|>[[115, 848, 882, 900]]<|/det|> +We have included additional experimental and simulation results to demonstrate that our imposed migration rate leads to deterministic fluctuating or stable states. This point will be elaborated upon in detail in the following responses to specific comments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 177]]<|/det|> +The visualizations are effective and thorough. However, the authors often make claims about the interpretation of visualizations that need to be backed up by statistical tests. I have attempted to identify reasonable statistical tests when a test is lacking. There are also several instances where further clarification could help a broad readership understand the study. These instances are pointed out under both Major and Minor Comments. + +<|ref|>text<|/ref|><|det|>[[115, 187, 882, 291]]<|/det|> +We have now clarified the results of statistical tests when making claims about the interpretation of visualizations throughout the manuscript. We have conducted and reported appropriate statistical tests to support our visual interpretations, ensuring that our claims are robust and well- substantiated. Additionally, we have followed the reviewer's advice and added further clarification to points that may not be clear to a broad audience. These clarifications will be discussed in detail in our responses to the specific major and minor comments provided by the reviewer. + +<|ref|>sub_title<|/ref|><|det|>[[115, 302, 255, 319]]<|/det|> +## Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 329, 882, 486]]<|/det|> +1. There is no explicit consideration of resources in their model. This makes sense in some respects, as the gLV can be derived in the adiabatic limit of certain consumer-resource models. Furthermore, their experimental manipulations of invasion are demographic rather than environmental, so it makes sense that a phenomenological model that does not explicitly consider microscopic interactions of resource consumption is sufficient. Progress has recently been made using phenomenological models to investigate the macroecological consequences of demographic manipulations (Shoemaker et al., 2023), which may provide outside support for the authors' modeling decisions. At a minimum the authors should provide additional justification for their modelling choices and why they are appropriate for their mode. + +<|ref|>text<|/ref|><|det|>[[115, 495, 882, 601]]<|/det|> +We thank the reviewer for this insightful comment on justifying our choice of the generalized Lotka- Volterra (gLV) model in this work. As a phenomenological model, gLV describes species interactions through a pair- wise interaction matrix, capturing how the abundance of one species influences the growth of others. The interaction matrix in the gLV framework is a high- level description that can incorporate various mechanisms, including resource competition, cross- protection, cross- feeding, and pH- mediated interactions. + +<|ref|>text<|/ref|><|det|>[[115, 610, 882, 681]]<|/det|> +As the reviewer pointed out, the gLV model can be derived in the adiabatic limit of certain consumer- resource models. We found that a pH- explicit model can also be reduced to gLV in the adiabatic limit, where the gLV interaction matrix is a function of the pH effect. We would like to emphasize the following points: + +<|ref|>text<|/ref|><|det|>[[115, 690, 882, 760]]<|/det|> +1) Multiple Interaction Mechanisms: pH-mediated interaction is not the only mechanism in our experiment. Some communities show fluctuating biomass while maintaining stable pH levels, indicating other mechanisms, such as cross-toxin interactions, are at play, particularly under high nutrient concentrations. + +<|ref|>text<|/ref|><|det|>[[115, 778, 492, 795]]<|/det|> +2) Limitations of Solely pH-Mediated Models: + +<|ref|>text<|/ref|><|det|>[[115, 797, 882, 884]]<|/det|> +Our model considering only pH- mediated interactions cannot explain all experimental observations. For instance, our experiments and gLV simulations show fluctuating communities with higher diversity and invasibility (Hu et al. 2022), while our pH- only models predict lower diversity and invasibility (Supplementary Fig. 10-11 of Hu et al. 2022) (Hu et al. 2022), contrary to our experimental findings. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 370, 108]]<|/det|> +## 3) Combined Model Approach: + +<|ref|>text<|/ref|><|det|>[[115, 108, 882, 198]]<|/det|> +We developed a model that integrates pH- mediated environmental effects with gLV- type species interactions. This combined framework successfully explains key experimental observations and, crucially, can be reduced to a pure gLV interaction matrix in the adiabatic limit- - where the pH dynamics evolve much faster than species growth, or when pH reaches stable state. This reduction explicitly demonstrates how pH influences the structure of the gLV interaction matrix + +<|ref|>text<|/ref|><|det|>[[115, 206, 882, 277]]<|/det|> +These justifications support our use of the gLV model and align with recent progress in using phenomenological models for demographic manipulations (Shoemaker et al., 2023). We have added this explanation to the manuscript to provide additional justification for our modeling choices. + +<|ref|>text<|/ref|><|det|>[[115, 285, 882, 426]]<|/det|> +2. However, the authors also manipulate resource concentration as a means to manipulate the strength of competitive interactions. This manipulation is done by increasing resource concentration, changing the pH, which is a feature of the environment that does not appear in the model and does not appear to be measured. So, while their invasion manipulations are demographic, it reads as though the difference in invasion outcomes between high and low nutrient treatments is driven by the environment. In the manuscript's current form, I imagine that it would be difficult for the reader to understand how the manipulation of resource concentration can be modeled as an increase in the strength of competitive interactions in a phenomenological gLV. + +<|ref|>text<|/ref|><|det|>[[115, 434, 882, 540]]<|/det|> +We appreciate the reviewer for this insightful comment. We have performed pair- wise coculture experiments among the species in the pool and found that the fraction of coexistence between pairs of species decreased, while the fraction of competitive exclusion (only one species survives) increased when nutrient concentration was increased (Hu et al. 2022). We now cite these pair- wise coculture results in the manuscript to demonstrate more clearly that the average interaction between species increases with nutrient concentration. + +<|ref|>text<|/ref|><|det|>[[115, 548, 882, 672]]<|/det|> +Previous work from our group (Ratzke, Barrere, and Gore 2020) has shown that increasing glucose and urea concentrations in the culture medium increases inter- species interaction strength among different soil bacterial species. Specifically, some species consume glucose and produce organic acids, leading to a decrease in pH, while others consume organic acids and increase the pH. Additionally, some species consume urea and produce ammonium, which also increases pH. These interactions modify the pH in different directions and affect species' growth and death rates, explaining the pH- mediated interaction under high nutrient concentrations. + +<|ref|>text<|/ref|><|det|>[[115, 681, 882, 787]]<|/det|> +Our experiments show that without glucose and urea, pH does not significantly change, indicating weak pH- mediated interactions. However, we also observed that communities can fluctuate in biomass without corresponding pH fluctuations (see figure below), suggesting that pH is not the sole driver of strong interactions under high nutrient concentrations. Our ongoing spent- medium culture experiments show that other types of inter- species interactions, such as cross- toxin effects, also increase with nutrient concentration, contributing to the overall interaction strength. + +<|ref|>text<|/ref|><|det|>[[115, 795, 882, 901]]<|/det|> +In our experiments, increasing nutrient concentration led to increased interaction strength and decreased community diversity. While existing resource- consumer models often display independence between resource concentration and interaction strength, our new pH model combines pH- mediated effects with gLV- type interactions, directly considering the quantitative interdependence between pH modification by species and pH effects on species growth, which can be measured experimentally. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 160]]<|/det|> +We agree with the reviewer that directly relating nutrient concentration to interaction strength is an important research direction, and we are actively working on relevant projects. We have added these explanations to the manuscript to clarify how manipulation of resource concentration can be modeled as an increase in competitive interaction strength in a phenomenological gLV framework. + +<|ref|>image<|/ref|><|det|>[[137, 174, 857, 391]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 401, 883, 473]]<|/det|> +
Figure. Microbial communities can exhibit fluctuations in biomass without corresponding fluctuations in pH in our experiment. The biomass (OD) of a microbial community fluctuates between days 6 and 10, while the pH time series stabilize during the same period (between days 6 and 10). The three curves represent three replicates of the same community.
+ +<|ref|>text<|/ref|><|det|>[[114, 481, 883, 675]]<|/det|> +3. The connection between interaction coefficients and growth-mediated pH is difficult to see given that pH tends to be incorporated into terms related to growth, both for models such as Monod growth (e.g., Houtsma et al., 1996) as well as Michaelis-Menten kinetics (chapter 10 of Cornish-Bowden, 2012). I suppose that pH-dependent competition coefficients could be derived if one started with a consumer-resource model where growth terms were pH-dependent and took the adiabatic limit. At minimum a form of the gLV needs to be derived so the reader can see the connection between increased resource concentration, change in pH, and increase in the strength of competitive interactions. However, it is also unclear that a phenomenological gLV is appropriate since the pH changes within a transfer cycle due to the growth of the community. Since the change in pH within a transfer cycle is on the same timescale of the growth rate, I do not see how a phenomenological gLV can serve as an appropriate model. + +<|ref|>text<|/ref|><|det|>[[115, 683, 884, 772]]<|/det|> +We thank the reviewer for this insightful comment. As explained in our response to major comment, we have found that existing resource- consumer models do not explicitly relate resource concentration to pH changes and interactions. Recognizing the importance of incorporating pH- dependent growth into the model, we developed a model combining pH effects with gLV- type interactions to explain our experimental observations, which are consistent with gLV predictions. + +<|ref|>text<|/ref|><|det|>[[115, 780, 883, 903]]<|/det|> +This pH model accounts for species' modifications of environmental pH and the pH- dependent growth of species. As the reviewer suggested, we found that this model can be reduced to a pure gLV- type interaction matrix in the adiabatic limit, allowing us to explicitly demonstrate how pH effects influence the phenomenological interaction matrix in the gLV model. In our approach, we considered linear functions for both species' modifications of environmental pH and the impact of environmental pH on species growth. This choice was made to capture the key features of community dynamics in a minimal model and because the linear form facilitates the reduction of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 220]]<|/det|> +\(\mathrm{pH}\) - mediated interactions into gLV- type interactions in the adiabatic limit. The results indicate that the presence of \(\mathrm{pH}\) effects increases both the mean and standard deviation of the distribution of effective inter- species interaction strengths \(\alpha_{ij}^{*}\) (see figure below). In the limit where gLV interaction strength is set to zero and only \(\mathrm{pH}\) - mediated interactions exist, we still observe a distribution of effective inter- species interaction strengths \((\alpha_{ij}^{*})\) (see figure below). These findings suggest that the presence of \(\mathrm{pH}\) effects in the model leads to an increase in the mean and standard deviation of gLV- type interaction strengths \((\alpha_{ij}^{*})\) . + +<|ref|>text<|/ref|><|det|>[[115, 230, 882, 457]]<|/det|> +Furthermore, we found that as we increased the \(\mathrm{pH}\) - mediated interaction strength and species pool size in the model, the invasion probability decreased (new Supplementary Fig. 23). When both \(\mathrm{pH}\) - mediated and gLV- type interaction strengths were increased simultaneously, the invasion probability decreased in a manner similar to that observed when only the gLV- type interaction strength was increased (new Supplementary Fig. 23). In the presence of \(\mathrm{pH}\) - mediated interaction strength in the model, we observed that the survival fraction was approximately equal to the invasion probability under various conditions (new Supplementary Fig. 23). These results suggest that our conclusion—that invasion probability decreases with interaction strength and species pool size—is robust to the presence of \(\mathrm{pH}\) effects in the model. Meanwhile, the survival fraction serves as a good predictor of invasion probability in both the gLV and \(\mathrm{pH}\) models. Our results support the idea that the gLV model phenomenologically describes species interactions within the community and predicts robust patterns in community invasion outcomes, which can be qualitatively reproduced in a \(\mathrm{pH}\) model or a combined \(\mathrm{pH}\) and gLV model. + +<|ref|>text<|/ref|><|det|>[[115, 466, 882, 590]]<|/det|> +Our previous measurements of \(\mathrm{pH}\) and biomass dynamics within one transfer cycle (24 hours) show that \(\mathrm{pH}\) dynamics are faster than population dynamics (Ratzke, Denk, and Gore 2018). Furthermore, the reduction of our \(\mathrm{pH}\) model to gLV does not require time- scale separation when the \(\mathrm{pH}\) and population dynamics reach stable states. More importantly, gLV provides a phenomenological and coarse- grained description of inter- species interactions averaged across different mechanisms and time scales, helping us characterize collective community dynamical regimes qualitatively. + +<|ref|>text<|/ref|><|det|>[[115, 598, 883, 843]]<|/det|> +In summary, we agree with the reviewer that incorporating a \(\mathrm{pH}\) - explicit model is crucial for understanding how increasing nutrients and \(\mathrm{pH}\) can enhance inter- species interactions. We have revised the manuscript to include this explanation, showing the derivation of the gLV form and its connection to \(\mathrm{pH}\) - mediated interactions. In our group, we have been investigating the dependence of community diversity and dynamics on resource concentration across various consumer- resource models (e.g., linear growth or Monod growth). However, we have not observed that increasing resource concentration leads to a decrease in diversity and stability within these models, as seen in our experiments. We also explored a consumer- resource model with \(\mathrm{pH}\) - dependent growth terms, but similarly, we did not observe a decrease in diversity and stability with increased resource concentration in any of the models we tested. We agree with the reviewer that it is both interesting and important to explicitly relate resource concentration to changes in \(\mathrm{pH}\) and the subsequent increase in the strength of competitive interactions, this remains an open question in our ongoing projects. We have included a discussion of our new model, which combines \(\mathrm{pH}\) - mediated interactions and gLV- type interactions, in the supplementary materials: + +<|ref|>text<|/ref|><|det|>[[116, 860, 527, 877]]<|/det|> +Theoretical alternatives to the Lotka- Volterra model + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 882, 179]]<|/det|> +To directly model the pH- mediated interactions in our framework, we consider a minimal model where the pH value \((p\) in the model) influences the species' per capita growth rates linearly, and, reciprocally, the species modify the environmental pH in a linear manner. This approach serves as a straightforward extension of the generalized Lotka- Volterra (gLV) model, which traditionally handles species interactions without considering environmental feedbacks such as pH. + +<|ref|>text<|/ref|><|det|>[[114, 183, 883, 308]]<|/det|> +In this extended model, the interaction between species and pH is twofold: species can alter the pH of their environment, and this altered pH, in turn, affects their growth rates. This dual influence allows the model to capture more complex ecological dynamics, where pH acts as a mediating factor that can shift the balance between competition, cooperation, and exploitation among species. Depending on the specific parameters chosen—such as the sensitivity of growth rates to pH changes and the extent to which species modify pH—the model can simulate a variety of interaction scenarios. + +<|ref|>text<|/ref|><|det|>[[114, 312, 883, 439]]<|/det|> +For instance, a species that raises the environmental pH could either inhibit or promote the growth of other species, depending on whether those species thrive in higher or lower pH conditions. Similarly, species that lower the pH could create environments that are hostile or favorable to others, depending on their pH preferences. This dynamic allows the model to represent competitive interactions (where species indirectly harm each other by altering pH), cooperative interactions (where species create favorable conditions for each other), and exploitative interactions (where one species benefits at the expense of another by altering the pH). + +<|ref|>text<|/ref|><|det|>[[114, 442, 883, 567]]<|/det|> +By incorporating pH- mediated interactions, this model adds a layer of realism to the gLV framework, making it more applicable to ecosystems where environmental factors like pH play a critical role in shaping species interactions. The linear relationships assumed in this model are not just mathematically convenient; they also provide a minimal yet powerful way to explore how environmental feedbacks can influence community dynamics. This extension allows for the modeling of a broader range of ecological scenarios, potentially offering new insights into how species coexist and compete in pH- sensitive environments. + +<|ref|>equation<|/ref|><|det|>[[333, 571, 880, 686]]<|/det|> +\[\begin{array}{l}{\frac{dN_{i}}{d t} = N_{i}\left(1 - N_{i} - \sum_{j}\alpha_{i j}N_{j} + g_{i}p\right)}\\ {\dot{p} = -\delta p + \beta \sum_{j}k_{j}N_{j}} \end{array} \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[114, 689, 882, 747]]<|/det|> +In the adiabatic limit, where the rate of pH change is much faster than the species' growth rates (time scale separation), or at steady state, we can assume \(\dot{p} = - \delta p + \beta \sum_{j} k_{j} N_{j} = 0\) . This implies that \(p \equiv \beta^{*} \sum k_{j} N_{j}\) , where \(\beta^{*} = \beta / \delta\) . Substituting \(p \equiv \beta^{*} \sum k_{j} N_{j}\) into equation (2), we obtained: + +<|ref|>equation<|/ref|><|det|>[[368, 751, 880, 799]]<|/det|> +\[\frac{dN_{i}}{dt} = N_{i}\left(1 - \frac{N_{i} + \sum\alpha_{i j}^{*}N_{j}}{K_{i}^{*}}\right) \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[114, 805, 883, 905]]<|/det|> +where the effective gLV- type interaction strength is given by \(\alpha_{i j}^{*} = \frac{(\alpha_{i j} - \beta^{*}g_{i}k_{j})}{(1 - \beta^{*}g_{i}k_{i})}\) , and the effective carrying capacity can be calculated through \(\frac{1}{K_{i}^{*}} = (1 - \beta^{*}g_{i}k_{i})\) . Here, \(g_{i}\) quantifies how pH influences species growth, while \(k_{j}\) quantifies how species alter the environmental pH. The parameter \(\delta\) represents the recovery rate of pH due to the addition of fresh medium at the end of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 214]]<|/det|> +each serial dilution cycle (with pH being neutral, or 7, after each addition). In the model, \(p = 0\) corresponds to neutral \(\mathrm{pH} = 7\) in the experiment, \(p > 0\) and \(p< 0\) represents alkaline and acidic \(\mathrm{pH}\) respectively. The parameter \(\beta\) represents the environmental coupling strength, which quantifies the impact of species on environmental \(\mathrm{pH}\) and reflects the phosphate buffering concentration in the experiment. The normalized environmental coupling strength, considering the competing effects of \(\mathrm{pH}\) recovery \((\delta)\) and species- induced \(\mathrm{pH}\) changes (determined by \(\beta\) ), is given by \(\beta^{*} = \beta /\delta\) . + +<|ref|>text<|/ref|><|det|>[[115, 222, 882, 352]]<|/det|> +We found that the mean and standard deviation of the effective interaction strength under \(\mathrm{pH}\) influence, \(\alpha_{ij}^{*}\) , are larger than the original gLV interaction strength, \(\alpha_{ij}\) (see figure below). Even when gLV interactions are set to zero, \(\mathrm{pH}\) - mediated interactions alone produce a non- zero distribution of \(\alpha_{ij}^{*}\) (see figure below). These results demonstrate that \(\mathrm{pH}\) - mediated interactions can be effectively incorporated into the gLV framework. The compatibility of the gLV model with pH- mediated interactions justifies our choice, as it allows us to account for environmental factors like \(\mathrm{pH}\) without sacrificing the simplicity and analytical power of the gLV model. + +<|ref|>text<|/ref|><|det|>[[115, 359, 882, 484]]<|/det|> +To further explore the pH model's predictions on invasion outcomes, we simulated the model combining both \(\mathrm{pH}\) and gLV interaction effects across various parameter spaces. We found that even when considering only the \(\mathrm{pH}\) effect, the model predicts a decrease in invasion probability with increasing \(\mathrm{pH}\) interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) and species pool size (Supplementary Fig. 23), which qualitatively aligns with the predictions of the pure gLV model (Fig. 2f). In this purely pH- mediated interaction regime, the survival fraction is approximately equal to the invasion probability (Supplementary Fig. 23). + +<|ref|>text<|/ref|><|det|>[[115, 492, 882, 583]]<|/det|> +Moreover, when both gLV interaction strength (mean of \(\alpha_{ij}\) ) and pH- mediated interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) are increased simultaneously, the invasion probability decreases (Supplementary Fig. 23) in a manner similar to that predicted by the gLV model alone (Fig. 2f). In all conditions, the survival fraction remains an efficient predictor of invasion probability (Supplementary Fig. 23), as observed in the pure gLV model (Fig. 4). + +<|ref|>text<|/ref|><|det|>[[115, 591, 882, 697]]<|/det|> +These results demonstrate that the dependence of invasion probability on interaction strength, species pool size, and survival fraction is robust across both pure \(\mathrm{pH}\) and combined \(\mathrm{pH}\) - gLV models. This further justifies our choice of the gLV model, as it successfully predicts key features of invasion behavior in communities. By incorporating \(\mathrm{pH}\) - mediated interactions into the gLV framework, we capture the added complexity of \(\mathrm{pH}\) effects while retaining the simplicity and analytical power of the gLV model. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[200, 88, 796, 450]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 461, 884, 625]]<|/det|> +
Figure. The presence of pH-mediated interactions increases the mean and standard deviation of effective gLV-type interactions. a, The gLV-type interaction \(\alpha_{ij}\) follows a uniform distribution \(U[0,1]\) , with a mean and standard deviation of 0.5 and 0.29, respectively. b, Under the influence of pH, the effective interaction \(\alpha_{ij}^{*} = \frac{(\alpha_{ij} - \beta^{*}g_{i}k_{j})}{(1 - \beta^{*}g_{i}k_{i})}\) shows a larger mean interaction strength of 0.52 and a standard deviation of 0.37 compared to the pure gLV model. In this scenario, \(\alpha_{ij}\) still follows \(U[0,1]\) , while the pH modification parameters \(g_{i}\) and \(k_{i}\) are sampled from a uniform distribution \(U[-1,1]\) . The environmental coupling strength \(\beta^{*}\) is set to 0.5. c, The pure pH model without gLV-type interactions produces a distribution of effective \(\alpha_{ij}^{*}\) with a standard deviation of 0.18.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 87, 875, 538]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 546, 882, 725]]<|/det|> +
Supplementary Fig. 23. The invasion probability decreases with increasing pH-mediated interaction strength and gLV-type interaction strength, while the survival fraction remains approximately equal to the invasion probability. a, The pure pH model, without gLV-type interactions, predicts that invasion probability decreases with increasing pH interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) and species pool size. b, In the pure pH model, the survival fraction is approximately equal to the invasion probability, even without gLV-type interactions. c, When both pH interaction strength (mean of \(\beta^{*}g_{i}k_{i}\) ) and gLV-type interaction strength (mean of \(\alpha_{ij}\) ) increase simultaneously, the invasion probability decreases. d, The survival fraction remains approximately equal to the invasion probability when combining the pH model with the gLV model. The points and color maps depict the mean value over 100 simulations.
+ +<|ref|>text<|/ref|><|det|>[[115, 733, 737, 752]]<|/det|> +The discussion on the pH model is referenced in the main text on page 5 and 6: + +<|ref|>text<|/ref|><|det|>[[115, 758, 881, 811]]<|/det|> +We also developed a model that directly incorporates pH- mediated growth within the Lotka- Volterra framework, allowing interactions to be expressed as a function of pH modifications. This new model suggests that the presence of pH effects increases the effective inter- species interaction + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 126]]<|/det|> +strengths and yields predictions similar to those of the canonical Lotka- Volterra model (Supplementary Fig. 23). + +<|ref|>text<|/ref|><|det|>[[115, 132, 883, 169]]<|/det|> +As the reviewer suggested, we now add justification for the choice of Lotka- Volterra model in the Supplement: + +<|ref|>text<|/ref|><|det|>[[115, 175, 553, 193]]<|/det|> +Justification for the choice of the Lotka- Volterra model + +<|ref|>text<|/ref|><|det|>[[115, 199, 882, 289]]<|/det|> +As a phenomenological model, generalized Lotka- Volterra (gLV) model describes species interactions through a pair- wise interaction matrix, capturing how the abundance of one species influences the growth of others. The interaction matrix in the gLV framework is a high- level description that can incorporate various mechanisms, including resource competition, cross- protection, cross- toxin, cross- feeding, and pH- mediated interactions. + +<|ref|>text<|/ref|><|det|>[[115, 296, 882, 472]]<|/det|> +It is important to emphasize that the pH- mediated interaction is not the only sole mechanism in our experiment. Some communities show fluctuating biomass while maintaining stable pH levels, indicating other mechanisms, such as cross- toxin interactions, are at play, particularly under high nutrient concentrations. Furthermore, our model considering only pH- mediated interactions cannot explain all experimental observations. For instance, our experiments and gLV simulations show fluctuating communities with higher diversity and invasibility (Hu et al. 2022), while our pH- only models predict lower diversity and invasibility (Supplementary Fig. 10- 11 of Hu et al. 2022) (Hu et al. 2022), contrary to our experimental findings. These justifications support our use of the gLV model and align with recent progress in using phenomenological models for demographic manipulations (Shoemaker, Sánchez, and Grilli 2023). + +<|ref|>text<|/ref|><|det|>[[115, 480, 882, 586]]<|/det|> +To further justify our modelling approach, where increasing nutrient levels in the experiment correspond to corresponds to amplifying average interaction strength in the gLV model, we conducted pairwise coculture experiments. These experiments revealed that as nutrient concentration increased, the fraction of species pairs that coexisted decreased, while the fraction of competitive exclusions (where only one species survives) increased (Hu et al. 2022), reflecting the increase in interspecies interaction strength within the framework of the gLV model. + +<|ref|>text<|/ref|><|det|>[[115, 595, 882, 735]]<|/det|> +4. My understanding is that the term "fluctuations" in the context of this study means fluctuations induced by chaotic dynamics. I understand that these are not meant to be viewed as stochastic fluctuations, but in my experience, I have found that only a fraction of eco/evo readers understand the distinction between fluctuations induced by deterministic vs. stochastic effects. It would aid the typical reader if the authors clarified what form of fluctuations they are focused on in the Introduction, specified the type of fluctuation whenever the term is used in the manuscript (e.g., "fluctuations" and "deterministic fluctuations"), and briefly addressed in the Discussion how the consideration of stochastic fluctuations might factor into their subsequent research efforts. + +<|ref|>text<|/ref|><|det|>[[115, 744, 882, 797]]<|/det|> +We appreciate the reviewer for raising this important point. In this study, all fluctuations are referred to as deterministic fluctuations (chaos or limit cycle oscillations) driven by inter- species interactions, rather than stochastic fluctuations driven by demographic noise. + +<|ref|>text<|/ref|><|det|>[[115, 806, 882, 895]]<|/det|> +The reason we believe our experiment is in the deterministic population dynamics regime, rather than the stochastic regime, is due to the large population size in our experimental communities. Colony plating and counting in our experiment indicate that the CFU is on the order of \(10^{9}\) per mL. We cultured each community in a \(300~\mu \mathrm{L}\) medium, consisting of around \(3\times 10^{8}\) cells, and transferred \(10~\mu \mathrm{L}\) of the community cultures into a new plate with \(300~\mu \mathrm{L}\) of fresh media in each + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 144]]<|/det|> +dilution cycle, transferring about \(10^{7}\) cells. The relative ratio of deterministic population growth to stochastic birth and death is on the order of \(1 / \sqrt{n}\) , which is very low given the total population size of \(10^{7}\) to \(3 \times 10^{8}\) cells in our experiment. + +<|ref|>text<|/ref|><|det|>[[115, 154, 882, 243]]<|/det|> +Additionally, our communities display stable species composition in stable communities, with sequencing results showing that species composition does not exhibit significant stochastic fluctuations (Hu et al. 2022). This suggests that stochastic fluctuations play a less important role in our experiment. We are indeed very interested in how demographic noise drives stochastic fluctuations in communities, and working on a subsequent research project on this topic. + +<|ref|>text<|/ref|><|det|>[[115, 251, 882, 322]]<|/det|> +We have followed the reviewer's suggestion and clarified the distinction between deterministic and stochastic fluctuations in the manuscript. We have specified the type of fluctuation whenever the term is used in the manuscript (e.g., "deterministic fluctuations"). We have also added a brief discussion on how consideration of stochastic fluctuations might factor into future research. + +<|ref|>text<|/ref|><|det|>[[115, 332, 549, 350]]<|/det|> +We revised the Introduction on page 3 of the main text: + +<|ref|>text<|/ref|><|det|>[[115, 359, 882, 412]]<|/det|> +These deterministic fluctuations in communities are chaotic dynamics or limit cycle oscillations driven by inter- species interactions, rather than stochastic fluctuations driven by demographic noise, because of the large population size regime in this study (see Supplement). + +<|ref|>text<|/ref|><|det|>[[115, 420, 882, 456]]<|/det|> +We addressed how the consideration of stochastic fluctuations might factor into their subsequent research efforts in the Discussion, on page 10 of the main text: + +<|ref|>text<|/ref|><|det|>[[115, 465, 882, 553]]<|/det|> +Beyond the deterministic fluctuations observed under large population sizes in this work, it is important to study invasions under stochastic dynamics driven by demographic noise in subsequent research. Theory shows that demographic noise can drive stochastic transitions between alternative stable states, leading to another type of community fluctuations (Kessler and Shnerb 2015). + +<|ref|>text<|/ref|><|det|>[[115, 562, 797, 580]]<|/det|> +We also added relevant discussion in supplementary materials to make this point clear: + +<|ref|>text<|/ref|><|det|>[[115, 590, 882, 820]]<|/det|> +In this study, all fluctuations are referred to as deterministic fluctuations (chaos or limit cycle oscillations) driven by inter- species interactions, rather than stochastic fluctuations driven by demographic noise. The reason we believe our experiment is in the deterministic population dynamics regime, rather than the stochastic regime, is due to the large population size in our experimental communities. Colony plating and counting in our experiment indicate that the CFU is on the order of \(10^{9}\) per mL. We cultured each community in a \(300~\mu \mathrm{L}\) medium, consisting of around \(3 \times 10^{8}\) cells, and transferred \(10~\mu \mathrm{L}\) of the community cultures into a new plate with \(300~\mu \mathrm{L}\) of fresh media in each dilution cycle, transferring about \(10^{7}\) cells. The relative ratio of deterministic population growth to stochastic birth and death is on the order of \(1 / \sqrt{n}\) , which is very low given the total population size of \(10^{7}\) to \(3 \times 10^{8}\) cells in our experiment. Additionally, our communities display stable species composition in stable communities, with sequencing results showing that species composition does not exhibit significant stochastic fluctuations (Hu et al. 2022). This suggests that stochastic fluctuations play a less important role in our experiment. + +<|ref|>text<|/ref|><|det|>[[115, 829, 882, 881]]<|/det|> +5. It is worth briefly mentioning in the supplement why continued migration from the regional pool was a necessarily experimental detail for this study. Specifically, how the absence of experimentally-imposed migration would correspond to a gLV with zero migration, the analytic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 125]]<|/det|> +results of which would be decidedly less rich (e.g., no chaos, etc.). Broad readership may not pick up on this detail. + +<|ref|>text<|/ref|><|det|>[[115, 135, 882, 188]]<|/det|> +We have followed the reviewer's suggestion and discussed the importance of dispersal in the supplement to emphasize how dispersal from the regional pool contributes to maintaining community diversity and enabling persistent fluctuations: + +<|ref|>text<|/ref|><|det|>[[114, 197, 882, 354]]<|/det|> +We introduced a dispersal rate of \(10^{- 5}\) in both of our experiments and gLV simulations. The dispersal from the species pool to the local community is important for maintaining persistent fluctuations in both gLV simulation and our experiment. We found that the lack of dispersal in the gLV model leads to a significantly lower fraction of fluctuating communities (Supplementary Fig. 24). Similarly, the fraction of fluctuating communities is much lower in our experimental communities without daily dispersal (Supplementary Fig. 25). Without dispersal from the species pool, some species reach the extinction boundary due to dramatic fluctuations and cannot recover. This results in a continuous decrease in community fluctuations in both the model and the experiment. + +<|ref|>image<|/ref|><|det|>[[118, 365, 883, 564]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 576, 883, 716]]<|/det|> +Supplementary Fig. 24. Non- zero dispersal sustains persistent community fluctuations in gLV model. The panels show the theoretical phase diagrams of community fluctuation fraction under different dispersal rates ( \(D = 0\) , \(D = 10^{- 7}\) , \(D = 10^{- 6}\) ). Communities under no dispersal ( \(D = 0\) , left panels) exhibit a low fluctuation fraction in the persistent fluctuation phase. The patterns of ecological diversity and dynamics do not significantly change as the dispersal rate varies from \(D = 10^{- 7}\) (middle panels) to \(D = 10^{- 6}\) (right panels). The dashed line and solid line in the figures represent survival boundary and stability boundary, respectively. The color maps depict the mean value over 1000 simulations. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[345, 98, 630, 271]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 281, 883, 404]]<|/det|> +
Supplementary Fig. 25. Zero dispersal leads to stable communities under high nutrient conditions (strong interactions) in the experiment. The biomass of eight distinct microbial communities ( \(S = 24\) ) consistently reaches stable states when exposed to high nutrient concentrations (strong interactions) in the absence of species dispersal from the species pool to the community. In contrast, when dispersal is present, a significant proportion of communities exhibit fluctuations under the same high nutrient conditions and species pool size, as previously reported in Fig. 1d and in our previous paper (Hu et al. 2022) (Fig. 2C).
+ +<|ref|>text<|/ref|><|det|>[[115, 412, 882, 519]]<|/det|> +6. Related, did the authors perform any experiments without daily migration from the regional pool? Contrasting the results of this study with that type of experiment would strengthen their claims and provide further opportunities to test the utility of the gLV. Alternatively, if there are there any published experiments on invasion analysis using a similar experimental setting without imposing migration, then such results could be verbally compared to the results of their experiment. + +<|ref|>text<|/ref|><|det|>[[115, 528, 883, 720]]<|/det|> +We conducted experiments without daily migration from the regional pool and observed that the fraction of fluctuating communities was significantly lower compared to experiments with daily dispersal. In the absence of dispersal, some species reached the extinction threshold due to dramatic fluctuations and were unable to recover, resulting in a continuous decrease in community diversity and the eventual disappearance of persistent fluctuations. These findings are consistent with the predictions of the gLV model without migration, which also shows a lower fraction of fluctuating communities. While we have not yet performed invasion experiments without dispersal, we agree with the reviewer that this would be an important and interesting experiment to pursue in our ongoing research. We have incorporated this comparison and discussion into the manuscript to emphasize the importance of dispersal in maintaining community diversity and enabling persistent fluctuations. + +<|ref|>text<|/ref|><|det|>[[115, 729, 881, 765]]<|/det|> +7. Is the experimentally-imposed migration rate sufficient to induce chaotic dynamics in the context of their gLV model? I searched for this detail in the supplement but did not find it. + +<|ref|>text<|/ref|><|det|>[[115, 774, 882, 897]]<|/det|> +The dispersal rate in our experiments and gLV simulations is \(10^{- 5}\) . We found that different levels of dispersal rates can sustain persistent fluctuations (chaos or limit cycle oscillations) in the gLV model. As long as the extinction-prone species can come back and bloom through dispersal, the persistent fluctuation is not influenced by specific values of the dispersal rate. Only a zero- dispersal rate leads to a significantly lower fraction of fluctuating communities in the model. Without dispersal from the species pool, some species hit the extinction boundary due to dramatic fluctuations and cannot recover, resulting in a continuous decrease in community fluctuations. We + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 126]]<|/det|> +have discussed the consistency between dispersal rates in the experimental and simulation settings in the supplement to clarify this point. + +<|ref|>text<|/ref|><|det|>[[115, 134, 881, 171]]<|/det|> +8. I would also encourage the authors to make both their code and raw data available on public repositories to ensure transparency and reproducibility. + +<|ref|>text<|/ref|><|det|>[[115, 180, 882, 233]]<|/det|> +We thank the reviewer for raising this important point. We planned to make the code and raw data available in public repositories before publication. We have now uploaded our raw data and code to public repositories to ensure transparency and reproducibility: + +<|ref|>text<|/ref|><|det|>[[115, 241, 870, 331]]<|/det|> +Data and materials availability: Isolates and communities are available upon request. All data are available in the supplementary materials and deposited on Dryad (https://datadryad.org/stash/share/Mi09U1xtHkQ8_0D4DPuVDzoSp0-hcIT8oG76h8edCdM). All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +<|ref|>text<|/ref|><|det|>[[115, 338, 883, 444]]<|/det|> +9. Lines 148-149: It would help the reader if justification for the extinction threshold was provided in the main text. In lines 81-82 of the supplement the authors describe the lower bound on detection due to sequencing, but it is not clear how they arrived at this particular value. It would also help if there was a comparison between the chosen threshold and the inverse of the typical total abundance of the community (all cells), the threshold for true extinction, to provide context for the detection limitation. + +<|ref|>text<|/ref|><|det|>[[115, 454, 882, 508]]<|/det|> +We appreciate the reviewer for this important comment, and have added the justification of the choice of extinction threshold in the supplement and refer it in the main text to provide context for the detection limitation and comparison with the typical total abundance of the community: + +<|ref|>text<|/ref|><|det|>[[115, 516, 552, 534]]<|/det|> +We chose the survival threshold for three main reasons: + +<|ref|>text<|/ref|><|det|>[[145, 543, 883, 666]]<|/det|> +1. Distinction from dispersal rate: The survival threshold should be significantly higher than the dispersal rate to distinguish truly surviving species from those whose low abundance is only sustained by dispersal. Since we used a dispersal rate of \(10^{-5}\) , the threshold should be high enough to be separated from the dispersal floor but not too high to falsely classify surviving species as extinct. Simulation results of gLV suggest that a threshold of \(8 \times 10^{-4}\) efficiently separates surviving species from extinct ones (Supplementary Fig. 26). + +<|ref|>text<|/ref|><|det|>[[145, 675, 883, 799]]<|/det|> +2. Sequencing depth: The sequencing depth is on the order of \(10^{4}\) . The number of cells transferred in each dilution cycle is on the order of \(10^{7}\) cells, and the number of cells used in DNA extraction and amplicon sequencing is on the order of \(10^{6}\) cells. Therefore, the detection limit in our sequencing data is primarily determined by the sequencing depth of each community. Any threshold below the order of \(10^{-4}\) would be inconsistent with the detection limit of our sequencing depth. We chose \(8 \times 10^{-4}\) , which is sufficiently above the detection limit but not too high to exclude low-abundance surviving species. + +<|ref|>text<|/ref|><|det|>[[145, 808, 883, 896]]<|/det|> +3. Robustness of conclusion: We found that varying the survival threshold between \(10^{-4}\) and \(10^{-3}\) does not alter our key conclusions. Specifically, a survival threshold of \(10^{-4}\) yielded exactly the same number of successful invasions as a threshold of \(8 \times 10^{-4}\) in our experiment. The survival threshold of \(10^{-3}\) resulted in 61 successful invasions out of 244 total invasion tests, compared to 63 successful invasions out of 244 total invasion tests + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 89, 884, 195]]<|/det|> +under the \(8 \times 10^{- 4}\) threshold. There were only two cases where the invader abundance fell between \(8 \times 10^{- 4}\) and \(10^{- 3}\) , leading to a minor quantitative difference in the number of successful invasions. We further verified that this small difference does not affect our major conclusions, including (1) that fluctuating communities are more invisible than stable communities, and (2) that invasion probability decreases with increasing species pool and interaction strength. + +<|ref|>image<|/ref|><|det|>[[174, 206, 825, 563]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 577, 883, 814]]<|/det|> +
Supplementary Fig. 26. The survival threshold efficiently separates surviving species from extinct species, where the species abundances display a bimodal distribution in the simulations. a, The extinction threshold of \(8 \times 10^{-4}\) (horizontal dashed line) clearly separates the high-abundant, surviving species from the low-abundant "extinct" species \((S = 50, < \alpha_{ij} > = 0.2)\) . Such "extinct" species would reach zero abundance if dispersal is interrupted (c). b, The extinction threshold of \(8 \times 10^{-4}\) (horizontal dashed line) similarly separates the high-abundant, surviving species from the low-abundant "extinct" species under different interaction strength \((S = 50, < \alpha_{ij} > = 0.6)\) . c, After stopping dispersal at \(t = 1000\) , only species above the extinction threshold survive with stable abundances, while the others undergo extinction \((S = 50, < \alpha_{ij} > = 0.6)\) . This demonstrates that the extinction threshold of \(8 \times 10^{-4}\) efficiently classifies surviving species versus those that would go extinct without dispersal. d, The histogram shows the number of species exhibiting the indicated abundances at steady state. The dataset was generated from 10 in silico communities randomly sampled \((S = 50, < \alpha_{ij} > = 0.2)\) .
+ +<|ref|>text<|/ref|><|det|>[[115, 822, 883, 859]]<|/det|> +We have referred to the justification of the choice of extinction threshold in in the main text on page 4: + +<|ref|>text<|/ref|><|det|>[[115, 868, 883, 905]]<|/det|> +relative invader abundance exceed extinction threshold \(8 \times 10^{- 4}\) on the last day 12; the rationale behind this choice of extinction threshold is explained in the Supplement. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 161]]<|/det|> +10. Lines 208-211: I am unaware of models where the competition coefficients between species can be examined as a function of media modification. If such a model exists, could the authors briefly describe it in their supplement to help the reader understand how environmental variables (e.g., pH) map onto competition coefficients in a gLV model? + +<|ref|>text<|/ref|><|det|>[[115, 169, 883, 328]]<|/det|> +We have developed a model that combines the pH effect with gLV- type interactions to explain our experimental observations, consistent with gLV predictions. This pH model considers species' modifications of environmental pH and the pH- dependent growth of species. In our model, the interaction matrix in the gLV framework is influenced by pH changes induced by species interactions. This combined pH- gLV model can be reduced to a pure gLV- type interaction matrix in the adiabatic limit, allowing us to explicitly show how the pH effect influences the phenomenological interaction matrix in the gLV model. We have added a detailed description of this pH model in the supplement to help readers understand how environmental variables, such as pH, map onto competition coefficients in a gLV model. + +<|ref|>text<|/ref|><|det|>[[115, 335, 883, 494]]<|/det|> +In our group, we have been investigating how community diversity and dynamics depend on resource concentration across various consumer- resource models (e.g., linear growth and Monod growth). However, unlike our experimental observations, we did not find that increasing resource concentration leads to a decrease in diversity and stability within these models. We also tested a consumer- resource model with pH- dependent growth terms, but similarly, we did not observe a decrease in diversity and stability with increased resource concentration in any of the models. We agree with the reviewer that explicitly relating resource concentration to changes in pH and the resulting increase in the strength of competitive interactions is both interesting and important; however, this remains an open question in our ongoing research. + +<|ref|>sub_title<|/ref|><|det|>[[117, 501, 664, 519]]<|/det|> +## 11. Lines 275-280: How are alternative stable states determined here? + +<|ref|>text<|/ref|><|det|>[[115, 525, 883, 633]]<|/det|> +We thank the reviewer for this important question. As proved in previous theoretical work (Fried, Shnerb, and Kessler 2017; Bunin 2017) and shown in our experiments (new supplementary Fig. 22), we found that the same set of species starting from different initial species compositions can reach different alternative stable states under high nutrient concentration (strong interaction). In contrast, they reach a single global stable state under low nutrient concentration (weak interaction), with all communities receiving daily dispersal of species from the pool. + +<|ref|>text<|/ref|><|det|>[[115, 640, 882, 712]]<|/det|> +The observed alternative stable states under high nutrient concentration (strong interaction) exhibit a priority effect, which helps explain why invasion probability is generally lower than the survival fraction under these conditions (bottom left points in Fig. 3c). We have added a detailed description of the determination of alternative stable states in the supplement to clarify this point. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[164, 94, 787, 352]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 368, 883, 612]]<|/det|> +Supplementary Fig. 22. Communities reach global stable states under low nutrient conditions (weak interaction) but reach alternative stable states under high nutrient conditions (strong interaction) when starting from different initial species compositions. Each bar represents a final community stable state after 7 daily dilution cycles starting from a particular initial condition. The communities assemble from the same species in the original pool ( \(S = 12\) for the left and middle communities, \(S = 24\) for the right communities), under low- nutrient (weak interaction) and high- nutrient (strong interaction) conditions, respectively. For each initial condition, one of the species occupies \(99\%\) volume of the initial inoculum, while the other species in the pool together occupy only \(1\%\) volume of the initial inoculum. The results show that these very different initial species compositions lead to the same global stable state under low nutrient conditions (weak interaction) but result in alternative stable states under high nutrient conditions (strong interaction). This indicates the presence of alternative stable states and priority effect under high nutrient (strong interaction), where the initial composition influences the final community structure. + +<|ref|>text<|/ref|><|det|>[[116, 621, 882, 675]]<|/det|> +12. Fig. 1d: Why are all but two of the "fluctuating" communities decreasing in biomass from day four to five. Could this simultaneous decrease in biomass be driven by experimental details rather than by the intrinsic dynamics of the communities? + +<|ref|>text<|/ref|><|det|>[[115, 684, 884, 792]]<|/det|> +We thank the reviewer for raising this important point. We cultured both stable and fluctuating communities in a mixed manner on the same 96- well deep plates and subjected them to the same experimental processes, including daily dilution and dispersal. The total biomass and sequencing results of stable communities do not show any different behaviors from day 4 to day 5, suggesting that the behaviors of fluctuating communities were not driven by experimental details. Additionally, control wells containing only fresh medium on the same deep- well plates showed no contamination. + +<|ref|>text<|/ref|><|det|>[[115, 799, 883, 905]]<|/det|> +While six of the fluctuating communities decrease in biomass from day four to day five and two of them increase, this pattern is likely due to the small sample size, as we only have eight time series, each spanning just six days. Although this synchrony is not the focus of our current work, it could potentially be explained by the alternating growth cycles of fermentation species and respiration species in our species pool. According to previous studies (Estrela et al. 2022), when fermentation species dominate and grow rapidly, they produce significant amounts of organic acid + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 281]]<|/det|> +by consuming glucose, leading to highly acidic conditions. This acidity inhibits the growth of respiration species and can even result in the self- destruction of the fermentation species (Ratzke, Denk, and Gore 2018). During these cycles, nutrients are not efficiently utilized, resulting in low biomass and pH. In the subsequent cycle, respiration species may become dominant as the acidic conditions from the previous cycle have reduced the fermentation species population. This shift can lead to a higher pH environment where fermentation species do not self- destruct, allowing them to dominate in the next cycle. This alternating dominance between fermentation and respiration species could potentially explain why six of our communities fluctuate in a seemingly synchronized manner. We are currently working on a project to study the mechanism of these intrinsic fermentation and respiration cycles in our communities but do not yet have sufficient data to draw definitive conclusions. + +<|ref|>text<|/ref|><|det|>[[116, 291, 652, 308]]<|/det|> +13. Fig. 1g; lines 380-382: What statistical test was performed here? + +<|ref|>text<|/ref|><|det|>[[115, 319, 883, 354]]<|/det|> +We performed a two independent samples Student's t- test to compare the groups. We have now clarified this point in the figure caption and manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 363, 883, 398]]<|/det|> +14. Fig. 2f: What do the dashed and solid grey lines represent? Could the authors include a legend in the figure? + +<|ref|>text<|/ref|><|det|>[[115, 408, 883, 444]]<|/det|> +We have added legends to Fig. 2f to explain the solid and dashed lines. The solid grey lines represent the stability boundary, and the dashed grey lines represent the surviving boundary. + +<|ref|>text<|/ref|><|det|>[[115, 453, 740, 471]]<|/det|> +15. Fig. 4c: Could the authors add an axis label for the colorbar in the revision? + +<|ref|>text<|/ref|><|det|>[[115, 481, 794, 499]]<|/det|> +We have added the axis label "priority effect" for the colorbar in Fig. 4c, as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 508, 883, 561]]<|/det|> +16. Fig. 4d: "Effect on resident community" is a nice term for those unfamiliar with these types of experiments, but it still reads as somewhat vague. Could the authors describe what this term means in the figure legend and provide an equation for how the quantity was estimated in the supplement? + +<|ref|>text<|/ref|><|det|>[[115, 570, 883, 676]]<|/det|> +We thank the reviewer for this suggestion. The invasion effect on the resident community is measured as the proportion of change in surviving species before and after the invasion, calculated as 1 minus the ratio of overlapping species to total species (1 - (number of overlapping species / total number of species)). We have added the mathematical definition of "Effect on resident community" in Fig. 4d and its figure caption. We have also included the equations for how this quantity was calculated in the manuscript and the supplement. + +<|ref|>text<|/ref|><|det|>[[115, 686, 883, 720]]<|/det|> +17. Fig. 5: What timepoints are used to calculate the fold change? Are the same timepoints used for each community? Is the outcome of the statistical test robust to the choice of timepoints? + +<|ref|>text<|/ref|><|det|>[[115, 730, 883, 782]]<|/det|> +We thank the reviewer for this important question. We have clarified in the manuscript that the fold change of biomass was calculated using the biomass on day 6 (before the invasion) and day 12 (after the invasion colonization was well completed) across all communities. + +<|ref|>text<|/ref|><|det|>[[115, 792, 883, 896]]<|/det|> +As the reviewer suggested, we further examined the robustness of the statistical test to the choice of timepoints. We found that the same statistical difference was observed when calculating the fold change using biomass on day 6 (before the invasion) and the average biomass of day 10, day 11, day 12 (after the invader colonization). This indicates that the outcome of the statistical test is robust to the choice of timepoints. We have included this additional analysis in the manuscript to ensure clarity and robustness. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 90, 870, 321]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 332, 883, 543]]<|/det|> +
Supplementary Fig. 27. The mean fold change in biomass under high nutrient conditions is greater than under low nutrient conditions, which is robust to the choice of time points. a, Invasions into resident communities under low nutrient conditions (weak interactions) result in a statistically lower fold change in biomass compared to communities under high nutrient conditions (strong interactions) \((p< 0.001)\) . The number of successful invasions is \(n = 51\) (low nutrient) and \(n = 11\) (high nutrient). The fold change in biomass was calculated by comparing the biomass on day 6 (before invasion) with that on day 12 (after invasion colonization was fully established) across all communities. b, Similarly, invasions into resident communities under low nutrient conditions (weak interactions) cause a statistically lower fold change in biomass than those under high nutrient conditions (strong interactions) \((p< 0.001)\) . The fold change was calculated by comparing the biomass on day 6 (before invasion) with the average biomass of days 10, 11, and 12 (after invader colonization) across all communities.
+ +<|ref|>text<|/ref|><|det|>[[115, 551, 882, 622]]<|/det|> +18. Supplement line 52: The sampling detection limit is \(\sim 10^{\wedge}\{-4\}\) but the chosen dilution rate was \(10^{\wedge}\{-5\}\) . How does the difference between dilution rates and detection limit shape the observed outcomes of the experiment? If it does, it may be worth describing the outcomes in different parameter limits to the reader (i.e., sampling limit much greater than dilution rate and vice-versa). + +<|ref|>text<|/ref|><|det|>[[115, 631, 882, 754]]<|/det|> +We thank the reviewer for this important comment. As shown in the simulation results with gLV, the abundance of surviving species and successful invaders are all well above the surviving threshold \((8\times 10^{- 4})\) and the sampling detection limit \((10^{- 4})\) . Therefore, the measured diversity and invasion success in this work are not influenced by the existence of the sampling detection limit \((10^{- 4})\) . In other words, a better sampling detection limit (e.g., \(10^{- 5}\) or even higher depth) would not change the measured diversity and invasion probability in our work, and thus would not change our observations and conclusions. + +<|ref|>text<|/ref|><|det|>[[115, 763, 882, 835]]<|/det|> +With a detection limit of \(10^{- 4}\) , we indeed cannot detect species whose low abundance is only sustained by the dispersal rate \((10^{- 5})\) . However, this does not impact our study because we focus on the invasion of surviving species whose abundances are high. We have added a description of these outcomes in different parameter limits to the supplement to provide further clarity. + +<|ref|>text<|/ref|><|det|>[[115, 843, 882, 896]]<|/det|> +19. Supplement: Lines 52, 63: I am unfamiliar with the term “dispersal rate” used to describe the process of diluting cultures in a serial transfer experiment. The method used by the authors is different from the standard process of serial dilution, so I think some justification of the term as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 125]]<|/det|> +well as an explanation of how it connects to the mathematical definition of dispersal (Eq. S1) in the supplement is warranted. + +<|ref|>text<|/ref|><|det|>[[115, 134, 882, 258]]<|/det|> +Daily dilution and daily dispersal are two different steps in our experiment. We performed a 30- fold daily dilution by transferring \(10 \mu \mathrm{L}\) of the community cultures into a new plate with \(300 \mu \mathrm{L}\) of fresh media. To apply a \(10^{- 5}\) daily dispersal, we diluted the monoculture of each species in the community by a \(10^{5}\) factor before inoculating \(10 \mu \mathrm{L}\) of diluted monoculture into the wells containing the corresponding experimental community matching each species pool. Therefore, the volume ratio between the dispersal from each species monoculture in the pool and the transfer of each community is \(10^{- 5}\) . + +<|ref|>text<|/ref|><|det|>[[115, 266, 882, 389]]<|/det|> +We chose the term "dispersal rate" according to the ecology literature that studies the migration of species from the mainland or an outside habitat to a local community (Handel 2014). This low dispersal rate is sufficient to avoid the complete extinction of species due to occasional low abundance in persistent fluctuations. In our gLV simulation and experiment, some species hit the extinction boundary due to persistent fluctuation and cannot recover without dispersal, leading to the eventual disappearance of fluctuations due to the decrease in diversity over time. Therefore, the small dispersal rate is important to sustain persistent fluctuations in our community. + +<|ref|>text<|/ref|><|det|>[[115, 398, 882, 451]]<|/det|> +The dispersal rate for each species in our model is also chosen to be \(10^{- 5}\) to match the experiment, and we found that the results do not vary significantly with specific values of the dispersal rate in the gLV model. + +<|ref|>text<|/ref|><|det|>[[115, 460, 882, 513]]<|/det|> +We have followed the reviewer's suggestion and added more comments on the dispersal rate in the supplementary materials to clarify its connection to the mathematical definition of dispersal (Eq. S1). + +<|ref|>text<|/ref|><|det|>[[115, 530, 882, 618]]<|/det|> +20. Supplement lines 100-119: Does the absence of serial dilution being explicitly encoded into the simulation impact the results? Serial dilutions have been explicitly incorporated into mechanistic (Marsland et al., 2020) and phenomenological (Shoemaker et al., 2023) models of community dynamics in an experimental context. Could the authors provide justification of why serial dilution does not need to be explicitly encoded into their simulation? + +<|ref|>text<|/ref|><|det|>[[115, 627, 882, 697]]<|/det|> +We thank the reviewer for this important question. In our previous work (Hu et al. 2022) and other studies in our group, we found that continuous simulation of gLV yields similar qualitative outcomes as simulations incorporating serial dilutions. Specifically, we observed similar dynamical phases in simulations with or without serial dilutions. + +<|ref|>text<|/ref|><|det|>[[115, 707, 882, 777]]<|/det|> +We agree with the reviewer that it is important to show how our results change if we consider a 30- fold daily dilution in our model. We have now added these results to the supplementary materials, demonstrating that the consideration of serial dilution does not change the pattern of invasion outcomes in our simulations. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 88, 860, 313]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 327, 883, 432]]<|/det|> +
Supplementary Fig. 28. Under serial dilutions in the gLV model, the invasion probability decreases with increasing interaction strength and species pool size, the survival fraction remains approximately equal to the invasion probability. a, Invasion probability decreases with increasing interaction strength and species pool size under serial dilutions. b, The survival fraction is approximately equal to the invasion probability under serial dilutions in the gLV model. The points and color maps depict the mean value over 100 simulations.
+ +<|ref|>text<|/ref|><|det|>[[115, 441, 882, 494]]<|/det|> +21. Supplement lines 109-111: What are the units of time and how do they compare to the timescales of the experiments? Is the timescale of the simulation informed by the timescale of the experiment? + +<|ref|>text<|/ref|><|det|>[[115, 502, 882, 626]]<|/det|> +We thank the reviewer for this important question. The unit of time in the simulation is \(1 / r\) , where \(r\) is the growth rate of species in the gLV model, which is set to be unit 1 in our simulations. We are interested in the steady-state behaviors of invasion rather than the effects of transient dynamics. Our simulation results show that \(t = 10^{3}\) is long enough for the communities to complete their transient dynamics from initial conditions to their final fluctuating or stable state. In the steady-state regime, the results do not vary with the time window. As shown in our previous work, the fraction of fluctuations and survival fraction do not vary with time after reaching the steady state. + +<|ref|>text<|/ref|><|det|>[[115, 635, 882, 760]]<|/det|> +We further demonstrate that invasion probability results remain consistent when introducing the invader at \(t = 2 \times 10^{3}\) compared to \(t = 10^{3}\) . Our experimental communities typically reach steady states by day 6, according to species composition and community biomass time series (Supplementary Fig. 3- 11). We found that stable communities' species compositions usually do not significantly vary after day 4, while fluctuating communities' species compositions continue to fluctuate on days 6 and 10 (Hu et al. 2022). Therefore, both our simulation and experiment characterize invasion behavior under community steady states. + +<|ref|>text<|/ref|><|det|>[[115, 769, 882, 874]]<|/det|> +According to the growth curves of the isolates in our experiments (Supplementary Fig. 19), the characteristic growth rate of the isolates is around 1 \((1 / h)\) . Therefore, each daily dilution cycle approximately corresponds to 24 unit simulation time when the growth rate in the model is set to unit 1. This means that the one cycle timescale is on the order of 100 unit times based on this estimation. We have added a discussion of this point in the supplementary materials to clarify the relationship between the timescales of the simulation and the experiments. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 90, 881, 315]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 327, 883, 483]]<|/det|> +
Supplementary Fig. 29. The invasion probability decreases with increasing interaction strength and species pool size across different time windows, with the survival fraction remaining approximately equal to the invasion probability. a, The invasion probability decreases as interaction strength and species pool size increase. b, The survival fraction closely mirrors the invasion probability. To assess whether invader or resident species survived, we identified species whose abundance exceeded the extinction threshold at any point during the last 24 time units of the simulation. This approach yielded invasion probability patterns consistent with those observed in a 100-unit time window. The points and color maps depict the mean value over 100 simulations.
+ +<|ref|>text<|/ref|><|det|>[[114, 492, 883, 633]]<|/det|> +22. Supplement lines 147-148: It's unclear what the CV represents. My understanding is that each CV is calculated over time for each species for a given simulation iteration. Since the dynamics are deterministic and the interaction coefficients are a form of quenched disorder, what random variable is the CV calculated over? Does the distribution of CVs demonstrate a clear bimodality with the \(10^{\wedge}\{-3\}\) cutoff representing the valley between the two peaks? It would help the reader if 1) additional context was provided for the CV and what it represents as well as 2) distributions of simulated CVs plotted to demonstrate the intuition behind classifying communities into stable/fluctuating classes. + +<|ref|>text<|/ref|><|det|>[[114, 643, 883, 750]]<|/det|> +We thank the reviewer for this important comment. The CV represents the coefficient of variation of species abundance. We first calculate the CV of each species' abundance \(N_{i}\) over the time window between \(t = 10^{3} - 100\) and \(t = 10^{3}\) , then pick the maximal one among the species abundance CVs across all species in the community. We then identify the maximum CV among all species in the community. A community is considered fluctuating if this maximum CV exceeds a threshold, as stable communities are characterized by all species abundances that have reached stable states. + +<|ref|>text<|/ref|><|det|>[[114, 758, 883, 847]]<|/det|> +As the reviewer correctly noted, steady- state communities exhibit small maximum CV values for species abundances, while fluctuating communities show relatively large maximum CV values, resulting in a bimodal distribution. The threshold of \(10^{- 3}\) serves as an efficient valley threshold to separate the two peaks. We have added the figure and a detailed discussion in the supplementary materials to clarify this point. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[305, 99, 661, 315]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 325, 886, 437]]<|/det|> +
Supplementary Fig. 31. The threshold of \(10^{-3}\) for the maximal CV of species abundance effectively separates fluctuating communities from stable ones, where the maximal CV of species abundance exhibits a bimodal distribution in the simulations. The histogram displays the number of communities with the indicated maximal CV of species abundance at steady state. The dataset was generated from 2000 in silico communities, randomly sampled with \(< \alpha_{ij} > \in [0.02, 1.1]\) and \(S \in [2, 60]\) .
+ +<|ref|>text<|/ref|><|det|>[[114, 446, 883, 606]]<|/det|> +23. Supplement lines 160-163, Fig. S12c, d: Is some degree of correlation expected since biomass was used to calculate the abundance of each species? This seems similar to the case presented in. Garud et al., where the same parameter factors into both sides of the relationship (pg. 16 and 17 of supplement; 2019). Here the authors partitioned synonymous sites into two categories, providing two estimates of the quantities of interest. These two quantities are conditionally independent of the parameter that factors into both sides of the proposed relationship due to the Poisson thinning property. One quantity is then used to calculate the left side of the relationship while the other is used to calculate the right side. Is a similar analysis appropriate in this case given that total biomass factors into both sides of the quantities examined in Fig. S12c, d? + +<|ref|>text<|/ref|><|det|>[[114, 614, 883, 791]]<|/det|> +We appreciate the reviewer's insightful question. We found that the CV of community biomass is an effective indicator for classifying fluctuating and stable communities in our experiment (as shown in panels a and b of the figure below). Additionally, we demonstrate that both the normalized variation of absolute species abundance (the product of total biomass and species relative abundance by sequencing) and the normalized variation of relative species abundance (relative species composition by sequencing) show a significant positive correlation with biomass CV (correlation=0.91, \(\mathrm{p} = 4.67 \times 10^{- 10}\) ; correlation=0.76, \(\mathrm{p} = 1.06 \times 10^{- 5}\) ). As the reviewer noted, the normalized variation of absolute species abundance is indeed coupled with biomass CV because biomass is used in calculating absolute species abundance. However, the normalized variation of relative species abundance, derived from sequencing data, is independent of biomass. + +<|ref|>text<|/ref|><|det|>[[114, 799, 883, 906]]<|/det|> +To further validate our classification approach, we applied the \(K\) - means clustering classification algorithm to biomass CV alone, normalized variation of absolute species abundance versus biomass CV (panel c), and normalized variation of relative species abundance versus biomass CV (panel d). All analyses yielded the same classification outcome for fluctuating and stable communities. We have now added these discussions to the supplementary materials to provide a clearer understanding of our methodology and results. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 90, 872, 760]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 762, 883, 903]]<|/det|> +Supplementary Fig. 12. Classification of fluctuating and stable resident communities in experiment. a, The standard deviation of community biomass over day 4, day 5 and day 6 show that the stability threshold of 0.05 can separate the communities into stable ones (purple points) with small biomass deviation and fluctuating ones (orange points) with relatively large biomass deviation under high nutrient. b, The standard deviation of community biomass under low nutrient are small (all below the stability threshold of 0.05), which were naturally classified into stable communities. c, Similarly, the standard deviation of community biomass over days 3, 4, 5, and 6 under high nutrient conditions confirms that the stability threshold of 0.05 can distinguish between + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 882, 337]]<|/det|> +stable communities (purple points) with low biomass deviation and fluctuating communities (orange points) with higher biomass deviation. d, Under low nutrient conditions, the standard deviation of community biomass over days 3, 4, 5, and 6 remains below the stability threshold of 0.05, consistently classifying the communities as stable. e, The average coefficient of (temporal) variation for absolute species abundances \((N_{i}\) , computed as the product of total biomass and species relative abundance) exhibit a strong positive correlation with standard deviation of biomass in the experimental communities (correlation \(= 0.91\) , \(p = 4.67 \times 10^{- 10}\) ). \(K\) - means clustering method classifies the points into two clusters where fluctuating communities locate on top right region and stable communities locate on bottom left region. f, The average coefficient of (temporal) variation for relative species abundances \((N_{i}^{*}\) , relative species abundance through 16s sequencing) also exhibits a strong positive correlation with standard deviation of biomass in the experimental communities (correlation \(= 0.76\) , \(p = 1.06 \times 10^{- 5}\) ). \(K\) - means clustering method classifies the communities into stable ones (purple and gray points) and fluctuating ones (orange points). The results suggest that fluctuation in community biomass cooccurs with fluctuation in relative species abundances. + +<|ref|>text<|/ref|><|det|>[[115, 345, 882, 400]]<|/det|> +24. An alternative option could be to examine the relationship between the CV of biomass (OD) and the CV of relative abundances for each ASV, allowing for the identification of community members that disproportionately contribute to the fluctuations in biomass. + +<|ref|>text<|/ref|><|det|>[[115, 407, 882, 601]]<|/det|> +We thank the reviewer for this suggestion. The reason we do not calculate the CV of relative abundance for each ASV is that the read number of low abundance ASVs is small and significantly influenced by limited sequencing depth and variation in amplification efficiency for different sequences. While highly abundant ASVs can reach stable states in some stable communities (as shown in the figure below), low abundance ASVs often display fluctuations due to large noise effects from sampling a small number of reads and other amplification and sequencing noise. Calculating the average CV across all ASVs, including those with small numbers of reads, would amplify the detection variation caused by these small numbers and noise, potentially skewing the classification of community dynamics as fluctuating or stable. To mitigate these issues, we focus on community-level metrics that are less influenced by the noise associated with low abundance ASVs. This approach ensures a more robust classification of community dynamics. + +<|ref|>text<|/ref|><|det|>[[115, 608, 882, 662]]<|/det|> +25. Fig. S2: Is there any phylogenetic structure to these results? Does the placement of a species on the phylogeny relative to the phylogenetic composition of a given community determine species invasibility? + +<|ref|>text<|/ref|><|det|>[[115, 670, 882, 795]]<|/det|> +We thank the reviewer for this insightful question. To study the effect of phylogenetic overlap between invaders and resident species on invasion outcomes, we calculated the overlap fraction of resident species that share the same phylogeny with the invaders across different phylogenetic levels, weighted by the abundance of the resident species. Our analysis revealed a statistically significant positive correlation between this overlap fraction and invasion success, as measured by the final abundance of the invader after colonization. Specifically, invaders that are phylogenetically closer to the resident species tend to achieve higher post-invasion abundances. + +<|ref|>text<|/ref|><|det|>[[115, 802, 882, 891]]<|/det|> +Our interpretation of this positive correlation aligns with our finding that the survival fraction is approximately equal to the invasion probability. A higher fraction of resident species sharing the same phylogeny as the invader indicates that this phylogenetic type is advantageous within the resident community, thereby increasing the likelihood of the invader's survival and success in this environment. We have included these findings on page 9 of the main text and in the supplementary + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 883, 125]]<|/det|> +materials to provide a more comprehensive understanding of how phylogenetic structure influences invasion outcome: + +<|ref|>text<|/ref|><|det|>[[113, 135, 883, 171]]<|/det|> +Interestingly, invaders that are phylogenetically closer to resident species tend to achieve higher post- invasion abundances (Supplementary Fig. 32). + +<|ref|>image<|/ref|><|det|>[[257, 184, 728, 666]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 678, 883, 784]]<|/det|> +Supplementary Fig. 32. Invaders that are phylogenetically closer to resident species tend to achieve higher post- invasion abundances. The overlap fraction of resident species sharing the same phylogeny with invaders shows a statistically significant positive correlation with invader abundance after colonization, across different phylogenetic levels, including phylum, class, order, family, and genus. The overlap fraction at the kingdom level is always 1, as all resident species and invaders in the experiment belong to the same kingdom, Bacteria. + +<|ref|>text<|/ref|><|det|>[[114, 792, 883, 863]]<|/det|> +26. Fig. S12: "The standard deviation of community biomass over day 5, day 6 and day 7" this detail is confusing since the timeseries represented in Fig. 1d ends at day six. What was the rational behind using only these three timepoints? Some justification of using these three timepoints is needed in the Supplement. + +<|ref|>text<|/ref|><|det|>[[113, 872, 883, 908]]<|/det|> +We thank the reviewer for this important comment. We apologize for the typo. The correct sentence should read "The standard deviation of community biomass over day 4, day 5, and day 6," + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 230]]<|/det|> +consistent with the text in the supplementary materials: "We also calculated the average coefficient of variation (CV) for species abundances from day 4, day 5, to day 6." We aimed to classify the steady- state dynamical behavior of communities and therefore tried to avoid transient dynamics influencing our classification of fluctuation and stability. The reason we chose days 4, 5, and 6 to calculate the CV for classifying fluctuating and stable communities is that some communities had not reached steady- state dynamics before day 3 (as shown in the Fig. 1d, Supplementary Fig. 4- 11, showing transient dynamics occur before day 3). We found that most communities typically reach steady- state by day 4, so we used this as the starting point for calculating the CV of dynamics. + +<|ref|>text<|/ref|><|det|>[[115, 238, 884, 292]]<|/det|> +We further checked that the CV calculated using data from days 3, 4, 5, and 6 alone yields the same classification results, demonstrating that our classification is not sensitive to the choice of time windows. We have added these new results and figures to the supplementary materials. + +<|ref|>image<|/ref|><|det|>[[120, 303, 872, 745]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 757, 883, 898]]<|/det|> +Supplementary Fig. 12. Classification of fluctuating and stable resident communities in experiment is robust to choice of time window. a, The standard deviation of community biomass over days 4, 5, and 6 under high nutrient conditions shows that a stability threshold of 0.05 effectively separates the communities into stable (purple points) with low biomass deviation and fluctuating (orange points) with relatively high biomass deviation. b, Under low nutrient conditions, the standard deviation of community biomass over days 4, 5, and 6 is consistently below the stability threshold of 0.05, classifying all communities as stable. c, Similarly, the standard deviation of community biomass over days 3, 4, 5, and 6 under high nutrient conditions + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 177]]<|/det|> +confirms that the stability threshold of 0.05 can distinguish between stable communities (purple points) with low biomass deviation and fluctuating communities (orange points) with higher biomass deviation. d, Under low nutrient conditions, the standard deviation of community biomass over days 3, 4, 5, and 6 remains below the stability threshold of 0.05, consistently classifying the communities as stable. + +<|ref|>text<|/ref|><|det|>[[115, 187, 882, 222]]<|/det|> +27. Fig. S13: The figure is a useful visualization, but in its current form it is difficult to validate the claims made in the legend. + +<|ref|>text<|/ref|><|det|>[[115, 232, 882, 302]]<|/det|> +- "Invisibility positively correlates with richness when varying interaction strength" Is a claim being made here about the direction in which the correlation changes with a change in interaction strength? It's not clear to me whether this claim is about the existence of positive correlations among treatments or the difference in positive correlations between treatments. + +<|ref|>text<|/ref|><|det|>[[115, 310, 882, 381]]<|/det|> +We thank the reviewer for this comment. When we fixed the species pool size at \(S = 20\) , we found that the data points for \(S = 20\) under low nutrient and high nutrient conditions display a significant positive correlation between invasibility and richness. This finding is consistent with the gLV simulation results shown in Fig. 4a. + +<|ref|>text<|/ref|><|det|>[[115, 390, 882, 460]]<|/det|> +To clarify this point, we have plotted the data in a separate new figure and tested the statistical significance of the positive correlation (correlation coefficient \(= 0.7\) , \(\mathrm{p} = 1.06 \times 10^{- 4}\) ). This approach makes it clearer that the claim is about the existence of positive correlations within treatments rather than differences between treatments. + +<|ref|>text<|/ref|><|det|>[[115, 470, 882, 558]]<|/det|> +- "Invisibility positively correlates with richness when randomly sample \(S = 20\) communities under high nutrient, due to fluctuating communities display larger richness and larger invasion probability." I am having a hard time parsing this statement. Is a claim being made about correlation being higher in high nutrient \(S = 20\) fluctuating communities relative to high nutrient \(S = 20\) stable communities? + +<|ref|>text<|/ref|><|det|>[[115, 568, 882, 674]]<|/det|> +When analyzing the data points under high nutrient conditions with \(S = 20\) , we found a significant positive correlation between invasibility and richness (correlation coefficient \(= 0.5\) , \(\mathrm{p} = 0.047\) ), as shown in the figure below. This positive correlation arises because fluctuating communities (orange points) are more diverse and more invisible than stable communities (purple points). As a result, fluctuating communities are located in the top right region while stable communities are located in the bottom left region of the figure below. + +<|ref|>text<|/ref|><|det|>[[115, 683, 882, 805]]<|/det|> +To clarify this point, we further examined the correlation within stable (purple points) and fluctuating (orange points) communities separately. We confirmed that neither stable nor fluctuating communities displayed a statistically significant correlation between diversity and invasibility ( \(\mathrm{p} = 0.16\) for stable and \(\mathrm{p} = 0.15\) for fluctuating). Therefore, the overall positive correlation when combining the data points is due to the higher invasibility and diversity of fluctuating communities compared to stable ones. We have added a new figure and detailed discussion in the supplementary materials to elucidate this finding. + +<|ref|>text<|/ref|><|det|>[[115, 814, 882, 902]]<|/det|> +- The legend could use some retooling for clarity. Furthermore, if the claims are about the increase in correlation in one treatment vs. another, then additional statistical analyses are necessary. It seems like the authors are making three claims, which would require three tests. The question is what statistical model to use. A full regression analysis to examine the increase in slope between two treatments while controlling for potential cofounders could be seen as necessary. Alternatively, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 160]]<|/det|> +the authors could test for the difference between two correlation coefficients using Fisher's Z statistic with a null distribution obtained by permuting community identity for a given pair of treatments (Snedecor & Cochran, 1989). This statistic was recently used to test for the change in correlation coefficients in experimental microbial communities (Eq. 21 in Shoemaker et al., 2023). + +<|ref|>text<|/ref|><|det|>[[115, 169, 883, 206]]<|/det|> +We thank the reviewer for this comment. To clearly clarify our statements, we have added three new figures and performed additional statistical tests to show the following: + +<|ref|>text<|/ref|><|det|>[[142, 214, 884, 393]]<|/det|> +1. Invisibility positively correlates with richness when varying interaction strength: We observe a positive correlation between invasibility and richness for \(\mathrm{S} = 20\) communities under low and high nutrient conditions (correlation coefficient \(= 0.7\) , \(\mathrm{p} = 1.06 \times 10^{-4}\) ). +2. Invisibility positively correlates with richness when randomly sampling \(\mathrm{S} = 20\) communities under high nutrient: This is due to fluctuating communities displaying larger richness and larger invasion probability (correlation coefficient \(= 0.5\) , \(\mathrm{p} = 0.047\) ). +3. Invisibility negatively correlates with richness when increasing species pool size from \(\mathrm{S} = 12\) to \(\mathrm{S} = 20\) under low nutrients: This correlation is statistically significant (correlation coefficient \(= -0.62\) , \(\mathrm{p} = 0.014\) ). + +<|ref|>text<|/ref|><|det|>[[115, 401, 882, 473]]<|/det|> +Additionally, we show that under high nutrient conditions with \(\mathrm{S} = 20\) , neither stable communities (purple points) nor fluctuating communities (orange points) display any statistically significant correlation between diversity and invasibility ( \(\mathrm{p} = 0.16\) for stable and \(\mathrm{p} = 0.15\) for fluctuating). We have revised the legend and added these new analyses and figures to the supplementary materials. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[113, 88, 872, 610]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 618, 883, 847]]<|/det|> +Supplementary Fig. 13. Different invasibility- richness relationships in experiment depending upon how the richness is changed (a). b, Invasibility positively correlates with richness when varying interaction strength under fixed species pool (positive correlation between \(S = 20\) communities under low and high nutrient, correlation is calculated across all data points in panel b, correlation coefficient \(= 0.7\) , \(p = 1.06 \times 10^{- 4}\) ). c, Invasibility positively correlates with richness when randomly sample \(S = 20\) communities under high nutrient, due to fluctuating communities display larger richness and larger invasion probability (correlation is calculated across all data points in panel c, correlation coefficient \(= 0.5\) , \(p = 0.047\) ). Neither stable communities (purple points in panel c) nor fluctuating communities (orange points in panel c) display any statistically significant correlation between diversity and invasibility ( \(p = 0.16\) for stable and \(p = 0.15\) for fluctuating). d, Invasibility negatively correlates with richness when increasing species pool size from \(S = 12\) to \(S = 20\) under low nutrient (correlation is calculated across all data points in panel d, correlation coefficient \(= -0.62\) , \(p = 0.014\) ). + +<|ref|>text<|/ref|><|det|>[[114, 856, 883, 891]]<|/det|> +28. Fig. S15, 16: Some type of statistical test is necessary to establish the claim that invasions lead to changes in community composition. There are multiple ways to accomplish this task and the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 160]]<|/det|> +authors may have their own idea. One immediate option strikes me: calculate a paired t- statistic for each community between the control and successfully invaded community, demonstrating that absolute value of the t- statistics is significantly greater than zero. Null distributions could be obtained by permuting control/invade labels of each species within each community. + +<|ref|>text<|/ref|><|det|>[[115, 169, 882, 310]]<|/det|> +We thank the reviewer for the thoughtful suggestions regarding the statistical analysis of invasion effects on community composition. We followed the reviewer's recommendation to calculate the t- statistic for each community by comparing the control and successfully invaded communities, and to compare these values against a Null Distribution obtained by permuting the control/invade labels within each community. Upon conducting this analysis, we observed that the t- statistics for all communities did not show significant differences when compared to the Null Distributions. While this might seem unexpected, it is actually consistent with the underlying assumptions of our experimental and modeling framework. + +<|ref|>text<|/ref|><|det|>[[115, 319, 883, 512]]<|/det|> +The reviewer's suggestion appears to be based on the assumption that invasion would cause significant changes in community composition, implying non- random effects—where the invasion typically has consistent and predictable impacts on the community, whether by increasing diversity, decreasing it, or causing other changes. However, in our study, this assumption does not hold true. Both the invader and resident species were chosen randomly, reflecting the inherent randomness of the ecological network (modeled using a generalized Lotka- Volterra (gLV) model). Given this random selection, the interactions between species are also random. As a result, the impact of an invader on the resident community is not deterministic but rather stochastic—an invader may cause the appearance of new species or lead to the extinction of some existing species. This stochastic nature of species interactions means that the effect of invasion does not necessarily result in a t- statistic that significantly deviates from the Null Distribution. + +<|ref|>text<|/ref|><|det|>[[115, 520, 882, 592]]<|/det|> +In essence, the lack of significant differences between the t- statistic and the Null Distribution in our experimental data aligns with the random nature of species interactions in the gLV model. It suggests that in such a random ecological network, invasions do not consistently lead to systematic changes in community composition that would be detectable as a significant t- statistic. + +<|ref|>text<|/ref|><|det|>[[116, 600, 682, 620]]<|/det|> +We revised the Supplement to clarify the significance of invasion effect: + +<|ref|>text<|/ref|><|det|>[[115, 628, 882, 734]]<|/det|> +To demonstrate that the invasion causes a statistically significant effect on community structure under high nutrient conditions, we performed a one- sample t- test on the invasion effect data shown in Fig. 5d (right panel, under high nutrient conditions). The results indicate that the invasion effect is significantly greater than zero \((\mathrm{p} = 1.11 \times 10^{- 6})\) . The invasion effect is measured as the proportion of change in surviving species before the invasion (on day 6) and after the invasion (on day 12), calculated through: 1 - (number of overlapping species / total number of species). + +<|ref|>text<|/ref|><|det|>[[115, 742, 882, 814]]<|/det|> +29. Fig. S17, S18: Similar to Fig. S15 and S16, but now there are different invader species for each community. The authors could perform a paired t-test for each invader species, pooling observations across communities. A null could be generated for each invader species by permuting control/invade labels within each species within each community. + +<|ref|>text<|/ref|><|det|>[[115, 822, 882, 876]]<|/det|> +We thank the reviewer for the suggestion regarding the analysis of Figures S17 and S18. We followed the reviewer's suggestion and conducted the paired t- tests as recommended. However, similar to the findings in Figures S15 and S16, the results showed no significant differences + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 125]]<|/det|> +between the t- statistics and the corresponding null distributions for each invader species. This outcome aligns with the inherent stochasticity in our experimental and modeling framework. + +<|ref|>text<|/ref|><|det|>[[115, 134, 882, 222]]<|/det|> +In our study, different invader species were randomly assigned to each community, and the interactions between species within these communities were also random. This randomness reflects the stochastic nature of the ecological networks in our experiment and the generalized Lotka- Volterra (gLV) framework. Consequently, the impact of each invader on the communities varied randomly, without a consistent or predictable pattern of change in community composition. + +<|ref|>text<|/ref|><|det|>[[115, 231, 882, 354]]<|/det|> +The reviewer's suggestion seems to assume that the invasion by different species would lead to systematic and significant changes in community composition across different communities, which would be detectable by the paired t- tests. However, given the random selection and interactions of species in our study, such systematic effects are not expected. The random nature of species interactions means that the effects of different invaders on community composition are likely to be random, leading to t- statistics that do not significantly deviate from the null distributions generated by permuting control/invade labels. + +<|ref|>text<|/ref|><|det|>[[115, 364, 682, 382]]<|/det|> +We revised the Supplement to clarify the significance of invasion effect: + +<|ref|>text<|/ref|><|det|>[[115, 391, 882, 496]]<|/det|> +To demonstrate that the invasion causes a statistically significant effect on community structure under low nutrient conditions, we performed a one- sample t- test on the invasion effect data shown in Fig. 5d (left panel, under low nutrient conditions). The results indicate that the invasion effect is significantly greater than zero ( \(\mathrm{p} = 2.07 \times 10^{- 25}\) ). The invasion effect is measured as the proportion of change in surviving species before the invasion (on day 6) and after the invasion (on day 12), calculated through: 1 - (number of overlapping species / total number of species). + +<|ref|>text<|/ref|><|det|>[[115, 506, 882, 592]]<|/det|> +30. Figs. S15-S18: Is there any relationship between the relative abundance of the invading species and the change in relative abundance of the remaining species between the control/invade treatments? This may not be the most appropriate analysis for compositional data, but you plot the relative abundance of the invading species vs. the mean difference in relative abundance between treatments for the remaining species, do you see a clear relationship? + +<|ref|>text<|/ref|><|det|>[[115, 602, 882, 743]]<|/det|> +We thank the reviewer for the insightful comments and suggestions on our manuscript. We have followed the reviewer's recommendation regarding Supplementary Figures 15- 18 to investigate the relationship between the relative abundance of the invading species and the change in relative abundance of the remaining species between the control/invasion treatments. Specifically, we plotted the relative abundance of the invading species against the mean difference in relative abundance between treatments for the remaining species. We conducted this analysis and found a clear relationship. The results and corresponding plots have been included in the supplementary materials for your review. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 92, 875, 404]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 416, 883, 594]]<|/det|> +Supplementary Fig. 33. The Invasion effect positively correlates with the final abundance of invaders in the invaded communities after colonization. a, Simulating \(S = 32\) communities with gLV shows positive correlations between invasion effect and final invader abundance under various average interaction strengths including \(< \alpha_{ij} > = 0.3\) (correlation coefficient \(= 0.23\) , \(p = 4.3 \times 10^{- 13}\) ), \(< \alpha_{ij} > = 0.6\) (correlation coefficient \(= 0.75\) , \(p = 1.4 \times 10^{- 126}\) ), \(< \alpha_{ij} > = 1.0\) (correlation coefficient \(= 0.55\) , \(p = 2.6 \times 10^{- 25}\) ). \(n = 1000\) simulations for each interaction strength. b, In the experiment, there is a weak positive correlation between the invasion effect and final invader abundance under low nutrient conditions (weak interaction) (correlation coefficient \(= 0.35\) , \(p = 0.013\) , \(n = 51\) ). There is no statistically significant correlation under high nutrient conditions (strong interaction) (correlation coefficient \(= 0.37\) , \(p = 0.23\) , \(n = 12\) ). + +<|ref|>text<|/ref|><|det|>[[115, 601, 882, 674]]<|/det|> +31. Fig. S19-S21: The authors' claims about the lack of correlations appear correct but I think the correlation coefficient should be provided along with the non-significant P-value. Statistical significance can be assessed by permuting x and y vectors. Permutations should be constrained on species identity for Fig. S19. + +<|ref|>text<|/ref|><|det|>[[115, 682, 882, 736]]<|/det|> +We thank the reviewer for this important suggestion. We have followed the reviewer's comment and added the correlation coefficient and non- significant P- value (obtained by permuting x and y vectors, constrained on species identity for Fig. S19) to the supplementary materials: + +<|ref|>text<|/ref|><|det|>[[115, 744, 882, 833]]<|/det|> +The correlation coefficient between invasion probability and invader growth rates is 0.212, p- value \(= 0.584\) under high nutrient; correlation coefficient \(= - 0.334\) , p- value \(= 0.380\) under low nutrient. The correlation coefficient between invasion probability and invader carrying capacities is 0.076, p- value \(= 0.846\) under high nutrient; correlation coefficient \(= - 0.324\) , p- value \(= 0.394\) under low nutrient. + +<|ref|>text<|/ref|><|det|>[[115, 841, 882, 900]]<|/det|> +Supplementary Fig. 20. There is no statistically significant correlation between invasion effect and invader properties. Under high nutrient, invasion effect does not show statistically significant correlation with carrying capacity (a) (correlation coefficient \(= 0.281\) , p- value \(= 0.377\) ) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 169]]<|/det|> +and growth rate (b) (correlation coefficient=0.023, p- value=0.944). Under low nutrient, invasion effect does not show statistically significant correlation with carrying capacity (c) (correlation coefficient=0.208, p- value=0.143) and growth rate (d) (correlation coefficient=0.200, p- value=0.160). + +<|ref|>text<|/ref|><|det|>[[114, 181, 883, 340]]<|/det|> +Supplementary Fig. 21. There is no statistically significant correlation between invasion effect and invasion probability. Under high nutrient, invasion effect does not show statistically significant correlation with invasion probability of invaders (a) (correlation coefficient=0.127, p- value=0.694) and invasion probability of resident communities (b) (correlation coefficient=0.105, p- value=0.745). Under low nutrient, invasion effect does not show statistically significant correlation with invasion probability of invaders (c) (correlation coefficient=- 0.086, p- value=0.550) and invasion probability of resident communities (d) (correlation coefficient=318, p- value=276). + +<|ref|>sub_title<|/ref|><|det|>[[115, 353, 257, 370]]<|/det|> +## Minor Comments + +<|ref|>text<|/ref|><|det|>[[115, 380, 883, 416]]<|/det|> +1) Both passive voice and active voice are used throughout the main manuscript and supplement. Consult the journal style guide and use the appropriate voice throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 423, 883, 460]]<|/det|> +We have revised the manuscript to consistently use the active voice throughout, based on the journal style guide. + +<|ref|>text<|/ref|><|det|>[[115, 469, 883, 505]]<|/det|> +2) Line 76: Should "occupy all available niches and resources" be "occupy all available niches by consuming all resources"? + +<|ref|>text<|/ref|><|det|>[[115, 515, 792, 534]]<|/det|> +We have revised the text to: "occupy all available niches by consuming all resources". + +<|ref|>text<|/ref|><|det|>[[115, 542, 883, 578]]<|/det|> +3) Line 85-86: Given the experiment performed, would be more apt to say that the question is whether the dynamics are stationary with respect to deterministic fluctuations? + +<|ref|>text<|/ref|><|det|>[[115, 587, 883, 640]]<|/det|> +We have revised the text to: "A rarely emphasized property is the residents' dynamics: are the species abundances constant over time, consistent with a stable state, or are they deterministically fluctuating?" + +<|ref|>text<|/ref|><|det|>[[115, 650, 425, 667]]<|/det|> +4) Line 192: Should "effect" be plural? + +<|ref|>text<|/ref|><|det|>[[115, 677, 415, 694]]<|/det|> +We have revised the text to: "effects." + +<|ref|>text<|/ref|><|det|>[[115, 705, 883, 740]]<|/det|> +5) Line 235: Is "niches and resources" redundant here? My understanding that the niche is resource niche in the context of this study. + +<|ref|>text<|/ref|><|det|>[[115, 750, 641, 767]]<|/det|> +We have revised the text to only use "niches" to avoid redundancy. + +<|ref|>text<|/ref|><|det|>[[115, 777, 718, 795]]<|/det|> +6) Lines 304-305: "stronger secondary effect" & "stronger secondary effects" + +<|ref|>text<|/ref|><|det|>[[115, 805, 567, 822]]<|/det|> +We have revised the text to: "stronger secondary effects". + +<|ref|>text<|/ref|><|det|>[[115, 833, 341, 849]]<|/det|> +7) Lines 378-379: Grammar. + +<|ref|>text<|/ref|><|det|>[[115, 860, 883, 895]]<|/det|> +We have revised the text to: "The representative time course of relative species abundance shows that the invader successfully invades and grows in the fluctuating community." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 672, 109]]<|/det|> +8) Lines 379-380: "invasion probability to" \(\hat{\mathbf{e}}\) "invasion probability of" + +<|ref|>text<|/ref|><|det|>[[115, 117, 540, 136]]<|/det|> +We have revised the text to: "invasion probability of". + +<|ref|>text<|/ref|><|det|>[[115, 144, 765, 163]]<|/det|> +9) Line 389: "invaders successfully invade" or "an invader successfully invades"? + +<|ref|>text<|/ref|><|det|>[[115, 172, 610, 190]]<|/det|> +We have revised the text to: "an invader successfully invades". + +<|ref|>text<|/ref|><|det|>[[115, 199, 741, 218]]<|/det|> +10) Line 437: "high nutrient" \(\hat{\mathbf{e}}\) "high nutrient conditions" or something similar. + +<|ref|>text<|/ref|><|det|>[[115, 227, 549, 245]]<|/det|> +We have revised the text to: "high nutrient conditions". + +<|ref|>text<|/ref|><|det|>[[115, 254, 883, 291]]<|/det|> +11) Supplement lines 75-76: Please summarize the DADA2 parameters used in your script and make your DADA2 pipeline available in a public code repository. + +<|ref|>text<|/ref|><|det|>[[115, 299, 883, 336]]<|/det|> +We have summarized the DADA2 parameters used in our script and made the DADA2 pipeline available in a public code repository: + +<|ref|>text<|/ref|><|det|>[[115, 344, 727, 364]]<|/det|> +https://github.com/Jiliang-Hu/Collective-dynamical-regimes-predict-invasion + +<|ref|>text<|/ref|><|det|>[[115, 371, 826, 390]]<|/det|> +12) Supplement lines 79-81: Please make your raxml code available in a public repository. + +<|ref|>text<|/ref|><|det|>[[115, 399, 761, 418]]<|/det|> +We have made all code, including the raxml code, available in a public repository: + +<|ref|>text<|/ref|><|det|>[[115, 426, 727, 445]]<|/det|> +https://github.com/Jiliang-Hu/Collective-dynamical-regimes-predict-invasion + +<|ref|>text<|/ref|><|det|>[[115, 453, 883, 490]]<|/det|> +13) Supplement lines 123-125: This sentence reads as if steady state is defined as the state where community properties change with time. Is this supposed to be the case? + +<|ref|>text<|/ref|><|det|>[[115, 498, 883, 570]]<|/det|> +We thank the reviewer for raising this point. We have revised the sentence to: "We define the steady state of simulated communities as the community state in which community properties (e.g., survival fraction, fluctuation fraction, and invasion probability) do not significantly change as time goes on." + +<|ref|>text<|/ref|><|det|>[[115, 578, 883, 632]]<|/det|> +14) Supplement lines 144-145: How is a window of time of 100 units analogous to a timescale of 24 hours in the experiment? Were growth rates in the simulation parameterized to correspond to growth rates in the experiment? + +<|ref|>text<|/ref|><|det|>[[115, 640, 883, 765]]<|/det|> +According to the growth curves of the isolates in our experiments (see figure below), the characteristic growth rate of the isolates is around 1 (1/h). Therefore, each daily dilution cycle approximately corresponds to 24 unit simulation time when the growth rate in the model is unit 1. This means the one cycle timescale is on the order of 100 unit times based on this estimation. We found the results with a time window of 24 units of simulation time are not qualitatively different from the time window of 100 that we chose, demonstrating the robustness of our findings. We have added this discussion to the supplementary materials for clarity. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 88, 880, 315]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 325, 883, 485]]<|/det|> +Supplementary Fig. 29. The invasion probability decreases with increasing interaction strength and species pool size across different time windows, with the survival fraction remaining approximately equal to the invasion probability. a, The invasion probability decreases as interaction strength and species pool size increase. b, The survival fraction closely mirrors the invasion probability. To assess whether invader or resident species survived, we identified species whose abundance exceeded the extinction threshold at any point during the last 24 time units of the simulation. This approach yielded invasion probability patterns consistent with those observed in a 100- unit time window. The points and color maps depict the mean value over 100 simulations. + +<|ref|>text<|/ref|><|det|>[[115, 493, 883, 562]]<|/det|> +15) Supplement lines 167-168: Can you plot the results from varying the choice of time window? We have added figures of the results from varying the choice of time window in the supplementary materials. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 92, 875, 533]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 544, 883, 773]]<|/det|> +Supplementary Fig. 12. Classification of fluctuating and stable resident communities in experiment is robust to choice of time window. a, The standard deviation of community biomass over days 4, 5, and 6 under high nutrient conditions shows that a stability threshold of 0.05 effectively separates the communities into stable (purple points) with low biomass deviation and fluctuating (orange points) with relatively high biomass deviation. b, Under low nutrient conditions, the standard deviation of community biomass over days 4, 5, and 6 is consistently below the stability threshold of 0.05, classifying all communities as stable. c, Similarly, the standard deviation of community biomass over days 3, 4, 5, and 6 under high nutrient conditions confirms that the stability threshold of 0.05 can distinguish between stable communities (purple points) with low biomass deviation and fluctuating communities (orange points) with higher biomass deviation. d, Under low nutrient conditions, the standard deviation of community biomass over days 3, 4, 5, and 6 remains below the stability threshold of 0.05, consistently classifying the communities as stable. + +<|ref|>text<|/ref|><|det|>[[116, 782, 562, 800]]<|/det|> +16) Supplement lines 174: "Algorithm" should be plural. + +<|ref|>text<|/ref|><|det|>[[116, 809, 445, 827]]<|/det|> +We have revised the text to: "algorithms". + +<|ref|>text<|/ref|><|det|>[[115, 836, 882, 908]]<|/det|> +17) Fig S1: Would an alternative color scale help the reader? It does not appear that colors are assigned based on taxonomy. Assigning different shades of a given color to the species belonging to a given phylum may help with visualization (e.g., Firmicutes get different shades of blue, etc.). We have assigned the same type of color to the species that belong to the same phylum to help + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 882, 178]]<|/det|> +visualize the phylogeny, as suggested. The new color vectors span different shades of colors based on the phylum classification, as requested by the reviewer. Species belonging to the Firmicutes phylum are assigned different shades of blue, Proteobacteria species are assigned different shades of green, Bacteroidota species are assigned different shades of red, Actinobacteriota species are assigned different shades of purple, Cyanobacteria species are assigned different shades of yellow. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[228, 88, 777, 910]]<|/det|> +Bacteria-Firmicutes-Bacilli-Lactobacillales-Streptococcaceae-Lactococcus Bacteria-Firmicutes-Bacilli-Lactobacillales-Leuconostocaceae-Leuconostoc Bacteria-Firmicutes-Bacilli-Lactobacillales-Leuconostocaeae-Leuconostoc Bacteria-Firmicutes-Bacilli-Exiguobacteriales-Exiguobacteriaceae-Exiguobacterium Bacteria-Firmicutes-Bacilli-Bacillales-Planococcaceae-Lysinibacillus Bacteria-Firmicutes-Bacilli-Staphylococcales-Staphylococcaceae-Staphylococcus Bacteria-Firmicutes-Bacilli-Bacillales-Bacillaceae-Bacillus Bacteria-Firmicutes-Bacilli-Lactobacillales-Streptococcaceae-Lactococcus Bacteria-Firmicutes-Bacilli-Bacillales-Planococcaceae-NA Bacteria-Firmicutes-Bacilli-Staphylococcales-Staphylococcaceae-Staphylococcus Bacteria-Firmicutes-Bacilli-Bacillales-Bacillaceae-Bacillus Bacteria-Firmicutes-Bacilli-Exiguobacteriales-Exiguobacteriaceae-Exiguobacterium Bacteria-Firmicutes-Bacilli-Lactobacillales-Leuconostocaceae-Leuconostoc Bacteria-Firmicutes-Bacilli-Exiguobacteriales-Exiguobacteriaceae-Exiguobacterium Bacteria-Firmicutes-Bacilli-Bacillales-Bacillaceae-Bacillus Bacteria-Firmicutes-Bacilli-Lactobacillales-Streptococcaceae-Lactococcus Bacteria-Firmicutes-Clostridia-Lachnospiraales-Lachnospiraceae-Lachnospiraceae_K4A136_group Bacteria-Firmicutes-Bacilli-Bacillales-Planococcaceae-Lysinibacillus Bacteria-Firmicutes-Clostridia-Lachnospiraales-Lachnospiraceae-Agathobacter Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Raoultella Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Klebsiella Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Pluralibacter Bacteria-Proteobacteria-Gammaproteobacteria-Aeromonadales-Aeromonadaceae-Aeromonas Bacteria-Proteobacteria-Gammaproteobacteria-Enterobacterales-FNA-NA Bacteria-Proteobacteria-Gammaproteobacteria-Enterobacterales-Erwiniaceae-Pantoea Bacteria-Proteobacteria-Alphaproteobacteria-Rhizobiales-Rhizobiaceae-Ochrobactrum Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Pseudomonadaceae-Pseudomonas Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Escherichia/Shigella Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Moraxellaceae-Acinetobacter Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Pseudomonadaceae-Pseudomonas Bacteria-Proteobacteria-Gammaproteobacteria-Burkholderiales-Oxalobacteraceae-Herbaspirillum Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Pseudomonadaceae-Pseudomonas Bacteria-Proteobacteria-Gammaproteobacteria-Burkholderiales-Oxalobacteraceae-Stenotrophomonas Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-NA Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Raoultella Bacteria-Proteobacteria-Gammaproteobacteria-Aeromonadales-Aeromonadaceae-Aeromonas Bacteria-Proteobacteria-Gammaproteobacteria-Burkholderiales-Comamonadaceae-Acidovorax Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Citrobacter Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Erwiniaceae-Pantoea Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Pseudomonadaceae-Pseudomonas Bacteria-Proteobacteria-Gammaproteobacteria-Etnerobacterales-Enterobacteriaceae-Klebsiella Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Pseudomonadaceae-Pseudomonas Bacteria-Proteobacteria-Gammaproteobacteria-Pseudomonadales-Pseudomonadaceae-Pseudomonas 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+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 230]]<|/det|> +Supplementary Fig. 1. Taxonomic identity of the bacterial isolates. The identities have been inferred from the ASV (Methods) of 16S sequencing, which allow the classification of the 80 isolates down to the genus level. Colors are consistent with those in the main text and other supplementary figures. Species belonging to the Firmicutes phylum are assigned different shades of blue, Proteobacteria species are assigned different shades of green, Bacteroidota species are assigned different shades of red, Actinobacteriota species are assigned different shades of purple, Cyanobacteria species are assigned different shades of yellow. + +<|ref|>text<|/ref|><|det|>[[115, 240, 828, 260]]<|/det|> +18) Figs. S8-S11: Can you plot the extinction threshold as a dashed/dotted horizontal line? + +<|ref|>text<|/ref|><|det|>[[114, 267, 884, 305]]<|/det|> +The current Figs. S8-S11 y-axis starts from the extinction threshold. The bottom boundary of the plot is the extinction threshold. We have clarified this point in the figure caption. + +<|ref|>text<|/ref|><|det|>[[114, 312, 883, 349]]<|/det|> +19) Fig. S12: Consider plotting the cutoff of 0.05 as a horizontal dashed line for reference in subplots a and b and as a vertical dashed line in subplots c and d. + +<|ref|>text<|/ref|><|det|>[[114, 357, 883, 395]]<|/det|> +We have added the cutoff of 0.05 in the figures as a horizontal dashed line in subplots a and b, and as a vertical dashed line in subplots c and d, to help illustrate the classification boundary. + +<|ref|>text<|/ref|><|det|>[[114, 402, 883, 439]]<|/det|> +20) Fig. S14: How were priority effects quantified? What does the y-axis of the priority effect plot represent? + +<|ref|>text<|/ref|><|det|>[[114, 438, 883, 544]]<|/det|> +The priority effect in Fig. S14 follows the same definition of the priority effect in the main text, which is quantified by calculating the difference between the survival fraction of resident species and the invasion probability of species that invade after the resident communities have assembled, where the difference was normalized by the survival fraction. The priority effect is defined as: (survival fraction – invasion probability)/(survival fraction). We have added this definition in the caption of the figure. + +<|ref|>sub_title<|/ref|><|det|>[[115, 554, 205, 569]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[114, 570, 883, 606]]<|/det|> +Cornish- Bowden, A. (2012). Fundamentals of enzyme kinetics (4th, completely revised and greatly enlarged edition ed.). Wiley- Blackwell. + +<|ref|>text<|/ref|><|det|>[[114, 613, 884, 666]]<|/det|> +Garud, N. R., Good, B. H., Hallatschek, O., & Pollard, K. S. (2019). Evolutionary dynamics of bacteria in the gut microbiome within and across hosts. PLOS Biology, 17(1), e3000102. https://doi.org/10.1371/journal.pbio.3000102 + +<|ref|>text<|/ref|><|det|>[[114, 666, 883, 770]]<|/det|> +Houtsma, P. C., Kant- Muermans, M. L., Rombouts, F. M., & Zwietering, M. H. (1996). Model for the combined effects of temperature, pH, and sodium lactate on growth rates of Listeria innocua in broth and Bologna- type sausages. Applied and Environmental Microbiology, 62(5), 1616–1622. Marsland, R., Cui, W., Goldford, J., & Mehta, P. (2020). The Community Simulator: A Python package for microbial ecology. PLOS ONE, 15(3), e0230430. https://doi.org/10.1371/journal.pone.0230430 + +<|ref|>text<|/ref|><|det|>[[114, 770, 883, 841]]<|/det|> +Shoemaker, W. R., Sánchez, Á., & Grilli, J. (2023). Macroecological laws in experimental microbial systems (p. 2023.07.24.550281). bioRxiv. https://doi.org/10.1101/2023.07.24.550281 Snedecor, G. W., & Cochran, W. G. (1989). Statistical methods (8th ed). Iowa State University Press. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 417, 108]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 117, 883, 362]]<|/det|> +In this manuscript, Hu et al. aim to identify characteristics of microbial communities that determine their invasibility. They first carried out experimental invasions with assembled communities, finding that more diverse communities are more invasive. To further explore this positive invasibility- diversity relationship, a Lotka- Volterra model was used to predict the effect of changing interspecies interaction strength and species pool size on invasibility. This showed that decreasing interaction strength and pool size increased invasibility. This was confirmed experimentally by changing the concentration of glucose and urea to tune interaction strength, and by changing species pool size. These three key determinants of invasibility (interaction strength, pool size, dynamical regime) determine the survival fraction, defined as the fraction of the initial species pool that survives the assembly process. The survival fraction correlates positively with community invasibility, serving as a unifying predictor. They find that under strong interaction strength, the invasion probability is lower than the survival fraction, indicating a priority effect. The strength of interactions is also shown to determine the impact of invasion on the resident community. Finally, the properties of invaders were briefly discussed. + +<|ref|>text<|/ref|><|det|>[[115, 370, 882, 476]]<|/det|> +I see this as a valuable and novel contribution to the field. While the long- standing biotic resistance hypothesis predicts that more diverse communities should be less invasive due to niche filling, empirical evidence for this is mixed. By considering how diversity is achieved, the authors show that invasibility can be predicted from community features, which has not been done previously. A particular strength of the manuscript is the integration of modelling and experiments to gain mechanistic insight into relationships observed experimentally. + +<|ref|>text<|/ref|><|det|>[[115, 485, 882, 537]]<|/det|> +I have two major comments regarding the tuning of interspecies interactions and determining the impact of invasion. In both cases, limitations of the findings of the manuscript need to be made more explicit. + +<|ref|>text<|/ref|><|det|>[[115, 547, 882, 740]]<|/det|> +The authors state that increasing interaction strength decreases invasion probability. This is done experimentally by increasing the strength of competitive interactions. However, previous work (ref 30) has demonstrated that the type of interaction between the invader/residents, or between residents, impacts the invasion outcome. For example, positive interactions (e.g. facilitation) between the invader and resident community increases invasion probability (as posited by the diversity begets diversity hypothesis). Increasing interaction strength in this case could increase community invasibility, which is a possibility not considered by this study. While I recognize that experimental manipulation of interaction strength is difficult, I would recommend running the model with a distribution of interactions that considers positive interactions, to show the generality of their conclusions. If this has already been done (this is not clear) this should be included in the supplement. + +<|ref|>text<|/ref|><|det|>[[115, 750, 882, 819]]<|/det|> +We thank the reviewer for this insightful comment. We agree that stronger facilitative interactions between invaders and resident species can increase invasion probability. Our pair- wise coculture experiments show that competitive interactions dominate in our experiment, so our modeling has primarily focused on competitive interactions. + +<|ref|>text<|/ref|><|det|>[[115, 829, 882, 881]]<|/det|> +To address the reviewer's suggestion, we have extended our model to include a distribution of interactions that consider both positive and negative interactions. We found that the invasion probability displays similar qualitative patterns with species pool size, interaction strength, and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 126]]<|/det|> +dynamical regimes. Specifically, we observed that invasion probability decreases with increasing species pool size and interaction strength. + +<|ref|>text<|/ref|><|det|>[[115, 135, 882, 206]]<|/det|> +These new results demonstrate that our conclusions are robust across different interaction regimes. We have included these results and the corresponding discussion in the supplementary material. To make this point clear, we now clarify on page 5 of the main text when we introduce the simulation setup: + +<|ref|>text<|/ref|><|det|>[[115, 215, 882, 268]]<|/det|> +We simulated the dynamics of communities with different species pool sizes \(S\) and competitive interaction matrices because competition is the dominant interaction type in our experiments (Hu et al. 2022). + +<|ref|>image<|/ref|><|det|>[[293, 282, 713, 558]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 567, 883, 787]]<|/det|> +Supplementary Fig. 30. The invasion probability decreases with interaction strength and species pool size in presence of positive interactions. To test whether the existence of positive (facilitative) interactions in the ecological network could change our conclusions, we sampled values of \(\alpha_{ij}\) from a uniform distribution \([- \alpha_0, \alpha_0]\) , where \(\alpha_0\) varies between [0, 1.4] on the phase diagram. The invasion probability decreases with interaction strength and species pool size, analogous to those exhibited by communities with exclusively negative interactions (Fig. 2f). Note that the strength of interactions coincides with \(\mathrm{Std}(\alpha_{ij})\) in this case, since the mean of \(\alpha_{ij}\) is zero (both moments factor into the interaction strength metric \(\mathrm{std}(\alpha_{ij}) / (1 - < \alpha_{ij} > )\) that determines stability (Allesina and Tang 2012)). In these simulations, the linear interaction function in the gLV \((\alpha_{ij}N_j)\) was replaced with Monod function \((\alpha_{ij}N_j / (N_j + 1))\) to avoid unbounded growth due to positive interactions (Qian and Akçay 2020; Bunin 2017). The points and color maps depict the mean value over 100 simulations. + +<|ref|>text<|/ref|><|det|>[[115, 796, 813, 815]]<|/det|> +This new supplementary Fig. 30 is now referenced in the main text on page 5 as follows: + +<|ref|>text<|/ref|><|det|>[[115, 823, 883, 859]]<|/det|> +"In addition, we found that neither serial dilutions nor the existence of positive (facilitative) interspecies interactions qualitatively affects this result (Supplementary Fig. 28- 30)." + +<|ref|>text<|/ref|><|det|>[[115, 868, 884, 904]]<|/det|> +The limitations of the study in determining the impact of successful invasions on the structure of the resident community should be more explicit. The impact of successful invasions on the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 352]]<|/det|> +structure of the resident community was measured experimentally by the fold change in biomass, and the invasion effect on the community using 16s sequencing data. However, the fold change in biomass provides little insight on invasion impact. It is not possible to distinguish between the change in biomass of the resident community, and the increase in biomass of the successful invader. Thus, a lower change in biomass in the low nutrient regime may be due to the fact that the invader has less nutrients to grow on, and the converse for the high nutrient regime. Moreover, while species abundance data shows a statistically significant difference in community composition in the higher nutrient regime, it is important that the authors provide information about the effect size. For example, as a \(95\%\) confidence interval for the difference between the invasion success under high nutrient conditions and the invasion success under low nutrient conditions. Finally, it is hard to conclude what the actual effect of invasion is using the selected measures. For example, though species composition may have changed, the invader could be functionally redundant with the species that were excluded, resulting in no change to community functioning. While a comprehensive assessment of invasion impact is out of the scope of this paper, I would recommend for these limitations to be discussed explicitly in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 360, 882, 431]]<|/det|> +We thank the reviewer for raising these important points. We agree that the fold change of biomass increases more under high nutrients than low nutrients, which might be due to the more available resources for the invader under high nutrients. However, the reason we found this increase to be noteworthy is for several reasons: + +<|ref|>text<|/ref|><|det|>[[144, 439, 883, 563]]<|/det|> +1. Community and species biomass variability: We found that communities and single species can display both high and low total biomass under high nutrients (Supplementary Figs. 4-5, Fig. 19), indicating that species in the community may or may not grow to high biomass even under high nutrient supply. Interestingly, we did not observe any invader successfully invading those high biomass communities (OD \(>0.4\) ). Invaders only succeeded in invading low biomass communities (OD \(< 0.4\) ), increasing the community biomass after successful invasions under high nutrients (Figs. S4-S5). + +<|ref|>text<|/ref|><|det|>[[144, 573, 883, 661]]<|/det|> +2. Lack of correlation with invader growth: We found no statistically significant correlation between invasion probability and the growth rate or carrying capacity of invaders (Supplementary Fig. 19). This indicates that high biomass invaders under high nutrients are not necessarily the most successful invaders, suggesting that the increase in total biomass after invasion under high nutrients may not be solely due to invader growth. + +<|ref|>text<|/ref|><|det|>[[115, 670, 882, 723]]<|/det|> +However, we acknowledge that the comparison of the fold change of biomass between two different nutrient regimes may not be highly informative and could confuse the reader. We have therefore added comments on this limitation in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 732, 882, 803]]<|/det|> +To better demonstrate the invasion effect on community composition, we have followed the reviewer's suggestion and calculated the effect size and the \(95\%\) confidence interval for the difference in invasion success under high nutrient conditions versus low nutrient conditions. These results are now included on page 8 of the main text: + +<|ref|>text<|/ref|><|det|>[[115, 812, 882, 865]]<|/det|> +The effect size on community composition caused by increasing from low nutrient (weak interaction) to high nutrient (strong interaction) conditions is 0.14, with a \(95\%\) confidence interval of [0.021, 0.259]. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 213]]<|/det|> +We agree that though species composition may have changed, the invader could be functionally redundant with the species that were excluded, resulting in no change to community functioning. We have added a discussion in the manuscript acknowledging that our definition of invasion effect in this work is limited to the impact on total biomass and community composition. We do not study the invasion effect on community function and cannot rule out the possibility that the community remains functionally unchanged due to functional redundancy between the invader and resident species replaced by the invader. + +<|ref|>text<|/ref|><|det|>[[115, 221, 882, 256]]<|/det|> +We added a comment in the conclusion part on page 10 of the main text to discuss this important limitation: + +<|ref|>text<|/ref|><|det|>[[115, 265, 882, 372]]<|/det|> +Our definition of the invasion effect in this work focuses on the impact on total biomass and community composition. We do not study the invasion effect on community function and cannot rule out the possibility that the community remains functionally unchanged due to functional redundancy between the invader and resident species replaced by the invader. Future research needs to include analysis of functional traits and ecosystem processes to fully understand the functional impact of invasions. + +<|ref|>text<|/ref|><|det|>[[115, 380, 223, 397]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 406, 882, 476]]<|/det|> +1) - I strongly recommend including explicit definitions of key terms, which would improve clarity of the manuscript. For example, the definition of community diversity as the number of species that survive the assembly process is not made explicit in line 152. What 'rich dynamics' (line 191) or richness (line 195, 222 and others) refers to is also unclear to me. + +<|ref|>text<|/ref|><|det|>[[115, 485, 882, 539]]<|/det|> +We thank the reviewer for this comment. We have now explicitly clarified the definitions of key terms, including "diversity," "richness," and "rich dynamics," in the manuscript to improve clarity. We revised the text on page 4 of the main text: + +<|ref|>text<|/ref|><|det|>[[115, 548, 882, 601]]<|/det|> +our experimental results display a significant \((p = 0.036)\) positive correlation between invasion probability and community diversity, where the diversity is defined as the number of species that survive the assembly process over 6 days (correlation coefficient \(= 0.51\) , Fig. 1c). + +<|ref|>text<|/ref|><|det|>[[115, 611, 714, 629]]<|/det|> +We revised the text on page 5 of the main text to clarify the term "richness": + +<|ref|>text<|/ref|><|det|>[[115, 638, 882, 673]]<|/det|> +we found a positive correlation between invasion probability and richness (the number of resident species coexisting before invasion) + +<|ref|>text<|/ref|><|det|>[[115, 682, 882, 753]]<|/det|> +We replaced "rich dynamics and invasion outcomes" with "various dynamics and invasion outcomes" on page 5 of the main text to make it clear. In this sentence, we want to express that we observed various behaviors including invasion success or failure in communities with stable or fluctuating dynamics. + +<|ref|>text<|/ref|><|det|>[[115, 762, 882, 798]]<|/det|> +Our simulations revealed a wide range of dynamics and invasion outcomes under strong interaction strength between species (Fig. 2a, Supplementary Fig. 31). + +<|ref|>text<|/ref|><|det|>[[115, 807, 882, 877]]<|/det|> +2) - The findings of this study could be embedded more explicitly into existing concepts in invasion ecology, which is dominated by niche theory and resource competition. For example, in lines 175-176 the authors state that fluctuating communities are more invisible. The basis of this relationship is not made clear to the reader - I assumed that this means more niches are open at any given point + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 125]]<|/det|> +in time. Moreover, why strong interspecies interactions and a larger species pool decrease invasibility is not discussed. It would also be helpful to discuss this more in the conclusion. + +<|ref|>text<|/ref|><|det|>[[115, 134, 882, 344]]<|/det|> +We thank the reviewer for raising this point. We have added more discussion and citations to clarify the basis of the relationship between community fluctuation and increased invasibility, interpreting that fluctuating communities can create more temporal niches for invader species. There are two reasons we did not make a strong statement on this point: 1) It might need further experiment and study, such as temporal metabolome screening, are required to clearly illustrate the mechanism of higher invasibility in fluctuating communities due to time- varying niches, resources, and available metabolites. While this is beyond the scope of this work, it is an interesting direction for our future research. 2) there is some debate in the literature on the explanatory power of the niche concept in predicting invasion outcomes. Even species that have already occupied a niche can be invaded and outcompeted by another species that consumes the resource more efficiently. Therefore, the absence of available niches may not necessarily lead to failed invasions, as invaders can encroach on currently occupied niches. + +<|ref|>text<|/ref|><|det|>[[115, 354, 882, 529]]<|/det|> +We have added a discussion of these points in the manuscript, as recommended by the reviewer. Regarding the observation that invasion probability decreases with species pool size and interaction strength, we have added more discussion in the conclusion section of the manuscript. In the generalized Lotka- Volterra (gLV) framework, interactions can be mathematically expressed in terms of niche overlap and resource competition, similar to the linear resource- consumer model. Therefore, stronger interaction strength corresponds to larger niche overlap and greater resource consumption. Similarly, a larger species pool leads to increased total interaction (more niche overlap) between community species and invader species, thereby inhibiting invasion more strongly. We have included these discussions and cited relevant literature in the conclusion, as recommended by the reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 538, 882, 574]]<|/det|> +We revised the main text on page 4 and 5 to relate our results to the framework of niche theory and resource consumption in invasion ecology: + +<|ref|>text<|/ref|><|det|>[[115, 583, 882, 740]]<|/det|> +Our experimental tests of invasion demonstrate that, for fixed species pool size and species interaction strength regime (nutrient concentrations), more diverse communities are more invisible because fluctuating communities are both more diverse and more susceptible to invasion. However, when species pool size or nutrient concentration is varied, this relationship does not always hold (Fig. 2 and 3). This increased invasibility under fluctuation can be interpreted through the lens of niche theory, where fluctuating communities create fluctuating niche availability for invader species (Li and Stevens 2012). Temporal fluctuations in resource availability and environmental conditions allow invaders to exploit niches that may not be consistently available in stable communities (Li and Stevens 2012; Warner and Chesson 1985; Levin and Paine 1974). + +<|ref|>text<|/ref|><|det|>[[115, 750, 881, 785]]<|/det|> +We add a discussion on page 5 of the main text on why strong interspecies interactions and a larger species pool decrease invasibility is not discussed: + +<|ref|>text<|/ref|><|det|>[[115, 794, 882, 900]]<|/det|> +In the generalized Lotka- Volterra (gLV) framework, interactions can be mathematically expressed in terms of niche overlap and resource competition (Dalmedigos and Bunin 2020). Stronger interaction strength corresponds to larger niche overlap and greater resource consumption, making it harder for invaders to establish. Similarly, a larger species pool increases the total interaction (more niche overlap) between community species and invader species, thereby inhibiting invasion more strongly (Dalmedigos and Bunin 2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 195]]<|/det|> +3) - I think that for those unfamiliar with previous work from this group, how interaction strength, species pool size and dynamical regime combine to determine survival fraction is difficult to understand. More explanation about how these features interface is necessary for clarity of the manuscript, since they are not independent. For example, it is not immediately clear why there are stable/fluctuating regimes for communities under high nutrient conditions, and not for low nutrient conditions + +<|ref|>text<|/ref|><|det|>[[115, 205, 882, 276]]<|/det|> +We appreciate this important point raised by the reviewer and agree it is crucial to introduce how species pool size, interaction strength, and collective dynamical regimes combine to determine survival fraction. We have added a discussion on this point in the manuscript to provide more clarity. + +<|ref|>text<|/ref|><|det|>[[116, 285, 645, 303]]<|/det|> +We add a discussion on page 9 of the main text to clarify this point: + +<|ref|>text<|/ref|><|det|>[[115, 311, 882, 452]]<|/det|> +Our previous findings indicate that, on average, increasing species pool size and interaction strength both decrease the overall survival fraction(Hu et al. 2022). We also observed that increasing species pool size and interaction strength led to the emergence of some fluctuating communities(Hu et al. 2022). These fluctuating communities, despite the general trend, exhibit a higher survival fraction compared to stable communities assembled from the same species pool size and nutrient concentrations (interaction strength)(Hu et al. 2022). This suggests that while stronger interactions and larger species pools typically reduce survival, the dynamic nature of fluctuating communities allows them to maintain higher survival fractions. + +<|ref|>text<|/ref|><|det|>[[116, 459, 704, 477]]<|/det|> +We added text in the discussion and results part of the main text on page 6: + +<|ref|>text<|/ref|><|det|>[[115, 486, 882, 540]]<|/det|> +We only observed stable communities under low nutrients (weak interaction) because fluctuation only emerges when species pool size and interaction strength are large enough to cross the stability boundary (Hu et al. 2022). + +<|ref|>text<|/ref|><|det|>[[115, 546, 793, 565]]<|/det|> +We also more clearly introduced our previous work in the introduction part on page 3: + +<|ref|>text<|/ref|><|det|>[[115, 571, 882, 642]]<|/det|> +As species pool size and strength of interactions increase, we found that microbial ecosystems transition between three distinct dynamical phases, from a stable equilibrium in which all species coexist to partial coexistence to the emergence of persistent fluctuations in species abundances (Hu et al. 2022). + +<|ref|>text<|/ref|><|det|>[[115, 651, 882, 756]]<|/det|> +4) - The measure of dispersion used is not included in the text of the manuscript (i.e., on line 148, 153, 154, 172 and more, parameter estimates are given as mean +/- X, where X is a measure of dispersion, but which measure it is is not defined). Defining the measure of dispersion is crucial to allow for interpretation of the findings. Some figure legends mention that error bars represent the standard error of the mean, which I assume is the measure used by the authors, but this should be clearly stated in the text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 765, 882, 818]]<|/det|> +We thank the reviewer for pointing this out. We used the standard error of the mean (SEM) as the measure of dispersion across the manuscript. We now state this point clearly in the manuscript where the measure of dispersion appears for the first time. + +<|ref|>text<|/ref|><|det|>[[115, 828, 827, 846]]<|/det|> +We revised the main text on page 4 to clarify the use of SEM as the measure of dispersion: + +<|ref|>text<|/ref|><|det|>[[115, 856, 884, 890]]<|/det|> +Throughout the manuscript, we used the standard error of the mean (SEM) as the measure of dispersion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 802, 109]]<|/det|> +5) - State how invaders were chosen (line 146) - I assume they were chosen at random? + +<|ref|>text<|/ref|><|det|>[[115, 117, 883, 171]]<|/det|> +Yes, the invader species and resident species were both randomly chosen to study the invasion outcome from the perspective of the random ensemble. We have clarified this point in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 180, 483, 198]]<|/det|> +We revised the text on page 4 of the main text: + +<|ref|>text<|/ref|><|det|>[[115, 207, 883, 243]]<|/det|> +For each resident community, we performed 7- 9 independent invasion tests with different randomly chosen invader species on day 6 + +<|ref|>text<|/ref|><|det|>[[115, 251, 883, 288]]<|/det|> +6) - In the section discussing the model (lines 178-190), explicitly state at what relative abundance the invader is introduced relative to the community + +<|ref|>text<|/ref|><|det|>[[115, 295, 883, 333]]<|/det|> +We followed the reviewer's suggestion and explicitly stated that the dispersal rate \(D = 10^{- 5}\) in the simulations, which is the same as in the experiment. + +<|ref|>text<|/ref|><|det|>[[115, 342, 483, 360]]<|/det|> +We revised the text on page 5 of the main text: + +<|ref|>text<|/ref|><|det|>[[115, 369, 470, 387]]<|/det|> +\(D\) is the dispersal rate, which is set to \(D = 10^{- 5}\) + +<|ref|>text<|/ref|><|det|>[[115, 396, 883, 485]]<|/det|> +7) - In the representative time series of fig 2a, invasions are shown to cause a weak effect on the community when the invader grows to a low abundance relative to the rest of the community, whereas the invader causes a strong effect when it grows to high abundance. Is this true across other simulations, or in experiments? If this is the case, it would suggest that there is another factor that influences invasion effect aside from interaction strength. + +<|ref|>text<|/ref|><|det|>[[115, 493, 883, 686]]<|/det|> +We thank the reviewer for this question. In the simulation and experiment, we did observe that there are many cases where the invader grows to high abundance while leading to a weak effect on the community structure, and also cases where the invader grows to low abundance while causing a strong effect on the community structure. To systematically study the dependence of invader abundance on the invasion effect, we analyzed the experimental data and performed simulations. We found a statistically significant weak positive correlation between final invader abundance and invasion effect on community structure under various average interaction strengths (figure below). Furthermore, we also found a statistically significant weak positive correlation between final invader abundance and invasion effect in the experiment under low nutrient conditions (weak interaction), while no statistically significant correlation under high nutrient conditions (strong interaction) in the experiment (figure below). + +<|ref|>text<|/ref|><|det|>[[115, 695, 883, 731]]<|/det|> +We added these results in the supplementary materials and referred to the results in the main text on page 8: + +<|ref|>text<|/ref|><|det|>[[115, 740, 883, 777]]<|/det|> +We also observed a weak positive correlation between the invasion effect and the final abundance of invaders in the experiment and simulation (Supplementary Fig. 33). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 93, 875, 404]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 416, 884, 594]]<|/det|> +
Supplementary Fig. 33. The Invasion effect positively correlates with the final abundance of invaders in the invaded communities after colonization. a, Simulating \(S = 32\) communities with gLV shows positive correlations between invasion effect and final invader abundance under various average interaction strengths including \(< \alpha_{ij} > = 0.3\) (correlation coefficient \(= 0.23\) , \(\mathrm{p} = 4.3 \times 10^{- 13}\) , \(< \alpha_{ij} > = 0.6\) (correlation coefficient \(= 0.75\) , \(\mathrm{p} = 1.4 \times 10^{- 126}\) ), \(< \alpha_{ij} > = 1.0\) (correlation coefficient \(= 0.55\) , \(\mathrm{p} = 2.6 \times 10^{- 25}\) ). \(\mathrm{n} = 1000\) simulations for each interaction strength. b, In the experiment, there is a weak positive correlation between the invasion effect and final invader abundance under low nutrient conditions (weak interaction) (correlation coefficient \(= 0.35\) , \(\mathrm{p} = 0.013\) , \(\mathrm{n} = 51\) ). There is no statistically significant correlation under high nutrient conditions (strong interaction) (correlation coefficient \(= 0.37\) , \(\mathrm{p} = 0.23\) , \(\mathrm{n} = 12\) ).
+ +<|ref|>text<|/ref|><|det|>[[115, 602, 881, 638]]<|/det|> +8) - I would include (strong interaction) or (weak interaction) every time high/low nutrient conditions are mentioned for clarity. This is missing now in line 240 and others + +<|ref|>text<|/ref|><|det|>[[115, 647, 881, 684]]<|/det|> +We thank the reviewer for this suggestion. We have revised the manuscript to use "high nutrient (strong interaction)" and "low nutrient (weak interaction)" throughout to provide clarity. + +<|ref|>text<|/ref|><|det|>[[115, 692, 881, 746]]<|/det|> +9) - Remove "while resident community .... determining invasion outcome" from line 322-323. Invader properties have not been sufficiently explored in this manuscript to claim they don't play an important role in determining invasion outcome. + +<|ref|>text<|/ref|><|det|>[[115, 754, 883, 844]]<|/det|> +We thank the reviewer for raising this point. Although we found no statistically significant correlation between the invasion probability of invaders and the growth rate/carrying capacity of invaders in our experiments (Supplementary Fig. 19), we agree that the invader properties affecting invasion outcomes have not been sufficiently explored in this work. We have therefore deleted the sentence as recommended by the reviewer. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 202, 107]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[110, 115, 884, 900]]<|/det|> +Allesina, Stefano, and Si Tang. 2012. “Stability Criteria for Complex Ecosystems.” Nature. https://doi.org/10.1038/nature10832. Altieri, Ada, Felix Roy, Chiara Cammarota, and Giulio Biroli. 2021. “Properties of Equilibria and Glassy Phases of the Random Lotka- Volterra Model with Demographic Noise.” Physical Review Letters. https://doi.org/10.1103/PhysRevLett.126.258301. Bunin, Guy. 2017. “Ecological Communities with Lotka- Volterra Dynamics.” Physical Review E 95 (4): 042414. https://doi.org/10.1103/PhysRevE.95.042414. Case, T. J. 1990. “Invasion Resistance Arises in Strongly Interacting Species- Rich Model Competition Communities.” Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.87.24.9610. Dalmedigos, Itay, and Guy Bunin. 2020. “Dynamical Persistence in High- Diversity Resource- Consumer Communities.” PLoS Computational Biology. https://doi.org/10.1371/journal.pcbi.1008189. Debray, Reena, Robin A. Herbert, Alexander L. Jaffe, Alexander Crits- Christoph, Mary E. Power, and Britt Koskella. 2022. “Priority Effects in Microbiome Assembly.” Nature Reviews Microbiology. https://doi.org/10.1038/s41579- 021- 00604- w. Estrela, Sylvie, Jean C.C. Vila, Nanxi Lu, Djordje Bajic, Maria Rebolleda- Gomez, Chang Yu Chang, Joshua E. Goldford, Alicia Sanchez- Gorostiaga, and Alvaro Sanchez. 2022. “Functional Attractors in Microbial Community Assembly.” Cell Systems. https://doi.org/10.1016/j.cells.2021.09.011. Fried, Yael, Nadav M. Shnerb, and David A. Kessler. 2017. “Alternative Steady States in Ecological Networks.” Physical Review E. https://doi.org/10.1103/PhysRevE.96.012412. Handel, S. N. 2014. “Dispersal Ecology and Evolution.” Ecological Restoration. https://doi.org/10.3368/er.32.4.464. Hu, Jiliang, Daniel R. Amor, Matthieu Barbier, Guy Bunin, and Jeff Gore. 2022. “Emergent Phases of Ecological Diversity and Dynamics Mapped in Microcosms.” Science. https://doi.org/10.1126/science.abm7841. Kessler, David A., and Nadav M. Shnerb. 2015. “Generalized Model of Island Biodiversity.” Physical Review E - Statistical, Nonlinear, and Soft Matter Physics. https://doi.org/10.1103/PhysRevE.91.042705. Levin, S. A., and R. T. Paine. 1974. “Disturbance, Patch Formation, and Community Structure.” Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.71.7.2744. Li, Wei, and M. Henry H. Stevens. 2012. “Fluctuating Resource Availability Increases Invasibility in Microbial Microcosms.” Oikos. https://doi.org/10.1111/j.1600- 0706.2011.19762. x. Pearce, Michael T., Atish Agarwala, Atish Agarwala, and Daniel S. Fisher. 2020. “Stabilization + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 90, 802, 142]]<|/det|> +of Extensive Fine- Scale Diversity by Ecologically Driven Spatiotemporal Chaos." Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.1915313117. + +<|ref|>text<|/ref|><|det|>[[115, 152, 825, 206]]<|/det|> +Qian, Jimmy J., and Erol Akçay. 2020. "The Balance of Interaction Types Determines the Assembly and Stability of Ecological Communities." Nature Ecology and Evolution. https://doi.org/10.1038/s41559- 020- 1121- x. + +<|ref|>text<|/ref|><|det|>[[115, 215, 847, 269]]<|/det|> +Ratzke, Christoph, Julien Barrere, and Jeff Gore. 2020. "Strength of Species Interactions Determines Biodiversity and Stability in Microbial Communities." Nature Ecology and Evolution. https://doi.org/10.1038/s41559- 020- 1099- 4. + +<|ref|>text<|/ref|><|det|>[[115, 277, 865, 313]]<|/det|> +Ratzke, Christoph, Jonas Denk, and Jeff Gore. 2018. "Ecological Suicide in Microbes." Nature Ecology and Evolution. https://doi.org/10.1038/s41559- 018- 0535- 1. + +<|ref|>text<|/ref|><|det|>[[115, 321, 848, 357]]<|/det|> +Shoemaker, William R, Álvaro Sánchez, and Jacopo Grilli. 2023. "Macroecological Laws in Experimental Microbial Communities." BioRxiv. + +<|ref|>text<|/ref|><|det|>[[115, 366, 872, 419]]<|/det|> +Sprockett, Daniel, Tadashi Fukami, and David A. Relman. 2018. "Role of Priority Effects in the Early- Life Assembly of the Gut Microbiota." Nature Reviews Gastroenterology and Hepatology. https://doi.org/10.1038/nrgastro.2017.173. + +<|ref|>text<|/ref|><|det|>[[115, 428, 872, 464]]<|/det|> +Warner, R. R., and P. L. Chesson. 1985. "Coexistence Mediated by Recruitment Fluctuations: A Field Guide to the Storage Effect." American Naturalist. https://doi.org/10.1086/284379. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 222, 108]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 111, 300, 128]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 130, 877, 189]]<|/det|> +The authors have addressed all my concerns, and added useful new analyses and discussions that clarify the manuscript and the modeling choices they made. I have no more concerns that would need to be resolved before publication. + +<|ref|>text<|/ref|><|det|>[[115, 220, 839, 260]]<|/det|> +We thank the reviewer for the encouraging feedback on our manuscript and for the valuable suggestions provided during the revision process. + +<|ref|>text<|/ref|><|det|>[[115, 290, 880, 350]]<|/det|> +As an extremely minor point, I found the spread of the points in Fig. 5c and d to be a bit large, to the point where my eye didn't immediately parse the two clouds as separate categories - but that's presumably a matter of taste. + +<|ref|>text<|/ref|><|det|>[[115, 361, 876, 441]]<|/det|> +We have retained the original spread of the points in Fig. 5c and d, as reducing it would increase overlap among low nutrient data points (gray ones), making them harder to distinguish. We used different colors for data points under low and high nutrient conditions to help readers differentiate the two clusters more clearly. + +<|ref|>text<|/ref|><|det|>[[115, 473, 352, 490]]<|/det|> +Remarks on code availability: + +<|ref|>text<|/ref|><|det|>[[115, 492, 875, 572]]<|/det|> +No readme files, but the data looks complete. Both the sequencing data analysis code and the simulation code is clear and well- documented. I did not attempt to run the code, but as far as I can tell, the provided code only gives the backbone of the simulations and does not include code needed to reproduce the figures directly. + +<|ref|>text<|/ref|><|det|>[[115, 604, 819, 642]]<|/det|> +We have added detailed README files on GitHub to assist readers in understanding and running the code. + +<|ref|>text<|/ref|><|det|>[[115, 654, 880, 694]]<|/det|> +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +<|ref|>text<|/ref|><|det|>[[115, 725, 300, 782]]<|/det|> +Reviewer #2: Remarks to the Author: Review #2 + +<|ref|>text<|/ref|><|det|>[[115, 805, 881, 865]]<|/det|> +This is an impressive revision, and the quality reflects a high level of effort from the authors. The authors addressed all my comments and gave thoughtful, much appreciated answers. I believe the manuscript should be published. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 838, 129]]<|/det|> +We thank the reviewer for the encouraging feedback on our manuscript and for the valuable suggestions that contributed to the revision process. + +<|ref|>text<|/ref|><|det|>[[115, 160, 828, 180]]<|/det|> +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +<|ref|>text<|/ref|><|det|>[[115, 201, 877, 240]]<|/det|> +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. + +<|ref|>text<|/ref|><|det|>[[115, 241, 870, 280]]<|/det|> +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. + +<|ref|>text<|/ref|><|det|>[[115, 281, 865, 340]]<|/det|> +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +<|ref|>text<|/ref|><|det|>[[115, 370, 870, 470]]<|/det|> +We have added file extensions to ensure compatibility, allowing readers to run the code directly in MATLAB. Additionally, we have included a detailed README file on GitHub to assist readers with setup, required packages, and instructions on how to run the code, as well as a link to the Dryad repository. The function LV_compute_invasion is defined within LV_Invade.m, so no additional files are needed. + +<|ref|>text<|/ref|><|det|>[[115, 482, 877, 522]]<|/det|> +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +<|ref|>text<|/ref|><|det|>[[116, 543, 381, 561]]<|/det|> +The Dryad repository looks good. + +<|ref|>text<|/ref|><|det|>[[115, 604, 621, 622]]<|/det|> +Below are some minor comments that do not require a response. + +<|ref|>text<|/ref|><|det|>[[115, 644, 872, 744]]<|/det|> +- The discussion of how pH mediated interactions can shape the strength of interaction in gLV is helpful. In general, I think a derivation of pH mediated interactions from the starting point of a consumer-resource model is needed, even if it's just for pedagogical reasons and all the heavy modeling is ultimately done using gLV, but such modeling efforts lie outside the scope of the paper. All-in-all the additions to the supplement make it a valuable resource. + +<|ref|>text<|/ref|><|det|>[[115, 765, 780, 784]]<|/det|> +- The elaboration on the connection to ergodicity in response to R1 was very helpful. + +<|ref|>text<|/ref|><|det|>[[115, 805, 457, 823]]<|/det|> +- The new color scheme should aid readers. + +<|ref|>text<|/ref|><|det|>[[115, 846, 827, 905]]<|/det|> +- "In our group, we have been investigating the dependence of community diversity and dynamics on resource concentration across various consumer-resource models (e.g., linear growth or Monod growth)." Very much looking forward to reading this. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 110, 882, 170]]<|/det|> +- The added analyses for the survival threshold are rigorous. The sequencing depth justification is particularly useful since my group has encountered studies where the order of magnitude of demographic manipulations is not justified given the depth of sampling (i.e., # reads). + +<|ref|>text<|/ref|><|det|>[[115, 191, 352, 208]]<|/det|> +Remarks on code availability: + +<|ref|>text<|/ref|><|det|>[[115, 211, 830, 230]]<|/det|> +My sole major comment is that the GitHub repo appears to be incomplete. Some specifics: + +<|ref|>text<|/ref|><|det|>[[115, 250, 878, 289]]<|/det|> +- The file names do not have extensions. I believe that the files are written in matlab, but I do not use that language so I cannot be sure. + +<|ref|>text<|/ref|><|det|>[[115, 291, 870, 330]]<|/det|> +- There is no README file. Some information about the working environment (e.g., packages) and how to run the code would be helpful, as well as a link to the Dryad repository. + +<|ref|>text<|/ref|><|det|>[[115, 332, 864, 391]]<|/det|> +- There are functions called in the files that do not appear to be defined or imported from other files in the repo. For example, LV_compute_invasion is called in LV_Invade but I do not see it defined in that file or in any of the other files in the repo. + +<|ref|>text<|/ref|><|det|>[[115, 433, 383, 450]]<|/det|> +I was unable to run the code as- is. + +<|ref|>text<|/ref|><|det|>[[115, 472, 870, 572]]<|/det|> +We have added file extensions to ensure compatibility, allowing readers to run the code directly in MATLAB. Additionally, we have included a detailed README file on GitHub to assist readers with setup, required packages, and instructions on how to run the code, as well as a link to the Dryad repository. The function LV_compute_invasion is defined within LV_Invade.m, so no additional files are needed. + +<|ref|>text<|/ref|><|det|>[[115, 584, 877, 624]]<|/det|> +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +<|ref|>text<|/ref|><|det|>[[115, 666, 222, 682]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 686, 300, 703]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 705, 870, 744]]<|/det|> +I would like to thank the authors for their thorough revision of this manuscript. All my concerns have been addressed and I have no further comments. + +<|ref|>text<|/ref|><|det|>[[115, 755, 825, 794]]<|/det|> +We thank the reviewer for their positive feedback and thoughtful suggestions, which were instrumental in improving our manuscript through the revision process. + +<|ref|>text<|/ref|><|det|>[[115, 816, 352, 833]]<|/det|> +Remarks on code availability: + +<|ref|>text<|/ref|><|det|>[[115, 836, 618, 853]]<|/det|> +The code is usable but needs a README file for further clarity. + +<|ref|>text<|/ref|><|det|>[[115, 865, 820, 904]]<|/det|> +We have added detailed README files on GitHub to assist readers in understanding and running the code. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 879, 130]]<|/det|> +Code availability: All codes used for simulation and analysis in this publication are available on GitHub (https://github.com/Jiliang- Hu/Collective- dynamical- regimes- predict- invasion). + +<--- Page Split ---> diff --git a/peer_reviews/1480909d25081190a76ef05fb0d72da63ea36322358e946b69f045ef9df801f9/supplementary_1_Peer Review File/images_list.json b/peer_reviews/1480909d25081190a76ef05fb0d72da63ea36322358e946b69f045ef9df801f9/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/1480909d25081190a76ef05fb0d72da63ea36322358e946b69f045ef9df801f9/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/1480909d25081190a76ef05fb0d72da63ea36322358e946b69f045ef9df801f9/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/1480909d25081190a76ef05fb0d72da63ea36322358e946b69f045ef9df801f9/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..af6aaceb8cf0702ccb2879e2e3fa8ab886611b3c --- /dev/null +++ b/peer_reviews/1480909d25081190a76ef05fb0d72da63ea36322358e946b69f045ef9df801f9/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,504 @@ + +# nature portfolio + +# Peer Review Information + +Journal: Nature Microbiology Manuscript Title: Longitudinal multi- omics analysis of host microbiome architecture and immune responses during short- term spaceflight Corresponding author name(s): Dr Christopher Mason + +## Editorial Notes: + +This manuscript has been previously reviewed at another journal. This document only contains reviewer comments, rebuttal and decision letters for versions considered at Nature Medicine. Mentions of prior referee reports have been redacted. + +<--- Page Split ---> + +# nature portfolio + +## Reviewer Comments & Decisions: + +Decision Letter, initial version: + +Message: 16th October 2023 + +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +Dear Chris, + +Thank you for your patience while your manuscript "Viral activation and ecological restructuring characterize a microbiome axis of spaceflight- associated immune activation" was under peer- review at Nature Microbiology. It has now been seen by 3 referees, whose expertise and comments you will find at the of this email. You will see from their comments below that while they find your work of interest, some important points are raised. 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If you cannot send it within this time, please let us know. + +We look forward to hearing from you soon. + +Yours sincerely, + +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\* + +Reviewer Expertise: + +Referee #1: human microbiome, virome Referee #2: skin microbiome, genomics Referee #3: microbiome, statistics + +Reviewers Comments: + +Reviewer #1 (Remarks to the Author): + +"Viral activation..." by Tierney presents a study of human and environmental microbe dynamics during space flight. The authors analyze samples from four astronauts during a three day flight, time points before and after, and also samples from their capsule. They analyze 750 samples from ten body sites and controls. Single cell RNA- seq was used to characterize activity of the astronaut immune system. The authors found that microbial diversity increased mid- flight, particularly viruses, and dropped after flight. A minority of the changes persisted after return to Earth. The transfer of microbial species from crew members to each other and their environment were tracked. The paper is limited by sample size and the descriptive nature, but the topic is fascinating and of great interest to a wide audience. + +Comments: + +What negative controls were applied to the metatranscriptomics? I'm wondering how secure the detections of eukaryotic- cell viruses were in these data. It would be helpful to comment on this further. + +The work is exciting, but the paper was a bit difficult to read. It presented excessive details from the analysis without being clear on why these details were important. The abstract did succeed in distilling out some of the most important points. I would suggest editing the paper further for brevity to highlight the most pertinent points. + +The authors mention that "The total contents of this database are available in the NASA Open Science Data Repository (OSD- 572, OSD- 573)(Overbye et. al [under review]). I searched and was unable to find the data supporting this study. The authors will need to clarify whether data will be freely available, provide straightforward guidance to finding it, and clarify whether this will be the case at + +<--- Page Split ---> + +# natureportfolio + +the time of publication. + +There were multiple typos in the text. Please edit carefully. Some were in the following lines: 77, 182, 257, 389. + +Reviewer #2 (Remarks to the Author): + +The writing of this manuscript has improved. The rationale for the experiments and limitations are now explained. Negative controls for skin now much better explained. However, what about the wipes that people were using to bathe themselves while in space? maybe the wipes contained microbial DNA in their solution that people are then applying to their skin. Or maybe the cleaning wipes that astronauts used caused dead DNA to be trapped on their skin. trapping of dead DNA with hospital- associated 'bath- in- bed' chlorhexidine wipes has been shown (PMID: 29753031) by skin microbiome researchers. This could explain fig 3 and fig 4B. + +The discussion could be compressed a lot. + +Overall, I think the microbiome data for this manuscript could be compressed from 5 figures to 2 or 3 and show the most important data that is truly significant. While the abstract states many findings, the conclusions in the paper include + +'The overall lack of bacterial metagenomic signal in the skin was interesting, 367 as it indicated that strains acquired during flight that displayed altered relative abundance but 368 limited transcriptional changes did not correlate to measurable host immune response. In other 369 words, there was limited evidence that strain- sharing drove an altered immune state in humans.' + +Many of the strongest bacterial skin microbiome alterations (Fig 3) were predominantly 230 metagenomic, as opposed to metatranscriptomic. We hypothesized that this may indicate the 231 acquisition of new but non- transcriptionally active species from the surrounding environment. this statement is oblique. Are the authors hypothesizing that that these microbes are dead? If so this is less of a major conclusion. + +Most viral activity was transiently increased; in other words, 249 even more dramatically than in the bacterial data, relatively speaking, viral abundances reset to 250 baseline almost immediately after flight (Fig 4B). + +Methods established for determining 'viral presence' in Fig 4B still has me wondering if any of this is real. Authors state that they did a benchmarking but that was with viruses from GenBank. In this case they have random shotgun reads that may or may not be weakly related viruses? Filtered for \(1\%\) total coverage or \(0.5\%\) seems extremely low. If this is just reads piling up in one location of a sequence deposited in RefSeq I don't think they can call this 'present' even at the genus level. A lot of these are odd named that seem like best match but might not hold up to scrutiny; e.g. sewage- associated circular DNA virus- 20 or lake Sarah- associated circular virus- 23, Gen_ unclassified + +<--- Page Split ---> + +# nature portfolio + +Gokushovirinae (which is shown as transient decrease and transient increase on skin)? This data seemed like very small changes were being reported and of viruses that have not been associated with skin. I also don't understand how metatranscriptomics yields all transient decrease and metagenomics all yields transient increase - sometimes of the same or similar genus. Which of these are DNA versus RNA viruses? + +StrainPhlAn and MetaPhlAn are designed for gut microbiome studies as authors acknowledge and yet they continue to use these marker gene based methods for skin data, undermining confidence in Figure 5. Their conclusions in text are "Overall (Fig 5B), we found that individuals appeared to acquire strains from the capsule by the 334 second mid- flight sampling point (day 3). During the L- 92 timepoint, there was minimal transfer 335 between the training capsule and the astronauts." And yet their conclusion in abstract is: 'We also used 48 strain- level tracking to measure the potential propagation of microbial species from the crew 49 members to each other and the environment, identifying microbes that were prone to seed the 50 capsule surface and move between the crew.' + +Methods: were the metatranscriptomics samples depleted of bacterial rRNA? Only described that human/mouse/rat [18S, 5S, 23S] was performed. Wondering if bacterial 16S rRNA also depleted? + +Reviewer #3 (Remarks to the Author): + +In this revision, the authors have responded to my comments on their previous draft. This is a much- improved manuscript. However, I still have some concerns listed below. + +1. In response to my previous comment, the authors included pre-flight (using a different capsule) and mid-flight microbial compositions of the flight of interest. The authors claim on page 45 of their rebuttal that "... overall the metagenomic community is relatively similar on Earth vs. in-flight". I find this a bit surprising. Several people are in the space capsule in close proximity to each other. Hence, if the microbial composition can change within each subject over the three day period, then why did it not change in the capsule environment. In fact, from the relative abundance plots provided on page 45 of the rebuttal document it does appear that the capsule environment has also changed. Of course with the authors that changes in the capsule environment from earth to space is difficult to interpret because they are not the same capsule that were measured at the two time points. + +2. Again, going back to my comment on the earlier draft, when microbes do not enter the capsule in flight, then how the changes in microbiome within and between subjects be explained as due to space travel? The changes in microbial compositions could be purely because several people are inside a capsule over three days. An ideal control would be if the same subjects were housed in the same capsule for three days on earth. Does the "pre-launch" data refer to this control group? I probably missed it if that is the case. Otherwise, I find the data of this project difficult to interpret. + +3. In response to my comment regarding correlation analyses, the authors note on page 46 that they combined data from all sites to construct correlations. Does it mean they treated all sites as one organ for computing correlations? Since these are relative abundance data, the standard concept of Pearson correlation is not appropriate. Did they use SPARCC or some of the other recent methods? From the heatmaps, I am puzzled that all correlations among the bacterial families are all positive. Why is that? Is it an artifact of the correlation tool used? Or is there a real biology? + +<--- Page Split ---> + +# nature portfolio + +4. It is true that linear models have a history in microbiome data analysis, but recently developed algorithms such as LinDA would be better alternatives to deal with compositionality in the microbiome data. There is a risk of high false discovery rates when compositionality is ignored. + +## Author Rebuttal to Initial comments + +Reviewers Comments: + +Reviewer #1 (Remarks to the Author): + +"Viral activation..." by Tierney presents a study of human and environmental microbe dynamics during space flight. The authors analyze samples from four astronauts during a three day flight, time points before and after, and also samples from their capsule. They analyze 750 samples from ten body sites and controls. Single cell RNA- seq was used to characterize activity of the astronaut immune system. The authors found that microbial diversity increased mid- flight, particularly viruses, and dropped after flight. A minority of the changes persisted after return to Earth. The transfer of microbial species from crew members to each other and their environment were tracked. The paper is limited by sample size and the descriptive nature, but the topic is fascinating and of great interest to a wide audience. + +## Comments: + +1. What negative controls were applied to the metatranscriptomics? I'm wondering how secure the detections of eukaryotic-cell viruses were in these data. It would be helpful to comment on this further. + +We executed metatranscriptomic and metagenomic sequencing on the in- flight and ground negative controls. In total, 30 controls were sequenced for metatranscriptomic samples. So, for the metatranscriptomic sequencing, we used metatranscriptomic control Isohelix swabs, which were included on every plate of samples. The updated data in the first revision included a second round of negative controls, added in accordance with the Reviewer's requests. Of note, these were only metagenomic sequencing controls (blanks), so they were used just for the DNA swabs. + +We agree that, fundamentally, decontamination via negative controls in metatranscriptomic microbiome data is challenging, especially as it relates to viral identification. For non- RNA life, algorithms are essentially filtering based on the expressed genes, which is not necessarily ideal. Even for RNA viruses, it is likely that we are removing some true- positive viruses and including false- positive ones, but our thresholds used for data processing should minimize bias. Also, we include multiple metrics and thresholds in the tables, which enables readers and researchers to select varying levels of confidence for the results they would want to use for follow- up studies. + +<--- Page Split ---> + +# natureportfolio + +As other Reviewers have commented, viral detection is extremely difficult and a nascent field, especially in low abundance short- read sequencing data - we have now attempted to address this in greater detail in the Supplementary Discussion, reproduced at the bottom of this document. + +We additionally, as part of our revisions and efforts to hone the text, have reduced the focus on the virome. We still have one main panel showing the diversity of viral life enriched in- flight, but we no longer discuss detailed strain names outside of phyla (which are easier to annotate and of higher confidence than finer resolution clades). + +2. The work is exciting, but the paper was a bit difficult to read. It presented excessive details from the analysis without being clear on why these details were important. The abstract did succeed in distilling out some of the most important points. I would suggest editing the paper further for brevity to highlight the most pertinent points. + +We have continued to refine the text in the manuscript, removing nearly 2,000 words from the main text and reworking the figures for simplicity (moving one entirely to the supplement). Most notably, we have added a Supplementary Discussion (reproduced in an Appendix at the bottom of this document) section, where we can address many of the specifics of the analysis that are + +<--- Page Split ---> + +# natureportfolio + +important but not necessarily critical for a casual reader. This includes, for example, the caveats regarding viral detection in the above point. + +3. The authors mention that "The total contents of this database are available in the NASA Open Science Data Repository (OSD-572, OSD-573)(Overbey et. al [under review]). I searched and was unable to find the data supporting this study. The authors will need to clarify whether data will be freely available, provide straightforward guidance to finding it, and clarify whether this will be the case at the time of publication. + +For the last round of revisions, we provided links to where the data was being curated by NASA's GeneLab Repository. This process is intensive and thorough - it requires uploading all files for GeneLab processing, QC, annotation, and confirmation for all \(\sim 750\) sequencing files from this manuscript, but this process is finally completed. All data will be released at the time of publication, and the preview links from the NASA GeneLab repository are available for the reviewers here: + +https://osdr.nasa.gov/bio/repo/data/studies/OSD- 572/preview/CuhxWdYAPRX4QJRLd74yzdXj0 n2OxrXm https://osdr.nasa.gov/bio/repo/data/studies/OSD- 573/preview/Ze2eyzuoTvJ7Cl0887nweUeBe9 GqYTZN https://osdr.nasa.gov/bio/repo/data/studies/OSD- 630/preview/BilzXsJxraKrE9sYDCsOh-MLL3yP ppSC + +4. There were multiple typos in the text. Please edit carefully. Some were in the following lines: 77, 182, 257, 389. + +We have addressed these - and others - as part of our editing process. We thank the Reviewer. + +Reviewer #2 (Remarks to the Author): + +1. The writing of this manuscript has improved. The rationale for the experiments and limitations are now explained. Negative controls for skin now much better explained. However, what about the wipes that people were using to bathe themselves while in space? maybe the wipes contained microbial DNA in their solution that people are then applying to their skin. Or maybe the cleaning wipes that astronauts used caused dead DNA to be trapped on their skin. trapping of dead DNA with hospital-associated 'bath-in-bed' chlorhexidine wipes has been shown (PMID: 29753031) by skin microbiome researchers. This could explain fig 3 and fig 4B. + +We are glad the Reviewer is pleased with our changes - thank you. We agree that, of course, wipes used by individuals to bathe themselves in space could be a confounder. + +<--- Page Split ---> + +# nature portfolio + +However, we reached out to the Commander of the Inspiration4 mission, who confirmed that "any wet wipes used by the crew were not reused, nor shared," which should limit any influence of this confounding variable. We have also noted this in the methods section for the paper, and we note the potential confounding effect of cleaning methods in the Supplementary Discussion. + +In the Methods we write: + +"We note that some crew members were using wet wipes [UPC: 036000317985] to bathe themselves in- flight in between swabbing; however not every crew member did so, and SpaceX did not require this to be a consistent protocol among the crew. Wet wipes used by the crew were not reused, nor shared, which should limit any influence of this confounding variable." + +<--- Page Split ---> + +# nature portfolio + +And in the Discussion: + +"They [sic future studies] additionally should encourage more detailed reporting on diet and cleaning methods (e.g., wet wipes) to adjust for potential confounders introducing foreign microbial DNA into the host." + +Related to consideration of the manuscript cited, we also note that it indicates "personalized" responses to wet wipe treatment. The responses we observed in our regression were, overall, shared between individuals. Also, we feel that our use of coverage thresholds and a variety of algorithmic approaches likely reduces the probability that merely lysed cells/contaminating DNA drove the majority of the observed effect. + +Also, we now address the "cleaning method" as a potential confounder as well as our thoughts on it in the Supplementary Discussion section (reproduced at the bottom of this document) on drawbacks and also include the update in the methods section. + +2. The discussion could be compressed a lot. + +We have now trimmed down the discussion, moving some of the excessive detail to a Supplementary Discussion section where it is still accessible but less distracting. + +3. Overall, I think the microbiome data for this manuscript could be compressed from 5 figures to 2 or 3 and show the most important data that is truly significant. While the abstract states many findings, the conclusions in the paper include + +"The overall lack of bacterial metagenomic signal in the skin was interesting, as it indicated that strains acquired during flight that displayed altered relative abundance but limited transcriptional changes did not correlate to measurable host immune response. In other words, there was limited evidence that strain- sharing drove an altered immune state in humans." + +"Many of the strongest bacterial skin microbiome alterations (Fig 3) were predominantly metagenomic, as opposed to metatranscriptomic. We hypothesized that this may indicate the acquisition of new but non- transcriptionally active species from the surrounding environment." this statement is oblique. Are the authors hypothesizing that that these microbes are dead? If so this is less of a major conclusion. + +"Most viral activity was transiently increased; in other words, 249 even more dramatically than in the bacterial data, relatively speaking, viral abundances reset to 250 baseline almost immediately after flight (Fig 4B)." + +We agree that our paper was a bit loquacious – however, we do feel it warrants more than 2- 3 + +<--- Page Split ---> + +# natureportfolio + +figures, in large part to highlight the scope of the dataset, which is the largest and most diverse of its kind (it is larger than all metagenomic samples taken in space combined, as indexed in NASA's GeneLab database). To address this point, we have taken the following steps: + +1) First, we have reduced the claims in the abstract. The Reviewer accurately calls out some of the most interesting results here, and we now focus on those. + +2) We clarify that we are not hypothesizing these microbes are dead, just not highly transcriptionally active to the point where it could be detected by an association study. We note that many of these organisms are filtered on a coverage threshold. We are likely filtering out some true positive shifts in lieu of emphasizing high-effect size taxa. + +<--- Page Split ---> + +# natureportfolio + +That "filter" provided by regression means that any more minimal change will likely not be detected when compared to, say, the more dramatic metagenomic shifts on the skin. + +We feel that the discordance between metagenomics and metatranscriptomics is actually one of the most interesting findings in this study, because it indicates that DNA presence does not correlate to dramatic changes in transcriptional activity. In other words, all the studies that rely on metagenomics alone, in general, may actually be missing a large portion of the picture and unable to target truly causal host- microbe relationships, which we think is an exciting result. + +3) We have reduced focus on the viral component of our findings, relegating certain panels to the supplement and indicating that, in low abundance data, viral classification is difficult. We additionally have moved the gene catalog panels entirely to the supplement. + +In total, our paper now has 5 simplified figures, and we have updated the abstract to more accurately reflect the key points highlighted by the Reviewer. + +4. Methods established for determining 'viral presence' in Fig 4B still has me wondering if any of this is real. Authors state that they did a benchmarking but that was with viruses from GenBank. In this case they have random shotgun reads that may or may not be weakly related viruses? Filtered for \(1\%\) total coverage or \(0.5\%\) seems extremely low. If this is just reads piling up in one location of a sequence deposited in RefSeq I don't think they can call this 'present' even at the genus level. A lot of these are odd named that seem like best match but might not hold up to scrutiny; e.g. sewage-associated circular DNA virus-20 or lake Sarah-associated circular virus-23, Gen_unclassified Gokushovirinase (which is shown as transient decrease and transient increase on skin)? This data seemed like very small changes were being reported and of viruses that have not been associated with skin. I also don't understand how metatranscriptomics yields all transient decrease and metagenomics all yields transient increase - sometimes of the same or similar genus. Which of these are DNA versus RNA viruses? + +In short, we agree that calling viruses is extremely difficult. The virome is not well explored. Some spurious alignments are likely false positives; others could be incomplete databases where the most related organism in the database has an unusual name. + +To account for challenges in viral detection, we have done the following: + +1) As in our first round of revisions, we worked at the genus level for higher confidence calls of taxa. +2) Benchmarked our approaches and used a diverse set of methods (note Supp Fig 18, where we show high accuracy at the genus level on the database we're using in calling viruses). +3) Extensively discuss the difficulty of viral classification in the results and the Supplementary Discussion (reproduced below). + +<--- Page Split ---> + +# natureportfolio + +4) Reduce the emphasis on viral analysis in the manuscript, such that unusual taxa are not highlighted, focusing instead on trends in viral classes (e.g., eukaryotic vs prokaryotic) and more on the high-confidence changes. + +The transient shift in viruses compared to bacteria is aligned with what we know about viral activation in space. Spaceflight changes viral communities and causes, in some cases, reactivation of latent infections (e.g., herpes viruses). This effect resets upon returning to Earth. + +Overall, we claim to be using state- of- the- art methods for viral classification, and now with the reduced emphasis on viral shifts and the stated caveats in the Supplementary Discussion, we hope that our analysis is acceptable for publication. + +<--- Page Split ---> + +# nature portfolio + +5. StrainPhlAn and MetaPhlAn are designed for gut microbiome studies as authors acknowledge and yet they continue to use these marker gene based methods for skin data, undermining confidence in Figure 5. Their conclusions in text are "Overall (Fig 5B), we found that individuals appeared to acquire strains from the capsule by the 334 second mid-flight sampling point (day 3). During the L-92 timepoint, there was minimal transfer 335 between the training capsule and the astronauts." And yet their conclusion in abstract is: 'We also used 48 strain-level tracking to measure the potential propagation of microbial species from the crew 49 members to each other and the environment, identifying microbes that were prone to seed the 50 capsule surface and move between the crew.' + +Thank you for this comment. We have fixed the discordance between the abstract and the text. Regarding marker gene- based approaches, we note that many methods used (e.g., Xtree) are not marker- gene based, which will help give orthogonal methods for the species measurements. In accordance with Reviewer requests in the first revision, we added MetaPhlAn4 and StranPhlAn, as they are established tools, but indeed, they were first based on stool samples. + +Fortunately, the recent updates to MetaPhlAn and StranPhlAn incorporate marker genes from more than just the gut microbiome. Specifically, they use databases requested by the Reviewers (e.g., Segata and Finn labs) in the initial round of review, and they also incorporate MAGs/genomes from the skin and oral niches. Therefore, as of their recent release, the developers of these tools have expressed confidence that their updated tools are now appropriate for more than just the gut microbiome. Specifically, the recent MetaPhlAn4 paper indicated that its default database includes marker genes from more than just the gut microbiome: + +"MetaPhlAn4 application to human and nonhuman metagenomes. To measure the increase of the fraction of classified reads when compared with MetaPhlAn3, we profiled 24,515 samples from 145 datasets spanning different human body sites (airways, gastrointestinal tract, oral, skin, and urogenital tract) and lifestyles, animal hosts (non- human primates, mice and ruminants) and other non- host- associated environments (soil, fresh water, and ocean)." + +Indeed, the paper on which we modeled our strain- sharing approach was used for the oral microbiome (https://www.nature.com/articles/s41586- 022- 05620- 1). Given these recent developments, as well as the range of other tools with which we have also processed these i4 data, we believe these results will be useful, relevant, and robust for the field. + +6. Methods: were the metatranscriptomics samples depleted of bacterial rRNA? Only described that human/mouse/rat [18S, 5S, 23S] was performed. Wondering if bacterial 16S rRNA also depleted? + +We did not deplete the bacterial 16S rRNA, but used the human/mouse/rat rRNA ribo-depletion kit from NEB. This method had been previously well-characterized and successful for bacterial, viral, and fungi metatranscriptomics analysis from clinical samples, and we have cited these manuscripts in our updated paper to help guide readers for more details: + +<--- Page Split ---> + +# natureportfolio + +https://www.nature.com/articles/s41467- 021- 21361- 7 https://genome.cshlp.org/content/early/2021/02/18/qr.268961.120.full.pdf + +Reviewer #3 (Remarks to the Author): + +In this revision, the authors have responded to my comments on their previous draft. This is a much- improved manuscript. However, I still have some concerns listed below. + +<--- Page Split ---> + +# natureportfolio + +1. In response to my previous comment, the authors included pre-flight (using a different capsule) and mid-flight microbial compositions of the flight of interest. The authors claim on page 45 of their rebuttal that "... overall the metagenomic community is relatively similar on Earth vs. in-flight". I find this a bit surprising. Several people are in the space capsule in close proximity to each other. Hence, if the microbial composition can change within each subject over the three day period, then why did it not change in the capsule environment. In fact, from the relative abundance plots provided on page 45 of the rebuttal document it does appear that the capsule environment has also changed. Of course with the authors that changes in the capsule environment from earth to space is difficult to interpret because they are not the same capsule that were measured at the two time points. + +This is an important comment. Indeed, as the capsule environment is not identical in- flight as on Earth, we have remedied the relevant comment in the text to indicate the changes. We feel that it was not worth heavily focusing on them, due to our choice not to carry out statistical analysis on the capsule samples. This was, as the reviewer indicated, because the pre- flight and mid- flight capsules were different. + +2. Again, going back to my comment on the earlier draft, when microbes do not enter the capsule in flight, then how the changes in microbiome within and between subjects be explained as due to space travel? The changes in microbial compositions could be purely because several people are inside a capsule over three days. An ideal control would be if the same subjects were housed in the same capsule for three days on earth. Does the "pre-launch" data refer to this control group? I probably missed it if that is the case. Otherwise, I find the data of this project difficult to interpret. + +The pre- flight samples refer to the same crew members sampled while not cohabitating in the months leading up to the spaceflight. Detected metagenomic shifts could arise, for example, from the abundance of organisms shifting to above the limit of detection by sequencing or transfer between individuals. Metatranscriptomic shifts do not require microbial transfer - a native species experiencing an increase in expression is all it would take for a detectable signal. + +We agree that a parallel ground study would be useful, but that data does not exist at present, and SpaceX could not release an additional unused Dragon capsule to sequence another cohort, but this has been requested for future missions with their flight operations team. However, we do not feel this is a critical control for this study, given the large number of negative and positive controls, what we observe in the discordant shifts between metagenomics and metatranscriptomics across the exact same body sites over time, and because of what is known about spaceflight and the microbiome. + +For example, spending time in a tight space does not normally cause herpesvirus activation in control cohorts. But spaceflight does activate herpes strains in \(61\%\) of people (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374706/) in spaceflight. We address this in the Discussion/Supplementary Discussion: + +<--- Page Split ---> + +# nature portfolio + +"Chief among our findings was that native microbiome shifts were highly correlated to host immune changes. Naturally, a microbial shift can affect the host immune system – or vice versa – without the initial cause being “space- specific” (i.e., due to microgravity of radiation). Strain sharing, for example, could be – and likely is – a function of humans sharing close quarters. That said, astronauts have been documented as experiencing immune and viral activation15; typically, this effect is not attributed solely to cohabitation, and we showed here that strains likely “acquired” from crew members in flight were not associated with immune cell changes. We claim, therefore, it is unlikely strain sharing due to close quarters – or even variable sanitation in- flight – explains the entirety of the link between host immune response and the microbiome. + +<--- Page Split ---> + +# nature portfolio + +Future manuscripts, of course, could leverage this dataset as well as data from analog astronaut studies on Earth to more rigorously test this hypothesis." + +In short, a portion of changes may be from cohabitation - but it is unlikely that all of them are, and this dataset is the largest to- date that enables such comparisons, which can help tease out these interactions when we begin to compare to other missions. Further of note, the changes that are almost surely from cohabitation - skin metagenomic shifts of specific taxa - are not correlated to immune cell gene expression changes. On the other hand, metatranscriptomic shifts in the oral microbiome, where there is no known exchange between individuals, are associated with immune cell gene expression changes. We thus claim that these data, combined with the known effects of spaceflight that are uniquely distinct from cohabitation, bolsters our claim that at least some of the changes are likely space- associated. It will, however, require future work to determine which of these shifts are consistently observed or mission- specific. + +3. In response to my comment regarding correlation analyses, the authors note on page 46 that they combined data from all sites to construct correlations. Does it mean they treated all sites as one organ for computing correlations? Since these are relative abundance data, the standard concept of Pearson correlation is not appropriate. Did they use SPARCC or some of the other recent methods? From the heatmaps, I am puzzled that all correlations among the bacterial families are all positive. Why is that? Is it an artifact of the correlation tool used? Or is there a real biology? + +We agree this analysis is worthy of a deeper dive than what we did; however, we are attempting in these revisions to balance requests for a shorter, tighter manuscript with additional analytic goals. Previously, this figure was referenced in one line in the results, and we feel the analysis requested would require (and warrant) much more text. Therefore, we have opted instead to remove this figure and recommend correlational network- based analyses as follow- ups in following work. We feel it is appropriate, as it did not change the main results of the paper (as highlighted by Reviewer 2) and is not the focus of the main results, but we have cited SPARCC in the discussion to highlight future directions and analytical approaches. + +4. It is true that linear models have a history in microbiome data analysis, but recently developed algorithms such as LinDA would be better alternatives to deal with compositionality in the microbiome data. There is a risk of high false discovery rates when compositionality is ignored. + +We agree that linear models have some limitations, and we have added to our revised paper a battery of methods to help reduce risk of analysis error. As the reviewer keenly notes, there are a number of alternative statistical/transformation approaches that we could try, but we believe our current comparison of methods is appropriate, given the standard in the microbiome field. Moreover, since we've used 11 methods in this paper and seen similar results across all of them, we believe that using LinDA to adjust for compositionality bias is a good idea, but one that should be robustly compared across a wide range of sample types in a future study (we now + +<--- Page Split ---> + +# nature portfolio + +cite LinDA in the manuscript as a potential additional analytic approach). We claim our concordance across transformation methods accounts for a degree of bias in compositional data, though in future work on this dataset, we will perform even more comparisons with additional methods. We address this in our Discussion section to highlight this for readers. + +We are grateful and very appreciative of the reviewers for their careful, thorough, and helpful reviews and hope they find the new manuscript satisfactory. + +# Appendix: + +<--- Page Split ---> + +# nature portfolio + +## Supplementary Discussion + +Specific human genes and their association with microbiome features + +An additional manuscript focuses more on the host- side of immune activation (Kim and Tierney et al, in review, Nature), reporting specific human genes that seem to be associated with microbial features and integrating additional datasets. However, for completeness, we briefly document here some human genes of interest that were microbiome- associated. By cell type, we documented the most strongly associated genes with microbial features (Supplementary Table 10). For bacteria, gene functions were annotated with, for example, long non- coding RNAs (across all cell types), immunoglobulin genes (CD14 monocytes), and interferon regulatory factors. We additionally uncovered associations with specific immune modulatory genes such as CXCL10, XCL1, CXCL8 (immune cell migration), NLRC5, HLA genes, CD1C (antigen presentation/co- stimulation), SLC2A9 (immune cell metabolism), IRF1, NR4A3, STAT1 (transcription factors that specify immune cell states) that increased across multiple immune cell types (B cells, CD4 T- cells, CD8 T- cells, CD14 monocytes, DCs, Natural Killer (NK) cells). + +Further notes on the complexity of viral classification + +In this study, we attempted to measure viral shifts as a function of flight as well. Measuring viral abundances in metagenomic and (particularly) metatranscriptomic data is extremely challenging. First, the decontamination process we used to remove environmental contaminants was not designed for organisms as ubiquitous and with such short, diverse genomes as viruses. Likely, we are removing many true positive viruses from our dataset. Second, we are also working with low biomass samples; it is hard enough to detect bacteria with high confidence, but viruses are another challenging matter entirely. + +Finally, and most importantly, taxonomic classification via short read alignment to viral genomes is deeply imperfect. We observed, for example, many significant viruses shifting with unusual names, often mapping to viral species not typically found in or on humans. Simply put, the viral universe is so vast that we expect these alignments are likely due to a combination of spurious read mapping and databases lacking the strains that are truly present. As a result, we are only able to work with state- of- the art methods, comparing the results across taxonomic ranks. + +We are confident in the results highlighted in the main text of this manuscript regarding viruses: mostly transient, pan- body shifts in- flight for both prokaryotic and eukaryotic viruses, some of which are correlated to immune cell gene expression changes. We compared multiple methods, finding concordant results, and we benchmarked the method used in the main text (Xtree alignment to GenBank) via rigorous testing on synthetic genomes (Supplementary Figure 18), finding accurate alignment at the genus level. Further, we identified viral genes as shifting in- flight in the functional/gene catalog analysis (Supplementary Figures 14- 17). That said, we are also certain that some of the taxonomic classifications are not accurate, so any atypical clades highlighted in the regression results (Supplementary Table 9) should be considered with appropriate caution. + +<--- Page Split ---> + +# nature portfolio + +Other drawbacks of this study and future opportunities + +There are several opportunities to expand upon this work in future studies and missions. Analytically, our lasso- based approach for immune- microbe- interaction modeling immune cell gene expression changes does not inherently allow for statistical inference or account for inter- individual variation. Further, some of our samples had very low biomass, requiring PCR- amplification (18 cycles) for RNA- sequencing data, which can increase duplicate rates of sequences. For this reason, we attempted to take a conservative and systematic modeling approach to our effort. Specifically, 1) we implemented multiple algorithms and compared their concordance, 2) set coverage thresholds for bacterial and viral taxa to filter probable false positives, 3) used multiple, state- of- the- art taxonomic classifiers and compared our findings among all of them, and 4) implemented and compared both generalized linear models and mixed effect models, bearing in mind that the latter can face interpretability challenges with smaller sample sizes. Additional modeling strategies, including network analyses2, could be implemented in addition to those we have tested here. For example, recently developed methods for controlling false positive rates in compositional data could be potentially useful for this manner of microbiome data1. + +We additionally used 76 negative controls to attempt to avert false positive signals, which can stem from contamination and the kitome. However, this approach is far from perfect and likely removes present organisms. Depending on their aim, future studies should alter collection methods to increase the amount of biomass collected sampling (e.g., using one swab for multiple skin sites) or examine relatively unbiased methods of amplification3. They additionally should encourage more detailed reporting on diet and cleaning methods (e.g., wet wipes) to adjust for potential confounders introducing foreign microbial DNA into the host. + +Additional experiments and missions can further test a microbiome- derived theory of spaceflight- associated immune c changes. In addition to stress- testing our findings and increasing sample sizes, future spaceflight studies should consider several enhancements. For instance, they should compare sequestered ground controls to discern differences between space- driven and proximity- driven immune shifts. Additionally, future efforts should design experiments that enable a deeper view into the causality of microbe immune associations rather than just noting their existence. Exploring some of these hypotheses through animal or organoid models could be valuable. + +1. Zhou, H., He, K., Chen, J. & Zhang, X. LinDA: linear models for differential abundance analysis of microbiome compositional data. Genome Biol. 23, 95 (2022). + +2. Friedman, J. & Alm, E. J. Inferring correlation networks from genomic survey data. PLoS Comput. + +Biol. 8, e1002687 (2012). + +<--- Page Split ---> + +# nature portfolio + +3. Ahsanuddin, S. et al. Assessment of REPLI-g Multiple Displacement Whole Genome Amplification (WGA) Techniques for Metagenomic Applications. J. Biomol. Tech. 28, 46–55 (2017). + +# Decision Letter, first revision: + +Message: Our ref: NMICROBIOL- 23082268A + +1st December 2023 + +Dear Dr. Mason, + +Thank you for submitting your revised manuscript "The microbiome architecture of short- term spaceflight and its potential link to host immune activation" (NMICROBIOL- 23082268A). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Microbiology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)-- we can not proceed with PDFs at this stage. + +We will ask for some additional text edits in line with the remaining concerns including toning down statements, discussing limitations and removing or reducing the section on strain sharing. We will send further instructions with the checklist mentioned below. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +Thank you again for your interest in Nature Microbiology Please do not hesitate to contact me if you have any questions. + +Sincerely, + +Reviewer #1 (Remarks to the Author): + +The authors have addressed my comments satisfactorily. + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. 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To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +# nature portfolio + +Reviewer #2 (Remarks to the Author): + +i have concerns that there are contaminants or read mapping issues with the methods, but i don't have any further suggestions given the samples obtained and processed for this study. + +I am still not sure that the authors can make the claim that they are seeing strain sharing based on strainphlan analysis without benchmarking for these species. + +no further comments. + +Reviewer #3 (Remarks to the Author): + +I thank the authors for their careful responses to my previous comments. In response to my concerns regarding the lack of proper negative control on earth, they cited an interesting article (Rooney et al., Front. Microbiol.) describing the effects of spaceflight and the herpesvirus activation. I am still having difficulty inferring that spaceflight is the cause for microbial shifts in the compositions. I am not sure if compared to pre- flight, during the three- day flight, the crew brushed their teeth, showered, changed their sleep patterns and diet. Thus, can the differences be partly due to changes in their daily activities along with staying in close proximity to one another for 3 days, and not entirely due to space flight. Granted space- flight does induce stress, as reported in the reference cited by the authors, but it is only part of the effect. I wonder if similar changes to microbiome will be seen for people taking a non- stop long distance flight from NYC to Australia. Note that on lines 227 - 232, the authors observed a reduction in beta- diversity among the crew members. Perhaps this is due to similar diet, environment, and hygiene practices during the three day space- flight. Comparisons with pre- flight specimens is not very convincing to me that changes are due to spaceflight and not due to behavior and environment. + +## Final Decision Letter: + +Message 9th February 2024 + +Dear Chris, + +I am pleased to accept your Article "Longitudinal multi- omics analysis of host microbiome architecture and immune responses during short- term spaceflight" for publication in Nature Microbiology. Thank you for having chosen to submit your work to us and many congratulations. + +<--- Page Split ---> + +# nature portfolio + +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Microbiology style. 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This document only contains reviewer comments, rebuttal and decision letters for versions considered at Nature Medicine. 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As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[160, 120, 883, 163]]<|/det|> +contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[160, 175, 883, 205]]<|/det|> +We hope to receive your revised paper within three weeks. If you cannot send it within this time, please let us know. + +<|ref|>text<|/ref|><|det|>[[160, 217, 480, 232]]<|/det|> +We look forward to hearing from you soon. + +<|ref|>text<|/ref|><|det|>[[160, 245, 278, 259]]<|/det|> +Yours sincerely, + +<|ref|>text<|/ref|><|det|>[[160, 287, 339, 297]]<|/det|> +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\* + +<|ref|>text<|/ref|><|det|>[[160, 315, 309, 329]]<|/det|> +Reviewer Expertise: + +<|ref|>text<|/ref|><|det|>[[160, 342, 460, 383]]<|/det|> +Referee #1: human microbiome, virome Referee #2: skin microbiome, genomics Referee #3: microbiome, statistics + +<|ref|>text<|/ref|><|det|>[[160, 410, 325, 424]]<|/det|> +Reviewers Comments: + +<|ref|>text<|/ref|><|det|>[[160, 438, 448, 452]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[159, 464, 920, 577]]<|/det|> +"Viral activation..." by Tierney presents a study of human and environmental microbe dynamics during space flight. The authors analyze samples from four astronauts during a three day flight, time points before and after, and also samples from their capsule. They analyze 750 samples from ten body sites and controls. Single cell RNA- seq was used to characterize activity of the astronaut immune system. The authors found that microbial diversity increased mid- flight, particularly viruses, and dropped after flight. A minority of the changes persisted after return to Earth. The transfer of microbial species from crew members to each other and their environment were tracked. The paper is limited by sample size and the descriptive nature, but the topic is fascinating and of great interest to a wide audience. + +<|ref|>text<|/ref|><|det|>[[160, 590, 246, 604]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[160, 617, 875, 660]]<|/det|> +What negative controls were applied to the metatranscriptomics? I'm wondering how secure the detections of eukaryotic- cell viruses were in these data. It would be helpful to comment on this further. + +<|ref|>text<|/ref|><|det|>[[160, 672, 914, 730]]<|/det|> +The work is exciting, but the paper was a bit difficult to read. It presented excessive details from the analysis without being clear on why these details were important. The abstract did succeed in distilling out some of the most important points. I would suggest editing the paper further for brevity to highlight the most pertinent points. + +<|ref|>text<|/ref|><|det|>[[160, 742, 918, 800]]<|/det|> +The authors mention that "The total contents of this database are available in the NASA Open Science Data Repository (OSD- 572, OSD- 573)(Overbye et. al [under review]). I searched and was unable to find the data supporting this study. The authors will need to clarify whether data will be freely available, provide straightforward guidance to finding it, and clarify whether this will be the case at + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 933, 88]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[160, 120, 333, 135]]<|/det|> +the time of publication. + +<|ref|>text<|/ref|><|det|>[[159, 148, 920, 178]]<|/det|> +There were multiple typos in the text. Please edit carefully. Some were in the following lines: 77, 182, 257, 389. + +<|ref|>text<|/ref|><|det|>[[160, 230, 448, 245]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[160, 258, 919, 356]]<|/det|> +The writing of this manuscript has improved. The rationale for the experiments and limitations are now explained. Negative controls for skin now much better explained. However, what about the wipes that people were using to bathe themselves while in space? maybe the wipes contained microbial DNA in their solution that people are then applying to their skin. Or maybe the cleaning wipes that astronauts used caused dead DNA to be trapped on their skin. trapping of dead DNA with hospital- associated 'bath- in- bed' chlorhexidine wipes has been shown (PMID: 29753031) by skin microbiome researchers. This could explain fig 3 and fig 4B. + +<|ref|>text<|/ref|><|det|>[[161, 368, 472, 383]]<|/det|> +The discussion could be compressed a lot. + +<|ref|>text<|/ref|><|det|>[[160, 409, 916, 452]]<|/det|> +Overall, I think the microbiome data for this manuscript could be compressed from 5 figures to 2 or 3 and show the most important data that is truly significant. While the abstract states many findings, the conclusions in the paper include + +<|ref|>text<|/ref|><|det|>[[160, 465, 916, 522]]<|/det|> +'The overall lack of bacterial metagenomic signal in the skin was interesting, 367 as it indicated that strains acquired during flight that displayed altered relative abundance but 368 limited transcriptional changes did not correlate to measurable host immune response. In other 369 words, there was limited evidence that strain- sharing drove an altered immune state in humans.' + +<|ref|>text<|/ref|><|det|>[[160, 535, 914, 605]]<|/det|> +Many of the strongest bacterial skin microbiome alterations (Fig 3) were predominantly 230 metagenomic, as opposed to metatranscriptomic. We hypothesized that this may indicate the 231 acquisition of new but non- transcriptionally active species from the surrounding environment. this statement is oblique. Are the authors hypothesizing that that these microbes are dead? If so this is less of a major conclusion. + +<|ref|>text<|/ref|><|det|>[[160, 617, 911, 661]]<|/det|> +Most viral activity was transiently increased; in other words, 249 even more dramatically than in the bacterial data, relatively speaking, viral abundances reset to 250 baseline almost immediately after flight (Fig 4B). + +<|ref|>text<|/ref|><|det|>[[160, 699, 923, 799]]<|/det|> +Methods established for determining 'viral presence' in Fig 4B still has me wondering if any of this is real. Authors state that they did a benchmarking but that was with viruses from GenBank. In this case they have random shotgun reads that may or may not be weakly related viruses? Filtered for \(1\%\) total coverage or \(0.5\%\) seems extremely low. If this is just reads piling up in one location of a sequence deposited in RefSeq I don't think they can call this 'present' even at the genus level. A lot of these are odd named that seem like best match but might not hold up to scrutiny; e.g. sewage- associated circular DNA virus- 20 or lake Sarah- associated circular virus- 23, Gen_ unclassified + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 45, 932, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[160, 120, 891, 190]]<|/det|> +Gokushovirinae (which is shown as transient decrease and transient increase on skin)? This data seemed like very small changes were being reported and of viruses that have not been associated with skin. I also don't understand how metatranscriptomics yields all transient decrease and metagenomics all yields transient increase - sometimes of the same or similar genus. Which of these are DNA versus RNA viruses? + +<|ref|>text<|/ref|><|det|>[[160, 203, 920, 315]]<|/det|> +StrainPhlAn and MetaPhlAn are designed for gut microbiome studies as authors acknowledge and yet they continue to use these marker gene based methods for skin data, undermining confidence in Figure 5. Their conclusions in text are "Overall (Fig 5B), we found that individuals appeared to acquire strains from the capsule by the 334 second mid- flight sampling point (day 3). During the L- 92 timepoint, there was minimal transfer 335 between the training capsule and the astronauts." And yet their conclusion in abstract is: 'We also used 48 strain- level tracking to measure the potential propagation of microbial species from the crew 49 members to each other and the environment, identifying microbes that were prone to seed the 50 capsule surface and move between the crew.' + +<|ref|>text<|/ref|><|det|>[[160, 340, 890, 370]]<|/det|> +Methods: were the metatranscriptomics samples depleted of bacterial rRNA? Only described that human/mouse/rat [18S, 5S, 23S] was performed. Wondering if bacterial 16S rRNA also depleted? + +<|ref|>text<|/ref|><|det|>[[160, 409, 448, 424]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[160, 437, 914, 465]]<|/det|> +In this revision, the authors have responded to my comments on their previous draft. This is a much- improved manuscript. However, I still have some concerns listed below. + +<|ref|>text<|/ref|><|det|>[[159, 479, 920, 604]]<|/det|> +1. In response to my previous comment, the authors included pre-flight (using a different capsule) and mid-flight microbial compositions of the flight of interest. The authors claim on page 45 of their rebuttal that "... overall the metagenomic community is relatively similar on Earth vs. in-flight". I find this a bit surprising. Several people are in the space capsule in close proximity to each other. Hence, if the microbial composition can change within each subject over the three day period, then why did it not change in the capsule environment. In fact, from the relative abundance plots provided on page 45 of the rebuttal document it does appear that the capsule environment has also changed. Of course with the authors that changes in the capsule environment from earth to space is difficult to interpret because they are not the same capsule that were measured at the two time points. + +<|ref|>text<|/ref|><|det|>[[159, 617, 920, 700]]<|/det|> +2. Again, going back to my comment on the earlier draft, when microbes do not enter the capsule in flight, then how the changes in microbiome within and between subjects be explained as due to space travel? The changes in microbial compositions could be purely because several people are inside a capsule over three days. An ideal control would be if the same subjects were housed in the same capsule for three days on earth. Does the "pre-launch" data refer to this control group? I probably missed it if that is the case. Otherwise, I find the data of this project difficult to interpret. + +<|ref|>text<|/ref|><|det|>[[159, 713, 916, 799]]<|/det|> +3. In response to my comment regarding correlation analyses, the authors note on page 46 that they combined data from all sites to construct correlations. Does it mean they treated all sites as one organ for computing correlations? Since these are relative abundance data, the standard concept of Pearson correlation is not appropriate. Did they use SPARCC or some of the other recent methods? From the heatmaps, I am puzzled that all correlations among the bacterial families are all positive. Why is that? Is it an artifact of the correlation tool used? Or is there a real biology? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[159, 133, 920, 177]]<|/det|> +4. It is true that linear models have a history in microbiome data analysis, but recently developed algorithms such as LinDA would be better alternatives to deal with compositionality in the microbiome data. There is a risk of high false discovery rates when compositionality is ignored. + +<|ref|>sub_title<|/ref|><|det|>[[75, 216, 350, 232]]<|/det|> +## Author Rebuttal to Initial comments + +<|ref|>text<|/ref|><|det|>[[86, 256, 266, 273]]<|/det|> +Reviewers Comments: + +<|ref|>text<|/ref|><|det|>[[86, 288, 387, 305]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[85, 319, 913, 450]]<|/det|> +"Viral activation..." by Tierney presents a study of human and environmental microbe dynamics during space flight. The authors analyze samples from four astronauts during a three day flight, time points before and after, and also samples from their capsule. They analyze 750 samples from ten body sites and controls. Single cell RNA- seq was used to characterize activity of the astronaut immune system. The authors found that microbial diversity increased mid- flight, particularly viruses, and dropped after flight. A minority of the changes persisted after return to Earth. The transfer of microbial species from crew members to each other and their environment were tracked. The paper is limited by sample size and the descriptive nature, but the topic is fascinating and of great interest to a wide audience. + +<|ref|>sub_title<|/ref|><|det|>[[86, 465, 178, 481]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[115, 496, 910, 530]]<|/det|> +1. What negative controls were applied to the metatranscriptomics? I'm wondering how secure the detections of eukaryotic-cell viruses were in these data. It would be helpful to comment on this further. + +<|ref|>text<|/ref|><|det|>[[143, 544, 913, 658]]<|/det|> +We executed metatranscriptomic and metagenomic sequencing on the in- flight and ground negative controls. In total, 30 controls were sequenced for metatranscriptomic samples. So, for the metatranscriptomic sequencing, we used metatranscriptomic control Isohelix swabs, which were included on every plate of samples. The updated data in the first revision included a second round of negative controls, added in accordance with the Reviewer's requests. Of note, these were only metagenomic sequencing controls (blanks), so they were used just for the DNA swabs. + +<|ref|>text<|/ref|><|det|>[[143, 673, 913, 787]]<|/det|> +We agree that, fundamentally, decontamination via negative controls in metatranscriptomic microbiome data is challenging, especially as it relates to viral identification. For non- RNA life, algorithms are essentially filtering based on the expressed genes, which is not necessarily ideal. Even for RNA viruses, it is likely that we are removing some true- positive viruses and including false- positive ones, but our thresholds used for data processing should minimize bias. Also, we include multiple metrics and thresholds in the tables, which enables readers and researchers to select varying levels of confidence for the results they would want to use for follow- up studies. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 88]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[144, 117, 913, 183]]<|/det|> +As other Reviewers have commented, viral detection is extremely difficult and a nascent field, especially in low abundance short- read sequencing data - we have now attempted to address this in greater detail in the Supplementary Discussion, reproduced at the bottom of this document. + +<|ref|>text<|/ref|><|det|>[[144, 197, 913, 263]]<|/det|> +We additionally, as part of our revisions and efforts to hone the text, have reduced the focus on the virome. We still have one main panel showing the diversity of viral life enriched in- flight, but we no longer discuss detailed strain names outside of phyla (which are easier to annotate and of higher confidence than finer resolution clades). + +<|ref|>text<|/ref|><|det|>[[115, 278, 913, 345]]<|/det|> +2. The work is exciting, but the paper was a bit difficult to read. It presented excessive details from the analysis without being clear on why these details were important. The abstract did succeed in distilling out some of the most important points. I would suggest editing the paper further for brevity to highlight the most pertinent points. + +<|ref|>text<|/ref|><|det|>[[144, 360, 913, 425]]<|/det|> +We have continued to refine the text in the manuscript, removing nearly 2,000 words from the main text and reworking the figures for simplicity (moving one entirely to the supplement). Most notably, we have added a Supplementary Discussion (reproduced in an Appendix at the bottom of this document) section, where we can address many of the specifics of the analysis that are + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 45, 932, 88]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[142, 117, 912, 151]]<|/det|> +important but not necessarily critical for a casual reader. This includes, for example, the caveats regarding viral detection in the above point. + +<|ref|>text<|/ref|><|det|>[[115, 166, 914, 250]]<|/det|> +3. The authors mention that "The total contents of this database are available in the NASA Open Science Data Repository (OSD-572, OSD-573)(Overbey et. al [under review]). I searched and was unable to find the data supporting this study. The authors will need to clarify whether data will be freely available, provide straightforward guidance to finding it, and clarify whether this will be the case at the time of publication. + +<|ref|>text<|/ref|><|det|>[[144, 266, 913, 362]]<|/det|> +For the last round of revisions, we provided links to where the data was being curated by NASA's GeneLab Repository. This process is intensive and thorough - it requires uploading all files for GeneLab processing, QC, annotation, and confirmation for all \(\sim 750\) sequencing files from this manuscript, but this process is finally completed. All data will be released at the time of publication, and the preview links from the NASA GeneLab repository are available for the reviewers here: + +<|ref|>text<|/ref|><|det|>[[144, 376, 900, 475]]<|/det|> +https://osdr.nasa.gov/bio/repo/data/studies/OSD- 572/preview/CuhxWdYAPRX4QJRLd74yzdXj0 n2OxrXm https://osdr.nasa.gov/bio/repo/data/studies/OSD- 573/preview/Ze2eyzuoTvJ7Cl0887nweUeBe9 GqYTZN https://osdr.nasa.gov/bio/repo/data/studies/OSD- 630/preview/BilzXsJxraKrE9sYDCsOh-MLL3yP ppSC + +<|ref|>text<|/ref|><|det|>[[113, 505, 912, 539]]<|/det|> +4. There were multiple typos in the text. Please edit carefully. Some were in the following lines: 77, 182, 257, 389. + +<|ref|>text<|/ref|><|det|>[[140, 555, 904, 573]]<|/det|> +We have addressed these - and others - as part of our editing process. We thank the Reviewer. + +<|ref|>text<|/ref|><|det|>[[86, 587, 387, 604]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 619, 913, 738]]<|/det|> +1. The writing of this manuscript has improved. The rationale for the experiments and limitations are now explained. Negative controls for skin now much better explained. However, what about the wipes that people were using to bathe themselves while in space? maybe the wipes contained microbial DNA in their solution that people are then applying to their skin. Or maybe the cleaning wipes that astronauts used caused dead DNA to be trapped on their skin. trapping of dead DNA with hospital-associated 'bath-in-bed' chlorhexidine wipes has been shown (PMID: 29753031) by skin microbiome researchers. This could explain fig 3 and fig 4B. + +<|ref|>text<|/ref|><|det|>[[141, 753, 911, 787]]<|/det|> +We are glad the Reviewer is pleased with our changes - thank you. We agree that, of course, wipes used by individuals to bathe themselves in space could be a confounder. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[144, 118, 914, 184]]<|/det|> +However, we reached out to the Commander of the Inspiration4 mission, who confirmed that "any wet wipes used by the crew were not reused, nor shared," which should limit any influence of this confounding variable. We have also noted this in the methods section for the paper, and we note the potential confounding effect of cleaning methods in the Supplementary Discussion. + +<|ref|>text<|/ref|><|det|>[[145, 198, 340, 214]]<|/det|> +In the Methods we write: + +<|ref|>text<|/ref|><|det|>[[144, 229, 912, 295]]<|/det|> +"We note that some crew members were using wet wipes [UPC: 036000317985] to bathe themselves in- flight in between swabbing; however not every crew member did so, and SpaceX did not require this to be a consistent protocol among the crew. Wet wipes used by the crew were not reused, nor shared, which should limit any influence of this confounding variable." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[145, 118, 322, 134]]<|/det|> +And in the Discussion: + +<|ref|>text<|/ref|><|det|>[[145, 149, 912, 199]]<|/det|> +"They [sic future studies] additionally should encourage more detailed reporting on diet and cleaning methods (e.g., wet wipes) to adjust for potential confounders introducing foreign microbial DNA into the host." + +<|ref|>text<|/ref|><|det|>[[145, 213, 912, 295]]<|/det|> +Related to consideration of the manuscript cited, we also note that it indicates "personalized" responses to wet wipe treatment. The responses we observed in our regression were, overall, shared between individuals. Also, we feel that our use of coverage thresholds and a variety of algorithmic approaches likely reduces the probability that merely lysed cells/contaminating DNA drove the majority of the observed effect. + +<|ref|>text<|/ref|><|det|>[[145, 309, 912, 357]]<|/det|> +Also, we now address the "cleaning method" as a potential confounder as well as our thoughts on it in the Supplementary Discussion section (reproduced at the bottom of this document) on drawbacks and also include the update in the methods section. + +<|ref|>text<|/ref|><|det|>[[115, 373, 448, 389]]<|/det|> +2. The discussion could be compressed a lot. + +<|ref|>text<|/ref|><|det|>[[141, 405, 912, 438]]<|/det|> +We have now trimmed down the discussion, moving some of the excessive detail to a Supplementary Discussion section where it is still accessible but less distracting. + +<|ref|>text<|/ref|><|det|>[[115, 453, 912, 504]]<|/det|> +3. Overall, I think the microbiome data for this manuscript could be compressed from 5 figures to 2 or 3 and show the most important data that is truly significant. While the abstract states many findings, the conclusions in the paper include + +<|ref|>text<|/ref|><|det|>[[203, 519, 912, 600]]<|/det|> +"The overall lack of bacterial metagenomic signal in the skin was interesting, as it indicated that strains acquired during flight that displayed altered relative abundance but limited transcriptional changes did not correlate to measurable host immune response. In other words, there was limited evidence that strain- sharing drove an altered immune state in humans." + +<|ref|>text<|/ref|><|det|>[[203, 615, 912, 696]]<|/det|> +"Many of the strongest bacterial skin microbiome alterations (Fig 3) were predominantly metagenomic, as opposed to metatranscriptomic. We hypothesized that this may indicate the acquisition of new but non- transcriptionally active species from the surrounding environment." this statement is oblique. Are the authors hypothesizing that that these microbes are dead? If so this is less of a major conclusion. + +<|ref|>text<|/ref|><|det|>[[203, 711, 912, 760]]<|/det|> +"Most viral activity was transiently increased; in other words, 249 even more dramatically than in the bacterial data, relatively speaking, viral abundances reset to 250 baseline almost immediately after flight (Fig 4B)." + +<|ref|>text<|/ref|><|det|>[[141, 775, 912, 792]]<|/det|> +We agree that our paper was a bit loquacious – however, we do feel it warrants more than 2- 3 + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 88]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[144, 117, 914, 167]]<|/det|> +figures, in large part to highlight the scope of the dataset, which is the largest and most diverse of its kind (it is larger than all metagenomic samples taken in space combined, as indexed in NASA's GeneLab database). To address this point, we have taken the following steps: + +<|ref|>text<|/ref|><|det|>[[171, 182, 912, 216]]<|/det|> +1) First, we have reduced the claims in the abstract. The Reviewer accurately calls out some of the most interesting results here, and we now focus on those. + +<|ref|>text<|/ref|><|det|>[[172, 231, 914, 299]]<|/det|> +2) We clarify that we are not hypothesizing these microbes are dead, just not highly transcriptionally active to the point where it could be detected by an association study. We note that many of these organisms are filtered on a coverage threshold. We are likely filtering out some true positive shifts in lieu of emphasizing high-effect size taxa. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 45, 932, 88]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[201, 118, 912, 151]]<|/det|> +That "filter" provided by regression means that any more minimal change will likely not be detected when compared to, say, the more dramatic metagenomic shifts on the skin. + +<|ref|>text<|/ref|><|det|>[[202, 165, 912, 263]]<|/det|> +We feel that the discordance between metagenomics and metatranscriptomics is actually one of the most interesting findings in this study, because it indicates that DNA presence does not correlate to dramatic changes in transcriptional activity. In other words, all the studies that rely on metagenomics alone, in general, may actually be missing a large portion of the picture and unable to target truly causal host- microbe relationships, which we think is an exciting result. + +<|ref|>text<|/ref|><|det|>[[173, 278, 912, 328]]<|/det|> +3) We have reduced focus on the viral component of our findings, relegating certain panels to the supplement and indicating that, in low abundance data, viral classification is difficult. We additionally have moved the gene catalog panels entirely to the supplement. + +<|ref|>text<|/ref|><|det|>[[142, 343, 911, 377]]<|/det|> +In total, our paper now has 5 simplified figures, and we have updated the abstract to more accurately reflect the key points highlighted by the Reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 392, 913, 579]]<|/det|> +4. Methods established for determining 'viral presence' in Fig 4B still has me wondering if any of this is real. Authors state that they did a benchmarking but that was with viruses from GenBank. In this case they have random shotgun reads that may or may not be weakly related viruses? Filtered for \(1\%\) total coverage or \(0.5\%\) seems extremely low. If this is just reads piling up in one location of a sequence deposited in RefSeq I don't think they can call this 'present' even at the genus level. A lot of these are odd named that seem like best match but might not hold up to scrutiny; e.g. sewage-associated circular DNA virus-20 or lake Sarah-associated circular virus-23, Gen_unclassified Gokushovirinase (which is shown as transient decrease and transient increase on skin)? This data seemed like very small changes were being reported and of viruses that have not been associated with skin. I also don't understand how metatranscriptomics yields all transient decrease and metagenomics all yields transient increase - sometimes of the same or similar genus. Which of these are DNA versus RNA viruses? + +<|ref|>text<|/ref|><|det|>[[144, 594, 912, 643]]<|/det|> +In short, we agree that calling viruses is extremely difficult. The virome is not well explored. Some spurious alignments are likely false positives; others could be incomplete databases where the most related organism in the database has an unusual name. + +<|ref|>text<|/ref|><|det|>[[144, 657, 711, 675]]<|/det|> +To account for challenges in viral detection, we have done the following: + +<|ref|>text<|/ref|><|det|>[[171, 690, 914, 791]]<|/det|> +1) As in our first round of revisions, we worked at the genus level for higher confidence calls of taxa. +2) Benchmarked our approaches and used a diverse set of methods (note Supp Fig 18, where we show high accuracy at the genus level on the database we're using in calling viruses). +3) Extensively discuss the difficulty of viral classification in the results and the Supplementary Discussion (reproduced below). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 90]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[173, 118, 912, 169]]<|/det|> +4) Reduce the emphasis on viral analysis in the manuscript, such that unusual taxa are not highlighted, focusing instead on trends in viral classes (e.g., eukaryotic vs prokaryotic) and more on the high-confidence changes. + +<|ref|>text<|/ref|><|det|>[[144, 184, 912, 233]]<|/det|> +The transient shift in viruses compared to bacteria is aligned with what we know about viral activation in space. Spaceflight changes viral communities and causes, in some cases, reactivation of latent infections (e.g., herpes viruses). This effect resets upon returning to Earth. + +<|ref|>text<|/ref|><|det|>[[144, 247, 912, 296]]<|/det|> +Overall, we claim to be using state- of- the- art methods for viral classification, and now with the reduced emphasis on viral shifts and the stated caveats in the Supplementary Discussion, we hope that our analysis is acceptable for publication. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[115, 117, 914, 254]]<|/det|> +5. StrainPhlAn and MetaPhlAn are designed for gut microbiome studies as authors acknowledge and yet they continue to use these marker gene based methods for skin data, undermining confidence in Figure 5. Their conclusions in text are "Overall (Fig 5B), we found that individuals appeared to acquire strains from the capsule by the 334 second mid-flight sampling point (day 3). During the L-92 timepoint, there was minimal transfer 335 between the training capsule and the astronauts." And yet their conclusion in abstract is: 'We also used 48 strain-level tracking to measure the potential propagation of microbial species from the crew 49 members to each other and the environment, identifying microbes that were prone to seed the 50 capsule surface and move between the crew.' + +<|ref|>text<|/ref|><|det|>[[144, 269, 912, 350]]<|/det|> +Thank you for this comment. We have fixed the discordance between the abstract and the text. Regarding marker gene- based approaches, we note that many methods used (e.g., Xtree) are not marker- gene based, which will help give orthogonal methods for the species measurements. In accordance with Reviewer requests in the first revision, we added MetaPhlAn4 and StranPhlAn, as they are established tools, but indeed, they were first based on stool samples. + +<|ref|>text<|/ref|><|det|>[[144, 364, 912, 494]]<|/det|> +Fortunately, the recent updates to MetaPhlAn and StranPhlAn incorporate marker genes from more than just the gut microbiome. Specifically, they use databases requested by the Reviewers (e.g., Segata and Finn labs) in the initial round of review, and they also incorporate MAGs/genomes from the skin and oral niches. Therefore, as of their recent release, the developers of these tools have expressed confidence that their updated tools are now appropriate for more than just the gut microbiome. Specifically, the recent MetaPhlAn4 paper indicated that its default database includes marker genes from more than just the gut microbiome: + +<|ref|>text<|/ref|><|det|>[[144, 508, 912, 589]]<|/det|> +"MetaPhlAn4 application to human and nonhuman metagenomes. To measure the increase of the fraction of classified reads when compared with MetaPhlAn3, we profiled 24,515 samples from 145 datasets spanning different human body sites (airways, gastrointestinal tract, oral, skin, and urogenital tract) and lifestyles, animal hosts (non- human primates, mice and ruminants) and other non- host- associated environments (soil, fresh water, and ocean)." + +<|ref|>text<|/ref|><|det|>[[144, 603, 912, 668]]<|/det|> +Indeed, the paper on which we modeled our strain- sharing approach was used for the oral microbiome (https://www.nature.com/articles/s41586- 022- 05620- 1). Given these recent developments, as well as the range of other tools with which we have also processed these i4 data, we believe these results will be useful, relevant, and robust for the field. + +<|ref|>text<|/ref|><|det|>[[115, 684, 911, 718]]<|/det|> +6. Methods: were the metatranscriptomics samples depleted of bacterial rRNA? Only described that human/mouse/rat [18S, 5S, 23S] was performed. Wondering if bacterial 16S rRNA also depleted? + +<|ref|>text<|/ref|><|det|>[[144, 732, 907, 799]]<|/det|> +We did not deplete the bacterial 16S rRNA, but used the human/mouse/rat rRNA ribo-depletion kit from NEB. This method had been previously well-characterized and successful for bacterial, viral, and fungi metatranscriptomics analysis from clinical samples, and we have cited these manuscripts in our updated paper to help guide readers for more details: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 89]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[144, 118, 715, 152]]<|/det|> +https://www.nature.com/articles/s41467- 021- 21361- 7 https://genome.cshlp.org/content/early/2021/02/18/qr.268961.120.full.pdf + +<|ref|>text<|/ref|><|det|>[[86, 182, 387, 199]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[85, 213, 891, 247]]<|/det|> +In this revision, the authors have responded to my comments on their previous draft. This is a much- improved manuscript. However, I still have some concerns listed below. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 45, 932, 90]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[117, 117, 914, 272]]<|/det|> +1. In response to my previous comment, the authors included pre-flight (using a different capsule) and mid-flight microbial compositions of the flight of interest. The authors claim on page 45 of their rebuttal that "... overall the metagenomic community is relatively similar on Earth vs. in-flight". I find this a bit surprising. Several people are in the space capsule in close proximity to each other. Hence, if the microbial composition can change within each subject over the three day period, then why did it not change in the capsule environment. In fact, from the relative abundance plots provided on page 45 of the rebuttal document it does appear that the capsule environment has also changed. Of course with the authors that changes in the capsule environment from earth to space is difficult to interpret because they are not the same capsule that were measured at the two time points. + +<|ref|>text<|/ref|><|det|>[[144, 286, 912, 368]]<|/det|> +This is an important comment. Indeed, as the capsule environment is not identical in- flight as on Earth, we have remedied the relevant comment in the text to indicate the changes. We feel that it was not worth heavily focusing on them, due to our choice not to carry out statistical analysis on the capsule samples. This was, as the reviewer indicated, because the pre- flight and mid- flight capsules were different. + +<|ref|>text<|/ref|><|det|>[[115, 381, 912, 484]]<|/det|> +2. Again, going back to my comment on the earlier draft, when microbes do not enter the capsule in flight, then how the changes in microbiome within and between subjects be explained as due to space travel? The changes in microbial compositions could be purely because several people are inside a capsule over three days. An ideal control would be if the same subjects were housed in the same capsule for three days on earth. Does the "pre-launch" data refer to this control group? I probably missed it if that is the case. Otherwise, I find the data of this project difficult to interpret. + +<|ref|>text<|/ref|><|det|>[[144, 498, 912, 580]]<|/det|> +The pre- flight samples refer to the same crew members sampled while not cohabitating in the months leading up to the spaceflight. Detected metagenomic shifts could arise, for example, from the abundance of organisms shifting to above the limit of detection by sequencing or transfer between individuals. Metatranscriptomic shifts do not require microbial transfer - a native species experiencing an increase in expression is all it would take for a detectable signal. + +<|ref|>text<|/ref|><|det|>[[144, 594, 912, 708]]<|/det|> +We agree that a parallel ground study would be useful, but that data does not exist at present, and SpaceX could not release an additional unused Dragon capsule to sequence another cohort, but this has been requested for future missions with their flight operations team. However, we do not feel this is a critical control for this study, given the large number of negative and positive controls, what we observe in the discordant shifts between metagenomics and metatranscriptomics across the exact same body sites over time, and because of what is known about spaceflight and the microbiome. + +<|ref|>text<|/ref|><|det|>[[144, 722, 912, 788]]<|/det|> +For example, spending time in a tight space does not normally cause herpesvirus activation in control cohorts. But spaceflight does activate herpes strains in \(61\%\) of people (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374706/) in spaceflight. We address this in the Discussion/Supplementary Discussion: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[143, 117, 914, 264]]<|/det|> +"Chief among our findings was that native microbiome shifts were highly correlated to host immune changes. Naturally, a microbial shift can affect the host immune system – or vice versa – without the initial cause being “space- specific” (i.e., due to microgravity of radiation). Strain sharing, for example, could be – and likely is – a function of humans sharing close quarters. That said, astronauts have been documented as experiencing immune and viral activation15; typically, this effect is not attributed solely to cohabitation, and we showed here that strains likely “acquired” from crew members in flight were not associated with immune cell changes. We claim, therefore, it is unlikely strain sharing due to close quarters – or even variable sanitation in- flight – explains the entirety of the link between host immune response and the microbiome. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 931, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[144, 118, 911, 151]]<|/det|> +Future manuscripts, of course, could leverage this dataset as well as data from analog astronaut studies on Earth to more rigorously test this hypothesis." + +<|ref|>text<|/ref|><|det|>[[144, 165, 913, 342]]<|/det|> +In short, a portion of changes may be from cohabitation - but it is unlikely that all of them are, and this dataset is the largest to- date that enables such comparisons, which can help tease out these interactions when we begin to compare to other missions. Further of note, the changes that are almost surely from cohabitation - skin metagenomic shifts of specific taxa - are not correlated to immune cell gene expression changes. On the other hand, metatranscriptomic shifts in the oral microbiome, where there is no known exchange between individuals, are associated with immune cell gene expression changes. We thus claim that these data, combined with the known effects of spaceflight that are uniquely distinct from cohabitation, bolsters our claim that at least some of the changes are likely space- associated. It will, however, require future work to determine which of these shifts are consistently observed or mission- specific. + +<|ref|>text<|/ref|><|det|>[[115, 357, 913, 459]]<|/det|> +3. In response to my comment regarding correlation analyses, the authors note on page 46 that they combined data from all sites to construct correlations. Does it mean they treated all sites as one organ for computing correlations? Since these are relative abundance data, the standard concept of Pearson correlation is not appropriate. Did they use SPARCC or some of the other recent methods? From the heatmaps, I am puzzled that all correlations among the bacterial families are all positive. Why is that? Is it an artifact of the correlation tool used? Or is there a real biology? + +<|ref|>text<|/ref|><|det|>[[144, 475, 913, 602]]<|/det|> +We agree this analysis is worthy of a deeper dive than what we did; however, we are attempting in these revisions to balance requests for a shorter, tighter manuscript with additional analytic goals. Previously, this figure was referenced in one line in the results, and we feel the analysis requested would require (and warrant) much more text. Therefore, we have opted instead to remove this figure and recommend correlational network- based analyses as follow- ups in following work. We feel it is appropriate, as it did not change the main results of the paper (as highlighted by Reviewer 2) and is not the focus of the main results, but we have cited SPARCC in the discussion to highlight future directions and analytical approaches. + +<|ref|>text<|/ref|><|det|>[[115, 617, 913, 667]]<|/det|> +4. It is true that linear models have a history in microbiome data analysis, but recently developed algorithms such as LinDA would be better alternatives to deal with compositionality in the microbiome data. There is a risk of high false discovery rates when compositionality is ignored. + +<|ref|>text<|/ref|><|det|>[[144, 683, 913, 797]]<|/det|> +We agree that linear models have some limitations, and we have added to our revised paper a battery of methods to help reduce risk of analysis error. As the reviewer keenly notes, there are a number of alternative statistical/transformation approaches that we could try, but we believe our current comparison of methods is appropriate, given the standard in the microbiome field. Moreover, since we've used 11 methods in this paper and seen similar results across all of them, we believe that using LinDA to adjust for compositionality bias is a good idea, but one that should be robustly compared across a wide range of sample types in a future study (we now + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 932, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[144, 118, 912, 183]]<|/det|> +cite LinDA in the manuscript as a potential additional analytic approach). We claim our concordance across transformation methods accounts for a degree of bias in compositional data, though in future work on this dataset, we will perform even more comparisons with additional methods. We address this in our Discussion section to highlight this for readers. + +<|ref|>text<|/ref|><|det|>[[141, 197, 910, 231]]<|/det|> +We are grateful and very appreciative of the reviewers for their careful, thorough, and helpful reviews and hope they find the new manuscript satisfactory. + +<|ref|>title<|/ref|><|det|>[[86, 280, 162, 295]]<|/det|> +# Appendix: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 931, 88]]<|/det|> +# nature portfolio + +<|ref|>sub_title<|/ref|><|det|>[[87, 118, 297, 135]]<|/det|> +## Supplementary Discussion + +<|ref|>text<|/ref|><|det|>[[87, 150, 585, 165]]<|/det|> +Specific human genes and their association with microbiome features + +<|ref|>text<|/ref|><|det|>[[85, 177, 912, 354]]<|/det|> +An additional manuscript focuses more on the host- side of immune activation (Kim and Tierney et al, in review, Nature), reporting specific human genes that seem to be associated with microbial features and integrating additional datasets. However, for completeness, we briefly document here some human genes of interest that were microbiome- associated. By cell type, we documented the most strongly associated genes with microbial features (Supplementary Table 10). For bacteria, gene functions were annotated with, for example, long non- coding RNAs (across all cell types), immunoglobulin genes (CD14 monocytes), and interferon regulatory factors. We additionally uncovered associations with specific immune modulatory genes such as CXCL10, XCL1, CXCL8 (immune cell migration), NLRC5, HLA genes, CD1C (antigen presentation/co- stimulation), SLC2A9 (immune cell metabolism), IRF1, NR4A3, STAT1 (transcription factors that specify immune cell states) that increased across multiple immune cell types (B cells, CD4 T- cells, CD8 T- cells, CD14 monocytes, DCs, Natural Killer (NK) cells). + +<|ref|>text<|/ref|><|det|>[[87, 369, 465, 384]]<|/det|> +Further notes on the complexity of viral classification + +<|ref|>text<|/ref|><|det|>[[85, 396, 912, 509]]<|/det|> +In this study, we attempted to measure viral shifts as a function of flight as well. Measuring viral abundances in metagenomic and (particularly) metatranscriptomic data is extremely challenging. First, the decontamination process we used to remove environmental contaminants was not designed for organisms as ubiquitous and with such short, diverse genomes as viruses. Likely, we are removing many true positive viruses from our dataset. Second, we are also working with low biomass samples; it is hard enough to detect bacteria with high confidence, but viruses are another challenging matter entirely. + +<|ref|>text<|/ref|><|det|>[[85, 523, 912, 620]]<|/det|> +Finally, and most importantly, taxonomic classification via short read alignment to viral genomes is deeply imperfect. We observed, for example, many significant viruses shifting with unusual names, often mapping to viral species not typically found in or on humans. Simply put, the viral universe is so vast that we expect these alignments are likely due to a combination of spurious read mapping and databases lacking the strains that are truly present. As a result, we are only able to work with state- of- the art methods, comparing the results across taxonomic ranks. + +<|ref|>text<|/ref|><|det|>[[85, 635, 912, 780]]<|/det|> +We are confident in the results highlighted in the main text of this manuscript regarding viruses: mostly transient, pan- body shifts in- flight for both prokaryotic and eukaryotic viruses, some of which are correlated to immune cell gene expression changes. We compared multiple methods, finding concordant results, and we benchmarked the method used in the main text (Xtree alignment to GenBank) via rigorous testing on synthetic genomes (Supplementary Figure 18), finding accurate alignment at the genus level. Further, we identified viral genes as shifting in- flight in the functional/gene catalog analysis (Supplementary Figures 14- 17). That said, we are also certain that some of the taxonomic classifications are not accurate, so any atypical clades highlighted in the regression results (Supplementary Table 9) should be considered with appropriate caution. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[559, 44, 931, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[87, 120, 481, 135]]<|/det|> +Other drawbacks of this study and future opportunities + +<|ref|>text<|/ref|><|det|>[[85, 145, 914, 370]]<|/det|> +There are several opportunities to expand upon this work in future studies and missions. Analytically, our lasso- based approach for immune- microbe- interaction modeling immune cell gene expression changes does not inherently allow for statistical inference or account for inter- individual variation. Further, some of our samples had very low biomass, requiring PCR- amplification (18 cycles) for RNA- sequencing data, which can increase duplicate rates of sequences. For this reason, we attempted to take a conservative and systematic modeling approach to our effort. Specifically, 1) we implemented multiple algorithms and compared their concordance, 2) set coverage thresholds for bacterial and viral taxa to filter probable false positives, 3) used multiple, state- of- the- art taxonomic classifiers and compared our findings among all of them, and 4) implemented and compared both generalized linear models and mixed effect models, bearing in mind that the latter can face interpretability challenges with smaller sample sizes. Additional modeling strategies, including network analyses2, could be implemented in addition to those we have tested here. For example, recently developed methods for controlling false positive rates in compositional data could be potentially useful for this manner of microbiome data1. + +<|ref|>text<|/ref|><|det|>[[123, 385, 873, 499]]<|/det|> +We additionally used 76 negative controls to attempt to avert false positive signals, which can stem from contamination and the kitome. However, this approach is far from perfect and likely removes present organisms. Depending on their aim, future studies should alter collection methods to increase the amount of biomass collected sampling (e.g., using one swab for multiple skin sites) or examine relatively unbiased methods of amplification3. They additionally should encourage more detailed reporting on diet and cleaning methods (e.g., wet wipes) to adjust for potential confounders introducing foreign microbial DNA into the host. + +<|ref|>text<|/ref|><|det|>[[123, 513, 873, 641]]<|/det|> +Additional experiments and missions can further test a microbiome- derived theory of spaceflight- associated immune c changes. In addition to stress- testing our findings and increasing sample sizes, future spaceflight studies should consider several enhancements. For instance, they should compare sequestered ground controls to discern differences between space- driven and proximity- driven immune shifts. Additionally, future efforts should design experiments that enable a deeper view into the causality of microbe immune associations rather than just noting their existence. Exploring some of these hypotheses through animal or organoid models could be valuable. + +<|ref|>text<|/ref|><|det|>[[123, 654, 860, 702]]<|/det|> +1. Zhou, H., He, K., Chen, J. & Zhang, X. LinDA: linear models for differential abundance analysis of microbiome compositional data. Genome Biol. 23, 95 (2022). + +<|ref|>text<|/ref|><|det|>[[122, 720, 857, 738]]<|/det|> +2. Friedman, J. & Alm, E. J. Inferring correlation networks from genomic survey data. PLoS Comput. + +<|ref|>text<|/ref|><|det|>[[159, 754, 341, 770]]<|/det|> +Biol. 8, e1002687 (2012). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[595, 44, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[121, 118, 865, 168]]<|/det|> +3. Ahsanuddin, S. et al. Assessment of REPLI-g Multiple Displacement Whole Genome Amplification (WGA) Techniques for Metagenomic Applications. J. Biomol. Tech. 28, 46–55 (2017). + +<|ref|>title<|/ref|><|det|>[[113, 224, 336, 239]]<|/det|> +# Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[115, 279, 454, 295]]<|/det|> +Message: Our ref: NMICROBIOL- 23082268A + +<|ref|>text<|/ref|><|det|>[[198, 307, 345, 321]]<|/det|> +1st December 2023 + +<|ref|>text<|/ref|><|det|>[[198, 335, 320, 349]]<|/det|> +Dear Dr. Mason, + +<|ref|>text<|/ref|><|det|>[[198, 362, 875, 446]]<|/det|> +Thank you for submitting your revised manuscript "The microbiome architecture of short- term spaceflight and its potential link to host immune activation" (NMICROBIOL- 23082268A). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Microbiology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[198, 459, 874, 502]]<|/det|> +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)-- we can not proceed with PDFs at this stage. + +<|ref|>text<|/ref|><|det|>[[198, 514, 855, 557]]<|/det|> +We will ask for some additional text edits in line with the remaining concerns including toning down statements, discussing limitations and removing or reducing the section on strain sharing. We will send further instructions with the checklist mentioned below. + +<|ref|>text<|/ref|><|det|>[[198, 569, 880, 627]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[198, 638, 867, 667]]<|/det|> +Thank you again for your interest in Nature Microbiology Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[198, 680, 271, 694]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[198, 735, 486, 750]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[198, 762, 622, 777]]<|/det|> +The authors have addressed my comments satisfactorily. + +<|ref|>text<|/ref|><|det|>[[115, 852, 883, 953]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 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To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[595, 44, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[198, 147, 485, 162]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[198, 175, 875, 219]]<|/det|> +i have concerns that there are contaminants or read mapping issues with the methods, but i don't have any further suggestions given the samples obtained and processed for this study. + +<|ref|>text<|/ref|><|det|>[[198, 230, 868, 260]]<|/det|> +I am still not sure that the authors can make the claim that they are seeing strain sharing based on strainphlan analysis without benchmarking for these species. + +<|ref|>text<|/ref|><|det|>[[198, 272, 359, 286]]<|/det|> +no further comments. + +<|ref|>text<|/ref|><|det|>[[198, 313, 485, 328]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[197, 339, 879, 551]]<|/det|> +I thank the authors for their careful responses to my previous comments. In response to my concerns regarding the lack of proper negative control on earth, they cited an interesting article (Rooney et al., Front. Microbiol.) describing the effects of spaceflight and the herpesvirus activation. I am still having difficulty inferring that spaceflight is the cause for microbial shifts in the compositions. I am not sure if compared to pre- flight, during the three- day flight, the crew brushed their teeth, showered, changed their sleep patterns and diet. Thus, can the differences be partly due to changes in their daily activities along with staying in close proximity to one another for 3 days, and not entirely due to space flight. Granted space- flight does induce stress, as reported in the reference cited by the authors, but it is only part of the effect. I wonder if similar changes to microbiome will be seen for people taking a non- stop long distance flight from NYC to Australia. Note that on lines 227 - 232, the authors observed a reduction in beta- diversity among the crew members. Perhaps this is due to similar diet, environment, and hygiene practices during the three day space- flight. Comparisons with pre- flight specimens is not very convincing to me that changes are due to spaceflight and not due to behavior and environment. + +<|ref|>sub_title<|/ref|><|det|>[[112, 641, 272, 656]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[120, 659, 339, 673]]<|/det|> +Message 9th February 2024 + +<|ref|>text<|/ref|><|det|>[[198, 675, 281, 688]]<|/det|> +Dear Chris, + +<|ref|>text<|/ref|><|det|>[[198, 719, 879, 777]]<|/det|> +I am pleased to accept your Article "Longitudinal multi- omics analysis of host microbiome architecture and immune responses during short- term spaceflight" for publication in Nature Microbiology. Thank you for having chosen to submit your work to us and many congratulations. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[596, 45, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[198, 134, 874, 179]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Microbiology style. We look particularly carefully at the titles of all papers to ensure that they are relatively brief and understandable. + +<|ref|>text<|/ref|><|det|>[[198, 194, 872, 254]]<|/det|> +Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. 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Recipients of the link with a subscription will also be able to download and print the PDF. + +<|ref|>text<|/ref|><|det|>[[198, 625, 814, 655]]<|/det|> +As soon as your article is published, you will receive an automated email with your shareable link. + +<|ref|>text<|/ref|><|det|>[[198, 685, 335, 700]]<|/det|> +With kind regards, + +<--- Page Split ---> diff --git a/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/images_list.json b/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..6f01f06d932d41c31b513c6183eabb684a727784 --- /dev/null +++ b/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Fig. 5: ABGs taken across distinct respiratory challenges. a, In a respiratory challenge operated with independent actuation, a representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \\(\\mathrm{pCO_2}\\) values from discrete arterial blood gases taken. b, In a respiratory challenge operated with synchronized actuation, a representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \\(\\mathrm{pCO_2}\\) values from discrete arterial blood gases taken during one full respiratory challenge with synchronized actuation. The respiratory challenges depicted in a, and b, are taken from the same animal. c, In another animal, a respiratory challenge began with a 2 minute period of unsupported ventilation and subsequent synchronized actuation. A representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \\(\\mathrm{pCO_2}\\) values from discrete arterial blood gases taken. Gray shading indicates the period of time where the system is off and respiration is unassisted. Light green shading indicates the standard range", + "footnote": [], + "bbox": [ + [ + 120, + 256, + 880, + 670 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Extended_Data_Figure_1.jpg", + "caption": "Extended Data Fig. 1. Controlling actuation via different pneumatic waveforms. Input waveforms of a (a) curved, (b) square, and (c) triangle shape can be programmed into the", + "footnote": [], + "bbox": [], + "page_idx": 21 + } +] \ No newline at end of file diff --git a/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a61c713bd8a1080a0369b50cfe14fb5eaff1af5d --- /dev/null +++ b/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,647 @@ + +# An implantable soft robotic ventilator augments inspiration in a pig model of respiratory insufficiency + +Corresponding author: Ellen Roche + +## Editorial note + +This document includes relevant written communications between the manuscript's corresponding author and the editor and reviewers of the manuscript during peer review. It includes decision letters relaying any editorial points and peer- review reports, and the authors' replies to these (under 'Rebuttal' headings). The editorial decisions are signed by the manuscript's handling editor, yet the editorial team and ultimately the journal's Chief Editor share responsibility for all decisions. + +Any relevant documents attached to the decision letters are referred to as Appendix #, and can be found appended to this document. Any information deemed confidential has been redacted or removed. Earlier versions of the manuscript are not published, yet the originally submitted version may be available as a preprint. Because of editorial edits and changes during peer review, the published title of the paper and the title mentioned in below correspondence may differ. + +## Correspondence + +Mon 04 Apr 2022 Decision on Article nBME- 21- 2902 + +Dear Prof Roche, + +Thank you again for submitting to Nature Biomedical Engineering your manuscript, "An implantable ventilator augments inspiration in an in vivo porcine model". As noted in previous e- mail correspondence, the manuscript has been seen by three experts, yet despite our chasing efforts, one reviewer has failed to provide a report. The feedback from two reviewers, which I had already forwarded to you, is also included at the end of this message. + +You will see that the reviewers appreciate the work. However, they express concerns about the degree of support for the claims, and provide useful suggestions for improvement. We hope that with significant further work you can address the criticisms and convince the reviewers of the merits of the study. In particular, we would expect that a revised version of the manuscript addresses the concerns on the safety and performance of the implantable ventilator, and includes additional caveats as to the expected bottlenecks that would need to be overcome before eventual human trials of the device. Importantly, please make sure that device characterization and methodology reporting are thorough. + +When you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that explains the main improvements included in the revision and responds to any points highlighted in this decision. + +Please follow the following recommendations: + +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third- party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0. + +<--- Page Split ---> + +\* If you and your co-authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the reason(s). + +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +We hope that you will be able to resubmit the manuscript within 20 weeks from the receipt of this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +We hope that you will find the referee reports helpful when revising the work. Please do not hesitate to contact me should you have any questions. + +Best wishes, + +Pep + +Pep Pamies Chief Editor, Nature Biomedical Engineering + +Reviewer #2 (Report for the authors (Required)): + +This paper is the first demonstration of an in vivo implanted system for assisting in breathing and for contracting diaphragm. The use of external ventilators is very critical, and having an implanted system would solve major problems for patients with diaphragm dysfunctions. + +I appreciated the paper: the motivations are clear, the in vivo tests are sufficiently solid (even if quite short) and the future impact could be dramatic. + +On the other hand, I have identified some major and minor issues which prevent me to give a positive assessment. + +1. First of all, the engineering part is quite limited. All the used components are not optimized for the application. Soft actuators design, size and distribution are not considered in the study protocol (see also comment 4). Sensors and controllers are commercial. The most relevant parts of the paper are the animal test and the physiological measurements. + +2. The clinical motivation of this work is very clearly presented at the beginning. The authors are invited to discuss (possibly in the discussion section) if the target patients for this kind of device are eligible to undergo such complex implant surgery procedure. This might be crucial to foresee future clinical employments of the device. + +3. In the introduction section the authors should better contextualize their work not only with reference to soft actuators but also to fully implantable robots. Few examples and field definition were recently reported in the state of the art. Just as examples, please refer to: - Damian, D. D., Price, K., Arabagi, S., Berra, I., Machaidze, Z., Manjila, S., ... & Dupont, P. E. (2018). In vivo tissue regeneration with robotic implants. Science Robotics, 3(14). - Iacovacci, V., Tamadon, I., Kauffmann, E. F., Pane, S., Simoni, V., Marziale, L., ... + +<--- Page Split ---> + +& Menciassi, A. (2021). A fully implantable device for intraperitoneal drug delivery refilled by ingestible capsules. Science Robotics, 6(57), eabh3328. - Menciassi, A., & Iacovacci, V. (2020). Implantable biorobotic organs. APL bioengineering, 4(4), 040402. + +4. It is not clear how the number of PAMs and the overall output force required were set. Please clarify on this and comment on the role played by spatial distribution of the two actuators on the diaphragm surface. What about the needed PAM contraction? Should this be adjusted for each subject and then be constant over the respiratory task? + +5. The authors employed a custom controller aimed at synchronizing the soft robotic actuator and natural breathing. However, both sensing (spirometry) and control rely on external (bulky?) data acquisition and control platforms. This appears a bit in contrast with the original motivation to outperform over invasive ventilation systems. No concrete paths towards implantations are given. + +6. The caption of figure 2 is very informative. However, it would be useful to add some labels on the axes, graphs title, etc., to make figures readability more straightforward. + +7. The in vivo test is very short, so all considerations about materials, biocompatibility, stability etc. are missing. + +8. In line 512, 6 pigs are mentioned. But in the rest of the papers we had 5 pigs. + +Reviewer #3 (Report for the authors (Required)): + +This work by Drs. Hu and Roche developed an implantable device that can substitute a mechanical ventilator commonly used in the contemporary clinical care and yet, avoid the various shortcomings of it. The authors build a robotic actuator which is overlaid to the subject's diaphragm and activated by the host's inspiratory effort, which in turn, is balloon inflated and substitutes the function of the native diaphragm. + +The authors challenge an important clinical question, with a good understanding of the respiratory cycle and the role of the diaphragmatic motion. The concept underlying the current work is interesting and innovative. I acknowledge that this is a prototype, however the current manuscript do have room for improvement. Additionally, considering the invasiveness of the implantation associated with their device, whether the strength of the system is enough to overcome the invasiveness associated with the procedure should be discussed more in depth. + +Here are some major comments for the authors. + +1. The authors fail to analyze the actual blood gas levels with arterial blood. The authors state that the responsiveness of the diaphragm can vary between subjects. How can the authors be sure that the blood gas levels are maintained at a relatively stable state with the device instillation? Please be aware that maintaining the blood acid-base balance in a homeostatic state is a critical role of respiration in every living creature. + +2. How is the level of inspiration controlled with their device? The degree of inspiration should be controllable according to the subjects needs in various clinical situation (for example, in early sepsis, it is natural to be in a hyperventilated state) but the authors do not show that their device is versatile enough to accommodate this. What happens to the subject's respiration if the bladder in the system is pressurized more? Additionally, what about the opposite where there is no need for a deep inspiration? + +3. Likewise, I would like to see how the respiratory mechanics change according to how fast the bladder in their system is inflated. More information should be given on this. The respiratory mechanics are shown as simple bar graphs in Figures 5a, b and c, whereas the gradient or slope of the Campbell diagram may also be important. + +4. The authors should be commended for doing a nice job in synchronizing the device to the subject's respiratory effort. However, the trigger for this is the spirometer that is installed into the subject's airway. To really overcome the weakness of the contemporary mechanical ventilators, the authors should think of better methods that do not touch the respiratory tract to sense the intrinsic respiratory effort. + +<--- Page Split ---> + +There are also some minor comments that might help. + +1. Supplementary Video Online is not that informative as it plays in a real-time. It would be better if the video is played more slowly. + +2. The finding should be supported by adequate statistical analysis. + +2.1. Although somewhat obvious from the graphs, there should be some statistical analysis to show the difference in the variation of peak inspiratory flow and tidal volume of Figure 3e and f. + +2.2. The pairwise comparisons should be done for Figure 5a, b, and c with the data acquired at the spontaneous respiration (SR) as the reference, not the actuator assisted ventilation (AAV). + +2.3. How many samples were taken for each subjects in each graph. This should be noted. + +3. In Figures 2c, d and e, when did the authors gather data after the device was turned off or on? The same questions goes for synchronized actuation in Figures 3e and f, Figures 5a, b and c. + +4. Figure 4a and b miss the legends for y-axis. + +5. The overall structure of the Discussion could be improved. The contents of each paragraphs tend to jump, making it difficult to follow. + +<--- Page Split ---> + +## Sun 16 Oct 2022 Decision on Article nBME-21-2902A + +Dear Prof Roche, + +Thank you for your patience in waiting for the guidelines for the final submission of your manuscript, "An implantable ventilator augments inspiration in an in vivo porcine model" to Nature Biomedical Engineering. Please carefully follow the instructions provided in the attached file. + +Also, please consider the minor points from Reviewer #3. + +For primary research originally submitted after December 1, 2019, we encourage authors to take up transparent peer review. If you are eligible and opt in to transparent peer review, we will publish, as a single supplementary file, all the reviewer comments for all the versions of the manuscript, your rebuttal letters, and the editorial decision letters. When submitting the final version of your manuscript please indicate whether you opt in to transparent peer review. In the interest of confidentiality, we allow redactions to the rebuttal letters and to the reviewer comments. If you are concerned about the release of confidential data, please indicate in the cover letter what specific information you would like to have removed; we cannot incorporate redactions for any other reasons. More information on transparent peer review is available. + +When you are ready to submit the final version of your manuscript, please upload the files specified in the instructions file. + +If you have any further questions, please feel free to contact me. + +Best regards, + +Pep + +Pep Pamies Chief Editor, Nature Biomedical Engineering + +Reviewer #2: + +Report for the authors (Required): + +The paper has been substantially improved and now the contribution of the work, the methodology behind and the main limitations of the obtained results have been reported. I think these additional parts (and additional tests, which I really appreciate) can help to position the paper in the state of the art and help the readers to understand the most critical elements for further developments. I am sure that some activities reported as "future steps" are not trivial at all (miniaturization of the electronics, biocompatibility, neural triggering), but the results, as a first proof of concept in vivo, deserve to be published. + +Reviewer #3: + +Report for the authors (Required): + +This report by Drs. Hu and Roche is a revised version of the manuscript previously submitted to the Nature BME. The manuscript has been significantly improved and much of the parts have been clarified. A significant proportion of the previous questions have been resolved. I have two minor comments/suggestions remaining. + +1. The blood gas analysis allows us to see how the system developed by the authors translate into the respiration of a given subject/animal but there are some comments related to this. + +1.1. I am actually not sure whether the acidosis seen in Fig. 5b is a result of metabolic acidosis. Although the + +<--- Page Split ---> + +blood gas results may be different between humans and swines, I think the blood gas analysis in Fig. 5b is a mixed form of both respiratory and metabolic acidosis. + +1.2. How many animals were analyzed for the blood gas? + +2. Although I agree that there is a lot to discuss, the length of the Discussion is actually quite long. + +Nature Biomedical Engineering is a Transformative Journal. Authors may publish their research with us through the traditional subscription- access route, or make their paper immediately open access through payment of an article- processing charge. More information about publication options is available. + +You may need to take specific actions to comply with funder and institutional open- access mandates. If the work described in the accepted manuscript is supported by a funder that requires immediate open access (as outlined, for example, by Plan S) and your manuscript was originally submitted on or after January 1st 2021, then you will need to select the gold OA route. Authors selecting subscription publication will need to accept our standard licensing terms (including our self- archiving policies), and these will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<--- Page Split ---> + +Rebuttal 1 + +<--- Page Split ---> + +# Manuscript nBME-21-2902 : Response to Reviewers' Comments + +We thank the reviewers for their thoughtful and detailed feedback. We have addressed each of these comments in turn, and have included corresponding modifications to the text. We feel the reviewer's comments and the subsequent revisions have substantially clarified and strengthened the manuscript. For clarity, the changes made to the manuscript- including the new Extended Data- are shown in blue in both this response and in the manuscript. Changes made to the Supplemental Information are shown in orange in this document. + +## Comments from Editor + +You will see that the reviewers appreciate the work. However, they express concerns about the degree of support for the claims, and provide useful suggestions for improvement. We hope that with significant further work you can address the criticisms and convince the reviewers of the merits of the study. In particular, we would expect that a revised version of the manuscript addresses the concerns on the safety and performance of the implantable ventilator, and includes additional caveats as to the expected bottlenecks that would need to be overcome before eventual human trials of the device. Importantly, please make sure that device characterization and methodology reporting are thorough. + +## Answer to the Editor + +We thank the Editor for considering our manuscript for Nature Biomedical Engineering. Here, we present additional data and discussion to address the reviewer comments on safety and performance. Overall, we have conducted additional large animal experiments to better characterize our device and evaluate its performance. We investigated different actuation regimes and introduced two new metrics of performance: ultrasonography (seen in Fig. 2, 4, and Extended Data Fig. 1 and 2) and blood gas analysis (seen in Fig. 5 and Extended Data Table 1), used to directly assess diaphragm displacement and to evaluate the repercussions on gas exchange, respectively. Characterization of the actuators was performed both in vitro and in vivo. We have expanded and reworked the discussion to incorporate further considerations for clinical translation, including current limitations, clinical concerns, and the future preclinical work needed before human implantation. We feel that these additions to our manuscript have substantially strengthened our claims. + +Both reviewers comment on aspects of device characterization. Therefore, we have included two additional figures in the Extended Data (Extended Data Fig. 1 and 2), with a detailed discussion included in the section titled "Controlling PAM actuator performance via pressurization" in the Supplementary Notes. Additionally, both reviewers comment on discussing the considerations for translation. Our discussion has been largely rewritten and expanded to address the additional insights provided by the reviewers. Detailed individual responses to each reviewer comment are included below. + +<--- Page Split ---> + +## Reviewer #2 + +## Overall Reviewer Comment + +Overall Reviewer CommentThis paper is the first demonstration of an in vivo implanted system for assisting in breathing and for contracting diaphragm. The use of external ventilators is very critical, and having an implanted system would solve major problems for patients with diaphragm dysfunctions. I appreciated the paper: the motivations are clear, the in vivo tests are sufficiently solid (even if quite short) and the future impact could be dramatic. On the other hand, I have identified some major and minor issues which prevent me to give a positive assessment. + +## Response to Overall Comment + +Response to Overall CommentWe agree with Reviewer #2's summary of the significance of our work. We believe the reviewer's comments have significantly improved this body of work and hope our responses are to their satisfaction. + +## Comment 1 + +Comment 1First of all, the engineering part is quite limited. All the used components are not optimized for the application. Soft actuators design, size and distribution are not considered in the study protocol (see also comment 4). Sensors and controllers are commercial. The most relevant parts of the paper are the animal test and the physiological measurements. + +## Response to comment 1 + +We thank the reviewer for this comment, and we agree that the focus of our paper is not in presenting any individual actuator, sensor, or controller. Instead, we demonstrate the full integration of soft actuators fitted to the diaphragm operated by a custom- built control box that provides device actuation synchronized to native respiratory effort, and ultimately study the interaction and augmentation of this soft robotic system on in vivo respiratory physiology. This body of work aims to prove feasibility and proof- of- concept, serving as the first step in the long journey towards translating this work to the clinic. + +We fully agree that our initial presentation has obscured our work done to develop the soft robotic system for this application, and we have worked to update the manuscript to better communicate this. Please see updates to the supplemental Information titled "Controlling PAM actuator performance via pressurization" and Fig. S1 and S2 for an improved description of the characterization work of the system. + +A specific response regarding soft actuator design, size, and distribution can be found in the response to comment 4. + +<--- Page Split ---> + +## Comment 2 + +Comment 2The clinical motivation of this work is very clearly presented at the beginning. The authors are invited to discuss (possibly in the discussion section) if the target patients for this kind of device are eligible to undergo such complex implant surgery procedure. This might be crucial to foresee future clinical employments of the device. + +## Response to comment 2 + +Response to comment 2Again, we appreciate this comment. Due to the mechanical nature of the device—as opposed to biopharmaceutical interventions—this technology is not restricted to a single disease type, and instead the target patient population is defined by patients with mechanical respiratory failure involving the diaphragm who would benefit from long- term mechanical augmentation of diaphragm function. Although such a surgical intervention is invasive and might lead to complications, it has been well demonstrated that thoracic surgery is feasible in patients with peri- operative risk (e.g. lung transplant for terminal respiratory failure). Therefore implantation of our device may be considered, especially in a highly skilled environment. We therefore added the following paragraphs regarding considerations for the translation to the clinical field to the discussion of the manuscript. + +## Towards clinical translation + +Towards clinical translationEnvisioning a translation to the clinical field, the following considerations might help to optimize the management and pave the way to human application. The diseases leading to chronic diaphragmatic dysfunction are numerous and feature very different pathophysiologies. Therefore, a thorough understanding of the underlying pathology as well as its specificity are critically needed to help optimize the management and anticipate complications46. Moreover, patient selection and indication will need to be clearly defined in order to select the patients who will benefit from this therapy the most. Here, we present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy. + +Owing to the complexity of the procedure, a multidisciplinary team highly trained in advanced thoracic surgery is required to build expertise and develop this technology, ideally in a high- volume center47. Technological improvement is required to provide the least invasive approach of implantation. In this regard, a thoracoscopic route might be beneficial and will be the subject of future work. Given the invasive nature of implantable devices, the diaphragm assist platform is targeted towards patients with chronic- to- permanent ventilator dependence. We recognize that surgery in patients suffering severe diaphragm dysfunction causing respiratory failure can carry a high morbidity and mortality. Peri- operative complication can be numerous; one of the most feared is the worsening of the pulmonary status, which may itself precipitate the need for long- term ventilation48. Nevertheless, it has been well demonstrated that complex thoracic surgery is feasible even in very frail patients. Lung transplantation for terminal respiratory disease49 is one of the most striking examples. Thus, surgery could still be considered in a suitable target population that would ultimately benefit from this mechanical augmentation of + +<--- Page Split ---> + +diaphragm function, such as a range of neuromuscular disorders. The concept of diaphragm assist is in itself a means of preventing further complications from chronic respiratory failure and preserving key aspects of quality of life–like speech and mobility. + +## Comment 3 + +In the introduction section the authors should better contextualize their work not only with reference to soft actuators but also to fully implantable robots. Few examples and field definition were recently reported in the state of the art. Just as examples, please refer to: - Damian, D. D., Price, K., Arabagi, S., Berra, I., Machaidze, Z., Manjila, S., ... & Dupont, P. E. (2018). In vivo tissue regeneration with robotic implants. Science Robotics, 3(14). - Iacovacci, V., Tamadon, I., Kauffmann, E. F., Pane, S., Simoni, V., Marziale, L., ... & Menciassi, A. (2021). A fully implantable device for intraperitoneal drug delivery refilled by ingestible capsules. Science Robotics, 6(57), eabh3328. - Menciassi, A., & Iacovacci, V. (2020). Implantable biorobotic organs. APL bioengineering, 4(4), 040402. + +## Response to comment 3 + +We agree that the introduction is better served with a broader and more recent context of fully implantable robots. The text has been updated to: + +Previously, fully implanted soft actuators have shown the ability to augment heart function \(^{7 - 11}\) and many other newly developed implantable robotics have shown utility in a broad spread of biological applications \(^{12 - 20}\) . + +With the additional citation of the following sources: + +9. Payne, C. J. et al. An Implantable Extracardiac Soft Robotic Device for the Failing Heart: Mechanical Coupling and Synchronization. Soft Robot. 4, 241-250 (2017). +10. Saeed, M. Y. et al. Dynamic Augmentation of Left Ventricle and Mitral Valve Function With an Implantable Soft Robotic Device. Basic to Transl. Sci. 5, 229-242 (2020). +11. Hong, Y. J., Jeong, H., Cho, K. W., Lu, N. & Kim, D. H. Wearable and Implantable Devices for Cardiovascular Healthcare: from Monitoring to Therapy Based on Flexible and Stretchable Electronics. Adv. Funct. Mater. 29, 1808247 (2019). +12. Damian, D. D. et al. In vivo tissue regeneration with robotic implants. Sci. Robot. 3, (2018). +13. Iacovacci, V. et al. A fully implantable device for intraperitoneal drug delivery refilled by ingestible capsules. Sci. Robot. 6, 3328 (2021). +14. Dolan, E. B. et al. An actuatable soft reservoir modulates host foreign body response. Sci. Robot. 4, (2019). +15. Menciassi, A. & Iacovacci, V. Implantable biorobotic organs. APL Bioeng. 4, 1-4 (2020). +16. Perez-Guagnelli, E. et al. Characterization, Simulation and Control of a Soft Helical Pneumatic Implantable Robot for Tissue Regeneration. IEEE Trans. Med. Robot. Bionics 2, 94-103 (2020). + +<--- Page Split ---> + +19. Pane, S., Mazzocchi, T., Iacovacci, V., Ricotti, L. & Menciassi, A. Smart implantable artificial bladder: An integrated design for organ replacement. IEEE Trans. Biomed. Eng. 68, 2088–2097 (2021). +20. Amiri Moghadam, A. A. et al. Using Soft Robotic Technology to Fabricate a Proof-of-Concept Transcatheter Tricuspid Valve Replacement (TTVR) Device. Adv. Mater. Technol. 4, (2019). + +## Comment 4 + +It is not clear how the number of PAMs and the overall output force required were set. Please clarify on this and comment on the role played by spatial distribution of the two actuators on the diaphragm surface. What about the needed PAM contraction? Should this be adjusted for each subject and then be constant over the respiratory task? + +## Response to comment 4 + +We agree that our initial manuscript did not clearly communicate these aspects of the work. + +In brief, shape of the pressurization curve was chosen via a comparison of different input waveforms seen in the data presented in Extended Data Fig. 1 with the following conclusion in the Supplemental Notes: "Overall, the curved waveform used in the majority of the study represents a pressurization scheme that aims to optimize between the tradeoffs of the square wave and triangular wave, generating the best tidal volumes and biomimetic PV loops." + +The pressurization curve was scaled to different depths of pressurization. Because we are aiming for maximal augmentation in the state of simulated diaphragm failure, this study actuates the device at a maximum of 20 psi, captured in Extended Data Fig. 2 and described via the following statement in the Supplemental Notes: "The degree of pressurization has a positive, but nonlinear effect on the amount of diaphragm displacement generated (Extended Data Fig. 2g- k)." + +In cases where less augmentation is needed, level of augmentation can be tuned via the pressurization. Please see the new section of the Supplemental Information titled "Controlling PAM actuator performance via pressurization" and Extended Data Fig. 1 and 2 for full details regarding how the overall output force and device performance was determined by controlling the pressurization waveform and depth of pressurization. + +The choice to use two actuators—one on each hemidiaphragm—was due to the issue that the introduction of each actuator displaces potential lung volume in the thoracic cavity. The filled actuator size is 17 mL at 20 psi, so the use of additional actuators would require augmentation that provides benefits beyond this filled volume. The two hemidiaphragms are semi- independent (Whitelaw WA. J Appl Physiol 62, 180- 6 (1985)), meaning that augmentation and displacement on one side doesn't transfer to the other, which is why clinically some people experience unilateral diaphragm paralysis (Gibson G. Thorax 44, 960- 970 (1989), Celli, B. Semin Respir + +<--- Page Split ---> + +Crit Care Med 23, 3, 275- 281 (2002)). The use of two actuators represents the minimum volume of actuators to act upon both semi- independent hemidiaphragms. For a potential alternative design, actuators that provide greater coverage of the diaphragm with minimal increase in occupied thoracic volume could provide a greater surface area to distribute force and provide more homogeneous diaphragm displacement. Designing actuators that lend themselves to this configuration is one direction of future work that the diaphragm assist system would benefit from. + +Regarding the spatial distribution of the two linear PAM actuators used in this study, the PAMs are placed in the antero- posterior direction, the left actuator being lateral to the heart. Specific placement is reflected in the methods text: "The anterior portion is attached to the sternum and the posterior attachment is made to the lowest posterior rib in the most medial position that can be achieved without disrupting the region of the major arteries and veins, esophagus, and spine." This is best visualized via the coronal view of the fluoroscopy in Supplemental Video 1. This placement aims to place the PAM across the peak of the dome of the actuator and laterally down the rostral and dorsal edge of the subject's ribcage. + +We agree that the PAM contraction necessary to augment diaphragmatic motion is a key design feature. At zero pressurization, the actuator should passively fit along the peak arclength of the end expiratory diaphragm. The theoretical maximum contraction length should be the straight line distance between the two points of attachment. In order to anchor the actuator via sutures, the actuator requires some region of passive material. We developed the reported actuator dimensions empirically in accordance with our work in swine cadavers to appropriately fit the arclength and anatomy of the diaphragm in 30- 40kg subjects. The actuator reported here has a relaxed length of 25 cm, and a contracted length of 21cm. There exists approximately 3.5 cm of PET mesh at each end of the actuator which is used as a suture attachment location. We agree that the actuator size and level of contraction can and should be fitted to individual patients. However, given the nature of animal experiments, we do not have access to "patient data" and "patient dimensions" ahead of the procedure. We control for variation in patient dimensions by controlling swine size, using only female Yorkshire swine in the 30- 40kg range. The actuator is implanted in a manner where the actuator fits snugly against the diaphragm, with the 7 cm of extra mesh as a buffer for interanimal variability. A next generation actuator for this diaphragm assist system could be designed in a manner that is not limited by the straight line distance and could also provide additional downward motion beyond the geometric "chord" of the arclength of the diaphragm. This consideration is briefly captured in the discussion via: "We present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy." + +<--- Page Split ---> + +## Comment 5 + +Comment 5The authors employed a custom controller aimed at synchronizing the soft robotic actuator and natural breathing. However, both sensing (spirometry) and control rely on external (bulky?) data acquisition and control platforms. This appears a bit in contrast with the original motivation to outperform over invasive ventilation systems. No concrete paths towards implantations are given. + +## Response to comment 5 + +We agree that the current control system and synchronization method prevent its application in an outpatient setting, which represents the long- term objective of this type of device. The present work was designed as a proof- of- concept study. For our purposes, we developed a control system whose components can be easily accessed, modified, and then optimized. Consequently, the size of the current system prevents the outpatient use. + +We therefore added the following section in the discussion to present concrete paths toward this endeavor: + +An ideal next generation control system aims to trigger from a more upstream neural signal- such as the electrical activity of the diaphragm- to provide an earlier signal that enables an advanced control system to optimize synchronization, removing delays and asynchrony. Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. To fully realize untethering from bulky machines- like standard mechanical ventilators- the external components that control and power the system require miniaturization. Future work will aim to eventually miniaturize the system to the scale of a small backpack- one that could be worn by the patient or attached to an electric wheelchair. The process of miniaturization and portability has proved to be possible in similar complex devices, such as ventricular assist devices (e.g. Thoratec HearMate III) or total artificial hearts (e.g. Syncardia TAH, Carmat Aeson)42- 45. + +In combination with the following text from the original manuscript: + +We envision further translational potential of this technology when combined with the development of smaller and more portable pneumatic energy sources54,55 as the field of soft robotics advances. With the integration of a portable pump and control system in the future, this technology could provide an additional level of patient autonomy via increased mobility. + +<--- Page Split ---> + +## Comment 6 + +Comment 6The caption of figure 2 is very informative. However, it would be useful to add some labels on the axes, graphs title, etc., to make figures readability more straightforward. + +## Response to comment 6 + +Response to comment 6We thank the reviewer for pointing this out. We have added more labels and graphics to the original Figure 2 (now Figure 3) to improve readability. Specifically, we have added gray dashed lines to visually indicate the selection of data in Fig. 3c- e from Fig. 3b. and labeled the green "Range of Normal" + +## Comment 7 + +Comment 7The in vivo test is very short, so all considerations about materials, biocompatibility, stability etc. are missing. + +## Response to comment 7 + +We agree that the acute nature of the study did not allow for important longer term testing of materials and stability. + +Regarding stability, we conducted acute fatigue testing, showing resilience of the actuators to at least 3000 cycles of actuation in vivo without failure at the end of the study. Actuators for this study were designed to last through a one- day sacrificial study. Future work necessitates full characterization of the lifetime of updated actuators. This will be a key future design requirement. + +Regarding materials and biocompatibility, the actuators were manufactured from commercially available materials for ease of prototyping. We did consider the future biocompatibility of the device during material selection, opting for materials with established, regulatory- approved counterparts. We have updated the discussion to address this limitation as follows: + +Due to the focus on feasibility, we acknowledge that there are limitations in these acute studies from the lens of regulatory approval and clinical translation. We do not study device biocompatibility or long- term device operation. The device was constructed from types of polymers that are already used in established medical devices \(^{50 - 53}\) , such as poly(ethylene terephthalate) (PET) and polyurethanes (See Supplemental Information). Because our device focuses on mechanical interaction, as opposed to biochemical interactions with the body, the materials used in the device can easily be substituted with regulatory- approved materials in future iterations. With improved performance and stability, future long- term studies will need to investigate the long- term effects of the system including tissue remodeling and the ability to provide full- time respiratory support. + +Further details on material selection can be found in the updated Supplemental Information section titled Considerations for PAM materials selection. + +<--- Page Split ---> + +## Comment 8 + +In line 512, 6 pigs are mentioned. But in the rest of the paper we had 5 pigs. + +## Response to comment 8 + +We thank the reviewer for pointing out the need for clarification. In our first submission, the original Fig. 3 displays the data for the 6 total pigs mentioned in line 512 (named A- F) when testing synchronized vs. independent actuation. The original Fig. 2 does in fact only display the data for 5 total pigs (A- E) because for pig F, we did not collect a sufficient amount of the baseline data during a period of unsupported ventilation to make the comparison shown in the original Fig. 2. + +For this revised submission, given the additional data gathered and used for the updated Figures 2, 4, 5, S1, and S2, we have updated the referenced text accordingly: "We used a total of twelve swine during the development and testing of our system, and we present data from nine swine in the manuscript. Different subsets of subjects were used for the experimental investigations reported; not all subjects were used in every experimental investigation." + +<--- Page Split ---> + +## Reviewer #3: + +## Overall Reviewer Comment + +Overall This work by Drs. Hu and Roche developed an implantable device that can substitute a mechanical ventilator commonly used in contemporary clinical care and yet, avoid the various shortcomings of it. The authors build a robotic actuator which is overlaid to the subject's diaphragm and activated by the host's inspiratory effort, which in turn, is balloon inflated and substitutes the function of the native diaphragm. + +The authors challenge an important clinical question, with a good understanding of the respiratory cycle and the role of the diaphragmatic motion. The concept underlying the current work is interesting and innovative. I acknowledge that this is a prototype, however the current manuscript do have room for improvement. + +Additionally, considering the invasiveness of the implantation associated with their device, whether the strength of the system is enough to overcome the invasiveness associated with the procedure should be discussed more in depth. + +## Overall Response Response + +We agree with Reviewer #3's summary of the significance of our work and the proof- of- concept status of this study. We believe the reviewer's comments have significantly improved this body of work and hope our responses are to their satisfaction. + +Additionally, we thank the reviewer for this relevant comment specifically on the considerations between performance and invasiveness. We demonstrated in this work the ability of the device to significantly augment respiratory function, such as tidal volume and minute ventilation, and the ability to restore a normal range of minute ventilation. We further investigated in vivo the effect on gas exchange using blood gas analysis (see Response to comment 1) and explored diaphragm motion using ultrasound. The performance of the device demonstrates strong feasibility of this soft robotic strategy, but we acknowledge that there are limitations and "A core goal of the next generation system is to further improve the tidal volume augmentation, which will need to be achieved through both actuator design and control system development." Establishing more robust performance and longer respiratory trials will be necessary for future translation. + +In addition, updates to the external triggering and control systems will be critical for realizing our vision of untethering from bulky machinery. This future work is proposed in our discussion section: "Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. To fully realize untethering from bulky machines- like standard mechanical ventilators- the external components that control and power the system require miniaturization. Future work will aim to eventually miniaturize the system to the scale of a small backpack- one that could be worn by the patient or attached to a belt or an electric wheelchair." Given an improved next- generation system that can provide long- term ventilatory support to an appropriate patient population, the + +<--- Page Split ---> + +rescue of respiratory performance that avoids further worsening of patient status and preserves key quality of life measures- like speech and mobility- may justify the surgical procedure. + +We agree that such a surgical intervention is invasive and may lead to complications. However, it has been well demonstrated that thoracic surgery is feasible in patients with high peri- operative risk (e.g. lung transplant for terminal respiratory failure). Therefore implantation of our device may be considered, especially in a highly skilled environment. We therefore add the following paragraphs in the discussion, and make general considerations for the translation to the clinical field. + +## Towards clinical translation + +Envisioning a translation to the clinical field, the following considerations might help to optimize the management and pave the way to human application. The diseases leading to chronic diaphragmatic dysfunction are numerous and feature very different pathophysiologies. Therefore, a thorough understanding of the underlying pathology as well as its specificity are critically needed to help optimize the management and anticipate complications46. Moreover, patient selection and indication will need to be clearly defined in order to select the patients who will benefit from this therapy the most. Here, we present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy. + +Owing to the complexity of the procedure, a multidisciplinary team highly trained in advanced thoracic surgery is required to build expertise and develop this technology, ideally in a high- volume center47. Technological improvement is required to provide the least invasive approach of implantation. In this regard, a thoracoscopic route might be beneficial and will be the subject of future work. Given the invasive nature of implantable devices, the diaphragm assist platform is targeted towards patients with chronic- to- permanent ventilator dependence. We recognize that surgery in patients suffering severe diaphragm dysfunction causing respiratory failure can carry a high morbidity and mortality. Peri- operative complication can be numerous; one of the most feared is the worsening of the pulmonary status, which may itself precipitate the need for long- term ventilation48. Nevertheless, it has been well demonstrated that complex thoracic surgery is feasible even in very frail patients. Lung transplantation for terminal respiratory disease49 is one of the most striking examples. Thus, surgery could still be considered in a suitable target population that would ultimately benefit from this mechanical augmentation of diaphragm function, such as a range of neuromuscular disorders. The concept of diaphragm assist is in itself a means of preventing further complications from chronic respiratory failure and preserving key aspects of quality of life- like speech and mobility. + +<--- Page Split ---> + +## Major comments + +Here are some major comments for the authors. + +## Comment 1 + +Comment 1The authors fail to analyze the actual blood gas levels with arterial blood. The authors state that the responsiveness of the diaphragm can vary between subjects. How can the authors be sure that the blood gas levels are maintained at a relatively stable state with the device instillation? Please be aware that maintaining the blood acid- base balance in a homeostatic state is a critical role of respiration in every living creature. + +## Response to comment 1 + +We agree that arterial blood gas (ABG) levels are the clinical gold standard indicator of respiratory status. + +To this end, we have included an additional section, figure (Fig. 5), and Extended Data Table 1, capturing the effect of synchronization on the blood gas balance. The manuscript text and figure are copied below: + +## Effect of synchronization on blood gas exchange + +Physiologically, ventilation is necessary to bring in oxygen \((O_{2})\) and to clear out accumulated carbon dioxide \((CO_{2})\) from the blood. Arterial blood gases (ABGs) are discrete blood analyses that give a snapshot view of the gas exchange and acid- base homeostasis, providing measurement of partial pressure of \(O_{2}\) \((P_{a}O_{2})\) and \(CO2\) \((P_{a}CO_{2})\) , pH, and bicarbonates \((HCO_{3}^{- })\) in arterial blood. \(P_{a}CO_{2}\) is directly and inversely proportional to alveolar ventilation and is therefore a representative metric of ventilatory function. Only pH and \(pCO_{2}\) are depicted here in Fig. 5, but the full ABG parameters are reported in Extended Data Table 1 and discussed in the Supplementary Notes. + +As shown in the prior section, the high variance from independently actuated ventilation showed mixed constructive and destructive interference (Fig. 4e,f) which led to worse ventilation outcomes. The same variance in the peak inspiratory flows and tidal volumes over time due to independent vs. synchronized actuation can be seen in Fig. 5a and Fig. 5b. In these two respiratory challenges, the subject was switched directly from the standard mechanical ventilation to our diaphragm assist system, evaluating its ability to maintain gas exchange. + +In the respiratory challenge operated with independent actuation (Fig. 5a), we see high levels of hypercarbia over time. As a result, respiratory acidosis develops, which is a direct consequence of increased \(P_{a}CO_{2}\) (Extended Data Table 1a). Contrastingly, in a respiratory challenge operated with synchronized actuation in the same animal (Fig. 5b), \(pCO_{2}\) levels are relatively well maintained. The acidemia observed for this trial is rather of metabolic cause (called metabolic acidosis) (Extended Data Table 1b, see Supplementary Notes). + +<--- Page Split ---> + +In another experiment, a respiratory trial was initiated with 2 minutes of unsupported ventilation and then switched to our diaphragm assist system, evaluating its ability to recover from a period of unsupported ventilation. During the 2 minutes of unsupported ventilation, high levels of \(\mathrm{CO_2}\) accumulate quickly over this brief amount of time (Fig. 5c). After two minutes, the diaphragm assist system is actuated with synchronized actuation. The increasing acidification and accumulation of \(\mathrm{CO_2}\) reverses and some recovery from the hypercarbic state is seen in the first 10 minutes, with a slight uptick in the \(\mathrm{CO_2}\) around 15 minutes into the challenge. + +![](images/Figure_5.jpg) + +
Fig. 5: ABGs taken across distinct respiratory challenges. a, In a respiratory challenge operated with independent actuation, a representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \(\mathrm{pCO_2}\) values from discrete arterial blood gases taken. b, In a respiratory challenge operated with synchronized actuation, a representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \(\mathrm{pCO_2}\) values from discrete arterial blood gases taken during one full respiratory challenge with synchronized actuation. The respiratory challenges depicted in a, and b, are taken from the same animal. c, In another animal, a respiratory challenge began with a 2 minute period of unsupported ventilation and subsequent synchronized actuation. A representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \(\mathrm{pCO_2}\) values from discrete arterial blood gases taken. Gray shading indicates the period of time where the system is off and respiration is unassisted. Light green shading indicates the standard range
+ +<--- Page Split ---> + +of normal values for each arterial blood gas metric. Complete ABGs can be found in Extended Data Table 1. + +Due to their discrete nature, in contrast to the continuous signals like flow and volume collected by our data acquisition system, the ABG data is much sparser because ABGs were only taken during a subset of respiratory challenges. For the respiratory challenges where ABGs were taken, we collect them every 2 or 5 minutes (2 minutes to capture the effect of 2 minutes of unsupported ventilation, as seen in Fig. 5c). This is captured in the Methods section with the following text: + +For experiments investigating gas exchange, ABGs were collected at 2 or 5- minute intervals during the challenge. + +## Comment 2 + +How is the level of inspiration controlled with their device? The degree of inspiration should be controllable according to the subjects needs in various clinical situations (for example, in early sepsis, it is natural to be in a hyperventilated state) but the authors do not show that their device is versatile enough to accommodate this. What happens to the subject's respiration if the bladder in the system is pressurized more? Additionally, what about the opposite where there is no need for a deep inspiration? + +## Response to comment 2 + +We thank the reviewer for this relevant comment. We agree that in a clinical setting, the degree of inspiration should be tunable. To demonstrate this capacity, we conducted significant further experimentation that substantially improved our understanding of our device. + +The degree of assistance provided by the device is mainly determined by the level of pressurization of the PAM, which is set by the user in the control system. A pressure actuation curve (selected by the user), once triggered, is transmitted to the electropneumatic regulator. In the present study, we simulate severe diaphragmatic failure in all subjects, reflected by the low unassisted tidal volumes (see Fig. 3). Therefore, the maximal possible augmentation was required to maintain respiratory homeostasis for all the subjects in this study. + +Looking towards future translation, as pointed out by the reviewer, the subject might need different degrees of assistance (i.e., different levels of pressurization), depending on the clinical situation and metabolic state. To further characterize the device and understand the effect of different pressurization of the PAM on respiratory mechanics, we conducted a series of in vitro and in vivo experiments during which we adjusted the degree of pressurization (5, 10, 15, and 20 PSI). The characterization data regarding degree of pressurization is presented in our new Extended Data Fig. 2. + +<--- Page Split ---> +![](images/Extended_Data_Figure_1.jpg) + + +Extended Data Fig. 2. Tuning actuation depth via level of pressurization. The actuator pressure profile for a curved waveform scaled to have a peak nominal pressure of (a) 5 psi, (b) 10 psi, (c) 15 psi, (d) 20 psi. The peak forced generated by different levels of actuation were characterized in vitro on a (e) classic Instron tensile test setup and (f) our modified flexural test setup (depicted in Fig. S5). Diaphragm displacement generated by actuations of (g) 5 psi, (h) 10 psi, (i) 15 psi, (j) 20 psi visualized via M-mode ultrasound. (k) The average diaphragm displacement per breath from one sample subject via M-mode ultrasound. (l) Tidal volume achieved via different levels of pressurization from one sample subject. Significance is indicated by \(^{*}p< 0.05\) for a two- sample t test. (m) Respiratory Campbell diagram plotting the pleural pressure- volume loops for representative breaths from different levels of actuation. + +<--- Page Split ---> + +This data supports the following update to the text of the main manuscript: + +Actuator behavior is governed by the degree of pressurization. Set pressurization waveforms are programmed to the control system and electropneumatic regulators. In vitro and in vivo characterization of actuator behavior when controlled by different pressurization waveforms is included in the Extended Data (Extended Data Fig. 1 and Extended Data Fig. 2). + +Details for this characterization are updated in the Methods section of the manuscript as follows: Actuator characterization was conducted both in vitro and in vivo. For the in vitro characterization, actuator performance was measured via Instron testing. Classic tensile testing was conducted to measure the contractile force. A modified flexural bend setup (Fig. S5) was used to measure the perpendicular force applied to the diaphragm via arclength shortening. For the in vivo characterization, performance of the diaphragm assist system was evaluated through the diaphragm displacement (via ultrasonography) and the functional metrics (tidal volume, Campbell diagram) (Extended Data Fig. 1 and 2). Different pressurization shapes and levels were input into the actuator (Extended Data Fig. 1 and 2) and the resulting behavior was measured. Further details can be found in the Supplementary Information. + +Detailed discussion of this new characterization data regarding different levels of pressurization are found in the below portion of the Controlling PAM actuator performance via pressurization section of the Supplemental Notes: + +PAM performance can also be tuned via depth of pressurization by scaling the input curved waveform shown in Extended Data Fig. 2a to different peak pressures (5, 10, 15, and 20 psi), the resulting actuator pressure waveforms are shown in Extended Data Fig. 2a- d. The relationship between pressurization and forces generated is linear (Extended Data Fig. 2e,f) which corroborates previous McKibben characterization work24. We characterize the response of one subject to the varying degrees of pressurization. The degree of pressurization has a positive, but nonlinear effect on the amount of diaphragm displacement generated (Extended Data Fig. 2g- k). In this subject, we demonstrate tunability of the degree of augmentation via changes in pressurization, with the greatest range of responsiveness being between 0 and 10 psi. Additional increases taper off between 10 and 20 psi, which matches the understanding of how McKibben actuators operate, as they first expand and fill to their maximum volume, achieving maximum contraction, and beyond that they increase force generation24. In terms of respiratory mechanics, the degree of pressurization does not have a large effect on the change in pleural pressure (Extended Data Fig. 2m) unlike the different waveform shapes in Extended Data Fig. 2p. + +Notably, interanimal variability is undeniably a factor contributing to overall performance, as evident in the varied responsiveness to the device seen in Fig. 3. Even in a case of low augmentation, we saw a nonlinear but tunable response to different levels of pressurization. The absolute degrees of augmentation shown in Extended Data Fig. 2k- m will obviously not hold across different animals, but we expect that the relative effect of tuning pressure should. + +<--- Page Split ---> + +## Comment 3 + +Comment 3Likewise, I would like to see how the respiratory mechanics change according to how fast the bladder in their system is inflated. More information should be given on this. The respiratory mechanics are shown as simple bar graphs in Figures 5a, b and c, whereas the gradient or slope of the Campbell diagram may also be important. + +## Response to comment 3 + +Response to comment 3We have included a robust characterization of the effect of changing the manner of bladder inflation in the Supplemental Notes section titled Controlling PAM actuator performance via pressurization and in Extended data Fig 1 reproduced below, demonstrating the effect of different input waveforms on actuator forces and in vivo respiratory mechanics. + +<--- Page Split ---> +![PLACEHOLDER_24_0] + +
Extended Data Fig. 1. Controlling actuation via different pneumatic waveforms. Input waveforms of a (a) curved, (b) square, and (c) triangle shape can be programmed into the
+ +<--- Page Split ---> + +custom- built control system. The effective output pressure of the electropneumatic regulator for the (d) curved, (e) square, and (f) triangle shape drives actuation. The PAM actuation forces were characterized for different waveforms in vitro on a classic Instron tensile test setup (g,h,i) and our modified flexural test setup (j,k,l) (depicted in Fig. S5). Input waveforms of a (m) curved, (n) square, and (o) triangle shape generate different shapes of diaphragm displacement as visualized via M- mode ultrasound. (p) Average diaphragm displacement from m,n,o. (q) Average tidal volume and (r) respiratory Campbell diagram plotting the pleural pressure- volume loops for representative breaths from different waveform shapes. Significance is indicated by \(^{*}\mathrm{p}< 0.05,^{**}\mathrm{p}< 0.01,^{***}\mathrm{p}< 0.001\) for a two- sample t test. + +Detailed discussion of this new characterization data regarding rates of pressurization are found in the below portion of the Controlling PAM actuator performance via pressurization section of the Supplementary Notes: + +Different input shapes explore the effect of rate of pressurization (Extended Data Fig. 1a- c). The fidelity to these idealized waveforms is limited by the control resolution of the electropneumatic regulators, and ultimately result in the output pressurization curves of Extended Data Fig. 1d- f. These actuation pressure curves ultimately govern the mechanical performance of the actuators. The actuators are characterized in vitro via tensile and flexural testing, as described in the Supplemental methods. The tensile force (Extended Data Fig. 1g- i) represents the contractile force applied to the points of attachment on the ribs, and the flexural force (Extended Data Fig. 1j- l) represents the force perpendicular to the actuator towards the diaphragm. + +Different actuation pressure waveforms result in different displacements, (seen in the M- mode ultrasound in Extended Data Fig. 1m- o and quantified in Extended Data Fig. 1p), tidal volumes (Extended Data Fig. 1q) and different respiratory mechanics (Extended Data Fig. 1r). Notably, the square wave pressurization is distinct from the behavior of the curved wave and triangle wave, especially with regards to the average diaphragm displacement and the Campbell diagram. We note that the square wave achieves similar tidal volumes to the other waveforms while drawing more negative pleural pressures. The slope of the Campbell diagram, taken at the two points in the loop where, can be viewed as a representation of compliance of the system. A negative pleural pressure drives flow via the gradient from atmospheric pressure at the airway opening to the negative alveolar pressure, so we evaluate the absolute value of compliance. The slope generated by the square wave (12.1 mL/cmH₂O) is considerably lower (i.e., the system is stiffer) than that of the curved (15.9 mL/cmH₂O) and triangle wave (15.1 mL/cmH₂O), which both have slopes that more closely resemble those that of spontaneous respiration (25.6 mL/cmH₂O). These values are overall relatively stiff and are likely due to the low lung volumes for this subject. Qualitatively, we observe that the square wave results in "sharper" breaths that pull on the chest wall more aggressively compared to the gentler inflation of the curved and triangle wave, matching the much higher tensile forces generated by the square wave from in vitro testing. + +The curved and triangular pressurization input are similar in their pressure- volume (PV) loops; however, the curved input achieves higher tidal volumes with marginally smaller levels of + +<--- Page Split ---> + +diaphragm displacement (Extended Data Fig. 1p-r), which could be attributed to the shorter time in which the actuator operates at a high pressure filled state which may not provide enough time for lung filling. Overall, the curved waveform used in the majority of the study (Fig.2- 7 in the main text) represents a pressurization scheme that aims to combine the benefits of the square wave and triangular wave, generating the best tidal volumes and biomimetic PV loops. + +Methods for this characterization in Extended Data Fig. 1 are described along with the methods of Extended Data Fig. 2 in Supplementary methods McKibben PAM Mechanical Characterization Methods. + +## Comment 4 + +The authors should be commended for doing a nice job in synchronizing the device to the subject's respiratory effort. However, the trigger for this is the spirometer that is installed into the subject's airway. To really overcome the weakness of the contemporary mechanical ventilators, the authors should think of better methods that do not touch the respiratory tract to sense the intrinsic respiratory effort. + +## Response to comment 4 + +We agree that a synchronization method that does not involve the patient airways is required to overcome the tethered limitations of contemporary ventilators and will be required for clinical translation. We therefore added two additional sections in the discussion to discuss this limitation and provide pathways for future work as follows: + +First, + +Some neuromuscular signals, like the electrical activity of the diaphragm (Edi), contain detailed information about both inspiration and expiration times35,36. Edi amplitude is also proportional to the neural drive, as well as the degree of contraction of the diaphragmatic muscle, therefore opening up the possibility of adaptive control. Triggering from Edi measured at the esophageal level via a feeding tube37 may be warranted to improve mechanical ventilation. This method, known as neurally adjusted ventilatory assist, is available in the clinical setting with mechanical ventilation and may improve respiratory weaning of patients that are challenging to wean36. The same principle could be applied to our diaphragm assist system; using a more upstream signal with greater information on the native respiratory effort would allow for a more robust control system. + +Second, + +Synchronization is critical to device performance, and thus future work lies in building a next generation control system; this includes creating a system that is cognizant of the beginning of expiration as opposed to inspiration, an automated control system that removes the error of manual titration, and further investigation of dynamic actuation curves. An ideal next generation control system aims to trigger from a more upstream neural signal—such as the electrical activity + +<--- Page Split ---> + +of the diaphragm- to provide an earlier signal that enables an advanced control system to optimize synchronization, removing delays and asynchrony. Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. + +## Minor comments + +There are also some minor comments that might help. + +## Comment M1 + +Comment M1Supplementary Video Online is not that informative as it plays in a real- time. It would be better if the video is played more slowly. + +## Response to comment M1 + +We have amended the video to play both in real- time and at a \(0.3x\) speed for clarity. + +## Comment M2 + +Comment M2The finding should be supported by adequate statistical analysis. + +## Response to comment M2 + +Response to comment M2We appreciate this comment, and have detailed the statistical analysis presented in the section "Statistical analysis" in the Methods included here. We have also responded to the specific reviewers comments in the subsequent subcomments. + +## Statistical analysis + +Statistical tests were conducted as described in the respective figure captions for Fig. 3, 4, 7, and Extended Data Fig. 1 and 2. For Fig. 3c,d and Fig. 7a- c, two- sided Wilcoxon rank- sum analyses were conducted in MATLAB (MathWorks, Portola Valley, CA, USA) via the "ranksum" function. Fig. 4e,f depicts two sets of statistical tests. A two- sided Welch's t- test without assuming equal variances was conducted in order to compare the means of the populations via the "ttest2" function in MATLAB with an "unequal" variance type specification. Additionally, a 2- sample F- test for equal variances was conducted to compare and confirm unequal variances via the "vartest2" function in MATLAB. For the Extended Data Fig. 1 and 2, two- sided t- tests were conducted via the "ttest2" function in MATLAB. + +Comment M2.1. Although somewhat obvious from the graphs, there should be some statistical analysis to show the difference in the variation of peak inspiratory flow and tidal volume of Figure 3e and f. + +## Response to comment M2.1 + +We have added significance bars for two sets of statistical tests conducted. The black bars represent the significance from a Welch's t- test to compare the mean of the two populations, and the gray bars represent significance from a 2- sample F- test for equal variances to compare + +<--- Page Split ---> + +the variance of the two populations. This is seen in the updated figure caption (Black significance bars are results from Welch's t- test comparing means. Gray significance bars are results from a 2- sample F- test for equal variances comparing variances. Significance is indicated by \(^{*}p< 0.05,^{**}p< 0.01,^{***}p< 0.001\) for both statistical tests.) and figure for Fig. 4. + +## Comment M2.2 + +The pairwise comparisons should be done for Figure 5a, b, and c with the data acquired at the spontaneous respiration (SR) as the reference, not the actuator assisted ventilation (AAV). + +Response to comment M2.2 + +We have added the additional set of significance bars using SR (comparing SR and mechanical ventilation (MV)) as the reference in Fig. 7a- c. + +## Comment M2.3 + +How many samples were taken for each subjects in each graph. This should be noted. + +Response to comment M2.3 + +We have included the range of sample size for each type of plot in the figure captions for the updated Fig. 3c,d (( \(n = 11 - 27\) breaths)), Fig. 4e,f (( \(n = 119 - 419\) breaths)) and 7a- c (( \(n = 11 - 32\) breaths)) in addition to the individual data points on the figures. + +## Comment M3 + +In Figures 2c, d and e, when did the authors gather data after the device was turned off or on? The same questions goes for synchronized actuation in Figures 3e and f, Figures 5a, b and c. Response to comment M3 + +We have made updates to the figures and figure captions to clarify the data analysis. + +The data used in the updated Fig. 3c,d,e (original Fig. 2c,d,e) are gathered from the 30 seconds immediately before and after the device is turned on/off. We have added the dashed gray line graphics to Figure 3 to illustrate this, and have made the following update to the figure caption: + +c,d, Comparison of the average (c) peak inspiratory flow and (d) tidal volume in the 30 second period immediately before and after the point where the assist is turned on at the beginning (left two bars per subject) and off at end (right two bars per subject) of the respiratory challenge (as represented by the arrows in b and the gray dashed lines in b- e) across 5 subjects ( \(n = 11 - 27\) breaths). Each gray dot represents one breath. e, Body weight normalized minute ventilation achieved during the 30 second period immediately before and after the assist is turned on at the beginning and off at the end of the respiratory challenge. + +<--- Page Split ---> +![PLACEHOLDER_29_0] + + +The data used in updated Fig. 4e,f (original Fig. 3e,f) span from 300s from the start of the challenge to the end of the respiratory challenge. The 300s exclusion aims to remove the period of time in which the animal's respiratory state adjusts to the new ventilatory state, so that Fig. 4 captures a steady state variance. We have made the following update to the figure caption: + +e,f, A swarm plot comparing the steady state (e) tidal volumes and (f) peak inspiratory flows generated with independent actuation and with synchronized actuation for 6 different subjects (n = 119 - 419 breaths). + +<--- Page Split ---> +![PLACEHOLDER_30_0] + + +The data used in updated Fig. 7a,b,c (original Fig. 5a,b,c) are gathered from representative 30 or 60 second segments from the data during and surrounding one respiratory challenge per subject. Because spontaneous respiration (SR) and the synchronized actuator assisted ventilation (AAV) both rely on the animal's native respiratory rate (range: 26- 32) while the mechanical ventilation (MV) has a set slow respiratory rate (range: 15- 20 bpm), 30 second increments were chosen for the SR and AAV segments while 60 seconds increments were chosen for the the MV segments to capture a sizeable sample of breaths. Data segments attempted to capture the closest to steady state achieved in the span of the respiratory challenge. The MV data segments were chosen from the steady state data collected immediately before the initiation of the respiratory system. SR and AAV were chosen from the end of the respiratory challenge, similar to the data selection from the end of the challenge used for updated Fig. 3c,d,e. We have made the following update to the figure caption for updated Fig. 7a,b,c: + +a,b,c, Average change in (a) pleural pressure \((\mathsf{P}_{\mathsf{pl}})\) , (b) abdominal pressure \((\mathsf{P}_{\mathsf{ab}})\) , and (c) transdiaphragmatic pressure \((\mathsf{P}_{\mathsf{di}})\) per breath under mechanical ventilation (MV), actuator assisted ventilation (AAV), and spontaneous respiration (SR) taken from a representative steady- state segment from one respiratory challenge per subject ( \(n = 11 - 32\) breaths). + +<--- Page Split ---> +![PLACEHOLDER_31_0] + + +## Comment M4 + +Figure 4a and b miss the legends for y- axis. Response to comment M4 Thank you. We have added the y- axis labels. + +## Comment M5 + +The overall structure of the Discussion could be improved. The contents of each paragraphs tend to jump, making it difficult to follow. + +## Response to comment M5 + +We thank the reviewer for this comment and have significantly re- ordered the discussion section. We have also added subheadings (Contributions, Overall limitations, Towards clinical + +<--- Page Split ---> + +translation) to aid clarity. We hope that it is more readable and flows better after these modifications. The full updated discussion is included here: + +## Discussion + +In this work, we use pneumatic soft robotic actuators to support and augment respiration, demonstrating acute augmentation of physiological metrics of respiration, and feasibility as a proof- of- concept device. A set of two McKibben- style PAMs surgically implanted superior to the diaphragm are capable of providing mechanical support to the diaphragm in a large animal model of respiratory insufficiency. We thoroughly characterized the in vitro mechanical properties of the device and investigated its interactions with the respiratory system and the subject, using multimodal metrics to evaluate respiratory function (e.g. tidal volume, inspiratory flow), biomechanics (cavity pressures, WOB), motion (ultrasonography and fluoroscopy), and gas exchange (ABGs). + +## Contributions + +The diaphragm assist system generated substantial augmentation in respiratory function—measured via peak inspiratory flow (a direct metric of inspiratory function), and tidal volume and minute ventilation (metrics of ventilation)—in our most responsive subject. Subject A had the highest change in peak inspiratory pressure, tidal volume, and minute ventilation; the corresponding large augmentation in peak inspiratory pressure indicates that the volume and minute ventilation augmentation are specifically due to the soft robotic actuators augmenting the diaphragm's inspiratory function. Responsiveness to the system varied across subjects. + +Variance in responsiveness is likely dependent on a combination of many factors. One factor is the level of preserved respiratory baseline. The weak response in the subject with a relatively high preserved weight- normalized minute ventilation (subject E) suggests that the assist system may have weak augmentation or even a disruptive effect in cases of well- preserved diaphragm function. Other potential factors include precise actuator placement, actuator fit, and anatomical variations. + +We showed that synchronization with the native respiratory effort is a critical design element in our system. Synchronous actuation is key to consistent, low- variance respiratory waveforms and tidal volumes. Like standard mechanical ventilation, off- cycle actuation of the actuators can lead to a destructive interference with the underlying respiratory effort, resulting in a poor augmentation and poor blood acid- base balance. In evaluating the effect of synchronization on the system's ability to maintain appropriate gas exchange, we demonstrated that despite generating a similar range of tidal volumes, independent actuation led to an inability to maintain appropriate \(\mathsf{pCO}_2\) levels and resulted in respiratory acidosis. Contrastingly, in two trials of well- synchronized actuation, we observed some capacity of the device to maintain and recover baseline \(\mathsf{pCO}_2\) levels. + +The control system used in this study was a simple but effective first- generation system with many directions for improvement. The synchronization triggered from airway flow—which is also + +<--- Page Split ---> + +the metric used by gold standard clinical ventilatory support options for triggering—but flow is also the most downstream signal in neuro- ventilatory coupling. The downstream nature of the signal is a potential source of delays and asynchrony34. In order to achieve consistent assistance from breath to breath, the synchronization must be optimized for the alignment that maximizes constructive interference. The system relied on a manually titrated threshold set for the flow sensor data. It is designed to be triggered at the start of an inspiratory flow effort, which is related to \(V_0\). However, the manual nature of the system meant that if the threshold was set too low, noise in the flow signal could cause pre- emptive or false triggering (as evidenced by the negative values for \(P_0 - V_0\)). Our alignment analysis reveals two important considerations for improvements towards this goal. The first consideration is that the influence of alignment changes with the degree of preserved respiratory function, as seen with the difference in results between the intact and the severed phrenic nerve. When the phrenic nerve is severed, all diaphragm motion is governed by the actuators, and misaligned actuation with the remaining native respiratory effort—expansion of the ribcage—results in more consequential destructive interference. Whereas when the phrenic nerve is intact, the net diaphragm motion results from a combination of native diaphragm function and the effect of the actuators, because the actuators only operate along 2 discrete lines on the diaphragm. The contraction of the rest of the native diaphragm motion is still synchronized with the ribcage motion, so the effects of misalignment are less apparent. This implies that optimal alignment parameters may be different for different disease states and the control system will need to be dynamic and adaptive to changes in respiratory function, even within the same patient. The second consideration is that the actuation curve's relationship to the beginning of expiration \((V_{pk})\) is more influential than the relationship to the beginning of inspiration \((V_0)\). This implies that an updated system should trigger from a signal related to expiration as opposed to the beginning of inspiration. Some neuromuscular signals, like the electrical activity of the diaphragm (Edi), contain detailed information about both inspiration and expiration times35,36. Edi amplitude is also proportional to the neural drive, as well as the degree of contraction of the diaphragmatic muscle, therefore opening up the possibility of adaptive control. Triggering from Edi measured at the esophageal level via a feeding tube37 may be warranted to improve mechanical ventilation. This method, known as neurally adjusted ventilatory assist, is available in the clinical setting with mechanical ventilation and may improve respiratory weaning of patients that are challenging to wean36. The same principle could be applied to our diaphragm assist system; using a more upstream signal with greater information on the native respiratory effort would allow for a more robust control system. + +Overall, we show that the strategy to augment the native function of the diaphragm with soft robotics acts as a form of negative pressure ventilation by driving ventilation through the generation of a negative pressure in the thoracic cavity. Our diaphragm assist system is biomechanically similar to that of spontaneous breathing, sharing a substantial portion of the work of breathing in our best responding subject. By functioning as an assist device—as opposed to completely overtaking breathing—our system has the potential to be compatible with voluntary use of the diaphragm. Maneuvers such as voluntary deep breaths or drinking through a straw—abilities related to patient autonomy and quality of life—can be preserved with this implantable ventilator strategy. Additionally, in contrast to current modes of mechanical + +<--- Page Split ---> + +ventilation, recapitulation of native biomechanics, as shown with this system, can avoid the deleterious effects that arise secondary to the use of positive pressure ventilation, such as barotrauma38,39 or hemodynamic changes in patients with concurrent cardiac pathologies40,41. + +## Overall limitations + +In this study, we demonstrate the foundational work towards a soft robotic implantable ventilator. Translationally, there are many hurdles to overcome between the proof- of- concept state presented here and the ultimately envisioned system, and we discuss them in the subsequent text. + +Given that we saw variable responsiveness to the device across subjects, additional studies are needed to understand what factors in system design and implantation can replicate high responsiveness. Our system could generate the low end of acceptable minute ventilations but relied on high respiratory rates to do so. Given the presence of dead space, low tidal volumes result in less alveolar ventilation than if the same minute ventilation achieved with higher tidal volumes and a lower respiratory rate. A core goal of the next generation system is to further improve the tidal volume augmentation, which will need to be achieved through both actuator design and control system development. + +Here, we used the classic McKibben actuator; a more application- specific or customized actuator type may allow for further increases in tidal volumes in future work. Other factors in actuator design, such as the number, layout, and positioning of actuators, will also be critical. We demonstrated tunability of assist by controlling pressurization, but an updated design will require finer characterization. Synchronization is critical to device performance, and thus future work lies in building a next generation control system; this includes creating a system that is cognizant of the beginning of expiration as opposed to inspiration, an automated control system that removes the error of manual titration, and further investigation of dynamic actuation curves. An ideal next generation control system aims to trigger from a more upstream neural signal—such as the electrical activity of the diaphragm—to provide an earlier signal that enables an advanced control system to optimize synchronization, removing delays and asynchrony. Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. To fully realize untethering from bulky machines—like standard mechanical ventilators—the external components that control and power the system require miniaturization. Future work will aim to eventually miniaturize the system to the scale of a small backpack—one that could be worn by the patient or attached to a belt or an electric wheelchair. The process of miniaturization and portability has proved to be possible in similar complex devices, such as ventricular assist devices (e.g. Thoratec HeartMate III) or total artificial hearts (e.g. Syncardia TAH, Carmat Aeson)42–45. + +## Towards clinical translation + +Envisioning a translation to the clinical field, the following considerations might help to optimize the management and pave the way to human application. The diseases leading to chronic + +<--- Page Split ---> + +diaphragmatic dysfunction are numerous and feature very different pathophysiologies. Therefore, a thorough understanding of the underlying pathology as well as its specificity are critically needed to help optimize the management and anticipate complications46. Moreover, patient selection and indication will need to be clearly defined, in order to select the patients who will benefit from this therapy the most. Here, we present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy. + +Owing to the complexity of the procedure, a multidisciplinary team highly trained in advanced thoracic surgery is required to build expertise and develop this technology, ideally in a high- volume center47. Technological improvement is required to provide the least invasive approach of implantation. In this regard, a thoracoscopic route might be beneficial and will be the subject of future work. Given the invasive nature of implantable devices, the diaphragm assist platform is targeted towards patients with chronic- to- permanent ventilator dependence. We recognize that surgery in patients suffering severe diaphragm dysfunction causing respiratory failure can carry a high morbidity and mortality. Peri- operative complications can be numerous; one of the most feared is the worsening of the pulmonary status, which may itself precipitate the need for long- term ventilation48. Nevertheless, it has been well demonstrated that complex thoracic surgery is feasible even in very frail patients. Lung transplantation for terminal respiratory disease49 is one of the most striking examples. Thus, surgery could still be considered in a suitable target population that would ultimately benefit from this mechanical augmentation of diaphragm function, such as a range of neuromuscular disorders. The concept of diaphragm assist is in itself a means of preventing further complications from chronic respiratory failure and preserving key aspects of quality of life- like speech and mobility. + +Due to the focus on feasibility, we acknowledge that there are limitations in these acute studies from the lens of regulatory approval and clinical translation. We do not study device biocompatibility or long- term device operation. The device was constructed from types of polymers that are already used in established medical devices50- 53, such as poly(ethylene terephthalate) (PET) and polyurethanes (See Supplemental Information). Because our device focuses on mechanical interaction, as opposed to biochemical interactions with the body, the materials used in the device can easily be substituted with regulatory- approved materials in future iterations. With improved performance and stability, future long- term studies will need to investigate the long- term effects of the system including tissue remodeling and the ability to provide full- time respiratory support. + +Although this technology requires further advancements in the net tidal volumes it can generate before it can fully match the ventilation capacity of a current mechanical ventilator, it is the first study to report the ability to rescue ventilation with an implantable ventilator. We envision further translational potential of this technology when combined with the development of smaller and more portable pneumatic energy sources54,55 as the field of soft robotics advances. With the integration of a portable pump and control system in the future, this technology could provide an additional level of patient autonomy via increased mobility. Motivated by the encouraging results + +<--- Page Split ---> + +of this study, we believe this technology, with optimized design, has the potential to provide a radically different ventilation technology that preserves key metrics of quality of life for people with end- stage mechanical respiratory failure. + +<--- Page Split ---> + +Rebuttal 2 + +<--- Page Split ---> + +As requested, we carefully considered comments of Reviewer 3. In the paragraph "Effect of synchronization on blood gas exchange", we clarified the number of subjects included for this analysis (comment 1.1). We agree that the acidemia observed in Fig. 5b is of mixed cause and we modified the text accordingly (comment 1.2). Although the discussion is quite long (comment 2), the current version has been drastically improved thanks the suggestions from both reviewers. We believe that shortening the discussion would affect its quality. Therefore, we didn't modify it, unless the Editor feels it is essential. + +<--- Page Split ---> diff --git a/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..3a844523b33aaed68489618db4741b89628e7381 --- /dev/null +++ b/peer_reviews/14a747f8d0c65ea70689f25db083256e23654debca39c9e2cc46b1dc50c26dba/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,882 @@ +<|ref|>title<|/ref|><|det|>[[93, 135, 799, 165]]<|/det|> +# An implantable soft robotic ventilator augments inspiration in a pig model of respiratory insufficiency + +<|ref|>text<|/ref|><|det|>[[94, 178, 357, 193]]<|/det|> +Corresponding author: Ellen Roche + +<|ref|>sub_title<|/ref|><|det|>[[93, 207, 202, 221]]<|/det|> +## Editorial note + +<|ref|>text<|/ref|><|det|>[[93, 237, 881, 309]]<|/det|> +This document includes relevant written communications between the manuscript's corresponding author and the editor and reviewers of the manuscript during peer review. It includes decision letters relaying any editorial points and peer- review reports, and the authors' replies to these (under 'Rebuttal' headings). The editorial decisions are signed by the manuscript's handling editor, yet the editorial team and ultimately the journal's Chief Editor share responsibility for all decisions. + +<|ref|>text<|/ref|><|det|>[[93, 323, 889, 395]]<|/det|> +Any relevant documents attached to the decision letters are referred to as Appendix #, and can be found appended to this document. Any information deemed confidential has been redacted or removed. Earlier versions of the manuscript are not published, yet the originally submitted version may be available as a preprint. Because of editorial edits and changes during peer review, the published title of the paper and the title mentioned in below correspondence may differ. + +<|ref|>sub_title<|/ref|><|det|>[[93, 409, 226, 423]]<|/det|> +## Correspondence + +<|ref|>text<|/ref|><|det|>[[93, 439, 368, 468]]<|/det|> +Mon 04 Apr 2022 Decision on Article nBME- 21- 2902 + +<|ref|>text<|/ref|><|det|>[[93, 482, 223, 496]]<|/det|> +Dear Prof Roche, + +<|ref|>text<|/ref|><|det|>[[92, 510, 903, 582]]<|/det|> +Thank you again for submitting to Nature Biomedical Engineering your manuscript, "An implantable ventilator augments inspiration in an in vivo porcine model". As noted in previous e- mail correspondence, the manuscript has been seen by three experts, yet despite our chasing efforts, one reviewer has failed to provide a report. The feedback from two reviewers, which I had already forwarded to you, is also included at the end of this message. + +<|ref|>text<|/ref|><|det|>[[92, 596, 900, 698]]<|/det|> +You will see that the reviewers appreciate the work. However, they express concerns about the degree of support for the claims, and provide useful suggestions for improvement. We hope that with significant further work you can address the criticisms and convince the reviewers of the merits of the study. In particular, we would expect that a revised version of the manuscript addresses the concerns on the safety and performance of the implantable ventilator, and includes additional caveats as to the expected bottlenecks that would need to be overcome before eventual human trials of the device. Importantly, please make sure that device characterization and methodology reporting are thorough. + +<|ref|>text<|/ref|><|det|>[[92, 711, 900, 755]]<|/det|> +When you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that explains the main improvements included in the revision and responds to any points highlighted in this decision. + +<|ref|>text<|/ref|><|det|>[[93, 768, 435, 783]]<|/det|> +Please follow the following recommendations: + +<|ref|>text<|/ref|><|det|>[[92, 797, 839, 826]]<|/det|> +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +<|ref|>text<|/ref|><|det|>[[92, 870, 904, 965]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third- party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 65, 864, 94]]<|/det|> +\* If you and your co-authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +<|ref|>text<|/ref|><|det|>[[90, 108, 876, 137]]<|/det|> +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the reason(s). + +<|ref|>text<|/ref|><|det|>[[90, 150, 876, 179]]<|/det|> +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +<|ref|>text<|/ref|><|det|>[[90, 193, 900, 222]]<|/det|> +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +<|ref|>text<|/ref|><|det|>[[92, 236, 728, 250]]<|/det|> +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +<|ref|>text<|/ref|><|det|>[[92, 264, 904, 322]]<|/det|> +We hope that you will be able to resubmit the manuscript within 20 weeks from the receipt of this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[92, 336, 857, 365]]<|/det|> +We hope that you will find the referee reports helpful when revising the work. Please do not hesitate to contact me should you have any questions. + +<|ref|>text<|/ref|><|det|>[[92, 379, 188, 393]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[92, 408, 124, 421]]<|/det|> +Pep + +<|ref|>text<|/ref|><|det|>[[92, 450, 425, 478]]<|/det|> +Pep Pamies Chief Editor, Nature Biomedical Engineering + +<|ref|>text<|/ref|><|det|>[[92, 550, 456, 564]]<|/det|> +Reviewer #2 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[92, 578, 901, 621]]<|/det|> +This paper is the first demonstration of an in vivo implanted system for assisting in breathing and for contracting diaphragm. The use of external ventilators is very critical, and having an implanted system would solve major problems for patients with diaphragm dysfunctions. + +<|ref|>text<|/ref|><|det|>[[92, 635, 888, 663]]<|/det|> +I appreciated the paper: the motivations are clear, the in vivo tests are sufficiently solid (even if quite short) and the future impact could be dramatic. + +<|ref|>text<|/ref|><|det|>[[92, 678, 850, 706]]<|/det|> +On the other hand, I have identified some major and minor issues which prevent me to give a positive assessment. + +<|ref|>text<|/ref|><|det|>[[92, 707, 884, 764]]<|/det|> +1. First of all, the engineering part is quite limited. All the used components are not optimized for the application. Soft actuators design, size and distribution are not considered in the study protocol (see also comment 4). Sensors and controllers are commercial. The most relevant parts of the paper are the animal test and the physiological measurements. + +<|ref|>text<|/ref|><|det|>[[92, 778, 901, 835]]<|/det|> +2. The clinical motivation of this work is very clearly presented at the beginning. The authors are invited to discuss (possibly in the discussion section) if the target patients for this kind of device are eligible to undergo such complex implant surgery procedure. This might be crucial to foresee future clinical employments of the device. + +<|ref|>text<|/ref|><|det|>[[92, 850, 901, 920]]<|/det|> +3. In the introduction section the authors should better contextualize their work not only with reference to soft actuators but also to fully implantable robots. Few examples and field definition were recently reported in the state of the art. Just as examples, please refer to: - Damian, D. D., Price, K., Arabagi, S., Berra, I., Machaidze, Z., Manjila, S., ... & Dupont, P. E. (2018). In vivo tissue regeneration with robotic implants. Science Robotics, 3(14). - Iacovacci, V., Tamadon, I., Kauffmann, E. F., Pane, S., Simoni, V., Marziale, L., ... + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 65, 900, 108]]<|/det|> +& Menciassi, A. (2021). A fully implantable device for intraperitoneal drug delivery refilled by ingestible capsules. Science Robotics, 6(57), eabh3328. - Menciassi, A., & Iacovacci, V. (2020). Implantable biorobotic organs. APL bioengineering, 4(4), 040402. + +<|ref|>text<|/ref|><|det|>[[92, 121, 880, 180]]<|/det|> +4. It is not clear how the number of PAMs and the overall output force required were set. Please clarify on this and comment on the role played by spatial distribution of the two actuators on the diaphragm surface. What about the needed PAM contraction? Should this be adjusted for each subject and then be constant over the respiratory task? + +<|ref|>text<|/ref|><|det|>[[92, 193, 875, 250]]<|/det|> +5. The authors employed a custom controller aimed at synchronizing the soft robotic actuator and natural breathing. However, both sensing (spirometry) and control rely on external (bulky?) data acquisition and control platforms. This appears a bit in contrast with the original motivation to outperform over invasive ventilation systems. No concrete paths towards implantations are given. + +<|ref|>text<|/ref|><|det|>[[92, 263, 875, 292]]<|/det|> +6. The caption of figure 2 is very informative. However, it would be useful to add some labels on the axes, graphs title, etc., to make figures readability more straightforward. + +<|ref|>text<|/ref|><|det|>[[92, 306, 857, 335]]<|/det|> +7. The in vivo test is very short, so all considerations about materials, biocompatibility, stability etc. are missing. + +<|ref|>text<|/ref|><|det|>[[92, 349, 685, 364]]<|/det|> +8. In line 512, 6 pigs are mentioned. But in the rest of the papers we had 5 pigs. + +<|ref|>text<|/ref|><|det|>[[93, 406, 456, 421]]<|/det|> +Reviewer #3 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[92, 435, 903, 492]]<|/det|> +This work by Drs. Hu and Roche developed an implantable device that can substitute a mechanical ventilator commonly used in the contemporary clinical care and yet, avoid the various shortcomings of it. The authors build a robotic actuator which is overlaid to the subject's diaphragm and activated by the host's inspiratory effort, which in turn, is balloon inflated and substitutes the function of the native diaphragm. + +<|ref|>text<|/ref|><|det|>[[92, 506, 898, 592]]<|/det|> +The authors challenge an important clinical question, with a good understanding of the respiratory cycle and the role of the diaphragmatic motion. The concept underlying the current work is interesting and innovative. I acknowledge that this is a prototype, however the current manuscript do have room for improvement. Additionally, considering the invasiveness of the implantation associated with their device, whether the strength of the system is enough to overcome the invasiveness associated with the procedure should be discussed more in depth. + +<|ref|>text<|/ref|><|det|>[[93, 606, 450, 620]]<|/det|> +Here are some major comments for the authors. + +<|ref|>text<|/ref|><|det|>[[92, 621, 880, 691]]<|/det|> +1. The authors fail to analyze the actual blood gas levels with arterial blood. The authors state that the responsiveness of the diaphragm can vary between subjects. How can the authors be sure that the blood gas levels are maintained at a relatively stable state with the device instillation? Please be aware that maintaining the blood acid-base balance in a homeostatic state is a critical role of respiration in every living creature. + +<|ref|>text<|/ref|><|det|>[[92, 706, 901, 777]]<|/det|> +2. How is the level of inspiration controlled with their device? The degree of inspiration should be controllable according to the subjects needs in various clinical situation (for example, in early sepsis, it is natural to be in a hyperventilated state) but the authors do not show that their device is versatile enough to accommodate this. What happens to the subject's respiration if the bladder in the system is pressurized more? Additionally, what about the opposite where there is no need for a deep inspiration? + +<|ref|>text<|/ref|><|det|>[[92, 791, 888, 849]]<|/det|> +3. Likewise, I would like to see how the respiratory mechanics change according to how fast the bladder in their system is inflated. More information should be given on this. The respiratory mechanics are shown as simple bar graphs in Figures 5a, b and c, whereas the gradient or slope of the Campbell diagram may also be important. + +<|ref|>text<|/ref|><|det|>[[92, 863, 900, 920]]<|/det|> +4. The authors should be commended for doing a nice job in synchronizing the device to the subject's respiratory effort. However, the trigger for this is the spirometer that is installed into the subject's airway. To really overcome the weakness of the contemporary mechanical ventilators, the authors should think of better methods that do not touch the respiratory tract to sense the intrinsic respiratory effort. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 80, 497, 94]]<|/det|> +There are also some minor comments that might help. + +<|ref|>text<|/ref|><|det|>[[90, 94, 900, 123]]<|/det|> +1. Supplementary Video Online is not that informative as it plays in a real-time. It would be better if the video is played more slowly. + +<|ref|>text<|/ref|><|det|>[[92, 136, 595, 151]]<|/det|> +2. The finding should be supported by adequate statistical analysis. + +<|ref|>text<|/ref|><|det|>[[92, 151, 864, 177]]<|/det|> +2.1. Although somewhat obvious from the graphs, there should be some statistical analysis to show the difference in the variation of peak inspiratory flow and tidal volume of Figure 3e and f. + +<|ref|>text<|/ref|><|det|>[[92, 178, 831, 205]]<|/det|> +2.2. The pairwise comparisons should be done for Figure 5a, b, and c with the data acquired at the spontaneous respiration (SR) as the reference, not the actuator assisted ventilation (AAV). + +<|ref|>text<|/ref|><|det|>[[92, 206, 770, 220]]<|/det|> +2.3. How many samples were taken for each subjects in each graph. This should be noted. + +<|ref|>text<|/ref|><|det|>[[92, 234, 896, 264]]<|/det|> +3. In Figures 2c, d and e, when did the authors gather data after the device was turned off or on? The same questions goes for synchronized actuation in Figures 3e and f, Figures 5a, b and c. + +<|ref|>text<|/ref|><|det|>[[92, 278, 440, 293]]<|/det|> +4. Figure 4a and b miss the legends for y-axis. + +<|ref|>text<|/ref|><|det|>[[90, 307, 900, 336]]<|/det|> +5. The overall structure of the Discussion could be improved. The contents of each paragraphs tend to jump, making it difficult to follow. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 65, 380, 94]]<|/det|> +## Sun 16 Oct 2022 Decision on Article nBME-21-2902A + +<|ref|>text<|/ref|><|det|>[[93, 107, 224, 122]]<|/det|> +Dear Prof Roche, + +<|ref|>text<|/ref|><|det|>[[93, 136, 881, 180]]<|/det|> +Thank you for your patience in waiting for the guidelines for the final submission of your manuscript, "An implantable ventilator augments inspiration in an in vivo porcine model" to Nature Biomedical Engineering. Please carefully follow the instructions provided in the attached file. + +<|ref|>text<|/ref|><|det|>[[93, 193, 519, 208]]<|/det|> +Also, please consider the minor points from Reviewer #3. + +<|ref|>text<|/ref|><|det|>[[92, 221, 880, 351]]<|/det|> +For primary research originally submitted after December 1, 2019, we encourage authors to take up transparent peer review. If you are eligible and opt in to transparent peer review, we will publish, as a single supplementary file, all the reviewer comments for all the versions of the manuscript, your rebuttal letters, and the editorial decision letters. When submitting the final version of your manuscript please indicate whether you opt in to transparent peer review. In the interest of confidentiality, we allow redactions to the rebuttal letters and to the reviewer comments. If you are concerned about the release of confidential data, please indicate in the cover letter what specific information you would like to have removed; we cannot incorporate redactions for any other reasons. More information on transparent peer review is available. + +<|ref|>text<|/ref|><|det|>[[92, 363, 877, 393]]<|/det|> +When you are ready to submit the final version of your manuscript, please upload the files specified in the instructions file. + +<|ref|>text<|/ref|><|det|>[[92, 406, 572, 421]]<|/det|> +If you have any further questions, please feel free to contact me. + +<|ref|>text<|/ref|><|det|>[[93, 434, 194, 449]]<|/det|> +Best regards, + +<|ref|>text<|/ref|><|det|>[[93, 464, 125, 477]]<|/det|> +Pep + +<|ref|>text<|/ref|><|det|>[[92, 507, 425, 536]]<|/det|> +Pep Pamies Chief Editor, Nature Biomedical Engineering + +<|ref|>text<|/ref|><|det|>[[92, 606, 194, 620]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[93, 621, 347, 635]]<|/det|> +Report for the authors (Required): + +<|ref|>text<|/ref|><|det|>[[92, 636, 883, 722]]<|/det|> +The paper has been substantially improved and now the contribution of the work, the methodology behind and the main limitations of the obtained results have been reported. I think these additional parts (and additional tests, which I really appreciate) can help to position the paper in the state of the art and help the readers to understand the most critical elements for further developments. I am sure that some activities reported as "future steps" are not trivial at all (miniaturization of the electronics, biocompatibility, neural triggering), but the results, as a first proof of concept in vivo, deserve to be published. + +<|ref|>text<|/ref|><|det|>[[92, 764, 194, 778]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[93, 779, 347, 793]]<|/det|> +Report for the authors (Required): + +<|ref|>text<|/ref|><|det|>[[92, 793, 902, 850]]<|/det|> +This report by Drs. Hu and Roche is a revised version of the manuscript previously submitted to the Nature BME. The manuscript has been significantly improved and much of the parts have been clarified. A significant proportion of the previous questions have been resolved. I have two minor comments/suggestions remaining. + +<|ref|>text<|/ref|><|det|>[[92, 863, 857, 892]]<|/det|> +1. The blood gas analysis allows us to see how the system developed by the authors translate into the respiration of a given subject/animal but there are some comments related to this. + +<|ref|>text<|/ref|><|det|>[[90, 905, 902, 920]]<|/det|> +1.1. I am actually not sure whether the acidosis seen in Fig. 5b is a result of metabolic acidosis. Although the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 65, 900, 94]]<|/det|> +blood gas results may be different between humans and swines, I think the blood gas analysis in Fig. 5b is a mixed form of both respiratory and metabolic acidosis. + +<|ref|>text<|/ref|><|det|>[[93, 108, 523, 123]]<|/det|> +1.2. How many animals were analyzed for the blood gas? + +<|ref|>text<|/ref|><|det|>[[92, 136, 821, 152]]<|/det|> +2. Although I agree that there is a lot to discuss, the length of the Discussion is actually quite long. + +<|ref|>text<|/ref|><|det|>[[92, 220, 864, 265]]<|/det|> +Nature Biomedical Engineering is a Transformative Journal. Authors may publish their research with us through the traditional subscription- access route, or make their paper immediately open access through payment of an article- processing charge. More information about publication options is available. + +<|ref|>text<|/ref|><|det|>[[92, 279, 888, 365]]<|/det|> +You may need to take specific actions to comply with funder and institutional open- access mandates. If the work described in the accepted manuscript is supported by a funder that requires immediate open access (as outlined, for example, by Plan S) and your manuscript was originally submitted on or after January 1st 2021, then you will need to select the gold OA route. Authors selecting subscription publication will need to accept our standard licensing terms (including our self- archiving policies), and these will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[25, 0, 999, 0]]<|/det|> +Rebuttal 1 + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[197, 90, 800, 149]]<|/det|> +# Manuscript nBME-21-2902 : Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[114, 168, 875, 280]]<|/det|> +We thank the reviewers for their thoughtful and detailed feedback. We have addressed each of these comments in turn, and have included corresponding modifications to the text. We feel the reviewer's comments and the subsequent revisions have substantially clarified and strengthened the manuscript. For clarity, the changes made to the manuscript- including the new Extended Data- are shown in blue in both this response and in the manuscript. Changes made to the Supplemental Information are shown in orange in this document. + +<|ref|>sub_title<|/ref|><|det|>[[115, 308, 444, 335]]<|/det|> +## Comments from Editor + +<|ref|>text<|/ref|><|det|>[[114, 345, 881, 495]]<|/det|> +You will see that the reviewers appreciate the work. However, they express concerns about the degree of support for the claims, and provide useful suggestions for improvement. We hope that with significant further work you can address the criticisms and convince the reviewers of the merits of the study. In particular, we would expect that a revised version of the manuscript addresses the concerns on the safety and performance of the implantable ventilator, and includes additional caveats as to the expected bottlenecks that would need to be overcome before eventual human trials of the device. Importantly, please make sure that device characterization and methodology reporting are thorough. + +<|ref|>sub_title<|/ref|><|det|>[[115, 513, 280, 530]]<|/det|> +## Answer to the Editor + +<|ref|>text<|/ref|><|det|>[[114, 530, 881, 750]]<|/det|> +We thank the Editor for considering our manuscript for Nature Biomedical Engineering. Here, we present additional data and discussion to address the reviewer comments on safety and performance. Overall, we have conducted additional large animal experiments to better characterize our device and evaluate its performance. We investigated different actuation regimes and introduced two new metrics of performance: ultrasonography (seen in Fig. 2, 4, and Extended Data Fig. 1 and 2) and blood gas analysis (seen in Fig. 5 and Extended Data Table 1), used to directly assess diaphragm displacement and to evaluate the repercussions on gas exchange, respectively. Characterization of the actuators was performed both in vitro and in vivo. We have expanded and reworked the discussion to incorporate further considerations for clinical translation, including current limitations, clinical concerns, and the future preclinical work needed before human implantation. We feel that these additions to our manuscript have substantially strengthened our claims. + +<|ref|>text<|/ref|><|det|>[[114, 768, 855, 898]]<|/det|> +Both reviewers comment on aspects of device characterization. Therefore, we have included two additional figures in the Extended Data (Extended Data Fig. 1 and 2), with a detailed discussion included in the section titled "Controlling PAM actuator performance via pressurization" in the Supplementary Notes. Additionally, both reviewers comment on discussing the considerations for translation. Our discussion has been largely rewritten and expanded to address the additional insights provided by the reviewers. Detailed individual responses to each reviewer comment are included below. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 92, 299, 118]]<|/det|> +## Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[116, 130, 338, 147]]<|/det|> +## Overall Reviewer Comment + +<|ref|>text<|/ref|><|det|>[[113, 148, 872, 277]]<|/det|> +Overall Reviewer CommentThis paper is the first demonstration of an in vivo implanted system for assisting in breathing and for contracting diaphragm. The use of external ventilators is very critical, and having an implanted system would solve major problems for patients with diaphragm dysfunctions. I appreciated the paper: the motivations are clear, the in vivo tests are sufficiently solid (even if quite short) and the future impact could be dramatic. On the other hand, I have identified some major and minor issues which prevent me to give a positive assessment. + +<|ref|>sub_title<|/ref|><|det|>[[116, 295, 364, 312]]<|/det|> +## Response to Overall Comment + +<|ref|>text<|/ref|><|det|>[[115, 313, 878, 367]]<|/det|> +Response to Overall CommentWe agree with Reviewer #2's summary of the significance of our work. We believe the reviewer's comments have significantly improved this body of work and hope our responses are to their satisfaction. + +<|ref|>sub_title<|/ref|><|det|>[[115, 388, 210, 404]]<|/det|> +## Comment 1 + +<|ref|>text<|/ref|><|det|>[[115, 405, 861, 479]]<|/det|> +Comment 1First of all, the engineering part is quite limited. All the used components are not optimized for the application. Soft actuators design, size and distribution are not considered in the study protocol (see also comment 4). Sensors and controllers are commercial. The most relevant parts of the paper are the animal test and the physiological measurements. + +<|ref|>sub_title<|/ref|><|det|>[[115, 498, 311, 514]]<|/det|> +## Response to comment 1 + +<|ref|>text<|/ref|><|det|>[[114, 515, 866, 644]]<|/det|> +We thank the reviewer for this comment, and we agree that the focus of our paper is not in presenting any individual actuator, sensor, or controller. Instead, we demonstrate the full integration of soft actuators fitted to the diaphragm operated by a custom- built control box that provides device actuation synchronized to native respiratory effort, and ultimately study the interaction and augmentation of this soft robotic system on in vivo respiratory physiology. This body of work aims to prove feasibility and proof- of- concept, serving as the first step in the long journey towards translating this work to the clinic. + +<|ref|>text<|/ref|><|det|>[[114, 661, 870, 753]]<|/det|> +We fully agree that our initial presentation has obscured our work done to develop the soft robotic system for this application, and we have worked to update the manuscript to better communicate this. Please see updates to the supplemental Information titled "Controlling PAM actuator performance via pressurization" and Fig. S1 and S2 for an improved description of the characterization work of the system. + +<|ref|>text<|/ref|><|det|>[[114, 772, 849, 808]]<|/det|> +A specific response regarding soft actuator design, size, and distribution can be found in the response to comment 4. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 211, 105]]<|/det|> +## Comment 2 + +<|ref|>text<|/ref|><|det|>[[115, 107, 874, 180]]<|/det|> +Comment 2The clinical motivation of this work is very clearly presented at the beginning. The authors are invited to discuss (possibly in the discussion section) if the target patients for this kind of device are eligible to undergo such complex implant surgery procedure. This might be crucial to foresee future clinical employments of the device. + +<|ref|>sub_title<|/ref|><|det|>[[115, 200, 313, 216]]<|/det|> +## Response to comment 2 + +<|ref|>text<|/ref|><|det|>[[114, 217, 881, 400]]<|/det|> +Response to comment 2Again, we appreciate this comment. Due to the mechanical nature of the device—as opposed to biopharmaceutical interventions—this technology is not restricted to a single disease type, and instead the target patient population is defined by patients with mechanical respiratory failure involving the diaphragm who would benefit from long- term mechanical augmentation of diaphragm function. Although such a surgical intervention is invasive and might lead to complications, it has been well demonstrated that thoracic surgery is feasible in patients with peri- operative risk (e.g. lung transplant for terminal respiratory failure). Therefore implantation of our device may be considered, especially in a highly skilled environment. We therefore added the following paragraphs regarding considerations for the translation to the clinical field to the discussion of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[118, 419, 333, 435]]<|/det|> +## Towards clinical translation + +<|ref|>text<|/ref|><|det|>[[113, 454, 876, 638]]<|/det|> +Towards clinical translationEnvisioning a translation to the clinical field, the following considerations might help to optimize the management and pave the way to human application. The diseases leading to chronic diaphragmatic dysfunction are numerous and feature very different pathophysiologies. Therefore, a thorough understanding of the underlying pathology as well as its specificity are critically needed to help optimize the management and anticipate complications46. Moreover, patient selection and indication will need to be clearly defined in order to select the patients who will benefit from this therapy the most. Here, we present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy. + +<|ref|>text<|/ref|><|det|>[[113, 657, 871, 896]]<|/det|> +Owing to the complexity of the procedure, a multidisciplinary team highly trained in advanced thoracic surgery is required to build expertise and develop this technology, ideally in a high- volume center47. Technological improvement is required to provide the least invasive approach of implantation. In this regard, a thoracoscopic route might be beneficial and will be the subject of future work. Given the invasive nature of implantable devices, the diaphragm assist platform is targeted towards patients with chronic- to- permanent ventilator dependence. We recognize that surgery in patients suffering severe diaphragm dysfunction causing respiratory failure can carry a high morbidity and mortality. Peri- operative complication can be numerous; one of the most feared is the worsening of the pulmonary status, which may itself precipitate the need for long- term ventilation48. Nevertheless, it has been well demonstrated that complex thoracic surgery is feasible even in very frail patients. Lung transplantation for terminal respiratory disease49 is one of the most striking examples. Thus, surgery could still be considered in a suitable target population that would ultimately benefit from this mechanical augmentation of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 144]]<|/det|> +diaphragm function, such as a range of neuromuscular disorders. The concept of diaphragm assist is in itself a means of preventing further complications from chronic respiratory failure and preserving key aspects of quality of life–like speech and mobility. + +<|ref|>sub_title<|/ref|><|det|>[[115, 181, 211, 197]]<|/det|> +## Comment 3 + +<|ref|>text<|/ref|><|det|>[[114, 199, 880, 365]]<|/det|> +In the introduction section the authors should better contextualize their work not only with reference to soft actuators but also to fully implantable robots. Few examples and field definition were recently reported in the state of the art. Just as examples, please refer to: - Damian, D. D., Price, K., Arabagi, S., Berra, I., Machaidze, Z., Manjila, S., ... & Dupont, P. E. (2018). In vivo tissue regeneration with robotic implants. Science Robotics, 3(14). - Iacovacci, V., Tamadon, I., Kauffmann, E. F., Pane, S., Simoni, V., Marziale, L., ... & Menciassi, A. (2021). A fully implantable device for intraperitoneal drug delivery refilled by ingestible capsules. Science Robotics, 6(57), eabh3328. - Menciassi, A., & Iacovacci, V. (2020). Implantable biorobotic organs. APL bioengineering, 4(4), 040402. + +<|ref|>sub_title<|/ref|><|det|>[[115, 384, 313, 400]]<|/det|> +## Response to comment 3 + +<|ref|>text<|/ref|><|det|>[[115, 401, 863, 437]]<|/det|> +We agree that the introduction is better served with a broader and more recent context of fully implantable robots. The text has been updated to: + +<|ref|>text<|/ref|><|det|>[[115, 455, 860, 510]]<|/det|> +Previously, fully implanted soft actuators have shown the ability to augment heart function \(^{7 - 11}\) and many other newly developed implantable robotics have shown utility in a broad spread of biological applications \(^{12 - 20}\) . + +<|ref|>text<|/ref|><|det|>[[115, 530, 525, 547]]<|/det|> +With the additional citation of the following sources: + +<|ref|>text<|/ref|><|det|>[[163, 549, 883, 896]]<|/det|> +9. Payne, C. J. et al. An Implantable Extracardiac Soft Robotic Device for the Failing Heart: Mechanical Coupling and Synchronization. Soft Robot. 4, 241-250 (2017). +10. Saeed, M. Y. et al. Dynamic Augmentation of Left Ventricle and Mitral Valve Function With an Implantable Soft Robotic Device. Basic to Transl. Sci. 5, 229-242 (2020). +11. Hong, Y. J., Jeong, H., Cho, K. W., Lu, N. & Kim, D. H. Wearable and Implantable Devices for Cardiovascular Healthcare: from Monitoring to Therapy Based on Flexible and Stretchable Electronics. Adv. Funct. Mater. 29, 1808247 (2019). +12. Damian, D. D. et al. In vivo tissue regeneration with robotic implants. Sci. Robot. 3, (2018). +13. Iacovacci, V. et al. A fully implantable device for intraperitoneal drug delivery refilled by ingestible capsules. Sci. Robot. 6, 3328 (2021). +14. Dolan, E. B. et al. An actuatable soft reservoir modulates host foreign body response. Sci. Robot. 4, (2019). +15. Menciassi, A. & Iacovacci, V. Implantable biorobotic organs. APL Bioeng. 4, 1-4 (2020). +16. Perez-Guagnelli, E. et al. Characterization, Simulation and Control of a Soft Helical Pneumatic Implantable Robot for Tissue Regeneration. IEEE Trans. Med. Robot. Bionics 2, 94-103 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[168, 88, 868, 200]]<|/det|> +19. Pane, S., Mazzocchi, T., Iacovacci, V., Ricotti, L. & Menciassi, A. Smart implantable artificial bladder: An integrated design for organ replacement. IEEE Trans. Biomed. Eng. 68, 2088–2097 (2021). +20. Amiri Moghadam, A. A. et al. Using Soft Robotic Technology to Fabricate a Proof-of-Concept Transcatheter Tricuspid Valve Replacement (TTVR) Device. Adv. Mater. Technol. 4, (2019). + +<|ref|>sub_title<|/ref|><|det|>[[115, 238, 210, 254]]<|/det|> +## Comment 4 + +<|ref|>text<|/ref|><|det|>[[115, 255, 875, 327]]<|/det|> +It is not clear how the number of PAMs and the overall output force required were set. Please clarify on this and comment on the role played by spatial distribution of the two actuators on the diaphragm surface. What about the needed PAM contraction? Should this be adjusted for each subject and then be constant over the respiratory task? + +<|ref|>sub_title<|/ref|><|det|>[[116, 346, 312, 363]]<|/det|> +## Response to comment 4 + +<|ref|>text<|/ref|><|det|>[[115, 364, 840, 382]]<|/det|> +We agree that our initial manuscript did not clearly communicate these aspects of the work. + +<|ref|>text<|/ref|><|det|>[[115, 400, 868, 492]]<|/det|> +In brief, shape of the pressurization curve was chosen via a comparison of different input waveforms seen in the data presented in Extended Data Fig. 1 with the following conclusion in the Supplemental Notes: "Overall, the curved waveform used in the majority of the study represents a pressurization scheme that aims to optimize between the tradeoffs of the square wave and triangular wave, generating the best tidal volumes and biomimetic PV loops." + +<|ref|>text<|/ref|><|det|>[[115, 510, 883, 621]]<|/det|> +The pressurization curve was scaled to different depths of pressurization. Because we are aiming for maximal augmentation in the state of simulated diaphragm failure, this study actuates the device at a maximum of 20 psi, captured in Extended Data Fig. 2 and described via the following statement in the Supplemental Notes: "The degree of pressurization has a positive, but nonlinear effect on the amount of diaphragm displacement generated (Extended Data Fig. 2g- k)." + +<|ref|>text<|/ref|><|det|>[[115, 639, 863, 732]]<|/det|> +In cases where less augmentation is needed, level of augmentation can be tuned via the pressurization. Please see the new section of the Supplemental Information titled "Controlling PAM actuator performance via pressurization" and Extended Data Fig. 1 and 2 for full details regarding how the overall output force and device performance was determined by controlling the pressurization waveform and depth of pressurization. + +<|ref|>text<|/ref|><|det|>[[115, 768, 881, 896]]<|/det|> +The choice to use two actuators—one on each hemidiaphragm—was due to the issue that the introduction of each actuator displaces potential lung volume in the thoracic cavity. The filled actuator size is 17 mL at 20 psi, so the use of additional actuators would require augmentation that provides benefits beyond this filled volume. The two hemidiaphragms are semi- independent (Whitelaw WA. J Appl Physiol 62, 180- 6 (1985)), meaning that augmentation and displacement on one side doesn't transfer to the other, which is why clinically some people experience unilateral diaphragm paralysis (Gibson G. Thorax 44, 960- 970 (1989), Celli, B. Semin Respir + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 87, 879, 216]]<|/det|> +Crit Care Med 23, 3, 275- 281 (2002)). The use of two actuators represents the minimum volume of actuators to act upon both semi- independent hemidiaphragms. For a potential alternative design, actuators that provide greater coverage of the diaphragm with minimal increase in occupied thoracic volume could provide a greater surface area to distribute force and provide more homogeneous diaphragm displacement. Designing actuators that lend themselves to this configuration is one direction of future work that the diaphragm assist system would benefit from. + +<|ref|>text<|/ref|><|det|>[[114, 234, 877, 383]]<|/det|> +Regarding the spatial distribution of the two linear PAM actuators used in this study, the PAMs are placed in the antero- posterior direction, the left actuator being lateral to the heart. Specific placement is reflected in the methods text: "The anterior portion is attached to the sternum and the posterior attachment is made to the lowest posterior rib in the most medial position that can be achieved without disrupting the region of the major arteries and veins, esophagus, and spine." This is best visualized via the coronal view of the fluoroscopy in Supplemental Video 1. This placement aims to place the PAM across the peak of the dome of the actuator and laterally down the rostral and dorsal edge of the subject's ribcage. + +<|ref|>text<|/ref|><|det|>[[113, 400, 880, 787]]<|/det|> +We agree that the PAM contraction necessary to augment diaphragmatic motion is a key design feature. At zero pressurization, the actuator should passively fit along the peak arclength of the end expiratory diaphragm. The theoretical maximum contraction length should be the straight line distance between the two points of attachment. In order to anchor the actuator via sutures, the actuator requires some region of passive material. We developed the reported actuator dimensions empirically in accordance with our work in swine cadavers to appropriately fit the arclength and anatomy of the diaphragm in 30- 40kg subjects. The actuator reported here has a relaxed length of 25 cm, and a contracted length of 21cm. There exists approximately 3.5 cm of PET mesh at each end of the actuator which is used as a suture attachment location. We agree that the actuator size and level of contraction can and should be fitted to individual patients. However, given the nature of animal experiments, we do not have access to "patient data" and "patient dimensions" ahead of the procedure. We control for variation in patient dimensions by controlling swine size, using only female Yorkshire swine in the 30- 40kg range. The actuator is implanted in a manner where the actuator fits snugly against the diaphragm, with the 7 cm of extra mesh as a buffer for interanimal variability. A next generation actuator for this diaphragm assist system could be designed in a manner that is not limited by the straight line distance and could also provide additional downward motion beyond the geometric "chord" of the arclength of the diaphragm. This consideration is briefly captured in the discussion via: "We present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 210, 105]]<|/det|> +## Comment 5 + +<|ref|>text<|/ref|><|det|>[[115, 107, 877, 198]]<|/det|> +Comment 5The authors employed a custom controller aimed at synchronizing the soft robotic actuator and natural breathing. However, both sensing (spirometry) and control rely on external (bulky?) data acquisition and control platforms. This appears a bit in contrast with the original motivation to outperform over invasive ventilation systems. No concrete paths towards implantations are given. + +<|ref|>sub_title<|/ref|><|det|>[[116, 218, 312, 234]]<|/det|> +## Response to comment 5 + +<|ref|>text<|/ref|><|det|>[[115, 253, 872, 345]]<|/det|> +We agree that the current control system and synchronization method prevent its application in an outpatient setting, which represents the long- term objective of this type of device. The present work was designed as a proof- of- concept study. For our purposes, we developed a control system whose components can be easily accessed, modified, and then optimized. Consequently, the size of the current system prevents the outpatient use. + +<|ref|>text<|/ref|><|det|>[[115, 364, 880, 400]]<|/det|> +We therefore added the following section in the discussion to present concrete paths toward this endeavor: + +<|ref|>text<|/ref|><|det|>[[114, 418, 882, 619]]<|/det|> +An ideal next generation control system aims to trigger from a more upstream neural signal- such as the electrical activity of the diaphragm- to provide an earlier signal that enables an advanced control system to optimize synchronization, removing delays and asynchrony. Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. To fully realize untethering from bulky machines- like standard mechanical ventilators- the external components that control and power the system require miniaturization. Future work will aim to eventually miniaturize the system to the scale of a small backpack- one that could be worn by the patient or attached to an electric wheelchair. The process of miniaturization and portability has proved to be possible in similar complex devices, such as ventricular assist devices (e.g. Thoratec HearMate III) or total artificial hearts (e.g. Syncardia TAH, Carmat Aeson)42- 45. + +<|ref|>text<|/ref|><|det|>[[115, 639, 642, 657]]<|/det|> +In combination with the following text from the original manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 675, 877, 748]]<|/det|> +We envision further translational potential of this technology when combined with the development of smaller and more portable pneumatic energy sources54,55 as the field of soft robotics advances. With the integration of a portable pump and control system in the future, this technology could provide an additional level of patient autonomy via increased mobility. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 210, 105]]<|/det|> +## Comment 6 + +<|ref|>text<|/ref|><|det|>[[115, 107, 860, 144]]<|/det|> +Comment 6The caption of figure 2 is very informative. However, it would be useful to add some labels on the axes, graphs title, etc., to make figures readability more straightforward. + +<|ref|>sub_title<|/ref|><|det|>[[115, 163, 313, 180]]<|/det|> +## Response to comment 6 + +<|ref|>text<|/ref|><|det|>[[115, 181, 880, 253]]<|/det|> +Response to comment 6We thank the reviewer for pointing this out. We have added more labels and graphics to the original Figure 2 (now Figure 3) to improve readability. Specifically, we have added gray dashed lines to visually indicate the selection of data in Fig. 3c- e from Fig. 3b. and labeled the green "Range of Normal" + +<|ref|>sub_title<|/ref|><|det|>[[115, 273, 210, 289]]<|/det|> +## Comment 7 + +<|ref|>text<|/ref|><|det|>[[115, 290, 875, 327]]<|/det|> +Comment 7The in vivo test is very short, so all considerations about materials, biocompatibility, stability etc. are missing. + +<|ref|>sub_title<|/ref|><|det|>[[115, 346, 312, 363]]<|/det|> +## Response to comment 7 + +<|ref|>text<|/ref|><|det|>[[115, 364, 850, 400]]<|/det|> +We agree that the acute nature of the study did not allow for important longer term testing of materials and stability. + +<|ref|>text<|/ref|><|det|>[[115, 418, 879, 510]]<|/det|> +Regarding stability, we conducted acute fatigue testing, showing resilience of the actuators to at least 3000 cycles of actuation in vivo without failure at the end of the study. Actuators for this study were designed to last through a one- day sacrificial study. Future work necessitates full characterization of the lifetime of updated actuators. This will be a key future design requirement. + +<|ref|>text<|/ref|><|det|>[[115, 529, 867, 602]]<|/det|> +Regarding materials and biocompatibility, the actuators were manufactured from commercially available materials for ease of prototyping. We did consider the future biocompatibility of the device during material selection, opting for materials with established, regulatory- approved counterparts. We have updated the discussion to address this limitation as follows: + +<|ref|>text<|/ref|><|det|>[[114, 620, 870, 804]]<|/det|> +Due to the focus on feasibility, we acknowledge that there are limitations in these acute studies from the lens of regulatory approval and clinical translation. We do not study device biocompatibility or long- term device operation. The device was constructed from types of polymers that are already used in established medical devices \(^{50 - 53}\) , such as poly(ethylene terephthalate) (PET) and polyurethanes (See Supplemental Information). Because our device focuses on mechanical interaction, as opposed to biochemical interactions with the body, the materials used in the device can easily be substituted with regulatory- approved materials in future iterations. With improved performance and stability, future long- term studies will need to investigate the long- term effects of the system including tissue remodeling and the ability to provide full- time respiratory support. + +<|ref|>text<|/ref|><|det|>[[115, 822, 841, 859]]<|/det|> +Further details on material selection can be found in the updated Supplemental Information section titled Considerations for PAM materials selection. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 210, 105]]<|/det|> +## Comment 8 + +<|ref|>text<|/ref|><|det|>[[115, 107, 719, 125]]<|/det|> +In line 512, 6 pigs are mentioned. But in the rest of the paper we had 5 pigs. + +<|ref|>sub_title<|/ref|><|det|>[[115, 145, 312, 161]]<|/det|> +## Response to comment 8 + +<|ref|>text<|/ref|><|det|>[[115, 163, 872, 272]]<|/det|> +We thank the reviewer for pointing out the need for clarification. In our first submission, the original Fig. 3 displays the data for the 6 total pigs mentioned in line 512 (named A- F) when testing synchronized vs. independent actuation. The original Fig. 2 does in fact only display the data for 5 total pigs (A- E) because for pig F, we did not collect a sufficient amount of the baseline data during a period of unsupported ventilation to make the comparison shown in the original Fig. 2. + +<|ref|>text<|/ref|><|det|>[[115, 290, 870, 382]]<|/det|> +For this revised submission, given the additional data gathered and used for the updated Figures 2, 4, 5, S1, and S2, we have updated the referenced text accordingly: "We used a total of twelve swine during the development and testing of our system, and we present data from nine swine in the manuscript. Different subsets of subjects were used for the experimental investigations reported; not all subjects were used in every experimental investigation." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 92, 308, 118]]<|/det|> +## Reviewer #3: + +<|ref|>sub_title<|/ref|><|det|>[[116, 148, 338, 165]]<|/det|> +## Overall Reviewer Comment + +<|ref|>text<|/ref|><|det|>[[115, 167, 872, 258]]<|/det|> +Overall This work by Drs. Hu and Roche developed an implantable device that can substitute a mechanical ventilator commonly used in contemporary clinical care and yet, avoid the various shortcomings of it. The authors build a robotic actuator which is overlaid to the subject's diaphragm and activated by the host's inspiratory effort, which in turn, is balloon inflated and substitutes the function of the native diaphragm. + +<|ref|>text<|/ref|><|det|>[[115, 259, 866, 330]]<|/det|> +The authors challenge an important clinical question, with a good understanding of the respiratory cycle and the role of the diaphragmatic motion. The concept underlying the current work is interesting and innovative. I acknowledge that this is a prototype, however the current manuscript do have room for improvement. + +<|ref|>text<|/ref|><|det|>[[115, 349, 876, 404]]<|/det|> +Additionally, considering the invasiveness of the implantation associated with their device, whether the strength of the system is enough to overcome the invasiveness associated with the procedure should be discussed more in depth. + +<|ref|>sub_title<|/ref|><|det|>[[116, 423, 346, 440]]<|/det|> +## Overall Response Response + +<|ref|>text<|/ref|><|det|>[[115, 441, 874, 495]]<|/det|> +We agree with Reviewer #3's summary of the significance of our work and the proof- of- concept status of this study. We believe the reviewer's comments have significantly improved this body of work and hope our responses are to their satisfaction. + +<|ref|>text<|/ref|><|det|>[[113, 514, 875, 715]]<|/det|> +Additionally, we thank the reviewer for this relevant comment specifically on the considerations between performance and invasiveness. We demonstrated in this work the ability of the device to significantly augment respiratory function, such as tidal volume and minute ventilation, and the ability to restore a normal range of minute ventilation. We further investigated in vivo the effect on gas exchange using blood gas analysis (see Response to comment 1) and explored diaphragm motion using ultrasound. The performance of the device demonstrates strong feasibility of this soft robotic strategy, but we acknowledge that there are limitations and "A core goal of the next generation system is to further improve the tidal volume augmentation, which will need to be achieved through both actuator design and control system development." Establishing more robust performance and longer respiratory trials will be necessary for future translation. + +<|ref|>text<|/ref|><|det|>[[114, 734, 879, 900]]<|/det|> +In addition, updates to the external triggering and control systems will be critical for realizing our vision of untethering from bulky machinery. This future work is proposed in our discussion section: "Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. To fully realize untethering from bulky machines- like standard mechanical ventilators- the external components that control and power the system require miniaturization. Future work will aim to eventually miniaturize the system to the scale of a small backpack- one that could be worn by the patient or attached to a belt or an electric wheelchair." Given an improved next- generation system that can provide long- term ventilatory support to an appropriate patient population, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 872, 125]]<|/det|> +rescue of respiratory performance that avoids further worsening of patient status and preserves key quality of life measures- like speech and mobility- may justify the surgical procedure. + +<|ref|>text<|/ref|><|det|>[[115, 143, 875, 253]]<|/det|> +We agree that such a surgical intervention is invasive and may lead to complications. However, it has been well demonstrated that thoracic surgery is feasible in patients with high peri- operative risk (e.g. lung transplant for terminal respiratory failure). Therefore implantation of our device may be considered, especially in a highly skilled environment. We therefore add the following paragraphs in the discussion, and make general considerations for the translation to the clinical field. + +<|ref|>sub_title<|/ref|><|det|>[[118, 272, 334, 289]]<|/det|> +## Towards clinical translation + +<|ref|>text<|/ref|><|det|>[[114, 308, 877, 492]]<|/det|> +Envisioning a translation to the clinical field, the following considerations might help to optimize the management and pave the way to human application. The diseases leading to chronic diaphragmatic dysfunction are numerous and feature very different pathophysiologies. Therefore, a thorough understanding of the underlying pathology as well as its specificity are critically needed to help optimize the management and anticipate complications46. Moreover, patient selection and indication will need to be clearly defined in order to select the patients who will benefit from this therapy the most. Here, we present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy. + +<|ref|>text<|/ref|><|det|>[[114, 510, 875, 804]]<|/det|> +Owing to the complexity of the procedure, a multidisciplinary team highly trained in advanced thoracic surgery is required to build expertise and develop this technology, ideally in a high- volume center47. Technological improvement is required to provide the least invasive approach of implantation. In this regard, a thoracoscopic route might be beneficial and will be the subject of future work. Given the invasive nature of implantable devices, the diaphragm assist platform is targeted towards patients with chronic- to- permanent ventilator dependence. We recognize that surgery in patients suffering severe diaphragm dysfunction causing respiratory failure can carry a high morbidity and mortality. Peri- operative complication can be numerous; one of the most feared is the worsening of the pulmonary status, which may itself precipitate the need for long- term ventilation48. Nevertheless, it has been well demonstrated that complex thoracic surgery is feasible even in very frail patients. Lung transplantation for terminal respiratory disease49 is one of the most striking examples. Thus, surgery could still be considered in a suitable target population that would ultimately benefit from this mechanical augmentation of diaphragm function, such as a range of neuromuscular disorders. The concept of diaphragm assist is in itself a means of preventing further complications from chronic respiratory failure and preserving key aspects of quality of life- like speech and mobility. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 311, 114]]<|/det|> +## Major comments + +<|ref|>text<|/ref|><|det|>[[115, 123, 500, 140]]<|/det|> +Here are some major comments for the authors. + +<|ref|>sub_title<|/ref|><|det|>[[115, 160, 209, 176]]<|/det|> +## Comment 1 + +<|ref|>text<|/ref|><|det|>[[115, 178, 882, 270]]<|/det|> +Comment 1The authors fail to analyze the actual blood gas levels with arterial blood. The authors state that the responsiveness of the diaphragm can vary between subjects. How can the authors be sure that the blood gas levels are maintained at a relatively stable state with the device instillation? Please be aware that maintaining the blood acid- base balance in a homeostatic state is a critical role of respiration in every living creature. + +<|ref|>sub_title<|/ref|><|det|>[[115, 290, 311, 306]]<|/det|> +## Response to comment 1 + +<|ref|>text<|/ref|><|det|>[[115, 307, 808, 343]]<|/det|> +We agree that arterial blood gas (ABG) levels are the clinical gold standard indicator of respiratory status. + +<|ref|>text<|/ref|><|det|>[[115, 360, 879, 415]]<|/det|> +To this end, we have included an additional section, figure (Fig. 5), and Extended Data Table 1, capturing the effect of synchronization on the blood gas balance. The manuscript text and figure are copied below: + +<|ref|>sub_title<|/ref|><|det|>[[115, 434, 536, 452]]<|/det|> +## Effect of synchronization on blood gas exchange + +<|ref|>text<|/ref|><|det|>[[114, 470, 875, 618]]<|/det|> +Physiologically, ventilation is necessary to bring in oxygen \((O_{2})\) and to clear out accumulated carbon dioxide \((CO_{2})\) from the blood. Arterial blood gases (ABGs) are discrete blood analyses that give a snapshot view of the gas exchange and acid- base homeostasis, providing measurement of partial pressure of \(O_{2}\) \((P_{a}O_{2})\) and \(CO2\) \((P_{a}CO_{2})\) , pH, and bicarbonates \((HCO_{3}^{- })\) in arterial blood. \(P_{a}CO_{2}\) is directly and inversely proportional to alveolar ventilation and is therefore a representative metric of ventilatory function. Only pH and \(pCO_{2}\) are depicted here in Fig. 5, but the full ABG parameters are reported in Extended Data Table 1 and discussed in the Supplementary Notes. + +<|ref|>text<|/ref|><|det|>[[114, 636, 879, 746]]<|/det|> +As shown in the prior section, the high variance from independently actuated ventilation showed mixed constructive and destructive interference (Fig. 4e,f) which led to worse ventilation outcomes. The same variance in the peak inspiratory flows and tidal volumes over time due to independent vs. synchronized actuation can be seen in Fig. 5a and Fig. 5b. In these two respiratory challenges, the subject was switched directly from the standard mechanical ventilation to our diaphragm assist system, evaluating its ability to maintain gas exchange. + +<|ref|>text<|/ref|><|det|>[[114, 764, 879, 874]]<|/det|> +In the respiratory challenge operated with independent actuation (Fig. 5a), we see high levels of hypercarbia over time. As a result, respiratory acidosis develops, which is a direct consequence of increased \(P_{a}CO_{2}\) (Extended Data Table 1a). Contrastingly, in a respiratory challenge operated with synchronized actuation in the same animal (Fig. 5b), \(pCO_{2}\) levels are relatively well maintained. The acidemia observed for this trial is rather of metabolic cause (called metabolic acidosis) (Extended Data Table 1b, see Supplementary Notes). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 877, 217]]<|/det|> +In another experiment, a respiratory trial was initiated with 2 minutes of unsupported ventilation and then switched to our diaphragm assist system, evaluating its ability to recover from a period of unsupported ventilation. During the 2 minutes of unsupported ventilation, high levels of \(\mathrm{CO_2}\) accumulate quickly over this brief amount of time (Fig. 5c). After two minutes, the diaphragm assist system is actuated with synchronized actuation. The increasing acidification and accumulation of \(\mathrm{CO_2}\) reverses and some recovery from the hypercarbic state is seen in the first 10 minutes, with a slight uptick in the \(\mathrm{CO_2}\) around 15 minutes into the challenge. + +<|ref|>image<|/ref|><|det|>[[120, 256, 880, 670]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 672, 880, 893]]<|/det|> +
Fig. 5: ABGs taken across distinct respiratory challenges. a, In a respiratory challenge operated with independent actuation, a representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \(\mathrm{pCO_2}\) values from discrete arterial blood gases taken. b, In a respiratory challenge operated with synchronized actuation, a representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \(\mathrm{pCO_2}\) values from discrete arterial blood gases taken during one full respiratory challenge with synchronized actuation. The respiratory challenges depicted in a, and b, are taken from the same animal. c, In another animal, a respiratory challenge began with a 2 minute period of unsupported ventilation and subsequent synchronized actuation. A representative set of peak actuation pressure, peak inspiratory flow, and tidal volumes, and the pH and \(\mathrm{pCO_2}\) values from discrete arterial blood gases taken. Gray shading indicates the period of time where the system is off and respiration is unassisted. Light green shading indicates the standard range
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 866, 125]]<|/det|> +of normal values for each arterial blood gas metric. Complete ABGs can be found in Extended Data Table 1. + +<|ref|>text<|/ref|><|det|>[[114, 143, 874, 253]]<|/det|> +Due to their discrete nature, in contrast to the continuous signals like flow and volume collected by our data acquisition system, the ABG data is much sparser because ABGs were only taken during a subset of respiratory challenges. For the respiratory challenges where ABGs were taken, we collect them every 2 or 5 minutes (2 minutes to capture the effect of 2 minutes of unsupported ventilation, as seen in Fig. 5c). This is captured in the Methods section with the following text: + +<|ref|>text<|/ref|><|det|>[[115, 253, 839, 290]]<|/det|> +For experiments investigating gas exchange, ABGs were collected at 2 or 5- minute intervals during the challenge. + +<|ref|>sub_title<|/ref|><|det|>[[115, 329, 210, 345]]<|/det|> +## Comment 2 + +<|ref|>text<|/ref|><|det|>[[114, 346, 880, 456]]<|/det|> +How is the level of inspiration controlled with their device? The degree of inspiration should be controllable according to the subjects needs in various clinical situations (for example, in early sepsis, it is natural to be in a hyperventilated state) but the authors do not show that their device is versatile enough to accommodate this. What happens to the subject's respiration if the bladder in the system is pressurized more? Additionally, what about the opposite where there is no need for a deep inspiration? + +<|ref|>sub_title<|/ref|><|det|>[[115, 475, 312, 492]]<|/det|> +## Response to comment 2 + +<|ref|>text<|/ref|><|det|>[[115, 511, 874, 565]]<|/det|> +We thank the reviewer for this relevant comment. We agree that in a clinical setting, the degree of inspiration should be tunable. To demonstrate this capacity, we conducted significant further experimentation that substantially improved our understanding of our device. + +<|ref|>text<|/ref|><|det|>[[114, 584, 875, 694]]<|/det|> +The degree of assistance provided by the device is mainly determined by the level of pressurization of the PAM, which is set by the user in the control system. A pressure actuation curve (selected by the user), once triggered, is transmitted to the electropneumatic regulator. In the present study, we simulate severe diaphragmatic failure in all subjects, reflected by the low unassisted tidal volumes (see Fig. 3). Therefore, the maximal possible augmentation was required to maintain respiratory homeostasis for all the subjects in this study. + +<|ref|>text<|/ref|><|det|>[[114, 713, 875, 841]]<|/det|> +Looking towards future translation, as pointed out by the reviewer, the subject might need different degrees of assistance (i.e., different levels of pressurization), depending on the clinical situation and metabolic state. To further characterize the device and understand the effect of different pressurization of the PAM on respiratory mechanics, we conducted a series of in vitro and in vivo experiments during which we adjusted the degree of pressurization (5, 10, 15, and 20 PSI). The characterization data regarding degree of pressurization is presented in our new Extended Data Fig. 2. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 90, 907, 704]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 704, 880, 888]]<|/det|> +Extended Data Fig. 2. Tuning actuation depth via level of pressurization. The actuator pressure profile for a curved waveform scaled to have a peak nominal pressure of (a) 5 psi, (b) 10 psi, (c) 15 psi, (d) 20 psi. The peak forced generated by different levels of actuation were characterized in vitro on a (e) classic Instron tensile test setup and (f) our modified flexural test setup (depicted in Fig. S5). Diaphragm displacement generated by actuations of (g) 5 psi, (h) 10 psi, (i) 15 psi, (j) 20 psi visualized via M-mode ultrasound. (k) The average diaphragm displacement per breath from one sample subject via M-mode ultrasound. (l) Tidal volume achieved via different levels of pressurization from one sample subject. Significance is indicated by \(^{*}p< 0.05\) for a two- sample t test. (m) Respiratory Campbell diagram plotting the pleural pressure- volume loops for representative breaths from different levels of actuation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 707, 106]]<|/det|> +This data supports the following update to the text of the main manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 107, 861, 180]]<|/det|> +Actuator behavior is governed by the degree of pressurization. Set pressurization waveforms are programmed to the control system and electropneumatic regulators. In vitro and in vivo characterization of actuator behavior when controlled by different pressurization waveforms is included in the Extended Data (Extended Data Fig. 1 and Extended Data Fig. 2). + +<|ref|>text<|/ref|><|det|>[[114, 199, 881, 383]]<|/det|> +Details for this characterization are updated in the Methods section of the manuscript as follows: Actuator characterization was conducted both in vitro and in vivo. For the in vitro characterization, actuator performance was measured via Instron testing. Classic tensile testing was conducted to measure the contractile force. A modified flexural bend setup (Fig. S5) was used to measure the perpendicular force applied to the diaphragm via arclength shortening. For the in vivo characterization, performance of the diaphragm assist system was evaluated through the diaphragm displacement (via ultrasonography) and the functional metrics (tidal volume, Campbell diagram) (Extended Data Fig. 1 and 2). Different pressurization shapes and levels were input into the actuator (Extended Data Fig. 1 and 2) and the resulting behavior was measured. Further details can be found in the Supplementary Information. + +<|ref|>text<|/ref|><|det|>[[115, 400, 875, 456]]<|/det|> +Detailed discussion of this new characterization data regarding different levels of pressurization are found in the below portion of the Controlling PAM actuator performance via pressurization section of the Supplemental Notes: + +<|ref|>text<|/ref|><|det|>[[114, 473, 870, 751]]<|/det|> +PAM performance can also be tuned via depth of pressurization by scaling the input curved waveform shown in Extended Data Fig. 2a to different peak pressures (5, 10, 15, and 20 psi), the resulting actuator pressure waveforms are shown in Extended Data Fig. 2a- d. The relationship between pressurization and forces generated is linear (Extended Data Fig. 2e,f) which corroborates previous McKibben characterization work24. We characterize the response of one subject to the varying degrees of pressurization. The degree of pressurization has a positive, but nonlinear effect on the amount of diaphragm displacement generated (Extended Data Fig. 2g- k). In this subject, we demonstrate tunability of the degree of augmentation via changes in pressurization, with the greatest range of responsiveness being between 0 and 10 psi. Additional increases taper off between 10 and 20 psi, which matches the understanding of how McKibben actuators operate, as they first expand and fill to their maximum volume, achieving maximum contraction, and beyond that they increase force generation24. In terms of respiratory mechanics, the degree of pressurization does not have a large effect on the change in pleural pressure (Extended Data Fig. 2m) unlike the different waveform shapes in Extended Data Fig. 2p. + +<|ref|>text<|/ref|><|det|>[[115, 767, 883, 858]]<|/det|> +Notably, interanimal variability is undeniably a factor contributing to overall performance, as evident in the varied responsiveness to the device seen in Fig. 3. Even in a case of low augmentation, we saw a nonlinear but tunable response to different levels of pressurization. The absolute degrees of augmentation shown in Extended Data Fig. 2k- m will obviously not hold across different animals, but we expect that the relative effect of tuning pressure should. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 210, 105]]<|/det|> +## Comment 3 + +<|ref|>text<|/ref|><|det|>[[115, 108, 857, 180]]<|/det|> +Comment 3Likewise, I would like to see how the respiratory mechanics change according to how fast the bladder in their system is inflated. More information should be given on this. The respiratory mechanics are shown as simple bar graphs in Figures 5a, b and c, whereas the gradient or slope of the Campbell diagram may also be important. + +<|ref|>sub_title<|/ref|><|det|>[[115, 200, 312, 216]]<|/det|> +## Response to comment 3 + +<|ref|>text<|/ref|><|det|>[[115, 218, 842, 290]]<|/det|> +Response to comment 3We have included a robust characterization of the effect of changing the manner of bladder inflation in the Supplemental Notes section titled Controlling PAM actuator performance via pressurization and in Extended data Fig 1 reproduced below, demonstrating the effect of different input waveforms on actuator forces and in vivo respiratory mechanics. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 80, 876, 855]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[112, 853, 837, 890]]<|/det|> +
Extended Data Fig. 1. Controlling actuation via different pneumatic waveforms. Input waveforms of a (a) curved, (b) square, and (c) triangle shape can be programmed into the
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 880, 254]]<|/det|> +custom- built control system. The effective output pressure of the electropneumatic regulator for the (d) curved, (e) square, and (f) triangle shape drives actuation. The PAM actuation forces were characterized for different waveforms in vitro on a classic Instron tensile test setup (g,h,i) and our modified flexural test setup (j,k,l) (depicted in Fig. S5). Input waveforms of a (m) curved, (n) square, and (o) triangle shape generate different shapes of diaphragm displacement as visualized via M- mode ultrasound. (p) Average diaphragm displacement from m,n,o. (q) Average tidal volume and (r) respiratory Campbell diagram plotting the pleural pressure- volume loops for representative breaths from different waveform shapes. Significance is indicated by \(^{*}\mathrm{p}< 0.05,^{**}\mathrm{p}< 0.01,^{***}\mathrm{p}< 0.001\) for a two- sample t test. + +<|ref|>text<|/ref|><|det|>[[115, 272, 880, 327]]<|/det|> +Detailed discussion of this new characterization data regarding rates of pressurization are found in the below portion of the Controlling PAM actuator performance via pressurization section of the Supplementary Notes: + +<|ref|>text<|/ref|><|det|>[[114, 345, 880, 493]]<|/det|> +Different input shapes explore the effect of rate of pressurization (Extended Data Fig. 1a- c). The fidelity to these idealized waveforms is limited by the control resolution of the electropneumatic regulators, and ultimately result in the output pressurization curves of Extended Data Fig. 1d- f. These actuation pressure curves ultimately govern the mechanical performance of the actuators. The actuators are characterized in vitro via tensile and flexural testing, as described in the Supplemental methods. The tensile force (Extended Data Fig. 1g- i) represents the contractile force applied to the points of attachment on the ribs, and the flexural force (Extended Data Fig. 1j- l) represents the force perpendicular to the actuator towards the diaphragm. + +<|ref|>text<|/ref|><|det|>[[113, 510, 881, 842]]<|/det|> +Different actuation pressure waveforms result in different displacements, (seen in the M- mode ultrasound in Extended Data Fig. 1m- o and quantified in Extended Data Fig. 1p), tidal volumes (Extended Data Fig. 1q) and different respiratory mechanics (Extended Data Fig. 1r). Notably, the square wave pressurization is distinct from the behavior of the curved wave and triangle wave, especially with regards to the average diaphragm displacement and the Campbell diagram. We note that the square wave achieves similar tidal volumes to the other waveforms while drawing more negative pleural pressures. The slope of the Campbell diagram, taken at the two points in the loop where, can be viewed as a representation of compliance of the system. A negative pleural pressure drives flow via the gradient from atmospheric pressure at the airway opening to the negative alveolar pressure, so we evaluate the absolute value of compliance. The slope generated by the square wave (12.1 mL/cmH₂O) is considerably lower (i.e., the system is stiffer) than that of the curved (15.9 mL/cmH₂O) and triangle wave (15.1 mL/cmH₂O), which both have slopes that more closely resemble those that of spontaneous respiration (25.6 mL/cmH₂O). These values are overall relatively stiff and are likely due to the low lung volumes for this subject. Qualitatively, we observe that the square wave results in "sharper" breaths that pull on the chest wall more aggressively compared to the gentler inflation of the curved and triangle wave, matching the much higher tensile forces generated by the square wave from in vitro testing. + +<|ref|>text<|/ref|><|det|>[[115, 860, 866, 896]]<|/det|> +The curved and triangular pressurization input are similar in their pressure- volume (PV) loops; however, the curved input achieves higher tidal volumes with marginally smaller levels of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 880, 181]]<|/det|> +diaphragm displacement (Extended Data Fig. 1p-r), which could be attributed to the shorter time in which the actuator operates at a high pressure filled state which may not provide enough time for lung filling. Overall, the curved waveform used in the majority of the study (Fig.2- 7 in the main text) represents a pressurization scheme that aims to combine the benefits of the square wave and triangular wave, generating the best tidal volumes and biomimetic PV loops. + +<|ref|>text<|/ref|><|det|>[[115, 217, 875, 272]]<|/det|> +Methods for this characterization in Extended Data Fig. 1 are described along with the methods of Extended Data Fig. 2 in Supplementary methods McKibben PAM Mechanical Characterization Methods. + +<|ref|>sub_title<|/ref|><|det|>[[115, 291, 210, 307]]<|/det|> +## Comment 4 + +<|ref|>text<|/ref|><|det|>[[115, 309, 880, 400]]<|/det|> +The authors should be commended for doing a nice job in synchronizing the device to the subject's respiratory effort. However, the trigger for this is the spirometer that is installed into the subject's airway. To really overcome the weakness of the contemporary mechanical ventilators, the authors should think of better methods that do not touch the respiratory tract to sense the intrinsic respiratory effort. + +<|ref|>sub_title<|/ref|><|det|>[[115, 420, 312, 437]]<|/det|> +## Response to comment 4 + +<|ref|>text<|/ref|><|det|>[[115, 438, 876, 510]]<|/det|> +We agree that a synchronization method that does not involve the patient airways is required to overcome the tethered limitations of contemporary ventilators and will be required for clinical translation. We therefore added two additional sections in the discussion to discuss this limitation and provide pathways for future work as follows: + +<|ref|>text<|/ref|><|det|>[[115, 530, 156, 546]]<|/det|> +First, + +<|ref|>text<|/ref|><|det|>[[114, 566, 876, 749]]<|/det|> +Some neuromuscular signals, like the electrical activity of the diaphragm (Edi), contain detailed information about both inspiration and expiration times35,36. Edi amplitude is also proportional to the neural drive, as well as the degree of contraction of the diaphragmatic muscle, therefore opening up the possibility of adaptive control. Triggering from Edi measured at the esophageal level via a feeding tube37 may be warranted to improve mechanical ventilation. This method, known as neurally adjusted ventilatory assist, is available in the clinical setting with mechanical ventilation and may improve respiratory weaning of patients that are challenging to wean36. The same principle could be applied to our diaphragm assist system; using a more upstream signal with greater information on the native respiratory effort would allow for a more robust control system. + +<|ref|>text<|/ref|><|det|>[[115, 769, 182, 785]]<|/det|> +Second, + +<|ref|>text<|/ref|><|det|>[[115, 804, 878, 895]]<|/det|> +Synchronization is critical to device performance, and thus future work lies in building a next generation control system; this includes creating a system that is cognizant of the beginning of expiration as opposed to inspiration, an automated control system that removes the error of manual titration, and further investigation of dynamic actuation curves. An ideal next generation control system aims to trigger from a more upstream neural signal—such as the electrical activity + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 847, 162]]<|/det|> +of the diaphragm- to provide an earlier signal that enables an advanced control system to optimize synchronization, removing delays and asynchrony. Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. + +<|ref|>sub_title<|/ref|><|det|>[[116, 190, 359, 216]]<|/det|> +## Minor comments + +<|ref|>text<|/ref|><|det|>[[115, 229, 547, 247]]<|/det|> +There are also some minor comments that might help. + +<|ref|>sub_title<|/ref|><|det|>[[115, 266, 224, 283]]<|/det|> +## Comment M1 + +<|ref|>text<|/ref|><|det|>[[115, 284, 879, 320]]<|/det|> +Comment M1Supplementary Video Online is not that informative as it plays in a real- time. It would be better if the video is played more slowly. + +<|ref|>sub_title<|/ref|><|det|>[[115, 339, 325, 356]]<|/det|> +## Response to comment M1 + +<|ref|>text<|/ref|><|det|>[[115, 357, 783, 375]]<|/det|> +We have amended the video to play both in real- time and at a \(0.3x\) speed for clarity. + +<|ref|>sub_title<|/ref|><|det|>[[115, 394, 225, 411]]<|/det|> +## Comment M2 + +<|ref|>text<|/ref|><|det|>[[115, 412, 630, 430]]<|/det|> +Comment M2The finding should be supported by adequate statistical analysis. + +<|ref|>sub_title<|/ref|><|det|>[[115, 450, 327, 466]]<|/det|> +## Response to comment M2 + +<|ref|>text<|/ref|><|det|>[[115, 468, 872, 522]]<|/det|> +Response to comment M2We appreciate this comment, and have detailed the statistical analysis presented in the section "Statistical analysis" in the Methods included here. We have also responded to the specific reviewers comments in the subsequent subcomments. + +<|ref|>sub_title<|/ref|><|det|>[[115, 541, 278, 558]]<|/det|> +## Statistical analysis + +<|ref|>text<|/ref|><|det|>[[114, 577, 879, 741]]<|/det|> +Statistical tests were conducted as described in the respective figure captions for Fig. 3, 4, 7, and Extended Data Fig. 1 and 2. For Fig. 3c,d and Fig. 7a- c, two- sided Wilcoxon rank- sum analyses were conducted in MATLAB (MathWorks, Portola Valley, CA, USA) via the "ranksum" function. Fig. 4e,f depicts two sets of statistical tests. A two- sided Welch's t- test without assuming equal variances was conducted in order to compare the means of the populations via the "ttest2" function in MATLAB with an "unequal" variance type specification. Additionally, a 2- sample F- test for equal variances was conducted to compare and confirm unequal variances via the "vartest2" function in MATLAB. For the Extended Data Fig. 1 and 2, two- sided t- tests were conducted via the "ttest2" function in MATLAB. + +<|ref|>text<|/ref|><|det|>[[115, 778, 870, 833]]<|/det|> +Comment M2.1. Although somewhat obvious from the graphs, there should be some statistical analysis to show the difference in the variation of peak inspiratory flow and tidal volume of Figure 3e and f. + +<|ref|>sub_title<|/ref|><|det|>[[115, 835, 342, 851]]<|/det|> +## Response to comment M2.1 + +<|ref|>text<|/ref|><|det|>[[115, 853, 875, 907]]<|/det|> +We have added significance bars for two sets of statistical tests conducted. The black bars represent the significance from a Welch's t- test to compare the mean of the two populations, and the gray bars represent significance from a 2- sample F- test for equal variances to compare + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 864, 163]]<|/det|> +the variance of the two populations. This is seen in the updated figure caption (Black significance bars are results from Welch's t- test comparing means. Gray significance bars are results from a 2- sample F- test for equal variances comparing variances. Significance is indicated by \(^{*}p< 0.05,^{**}p< 0.01,^{***}p< 0.001\) for both statistical tests.) and figure for Fig. 4. + +<|ref|>sub_title<|/ref|><|det|>[[115, 181, 241, 198]]<|/det|> +## Comment M2.2 + +<|ref|>text<|/ref|><|det|>[[115, 199, 870, 235]]<|/det|> +The pairwise comparisons should be done for Figure 5a, b, and c with the data acquired at the spontaneous respiration (SR) as the reference, not the actuator assisted ventilation (AAV). + +<|ref|>text<|/ref|><|det|>[[115, 236, 343, 252]]<|/det|> +Response to comment M2.2 + +<|ref|>text<|/ref|><|det|>[[115, 253, 876, 290]]<|/det|> +We have added the additional set of significance bars using SR (comparing SR and mechanical ventilation (MV)) as the reference in Fig. 7a- c. + +<|ref|>sub_title<|/ref|><|det|>[[115, 309, 241, 325]]<|/det|> +## Comment M2.3 + +<|ref|>text<|/ref|><|det|>[[115, 327, 803, 345]]<|/det|> +How many samples were taken for each subjects in each graph. This should be noted. + +<|ref|>text<|/ref|><|det|>[[115, 346, 343, 362]]<|/det|> +Response to comment M2.3 + +<|ref|>text<|/ref|><|det|>[[115, 364, 863, 418]]<|/det|> +We have included the range of sample size for each type of plot in the figure captions for the updated Fig. 3c,d (( \(n = 11 - 27\) breaths)), Fig. 4e,f (( \(n = 119 - 419\) breaths)) and 7a- c (( \(n = 11 - 32\) breaths)) in addition to the individual data points on the figures. + +<|ref|>sub_title<|/ref|><|det|>[[115, 437, 226, 454]]<|/det|> +## Comment M3 + +<|ref|>text<|/ref|><|det|>[[115, 456, 866, 510]]<|/det|> +In Figures 2c, d and e, when did the authors gather data after the device was turned off or on? The same questions goes for synchronized actuation in Figures 3e and f, Figures 5a, b and c. Response to comment M3 + +<|ref|>text<|/ref|><|det|>[[115, 511, 789, 530]]<|/det|> +We have made updates to the figures and figure captions to clarify the data analysis. + +<|ref|>text<|/ref|><|det|>[[115, 547, 879, 602]]<|/det|> +The data used in the updated Fig. 3c,d,e (original Fig. 2c,d,e) are gathered from the 30 seconds immediately before and after the device is turned on/off. We have added the dashed gray line graphics to Figure 3 to illustrate this, and have made the following update to the figure caption: + +<|ref|>text<|/ref|><|det|>[[115, 619, 880, 750]]<|/det|> +c,d, Comparison of the average (c) peak inspiratory flow and (d) tidal volume in the 30 second period immediately before and after the point where the assist is turned on at the beginning (left two bars per subject) and off at end (right two bars per subject) of the respiratory challenge (as represented by the arrows in b and the gray dashed lines in b- e) across 5 subjects ( \(n = 11 - 27\) breaths). Each gray dot represents one breath. e, Body weight normalized minute ventilation achieved during the 30 second period immediately before and after the assist is turned on at the beginning and off at the end of the respiratory challenge. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 483, 633]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 654, 880, 729]]<|/det|> +The data used in updated Fig. 4e,f (original Fig. 3e,f) span from 300s from the start of the challenge to the end of the respiratory challenge. The 300s exclusion aims to remove the period of time in which the animal's respiratory state adjusts to the new ventilatory state, so that Fig. 4 captures a steady state variance. We have made the following update to the figure caption: + +<|ref|>text<|/ref|><|det|>[[114, 747, 882, 800]]<|/det|> +e,f, A swarm plot comparing the steady state (e) tidal volumes and (f) peak inspiratory flows generated with independent actuation and with synchronized actuation for 6 different subjects (n = 119 - 419 breaths). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 88, 420, 483]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 501, 876, 742]]<|/det|> +The data used in updated Fig. 7a,b,c (original Fig. 5a,b,c) are gathered from representative 30 or 60 second segments from the data during and surrounding one respiratory challenge per subject. Because spontaneous respiration (SR) and the synchronized actuator assisted ventilation (AAV) both rely on the animal's native respiratory rate (range: 26- 32) while the mechanical ventilation (MV) has a set slow respiratory rate (range: 15- 20 bpm), 30 second increments were chosen for the SR and AAV segments while 60 seconds increments were chosen for the the MV segments to capture a sizeable sample of breaths. Data segments attempted to capture the closest to steady state achieved in the span of the respiratory challenge. The MV data segments were chosen from the steady state data collected immediately before the initiation of the respiratory system. SR and AAV were chosen from the end of the respiratory challenge, similar to the data selection from the end of the challenge used for updated Fig. 3c,d,e. We have made the following update to the figure caption for updated Fig. 7a,b,c: + +<|ref|>text<|/ref|><|det|>[[114, 758, 825, 833]]<|/det|> +a,b,c, Average change in (a) pleural pressure \((\mathsf{P}_{\mathsf{pl}})\) , (b) abdominal pressure \((\mathsf{P}_{\mathsf{ab}})\) , and (c) transdiaphragmatic pressure \((\mathsf{P}_{\mathsf{di}})\) per breath under mechanical ventilation (MV), actuator assisted ventilation (AAV), and spontaneous respiration (SR) taken from a representative steady- state segment from one respiratory challenge per subject ( \(n = 11 - 32\) breaths). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 100, 352, 660]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[115, 675, 226, 691]]<|/det|> +## Comment M4 + +<|ref|>text<|/ref|><|det|>[[115, 693, 475, 748]]<|/det|> +Figure 4a and b miss the legends for y- axis. Response to comment M4 Thank you. We have added the y- axis labels. + +<|ref|>sub_title<|/ref|><|det|>[[115, 766, 226, 783]]<|/det|> +## Comment M5 + +<|ref|>text<|/ref|><|det|>[[115, 784, 852, 820]]<|/det|> +The overall structure of the Discussion could be improved. The contents of each paragraphs tend to jump, making it difficult to follow. + +<|ref|>sub_title<|/ref|><|det|>[[115, 822, 328, 839]]<|/det|> +## Response to comment M5 + +<|ref|>text<|/ref|><|det|>[[115, 840, 864, 876]]<|/det|> +We thank the reviewer for this comment and have significantly re- ordered the discussion section. We have also added subheadings (Contributions, Overall limitations, Towards clinical + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 800, 124]]<|/det|> +translation) to aid clarity. We hope that it is more readable and flows better after these modifications. The full updated discussion is included here: + +<|ref|>sub_title<|/ref|><|det|>[[115, 145, 214, 161]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[114, 163, 875, 327]]<|/det|> +In this work, we use pneumatic soft robotic actuators to support and augment respiration, demonstrating acute augmentation of physiological metrics of respiration, and feasibility as a proof- of- concept device. A set of two McKibben- style PAMs surgically implanted superior to the diaphragm are capable of providing mechanical support to the diaphragm in a large animal model of respiratory insufficiency. We thoroughly characterized the in vitro mechanical properties of the device and investigated its interactions with the respiratory system and the subject, using multimodal metrics to evaluate respiratory function (e.g. tidal volume, inspiratory flow), biomechanics (cavity pressures, WOB), motion (ultrasonography and fluoroscopy), and gas exchange (ABGs). + +<|ref|>sub_title<|/ref|><|det|>[[116, 347, 236, 364]]<|/det|> +## Contributions + +<|ref|>text<|/ref|><|det|>[[114, 382, 880, 511]]<|/det|> +The diaphragm assist system generated substantial augmentation in respiratory function—measured via peak inspiratory flow (a direct metric of inspiratory function), and tidal volume and minute ventilation (metrics of ventilation)—in our most responsive subject. Subject A had the highest change in peak inspiratory pressure, tidal volume, and minute ventilation; the corresponding large augmentation in peak inspiratory pressure indicates that the volume and minute ventilation augmentation are specifically due to the soft robotic actuators augmenting the diaphragm's inspiratory function. Responsiveness to the system varied across subjects. + +<|ref|>text<|/ref|><|det|>[[114, 529, 879, 639]]<|/det|> +Variance in responsiveness is likely dependent on a combination of many factors. One factor is the level of preserved respiratory baseline. The weak response in the subject with a relatively high preserved weight- normalized minute ventilation (subject E) suggests that the assist system may have weak augmentation or even a disruptive effect in cases of well- preserved diaphragm function. Other potential factors include precise actuator placement, actuator fit, and anatomical variations. + +<|ref|>text<|/ref|><|det|>[[114, 657, 877, 840]]<|/det|> +We showed that synchronization with the native respiratory effort is a critical design element in our system. Synchronous actuation is key to consistent, low- variance respiratory waveforms and tidal volumes. Like standard mechanical ventilation, off- cycle actuation of the actuators can lead to a destructive interference with the underlying respiratory effort, resulting in a poor augmentation and poor blood acid- base balance. In evaluating the effect of synchronization on the system's ability to maintain appropriate gas exchange, we demonstrated that despite generating a similar range of tidal volumes, independent actuation led to an inability to maintain appropriate \(\mathsf{pCO}_2\) levels and resulted in respiratory acidosis. Contrastingly, in two trials of well- synchronized actuation, we observed some capacity of the device to maintain and recover baseline \(\mathsf{pCO}_2\) levels. + +<|ref|>text<|/ref|><|det|>[[114, 859, 872, 895]]<|/det|> +The control system used in this study was a simple but effective first- generation system with many directions for improvement. The synchronization triggered from airway flow—which is also + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 80, 884, 716]]<|/det|> +the metric used by gold standard clinical ventilatory support options for triggering—but flow is also the most downstream signal in neuro- ventilatory coupling. The downstream nature of the signal is a potential source of delays and asynchrony34. In order to achieve consistent assistance from breath to breath, the synchronization must be optimized for the alignment that maximizes constructive interference. The system relied on a manually titrated threshold set for the flow sensor data. It is designed to be triggered at the start of an inspiratory flow effort, which is related to \(V_0\). However, the manual nature of the system meant that if the threshold was set too low, noise in the flow signal could cause pre- emptive or false triggering (as evidenced by the negative values for \(P_0 - V_0\)). Our alignment analysis reveals two important considerations for improvements towards this goal. The first consideration is that the influence of alignment changes with the degree of preserved respiratory function, as seen with the difference in results between the intact and the severed phrenic nerve. When the phrenic nerve is severed, all diaphragm motion is governed by the actuators, and misaligned actuation with the remaining native respiratory effort—expansion of the ribcage—results in more consequential destructive interference. Whereas when the phrenic nerve is intact, the net diaphragm motion results from a combination of native diaphragm function and the effect of the actuators, because the actuators only operate along 2 discrete lines on the diaphragm. The contraction of the rest of the native diaphragm motion is still synchronized with the ribcage motion, so the effects of misalignment are less apparent. This implies that optimal alignment parameters may be different for different disease states and the control system will need to be dynamic and adaptive to changes in respiratory function, even within the same patient. The second consideration is that the actuation curve's relationship to the beginning of expiration \((V_{pk})\) is more influential than the relationship to the beginning of inspiration \((V_0)\). This implies that an updated system should trigger from a signal related to expiration as opposed to the beginning of inspiration. Some neuromuscular signals, like the electrical activity of the diaphragm (Edi), contain detailed information about both inspiration and expiration times35,36. Edi amplitude is also proportional to the neural drive, as well as the degree of contraction of the diaphragmatic muscle, therefore opening up the possibility of adaptive control. Triggering from Edi measured at the esophageal level via a feeding tube37 may be warranted to improve mechanical ventilation. This method, known as neurally adjusted ventilatory assist, is available in the clinical setting with mechanical ventilation and may improve respiratory weaning of patients that are challenging to wean36. The same principle could be applied to our diaphragm assist system; using a more upstream signal with greater information on the native respiratory effort would allow for a more robust control system. + +<|ref|>text<|/ref|><|det|>[[114, 730, 884, 896]]<|/det|> +Overall, we show that the strategy to augment the native function of the diaphragm with soft robotics acts as a form of negative pressure ventilation by driving ventilation through the generation of a negative pressure in the thoracic cavity. Our diaphragm assist system is biomechanically similar to that of spontaneous breathing, sharing a substantial portion of the work of breathing in our best responding subject. By functioning as an assist device—as opposed to completely overtaking breathing—our system has the potential to be compatible with voluntary use of the diaphragm. Maneuvers such as voluntary deep breaths or drinking through a straw—abilities related to patient autonomy and quality of life—can be preserved with this implantable ventilator strategy. Additionally, in contrast to current modes of mechanical + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 857, 144]]<|/det|> +ventilation, recapitulation of native biomechanics, as shown with this system, can avoid the deleterious effects that arise secondary to the use of positive pressure ventilation, such as barotrauma38,39 or hemodynamic changes in patients with concurrent cardiac pathologies40,41. + +<|ref|>sub_title<|/ref|><|det|>[[116, 162, 274, 179]]<|/det|> +## Overall limitations + +<|ref|>text<|/ref|><|det|>[[115, 198, 857, 272]]<|/det|> +In this study, we demonstrate the foundational work towards a soft robotic implantable ventilator. Translationally, there are many hurdles to overcome between the proof- of- concept state presented here and the ultimately envisioned system, and we discuss them in the subsequent text. + +<|ref|>text<|/ref|><|det|>[[114, 290, 877, 438]]<|/det|> +Given that we saw variable responsiveness to the device across subjects, additional studies are needed to understand what factors in system design and implantation can replicate high responsiveness. Our system could generate the low end of acceptable minute ventilations but relied on high respiratory rates to do so. Given the presence of dead space, low tidal volumes result in less alveolar ventilation than if the same minute ventilation achieved with higher tidal volumes and a lower respiratory rate. A core goal of the next generation system is to further improve the tidal volume augmentation, which will need to be achieved through both actuator design and control system development. + +<|ref|>text<|/ref|><|det|>[[113, 455, 881, 805]]<|/det|> +Here, we used the classic McKibben actuator; a more application- specific or customized actuator type may allow for further increases in tidal volumes in future work. Other factors in actuator design, such as the number, layout, and positioning of actuators, will also be critical. We demonstrated tunability of assist by controlling pressurization, but an updated design will require finer characterization. Synchronization is critical to device performance, and thus future work lies in building a next generation control system; this includes creating a system that is cognizant of the beginning of expiration as opposed to inspiration, an automated control system that removes the error of manual titration, and further investigation of dynamic actuation curves. An ideal next generation control system aims to trigger from a more upstream neural signal—such as the electrical activity of the diaphragm—to provide an earlier signal that enables an advanced control system to optimize synchronization, removing delays and asynchrony. Neural triggering via implanted electrodes would also untether the current system from the flow instrumentation, freeing the patient from interventions at the mouth or trachea. To fully realize untethering from bulky machines—like standard mechanical ventilators—the external components that control and power the system require miniaturization. Future work will aim to eventually miniaturize the system to the scale of a small backpack—one that could be worn by the patient or attached to a belt or an electric wheelchair. The process of miniaturization and portability has proved to be possible in similar complex devices, such as ventricular assist devices (e.g. Thoratec HeartMate III) or total artificial hearts (e.g. Syncardia TAH, Carmat Aeson)42–45. + +<|ref|>sub_title<|/ref|><|det|>[[118, 823, 355, 840]]<|/det|> +## Towards clinical translation + +<|ref|>text<|/ref|><|det|>[[115, 860, 870, 896]]<|/det|> +Envisioning a translation to the clinical field, the following considerations might help to optimize the management and pave the way to human application. The diseases leading to chronic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 880, 236]]<|/det|> +diaphragmatic dysfunction are numerous and feature very different pathophysiologies. Therefore, a thorough understanding of the underlying pathology as well as its specificity are critically needed to help optimize the management and anticipate complications46. Moreover, patient selection and indication will need to be clearly defined, in order to select the patients who will benefit from this therapy the most. Here, we present a generalized mechanical strategy for diaphragm support, but the parameters of actuator design or actuation control will need to be optimized and specialized per the needs of a given pathology as well as individual patient anatomy. + +<|ref|>text<|/ref|><|det|>[[114, 253, 876, 548]]<|/det|> +Owing to the complexity of the procedure, a multidisciplinary team highly trained in advanced thoracic surgery is required to build expertise and develop this technology, ideally in a high- volume center47. Technological improvement is required to provide the least invasive approach of implantation. In this regard, a thoracoscopic route might be beneficial and will be the subject of future work. Given the invasive nature of implantable devices, the diaphragm assist platform is targeted towards patients with chronic- to- permanent ventilator dependence. We recognize that surgery in patients suffering severe diaphragm dysfunction causing respiratory failure can carry a high morbidity and mortality. Peri- operative complications can be numerous; one of the most feared is the worsening of the pulmonary status, which may itself precipitate the need for long- term ventilation48. Nevertheless, it has been well demonstrated that complex thoracic surgery is feasible even in very frail patients. Lung transplantation for terminal respiratory disease49 is one of the most striking examples. Thus, surgery could still be considered in a suitable target population that would ultimately benefit from this mechanical augmentation of diaphragm function, such as a range of neuromuscular disorders. The concept of diaphragm assist is in itself a means of preventing further complications from chronic respiratory failure and preserving key aspects of quality of life- like speech and mobility. + +<|ref|>text<|/ref|><|det|>[[114, 565, 872, 750]]<|/det|> +Due to the focus on feasibility, we acknowledge that there are limitations in these acute studies from the lens of regulatory approval and clinical translation. We do not study device biocompatibility or long- term device operation. The device was constructed from types of polymers that are already used in established medical devices50- 53, such as poly(ethylene terephthalate) (PET) and polyurethanes (See Supplemental Information). Because our device focuses on mechanical interaction, as opposed to biochemical interactions with the body, the materials used in the device can easily be substituted with regulatory- approved materials in future iterations. With improved performance and stability, future long- term studies will need to investigate the long- term effects of the system including tissue remodeling and the ability to provide full- time respiratory support. + +<|ref|>text<|/ref|><|det|>[[114, 767, 881, 896]]<|/det|> +Although this technology requires further advancements in the net tidal volumes it can generate before it can fully match the ventilation capacity of a current mechanical ventilator, it is the first study to report the ability to rescue ventilation with an implantable ventilator. We envision further translational potential of this technology when combined with the development of smaller and more portable pneumatic energy sources54,55 as the field of soft robotics advances. With the integration of a portable pump and control system in the future, this technology could provide an additional level of patient autonomy via increased mobility. Motivated by the encouraging results + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 857, 144]]<|/det|> +of this study, we believe this technology, with optimized design, has the potential to provide a radically different ventilation technology that preserves key metrics of quality of life for people with end- stage mechanical respiratory failure. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[25, 0, 1000, 0]]<|/det|> +Rebuttal 2 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[79, 117, 920, 205]]<|/det|> +As requested, we carefully considered comments of Reviewer 3. In the paragraph "Effect of synchronization on blood gas exchange", we clarified the number of subjects included for this analysis (comment 1.1). We agree that the acidemia observed in Fig. 5b is of mixed cause and we modified the text accordingly (comment 1.2). Although the discussion is quite long (comment 2), the current version has been drastically improved thanks the suggestions from both reviewers. We believe that shortening the discussion would affect its quality. Therefore, we didn't modify it, unless the Editor feels it is essential. + +<--- Page Split ---> diff --git a/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/images_list.json b/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/supplementary_0_Transparent Peer review file.mmd b/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/supplementary_0_Transparent Peer review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8cecb33401a9df96e0b7b8d55b91e69e3cc67aaa --- /dev/null +++ b/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/supplementary_0_Transparent Peer review file.mmd @@ -0,0 +1,647 @@ + +# nature portfolio + +# Peer Review File + +## Many plants naturalized as aliens abroad have also become more common within their native regions + +Corresponding Author: Ms Rashmi Paudel + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +This paper addresses a highly novel question, namely whether species that are successful as non- native species have also become more successful within their native range. I am familiar with the invasions literature and I am unaware of any previous study that has addressed this question. The analyses themselves are conducted soundly and the work is clearly described. I have no major concerns about this manuscript. I do have one suggestion that I believe should be addressed in some way, as well as several additional thoughts that could add additional interpretation to their findings. I detail these considerations below. + +The one issue that I believe needs to be better addressed has to do with their choices about where to split the native range data, temporally, i.e., on deciding on a specific year to split "historic" from "recent" distributions with a region. A few of their data sets have natural splits between these periods, e.g., Denmark (with historic data from the 1800s and modern data from less than a decade ago), but more than half of their data sets appear to have been arbitrarily split at 1990 or 2000, e.g., the Netherlands data set is split as before 1990 and after 1990. At a minimum the manuscript should be revised to explain the rationale for these splits. Why are some split at 1990 and why others at 2000 or even, in one case, at 1971. I'm guessing they have some reasonable reason for this, but this isn't explained and so it makes the reader feel unsure about these decisions. They mention one data set where they look at multiple possible splits, but I really would have liked to have seen an analysis with a few more of these data sets that considered if the year of the split (e.g., 1980 vs. 1990 vs. 2000) ends up impacting the patterns observed. I imagine that their results are pretty robust to the precise year of splits, but I'm not sure. I think addressing this in some way would be useful, even if was just to show this with 2 or 3 more of their study regions. If it proves impractical to do such analyses then I would still expect to see a short paragraph added (or perhaps 2- 3 sentences added to an existing paragraph) to the discussion that addresses this concern. + +This is super minor, but on line 64 they state that approximately \(25\%\) of the planet's species are threatened with extinction. This seems a little high to be well supported. I would like to see the number revised and or the addition of citations to support this claim. + +This study is likely to have an artifactual bias against detecting change in occupancy of species that were historically abundant. Note that this makes their key finding "harder" to detect, i.e., they found their result in spite of the fact that there's a bias making this result less likely to be observed. This is worth discussing, particularly in the context of explaining why they find a stronger connection between historic occupancy and naturalized success vs. change in occupancy and naturalized success. The issue is that any species that was historically common, i.e., found in most grid cells within a region, cannot add many new grid cells, since they already occupy most of them. This consideration will vary among regions depending upon how fully the common species occupy the entire set of grid cells. So, if the most common species only occupies \(40\%\) of the grid cells in the historic period than this consideration won't be too important; alternatively if the most common species historically occupied \(90\%\) of the grid cells (and could only at most occupy the final \(10\%\) ) than this consideration will be very important. Looking at Fig. S1. I would guess that a region like Austria had common species that occupied almost all of the grid cells historically, which would explain the bow downward in the most common species in the plot, whereas Great Britain, probably did not. In any case, regardless of my exact speculations, I think mentioning this would probably be worthwhile. + +While certainly not essential, it would be nice to know if the common species, which became more common through time in + +<--- Page Split ---> + +the native range, belong to some easily identifiable group. I can imagine, for example, that most of these species might be agricultural weeds, or perhaps pasture species, etc. Any easy to run analyses that could help elucidate this would provide additional context to the work. + +I was a bit surprised the manuscript doesn't mention the "distribution- abundance" relationship, particularly surrounding the discussion of change in local abundance. The distribution- abundance relationship is well described in Jim Brown's book of Macroeology and there are a number of journal articles published on that topic in the 80s and 90s. Basically the pattern (which seems to be pretty robust to taxonomic groups and spatial scales) is that there is a positive correlation between frequency of occurrence and average abundance at sites of occurrence. So, species found at lots of sites tend to also be more abundant at those sites, whereas species found at few sites tend to also have low abundance where they are found. There is disagreement about why this happens, but not really disagreement that it happens. Sometimes there's a more triangular (less linear) relationship, such that some species found at few sites are abundant where they are found, but what never happens is having species found at lots of places that on average are found in low abundance where they do occur. What this means, relative to this paper, is that the species that have increased in frequency are also very likely to have increased in abundance as well. + +Dov Sax + +(Remarks on code availability) not applicable + +Reviewer #2 + +(Remarks to the Author) + +The aggregated dataset is impressive. The long history of plant records and surveys in Europe allows a unique gathering of information on plant species occupancy and the authors investigate long- lasting questions on the association between species commonness and their ability to naturalize globally. The research questions are relevant to invasion ecology and insights into these dynamics could have important implications to allow managers to target efforts of early detection and control. I also reviewed the code and analysis for Austria, and I am extremely satisfied with the documentation provided and the conciseness of it - great job! With that said, I bring below several important overall topics to consideration: + +Given (i) the constraints in including all 10 countries/regions in a single model, the authors' solution by considering them as independent "datasets" modeling each region separately although many share political boundaries, (ii) the low variability explained by the models, and (iii) the narrow geographical scope of the sources regions of species to establish elsewhere, I am having a hard time to be convinced that early occupancy and occupancy change index are driving forces of the number of global regions with naturalization for a given species, and the broad generalizations brought in the title (as if all naturalized plants across the globe follow a similar pattern) and manuscript. Interestingly, the authors bring such caution themselves in L208- 209, and it reinforces that the generalization brought up in this manuscript can be unrealistic. + +My next big concerns rely on the predictors chosen to be in the model, and not exploration effect sizes (only significance was reported). Given that early occupancy is used to calculate the occupancy change index, one would expect a high correlation among them as well as a lack of independence, producing confounded effects of each variable on the global naturalization metrics (naturalized vs not naturalized; and number of global regions with naturalization). How correlated the predictors are? How can you justify the use of both variables in the same model while interpreting their effects? With respect to effect size and model interpretation, hurdle model effect sizes need to be back- transformed to be interpreted adequately. However, the values presented in Table 2 are values directly extracted from the model outputs. + +Across all models, the predictors explained a low portion of the variability within the response variable (13% to 28%). I wonder if the effects of early occupancy and the occupancy change index would have a strong effect (dependent on the model) if other important variables were included, such as predictors that account for human influence (such as Global Human Modification; Kennedy, C. M., Oakleaf, J. R., Theobald, D. M., Baruch- Mordo, S., & Kiesecker, J. (2018). Global human modification. https://doi.org/10.6084/m9.figshare.728307, figshare), productivity (net primary productivity - NPP), and other environmental variables that have been shown to strongly influence the establishment of non- native plants across the globe. Therefore, I would recommend incorporating other drivers of the establishment (such as the ones I have just mentioned) in the model to allow a more accurate understanding of the relative importance of the different forms of occupancy (if both can actually be in a single model) investigated in the manuscript. + +Overall, the consistency in terminology used can be largely improved. Doing so, will allow the readers to follow the thought process and story of the paper more easily, as well as connect the different components across the sections. Here are my recommendations: (1) the words 'countries', 'native range', and 'regions' are used interchangeably, when they shouldn't. I recommend if using regions, to clarify in their first appearance that they correspond to the entirety of their respective country in X number of cases. I would prefer to not read 'native range' in the context of the paper as be synonym of a region, given that, as pointed out in the paper (figure S6) there are several species that are native to multiple countries/regions (side note: the number of common species across countries/regions should be added to the methods section). (2) I strongly suggest the revision of the terminology associated with referring to non- native species as aliens. I suggest the authors revise the discussion provided here (https://doi.org/10.1111/brv.13071) and here (https://doi.org/10.1002/fee.2561), and consider a complete switch to 'non- native', including in the title. (3) the use of 'at home' and 'winners at home' is confusing, and it is not consistently used across the manuscript. Particularly when the 'winners at home' are associated with the distribution of + +<--- Page Split ---> + +species within a political boundary (such as country) rather than its native range (which more frequently than not does not follow such boundaries). Additionally, by referring as "whether species that are increasing at home" [L99] implies that the authors directly measured direct expansion in species range, which wasn't the case and was explained in the methods on L3314- L317. (4) the interchangeable use of "changes in native- range commonness" and "occupancy change index" makes it hard to follow. + +Legends of figures: I would suggest the revision of the legend of all figures and tables to be completely understandable in isolation. For example, in table 2 the model results show results for both "naturalized or not" and for the "number of regions where naturalized", not only the later as directed. The understanding of hurdle models can be not trivial, so the more detailed explanation of what exactly the Bernoulli and zero- truncated count parts means biologically is strongly encouraged. Another example, Figure S6 legend is quite uninformative, and can only be understood after reading the main text. I pointed out here a couple examples, but all legends should be revised for clarity. These are suggestions that I believe will improve the accurate understanding of your paper and its biological implication. + +Early occupancy was not clearly explained anywhere in the main manuscript or supplement. How was this data specifically obtained given the earliest period of data available for a country/region? And more generally, how occupancy was defined? Let's say there is a period of 3 years and in y1 a species was present in 6 out of 10 cells; y2, in 4 cells being 2 new ones compared to y1; y3 in 7 cells being one new one. What is the occupancy of this species? Given the disparity of sources and formats the data was obtained in the first place for each country/region, was the count of cells to obtain occupancy consistent across the country/region? How? + +I believe that the abstract does not contain enough information to understand how the knowledge gap was analyzed, so I suggest a thorough revision. For example, in L45- L46, "particularly common plant species" where? The abstract presents the results from the truncated negative binomial portion of the model only, therefore defining what 'global naturalization' means in L46- 47 is necessary. Also, a basic ecological interpretation/definition of "occupancy- change index" and "early period occupancy" would allow a larger audience to benefit from these findings. The latter was not formally defined in the paper, and it hampers the understanding of the choice of approach and the findings, as I mentioned in another piece of this review. Lastly, the abstract would gain a larger audience by having a closing statement with the implication for management and policy- related actions for species that follow the pattern described in this manuscript. + +Overall structure of the paper: In my first read of the main paper, I would argue that the content necessary to fully understand the analysis and research findings isn't present. The authors should keep in mind that the methods section only appears at the end of the paper, so other sections should provide enough information about the methods and definitions of terms used that allow the readers to accurately understand the results and discussion. + +How similar are the boundaries of the 10 focal regions compared to the same regions from GloNAF? + +Specific comments and recommendations: + +- I am curious to understand why "declining species" was a relevant keyword selected by the authors. +- L84: add citation to support statement. +- L88: a good example in which countries and ranges are used interchangeably. Clarifying language would improve the understanding and cohesion of this paper. +- L104: the statement "largely the same species" has dubious meaning, clarify. +- L105: the statement "two (or more) periods" has no context up to this point and hinders the reader from grasping the methods used in the paper in general terms. Also, to the best of my understanding of this paper, for each country/region, each main model shown in the main manuscript contains only the comparison between two time periods. Adding "or more" is confusing and might better if brought up later when nuances in the results are explained. +- All content presented in the supplement should be referenced in the main text. +- L106: "for each native species in each region" how about species that are present in more than one region? There is some mention of them when Figure S6 is referred to, but given the proximity of each of the countries/regions used in this study some short explanation on why region rather than native range extrapolating political boundaries were chosen. +- L107: "occupancy-change index" hasn't been explained and needs clarification. +- L109-110: "the number of regions where the species has become naturalized" this text is confusing. It seems that one is referring to the 10 regions, but in fact, it is from the regions defined by GloNAF to defined where a species is naturalized or not. +- L110: "early period" is mentioned in the abstract and here, but the term hasn't been described yet. +- L121-122: this statement contradicts statements on L314-317. These species are more common than what would expected given their occupancy in the early period. +- L125-126: with respect to "the zero-truncated count part of the hurdle model, not with the Bernoulli part", I suggest changing the language similar to above: the likelihood of being naturalized outside native range vs naturalized in more regions at the global scale. +- L131: to convey the message more clearly, it might be helpful to associate the occupancy- change index as a metric of commonness early on in the text and use this term across the paper. +- L136: this statement "increased in occupancy" is unclear. Since when? +- L145-148: statements seem repeated from the introduction. I suggested the authors be mindful of which information is essential and necessary in the discussion by focusing on an in- depth discussion of the results. +- L149-150: what is the environmental variability within the native range studied per species? is the set of species used in this study representative of species distributed in a wide range of environmental conditions? +- L152-154: are these traits present in the focal species studied here? Could such information be pulled from global + +<--- Page Split ---> + +databases, such as TRY, and incorporated here? + +- L186-187: if the early period chosen had a specific reasoning for it, it should be clarified in the introduction, not in the discussion. + +- L202-204: I cannot follow the connection of this sentence to the previous after. "richer-get-richer" is a term generally used in the context of species richness, and it doesn't seem to apply here, but also the directionality of the negative is the opposite in the sentence? Consider revising and defining "Matthew effect" and or "richer-get-richer". + +- L223: how were "losers" quantified in this paper? Similar language also shows up in the keywords, and it makes it confusing. + +- L228-229: why habitat specificity might have not changed? + +- L245-251: this discussion is really interesting and I would suggest to be the driving force of the importance of this study and findings (if changes in the methods are performed and conclusions hold) - to aid ways in which findings from core science can be transferred to managers and policymakers. + +(Remarks on code availability) + +the results for "Austria" are reproducible - from analysis to figures. According to the authors and my understanding of their methods, each model was run the same way, only the input data for other regions (data available on figshare) changes. + +## Reviewer #3 + +(Remarks to the Author) + +The study aims to compare whether the changes in select plant species' native range size correlates with naturalization history elsewhere. The authors examine changes in grid occupancy drawing on historic grid- based surveys of the vascular flora of 10 areas in Europe. The premise is interesting and the results, though correlative, make intuitive sense. However, there are some methodological concerns that render the conclusion that plants that have naturalized as aliens abroad have also become more common in their native range unearned. + +As the authors note, there are many definitions of commonality, and arguably the one being used in this study is not truly a metric of such. At best, the authors are examining a proxy of range size. The authors do a good job of mentioning potential limitations - e.g., one cannot know how abundant these species are within each grid cell. Further, it is likely that the surveys upon which the study relies were conducted with varying protocols and specific objectives, certainly across regions and possibly even over time. Even if the surveys were more or less standardized, the analyses conducted here can produce misleading results for species that have been recorded more efficiently/accurately in one survey than the others. + +More importantly, the assayed regions do not represent the full native range of the species examined. It is possibly for any given species that while, say, in the Czech Republic its range has increased, the range may have decreased in other parts of its native range. Thus, it is unknown how a species' entire native range size has changed. Though the authors claim that the general positive correlation between occupancy- change indices they observed among regions for the same species indicates that native range 'winners' and 'losers' were generally consistent across regions, these regions may constitute a small or biased sampling of these species' entire native ranges. Also, many of the species that have naturalized elsewhere are known to have fairly large native ranges that extend well beyond the regions included in the study. Further, it seems that only 44 species (among thousands) were present in multiple regions. Along these lines, without more context regarding the full native ranges of these species it is difficult to say whether the results of this study, though suggestive, truly provide strong evidence that many plant species that are spreading as naturalized aliens around the globe also have high occupancies or are increasing in occupancy in their native range. + +GloNAF regions are used as the unit of analyses regarding naturalized ranges. However, the manuscript never mentions what these regions are. How were they defined? Based on the map provided in the supplements, it seems that these regions largely follow geopolitical boundaries and come in many shapes and sizes. Thus, the number of regions where a species has become naturalized may not be a suitable metric for the degree of global naturalization (and comparison with occupancy in a limited sampling of these species' native ranges). + +The methods require more detail. Pertinent information is often relegated to the supplements or other publications. For instance, the authors should note how many species were examined in the main text so that the numbers they present and discuss can be understood in context. While it is fine to refer to methods in previous studies, there should at least be enough information in the manuscript for the reader to be able to interpret the results. For instance, it was necessary to refer back to Telfer (2002) repeatedly to understand the figures presented in the results as well as some of the choices made in the study. Along these lines, the grid counts for each region were not done the same way. For instance, in Denmark, the number of occupied grid cells of each species in each region was calculated by multiplying the regional abundance of each species by the total number of referenced grid cells for each region, combining the grid- cell data for each taxon across the 11 regions of the country that were surveyed to get one single value. In contrast, simple grid cell counts were used in some other regions. While there is no reason not to use available data, this makes the results from each region (which were modeled separately) less comparable, and I recommend that the authors harmonize the approach to grid cell counting and present those results as well. + +Additional comments: + +The 'winners' and 'losers' angle seems a bit colloquial. + +Table 1 is not referenced in the text correctly. + +Fig S6 - x and y are not defined. + +<--- Page Split ---> + +Unscale the occupancy index when presenting and discussing the results – the scaled values are confusing to interpret and the index is already ultrametric. + +The layout of Fig.2 is a bit confusing with the inset with multiple abbreviations and asterisks. Also, why not just replace this figure with the corresponding one in the supplements that show the raw data as noted in the caption (S5)? Where were the 1/6 and 5/6 quantiles chosen for illustration? + +As GloNAF data are not freely accessible, please present information on which specific regions each species was naturalized in. + +Are the identities of the grid cells occupied by each species known? If so, perhaps the potential drivers of range change could be examined. + +The "Gridcells_earlyperiod" and "Gridcells_laterperiod" values for Thierache are not whole numbers—according to the metadata these should be simple counts of the number of cells occupied by each species and the supplementary methods do not state any special circumstances (unlike Germany or Denmark). + +(Remarks on code availability) I did not try running the code but it looked reasonable. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The authors have addressed all of my concerns. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +I appreciate the careful point- by- point revisions given in response to my previous comments and concerns. I appreciate the thorough revision of the text to improve the consistency of terms used—the main text is now a lot easier to digest. Moving forward, I have two broad, major comments that are detailed below. Then, those are followed by minor comments: + +1) I mentioned this before and I noticed that Reviewer 3 also made a comment on this: using the regions as units of native ranges, particularly because they follow political boundaries. So, could you provide the supplement with how many species are present across all regions? How many species are present in all regions but one? And so forth? And how many species are uniquely present in a single region? + +2) Woodiness was added in complementary models as a way to address some of the concerns of Reviewer Dov Sax. If this inclusion is kept, the main text would need some introduction of the relatedness of woodiness, range expansion, and probability of becoming naturalized, so, therefore, justifying why this a reasonable trait to be evaluated. Lines L171-173 do not justify sufficiently. I would pull as base of some of the arguments and justification given in the rebuttal. + +Minor comments: + +Results: The tables with the main results of your models (i.e., mention of tables S14- S30 should potentially show up earlier, as it is the results of the main models (without woodiness) + +L91- 93: The statement is somewhat confusing. Also, should it be "increasing their occupancy" rather than "increasing" only in L92? Please, revise + +L103: do you mean "range over time"? + +L199- 200: would you be able to provide either a table or a simple graph per region with how many species out of the total per region were present in all its grid cells? This would help the reader to be aware of how many species, from the poll studies, have this pattern. + +L228: "...species with high early..."? + +(Remarks on code availability) I reviewed the code during the first round of revisions. + +Reviewer #4 + +(Remarks to the Author) + +<--- Page Split ---> + +This is a broad analysis staying that certain plant species, likely due to a combination of human actions and the plant features, are favored under human uses of the landscape in their ranges and in new regions. The novelty relies on including change in abundance/occupancy in the native range as a predictor of naturalization somewhere else. These findings could be used to generate list of species that could become invasive, lists that could be compared with already generated watch lists to assess how much information this predictor is adding. + +Since changes in occupancy/abundance were not analyzed as a function of other drivers than time, e.g., human activities targeting particular habitats/plant communities, results might very indirectly be assessing the causes of naturalization, because increase in occurrence and naturalization might have to do with habitats selected rather than intrinsic features of the plant species. This is a point brought by the reviewers that has been dismissed by the authors (see next comment). Analyzing what it made those species increase in their native and introduced ranges would be of greater consequence for management and conservation. + +Much more informative would have been to analyze features of the species that were already abundant and that increased their occurrences, e.g., are ruderal species over- represented in that group? What are the main traits characterizing those species? That again would provide more useful information for management and conservation. Maybe the data is not available for all, but it could be done for the ones that it is. Line 207- 216 make that point. Many studies are using global trait data sets to do it, if authors have decided not to do it that's their choice but claiming that the reason for not doing it is that that information is not available is not accurate. + +It looks like early occupancy, and to some extent woodiness, are a better predictor of naturalization than change in occupancy. Table S3, this should be emphasized more in the main text because data on changes overtime may not be available, but actual native range and woodiness are, and those could be used on their own as predictors. Especially considering that change in occupancy is being predicted by early occupancy. Also, adding information on how much variance was additionally accounted for by including change in occupancy, vs a model with early occupancy and woodiness only, would help to understand the scope of this predictor. + +My suggestion would be to change 'region' for countries. Region usually indicates ecological, e.g., climatic, differences, but these data sets reflect political units. Sorting the data into actual ecological regions might have shown more interesting/informative results. + +It is not clear if changes in occupancy overtime were standardized by the period of time between census, i.e., more change expected if longer time between censuses. + +I can't tell the difference between Table S3 and the ones that follow for each country, information is the same. + +(Remarks on code availability) + +The analyses are done using standard techniques and standard software packages. + +Version 2: + +Reviewer comments: + +Reviewer #2 + +(Remarks to the Author) + +I have now revisited the authors' responses to the inquiries raised by Reviewer #4 and find that they have made appropriate revisions and/or provided clear and well- justified explanations, both in the rebuttal and in the manuscript, for not implementing certain suggestions. I am satisfied with the current version of the manuscript. + +As Reviewer #2, I also appreciate the authors' thorough and clear responses to my own comments. Thank you for the careful attention to detail in your point- by- point reply. + +Reviewer #2 + +(Remarks on code availability) I reviewed the code during the first round of revisions. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Dear reviewers, + +We have now revised the manuscript entitled "Plants that have naturalized as aliens abroad have also become more common at home during the Anthropocene" ("Many plants naturalized as aliens abroad have also become more common within their native regions" in revised version), based on the helpful and constructive comments. Below we provide our point- by- point responses to the comments. Please, note that the line numbers refer to the clean version of the manuscript with highlights and our responses are in blue. + +Sincerely, RASHMI Paudel (on behalf of all authors) + +Reviewer #1 (Remarks to the Author): + +This paper addresses a highly novel question, namely whether species that are successful as non- native species have also become more successful within their native range. I am familiar with the invasions literature and I am unaware of any previous study that has addressed this question. The analyses themselves are conducted soundly and the work is clearly described. I have no major concerns about this manuscript. I do have one suggestion that I believe should be addressed in some way, as well as several additional thoughts that could add additional interpretation to their findings. I detail these considerations below. + +RESPONSE: We thank the reviewer (Dov Sax) for his positive and constructive comments. + +The one issue that I believe needs to be better addressed has to do with their choices about where to split the native range data, temporally, i.e., on deciding on a specific year to split "historic" from "recent" distributions with a region. A few of their data sets have natural splits between these periods, e.g., Denmark (with historic data from the 1800s and modern data from less than a decade ago), but more than half of their data sets appear to have been arbitrarily split at 1990 or 2000, e.g., the Netherlands data set is split as before 1990 and after 1990. At a minimum the manuscript should be revised to explain the rationale for these splits. Why are some split at 1990 and why others at 2000 or even, in one case, at 1971. I'm guessing they have some reasonable reason for this, but this isn't explained and so it makes the reader feel unsure about these decisions. They mention one data set where they look at multiple possible splits, but I really would have liked to have seen an analysis with a few more of these data sets that considered if the year of the split (e.g., 1980 vs. 1990 vs. 2000) ends up impacting the patterns observed. I imagine that their results are pretty robust to the precise year of splits, but I'm not sure. I think addressing this in some way would be useful, even if was just to show this with 2 or 3 more of their study regions. If it proves impractical to do such analyses then I would still expect to see a short paragraph added (or perhaps 2- 3 sentences added to an existing paragraph) to the discussion that addresses this concern. + +<--- Page Split ---> + +RESPONSE: We now provide information on the choices of the splits (lines 323- 324) as "Most of the data sources provide data for only two time periods, limiting us to the temporal splits available in the original datasets". Most of the datasets provided data for only two time periods and we were therefore limited to the splits chosen in the original datasets. For the Netherlands, however, we can also extract the grid- cell numbers using different years of the split, therefore, to see how robust the results are with regard to the chosen split 1990, we now also extracted data using the year 2000 as split. We chose 2000 because it was also the year of split for some of the other datasets. Like we already found for Great Britain and Ireland, the patterns for the Netherlands were very similar for the different years of the split. We added these results to the Supplement (TableS30). + +This is super minor, but on line 64 they state that approximately \(25\%\) of the planet's species are threatened with extinction. This seems a little high to be well supported. I would like to see the number revised and or the addition of citations to support this claim. RESPONSE: We now specify that the \(25\%\) applies to the animal and plant species that have been assessed, and we refer to the IPBES 2019 report (lines 64- 65). + +This study is likely to have an artifactual bias against detecting change in occupancy of species that were historically abundant. Note that this makes their key finding "harder" to detect, i.e., they found their result in spite of the fact that there's a bias making this result less likely to be observed. This is worth discussing, particularly in the context of explaining why they find a stronger connection between historic occupancy and naturalized success vs. change in occupancy and naturalized success. The issue is that any species that was historically common, i.e., found in most grid cells within a region, cannot add many new grid cells, since they already occupy most of them. This consideration will vary among regions depending upon how fully the common species occupy the entire set of grid cells. So, if the most common species only occupies \(40\%\) of the grid cells in the historic period than this consideration won't be too important; alternatively, if the most common species historically occupied \(90\%\) of the grid cells (and could only at most occupy the final \(10\%\) ) than this consideration will be very important. Looking at Fig. S1. I would guess that a region like Austria had common species that occupied almost all of the grid cells historically, which would explain the bow downward in the most common species in the plot, whereas Great Britain, probably did not. In any case, regardless of my exact speculations, I think mentioning this would probably be worthwhile. RESPONSE: We now discuss this consideration in lines 199- 205. + +While certainly not essential, it would be nice to know if the common species, which became more common through time in the native range, belong to some easily identifiable group. I can imagine, for example, that most of these species might be agricultural weeds, or perhaps pasture species, etc. Any easy to run analyses that could help elucidate this would provide additional context to the work. + +<--- Page Split ---> + +RESPONSE: We agree that, although it would not be essential for answering our research question, adding such information would be very interesting. Unfortunately, habitat information is currently not available for all 3920 species in our datasets. Instead, we now added information on woodiness of the species (where we assume that woody species are typical for forest habitats and non- woody species for open habitats). We found that while woody species had higher occupancy- change values than non- woody species in six of the 10 native regions (Table S2), woody species were less likely to become widely naturalized. Nevertheless, the positive association between naturalization and occupancy change remained largely unaffected by inclusion of woodiness as an additional variable in the hurdle models. This shows that our results are robust. We added the results of the additional analyses in the Supplements (Tables S3, S4- 13).) and refer to them in the Discussion (lines 173- 185 & lines 238- 245). + +I was a bit surprised the manuscript doesn't mention the "distribution- abundance" relationship, particularly surrounding the discussion of change in local abundance. The distribution- abundance relationship is well described in Jim Brown's book of Macroeology and there are a number of journal articles published on that topic in the 80s and 90s. Basically the pattern (which seems to be pretty robust to taxonomic groups and spatial scales) is that there is a positive correlation between frequency of occurrence and average abundance at sites of occurrence. So, species found at lots of sites tend to also be more abundant at those sites, whereas species found at few sites tend to also have low abundance where they are found. There is disagreement about why this happens, but not really disagreement that it happens. Sometimes there's a more triangular (less linear) relationship, such that some species found at few sites are abundant where they are found, but what never happens is having species found at lots of places that on average are found in low abundance where they do occur. What this means, relative to this paper, is that the species that have increased in frequency are also very likely to have increased in abundance as well. + +RESPONSE: We thank the reviewer (Dov Sax) for pointing this out, and we now mention the "distribution- abundance" relationship in the Discussion as "The local abundance of species is usually positively related to the other measures of a species' distribution [e.g. 50, 51]. Previous studies across various spatial scales and taxonomic groups, have also shown that species increasing their occupancy are also very likely to increase in abundance at the sites where they occur [e.g. 52, 53]." (lines 278- 281) and refer to Jim Brown's book in the Introduction (line 98, reference number 34). + +Dov Sax + +Reviewer #1 (Remarks on code availability): + +not applicable + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +The aggregated dataset is impressive. The long history of plant records and surveys in Europe allows a unique gathering of information on plant species occupancy and the authors investigate long- lasting questions on the association between species commonness and their ability to naturalize globally. The research questions are relevant to invasion ecology and insights into these dynamics could have important implications to allow managers to target efforts of early detection and control. I also reviewed the code and analysis for Austria, and I am extremely satisfied with the documentation provided and the conciseness of it - great job! With that said, I bring below several important overall topics to consideration: + +RESPONSE: We thank the reviewer for the compliments and the constructive comments. + +Given (i) the constraints in including all 10 countries/regions in a single model, the authors' solution by considering them as independent "datasets" modeling each region separately although many share political boundaries, (ii) the low variability explained by the models, and (iii) the narrow geographical scope of the sources regions of species to establish elsewhere, I am having a hard time to be convinced that early occupancy and occupancy change index are driving forces of the number of global regions with naturalization for a given species, and the broad generalizations brought in the title (as if all naturalized plants across the globe follow a similar pattern) and manuscript. Interestingly, the authors bring such caution themselves in L208- 209, and it reinforces that the generalization brought up in this manuscript can be unrealistic. + +RESPONSE: We did not intend to say that all plants that have naturalized have also become more common at home. We have now carefully checked the text and toned down any broad generalizations that are not directly supported by our data. For example, to make it clear that not all plants that have naturalized have become more common at home, we now write "Many plants ..." Instead of just "Plants ...". Although we used early occupancy and the occupancy- change index as predictors in the models, and naturalization as response variable, we did not imply that early occupancy and the occupancy- change index are the driving forces of the number of global regions with naturalization for a given species. Instead, we believe that our results suggest that both commonness at home and naturalization elsewhere are correlated because they share similar drivers. We now mention this more explicitly (lines 102- 104 & 156- 157). + +My next big concerns rely on the predictors chosen to be in the model, and not exploration effect sizes (only significance was reported). Given that early occupancy is used to calculate the occupancy change index, one would expect a high correlation among them as well as a lack of independence, producing confounded effects of each variable on the global naturalization metrics (naturalized vs not naturalized; and number of global regions with naturalization). How correlated the predictors are? How can you justify the use of both variables in the same model while interpreting their effects? + +RESPONSE: We can understand the reviewer's concern about possible correlations between early occupancy and the occupancy- change index. However, the main reason why we chose to use the + +<--- Page Split ---> + +approach by Telfer et al. (2002) for calculating the occupancy-change index is that this approach avoids such a correlation. The occupancy-change index corresponds to the residuals of the regression of logit-transformed latter occupancy on logit-transformed early occupancy. So, for each early occupancy value, we have a symmetrical distribution of negative and positive occupancy-change index values (i.e. residuals), as can be seen in Fig. S4. We now explain this more clearly in the manuscript (lines 400-402). We also mention at the end of the Introduction (lines 116-117) that the occupancy-change index is not correlated with initial occupancy. Nevertheless, we now also calculated Pearson correlation coefficients between early occupancy and the occupancy-change index, and they were indeed low: + +
RegionPearson correlation between early occupancy and occupancy change indexP value
Austria-0.042&lt;0.05
Czech Republic0.0400.087
Denmark-0.0050.871
Flanders-0.0260.454
Germany0.0360.137
Great Britain0.176&lt;0.01
Ireland0.0630.057
The Netherlands0.0160.595
Switzerland0.0030.889
Thiérache-0.0140.703
+ +Regarding the effect sizes, in addition to Table 2, which just provides a broad overview, we have also provided the full model results, including model estimates along with their respective standard errors and significance value, in supplementary Tables S14- S23. In these models, we scaled the early occupancy to mean of zero and a standard deviation of one, this was not necessary for the occupancy- change index, as it corresponds to standardized residuals, which are already scaled to a mean of zero and a standard deviation of one. Therefore, we believe that since the estimates are based on standardized values, the interpretation of the model coefficients (as effect sizes) is straightforward. + +With respect to effect size and model interpretation, hurdle model effect sizes need to be backtransformed to be interpreted adequately. However, the values presented in Table 2 are values directly extracted from the model outputs. + +RESPONSE: Indeed, in Table 2, we provide the model estimates of the Bernoulli and zerotruncated count parts of the hurdle models. This table mainly serves as an overview of which effects were significant in the 10 different regions. The full models' outputs are provided in Table S14- S23. We are not entirely sure how the reviewer would like to see these estimates back + +<--- Page Split ---> + +transformed. For the Bernoulli part, we could use the model estimates to calculate odds ratios, but for the zero- truncated count part, there is to our knowledge no equivalent. However, Figure 2 shows, based on the coefficients of both parts of the hurdle model, the predicted relationships for the number of regions where a species is naturalized. So, we believe that what the reviewer wants is already visualized in this figure. In addition, the predicted relationships for the Bernoulli and zero- truncated count parts separately are shown in Figures S1 and S2. + +Across all models, the predictors explained a low portion of the variability within the response variable (13% to 28%). I wonder if the effects of early occupancy and the occupancy change index would have a strong effect (dependent on the model) if other important variables were included, such as predictors that account for human influence (such as Global Human Modification; Kennedy, C. M., Oakleaf, J. R., Theobald, D. M., Baruch- Mordo, S., & Kiesecker, J. (2018). Global human modification. https://doi.org/10.6084/m9.figshare.7283087, figshare), productivity (net primary productivity – NPP), and other environmental variables that have been shown to strongly influence the establishment of non- native plants across the globe. Therefore, I would recommend incorporating other drivers of the establishment (such as the ones I have just mentioned) in the model to allow a more accurate understanding of the relative importance of the different forms of occupancy (if both can actually be in a single model) investigated in the manuscript. + +RESPONSE: Given that many factors known to affect the naturalization process, we believe that 13- 28% is not a low portion of the variability for this kind of studies. Nevertheless, we fully agree that other predictors may explain more of the variation in global naturalization success, and some of authors of this study have done such analyses. However, the aim of the current analyses was not to build a predictive model for global naturalization success. Instead, our objective was to assess whether most of the species that have started to expand outside their native ranges have also expanded within their native ranges. Therefore, although we believe that the inclusion of other predictors will increase the proportion of explained variance, it will not provide additional insights into our research question. Moreover, the variables suggested by the reviewer (i.e. human modification and NPP) are characteristics of spatial units (e.g. grid cells or regions). Therefore, such variables are useful for explaining spatial patterns in naturalized plant richness. In our study, however, the units of analysis are species, and our measures of naturalization success are not spatially explicit (i.e. our models predict naturalization incidence and number of regions, but not where a species is naturalized). Adding these variables to our analysis would therefore not be possible, and we do not believe that they would help to answer our research question or change the current results. However, based on this comment and on a comment of Reviewer #1, we now performed additional analyses in which we included woodiness, a trait that is available for most species, as another species- level “predictor” in the model. The results for the association of naturalization success with the change in occurrence frequency remained largely the same, and the portion of variation explained by the models only slightly increased (the R2 values range from 14 to 28 percent). These additional analyses have been added to the Supplements. + +<--- Page Split ---> + +Overall, the consistency in terminology used can be largely improved. Doing so, will allow the readers to follow the thought process and story of the paper more easily, as well as connect the different components across the sections. Here are my recommendations: (1) the words 'countries', 'native range', and 'regions' are used interchangeably, when they shouldn't. I recommend if using regions, to clarify in their first appearance that they correspond to the entirety of their respective country in X number of cases. I would prefer to not read 'native range' in the context of the paper as by synonym of a region, given that, as pointed out in the paper (figure S6) there are several species that are native to multiple countries/regions (side note: the number of common species across countries/regions should be added to the methods section). (2) I strongly suggest the revision of the terminology associated with referring to non-native species as aliens. + +I suggest the authors revise the discussion provided here (https://doi.org/10.1111/brv.13071) and here (https://doi.org/10.1002/fee.2561), and consider a complete switch to 'non- native', including in the title. (3) the use of "at home" and "winners at home" is confusing, and it is not consistently used across the manuscript. Particularly when the "winners at home" are associated with the distribution of species within a political boundary (such as country) rather than its native range (which more frequently than not does not follow such boundaries). Additionally, by referring as "whether species that are increasing at home" [L99] implies that the authors directly measured direct expansion in species range, which wasn't the case and was explained in the methods on L3314- L317. (4) the interchangeable use of "changes in native- range commonness" and "occupancy change index" makes it hard to follow. + +RESPONSE: We thank the reviewer for spotting the inconsistencies in terminology and for the constructive suggestions. We now use consistent terminology throughout the manuscript. + +(1) When referring to the regions, we now consistently use 'regions' (or 'native regions') instead of 'countries' or 'native range'. However, we still use 'native range' when we really mean the entire native range of a species. In response to the side note mentioned by the reviewer under point 1, we have now added the number of common species across the native regions to Figure S6. + +(2) We prefer to keep the term 'alien' throughout the manuscript for several reasons. First, 'alien' is the term recommended by the widely used invasion stages frameworks of Richardson et al. (2000, Diversity and Distributions 6:93-107, DOI:10.1046/j.1472-4642.2000.00083.x) and Blackburn et al. (2011, Trends in Ecology and Evolution 26:333-339, doi:10.1016/j.tree.2011.03.023), and it also the term used in the recent IPBES assessment ("Thematic Assessment Report on Invasive Alien Species and their Control"; https://www.ipbes.net/ias), a work that has set the standards for the current invasion research. So, using another term, in our opinion, will not tame the terminological tempest in invasion science. Furthermore, we cannot avoid the term 'alien' because it is part of the name of the main database (the Global Naturalized Alien Flora; GLoNAF) used for the data on naturalization success. We have published many papers that use the GLoNAF database, and we consistently used the term "alien". Thus, for the sake of consistency of our own work, we prefer to continue using the same term. Second, we are aware that the term 'alien' has unfortunately become politicized, particularly in North America. However, when we have to come up with a new term each time a + +<--- Page Split ---> + +term becomes politicized, the terminological chaos in invasion biology will increase rather than decrease. In this regard, it should also be noted that the term 'non- native' is also considered harmful by some researchers (see the database of harmful terminology in ecology and evolution, https://www.eeblanguageproject.com/repository, associated with Cheng et al. (2023, Trends in Ecology and Evolution 5:381- 384, https://doi.org/10.1016/j.tree.2022.12.011). Having said this, as much as we prefer the term 'alien', if the editor insists on us replacing 'alien' with another term, we are willing to do so. + +(3) We now avoid the term 'at home' and instead use 'in their native regions'. +(4) We used "changes in native-range commonness" only once in the manuscript (line 160 of the previous version), and there we do not want to change it to "occupancy change index". This is because we were not referring exclusively to the index that we used but to any change in commonness. However, we now replaced it with "temporal changes in measures of commonness within native regions" (line 189). + +Legends of figures: I would suggest the revision of the legend of all figures and tables to be completely understandable in isolation. For example, in table 2 the model results show results for both "naturalized or not" and for the "number of regions where naturalized", not only the later as directed. The understanding of hurdle models can be not trivial, so the more detailed explanation of what exactly the Bernoulli and zero-truncated count parts means biologically is strongly encouraged. Another example, Figure S6 legend is quite uninformative, and can only be understood after reading the main text. I pointed out here a couple examples, but all legends should be revised for clarity. These are suggestions that I believe will improve the accurate understanding of your paper and its biological implication. + +RESPONSE: We now have thoroughly revised all legends, including Table 2 and Figure S6, which is now Figure S3 (lines 659- 672 & lines 147- 150 in supplementary). + +Early occupancy was not clearly explained anywhere in the main manuscript or supplement. How was this data specifically obtained given the earliest period of data available for a country/region? And more generally, how occupancy was defined? Let's say there is a period of 3 years and in y1 a species was present in 6 out of 10 cells; y2, in 4 cells being 2 new ones compared to y1; y3 in 7 cells being one new one. What is the occupancy of this species? Given the disparity of sources and formats the data was obtained in the first place for each country/region, was the count of cells to obtain occupancy consistent across the country/region? How? + +RESPONSE: We have now moved the definition of "occupancy" and "early occupancy" to the end of the Introduction as "Here, we test the hypothesis that many of the plant species that have become widely naturalized across the globe are also increasing in occupancy (i.e. the proportion of grid cells across a region in which a species has been recorded) within their native regions. To test this hypothesis, one would ideally have time series data of grid- cell occupancies for the entire native ranges of species. However, as such data is not available, we instead retrieved data on grid- cell occupancies of vascular plant species during an early period (i.e. early occupancy) and a later period, each usually covering multiple years, for 10 regions in Europe, which are referred as + +<--- Page Split ---> + +native regions (Fig. 1)." (lines 106- 107 & 110). We also defined early occupancy again in Method section (line 371). + +Most datasets only provide the number of grid cells where a particular species is present without specifying in which grid cells the species occurs. So, if a species was observed in 10 grid cells in the first period and in 10 grid cells in the second period, these could be the same grid cells, but they could also be totally different grid cells. Furthermore, each period with occupancy data was multiple years, and occupancy was then the number of grid cells in which a species has been observed during that multi- year period. So, when the period was three years (as in the example of the reviewer), we only have data on the number of grid cells in which a species has been observed during these three years, irrespective of whether it was in the first, second or third year or any combination of those. In other words, we have data on the total number of grid cells for the period, which usually lasted multiple years, but not for year 1, year 2 and year 3 separately. Additionally, we only have information on the total number of grid cell for each period but not their identities. We now mention this explicitly in lines 111, 322- 323 & 364- 366. + +As mentioned in the manuscript, the datasets for the different regions varied with regard to the early and later periods, the durations of these periods, and the number and sizes of the grid cells. However, within a region and period, the count of cells to obtain occupancy was consistent across species, at least for nine of the ten datasets. Therefore, and because the occupancy calculated for a particular region was relative to the total number of grid cells of that region, we believe our approach ensures comparability across regions. The only exception was the Thierache region, where in the early period the number of grid cells was an approximation obtained by converting ordinal rarity classes that were used in the late \(19^{\text{th}}\) century to a mean number of occupied grid cells per rarity class. This might, as discussed in lines 217- 226, be one of the reasons why the results of the Thierache region deviate from those of the others. + +I believe that the abstract does not contain enough information to understand how the knowledge gap was analyzed, so I suggest a thorough revision. For example, in L45- L46, "particularly common plant species" where? The abstract presents the results from the truncated negative binomial portion of the model only, therefore defining what 'global naturalization' means in L46- 47 is necessary. Also, a basic ecological interpretation/definition of "occupancy- change index" and "early period occupancy" would allow a larger audience to benefit from these findings. The latter was not formally defined in the paper, and it hampers the understanding of the choice of approach and the findings, as I mentioned in another piece of this review. Lastly, the abstract would gain a larger audience by having a closing statement with the implication for management and policy- related actions for species that follow the pattern described in this manuscript. + +RESPONSE: We have now thoroughly revised the Abstract and believe that we have addressed all major points made by the reviewer, despite the strict limit of 150 words. + +<--- Page Split ---> + +Overall structure of the paper: In my first read of the main paper, I would argue that the content necessary to fully understand the analysis and research findings isn't present. The authors should keep in mind that the methods section only appears at the end of the paper, so other sections should provide enough information about the methods and definitions of terms used that allow the readers to accurately understand the results and discussion. + +RESPONSE: We are fully aware that the Methods section is placed at the end of the article and have therefore now provided a concise overview of our approach at the end of the Introduction (lines 105- 124). We also double checked whether there were any cases where definitions of terms were included only in the Methods. When that was the case, we moved them into the earlier sections. + +How similar are the boundaries of the 10 focal regions compared to the same regions from GloNAF? + +RESPONSE: Five of the focal regions (the Netherlands, Flanders, Germany, Switzerland and the Czech Republic) have exactly matching GloNAF regions. For the focal regions Austria, Ireland and Great Britain, GloNAF has data for the different subregions (e.g. England, Scotland and Wales for Great Britain). For the focal regions Denmark (southeast) and Thierache, there are no exactly matching regions in GloNAF, but GloNAF has data for the corresponding countries (Denmark and France). We have not added this information to the manuscript, as we do not see why it would matter whether the focal regions match GloNAF regions. However, if the editor wants us to add this information, we will be happy to do so. + +Specific comments and recommendations: + +- I am curious to understand why "declining species" was a relevant keyword selected by the authors. + +RESPONSE: We tried to include keywords that are not yet used in the Title or Abstract, so that search engines would have a higher chance to find our paper. We included "declining species" because this term is frequently used for species that used to be common but have become rare recently. As this applies to many of the species that have a negative occupancy-change index, we think that the term is appropriate. While we chose to frame the perspective of our manuscript (e.g., in the title or abstract) in terms of species that have increased in commonness, the finding that species that are declining in their native range are less likely to be naturalized elsewhere is an equally valid and interesting extension of our results. We now mention this explicitly in the Discussion section (lines 155- 156). A search for "declining species" in Web of Science (12 June 2024) gave 747 results. Therefore, we consider that the use of this keyword will help people with an interest in declining species to find our manuscript. + +- L84: add citation to support statement. +RESPONSE: We have now added a citation (line 86). + +<--- Page Split ---> + +- L88: a good example in which countries and ranges are used interchangeably. Clarifying language would improve the understanding and cohesion of this paper. RESPONSE: We now used the standardized term "region" to improve cohesion (lines 92). + +- L104: the statement "largely the same species" has dubious meaning, clarify. RESPONSE: We rephrased the sentence as "Here, we test the hypothesis that many of the plant species that have become widely naturalized across the globe are also increasing in occupancy (i.e. the proportion of grid cells across a region in which a species has been recorded) within their native regions" (lines 105-107). + +- L105: the statement "two (or more) periods" has no context up to this point and hinders the reader from grasping the methods used in the paper in general terms. Also, to the best of my understanding of this paper, for each country/region, each main model shown in the main manuscript contains only the comparison between two time periods. Adding "or more" is confusing and might better if brought up later when nuances in the results are explained. RESPONSE: We now removed "or more" from this sentence and also rephrased the sentence (line 109-112). + +- All content presented in the supplement should be referenced in the main text. RESPONSE: All content presented in the supplement is now referenced in the main text. Note, however, that we do not directly refer to Table S26 and Table S29 in the main text but that we refer to these tables in the elaborate descriptions of the individual datasets in the Supplementary Methods (to which we refer in the main text). + +- L106: "for each native species in each region" how about species that are present in more than one region? There is some mention of them when Figure S6 is referred to, but given the proximity of each of the countries/regions used in this study some short explanation on why region rather than native range extrapolating political boundaries were chosen. RESPONSE: We would have liked to have data on changes in occupancy for the entire native ranges of species. However, as data on grid cell occupancy are only available for some of the regions that are part of the species' native ranges, this was unfortunately not possible. Therefore, we had to use data for separate regions, and indeed, as mentioned in the manuscript, some species occur in multiple data sets. We now mention already at the end of the Introduction the reason for analyzing regions rather than native range (lines 107-112) and the reason for analyzing each region separately (lines 123-124). + +- L107: "occupancy-change index" hasn't been explained and needs clarification. RESPONSE: We now added an explanation in lines112-116 of the Introduction and in lines 369-372 of the Methods section. + +<--- Page Split ---> + +- L109-110: "the number of regions where the species has become naturalized" this text is confusing. It seems that one is referring to the 10 regions, but in fact, it is from the regions defined by GloNAF to defined where a species is naturalized or not. + +RESPONSE: We now rephrased the sentence as "We then used hurdle models to analyse how global naturalization success — a combination of naturalization incidence (i.e. whether or not a species has become naturalized, which can be modelled by using a Bernoulli distribution) and naturalization extent (i.e. the number of regions where a naturalized species has become naturalized, which can be modelled using a zero-truncated negative binomial distribution) — correlates with occupancy in the early period and the occupancy change within the species' native regions." (lines 117- 123). + +- L110: "early period" is mentioned in the abstract and here, but the term hasn't been described yet. + +RESPONSE: We now make it clear earlier in this paragraph of the Introduction that there were two periods, an early period and a later period (lines 110- 111). + +- L121-L122: this statement contradicts statements on L314-317. These species are more common than what would expected given their occupancy in the early period. RESPONSE: We changed the statement in the previous L121-L122 (now lines 135-137) accordingly to "So, overall, our findings indicate that many species that have increased in occupancy in their native regions more than species with an identical early occupancy, have also become widely naturalized elsewhere in the world". + +- L125-L126: with respect to "the zero-truncated count part of the hurdle model, not with the Bernoulli part", I suggest changing the language similar to above: the likelihood of being naturalized outside native range vs naturalized in more regions at the global scale. + +RESPONSE: We have now revised the statement (lines 130- 132). + +- L131: to convey the message more clearly, it might be helpful to associate the occupancy-change index as a metric of commonness early on in the text and use this term across the paper. RESPONSE: We thank the reviewer for this suggestion. However, the occupancy change index is a metric of the change in commonness, not a metric of commonness per se. As commonness has multiple dimensions, we would prefer not to replace occupancy-change index with the commonness-change index throughout the text. + +- L136: this statement "increased in occupancy" is unclear. Since when? + +RESPONSE: The increase in occupancy has been observed since the period for which we have early occupancy data across regions. We have rephrased the sentence as "but also for species that have since then increased in occupancy within their native regions (Table 2)." to clarify this (lines 149- 150). + +<--- Page Split ---> + +- L145-148: statements seem repeated from the introduction. I suggested the authors be mindful of which information is essential and necessary in the discussion by focusing on an in-depth discussion of the results. + +RESPONSE: As we think that it is more important to mention these possible explanations in the Discussion than in the Introduction, we have now removed the similar statement from the Introduction. + +- L149-150: what is the environmental variability within the native range studied per species? is the set of species used in this study representative of species distributed in a wide range of environmental conditions? + +RESPONSE: For each of the 10 focal regions, the datasets include the vast majority of plant species that are native there. So, the datasets should include both species that occur in a wide range of environmental conditions and species that occur in only a subset of environmental conditions. However, as we only have data on the number of grid cells occupied by a species and no data on which grid cells they actually occur in, we do not have measures of the environmental variability each species experiences within the native region. + +- L152-154: are these traits present in the focal species studied here? Could such information be pulled from global databases, such as TRY, and incorporated here? + +RESPONSE: We agree that an analysis using trait data would be nice, but even in global databases such as TRY the number of species with data for specific traits is still very poor. This also applies to data on dispersal abilities and autonomous self-fertilization. The largest dataset on autonomous self-fertilization was compiled by Razanajatovo et al. (2016; Nature Communications 7:13313), and included only 1752 of the ca. 350,000 species globally. However, in additional analyses, we now considered the woodiness of the species. We chose woodiness because it is indicative of both growth form and habitat type (i.e. regarding whether the species is likely to occur in open [non- woody] or closed [woody] habitats), and because it is available for all species in our study. We found that while woody species had higher occupancy- change values than non- woody species in six of the 10 native regions (Table S2), woody species were less likely to become widely naturalized. Nevertheless, the positive association between naturalization and occupancy change remained largely unaffected by inclusion of woodiness as an additional variable in the hurdle models. This shows that our results are robust. We added the results of the additional analyses in the supplements (Tables S3, S4- S13) and refer to them in the Discussion (lines 171- 185 & lines 238- 245). + +- L186-187: if the early period chosen had a specific reasoning for it, it should be clarified in the introduction, not in the discussion. + +RESPONSE: We did not have any specific reasoning for that early period. It was simply the period for which data happened to be available. So, we did not have any a priori hypothesis about how the years of the early period would affect the results. Therefore, we believe that the early period of the Thierache period does not require a clarification in the Introduction. + +<--- Page Split ---> + +- L202-204: I cannot follow the connection of this sentence to the previous after. "richer-get-richer" is a term generally used in the context of species richness, and it doesn't seem to apply here, but also the directionality of the negative is the opposite in the sentence? Consider revising and defining "Matthew effect" and or "richer-get-richer". + +RESPONSE: In principle, it is repeating the preceding sentence saying that the successful species become even more successful. As it is not essential to compare this to the Matthew effect and the richer-get-richer effect, we decided to delete the sentence about these effects. + +- L223: how were "losers" quantified in this paper? Similar language also shows up in the keywords, and it makes it confusing. + +RESPONSE: "Losers" referred to species that have declined (i.e. have a negative change in occupancy). Based on this comment and a comment by Reviewer #3, we decided to remove the term 'loser' (and to be consistent, also the term 'winner') from the manuscript to avoid any confusion. + +- L228-229: why habitat specificity might have not changed? + +RESPONSE: We do not exclude the possibility, as habitat specificity could in principle change through evolution. However, we think it is very unlikely that this will have happened for many species within less than a century. As a new framework on the dimensions of rarity, added occupancy as a dimension, and removed habitat specificity as a dimension (Crisfield et al. 2024, doi: 10.1111/ecog.07037), we decided to remove the text about habitat specificity. + +- L245-251: this discussion is really interesting, and I would suggest to be the driving force of the importance of this study and (if changes in the methods are performed and conclusions hold) - to aid ways in which findings from core science can be transferred to managers and policymakers. + +RESPONSE: We thank the reviewer for pointing this out. We added a few sentences to emphasize how our research can help managers and policymakers (lines 304- 306). + +Reviewer #2 (Remarks on code availability): + +the results for "Austria" are reproducible - from analysis to figures. According to the authors and my understanding of their methods, each model was run the same way, only the input data for other regions (data available on figshare) changes. + +RESPONSE: That is correct. + +Reviewer #3 (Remarks to the Author): + +The study aims to compare whether the changes in select plant species' native range size correlates with naturalization history elsewhere. The authors examine changes in grid occupancy + +<--- Page Split ---> + +drawing on historic grid- based surveys of the vascular flora of 10 areas in Europe. The premise is interesting and the results, though correlative, make intuitive sense. However, there are some methodological concerns that render the conclusion that plants that have naturalized as aliens abroad have also become more common in their native range unearned. RESPONSE: We thank the reviewer for the general support of the manuscript and the insightful comments. + +As the authors note, there are many definitions of commonality, and arguably the one being used in this study is not truly a metric of such. At best, the authors are examining a proxy of range size. The authors do a good job of mentioning potential limitations - e.g., one cannot know how abundant these species are within each grid cell. Further, it is likely that the surveys upon which the study relies were conducted with varying protocols and specific objectives, certainly across regions and possibly even over time. Even if the surveys were more or less standardized, the analyses conducted here can produce misleading results for species that have been recorded more efficiently/accurately in one survey than the others. + +RESPONSE: We agree with the reviewer that there are many definitions of commonness, and we indeed point out in our manuscript that commonness has multiple dimensions. While we cannot say how abundant a species is within a grid cell, we politely disagree with the reviewer that our metric (i.e. the grid- cell occupancy frequency in a region) would not truly be a metric of commonness. We now added a reference to the recent review by Crisfield et al. (2024, Ecography e07037, doi: 10.1111/ecog.07037), which explicitly defines occupancy as a dimension of commonness. In fact, the authors proposed to replace the habitat specificity category of Rabinowitz's classification by occupancy. Furthermore, as also pointed out by Reviewer #1, positive abundance- occupancy relationships are commonly found across taxa, and we now mention this in the Discussion (lines 278- 281). + +We also agree with the reviewer that the different data sets that we used may have varying protocols and objectives, possibly even over time. However, because each region was analysed separately, we do not think that variation in protocols among regions is problematic. Variation in protocols over time within a region is not problematic either, as this is accounted for by the Telfer method that we used to calculate the occupancy- change index. We explain this in the Methods section (lines 372- 378). However, we cannot exclude that in some of the regions there have been changes in how accurately certain groups of species were recorded, and we now mention this potential limitation (lines 380- 383). Moreover, we would like to emphasize that despite the variation among the 10 datasets in different aspects, our results remain largely consistent across regions, which we believe strengthens our conclusions. + +More importantly, the assayed regions do not represent the full native range of the species examined. It is possibly for any given species that while, say, in the Czech Republic its range has increased, the range may have decreased in other parts of its native range. Thus, it is unknown how a species' entire native range size has changed. Though the authors claim that the general + +<--- Page Split ---> + +positive correlation between occupancy- change indices they observed among regions for the same species indicates that native range 'winners' and 'losers' were generally consistent across regions, these regions may constitute a small or biased sampling of these species' entire native ranges. Also, many of the species that have naturalized elsewhere are known to have fairly large native ranges that extend well beyond the regions included in the study. Further, it seems that only 44 species (among thousands) were present in multiple regions. Along these lines, without more context regarding the full native ranges of these species it is difficult to say whether the results of this study, though suggestive, truly provide strong evidence that many plant species that are spreading as naturalized aliens around the globe also have high occupancies or are increasing in occupancy in their native range. + +RESPONSE: We appreciate the insightful comments from the reviewer. As acknowledged in our manuscript, one of the limitations of our study is that grid- cell occupancy data (for at least two time periods) is only available for regions in north- western and central Europe. There are more regions with grid- cell occupancy data, but these regions unfortunately do not yet have repeated surveys. Consequently, we paid attention to the fact that we cannot generalize our findings to the entire native range of species (lines 208- 209, previous version and lines 251- 253 in revised version). However, we do suggest that similar anthropogenic changes may have comparable effects on species occupancy in other native regions, though further studies are required when more data become available. + +Regarding the reviewer's concern about the number of species present in multiple regions, we believe that the reviewer misunderstood our correlations between occupancy change indices. We did not find that only 44 species occur in multiple regions. What we found is that in 44 out of the 45 possible pairwise combinations of regions, the occupancy- change indices of the species that occurred in both regions of a pair were positively correlated. We believe this is pretty strong evidence that species that have increased in occupancy in one native region usually also have increased in occupancy in other native regions, even though we do not have data for the entire native range. In Fig. S6 (Fig. S3 in revised version), these correlations are shown, and we now also added the number of species shared between the regions in each pair. Additionally, we have now toned down throughout the manuscript any sentences in which we made broad generalization of native ranges, including the title. + +GloNAF regions are used as the unit of analyses regarding naturalized ranges. However, the manuscript never mentions what these regions are. How were they defined? Based on the map provided in the supplements, it seems that these regions largely follow geopolitical boundaries and come in many shapes and sizes. Thus, the number of regions where a species has become naturalized may not be a suitable metric for the degree of global naturalization (and comparison with occupancy in a limited sampling of these species' native ranges). + +RESPONSE: We thank the reviewer for pointing out that we failed to mention what the GloNAF regions are. The GloNAF database is a compilation of lists of naturalized alien plants for different regions around the globe. The version we used (version 2.0), contains list of naturalized vascular + +<--- Page Split ---> + +plant taxa for 920 non- overlapping regions. These regions include both mainland regions and islands, and most of them indeed follow geopolitical boundaries, because flora books and species inventories, which are the main data sources of GloNAF, are mostly done for administrative regions. As a consequence, the regions vary in size from 0.045 to 2336618 km \(^2\) (median size is 34382.71 km \(^2\) ). Instead of the number of GloNAF regions, one could use the cumulative area of the regions in which they are naturalized, but this is highly correlated with the number of regions (Spearman rho = 0.770), as shown in Pyšek et al. 2017 (Preslia 89:203- 274, DOI: 10.23855/preslia.2017.203). We now added more detailed information on the GloNAF database in the Methods (lines 410- 415). + +The methods require more detail. Pertinent information is often relegated to the supplements or other publications. For instance, the authors should note how many species were examined in the main text so that the numbers they present and discuss can be understood in context. While it is fine to refer to methods in previous studies, there should at least be enough information in the manuscript for the reader to be able to interpret the results. For instance, it was necessary to refer back to Telfer (2002) repeatedly to understand the figures presented in the results as well as some of the choices made in the study. Along these lines, the grid counts for each region were not done the same way. For instance, in Denmark, the number of occupied grid cells of each species in each region was calculated by multiplying the regional abundance of each species by the total number of referenced grid cells for each region, combining the grid- cell data for each taxon across the 11 regions of the country that were surveyed to get one single value. In contrast, simple grid cell counts were used in some other regions. While there is no reason not to use available data, this makes the results from each region (which were modeled separately) less comparable, and I recommend that the authors harmonize the approach to grid cell counting and present those results as well. + +RESPONSE: The numbers of species in each dataset are provided in Table 1 of the main text. We now also added these numbers in brackets behind each region in lines 313- 318. We also moved some information about the regions that was not yet provided in Table 1 of the main text from the Supplements to the main text (lines 321- 330). Furthermore, we now provide more detailed information regarding our choices that were based on Telfer (2000) in the 'Index of occupancy change in native regions' subsection of the Methods. In addition, as recommended by Reviewer #2, we also revised all the figures and table captions to make them more informative and understandable in isolation (Fig. 2, Fig. S1- S5, Table 2, Table S1- S31). + +Data on changes in grid- cell occupancy are scarce, and there is variation in how these data were collected in the different regions. However, the total count of grid cells was generally consistent across regions. In the case of Denmark, there were 14 subregions, and not all of them were immediately adjacent to the other subregions. The paper that provides the data for Denmark, Nielsen et al. (2019), determined a species' abundance in each subregion by dividing the number of occupied grid cells of each species by the total number of grid cells for the subregion. Since, Nielsen et al. (2019) provide such abundance data only for 11 subregions, out of 14 subregions, we back calculated the number of grid cells occupied by a species in each of the 11 subregions. + +<--- Page Split ---> + +Then we combined them across the 11 subregions to get one single occupancy value for each species. This way we made the data more comparable to the data that we have for the other regions, as recommended by the reviewer. We now explain our calculation of grid- cell occupancy for Denmark in more detail in the Methods (lines 340- 347). + +Additional comments: + +The 'winners' and 'losers' angle seems a bit colloquial. + +RESPONSE: In response to this comment and a similar comment by one of the other reviewers, we decided to remove these terms from the manuscript. + +Table 1 is not referenced in the text correctly. + +RESPONSE: While we previously cited Table 1 in the Methods, when describing the 10 focal regions, we have now also included a citation to Table 1 at the end of the Introduction (line 124). + +Fig S6 - x and y are not defined. + +RESPONSE: We now added the axis labels in Fig. S6 (Fig. S3 in revised version). + +Unscale the occupancy index when presenting and discussing the results - the scaled values are confusing to interpret and the index is already ultrametric. + +RESPONSE: We thank the reviewer for this comment. We now realized that the unscaled occupancy- change index values are already standardized because they correspond to the standardized residuals of the logit- logit regression used to calculate the index. In other words, the values were already centered to zero with a standard deviation of one prior to scaling them. So, we now use unscaled values for the occupancy- change index. + +The layout of Fig.2 is a bit confusing with the inset with multiple abbreviations and asterisks. Also, why not just replace this figure with the corresponding one in the supplements that show the raw data as noted in the caption (S5)? + +RESPONSE: We followed the reviewer's advice and replace Fig. 2 with Fig. S5 of previous version. + +Where were the 1/6 and 5/6 quantiles chosen for illustration? + +RESPONSE: We chose the 1/6th and 5/6th quantiles to illustrate whether or not the relationship between global naturalization and occupancy change depended on the occupancy in the early period. We wanted to show this relationship not only for the median occupancy in the early period but also for a higher and a lower occupancy in the early period. So, we categorized species according to whether they were relatively common, intermediately common or rare during the earlier time period. To achieve this, we divided the data points into three equally- sized groups and, we show the lines for the centres (medians) of these groups, which are the \(1 / 6^{\text{th}}\) , \(3 / 6^{\text{th}}\) (median) and \(5 / 6^{\text{th}}\) quantiles. We could have chosen more groups, but then the figures would be + +<--- Page Split ---> + +very busy. We now added more details on the choice of the quantiles in the Methods (lines 440- 446). + +As GloNAF data are not freely accessible, please present information on which specific regions each species was naturalized in. + +RESPONSE: We now uploaded the data on fishware. Please, also note that the 2019 version of GloNAF has been published as a data paper, and that the most recent data has always been freely shared upon request. + +Are the identities of the grid cells occupied by each species known? If so, perhaps the potential drivers of range change could be examined. + +RESPONSE: Indeed, it would be very interesting to actually examine the potential drivers of range change. However, for all datasets, we only have the number of grid cells where a particular species is present without specifying the identities of the grid cells. We mention this in lines 364- 366. + +The "Gridcells_earlyperiod" and "Gridcells_laterperiod" values for Thierache are not whole numbers- according to the metadata these should be simple counts of the number of cells occupied by each species and the supplementary methods do not state any special circumstances (unlike Germany or Denmark). + +RESPONSE: We thank the reviewer for pointing this out. We mentioned the reason for this indirectly in line 187 of the previous version, but we now realize that we did not explain this in full detail in the Methods. For Thierache, the authors of the original dataset had 'proper' grid- cell occupancy data for the latter period (that is why the species have whole numbers for that period in the dataset. However, for the early period, the data were not actual grid- cell frequencies but verbal descriptions of how widespread the species were. These verbal descriptions were converted by the authors into grid- cell occupancies, and this resulted in some numbers that are not whole. We now also moved information about the Thierache region from the supplementary to the main manuscript (Methods section line 338- 340). + +Reviewer #3 (Remarks on code availability): + +I did not try running the code but it looked reasonable. + +<--- Page Split ---> + +Dear Reviewers, + +Dear Reviewers,We were pleased to read that Reviewer #1 was happy with the changes that we had made, and we thank Reviewers #2 and #4 for their constructive comments. According to the new suggestions, we have made further revisions to our manuscript entitled "Many plants naturalized as aliens abroad have also become more common within their native regions". Below we provide point- by- point responses to all comments. Please, note that the line numbers refer to the clean version of the manuscript with highlights and our responses are in blue. + +Sincerely, + +Rashmi Paudel (on behalf of all authors) + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have addressed all of my concerns. + +RESPONSE: We thank the reviewer for their time, and we are pleased that we have addressed all of their concerns. + +Reviewer #2 (Remarks to the Author): + +I appreciate the careful point- by- point revisions given in response to my previous comments and concerns. I appreciate the thorough revision of the text to improve the consistency of terms used—the main text is now a lot easier to digest. Moving forward, I have two broad, major comments that are detailed below. Then, those are followed by minor comments: RESPONSE: We are pleased that the reviewer appreciates the thorough revisions of the text, and we thank them for the constructive comments. + +1) I mentioned this before and I noticed that Reviewer 3 also made a comment on this: using the regions as units of native ranges, particularly because they follow political boundaries. So, could you provide the supplement with how many species are present across all regions? How many species are present in all regions but one? And so forth? And how many species are uniquely present in a single region? + +RESPONSE: We have now added a table in the Supplements that provides a summary of how many species are present in how many of the 10 regions (Table S36), and we refer to it in the main text (line 392). Among the 3920 unique species across all ten regions, 288 species are present in all regions, and 1261 are present in only one region. Additionally, we have provided an Excel file in the data repository detailing the presence and absence of all 3,920 species across the 10 regions. + +
# regions where species is present# species
10288
9186
8144
7130
+ +<--- Page Split ---> + + +
6165
5218
4356
3487
2685
11261
+ +2) Woodiness was added in complementary models as a way to address some of the concerns of Reviewer Dov Sax. If this inclusion is kept, the main text would need some introduction of the relatedness of woodiness, range expansion, and probability of becoming naturalized, so, therefore, justifying why this a reasonable trait to be evaluated. Lines L171-173 do not justify sufficiently. I would pull as base of some of the arguments and justification given in the rebuttal. + +RESPONSE: We thank the reviewer for pointing this out, and we now introduce the potential importance of woodiness (and other traits) in the Introduction (Lines 104- 117). + +Minor comments: + +Results: The tables with the main results of your models (i.e., mention of tables S14- S30 should potentially show up earlier, as it is the results of the main models (without woodiness) + +RESPONSE: We previously referred to Tables S14- S30 (Tables S12- S21 in the revised version) in the caption of Table 2, which summarizes the estimates and significance of all models. We have now also referred to them when we first mention Table 2 in the Results section (Line 163). + +L91- 93: The statement is somewhat confusing. Also, should it be "increasing their occupancy" rather than "increasing" only in L92? Please, revise + +RESPONSE: We thank the reviewer for spotting this. Indeed, it should be "increasing their occupancy". We have now revised the statement as "However, this concept has not been assessed in plants. The findings that naturalized plants and those spreading in their native range share a common set of traits suggests that it may be the case" (Lines 120- 122). + +L103: do you mean "range over time"? + +RESPONSE: We thank the reviewer for pointing this out, and we have now revised the text accordingly (Line132). + +L199- 200: would you be able to provide either a table or a simple graph per region with how many species out of the total per region were present in all its grid cells? This would help the reader to be aware of how many species, from the poll studies, have this pattern. + +RESPONSE: Across all regions, no single species is present in all grid cells of its respective region. However, some species were present in nearly all grid cells. To illustrate this, we have updated Fig. S4 (Fig. S3 in the revised version) by adding a vertical line representing the logit of the total number of grid cells in each region. This allows for a clear visualization of species that are close to this threshold. + +<--- Page Split ---> + +In addition, the following table, which has been added to the supplements (Table S25), and is referred to in line 243, provides the number of species present in at least 95% of the total grid cells per region, during the earlier time period: + +
Regions# total grid cells# species present in all grid cells# species present in more than 95% grid cells# total native species used in analysis
Austria2600022419
Czech Republic2551001834
Denmark26305921
Flanders985029861
Germany120240651715
Great Britain2852001355
Ireland100708910
The Netherlands16850301115
Switzerland1827002307
Thérache12900775
+ +L228: "...species with high early..."? RESPONSE: Corrected accordingly (Line 271) by adding "with". + +Reviewer #2 (Remarks on code availability): + +I reviewed the code during the first round of revisions. + +Reviewer #4 (Remarks to the Author): + +This is a broad analysis staying that certain plant species, likely due to a combination of human actions and the plant features, are favored under human uses of the landscape in their ranges and in new regions. The novelty relies on including change in abundance/occupancy in the native range as a predictor of naturalization somewhere else. These findings could be used to generate list of species that could become invasive, lists that could be compared with already generated watch lists to assess how much information this predictor is adding. + +RESPONSE: We thank the reviewer for their compliments, for recognizing the potential application of our research, and for their constructive feedback. + +Since changes in occupancy/abundance were not analyzed as a function of other drivers than time, e.g., human activities targeting particular habitats/plant communities, results might very indirectly be assessing the causes of naturalization, because increase in occurrence and naturalization might have to do with habitats selected rather than intrinsic features of the plant species. This is a point brought by the reviewers that has been dismissed by the authors (see next comment). Analyzing what it made those species increase in their native and + +<--- Page Split ---> + +introduced ranges would be of greater consequence for management and conservation. RESPONSE: Our main objective was to assess whether species that are increasing at home are also the ones that are increasing elsewhere. If this is the case, this would mean that information on native occupancy dynamics could inform invasion risk assessments (irrespective of the traits that underlie the occupancy dynamics). We now mention this more explicitly in the manuscript (lines 63- 64 & lines 294- 295). However, we appreciate the reviewer's insightful observation and agree that multiple factors other than time could influence species occupancy in their native regions and their naturalization success. As we mentioned in our previous response, we do not have information on the actual grid cells in which the species occurred, because most datasets only provide the number of grid cells where a particular species is present without specifying in which grid cells the species occurs. Therefore, we cannot explicitly test the role of habitats in driving occupancy patterns. In addition, although such an analysis would be very interesting, it would go far beyond our objective of testing whether species that have increased in occupancy in their native regions are largely the same ones that have increased globally as naturalized alien species. + +We politely disagree that we dismissed the "habitat" comment of the previous reviewer. In response to the similar comment by Dov Sax to the previous version of our manuscript, and as stated in our previous rebuttal, we chose to add information on woodiness because it is indicative of both growth form and habitat type. Where we assume that woody species are likely to occur in closed or forest habitats, whereas non- woody species predominantly occur in open habitats. We believe that ultimately the habitat associations of species will depend on their intrinsic features. Although we cited already several papers that have analysed how changes in native occurrence relate to species features, we have now —in response to this comment and the reviewer's subsequent comment— analysed whether species that were common and have further increased are characterized by certain ecological strategies (Grime's competitor, stress tolerator and ruderal strategies) and by ecological indicator values. For more details, see our response to the next comment. + +Much more informative would have been to analyze features of the species that were already abundant and that increased their occurrences, e.g., are ruderal species over- represented in that group? What are the main traits characterizing those species? That again would provide more useful information for management and conservation. Maybe the data is not available for all, but it could be done for the ones that it is. Line 207- 216 make that point. Many studies are using global trait data sets to do it, if authors have decided not to do it that's their choice but claiming that the reason for not doing it is that that information is not available is not accurate. + +RESPONSE: Even though many studies are using global trait data sets, we would like to reiterate that these data sets are very incomplete. In a recent analysis of trait- data availability for naturalized alien species, it was shown that there are only ten traits with data available for more than \(50\%\) of the species (https://ecoevorxiv.org/repository/view/7852/), and we have now also included this information in the manuscript (lines 297- 299). Woodiness is one of the few traits that is available for most plant species, and therefore we had already included this trait during the previous revision. We believe that the results of studies based on very incomplete trait data should be interpreted with caution (as there might be a bias in the availability of data). Nevertheless, we fully agree that the analyses proposed by the reviewer might be informative. Therefore, we have now added data from a global dataset on + +<--- Page Split ---> + +CSR- strategies (available for 2125 of the 3920 species in our data sets) from Guo et al. (2018), and data on Ellenberg ecological indicator values (available for 2893 of the 3920 species from Tichý et al. (2023) and the Pladias database of the Czech Flora and Vegetation; Chytry et al. (2021)). + +We classified species as widespread and expanding if they had an early occupancy higher than the median and if they had a positive occupancy change. We then analysed, in line with the reviewer's suggestion, whether the trait value of this group of species differed from all other species. These additional analyses showed that the group of species that were already abundant and also increased their occurrences, are overall characterized by high values along the competitor axis of Grime's CSR- strategy triangle (in 9 of the 10 regions) and low values along the ruderal and stress- tolerator strategies. Furthermore, this group of species had significantly lower Ellenberg indicator values for light, and higher Ellenberg indicator values for nutrients, in all ten native regions. We present these additional results in the Supplements (Tables S33- S34, Fig. S4- Fig. S10) and refer to them in the Discussion (lines301- 316). + +References: Chytry M., et al. Pladias Database of the Czech Flora and Vegetation. Preslia 93, 1- 87 (2021). + +Guo, W.Y., et al., The role of adaptive strategies in plant naturalization. Ecology letters 21(9), 1380- 1389 (2018). + +It looks like early occupancy, and to some extent woodiness, are a better predictor of naturalization than change in occupancy, Table S3, this should be emphasized more in the main text because data on changes overtime may not be available, but actual native range and woodiness are, and those could be used on their own as predictors. Especially considering that change in occupancy is being predicted by early occupancy. Also, adding information on how much variance was additionally accounted for by including change in occupancy, vs a model with early occupancy and woodiness only, would help to understand the scope of this predictor. + +RESPONSE: We thank the reviewer for this suggestion. We have now emphasized Table S3 (Table S1 in the revised version) more strongly in the main manuscript (lines 156- 161, lines 215- 218 & lines 299- 301). + +We also would like to point out that the change in occupancy is not being predicted by early occupancy. The change in occupancy corresponds to the residuals of a regression of the logit of late occupancy vs the logit of early occupancy. Consequently, if one then relates the change in occupancy to early occupancy, there is no significant relationship. This is mentioned in line 146, lines 444- 446 & lines 450- 452. + +To assess the variance explained by different models, we ran four models: Model I, which includes only early occupancy as a predictor of naturalization success; Model II, which incorporates both early occupancy and occupancy change; Model III, which includes early occupancy and woodiness; and Model IV, which combines all three predictors—early occupancy, occupancy change, and woodiness. The calculated Pseudo \(R^2\) values (by Cragg and Uhler), r2CU showed that models incorporating occupancy change (Model II and Model IV) consistently had higher explanatory power compared to their counterparts (Model I and + +<--- Page Split ---> + +Model III), highlighting the role of occupancy change in predicting naturalization success. Although the change in explained variance is not huge, we would like to point out that, as suggested by the previous reviewer #1 (and discussed in lines 238- 250), the association between occupancy- change and global naturalization success may be an underestimate. We have now added a supplementary table (TableS24) comparing the pseudo R2 values across all models, and we briefly refer to these results in the main text (lines 216 & 237). + +My suggestion would be to change 'region' for countries. Region usually indicates ecological, e.g., climatic, differences, but these data sets reflect political units. Sorting the data into actual ecological regions might have shown more interesting/informative results. + +RESPONSE: We thank the reviewer for this suggestion, however we prefer to use 'regions' instead of 'countries' because three of the native regions in our study are only part of countries. Referring, for example, to Thierache as 'France' would be misleading. However, if the editor prefers us to use 'countries' or another term, we are willing to change it. We now added "(countries or parts thereof) at first mentioning of 'European regions' in the Abstract (line 59) and in the Methods (line384). + +It is not clear if changes in occupancy overtime were standardized by the period of time between census, i.e., more change expected if longer time between censuses. RESPONSE: The changes in occupancy over time are standardized within each of the regions, as the period is the same for all species within a region. We added a note to clarify this at lines 495- 496. However, the changes in occupancy over time are not standardized across regions. As we only compared changes in occupancy within regions, a standardization across regions would not change the conclusions. + +I can't tell the difference between Table S3 and the ones that follow for each country, information is the same. + +RESPONSE: Table S3 (Table S1 in the revised version) provides an overview of the estimates and significances for the analyses that included woodiness and is directly comparable to Table 2 in the main text. Tables S2- S11 (in the revised version) provides the detailed results for each region separately, and we now explain this in the caption of Table S1. + +Reviewer #4 (Remarks on code availability): + +The analyses are done using standard techniques and standard software packages. + +<--- Page Split ---> diff --git a/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/supplementary_0_Transparent Peer review file_det.mmd b/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/supplementary_0_Transparent Peer review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..353dbb81011757f492c3ff6d099971221c0176f2 --- /dev/null +++ b/peer_reviews/1b241a020ab52e2d1f7b7f61afee2f55b88ee62e2b3e58a8dee0df770f9607af/supplementary_0_Transparent Peer review file/supplementary_0_Transparent Peer review file_det.mmd @@ -0,0 +1,900 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[74, 96, 296, 119]]<|/det|> +# Peer Review File + +<|ref|>sub_title<|/ref|><|det|>[[72, 161, 899, 210]]<|/det|> +## Many plants naturalized as aliens abroad have also become more common within their native regions + +<|ref|>text<|/ref|><|det|>[[73, 224, 437, 240]]<|/det|> +Corresponding Author: Ms Rashmi Paudel + +<|ref|>text<|/ref|><|det|>[[72, 274, 865, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 339]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 352, 220, 366]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 378, 160, 392]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 404, 238, 417]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 417, 916, 496]]<|/det|> +This paper addresses a highly novel question, namely whether species that are successful as non- native species have also become more successful within their native range. I am familiar with the invasions literature and I am unaware of any previous study that has addressed this question. The analyses themselves are conducted soundly and the work is clearly described. I have no major concerns about this manuscript. I do have one suggestion that I believe should be addressed in some way, as well as several additional thoughts that could add additional interpretation to their findings. I detail these considerations below. + +<|ref|>text<|/ref|><|det|>[[72, 508, 914, 679]]<|/det|> +The one issue that I believe needs to be better addressed has to do with their choices about where to split the native range data, temporally, i.e., on deciding on a specific year to split "historic" from "recent" distributions with a region. A few of their data sets have natural splits between these periods, e.g., Denmark (with historic data from the 1800s and modern data from less than a decade ago), but more than half of their data sets appear to have been arbitrarily split at 1990 or 2000, e.g., the Netherlands data set is split as before 1990 and after 1990. At a minimum the manuscript should be revised to explain the rationale for these splits. Why are some split at 1990 and why others at 2000 or even, in one case, at 1971. I'm guessing they have some reasonable reason for this, but this isn't explained and so it makes the reader feel unsure about these decisions. They mention one data set where they look at multiple possible splits, but I really would have liked to have seen an analysis with a few more of these data sets that considered if the year of the split (e.g., 1980 vs. 1990 vs. 2000) ends up impacting the patterns observed. I imagine that their results are pretty robust to the precise year of splits, but I'm not sure. I think addressing this in some way would be useful, even if was just to show this with 2 or 3 more of their study regions. If it proves impractical to do such analyses then I would still expect to see a short paragraph added (or perhaps 2- 3 sentences added to an existing paragraph) to the discussion that addresses this concern. + +<|ref|>text<|/ref|><|det|>[[72, 691, 923, 732]]<|/det|> +This is super minor, but on line 64 they state that approximately \(25\%\) of the planet's species are threatened with extinction. This seems a little high to be well supported. I would like to see the number revised and or the addition of citations to support this claim. + +<|ref|>text<|/ref|><|det|>[[72, 743, 922, 912]]<|/det|> +This study is likely to have an artifactual bias against detecting change in occupancy of species that were historically abundant. Note that this makes their key finding "harder" to detect, i.e., they found their result in spite of the fact that there's a bias making this result less likely to be observed. This is worth discussing, particularly in the context of explaining why they find a stronger connection between historic occupancy and naturalized success vs. change in occupancy and naturalized success. The issue is that any species that was historically common, i.e., found in most grid cells within a region, cannot add many new grid cells, since they already occupy most of them. This consideration will vary among regions depending upon how fully the common species occupy the entire set of grid cells. So, if the most common species only occupies \(40\%\) of the grid cells in the historic period than this consideration won't be too important; alternatively if the most common species historically occupied \(90\%\) of the grid cells (and could only at most occupy the final \(10\%\) ) than this consideration will be very important. Looking at Fig. S1. I would guess that a region like Austria had common species that occupied almost all of the grid cells historically, which would explain the bow downward in the most common species in the plot, whereas Great Britain, probably did not. In any case, regardless of my exact speculations, I think mentioning this would probably be worthwhile. + +<|ref|>text<|/ref|><|det|>[[70, 924, 911, 939]]<|/det|> +While certainly not essential, it would be nice to know if the common species, which became more common through time in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 905, 87]]<|/det|> +the native range, belong to some easily identifiable group. I can imagine, for example, that most of these species might be agricultural weeds, or perhaps pasture species, etc. Any easy to run analyses that could help elucidate this would provide additional context to the work. + +<|ref|>text<|/ref|><|det|>[[72, 99, 915, 243]]<|/det|> +I was a bit surprised the manuscript doesn't mention the "distribution- abundance" relationship, particularly surrounding the discussion of change in local abundance. The distribution- abundance relationship is well described in Jim Brown's book of Macroeology and there are a number of journal articles published on that topic in the 80s and 90s. Basically the pattern (which seems to be pretty robust to taxonomic groups and spatial scales) is that there is a positive correlation between frequency of occurrence and average abundance at sites of occurrence. So, species found at lots of sites tend to also be more abundant at those sites, whereas species found at few sites tend to also have low abundance where they are found. There is disagreement about why this happens, but not really disagreement that it happens. Sometimes there's a more triangular (less linear) relationship, such that some species found at few sites are abundant where they are found, but what never happens is having species found at lots of places that on average are found in low abundance where they do occur. What this means, relative to this paper, is that the species that have increased in frequency are also very likely to have increased in abundance as well. + +<|ref|>text<|/ref|><|det|>[[73, 255, 134, 268]]<|/det|> +Dov Sax + +<|ref|>text<|/ref|><|det|>[[73, 294, 282, 321]]<|/det|> +(Remarks on code availability) not applicable + +<|ref|>text<|/ref|><|det|>[[73, 333, 161, 346]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 359, 238, 372]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 372, 918, 450]]<|/det|> +The aggregated dataset is impressive. The long history of plant records and surveys in Europe allows a unique gathering of information on plant species occupancy and the authors investigate long- lasting questions on the association between species commonness and their ability to naturalize globally. The research questions are relevant to invasion ecology and insights into these dynamics could have important implications to allow managers to target efforts of early detection and control. I also reviewed the code and analysis for Austria, and I am extremely satisfied with the documentation provided and the conciseness of it - great job! With that said, I bring below several important overall topics to consideration: + +<|ref|>text<|/ref|><|det|>[[72, 461, 917, 556]]<|/det|> +Given (i) the constraints in including all 10 countries/regions in a single model, the authors' solution by considering them as independent "datasets" modeling each region separately although many share political boundaries, (ii) the low variability explained by the models, and (iii) the narrow geographical scope of the sources regions of species to establish elsewhere, I am having a hard time to be convinced that early occupancy and occupancy change index are driving forces of the number of global regions with naturalization for a given species, and the broad generalizations brought in the title (as if all naturalized plants across the globe follow a similar pattern) and manuscript. Interestingly, the authors bring such caution themselves in L208- 209, and it reinforces that the generalization brought up in this manuscript can be unrealistic. + +<|ref|>text<|/ref|><|det|>[[72, 567, 922, 660]]<|/det|> +My next big concerns rely on the predictors chosen to be in the model, and not exploration effect sizes (only significance was reported). Given that early occupancy is used to calculate the occupancy change index, one would expect a high correlation among them as well as a lack of independence, producing confounded effects of each variable on the global naturalization metrics (naturalized vs not naturalized; and number of global regions with naturalization). How correlated the predictors are? How can you justify the use of both variables in the same model while interpreting their effects? With respect to effect size and model interpretation, hurdle model effect sizes need to be back- transformed to be interpreted adequately. However, the values presented in Table 2 are values directly extracted from the model outputs. + +<|ref|>text<|/ref|><|det|>[[72, 671, 918, 789]]<|/det|> +Across all models, the predictors explained a low portion of the variability within the response variable (13% to 28%). I wonder if the effects of early occupancy and the occupancy change index would have a strong effect (dependent on the model) if other important variables were included, such as predictors that account for human influence (such as Global Human Modification; Kennedy, C. M., Oakleaf, J. R., Theobald, D. M., Baruch- Mordo, S., & Kiesecker, J. (2018). Global human modification. https://doi.org/10.6084/m9.figshare.728307, figshare), productivity (net primary productivity - NPP), and other environmental variables that have been shown to strongly influence the establishment of non- native plants across the globe. Therefore, I would recommend incorporating other drivers of the establishment (such as the ones I have just mentioned) in the model to allow a more accurate understanding of the relative importance of the different forms of occupancy (if both can actually be in a single model) investigated in the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 801, 920, 945]]<|/det|> +Overall, the consistency in terminology used can be largely improved. Doing so, will allow the readers to follow the thought process and story of the paper more easily, as well as connect the different components across the sections. Here are my recommendations: (1) the words 'countries', 'native range', and 'regions' are used interchangeably, when they shouldn't. I recommend if using regions, to clarify in their first appearance that they correspond to the entirety of their respective country in X number of cases. I would prefer to not read 'native range' in the context of the paper as be synonym of a region, given that, as pointed out in the paper (figure S6) there are several species that are native to multiple countries/regions (side note: the number of common species across countries/regions should be added to the methods section). (2) I strongly suggest the revision of the terminology associated with referring to non- native species as aliens. I suggest the authors revise the discussion provided here (https://doi.org/10.1111/brv.13071) and here (https://doi.org/10.1002/fee.2561), and consider a complete switch to 'non- native', including in the title. (3) the use of 'at home' and 'winners at home' is confusing, and it is not consistently used across the manuscript. Particularly when the 'winners at home' are associated with the distribution of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 923, 112]]<|/det|> +species within a political boundary (such as country) rather than its native range (which more frequently than not does not follow such boundaries). Additionally, by referring as "whether species that are increasing at home" [L99] implies that the authors directly measured direct expansion in species range, which wasn't the case and was explained in the methods on L3314- L317. (4) the interchangeable use of "changes in native- range commonness" and "occupancy change index" makes it hard to follow. + +<|ref|>text<|/ref|><|det|>[[72, 124, 923, 218]]<|/det|> +Legends of figures: I would suggest the revision of the legend of all figures and tables to be completely understandable in isolation. For example, in table 2 the model results show results for both "naturalized or not" and for the "number of regions where naturalized", not only the later as directed. The understanding of hurdle models can be not trivial, so the more detailed explanation of what exactly the Bernoulli and zero- truncated count parts means biologically is strongly encouraged. Another example, Figure S6 legend is quite uninformative, and can only be understood after reading the main text. I pointed out here a couple examples, but all legends should be revised for clarity. These are suggestions that I believe will improve the accurate understanding of your paper and its biological implication. + +<|ref|>text<|/ref|><|det|>[[72, 228, 923, 310]]<|/det|> +Early occupancy was not clearly explained anywhere in the main manuscript or supplement. How was this data specifically obtained given the earliest period of data available for a country/region? And more generally, how occupancy was defined? Let's say there is a period of 3 years and in y1 a species was present in 6 out of 10 cells; y2, in 4 cells being 2 new ones compared to y1; y3 in 7 cells being one new one. What is the occupancy of this species? Given the disparity of sources and formats the data was obtained in the first place for each country/region, was the count of cells to obtain occupancy consistent across the country/region? How? + +<|ref|>text<|/ref|><|det|>[[72, 320, 923, 425]]<|/det|> +I believe that the abstract does not contain enough information to understand how the knowledge gap was analyzed, so I suggest a thorough revision. For example, in L45- L46, "particularly common plant species" where? The abstract presents the results from the truncated negative binomial portion of the model only, therefore defining what 'global naturalization' means in L46- 47 is necessary. Also, a basic ecological interpretation/definition of "occupancy- change index" and "early period occupancy" would allow a larger audience to benefit from these findings. The latter was not formally defined in the paper, and it hampers the understanding of the choice of approach and the findings, as I mentioned in another piece of this review. Lastly, the abstract would gain a larger audience by having a closing statement with the implication for management and policy- related actions for species that follow the pattern described in this manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 436, 918, 490]]<|/det|> +Overall structure of the paper: In my first read of the main paper, I would argue that the content necessary to fully understand the analysis and research findings isn't present. The authors should keep in mind that the methods section only appears at the end of the paper, so other sections should provide enough information about the methods and definitions of terms used that allow the readers to accurately understand the results and discussion. + +<|ref|>text<|/ref|><|det|>[[72, 500, 757, 516]]<|/det|> +How similar are the boundaries of the 10 focal regions compared to the same regions from GloNAF? + +<|ref|>text<|/ref|><|det|>[[72, 527, 365, 541]]<|/det|> +Specific comments and recommendations: + +<|ref|>text<|/ref|><|det|>[[72, 540, 920, 944]]<|/det|> +- I am curious to understand why "declining species" was a relevant keyword selected by the authors. +- L84: add citation to support statement. +- L88: a good example in which countries and ranges are used interchangeably. Clarifying language would improve the understanding and cohesion of this paper. +- L104: the statement "largely the same species" has dubious meaning, clarify. +- L105: the statement "two (or more) periods" has no context up to this point and hinders the reader from grasping the methods used in the paper in general terms. Also, to the best of my understanding of this paper, for each country/region, each main model shown in the main manuscript contains only the comparison between two time periods. Adding "or more" is confusing and might better if brought up later when nuances in the results are explained. +- All content presented in the supplement should be referenced in the main text. +- L106: "for each native species in each region" how about species that are present in more than one region? There is some mention of them when Figure S6 is referred to, but given the proximity of each of the countries/regions used in this study some short explanation on why region rather than native range extrapolating political boundaries were chosen. +- L107: "occupancy-change index" hasn't been explained and needs clarification. +- L109-110: "the number of regions where the species has become naturalized" this text is confusing. It seems that one is referring to the 10 regions, but in fact, it is from the regions defined by GloNAF to defined where a species is naturalized or not. +- L110: "early period" is mentioned in the abstract and here, but the term hasn't been described yet. +- L121-122: this statement contradicts statements on L314-317. These species are more common than what would expected given their occupancy in the early period. +- L125-126: with respect to "the zero-truncated count part of the hurdle model, not with the Bernoulli part", I suggest changing the language similar to above: the likelihood of being naturalized outside native range vs naturalized in more regions at the global scale. +- L131: to convey the message more clearly, it might be helpful to associate the occupancy- change index as a metric of commonness early on in the text and use this term across the paper. +- L136: this statement "increased in occupancy" is unclear. Since when? +- L145-148: statements seem repeated from the introduction. I suggested the authors be mindful of which information is essential and necessary in the discussion by focusing on an in- depth discussion of the results. +- L149-150: what is the environmental variability within the native range studied per species? is the set of species used in this study representative of species distributed in a wide range of environmental conditions? +- L152-154: are these traits present in the focal species studied here? Could such information be pulled from global + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 410, 60]]<|/det|> +databases, such as TRY, and incorporated here? + +<|ref|>text<|/ref|><|det|>[[72, 60, 880, 86]]<|/det|> +- L186-187: if the early period chosen had a specific reasoning for it, it should be clarified in the introduction, not in the discussion. + +<|ref|>text<|/ref|><|det|>[[72, 86, 920, 126]]<|/det|> +- L202-204: I cannot follow the connection of this sentence to the previous after. "richer-get-richer" is a term generally used in the context of species richness, and it doesn't seem to apply here, but also the directionality of the negative is the opposite in the sentence? Consider revising and defining "Matthew effect" and or "richer-get-richer". + +<|ref|>text<|/ref|><|det|>[[72, 126, 866, 153]]<|/det|> +- L223: how were "losers" quantified in this paper? Similar language also shows up in the keywords, and it makes it confusing. + +<|ref|>text<|/ref|><|det|>[[72, 153, 483, 166]]<|/det|> +- L228-229: why habitat specificity might have not changed? + +<|ref|>text<|/ref|><|det|>[[72, 166, 920, 205]]<|/det|> +- L245-251: this discussion is really interesting and I would suggest to be the driving force of the importance of this study and findings (if changes in the methods are performed and conclusions hold) - to aid ways in which findings from core science can be transferred to managers and policymakers. + +<|ref|>text<|/ref|><|det|>[[73, 231, 283, 243]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 243, 900, 270]]<|/det|> +the results for "Austria" are reproducible - from analysis to figures. According to the authors and my understanding of their methods, each model was run the same way, only the input data for other regions (data available on figshare) changes. + +<|ref|>sub_title<|/ref|><|det|>[[73, 282, 162, 295]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 308, 238, 321]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 321, 914, 386]]<|/det|> +The study aims to compare whether the changes in select plant species' native range size correlates with naturalization history elsewhere. The authors examine changes in grid occupancy drawing on historic grid- based surveys of the vascular flora of 10 areas in Europe. The premise is interesting and the results, though correlative, make intuitive sense. However, there are some methodological concerns that render the conclusion that plants that have naturalized as aliens abroad have also become more common in their native range unearned. + +<|ref|>text<|/ref|><|det|>[[72, 398, 917, 476]]<|/det|> +As the authors note, there are many definitions of commonality, and arguably the one being used in this study is not truly a metric of such. At best, the authors are examining a proxy of range size. The authors do a good job of mentioning potential limitations - e.g., one cannot know how abundant these species are within each grid cell. Further, it is likely that the surveys upon which the study relies were conducted with varying protocols and specific objectives, certainly across regions and possibly even over time. Even if the surveys were more or less standardized, the analyses conducted here can produce misleading results for species that have been recorded more efficiently/accurately in one survey than the others. + +<|ref|>text<|/ref|><|det|>[[72, 488, 920, 633]]<|/det|> +More importantly, the assayed regions do not represent the full native range of the species examined. It is possibly for any given species that while, say, in the Czech Republic its range has increased, the range may have decreased in other parts of its native range. Thus, it is unknown how a species' entire native range size has changed. Though the authors claim that the general positive correlation between occupancy- change indices they observed among regions for the same species indicates that native range 'winners' and 'losers' were generally consistent across regions, these regions may constitute a small or biased sampling of these species' entire native ranges. Also, many of the species that have naturalized elsewhere are known to have fairly large native ranges that extend well beyond the regions included in the study. Further, it seems that only 44 species (among thousands) were present in multiple regions. Along these lines, without more context regarding the full native ranges of these species it is difficult to say whether the results of this study, though suggestive, truly provide strong evidence that many plant species that are spreading as naturalized aliens around the globe also have high occupancies or are increasing in occupancy in their native range. + +<|ref|>text<|/ref|><|det|>[[72, 645, 923, 711]]<|/det|> +GloNAF regions are used as the unit of analyses regarding naturalized ranges. However, the manuscript never mentions what these regions are. How were they defined? Based on the map provided in the supplements, it seems that these regions largely follow geopolitical boundaries and come in many shapes and sizes. Thus, the number of regions where a species has become naturalized may not be a suitable metric for the degree of global naturalization (and comparison with occupancy in a limited sampling of these species' native ranges). + +<|ref|>text<|/ref|><|det|>[[72, 723, 920, 880]]<|/det|> +The methods require more detail. Pertinent information is often relegated to the supplements or other publications. For instance, the authors should note how many species were examined in the main text so that the numbers they present and discuss can be understood in context. While it is fine to refer to methods in previous studies, there should at least be enough information in the manuscript for the reader to be able to interpret the results. For instance, it was necessary to refer back to Telfer (2002) repeatedly to understand the figures presented in the results as well as some of the choices made in the study. Along these lines, the grid counts for each region were not done the same way. For instance, in Denmark, the number of occupied grid cells of each species in each region was calculated by multiplying the regional abundance of each species by the total number of referenced grid cells for each region, combining the grid- cell data for each taxon across the 11 regions of the country that were surveyed to get one single value. In contrast, simple grid cell counts were used in some other regions. While there is no reason not to use available data, this makes the results from each region (which were modeled separately) less comparable, and I recommend that the authors harmonize the approach to grid cell counting and present those results as well. + +<|ref|>text<|/ref|><|det|>[[73, 894, 222, 906]]<|/det|> +Additional comments: + +<|ref|>text<|/ref|><|det|>[[72, 907, 450, 920]]<|/det|> +The 'winners' and 'losers' angle seems a bit colloquial. + +<|ref|>text<|/ref|><|det|>[[73, 920, 380, 933]]<|/det|> +Table 1 is not referenced in the text correctly. + +<|ref|>text<|/ref|><|det|>[[73, 933, 296, 945]]<|/det|> +Fig S6 - x and y are not defined. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 72]]<|/det|> +Unscale the occupancy index when presenting and discussing the results – the scaled values are confusing to interpret and the index is already ultrametric. + +<|ref|>text<|/ref|><|det|>[[72, 72, 912, 111]]<|/det|> +The layout of Fig.2 is a bit confusing with the inset with multiple abbreviations and asterisks. Also, why not just replace this figure with the corresponding one in the supplements that show the raw data as noted in the caption (S5)? Where were the 1/6 and 5/6 quantiles chosen for illustration? + +<|ref|>text<|/ref|><|det|>[[72, 111, 860, 138]]<|/det|> +As GloNAF data are not freely accessible, please present information on which specific regions each species was naturalized in. + +<|ref|>text<|/ref|><|det|>[[72, 138, 890, 164]]<|/det|> +Are the identities of the grid cells occupied by each species known? If so, perhaps the potential drivers of range change could be examined. + +<|ref|>text<|/ref|><|det|>[[72, 164, 910, 204]]<|/det|> +The "Gridcells_earlyperiod" and "Gridcells_laterperiod" values for Thierache are not whole numbers—according to the metadata these should be simple counts of the number of cells occupied by each species and the supplementary methods do not state any special circumstances (unlike Germany or Denmark). + +<|ref|>text<|/ref|><|det|>[[73, 230, 440, 257]]<|/det|> +(Remarks on code availability) I did not try running the code but it looked reasonable. + +<|ref|>text<|/ref|><|det|>[[73, 268, 142, 281]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 294, 219, 307]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 320, 160, 333]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 346, 402, 372]]<|/det|> +(Remarks to the Author) The authors have addressed all of my concerns. + +<|ref|>text<|/ref|><|det|>[[73, 384, 283, 398]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 423, 162, 437]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 450, 238, 462]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 462, 912, 502]]<|/det|> +I appreciate the careful point- by- point revisions given in response to my previous comments and concerns. I appreciate the thorough revision of the text to improve the consistency of terms used—the main text is now a lot easier to digest. Moving forward, I have two broad, major comments that are detailed below. Then, those are followed by minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 514, 916, 568]]<|/det|> +1) I mentioned this before and I noticed that Reviewer 3 also made a comment on this: using the regions as units of native ranges, particularly because they follow political boundaries. So, could you provide the supplement with how many species are present across all regions? How many species are present in all regions but one? And so forth? And how many species are uniquely present in a single region? + +<|ref|>text<|/ref|><|det|>[[72, 579, 914, 633]]<|/det|> +2) Woodiness was added in complementary models as a way to address some of the concerns of Reviewer Dov Sax. If this inclusion is kept, the main text would need some introduction of the relatedness of woodiness, range expansion, and probability of becoming naturalized, so, therefore, justifying why this a reasonable trait to be evaluated. Lines L171-173 do not justify sufficiently. I would pull as base of some of the arguments and justification given in the rebuttal. + +<|ref|>text<|/ref|><|det|>[[73, 645, 192, 658]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 670, 914, 699]]<|/det|> +Results: The tables with the main results of your models (i.e., mention of tables S14- S30 should potentially show up earlier, as it is the results of the main models (without woodiness) + +<|ref|>text<|/ref|><|det|>[[72, 710, 911, 738]]<|/det|> +L91- 93: The statement is somewhat confusing. Also, should it be "increasing their occupancy" rather than "increasing" only in L92? Please, revise + +<|ref|>text<|/ref|><|det|>[[73, 750, 336, 763]]<|/det|> +L103: do you mean "range over time"? + +<|ref|>text<|/ref|><|det|>[[72, 776, 900, 816]]<|/det|> +L199- 200: would you be able to provide either a table or a simple graph per region with how many species out of the total per region were present in all its grid cells? This would help the reader to be aware of how many species, from the poll studies, have this pattern. + +<|ref|>text<|/ref|><|det|>[[73, 828, 323, 842]]<|/det|> +L228: "...species with high early..."? + +<|ref|>text<|/ref|><|det|>[[73, 866, 439, 893]]<|/det|> +(Remarks on code availability) I reviewed the code during the first round of revisions. + +<|ref|>text<|/ref|><|det|>[[73, 905, 161, 918]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 931, 238, 945]]<|/det|> +(Remarks to the Author) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 920, 113]]<|/det|> +This is a broad analysis staying that certain plant species, likely due to a combination of human actions and the plant features, are favored under human uses of the landscape in their ranges and in new regions. The novelty relies on including change in abundance/occupancy in the native range as a predictor of naturalization somewhere else. These findings could be used to generate list of species that could become invasive, lists that could be compared with already generated watch lists to assess how much information this predictor is adding. + +<|ref|>text<|/ref|><|det|>[[73, 125, 907, 205]]<|/det|> +Since changes in occupancy/abundance were not analyzed as a function of other drivers than time, e.g., human activities targeting particular habitats/plant communities, results might very indirectly be assessing the causes of naturalization, because increase in occurrence and naturalization might have to do with habitats selected rather than intrinsic features of the plant species. This is a point brought by the reviewers that has been dismissed by the authors (see next comment). Analyzing what it made those species increase in their native and introduced ranges would be of greater consequence for management and conservation. + +<|ref|>text<|/ref|><|det|>[[72, 216, 920, 296]]<|/det|> +Much more informative would have been to analyze features of the species that were already abundant and that increased their occurrences, e.g., are ruderal species over- represented in that group? What are the main traits characterizing those species? That again would provide more useful information for management and conservation. Maybe the data is not available for all, but it could be done for the ones that it is. Line 207- 216 make that point. Many studies are using global trait data sets to do it, if authors have decided not to do it that's their choice but claiming that the reason for not doing it is that that information is not available is not accurate. + +<|ref|>text<|/ref|><|det|>[[72, 307, 923, 387]]<|/det|> +It looks like early occupancy, and to some extent woodiness, are a better predictor of naturalization than change in occupancy. Table S3, this should be emphasized more in the main text because data on changes overtime may not be available, but actual native range and woodiness are, and those could be used on their own as predictors. Especially considering that change in occupancy is being predicted by early occupancy. Also, adding information on how much variance was additionally accounted for by including change in occupancy, vs a model with early occupancy and woodiness only, would help to understand the scope of this predictor. + +<|ref|>text<|/ref|><|det|>[[72, 398, 916, 440]]<|/det|> +My suggestion would be to change 'region' for countries. Region usually indicates ecological, e.g., climatic, differences, but these data sets reflect political units. Sorting the data into actual ecological regions might have shown more interesting/informative results. + +<|ref|>text<|/ref|><|det|>[[70, 450, 910, 478]]<|/det|> +It is not clear if changes in occupancy overtime were standardized by the period of time between census, i.e., more change expected if longer time between censuses. + +<|ref|>text<|/ref|><|det|>[[70, 489, 816, 504]]<|/det|> +I can't tell the difference between Table S3 and the ones that follow for each country, information is the same. + +<|ref|>text<|/ref|><|det|>[[72, 529, 288, 543]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 543, 647, 557]]<|/det|> +The analyses are done using standard techniques and standard software packages. + +<|ref|>text<|/ref|><|det|>[[72, 568, 140, 581]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[72, 594, 220, 608]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 620, 161, 633]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 646, 238, 659]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 659, 920, 700]]<|/det|> +I have now revisited the authors' responses to the inquiries raised by Reviewer #4 and find that they have made appropriate revisions and/or provided clear and well- justified explanations, both in the rebuttal and in the manuscript, for not implementing certain suggestions. I am satisfied with the current version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[70, 710, 923, 738]]<|/det|> +As Reviewer #2, I also appreciate the authors' thorough and clear responses to my own comments. Thank you for the careful attention to detail in your point- by- point reply. + +<|ref|>text<|/ref|><|det|>[[72, 750, 161, 763]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 776, 439, 803]]<|/det|> +(Remarks on code availability) I reviewed the code during the first round of revisions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 242, 107]]<|/det|> +Dear reviewers, + +<|ref|>text<|/ref|><|det|>[[114, 130, 884, 248]]<|/det|> +We have now revised the manuscript entitled "Plants that have naturalized as aliens abroad have also become more common at home during the Anthropocene" ("Many plants naturalized as aliens abroad have also become more common within their native regions" in revised version), based on the helpful and constructive comments. Below we provide our point- by- point responses to the comments. Please, note that the line numbers refer to the clean version of the manuscript with highlights and our responses are in blue. + +<|ref|>text<|/ref|><|det|>[[114, 260, 437, 297]]<|/det|> +Sincerely, RASHMI Paudel (on behalf of all authors) + +<|ref|>text<|/ref|><|det|>[[115, 339, 418, 357]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 379, 863, 516]]<|/det|> +This paper addresses a highly novel question, namely whether species that are successful as non- native species have also become more successful within their native range. I am familiar with the invasions literature and I am unaware of any previous study that has addressed this question. The analyses themselves are conducted soundly and the work is clearly described. I have no major concerns about this manuscript. I do have one suggestion that I believe should be addressed in some way, as well as several additional thoughts that could add additional interpretation to their findings. I detail these considerations below. + +<|ref|>text<|/ref|><|det|>[[115, 519, 825, 537]]<|/det|> +RESPONSE: We thank the reviewer (Dov Sax) for his positive and constructive comments. + +<|ref|>text<|/ref|><|det|>[[113, 558, 881, 898]]<|/det|> +The one issue that I believe needs to be better addressed has to do with their choices about where to split the native range data, temporally, i.e., on deciding on a specific year to split "historic" from "recent" distributions with a region. A few of their data sets have natural splits between these periods, e.g., Denmark (with historic data from the 1800s and modern data from less than a decade ago), but more than half of their data sets appear to have been arbitrarily split at 1990 or 2000, e.g., the Netherlands data set is split as before 1990 and after 1990. At a minimum the manuscript should be revised to explain the rationale for these splits. Why are some split at 1990 and why others at 2000 or even, in one case, at 1971. I'm guessing they have some reasonable reason for this, but this isn't explained and so it makes the reader feel unsure about these decisions. They mention one data set where they look at multiple possible splits, but I really would have liked to have seen an analysis with a few more of these data sets that considered if the year of the split (e.g., 1980 vs. 1990 vs. 2000) ends up impacting the patterns observed. I imagine that their results are pretty robust to the precise year of splits, but I'm not sure. I think addressing this in some way would be useful, even if was just to show this with 2 or 3 more of their study regions. If it proves impractical to do such analyses then I would still expect to see a short paragraph added (or perhaps 2- 3 sentences added to an existing paragraph) to the discussion that addresses this concern. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 276]]<|/det|> +RESPONSE: We now provide information on the choices of the splits (lines 323- 324) as "Most of the data sources provide data for only two time periods, limiting us to the temporal splits available in the original datasets". Most of the datasets provided data for only two time periods and we were therefore limited to the splits chosen in the original datasets. For the Netherlands, however, we can also extract the grid- cell numbers using different years of the split, therefore, to see how robust the results are with regard to the chosen split 1990, we now also extracted data using the year 2000 as split. We chose 2000 because it was also the year of split for some of the other datasets. Like we already found for Great Britain and Ireland, the patterns for the Netherlands were very similar for the different years of the split. We added these results to the Supplement (TableS30). + +<|ref|>text<|/ref|><|det|>[[114, 293, 882, 393]]<|/det|> +This is super minor, but on line 64 they state that approximately \(25\%\) of the planet's species are threatened with extinction. This seems a little high to be well supported. I would like to see the number revised and or the addition of citations to support this claim. RESPONSE: We now specify that the \(25\%\) applies to the animal and plant species that have been assessed, and we refer to the IPBES 2019 report (lines 64- 65). + +<|ref|>text<|/ref|><|det|>[[113, 412, 879, 748]]<|/det|> +This study is likely to have an artifactual bias against detecting change in occupancy of species that were historically abundant. Note that this makes their key finding "harder" to detect, i.e., they found their result in spite of the fact that there's a bias making this result less likely to be observed. This is worth discussing, particularly in the context of explaining why they find a stronger connection between historic occupancy and naturalized success vs. change in occupancy and naturalized success. The issue is that any species that was historically common, i.e., found in most grid cells within a region, cannot add many new grid cells, since they already occupy most of them. This consideration will vary among regions depending upon how fully the common species occupy the entire set of grid cells. So, if the most common species only occupies \(40\%\) of the grid cells in the historic period than this consideration won't be too important; alternatively, if the most common species historically occupied \(90\%\) of the grid cells (and could only at most occupy the final \(10\%\) ) than this consideration will be very important. Looking at Fig. S1. I would guess that a region like Austria had common species that occupied almost all of the grid cells historically, which would explain the bow downward in the most common species in the plot, whereas Great Britain, probably did not. In any case, regardless of my exact speculations, I think mentioning this would probably be worthwhile. RESPONSE: We now discuss this consideration in lines 199- 205. + +<|ref|>text<|/ref|><|det|>[[115, 772, 875, 870]]<|/det|> +While certainly not essential, it would be nice to know if the common species, which became more common through time in the native range, belong to some easily identifiable group. I can imagine, for example, that most of these species might be agricultural weeds, or perhaps pasture species, etc. Any easy to run analyses that could help elucidate this would provide additional context to the work. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 884, 308]]<|/det|> +RESPONSE: We agree that, although it would not be essential for answering our research question, adding such information would be very interesting. Unfortunately, habitat information is currently not available for all 3920 species in our datasets. Instead, we now added information on woodiness of the species (where we assume that woody species are typical for forest habitats and non- woody species for open habitats). We found that while woody species had higher occupancy- change values than non- woody species in six of the 10 native regions (Table S2), woody species were less likely to become widely naturalized. Nevertheless, the positive association between naturalization and occupancy change remained largely unaffected by inclusion of woodiness as an additional variable in the hurdle models. This shows that our results are robust. We added the results of the additional analyses in the Supplements (Tables S3, S4- 13).) and refer to them in the Discussion (lines 173- 185 & lines 238- 245). + +<|ref|>text<|/ref|><|det|>[[113, 328, 884, 589]]<|/det|> +I was a bit surprised the manuscript doesn't mention the "distribution- abundance" relationship, particularly surrounding the discussion of change in local abundance. The distribution- abundance relationship is well described in Jim Brown's book of Macroeology and there are a number of journal articles published on that topic in the 80s and 90s. Basically the pattern (which seems to be pretty robust to taxonomic groups and spatial scales) is that there is a positive correlation between frequency of occurrence and average abundance at sites of occurrence. So, species found at lots of sites tend to also be more abundant at those sites, whereas species found at few sites tend to also have low abundance where they are found. There is disagreement about why this happens, but not really disagreement that it happens. Sometimes there's a more triangular (less linear) relationship, such that some species found at few sites are abundant where they are found, but what never happens is having species found at lots of places that on average are found in low abundance where they do occur. What this means, relative to this paper, is that the species that have increased in frequency are also very likely to have increased in abundance as well. + +<|ref|>text<|/ref|><|det|>[[114, 589, 884, 727]]<|/det|> +RESPONSE: We thank the reviewer (Dov Sax) for pointing this out, and we now mention the "distribution- abundance" relationship in the Discussion as "The local abundance of species is usually positively related to the other measures of a species' distribution [e.g. 50, 51]. Previous studies across various spatial scales and taxonomic groups, have also shown that species increasing their occupancy are also very likely to increase in abundance at the sites where they occur [e.g. 52, 53]." (lines 278- 281) and refer to Jim Brown's book in the Introduction (line 98, reference number 34). + +<|ref|>text<|/ref|><|det|>[[115, 750, 180, 765]]<|/det|> +Dov Sax + +<|ref|>text<|/ref|><|det|>[[115, 788, 464, 806]]<|/det|> +Reviewer #1 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[115, 828, 230, 845]]<|/det|> +not applicable + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 419, 108]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 129, 870, 290]]<|/det|> +The aggregated dataset is impressive. The long history of plant records and surveys in Europe allows a unique gathering of information on plant species occupancy and the authors investigate long- lasting questions on the association between species commonness and their ability to naturalize globally. The research questions are relevant to invasion ecology and insights into these dynamics could have important implications to allow managers to target efforts of early detection and control. I also reviewed the code and analysis for Austria, and I am extremely satisfied with the documentation provided and the conciseness of it - great job! With that said, I bring below several important overall topics to consideration: + +<|ref|>text<|/ref|><|det|>[[115, 290, 820, 308]]<|/det|> +RESPONSE: We thank the reviewer for the compliments and the constructive comments. + +<|ref|>text<|/ref|><|det|>[[114, 329, 884, 507]]<|/det|> +Given (i) the constraints in including all 10 countries/regions in a single model, the authors' solution by considering them as independent "datasets" modeling each region separately although many share political boundaries, (ii) the low variability explained by the models, and (iii) the narrow geographical scope of the sources regions of species to establish elsewhere, I am having a hard time to be convinced that early occupancy and occupancy change index are driving forces of the number of global regions with naturalization for a given species, and the broad generalizations brought in the title (as if all naturalized plants across the globe follow a similar pattern) and manuscript. Interestingly, the authors bring such caution themselves in L208- 209, and it reinforces that the generalization brought up in this manuscript can be unrealistic. + +<|ref|>text<|/ref|><|det|>[[114, 508, 884, 707]]<|/det|> +RESPONSE: We did not intend to say that all plants that have naturalized have also become more common at home. We have now carefully checked the text and toned down any broad generalizations that are not directly supported by our data. For example, to make it clear that not all plants that have naturalized have become more common at home, we now write "Many plants ..." Instead of just "Plants ...". Although we used early occupancy and the occupancy- change index as predictors in the models, and naturalization as response variable, we did not imply that early occupancy and the occupancy- change index are the driving forces of the number of global regions with naturalization for a given species. Instead, we believe that our results suggest that both commonness at home and naturalization elsewhere are correlated because they share similar drivers. We now mention this more explicitly (lines 102- 104 & 156- 157). + +<|ref|>text<|/ref|><|det|>[[114, 728, 879, 867]]<|/det|> +My next big concerns rely on the predictors chosen to be in the model, and not exploration effect sizes (only significance was reported). Given that early occupancy is used to calculate the occupancy change index, one would expect a high correlation among them as well as a lack of independence, producing confounded effects of each variable on the global naturalization metrics (naturalized vs not naturalized; and number of global regions with naturalization). How correlated the predictors are? How can you justify the use of both variables in the same model while interpreting their effects? + +<|ref|>text<|/ref|><|det|>[[114, 869, 884, 907]]<|/det|> +RESPONSE: We can understand the reviewer's concern about possible correlations between early occupancy and the occupancy- change index. However, the main reason why we chose to use the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 884, 268]]<|/det|> +approach by Telfer et al. (2002) for calculating the occupancy-change index is that this approach avoids such a correlation. The occupancy-change index corresponds to the residuals of the regression of logit-transformed latter occupancy on logit-transformed early occupancy. So, for each early occupancy value, we have a symmetrical distribution of negative and positive occupancy-change index values (i.e. residuals), as can be seen in Fig. S4. We now explain this more clearly in the manuscript (lines 400-402). We also mention at the end of the Introduction (lines 116-117) that the occupancy-change index is not correlated with initial occupancy. Nevertheless, we now also calculated Pearson correlation coefficients between early occupancy and the occupancy-change index, and they were indeed low: + +<|ref|>table<|/ref|><|det|>[[114, 268, 881, 578]]<|/det|> + +
RegionPearson correlation between early occupancy and occupancy change indexP value
Austria-0.042&lt;0.05
Czech Republic0.0400.087
Denmark-0.0050.871
Flanders-0.0260.454
Germany0.0360.137
Great Britain0.176&lt;0.01
Ireland0.0630.057
The Netherlands0.0160.595
Switzerland0.0030.889
Thiérache-0.0140.703
+ +<|ref|>text<|/ref|><|det|>[[113, 597, 884, 755]]<|/det|> +Regarding the effect sizes, in addition to Table 2, which just provides a broad overview, we have also provided the full model results, including model estimates along with their respective standard errors and significance value, in supplementary Tables S14- S23. In these models, we scaled the early occupancy to mean of zero and a standard deviation of one, this was not necessary for the occupancy- change index, as it corresponds to standardized residuals, which are already scaled to a mean of zero and a standard deviation of one. Therefore, we believe that since the estimates are based on standardized values, the interpretation of the model coefficients (as effect sizes) is straightforward. + +<|ref|>text<|/ref|><|det|>[[114, 767, 881, 825]]<|/det|> +With respect to effect size and model interpretation, hurdle model effect sizes need to be backtransformed to be interpreted adequately. However, the values presented in Table 2 are values directly extracted from the model outputs. + +<|ref|>text<|/ref|><|det|>[[114, 827, 882, 902]]<|/det|> +RESPONSE: Indeed, in Table 2, we provide the model estimates of the Bernoulli and zerotruncated count parts of the hurdle models. This table mainly serves as an overview of which effects were significant in the 10 different regions. The full models' outputs are provided in Table S14- S23. We are not entirely sure how the reviewer would like to see these estimates back + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 884, 201]]<|/det|> +transformed. For the Bernoulli part, we could use the model estimates to calculate odds ratios, but for the zero- truncated count part, there is to our knowledge no equivalent. However, Figure 2 shows, based on the coefficients of both parts of the hurdle model, the predicted relationships for the number of regions where a species is naturalized. So, we believe that what the reviewer wants is already visualized in this figure. In addition, the predicted relationships for the Bernoulli and zero- truncated count parts separately are shown in Figures S1 and S2. + +<|ref|>text<|/ref|><|det|>[[113, 220, 870, 459]]<|/det|> +Across all models, the predictors explained a low portion of the variability within the response variable (13% to 28%). I wonder if the effects of early occupancy and the occupancy change index would have a strong effect (dependent on the model) if other important variables were included, such as predictors that account for human influence (such as Global Human Modification; Kennedy, C. M., Oakleaf, J. R., Theobald, D. M., Baruch- Mordo, S., & Kiesecker, J. (2018). Global human modification. https://doi.org/10.6084/m9.figshare.7283087, figshare), productivity (net primary productivity – NPP), and other environmental variables that have been shown to strongly influence the establishment of non- native plants across the globe. Therefore, I would recommend incorporating other drivers of the establishment (such as the ones I have just mentioned) in the model to allow a more accurate understanding of the relative importance of the different forms of occupancy (if both can actually be in a single model) investigated in the manuscript. + +<|ref|>text<|/ref|><|det|>[[113, 460, 884, 867]]<|/det|> +RESPONSE: Given that many factors known to affect the naturalization process, we believe that 13- 28% is not a low portion of the variability for this kind of studies. Nevertheless, we fully agree that other predictors may explain more of the variation in global naturalization success, and some of authors of this study have done such analyses. However, the aim of the current analyses was not to build a predictive model for global naturalization success. Instead, our objective was to assess whether most of the species that have started to expand outside their native ranges have also expanded within their native ranges. Therefore, although we believe that the inclusion of other predictors will increase the proportion of explained variance, it will not provide additional insights into our research question. Moreover, the variables suggested by the reviewer (i.e. human modification and NPP) are characteristics of spatial units (e.g. grid cells or regions). Therefore, such variables are useful for explaining spatial patterns in naturalized plant richness. In our study, however, the units of analysis are species, and our measures of naturalization success are not spatially explicit (i.e. our models predict naturalization incidence and number of regions, but not where a species is naturalized). Adding these variables to our analysis would therefore not be possible, and we do not believe that they would help to answer our research question or change the current results. However, based on this comment and on a comment of Reviewer #1, we now performed additional analyses in which we included woodiness, a trait that is available for most species, as another species- level “predictor” in the model. The results for the association of naturalization success with the change in occurrence frequency remained largely the same, and the portion of variation explained by the models only slightly increased (the R2 values range from 14 to 28 percent). These additional analyses have been added to the Supplements. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 881, 293]]<|/det|> +Overall, the consistency in terminology used can be largely improved. Doing so, will allow the readers to follow the thought process and story of the paper more easily, as well as connect the different components across the sections. Here are my recommendations: (1) the words 'countries', 'native range', and 'regions' are used interchangeably, when they shouldn't. I recommend if using regions, to clarify in their first appearance that they correspond to the entirety of their respective country in X number of cases. I would prefer to not read 'native range' in the context of the paper as by synonym of a region, given that, as pointed out in the paper (figure S6) there are several species that are native to multiple countries/regions (side note: the number of common species across countries/regions should be added to the methods section). (2) I strongly suggest the revision of the terminology associated with referring to non-native species as aliens. + +<|ref|>text<|/ref|><|det|>[[113, 293, 880, 476]]<|/det|> +I suggest the authors revise the discussion provided here (https://doi.org/10.1111/brv.13071) and here (https://doi.org/10.1002/fee.2561), and consider a complete switch to 'non- native', including in the title. (3) the use of "at home" and "winners at home" is confusing, and it is not consistently used across the manuscript. Particularly when the "winners at home" are associated with the distribution of species within a political boundary (such as country) rather than its native range (which more frequently than not does not follow such boundaries). Additionally, by referring as "whether species that are increasing at home" [L99] implies that the authors directly measured direct expansion in species range, which wasn't the case and was explained in the methods on L3314- L317. (4) the interchangeable use of "changes in native- range commonness" and "occupancy change index" makes it hard to follow. + +<|ref|>text<|/ref|><|det|>[[113, 477, 884, 515]]<|/det|> +RESPONSE: We thank the reviewer for spotting the inconsistencies in terminology and for the constructive suggestions. We now use consistent terminology throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[113, 516, 884, 612]]<|/det|> +(1) When referring to the regions, we now consistently use 'regions' (or 'native regions') instead of 'countries' or 'native range'. However, we still use 'native range' when we really mean the entire native range of a species. In response to the side note mentioned by the reviewer under point 1, we have now added the number of common species across the native regions to Figure S6. + +<|ref|>text<|/ref|><|det|>[[112, 615, 884, 896]]<|/det|> +(2) We prefer to keep the term 'alien' throughout the manuscript for several reasons. First, 'alien' is the term recommended by the widely used invasion stages frameworks of Richardson et al. (2000, Diversity and Distributions 6:93-107, DOI:10.1046/j.1472-4642.2000.00083.x) and Blackburn et al. (2011, Trends in Ecology and Evolution 26:333-339, doi:10.1016/j.tree.2011.03.023), and it also the term used in the recent IPBES assessment ("Thematic Assessment Report on Invasive Alien Species and their Control"; https://www.ipbes.net/ias), a work that has set the standards for the current invasion research. So, using another term, in our opinion, will not tame the terminological tempest in invasion science. Furthermore, we cannot avoid the term 'alien' because it is part of the name of the main database (the Global Naturalized Alien Flora; GLoNAF) used for the data on naturalization success. We have published many papers that use the GLoNAF database, and we consistently used the term "alien". Thus, for the sake of consistency of our own work, we prefer to continue using the same term. Second, we are aware that the term 'alien' has unfortunately become politicized, particularly in North America. However, when we have to come up with a new term each time a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 884, 227]]<|/det|> +term becomes politicized, the terminological chaos in invasion biology will increase rather than decrease. In this regard, it should also be noted that the term 'non- native' is also considered harmful by some researchers (see the database of harmful terminology in ecology and evolution, https://www.eeblanguageproject.com/repository, associated with Cheng et al. (2023, Trends in Ecology and Evolution 5:381- 384, https://doi.org/10.1016/j.tree.2022.12.011). Having said this, as much as we prefer the term 'alien', if the editor insists on us replacing 'alien' with another term, we are willing to do so. + +<|ref|>text<|/ref|><|det|>[[114, 230, 884, 348]]<|/det|> +(3) We now avoid the term 'at home' and instead use 'in their native regions'. +(4) We used "changes in native-range commonness" only once in the manuscript (line 160 of the previous version), and there we do not want to change it to "occupancy change index". This is because we were not referring exclusively to the index that we used but to any change in commonness. However, we now replaced it with "temporal changes in measures of commonness within native regions" (line 189). + +<|ref|>text<|/ref|><|det|>[[114, 366, 872, 536]]<|/det|> +Legends of figures: I would suggest the revision of the legend of all figures and tables to be completely understandable in isolation. For example, in table 2 the model results show results for both "naturalized or not" and for the "number of regions where naturalized", not only the later as directed. The understanding of hurdle models can be not trivial, so the more detailed explanation of what exactly the Bernoulli and zero-truncated count parts means biologically is strongly encouraged. Another example, Figure S6 legend is quite uninformative, and can only be understood after reading the main text. I pointed out here a couple examples, but all legends should be revised for clarity. These are suggestions that I believe will improve the accurate understanding of your paper and its biological implication. + +<|ref|>text<|/ref|><|det|>[[115, 535, 882, 574]]<|/det|> +RESPONSE: We now have thoroughly revised all legends, including Table 2 and Figure S6, which is now Figure S3 (lines 659- 672 & lines 147- 150 in supplementary). + +<|ref|>text<|/ref|><|det|>[[114, 594, 880, 752]]<|/det|> +Early occupancy was not clearly explained anywhere in the main manuscript or supplement. How was this data specifically obtained given the earliest period of data available for a country/region? And more generally, how occupancy was defined? Let's say there is a period of 3 years and in y1 a species was present in 6 out of 10 cells; y2, in 4 cells being 2 new ones compared to y1; y3 in 7 cells being one new one. What is the occupancy of this species? Given the disparity of sources and formats the data was obtained in the first place for each country/region, was the count of cells to obtain occupancy consistent across the country/region? How? + +<|ref|>text<|/ref|><|det|>[[114, 754, 884, 902]]<|/det|> +RESPONSE: We have now moved the definition of "occupancy" and "early occupancy" to the end of the Introduction as "Here, we test the hypothesis that many of the plant species that have become widely naturalized across the globe are also increasing in occupancy (i.e. the proportion of grid cells across a region in which a species has been recorded) within their native regions. To test this hypothesis, one would ideally have time series data of grid- cell occupancies for the entire native ranges of species. However, as such data is not available, we instead retrieved data on grid- cell occupancies of vascular plant species during an early period (i.e. early occupancy) and a later period, each usually covering multiple years, for 10 regions in Europe, which are referred as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 127]]<|/det|> +native regions (Fig. 1)." (lines 106- 107 & 110). We also defined early occupancy again in Method section (line 371). + +<|ref|>text<|/ref|><|det|>[[114, 145, 883, 368]]<|/det|> +Most datasets only provide the number of grid cells where a particular species is present without specifying in which grid cells the species occurs. So, if a species was observed in 10 grid cells in the first period and in 10 grid cells in the second period, these could be the same grid cells, but they could also be totally different grid cells. Furthermore, each period with occupancy data was multiple years, and occupancy was then the number of grid cells in which a species has been observed during that multi- year period. So, when the period was three years (as in the example of the reviewer), we only have data on the number of grid cells in which a species has been observed during these three years, irrespective of whether it was in the first, second or third year or any combination of those. In other words, we have data on the total number of grid cells for the period, which usually lasted multiple years, but not for year 1, year 2 and year 3 separately. Additionally, we only have information on the total number of grid cell for each period but not their identities. We now mention this explicitly in lines 111, 322- 323 & 364- 366. + +<|ref|>text<|/ref|><|det|>[[114, 386, 883, 570]]<|/det|> +As mentioned in the manuscript, the datasets for the different regions varied with regard to the early and later periods, the durations of these periods, and the number and sizes of the grid cells. However, within a region and period, the count of cells to obtain occupancy was consistent across species, at least for nine of the ten datasets. Therefore, and because the occupancy calculated for a particular region was relative to the total number of grid cells of that region, we believe our approach ensures comparability across regions. The only exception was the Thierache region, where in the early period the number of grid cells was an approximation obtained by converting ordinal rarity classes that were used in the late \(19^{\text{th}}\) century to a mean number of occupied grid cells per rarity class. This might, as discussed in lines 217- 226, be one of the reasons why the results of the Thierache region deviate from those of the others. + +<|ref|>text<|/ref|><|det|>[[114, 589, 880, 810]]<|/det|> +I believe that the abstract does not contain enough information to understand how the knowledge gap was analyzed, so I suggest a thorough revision. For example, in L45- L46, "particularly common plant species" where? The abstract presents the results from the truncated negative binomial portion of the model only, therefore defining what 'global naturalization' means in L46- 47 is necessary. Also, a basic ecological interpretation/definition of "occupancy- change index" and "early period occupancy" would allow a larger audience to benefit from these findings. The latter was not formally defined in the paper, and it hampers the understanding of the choice of approach and the findings, as I mentioned in another piece of this review. Lastly, the abstract would gain a larger audience by having a closing statement with the implication for management and policy- related actions for species that follow the pattern described in this manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 811, 870, 850]]<|/det|> +RESPONSE: We have now thoroughly revised the Abstract and believe that we have addressed all major points made by the reviewer, despite the strict limit of 150 words. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 879, 188]]<|/det|> +Overall structure of the paper: In my first read of the main paper, I would argue that the content necessary to fully understand the analysis and research findings isn't present. The authors should keep in mind that the methods section only appears at the end of the paper, so other sections should provide enough information about the methods and definitions of terms used that allow the readers to accurately understand the results and discussion. + +<|ref|>text<|/ref|><|det|>[[114, 191, 883, 286]]<|/det|> +RESPONSE: We are fully aware that the Methods section is placed at the end of the article and have therefore now provided a concise overview of our approach at the end of the Introduction (lines 105- 124). We also double checked whether there were any cases where definitions of terms were included only in the Methods. When that was the case, we moved them into the earlier sections. + +<|ref|>text<|/ref|><|det|>[[114, 309, 883, 346]]<|/det|> +How similar are the boundaries of the 10 focal regions compared to the same regions from GloNAF? + +<|ref|>text<|/ref|><|det|>[[114, 349, 884, 507]]<|/det|> +RESPONSE: Five of the focal regions (the Netherlands, Flanders, Germany, Switzerland and the Czech Republic) have exactly matching GloNAF regions. For the focal regions Austria, Ireland and Great Britain, GloNAF has data for the different subregions (e.g. England, Scotland and Wales for Great Britain). For the focal regions Denmark (southeast) and Thierache, there are no exactly matching regions in GloNAF, but GloNAF has data for the corresponding countries (Denmark and France). We have not added this information to the manuscript, as we do not see why it would matter whether the focal regions match GloNAF regions. However, if the editor wants us to add this information, we will be happy to do so. + +<|ref|>text<|/ref|><|det|>[[115, 530, 457, 546]]<|/det|> +Specific comments and recommendations: + +<|ref|>text<|/ref|><|det|>[[115, 549, 857, 586]]<|/det|> +- I am curious to understand why "declining species" was a relevant keyword selected by the authors. + +<|ref|>text<|/ref|><|det|>[[114, 589, 884, 806]]<|/det|> +RESPONSE: We tried to include keywords that are not yet used in the Title or Abstract, so that search engines would have a higher chance to find our paper. We included "declining species" because this term is frequently used for species that used to be common but have become rare recently. As this applies to many of the species that have a negative occupancy-change index, we think that the term is appropriate. While we chose to frame the perspective of our manuscript (e.g., in the title or abstract) in terms of species that have increased in commonness, the finding that species that are declining in their native range are less likely to be naturalized elsewhere is an equally valid and interesting extension of our results. We now mention this explicitly in the Discussion section (lines 155- 156). A search for "declining species" in Web of Science (12 June 2024) gave 747 results. Therefore, we consider that the use of this keyword will help people with an interest in declining species to find our manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 829, 528, 865]]<|/det|> +- L84: add citation to support statement. +RESPONSE: We have now added a citation (line 86). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 828, 149]]<|/det|> +- L88: a good example in which countries and ranges are used interchangeably. Clarifying language would improve the understanding and cohesion of this paper. RESPONSE: We now used the standardized term "region" to improve cohesion (lines 92). + +<|ref|>text<|/ref|><|det|>[[114, 169, 884, 269]]<|/det|> +- L104: the statement "largely the same species" has dubious meaning, clarify. RESPONSE: We rephrased the sentence as "Here, we test the hypothesis that many of the plant species that have become widely naturalized across the globe are also increasing in occupancy (i.e. the proportion of grid cells across a region in which a species has been recorded) within their native regions" (lines 105-107). + +<|ref|>text<|/ref|><|det|>[[113, 289, 863, 428]]<|/det|> +- L105: the statement "two (or more) periods" has no context up to this point and hinders the reader from grasping the methods used in the paper in general terms. Also, to the best of my understanding of this paper, for each country/region, each main model shown in the main manuscript contains only the comparison between two time periods. Adding "or more" is confusing and might better if brought up later when nuances in the results are explained. RESPONSE: We now removed "or more" from this sentence and also rephrased the sentence (line 109-112). + +<|ref|>text<|/ref|><|det|>[[113, 448, 870, 547]]<|/det|> +- All content presented in the supplement should be referenced in the main text. RESPONSE: All content presented in the supplement is now referenced in the main text. Note, however, that we do not directly refer to Table S26 and Table S29 in the main text but that we refer to these tables in the elaborate descriptions of the individual datasets in the Supplementary Methods (to which we refer in the main text). + +<|ref|>text<|/ref|><|det|>[[113, 568, 880, 787]]<|/det|> +- L106: "for each native species in each region" how about species that are present in more than one region? There is some mention of them when Figure S6 is referred to, but given the proximity of each of the countries/regions used in this study some short explanation on why region rather than native range extrapolating political boundaries were chosen. RESPONSE: We would have liked to have data on changes in occupancy for the entire native ranges of species. However, as data on grid cell occupancy are only available for some of the regions that are part of the species' native ranges, this was unfortunately not possible. Therefore, we had to use data for separate regions, and indeed, as mentioned in the manuscript, some species occur in multiple data sets. We now mention already at the end of the Introduction the reason for analyzing regions rather than native range (lines 107-112) and the reason for analyzing each region separately (lines 123-124). + +<|ref|>text<|/ref|><|det|>[[113, 808, 870, 866]]<|/det|> +- L107: "occupancy-change index" hasn't been explained and needs clarification. RESPONSE: We now added an explanation in lines112-116 of the Introduction and in lines 369-372 of the Methods section. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 840, 148]]<|/det|> +- L109-110: "the number of regions where the species has become naturalized" this text is confusing. It seems that one is referring to the 10 regions, but in fact, it is from the regions defined by GloNAF to defined where a species is naturalized or not. + +<|ref|>text<|/ref|><|det|>[[114, 150, 884, 289]]<|/det|> +RESPONSE: We now rephrased the sentence as "We then used hurdle models to analyse how global naturalization success — a combination of naturalization incidence (i.e. whether or not a species has become naturalized, which can be modelled by using a Bernoulli distribution) and naturalization extent (i.e. the number of regions where a naturalized species has become naturalized, which can be modelled using a zero-truncated negative binomial distribution) — correlates with occupancy in the early period and the occupancy change within the species' native regions." (lines 117- 123). + +<|ref|>text<|/ref|><|det|>[[114, 310, 883, 348]]<|/det|> +- L110: "early period" is mentioned in the abstract and here, but the term hasn't been described yet. + +<|ref|>text<|/ref|><|det|>[[114, 350, 870, 388]]<|/det|> +RESPONSE: We now make it clear earlier in this paragraph of the Introduction that there were two periods, an early period and a later period (lines 110- 111). + +<|ref|>text<|/ref|><|det|>[[114, 409, 884, 528]]<|/det|> +- L121-L122: this statement contradicts statements on L314-317. These species are more common than what would expected given their occupancy in the early period. RESPONSE: We changed the statement in the previous L121-L122 (now lines 135-137) accordingly to "So, overall, our findings indicate that many species that have increased in occupancy in their native regions more than species with an identical early occupancy, have also become widely naturalized elsewhere in the world". + +<|ref|>text<|/ref|><|det|>[[114, 548, 864, 605]]<|/det|> +- L125-L126: with respect to "the zero-truncated count part of the hurdle model, not with the Bernoulli part", I suggest changing the language similar to above: the likelihood of being naturalized outside native range vs naturalized in more regions at the global scale. + +<|ref|>text<|/ref|><|det|>[[115, 606, 627, 623]]<|/det|> +RESPONSE: We have now revised the statement (lines 130- 132). + +<|ref|>text<|/ref|><|det|>[[114, 643, 884, 760]]<|/det|> +- L131: to convey the message more clearly, it might be helpful to associate the occupancy-change index as a metric of commonness early on in the text and use this term across the paper. RESPONSE: We thank the reviewer for this suggestion. However, the occupancy change index is a metric of the change in commonness, not a metric of commonness per se. As commonness has multiple dimensions, we would prefer not to replace occupancy-change index with the commonness-change index throughout the text. + +<|ref|>text<|/ref|><|det|>[[114, 781, 684, 799]]<|/det|> +- L136: this statement "increased in occupancy" is unclear. Since when? + +<|ref|>text<|/ref|><|det|>[[114, 802, 879, 886]]<|/det|> +RESPONSE: The increase in occupancy has been observed since the period for which we have early occupancy data across regions. We have rephrased the sentence as "but also for species that have since then increased in occupancy within their native regions (Table 2)." to clarify this (lines 149- 150). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 869, 145]]<|/det|> +- L145-148: statements seem repeated from the introduction. I suggested the authors be mindful of which information is essential and necessary in the discussion by focusing on an in-depth discussion of the results. + +<|ref|>text<|/ref|><|det|>[[115, 146, 874, 201]]<|/det|> +RESPONSE: As we think that it is more important to mention these possible explanations in the Discussion than in the Introduction, we have now removed the similar statement from the Introduction. + +<|ref|>text<|/ref|><|det|>[[115, 220, 879, 278]]<|/det|> +- L149-150: what is the environmental variability within the native range studied per species? is the set of species used in this study representative of species distributed in a wide range of environmental conditions? + +<|ref|>text<|/ref|><|det|>[[115, 279, 883, 399]]<|/det|> +RESPONSE: For each of the 10 focal regions, the datasets include the vast majority of plant species that are native there. So, the datasets should include both species that occur in a wide range of environmental conditions and species that occur in only a subset of environmental conditions. However, as we only have data on the number of grid cells occupied by a species and no data on which grid cells they actually occur in, we do not have measures of the environmental variability each species experiences within the native region. + +<|ref|>text<|/ref|><|det|>[[115, 418, 883, 455]]<|/det|> +- L152-154: are these traits present in the focal species studied here? Could such information be pulled from global databases, such as TRY, and incorporated here? + +<|ref|>text<|/ref|><|det|>[[114, 456, 883, 732]]<|/det|> +RESPONSE: We agree that an analysis using trait data would be nice, but even in global databases such as TRY the number of species with data for specific traits is still very poor. This also applies to data on dispersal abilities and autonomous self-fertilization. The largest dataset on autonomous self-fertilization was compiled by Razanajatovo et al. (2016; Nature Communications 7:13313), and included only 1752 of the ca. 350,000 species globally. However, in additional analyses, we now considered the woodiness of the species. We chose woodiness because it is indicative of both growth form and habitat type (i.e. regarding whether the species is likely to occur in open [non- woody] or closed [woody] habitats), and because it is available for all species in our study. We found that while woody species had higher occupancy- change values than non- woody species in six of the 10 native regions (Table S2), woody species were less likely to become widely naturalized. Nevertheless, the positive association between naturalization and occupancy change remained largely unaffected by inclusion of woodiness as an additional variable in the hurdle models. This shows that our results are robust. We added the results of the additional analyses in the supplements (Tables S3, S4- S13) and refer to them in the Discussion (lines 171- 185 & lines 238- 245). + +<|ref|>text<|/ref|><|det|>[[115, 751, 875, 788]]<|/det|> +- L186-187: if the early period chosen had a specific reasoning for it, it should be clarified in the introduction, not in the discussion. + +<|ref|>text<|/ref|><|det|>[[115, 790, 883, 868]]<|/det|> +RESPONSE: We did not have any specific reasoning for that early period. It was simply the period for which data happened to be available. So, we did not have any a priori hypothesis about how the years of the early period would affect the results. Therefore, we believe that the early period of the Thierache period does not require a clarification in the Introduction. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 875, 170]]<|/det|> +- L202-204: I cannot follow the connection of this sentence to the previous after. "richer-get-richer" is a term generally used in the context of species richness, and it doesn't seem to apply here, but also the directionality of the negative is the opposite in the sentence? Consider revising and defining "Matthew effect" and or "richer-get-richer". + +<|ref|>text<|/ref|><|det|>[[115, 171, 880, 227]]<|/det|> +RESPONSE: In principle, it is repeating the preceding sentence saying that the successful species become even more successful. As it is not essential to compare this to the Matthew effect and the richer-get-richer effect, we decided to delete the sentence about these effects. + +<|ref|>text<|/ref|><|det|>[[115, 249, 883, 286]]<|/det|> +- L223: how were "losers" quantified in this paper? Similar language also shows up in the keywords, and it makes it confusing. + +<|ref|>text<|/ref|><|det|>[[115, 286, 883, 360]]<|/det|> +RESPONSE: "Losers" referred to species that have declined (i.e. have a negative change in occupancy). Based on this comment and a comment by Reviewer #3, we decided to remove the term 'loser' (and to be consistent, also the term 'winner') from the manuscript to avoid any confusion. + +<|ref|>text<|/ref|><|det|>[[115, 379, 596, 397]]<|/det|> +- L228-229: why habitat specificity might have not changed? + +<|ref|>text<|/ref|><|det|>[[115, 399, 876, 499]]<|/det|> +RESPONSE: We do not exclude the possibility, as habitat specificity could in principle change through evolution. However, we think it is very unlikely that this will have happened for many species within less than a century. As a new framework on the dimensions of rarity, added occupancy as a dimension, and removed habitat specificity as a dimension (Crisfield et al. 2024, doi: 10.1111/ecog.07037), we decided to remove the text about habitat specificity. + +<|ref|>text<|/ref|><|det|>[[115, 518, 856, 595]]<|/det|> +- L245-251: this discussion is really interesting, and I would suggest to be the driving force of the importance of this study and (if changes in the methods are performed and conclusions hold) - to aid ways in which findings from core science can be transferred to managers and policymakers. + +<|ref|>text<|/ref|><|det|>[[115, 598, 805, 636]]<|/det|> +RESPONSE: We thank the reviewer for pointing this out. We added a few sentences to emphasize how our research can help managers and policymakers (lines 304- 306). + +<|ref|>text<|/ref|><|det|>[[115, 658, 464, 676]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[115, 697, 881, 755]]<|/det|> +the results for "Austria" are reproducible - from analysis to figures. According to the authors and my understanding of their methods, each model was run the same way, only the input data for other regions (data available on figshare) changes. + +<|ref|>text<|/ref|><|det|>[[115, 757, 328, 774]]<|/det|> +RESPONSE: That is correct. + +<|ref|>text<|/ref|><|det|>[[115, 817, 419, 835]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 857, 883, 895]]<|/det|> +The study aims to compare whether the changes in select plant species' native range size correlates with naturalization history elsewhere. The authors examine changes in grid occupancy + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 874, 210]]<|/det|> +drawing on historic grid- based surveys of the vascular flora of 10 areas in Europe. The premise is interesting and the results, though correlative, make intuitive sense. However, there are some methodological concerns that render the conclusion that plants that have naturalized as aliens abroad have also become more common in their native range unearned. RESPONSE: We thank the reviewer for the general support of the manuscript and the insightful comments. + +<|ref|>text<|/ref|><|det|>[[113, 230, 880, 388]]<|/det|> +As the authors note, there are many definitions of commonality, and arguably the one being used in this study is not truly a metric of such. At best, the authors are examining a proxy of range size. The authors do a good job of mentioning potential limitations - e.g., one cannot know how abundant these species are within each grid cell. Further, it is likely that the surveys upon which the study relies were conducted with varying protocols and specific objectives, certainly across regions and possibly even over time. Even if the surveys were more or less standardized, the analyses conducted here can produce misleading results for species that have been recorded more efficiently/accurately in one survey than the others. + +<|ref|>text<|/ref|><|det|>[[114, 389, 884, 589]]<|/det|> +RESPONSE: We agree with the reviewer that there are many definitions of commonness, and we indeed point out in our manuscript that commonness has multiple dimensions. While we cannot say how abundant a species is within a grid cell, we politely disagree with the reviewer that our metric (i.e. the grid- cell occupancy frequency in a region) would not truly be a metric of commonness. We now added a reference to the recent review by Crisfield et al. (2024, Ecography e07037, doi: 10.1111/ecog.07037), which explicitly defines occupancy as a dimension of commonness. In fact, the authors proposed to replace the habitat specificity category of Rabinowitz's classification by occupancy. Furthermore, as also pointed out by Reviewer #1, positive abundance- occupancy relationships are commonly found across taxa, and we now mention this in the Discussion (lines 278- 281). + +<|ref|>text<|/ref|><|det|>[[114, 608, 884, 807]]<|/det|> +We also agree with the reviewer that the different data sets that we used may have varying protocols and objectives, possibly even over time. However, because each region was analysed separately, we do not think that variation in protocols among regions is problematic. Variation in protocols over time within a region is not problematic either, as this is accounted for by the Telfer method that we used to calculate the occupancy- change index. We explain this in the Methods section (lines 372- 378). However, we cannot exclude that in some of the regions there have been changes in how accurately certain groups of species were recorded, and we now mention this potential limitation (lines 380- 383). Moreover, we would like to emphasize that despite the variation among the 10 datasets in different aspects, our results remain largely consistent across regions, which we believe strengthens our conclusions. + +<|ref|>text<|/ref|><|det|>[[115, 828, 883, 906]]<|/det|> +More importantly, the assayed regions do not represent the full native range of the species examined. It is possibly for any given species that while, say, in the Czech Republic its range has increased, the range may have decreased in other parts of its native range. Thus, it is unknown how a species' entire native range size has changed. Though the authors claim that the general + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 288]]<|/det|> +positive correlation between occupancy- change indices they observed among regions for the same species indicates that native range 'winners' and 'losers' were generally consistent across regions, these regions may constitute a small or biased sampling of these species' entire native ranges. Also, many of the species that have naturalized elsewhere are known to have fairly large native ranges that extend well beyond the regions included in the study. Further, it seems that only 44 species (among thousands) were present in multiple regions. Along these lines, without more context regarding the full native ranges of these species it is difficult to say whether the results of this study, though suggestive, truly provide strong evidence that many plant species that are spreading as naturalized aliens around the globe also have high occupancies or are increasing in occupancy in their native range. + +<|ref|>text<|/ref|><|det|>[[114, 290, 883, 456]]<|/det|> +RESPONSE: We appreciate the insightful comments from the reviewer. As acknowledged in our manuscript, one of the limitations of our study is that grid- cell occupancy data (for at least two time periods) is only available for regions in north- western and central Europe. There are more regions with grid- cell occupancy data, but these regions unfortunately do not yet have repeated surveys. Consequently, we paid attention to the fact that we cannot generalize our findings to the entire native range of species (lines 208- 209, previous version and lines 251- 253 in revised version). However, we do suggest that similar anthropogenic changes may have comparable effects on species occupancy in other native regions, though further studies are required when more data become available. + +<|ref|>text<|/ref|><|det|>[[114, 475, 884, 692]]<|/det|> +Regarding the reviewer's concern about the number of species present in multiple regions, we believe that the reviewer misunderstood our correlations between occupancy change indices. We did not find that only 44 species occur in multiple regions. What we found is that in 44 out of the 45 possible pairwise combinations of regions, the occupancy- change indices of the species that occurred in both regions of a pair were positively correlated. We believe this is pretty strong evidence that species that have increased in occupancy in one native region usually also have increased in occupancy in other native regions, even though we do not have data for the entire native range. In Fig. S6 (Fig. S3 in revised version), these correlations are shown, and we now also added the number of species shared between the regions in each pair. Additionally, we have now toned down throughout the manuscript any sentences in which we made broad generalization of native ranges, including the title. + +<|ref|>text<|/ref|><|det|>[[114, 714, 880, 850]]<|/det|> +GloNAF regions are used as the unit of analyses regarding naturalized ranges. However, the manuscript never mentions what these regions are. How were they defined? Based on the map provided in the supplements, it seems that these regions largely follow geopolitical boundaries and come in many shapes and sizes. Thus, the number of regions where a species has become naturalized may not be a suitable metric for the degree of global naturalization (and comparison with occupancy in a limited sampling of these species' native ranges). + +<|ref|>text<|/ref|><|det|>[[115, 832, 883, 890]]<|/det|> +RESPONSE: We thank the reviewer for pointing out that we failed to mention what the GloNAF regions are. The GloNAF database is a compilation of lists of naturalized alien plants for different regions around the globe. The version we used (version 2.0), contains list of naturalized vascular + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 884, 268]]<|/det|> +plant taxa for 920 non- overlapping regions. These regions include both mainland regions and islands, and most of them indeed follow geopolitical boundaries, because flora books and species inventories, which are the main data sources of GloNAF, are mostly done for administrative regions. As a consequence, the regions vary in size from 0.045 to 2336618 km \(^2\) (median size is 34382.71 km \(^2\) ). Instead of the number of GloNAF regions, one could use the cumulative area of the regions in which they are naturalized, but this is highly correlated with the number of regions (Spearman rho = 0.770), as shown in Pyšek et al. 2017 (Preslia 89:203- 274, DOI: 10.23855/preslia.2017.203). We now added more detailed information on the GloNAF database in the Methods (lines 410- 415). + +<|ref|>text<|/ref|><|det|>[[113, 288, 877, 590]]<|/det|> +The methods require more detail. Pertinent information is often relegated to the supplements or other publications. For instance, the authors should note how many species were examined in the main text so that the numbers they present and discuss can be understood in context. While it is fine to refer to methods in previous studies, there should at least be enough information in the manuscript for the reader to be able to interpret the results. For instance, it was necessary to refer back to Telfer (2002) repeatedly to understand the figures presented in the results as well as some of the choices made in the study. Along these lines, the grid counts for each region were not done the same way. For instance, in Denmark, the number of occupied grid cells of each species in each region was calculated by multiplying the regional abundance of each species by the total number of referenced grid cells for each region, combining the grid- cell data for each taxon across the 11 regions of the country that were surveyed to get one single value. In contrast, simple grid cell counts were used in some other regions. While there is no reason not to use available data, this makes the results from each region (which were modeled separately) less comparable, and I recommend that the authors harmonize the approach to grid cell counting and present those results as well. + +<|ref|>text<|/ref|><|det|>[[114, 590, 884, 747]]<|/det|> +RESPONSE: The numbers of species in each dataset are provided in Table 1 of the main text. We now also added these numbers in brackets behind each region in lines 313- 318. We also moved some information about the regions that was not yet provided in Table 1 of the main text from the Supplements to the main text (lines 321- 330). Furthermore, we now provide more detailed information regarding our choices that were based on Telfer (2000) in the 'Index of occupancy change in native regions' subsection of the Methods. In addition, as recommended by Reviewer #2, we also revised all the figures and table captions to make them more informative and understandable in isolation (Fig. 2, Fig. S1- S5, Table 2, Table S1- S31). + +<|ref|>text<|/ref|><|det|>[[114, 748, 884, 907]]<|/det|> +Data on changes in grid- cell occupancy are scarce, and there is variation in how these data were collected in the different regions. However, the total count of grid cells was generally consistent across regions. In the case of Denmark, there were 14 subregions, and not all of them were immediately adjacent to the other subregions. The paper that provides the data for Denmark, Nielsen et al. (2019), determined a species' abundance in each subregion by dividing the number of occupied grid cells of each species by the total number of grid cells for the subregion. Since, Nielsen et al. (2019) provide such abundance data only for 11 subregions, out of 14 subregions, we back calculated the number of grid cells occupied by a species in each of the 11 subregions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 169]]<|/det|> +Then we combined them across the 11 subregions to get one single occupancy value for each species. This way we made the data more comparable to the data that we have for the other regions, as recommended by the reviewer. We now explain our calculation of grid- cell occupancy for Denmark in more detail in the Methods (lines 340- 347). + +<|ref|>text<|/ref|><|det|>[[115, 191, 294, 207]]<|/det|> +Additional comments: + +<|ref|>text<|/ref|><|det|>[[115, 210, 550, 227]]<|/det|> +The 'winners' and 'losers' angle seems a bit colloquial. + +<|ref|>text<|/ref|><|det|>[[115, 230, 872, 267]]<|/det|> +RESPONSE: In response to this comment and a similar comment by one of the other reviewers, we decided to remove these terms from the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 289, 480, 307]]<|/det|> +Table 1 is not referenced in the text correctly. + +<|ref|>text<|/ref|><|det|>[[115, 309, 849, 367]]<|/det|> +RESPONSE: While we previously cited Table 1 in the Methods, when describing the 10 focal regions, we have now also included a citation to Table 1 at the end of the Introduction (line 124). + +<|ref|>text<|/ref|><|det|>[[115, 389, 370, 407]]<|/det|> +Fig S6 - x and y are not defined. + +<|ref|>text<|/ref|><|det|>[[115, 409, 737, 427]]<|/det|> +RESPONSE: We now added the axis labels in Fig. S6 (Fig. S3 in revised version). + +<|ref|>text<|/ref|><|det|>[[115, 448, 883, 487]]<|/det|> +Unscale the occupancy index when presenting and discussing the results - the scaled values are confusing to interpret and the index is already ultrametric. + +<|ref|>text<|/ref|><|det|>[[115, 489, 883, 587]]<|/det|> +RESPONSE: We thank the reviewer for this comment. We now realized that the unscaled occupancy- change index values are already standardized because they correspond to the standardized residuals of the logit- logit regression used to calculate the index. In other words, the values were already centered to zero with a standard deviation of one prior to scaling them. So, we now use unscaled values for the occupancy- change index. + +<|ref|>text<|/ref|><|det|>[[115, 608, 880, 666]]<|/det|> +The layout of Fig.2 is a bit confusing with the inset with multiple abbreviations and asterisks. Also, why not just replace this figure with the corresponding one in the supplements that show the raw data as noted in the caption (S5)? + +<|ref|>text<|/ref|><|det|>[[115, 668, 820, 705]]<|/det|> +RESPONSE: We followed the reviewer's advice and replace Fig. 2 with Fig. S5 of previous version. + +<|ref|>text<|/ref|><|det|>[[115, 728, 612, 746]]<|/det|> +Where were the 1/6 and 5/6 quantiles chosen for illustration? + +<|ref|>text<|/ref|><|det|>[[115, 748, 884, 907]]<|/det|> +RESPONSE: We chose the 1/6th and 5/6th quantiles to illustrate whether or not the relationship between global naturalization and occupancy change depended on the occupancy in the early period. We wanted to show this relationship not only for the median occupancy in the early period but also for a higher and a lower occupancy in the early period. So, we categorized species according to whether they were relatively common, intermediately common or rare during the earlier time period. To achieve this, we divided the data points into three equally- sized groups and, we show the lines for the centres (medians) of these groups, which are the \(1 / 6^{\text{th}}\) , \(3 / 6^{\text{th}}\) (median) and \(5 / 6^{\text{th}}\) quantiles. We could have chosen more groups, but then the figures would be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 881, 129]]<|/det|> +very busy. We now added more details on the choice of the quantiles in the Methods (lines 440- 446). + +<|ref|>text<|/ref|><|det|>[[115, 150, 870, 188]]<|/det|> +As GloNAF data are not freely accessible, please present information on which specific regions each species was naturalized in. + +<|ref|>text<|/ref|><|det|>[[115, 190, 864, 248]]<|/det|> +RESPONSE: We now uploaded the data on fishware. Please, also note that the 2019 version of GloNAF has been published as a data paper, and that the most recent data has always been freely shared upon request. + +<|ref|>text<|/ref|><|det|>[[115, 269, 882, 307]]<|/det|> +Are the identities of the grid cells occupied by each species known? If so, perhaps the potential drivers of range change could be examined. + +<|ref|>text<|/ref|><|det|>[[115, 309, 882, 387]]<|/det|> +RESPONSE: Indeed, it would be very interesting to actually examine the potential drivers of range change. However, for all datasets, we only have the number of grid cells where a particular species is present without specifying the identities of the grid cells. We mention this in lines 364- 366. + +<|ref|>text<|/ref|><|det|>[[115, 408, 882, 487]]<|/det|> +The "Gridcells_earlyperiod" and "Gridcells_laterperiod" values for Thierache are not whole numbers- according to the metadata these should be simple counts of the number of cells occupied by each species and the supplementary methods do not state any special circumstances (unlike Germany or Denmark). + +<|ref|>text<|/ref|><|det|>[[114, 489, 883, 667]]<|/det|> +RESPONSE: We thank the reviewer for pointing this out. We mentioned the reason for this indirectly in line 187 of the previous version, but we now realize that we did not explain this in full detail in the Methods. For Thierache, the authors of the original dataset had 'proper' grid- cell occupancy data for the latter period (that is why the species have whole numbers for that period in the dataset. However, for the early period, the data were not actual grid- cell frequencies but verbal descriptions of how widespread the species were. These verbal descriptions were converted by the authors into grid- cell occupancies, and this resulted in some numbers that are not whole. We now also moved information about the Thierache region from the supplementary to the main manuscript (Methods section line 338- 340). + +<|ref|>text<|/ref|><|det|>[[115, 689, 464, 706]]<|/det|> +Reviewer #3 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[115, 728, 553, 746]]<|/det|> +I did not try running the code but it looked reasonable. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 86, 253, 100]]<|/det|> +Dear Reviewers, + +<|ref|>text<|/ref|><|det|>[[117, 102, 881, 222]]<|/det|> +Dear Reviewers,We were pleased to read that Reviewer #1 was happy with the changes that we had made, and we thank Reviewers #2 and #4 for their constructive comments. According to the new suggestions, we have made further revisions to our manuscript entitled "Many plants naturalized as aliens abroad have also become more common within their native regions". Below we provide point- by- point responses to all comments. Please, note that the line numbers refer to the clean version of the manuscript with highlights and our responses are in blue. + +<|ref|>text<|/ref|><|det|>[[118, 225, 198, 239]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[118, 241, 447, 257]]<|/det|> +Rashmi Paudel (on behalf of all authors) + +<|ref|>sub_title<|/ref|><|det|>[[118, 293, 315, 310]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 328, 430, 345]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 363, 510, 379]]<|/det|> +The authors have addressed all of my concerns. + +<|ref|>text<|/ref|><|det|>[[118, 380, 800, 414]]<|/det|> +RESPONSE: We thank the reviewer for their time, and we are pleased that we have addressed all of their concerns. + +<|ref|>text<|/ref|><|det|>[[118, 432, 430, 449]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 467, 878, 570]]<|/det|> +I appreciate the careful point- by- point revisions given in response to my previous comments and concerns. I appreciate the thorough revision of the text to improve the consistency of terms used—the main text is now a lot easier to digest. Moving forward, I have two broad, major comments that are detailed below. Then, those are followed by minor comments: RESPONSE: We are pleased that the reviewer appreciates the thorough revisions of the text, and we thank them for the constructive comments. + +<|ref|>text<|/ref|><|det|>[[117, 588, 866, 675]]<|/det|> +1) I mentioned this before and I noticed that Reviewer 3 also made a comment on this: using the regions as units of native ranges, particularly because they follow political boundaries. So, could you provide the supplement with how many species are present across all regions? How many species are present in all regions but one? And so forth? And how many species are uniquely present in a single region? + +<|ref|>text<|/ref|><|det|>[[117, 676, 881, 780]]<|/det|> +RESPONSE: We have now added a table in the Supplements that provides a summary of how many species are present in how many of the 10 regions (Table S36), and we refer to it in the main text (line 392). Among the 3920 unique species across all ten regions, 288 species are present in all regions, and 1261 are present in only one region. Additionally, we have provided an Excel file in the data repository detailing the presence and absence of all 3,920 species across the 10 regions. + +<|ref|>table<|/ref|><|det|>[[275, 795, 720, 898]]<|/det|> + +
# regions where species is present# species
10288
9186
8144
7130
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[275, 82, 720, 205]]<|/det|> + +
6165
5218
4356
3487
2685
11261
+ +<|ref|>text<|/ref|><|det|>[[117, 221, 876, 325]]<|/det|> +2) Woodiness was added in complementary models as a way to address some of the concerns of Reviewer Dov Sax. If this inclusion is kept, the main text would need some introduction of the relatedness of woodiness, range expansion, and probability of becoming naturalized, so, therefore, justifying why this a reasonable trait to be evaluated. Lines L171-173 do not justify sufficiently. I would pull as base of some of the arguments and justification given in the rebuttal. + +<|ref|>text<|/ref|><|det|>[[118, 326, 875, 360]]<|/det|> +RESPONSE: We thank the reviewer for pointing this out, and we now introduce the potential importance of woodiness (and other traits) in the Introduction (Lines 104- 117). + +<|ref|>text<|/ref|><|det|>[[118, 378, 266, 394]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[118, 412, 841, 465]]<|/det|> +Results: The tables with the main results of your models (i.e., mention of tables S14- S30 should potentially show up earlier, as it is the results of the main models (without woodiness) + +<|ref|>text<|/ref|><|det|>[[118, 466, 880, 535]]<|/det|> +RESPONSE: We previously referred to Tables S14- S30 (Tables S12- S21 in the revised version) in the caption of Table 2, which summarizes the estimates and significance of all models. We have now also referred to them when we first mention Table 2 in the Results section (Line 163). + +<|ref|>text<|/ref|><|det|>[[118, 552, 790, 587]]<|/det|> +L91- 93: The statement is somewhat confusing. Also, should it be "increasing their occupancy" rather than "increasing" only in L92? Please, revise + +<|ref|>text<|/ref|><|det|>[[118, 588, 856, 656]]<|/det|> +RESPONSE: We thank the reviewer for spotting this. Indeed, it should be "increasing their occupancy". We have now revised the statement as "However, this concept has not been assessed in plants. The findings that naturalized plants and those spreading in their native range share a common set of traits suggests that it may be the case" (Lines 120- 122). + +<|ref|>text<|/ref|><|det|>[[118, 692, 438, 707]]<|/det|> +L103: do you mean "range over time"? + +<|ref|>text<|/ref|><|det|>[[118, 710, 880, 742]]<|/det|> +RESPONSE: We thank the reviewer for pointing this out, and we have now revised the text accordingly (Line132). + +<|ref|>text<|/ref|><|det|>[[118, 760, 880, 811]]<|/det|> +L199- 200: would you be able to provide either a table or a simple graph per region with how many species out of the total per region were present in all its grid cells? This would help the reader to be aware of how many species, from the poll studies, have this pattern. + +<|ref|>text<|/ref|><|det|>[[118, 813, 880, 899]]<|/det|> +RESPONSE: Across all regions, no single species is present in all grid cells of its respective region. However, some species were present in nearly all grid cells. To illustrate this, we have updated Fig. S4 (Fig. S3 in the revised version) by adding a vertical line representing the logit of the total number of grid cells in each region. This allows for a clear visualization of species that are close to this threshold. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 103, 880, 154]]<|/det|> +In addition, the following table, which has been added to the supplements (Table S25), and is referred to in line 243, provides the number of species present in at least 95% of the total grid cells per region, during the earlier time period: + +<|ref|>table<|/ref|><|det|>[[56, 169, 880, 450]]<|/det|> + +
Regions# total grid cells# species present in all grid cells# species present in more than 95% grid cells# total native species used in analysis
Austria2600022419
Czech Republic2551001834
Denmark26305921
Flanders985029861
Germany120240651715
Great Britain2852001355
Ireland100708910
The Netherlands16850301115
Switzerland1827002307
Thérache12900775
+ +<|ref|>text<|/ref|><|det|>[[117, 467, 628, 501]]<|/det|> +L228: "...species with high early..."? RESPONSE: Corrected accordingly (Line 271) by adding "with". + +<|ref|>text<|/ref|><|det|>[[118, 520, 477, 536]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[117, 554, 565, 570]]<|/det|> +I reviewed the code during the first round of revisions. + +<|ref|>text<|/ref|><|det|>[[118, 589, 430, 605]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 623, 880, 748]]<|/det|> +This is a broad analysis staying that certain plant species, likely due to a combination of human actions and the plant features, are favored under human uses of the landscape in their ranges and in new regions. The novelty relies on including change in abundance/occupancy in the native range as a predictor of naturalization somewhere else. These findings could be used to generate list of species that could become invasive, lists that could be compared with already generated watch lists to assess how much information this predictor is adding. + +<|ref|>text<|/ref|><|det|>[[117, 747, 880, 780]]<|/det|> +RESPONSE: We thank the reviewer for their compliments, for recognizing the potential application of our research, and for their constructive feedback. + +<|ref|>text<|/ref|><|det|>[[117, 799, 880, 902]]<|/det|> +Since changes in occupancy/abundance were not analyzed as a function of other drivers than time, e.g., human activities targeting particular habitats/plant communities, results might very indirectly be assessing the causes of naturalization, because increase in occurrence and naturalization might have to do with habitats selected rather than intrinsic features of the plant species. This is a point brought by the reviewers that has been dismissed by the authors (see next comment). Analyzing what it made those species increase in their native and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 85, 880, 345]]<|/det|> +introduced ranges would be of greater consequence for management and conservation. RESPONSE: Our main objective was to assess whether species that are increasing at home are also the ones that are increasing elsewhere. If this is the case, this would mean that information on native occupancy dynamics could inform invasion risk assessments (irrespective of the traits that underlie the occupancy dynamics). We now mention this more explicitly in the manuscript (lines 63- 64 & lines 294- 295). However, we appreciate the reviewer's insightful observation and agree that multiple factors other than time could influence species occupancy in their native regions and their naturalization success. As we mentioned in our previous response, we do not have information on the actual grid cells in which the species occurred, because most datasets only provide the number of grid cells where a particular species is present without specifying in which grid cells the species occurs. Therefore, we cannot explicitly test the role of habitats in driving occupancy patterns. In addition, although such an analysis would be very interesting, it would go far beyond our objective of testing whether species that have increased in occupancy in their native regions are largely the same ones that have increased globally as naturalized alien species. + +<|ref|>text<|/ref|><|det|>[[117, 363, 880, 571]]<|/det|> +We politely disagree that we dismissed the "habitat" comment of the previous reviewer. In response to the similar comment by Dov Sax to the previous version of our manuscript, and as stated in our previous rebuttal, we chose to add information on woodiness because it is indicative of both growth form and habitat type. Where we assume that woody species are likely to occur in closed or forest habitats, whereas non- woody species predominantly occur in open habitats. We believe that ultimately the habitat associations of species will depend on their intrinsic features. Although we cited already several papers that have analysed how changes in native occurrence relate to species features, we have now —in response to this comment and the reviewer's subsequent comment— analysed whether species that were common and have further increased are characterized by certain ecological strategies (Grime's competitor, stress tolerator and ruderal strategies) and by ecological indicator values. For more details, see our response to the next comment. + +<|ref|>text<|/ref|><|det|>[[117, 589, 880, 727]]<|/det|> +Much more informative would have been to analyze features of the species that were already abundant and that increased their occurrences, e.g., are ruderal species over- represented in that group? What are the main traits characterizing those species? That again would provide more useful information for management and conservation. Maybe the data is not available for all, but it could be done for the ones that it is. Line 207- 216 make that point. Many studies are using global trait data sets to do it, if authors have decided not to do it that's their choice but claiming that the reason for not doing it is that that information is not available is not accurate. + +<|ref|>text<|/ref|><|det|>[[117, 728, 880, 902]]<|/det|> +RESPONSE: Even though many studies are using global trait data sets, we would like to reiterate that these data sets are very incomplete. In a recent analysis of trait- data availability for naturalized alien species, it was shown that there are only ten traits with data available for more than \(50\%\) of the species (https://ecoevorxiv.org/repository/view/7852/), and we have now also included this information in the manuscript (lines 297- 299). Woodiness is one of the few traits that is available for most plant species, and therefore we had already included this trait during the previous revision. We believe that the results of studies based on very incomplete trait data should be interpreted with caution (as there might be a bias in the availability of data). Nevertheless, we fully agree that the analyses proposed by the reviewer might be informative. Therefore, we have now added data from a global dataset on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 155]]<|/det|> +CSR- strategies (available for 2125 of the 3920 species in our data sets) from Guo et al. (2018), and data on Ellenberg ecological indicator values (available for 2893 of the 3920 species from Tichý et al. (2023) and the Pladias database of the Czech Flora and Vegetation; Chytry et al. (2021)). + +<|ref|>text<|/ref|><|det|>[[118, 171, 880, 346]]<|/det|> +We classified species as widespread and expanding if they had an early occupancy higher than the median and if they had a positive occupancy change. We then analysed, in line with the reviewer's suggestion, whether the trait value of this group of species differed from all other species. These additional analyses showed that the group of species that were already abundant and also increased their occurrences, are overall characterized by high values along the competitor axis of Grime's CSR- strategy triangle (in 9 of the 10 regions) and low values along the ruderal and stress- tolerator strategies. Furthermore, this group of species had significantly lower Ellenberg indicator values for light, and higher Ellenberg indicator values for nutrients, in all ten native regions. We present these additional results in the Supplements (Tables S33- S34, Fig. S4- Fig. S10) and refer to them in the Discussion (lines301- 316). + +<|ref|>text<|/ref|><|det|>[[118, 364, 879, 398]]<|/det|> +References: Chytry M., et al. Pladias Database of the Czech Flora and Vegetation. Preslia 93, 1- 87 (2021). + +<|ref|>text<|/ref|><|det|>[[118, 414, 879, 448]]<|/det|> +Guo, W.Y., et al., The role of adaptive strategies in plant naturalization. Ecology letters 21(9), 1380- 1389 (2018). + +<|ref|>text<|/ref|><|det|>[[118, 466, 880, 606]]<|/det|> +It looks like early occupancy, and to some extent woodiness, are a better predictor of naturalization than change in occupancy, Table S3, this should be emphasized more in the main text because data on changes overtime may not be available, but actual native range and woodiness are, and those could be used on their own as predictors. Especially considering that change in occupancy is being predicted by early occupancy. Also, adding information on how much variance was additionally accounted for by including change in occupancy, vs a model with early occupancy and woodiness only, would help to understand the scope of this predictor. + +<|ref|>text<|/ref|><|det|>[[118, 607, 879, 658]]<|/det|> +RESPONSE: We thank the reviewer for this suggestion. We have now emphasized Table S3 (Table S1 in the revised version) more strongly in the main manuscript (lines 156- 161, lines 215- 218 & lines 299- 301). + +<|ref|>text<|/ref|><|det|>[[118, 676, 880, 762]]<|/det|> +We also would like to point out that the change in occupancy is not being predicted by early occupancy. The change in occupancy corresponds to the residuals of a regression of the logit of late occupancy vs the logit of early occupancy. Consequently, if one then relates the change in occupancy to early occupancy, there is no significant relationship. This is mentioned in line 146, lines 444- 446 & lines 450- 452. + +<|ref|>text<|/ref|><|det|>[[118, 780, 880, 902]]<|/det|> +To assess the variance explained by different models, we ran four models: Model I, which includes only early occupancy as a predictor of naturalization success; Model II, which incorporates both early occupancy and occupancy change; Model III, which includes early occupancy and woodiness; and Model IV, which combines all three predictors—early occupancy, occupancy change, and woodiness. The calculated Pseudo \(R^2\) values (by Cragg and Uhler), r2CU showed that models incorporating occupancy change (Model II and Model IV) consistently had higher explanatory power compared to their counterparts (Model I and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 880, 189]]<|/det|> +Model III), highlighting the role of occupancy change in predicting naturalization success. Although the change in explained variance is not huge, we would like to point out that, as suggested by the previous reviewer #1 (and discussed in lines 238- 250), the association between occupancy- change and global naturalization success may be an underestimate. We have now added a supplementary table (TableS24) comparing the pseudo R2 values across all models, and we briefly refer to these results in the main text (lines 216 & 237). + +<|ref|>text<|/ref|><|det|>[[118, 207, 880, 258]]<|/det|> +My suggestion would be to change 'region' for countries. Region usually indicates ecological, e.g., climatic, differences, but these data sets reflect political units. Sorting the data into actual ecological regions might have shown more interesting/informative results. + +<|ref|>text<|/ref|><|det|>[[118, 259, 881, 363]]<|/det|> +RESPONSE: We thank the reviewer for this suggestion, however we prefer to use 'regions' instead of 'countries' because three of the native regions in our study are only part of countries. Referring, for example, to Thierache as 'France' would be misleading. However, if the editor prefers us to use 'countries' or another term, we are willing to change it. We now added "(countries or parts thereof) at first mentioning of 'European regions' in the Abstract (line 59) and in the Methods (line384). + +<|ref|>text<|/ref|><|det|>[[118, 380, 880, 502]]<|/det|> +It is not clear if changes in occupancy overtime were standardized by the period of time between census, i.e., more change expected if longer time between censuses. RESPONSE: The changes in occupancy over time are standardized within each of the regions, as the period is the same for all species within a region. We added a note to clarify this at lines 495- 496. However, the changes in occupancy over time are not standardized across regions. As we only compared changes in occupancy within regions, a standardization across regions would not change the conclusions. + +<|ref|>text<|/ref|><|det|>[[118, 520, 822, 554]]<|/det|> +I can't tell the difference between Table S3 and the ones that follow for each country, information is the same. + +<|ref|>text<|/ref|><|det|>[[118, 555, 870, 623]]<|/det|> +RESPONSE: Table S3 (Table S1 in the revised version) provides an overview of the estimates and significances for the analyses that included woodiness and is directly comparable to Table 2 in the main text. Tables S2- S11 (in the revised version) provides the detailed results for each region separately, and we now explain this in the caption of Table S1. + +<|ref|>text<|/ref|><|det|>[[118, 641, 476, 658]]<|/det|> +Reviewer #4 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[118, 676, 795, 694]]<|/det|> +The analyses are done using standard techniques and standard software packages. + +<--- Page Split ---> diff --git a/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/images_list.json b/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1e4cb92d8e7d1910f6718426b1d0f582f57cfffd --- /dev/null +++ b/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,256 @@ + +# nature portfolio + +Peer Review File + +# Exploring the Programmability of Autocatalytic Chemical Reaction Networks + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +Reviewer #1 (Remarks to the Author):In the manuscript entitled "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," the authors present a novel experimental study on the batch kinetics and CSTR dynamics trypsin- catalyzed autocatalytic reaction network and its capability to perform some logic operations. According to the presented results the addition of metal ions (La(III), Ca(III), Nd(III)) opens an effective way to control the kinetics of the autocatalysis. In CSTR experiments, Nd(III) has a nonlinear effect depending on the presence of the second cation. The capability of the system to perform logic operations is demonstrated. The interpretation of the experiments is valid and robust. The presented results remarkably contribute to the development of designing intelligent chemical systems. The methodology is appropriate and presentation of the data is clear. The manuscript references previous literature appropriately. + +Questions and comments: + +(1) Could the authors discuss the system's robustness, especially in the context of logic operations? + +(2) The CSTR experiments were performed in two serial reactors. According to the theory of serial CSTRs reactions that produce bistability in a single CSTR (with two stable, one unstable steady states), in a series of CSTRs with N reactors, have up to \(S2^{\wedge}(N + 1) - 1\) \(S\) steady states, of which only \(S N + 1\) \(S\) are stable. (A. Varma, Ind. Eng. Chem. Fundam. 1980, 19, 316. ;G. Dangelmayr, I. Stewart, SIAM J. Appl. Math. 1985, 45, 895). It seems that this multiplicity of states may appear in the experiments presented in the manuscript. Could the author comment on it? Would this multiplicity affect the operation of the system? + +(3) In the context of logic operations, it seems that an obvious question is how to connect two more logic gates based on the presented configurations to perform somewhat more examples of computations. + +<--- Page Split ---> + +(4) Could the authors clarify the meaning of "Bistability in temporal logic operations"? What are the characteristics of the two stable states, and how the coexistence of these states can be observed? + +(5) In the conclusions, the authors state, "We envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive, adaptive, and other life-like properties characteristic for intelligent systems." What are the main steps of this novel strategy, and in what type of systems can it be applied? + +I suggest addressing the above questions and comments and revising the manuscript. + +## Reviewer #2 (Remarks to the Author): + +The manuscript "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," written by Dmitrii V. Kriukov, Jurriaan Huskens, and Albert S. Y. Wong, is concerned with the application of trypsin catalysis as a chemical logic gate. The subject is interesting but not new because the first chemical logic gates were described 40 years ago. According to my knowledge, the application of trypsin-catalyzed reaction for chemical information processing is a new element in the study. The logic gates are useful when concatenating them into more complex information processing devices. This does not seem easy within the presented approach because concentrations of metal ions are used as the gate input, but the output is extracted from time-dependent trypsin concentration [Tr](t). This means that connecting two gates requires a device (presumably electronic) that analyzes [Tr](t) and translates the result to the ion pump rates of another CSTR. Moreover, the results of Fig. 4 suggest that a gate can make a few operations per hour, which is rather slow to attract industrial attention. Therefore, considering the limited practical applicability of the presented medium and narrow field of study, I do not recommend publication in a journal focused on a wide audience. The results are better suited for a specialized journal focused on natural or unconventional computing. + +In my opinion, the present version of the manuscript is poorly written and does not include + +<--- Page Split ---> + +all the information needed to understand what was done. + +Here are some remarks on manuscript fragments that must be improved before it is submitted to another journal. + +The authors refer to a mathematical model that is not well described. The model variables should be listed. I also expected to find the kinetic equations with flow terms included. The article SI just gives the set of reactions and comments on the reactions. + +The mathematical symbols are used without their precise definition in the text. What is [A]feed (Fig.3 caption)? According to what I read, the symbol [A]0 denotes the concentration of reagent A at the beginning of the experiment (t=0). How shall I understand Fig. 3a, where [Nd3+J0 is plotted as a function of time, and its caption says that [Nd]0 was changed? + +In some places (for example, p.3, lines 13/14), the numerical values of variables are given without the corresponding units. + +## Reviewer #3 (Remarks to the Author): + +This is an interesting paper, with some thought provoking ideas. The authors use metal ions to control the rate of autocatalysis with trypsin and this feature is used to program the output response of the autocatalyst in a flow reactor. They mention implications in terms of eg neuromorphic computing. Some of the manuscript could be more clearly written, and I am unclear on the interpretation of results in some parts. In the abstract It is not immediately clear what is meant by "reconfigured in a programmable manner"; this could do with clearer explanation. What are you reconfiguring? There has been quite a lot done with computing in eg reaction diffusion systems; using light, chemical inputs etc to implement Boolean logic and image processing - can it be better pinpointed what is the difference here? Some explanation of a neuromorphic system and the desired features of such a system in the introduction would be useful for the more general audience. + +<--- Page Split ---> + +Figure 2. I'm not sure that fig 2d data can be interpreted as Nd is an" inhibitor" in the traditional sense, since without the metal, autocatalysis doesn't proceed. Technically, it results in a lower rate only as the concentration of Nd is increased above a threshold value. Possibly there is some initial binding of Nd to Tr to form an active state but further binding results in an inactive state - similar to binding of acid to enzymes. Nevertheless, the experimental results are still the same, it is just interpretation that I am unclear on. + +<--- Page Split ---> + +Changes to the text of our manuscript, based on the below reviewers' comments, are highlighted in yellow and indicated with "Page XX, line YY", referring to the revised version. + +## Reviewer #1: + +In the manuscript entitled "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," the authors present a novel experimental study on the batch kinetics and CSTR dynamics trypsin- catalyzed autocatalytic reaction network and its capability to perform some logic operations. According to the presented results the addition of metal ions (La(III), Ca(II), Nd(III)) opens an effective way to control the kinetics of the autocatalysis. In CSTR experiments, Nd(III) has a nonlinear effect depending on the presence of the second cation. The capability of the system to perform logic operations is demonstrated. The interpretation of the experiments is valid and robust. The presented results remarkably contribute to the development of designing intelligent chemical systems. The methodology is appropriate and presentation of the data is clear. The manuscript references previous literature appropriately. + +We thank the reviewer for their positive comments on our manuscript. Below, we indicate how we have used their constructive comments to improve the manuscript. + +(1) Could the authors discuss the system's robustness, especially in the context of logic operations? + +The reviewer correctly pointed out that a discussion on the robustness of the system was not included. Robustness is a network property which ensures that specific functions of the system are maintained [Kitano, H. Nat. Rev. Gen. (2004)]. In our work, robustness can be defined as the parameter window wherein the desired logic operation can be obtained. We did discuss that the various logic operations can be found in a "narrow range of parameters" (page 4, line 44) but we did not comment on the differences between the operations in terms of their robustness. We have incorporated the suggestion of the reviewer as follows: + +- Page 4, line 47: The phase plot shows that a parameter window exists to maintain each logic operation, ensuring that the desired functions of the system are robust39. The robustness, however, differs per operation. +- Additional reference: 39. Kitano, H. Biological Robustness Nat. Rev. Gen. 5, 826-837 (2004). + +(2) The CSTR experiments were performed in two serial reactors. According to the theory of serial CSTRs reactions that produce bistability in a single CSTR (with two stable, one unstable steady states), in a series of CSTRs with N reactors, have up to \(S2^{\wedge}N + 1\) - 1 IS steady states, of which only \(SN + 1\) IS are stable. (A. Varma, Ind. Eng. Chem. Fundam. 1980, 19, 316. ;G. Dangelmayr, I. Stewart, SIAM J. Appl. Math. 1985, 45, 895). It seems that this multiplicity of states may appear in the experiments presented in the manuscript. Could the author comment on it? Would this multiplicity affect the operation of the system? + +The reviewer provided an interesting perspective and appealing strategy for constructing multiple states in our system. We gladly take this perspective on board for our future studies (see our answer to comment 5). + +Here, to clarify our work, the experimental setup indeed comprises two CSTRs but we noted that the first reactor is the main reaction chamber and that the second reactor serves as a detection chamber (page 13, line 14- 15). The residence time in the second reactor was deliberately made twice as small as the first reactor to ensure that we could detect the output signal as pseudo- online. In addition, mixture of DMSO and DMFA was used to dissolve the detection molecule (BAPNA) and reduce the rate of trypsinogen conversion. We checked experimentally that even small percentage of DMSO slows down Tg conversion dramatically. Hence, we did not actually perform our experiments in serial CSTRs but in one CSTR: The second reactor was engineered to allow for the fast detection of trypsin concentration by converting BAPNA + +<--- Page Split ---> + +into pNA (detectable moiety at \(405 \mathrm{nm}\) ) without any side processes that could potentially lead to multiplicity of steady states. + +We extended the method section as follows: + +- Page 14, line 14: First reactor served as a main reaction chamber whereas the second was receiving its outflow and reporting solution at the constant (2:1) ratio. The residence time in the second reactor was deliberately made twice as small as the first reactor to ensure that we could detect the output signal as pseudo-online. Reporting solution consisted of \(4 \mathrm{mM}\) BAPNA in mixture of MQ:DMSO:DMAF (0.2:0.08:0.72). The mixture of DMSO and DMFA was used to dissolve the detection molecule (BAPNA) and reduce the rate of trypsinogen conversion. Hence, the second reactor was engineered to allow for a fast detection of \([Tr]\) by converting BAPNA into pNA (detectable moiety at \(405 \mathrm{nm}\) ) without any side processes. + +(3) In the context of logic operations, it seems that an obvious question is how to connect two more logic gates based on the presented configurations to perform somewhat more examples of computations. + +We can relate to the comment from the reviewer. Briefly, it is possible to have sequential logic gates when output from a reactor feeds the next reactor with \([Tr]\) . Our method of CSTR fabrication, in fact, does not restrict to a sequence of two reactors but also allows for the design of spatially- coupled CSTRs of other configurations (serial, parallel, arrays). It will require two conditions: supply of the same reactants further down the chain (but without \([Tr]_0\) ), and elimination of significant portion of the liquid from previous reactors to avoid buildup of the flow and concentration catalytic ions. Our intentions, however, are not to connect logic gates. In our future studies, we will compare various configurations and examine the capacity of autocatalytic processes to perform (primitive) nonlinear operations in flow, including the introduction of spike- driven conditions (a method commonly used in neuromorphic processing). In this regard, the XOR- gate can be considered as a primitive nonlinear operation [Chen, T. et al. Nature, 577, 341- 345 (2020)]. The latter sentence was added to the manuscript: + +- Page 5, line 48: Additionally, a trypsin inhibitor was incorporated into the network to create a bistable system capable of long-term depression of the input and history dependency in the output (i.e., characteristics for neuromorphic behavior). In this regard, the XOR-gate can be considered as a primitive nonlinear operation36. Building on this foundation, future work could include the introduction of spike-driven conditions to perform other nonlinear operations under out-of-equilibrium conditions.9 + +- Additional reference: 36. Chen, T. et al. Classification with a disordered dopant-atom network in silicon Nature, 577, 341-345 (2020). + +(4) Could the authors clarify the meaning of "Bistability in temporal logic operations"? What are the characteristics of the two stable states, and how the coexistence of these states can be observed? + +We appreciate the questions of reviewer and apologize for lack of clarity with regards to the subheading "Bistability in temporal logic operations". We reported that "the response became bistable (page 5, line 26)" and this phenomenological observation is supported by our model but we didn't include the prediction of the parameter space wherein co- existence of such states can be observed. We are exploring the control over stability of steady states in the presence of metal ions in separate work. + +In this section, we showed that the autocatalytic system can be maintained at a low trypsin concentration by introducing an inhibitor (Soybean Trypsin Inhibitor) in the network. The incorporation of the inhibitor enables a stable and low steady state, as \(Tr\) becomes inactive, but does not change the stability of the high steady state, which is supported by autocatalytic production of \(Tr\) . Without the inhibitor, the low steady state has to be stabilized by continuously depleting \(Tr\) using flow, which leads to an unstable steady state. + +<--- Page Split ---> + +We made the following changes: + +Page 5, line 7: Increasing the control over Bistability in temporal logic operations- Page 5, line 11: The use of an external component such as an inhibitor for thresholding provides further control over the network properties. Without the inhibitor, the low steady state was stabilized by continuously depleting \(Tr\) using flow, which leads to an unstable steady state. The incorporation of the inhibitor enables a stable and low steady state, as \(Tr\) becomes inactive, but does not change the stability of the high steady state, which is supported by autocatalytic production of \(Tr\) . \(^{30}\) - Page 5, line 48: Additionally, a trypsin inhibitor was incorporated into the network to create a bistable system capable of long- term depression of the input and history dependency in the output (i.e., characteristics for neuromorphic behavior). + +(5) In the conclusions, the authors state, "We envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive, adaptive, and other life-like properties characteristic for intelligent systems." What are the main steps of this novel strategy, and in what type of systems can it be applied? + +We appreciate the questions of reviewer, and gladly take this opportunity to elaborate how we foresee follow- up studies based on this work. This work can be extended with perturbation studies in a single CSTR but also extended to configurations comprising multiple bistable systems in series-, parallel- or array- coupled CSTRs. As mentioned above, in our answer to comment 3, such studies allow us to elucidate the capacity of autocatalytic reactions to perform (primitive) nonlinear operations in flow. The implementation of different configurations will be a crucial next step is to determine how exactly the states in such molecular systems can be changed, retained, and used to build responses that are more complex than those shown in the current manuscript. The strategy to systematically increase the number of collective feedback loops in the system is based on the concept that interconnected feedback loops could bestow CRNs with intelligent behavior (i.e., the capacity to perceive and retain information, and apply it towards adaptive behavior). + +We incorporated the following sentence in the conclusions of the manuscript: + +- Page 6, line 2: The implementation of different configurations of multiple autocatalytic systems (based on series-, parallel- or array-coupled CSTRs) will be a crucial next step to systematically increase the number of collective feedback loops in the system. It will provide the potential to bestow CRNs with the capacity to perceive and retain information and apply it towards adaptive behavior. Hence, we envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive \(^{41}\) , adaptive \(^{42}\) , and other life-like properties \(^{2}\) characteristic for intelligent systems. + +<--- Page Split ---> + +## Reviewer #2: + +The manuscript "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," written by Dmitrii V. Kriukov, Jurriaan Huskens, and Albert S. Y. Wong, is concerned with the application of trypsin catalysis as a chemical logic gate. The subject is interesting but not new because the first chemical logic gates were described 40 years ago. According to my knowledge, the application of trypsin- catalyzed reaction for chemical information processing is a new element in the study. The logic gates are useful when concatenating them into more complex information processing devices. This does not seem easy within the presented approach because concentrations of metal ions are used as the gate input, but the output is extracted from time- dependent trypsin concentration \([Tr](t)\) . This means that connecting two gates requires a device (presumably electronic) that analyzes \([Tr](t)\) and translates the result to the ion pump rates of another CSTR. Moreover, the results of Fig. 4 suggest that a gate can make a few operations per hour, which is rather slow to attract industrial attention. Therefore, considering the limited practical applicability of the presented medium and narrow field of study, I do not recommend publication in a journal focused on a wide audience. The results are better suited for a specialized journal focused on natural or unconventional computing. In my opinion, the present version of the manuscript is poorly written and does not include all the information needed to understand what was done. Here are some remarks on manuscript fragments that must be improved before it is submitted to another journal. + +The reviewer acknowledges that "the application of trypsin- catalyzed reaction for information processing is a new element in the study" but expresses their concerns about the novelty with regards to existing work based on chemical logic gates and the practical applicability of our approach. We gladly provide our view on these aspects in this rebuttal and have elaborated the conclusions as a result. + +First, the reviewer correctly points out that our system, or any chemical system for that matter, cannot compete with the state- of- the- art technologies in computing. Among other reasons, the time scales for transitions between states based on molecular interactions (in our case hours) are nowhere near those that are based on electronic or photonic interactions (fractions of a second). To clarify, our intentions are not to connect logic gates as suggested by the reviewer's comment nor to compete with, emulate, or mimic methods in traditional computing. + +We have added new sections to the introduction to emphasize a connection between autocatalytic and neuromorphic computational systems as follows: + +- Page 1, Line 30: That is, they have the ability to perceive information and retain it as knowledge to execute complex tasks13, highlighting how inherent analogue processes can enable biological computation. Opportunities in rethinking the design of neuromorphic systems lie in using analogue and approximate computing.4,17- Additional reference: 17. Valiant, L., Probably Approximately Correct: Nature's Algorithms for Learning and Prospering in a Complex World. 2013. + +This manuscript aims to set up a practical experimental foundation to use autocatalytic reactions, and chemical reaction networks in general, to perform (primitive) nonlinear operations. In this regard, the XOR- gate can be considered as a primitive nonlinear operation [Chen, T. et al. Nature, 577, 341- 345 (2020)]. + +- Page 5, line 48: Additionally, a trypsin inhibitor was incorporated into the network to create a system capable of long-term depression of the input and history dependency in the output (i.e., characteristics for neuromorphic behaviour). In this regard, the XOR-gate can be considered as a primitive nonlinear operation36. Building on this foundation, future work could include the introduction of spike-driven conditions to perform other nonlinear operations under out-of-equilibrium conditions.9 + +- Additional reference: 36. Chen, T. et al. Classification with a disordered dopant-atom network in silicon Nature, 577, 341-345 (2020). + +<--- Page Split ---> + +While sequential logic gates is not within the scope of this work, we wish to state that it is possible to perform such experiments. Our method of CSTR fabrication, in fact, does not restrict to a sequence of two reactors but also allows for the design of spatially coupled CSTRs of other configurations (serial, parallel, arrays) as well. The emphasis in our future work, however, is not to connect reactors to combine gates. The implementation of different configurations will be a crucial next step is to determine how exactly the states in such molecular systems can be changed, retained, and used to build responses that are more complex than those shown in the current manuscript. The strategy to systematically increase the number of collective feedback loops in the system is based on the concept that interconnected feedback loops could bestow CRNs with intelligent behavior (i.e., the capacity to perceive and retain information, and apply it towards adaptive behavior). We incorporated the following sentence in the conclusions of the manuscript: + +- Page 6, line 2: The implementation of different configurations of multiple autocatalytic systems (based on series-, parallel- or array-coupled CSTRs) will be a crucial next step to systematically increase the number of collective feedback loops in the system. It will provide the potential to bestow CRNs with the capacity to perceive and retain information and apply it towards adaptive behavior. Hence, we envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive, adaptive, and other life-like properties characteristic for intelligent systems. + +Second, the observation that the range of logics is controllable based on a kinetic parameter sets this work apart from "the first chemical logic gates described 40 years ago (reviewer comment line 3)": Our system can accept instructions to perform a range of logic operations and demonstrates that autocatalytic reactions can be programmable. Furthermore, we demonstrated that \(i\) ) the output signal can be reset, \(ii\) ) the method of creating logic gates is not restricted to \(\mathrm{Nd}^{3 + }\) , and ions can be combined to change the phase space, and iii) Boolean functions can be readily tuned and modeled mathematically. + +We incorporated the following section in the main text to clarify the novelty with regards to chemical logic gates as follows: + +- Page 5, line 40: We showed demonstrated that trypsin autocatalysis can be controlled to emulate polynomial functions with different degrees and Boolean functions with various outcomes (e.g., AND, OR, XOR, NAND, NOR), demonstrating that autocatalytic reactions can be programmable. Furthermore, we demonstrated that \(i\) ) the output signal can be reset, \(ii\) ) multiple ions can be combined to change the phase space, and \(iii\) ) Boolean functions can be readily tuned and modelled mathematically, and \(iv\) ) the history-dependent nature of autocatalysis in flow can retain information. That a range of logic are tunable and controllable based on a kinetic parameter sets this work apart from traditional molecular logic gates40. + +- Additional reference: 40. Andréasson, J. & Pischel, U. Molecules with a sense of logic: a progress report. Chem. Soc. Rev., 44, 1053-1069 (2015). + +Third, the comment "the present version of the manuscript is poorly written and does not include all the information needed to understand what was done" seems to relate to the description of the mathematical model (i.e., the "manuscript fragments that must be improved"). We provided our answer below, wherein we clarified, and rectified, the possible confusion that came from our distribution of details on the model (supplementary information vs. supplementary materials). + +The authors refer to a mathematical model that is not well described. The model variables should be listed. I also expected to find the kinetic equations with flow terms included. The article SI just gives the set of reactions and comments on the reactions. + +We can relate to the reviewers' requests (i.e., to list the model variables, incorporate kinetic equations, and provide an SI that gives more that the set of reactions). However, we do wish to point out that this assessment is not entirely accurate. To clarify, the mathematical model was provided as a set of ready- to + +<--- Page Split ---> + +use scripts in supplementary materials. We described how the model is built and used in our work (with a reference to both supplementary information and supplementary information) in the methods section of the main text (page 13, line 32- 43). Nevertheless, we extended the Supplementary Information per request of the reviewer: + +- Supplementary Information, Page 2: We incorporated a process scheme (new Supplementary Scheme 1) to explain the modelling workflow.- Supplementary Information, Page 3: New section (Equations for the model) has been added to elaborate on equations used for the model.- Supplementary Information, Page 6-7: Supplementary table is updated and split in two tables to clarify the chemical meaning of the processes reflected in the new section 'Equations for the model'. + +The mathematical symbols are used without their precise definition in the text. What is [A]feed (Fig.3 caption)? According to what I read, the symbol [A]0 denotes the concentration of reagent A at the beginning of the experiment \((t = 0)\) . How shall I understand Fig. 3a, where \(\mathrm{[Nd3 + ]0}\) is plotted as a function of time, and its caption says that [Nd]0 was changed? + +The reviewer correctly pointed out that that the assignment of symbols is inconsistent in the manuscript. There are two occasions in the main text where we did not explicitly write that the initial concentration of the ions can be abbreviated with brackets and the zero as subscript. We have corrected this as follows: + +- Page 2, line 41: Fig. 2b-c show that \([Tr]\) increases until it saturates as the initial concentration of \(\mathrm{Ca^{2 + }}\) and \(\mathrm{La^{3 + }}\) \(\mathrm{[Ca^{2 + }]_{0}}\) and \(\mathrm{[La^{3 + }]_{0}}\) are increased. ii) \(\mathrm{Nd^{3 + }}\) , in contrast, can accelerate and decelerate the rate of autocatalysis. Fig. 2d shows that the \([Tr]\) increases when the initial concentration of \(\mathrm{Nd^{3 + }}\) \(\mathrm{[Nd^{3 + }]_{0}}\) increases from 0 to \(0.3\mathrm{mM}\) . + +In another section, we corrected: + +- Page 7, line 11: \([Tr]\) denotes concentration of \(Tr\) ; t and t denote time and residence time, respectively. + +Specifically for Fig. 3a, \(\mathrm{[Nd^{3 + }]_{0}}\) is changed over time using our flow setup (Methods section, page 13, line 11). In our setup, we use stock solutions of the components of the system and store them in glass syringes, which content is connected by polytetrafluoroethylene tubing's to the CSTR. The low- pressure pumps are used to independently control the syringes and feed each stock solution into the CSTR. The feeding concentrations for the components \((Tg, Tr, I,\) and \(X\) ) are abbreviated as \([Tg]_{\mathrm{feed}}\) , \([Tr]_{\mathrm{feed}}\) , \([I]_{\mathrm{feed}}\) , \([X]_{\mathrm{feed}}\) , respectively. Initial concentrations \((Tg]_{0}\) , \([Tr]_{0}\) , \([I]_{0}\) , \([X]_{0}\) ) reported in the figure captions and legends are calculated based on the feeding concentration and flow rate of each component. Hence, when we changed the initial concentration of \(\mathrm{[Nd]_{0}}\) , we meant that we increased the inflow rate of a stock solution with \(\mathrm{Nd^{3 + }}\) . At the same time, we decreased the supply of the buffer to balance the overall flowrate. + +We have extended the method section with an explanation of the experimental setup: + +- Page 14, line 22: In our setup, we use stock solutions of the components of the system and store them in glass syringes, which content is connected by polytetrafluoroethylene tubing's to the CSTR. The low-pressure pumps are used to independently control the syringes and feed each stock solution into the CSTR. The feeding concentrations for the components \((Tg, Tr, I,\) and \(X\) ) are abbreviated as \([Tg]_{\mathrm{feed}}\) , \([Tr]_{\mathrm{feed}}\) , \([I]_{\mathrm{feed}}\) , \([X]_{\mathrm{feed}}\) , respectively. Initial concentration \((Tg]_{0}\) , \([Tr]_{0}\) , \([I]_{0}\) , \([X]_{0}\) ) reported in the figure captions and legends are calculated based on the feeding concentration and flow rate of each component. The total flow rate is kept constant throughout the experiments. + +In some places (for example, p.3, lines 13/14), the numerical values of variables are given without the corresponding units. + +We found two instances and corrected them as follows: + +<--- Page Split ---> + +- Page 3, line 28: In accordance with our batch experiments, a maximum in \([Tr]\) could indeed be reached when the input satisfied the condition \(0.20 \leq [\mathrm{Nd}^{3+}]_0 \leq 0.40 \mathrm{mM}\) . + +- Page 13, line 45: Proteins were stained by Bradford technique, namely, \(2\mathrm{g}\) of Coomassie Blue R250 in \(1\mathrm{L}\) of \(10\%\) acetic acid and \(40\%\) ethanol solution. + +<--- Page Split ---> + +## Reviewer #3: + +This is an interesting paper, with some thought provoking ideas. The authors use metal ions to control the rate of autocatalysis with trypsin and this feature is used to program the output response of the autocatalyst in a flow reactor. They mention implications in terms of eg neuromorphic computing. Some of the manuscript could be more clearly written, and I am unclear on the interpretation of results in some parts. + +We appreciate that the reviewer sees the manuscript as interesting and thought provoking. We agree that the clarity in the manuscript can be improved and thank the reviewer for their constructive comments. + +In the abstract It is not immediately clear what is meant by "reconfigured in a programmable manner"; this could do with clearer explanation. What are you reconfiguring? There has been quite a lot done with computing in eg reaction diffusion systems; using light, chemical inputs etc to implement Boolean logic and image processing - can it be better pinpointed what is the difference here? + +The reviewer is correct in their request for clarity with regards to reconfiguration and programmability, and the difference of our systems towards other existing work. Reconfigure refers to the rewiring of feedback loops [Kholodenko, B. N. Nat. Rev. Mol. Cell Biol. 7, 165- 176 (2006)]. This reference was already provided and we have included the citation as follows: + +- Page 1, Line 15: How this chemical analogue of a positive feedback mechanism can be controlled reconfigured in a programmable manner is, however, unknown.- Page 1, Line 35: How feedback loops in CRNs can be tuned, scaled, and reconfigured (or, rewired)28 in a programmable manner (i.e., accept instructions to perform a range of tasks, rather than just one), however, remains elusive. + +To clarify our work in this context, we showed that the intrinsic rates in metal ion- induced autocatalysis (scheme 1) can be "reconfigured" when multiple ions are present in the same solution. The mapping of a chemical output onto polynomial functions as demonstrated in Fig. 3 underscores the flexibility of using metal ions in reconfiguring the autocatalytic network. + +Accordingly, we have changed the manuscript as follows: + +- Page 4, Line 9: The mapping of a chemical output onto polynomial functions as demonstrated here underscores the flexibility of using metal ions in controlling (or, reconfiguring) the autocatalytic network. + +We also showed that "tuning" was achieved by changing an operation as a function of the rate of the autocatalysis reaction. More specifically, we changed the input concentration of \(\mathrm{Nd}^{3 + }\) , which affected the steady state concentration of \(Tr\) . The same input sequence \(\left(\mathrm{Nd}^{3 + }\right)_{100}\) ; \(\left(\mathrm{Nd}^{3 + }\right)_{10}\) ; \(\left(\mathrm{Nd}^{3 + }\right)_{10}\) ; \(\left[\mathrm{Nd}^{3 + }\right]_{10}\) ; \(\left[\mathrm{Nd}^{3 + }\right]_{10}\) ) therefore allowed a range of different logic operations. That a diverse set of functions can be chosen by sets of initial conditions as presented in Fig. 4 demonstrates that autocatalytic reactions can be "programmable". We incorporated the following section in the main text to clarify the novelty with regards to chemical logic gates: + +- Page 5, line 35: We showed demonstrated that trypsin autocatalysis can be controlled to emulate polynomial functions with different degrees and Boolean functions with various outcomes (e.g., AND, OR, XOR, NAND, NOR), demonstrating that autocatalytic reactions can be programmable. Furthermore, we demonstrated that i) the output signal can be reset, ii) multiple ions can be combined to change the phase space, and iii) Boolean functions can be readily tuned and modelled mathematically, and iv) the history-dependent nature of autocatalysis in flow can retain information. That a range of logic are tuneable and controllable based on a kinetic parameter sets this work apart from traditional molecular logic gates40. + +- Additional reference: 40. Andréasson, J. & Pischel, U. Molecules with a sense of logic: a progress report. Chem. Soc. Rev., 44, 1053-1069 (2015). + +<--- Page Split ---> + +Some explanation of a neuromorphic system and the desired features of such a system in the introduction would be useful for the more general audience. + +Biological neural computation is inherently analogue and stochastic. Most neuromorphic hardware design first define hardware and subsequently develop the algorithm and application. Despite tremendous progress in neuromorphic processors, opportunities in rethinking the design neuromorphic systems lie in using analogue, approximate and mixed- signal computing [Schuman, C. D. et al. Nat. Comput. Sci. 2, 10- 19 (2022)]. We consider that the nonlinear kinetics of autocatalytic reactions could suggest chemical equivalents to electronic artificial neurons. [Arcadia, C. E. et al. Chem. Sci. 12, 5464- 5472 (2021)]. + +We have added new sections to the introduction to emphasize a connection between autocatalytic and neuromorphic computational systems as follows: + +- Page 1, Line 30: That is, they have the ability to perceive information and retain it as knowledge to execute complex tasks13, highlighting how inherent analogue processes can enable biological computation. Opportunities in rethinking the design of neuromorphic systems lie in using analogue and approximate computing.4,17- Additional reference: 17. Valiant, L., Probably Approximately Correct: Nature's Algorithms for Learning and Prospering in a Complex World. 2013.- Page 1, Line 40: Autocatalysis — a chemical process in which the product acts as the catalyst for its own formation — is at the core of the mechanisms of the aforementioned examples of CRNs, facilitating a fast and nonlinear response to stimuli from the environment28. The nonlinearity of artificial neurons can, essentially, be resembled by the kinetic feature of autocatalytic reactions.10 + +Figure 2. I'm not sure that fig 2d data can be interpreted as Nd is an" inhibitor" in the traditional sense, since without the metal, autocatalysis doesn't proceed. Technically, it results in a lower rate only as the concentration of Nd is increased above a threshold value. Possibly there is some initial binding of Nd to Tr to form an active state but further binding results in an inactive state - similar to binding of acid to enzymes. Nevertheless, the experimental results are still the same, it is just interpretation that I am unclear on. + +The reviewer is correct. We agree that the term "inhibition" should not be used to describe the referred experimental results. Therefore, we change the term "inhibiting" to "slowing down" in the main text as suggested by the reviewer. + +- Page 3, Line 5: Based on these batch experiments, we assume that \(i\) autocatalysis cannot occur without any of the metal ions; \(ii\) binding of the ions to \(Tr\) (depicted as \([TrX]\) ) can 'activate' autocatalysis, changing the apparent rate constant for the conversion of \(Tg\) into \(Tr\) (indicated by \(k_x\) ); \(iii\) binding of \(\mathrm{Nd}^{3 + }\) to \(Tg\) (depicted as \([\mathrm{Nd}^{3 + }Tg]\) ) can 'de-activate' autocatalysis, slowing down the conversion of \(Tg\) into \(Tr\) . + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The authors answered my questions correctly and corrected the related parts in the modified version of the manuscript. In the revised version, it is more apparent that their intention is not to create a chemical analog of a digital computer with logic gates but to mimic biological computation by designing a neuromorphic like system. In the introduction, the authors should write a few more sentences about the basics of biological computation and neuromorphic systems to help readers become more familiar with these topics. After this minor revision, I suggest accepting the manuscript. + +<--- Page Split ---> + +## Reviewer #1: + +The authors answered my questions correctly and corrected the related parts in the modified version of the manuscript. In the revised version, it is more apparent that their intention is not to create a chemical analog of a digital computer with logic gates but to mimic biological computation by designing a neuromorphic like system. In the introduction, the authors should write a few more sentences about the basics of biological computation and neuromorphic systems to help readers become more familiar with these topics. After this minor revision, I suggest accepting the manuscript. + +We thank the reviewer for their positive comments on our revised manuscript and their suggestion to accept this version for publication. We acknowledge that few more sentences about the basics of biological computation and neuromorphic systems will further help readers become more familiar with these topics. Accordingly, we incorporated a section in the beginning of the introduction: + +- Page 1, line 25: Living systems, from a simple slime mold to a more complex Venus flytrap to a highly sophisticated cephalopod, exhibit intelligent behavior1. That is, they have the ability to perceive information and retain it as knowledge to execute complex tasks2. The underlying processes by which decisions are made are fundamentally different from conventional (digital) computing, as they rely on complex, decentralized networks of biochemical reactions that operate in parallel2. Artificial neuromorphic systems take inspiration from natural and biological processes3, particularly from how neurons process and transmit signals in the brain4. Rethinking the design of neuromorphic systems do not necessarily restrict to neural architectures5 and opportunities may lie in using analogue and approximate computing that arise from purely (bio)chemical processes6. + +- Additional reference: 3. Castro, L. N. de. Fundamentals of natural computing: an overview. Phys. Life Rev. 4, 1-36 (2007). + +<--- Page Split ---> diff --git a/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..77cf438010de1928c712c762393391335d0b4192 --- /dev/null +++ b/peer_reviews/32940fc48c75a8c84b7e9529384600e938308ff28d38e828a0d8c6b0223ef540/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,349 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[66, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[110, 154, 886, 210]]<|/det|> +# Exploring the Programmability of Autocatalytic Chemical Reaction Networks + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 784]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 315, 101]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[118, 136, 437, 154]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 161, 880, 442]]<|/det|> +Reviewer #1 (Remarks to the Author):In the manuscript entitled "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," the authors present a novel experimental study on the batch kinetics and CSTR dynamics trypsin- catalyzed autocatalytic reaction network and its capability to perform some logic operations. According to the presented results the addition of metal ions (La(III), Ca(III), Nd(III)) opens an effective way to control the kinetics of the autocatalysis. In CSTR experiments, Nd(III) has a nonlinear effect depending on the presence of the second cation. The capability of the system to perform logic operations is demonstrated. The interpretation of the experiments is valid and robust. The presented results remarkably contribute to the development of designing intelligent chemical systems. The methodology is appropriate and presentation of the data is clear. The manuscript references previous literature appropriately. + +<|ref|>text<|/ref|><|det|>[[118, 475, 335, 492]]<|/det|> +Questions and comments: + +<|ref|>text<|/ref|><|det|>[[118, 527, 833, 571]]<|/det|> +(1) Could the authors discuss the system's robustness, especially in the context of logic operations? + +<|ref|>text<|/ref|><|det|>[[115, 604, 884, 808]]<|/det|> +(2) The CSTR experiments were performed in two serial reactors. According to the theory of serial CSTRs reactions that produce bistability in a single CSTR (with two stable, one unstable steady states), in a series of CSTRs with N reactors, have up to \(S2^{\wedge}(N + 1) - 1\) \(S\) steady states, of which only \(S N + 1\) \(S\) are stable. (A. Varma, Ind. Eng. Chem. Fundam. 1980, 19, 316. ;G. Dangelmayr, I. Stewart, SIAM J. Appl. Math. 1985, 45, 895). It seems that this multiplicity of states may appear in the experiments presented in the manuscript. Could the author comment on it? Would this multiplicity affect the operation of the system? + +<|ref|>text<|/ref|><|det|>[[117, 840, 856, 911]]<|/det|> +(3) In the context of logic operations, it seems that an obvious question is how to connect two more logic gates based on the presented configurations to perform somewhat more examples of computations. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 875, 155]]<|/det|> +(4) Could the authors clarify the meaning of "Bistability in temporal logic operations"? What are the characteristics of the two stable states, and how the coexistence of these states can be observed? + +<|ref|>text<|/ref|><|det|>[[117, 188, 877, 312]]<|/det|> +(5) In the conclusions, the authors state, "We envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive, adaptive, and other life-like properties characteristic for intelligent systems." What are the main steps of this novel strategy, and in what type of systems can it be applied? + +<|ref|>text<|/ref|><|det|>[[118, 345, 820, 364]]<|/det|> +I suggest addressing the above questions and comments and revising the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[118, 422, 438, 440]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 448, 875, 860]]<|/det|> +The manuscript "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," written by Dmitrii V. Kriukov, Jurriaan Huskens, and Albert S. Y. Wong, is concerned with the application of trypsin catalysis as a chemical logic gate. The subject is interesting but not new because the first chemical logic gates were described 40 years ago. According to my knowledge, the application of trypsin-catalyzed reaction for chemical information processing is a new element in the study. The logic gates are useful when concatenating them into more complex information processing devices. This does not seem easy within the presented approach because concentrations of metal ions are used as the gate input, but the output is extracted from time-dependent trypsin concentration [Tr](t). This means that connecting two gates requires a device (presumably electronic) that analyzes [Tr](t) and translates the result to the ion pump rates of another CSTR. Moreover, the results of Fig. 4 suggest that a gate can make a few operations per hour, which is rather slow to attract industrial attention. Therefore, considering the limited practical applicability of the presented medium and narrow field of study, I do not recommend publication in a journal focused on a wide audience. The results are better suited for a specialized journal focused on natural or unconventional computing. + +<|ref|>text<|/ref|><|det|>[[115, 893, 867, 912]]<|/det|> +In my opinion, the present version of the manuscript is poorly written and does not include + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 595, 101]]<|/det|> +all the information needed to understand what was done. + +<|ref|>text<|/ref|><|det|>[[118, 136, 810, 180]]<|/det|> +Here are some remarks on manuscript fragments that must be improved before it is submitted to another journal. + +<|ref|>text<|/ref|><|det|>[[118, 214, 867, 285]]<|/det|> +The authors refer to a mathematical model that is not well described. The model variables should be listed. I also expected to find the kinetic equations with flow terms included. The article SI just gives the set of reactions and comments on the reactions. + +<|ref|>text<|/ref|><|det|>[[117, 318, 876, 441]]<|/det|> +The mathematical symbols are used without their precise definition in the text. What is [A]feed (Fig.3 caption)? According to what I read, the symbol [A]0 denotes the concentration of reagent A at the beginning of the experiment (t=0). How shall I understand Fig. 3a, where [Nd3+J0 is plotted as a function of time, and its caption says that [Nd]0 was changed? + +<|ref|>text<|/ref|><|det|>[[118, 475, 853, 520]]<|/det|> +In some places (for example, p.3, lines 13/14), the numerical values of variables are given without the corresponding units. + +<|ref|>sub_title<|/ref|><|det|>[[118, 580, 438, 597]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 604, 877, 912]]<|/det|> +This is an interesting paper, with some thought provoking ideas. The authors use metal ions to control the rate of autocatalysis with trypsin and this feature is used to program the output response of the autocatalyst in a flow reactor. They mention implications in terms of eg neuromorphic computing. Some of the manuscript could be more clearly written, and I am unclear on the interpretation of results in some parts. In the abstract It is not immediately clear what is meant by "reconfigured in a programmable manner"; this could do with clearer explanation. What are you reconfiguring? There has been quite a lot done with computing in eg reaction diffusion systems; using light, chemical inputs etc to implement Boolean logic and image processing - can it be better pinpointed what is the difference here? Some explanation of a neuromorphic system and the desired features of such a system in the introduction would be useful for the more general audience. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 870, 234]]<|/det|> +Figure 2. I'm not sure that fig 2d data can be interpreted as Nd is an" inhibitor" in the traditional sense, since without the metal, autocatalysis doesn't proceed. Technically, it results in a lower rate only as the concentration of Nd is increased above a threshold value. Possibly there is some initial binding of Nd to Tr to form an active state but further binding results in an inactive state - similar to binding of acid to enzymes. Nevertheless, the experimental results are still the same, it is just interpretation that I am unclear on. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 135, 880, 168]]<|/det|> +Changes to the text of our manuscript, based on the below reviewers' comments, are highlighted in yellow and indicated with "Page XX, line YY", referring to the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[115, 179, 216, 195]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 201, 883, 346]]<|/det|> +In the manuscript entitled "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," the authors present a novel experimental study on the batch kinetics and CSTR dynamics trypsin- catalyzed autocatalytic reaction network and its capability to perform some logic operations. According to the presented results the addition of metal ions (La(III), Ca(II), Nd(III)) opens an effective way to control the kinetics of the autocatalysis. In CSTR experiments, Nd(III) has a nonlinear effect depending on the presence of the second cation. The capability of the system to perform logic operations is demonstrated. The interpretation of the experiments is valid and robust. The presented results remarkably contribute to the development of designing intelligent chemical systems. The methodology is appropriate and presentation of the data is clear. The manuscript references previous literature appropriately. + +<|ref|>text<|/ref|><|det|>[[115, 353, 883, 386]]<|/det|> +We thank the reviewer for their positive comments on our manuscript. Below, we indicate how we have used their constructive comments to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 408, 830, 426]]<|/det|> +(1) Could the authors discuss the system's robustness, especially in the context of logic operations? + +<|ref|>text<|/ref|><|det|>[[115, 431, 883, 529]]<|/det|> +The reviewer correctly pointed out that a discussion on the robustness of the system was not included. Robustness is a network property which ensures that specific functions of the system are maintained [Kitano, H. Nat. Rev. Gen. (2004)]. In our work, robustness can be defined as the parameter window wherein the desired logic operation can be obtained. We did discuss that the various logic operations can be found in a "narrow range of parameters" (page 4, line 44) but we did not comment on the differences between the operations in terms of their robustness. We have incorporated the suggestion of the reviewer as follows: + +<|ref|>text<|/ref|><|det|>[[144, 534, 883, 600]]<|/det|> +- Page 4, line 47: The phase plot shows that a parameter window exists to maintain each logic operation, ensuring that the desired functions of the system are robust39. The robustness, however, differs per operation. +- Additional reference: 39. Kitano, H. Biological Robustness Nat. Rev. Gen. 5, 826-837 (2004). + +<|ref|>text<|/ref|><|det|>[[115, 621, 883, 720]]<|/det|> +(2) The CSTR experiments were performed in two serial reactors. According to the theory of serial CSTRs reactions that produce bistability in a single CSTR (with two stable, one unstable steady states), in a series of CSTRs with N reactors, have up to \(S2^{\wedge}N + 1\) - 1 IS steady states, of which only \(SN + 1\) IS are stable. (A. Varma, Ind. Eng. Chem. Fundam. 1980, 19, 316. ;G. Dangelmayr, I. Stewart, SIAM J. Appl. Math. 1985, 45, 895). It seems that this multiplicity of states may appear in the experiments presented in the manuscript. Could the author comment on it? Would this multiplicity affect the operation of the system? + +<|ref|>text<|/ref|><|det|>[[115, 725, 883, 759]]<|/det|> +The reviewer provided an interesting perspective and appealing strategy for constructing multiple states in our system. We gladly take this perspective on board for our future studies (see our answer to comment 5). + +<|ref|>text<|/ref|><|det|>[[115, 765, 883, 896]]<|/det|> +Here, to clarify our work, the experimental setup indeed comprises two CSTRs but we noted that the first reactor is the main reaction chamber and that the second reactor serves as a detection chamber (page 13, line 14- 15). The residence time in the second reactor was deliberately made twice as small as the first reactor to ensure that we could detect the output signal as pseudo- online. In addition, mixture of DMSO and DMFA was used to dissolve the detection molecule (BAPNA) and reduce the rate of trypsinogen conversion. We checked experimentally that even small percentage of DMSO slows down Tg conversion dramatically. Hence, we did not actually perform our experiments in serial CSTRs but in one CSTR: The second reactor was engineered to allow for the fast detection of trypsin concentration by converting BAPNA + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 123]]<|/det|> +into pNA (detectable moiety at \(405 \mathrm{nm}\) ) without any side processes that could potentially lead to multiplicity of steady states. + +<|ref|>text<|/ref|><|det|>[[115, 130, 433, 146]]<|/det|> +We extended the method section as follows: + +<|ref|>text<|/ref|><|det|>[[144, 153, 882, 281]]<|/det|> +- Page 14, line 14: First reactor served as a main reaction chamber whereas the second was receiving its outflow and reporting solution at the constant (2:1) ratio. The residence time in the second reactor was deliberately made twice as small as the first reactor to ensure that we could detect the output signal as pseudo-online. Reporting solution consisted of \(4 \mathrm{mM}\) BAPNA in mixture of MQ:DMSO:DMAF (0.2:0.08:0.72). The mixture of DMSO and DMFA was used to dissolve the detection molecule (BAPNA) and reduce the rate of trypsinogen conversion. Hence, the second reactor was engineered to allow for a fast detection of \([Tr]\) by converting BAPNA into pNA (detectable moiety at \(405 \mathrm{nm}\) ) without any side processes. + +<|ref|>text<|/ref|><|det|>[[115, 304, 881, 337]]<|/det|> +(3) In the context of logic operations, it seems that an obvious question is how to connect two more logic gates based on the presented configurations to perform somewhat more examples of computations. + +<|ref|>text<|/ref|><|det|>[[115, 344, 882, 519]]<|/det|> +We can relate to the comment from the reviewer. Briefly, it is possible to have sequential logic gates when output from a reactor feeds the next reactor with \([Tr]\) . Our method of CSTR fabrication, in fact, does not restrict to a sequence of two reactors but also allows for the design of spatially- coupled CSTRs of other configurations (serial, parallel, arrays). It will require two conditions: supply of the same reactants further down the chain (but without \([Tr]_0\) ), and elimination of significant portion of the liquid from previous reactors to avoid buildup of the flow and concentration catalytic ions. Our intentions, however, are not to connect logic gates. In our future studies, we will compare various configurations and examine the capacity of autocatalytic processes to perform (primitive) nonlinear operations in flow, including the introduction of spike- driven conditions (a method commonly used in neuromorphic processing). In this regard, the XOR- gate can be considered as a primitive nonlinear operation [Chen, T. et al. Nature, 577, 341- 345 (2020)]. The latter sentence was added to the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 526, 882, 602]]<|/det|> +- Page 5, line 48: Additionally, a trypsin inhibitor was incorporated into the network to create a bistable system capable of long-term depression of the input and history dependency in the output (i.e., characteristics for neuromorphic behavior). In this regard, the XOR-gate can be considered as a primitive nonlinear operation36. Building on this foundation, future work could include the introduction of spike-driven conditions to perform other nonlinear operations under out-of-equilibrium conditions.9 + +<|ref|>text<|/ref|><|det|>[[144, 621, 881, 653]]<|/det|> +- Additional reference: 36. Chen, T. et al. Classification with a disordered dopant-atom network in silicon Nature, 577, 341-345 (2020). + +<|ref|>text<|/ref|><|det|>[[115, 678, 881, 710]]<|/det|> +(4) Could the authors clarify the meaning of "Bistability in temporal logic operations"? What are the characteristics of the two stable states, and how the coexistence of these states can be observed? + +<|ref|>text<|/ref|><|det|>[[115, 717, 882, 797]]<|/det|> +We appreciate the questions of reviewer and apologize for lack of clarity with regards to the subheading "Bistability in temporal logic operations". We reported that "the response became bistable (page 5, line 26)" and this phenomenological observation is supported by our model but we didn't include the prediction of the parameter space wherein co- existence of such states can be observed. We are exploring the control over stability of steady states in the presence of metal ions in separate work. + +<|ref|>text<|/ref|><|det|>[[115, 805, 882, 885]]<|/det|> +In this section, we showed that the autocatalytic system can be maintained at a low trypsin concentration by introducing an inhibitor (Soybean Trypsin Inhibitor) in the network. The incorporation of the inhibitor enables a stable and low steady state, as \(Tr\) becomes inactive, but does not change the stability of the high steady state, which is supported by autocatalytic production of \(Tr\) . Without the inhibitor, the low steady state has to be stabilized by continuously depleting \(Tr\) using flow, which leads to an unstable steady state. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 352, 107]]<|/det|> +We made the following changes: + +<|ref|>text<|/ref|><|det|>[[144, 112, 884, 273]]<|/det|> +Page 5, line 7: Increasing the control over Bistability in temporal logic operations- Page 5, line 11: The use of an external component such as an inhibitor for thresholding provides further control over the network properties. Without the inhibitor, the low steady state was stabilized by continuously depleting \(Tr\) using flow, which leads to an unstable steady state. The incorporation of the inhibitor enables a stable and low steady state, as \(Tr\) becomes inactive, but does not change the stability of the high steady state, which is supported by autocatalytic production of \(Tr\) . \(^{30}\) - Page 5, line 48: Additionally, a trypsin inhibitor was incorporated into the network to create a bistable system capable of long- term depression of the input and history dependency in the output (i.e., characteristics for neuromorphic behavior). + +<|ref|>text<|/ref|><|det|>[[115, 295, 882, 362]]<|/det|> +(5) In the conclusions, the authors state, "We envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive, adaptive, and other life-like properties characteristic for intelligent systems." What are the main steps of this novel strategy, and in what type of systems can it be applied? + +<|ref|>text<|/ref|><|det|>[[115, 366, 882, 529]]<|/det|> +We appreciate the questions of reviewer, and gladly take this opportunity to elaborate how we foresee follow- up studies based on this work. This work can be extended with perturbation studies in a single CSTR but also extended to configurations comprising multiple bistable systems in series-, parallel- or array- coupled CSTRs. As mentioned above, in our answer to comment 3, such studies allow us to elucidate the capacity of autocatalytic reactions to perform (primitive) nonlinear operations in flow. The implementation of different configurations will be a crucial next step is to determine how exactly the states in such molecular systems can be changed, retained, and used to build responses that are more complex than those shown in the current manuscript. The strategy to systematically increase the number of collective feedback loops in the system is based on the concept that interconnected feedback loops could bestow CRNs with intelligent behavior (i.e., the capacity to perceive and retain information, and apply it towards adaptive behavior). + +<|ref|>text<|/ref|><|det|>[[115, 534, 671, 552]]<|/det|> +We incorporated the following sentence in the conclusions of the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 557, 882, 671]]<|/det|> +- Page 6, line 2: The implementation of different configurations of multiple autocatalytic systems (based on series-, parallel- or array-coupled CSTRs) will be a crucial next step to systematically increase the number of collective feedback loops in the system. It will provide the potential to bestow CRNs with the capacity to perceive and retain information and apply it towards adaptive behavior. Hence, we envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive \(^{41}\) , adaptive \(^{42}\) , and other life-like properties \(^{2}\) characteristic for intelligent systems. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 216, 106]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[114, 112, 883, 369]]<|/det|> +The manuscript "Exploring the Programmability of Autocatalytic Chemical Reaction Networks," written by Dmitrii V. Kriukov, Jurriaan Huskens, and Albert S. Y. Wong, is concerned with the application of trypsin catalysis as a chemical logic gate. The subject is interesting but not new because the first chemical logic gates were described 40 years ago. According to my knowledge, the application of trypsin- catalyzed reaction for chemical information processing is a new element in the study. The logic gates are useful when concatenating them into more complex information processing devices. This does not seem easy within the presented approach because concentrations of metal ions are used as the gate input, but the output is extracted from time- dependent trypsin concentration \([Tr](t)\) . This means that connecting two gates requires a device (presumably electronic) that analyzes \([Tr](t)\) and translates the result to the ion pump rates of another CSTR. Moreover, the results of Fig. 4 suggest that a gate can make a few operations per hour, which is rather slow to attract industrial attention. Therefore, considering the limited practical applicability of the presented medium and narrow field of study, I do not recommend publication in a journal focused on a wide audience. The results are better suited for a specialized journal focused on natural or unconventional computing. In my opinion, the present version of the manuscript is poorly written and does not include all the information needed to understand what was done. Here are some remarks on manuscript fragments that must be improved before it is submitted to another journal. + +<|ref|>text<|/ref|><|det|>[[115, 376, 882, 441]]<|/det|> +The reviewer acknowledges that "the application of trypsin- catalyzed reaction for information processing is a new element in the study" but expresses their concerns about the novelty with regards to existing work based on chemical logic gates and the practical applicability of our approach. We gladly provide our view on these aspects in this rebuttal and have elaborated the conclusions as a result. + +<|ref|>text<|/ref|><|det|>[[115, 447, 882, 545]]<|/det|> +First, the reviewer correctly points out that our system, or any chemical system for that matter, cannot compete with the state- of- the- art technologies in computing. Among other reasons, the time scales for transitions between states based on molecular interactions (in our case hours) are nowhere near those that are based on electronic or photonic interactions (fractions of a second). To clarify, our intentions are not to connect logic gates as suggested by the reviewer's comment nor to compete with, emulate, or mimic methods in traditional computing. + +<|ref|>text<|/ref|><|det|>[[115, 550, 882, 584]]<|/det|> +We have added new sections to the introduction to emphasize a connection between autocatalytic and neuromorphic computational systems as follows: + +<|ref|>text<|/ref|><|det|>[[142, 589, 882, 688]]<|/det|> +- Page 1, Line 30: That is, they have the ability to perceive information and retain it as knowledge to execute complex tasks13, highlighting how inherent analogue processes can enable biological computation. Opportunities in rethinking the design of neuromorphic systems lie in using analogue and approximate computing.4,17- Additional reference: 17. Valiant, L., Probably Approximately Correct: Nature's Algorithms for Learning and Prospering in a Complex World. 2013. + +<|ref|>text<|/ref|><|det|>[[115, 694, 882, 744]]<|/det|> +This manuscript aims to set up a practical experimental foundation to use autocatalytic reactions, and chemical reaction networks in general, to perform (primitive) nonlinear operations. In this regard, the XOR- gate can be considered as a primitive nonlinear operation [Chen, T. et al. Nature, 577, 341- 345 (2020)]. + +<|ref|>text<|/ref|><|det|>[[144, 750, 882, 848]]<|/det|> +- Page 5, line 48: Additionally, a trypsin inhibitor was incorporated into the network to create a system capable of long-term depression of the input and history dependency in the output (i.e., characteristics for neuromorphic behaviour). In this regard, the XOR-gate can be considered as a primitive nonlinear operation36. Building on this foundation, future work could include the introduction of spike-driven conditions to perform other nonlinear operations under out-of-equilibrium conditions.9 + +<|ref|>text<|/ref|><|det|>[[144, 847, 882, 879]]<|/det|> +- Additional reference: 36. Chen, T. et al. Classification with a disordered dopant-atom network in silicon Nature, 577, 341-345 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 250]]<|/det|> +While sequential logic gates is not within the scope of this work, we wish to state that it is possible to perform such experiments. Our method of CSTR fabrication, in fact, does not restrict to a sequence of two reactors but also allows for the design of spatially coupled CSTRs of other configurations (serial, parallel, arrays) as well. The emphasis in our future work, however, is not to connect reactors to combine gates. The implementation of different configurations will be a crucial next step is to determine how exactly the states in such molecular systems can be changed, retained, and used to build responses that are more complex than those shown in the current manuscript. The strategy to systematically increase the number of collective feedback loops in the system is based on the concept that interconnected feedback loops could bestow CRNs with intelligent behavior (i.e., the capacity to perceive and retain information, and apply it towards adaptive behavior). We incorporated the following sentence in the conclusions of the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 256, 882, 369]]<|/det|> +- Page 6, line 2: The implementation of different configurations of multiple autocatalytic systems (based on series-, parallel- or array-coupled CSTRs) will be a crucial next step to systematically increase the number of collective feedback loops in the system. It will provide the potential to bestow CRNs with the capacity to perceive and retain information and apply it towards adaptive behavior. Hence, we envision that this work will offer novel strategies to exploit the programmability of small and simple chemical reaction networks for building artificial systems with responsive, adaptive, and other life-like properties characteristic for intelligent systems. + +<|ref|>text<|/ref|><|det|>[[115, 376, 882, 473]]<|/det|> +Second, the observation that the range of logics is controllable based on a kinetic parameter sets this work apart from "the first chemical logic gates described 40 years ago (reviewer comment line 3)": Our system can accept instructions to perform a range of logic operations and demonstrates that autocatalytic reactions can be programmable. Furthermore, we demonstrated that \(i\) ) the output signal can be reset, \(ii\) ) the method of creating logic gates is not restricted to \(\mathrm{Nd}^{3 + }\) , and ions can be combined to change the phase space, and iii) Boolean functions can be readily tuned and modeled mathematically. + +<|ref|>text<|/ref|><|det|>[[115, 479, 880, 512]]<|/det|> +We incorporated the following section in the main text to clarify the novelty with regards to chemical logic gates as follows: + +<|ref|>text<|/ref|><|det|>[[144, 519, 882, 647]]<|/det|> +- Page 5, line 40: We showed demonstrated that trypsin autocatalysis can be controlled to emulate polynomial functions with different degrees and Boolean functions with various outcomes (e.g., AND, OR, XOR, NAND, NOR), demonstrating that autocatalytic reactions can be programmable. Furthermore, we demonstrated that \(i\) ) the output signal can be reset, \(ii\) ) multiple ions can be combined to change the phase space, and \(iii\) ) Boolean functions can be readily tuned and modelled mathematically, and \(iv\) ) the history-dependent nature of autocatalysis in flow can retain information. That a range of logic are tunable and controllable based on a kinetic parameter sets this work apart from traditional molecular logic gates40. + +<|ref|>text<|/ref|><|det|>[[144, 648, 880, 680]]<|/det|> +- Additional reference: 40. Andréasson, J. & Pischel, U. Molecules with a sense of logic: a progress report. Chem. Soc. Rev., 44, 1053-1069 (2015). + +<|ref|>text<|/ref|><|det|>[[115, 686, 882, 768]]<|/det|> +Third, the comment "the present version of the manuscript is poorly written and does not include all the information needed to understand what was done" seems to relate to the description of the mathematical model (i.e., the "manuscript fragments that must be improved"). We provided our answer below, wherein we clarified, and rectified, the possible confusion that came from our distribution of details on the model (supplementary information vs. supplementary materials). + +<|ref|>text<|/ref|><|det|>[[115, 790, 882, 838]]<|/det|> +The authors refer to a mathematical model that is not well described. The model variables should be listed. I also expected to find the kinetic equations with flow terms included. The article SI just gives the set of reactions and comments on the reactions. + +<|ref|>text<|/ref|><|det|>[[115, 846, 882, 894]]<|/det|> +We can relate to the reviewers' requests (i.e., to list the model variables, incorporate kinetic equations, and provide an SI that gives more that the set of reactions). However, we do wish to point out that this assessment is not entirely accurate. To clarify, the mathematical model was provided as a set of ready- to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 154]]<|/det|> +use scripts in supplementary materials. We described how the model is built and used in our work (with a reference to both supplementary information and supplementary information) in the methods section of the main text (page 13, line 32- 43). Nevertheless, we extended the Supplementary Information per request of the reviewer: + +<|ref|>text<|/ref|><|det|>[[143, 161, 883, 272]]<|/det|> +- Supplementary Information, Page 2: We incorporated a process scheme (new Supplementary Scheme 1) to explain the modelling workflow.- Supplementary Information, Page 3: New section (Equations for the model) has been added to elaborate on equations used for the model.- Supplementary Information, Page 6-7: Supplementary table is updated and split in two tables to clarify the chemical meaning of the processes reflected in the new section 'Equations for the model'. + +<|ref|>text<|/ref|><|det|>[[115, 280, 883, 345]]<|/det|> +The mathematical symbols are used without their precise definition in the text. What is [A]feed (Fig.3 caption)? According to what I read, the symbol [A]0 denotes the concentration of reagent A at the beginning of the experiment \((t = 0)\) . How shall I understand Fig. 3a, where \(\mathrm{[Nd3 + ]0}\) is plotted as a function of time, and its caption says that [Nd]0 was changed? + +<|ref|>text<|/ref|><|det|>[[115, 351, 883, 400]]<|/det|> +The reviewer correctly pointed out that that the assignment of symbols is inconsistent in the manuscript. There are two occasions in the main text where we did not explicitly write that the initial concentration of the ions can be abbreviated with brackets and the zero as subscript. We have corrected this as follows: + +<|ref|>text<|/ref|><|det|>[[143, 406, 883, 473]]<|/det|> +- Page 2, line 41: Fig. 2b-c show that \([Tr]\) increases until it saturates as the initial concentration of \(\mathrm{Ca^{2 + }}\) and \(\mathrm{La^{3 + }}\) \(\mathrm{[Ca^{2 + }]_{0}}\) and \(\mathrm{[La^{3 + }]_{0}}\) are increased. ii) \(\mathrm{Nd^{3 + }}\) , in contrast, can accelerate and decelerate the rate of autocatalysis. Fig. 2d shows that the \([Tr]\) increases when the initial concentration of \(\mathrm{Nd^{3 + }}\) \(\mathrm{[Nd^{3 + }]_{0}}\) increases from 0 to \(0.3\mathrm{mM}\) . + +<|ref|>text<|/ref|><|det|>[[115, 479, 353, 495]]<|/det|> +In another section, we corrected: + +<|ref|>text<|/ref|><|det|>[[143, 501, 881, 535]]<|/det|> +- Page 7, line 11: \([Tr]\) denotes concentration of \(Tr\) ; t and t denote time and residence time, respectively. + +<|ref|>text<|/ref|><|det|>[[115, 540, 883, 686]]<|/det|> +Specifically for Fig. 3a, \(\mathrm{[Nd^{3 + }]_{0}}\) is changed over time using our flow setup (Methods section, page 13, line 11). In our setup, we use stock solutions of the components of the system and store them in glass syringes, which content is connected by polytetrafluoroethylene tubing's to the CSTR. The low- pressure pumps are used to independently control the syringes and feed each stock solution into the CSTR. The feeding concentrations for the components \((Tg, Tr, I,\) and \(X\) ) are abbreviated as \([Tg]_{\mathrm{feed}}\) , \([Tr]_{\mathrm{feed}}\) , \([I]_{\mathrm{feed}}\) , \([X]_{\mathrm{feed}}\) , respectively. Initial concentrations \((Tg]_{0}\) , \([Tr]_{0}\) , \([I]_{0}\) , \([X]_{0}\) ) reported in the figure captions and legends are calculated based on the feeding concentration and flow rate of each component. Hence, when we changed the initial concentration of \(\mathrm{[Nd]_{0}}\) , we meant that we increased the inflow rate of a stock solution with \(\mathrm{Nd^{3 + }}\) . At the same time, we decreased the supply of the buffer to balance the overall flowrate. + +<|ref|>text<|/ref|><|det|>[[115, 693, 727, 710]]<|/det|> +We have extended the method section with an explanation of the experimental setup: + +<|ref|>text<|/ref|><|det|>[[143, 716, 883, 828]]<|/det|> +- Page 14, line 22: In our setup, we use stock solutions of the components of the system and store them in glass syringes, which content is connected by polytetrafluoroethylene tubing's to the CSTR. The low-pressure pumps are used to independently control the syringes and feed each stock solution into the CSTR. The feeding concentrations for the components \((Tg, Tr, I,\) and \(X\) ) are abbreviated as \([Tg]_{\mathrm{feed}}\) , \([Tr]_{\mathrm{feed}}\) , \([I]_{\mathrm{feed}}\) , \([X]_{\mathrm{feed}}\) , respectively. Initial concentration \((Tg]_{0}\) , \([Tr]_{0}\) , \([I]_{0}\) , \([X]_{0}\) ) reported in the figure captions and legends are calculated based on the feeding concentration and flow rate of each component. The total flow rate is kept constant throughout the experiments. + +<|ref|>text<|/ref|><|det|>[[115, 852, 883, 885]]<|/det|> +In some places (for example, p.3, lines 13/14), the numerical values of variables are given without the corresponding units. + +<|ref|>text<|/ref|><|det|>[[115, 892, 513, 908]]<|/det|> +We found two instances and corrected them as follows: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[142, 90, 883, 120]]<|/det|> +- Page 3, line 28: In accordance with our batch experiments, a maximum in \([Tr]\) could indeed be reached when the input satisfied the condition \(0.20 \leq [\mathrm{Nd}^{3+}]_0 \leq 0.40 \mathrm{mM}\) . + +<|ref|>text<|/ref|><|det|>[[144, 120, 883, 153]]<|/det|> +- Page 13, line 45: Proteins were stained by Bradford technique, namely, \(2\mathrm{g}\) of Coomassie Blue R250 in \(1\mathrm{L}\) of \(10\%\) acetic acid and \(40\%\) ethanol solution. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 216, 106]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 113, 882, 179]]<|/det|> +This is an interesting paper, with some thought provoking ideas. The authors use metal ions to control the rate of autocatalysis with trypsin and this feature is used to program the output response of the autocatalyst in a flow reactor. They mention implications in terms of eg neuromorphic computing. Some of the manuscript could be more clearly written, and I am unclear on the interpretation of results in some parts. + +<|ref|>text<|/ref|><|det|>[[115, 185, 882, 218]]<|/det|> +We appreciate that the reviewer sees the manuscript as interesting and thought provoking. We agree that the clarity in the manuscript can be improved and thank the reviewer for their constructive comments. + +<|ref|>text<|/ref|><|det|>[[115, 240, 882, 305]]<|/det|> +In the abstract It is not immediately clear what is meant by "reconfigured in a programmable manner"; this could do with clearer explanation. What are you reconfiguring? There has been quite a lot done with computing in eg reaction diffusion systems; using light, chemical inputs etc to implement Boolean logic and image processing - can it be better pinpointed what is the difference here? + +<|ref|>text<|/ref|><|det|>[[115, 311, 882, 376]]<|/det|> +The reviewer is correct in their request for clarity with regards to reconfiguration and programmability, and the difference of our systems towards other existing work. Reconfigure refers to the rewiring of feedback loops [Kholodenko, B. N. Nat. Rev. Mol. Cell Biol. 7, 165- 176 (2006)]. This reference was already provided and we have included the citation as follows: + +<|ref|>text<|/ref|><|det|>[[144, 382, 882, 462]]<|/det|> +- Page 1, Line 15: How this chemical analogue of a positive feedback mechanism can be controlled reconfigured in a programmable manner is, however, unknown.- Page 1, Line 35: How feedback loops in CRNs can be tuned, scaled, and reconfigured (or, rewired)28 in a programmable manner (i.e., accept instructions to perform a range of tasks, rather than just one), however, remains elusive. + +<|ref|>text<|/ref|><|det|>[[115, 469, 882, 536]]<|/det|> +To clarify our work in this context, we showed that the intrinsic rates in metal ion- induced autocatalysis (scheme 1) can be "reconfigured" when multiple ions are present in the same solution. The mapping of a chemical output onto polynomial functions as demonstrated in Fig. 3 underscores the flexibility of using metal ions in reconfiguring the autocatalytic network. + +<|ref|>text<|/ref|><|det|>[[115, 542, 532, 559]]<|/det|> +Accordingly, we have changed the manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[144, 565, 882, 614]]<|/det|> +- Page 4, Line 9: The mapping of a chemical output onto polynomial functions as demonstrated here underscores the flexibility of using metal ions in controlling (or, reconfiguring) the autocatalytic network. + +<|ref|>text<|/ref|><|det|>[[115, 620, 882, 735]]<|/det|> +We also showed that "tuning" was achieved by changing an operation as a function of the rate of the autocatalysis reaction. More specifically, we changed the input concentration of \(\mathrm{Nd}^{3 + }\) , which affected the steady state concentration of \(Tr\) . The same input sequence \(\left(\mathrm{Nd}^{3 + }\right)_{100}\) ; \(\left(\mathrm{Nd}^{3 + }\right)_{10}\) ; \(\left(\mathrm{Nd}^{3 + }\right)_{10}\) ; \(\left[\mathrm{Nd}^{3 + }\right]_{10}\) ; \(\left[\mathrm{Nd}^{3 + }\right]_{10}\) ) therefore allowed a range of different logic operations. That a diverse set of functions can be chosen by sets of initial conditions as presented in Fig. 4 demonstrates that autocatalytic reactions can be "programmable". We incorporated the following section in the main text to clarify the novelty with regards to chemical logic gates: + +<|ref|>text<|/ref|><|det|>[[144, 740, 882, 870]]<|/det|> +- Page 5, line 35: We showed demonstrated that trypsin autocatalysis can be controlled to emulate polynomial functions with different degrees and Boolean functions with various outcomes (e.g., AND, OR, XOR, NAND, NOR), demonstrating that autocatalytic reactions can be programmable. Furthermore, we demonstrated that i) the output signal can be reset, ii) multiple ions can be combined to change the phase space, and iii) Boolean functions can be readily tuned and modelled mathematically, and iv) the history-dependent nature of autocatalysis in flow can retain information. That a range of logic are tuneable and controllable based on a kinetic parameter sets this work apart from traditional molecular logic gates40. + +<|ref|>text<|/ref|><|det|>[[144, 869, 882, 901]]<|/det|> +- Additional reference: 40. Andréasson, J. & Pischel, U. Molecules with a sense of logic: a progress report. Chem. Soc. Rev., 44, 1053-1069 (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 882, 138]]<|/det|> +Some explanation of a neuromorphic system and the desired features of such a system in the introduction would be useful for the more general audience. + +<|ref|>text<|/ref|><|det|>[[115, 144, 882, 243]]<|/det|> +Biological neural computation is inherently analogue and stochastic. Most neuromorphic hardware design first define hardware and subsequently develop the algorithm and application. Despite tremendous progress in neuromorphic processors, opportunities in rethinking the design neuromorphic systems lie in using analogue, approximate and mixed- signal computing [Schuman, C. D. et al. Nat. Comput. Sci. 2, 10- 19 (2022)]. We consider that the nonlinear kinetics of autocatalytic reactions could suggest chemical equivalents to electronic artificial neurons. [Arcadia, C. E. et al. Chem. Sci. 12, 5464- 5472 (2021)]. + +<|ref|>text<|/ref|><|det|>[[115, 248, 882, 281]]<|/det|> +We have added new sections to the introduction to emphasize a connection between autocatalytic and neuromorphic computational systems as follows: + +<|ref|>text<|/ref|><|det|>[[144, 288, 882, 449]]<|/det|> +- Page 1, Line 30: That is, they have the ability to perceive information and retain it as knowledge to execute complex tasks13, highlighting how inherent analogue processes can enable biological computation. Opportunities in rethinking the design of neuromorphic systems lie in using analogue and approximate computing.4,17- Additional reference: 17. Valiant, L., Probably Approximately Correct: Nature's Algorithms for Learning and Prospering in a Complex World. 2013.- Page 1, Line 40: Autocatalysis — a chemical process in which the product acts as the catalyst for its own formation — is at the core of the mechanisms of the aforementioned examples of CRNs, facilitating a fast and nonlinear response to stimuli from the environment28. The nonlinearity of artificial neurons can, essentially, be resembled by the kinetic feature of autocatalytic reactions.10 + +<|ref|>text<|/ref|><|det|>[[115, 470, 882, 551]]<|/det|> +Figure 2. I'm not sure that fig 2d data can be interpreted as Nd is an" inhibitor" in the traditional sense, since without the metal, autocatalysis doesn't proceed. Technically, it results in a lower rate only as the concentration of Nd is increased above a threshold value. Possibly there is some initial binding of Nd to Tr to form an active state but further binding results in an inactive state - similar to binding of acid to enzymes. Nevertheless, the experimental results are still the same, it is just interpretation that I am unclear on. + +<|ref|>text<|/ref|><|det|>[[115, 558, 882, 606]]<|/det|> +The reviewer is correct. We agree that the term "inhibition" should not be used to describe the referred experimental results. Therefore, we change the term "inhibiting" to "slowing down" in the main text as suggested by the reviewer. + +<|ref|>text<|/ref|><|det|>[[144, 613, 882, 695]]<|/det|> +- Page 3, Line 5: Based on these batch experiments, we assume that \(i\) autocatalysis cannot occur without any of the metal ions; \(ii\) binding of the ions to \(Tr\) (depicted as \([TrX]\) ) can 'activate' autocatalysis, changing the apparent rate constant for the conversion of \(Tg\) into \(Tr\) (indicated by \(k_x\) ); \(iii\) binding of \(\mathrm{Nd}^{3 + }\) to \(Tg\) (depicted as \([\mathrm{Nd}^{3 + }Tg]\) ) can 'de-activate' autocatalysis, slowing down the conversion of \(Tg\) into \(Tr\) . + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 85, 329, 101]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[119, 137, 438, 154]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 162, 874, 338]]<|/det|> +The authors answered my questions correctly and corrected the related parts in the modified version of the manuscript. In the revised version, it is more apparent that their intention is not to create a chemical analog of a digital computer with logic gates but to mimic biological computation by designing a neuromorphic like system. In the introduction, the authors should write a few more sentences about the basics of biological computation and neuromorphic systems to help readers become more familiar with these topics. After this minor revision, I suggest accepting the manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 145, 216, 161]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 168, 882, 265]]<|/det|> +The authors answered my questions correctly and corrected the related parts in the modified version of the manuscript. In the revised version, it is more apparent that their intention is not to create a chemical analog of a digital computer with logic gates but to mimic biological computation by designing a neuromorphic like system. In the introduction, the authors should write a few more sentences about the basics of biological computation and neuromorphic systems to help readers become more familiar with these topics. After this minor revision, I suggest accepting the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 270, 882, 335]]<|/det|> +We thank the reviewer for their positive comments on our revised manuscript and their suggestion to accept this version for publication. We acknowledge that few more sentences about the basics of biological computation and neuromorphic systems will further help readers become more familiar with these topics. Accordingly, we incorporated a section in the beginning of the introduction: + +<|ref|>text<|/ref|><|det|>[[152, 340, 882, 500]]<|/det|> +- Page 1, line 25: Living systems, from a simple slime mold to a more complex Venus flytrap to a highly sophisticated cephalopod, exhibit intelligent behavior1. That is, they have the ability to perceive information and retain it as knowledge to execute complex tasks2. The underlying processes by which decisions are made are fundamentally different from conventional (digital) computing, as they rely on complex, decentralized networks of biochemical reactions that operate in parallel2. Artificial neuromorphic systems take inspiration from natural and biological processes3, particularly from how neurons process and transmit signals in the brain4. Rethinking the design of neuromorphic systems do not necessarily restrict to neural architectures5 and opportunities may lie in using analogue and approximate computing that arise from purely (bio)chemical processes6. + +<|ref|>text<|/ref|><|det|>[[142, 500, 880, 533]]<|/det|> +- Additional reference: 3. Castro, L. N. de. Fundamentals of natural computing: an overview. Phys. Life Rev. 4, 1-36 (2007). + +<--- Page Split ---> diff --git a/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/images_list.json b/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..3a8559960ce57ef621e3d7c3b7410a853812d36b --- /dev/null +++ b/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,265 @@ +[ + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating. a, Zeta potential of the PTB or PTB@SA(0.10) coating on Si. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n = 3}\\) . b, c, Number of viable S. aureus (b) and E. coli (c) recovered from bare substrate, PTB or PTB@SA(0.10) coating as confirmed by colony counting. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n = 3}\\) . d, e, CLSM images showing the patterned adherence of S. aureus on bare substrate with using the micropatterned PTB@SA coating as the resistant layer. f, g SEM images of unmodified (f) or PTB@SA(0.10) coating-modified urinary catheters (g) recovered after indwelling for 1 week. The arrow indicates scattered bacteria on the PTB@SA(0.10) coating. h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n = 4}\\) . i, The number of white blood cells in rabbit urine after different catheters were used for 1 week. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n = 4}\\) . j, Gross observation of the rabbits' urethra, and the yellow circles represent the sampling site of the tissue section. k, Hematoxylin and erosion (H&E) staining and immunochemical staining with anti-CD45 antibody (green) and anti-CD68 (brown) antibody in rabbit urethral tissue. l, Quantification of the", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n = 4}\\) . \\(\\mathrm{^{**}\\mathrm{P< 0.01}}\\) .", + "footnote": [], + "bbox": [ + [ + 339, + 360, + 671, + 562 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \\(\\pm \\mathrm{s.d.}\\) ; \\(n = 4\\) . \\(^{**}P< 0.01\\) .", + "footnote": [], + "bbox": [ + [ + 339, + 321, + 671, + 526 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure S21. Quantitative assessment of the edema severity in control and PTB@SA-coated groups. Data are presented as the mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 4\\) .\\*\\* P<0.01.", + "footnote": [], + "bbox": [ + [ + 345, + 105, + 699, + 296 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury. a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \\(76\\%\\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments.", + "footnote": [], + "bbox": [ + [ + 152, + 90, + 840, + 800 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure S41. Immunofluorescence staining images showing collagen deposition in urethral tissue. (a) Immunofluorescence staining of Collagen I at the urethral injury site after different treatments for 1 month. Nuclei (blue) was stained with DAPI, i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst-releasing; vi, PTB@SA-Rapamycin. (b) The urethral tissue of normal rabbits was sectioned for immunostaining with Collagen I. Nuclei (blue) was stained with DAPI. (c) Quantification of the Collagen I fluorescence intensity in normal rabbit urethral tissue and PTB@SA-Rapamycin catheter-mediated urethral injury healing. Data are", + "footnote": [], + "bbox": [ + [ + 151, + 150, + 844, + 765 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure S45. The initial body weight and the weight of the rabbits in each group at 1, 2, 3 and 4 weeks after the urethra was injured by electrocoagulation. The data are presented as the mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 5\\) . At each time point, there was no statistical difference in body weight between the treatment groups and the blank control group.", + "footnote": [], + "bbox": [ + [ + 315, + 287, + 650, + 473 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "FigureR1. Representative images of retrograde urethrography after 30 days. The yellow arrow indicates the coagulation site.", + "footnote": [], + "bbox": [ + [ + 205, + 95, + 795, + 393 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure S40. Rabbit urethral stricture in unmodified urinary catheter group and PTB@SA-Rapamycin group on the 14th day after removal of catheter. (a) Representative retrograde urethrogram using \\(76\\%\\) meglumine diatrizoate as contrast agent. (b) Lumen reduction immediately after catheter removal or 2 weeks later as determined by retrograde urethrography. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 5\\) . (c) Comparison of gross specimens, H&E staining, Masson staining and \\(\\alpha\\) -SMA expression between unmodified urinary catheter group and PTB@SA-Rapamycin group at 14 days after catheter removal. Yellow triangles indicate urethral scar tissue, and the dotted lines indicate the boundary between the submucosa and the muscularis. (d, e) Quantitative results of collagen density and \\(\\alpha\\) -SMA positive area in Figure S40c. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 5\\) . \\*\\*\\* P<0.001.", + "footnote": [], + "bbox": [ + [ + 150, + 202, + 840, + 708 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Figure S47. Formation and hybridization of PTH the nanofilm. (a) AFM image of the PTH nanofilm. (b) CD spectra of native HSA and the PTH nanofilm. (c) ThT fluorescence change as a function of phase transition time, with the insets showing the corresponding fluorescence microscopic image for ThT staining and the optical microscopy image for Congo red staining. (d) The CLSM image shows that SA was successfully entrapped in the nanofilm to form a hybrid nanofilm. (e) WCA of bare Si, PTH and PTH@SA coated Si. The data are presented as the mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 4\\) . (f) XPS spectra of pristine Si, PTH and PTH@SA nanofilm coated Si. (g) High resolution \\(\\mathrm{C_{1s}}\\) deconvolution spectra of the PTH and PTH@SA nanofilm. (h-k) The frequency and adsorption mass of HSA (h), PTH (i), the mixture of HSA and SA (j) and PTH@SA (k) adsorbed on the Au chip as a function of time.", + "footnote": [], + "bbox": [ + [ + 160, + 163, + 830, + 712 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Figure S37. Comparison of urethral diameter in normal healthy rabbits and rabbits using PTB@SA-Rapamycin catheter after urethral injury. (a) Representative retrograde urethrogram of healthy rabbits. (b) Representative retrograde urethrogram of the rabbit in the anti-fibrotic catheter group. (c) The ratio of urethra diameter to femoral shaft diameter in normal healthy rabbits and rabbits in anti-fibrotic catheter (PTB@SA-Rapamycin) group. Data are presented as the mean \\(\\pm \\mathrm{s.d.}\\) ; \\(n = 5\\) . ns means no statistical difference.", + "footnote": [], + "bbox": [ + [ + 150, + 540, + 833, + 700 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Figure S20. In vitro evaluation of the encrustation performance of bare silicone catheters and the PTB@SA nanofilm-modified catheters. (a) The weight of crystals deposited on bare catheters or the PTB@SA coated catheters after exposure to artificial urine, artificial urine containing Proteus mirabilis (P. mirabilis), or human urine. Data are presented as the mean \\(\\pm\\) s.d; n=4. \\* P<0.05. (b) The weight of crystals deposited on bare catheters or the PTB@SA coated catheters during the first week. Data are presented as the mean \\(\\pm\\) s.d; n=4. \\* P<0.05. (c) SEM of bare catheter and the", + "footnote": [], + "bbox": [ + [ + 165, + 99, + 835, + 778 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Figure R2. Friction coefficients of bare urinary catheter and the PTB@SA nanofilm-modified catheter. Data are presented as the mean \\(\\pm\\) s.d; n=3. \\*\\*\\* P<0.001.", + "footnote": [], + "bbox": [ + [ + 325, + 673, + 622, + 833 + ] + ], + "page_idx": 27 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Figure R1. Representative images of retrograde urethrography after 30 days. The yellow arrow indicates the coagulation site.", + "footnote": [], + "bbox": [ + [ + 205, + 93, + 795, + 393 + ] + ], + "page_idx": 28 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury. a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \\(76\\%\\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments.", + "footnote": [], + "bbox": [ + [ + 152, + 92, + 840, + 800 + ] + ], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury.", + "footnote": [], + "bbox": [ + [ + 153, + 88, + 840, + 789 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Figure S37. Comparison of urethral diameter in normal healthy rabbits and rabbits using PTB@SA-Rapamycin catheter after urethral injury. (a) Representative retrograde urethrogram of healthy rabbits. (b) Representative retrograde urethrogram of the rabbit in the anti-fibrotic catheter group. (c) The ratio of urethra diameter to femoral shaft diameter in normal healthy rabbits and rabbits in anti-fibrotic catheter (PTB@SA-Rapamycin) group. Data are presented as the mean ± s.d.; n=5. ns means no statistical difference.", + "footnote": [], + "bbox": [ + [ + 147, + 360, + 815, + 513 + ] + ], + "page_idx": 40 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Figure S40. Rabbit urethral stricture in unmodified urinary catheter group and PTB@SA-Rapamycin group on the 14th day after removal of catheter. (a) Representative retrograde urethrogram using \\(76\\%\\) meglumine dinitrozoate as contrast agent. (b) Lumen reduction immediately after catheter removal or 2 weeks later as determined by retrograde urethrography. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 5\\) . (c) Comparison of gross specimens, H&E staining, Masson staining and \\(\\alpha\\) -SMA expression between unmodified urinary catheter group and PTB@SA-Rapamycin group at 14 days after catheter removal. Yellow triangles indicate urethral scar tissue, and the dotted lines indicate the boundary between the submucosa and the muscularis. (d, e) Quantitative results of collagen density and \\(\\alpha\\) -SMA positive area in Figure S40c. Data are mean \\(\\pm\\) s.d.; \\(\\mathrm{n} = 5\\) . \\*\\*\\* P<0.001.", + "footnote": [], + "bbox": [ + [ + 150, + 90, + 833, + 600 + ] + ], + "page_idx": 41 + } +] \ No newline at end of file diff --git a/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..fc4b94e8df99f4695b7b1df2f805af2fa625fbbc --- /dev/null +++ b/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,650 @@ + +# nature portfolio + +Peer Review File + +Rectifying disorder of extracellular matrix to suppress urethral stricture by protein nanofilm- controlled drug delivery from urinary catheter + +![](images/Figure_3.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +In the clinic, delivery of numerous antifibrotic drugs by irrigation or submucosal injection showed the low effectiveness against urethral stricture. Here, the authors raised a strategy for both antibacterial therapy and maintenance of extracellular homeostasis for urethral injury. In general, this work seems to be quite interesting and I would like to recommend the acceptance of this work after authors can well address the following questions before its final acceptance. + +1) Author mentioned that the HE staining in the control group showed abundant inflammatory cell infiltration of the urethra (Fig. 3j). Since HE images could not differentiate the type of cells, the quantification of inflammatory cells (Fig. 3k) should be performed with specific antibodies using ELISA kit. + +2) Author explained that at the end of catheterization period, the surface of pristine SR catheter was contaminated by the dense E. coli biofilm (Figure 3h). However, there is no qualification and quantification of biofilm formation assay (e.g. crystal violet) in this study. + +3) Author initially seeded the bacteria on the PTB@SA Rapamycin catheters and performed in vitro culture for 20 hours before implantation. However, during in vitro experiment, several parts of bacteria will be eliminated. Since the number of bacteria implanted was different, it will affect the in vivo result, such as inflammatory response, etc. How do the authors explain this finding? Also, the CFU of bacteria after in vivo implantation should be quantified to check its antibacterial efficacy in vivo. + +4) The rabbit implanted with PTB@SA Rapamycin catheters was not swelling (edema) compared with control. Therefore, the quantification scoring system to check the significancy of edema should be performed to support this sentence. + +5) According to the Figure 6d and s36, there was an obvious change in epithelium thickness between different group, especially in the burst-releasing group. Please explain the correlation of each group with the epithelium thickness. + +6) According to the Figure 6d, the nuclei in a-SMA staining was obviously observed only in group i, while the other group showed no or very few of nuclei. Meanwhile, in MMP-1 and collagen I staining, nuclei were highly observed in all of the groups. Please explain. + +7) Antibiotic resistance often occurs in clinical application. Since antibiotic is also used in this system, please explain whether this material could avoid the antibiotic resistance after long-term implantation in vivo. + +8) Author should add the explanation about the impact of the presence of E. coli on urethral fibroblast in co-culture experiment. + +9) The images of sections in Fig. S37 are not clear. Clear images at a high magnification should be provided. + +10) Author mentioned that the body weight of the rabbits in each group showed a consistent slight drop within two weeks after urethral coagulation, and then gradually recovered, which may be related to surgical stress (supplementary figure 41). However, there is no statistical analysis that supports the significant difference in body weight. + +<--- Page Split ---> + +Reviewer #2: + +Remarks to the Author: + +This study was designed to investigate the efficacy of rapamycin sustained release nanofilm coated catheters in preventing urethral stricture in a rabbit urethral injury model. + +In addition, the researchers have conducted basic experiments on the antibacterial and drug- release effects of catheters, which we believe are appropriate. + +However, there are several points that should be considered to improve this study in animal experiments. + +1, In the introduction, the author states that local therapy in the urethra has limited efficacy and feasibility in terms of drug retention and effectiveness. However, paclitaxel- coated balloon dilation therapy has already been reported in practice in human patients with anterior urethral strictures and has been shown to be useful and safe (The Journal of Urology, Vol. 207, 866- 875, April 2022). The authors should mention this. + +2, This study investigates the effect of stricture prevention after injury to the normal urethra. In other words, the results of this study show only a stenosis- preventive effect on a model of 'urethral injury' not 'urethral stricture'. Urethral stricture after urethral injury and restenosis after treatment of urethral stricture have completely different etiologies. The cited paper confuses the paper on the effect of prevention of stricture after urethral injury with the paper on the effect of prevention of restenosis after treatment of urethral stricture, and the authors should consider each separately. + +3, Many methods have been reported for creating a urethral stricture/injury model. The author has shown stenosis in a control group by impairing it with electrocautery, is this a well- established method? Also, the author divides the rabbits into 6 groups of 3 rabbits each to evaluate the effect of the drug- releasing catheter. Is three rabbits a sufficient number of rabbits to evaluate this experiment? + +4, The author performed urethrography and histological evaluations of the rabbit urethra 30 days later. Were these evaluations performed immediately after removal of the urethral catheter? Immediately after removal of a urethral catheter is not an appropriate time for evaluation of stricture because of the residual effects of physical dilatation caused by catheter placement. In humans, it has been reported that it takes several months for fibrosis of the urethra to be completed (Urology, Vol. 77, 1477- 1481, June 2011). Even in animals, it should be evaluated at least several weeks after catheter removal. + +Reviewer #3: + +Remarks to the Author: + +Through this manuscript, the research team reported a novel nanofilm that is used to coat urinary catheter. This nanofilm self- assembled through the deposition of aggregated BSA together with sodium alginate (SA). The aggregation was triggered by a process, termed phase transition bovine serum albumin (PTB). This nanofilm sustained a constant (zero- order) release of encapsulated drug, rapamycin, with in 50 days of observation. The nanofilm delivered rapamycin significantly inhibited fibrosis and urethral stricture as compared to non- coated urinary catheter, systemically administered rapamycin, and other control treatment. This work has immediate clinical significance and profound technical novelty. The characterizations of nanofilm, drug release, and related efficacy are thorough and sound especially the study design for drug release. The description of methods are clear and have sufficient details to reproduce results. Overall, this manuscript merit the acceptance for publication on this journal after minor revision and clarification for the following points. + +1, A revision of abstract might be beneficial as the current version does not highlight the important + +<--- Page Split ---> + +results and conclusions sufficiently. + +2, The choice of BSA as the main materials of the nanofilm may need additional justification. The immunogenicity of BSA to human needs to be considered and discussed. If there is evidence the BSA in nanofilm will not induce humoral responses in human and other speeches, please provide evidence and reference to reinforce this point. + +3. It is unclear whether PTB would only work for BSA, or any proteins as long as they can complete an alfa-helix to beta-sheet conversion. Particularly, it is intriguing whether the PTB will work with human albumin? + +4, The CD data that support helix-to-sheet conversion is not sufficient. It is not convincing the end product is a beta-sheet-only material with only CD spectra. Though, whether this claim is true or not seems not affecting functionality of the nanofilm. + +5, On page 14, it is not clear why a balanced composition of positively and negatively charged amino acid residues is critical for anti- fouling and anti- biofilm surface. + +6, On page 25, this description is confusing "Compared with the unmodified catheter, the anti-fibrotic catheter (i.e., PTB@SA- Rapamycin catheter) decreased lumen reduction from \(56.1\%\) to \(9.8\%\) (Fig. 6a, b), with a mean percentage improvement of \(82.5\%\) , which was superior to the values reported in preclinical studies of other local treatments (Fig. 6c, Table S5)." It is suggested to break this description into at least two sentences. + +7, For efficacy study (urethral stricture), it would be beneficial compare lumen diameters of subgroup VI with healthy (non- injuries) rabbit lump diameters to give a complete picture of treatment outcome. In addition, the group size \((n = 3)\) is too small to generate robust mean and conclusion. + +Reviewer #4: + +Remarks to the Author: Comments to the author + +The authors of this manuscript have done an excellent work designing a catheter covered with a protein nanofilm capable of preventing urethral stricture by prevention of bacterial colonization and controlled release of rapamycin. The authors examined the physical characteristics, antibacterial properties, and drug release functions of the protein nanofilm. By indwelling the hybrid coating- modified catheter in the urethra of adult male rabbits, the authors demonstrated that the catheter could effectively prevent the development of urethral stricture. + +Generally, this work is innovative and great. A few comments are as follows: + +Q1 + +In the first paragraph of the introduction, the author pointed out a clinical problem that current curative treatment options, such as urethrotomy, dilatation and urethroplasty, for urethral stricture could not achieve satisfactory results. This clinical problem exists in patients who have already developed severe urethral strictures. However, the animal model used in this study only simulated the acute urethral injury, and the results could only demonstrate the fact that PTB@SA- Rapamycin catheter was able to prevent the occurrence of urethral stricture. Therefore, the clinical problem raised in the introduction should be revised. + +Q2 + +Why did the authors choose rapamycin as the therapeutic component preventing the urethral stricture? A meta- analysis published in European Urology by Pang et al. showed that mitomycin C had + +<--- Page Split ---> + +the best effect on urethral stricture among drugs used in the included clinical trials. Compared with other drugs, what are the advantages and disadvantages of rapamycin in treating urethral stricture? + +Q3 + +The author mentioned that the nanofilm surface exhibited abundant functional groups, which enabled the nanofilms to undergo ligand bonding, electrostatic interaction, hydrophobic interaction and hydrogen bonding with virtually arbitrary material, including metal, organic or inorganic materials. According to our experience, this property of the nanofilm makes it likely to interact with various organic and inorganic substances in urine and result in surfaces blockade, stone formation and catheter blockage. Is there any data showing the appearance of the hybrid nanofilm- coated catheters after indwelling for 30 days? We want to check if the surface of all catheters were still clear at the end of the experiment. In fact, bacterial contamination and stone formation are both thorny challenges in the development of functional urinary catheters. + +Q4 + +The nanofilm showed a consistent WCA approximately \(80^{\circ}\) . This means the nanofilm- coated catheter is not very hydrophilic and has higher friction with urethral. Was lubricant used during indwelling catheters. If lubricant was used, were there any experiments investigating if the lubricant had any effect on the stability of the nanofilm and the controlled drug release? Catheters for clinical use are often covered with super hydrophilic film or lubricants to avoid urethral injury and inflammation. Consistently, the authors observed that the pristine urinary catheter caused edema and necrosis in rabbits' urethral mucosa after indwelling for 1 month. Parameters about the friction should be compared among pristine urinary catheter and nanofilm coated catheters. + +Q5 Reference should be added for the sentence "... the PTB@SA nanofilm still exhibited a low negative surface zeta potential, and thus may keep a good anti- biofilm ability." + +Q6 + +We noticed that four rabbits were in each group for the evaluation of the antibacterial biofilm performance of the nanofilm and three rabbits were in each group evaluate the effect of nanofilm on urethral stricture. How did the authors decide the sample size for each experiment? Why did experiments with more complex surgical procedures (more likely to be biased) have smaller sample sizes? + +Q7 + +The authors cannot directly compare the results of independent experiments performed by different operators under different experimental conditions (such as surgical instruments, degree of urethral injury and therapy duration) to conclude that the effect of nanofilm in this study was better than that of drugs reported in other studies. + +Q8 + +In the figure legend of figure 6, the sentence "(b, d, e) i, Control, ii; Unmodified catheter; iii,..." should be revised. Only a and d are numbered. Please check the use of commas and semicolons. + +Q9 + +At least, there are some errors in references 56. Some authors are missing and the original title should be "Sirolimus- eluting Biodegradable Poly- l- Lactic Acid Stent to Suppress Granulation Tissue Formation in the Rat Urethra." + +<--- Page Split ---> + +## Dear reviewers, + +We sincerely thank all referees for their valuable comments. We have made the revisions to all the comments in the revised manuscript (marked in red color) and supporting information (SI). The following is the point- to- point response to the reviewers' comments. + +## Reviewer #1 + +In the clinic, delivery of numerous antifibrotic drugs by irrigation or submucosal injection showed the low effectiveness against urethral stricture. Here, the authors raised a strategy for both antibacterial therapy and maintenance of extracellular homeostasis for urethral injury. In general, this work seems to be quite interesting and I would like to recommend the acceptance of this work after authors can well address the following questions before its final acceptance. + +1) Author mentioned that the HE staining in the control group showed abundant inflammatory cell infiltration of the urethra (Fig. 3j). Since HE images could not differentiate the type of cells, the quantification of inflammatory cells (Fig. 3k) should be performed with specific antibodies using ELISA kit. + +Response: We are extremely grateful to Reviewer 1 for your helpful comments. Through H&E staining, we found that compared with the control group, the infiltrated area of cells with high nucleocytoplasmic ratio cells in the urethral tissue of the PTB@SA coating group was significantly reduced, suggesting that the distribution of inflammatory cells between the two groups may be different. To better define and localize the infiltration of inflammatory cells in urethral tissue, we performed immunochemical staining with CD45 (expressed in leukocytes) and CD68 (expressed in macrophages) antibodies. As shown in Fig. 3k, in addition to a significant decrease in the area of positive cells, inflammatory cells (including both leukocytes and macrophages) were confined to the epithelial mucosa of urethral tissues in the PTB@SA nanofilm-modified catheter group, while a large number of inflammatory cells were diffusively infiltrated in the mucosa and submucosa of the unmodified catheter group. The above discussion has been incorporated into the revised manuscript (Page 17). + +<--- Page Split ---> +![](images/Figure_3.jpg) + +
Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating. a, Zeta potential of the PTB or PTB@SA(0.10) coating on Si. Data are mean \(\pm\) s.d.; \(\mathrm{n = 3}\) . b, c, Number of viable S. aureus (b) and E. coli (c) recovered from bare substrate, PTB or PTB@SA(0.10) coating as confirmed by colony counting. Data are mean \(\pm\) s.d.; \(\mathrm{n = 3}\) . d, e, CLSM images showing the patterned adherence of S. aureus on bare substrate with using the micropatterned PTB@SA coating as the resistant layer. f, g SEM images of unmodified (f) or PTB@SA(0.10) coating-modified urinary catheters (g) recovered after indwelling for 1 week. The arrow indicates scattered bacteria on the PTB@SA(0.10) coating. h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . i, The number of white blood cells in rabbit urine after different catheters were used for 1 week. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . j, Gross observation of the rabbits' urethra, and the yellow circles represent the sampling site of the tissue section. k, Hematoxylin and erosion (H&E) staining and immunochemical staining with anti-CD45 antibody (green) and anti-CD68 (brown) antibody in rabbit urethral tissue. l, Quantification of the
+ +<--- Page Split ---> + +area of inflammatory cell infiltration in the H&E staining images of the urethra. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . m, Quantification of CD45 (l) and CD68 (m) positive area in Fig. 3k. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . \(\mathrm{P< 0.05}\) , \(\mathrm{^{**}\mathrm{P< 0.01}}\) , \(\mathrm{^{***}\mathrm{P< 0.001}}\) , ns means no statistical difference. + +2) Author explained that at the end of catheterization period, the surface of pristine SR catheter was contaminated by the dense E. coli biofilm (Figure 3h). However, there is no qualification and quantification of biofilm formation assay (e.g. crystal violet) in this study. + +Response: Thank the reviewer for this comment. Since crystal violet also stains the protein coating to bias the optical density of the sample1, we alternatively used the number of bacteria per unit catheter surface area to evaluate the in vivo anti-biofilm performance of the PTB@SA coating. After the catheter was indwelled in the rabbit urethra for 7 days, the surface bacterial density was determined by colony counting. Compared with the control group, the resistance efficiency of the PTB@SA coating against E. coli was \(85.9\%\) , which is consistent with the SEM image results of the recovered catheter (Fig. 3h in the revised manuscript). + +![](images/Figure_3.jpg) + +
Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . \(\mathrm{^{**}\mathrm{P< 0.01}}\) .
+ +3) Author initially seeded the bacteria on the PTB@SA Rapamycin catheters and performed in vitro culture for 20 hours before implantation. However, during in vitro experiment, several parts of bacteria will be eliminated. Since the number of bacteria implanted was different, it will affect the in vivo result, such as inflammatory response, etc. How do the authors explain this finding? Also, the CFU of bacteria after in vivo implantation should be quantified to check its antibacterial efficacy in vivo. + +Response: Thank the reviewer for this comment. Here, we adopted the pre- seeding method, a typical method widely used to characterize antifouling property in animal experiments2,3, to evaluate the efficacy of the PTB@SA coating in preventing catheter- associated urinary tract infections. In fact, microorganisms transferred from the perianal or skin during catheterization, and/or pathogenic bacteria migrating along the luminal pathway have been reported to be important sources of infection for catheter- associated urinary tract infections4. Bacterial biofilms developed from bacteria that colonize on the material surfaces not only provide shelter for bacteria but also participate in + +<--- Page Split ---> + +quorum- sensing signaling5. As a result, compared with planktonic bacteria, bacteria surviving in biofilms exhibit strong resistance to antibiotics and mechanical challenges, which will cause refractory and recurrent urinary tract infections. Therefore, in order to reasonably simulate the bacterial contamination that catheters may be exposed to in practical applications and evaluate the consequences caused in vivo, unmodified urinary catheters and PTB@SA nanofilm- modified catheters were all incubated in artificial urine containing E. coli at a consistent final bacterial concentration of \(10^{6}\) CFU/mL, and all other experimental conditions were the same for both groups. The surface properties of the catheter modified by the PTB@SA coating make it difficult for bacteria to attach stably, so the coating exhibits an ideal preventive effect on catheter- associated urinary tract infection. The bacterial load of the recovered catheters of the two groups was evaluated by colony counting. As shown in Fig 3h, the number of bacteria on the surface of the PTB@SA coating was significantly lower than that of the control group (P<0.01). + +![](images/Figure_unknown_0.jpg) + +
Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \(\pm \mathrm{s.d.}\) ; \(n = 4\) . \(^{**}P< 0.01\) .
+ +4) The rabbit implanted with PTB@SA Rapamycin catheters was not swelling (edema) compared with control. Therefore, the quantification scoring system to check the significancy of edema should be performed to support this sentence. + +Response: Thanks to the reviewer for your helpful comments. In response to this comment, edema was scored semiquantitatively on a 3- point scale in tissue sections, with 0 being the lowest and 2 being the highest scores, as previously described6. As shown in Supplementary Fig. 21, consistent with the macroscopic appearance of the specimens, the urethral tissue of the control group had a higher edema score compared with the PTB@SA- coated catheter (P<0.01). The above discussion has been incorporated into the revised manuscript (Page 17). + +<--- Page Split ---> +![](images/Figure_6.jpg) + +
Figure S21. Quantitative assessment of the edema severity in control and PTB@SA-coated groups. Data are presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 4\) .\*\* P<0.01.
+ +5) According to the Figure 6d and s36, there was an obvious change in epithelium thickness between different group, especially in the burst-releasing group. Please explain the correlation of each group with the epithelium thickness. + +Response: Thanks for the reviewer's comment. We carefully compared the overall condition of the rabbit urethral tissue sections in each group and concluded that the thickness of the urothelium in each group was not related to the treatment received, but the thickness and collagen abundance of submucosal connective tissue in the presence of rapamycin sustained- release catheter were significantly lower than other groups, as shown in Figure 6 and S38. In fact, on the one hand, the histological morphology of the urethral epithelium is related to the location of the specimen. The urethral injury site in this experiment was about \(1\mathrm{cm}\) distal to the opening of ejaculator duct, which was exactly at the position where the prostatic urethra (mainly transitional epithelium) transited to the membranous urethra (typically stratified columnar epithelium) \(^7\) . On the other hand, even for different lateral walls of the urethra in the same cross-section, the thickness of the epithelium varies slightly, as has been observed in the published literature (Figure 3, 4 of the reference) \(^8\) . + +6) According to the Figure 6d, the nuclei in \(\alpha\) -SMA staining was obviously observed only in group i, while the other group showed no or very few of nuclei. Meanwhile, in MMP-1 and collagen I staining, nuclei were highly observed in all of the groups. Please explain. + +Response: We greatly appreciate this helpful comment. In the \(\alpha\) -SMA- stained tissue, the nuclei were indeed not clearly stained because of a mistake in our staining procedure. For this, we re- stained and analyzed accordingly. The corresponding results have been revised in Fig 6d and 6e. + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury. a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \(76\%\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments.
+ +<--- Page Split ---> + +Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . c, Corresponding results of the PTB@SA- Rapamycin catheter compared with other preclinical studies of topical therapy to suppress urethral stricture. d, Gross specimen, H&E staining and immunohistochemical staining with anti- alpha smooth muscle actin antibody (α- SMA, brown), anti- matrix metalloproteinase 1 antibody (MMP1, brown), and type I collagen antibody (Collagen I, green) of the urethral injury sites at 1 month. Nuclei (blue) were stained with DAPI. Yellow triangles indicate urethral scar tissue. The asterisks represent urethral luminal side, and the dotted lines indicate the boundary between the submucosa and the muscularis. e, Quantification of \(\alpha\) - SMA, MMP1 positive area and Collagen I fluorescence intensity in Fig. 6d. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . f, g, Hematological examination to show the changes of alanine aminotransferase (ALT, f) and aspartate aminotransferase (AST, g) with different treatments for 1 month. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . h, H&E staining of rabbit liver after systemic administration or indwelling rapamycin sustained- release catheter for 1 month. (a, d) i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst- releasing; vi, PTB@SA- Rapamycin. \* \(\mathrm{P< 0.05}\) , \*\* \(\mathrm{P< 0.01}\) , \*\*\* \(\mathrm{P< 0.001}\) , \*\*\*\* \(\mathrm{P< 0.0001}\) , ns means no statistical difference. + +7) Antibiotic resistance often occurs in clinical application. Since antibiotic is also used in this system, please explain whether this material could avoid the antibiotic resistance after long-term implantation in vivo. + +Response: Thanks for the reviewer's comment. Here, we need to clarify that the antibacterial performance of the functionalized urinary catheter is mainly derived from the excellent antibacterial adhesion property of the PTB@SA nanofilm, and the rapamycin contained in the system is not a typical antibiotic, so it will not induce bacteria drug resistance. As a classic mTOR pathway inhibitor, rapamycin is widely used in the prevention of coronary artery stenosis in clinical practice, and shows favorable biological safety9. Inspired by this, in the present work, controlled release of rapamycin from the coating on the catheter surface was the main contributor to the inhibition of stricture formation after urethral injury, and the effect of preventing catheter- related urinary tract infections depended on the anti- biofilm property of the hybrid coating. The above discussion has been incorporated into the revised manuscript (Page 15). + +## 8) Author should add the explanation about the impact of the presence of E. coli on urethral fibroblast in co-culture experiment. + +Response: Thanks for the reviewer's comment. The proliferation and activation of fibroblasts is a key link in the occurrence and development of urethral stricture10. The inflammatory response caused by bacteria induces changes in the biological behavior of fibroblasts through a variety of cytokines (such as TGF- \(\beta 1\) , TNF- \(\alpha\) , IL- 6, etc.)11, which eventually promotes the formation of urethral strictures and even leads to the failure of urethroplasty12. As shown by CD45 and CD68 staining of urethral tissue, unmodified catheters were more susceptible to biofilm contamination and urethral inflammation than the coated group (Fig. 3k- m). Therefore, the PTB@SA nanofilm with potent anti- biofilm property is a strong candidate for designing drug- loaded coatings on the surface of urinary catheters to regulate tissue healing, which can effectively attenuate the fibrotic process initiated by inflammation. The above discussion has been incorporated into the revised manuscript (Page 17). + +9) The images of sections in Fig. S37 are not clear. Clear images at a high magnification should + +<--- Page Split ---> + +## be provided. + +Response: Thanks for the reviewer's comment. We have supplied clear images at high magnification to the revised supplementary information (Page S30, Supplementary Fig. 41). + +![](images/Figure_unknown_2.jpg) + +
Figure S41. Immunofluorescence staining images showing collagen deposition in urethral tissue. (a) Immunofluorescence staining of Collagen I at the urethral injury site after different treatments for 1 month. Nuclei (blue) was stained with DAPI, i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst-releasing; vi, PTB@SA-Rapamycin. (b) The urethral tissue of normal rabbits was sectioned for immunostaining with Collagen I. Nuclei (blue) was stained with DAPI. (c) Quantification of the Collagen I fluorescence intensity in normal rabbit urethral tissue and PTB@SA-Rapamycin catheter-mediated urethral injury healing. Data are
+ +<--- Page Split ---> + +presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . ns means no statistical difference. + +10) Author mentioned that the body weight of the rabbits in each group showed a consistent slight drop within two weeks after urethral coagulation, and then gradually recovered, which may be related to surgical stress (supplementary figure 41). However, there is no statistical analysis that supports the significant difference in body weight. + +Response: Thanks to the reviewer for this valuable comment. To support our conclusion, one- way ANOVA was performed on the body weight of each group at each time point to confirm that there was no statistical difference in the body weight of rabbits in each treatment group and the blank control group. We have supplied a related description in Supplementary Fig. 45. + +![](images/Figure_unknown_3.jpg) + +
Figure S45. The initial body weight and the weight of the rabbits in each group at 1, 2, 3 and 4 weeks after the urethra was injured by electrocoagulation. The data are presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . At each time point, there was no statistical difference in body weight between the treatment groups and the blank control group.
+ +<--- Page Split ---> + +## Reviewer #2 + +This study was designed to investigate the efficacy of rapamycin sustained release nanofilm coated catheters in preventing urethral stricture in a rabbit urethral injury model. In addition, the researchers have conducted basic experiments on the antibacterial and drug- release effects of catheters, which we believe are appropriate. However, there are several points that should be considered to improve this study in animal experiments. + +1, In the introduction, the author states that local therapy in the urethra has limited efficacy and feasibility in terms of drug retention and effectiveness. However, paclitaxel- coated balloon dilation therapy has already been reported in practice in human patients with anterior urethral strictures and has been shown to be useful and safe (The Journal of Urology, Vol. 207, 866- 875, April 2022). The authors should mention this. + +Response: Thanks to the reviewer for your helpful comments. For patients with urethral strictures, paclitaxel- coated balloons are indeed a beneficial option that combines mechanical dilation and local drug delivery, indicating that local therapy to intervene in the progression of urethral strictures is a feasible and promising strategy. Here, we attempted to combine intraurethral drug delivery with widely used urinary catheters to develop functionalized urinary catheters with the anti- fibrotic effect, which could hopefully evolve treatment after urethral strictures to positive prophylaxis, especially for strictures caused by transurethral procedures and traumatic catheterization. We have supplied relevant content in the Introduction section (Page 3) as follows. + +Although systemically administered antifibrotic agents have shown efficacy in attenuating tissue/organ fibrosis in animal models \(^{13,14}\) , off- target side effects have greatly limited their success in clinical trials \(^{15}\) . By contrast, the successful attempt of a paclitaxel- coated balloon combining mechanical dilation and local drug delivery in the treatment of recurrent urethral strictures suggests the feasibility and promise of local therapy to interfere with urethral strictures \(^{16}\) . Currently, in order to inhibit secondary strictures after urethral injury, various antifibrotic drugs have been administered locally by hydrostatic pressure, submucosal injection, urethral irrigation, drug- eluting stents and catheters \(^{17 - 21}\) . + +2, This study investigates the effect of stricture prevention after injury to the normal urethra. In other words, the results of this study show only a stenosis- preventive effect on a model of 'urethral injury' not 'urethral stricture'. Urethral stricture after urethral injury and restenosis after treatment of urethral stricture have completely different etiologies. The cited paper confuses the paper on the effect of prevention of stricture after urethral injury with the paper on the effect of prevention of restenosis after treatment of urethral stricture, and the authors should consider each separately. + +Response: Thanks to the reviewer for your professional comments. Admittedly, the results of animal experiments provide strong support for the conclusion that the anti- fibrotic catheter has a good preventive effect on urethral stricture secondary to urethral injury. We apologize for the ambiguity caused by our inappropriate description and have revised the Introduction as follows to emphasize that this study addresses urethral strictures secondary to urethral injury (Page 2). + +Urethral stricture is a common disease (200- 1200 cases per 100000 individuals \(^{22}\) ) following urethral injury. The pathological state of extracellular matrix (ECM) metabolic disorder caused by injury (including surgery, pelvic fracture, inflammatory injury and traumatic catheterization) results + +<--- Page Split ---> + +in the replacement of normal urethral tissue by dense fibers interspersed with fibroblasts22. This aggravated fibrosis eventually leads to progressive urethral lumen reduction consequent symptomatic dysuria and even renal impairment. With the growing demand for healthcare brought about by the aging population and advances in medical technology, the increasing incidence of mucosal injury and secondary urethral strictures caused by various transurethral procedures has attracted great attention23,24. Especially in patients with spinal cord injury or in intensive care, urethral stricture or erosion due to long- term catheterization has been reported as high as \(8.7\%^{25}\) . Once urethral injury progresses to urethral stricture, subsequent treatment is extremely troublesome, which will pose challenges to both patients and urologists. The long- term success rate of the most commonly used endoscopic treatment is only \(20 - 30\%^{22}\) , and although urethroplasty has developed rapidly in recent years, fibrous scarring may still develop in the urethral submucosa after substitute surgery, and this open surgery is less suitable for the elderly and frail patients. Indeed, the pathological state of ECM metabolic disorder and subsequent scar repair is not be rectified regardless of the treatment26. Therefore, there is an urgent need to develop alternative strategies other than surgery and attempt to focus on regulating healing by inhibiting fibrosis progression following urethral injury, thereby preventing urethral strictures. + +3. Many methods have been reported for creating a urethral stricture/injury model. The author has shown stenosis in a control group by impairing it with electrocautery, is this a well-established method? Also, the author divides the rabbits into 6 groups of 3 rabbits each to evaluate the effect of the drug-releasing catheter. Is three rabbits a sufficient number of rabbits to evaluate this experiment? + +Response: Thanks to the reviewer for your helpful comments. There are a variety of modalities commonly used to cause urethral injury in animals, mainly including urethrotomy, electrocoagulation, and ligation. According to a study reported by the Journal of Urology in 2012, among the three injury methods mentioned above, electrocoagulation showed more enhanced fibrosis with the highest similarity to the human stricture specimens27. In addition, our group has rich experience in the model of urethral injury caused by electrocoagulation, and the outcome and pathological changes of urethral stricture caused by this method were studied in detail28. The results showed that all rabbits subjected to electrocoagulation developed significant urethral stricture, and the tissue of the stricture site showed typical fibrosis characteristics. In view of the above reasons, electrocoagulation was selected as an effective method for the formation of urethral injury in this study, and the effect of different treatments was further evaluated. + +Regarding the sample size of each group, we performed animal experiments to evaluate the effect of the PTB@SA- Rapamycin catheter in a larger sample size (n=5) and revised the updated results in the revised manuscript. Representative images of retrograde urethrography are shown below (Fig. R1). + +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
FigureR1. Representative images of retrograde urethrography after 30 days. The yellow arrow indicates the coagulation site.
+ +4. The author performed urethrography and histological evaluations of the rabbit urethra 30 days later. Were these evaluations performed immediately after removal of the urethral catheter? Immediately after removal of a urethral catheter is not an appropriate time for evaluation of stricture because of the residual effects of physical dilatation caused by catheter placement. In humans, it has been reported that it takes several months for fibrosis of the urethra to be completed (Urology, Vol. 77, 1477-1481, June 2011). Even in animals, it should be evaluated at least several weeks after catheter removal. + +Response: Thanks to the reviewer for this professional comment. To respond this comment, we then supplemented the animal experiment to perform retrograde urethrography and histological evaluation at 2 weeks after catheter removal (Supplementary Fig. 40). Being similar to the evaluation conclusion from the case of immediate group, at 2 weeks after catheter removal, the degree of urethral lumen reduction in the PTB@SA- Rapamycin group remained significantly lower than that of the unmodified catheter (Supplementary Fig. 40 a, b). The urethral gross specimens in the unmodified catheter group showed white urethral scar and abundant collagen fibers in the submucosa, while the urethral mucosa in the PTB@SA- Rapamycin group was smooth and ruddy, and correspondingly the density of collagen in the submucosa was also reduced (Supplementary Fig. 40 c, d). Furthermore, \(\alpha\) -SMA, a marker of myofibroblast activation, is important in predicting the clinical progression of fibrotic diseases including liver fibrosis and urethral strictures29,30. After 30 days of catheterization and 2 weeks after catheter removal, the expression of \(\alpha\) -SMA, in the healed urethral tissue treated with anti-fibrotic catheter was significantly and consistently lower than that in the unmodified catheter group, indicating that fibroblast activation and subsequent ECM synthesis were inhibited in the PTB@SA- Rapamycin group, which also suggested that the risk of disease progression might be reduced. + +<--- Page Split ---> + +Overall, our experimental results suggest that the anti-fibrotic catheter can effectively regulate ECM metabolism in the process of injury healing to reduce the deposition of excess ECM in the submucosa, and ultimately successfully intervene in the formation of stricture after urethral injury. This functional urinary catheter may provide a prophylactic and beneficial option for those at high risk of urethral strictures, especially those undergoing traumatic catheterization and transurethral procedures. + +![](images/Figure_unknown_5.jpg) + +
Figure S40. Rabbit urethral stricture in unmodified urinary catheter group and PTB@SA-Rapamycin group on the 14th day after removal of catheter. (a) Representative retrograde urethrogram using \(76\%\) meglumine diatrizoate as contrast agent. (b) Lumen reduction immediately after catheter removal or 2 weeks later as determined by retrograde urethrography. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . (c) Comparison of gross specimens, H&E staining, Masson staining and \(\alpha\) -SMA expression between unmodified urinary catheter group and PTB@SA-Rapamycin group at 14 days after catheter removal. Yellow triangles indicate urethral scar tissue, and the dotted lines indicate the boundary between the submucosa and the muscularis. (d, e) Quantitative results of collagen density and \(\alpha\) -SMA positive area in Figure S40c. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . \*\*\* P<0.001.
+ +<--- Page Split ---> + +## Reviewer #3 + +Through this manuscript, the research team reported a novel nanofilm that is used to coat urinary catheter. This nanofilm self- assembled through the deposition of aggregated BSA together with sodium alginate (SA). The aggregation was triggered by a process, termed phase transition bovine serum albumin (PTB). This nanofilm sustained a constant (zero- order) release of encapsulated drug, rapamycin, within 50 days of observation. The nanofilm delivered rapamycin significantly inhibited fibrosis and urethral stricture as compared to non- coated urinary catheter, systemically administered rapamycin, and other control treatment. This work has immediate clinical significance and profound technical novelty. The characterizations of nanofilm, drug release, and related efficacy are thorough and sound especially the study design for drug release. The description of methods are clear and have sufficient details to reproduce results. Overall, this manuscript merit the acceptance for publication on this journal after minor revision and clarification for the following points. + +## 1, A revision of abstract might be beneficial as the current version does not highlight the important results and conclusions sufficiently. + +Response: Thanks for this valuable comment. We have revised the Abstract in the manuscript as follows to emphasize the significance of our study. + +Urethral stricture secondary to urethral injury, afflicting both patients and urologists, is initiated by excessive deposition of extracellular matrix in the submucosal and periurethral tissues. Although various anti- fibrotic drugs have been applied to urethral stricture by irrigation or submucosal injection, their clinical feasibility and effectiveness are limited. Here, to target the pathological state of the extracellular matrix, we designed a protein- based nanofilm- controlled drug delivery system and assembled it on the catheter. This approach, which integrates excellent anti- biofilm property with stable and controlled drug delivery for tens of days in one step, ensures optimal efficacy and negligible side effects while preventing biofilm- related infections. In a rabbit model of urethral injury, the anti- fibrotic catheter maintains extracellular matrix homeostasis by reducing fibroblast- derived collagen production and enhancing metalloproteinase 1- induced collagen degradation, resulting in the greatest improvement in lumen stenosis than other topical therapies for urethral stricture prevention. Such facilely fabricated biocompatible coating with antibacterial contamination and sustained- drug- release functionality could not only benefit populations at high risk of urethral stricture, but also serve as an advanced paradigm for a range of biomedical applications. + +2, The choice of BSA as the main materials of the nanofilm may need additional justification. The immunogenicity of BSA to human needs to be considered and discussed. If there is evidence the BSA in nanofilm will not induce humoral responses in human and other speeches, please provide evidence and reference to reinforce this point. + +Response: Thanks to the reviewer for your helpful comments. The readily available BSA was chosen as the main material for the nanofilm because it is a natural polymer derived from the organism and has natural anti- adsorption property. The anti- biofilm and anti- protein adsorption properties of the macroscopic PTB nanofilm transformed from native BSA under the induction of TCEP were further improved (indicated by higher efficiency and greater stability) \(^{31}\) , which are desirable surface characteristics for various medical devices including urinary catheters. Based on + +<--- Page Split ---> + +the above, BSA is widely used in the field of designing new wound dressings and shows no biosafety concerns32,33. For the coating of surface devices such as urinary catheters, as long as the BSA in the coating does not penetrate into the human body, it is unlikely to activate immune cells and further trigger an immune response. + +As previously demonstrated by our group, the PTB- based cream neither irritated the rabbit skin nor penetrated the skin to cause potential side effects34. The subcutaneous implantation experiment also showed that the PTB coating did not induce foreign body giant cell reaction or inflammatory necrosis31, which is consistent with the results of the intraurethral implantation experiment reported in this work (Supplementary Fig. 19). In addition, human serum albumin (HSA), which is highly similar to BSA in terms of gene sequence, can also react with TCEP to form a macroscopic coating, and the corresponding experimental results are shown in Supplementary Fig. 47. In the future, for implant surface coatings that require long- term direct contact with blood, alternatively using HSA instead of BSA to react with TCEP can better meet the higher immunogenicity requirements. + +## 3. It is unclear whether PTB would only work for BSA, or any proteins as long as they can complete an alfa-helix to beta-sheet conversion. Particularly, it is intriguing whether the PTB will work with human albumin? + +Response: Thanks to the reviewer for your helpful comments. In fact, similar reactions to form nanofilms by protein self- assembly triggered by reducing agents have been observed in a series of commonly used proteins such as insulin, lysozyme and \(\alpha\) - lactalbumin35,36. In our previous study, these proteins that can undergo amyloid- like assembly were identified as proteins with the following 3 characteristics, including (1) a high fibrillation propensity segment, (2) abundant alpha- helices and (3) the reduction of S- S bonds by TCEP36. As the homologous protein of BSA, HSA can also undergo a similar reaction, and the corresponding results are shown in Supplementary Fig. 47. As indicated by AFM, the PTH nanofilm was formed by close packing of nanoscale particles (Supplementary Fig. 47 a). Far- UV circular dichroism (CD) spectra confirmed the loss of \(\alpha\) - helix (208 and 222 nm), accompanied by a significant increase in \(\beta\) - sheet (216 nm) in the PTH nanofilm (Supplementary Fig. 47 b). The ThT fluorescence results of the phase transition system reflected the continuous accumulation of \(\beta\) - sheet structure in the reaction system, and the successful staining of the nanofilm with ThT and Congo red also indicated that the resultant nanofilm was rich in \(\beta\) - sheet (Supplementary Fig. 47 c). Based on the above, we further doped sodium alginate (SA) into the phase transition system and confirmed that SA was successfully integrated into the nanofilm (Supplementary Fig. 47 d). Compared with bare Si, both the water contact angle and surface elements changed significantly after incubating with the phase transition solution (Supplementary Fig. 47 e, f), indicating that the PTH or PTH@SA nanofilm was successfully coated on Si. The robust adhesion of the nanofilm originates from various polar or nonpolar functional groups exposed on the nanofilm surface that can interact with the underlying substrate in a variety of ways. As revealed by the high- resolution XPS spectra of \(\mathrm{C_{18}}\) of the nanofilm (Supplementary Fig. 47 g), the nanofilm typically presented structures including aliphatic carbon (C- H/C- C), amines (C- N), hydroxyls (C- O), thiols (C- S) amides (O=C- N), and carboxyl groups (O=C- O). To further characterize the adsorption capacity of the samples, solutions with different components were pumped into the chamber of the QCM- D. After 1 h, the adsorption mass of the PTH and PTH@SA nanoparticles on the Au chip exceeded 2000 ng/cm2, which was significantly higher than that of HSA and the mixture of HSA and SA (Supplementary Fig. 47 h- k). The above results indicate that + +<--- Page Split ---> + +HSA can also undergo a similar phase transition process triggered by TCEP, and the SA- doped polysaccharide- protein composite nanofilm can be easily obtained by adding SA to the phase transition system. The corresponding description and discussion have been incorporated into the revised manuscript (Page 31) and Supplementary Information (Page S35- S36). + +![](images/Figure_unknown_6.jpg) + +
Figure S47. Formation and hybridization of PTH the nanofilm. (a) AFM image of the PTH nanofilm. (b) CD spectra of native HSA and the PTH nanofilm. (c) ThT fluorescence change as a function of phase transition time, with the insets showing the corresponding fluorescence microscopic image for ThT staining and the optical microscopy image for Congo red staining. (d) The CLSM image shows that SA was successfully entrapped in the nanofilm to form a hybrid nanofilm. (e) WCA of bare Si, PTH and PTH@SA coated Si. The data are presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 4\) . (f) XPS spectra of pristine Si, PTH and PTH@SA nanofilm coated Si. (g) High resolution \(\mathrm{C_{1s}}\) deconvolution spectra of the PTH and PTH@SA nanofilm. (h-k) The frequency and adsorption mass of HSA (h), PTH (i), the mixture of HSA and SA (j) and PTH@SA (k) adsorbed on the Au chip as a function of time.
+ +<--- Page Split ---> + +4, The CD data that support helix-to-sheet conversion is not sufficient. It is not convincing the end product is a beta-sheet-only material with only CD spectra. Though, whether this claim is true or not seems not affecting functionality of the nanofilm. + +Response: Thanks to the reviewer for your helpful comments. We apologize for the ambiguity caused by our inappropriate wording. CD is a spectroscopic technique commonly used to investigate protein secondary structures through characteristic CD spectra produced by major protein secondary structure \(^{37}\) . As shown in Fig. 1d, the negative \(\alpha\) - helix peak for the native BSA at 208 and 222 nm was shifted to the single negative band at 216 nm for \(\beta\) - sheet structure after the phase transition \(^{38}\) , indicating that the TCEP- induced protein unfolding was accompanied by a change in major secondary structure from \(\alpha\) - helix to \(\beta\) - sheet, rather than \(\beta\) - sheet being the only protein secondary structure in the nanofilm. In addition, the deconvolution of the amide I and II in the FTIR spectra of the PTB and PTB@SA nanofilm also supported the increased \(\beta\) - sheet structure in nanofilms compared with the native BSA (Supplementary Fig. 2). We have rephrased the corresponding description in the revised manuscript to articulate our point (Page 6). + +## 5, On page 14, it is not clear why a balanced composition of positively and negatively charged amino acid residues is critical for anti-fouling and anti-biofilm surface. + +Response: Thanks to the reviewer for your helpful comments. BSA is a macromolecule with natural antifouling properties, which is related to the balance of positive and negative charges on albumin protein surface (the balance of glutamic acid and lysine) \(^{31,39}\) . This mixed- charge surface, similar to zwitterionic polymers, can effectively resist contamination by proteins and bacteria through hydration. However, fabricating of BSA coating on multiple classes of materials have been limited by surface chemistry. Based on the mixed- charge principle, some scholars have successfully constructed natural peptide surfaces with antifouling properties by selecting appropriate amino acid residues \(^{27}\) . In this study, we used a reducing agent to induce BSA to unfold and further self- assemble into a macroscopic nanofilm, which is a controllable process rather than just non- specific adsorption of proteins on the surface. The resultant biobased coating has a near- neutral surface charge, as reflected by the zeta potential results of the material (Fig. 3a). In this way, such a coating with both hydrogen bonding groups and zwitterionic groups can not only solvate the material through electrostatic interactions, but also form hydrogen bonds with water molecules through peptide bonds \(^{40}\) , thereby forming a hydration layer on the surface as a barrier to prevent protein or microorganisms from contacting, and finally achieve the effect of anti- protein adsorption and anti- biofilm synergistically. The related discussion has been supplemented and revised in the manuscript (Page 15). + +6, On page 25, this description is confusing "Compared with the unmodified catheter, the antifibrotic catheter (i.e., PTB@SA- Rapamycin catheter) decreased lumen reduction from \(56.1\%\) to \(9.8\%\) (Fig. 6a, b), with a mean percentage improvement of \(82.5\%\) , which was superior to the values reported in preclinical studies of other local treatments (Fig. 6c, Table S5)." It is suggested to break this description into at least two sentences. + +Response: Thanks to the reviewer for the reminder. To make the presentation more concise, we have split this description into the following 2 sentences and amended it based on the results of the supplementary animal experiments. "Compared with the unmodified catheter, the anti- fibrotic + +<--- Page Split ---> + +catheter (i.e., PTB@SA- Rapamycin catheter) decreased lumen reduction from \(51.8\%\) to \(10.6\%\) (Fig. 6a, b). Such a mean percent improvement of up to \(79.2\%\) is superior to values reported in preclinical studies of other topical treatments (Fig. 6c, Table S5).” + +7. For efficacy study (ureteral stricture), it would be beneficial compare lumen diameters of subgroup VI with healthy (non-injuries) rabbit lump diameters to give a complete picture of treatment outcome. In addition, the group size \((n = 3)\) is too small to generate robust mean and conclusion. + +Response: Thanks to the reviewer for this valuable comment. Retrograde urethrography was performed to evaluate the diameter of the urethra in normal healthy rabbits and subgroup VI (PTB@SA- Rapamycin). As shown in Supplementary Fig. 37, the ratio of urethral diameter to individual femoral shaft diameter did not show a statistical difference between the above two groups, further suggesting that the anti- fibrotic catheter is effective in preventing stricture formation by modulating the tissue healing process. + +Regarding the sample size, we sincerely accepted the reviewer's suggestion and supplemented animal experiments to increase the sample size of each group to 5. We have revised the relevant data (Fig. 6 and Supplementary Fig. 37–45) and the corresponding descriptions in the revised manuscript (Page 27–31). In addition, we collected optical photographs of urethral lesions in each group and integrated them in Fig. 6d. It can be observed that except for the PTB@SA- rapamycin group, the rabbit urethral injury developed into whitish, hard, wrinkled and even raised scars after 1 month in the other groups. However, in the anti- fibrotic catheter group, the urethral injury repaired well with smooth and rosy urethral mucosa. Overall, the results of animal experiments definitively demonstrate the efficacy and safety of the anti- fibrotic catheter in preventing stricture formation after urethral injury. + +![](images/Figure_unknown_7.jpg) + +
Figure S37. Comparison of urethral diameter in normal healthy rabbits and rabbits using PTB@SA-Rapamycin catheter after urethral injury. (a) Representative retrograde urethrogram of healthy rabbits. (b) Representative retrograde urethrogram of the rabbit in the anti-fibrotic catheter group. (c) The ratio of urethra diameter to femoral shaft diameter in normal healthy rabbits and rabbits in anti-fibrotic catheter (PTB@SA-Rapamycin) group. Data are presented as the mean \(\pm \mathrm{s.d.}\) ; \(n = 5\) . ns means no statistical difference.
+ +<--- Page Split ---> + +## Comments to the author + +The authors of this manuscript have done an excellent work designing a catheter covered with a protein nanofilm capable of preventing urethral stricture by prevention of bacterial colonization and controlled release of rapamycin. The authors examined the physical characteristics, antibacterial properties, and drug release functions of the protein nanofilm. By indwelling the hybrid coating- modified catheter in the urethra of adult male rabbits, the authors demonstrated that the catheter could effectively prevent the development of urethral stricture. + +Generally, this work is innovative and great. A few comments are as follows: + +## Q1 + +In the first paragraph of the introduction, the author pointed out a clinical problem that current curative treatment options, such as urethrotomy, dilatation and urethroplasty, for urethral stricture could not achieve satisfactory results. This clinical problem exists in patients who have already developed severe urethral strictures. However, the animal model used in this study only simulated the acute urethral injury, and the results could only demonstrate the fact that PTB@SA- Rapamycin catheter was able to prevent the occurrence of urethral stricture. Therefore, the clinical problem raised in the introduction should be revised. + +Response: Thanks to the reviewer for your helpful comments. We have revised the Introduction to clarify precisely the clinical concerns of this work. Urethral stricture is a common disease after urethral injury. The incidence of mucosal injury and secondary urethral strictures after various transurethral procedures, including traumatic catheterization, tends to increase with an aging population and advances in medical technology. Due to the complexity of its treatment, once the urethral injury develops into urethral stricture, it will pose challenges to both patients and urologists. This situation has also prompted researchers and clinicians to explore novel and clinically promising alternative or adjunctive strategies beyond surgery. In this work, targeting the well- defined pathological basis of ECM metabolism dysregulation in urethral strictures, our main intention is to combine a local anti- fibrotic drug delivery system with the urinary catheter to construct a novel drug- loaded device that can prevent the formation of urethral stricture by inhibiting fibrosis process. We apologize for the ambiguity caused by our inappropriate description and have revised the Introduction as follows to emphasize that this study addresses urethral strictures secondary to urethral injury (Page 2). + +Urethral stricture is a common disease (200- 1200 cases per 100000 individuals22) following urethral injury. The pathological state of extracellular matrix (ECM) metabolic disorder caused by injury (including surgery, pelvic fracture, inflammatory injury and traumatic catheterization) results in the replacement of normal urethral tissue by dense fibers interspersed with fibroblasts22. This aggravated fibrosis eventually leads to progressive urethral lumen reduction consequent symptomatic dysuria and even renal impairment. With the growing demand for healthcare brought about by the aging population and advances in medical technology, the increasing incidence of mucosal injury and secondary urethral strictures caused by various transurethral procedures has attracted great attention23,24. Especially in patients with spinal cord injury or in intensive care, urethral stricture or erosion due to long- term catheterization has been reported as high as 8.7%25. Once urethral injury progresses to urethral stricture, subsequent treatment is extremely troublesome, + +<--- Page Split ---> + +which will pose challenges to both patients and urologists. The long- term success rate of the most commonly used endoscopic treatment is only \(20 - 30\%^{22}\) , and although urethroplasty has developed rapidly in recent years, fibrous scarring may still develop in the urethral submucosa after substitute surgery, and this open surgery is less suitable for the elderly and frail patients. Indeed, the pathological state of ECM metabolic disorder and subsequent scar repair is not be rectified regardless of the treatment \(^{26}\) . Therefore, there is an urgent need to develop alternative strategies other than surgery and attempt to focus on regulating healing by inhibiting fibrosis progression following urethral injury, thereby preventing urethral strictures. + +## Q2 + +Why did the authors choose rapamycin as the therapeutic component preventing the urethral stricture? A meta- analysis published in European Urology by Pang et al. showed that mitomycin C had the best effect on urethral stricture among drugs used in the included clinical trials. Compared with other drugs, what are the advantages and disadvantages of rapamycin in treating urethral stricture? + +Response: Thanks to the reviewer for this comment. it should be pointed out that as a proof- of- concept study, the developed drug delivery system in this work is versatile and scalable. As shown in Supplementary Fig. 46, the PTB@SA nanofilm can also be used for long- term delivery of paclitaxel. Thus, it is feasible to encapsulate and immobilize other therapeutic agents using a similar strategy. In terms of preventing urethral strictures, we chose rapamycin as the therapeutic component of drug- loaded urinary catheters for the following two reasons: + +1) Rapamycin (also known as sirolimus), which was initially used to prevent immune rejection response after transplantation, later also played an important role in inhibiting intimal hyperplasia and preventing coronary restenosis due to its favorable antiproliferative and antifibrotic effects. Inspired by this, our group verified the potential availability of rapamycin in inhibiting urethral stricture after urethral injury through a series of in vitro and in vivo experiments. For instance, after urethral injury, fibroblast proliferation and collagen deposition in rabbit urethral tissue were significantly inhibited by intraurethral perfusion of rapamycin for 4 weeks \(^{41}\) . In addition, the cell proliferation and collagen synthesis of human urethral scar-derived fibroblasts were also inhibited in a dose-dependent manner under treatment with rapamycin \(^{42}\) . These studies laid a solid research foundation for this work and encouraged us to further utilize rapamycin to construct a local drug delivery system for intervening urethral stricture formation. + +2) In addition to efficacy, the safety of drug-loaded devices also has important implications for their clinical prospects. Admittedly, local application of mitomycin-C (MMC) showed encouraging results in the prevention and treatment of urethral stricture. However, as a cytotoxic chemotherapeutic agent, topical application of MMC to the mucosa has been reported to cause side effects such as fibrinous debris (which further causes airway obstruction), corneal edema and perforation, necrotizing scleritis and corneal ulceration \(^{43,44}\) . Moreover, a prospective study showed that 68% of subjects experienced mild to moderate urinary adverse events (including ureteral stenosis, hydronephrosis, vomiting, flank pain, hematuria and urinary tract infection) after using a sustained-release hydrogel polymer-based formulation containing MMC \(^{45}\) . Besides, according to a multi-institutional study published in the Journal of Urology, severe complications such as osteitis pubis, rectourethral fistula and necrosis of the bladder floor + +<--- Page Split ---> + +occurred in \(7\%\) of patients undergoing endoscopic incision followed by MMC injection46. In contrast, rapamycin, a commonly used and classic therapeutic component of coronary drug-eluting stents, has negligible side effects through topical application47. The satisfactory outcome of rapamycin-eluting coronary stents in long-term clinical practice demonstrates the availability and safety of rapamycin in the field of local drug delivery, which also encouraged us to integrate rapamycin into the surface coating of the urinary catheter to achieve intraurethral drug therapy. The above discussion is condensed and supplemented in the revised manuscript (Page 30\~31). + +## Q3 + +The author mentioned that the nanofilm surface exhibited abundant functional groups, which enabled the nanofilms to undergo ligand bonding, electrostatic interaction, hydrophobic interaction and hydrogen bonding with virtually arbitrary material, including metal, organic or inorganic materials. According to our experience, this property of the nanofilm makes it likely to interact with various organic and inorganic substances in urine and result in surfaces blockade, stone formation and catheter blockage. Is there any data showing the appearance of the hybrid nanofilm- coated catheters after indwelling for 30 days? We want to check if the surface of all catheters were still clear at the end of the experiment. In fact, bacterial contamination and stone formation are both thorny challenges in the development of functional urinary catheters. + +Response: Thank the reviewer for this helpful comment. Encrustation is indeed a thorny problem for patients who require long- term indwelling catheters, which involves the deposition of inorganic salts on the surface of the device or the inner wall of the lumen, and further leads to pain, difficult removal of catheter, blockage of urinary flow and intractable bacterial biofilms. Two important aspects that promote the development of crusts include supersaturation of crystals in the urine and bacterial infection. However, due to the unique calcium metabolism of rabbits, that is, almost all calcium in the diet can be absorbed while the excess calcium is excreted through the kidney to maintain blood calcium stability, the calcium in rabbit urine is affected by the combination of diet, water intake, physical activity and other hormones48,49. To better exclude the influence of irrelevant variables on the results, we performed a well- established in vitro encrustation experiment to compare the formation of urinary encrustations on bare and PTB@SA- modified urinary catheters in artificial urine, artificial urine in the presence of \(P\) . mirabilis or human urine50. As shown in Supplementary Fig. 20 a and b, there was no difference in encrustation weight between the control and PTB@SA- coated samples exposed to the same urine environment at each time point, except that the weight of crystals formed in human urine on day 3 was smaller in the PTB@SA group. At the same time point, the presence of \(P\) . mirabilis significantly aggravated the encrustation, because the urease produced by \(P\) . mirabilis would increase the pH of urine and promote the deposition of calcium phosphate and magnesium51. After 30 days, both the bare catheter and the PTB@SA coated surfaces were covered with cauliflower- like smooth deposits and interspersed with large coffin- like crystals (Supplementary Fig.20 c). Furthermore, we performed Energy Dispersive Spectroscopy (EDS) analysis of these deposits and determined that the smooth layer was mainly composed of Ca, C, P and O, presumably being calcium carbonate apatite crystallites. while the large coffin- shaped crystals were composed of Mg, O and P, which could be assigned to struvite (magnesium phosphate) (Supplementary Fig.20 d- i). Overall, the PTB@SA nanofilm did not induce more severe encrustation formation on the device surface within 1 month, indicating that it would not pose an + +<--- Page Split ---> + +additional threat when applied to construct functional urinary catheters. Corresponding results and discussions have been incorporated into the revised manuscript (Page 16) and supporting information (Page S15\~S16). + +It is worth pointing out that since the PTB@SA coating has a balanced surface charge distribution similar to that of zwitterionic polymers, it can effectively avoid bacterial adhesion and biofilm formation, which may contribute to reduce encrustation caused by \(P\) . mirabilis adhesion and its subsequent migration along the catheter surface4. However, in this in vitro encrustation model, the coating failed to kill \(P\) . mirabilis present in the device and thus exhibited a similar encrustation propensity to the unmodified catheter. As stated by the reviewers, anti- encrustation is an important challenge for medical devices such as urinary catheters and ureteral stents. Although the performance of the coating reported in this work in reducing crusts is not superior enough, this will become the focus of our next research work. + +<--- Page Split ---> +![](images/Figure_unknown_8.jpg) + +
Figure S20. In vitro evaluation of the encrustation performance of bare silicone catheters and the PTB@SA nanofilm-modified catheters. (a) The weight of crystals deposited on bare catheters or the PTB@SA coated catheters after exposure to artificial urine, artificial urine containing Proteus mirabilis (P. mirabilis), or human urine. Data are presented as the mean \(\pm\) s.d; n=4. \* P<0.05. (b) The weight of crystals deposited on bare catheters or the PTB@SA coated catheters during the first week. Data are presented as the mean \(\pm\) s.d; n=4. \* P<0.05. (c) SEM of bare catheter and the
+ +<--- Page Split ---> + +PTB@SA coating after 30 days of encrustation experiment in vitro. (d) SEM image of bare catheter surface after encrustation experiment. (e, f) EDS analysis of area A (e) and B (f) in Fig S20 d. (g) SEM image of the PTB@SA coating surface after encrustation experiment. (h, i) EDS analysis of area A (h) and B (i) in Fig S20 g. + +## Q4 + +The nanofilm showed a consistent WCA approximately \(80^{\circ}\) . This means the nanofilm- coated catheter is not very hydrophilic and has higher friction with urethral. Was lubricant used during indwelling catheters. If lubricant was used, were there any experiments investigating if the lubricant had any effect on the stability of the nanofilm and the controlled drug release? Catheters for clinical use are often covered with super hydrophilic film or lubricants to avoid urethral injury and inflammation. Consistently, the authors observed that the pristine urinary catheter caused edema and necrosis in rabbits' urethral mucosa after indwelling for 1 month. Parameters about the friction should be compared among pristine urinary catheter and nanofilm coated catheters. + +Response: Thanks to the reviewer for this helpful comment. The abundant functional groups exposed on the nanofilm surface, especially the sodium alginate contained therein, allow the coating to interact with water molecules to hydrate and lubricate the catheter to a certain extent. Furthermore, the coefficient of friction (COF) of the saline- wetted unmodified urinary catheter and the PTB@SA- coated urinary catheter was characterized by a coefficient of friction meter. As shown in Figure R2, the COF of the PTB@SA membrane was lower than that of the unmodified catheter. Therefore, in all animal experiments involving indwelling urinary catheters, the catheters were lubricated with saline prior to catheterization. This organic- free physiological solution did not affect the controlled release of the encapsulated drug, and theoretically other water- soluble lubricants are also suitable. The urethral implantation experiment (Supplementary Fig. 19) and H&E staining of the uninjured urethra in each group in the urethral injury experiment (Supplementary Fig. 38) showed that catheterization performed by this method and indwelling catheter for one month did not cause edema, injury or necrosis in the urethral mucosa and submucosa, indicating that the functionalized urinary catheter has good histocompatibility and practical prospects, while the urethral edema and inflammation shown in Fig. 3 in the control catheter group were mainly due to bacterial urinary tract infection caused by the dense bacterial biofilm on the pristine urinary catheter surface. + +![](images/Figure_unknown_9.jpg) + +
Figure R2. Friction coefficients of bare urinary catheter and the PTB@SA nanofilm-modified catheter. Data are presented as the mean \(\pm\) s.d; n=3. \*\*\* P<0.001.
+ +<--- Page Split ---> + +## Q5 + +Reference should be added for the sentence "... the PTB@SA nanofilm still exhibited a low negative surface zeta potential, and thus may keep a good anti- biofilm ability." + +Response: Thank the reviewer for this comment. Regarding the reason for the excellent anti- biofilm performance of the PTB@SA nanofilm, we supplied the relevant discussion in page 15 and cite reference as Ref. 43, which demonstrates the formation of ultra- low fouling peptides from certain natural amino acids based on the mixed charge design principle. Similarly, the balanced distribution of charged amino acids on the nanofilm surface in this work can also form a hydration layer on the surface of the material, which acts as a barrier against bacterial adhesion and thus resists biofilm formation. + +## Q6 + +We noticed that four rabbits were in each group for the evaluation of the antibacterial biofilm performance of the nanofilm and three rabbits were in each group evaluate the effect of nanofilm on urethral stricture. How did the authors decide the sample size for each experiment? Why did experiments with more complex surgical procedures (more likely to be biased) have smaller sample sizes? + +Response: Thank the reviewer for this comment. For the complex animal model such as urethral injury, in order to better confirm the efficacy of the anti- fibrotic catheter, we supplemented the animal experiment to increase the sample size of each group to 5. Representative images of retrograde urethrography are shown below (Fig.R1). In addition, we collected optical photographs of urethral lesions in each group and integrated them in Fig. 6d. It can be observed that except for the PTB@SA- rapamycin group, the rabbit urethral injury developed into whitish, stiff, wrinkled and even raised scars after 1 month in the other groups. However, in the anti- fibrotic catheter group, the urethral injury repaired well with smooth and ruddy urethral mucosa. We have revised the relevant data (Fig. 6 and Supplementary Fig. 37- 45) and the corresponding descriptions in the revised manuscript (Page 27- 31). Overall, the results of animal experiments definitively demonstrate the efficacy and safety of the anti- fibrotic catheter in preventing stricture formation after urethral injury. + +<--- Page Split ---> +![](images/Figure_6.jpg) + +
Figure R1. Representative images of retrograde urethrography after 30 days. The yellow arrow indicates the coagulation site.
+ +<--- Page Split ---> +![](images/Figure_6.jpg) + +
Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury. a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \(76\%\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments.
+ +<--- Page Split ---> + +Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . c, Corresponding results of the PTB@SA- Rapamycin catheter compared with other preclinical studies of topical therapy to suppress urethral stricture. d, Gross specimen, H&E staining and immunohistochemical staining with anti- alpha smooth muscle actin antibody (α- SMA, brown), anti- matrix metalloproteinase 1 antibody (MMP1, brown), and type I collagen antibody (Collagen I, green) of the urethral injury sites at 1 month. Nuclei (blue) were stained with DAPI. Yellow triangles indicate urethral scar tissue. The asterisks represent urethral luminal side, and the dotted lines indicate the boundary between the submucosa and the muscularis. e, Quantification of \(\alpha\) - SMA, MMP1 positive area and Collagen I fluorescence intensity in Fig. 6d. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . f, g, Hematological examination to show the changes of alanine aminotransferase (ALT, f) and aspartate aminotransferase (AST, g) with different treatments for 1 month. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . h, H&E staining of rabbit liver after systemic administration or indwelling rapamycin sustained- release catheter for 1 month. (a, d) i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst- releasing; vi, PTB@SA- Rapamycin. \* \(\mathrm{P< 0.05}\) , \*\* \(\mathrm{P< 0.01}\) , \*\*\*\* \(\mathrm{P< 0.001}\) , \*\*\*\* \(\mathrm{P< 0.0001}\) , ns means no statistical difference. + +Q7 + +The authors cannot directly compare the results of independent experiments performed by different operators under different experimental conditions (such as surgical instruments, degree of urethral injury and therapy duration) to conclude that the effect of nanofilm in this study was better than that of drugs reported in other studies. + +Response: Thank the reviewer for this comment. We fully agree with the reviewer's comments and supplied the following description to the Methods (Page 43). In order to exclude the interference of various experimental conditions to more objectively compare the preventive effect on urethral stricture reported in independent studies, we reprocessed the original data from each study and calculated the mean percent improvement in lumen stenosis for each intervention according to the following formula to quantify the improvement in severity of urethral strictures with different treatments (Fig. 6c), Where Lumen reduction(Control) represents the reduction degree of the urethral lumen in the control group, and Lumen reduction(Experiment) represents the reduction degree of the urethral lumen in the experimental group. + +\[\mathrm{Mean~percent~improvement} = \frac{\mathrm{Lumen~reduction(Control)} - \mathrm{Lumen~reduction(Experiment)}}{\mathrm{Lumen~reduction(Control)}}\times 100\%\] + +The relevant information of each study, including the drug used, the method of administration, and the outcomes of the experimental and control group, are all listed in detail in Table S5. + +<--- Page Split ---> + + +Table S5. Overview of preclinical outcomes of topical therapy to prevent urethral strictures. + +
StudyTopical interventionLumen reductionMean percent improvements in lumen stenosis
Control groupExperimental group
Kurt 2017[7]40 mg Triamcinolone, submucosal injection, once91.0%49.0%46.2%
Chong 2011[8]0.1 mg Rapamycin, urethral irrigation, daily for 28 days69.1%56.6%18.1%
1 mg Rapamycin, urethral irrigation, daily for 28 days69.1%36.5%47.2%
Kurt 2017[7]0.5 mg/mL Mitomycin-C (MMC), hydropathic compress, once91.0%45.0%50.5%
0.2 mg Insulin-like growth factor 1 (IGF-1), impregnated collagen sutured to the catheter, catheterization for 14 days79.8%39.3%50.8%
Shinchi 2019[9]0.01 mg Docetaxel, urethral irrigation, daily for 28 days84.7%48.0%43.3%
0.1 mg Docetaxel, urethral irrigation, daily for 28 days84.7%36.9%56.4%
This research3 mg Rapamycin, sustained release coating modified catheter, catheterization for 30 days51.8%10.6%79.2%
+ +In summary, by comparing the mean percent improvement in lumen stenosis between this study and the results reported in other literatures, rather than the value of urethral lumen in independent studies, the influence of experimental conditions on the comparison results can be offset to a certain extent. The mean percent improvement in luminal stenosis with the anti- fibrotic catheter was as high as \(79.2\%\) , suggesting a potential advantage of the PTB@SA- rapamycin catheter in the prevention of urethral strictures compared with other topical dosage regimens. + +## Q8 + +In the figure legend of figure 6, the sentence "(b, d, e) i, Control, ii; Unmodified catheter; iii,..." should be revised. Only a and d are numbered. Please check the use of commas and semicolons. + +Response: Thank the reviewer for this comment, and we are sorry for this error in the legend. We have made revisions in the revised manuscript. + +## Q9 + +At least, there are some errors in references 56. Some authors are missing and the original title should be "Sirolimus- eluting Biodegradable Poly- L- Lactic Acid Stent to Suppress Granulation Tissue Formation in the Rat Urethra." + +Response: Thank the reviewer for this comment. We have corrected this reference as follows and proofread all references cited in the article. + +"Kim, K. Y. et al. Sirolimus- eluting Biodegradable Poly- L- Lactic Acid Stent to Suppress Granulation Tissue Formation in the Rat Urethra. Radiology 286, 140- 148 (2017)." + +<--- Page Split ---> + +## References: + +1. Nilles, J., Weiss, J. & Theile, D. Crystal violet staining is a reliable alternative to bicinchoninic acid assay-based normalization. Biotechniques 73, 131–135 (2022). +2. Riol, M. et al. Staphylococcus epidermidis originating from titanium implants infects surrounding tissue and immune cells. Acta Biomater. 10, 5202–5212 (2014). +3. Gu, J., Su, Y., Liu, P., Li, P. & Yang, P. An Environmentally Benign Antimicrobial Coating Based on a Protein Supramolecular Assembly. ACS Appl. Mater. Interfaces 9, 198–210 (2017). +4. Ramstedt, M. et al. Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations. Macromol. Biosci. 19, 1–26 (2019). +5. Solano, C., Echeverz, M. & Lasa, I. Biofilm dispersion and quorum sensing. Curr. Opin. Microbiol. 18, 96–104 (2014). +6. Zhang, N. et al. Different types of T-effector cells orchestrate mucosal inflammation in chronic sinus disease. J. Allergy Clin. Immunol. 122, 961–968 (2008). +7. Uthamanthil, R. K. et al. Urinary catheterization of male rabbits: A new technique and a review of urogenital anatomy. Journal of the American Association for Laboratory Animal Science vol. 52 180–185 at (2013). +8. Hua, X. et al. An Experimental Model of Anterior Urethral Stricture in Rabbits With Local Injections of Bleomycin. Urology 116, 230.e9-230.e15 (2018). +9. Abizaid, A. Sirolimus-eluting coronary stents: A review. Vasc. Health Risk Manag. 3, 191–201 (2007). +10. Rashidbenam, Z. et al. Overview of Urethral Reconstruction by Tissue Engineering: Current Strategies, Clinical Status and Future Direction. Tissue Eng. Regen. Med. 16, 365–384 (2019). +11. Ueshima, E. et al. Macrophage-secreted TGF-β1 contributes to fibroblast activation and ureteral stricture after ablation injury. Am. J. Physiol. - Ren. Physiol. 317, F52–F64 (2019). +12. Chapman, D., Kinnaird, A. & Rourke, K. Independent Predictors of Stricture Recurrence Following Urethroplasty for Isolated Bulbar Urethral Strictures. J. Urol. 198, 1107–1112 (2017). +13. Kurt, O. et al. Effect of Tadalafil on Prevention of Urethral Stricture after Urethral Injury: An Experimental Study. Urology 91, 243.e1-243.e6 (2016). +14. Yoshizaki, A. et al. Treatment with rapamycin prevents fibrosis in tight-skin and bleomycin-induced mouse models of systemic sclerosis. Arthritis Rheum. 62, 2476–2487 (2010). +15. Rostaing, L. & Kamar, N. mTOR inhibitor/proliferation signal inhibitors: entering or leaving the field? J. Nephrol. 23, 133–142 (2010). +16. N., F.-R. One-Year Results for the ROBUST III Randomized Controlled Trial Evaluating the Optilume® Drug-Coated Balloon for Anterior Urethral Strictures. Letter. J. Urol. 207, 866–875 (2022). +17. Guzmán-Esquivel, J. et al. Metalloproteinase-1 usefulness in urethral stricture treatment. Int. Urol. Nephrol. 43, 763–769 (2011). +18. Shinchi, M. et al. Insulin-like growth factor 1 sustained-release collagen on urethral catheter prevents stricture after urethral injury in a rabbit model. Int. J. Urol. 26, 572–577 (2019). +19. Kurt, O. et al. Effect of mitomycin - C and triamcinolone on preventing urethral strictures. Int. Braz J Urol 43, 939–945 (2017). +20. Fu, D., Chong, T., Li, H., Zhang, H. & Wang, Z. Docetaxel inhibits urethral stricture formation, + +<--- Page Split ---> + +an initial study in rabbit model. PLoS One 9, 1–6 (2014). + +21. Chong, T. et al. Rapamycin inhibits formation of urethral stricture in rabbits. J. Pharmacol. Exp. Ther. 338, 47–52 (2011). + +22. Hampson, L. A., McAninch, J. W. & Breyer, B. N. Male urethral strictures and their management. Nat. Rev. Urol. 11, 43–50 (2014). + +23. Lumen, N. et al. Etiology of Urethral Stricture Disease in the 21st Century. J. Urol. 182, 983–987 (2009). + +24. Chen, M. L., Correa, A. F. & Santucci, R. A. Urethral Strictures and Stenoses Caused by Prostate Therapy. Rev. Urol. 18, 90–102 (2016). + +25. Hollingsworth, J. M. et al. Determining the Noninfectious Complications of Indwelling Urethral Catheters. Ann. Intern. Med. 159, 401–410 (2013). + +26. Prihadi, J. C., Sugandi, S., Siregar, N. C., Soejono, G. & Harahap, A. Imbalance in extracellular matrix degradation in urethral stricture. Res. Reports Urol. 10, 227–232 (2018). + +27. Sievert, K. D. et al. Introducing a large animal model to create urethral stricture similar to human stricture disease: A comparative experimental microscopic study. J. Urol. 187, 1101–1109 (2012). + +28. Delai, F. et al. Development and characterization of urethral stricture model in rabbits. J. Med. Coll. PLA 25, 351–358 (2010). + +29. Hirano, Y. et al. Myofibroblast-dominant proliferation associated with severe fibrosis in bulbar urethral strictures. Int. J. Urol. (2022) doi:https://doi.org/10.1111/iju.15053. + +30. Sanyal, A. J. et al. The Natural History of Advanced Fibrosis Due to Nonalcoholic Steatohepatitis: Data From the Simtuzumab Trials. Hepatology 70, 1913–1927 (2019). + +31. Hu, X. et al. Amyloid-Like Protein Aggregates: A New Class of Bioinspired Materials Merging an Interfacial Anchor with Antifouling. Adv. Mater. 32, 1–11 (2020). + +32. Zhang, F. et al. Stretchable and biocompatible bovine serum albumin fibrous films supported silver for accelerated bacteria-infected wound healing. Chem. Eng. J. 417, 129145 (2021). + +33. Ouyang, J. et al. A facile and general method for synthesis of antibiotic-free protein-based hydrogel: Wound dressing for the eradication of drug-resistant bacteria and biofilms. Bioact. Mater. 18, 446–458 (2022). + +34. Chang, M. et al. Suppression of Sunscreen Leakage in Water by Amyloid-like Protein Aggregates. ACS Appl. Mater. Interfaces 13, 42451–42460 (2021). + +35. Liu, Y., Tao, F., Miao, S. & Yang, P. Controlling the Structure and Function of Protein Thin Films through Amyloid-like Aggregation. Acc. Chem. Res. 54, 3016–3027 (2021). + +36. Li, C., Xu, L., Zuo, Y. Y. & Yang, P. Tuning protein assembly pathways through superfast amyloid-like aggregation. Biomater. Sci. 6, 836–841 (2018). + +37. Louis-Jeune, C., Andrade-Navarro, M. A. & Perez-Iratxeta, C. Prediction of protein secondary structure from circular dichroism using theoretically derived spectra. Proteins Struct. Funct. Bioinforma. 80, 374–381 (2012). + +38. Venyaminov, S. Y., Baikalov, I. A., Wu, C. S. C. & Yang, J. T. Some problems of CD analyses of protein conformation. Anal. Biochem. 198, 250–255 (1991). + +39. Chen, S., Cao, Z. & Jiang, S. Ultra-low fouling peptide surfaces derived from natural amino acids. Biomaterials 30, 5892–5896 (2009). + +40. Wang, F. et al. Review of the research on anti-protein fouling coatings materials. Prog. Org. Coatings 147, 105860 (2020). + +<--- Page Split ---> + +41. Chong, T. et al. Rapamycin inhibits formation of urethral stricture in rabbits. J. Pharmacol. Exp. Ther. 338, 47–52 (2011). + +42. Fu, D. et al. Rapamycin Inhibits the Growth and Collagen Production of Fibroblasts Derived from Human Urethral Scar Tissue. Biomed Res. Int. 2018, 1–9 (2018). + +43. McCurdy Hueman, E. & Simpson, C. B. Airway complications from topical mitomycin C. Otolaryngol. - Head Neck Surg. 133, 831–835 (2005). + +44. Cinik, R. et al. The Effect of Everolimus on Scar Formation in Glaucoma Filtering Surgery in a Rabbit Model. Curr. Eye Res. 41, 1438–1446 (2016). + +45. Porta, C. et al. An evaluation of UGN-101, a sustained-release hydrogel polymer-based formulation containing mitomycin-C, for the treatment of upper urothelial carcinomas. Expert Opin. Pharmacother. 21, 2199–2204 (2020). + +46. Redshaw, J. D. et al. Intralesional injection of mitomycin C at transurethral incision of bladder neck contracture may offer limited benefit: TURNS study group. J. Urol. 193, 587–592 (2015). + +47. Roos, J. C. P. & Murthy, R. Sirolimus (rapamycin) for the targeted treatment of the fibrotic sequelae of Graves' orbitopathy. Eye 33, 679–682 (2019). + +48. Redrobe, S. Calcium metabolism in rabbits. Semin. Avian Exot. Pet Med. 11, 94–101 (2002). + +49. Clauss, M. et al. Influence of diet on calcium metabolism, tissue calcification and urinary sludge in rabbits (Oryctolagus cuniculus). J. Anim. Physiol. Anim. Nutr. (Berl). 96, 798–807 (2012). + +50. Jones, D. S., Djokic, J. & Gorman, S. P. Characterization and optimization of experimental variables within a reproducible bladder encrustation model and in vitro evaluation of the efficacy of urease inhibitors for the prevention of medical device-related encrustation. J. Biomed. Mater. Res. - Part B Appl. Biomater. 76, 1–7 (2006). + +51. Yao, Q. et al. Bio-inspired antibacterial coatings on urinary stents for encrustation prevention. J. Mater. Chem. B 10, 2584–2596 (2021). + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: I recognized that the authors made proper efforts for revision. The revised manuscript becomes acceptable. + +Reviewer #3: Remarks to the Author: The authors revised manuscript thoroughly and carefully. The manuscript is ready for publication. + +Reviewer #4: Remarks to the Author: Thanks for your kind reply and revision. + +Reviewer #5: + +Remarks to the Author: + +This is a tremendous body of work, very meticulous and thoughtful. Most of the responses were in- depth and most of the requested changes were made. I would like to congratulate the authors with completion of this project. There are only 3 additional comments: + +1) in response to Reviewer#2 there is no direct explanation to the question #4 on what the reason is to sacrifice the animals so early after catheter removal. In real life it takes weeks for strictures to mature and appear clinically significant. Other animal models of stricture disease use a minimum of 4 weeks to 6 months before declaring a resolution/non-formation of stricture. In humans this time is even longer (no one believes success if it is reported less than 8-12 months since the treatment. I understand that authors saw all kind of indirect evidence and hopeful signs of no stricture formation in treatment group, but at 2 weeks these findings have no clinical significance. + +2) Why is catheter staying for 4 weeks? under what clinical circumstances a urethral catheter would stay for that long? Not after transurethral procedures (3-7 days typically), not after traumatic catheter (7-14 days), not after prostatectomy (3-14 days). Why 4 weeks? + +3) in many instances the retrograde urethrograms are shown in wrong orientation. Typically, distal portion of urethra is either shown facing 3 or 9 o'clock position (consistently through all images), cephalad is at 12 o'clock, caudad is at 6 o'clock. At least in S37 and in figure 6 the orientation is unknown and this makes these figures very confusing. Additionally, some of the radiographs are darker and with poor contrast making it difficult to assess urethral lumen, I would recommend revising these images to have consistent orientation and brightness/contrast. + +<--- Page Split ---> + +## Dear Reviewers, + +We sincerely appreciate your valuable comments. We have made the revisions to all the comments in the revised manuscript (marked in red color) and supporting information (SI). The following is the point- to- point response to the reviewers' comments. + +This is a tremendous body of work, very meticulous and thoughtful. Most of the responses were in- depth and most of the requested changes were made. I would like to congratulate the authors with completion of this project. There are only 3 additional comments: 1) in response to Reviewer#2 there is no direct explanation to the question #4 on what the reason is to sacrifice the animals so early after catheter removal. In real life it takes weeks for strictures to mature and appear clinically significant. Other animal models of stricture disease use a minimum of 4 weeks to 6 months before declaring a resolution/non- formation of stricture. In humans this time is even longer (no one believes success if it is reported less than 8- 12 months since the treatment. I understand that authors saw all kind of indirect evidence and hopeful signs of no stricture formation in treatment group, but at 2 weeks these findings have no clinical significance. + +Response: Thanks to the reviewer for this valuable comment, we will further explore the long- term effects of the anti- fibrotic catheter in our future experiments. In response to this comment, we supplemented this limitation in the corresponding section of Results and Discussion on page 26 as follows: "The above results suggest that the anti- fibrotic catheter has shown impressive preliminary results in retarding the progression of urethral injuries to strictures, but do have a limitation that its long- term effect (six months to one year) in inhibiting urethral strictures need to be clarified in future experiments." In addition, in the Summary section (page 31), we have revised the wording as follows to make the statement more rigorous and objective. "In this regard, the promotion of PTB@SA- Rapamycin catheters as an alternative to conventional catheters is expected to be of great benefit to numerous people at high risk for urethral strictures (eg, undergoing transurethral intervention, traumatic catheterization or urethroplasty)." + +2) Why is catheter staying for 4 weeks? under what clinical circumstances a urethral catheter would stay for that long? Not after transurethral procedures (3-7 days typically), not after traumatic catheter (7-14 days), not after prostatectomy (3-14 days). Why 4 weeks? + +Response: Thanks to the reviewer for this valuable comment. As mentioned by the reviewer, the intervention time used in the animal experiment should take into account the actual clinical needs. The specific reasons for indwelling the catheter for 1 month after urethral injury are stated as follows. + +1) Due to the unique anatomical structure of the urethra and the stimulating effect of urine, the healing time of urethral wounds is longer than that of skin tissue, with each healing stage lagging behind that of skin. It has been reported that rat urethral injury ends the proliferative phase characterized by fibroblast proliferation activation and angiogenesis on the 10th day1, and the subsequent maturation and remodeling phase involving the arrangement of collagen and other connective tissues around the urethra is a key stage of urethral fibrosis2. Therefore, in order to effectively inhibit urethral stricture, the drug release period should completely cover all stages of urethral injury healing. Our previous studies have shown that continuous transurethral infusion of anti-fibrotic drugs (such as rapamycin or docetaxel) for 28 days after urethral injury can effectively + +<--- Page Split ---> + +inhibit urethral stricture \(^{3,4}\) , and other experimental studies on the prevention of urethral strictures by topical administration also commonly used 1 month as the duration of drug action \(^{5 - 7}\) . + +2) According to the Campbell-Walsh urology and European Association of Urology (EAU) guidelines on urologic trauma \(^{8,9}\) , partial posterior urethral rupture require catheterization to drain urine and provide a support surface for mucosal repair until the injury heals. After urethral reunion, catheterization for 4-6 weeks is also recommended. For urethral injuries that cannot be treated conservatively, EAU recommends catheterization for 2-3 weeks after urethroplasty. Based on the above, in order to assess the promise of the anti-fibrotic catheter in inhibiting the progression of urethral injury to urethral strictures and preventing recurrent strictures at the incision site of urethroplasty, we evaluated its efficacy and safety after 1 month of indwelling. + +In summary, in the consideration of the pathophysiology of urethral injury healing and the current clinical management standards, and also combining with literature research and our previous studies, we set 1 month as the intervention time and proved the beneficial effect of the anti-fibrotic catheter in inhibiting urethral strictures. + +3) in many instances the retrograde urethrograms are shown in wrong orientation. Typically, distal portion of urethra is either shown facing 3 or 9 o'clock position (consistently through all images), cephalad is at 12 o'clock, caudad is at 6 o'clock. At least in S37 and in figure 6 the orientation is unknown and this makes these figures very confusing. Additionally, some of the radiographs are darker and with poor contrast making it difficult to assess urethral lumen, I would recommend revising these images to have consistent orientation and brightness/contrast. + +Response: Thanks to the reviewer for this helpful suggestion. In order to make the urethrography images clearer, we unified the display directions of all urethrography images in this paper so that the cephalad is at 12 o'clock and the caudal side is at 6 o'clock. In addition, the brightness and contrast of some images have been adjusted. We have updated all relevant figures in the manuscript and supporting information (Figure 6, FigureS37 and Figure S40). + +<--- Page Split ---> +![](images/Figure_unknown_10.jpg) + +
Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury.
+ +a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \(76\%\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments. Data are mean \(\pm\) s.d.; \(n = 5\) . c, Corresponding results of the PTB@SA- Rapamycin catheter compared + +<--- Page Split ---> + +with other preclinical studies of topical therapy to suppress urethral stricture. d, Gross specimen, H&E staining and immunohistochemical staining with anti-alpha smooth muscle actin antibody (α- SMA, brown), anti-matrix metalloproteinase 1 antibody (MMP1, brown), and type I collagen antibody (Collagen I, green) of the urethral injury sites at 1 month. Nuclei (blue) were stained with DAPI. Yellow triangles indicate urethral scar tissue. The asterisks represent urethral luminal side, and the dotted lines indicate the boundary between the submucosa and the muscularis. e, Quantification of α- SMA, MMP1 positive area and Collagen I fluorescence intensity in Fig. 6d. Data are mean ± s.d.; n=5. f, g, Hematological examination to show the changes of alanine aminotransferase (ALT, f) and aspartate aminotransferase (AST, g) with different treatments for 1 month. Data are mean ± s.d.; n=5. h, H&E staining of rabbit liver after systemic administration or indwelling rapamycin sustained-release catheter for 1 month. (a, d) i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst-releasing; vi, PTB@SA-Rapamycin. \* P<0.05, \*\* P<0.01, \*\*\* P<0.001, \*\*\*\* P<0.0001, ns means no statistical difference. + +![](images/Figure_unknown_11.jpg) + +
Figure S37. Comparison of urethral diameter in normal healthy rabbits and rabbits using PTB@SA-Rapamycin catheter after urethral injury. (a) Representative retrograde urethrogram of healthy rabbits. (b) Representative retrograde urethrogram of the rabbit in the anti-fibrotic catheter group. (c) The ratio of urethra diameter to femoral shaft diameter in normal healthy rabbits and rabbits in anti-fibrotic catheter (PTB@SA-Rapamycin) group. Data are presented as the mean ± s.d.; n=5. ns means no statistical difference.
+ +<--- Page Split ---> +![PLACEHOLDER_42_0] + +
Figure S40. Rabbit urethral stricture in unmodified urinary catheter group and PTB@SA-Rapamycin group on the 14th day after removal of catheter. (a) Representative retrograde urethrogram using \(76\%\) meglumine dinitrozoate as contrast agent. (b) Lumen reduction immediately after catheter removal or 2 weeks later as determined by retrograde urethrography. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . (c) Comparison of gross specimens, H&E staining, Masson staining and \(\alpha\) -SMA expression between unmodified urinary catheter group and PTB@SA-Rapamycin group at 14 days after catheter removal. Yellow triangles indicate urethral scar tissue, and the dotted lines indicate the boundary between the submucosa and the muscularis. (d, e) Quantitative results of collagen density and \(\alpha\) -SMA positive area in Figure S40c. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . \*\*\* P<0.001.
+ +<--- Page Split ---> + +## References: + +1. Ninan, N., Thomas, S. & Grohens, Y. Wound healing in urology. Adv. Drug Deliv. Rev. 82–83, 93–105 (2015). +2. Prihadi, J. C., Sugandi, S., Siregar, N. C., Soejono, G. & Harahap, A. Imbalance in extracellular matrix degradation in urethral stricture. Res. Reports Urol. 10, 227–232 (2018). +3. Chong, T. et al. Rapamycin inhibits formation of urethral stricture in rabbits. J. Pharmacol. Exp. Ther. 338, 47–52 (2011). +4. Fu, D., Chong, T., Li, H., Zhang, H. & Wang, Z. Docetaxel inhibits urethral stricture formation, an initial study in rabbit model. PLoS One 9, 1–6 (2014). +5. Wang, Z., Li, Q., Wang, P. & Yang, M. Biodegradable drug-eluting urethral stent in limiting urethral stricture formation after urethral injury: An experimental study in rabbit. J. Bioact. Compat. Polym. 35, 378–388 (2020). +6. Shin, J. H. et al. Tissue hyperplasia: Influence of a paclitaxel-eluting covered stent - Preliminary study in a canine urethral model. Radiology 234, 438–444 (2005). +7. Wang, L. et al. Electrospun nanoyarn and exosomes of adipose-derived stem cells for urethral regeneration: Evaluations in vitro and in vivo. Colloids Surfaces B Biointerfaces 209, 112218 (2022). +8. Partin, A. W., Wein, A. J., Kavoussi, L. R., Peters, C. A. & Dmochowski, R. R. Campbell-Walsh urology. (Elsevier Health Sciences, 2020). +9. Lumen, N. et al. Review of the current management of lower urinary tract injuries by the EAU trauma guidelines panel. Eur. Urol. 67, 925–929 (2015). + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #5: Remarks to the Author: All questions answered, changes made as requested. + +<--- Page Split ---> diff --git a/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..13994ee4246cf79edc298ea09c17a2adfc846e31 --- /dev/null +++ b/peer_reviews/32ace780350ede0e71dbb5f19a5d38ed0113d460f7f9c162f2955552d59e16e4/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,845 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[107, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[107, 154, 888, 240]]<|/det|> +Rectifying disorder of extracellular matrix to suppress urethral stricture by protein nanofilm- controlled drug delivery from urinary catheter + +<|ref|>image<|/ref|><|det|>[[93, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 286, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[116, 120, 216, 133]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[116, 136, 291, 149]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 150, 875, 224]]<|/det|> +In the clinic, delivery of numerous antifibrotic drugs by irrigation or submucosal injection showed the low effectiveness against urethral stricture. Here, the authors raised a strategy for both antibacterial therapy and maintenance of extracellular homeostasis for urethral injury. In general, this work seems to be quite interesting and I would like to recommend the acceptance of this work after authors can well address the following questions before its final acceptance. + +<|ref|>text<|/ref|><|det|>[[116, 238, 875, 298]]<|/det|> +1) Author mentioned that the HE staining in the control group showed abundant inflammatory cell infiltration of the urethra (Fig. 3j). Since HE images could not differentiate the type of cells, the quantification of inflammatory cells (Fig. 3k) should be performed with specific antibodies using ELISA kit. + +<|ref|>text<|/ref|><|det|>[[116, 313, 867, 357]]<|/det|> +2) Author explained that at the end of catheterization period, the surface of pristine SR catheter was contaminated by the dense E. coli biofilm (Figure 3h). However, there is no qualification and quantification of biofilm formation assay (e.g. crystal violet) in this study. + +<|ref|>text<|/ref|><|det|>[[115, 372, 863, 460]]<|/det|> +3) Author initially seeded the bacteria on the PTB@SA Rapamycin catheters and performed in vitro culture for 20 hours before implantation. However, during in vitro experiment, several parts of bacteria will be eliminated. Since the number of bacteria implanted was different, it will affect the in vivo result, such as inflammatory response, etc. How do the authors explain this finding? Also, the CFU of bacteria after in vivo implantation should be quantified to check its antibacterial efficacy in vivo. + +<|ref|>text<|/ref|><|det|>[[115, 476, 867, 520]]<|/det|> +4) The rabbit implanted with PTB@SA Rapamycin catheters was not swelling (edema) compared with control. Therefore, the quantification scoring system to check the significancy of edema should be performed to support this sentence. + +<|ref|>text<|/ref|><|det|>[[115, 535, 867, 580]]<|/det|> +5) According to the Figure 6d and s36, there was an obvious change in epithelium thickness between different group, especially in the burst-releasing group. Please explain the correlation of each group with the epithelium thickness. + +<|ref|>text<|/ref|><|det|>[[115, 595, 866, 640]]<|/det|> +6) According to the Figure 6d, the nuclei in a-SMA staining was obviously observed only in group i, while the other group showed no or very few of nuclei. Meanwhile, in MMP-1 and collagen I staining, nuclei were highly observed in all of the groups. Please explain. + +<|ref|>text<|/ref|><|det|>[[115, 655, 872, 699]]<|/det|> +7) Antibiotic resistance often occurs in clinical application. Since antibiotic is also used in this system, please explain whether this material could avoid the antibiotic resistance after long-term implantation in vivo. + +<|ref|>text<|/ref|><|det|>[[112, 715, 872, 744]]<|/det|> +8) Author should add the explanation about the impact of the presence of E. coli on urethral fibroblast in co-culture experiment. + +<|ref|>text<|/ref|><|det|>[[112, 759, 852, 788]]<|/det|> +9) The images of sections in Fig. S37 are not clear. Clear images at a high magnification should be provided. + +<|ref|>text<|/ref|><|det|>[[115, 804, 879, 863]]<|/det|> +10) Author mentioned that the body weight of the rabbits in each group showed a consistent slight drop within two weeks after urethral coagulation, and then gradually recovered, which may be related to surgical stress (supplementary figure 41). However, there is no statistical analysis that supports the significant difference in body weight. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 216, 118]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 120, 291, 133]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 135, 863, 164]]<|/det|> +This study was designed to investigate the efficacy of rapamycin sustained release nanofilm coated catheters in preventing urethral stricture in a rabbit urethral injury model. + +<|ref|>text<|/ref|><|det|>[[115, 164, 866, 194]]<|/det|> +In addition, the researchers have conducted basic experiments on the antibacterial and drug- release effects of catheters, which we believe are appropriate. + +<|ref|>text<|/ref|><|det|>[[115, 194, 802, 223]]<|/det|> +However, there are several points that should be considered to improve this study in animal experiments. + +<|ref|>text<|/ref|><|det|>[[115, 238, 867, 313]]<|/det|> +1, In the introduction, the author states that local therapy in the urethra has limited efficacy and feasibility in terms of drug retention and effectiveness. However, paclitaxel- coated balloon dilation therapy has already been reported in practice in human patients with anterior urethral strictures and has been shown to be useful and safe (The Journal of Urology, Vol. 207, 866- 875, April 2022). The authors should mention this. + +<|ref|>text<|/ref|><|det|>[[115, 328, 876, 418]]<|/det|> +2, This study investigates the effect of stricture prevention after injury to the normal urethra. In other words, the results of this study show only a stenosis- preventive effect on a model of 'urethral injury' not 'urethral stricture'. Urethral stricture after urethral injury and restenosis after treatment of urethral stricture have completely different etiologies. The cited paper confuses the paper on the effect of prevention of stricture after urethral injury with the paper on the effect of prevention of restenosis after treatment of urethral stricture, and the authors should consider each separately. + +<|ref|>text<|/ref|><|det|>[[115, 432, 866, 507]]<|/det|> +3, Many methods have been reported for creating a urethral stricture/injury model. The author has shown stenosis in a control group by impairing it with electrocautery, is this a well- established method? Also, the author divides the rabbits into 6 groups of 3 rabbits each to evaluate the effect of the drug- releasing catheter. Is three rabbits a sufficient number of rabbits to evaluate this experiment? + +<|ref|>text<|/ref|><|det|>[[115, 521, 872, 626]]<|/det|> +4, The author performed urethrography and histological evaluations of the rabbit urethra 30 days later. Were these evaluations performed immediately after removal of the urethral catheter? Immediately after removal of a urethral catheter is not an appropriate time for evaluation of stricture because of the residual effects of physical dilatation caused by catheter placement. In humans, it has been reported that it takes several months for fibrosis of the urethra to be completed (Urology, Vol. 77, 1477- 1481, June 2011). Even in animals, it should be evaluated at least several weeks after catheter removal. + +<|ref|>text<|/ref|><|det|>[[115, 670, 216, 684]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 687, 291, 700]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 701, 876, 865]]<|/det|> +Through this manuscript, the research team reported a novel nanofilm that is used to coat urinary catheter. This nanofilm self- assembled through the deposition of aggregated BSA together with sodium alginate (SA). The aggregation was triggered by a process, termed phase transition bovine serum albumin (PTB). This nanofilm sustained a constant (zero- order) release of encapsulated drug, rapamycin, with in 50 days of observation. The nanofilm delivered rapamycin significantly inhibited fibrosis and urethral stricture as compared to non- coated urinary catheter, systemically administered rapamycin, and other control treatment. This work has immediate clinical significance and profound technical novelty. The characterizations of nanofilm, drug release, and related efficacy are thorough and sound especially the study design for drug release. The description of methods are clear and have sufficient details to reproduce results. Overall, this manuscript merit the acceptance for publication on this journal after minor revision and clarification for the following points. + +<|ref|>text<|/ref|><|det|>[[115, 879, 855, 894]]<|/det|> +1, A revision of abstract might be beneficial as the current version does not highlight the important + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 377, 104]]<|/det|> +results and conclusions sufficiently. + +<|ref|>text<|/ref|><|det|>[[115, 119, 872, 179]]<|/det|> +2, The choice of BSA as the main materials of the nanofilm may need additional justification. The immunogenicity of BSA to human needs to be considered and discussed. If there is evidence the BSA in nanofilm will not induce humoral responses in human and other speeches, please provide evidence and reference to reinforce this point. + +<|ref|>text<|/ref|><|det|>[[115, 194, 877, 238]]<|/det|> +3. It is unclear whether PTB would only work for BSA, or any proteins as long as they can complete an alfa-helix to beta-sheet conversion. Particularly, it is intriguing whether the PTB will work with human albumin? + +<|ref|>text<|/ref|><|det|>[[115, 253, 870, 298]]<|/det|> +4, The CD data that support helix-to-sheet conversion is not sufficient. It is not convincing the end product is a beta-sheet-only material with only CD spectra. Though, whether this claim is true or not seems not affecting functionality of the nanofilm. + +<|ref|>text<|/ref|><|det|>[[115, 313, 870, 342]]<|/det|> +5, On page 14, it is not clear why a balanced composition of positively and negatively charged amino acid residues is critical for anti- fouling and anti- biofilm surface. + +<|ref|>text<|/ref|><|det|>[[115, 357, 806, 445]]<|/det|> +6, On page 25, this description is confusing "Compared with the unmodified catheter, the anti-fibrotic catheter (i.e., PTB@SA- Rapamycin catheter) decreased lumen reduction from \(56.1\%\) to \(9.8\%\) (Fig. 6a, b), with a mean percentage improvement of \(82.5\%\) , which was superior to the values reported in preclinical studies of other local treatments (Fig. 6c, Table S5)." It is suggested to break this description into at least two sentences. + +<|ref|>text<|/ref|><|det|>[[115, 461, 878, 506]]<|/det|> +7, For efficacy study (urethral stricture), it would be beneficial compare lumen diameters of subgroup VI with healthy (non- injuries) rabbit lump diameters to give a complete picture of treatment outcome. In addition, the group size \((n = 3)\) is too small to generate robust mean and conclusion. + +<|ref|>text<|/ref|><|det|>[[115, 550, 216, 564]]<|/det|> +Reviewer #4: + +<|ref|>text<|/ref|><|det|>[[115, 567, 300, 595]]<|/det|> +Remarks to the Author: Comments to the author + +<|ref|>text<|/ref|><|det|>[[115, 597, 857, 686]]<|/det|> +The authors of this manuscript have done an excellent work designing a catheter covered with a protein nanofilm capable of preventing urethral stricture by prevention of bacterial colonization and controlled release of rapamycin. The authors examined the physical characteristics, antibacterial properties, and drug release functions of the protein nanofilm. By indwelling the hybrid coating- modified catheter in the urethra of adult male rabbits, the authors demonstrated that the catheter could effectively prevent the development of urethral stricture. + +<|ref|>text<|/ref|><|det|>[[115, 686, 686, 701]]<|/det|> +Generally, this work is innovative and great. A few comments are as follows: + +<|ref|>text<|/ref|><|det|>[[115, 717, 138, 730]]<|/det|> +Q1 + +<|ref|>text<|/ref|><|det|>[[115, 731, 880, 833]]<|/det|> +In the first paragraph of the introduction, the author pointed out a clinical problem that current curative treatment options, such as urethrotomy, dilatation and urethroplasty, for urethral stricture could not achieve satisfactory results. This clinical problem exists in patients who have already developed severe urethral strictures. However, the animal model used in this study only simulated the acute urethral injury, and the results could only demonstrate the fact that PTB@SA- Rapamycin catheter was able to prevent the occurrence of urethral stricture. Therefore, the clinical problem raised in the introduction should be revised. + +<|ref|>text<|/ref|><|det|>[[115, 849, 138, 862]]<|/det|> +Q2 + +<|ref|>text<|/ref|><|det|>[[115, 864, 875, 893]]<|/det|> +Why did the authors choose rapamycin as the therapeutic component preventing the urethral stricture? A meta- analysis published in European Urology by Pang et al. showed that mitomycin C had + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 866, 120]]<|/det|> +the best effect on urethral stricture among drugs used in the included clinical trials. Compared with other drugs, what are the advantages and disadvantages of rapamycin in treating urethral stricture? + +<|ref|>text<|/ref|><|det|>[[115, 135, 139, 148]]<|/det|> +Q3 + +<|ref|>text<|/ref|><|det|>[[115, 149, 877, 283]]<|/det|> +The author mentioned that the nanofilm surface exhibited abundant functional groups, which enabled the nanofilms to undergo ligand bonding, electrostatic interaction, hydrophobic interaction and hydrogen bonding with virtually arbitrary material, including metal, organic or inorganic materials. According to our experience, this property of the nanofilm makes it likely to interact with various organic and inorganic substances in urine and result in surfaces blockade, stone formation and catheter blockage. Is there any data showing the appearance of the hybrid nanofilm- coated catheters after indwelling for 30 days? We want to check if the surface of all catheters were still clear at the end of the experiment. In fact, bacterial contamination and stone formation are both thorny challenges in the development of functional urinary catheters. + +<|ref|>text<|/ref|><|det|>[[115, 300, 139, 313]]<|/det|> +Q4 + +<|ref|>text<|/ref|><|det|>[[115, 314, 868, 432]]<|/det|> +The nanofilm showed a consistent WCA approximately \(80^{\circ}\) . This means the nanofilm- coated catheter is not very hydrophilic and has higher friction with urethral. Was lubricant used during indwelling catheters. If lubricant was used, were there any experiments investigating if the lubricant had any effect on the stability of the nanofilm and the controlled drug release? Catheters for clinical use are often covered with super hydrophilic film or lubricants to avoid urethral injury and inflammation. Consistently, the authors observed that the pristine urinary catheter caused edema and necrosis in rabbits' urethral mucosa after indwelling for 1 month. Parameters about the friction should be compared among pristine urinary catheter and nanofilm coated catheters. + +<|ref|>text<|/ref|><|det|>[[115, 448, 852, 492]]<|/det|> +Q5 Reference should be added for the sentence "... the PTB@SA nanofilm still exhibited a low negative surface zeta potential, and thus may keep a good anti- biofilm ability." + +<|ref|>text<|/ref|><|det|>[[115, 506, 139, 520]]<|/det|> +Q6 + +<|ref|>text<|/ref|><|det|>[[115, 521, 864, 595]]<|/det|> +We noticed that four rabbits were in each group for the evaluation of the antibacterial biofilm performance of the nanofilm and three rabbits were in each group evaluate the effect of nanofilm on urethral stricture. How did the authors decide the sample size for each experiment? Why did experiments with more complex surgical procedures (more likely to be biased) have smaller sample sizes? + +<|ref|>text<|/ref|><|det|>[[115, 611, 139, 624]]<|/det|> +Q7 + +<|ref|>text<|/ref|><|det|>[[115, 625, 872, 685]]<|/det|> +The authors cannot directly compare the results of independent experiments performed by different operators under different experimental conditions (such as surgical instruments, degree of urethral injury and therapy duration) to conclude that the effect of nanofilm in this study was better than that of drugs reported in other studies. + +<|ref|>text<|/ref|><|det|>[[115, 701, 139, 714]]<|/det|> +Q8 + +<|ref|>text<|/ref|><|det|>[[115, 715, 872, 744]]<|/det|> +In the figure legend of figure 6, the sentence "(b, d, e) i, Control, ii; Unmodified catheter; iii,..." should be revised. Only a and d are numbered. Please check the use of commas and semicolons. + +<|ref|>text<|/ref|><|det|>[[115, 760, 139, 772]]<|/det|> +Q9 + +<|ref|>text<|/ref|><|det|>[[115, 774, 852, 818]]<|/det|> +At least, there are some errors in references 56. Some authors are missing and the original title should be "Sirolimus- eluting Biodegradable Poly- l- Lactic Acid Stent to Suppress Granulation Tissue Formation in the Rat Urethra." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 87, 268, 101]]<|/det|> +## Dear reviewers, + +<|ref|>text<|/ref|><|det|>[[148, 104, 850, 158]]<|/det|> +We sincerely thank all referees for their valuable comments. We have made the revisions to all the comments in the revised manuscript (marked in red color) and supporting information (SI). The following is the point- to- point response to the reviewers' comments. + +<|ref|>sub_title<|/ref|><|det|>[[148, 179, 252, 195]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[148, 198, 850, 288]]<|/det|> +In the clinic, delivery of numerous antifibrotic drugs by irrigation or submucosal injection showed the low effectiveness against urethral stricture. Here, the authors raised a strategy for both antibacterial therapy and maintenance of extracellular homeostasis for urethral injury. In general, this work seems to be quite interesting and I would like to recommend the acceptance of this work after authors can well address the following questions before its final acceptance. + +<|ref|>text<|/ref|><|det|>[[148, 308, 850, 380]]<|/det|> +1) Author mentioned that the HE staining in the control group showed abundant inflammatory cell infiltration of the urethra (Fig. 3j). Since HE images could not differentiate the type of cells, the quantification of inflammatory cells (Fig. 3k) should be performed with specific antibodies using ELISA kit. + +<|ref|>text<|/ref|><|det|>[[147, 382, 852, 603]]<|/det|> +Response: We are extremely grateful to Reviewer 1 for your helpful comments. Through H&E staining, we found that compared with the control group, the infiltrated area of cells with high nucleocytoplasmic ratio cells in the urethral tissue of the PTB@SA coating group was significantly reduced, suggesting that the distribution of inflammatory cells between the two groups may be different. To better define and localize the infiltration of inflammatory cells in urethral tissue, we performed immunochemical staining with CD45 (expressed in leukocytes) and CD68 (expressed in macrophages) antibodies. As shown in Fig. 3k, in addition to a significant decrease in the area of positive cells, inflammatory cells (including both leukocytes and macrophages) were confined to the epithelial mucosa of urethral tissues in the PTB@SA nanofilm-modified catheter group, while a large number of inflammatory cells were diffusively infiltrated in the mucosa and submucosa of the unmodified catheter group. The above discussion has been incorporated into the revised manuscript (Page 17). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[170, 80, 830, 652]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 660, 850, 900]]<|/det|> +
Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating. a, Zeta potential of the PTB or PTB@SA(0.10) coating on Si. Data are mean \(\pm\) s.d.; \(\mathrm{n = 3}\) . b, c, Number of viable S. aureus (b) and E. coli (c) recovered from bare substrate, PTB or PTB@SA(0.10) coating as confirmed by colony counting. Data are mean \(\pm\) s.d.; \(\mathrm{n = 3}\) . d, e, CLSM images showing the patterned adherence of S. aureus on bare substrate with using the micropatterned PTB@SA coating as the resistant layer. f, g SEM images of unmodified (f) or PTB@SA(0.10) coating-modified urinary catheters (g) recovered after indwelling for 1 week. The arrow indicates scattered bacteria on the PTB@SA(0.10) coating. h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . i, The number of white blood cells in rabbit urine after different catheters were used for 1 week. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . j, Gross observation of the rabbits' urethra, and the yellow circles represent the sampling site of the tissue section. k, Hematoxylin and erosion (H&E) staining and immunochemical staining with anti-CD45 antibody (green) and anti-CD68 (brown) antibody in rabbit urethral tissue. l, Quantification of the
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +area of inflammatory cell infiltration in the H&E staining images of the urethra. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . m, Quantification of CD45 (l) and CD68 (m) positive area in Fig. 3k. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . \(\mathrm{P< 0.05}\) , \(\mathrm{^{**}\mathrm{P< 0.01}}\) , \(\mathrm{^{***}\mathrm{P< 0.001}}\) , ns means no statistical difference. + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 213]]<|/det|> +2) Author explained that at the end of catheterization period, the surface of pristine SR catheter was contaminated by the dense E. coli biofilm (Figure 3h). However, there is no qualification and quantification of biofilm formation assay (e.g. crystal violet) in this study. + +<|ref|>text<|/ref|><|det|>[[147, 215, 851, 344]]<|/det|> +Response: Thank the reviewer for this comment. Since crystal violet also stains the protein coating to bias the optical density of the sample1, we alternatively used the number of bacteria per unit catheter surface area to evaluate the in vivo anti-biofilm performance of the PTB@SA coating. After the catheter was indwelled in the rabbit urethra for 7 days, the surface bacterial density was determined by colony counting. Compared with the control group, the resistance efficiency of the PTB@SA coating against E. coli was \(85.9\%\) , which is consistent with the SEM image results of the recovered catheter (Fig. 3h in the revised manuscript). + +<|ref|>image<|/ref|><|det|>[[339, 360, 671, 562]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 586, 818, 639]]<|/det|> +
Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \(\pm\) s.d.; \(\mathrm{n = 4}\) . \(\mathrm{^{**}\mathrm{P< 0.01}}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 659, 850, 768]]<|/det|> +3) Author initially seeded the bacteria on the PTB@SA Rapamycin catheters and performed in vitro culture for 20 hours before implantation. However, during in vitro experiment, several parts of bacteria will be eliminated. Since the number of bacteria implanted was different, it will affect the in vivo result, such as inflammatory response, etc. How do the authors explain this finding? Also, the CFU of bacteria after in vivo implantation should be quantified to check its antibacterial efficacy in vivo. + +<|ref|>text<|/ref|><|det|>[[147, 771, 851, 899]]<|/det|> +Response: Thank the reviewer for this comment. Here, we adopted the pre- seeding method, a typical method widely used to characterize antifouling property in animal experiments2,3, to evaluate the efficacy of the PTB@SA coating in preventing catheter- associated urinary tract infections. In fact, microorganisms transferred from the perianal or skin during catheterization, and/or pathogenic bacteria migrating along the luminal pathway have been reported to be important sources of infection for catheter- associated urinary tract infections4. Bacterial biofilms developed from bacteria that colonize on the material surfaces not only provide shelter for bacteria but also participate in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 306]]<|/det|> +quorum- sensing signaling5. As a result, compared with planktonic bacteria, bacteria surviving in biofilms exhibit strong resistance to antibiotics and mechanical challenges, which will cause refractory and recurrent urinary tract infections. Therefore, in order to reasonably simulate the bacterial contamination that catheters may be exposed to in practical applications and evaluate the consequences caused in vivo, unmodified urinary catheters and PTB@SA nanofilm- modified catheters were all incubated in artificial urine containing E. coli at a consistent final bacterial concentration of \(10^{6}\) CFU/mL, and all other experimental conditions were the same for both groups. The surface properties of the catheter modified by the PTB@SA coating make it difficult for bacteria to attach stably, so the coating exhibits an ideal preventive effect on catheter- associated urinary tract infection. The bacterial load of the recovered catheters of the two groups was evaluated by colony counting. As shown in Fig 3h, the number of bacteria on the surface of the PTB@SA coating was significantly lower than that of the control group (P<0.01). + +<|ref|>image<|/ref|><|det|>[[339, 321, 671, 526]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 549, 818, 602]]<|/det|> +
Figure. 3 The anti-biofilm performance and biocompatibility of the hybrid coating h, In vivo anti-biofilm efficiency of the hybrid coating measured by colony counting. Data are mean \(\pm \mathrm{s.d.}\) ; \(n = 4\) . \(^{**}P< 0.01\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 622, 850, 676]]<|/det|> +4) The rabbit implanted with PTB@SA Rapamycin catheters was not swelling (edema) compared with control. Therefore, the quantification scoring system to check the significancy of edema should be performed to support this sentence. + +<|ref|>text<|/ref|><|det|>[[147, 679, 850, 789]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. In response to this comment, edema was scored semiquantitatively on a 3- point scale in tissue sections, with 0 being the lowest and 2 being the highest scores, as previously described6. As shown in Supplementary Fig. 21, consistent with the macroscopic appearance of the specimens, the urethral tissue of the control group had a higher edema score compared with the PTB@SA- coated catheter (P<0.01). The above discussion has been incorporated into the revised manuscript (Page 17). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[345, 105, 699, 296]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 308, 850, 344]]<|/det|> +
Figure S21. Quantitative assessment of the edema severity in control and PTB@SA-coated groups. Data are presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 4\) .\*\* P<0.01.
+ +<|ref|>text<|/ref|><|det|>[[147, 363, 850, 416]]<|/det|> +5) According to the Figure 6d and s36, there was an obvious change in epithelium thickness between different group, especially in the burst-releasing group. Please explain the correlation of each group with the epithelium thickness. + +<|ref|>text<|/ref|><|det|>[[147, 418, 852, 620]]<|/det|> +Response: Thanks for the reviewer's comment. We carefully compared the overall condition of the rabbit urethral tissue sections in each group and concluded that the thickness of the urothelium in each group was not related to the treatment received, but the thickness and collagen abundance of submucosal connective tissue in the presence of rapamycin sustained- release catheter were significantly lower than other groups, as shown in Figure 6 and S38. In fact, on the one hand, the histological morphology of the urethral epithelium is related to the location of the specimen. The urethral injury site in this experiment was about \(1\mathrm{cm}\) distal to the opening of ejaculator duct, which was exactly at the position where the prostatic urethra (mainly transitional epithelium) transited to the membranous urethra (typically stratified columnar epithelium) \(^7\) . On the other hand, even for different lateral walls of the urethra in the same cross-section, the thickness of the epithelium varies slightly, as has been observed in the published literature (Figure 3, 4 of the reference) \(^8\) . + +<|ref|>text<|/ref|><|det|>[[148, 640, 850, 694]]<|/det|> +6) According to the Figure 6d, the nuclei in \(\alpha\) -SMA staining was obviously observed only in group i, while the other group showed no or very few of nuclei. Meanwhile, in MMP-1 and collagen I staining, nuclei were highly observed in all of the groups. Please explain. + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 750]]<|/det|> +Response: We greatly appreciate this helpful comment. In the \(\alpha\) -SMA- stained tissue, the nuclei were indeed not clearly stained because of a mistake in our staining procedure. For this, we re- stained and analyzed accordingly. The corresponding results have been revised in Fig 6d and 6e. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 90, 840, 800]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 808, 850, 900]]<|/det|> +
Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury. a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \(76\%\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 344]]<|/det|> +Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . c, Corresponding results of the PTB@SA- Rapamycin catheter compared with other preclinical studies of topical therapy to suppress urethral stricture. d, Gross specimen, H&E staining and immunohistochemical staining with anti- alpha smooth muscle actin antibody (α- SMA, brown), anti- matrix metalloproteinase 1 antibody (MMP1, brown), and type I collagen antibody (Collagen I, green) of the urethral injury sites at 1 month. Nuclei (blue) were stained with DAPI. Yellow triangles indicate urethral scar tissue. The asterisks represent urethral luminal side, and the dotted lines indicate the boundary between the submucosa and the muscularis. e, Quantification of \(\alpha\) - SMA, MMP1 positive area and Collagen I fluorescence intensity in Fig. 6d. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . f, g, Hematological examination to show the changes of alanine aminotransferase (ALT, f) and aspartate aminotransferase (AST, g) with different treatments for 1 month. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . h, H&E staining of rabbit liver after systemic administration or indwelling rapamycin sustained- release catheter for 1 month. (a, d) i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst- releasing; vi, PTB@SA- Rapamycin. \* \(\mathrm{P< 0.05}\) , \*\* \(\mathrm{P< 0.01}\) , \*\*\* \(\mathrm{P< 0.001}\) , \*\*\*\* \(\mathrm{P< 0.0001}\) , ns means no statistical difference. + +<|ref|>text<|/ref|><|det|>[[148, 363, 850, 416]]<|/det|> +7) Antibiotic resistance often occurs in clinical application. Since antibiotic is also used in this system, please explain whether this material could avoid the antibiotic resistance after long-term implantation in vivo. + +<|ref|>text<|/ref|><|det|>[[147, 418, 852, 602]]<|/det|> +Response: Thanks for the reviewer's comment. Here, we need to clarify that the antibacterial performance of the functionalized urinary catheter is mainly derived from the excellent antibacterial adhesion property of the PTB@SA nanofilm, and the rapamycin contained in the system is not a typical antibiotic, so it will not induce bacteria drug resistance. As a classic mTOR pathway inhibitor, rapamycin is widely used in the prevention of coronary artery stenosis in clinical practice, and shows favorable biological safety9. Inspired by this, in the present work, controlled release of rapamycin from the coating on the catheter surface was the main contributor to the inhibition of stricture formation after urethral injury, and the effect of preventing catheter- related urinary tract infections depended on the anti- biofilm property of the hybrid coating. The above discussion has been incorporated into the revised manuscript (Page 15). + +<|ref|>sub_title<|/ref|><|det|>[[147, 622, 849, 656]]<|/det|> +## 8) Author should add the explanation about the impact of the presence of E. coli on urethral fibroblast in co-culture experiment. + +<|ref|>text<|/ref|><|det|>[[147, 659, 852, 860]]<|/det|> +Response: Thanks for the reviewer's comment. The proliferation and activation of fibroblasts is a key link in the occurrence and development of urethral stricture10. The inflammatory response caused by bacteria induces changes in the biological behavior of fibroblasts through a variety of cytokines (such as TGF- \(\beta 1\) , TNF- \(\alpha\) , IL- 6, etc.)11, which eventually promotes the formation of urethral strictures and even leads to the failure of urethroplasty12. As shown by CD45 and CD68 staining of urethral tissue, unmodified catheters were more susceptible to biofilm contamination and urethral inflammation than the coated group (Fig. 3k- m). Therefore, the PTB@SA nanofilm with potent anti- biofilm property is a strong candidate for designing drug- loaded coatings on the surface of urinary catheters to regulate tissue healing, which can effectively attenuate the fibrotic process initiated by inflammation. The above discussion has been incorporated into the revised manuscript (Page 17). + +<|ref|>text<|/ref|><|det|>[[147, 882, 848, 899]]<|/det|> +9) The images of sections in Fig. S37 are not clear. Clear images at a high magnification should + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 87, 244, 100]]<|/det|> +## be provided. + +<|ref|>text<|/ref|><|det|>[[148, 105, 850, 140]]<|/det|> +Response: Thanks for the reviewer's comment. We have supplied clear images at high magnification to the revised supplementary information (Page S30, Supplementary Fig. 41). + +<|ref|>image<|/ref|><|det|>[[151, 150, 844, 765]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 772, 851, 899]]<|/det|> +
Figure S41. Immunofluorescence staining images showing collagen deposition in urethral tissue. (a) Immunofluorescence staining of Collagen I at the urethral injury site after different treatments for 1 month. Nuclei (blue) was stained with DAPI, i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst-releasing; vi, PTB@SA-Rapamycin. (b) The urethral tissue of normal rabbits was sectioned for immunostaining with Collagen I. Nuclei (blue) was stained with DAPI. (c) Quantification of the Collagen I fluorescence intensity in normal rabbit urethral tissue and PTB@SA-Rapamycin catheter-mediated urethral injury healing. Data are
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 86, 632, 101]]<|/det|> +presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . ns means no statistical difference. + +<|ref|>text<|/ref|><|det|>[[147, 122, 850, 195]]<|/det|> +10) Author mentioned that the body weight of the rabbits in each group showed a consistent slight drop within two weeks after urethral coagulation, and then gradually recovered, which may be related to surgical stress (supplementary figure 41). However, there is no statistical analysis that supports the significant difference in body weight. + +<|ref|>text<|/ref|><|det|>[[147, 196, 850, 269]]<|/det|> +Response: Thanks to the reviewer for this valuable comment. To support our conclusion, one- way ANOVA was performed on the body weight of each group at each time point to confirm that there was no statistical difference in the body weight of rabbits in each treatment group and the blank control group. We have supplied a related description in Supplementary Fig. 45. + +<|ref|>image<|/ref|><|det|>[[315, 287, 650, 473]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 493, 850, 566]]<|/det|> +
Figure S45. The initial body weight and the weight of the rabbits in each group at 1, 2, 3 and 4 weeks after the urethra was injured by electrocoagulation. The data are presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . At each time point, there was no statistical difference in body weight between the treatment groups and the blank control group.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 86, 254, 101]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[149, 105, 851, 195]]<|/det|> +This study was designed to investigate the efficacy of rapamycin sustained release nanofilm coated catheters in preventing urethral stricture in a rabbit urethral injury model. In addition, the researchers have conducted basic experiments on the antibacterial and drug- release effects of catheters, which we believe are appropriate. However, there are several points that should be considered to improve this study in animal experiments. + +<|ref|>text<|/ref|><|det|>[[148, 216, 851, 306]]<|/det|> +1, In the introduction, the author states that local therapy in the urethra has limited efficacy and feasibility in terms of drug retention and effectiveness. However, paclitaxel- coated balloon dilation therapy has already been reported in practice in human patients with anterior urethral strictures and has been shown to be useful and safe (The Journal of Urology, Vol. 207, 866- 875, April 2022). The authors should mention this. + +<|ref|>text<|/ref|><|det|>[[148, 308, 853, 455]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. For patients with urethral strictures, paclitaxel- coated balloons are indeed a beneficial option that combines mechanical dilation and local drug delivery, indicating that local therapy to intervene in the progression of urethral strictures is a feasible and promising strategy. Here, we attempted to combine intraurethral drug delivery with widely used urinary catheters to develop functionalized urinary catheters with the anti- fibrotic effect, which could hopefully evolve treatment after urethral strictures to positive prophylaxis, especially for strictures caused by transurethral procedures and traumatic catheterization. We have supplied relevant content in the Introduction section (Page 3) as follows. + +<|ref|>text<|/ref|><|det|>[[148, 457, 851, 602]]<|/det|> +Although systemically administered antifibrotic agents have shown efficacy in attenuating tissue/organ fibrosis in animal models \(^{13,14}\) , off- target side effects have greatly limited their success in clinical trials \(^{15}\) . By contrast, the successful attempt of a paclitaxel- coated balloon combining mechanical dilation and local drug delivery in the treatment of recurrent urethral strictures suggests the feasibility and promise of local therapy to interfere with urethral strictures \(^{16}\) . Currently, in order to inhibit secondary strictures after urethral injury, various antifibrotic drugs have been administered locally by hydrostatic pressure, submucosal injection, urethral irrigation, drug- eluting stents and catheters \(^{17 - 21}\) . + +<|ref|>text<|/ref|><|det|>[[148, 622, 851, 750]]<|/det|> +2, This study investigates the effect of stricture prevention after injury to the normal urethra. In other words, the results of this study show only a stenosis- preventive effect on a model of 'urethral injury' not 'urethral stricture'. Urethral stricture after urethral injury and restenosis after treatment of urethral stricture have completely different etiologies. The cited paper confuses the paper on the effect of prevention of stricture after urethral injury with the paper on the effect of prevention of restenosis after treatment of urethral stricture, and the authors should consider each separately. + +<|ref|>text<|/ref|><|det|>[[148, 752, 851, 843]]<|/det|> +Response: Thanks to the reviewer for your professional comments. Admittedly, the results of animal experiments provide strong support for the conclusion that the anti- fibrotic catheter has a good preventive effect on urethral stricture secondary to urethral injury. We apologize for the ambiguity caused by our inappropriate description and have revised the Introduction as follows to emphasize that this study addresses urethral strictures secondary to urethral injury (Page 2). + +<|ref|>text<|/ref|><|det|>[[149, 845, 850, 899]]<|/det|> +Urethral stricture is a common disease (200- 1200 cases per 100000 individuals \(^{22}\) ) following urethral injury. The pathological state of extracellular matrix (ECM) metabolic disorder caused by injury (including surgery, pelvic fracture, inflammatory injury and traumatic catheterization) results + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 380]]<|/det|> +in the replacement of normal urethral tissue by dense fibers interspersed with fibroblasts22. This aggravated fibrosis eventually leads to progressive urethral lumen reduction consequent symptomatic dysuria and even renal impairment. With the growing demand for healthcare brought about by the aging population and advances in medical technology, the increasing incidence of mucosal injury and secondary urethral strictures caused by various transurethral procedures has attracted great attention23,24. Especially in patients with spinal cord injury or in intensive care, urethral stricture or erosion due to long- term catheterization has been reported as high as \(8.7\%^{25}\) . Once urethral injury progresses to urethral stricture, subsequent treatment is extremely troublesome, which will pose challenges to both patients and urologists. The long- term success rate of the most commonly used endoscopic treatment is only \(20 - 30\%^{22}\) , and although urethroplasty has developed rapidly in recent years, fibrous scarring may still develop in the urethral submucosa after substitute surgery, and this open surgery is less suitable for the elderly and frail patients. Indeed, the pathological state of ECM metabolic disorder and subsequent scar repair is not be rectified regardless of the treatment26. Therefore, there is an urgent need to develop alternative strategies other than surgery and attempt to focus on regulating healing by inhibiting fibrosis progression following urethral injury, thereby preventing urethral strictures. + +<|ref|>text<|/ref|><|det|>[[148, 400, 851, 491]]<|/det|> +3. Many methods have been reported for creating a urethral stricture/injury model. The author has shown stenosis in a control group by impairing it with electrocautery, is this a well-established method? Also, the author divides the rabbits into 6 groups of 3 rabbits each to evaluate the effect of the drug-releasing catheter. Is three rabbits a sufficient number of rabbits to evaluate this experiment? + +<|ref|>text<|/ref|><|det|>[[148, 493, 851, 695]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. There are a variety of modalities commonly used to cause urethral injury in animals, mainly including urethrotomy, electrocoagulation, and ligation. According to a study reported by the Journal of Urology in 2012, among the three injury methods mentioned above, electrocoagulation showed more enhanced fibrosis with the highest similarity to the human stricture specimens27. In addition, our group has rich experience in the model of urethral injury caused by electrocoagulation, and the outcome and pathological changes of urethral stricture caused by this method were studied in detail28. The results showed that all rabbits subjected to electrocoagulation developed significant urethral stricture, and the tissue of the stricture site showed typical fibrosis characteristics. In view of the above reasons, electrocoagulation was selected as an effective method for the formation of urethral injury in this study, and the effect of different treatments was further evaluated. + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 768]]<|/det|> +Regarding the sample size of each group, we performed animal experiments to evaluate the effect of the PTB@SA- Rapamycin catheter in a larger sample size (n=5) and revised the updated results in the revised manuscript. Representative images of retrograde urethrography are shown below (Fig. R1). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[205, 95, 795, 393]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 419, 848, 454]]<|/det|> +
FigureR1. Representative images of retrograde urethrography after 30 days. The yellow arrow indicates the coagulation site.
+ +<|ref|>text<|/ref|><|det|>[[147, 474, 850, 602]]<|/det|> +4. The author performed urethrography and histological evaluations of the rabbit urethra 30 days later. Were these evaluations performed immediately after removal of the urethral catheter? Immediately after removal of a urethral catheter is not an appropriate time for evaluation of stricture because of the residual effects of physical dilatation caused by catheter placement. In humans, it has been reported that it takes several months for fibrosis of the urethra to be completed (Urology, Vol. 77, 1477-1481, June 2011). Even in animals, it should be evaluated at least several weeks after catheter removal. + +<|ref|>text<|/ref|><|det|>[[147, 604, 851, 899]]<|/det|> +Response: Thanks to the reviewer for this professional comment. To respond this comment, we then supplemented the animal experiment to perform retrograde urethrography and histological evaluation at 2 weeks after catheter removal (Supplementary Fig. 40). Being similar to the evaluation conclusion from the case of immediate group, at 2 weeks after catheter removal, the degree of urethral lumen reduction in the PTB@SA- Rapamycin group remained significantly lower than that of the unmodified catheter (Supplementary Fig. 40 a, b). The urethral gross specimens in the unmodified catheter group showed white urethral scar and abundant collagen fibers in the submucosa, while the urethral mucosa in the PTB@SA- Rapamycin group was smooth and ruddy, and correspondingly the density of collagen in the submucosa was also reduced (Supplementary Fig. 40 c, d). Furthermore, \(\alpha\) -SMA, a marker of myofibroblast activation, is important in predicting the clinical progression of fibrotic diseases including liver fibrosis and urethral strictures29,30. After 30 days of catheterization and 2 weeks after catheter removal, the expression of \(\alpha\) -SMA, in the healed urethral tissue treated with anti-fibrotic catheter was significantly and consistently lower than that in the unmodified catheter group, indicating that fibroblast activation and subsequent ECM synthesis were inhibited in the PTB@SA- Rapamycin group, which also suggested that the risk of disease progression might be reduced. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 194]]<|/det|> +Overall, our experimental results suggest that the anti-fibrotic catheter can effectively regulate ECM metabolism in the process of injury healing to reduce the deposition of excess ECM in the submucosa, and ultimately successfully intervene in the formation of stricture after urethral injury. This functional urinary catheter may provide a prophylactic and beneficial option for those at high risk of urethral strictures, especially those undergoing traumatic catheterization and transurethral procedures. + +<|ref|>image<|/ref|><|det|>[[150, 202, 840, 708]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 716, 851, 881]]<|/det|> +
Figure S40. Rabbit urethral stricture in unmodified urinary catheter group and PTB@SA-Rapamycin group on the 14th day after removal of catheter. (a) Representative retrograde urethrogram using \(76\%\) meglumine diatrizoate as contrast agent. (b) Lumen reduction immediately after catheter removal or 2 weeks later as determined by retrograde urethrography. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . (c) Comparison of gross specimens, H&E staining, Masson staining and \(\alpha\) -SMA expression between unmodified urinary catheter group and PTB@SA-Rapamycin group at 14 days after catheter removal. Yellow triangles indicate urethral scar tissue, and the dotted lines indicate the boundary between the submucosa and the muscularis. (d, e) Quantitative results of collagen density and \(\alpha\) -SMA positive area in Figure S40c. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . \*\*\* P<0.001.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 86, 252, 101]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[148, 123, 851, 325]]<|/det|> +Through this manuscript, the research team reported a novel nanofilm that is used to coat urinary catheter. This nanofilm self- assembled through the deposition of aggregated BSA together with sodium alginate (SA). The aggregation was triggered by a process, termed phase transition bovine serum albumin (PTB). This nanofilm sustained a constant (zero- order) release of encapsulated drug, rapamycin, within 50 days of observation. The nanofilm delivered rapamycin significantly inhibited fibrosis and urethral stricture as compared to non- coated urinary catheter, systemically administered rapamycin, and other control treatment. This work has immediate clinical significance and profound technical novelty. The characterizations of nanofilm, drug release, and related efficacy are thorough and sound especially the study design for drug release. The description of methods are clear and have sufficient details to reproduce results. Overall, this manuscript merit the acceptance for publication on this journal after minor revision and clarification for the following points. + +<|ref|>sub_title<|/ref|><|det|>[[149, 345, 848, 380]]<|/det|> +## 1, A revision of abstract might be beneficial as the current version does not highlight the important results and conclusions sufficiently. + +<|ref|>text<|/ref|><|det|>[[149, 382, 848, 417]]<|/det|> +Response: Thanks for this valuable comment. We have revised the Abstract in the manuscript as follows to emphasize the significance of our study. + +<|ref|>text<|/ref|><|det|>[[148, 419, 851, 696]]<|/det|> +Urethral stricture secondary to urethral injury, afflicting both patients and urologists, is initiated by excessive deposition of extracellular matrix in the submucosal and periurethral tissues. Although various anti- fibrotic drugs have been applied to urethral stricture by irrigation or submucosal injection, their clinical feasibility and effectiveness are limited. Here, to target the pathological state of the extracellular matrix, we designed a protein- based nanofilm- controlled drug delivery system and assembled it on the catheter. This approach, which integrates excellent anti- biofilm property with stable and controlled drug delivery for tens of days in one step, ensures optimal efficacy and negligible side effects while preventing biofilm- related infections. In a rabbit model of urethral injury, the anti- fibrotic catheter maintains extracellular matrix homeostasis by reducing fibroblast- derived collagen production and enhancing metalloproteinase 1- induced collagen degradation, resulting in the greatest improvement in lumen stenosis than other topical therapies for urethral stricture prevention. Such facilely fabricated biocompatible coating with antibacterial contamination and sustained- drug- release functionality could not only benefit populations at high risk of urethral stricture, but also serve as an advanced paradigm for a range of biomedical applications. + +<|ref|>text<|/ref|><|det|>[[148, 715, 850, 787]]<|/det|> +2, The choice of BSA as the main materials of the nanofilm may need additional justification. The immunogenicity of BSA to human needs to be considered and discussed. If there is evidence the BSA in nanofilm will not induce humoral responses in human and other speeches, please provide evidence and reference to reinforce this point. + +<|ref|>text<|/ref|><|det|>[[148, 790, 851, 899]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. The readily available BSA was chosen as the main material for the nanofilm because it is a natural polymer derived from the organism and has natural anti- adsorption property. The anti- biofilm and anti- protein adsorption properties of the macroscopic PTB nanofilm transformed from native BSA under the induction of TCEP were further improved (indicated by higher efficiency and greater stability) \(^{31}\) , which are desirable surface characteristics for various medical devices including urinary catheters. Based on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 157]]<|/det|> +the above, BSA is widely used in the field of designing new wound dressings and shows no biosafety concerns32,33. For the coating of surface devices such as urinary catheters, as long as the BSA in the coating does not penetrate into the human body, it is unlikely to activate immune cells and further trigger an immune response. + +<|ref|>text<|/ref|><|det|>[[148, 160, 851, 325]]<|/det|> +As previously demonstrated by our group, the PTB- based cream neither irritated the rabbit skin nor penetrated the skin to cause potential side effects34. The subcutaneous implantation experiment also showed that the PTB coating did not induce foreign body giant cell reaction or inflammatory necrosis31, which is consistent with the results of the intraurethral implantation experiment reported in this work (Supplementary Fig. 19). In addition, human serum albumin (HSA), which is highly similar to BSA in terms of gene sequence, can also react with TCEP to form a macroscopic coating, and the corresponding experimental results are shown in Supplementary Fig. 47. In the future, for implant surface coatings that require long- term direct contact with blood, alternatively using HSA instead of BSA to react with TCEP can better meet the higher immunogenicity requirements. + +<|ref|>sub_title<|/ref|><|det|>[[148, 345, 850, 398]]<|/det|> +## 3. It is unclear whether PTB would only work for BSA, or any proteins as long as they can complete an alfa-helix to beta-sheet conversion. Particularly, it is intriguing whether the PTB will work with human albumin? + +<|ref|>text<|/ref|><|det|>[[147, 400, 851, 900]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. In fact, similar reactions to form nanofilms by protein self- assembly triggered by reducing agents have been observed in a series of commonly used proteins such as insulin, lysozyme and \(\alpha\) - lactalbumin35,36. In our previous study, these proteins that can undergo amyloid- like assembly were identified as proteins with the following 3 characteristics, including (1) a high fibrillation propensity segment, (2) abundant alpha- helices and (3) the reduction of S- S bonds by TCEP36. As the homologous protein of BSA, HSA can also undergo a similar reaction, and the corresponding results are shown in Supplementary Fig. 47. As indicated by AFM, the PTH nanofilm was formed by close packing of nanoscale particles (Supplementary Fig. 47 a). Far- UV circular dichroism (CD) spectra confirmed the loss of \(\alpha\) - helix (208 and 222 nm), accompanied by a significant increase in \(\beta\) - sheet (216 nm) in the PTH nanofilm (Supplementary Fig. 47 b). The ThT fluorescence results of the phase transition system reflected the continuous accumulation of \(\beta\) - sheet structure in the reaction system, and the successful staining of the nanofilm with ThT and Congo red also indicated that the resultant nanofilm was rich in \(\beta\) - sheet (Supplementary Fig. 47 c). Based on the above, we further doped sodium alginate (SA) into the phase transition system and confirmed that SA was successfully integrated into the nanofilm (Supplementary Fig. 47 d). Compared with bare Si, both the water contact angle and surface elements changed significantly after incubating with the phase transition solution (Supplementary Fig. 47 e, f), indicating that the PTH or PTH@SA nanofilm was successfully coated on Si. The robust adhesion of the nanofilm originates from various polar or nonpolar functional groups exposed on the nanofilm surface that can interact with the underlying substrate in a variety of ways. As revealed by the high- resolution XPS spectra of \(\mathrm{C_{18}}\) of the nanofilm (Supplementary Fig. 47 g), the nanofilm typically presented structures including aliphatic carbon (C- H/C- C), amines (C- N), hydroxyls (C- O), thiols (C- S) amides (O=C- N), and carboxyl groups (O=C- O). To further characterize the adsorption capacity of the samples, solutions with different components were pumped into the chamber of the QCM- D. After 1 h, the adsorption mass of the PTH and PTH@SA nanoparticles on the Au chip exceeded 2000 ng/cm2, which was significantly higher than that of HSA and the mixture of HSA and SA (Supplementary Fig. 47 h- k). The above results indicate that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 158]]<|/det|> +HSA can also undergo a similar phase transition process triggered by TCEP, and the SA- doped polysaccharide- protein composite nanofilm can be easily obtained by adding SA to the phase transition system. The corresponding description and discussion have been incorporated into the revised manuscript (Page 31) and Supplementary Information (Page S35- S36). + +<|ref|>image<|/ref|><|det|>[[160, 163, 830, 712]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 716, 850, 900]]<|/det|> +
Figure S47. Formation and hybridization of PTH the nanofilm. (a) AFM image of the PTH nanofilm. (b) CD spectra of native HSA and the PTH nanofilm. (c) ThT fluorescence change as a function of phase transition time, with the insets showing the corresponding fluorescence microscopic image for ThT staining and the optical microscopy image for Congo red staining. (d) The CLSM image shows that SA was successfully entrapped in the nanofilm to form a hybrid nanofilm. (e) WCA of bare Si, PTH and PTH@SA coated Si. The data are presented as the mean \(\pm\) s.d.; \(\mathrm{n} = 4\) . (f) XPS spectra of pristine Si, PTH and PTH@SA nanofilm coated Si. (g) High resolution \(\mathrm{C_{1s}}\) deconvolution spectra of the PTH and PTH@SA nanofilm. (h-k) The frequency and adsorption mass of HSA (h), PTH (i), the mixture of HSA and SA (j) and PTH@SA (k) adsorbed on the Au chip as a function of time.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 103, 850, 158]]<|/det|> +4, The CD data that support helix-to-sheet conversion is not sufficient. It is not convincing the end product is a beta-sheet-only material with only CD spectra. Though, whether this claim is true or not seems not affecting functionality of the nanofilm. + +<|ref|>text<|/ref|><|det|>[[148, 160, 851, 362]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. We apologize for the ambiguity caused by our inappropriate wording. CD is a spectroscopic technique commonly used to investigate protein secondary structures through characteristic CD spectra produced by major protein secondary structure \(^{37}\) . As shown in Fig. 1d, the negative \(\alpha\) - helix peak for the native BSA at 208 and 222 nm was shifted to the single negative band at 216 nm for \(\beta\) - sheet structure after the phase transition \(^{38}\) , indicating that the TCEP- induced protein unfolding was accompanied by a change in major secondary structure from \(\alpha\) - helix to \(\beta\) - sheet, rather than \(\beta\) - sheet being the only protein secondary structure in the nanofilm. In addition, the deconvolution of the amide I and II in the FTIR spectra of the PTB and PTB@SA nanofilm also supported the increased \(\beta\) - sheet structure in nanofilms compared with the native BSA (Supplementary Fig. 2). We have rephrased the corresponding description in the revised manuscript to articulate our point (Page 6). + +<|ref|>sub_title<|/ref|><|det|>[[148, 381, 848, 417]]<|/det|> +## 5, On page 14, it is not clear why a balanced composition of positively and negatively charged amino acid residues is critical for anti-fouling and anti-biofilm surface. + +<|ref|>text<|/ref|><|det|>[[147, 418, 851, 732]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. BSA is a macromolecule with natural antifouling properties, which is related to the balance of positive and negative charges on albumin protein surface (the balance of glutamic acid and lysine) \(^{31,39}\) . This mixed- charge surface, similar to zwitterionic polymers, can effectively resist contamination by proteins and bacteria through hydration. However, fabricating of BSA coating on multiple classes of materials have been limited by surface chemistry. Based on the mixed- charge principle, some scholars have successfully constructed natural peptide surfaces with antifouling properties by selecting appropriate amino acid residues \(^{27}\) . In this study, we used a reducing agent to induce BSA to unfold and further self- assemble into a macroscopic nanofilm, which is a controllable process rather than just non- specific adsorption of proteins on the surface. The resultant biobased coating has a near- neutral surface charge, as reflected by the zeta potential results of the material (Fig. 3a). In this way, such a coating with both hydrogen bonding groups and zwitterionic groups can not only solvate the material through electrostatic interactions, but also form hydrogen bonds with water molecules through peptide bonds \(^{40}\) , thereby forming a hydration layer on the surface as a barrier to prevent protein or microorganisms from contacting, and finally achieve the effect of anti- protein adsorption and anti- biofilm synergistically. The related discussion has been supplemented and revised in the manuscript (Page 15). + +<|ref|>text<|/ref|><|det|>[[148, 751, 850, 842]]<|/det|> +6, On page 25, this description is confusing "Compared with the unmodified catheter, the antifibrotic catheter (i.e., PTB@SA- Rapamycin catheter) decreased lumen reduction from \(56.1\%\) to \(9.8\%\) (Fig. 6a, b), with a mean percentage improvement of \(82.5\%\) , which was superior to the values reported in preclinical studies of other local treatments (Fig. 6c, Table S5)." It is suggested to break this description into at least two sentences. + +<|ref|>text<|/ref|><|det|>[[148, 844, 850, 899]]<|/det|> +Response: Thanks to the reviewer for the reminder. To make the presentation more concise, we have split this description into the following 2 sentences and amended it based on the results of the supplementary animal experiments. "Compared with the unmodified catheter, the anti- fibrotic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +catheter (i.e., PTB@SA- Rapamycin catheter) decreased lumen reduction from \(51.8\%\) to \(10.6\%\) (Fig. 6a, b). Such a mean percent improvement of up to \(79.2\%\) is superior to values reported in preclinical studies of other topical treatments (Fig. 6c, Table S5).” + +<|ref|>text<|/ref|><|det|>[[148, 160, 851, 232]]<|/det|> +7. For efficacy study (ureteral stricture), it would be beneficial compare lumen diameters of subgroup VI with healthy (non-injuries) rabbit lump diameters to give a complete picture of treatment outcome. In addition, the group size \((n = 3)\) is too small to generate robust mean and conclusion. + +<|ref|>text<|/ref|><|det|>[[148, 235, 853, 343]]<|/det|> +Response: Thanks to the reviewer for this valuable comment. Retrograde urethrography was performed to evaluate the diameter of the urethra in normal healthy rabbits and subgroup VI (PTB@SA- Rapamycin). As shown in Supplementary Fig. 37, the ratio of urethral diameter to individual femoral shaft diameter did not show a statistical difference between the above two groups, further suggesting that the anti- fibrotic catheter is effective in preventing stricture formation by modulating the tissue healing process. + +<|ref|>text<|/ref|><|det|>[[148, 345, 851, 529]]<|/det|> +Regarding the sample size, we sincerely accepted the reviewer's suggestion and supplemented animal experiments to increase the sample size of each group to 5. We have revised the relevant data (Fig. 6 and Supplementary Fig. 37–45) and the corresponding descriptions in the revised manuscript (Page 27–31). In addition, we collected optical photographs of urethral lesions in each group and integrated them in Fig. 6d. It can be observed that except for the PTB@SA- rapamycin group, the rabbit urethral injury developed into whitish, hard, wrinkled and even raised scars after 1 month in the other groups. However, in the anti- fibrotic catheter group, the urethral injury repaired well with smooth and rosy urethral mucosa. Overall, the results of animal experiments definitively demonstrate the efficacy and safety of the anti- fibrotic catheter in preventing stricture formation after urethral injury. + +<|ref|>image<|/ref|><|det|>[[150, 540, 833, 700]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 716, 851, 825]]<|/det|> +
Figure S37. Comparison of urethral diameter in normal healthy rabbits and rabbits using PTB@SA-Rapamycin catheter after urethral injury. (a) Representative retrograde urethrogram of healthy rabbits. (b) Representative retrograde urethrogram of the rabbit in the anti-fibrotic catheter group. (c) The ratio of urethra diameter to femoral shaft diameter in normal healthy rabbits and rabbits in anti-fibrotic catheter (PTB@SA-Rapamycin) group. Data are presented as the mean \(\pm \mathrm{s.d.}\) ; \(n = 5\) . ns means no statistical difference.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 123, 321, 137]]<|/det|> +## Comments to the author + +<|ref|>text<|/ref|><|det|>[[148, 141, 851, 252]]<|/det|> +The authors of this manuscript have done an excellent work designing a catheter covered with a protein nanofilm capable of preventing urethral stricture by prevention of bacterial colonization and controlled release of rapamycin. The authors examined the physical characteristics, antibacterial properties, and drug release functions of the protein nanofilm. By indwelling the hybrid coating- modified catheter in the urethra of adult male rabbits, the authors demonstrated that the catheter could effectively prevent the development of urethral stricture. + +<|ref|>text<|/ref|><|det|>[[149, 253, 693, 269]]<|/det|> +Generally, this work is innovative and great. A few comments are as follows: + +<|ref|>sub_title<|/ref|><|det|>[[149, 291, 174, 304]]<|/det|> +## Q1 + +<|ref|>text<|/ref|><|det|>[[148, 308, 851, 436]]<|/det|> +In the first paragraph of the introduction, the author pointed out a clinical problem that current curative treatment options, such as urethrotomy, dilatation and urethroplasty, for urethral stricture could not achieve satisfactory results. This clinical problem exists in patients who have already developed severe urethral strictures. However, the animal model used in this study only simulated the acute urethral injury, and the results could only demonstrate the fact that PTB@SA- Rapamycin catheter was able to prevent the occurrence of urethral stricture. Therefore, the clinical problem raised in the introduction should be revised. + +<|ref|>text<|/ref|><|det|>[[148, 437, 851, 695]]<|/det|> +Response: Thanks to the reviewer for your helpful comments. We have revised the Introduction to clarify precisely the clinical concerns of this work. Urethral stricture is a common disease after urethral injury. The incidence of mucosal injury and secondary urethral strictures after various transurethral procedures, including traumatic catheterization, tends to increase with an aging population and advances in medical technology. Due to the complexity of its treatment, once the urethral injury develops into urethral stricture, it will pose challenges to both patients and urologists. This situation has also prompted researchers and clinicians to explore novel and clinically promising alternative or adjunctive strategies beyond surgery. In this work, targeting the well- defined pathological basis of ECM metabolism dysregulation in urethral strictures, our main intention is to combine a local anti- fibrotic drug delivery system with the urinary catheter to construct a novel drug- loaded device that can prevent the formation of urethral stricture by inhibiting fibrosis process. We apologize for the ambiguity caused by our inappropriate description and have revised the Introduction as follows to emphasize that this study addresses urethral strictures secondary to urethral injury (Page 2). + +<|ref|>text<|/ref|><|det|>[[148, 697, 851, 899]]<|/det|> +Urethral stricture is a common disease (200- 1200 cases per 100000 individuals22) following urethral injury. The pathological state of extracellular matrix (ECM) metabolic disorder caused by injury (including surgery, pelvic fracture, inflammatory injury and traumatic catheterization) results in the replacement of normal urethral tissue by dense fibers interspersed with fibroblasts22. This aggravated fibrosis eventually leads to progressive urethral lumen reduction consequent symptomatic dysuria and even renal impairment. With the growing demand for healthcare brought about by the aging population and advances in medical technology, the increasing incidence of mucosal injury and secondary urethral strictures caused by various transurethral procedures has attracted great attention23,24. Especially in patients with spinal cord injury or in intensive care, urethral stricture or erosion due to long- term catheterization has been reported as high as 8.7%25. Once urethral injury progresses to urethral stricture, subsequent treatment is extremely troublesome, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 232]]<|/det|> +which will pose challenges to both patients and urologists. The long- term success rate of the most commonly used endoscopic treatment is only \(20 - 30\%^{22}\) , and although urethroplasty has developed rapidly in recent years, fibrous scarring may still develop in the urethral submucosa after substitute surgery, and this open surgery is less suitable for the elderly and frail patients. Indeed, the pathological state of ECM metabolic disorder and subsequent scar repair is not be rectified regardless of the treatment \(^{26}\) . Therefore, there is an urgent need to develop alternative strategies other than surgery and attempt to focus on regulating healing by inhibiting fibrosis progression following urethral injury, thereby preventing urethral strictures. + +<|ref|>sub_title<|/ref|><|det|>[[148, 254, 175, 268]]<|/det|> +## Q2 + +<|ref|>text<|/ref|><|det|>[[148, 272, 851, 361]]<|/det|> +Why did the authors choose rapamycin as the therapeutic component preventing the urethral stricture? A meta- analysis published in European Urology by Pang et al. showed that mitomycin C had the best effect on urethral stricture among drugs used in the included clinical trials. Compared with other drugs, what are the advantages and disadvantages of rapamycin in treating urethral stricture? + +<|ref|>text<|/ref|><|det|>[[148, 364, 851, 472]]<|/det|> +Response: Thanks to the reviewer for this comment. it should be pointed out that as a proof- of- concept study, the developed drug delivery system in this work is versatile and scalable. As shown in Supplementary Fig. 46, the PTB@SA nanofilm can also be used for long- term delivery of paclitaxel. Thus, it is feasible to encapsulate and immobilize other therapeutic agents using a similar strategy. In terms of preventing urethral strictures, we chose rapamycin as the therapeutic component of drug- loaded urinary catheters for the following two reasons: + +<|ref|>text<|/ref|><|det|>[[149, 475, 851, 694]]<|/det|> +1) Rapamycin (also known as sirolimus), which was initially used to prevent immune rejection response after transplantation, later also played an important role in inhibiting intimal hyperplasia and preventing coronary restenosis due to its favorable antiproliferative and antifibrotic effects. Inspired by this, our group verified the potential availability of rapamycin in inhibiting urethral stricture after urethral injury through a series of in vitro and in vivo experiments. For instance, after urethral injury, fibroblast proliferation and collagen deposition in rabbit urethral tissue were significantly inhibited by intraurethral perfusion of rapamycin for 4 weeks \(^{41}\) . In addition, the cell proliferation and collagen synthesis of human urethral scar-derived fibroblasts were also inhibited in a dose-dependent manner under treatment with rapamycin \(^{42}\) . These studies laid a solid research foundation for this work and encouraged us to further utilize rapamycin to construct a local drug delivery system for intervening urethral stricture formation. + +<|ref|>text<|/ref|><|det|>[[149, 697, 851, 899]]<|/det|> +2) In addition to efficacy, the safety of drug-loaded devices also has important implications for their clinical prospects. Admittedly, local application of mitomycin-C (MMC) showed encouraging results in the prevention and treatment of urethral stricture. However, as a cytotoxic chemotherapeutic agent, topical application of MMC to the mucosa has been reported to cause side effects such as fibrinous debris (which further causes airway obstruction), corneal edema and perforation, necrotizing scleritis and corneal ulceration \(^{43,44}\) . Moreover, a prospective study showed that 68% of subjects experienced mild to moderate urinary adverse events (including ureteral stenosis, hydronephrosis, vomiting, flank pain, hematuria and urinary tract infection) after using a sustained-release hydrogel polymer-based formulation containing MMC \(^{45}\) . Besides, according to a multi-institutional study published in the Journal of Urology, severe complications such as osteitis pubis, rectourethral fistula and necrosis of the bladder floor + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 85, 850, 214]]<|/det|> +occurred in \(7\%\) of patients undergoing endoscopic incision followed by MMC injection46. In contrast, rapamycin, a commonly used and classic therapeutic component of coronary drug-eluting stents, has negligible side effects through topical application47. The satisfactory outcome of rapamycin-eluting coronary stents in long-term clinical practice demonstrates the availability and safety of rapamycin in the field of local drug delivery, which also encouraged us to integrate rapamycin into the surface coating of the urinary catheter to achieve intraurethral drug therapy. The above discussion is condensed and supplemented in the revised manuscript (Page 30\~31). + +<|ref|>sub_title<|/ref|><|det|>[[149, 236, 174, 249]]<|/det|> +## Q3 + +<|ref|>text<|/ref|><|det|>[[148, 252, 851, 436]]<|/det|> +The author mentioned that the nanofilm surface exhibited abundant functional groups, which enabled the nanofilms to undergo ligand bonding, electrostatic interaction, hydrophobic interaction and hydrogen bonding with virtually arbitrary material, including metal, organic or inorganic materials. According to our experience, this property of the nanofilm makes it likely to interact with various organic and inorganic substances in urine and result in surfaces blockade, stone formation and catheter blockage. Is there any data showing the appearance of the hybrid nanofilm- coated catheters after indwelling for 30 days? We want to check if the surface of all catheters were still clear at the end of the experiment. In fact, bacterial contamination and stone formation are both thorny challenges in the development of functional urinary catheters. + +<|ref|>text<|/ref|><|det|>[[147, 437, 851, 900]]<|/det|> +Response: Thank the reviewer for this helpful comment. Encrustation is indeed a thorny problem for patients who require long- term indwelling catheters, which involves the deposition of inorganic salts on the surface of the device or the inner wall of the lumen, and further leads to pain, difficult removal of catheter, blockage of urinary flow and intractable bacterial biofilms. Two important aspects that promote the development of crusts include supersaturation of crystals in the urine and bacterial infection. However, due to the unique calcium metabolism of rabbits, that is, almost all calcium in the diet can be absorbed while the excess calcium is excreted through the kidney to maintain blood calcium stability, the calcium in rabbit urine is affected by the combination of diet, water intake, physical activity and other hormones48,49. To better exclude the influence of irrelevant variables on the results, we performed a well- established in vitro encrustation experiment to compare the formation of urinary encrustations on bare and PTB@SA- modified urinary catheters in artificial urine, artificial urine in the presence of \(P\) . mirabilis or human urine50. As shown in Supplementary Fig. 20 a and b, there was no difference in encrustation weight between the control and PTB@SA- coated samples exposed to the same urine environment at each time point, except that the weight of crystals formed in human urine on day 3 was smaller in the PTB@SA group. At the same time point, the presence of \(P\) . mirabilis significantly aggravated the encrustation, because the urease produced by \(P\) . mirabilis would increase the pH of urine and promote the deposition of calcium phosphate and magnesium51. After 30 days, both the bare catheter and the PTB@SA coated surfaces were covered with cauliflower- like smooth deposits and interspersed with large coffin- like crystals (Supplementary Fig.20 c). Furthermore, we performed Energy Dispersive Spectroscopy (EDS) analysis of these deposits and determined that the smooth layer was mainly composed of Ca, C, P and O, presumably being calcium carbonate apatite crystallites. while the large coffin- shaped crystals were composed of Mg, O and P, which could be assigned to struvite (magnesium phosphate) (Supplementary Fig.20 d- i). Overall, the PTB@SA nanofilm did not induce more severe encrustation formation on the device surface within 1 month, indicating that it would not pose an + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +additional threat when applied to construct functional urinary catheters. Corresponding results and discussions have been incorporated into the revised manuscript (Page 16) and supporting information (Page S15\~S16). + +<|ref|>text<|/ref|><|det|>[[148, 142, 851, 305]]<|/det|> +It is worth pointing out that since the PTB@SA coating has a balanced surface charge distribution similar to that of zwitterionic polymers, it can effectively avoid bacterial adhesion and biofilm formation, which may contribute to reduce encrustation caused by \(P\) . mirabilis adhesion and its subsequent migration along the catheter surface4. However, in this in vitro encrustation model, the coating failed to kill \(P\) . mirabilis present in the device and thus exhibited a similar encrustation propensity to the unmodified catheter. As stated by the reviewers, anti- encrustation is an important challenge for medical devices such as urinary catheters and ureteral stents. Although the performance of the coating reported in this work in reducing crusts is not superior enough, this will become the focus of our next research work. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[165, 99, 835, 778]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 790, 851, 900]]<|/det|> +
Figure S20. In vitro evaluation of the encrustation performance of bare silicone catheters and the PTB@SA nanofilm-modified catheters. (a) The weight of crystals deposited on bare catheters or the PTB@SA coated catheters after exposure to artificial urine, artificial urine containing Proteus mirabilis (P. mirabilis), or human urine. Data are presented as the mean \(\pm\) s.d; n=4. \* P<0.05. (b) The weight of crystals deposited on bare catheters or the PTB@SA coated catheters during the first week. Data are presented as the mean \(\pm\) s.d; n=4. \* P<0.05. (c) SEM of bare catheter and the
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 852, 158]]<|/det|> +PTB@SA coating after 30 days of encrustation experiment in vitro. (d) SEM image of bare catheter surface after encrustation experiment. (e, f) EDS analysis of area A (e) and B (f) in Fig S20 d. (g) SEM image of the PTB@SA coating surface after encrustation experiment. (h, i) EDS analysis of area A (h) and B (i) in Fig S20 g. + +<|ref|>sub_title<|/ref|><|det|>[[148, 179, 175, 193]]<|/det|> +## Q4 + +<|ref|>text<|/ref|><|det|>[[147, 196, 852, 360]]<|/det|> +The nanofilm showed a consistent WCA approximately \(80^{\circ}\) . This means the nanofilm- coated catheter is not very hydrophilic and has higher friction with urethral. Was lubricant used during indwelling catheters. If lubricant was used, were there any experiments investigating if the lubricant had any effect on the stability of the nanofilm and the controlled drug release? Catheters for clinical use are often covered with super hydrophilic film or lubricants to avoid urethral injury and inflammation. Consistently, the authors observed that the pristine urinary catheter caused edema and necrosis in rabbits' urethral mucosa after indwelling for 1 month. Parameters about the friction should be compared among pristine urinary catheter and nanofilm coated catheters. + +<|ref|>text<|/ref|><|det|>[[147, 363, 852, 658]]<|/det|> +Response: Thanks to the reviewer for this helpful comment. The abundant functional groups exposed on the nanofilm surface, especially the sodium alginate contained therein, allow the coating to interact with water molecules to hydrate and lubricate the catheter to a certain extent. Furthermore, the coefficient of friction (COF) of the saline- wetted unmodified urinary catheter and the PTB@SA- coated urinary catheter was characterized by a coefficient of friction meter. As shown in Figure R2, the COF of the PTB@SA membrane was lower than that of the unmodified catheter. Therefore, in all animal experiments involving indwelling urinary catheters, the catheters were lubricated with saline prior to catheterization. This organic- free physiological solution did not affect the controlled release of the encapsulated drug, and theoretically other water- soluble lubricants are also suitable. The urethral implantation experiment (Supplementary Fig. 19) and H&E staining of the uninjured urethra in each group in the urethral injury experiment (Supplementary Fig. 38) showed that catheterization performed by this method and indwelling catheter for one month did not cause edema, injury or necrosis in the urethral mucosa and submucosa, indicating that the functionalized urinary catheter has good histocompatibility and practical prospects, while the urethral edema and inflammation shown in Fig. 3 in the control catheter group were mainly due to bacterial urinary tract infection caused by the dense bacterial biofilm on the pristine urinary catheter surface. + +<|ref|>image<|/ref|><|det|>[[325, 673, 622, 833]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 844, 849, 880]]<|/det|> +
Figure R2. Friction coefficients of bare urinary catheter and the PTB@SA nanofilm-modified catheter. Data are presented as the mean \(\pm\) s.d; n=3. \*\*\* P<0.001.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 87, 174, 100]]<|/det|> +## Q5 + +<|ref|>text<|/ref|><|det|>[[149, 104, 848, 140]]<|/det|> +Reference should be added for the sentence "... the PTB@SA nanofilm still exhibited a low negative surface zeta potential, and thus may keep a good anti- biofilm ability." + +<|ref|>text<|/ref|><|det|>[[148, 141, 851, 269]]<|/det|> +Response: Thank the reviewer for this comment. Regarding the reason for the excellent anti- biofilm performance of the PTB@SA nanofilm, we supplied the relevant discussion in page 15 and cite reference as Ref. 43, which demonstrates the formation of ultra- low fouling peptides from certain natural amino acids based on the mixed charge design principle. Similarly, the balanced distribution of charged amino acids on the nanofilm surface in this work can also form a hydration layer on the surface of the material, which acts as a barrier against bacterial adhesion and thus resists biofilm formation. + +<|ref|>sub_title<|/ref|><|det|>[[149, 290, 175, 304]]<|/det|> +## Q6 + +<|ref|>text<|/ref|><|det|>[[148, 308, 850, 399]]<|/det|> +We noticed that four rabbits were in each group for the evaluation of the antibacterial biofilm performance of the nanofilm and three rabbits were in each group evaluate the effect of nanofilm on urethral stricture. How did the authors decide the sample size for each experiment? Why did experiments with more complex surgical procedures (more likely to be biased) have smaller sample sizes? + +<|ref|>text<|/ref|><|det|>[[148, 401, 851, 602]]<|/det|> +Response: Thank the reviewer for this comment. For the complex animal model such as urethral injury, in order to better confirm the efficacy of the anti- fibrotic catheter, we supplemented the animal experiment to increase the sample size of each group to 5. Representative images of retrograde urethrography are shown below (Fig.R1). In addition, we collected optical photographs of urethral lesions in each group and integrated them in Fig. 6d. It can be observed that except for the PTB@SA- rapamycin group, the rabbit urethral injury developed into whitish, stiff, wrinkled and even raised scars after 1 month in the other groups. However, in the anti- fibrotic catheter group, the urethral injury repaired well with smooth and ruddy urethral mucosa. We have revised the relevant data (Fig. 6 and Supplementary Fig. 37- 45) and the corresponding descriptions in the revised manuscript (Page 27- 31). Overall, the results of animal experiments definitively demonstrate the efficacy and safety of the anti- fibrotic catheter in preventing stricture formation after urethral injury. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[205, 93, 795, 393]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 419, 848, 454]]<|/det|> +
Figure R1. Representative images of retrograde urethrography after 30 days. The yellow arrow indicates the coagulation site.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 92, 840, 800]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 808, 850, 900]]<|/det|> +
Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury. a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \(76\%\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 343]]<|/det|> +Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . c, Corresponding results of the PTB@SA- Rapamycin catheter compared with other preclinical studies of topical therapy to suppress urethral stricture. d, Gross specimen, H&E staining and immunohistochemical staining with anti- alpha smooth muscle actin antibody (α- SMA, brown), anti- matrix metalloproteinase 1 antibody (MMP1, brown), and type I collagen antibody (Collagen I, green) of the urethral injury sites at 1 month. Nuclei (blue) were stained with DAPI. Yellow triangles indicate urethral scar tissue. The asterisks represent urethral luminal side, and the dotted lines indicate the boundary between the submucosa and the muscularis. e, Quantification of \(\alpha\) - SMA, MMP1 positive area and Collagen I fluorescence intensity in Fig. 6d. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . f, g, Hematological examination to show the changes of alanine aminotransferase (ALT, f) and aspartate aminotransferase (AST, g) with different treatments for 1 month. Data are mean \(\pm\) s.d.; \(\mathrm{n = 5}\) . h, H&E staining of rabbit liver after systemic administration or indwelling rapamycin sustained- release catheter for 1 month. (a, d) i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst- releasing; vi, PTB@SA- Rapamycin. \* \(\mathrm{P< 0.05}\) , \*\* \(\mathrm{P< 0.01}\) , \*\*\*\* \(\mathrm{P< 0.001}\) , \*\*\*\* \(\mathrm{P< 0.0001}\) , ns means no statistical difference. + +<|ref|>text<|/ref|><|det|>[[148, 364, 175, 378]]<|/det|> +Q7 + +<|ref|>text<|/ref|><|det|>[[148, 381, 850, 455]]<|/det|> +The authors cannot directly compare the results of independent experiments performed by different operators under different experimental conditions (such as surgical instruments, degree of urethral injury and therapy duration) to conclude that the effect of nanofilm in this study was better than that of drugs reported in other studies. + +<|ref|>text<|/ref|><|det|>[[148, 455, 851, 620]]<|/det|> +Response: Thank the reviewer for this comment. We fully agree with the reviewer's comments and supplied the following description to the Methods (Page 43). In order to exclude the interference of various experimental conditions to more objectively compare the preventive effect on urethral stricture reported in independent studies, we reprocessed the original data from each study and calculated the mean percent improvement in lumen stenosis for each intervention according to the following formula to quantify the improvement in severity of urethral strictures with different treatments (Fig. 6c), Where Lumen reduction(Control) represents the reduction degree of the urethral lumen in the control group, and Lumen reduction(Experiment) represents the reduction degree of the urethral lumen in the experimental group. + +<|ref|>equation<|/ref|><|det|>[[175, 623, 822, 654]]<|/det|> +\[\mathrm{Mean~percent~improvement} = \frac{\mathrm{Lumen~reduction(Control)} - \mathrm{Lumen~reduction(Experiment)}}{\mathrm{Lumen~reduction(Control)}}\times 100\%\] + +<|ref|>text<|/ref|><|det|>[[148, 660, 850, 695]]<|/det|> +The relevant information of each study, including the drug used, the method of administration, and the outcomes of the experimental and control group, are all listed in detail in Table S5. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[163, 115, 840, 365]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[148, 86, 839, 102]]<|/det|> +Table S5. Overview of preclinical outcomes of topical therapy to prevent urethral strictures. + +
StudyTopical interventionLumen reductionMean percent improvements in lumen stenosis
Control groupExperimental group
Kurt 2017[7]40 mg Triamcinolone, submucosal injection, once91.0%49.0%46.2%
Chong 2011[8]0.1 mg Rapamycin, urethral irrigation, daily for 28 days69.1%56.6%18.1%
1 mg Rapamycin, urethral irrigation, daily for 28 days69.1%36.5%47.2%
Kurt 2017[7]0.5 mg/mL Mitomycin-C (MMC), hydropathic compress, once91.0%45.0%50.5%
0.2 mg Insulin-like growth factor 1 (IGF-1), impregnated collagen sutured to the catheter, catheterization for 14 days79.8%39.3%50.8%
Shinchi 2019[9]0.01 mg Docetaxel, urethral irrigation, daily for 28 days84.7%48.0%43.3%
0.1 mg Docetaxel, urethral irrigation, daily for 28 days84.7%36.9%56.4%
This research3 mg Rapamycin, sustained release coating modified catheter, catheterization for 30 days51.8%10.6%79.2%
+ +<|ref|>text<|/ref|><|det|>[[148, 381, 851, 492]]<|/det|> +In summary, by comparing the mean percent improvement in lumen stenosis between this study and the results reported in other literatures, rather than the value of urethral lumen in independent studies, the influence of experimental conditions on the comparison results can be offset to a certain extent. The mean percent improvement in luminal stenosis with the anti- fibrotic catheter was as high as \(79.2\%\) , suggesting a potential advantage of the PTB@SA- rapamycin catheter in the prevention of urethral strictures compared with other topical dosage regimens. + +<|ref|>sub_title<|/ref|><|det|>[[148, 513, 175, 527]]<|/det|> +## Q8 + +<|ref|>text<|/ref|><|det|>[[148, 530, 850, 583]]<|/det|> +In the figure legend of figure 6, the sentence "(b, d, e) i, Control, ii; Unmodified catheter; iii,..." should be revised. Only a and d are numbered. Please check the use of commas and semicolons. + +<|ref|>text<|/ref|><|det|>[[148, 586, 850, 621]]<|/det|> +Response: Thank the reviewer for this comment, and we are sorry for this error in the legend. We have made revisions in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 643, 175, 657]]<|/det|> +## Q9 + +<|ref|>text<|/ref|><|det|>[[148, 660, 850, 714]]<|/det|> +At least, there are some errors in references 56. Some authors are missing and the original title should be "Sirolimus- eluting Biodegradable Poly- L- Lactic Acid Stent to Suppress Granulation Tissue Formation in the Rat Urethra." + +<|ref|>text<|/ref|><|det|>[[148, 716, 850, 750]]<|/det|> +Response: Thank the reviewer for this comment. We have corrected this reference as follows and proofread all references cited in the article. + +<|ref|>text<|/ref|><|det|>[[148, 753, 850, 787]]<|/det|> +"Kim, K. Y. et al. Sirolimus- eluting Biodegradable Poly- L- Lactic Acid Stent to Suppress Granulation Tissue Formation in the Rat Urethra. Radiology 286, 140- 148 (2017)." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 112, 253, 128]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[145, 140, 852, 900]]<|/det|> +1. Nilles, J., Weiss, J. & Theile, D. Crystal violet staining is a reliable alternative to bicinchoninic acid assay-based normalization. Biotechniques 73, 131–135 (2022). +2. Riol, M. et al. Staphylococcus epidermidis originating from titanium implants infects surrounding tissue and immune cells. Acta Biomater. 10, 5202–5212 (2014). +3. Gu, J., Su, Y., Liu, P., Li, P. & Yang, P. An Environmentally Benign Antimicrobial Coating Based on a Protein Supramolecular Assembly. ACS Appl. Mater. Interfaces 9, 198–210 (2017). +4. Ramstedt, M. et al. Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations. Macromol. Biosci. 19, 1–26 (2019). +5. Solano, C., Echeverz, M. & Lasa, I. Biofilm dispersion and quorum sensing. Curr. Opin. Microbiol. 18, 96–104 (2014). +6. Zhang, N. et al. Different types of T-effector cells orchestrate mucosal inflammation in chronic sinus disease. J. Allergy Clin. Immunol. 122, 961–968 (2008). +7. Uthamanthil, R. K. et al. Urinary catheterization of male rabbits: A new technique and a review of urogenital anatomy. Journal of the American Association for Laboratory Animal Science vol. 52 180–185 at (2013). +8. Hua, X. et al. An Experimental Model of Anterior Urethral Stricture in Rabbits With Local Injections of Bleomycin. Urology 116, 230.e9-230.e15 (2018). +9. Abizaid, A. Sirolimus-eluting coronary stents: A review. Vasc. Health Risk Manag. 3, 191–201 (2007). +10. Rashidbenam, Z. et al. Overview of Urethral Reconstruction by Tissue Engineering: Current Strategies, Clinical Status and Future Direction. Tissue Eng. Regen. Med. 16, 365–384 (2019). +11. Ueshima, E. et al. Macrophage-secreted TGF-β1 contributes to fibroblast activation and ureteral stricture after ablation injury. Am. J. Physiol. - Ren. Physiol. 317, F52–F64 (2019). +12. Chapman, D., Kinnaird, A. & Rourke, K. Independent Predictors of Stricture Recurrence Following Urethroplasty for Isolated Bulbar Urethral Strictures. J. Urol. 198, 1107–1112 (2017). +13. Kurt, O. et al. Effect of Tadalafil on Prevention of Urethral Stricture after Urethral Injury: An Experimental Study. Urology 91, 243.e1-243.e6 (2016). +14. Yoshizaki, A. et al. Treatment with rapamycin prevents fibrosis in tight-skin and bleomycin-induced mouse models of systemic sclerosis. Arthritis Rheum. 62, 2476–2487 (2010). +15. Rostaing, L. & Kamar, N. mTOR inhibitor/proliferation signal inhibitors: entering or leaving the field? J. Nephrol. 23, 133–142 (2010). +16. N., F.-R. One-Year Results for the ROBUST III Randomized Controlled Trial Evaluating the Optilume® Drug-Coated Balloon for Anterior Urethral Strictures. Letter. J. Urol. 207, 866–875 (2022). +17. Guzmán-Esquivel, J. et al. Metalloproteinase-1 usefulness in urethral stricture treatment. Int. Urol. Nephrol. 43, 763–769 (2011). +18. Shinchi, M. et al. Insulin-like growth factor 1 sustained-release collagen on urethral catheter prevents stricture after urethral injury in a rabbit model. Int. J. Urol. 26, 572–577 (2019). +19. Kurt, O. et al. Effect of mitomycin - C and triamcinolone on preventing urethral strictures. Int. Braz J Urol 43, 939–945 (2017). +20. Fu, D., Chong, T., Li, H., Zhang, H. & Wang, Z. Docetaxel inhibits urethral stricture formation, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[198, 85, 590, 101]]<|/det|> +an initial study in rabbit model. PLoS One 9, 1–6 (2014). + +<|ref|>text<|/ref|><|det|>[[147, 105, 850, 140]]<|/det|> +21. Chong, T. et al. Rapamycin inhibits formation of urethral stricture in rabbits. J. Pharmacol. Exp. Ther. 338, 47–52 (2011). + +<|ref|>text<|/ref|><|det|>[[147, 143, 848, 177]]<|/det|> +22. Hampson, L. A., McAninch, J. W. & Breyer, B. N. Male urethral strictures and their management. Nat. Rev. Urol. 11, 43–50 (2014). + +<|ref|>text<|/ref|><|det|>[[147, 180, 848, 214]]<|/det|> +23. Lumen, N. et al. Etiology of Urethral Stricture Disease in the 21st Century. J. Urol. 182, 983–987 (2009). + +<|ref|>text<|/ref|><|det|>[[147, 217, 848, 251]]<|/det|> +24. Chen, M. L., Correa, A. F. & Santucci, R. A. Urethral Strictures and Stenoses Caused by Prostate Therapy. Rev. Urol. 18, 90–102 (2016). + +<|ref|>text<|/ref|><|det|>[[147, 254, 848, 288]]<|/det|> +25. Hollingsworth, J. M. et al. Determining the Noninfectious Complications of Indwelling Urethral Catheters. Ann. Intern. Med. 159, 401–410 (2013). + +<|ref|>text<|/ref|><|det|>[[147, 290, 848, 325]]<|/det|> +26. Prihadi, J. C., Sugandi, S., Siregar, N. C., Soejono, G. & Harahap, A. Imbalance in extracellular matrix degradation in urethral stricture. Res. Reports Urol. 10, 227–232 (2018). + +<|ref|>text<|/ref|><|det|>[[147, 328, 848, 380]]<|/det|> +27. Sievert, K. D. et al. Introducing a large animal model to create urethral stricture similar to human stricture disease: A comparative experimental microscopic study. J. Urol. 187, 1101–1109 (2012). + +<|ref|>text<|/ref|><|det|>[[147, 383, 848, 417]]<|/det|> +28. Delai, F. et al. Development and characterization of urethral stricture model in rabbits. J. Med. Coll. PLA 25, 351–358 (2010). + +<|ref|>text<|/ref|><|det|>[[147, 420, 848, 454]]<|/det|> +29. Hirano, Y. et al. Myofibroblast-dominant proliferation associated with severe fibrosis in bulbar urethral strictures. Int. J. Urol. (2022) doi:https://doi.org/10.1111/iju.15053. + +<|ref|>text<|/ref|><|det|>[[147, 457, 848, 491]]<|/det|> +30. Sanyal, A. J. et al. The Natural History of Advanced Fibrosis Due to Nonalcoholic Steatohepatitis: Data From the Simtuzumab Trials. Hepatology 70, 1913–1927 (2019). + +<|ref|>text<|/ref|><|det|>[[147, 494, 848, 528]]<|/det|> +31. Hu, X. et al. Amyloid-Like Protein Aggregates: A New Class of Bioinspired Materials Merging an Interfacial Anchor with Antifouling. Adv. Mater. 32, 1–11 (2020). + +<|ref|>text<|/ref|><|det|>[[147, 531, 848, 565]]<|/det|> +32. Zhang, F. et al. Stretchable and biocompatible bovine serum albumin fibrous films supported silver for accelerated bacteria-infected wound healing. Chem. Eng. J. 417, 129145 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 568, 848, 620]]<|/det|> +33. Ouyang, J. et al. A facile and general method for synthesis of antibiotic-free protein-based hydrogel: Wound dressing for the eradication of drug-resistant bacteria and biofilms. Bioact. Mater. 18, 446–458 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 623, 848, 658]]<|/det|> +34. Chang, M. et al. Suppression of Sunscreen Leakage in Water by Amyloid-like Protein Aggregates. ACS Appl. Mater. Interfaces 13, 42451–42460 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 660, 848, 695]]<|/det|> +35. Liu, Y., Tao, F., Miao, S. & Yang, P. Controlling the Structure and Function of Protein Thin Films through Amyloid-like Aggregation. Acc. Chem. Res. 54, 3016–3027 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 697, 848, 732]]<|/det|> +36. Li, C., Xu, L., Zuo, Y. Y. & Yang, P. Tuning protein assembly pathways through superfast amyloid-like aggregation. Biomater. Sci. 6, 836–841 (2018). + +<|ref|>text<|/ref|><|det|>[[147, 734, 848, 787]]<|/det|> +37. Louis-Jeune, C., Andrade-Navarro, M. A. & Perez-Iratxeta, C. Prediction of protein secondary structure from circular dichroism using theoretically derived spectra. Proteins Struct. Funct. Bioinforma. 80, 374–381 (2012). + +<|ref|>text<|/ref|><|det|>[[147, 790, 848, 824]]<|/det|> +38. Venyaminov, S. Y., Baikalov, I. A., Wu, C. S. C. & Yang, J. T. Some problems of CD analyses of protein conformation. Anal. Biochem. 198, 250–255 (1991). + +<|ref|>text<|/ref|><|det|>[[147, 827, 848, 860]]<|/det|> +39. Chen, S., Cao, Z. & Jiang, S. Ultra-low fouling peptide surfaces derived from natural amino acids. Biomaterials 30, 5892–5896 (2009). + +<|ref|>text<|/ref|><|det|>[[147, 864, 848, 898]]<|/det|> +40. Wang, F. et al. Review of the research on anti-protein fouling coatings materials. Prog. Org. Coatings 147, 105860 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 85, 850, 120]]<|/det|> +41. Chong, T. et al. Rapamycin inhibits formation of urethral stricture in rabbits. J. Pharmacol. Exp. Ther. 338, 47–52 (2011). + +<|ref|>text<|/ref|><|det|>[[145, 123, 850, 158]]<|/det|> +42. Fu, D. et al. Rapamycin Inhibits the Growth and Collagen Production of Fibroblasts Derived from Human Urethral Scar Tissue. Biomed Res. Int. 2018, 1–9 (2018). + +<|ref|>text<|/ref|><|det|>[[145, 161, 850, 196]]<|/det|> +43. McCurdy Hueman, E. & Simpson, C. B. Airway complications from topical mitomycin C. Otolaryngol. - Head Neck Surg. 133, 831–835 (2005). + +<|ref|>text<|/ref|><|det|>[[145, 198, 850, 233]]<|/det|> +44. Cinik, R. et al. The Effect of Everolimus on Scar Formation in Glaucoma Filtering Surgery in a Rabbit Model. Curr. Eye Res. 41, 1438–1446 (2016). + +<|ref|>text<|/ref|><|det|>[[145, 235, 850, 289]]<|/det|> +45. Porta, C. et al. An evaluation of UGN-101, a sustained-release hydrogel polymer-based formulation containing mitomycin-C, for the treatment of upper urothelial carcinomas. Expert Opin. Pharmacother. 21, 2199–2204 (2020). + +<|ref|>text<|/ref|><|det|>[[145, 291, 850, 326]]<|/det|> +46. Redshaw, J. D. et al. Intralesional injection of mitomycin C at transurethral incision of bladder neck contracture may offer limited benefit: TURNS study group. J. Urol. 193, 587–592 (2015). + +<|ref|>text<|/ref|><|det|>[[145, 328, 850, 363]]<|/det|> +47. Roos, J. C. P. & Murthy, R. Sirolimus (rapamycin) for the targeted treatment of the fibrotic sequelae of Graves' orbitopathy. Eye 33, 679–682 (2019). + +<|ref|>text<|/ref|><|det|>[[145, 365, 830, 381]]<|/det|> +48. Redrobe, S. Calcium metabolism in rabbits. Semin. Avian Exot. Pet Med. 11, 94–101 (2002). + +<|ref|>text<|/ref|><|det|>[[145, 383, 850, 418]]<|/det|> +49. Clauss, M. et al. Influence of diet on calcium metabolism, tissue calcification and urinary sludge in rabbits (Oryctolagus cuniculus). J. Anim. Physiol. Anim. Nutr. (Berl). 96, 798–807 (2012). + +<|ref|>text<|/ref|><|det|>[[145, 420, 850, 492]]<|/det|> +50. Jones, D. S., Djokic, J. & Gorman, S. P. Characterization and optimization of experimental variables within a reproducible bladder encrustation model and in vitro evaluation of the efficacy of urease inhibitors for the prevention of medical device-related encrustation. J. Biomed. Mater. Res. - Part B Appl. Biomater. 76, 1–7 (2006). + +<|ref|>text<|/ref|><|det|>[[145, 494, 848, 528]]<|/det|> +51. Yao, Q. et al. Bio-inspired antibacterial coatings on urinary stents for encrustation prevention. J. Mater. Chem. B 10, 2584–2596 (2021). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 286, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 120, 832, 180]]<|/det|> +Reviewer #1: Remarks to the Author: I recognized that the authors made proper efforts for revision. The revised manuscript becomes acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 224, 842, 269]]<|/det|> +Reviewer #3: Remarks to the Author: The authors revised manuscript thoroughly and carefully. The manuscript is ready for publication. + +<|ref|>text<|/ref|><|det|>[[115, 313, 413, 357]]<|/det|> +Reviewer #4: Remarks to the Author: Thanks for your kind reply and revision. + +<|ref|>text<|/ref|><|det|>[[115, 402, 216, 415]]<|/det|> +Reviewer #5: + +<|ref|>text<|/ref|><|det|>[[115, 417, 293, 430]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 432, 872, 475]]<|/det|> +This is a tremendous body of work, very meticulous and thoughtful. Most of the responses were in- depth and most of the requested changes were made. I would like to congratulate the authors with completion of this project. There are only 3 additional comments: + +<|ref|>text<|/ref|><|det|>[[115, 477, 879, 580]]<|/det|> +1) in response to Reviewer#2 there is no direct explanation to the question #4 on what the reason is to sacrifice the animals so early after catheter removal. In real life it takes weeks for strictures to mature and appear clinically significant. Other animal models of stricture disease use a minimum of 4 weeks to 6 months before declaring a resolution/non-formation of stricture. In humans this time is even longer (no one believes success if it is reported less than 8-12 months since the treatment. I understand that authors saw all kind of indirect evidence and hopeful signs of no stricture formation in treatment group, but at 2 weeks these findings have no clinical significance. + +<|ref|>text<|/ref|><|det|>[[115, 594, 880, 640]]<|/det|> +2) Why is catheter staying for 4 weeks? under what clinical circumstances a urethral catheter would stay for that long? Not after transurethral procedures (3-7 days typically), not after traumatic catheter (7-14 days), not after prostatectomy (3-14 days). Why 4 weeks? + +<|ref|>text<|/ref|><|det|>[[115, 655, 880, 744]]<|/det|> +3) in many instances the retrograde urethrograms are shown in wrong orientation. Typically, distal portion of urethra is either shown facing 3 or 9 o'clock position (consistently through all images), cephalad is at 12 o'clock, caudad is at 6 o'clock. At least in S37 and in figure 6 the orientation is unknown and this makes these figures very confusing. Additionally, some of the radiographs are darker and with poor contrast making it difficult to assess urethral lumen, I would recommend revising these images to have consistent orientation and brightness/contrast. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 86, 273, 100]]<|/det|> +## Dear Reviewers, + +<|ref|>text<|/ref|><|det|>[[149, 104, 850, 157]]<|/det|> +We sincerely appreciate your valuable comments. We have made the revisions to all the comments in the revised manuscript (marked in red color) and supporting information (SI). The following is the point- to- point response to the reviewers' comments. + +<|ref|>text<|/ref|><|det|>[[148, 178, 852, 377]]<|/det|> +This is a tremendous body of work, very meticulous and thoughtful. Most of the responses were in- depth and most of the requested changes were made. I would like to congratulate the authors with completion of this project. There are only 3 additional comments: 1) in response to Reviewer#2 there is no direct explanation to the question #4 on what the reason is to sacrifice the animals so early after catheter removal. In real life it takes weeks for strictures to mature and appear clinically significant. Other animal models of stricture disease use a minimum of 4 weeks to 6 months before declaring a resolution/non- formation of stricture. In humans this time is even longer (no one believes success if it is reported less than 8- 12 months since the treatment. I understand that authors saw all kind of indirect evidence and hopeful signs of no stricture formation in treatment group, but at 2 weeks these findings have no clinical significance. + +<|ref|>text<|/ref|><|det|>[[148, 380, 852, 583]]<|/det|> +Response: Thanks to the reviewer for this valuable comment, we will further explore the long- term effects of the anti- fibrotic catheter in our future experiments. In response to this comment, we supplemented this limitation in the corresponding section of Results and Discussion on page 26 as follows: "The above results suggest that the anti- fibrotic catheter has shown impressive preliminary results in retarding the progression of urethral injuries to strictures, but do have a limitation that its long- term effect (six months to one year) in inhibiting urethral strictures need to be clarified in future experiments." In addition, in the Summary section (page 31), we have revised the wording as follows to make the statement more rigorous and objective. "In this regard, the promotion of PTB@SA- Rapamycin catheters as an alternative to conventional catheters is expected to be of great benefit to numerous people at high risk for urethral strictures (eg, undergoing transurethral intervention, traumatic catheterization or urethroplasty)." + +<|ref|>text<|/ref|><|det|>[[148, 604, 850, 657]]<|/det|> +2) Why is catheter staying for 4 weeks? under what clinical circumstances a urethral catheter would stay for that long? Not after transurethral procedures (3-7 days typically), not after traumatic catheter (7-14 days), not after prostatectomy (3-14 days). Why 4 weeks? + +<|ref|>text<|/ref|><|det|>[[148, 679, 852, 732]]<|/det|> +Response: Thanks to the reviewer for this valuable comment. As mentioned by the reviewer, the intervention time used in the animal experiment should take into account the actual clinical needs. The specific reasons for indwelling the catheter for 1 month after urethral injury are stated as follows. + +<|ref|>text<|/ref|><|det|>[[148, 735, 852, 898]]<|/det|> +1) Due to the unique anatomical structure of the urethra and the stimulating effect of urine, the healing time of urethral wounds is longer than that of skin tissue, with each healing stage lagging behind that of skin. It has been reported that rat urethral injury ends the proliferative phase characterized by fibroblast proliferation activation and angiogenesis on the 10th day1, and the subsequent maturation and remodeling phase involving the arrangement of collagen and other connective tissues around the urethra is a key stage of urethral fibrosis2. Therefore, in order to effectively inhibit urethral stricture, the drug release period should completely cover all stages of urethral injury healing. Our previous studies have shown that continuous transurethral infusion of anti-fibrotic drugs (such as rapamycin or docetaxel) for 28 days after urethral injury can effectively + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 120]]<|/det|> +inhibit urethral stricture \(^{3,4}\) , and other experimental studies on the prevention of urethral strictures by topical administration also commonly used 1 month as the duration of drug action \(^{5 - 7}\) . + +<|ref|>text<|/ref|><|det|>[[148, 123, 852, 270]]<|/det|> +2) According to the Campbell-Walsh urology and European Association of Urology (EAU) guidelines on urologic trauma \(^{8,9}\) , partial posterior urethral rupture require catheterization to drain urine and provide a support surface for mucosal repair until the injury heals. After urethral reunion, catheterization for 4-6 weeks is also recommended. For urethral injuries that cannot be treated conservatively, EAU recommends catheterization for 2-3 weeks after urethroplasty. Based on the above, in order to assess the promise of the anti-fibrotic catheter in inhibiting the progression of urethral injury to urethral strictures and preventing recurrent strictures at the incision site of urethroplasty, we evaluated its efficacy and safety after 1 month of indwelling. + +<|ref|>text<|/ref|><|det|>[[148, 272, 852, 343]]<|/det|> +In summary, in the consideration of the pathophysiology of urethral injury healing and the current clinical management standards, and also combining with literature research and our previous studies, we set 1 month as the intervention time and proved the beneficial effect of the anti-fibrotic catheter in inhibiting urethral strictures. + +<|ref|>text<|/ref|><|det|>[[147, 363, 852, 492]]<|/det|> +3) in many instances the retrograde urethrograms are shown in wrong orientation. Typically, distal portion of urethra is either shown facing 3 or 9 o'clock position (consistently through all images), cephalad is at 12 o'clock, caudad is at 6 o'clock. At least in S37 and in figure 6 the orientation is unknown and this makes these figures very confusing. Additionally, some of the radiographs are darker and with poor contrast making it difficult to assess urethral lumen, I would recommend revising these images to have consistent orientation and brightness/contrast. + +<|ref|>text<|/ref|><|det|>[[148, 511, 850, 602]]<|/det|> +Response: Thanks to the reviewer for this helpful suggestion. In order to make the urethrography images clearer, we unified the display directions of all urethrography images in this paper so that the cephalad is at 12 o'clock and the caudal side is at 6 o'clock. In addition, the brightness and contrast of some images have been adjusted. We have updated all relevant figures in the manuscript and supporting information (Figure 6, FigureS37 and Figure S40). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[153, 88, 840, 789]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 793, 850, 828]]<|/det|> +
Figure. 6 The sustained-release coating of rapamycin on the urinary catheter attenuates collagen deposition and inhibits the formation of strictures post urethral injury.
+ +<|ref|>text<|/ref|><|det|>[[147, 830, 850, 902]]<|/det|> +a, Representative retrograde urethrogram of rabbits with different treatments after urethral electrocoagulation, using \(76\%\) Meglumine Diatrizoate as a contrast agent. b, Quantitative analysis of urethral lumen reduction and submucosal collagen density in rabbits with different treatments. Data are mean \(\pm\) s.d.; \(n = 5\) . c, Corresponding results of the PTB@SA- Rapamycin catheter compared + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 324]]<|/det|> +with other preclinical studies of topical therapy to suppress urethral stricture. d, Gross specimen, H&E staining and immunohistochemical staining with anti-alpha smooth muscle actin antibody (α- SMA, brown), anti-matrix metalloproteinase 1 antibody (MMP1, brown), and type I collagen antibody (Collagen I, green) of the urethral injury sites at 1 month. Nuclei (blue) were stained with DAPI. Yellow triangles indicate urethral scar tissue. The asterisks represent urethral luminal side, and the dotted lines indicate the boundary between the submucosa and the muscularis. e, Quantification of α- SMA, MMP1 positive area and Collagen I fluorescence intensity in Fig. 6d. Data are mean ± s.d.; n=5. f, g, Hematological examination to show the changes of alanine aminotransferase (ALT, f) and aspartate aminotransferase (AST, g) with different treatments for 1 month. Data are mean ± s.d.; n=5. h, H&E staining of rabbit liver after systemic administration or indwelling rapamycin sustained-release catheter for 1 month. (a, d) i, Control, ii; Unmodified catheter; iii, Systemic administration; iv, PTB@SA; v, Burst-releasing; vi, PTB@SA-Rapamycin. \* P<0.05, \*\* P<0.01, \*\*\* P<0.001, \*\*\*\* P<0.0001, ns means no statistical difference. + +<|ref|>image<|/ref|><|det|>[[147, 360, 815, 513]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 523, 851, 632]]<|/det|> +
Figure S37. Comparison of urethral diameter in normal healthy rabbits and rabbits using PTB@SA-Rapamycin catheter after urethral injury. (a) Representative retrograde urethrogram of healthy rabbits. (b) Representative retrograde urethrogram of the rabbit in the anti-fibrotic catheter group. (c) The ratio of urethra diameter to femoral shaft diameter in normal healthy rabbits and rabbits in anti-fibrotic catheter (PTB@SA-Rapamycin) group. Data are presented as the mean ± s.d.; n=5. ns means no statistical difference.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 90, 833, 600]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 628, 851, 793]]<|/det|> +
Figure S40. Rabbit urethral stricture in unmodified urinary catheter group and PTB@SA-Rapamycin group on the 14th day after removal of catheter. (a) Representative retrograde urethrogram using \(76\%\) meglumine dinitrozoate as contrast agent. (b) Lumen reduction immediately after catheter removal or 2 weeks later as determined by retrograde urethrography. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . (c) Comparison of gross specimens, H&E staining, Masson staining and \(\alpha\) -SMA expression between unmodified urinary catheter group and PTB@SA-Rapamycin group at 14 days after catheter removal. Yellow triangles indicate urethral scar tissue, and the dotted lines indicate the boundary between the submucosa and the muscularis. (d, e) Quantitative results of collagen density and \(\alpha\) -SMA positive area in Figure S40c. Data are mean \(\pm\) s.d.; \(\mathrm{n} = 5\) . \*\*\* P<0.001.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 87, 238, 101]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[145, 105, 852, 475]]<|/det|> +1. Ninan, N., Thomas, S. & Grohens, Y. Wound healing in urology. Adv. Drug Deliv. Rev. 82–83, 93–105 (2015). +2. Prihadi, J. C., Sugandi, S., Siregar, N. C., Soejono, G. & Harahap, A. Imbalance in extracellular matrix degradation in urethral stricture. Res. Reports Urol. 10, 227–232 (2018). +3. Chong, T. et al. Rapamycin inhibits formation of urethral stricture in rabbits. J. Pharmacol. Exp. Ther. 338, 47–52 (2011). +4. Fu, D., Chong, T., Li, H., Zhang, H. & Wang, Z. Docetaxel inhibits urethral stricture formation, an initial study in rabbit model. PLoS One 9, 1–6 (2014). +5. Wang, Z., Li, Q., Wang, P. & Yang, M. Biodegradable drug-eluting urethral stent in limiting urethral stricture formation after urethral injury: An experimental study in rabbit. J. Bioact. Compat. Polym. 35, 378–388 (2020). +6. Shin, J. H. et al. Tissue hyperplasia: Influence of a paclitaxel-eluting covered stent - Preliminary study in a canine urethral model. Radiology 234, 438–444 (2005). +7. Wang, L. et al. Electrospun nanoyarn and exosomes of adipose-derived stem cells for urethral regeneration: Evaluations in vitro and in vivo. Colloids Surfaces B Biointerfaces 209, 112218 (2022). +8. Partin, A. W., Wein, A. J., Kavoussi, L. R., Peters, C. A. & Dmochowski, R. R. Campbell-Walsh urology. (Elsevier Health Sciences, 2020). +9. Lumen, N. et al. Review of the current management of lower urinary tract injuries by the EAU trauma guidelines panel. Eur. Urol. 67, 925–929 (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 286, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 120, 510, 165]]<|/det|> +Reviewer #5: Remarks to the Author: All questions answered, changes made as requested. + +<--- Page Split ---> diff --git a/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/images_list.json b/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..2a8d8d4fc48abb5157b8cc06f75655b1d109feaf --- /dev/null +++ b/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,197 @@ + +# nature portfolio + +Peer Review File + +A unifying criterion of the boiling crisis + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +## REVIEWER COMMENTS + +Reviewer #2 (Remarks to the Author): + +In my opinion, the paper has been considerably improved further to the comments of all reviewers. In particular, all my personal comments were addressed more than satisfactorily. + +I am not yet fully convinced that this theory represents the final answer to a long and historical debate about the causes of critical heat flux in boiling. However it is for sure an original and fresh contribution, that is worth to be published and discussed among the scientific community. + +<--- Page Split ---> + +## Reviewer's Comments + +I thank the authors for responding to my earlier comments. Again, I emphasize that the authors have proposed a hypothesis, developed a model for critical heat flux and validated the predictions with their own data. What they propose is not a law as there are so many exceptions. In response to my earlier comments the authors themselves acknowledge that operating conditions affect the three boiling parameters (and in turn the predicted critical heat flux). The operating conditions can be size of the surface, morphology of the surface and orientation of the surface in relation to gravitational vector. As such, I am unable to accept what the authors claim to be a law! They have simply used their own data to prove a point. I suggest that the authors change the title of the paper to: "A unifying model for the boiling crisis". + +There are several other issues with their development of the model: + +(i) In response to my earlier comment (iii) the authors report that the ratio of the wait time to the growth time decreases from 5.6 to 2.5 as heat flux was increased 14 times. This is not consistent with the many data reported in the literature. Waiting time depends among other variables on the spatial and temporal variation of heat transfer on the fluid side, on the thickness of the substrate and the thermophysical properties of the substrate. In fact, waiting time can be smaller than the growth period. + +(ii) With respect to my earlier comment (iv) critical heat flux for a contact angle of \(85^{\circ}\) has been reported to be half of that for a contact angle of about zero. See the work of Winterton on a horizontal surface and that of Liaw for a vertical surface. + +(iii) The authors do not discuss the merger of bubbles normal to the surface. In fact, this can be the main mode responsible for critical heat flux on well wetted horizontal surfaces. + +(iv) Critical heat flux on a horizontal surface can be affected not only by the contact angle, the size of the surface and the size of the surrounding surface also influence it. + +<--- Page Split ---> + +(v) Recently I saw a paper published in the Journal of Electronic Packaging Dec. 2021, by She and Dhir. The authors clearly show the existence of vapor columns near the critical heat flux, and also the effect of contact angle, size of the heater and size of the surrounding vessel. How would a frequency be defined when bubbles at a nucleation site merge in the vertical direction? + +Finally, I am not convinced that the authors have developed a universal law when they only use their own data to validate their model. I will agree to acceptance of the paper provided the title of the paper is changed. + +<--- Page Split ---> + +## Referee #1 (Remarks to the Author): + +I thank the authors for responding to my earlier comments. Again, I emphasize that the authors have proposed a hypothesis, developed a model for critical heat flux and validated the predictions with their own data. What they propose is not a law as there are so many exceptions. In response to my earlier comments the authors themselves acknowledge that operating conditions affect the three boiling parameters (and in turn the predicted critical heat flux). The operating conditions can be size of the surface, morphology of the surface and orientation of the surface in relation to gravitational vector. As such, I am unable to accept what the authors claim to be a law! They have simply used their own data to prove a point. I suggest that the authors change the title of the paper to: "A unifying model for the boiling crisis". + +## Dear Referee #1, + +We are thankful for your careful and thoughtful review of our revised paper. We answer your specific questions and comments below using RED fonts. Changes to the manuscript motivated by your questions and comments are also written in RED fonts. + +It seems that the major concern relates to the choice of the word "law" in the title and throughout the manuscript, and we wish to address this comment immediately hereafter. + +After careful consideration, we think that a better word to describe what we achieved is "criterion." We prefer to use "criterion" rather than "model" because we believe that our work goes beyond the model, as we also obtain (using the model) a non- dimensional scaling criterion to determine whether boiling is stable (i.e., \(N'' \pi \mathrm{R}^2 \mathrm{ft}_{\mathrm{g}} < \mathrm{C}\) ) or a boiling crisis may occur (i.e., \(N'' \pi \mathrm{R}^2 \mathrm{ft}_{\mathrm{g}} = \mathrm{C}\) ), and support this criterion with experimental results. Thus, we feel that the word "criterion" is more appropriate than "model". + +There are several other issues with their development of the model: + +(i) In response to my earlier comment (iii) the authors report that the ratio of the wait time to the growth time decreases from 5.6 to 2.5 as heat flux was increased 14 times. This is not consistent with the many data reported in the literature. Waiting time depends among other variables on the spatial and temporal variation of heat transfer on the fluid side, on the thickness of the substrate and the thermophysical properties of the substrate. In fact, waiting time can be smaller than the growth period. + +We completely agree with your comment. + +In fact, we emphasize that our dataset covers a much broader wait time to growth time range compared to the mentioned above (see Extended Data Table 2 and 3 of the manuscript). In particular, at the boiling crisis, our \(\mathrm{ft}_{\mathrm{g}}\) values range between 0.28 and 0.53. A value of 0.28 means that the wait time is approximately 2.6 times longer than the growth time. However, a value of 0.53 means that ration between the wait time and growth time is 0.88, i.e., the wait time is smaller than the growth time, which agrees with your statement. Note that, an \(\mathrm{ft}_{\mathrm{g}}\) smaller than 0.5 indicates that the wait time is longer than the growth time. Vice versa, if \(\mathrm{ft}_{\mathrm{g}}\) is larger than 0.5, the growth time is longer than the wait time. + +We believe the confusion arose from the fact that in our answer to question (iii) of your earlier comments (i.e., "It can be deduced from the data that for DI water and ITO the ratio of waiting time to growth time is about 5 at half of the critical heat flux and 2 near critical heat flux. These ratios are not supported by numerical or experimental data reported in the literature."), our focus was to support our data with data obtained in the same conditions by other scientists in the conditions you mentioned, i.e., water and ITO, for which the available data are, to the best of our knowledge, the pool boiling data of Gerardi [1,2], as discussed in our earlier rebuttal. Clearly, for other surfaces and operating conditions the wait time to growth time ratios can be different, as supported by our data. + +<--- Page Split ---> + +We hope that this clarification addresses your follow- up comment. As these data were already in the manuscript, no change was necessary. However, we added a section to clearly state the range of our experimental data. + +[1] Gerardi, C. Investigation of the pool boiling heat transfer enhancement of nano- engineered fluids by means of high- speed infrared thermography. (Massachusetts Institute of Technology, 2009). + +[2] Gerardi, C., Buongiorno, J., Hu, L. & McKrell, T. Infrared thermometry study of nanofluid pool boiling phenomena. Nanoscale Res Lett 6, 1- 17 (2011). + +(ii) With respect to my earlier comment (iv) critical heat flux for a contact angle of \(85^{\circ}\) has been reported to be half of that for a contact angle of about zero. See the work of Winterton on a horizontal surface and that of Liaw for a vertical surface. + +We emphasize that, in response to your earlier comment (iv) (i.e., "The critical heat flux reported for ITO and deionized water for a contact angle of 85 degrees is much higher than reported in the literature."), we provided evidence that the CHF values we measured with water on ITO are indeed consistent with those reported in literature on similar surfaces. + +However, we believe that surface wettability is not a unique indicator of the CHF limit on the boiling surface. Surface morphology plays an equally important, if not more important role. + +In support of this statement, we wish to cite the work of O' Hanley et al. [3]. They have conducted a separate effect study of pool boiling CHF where they were able to change the surface wettability without changing the surface morphology to show that the CHF limit does not change for contact angles ranging between 112 and 0 degrees. + +We may also reference a recent work from our group [4], aimed at elucidating the separate effect of wettability and surface changes (promoted by oxidation). By oxidizing a zircaloy surface, we have been able to obtain surfaces with different wettability without changing the surface morphology (we did surface characterization on the same exact spot of the boiling surface before and after oxidation). We have ascertained that changes of wettability from 50 to 30 degrees do not affect the boiling curves or the CHF. CHF only changes when the oxidation process modifies structurally the surface (and so the change in contact angle is a combination of a change in the intrinsic wettability and the surface morphology) [4]. + +We noticed that the in the work of Winterton [5], the change of contact angle are attributed to oxidation. As the surface is aluminum, it is likely that the oxidation has created morphological changes to the surface. Similarly, Liaw and Dhir [6] explored the effect of contact angle by oxidizing copper surfaces, which are also subject to morphological changes when oxidized. + +In summary, while we do not question the results of previous works, we feel that it is incautious to compare the boiling performance of two morphologically different surfaces based on the contact angle only. We also wish to re- emphasize that our CHF results, as discussed in response to your earlier comment, are in close agreement with CHF results from literature obtained in the same experimental conditions. + +[3] O'Hanley, H., Coyle, C., Buongiorno, J., McKrell, T., Hu, L.W., Rubner, M. and Cohen, R., 2013. Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux. Applied Physics Letters, 103(2), p.024102. + +[4] Seong, J.H., Wang, C., Phillips, B. and Bucci, M., 2022. Separate effect of oxidation on the subcooled flow boiling performance of Zircaloy- 4 at atmospheric pressure. International Journal of Heat and Mass Transfer, 188, p.122620. + +<--- Page Split ---> + +[5] Liu, Z. and Winterton, R.H.S., 1991. A general correlation for saturated and subcooled flow boiling in tubes and annuli, based on a nucleate pool boiling equation. International journal of heat and mass transfer, 34(11), pp.2759- 2766. + +[6] Liaw, S.P. and Dhir, D.V.K., 1986. Effect of surface wettability on transition boiling heat transfer from a vertical surface. In International Heat Transfer Conference Digital Library. Begel House Inc. + +(iii) The authors do not discuss the merger of bubbles normal to the surface. In fact, this can be the main mode responsible for critical heat flux on well wetted horizontal surfaces. + +This point is very controversial. In fact, there is no consensus in the community. We tried to capture the essence of this controversy in the introduction of our paper: + +"The boiling crisis is a century- old scientific problem. For years, it has been viewed as the outcome of a hydrodynamic instability occurring far from the heated surface. Reference source not found. When ... which eventually dries out. Antithetical descriptions consider the boiling crisis as a near- wall instability related to the characteristic of the nucleate boiling process at the heated surface. For instance, ..." + +An experimental work supporting the near- wall nature of the boiling crisis by Gong et al. [7] has shown that in pool boiling (with an horizontal surface) the CHF limit does not depend on the height of the liquid pool, down to liquid heights in the order of a millimeter, which is the order of magnitude of the bubble footprint radius and departure diameters (with 1 mm tall liquid pools there are no Kelvin- Helmholtz instabilities in the liquid far from the wall, nor merging of bubbles normal to the surface). + +Crucially, we have repeated the same experiments in our pool boiling apparatus and made a similar observation. + +However, while we think we should keep an open mind with respect to this important question, our results seem to support the idea that the boiling crisis in nucleate boiling is triggered by near- wall instabilities, rather than far- field hydrodynamic effects (as we only used information related to the dynamic of bubbles at the heating surface to predict the boiling crisis). This is noteworthy, as our model also yields the same scaling of the critical heat flux (CHF) with the physical properties of the fluid and operating conditions (as shown in the paper) predicted by the Kutateladze- Zuber correlation, i.e., a far field model. Briefly, our idea seems to reconcile far- field and near- wall views of the boiling crisis. Motivated by your comment, we have added a short sentence to clarify this aspect in the revised manuscript. + +[7] Gong, S., Ma, W. and Gu, H., 2014. An experimental investigation on bubble dynamics and boiling crisis in liquid films. International Journal of Heat and Mass Transfer, 79, pp.694- 703. + +(iv) Critical heat flux on a horizontal surface can be affected not only by the contact angle, the size of the surface and the size of the surrounding surface also influence it. + +We agree that the CHF limit (i.e., the maximum heat flux that can be removed in nucleate boiling in W/m2) depends on a plethora of parameters such contact angles, surface size, size of the surrounding surface, and many more. However, as mentioned in our initial rebuttal, we emphasize that our goal is not to understand how a surface or operating conditions (i.e., the blue boxes in the figure below) modify our three boiling parameters (i.e., the orange boxes), but to reveal that the boiling crisis (the green box) is the result of the same stochastic process, which can be predicted from the three parameters using a unique criterion, i.e., Eq. 1 (N'' \(\pi \mathrm{R}^{2}\) \(\mathrm{f}_{\mathrm{tg}} =\) C), no matter the surface morphology and wettability, the fluid and operating conditions, the size of the boiling surface and the size of the surrounding surface. + +<--- Page Split ---> +![PLACEHOLDER_7_0] + + +The size of the surface and the size of the surrounding surface, and all the other parameter may directly and indirectly affect the bubble dynamics, provide different flow recirculation conditions, bubble detaching forces, convective cooling effects, and so on. However, the process leading to the boiling crisis should be the same, i.e., the same criterion applies to small surfaces. + +For the sake of clarity (as mentioned in our paper and discussed in the Stochastic Model description of the Methods section), we emphasize that the percolation threshold is slightly dependent on the nondimensional boiling area\* (for small values of the latter). + +\* As written in the paper, the nondimensional boiling area is defined as \(\mathrm{Ah} / \pi \mathrm{R}^2\) where Ah is the area of the boiling surface and R is the average bubble footprint radius. In our analysis we assumed that the surface is not oblate, i.e., it does not have a principal direction. + +(v) Recently I saw a paper published in the Journal of Electronic Packaging Dec. 2021, by She and Dhir. The authors clearly show the existence of vapor columns near the critical heat flux, and also the effect of contact angle, size of the heater and size of the surrounding vessel. How would a frequency be defined when bubbles at a nucleation site merge in the vertical direction? + +The pictures in the paper of She and Dhir [8] show indeed the presence of a vapor column far from the surface, which is typical. Also, from what we can see (we tried to zoom in Figs. 6, 9 and 11 of the paper), we think that the dark shadows corresponding to the boiling surface may indicate that individual bubbles still nucleate under the vapor column). However, we are afraid that these pictures do not shed any light on what is happening on the surface itself (as the space and time resolution of the images is too coarse, and there is no direct optical access to the boiling surface). It is impossible to say if there is bubble nucleation and detachment from the surface (with merging of the detached bubble with the hovering bubble column) or there are tiny, permanently dry spots connected to the hovering vapor column with vapor stems. However, we can exclude that the base of the large vapor column is completely and constantly dry (as this would be a post- CHF heat transfer regime!). + +In brief, there are two possible answers to your question (i.e., "How would a frequency be defined when bubbles at a nucleation site merge in the vertical direction?"): + +- If bubbles detach from the surface to merge with the hovering vapor column, their growth time is still defined as the time from nucleation until the moment they are completely detached, and the frequency is still defined as the inverse of the bubble period (which is the sum of growth and wait time).- If there are tiny, permanently dry spots connected to the hovering vapor column, the product ftg is simply equal to 1 (but the criterion still holds!). Note that what we really need to know is ftg (not the frequency), i.e., the probability that a site is sustaining a bubble (or a dry spot). + +We wish to emphasize that one could elucidate these aspects by using imaging techniques similar to ours (for example our IR measurements enable direct optical access to the boiling surface and are taken at 2000 frames per second and 100 microns per pixel). From what we can see from our side view of the experiment, our pool boiling process does not look different from the images shown by She and Dhir [8]. However, the infrared + +<--- Page Split ---> + +imaging of the boiling surface reveals a much more complicated process, which cannot be captured with side views. + +The trends observed by She and Dhir [8] make perfect sense. However, we humbly submit that advanced measurement techniques enabling direct optical access to the boiling surface and a very high temporal and spatial resolution are necessary to capture and understand the dynamic of the boiling process and the boiling crisis. + +[8] She, Z. and Dhir, V.K., 2021. Parametric effects of heater size, contact angle, and surrounding vessel size on pool boiling critical heat flux from horizontal surfaces. Journal of Electronic Packaging, 143(4). + +Finally, I am not convinced that the authors have developed a universal law when they only use their own data to validate their model. I will agree to acceptance of the paper provided the title of the paper is changed. + +We wish to clarify, as also mentioned in the previous rebuttal, that we never made the claim that our criterion is "universal" but "unifying." We believe we have already clarified the meaning of "unifying" in our R1 version of the paper, e.g., "We emphasize that, in this context, the word unifying is used because this law combines and captures the synergistic and intertwined effect of the length and time scales involved in the boiling process, i.e., nucleation site density, bubble size, growth time and departure frequency. ..." + +We have already addressed the comment related to the title and the use of the word "law" at the beginning of the rebuttal. As discussed, we wish to title our paper "A unifying criterion of the boiling crisis." We trust that you will find our proposal appropriate. Accordingly, the word "law" has been changed with "criterion" throughout the manuscript. + +## Referee #2 (Remarks to the Author): + +In my opinion, the paper has been considerably improved further to the comments of all reviewers. In particular, all my personal comments were addressed more than satisfactorily. + +I am not yet fully convinced that this theory represents the final answer to a long and historical debate about the causes of critical heat flux in boiling. However it is for sure an original and fresh contribution, that is worth to be published and discussed among the scientific community. + +## Dear Referee #2, + +We appreciate your positive feedback. The boiling crisis has been indeed the subject of a long debate (in fact, more than on hundred years old). We are glad to shake this debate with (as you say) "an original and fresh idea" and first- of- a- kind data revealing new physical mechanisms. We are excited to share our findings with the community and see other scientists to critically evaluate and build upon our work. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +With the change of the title of the paper and related text my main concern has been alleviated. However, the authors keep missing the point that in pool boiling of inviscid fluids it is the balance of buoyancy and surface tension forces that determines the maximum rate of vapor removal from the surface. From their work it is not clear under what physical situations it is the far field or the near field instability determines the outcome. The discussion of the authors on the effect of contact angle, the size of the heater and the size of the surrounding vessel and the contact angle of the + +surface surrounding the heater is lacking. At this stage I agree to support the publication of the paper in its revised form. + +<--- Page Split ---> + +## Referee #1 (Remarks to the Author): + +With the change of the title of the paper and related text my main concern has been alleviated. However, the authors keep missing the point that in pool boiling of inviscid fluids it is the balance of buoyancy and surface tension forces that determines the maximum rate of vapor removal from the surface. From their work it is not clear under what physical situations it is the far field or the near field instability determines the outcome. The discussion of the authors on the effect of contact angle, the size of the heater and the size of the surrounding vessel and the contact angle of the surface surrounding the heater is lacking. At this stage I agree to support the publication of the paper in its revised form. + +## Dear Referee #1, + +We appreciate your final recommendation. + +We understand your comment about the role of buoyancy and surface tension for pool boiling conditions. However, we think that the role of these forces is accounted for through the fundamental parameters describing the bubble dynamics (i.e., bubbler radius, growth time, departure frequency, and nucleation site density). We emphasize that our model aims at capturing the connection between these fundamental parameters and the boiling crisis. + +Similarly, as already mentioned in our previous rebuttal, we agree that the CHF limit (i.e., the maximum heat flux that can be removed in nucleate boiling in \(\mathsf{W} / \mathsf{m}2\) ) depends on a plethora of parameters such contact angles, surface size, size of the surrounding surface, and many more. However, we believe that the role of these parameters is to affect the bubble dynamics and, consequently, the boiling crisis. Same as before, we emphasize that our model aims at capturing the connection between the parameters describing the bubble dynamics and the boiling crisis. + +We also wish to mention that we discuss the effect of contact angle in our paper. Precisely, we wrote: "We emphasize that, while we did not test hydrophobic surfaces with static contact angles much larger than \(90^{\circ}\) , our paradigm contemplates all surface conditions. For instance, on hydrophobic surface, depending on nucleation sites size distribution and nucleation temperature, the boiling crisis may occur with a large number of small bubbles (i.e., with a small footprint) and a short wait time (i.e., a high \(f t_{g})^{2}\) . In some other cases, the bubble departure diameter on hydrophobic surfaces may be significantly higher than on hydrophilic surfaces \(^{24}\) , and the boiling crisis may happen with a combination of large bubble footprint radius and smaller nucleation site density (and likely higher \(f t_{g}\) product). However, while experiments on superhydrophobic surfaces may be run in the future, the critical condition expressed by Equation (1) should not change." + +Based on your comment, we modified this sentence to mention possible other effects (e.g., such as the size effects discussed in the Methods section), as follows: + +"We emphasize that, while we did not test hydrophobic surfaces with static contact angles much larger than \(90^{\circ}\) , our paradigm contemplates all surface conditions and, possibly, heater geometry effects. For instance, on hydrophobic surface, ... ... combination of large bubble footprint radius and smaller nucleation site density (and likely higher \(f t_{g}\) product). However, while experiments on superhydrophobic surfaces and considering other effects (e.g., heater size and lateral confinement) may be run in the future, the critical condition expressed by Equation (1) should not change." + +Overall, the fact that the critical behavior can be captured using near- wall parameters for surfaces with different boiling behavior (i.e., nucleation site density, bubble growth time and departure frequency, and average footprint radius) and different CHF limits under the same or different operating conditions is in our view, a strong indication that the mechanisms triggering the boiling crisis can be found in the near- wall region. This is the reason why we wrote that our work "corroborates the hypothesis that the boiling crisis is a near- wall phenomenon." + +We are truly grateful for your constructive criticism throughout the rebuttal process. We are excited to share our findings with the community and see other scientists to critically evaluate and build upon our work. + +<--- Page Split ---> diff --git a/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..462d5b78b6a284740847317847c3701d0145c3b3 --- /dev/null +++ b/peer_reviews/32bd9c665f2b795ae3089961474735a437de5b3e9fd200d28fc75d3f8bcd0289/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,270 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[67, 110, 363, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[95, 155, 730, 186]]<|/det|> +A unifying criterion of the boiling crisis + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 783]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 866, 138]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[118, 212, 295, 227]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 272, 404, 288]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 332, 866, 367]]<|/det|> +In my opinion, the paper has been considerably improved further to the comments of all reviewers. In particular, all my personal comments were addressed more than satisfactorily. + +<|ref|>text<|/ref|><|det|>[[118, 380, 852, 434]]<|/det|> +I am not yet fully convinced that this theory represents the final answer to a long and historical debate about the causes of critical heat flux in boiling. However it is for sure an original and fresh contribution, that is worth to be published and discussed among the scientific community. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[388, 91, 609, 111]]<|/det|> +## Reviewer's Comments + +<|ref|>text<|/ref|><|det|>[[114, 154, 882, 393]]<|/det|> +I thank the authors for responding to my earlier comments. Again, I emphasize that the authors have proposed a hypothesis, developed a model for critical heat flux and validated the predictions with their own data. What they propose is not a law as there are so many exceptions. In response to my earlier comments the authors themselves acknowledge that operating conditions affect the three boiling parameters (and in turn the predicted critical heat flux). The operating conditions can be size of the surface, morphology of the surface and orientation of the surface in relation to gravitational vector. As such, I am unable to accept what the authors claim to be a law! They have simply used their own data to prove a point. I suggest that the authors change the title of the paper to: "A unifying model for the boiling crisis". + +<|ref|>text<|/ref|><|det|>[[171, 405, 792, 426]]<|/det|> +There are several other issues with their development of the model: + +<|ref|>text<|/ref|><|det|>[[115, 437, 882, 589]]<|/det|> +(i) In response to my earlier comment (iii) the authors report that the ratio of the wait time to the growth time decreases from 5.6 to 2.5 as heat flux was increased 14 times. This is not consistent with the many data reported in the literature. Waiting time depends among other variables on the spatial and temporal variation of heat transfer on the fluid side, on the thickness of the substrate and the thermophysical properties of the substrate. In fact, waiting time can be smaller than the growth period. + +<|ref|>text<|/ref|><|det|>[[115, 608, 882, 694]]<|/det|> +(ii) With respect to my earlier comment (iv) critical heat flux for a contact angle of \(85^{\circ}\) has been reported to be half of that for a contact angle of about zero. See the work of Winterton on a horizontal surface and that of Liaw for a vertical surface. + +<|ref|>text<|/ref|><|det|>[[115, 716, 882, 778]]<|/det|> +(iii) The authors do not discuss the merger of bubbles normal to the surface. In fact, this can be the main mode responsible for critical heat flux on well wetted horizontal surfaces. + +<|ref|>text<|/ref|><|det|>[[115, 800, 882, 863]]<|/det|> +(iv) Critical heat flux on a horizontal surface can be affected not only by the contact angle, the size of the surface and the size of the surrounding surface also influence it. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 199]]<|/det|> +(v) Recently I saw a paper published in the Journal of Electronic Packaging Dec. 2021, by She and Dhir. The authors clearly show the existence of vapor columns near the critical heat flux, and also the effect of contact angle, size of the heater and size of the surrounding vessel. How would a frequency be defined when bubbles at a nucleation site merge in the vertical direction? + +<|ref|>text<|/ref|><|det|>[[115, 238, 882, 303]]<|/det|> +Finally, I am not convinced that the authors have developed a universal law when they only use their own data to validate their model. I will agree to acceptance of the paper provided the title of the paper is changed. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 364, 105]]<|/det|> +## Referee #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 120, 882, 244]]<|/det|> +I thank the authors for responding to my earlier comments. Again, I emphasize that the authors have proposed a hypothesis, developed a model for critical heat flux and validated the predictions with their own data. What they propose is not a law as there are so many exceptions. In response to my earlier comments the authors themselves acknowledge that operating conditions affect the three boiling parameters (and in turn the predicted critical heat flux). The operating conditions can be size of the surface, morphology of the surface and orientation of the surface in relation to gravitational vector. As such, I am unable to accept what the authors claim to be a law! They have simply used their own data to prove a point. I suggest that the authors change the title of the paper to: "A unifying model for the boiling crisis". + +<|ref|>sub_title<|/ref|><|det|>[[116, 260, 229, 274]]<|/det|> +## Dear Referee #1, + +<|ref|>text<|/ref|><|det|>[[116, 290, 882, 336]]<|/det|> +We are thankful for your careful and thoughtful review of our revised paper. We answer your specific questions and comments below using RED fonts. Changes to the manuscript motivated by your questions and comments are also written in RED fonts. + +<|ref|>text<|/ref|><|det|>[[115, 351, 880, 382]]<|/det|> +It seems that the major concern relates to the choice of the word "law" in the title and throughout the manuscript, and we wish to address this comment immediately hereafter. + +<|ref|>text<|/ref|><|det|>[[115, 397, 882, 477]]<|/det|> +After careful consideration, we think that a better word to describe what we achieved is "criterion." We prefer to use "criterion" rather than "model" because we believe that our work goes beyond the model, as we also obtain (using the model) a non- dimensional scaling criterion to determine whether boiling is stable (i.e., \(N'' \pi \mathrm{R}^2 \mathrm{ft}_{\mathrm{g}} < \mathrm{C}\) ) or a boiling crisis may occur (i.e., \(N'' \pi \mathrm{R}^2 \mathrm{ft}_{\mathrm{g}} = \mathrm{C}\) ), and support this criterion with experimental results. Thus, we feel that the word "criterion" is more appropriate than "model". + +<|ref|>text<|/ref|><|det|>[[115, 493, 569, 508]]<|/det|> +There are several other issues with their development of the model: + +<|ref|>text<|/ref|><|det|>[[115, 522, 882, 600]]<|/det|> +(i) In response to my earlier comment (iii) the authors report that the ratio of the wait time to the growth time decreases from 5.6 to 2.5 as heat flux was increased 14 times. This is not consistent with the many data reported in the literature. Waiting time depends among other variables on the spatial and temporal variation of heat transfer on the fluid side, on the thickness of the substrate and the thermophysical properties of the substrate. In fact, waiting time can be smaller than the growth period. + +<|ref|>text<|/ref|><|det|>[[145, 616, 425, 630]]<|/det|> +We completely agree with your comment. + +<|ref|>text<|/ref|><|det|>[[144, 646, 882, 755]]<|/det|> +In fact, we emphasize that our dataset covers a much broader wait time to growth time range compared to the mentioned above (see Extended Data Table 2 and 3 of the manuscript). In particular, at the boiling crisis, our \(\mathrm{ft}_{\mathrm{g}}\) values range between 0.28 and 0.53. A value of 0.28 means that the wait time is approximately 2.6 times longer than the growth time. However, a value of 0.53 means that ration between the wait time and growth time is 0.88, i.e., the wait time is smaller than the growth time, which agrees with your statement. Note that, an \(\mathrm{ft}_{\mathrm{g}}\) smaller than 0.5 indicates that the wait time is longer than the growth time. Vice versa, if \(\mathrm{ft}_{\mathrm{g}}\) is larger than 0.5, the growth time is longer than the wait time. + +<|ref|>text<|/ref|><|det|>[[144, 771, 882, 893]]<|/det|> +We believe the confusion arose from the fact that in our answer to question (iii) of your earlier comments (i.e., "It can be deduced from the data that for DI water and ITO the ratio of waiting time to growth time is about 5 at half of the critical heat flux and 2 near critical heat flux. These ratios are not supported by numerical or experimental data reported in the literature."), our focus was to support our data with data obtained in the same conditions by other scientists in the conditions you mentioned, i.e., water and ITO, for which the available data are, to the best of our knowledge, the pool boiling data of Gerardi [1,2], as discussed in our earlier rebuttal. Clearly, for other surfaces and operating conditions the wait time to growth time ratios can be different, as supported by our data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[142, 105, 886, 137]]<|/det|> +We hope that this clarification addresses your follow- up comment. As these data were already in the manuscript, no change was necessary. However, we added a section to clearly state the range of our experimental data. + +<|ref|>text<|/ref|><|det|>[[142, 151, 884, 184]]<|/det|> +[1] Gerardi, C. Investigation of the pool boiling heat transfer enhancement of nano- engineered fluids by means of high- speed infrared thermography. (Massachusetts Institute of Technology, 2009). + +<|ref|>text<|/ref|><|det|>[[141, 190, 884, 221]]<|/det|> +[2] Gerardi, C., Buongiorno, J., Hu, L. & McKrell, T. Infrared thermometry study of nanofluid pool boiling phenomena. Nanoscale Res Lett 6, 1- 17 (2011). + +<|ref|>text<|/ref|><|det|>[[115, 258, 883, 305]]<|/det|> +(ii) With respect to my earlier comment (iv) critical heat flux for a contact angle of \(85^{\circ}\) has been reported to be half of that for a contact angle of about zero. See the work of Winterton on a horizontal surface and that of Liaw for a vertical surface. + +<|ref|>text<|/ref|><|det|>[[145, 320, 883, 383]]<|/det|> +We emphasize that, in response to your earlier comment (iv) (i.e., "The critical heat flux reported for ITO and deionized water for a contact angle of 85 degrees is much higher than reported in the literature."), we provided evidence that the CHF values we measured with water on ITO are indeed consistent with those reported in literature on similar surfaces. + +<|ref|>text<|/ref|><|det|>[[144, 398, 880, 429]]<|/det|> +However, we believe that surface wettability is not a unique indicator of the CHF limit on the boiling surface. Surface morphology plays an equally important, if not more important role. + +<|ref|>text<|/ref|><|det|>[[145, 444, 883, 505]]<|/det|> +In support of this statement, we wish to cite the work of O' Hanley et al. [3]. They have conducted a separate effect study of pool boiling CHF where they were able to change the surface wettability without changing the surface morphology to show that the CHF limit does not change for contact angles ranging between 112 and 0 degrees. + +<|ref|>text<|/ref|><|det|>[[144, 520, 883, 630]]<|/det|> +We may also reference a recent work from our group [4], aimed at elucidating the separate effect of wettability and surface changes (promoted by oxidation). By oxidizing a zircaloy surface, we have been able to obtain surfaces with different wettability without changing the surface morphology (we did surface characterization on the same exact spot of the boiling surface before and after oxidation). We have ascertained that changes of wettability from 50 to 30 degrees do not affect the boiling curves or the CHF. CHF only changes when the oxidation process modifies structurally the surface (and so the change in contact angle is a combination of a change in the intrinsic wettability and the surface morphology) [4]. + +<|ref|>text<|/ref|><|det|>[[145, 644, 882, 707]]<|/det|> +We noticed that the in the work of Winterton [5], the change of contact angle are attributed to oxidation. As the surface is aluminum, it is likely that the oxidation has created morphological changes to the surface. Similarly, Liaw and Dhir [6] explored the effect of contact angle by oxidizing copper surfaces, which are also subject to morphological changes when oxidized. + +<|ref|>text<|/ref|><|det|>[[145, 721, 882, 783]]<|/det|> +In summary, while we do not question the results of previous works, we feel that it is incautious to compare the boiling performance of two morphologically different surfaces based on the contact angle only. We also wish to re- emphasize that our CHF results, as discussed in response to your earlier comment, are in close agreement with CHF results from literature obtained in the same experimental conditions. + +<|ref|>text<|/ref|><|det|>[[145, 798, 882, 844]]<|/det|> +[3] O'Hanley, H., Coyle, C., Buongiorno, J., McKrell, T., Hu, L.W., Rubner, M. and Cohen, R., 2013. Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux. Applied Physics Letters, 103(2), p.024102. + +<|ref|>text<|/ref|><|det|>[[145, 860, 882, 906]]<|/det|> +[4] Seong, J.H., Wang, C., Phillips, B. and Bucci, M., 2022. Separate effect of oxidation on the subcooled flow boiling performance of Zircaloy- 4 at atmospheric pressure. International Journal of Heat and Mass Transfer, 188, p.122620. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 105, 882, 151]]<|/det|> +[5] Liu, Z. and Winterton, R.H.S., 1991. A general correlation for saturated and subcooled flow boiling in tubes and annuli, based on a nucleate pool boiling equation. International journal of heat and mass transfer, 34(11), pp.2759- 2766. + +<|ref|>text<|/ref|><|det|>[[144, 166, 882, 198]]<|/det|> +[6] Liaw, S.P. and Dhir, D.V.K., 1986. Effect of surface wettability on transition boiling heat transfer from a vertical surface. In International Heat Transfer Conference Digital Library. Begel House Inc. + +<|ref|>text<|/ref|><|det|>[[115, 212, 882, 243]]<|/det|> +(iii) The authors do not discuss the merger of bubbles normal to the surface. In fact, this can be the main mode responsible for critical heat flux on well wetted horizontal surfaces. + +<|ref|>text<|/ref|><|det|>[[142, 259, 882, 290]]<|/det|> +This point is very controversial. In fact, there is no consensus in the community. We tried to capture the essence of this controversy in the introduction of our paper: + +<|ref|>text<|/ref|><|det|>[[145, 305, 883, 367]]<|/det|> +"The boiling crisis is a century- old scientific problem. For years, it has been viewed as the outcome of a hydrodynamic instability occurring far from the heated surface. Reference source not found. When ... which eventually dries out. Antithetical descriptions consider the boiling crisis as a near- wall instability related to the characteristic of the nucleate boiling process at the heated surface. For instance, ..." + +<|ref|>text<|/ref|><|det|>[[145, 382, 882, 459]]<|/det|> +An experimental work supporting the near- wall nature of the boiling crisis by Gong et al. [7] has shown that in pool boiling (with an horizontal surface) the CHF limit does not depend on the height of the liquid pool, down to liquid heights in the order of a millimeter, which is the order of magnitude of the bubble footprint radius and departure diameters (with 1 mm tall liquid pools there are no Kelvin- Helmholtz instabilities in the liquid far from the wall, nor merging of bubbles normal to the surface). + +<|ref|>text<|/ref|><|det|>[[144, 475, 880, 490]]<|/det|> +Crucially, we have repeated the same experiments in our pool boiling apparatus and made a similar observation. + +<|ref|>text<|/ref|><|det|>[[144, 505, 883, 629]]<|/det|> +However, while we think we should keep an open mind with respect to this important question, our results seem to support the idea that the boiling crisis in nucleate boiling is triggered by near- wall instabilities, rather than far- field hydrodynamic effects (as we only used information related to the dynamic of bubbles at the heating surface to predict the boiling crisis). This is noteworthy, as our model also yields the same scaling of the critical heat flux (CHF) with the physical properties of the fluid and operating conditions (as shown in the paper) predicted by the Kutateladze- Zuber correlation, i.e., a far field model. Briefly, our idea seems to reconcile far- field and near- wall views of the boiling crisis. Motivated by your comment, we have added a short sentence to clarify this aspect in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[142, 644, 882, 675]]<|/det|> +[7] Gong, S., Ma, W. and Gu, H., 2014. An experimental investigation on bubble dynamics and boiling crisis in liquid films. International Journal of Heat and Mass Transfer, 79, pp.694- 703. + +<|ref|>text<|/ref|><|det|>[[115, 690, 882, 721]]<|/det|> +(iv) Critical heat flux on a horizontal surface can be affected not only by the contact angle, the size of the surface and the size of the surrounding surface also influence it. + +<|ref|>text<|/ref|><|det|>[[144, 736, 883, 861]]<|/det|> +We agree that the CHF limit (i.e., the maximum heat flux that can be removed in nucleate boiling in W/m2) depends on a plethora of parameters such contact angles, surface size, size of the surrounding surface, and many more. However, as mentioned in our initial rebuttal, we emphasize that our goal is not to understand how a surface or operating conditions (i.e., the blue boxes in the figure below) modify our three boiling parameters (i.e., the orange boxes), but to reveal that the boiling crisis (the green box) is the result of the same stochastic process, which can be predicted from the three parameters using a unique criterion, i.e., Eq. 1 (N'' \(\pi \mathrm{R}^{2}\) \(\mathrm{f}_{\mathrm{tg}} =\) C), no matter the surface morphology and wettability, the fluid and operating conditions, the size of the boiling surface and the size of the surrounding surface. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[310, 85, 718, 241]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 255, 883, 318]]<|/det|> +The size of the surface and the size of the surrounding surface, and all the other parameter may directly and indirectly affect the bubble dynamics, provide different flow recirculation conditions, bubble detaching forces, convective cooling effects, and so on. However, the process leading to the boiling crisis should be the same, i.e., the same criterion applies to small surfaces. + +<|ref|>text<|/ref|><|det|>[[144, 333, 883, 380]]<|/det|> +For the sake of clarity (as mentioned in our paper and discussed in the Stochastic Model description of the Methods section), we emphasize that the percolation threshold is slightly dependent on the nondimensional boiling area\* (for small values of the latter). + +<|ref|>text<|/ref|><|det|>[[144, 394, 883, 441]]<|/det|> +\* As written in the paper, the nondimensional boiling area is defined as \(\mathrm{Ah} / \pi \mathrm{R}^2\) where Ah is the area of the boiling surface and R is the average bubble footprint radius. In our analysis we assumed that the surface is not oblate, i.e., it does not have a principal direction. + +<|ref|>text<|/ref|><|det|>[[115, 455, 883, 518]]<|/det|> +(v) Recently I saw a paper published in the Journal of Electronic Packaging Dec. 2021, by She and Dhir. The authors clearly show the existence of vapor columns near the critical heat flux, and also the effect of contact angle, size of the heater and size of the surrounding vessel. How would a frequency be defined when bubbles at a nucleation site merge in the vertical direction? + +<|ref|>text<|/ref|><|det|>[[144, 532, 883, 672]]<|/det|> +The pictures in the paper of She and Dhir [8] show indeed the presence of a vapor column far from the surface, which is typical. Also, from what we can see (we tried to zoom in Figs. 6, 9 and 11 of the paper), we think that the dark shadows corresponding to the boiling surface may indicate that individual bubbles still nucleate under the vapor column). However, we are afraid that these pictures do not shed any light on what is happening on the surface itself (as the space and time resolution of the images is too coarse, and there is no direct optical access to the boiling surface). It is impossible to say if there is bubble nucleation and detachment from the surface (with merging of the detached bubble with the hovering bubble column) or there are tiny, permanently dry spots connected to the hovering vapor column with vapor stems. However, we can exclude that the base of the large vapor column is completely and constantly dry (as this would be a post- CHF heat transfer regime!). + +<|ref|>text<|/ref|><|det|>[[144, 687, 881, 717]]<|/det|> +In brief, there are two possible answers to your question (i.e., "How would a frequency be defined when bubbles at a nucleation site merge in the vertical direction?"): + +<|ref|>text<|/ref|><|det|>[[144, 733, 883, 829]]<|/det|> +- If bubbles detach from the surface to merge with the hovering vapor column, their growth time is still defined as the time from nucleation until the moment they are completely detached, and the frequency is still defined as the inverse of the bubble period (which is the sum of growth and wait time).- If there are tiny, permanently dry spots connected to the hovering vapor column, the product ftg is simply equal to 1 (but the criterion still holds!). Note that what we really need to know is ftg (not the frequency), i.e., the probability that a site is sustaining a bubble (or a dry spot). + +<|ref|>text<|/ref|><|det|>[[144, 843, 883, 905]]<|/det|> +We wish to emphasize that one could elucidate these aspects by using imaging techniques similar to ours (for example our IR measurements enable direct optical access to the boiling surface and are taken at 2000 frames per second and 100 microns per pixel). From what we can see from our side view of the experiment, our pool boiling process does not look different from the images shown by She and Dhir [8]. However, the infrared + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 882, 121]]<|/det|> +imaging of the boiling surface reveals a much more complicated process, which cannot be captured with side views. + +<|ref|>text<|/ref|><|det|>[[144, 135, 882, 199]]<|/det|> +The trends observed by She and Dhir [8] make perfect sense. However, we humbly submit that advanced measurement techniques enabling direct optical access to the boiling surface and a very high temporal and spatial resolution are necessary to capture and understand the dynamic of the boiling process and the boiling crisis. + +<|ref|>text<|/ref|><|det|>[[144, 213, 882, 245]]<|/det|> +[8] She, Z. and Dhir, V.K., 2021. Parametric effects of heater size, contact angle, and surrounding vessel size on pool boiling critical heat flux from horizontal surfaces. Journal of Electronic Packaging, 143(4). + +<|ref|>text<|/ref|><|det|>[[116, 260, 882, 291]]<|/det|> +Finally, I am not convinced that the authors have developed a universal law when they only use their own data to validate their model. I will agree to acceptance of the paper provided the title of the paper is changed. + +<|ref|>text<|/ref|><|det|>[[115, 305, 882, 383]]<|/det|> +We wish to clarify, as also mentioned in the previous rebuttal, that we never made the claim that our criterion is "universal" but "unifying." We believe we have already clarified the meaning of "unifying" in our R1 version of the paper, e.g., "We emphasize that, in this context, the word unifying is used because this law combines and captures the synergistic and intertwined effect of the length and time scales involved in the boiling process, i.e., nucleation site density, bubble size, growth time and departure frequency. ..." + +<|ref|>text<|/ref|><|det|>[[115, 397, 882, 460]]<|/det|> +We have already addressed the comment related to the title and the use of the word "law" at the beginning of the rebuttal. As discussed, we wish to title our paper "A unifying criterion of the boiling crisis." We trust that you will find our proposal appropriate. Accordingly, the word "law" has been changed with "criterion" throughout the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 475, 364, 490]]<|/det|> +## Referee #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 505, 882, 552]]<|/det|> +In my opinion, the paper has been considerably improved further to the comments of all reviewers. In particular, all my personal comments were addressed more than satisfactorily. + +<|ref|>text<|/ref|><|det|>[[115, 544, 882, 589]]<|/det|> +I am not yet fully convinced that this theory represents the final answer to a long and historical debate about the causes of critical heat flux in boiling. However it is for sure an original and fresh contribution, that is worth to be published and discussed among the scientific community. + +<|ref|>sub_title<|/ref|><|det|>[[115, 604, 229, 618]]<|/det|> +## Dear Referee #2, + +<|ref|>text<|/ref|><|det|>[[115, 634, 882, 695]]<|/det|> +We appreciate your positive feedback. The boiling crisis has been indeed the subject of a long debate (in fact, more than on hundred years old). We are glad to shake this debate with (as you say) "an original and fresh idea" and first- of- a- kind data revealing new physical mechanisms. We are excited to share our findings with the community and see other scientists to critically evaluate and build upon our work. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 145, 404, 160]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 203, 872, 313]]<|/det|> +With the change of the title of the paper and related text my main concern has been alleviated. However, the authors keep missing the point that in pool boiling of inviscid fluids it is the balance of buoyancy and surface tension forces that determines the maximum rate of vapor removal from the surface. From their work it is not clear under what physical situations it is the far field or the near field instability determines the outcome. The discussion of the authors on the effect of contact angle, the size of the heater and the size of the surrounding vessel and the contact angle of the + +<|ref|>text<|/ref|><|det|>[[118, 327, 835, 362]]<|/det|> +surface surrounding the heater is lacking. At this stage I agree to support the publication of the paper in its revised form. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 364, 105]]<|/det|> +## Referee #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 120, 883, 229]]<|/det|> +With the change of the title of the paper and related text my main concern has been alleviated. However, the authors keep missing the point that in pool boiling of inviscid fluids it is the balance of buoyancy and surface tension forces that determines the maximum rate of vapor removal from the surface. From their work it is not clear under what physical situations it is the far field or the near field instability determines the outcome. The discussion of the authors on the effect of contact angle, the size of the heater and the size of the surrounding vessel and the contact angle of the surface surrounding the heater is lacking. At this stage I agree to support the publication of the paper in its revised form. + +<|ref|>sub_title<|/ref|><|det|>[[116, 245, 229, 259]]<|/det|> +## Dear Referee #1, + +<|ref|>text<|/ref|><|det|>[[117, 275, 402, 290]]<|/det|> +We appreciate your final recommendation. + +<|ref|>text<|/ref|><|det|>[[115, 305, 882, 368]]<|/det|> +We understand your comment about the role of buoyancy and surface tension for pool boiling conditions. However, we think that the role of these forces is accounted for through the fundamental parameters describing the bubble dynamics (i.e., bubbler radius, growth time, departure frequency, and nucleation site density). We emphasize that our model aims at capturing the connection between these fundamental parameters and the boiling crisis. + +<|ref|>text<|/ref|><|det|>[[115, 382, 882, 461]]<|/det|> +Similarly, as already mentioned in our previous rebuttal, we agree that the CHF limit (i.e., the maximum heat flux that can be removed in nucleate boiling in \(\mathsf{W} / \mathsf{m}2\) ) depends on a plethora of parameters such contact angles, surface size, size of the surrounding surface, and many more. However, we believe that the role of these parameters is to affect the bubble dynamics and, consequently, the boiling crisis. Same as before, we emphasize that our model aims at capturing the connection between the parameters describing the bubble dynamics and the boiling crisis. + +<|ref|>text<|/ref|><|det|>[[115, 475, 883, 617]]<|/det|> +We also wish to mention that we discuss the effect of contact angle in our paper. Precisely, we wrote: "We emphasize that, while we did not test hydrophobic surfaces with static contact angles much larger than \(90^{\circ}\) , our paradigm contemplates all surface conditions. For instance, on hydrophobic surface, depending on nucleation sites size distribution and nucleation temperature, the boiling crisis may occur with a large number of small bubbles (i.e., with a small footprint) and a short wait time (i.e., a high \(f t_{g})^{2}\) . In some other cases, the bubble departure diameter on hydrophobic surfaces may be significantly higher than on hydrophilic surfaces \(^{24}\) , and the boiling crisis may happen with a combination of large bubble footprint radius and smaller nucleation site density (and likely higher \(f t_{g}\) product). However, while experiments on superhydrophobic surfaces may be run in the future, the critical condition expressed by Equation (1) should not change." + +<|ref|>text<|/ref|><|det|>[[115, 632, 881, 662]]<|/det|> +Based on your comment, we modified this sentence to mention possible other effects (e.g., such as the size effects discussed in the Methods section), as follows: + +<|ref|>text<|/ref|><|det|>[[115, 663, 882, 742]]<|/det|> +"We emphasize that, while we did not test hydrophobic surfaces with static contact angles much larger than \(90^{\circ}\) , our paradigm contemplates all surface conditions and, possibly, heater geometry effects. For instance, on hydrophobic surface, ... ... combination of large bubble footprint radius and smaller nucleation site density (and likely higher \(f t_{g}\) product). However, while experiments on superhydrophobic surfaces and considering other effects (e.g., heater size and lateral confinement) may be run in the future, the critical condition expressed by Equation (1) should not change." + +<|ref|>text<|/ref|><|det|>[[115, 756, 882, 834]]<|/det|> +Overall, the fact that the critical behavior can be captured using near- wall parameters for surfaces with different boiling behavior (i.e., nucleation site density, bubble growth time and departure frequency, and average footprint radius) and different CHF limits under the same or different operating conditions is in our view, a strong indication that the mechanisms triggering the boiling crisis can be found in the near- wall region. This is the reason why we wrote that our work "corroborates the hypothesis that the boiling crisis is a near- wall phenomenon." + +<|ref|>text<|/ref|><|det|>[[115, 848, 881, 879]]<|/det|> +We are truly grateful for your constructive criticism throughout the rebuttal process. We are excited to share our findings with the community and see other scientists to critically evaluate and build upon our work. + +<--- Page Split ---> diff --git a/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/images_list.json b/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..47f688aed7604e54ee5270671f38f50a20838ba9 --- /dev/null +++ b/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,55 @@ +[ + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4. Predicted aboveground biomass (AGB) for edge \\(\\mathrm{(N = 28h a)}\\) versus interior \\(\\mathrm{(N = 16h a)}\\) forest plots within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia, the world's longest-running experimental study of habitat fragmentation. Points represent model predictions of AGB in edge versus interior forest plots from linear mixed modelling and error bars denote \\(95\\%\\) confidence intervals. 44 1-ha plots used for AGB predictions contained tree measurements on more than 12,000 individual stems \\(\\geq 10\\mathrm{cm}\\) diameter across 1026 tree species. The shaded dark grey area corresponds to AGB loss caused by fragmentation-related changes in forest structure owing to edge effects on tree mortality, growth and recruitment. The red area corresponds to AGB loss caused by edge effects on tree allometry, calculated by comparing AGB estimates using an allometric model that considered edge effects on tree allometry with an allometric model developed for interior forests.\"", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Figure 5. The Biological Dynamics of Forest Fragments Project (BDFFP), the world's longest-running experimental study of habitat fragmentation, is located in Central Amazonia. The BDFFP sites are composed of forest fragments originally isolated in 1980-1983 after the conversion of the surrounding mature forest into cattle pastures. The forest fragments are surrounded by a 100 m matrix, regularly cleaned by cutting the regrowth vegetation to keep the forest fragment isolated.", + "footnote": [], + "bbox": [ + [ + 130, + 315, + 860, + 617 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure 6. Allometric models for woody volume estimates were developed from tree measurements using a Terrestrial Laser Scanner (TLS) within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia. Six transects (five of \\(100 \\times 10 \\mathrm{m}\\) at the edges and one of \\(30 \\times 10 \\mathrm{m}\\) at the forest interior), denoted as black lines in the Colosso and Dimona sites, allowed us obtain high quality point clouds to segment and extract 315 trees. Our findings demonstrate that edge effects on tree allometry penetrated \\(55 \\mathrm{m}\\) from the forest edges. Tree measurements of stem size combined with species identification across 44 1-ha permanent plots within Florestal, Dimona, Colosso and Porto Alegre were used to estimate the aboveground biomass (AGB) in edge (yellow plots) and interior (white plots) forest plots. Comparisons of AGB values using edge- versus interior-specific allometric equations were made to predict the influences of tree allometry on the forest AGB.", + "footnote": [], + "bbox": [ + [ + 120, + 100, + 876, + 510 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "“Figure 4. Predicted aboveground biomass (AGB) for edge \\(\\mathrm{(N = 28~ha)}\\) versus interior \\(\\mathrm{(N = 16}\\) ha) forest plots within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia, the world's longest-running experimental study of habitat fragmentation. Points represent model predictions of AGB in edge versus interior forest plots from linear mixed modelling and error bars denote \\(95\\%\\) confidence intervals. \\(44.1\\) -ha plots used for AGB predictions contained tree measurements on more than 12,000 individual stems \\(\\geq 10\\mathrm{cm}\\) diameter across 1026", + "footnote": [], + "bbox": [ + [ + 128, + 370, + 696, + 720 + ] + ], + "page_idx": 12 + } +] \ No newline at end of file diff --git a/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..276abcbb208519c073cbba08799c12fb8688b8a0 --- /dev/null +++ b/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,351 @@ + +# nature portfolio + +Peer Review File + +Edge effects on tree architecture exacerbate biomass loss of fragmented Amazonian forests + +![](images/Figure_4.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The study presents new insights into the effects of forest fragmentation on above ground biomass and individual tree architecture in Amazonian forests. The main finding is that forest fragmentation is not only reducing above- ground biomass through edge effects on forest structure, but also by affecting tree architecture and allometry. The authors use terrestrial lidar data to quantify tree architectures and allometry and permanent plot data from long- term experimental sites in Amazonia to quantify above- ground biomass. + +The study is interesting from two different perspective. First, the study addresses a topic that is relevant to understand general patterns of tree architecture in response to changing environmental conditions. Second, the findings have important implications for quantifying biomass and carbon stocks of tropical forests, because the authors show that changes in tree allometry following forest fragmentation may lead to an overestimation of biomass at forest edges, if differences in allometry are not being accounted for in allometric equations. While I find the study very interesting and basically well conducted, there are a few things that remain unclear. Before considering the paper for publication, it would be very helpful if the authors could clarify a few points that I am outlining in the following. + +AGB of forest edges and interior: + +In figure 4, the authors report that edge effects on tree allometry cause an additional reduction in AGB, which is one of the key findings. I have a few questions and probably some doubts about that finding. + +First, I think I do not fully understand the difference between the AGB estimate for forest edges and the forest edges + allometric effects. Is the estimation of AGB for forest edges based on allometric equations that do not take the allometry of trees at the edges into account, while the additional \(6.6 \text{Mg ha - 1}\) result from considering differences in allometry? + +Second, the sample sizes for edge and interior plots strongly differ (30 vs. 6). I think it is crucial to clarify how the plot locations were selected (e.g. randomly vs purposefully selected as representative of the larger area). Even in primary forests, forest structures may spatially vary strongly (e.g. Ehbrecht et al. 2021). With increasing sample size, usually more variability is being captured during sampling. That makes me wonder whether the differences in AGB could just be an artefact resulting from differences in sample size. How do the AGB estimates of edge and interior compare to Amazon- wide estimates of AGB? I think the discussion could benefit from providing a few more references on how edge effects on AGB compare to findings from other studies. + +Third, I do not fully understand how the authors define forest edges. In Supplementary Figure 1, the BDFFP study site is shown with different transect length for edge (100 m) and interior (30 m) forests. Does the length of these transects represent the area of forest edges (in terms of depth/width) used for comparing AGB between interior and edges? In the results section, the authors state that they compared AGB estimates within 55 m from forest margins to predict impacts of edge effects on tree allometry and subsequently AGB. In the next paragraph, they state that within 100 m from forest margins AGB is reduced compared to interior forest. Some of the 100 m transects shown in + +<--- Page Split ---> + +Supplementary Figure 1 cover the entire forest patch (where is the interior part then?). First, I am wondering why the authors did not use the information from the entire \(100m\) transect for the allometry part? Second, it remains unclear whether AGB and interior structure in 1 ha and maybe 10 ha fragments are comparable to those of 100 ha fragments, as the interior parts in the small fragments may also already show differences in allometry? Other studies for example found deep reaching edge effects of up to \(200m\) (see Nguyen et al., 2023, https://doi.org/10.1007/s10980-023-01609- x). Overall, the study design descriptions leave me a bit puzzled. I think the paper could benefit from a more straightforward study site and study design description. For example, I would recommend to include a map that shows the location of the plots that were used to estimate AGB for edges and interior and provide a clear definition of forest edge in terms of area and distance from the forest margin. + +## Tree size thresholds: + +In the results section about edge effects on architectural traits, the authors mention that trees above 20 m in height were considered to have established before forest fragmentation and that trees below \(20m\) were most likely post- fragmentation recruits. In Supplementary Figure 4, the authors show that is a considerable number of trees smaller than \(20m\) (in 2019) that were first measured in the early 1980's. Doesn't this imply that the threshold is rather arbitrary and that there is likely a not too small proportion of trees that are \(< 20m\) but that recruited before the experiment was established? Wouldn't it make sense to derive such a threshold from tree growth models? How would different thresholds affect the results? + +## Competition: + +In different sections and paragraphs of the text, the authors state that crown asymmetry indicates the capability to avoid competition for light. I just want to highlight that there are also studies showing that crown asymmetry can also be considered a measure of competition intensity and not necessarily as a measure of competition avoidance (Seidel et al. 2011 https://doi.org/10.1016/j.foreco.2011.03.008). + +## Tree heights: + +At several points, the authors speak of reductions in tree height in forest edges. That term always left me a bit confused when reading the manuscript. As the authors mention, trees can be shorter near edges because of damages or mortality of upper crown parts. But is this generally the case for the studied trees in the study sites? Speaking of reduction in tree height in edges implies that something has reduced the height, e.g. a damage. But couldn't it be that some trees are simply shorter due to the different environmental conditions near edges? For example, under better light conditions trees might need to invest less into height growth in order to capture light. In case there is a considerable number of trees that are not shorter because of damages/crown mortality, but rather of different growing conditions or simply age, I suggest to rather speak of "lower" tree heights instead of "reduced" or "reduction". + +## Minor comments: + +The meaning of the last sentence of first paragraph of methods section is unclear. + +<--- Page Split ---> + +Summarizing, I think it is a very relevant and interesting study. However, I see some room for improving the manuscript, especially by a clearer description of the study design. Methods sections should be written in a way that a study is reproducible. In the current form, I would find it difficult to reproduce the study due to a lack of clarity. As a reader, I was always jumping back and forth between results, methods, discussion and SI to get how and what the authors did (which left me a bit confused here and there). By streamlining the outline and text the manuscript could be greatly improved I think. I hope my comments and suggestions can help to improve the manuscript. + +Reviewer #2 (Remarks to the Author): + +Amazonian forests are becoming more fragmented. This manuscript employs TLS across Amazonian sites to assess edge effects on tree architecture and allometry/biomass. In a nutshell, authors found that biomass increases due to enhanced light capture were more than offset by branch loss due to increased susceptibility to disturbance and damage at forest edges (eg higher wind turbulence) for new (colonizing) and established individuals. + +TLS- based studies like this are increasing in prominence and offer direct methods to measure individual tree biomass and associated biomass without destructive harvest. Results are novel, and the implications on large- scale biomass estimation potentially transformative. That said, I think that it is important to recognize some of the studies limitations: especially its limited sample size and extent as well as relative inattention to the role of inter- species trait differences. For the most part, species are lumped and I wonder how limiting factor would affect a wider ranging study. These limitations are part of the nature of doing labor- intensive, fine- scaled TLS scans so that's fine: it is what it is. Authors would be recommended to better acknowledge these limitations, and not (as they do in the abstract) state they found "20% ... losses in fragmented Amazonian forests" when in fact they only scanned 315 trees. A second minor issues is the grammar and readability, which needs attention before considering publication. + +Some minor edits include: + +Abstract: "apace"? + +RESULTS/FIGURES + +Supp Fig. 5 is confusing, and neither the caption nor corresponding text explain how the red line was calculated. + +<--- Page Split ---> + +Supplementary Figure 6. There does not appear to be an explanation for how partitioning of variance was done. + +Edge effects on tree allometry + +"76" - "76 m"? + +Fig. 4 - what is FE+allometric - this is unclear here but better defined in the Disc. + +## DISCUSSION + +Unclear sentence possessing the phrase "at the expense of lower mechanical stability 44". Consider revising. + +## METHODS + +Table 1: Could the first trait be more clearly labeled (e.g. "density")? + +<--- Page Split ---> + +## POINT-BY-POINT RESPONSE TO REVIEWERS' COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The study presents new insights into the effects of forest fragmentation on above ground biomass and individual tree architecture in Amazonian forests. The main finding is that forest fragmentation is not only reducing above- ground biomass through edge effects on forest structure, but also by affecting tree architecture and allometry. The authors use terrestrial lidar data to quantify tree architectures and allometry and permanent plot data from long- term experimental sites in Amazonia to quantify above- ground biomass. + +The study is interesting from two different perspectives. First, the study addresses a topic that is relevant to understand general patterns of tree architecture in response to changing environmental conditions. Second, the findings have important implications for quantifying biomass and carbon stocks of tropical forests, because the authors show that changes in tree allometry following forest fragmentation may lead to an overestimation of biomass at forest edges, if differences in allometry are not being accounted for in allometric equations. While I find the study very interesting and basically well conducted, there are a few things that remain unclear. Before considering the paper for publication, it would be very helpful if the authors could clarify a few points that I am outlining in the following. + +AGB of forest edges and interior: + +In figure 4, the authors report that edge effects on tree allometry cause an additional reduction in AGB, which is one of the key findings. I have a few questions and probably some doubts about that finding. + +First, I think I do not fully understand the difference between the AGB estimate for forest edges and the forest edges + allometric effects. Is the estimation of AGB for forest edges based on allometric equations that do not take the allometry of trees at the edges into account, while the additional \(6.6\mathrm{Mg}\) ha- 1 result from considering differences in allometry? + +<--- Page Split ---> + +You are right - the additional AGB loss results from considering differences in allometry caused by edge effects, in addition to edge effects on forest structure during the 40 years of experiment (a combination of tree mortality, tree growth, and recruitment that resulted in changes in tree size, tree density and species composition). We have now made this clear in the methods, results and discussion to avoid confusion regarding the additional edge effects on forest AGB caused by changes in tree architecture. More specifically in the Results section: + +"We used allometric models to predict woody volume in both edge and interior forests, unabling us to estimate aboveground biomass (AGB) across larger spatial scales. Linear mixed models applied to data from 44 1- ha permanent plots revealed a statistically significant reduction in AGB of \(24.7\mathrm{Mg}\mathrm{ha}^{- 1}\) due to edge effects \((t = - 3.1;P\) - value \(= 0.003\) ). This reduction accounted for nearly \(10\%\) of the AGB of structurally intact forests \((282.2\pm 15.3\mathrm{Mg}\mathrm{ha}^{- 1})\) and comprised two components: first, there was an \(18.7\mathrm{Mg}\mathrm{ha}^{- 1}\) decline in AGB due to edge effects on forest structure - caused by fragmentation- related variation in tree size, tree density and species composition - within \(100\mathrm{m}\) from the forest margins; second, there was a \(6.0\mathrm{Mg}\mathrm{ha}^{- 1}\) decline in AGB caused by edge effects on tree allometry within \(55\mathrm{m}\) from the forest margins. These distance thresholds were chosen based on previous studies indicating stronger edge effects within \(100\mathrm{m}\) from forest edges on forest structure, and our own study indicating stronger edge effects on tree allometry within 55 m from the forest edges (see Methods for detailed explanations). We visually represented the predicted reduction in AGB caused by edge effects on both forest structure and tree allometry, comparing them to control interior forest plots. Notably, tree allometry alone contributed to one- third of the total AGB decline resulting from edge effects (Figure 4). + +<--- Page Split ---> +![](images/Figure_5.jpg) + +
Figure 4. Predicted aboveground biomass (AGB) for edge \(\mathrm{(N = 28h a)}\) versus interior \(\mathrm{(N = 16h a)}\) forest plots within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia, the world's longest-running experimental study of habitat fragmentation. Points represent model predictions of AGB in edge versus interior forest plots from linear mixed modelling and error bars denote \(95\%\) confidence intervals. 44 1-ha plots used for AGB predictions contained tree measurements on more than 12,000 individual stems \(\geq 10\mathrm{cm}\) diameter across 1026 tree species. The shaded dark grey area corresponds to AGB loss caused by fragmentation-related changes in forest structure owing to edge effects on tree mortality, growth and recruitment. The red area corresponds to AGB loss caused by edge effects on tree allometry, calculated by comparing AGB estimates using an allometric model that considered edge effects on tree allometry with an allometric model developed for interior forests."
+ +<--- Page Split ---> + +Second, the sample sizes for edge and interior plots strongly differ (30 vs. 6). I think it is crucial to clarify how the plot locations were selected (e.g. randomly vs purposefully selected as representative of the larger area). Even in primary forests, forest structures may spatially vary strongly (e.g. Ehbrecht et al. 2021). With increasing sample size, usually more variability is being captured during sampling. That makes me wonder whether the differences in AGB could just be an artefact resulting from differences in sample size. How do the AGB estimates of edge and interior compare to Amazon- wide estimates of AGB? I think the discussion could benefit from providing a few more references on how edge effects on AGB compare to findings from other studies. + +We agree - we have increased the sample size to increase the likelihood of capturing the variability between interior and edge plots. For this, we used other plots near Colosso and Dimona (our TLS sample sites), namely Porto Alegre and Florestal. This increased the number of interior plots from 6 to 16. We also employed linear mixed modelling to analyse AGB values, and included forest site (Colosso, Dimona, Florestal e Porto Alegre) as a random variable to accommodate any unique differences between forest sites that could impact species composition and forest structure, such as soil and topography. + +Regarding plot selection, the BDFFP sites are composed of forest fragments originally isolated in 1980- 1983 after the conversion of the surrounding mature forest into cattle pastures. The project was designed specifically to investigate the relationship between the size of a forest fragment and its stability and functioning. The experimental design of BDFFP is based on comparisons of a replicated series of forest fragments or reserves of different sizes before and after they were isolated from continuous forests (Bierreghard et al, 1992). This controlled experiment is ideal to measure the edge effects on ecosystem properties. We have included some of these details in the first paragraph of the Methods. + +We have also included references in the Discussion that compare our AGB findings with other studies, and how edge effects may affect these values. More specifically: "Variation in the woody volume of trees, coupled with variation in the wood density caused by shifts in species composition, determine the spatial patterns of AGB, which vary considerably across undisturbed Amazonian forests. Intact forests at a site about \(15\mathrm{km}\) south of our study area, in similar lowland forests, were found to have mean AGB values of \(325.5 + \mathrm{CI}_{95\%}13.6\mathrm{Mg}\mathrm{ha}^{-1}\) + +<--- Page Split ---> + +in comparison to our estimates of \(282.2 + 15.3 \mathrm{Mg ha}^{- 1}\) . This demonstrates that our estimates of AGB are conservative. Indeed, AGB estimates can vary significantly among equations, as the choice of allometric models and measurement uncertainty, leading to uncertainties of up to \(31\%\) and \(16\%\) , respectively, in the AGB estimation of Amazonian forests. Furthermore, local environmental conditions that vary at small spatial scales, such as soil fertility, can account for a third of the variation in AGB in terra- firme Amazonian forests. + +Forests in edges tend to experience a dramatic decrease in AGB caused by changes in forest structure, and are often structurally similar to secondary forests. We observed a reduction of 18.7 \(\mathrm{Mg ha}^{- 1}\) (6.6%) in the AGB of forest fragments owing to changes in forest structure within the first \(100 \mathrm{m}\) from the forest edges. This reduction resulted from combined edge effects on tree mortality, growth and recruitment that influence tree size, tree density and species composition. Forest fragmentation not only increases the mortality of large trees, but can also lead to higher growth rates of large trees and the recruitment of new individuals. However, large tree mortality represents a significant proportion of biomass loss, contributing to the high carbon emissions of fragmented ecosystems. The observed reduction in AGB in our study area near the edges was lower than anticipated, potentially due to the controlled conditions in the BDFFP that minimise additional anthropogenic influences such as illegal logging, hunting, fire penetration and pollution. Indeed, edge effects on forest structure in Amazonian forests can extend up to \(1000 \mathrm{m}\) , as fragments are more susceptible to recurring disturbances from fires and illegal logging, and sensitive to the land use in the matrix surrounding the forest fragment. Moreover, edge effects can be stronger in the initial decades post- fragmentation, with up to \(36\%\) of the forest biomass lost in the first 10 to 17 years after fragmentation, potentially followed by a recovery in the subsequent decades. Long- term monitoring of edge and interior forest plots is crucial to investigating edge effects on AGB dynamics, as confounding environmental factors such as soil and topography, which shape species composition and forest structure, can influence the recovery of forest edges and our ability to quantify it. + +Third, I do not fully understand how the authors define forest edges. In Supplementary Figure 1, the BDFFP study site is shown with different transect length for edge (100 m) and interior (30 m) + +<--- Page Split ---> + +forests. Does the length of these transects represent the area of forest edges (in terms of depth/width) used for comparing AGB between interior and edges? In the results section, the authors state that they compared AGB estimates within \(55\mathrm{m}\) from forest margins to predict impacts of edge effects on tree allometry and subsequently AGB. In the next paragraph, they state that within \(100\mathrm{m}\) from forest margins AGB is reduced compared to interior forest. Some of the \(100\mathrm{m}\) transects shown in Supplementary Figure 1 cover the entire forest patch (where is the interior part then?). First, I am wondering why the authors did not use the information from the entire \(100\mathrm{m}\) transect for the allometry part? Second, it remains unclear whether AGB and interior structure in 1 ha and maybe 10 ha fragments are comparable to those of 100 ha fragments, as the interior parts in the small fragments may also already show differences in allometry? Other studies for example found deep reaching edge effects of up to \(200\mathrm{m}\) (see Nguyen et al., 2023, https://doi.org/10.1007/s10980- 023- 01609- x). Overall, the study design descriptions leave me a bit puzzled. I think the paper could benefit from a more straightforward study site and study design description. For example, I would recommend to include a map that shows the location of the plots that were used to estimate AGB for edges and interior and provide a clear definition of forest edge in terms of area and distance from the forest margin. + +Thank you for this comment. The text explaining edge effects extent on allometry was unclear. We have revised it to explain it in more detail. More specifically in the Results section: + +"We used allometric models to predict woody volume in both edge and interior forests, enabling us to estimate aboveground biomass (AGB) across larger spatial scales. Linear mixed models applied to data from \(44\mathrm{1 - ha}\) permanent plots revealed a statistically significant reduction in AGB of \(24.7\mathrm{Mg ha^{- 1}}\) due to edge effects \((t = - 3.1;P\) - value \(= 0.003\) ). This reduction accounted for nearly \(10\%\) of the AGB of structurally intact forests \((282.2\pm 15.3\mathrm{Mg ha^{- 1}})\) and comprised two components: first, there was an \(18.7\mathrm{Mg ha^{- 1}}\) decline in AGB due to edge effects on forest structure - caused by fragmentation- related variation in tree size, tree density and species composition - within \(100\mathrm{m}\) from the forest margins; second, there was a \(6.0\mathrm{Mg ha^{- 1}}\) decline in AGB caused by edge effects on tree allometry within \(55\mathrm{m}\) from the forest margins. These distance thresholds were chosen based on previous studies indicating stronger edge effects within \(100\mathrm{m}\) from forest edges on forest structure, and our own study indicating stronger edge effects on tree allometry within 55 + +<--- Page Split ---> + +m from the forest edges (see Methods for detailed explanations). We visually represented the predicted reduction in AGB caused by edge effects on both forest structure and tree allometry, comparing them to control interior forest plots. Notably, tree allometry alone contributed to one- third of the total AGB decline resulting from edge effects (Figure 4)." + +We have also included two maps that describe the BDFFP experiment in more detail (Figure 5), and a map that shows where the permanent plots (where field- based tree measurements were done for AGB estimation) and TLS transects were located (Figure 6). + +![](images/Figure_6.jpg) + +
Figure 5. The Biological Dynamics of Forest Fragments Project (BDFFP), the world's longest-running experimental study of habitat fragmentation, is located in Central Amazonia. The BDFFP sites are composed of forest fragments originally isolated in 1980-1983 after the conversion of the surrounding mature forest into cattle pastures. The forest fragments are surrounded by a 100 m matrix, regularly cleaned by cutting the regrowth vegetation to keep the forest fragment isolated.
+ +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Figure 6. Allometric models for woody volume estimates were developed from tree measurements using a Terrestrial Laser Scanner (TLS) within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia. Six transects (five of \(100 \times 10 \mathrm{m}\) at the edges and one of \(30 \times 10 \mathrm{m}\) at the forest interior), denoted as black lines in the Colosso and Dimona sites, allowed us obtain high quality point clouds to segment and extract 315 trees. Our findings demonstrate that edge effects on tree allometry penetrated \(55 \mathrm{m}\) from the forest edges. Tree measurements of stem size combined with species identification across 44 1-ha permanent plots within Florestal, Dimona, Colosso and Porto Alegre were used to estimate the aboveground biomass (AGB) in edge (yellow plots) and interior (white plots) forest plots. Comparisons of AGB values using edge- versus interior-specific allometric equations were made to predict the influences of tree allometry on the forest AGB.
+ +Tree size thresholds: + +<--- Page Split ---> + +In the results section about edge effects on architectural traits, the authors mention that trees above \(20\mathrm{m}\) in height were considered to have established before forest fragmentation and that trees below \(20\mathrm{m}\) were most likely post- fragmentation recruits. In Supplementary Figure 4, the authors show that is a considerable number of trees smaller than \(20\mathrm{m}\) (in 2019) that were first measured in the early 1980's. Doesn't this imply that the threshold is rather arbitrary and that there is likely a not too small proportion of trees that are \(< 20\mathrm{m}\) but that recruited before the experiment was established? Wouldn't it make sense to derive such a threshold from tree growth models? How would different thresholds affect the results? + +Thank you for your question and suggestions. Considering the high number of species in our study area (over 1000 species in 44 1- ha plots), and that growth trajectories can vary considerably among species, we are not able to derive such thresholds from tree growth models. And this threshold does not impact our results, as we used this threshold only to give a perspective that large trees are those that most probably have survived the 40 years of forest fragmentation. Indeed, \(1 / 3\) of all trees \(\leq 20\mathrm{m}\) in height are those that have survived the fragmentation effects since the fragments were isolated in 1980, and thus correspond to short- stature adult individuals that, analogous to the tall surviving trees, have experienced edge effects in their adult stage of life. + +As the fragment isolation occurred in 1980, the tall trees of our dataset are individuals that likely have survived the fragmentation effects, and differences in their architecture with forest fragmentation may reflect the ability of adult plants to acclimate to edge effects. On the other hand, short trees can be included in three groups: 1) \(\sim 2 / 3\) of these trees are less than 30 years old recruits that have colonised the area after the establishment of the forest fragments; 2) surviving trees from understory species at varying ontogenetic stages; and 3) trees from slow- growing species, including upper canopy species at varying ontogenetic stages. Trees in group 1 have already been exposed to edge effects during their juvenile phase. Conversely, changes in the architecture of trees in groups 2 and 3 reflect acclimation of short- stature adult individuals to edge effects that, analogous to the tall surviving trees, change their architecture during the adult phase. + +<--- Page Split ---> + +Competition: + +In different sections and paragraphs of the text, the authors state that crown asymmetry indicates the capability to avoid competition for light. I just want to highlight that there are also studies showing that crown asymmetry can also be considered a measure of competition intensity and not necessarily as a measure of competition avoidance (Seidel et al. 2011 https://doi.org/10.1016/j.foreco.2011.03.008). + +Thank you for this reference. We have included in the ecological interpretation of asymmetry the following: + +"Tree asymmetry is a result of competitive pressure from neighbouring trees \(^{80}\) " + +Tree heights: + +At several points, the authors speak of reductions in tree height in forest edges. That term always left me a bit confused when reading the manuscript. As the authors mention, trees can be shorter near edges because of damages or mortality of upper crown parts. But is this generally the case for the studied trees in the study sites? Speaking of reduction in tree height in edges implies that something has reduced the height, e.g. a damage. But couldn't it be that some trees are simply shorter due to the different environmental conditions near edges? For example, under better light conditions trees might need to invest less into height growth in order to capture light. In case there is a considerable number of trees that are not shorter because of damages/crown mortality, but rather of different growing conditions or simply age, I suggest to rather speak of "lower" tree heights instead of "reduced" or "reduction". + +Thank you for this great comment. This makes sense and we agree with the reviewer. We have added the following to the discussion: + +"This resulted in a 30% decline in woody volume for large trees, possibly due to factors including higher microclimatic stress, increased wind speeds, proliferating lianas, and damages that induced mortality of large trees and branch loss \(^{23,28,47}\) . These effects may have led to collateral damage to neighbouring trees, resulting in reduced heights near the forest edges \(^{31,48,49}\) . Alternatively, trees in the edges may have grown less in height, or edge effects may have favoured shorter individuals or + +<--- Page Split ---> + +species acclimated to edge conditions, as the height- to- diameter ratio is a strong determinant of mechanical safety50. Consequently, a potential combination of stem breakage from damages caused by neighbouring trees and selective forces favouring shorter trees for a given DBH led to reduced woody volume in large trees. This aligns with the significant negative effects of human- induced disturbances on tree biomass31. + +Minor comments: + +The meaning of the last sentence of first paragraph of methods section is unclear. + +We removed the sentenced "All trees that are in permanent plots within the BDFFP project", which comprised of the last sentence of first paragraph of Methods section. + +Summarizing, I think it is a very relevant and interesting study. However, I see some room for improving the manuscript, especially by a clearer description of the study design. Methods sections should be written in a way that a study is reproducible. In the current form, I would find it difficult to reproduce the study due to a lack of clarity. As a reader, I was always jumping back and forth between results, methods, discussion and SI to get how and what the authors did (which left me a bit confused here and there). By streamlining the outline and text the manuscript could be greatly improved I think. I hope my comments and suggestions can help to improve the manuscript. + +Thank you for reviewing this manuscript in great detail. We believe that your comments were all carefully addressed, which have improved the paper considerably. We included more details in the Methods section and incorporated them in the Results section to make the text clearer. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +Amazonian forests are becoming more fragmented. This manuscript employs TLS across Amazonian sites to assess edge effects on tree architecture and allometry/biomass. In a nutshell, authors found that biomass increases due to enhanced light capture were more than offset by branch loss due to increased susceptibility to disturbance and damage at forest edges (eg higher wind turbulence) for new (colonizing) and established individuals. + +TLS- based studies like this are increasing in prominence and offer direct methods to measure individual tree biomass and associated biomass without destructive harvest. Results are novel, and the implications on large- scale biomass estimation potentially transformative. That said, I think that it is important to recognize some of the studies limitations: especially its limited sample size and extent as well as relative inattention to the role of inter- species trait differences. For the most part, species are lumped and I wonder how limiting factor would affect a wider ranging study. These limitations are part of the nature of doing labor- intensive, fine- scaled TLS scans so that's fine: it is what it is. Authors would be recommended to better acknowledge these limitations, and not (as they do in the abstract) state they found " \(20\%\) ... losses in fragmented Amazonian forests" when in fact they only scanned 315 trees. + +Thank you very much for reviewing this manuscript and for this comment. We agree with you that we did not account for the within- species variability, when in fact part of our findings were potentially due to a shift in species composition. The within- plot variability represented the largest proportion of variability in all architectural traits. We have included this paragraph in our Results section to demonstrate it: + +"The within- plot variability, that can be seen as local effects arising from edge effects, as well as species- specific and ontogenetic influences accounted for most of the trait variability (Supplementary Figure 5). The within- plot variability also includes analytical errors, such as those arising from measurement, co- registration, tree extraction and QSM – although we were unable to quantify them." + +We also included in the Discussion a few sentences that acknowledge the importance of species for trait variability and the limitations of our study: + +<--- Page Split ---> + +"Despite our efforts to understand architectural variation in Central Amazonian forests with edge effects, the mechanisms allowing species to change their architecture remain elusive. The within- plot variability, that can be seen as local effects arising from edge effects, as well as species- specific and ontogenetic influences accounted for most of architectural variability. These results may help elucidate the generality of our findings in architectural variation across Central Amazonia, although large- scale Amazonian gradients in topography, edaphic properties and climate remain to be tested. Moreover, a shift in species composition caused by edge effects may have partially contributed to our observed changes in tree architecture65. We propose that future research on tree architecture should continue to unravel the interactions of the environment with functional diversity within species. TLS- based data, combined with molecular, genetic and physiological processes regulating tree architecture, can help resolve debates concerning the mechanisms by which trees change their architecture1,69 and enhance predictions of plant responses to global changes." + +A second minor issues is the grammar and readability, which needs attention before considering publication. + +Thank you for this. We have now revised the grammar and readability throughout this manuscript. + +Some minor edits include: + +Abstract: + +"apace"? + +We meant "apace" as synonym of "rapidly". We are no longer using this term though, as we have deleted the first sentences to make the abstract more concise. + +## RESULTS/FIGURES + +Supp Fig. 5 is confusing, and neither the caption nor corresponding text explain how the red line was calculated. + +<--- Page Split ---> + +Thank you. We have included a description of how the vertical red lines (strongest edge effects on each architectural variable) was calculated. Please note that the edge effect extent found in these analyses did not affect any further analysis in AGB, as we have done it only to understand to what extent edge effects can affect architectural traits. + +"To estimate the extent of edge effects on each architectural trait, we used mixed linear models (LME, Eq. 1) that contained a variable representing the plot category of location near an edge or in the forest fragment interior (edge effects), following Nunes and colleagues38. The model also included a variable that represented tree height (H), considering that architectural traits co- vary with tree size and ontogenetic stage17,39. Edge effects and tree height were treated as additive terms to examine the significance of fragmentation and tree height on the variation of architectural traits. We also included an interaction term edge effects \(\times\) tree height, as fragmentation may have different effects on trees of different heights (Eq. 5). To examine the influences of distance from edges on the allometric relationships between woody volume and \(\mathrm{DBH}^2\mathrm{H}\) or woody volume and DBH, we tested how the log transformed variables interacted with edge effects (Eq. 6 and Eq. 7). Nested effects of forest site (Colosso versus Dimona sites), fragment size (1, 10 or 100 ha) and plot (or transect) identity were treated as random variables \((\mu)\) , allowing us to account for the nested spatial variation in architectural traits and to include any idiosyncratic differences between forest site, fragment size and micro- environmental variation (i.e., topography, soil) between plots. + +Architectural trait \(= \beta_{0} + \beta_{1}\times\) (edge effects) \(+ \beta_{2}\times \mathrm{H} + \beta_{3}\times\) (edge effects) \(\times \mathrm{H} + \mu_{i} + \epsilon_{i}\) (Eq. 5) + +\(\ln (\mathrm{woody volume}) = \beta_{0} + \beta_{1}\times\) (edge effects) \(\times \ln (\mathrm{DBH}^2\mathrm{H}) + \mu_{i} + \epsilon_{i}\) (Eq. 6) + +\(\ln (\mathrm{woody volume}) = \beta_{0} + \beta_{1}\times\) (edge effects) \(\times \ln (\mathrm{DBH}) + \mu_{i} + \epsilon_{i}\) (Eq. 7) + +where \(\beta_{0}\) to \(\beta_{3}\) are the model parameters, \(\mu_{i}\) is the random intercept for the nested effects of region i, fragment size i and plot identity i, and \(\epsilon_{i}\) is the normally distributed residual error. + +We then tested the influence of distance to edges on each architectural trait with distances to edges varying between 1 and \(100\mathrm{m}\) , including tree woody volume. We then tested the influence of distance to edges, varying from 1 to \(100\mathrm{m}\) , on each architectural trait; we determined the edge + +<--- Page Split ---> + +effects extent for each architectural trait based on the maximum absolute t- value of the term "edge effects" of the model (Supplementary Figure 4). The edge effects extent was then used to categorise our analysis into edge versus interior trees during all trait analyses." + +Supplementary Figure 6. There does not appear to be an explanation for how partitioning of variance was done. + +Thank you for this comment. We have now included the following in the Supplementary Methods 5: + +"The spatial position with plot identity nested within landscape, and landscape nested within forest region had effects that varied depending on the architectural metric (Supplementary Figure 6). We examined the explained variance by the random variables of Eq.5 to investigate the spatial variability of architectural traits arising from region, landscape and plot (Supplementary Figure 6). The LME models were fitted using the lme function in the "nlme" R package." + +Edge effects on tree allometry + +"76" - "76 m"? + +Thank you. We have included 76 m. + +Fig. 4 - what is FE+allometric - this is unclear here but better defined in the Disc. + +We agree with the reviewer that this was unclear. We have updated the Results with a new Figure 4 and more details on what these changes in AGB represent: + +"We used allometric models to predict woody volume in both edge and interior forests, unabling us to estimate aboveground biomass (AGB) across larger spatial scales. Linear mixed models applied to data from 44 1- ha permanent plots revealed a statistically significant reduction in AGB of \(24.7\mathrm{Mg}\mathrm{ha}^{- 1}\) due to edge effects \((t = - 3.1;P\) - value \(= 0.003\) ). This reduction accounted for nearly \(10\%\) of the AGB of structurally intact forests \((282.2\pm 15.3\mathrm{Mg}\mathrm{ha}^{- 1})\) and comprised two components: first, there was an \(18.7\mathrm{Mg}\mathrm{ha}^{- 1}\) decline in AGB due to edge effects on forest structure + +<--- Page Split ---> + +- caused by fragmentation-related variation in tree size, tree density and species composition - within \(100\mathrm{m}\) from the forest margins; second, there was a \(6.0\mathrm{Mg ha^{-1}}\) decline in AGB caused by edge effects on tree allometry within \(55\mathrm{m}\) from the forest margins. These distance thresholds were chosen based on previous studies indicating stronger edge effects within \(100\mathrm{m}\) from forest edges on forest structure, and our own study indicating stronger edge effects on tree allometry within 55 m from the forest edges (see Methods for detailed explanations). We visually represented the predicted reduction in AGB caused by edge effects on both forest structure and tree allometry, comparing them to control interior forest plots. Notably, tree allometry alone contributed to one-third of the total AGB decline resulting from edge effects (Figure 4)." + +![PLACEHOLDER_20_0] + +
“Figure 4. Predicted aboveground biomass (AGB) for edge \(\mathrm{(N = 28~ha)}\) versus interior \(\mathrm{(N = 16}\) ha) forest plots within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia, the world's longest-running experimental study of habitat fragmentation. Points represent model predictions of AGB in edge versus interior forest plots from linear mixed modelling and error bars denote \(95\%\) confidence intervals. \(44.1\) -ha plots used for AGB predictions contained tree measurements on more than 12,000 individual stems \(\geq 10\mathrm{cm}\) diameter across 1026
+ +<--- Page Split ---> + +tree species. The shaded dark grey area corresponds to AGB loss caused by fragmentation- related changes in forest structure owing to edge effects on tree mortality, growth and recruitment. The red area corresponds to AGB loss caused by edge effects on tree allometry, calculated by comparing AGB estimates using an allometric model that considered edge effects on tree allometry with an allometric model developed for interior forests." + +## DISCUSSION + +Unclear sentence possessing the phrase "at the expense of lower mechanical stability 44". Consider revising. + +Thank you. We have revised it to "this may lead to a lower mechanical stability". + +## METHODS + +Table 1: Could the first trait be more clearly labeled (e.g. "density")? + +Thank you for your question. The trait trunk or branch area per unit volume represents the surface area per unit volume of wood. This trait has been labeled as "surface area per unit volume" in 1978 by Halle et al. in the book "Tropical Trees and Forests: An Architectural Analysis". This trait is interesting from two perspectives: first, it is related to how thick the branches and trunks are, as low values represent branches and trunks that are thicker because they have large volume, and thus can be linked to higher support of aerial structures for light capture and productivity. Second, higher surface areas (thinner branches and trunks) indicate higher interaction with the atmosphere, including higher respiration rates of the living tissues. This book was our inspiration to use this trait to potentially understand how edge effects affected architectural traits linked to structure for light capture. We have kept the same name along the manuscript for consistency with the book. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +Dear Nunes et al., + +many thanks for the thorough revision of the manuscript. I really appreciate your detailed feedback on my comments and the additional analyses. I only have a few further minor comments, mainly for clarification: + +L 38 – The term “50% more wood” is a bit ambiguous. Do you mean more biomass or more volume (or productivity)? + +L 39- 41. I think the first and second half of the sentence kind of contradict. Maybe remove the first half (which relates to the previous sentence?) and start with something like “however, a disproportionally lower height in some large trees led to a 30% decline in their woody volume”? + +L102- 104. I would generally suggest to avoid phrases like “first study” or “first to show…”. + +L 319. Why are your estimates conservative? Maybe you could add a “…, because AGB estimates can vary significantly among equations, …” (if that’s why you think you’re estimates are conservative) + +L 415. I think something went wrong during the revision of the manuscript. In the methods section on TLS, the previous paragraph is repeated. + +Reviewer #2 (Remarks to the Author): + +[Editor's note: the reviewer had no further concerns] + +<--- Page Split ---> + +Point- by- point response to the reviewers + +Reviewer #1 (Remarks to the Author): + +Dear Nunes et al., + +many thanks for the thorough revision of the manuscript. I really appreciate your detailed feedback on my comments and the additional analyses. I only have a few further minor comments, mainly for clarification: + +L 38 – The term “50% more wood” is a bit ambiguous. Do you mean more biomass or more volume (or productivity)? + +More woody volume. We have included this term in the abstract. + +L 39- 41. I think the first and second half of the sentence kind of contradict. Maybe remove the first half (which relates to the previous sentence?) and start with something like “however, a disproportionally lower height in some large trees led to a 30% decline in their woody volume”? + +Thank you. It does make sense the reviewer's suggestion – we have removed the first half. + +L102- 104. I would generally suggest to avoid phrases like “first study” or “first to show...”. + +We have removed the sentence that mentioned these terms. + +L 319. Why are your estimates conservative? Maybe you could add a “... because AGB estimates can vary significantly among equations, ...” (if that’s why you think you’re estimates are conservative) + +Our estimates are conservative because they are lower than estimates for the same region. And this might arise from variations related to the choice of allometric models and measurement uncertainty, as we explained in the following sentence. We have included this in the Discussion as “This demonstrates that our estimates of AGB are conservative given their lower values relative to other estimates for the same region.” + +L 415. I think something went wrong during the revision of the manuscript. In the methods section on TLS, the previous paragraph is repeated. + +Thank you very much. We have corrected this. + +Reviewer #2 (Remarks to the Author): + +[Editor's note: the reviewer had no further concerns] + +<--- Page Split ---> diff --git a/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..ee57c5e2204443303174e47248aa5428f76954e0 --- /dev/null +++ b/peer_reviews/32c379bc583225652929f6dbd86afe289084c66935a92e09bc78ed875d01f835/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,471 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 900, 211]]<|/det|> +Edge effects on tree architecture exacerbate biomass loss of fragmented Amazonian forests + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 147, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 175, 877, 284]]<|/det|> +The study presents new insights into the effects of forest fragmentation on above ground biomass and individual tree architecture in Amazonian forests. The main finding is that forest fragmentation is not only reducing above- ground biomass through edge effects on forest structure, but also by affecting tree architecture and allometry. The authors use terrestrial lidar data to quantify tree architectures and allometry and permanent plot data from long- term experimental sites in Amazonia to quantify above- ground biomass. + +<|ref|>text<|/ref|><|det|>[[114, 294, 881, 441]]<|/det|> +The study is interesting from two different perspective. First, the study addresses a topic that is relevant to understand general patterns of tree architecture in response to changing environmental conditions. Second, the findings have important implications for quantifying biomass and carbon stocks of tropical forests, because the authors show that changes in tree allometry following forest fragmentation may lead to an overestimation of biomass at forest edges, if differences in allometry are not being accounted for in allometric equations. While I find the study very interesting and basically well conducted, there are a few things that remain unclear. Before considering the paper for publication, it would be very helpful if the authors could clarify a few points that I am outlining in the following. + +<|ref|>text<|/ref|><|det|>[[116, 452, 357, 468]]<|/det|> +AGB of forest edges and interior: + +<|ref|>text<|/ref|><|det|>[[115, 480, 872, 515]]<|/det|> +In figure 4, the authors report that edge effects on tree allometry cause an additional reduction in AGB, which is one of the key findings. I have a few questions and probably some doubts about that finding. + +<|ref|>text<|/ref|><|det|>[[115, 526, 881, 599]]<|/det|> +First, I think I do not fully understand the difference between the AGB estimate for forest edges and the forest edges + allometric effects. Is the estimation of AGB for forest edges based on allometric equations that do not take the allometry of trees at the edges into account, while the additional \(6.6 \text{Mg ha - 1}\) result from considering differences in allometry? + +<|ref|>text<|/ref|><|det|>[[114, 608, 880, 755]]<|/det|> +Second, the sample sizes for edge and interior plots strongly differ (30 vs. 6). I think it is crucial to clarify how the plot locations were selected (e.g. randomly vs purposefully selected as representative of the larger area). Even in primary forests, forest structures may spatially vary strongly (e.g. Ehbrecht et al. 2021). With increasing sample size, usually more variability is being captured during sampling. That makes me wonder whether the differences in AGB could just be an artefact resulting from differences in sample size. How do the AGB estimates of edge and interior compare to Amazon- wide estimates of AGB? I think the discussion could benefit from providing a few more references on how edge effects on AGB compare to findings from other studies. + +<|ref|>text<|/ref|><|det|>[[114, 765, 877, 892]]<|/det|> +Third, I do not fully understand how the authors define forest edges. In Supplementary Figure 1, the BDFFP study site is shown with different transect length for edge (100 m) and interior (30 m) forests. Does the length of these transects represent the area of forest edges (in terms of depth/width) used for comparing AGB between interior and edges? In the results section, the authors state that they compared AGB estimates within 55 m from forest margins to predict impacts of edge effects on tree allometry and subsequently AGB. In the next paragraph, they state that within 100 m from forest margins AGB is reduced compared to interior forest. Some of the 100 m transects shown in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 882, 272]]<|/det|> +Supplementary Figure 1 cover the entire forest patch (where is the interior part then?). First, I am wondering why the authors did not use the information from the entire \(100m\) transect for the allometry part? Second, it remains unclear whether AGB and interior structure in 1 ha and maybe 10 ha fragments are comparable to those of 100 ha fragments, as the interior parts in the small fragments may also already show differences in allometry? Other studies for example found deep reaching edge effects of up to \(200m\) (see Nguyen et al., 2023, https://doi.org/10.1007/s10980-023-01609- x). Overall, the study design descriptions leave me a bit puzzled. I think the paper could benefit from a more straightforward study site and study design description. For example, I would recommend to include a map that shows the location of the plots that were used to estimate AGB for edges and interior and provide a clear definition of forest edge in terms of area and distance from the forest margin. + +<|ref|>sub_title<|/ref|><|det|>[[116, 312, 267, 327]]<|/det|> +## Tree size thresholds: + +<|ref|>text<|/ref|><|det|>[[114, 339, 883, 483]]<|/det|> +In the results section about edge effects on architectural traits, the authors mention that trees above 20 m in height were considered to have established before forest fragmentation and that trees below \(20m\) were most likely post- fragmentation recruits. In Supplementary Figure 4, the authors show that is a considerable number of trees smaller than \(20m\) (in 2019) that were first measured in the early 1980's. Doesn't this imply that the threshold is rather arbitrary and that there is likely a not too small proportion of trees that are \(< 20m\) but that recruited before the experiment was established? Wouldn't it make sense to derive such a threshold from tree growth models? How would different thresholds affect the results? + +<|ref|>sub_title<|/ref|><|det|>[[116, 497, 212, 512]]<|/det|> +## Competition: + +<|ref|>text<|/ref|><|det|>[[116, 524, 875, 595]]<|/det|> +In different sections and paragraphs of the text, the authors state that crown asymmetry indicates the capability to avoid competition for light. I just want to highlight that there are also studies showing that crown asymmetry can also be considered a measure of competition intensity and not necessarily as a measure of competition avoidance (Seidel et al. 2011 https://doi.org/10.1016/j.foreco.2011.03.008). + +<|ref|>sub_title<|/ref|><|det|>[[116, 608, 212, 623]]<|/det|> +## Tree heights: + +<|ref|>text<|/ref|><|det|>[[114, 635, 884, 816]]<|/det|> +At several points, the authors speak of reductions in tree height in forest edges. That term always left me a bit confused when reading the manuscript. As the authors mention, trees can be shorter near edges because of damages or mortality of upper crown parts. But is this generally the case for the studied trees in the study sites? Speaking of reduction in tree height in edges implies that something has reduced the height, e.g. a damage. But couldn't it be that some trees are simply shorter due to the different environmental conditions near edges? For example, under better light conditions trees might need to invest less into height growth in order to capture light. In case there is a considerable number of trees that are not shorter because of damages/crown mortality, but rather of different growing conditions or simply age, I suggest to rather speak of "lower" tree heights instead of "reduced" or "reduction". + +<|ref|>sub_title<|/ref|><|det|>[[116, 831, 248, 846]]<|/det|> +## Minor comments: + +<|ref|>text<|/ref|><|det|>[[116, 858, 712, 874]]<|/det|> +The meaning of the last sentence of first paragraph of methods section is unclear. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 877, 217]]<|/det|> +Summarizing, I think it is a very relevant and interesting study. However, I see some room for improving the manuscript, especially by a clearer description of the study design. Methods sections should be written in a way that a study is reproducible. In the current form, I would find it difficult to reproduce the study due to a lack of clarity. As a reader, I was always jumping back and forth between results, methods, discussion and SI to get how and what the authors did (which left me a bit confused here and there). By streamlining the outline and text the manuscript could be greatly improved I think. I hope my comments and suggestions can help to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 256, 393, 273]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 284, 881, 375]]<|/det|> +Amazonian forests are becoming more fragmented. This manuscript employs TLS across Amazonian sites to assess edge effects on tree architecture and allometry/biomass. In a nutshell, authors found that biomass increases due to enhanced light capture were more than offset by branch loss due to increased susceptibility to disturbance and damage at forest edges (eg higher wind turbulence) for new (colonizing) and established individuals. + +<|ref|>text<|/ref|><|det|>[[113, 413, 884, 614]]<|/det|> +TLS- based studies like this are increasing in prominence and offer direct methods to measure individual tree biomass and associated biomass without destructive harvest. Results are novel, and the implications on large- scale biomass estimation potentially transformative. That said, I think that it is important to recognize some of the studies limitations: especially its limited sample size and extent as well as relative inattention to the role of inter- species trait differences. For the most part, species are lumped and I wonder how limiting factor would affect a wider ranging study. These limitations are part of the nature of doing labor- intensive, fine- scaled TLS scans so that's fine: it is what it is. Authors would be recommended to better acknowledge these limitations, and not (as they do in the abstract) state they found "20% ... losses in fragmented Amazonian forests" when in fact they only scanned 315 trees. A second minor issues is the grammar and readability, which needs attention before considering publication. + +<|ref|>text<|/ref|><|det|>[[115, 655, 307, 671]]<|/det|> +Some minor edits include: + +<|ref|>text<|/ref|><|det|>[[115, 713, 184, 755]]<|/det|> +Abstract: "apace"? + +<|ref|>text<|/ref|><|det|>[[115, 795, 250, 812]]<|/det|> +RESULTS/FIGURES + +<|ref|>text<|/ref|><|det|>[[113, 852, 854, 887]]<|/det|> +Supp Fig. 5 is confusing, and neither the caption nor corresponding text explain how the red line was calculated. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 117, 857, 153]]<|/det|> +Supplementary Figure 6. There does not appear to be an explanation for how partitioning of variance was done. + +<|ref|>text<|/ref|><|det|>[[115, 165, 340, 182]]<|/det|> +Edge effects on tree allometry + +<|ref|>text<|/ref|><|det|>[[115, 194, 224, 209]]<|/det|> +"76" - "76 m"? + +<|ref|>text<|/ref|><|det|>[[115, 221, 700, 238]]<|/det|> +Fig. 4 - what is FE+allometric - this is unclear here but better defined in the Disc. + +<|ref|>sub_title<|/ref|><|det|>[[115, 250, 208, 266]]<|/det|> +## DISCUSSION + +<|ref|>text<|/ref|><|det|>[[115, 278, 844, 314]]<|/det|> +Unclear sentence possessing the phrase "at the expense of lower mechanical stability 44". Consider revising. + +<|ref|>sub_title<|/ref|><|det|>[[115, 353, 194, 369]]<|/det|> +## METHODS + +<|ref|>text<|/ref|><|det|>[[115, 381, 615, 399]]<|/det|> +Table 1: Could the first trait be more clearly labeled (e.g. "density")? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[113, 91, 677, 111]]<|/det|> +## POINT-BY-POINT RESPONSE TO REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 153, 438, 172]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 189, 884, 339]]<|/det|> +The study presents new insights into the effects of forest fragmentation on above ground biomass and individual tree architecture in Amazonian forests. The main finding is that forest fragmentation is not only reducing above- ground biomass through edge effects on forest structure, but also by affecting tree architecture and allometry. The authors use terrestrial lidar data to quantify tree architectures and allometry and permanent plot data from long- term experimental sites in Amazonia to quantify above- ground biomass. + +<|ref|>text<|/ref|><|det|>[[113, 355, 884, 585]]<|/det|> +The study is interesting from two different perspectives. First, the study addresses a topic that is relevant to understand general patterns of tree architecture in response to changing environmental conditions. Second, the findings have important implications for quantifying biomass and carbon stocks of tropical forests, because the authors show that changes in tree allometry following forest fragmentation may lead to an overestimation of biomass at forest edges, if differences in allometry are not being accounted for in allometric equations. While I find the study very interesting and basically well conducted, there are a few things that remain unclear. Before considering the paper for publication, it would be very helpful if the authors could clarify a few points that I am outlining in the following. + +<|ref|>text<|/ref|><|det|>[[115, 637, 380, 655]]<|/det|> +AGB of forest edges and interior: + +<|ref|>text<|/ref|><|det|>[[114, 672, 883, 744]]<|/det|> +In figure 4, the authors report that edge effects on tree allometry cause an additional reduction in AGB, which is one of the key findings. I have a few questions and probably some doubts about that finding. + +<|ref|>text<|/ref|><|det|>[[114, 761, 883, 858]]<|/det|> +First, I think I do not fully understand the difference between the AGB estimate for forest edges and the forest edges + allometric effects. Is the estimation of AGB for forest edges based on allometric equations that do not take the allometry of trees at the edges into account, while the additional \(6.6\mathrm{Mg}\) ha- 1 result from considering differences in allometry? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 240]]<|/det|> +You are right - the additional AGB loss results from considering differences in allometry caused by edge effects, in addition to edge effects on forest structure during the 40 years of experiment (a combination of tree mortality, tree growth, and recruitment that resulted in changes in tree size, tree density and species composition). We have now made this clear in the methods, results and discussion to avoid confusion regarding the additional edge effects on forest AGB caused by changes in tree architecture. More specifically in the Results section: + +<|ref|>text<|/ref|><|det|>[[112, 255, 885, 642]]<|/det|> +"We used allometric models to predict woody volume in both edge and interior forests, unabling us to estimate aboveground biomass (AGB) across larger spatial scales. Linear mixed models applied to data from 44 1- ha permanent plots revealed a statistically significant reduction in AGB of \(24.7\mathrm{Mg}\mathrm{ha}^{- 1}\) due to edge effects \((t = - 3.1;P\) - value \(= 0.003\) ). This reduction accounted for nearly \(10\%\) of the AGB of structurally intact forests \((282.2\pm 15.3\mathrm{Mg}\mathrm{ha}^{- 1})\) and comprised two components: first, there was an \(18.7\mathrm{Mg}\mathrm{ha}^{- 1}\) decline in AGB due to edge effects on forest structure - caused by fragmentation- related variation in tree size, tree density and species composition - within \(100\mathrm{m}\) from the forest margins; second, there was a \(6.0\mathrm{Mg}\mathrm{ha}^{- 1}\) decline in AGB caused by edge effects on tree allometry within \(55\mathrm{m}\) from the forest margins. These distance thresholds were chosen based on previous studies indicating stronger edge effects within \(100\mathrm{m}\) from forest edges on forest structure, and our own study indicating stronger edge effects on tree allometry within 55 m from the forest edges (see Methods for detailed explanations). We visually represented the predicted reduction in AGB caused by edge effects on both forest structure and tree allometry, comparing them to control interior forest plots. Notably, tree allometry alone contributed to one- third of the total AGB decline resulting from edge effects (Figure 4). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[133, 105, 870, 555]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 577, 884, 858]]<|/det|> +
Figure 4. Predicted aboveground biomass (AGB) for edge \(\mathrm{(N = 28h a)}\) versus interior \(\mathrm{(N = 16h a)}\) forest plots within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia, the world's longest-running experimental study of habitat fragmentation. Points represent model predictions of AGB in edge versus interior forest plots from linear mixed modelling and error bars denote \(95\%\) confidence intervals. 44 1-ha plots used for AGB predictions contained tree measurements on more than 12,000 individual stems \(\geq 10\mathrm{cm}\) diameter across 1026 tree species. The shaded dark grey area corresponds to AGB loss caused by fragmentation-related changes in forest structure owing to edge effects on tree mortality, growth and recruitment. The red area corresponds to AGB loss caused by edge effects on tree allometry, calculated by comparing AGB estimates using an allometric model that considered edge effects on tree allometry with an allometric model developed for interior forests."
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 317]]<|/det|> +Second, the sample sizes for edge and interior plots strongly differ (30 vs. 6). I think it is crucial to clarify how the plot locations were selected (e.g. randomly vs purposefully selected as representative of the larger area). Even in primary forests, forest structures may spatially vary strongly (e.g. Ehbrecht et al. 2021). With increasing sample size, usually more variability is being captured during sampling. That makes me wonder whether the differences in AGB could just be an artefact resulting from differences in sample size. How do the AGB estimates of edge and interior compare to Amazon- wide estimates of AGB? I think the discussion could benefit from providing a few more references on how edge effects on AGB compare to findings from other studies. + +<|ref|>text<|/ref|><|det|>[[113, 334, 884, 512]]<|/det|> +We agree - we have increased the sample size to increase the likelihood of capturing the variability between interior and edge plots. For this, we used other plots near Colosso and Dimona (our TLS sample sites), namely Porto Alegre and Florestal. This increased the number of interior plots from 6 to 16. We also employed linear mixed modelling to analyse AGB values, and included forest site (Colosso, Dimona, Florestal e Porto Alegre) as a random variable to accommodate any unique differences between forest sites that could impact species composition and forest structure, such as soil and topography. + +<|ref|>text<|/ref|><|det|>[[113, 526, 884, 730]]<|/det|> +Regarding plot selection, the BDFFP sites are composed of forest fragments originally isolated in 1980- 1983 after the conversion of the surrounding mature forest into cattle pastures. The project was designed specifically to investigate the relationship between the size of a forest fragment and its stability and functioning. The experimental design of BDFFP is based on comparisons of a replicated series of forest fragments or reserves of different sizes before and after they were isolated from continuous forests (Bierreghard et al, 1992). This controlled experiment is ideal to measure the edge effects on ecosystem properties. We have included some of these details in the first paragraph of the Methods. + +<|ref|>text<|/ref|><|det|>[[113, 745, 884, 901]]<|/det|> +We have also included references in the Discussion that compare our AGB findings with other studies, and how edge effects may affect these values. More specifically: "Variation in the woody volume of trees, coupled with variation in the wood density caused by shifts in species composition, determine the spatial patterns of AGB, which vary considerably across undisturbed Amazonian forests. Intact forests at a site about \(15\mathrm{km}\) south of our study area, in similar lowland forests, were found to have mean AGB values of \(325.5 + \mathrm{CI}_{95\%}13.6\mathrm{Mg}\mathrm{ha}^{-1}\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 248]]<|/det|> +in comparison to our estimates of \(282.2 + 15.3 \mathrm{Mg ha}^{- 1}\) . This demonstrates that our estimates of AGB are conservative. Indeed, AGB estimates can vary significantly among equations, as the choice of allometric models and measurement uncertainty, leading to uncertainties of up to \(31\%\) and \(16\%\) , respectively, in the AGB estimation of Amazonian forests. Furthermore, local environmental conditions that vary at small spatial scales, such as soil fertility, can account for a third of the variation in AGB in terra- firme Amazonian forests. + +<|ref|>text<|/ref|><|det|>[[112, 262, 885, 802]]<|/det|> +Forests in edges tend to experience a dramatic decrease in AGB caused by changes in forest structure, and are often structurally similar to secondary forests. We observed a reduction of 18.7 \(\mathrm{Mg ha}^{- 1}\) (6.6%) in the AGB of forest fragments owing to changes in forest structure within the first \(100 \mathrm{m}\) from the forest edges. This reduction resulted from combined edge effects on tree mortality, growth and recruitment that influence tree size, tree density and species composition. Forest fragmentation not only increases the mortality of large trees, but can also lead to higher growth rates of large trees and the recruitment of new individuals. However, large tree mortality represents a significant proportion of biomass loss, contributing to the high carbon emissions of fragmented ecosystems. The observed reduction in AGB in our study area near the edges was lower than anticipated, potentially due to the controlled conditions in the BDFFP that minimise additional anthropogenic influences such as illegal logging, hunting, fire penetration and pollution. Indeed, edge effects on forest structure in Amazonian forests can extend up to \(1000 \mathrm{m}\) , as fragments are more susceptible to recurring disturbances from fires and illegal logging, and sensitive to the land use in the matrix surrounding the forest fragment. Moreover, edge effects can be stronger in the initial decades post- fragmentation, with up to \(36\%\) of the forest biomass lost in the first 10 to 17 years after fragmentation, potentially followed by a recovery in the subsequent decades. Long- term monitoring of edge and interior forest plots is crucial to investigating edge effects on AGB dynamics, as confounding environmental factors such as soil and topography, which shape species composition and forest structure, can influence the recovery of forest edges and our ability to quantify it. + +<|ref|>text<|/ref|><|det|>[[114, 850, 882, 896]]<|/det|> +Third, I do not fully understand how the authors define forest edges. In Supplementary Figure 1, the BDFFP study site is shown with different transect length for edge (100 m) and interior (30 m) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 87, 885, 503]]<|/det|> +forests. Does the length of these transects represent the area of forest edges (in terms of depth/width) used for comparing AGB between interior and edges? In the results section, the authors state that they compared AGB estimates within \(55\mathrm{m}\) from forest margins to predict impacts of edge effects on tree allometry and subsequently AGB. In the next paragraph, they state that within \(100\mathrm{m}\) from forest margins AGB is reduced compared to interior forest. Some of the \(100\mathrm{m}\) transects shown in Supplementary Figure 1 cover the entire forest patch (where is the interior part then?). First, I am wondering why the authors did not use the information from the entire \(100\mathrm{m}\) transect for the allometry part? Second, it remains unclear whether AGB and interior structure in 1 ha and maybe 10 ha fragments are comparable to those of 100 ha fragments, as the interior parts in the small fragments may also already show differences in allometry? Other studies for example found deep reaching edge effects of up to \(200\mathrm{m}\) (see Nguyen et al., 2023, https://doi.org/10.1007/s10980- 023- 01609- x). Overall, the study design descriptions leave me a bit puzzled. I think the paper could benefit from a more straightforward study site and study design description. For example, I would recommend to include a map that shows the location of the plots that were used to estimate AGB for edges and interior and provide a clear definition of forest edge in terms of area and distance from the forest margin. + +<|ref|>text<|/ref|><|det|>[[114, 554, 881, 600]]<|/det|> +Thank you for this comment. The text explaining edge effects extent on allometry was unclear. We have revised it to explain it in more detail. More specifically in the Results section: + +<|ref|>text<|/ref|><|det|>[[112, 615, 886, 898]]<|/det|> +"We used allometric models to predict woody volume in both edge and interior forests, enabling us to estimate aboveground biomass (AGB) across larger spatial scales. Linear mixed models applied to data from \(44\mathrm{1 - ha}\) permanent plots revealed a statistically significant reduction in AGB of \(24.7\mathrm{Mg ha^{- 1}}\) due to edge effects \((t = - 3.1;P\) - value \(= 0.003\) ). This reduction accounted for nearly \(10\%\) of the AGB of structurally intact forests \((282.2\pm 15.3\mathrm{Mg ha^{- 1}})\) and comprised two components: first, there was an \(18.7\mathrm{Mg ha^{- 1}}\) decline in AGB due to edge effects on forest structure - caused by fragmentation- related variation in tree size, tree density and species composition - within \(100\mathrm{m}\) from the forest margins; second, there was a \(6.0\mathrm{Mg ha^{- 1}}\) decline in AGB caused by edge effects on tree allometry within \(55\mathrm{m}\) from the forest margins. These distance thresholds were chosen based on previous studies indicating stronger edge effects within \(100\mathrm{m}\) from forest edges on forest structure, and our own study indicating stronger edge effects on tree allometry within 55 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 188]]<|/det|> +m from the forest edges (see Methods for detailed explanations). We visually represented the predicted reduction in AGB caused by edge effects on both forest structure and tree allometry, comparing them to control interior forest plots. Notably, tree allometry alone contributed to one- third of the total AGB decline resulting from edge effects (Figure 4)." + +<|ref|>text<|/ref|><|det|>[[113, 202, 884, 276]]<|/det|> +We have also included two maps that describe the BDFFP experiment in more detail (Figure 5), and a map that shows where the permanent plots (where field- based tree measurements were done for AGB estimation) and TLS transects were located (Figure 6). + +<|ref|>image<|/ref|><|det|>[[130, 315, 860, 617]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 662, 884, 789]]<|/det|> +
Figure 5. The Biological Dynamics of Forest Fragments Project (BDFFP), the world's longest-running experimental study of habitat fragmentation, is located in Central Amazonia. The BDFFP sites are composed of forest fragments originally isolated in 1980-1983 after the conversion of the surrounding mature forest into cattle pastures. The forest fragments are surrounded by a 100 m matrix, regularly cleaned by cutting the regrowth vegetation to keep the forest fragment isolated.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 100, 876, 510]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 525, 884, 805]]<|/det|> +
Figure 6. Allometric models for woody volume estimates were developed from tree measurements using a Terrestrial Laser Scanner (TLS) within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia. Six transects (five of \(100 \times 10 \mathrm{m}\) at the edges and one of \(30 \times 10 \mathrm{m}\) at the forest interior), denoted as black lines in the Colosso and Dimona sites, allowed us obtain high quality point clouds to segment and extract 315 trees. Our findings demonstrate that edge effects on tree allometry penetrated \(55 \mathrm{m}\) from the forest edges. Tree measurements of stem size combined with species identification across 44 1-ha permanent plots within Florestal, Dimona, Colosso and Porto Alegre were used to estimate the aboveground biomass (AGB) in edge (yellow plots) and interior (white plots) forest plots. Comparisons of AGB values using edge- versus interior-specific allometric equations were made to predict the influences of tree allometry on the forest AGB.
+ +<|ref|>text<|/ref|><|det|>[[115, 859, 279, 875]]<|/det|> +Tree size thresholds: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 291]]<|/det|> +In the results section about edge effects on architectural traits, the authors mention that trees above \(20\mathrm{m}\) in height were considered to have established before forest fragmentation and that trees below \(20\mathrm{m}\) were most likely post- fragmentation recruits. In Supplementary Figure 4, the authors show that is a considerable number of trees smaller than \(20\mathrm{m}\) (in 2019) that were first measured in the early 1980's. Doesn't this imply that the threshold is rather arbitrary and that there is likely a not too small proportion of trees that are \(< 20\mathrm{m}\) but that recruited before the experiment was established? Wouldn't it make sense to derive such a threshold from tree growth models? How would different thresholds affect the results? + +<|ref|>text<|/ref|><|det|>[[113, 306, 885, 511]]<|/det|> +Thank you for your question and suggestions. Considering the high number of species in our study area (over 1000 species in 44 1- ha plots), and that growth trajectories can vary considerably among species, we are not able to derive such thresholds from tree growth models. And this threshold does not impact our results, as we used this threshold only to give a perspective that large trees are those that most probably have survived the 40 years of forest fragmentation. Indeed, \(1 / 3\) of all trees \(\leq 20\mathrm{m}\) in height are those that have survived the fragmentation effects since the fragments were isolated in 1980, and thus correspond to short- stature adult individuals that, analogous to the tall surviving trees, have experienced edge effects in their adult stage of life. + +<|ref|>text<|/ref|><|det|>[[113, 525, 885, 782]]<|/det|> +As the fragment isolation occurred in 1980, the tall trees of our dataset are individuals that likely have survived the fragmentation effects, and differences in their architecture with forest fragmentation may reflect the ability of adult plants to acclimate to edge effects. On the other hand, short trees can be included in three groups: 1) \(\sim 2 / 3\) of these trees are less than 30 years old recruits that have colonised the area after the establishment of the forest fragments; 2) surviving trees from understory species at varying ontogenetic stages; and 3) trees from slow- growing species, including upper canopy species at varying ontogenetic stages. Trees in group 1 have already been exposed to edge effects during their juvenile phase. Conversely, changes in the architecture of trees in groups 2 and 3 reflect acclimation of short- stature adult individuals to edge effects that, analogous to the tall surviving trees, change their architecture during the adult phase. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 220, 108]]<|/det|> +Competition: + +<|ref|>text<|/ref|><|det|>[[113, 124, 884, 250]]<|/det|> +In different sections and paragraphs of the text, the authors state that crown asymmetry indicates the capability to avoid competition for light. I just want to highlight that there are also studies showing that crown asymmetry can also be considered a measure of competition intensity and not necessarily as a measure of competition avoidance (Seidel et al. 2011 https://doi.org/10.1016/j.foreco.2011.03.008). + +<|ref|>text<|/ref|><|det|>[[115, 265, 883, 312]]<|/det|> +Thank you for this reference. We have included in the ecological interpretation of asymmetry the following: + +<|ref|>text<|/ref|><|det|>[[115, 328, 741, 348]]<|/det|> +"Tree asymmetry is a result of competitive pressure from neighbouring trees \(^{80}\) " + +<|ref|>text<|/ref|><|det|>[[115, 400, 220, 418]]<|/det|> +Tree heights: + +<|ref|>text<|/ref|><|det|>[[113, 434, 884, 690]]<|/det|> +At several points, the authors speak of reductions in tree height in forest edges. That term always left me a bit confused when reading the manuscript. As the authors mention, trees can be shorter near edges because of damages or mortality of upper crown parts. But is this generally the case for the studied trees in the study sites? Speaking of reduction in tree height in edges implies that something has reduced the height, e.g. a damage. But couldn't it be that some trees are simply shorter due to the different environmental conditions near edges? For example, under better light conditions trees might need to invest less into height growth in order to capture light. In case there is a considerable number of trees that are not shorter because of damages/crown mortality, but rather of different growing conditions or simply age, I suggest to rather speak of "lower" tree heights instead of "reduced" or "reduction". + +<|ref|>text<|/ref|><|det|>[[115, 707, 883, 753]]<|/det|> +Thank you for this great comment. This makes sense and we agree with the reviewer. We have added the following to the discussion: + +<|ref|>text<|/ref|><|det|>[[113, 769, 884, 894]]<|/det|> +"This resulted in a 30% decline in woody volume for large trees, possibly due to factors including higher microclimatic stress, increased wind speeds, proliferating lianas, and damages that induced mortality of large trees and branch loss \(^{23,28,47}\) . These effects may have led to collateral damage to neighbouring trees, resulting in reduced heights near the forest edges \(^{31,48,49}\) . Alternatively, trees in the edges may have grown less in height, or edge effects may have favoured shorter individuals or + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 213]]<|/det|> +species acclimated to edge conditions, as the height- to- diameter ratio is a strong determinant of mechanical safety50. Consequently, a potential combination of stem breakage from damages caused by neighbouring trees and selective forces favouring shorter trees for a given DBH led to reduced woody volume in large trees. This aligns with the significant negative effects of human- induced disturbances on tree biomass31. + +<|ref|>text<|/ref|><|det|>[[114, 266, 257, 284]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[114, 301, 752, 321]]<|/det|> +The meaning of the last sentence of first paragraph of methods section is unclear. + +<|ref|>text<|/ref|><|det|>[[114, 337, 883, 384]]<|/det|> +We removed the sentenced "All trees that are in permanent plots within the BDFFP project", which comprised of the last sentence of first paragraph of Methods section. + +<|ref|>text<|/ref|><|det|>[[113, 434, 884, 612]]<|/det|> +Summarizing, I think it is a very relevant and interesting study. However, I see some room for improving the manuscript, especially by a clearer description of the study design. Methods sections should be written in a way that a study is reproducible. In the current form, I would find it difficult to reproduce the study due to a lack of clarity. As a reader, I was always jumping back and forth between results, methods, discussion and SI to get how and what the authors did (which left me a bit confused here and there). By streamlining the outline and text the manuscript could be greatly improved I think. I hope my comments and suggestions can help to improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 627, 883, 700]]<|/det|> +Thank you for reviewing this manuscript in great detail. We believe that your comments were all carefully addressed, which have improved the paper considerably. We included more details in the Methods section and incorporated them in the Results section to make the text clearer. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 438, 109]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 124, 883, 250]]<|/det|> +Amazonian forests are becoming more fragmented. This manuscript employs TLS across Amazonian sites to assess edge effects on tree architecture and allometry/biomass. In a nutshell, authors found that biomass increases due to enhanced light capture were more than offset by branch loss due to increased susceptibility to disturbance and damage at forest edges (eg higher wind turbulence) for new (colonizing) and established individuals. + +<|ref|>text<|/ref|><|det|>[[113, 264, 884, 521]]<|/det|> +TLS- based studies like this are increasing in prominence and offer direct methods to measure individual tree biomass and associated biomass without destructive harvest. Results are novel, and the implications on large- scale biomass estimation potentially transformative. That said, I think that it is important to recognize some of the studies limitations: especially its limited sample size and extent as well as relative inattention to the role of inter- species trait differences. For the most part, species are lumped and I wonder how limiting factor would affect a wider ranging study. These limitations are part of the nature of doing labor- intensive, fine- scaled TLS scans so that's fine: it is what it is. Authors would be recommended to better acknowledge these limitations, and not (as they do in the abstract) state they found " \(20\%\) ... losses in fragmented Amazonian forests" when in fact they only scanned 315 trees. + +<|ref|>text<|/ref|><|det|>[[114, 536, 883, 662]]<|/det|> +Thank you very much for reviewing this manuscript and for this comment. We agree with you that we did not account for the within- species variability, when in fact part of our findings were potentially due to a shift in species composition. The within- plot variability represented the largest proportion of variability in all architectural traits. We have included this paragraph in our Results section to demonstrate it: + +<|ref|>text<|/ref|><|det|>[[114, 677, 883, 800]]<|/det|> +"The within- plot variability, that can be seen as local effects arising from edge effects, as well as species- specific and ontogenetic influences accounted for most of the trait variability (Supplementary Figure 5). The within- plot variability also includes analytical errors, such as those arising from measurement, co- registration, tree extraction and QSM – although we were unable to quantify them." + +<|ref|>text<|/ref|><|det|>[[114, 810, 882, 856]]<|/det|> +We also included in the Discussion a few sentences that acknowledge the importance of species for trait variability and the limitations of our study: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 885, 422]]<|/det|> +"Despite our efforts to understand architectural variation in Central Amazonian forests with edge effects, the mechanisms allowing species to change their architecture remain elusive. The within- plot variability, that can be seen as local effects arising from edge effects, as well as species- specific and ontogenetic influences accounted for most of architectural variability. These results may help elucidate the generality of our findings in architectural variation across Central Amazonia, although large- scale Amazonian gradients in topography, edaphic properties and climate remain to be tested. Moreover, a shift in species composition caused by edge effects may have partially contributed to our observed changes in tree architecture65. We propose that future research on tree architecture should continue to unravel the interactions of the environment with functional diversity within species. TLS- based data, combined with molecular, genetic and physiological processes regulating tree architecture, can help resolve debates concerning the mechanisms by which trees change their architecture1,69 and enhance predictions of plant responses to global changes." + +<|ref|>text<|/ref|><|det|>[[113, 456, 883, 503]]<|/det|> +A second minor issues is the grammar and readability, which needs attention before considering publication. + +<|ref|>text<|/ref|><|det|>[[113, 510, 880, 531]]<|/det|> +Thank you for this. We have now revised the grammar and readability throughout this manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 574, 323, 592]]<|/det|> +Some minor edits include: + +<|ref|>text<|/ref|><|det|>[[115, 611, 189, 628]]<|/det|> +Abstract: + +<|ref|>text<|/ref|><|det|>[[115, 647, 188, 664]]<|/det|> +"apace"? + +<|ref|>text<|/ref|><|det|>[[115, 682, 882, 728]]<|/det|> +We meant "apace" as synonym of "rapidly". We are no longer using this term though, as we have deleted the first sentences to make the abstract more concise. + +<|ref|>sub_title<|/ref|><|det|>[[115, 780, 290, 799]]<|/det|> +## RESULTS/FIGURES + +<|ref|>text<|/ref|><|det|>[[115, 816, 882, 862]]<|/det|> +Supp Fig. 5 is confusing, and neither the caption nor corresponding text explain how the red line was calculated. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 188]]<|/det|> +Thank you. We have included a description of how the vertical red lines (strongest edge effects on each architectural variable) was calculated. Please note that the edge effect extent found in these analyses did not affect any further analysis in AGB, as we have done it only to understand to what extent edge effects can affect architectural traits. + +<|ref|>text<|/ref|><|det|>[[112, 202, 885, 565]]<|/det|> +"To estimate the extent of edge effects on each architectural trait, we used mixed linear models (LME, Eq. 1) that contained a variable representing the plot category of location near an edge or in the forest fragment interior (edge effects), following Nunes and colleagues38. The model also included a variable that represented tree height (H), considering that architectural traits co- vary with tree size and ontogenetic stage17,39. Edge effects and tree height were treated as additive terms to examine the significance of fragmentation and tree height on the variation of architectural traits. We also included an interaction term edge effects \(\times\) tree height, as fragmentation may have different effects on trees of different heights (Eq. 5). To examine the influences of distance from edges on the allometric relationships between woody volume and \(\mathrm{DBH}^2\mathrm{H}\) or woody volume and DBH, we tested how the log transformed variables interacted with edge effects (Eq. 6 and Eq. 7). Nested effects of forest site (Colosso versus Dimona sites), fragment size (1, 10 or 100 ha) and plot (or transect) identity were treated as random variables \((\mu)\) , allowing us to account for the nested spatial variation in architectural traits and to include any idiosyncratic differences between forest site, fragment size and micro- environmental variation (i.e., topography, soil) between plots. + +<|ref|>text<|/ref|><|det|>[[112, 614, 857, 636]]<|/det|> +Architectural trait \(= \beta_{0} + \beta_{1}\times\) (edge effects) \(+ \beta_{2}\times \mathrm{H} + \beta_{3}\times\) (edge effects) \(\times \mathrm{H} + \mu_{i} + \epsilon_{i}\) (Eq. 5) + +<|ref|>text<|/ref|><|det|>[[112, 650, 850, 672]]<|/det|> +\(\ln (\mathrm{woody volume}) = \beta_{0} + \beta_{1}\times\) (edge effects) \(\times \ln (\mathrm{DBH}^2\mathrm{H}) + \mu_{i} + \epsilon_{i}\) (Eq. 6) + +<|ref|>text<|/ref|><|det|>[[112, 687, 620, 707]]<|/det|> +\(\ln (\mathrm{woody volume}) = \beta_{0} + \beta_{1}\times\) (edge effects) \(\times \ln (\mathrm{DBH}) + \mu_{i} + \epsilon_{i}\) (Eq. 7) + +<|ref|>text<|/ref|><|det|>[[112, 723, 883, 770]]<|/det|> +where \(\beta_{0}\) to \(\beta_{3}\) are the model parameters, \(\mu_{i}\) is the random intercept for the nested effects of region i, fragment size i and plot identity i, and \(\epsilon_{i}\) is the normally distributed residual error. + +<|ref|>text<|/ref|><|det|>[[113, 822, 884, 895]]<|/det|> +We then tested the influence of distance to edges on each architectural trait with distances to edges varying between 1 and \(100\mathrm{m}\) , including tree woody volume. We then tested the influence of distance to edges, varying from 1 to \(100\mathrm{m}\) , on each architectural trait; we determined the edge + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 161]]<|/det|> +effects extent for each architectural trait based on the maximum absolute t- value of the term "edge effects" of the model (Supplementary Figure 4). The edge effects extent was then used to categorise our analysis into edge versus interior trees during all trait analyses." + +<|ref|>text<|/ref|><|det|>[[114, 213, 884, 259]]<|/det|> +Supplementary Figure 6. There does not appear to be an explanation for how partitioning of variance was done. + +<|ref|>text<|/ref|><|det|>[[114, 275, 883, 320]]<|/det|> +Thank you for this comment. We have now included the following in the Supplementary Methods 5: + +<|ref|>text<|/ref|><|det|>[[113, 337, 884, 461]]<|/det|> +"The spatial position with plot identity nested within landscape, and landscape nested within forest region had effects that varied depending on the architectural metric (Supplementary Figure 6). We examined the explained variance by the random variables of Eq.5 to investigate the spatial variability of architectural traits arising from region, landscape and plot (Supplementary Figure 6). The LME models were fitted using the lme function in the "nlme" R package." + +<|ref|>text<|/ref|><|det|>[[114, 506, 355, 525]]<|/det|> +Edge effects on tree allometry + +<|ref|>text<|/ref|><|det|>[[115, 541, 235, 559]]<|/det|> +"76" - "76 m"? + +<|ref|>text<|/ref|><|det|>[[115, 578, 401, 596]]<|/det|> +Thank you. We have included 76 m. + +<|ref|>text<|/ref|><|det|>[[113, 648, 755, 668]]<|/det|> +Fig. 4 - what is FE+allometric - this is unclear here but better defined in the Disc. + +<|ref|>text<|/ref|><|det|>[[114, 685, 883, 731]]<|/det|> +We agree with the reviewer that this was unclear. We have updated the Results with a new Figure 4 and more details on what these changes in AGB represent: + +<|ref|>text<|/ref|><|det|>[[113, 746, 884, 898]]<|/det|> +"We used allometric models to predict woody volume in both edge and interior forests, unabling us to estimate aboveground biomass (AGB) across larger spatial scales. Linear mixed models applied to data from 44 1- ha permanent plots revealed a statistically significant reduction in AGB of \(24.7\mathrm{Mg}\mathrm{ha}^{- 1}\) due to edge effects \((t = - 3.1;P\) - value \(= 0.003\) ). This reduction accounted for nearly \(10\%\) of the AGB of structurally intact forests \((282.2\pm 15.3\mathrm{Mg}\mathrm{ha}^{- 1})\) and comprised two components: first, there was an \(18.7\mathrm{Mg}\mathrm{ha}^{- 1}\) decline in AGB due to edge effects on forest structure + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 884, 319]]<|/det|> +- caused by fragmentation-related variation in tree size, tree density and species composition - within \(100\mathrm{m}\) from the forest margins; second, there was a \(6.0\mathrm{Mg ha^{-1}}\) decline in AGB caused by edge effects on tree allometry within \(55\mathrm{m}\) from the forest margins. These distance thresholds were chosen based on previous studies indicating stronger edge effects within \(100\mathrm{m}\) from forest edges on forest structure, and our own study indicating stronger edge effects on tree allometry within 55 m from the forest edges (see Methods for detailed explanations). We visually represented the predicted reduction in AGB caused by edge effects on both forest structure and tree allometry, comparing them to control interior forest plots. Notably, tree allometry alone contributed to one-third of the total AGB decline resulting from edge effects (Figure 4)." + +<|ref|>image<|/ref|><|det|>[[128, 370, 696, 720]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 742, 884, 893]]<|/det|> +
“Figure 4. Predicted aboveground biomass (AGB) for edge \(\mathrm{(N = 28~ha)}\) versus interior \(\mathrm{(N = 16}\) ha) forest plots within the Biological Dynamics of Forest Fragments Project (BDFFP) in Central Amazonia, the world's longest-running experimental study of habitat fragmentation. Points represent model predictions of AGB in edge versus interior forest plots from linear mixed modelling and error bars denote \(95\%\) confidence intervals. \(44.1\) -ha plots used for AGB predictions contained tree measurements on more than 12,000 individual stems \(\geq 10\mathrm{cm}\) diameter across 1026
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 213]]<|/det|> +tree species. The shaded dark grey area corresponds to AGB loss caused by fragmentation- related changes in forest structure owing to edge effects on tree mortality, growth and recruitment. The red area corresponds to AGB loss caused by edge effects on tree allometry, calculated by comparing AGB estimates using an allometric model that considered edge effects on tree allometry with an allometric model developed for interior forests." + +<|ref|>sub_title<|/ref|><|det|>[[114, 265, 234, 283]]<|/det|> +## DISCUSSION + +<|ref|>text<|/ref|><|det|>[[114, 300, 883, 347]]<|/det|> +Unclear sentence possessing the phrase "at the expense of lower mechanical stability 44". Consider revising. + +<|ref|>text<|/ref|><|det|>[[114, 363, 880, 383]]<|/det|> +Thank you. We have revised it to "this may lead to a lower mechanical stability". + +<|ref|>sub_title<|/ref|><|det|>[[114, 427, 213, 445]]<|/det|> +## METHODS + +<|ref|>text<|/ref|><|det|>[[114, 462, 658, 482]]<|/det|> +Table 1: Could the first trait be more clearly labeled (e.g. "density")? + +<|ref|>text<|/ref|><|det|>[[113, 498, 885, 753]]<|/det|> +Thank you for your question. The trait trunk or branch area per unit volume represents the surface area per unit volume of wood. This trait has been labeled as "surface area per unit volume" in 1978 by Halle et al. in the book "Tropical Trees and Forests: An Architectural Analysis". This trait is interesting from two perspectives: first, it is related to how thick the branches and trunks are, as low values represent branches and trunks that are thicker because they have large volume, and thus can be linked to higher support of aerial structures for light capture and productivity. Second, higher surface areas (thinner branches and trunks) indicate higher interaction with the atmosphere, including higher respiration rates of the living tissues. This book was our inspiration to use this trait to potentially understand how edge effects affected architectural traits linked to structure for light capture. We have kept the same name along the manuscript for consistency with the book. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 300, 107]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 147, 393, 164]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 176, 247, 192]]<|/det|> +Dear Nunes et al., + +<|ref|>text<|/ref|><|det|>[[115, 203, 867, 256]]<|/det|> +many thanks for the thorough revision of the manuscript. I really appreciate your detailed feedback on my comments and the additional analyses. I only have a few further minor comments, mainly for clarification: + +<|ref|>text<|/ref|><|det|>[[115, 267, 867, 303]]<|/det|> +L 38 – The term “50% more wood” is a bit ambiguous. Do you mean more biomass or more volume (or productivity)? + +<|ref|>text<|/ref|><|det|>[[115, 314, 870, 368]]<|/det|> +L 39- 41. I think the first and second half of the sentence kind of contradict. Maybe remove the first half (which relates to the previous sentence?) and start with something like “however, a disproportionally lower height in some large trees led to a 30% decline in their woody volume”? + +<|ref|>text<|/ref|><|det|>[[115, 379, 771, 397]]<|/det|> +L102- 104. I would generally suggest to avoid phrases like “first study” or “first to show…”. + +<|ref|>text<|/ref|><|det|>[[115, 408, 857, 444]]<|/det|> +L 319. Why are your estimates conservative? Maybe you could add a “…, because AGB estimates can vary significantly among equations, …” (if that’s why you think you’re estimates are conservative) + +<|ref|>text<|/ref|><|det|>[[115, 454, 860, 490]]<|/det|> +L 415. I think something went wrong during the revision of the manuscript. In the methods section on TLS, the previous paragraph is repeated. + +<|ref|>text<|/ref|><|det|>[[115, 529, 393, 546]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 558, 504, 575]]<|/det|> +[Editor's note: the reviewer had no further concerns] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 83, 426, 99]]<|/det|> +Point- by- point response to the reviewers + +<|ref|>text<|/ref|><|det|>[[93, 123, 404, 139]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[93, 155, 249, 170]]<|/det|> +Dear Nunes et al., + +<|ref|>text<|/ref|><|det|>[[92, 187, 881, 236]]<|/det|> +many thanks for the thorough revision of the manuscript. I really appreciate your detailed feedback on my comments and the additional analyses. I only have a few further minor comments, mainly for clarification: + +<|ref|>text<|/ref|><|det|>[[92, 252, 891, 285]]<|/det|> +L 38 – The term “50% more wood” is a bit ambiguous. Do you mean more biomass or more volume (or productivity)? + +<|ref|>text<|/ref|><|det|>[[92, 294, 617, 310]]<|/det|> +More woody volume. We have included this term in the abstract. + +<|ref|>text<|/ref|><|det|>[[92, 336, 891, 401]]<|/det|> +L 39- 41. I think the first and second half of the sentence kind of contradict. Maybe remove the first half (which relates to the previous sentence?) and start with something like “however, a disproportionally lower height in some large trees led to a 30% decline in their woody volume”? + +<|ref|>text<|/ref|><|det|>[[92, 411, 835, 428]]<|/det|> +Thank you. It does make sense the reviewer's suggestion – we have removed the first half. + +<|ref|>text<|/ref|><|det|>[[92, 453, 890, 470]]<|/det|> +L102- 104. I would generally suggest to avoid phrases like “first study” or “first to show...”. + +<|ref|>text<|/ref|><|det|>[[92, 479, 589, 495]]<|/det|> +We have removed the sentence that mentioned these terms. + +<|ref|>text<|/ref|><|det|>[[92, 520, 861, 569]]<|/det|> +L 319. Why are your estimates conservative? Maybe you could add a “... because AGB estimates can vary significantly among equations, ...” (if that’s why you think you’re estimates are conservative) + +<|ref|>text<|/ref|><|det|>[[92, 579, 895, 660]]<|/det|> +Our estimates are conservative because they are lower than estimates for the same region. And this might arise from variations related to the choice of allometric models and measurement uncertainty, as we explained in the following sentence. We have included this in the Discussion as “This demonstrates that our estimates of AGB are conservative given their lower values relative to other estimates for the same region.” + +<|ref|>text<|/ref|><|det|>[[92, 685, 886, 718]]<|/det|> +L 415. I think something went wrong during the revision of the manuscript. In the methods section on TLS, the previous paragraph is repeated. + +<|ref|>text<|/ref|><|det|>[[93, 728, 474, 743]]<|/det|> +Thank you very much. We have corrected this. + +<|ref|>text<|/ref|><|det|>[[93, 792, 404, 807]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[92, 824, 557, 840]]<|/det|> +[Editor's note: the reviewer had no further concerns] + +<--- Page Split ---> diff --git a/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2707e9a7844cca43bd41806fd0fe7359df88d492 --- /dev/null +++ b/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,254 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R1. Motion trajectories ( \\(\\mathrm{n} = 10\\) independent samples, \\(\\mathrm{t} = 20\\) s) of (a) D-Arg NMs and (c) L-Arg NMs and speed distributions ( \\(\\mathrm{n} = 10\\) independent samples, \\(\\mathrm{t} = 20\\) s) of (b) D-Arg NMs and (d) L-Arg NMs in the cancer cellular environment.", + "footnote": [], + "bbox": [ + [ + 315, + 433, + 680, + 686 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_4a.jpg", + "caption": "Fig. 4a and b. (a) Schematic diagram of the transwell model; (b) Representative CLSM images of bEnd.3 cells in the upper chamber and Gl261 cells in the lower chamber of the transwell system treated with different samples for \\(6\\mathrm{h}\\) (blue: nucleus, red: Cy5-labelled PACs, green: DiL-labelled Lip or NO-Lip; Scale bar: \\(50\\mu \\mathrm{m}\\) ; \\(\\mathrm{n} = 3\\) independent samples).", + "footnote": [], + "bbox": [ + [ + 272, + 90, + 737, + 250 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_62.jpg", + "caption": "Supplementary Figure 62. Cy5 fluorescence imaging of the brain after intravenous injection of different samples for 7 and \\(12\\mathrm{h}\\) (n = 5 independent samples; Scale bar: \\(1\\mathrm{cm}\\) ).", + "footnote": [], + "bbox": [], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_63.jpg", + "caption": "Supplementary Figure 63. Cy5 fluorescence imaging of the major organs after intravenous injection of different samples for 7 and \\(12\\mathrm{h}\\) ( \\(\\mathrm{n} = 5\\) independent samples; Scale bar: \\(1\\mathrm{cm}\\) ).", + "footnote": [], + "bbox": [ + [ + 290, + 90, + 710, + 410 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_64.jpg", + "caption": "Supplementary Figure 64. Cy5 fluorescence imaging of the major organs after intravenous injection of different samples for \\(24\\mathrm{h}\\) ( \\(\\mathrm{n} = 5\\) independent samples; Scale bar: \\(1\\mathrm{cm}\\) ).", + "footnote": [], + "bbox": [ + [ + 212, + 498, + 785, + 686 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_7.jpg", + "caption": "Fig. 7. Anti-tumor efficacy of NO-Lip@PAC@Cur NMs in GBM model mice (female). (a) Treatment protocols for orthotopic brain-GBM-tumor-bearing models. By Figdraw; (b) Representative IVIS spectrum images and (c) quantified signal intensity (n = 6 independent samples per group) ; (d) Kaplan-Meier survival curves (n = 8 independent samples) of GBM model mice with different treatments; (e) Representative H&E (Scale bar: 4 mm), TUNEL, and Ki67 staining images (Scale bar: 500 μm) of dissected brain tissues at the end of treatment; (f) Tunel and (g) Ki67 quantitative fluorescence analysis; (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: LipPAC@Cur, VI: NO-Lip@PLC@Cur, VII: NO-Lip@PAC@Cur; n = 6 independent samples); (h) Representative Bio-TEM images of brain tumor (I: PBS, II: magnification of I, III: NO-Lip@PAC@Cur, IV: magnification of III; Scale bar of I and III: 5 μm; Scale bar of II and IV: 200 nm); Representative TEM-Mapping (P and Ca) of brain tumor cellular mitochondria after treated with (i) control and (j) NO-", + "footnote": [], + "bbox": [ + [ + 196, + 95, + 802, + 650 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_72.jpg", + "caption": "Supplementary Figure 72. Blood biochemical parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip-PAC@Cur, VI: NO-Lip@PLC@Cur, VII: NO-Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean ± SD. Significance was calculated via one-way ANOVA.", + "footnote": [], + "bbox": [], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_75.jpg", + "caption": "Supplementary Figure 75. Anti-tumor efficacy of NO-Lip@PAC@Cur NMs in GBM model mice (male). (a) Treatment protocols for orthotopic GBM models. By Figdraw; (b) Representative IVIS spectrum images and (c) quantified signal intensity \\(\\mathrm{n} = 6\\) independent samples per group); (d) Representative H&E images of dissected brain tissues at the end of treatment (Scale bar: \\(2\\mathrm{mm}\\) ); (e) Tumor percentage after treatment with different samples (tumor percentage \\(=\\) (tumor area/brain area) \\(\\times 100\\%\\) ); (f) Changes in body weight of mice in different treatment groups. I: PBS, II: TMZ, III: NO-Lip@PAC@Cur; \\(\\mathrm{n} = 6\\) independent samples. Data were presented as mean \\(\\pm \\mathrm{SD}\\) .", + "footnote": [], + "bbox": [ + [ + 180, + 333, + 835, + 744 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_3h.jpg", + "caption": "Fig. 3h-k. (h) Representative fluorescence images of different samples at the exit of the \\(\\Psi\\) -shaped microfluidic channel (Scale bar: \\(200\\mu \\mathrm{m}\\) ) and (i) the corresponding fluorescence quantification in the presence of bEnd.3 cellular lysates ( \\(\\mathrm{n} = 3\\) independent samples); (j) Representative fluorescence images of different samples at the exit of the \\(\\Psi\\) -shaped microfluidic channel (Scale bar: \\(200\\mu \\mathrm{m}\\) ) and (k) the corresponding fluorescence quantification in the presence of bEnd.3 and Gl261 cellular lysates ( \\(\\mathrm{n} = 3\\) independent samples).", + "footnote": [], + "bbox": [ + [ + 196, + 410, + 795, + 565 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_4c.jpg", + "caption": "Fig. 4c-f. Quantitative analysis of red and green fluorescence in the (c) upper and (d) lower compartments (I: Control, II: Lip@PAC, III: NO-Lip@PAC, n = 3 independent samples); (e) BBB transport efficiency of different samples (I: Lip@PAC, II: NO-Lip@PAC; n = 3 independent samples); (f) Paracellular permeability of FD-4 treated with different samples for 24 h (I: Control, II: Lip@PAC, III: NO-Lip@PAC; n = 3 independent samples).", + "footnote": [], + "bbox": [], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_5g.jpg", + "caption": "Fig. 5g. Representative CLSM images of cytoplasmic \\(\\mathrm{Ca^{2 + }}\\) and mitochondrial \\(\\mathrm{Ca^{2 + }}\\) treated with different samples for \\(24\\mathrm{h}\\) and the fluorescence distribution curves along selected lines (I: Control, II: Lip@PLC, III: NO-Lip@PAC, IV: NO-Lip@PAC@Cur; indicated by the white lines in the images; Blue: nucleus, green: Fluo-4-labelled cytoplasmic \\(\\mathrm{Ca^{2 + }}\\) , red: Rhod-2-labelled mitochondrial \\(\\mathrm{Ca^{2 + }}\\) ; Scale bar: \\(20\\mu \\mathrm{m}\\) ; \\(\\mathrm{n} = 3\\) independent samples).", + "footnote": [], + "bbox": [ + [ + 231, + 220, + 757, + 410 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_57.jpg", + "caption": "Supplementary Figure 57. Representative CLSM images of cytoplasmic \\(\\mathrm{Ca^{2 + }}\\) and", + "footnote": [], + "bbox": [ + [ + 268, + 553, + 730, + 875 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_5b.jpg", + "caption": "Fig. 5b and c. (b) Intracellular \\(\\mathrm{Ca^{2 + }}\\) concentration in bEnd.3 cells and Gl261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; n = 3 independent samples); (c) \\(\\mathrm{Ca^{2 + }}\\) concentration in mitochondria and other organelles treated with different samples for 24 h in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; n = 3 independent samples).", + "footnote": [], + "bbox": [], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_56.jpg", + "caption": "Supplementary Figure 56. (a) Representative bio-TEM images of GI261 cell treated with NO-Lip@PAC; (b) Representative bio-TEM images of GI261 cellular mitochondria treated with (I) PBS, (II) NO-Lip@PAC and (III) NO-Lip@PAC@Cur.", + "footnote": [], + "bbox": [], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_5b.jpg", + "caption": "Fig. 5b and c. (b) Intracellular \\(\\mathrm{Ca^{2 + }}\\) concentration in bEnd.3 cells and GI261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \\(\\mathrm{n} = 3\\) independent samples); (c) \\(\\mathrm{Ca^{2 + }}\\) concentration in mitochondria and other organelles treated with different samples for 24 h in GI261 cells. (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \\(\\mathrm{n} = 3\\) independent samples)", + "footnote": [], + "bbox": [ + [ + 267, + 612, + 717, + 782 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_6a.jpg", + "caption": "Fig. 6a. Schematic diagram of the assessment of the targeting ability of different samples in a GBM model mouse.", + "footnote": [], + "bbox": [ + [ + 238, + 580, + 775, + 668 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_48.jpg", + "caption": "Supplementary Figure 48. Representative CLSM images of different samples co-incubated with Gl261 cells for \\(2\\mathrm{h}\\) (blue: Hoechst 33342 labeled nucleus, green: MiTo-Tracker labeled mitochondria; red: Cy5-labeled different samples; Scale bar: \\(50\\mu \\mathrm{m}\\) ).", + "footnote": [], + "bbox": [], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_5c.jpg", + "caption": "Fig. 5c. \\(\\mathrm{Ca^{2 + }}\\) concentration in mitochondria and other organelles treated with different samples for \\(24\\mathrm{h}\\) in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \\(\\mathrm{n} = 3\\) independent samples).", + "footnote": [], + "bbox": [], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Fig. 2. Preparation of NO-Lip@PAC NMs and characterization of their degradation behavior in response to NO. (a) TEM images (Scale bar: 500 nm), (b) DLS and (c) Zeta potential of different samples (n = 3 independent samples); (d) Representative confocal laser scanning microscope (CLSM) images of NO-Lip@PAC (Scale bar: 50 μm, green: DiO labeled NO-Lip, red: Cy5 labeled PAC; n = 3 independent samples); Representative DLS changes of NO-Lip@PAC NMs incubated with (e) PBS and (f) 100 μM H2O2 for different times (n = 3 independent samples); (g) Representative TEM images of NO-Lip@PAC NMs incubated with PBS and 100 μM H2O2 for different times (Scale bar 500 nm; red arrows indicate PAC released by lipid degradation; n = 3 independent samples); (h) Representative CLSM images of NO-Lip@PAC incubated with HUVECs and G1261 cellular lysates incubated for different times (Scale bar: 10 μm; green: DiO labeled Lip or NO-Lip, red: Cy5 labeled PAC;", + "footnote": [], + "bbox": [], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig. 3. Movement behavior of different samples and characterization of their chemotaxis in static and dynamic environments. Normalized motion trajectories (n = 20 independent samples) and motion speed distribution plots (n = 50 independent samples) of Lip@PAC NPs in (a) bEnd.3 and (b) Gl261 cellular environment (Supplementary Movie 9-10); Normalized motion trajectories (n = 20 independent samples) and motion speed distribution plots (n = 50 independent samples) of NO-Lip@PAC NMs in (c) bEnd.3 and (d) Gl261 cellular environment (Supplementary Movie 11-12); (e) Schematic of the Y-channel model; (f) Representative fluorescence images (Scale bar: \\(1000\\mu \\mathrm{m}\\) ) and (g) fluorescence quantification of NO-Lip@PAC NMs in Y-channel regions (ii) and (iii) at different times (n =3 independent samples); (h) Representative fluorescence images of different samples at the exit of the \\(\\Psi\\) -shaped microfluidic channel (Scale bar: \\(200\\mu \\mathrm{m}\\) ) and (i) the corresponding", + "footnote": [], + "bbox": [ + [ + 184, + 150, + 805, + 666 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Figure_5b.jpg", + "caption": "Fig. 5b and c. (b) Intracellular \\(\\mathrm{Ca^{2 + }}\\) concentration in bEnd.3 cells and Gl261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \\(\\mathrm{n} = 3\\) independent samples); (c) \\(\\mathrm{Ca^{2 + }}\\) concentration in mitochondria and other organelles treated with different samples for \\(24\\mathrm{h}\\) in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \\(\\mathrm{n} = 3\\) independent samples).", + "footnote": [], + "bbox": [], + "page_idx": 33 + } +] \ No newline at end of file diff --git a/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d0cba7787ba57acd9a7466244c825436eb16cb8a --- /dev/null +++ b/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,1071 @@ + +# nature portfolio + +Peer Review File + +# Size-variable self-feedback nanomotors for glioblastoma therapy via mitochondrial mineralization + +Corresponding Author: Professor Chun Mao + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Chen et al. report a novel size- variable self- feedback nanomotor system tailored for GBM treatment, leveraging the unique high- calcium microenvironment of GBM. By designing NO responsive degradable liposomes, the system achieved specific selection of tumor microenvironment, nanoparticle size conversion, and mitochondrial mineralization, ultimately inducing tumor cell death. It sets up a dual strategy for targeting tumor cells, namely chemotaxis and self- feedback effects. This strategy has highly innovation. The results of the in vivo study are satisfactory. If the author can provide responses or modifications to the following questions, then this manuscript can be recommended for publication. + +1. Obviously, the author confused the terms nanomotor and nanorobot, and should identify one of them. I think either one can be used. + +2. In this study, the authors used L-arginine as a raw material, so what about D-arginine? The motion ability of nanomotor constructed by D-arginine can be explored. + +3. In the experiment simulating the tumor microenvironment, \(100\mu \mathrm{M}H_2O_2\) was used. Is it close to the actual level of ROS in the tumor microenvironment? + +4. Does the degradation behavior that occurs in response to NO occur during the penetration of BBB or after penetration? +5. Is the concept of "Size-variable" important? Why does it appear in the title? I suggest changing it to "Trend of inflammation and self-feedback degradation of nanomotors for glioblastoma therapy via 2 mitochondrial mineralization". + +6. Have the authors studied whether there is a difference in the motion life between the shell and the core of this size-variable nanomotor? What factors is this related to? + +7. Does the brain-targeting efficiency have an advantage compared with most of the values in the literature? It is suggested that the author discuss this. + +Reviewer #2 + +(Remarks to the Author) + +\*\*\* SUMMARY \*\*\* + +The proposed manuscript aims at developing nitric oxide powered nanomotors leveraging the high calcium- microenvironment of glioblastoma (GBM) as a targeted treatment strategy. The nanomotors (NMs) are composed of a degradable lipid shell containing nitric oxide- releasing lipid (NO) and nitric oxide- responsive lipids, a nanomotor core composed of L- arginine derivatives and monomers rich in carboxyl groups (PAC) and the drug curcumin. The authors first characterized the NMs in terms of composition, size, surface charge and ability to degrade in response to hydrogen peroxide. The authors then demonstrated that NMs are predominantly responsive to a GBM cell line lysate (GI261) showing nitric oxide dependent movement as opposed to a blood brain barrier (BBB) cell line (bEnd.3) cellular lysate. They further showed the ability of the NO- NMs to pass through a single layer BBB in vitro model without any apparent disruption with increase cellular uptake and mitochondrial co- localization in GI261 GBM cell line. NO- NMs loaded with PAC could cause mitochondrial mineralization, and ultimately cell death, predominantly in GBM cells with low impact on BBB cells. In vivo testing using a mouse GBM model revealed the accumulation of NO- NMs mostly in the brain tissue, liver and kidneys. The presence of curcumin, even though the NO- lipids showed low encapsulation efficiency, through its action on Ca2+ ions, enhanced the efficiency of the NO- NMs and increased mitochondrial mineralization. Consequently, NO- NMs containing curcumin resulted in a net tumor reduction, a lower impact on animal weight and an increased survival rate as compared to the chemotherapeutic drug temozolomide and controls. Taken together, those results provide valuable ideas for designing + +<--- Page Split ---> + +future therapeutic targeting GBM. + +## \*\*\* GENERAL APPRECIATION \*\*\* + +The experimental work presented in this study is both thorough and extensive, highlighting commendable efforts by the authors to demonstrate the capabilities of their approach, especially for the in vitro assays. A complete proof of concept is provided, supported by in vitro assays and some preliminary in vivo experiments with a GBM mouse model. The authors corroborate their findings using at least three different approaches, making the results generally convincing and aligned with the scientific literature. The supplementary data are quite extensive cumulating 70 supplementary figures, further supporting the conclusions of the study. The text is well- written, with few syntax and typographical errors. Figures are coherent and clear, and most of the quantitative analyses are supported by robust statistical methods. + +One of the major flaws identified in the study is the small number of mice used per experimental condition, with only three mice per group. This limited sample size, which is a major flaw, may affect the reliability and generalizability of the findings event if the data shown are generally convincing. In addition, GBM is clinically observed more frequently in biological men, suggesting a sex- specificity in its occurrence. Despite this, it is crucial for researchers to use both male and female mice in their studies to ensure that their findings are robust and applicable across sexes. This approach would provide a more comprehensive understanding of the disease and its potential treatments. In this study, the authors only used female mice. This is a major limitation of the study that should be discussed. + +Another important concern is the fact the research team has previously published a highly similar article in 2023 (DOI: 10.1038/s41467- 022- 35709- 0), utilizing the same general methodology and a similar experimental approach. In this new work, the authors are encouraged to highlight the novelty of their findings, emphasizing advancements and unique contributions that distinguish it from their earlier research work. + +## \*\*\* SPECIFIC COMMENTS \*\*\* + +The following specific comments should be considered by the authors to provide more clarity and improve the manuscript: + +## Introduction: + +- The current therapeutic approaches to treat GBM are wider than what is being listed in the introduction section, which mostly focus on immunotherapeutic strategies and gene therapies, especially for drug delivery (local and systemic) approach currently being studied in the field. + +## Results: + +- Figure 2 and Figure S18: Please clarify the rationale for using HUVEC cells in part of the study and the bEnd.3 cell line for the remainder. + +- Line 195: precise the technic used to determine the iNOS in bEnd.3 and Gl261 cells. +- Figure 3 h-k: The fluorescence maker diffusing toward Gl261 cell lysate with the NO-Lip@PAC condition is only slightly higher compared to bEnd.3 cell lysate. Quantitative fluorescence distribution data should be supported with statistical analysis to ensure accuracy and validity of the conclusion. +- Lines 318-321: precise the p Values for the fold increased in fluorescence and transport rate values provide. +- Figure 5g: Co-localization analysis typically presents red and green fluorescence data without accounting for the relative fluorescence intensity of each sample. For example, green fluorescence, which represents cytoplasmic Ca2+ levels fluctuate significantly between experimental conditions. The overlapping between the red and green channel is also high for condition II but is not discussed at all. Therefore, it is also essential to consider relative ratios to accurately interpret the results. + +- Lines 397-398: the Zeta potential value for NO-Lip@PAC@Cur NMs is quite low (> -20 to -30 mV or < 20 to 30 mV) and could result in poorly stable colloidal solution with the tendency to form aggregates. The authors are encouraged to discuss the stability of their system as this statement is supported with the DLS data obtained for different Lip/Cur drug ratios tested (results in Supp file) where aggregates are easily formed. + +- Lines 407-414 and lines 426-428: precise the p Values for the fold increased in fluorescence and transport rate values provide. + +- Lines 432-433: To complete the demonstration, the author should also provide data for NO-Lip@PAC-treated Gl261. Why only use the control and NO-Lip@PAC@Cur to assess the presence of mitochondrial calcification? + +- Lines 476-478: precise the NMs concentration used. + +- Figure 7a: the schematic showing the steps and timeline to create the GBM mouse model should be introduced in Figure 6 instead, or at least, the text should refer to it as the steps to create the GBM tumour mouse model. + +- The authors should emphasize the limitations of their proposed delivery system and the overall study, particularly highlighting the low number of mice per experimental condition. + +## Conclusion: + +- Since NO-NMs tend to accumulate in various organs such as the liver and kidneys, one potential improvement to limit drug usage, increase accumulation toward the brain tissue could be the addition of brain BBB shuttle peptides and limit potential adversarial impacts. This would maximize brain tissue accumulation, like current practices with many brain-targeted delivery vehicles. The authors are encouraged to provide future improvements for their system. + +## Methods: + +- Replace rpm values with corresponding rcf (g equivalent) values or provide the centrifuge rotor dimension- Precise the number of mice used per experimental conditions and different tests. + +<--- Page Split ---> + +Supplementary data: + +Supplementary data:- Precise the origin (species) of the blood sample used for erythrocyte morphology and hemolysis rate tests- Line 292- 293: According to Figure S40, inlets (i) and (iii) should be the buffer I and II (cell lysates), whereas inlet (ii) should be PAC samples. However, the authors wrote: "When inlets (i), (ii) were pumped with bEnd.3 cellular lysates, and inlet (iii) was pumped with Lip@PAC NPs or NO- Lip@PAC NMs, there was no fluid shift (Figure 3h and 3i)"- Figure S37 g: Provide statistic analysis results- Figure S38 b: Precise in the figure caption how iNOS levels were measured. Also provide statistic results- Figure S40: Precise in the figure caption the composition of buffer I and II for the different experimental conditions tested- Figure S46: Provide statistic analysis results- Figure S47: Based on the fluorescence intensity in the red channel for the Lip@PAC condition, we would expect to see more "yellow" in the merge composite images when zones in green and red fluorescence overlap.- Figure S49: The zeta potential value obtained for NO- Lip@PAC@Cur is quite low, which can result in poorly stable particles with a higher tendency to form aggregates. The authors are encouraged to discuss those data as they agree with the formation of large aggregates for higher drug/lipid ratio (see corresponding comment in the "results section" above.- Figure S52, S53, S63, S68 and S69: provide statistic analysis results + +\\*\\*\\* MINOR COMMENTS \\*\\*\\* + +Introduction: - Figure 1a: replace "hydration" by "hydration" + +Results: + +Results:- Figure 4 caption, lines 249- 250: there seems to be repeated legend descriptions: "(l: Lip@PAC, II: NO- Lip@PAC I: Lip@PAC, II: NO- Lip@PAC)"- Figure 5c: replace "VI" by "IV" in the x- axis label.- Figure 5 caption (line 368): "(m)" should be "(l)" instead- Lines 512 and 567: commas with a red font color + +Methods: + +Methods:- Line 647: The authors wrote "high- sucrose Dalberg's modified Eagle's medium (DMEM, containing 4.5 g L- 1 648 D- glucose)". Did the authors mean Dubelcco's modified Eagle's medium?- Line 752: replace "1 x 105 cells mL- 1" by "1 x 105 cells mL- 1"- Line 793: replace "Aliexa" by "Alexa"- Lines 802- 807: consider revising the syntax.- Line 818: replace "performed with H&E" by "stained with H&E"- Line 826: replace "finished" by "performed" + +Supplementary data: + +Supplementary data:- Lines 63- 65 & lines 113- 116 & lines 166- 168: revise the syntax.- Line 303: Figure S32 caption is missing the "(e)"- Line 314: Figure S34 caption, replace "(D)" by "(d)"- Line 314: Figure S34 caption is missing the "(e)"- Figure S35b: replace "Posioton" in the x- axis label with "Position" + +Reviewer #3 + +(Remarks to the Author) + +This work presents a novel size- variable self- feedback nanomotor system (NO- Lip@PAC@Cur NMs) for the treatment of glioblastoma (GBM). The system is composed of a self- feedback degradable lipid shell, a nanomotor core with motion ability, and the drug curcumin (Cur) that inhibits calcium ion efflux, which can induce the mitochondrial mineralization. Overall, the design concept of this work is highly innovative. There have been no related studies on treating GBM through mitochondrial mineralization to date. The writing is relatively smooth, the data volume is substantial, and the manuscript is well organized. It is recommended that the work be accepted for publication after minor revisions. The detailed suggestions were listed as follows. + +1. Introduction Section: It is suggested to more thoroughly analyze the limitations of current GBM treatment strategies, such as surgery, radiotherapy, chemotherapy, and immunotherapy. These limitations include drug resistance and the immunosuppressive microenvironment, which can better highlight the necessity and innovativeness of this study. +2. Nanomotor Fabrication and Characterization: The description of some steps in the preparation and characterization of the nanomotors is relatively brief. For example, when synthesizing NOR and NOD, only the raw materials used and the reaction conditions are mentioned, without detailed synthesis steps and purification methods. It is recommended to supplement more detailed experimental steps and operational details to facilitate better reproducibility by other researchers. +3. The data labeling and legend descriptions in some figures (such as Figures 2 and 3) are not clear enough. For example, in Figure 2, the markings for different samples (such as I: PAC, II: NO-Lip, III: NO-Lip@PAC) are not conspicuous enough and can be easily confused. It is suggested to optimize the design of the figures to make the data and information more intuitive and understandable, while ensuring that the labels and legends in the figures are clear and accurate. +4. Some sentences in the text contain grammatical errors or are not expressed accurately. For example, in the sentence "However, the infiltrative growth pattern and inherent heterogeneity of GBM, coupled with the side effects of TMZ treatment + +<--- Page Split ---> + +(including hematologic toxicity and thrombocytopenia associated with long- term and high- dose administration), have significantly limited the efficacy of this therapeutic strategy," the use of "coupled with" is somewhat awkward. It is suggested to change it to "combined with" to make the sentence smoother. + +5. In several experiments (such as cell viability tests and animal experiments), the text only mentions the sample size of some experiments (such as \("n = 3"\) or \("n = 8"\) ), but does not specify the repetition times and sample sizes of all experiments. For example, in the experiment detecting the effects of different samples on cell viability, only \("n = 3"\) is mentioned, without indicating whether it is an independent repeated experiment. It is recommended to clearly label the repetition times (such as the number of independent repeated experiments) and sample sizes in all experimental sections to enhance the reliability and reproducibility of the experimental results. + +6. In the study, the reason for selecting the specific ratio was not detailed, nor was the impact of other ratios on the experimental results assessed. It is suggested to supplement experimental data comparisons of different drug-lipid ratios to demonstrate the rationality of the selected ratio and explore whether there is a more optimal ratio. + +7. In some experiments, the control groups are not comprehensive enough. For example, in the study of the effects of nanomotors on intracellular calcium ion levels, although a blank control group was set up, a control group with only the drug (such as Cur) without the nanomotor carrier was not included. It is recommended to improve the control group settings to exclude the potential effects of the drug itself on the experimental results. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) All the concerns are addressed during the revision and now the manuscript can be accepted without change. + +Reviewer #2 + +(Remarks to the Author) + +I confirm that all major and minor comments provided during the review process have been thoroughly addressed and/or discussed. I am confident that the manuscript now meets the necessary standards and is suitable for publication in its current form. + +Reviewer #3 + +(Remarks to the Author) + +The authors have properly addressed all my concerns, I would like to recommend the acceptance for publication + +<--- Page Split ---> + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +Chen et al. report a novel size- variable self- feedback nanomotor system tailored for GBM treatment, leveraging the unique high- calcium microenvironment of GBM. By designing NO responsive degradable liposomes, the system achieved specific selection of tumor microenvironment, nanoparticle size conversion, and mitochondrial mineralization, ultimately inducing tumor cell death. It sets up a dual strategy for targeting tumor cells, namely chemotaxis and self- feedback effects. This strategy has highly innovation. The results of the in vivo study are satisfactory. If the author can provide responses or modifications to the following questions, then this manuscript can be recommended for publication. + +Answer: Many thanks to you for the recognition and valuable suggestions on this manuscript. These suggestions are very important for us to improve the quality of the manuscript. The issues raised by the reviewer were taken seriously and point- to- point revisions were made. + +1. Obviously, the author confused the terms nanomotor and nanorobot, and should identify one of them. I think either one can be used. + +Answer: Many thanks to you for your valuable comments. + +Regarding the terminology used for nanorobots and nanomotors, we understand your concern for consistency in terminology. In our work, we have used both "nanorobots" and "nanomotors", but they refer to the same system in our work. This diversity in terminology is primarily due to the following reasons. + +(1) Nanomotors: Refers to nanoscale devices that can convert chemical energy, light energy, or magnetic energy into mechanical movement, with a core function focused on achieving autonomous movement capability (Chem. Soc. Rev. 2022, 51, 10083-10119). This term is typically used to describe nanosystems with autonomous movement capabilities, emphasizing their ability to respond to external stimuli (such as iNOS concentration gradients) and generate directional movement. In our work, the targeting ability of NO-Lip@PAC@Cur NMs was able to actively generate motion in response to iNOS concentration gradients, so we used the term "nanomotor" to describe its motility. + +(2) Nanorobots: Refers to intelligent nanofabricated systems with multiple functions. Apart from mobility, they typically integrate sensing, navigation, targeting, and task execution modules (such as drug release). They can respond to environmental signals to perform complex operations (Adv. Mater. 2022, 34, 2201051). This term is used more broadly to describe nanostructures with diverse functionalities, including not only mobility but also recognition, regulation, and therapeutic capabilities. In our work, PAC NMs not only moves, but also integrates the ability to target mitochondria and recruit \(\mathrm{Ca^{2 + }}\) . Therefore, this is why we use the term "nanorobot" in our manuscript to describe its overall function. + +To ensure consistency and clarity of terminology, we will use the term "nanomotors" uniformly in the revised manuscript to describe our system, in order to maintain consistency with our previously published articles. + +<--- Page Split ---> + +2. In this study, the authors used L-arginine as a raw material, so what about D-arginine? The motion ability of nanomotor constructed by D-arginine can be explored. + +Answer: Many thanks to you for your valuable comments. + +The main reason we chose L- arginine (L- Arg) is that it can be catalyzed by inducible nitric oxide synthase (iNOS), which is highly expressed in tumor tissues specifically, and undergoes a chemotactic effect on the iNOS concentration gradient through enzyme- substrate- specific interactions, thus achieving effective targeting of tumor tissues. Theoretically, in the tumor microenvironment, L- Arg can produce NO in two ways. On the one hand, L- Arg can be catalyzed by iNOS to produce NO, and on the other hand, L- Arg can react with \(\mathrm{H}_2\mathrm{O}_2\) to produce NO. The principles of the two processes are as follows, respectively. + +(1) The mechanism by which iNOS catalyzes L-Arg is a two-step redox process that depends on multiple cofactors: First, the guanidinium group of L-Arg is hydroxylated to produce N-hydroxy-L-Arg (N-OH-L-Arg), which consumes both NADPH and \(\mathrm{O}_2\) (L-Arg + \(\mathrm{O}_2 + \mathrm{NADPH} + \mathrm{H}^+ \leftrightarrow \mathrm{NOH-L-Arg} + \mathrm{H}_2\mathrm{O} + \mathrm{NADP}^+\) ); further oxidation of NOH-L-Arg proceeds via an atypical mechanism in which an electron from NADPH, an electron from NOH-L-Arg itself, and \(\mathrm{O}_2\) come together to form a dioxygen-iron complex \((\mathrm{Fe}^{3 + } - \mathrm{O} - \mathrm{O}^{-})\) that attacks the NOH-L-Arg This complex attacks the guanidinium carbon of the NOH-L-Arg radical, leading to oxygen atom doping and C-N bond breaking (NOH-L-Arg + \(\mathrm{O}_2 + 1 / 2\) (NADPH + \(\mathrm{H}^+ \leftrightarrow \mathrm{L}\) - citrulline + \(\mathrm{NO} + \mathrm{H}_2\mathrm{O} + 1 / 2\mathrm{NADP}^+\) ) (Science 1997, 278, 425-431; J. Chem. Inf. Model. 2011, 51, 1325-1335). This process places special demands on the chirality of Arg, as tetrahydrobiopterin (H4B) stabilizes the dimeric structure of the enzyme in this process and also assists in proton transfer and neutralization of radical intermediates through a network of hydrogen bonds. The stereoselectivity of the active site of iNOS is strictly matched to the S-configuration of L-Arg, where the \(\alpha\) - amino acid, carboxylic acid moiety, and guanidinium group of L-Arg form stable interactions with key amino acid residues (e.g., Glu371) and H4B, respectively, while the nitrogen atom at the end of its guanidinium group directly coordinates with heme iron to initiate oxygen activation (Front. Biosci. 2003, 8, 193-209; Faseb J. 1996, 10, 552-558; Biochim. Biophys. Acta 1999, 1411, 217-230; Nat. Struct. Mol. Biol. 1999, 6, 233-242). However, D-Arg is difficult for iNOS to recognize and catalyze, possibly due to its R-configuration causing the spatial orientation of its side chain to flip, preventing the guanidino group from properly binding to heme iron, and disrupting the electrostatic interactions between the \(\alpha\) - carboxyl group and the active site. BH4 is also unable to stabilize the transition state of D-Arg via hydrogen bonding, thereby disrupting the integrity of the electron transport chain (NADPH \(\rightarrow\) FAD \(\rightarrow\) FMN \(\rightarrow\) HEM) and the activation process of oxygen molecules. + +(2) In addition to the above pathway, L-Arg can also react with \(\mathrm{H}_2\mathrm{O}_2\) , which is based on the oxidation of the electron-rich guanidino group (-HN-C(=NH)-NH₂) on the side chain of Arg by \(\mathrm{H}_2\mathrm{O}_2\) . The reaction undergoes nucleophilic addition to form an unstable adduct, followed by deamination and oxidation, which ultimately converts the guanidino group to a urea group (-NH-C(=O)-NH₂) to produce the product L-citrulline with the release of NO and water. This process does not strictly require the + +<--- Page Split ---> + +chirality of Arg, and D- Arg is also capable of producing NO by this process. + +chirality of Arg, and D- Arg is also capable of producing NO by this process.Thus, theoretically, D- Arg cannot be recognized and catalyzed by iNOS, and nanomotors constructed from them cannot exert a chemotactic effect on iNOS concentration gradients. However, they should be able to react with the high concentrations of \(\mathrm{H}_2\mathrm{O}_2\) in tumor tissue, thereby exhibiting a certain degree of enhanced Brownian motion (Small 2023, 19, 2207823; Hepatology 2002, 36, 573- 581; Biomaterials 2021, 269, 120642). To verify this conjecture, we constructed nanomotors driven by L- Arg or D- Arg, namely D- Arg NMs and L- Arg NMs, respectively, and investigated their motional behaviors in the cancer cell environment. As shown in Fig. R1, the average speed of D- Arg NMs in cancer cells was about 1.6 \(\mu \mathrm{m / s}\) , which was slightly higher than that of Brownian motion (1.0 \(\mu \mathrm{m / s}\) ), indicating an enhanced Brownian motion. This is mainly due to the oxidative effect of \(\mathrm{H}_2\mathrm{O}_2\) on D- Arg NMs and the production of asymmetric NO. The average speed of L- Arg NMs in the cancer cell environment was about 3.7 \(\mu \mathrm{m / s}\) , which was higher than that of D- Arg NMs (1.6 \(\mu \mathrm{m / s}\) ), attributed to the ability of L- Arg NMs to react with \(\mathrm{H}_2\mathrm{O}_2\) and iNOS in cancer cells to produce more NO to drive them to undergo enhanced Brownian motion. + +![](images/Figure_unknown_0.jpg) + +
Fig. R1. Motion trajectories ( \(\mathrm{n} = 10\) independent samples, \(\mathrm{t} = 20\) s) of (a) D-Arg NMs and (c) L-Arg NMs and speed distributions ( \(\mathrm{n} = 10\) independent samples, \(\mathrm{t} = 20\) s) of (b) D-Arg NMs and (d) L-Arg NMs in the cancer cellular environment.
+ +3. In the experiment simulating the tumor microenvironment, \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) was used. Is it close to the actual level of ROS in the tumor microenvironment? + +Answer: Many thanks to you for your valuable comments. + +Studies have shown that the concentration of ROS in the tumor microenvironment is not less than \(100\mu \mathrm{M}\) (Nat. Rev. Drug Discov. 2009, 8, 579- 591; Nat. Rev. Mol. Cell Biol. 2020, 21, 363- 383; Nat. Rev. Drug Discov. 2013, 12, 931- 947). ROS contains a variety of molecules with complex components and variable states. It is very difficult + +<--- Page Split ---> + +to fully simulate the components of ROS in vitro. Studies have shown that the \(\mathrm{H}_2\mathrm{O}_2\) (a relatively stable component) in the tumor microenvironment is about \(10\mathrm{- }100\mu \mathrm{M}\) (ACS Nano 2019, 13, 2643- 2653; Cancer Lett. 2007, 252, 1- 8; Coord. Chem. Rev. 2023, 481, 215049). Therefore, researchers generally choose \(\mathrm{H}_2\mathrm{O}_2\) to simulate ROS in an in vitro environment at a concentration of about \(50\mathrm{- }200\mu \mathrm{M}\) . For instance, Mao et al. use 50 and \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to evaluate the aggregating behavior of tAuNP and mAuNP/Lu (Angew. Chem. Int. Ed. 2021, 60, 23805- 23811); Lv et al. use 50, 100 and \(200\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to evaluate the self- propelled motion of the HTiPC nanomotors (ACS Nano 2024, 18, 13910- 13923); Ye et al. use \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic the tumor environment to assess the lysosomal escape efficacy of the nanomotor (Adv. Funct. Mater. 2025, 35, 2416265); Zhang et al. use \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic the tumor environment to assess the in vitro cytotoxicity of different samples (Nano Today 2022, 45, 101542); Zhu et al. use \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic the tumor environment to assess the catalytic capacity of \(\mathrm{Ce6@MnO_2}\) (Adv. Funct. Mater. 2016, 26, 5490- 5498). In summary, we used \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic ROS in the tumor microenvironment in our experiments to evaluate the responsive degradation behavior of NO- Lip@PAC NMs. + +4. Does the degradation behavior that occurs in response to NO occur during the penetration of BBB or after penetration? + +Answer: Many thanks to you for your valuable comment. + +NO- Lip@PAC@Cur NMs are able to sense the iNOS concentration gradient formed at the damaged blood- brain barrier (BBB) at the brain tumor site, and thus are able to cross the BBB via chemotaxis. The tumor site has higher concentration of iNOS, NO- Lip@PAC@Cur NMs are able to generate more NO at the tumor site, and thus their degradation behavior occurs after crossing the BBB. We verified this in an in vitro transwell model. Specifically, the upper chamber of the transwell was inoculated with bEnd.3 cells to form the BBB, and the lower chamber was inoculated with GI261 cells, resulting in an iNOS concentration gradient between the upper and lower chambers. Then, we added Lip@PAC NPs and NO- Lip@PAC NMs (50 \(\mu \mathrm{g}\mathrm{mL}^{- 1}\) ) to the upper chamber, respectively, and incubated for 6 h. Fluorescence images of the upper and lower chambers of the transwell model were recorded using CLSM. As shown in Fig. 4b, most of the NO- Lip@PAC in the bEnd.3 cells in the upper compartment remained intact (the red fluorescence representing PAC and the green fluorescence representing Lip or NO- Lip were highly co- localized). When they penetrated the BBB and entered the GI261 cells in the lower chamber, the red fluorescence and green fluorescence gradually separated, indicating that NO- Lip@PAC degraded after crossing the BBB. + +<--- Page Split ---> +![](images/Figure_4a.jpg) + +
Fig. 4a and b. (a) Schematic diagram of the transwell model; (b) Representative CLSM images of bEnd.3 cells in the upper chamber and Gl261 cells in the lower chamber of the transwell system treated with different samples for \(6\mathrm{h}\) (blue: nucleus, red: Cy5-labelled PACs, green: DiL-labelled Lip or NO-Lip; Scale bar: \(50\mu \mathrm{m}\) ; \(\mathrm{n} = 3\) independent samples).
+ +5. Is the concept of "Size-variable" important? Why does it appear in the title? I suggest changing it to "Trend of inflammation and self-feedback degradation of nanomotors for glioblastoma therapy via mitochondrial mineralization". + +Answer: Many thanks to you for your valuable comments. + +Size is a very important factor to consider when designing drug delivery systems for tumor therapy. Studies have shown that there is a size dependence of nanoparticles retention and penetration behavior in the tumor region: large- sized nanoparticles (200 nm- 1200 nm) can be efficiently branched near tumor blood vessels (Nano Lett. 2009 9, 1909e15; ACS Nano 2014, 8, 5696e706; Small 2022, 18, 2200115), whereas small- sized nanoparticles (< 200 nm) have a higher level of permeability within tumor tissue (Acta. Pharm. Sin. B 2019, 9, 410e20; ACS Nano 2017, 11, 4582e92). However, small- sized nanoparticles are easily affected by the high- pressure microenvironment of the tumor mesenchyme during aggregation in the tumor microenvironment and are reversed pumped back to the circulatory system, resulting in a significant reduction in delivery efficiency (Proc. Natl. Acad. Sci. 2014, 111, 15344- 15349; Proc. Natl. Acad. Sci. 2022, 119, e2211228119l; Nat. Rev. Cancer 2018, 18, 359e76). To resolve this contradiction, we construct size- variable self- feedback nanomotors NO- Lip@PAC@Cur NMs (with an initial size of about \(500\mathrm{nm}\) ). These nanomotors enable efficient brain tumor delivery through dual functionality: the large- sized nanomotor ( \(\sim 500\mathrm{nm}\) ) is able to crossing the BBB via chemotaxis, and more readily aggregates in the tumor microenvironment without being reverse- pumped back into the circulatory system. Subsequently, it can be degraded in response to NO released during chemotactic targeting, resulting in the release of small- sized PAC NMs ( \(\sim 50\mathrm{nm}\) ). The small- sized PAC NMs can be utilized to further achieve deep penetration into brain tumors by taking advantage of the size advantage and motility effect. The term "size- variable" in the title is intended to emphasize the central contribution of the size- variable property to the breakthrough of the blood- brain barrier for the deep penetration of brain tumors. We appreciate the valuable comments provided by the reviewer. After careful consideration, we have decided to incorporate this idea into the + +<--- Page Split ---> + +title and kindly request the reviewer's approval. + +6. Have the authors studied whether there is a difference in the motion life between the shell and the core of this size-variable nanomotor? What factors is this related to? Answer: Many thanks to you for your valuable comments. + +We investigated the motion life of the outer shell (NO- Lip NMs), inner core (PAC NMs) and NO- Lip@PAC NMs in Gl261 cellular lysate. As shown in Supplementary Fig. 34a and b, the average speed of PAC NMs decreased from \(2.9 \mu \mathrm{m / s}\) (6 h) to \(1.6 \mu \mathrm{m / s}\) (24 h). This diminished motility could be attributed to the enzymatic depletion of L- Arg in the nanomotors. As shown in Supplementary Fig. 34c and d, the average speed of NO- Lip NMs decreased from \(3.5 \mu \mathrm{m / s}\) (2 h) to \(1.8 \mu \mathrm{m / s}\) (6 h). The shortened motility lifetime was not only related to the depletion of L- Arg, but also to its ability to response to NO degradation. + +The initial motility of NO- Lip@PAC NMs depends on L- Arg on the liposome shell. As NO accumulates, it causes the liposome shell to degrade and release the loaded PAC NMs, at which time the motility comes from L- Arg on the PAC NMs. We labeled the lipid shell of NO- Lip@PAC NMs with DiO to produce green fluorescence (named DiO- NO- Lip@PAC NMs), the core PAC of NO- Lip@PAC NMs with Cy5 to produce red fluorescence (named NO- Lip@PAC- Cy5 NMs), and separately studied the movement behavior of the shell (NO- Lip) and core (PAC) after incubation with Gl261 cellular lysate for different times. As shown in Supplementary Fig. 34e- h, when incubated with Gl261 cellular lysate for 2 h, DiO- NO- Lip@PAC NMs exhibited enhanced Brownian motion with a speed of \(3.4 \mu \mathrm{m / s}\) , which was comparable to the speed of NO- Lip@PAC- Cy5 NMs (3.3 \(\mu \mathrm{m / s}\) ), indicating that the movement at this time depended on L- Arg on the liposome shell. When incubated with Gl261 cellular lysate for 4 h, the movement speed of NO- Lip@PAC- Cy5 NMs decreased to \(2.6 \mu \mathrm{m / s}\) , comparable to that of DiO- NO- Lip@PAC NMs (2.7 \(\mu \mathrm{m / s}\) ). When the incubation time was extended to 6 h, as the lipid bilayer degraded, the speed of DiO- NO- Lip@PAC NMs decreased to \(2.0 \mu \mathrm{m / s}\) , while NO- Lip@PAC- Cy5 NMs continued to exhibit a speed of \(3.5 \mu \mathrm{m / s}\) , indicating that the movement capacity at this time originated from L- Arg on the PAC NMs. + +In summary, the motion life of the shell (NO- Lip NMs) was approximately 6 h, while that of the core nanomotor (PAC NMs) was approximately 24 h. + +<--- Page Split ---> +![](images/Supplementary_Figure_62.jpg) + + +Supplementary Figure 34. Motion life of different nanomotors. (a) Trajectories (n = 5 independent samples) and (b) average speeds (n = 5 independent samples) of PAC NMs incubated with Gl261 cellular lysate for different times; (c) Trajectories (n = 5 independent samples) and (d) average speeds (n = 5 independent samples) of NO- Lip NMs incubated with Gl261 cellular lysate for different times; (e) Trajectories (n = 5 independent samples) and (f) average speeds (n = 5 independent samples) of DiO- NO- Lip@PAC NMs incubated with Gl261 cellular lysate for different times; (g) Trajectories (n = 5 independent samples) and (h) average speeds (n = 5 independent samples) of DiO- NO- Lip@PAC NMs incubated with Gl261 cellular lysate for different times. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +7. Does the brain-targeting efficiency have an advantage compared with most of the values in the literature? It is suggested that the author discuss this. + +<--- Page Split ---> + +**Answer:** Many thanks to you for your valuable comments. + +Brain-targeting efficiencies from recent years in the literature are summarized in **Supplementary Table 1.** Brain accumulation in most studies was in the range of 4.5-15% ID/g. The accumulation of NO-Lip@PAC NMs group in the brain (29.3% ID/g)was higher than most of the values reported in the literature so far, further suggesting that NO-Lip@PAC NMs were able to recognize the highly expressed iNOS in the tumor microenvironment and cross the BBB, accumulating in brain tumors. + +**Supplementary Table1.** Summary of the targeted efficiency of GBM in different articles. + +
MaterialsTargeted
strategy
Treatment
strategy
Brain
targeting
efficiency
Ref
NP-siRNA-CTX.molecular
recognition
gene therapy/1
BPLP-PLAs NPsmolecular
recognition
immunotherapy/2
iRGD-loaded SPNPsmolecular
recognition
gene therapy/3
siRNA micelles.molecular
recognition
gene therapy~15% ID/g4
MTX@MnO2-Opcamolecular
recognition
chemotherapy/5
Iron oxide nanoparticlemolecular
recognition
radiotherapy/6
CpG-exo/TGMmolecular
recognition
immunotherapy/7
TrQβ@b-3WJ iSCRLet-7gmolecular
recognition
gene therapy and
radiotherapy
/8
BSO-CAT@MOF-199
@DDM
molecular
recognition
immunotherapy/9
ABNPs@mRNAmolecular
recognition
gene therapy7.22% ID/g10
Cannabidiol prodrugmolecular
recognition
molecularly
targeted therapy
/11
\(Cu_{2}-xSe\)NPshomingimmunotherapy/12
\(Au@Cu_{2}-xSe\)NPsmolecular
recognition
immunotherapy13
CRISPR/Cas12a
nanocapsule system
/gene therapy and
molecularly
targeted therapy
6.1% ID/g14
Lipid nanoparticles/gene therapy/15
AMVY@NPsmolecular
recognition
molecularly
targeted therapy
/16
Silk fibroin microneedle/molecularly
targeted therapy
/17
ANCss(Cas9/sgRNA)moleculargene therapy11.8% ID/g18
+ +<--- Page Split ---> + +
recognition
CSI@Ex-Amolecular recognitionsonodynamic therapy~ 7.5% ID/g19
Fe-CDs@Angmolecular recognition/4.5% ID/g20
poly(MIs)/PTX@PEI/siPGK1@CCMhomingchemotherapy and radiotherapy~ 6.0% ID/g21
Ang-NP@RNPmolecular recognitiongene therapy12.9% ID/g22
D-iGSNPsmolecular recognitionradiotherapy~ 9.0% ID23
Ang-NCss(siRNA)molecular recognitiongene therapy6.69% ID/g24
NO-Lip@PAC@Curchemotaxismitochondrial mineralization29.3% ID/gThis work
+ +## References + +1. Wang, K., et al. siRNA nanoparticle suppresses drug-resistant gene and prolongs survival in an orthotopic glioblastoma xenograft mouse model. *Adv. Funct. Mater.* 31, 2007166 (2021). + +2. Kim, G. B., et al. High-affinity mutant interleukin-13 targeted CAR T cells enhance delivery of clickable biodegradable fluorescent nanoparticles to glioblastoma. *Bioact. Mater.* 5, 624-635 (2020). + +3. Gregory, J. V., et al. Systemic brain tumor delivery of synthetic protein nanoparticles for glioblastoma therapy. *Nat. Commun.* 11, 5687 (2020). + +4. Jiang, T., et al. Cation-Free siRNA Micelles as effective drug delivery Platform platform and potent RNAi nanomedicines for glioblastoma therapy. *Adv. Mater.* 33, 2104779 (2021). + +5. Dong, C. Y., et al. Neisseria meningitidis opca protein/MnO₂ hybrid nanoparticles for overcoming the blood-brain barrier to treat glioblastoma. *Adv. Mater.* 34, 2109213 (2022). + +6. Chiarelli, P. A., et al. Iron oxide nanoparticle-mediated radiation delivery for glioblastoma treatment. *Mater. Today* 56, 66-78 (2022). + +7. Cui, J., et al. Immune exosomes loading self-assembled nanomicelles traverse the blood-brain barrier for chemo-immunotherapy against glioblastoma. *ACS Nano* 17, 1464-1484 (2023). + +8. Pang, H. H., et al. Bioengineered bacteriophage-like nanoparticles as RNAi therapeutics to enhance radiotherapy against glioblastomas. *ACS Nano.* 17, 10407-10422 (2023). + +9. Huang, Q. X., et al. Metal-organic framework nanoagent induces curoptosis for effective immunotherapy of malignant glioblastoma. *Nano Today* 51, 101911 (2023). + +10. Liu, Y., et al. Non-invasive PTEN mRNA brain delivery effectively mitigates growth of orthotopic glioblastoma. *Nano Today* 49, 101790 (2023). + +11. Zhou, S., et al. Reprogramming systemic and local immune function to empower + +<--- Page Split ---> + +immunotherapy against glioblastoma. Nat. Commun. 14, 435 (2023).12. Wang, T., et al. Antigen self-presented personalized nanovaccines boost the immunotherapy of highly invasive and metastatic tumors. ACS Nano 18, 6333- 6347 (2024).13. Zhang, H., et al. Boost infiltration and activity of T cells via inhibiting ecto- 5'- nucleotide (CD73) immune checkpoint to enhance glioblastoma immunotherapy. ACS Nano 18, 23001- 23013 (2024).14. Ruan, W., et al. Brain- targeted Cas12a ribonucleoprotein nanocapsules enable synergetic gene co- editing leading to potent inhibition of orthotopic glioblastoma. Adv. Sci. 11, 2402178 (2024).15. Rouatbi, N., et al. RNA lipid nanoparticles as efficient in vivo CRISPR- Cas9 gene editing tool for therapeutic target validation in glioblastoma cancer stem cells. J. Control. Release 375, 776- 787 (2024).16. Qi, J., et al. Stepwise- targeting and hypoxia- responsive liposome AMVY®NPs carrying siYAP and verteporfin for glioblastoma therapy. J. Nanobiotechnology 22, 495 (2024).17. Wang, Z., et al. Silk microneedle patch capable of on- demand multidrug delivery to the brain for glioblastoma treatment. Adv. Mater. 34, 2106606 (2022).18. Zou, Y., et al. Blood- brain barrier- penetrating single CRISPR- Cas9 nanocapsules for effective and safe glioblastoma gene therapy. Sci. Adv. 8, eabm8011 (2022).19. Wu, T., Liu, Y., Cao, Y. & Liu, Z. Engineering macrophage exosome disguised biodegradable nanoplatform for enhanced sonodynamic therapy of glioblastoma. Adv. Mater. 34, 2110364 (2022).20. Muhammad, P., et al. Carbon dots supported single Fe atom nanozyme for drug- resistant glioblastoma therapy by activating autophagy- lysosome pathway. Nano Today 45, 101530 (2022).21. Wang, Z., et al. Biomimetic hypoxia- triggered RNAi nanomedicine for synergistically mediating chemo/radiotherapy of glioblastoma. J. Nanobiotechnology 21, 210 (2023).22. Ruan, W., et al. Brain- targeted CRISPR/Cas9 nanomedicine for effective glioblastoma therapy. J. Control. Release 351, 739- 751 (2022).23. Dong, C.- Y., et al. Mult functionalized gold sub- nanometer particles for sensitizing radiotherapy against glioblastoma. Small 17, e2006582 (2021).24. Zou, Y., et al. Single siRNA nanocapsules for effective siRNA brain delivery and glioblastoma treatment. Adv. Mater. 32, 2000416 (2020). + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +\*\*\* SUMMARY \*\*\* + +The proposed manuscript aims at developing nitric oxide powered nanomotors leveraging the high calcium- microenvironment of glioblastoma (GBM) as a targeted treatment strategy. The nanomotors (NMs) are composed of a degradable lipid shell containing nitric oxide- releasing lipid (NO) and nitric oxide- responsive lipids, a nanomotor core composed of L- arginine derivatives and monomers rich in carboxyl groups (PAC) and the drug curcumin. The authors first characterized the NMs in terms of composition, size, surface charge and ability to degrade in response to hydrogen peroxide. The authors then demonstrated that NMs are predominantly responsive to a GBM cell line lysate (GI261) showing nitric oxide dependent movement as opposed to a blood brain barrier (BBB) cell line (bEnd.3) cellular lysate. They further showed the ability of the NO- NMs to pass through a single layer BBB in vitro model without any apparent disruption with increase cellular uptake and mitochondrial co- localization in GI261 GBM cell line. NO- NMs loaded with PAC could cause mitochondrial mineralization, and ultimately cell death, predominantly in GBM cells with low impact on BBB cells. In vivo testing using a mouse GBM model revealed the accumulation of NO- NMs mostly in the brain tissue, liver and kidneys. The presence of curcumin, even though the NO- lipids showed low encapsulation efficiency, through its action on \(\mathrm{Ca^{2 + }}\) ions, enhanced the efficiency of the NO- NMs and increased mitochondrial mineralization. Consequently, NO- NMs containing curcumin resulted in a net tumor reduction, a lower impact on animal weight and an increased survival rate as compared to the chemotherapeutic drug temozolomide and controls. Taken together, those results provide valuable ideas for designing future therapeutic targeting GBM. + +## 1. \*\*\*GENERAL APPRECIATION \*\*\* + +The experimental work presented in this study is both thorough and extensive, highlighting commendable efforts by the authors to demonstrate the capabilities of their approach, especially for the in vitro assays. A complete proof of concept is provided, supported by in vitro assays and some preliminary in vivo experiments with a GBM mouse model. The authors corroborate their findings using at least three different approaches, making the results generally convincing and aligned with the scientific literature. The supplementary data are quite extensive cumulating 70 supplementary figures, further supporting the conclusions of the study. The text is well- written, with few syntax and typographical errors. Figures are coherent and clear, and most of the quantitative analyses are supported by robust statistical methods. + +Answer: Thank you very much for taking the time to review our manuscript. We greatly appreciate your suggestions, which are important for improving the quality of the paper. We highly value each of your suggestions and have responded to each of them. + +2. One of the major flaws identified in the study is the small number of mice used per experimental condition, with only three mice per group. This limited sample size, which is a major flaw, may affect the reliability and generalizability of the findings + +<--- Page Split ---> + +event if the data shown are generally convincing. In addition, GBM is clinically observed more frequently in biological men, suggesting a sex- specificity in its occurrence. Despite this, it is crucial for researchers to use both male and female mice in their studies to ensure that their findings are robust and applicable across sexes. This approach would provide a more comprehensive understanding of the disease and its potential treatments. In this study, the authors only used female mice. This is a major limitation of the study that should be discussed. + +Answer: Many thanks to you for your valuable comments. + +In the revised manuscript, we increased the sample size for animal experiments evaluating in vivo targeting ability and therapeutic efficacy to \(\mathrm{n} = 5\) or \(\mathrm{n} = 6\) independent samples, respectively (the sample size in Fig. 6, Supplementary Fig. 62, 63, and 64 was increased to \(\mathrm{n} = 5\) , the sample size in Fig. 7, Supplementary Fig. 65, 66, 67 and 69 was increased to \(\mathrm{n} = 6\) ). As shown below, the overall targeting and therapeutic efficacy did not change significantly after the increase in sample size. + +![](images/Supplementary_Figure_63.jpg) + + +<--- Page Split ---> + +Fig. 6. Targeting ability of NO- Lip@PAC NMs in GBM model mice. (a) Schematic diagram of the assessment of the targeting ability of different samples in a GBM model mouse; In vivo fluorescence imaging of mice injected with (b) PBS, (c) Lip@PAC or (d) NO- Lip@PAC at various time points (n = 5 independent samples); (e) Quantification of the mean fluorescence intensities of the brain sites from mice in a- c at various time points (I: PBS, II: Lip@PLC, III: NO- Lip@PAC, n = 5 independent samples); (f) Cy5 fluorescence imaging of the brain after intravenous injection of different samples for \(24\mathrm{h}\) (n = 5 independent samples; Scale bar: \(1\mathrm{cm}\) ) and (g) the corresponding quantitative analysis (I: Control, II: Lip@PLC, III: NO- Lip@PAC, n = 5 independent samples); (h) Quantitative analysis of different sample accumulations in major organs, expressed as injected dose per gram of tissue (% ID/g) (n = 5 independent samples); (i) Representative CLSM images of brain tumors in mice (Blue: nucleus, green: FITC- CD31, red: Cy5- labelled different samples; Scale bar: \(500\mu \mathrm{m}\) ) and (j) red fluorescence distribution curves (I: PBS, II: Lip@PLC, III: NO- Lip@PAC) along selected lines (indicated by white lines in the images). Data in b, c and e were presented as mean ± SD. Significance was calculated via two- sample t- test. + +![](images/Supplementary_Figure_64.jpg) + +
Supplementary Figure 62. Cy5 fluorescence imaging of the brain after intravenous injection of different samples for 7 and \(12\mathrm{h}\) (n = 5 independent samples; Scale bar: \(1\mathrm{cm}\) ).
+ +<--- Page Split ---> +![](images/Figure_7.jpg) + +
Supplementary Figure 63. Cy5 fluorescence imaging of the major organs after intravenous injection of different samples for 7 and \(12\mathrm{h}\) ( \(\mathrm{n} = 5\) independent samples; Scale bar: \(1\mathrm{cm}\) ).
+ +![](images/Supplementary_Figure_72.jpg) + +
Supplementary Figure 64. Cy5 fluorescence imaging of the major organs after intravenous injection of different samples for \(24\mathrm{h}\) ( \(\mathrm{n} = 5\) independent samples; Scale bar: \(1\mathrm{cm}\) ).
+ +<--- Page Split ---> +![](images/Supplementary_Figure_75.jpg) + +
Fig. 7. Anti-tumor efficacy of NO-Lip@PAC@Cur NMs in GBM model mice (female). (a) Treatment protocols for orthotopic brain-GBM-tumor-bearing models. By Figdraw; (b) Representative IVIS spectrum images and (c) quantified signal intensity (n = 6 independent samples per group) ; (d) Kaplan-Meier survival curves (n = 8 independent samples) of GBM model mice with different treatments; (e) Representative H&E (Scale bar: 4 mm), TUNEL, and Ki67 staining images (Scale bar: 500 μm) of dissected brain tissues at the end of treatment; (f) Tunel and (g) Ki67 quantitative fluorescence analysis; (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: LipPAC@Cur, VI: NO-Lip@PLC@Cur, VII: NO-Lip@PAC@Cur; n = 6 independent samples); (h) Representative Bio-TEM images of brain tumor (I: PBS, II: magnification of I, III: NO-Lip@PAC@Cur, IV: magnification of III; Scale bar of I and III: 5 μm; Scale bar of II and IV: 200 nm); Representative TEM-Mapping (P and Ca) of brain tumor cellular mitochondria after treated with (i) control and (j) NO-
+ +<--- Page Split ---> + +Lip@PAC@Cur (Scale bar: 200 nm). Data in c, f and g were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +![](images/Figure_3h.jpg) + + +Supplementary Figure 65. Pharmacokinetic profiles of Cur and NO- Lip@PAC@Cur. \(n = 6\) independent samples. Data were presented as mean ± SD. + +![](images/Figure_4c.jpg) + + +Supplementary Figure 66. Tumor percentage after treatment with different samples (tumor percentage = (tumor area/brain area) \(\times 100\%\) ; I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip@PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; \(n = 6\) independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +![](images/Figure_5g.jpg) + + +Supplementary Figure 67. Hemolysis rate of the RBC solution after being treated with (a) different samples (I: negative, II: positive, III: PAC@Cur, IV:Lip- PAC@Cur, V:NO- Lip@PLC@Cur, VI: NO- Lip@PAC@Cur) and (b) different concentrations of + +<--- Page Split ---> + +NO- Lip@PAC@Cur for 3 h. \(\mathrm{n} = 6\) independent samples. Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +![](images/Supplementary_Figure_57.jpg) + + +Supplementary Figure 69. Changes in body weight of mice in different treatment groups (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip@PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; \(\mathrm{n} = 6\) independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +![](images/Figure_5b.jpg) + + +Supplementary Figure 71. Hematological parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip- PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; \(\mathrm{n} = 6\) independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<--- Page Split ---> +![](images/Supplementary_Figure_56.jpg) + +
Supplementary Figure 72. Blood biochemical parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip-PAC@Cur, VI: NO-Lip@PLC@Cur, VII: NO-Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean ± SD. Significance was calculated via one-way ANOVA.
+ +As mentioned by the reviewer, the use of 6- 8- week- old C57BL/6 female mice in the model construction was chosen based on a comprehensive consideration of the modeling methods used in most current studies for the in situ GI261 mouse model (Nat. Nanotechnol. 2025, 20, 683- 696; J. Nanobiotechnol. 2023, 21, 210; Nano Today 2022, 45, 101530). The choice was primarily based on two considerations: first, differences in androgen levels among male individuals may affect the efficacy of brain tumor treatment, while female mice can effectively avoid this issue. Second, in experiments involving a large number of male animals, cohabiting male mice are prone to intense biting and fighting, which not only poses management challenges but also leads to additional animal casualties (Nature 2014, 509, 282- 283; Hypertension 2016, 68, 1139- 1144). Additionally, to more comprehensively evaluate the therapeutic efficacy, we further established an in situ GI261 model using 6- 8- week- old C57BL/6 male mice and investigated the efficacy of NO- Lip@PAC@Cur NMs in this model. As shown in Supplementary Fig. 75a- c, quantitative analysis of in vivo bioluminescence imaging and total radioluminescence intensity revealed that the bioluminescence signal in the PBS group continued to increase over time and reached its peak at the end of treatment (54.4 times of the initial radioluminescence intensity), indicating rapid tumor growth. Following free TMZ treatment, the fluorescence intensity of representative tumors in the mouse brain decreased, indicating mild inhibition of tumor growth (40.6 times of the initial radioluminescence intensity). In contrast, the anti- GBM growth effect was enhanced in the NO- Lip@PAC@Cur group, + +<--- Page Split ---> + +with a significant reduction in bioluminescence signals (only 9.6 times of the initial radioluminescence intensity). At the end of treatment, the brain tumor area was largest in the PBS group, accounting for \(39.6\%\) of the entire brain. Brain tumor area in mice treated with free TMZ were reduced, accounting for \(26.1\%\) of the entire brain. In contrast, NO- Lip@PAC@Cur significantly inhibited brain tumor growth, with tumor area accounting for \(9.0\%\) of the entire brain at the end of treatment in mice (Supplementary Fig. 75d and e). Mice in the PBS and TMZ groups experienced significant weight loss during treatment, which may be attributed to the inevitable damage caused by chemotherapy drugs to normal tissues and their functions during treatment. In contrast, no significant weight loss trend was observed in mice treated with the NO- Lip@PAC@Cur NMs during treatment (Supplementary Fig. 75f). The therapeutic efficacy of NO- Lip@PAC@Cur NMs in C57 male mice was similar to that in C57BL/6 female mice. + +![](images/Figure_5b.jpg) + +
Supplementary Figure 75. Anti-tumor efficacy of NO-Lip@PAC@Cur NMs in GBM model mice (male). (a) Treatment protocols for orthotopic GBM models. By Figdraw; (b) Representative IVIS spectrum images and (c) quantified signal intensity \(\mathrm{n} = 6\) independent samples per group); (d) Representative H&E images of dissected brain tissues at the end of treatment (Scale bar: \(2\mathrm{mm}\) ); (e) Tumor percentage after treatment with different samples (tumor percentage \(=\) (tumor area/brain area) \(\times 100\%\) ); (f) Changes in body weight of mice in different treatment groups. I: PBS, II: TMZ, III: NO-Lip@PAC@Cur; \(\mathrm{n} = 6\) independent samples. Data were presented as mean \(\pm \mathrm{SD}\) .
+ +<--- Page Split ---> + +Significance was calculated via one- way ANOVA. + +3. Another important concern is the fact the research team has previously published a highly similar article in 2023 (DOI: 10.1038/s41467-022-35709-0), utilizing the same general methodology and a similar experimental approach. In this new work, the authors are encouraged to highlight the novelty of their findings, emphasizing advancements and unique contributions that distinguish it from their earlier research work. + +Answer: Many thanks to you for your valuable comments. + +H. Chen et al. designed a chemotactic nanomotor, which was loaded with the brain endothelial cell-targeted drug angiotensin-2 and the anticancer drug (lonidamine modified with the mitochondrial-targeted drug triphenylphosphine, TLND), named Ang-PAMSe/TLND. This nanomotor can sustainably release high concentrations of NO over an extended period. The generated-high concentration NO can regulate the tumor's immunosuppressive microenvironment through mechanisms such as inducing tumor immunogenic cell death, promoting dendritic cell maturation, facilitating cytotoxic T cell infiltration, and modulating the tumor microenvironment. This promoted the maturation of antigen-presenting cells and T cell activation, further activating the body's systemic anti-tumor immune response and inhibiting tumor metastasis and recurrence. + +Unlike previous work, this work proposes a novel size-variable self- feedback nanomotor (NO- Lip@PAC@Cur NMs) specifically tailored for GBM treatment, leveraging the unique high- calcium microenvironment of GBM. Under the drive of high iNOS expression in the GBM microenvironment, larger size- variable self- feedback nanomotors (approximately 500 nm) can penetrate the BBB via chemotaxis. During chemotaxis, accumulated NO cause the self- feedback lipid shell to gradually degrade, releasing smaller PAC NMs (approximately 50 nm). These smaller nanomotors target mitochondria, where they recruit \(\mathrm{Ca^{2 + }}\) and curcumin to jointly induce mitochondrial mineralization, ultimately leading to tumor cell death and inhibiting GBM progression. + +A comparison of the two works is summarized in Table R1. First, in terms of material composition, previous work primarily utilized L- Arg derivatives (the power source component of the nanomotor) as monomers, constructing the nanomotor through radical polymerization reactions. And then loaded with TLND. In contrast, this work modifies L- Arg within the liposome structure while simultaneously loading curcumin, expanding the construction method of nanomotors from polymer materials synthesized via radical polymerization reactions to liposomes, which holds greater potential for future application and commercialization. Secondly, the two works designs have obvious differences in their specific approaches to brain tumor tissue. Previous work mainly utilized the unique metabolic pathways of tumor tissue, such as the unique metabolic symbiosis system of tumor cells, which has been widely used in many brain tumor treatment studies (Adv. Funct. Mater. 2025, 2419395; ACS Nano 2025, 19, 21365- 21384; Nat. Commun. 2023, 14, 435). This work utilizes the high calcium environment unique to brain tumor tissue and introduces the concept of + +<--- Page Split ---> + +mitochondrial mineralization into brain tumor treatment, confirming the feasibility of mineralization effects in significantly improving brain tumor treatment outcomes. This approach has not been reported in other studies and is highly innovative. Furthermore, the two works also differ in their design of mitochondrial targeting strategies. Previous work primarily modified LND with positively charged triphenylphosphine (TPP), utilizing its positive charge to target the negatively charged mitochondrial membrane. However, since the membranes of other organelles within the cell are also negatively charged, albeit to a slightly lesser extent than mitochondria (Ann. N. Y. Acad. Sci. 2008, 1147: 105-111), the specificity of this mitochondrial targeting approach is not particularly pronounced. In contrast, this study first reduces the size of the nanomotor using the size effect (from large to small), then employs iNOS, which is highly expressed in mitochondria, as a chemical attractant (Febs J. 2007, 274, 2135-2147; Anesthesiology 2009, 110, 166-181) to induce the nanomotor to further chemotactically target mitochondria upon entering tumor cells. This method of targeting mitochondria has not been reported previously. + +Overall, this work verifies the feasibility of mineralization in brain tumor treatment through various designs, which broadens the scope of brain tumor treatment and has obvious advantages and innovations that differ from previous work. + +Once again, we would like to thank the reviewers for their insightful comments, which have given us a deeper understanding of the strengths of this study. + +Table R1. Comparison of two works. + +
Material compositionLoaded drugsSpecificityTargeted strategyMitochondria-targeting strategyPenetration strategyTreat ment appro achRef.
Ang-PAMS/T LNDchloridr amineunique metabolic pathways in brain tumor tissuesbrain endothelial cell recognition + chemotactic targeting of brain tumor cellsmaterial modification with positively charged triphenylphosphine (TPP) through charge attraction targeting mitochondriananomotor movement achieves deep penetrationimmunother apyNat. Com mun . 202 3, 14, 941.
NO-Lip@PAC@Curcurcum inthe high calcium environmen t unique to brain tumor tissuechemotaxis targeting the microenvironment of brain tumorutilizing size-dependent effects and chemotactic targeting effects of high levels of iNOS specific to mitochondriavariable sizes and nanomotor movement achieve further penetrationmitochondrial miner alizati onThis work
+ +## \\*\\*\\* SPECIFIC COMMENTS \\*\\*\\* + +The following specific comments should be considered by the authors to provide more clarity and improve the manuscript: + +<--- Page Split ---> + +Introduction: + +4. The current therapeutic approaches to treat GBM are wider than what is being listed in the introduction section, which mostly focus on immunotherapeutic strategies and gene therapies, especially for drug delivery (local and systemic) approach currently being studied in the field. + +Answer: Many thanks to you for your valuable comments. + +We have described the limitations of GBM treatment strategies in detail in Introduction. The revised Introduction is as follows. + +Glioblastoma (GBM) is one of the most aggressive and deadly brain tumors, classified by the World Health Organization as the most malignant glioma (Grade IV). The standard treatment for GBM typically involves a combination of surgical resection followed by radiotherapy and/or chemotherapy. However, the characteristic infiltrative growth of GBM makes it difficult to eradicate surgically and may damage critical brain functional areas. The efficacy of first- line chemotherapeutic agents such as temozolomide (TMZ) is often limited by the inherent resistance of tumor cells and severe systemic toxicity (including hematologic toxicity and thrombocytopenia associated with long- term and high- dose administration). The presence of the blood- brain barrier (BBB) also prevents most drugs to enter the tumor cells. Although radiotherapy has shown good cytotoxic effects, its low selectivity and specificity can also cause irreversible damage to normal tissues. Consequently, the median survival for GBM patients remains low at 14.6- 20.5 months, with a 5- year survival rate of less than \(10\%\) . Emerging modalities such as electro- fields therapy, and focused ultrasound therapy have also shown promising advancements in solid tumor therapy in clinic or pre- clinical settings. In situ drug delivery strategies for GBM (convection- enhanced delivery (CED), implantation of slow- release devices) circumvent the BBB by delivering the drug directly to the tumor or postoperative residual cavity, achieving high local drug exposure and reducing systemic toxicity. However, higher operational requirements, the need for more complex equipment, unpredictable and heterogeneous drug distribution, and susceptibility to localized brain tissue injury, edema, or inflammation may limit their application. Therefore, developing targeted therapeutic strategies specifically for GBM has emerged as a critical area of research. + +The unique microenvironment of GBM provides valuable insights for the design of targeted therapeutic strategies (Supplementary Table 1). GBM is characterized by an immunosuppressive tumor microenvironment, often referred to as a "cold" tumor, which has spurred researchers to actively explore novel immunotherapeutic approaches for GBM. These include tumor vaccines, immune checkpoint inhibitors (ICIs), and chimeric antigen receptor T- cell (CAR- T) therapies, etc. However, the efficacy of immunotherapy is affected by the individual patient variability, leading to insufficient or excessive immune responses that limit its broad application. In addition to immunotherapy, molecular targeted therapies have been developed to target cellular molecules that promote the proliferation and differentiation of GBM, such as anti- angiogenic therapy and tyrosine kinase inhibitors. However, their effectiveness is often limited by factors such as drug + +<--- Page Split ---> + +resistance in tumor cells and high recurrence rates following treatment16. Gene therapy represents another promising approach, targeting specific genes involved in the proliferation, migration, invasion, apoptosis, and angiogenesis of malignant glioma cells including gene editing corrections using CRISPR-Cas9, or suppressing immune-suppressive genes expressed in brain tumors to reprogram the tumor immune microenvironment3. However, challenges such as the poor stability of nucleic acids in vivo, variable transfection efficiency, and high treatment costs have restricted its widespread application3. Therefore, there is a pressing need to find new therapeutic strategies specifically for GBM. + +## Results: + +5. Figure 2 and Figure S18: Please clarify the rationale for using HUVEC cells in part of the study and the bEnd.3 cell line for the remainder. + +Answer: Many thanks to you for your valuable comments. + +As shown in Table R2, we have summarized the cells used in different experiments. When evaluating the degradation behavior of NO- Lip@PAC, we used HUVECs cells, primarily because the in vivo administration method of NO- Lip@PAC@Cur NMs is intravenous injection. HUVECs are human umbilical vein endothelial cells, which can simulate the normal vascular endothelial cell environment in the bloodstream, indicating that they are not degraded during circulation. When NO- Lip@PAC@Cur NMs circulate to the environment surrounding brain tumors, they can penetrate the BBB via chemotaxis and release the loaded cargo through degradation, increasing mitochondrial calcium levels in cells and ultimately leading to brain tumor cell death. Therefore, we used bEnd.3 cells in experiments involving motility, chemotaxis, in vitro BBB penetration ability, and cellular \(\mathrm{Ca^{2 + }}\) content to simulate normal cells in the brain tumor microenvironment. + +Table R2. Summary of cells used in different experiments + +
Experiment nameExperiment purposeCells usedReasons for selection
assessment of NO-Lip@PAC degradation behaviorevaluate the selective degradation behavior of NO-Lip@PAC in normal cell and cancer cell environmentsHUVECssimulate normal vascular cells in blood circulation
the dynamic behavior of different samplesexplore the motility behavior of Lip@PAC and NO-Lip@PAC in normal cell and cancer cell environmentsbEnd.3simulate normal vascular cells surrounding the tumor microenvironment
chemotactic behavior of different samplesexplore the chemotactic behavior of Lip@PAC and NO-Lip@PAC in normal cell and cancer cell environmentsbEnd.3simulate normal vascular cells surrounding the tumor microenvironment
+ +<--- Page Split ---> + + +
evaluation of ability to penetrate the BBBevaluate the ability of different samples to cross the BBBbEnd.3bEnd.3 can form a dense cell layer that can be used to simulate the BBB in vitro
Ca2+ contentevaluate the effects of different samples on Ca2+ content in cellsbEnd.3simulate normal cells in the brain to contrast with brain tumor cells
cell activityinvestigate cell viability after treating different samples with bEnd.3 and Gl261 cellsbEnd.3simulate normal cells in the brain to contrast with brain tumor cells
+ +# 6. Line 195: precise the technic used to determine the iNOS in bEnd.3 and Gl261 cells. + +**Answer:** Many thanks to you for your valuable comments. + +We used the mouse inducible nitric oxide synthase (iNOS) ELISA research kit (purchased from Jiangsu Enzyme Immunoassay, product number MM-0454M1). The specific steps are as follows. + +(1) Collect bend.3 and Gl261 cells, sonicate the cells, and centrifuge to obtain the supernatant as the test sample. + +(2) Sample addition: Set up blank wells (blank control wells without sample or enzyme-labeled reagents, with all other steps performed identically), standard wells,and sample wells. Add 50 μL standard solution to the enzyme-labeled coated plate wells. In the sample wells, first add 40 μL sample diluent, then add 10 μL the sample (final sample dilution is 5-fold). Add the sample to the bottom of the enzyme-labeled plate wells, avoiding contact with the well walls, and gently mix. + +(3) Incubation: Cover the plate with a sealing membrane and incubate at 37 °C for 30 min. + +(4) Solution preparation: Dilute the 30x concentrated wash solution with distilled water at a 30x dilution ratio and set aside. + +(5) Washing: Carefully remove the sealing membrane, discard the liquid, and centrifuge to remove excess liquid. Add washing solution to each well, let stand for 30 seconds, then discard. Repeat this process 5 times, then blot dry. + +(6) Enzyme addition: Add 50 μL of enzyme-labeled reagent to each well, excluding the blank well. + +(7) Incubation: Follow the same procedure as in (3). + +(8) Washing: Follow the same procedure as in (5). + +(9) Color development: Add 50 μL color developer A to each well, followed by 50 μL of color developer B. Gently mix by shaking, then incubate at 37 °C in the dark for 10 min. + +(10) Termination: Add 50 μL stop solution to each well to terminate the reaction (the color will immediately change from blue to yellow). + +(11) Measurement: Adjust the blank well to zero, then measure the absorbance (OD value) of each well at a wavelength of 450 nm. The measurement should be performed within 15 min after adding the stop solution. + +<--- Page Split ---> + +7. Figure 3 h-k: The fluorescence maker diffusing toward Gl261 cell lysate with the NO-Lip@PAC condition is only slightly higher compared to bEnd.3 cell lysate. Quantitative fluorescence distribution data should be supported with statistical analysis to ensure accuracy and validity of the conclusion. + +Answer: Many thanks to you for your valuable comments. + +According to the reviewer's suggestion, we quantified the fluorescence intensity of regions (i) and (iii) under different conditions, and statistical analysis was also added to ensure accuracy and validity of the conclusion. As shown in Supplementary Fig. 42, when both regions (i) and (iii) were exposed to bEnd.3 cellular lysate, the fluorescence intensity of Lip@PAC and NO-Lip@PAC was comparable on both sides. However, when regions (i) and (iii) were each separately exposed to Gl261 and bEnd.3 cellular lysate, there was no difference in fluorescence intensity between the two sides for Lip@PAC, the fluorescence intensity of NO-Lip@PAC in Gl261 cellular lysate was higher than that on the side of bEnd.3 cellular lysate (3.0 times higher than it), indicating that NO-Lip@PAC can diffuse from channel (ii) to channel (iii) with higher iNOS concentration. + +![](images/Figure_6a.jpg) + +
Fig. 3h-k. (h) Representative fluorescence images of different samples at the exit of the \(\Psi\) -shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (i) the corresponding fluorescence quantification in the presence of bEnd.3 cellular lysates ( \(\mathrm{n} = 3\) independent samples); (j) Representative fluorescence images of different samples at the exit of the \(\Psi\) -shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (k) the corresponding fluorescence quantification in the presence of bEnd.3 and Gl261 cellular lysates ( \(\mathrm{n} = 3\) independent samples).
+ +![](images/Supplementary_Figure_48.jpg) + + +<--- Page Split ---> + +Supplementary Figure 41. (a) Quantification of fluorescence of different materials at (i) and (iii) at the channel outlet when passing bEnd.3 cellular lysate at \(\Psi\) - shaped microfluidic inlets (i) and (iii) (n = 3 independent samples); (b) Quantification of fluorescence of different materials at the channel outlet in (i) and (iii) when Gl261 or bEnd.3 cellular lysates were passed through the \(\Psi\) - shaped microfluidic inlets (i) and (iii), respectively (n = 3 independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via two- sample t- test. + +8. Lines 318-321: precise the p Values for the fold increased in fluorescence and transport rate values provide. + +Answer: Many thanks to you for your valuable comments. + +We have provided the fluorescence increase multiples and p- values for the transfer rate in the revised manuscript. The revised sections are as follows. + +In addition, the red fluorescence intensity in bEnd.3 cells in the upper chambers treated with NO- Lip@PAC NMs was lower than that treated with Lip@PAC NPs (Fig. 4c), while Gl261 cells in the lower chambers had stronger red fluorescence signals, and fluorescence quantification showed that their intensity was 8.7 times higher than that of Lip@PAC NPs (Fig. 4c and 4d). The calculation of the transport rate in Fig. 4e showed that the transport efficiency of Lip@PAC NPs was only about \(13.7\%\) , while that of NO- Lip@PAC NMs reached about \(63.5\%\) (4.6 times higher than that of Lip@PAC). + +![](images/Figure_5c.jpg) + +
Fig. 4c-f. Quantitative analysis of red and green fluorescence in the (c) upper and (d) lower compartments (I: Control, II: Lip@PAC, III: NO-Lip@PAC, n = 3 independent samples); (e) BBB transport efficiency of different samples (I: Lip@PAC, II: NO-Lip@PAC; n = 3 independent samples); (f) Paracellular permeability of FD-4 treated with different samples for 24 h (I: Control, II: Lip@PAC, III: NO-Lip@PAC; n = 3 independent samples).
+ +<--- Page Split ---> + +9. Figure 5g: Co-localization analysis typically presents red and green fluorescence data without accounting for the relative fluorescence intensity of each sample. For example, green fluorescence, which represents cytoplasmic \(\mathrm{Ca^{2 + }}\) levels fluctuate significantly between experimental conditions. The overlapping between the red and green channel is also high for condition II but is not discussed at all. Therefore, it is also essential to consider relative ratios to accurately interpret the results. + +Answer: Many thanks to you for your valuable comments. + +The reasons for green and red fluorescence fluctuate significantly between experimental conditions are as follows. L- Arg in NO- Lip@PAC can react with iNOS (highly expressed in tumor cells) to form NO, which in turn causes endoplasmic reticulum stress and releases \(\mathrm{Ca^{2 + }}\) , leading to an increase of \(\mathrm{Ca^{2 + }}\) levels in the cytoplasm. After targeting mitochondria, PAC can recruit \(\mathrm{Ca^{2 + }}\) from the cytoplasm to the region surrounding the mitochondria, further increasing mitochondrial \(\mathrm{Ca^{2 + }}\) levels. Therefore, the green fluorescence representing cytoplasmic \(\mathrm{Ca^{2 + }}\) and the red fluorescence representing mitochondrial \(\mathrm{Ca^{2 + }}\) in the NO- Lip@PAC treatment group were higher than those in the Control and Lip@PLC treatment group. In the NO- Lip@PAC@Cur treatment group, based on the aforementioned pathways, Cur can inhibit \(\mathrm{Ca^{2 + }}\) efflux from the cytoplasm, resulting in higher cytoplasmic \(\mathrm{Ca^{2 + }}\) and mitochondrial \(\mathrm{Ca^{2 + }}\) levels compared to other groups. Thus, under different experimental conditions, the intensity of green fluorescence representing cytoplasmic \(\mathrm{Ca^{2 + }}\) and red fluorescence representing mitochondrial \(\mathrm{Ca^{2 + }}\) differed a lot (Fig. 5g, Supplementary Fig. 57, and 58), the green and red fluorescence intensities of the Lip@PLC group were not significantly different from those of the control group, while the green and red fluorescence intensities of the NO- Lip@PAC group were significantly higher than those of the control group (2.4- fold and 1.9- fold higher, respectively). And the green and red fluorescence intensities of the NO- Lip@PAC@Cur group were 7.2 and 2.4 times higher than those of the control group, respectively. + +In the previous colocalization analysis of Sample II, the sample line did not fully traverse the entire cell, resulting in a high overlap between the red and green channels of Sample II. Therefore, we re- selected more representative fluorescence images and colocalization analyses. As shown in Fig. 5g and Supplementary Fig. 57, colocalization analysis showed that the colocalization of red fluorescence and green fluorescence in the Lip@PLC treatment group was poor, and the overlap of red fluorescence and green fluorescence in the NO- Lip@PAC and NO- Lip@PAC@Cur NMs group was higher, which further proved the above process. + +Since red fluorescence represents mitochondrial \(\mathrm{Ca^{2 + }}\) and green fluorescence represents cytoplasmic \(\mathrm{Ca^{2 + }}\) , the ratio of red to green fluorescence is not comparable. Therefore, we compared the red and green fluorescence intensities of different treatment groups with those of the blank group, respectively. As shown in Supplementary Fig. 57, the green and red fluorescence intensities of the Lip@PAC group did not differ from those of the control group. The green and red fluorescence of the NO- Lip@PAC group were significantly higher than those of the control group (2.4- and 1.9- times higher, respectively), indicating that NO can induce endoplasmic + +<--- Page Split ---> + +reticulum stress, leading to the release of \(\mathrm{Ca^{2 + }}\) and an increase in \(\mathrm{Ca^{2 + }}\) levels in the cytoplasm. PAC NMs can recruit \(\mathrm{Ca^{2 + }}\) around mitochondria, resulting in an increase in mitochondrial \(\mathrm{Ca^{2 + }}\) levels. The green and red fluorescence intensities of the NO- Lip@PAC@Cur group were 2.6 and 1.4 times higher than those of the NO- Lip@PAC group, respectively, indicating that Cur could inhibit \(\mathrm{Ca^{2 + }}\) efflux in the cytoplasm and further increase the \(\mathrm{Ca^{2 + }}\) levels in the cytoplasm and mitochondria. + +![](images/Figure_2.jpg) + +
Fig. 5g. Representative CLSM images of cytoplasmic \(\mathrm{Ca^{2 + }}\) and mitochondrial \(\mathrm{Ca^{2 + }}\) treated with different samples for \(24\mathrm{h}\) and the fluorescence distribution curves along selected lines (I: Control, II: Lip@PLC, III: NO-Lip@PAC, IV: NO-Lip@PAC@Cur; indicated by the white lines in the images; Blue: nucleus, green: Fluo-4-labelled cytoplasmic \(\mathrm{Ca^{2 + }}\) , red: Rhod-2-labelled mitochondrial \(\mathrm{Ca^{2 + }}\) ; Scale bar: \(20\mu \mathrm{m}\) ; \(\mathrm{n} = 3\) independent samples).
+ +![](images/Figure_3.jpg) + +
Supplementary Figure 57. Representative CLSM images of cytoplasmic \(\mathrm{Ca^{2 + }}\) and
+ +<--- Page Split ---> + +mitochondrial \(\mathrm{Ca^{2 + }}\) of Gl261 cells co-incubated with different samples for \(24\mathrm{h}\) (blue: Hoechst 33342 labeled nucleus, green: Fluo-4- labeled cytoplasmic \(\mathrm{Ca^{2 + }}\) ; red: Rhod-2- labeled mitochondrial \(\mathrm{Ca^{2 + }}\) ; Scale bar: \(20\mu \mathrm{m}\) ). + +![](images/Figure_5b.jpg) + + +Supplementary Figure 58. Representative CLSM images corresponding quantitative analysis of (a) green fluorescence (Fluo- 4- labeled cytoplasmic \(\mathrm{Ca^{2 + }}\) ) and (b) red fluorescence (Rhod- 2- labeled mitochondrial \(\mathrm{Ca^{2 + }}\) ) intensity in Supplementary Figure 57 (I: Control, II: Lip@PLC, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +10. Lines 397-398: the Zeta potential value for NO-Lip@PAC@Cur NMs is quite low \((\succ -20\) to \(-30\mathrm{mV}\) or \(< 20\) to \(30\mathrm{mV}\) ) and could result in poorly stable colloidal solution with the tendency to form aggregates. The authors are encouraged to discuss the stability of their system as this statement is supported with the DLS data obtained for different Lip/Cur drug ratios tested (results in Supp file) where aggregates are easily formed. + +Answer: Many thanks to you for your valuable comments. + +The reviewer's questions raised our concerns about the surface charge and stability of the material. We characterized the stability of NO- Lip@PAC@Cur NMs by investigating changes in DLS and zeta potential at different time points in PBS environment. As shown in Supplementary Fig. 52a and b, the DLS and zeta potential of NO- Lip@PAC@Cur NMs remained unchanged within 7 days, with values of \(598.8\mathrm{nm}\) and \(- 13.9\mathrm{mV}\) , respectively. Additionally, the optical images in Supplementary Fig. 52c indicate that no significant precipitation was observed in PBS after 7 days incubation, demonstrating their excellent stability. + +The surface potential of liposomes reported in other studies is approximately - 10 to \(- 20\mathrm{mV}\) . For example, Chen et al. reported that the zeta potential of liposome- coated titanium dioxide (MIL/TiO₂) nanoparticles was approximately - 11.0 mV (Nat. Nanotechnol. 2023, 18, 1492- 1501); Jiang et al. constructed biomimetic hybrid liposomes (P- RL), with a zeta potential of approximately - 15.0 mV (ACS Nano 2021, 15, 4173- 4185); Liu et al. constructed the liposome nanoparticles (LPs), with a zeta potential of - 19.87 mV (Acta Pharm. Sin. B 2023, 13, 3817e3833). These are similar to the zeta potential (- 14.0 mV) of the NO- Lip@PAC@Cur NMs in this study. + +<--- Page Split ---> + +Additionally, the relatively low absolute value of the NO- Lip@PAC@Cur NMs potential may be attributed to the presence of L- Arg structures on the liposome surface, as the positive charge of Arg reduces the surface negative charge. + +![PLACEHOLDER_34_0] + + +Supplementary Figure 52. (a) DLS, (b) zeta potential and (c) optical images of NO- Lip@PAC@Cur NMs incubate with PBS for different time (n = 3 independent samples). Data were shown as the mean ± s.d. + +11. Lines 407-414 and lines 426-428: precise the p Values for the fold increased in fluorescence and transport rate values provide. + +Answer: Many thanks to you for your valuable comments. + +We have provided the p- values for Fig. 5b, 5c, Supplementary Fig. 53, 54, and 55 in the revised manuscript. The revised sections are as follows. + +![PLACEHOLDER_34_1] + +
Fig. 5b and c. (b) Intracellular \(\mathrm{Ca^{2 + }}\) concentration in bEnd.3 cells and Gl261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; n = 3 independent samples); (c) \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for 24 h in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; n = 3 independent samples).
+ +<--- Page Split ---> +![PLACEHOLDER_35_0] + + +Supplementary Figure 53. Fluorescence quantification of intracellular NO in bEnd.3 and Gl261 cells treated with different samples for 6 h (I: Control, II: Lip@PLC, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +![PLACEHOLDER_35_1] + + +Supplementary Figure 54. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with NO- Lip@PAC@Cur for different time in Gl261 cells. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +![PLACEHOLDER_35_2] + + +Supplementary Figure 55. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with different samples in Gl261 cells (I: Control, II: A23187, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +12. Lines 432-433: To complete the demonstration, the author should also provide + +<--- Page Split ---> + +data for NO- Lip@PAC- treated GI261. Why only use the control and NO- Lip@PAC@Cur to assess the presence of mitochondrial calcification? + +Answer: Many thanks to you for your valuable comments. + +Based on the reviewer's suggestion, we have added Bio- TEM images of GI261 cells treated with NO- Lip@PAC. As shown in Supplementary Fig. 57a, the cell membranes of NO- Lip@PAC- treated GI261 cells remain largely intact, with most mitochondria retaining their structural integrity. Only a small number of mitochondria exhibit structural abnormalities, which may be attributed to the NO generated by the interaction between NO- Lip@PAC and high concentrations of iNOS in the tumor microenvironment, leading to endoplasmic reticulum stress and the release of \(\mathrm{Ca^{2 + }}\) , thereby causing mitochondrial calcium overload. This result is consistent with the findings in Fig. 5b and 5c, where \(\mathrm{Ca^{2 + }}\) levels in cells and mitochondria were elevated. + +![PLACEHOLDER_36_0] + +
Supplementary Figure 56. (a) Representative bio-TEM images of GI261 cell treated with NO-Lip@PAC; (b) Representative bio-TEM images of GI261 cellular mitochondria treated with (I) PBS, (II) NO-Lip@PAC and (III) NO-Lip@PAC@Cur.
+ +![PLACEHOLDER_36_1] + +
Fig. 5b and c. (b) Intracellular \(\mathrm{Ca^{2 + }}\) concentration in bEnd.3 cells and GI261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples); (c) \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for 24 h in GI261 cells. (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples)
+ +<--- Page Split ---> + +13. Lines 476-478: precise the NMs concentration used. + +Answer: Many thanks to you for your valuable comments. + +We have added the concentrations of the different samples used in the MTT experiment to the revised manuscript. The revised sections are as follows. + +The impact of the mitochondrial mineralization process on cellular activity was also explored. As shown in Fig. 5k, 3-(4,5-dimethylthiazol- 2- yl)- 2,5- biphenyl tetrazolium bromide (MTT) results showed that NO- Lip@PAC@Cur NMs had a concentration- dependent cytotoxicity against Gl261 cells, as the concentration increased from 50 to \(800\mu \mathrm{g}\mathrm{mL}^{- 1}\) , the cell activity decreased from \(80.2\%\) to \(24.5\%\) . In addition, the cytotoxicity of different samples on Gl261 and bEnd.3 cells was compared (Fig. 5l), the cell viability of Gl261 cells in the NO- Lip@PAC NMs group \((200\mu \mathrm{g}\mathrm{mL}^{- 1})\) was \(74.6\%\) , while the viability decreased to \(44.5\%\) when Cur was loaded, indicating that mitochondrial mineralization in tumor cells resulted in significant cytotoxicity effects. Meanwhile, the viability of bEnd.3 cells treated with NO- Lip@PAC@Cur NMs \((200\mu \mathrm{g}\mathrm{mL}^{- 1})\) was \(83.8\%\) , with no significant damage to normal cells, due to the absence of overexpressed iNOS in normal cells, which did not undergo mitochondrial mineralization. + +14. Figure 7a: the schematic showing the steps and timeline to create the GBM mouse model should be introduced in Figure 6 instead, or at least, the text should refer to it as the steps to create the GBM tumor mouse model. + +Answer: Many thanks to you for your valuable comments. + +We have added the steps for creating the GBM mouse model and a schematic diagram of the assessment of the targeting properties of different materials to Fig. 6. The revised Fig. 6a is as follows. + +![PLACEHOLDER_37_0] + +
Fig. 6a. Schematic diagram of the assessment of the targeting ability of different samples in a GBM model mouse.
+ +15. The authors should emphasize the limitations of their proposed delivery system and the overall study, particularly highlighting the low number of mice per experimental condition. + +16. Since NO-NMs tend to accumulate in various organs such as the liver and kidneys, one potential improvement to limit drug usage, increase accumulation toward the brain tissue could be the addition of brain BBB shuttle peptides and limit potential adversarial impacts. This would maximize brain tissue accumulation, like current practices with many brain-targeted delivery vehicles. The authors are encouraged to provide future improvements for their system. + +<--- Page Split ---> + +Answer: Many thanks to you for your valuable comments. + +Given that these two issues have overlapping aspects, we will address them together. + +In agreement with the reviewer's previous suggestions, we have increased the sample size for animal experiments evaluating in vivo targeting ability and therapeutic efficacy to \(\mathrm{n} = 5\) or \(\mathrm{n} = 6\) independent samples, respectively (the sample size in Fig. 6, Supplementary Fig. 62, 63, and 64 was increased to \(\mathrm{n} = 5\) , the sample size in Fig. 7, Supplementary Fig. 65, 66, 67 and 39 was increased to \(\mathrm{n} = 6\) ). + +Additionally, we have further discussed the limitations of this study in the conclusion section, and the revised Conclusion is as follows. + +## Conclusion + +In summary, we successfully developed size- variable self- feedback nanomotors NO- \(\mathrm{Lip@PAC@Cur}\) NMs, and verified their therapeutic efficacy against GBM. The lipid shell of NO- \(\mathrm{Lip@PAC}\) NMs degraded in response to the NO generated during chemotactic targeting to the GBM microenvironment, thereby releasing the loaded Cur and PAC NMs. The released NO induced endoplasmic reticulum stress and subsequent \(\mathrm{Ca^{2 + }}\) release, while Cur inhibited \(\mathrm{Ca^{2 + }}\) efflux. This dual action resulted in an increase in the intracellular \(\mathrm{Ca^{2 + }}\) concentration (2.7 times higher than that in the control group). Additionally, PAC NMs targeted mitochondria via chemotaxis, where the carboxyl groups recruited \(\mathrm{Ca^{2 + }}\) from the cytoplasm, thereby increasing the local mitochondrial \(\mathrm{Ca^{2 + }}\) concentration to 6.2 times higher than that in the control group. Fluorescence imaging and TEM- mapping of \(\mathrm{Ca^{2 + }}\) in tumor cell mitochondria revealed that mitochondria in the control group. Fluorescence imaging and TEM- mapping of \(\mathrm{Ca^{2+}}\) in tumor cell mitochondria revealed that mitochondria in the NO- \(\mathrm{Lip@PAC@Cur}\) NMs- treated group exhibited stronger fluorescence signals. This indicates that NO- \(\mathrm{Lip@PAC@Cur}\) NMs effectively induced mitochondrial dysfunction, loss of mitochondrial membrane potential, and a significant decrease in ATP- generating capacity from \(8.9~\mu \mathrm{M}\) to \(2.4~\mu \mathrm{M}\) . In vivo experiments demonstrated that NO- \(\mathrm{Lip@PAC}\) NMs could recognize the highly expressed iNOS in the tumor microenvironment, cross the BBB, and accumulate in brain tumors. Specifically, the accumulation in brain tissues of GBM model mice reached \(29.3\%\) ID/g, which was 3.6 times higher than that of the \(\mathrm{Lip@PAC}\) NMs group. The treatment results showed that NO- \(\mathrm{Lip@PAC@Cur}\) NMs effectively inhibited the growth of tumor by inducing mitochondrial mineralization and subsequent tumor cell death (the brain tumor area accounted for \(9.5\%\) of the whole brain in the NO- \(\mathrm{Lip@PAC@Cur}\) NMs group at the end of the treatment, which was \(22.5\%\) of that in the PBS group). Compared with the chemotherapeutic drug TMZ, NO- \(\mathrm{Lip@PAC@Cur}\) NMs exhibited favorable biocompatibility. At the end of the treatment the weight of the mice remained basically unchanged, and blood biochemistry and hematology indices were within normal ranges. Additionally, histological analysis using H&E staining revealed no significant damage to major organs. Given that tumor cell mitochondria are crucial for their growth and proliferation, the strategy of specifically targeting mitochondrial mineralization in tumor cells is expected to provide valuable ideas for designing + +<--- Page Split ---> + +therapeutic strategies specifically for GBM. Due to the easy accumulation of NMs in organs such as the liver and kidneys, the injected dose is often limited, which in turn restricts the delivery efficiency of the drug to brain tissue. To overcome this bottleneck, a promising strategy is to use composite targeting systems, such as the combination of molecular recognition targeting and microenvironment recognition targeting, which is expected to direct more drug molecules across the BBB to enter the brain tissue, thereby enhancing drug accumulation concentrations in the brain while reducing systemic exposure and limiting potential liver and kidney toxicity. + +## Methods: + +17. Replace rpm values with corresponding rcf (g equivalent) values or provide the centrifuge rotor dimension. + +Answer: Many thanks to you for your valuable comments. + +We have made corresponding revisions to the experimental section of the revised manuscript, highlighting the revised sections in yellow background. + +18. Precise the number of mice used per experimental conditions and different tests. + +Answer: Many thanks to you for your valuable comments. + +We have added the number of repeated experiments and the number of mice used in animal experiments to the revised manuscript. The revised sections are highlighted in yellow. Modifications have been made to the figure captions in Fig. 3- 7, and the supporting information in Supplementary Fig. 53, 54, 71 and 72, etc. + +## Supplementary data: + +19. Precise the origin (species) of the blood sample used for erythrocyte morphology and hemolysis rate tests. + +Answer: Many thanks to you for your valuable suggestion. + +The source of blood samples for red blood cell morphology and hemolysis rate tests from C57BL/6 mice have been added to the revised manuscript. + +20. Line 292-293: According to Figure S40, inlets (i) and (iii) should be the buffer I and II (cell lysates), whereas inlet (ii) should be PAC samples. However, the authors wrote: "When inlets (i), (ii) were pumped with bEnd.3 cellular lysates, and inlet (iii) was pumped with Lip@PAC NPs or NO-Lip@PAC NMs, there was no fluid shift (Figure 3h and 3i)". + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding revisions in the manuscript, and the revised sections are as follows. + +When inlets (i), (iii) were pumped with bEnd.3 cellular lysates, and inlet (ii) was pumped with Lip@PAC NPs or NO-Lip@PAC NMs, there was no fluid shift. + +21. Figure S37 g: Provide statistic analysis results. + +Answer: Many thanks to you for your advice. + +<--- Page Split ---> + +We have marked the results of the statistical analysis in the figure, and the revised Supplementary Fig. 38 (original Supplementary Fig. 37) is as follows. + +![PLACEHOLDER_40_0] + + +Supplementary Figure 37. When collagen gel containing \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) of bEnd.3 was filled in the right, the normalized movement trajectories \(\mathrm{(n = 10}\) independent samples) of (a) Lip@PAC and (b) NO- Lip@PAC recorded in the observation area; When collagen gel containing \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) of Gl261 was filled in the right, the normalized movement trajectories of (c) Lip@PAC and (d) NO- Lip@PAC recorded in the observation area; (f) Speed \(\mathrm{(n = 10}\) independent samples) and (g) chemotaxis index \(\mathrm{(n = 10}\) independent samples) in different environments (I: Lip@PAC in bEnd.3cellular lysate, II: NO- Lip@PAC in bEnd.3 cellular lysate, III: Lip@PAC in Gl261 cellular lysate, IV: NO- Lip@PAC in Gl261 cellular lysate). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +22. Figure S38 b: Precise in the figure caption how iNOS levels were measured. Also provide statistic results. + +Answer: Many thanks to you for your valuable comments. + +We used the mouse inducible nitric oxide synthase (iNOS) ELISA research kit (purchased from Jiangsu Enzyme Immunoassay, product number MM- 0454M1), with the following specific steps: + +(1). Collect samples to be tested from different locations in the Y-shaped channel. +(2) Sample addition: Set up blank wells (blank control wells without sample or enzyme-labeled reagents, with all other steps performed identically), standard wells, and sample wells. Add \(50 \mu \mathrm{L}\) standard solution to the enzyme-labeled coated plate wells. In the sample wells, first add \(40 \mu \mathrm{L}\) sample diluent, then add \(10 \mu \mathrm{L}\) the sample (final sample dilution is 5-fold). Add the sample to the bottom of the enzyme-labeled + +<--- Page Split ---> + +plate wells, avoiding contact with the well walls, and gently mix. + +(3) Incubation: Cover the plate with a sealing membrane and incubate at \(37^{\circ}\mathrm{C}\) for 30 min. + +(4) Solution preparation: Dilute the \(30 \times\) concentrated wash solution with distilled water at a \(30 \times\) dilution ratio and set aside. + +(5) Washing: Carefully remove the sealing membrane, discard the liquid, and centrifuge to remove excess liquid. Add washing solution to each well, let stand for 30 seconds, then discard. Repeat this process 5 times, then blot dry. + +(6) Enzyme addition: Add \(50 \mu \mathrm{L}\) of enzyme-labeled reagent to each well, excluding the blank well. + +(7) Incubation: Follow the same procedure as in (3). + +(8) Washing: Follow the same procedure as in (5). + +(9) Color development: Add \(50 \mu \mathrm{L}\) color developer A to each well, followed by \(50 \mu \mathrm{L}\) of color developer B. Gently mix by shaking, then incubate at \(37^{\circ}\mathrm{C}\) in the dark for 10 min. + +(10) Termination: Add \(50 \mu \mathrm{L}\) stop solution to each well to terminate the reaction (the color will immediately change from blue to yellow). + +(11) Measurement: Adjust the blank well to zero, then measure the absorbance (OD value) of each well at a wavelength of \(450 \mathrm{nm}\) . The measurement should be performed within 15 min after adding the stop solution. + +The revised Supplementary Fig. 38 is as follows. + +![PLACEHOLDER_41_0] + + +Supplementary Figure 38. (a) Schematic diagram of iNOS concentrations detection at positions I, I', II, II', III and IV in the Y-shaped channel and (b) iNOS concentrations at different position, where the bEnd.3 or Gl261 cellular lysates at initial density of \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) was mixed with the equal volume of agarose solution in regions (ii) and (iii) to form the network gel. And the values were detected at 15 min after the agarose solidified. \(n = 3\) independent samples. Data were presented as mean \(\pm \mathrm{SD}\) . Significance was calculated via one-way ANOVA. + +23. Figure S40: Precise in the figure caption the composition of buffer I and II for the different experimental conditions tested. + +Answer: Many thanks to you for your valuable comments. + +We have precisely labeled the components of buffers I and II under different experimental conditions in Supplementary Fig. 40. The revised Supplementary Fig. + +<--- Page Split ---> + +40 is as follows. + +![PLACEHOLDER_42_0] + + +Supplementary Figure 40. (a) Schematic diagram of \(\Psi\) - shaped microfluidic channel; experimental schematics for (b) Fig. 3h and (c) Fig. 3j. + +24. Figure S46: Provide statistical analysis results + +Answer: Many thanks to you for your valuable comments. + +We have marked the results of the statistical analysis in the figure, and the revised Supplementary Fig. 47 (original Supplementary Fig. 46) is as follows. + +![PLACEHOLDER_42_1] + + +Supplementary Figure 47. Representative CLSM images corresponding quantitative analysis of red fluorescence intensity in Supplementary Figure 46. \(n = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via two- sample t- test. + +25. Figure S47: Based on the fluorescence intensity in the red channel for the Lip@PAC condition, we would expect to see more "yellow" in the merge composite images when zones in green and red fluorescence overlap. + +Answer: Many thanks to you for your valuable comments. + +As the reviewer pointed out, when red and green overlap significantly and have comparable intensities, yellow may appear, as observed in the PAC group and NO- Lip@PAC- treated cells. For Lip@PAC, the yellow color in the fluorescence overlay images is not prominent. This may be due to the weaker red fluorescence and lower colocalization with green mitochondria, resulting in the "yellow" appearing less distinct when red and green fluorescence regions overlap. + +<--- Page Split ---> +![PLACEHOLDER_43_0] + +
Supplementary Figure 48. Representative CLSM images of different samples co-incubated with Gl261 cells for \(2\mathrm{h}\) (blue: Hoechst 33342 labeled nucleus, green: MiTo-Tracker labeled mitochondria; red: Cy5-labeled different samples; Scale bar: \(50\mu \mathrm{m}\) ).
+ +26. Figure S49: The zeta potential value obtained for NO-Lip@PAC@Cur is quite low, which can result in poorly stable particles with a higher tendency to form aggregates. The authors are encouraged to discuss those data as they agree with the formation of large aggregates for higher drug/lipid ratio (see corresponding comment in the "results section" above. + +Answer: Many thanks to you for your valuable comments. + +We have addressed the meaning of zeta potential and the stability of the liposomes constructed in this paper in Question 10. The main conclusion is that the zeta potential of the liposomes constructed in this work is similar to that of similar liposomes reported in many other works. And we have also measured their stability, they all exhibit good dispersibility and stability when incubated in PBS for 7 days. + +The reviewer's insightful comment has also drawn our attention back to this issue. As the reviewer speculated, the gradual aggregation observed with increasing drug/lipid ratio may indicate particle instability. However, at the drug/lipid ratio we selected (1:10), NO- Lip@PAC@Cur NMs exhibited acceptable stability. We once again thank the reviewer for the kind reminder. We have added this discussion to the revised manuscript, which also provides valuable insights for our future material design. + +27. Figure S52, S53, S63, S68 and S69: provide statistic analysis results. + +<--- Page Split ---> + +**Answer:** Many thanks to you for your valuable comments. + +We have marked the results of the statistical analysis in the figure. The modified Supplementary Fig. 54, 55, 66, 71 and 72 (original S52, S53, S63, S68, and S69, respectively) are as follows. + +![PLACEHOLDER_44_0] + + +Supplementary Figure 54. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with NO- Lip@PAC@Cur for different time in Gl261 cells. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +![PLACEHOLDER_44_1] + + +Supplementary Figure 55. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with different samples in Gl261 cells (I: Control, II: A23187, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +![PLACEHOLDER_44_2] + + +<--- Page Split ---> + +Supplementary Figure 66. Tumor percentage after treatment with different samples (tumor percentage = (tumor area/brain area) \(\times 100\%\) ; I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip@PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +![PLACEHOLDER_45_0] + + +Supplementary Figure 71. Hematological parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV:PAC@Cur, V: Lip- PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<--- Page Split ---> +![PLACEHOLDER_46_0] + + +Supplementary Figure 72. Blood biochemical parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip- PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +## \\*\\*\\* MINOR COMMENTS \\*\\*\\* + +Introduction: + +28. Figure 1a: replace "hydration" by "hydration" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding modifications in Fig. 1a, and the modified Fig. 1 is as follows. + +![PLACEHOLDER_46_1] + + +<--- Page Split ---> + +Fig. 1. Schematic diagram of (a) preparation of NO- Lip@PAC@Cur and its schematic diagram in response to NO degradation and (b) NO- Lip@PAC@Cur selectively inducing mitochondrial mineralization for the treatment of GBM. By Figdraw. + +Results: + +29. Figure 4 caption, lines 249-250: there seems to be repeated legend descriptions: "(I: Lip@PAC, II: NO-Lip@PAC I: Lip@PAC, II: NO-Lip@PAC)" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding revisions in the revised manuscript, and the revised figure captions are as follows. + +Fig. 4. Characterization of the ability of different samples to cross the BBB in vitro and the mitochondrial targeting performance. (a) Schematic diagram of the transwell model; (b) Representative CLSM images of bEnd.3 cells in the upper chamber and GL261 cells in the lower chamber of the transwell system treated with different samples for 6 h (blue: nucleus, red: Cy5-labelled PACs, green: DiL-labelled Lip or NO-Lip; Scale bar: \(50 \mu \mathrm{m}; \mathrm{n} = 3\) independent samples); Quantitative analysis of red and green fluorescence in the (c) upper and (d) lower compartments (I: Control, II: Lip@PAC, III: NO-Lip@PAC; \(\mathrm{n} = 3\) independent samples); (e) BBB transport efficiency of different samples (I: Lip@PAC, II: NO-Lip@PAC; \(\mathrm{n} = 3\) independent samples); (f) Paracellular permeability of FD-4 treated with different samples for 24 h (I: Control, II: Lip@PAC, III: NO-Lip@PAC; \(\mathrm{n} = 3\) independent samples); (g) Representative CLSM images of Gl261 cells treated with different samples for 2 h, 6 h and 12 h (blue: nucleus, green: DiL-labelled Lip or NO-Lip, red: Cy5-labelled PAC; Scale bar: \(50 \mu \mathrm{m}; \mathrm{n} = 3\) independent samples); (h) Representative CLSM images of colocalization of mitochondrial treated with different samples for 2 h and corresponding fluorescence curves (I: PAC, II: PLC, III: Lip@PAC, IV: NO- Lip@PAC; Blue: nucleus, green: mito- tracker-labelled mitochondria, red: Cy5- labelled different samples; Scale bar: \(50 \mu \mathrm{m}; \mathrm{n} = 3\) independent samples); (i) Schematic illustration of using the Y- channel model to assess the chemotaxis of different samples towards mitochondria. By Figdraw; Representative fluorescence images of (j) PLC NPs and (l) PAC NMs at different times in Y- channel regions (ii) and (iii) (Scale bar: \(1000 \mu \mathrm{m}\) ) and fluorescence quantification of (k) PLC and (m) PAC. Data in c, d, e, f, k and m were presented as mean \(\pm\) SD. Significance was calculated via two- sample t- test and one- way ANOVA. + +30. Figure 5c: replace "VI" by "IV" in the x-axis label. + +31. Figure 5 caption (line 368): "(m)" should be "(l)" instead + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding revisions in the revised manuscript. The revised Fig. 5c and caption are as follows. + +<--- Page Split ---> +![PLACEHOLDER_48_0] + +
Fig. 5c. \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for \(24\mathrm{h}\) in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples).
+ +32. Lines 512 and 567: commas with a red font color + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding revisions in the revised manuscript. + +Methods: + +33. Line 647: The authors wrote "high-sucrose Dalberg's modified Eagle's medium (DMEM, containing \(4.5\mathrm{gL^{-1}}\) 648 D-glucose)". Did the authors mean Dubelcco's modified Eagle's medium? + +Answer: Many thanks to you for your valuable comments. + +High-sucrose Dalberg's modified Eagle's medium (DMEM) refers to Dubelcco's modified Eagle's medium. We have made corresponding modifications in the revised manuscript, and the modified sections are shown as follows: "Gl261 and Gl261-Luc cells were cultured in complete culture medium containing \(89\%\) v/v high-sugar Dubelcco's modified Eagle's medium (DMEM with \(4.5\mathrm{gL^{-1}}\) D-glucose, Jiangsu KeyGEN BioTECH Corp., CO., Ltd.)". + +34. Line 752: replace " \(1 \times 10^{5}\) cells mL\(^{-1}\)" by " \(1 \times 10^{5}\) cells mL\(^{-1}\)" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +For Alizarin Red S staining, Gl261 cells (1.0 mL, \(1 \times 10^{5}\) cells mL\(^{- 1}\) ) were inoculated in confocal dishes and incubated overnight. + +35. Line 793: replace "Aliexa" by "Alexa" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<--- Page Split ---> + +The cell membranes of cerebrovascular endothelial cells were labeled with rabbit anti- mouse CD31 antibody and Alexa Fluor 488- coupled goat anti- rabbit IgG, and the nucleus were labeled with DAPI, respectively. + +36. Lines 802-807: consider revising the syntax. + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +To investigate the in vivo delivery efficiency and biodistribution of the nanomotors, \(200.0~\mu \mathrm{L}\) of different samples ( \(2.0\mathrm{mgmL}^{- 1}\) , Lip@PAC or NO- Lip@PAC) was injected intravenously. and \(200.0~\mu \mathrm{L}\) of PBS was injected as control. After \(24\mathrm{h}\) , the mice were euthanized, and the brain tissue and major organs (heart, liver, spleen, lung, and kidney) were collected and weighed. Then \(1.0\mathrm{mL}\) RIPA (Biosharp, BL504A) lysis buffer was added to every \(100.0\mathrm{mg}\) of tissue, and tissue homogenate was prepared using the tissue grinder (frequency: \(70\mathrm{Hz}\) , time: \(8\mathrm{min}\) , run times: 8 times). The homogenate was centrifuge ( \(4^{\circ}\mathrm{C}\) , \(1006\times g\) , \(10\mathrm{min}\) ), and the supernatant was collected. The supernatant was diluted and the fluorescence intensity was measured using a multifunctional enzyme- linked immunosorbent assay reader. The injection dose percentage (% \(\mathrm{ID / g}\) ) of each group of samples was calculated based on the sample concentration fluorescence intensity standard curve and the initial injection dose. + +37. Line 818: replace "performed with H&E" by "stained with H&E" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +Then the tissues were embedded in paraffin, and stained with H&E staining to evaluate the histopathological changes after different treatments. + +38. Line 826: replace "finished" by "performed" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +Differences between the two groups were analyzed by a two- sample t- test. Differences among multiple groups were analyzed using one- way analysis of variance (ANOVA) with two- tailed LSD or Dunnett T3 multiple- comparisons tests. All statistical analyses were performed on Excel v.2019, SPSS v.16.0 and GraphPad Prism v.9.0. + +Supplementary data: + +39. Lines 63-65 & lines 113-116 & lines 166-168: revise the syntax. + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<--- Page Split ---> + +Lines 63- 65: + +After the reaction was completed, the reaction solution was washed repeatedly with saturated \(\mathrm{NaHCO_3}\) solution (about \(500~\mathrm{mL}\) ) and saturated \(\mathrm{NaCl}\) solution (about 500 mL), after which the anhydrous \(\mathrm{MgSO_4}\) was added and the mixture was dried for \(4\mathrm{h}\) . The obtained mixed solution was dried using a vacuum rotary evaporator to obtain the crude product. + +Lines 113- 116: + +The product was resuspended in distilled water (1.0 mL), \(\mathrm{Cy5}\) maleimide (20.0 \(\mu \mathrm{L}\) , 1.0 mg \(\mathrm{mL}^{- 1}\) ) was added, and the reaction was stirred at room temperature under \(\mathrm{N}_2\) protection in the absence of light for \(24\mathrm{h}\) . + +Lines 166- 168: + +Intracellular \(\mathrm{Ca^{2 + }}\) was labeled with Fluo- 4 (S1060, Beyotime Biotechnology) for green fluorescence, mitochondrial \(\mathrm{Ca^{2 + }}\) was labeled with Rhod- 2 (purchased from Shanghai yuanye Bio- Technology Co., Ltd) for red fluorescence. The cells were fixed with \(4\%\) paraformaldehyde. + +40. Line 303: Figure S32 caption is missing the "(e)" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +Supplementary Figure 31. MSD versus time interval \((\Delta t)\) analyzed from tracking trajectories in different environments ( \(\mathrm{n} = 5\) independent samples). (a) Lip NPs in bEnd.3 cellular environment, (b) Lip NPs in Gl261 cellular environment, (c) NO- Lip NMs in bEnd.3 cellular environment and (d) NO- Lip NMs in Gl261 cellular environment; and (e) diffusion coefficient values determined from the slope of the linear fitting curves of average MSD plots ( \(\mathrm{n} = 10\) independent samples) (I: Lip NPs in bEnd.3 cellular environment, II: Lip NPs in Gl261 cellular environment, III: NO- Lip NMs in bEnd.3 cellular environment, IV: NO- Lip NMs in Gl261 cellular environment). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +41. Line 314: Figure S34 caption, replace "(D)" by "(d)" + +42. Line 314: Figure S34 caption is missing the "(e)" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +Supplementary Figure 33. MSD versus time interval \((\Delta t)\) analyzed from tracking trajectories in different environments ( \(\mathrm{n} = 5\) independent samples). (a) Lip@PAC NPs in bEnd.3 cellular environment, (b) Lip@PAC NPs in Gl261 cellular environment, (c) NO- Lip@PAC NMs in bEnd.3 cellular environment and (d) NO- Lip@PAC NMs in Gl261 cellular environment; and (e) diffusion coefficient values determined from the slope of the linear fitting curves of average MSD plots ( \(\mathrm{n} = 10\) ) (I: Lip@PAC NPs in + +<--- Page Split ---> + +bEnd.3 cellular environment, II: Lip@PAC NPs in Gl261 cellular environment, III: NO- Lip@PAC NMs in bEnd.3 cellular environment, IV: NO- Lip@PAC NMs in Gl261 cellular environment). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +43. Figure S35b: replace "Posioton" in the x-axis label with "Position" + +Answer: Many thanks to you for your kind reminding. + +We have made the corresponding changes in the revised manuscript, and the revised Supplementary Figure 35b (original Supplementary Fig. 35) is as follows. + +![PLACEHOLDER_51_0] + + +Supplementary Figure 35. (a) Schematic diagram of iNOS concentrations detection at positions I, II, and III in the straight channel and (b) iNOS concentrations at different position, where the Gl261 cellular lysates at initial density of \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) was mixed with the equal volume of agarose solution in regions (ii) to form the network gels. And the values were detected at \(15 \mathrm{min}\) after the agarose solidified. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +We sincerely thank the reviewer for their careful review and valuable constructive comments. We appreciate the time and effort you have devoted to the extremely thorough and meticulous review of our work. We are honored to have received your professional guidance, which has greatly improved the overall quality of our manuscript. This has been an invaluable learning and growth opportunity for us. + +<--- Page Split ---> + +This work presents a novel size- variable self- feedback nanomotor system (NO- Lip@PAC@Cur NMs) for the treatment of glioblastoma (GBM). The system is composed of a self- feedback degradable lipid shell, a nanomotor core with motion ability, and the drug curcumin (Cur) that inhibits calcium ion efflux, which can induce the mitochondrial mineralization. Overall, the design concept of this work is highly innovative. There have been no related studies on treating GBM through mitochondrial mineralization to date. The writing is relatively smooth, the data volume is substantial, and the manuscript is well organized. It is recommended that the work be accepted for publication after minor revisions. The detailed suggestions were listed as follows. + +Answer: We appreciate the reviewer's encouraging comments and admire the professionalism of the reviewer during the review process of the manuscript. These suggestions are very important for us to improve the quality of the manuscript. The issues raised by the reviewer were taken seriously and point- to- point revisions were made. + +1. Introduction Section: It is suggested to more thoroughly analyze the limitations of current GBM treatment strategies, such as surgery, radiotherapy, chemotherapy, and immunotherapy. These limitations include drug resistance and the immunosuppressive microenvironment, which can better highlight the necessity and innovativeness of this study. + +Answer: Many thanks to you for your valuable comments. + +We have described the limitations of GBM treatment strategies in detail in Introduction. The revised Introduction is as follows: + +Glioblastoma (GBM) is one of the most aggressive and deadly brain tumors, classified by the World Health Organization as the most malignant glioma (Grade IV). The standard treatment for GBM typically involves a combination of surgical resection followed by radiotherapy and/or chemotherapy. However, the characteristic infiltrative growth of GBM makes it difficult to eradicate surgically and may damage critical brain functional areas. The efficacy of first- line chemotherapeutic agents such as temozolomide (TMZ) is often limited by the inherent resistance of tumor cells and severe systemic toxicity (including hematologic toxicity and thrombocytopenia associated with long- term and high- dose administration). The presence of the blood- brain barrier (BBB) also prevents most drugs to enter the tumor cells. Although radiotherapy has shown good cytotoxic effects, its low selectivity and specificity can also cause irreversible damage to normal tissues. Consequently, the median survival for GBM patients remains low at 14.6- 20.5 months, with a 5- year survival rate of less than \(10\%\) . Emerging modalities such as electro- fields therapy, and focused ultrasound therapy have also shown promising advancements in solid tumor therapy in clinic or pre- clinical settings. In situ drug delivery strategies for GBM (convection- enhanced delivery (CED), implantation of slow- release devices) circumvent the BBB by delivering the drug directly to the tumor or postoperative residual cavity, achieving + +<--- Page Split ---> + +high local drug exposure and reducing systemic toxicity. However, higher operational requirements, the need for more complex equipment, unpredictable and heterogeneous drug distribution, and susceptibility to localized brain tissue injury, edema, or inflammation may limit their application6. Therefore, developing targeted therapeutic strategies specifically for GBM has emerged as a critical area of research. + +The unique microenvironment of GBM provides valuable insights for the design of targeted therapeutic strategies (Supplementary Table 1). GBM is characterized by an immunosuppressive tumor microenvironment, often referred to as a "cold" tumor, which has spurred researchers to actively explore novel immunotherapeutic approaches for GBM. These include tumor vaccines1,7,8, immune checkpoint inhibitors (ICIs)9, and chimeric antigen receptor T- cell (CAR- T) therapies10, etc. However, the efficacy of immunotherapy is affected by the individual patient variability, leading to insufficient or excessive immune responses that limit its broad application11. In addition to immunotherapy, molecular targeted therapies have been developed to target cellular molecules that promote the proliferation and differentiation of GBM, such as anti- angiogenic therapy12,13 and tyrosine kinase inhibitors14,15. However, their effectiveness is often limited by factors such as drug resistance in tumor cells and high recurrence rates following treatment16. Gene therapy represents another promising approach, targeting specific genes involved in the proliferation, migration, invasion, apoptosis, and angiogenesis of malignant glioma cells including gene editing corrections using CRISPR- Cas9, or suppressing immune- suppressive genes expressed in brain tumors to reprogram the tumor immune microenvironment3. However, challenges such as the poor stability of nucleic acids in vivo, variable transfection efficiency, and high treatment costs have restricted its widespread application3. Therefore, there is a pressing need to find new therapeutic strategies specifically for GBM. + +2. Nanomotor Fabrication and Characterization: The description of some steps in the preparation and characterization of the nanomotors is relatively brief. For example, when synthesizing NOR and NOD, only the raw materials used and the reaction conditions are mentioned, without detailed synthesis steps and purification methods. It is recommended to supplement more detailed experimental steps and operational details to facilitate better reproducibility by other researchers. + +Answer: Many thanks to you for your valuable comments. + +We have further improved the synthesis steps and purification methods of NOR and NOD in the supporting information. The revised parts are highlighted in yellow and the revised experimental steps are as follows. + +## Preparation of NO-responsive degradable lipid (NOD) + +NOD was prepared according to previous literature. Myristic acid (228.0 mg, 1.0 mmol) and HCTU (496.0 mg, 1.2 mmol) were dispersed in tetrahydrofuran (THF, 15.0 mL) and stirred for 10 min until dissolved at \(0^{\circ}\mathrm{C}\) in the \(\mathrm{N}_2\) environment. Next, OPD (216.0 mg, 2 mmol) was dissolved in acetonitrile (20.0 mL) and added it to the above system, continue stirring for 10 min. Finally, triisopropanolamine (574.0 mg, + +<--- Page Split ---> + +3.0 mmol) was added to the above mixed system and stirred at room temperature for \(24\mathrm{h}\) . The obtained mixed solution was dried using vacuum rotary evaporator to obtain the crude product. Finally, using petroleum ether/ethyl acetate (v:v, 1:1) as the eluent, the crude product was purified by column chromatography to obtain the final product NOD. + +## Preparation of NO-releasing lipid (NOR) + +NOR was prepared according to previous literature. Boc- arg(Pbf)- OH (105.3 mg, 0.2 mmol), HOBT (40.5 mg, 0.3 mmol), and HBTU (113.8 mg, 0.3 mmol) were dispersed in anhydrous DMF (2.0 mL) and stirred for \(10\mathrm{min}\) to dissolve at \(0^{\circ}\mathrm{C}\) in the \(\mathrm{N}_2\) environment. Then DSPE (104.8 mg, 0.1 mmol) was dissolved in anhydrous trichloromethane (15.0 mL) and added to the above system, continue stirring for \(10\mathrm{min}\) . Finally, DIPEA (200.0 μL, 1.2 mmol) was added to the above mixed solution, and the reaction was stirred at room temperature for \(24\mathrm{h}\) . After the reaction was completed, washed the reaction solution repeatedly with saturated \(\mathrm{NaHCO_3}\) solution (about \(500\mathrm{mL}\) ) and saturated \(\mathrm{NaCl}\) solution (about \(500\mathrm{mL}\) ), then added anhydrous \(\mathrm{MgSO_4}\) and dried for \(4\mathrm{h}\) . The obtained mixed solution was dried using a vacuum rotary evaporator to obtain the crude product. Using dichloromethane (DCM)/methanol (MeOH) (v:v, 12:1) as the eluent, the crude product was purified by column chromatography. The solution was neutralized to neutral with saturated \(\mathrm{NaHCO_3}\) solution. Collected the organic phase and precipitated with anhydrous ether at \(4^{\circ}\mathrm{C}\) to obtain the pure product NOR. + +3. The data labeling and legend descriptions in some figures (such as Figures 2 and 3) are not clear enough. For example, in Figure 2, the markings for different samples (such as I: PAC, II: NO-Lip, III: NO-Lip@PAC) are not conspicuous enough and can be easily confused. It is suggested to optimize the design of the figures to make the data and information more intuitive and understandable, while ensuring that the labels and legends in the figures are clear and accurate. + +Answer: Many thanks to you for your valuable comments. + +We have rearranged the figures in Fig. 2 and optimized the legend descriptions of Fig. 2 and 3 in the revised manuscript, and the revised Fig. 2 and 3 are as follows. + +<--- Page Split ---> +![PLACEHOLDER_55_0] + +
Fig. 2. Preparation of NO-Lip@PAC NMs and characterization of their degradation behavior in response to NO. (a) TEM images (Scale bar: 500 nm), (b) DLS and (c) Zeta potential of different samples (n = 3 independent samples); (d) Representative confocal laser scanning microscope (CLSM) images of NO-Lip@PAC (Scale bar: 50 μm, green: DiO labeled NO-Lip, red: Cy5 labeled PAC; n = 3 independent samples); Representative DLS changes of NO-Lip@PAC NMs incubated with (e) PBS and (f) 100 μM H2O2 for different times (n = 3 independent samples); (g) Representative TEM images of NO-Lip@PAC NMs incubated with PBS and 100 μM H2O2 for different times (Scale bar 500 nm; red arrows indicate PAC released by lipid degradation; n = 3 independent samples); (h) Representative CLSM images of NO-Lip@PAC incubated with HUVECs and G1261 cellular lysates incubated for different times (Scale bar: 10 μm; green: DiO labeled Lip or NO-Lip, red: Cy5 labeled PAC;
+ +<--- Page Split ---> + +Purple arrows indicate PAC released by lipid degradation; \(\mathrm{n} = 3\) independent samples). Data in b and c were presented as mean \(\pm \mathrm{SD}\) . + +![PLACEHOLDER_56_0] + +
Fig. 3. Movement behavior of different samples and characterization of their chemotaxis in static and dynamic environments. Normalized motion trajectories (n = 20 independent samples) and motion speed distribution plots (n = 50 independent samples) of Lip@PAC NPs in (a) bEnd.3 and (b) Gl261 cellular environment (Supplementary Movie 9-10); Normalized motion trajectories (n = 20 independent samples) and motion speed distribution plots (n = 50 independent samples) of NO-Lip@PAC NMs in (c) bEnd.3 and (d) Gl261 cellular environment (Supplementary Movie 11-12); (e) Schematic of the Y-channel model; (f) Representative fluorescence images (Scale bar: \(1000\mu \mathrm{m}\) ) and (g) fluorescence quantification of NO-Lip@PAC NMs in Y-channel regions (ii) and (iii) at different times (n =3 independent samples); (h) Representative fluorescence images of different samples at the exit of the \(\Psi\) -shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (i) the corresponding
+ +<--- Page Split ---> + +fluorescence quantification in the presence of bEnd.3 cellular lysates (n = 3 independent samples); (j) Representative fluorescence images of different samples at the exit of the \(\Psi\) - shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (k) the corresponding fluorescence quantification in the presence of bEnd.3 and Gl261 cellular lysates (n = 3 independent samples). Data in g were presented as mean \(\pm \mathrm{SD}\) . Significance was calculated via two- sample t- test. + +4. Some sentences in the text contain grammatical errors or are not expressed accurately. For example, in the sentence "However, the infiltrative growth pattern and inherent heterogeneity of GBM, coupled with the side effects of TMZ treatment (including hematologic toxicity and thrombocytopenia associated with long-term and high-dose administration), have significantly limited the efficacy of this therapeutic strategy," the use of "coupled with" is somewhat awkward. It is suggested to change it to "combined with" to make the sentence smoother. + +Answer: Many thanks to you for your valuable comments. + +We have revised the reworded sentences according to the reviewer's suggestions, while we have checked and corrected spelling and grammatical errors in the manuscript and supporting information one by one, and we have touched up the text to enhance the language. The revised sections are highlighted in yellow. + +5. In several experiments (such as cell viability tests and animal experiments), the text only mentions the sample size of some experiments (such as "n = 3" or "n = 8"), but does not specify the repetition times and sample sizes of all experiments. For example, in the experiment detecting the effects of different samples on cell viability, only "n = 3" is mentioned, without indicating whether it is an independent repeated experiment. It is recommended to clearly label the repetition times (such as the number of independent repeated experiments) and sample sizes in all experimental sections to enhance the reliability and reproducibility of the experimental results. + +Answer: Many thanks to you for your valuable comments. + +We have added the number of repeated experiments and the number of mice used in animal experiments to the revised manuscript. The revised sections are highlighted in yellow. Modifications have been made to the figure captions in Fig. 3- 7, and the supporting information in Supplementary Fig. 53, 54, 71 and 72, etc. + +6. In the study, the reason for selecting the specific ratio was not detailed, nor was the impact of other ratios on the experimental results assessed. It is suggested to supplement experimental data comparisons of different drug-lipid ratios to demonstrate the rationality of the selected ratio and explore whether there is a more optimal ratio. + +Answer: Many thanks to you for your valuable comments. + +We prepared NO- Lip@PAC@Cur NMs with different drug- lipid ratios and tested their encapsulation rate and drug loading to determine the optimal loading ratio of Cur. As shown in Supplementary Fig. 49, the encapsulation rate of Cur gradually decreased and the drug loading amount gradually increased with the increase of the + +<--- Page Split ---> + +drug- lipid ratio. However, Cur is a hydrophobic drug, excessive Cur insertion into the phospholipid bilayer will disrupt the original tight arrangement of phospholipid molecules, resulting in changes in the fluidity and permeability of the membrane. This disturbance ultimately reduces liposome stability, which is manifested by an increase in the average particle size of DLS, a wider distribution, and liposome clustering (Carbohyd. Polym. 2017, 156, 322- 332). This is further confirmed by the DLS results in Supplementary Fig. 50, with the increase of drug- to- lipid ratio, the average DLS of NO- Lip@PAC@Cur NMs gradually increased. While the drug- lipid ratio was greater than 1/10, the DLS showed a double peak, indicating that the DLS distribution was not homogeneous and agglomeration occurred. Based on these observations, we finally chose the drug- lipid ratio of 1/10 for the study of subsequent experiments. + +![PLACEHOLDER_58_0] + + +Supplementary Figure 49. Encapsulation rate and loading of Cur with different drug- lipid ratios. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. + +![PLACEHOLDER_58_1] + + +Supplementary Figure 50. DLS of NO- Lip@PAC@Cur synthesized with different drug/lipid ratios. + +7. In some experiments, the control groups are not comprehensive enough. For example, in the study of the effects of nanomotors on intracellular calcium ion levels, + +<--- Page Split ---> + +although a blank control group was set up, a control group with only the drug (such as Cur) without the nanomotor carrier was not included. It is recommended to improve the control group settings to exclude the potential effects of the drug itself on the experimental results. + +Answer: Many thanks to you for your valuable comments. + +In our revised manuscript, we investigated the effect of Cur on cellular \(\mathrm{Ca^{2 + }}\) and mitochondrial \(\mathrm{Ca^{2 + }}\) content. As shown in Fig. 5b, the \(\mathrm{Ca^{2 + }}\) content of Cur- treated Gl261 cells increased to \(0.30\mu \mathrm{mol}\) , which was comparable to the \(\mathrm{Ca^{2 + }}\) content in the NO- Lip@PAC- treated cells (0.27 \(\mu \mathrm{mol}\) ). This increase may be due to Cur or the high concentration of NO causing the endoplasmic reticulum to stress and release more \(\mathrm{Ca^{2 + }}\) into the cytoplasm, and the decrease in endoplasmic reticulum \(\mathrm{Ca^{2 + }}\) leading to \(\mathrm{Ca^{2 + }}\) influx from the extracellular space. The intracellular \(\mathrm{Ca^{2 + }}\) content of cells treated with NO- Lip@PAC@Cur was higher (0.46 \(\mu \mathrm{mol}\) ), 2.7- fold higher than that of the control group, indicating that the inhibition of \(\mathrm{Ca^{2 + }}\) efflux by Cur could further increase the intracellular \(\mathrm{Ca^{2 + }}\) level, confirming that Cur and NO could act synergistically to enhance mineralization. + +The mitochondrial \(\mathrm{Ca^{2 + }}\) content in Cur- treated cells was \(0.18\mu \mathrm{mol}\) , which was comparable to that in the A23187 and NO- Lip@PAC treated- group (0.20 \(\mu \mathrm{mol}\) and \(0.19\mu \mathrm{mol}\) , respectively), but the concentration was much lower than that in the NO- Lip@PAC@Cur group (0.36 \(\mu \mathrm{mol}\) ), suggesting that Cur can cause mitochondrial calcium overload, but cannot induce mitochondrial mineralization. + +![PLACEHOLDER_59_0] + +
Fig. 5b and c. (b) Intracellular \(\mathrm{Ca^{2 + }}\) concentration in bEnd.3 cells and Gl261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples); (c) \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for \(24\mathrm{h}\) in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples).
+ +<--- Page Split ---> diff --git a/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7922b152da12009fdad88bf5bac0efa22db947a6 --- /dev/null +++ b/peer_reviews/32ca75acff7dac8e378d5e299b6a5f0c8484b4559953dfff100e4c0150303856/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1391 @@ +<|ref|>title<|/ref|><|det|>[[72, 50, 296, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 296, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 160, 856, 211]]<|/det|> +# Size-variable self-feedback nanomotors for glioblastoma therapy via mitochondrial mineralization + +<|ref|>text<|/ref|><|det|>[[73, 224, 454, 241]]<|/det|> +Corresponding Author: Professor Chun Mao + +<|ref|>text<|/ref|><|det|>[[70, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 220, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 419]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 419, 914, 496]]<|/det|> +Chen et al. report a novel size- variable self- feedback nanomotor system tailored for GBM treatment, leveraging the unique high- calcium microenvironment of GBM. By designing NO responsive degradable liposomes, the system achieved specific selection of tumor microenvironment, nanoparticle size conversion, and mitochondrial mineralization, ultimately inducing tumor cell death. It sets up a dual strategy for targeting tumor cells, namely chemotaxis and self- feedback effects. This strategy has highly innovation. The results of the in vivo study are satisfactory. If the author can provide responses or modifications to the following questions, then this manuscript can be recommended for publication. + +<|ref|>text<|/ref|><|det|>[[70, 508, 921, 536]]<|/det|> +1. Obviously, the author confused the terms nanomotor and nanorobot, and should identify one of them. I think either one can be used. + +<|ref|>text<|/ref|><|det|>[[70, 536, 905, 563]]<|/det|> +2. In this study, the authors used L-arginine as a raw material, so what about D-arginine? The motion ability of nanomotor constructed by D-arginine can be explored. + +<|ref|>text<|/ref|><|det|>[[70, 562, 911, 588]]<|/det|> +3. In the experiment simulating the tumor microenvironment, \(100\mu \mathrm{M}H_2O_2\) was used. Is it close to the actual level of ROS in the tumor microenvironment? + +<|ref|>text<|/ref|><|det|>[[70, 588, 920, 615]]<|/det|> +4. Does the degradation behavior that occurs in response to NO occur during the penetration of BBB or after penetration? +5. Is the concept of "Size-variable" important? Why does it appear in the title? I suggest changing it to "Trend of inflammation and self-feedback degradation of nanomotors for glioblastoma therapy via 2 mitochondrial mineralization". + +<|ref|>text<|/ref|><|det|>[[70, 615, 875, 642]]<|/det|> +6. Have the authors studied whether there is a difference in the motion life between the shell and the core of this size-variable nanomotor? What factors is this related to? + +<|ref|>text<|/ref|><|det|>[[70, 652, 910, 678]]<|/det|> +7. Does the brain-targeting efficiency have an advantage compared with most of the values in the literature? It is suggested that the author discuss this. + +<|ref|>text<|/ref|><|det|>[[73, 691, 162, 704]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 717, 238, 730]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 730, 200, 742]]<|/det|> +\*\*\* SUMMARY \*\*\* + +<|ref|>text<|/ref|><|det|>[[70, 744, 915, 939]]<|/det|> +The proposed manuscript aims at developing nitric oxide powered nanomotors leveraging the high calcium- microenvironment of glioblastoma (GBM) as a targeted treatment strategy. The nanomotors (NMs) are composed of a degradable lipid shell containing nitric oxide- releasing lipid (NO) and nitric oxide- responsive lipids, a nanomotor core composed of L- arginine derivatives and monomers rich in carboxyl groups (PAC) and the drug curcumin. The authors first characterized the NMs in terms of composition, size, surface charge and ability to degrade in response to hydrogen peroxide. The authors then demonstrated that NMs are predominantly responsive to a GBM cell line lysate (GI261) showing nitric oxide dependent movement as opposed to a blood brain barrier (BBB) cell line (bEnd.3) cellular lysate. They further showed the ability of the NO- NMs to pass through a single layer BBB in vitro model without any apparent disruption with increase cellular uptake and mitochondrial co- localization in GI261 GBM cell line. NO- NMs loaded with PAC could cause mitochondrial mineralization, and ultimately cell death, predominantly in GBM cells with low impact on BBB cells. In vivo testing using a mouse GBM model revealed the accumulation of NO- NMs mostly in the brain tissue, liver and kidneys. The presence of curcumin, even though the NO- lipids showed low encapsulation efficiency, through its action on Ca2+ ions, enhanced the efficiency of the NO- NMs and increased mitochondrial mineralization. Consequently, NO- NMs containing curcumin resulted in a net tumor reduction, a lower impact on animal weight and an increased survival rate as compared to the chemotherapeutic drug temozolomide and controls. Taken together, those results provide valuable ideas for designing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 48, 297, 61]]<|/det|> +future therapeutic targeting GBM. + +<|ref|>sub_title<|/ref|><|det|>[[73, 73, 312, 86]]<|/det|> +## \*\*\* GENERAL APPRECIATION \*\*\* + +<|ref|>text<|/ref|><|det|>[[72, 87, 920, 179]]<|/det|> +The experimental work presented in this study is both thorough and extensive, highlighting commendable efforts by the authors to demonstrate the capabilities of their approach, especially for the in vitro assays. A complete proof of concept is provided, supported by in vitro assays and some preliminary in vivo experiments with a GBM mouse model. The authors corroborate their findings using at least three different approaches, making the results generally convincing and aligned with the scientific literature. The supplementary data are quite extensive cumulating 70 supplementary figures, further supporting the conclusions of the study. The text is well- written, with few syntax and typographical errors. Figures are coherent and clear, and most of the quantitative analyses are supported by robust statistical methods. + +<|ref|>text<|/ref|><|det|>[[72, 190, 911, 281]]<|/det|> +One of the major flaws identified in the study is the small number of mice used per experimental condition, with only three mice per group. This limited sample size, which is a major flaw, may affect the reliability and generalizability of the findings event if the data shown are generally convincing. In addition, GBM is clinically observed more frequently in biological men, suggesting a sex- specificity in its occurrence. Despite this, it is crucial for researchers to use both male and female mice in their studies to ensure that their findings are robust and applicable across sexes. This approach would provide a more comprehensive understanding of the disease and its potential treatments. In this study, the authors only used female mice. This is a major limitation of the study that should be discussed. + +<|ref|>text<|/ref|><|det|>[[73, 294, 900, 346]]<|/det|> +Another important concern is the fact the research team has previously published a highly similar article in 2023 (DOI: 10.1038/s41467- 022- 35709- 0), utilizing the same general methodology and a similar experimental approach. In this new work, the authors are encouraged to highlight the novelty of their findings, emphasizing advancements and unique contributions that distinguish it from their earlier research work. + +<|ref|>sub_title<|/ref|><|det|>[[73, 358, 285, 372]]<|/det|> +## \*\*\* SPECIFIC COMMENTS \*\*\* + +<|ref|>text<|/ref|><|det|>[[73, 385, 904, 399]]<|/det|> +The following specific comments should be considered by the authors to provide more clarity and improve the manuscript: + +<|ref|>sub_title<|/ref|><|det|>[[72, 412, 159, 424]]<|/det|> +## Introduction: + +<|ref|>text<|/ref|><|det|>[[72, 425, 880, 464]]<|/det|> +- The current therapeutic approaches to treat GBM are wider than what is being listed in the introduction section, which mostly focus on immunotherapeutic strategies and gene therapies, especially for drug delivery (local and systemic) approach currently being studied in the field. + +<|ref|>sub_title<|/ref|><|det|>[[72, 477, 132, 489]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[70, 489, 920, 525]]<|/det|> +- Figure 2 and Figure S18: Please clarify the rationale for using HUVEC cells in part of the study and the bEnd.3 cell line for the remainder. + +<|ref|>text<|/ref|><|det|>[[72, 515, 905, 666]]<|/det|> +- Line 195: precise the technic used to determine the iNOS in bEnd.3 and Gl261 cells. +- Figure 3 h-k: The fluorescence maker diffusing toward Gl261 cell lysate with the NO-Lip@PAC condition is only slightly higher compared to bEnd.3 cell lysate. Quantitative fluorescence distribution data should be supported with statistical analysis to ensure accuracy and validity of the conclusion. +- Lines 318-321: precise the p Values for the fold increased in fluorescence and transport rate values provide. +- Figure 5g: Co-localization analysis typically presents red and green fluorescence data without accounting for the relative fluorescence intensity of each sample. For example, green fluorescence, which represents cytoplasmic Ca2+ levels fluctuate significantly between experimental conditions. The overlapping between the red and green channel is also high for condition II but is not discussed at all. Therefore, it is also essential to consider relative ratios to accurately interpret the results. + +<|ref|>text<|/ref|><|det|>[[72, 648, 916, 700]]<|/det|> +- Lines 397-398: the Zeta potential value for NO-Lip@PAC@Cur NMs is quite low (> -20 to -30 mV or < 20 to 30 mV) and could result in poorly stable colloidal solution with the tendency to form aggregates. The authors are encouraged to discuss the stability of their system as this statement is supported with the DLS data obtained for different Lip/Cur drug ratios tested (results in Supp file) where aggregates are easily formed. + +<|ref|>text<|/ref|><|det|>[[72, 699, 888, 725]]<|/det|> +- Lines 407-414 and lines 426-428: precise the p Values for the fold increased in fluorescence and transport rate values provide. + +<|ref|>text<|/ref|><|det|>[[72, 725, 910, 750]]<|/det|> +- Lines 432-433: To complete the demonstration, the author should also provide data for NO-Lip@PAC-treated Gl261. Why only use the control and NO-Lip@PAC@Cur to assess the presence of mitochondrial calcification? + +<|ref|>text<|/ref|><|det|>[[72, 750, 440, 763]]<|/det|> +- Lines 476-478: precise the NMs concentration used. + +<|ref|>text<|/ref|><|det|>[[72, 763, 914, 790]]<|/det|> +- Figure 7a: the schematic showing the steps and timeline to create the GBM mouse model should be introduced in Figure 6 instead, or at least, the text should refer to it as the steps to create the GBM tumour mouse model. + +<|ref|>text<|/ref|><|det|>[[72, 790, 852, 816]]<|/det|> +- The authors should emphasize the limitations of their proposed delivery system and the overall study, particularly highlighting the low number of mice per experimental condition. + +<|ref|>sub_title<|/ref|><|det|>[[72, 828, 157, 841]]<|/det|> +## Conclusion: + +<|ref|>text<|/ref|><|det|>[[72, 841, 920, 894]]<|/det|> +- Since NO-NMs tend to accumulate in various organs such as the liver and kidneys, one potential improvement to limit drug usage, increase accumulation toward the brain tissue could be the addition of brain BBB shuttle peptides and limit potential adversarial impacts. This would maximize brain tissue accumulation, like current practices with many brain-targeted delivery vehicles. The authors are encouraged to provide future improvements for their system. + +<|ref|>sub_title<|/ref|><|det|>[[72, 907, 137, 919]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[72, 920, 800, 946]]<|/det|> +- Replace rpm values with corresponding rcf (g equivalent) values or provide the centrifuge rotor dimension- Precise the number of mice used per experimental conditions and different tests. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 60, 218, 73]]<|/det|> +Supplementary data: + +<|ref|>text<|/ref|><|det|>[[72, 73, 914, 255]]<|/det|> +Supplementary data:- Precise the origin (species) of the blood sample used for erythrocyte morphology and hemolysis rate tests- Line 292- 293: According to Figure S40, inlets (i) and (iii) should be the buffer I and II (cell lysates), whereas inlet (ii) should be PAC samples. However, the authors wrote: "When inlets (i), (ii) were pumped with bEnd.3 cellular lysates, and inlet (iii) was pumped with Lip@PAC NPs or NO- Lip@PAC NMs, there was no fluid shift (Figure 3h and 3i)"- Figure S37 g: Provide statistic analysis results- Figure S38 b: Precise in the figure caption how iNOS levels were measured. Also provide statistic results- Figure S40: Precise in the figure caption the composition of buffer I and II for the different experimental conditions tested- Figure S46: Provide statistic analysis results- Figure S47: Based on the fluorescence intensity in the red channel for the Lip@PAC condition, we would expect to see more "yellow" in the merge composite images when zones in green and red fluorescence overlap.- Figure S49: The zeta potential value obtained for NO- Lip@PAC@Cur is quite low, which can result in poorly stable particles with a higher tendency to form aggregates. The authors are encouraged to discuss those data as they agree with the formation of large aggregates for higher drug/lipid ratio (see corresponding comment in the "results section" above.- Figure S52, S53, S63, S68 and S69: provide statistic analysis results + +<|ref|>text<|/ref|><|det|>[[73, 268, 262, 281]]<|/det|> +\\*\\*\\* MINOR COMMENTS \\*\\*\\* + +<|ref|>text<|/ref|><|det|>[[73, 295, 380, 321]]<|/det|> +Introduction: - Figure 1a: replace "hydration" by "hydration" + +<|ref|>text<|/ref|><|det|>[[73, 334, 131, 346]]<|/det|> +Results: + +<|ref|>text<|/ref|><|det|>[[72, 346, 860, 412]]<|/det|> +Results:- Figure 4 caption, lines 249- 250: there seems to be repeated legend descriptions: "(l: Lip@PAC, II: NO- Lip@PAC I: Lip@PAC, II: NO- Lip@PAC)"- Figure 5c: replace "VI" by "IV" in the x- axis label.- Figure 5 caption (line 368): "(m)" should be "(l)" instead- Lines 512 and 567: commas with a red font color + +<|ref|>text<|/ref|><|det|>[[72, 425, 135, 437]]<|/det|> +Methods: + +<|ref|>text<|/ref|><|det|>[[72, 437, 866, 528]]<|/det|> +Methods:- Line 647: The authors wrote "high- sucrose Dalberg's modified Eagle's medium (DMEM, containing 4.5 g L- 1 648 D- glucose)". Did the authors mean Dubelcco's modified Eagle's medium?- Line 752: replace "1 x 105 cells mL- 1" by "1 x 105 cells mL- 1"- Line 793: replace "Aliexa" by "Alexa"- Lines 802- 807: consider revising the syntax.- Line 818: replace "performed with H&E" by "stained with H&E"- Line 826: replace "finished" by "performed" + +<|ref|>text<|/ref|><|det|>[[72, 541, 199, 553]]<|/det|> +Supplementary data: + +<|ref|>text<|/ref|><|det|>[[72, 553, 525, 618]]<|/det|> +Supplementary data:- Lines 63- 65 & lines 113- 116 & lines 166- 168: revise the syntax.- Line 303: Figure S32 caption is missing the "(e)"- Line 314: Figure S34 caption, replace "(D)" by "(d)"- Line 314: Figure S34 caption is missing the "(e)"- Figure S35b: replace "Posioton" in the x- axis label with "Position" + +<|ref|>text<|/ref|><|det|>[[72, 630, 163, 643]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 658, 238, 671]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 671, 914, 763]]<|/det|> +This work presents a novel size- variable self- feedback nanomotor system (NO- Lip@PAC@Cur NMs) for the treatment of glioblastoma (GBM). The system is composed of a self- feedback degradable lipid shell, a nanomotor core with motion ability, and the drug curcumin (Cur) that inhibits calcium ion efflux, which can induce the mitochondrial mineralization. Overall, the design concept of this work is highly innovative. There have been no related studies on treating GBM through mitochondrial mineralization to date. The writing is relatively smooth, the data volume is substantial, and the manuscript is well organized. It is recommended that the work be accepted for publication after minor revisions. The detailed suggestions were listed as follows. + +<|ref|>text<|/ref|><|det|>[[70, 775, 920, 944]]<|/det|> +1. Introduction Section: It is suggested to more thoroughly analyze the limitations of current GBM treatment strategies, such as surgery, radiotherapy, chemotherapy, and immunotherapy. These limitations include drug resistance and the immunosuppressive microenvironment, which can better highlight the necessity and innovativeness of this study. +2. Nanomotor Fabrication and Characterization: The description of some steps in the preparation and characterization of the nanomotors is relatively brief. For example, when synthesizing NOR and NOD, only the raw materials used and the reaction conditions are mentioned, without detailed synthesis steps and purification methods. It is recommended to supplement more detailed experimental steps and operational details to facilitate better reproducibility by other researchers. +3. The data labeling and legend descriptions in some figures (such as Figures 2 and 3) are not clear enough. For example, in Figure 2, the markings for different samples (such as I: PAC, II: NO-Lip, III: NO-Lip@PAC) are not conspicuous enough and can be easily confused. It is suggested to optimize the design of the figures to make the data and information more intuitive and understandable, while ensuring that the labels and legends in the figures are clear and accurate. +4. Some sentences in the text contain grammatical errors or are not expressed accurately. For example, in the sentence "However, the infiltrative growth pattern and inherent heterogeneity of GBM, coupled with the side effects of TMZ treatment + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 918, 85]]<|/det|> +(including hematologic toxicity and thrombocytopenia associated with long- term and high- dose administration), have significantly limited the efficacy of this therapeutic strategy," the use of "coupled with" is somewhat awkward. It is suggested to change it to "combined with" to make the sentence smoother. + +<|ref|>text<|/ref|><|det|>[[72, 85, 918, 166]]<|/det|> +5. In several experiments (such as cell viability tests and animal experiments), the text only mentions the sample size of some experiments (such as \("n = 3"\) or \("n = 8"\) ), but does not specify the repetition times and sample sizes of all experiments. For example, in the experiment detecting the effects of different samples on cell viability, only \("n = 3"\) is mentioned, without indicating whether it is an independent repeated experiment. It is recommended to clearly label the repetition times (such as the number of independent repeated experiments) and sample sizes in all experimental sections to enhance the reliability and reproducibility of the experimental results. + +<|ref|>text<|/ref|><|det|>[[72, 166, 918, 204]]<|/det|> +6. In the study, the reason for selecting the specific ratio was not detailed, nor was the impact of other ratios on the experimental results assessed. It is suggested to supplement experimental data comparisons of different drug-lipid ratios to demonstrate the rationality of the selected ratio and explore whether there is a more optimal ratio. + +<|ref|>text<|/ref|><|det|>[[72, 204, 918, 255]]<|/det|> +7. In some experiments, the control groups are not comprehensive enough. For example, in the study of the effects of nanomotors on intracellular calcium ion levels, although a blank control group was set up, a control group with only the drug (such as Cur) without the nanomotor carrier was not included. It is recommended to improve the control group settings to exclude the potential effects of the drug itself on the experimental results. + +<|ref|>text<|/ref|><|det|>[[72, 268, 144, 281]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 295, 218, 308]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 321, 161, 334]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 347, 816, 375]]<|/det|> +(Remarks to the Author) All the concerns are addressed during the revision and now the manuscript can be accepted without change. + +<|ref|>text<|/ref|><|det|>[[72, 386, 161, 399]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 412, 238, 425]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 426, 925, 464]]<|/det|> +I confirm that all major and minor comments provided during the review process have been thoroughly addressed and/or discussed. I am confident that the manuscript now meets the necessary standards and is suitable for publication in its current form. + +<|ref|>text<|/ref|><|det|>[[72, 476, 161, 489]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 503, 238, 515]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 516, 839, 530]]<|/det|> +The authors have properly addressed all my concerns, I would like to recommend the acceptance for publication + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 910, 120]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 86, 460, 101]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 104, 850, 268]]<|/det|> +Chen et al. report a novel size- variable self- feedback nanomotor system tailored for GBM treatment, leveraging the unique high- calcium microenvironment of GBM. By designing NO responsive degradable liposomes, the system achieved specific selection of tumor microenvironment, nanoparticle size conversion, and mitochondrial mineralization, ultimately inducing tumor cell death. It sets up a dual strategy for targeting tumor cells, namely chemotaxis and self- feedback effects. This strategy has highly innovation. The results of the in vivo study are satisfactory. If the author can provide responses or modifications to the following questions, then this manuscript can be recommended for publication. + +<|ref|>text<|/ref|><|det|>[[149, 271, 850, 343]]<|/det|> +Answer: Many thanks to you for the recognition and valuable suggestions on this manuscript. These suggestions are very important for us to improve the quality of the manuscript. The issues raised by the reviewer were taken seriously and point- to- point revisions were made. + +<|ref|>text<|/ref|><|det|>[[149, 363, 850, 398]]<|/det|> +1. Obviously, the author confused the terms nanomotor and nanorobot, and should identify one of them. I think either one can be used. + +<|ref|>text<|/ref|><|det|>[[149, 400, 624, 417]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 419, 850, 491]]<|/det|> +Regarding the terminology used for nanorobots and nanomotors, we understand your concern for consistency in terminology. In our work, we have used both "nanorobots" and "nanomotors", but they refer to the same system in our work. This diversity in terminology is primarily due to the following reasons. + +<|ref|>text<|/ref|><|det|>[[148, 493, 850, 657]]<|/det|> +(1) Nanomotors: Refers to nanoscale devices that can convert chemical energy, light energy, or magnetic energy into mechanical movement, with a core function focused on achieving autonomous movement capability (Chem. Soc. Rev. 2022, 51, 10083-10119). This term is typically used to describe nanosystems with autonomous movement capabilities, emphasizing their ability to respond to external stimuli (such as iNOS concentration gradients) and generate directional movement. In our work, the targeting ability of NO-Lip@PAC@Cur NMs was able to actively generate motion in response to iNOS concentration gradients, so we used the term "nanomotor" to describe its motility. + +<|ref|>text<|/ref|><|det|>[[148, 660, 850, 824]]<|/det|> +(2) Nanorobots: Refers to intelligent nanofabricated systems with multiple functions. Apart from mobility, they typically integrate sensing, navigation, targeting, and task execution modules (such as drug release). They can respond to environmental signals to perform complex operations (Adv. Mater. 2022, 34, 2201051). This term is used more broadly to describe nanostructures with diverse functionalities, including not only mobility but also recognition, regulation, and therapeutic capabilities. In our work, PAC NMs not only moves, but also integrates the ability to target mitochondria and recruit \(\mathrm{Ca^{2 + }}\) . Therefore, this is why we use the term "nanorobot" in our manuscript to describe its overall function. + +<|ref|>text<|/ref|><|det|>[[149, 826, 857, 880]]<|/det|> +To ensure consistency and clarity of terminology, we will use the term "nanomotors" uniformly in the revised manuscript to describe our system, in order to maintain consistency with our previously published articles. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 848, 120]]<|/det|> +2. In this study, the authors used L-arginine as a raw material, so what about D-arginine? The motion ability of nanomotor constructed by D-arginine can be explored. + +<|ref|>text<|/ref|><|det|>[[148, 123, 625, 139]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 141, 850, 288]]<|/det|> +The main reason we chose L- arginine (L- Arg) is that it can be catalyzed by inducible nitric oxide synthase (iNOS), which is highly expressed in tumor tissues specifically, and undergoes a chemotactic effect on the iNOS concentration gradient through enzyme- substrate- specific interactions, thus achieving effective targeting of tumor tissues. Theoretically, in the tumor microenvironment, L- Arg can produce NO in two ways. On the one hand, L- Arg can be catalyzed by iNOS to produce NO, and on the other hand, L- Arg can react with \(\mathrm{H}_2\mathrm{O}_2\) to produce NO. The principles of the two processes are as follows, respectively. + +<|ref|>text<|/ref|><|det|>[[147, 290, 850, 788]]<|/det|> +(1) The mechanism by which iNOS catalyzes L-Arg is a two-step redox process that depends on multiple cofactors: First, the guanidinium group of L-Arg is hydroxylated to produce N-hydroxy-L-Arg (N-OH-L-Arg), which consumes both NADPH and \(\mathrm{O}_2\) (L-Arg + \(\mathrm{O}_2 + \mathrm{NADPH} + \mathrm{H}^+ \leftrightarrow \mathrm{NOH-L-Arg} + \mathrm{H}_2\mathrm{O} + \mathrm{NADP}^+\) ); further oxidation of NOH-L-Arg proceeds via an atypical mechanism in which an electron from NADPH, an electron from NOH-L-Arg itself, and \(\mathrm{O}_2\) come together to form a dioxygen-iron complex \((\mathrm{Fe}^{3 + } - \mathrm{O} - \mathrm{O}^{-})\) that attacks the NOH-L-Arg This complex attacks the guanidinium carbon of the NOH-L-Arg radical, leading to oxygen atom doping and C-N bond breaking (NOH-L-Arg + \(\mathrm{O}_2 + 1 / 2\) (NADPH + \(\mathrm{H}^+ \leftrightarrow \mathrm{L}\) - citrulline + \(\mathrm{NO} + \mathrm{H}_2\mathrm{O} + 1 / 2\mathrm{NADP}^+\) ) (Science 1997, 278, 425-431; J. Chem. Inf. Model. 2011, 51, 1325-1335). This process places special demands on the chirality of Arg, as tetrahydrobiopterin (H4B) stabilizes the dimeric structure of the enzyme in this process and also assists in proton transfer and neutralization of radical intermediates through a network of hydrogen bonds. The stereoselectivity of the active site of iNOS is strictly matched to the S-configuration of L-Arg, where the \(\alpha\) - amino acid, carboxylic acid moiety, and guanidinium group of L-Arg form stable interactions with key amino acid residues (e.g., Glu371) and H4B, respectively, while the nitrogen atom at the end of its guanidinium group directly coordinates with heme iron to initiate oxygen activation (Front. Biosci. 2003, 8, 193-209; Faseb J. 1996, 10, 552-558; Biochim. Biophys. Acta 1999, 1411, 217-230; Nat. Struct. Mol. Biol. 1999, 6, 233-242). However, D-Arg is difficult for iNOS to recognize and catalyze, possibly due to its R-configuration causing the spatial orientation of its side chain to flip, preventing the guanidino group from properly binding to heme iron, and disrupting the electrostatic interactions between the \(\alpha\) - carboxyl group and the active site. BH4 is also unable to stabilize the transition state of D-Arg via hydrogen bonding, thereby disrupting the integrity of the electron transport chain (NADPH \(\rightarrow\) FAD \(\rightarrow\) FMN \(\rightarrow\) HEM) and the activation process of oxygen molecules. + +<|ref|>text<|/ref|><|det|>[[148, 790, 850, 900]]<|/det|> +(2) In addition to the above pathway, L-Arg can also react with \(\mathrm{H}_2\mathrm{O}_2\) , which is based on the oxidation of the electron-rich guanidino group (-HN-C(=NH)-NH₂) on the side chain of Arg by \(\mathrm{H}_2\mathrm{O}_2\) . The reaction undergoes nucleophilic addition to form an unstable adduct, followed by deamination and oxidation, which ultimately converts the guanidino group to a urea group (-NH-C(=O)-NH₂) to produce the product L-citrulline with the release of NO and water. This process does not strictly require the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 765, 102]]<|/det|> +chirality of Arg, and D- Arg is also capable of producing NO by this process. + +<|ref|>text<|/ref|><|det|>[[147, 104, 854, 400]]<|/det|> +chirality of Arg, and D- Arg is also capable of producing NO by this process.Thus, theoretically, D- Arg cannot be recognized and catalyzed by iNOS, and nanomotors constructed from them cannot exert a chemotactic effect on iNOS concentration gradients. However, they should be able to react with the high concentrations of \(\mathrm{H}_2\mathrm{O}_2\) in tumor tissue, thereby exhibiting a certain degree of enhanced Brownian motion (Small 2023, 19, 2207823; Hepatology 2002, 36, 573- 581; Biomaterials 2021, 269, 120642). To verify this conjecture, we constructed nanomotors driven by L- Arg or D- Arg, namely D- Arg NMs and L- Arg NMs, respectively, and investigated their motional behaviors in the cancer cell environment. As shown in Fig. R1, the average speed of D- Arg NMs in cancer cells was about 1.6 \(\mu \mathrm{m / s}\) , which was slightly higher than that of Brownian motion (1.0 \(\mu \mathrm{m / s}\) ), indicating an enhanced Brownian motion. This is mainly due to the oxidative effect of \(\mathrm{H}_2\mathrm{O}_2\) on D- Arg NMs and the production of asymmetric NO. The average speed of L- Arg NMs in the cancer cell environment was about 3.7 \(\mu \mathrm{m / s}\) , which was higher than that of D- Arg NMs (1.6 \(\mu \mathrm{m / s}\) ), attributed to the ability of L- Arg NMs to react with \(\mathrm{H}_2\mathrm{O}_2\) and iNOS in cancer cells to produce more NO to drive them to undergo enhanced Brownian motion. + +<|ref|>image<|/ref|><|det|>[[315, 433, 680, 686]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 696, 850, 752]]<|/det|> +
Fig. R1. Motion trajectories ( \(\mathrm{n} = 10\) independent samples, \(\mathrm{t} = 20\) s) of (a) D-Arg NMs and (c) L-Arg NMs and speed distributions ( \(\mathrm{n} = 10\) independent samples, \(\mathrm{t} = 20\) s) of (b) D-Arg NMs and (d) L-Arg NMs in the cancer cellular environment.
+ +<|ref|>text<|/ref|><|det|>[[147, 771, 848, 806]]<|/det|> +3. In the experiment simulating the tumor microenvironment, \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) was used. Is it close to the actual level of ROS in the tumor microenvironment? + +<|ref|>text<|/ref|><|det|>[[148, 808, 625, 825]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 827, 850, 900]]<|/det|> +Studies have shown that the concentration of ROS in the tumor microenvironment is not less than \(100\mu \mathrm{M}\) (Nat. Rev. Drug Discov. 2009, 8, 579- 591; Nat. Rev. Mol. Cell Biol. 2020, 21, 363- 383; Nat. Rev. Drug Discov. 2013, 12, 931- 947). ROS contains a variety of molecules with complex components and variable states. It is very difficult + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 380]]<|/det|> +to fully simulate the components of ROS in vitro. Studies have shown that the \(\mathrm{H}_2\mathrm{O}_2\) (a relatively stable component) in the tumor microenvironment is about \(10\mathrm{- }100\mu \mathrm{M}\) (ACS Nano 2019, 13, 2643- 2653; Cancer Lett. 2007, 252, 1- 8; Coord. Chem. Rev. 2023, 481, 215049). Therefore, researchers generally choose \(\mathrm{H}_2\mathrm{O}_2\) to simulate ROS in an in vitro environment at a concentration of about \(50\mathrm{- }200\mu \mathrm{M}\) . For instance, Mao et al. use 50 and \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to evaluate the aggregating behavior of tAuNP and mAuNP/Lu (Angew. Chem. Int. Ed. 2021, 60, 23805- 23811); Lv et al. use 50, 100 and \(200\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to evaluate the self- propelled motion of the HTiPC nanomotors (ACS Nano 2024, 18, 13910- 13923); Ye et al. use \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic the tumor environment to assess the lysosomal escape efficacy of the nanomotor (Adv. Funct. Mater. 2025, 35, 2416265); Zhang et al. use \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic the tumor environment to assess the in vitro cytotoxicity of different samples (Nano Today 2022, 45, 101542); Zhu et al. use \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic the tumor environment to assess the catalytic capacity of \(\mathrm{Ce6@MnO_2}\) (Adv. Funct. Mater. 2016, 26, 5490- 5498). In summary, we used \(100\mu \mathrm{M}\mathrm{H}_2\mathrm{O}_2\) to mimic ROS in the tumor microenvironment in our experiments to evaluate the responsive degradation behavior of NO- Lip@PAC NMs. + +<|ref|>text<|/ref|><|det|>[[147, 400, 848, 435]]<|/det|> +4. Does the degradation behavior that occurs in response to NO occur during the penetration of BBB or after penetration? + +<|ref|>text<|/ref|><|det|>[[148, 437, 617, 454]]<|/det|> +Answer: Many thanks to you for your valuable comment. + +<|ref|>text<|/ref|><|det|>[[147, 456, 850, 768]]<|/det|> +NO- Lip@PAC@Cur NMs are able to sense the iNOS concentration gradient formed at the damaged blood- brain barrier (BBB) at the brain tumor site, and thus are able to cross the BBB via chemotaxis. The tumor site has higher concentration of iNOS, NO- Lip@PAC@Cur NMs are able to generate more NO at the tumor site, and thus their degradation behavior occurs after crossing the BBB. We verified this in an in vitro transwell model. Specifically, the upper chamber of the transwell was inoculated with bEnd.3 cells to form the BBB, and the lower chamber was inoculated with GI261 cells, resulting in an iNOS concentration gradient between the upper and lower chambers. Then, we added Lip@PAC NPs and NO- Lip@PAC NMs (50 \(\mu \mathrm{g}\mathrm{mL}^{- 1}\) ) to the upper chamber, respectively, and incubated for 6 h. Fluorescence images of the upper and lower chambers of the transwell model were recorded using CLSM. As shown in Fig. 4b, most of the NO- Lip@PAC in the bEnd.3 cells in the upper compartment remained intact (the red fluorescence representing PAC and the green fluorescence representing Lip or NO- Lip were highly co- localized). When they penetrated the BBB and entered the GI261 cells in the lower chamber, the red fluorescence and green fluorescence gradually separated, indicating that NO- Lip@PAC degraded after crossing the BBB. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[272, 90, 737, 250]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 252, 850, 344]]<|/det|> +
Fig. 4a and b. (a) Schematic diagram of the transwell model; (b) Representative CLSM images of bEnd.3 cells in the upper chamber and Gl261 cells in the lower chamber of the transwell system treated with different samples for \(6\mathrm{h}\) (blue: nucleus, red: Cy5-labelled PACs, green: DiL-labelled Lip or NO-Lip; Scale bar: \(50\mu \mathrm{m}\) ; \(\mathrm{n} = 3\) independent samples).
+ +<|ref|>text<|/ref|><|det|>[[148, 362, 850, 416]]<|/det|> +5. Is the concept of "Size-variable" important? Why does it appear in the title? I suggest changing it to "Trend of inflammation and self-feedback degradation of nanomotors for glioblastoma therapy via mitochondrial mineralization". + +<|ref|>text<|/ref|><|det|>[[148, 419, 625, 435]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 437, 851, 900]]<|/det|> +Size is a very important factor to consider when designing drug delivery systems for tumor therapy. Studies have shown that there is a size dependence of nanoparticles retention and penetration behavior in the tumor region: large- sized nanoparticles (200 nm- 1200 nm) can be efficiently branched near tumor blood vessels (Nano Lett. 2009 9, 1909e15; ACS Nano 2014, 8, 5696e706; Small 2022, 18, 2200115), whereas small- sized nanoparticles (< 200 nm) have a higher level of permeability within tumor tissue (Acta. Pharm. Sin. B 2019, 9, 410e20; ACS Nano 2017, 11, 4582e92). However, small- sized nanoparticles are easily affected by the high- pressure microenvironment of the tumor mesenchyme during aggregation in the tumor microenvironment and are reversed pumped back to the circulatory system, resulting in a significant reduction in delivery efficiency (Proc. Natl. Acad. Sci. 2014, 111, 15344- 15349; Proc. Natl. Acad. Sci. 2022, 119, e2211228119l; Nat. Rev. Cancer 2018, 18, 359e76). To resolve this contradiction, we construct size- variable self- feedback nanomotors NO- Lip@PAC@Cur NMs (with an initial size of about \(500\mathrm{nm}\) ). These nanomotors enable efficient brain tumor delivery through dual functionality: the large- sized nanomotor ( \(\sim 500\mathrm{nm}\) ) is able to crossing the BBB via chemotaxis, and more readily aggregates in the tumor microenvironment without being reverse- pumped back into the circulatory system. Subsequently, it can be degraded in response to NO released during chemotactic targeting, resulting in the release of small- sized PAC NMs ( \(\sim 50\mathrm{nm}\) ). The small- sized PAC NMs can be utilized to further achieve deep penetration into brain tumors by taking advantage of the size advantage and motility effect. The term "size- variable" in the title is intended to emphasize the central contribution of the size- variable property to the breakthrough of the blood- brain barrier for the deep penetration of brain tumors. We appreciate the valuable comments provided by the reviewer. After careful consideration, we have decided to incorporate this idea into the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 533, 102]]<|/det|> +title and kindly request the reviewer's approval. + +<|ref|>text<|/ref|><|det|>[[147, 122, 848, 175]]<|/det|> +6. Have the authors studied whether there is a difference in the motion life between the shell and the core of this size-variable nanomotor? What factors is this related to? Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 177, 850, 325]]<|/det|> +We investigated the motion life of the outer shell (NO- Lip NMs), inner core (PAC NMs) and NO- Lip@PAC NMs in Gl261 cellular lysate. As shown in Supplementary Fig. 34a and b, the average speed of PAC NMs decreased from \(2.9 \mu \mathrm{m / s}\) (6 h) to \(1.6 \mu \mathrm{m / s}\) (24 h). This diminished motility could be attributed to the enzymatic depletion of L- Arg in the nanomotors. As shown in Supplementary Fig. 34c and d, the average speed of NO- Lip NMs decreased from \(3.5 \mu \mathrm{m / s}\) (2 h) to \(1.8 \mu \mathrm{m / s}\) (6 h). The shortened motility lifetime was not only related to the depletion of L- Arg, but also to its ability to response to NO degradation. + +<|ref|>text<|/ref|><|det|>[[147, 326, 852, 658]]<|/det|> +The initial motility of NO- Lip@PAC NMs depends on L- Arg on the liposome shell. As NO accumulates, it causes the liposome shell to degrade and release the loaded PAC NMs, at which time the motility comes from L- Arg on the PAC NMs. We labeled the lipid shell of NO- Lip@PAC NMs with DiO to produce green fluorescence (named DiO- NO- Lip@PAC NMs), the core PAC of NO- Lip@PAC NMs with Cy5 to produce red fluorescence (named NO- Lip@PAC- Cy5 NMs), and separately studied the movement behavior of the shell (NO- Lip) and core (PAC) after incubation with Gl261 cellular lysate for different times. As shown in Supplementary Fig. 34e- h, when incubated with Gl261 cellular lysate for 2 h, DiO- NO- Lip@PAC NMs exhibited enhanced Brownian motion with a speed of \(3.4 \mu \mathrm{m / s}\) , which was comparable to the speed of NO- Lip@PAC- Cy5 NMs (3.3 \(\mu \mathrm{m / s}\) ), indicating that the movement at this time depended on L- Arg on the liposome shell. When incubated with Gl261 cellular lysate for 4 h, the movement speed of NO- Lip@PAC- Cy5 NMs decreased to \(2.6 \mu \mathrm{m / s}\) , comparable to that of DiO- NO- Lip@PAC NMs (2.7 \(\mu \mathrm{m / s}\) ). When the incubation time was extended to 6 h, as the lipid bilayer degraded, the speed of DiO- NO- Lip@PAC NMs decreased to \(2.0 \mu \mathrm{m / s}\) , while NO- Lip@PAC- Cy5 NMs continued to exhibit a speed of \(3.5 \mu \mathrm{m / s}\) , indicating that the movement capacity at this time originated from L- Arg on the PAC NMs. + +<|ref|>text<|/ref|><|det|>[[148, 660, 848, 696]]<|/det|> +In summary, the motion life of the shell (NO- Lip NMs) was approximately 6 h, while that of the core nanomotor (PAC NMs) was approximately 24 h. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[163, 95, 787, 631]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 641, 850, 844]]<|/det|> +Supplementary Figure 34. Motion life of different nanomotors. (a) Trajectories (n = 5 independent samples) and (b) average speeds (n = 5 independent samples) of PAC NMs incubated with Gl261 cellular lysate for different times; (c) Trajectories (n = 5 independent samples) and (d) average speeds (n = 5 independent samples) of NO- Lip NMs incubated with Gl261 cellular lysate for different times; (e) Trajectories (n = 5 independent samples) and (f) average speeds (n = 5 independent samples) of DiO- NO- Lip@PAC NMs incubated with Gl261 cellular lysate for different times; (g) Trajectories (n = 5 independent samples) and (h) average speeds (n = 5 independent samples) of DiO- NO- Lip@PAC NMs incubated with Gl261 cellular lysate for different times. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[148, 864, 848, 899]]<|/det|> +7. Does the brain-targeting efficiency have an advantage compared with most of the values in the literature? It is suggested that the author discuss this. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 625, 101]]<|/det|> +**Answer:** Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 106, 850, 212]]<|/det|> +Brain-targeting efficiencies from recent years in the literature are summarized in **Supplementary Table 1.** Brain accumulation in most studies was in the range of 4.5-15% ID/g. The accumulation of NO-Lip@PAC NMs group in the brain (29.3% ID/g)was higher than most of the values reported in the literature so far, further suggesting that NO-Lip@PAC NMs were able to recognize the highly expressed iNOS in the tumor microenvironment and cross the BBB, accumulating in brain tumors. + +<|ref|>text<|/ref|><|det|>[[148, 236, 812, 266]]<|/det|> +**Supplementary Table1.** Summary of the targeted efficiency of GBM in different articles. + +<|ref|>table<|/ref|><|det|>[[92, 285, 905, 910]]<|/det|> + +
MaterialsTargeted
strategy
Treatment
strategy
Brain
targeting
efficiency
Ref
NP-siRNA-CTX.molecular
recognition
gene therapy/1
BPLP-PLAs NPsmolecular
recognition
immunotherapy/2
iRGD-loaded SPNPsmolecular
recognition
gene therapy/3
siRNA micelles.molecular
recognition
gene therapy~15% ID/g4
MTX@MnO2-Opcamolecular
recognition
chemotherapy/5
Iron oxide nanoparticlemolecular
recognition
radiotherapy/6
CpG-exo/TGMmolecular
recognition
immunotherapy/7
TrQβ@b-3WJ iSCRLet-7gmolecular
recognition
gene therapy and
radiotherapy
/8
BSO-CAT@MOF-199
@DDM
molecular
recognition
immunotherapy/9
ABNPs@mRNAmolecular
recognition
gene therapy7.22% ID/g10
Cannabidiol prodrugmolecular
recognition
molecularly
targeted therapy
/11
\(Cu_{2}-xSe\)NPshomingimmunotherapy/12
\(Au@Cu_{2}-xSe\)NPsmolecular
recognition
immunotherapy13
CRISPR/Cas12a
nanocapsule system
/gene therapy and
molecularly
targeted therapy
6.1% ID/g14
Lipid nanoparticles/gene therapy/15
AMVY@NPsmolecular
recognition
molecularly
targeted therapy
/16
Silk fibroin microneedle/molecularly
targeted therapy
/17
ANCss(Cas9/sgRNA)moleculargene therapy11.8% ID/g18
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[91, 81, 904, 338]]<|/det|> +
recognition
CSI@Ex-Amolecular recognitionsonodynamic therapy~ 7.5% ID/g19
Fe-CDs@Angmolecular recognition/4.5% ID/g20
poly(MIs)/PTX@PEI/siPGK1@CCMhomingchemotherapy and radiotherapy~ 6.0% ID/g21
Ang-NP@RNPmolecular recognitiongene therapy12.9% ID/g22
D-iGSNPsmolecular recognitionradiotherapy~ 9.0% ID23
Ang-NCss(siRNA)molecular recognitiongene therapy6.69% ID/g24
NO-Lip@PAC@Curchemotaxismitochondrial mineralization29.3% ID/gThis work
+ +<|ref|>sub_title<|/ref|><|det|>[[147, 363, 248, 378]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[147, 393, 850, 447]]<|/det|> +1. Wang, K., et al. siRNA nanoparticle suppresses drug-resistant gene and prolongs survival in an orthotopic glioblastoma xenograft mouse model. *Adv. Funct. Mater.* 31, 2007166 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 448, 850, 502]]<|/det|> +2. Kim, G. B., et al. High-affinity mutant interleukin-13 targeted CAR T cells enhance delivery of clickable biodegradable fluorescent nanoparticles to glioblastoma. *Bioact. Mater.* 5, 624-635 (2020). + +<|ref|>text<|/ref|><|det|>[[147, 504, 850, 540]]<|/det|> +3. Gregory, J. V., et al. Systemic brain tumor delivery of synthetic protein nanoparticles for glioblastoma therapy. *Nat. Commun.* 11, 5687 (2020). + +<|ref|>text<|/ref|><|det|>[[147, 541, 853, 595]]<|/det|> +4. Jiang, T., et al. Cation-Free siRNA Micelles as effective drug delivery Platform platform and potent RNAi nanomedicines for glioblastoma therapy. *Adv. Mater.* 33, 2104779 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 597, 850, 650]]<|/det|> +5. Dong, C. Y., et al. Neisseria meningitidis opca protein/MnO₂ hybrid nanoparticles for overcoming the blood-brain barrier to treat glioblastoma. *Adv. Mater.* 34, 2109213 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 652, 850, 687]]<|/det|> +6. Chiarelli, P. A., et al. Iron oxide nanoparticle-mediated radiation delivery for glioblastoma treatment. *Mater. Today* 56, 66-78 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 689, 853, 743]]<|/det|> +7. Cui, J., et al. Immune exosomes loading self-assembled nanomicelles traverse the blood-brain barrier for chemo-immunotherapy against glioblastoma. *ACS Nano* 17, 1464-1484 (2023). + +<|ref|>text<|/ref|><|det|>[[147, 745, 850, 799]]<|/det|> +8. Pang, H. H., et al. Bioengineered bacteriophage-like nanoparticles as RNAi therapeutics to enhance radiotherapy against glioblastomas. *ACS Nano.* 17, 10407-10422 (2023). + +<|ref|>text<|/ref|><|det|>[[147, 801, 850, 855]]<|/det|> +9. Huang, Q. X., et al. Metal-organic framework nanoagent induces curoptosis for effective immunotherapy of malignant glioblastoma. *Nano Today* 51, 101911 (2023). + +<|ref|>text<|/ref|><|det|>[[147, 857, 850, 892]]<|/det|> +10. Liu, Y., et al. Non-invasive PTEN mRNA brain delivery effectively mitigates growth of orthotopic glioblastoma. *Nano Today* 49, 101790 (2023). + +<|ref|>text<|/ref|><|det|>[[147, 894, 850, 911]]<|/det|> +11. Zhou, S., et al. Reprogramming systemic and local immune function to empower + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 85, 853, 736]]<|/det|> +immunotherapy against glioblastoma. Nat. Commun. 14, 435 (2023).12. Wang, T., et al. Antigen self-presented personalized nanovaccines boost the immunotherapy of highly invasive and metastatic tumors. ACS Nano 18, 6333- 6347 (2024).13. Zhang, H., et al. Boost infiltration and activity of T cells via inhibiting ecto- 5'- nucleotide (CD73) immune checkpoint to enhance glioblastoma immunotherapy. ACS Nano 18, 23001- 23013 (2024).14. Ruan, W., et al. Brain- targeted Cas12a ribonucleoprotein nanocapsules enable synergetic gene co- editing leading to potent inhibition of orthotopic glioblastoma. Adv. Sci. 11, 2402178 (2024).15. Rouatbi, N., et al. RNA lipid nanoparticles as efficient in vivo CRISPR- Cas9 gene editing tool for therapeutic target validation in glioblastoma cancer stem cells. J. Control. Release 375, 776- 787 (2024).16. Qi, J., et al. Stepwise- targeting and hypoxia- responsive liposome AMVY®NPs carrying siYAP and verteporfin for glioblastoma therapy. J. Nanobiotechnology 22, 495 (2024).17. Wang, Z., et al. Silk microneedle patch capable of on- demand multidrug delivery to the brain for glioblastoma treatment. Adv. Mater. 34, 2106606 (2022).18. Zou, Y., et al. Blood- brain barrier- penetrating single CRISPR- Cas9 nanocapsules for effective and safe glioblastoma gene therapy. Sci. Adv. 8, eabm8011 (2022).19. Wu, T., Liu, Y., Cao, Y. & Liu, Z. Engineering macrophage exosome disguised biodegradable nanoplatform for enhanced sonodynamic therapy of glioblastoma. Adv. Mater. 34, 2110364 (2022).20. Muhammad, P., et al. Carbon dots supported single Fe atom nanozyme for drug- resistant glioblastoma therapy by activating autophagy- lysosome pathway. Nano Today 45, 101530 (2022).21. Wang, Z., et al. Biomimetic hypoxia- triggered RNAi nanomedicine for synergistically mediating chemo/radiotherapy of glioblastoma. J. Nanobiotechnology 21, 210 (2023).22. Ruan, W., et al. Brain- targeted CRISPR/Cas9 nanomedicine for effective glioblastoma therapy. J. Control. Release 351, 739- 751 (2022).23. Dong, C.- Y., et al. Mult functionalized gold sub- nanometer particles for sensitizing radiotherapy against glioblastoma. Small 17, e2006582 (2021).24. Zou, Y., et al. Single siRNA nanocapsules for effective siRNA brain delivery and glioblastoma treatment. Adv. Mater. 32, 2000416 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 86, 460, 101]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 104, 323, 118]]<|/det|> +\*\*\* SUMMARY \*\*\* + +<|ref|>text<|/ref|><|det|>[[147, 123, 850, 547]]<|/det|> +The proposed manuscript aims at developing nitric oxide powered nanomotors leveraging the high calcium- microenvironment of glioblastoma (GBM) as a targeted treatment strategy. The nanomotors (NMs) are composed of a degradable lipid shell containing nitric oxide- releasing lipid (NO) and nitric oxide- responsive lipids, a nanomotor core composed of L- arginine derivatives and monomers rich in carboxyl groups (PAC) and the drug curcumin. The authors first characterized the NMs in terms of composition, size, surface charge and ability to degrade in response to hydrogen peroxide. The authors then demonstrated that NMs are predominantly responsive to a GBM cell line lysate (GI261) showing nitric oxide dependent movement as opposed to a blood brain barrier (BBB) cell line (bEnd.3) cellular lysate. They further showed the ability of the NO- NMs to pass through a single layer BBB in vitro model without any apparent disruption with increase cellular uptake and mitochondrial co- localization in GI261 GBM cell line. NO- NMs loaded with PAC could cause mitochondrial mineralization, and ultimately cell death, predominantly in GBM cells with low impact on BBB cells. In vivo testing using a mouse GBM model revealed the accumulation of NO- NMs mostly in the brain tissue, liver and kidneys. The presence of curcumin, even though the NO- lipids showed low encapsulation efficiency, through its action on \(\mathrm{Ca^{2 + }}\) ions, enhanced the efficiency of the NO- NMs and increased mitochondrial mineralization. Consequently, NO- NMs containing curcumin resulted in a net tumor reduction, a lower impact on animal weight and an increased survival rate as compared to the chemotherapeutic drug temozolomide and controls. Taken together, those results provide valuable ideas for designing future therapeutic targeting GBM. + +<|ref|>sub_title<|/ref|><|det|>[[150, 548, 476, 564]]<|/det|> +## 1. \*\*\*GENERAL APPRECIATION \*\*\* + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 750]]<|/det|> +The experimental work presented in this study is both thorough and extensive, highlighting commendable efforts by the authors to demonstrate the capabilities of their approach, especially for the in vitro assays. A complete proof of concept is provided, supported by in vitro assays and some preliminary in vivo experiments with a GBM mouse model. The authors corroborate their findings using at least three different approaches, making the results generally convincing and aligned with the scientific literature. The supplementary data are quite extensive cumulating 70 supplementary figures, further supporting the conclusions of the study. The text is well- written, with few syntax and typographical errors. Figures are coherent and clear, and most of the quantitative analyses are supported by robust statistical methods. + +<|ref|>text<|/ref|><|det|>[[148, 753, 850, 824]]<|/det|> +Answer: Thank you very much for taking the time to review our manuscript. We greatly appreciate your suggestions, which are important for improving the quality of the paper. We highly value each of your suggestions and have responded to each of them. + +<|ref|>text<|/ref|><|det|>[[148, 844, 849, 899]]<|/det|> +2. One of the major flaws identified in the study is the small number of mice used per experimental condition, with only three mice per group. This limited sample size, which is a major flaw, may affect the reliability and generalizability of the findings + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 213]]<|/det|> +event if the data shown are generally convincing. In addition, GBM is clinically observed more frequently in biological men, suggesting a sex- specificity in its occurrence. Despite this, it is crucial for researchers to use both male and female mice in their studies to ensure that their findings are robust and applicable across sexes. This approach would provide a more comprehensive understanding of the disease and its potential treatments. In this study, the authors only used female mice. This is a major limitation of the study that should be discussed. + +<|ref|>text<|/ref|><|det|>[[148, 215, 625, 232]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 234, 850, 344]]<|/det|> +In the revised manuscript, we increased the sample size for animal experiments evaluating in vivo targeting ability and therapeutic efficacy to \(\mathrm{n} = 5\) or \(\mathrm{n} = 6\) independent samples, respectively (the sample size in Fig. 6, Supplementary Fig. 62, 63, and 64 was increased to \(\mathrm{n} = 5\) , the sample size in Fig. 7, Supplementary Fig. 65, 66, 67 and 69 was increased to \(\mathrm{n} = 6\) ). As shown below, the overall targeting and therapeutic efficacy did not change significantly after the increase in sample size. + +<|ref|>image<|/ref|><|det|>[[207, 355, 785, 867]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 400]]<|/det|> +Fig. 6. Targeting ability of NO- Lip@PAC NMs in GBM model mice. (a) Schematic diagram of the assessment of the targeting ability of different samples in a GBM model mouse; In vivo fluorescence imaging of mice injected with (b) PBS, (c) Lip@PAC or (d) NO- Lip@PAC at various time points (n = 5 independent samples); (e) Quantification of the mean fluorescence intensities of the brain sites from mice in a- c at various time points (I: PBS, II: Lip@PLC, III: NO- Lip@PAC, n = 5 independent samples); (f) Cy5 fluorescence imaging of the brain after intravenous injection of different samples for \(24\mathrm{h}\) (n = 5 independent samples; Scale bar: \(1\mathrm{cm}\) ) and (g) the corresponding quantitative analysis (I: Control, II: Lip@PLC, III: NO- Lip@PAC, n = 5 independent samples); (h) Quantitative analysis of different sample accumulations in major organs, expressed as injected dose per gram of tissue (% ID/g) (n = 5 independent samples); (i) Representative CLSM images of brain tumors in mice (Blue: nucleus, green: FITC- CD31, red: Cy5- labelled different samples; Scale bar: \(500\mu \mathrm{m}\) ) and (j) red fluorescence distribution curves (I: PBS, II: Lip@PLC, III: NO- Lip@PAC) along selected lines (indicated by white lines in the images). Data in b, c and e were presented as mean ± SD. Significance was calculated via two- sample t- test. + +<|ref|>image<|/ref|><|det|>[[320, 419, 676, 613]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 621, 849, 675]]<|/det|> +
Supplementary Figure 62. Cy5 fluorescence imaging of the brain after intravenous injection of different samples for 7 and \(12\mathrm{h}\) (n = 5 independent samples; Scale bar: \(1\mathrm{cm}\) ).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[290, 90, 710, 410]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 418, 850, 473]]<|/det|> +
Supplementary Figure 63. Cy5 fluorescence imaging of the major organs after intravenous injection of different samples for 7 and \(12\mathrm{h}\) ( \(\mathrm{n} = 5\) independent samples; Scale bar: \(1\mathrm{cm}\) ).
+ +<|ref|>image<|/ref|><|det|>[[212, 498, 785, 686]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 695, 850, 751]]<|/det|> +
Supplementary Figure 64. Cy5 fluorescence imaging of the major organs after intravenous injection of different samples for \(24\mathrm{h}\) ( \(\mathrm{n} = 5\) independent samples; Scale bar: \(1\mathrm{cm}\) ).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[196, 95, 802, 650]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 660, 852, 901]]<|/det|> +
Fig. 7. Anti-tumor efficacy of NO-Lip@PAC@Cur NMs in GBM model mice (female). (a) Treatment protocols for orthotopic brain-GBM-tumor-bearing models. By Figdraw; (b) Representative IVIS spectrum images and (c) quantified signal intensity (n = 6 independent samples per group) ; (d) Kaplan-Meier survival curves (n = 8 independent samples) of GBM model mice with different treatments; (e) Representative H&E (Scale bar: 4 mm), TUNEL, and Ki67 staining images (Scale bar: 500 μm) of dissected brain tissues at the end of treatment; (f) Tunel and (g) Ki67 quantitative fluorescence analysis; (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: LipPAC@Cur, VI: NO-Lip@PLC@Cur, VII: NO-Lip@PAC@Cur; n = 6 independent samples); (h) Representative Bio-TEM images of brain tumor (I: PBS, II: magnification of I, III: NO-Lip@PAC@Cur, IV: magnification of III; Scale bar of I and III: 5 μm; Scale bar of II and IV: 200 nm); Representative TEM-Mapping (P and Ca) of brain tumor cellular mitochondria after treated with (i) control and (j) NO-
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 848, 120]]<|/det|> +Lip@PAC@Cur (Scale bar: 200 nm). Data in c, f and g were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[330, 145, 658, 315]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 325, 853, 362]]<|/det|> +Supplementary Figure 65. Pharmacokinetic profiles of Cur and NO- Lip@PAC@Cur. \(n = 6\) independent samples. Data were presented as mean ± SD. + +<|ref|>image<|/ref|><|det|>[[377, 390, 593, 555]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 566, 850, 658]]<|/det|> +Supplementary Figure 66. Tumor percentage after treatment with different samples (tumor percentage = (tumor area/brain area) \(\times 100\%\) ; I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip@PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; \(n = 6\) independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[277, 688, 707, 840]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 845, 850, 900]]<|/det|> +Supplementary Figure 67. Hemolysis rate of the RBC solution after being treated with (a) different samples (I: negative, II: positive, III: PAC@Cur, IV:Lip- PAC@Cur, V:NO- Lip@PLC@Cur, VI: NO- Lip@PAC@Cur) and (b) different concentrations of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 849, 121]]<|/det|> +NO- Lip@PAC@Cur for 3 h. \(\mathrm{n} = 6\) independent samples. Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[281, 155, 714, 312]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 325, 850, 399]]<|/det|> +Supplementary Figure 69. Changes in body weight of mice in different treatment groups (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip@PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; \(\mathrm{n} = 6\) independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[200, 425, 780, 799]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 807, 850, 899]]<|/det|> +Supplementary Figure 71. Hematological parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip- PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; \(\mathrm{n} = 6\) independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[195, 108, 780, 390]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 399, 850, 493]]<|/det|> +
Supplementary Figure 72. Blood biochemical parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip-PAC@Cur, VI: NO-Lip@PLC@Cur, VII: NO-Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean ± SD. Significance was calculated via one-way ANOVA.
+ +<|ref|>text<|/ref|><|det|>[[147, 511, 852, 900]]<|/det|> +As mentioned by the reviewer, the use of 6- 8- week- old C57BL/6 female mice in the model construction was chosen based on a comprehensive consideration of the modeling methods used in most current studies for the in situ GI261 mouse model (Nat. Nanotechnol. 2025, 20, 683- 696; J. Nanobiotechnol. 2023, 21, 210; Nano Today 2022, 45, 101530). The choice was primarily based on two considerations: first, differences in androgen levels among male individuals may affect the efficacy of brain tumor treatment, while female mice can effectively avoid this issue. Second, in experiments involving a large number of male animals, cohabiting male mice are prone to intense biting and fighting, which not only poses management challenges but also leads to additional animal casualties (Nature 2014, 509, 282- 283; Hypertension 2016, 68, 1139- 1144). Additionally, to more comprehensively evaluate the therapeutic efficacy, we further established an in situ GI261 model using 6- 8- week- old C57BL/6 male mice and investigated the efficacy of NO- Lip@PAC@Cur NMs in this model. As shown in Supplementary Fig. 75a- c, quantitative analysis of in vivo bioluminescence imaging and total radioluminescence intensity revealed that the bioluminescence signal in the PBS group continued to increase over time and reached its peak at the end of treatment (54.4 times of the initial radioluminescence intensity), indicating rapid tumor growth. Following free TMZ treatment, the fluorescence intensity of representative tumors in the mouse brain decreased, indicating mild inhibition of tumor growth (40.6 times of the initial radioluminescence intensity). In contrast, the anti- GBM growth effect was enhanced in the NO- Lip@PAC@Cur group, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 325]]<|/det|> +with a significant reduction in bioluminescence signals (only 9.6 times of the initial radioluminescence intensity). At the end of treatment, the brain tumor area was largest in the PBS group, accounting for \(39.6\%\) of the entire brain. Brain tumor area in mice treated with free TMZ were reduced, accounting for \(26.1\%\) of the entire brain. In contrast, NO- Lip@PAC@Cur significantly inhibited brain tumor growth, with tumor area accounting for \(9.0\%\) of the entire brain at the end of treatment in mice (Supplementary Fig. 75d and e). Mice in the PBS and TMZ groups experienced significant weight loss during treatment, which may be attributed to the inevitable damage caused by chemotherapy drugs to normal tissues and their functions during treatment. In contrast, no significant weight loss trend was observed in mice treated with the NO- Lip@PAC@Cur NMs during treatment (Supplementary Fig. 75f). The therapeutic efficacy of NO- Lip@PAC@Cur NMs in C57 male mice was similar to that in C57BL/6 female mice. + +<|ref|>image<|/ref|><|det|>[[180, 333, 835, 744]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 752, 853, 900]]<|/det|> +
Supplementary Figure 75. Anti-tumor efficacy of NO-Lip@PAC@Cur NMs in GBM model mice (male). (a) Treatment protocols for orthotopic GBM models. By Figdraw; (b) Representative IVIS spectrum images and (c) quantified signal intensity \(\mathrm{n} = 6\) independent samples per group); (d) Representative H&E images of dissected brain tissues at the end of treatment (Scale bar: \(2\mathrm{mm}\) ); (e) Tumor percentage after treatment with different samples (tumor percentage \(=\) (tumor area/brain area) \(\times 100\%\) ); (f) Changes in body weight of mice in different treatment groups. I: PBS, II: TMZ, III: NO-Lip@PAC@Cur; \(\mathrm{n} = 6\) independent samples. Data were presented as mean \(\pm \mathrm{SD}\) .
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 556, 102]]<|/det|> +Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[148, 122, 850, 232]]<|/det|> +3. Another important concern is the fact the research team has previously published a highly similar article in 2023 (DOI: 10.1038/s41467-022-35709-0), utilizing the same general methodology and a similar experimental approach. In this new work, the authors are encouraged to highlight the novelty of their findings, emphasizing advancements and unique contributions that distinguish it from their earlier research work. + +<|ref|>text<|/ref|><|det|>[[149, 234, 625, 251]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 252, 850, 455]]<|/det|> +H. Chen et al. designed a chemotactic nanomotor, which was loaded with the brain endothelial cell-targeted drug angiotensin-2 and the anticancer drug (lonidamine modified with the mitochondrial-targeted drug triphenylphosphine, TLND), named Ang-PAMSe/TLND. This nanomotor can sustainably release high concentrations of NO over an extended period. The generated-high concentration NO can regulate the tumor's immunosuppressive microenvironment through mechanisms such as inducing tumor immunogenic cell death, promoting dendritic cell maturation, facilitating cytotoxic T cell infiltration, and modulating the tumor microenvironment. This promoted the maturation of antigen-presenting cells and T cell activation, further activating the body's systemic anti-tumor immune response and inhibiting tumor metastasis and recurrence. + +<|ref|>text<|/ref|><|det|>[[148, 456, 850, 640]]<|/det|> +Unlike previous work, this work proposes a novel size-variable self- feedback nanomotor (NO- Lip@PAC@Cur NMs) specifically tailored for GBM treatment, leveraging the unique high- calcium microenvironment of GBM. Under the drive of high iNOS expression in the GBM microenvironment, larger size- variable self- feedback nanomotors (approximately 500 nm) can penetrate the BBB via chemotaxis. During chemotaxis, accumulated NO cause the self- feedback lipid shell to gradually degrade, releasing smaller PAC NMs (approximately 50 nm). These smaller nanomotors target mitochondria, where they recruit \(\mathrm{Ca^{2 + }}\) and curcumin to jointly induce mitochondrial mineralization, ultimately leading to tumor cell death and inhibiting GBM progression. + +<|ref|>text<|/ref|><|det|>[[148, 641, 850, 900]]<|/det|> +A comparison of the two works is summarized in Table R1. First, in terms of material composition, previous work primarily utilized L- Arg derivatives (the power source component of the nanomotor) as monomers, constructing the nanomotor through radical polymerization reactions. And then loaded with TLND. In contrast, this work modifies L- Arg within the liposome structure while simultaneously loading curcumin, expanding the construction method of nanomotors from polymer materials synthesized via radical polymerization reactions to liposomes, which holds greater potential for future application and commercialization. Secondly, the two works designs have obvious differences in their specific approaches to brain tumor tissue. Previous work mainly utilized the unique metabolic pathways of tumor tissue, such as the unique metabolic symbiosis system of tumor cells, which has been widely used in many brain tumor treatment studies (Adv. Funct. Mater. 2025, 2419395; ACS Nano 2025, 19, 21365- 21384; Nat. Commun. 2023, 14, 435). This work utilizes the high calcium environment unique to brain tumor tissue and introduces the concept of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 362]]<|/det|> +mitochondrial mineralization into brain tumor treatment, confirming the feasibility of mineralization effects in significantly improving brain tumor treatment outcomes. This approach has not been reported in other studies and is highly innovative. Furthermore, the two works also differ in their design of mitochondrial targeting strategies. Previous work primarily modified LND with positively charged triphenylphosphine (TPP), utilizing its positive charge to target the negatively charged mitochondrial membrane. However, since the membranes of other organelles within the cell are also negatively charged, albeit to a slightly lesser extent than mitochondria (Ann. N. Y. Acad. Sci. 2008, 1147: 105-111), the specificity of this mitochondrial targeting approach is not particularly pronounced. In contrast, this study first reduces the size of the nanomotor using the size effect (from large to small), then employs iNOS, which is highly expressed in mitochondria, as a chemical attractant (Febs J. 2007, 274, 2135-2147; Anesthesiology 2009, 110, 166-181) to induce the nanomotor to further chemotactically target mitochondria upon entering tumor cells. This method of targeting mitochondria has not been reported previously. + +<|ref|>text<|/ref|><|det|>[[148, 363, 849, 416]]<|/det|> +Overall, this work verifies the feasibility of mineralization in brain tumor treatment through various designs, which broadens the scope of brain tumor treatment and has obvious advantages and innovations that differ from previous work. + +<|ref|>text<|/ref|><|det|>[[148, 418, 849, 454]]<|/det|> +Once again, we would like to thank the reviewers for their insightful comments, which have given us a deeper understanding of the strengths of this study. + +<|ref|>table<|/ref|><|det|>[[85, 491, 912, 840]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[168, 475, 473, 490]]<|/det|> +Table R1. Comparison of two works. + +
Material compositionLoaded drugsSpecificityTargeted strategyMitochondria-targeting strategyPenetration strategyTreat ment appro achRef.
Ang-PAMS/T LNDchloridr amineunique metabolic pathways in brain tumor tissuesbrain endothelial cell recognition + chemotactic targeting of brain tumor cellsmaterial modification with positively charged triphenylphosphine (TPP) through charge attraction targeting mitochondriananomotor movement achieves deep penetrationimmunother apyNat. Com mun . 202 3, 14, 941.
NO-Lip@PAC@Curcurcum inthe high calcium environmen t unique to brain tumor tissuechemotaxis targeting the microenvironment of brain tumorutilizing size-dependent effects and chemotactic targeting effects of high levels of iNOS specific to mitochondriavariable sizes and nanomotor movement achieve further penetrationmitochondrial miner alizati onThis work
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 857, 427, 874]]<|/det|> +## \\*\\*\\* SPECIFIC COMMENTS \\*\\*\\* + +<|ref|>text<|/ref|><|det|>[[148, 878, 849, 913]]<|/det|> +The following specific comments should be considered by the authors to provide more clarity and improve the manuscript: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 255, 101]]<|/det|> +Introduction: + +<|ref|>text<|/ref|><|det|>[[148, 104, 849, 177]]<|/det|> +4. The current therapeutic approaches to treat GBM are wider than what is being listed in the introduction section, which mostly focus on immunotherapeutic strategies and gene therapies, especially for drug delivery (local and systemic) approach currently being studied in the field. + +<|ref|>text<|/ref|><|det|>[[148, 178, 625, 195]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 196, 849, 232]]<|/det|> +We have described the limitations of GBM treatment strategies in detail in Introduction. The revised Introduction is as follows. + +<|ref|>text<|/ref|><|det|>[[147, 250, 850, 678]]<|/det|> +Glioblastoma (GBM) is one of the most aggressive and deadly brain tumors, classified by the World Health Organization as the most malignant glioma (Grade IV). The standard treatment for GBM typically involves a combination of surgical resection followed by radiotherapy and/or chemotherapy. However, the characteristic infiltrative growth of GBM makes it difficult to eradicate surgically and may damage critical brain functional areas. The efficacy of first- line chemotherapeutic agents such as temozolomide (TMZ) is often limited by the inherent resistance of tumor cells and severe systemic toxicity (including hematologic toxicity and thrombocytopenia associated with long- term and high- dose administration). The presence of the blood- brain barrier (BBB) also prevents most drugs to enter the tumor cells. Although radiotherapy has shown good cytotoxic effects, its low selectivity and specificity can also cause irreversible damage to normal tissues. Consequently, the median survival for GBM patients remains low at 14.6- 20.5 months, with a 5- year survival rate of less than \(10\%\) . Emerging modalities such as electro- fields therapy, and focused ultrasound therapy have also shown promising advancements in solid tumor therapy in clinic or pre- clinical settings. In situ drug delivery strategies for GBM (convection- enhanced delivery (CED), implantation of slow- release devices) circumvent the BBB by delivering the drug directly to the tumor or postoperative residual cavity, achieving high local drug exposure and reducing systemic toxicity. However, higher operational requirements, the need for more complex equipment, unpredictable and heterogeneous drug distribution, and susceptibility to localized brain tissue injury, edema, or inflammation may limit their application. Therefore, developing targeted therapeutic strategies specifically for GBM has emerged as a critical area of research. + +<|ref|>text<|/ref|><|det|>[[148, 679, 850, 899]]<|/det|> +The unique microenvironment of GBM provides valuable insights for the design of targeted therapeutic strategies (Supplementary Table 1). GBM is characterized by an immunosuppressive tumor microenvironment, often referred to as a "cold" tumor, which has spurred researchers to actively explore novel immunotherapeutic approaches for GBM. These include tumor vaccines, immune checkpoint inhibitors (ICIs), and chimeric antigen receptor T- cell (CAR- T) therapies, etc. However, the efficacy of immunotherapy is affected by the individual patient variability, leading to insufficient or excessive immune responses that limit its broad application. In addition to immunotherapy, molecular targeted therapies have been developed to target cellular molecules that promote the proliferation and differentiation of GBM, such as anti- angiogenic therapy and tyrosine kinase inhibitors. However, their effectiveness is often limited by factors such as drug + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 251]]<|/det|> +resistance in tumor cells and high recurrence rates following treatment16. Gene therapy represents another promising approach, targeting specific genes involved in the proliferation, migration, invasion, apoptosis, and angiogenesis of malignant glioma cells including gene editing corrections using CRISPR-Cas9, or suppressing immune-suppressive genes expressed in brain tumors to reprogram the tumor immune microenvironment3. However, challenges such as the poor stability of nucleic acids in vivo, variable transfection efficiency, and high treatment costs have restricted its widespread application3. Therefore, there is a pressing need to find new therapeutic strategies specifically for GBM. + +<|ref|>sub_title<|/ref|><|det|>[[148, 272, 220, 287]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[147, 290, 848, 325]]<|/det|> +5. Figure 2 and Figure S18: Please clarify the rationale for using HUVEC cells in part of the study and the bEnd.3 cell line for the remainder. + +<|ref|>text<|/ref|><|det|>[[148, 327, 625, 343]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 345, 851, 565]]<|/det|> +As shown in Table R2, we have summarized the cells used in different experiments. When evaluating the degradation behavior of NO- Lip@PAC, we used HUVECs cells, primarily because the in vivo administration method of NO- Lip@PAC@Cur NMs is intravenous injection. HUVECs are human umbilical vein endothelial cells, which can simulate the normal vascular endothelial cell environment in the bloodstream, indicating that they are not degraded during circulation. When NO- Lip@PAC@Cur NMs circulate to the environment surrounding brain tumors, they can penetrate the BBB via chemotaxis and release the loaded cargo through degradation, increasing mitochondrial calcium levels in cells and ultimately leading to brain tumor cell death. Therefore, we used bEnd.3 cells in experiments involving motility, chemotaxis, in vitro BBB penetration ability, and cellular \(\mathrm{Ca^{2 + }}\) content to simulate normal cells in the brain tumor microenvironment. + +<|ref|>table<|/ref|><|det|>[[137, 600, 925, 901]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[147, 586, 620, 602]]<|/det|> +Table R2. Summary of cells used in different experiments + +
Experiment nameExperiment purposeCells usedReasons for selection
assessment of NO-Lip@PAC degradation behaviorevaluate the selective degradation behavior of NO-Lip@PAC in normal cell and cancer cell environmentsHUVECssimulate normal vascular cells in blood circulation
the dynamic behavior of different samplesexplore the motility behavior of Lip@PAC and NO-Lip@PAC in normal cell and cancer cell environmentsbEnd.3simulate normal vascular cells surrounding the tumor microenvironment
chemotactic behavior of different samplesexplore the chemotactic behavior of Lip@PAC and NO-Lip@PAC in normal cell and cancer cell environmentsbEnd.3simulate normal vascular cells surrounding the tumor microenvironment
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[139, 82, 923, 268]]<|/det|> + +
evaluation of ability to penetrate the BBBevaluate the ability of different samples to cross the BBBbEnd.3bEnd.3 can form a dense cell layer that can be used to simulate the BBB in vitro
Ca2+ contentevaluate the effects of different samples on Ca2+ content in cellsbEnd.3simulate normal cells in the brain to contrast with brain tumor cells
cell activityinvestigate cell viability after treating different samples with bEnd.3 and Gl261 cellsbEnd.3simulate normal cells in the brain to contrast with brain tumor cells
+ +<|ref|>title<|/ref|><|det|>[[147, 289, 853, 302]]<|/det|> +# 6. Line 195: precise the technic used to determine the iNOS in bEnd.3 and Gl261 cells. + +<|ref|>text<|/ref|><|det|>[[147, 308, 627, 320]]<|/det|> +**Answer:** Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 326, 850, 377]]<|/det|> +We used the mouse inducible nitric oxide synthase (iNOS) ELISA research kit (purchased from Jiangsu Enzyme Immunoassay, product number MM-0454M1). The specific steps are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 382, 850, 414]]<|/det|> +(1) Collect bend.3 and Gl261 cells, sonicate the cells, and centrifuge to obtain the supernatant as the test sample. + +<|ref|>text<|/ref|><|det|>[[147, 418, 850, 525]]<|/det|> +(2) Sample addition: Set up blank wells (blank control wells without sample or enzyme-labeled reagents, with all other steps performed identically), standard wells,and sample wells. Add 50 μL standard solution to the enzyme-labeled coated plate wells. In the sample wells, first add 40 μL sample diluent, then add 10 μL the sample (final sample dilution is 5-fold). Add the sample to the bottom of the enzyme-labeled plate wells, avoiding contact with the well walls, and gently mix. + +<|ref|>text<|/ref|><|det|>[[147, 530, 850, 561]]<|/det|> +(3) Incubation: Cover the plate with a sealing membrane and incubate at 37 °C for 30 min. + +<|ref|>text<|/ref|><|det|>[[147, 567, 850, 599]]<|/det|> +(4) Solution preparation: Dilute the 30x concentrated wash solution with distilled water at a 30x dilution ratio and set aside. + +<|ref|>text<|/ref|><|det|>[[147, 604, 850, 655]]<|/det|> +(5) Washing: Carefully remove the sealing membrane, discard the liquid, and centrifuge to remove excess liquid. Add washing solution to each well, let stand for 30 seconds, then discard. Repeat this process 5 times, then blot dry. + +<|ref|>text<|/ref|><|det|>[[147, 660, 850, 691]]<|/det|> +(6) Enzyme addition: Add 50 μL of enzyme-labeled reagent to each well, excluding the blank well. + +<|ref|>text<|/ref|><|det|>[[147, 697, 571, 710]]<|/det|> +(7) Incubation: Follow the same procedure as in (3). + +<|ref|>text<|/ref|><|det|>[[147, 715, 556, 729]]<|/det|> +(8) Washing: Follow the same procedure as in (5). + +<|ref|>text<|/ref|><|det|>[[147, 734, 850, 784]]<|/det|> +(9) Color development: Add 50 μL color developer A to each well, followed by 50 μL of color developer B. Gently mix by shaking, then incubate at 37 °C in the dark for 10 min. + +<|ref|>text<|/ref|><|det|>[[147, 790, 850, 822]]<|/det|> +(10) Termination: Add 50 μL stop solution to each well to terminate the reaction (the color will immediately change from blue to yellow). + +<|ref|>text<|/ref|><|det|>[[147, 827, 850, 877]]<|/det|> +(11) Measurement: Adjust the blank well to zero, then measure the absorbance (OD value) of each well at a wavelength of 450 nm. The measurement should be performed within 15 min after adding the stop solution. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 157]]<|/det|> +7. Figure 3 h-k: The fluorescence maker diffusing toward Gl261 cell lysate with the NO-Lip@PAC condition is only slightly higher compared to bEnd.3 cell lysate. Quantitative fluorescence distribution data should be supported with statistical analysis to ensure accuracy and validity of the conclusion. + +<|ref|>text<|/ref|><|det|>[[149, 159, 625, 175]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 178, 852, 380]]<|/det|> +According to the reviewer's suggestion, we quantified the fluorescence intensity of regions (i) and (iii) under different conditions, and statistical analysis was also added to ensure accuracy and validity of the conclusion. As shown in Supplementary Fig. 42, when both regions (i) and (iii) were exposed to bEnd.3 cellular lysate, the fluorescence intensity of Lip@PAC and NO-Lip@PAC was comparable on both sides. However, when regions (i) and (iii) were each separately exposed to Gl261 and bEnd.3 cellular lysate, there was no difference in fluorescence intensity between the two sides for Lip@PAC, the fluorescence intensity of NO-Lip@PAC in Gl261 cellular lysate was higher than that on the side of bEnd.3 cellular lysate (3.0 times higher than it), indicating that NO-Lip@PAC can diffuse from channel (ii) to channel (iii) with higher iNOS concentration. + +<|ref|>image<|/ref|><|det|>[[196, 410, 795, 565]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 585, 850, 715]]<|/det|> +
Fig. 3h-k. (h) Representative fluorescence images of different samples at the exit of the \(\Psi\) -shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (i) the corresponding fluorescence quantification in the presence of bEnd.3 cellular lysates ( \(\mathrm{n} = 3\) independent samples); (j) Representative fluorescence images of different samples at the exit of the \(\Psi\) -shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (k) the corresponding fluorescence quantification in the presence of bEnd.3 and Gl261 cellular lysates ( \(\mathrm{n} = 3\) independent samples).
+ +<|ref|>image<|/ref|><|det|>[[303, 747, 684, 888]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 214]]<|/det|> +Supplementary Figure 41. (a) Quantification of fluorescence of different materials at (i) and (iii) at the channel outlet when passing bEnd.3 cellular lysate at \(\Psi\) - shaped microfluidic inlets (i) and (iii) (n = 3 independent samples); (b) Quantification of fluorescence of different materials at the channel outlet in (i) and (iii) when Gl261 or bEnd.3 cellular lysates were passed through the \(\Psi\) - shaped microfluidic inlets (i) and (iii), respectively (n = 3 independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via two- sample t- test. + +<|ref|>text<|/ref|><|det|>[[147, 233, 848, 270]]<|/det|> +8. Lines 318-321: precise the p Values for the fold increased in fluorescence and transport rate values provide. + +<|ref|>text<|/ref|><|det|>[[148, 271, 625, 288]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 290, 848, 326]]<|/det|> +We have provided the fluorescence increase multiples and p- values for the transfer rate in the revised manuscript. The revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 327, 852, 474]]<|/det|> +In addition, the red fluorescence intensity in bEnd.3 cells in the upper chambers treated with NO- Lip@PAC NMs was lower than that treated with Lip@PAC NPs (Fig. 4c), while Gl261 cells in the lower chambers had stronger red fluorescence signals, and fluorescence quantification showed that their intensity was 8.7 times higher than that of Lip@PAC NPs (Fig. 4c and 4d). The calculation of the transport rate in Fig. 4e showed that the transport efficiency of Lip@PAC NPs was only about \(13.7\%\) , while that of NO- Lip@PAC NMs reached about \(63.5\%\) (4.6 times higher than that of Lip@PAC). + +<|ref|>image<|/ref|><|det|>[[293, 494, 685, 755]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 770, 850, 881]]<|/det|> +
Fig. 4c-f. Quantitative analysis of red and green fluorescence in the (c) upper and (d) lower compartments (I: Control, II: Lip@PAC, III: NO-Lip@PAC, n = 3 independent samples); (e) BBB transport efficiency of different samples (I: Lip@PAC, II: NO-Lip@PAC; n = 3 independent samples); (f) Paracellular permeability of FD-4 treated with different samples for 24 h (I: Control, II: Lip@PAC, III: NO-Lip@PAC; n = 3 independent samples).
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 195]]<|/det|> +9. Figure 5g: Co-localization analysis typically presents red and green fluorescence data without accounting for the relative fluorescence intensity of each sample. For example, green fluorescence, which represents cytoplasmic \(\mathrm{Ca^{2 + }}\) levels fluctuate significantly between experimental conditions. The overlapping between the red and green channel is also high for condition II but is not discussed at all. Therefore, it is also essential to consider relative ratios to accurately interpret the results. + +<|ref|>text<|/ref|><|det|>[[149, 198, 625, 214]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 216, 850, 602]]<|/det|> +The reasons for green and red fluorescence fluctuate significantly between experimental conditions are as follows. L- Arg in NO- Lip@PAC can react with iNOS (highly expressed in tumor cells) to form NO, which in turn causes endoplasmic reticulum stress and releases \(\mathrm{Ca^{2 + }}\) , leading to an increase of \(\mathrm{Ca^{2 + }}\) levels in the cytoplasm. After targeting mitochondria, PAC can recruit \(\mathrm{Ca^{2 + }}\) from the cytoplasm to the region surrounding the mitochondria, further increasing mitochondrial \(\mathrm{Ca^{2 + }}\) levels. Therefore, the green fluorescence representing cytoplasmic \(\mathrm{Ca^{2 + }}\) and the red fluorescence representing mitochondrial \(\mathrm{Ca^{2 + }}\) in the NO- Lip@PAC treatment group were higher than those in the Control and Lip@PLC treatment group. In the NO- Lip@PAC@Cur treatment group, based on the aforementioned pathways, Cur can inhibit \(\mathrm{Ca^{2 + }}\) efflux from the cytoplasm, resulting in higher cytoplasmic \(\mathrm{Ca^{2 + }}\) and mitochondrial \(\mathrm{Ca^{2 + }}\) levels compared to other groups. Thus, under different experimental conditions, the intensity of green fluorescence representing cytoplasmic \(\mathrm{Ca^{2 + }}\) and red fluorescence representing mitochondrial \(\mathrm{Ca^{2 + }}\) differed a lot (Fig. 5g, Supplementary Fig. 57, and 58), the green and red fluorescence intensities of the Lip@PLC group were not significantly different from those of the control group, while the green and red fluorescence intensities of the NO- Lip@PAC group were significantly higher than those of the control group (2.4- fold and 1.9- fold higher, respectively). And the green and red fluorescence intensities of the NO- Lip@PAC@Cur group were 7.2 and 2.4 times higher than those of the control group, respectively. + +<|ref|>text<|/ref|><|det|>[[148, 604, 850, 750]]<|/det|> +In the previous colocalization analysis of Sample II, the sample line did not fully traverse the entire cell, resulting in a high overlap between the red and green channels of Sample II. Therefore, we re- selected more representative fluorescence images and colocalization analyses. As shown in Fig. 5g and Supplementary Fig. 57, colocalization analysis showed that the colocalization of red fluorescence and green fluorescence in the Lip@PLC treatment group was poor, and the overlap of red fluorescence and green fluorescence in the NO- Lip@PAC and NO- Lip@PAC@Cur NMs group was higher, which further proved the above process. + +<|ref|>text<|/ref|><|det|>[[148, 753, 850, 899]]<|/det|> +Since red fluorescence represents mitochondrial \(\mathrm{Ca^{2 + }}\) and green fluorescence represents cytoplasmic \(\mathrm{Ca^{2 + }}\) , the ratio of red to green fluorescence is not comparable. Therefore, we compared the red and green fluorescence intensities of different treatment groups with those of the blank group, respectively. As shown in Supplementary Fig. 57, the green and red fluorescence intensities of the Lip@PAC group did not differ from those of the control group. The green and red fluorescence of the NO- Lip@PAC group were significantly higher than those of the control group (2.4- and 1.9- times higher, respectively), indicating that NO can induce endoplasmic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 195]]<|/det|> +reticulum stress, leading to the release of \(\mathrm{Ca^{2 + }}\) and an increase in \(\mathrm{Ca^{2 + }}\) levels in the cytoplasm. PAC NMs can recruit \(\mathrm{Ca^{2 + }}\) around mitochondria, resulting in an increase in mitochondrial \(\mathrm{Ca^{2 + }}\) levels. The green and red fluorescence intensities of the NO- Lip@PAC@Cur group were 2.6 and 1.4 times higher than those of the NO- Lip@PAC group, respectively, indicating that Cur could inhibit \(\mathrm{Ca^{2 + }}\) efflux in the cytoplasm and further increase the \(\mathrm{Ca^{2 + }}\) levels in the cytoplasm and mitochondria. + +<|ref|>image<|/ref|><|det|>[[231, 220, 757, 410]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 418, 850, 529]]<|/det|> +
Fig. 5g. Representative CLSM images of cytoplasmic \(\mathrm{Ca^{2 + }}\) and mitochondrial \(\mathrm{Ca^{2 + }}\) treated with different samples for \(24\mathrm{h}\) and the fluorescence distribution curves along selected lines (I: Control, II: Lip@PLC, III: NO-Lip@PAC, IV: NO-Lip@PAC@Cur; indicated by the white lines in the images; Blue: nucleus, green: Fluo-4-labelled cytoplasmic \(\mathrm{Ca^{2 + }}\) , red: Rhod-2-labelled mitochondrial \(\mathrm{Ca^{2 + }}\) ; Scale bar: \(20\mu \mathrm{m}\) ; \(\mathrm{n} = 3\) independent samples).
+ +<|ref|>image<|/ref|><|det|>[[268, 553, 730, 875]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 881, 850, 899]]<|/det|> +
Supplementary Figure 57. Representative CLSM images of cytoplasmic \(\mathrm{Ca^{2 + }}\) and
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 849, 140]]<|/det|> +mitochondrial \(\mathrm{Ca^{2 + }}\) of Gl261 cells co-incubated with different samples for \(24\mathrm{h}\) (blue: Hoechst 33342 labeled nucleus, green: Fluo-4- labeled cytoplasmic \(\mathrm{Ca^{2 + }}\) ; red: Rhod-2- labeled mitochondrial \(\mathrm{Ca^{2 + }}\) ; Scale bar: \(20\mu \mathrm{m}\) ). + +<|ref|>image<|/ref|><|det|>[[275, 174, 686, 330]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 344, 850, 455]]<|/det|> +Supplementary Figure 58. Representative CLSM images corresponding quantitative analysis of (a) green fluorescence (Fluo- 4- labeled cytoplasmic \(\mathrm{Ca^{2 + }}\) ) and (b) red fluorescence (Rhod- 2- labeled mitochondrial \(\mathrm{Ca^{2 + }}\) ) intensity in Supplementary Figure 57 (I: Control, II: Lip@PLC, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 473, 850, 584]]<|/det|> +10. Lines 397-398: the Zeta potential value for NO-Lip@PAC@Cur NMs is quite low \((\succ -20\) to \(-30\mathrm{mV}\) or \(< 20\) to \(30\mathrm{mV}\) ) and could result in poorly stable colloidal solution with the tendency to form aggregates. The authors are encouraged to discuss the stability of their system as this statement is supported with the DLS data obtained for different Lip/Cur drug ratios tested (results in Supp file) where aggregates are easily formed. + +<|ref|>text<|/ref|><|det|>[[148, 586, 625, 603]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 605, 850, 750]]<|/det|> +The reviewer's questions raised our concerns about the surface charge and stability of the material. We characterized the stability of NO- Lip@PAC@Cur NMs by investigating changes in DLS and zeta potential at different time points in PBS environment. As shown in Supplementary Fig. 52a and b, the DLS and zeta potential of NO- Lip@PAC@Cur NMs remained unchanged within 7 days, with values of \(598.8\mathrm{nm}\) and \(- 13.9\mathrm{mV}\) , respectively. Additionally, the optical images in Supplementary Fig. 52c indicate that no significant precipitation was observed in PBS after 7 days incubation, demonstrating their excellent stability. + +<|ref|>text<|/ref|><|det|>[[147, 752, 850, 900]]<|/det|> +The surface potential of liposomes reported in other studies is approximately - 10 to \(- 20\mathrm{mV}\) . For example, Chen et al. reported that the zeta potential of liposome- coated titanium dioxide (MIL/TiO₂) nanoparticles was approximately - 11.0 mV (Nat. Nanotechnol. 2023, 18, 1492- 1501); Jiang et al. constructed biomimetic hybrid liposomes (P- RL), with a zeta potential of approximately - 15.0 mV (ACS Nano 2021, 15, 4173- 4185); Liu et al. constructed the liposome nanoparticles (LPs), with a zeta potential of - 19.87 mV (Acta Pharm. Sin. B 2023, 13, 3817e3833). These are similar to the zeta potential (- 14.0 mV) of the NO- Lip@PAC@Cur NMs in this study. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 140]]<|/det|> +Additionally, the relatively low absolute value of the NO- Lip@PAC@Cur NMs potential may be attributed to the presence of L- Arg structures on the liposome surface, as the positive charge of Arg reduces the surface negative charge. + +<|ref|>image<|/ref|><|det|>[[238, 163, 772, 283]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 288, 850, 344]]<|/det|> +Supplementary Figure 52. (a) DLS, (b) zeta potential and (c) optical images of NO- Lip@PAC@Cur NMs incubate with PBS for different time (n = 3 independent samples). Data were shown as the mean ± s.d. + +<|ref|>text<|/ref|><|det|>[[148, 362, 850, 399]]<|/det|> +11. Lines 407-414 and lines 426-428: precise the p Values for the fold increased in fluorescence and transport rate values provide. + +<|ref|>text<|/ref|><|det|>[[148, 400, 626, 418]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 418, 850, 455]]<|/det|> +We have provided the p- values for Fig. 5b, 5c, Supplementary Fig. 53, 54, and 55 in the revised manuscript. The revised sections are as follows. + +<|ref|>image<|/ref|><|det|>[[275, 483, 730, 651]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 659, 850, 770]]<|/det|> +
Fig. 5b and c. (b) Intracellular \(\mathrm{Ca^{2 + }}\) concentration in bEnd.3 cells and Gl261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; n = 3 independent samples); (c) \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for 24 h in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; n = 3 independent samples).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[345, 96, 636, 255]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 269, 850, 343]]<|/det|> +Supplementary Figure 53. Fluorescence quantification of intracellular NO in bEnd.3 and Gl261 cells treated with different samples for 6 h (I: Control, II: Lip@PLC, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[370, 368, 592, 537]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 546, 850, 603]]<|/det|> +Supplementary Figure 54. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with NO- Lip@PAC@Cur for different time in Gl261 cells. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[370, 627, 592, 777]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 787, 850, 861]]<|/det|> +Supplementary Figure 55. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with different samples in Gl261 cells (I: Control, II: A23187, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 880, 848, 899]]<|/det|> +12. Lines 432-433: To complete the demonstration, the author should also provide + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 848, 121]]<|/det|> +data for NO- Lip@PAC- treated GI261. Why only use the control and NO- Lip@PAC@Cur to assess the presence of mitochondrial calcification? + +<|ref|>text<|/ref|><|det|>[[148, 123, 625, 140]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 141, 850, 308]]<|/det|> +Based on the reviewer's suggestion, we have added Bio- TEM images of GI261 cells treated with NO- Lip@PAC. As shown in Supplementary Fig. 57a, the cell membranes of NO- Lip@PAC- treated GI261 cells remain largely intact, with most mitochondria retaining their structural integrity. Only a small number of mitochondria exhibit structural abnormalities, which may be attributed to the NO generated by the interaction between NO- Lip@PAC and high concentrations of iNOS in the tumor microenvironment, leading to endoplasmic reticulum stress and the release of \(\mathrm{Ca^{2 + }}\) , thereby causing mitochondrial calcium overload. This result is consistent with the findings in Fig. 5b and 5c, where \(\mathrm{Ca^{2 + }}\) levels in cells and mitochondria were elevated. + +<|ref|>image<|/ref|><|det|>[[309, 338, 696, 521]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 529, 850, 584]]<|/det|> +
Supplementary Figure 56. (a) Representative bio-TEM images of GI261 cell treated with NO-Lip@PAC; (b) Representative bio-TEM images of GI261 cellular mitochondria treated with (I) PBS, (II) NO-Lip@PAC and (III) NO-Lip@PAC@Cur.
+ +<|ref|>image<|/ref|><|det|>[[267, 612, 717, 782]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 789, 850, 901]]<|/det|> +
Fig. 5b and c. (b) Intracellular \(\mathrm{Ca^{2 + }}\) concentration in bEnd.3 cells and GI261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples); (c) \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for 24 h in GI261 cells. (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples)
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 103, 601, 120]]<|/det|> +13. Lines 476-478: precise the NMs concentration used. + +<|ref|>text<|/ref|><|det|>[[149, 123, 625, 140]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[149, 141, 848, 177]]<|/det|> +We have added the concentrations of the different samples used in the MTT experiment to the revised manuscript. The revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[148, 179, 850, 418]]<|/det|> +The impact of the mitochondrial mineralization process on cellular activity was also explored. As shown in Fig. 5k, 3-(4,5-dimethylthiazol- 2- yl)- 2,5- biphenyl tetrazolium bromide (MTT) results showed that NO- Lip@PAC@Cur NMs had a concentration- dependent cytotoxicity against Gl261 cells, as the concentration increased from 50 to \(800\mu \mathrm{g}\mathrm{mL}^{- 1}\) , the cell activity decreased from \(80.2\%\) to \(24.5\%\) . In addition, the cytotoxicity of different samples on Gl261 and bEnd.3 cells was compared (Fig. 5l), the cell viability of Gl261 cells in the NO- Lip@PAC NMs group \((200\mu \mathrm{g}\mathrm{mL}^{- 1})\) was \(74.6\%\) , while the viability decreased to \(44.5\%\) when Cur was loaded, indicating that mitochondrial mineralization in tumor cells resulted in significant cytotoxicity effects. Meanwhile, the viability of bEnd.3 cells treated with NO- Lip@PAC@Cur NMs \((200\mu \mathrm{g}\mathrm{mL}^{- 1})\) was \(83.8\%\) , with no significant damage to normal cells, due to the absence of overexpressed iNOS in normal cells, which did not undergo mitochondrial mineralization. + +<|ref|>text<|/ref|><|det|>[[149, 436, 850, 491]]<|/det|> +14. Figure 7a: the schematic showing the steps and timeline to create the GBM mouse model should be introduced in Figure 6 instead, or at least, the text should refer to it as the steps to create the GBM tumor mouse model. + +<|ref|>text<|/ref|><|det|>[[149, 493, 625, 510]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[149, 512, 849, 566]]<|/det|> +We have added the steps for creating the GBM mouse model and a schematic diagram of the assessment of the targeting properties of different materials to Fig. 6. The revised Fig. 6a is as follows. + +<|ref|>image<|/ref|><|det|>[[238, 580, 775, 668]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 678, 849, 715]]<|/det|> +
Fig. 6a. Schematic diagram of the assessment of the targeting ability of different samples in a GBM model mouse.
+ +<|ref|>text<|/ref|><|det|>[[149, 733, 850, 787]]<|/det|> +15. The authors should emphasize the limitations of their proposed delivery system and the overall study, particularly highlighting the low number of mice per experimental condition. + +<|ref|>text<|/ref|><|det|>[[148, 789, 852, 899]]<|/det|> +16. Since NO-NMs tend to accumulate in various organs such as the liver and kidneys, one potential improvement to limit drug usage, increase accumulation toward the brain tissue could be the addition of brain BBB shuttle peptides and limit potential adversarial impacts. This would maximize brain tissue accumulation, like current practices with many brain-targeted delivery vehicles. The authors are encouraged to provide future improvements for their system. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 625, 102]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 104, 849, 139]]<|/det|> +Given that these two issues have overlapping aspects, we will address them together. + +<|ref|>text<|/ref|><|det|>[[148, 141, 850, 232]]<|/det|> +In agreement with the reviewer's previous suggestions, we have increased the sample size for animal experiments evaluating in vivo targeting ability and therapeutic efficacy to \(\mathrm{n} = 5\) or \(\mathrm{n} = 6\) independent samples, respectively (the sample size in Fig. 6, Supplementary Fig. 62, 63, and 64 was increased to \(\mathrm{n} = 5\) , the sample size in Fig. 7, Supplementary Fig. 65, 66, 67 and 39 was increased to \(\mathrm{n} = 6\) ). + +<|ref|>text<|/ref|><|det|>[[148, 234, 849, 269]]<|/det|> +Additionally, we have further discussed the limitations of this study in the conclusion section, and the revised Conclusion is as follows. + +<|ref|>sub_title<|/ref|><|det|>[[148, 289, 247, 305]]<|/det|> +## Conclusion + +<|ref|>text<|/ref|><|det|>[[147, 305, 850, 900]]<|/det|> +In summary, we successfully developed size- variable self- feedback nanomotors NO- \(\mathrm{Lip@PAC@Cur}\) NMs, and verified their therapeutic efficacy against GBM. The lipid shell of NO- \(\mathrm{Lip@PAC}\) NMs degraded in response to the NO generated during chemotactic targeting to the GBM microenvironment, thereby releasing the loaded Cur and PAC NMs. The released NO induced endoplasmic reticulum stress and subsequent \(\mathrm{Ca^{2 + }}\) release, while Cur inhibited \(\mathrm{Ca^{2 + }}\) efflux. This dual action resulted in an increase in the intracellular \(\mathrm{Ca^{2 + }}\) concentration (2.7 times higher than that in the control group). Additionally, PAC NMs targeted mitochondria via chemotaxis, where the carboxyl groups recruited \(\mathrm{Ca^{2 + }}\) from the cytoplasm, thereby increasing the local mitochondrial \(\mathrm{Ca^{2 + }}\) concentration to 6.2 times higher than that in the control group. Fluorescence imaging and TEM- mapping of \(\mathrm{Ca^{2 + }}\) in tumor cell mitochondria revealed that mitochondria in the control group. Fluorescence imaging and TEM- mapping of \(\mathrm{Ca^{2+}}\) in tumor cell mitochondria revealed that mitochondria in the NO- \(\mathrm{Lip@PAC@Cur}\) NMs- treated group exhibited stronger fluorescence signals. This indicates that NO- \(\mathrm{Lip@PAC@Cur}\) NMs effectively induced mitochondrial dysfunction, loss of mitochondrial membrane potential, and a significant decrease in ATP- generating capacity from \(8.9~\mu \mathrm{M}\) to \(2.4~\mu \mathrm{M}\) . In vivo experiments demonstrated that NO- \(\mathrm{Lip@PAC}\) NMs could recognize the highly expressed iNOS in the tumor microenvironment, cross the BBB, and accumulate in brain tumors. Specifically, the accumulation in brain tissues of GBM model mice reached \(29.3\%\) ID/g, which was 3.6 times higher than that of the \(\mathrm{Lip@PAC}\) NMs group. The treatment results showed that NO- \(\mathrm{Lip@PAC@Cur}\) NMs effectively inhibited the growth of tumor by inducing mitochondrial mineralization and subsequent tumor cell death (the brain tumor area accounted for \(9.5\%\) of the whole brain in the NO- \(\mathrm{Lip@PAC@Cur}\) NMs group at the end of the treatment, which was \(22.5\%\) of that in the PBS group). Compared with the chemotherapeutic drug TMZ, NO- \(\mathrm{Lip@PAC@Cur}\) NMs exhibited favorable biocompatibility. At the end of the treatment the weight of the mice remained basically unchanged, and blood biochemistry and hematology indices were within normal ranges. Additionally, histological analysis using H&E staining revealed no significant damage to major organs. Given that tumor cell mitochondria are crucial for their growth and proliferation, the strategy of specifically targeting mitochondrial mineralization in tumor cells is expected to provide valuable ideas for designing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 232]]<|/det|> +therapeutic strategies specifically for GBM. Due to the easy accumulation of NMs in organs such as the liver and kidneys, the injected dose is often limited, which in turn restricts the delivery efficiency of the drug to brain tissue. To overcome this bottleneck, a promising strategy is to use composite targeting systems, such as the combination of molecular recognition targeting and microenvironment recognition targeting, which is expected to direct more drug molecules across the BBB to enter the brain tissue, thereby enhancing drug accumulation concentrations in the brain while reducing systemic exposure and limiting potential liver and kidney toxicity. + +<|ref|>sub_title<|/ref|><|det|>[[148, 271, 226, 287]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[148, 289, 848, 324]]<|/det|> +17. Replace rpm values with corresponding rcf (g equivalent) values or provide the centrifuge rotor dimension. + +<|ref|>text<|/ref|><|det|>[[148, 326, 625, 343]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 345, 848, 380]]<|/det|> +We have made corresponding revisions to the experimental section of the revised manuscript, highlighting the revised sections in yellow background. + +<|ref|>text<|/ref|><|det|>[[148, 400, 827, 417]]<|/det|> +18. Precise the number of mice used per experimental conditions and different tests. + +<|ref|>text<|/ref|><|det|>[[148, 419, 625, 435]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 437, 850, 510]]<|/det|> +We have added the number of repeated experiments and the number of mice used in animal experiments to the revised manuscript. The revised sections are highlighted in yellow. Modifications have been made to the figure captions in Fig. 3- 7, and the supporting information in Supplementary Fig. 53, 54, 71 and 72, etc. + +<|ref|>sub_title<|/ref|><|det|>[[148, 530, 316, 546]]<|/det|> +## Supplementary data: + +<|ref|>text<|/ref|><|det|>[[148, 548, 848, 583]]<|/det|> +19. Precise the origin (species) of the blood sample used for erythrocyte morphology and hemolysis rate tests. + +<|ref|>text<|/ref|><|det|>[[148, 586, 628, 603]]<|/det|> +Answer: Many thanks to you for your valuable suggestion. + +<|ref|>text<|/ref|><|det|>[[148, 604, 848, 639]]<|/det|> +The source of blood samples for red blood cell morphology and hemolysis rate tests from C57BL/6 mice have been added to the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 659, 850, 750]]<|/det|> +20. Line 292-293: According to Figure S40, inlets (i) and (iii) should be the buffer I and II (cell lysates), whereas inlet (ii) should be PAC samples. However, the authors wrote: "When inlets (i), (ii) were pumped with bEnd.3 cellular lysates, and inlet (iii) was pumped with Lip@PAC NPs or NO-Lip@PAC NMs, there was no fluid shift (Figure 3h and 3i)". + +<|ref|>text<|/ref|><|det|>[[148, 753, 592, 770]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[148, 771, 848, 805]]<|/det|> +We have made the corresponding revisions in the manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[148, 807, 848, 843]]<|/det|> +When inlets (i), (iii) were pumped with bEnd.3 cellular lysates, and inlet (ii) was pumped with Lip@PAC NPs or NO-Lip@PAC NMs, there was no fluid shift. + +<|ref|>text<|/ref|><|det|>[[148, 863, 558, 880]]<|/det|> +21. Figure S37 g: Provide statistic analysis results. + +<|ref|>text<|/ref|><|det|>[[148, 882, 522, 899]]<|/det|> +Answer: Many thanks to you for your advice. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 122]]<|/det|> +We have marked the results of the statistical analysis in the figure, and the revised Supplementary Fig. 38 (original Supplementary Fig. 37) is as follows. + +<|ref|>image<|/ref|><|det|>[[175, 147, 785, 448]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 454, 851, 640]]<|/det|> +Supplementary Figure 37. When collagen gel containing \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) of bEnd.3 was filled in the right, the normalized movement trajectories \(\mathrm{(n = 10}\) independent samples) of (a) Lip@PAC and (b) NO- Lip@PAC recorded in the observation area; When collagen gel containing \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) of Gl261 was filled in the right, the normalized movement trajectories of (c) Lip@PAC and (d) NO- Lip@PAC recorded in the observation area; (f) Speed \(\mathrm{(n = 10}\) independent samples) and (g) chemotaxis index \(\mathrm{(n = 10}\) independent samples) in different environments (I: Lip@PAC in bEnd.3cellular lysate, II: NO- Lip@PAC in bEnd.3 cellular lysate, III: Lip@PAC in Gl261 cellular lysate, IV: NO- Lip@PAC in Gl261 cellular lysate). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 678, 850, 714]]<|/det|> +22. Figure S38 b: Precise in the figure caption how iNOS levels were measured. Also provide statistic results. + +<|ref|>text<|/ref|><|det|>[[148, 716, 625, 733]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 734, 850, 788]]<|/det|> +We used the mouse inducible nitric oxide synthase (iNOS) ELISA research kit (purchased from Jiangsu Enzyme Immunoassay, product number MM- 0454M1), with the following specific steps: + +<|ref|>text<|/ref|><|det|>[[147, 789, 852, 899]]<|/det|> +(1). Collect samples to be tested from different locations in the Y-shaped channel. +(2) Sample addition: Set up blank wells (blank control wells without sample or enzyme-labeled reagents, with all other steps performed identically), standard wells, and sample wells. Add \(50 \mu \mathrm{L}\) standard solution to the enzyme-labeled coated plate wells. In the sample wells, first add \(40 \mu \mathrm{L}\) sample diluent, then add \(10 \mu \mathrm{L}\) the sample (final sample dilution is 5-fold). Add the sample to the bottom of the enzyme-labeled + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 675, 102]]<|/det|> +plate wells, avoiding contact with the well walls, and gently mix. + +<|ref|>text<|/ref|><|det|>[[147, 104, 850, 140]]<|/det|> +(3) Incubation: Cover the plate with a sealing membrane and incubate at \(37^{\circ}\mathrm{C}\) for 30 min. + +<|ref|>text<|/ref|><|det|>[[147, 141, 850, 177]]<|/det|> +(4) Solution preparation: Dilute the \(30 \times\) concentrated wash solution with distilled water at a \(30 \times\) dilution ratio and set aside. + +<|ref|>text<|/ref|><|det|>[[147, 178, 850, 233]]<|/det|> +(5) Washing: Carefully remove the sealing membrane, discard the liquid, and centrifuge to remove excess liquid. Add washing solution to each well, let stand for 30 seconds, then discard. Repeat this process 5 times, then blot dry. + +<|ref|>text<|/ref|><|det|>[[147, 234, 850, 269]]<|/det|> +(6) Enzyme addition: Add \(50 \mu \mathrm{L}\) of enzyme-labeled reagent to each well, excluding the blank well. + +<|ref|>text<|/ref|><|det|>[[147, 271, 570, 288]]<|/det|> +(7) Incubation: Follow the same procedure as in (3). + +<|ref|>text<|/ref|><|det|>[[147, 289, 555, 306]]<|/det|> +(8) Washing: Follow the same procedure as in (5). + +<|ref|>text<|/ref|><|det|>[[147, 308, 850, 362]]<|/det|> +(9) Color development: Add \(50 \mu \mathrm{L}\) color developer A to each well, followed by \(50 \mu \mathrm{L}\) of color developer B. Gently mix by shaking, then incubate at \(37^{\circ}\mathrm{C}\) in the dark for 10 min. + +<|ref|>text<|/ref|><|det|>[[147, 363, 850, 399]]<|/det|> +(10) Termination: Add \(50 \mu \mathrm{L}\) stop solution to each well to terminate the reaction (the color will immediately change from blue to yellow). + +<|ref|>text<|/ref|><|det|>[[147, 400, 850, 455]]<|/det|> +(11) Measurement: Adjust the blank well to zero, then measure the absorbance (OD value) of each well at a wavelength of \(450 \mathrm{nm}\) . The measurement should be performed within 15 min after adding the stop solution. + +<|ref|>text<|/ref|><|det|>[[167, 474, 577, 492]]<|/det|> +The revised Supplementary Fig. 38 is as follows. + +<|ref|>image<|/ref|><|det|>[[270, 503, 707, 647]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 658, 850, 788]]<|/det|> +Supplementary Figure 38. (a) Schematic diagram of iNOS concentrations detection at positions I, I', II, II', III and IV in the Y-shaped channel and (b) iNOS concentrations at different position, where the bEnd.3 or Gl261 cellular lysates at initial density of \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) was mixed with the equal volume of agarose solution in regions (ii) and (iii) to form the network gel. And the values were detected at 15 min after the agarose solidified. \(n = 3\) independent samples. Data were presented as mean \(\pm \mathrm{SD}\) . Significance was calculated via one-way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 807, 850, 843]]<|/det|> +23. Figure S40: Precise in the figure caption the composition of buffer I and II for the different experimental conditions tested. + +<|ref|>text<|/ref|><|det|>[[147, 845, 625, 862]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 863, 850, 899]]<|/det|> +We have precisely labeled the components of buffers I and II under different experimental conditions in Supplementary Fig. 40. The revised Supplementary Fig. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 281, 102]]<|/det|> +40 is as follows. + +<|ref|>image<|/ref|><|det|>[[160, 134, 845, 230]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 233, 848, 270]]<|/det|> +Supplementary Figure 40. (a) Schematic diagram of \(\Psi\) - shaped microfluidic channel; experimental schematics for (b) Fig. 3h and (c) Fig. 3j. + +<|ref|>text<|/ref|><|det|>[[148, 288, 552, 306]]<|/det|> +24. Figure S46: Provide statistical analysis results + +<|ref|>text<|/ref|><|det|>[[148, 308, 625, 325]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 327, 850, 363]]<|/det|> +We have marked the results of the statistical analysis in the figure, and the revised Supplementary Fig. 47 (original Supplementary Fig. 46) is as follows. + +<|ref|>image<|/ref|><|det|>[[348, 386, 668, 540]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 547, 850, 621]]<|/det|> +Supplementary Figure 47. Representative CLSM images corresponding quantitative analysis of red fluorescence intensity in Supplementary Figure 46. \(n = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via two- sample t- test. + +<|ref|>text<|/ref|><|det|>[[148, 640, 850, 694]]<|/det|> +25. Figure S47: Based on the fluorescence intensity in the red channel for the Lip@PAC condition, we would expect to see more "yellow" in the merge composite images when zones in green and red fluorescence overlap. + +<|ref|>text<|/ref|><|det|>[[148, 696, 625, 713]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 715, 850, 825]]<|/det|> +As the reviewer pointed out, when red and green overlap significantly and have comparable intensities, yellow may appear, as observed in the PAC group and NO- Lip@PAC- treated cells. For Lip@PAC, the yellow color in the fluorescence overlay images is not prominent. This may be due to the weaker red fluorescence and lower colocalization with green mitochondria, resulting in the "yellow" appearing less distinct when red and green fluorescence regions overlap. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[239, 85, 759, 451]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 455, 849, 511]]<|/det|> +
Supplementary Figure 48. Representative CLSM images of different samples co-incubated with Gl261 cells for \(2\mathrm{h}\) (blue: Hoechst 33342 labeled nucleus, green: MiTo-Tracker labeled mitochondria; red: Cy5-labeled different samples; Scale bar: \(50\mu \mathrm{m}\) ).
+ +<|ref|>text<|/ref|><|det|>[[147, 530, 852, 621]]<|/det|> +26. Figure S49: The zeta potential value obtained for NO-Lip@PAC@Cur is quite low, which can result in poorly stable particles with a higher tendency to form aggregates. The authors are encouraged to discuss those data as they agree with the formation of large aggregates for higher drug/lipid ratio (see corresponding comment in the "results section" above. + +<|ref|>text<|/ref|><|det|>[[147, 623, 625, 640]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 641, 850, 733]]<|/det|> +We have addressed the meaning of zeta potential and the stability of the liposomes constructed in this paper in Question 10. The main conclusion is that the zeta potential of the liposomes constructed in this work is similar to that of similar liposomes reported in many other works. And we have also measured their stability, they all exhibit good dispersibility and stability when incubated in PBS for 7 days. + +<|ref|>text<|/ref|><|det|>[[147, 734, 850, 863]]<|/det|> +The reviewer's insightful comment has also drawn our attention back to this issue. As the reviewer speculated, the gradual aggregation observed with increasing drug/lipid ratio may indicate particle instability. However, at the drug/lipid ratio we selected (1:10), NO- Lip@PAC@Cur NMs exhibited acceptable stability. We once again thank the reviewer for the kind reminder. We have added this discussion to the revised manuscript, which also provides valuable insights for our future material design. + +<|ref|>text<|/ref|><|det|>[[147, 881, 735, 899]]<|/det|> +27. Figure S52, S53, S63, S68 and S69: provide statistic analysis results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 625, 101]]<|/det|> +**Answer:** Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 103, 850, 158]]<|/det|> +We have marked the results of the statistical analysis in the figure. The modified Supplementary Fig. 54, 55, 66, 71 and 72 (original S52, S53, S63, S68, and S69, respectively) are as follows. + +<|ref|>image<|/ref|><|det|>[[373, 169, 590, 330]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 342, 850, 398]]<|/det|> +Supplementary Figure 54. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with NO- Lip@PAC@Cur for different time in Gl261 cells. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[378, 427, 585, 569]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 584, 850, 658]]<|/det|> +Supplementary Figure 55. \(\mathrm{Ca^{2 + }}\) content in mitochondria treated with different samples in Gl261 cells (I: Control, II: A23187, III: NO- Lip@PAC, IV: NO- Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[350, 686, 616, 886]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 177]]<|/det|> +Supplementary Figure 66. Tumor percentage after treatment with different samples (tumor percentage = (tumor area/brain area) \(\times 100\%\) ; I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip@PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>image<|/ref|><|det|>[[189, 207, 787, 592]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 602, 850, 694]]<|/det|> +Supplementary Figure 71. Hematological parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV:PAC@Cur, V: Lip- PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[217, 91, 758, 353]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 363, 850, 455]]<|/det|> +Supplementary Figure 72. Blood biochemical parameters of GBM in C57BL/6 mice in different treatment groups at the end of treatment (I: sham, II: PBS, III: TMZ, IV: PAC@Cur, V: Lip- PAC@Cur, VI: NO- Lip@PLC@Cur, VII: NO- Lip@PAC@Cur; n = 6 independent samples). Data were presented as mean ± SD. Significance was calculated via one- way ANOVA. + +<|ref|>sub_title<|/ref|><|det|>[[149, 493, 407, 509]]<|/det|> +## \\*\\*\\* MINOR COMMENTS \\*\\*\\* + +<|ref|>text<|/ref|><|det|>[[148, 513, 256, 527]]<|/det|> +Introduction: + +<|ref|>text<|/ref|><|det|>[[148, 530, 551, 547]]<|/det|> +28. Figure 1a: replace "hydration" by "hydration" + +<|ref|>text<|/ref|><|det|>[[148, 549, 600, 565]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 567, 848, 602]]<|/det|> +We have made the corresponding modifications in Fig. 1a, and the modified Fig. 1 is as follows. + +<|ref|>image<|/ref|><|det|>[[250, 610, 748, 911]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 159]]<|/det|> +Fig. 1. Schematic diagram of (a) preparation of NO- Lip@PAC@Cur and its schematic diagram in response to NO degradation and (b) NO- Lip@PAC@Cur selectively inducing mitochondrial mineralization for the treatment of GBM. By Figdraw. + +<|ref|>text<|/ref|><|det|>[[148, 178, 215, 194]]<|/det|> +Results: + +<|ref|>text<|/ref|><|det|>[[148, 196, 848, 232]]<|/det|> +29. Figure 4 caption, lines 249-250: there seems to be repeated legend descriptions: "(I: Lip@PAC, II: NO-Lip@PAC I: Lip@PAC, II: NO-Lip@PAC)" + +<|ref|>text<|/ref|><|det|>[[148, 234, 608, 250]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[148, 252, 848, 287]]<|/det|> +We have made the corresponding revisions in the revised manuscript, and the revised figure captions are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 306, 850, 750]]<|/det|> +Fig. 4. Characterization of the ability of different samples to cross the BBB in vitro and the mitochondrial targeting performance. (a) Schematic diagram of the transwell model; (b) Representative CLSM images of bEnd.3 cells in the upper chamber and GL261 cells in the lower chamber of the transwell system treated with different samples for 6 h (blue: nucleus, red: Cy5-labelled PACs, green: DiL-labelled Lip or NO-Lip; Scale bar: \(50 \mu \mathrm{m}; \mathrm{n} = 3\) independent samples); Quantitative analysis of red and green fluorescence in the (c) upper and (d) lower compartments (I: Control, II: Lip@PAC, III: NO-Lip@PAC; \(\mathrm{n} = 3\) independent samples); (e) BBB transport efficiency of different samples (I: Lip@PAC, II: NO-Lip@PAC; \(\mathrm{n} = 3\) independent samples); (f) Paracellular permeability of FD-4 treated with different samples for 24 h (I: Control, II: Lip@PAC, III: NO-Lip@PAC; \(\mathrm{n} = 3\) independent samples); (g) Representative CLSM images of Gl261 cells treated with different samples for 2 h, 6 h and 12 h (blue: nucleus, green: DiL-labelled Lip or NO-Lip, red: Cy5-labelled PAC; Scale bar: \(50 \mu \mathrm{m}; \mathrm{n} = 3\) independent samples); (h) Representative CLSM images of colocalization of mitochondrial treated with different samples for 2 h and corresponding fluorescence curves (I: PAC, II: PLC, III: Lip@PAC, IV: NO- Lip@PAC; Blue: nucleus, green: mito- tracker-labelled mitochondria, red: Cy5- labelled different samples; Scale bar: \(50 \mu \mathrm{m}; \mathrm{n} = 3\) independent samples); (i) Schematic illustration of using the Y- channel model to assess the chemotaxis of different samples towards mitochondria. By Figdraw; Representative fluorescence images of (j) PLC NPs and (l) PAC NMs at different times in Y- channel regions (ii) and (iii) (Scale bar: \(1000 \mu \mathrm{m}\) ) and fluorescence quantification of (k) PLC and (m) PAC. Data in c, d, e, f, k and m were presented as mean \(\pm\) SD. Significance was calculated via two- sample t- test and one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[148, 769, 595, 787]]<|/det|> +30. Figure 5c: replace "VI" by "IV" in the x-axis label. + +<|ref|>text<|/ref|><|det|>[[148, 789, 643, 806]]<|/det|> +31. Figure 5 caption (line 368): "(m)" should be "(l)" instead + +<|ref|>text<|/ref|><|det|>[[148, 808, 593, 825]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[148, 826, 848, 862]]<|/det|> +We have made the corresponding revisions in the revised manuscript. The revised Fig. 5c and caption are as follows. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[345, 105, 642, 313]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 325, 850, 381]]<|/det|> +
Fig. 5c. \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for \(24\mathrm{h}\) in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples).
+ +<|ref|>text<|/ref|><|det|>[[148, 400, 580, 417]]<|/det|> +32. Lines 512 and 567: commas with a red font color + +<|ref|>text<|/ref|><|det|>[[148, 419, 593, 436]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[166, 438, 728, 455]]<|/det|> +We have made the corresponding revisions in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 475, 226, 490]]<|/det|> +Methods: + +<|ref|>text<|/ref|><|det|>[[148, 492, 850, 546]]<|/det|> +33. Line 647: The authors wrote "high-sucrose Dalberg's modified Eagle's medium (DMEM, containing \(4.5\mathrm{gL^{-1}}\) 648 D-glucose)". Did the authors mean Dubelcco's modified Eagle's medium? + +<|ref|>text<|/ref|><|det|>[[148, 548, 625, 565]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 566, 850, 677]]<|/det|> +High-sucrose Dalberg's modified Eagle's medium (DMEM) refers to Dubelcco's modified Eagle's medium. We have made corresponding modifications in the revised manuscript, and the modified sections are shown as follows: "Gl261 and Gl261-Luc cells were cultured in complete culture medium containing \(89\%\) v/v high-sugar Dubelcco's modified Eagle's medium (DMEM with \(4.5\mathrm{gL^{-1}}\) D-glucose, Jiangsu KeyGEN BioTECH Corp., CO., Ltd.)". + +<|ref|>text<|/ref|><|det|>[[148, 696, 682, 714]]<|/det|> +34. Line 752: replace " \(1 \times 10^{5}\) cells mL\(^{-1}\)" by " \(1 \times 10^{5}\) cells mL\(^{-1}\)" + +<|ref|>text<|/ref|><|det|>[[148, 716, 593, 732]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 734, 850, 769]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 770, 850, 806]]<|/det|> +For Alizarin Red S staining, Gl261 cells (1.0 mL, \(1 \times 10^{5}\) cells mL\(^{- 1}\) ) were inoculated in confocal dishes and incubated overnight. + +<|ref|>text<|/ref|><|det|>[[148, 825, 496, 842]]<|/det|> +35. Line 793: replace "Aliexa" by "Alexa" + +<|ref|>text<|/ref|><|det|>[[148, 845, 593, 861]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 863, 850, 898]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 140]]<|/det|> +The cell membranes of cerebrovascular endothelial cells were labeled with rabbit anti- mouse CD31 antibody and Alexa Fluor 488- coupled goat anti- rabbit IgG, and the nucleus were labeled with DAPI, respectively. + +<|ref|>text<|/ref|><|det|>[[148, 159, 540, 176]]<|/det|> +36. Lines 802-807: consider revising the syntax. + +<|ref|>text<|/ref|><|det|>[[148, 178, 593, 195]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[148, 197, 849, 232]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 234, 850, 473]]<|/det|> +To investigate the in vivo delivery efficiency and biodistribution of the nanomotors, \(200.0~\mu \mathrm{L}\) of different samples ( \(2.0\mathrm{mgmL}^{- 1}\) , Lip@PAC or NO- Lip@PAC) was injected intravenously. and \(200.0~\mu \mathrm{L}\) of PBS was injected as control. After \(24\mathrm{h}\) , the mice were euthanized, and the brain tissue and major organs (heart, liver, spleen, lung, and kidney) were collected and weighed. Then \(1.0\mathrm{mL}\) RIPA (Biosharp, BL504A) lysis buffer was added to every \(100.0\mathrm{mg}\) of tissue, and tissue homogenate was prepared using the tissue grinder (frequency: \(70\mathrm{Hz}\) , time: \(8\mathrm{min}\) , run times: 8 times). The homogenate was centrifuge ( \(4^{\circ}\mathrm{C}\) , \(1006\times g\) , \(10\mathrm{min}\) ), and the supernatant was collected. The supernatant was diluted and the fluorescence intensity was measured using a multifunctional enzyme- linked immunosorbent assay reader. The injection dose percentage (% \(\mathrm{ID / g}\) ) of each group of samples was calculated based on the sample concentration fluorescence intensity standard curve and the initial injection dose. + +<|ref|>text<|/ref|><|det|>[[148, 492, 711, 509]]<|/det|> +37. Line 818: replace "performed with H&E" by "stained with H&E" + +<|ref|>text<|/ref|><|det|>[[148, 511, 593, 528]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 530, 850, 565]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 566, 849, 602]]<|/det|> +Then the tissues were embedded in paraffin, and stained with H&E staining to evaluate the histopathological changes after different treatments. + +<|ref|>text<|/ref|><|det|>[[147, 621, 541, 638]]<|/det|> +38. Line 826: replace "finished" by "performed" + +<|ref|>text<|/ref|><|det|>[[148, 640, 593, 657]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 659, 849, 694]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 696, 850, 787]]<|/det|> +Differences between the two groups were analyzed by a two- sample t- test. Differences among multiple groups were analyzed using one- way analysis of variance (ANOVA) with two- tailed LSD or Dunnett T3 multiple- comparisons tests. All statistical analyses were performed on Excel v.2019, SPSS v.16.0 and GraphPad Prism v.9.0. + +<|ref|>text<|/ref|><|det|>[[148, 808, 316, 824]]<|/det|> +Supplementary data: + +<|ref|>text<|/ref|><|det|>[[147, 826, 699, 842]]<|/det|> +39. Lines 63-65 & lines 113-116 & lines 166-168: revise the syntax. + +<|ref|>text<|/ref|><|det|>[[148, 845, 593, 861]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 863, 849, 898]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 253, 101]]<|/det|> +Lines 63- 65: + +<|ref|>text<|/ref|><|det|>[[148, 103, 850, 196]]<|/det|> +After the reaction was completed, the reaction solution was washed repeatedly with saturated \(\mathrm{NaHCO_3}\) solution (about \(500~\mathrm{mL}\) ) and saturated \(\mathrm{NaCl}\) solution (about 500 mL), after which the anhydrous \(\mathrm{MgSO_4}\) was added and the mixture was dried for \(4\mathrm{h}\) . The obtained mixed solution was dried using a vacuum rotary evaporator to obtain the crude product. + +<|ref|>text<|/ref|><|det|>[[148, 198, 270, 213]]<|/det|> +Lines 113- 116: + +<|ref|>text<|/ref|><|det|>[[148, 216, 850, 270]]<|/det|> +The product was resuspended in distilled water (1.0 mL), \(\mathrm{Cy5}\) maleimide (20.0 \(\mu \mathrm{L}\) , 1.0 mg \(\mathrm{mL}^{- 1}\) ) was added, and the reaction was stirred at room temperature under \(\mathrm{N}_2\) protection in the absence of light for \(24\mathrm{h}\) . + +<|ref|>text<|/ref|><|det|>[[148, 272, 272, 287]]<|/det|> +Lines 166- 168: + +<|ref|>text<|/ref|><|det|>[[148, 289, 850, 362]]<|/det|> +Intracellular \(\mathrm{Ca^{2 + }}\) was labeled with Fluo- 4 (S1060, Beyotime Biotechnology) for green fluorescence, mitochondrial \(\mathrm{Ca^{2 + }}\) was labeled with Rhod- 2 (purchased from Shanghai yuanye Bio- Technology Co., Ltd) for red fluorescence. The cells were fixed with \(4\%\) paraformaldehyde. + +<|ref|>text<|/ref|><|det|>[[148, 381, 580, 399]]<|/det|> +40. Line 303: Figure S32 caption is missing the "(e)" + +<|ref|>text<|/ref|><|det|>[[148, 401, 593, 418]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[148, 420, 850, 454]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 474, 850, 658]]<|/det|> +Supplementary Figure 31. MSD versus time interval \((\Delta t)\) analyzed from tracking trajectories in different environments ( \(\mathrm{n} = 5\) independent samples). (a) Lip NPs in bEnd.3 cellular environment, (b) Lip NPs in Gl261 cellular environment, (c) NO- Lip NMs in bEnd.3 cellular environment and (d) NO- Lip NMs in Gl261 cellular environment; and (e) diffusion coefficient values determined from the slope of the linear fitting curves of average MSD plots ( \(\mathrm{n} = 10\) independent samples) (I: Lip NPs in bEnd.3 cellular environment, II: Lip NPs in Gl261 cellular environment, III: NO- Lip NMs in bEnd.3 cellular environment, IV: NO- Lip NMs in Gl261 cellular environment). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 678, 608, 696]]<|/det|> +41. Line 314: Figure S34 caption, replace "(D)" by "(d)" + +<|ref|>text<|/ref|><|det|>[[148, 697, 580, 714]]<|/det|> +42. Line 314: Figure S34 caption is missing the "(e)" + +<|ref|>text<|/ref|><|det|>[[148, 716, 593, 732]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[148, 734, 850, 768]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised sections are as follows. + +<|ref|>text<|/ref|><|det|>[[147, 788, 850, 899]]<|/det|> +Supplementary Figure 33. MSD versus time interval \((\Delta t)\) analyzed from tracking trajectories in different environments ( \(\mathrm{n} = 5\) independent samples). (a) Lip@PAC NPs in bEnd.3 cellular environment, (b) Lip@PAC NPs in Gl261 cellular environment, (c) NO- Lip@PAC NMs in bEnd.3 cellular environment and (d) NO- Lip@PAC NMs in Gl261 cellular environment; and (e) diffusion coefficient values determined from the slope of the linear fitting curves of average MSD plots ( \(\mathrm{n} = 10\) ) (I: Lip@PAC NPs in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 158]]<|/det|> +bEnd.3 cellular environment, II: Lip@PAC NPs in Gl261 cellular environment, III: NO- Lip@PAC NMs in bEnd.3 cellular environment, IV: NO- Lip@PAC NMs in Gl261 cellular environment). Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 177, 722, 195]]<|/det|> +43. Figure S35b: replace "Posioton" in the x-axis label with "Position" + +<|ref|>text<|/ref|><|det|>[[147, 197, 595, 214]]<|/det|> +Answer: Many thanks to you for your kind reminding. + +<|ref|>text<|/ref|><|det|>[[147, 216, 850, 252]]<|/det|> +We have made the corresponding changes in the revised manuscript, and the revised Supplementary Figure 35b (original Supplementary Fig. 35) is as follows. + +<|ref|>image<|/ref|><|det|>[[303, 279, 720, 422]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 435, 850, 565]]<|/det|> +Supplementary Figure 35. (a) Schematic diagram of iNOS concentrations detection at positions I, II, and III in the straight channel and (b) iNOS concentrations at different position, where the Gl261 cellular lysates at initial density of \(5 \times 10^{6}\) cells \(\mathrm{mL}^{- 1}\) was mixed with the equal volume of agarose solution in regions (ii) to form the network gels. And the values were detected at \(15 \mathrm{min}\) after the agarose solidified. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. Significance was calculated via one- way ANOVA. + +<|ref|>text<|/ref|><|det|>[[147, 585, 850, 677]]<|/det|> +We sincerely thank the reviewer for their careful review and valuable constructive comments. We appreciate the time and effort you have devoted to the extremely thorough and meticulous review of our work. We are honored to have received your professional guidance, which has greatly improved the overall quality of our manuscript. This has been an invaluable learning and growth opportunity for us. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 122, 850, 305]]<|/det|> +This work presents a novel size- variable self- feedback nanomotor system (NO- Lip@PAC@Cur NMs) for the treatment of glioblastoma (GBM). The system is composed of a self- feedback degradable lipid shell, a nanomotor core with motion ability, and the drug curcumin (Cur) that inhibits calcium ion efflux, which can induce the mitochondrial mineralization. Overall, the design concept of this work is highly innovative. There have been no related studies on treating GBM through mitochondrial mineralization to date. The writing is relatively smooth, the data volume is substantial, and the manuscript is well organized. It is recommended that the work be accepted for publication after minor revisions. The detailed suggestions were listed as follows. + +<|ref|>text<|/ref|><|det|>[[149, 308, 850, 398]]<|/det|> +Answer: We appreciate the reviewer's encouraging comments and admire the professionalism of the reviewer during the review process of the manuscript. These suggestions are very important for us to improve the quality of the manuscript. The issues raised by the reviewer were taken seriously and point- to- point revisions were made. + +<|ref|>text<|/ref|><|det|>[[149, 418, 850, 508]]<|/det|> +1. Introduction Section: It is suggested to more thoroughly analyze the limitations of current GBM treatment strategies, such as surgery, radiotherapy, chemotherapy, and immunotherapy. These limitations include drug resistance and the immunosuppressive microenvironment, which can better highlight the necessity and innovativeness of this study. + +<|ref|>text<|/ref|><|det|>[[149, 511, 625, 527]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[149, 530, 850, 565]]<|/det|> +We have described the limitations of GBM treatment strategies in detail in Introduction. The revised Introduction is as follows: + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 899]]<|/det|> +Glioblastoma (GBM) is one of the most aggressive and deadly brain tumors, classified by the World Health Organization as the most malignant glioma (Grade IV). The standard treatment for GBM typically involves a combination of surgical resection followed by radiotherapy and/or chemotherapy. However, the characteristic infiltrative growth of GBM makes it difficult to eradicate surgically and may damage critical brain functional areas. The efficacy of first- line chemotherapeutic agents such as temozolomide (TMZ) is often limited by the inherent resistance of tumor cells and severe systemic toxicity (including hematologic toxicity and thrombocytopenia associated with long- term and high- dose administration). The presence of the blood- brain barrier (BBB) also prevents most drugs to enter the tumor cells. Although radiotherapy has shown good cytotoxic effects, its low selectivity and specificity can also cause irreversible damage to normal tissues. Consequently, the median survival for GBM patients remains low at 14.6- 20.5 months, with a 5- year survival rate of less than \(10\%\) . Emerging modalities such as electro- fields therapy, and focused ultrasound therapy have also shown promising advancements in solid tumor therapy in clinic or pre- clinical settings. In situ drug delivery strategies for GBM (convection- enhanced delivery (CED), implantation of slow- release devices) circumvent the BBB by delivering the drug directly to the tumor or postoperative residual cavity, achieving + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 849, 177]]<|/det|> +high local drug exposure and reducing systemic toxicity. However, higher operational requirements, the need for more complex equipment, unpredictable and heterogeneous drug distribution, and susceptibility to localized brain tissue injury, edema, or inflammation may limit their application6. Therefore, developing targeted therapeutic strategies specifically for GBM has emerged as a critical area of research. + +<|ref|>text<|/ref|><|det|>[[148, 179, 850, 566]]<|/det|> +The unique microenvironment of GBM provides valuable insights for the design of targeted therapeutic strategies (Supplementary Table 1). GBM is characterized by an immunosuppressive tumor microenvironment, often referred to as a "cold" tumor, which has spurred researchers to actively explore novel immunotherapeutic approaches for GBM. These include tumor vaccines1,7,8, immune checkpoint inhibitors (ICIs)9, and chimeric antigen receptor T- cell (CAR- T) therapies10, etc. However, the efficacy of immunotherapy is affected by the individual patient variability, leading to insufficient or excessive immune responses that limit its broad application11. In addition to immunotherapy, molecular targeted therapies have been developed to target cellular molecules that promote the proliferation and differentiation of GBM, such as anti- angiogenic therapy12,13 and tyrosine kinase inhibitors14,15. However, their effectiveness is often limited by factors such as drug resistance in tumor cells and high recurrence rates following treatment16. Gene therapy represents another promising approach, targeting specific genes involved in the proliferation, migration, invasion, apoptosis, and angiogenesis of malignant glioma cells including gene editing corrections using CRISPR- Cas9, or suppressing immune- suppressive genes expressed in brain tumors to reprogram the tumor immune microenvironment3. However, challenges such as the poor stability of nucleic acids in vivo, variable transfection efficiency, and high treatment costs have restricted its widespread application3. Therefore, there is a pressing need to find new therapeutic strategies specifically for GBM. + +<|ref|>text<|/ref|><|det|>[[148, 586, 849, 694]]<|/det|> +2. Nanomotor Fabrication and Characterization: The description of some steps in the preparation and characterization of the nanomotors is relatively brief. For example, when synthesizing NOR and NOD, only the raw materials used and the reaction conditions are mentioned, without detailed synthesis steps and purification methods. It is recommended to supplement more detailed experimental steps and operational details to facilitate better reproducibility by other researchers. + +<|ref|>text<|/ref|><|det|>[[149, 696, 625, 712]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[149, 715, 849, 768]]<|/det|> +We have further improved the synthesis steps and purification methods of NOR and NOD in the supporting information. The revised parts are highlighted in yellow and the revised experimental steps are as follows. + +<|ref|>sub_title<|/ref|><|det|>[[148, 789, 618, 806]]<|/det|> +## Preparation of NO-responsive degradable lipid (NOD) + +<|ref|>text<|/ref|><|det|>[[149, 808, 849, 899]]<|/det|> +NOD was prepared according to previous literature. Myristic acid (228.0 mg, 1.0 mmol) and HCTU (496.0 mg, 1.2 mmol) were dispersed in tetrahydrofuran (THF, 15.0 mL) and stirred for 10 min until dissolved at \(0^{\circ}\mathrm{C}\) in the \(\mathrm{N}_2\) environment. Next, OPD (216.0 mg, 2 mmol) was dissolved in acetonitrile (20.0 mL) and added it to the above system, continue stirring for 10 min. Finally, triisopropanolamine (574.0 mg, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 175]]<|/det|> +3.0 mmol) was added to the above mixed system and stirred at room temperature for \(24\mathrm{h}\) . The obtained mixed solution was dried using vacuum rotary evaporator to obtain the crude product. Finally, using petroleum ether/ethyl acetate (v:v, 1:1) as the eluent, the crude product was purified by column chromatography to obtain the final product NOD. + +<|ref|>sub_title<|/ref|><|det|>[[148, 197, 504, 214]]<|/det|> +## Preparation of NO-releasing lipid (NOR) + +<|ref|>text<|/ref|><|det|>[[147, 216, 850, 492]]<|/det|> +NOR was prepared according to previous literature. Boc- arg(Pbf)- OH (105.3 mg, 0.2 mmol), HOBT (40.5 mg, 0.3 mmol), and HBTU (113.8 mg, 0.3 mmol) were dispersed in anhydrous DMF (2.0 mL) and stirred for \(10\mathrm{min}\) to dissolve at \(0^{\circ}\mathrm{C}\) in the \(\mathrm{N}_2\) environment. Then DSPE (104.8 mg, 0.1 mmol) was dissolved in anhydrous trichloromethane (15.0 mL) and added to the above system, continue stirring for \(10\mathrm{min}\) . Finally, DIPEA (200.0 μL, 1.2 mmol) was added to the above mixed solution, and the reaction was stirred at room temperature for \(24\mathrm{h}\) . After the reaction was completed, washed the reaction solution repeatedly with saturated \(\mathrm{NaHCO_3}\) solution (about \(500\mathrm{mL}\) ) and saturated \(\mathrm{NaCl}\) solution (about \(500\mathrm{mL}\) ), then added anhydrous \(\mathrm{MgSO_4}\) and dried for \(4\mathrm{h}\) . The obtained mixed solution was dried using a vacuum rotary evaporator to obtain the crude product. Using dichloromethane (DCM)/methanol (MeOH) (v:v, 12:1) as the eluent, the crude product was purified by column chromatography. The solution was neutralized to neutral with saturated \(\mathrm{NaHCO_3}\) solution. Collected the organic phase and precipitated with anhydrous ether at \(4^{\circ}\mathrm{C}\) to obtain the pure product NOR. + +<|ref|>text<|/ref|><|det|>[[148, 511, 850, 620]]<|/det|> +3. The data labeling and legend descriptions in some figures (such as Figures 2 and 3) are not clear enough. For example, in Figure 2, the markings for different samples (such as I: PAC, II: NO-Lip, III: NO-Lip@PAC) are not conspicuous enough and can be easily confused. It is suggested to optimize the design of the figures to make the data and information more intuitive and understandable, while ensuring that the labels and legends in the figures are clear and accurate. + +<|ref|>text<|/ref|><|det|>[[148, 622, 625, 638]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 641, 850, 677]]<|/det|> +We have rearranged the figures in Fig. 2 and optimized the legend descriptions of Fig. 2 and 3 in the revised manuscript, and the revised Fig. 2 and 3 are as follows. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[191, 95, 810, 675]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 679, 853, 901]]<|/det|> +
Fig. 2. Preparation of NO-Lip@PAC NMs and characterization of their degradation behavior in response to NO. (a) TEM images (Scale bar: 500 nm), (b) DLS and (c) Zeta potential of different samples (n = 3 independent samples); (d) Representative confocal laser scanning microscope (CLSM) images of NO-Lip@PAC (Scale bar: 50 μm, green: DiO labeled NO-Lip, red: Cy5 labeled PAC; n = 3 independent samples); Representative DLS changes of NO-Lip@PAC NMs incubated with (e) PBS and (f) 100 μM H2O2 for different times (n = 3 independent samples); (g) Representative TEM images of NO-Lip@PAC NMs incubated with PBS and 100 μM H2O2 for different times (Scale bar 500 nm; red arrows indicate PAC released by lipid degradation; n = 3 independent samples); (h) Representative CLSM images of NO-Lip@PAC incubated with HUVECs and G1261 cellular lysates incubated for different times (Scale bar: 10 μm; green: DiO labeled Lip or NO-Lip, red: Cy5 labeled PAC;
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 853, 121]]<|/det|> +Purple arrows indicate PAC released by lipid degradation; \(\mathrm{n} = 3\) independent samples). Data in b and c were presented as mean \(\pm \mathrm{SD}\) . + +<|ref|>image<|/ref|><|det|>[[184, 150, 805, 666]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 678, 850, 899]]<|/det|> +
Fig. 3. Movement behavior of different samples and characterization of their chemotaxis in static and dynamic environments. Normalized motion trajectories (n = 20 independent samples) and motion speed distribution plots (n = 50 independent samples) of Lip@PAC NPs in (a) bEnd.3 and (b) Gl261 cellular environment (Supplementary Movie 9-10); Normalized motion trajectories (n = 20 independent samples) and motion speed distribution plots (n = 50 independent samples) of NO-Lip@PAC NMs in (c) bEnd.3 and (d) Gl261 cellular environment (Supplementary Movie 11-12); (e) Schematic of the Y-channel model; (f) Representative fluorescence images (Scale bar: \(1000\mu \mathrm{m}\) ) and (g) fluorescence quantification of NO-Lip@PAC NMs in Y-channel regions (ii) and (iii) at different times (n =3 independent samples); (h) Representative fluorescence images of different samples at the exit of the \(\Psi\) -shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (i) the corresponding
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 849, 196]]<|/det|> +fluorescence quantification in the presence of bEnd.3 cellular lysates (n = 3 independent samples); (j) Representative fluorescence images of different samples at the exit of the \(\Psi\) - shaped microfluidic channel (Scale bar: \(200\mu \mathrm{m}\) ) and (k) the corresponding fluorescence quantification in the presence of bEnd.3 and Gl261 cellular lysates (n = 3 independent samples). Data in g were presented as mean \(\pm \mathrm{SD}\) . Significance was calculated via two- sample t- test. + +<|ref|>text<|/ref|><|det|>[[148, 216, 850, 343]]<|/det|> +4. Some sentences in the text contain grammatical errors or are not expressed accurately. For example, in the sentence "However, the infiltrative growth pattern and inherent heterogeneity of GBM, coupled with the side effects of TMZ treatment (including hematologic toxicity and thrombocytopenia associated with long-term and high-dose administration), have significantly limited the efficacy of this therapeutic strategy," the use of "coupled with" is somewhat awkward. It is suggested to change it to "combined with" to make the sentence smoother. + +<|ref|>text<|/ref|><|det|>[[149, 345, 625, 362]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 364, 850, 436]]<|/det|> +We have revised the reworded sentences according to the reviewer's suggestions, while we have checked and corrected spelling and grammatical errors in the manuscript and supporting information one by one, and we have touched up the text to enhance the language. The revised sections are highlighted in yellow. + +<|ref|>text<|/ref|><|det|>[[148, 455, 852, 602]]<|/det|> +5. In several experiments (such as cell viability tests and animal experiments), the text only mentions the sample size of some experiments (such as "n = 3" or "n = 8"), but does not specify the repetition times and sample sizes of all experiments. For example, in the experiment detecting the effects of different samples on cell viability, only "n = 3" is mentioned, without indicating whether it is an independent repeated experiment. It is recommended to clearly label the repetition times (such as the number of independent repeated experiments) and sample sizes in all experimental sections to enhance the reliability and reproducibility of the experimental results. + +<|ref|>text<|/ref|><|det|>[[149, 605, 625, 621]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 623, 850, 696]]<|/det|> +We have added the number of repeated experiments and the number of mice used in animal experiments to the revised manuscript. The revised sections are highlighted in yellow. Modifications have been made to the figure captions in Fig. 3- 7, and the supporting information in Supplementary Fig. 53, 54, 71 and 72, etc. + +<|ref|>text<|/ref|><|det|>[[148, 715, 850, 805]]<|/det|> +6. In the study, the reason for selecting the specific ratio was not detailed, nor was the impact of other ratios on the experimental results assessed. It is suggested to supplement experimental data comparisons of different drug-lipid ratios to demonstrate the rationality of the selected ratio and explore whether there is a more optimal ratio. + +<|ref|>text<|/ref|><|det|>[[149, 808, 625, 824]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 826, 850, 899]]<|/det|> +We prepared NO- Lip@PAC@Cur NMs with different drug- lipid ratios and tested their encapsulation rate and drug loading to determine the optimal loading ratio of Cur. As shown in Supplementary Fig. 49, the encapsulation rate of Cur gradually decreased and the drug loading amount gradually increased with the increase of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 289]]<|/det|> +drug- lipid ratio. However, Cur is a hydrophobic drug, excessive Cur insertion into the phospholipid bilayer will disrupt the original tight arrangement of phospholipid molecules, resulting in changes in the fluidity and permeability of the membrane. This disturbance ultimately reduces liposome stability, which is manifested by an increase in the average particle size of DLS, a wider distribution, and liposome clustering (Carbohyd. Polym. 2017, 156, 322- 332). This is further confirmed by the DLS results in Supplementary Fig. 50, with the increase of drug- to- lipid ratio, the average DLS of NO- Lip@PAC@Cur NMs gradually increased. While the drug- lipid ratio was greater than 1/10, the DLS showed a double peak, indicating that the DLS distribution was not homogeneous and agglomeration occurred. Based on these observations, we finally chose the drug- lipid ratio of 1/10 for the study of subsequent experiments. + +<|ref|>image<|/ref|><|det|>[[350, 321, 666, 485]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 492, 850, 530]]<|/det|> +Supplementary Figure 49. Encapsulation rate and loading of Cur with different drug- lipid ratios. \(\mathrm{n} = 3\) independent samples. Data were presented as mean \(\pm\) SD. + +<|ref|>image<|/ref|><|det|>[[191, 563, 789, 797]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 806, 848, 844]]<|/det|> +Supplementary Figure 50. DLS of NO- Lip@PAC@Cur synthesized with different drug/lipid ratios. + +<|ref|>text<|/ref|><|det|>[[147, 863, 850, 900]]<|/det|> +7. In some experiments, the control groups are not comprehensive enough. For example, in the study of the effects of nanomotors on intracellular calcium ion levels, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 158]]<|/det|> +although a blank control group was set up, a control group with only the drug (such as Cur) without the nanomotor carrier was not included. It is recommended to improve the control group settings to exclude the potential effects of the drug itself on the experimental results. + +<|ref|>text<|/ref|><|det|>[[148, 160, 625, 177]]<|/det|> +Answer: Many thanks to you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[147, 179, 850, 379]]<|/det|> +In our revised manuscript, we investigated the effect of Cur on cellular \(\mathrm{Ca^{2 + }}\) and mitochondrial \(\mathrm{Ca^{2 + }}\) content. As shown in Fig. 5b, the \(\mathrm{Ca^{2 + }}\) content of Cur- treated Gl261 cells increased to \(0.30\mu \mathrm{mol}\) , which was comparable to the \(\mathrm{Ca^{2 + }}\) content in the NO- Lip@PAC- treated cells (0.27 \(\mu \mathrm{mol}\) ). This increase may be due to Cur or the high concentration of NO causing the endoplasmic reticulum to stress and release more \(\mathrm{Ca^{2 + }}\) into the cytoplasm, and the decrease in endoplasmic reticulum \(\mathrm{Ca^{2 + }}\) leading to \(\mathrm{Ca^{2 + }}\) influx from the extracellular space. The intracellular \(\mathrm{Ca^{2 + }}\) content of cells treated with NO- Lip@PAC@Cur was higher (0.46 \(\mu \mathrm{mol}\) ), 2.7- fold higher than that of the control group, indicating that the inhibition of \(\mathrm{Ca^{2 + }}\) efflux by Cur could further increase the intracellular \(\mathrm{Ca^{2 + }}\) level, confirming that Cur and NO could act synergistically to enhance mineralization. + +<|ref|>text<|/ref|><|det|>[[147, 380, 850, 472]]<|/det|> +The mitochondrial \(\mathrm{Ca^{2 + }}\) content in Cur- treated cells was \(0.18\mu \mathrm{mol}\) , which was comparable to that in the A23187 and NO- Lip@PAC treated- group (0.20 \(\mu \mathrm{mol}\) and \(0.19\mu \mathrm{mol}\) , respectively), but the concentration was much lower than that in the NO- Lip@PAC@Cur group (0.36 \(\mu \mathrm{mol}\) ), suggesting that Cur can cause mitochondrial calcium overload, but cannot induce mitochondrial mineralization. + +<|ref|>image<|/ref|><|det|>[[201, 508, 777, 703]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 715, 850, 825]]<|/det|> +
Fig. 5b and c. (b) Intracellular \(\mathrm{Ca^{2 + }}\) concentration in bEnd.3 cells and Gl261 cells after treated with different samples (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples); (c) \(\mathrm{Ca^{2 + }}\) concentration in mitochondria and other organelles treated with different samples for \(24\mathrm{h}\) in Gl261 cells (I: Control, II: Cur, III: Lip@PLC, IV: NO-Lip@PAC, V: NO-Lip@PAC@Cur; \(\mathrm{n} = 3\) independent samples).
+ +<--- Page Split ---> diff --git a/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c3d1db7a579311ef5af384c075c97c22eb2233fa --- /dev/null +++ b/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,158 @@ + +# nature portfolio + +Peer Review File + +# Direct Oxygen Insertion into C-C Bond of Styrenes with Air + +Corresponding Author: Professor Ning Jiao + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors developed an oxidative coupling reaction of styrenes with excess amounts of sulfonyl chlorides in the presence of DIPEA and Na3PO4·12H2O under air and white LED irradiations. Desired aryl vinyl ethers were obtained in moderate yield. This reaction is mechanistically interesting, but synthetically not so interesting. Because the substrates are limited to electron- rich styrenes, and highly efficient preparation methods of aryl vinyl ethers have already been reported: for examples, J. Org. Chem. 2004, 69, 5087- 5092 5087; J. Org. Chem. 2001, 66, 9043; etc. Overall, the novelty and synthetic values shown in this manuscript are not enough as a paper in Nat. Commun. + +Reviewer #2 + +(Remarks to the Author) + +The work reported by Jiao and coworkers describes a photochemical method for the oxygen atom insertion into the Ar- C(sp2) \(\sigma\) - bond of styrenes with aryl sulfonyl chlorides. The process leads to a viable approach to interesting sulfonyl vinyl aryl ethers. The process is carried out by using feedstock styrenes and aryl sulfonyl chlorides under mild metal free conditions in the presence of DIPEA and Na3PO3 and air as terminal oxidant with visible light to give synthetically valued sulfonyl vinyl aryl ethers. Mechanistically, the chemistry through radical- induced 1,2- aryl migration C- C \(\sigma\) - bond cleavage is very interesting and innovative. I recommend the work to Nat Commun. + +1) In the exploration and optimization of the reaction, other bases such TEA, DABCO or Ph3P delivered lower efficiency than DIPEA. A rational for the observation should be provided. Similarly, why did Na3PO4 give the highest yield? + +2) In the reaction scope study, it seems that electron-rich styrenes are favorable substrates for the process. Would simple vinyl pyrrole, thiophene or furane work? + +3) Furthermore, the proposed reaction mechanism with presumptive radical VI might support the observation that electron- donating groups could stabilize the intermediate. + +4) Typo: Line 159: please change 'VII' to 'VI'. + +Reviewer #3 + +(Remarks to the Author) + +Jiao and coworkers developed interesting oxidation reaction of styrenes with molecular oxygen. Under radical pathway with photoirradiation, single oxygen atom was selectively inserted between aryl ring and C=C double bond. The reaction is unique and interesting. Functional group compatibility is reasonably good and so the moderate yields in many entries are not problematic. The reaction was restricted to styrene derivatives, but the novelty of the work is sufficient for publication in Nature Commun, in my perspective. The proposed radical mechanism is reasonable based on experimental results as well as precedent reports. On the other hand, there are some unclear points, which should be revised in responses to the requests below. + +Minor revision requests: + +1) Table 1, entry 11: The reaction proceeded in 35% yield even without light at 35 C. The value in entry 11 was higher than entry 12, that is confusing. Is the data correct? If so the basic concept of the work may change completely. I am afraid the value may be wrong. + +2) Experimental detail: In SI, the authors described "quartz tube with a rubber septum" was used for the reaction, but in the + +<--- Page Split ---> + +photo of the reaction set- up, it seems greaseless schlenk tube was used. Is it necessary to use quartz tube? Accurate information for the reaction vessel and the reactionset- up are important foe readers. Please check the details once again. + +3) SI: Table S2, S3, S4, S5: The best data is missing in Table S2, S3, S4, S5 of SI. It would be much better for readers to understand the optimum conditions, by adding the best conditions in each optimization table. + +4) Light source: In this study, a white LED (Kessil) was used and no other light source was investigated. Based on the UV-vis data provided, blue LED and/or violet LED may also be useful for the reaction. What is the reason to select white LED for this reaction? Is it essential? Additional data with other light source may be useful for readers. + +5) The reaction temp: How did authors keep the reaction temp at \(35^{\circ}C\) ? Is it the temp observed by irradiating 90W white LED (Kessil) in the reaction set-up? + +Version 1: + +Reviewer comments: + +Reviewer #2 + +(Remarks to the Author) + +The authors have addressed the issues raised by reviewers. I recommend it for Nat Commun without further revision. + +Reviewer #3 + +(Remarks to the Author) + +The authors have appropriately responded to the previous requests. Revised manuscript is now suitable for publication without further revisions. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Reviewer #1 (comments): + +The authors developed an oxidative coupling reaction of styrenes with excess amounts of sulfonyl chlorides in the presence of DIPEA and Na3PO4·12H2O under air and white LED irradiations. Desired aryl vinyl ethers were obtained in moderate yield. This reaction is mechanistically interesting, but synthetically not so interesting. Because the substrates are limited to electron- rich styrenes, and highly efficient preparation methods of aryl vinyl ethers have already been reported: for examples, J. Org. Chem. 2004, 69, 5087- 5092 5087; J. Org. Chem. 2001, 66, 9043; etc. Overall, the novelty and synthetic values shown in this manuscript are not enough as a paper in Nat. Commun. + +Answer: Thank the reviewer very much for reviewing our manuscript. The positive view and valuable questions and suggestions are all highly appreciated. + +As the reviewer mentioned, there indeed are reports in the literatures about preparation methods of aryl vinyl ethers. However, our research focus is significantly different. As we all know, due to its high thermodynamic stability, the selective cleavage and functionalization of the inert Ar- C(sp \(^2\) ) \(\sigma\) - bond of alkenes remains a challenging issue. Up to now, there are only four literatures have been reported about Ar- C(sp \(^2\) ) bond functionalization transformations (J. Am. Chem. Soc. 2012, 134, 11308; Nat. Chem. 2017, 9, 361; J. Am. Chem. Soc. 2020, 142, 20973 and Research 2020, 2020, 7947029. By utilizing the strategy of 1,2- aryl migration, this manuscript represents a novel approach to the functionalization of Ar- C(sp \(^2\) ) single bond. Furthermore, in the presence of air or dioxygen, this work realized the first direct skeletal modification of styrenes through Ar- C(sp \(^2\) ) \(\sigma\) - bond oxygen insertion reaction, resulting in the formation of corresponding aryl ether frameworks under mild reaction conditions. We believe that this research offers an innovative approach for the advancement of fields including C- C bond activation and alkene chemistry. + +\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* + +Reviewer #2 (comments): + +The work reported by Jiao and coworkers describes a photochemical method for the oxygen atom insertion into the Ar- C(sp \(^2\) ) \(\sigma\) - bond of styrenes with aryl sulfonyl chlorides. The process leads to a viable approach to interesting sulfonyl vinyl aryl ethers. The process is carried out by using feedstock styrenes and aryl sulfonyl chlorides under mild metal free conditions in the presence of DIPEA and Na3PO3 and air as terminal oxidant with visible light to give synthetically valued sulfonyl vinyl aryl ethers. Mechanistically, the chemistry through radical- induced 1,2- aryl migration C- C \(\sigma\) - bond cleavage is very interesting and innovative. I recommend the work to Nat Commun. + +Answer: Thank the reviewer so much for reviewing our manuscript. The positive view and valuable questions and suggestions are all highly appreciated. The manuscript has been carefully revised based on the valuable comments. + +1) In the exploration and optimization of the reaction, other bases such TEA, DABCO or Ph3P delivered lower efficiency than DIPEA. A rational for the observation should be provided. Similarly, why did Na3PO4 give the highest yield? + +<--- Page Split ---> + +Answer: Thank the reviewer very much for the suggestions. In the EDA complex, DIPEA functions as a potent electron donor, while its ability to form the sulfonamide salt with TsCl is hindered by the presence of two bulky iPr groups. Inorganic base was crucial to the reaction, strong base would destroy the stability of the EDA complex, while weak base would decrease the efficiency of HCl elimination step. In this aspect, as a moderate-strength inorganic base, \(\mathrm{Na_3PO_4}\) could give the highest yield. The rational for the observation have been added in the revised manuscript. + +2) In the reaction scope study, it seems that electron-rich styrenes are favorable substrates for the process. Would simple vinyl pyrrole, thiophene or furane work? + +Answer: The reviewer's suggestion is gratefully appreciated. We have tried some other electron- rich aromatic heterocyclic compounds as shown below, however, only trace products could be obtained under the standard conditions and significant decomposition of most sulfonyl chlorides occurred during the reactions. + +![PLACEHOLDER_3_0] + + +3) Furthermore, the proposed reaction mechanism with presumptive radical VI might support the observation that electron-donating groups could stabilize the intermediate. + +Answer: We express our sincere gratitude for the professional and constructive suggestions provided by the reviewer. We agree with your opinion about the proposed reaction mechanism. + +4) Typo: Line 159: please change 'VII' to 'VI'. + +Answer: We appreciate the reviewer very much for carefully reviewing our manuscript. The mistake has been corrected in its right format. + +************************************************************************************ + +Reviewer #3 (comments): + +Jiao and coworkers developed interesting oxidation reaction of styrenes with molecular oxygen. Under radical pathway with photoirradiation, single oxygen atom was selectively inserted between aryl ring and \(\mathrm{C} = \mathrm{C}\) double bond. The reaction is unique and interesting. Functional group compatibility is reasonably good and so the moderate yields in many entries are not problematic. The reaction was restricted to styrene derivatives, but the novelty of the work is sufficient for publication in Nature Commun, in my perspective. The proposed radical mechanism is reasonable based on experimental results as well as precedent reports. On the other hand, there are some unclear points, which should be revised in responses to the requests below. + +Answer: Thank the reviewer very much for reviewing our manuscript. The positive view and valuable questions and suggestions are all highly appreciated. The manuscript and SI have been carefully revised based on the valuable comments. + +Minor revision requests: + +<--- Page Split ---> + +1) Table 1, entry 11: The reaction proceeded in \(35\%\) yield even without light at \(35~\mathrm{C}\) . The value in entry 11 was higher than entry 12, that is confusing. Is the data correct? If so the basic concept of the work may change completely. I am afraid the value may be wrong. + +Answer: Thank the reviewer very much for reviewing our manuscript and the valuable question. EDA complex also could be activated thermally (J. Am. Chem. Soc. 1987, 109, 2780; Chem. Eur. J. 2015, 21, 8355), so the reaction could proceed in \(35\%\) yield without light at \(35^{\circ}\mathrm{C}\) . However, the stability of the EDA complex was compromised at elevated temperatures, resulting in a significant decrease in yields observed at \(60^{\circ}\mathrm{C}\) . + +2) Experimental detail: In SI, the authors described "quartz tube with a rubber septum" was used for the reaction, but in the photo of the reaction set-up, it seems graceless schlenk tube was used. Is it necessary to use quartz tube? Accurate information for the reaction vessel and the reaction set-up are important for readers. Please check the details once again. + +Answer: We appreciate the reviewer very much for carefully reviewing our manuscript. The oversight on our part is deeply regretted, all of the reactions were conducted in Schlenk tube. The SI has been carefully revised based on the valuable comments. + +3) SI: Table S2, S3, S4, S5: The best data is missing in Table S2, S3, S4, S5 of SI. It would be much better for readers to understand the optimum conditions, by adding the best conditions in each optimization table. + +Answer: Thank the reviewer very much for the kindly suggestion. The best conditions have been added in each optimization table. + +4) Light source: In this study, a white LED (Kessil) was used and no other light source was investigated. Based on the UV-vis data provided, blue LED and/or violet LED may also be useful for the reaction. What is the reason to select white LED for this reaction? Is it essential? Additional data with other light source may be useful for readers. + +Answer: We highly appreciate the reviewer's suggestion which are very helpful for us to improve our manuscript. We opted for a white LED as the light source for the investigation of the reaction due to its inclusion of nearly the entire spectrum within the visible light region. Other light sources were also investigated, and the results were summarized as below. These results have been added in the revised SI. + +![PLACEHOLDER_4_0] + + +<--- Page Split ---> + +5) The reaction temp: How did authors keep the reaction temp at \(35~\mathrm{C}\) ? Is it the temp observed by irradiating 90W white LED (Kessil) in the reaction set-up? + +Answer: Thank the reviewer very much for the constructive question. The reaction temperature was the observed ambient temp. that irradiated by a 90 W white LED from \(6\mathrm{cm}\) distance. + +<--- Page Split ---> diff --git a/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e4723657e0f0db443af5396b2f585745b30b4310 --- /dev/null +++ b/peer_reviews/32cc9b20d063e428cb72fea2ee5742fcb422ce4b81cacb415111a21e240467ba/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,220 @@ +<|ref|>title<|/ref|><|det|>[[72, 50, 295, 78]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 297, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 161, 884, 186]]<|/det|> +# Direct Oxygen Insertion into C-C Bond of Styrenes with Air + +<|ref|>text<|/ref|><|det|>[[73, 200, 444, 217]]<|/det|> +Corresponding Author: Professor Ning Jiao + +<|ref|>text<|/ref|><|det|>[[70, 250, 864, 265]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 302, 145, 315]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 329, 220, 342]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 355, 160, 368]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 381, 238, 394]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 395, 916, 472]]<|/det|> +The authors developed an oxidative coupling reaction of styrenes with excess amounts of sulfonyl chlorides in the presence of DIPEA and Na3PO4·12H2O under air and white LED irradiations. Desired aryl vinyl ethers were obtained in moderate yield. This reaction is mechanistically interesting, but synthetically not so interesting. Because the substrates are limited to electron- rich styrenes, and highly efficient preparation methods of aryl vinyl ethers have already been reported: for examples, J. Org. Chem. 2004, 69, 5087- 5092 5087; J. Org. Chem. 2001, 66, 9043; etc. Overall, the novelty and synthetic values shown in this manuscript are not enough as a paper in Nat. Commun. + +<|ref|>text<|/ref|><|det|>[[73, 485, 161, 498]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 512, 238, 524]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 525, 910, 601]]<|/det|> +The work reported by Jiao and coworkers describes a photochemical method for the oxygen atom insertion into the Ar- C(sp2) \(\sigma\) - bond of styrenes with aryl sulfonyl chlorides. The process leads to a viable approach to interesting sulfonyl vinyl aryl ethers. The process is carried out by using feedstock styrenes and aryl sulfonyl chlorides under mild metal free conditions in the presence of DIPEA and Na3PO3 and air as terminal oxidant with visible light to give synthetically valued sulfonyl vinyl aryl ethers. Mechanistically, the chemistry through radical- induced 1,2- aryl migration C- C \(\sigma\) - bond cleavage is very interesting and innovative. I recommend the work to Nat Commun. + +<|ref|>text<|/ref|><|det|>[[72, 601, 901, 640]]<|/det|> +1) In the exploration and optimization of the reaction, other bases such TEA, DABCO or Ph3P delivered lower efficiency than DIPEA. A rational for the observation should be provided. Similarly, why did Na3PO4 give the highest yield? + +<|ref|>text<|/ref|><|det|>[[72, 639, 900, 666]]<|/det|> +2) In the reaction scope study, it seems that electron-rich styrenes are favorable substrates for the process. Would simple vinyl pyrrole, thiophene or furane work? + +<|ref|>text<|/ref|><|det|>[[72, 655, 905, 682]]<|/det|> +3) Furthermore, the proposed reaction mechanism with presumptive radical VI might support the observation that electron- donating groups could stabilize the intermediate. + +<|ref|>text<|/ref|><|det|>[[73, 682, 380, 694]]<|/det|> +4) Typo: Line 159: please change 'VII' to 'VI'. + +<|ref|>text<|/ref|><|det|>[[73, 719, 161, 731]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 745, 238, 757]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 758, 916, 848]]<|/det|> +Jiao and coworkers developed interesting oxidation reaction of styrenes with molecular oxygen. Under radical pathway with photoirradiation, single oxygen atom was selectively inserted between aryl ring and C=C double bond. The reaction is unique and interesting. Functional group compatibility is reasonably good and so the moderate yields in many entries are not problematic. The reaction was restricted to styrene derivatives, but the novelty of the work is sufficient for publication in Nature Commun, in my perspective. The proposed radical mechanism is reasonable based on experimental results as well as precedent reports. On the other hand, there are some unclear points, which should be revised in responses to the requests below. + +<|ref|>text<|/ref|><|det|>[[73, 862, 239, 874]]<|/det|> +Minor revision requests: + +<|ref|>text<|/ref|><|det|>[[72, 875, 911, 914]]<|/det|> +1) Table 1, entry 11: The reaction proceeded in 35% yield even without light at 35 C. The value in entry 11 was higher than entry 12, that is confusing. Is the data correct? If so the basic concept of the work may change completely. I am afraid the value may be wrong. + +<|ref|>text<|/ref|><|det|>[[70, 926, 904, 940]]<|/det|> +2) Experimental detail: In SI, the authors described "quartz tube with a rubber septum" was used for the reaction, but in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 47, 900, 75]]<|/det|> +photo of the reaction set- up, it seems greaseless schlenk tube was used. Is it necessary to use quartz tube? Accurate information for the reaction vessel and the reactionset- up are important foe readers. Please check the details once again. + +<|ref|>text<|/ref|><|det|>[[70, 86, 900, 115]]<|/det|> +3) SI: Table S2, S3, S4, S5: The best data is missing in Table S2, S3, S4, S5 of SI. It would be much better for readers to understand the optimum conditions, by adding the best conditions in each optimization table. + +<|ref|>text<|/ref|><|det|>[[70, 126, 920, 167]]<|/det|> +4) Light source: In this study, a white LED (Kessil) was used and no other light source was investigated. Based on the UV-vis data provided, blue LED and/or violet LED may also be useful for the reaction. What is the reason to select white LED for this reaction? Is it essential? Additional data with other light source may be useful for readers. + +<|ref|>text<|/ref|><|det|>[[70, 178, 920, 206]]<|/det|> +5) The reaction temp: How did authors keep the reaction temp at \(35^{\circ}C\) ? Is it the temp observed by irradiating 90W white LED (Kessil) in the reaction set-up? + +<|ref|>text<|/ref|><|det|>[[72, 243, 144, 256]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 268, 220, 281]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 294, 162, 307]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 320, 238, 333]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 333, 870, 347]]<|/det|> +The authors have addressed the issues raised by reviewers. I recommend it for Nat Commun without further revision. + +<|ref|>text<|/ref|><|det|>[[72, 359, 162, 372]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 385, 238, 398]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 398, 888, 424]]<|/det|> +The authors have appropriately responded to the previous requests. Revised manuscript is now suitable for publication without further revisions. + +<|ref|>text<|/ref|><|det|>[[72, 778, 916, 831]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 832, 797, 845]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 845, 911, 897]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 897, 618, 911]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 86, 348, 100]]<|/det|> +Reviewer #1 (comments): + +<|ref|>text<|/ref|><|det|>[[177, 122, 820, 268]]<|/det|> +The authors developed an oxidative coupling reaction of styrenes with excess amounts of sulfonyl chlorides in the presence of DIPEA and Na3PO4·12H2O under air and white LED irradiations. Desired aryl vinyl ethers were obtained in moderate yield. This reaction is mechanistically interesting, but synthetically not so interesting. Because the substrates are limited to electron- rich styrenes, and highly efficient preparation methods of aryl vinyl ethers have already been reported: for examples, J. Org. Chem. 2004, 69, 5087- 5092 5087; J. Org. Chem. 2001, 66, 9043; etc. Overall, the novelty and synthetic values shown in this manuscript are not enough as a paper in Nat. Commun. + +<|ref|>text<|/ref|><|det|>[[178, 271, 819, 305]]<|/det|> +Answer: Thank the reviewer very much for reviewing our manuscript. The positive view and valuable questions and suggestions are all highly appreciated. + +<|ref|>text<|/ref|><|det|>[[177, 326, 820, 546]]<|/det|> +As the reviewer mentioned, there indeed are reports in the literatures about preparation methods of aryl vinyl ethers. However, our research focus is significantly different. As we all know, due to its high thermodynamic stability, the selective cleavage and functionalization of the inert Ar- C(sp \(^2\) ) \(\sigma\) - bond of alkenes remains a challenging issue. Up to now, there are only four literatures have been reported about Ar- C(sp \(^2\) ) bond functionalization transformations (J. Am. Chem. Soc. 2012, 134, 11308; Nat. Chem. 2017, 9, 361; J. Am. Chem. Soc. 2020, 142, 20973 and Research 2020, 2020, 7947029. By utilizing the strategy of 1,2- aryl migration, this manuscript represents a novel approach to the functionalization of Ar- C(sp \(^2\) ) single bond. Furthermore, in the presence of air or dioxygen, this work realized the first direct skeletal modification of styrenes through Ar- C(sp \(^2\) ) \(\sigma\) - bond oxygen insertion reaction, resulting in the formation of corresponding aryl ether frameworks under mild reaction conditions. We believe that this research offers an innovative approach for the advancement of fields including C- C bond activation and alkene chemistry. + +<|ref|>text<|/ref|><|det|>[[178, 565, 816, 580]]<|/det|> +\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* + +<|ref|>text<|/ref|><|det|>[[178, 586, 348, 600]]<|/det|> +Reviewer #2 (comments): + +<|ref|>text<|/ref|><|det|>[[178, 621, 820, 767]]<|/det|> +The work reported by Jiao and coworkers describes a photochemical method for the oxygen atom insertion into the Ar- C(sp \(^2\) ) \(\sigma\) - bond of styrenes with aryl sulfonyl chlorides. The process leads to a viable approach to interesting sulfonyl vinyl aryl ethers. The process is carried out by using feedstock styrenes and aryl sulfonyl chlorides under mild metal free conditions in the presence of DIPEA and Na3PO3 and air as terminal oxidant with visible light to give synthetically valued sulfonyl vinyl aryl ethers. Mechanistically, the chemistry through radical- induced 1,2- aryl migration C- C \(\sigma\) - bond cleavage is very interesting and innovative. I recommend the work to Nat Commun. + +<|ref|>text<|/ref|><|det|>[[178, 770, 819, 822]]<|/det|> +Answer: Thank the reviewer so much for reviewing our manuscript. The positive view and valuable questions and suggestions are all highly appreciated. The manuscript has been carefully revised based on the valuable comments. + +<|ref|>text<|/ref|><|det|>[[178, 844, 819, 897]]<|/det|> +1) In the exploration and optimization of the reaction, other bases such TEA, DABCO or Ph3P delivered lower efficiency than DIPEA. A rational for the observation should be provided. Similarly, why did Na3PO4 give the highest yield? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 820, 213]]<|/det|> +Answer: Thank the reviewer very much for the suggestions. In the EDA complex, DIPEA functions as a potent electron donor, while its ability to form the sulfonamide salt with TsCl is hindered by the presence of two bulky iPr groups. Inorganic base was crucial to the reaction, strong base would destroy the stability of the EDA complex, while weak base would decrease the efficiency of HCl elimination step. In this aspect, as a moderate-strength inorganic base, \(\mathrm{Na_3PO_4}\) could give the highest yield. The rational for the observation have been added in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[177, 234, 818, 268]]<|/det|> +2) In the reaction scope study, it seems that electron-rich styrenes are favorable substrates for the process. Would simple vinyl pyrrole, thiophene or furane work? + +<|ref|>text<|/ref|><|det|>[[177, 271, 820, 341]]<|/det|> +Answer: The reviewer's suggestion is gratefully appreciated. We have tried some other electron- rich aromatic heterocyclic compounds as shown below, however, only trace products could be obtained under the standard conditions and significant decomposition of most sulfonyl chlorides occurred during the reactions. + +<|ref|>image<|/ref|><|det|>[[305, 346, 690, 432]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[177, 455, 818, 490]]<|/det|> +3) Furthermore, the proposed reaction mechanism with presumptive radical VI might support the observation that electron-donating groups could stabilize the intermediate. + +<|ref|>text<|/ref|><|det|>[[177, 493, 820, 528]]<|/det|> +Answer: We express our sincere gratitude for the professional and constructive suggestions provided by the reviewer. We agree with your opinion about the proposed reaction mechanism. + +<|ref|>text<|/ref|><|det|>[[177, 548, 477, 563]]<|/det|> +4) Typo: Line 159: please change 'VII' to 'VI'. + +<|ref|>text<|/ref|><|det|>[[177, 567, 818, 601]]<|/det|> +Answer: We appreciate the reviewer very much for carefully reviewing our manuscript. The mistake has been corrected in its right format. + +<|ref|>text<|/ref|><|det|>[[177, 621, 816, 636]]<|/det|> +************************************************************************************ + +<|ref|>text<|/ref|><|det|>[[177, 642, 348, 656]]<|/det|> +Reviewer #3 (comments): + +<|ref|>text<|/ref|><|det|>[[177, 660, 820, 805]]<|/det|> +Jiao and coworkers developed interesting oxidation reaction of styrenes with molecular oxygen. Under radical pathway with photoirradiation, single oxygen atom was selectively inserted between aryl ring and \(\mathrm{C} = \mathrm{C}\) double bond. The reaction is unique and interesting. Functional group compatibility is reasonably good and so the moderate yields in many entries are not problematic. The reaction was restricted to styrene derivatives, but the novelty of the work is sufficient for publication in Nature Commun, in my perspective. The proposed radical mechanism is reasonable based on experimental results as well as precedent reports. On the other hand, there are some unclear points, which should be revised in responses to the requests below. + +<|ref|>text<|/ref|><|det|>[[177, 808, 820, 860]]<|/det|> +Answer: Thank the reviewer very much for reviewing our manuscript. The positive view and valuable questions and suggestions are all highly appreciated. The manuscript and SI have been carefully revised based on the valuable comments. + +<|ref|>text<|/ref|><|det|>[[177, 881, 337, 895]]<|/det|> +Minor revision requests: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 139]]<|/det|> +1) Table 1, entry 11: The reaction proceeded in \(35\%\) yield even without light at \(35~\mathrm{C}\) . The value in entry 11 was higher than entry 12, that is confusing. Is the data correct? If so the basic concept of the work may change completely. I am afraid the value may be wrong. + +<|ref|>text<|/ref|><|det|>[[177, 142, 821, 231]]<|/det|> +Answer: Thank the reviewer very much for reviewing our manuscript and the valuable question. EDA complex also could be activated thermally (J. Am. Chem. Soc. 1987, 109, 2780; Chem. Eur. J. 2015, 21, 8355), so the reaction could proceed in \(35\%\) yield without light at \(35^{\circ}\mathrm{C}\) . However, the stability of the EDA complex was compromised at elevated temperatures, resulting in a significant decrease in yields observed at \(60^{\circ}\mathrm{C}\) . + +<|ref|>text<|/ref|><|det|>[[177, 252, 820, 324]]<|/det|> +2) Experimental detail: In SI, the authors described "quartz tube with a rubber septum" was used for the reaction, but in the photo of the reaction set-up, it seems graceless schlenk tube was used. Is it necessary to use quartz tube? Accurate information for the reaction vessel and the reaction set-up are important for readers. Please check the details once again. + +<|ref|>text<|/ref|><|det|>[[178, 327, 820, 379]]<|/det|> +Answer: We appreciate the reviewer very much for carefully reviewing our manuscript. The oversight on our part is deeply regretted, all of the reactions were conducted in Schlenk tube. The SI has been carefully revised based on the valuable comments. + +<|ref|>text<|/ref|><|det|>[[178, 400, 820, 453]]<|/det|> +3) SI: Table S2, S3, S4, S5: The best data is missing in Table S2, S3, S4, S5 of SI. It would be much better for readers to understand the optimum conditions, by adding the best conditions in each optimization table. + +<|ref|>text<|/ref|><|det|>[[178, 456, 819, 491]]<|/det|> +Answer: Thank the reviewer very much for the kindly suggestion. The best conditions have been added in each optimization table. + +<|ref|>text<|/ref|><|det|>[[177, 511, 820, 582]]<|/det|> +4) Light source: In this study, a white LED (Kessil) was used and no other light source was investigated. Based on the UV-vis data provided, blue LED and/or violet LED may also be useful for the reaction. What is the reason to select white LED for this reaction? Is it essential? Additional data with other light source may be useful for readers. + +<|ref|>text<|/ref|><|det|>[[177, 585, 820, 675]]<|/det|> +Answer: We highly appreciate the reviewer's suggestion which are very helpful for us to improve our manuscript. We opted for a white LED as the light source for the investigation of the reaction due to its inclusion of nearly the entire spectrum within the visible light region. Other light sources were also investigated, and the results were summarized as below. These results have been added in the revised SI. + +<|ref|>image<|/ref|><|det|>[[177, 685, 816, 907]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 103, 819, 140]]<|/det|> +5) The reaction temp: How did authors keep the reaction temp at \(35~\mathrm{C}\) ? Is it the temp observed by irradiating 90W white LED (Kessil) in the reaction set-up? + +<|ref|>text<|/ref|><|det|>[[177, 141, 820, 177]]<|/det|> +Answer: Thank the reviewer very much for the constructive question. The reaction temperature was the observed ambient temp. that irradiated by a 90 W white LED from \(6\mathrm{cm}\) distance. + +<--- Page Split ---> diff --git a/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/images_list.json b/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..ed9bae5bc1bd588cc6575cceebabc76f01c692f3 --- /dev/null +++ b/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,18 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1 miR159 controls cell division and flower opening in rose.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2 miR159 influences transcript accumulation of cytokinin catabolism genes.", + "footnote": [], + "bbox": [], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1ef8b121238d293883c53deaf9b6b0174ed06580 --- /dev/null +++ b/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,976 @@ + +# nature portfolio + +Peer Review File + +Peer Review FilePetal size is controlled by the MYB73/TPL/HDA19- miR159- CKX6 module regulating cytokinin catabolism in Rosa hybrida + +![](images/Figure_1.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The authors are exploring the role of miR159 in regulating cytokinin levels to control petal development in rose, using virus- induced gene silencing to deduce roles for miR159, for the cytokinin oxidase CKX6, and for the transcription factor MYB73. The authors propose that these players control the transition from cell division to cell expansion in the petal, however the rose petal system they are using does not actually allow one to draw conclusions about such a transition. They may, however, with a more careful analysis be able to draw some conclusions about the role of these players in how cytokinin regulates cell division. + +Major concerns: + +1. The authors state that in "petals, cell division mostly ceases before anthesis, and flower opening is largely attributed to cell expansion," using this transition from bud closed to opening as their definition as to when cell division stops and cell expansion begins. However, the primary reference (Yamada et al 2009) the authors use for rose petal development contradicts this concept of petal transition, explicitly stating that for rose, "cell division does not stop at later stages of flower opening." Most interestingly, Yamada et al (Fig. 3) found sharp differences between what occurred for the adaxial and abaxial epidermal cells during petal development. The adaxial cells continued to divide through stage 6 at a fairly consistent rate, such that cell division was a major contributor to the adaxial petal area. In contrast the abaxial cells had largely ceased division by stage 2, well before bud opening, with cell expansion then being a major contributor to the abaxial petal area. Based on this background, the authors cannot infer how cytokinin is regulating the transition from cell division to cell expansion in rose petals. + +2. Although the authors cannot use their study to draw conclusions about the role of cytokinin in regulating the transition from cell division to cell expansion, there is the possibility of exploring the role of cytokinin in regulating cell division itself. For this the authors would need to perform a more careful analysis of the number of cells found in the adaxial and abaxial epidermal cell layers. Specifically, the authors only provide analysis at a single time point (e.g. day five) for their analysis of epidermal cell size in the petals, the size of the cells being suggestive as to whether changes in cytokinin activity is affecting cell division. But the authors do not indicate whether the images are from the adaxial or the abaxial surface. Given the sharp differences in the roles of cell division vs cell expansion for these two surfaces (see above), this is critical information and it would be preferable to provide cell size information for both adaxial and abaxial epidermal cells. In addition, due to the changes in timing of development for the control vs gene silenced petals, one would need to compare the petals at the same developmental stage (i.e. stage 6 at which the petal has fully expanded). From this analysis, the authors could measure cell size and petal area, and then determine the total number of cells per petal for the adaxial and abaxial epidermal layers, thereby indicating how much cytokinin is regulating cell division in the petal. Note that cell size alone is not sufficient to elucidate effects on cell division. Problematically, for their figures, the authors give petal size for fully expanded petals (e.g. days 6 and 7) but cell size at day 5 (before the petals are fully expanded), so the authors cannot directly determine the cell number per petal from the data presented in the manuscript. + +3. miR159 has a well-characterized role in the targeting of Mybs that regulate the response to GA, the best known such role being to suppress their activity so as to facilitate cell + +<--- Page Split ---> + +division. One would thus expect that such Mybs might be under control of miR159 in the rose petal for the same purpose. To this end the authors need to examine more than just CKX6 as a potential target to but also provide expression and cleavage information for the GA Mybs. + +4. The GA-mybs are the conserved targets for miR159 across multiple plant species, so the finding that CKX6 is a target in rose represents a non-conserved target. This raises the question as to how common the miR159-CKX6 pathway is as a means of regulating cytokinin levels. If a decrease in cytokinin levels is a common theme during leaf and petal development in different plant species, then it is likely that the expression of CKX's is regulated at the level of transcription not just through miR159 as the authors propose for rose. The authors thus need to clearly distinguish the effects of miR159 from transcriptional regulation during development of the petal. The authors show relative expression of CKX6 in control vs miR159 silenced lines at a single time point (Fig 5e, 3 days after stage 0). But it is unclear how much CKX6 expression changes over time and to what degree this is affected by silencing miR159. For example, the authors show a heatmap from a transcriptional database (Fig 2d) that expression of CKX6 increases about 80-fold from stage 0 to stage 2, but the effects of silencing miR159 only result in a 3-fold increase in CKX6 expression. The authors need to follow CKX6 expression throughout their developmental timecourse for the control and miR159 silenced lines to determine how much of an effect miR159 has on the regulation of CKX6 expression. + +## Reviewer #2 (Remarks to the Author): + +Jing et al report on the regulation of petal size in roses. They find that miR159 regulates the expression of CKX6, which codes for an enzyme degrading the hormone cytokinin. During organ formation, cytokinin regulates the transition of cells from the division phase to differentiation and growth. It is shown that altering the expression of miR159 or CKX6 alters flowering size in predicted ways, corroborating the regulatory connections between the genes and the concept that the miR159/cytokinin module regulates rose flower size. Furthermore, upstream transcriptional and epigenetic regulators of miR159 expression are detected and their functional relevance is demonstrated. Overall, this is an interesting and new story adding significant new knowledge to the field, the experimental work has been done mostly properly and the article is generally well written. I have some points to be considered. + +## Title + +I think the adjective "Rapid" is not justified as a rapid clearance of cytokinin is not truly shown. The notion "rapid" appears also in abstract and in the main text, it should be considered carefully (the drop in miR159 takes 5 days, line 85, this is not rapid). May be the impact of rose flower size may be mentioned in the title, e.g. add at the end "... and regulates rose flower size" + +## Abstract + +For the second sentence I would argue that the relevance of cytokinin to regulate the transition from cell proliferation to expansion is an established concept, it is well documented in roots and in the shoot meristem, it is not a largely unknown question. Key papers are Werner et al. (Plant Cell 15, 2532- 2550 2003) and Bartrina et al. (Plant Cell 23, 69- 80. 2011), more details on the root meristem can be found for example in work of the Sabatini + +<--- Page Split ---> + +group (Dello loio et al., Science 322, 1380- 1384, 2008). This background should be considered. + +## Introduction + +The introduction section is rather short. A few sentences about cytokinin (metabolism, maybe signaling, regulation of cell cycle and cell proliferation) should be included, as well as some known functions of miR159 (this can be partly shifted from Discussion section). + +Line 37: I doubt that the size of flowers is constant in a given species. There are large differences of flower size between different varieties of species. Please adapt the sentence. + +## Results + +Line 110- 115. The claimed transcript analysis of CKX6 is not shown on Fig. 2 but it would be necessary to include a detailed analysis of the changes occurring during petal development. + +Line 131: What are the canonical miR159 targets? And what makes up a "canonical" target? Some of that can be found in the Discussion but that information should be given in the Introduction. + +Lines 145- 146: citation style changed. I could not find any of the here mentioned publications in the reference section. + +Lines 188- 189: Fig. 7e only shows that RhMYB73 is a transcriptional repressor in general, MIR159 is not included here, right? + +## Figures + +Figs. 1a and b: What has been measured here – the precursor transcript or mature miR159? The y- axis is titled "relative miR159 abundance", but the legend says "pre- miR159 levels". In the Methods section, there is no mentioning of mature miRNA detection. + +Fig. 1e: In the Figure legend, only the P values for \*\*\* and \*\*\*\* are mentioned, but not for \*, which is indicated in this part figure. What exactly is the "flower development progress (d)" shown in Fig. 1c? + +Fig. 2. From where are these data? No source is given in the legend. The RhCKX6 transcript analysis should be more extensive, including a kinetic covering the critical developmental period (currently a GFP fusion gene analysis is shown in Fig. 2). + +Fig. 3e. Please add a quantification of the signals relative to the controls. In the current version the degree of changes cannot be evaluated. + +Fig. 4b Is there information on the degree of changes in relative expression in different phases of flower development? + +Fig. 5 There are large differences in cytokinin content in different measurements. Compare Fig. 5b and 5g, there is a 20- fold difference in the tZ content in TRV. How is that explained? + +Figs. 7a/S8: Please give a more detailed description of what can be seen here. What do "- , +" and "1x, 10x, 100x" mean exactly? + +<--- Page Split ---> + +## Discussion + +DiscussionThe discussion should be more focused, there are sections reporting rather broadly on general knowledge that can be shortened, part of the background should appear in the introduction. + +Line 253. The first heading does not read well, please rephrase. + +Line 257/258ff. The transition from division to differentiation involves "multiple phytohormones". I wonder why here a one- page long summary of other plant hormones is given, which are not considered in this work, while the known facts about cytokinin (see above) are not described. That section should be adapted. + +Line 289, "energetically costly", please explain; the continuation of the sentence is questionably, please think it over. + +Lines 307- 309: It might be worth mentioning that also cytokinin is involved in juvenile phase control (Werner et al., Nature Comm. 12, 5816, 2021) described here to be linked to a miR159- MYB33 module affecting miR156. + +How about the CKX6 genes in other species? Are they predicted targets of miR159? In Arabidopsis? + +Please consider the recent paper of Zou et al. on rose CKX6, putting it in the context of petal dehydration and show its regulation by RaNAP transcription factor (Molecular Horticulture 1, 13, 2021) + +## Methods + +Line 394: "Quantification" instead of "quantitative". + +Line 400. 100 mM 6- BA is a very high, presumably (almost) toxic concentration (usually 1- 5 \(\mu \mathrm{M}\) are used). Please check if that is correct. + +Cytokinin measurements. From how many plants were the samples, how many flowers (in approximation)? It would be good to include a table reporting the results for all cytokinin metabolites measured in the supplements, here the data are limited to few metabolites. + +Information on how pictures (BiFC, LUC) were evaluated is completely missing. + +There are some inconsistencies in units, as both \(\mu \mathrm{g}\) and microgram, \(\mathrm{mg / L}\) , \(\mathrm{ng / ml}\) and \(\mathrm{mg} \times \mathrm{l} \cdot \mathrm{l}\) are used, please unify. + +## Reviewer #3 (Remarks to the Author): + +Review of Rapid clearance of cytokinin controls transition from cell division to expansion during petal development in rose (Rosa hybrida) + +MiR159 is an evolutionarily conserved microRNA that regulates GAMYB transcription factors in angiosperms. Here, the authors report that rose miR159 regulates Cytokinin + +<--- Page Split ---> + +Oxidase/Dehydrogenase 6 (CKX6) to control petal size. The authors use a target mimicry strategy (TRV- STTM159), to sequester and/or degrade miR159, which resulted in flowers with smaller petals that have fewer cells. Among the predicted targets of miR159 that have increased expression levels after inactivating miR159 by STTM159, the authors found CKX6. In turn, using VIGS to silence CKX6 resulted in changes in cytokinin catabolism and larger petals. Furthermore, the authors show that rhMYB73 binds to the MIR159 promoter repressing its expression during flower development. + +In principle, I think that the acquisition of a new target by the evolutionarily conserved miR159 to control petal size in roses is interesting. However, I have concerns about the data supporting the regulation of CKX6 by miR159 and the proposed role of a miR159- CKX6 module. + +Main concerns: + +1- The authors mention that the underlying mechanism controlling the transition from cell proliferation to expansion in leaves remains largely unknown. However, there are known regulators controlling this transition, such as the miR319- regulated TCP (CIN- Like) transcription factors. + +miR319 is similar in sequence to miR159, and target mimicry against miR159 can cross target miR319 (Reichel and Millar, 2015). In addition, miR319- TCP controls petal growth and development (i.e., Nag et al., 2009). Therefore, I think that the authors need to consider the possibility that STTM159 could be affecting petal growth through the modification of the miR319- TCP module. + +The complete miR319/miR159 family of miRNAs in rose (which might contain several members) should be analyzed in STTM159 plants. The analysis of miRNA- targets should also include rose TCP transcription factors that are targets of miR319. + +2- MicroRNAs guide the cleavage of their targets at position 10-11 (Fig 3a). The authors did not find any cut at this position for CKX6, which argues against the regulation by miR159. The authors say that they analyzed CKX6 cleavage in rose petals in the Results section, but in Methods they say that the experiment was performed from 35S:pre- MIR159 transient overexpression plants (tobacco?). The cleavage site should be determined in wt rose petals. + +miR159 is strongly expressed in tobacco leaves, so I'm surprised that the authors could express large amounts of a GFP sensor for a miR159- target (Fig 3). The levels of mature miR159 should be determined in tobacco leaves to show the increase of miR159 after the expression of rose pre- miR159. + +The determination of mature miRNAs by qPCR can be tricky - for example, miRNAs from the same family can have differences in their 3' end, yet they regulate the same targets. It is better to determine miRNA levels by small RNA blots. + +The expression of the sensors in N. benthamiana leaves is patchy which might be caused by RNA silencing (independent of the miRNA). + +Overall, I don't think that the current manuscript shows clear evidence for the regulation of CKX6 by miR159. + +<--- Page Split ---> + +3- Inactivation of miR159 (by target mimicry or mir159a/b knock outs) in Arabidopsis causes pleiotropic developmental defects in leaves and stunted plants. Please, show and describe the plant growth and overall phenotypes of the VIGS lines (STTMIR159, and rhMYB73 and RhCKX6)- silenced lines. Also, indicate the number of plants analyzed in each case, and the distribution of the phenotypes observed (i.e., percentage of plants displaying the selected phenotypes). + +4- For VIGS, authors used fragments of approx. 400 bp for RhMYB73M159 and RhCKX6. These are long fragments. Are the authors confident that other MYBs or CKX genes were not affected? I think using artificial microRNAs would have been a more specific strategy. + +I think it would be important to include the phenotypes of roses overexpressing pre- miR159, which should down- regulate RhCKX6 and increase petal size. This vector is used in the N. benthamiana assays. + +5- The authors predict the regulation of several CKXs by miR159 in rose and arabidopsis (Supplementary Fig 4). The location of a miRNA- target site in a target gene is usually conserved during evolution and not variable as depicted in this figure. There is plenty of experimental information identifying miRNA targets in arabidopsis in publicly available databases. Please use this info to show the empirical data for the regulation by miR159 for the two predicted Arabidopsis targets. + +Other comments: + +1- Please include in the Supplementary Tables the description for the selected rose genes (or the description of their arabidopsis homologues). +2- L78 –“To understand the underlying mechanism of the transition between cell division and cell expansion, we previously conducted a transcriptome deep sequencing (RNA-seq) analysis of short RNAs and transcripts from petals to investigate gene expression profiles during the cell division and expansion phases.” – please include the citation for the article describing the RNAseq analysis of short RNAs and transcripts. + +<--- Page Split ---> + +## Response to Reviewers + +Manuscript No. NCOMMS- 22- 37721 + +Title: Rapid clearance of cytokinin controls transition from cell division to expansion during petal development in rose (Rosa hybrida) + +## Reviewer #1 + +## Comment #1 + +The authors state that in "petals, cell division mostly ceases before anthesis, and flower opening is largely attributed to cell expansion," using this transition from bud closed to opening as their definition as to when cell division stops and cell expansion begins. However, the primary reference (Yamada et al 2009) the authors use for rose petal development contradicts this concept of petal transition, explicitly stating that for rose, "cell division does not stop at later stages of flower opening." Most interestingly, Yamada et al (Fig. 3) found sharp differences between what occurred for the adaxial and abaxial epidermal cells during petal development. The adaxial cells continued to divide through stage 6 at a fairly consistent rate, such that cell division was a major contributor to the adaxial petal area. In contrast the abaxial cells had largely ceased division by stage 2, well before bud opening, with cell expansion then being a major contributor to the abaxial petal area. Based on this background, the authors cannot infer how cytokinin is regulating the transition from cell division to cell expansion in rose petals. + +Although the authors cannot use their study to draw conclusions about the role of cytokinin in regulating the transition from cell division to cell expansion, there is the possibility of exploring the role of cytokinin in regulating cell division itself. For this the authors would need to perform a more careful analysis of the number of cells found in the adaxial and abaxial epidermal cell layers. Specifically, the authors only provide analysis at a single time point (e.g. day five) for their analysis of epidermal cell size in the petals, the size of the cells being suggestive as to whether changes in cytokinin activity is affecting cell division. But the authors do not indicate whether the images are from the adaxial or the abaxial surface. Given the sharp differences in the roles of cell division vs + +<--- Page Split ---> + +cell expansion for these two surfaces (see above), this is critical information and it would be preferable to provide cell size information for both adaxial and abaxial epidermal cells. + +In addition, due to the changes in timing of development for the control vs gene silenced petals, one would need to compare the petals at the same developmental stage (i.e. stage 6 at which the petal has fully expanded). From this analysis, the authors could measure cell size and petal area, and then determine the total number of cells per petal for the adaxial and abaxial epidermal layers, thereby indicating how much cytokinin is regulating cell division in the petal. Note that cell size alone is not sufficient to elucidate effects on cell division. Problematically, for their figures, the authors give petal size for fully expanded petals (e.g. days 6 and 7) but cell size at day 5 (before the petals are fully expanded), so the authors cannot directly determine the cell number per petal from the data presented in the manuscript. + +## RESPONSE + +Thank you for your excellent advice. + +We would like to apologize for any confusion caused by the incomplete and misleading description in our previous version. We would like to clarify that all data presented was based on observations of abaxial epidermal cells. Our previous study utilized scanning electron microscopy to observe the anatomical structure of rose petals. We found that cell number and size of abaxial epidermal cells are closely related to petal size, which is why we focused our analysis on this particular cell type (Ma et al., 2008, Plant Physiology). + +In our previous version, we tried to demonstrate that abaxial epidermal cells in TRV- STTM159 lines entered the expansion stage earlier compared to TRV controls. To this end, we illustrated the cell size on day 5 (Fig.1f) and on the fully opened stage (Supplementary Fig.2b). + +According to your advice, we conducted further experiments, wherein we recorded the number of adaxial and abaxial epidermal cells in TRV controls and different gene silenced lines (TRV- STTM159, TRV- RhCKX6, and TRV- RhMYB73), following the procedure outlined by Yamada et al. (2009). Our findings suggested that silencing of miR159 resulted in a slower increase in the number of adaxial and abaxial epidermal cells, particularly in abaxial epidermal cells. Furthermore, the cell division period was reduced in TRV- STTM159 lines, as the plants in these lines attained full opening earlier than TRV controls. In contrast, silencing of either RhCKX6 or RhMYB73 showed an opposite + +<--- Page Split ---> + +phenotype to TRV- STTM159 lines. + +We added these data in the revised manuscript as Supplemental figure S1; Fig. 1f, g; Fig. 4e, f; and Fig. 8e,f. We also revised the title and our manuscript accordingly to avoid any misleading in the revised version. + +![](images/Figure_2.jpg) + +
Figure 1 miR159 controls cell division and flower opening in rose.
+ +f, g. The cell number of adaxial epidermis (f) and abaxial epidermis (g) in TRV control and TRV- STTM159 petals from days 1 after floral stage 0 to fully opened stage. Data are shown as means \(\pm\) SD from 3 biological replicates (n = 3). + +Please refer to the revised version for other Figures. + +## Comment #2 + +miR159 has a well- characterized role in the targeting of Mybs that regulate the response to GA, the best known such role being to suppress their activity so as to facilitate cell division. One would thus expect that such Mybs might be under control of miR159 in the rose petal for the same purpose. To this end the authors need to examine more than just CKX6 as a potential target to but also provide expression and cleavage information for the GA Mybs. + +## RESPONSE + +Thank you for your advice. According to your suggestion, we isolated the homologues of all seven Arabidopsis GAMYB genes (MYB33, MYB65, MYB81, MYB97, MYB101, MYB104, and MYB120). We predicted miR159 targets in three of them, including RhMYB33, RhMYB65, and RhMYB101. Both RNA- seq and qRT- PCR analysis showed that expression of RhMYB65 and RhMYB101 could not be detected in rose petals in all tested development stages (1 d, 3 d, and 5 d). Expression of RhMYB33 was detectable but was much lower than expression level of RhCKX6. In addition, + +<--- Page Split ---> + +expression of RhMYB33 slightly decreased in petals from 3 d to 7 d. RLM- RACE showed the miR159- dependent cleavage of RhMYB33 transcript in rose petals. We constructed an RhMYB33- Sensor and an RhMYB33m- Sensor constructs by cloning the coding sequence of green fluorescent protein (GFP) in- frame with an intact miR159- target region (for RhMYB33- Sensor) or a mutated miR159- target region (for RhMYB33m- Sensor). We then co- infiltrated each sensor construct in Nicotiana benthamiana leaves with a construct overexpressing the miR159 precursor (pre- MIR159) and detected lower GFP fluorescence from the pre- MIR159+RhMYB33- Sensor combination compared to the Sensor alone, but not from the pre- MIR159+RhMYB33m- Sensor combination. In addition, we tested GAs level in rose petals. Level of GA3 and GA7 was barely detectable, while level of GA1 and GA19 remained stable throughout the developmental time course. + +Based on these data, we considered that GAMYBs- mediated regulation of cell division is insignificant relative to RhCKX6- mediated regulation, although we could not completely exclude the possibility that miR159- RhMYB33 module is involved in regulation of petal cell division in roses. We added these data as Supplemental Figure S7 and discussed this issue in the revised version. + +![PLACEHOLDER_10_0] + + +Supplemental Figure S7 miR159- targeted RhMYB33 and GAs contents in rose petals during petal growth. + +a, Upper panel, schematic diagram of RhMYB33 mRNA. Red box, predicted cleavage site of miR159. Bottom panel, + +<--- Page Split ---> + +identification of cleavage sites using \(5^{\prime}\) RLM- RACE assay in rose petals. The positions of cleavage sites are indicated by arrowheads with the frequency of clones. + +b, Confocal imaging analysis of N. benthamiana leaves 3 days after co- infiltration of pre- MIR159 with RhMYB33- sensor- GFP or RhMYB33m- sensor- GFP, respectively. GFP fluorescence of N. benthamiana leaves 3 days after co- infiltration of the indicated constructs. The experiment was performed independently three times, and representative results are shown. Scale bars, \(5\mathrm{mm}\) . + +c, RT- qPCR analysis of RhMYB33 transcript levels in petals 1, 3, 5 days after stage 0. RhUBI2 was used as an internal control. Data are shown as means \(\pm\) SD from three biological replicates ( \(\mathrm{n} = 3\) ). Different lowercase letters above each bar indicate significant differences according to one- way ANOVA with Tukey's multiple comparisons test ( \(P< 0.05\) ). + +d, GA contents in petals 1, 3, 5 days after stage 0. Data are shown as means \(\pm\) SD from three biological replicates ( \(\mathrm{n} = 3\) ). + +## Comment #3 + +The GA- mybs are the conserved targets for miR159 across multiple plant species, so the finding that CKX6 is a target in rose represents a non- conserved target. This raises the question as to how common the miR159- CKX6 pathway is as a means of regulating cytokinin levels. If a decrease in cytokinin levels is a common theme during leaf and petal development in different plant species, then it is likely that the expression of CKX's is regulated at the level of transcription not just through miR159 as the authors propose for rose. The authors thus need to clearly distinguish the effects of miR159 from transcriptional regulation during development of the petal. The authors show relative expression of CKX6 in control vs miR159 silenced lines at a single time point (Fig 5e, 3 days after stage 0). But it is unclear how much CKX6 expression changes over time and to what degree this is affected by silencing miR159. For example, the authors show a heatmap from a transcriptional database (Fig 2d) that expression of CKX6 increases about 80- fold from stage 0 to stage 2, but the effects of silencing miR159 only result in a 3- fold increase in CKX6 expression. The authors need to follow CKX6 expression throughout their developmental time course for the control and miR159 silenced lines to determine how much of an effect miR159 has on the regulation of CKX6 expression. + +## RESPONSE + +Thank you for your excellent suggestion. We detected expression level of miR159 and RhCKX6 in petals throughout the developmental time course for the TRV control and TRV- STTM159 lines. The results showed that expression of RhCKX6 in TRV- STTM159 lines was significantly higher than TRV control throughout the developmental time course, especially in the earlier period. Meanwhile, + +<--- Page Split ---> + +expression of RhCKX6 increased in TRV- STTM159 lines in the development duration. + +We considered this might be two reasons, 1) the VIGS just knockdown the miR159 instead of knockout. The rest miR159 still functioned to influence accumulation of RhCKX6 transcripts. 2) Besides of miR159- mediated regulation, expression of RhCKX6 might be induced by some unknown factors during petal development as well. + +In addition, we tested the possible miR159- mediated cleavage of CKXs in more plants. We predicted miR159- target site in AtCKX5 (Arabidopsis), MdCKX6 (Malus demestica), and FvCKX6 (Fragaria vesca). We generated GFP- Sensor constructs for AtCKX5 (Arabidopsis), MdCKX6 (Malus demestica), and FvCKX6, and detected miR159- mediated cleavage of these three Sensors. RLM- RACE also confirmed miR159- mediated cleavage of FvCKX6 in petals of Fragaria vesca, indicating that miR159- mediated cleavage of CKXs could be a common regulation pathway. + +Based on these data, we considered miR159 played an essential role in regulation of accumulation of RhCKX6 transcripts, but we could not exclude the possibility that some other currently unknown factors might regulate expression of RhCKX6 as well. + +We added the results as Fig. 2e- g and Supplemental Figure S6, toned down our statement and discussed this issue in the revised version. + +![PLACEHOLDER_12_0] + +
Figure 2 miR159 influences transcript accumulation of cytokinin catabolism genes.
+ +e, f, RT- qPCR analysis of miR159 abundance and RhCKX6 transcript levels in rose petals at 1, 3, 5, and 7 days after stage 0. 5S rRNA was used as an internal control (e). RhUBI2 was used as an internal control (f). Data are shown as means \(\pm \mathrm{SD}\) are shown from three biological replicates ( \(\mathrm{n} = 3\) ). Different lowercase letters above each bar in (e and f) indicate significant differences according to one- way ANOVA with Tukey's multiple comparisons test ( \(P< 0.05\) ). g, RT- qPCR analysis of RhCKX6 transcript levels in petals of TRV control and TRV- STTM159 at 1, 3, and 5 days after stage 0. RhUBI2 was used as an internal control. Data are shown as means \(\pm \mathrm{SD}\) are shown from three biological replicates ( \(\mathrm{n} = 3\) ). Asterisks indicate statistically significant differences (two- sided Student's \(t\) - test, \(*\) , \(P< 0.05\) ; \(**\) , \(P< 0.01\) ; ns, no significant difference). + +<--- Page Split ---> +![PLACEHOLDER_13_0] + + +Supplemental Figure S6 Validation of miR159-targeted CKX in other species. + +a, b, c, Confocal imaging analysis of N. benthamiana leaves 3 days after co- infiltration of pre- MIR159 with AtCKX5- sensor- GFP or AtCKX5m- sensor- GFP (a); MdCKX6- sensor- GFP or MdCKX6m- sensor- GFP (b); FvCKX6- sensor- GFP or FvCKX6m- sensor- GFP (c). + +d, Validation of miR159- targeted cleavage of FvCKX6. Upper panel, schematic diagram of FvCKX6 mRNA. Red box, predicted cleavage site of miR159. Bottom panel, identification of cleavage sites using 5' RLM- RACE assay in strawberry petals. The positions of cleavage sites are indicated by arrowheads with the frequency of clones. + +<--- Page Split ---> + +## Reviewer #2 + +## Comment #1 + +Title + +I think the adjective "Rapid" is not justified as a rapid clearance of cytokinin is not truly shown. The notion "rapid" appears also in abstract and in the main text, it should be considered carefully (the drop in miR159 takes 5 days, line 85, this is not rapid). May be the impact of rose flower size may be mentioned in the title, e.g. add at the end "... and regulates rose flower size" + +## RESPONSE + +Many thanks for your excellent advice. As your suggestion, we have revised the title to "In rose, miR159 regulates petal cell division by modulating cytokinin catabolism". + +## Comment #2 + +Abstract + +For the second sentence I would argue that the relevance of cytokinin to regulate the transition from cell proliferation to expansion is an established concept, it is well documented in roots and in the shoot meristem, it is not a largely unknown question. Key papers are Werner et al. (Plant Cell 15, 2532- 2550 2003) and Bartrina et al. (Plant Cell 23, 69- 80. 2011), more details on the root meristem can be found for example in work of the Sabatini group (Dello Ioi o et al., Science 322, 1380- 1384, 2008). This background should be considered. + +## RESPONSE + +Many thanks for your excellent comments, which makes our description more exact. In abstract, we have edited the description. In addition, we have revised our Introduction section by adding the information of the key papers you suggested. + +## Comment #3 + +Introduction + +The introduction section is rather short. A few sentences about cytokinin (metabolism, maybe signaling, regulation of cell cycle and cell proliferation) should be included, as well as some known + +<--- Page Split ---> + +functions of miR159 (this can be partly shifted from Discussion section). + +Line 37: I doubt that the size of flowers is constant in a given species. There are large differences of flower size between different varieties of species. Please adapt the sentence. + +## RESPONSE + +Many thanks for your advice. We have revised the Introduction section by adding the information of cytokinin and function of miR159. + +We have deleted the sentence "In plants, the size of flowers and petals is constant within a certain species, but varies across different species" in the revised version. + +## Comment #4 + +Results + +Line 110- 115. The claimed transcript analysis of CKX6 is not shown on Fig. 2 but it would be necessary to include a detailed analysis of the changes occurring during petal development. + +## RESPONSE + +Thank you for your advice. We would like to apologize for the missing data. We have added the expression level of RhCKX6 in Fig. 2f in the revised version. + +## Comment #5 + +Line 131: What are the canonical miR159 targets? And what makes up a "canonical" target? Some of that can be found in the Discussion but that information should be given in the Introduction. + +## RESPONSE + +Many thanks for your suggestions. As your suggested, we have added the relevant description of the canonical miR159 targets in the Introduction section in the revised version. + +## Comment #6 + +Lines 145- 146: citation style changed. I could not find any of the here mentioned publications in the reference section. + +<--- Page Split ---> + +## RESPONSE + +Thank you for your advice. We would like to apologize for this mistake. We have corrected the citation and the Reference list. + +## Comment #7 + +Lines 188- 189: Fig. 7e only shows that RhMYB73 is a transcriptional repressor in general, MIR159 is not included here, right? + +## RESPONSE + +Thank you for pointing this out. As you mentioned, Fig. 7e only shows that RhMYB73 is a transcriptional repressor in general, MIR159 is not included here. We have corrected the description in the revised version. + +## Comment #8 + +Figures + +Figs. 1a and b: What has been measured here – the precursor transcript or mature miR159? The y- axis is titled “relative miR159 abundance”, but the legend says “pre- MIR159 levels”. In the Methods section, there is no mentioning of mature miRNA detection. + +Fig. 1e: In the Figure legend, only the P values for \*\*\* and \*\*\*\* are mentioned, but not for \*, which is indicated in this part figure. What exactly is the “flower development progress (d)” shown in Fig. 1c? + +## RESPONSE + +Thank you for your guidance. We would like to apologize for this mistake. Actually, both Figure 1a and b presented the mature miR159 abundance. We replaced the Figure 1a as the Northern Blot detection of mature miR159 in the revised version and moved the original Figure 1a to Supplementary Figure 2a. We added the methods of Northern Blot and qRT- PCR of mature miR159 in the Methods section in the revised version. We also revised the Figure legend and mentioned ‘\*’. The “flower development progress (d)” is the period of different stage of flower opening. We have updated the y- axis label of Figure 1c from “flower development progress (d)” to “Period of different + +<--- Page Split ---> + +stage of flower opening (d)" to more accurately represent the data. The y- axis label of Figure 4c, 6b, 8b, and Supplemental Fig. S10b were revised accordingly. + +## Comment #9 + +Fig. 2. From where are these data? No source is given in the legend. The RhCKX6 transcript analysis should be more extensive, including a kinetic covering the critical developmental period (currently a GFP fusion gene analysis is shown in Fig. 2). + +## RESPONSE + +Thank you for your guidance. We have included the source information in the Legend of Figure 2 and added the expression of the RhCKX6 gene in petals during petal development in Fig. 2f in the revised version. + +## Comment #10 + +Fig. 3e. Please add a quantification of the signals relative to the controls. In the current version the degree of changes cannot be evaluated. + +## RESPONSE + +Thank you for your guidance. We have added the quantification of the signals relative to the controls in Fig. 3d in the revised version. + +## Comment #11 + +Fig. 4b Is there information on the degree of changes in relative expression in different phases of flower development? + +## RESPONSE + +Thank you for your guidance. Fig. 4b is the expression of CKX6 in CKX6- silencing plants (TRV- RhCKX6) and control (TRV), which is test the degree of CKX6- silencing. We have added the expression of the RhCKX6 gene in petals during petal development in Fig. 2f in the revised version. + +<--- Page Split ---> + +## Comment #12 + +Fig. 5 There are large differences in cytokinin content in different measurements. Compare Fig. 5b and 5g, there is a 20- fold difference in the tZ content in TRV. How is that explained? + +## RESPONSE + +Thank you for pointing this out. The difference in tZ content observed in the TRV shown in Fig. 5b and 5g was due to the difference in the sampling time. In Fig. 5b, the petals were sampled for the determination of tZ content 5 days after stage 0, whereas in Fig. 5g, the petals were sampled 3 days after stage 0. According to Fig. 6a, the tZ content in the petals significantly reduces on the 5th day after stage 0, as compared to the 1st day. It is noteworthy that the petals were sampled on the 3rd day after stage 0 in Fig. 5g because the silencing of miR159 caused a shortened cell division period. We have revised the relevant description to avoid any misleading. + +## Comment #13 + +Fig. 7a/S8: Please give a more detailed description of what can be seen here. What do “- , +” and “1x, 10x, 100x” mean exactly? + +## RESPONSE + +Thank you for your guidance. We have added the description of “- , +” and “1x, 10x, 100x” in Figs. 7a/S11 legends. + +## Comment #14 + +Discussion + +The discussion should be more focused, there are sections reporting rather broadly on general knowledge that can be shortened, part of the background should appear in the introduction. + +Line 253. The first heading does not read well, please rephrase. + +## RESPONSE + +Many thanks for your excellent advice. We have revised the Discussion section according to your guidance. We deleted some general information and moved part of the background to the Introduction section. We have revised the first heading to “Cytokinin accumulation is vital to lateral + +<--- Page Split ---> + +organ development through controlling the duration of cell division". + +## Comment #15 + +Comment #15Line 257/258ff. The transition from division to differentiation involves "multiple phytohormones". I wonder why here a one- page long summary of other plant hormones is given, which are not considered in this work, while the known facts about cytokinin (see above) are not described. That section should be adapted. + +## RESPONSE + +RESPONSEMany thanks for your advice. We have deleted the un- relevant description and made it more focused on cytokinin. + +## Comment #16 + +Comment #16Line 289, "energetically costly", please explain; the continuation of the sentence is questionably, please think it over. + +## RESPONSE + +RESPONSEMany thanks for your advice. The phrase "energetically cost" is used to describe the negative regulation of cytokinin levels by miR159- mediated cleavage of RhCKX6. This regulatory pattern involves RhCKX6 transcripts being continuously produced, followed by their subsequent cleavage by miR159 in the early stages of petal development. As a result, considerable energy is expended to generate these transcripts, making the process energetically costly. We deleted this sentence to avoid any misleading in the revised version. + +## Comment #17 + +Comment #17Lines 307- 309: It might be worth mentioning that also cytokinin is involved in juvenile phase control (Werner et al., Nature Comm. 12, 5816, 2021) described here to be linked to a miR159- MYB33 module affecting miR156. + +## RESPONSE + +RESPONSEMany thanks for your advice. We have revised our Discussion section by adding the information of + +<--- Page Split ---> + +the report of Werner et al. (2021). + +## Comment #18 + +How about the CKX6 genes in other species? Are they predicted targets of miR159? In Arabidopsis? + +## RESPONSE + +Thank you for your guidance. + +We conducted further experiments to examine the possibility of miR159- mediated cleavage of CKXs in other plant species. Using bioinformatics analysis, we identified a miR159- target site in AtCKX5 (Arabidopsis), MdCKX6 (Malus demestica), and FvCKX6 (Fragaria vesca). We then created GFP- Sensor constructs for each of these CKXs, following the procedure described in our response to Comment #3 of reviewer 1. Our results revealed that miR159- mediated cleavage occurred for all three Sensors. To confirm this result, we performed RLM- RACE and found evidence of cleavage in FvCKX6 in the petals of Fragaria vesca. These findings suggest that miR159- mediated cleavage of CKXs represents a common regulation pathway across different plant species. + +We have added these results as Supplemental Figure S6, and mentioned the results in the revised version. + +## Comment #19 + +Please consider the recent paper of Zou et al. on rose CKX6, putting it in the context of petal dehydration and show its regulation by RaNAP transcription factor (Molecular Horticulture 1, 13, 2021) + +## RESPONSE + +Many thanks for your advice. We have added the relevant information of the report of Zou et al. (2021) in the Discussion section. + +## Comment #20 + +Methods + +Line 394: "Quantification" instead of "Quantitative". + +<--- Page Split ---> + +## RESPONSE + +Many thanks for your advice. We have replaced "Quantitative" with "Quantification". + +## Comment #21 + +Line 400. \(100\mathrm{mM}6\mathrm{- BA}\) is a very high, presumably (almost) toxic concentration (usually \(1 - 5\mu \mathrm{M}\) are used). Please check if that is correct. + +## RESPONSE + +Thank you for pointing this out. We would like to apologize for this mistake. It should be \(100\mu \mathrm{M}\) here. The concentration of 6- BA used and treatment procedure were followed a previous report (Wu et al., 2017). We have corrected the description and added relevant reference. + +## References + +Lin Wu, Nan Ma, Yangchao Jia, Yi Zhang, Ming Feng, Cai- Zhong Jiang, Chao Ma, Junping Gao. An ethylene- induced regulatory module delays flower senescence by regulating cytokinin content. Plant Physiology, 2017, 173: 853- 862. + +## Comment #22 + +Cytokinin measurements. From how many plants were the samples, how many flowers (in approximation)? It would be good to include a table reporting the results for all cytokinin metabolites measured in the supplements, here the data are limited to few metabolites. + +## RESPONSE + +Many thanks for your advice. To conduct the cytokinin test, we collected five flowers from five plants, and mixed them together. The mixed flowers were then divided into three separate samples for testing. We have added the sampling information in the Method section. In addition, we have added the results for all cytokinin metabolites measured as Supplementary Table S3 in the revised version. + +## Comment #23 + +Information on how pictures (BiFC, LUC) were evaluated is completely missing. + +<--- Page Split ---> + +## RESPONSE + +Many thanks for your advice. These information have been added in the revised Methods of Supplemental files. + +## Comment #24 + +There are some inconsistencies in units, as both \(\mu \mathrm{g}\) and microgram, \(\mathrm{mg / L}\) , \(\mathrm{ng / ml}\) and \(\mathrm{mg x 1 - 1}\) are used, please unify. + +## RESPONSE + +Many thanks for your advice. We have unified the units in the revised manuscript. + +## Reviewer #3 + +## Comment #1 + +The authors mention that the underlying mechanism controlling the transition from cell proliferation to expansion in leaves remains largely unknown. However, there are known regulators controlling this transition, such as the miR319- regulated TCP (CIN- Like) transcription factors. miR319 is similar in sequence to miR159, and target mimicry against miR159 can cross target miR319 (Reichel and Millar, 2015). In addition, miR319- TCP controls petal growth and development (i.e., Nag et al., 2009). Therefore, I think that the authors need to consider the possibility that STTM159 could be affecting petal growth through the modification of the miR319- TCP module. The complete miR319/miR159 family of miRNAs in rose (which might contain several members) should be analyzed in STTM159 plants. The analysis of miRNA- targets should also include rose TCP transcription factors that are targets of miR319. + +## RESPONSE + +Thank you for your excellent advice. According to your valuable suggestion, we have revised our statement, and now we have included the relevant reference of miR319- TCP in the revised version of our manuscript. Furthermore, we conducted Northern blot and qRT- PCR experiments to detect the levels of mature miR159 and miR319 in rose petals during the developmental time course. The results of our Northern blot revealed a significant reduction in miR159 levels from day 1 to day 5, + +<--- Page Split ---> + +whereas miR319 levels remained relatively constant from day 1 to day 3 and decreased on day 5. Our qRT- PCR data indicated that the expression level of miR319 in rose petals was much lower than that of miR159 from day 1 to day 5. These results were consistent with our previous miRNA- seq analysis of rose petals during earlier developmental stages (Pei et al., 2013). + +In Arabidopsis, miR319/TCPs controls floral organ morphology. Expression of the miR319- resistant form of TCP4 under the control of the petal- and stamen- specific AP3 promoter led to a complete absence of petals and stamens (Nag et al., 2009). + +After analyzing our RNA- seq data, we have found that the expression levels of TCP2, TCP4, and TCP4- x1, which are targeted by miR319, were not significantly altered in the petals of the miR159- silenced lines. Upon further confirmation using qRT- PCR, we have determined that TCP2/4/4- x1 expression levels remained unchanged in the petals of the miR159- silenced lines. + +We have added relevant results as Figure1a and Supplementary Figure S8, and discussed the possible role of miR319/TCPs in the Discussion section. + +![PLACEHOLDER_23_0] + + +## Supplemental Figure S8 Northern Blot of miR319 and expression of TCP genes in petals of miR159-silenced lines. + +a, RT-qPCR analysis of miR159 and miR319 levels in rose petals (1, 3 and 5 days after stage 0). Data are shown as means \(\pm\) SD from four biological replicates (n=3). 55 rRNA was used as an internal control. Asterisks indicate statistically significant differences (two- sided Student's \(t\) - test, \*, \(P < 0.05\) ; \*\*, \(P < 0.01\) ; \*\*\*, \(P < 0.001\) ; ns, no significant difference). + +b, Northern blotting analysis of miR319 abundance in rose petals 1, 3, and 5 day after floral bud reached stage 0. U6 was used as control. + +c, Heatmap analysis of miR159 and miR319 abundance in rose petals at stage 0 and stage 2. + +<--- Page Split ---> + +d, RT-qPCR analysis of RhTCPs in TRV- STTM159. RhUBI2 was used as an internal control. Data are shown as means \(\pm\) SD from three biological replicates ( \(\mathrm{n} = 3\) ). + +## References + +Haixia Pei, Nan Ma, Jiwei Chen, Yi Zheng, Ji Tian, Jing Li, Shuai Zhang, Zhangjun Fei, Junping Gao. Integrative analysis of miRNA and mRNA profiles in response to ethylene in rose petals during flower opening. PLoS One, 2013, 8: e64290. Anwesha Nag, Stacey King, & Thomas Jack. miR319a targeting of TCP4 is critical for petal growth and development in Arabidopsis. Proc. Natl Acad. Sci. USA, 2009, 106: 22534- 22539. + +## Comment #2 + +1) MicroRNAs guide the cleavage of their targets at position 10-11 (Fig 3a). The authors did not find any cut at this position for CKX6, which argues against the regulation by miR159. The authors say that they analyzed CKX6 cleavage in rose petals in the Results section, but in Methods they say that the experiment was performed from 35S:pre-MIR159 transient overexpression plants (tobacco?). The cleavage site should be determined in wt rose petals. + +2) miR159 is strongly expressed in tobacco leaves, so I'm surprised that the authors could express large amounts of a GFP sensor for a miR159-target (Fig 3). The levels of mature miR159 should be determined in tobacco leaves to show the increase of miR159 after the expression of rose pre-miR159. The expression of the sensors in N. benthamiana leaves is patchy which might be caused by RNA silencing (independent of the miRNA). + +3) The determination of mature miRNAs by qPCR can be tricky – for example, miRNAs from the same family can have differences in their 3' end, yet they regulate the same targets. It is better to determine miRNA levels by small RNA blots. + +Overall, I don't think that the current manuscript shows clear evidence for the regulation of CKX6 by miR159. + +## RESPONSE + +Thank you for your excellent advice. + +1) We would like to apologize for this mistake. For Figure 3a, the RLM-RACE was performed using rose petals and we corrected it in the revised version. According to your advice, we sequenced more + +<--- Page Split ---> + +clones for RLM- RACE of RhCKX6 in rose petals. In addition, we predicted miR159- target site in FvCKX6 (Fragaria vesca). RLM- RACE supported the miR159- mediated cleavage of FvCKX6 in petals of Fragaria vesca. These results indicated that miR159- mediated cleavage of CKX6 could be a common regulation pathway. + +![PLACEHOLDER_25_0] + + +## Supplemental Figure S6 miR159 targets FvCKX6 in planta. + +a, Confocal imaging analysis of N. benthamiana leaves 3 days after co- infiltration of pre- MIR159 with FvCKX6- sensor- GFP or FvCKX6m- sensor- GFP. + +b, Validation of miR159- targeted cleavage of FvCKX6. Upper panel, schematic diagram of FvCKX6 mRNA. Red box, predicted cleavage site of miR159. Bottom panel, identification of cleavage sites using 5' RLM- RACE assay in strawberry petals. The positions of cleavage sites are indicated by arrowheads with the frequency of clones. + +2) According to your suggestions, we detected the level of mature miR159 in tobacco leaves overexpressed rose pre-miR159. The data indicates that the abundance of mature miR159 in tobacco leaves expressing pSuper:pre-MIR159 was significantly higher as compared to those expressing pSuper empty vector. + +To prevent gene silencing, a P19 silencing suppressor was co- infiltrated in all combinations in the GFP- Sensor test. The intensity of GFP fluorescence was found to reduce in the pSuper:pre- MIR159+RhCKX6- Sensor combination, but not in the pSuper:pre- MIR159+RhCKX6m- Sensor combination (Fig. 3b). This supports that the decrease in intensity of GFP fluorescence was due to cleavage of RhCKX6- Sensor caused by miR159. + +<--- Page Split ---> +![PLACEHOLDER_26_0] + + +## The expression of mature miR159 in tobacco leaves overexpressed rose pre-miR159 + +RT- qPCR analysis of the mature miR159 in tobacco leaves overexpressed rose pre- miR159. Data are shown as means \(\pm \mathrm{SD}\) from four biological replicates \((n = 3)\) . 5S rRNA was used as an internal control. + +3) As you suggested, the levels of mature miR159 and miR319 were measured in rose petals throughout petal growth using Northern blot analysis. The results revealed a significant reduction in miR159 levels from day 1 to day 5, whereas miR319 levels remained relatively constant from day 1 to day 3 and decreased on day 5. + +Based on the data, it can be inferred that miR159 may have a regulatory role in the accumulation of RhCKX6 transcript levels in rose petals. + +We have added these relevant results as in Figure1a, Supplemental Figure S6 and Supplementary Figure S8, and revised relevant description in the revised manuscript. + +## Comment #3 + +Inactivation of miR159 (by target mimicry or mir159a/b knock outs) in Arabidopsis causes pleiotropic developmental defects in leaves and stunted plants. Please, show and describe the plant growth and overall phenotypes of the VIGS lines (STTMIR159, and rhMYB73 and RhCKX6)- silenced lines. Also, indicate the number of plants analyzed in each case, and the distribution of the phenotypes observed (i.e., percentage of plants displaying the selected phenotypes). + +## RESPONSE + +Thank you for your advice. For VIGS, the tissue- cultured plantlets were used for Agrobacterium + +<--- Page Split ---> + +mediated infection as described before (Sha et al., 2014; Tian et al., 2014; Chen et al., 2021). Since TRV virus just moved upward and induced gene silencing in the newly grown leaves and flowers after infiltration, we could only observe the phenotypes in these newly emerged leaves and flowers. We did not found that there are stunted newly emerged leaves and plants in TRV- STTM159, TRV- RhCKX6 and TRV- RhMYB73 silencing lines compared with control (TRV line). According to your valuable suggestions, we described the number of plants displaying the selected phenotypes for each VIGS lines in the VIGS method. + +## References + +Aihua Sha, Jinping Zhao, Kangquan Yin, Yang Tang, Yan Wang, Xiang Wei, Yiguo Hong, Yule Liu, Virus- Based MicroRNA Silencing in Plants, Plant Physiology, 2014, 164: 36- 47 Ji Tian, Haixia Pei, Shuai Zhang, Jiwei Chen, Wen Chen, Ruoyun Yang, Yonglu Meng, Jie You, Junping Gao, Nan Ma\*, TRV- GFP: a modified Tobacco rattle virus vector for efficient and visualizable analysis of gene function, Journal of Experimental Botany, 2014, 65: 311- 322. Jiwei Chen, Yang Li, Yonghong Li, Yuqi Li, Yi Wang, Chuyan Jiang, Patrick Choisy, Tao Xu, Youming Cai, Dong Pei, Cai- Zhong Jiang, Su- Sheng Gan, Junping Gao, Nan Ma. AUXIN RESPONSE FACTOR 18- HISTONE DEACETYLASE 6 module regulates floral organ identity in rose (Rosa hybrida). Plant Physiology, 2021, 186: 1074- 1087. + +## Comment #4 + +For VIGS, authors used fragments of approx. 400 bp for RhMYB73 miR159 and RhCKX6. These are long fragments. Are the authors confident that other MYBs or CKX genes were not affected? I think using artificial microRNAs would have been a more specific strategy. + +## RESPONSE + +Thank you for your excellent advice. For VIGS, the gene fragment insert is usually in the range of 300- 500 nucleotides to ensure efficient silencing of endogenous genes (Burch- Smith et al., 2004; Senthil- Kumar & Mysor, 2011). We chose the gene- specific UTR region to construct the TRV- MYB73 and TRV- CKX6 to avoid cross- silencing. According to your suggestions, we tested expression of two MYBs (RhMYB70/77), which are close to RhMYB73, in RhMYB73- silenced lines. Similarly, we tested the expression of two CKXs + +<--- Page Split ---> + +(RhCKX1/5), which are close to RhCKX6, in RhCKX6- silenced lines. We didn't find significant change of expression of RhMYB70/77 in RhMYB73- silenced lines compared to TRV control, indicating that RhMYB73 was specifically silenced. Similarly, the results indicated that RhCKX6 was specifically silenced. We added these results as Supplemental Figure S9 and Supplemental Figure S12d, e. + +![PLACEHOLDER_28_0] + + +## Supplemental Figure S9 Expression of RhCKX1 and RhCKX5 in TRV and RhCKX6-silenced lines. + +a, Schematic representation of the gene-specific fragment of RhCKX6 for construction of the TRV- CKX6 vector. b, Expression of RhCKX1 and RhCKX5 in TRV and RhCKX6- silenced plants. RhUBI2 was used as an internal control. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \((\mathrm{n} = 3)\) (two- sided Student's \(t\) - test, ns, no significant difference). + +![PLACEHOLDER_28_1] + + +## Supplemental Figure S12 Characterization of RhMYB73. + +d, Schematic representation of the gene- specific fragment of RhMYB73 for construction of the TRV- MYB73 vector. e, Expression of RhMYB70 and RhMYB77 in RhMYB73- silenced plants. RhUBI2 was used as an internal control. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \((\mathrm{n} = 3)\) (two- sided Student's \(t\) - test, ns, no significant difference). + +Meanwhile, we agreed with you that artificial microRNAs could be a more specific strategy, but we could not generate stable transgenic artificial miR159 lines in a short time. + +## References + +<--- Page Split ---> + +Tessa M. Burch- Smith, Jeffrey C. Anderson, Gregory B. Martin, S. P. Dinesh- Kumar. Applications and advantages of virus- induced gene silencing for gene function studies in plants. The Plant Journal, 2004, 39: 734- 746. + +Muthappa Senthil- Kumar, Kirankumar S. Mysor. New dimensions for VIGS in plant functional genomics. Trends in Plant Science, 2011, 16: 656- 665. + +## Comment #5 + +I think it would be important to include the phenotypes of roses overexpressing pre- miR159, which should down- regulate RhCKX6 and increase petal size. This vector is used in the N. benthamiana assays. + +## RESPONSE + +Thank you for your excellent advice. We conducted an experiment to investigate the impact of pre- miR159 overexpression on the size of rose petals. The study was based on the methods described in a previous publication (Liang et al., 2020, Plant Cell). Our findings revealed that overexpression of pre- miR159 resulted in larger petals compared to control plants and also extended the duration of cell division (from S0 to S2). + +We added these results as Supplemental Figure S10. + +![PLACEHOLDER_29_0] + + +<--- Page Split ---> + +## Supplemental Figure S10 Overexpression of MIR159 in rose petals. + +a,b, Flower opening progression of Control and MIR159- OE plants. The experiments were performed independently twice with similar results, and one representative set of results is shown. Scale bars, \(2\mathrm{cm}\) . Data are shown as means \(\pm \mathrm{SD}\) from 10 biological replicates \(\mathrm{(n = 10)}\) in b. + +c, RT- qPCR analysis of miR159 abundance and RhCKX6 transcript levels in petals of Control and MIR159- OE plants. 5S rRNA was used as an internal control of miR159. RhUBI2 was used as an internal control of RhCKX6. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \(\mathrm{(n = 3)}\) . + +d, Petal size of Control and MIR159- OE plants at the fully opened stage. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \(\mathrm{(n = 3)}\) . The numbers below the images indicate the petal size. Scale bar, \(1\mathrm{cm}\) . (two- sided Student's \(t\) - test, \(^{*},P< 0.05\) ; \(^{**}P< 0.01\) ). + +## Comment #6 + +The authors predict the regulation of several CKXs by miR159 in rose and arabidopsis (Supplementary Fig 4). The location of a miRNA- target site in a target gene is usually conserved during evolution and not variable as depicted in this figure. There is plenty of experimental information identifying miRNA targets in arabidopsis in publicly available databases. Please use this info to show the empirical data for the regulation by miR159 for the two predicted Arabidopsis targets. + +## RESPONSE + +Thank you for your guidance. We searched the public database for the regulation by miR159 for the two predicted Arabidopsis targets. We could found these two targets in the miR159 target survey but we failed to find the change of expression level of these two targets in miR159abc mutant. To test whether miR159- mediated cleavage of CKXs is a common regulatory pathway, we predicted miR159- target site in FvCKX6 (Fragaria vescac) as well. RLM- RACE confirmed the miR159- mediated cleavage of FvCKX6 in petals of Fragaria vescac, indicating that miR159- mediated cleavage of CKXs might be a common regulation pathway in petals. Supplemental Figure S6 and revised relevant description in the revised manuscript. + +## Comment #7 + +Other comments: + +Please include in the Supplementary Tables the description for the selected rose genes (or the + +<--- Page Split ---> + +description of their arabidopsis homologues). + +## RESPONSE + +Thank you for your advice. We have added the description for the selected genes in Rosa hybrid, Arabidopsis, Malus demestica, and Fragaria vesca in Supplementary Table S7. + +## Comment #8 + +L78 - "To understand the underlying mechanism of the transition between cell division and cell expansion, we previously conducted a transcriptome deep sequencing (RNA- seq) analysis of short RNAs and transcripts from petals to investigate gene expression profiles during the cell division and expansion phases." - please include the citation for the article describing the RNAseq analysis of short RNAs and transcripts. + +## RESPONSE + +Thank you for your advice. We have added the citation for describing the RNA- seq analysis of short RNAs and transcripts in the revised Method section. + +## References + +Ben Langmead, Cole Trapnell, Mihai Pop, Steven Salzberg. Ultrafast and memoryefficient alignment of short DNA sequences to the human genome. Genome Biology, 2009, 10: R25. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The authors have added the appropriate data and made the appropriate text revisions to address my previous concerns. + +## Reviewer #2 (Remarks to the Author): + +The manuscript by Jing et al. on the role of miR159 in regulating rose petal size has been improved significantly. Most of my points have been addressed. New data have been added which resolves previously open questions. However, I still have some remarks on the previous parts and, in particular, on some of the newly added sections. While the science looks sound to me the description of the results and their interpretation is sometimes not precise enough, which might be due to language problems. I think the authors need help in this matter. + +## Title + +The new title is improved but does in my opinion not match exactly the topic of the manuscript as miR159 appears not to regulate cell division per se but rather the transition from cell division to differentiation. Some suggestions: In rose, petal size is regulated by the MYB73/TPL/HDA19- miR156- CKX6 module In rose, petal size is controlled by the MYB73/TPL/HDA19- miR156- CKX6 module regulating (cell number through) cytokinin catabolism In rose, the MYB73/TPL/HDA19- miR156- CKX6 module regulates the transition from cell division to differentiation and growth and thus petal size + +## Abstract + +Line 22, "earlier cytokinin clearance" rather than "precocious cytokinin clearance", furthermore an "a" is missing "leading to 'a' shortened cell division period". Line 23, it is not the cell division itself that is prolonged but the "developmental cell division period". The reference to cell division instead of cell division period/cell division phase occurs at several occasions in the whole manuscript. Line 28, Instead of "correct timing of cell division and organ size" it is rather the "correct timing of the exit from the cell division phase and thus the regulation of organ size ..." + +## Introduction + +Line 35, The references do not reflect the mentioned "century- long fascination for size regulation of organisms". Line 37, "stepwise" should be deleted as these phases are dynamically linked Line 42, the number of cell is determined by the number of divisions, not by the rate of cell proliferation Line 46, precise what "arrest front" is meant here. Of cell division? Line 47, cytokinin takes a small "c" Line 59, "serval" is "several" There are numerous others of these small mistakes which I do not list all. Line 83 in a heading it is again not the "duration of cell division" which is controlled by miR159 but the duration of "cell division phase", and again in line 174, and in line 338 Line 122, I do not see the term "zeatin biosynthesis" in Fig. 2a Line 207, "cell numbers of cell numbers", please correct + +<--- Page Split ---> + +Line 211, "rapid clearance" was not shown + +## Discussion + +The first part of the Discussion describes size regulation of Arabidopsis leaves and maize by other hormones. While this is interesting it does not fit here, it may be used (in a short version) in the Introduction to describe already known systems of organ size regulation or later in the Discussion as a comparison. Start the Discussion with your own results. It should be concise, highlight the novelties of the findings and put these into perspective. + +In the reporting summary under Data analysis: "secondary structure" instead of "second structure" + +## Reviewer #3 (Remarks to the Author): + +The authors conducted additional experiments to generate new data. The revised manuscript has improved significantly. + +Specific comments: + +Figure S2c: The structure of the precursor is truncated and the miRNA has less than 21nt - more sequence needs to be added. + +Fig S8b: The authors show a blot to detect miR319. However, since miR319 and miR159 share a similar sequence, and miR319 is expressed at lower levels compared to miR159, it is likely that the blot is detecting miR159 through cross- hybridization instead of miR319. + +<--- Page Split ---> + +# Response to Reviewers + +Manuscript No. NCOMMS- 22- 37721 + +Title: In rose, miR159 regulates petal cell division by modulating cytokinin catabolism + +# Reviewer #1 + +## COMMENT + +The authors have added the appropriate data and made the appropriate text revisions to address my previous concerns. + +## RESPONSE + +Many thanks for your kind comment. + +<--- Page Split ---> + +## Reviewer #2 + +## COMMENT #1 + +The manuscript by Jing et al. on the role of miR159 in regulating rose petal size has been improved significantly. Most of my points have been addressed. New data have been added which resolves previously open questions. + +However, I still have some remarks on the previous parts and, in particular, on some of the newly added sections. While the science looks sound to me the description of the results and their interpretation is sometimes not precise enough, which might be due to language problems. I think the authors need help in this matter. + +## RESPONSE + +Thank you for your valuable advice. We have carefully revised our manuscript according to your suggestions and asked a professional scientific editing service to enhance the quality of writing and precision of interpretation (https://planteditors.com/). + +## COMMENT #2 + +The new title is improved but does in my opinion not match exactly the topic of the manuscript as miR159 appears not to regulate cell division per se but rather the transition from cell division to differentiation. Some suggestions: + +In rose, petal size is regulated by the MYB73/TPL/HDA19- miR159- CKX6 module. + +In rose, petal size is controlled by the MYB73/TPL/HDA19- miR159- CKX6 module regulating cytokinin catabolism. + +In rose, the MYB73/TPL/HDA19- miR159- CKX6 module regulates the transition from cell division to differentiation and growth and thus petal size. + +## RESPONSE + +Thank you for your excellent suggestions. We revised the title of our manuscript as 'In rose, petal + +<--- Page Split ---> + +size is controlled by the MYB73/TPL/HDA19- miR159- CKX6 module regulating cytokinin catabolism'. + +## COMMENT #3 + +Line 22, "earlier cytokinin clearance" rather than "precocious cytokinin clearance", furthermore an "a" is missing "leading to 'a' shortened cell division period". + +## RESPONSE + +Thank you for your advice. We revised the sentence accordingly. Please see Line 21- 22 in the revised version. + +## COMMENT #4 + +Line 23, it is not the cell division itself that is prolonged but the "developmental cell division period". The reference to cell division instead of cell division period/cell division phase occurs at several occasions in the whole manuscript. + +## RESPONSE + +Thank you for your advice. We corrected the relevant description accordingly. Please see Line 23, Line 71, Line 99, Line 189, Line 206, Line 269, Line 314, Line 322, and Line 381 in the revised version. + +## COMMENT #5 + +Line 28, Instead of "correct timing of cell division and organ size" it is rather the "correct timing of the exit from the cell division phase and thus the regulation of organ size ..." + +## RESPONSE + +Thank you for your advice. We corrected the description accordingly. Please see Line 28 in the revised version. + +<--- Page Split ---> + +## COMMENT #6 + +Line 35, The references do not reflect the mentioned "century- long fascination for size regulation of organisms". + +## RESPONSE + +Thank you for your advice. We revised this sentence to 'How the size of living organisms is regulated makes for a fascinating and attractive research question'. Please see Line 33- 34 in the revised version. + +## COMMENT #7 + +Line 37, "stepwise" should be deleted as these phases are dynamically linked + +## RESPONSE + +Thank you for your suggestion. We have deleted the "stepwise" in Line 36. + +## COMMENT #8 + +Line 42, the number of cell is determined by the number of divisions, not by the rate of cell proliferation + +## RESPONSE + +Thank you for your suggestion. We have corrected the description accordingly. Please see Line 40 in the revised version. + +## COMMENT #9 + +Line 46, precise what "arrest front" is meant here. Of cell division? + +<--- Page Split ---> + +## RESPONSE + +Thank you for your suggestion. We have corrected the description to 'cell- cycle arrest front' in Line 44 in the revised version. + +## COMMENT #10 + +Line 47, cytokinin takes a small "c" + +Line 59, "serval" is "several" + +## RESPONSE + +Thank you for your suggestion. We have corrected the description accordingly. + +## COMMENT #11 + +Line 83 in a heading it is again not the "duration of cell division" which is controlled by miR159 but the duration of "cell division phase", and again in line 174, and in line 338. + +## RESPONSE + +Thank you for your suggestion. We have corrected the description accordingly. Please see Line 89, Line 99, Line 189, Line 269, Line 314, Line 322, Line 332- 333, Line 381, Line 694, Line 752, Line 779- 780, Line 824, Line 877, Line 984, Line 1030, and Line 1087 in the revised version. + +## COMMENT #12 + +Line 122, I do not see the term "zeatin biosynthesis" in Fig. 2a + +## RESPONSE + +Thank you for your advice. Maybe the font of Fig. 2a is too small. We revised the figure by indicating the term of 'plant hormone signal transduction' and 'zeatin biosynthesis' with an arrow, respectively. + +<--- Page Split ---> +![PLACEHOLDER_39_0] + + +## COMMENT #13 + +Line 207, "cell numbers of cell numbers", please correct. + +## RESPONSE + +Sorry for this mistake. We corrected it. + +## COMMENT #14 + +Line 211, "rapid clearance" was not shown. + +## RESPONSE + +Thank you for pointing this out. We deleted the 'rapid'. Please see Line 227 in the revised version. + +## COMMENT #15 + +Discussion + +The first part of the Discussion describes size regulation of Arabidopsis leaves and maize by other hormones. While this is interesting it does not fit here, it may be used (in a short version) in the Introduction to describe already known systems of organ size regulation or later in the Discussion as a comparison. Start the Discussion with your own results. It should be concise, highlight the + +<--- Page Split ---> + +novelties of the findings and put these into perspective. + +## RESPONSE + +Thank you for your valuable advice. According to your suggestion, we shortened the discussion of size regulation of Arabidopsis leaves and maize by other hormones, and moved this part to Introduction section in the revised version. + +## COMMENT #16 + +In the reporting summary under Data analysis: "secondary structure" instead of "second structure" + +## RESPONSE + +Thank you for pointing this out. We have corrected the description in Date analysis of the reporting summary. + +<--- Page Split ---> + +## Reviewer #3 + +## COMMENT #1 + +Figure S2c: The structure of the precursor is truncated and the miRNA has less than 21nt- more sequence needs to be added. + +## RESPONSE + +Thank you for your valuable advice. We re- predicted the structure of rhy- MIR159 containing the 21nt of miR159 in the revised Figure S2c. + +![PLACEHOLDER_41_0] + + +## COMMENT #2 + +Fig S8b: The authors show a blot to detect miR319. However, since miR319 and miR159 share a similar sequence, and miR319 is expressed at lower levels compared to miR159, it is likely that the blot is detecting miR159 through cross- hybridization instead of miR319. + +## RESPONSE + +Thank you for pointing this out. + +To specifically detect miR159 and miR319, we used Locked Nucleic Acids (LNA)- modified oligonucleotide probes to ensure the specificity of Northern blot of miR159 and miR319 (Válóczi et al., 2004). LNA is a class of bicyclic high- affinity RNA analogues in which the furanose ring in the sugar- phosphate backbone is chemically locked in an N- type (C3'- endo) conformation by the introduction of a 2'- O,4'- C methylene bridge (Obika et al., 1997; Koshkin et al., 1998). The unprecedented thermal stability of LNA oligonucleotides together with their improved mismatch discrimination ensure the highly specificity of LNA- modified probes. + +miR159 probe: 5'- taGAGCTCCCTTCAATCCAAa- 3' miR319 probe: 5'- ggAGCTCCCTTCAGTCCAAa- 3' + +<--- Page Split ---> + +The lowercase letters indicate the LNA-modified oligonucleotide. In our previous results of Northern blot of miR319, we prolonged the exposure time to obtain the optimum image. To compare the expression level of miR159 and miR319, we re- conducted the Northern blot by using same exposure time (20 min) for both miR159 and miR319 in petals on 1, 3, and 5 days after stage 0. As shown in the below figure, the expression level of miR319 was much lower than miR159. We used these results as Fig S8b, and added relevant description of LNA probes in Legend of Figure 1a and Fig S8b in the revised version. + +![PLACEHOLDER_42_0] + + +## Reference: + +Válóczi A., Hornyik C., Varga N., Burgyán J., Kauppinen S., Havelda Z., 2004. Sensitive and specific detection of microRNAs by northern blot analysis using LNA- modified oligonucleotide probes. Nucleic Acids Res, 32: 175- 175. Obika S., Nanbu D., Hari Y., Morio K., In Y., Ishii J.K., Imanishi T., 1997. Synthesis of \(2^{\prime} - O,4^{\prime} - C\) methyleneuridine and cytidine. Novel bicyclic nucleosides having a fixed C3- endo sugar puckering. Tetrahedron Lett, 38: 8735- 8738. Koshkin A.A., Singh S.K., Nielsen P., Rajwanshi V.K., Kumar R., Meldgaard M., Olsen C.E., Wengel J., 1998. LNA (locked nucleic acids): synthesis of the adenine, cytosine, guanine, 5- methylcytosine, thymine and uracil bicyclonucleoside monomers, oligomerisation, and unprecedented nucleic acid recognition. Tetrahedron, 54: 3607- 3630. + +<--- Page Split ---> diff --git a/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..cfd07872450fd2b7b7f1638fef4c69a1bde49780 --- /dev/null +++ b/peer_reviews/32ce5cb8bf91cc8d1b87cd0c8e9fab5629e889c8ce4ce0d0a3916f1da8f3d615/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1348 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[108, 155, 872, 210]]<|/det|> +Peer Review FilePetal size is controlled by the MYB73/TPL/HDA19- miR159- CKX6 module regulating cytokinin catabolism in Rosa hybrida + +<|ref|>image<|/ref|><|det|>[[95, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 332, 100]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[119, 117, 450, 133]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 148, 870, 263]]<|/det|> +The authors are exploring the role of miR159 in regulating cytokinin levels to control petal development in rose, using virus- induced gene silencing to deduce roles for miR159, for the cytokinin oxidase CKX6, and for the transcription factor MYB73. The authors propose that these players control the transition from cell division to cell expansion in the petal, however the rose petal system they are using does not actually allow one to draw conclusions about such a transition. They may, however, with a more careful analysis be able to draw some conclusions about the role of these players in how cytokinin regulates cell division. + +<|ref|>text<|/ref|><|det|>[[119, 279, 251, 295]]<|/det|> +Major concerns: + +<|ref|>text<|/ref|><|det|>[[117, 310, 861, 523]]<|/det|> +1. The authors state that in "petals, cell division mostly ceases before anthesis, and flower opening is largely attributed to cell expansion," using this transition from bud closed to opening as their definition as to when cell division stops and cell expansion begins. However, the primary reference (Yamada et al 2009) the authors use for rose petal development contradicts this concept of petal transition, explicitly stating that for rose, "cell division does not stop at later stages of flower opening." Most interestingly, Yamada et al (Fig. 3) found sharp differences between what occurred for the adaxial and abaxial epidermal cells during petal development. The adaxial cells continued to divide through stage 6 at a fairly consistent rate, such that cell division was a major contributor to the adaxial petal area. In contrast the abaxial cells had largely ceased division by stage 2, well before bud opening, with cell expansion then being a major contributor to the abaxial petal area. Based on this background, the authors cannot infer how cytokinin is regulating the transition from cell division to cell expansion in rose petals. + +<|ref|>text<|/ref|><|det|>[[116, 538, 877, 862]]<|/det|> +2. Although the authors cannot use their study to draw conclusions about the role of cytokinin in regulating the transition from cell division to cell expansion, there is the possibility of exploring the role of cytokinin in regulating cell division itself. For this the authors would need to perform a more careful analysis of the number of cells found in the adaxial and abaxial epidermal cell layers. Specifically, the authors only provide analysis at a single time point (e.g. day five) for their analysis of epidermal cell size in the petals, the size of the cells being suggestive as to whether changes in cytokinin activity is affecting cell division. But the authors do not indicate whether the images are from the adaxial or the abaxial surface. Given the sharp differences in the roles of cell division vs cell expansion for these two surfaces (see above), this is critical information and it would be preferable to provide cell size information for both adaxial and abaxial epidermal cells. In addition, due to the changes in timing of development for the control vs gene silenced petals, one would need to compare the petals at the same developmental stage (i.e. stage 6 at which the petal has fully expanded). From this analysis, the authors could measure cell size and petal area, and then determine the total number of cells per petal for the adaxial and abaxial epidermal layers, thereby indicating how much cytokinin is regulating cell division in the petal. Note that cell size alone is not sufficient to elucidate effects on cell division. Problematically, for their figures, the authors give petal size for fully expanded petals (e.g. days 6 and 7) but cell size at day 5 (before the petals are fully expanded), so the authors cannot directly determine the cell number per petal from the data presented in the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 878, 863, 911]]<|/det|> +3. miR159 has a well-characterized role in the targeting of Mybs that regulate the response to GA, the best known such role being to suppress their activity so as to facilitate cell + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 858, 149]]<|/det|> +division. One would thus expect that such Mybs might be under control of miR159 in the rose petal for the same purpose. To this end the authors need to examine more than just CKX6 as a potential target to but also provide expression and cleavage information for the GA Mybs. + +<|ref|>text<|/ref|><|det|>[[117, 164, 875, 425]]<|/det|> +4. The GA-mybs are the conserved targets for miR159 across multiple plant species, so the finding that CKX6 is a target in rose represents a non-conserved target. This raises the question as to how common the miR159-CKX6 pathway is as a means of regulating cytokinin levels. If a decrease in cytokinin levels is a common theme during leaf and petal development in different plant species, then it is likely that the expression of CKX's is regulated at the level of transcription not just through miR159 as the authors propose for rose. The authors thus need to clearly distinguish the effects of miR159 from transcriptional regulation during development of the petal. The authors show relative expression of CKX6 in control vs miR159 silenced lines at a single time point (Fig 5e, 3 days after stage 0). But it is unclear how much CKX6 expression changes over time and to what degree this is affected by silencing miR159. For example, the authors show a heatmap from a transcriptional database (Fig 2d) that expression of CKX6 increases about 80-fold from stage 0 to stage 2, but the effects of silencing miR159 only result in a 3-fold increase in CKX6 expression. The authors need to follow CKX6 expression throughout their developmental timecourse for the control and miR159 silenced lines to determine how much of an effect miR159 has on the regulation of CKX6 expression. + +<|ref|>sub_title<|/ref|><|det|>[[120, 472, 449, 489]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 504, 870, 683]]<|/det|> +Jing et al report on the regulation of petal size in roses. They find that miR159 regulates the expression of CKX6, which codes for an enzyme degrading the hormone cytokinin. During organ formation, cytokinin regulates the transition of cells from the division phase to differentiation and growth. It is shown that altering the expression of miR159 or CKX6 alters flowering size in predicted ways, corroborating the regulatory connections between the genes and the concept that the miR159/cytokinin module regulates rose flower size. Furthermore, upstream transcriptional and epigenetic regulators of miR159 expression are detected and their functional relevance is demonstrated. Overall, this is an interesting and new story adding significant new knowledge to the field, the experimental work has been done mostly properly and the article is generally well written. I have some points to be considered. + +<|ref|>sub_title<|/ref|><|det|>[[119, 700, 155, 714]]<|/det|> +## Title + +<|ref|>text<|/ref|><|det|>[[119, 716, 870, 796]]<|/det|> +I think the adjective "Rapid" is not justified as a rapid clearance of cytokinin is not truly shown. The notion "rapid" appears also in abstract and in the main text, it should be considered carefully (the drop in miR159 takes 5 days, line 85, this is not rapid). May be the impact of rose flower size may be mentioned in the title, e.g. add at the end "... and regulates rose flower size" + +<|ref|>sub_title<|/ref|><|det|>[[119, 814, 190, 828]]<|/det|> +## Abstract + +<|ref|>text<|/ref|><|det|>[[119, 830, 877, 911]]<|/det|> +For the second sentence I would argue that the relevance of cytokinin to regulate the transition from cell proliferation to expansion is an established concept, it is well documented in roots and in the shoot meristem, it is not a largely unknown question. Key papers are Werner et al. (Plant Cell 15, 2532- 2550 2003) and Bartrina et al. (Plant Cell 23, 69- 80. 2011), more details on the root meristem can be found for example in work of the Sabatini + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 802, 115]]<|/det|> +group (Dello loio et al., Science 322, 1380- 1384, 2008). This background should be considered. + +<|ref|>sub_title<|/ref|><|det|>[[118, 133, 218, 147]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[118, 149, 874, 198]]<|/det|> +The introduction section is rather short. A few sentences about cytokinin (metabolism, maybe signaling, regulation of cell cycle and cell proliferation) should be included, as well as some known functions of miR159 (this can be partly shifted from Discussion section). + +<|ref|>text<|/ref|><|det|>[[118, 213, 868, 246]]<|/det|> +Line 37: I doubt that the size of flowers is constant in a given species. There are large differences of flower size between different varieties of species. Please adapt the sentence. + +<|ref|>sub_title<|/ref|><|det|>[[118, 263, 183, 277]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[118, 278, 875, 311]]<|/det|> +Line 110- 115. The claimed transcript analysis of CKX6 is not shown on Fig. 2 but it would be necessary to include a detailed analysis of the changes occurring during petal development. + +<|ref|>text<|/ref|><|det|>[[118, 326, 874, 375]]<|/det|> +Line 131: What are the canonical miR159 targets? And what makes up a "canonical" target? Some of that can be found in the Discussion but that information should be given in the Introduction. + +<|ref|>text<|/ref|><|det|>[[118, 392, 777, 424]]<|/det|> +Lines 145- 146: citation style changed. I could not find any of the here mentioned publications in the reference section. + +<|ref|>text<|/ref|><|det|>[[118, 440, 857, 473]]<|/det|> +Lines 188- 189: Fig. 7e only shows that RhMYB73 is a transcriptional repressor in general, MIR159 is not included here, right? + +<|ref|>sub_title<|/ref|><|det|>[[118, 490, 183, 504]]<|/det|> +## Figures + +<|ref|>text<|/ref|><|det|>[[118, 505, 875, 553]]<|/det|> +Figs. 1a and b: What has been measured here – the precursor transcript or mature miR159? The y- axis is titled "relative miR159 abundance", but the legend says "pre- miR159 levels". In the Methods section, there is no mentioning of mature miRNA detection. + +<|ref|>text<|/ref|><|det|>[[118, 570, 860, 618]]<|/det|> +Fig. 1e: In the Figure legend, only the P values for \*\*\* and \*\*\*\* are mentioned, but not for \*, which is indicated in this part figure. What exactly is the "flower development progress (d)" shown in Fig. 1c? + +<|ref|>text<|/ref|><|det|>[[118, 650, 878, 700]]<|/det|> +Fig. 2. From where are these data? No source is given in the legend. The RhCKX6 transcript analysis should be more extensive, including a kinetic covering the critical developmental period (currently a GFP fusion gene analysis is shown in Fig. 2). + +<|ref|>text<|/ref|><|det|>[[118, 716, 831, 748]]<|/det|> +Fig. 3e. Please add a quantification of the signals relative to the controls. In the current version the degree of changes cannot be evaluated. + +<|ref|>text<|/ref|><|det|>[[118, 764, 830, 797]]<|/det|> +Fig. 4b Is there information on the degree of changes in relative expression in different phases of flower development? + +<|ref|>text<|/ref|><|det|>[[118, 812, 868, 845]]<|/det|> +Fig. 5 There are large differences in cytokinin content in different measurements. Compare Fig. 5b and 5g, there is a 20- fold difference in the tZ content in TRV. How is that explained? + +<|ref|>text<|/ref|><|det|>[[118, 861, 863, 893]]<|/det|> +Figs. 7a/S8: Please give a more detailed description of what can be seen here. What do "- , +" and "1x, 10x, 100x" mean exactly? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 210, 99]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[119, 100, 830, 149]]<|/det|> +DiscussionThe discussion should be more focused, there are sections reporting rather broadly on general knowledge that can be shortened, part of the background should appear in the introduction. + +<|ref|>text<|/ref|><|det|>[[119, 164, 641, 181]]<|/det|> +Line 253. The first heading does not read well, please rephrase. + +<|ref|>text<|/ref|><|det|>[[119, 197, 856, 262]]<|/det|> +Line 257/258ff. The transition from division to differentiation involves "multiple phytohormones". I wonder why here a one- page long summary of other plant hormones is given, which are not considered in this work, while the known facts about cytokinin (see above) are not described. That section should be adapted. + +<|ref|>text<|/ref|><|det|>[[119, 278, 790, 311]]<|/det|> +Line 289, "energetically costly", please explain; the continuation of the sentence is questionably, please think it over. + +<|ref|>text<|/ref|><|det|>[[119, 326, 867, 375]]<|/det|> +Lines 307- 309: It might be worth mentioning that also cytokinin is involved in juvenile phase control (Werner et al., Nature Comm. 12, 5816, 2021) described here to be linked to a miR159- MYB33 module affecting miR156. + +<|ref|>text<|/ref|><|det|>[[119, 391, 833, 424]]<|/det|> +How about the CKX6 genes in other species? Are they predicted targets of miR159? In Arabidopsis? + +<|ref|>text<|/ref|><|det|>[[119, 440, 875, 489]]<|/det|> +Please consider the recent paper of Zou et al. on rose CKX6, putting it in the context of petal dehydration and show its regulation by RaNAP transcription factor (Molecular Horticulture 1, 13, 2021) + +<|ref|>sub_title<|/ref|><|det|>[[119, 505, 192, 520]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[119, 537, 528, 553]]<|/det|> +Line 394: "Quantification" instead of "quantitative". + +<|ref|>text<|/ref|><|det|>[[119, 570, 866, 602]]<|/det|> +Line 400. 100 mM 6- BA is a very high, presumably (almost) toxic concentration (usually 1- 5 \(\mu \mathrm{M}\) are used). Please check if that is correct. + +<|ref|>text<|/ref|><|det|>[[119, 618, 866, 667]]<|/det|> +Cytokinin measurements. From how many plants were the samples, how many flowers (in approximation)? It would be good to include a table reporting the results for all cytokinin metabolites measured in the supplements, here the data are limited to few metabolites. + +<|ref|>text<|/ref|><|det|>[[119, 683, 767, 700]]<|/det|> +Information on how pictures (BiFC, LUC) were evaluated is completely missing. + +<|ref|>text<|/ref|><|det|>[[119, 716, 874, 748]]<|/det|> +There are some inconsistencies in units, as both \(\mu \mathrm{g}\) and microgram, \(\mathrm{mg / L}\) , \(\mathrm{ng / ml}\) and \(\mathrm{mg} \times \mathrm{l} \cdot \mathrm{l}\) are used, please unify. + +<|ref|>sub_title<|/ref|><|det|>[[119, 796, 450, 813]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 829, 840, 862]]<|/det|> +Review of Rapid clearance of cytokinin controls transition from cell division to expansion during petal development in rose (Rosa hybrida) + +<|ref|>text<|/ref|><|det|>[[117, 878, 875, 911]]<|/det|> +MiR159 is an evolutionarily conserved microRNA that regulates GAMYB transcription factors in angiosperms. Here, the authors report that rose miR159 regulates Cytokinin + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 866, 198]]<|/det|> +Oxidase/Dehydrogenase 6 (CKX6) to control petal size. The authors use a target mimicry strategy (TRV- STTM159), to sequester and/or degrade miR159, which resulted in flowers with smaller petals that have fewer cells. Among the predicted targets of miR159 that have increased expression levels after inactivating miR159 by STTM159, the authors found CKX6. In turn, using VIGS to silence CKX6 resulted in changes in cytokinin catabolism and larger petals. Furthermore, the authors show that rhMYB73 binds to the MIR159 promoter repressing its expression during flower development. + +<|ref|>text<|/ref|><|det|>[[118, 213, 875, 278]]<|/det|> +In principle, I think that the acquisition of a new target by the evolutionarily conserved miR159 to control petal size in roses is interesting. However, I have concerns about the data supporting the regulation of CKX6 by miR159 and the proposed role of a miR159- CKX6 module. + +<|ref|>text<|/ref|><|det|>[[118, 295, 245, 310]]<|/det|> +Main concerns: + +<|ref|>text<|/ref|><|det|>[[118, 325, 844, 391]]<|/det|> +1- The authors mention that the underlying mechanism controlling the transition from cell proliferation to expansion in leaves remains largely unknown. However, there are known regulators controlling this transition, such as the miR319- regulated TCP (CIN- Like) transcription factors. + +<|ref|>text<|/ref|><|det|>[[118, 407, 878, 488]]<|/det|> +miR319 is similar in sequence to miR159, and target mimicry against miR159 can cross target miR319 (Reichel and Millar, 2015). In addition, miR319- TCP controls petal growth and development (i.e., Nag et al., 2009). Therefore, I think that the authors need to consider the possibility that STTM159 could be affecting petal growth through the modification of the miR319- TCP module. + +<|ref|>text<|/ref|><|det|>[[118, 504, 852, 553]]<|/det|> +The complete miR319/miR159 family of miRNAs in rose (which might contain several members) should be analyzed in STTM159 plants. The analysis of miRNA- targets should also include rose TCP transcription factors that are targets of miR319. + +<|ref|>text<|/ref|><|det|>[[118, 586, 875, 667]]<|/det|> +2- MicroRNAs guide the cleavage of their targets at position 10-11 (Fig 3a). The authors did not find any cut at this position for CKX6, which argues against the regulation by miR159. The authors say that they analyzed CKX6 cleavage in rose petals in the Results section, but in Methods they say that the experiment was performed from 35S:pre- MIR159 transient overexpression plants (tobacco?). The cleavage site should be determined in wt rose petals. + +<|ref|>text<|/ref|><|det|>[[118, 682, 853, 748]]<|/det|> +miR159 is strongly expressed in tobacco leaves, so I'm surprised that the authors could express large amounts of a GFP sensor for a miR159- target (Fig 3). The levels of mature miR159 should be determined in tobacco leaves to show the increase of miR159 after the expression of rose pre- miR159. + +<|ref|>text<|/ref|><|det|>[[118, 764, 871, 813]]<|/det|> +The determination of mature miRNAs by qPCR can be tricky - for example, miRNAs from the same family can have differences in their 3' end, yet they regulate the same targets. It is better to determine miRNA levels by small RNA blots. + +<|ref|>text<|/ref|><|det|>[[118, 829, 876, 862]]<|/det|> +The expression of the sensors in N. benthamiana leaves is patchy which might be caused by RNA silencing (independent of the miRNA). + +<|ref|>text<|/ref|><|det|>[[118, 878, 857, 910]]<|/det|> +Overall, I don't think that the current manuscript shows clear evidence for the regulation of CKX6 by miR159. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 116, 872, 215]]<|/det|> +3- Inactivation of miR159 (by target mimicry or mir159a/b knock outs) in Arabidopsis causes pleiotropic developmental defects in leaves and stunted plants. Please, show and describe the plant growth and overall phenotypes of the VIGS lines (STTMIR159, and rhMYB73 and RhCKX6)- silenced lines. Also, indicate the number of plants analyzed in each case, and the distribution of the phenotypes observed (i.e., percentage of plants displaying the selected phenotypes). + +<|ref|>text<|/ref|><|det|>[[118, 229, 855, 278]]<|/det|> +4- For VIGS, authors used fragments of approx. 400 bp for RhMYB73M159 and RhCKX6. These are long fragments. Are the authors confident that other MYBs or CKX genes were not affected? I think using artificial microRNAs would have been a more specific strategy. + +<|ref|>text<|/ref|><|det|>[[118, 294, 868, 342]]<|/det|> +I think it would be important to include the phenotypes of roses overexpressing pre- miR159, which should down- regulate RhCKX6 and increase petal size. This vector is used in the N. benthamiana assays. + +<|ref|>text<|/ref|><|det|>[[118, 359, 861, 456]]<|/det|> +5- The authors predict the regulation of several CKXs by miR159 in rose and arabidopsis (Supplementary Fig 4). The location of a miRNA- target site in a target gene is usually conserved during evolution and not variable as depicted in this figure. There is plenty of experimental information identifying miRNA targets in arabidopsis in publicly available databases. Please use this info to show the empirical data for the regulation by miR159 for the two predicted Arabidopsis targets. + +<|ref|>text<|/ref|><|det|>[[118, 489, 261, 504]]<|/det|> +Other comments: + +<|ref|>text<|/ref|><|det|>[[115, 537, 875, 650]]<|/det|> +1- Please include in the Supplementary Tables the description for the selected rose genes (or the description of their arabidopsis homologues). +2- L78 –“To understand the underlying mechanism of the transition between cell division and cell expansion, we previously conducted a transcriptome deep sequencing (RNA-seq) analysis of short RNAs and transcripts from petals to investigate gene expression profiles during the cell division and expansion phases.” – please include the citation for the article describing the RNAseq analysis of short RNAs and transcripts. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 94, 412, 115]]<|/det|> +## Response to Reviewers + +<|ref|>text<|/ref|><|det|>[[148, 154, 468, 171]]<|/det|> +Manuscript No. NCOMMS- 22- 37721 + +<|ref|>text<|/ref|><|det|>[[148, 191, 850, 237]]<|/det|> +Title: Rapid clearance of cytokinin controls transition from cell division to expansion during petal development in rose (Rosa hybrida) + +<|ref|>sub_title<|/ref|><|det|>[[149, 279, 290, 300]]<|/det|> +## Reviewer #1 + +<|ref|>sub_title<|/ref|><|det|>[[149, 317, 278, 336]]<|/det|> +## Comment #1 + +<|ref|>text<|/ref|><|det|>[[147, 350, 852, 672]]<|/det|> +The authors state that in "petals, cell division mostly ceases before anthesis, and flower opening is largely attributed to cell expansion," using this transition from bud closed to opening as their definition as to when cell division stops and cell expansion begins. However, the primary reference (Yamada et al 2009) the authors use for rose petal development contradicts this concept of petal transition, explicitly stating that for rose, "cell division does not stop at later stages of flower opening." Most interestingly, Yamada et al (Fig. 3) found sharp differences between what occurred for the adaxial and abaxial epidermal cells during petal development. The adaxial cells continued to divide through stage 6 at a fairly consistent rate, such that cell division was a major contributor to the adaxial petal area. In contrast the abaxial cells had largely ceased division by stage 2, well before bud opening, with cell expansion then being a major contributor to the abaxial petal area. Based on this background, the authors cannot infer how cytokinin is regulating the transition from cell division to cell expansion in rose petals. + +<|ref|>text<|/ref|><|det|>[[147, 682, 852, 895]]<|/det|> +Although the authors cannot use their study to draw conclusions about the role of cytokinin in regulating the transition from cell division to cell expansion, there is the possibility of exploring the role of cytokinin in regulating cell division itself. For this the authors would need to perform a more careful analysis of the number of cells found in the adaxial and abaxial epidermal cell layers. Specifically, the authors only provide analysis at a single time point (e.g. day five) for their analysis of epidermal cell size in the petals, the size of the cells being suggestive as to whether changes in cytokinin activity is affecting cell division. But the authors do not indicate whether the images are from the adaxial or the abaxial surface. Given the sharp differences in the roles of cell division vs + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 852, 135]]<|/det|> +cell expansion for these two surfaces (see above), this is critical information and it would be preferable to provide cell size information for both adaxial and abaxial epidermal cells. + +<|ref|>text<|/ref|><|det|>[[147, 145, 852, 386]]<|/det|> +In addition, due to the changes in timing of development for the control vs gene silenced petals, one would need to compare the petals at the same developmental stage (i.e. stage 6 at which the petal has fully expanded). From this analysis, the authors could measure cell size and petal area, and then determine the total number of cells per petal for the adaxial and abaxial epidermal layers, thereby indicating how much cytokinin is regulating cell division in the petal. Note that cell size alone is not sufficient to elucidate effects on cell division. Problematically, for their figures, the authors give petal size for fully expanded petals (e.g. days 6 and 7) but cell size at day 5 (before the petals are fully expanded), so the authors cannot directly determine the cell number per petal from the data presented in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 399, 275, 418]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[150, 433, 411, 449]]<|/det|> +Thank you for your excellent advice. + +<|ref|>text<|/ref|><|det|>[[147, 460, 852, 615]]<|/det|> +We would like to apologize for any confusion caused by the incomplete and misleading description in our previous version. We would like to clarify that all data presented was based on observations of abaxial epidermal cells. Our previous study utilized scanning electron microscopy to observe the anatomical structure of rose petals. We found that cell number and size of abaxial epidermal cells are closely related to petal size, which is why we focused our analysis on this particular cell type (Ma et al., 2008, Plant Physiology). + +<|ref|>text<|/ref|><|det|>[[147, 626, 852, 700]]<|/det|> +In our previous version, we tried to demonstrate that abaxial epidermal cells in TRV- STTM159 lines entered the expansion stage earlier compared to TRV controls. To this end, we illustrated the cell size on day 5 (Fig.1f) and on the fully opened stage (Supplementary Fig.2b). + +<|ref|>text<|/ref|><|det|>[[147, 710, 852, 895]]<|/det|> +According to your advice, we conducted further experiments, wherein we recorded the number of adaxial and abaxial epidermal cells in TRV controls and different gene silenced lines (TRV- STTM159, TRV- RhCKX6, and TRV- RhMYB73), following the procedure outlined by Yamada et al. (2009). Our findings suggested that silencing of miR159 resulted in a slower increase in the number of adaxial and abaxial epidermal cells, particularly in abaxial epidermal cells. Furthermore, the cell division period was reduced in TRV- STTM159 lines, as the plants in these lines attained full opening earlier than TRV controls. In contrast, silencing of either RhCKX6 or RhMYB73 showed an opposite + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 395, 106]]<|/det|> +phenotype to TRV- STTM159 lines. + +<|ref|>text<|/ref|><|det|>[[147, 118, 851, 190]]<|/det|> +We added these data in the revised manuscript as Supplemental figure S1; Fig. 1f, g; Fig. 4e, f; and Fig. 8e,f. We also revised the title and our manuscript accordingly to avoid any misleading in the revised version. + +<|ref|>image<|/ref|><|det|>[[150, 201, 844, 389]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 405, 644, 422]]<|/det|> +
Figure 1 miR159 controls cell division and flower opening in rose.
+ +<|ref|>text<|/ref|><|det|>[[147, 428, 850, 481]]<|/det|> +f, g. The cell number of adaxial epidermis (f) and abaxial epidermis (g) in TRV control and TRV- STTM159 petals from days 1 after floral stage 0 to fully opened stage. Data are shown as means \(\pm\) SD from 3 biological replicates (n = 3). + +<|ref|>text<|/ref|><|det|>[[147, 488, 517, 504]]<|/det|> +Please refer to the revised version for other Figures. + +<|ref|>sub_title<|/ref|><|det|>[[148, 547, 280, 566]]<|/det|> +## Comment #2 + +<|ref|>text<|/ref|><|det|>[[147, 580, 852, 709]]<|/det|> +miR159 has a well- characterized role in the targeting of Mybs that regulate the response to GA, the best known such role being to suppress their activity so as to facilitate cell division. One would thus expect that such Mybs might be under control of miR159 in the rose petal for the same purpose. To this end the authors need to examine more than just CKX6 as a potential target to but also provide expression and cleavage information for the GA Mybs. + +<|ref|>sub_title<|/ref|><|det|>[[148, 723, 275, 741]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 756, 852, 912]]<|/det|> +Thank you for your advice. According to your suggestion, we isolated the homologues of all seven Arabidopsis GAMYB genes (MYB33, MYB65, MYB81, MYB97, MYB101, MYB104, and MYB120). We predicted miR159 targets in three of them, including RhMYB33, RhMYB65, and RhMYB101. Both RNA- seq and qRT- PCR analysis showed that expression of RhMYB65 and RhMYB101 could not be detected in rose petals in all tested development stages (1 d, 3 d, and 5 d). Expression of RhMYB33 was detectable but was much lower than expression level of RhCKX6. In addition, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 853, 358]]<|/det|> +expression of RhMYB33 slightly decreased in petals from 3 d to 7 d. RLM- RACE showed the miR159- dependent cleavage of RhMYB33 transcript in rose petals. We constructed an RhMYB33- Sensor and an RhMYB33m- Sensor constructs by cloning the coding sequence of green fluorescent protein (GFP) in- frame with an intact miR159- target region (for RhMYB33- Sensor) or a mutated miR159- target region (for RhMYB33m- Sensor). We then co- infiltrated each sensor construct in Nicotiana benthamiana leaves with a construct overexpressing the miR159 precursor (pre- MIR159) and detected lower GFP fluorescence from the pre- MIR159+RhMYB33- Sensor combination compared to the Sensor alone, but not from the pre- MIR159+RhMYB33m- Sensor combination. In addition, we tested GAs level in rose petals. Level of GA3 and GA7 was barely detectable, while level of GA1 and GA19 remained stable throughout the developmental time course. + +<|ref|>text<|/ref|><|det|>[[147, 368, 854, 469]]<|/det|> +Based on these data, we considered that GAMYBs- mediated regulation of cell division is insignificant relative to RhCKX6- mediated regulation, although we could not completely exclude the possibility that miR159- RhMYB33 module is involved in regulation of petal cell division in roses. We added these data as Supplemental Figure S7 and discussed this issue in the revised version. + +<|ref|>image<|/ref|><|det|>[[155, 483, 840, 828]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 845, 850, 880]]<|/det|> +Supplemental Figure S7 miR159- targeted RhMYB33 and GAs contents in rose petals during petal growth. + +<|ref|>text<|/ref|><|det|>[[147, 883, 848, 899]]<|/det|> +a, Upper panel, schematic diagram of RhMYB33 mRNA. Red box, predicted cleavage site of miR159. Bottom panel, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +identification of cleavage sites using \(5^{\prime}\) RLM- RACE assay in rose petals. The positions of cleavage sites are indicated by arrowheads with the frequency of clones. + +<|ref|>text<|/ref|><|det|>[[147, 123, 850, 194]]<|/det|> +b, Confocal imaging analysis of N. benthamiana leaves 3 days after co- infiltration of pre- MIR159 with RhMYB33- sensor- GFP or RhMYB33m- sensor- GFP, respectively. GFP fluorescence of N. benthamiana leaves 3 days after co- infiltration of the indicated constructs. The experiment was performed independently three times, and representative results are shown. Scale bars, \(5\mathrm{mm}\) . + +<|ref|>text<|/ref|><|det|>[[147, 197, 850, 268]]<|/det|> +c, RT- qPCR analysis of RhMYB33 transcript levels in petals 1, 3, 5 days after stage 0. RhUBI2 was used as an internal control. Data are shown as means \(\pm\) SD from three biological replicates ( \(\mathrm{n} = 3\) ). Different lowercase letters above each bar indicate significant differences according to one- way ANOVA with Tukey's multiple comparisons test ( \(P< 0.05\) ). + +<|ref|>text<|/ref|><|det|>[[147, 272, 850, 306]]<|/det|> +d, GA contents in petals 1, 3, 5 days after stage 0. Data are shown as means \(\pm\) SD from three biological replicates ( \(\mathrm{n} = 3\) ). + +<|ref|>sub_title<|/ref|><|det|>[[148, 335, 280, 354]]<|/det|> +## Comment #3 + +<|ref|>text<|/ref|><|det|>[[147, 368, 852, 748]]<|/det|> +The GA- mybs are the conserved targets for miR159 across multiple plant species, so the finding that CKX6 is a target in rose represents a non- conserved target. This raises the question as to how common the miR159- CKX6 pathway is as a means of regulating cytokinin levels. If a decrease in cytokinin levels is a common theme during leaf and petal development in different plant species, then it is likely that the expression of CKX's is regulated at the level of transcription not just through miR159 as the authors propose for rose. The authors thus need to clearly distinguish the effects of miR159 from transcriptional regulation during development of the petal. The authors show relative expression of CKX6 in control vs miR159 silenced lines at a single time point (Fig 5e, 3 days after stage 0). But it is unclear how much CKX6 expression changes over time and to what degree this is affected by silencing miR159. For example, the authors show a heatmap from a transcriptional database (Fig 2d) that expression of CKX6 increases about 80- fold from stage 0 to stage 2, but the effects of silencing miR159 only result in a 3- fold increase in CKX6 expression. The authors need to follow CKX6 expression throughout their developmental time course for the control and miR159 silenced lines to determine how much of an effect miR159 has on the regulation of CKX6 expression. + +<|ref|>sub_title<|/ref|><|det|>[[148, 760, 275, 778]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 793, 852, 894]]<|/det|> +Thank you for your excellent suggestion. We detected expression level of miR159 and RhCKX6 in petals throughout the developmental time course for the TRV control and TRV- STTM159 lines. The results showed that expression of RhCKX6 in TRV- STTM159 lines was significantly higher than TRV control throughout the developmental time course, especially in the earlier period. Meanwhile, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 758, 107]]<|/det|> +expression of RhCKX6 increased in TRV- STTM159 lines in the development duration. + +<|ref|>text<|/ref|><|det|>[[147, 118, 852, 218]]<|/det|> +We considered this might be two reasons, 1) the VIGS just knockdown the miR159 instead of knockout. The rest miR159 still functioned to influence accumulation of RhCKX6 transcripts. 2) Besides of miR159- mediated regulation, expression of RhCKX6 might be induced by some unknown factors during petal development as well. + +<|ref|>text<|/ref|><|det|>[[147, 228, 852, 384]]<|/det|> +In addition, we tested the possible miR159- mediated cleavage of CKXs in more plants. We predicted miR159- target site in AtCKX5 (Arabidopsis), MdCKX6 (Malus demestica), and FvCKX6 (Fragaria vesca). We generated GFP- Sensor constructs for AtCKX5 (Arabidopsis), MdCKX6 (Malus demestica), and FvCKX6, and detected miR159- mediated cleavage of these three Sensors. RLM- RACE also confirmed miR159- mediated cleavage of FvCKX6 in petals of Fragaria vesca, indicating that miR159- mediated cleavage of CKXs could be a common regulation pathway. + +<|ref|>text<|/ref|><|det|>[[147, 395, 851, 468]]<|/det|> +Based on these data, we considered miR159 played an essential role in regulation of accumulation of RhCKX6 transcripts, but we could not exclude the possibility that some other currently unknown factors might regulate expression of RhCKX6 as well. + +<|ref|>text<|/ref|><|det|>[[147, 479, 850, 523]]<|/det|> +We added the results as Fig. 2e- g and Supplemental Figure S6, toned down our statement and discussed this issue in the revised version. + +<|ref|>image<|/ref|><|det|>[[159, 534, 840, 650]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 665, 772, 681]]<|/det|> +
Figure 2 miR159 influences transcript accumulation of cytokinin catabolism genes.
+ +<|ref|>text<|/ref|><|det|>[[147, 688, 852, 832]]<|/det|> +e, f, RT- qPCR analysis of miR159 abundance and RhCKX6 transcript levels in rose petals at 1, 3, 5, and 7 days after stage 0. 5S rRNA was used as an internal control (e). RhUBI2 was used as an internal control (f). Data are shown as means \(\pm \mathrm{SD}\) are shown from three biological replicates ( \(\mathrm{n} = 3\) ). Different lowercase letters above each bar in (e and f) indicate significant differences according to one- way ANOVA with Tukey's multiple comparisons test ( \(P< 0.05\) ). g, RT- qPCR analysis of RhCKX6 transcript levels in petals of TRV control and TRV- STTM159 at 1, 3, and 5 days after stage 0. RhUBI2 was used as an internal control. Data are shown as means \(\pm \mathrm{SD}\) are shown from three biological replicates ( \(\mathrm{n} = 3\) ). Asterisks indicate statistically significant differences (two- sided Student's \(t\) - test, \(*\) , \(P< 0.05\) ; \(**\) , \(P< 0.01\) ; ns, no significant difference). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[160, 100, 840, 640]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 642, 730, 657]]<|/det|> +Supplemental Figure S6 Validation of miR159-targeted CKX in other species. + +<|ref|>text<|/ref|><|det|>[[147, 660, 850, 712]]<|/det|> +a, b, c, Confocal imaging analysis of N. benthamiana leaves 3 days after co- infiltration of pre- MIR159 with AtCKX5- sensor- GFP or AtCKX5m- sensor- GFP (a); MdCKX6- sensor- GFP or MdCKX6m- sensor- GFP (b); FvCKX6- sensor- GFP or FvCKX6m- sensor- GFP (c). + +<|ref|>text<|/ref|><|det|>[[147, 716, 850, 768]]<|/det|> +d, Validation of miR159- targeted cleavage of FvCKX6. Upper panel, schematic diagram of FvCKX6 mRNA. Red box, predicted cleavage site of miR159. Bottom panel, identification of cleavage sites using 5' RLM- RACE assay in strawberry petals. The positions of cleavage sites are indicated by arrowheads with the frequency of clones. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 93, 292, 115]]<|/det|> +## Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[148, 131, 278, 150]]<|/det|> +## Comment #1 + +<|ref|>text<|/ref|><|det|>[[148, 165, 184, 179]]<|/det|> +Title + +<|ref|>text<|/ref|><|det|>[[147, 191, 852, 292]]<|/det|> +I think the adjective "Rapid" is not justified as a rapid clearance of cytokinin is not truly shown. The notion "rapid" appears also in abstract and in the main text, it should be considered carefully (the drop in miR159 takes 5 days, line 85, this is not rapid). May be the impact of rose flower size may be mentioned in the title, e.g. add at the end "... and regulates rose flower size" + +<|ref|>sub_title<|/ref|><|det|>[[148, 306, 275, 325]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 340, 850, 385]]<|/det|> +Many thanks for your excellent advice. As your suggestion, we have revised the title to "In rose, miR159 regulates petal cell division by modulating cytokinin catabolism". + +<|ref|>sub_title<|/ref|><|det|>[[148, 427, 280, 446]]<|/det|> +## Comment #2 + +<|ref|>text<|/ref|><|det|>[[148, 462, 212, 476]]<|/det|> +Abstract + +<|ref|>text<|/ref|><|det|>[[147, 488, 852, 644]]<|/det|> +For the second sentence I would argue that the relevance of cytokinin to regulate the transition from cell proliferation to expansion is an established concept, it is well documented in roots and in the shoot meristem, it is not a largely unknown question. Key papers are Werner et al. (Plant Cell 15, 2532- 2550 2003) and Bartrina et al. (Plant Cell 23, 69- 80. 2011), more details on the root meristem can be found for example in work of the Sabatini group (Dello Ioi o et al., Science 322, 1380- 1384, 2008). This background should be considered. + +<|ref|>sub_title<|/ref|><|det|>[[148, 658, 275, 677]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 692, 850, 765]]<|/det|> +Many thanks for your excellent comments, which makes our description more exact. In abstract, we have edited the description. In addition, we have revised our Introduction section by adding the information of the key papers you suggested. + +<|ref|>sub_title<|/ref|><|det|>[[148, 807, 280, 825]]<|/det|> +## Comment #3 + +<|ref|>text<|/ref|><|det|>[[148, 841, 239, 856]]<|/det|> +Introduction + +<|ref|>text<|/ref|><|det|>[[148, 868, 850, 912]]<|/det|> +The introduction section is rather short. A few sentences about cytokinin (metabolism, maybe signaling, regulation of cell cycle and cell proliferation) should be included, as well as some known + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 666, 106]]<|/det|> +functions of miR159 (this can be partly shifted from Discussion section). + +<|ref|>text<|/ref|><|det|>[[147, 118, 850, 162]]<|/det|> +Line 37: I doubt that the size of flowers is constant in a given species. There are large differences of flower size between different varieties of species. Please adapt the sentence. + +<|ref|>sub_title<|/ref|><|det|>[[148, 177, 275, 196]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 211, 850, 255]]<|/det|> +Many thanks for your advice. We have revised the Introduction section by adding the information of cytokinin and function of miR159. + +<|ref|>text<|/ref|><|det|>[[147, 266, 850, 310]]<|/det|> +We have deleted the sentence "In plants, the size of flowers and petals is constant within a certain species, but varies across different species" in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 352, 280, 371]]<|/det|> +## Comment #4 + +<|ref|>text<|/ref|><|det|>[[148, 387, 204, 402]]<|/det|> +Results + +<|ref|>text<|/ref|><|det|>[[147, 414, 850, 458]]<|/det|> +Line 110- 115. The claimed transcript analysis of CKX6 is not shown on Fig. 2 but it would be necessary to include a detailed analysis of the changes occurring during petal development. + +<|ref|>sub_title<|/ref|><|det|>[[148, 473, 275, 492]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 507, 850, 551]]<|/det|> +Thank you for your advice. We would like to apologize for the missing data. We have added the expression level of RhCKX6 in Fig. 2f in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 593, 280, 612]]<|/det|> +## Comment #5 + +<|ref|>text<|/ref|><|det|>[[147, 626, 850, 671]]<|/det|> +Line 131: What are the canonical miR159 targets? And what makes up a "canonical" target? Some of that can be found in the Discussion but that information should be given in the Introduction. + +<|ref|>sub_title<|/ref|><|det|>[[148, 686, 275, 704]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 720, 850, 764]]<|/det|> +Many thanks for your suggestions. As your suggested, we have added the relevant description of the canonical miR159 targets in the Introduction section in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 806, 280, 825]]<|/det|> +## Comment #6 + +<|ref|>text<|/ref|><|det|>[[147, 840, 850, 884]]<|/det|> +Lines 145- 146: citation style changed. I could not find any of the here mentioned publications in the reference section. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 93, 275, 112]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 127, 850, 171]]<|/det|> +Thank you for your advice. We would like to apologize for this mistake. We have corrected the citation and the Reference list. + +<|ref|>sub_title<|/ref|><|det|>[[148, 214, 280, 233]]<|/det|> +## Comment #7 + +<|ref|>text<|/ref|><|det|>[[148, 247, 850, 291]]<|/det|> +Lines 188- 189: Fig. 7e only shows that RhMYB73 is a transcriptional repressor in general, MIR159 is not included here, right? + +<|ref|>sub_title<|/ref|><|det|>[[148, 306, 275, 325]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 339, 851, 411]]<|/det|> +Thank you for pointing this out. As you mentioned, Fig. 7e only shows that RhMYB73 is a transcriptional repressor in general, MIR159 is not included here. We have corrected the description in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 455, 280, 473]]<|/det|> +## Comment #8 + +<|ref|>text<|/ref|><|det|>[[148, 489, 205, 504]]<|/det|> +Figures + +<|ref|>text<|/ref|><|det|>[[147, 515, 851, 588]]<|/det|> +Figs. 1a and b: What has been measured here – the precursor transcript or mature miR159? The y- axis is titled “relative miR159 abundance”, but the legend says “pre- MIR159 levels”. In the Methods section, there is no mentioning of mature miRNA detection. + +<|ref|>text<|/ref|><|det|>[[147, 598, 851, 670]]<|/det|> +Fig. 1e: In the Figure legend, only the P values for \*\*\* and \*\*\*\* are mentioned, but not for \*, which is indicated in this part figure. What exactly is the “flower development progress (d)” shown in Fig. 1c? + +<|ref|>sub_title<|/ref|><|det|>[[148, 686, 275, 705]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 719, 852, 904]]<|/det|> +Thank you for your guidance. We would like to apologize for this mistake. Actually, both Figure 1a and b presented the mature miR159 abundance. We replaced the Figure 1a as the Northern Blot detection of mature miR159 in the revised version and moved the original Figure 1a to Supplementary Figure 2a. We added the methods of Northern Blot and qRT- PCR of mature miR159 in the Methods section in the revised version. We also revised the Figure legend and mentioned ‘\*’. The “flower development progress (d)” is the period of different stage of flower opening. We have updated the y- axis label of Figure 1c from “flower development progress (d)” to “Period of different + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 135]]<|/det|> +stage of flower opening (d)" to more accurately represent the data. The y- axis label of Figure 4c, 6b, 8b, and Supplemental Fig. S10b were revised accordingly. + +<|ref|>sub_title<|/ref|><|det|>[[148, 177, 280, 196]]<|/det|> +## Comment #9 + +<|ref|>text<|/ref|><|det|>[[147, 210, 851, 283]]<|/det|> +Fig. 2. From where are these data? No source is given in the legend. The RhCKX6 transcript analysis should be more extensive, including a kinetic covering the critical developmental period (currently a GFP fusion gene analysis is shown in Fig. 2). + +<|ref|>sub_title<|/ref|><|det|>[[148, 297, 275, 316]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 331, 851, 404]]<|/det|> +Thank you for your guidance. We have included the source information in the Legend of Figure 2 and added the expression of the RhCKX6 gene in petals during petal development in Fig. 2f in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 445, 292, 464]]<|/det|> +## Comment #10 + +<|ref|>text<|/ref|><|det|>[[147, 479, 850, 523]]<|/det|> +Fig. 3e. Please add a quantification of the signals relative to the controls. In the current version the degree of changes cannot be evaluated. + +<|ref|>sub_title<|/ref|><|det|>[[148, 537, 275, 556]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 571, 850, 616]]<|/det|> +Thank you for your guidance. We have added the quantification of the signals relative to the controls in Fig. 3d in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 658, 289, 677]]<|/det|> +## Comment #11 + +<|ref|>text<|/ref|><|det|>[[147, 692, 850, 736]]<|/det|> +Fig. 4b Is there information on the degree of changes in relative expression in different phases of flower development? + +<|ref|>sub_title<|/ref|><|det|>[[148, 750, 275, 770]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 784, 850, 858]]<|/det|> +Thank you for your guidance. Fig. 4b is the expression of CKX6 in CKX6- silencing plants (TRV- RhCKX6) and control (TRV), which is test the degree of CKX6- silencing. We have added the expression of the RhCKX6 gene in petals during petal development in Fig. 2f in the revised version. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 93, 292, 112]]<|/det|> +## Comment #12 + +<|ref|>text<|/ref|><|det|>[[148, 126, 850, 172]]<|/det|> +Fig. 5 There are large differences in cytokinin content in different measurements. Compare Fig. 5b and 5g, there is a 20- fold difference in the tZ content in TRV. How is that explained? + +<|ref|>sub_title<|/ref|><|det|>[[148, 185, 275, 205]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 219, 852, 404]]<|/det|> +Thank you for pointing this out. The difference in tZ content observed in the TRV shown in Fig. 5b and 5g was due to the difference in the sampling time. In Fig. 5b, the petals were sampled for the determination of tZ content 5 days after stage 0, whereas in Fig. 5g, the petals were sampled 3 days after stage 0. According to Fig. 6a, the tZ content in the petals significantly reduces on the 5th day after stage 0, as compared to the 1st day. It is noteworthy that the petals were sampled on the 3rd day after stage 0 in Fig. 5g because the silencing of miR159 caused a shortened cell division period. We have revised the relevant description to avoid any misleading. + +<|ref|>sub_title<|/ref|><|det|>[[148, 444, 292, 463]]<|/det|> +## Comment #13 + +<|ref|>text<|/ref|><|det|>[[148, 478, 850, 523]]<|/det|> +Fig. 7a/S8: Please give a more detailed description of what can be seen here. What do “- , +” and “1x, 10x, 100x” mean exactly? + +<|ref|>sub_title<|/ref|><|det|>[[148, 537, 275, 556]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 570, 842, 615]]<|/det|> +Thank you for your guidance. We have added the description of “- , +” and “1x, 10x, 100x” in Figs. 7a/S11 legends. + +<|ref|>sub_title<|/ref|><|det|>[[148, 657, 292, 676]]<|/det|> +## Comment #14 + +<|ref|>text<|/ref|><|det|>[[148, 692, 230, 707]]<|/det|> +Discussion + +<|ref|>text<|/ref|><|det|>[[147, 719, 850, 763]]<|/det|> +The discussion should be more focused, there are sections reporting rather broadly on general knowledge that can be shortened, part of the background should appear in the introduction. + +<|ref|>text<|/ref|><|det|>[[148, 774, 598, 790]]<|/det|> +Line 253. The first heading does not read well, please rephrase. + +<|ref|>sub_title<|/ref|><|det|>[[148, 805, 275, 824]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 839, 850, 912]]<|/det|> +Many thanks for your excellent advice. We have revised the Discussion section according to your guidance. We deleted some general information and moved part of the background to the Introduction section. We have revised the first heading to “Cytokinin accumulation is vital to lateral + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 91, 641, 107]]<|/det|> +organ development through controlling the duration of cell division". + +<|ref|>sub_title<|/ref|><|det|>[[148, 149, 291, 168]]<|/det|> +## Comment #15 + +<|ref|>text<|/ref|><|det|>[[147, 182, 851, 283]]<|/det|> +Comment #15Line 257/258ff. The transition from division to differentiation involves "multiple phytohormones". I wonder why here a one- page long summary of other plant hormones is given, which are not considered in this work, while the known facts about cytokinin (see above) are not described. That section should be adapted. + +<|ref|>sub_title<|/ref|><|det|>[[148, 297, 275, 316]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 330, 850, 375]]<|/det|> +RESPONSEMany thanks for your advice. We have deleted the un- relevant description and made it more focused on cytokinin. + +<|ref|>sub_title<|/ref|><|det|>[[148, 416, 292, 435]]<|/det|> +## Comment #16 + +<|ref|>text<|/ref|><|det|>[[147, 450, 850, 495]]<|/det|> +Comment #16Line 289, "energetically costly", please explain; the continuation of the sentence is questionably, please think it over. + +<|ref|>sub_title<|/ref|><|det|>[[148, 510, 275, 529]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 543, 852, 700]]<|/det|> +RESPONSEMany thanks for your advice. The phrase "energetically cost" is used to describe the negative regulation of cytokinin levels by miR159- mediated cleavage of RhCKX6. This regulatory pattern involves RhCKX6 transcripts being continuously produced, followed by their subsequent cleavage by miR159 in the early stages of petal development. As a result, considerable energy is expended to generate these transcripts, making the process energetically costly. We deleted this sentence to avoid any misleading in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 741, 291, 760]]<|/det|> +## Comment #17 + +<|ref|>text<|/ref|><|det|>[[147, 774, 850, 846]]<|/det|> +Comment #17Lines 307- 309: It might be worth mentioning that also cytokinin is involved in juvenile phase control (Werner et al., Nature Comm. 12, 5816, 2021) described here to be linked to a miR159- MYB33 module affecting miR156. + +<|ref|>sub_title<|/ref|><|det|>[[148, 861, 275, 880]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 895, 850, 912]]<|/det|> +RESPONSEMany thanks for your advice. We have revised our Discussion section by adding the information of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 388, 106]]<|/det|> +the report of Werner et al. (2021). + +<|ref|>sub_title<|/ref|><|det|>[[148, 149, 292, 168]]<|/det|> +## Comment #18 + +<|ref|>text<|/ref|><|det|>[[147, 183, 849, 200]]<|/det|> +How about the CKX6 genes in other species? Are they predicted targets of miR159? In Arabidopsis? + +<|ref|>sub_title<|/ref|><|det|>[[148, 214, 275, 233]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 248, 360, 264]]<|/det|> +Thank you for your guidance. + +<|ref|>text<|/ref|><|det|>[[147, 275, 852, 494]]<|/det|> +We conducted further experiments to examine the possibility of miR159- mediated cleavage of CKXs in other plant species. Using bioinformatics analysis, we identified a miR159- target site in AtCKX5 (Arabidopsis), MdCKX6 (Malus demestica), and FvCKX6 (Fragaria vesca). We then created GFP- Sensor constructs for each of these CKXs, following the procedure described in our response to Comment #3 of reviewer 1. Our results revealed that miR159- mediated cleavage occurred for all three Sensors. To confirm this result, we performed RLM- RACE and found evidence of cleavage in FvCKX6 in the petals of Fragaria vesca. These findings suggest that miR159- mediated cleavage of CKXs represents a common regulation pathway across different plant species. + +<|ref|>text<|/ref|><|det|>[[148, 498, 850, 541]]<|/det|> +We have added these results as Supplemental Figure S6, and mentioned the results in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 585, 292, 603]]<|/det|> +## Comment #19 + +<|ref|>text<|/ref|><|det|>[[147, 618, 850, 689]]<|/det|> +Please consider the recent paper of Zou et al. on rose CKX6, putting it in the context of petal dehydration and show its regulation by RaNAP transcription factor (Molecular Horticulture 1, 13, 2021) + +<|ref|>sub_title<|/ref|><|det|>[[148, 705, 275, 723]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 738, 849, 781]]<|/det|> +Many thanks for your advice. We have added the relevant information of the report of Zou et al. (2021) in the Discussion section. + +<|ref|>sub_title<|/ref|><|det|>[[148, 825, 292, 843]]<|/det|> +## Comment #20 + +<|ref|>text<|/ref|><|det|>[[148, 859, 213, 873]]<|/det|> +Methods + +<|ref|>text<|/ref|><|det|>[[147, 887, 526, 902]]<|/det|> +Line 394: "Quantification" instead of "Quantitative". + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 93, 275, 112]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 127, 757, 143]]<|/det|> +Many thanks for your advice. We have replaced "Quantitative" with "Quantification". + +<|ref|>sub_title<|/ref|><|det|>[[148, 186, 290, 204]]<|/det|> +## Comment #21 + +<|ref|>text<|/ref|><|det|>[[148, 219, 850, 264]]<|/det|> +Line 400. \(100\mathrm{mM}6\mathrm{- BA}\) is a very high, presumably (almost) toxic concentration (usually \(1 - 5\mu \mathrm{M}\) are used). Please check if that is correct. + +<|ref|>sub_title<|/ref|><|det|>[[148, 279, 275, 297]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 312, 851, 385]]<|/det|> +Thank you for pointing this out. We would like to apologize for this mistake. It should be \(100\mu \mathrm{M}\) here. The concentration of 6- BA used and treatment procedure were followed a previous report (Wu et al., 2017). We have corrected the description and added relevant reference. + +<|ref|>sub_title<|/ref|><|det|>[[148, 397, 234, 412]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[148, 423, 850, 496]]<|/det|> +Lin Wu, Nan Ma, Yangchao Jia, Yi Zhang, Ming Feng, Cai- Zhong Jiang, Chao Ma, Junping Gao. An ethylene- induced regulatory module delays flower senescence by regulating cytokinin content. Plant Physiology, 2017, 173: 853- 862. + +<|ref|>sub_title<|/ref|><|det|>[[148, 538, 291, 557]]<|/det|> +## Comment #22 + +<|ref|>text<|/ref|><|det|>[[148, 571, 850, 644]]<|/det|> +Cytokinin measurements. From how many plants were the samples, how many flowers (in approximation)? It would be good to include a table reporting the results for all cytokinin metabolites measured in the supplements, here the data are limited to few metabolites. + +<|ref|>sub_title<|/ref|><|det|>[[148, 658, 275, 677]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 691, 851, 820]]<|/det|> +Many thanks for your advice. To conduct the cytokinin test, we collected five flowers from five plants, and mixed them together. The mixed flowers were then divided into three separate samples for testing. We have added the sampling information in the Method section. In addition, we have added the results for all cytokinin metabolites measured as Supplementary Table S3 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 862, 291, 881]]<|/det|> +## Comment #23 + +<|ref|>text<|/ref|><|det|>[[148, 896, 723, 912]]<|/det|> +Information on how pictures (BiFC, LUC) were evaluated is completely missing. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 93, 275, 112]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 126, 850, 171]]<|/det|> +Many thanks for your advice. These information have been added in the revised Methods of Supplemental files. + +<|ref|>sub_title<|/ref|><|det|>[[148, 214, 292, 233]]<|/det|> +## Comment #24 + +<|ref|>text<|/ref|><|det|>[[148, 247, 850, 291]]<|/det|> +There are some inconsistencies in units, as both \(\mu \mathrm{g}\) and microgram, \(\mathrm{mg / L}\) , \(\mathrm{ng / ml}\) and \(\mathrm{mg x 1 - 1}\) are used, please unify. + +<|ref|>sub_title<|/ref|><|det|>[[148, 305, 275, 325]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 340, 728, 356]]<|/det|> +Many thanks for your advice. We have unified the units in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 398, 291, 419]]<|/det|> +## Reviewer #3 + +<|ref|>sub_title<|/ref|><|det|>[[148, 435, 278, 454]]<|/det|> +## Comment #1 + +<|ref|>text<|/ref|><|det|>[[147, 468, 852, 736]]<|/det|> +The authors mention that the underlying mechanism controlling the transition from cell proliferation to expansion in leaves remains largely unknown. However, there are known regulators controlling this transition, such as the miR319- regulated TCP (CIN- Like) transcription factors. miR319 is similar in sequence to miR159, and target mimicry against miR159 can cross target miR319 (Reichel and Millar, 2015). In addition, miR319- TCP controls petal growth and development (i.e., Nag et al., 2009). Therefore, I think that the authors need to consider the possibility that STTM159 could be affecting petal growth through the modification of the miR319- TCP module. The complete miR319/miR159 family of miRNAs in rose (which might contain several members) should be analyzed in STTM159 plants. The analysis of miRNA- targets should also include rose TCP transcription factors that are targets of miR319. + +<|ref|>sub_title<|/ref|><|det|>[[148, 750, 275, 769]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 783, 852, 913]]<|/det|> +Thank you for your excellent advice. According to your valuable suggestion, we have revised our statement, and now we have included the relevant reference of miR319- TCP in the revised version of our manuscript. Furthermore, we conducted Northern blot and qRT- PCR experiments to detect the levels of mature miR159 and miR319 in rose petals during the developmental time course. The results of our Northern blot revealed a significant reduction in miR159 levels from day 1 to day 5, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 851, 191]]<|/det|> +whereas miR319 levels remained relatively constant from day 1 to day 3 and decreased on day 5. Our qRT- PCR data indicated that the expression level of miR319 in rose petals was much lower than that of miR159 from day 1 to day 5. These results were consistent with our previous miRNA- seq analysis of rose petals during earlier developmental stages (Pei et al., 2013). + +<|ref|>text<|/ref|><|det|>[[147, 200, 851, 273]]<|/det|> +In Arabidopsis, miR319/TCPs controls floral organ morphology. Expression of the miR319- resistant form of TCP4 under the control of the petal- and stamen- specific AP3 promoter led to a complete absence of petals and stamens (Nag et al., 2009). + +<|ref|>text<|/ref|><|det|>[[147, 284, 851, 384]]<|/det|> +After analyzing our RNA- seq data, we have found that the expression levels of TCP2, TCP4, and TCP4- x1, which are targeted by miR319, were not significantly altered in the petals of the miR159- silenced lines. Upon further confirmation using qRT- PCR, we have determined that TCP2/4/4- x1 expression levels remained unchanged in the petals of the miR159- silenced lines. + +<|ref|>text<|/ref|><|det|>[[147, 395, 851, 440]]<|/det|> +We have added relevant results as Figure1a and Supplementary Figure S8, and discussed the possible role of miR319/TCPs in the Discussion section. + +<|ref|>image<|/ref|><|det|>[[166, 454, 825, 712]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[147, 729, 850, 772]]<|/det|> +## Supplemental Figure S8 Northern Blot of miR319 and expression of TCP genes in petals of miR159-silenced lines. + +<|ref|>text<|/ref|><|det|>[[147, 781, 851, 852]]<|/det|> +a, RT-qPCR analysis of miR159 and miR319 levels in rose petals (1, 3 and 5 days after stage 0). Data are shown as means \(\pm\) SD from four biological replicates (n=3). 55 rRNA was used as an internal control. Asterisks indicate statistically significant differences (two- sided Student's \(t\) - test, \*, \(P < 0.05\) ; \*\*, \(P < 0.01\) ; \*\*\*, \(P < 0.001\) ; ns, no significant difference). + +<|ref|>text<|/ref|><|det|>[[147, 855, 850, 888]]<|/det|> +b, Northern blotting analysis of miR319 abundance in rose petals 1, 3, and 5 day after floral bud reached stage 0. U6 was used as control. + +<|ref|>text<|/ref|><|det|>[[147, 892, 707, 907]]<|/det|> +c, Heatmap analysis of miR159 and miR319 abundance in rose petals at stage 0 and stage 2. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 86, 850, 120]]<|/det|> +d, RT-qPCR analysis of RhTCPs in TRV- STTM159. RhUBI2 was used as an internal control. Data are shown as means \(\pm\) SD from three biological replicates ( \(\mathrm{n} = 3\) ). + +<|ref|>sub_title<|/ref|><|det|>[[148, 137, 234, 152]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[147, 164, 852, 293]]<|/det|> +Haixia Pei, Nan Ma, Jiwei Chen, Yi Zheng, Ji Tian, Jing Li, Shuai Zhang, Zhangjun Fei, Junping Gao. Integrative analysis of miRNA and mRNA profiles in response to ethylene in rose petals during flower opening. PLoS One, 2013, 8: e64290. Anwesha Nag, Stacey King, & Thomas Jack. miR319a targeting of TCP4 is critical for petal growth and development in Arabidopsis. Proc. Natl Acad. Sci. USA, 2009, 106: 22534- 22539. + +<|ref|>sub_title<|/ref|><|det|>[[149, 335, 280, 354]]<|/det|> +## Comment #2 + +<|ref|>text<|/ref|><|det|>[[147, 368, 852, 496]]<|/det|> +1) MicroRNAs guide the cleavage of their targets at position 10-11 (Fig 3a). The authors did not find any cut at this position for CKX6, which argues against the regulation by miR159. The authors say that they analyzed CKX6 cleavage in rose petals in the Results section, but in Methods they say that the experiment was performed from 35S:pre-MIR159 transient overexpression plants (tobacco?). The cleavage site should be determined in wt rose petals. + +<|ref|>text<|/ref|><|det|>[[147, 507, 852, 634]]<|/det|> +2) miR159 is strongly expressed in tobacco leaves, so I'm surprised that the authors could express large amounts of a GFP sensor for a miR159-target (Fig 3). The levels of mature miR159 should be determined in tobacco leaves to show the increase of miR159 after the expression of rose pre-miR159. The expression of the sensors in N. benthamiana leaves is patchy which might be caused by RNA silencing (independent of the miRNA). + +<|ref|>text<|/ref|><|det|>[[147, 645, 852, 740]]<|/det|> +3) The determination of mature miRNAs by qPCR can be tricky – for example, miRNAs from the same family can have differences in their 3' end, yet they regulate the same targets. It is better to determine miRNA levels by small RNA blots. + +<|ref|>text<|/ref|><|det|>[[147, 730, 850, 774]]<|/det|> +Overall, I don't think that the current manuscript shows clear evidence for the regulation of CKX6 by miR159. + +<|ref|>sub_title<|/ref|><|det|>[[148, 788, 275, 806]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[149, 822, 411, 838]]<|/det|> +Thank you for your excellent advice. + +<|ref|>text<|/ref|><|det|>[[148, 849, 850, 894]]<|/det|> +1) We would like to apologize for this mistake. For Figure 3a, the RLM-RACE was performed using rose petals and we corrected it in the revised version. According to your advice, we sequenced more + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 852, 191]]<|/det|> +clones for RLM- RACE of RhCKX6 in rose petals. In addition, we predicted miR159- target site in FvCKX6 (Fragaria vesca). RLM- RACE supported the miR159- mediated cleavage of FvCKX6 in petals of Fragaria vesca. These results indicated that miR159- mediated cleavage of CKX6 could be a common regulation pathway. + +<|ref|>image<|/ref|><|det|>[[156, 204, 833, 468]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[147, 480, 593, 496]]<|/det|> +## Supplemental Figure S6 miR159 targets FvCKX6 in planta. + +<|ref|>text<|/ref|><|det|>[[147, 503, 850, 538]]<|/det|> +a, Confocal imaging analysis of N. benthamiana leaves 3 days after co- infiltration of pre- MIR159 with FvCKX6- sensor- GFP or FvCKX6m- sensor- GFP. + +<|ref|>text<|/ref|><|det|>[[147, 541, 850, 594]]<|/det|> +b, Validation of miR159- targeted cleavage of FvCKX6. Upper panel, schematic diagram of FvCKX6 mRNA. Red box, predicted cleavage site of miR159. Bottom panel, identification of cleavage sites using 5' RLM- RACE assay in strawberry petals. The positions of cleavage sites are indicated by arrowheads with the frequency of clones. + +<|ref|>text<|/ref|><|det|>[[147, 618, 851, 719]]<|/det|> +2) According to your suggestions, we detected the level of mature miR159 in tobacco leaves overexpressed rose pre-miR159. The data indicates that the abundance of mature miR159 in tobacco leaves expressing pSuper:pre-MIR159 was significantly higher as compared to those expressing pSuper empty vector. + +<|ref|>text<|/ref|><|det|>[[147, 729, 851, 858]]<|/det|> +To prevent gene silencing, a P19 silencing suppressor was co- infiltrated in all combinations in the GFP- Sensor test. The intensity of GFP fluorescence was found to reduce in the pSuper:pre- MIR159+RhCKX6- Sensor combination, but not in the pSuper:pre- MIR159+RhCKX6m- Sensor combination (Fig. 3b). This supports that the decrease in intensity of GFP fluorescence was due to cleavage of RhCKX6- Sensor caused by miR159. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[164, 95, 430, 336]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[148, 350, 777, 367]]<|/det|> +## The expression of mature miR159 in tobacco leaves overexpressed rose pre-miR159 + +<|ref|>text<|/ref|><|det|>[[148, 374, 850, 408]]<|/det|> +RT- qPCR analysis of the mature miR159 in tobacco leaves overexpressed rose pre- miR159. Data are shown as means \(\pm \mathrm{SD}\) from four biological replicates \((n = 3)\) . 5S rRNA was used as an internal control. + +<|ref|>text<|/ref|><|det|>[[147, 432, 851, 533]]<|/det|> +3) As you suggested, the levels of mature miR159 and miR319 were measured in rose petals throughout petal growth using Northern blot analysis. The results revealed a significant reduction in miR159 levels from day 1 to day 5, whereas miR319 levels remained relatively constant from day 1 to day 3 and decreased on day 5. + +<|ref|>text<|/ref|><|det|>[[148, 544, 850, 588]]<|/det|> +Based on the data, it can be inferred that miR159 may have a regulatory role in the accumulation of RhCKX6 transcript levels in rose petals. + +<|ref|>text<|/ref|><|det|>[[148, 599, 850, 644]]<|/det|> +We have added these relevant results as in Figure1a, Supplemental Figure S6 and Supplementary Figure S8, and revised relevant description in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 686, 280, 705]]<|/det|> +## Comment #3 + +<|ref|>text<|/ref|><|det|>[[147, 720, 852, 847]]<|/det|> +Inactivation of miR159 (by target mimicry or mir159a/b knock outs) in Arabidopsis causes pleiotropic developmental defects in leaves and stunted plants. Please, show and describe the plant growth and overall phenotypes of the VIGS lines (STTMIR159, and rhMYB73 and RhCKX6)- silenced lines. Also, indicate the number of plants analyzed in each case, and the distribution of the phenotypes observed (i.e., percentage of plants displaying the selected phenotypes). + +<|ref|>sub_title<|/ref|><|det|>[[148, 861, 275, 880]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 895, 849, 912]]<|/det|> +Thank you for your advice. For VIGS, the tissue- cultured plantlets were used for Agrobacterium + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 852, 273]]<|/det|> +mediated infection as described before (Sha et al., 2014; Tian et al., 2014; Chen et al., 2021). Since TRV virus just moved upward and induced gene silencing in the newly grown leaves and flowers after infiltration, we could only observe the phenotypes in these newly emerged leaves and flowers. We did not found that there are stunted newly emerged leaves and plants in TRV- STTM159, TRV- RhCKX6 and TRV- RhMYB73 silencing lines compared with control (TRV line). According to your valuable suggestions, we described the number of plants displaying the selected phenotypes for each VIGS lines in the VIGS method. + +<|ref|>sub_title<|/ref|><|det|>[[148, 285, 234, 300]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[147, 312, 852, 551]]<|/det|> +Aihua Sha, Jinping Zhao, Kangquan Yin, Yang Tang, Yan Wang, Xiang Wei, Yiguo Hong, Yule Liu, Virus- Based MicroRNA Silencing in Plants, Plant Physiology, 2014, 164: 36- 47 Ji Tian, Haixia Pei, Shuai Zhang, Jiwei Chen, Wen Chen, Ruoyun Yang, Yonglu Meng, Jie You, Junping Gao, Nan Ma\*, TRV- GFP: a modified Tobacco rattle virus vector for efficient and visualizable analysis of gene function, Journal of Experimental Botany, 2014, 65: 311- 322. Jiwei Chen, Yang Li, Yonghong Li, Yuqi Li, Yi Wang, Chuyan Jiang, Patrick Choisy, Tao Xu, Youming Cai, Dong Pei, Cai- Zhong Jiang, Su- Sheng Gan, Junping Gao, Nan Ma. AUXIN RESPONSE FACTOR 18- HISTONE DEACETYLASE 6 module regulates floral organ identity in rose (Rosa hybrida). Plant Physiology, 2021, 186: 1074- 1087. + +<|ref|>sub_title<|/ref|><|det|>[[149, 593, 280, 612]]<|/det|> +## Comment #4 + +<|ref|>text<|/ref|><|det|>[[148, 626, 851, 699]]<|/det|> +For VIGS, authors used fragments of approx. 400 bp for RhMYB73 miR159 and RhCKX6. These are long fragments. Are the authors confident that other MYBs or CKX genes were not affected? I think using artificial microRNAs would have been a more specific strategy. + +<|ref|>sub_title<|/ref|><|det|>[[148, 713, 275, 732]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 746, 852, 896]]<|/det|> +Thank you for your excellent advice. For VIGS, the gene fragment insert is usually in the range of 300- 500 nucleotides to ensure efficient silencing of endogenous genes (Burch- Smith et al., 2004; Senthil- Kumar & Mysor, 2011). We chose the gene- specific UTR region to construct the TRV- MYB73 and TRV- CKX6 to avoid cross- silencing. According to your suggestions, we tested expression of two MYBs (RhMYB70/77), which are close to RhMYB73, in RhMYB73- silenced lines. Similarly, we tested the expression of two CKXs + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 852, 219]]<|/det|> +(RhCKX1/5), which are close to RhCKX6, in RhCKX6- silenced lines. We didn't find significant change of expression of RhMYB70/77 in RhMYB73- silenced lines compared to TRV control, indicating that RhMYB73 was specifically silenced. Similarly, the results indicated that RhCKX6 was specifically silenced. We added these results as Supplemental Figure S9 and Supplemental Figure S12d, e. + +<|ref|>image<|/ref|><|det|>[[155, 230, 465, 393]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[147, 432, 850, 476]]<|/det|> +## Supplemental Figure S9 Expression of RhCKX1 and RhCKX5 in TRV and RhCKX6-silenced lines. + +<|ref|>text<|/ref|><|det|>[[147, 484, 852, 555]]<|/det|> +a, Schematic representation of the gene-specific fragment of RhCKX6 for construction of the TRV- CKX6 vector. b, Expression of RhCKX1 and RhCKX5 in TRV and RhCKX6- silenced plants. RhUBI2 was used as an internal control. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \((\mathrm{n} = 3)\) (two- sided Student's \(t\) - test, ns, no significant difference). + +<|ref|>image<|/ref|><|det|>[[157, 577, 844, 702]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[147, 729, 583, 745]]<|/det|> +## Supplemental Figure S12 Characterization of RhMYB73. + +<|ref|>text<|/ref|><|det|>[[147, 753, 850, 824]]<|/det|> +d, Schematic representation of the gene- specific fragment of RhMYB73 for construction of the TRV- MYB73 vector. e, Expression of RhMYB70 and RhMYB77 in RhMYB73- silenced plants. RhUBI2 was used as an internal control. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \((\mathrm{n} = 3)\) (two- sided Student's \(t\) - test, ns, no significant difference). + +<|ref|>text<|/ref|><|det|>[[147, 832, 850, 875]]<|/det|> +Meanwhile, we agreed with you that artificial microRNAs could be a more specific strategy, but we could not generate stable transgenic artificial miR159 lines in a short time. + +<|ref|>sub_title<|/ref|><|det|>[[148, 888, 234, 902]]<|/det|> +## References + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 160]]<|/det|> +Tessa M. Burch- Smith, Jeffrey C. Anderson, Gregory B. Martin, S. P. Dinesh- Kumar. Applications and advantages of virus- induced gene silencing for gene function studies in plants. The Plant Journal, 2004, 39: 734- 746. + +<|ref|>text<|/ref|><|det|>[[147, 172, 850, 218]]<|/det|> +Muthappa Senthil- Kumar, Kirankumar S. Mysor. New dimensions for VIGS in plant functional genomics. Trends in Plant Science, 2011, 16: 656- 665. + +<|ref|>sub_title<|/ref|><|det|>[[148, 260, 280, 280]]<|/det|> +## Comment #5 + +<|ref|>text<|/ref|><|det|>[[147, 293, 851, 366]]<|/det|> +I think it would be important to include the phenotypes of roses overexpressing pre- miR159, which should down- regulate RhCKX6 and increase petal size. This vector is used in the N. benthamiana assays. + +<|ref|>sub_title<|/ref|><|det|>[[148, 380, 275, 400]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 414, 852, 542]]<|/det|> +Thank you for your excellent advice. We conducted an experiment to investigate the impact of pre- miR159 overexpression on the size of rose petals. The study was based on the methods described in a previous publication (Liang et al., 2020, Plant Cell). Our findings revealed that overexpression of pre- miR159 resulted in larger petals compared to control plants and also extended the duration of cell division (from S0 to S2). + +<|ref|>text<|/ref|><|det|>[[148, 554, 520, 570]]<|/det|> +We added these results as Supplemental Figure S10. + +<|ref|>image<|/ref|><|det|>[[152, 579, 610, 899]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 90, 653, 107]]<|/det|> +## Supplemental Figure S10 Overexpression of MIR159 in rose petals. + +<|ref|>text<|/ref|><|det|>[[147, 114, 852, 167]]<|/det|> +a,b, Flower opening progression of Control and MIR159- OE plants. The experiments were performed independently twice with similar results, and one representative set of results is shown. Scale bars, \(2\mathrm{cm}\) . Data are shown as means \(\pm \mathrm{SD}\) from 10 biological replicates \(\mathrm{(n = 10)}\) in b. + +<|ref|>text<|/ref|><|det|>[[147, 170, 852, 223]]<|/det|> +c, RT- qPCR analysis of miR159 abundance and RhCKX6 transcript levels in petals of Control and MIR159- OE plants. 5S rRNA was used as an internal control of miR159. RhUBI2 was used as an internal control of RhCKX6. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \(\mathrm{(n = 3)}\) . + +<|ref|>text<|/ref|><|det|>[[147, 226, 852, 279]]<|/det|> +d, Petal size of Control and MIR159- OE plants at the fully opened stage. Data are shown as means \(\pm \mathrm{SD}\) from three biological replicates \(\mathrm{(n = 3)}\) . The numbers below the images indicate the petal size. Scale bar, \(1\mathrm{cm}\) . (two- sided Student's \(t\) - test, \(^{*},P< 0.05\) ; \(^{**}P< 0.01\) ). + +<|ref|>sub_title<|/ref|><|det|>[[148, 334, 280, 353]]<|/det|> +## Comment #6 + +<|ref|>text<|/ref|><|det|>[[147, 367, 852, 524]]<|/det|> +The authors predict the regulation of several CKXs by miR159 in rose and arabidopsis (Supplementary Fig 4). The location of a miRNA- target site in a target gene is usually conserved during evolution and not variable as depicted in this figure. There is plenty of experimental information identifying miRNA targets in arabidopsis in publicly available databases. Please use this info to show the empirical data for the regulation by miR159 for the two predicted Arabidopsis targets. + +<|ref|>sub_title<|/ref|><|det|>[[148, 538, 275, 557]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 571, 852, 783]]<|/det|> +Thank you for your guidance. We searched the public database for the regulation by miR159 for the two predicted Arabidopsis targets. We could found these two targets in the miR159 target survey but we failed to find the change of expression level of these two targets in miR159abc mutant. To test whether miR159- mediated cleavage of CKXs is a common regulatory pathway, we predicted miR159- target site in FvCKX6 (Fragaria vescac) as well. RLM- RACE confirmed the miR159- mediated cleavage of FvCKX6 in petals of Fragaria vescac, indicating that miR159- mediated cleavage of CKXs might be a common regulation pathway in petals. Supplemental Figure S6 and revised relevant description in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 825, 279, 844]]<|/det|> +## Comment #7 + +<|ref|>text<|/ref|><|det|>[[148, 859, 273, 873]]<|/det|> +Other comments: + +<|ref|>text<|/ref|><|det|>[[147, 886, 850, 903]]<|/det|> +Please include in the Supplementary Tables the description for the selected rose genes (or the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 470, 106]]<|/det|> +description of their arabidopsis homologues). + +<|ref|>sub_title<|/ref|><|det|>[[148, 121, 275, 140]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 155, 850, 200]]<|/det|> +Thank you for your advice. We have added the description for the selected genes in Rosa hybrid, Arabidopsis, Malus demestica, and Fragaria vesca in Supplementary Table S7. + +<|ref|>sub_title<|/ref|><|det|>[[148, 242, 280, 261]]<|/det|> +## Comment #8 + +<|ref|>text<|/ref|><|det|>[[147, 275, 852, 404]]<|/det|> +L78 - "To understand the underlying mechanism of the transition between cell division and cell expansion, we previously conducted a transcriptome deep sequencing (RNA- seq) analysis of short RNAs and transcripts from petals to investigate gene expression profiles during the cell division and expansion phases." - please include the citation for the article describing the RNAseq analysis of short RNAs and transcripts. + +<|ref|>sub_title<|/ref|><|det|>[[148, 418, 275, 437]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 451, 850, 496]]<|/det|> +Thank you for your advice. We have added the citation for describing the RNA- seq analysis of short RNAs and transcripts in the revised Method section. + +<|ref|>sub_title<|/ref|><|det|>[[148, 508, 234, 523]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[148, 535, 850, 580]]<|/det|> +Ben Langmead, Cole Trapnell, Mihai Pop, Steven Salzberg. Ultrafast and memoryefficient alignment of short DNA sequences to the human genome. Genome Biology, 2009, 10: R25. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 332, 100]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[119, 116, 450, 133]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 149, 844, 181]]<|/det|> +The authors have added the appropriate data and made the appropriate text revisions to address my previous concerns. + +<|ref|>sub_title<|/ref|><|det|>[[119, 213, 450, 229]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 245, 872, 360]]<|/det|> +The manuscript by Jing et al. on the role of miR159 in regulating rose petal size has been improved significantly. Most of my points have been addressed. New data have been added which resolves previously open questions. However, I still have some remarks on the previous parts and, in particular, on some of the newly added sections. While the science looks sound to me the description of the results and their interpretation is sometimes not precise enough, which might be due to language problems. I think the authors need help in this matter. + +<|ref|>sub_title<|/ref|><|det|>[[119, 376, 156, 390]]<|/det|> +## Title + +<|ref|>text<|/ref|><|det|>[[118, 392, 870, 520]]<|/det|> +The new title is improved but does in my opinion not match exactly the topic of the manuscript as miR159 appears not to regulate cell division per se but rather the transition from cell division to differentiation. Some suggestions: In rose, petal size is regulated by the MYB73/TPL/HDA19- miR156- CKX6 module In rose, petal size is controlled by the MYB73/TPL/HDA19- miR156- CKX6 module regulating (cell number through) cytokinin catabolism In rose, the MYB73/TPL/HDA19- miR156- CKX6 module regulates the transition from cell division to differentiation and growth and thus petal size + +<|ref|>sub_title<|/ref|><|det|>[[118, 537, 190, 551]]<|/det|> +## Abstract + +<|ref|>text<|/ref|><|det|>[[118, 553, 860, 666]]<|/det|> +Line 22, "earlier cytokinin clearance" rather than "precocious cytokinin clearance", furthermore an "a" is missing "leading to 'a' shortened cell division period". Line 23, it is not the cell division itself that is prolonged but the "developmental cell division period". The reference to cell division instead of cell division period/cell division phase occurs at several occasions in the whole manuscript. Line 28, Instead of "correct timing of cell division and organ size" it is rather the "correct timing of the exit from the cell division phase and thus the regulation of organ size ..." + +<|ref|>sub_title<|/ref|><|det|>[[118, 684, 217, 698]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[118, 700, 860, 905]]<|/det|> +Line 35, The references do not reflect the mentioned "century- long fascination for size regulation of organisms". Line 37, "stepwise" should be deleted as these phases are dynamically linked Line 42, the number of cell is determined by the number of divisions, not by the rate of cell proliferation Line 46, precise what "arrest front" is meant here. Of cell division? Line 47, cytokinin takes a small "c" Line 59, "serval" is "several" There are numerous others of these small mistakes which I do not list all. Line 83 in a heading it is again not the "duration of cell division" which is controlled by miR159 but the duration of "cell division phase", and again in line 174, and in line 338 Line 122, I do not see the term "zeatin biosynthesis" in Fig. 2a Line 207, "cell numbers of cell numbers", please correct + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 468, 100]]<|/det|> +Line 211, "rapid clearance" was not shown + +<|ref|>sub_title<|/ref|><|det|>[[119, 117, 210, 131]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[119, 133, 876, 215]]<|/det|> +The first part of the Discussion describes size regulation of Arabidopsis leaves and maize by other hormones. While this is interesting it does not fit here, it may be used (in a short version) in the Introduction to describe already known systems of organ size regulation or later in the Discussion as a comparison. Start the Discussion with your own results. It should be concise, highlight the novelties of the findings and put these into perspective. + +<|ref|>text<|/ref|><|det|>[[119, 230, 839, 262]]<|/det|> +In the reporting summary under Data analysis: "secondary structure" instead of "second structure" + +<|ref|>sub_title<|/ref|><|det|>[[119, 310, 450, 327]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 343, 785, 376]]<|/det|> +The authors conducted additional experiments to generate new data. The revised manuscript has improved significantly. + +<|ref|>text<|/ref|><|det|>[[119, 392, 280, 407]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[119, 408, 861, 440]]<|/det|> +Figure S2c: The structure of the precursor is truncated and the miRNA has less than 21nt - more sequence needs to be added. + +<|ref|>text<|/ref|><|det|>[[119, 455, 865, 504]]<|/det|> +Fig S8b: The authors show a blot to detect miR319. However, since miR319 and miR159 share a similar sequence, and miR319 is expressed at lower levels compared to miR159, it is likely that the blot is detecting miR159 through cross- hybridization instead of miR319. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[148, 101, 380, 120]]<|/det|> +# Response to Reviewers + +<|ref|>text<|/ref|><|det|>[[148, 145, 523, 164]]<|/det|> +Manuscript No. NCOMMS- 22- 37721 + +<|ref|>text<|/ref|><|det|>[[148, 188, 850, 245]]<|/det|> +Title: In rose, miR159 regulates petal cell division by modulating cytokinin catabolism + +<|ref|>title<|/ref|><|det|>[[148, 287, 290, 307]]<|/det|> +# Reviewer #1 + +<|ref|>sub_title<|/ref|><|det|>[[148, 347, 278, 366]]<|/det|> +## COMMENT + +<|ref|>text<|/ref|><|det|>[[148, 388, 850, 431]]<|/det|> +The authors have added the appropriate data and made the appropriate text revisions to address my previous concerns. + +<|ref|>sub_title<|/ref|><|det|>[[148, 454, 275, 473]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 496, 414, 511]]<|/det|> +Many thanks for your kind comment. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 97, 292, 118]]<|/det|> +## Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[149, 157, 306, 177]]<|/det|> +## COMMENT #1 + +<|ref|>text<|/ref|><|det|>[[148, 198, 850, 270]]<|/det|> +The manuscript by Jing et al. on the role of miR159 in regulating rose petal size has been improved significantly. Most of my points have been addressed. New data have been added which resolves previously open questions. + +<|ref|>text<|/ref|><|det|>[[148, 281, 851, 381]]<|/det|> +However, I still have some remarks on the previous parts and, in particular, on some of the newly added sections. While the science looks sound to me the description of the results and their interpretation is sometimes not precise enough, which might be due to language problems. I think the authors need help in this matter. + +<|ref|>sub_title<|/ref|><|det|>[[148, 404, 275, 423]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 444, 851, 516]]<|/det|> +Thank you for your valuable advice. We have carefully revised our manuscript according to your suggestions and asked a professional scientific editing service to enhance the quality of writing and precision of interpretation (https://planteditors.com/). + +<|ref|>sub_title<|/ref|><|det|>[[149, 566, 308, 585]]<|/det|> +## COMMENT #2 + +<|ref|>text<|/ref|><|det|>[[148, 606, 851, 676]]<|/det|> +The new title is improved but does in my opinion not match exactly the topic of the manuscript as miR159 appears not to regulate cell division per se but rather the transition from cell division to differentiation. Some suggestions: + +<|ref|>text<|/ref|><|det|>[[148, 688, 744, 706]]<|/det|> +In rose, petal size is regulated by the MYB73/TPL/HDA19- miR159- CKX6 module. + +<|ref|>text<|/ref|><|det|>[[148, 716, 850, 760]]<|/det|> +In rose, petal size is controlled by the MYB73/TPL/HDA19- miR159- CKX6 module regulating cytokinin catabolism. + +<|ref|>text<|/ref|><|det|>[[148, 772, 850, 816]]<|/det|> +In rose, the MYB73/TPL/HDA19- miR159- CKX6 module regulates the transition from cell division to differentiation and growth and thus petal size. + +<|ref|>sub_title<|/ref|><|det|>[[148, 839, 275, 857]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 879, 850, 896]]<|/det|> +Thank you for your excellent suggestions. We revised the title of our manuscript as 'In rose, petal + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 135]]<|/det|> +size is controlled by the MYB73/TPL/HDA19- miR159- CKX6 module regulating cytokinin catabolism'. + +<|ref|>sub_title<|/ref|><|det|>[[148, 175, 308, 194]]<|/det|> +## COMMENT #3 + +<|ref|>text<|/ref|><|det|>[[148, 215, 850, 260]]<|/det|> +Line 22, "earlier cytokinin clearance" rather than "precocious cytokinin clearance", furthermore an "a" is missing "leading to 'a' shortened cell division period". + +<|ref|>sub_title<|/ref|><|det|>[[148, 281, 275, 300]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 322, 850, 366]]<|/det|> +Thank you for your advice. We revised the sentence accordingly. Please see Line 21- 22 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 415, 308, 434]]<|/det|> +## COMMENT #4 + +<|ref|>text<|/ref|><|det|>[[147, 456, 853, 530]]<|/det|> +Line 23, it is not the cell division itself that is prolonged but the "developmental cell division period". The reference to cell division instead of cell division period/cell division phase occurs at several occasions in the whole manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 551, 275, 569]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 591, 850, 663]]<|/det|> +Thank you for your advice. We corrected the relevant description accordingly. Please see Line 23, Line 71, Line 99, Line 189, Line 206, Line 269, Line 314, Line 322, and Line 381 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 712, 308, 731]]<|/det|> +## COMMENT #5 + +<|ref|>text<|/ref|><|det|>[[147, 753, 850, 798]]<|/det|> +Line 28, Instead of "correct timing of cell division and organ size" it is rather the "correct timing of the exit from the cell division phase and thus the regulation of organ size ..." + +<|ref|>sub_title<|/ref|><|det|>[[148, 819, 275, 838]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 860, 850, 904]]<|/det|> +Thank you for your advice. We corrected the description accordingly. Please see Line 28 in the revised version. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 128, 308, 147]]<|/det|> +## COMMENT #6 + +<|ref|>text<|/ref|><|det|>[[147, 169, 850, 214]]<|/det|> +Line 35, The references do not reflect the mentioned "century- long fascination for size regulation of organisms". + +<|ref|>sub_title<|/ref|><|det|>[[148, 235, 275, 254]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 275, 851, 348]]<|/det|> +Thank you for your advice. We revised this sentence to 'How the size of living organisms is regulated makes for a fascinating and attractive research question'. Please see Line 33- 34 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 397, 308, 416]]<|/det|> +## COMMENT #7 + +<|ref|>text<|/ref|><|det|>[[147, 438, 696, 455]]<|/det|> +Line 37, "stepwise" should be deleted as these phases are dynamically linked + +<|ref|>sub_title<|/ref|><|det|>[[148, 477, 275, 496]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 518, 680, 535]]<|/det|> +Thank you for your suggestion. We have deleted the "stepwise" in Line 36. + +<|ref|>sub_title<|/ref|><|det|>[[148, 583, 308, 602]]<|/det|> +## COMMENT #8 + +<|ref|>text<|/ref|><|det|>[[147, 624, 850, 668]]<|/det|> +Line 42, the number of cell is determined by the number of divisions, not by the rate of cell proliferation + +<|ref|>sub_title<|/ref|><|det|>[[148, 690, 275, 709]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 731, 850, 775]]<|/det|> +Thank you for your suggestion. We have corrected the description accordingly. Please see Line 40 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 824, 308, 843]]<|/det|> +## COMMENT #9 + +<|ref|>text<|/ref|><|det|>[[147, 865, 626, 882]]<|/det|> +Line 46, precise what "arrest front" is meant here. Of cell division? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 93, 275, 113]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 134, 850, 179]]<|/det|> +Thank you for your suggestion. We have corrected the description to 'cell- cycle arrest front' in Line 44 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[149, 228, 320, 248]]<|/det|> +## COMMENT #10 + +<|ref|>text<|/ref|><|det|>[[148, 269, 404, 285]]<|/det|> +Line 47, cytokinin takes a small "c" + +<|ref|>text<|/ref|><|det|>[[148, 297, 358, 312]]<|/det|> +Line 59, "serval" is "several" + +<|ref|>sub_title<|/ref|><|det|>[[148, 335, 275, 354]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 376, 707, 393]]<|/det|> +Thank you for your suggestion. We have corrected the description accordingly. + +<|ref|>sub_title<|/ref|><|det|>[[148, 440, 317, 460]]<|/det|> +## COMMENT #11 + +<|ref|>text<|/ref|><|det|>[[148, 482, 850, 527]]<|/det|> +Line 83 in a heading it is again not the "duration of cell division" which is controlled by miR159 but the duration of "cell division phase", and again in line 174, and in line 338. + +<|ref|>sub_title<|/ref|><|det|>[[148, 548, 275, 567]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 589, 850, 661]]<|/det|> +Thank you for your suggestion. We have corrected the description accordingly. Please see Line 89, Line 99, Line 189, Line 269, Line 314, Line 322, Line 332- 333, Line 381, Line 694, Line 752, Line 779- 780, Line 824, Line 877, Line 984, Line 1030, and Line 1087 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 711, 320, 730]]<|/det|> +## COMMENT #12 + +<|ref|>text<|/ref|><|det|>[[148, 752, 594, 768]]<|/det|> +Line 122, I do not see the term "zeatin biosynthesis" in Fig. 2a + +<|ref|>sub_title<|/ref|><|det|>[[148, 790, 275, 809]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 830, 850, 904]]<|/det|> +Thank you for your advice. Maybe the font of Fig. 2a is too small. We revised the figure by indicating the term of 'plant hormone signal transduction' and 'zeatin biosynthesis' with an arrow, respectively. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 99, 500, 333]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[149, 360, 320, 379]]<|/det|> +## COMMENT #13 + +<|ref|>text<|/ref|><|det|>[[148, 401, 553, 416]]<|/det|> +Line 207, "cell numbers of cell numbers", please correct. + +<|ref|>sub_title<|/ref|><|det|>[[148, 439, 275, 458]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[149, 481, 424, 496]]<|/det|> +Sorry for this mistake. We corrected it. + +<|ref|>sub_title<|/ref|><|det|>[[148, 545, 320, 564]]<|/det|> +## COMMENT #14 + +<|ref|>text<|/ref|><|det|>[[148, 587, 459, 602]]<|/det|> +Line 211, "rapid clearance" was not shown. + +<|ref|>sub_title<|/ref|><|det|>[[148, 624, 275, 643]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[147, 666, 844, 682]]<|/det|> +Thank you for pointing this out. We deleted the 'rapid'. Please see Line 227 in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[148, 730, 320, 749]]<|/det|> +## COMMENT #15 + +<|ref|>text<|/ref|><|det|>[[148, 773, 229, 787]]<|/det|> +Discussion + +<|ref|>text<|/ref|><|det|>[[147, 799, 852, 900]]<|/det|> +The first part of the Discussion describes size regulation of Arabidopsis leaves and maize by other hormones. While this is interesting it does not fit here, it may be used (in a short version) in the Introduction to describe already known systems of organ size regulation or later in the Discussion as a comparison. Start the Discussion with your own results. It should be concise, highlight the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 540, 106]]<|/det|> +novelties of the findings and put these into perspective. + +<|ref|>sub_title<|/ref|><|det|>[[148, 128, 275, 147]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 169, 851, 241]]<|/det|> +Thank you for your valuable advice. According to your suggestion, we shortened the discussion of size regulation of Arabidopsis leaves and maize by other hormones, and moved this part to Introduction section in the revised version. + +<|ref|>sub_title<|/ref|><|det|>[[149, 291, 320, 310]]<|/det|> +## COMMENT #16 + +<|ref|>text<|/ref|><|det|>[[147, 332, 846, 348]]<|/det|> +In the reporting summary under Data analysis: "secondary structure" instead of "second structure" + +<|ref|>sub_title<|/ref|><|det|>[[148, 370, 275, 388]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 410, 849, 455]]<|/det|> +Thank you for pointing this out. We have corrected the description in Date analysis of the reporting summary. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 97, 291, 118]]<|/det|> +## Reviewer #3 + +<|ref|>sub_title<|/ref|><|det|>[[148, 157, 307, 177]]<|/det|> +## COMMENT #1 + +<|ref|>text<|/ref|><|det|>[[148, 199, 850, 243]]<|/det|> +Figure S2c: The structure of the precursor is truncated and the miRNA has less than 21nt- more sequence needs to be added. + +<|ref|>sub_title<|/ref|><|det|>[[148, 264, 275, 283]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 305, 850, 349]]<|/det|> +Thank you for your valuable advice. We re- predicted the structure of rhy- MIR159 containing the 21nt of miR159 in the revised Figure S2c. + +<|ref|>image<|/ref|><|det|>[[158, 362, 504, 410]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[148, 473, 308, 492]]<|/det|> +## COMMENT #2 + +<|ref|>text<|/ref|><|det|>[[147, 513, 851, 586]]<|/det|> +Fig S8b: The authors show a blot to detect miR319. However, since miR319 and miR159 share a similar sequence, and miR319 is expressed at lower levels compared to miR159, it is likely that the blot is detecting miR159 through cross- hybridization instead of miR319. + +<|ref|>sub_title<|/ref|><|det|>[[148, 607, 275, 626]]<|/det|> +## RESPONSE + +<|ref|>text<|/ref|><|det|>[[148, 644, 377, 660]]<|/det|> +Thank you for pointing this out. + +<|ref|>text<|/ref|><|det|>[[147, 666, 852, 850]]<|/det|> +To specifically detect miR159 and miR319, we used Locked Nucleic Acids (LNA)- modified oligonucleotide probes to ensure the specificity of Northern blot of miR159 and miR319 (Válóczi et al., 2004). LNA is a class of bicyclic high- affinity RNA analogues in which the furanose ring in the sugar- phosphate backbone is chemically locked in an N- type (C3'- endo) conformation by the introduction of a 2'- O,4'- C methylene bridge (Obika et al., 1997; Koshkin et al., 1998). The unprecedented thermal stability of LNA oligonucleotides together with their improved mismatch discrimination ensure the highly specificity of LNA- modified probes. + +<|ref|>text<|/ref|><|det|>[[194, 861, 583, 906]]<|/det|> +miR159 probe: 5'- taGAGCTCCCTTCAATCCAAa- 3' miR319 probe: 5'- ggAGCTCCCTTCAGTCCAAa- 3' + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 265]]<|/det|> +The lowercase letters indicate the LNA-modified oligonucleotide. In our previous results of Northern blot of miR319, we prolonged the exposure time to obtain the optimum image. To compare the expression level of miR159 and miR319, we re- conducted the Northern blot by using same exposure time (20 min) for both miR159 and miR319 in petals on 1, 3, and 5 days after stage 0. As shown in the below figure, the expression level of miR319 was much lower than miR159. We used these results as Fig S8b, and added relevant description of LNA probes in Legend of Figure 1a and Fig S8b in the revised version. + +<|ref|>image<|/ref|><|det|>[[180, 308, 400, 440]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[148, 448, 232, 462]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 470, 852, 737]]<|/det|> +Válóczi A., Hornyik C., Varga N., Burgyán J., Kauppinen S., Havelda Z., 2004. Sensitive and specific detection of microRNAs by northern blot analysis using LNA- modified oligonucleotide probes. Nucleic Acids Res, 32: 175- 175. Obika S., Nanbu D., Hari Y., Morio K., In Y., Ishii J.K., Imanishi T., 1997. Synthesis of \(2^{\prime} - O,4^{\prime} - C\) methyleneuridine and cytidine. Novel bicyclic nucleosides having a fixed C3- endo sugar puckering. Tetrahedron Lett, 38: 8735- 8738. Koshkin A.A., Singh S.K., Nielsen P., Rajwanshi V.K., Kumar R., Meldgaard M., Olsen C.E., Wengel J., 1998. LNA (locked nucleic acids): synthesis of the adenine, cytosine, guanine, 5- methylcytosine, thymine and uracil bicyclonucleoside monomers, oligomerisation, and unprecedented nucleic acid recognition. Tetrahedron, 54: 3607- 3630. + +<--- Page Split ---> diff --git a/peer_reviews/332e454b289f21d2896af462c58287b7a803e707ce2ee1dbfd5469a667666e1f/supplementary_0_Peer Review Information/images_list.json b/peer_reviews/332e454b289f21d2896af462c58287b7a803e707ce2ee1dbfd5469a667666e1f/supplementary_0_Peer Review Information/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/332e454b289f21d2896af462c58287b7a803e707ce2ee1dbfd5469a667666e1f/supplementary_0_Peer Review Information/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/332e454b289f21d2896af462c58287b7a803e707ce2ee1dbfd5469a667666e1f/supplementary_0_Peer Review Information/supplementary_0_Peer Review Information.mmd b/peer_reviews/332e454b289f21d2896af462c58287b7a803e707ce2ee1dbfd5469a667666e1f/supplementary_0_Peer Review Information/supplementary_0_Peer Review Information.mmd new file mode 100644 index 0000000000000000000000000000000000000000..26ae6b7008ded30485436d5cf9ee80370c63f7e0 --- /dev/null +++ b/peer_reviews/332e454b289f21d2896af462c58287b7a803e707ce2ee1dbfd5469a667666e1f/supplementary_0_Peer Review Information/supplementary_0_Peer Review Information.mmd @@ -0,0 +1,664 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Microbiology Manuscript Title: Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2 Corresponding author name(s): Vincent Munster + +## Editorial Notes: + +Redactions - published data + +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +Dear Dr. Munster, + +Thank you very much for your enquiry about submitting your manuscript "Aerosol transmission of SARS- CoV- 2." to Nature Microbiology. It certainly sounds interesting, and we would be happy to consider it for publication. However, I'm sure you'll understand that we cannot make a firm decision about whether to send the paper out to review until we have carefully read the full paper (and appropriate background literature). + +In order to submit your complete manuscript to Nature Microbiology, please use the link below: + +{redacted} + +If you have any questions, please feel free to contact me. + +Yours sincerely, + +{redacted} + +<--- Page Split ---> + +# natureresearch + +## Decision Letter, first revision: + +Dear Dr. Munster, + +Thank you for your patience while your manuscript "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" was under peer- review at Nature Microbiology. It has now been seen by 4 referees, whose expertise and comments you will find at the of this email. You will see from their comments below that while they find your work of interest, some important points are raised. We are very interested in the possibility of publishing your study in Nature Microbiology, but would like to consider your response to these concerns in the form of a revised manuscript before we make a final decision on publication. + +In particular, both referee #1 and #2 ask to further confirm viral transmission in the competition assay by comparing histopathology and infectious viral titers between inoculated and sentinel animals. Here, referee #1 also suggests to characterize virus composition within the lungs. In addition, referee #2 asks to include an comparison of the Delta variant to increase clinical relevance of the study. Referee #3 points out that inoculation of the same amount from both variants in the competition assay need to be confirmed. This referee also makes several suggestions to adjust the discussion section and references. 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If you cannot send it within this time, please let us know. + +We look forward to hearing from you soon. + +{redacted} + +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\* + +Reviewer Expertise: + +Referee #1: Viral transmission, Animal model Referee #2: SARS- CoV- 2, Animal model Referee #3: Viral transmission, Bioaerosol Referee #4: Coronaviruses, Receptor interactions + +Reviewers Comments: + +Reviewer #1 (Remarks to the Author): + +The manuscript by Port et al., is a very interesting study demonstrating small particle aerosol transmission of SARS- CoV- 2 in hamsters in an innovative transmission caging system. Overall the study is well done, but I have some specific comments about the final section of the results "B.1.1.7 variant demonstrates increased airborne transmission competitiveness" + +1. Gross lung pathology was compared in the different sentinel hamsters. How did that compare to the inoculated donor animal lungs? Why was histopathology not compared? It would be very interesting to assess whether viral distribution (by immunohistochemistry) or microscopic pathology differed between donor and sentinel animals as well as between lineage A and UK variant infected animals. +2. In Fig 5G, the authors assessed percentages of different vial variants in the competition experiment in oropharyngeal swabs. It would be interesting to look at viral composition in the lungs, especially since the experiment was designed to assess small particle aerosol transmission. Distribution and replication of the two viruses might be different between the upper and lower respiratory tracts. + +Reviewer #2 (Remarks to the Author): + +This study develops and validates a caging system to monitor true aerosol transmission of SARS- CoV- 2 between Syrian golden hamsters. Applied to a comparison of aerosol transmission of the original lineage A and VOC alpha, increased airborne transmission of the VOC was observed. Experimental approaches and results are clearly presented. A validated experimental set- up to compare relative transmission efficiency of newly emerging SARS- CoV- 2 VOC is a major contribution to the field. Whereas use of the VOC alpha for a proof- of- concept study is fair, the actual clinical importance of alpha has vanished with the emergence of the now globally dominant delta VOC several + +<--- Page Split ---> + +# natureresearch + +months ago. Application of the system to VOC delta would consequently greatly advance the clinical impact of the study. + +Although data are overall of high quality, a major shortcoming is the overall reliance on viral RNA copy numbers to measure transmission success, which may or may not accurately reflect productive infection of sentinels. To illustrate the point, figure 5C shows approx. equal, high RNA copy numbers in three animals of the sentinel 2 group, and intermediate copy numbers in another animal of this group. Looking at actual infectious titers of animals in this group (figure 5D), however, only 1 of the sentinel 2 animals shows productive infection (high virus burden), while another shows intermediate burden and all others are essentially at detection level. What is the reason for this discrepancy, which undermines confidence in RNA copy number measurements as a readout for productive infection in this model? Please provide proof for productive infection of key experiments in form of infectious titers to fully support the conclusions drawn. + +Reviewer #3 (Remarks to the Author): + +Review of "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" by Port JR et al + +## Summary + +In this study by Port et al the authors developed an experimental set up in which the only transmission pathway between experimentally infected animals and recipient animals was through aerosol particles \(< 10\) um, and in fact most of the particles were in the \(< 5\) um range. The size of the particles going through the caging set up has been verified with an aerosolized solution of glycerin \(20\%\) in water. + +Using this set up the authors demonstrated transmission by aerosols between Syrian hamsters, for both the original lineage of SARS- CoV- 2 and the alpha variant. In additional experiments the authors showed that in competitive infection by aerosols the alpha variant out- competed the original strain. + +## Assessment + +Overall this original study has been well conducted, the critical data were convincingly obtained, the results are indeed novel although arguably not quite as novel as the authors assert. But it is undeniable that these results are of great importance for our understanding of SARS- CoV- 2 transmission and for the rational design of a pandemic control strategy. Several details and discussion topics would benefit from rewriting and some additional info. + +1) Definition of aerosols and "airborne infection" + +Admittedly the lack of standardization of terminology has been a bane of the field for a long time and continues to impede accurate discussion. The authors are correct to point out that many authors have used the term "airborne transmission to mean transmission by either large droplets or aerosols. However most authors, including infectious diseases and infection control practitioners, have used to term to mean aerosol transmission only and I think that the authors should also use that convention. The size cut- off for bio- aerosols involved in disease transmission has also been a contentious issue. It is now appreciated that in fact particles of up to 100- 200 um do not settle rapidly and can be carried away by air jets over several meters (see eg Milton DK J Pediatric Infect Dis 2020; 9(4) 413- 415). This whole spectrum of particles linger in the air (for a time depending in part on their size), can follow air currents, and thus can be thought of accurately as aerosols; and there are implications for mitigations by ventilation and adequate PPE such as N95s. That being said, the authors are, I believe, + +<--- Page Split ---> + +# natureresearch + +quite justified in putting an emphasis on "small" or "fine" aerosols \(< 5 - 10\) um. For humans infection it is certainly important to note that penetration below the glottis occurs only for particles \(< 20\mu m\) , and penetration into the alveolar region occur with particles \(< 5 - 6\) um ( Hinds W Aerosol technology 2nd ed; 1999). + +The authors demonstrated that in their set up no particles \(>10\) um were involved ( and most were in fact \(< 5\) um) and so no one can argue that they are not dealing with aerosol transmission and indeed with fine aerosol transmission. But their definitions, I would suggest, should standardize to the emerging consensus for terminology. + +## 2) Measurements of aerodynamic diameter + +It was essential for the central argument of the authors to carefully demonstrate that their setup excluded non- aerosol particles . They have done this conclusively using aerosols from a \(20\%\) glycerin solution but the discussion needs to be a little more rigorous because strictly speaking they have measured the physical diameter of the particles; to arrive at the aerodynamic diameter they must correct for the density of the particles; but as it happens the correction is indeed minimal (density of glycerol \(20\%\) at \(20C\) : approx. 1.05; details of correction: see Hinds W 2nd ed pp 53- 55). This should take only a line or two. + +## 3) Competition experiments + +For these experiments the donor animal was infected with a mixture of SARS- CoV- 2 lineage A and alpha variant. This opens the door the genesis of recombinant viruses in either the donor or recipient animals; coronaviruses, because of their "jumping polymerase" are notorious for their capacity to generate recombinants and have been referred to as viruses with "continuous segmented genomes". As it happened, the authors have guarded against this possible occurrence by doing complete genomic sequencing (using NGS) on most off the recovered isolates in recipient animals. + +However in 3 cases there was not enough RNA to do full sequencing and the identity of the isolate was inferred only through duplex qRT- PCR to detect a tell- tale mutation. Strictly speaking this would not rule out the presence of a recombinant virus in these 3 cases. I would suggest that the authors could supplement the data with a SNP assay targeting another identifying mutation elsewhere in the genome (say in the ORF1a), which should be doable even with a very small amount of available RNA. Alternatively they could just modify their discussion and point out that in these 3 cases the mutation associated with B.1.1.7 was selected for and given the other results with complete sequencing it appears very likely that the variant, and not a recombinant, was selected. + +Another point: I think that the 1:1 mix of the 2 lineages for inoculating the donor animal should be better explained; it is critical to make sure that approximately the same amount of TCID50s for each lineage be present. + +## 4) Discussion: lines 276-280 + +Actually there are other type of evidence, not just long range transmission, to prove aerosol transmission (see eg Tellier et al BMJ Infect Dis 2019; 19(1): 101); as well aerosol transmission also readily occurs at short range and in fact more readily so, and some authors have argued that at short distance it was predominant compared to large droplet transmission ( Chen et al, Building and Environment 2020; 176: 106859); I would argue against using Brankston et al ( ref 25) as a reference for this point as these authors understanding of virology is often inaccurate ( as exemplified by their stamen that influenza A virus infects erythrocytes...). + +## 5) Discussion + +It is not quite accurate that these results are the first "proof" of aerosol transmission of Covid as other + +<--- Page Split ---> + +# natureresearch + +lines of evidence have been published, including investigations of several outbreaks that would be essentially unexplainable without aerosols ( see eg Katelaris et al EID 2021; 27: 6, June 2021); as well, the ferret transmission experiments of Kutter et al ( ref 27) are compelling and although Kutter et al did not provide that calculation, based on the provided dimensions of the duct, the air flow and Stokes' law one can readily show that the maximum size of particles in their set up would be well within the aerosol range. + +So I think that in their discussion the authors should instead insist on the main (and considerable) strengths of this study : + +i) actual measurement of the maximum size of aerosols in their set up ( \(< 10 \text{um}\) )ii) the demonstration that small aerosols can transmit SARS-CoV-2 between hamstersiii) the demonstration that in mixed aerosol inocula the alpha variant out-compete the original lineage. The authors could with great benefits I think refer to an analogous result obtained with Influenza A virus by Koster et al (PLoS one 7(4): e33118), who showed than the pandemic strain of A(H1N1) was much more efficient at aerosol transmission than the seasonal A(H1N1) it replaced; this precedent with a different respiratory virus actually strengthen the plausibility of the results in this study and together they enhance our understanding of the pandemic potential of different respiratory viruses and the contribution of aerosol transmission to their pandemic potential. + +## 6) Discussion: I 294-295 + +For humans the threshold for effective penetration in the alveolar space has been shown to be \(< 5 - 6\) um ( Hinds WC Aerosol Technology 2nd ed0; but I am not aware of a similar determination of size cut off for other species including hamsters; and although it is difficult to believe that aerosols of \(< 5 \text{um}\) would not reach the lower resp tract of hamsters the discussion must distinguishes between what is experimentally proven and what is plausible based on first principles. + +7) ref 4 has been much criticized in part for its methodology and for the point they want to make the authors could replace it with one of many other, for example Greenhaig et al Lancet 2021; 397: 10285, p 1603-1605) + +8) line 81: "... allowed for 30 cage changes per hour": presumably "cage air changes per hour"? + +Reviewer #4 (Remarks to the Author): + +This manuscript describes a novel cage setup to study airborne transmission of SARS- CoV- 2 using the Syrian hamster model. The setup allows large droplets and aerosols to be tested and both B.1.1.7 and a lineage A variant have been studied. + +I am commenting solely on the section of the paper that deals with the interaction of the RBD of these viruses with human and hamster ACE2. + +It has previously been shown by several publications that the N501Y mutation in the RBD of B.1.1.7 leads to higher affinity for human ACE2. In this work, the authors state that they looked at the binding efficiency of the lineage A and B.1.1.7. RBDs to the hamster RBD in silico. This must be clarified. It seems that the authors have simply generated a figure showing the locations of the N501Y mutation and the relevant sites (H34Q and M82N) at which human and hamster ACE2 differ (with residues substituted in Coot - Figure 3). The word "efficiency" is unclear and suggests a deeper analysis. As far as I can tell, the authors have not performed any calculations to evaluate the relevant interaction + +<--- Page Split ---> + +# natureresearch + +energies (as might be expected of an in silico analysis). + +At line 151, a VSV entry assay is introduced, and this shows that B.1.1.7 entry is increased for both human and hamster ACE2. From there, the authors conclude that B1.1.7 binds tighter to hamster ACE2: line 159: "We next investigated if the enhanced binding affinity of B1.1.7 to hamster ACE2 ..." + +Given that human and hamster ACE2 do not differ in the region where RBD residue N501Y interacts with ACE2, it's not unreasonable to suggest that B.1.1.7 might also show higher affinity for hamster ACE2. However, neither the in silico work, nor the VSV assay (a binding studied would be required), establish that B.1.1.7 shows enhanced affinity for hamster ACE2 and the text should be qualified appropriately. + +## Author Rebuttal, first revision: + +Reviewer #1 (Remarks to the Author): + +The manuscript by Port et al., is a very interesting study demonstrating small particle aerosol transmission of SARS- CoV- 2 in hamsters in an innovative transmission caging system. Overall the study is well done, but I have some specific comments about the final section of the results "B.1.1.7 variant demonstrates increased airborne transmission competitiveness" + +1. Gross lung pathology was compared in the different sentinel hamsters. How did that compare to the inoculated donor animal lungs? Why was histopathology not compared? It would be very interesting to assess whether viral distribution (by immunohistochemistry) or microscopic pathology differed between donor and sentinel animals as well as between lineage A and UK variant infected animals. + +We thank the reviewer for the comment and have explored the relationship between exposure route and pathogenicity in several other studies. Typically, with directly inoculated hamsters the lungs display a little more marked gross pathology as compared to the sentinel animals, but the histopathology is very similar after transmission (van Doremalen, Science Translational Medicine https://www.science.org/doi/10.1126/scitranslmed.abh0755; Yinda et al., Emerging Microbes and Infection, https://www.tandfonline.com/doi/full/10.1080/22221751.2021.1943539). + +In addition, we see that disease, tropism and shedding within the respiratory tract are directly related to the exposure route (Port et al, Nature Communications, https://www.nature.com/articles/s41467- 021- 25156- 8). We also see that the pathology caused by the different VOCs does not strikingly differ in hamsters (Fischer et al, Nature Communication accepted, https://www.biorxiv.org/content/10.1101/2021.03.11.435000v1) nor in non- human primates (Munster et al., Science advances accepted, https://www.biorxiv.org/content/10.1101/2021.05.07.443115v1) + +<--- Page Split ---> + +# natureresearch + +For this study the emphasis was completely on transmission and not pathogenesis and therefor no samples from the inoculated animal and no samples for histological analysis were collected. However, we agree with the reviewer that more information on the various VOCs would be helpful and are planning future experiments comparing the gross and histopathology seen in sentinels as compared to donors. + +2. In Fig 5G, the authors assessed percentages of different vial variants in the competition experiment in oropharyngeal swabs. It would be interesting to look at viral composition in the lungs, especially since the experiment was designed to assess small particle aerosol transmission. Distribution and replication of the two viruses might be different between the upper and lower respiratory tracts. + +We fully agree with the reviewer and have reanalyzed the lung data by extraction of lung tissue samples and additional NGS analyses. We have added this new data in the results and have updated the discussion to incorporate the new data. To do so, we optimized our protocols and gain higher quality RNA from the lung samples, which we were able to sequence. We have modified the sgRNA data in Figure 5E to correspond to the new sequence data. The new data is shown in Fig 5 H. + +The following paragraphs have been changed in the results to reflect this: + +Line 261: + +"To determine the competitiveness of the variants we analyzed the relative composition of the two viruses in the swabs using next generation sequencing and compared the percentage of B.1.1.7/lineage A at 2 DPE in oral swab samples and at 5 DPE in lungs (Figure 5 G/H)." + +Line 276: + +"To investigate whether this pattern was also reflected in the lower respiratory tract, we sequenced viral RNA extracted from lung samples collected at 5 DPE for all donors, Sentinels 1 and Sentinels 2. One donor had increased amounts of lineage A variant (82%), while in the remaining seven animals the B.1.1.7 variant was increased in the lungs (73- 85% range). In the Sentinels 1 group, increased amounts of lineage A variant were found in two animals (72% and 99%), while B.1.1.7 was increased in the others (65%- 100%); in the Sentinels 2 group viral RNA sequences in two animals were 100% lineage A, and in the remaining four animals exclusively (99- 100%) B.1.1.7. Taken together, B.1.1.7 demonstrated increased competitiveness; after 10 out of 13 airborne transmission events B.1.1.7 outcompeted lineage A in the upper respiratory tract (swab samples) and only in three events infection with lineage A was established as the dominant variant. In the lower respiratory tract, B.1.1.7 outcompeted lineage A in 10 out of 14 events." + +In the discussion: + +<--- Page Split ---> + +# natureresearch + +## Line 346: + +"We observed that the variant profiles in the upper and lower respiratory tract were not always in accord. Of interest are also additional studies discerning this discrepancy in more detail and determining the source of virus involved in onwards transmission." + +Reviewer #2 (Remarks to the Author): + +This study develops and validates a caging system to monitor true aerosol transmission of SARS- CoV- 2 between Syrian golden hamsters. Applied to a comparison of aerosol transmission of the original lineage A and VOC alpha, increased airborne transmission of the VOC was observed. Experimental approaches and results are clearly presented. A validated experimental set- up to compare relative transmission efficiency of newly emerging SARS- CoV- 2 VOC is a major contribution to the field. Whereas use of the VOC alpha for a proof- of- concept study is fair, the actual clinical importance of alpha has vanished with the emergence of the now globally dominant delta VOC several months ago. Application of the system to VOC delta would consequently greatly advance the clinical impact of the study. + +We thank the reviewer for the positive comments. Whereas we agree with the need for real- time information on VOCs as soon as they are generated, the venue of scientific publishing does not work particularly allow for rapid dissemination of novel data. However, all our preliminary data gets directly shared with stakeholders such as the World Health Organization animal model workgroup and the SARS- CoV- 2 Evolution workgroups and within different entities of the USG (OWS and HHS) and publication ready data is directly put on preprint servers. + +More from a practical manner, it typically takes several months before we have access to novel VOCs, e.g. we got our first strain of the delta variant in at \(15^{\text{th}}\) of June, the next step would than be growing stocks to use in experiments and perform deep sequencing analyses to determine the integrity of the virus stock (e.g. no cleavage site deletions or bacterial contaminations) and determine the titer by titration. Typically, this can take anywhere between 3- 6 weeks. In addition, animal experiment will need an IACUC approval, which will a minimum of 2 months before an experimental outline gets approved and animal can be ordered. The actual experiment can take anywhere between 2- 6 weeks and an additional 6- 10 weeks for downstream processing like NGS and potentially histopathology. + +Obviously, we are trying to expedite our work to inform public health as much as possible, and vaccine and transmission experiments with the Delta variant have started but adding information on Delta in this manuscript is realistically impossible in a reasonable timeframe. In addition, the scope of the manuscript was to define the efficiency of aerosol transmission of SARS- CoV- 2 in a well- defined set- up. In addition, we determined that increased transmission is a function of increased airborne advantage as a phenotype of the novel VOCs. We think it can be expected that any clinical implication drawn from this data, would also be applicable to delta. + +<--- Page Split ---> + +# natureresearch + +Although data are overall of high quality, a major shortcoming is the overall reliance on viral RNA copy numbers to measure transmission success, which may or may not accurately reflect productive infection of sentinels. To illustrate the point, figure 5C shows approx. equal, high RNA copy numbers in three animals of the sentinel 2 group, and intermediate copy numbers in another animal of this group. Looking at actual infectious titers of animals in this group (figure 5D), however, only 1 of the sentinel 2 animals shows productive infection (high virus burden), while another shows intermediate burden and all others are essentially at detection level. What is the reason for this discrepancy, which undermines confidence in RNA copy number measurements as a readout for productive infection in this model? Please provide proof for productive infection of key experiments in form of infectious titers to fully support the conclusions drawn. + +We agree with the reviewer that solely relying on viral RNA copy numbers might not always accurately reflect productive infection of sentinels. However, real- time quantitative PCR assays are typically 2 log more sensitive than virus titration, it therefor is typically is a reliable marker for infection. The inclusion of subgenomic RNA qRT- PCR, a surrogate for virus replication, is directly associated with seroconversion of the animal in our previous hamster transmission experiments, and such was used as the main marker for infection. Subgenomic RNA only gets produced during active infection and rapidly degrades, as its not encapsulated in a viral envelope like genomic RNA as we have shown previously (Speranza Science Translational Medicine 2021). + +However, we agree with the reviewer that infectious virus, in addition to the shown viral genomic and subgenomic RNA in swabs and seroconversion, will provide conclusive results. We have therefor titrated swab samples and have added the infectious virus titers to key experiments in Figures 2 and 4 and we have modified the results section accordingly. + +Reviewer #3 (Remarks to the Author): + +Review of "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" by Port JR et al + +## Summary + +In this study by Port et al the authors developed an experimental set up in which the only transmission pathway between experimentally infected animals and recipient animals was through aerosol particles \(< 10 \text{um}\) , and in fact most of the particles were in the \(< 5 \text{um}\) range. The size of the particles going through the caging set up has been verified with an aerosolized solution of glycerin \(20\%\) in water. Using this set up the authors demonstrated transmission by aerosols between Syrian hamsters, for both the original lineage of SARS- CoV- 2 and the alpha variant. In additional experiments the authors showed that in competitive infection by aerosols the alpha variant outcompeted the original strain. + +<--- Page Split ---> + +# natureresearch + +## Assessment + +Overall this original study has been well conducted, the critical data were convincingly obtained, the results are indeed novel although arguably not quite as novel as the authors assert. But it is undeniable that these results are of great importance for our understanding of SARS- CoV- 2 transmission and for the rational design of a pandemic control strategy. + +Several details and discussion topics would benefit from rewriting and some additional info. + +1) Definition of aerosols and "airborne infection" + +Admittedly the lack of standardization of terminology has been a bane of the field for a long time and continues to impede accurate discussion. The authors are correct to point out that many authors have used the term "airborne transmission to mean transmission by either large droplets or aerosols. However most authors, including infectious diseases and infection control practitioners, have used to term to mean aerosol transmission only and I think that the authors should also use that convention. The size cut- off for bio- aerosols involved in disease transmission has also been a contentious issue. It is now appreciated that in fact particles of up to 100- 200 um do not settle rapidly and can be carried away by air jets over several meters (see eg Milton DK J Pediatric Infect Dis 2020; 9(4) 413- 415). This whole spectrum of particles linger in the air (for a time depending in part on their size), can follow air currents, and thus can be thought of accurately as aerosols; and there are implications for mitigations by ventilation and adequate PPE such as N95s. That being said, the authors are, I believe, quite justified in putting an emphasis on "small" or "fine" aerosols \(< 5 - 10 \text{um}\) . For humans infection it is certainly important to note that penetration below the glottis occurs only for particles \(< 20 \text{um}\) , and penetration into the alveolar region occur with particles \(< 5 - 6 \text{um}\) (Hinds W Aerosol technology 2nd ed; 1999). The authors demonstrated that in their set up no particles \(> 10 \text{um}\) were involved (and most were in fact \(< 5 \text{um}\) ) and so no one can argue that they are not dealing with aerosol transmission and indeed with fine aerosol transmission. But their definitions, I would suggest, should standardize to the emerging consensus for terminology. + +We thank the reviewer for the comments and insights and have tried as much possible to incorporate them in the manuscript. We agree with the reviewer that the definitions used throughout the literature can be quite opaque and have therefor tried to specify the definitions and conditions used in our experimental set- up as much as possible. According to the suggestions we have now updated manuscript accordingly: + +In the abstract line 18: + +"Aerosol transmission is thought to be a major transmission route of SARS- CoV- 2." + +We have changed the introduction to match this. Line 42: + +<--- Page Split ---> + +# natureresearch + +"Epidemiological data suggests that the principal mode of infection with SARS- CoV- 2 is via airborne transmission in addition to large droplet transmission 1- 5. The general definition held by the WHO states that large droplets disperse over a short distance and settle in the upper respiratory tract, while aerosols (<5 μm) can form droplet nuclei, travel also over long distance, and significantly deposit in the lower respiratory tract 6. For influenza A virus, another respiratory virus, studies have elucidated the airborne potential and discussed the relative contribution of large droplets vs. aerosols and the site of viral exposure and shedding 7- 10. Similar data for SARS- CoV- 2 is currently unavailable." + +## 2) Measurements of aerodynamic diameter + +It was essential for the central argument of the authors to carefully demonstrate that their setup excluded non- aerosol particles They have done this conclusively using aerosols from a \(20\%\) glycerin solution but the discussion needs to be a little more rigorous because strictly speaking they have measured the physical diameter of the particles; to arrive at the aerodynamic diameter they must correct for the density of the particles; but as it happens the correction is indeed minimal (density of glycerol \(20\%\) at \(20C\) : approx. 1.05; details of correction: see Hinds W 2nd ed pp 53- 55). This should take only a line or two. + +We thank the review for this important insight and have added: + +## Line 85: + +"The aerodynamic particle size of a particle is the particle size regardless of shape and material density that has the same settling rate as a spherical droplet of water. It is the principal parameter used for characterizing respiratory deposition 17. Therefore a \(5\mu m\) aerodynamical particle will act similarly to a \(5\mu m\) spherical droplet of water whether it is a from a \(20\%\) glycerol solution, or a mucus filled respiratory droplet. A \(20\%\) glycerol solution has a density of \(1.05g / cm^3\) therefore the geometrical diameter of the glycerol droplets are determined by multiplying the aerodynamic particle diameter by a correction factor of \(0.98^{18}\) ." + +## 3) Competition experiments + +For these experiments the donor animal was infected with a mixture of SARS- CoV- 2 lineage A and alpha variant. This opens the door the genesis of recombinant viruses in either the donor or recipient animals; coronaviruses, because of their "jumping polymerase" are notorious for their capacity to generate recombinants and have been referred to as viruses with "continuous segmented genomes". As it happened, the authors have guarded against this possible occurrence by doing complete genomic sequencing (using NGS) on most off the recovered isolates in recipient animals. However in 3 cases there was not enough RNA to do full sequencing and the identity of the isolate was inferred only through duplex qRT- PCR to detect a tell- tale mutation. Strictly speaking this would not rule out the presence of a recombinant virus in these 3 cases. I would suggest that the authors could + +<--- Page Split ---> + +# natureresearch + +supplement the data with a SNP assay targeting another identifying mutation elsewhere in the genome (say in the ORF1a), which should be doable even with a very small amount of available RNA. Alternatively they could just modify their discussion and point out that in these 3 cases the mutation associated with B.1.1.7 was selected for and given the other results with complete sequencing it appears very likely that the variant, and not a recombinant, was selected. + +Another point: I think that the 1:1 mix of the 2 lineages for inoculating the donor animal should be better explained; it is critical to make sure that approximately the same amount of TCID50s for each lineage be present. + +We thank the reviewer for his comments. Given the sequencing technology used (Illumina Highseq) we would not be able to distinguish recombination events happening unless these viruses would be selected for (as it would then show in in figure 5 G&H). the reason for this is that the NGS typically sequences very small fragments of approximately 300nt which makes it hard to attribute them to any particular genomes. PACBio sequencing, which could generate read lengths of up to 10,000 nucleotides would be the best method to study recombination events. In addition, we are also hampered by the relatively limited number of SNPs occurring in the B.1.1.7 compared to the WA1 variant (see table with all the specific nt differences between lineage A and B.1.1.7, relative to a 30,000 nucleotide genome), because of this similarity it is difficult to recognize recombination events unless using very specific validated assays (like the PACBio). + +<--- Page Split ---> + + +
genenucleotideamino acid
ORF1abC3267TT1001I
C5388AA1708D
T6954CI2230T
11288-11296 deletionSGF 3675-3677 deletion
spike21765-21770 deletionHV 69-70 deletion
21991-21993 deletionY144 deletion
A23063TN501Y
C23271AA570D
C23604AP681H
C23709TT716I
T24506GS982A
G24914CD1118H
Orf8C27972TQ27stop
G28048TR52I
A28111GY73C
N28280 GAT->CTAD3L
C28977TS235F
+ +We have addressed his comment by adding to the discussion: + +Line 335: + +“However, B.1.1.7 displayed an increased airborne transmission competitiveness over lineage A in a dual infection experiment both in the lower and upper respiratory tract. In three transmission events we could not confirm full viral sequences in oral swab samples. However, given all other events for which complete sequencing was done, it appears very likely that the variant, and not a recombinant, was selected.” + +In addition, we have now added additional clarification of the composition of the inoculum for the competition experiment. + +Line 517: + +<--- Page Split ---> + +# natureresearch + +"Donor hamsters \((N = 8)\) were infected intranasally as described above with \(1 \times 10^{2}\) TCID50 SARS- CoV- 2 (as confirmed by back titration of the inoculum) at a 1:1 ratio of lineage A and B.1.1.7 mixture (54.7% B.1.1.7, as confirmed by full genome sequencing of the inoculum)." + +## 4) Discussion: lines 276-280 + +Actually there are other type of evidence, not just long range transmission, to prove aerosol transmission (see eg Tellier et al BMJ Infect Dis 2019; 19(1): 101); as well aerosol transmission also readily occurs at short range and in fact more readily so, and some authors have argued that at short distance it was predominant compared to large droplet transmission ( Chen et al, Building and Environment 2020; 176: 106859); I would argue against using Brankston et al (ref 25) as a reference for this point as these authors understanding of virology is often inaccurate (as exemplified by their stamen that influenza A virus infects erythrocytes...). + +We thank the reviewer for this important comment. We have removed the ref 25 and have modified the discussion and the result section. + +## Line 291: + +"Epidemiological studies in humans and experimental studies in ferrets strongly suggest that aerosol transmission occurs and plays a major role in driving the SARS- CoV- 2 pandemic 22- 26. Yet formal experimental proof of aerosol transmission with particle diameter \(< 5 \mu m\) 6 in the absence of other transmission routes of SARS- CoV- 2 has not been provided, which would further inform on the importance of this transmission route 27. Here we demonstrated efficient transmission of SARS- CoV- 2 between Syrian hamsters via particles \(< 5 \mu m\) over 200 cm distance. Additionally, we present first qualitative analyses of the efficiency of transmission, showing that even within one hour transmission can occur at a distance of 200 cm between Syrian hamsters. + +Whereas several SARS- CoV- 2 airborne transmission studies in hamsters and ferrets have been performed, none of these studies were able to differentiate between large and small droplet transmission 14,15,25,28,29. " + +## 5) Discussion + +It is not quite accurate that these results are the first "proof" of aerosol transmission of Covid as other lines of evidence have been published, including investigations of several outbreaks that would be essentially unexplainable without aerosols (see eg Katalaris et al EID 2021; 27: 6, June 2021); as well, the ferret transmission experiments of Kutter et al (ref 27) are compelling and although Kutter et al did not provide that calculation, based on the provided dimensions of the duct, the air flow and Stokes' law one can readily show that the maximum size of particles in their set up would be well within the aerosol range. + +So I think that in their discussion the authors should instead insist on the main (and considerable) + +<--- Page Split ---> + +# natureresearch + +strengths of this study : + +strengths of this study :i) actual measurement of the maximum size of aerosols in their set up ( \(< 10 \text{um}\) )ii) the demonstration that small aerosols can transmit SARS- CoV- 2 between hamstersiii) the demonstration that in mixed aerosol inocula the alpha variant out- compete the original lineage. The authors could with great benefits I think refer to an analogous result obtained with Influenza A virus by Koster et al (PLoS one 7(4): e33118), who showed than the pandemic strain of A(H1N1) was much more efficient at aerosol transmission than the seasonal A(H1N1) it replaced; this precedent with a different respiratory virus actually strengthen the plausibility of the results in this study and together they enhance our understanding of the pandemic potential of different respiratory viruses and the contribution of aerosol transmission to their pandemic potential. + +We agree with the reviewer that various epidemiological and experimental studies have been published which very strongly suggest the large potential for SARS- CoV- 2 to be transmitted via aerosols. Coming more from an experimental background, the ongoing debate with animal transmission studies (since our work on influenza, Munster Science 2009, https://www.science.org/doi/full/10.1126/science.1177127), was that unless you show data on size exclusion towards small particles you need to refer to this as "Airborne" or "aerosol and droplet". + +Obviously, the work by Kutter et al, did provide the first experimental evidence in a set- up which strongly suggest transmission of SARS- CoV- 2 by smaller particles. + +We have modified the discussion to the reviewer's recommendations as listed above and have included the references as applicable. We have now modified, that this is the conclusive proof of aerosol transmission but have stressed that our experimental findings strengthen previous work, both experimental and epidemiological. + +We have also included the newly published work by Adenaiye et al, in the discussion which observed a higher viral load in fine aerosol but not coarse aerosols confirming the selective advantage observed in the hamster competition studies. + +Adenaiye, O. O. et al. Infectious SARS- CoV- 2 in Exhaled Aerosols and Efficacy of Masks During Early Mild Infection. Clin Infect Dis, doi:10.1093/cid/ciab797 (2021). + +## 6) Discussion: I 294-295 + +6) Discussion: I 294-295For humans the threshold for effective penetration in the alveolar space has been shown to be < 5-6 um (Hinds WC Aerosol Technology 2nd ed0; but I am not aware of a similar determination of size cut off for other species including hamsters; and although it is difficult to believe that aerosols of < 5um would not reach the lower resp tract of hamsters the discussion must distinguishes between what is experimentally proven and what is plausible based on first principles. + +<--- Page Split ---> + +# natureresearch + +Whereas we have never performed complete size exclusion experiments, we have conducted several aerosol inoculation studies in hamsters using experimentally generated aerosols (ranging from \(1 - 5 \mu m\) in size) by a 3- jet collision nebulizer (Biaera technologies, USA). With SARS- CoV- 2 we see the infection is present in the lower respiratory tract starting at 1 day post inoculation (Port et al, Nature Communications, https://www.nature.com/articles/s41467- 021- 25156- 8), compared to intranasal inoculation. Especially, the extend of replication in the type I and II pneumocytes is striking this early in infection (as is the compete upper and lower respiratory tract deposition of SARS- CoV- 2 in hamsters). The extend of replication at 1 dpi in the aerosol exposed via the IN exposed animals directly suggest efficient deposition of aerosols in the \(< 5 \mu m\) size range (Figure taken from Port et al, Nature Communications showing replication of SARS- CoV- 2 at 1 dpi). + +{redacted} + +## We have modified line 309: + +While respirable aerosol (<2.5 \(\mu m\) ), thoracic aerosol (<10 \(\mu m\) ) and inhalable aerosol in general 29 all may be relevant to infection with SARS- CoV- 2 30, it has been suggested that direct deposition into the lower respiratory tract may decrease the necessary infectious dose in humans 32. + +7) ref 4 has been much criticized in part for its methodology and for the point they want to make the authors could replace it with one of many other, for example Greenhaig et al Lancet 2021; 397: 10285, p 1603-1605) + +Upon the suggestion of the reviewer we have replaced the reference + +8) line 81: "... allowed for 30 cage changes per hour": presumably "cage air changes per hour"? + +We have changed to: + +"This allowed for 30 cage air changes per hour." + +Reviewer #4 (Remarks to the Author): + +This manuscript describes a novel cage setup to study airborne transmission of SARS- CoV- 2 using the Syrian hamster model. The setup allows large droplets and aerosols to be tested and both B.1.1.7 and a lineage A variant have been studied. + +<--- Page Split ---> + +# natureresearch + +I am commenting solely on the section of the paper that deals with the interaction of the RBD of these viruses with human and hamster ACE2. + +It has previously been shown by several publications that the N501Y mutation in the RBD of B.1.1.7 leads to higher affinity for human ACE2. In this work, the authors state that they looked at the binding efficiency of the lineage A and B.1.1.7. RBDs to the hamster RBD in silico. This must be clarified. It seems that the authors have simply generated a figure showing the locations of the N501Y mutation and the relevant sites (H34Q and M82N) at which human and hamster ACE2 differ (with residues substituted in Coot - Figure 3). The word "efficiency" is unclear and suggests a deeper analysis. As far as I can tell, the authors have not performed any calculations to evaluate the relevant interaction energies (as might be expected of an in silico analysis). + +At line 151, a VSV entry assay is introduced, and this shows that B.1.1.7 entry is increased for both human and hamster ACE2. From there, the authors conclude that B1.1.7 binds tighter to hamster ACE2: line 159: "We next investigated if the enhanced binding affinity of B1.1.7 to hamster ACE2 ..." + +Given that human and hamster ACE2 do not differ in the region where RBD residue N501Y interacts with ACE2, it's not unreasonable to suggest that B.1.1.7 might also show higher affinity for hamster ACE2. However, neither the in silico work, nor the VSV assay (a binding studied would be required), establish that B.1.1.7 shows enhanced affinity for hamster ACE2 and the text should be qualified appropriately. + +We thank the author for the comments and insight and fully agree that the text should be reworded to accurately reflect the analysis that was performed. We did not evaluate the relevant interaction energies or calculate in silico binding energies nor discern differences in binding. We have focused our in vitro work directly on entry studies where we show that the spike of B.1.1.7 has increased entry potential over the spike of WA1. We have therefor modified the results section to read as follows: + +## Line 137: + +"Increased cellular entry and respiratory shedding of B.1.1.7 variant in hamsters + +To investigate whether the increased transmission potential of B.1.1.7 on the population level is determined by changes in transmission potential at the individual level, we compared the airborne transmission kinetics of the B.1.1.7 with the prototype lineage A virus. First, we assessed the suitability of the Syrian hamster as a model to compare SARS- CoV- 2 variant transmission 19. Previous studies have demonstrated the B.1.1.7 spike binds with greater affinity to the human ACE2 than the lineage A spike, potentially explaining the increased transmission. Differences in the amino acid sequence were visualized by mapping onto a structure of the SARS- CoV- 2 spike protein in complex + +<--- Page Split ---> + +with human ACE2 (PDB ID 6M0J). At position 501 of the B.1.1.7 spike RBD, the asparagine residue is substituted by tyrosine. This substitution has been proposed to increase binding affinity to (human) ACE2 via increased interactions with residues on ACE2 by stacking of aromatic sidechains and hydrogen bond interactions (19). A sequence alignment between human and hamster ACE2 reveals that two residues differ within the interface with SARS- CoV- 2 RBD. At positions 34 and 82, histidine and methionine are replaced by glutamine and asparagine, respectively, in the hamster ACE2 (Figure 3 A, B). It is possible that subtle changes resulting from these substitutions in hamster ACE2, not captured in this visualization, could affect the binding interactions with the B.1.1.7 variant. Interestingly, the substitution to asparagine at position 82 introduces an N- linked glycosylation sequon (NYS). This residue is located at the periphery of the interface and makes minor contributions in the human complex. The occupancy and biological relevance of this putative site requires further study. To evaluate whether these sequence differences in hamster ACE2 may affect viral entry, we also directly compared viral entry using a VSV pseudotype entry assay. No significant difference in entry between human and hamster ACE2 with either lineage A or B.1.1.7 was observed. For both human and hamster ACE2, B.1.1.7 demonstrated significantly increased entry compared to the lineage A variant (human ACE2 median lineage A/B.1.1.7 = 156.8/256 (relative entry to no spike), p <0.0001 and hamster ACE2 median lineage A/B.1.1.7 = 144.6/197.5 (relative entry to no spike), p = 0.003, N = 14, Mann- Whitney test) (Figure 3 C). + +We next investigated if infection of hamsters with the B.1.1.7 variant translated to differences in viral replication and shedding dynamics in- vivo." + +## Decision Letter, second revision: + +Dear Dr. Munster, + +Thank you for submitting your revised manuscript "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" (NMICROBIOL- 21071818B). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Microbiology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)- - we can not proceed with PDFs at this stage. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<--- Page Split ---> + +# natureresearch + +Thank you again for your interest in Nature Microbiology Please do not hesitate to contact me if you have any questions. + +{redacted} + +Reviewer #1 (Remarks to the Author): + +The authors have adequately addressed my comments in the revision. + +Reviewer #2 (Remarks to the Author): + +My concerns have been addressed satisfactorily. This is an important study that advances the field. + +Reviewer #3 (Remarks to the Author): + +Lines 42- 50: the authors are still too restrictive in their definition of respiratory aerosols (and so is WHO in the citation offered...)at a time when a consensus is emerging that respiratory aerosols include particles up to \(100\mu m\) ( aerodynamic diameter. The authors should note also that droplet nuclei arise after rapid dessication of aerosol droplets from the respiratory tract into dry air and this phenomenon affects also particles greater than \(5\mu m\) , see eg Nicas et al J Occ Environ Hyg 2005; 2: 143- 154; and Xie et al Indoor Air 2007; 17: 211- 225. + +However this is essentially an editing problem for this manuscript because the authors' data are very robust to show transmission by particles \(< 5 - 10\mu m\) ( and mostly if not exclusively \(< 5\mu m\) ). And no one could rationally argue against transmission by aerosols under a broader definition if there is solid demonstration of transmission under a more restrictive definition of \(< 5\mu m\) . + +Nonetheless I would suggest to the authors to replace lines 44- 47 by something like this: "Respiratory aerosols have been described as ranging from \(0.1\) to \(100\mu m\) ( aerodynamic diameter), with the fraction of particles \(< 5\mu m\) being referred to as "fine aerosols" ( Coleman et al Clin Infect. + +2) + +Aerodynamic vs physical diameter + +This is still unclear in the text. If I understand correctly the experimental set up of the authors, they nebulized a solution of glycerin \(20\%\) into particles of up to \(20\mu m\) ; this is a measured physical diameter; their measurements of the diameter of particles that go through are a measurement of physical diameter (and not of aerodynamic diameter), please correct on lines 83 - 84 Owing to the density of glycerol \(20\%\) (approx. 1.05) the aerodynamic diameter will be greater (not smaller) by a factor of \(\sqrt{1.05} \approx 1.02\) (see Hinds pp 53- 55). Lines 85- 92 could be replaced by something much more succinct, I would suggest something along the lines of the following: + +<--- Page Split ---> + +# natureresearch + +"Owing to the greater density of glycerol \(20\%\) relative to water, the corresponding aerodynamic diameter can be obtained by applying a correction factor of 1.02, a minimal correction (ref 17, 18)" + +This is much shorter but still makes the point that the conceptual difference between physical diameter and aerodynamic diameter has not escaped your attention and that the demonstration of the experimental set up as excluding non- aerosol particles is rigorous. + +## Recombinant viruses + +I think that we are essentially in agreement. For samples where complete genomic sequences was feasible, the fact that only overlapping small fragments were sequenced is not a problem provided that only one genomic sequence ( alpha or original lineage) is obtained at all positions, which is the case here according to the data. Problems would arise if there was a mixture of signals from alpha and the original lineage at different positions, since then sequences of overlapping small fragments could not decide between a recombinant and a mixed infection. + +For samples where only a SNP assay could be done because of a viral load too low for sequencing, in theory you could be facing a recombinant since you are scoring only one position in the genomic sequence. The discussion of this issue offered by the authors is satisfactory. For future work the authors may want to consider 2 or more SNP assays scattered throughout the genome, which would be doable even with a low viral load sample. + +Reviewer #4 (Remarks to the Author): + +I have read the revised manuscript and the rebuttal provided by the authors. They have fully addressed the concerns that I raised in my initial review and I feel that the manuscript is now suitable for publication. + +## Decision Letter, final checks: + +Dear Dr. Munster, + +Thank you for your patience as we've prepared the guidelines for final submission of your Nature Microbiology manuscript, "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" (NMICROBIOL- 21071818B). Please carefully follow the step- by- step instructions provided in the attached file, and add a response in each row of the table to indicate the changes that you have made. Please also check and comment on any additional marked- up edits we have proposed within the text. 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If you have any questions about costs, Open Access requirements, or our legal forms, please contact ASJournals@springernature.com. + +Please use the following link for uploading these materials: {redacted} + +If you have any further questions, please feel free to contact me. + +{redacted} + +Reviewer #1: Remarks to the Author: The authors have adequately addressed my comments in the revision. + +<--- Page Split ---> + +# natureresearch + +Reviewer #2: Remarks to the Author: My concerns have been addressed satisfactorily. This is an important study that advances the field. + +Reviewer #3: Remarks to the Author: + +Lines 42- 50: the authors are still too restrictive in their definition of respiratory aerosols (and so is WHO in the citation offered...) at a time when a consensus is emerging that respiratory aerosols include particles up to \(100\mu m\) ( aerodynamic diameter. The authors should note also that droplet nuclei arise after rapid dessication of aerosol droplets from the respiratory tract into dry air and this phenomenon affects also particles greater than \(5\mu m\) , see eg Nicas et al J Occ Environ Hyg 2005; 2: 143- 154; and Xie et al Indoor Air 2007; 17: 211- 225. + +However this is essentially an editing problem for this manuscript because the authors' data are very robust to show transmission by particles \(< 5 - 10\mu m\) ( and mostly if not exclusively \(< 5\mu m\) ). And no one could rationally argue against transmission by aerosols under a broader definition if there is solid demonstration of transmission under a more restrictive definition of \(< 5\mu m\) . + +Nonetheless I would suggest to the authors to replace lines 44- 47 by something like this: "Respiratory aerosols have been described as ranging from 0.1 to \(100\mu m\) ( aerodynamic diameter), with the fraction of particles \(< 5\mu m\) being referred to as "fine aerosols" ( Coleman et al Clin Infect. Dise 2021; doi: 10.1093/cid/ciab691); fine aerosols remain suspended for longer periods and can penetrate all the way down into the alveolar space of the human respiratory tract ( ref: Hinds Aerosol Technology). For example influenza A... " + +2) + +Aerodynamic vs physical diameter + +This is still unclear in the text. If I understand correctly the experimental set up of the authors, they nebulized a solution of glycerin \(20\%\) into particles of up to \(20\mu m\) ; this is a measured physical diameter; their measurements of the diameter of particles that go through are a measurement of physical diameter ( and not of aerodynamic diameter), please correct on lines 83 - 84 Owing to the density of glycerol \(20\%\) ( approx. 1.05) the aerodynamic diameter will be greater (not smaller) by a factor of \(\sqrt{1.05} \approx 1.02\) ( see Hinds pp 53- 55). Lines 85- 92 could be replaced by something much more succinct, I would suggest something along the lines of the following: + +"Owing to the greater density of glycerol \(20\%\) relative to water, the corresponding aerodynamic diameter can be obtained by applying a correction factor of 1.02, a minimal correction ( ref 17, 18)" + +This is much shorter but still makes the point that the conceptual difference between physical diameter and aerodynamic diameter has not escaped your attention and that the demonstration of the experimental set up as excluding non- aerosol particles is rigorous. + +Recombinant viruses + +I think that we are essentially in agreement. For samples where complete genomic sequences was feasible, the fact that only overlapping small fragments were sequenced is not a problem provided that only one genomic sequence ( alpha or original lineage) is obtained at all positions, which is the + +<--- Page Split ---> + +# natureresearch + +case here according to the data. Problems would arise if there was a mixture of signals from alpha and the original lineage at different positions, since then sequences of overlapping small fragments could not decide between a recombinant and a mixed infection. + +For samples where only a SNP assay could be done because of a viral load too low for sequencing, in theory you could be facing a recombinant since you are scoring only one position in the genomic sequence. The discussion of this issue offered by the authors is satisfactory. For future work the authors may want to consider 2 or more SNP assays scattered throughout the genome, which would be doable even with a low viral load sample. + +Reviewer #4: Remarks to the Author: I have read the revised manuscript and the rebuttal provided by the authors. They have fully addressed the concerns that I raised in my initial review and I feel that the manuscript is now suitable for publication. + +## Final Decision Letter: + +Dear Dr. Munster, + +I am pleased to accept your Article "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" for publication in Nature Microbiology. Thank you for having chosen to submit your work to us and many congratulations. + +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Microbiology style. We look particularly carefully at the titles of all papers to ensure that they are relatively brief and understandable. + +Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. 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It certainly sounds interesting, and we would be happy to consider it for publication. However, I'm sure you'll understand that we cannot make a firm decision about whether to send the paper out to review until we have carefully read the full paper (and appropriate background literature). + +<|ref|>text<|/ref|><|det|>[[112, 668, 826, 685]]<|/det|> +In order to submit your complete manuscript to Nature Microbiology, please use the link below: + +<|ref|>text<|/ref|><|det|>[[115, 699, 199, 714]]<|/det|> +{redacted} + +<|ref|>text<|/ref|><|det|>[[115, 728, 545, 744]]<|/det|> +If you have any questions, please feel free to contact me. + +<|ref|>text<|/ref|><|det|>[[115, 758, 234, 773]]<|/det|> +Yours sincerely, + +<|ref|>text<|/ref|><|det|>[[115, 788, 199, 803]]<|/det|> +{redacted} + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[121, 145, 345, 160]]<|/det|> +## Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[119, 180, 253, 195]]<|/det|> +Dear Dr. Munster, + +<|ref|>text<|/ref|><|det|>[[115, 209, 875, 315]]<|/det|> +Thank you for your patience while your manuscript "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" was under peer- review at Nature Microbiology. It has now been seen by 4 referees, whose expertise and comments you will find at the of this email. You will see from their comments below that while they find your work of interest, some important points are raised. We are very interested in the possibility of publishing your study in Nature Microbiology, but would like to consider your response to these concerns in the form of a revised manuscript before we make a final decision on publication. + +<|ref|>text<|/ref|><|det|>[[115, 328, 877, 477]]<|/det|> +In particular, both referee #1 and #2 ask to further confirm viral transmission in the competition assay by comparing histopathology and infectious viral titers between inoculated and sentinel animals. Here, referee #1 also suggests to characterize virus composition within the lungs. In addition, referee #2 asks to include an comparison of the Delta variant to increase clinical relevance of the study. Referee #3 points out that inoculation of the same amount from both variants in the competition assay need to be confirmed. This referee also makes several suggestions to adjust the discussion section and references. Referee #4 points out that no in silico study, in which interaction energies have been evaluated, and no binding study was conducted. This referee asks to clarify this in the written text. The rest referees' reports are clear and the remaining issues should be straightforward to address. + +<|ref|>text<|/ref|><|det|>[[116, 492, 876, 537]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[116, 552, 842, 582]]<|/det|> +If you have not done so already please begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/nmicrobiol/info/final- submission/ + +<|ref|>text<|/ref|><|det|>[[116, 596, 877, 656]]<|/det|> +The usual length limit for a Nature Microbiology Article is six display items (figures or tables) and 3,000 words. We have some flexibility, and can allow a revised manuscript at 3,500 words, but please consider this a firm upper limit. 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Please see also 'Guidelines for Electronic Submission of Figures' at the end of this letter for further detail. + +<|ref|>text<|/ref|><|det|>[[115, 738, 870, 769]]<|/det|> +Figure legends must provide a brief description of the figure and the symbols used, within 350 words, including definitions of any error bars employed in the figures. + +<|ref|>text<|/ref|><|det|>[[115, 783, 842, 829]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- research/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +<|ref|>text<|/ref|><|det|>[[115, 842, 836, 858]]<|/det|> +- that unprocessed scans are clearly labelled and match the gels and western blots presented in + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 171, 158]]<|/det|> +figures. + +<|ref|>text<|/ref|><|det|>[[115, 159, 844, 204]]<|/det|> +-- that control panels for gels and western blots are appropriately described as loading on sample processing controls-- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +<|ref|>text<|/ref|><|det|>[[115, 232, 857, 277]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[115, 306, 875, 336]]<|/det|> +Please include a statement before the acknowledgements naming the author to whom correspondence and requests for materials should be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 351, 877, 426]]<|/det|> +Finally, we require authors to include a statement of their individual contributions to the paper - - such as experimental work, project planning, data analysis, etc. - - immediately after the acknowledgements. The statement should be short, and refer to authors by their initials. For details please see the Authorship section of our joint Editorial policies at http://www.nature.com/authors/editorial_policies/authorship.html + +<|ref|>text<|/ref|><|det|>[[116, 442, 313, 457]]<|/det|> +When revising your paper: + +<|ref|>text<|/ref|><|det|>[[115, 471, 880, 515]]<|/det|> +\* include a point- by- point response to any editorial suggestions and to our referees. Please include your response to the editorial suggestions in your cover letter, and please upload your response to the referees as a separate document. + +<|ref|>text<|/ref|><|det|>[[115, 530, 850, 560]]<|/det|> +\* ensure it complies with our format requirements for Letters as set out in our guide to authors at www.nature.com/nmicrobiol/info/gta/ + +<|ref|>text<|/ref|><|det|>[[115, 575, 825, 605]]<|/det|> +\* state in a cover note the length of the text, methods and legends; the number of references; number and estimated final size of figures and tables + +<|ref|>text<|/ref|><|det|>[[115, 620, 736, 635]]<|/det|> +\* resubmit electronically if possible using the link below to access your home page: + +<|ref|>text<|/ref|><|det|>[[116, 650, 198, 665]]<|/det|> +{redacted} + +<|ref|>text<|/ref|><|det|>[[115, 680, 870, 725]]<|/det|> +\*This url links to your confidential homepage and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this e- mail to co- authors, please delete this link to your homepage first. + +<|ref|>text<|/ref|><|det|>[[115, 739, 861, 768]]<|/det|> +Please ensure that all correspondence is marked with your Nature Microbiology reference number in the subject line. + +<|ref|>text<|/ref|><|det|>[[115, 784, 878, 858]]<|/det|> +Nature Microbiology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 840, 188]]<|/det|> +contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[115, 202, 836, 232]]<|/det|> +We hope to receive your revised paper within two months. If you cannot send it within this time, please let us know. + +<|ref|>text<|/ref|><|det|>[[116, 247, 435, 262]]<|/det|> +We look forward to hearing from you soon. + +<|ref|>text<|/ref|><|det|>[[116, 277, 199, 292]]<|/det|> +{redacted} + +<|ref|>text<|/ref|><|det|>[[116, 322, 294, 333]]<|/det|> +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\* + +<|ref|>text<|/ref|><|det|>[[116, 353, 263, 366]]<|/det|> +Reviewer Expertise: + +<|ref|>text<|/ref|><|det|>[[115, 381, 485, 440]]<|/det|> +Referee #1: Viral transmission, Animal model Referee #2: SARS- CoV- 2, Animal model Referee #3: Viral transmission, Bioaerosol Referee #4: Coronaviruses, Receptor interactions + +<|ref|>text<|/ref|><|det|>[[116, 456, 282, 470]]<|/det|> +Reviewers Comments: + +<|ref|>text<|/ref|><|det|>[[116, 485, 404, 500]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 515, 864, 575]]<|/det|> +The manuscript by Port et al., is a very interesting study demonstrating small particle aerosol transmission of SARS- CoV- 2 in hamsters in an innovative transmission caging system. Overall the study is well done, but I have some specific comments about the final section of the results "B.1.1.7 variant demonstrates increased airborne transmission competitiveness" + +<|ref|>text<|/ref|><|det|>[[115, 576, 881, 693]]<|/det|> +1. Gross lung pathology was compared in the different sentinel hamsters. How did that compare to the inoculated donor animal lungs? Why was histopathology not compared? It would be very interesting to assess whether viral distribution (by immunohistochemistry) or microscopic pathology differed between donor and sentinel animals as well as between lineage A and UK variant infected animals. +2. In Fig 5G, the authors assessed percentages of different vial variants in the competition experiment in oropharyngeal swabs. It would be interesting to look at viral composition in the lungs, especially since the experiment was designed to assess small particle aerosol transmission. Distribution and replication of the two viruses might be different between the upper and lower respiratory tracts. + +<|ref|>text<|/ref|><|det|>[[116, 723, 404, 738]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 753, 878, 857]]<|/det|> +This study develops and validates a caging system to monitor true aerosol transmission of SARS- CoV- 2 between Syrian golden hamsters. Applied to a comparison of aerosol transmission of the original lineage A and VOC alpha, increased airborne transmission of the VOC was observed. Experimental approaches and results are clearly presented. A validated experimental set- up to compare relative transmission efficiency of newly emerging SARS- CoV- 2 VOC is a major contribution to the field. Whereas use of the VOC alpha for a proof- of- concept study is fair, the actual clinical importance of alpha has vanished with the emergence of the now globally dominant delta VOC several + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 864, 173]]<|/det|> +months ago. Application of the system to VOC delta would consequently greatly advance the clinical impact of the study. + +<|ref|>text<|/ref|><|det|>[[115, 173, 880, 321]]<|/det|> +Although data are overall of high quality, a major shortcoming is the overall reliance on viral RNA copy numbers to measure transmission success, which may or may not accurately reflect productive infection of sentinels. To illustrate the point, figure 5C shows approx. equal, high RNA copy numbers in three animals of the sentinel 2 group, and intermediate copy numbers in another animal of this group. Looking at actual infectious titers of animals in this group (figure 5D), however, only 1 of the sentinel 2 animals shows productive infection (high virus burden), while another shows intermediate burden and all others are essentially at detection level. What is the reason for this discrepancy, which undermines confidence in RNA copy number measurements as a readout for productive infection in this model? Please provide proof for productive infection of key experiments in form of infectious titers to fully support the conclusions drawn. + +<|ref|>text<|/ref|><|det|>[[117, 351, 404, 366]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 380, 870, 411]]<|/det|> +Review of "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" by Port JR et al + +<|ref|>sub_title<|/ref|><|det|>[[115, 427, 190, 440]]<|/det|> +## Summary + +<|ref|>text<|/ref|><|det|>[[115, 441, 863, 515]]<|/det|> +In this study by Port et al the authors developed an experimental set up in which the only transmission pathway between experimentally infected animals and recipient animals was through aerosol particles \(< 10\) um, and in fact most of the particles were in the \(< 5\) um range. The size of the particles going through the caging set up has been verified with an aerosolized solution of glycerin \(20\%\) in water. + +<|ref|>text<|/ref|><|det|>[[115, 515, 870, 560]]<|/det|> +Using this set up the authors demonstrated transmission by aerosols between Syrian hamsters, for both the original lineage of SARS- CoV- 2 and the alpha variant. In additional experiments the authors showed that in competitive infection by aerosols the alpha variant out- competed the original strain. + +<|ref|>sub_title<|/ref|><|det|>[[115, 576, 206, 589]]<|/det|> +## Assessment + +<|ref|>text<|/ref|><|det|>[[115, 590, 863, 666]]<|/det|> +Overall this original study has been well conducted, the critical data were convincingly obtained, the results are indeed novel although arguably not quite as novel as the authors assert. But it is undeniable that these results are of great importance for our understanding of SARS- CoV- 2 transmission and for the rational design of a pandemic control strategy. Several details and discussion topics would benefit from rewriting and some additional info. + +<|ref|>text<|/ref|><|det|>[[115, 680, 480, 694]]<|/det|> +1) Definition of aerosols and "airborne infection" + +<|ref|>text<|/ref|><|det|>[[115, 695, 876, 857]]<|/det|> +Admittedly the lack of standardization of terminology has been a bane of the field for a long time and continues to impede accurate discussion. The authors are correct to point out that many authors have used the term "airborne transmission to mean transmission by either large droplets or aerosols. However most authors, including infectious diseases and infection control practitioners, have used to term to mean aerosol transmission only and I think that the authors should also use that convention. The size cut- off for bio- aerosols involved in disease transmission has also been a contentious issue. It is now appreciated that in fact particles of up to 100- 200 um do not settle rapidly and can be carried away by air jets over several meters (see eg Milton DK J Pediatric Infect Dis 2020; 9(4) 413- 415). This whole spectrum of particles linger in the air (for a time depending in part on their size), can follow air currents, and thus can be thought of accurately as aerosols; and there are implications for mitigations by ventilation and adequate PPE such as N95s. That being said, the authors are, I believe, + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 871, 203]]<|/det|> +quite justified in putting an emphasis on "small" or "fine" aerosols \(< 5 - 10\) um. For humans infection it is certainly important to note that penetration below the glottis occurs only for particles \(< 20\mu m\) , and penetration into the alveolar region occur with particles \(< 5 - 6\) um ( Hinds W Aerosol technology 2nd ed; 1999). + +<|ref|>text<|/ref|><|det|>[[115, 203, 872, 264]]<|/det|> +The authors demonstrated that in their set up no particles \(>10\) um were involved ( and most were in fact \(< 5\) um) and so no one can argue that they are not dealing with aerosol transmission and indeed with fine aerosol transmission. But their definitions, I would suggest, should standardize to the emerging consensus for terminology. + +<|ref|>sub_title<|/ref|><|det|>[[116, 278, 437, 292]]<|/det|> +## 2) Measurements of aerodynamic diameter + +<|ref|>text<|/ref|><|det|>[[115, 293, 872, 397]]<|/det|> +It was essential for the central argument of the authors to carefully demonstrate that their setup excluded non- aerosol particles . They have done this conclusively using aerosols from a \(20\%\) glycerin solution but the discussion needs to be a little more rigorous because strictly speaking they have measured the physical diameter of the particles; to arrive at the aerodynamic diameter they must correct for the density of the particles; but as it happens the correction is indeed minimal (density of glycerol \(20\%\) at \(20C\) : approx. 1.05; details of correction: see Hinds W 2nd ed pp 53- 55). This should take only a line or two. + +<|ref|>sub_title<|/ref|><|det|>[[116, 412, 325, 426]]<|/det|> +## 3) Competition experiments + +<|ref|>text<|/ref|><|det|>[[115, 427, 880, 516]]<|/det|> +For these experiments the donor animal was infected with a mixture of SARS- CoV- 2 lineage A and alpha variant. This opens the door the genesis of recombinant viruses in either the donor or recipient animals; coronaviruses, because of their "jumping polymerase" are notorious for their capacity to generate recombinants and have been referred to as viruses with "continuous segmented genomes". As it happened, the authors have guarded against this possible occurrence by doing complete genomic sequencing (using NGS) on most off the recovered isolates in recipient animals. + +<|ref|>text<|/ref|><|det|>[[115, 516, 880, 636]]<|/det|> +However in 3 cases there was not enough RNA to do full sequencing and the identity of the isolate was inferred only through duplex qRT- PCR to detect a tell- tale mutation. Strictly speaking this would not rule out the presence of a recombinant virus in these 3 cases. I would suggest that the authors could supplement the data with a SNP assay targeting another identifying mutation elsewhere in the genome (say in the ORF1a), which should be doable even with a very small amount of available RNA. Alternatively they could just modify their discussion and point out that in these 3 cases the mutation associated with B.1.1.7 was selected for and given the other results with complete sequencing it appears very likely that the variant, and not a recombinant, was selected. + +<|ref|>text<|/ref|><|det|>[[116, 636, 870, 681]]<|/det|> +Another point: I think that the 1:1 mix of the 2 lineages for inoculating the donor animal should be better explained; it is critical to make sure that approximately the same amount of TCID50s for each lineage be present. + +<|ref|>sub_title<|/ref|><|det|>[[116, 696, 330, 710]]<|/det|> +## 4) Discussion: lines 276-280 + +<|ref|>text<|/ref|><|det|>[[115, 711, 876, 815]]<|/det|> +Actually there are other type of evidence, not just long range transmission, to prove aerosol transmission (see eg Tellier et al BMJ Infect Dis 2019; 19(1): 101); as well aerosol transmission also readily occurs at short range and in fact more readily so, and some authors have argued that at short distance it was predominant compared to large droplet transmission ( Chen et al, Building and Environment 2020; 176: 106859); I would argue against using Brankston et al ( ref 25) as a reference for this point as these authors understanding of virology is often inaccurate ( as exemplified by their stamen that influenza A virus infects erythrocytes...). + +<|ref|>sub_title<|/ref|><|det|>[[116, 830, 216, 844]]<|/det|> +## 5) Discussion + +<|ref|>text<|/ref|><|det|>[[115, 844, 880, 859]]<|/det|> +It is not quite accurate that these results are the first "proof" of aerosol transmission of Covid as other + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 866, 232]]<|/det|> +lines of evidence have been published, including investigations of several outbreaks that would be essentially unexplainable without aerosols ( see eg Katelaris et al EID 2021; 27: 6, June 2021); as well, the ferret transmission experiments of Kutter et al ( ref 27) are compelling and although Kutter et al did not provide that calculation, based on the provided dimensions of the duct, the air flow and Stokes' law one can readily show that the maximum size of particles in their set up would be well within the aerosol range. + +<|ref|>text<|/ref|><|det|>[[115, 232, 848, 262]]<|/det|> +So I think that in their discussion the authors should instead insist on the main (and considerable) strengths of this study : + +<|ref|>text<|/ref|><|det|>[[115, 262, 875, 397]]<|/det|> +i) actual measurement of the maximum size of aerosols in their set up ( \(< 10 \text{um}\) )ii) the demonstration that small aerosols can transmit SARS-CoV-2 between hamstersiii) the demonstration that in mixed aerosol inocula the alpha variant out-compete the original lineage. The authors could with great benefits I think refer to an analogous result obtained with Influenza A virus by Koster et al (PLoS one 7(4): e33118), who showed than the pandemic strain of A(H1N1) was much more efficient at aerosol transmission than the seasonal A(H1N1) it replaced; this precedent with a different respiratory virus actually strengthen the plausibility of the results in this study and together they enhance our understanding of the pandemic potential of different respiratory viruses and the contribution of aerosol transmission to their pandemic potential. + +<|ref|>sub_title<|/ref|><|det|>[[116, 411, 300, 425]]<|/det|> +## 6) Discussion: I 294-295 + +<|ref|>text<|/ref|><|det|>[[115, 426, 875, 501]]<|/det|> +For humans the threshold for effective penetration in the alveolar space has been shown to be \(< 5 - 6\) um ( Hinds WC Aerosol Technology 2nd ed0; but I am not aware of a similar determination of size cut off for other species including hamsters; and although it is difficult to believe that aerosols of \(< 5 \text{um}\) would not reach the lower resp tract of hamsters the discussion must distinguishes between what is experimentally proven and what is plausible based on first principles. + +<|ref|>text<|/ref|><|det|>[[116, 515, 869, 560]]<|/det|> +7) ref 4 has been much criticized in part for its methodology and for the point they want to make the authors could replace it with one of many other, for example Greenhaig et al Lancet 2021; 397: 10285, p 1603-1605) + +<|ref|>text<|/ref|><|det|>[[115, 574, 838, 590]]<|/det|> +8) line 81: "... allowed for 30 cage changes per hour": presumably "cage air changes per hour"? + +<|ref|>text<|/ref|><|det|>[[116, 618, 404, 633]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 648, 877, 693]]<|/det|> +This manuscript describes a novel cage setup to study airborne transmission of SARS- CoV- 2 using the Syrian hamster model. The setup allows large droplets and aerosols to be tested and both B.1.1.7 and a lineage A variant have been studied. + +<|ref|>text<|/ref|><|det|>[[115, 708, 877, 738]]<|/det|> +I am commenting solely on the section of the paper that deals with the interaction of the RBD of these viruses with human and hamster ACE2. + +<|ref|>text<|/ref|><|det|>[[115, 752, 880, 857]]<|/det|> +It has previously been shown by several publications that the N501Y mutation in the RBD of B.1.1.7 leads to higher affinity for human ACE2. In this work, the authors state that they looked at the binding efficiency of the lineage A and B.1.1.7. RBDs to the hamster RBD in silico. This must be clarified. It seems that the authors have simply generated a figure showing the locations of the N501Y mutation and the relevant sites (H34Q and M82N) at which human and hamster ACE2 differ (with residues substituted in Coot - Figure 3). The word "efficiency" is unclear and suggests a deeper analysis. As far as I can tell, the authors have not performed any calculations to evaluate the relevant interaction + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 530, 158]]<|/det|> +energies (as might be expected of an in silico analysis). + +<|ref|>text<|/ref|><|det|>[[115, 172, 870, 219]]<|/det|> +At line 151, a VSV entry assay is introduced, and this shows that B.1.1.7 entry is increased for both human and hamster ACE2. From there, the authors conclude that B1.1.7 binds tighter to hamster ACE2: line 159: "We next investigated if the enhanced binding affinity of B1.1.7 to hamster ACE2 ..." + +<|ref|>text<|/ref|><|det|>[[115, 232, 864, 309]]<|/det|> +Given that human and hamster ACE2 do not differ in the region where RBD residue N501Y interacts with ACE2, it's not unreasonable to suggest that B.1.1.7 might also show higher affinity for hamster ACE2. However, neither the in silico work, nor the VSV assay (a binding studied would be required), establish that B.1.1.7 shows enhanced affinity for hamster ACE2 and the text should be qualified appropriately. + +<|ref|>sub_title<|/ref|><|det|>[[122, 364, 355, 379]]<|/det|> +## Author Rebuttal, first revision: + +<|ref|>text<|/ref|><|det|>[[116, 382, 393, 398]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 417, 882, 488]]<|/det|> +The manuscript by Port et al., is a very interesting study demonstrating small particle aerosol transmission of SARS- CoV- 2 in hamsters in an innovative transmission caging system. Overall the study is well done, but I have some specific comments about the final section of the results "B.1.1.7 variant demonstrates increased airborne transmission competitiveness" + +<|ref|>text<|/ref|><|det|>[[115, 490, 879, 562]]<|/det|> +1. Gross lung pathology was compared in the different sentinel hamsters. How did that compare to the inoculated donor animal lungs? Why was histopathology not compared? It would be very interesting to assess whether viral distribution (by immunohistochemistry) or microscopic pathology differed between donor and sentinel animals as well as between lineage A and UK variant infected animals. + +<|ref|>text<|/ref|><|det|>[[114, 574, 874, 682]]<|/det|> +We thank the reviewer for the comment and have explored the relationship between exposure route and pathogenicity in several other studies. Typically, with directly inoculated hamsters the lungs display a little more marked gross pathology as compared to the sentinel animals, but the histopathology is very similar after transmission (van Doremalen, Science Translational Medicine https://www.science.org/doi/10.1126/scitranslmed.abh0755; Yinda et al., Emerging Microbes and Infection, https://www.tandfonline.com/doi/full/10.1080/22221751.2021.1943539). + +<|ref|>text<|/ref|><|det|>[[113, 693, 879, 819]]<|/det|> +In addition, we see that disease, tropism and shedding within the respiratory tract are directly related to the exposure route (Port et al, Nature Communications, https://www.nature.com/articles/s41467- 021- 25156- 8). We also see that the pathology caused by the different VOCs does not strikingly differ in hamsters (Fischer et al, Nature Communication accepted, https://www.biorxiv.org/content/10.1101/2021.03.11.435000v1) nor in non- human primates (Munster et al., Science advances accepted, https://www.biorxiv.org/content/10.1101/2021.05.07.443115v1) + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 142, 882, 234]]<|/det|> +For this study the emphasis was completely on transmission and not pathogenesis and therefor no samples from the inoculated animal and no samples for histological analysis were collected. However, we agree with the reviewer that more information on the various VOCs would be helpful and are planning future experiments comparing the gross and histopathology seen in sentinels as compared to donors. + +<|ref|>text<|/ref|><|det|>[[114, 262, 878, 336]]<|/det|> +2. In Fig 5G, the authors assessed percentages of different vial variants in the competition experiment in oropharyngeal swabs. It would be interesting to look at viral composition in the lungs, especially since the experiment was designed to assess small particle aerosol transmission. Distribution and replication of the two viruses might be different between the upper and lower respiratory tracts. + +<|ref|>text<|/ref|><|det|>[[114, 363, 867, 456]]<|/det|> +We fully agree with the reviewer and have reanalyzed the lung data by extraction of lung tissue samples and additional NGS analyses. We have added this new data in the results and have updated the discussion to incorporate the new data. To do so, we optimized our protocols and gain higher quality RNA from the lung samples, which we were able to sequence. We have modified the sgRNA data in Figure 5E to correspond to the new sequence data. The new data is shown in Fig 5 H. + +<|ref|>text<|/ref|><|det|>[[116, 466, 666, 484]]<|/det|> +The following paragraphs have been changed in the results to reflect this: + +<|ref|>text<|/ref|><|det|>[[116, 495, 185, 511]]<|/det|> +Line 261: + +<|ref|>text<|/ref|><|det|>[[116, 522, 861, 578]]<|/det|> +"To determine the competitiveness of the variants we analyzed the relative composition of the two viruses in the swabs using next generation sequencing and compared the percentage of B.1.1.7/lineage A at 2 DPE in oral swab samples and at 5 DPE in lungs (Figure 5 G/H)." + +<|ref|>text<|/ref|><|det|>[[116, 589, 185, 604]]<|/det|> +Line 276: + +<|ref|>text<|/ref|><|det|>[[114, 616, 866, 818]]<|/det|> +"To investigate whether this pattern was also reflected in the lower respiratory tract, we sequenced viral RNA extracted from lung samples collected at 5 DPE for all donors, Sentinels 1 and Sentinels 2. One donor had increased amounts of lineage A variant (82%), while in the remaining seven animals the B.1.1.7 variant was increased in the lungs (73- 85% range). In the Sentinels 1 group, increased amounts of lineage A variant were found in two animals (72% and 99%), while B.1.1.7 was increased in the others (65%- 100%); in the Sentinels 2 group viral RNA sequences in two animals were 100% lineage A, and in the remaining four animals exclusively (99- 100%) B.1.1.7. Taken together, B.1.1.7 demonstrated increased competitiveness; after 10 out of 13 airborne transmission events B.1.1.7 outcompeted lineage A in the upper respiratory tract (swab samples) and only in three events infection with lineage A was established as the dominant variant. In the lower respiratory tract, B.1.1.7 outcompeted lineage A in 10 out of 14 events." + +<|ref|>text<|/ref|><|det|>[[116, 829, 246, 845]]<|/det|> +In the discussion: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[115, 144, 185, 159]]<|/det|> +## Line 346: + +<|ref|>text<|/ref|><|det|>[[115, 171, 852, 225]]<|/det|> +"We observed that the variant profiles in the upper and lower respiratory tract were not always in accord. Of interest are also additional studies discerning this discrepancy in more detail and determining the source of virus involved in onwards transmission." + +<|ref|>text<|/ref|><|det|>[[116, 245, 393, 261]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 281, 883, 444]]<|/det|> +This study develops and validates a caging system to monitor true aerosol transmission of SARS- CoV- 2 between Syrian golden hamsters. Applied to a comparison of aerosol transmission of the original lineage A and VOC alpha, increased airborne transmission of the VOC was observed. Experimental approaches and results are clearly presented. A validated experimental set- up to compare relative transmission efficiency of newly emerging SARS- CoV- 2 VOC is a major contribution to the field. Whereas use of the VOC alpha for a proof- of- concept study is fair, the actual clinical importance of alpha has vanished with the emergence of the now globally dominant delta VOC several months ago. Application of the system to VOC delta would consequently greatly advance the clinical impact of the study. + +<|ref|>text<|/ref|><|det|>[[114, 455, 883, 565]]<|/det|> +We thank the reviewer for the positive comments. Whereas we agree with the need for real- time information on VOCs as soon as they are generated, the venue of scientific publishing does not work particularly allow for rapid dissemination of novel data. However, all our preliminary data gets directly shared with stakeholders such as the World Health Organization animal model workgroup and the SARS- CoV- 2 Evolution workgroups and within different entities of the USG (OWS and HHS) and publication ready data is directly put on preprint servers. + +<|ref|>text<|/ref|><|det|>[[114, 575, 877, 721]]<|/det|> +More from a practical manner, it typically takes several months before we have access to novel VOCs, e.g. we got our first strain of the delta variant in at \(15^{\text{th}}\) of June, the next step would than be growing stocks to use in experiments and perform deep sequencing analyses to determine the integrity of the virus stock (e.g. no cleavage site deletions or bacterial contaminations) and determine the titer by titration. Typically, this can take anywhere between 3- 6 weeks. In addition, animal experiment will need an IACUC approval, which will a minimum of 2 months before an experimental outline gets approved and animal can be ordered. The actual experiment can take anywhere between 2- 6 weeks and an additional 6- 10 weeks for downstream processing like NGS and potentially histopathology. + +<|ref|>text<|/ref|><|det|>[[114, 731, 879, 859]]<|/det|> +Obviously, we are trying to expedite our work to inform public health as much as possible, and vaccine and transmission experiments with the Delta variant have started but adding information on Delta in this manuscript is realistically impossible in a reasonable timeframe. In addition, the scope of the manuscript was to define the efficiency of aerosol transmission of SARS- CoV- 2 in a well- defined set- up. In addition, we determined that increased transmission is a function of increased airborne advantage as a phenotype of the novel VOCs. We think it can be expected that any clinical implication drawn from this data, would also be applicable to delta. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 161, 877, 344]]<|/det|> +Although data are overall of high quality, a major shortcoming is the overall reliance on viral RNA copy numbers to measure transmission success, which may or may not accurately reflect productive infection of sentinels. To illustrate the point, figure 5C shows approx. equal, high RNA copy numbers in three animals of the sentinel 2 group, and intermediate copy numbers in another animal of this group. Looking at actual infectious titers of animals in this group (figure 5D), however, only 1 of the sentinel 2 animals shows productive infection (high virus burden), while another shows intermediate burden and all others are essentially at detection level. What is the reason for this discrepancy, which undermines confidence in RNA copy number measurements as a readout for productive infection in this model? Please provide proof for productive infection of key experiments in form of infectious titers to fully support the conclusions drawn. + +<|ref|>text<|/ref|><|det|>[[114, 355, 875, 500]]<|/det|> +We agree with the reviewer that solely relying on viral RNA copy numbers might not always accurately reflect productive infection of sentinels. However, real- time quantitative PCR assays are typically 2 log more sensitive than virus titration, it therefor is typically is a reliable marker for infection. The inclusion of subgenomic RNA qRT- PCR, a surrogate for virus replication, is directly associated with seroconversion of the animal in our previous hamster transmission experiments, and such was used as the main marker for infection. Subgenomic RNA only gets produced during active infection and rapidly degrades, as its not encapsulated in a viral envelope like genomic RNA as we have shown previously (Speranza Science Translational Medicine 2021). + +<|ref|>text<|/ref|><|det|>[[115, 511, 880, 584]]<|/det|> +However, we agree with the reviewer that infectious virus, in addition to the shown viral genomic and subgenomic RNA in swabs and seroconversion, will provide conclusive results. We have therefor titrated swab samples and have added the infectious virus titers to key experiments in Figures 2 and 4 and we have modified the results section accordingly. + +<|ref|>text<|/ref|><|det|>[[116, 623, 393, 639]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 659, 880, 695]]<|/det|> +Review of "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" by Port JR et al + +<|ref|>sub_title<|/ref|><|det|>[[115, 716, 187, 731]]<|/det|> +## Summary + +<|ref|>text<|/ref|><|det|>[[115, 733, 877, 860]]<|/det|> +In this study by Port et al the authors developed an experimental set up in which the only transmission pathway between experimentally infected animals and recipient animals was through aerosol particles \(< 10 \text{um}\) , and in fact most of the particles were in the \(< 5 \text{um}\) range. The size of the particles going through the caging set up has been verified with an aerosolized solution of glycerin \(20\%\) in water. Using this set up the authors demonstrated transmission by aerosols between Syrian hamsters, for both the original lineage of SARS- CoV- 2 and the alpha variant. In additional experiments the authors showed that in competitive infection by aerosols the alpha variant outcompeted the original strain. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[115, 164, 204, 179]]<|/det|> +## Assessment + +<|ref|>text<|/ref|><|det|>[[115, 181, 880, 253]]<|/det|> +Overall this original study has been well conducted, the critical data were convincingly obtained, the results are indeed novel although arguably not quite as novel as the authors assert. But it is undeniable that these results are of great importance for our understanding of SARS- CoV- 2 transmission and for the rational design of a pandemic control strategy. + +<|ref|>text<|/ref|><|det|>[[115, 253, 787, 270]]<|/det|> +Several details and discussion topics would benefit from rewriting and some additional info. + +<|ref|>text<|/ref|><|det|>[[115, 290, 479, 306]]<|/det|> +1) Definition of aerosols and "airborne infection" + +<|ref|>text<|/ref|><|det|>[[112, 308, 880, 638]]<|/det|> +Admittedly the lack of standardization of terminology has been a bane of the field for a long time and continues to impede accurate discussion. The authors are correct to point out that many authors have used the term "airborne transmission to mean transmission by either large droplets or aerosols. However most authors, including infectious diseases and infection control practitioners, have used to term to mean aerosol transmission only and I think that the authors should also use that convention. The size cut- off for bio- aerosols involved in disease transmission has also been a contentious issue. It is now appreciated that in fact particles of up to 100- 200 um do not settle rapidly and can be carried away by air jets over several meters (see eg Milton DK J Pediatric Infect Dis 2020; 9(4) 413- 415). This whole spectrum of particles linger in the air (for a time depending in part on their size), can follow air currents, and thus can be thought of accurately as aerosols; and there are implications for mitigations by ventilation and adequate PPE such as N95s. That being said, the authors are, I believe, quite justified in putting an emphasis on "small" or "fine" aerosols \(< 5 - 10 \text{um}\) . For humans infection it is certainly important to note that penetration below the glottis occurs only for particles \(< 20 \text{um}\) , and penetration into the alveolar region occur with particles \(< 5 - 6 \text{um}\) (Hinds W Aerosol technology 2nd ed; 1999). The authors demonstrated that in their set up no particles \(> 10 \text{um}\) were involved (and most were in fact \(< 5 \text{um}\) ) and so no one can argue that they are not dealing with aerosol transmission and indeed with fine aerosol transmission. But their definitions, I would suggest, should standardize to the emerging consensus for terminology. + +<|ref|>text<|/ref|><|det|>[[115, 675, 875, 766]]<|/det|> +We thank the reviewer for the comments and insights and have tried as much possible to incorporate them in the manuscript. We agree with the reviewer that the definitions used throughout the literature can be quite opaque and have therefor tried to specify the definitions and conditions used in our experimental set- up as much as possible. According to the suggestions we have now updated manuscript accordingly: + +<|ref|>text<|/ref|><|det|>[[115, 778, 285, 793]]<|/det|> +In the abstract line 18: + +<|ref|>text<|/ref|><|det|>[[115, 805, 733, 822]]<|/det|> +"Aerosol transmission is thought to be a major transmission route of SARS- CoV- 2." + +<|ref|>text<|/ref|><|det|>[[115, 834, 546, 850]]<|/det|> +We have changed the introduction to match this. Line 42: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 142, 882, 271]]<|/det|> +"Epidemiological data suggests that the principal mode of infection with SARS- CoV- 2 is via airborne transmission in addition to large droplet transmission 1- 5. The general definition held by the WHO states that large droplets disperse over a short distance and settle in the upper respiratory tract, while aerosols (<5 μm) can form droplet nuclei, travel also over long distance, and significantly deposit in the lower respiratory tract 6. For influenza A virus, another respiratory virus, studies have elucidated the airborne potential and discussed the relative contribution of large droplets vs. aerosols and the site of viral exposure and shedding 7- 10. Similar data for SARS- CoV- 2 is currently unavailable." + +<|ref|>sub_title<|/ref|><|det|>[[116, 290, 435, 306]]<|/det|> +## 2) Measurements of aerodynamic diameter + +<|ref|>text<|/ref|><|det|>[[114, 308, 877, 435]]<|/det|> +It was essential for the central argument of the authors to carefully demonstrate that their setup excluded non- aerosol particles They have done this conclusively using aerosols from a \(20\%\) glycerin solution but the discussion needs to be a little more rigorous because strictly speaking they have measured the physical diameter of the particles; to arrive at the aerodynamic diameter they must correct for the density of the particles; but as it happens the correction is indeed minimal (density of glycerol \(20\%\) at \(20C\) : approx. 1.05; details of correction: see Hinds W 2nd ed pp 53- 55). This should take only a line or two. + +<|ref|>text<|/ref|><|det|>[[116, 446, 593, 463]]<|/det|> +We thank the review for this important insight and have added: + +<|ref|>sub_title<|/ref|><|det|>[[116, 475, 175, 490]]<|/det|> +## Line 85: + +<|ref|>text<|/ref|><|det|>[[114, 502, 877, 630]]<|/det|> +"The aerodynamic particle size of a particle is the particle size regardless of shape and material density that has the same settling rate as a spherical droplet of water. It is the principal parameter used for characterizing respiratory deposition 17. Therefore a \(5\mu m\) aerodynamical particle will act similarly to a \(5\mu m\) spherical droplet of water whether it is a from a \(20\%\) glycerol solution, or a mucus filled respiratory droplet. A \(20\%\) glycerol solution has a density of \(1.05g / cm^3\) therefore the geometrical diameter of the glycerol droplets are determined by multiplying the aerodynamic particle diameter by a correction factor of \(0.98^{18}\) ." + +<|ref|>sub_title<|/ref|><|det|>[[116, 679, 323, 694]]<|/det|> +## 3) Competition experiments + +<|ref|>text<|/ref|><|det|>[[114, 696, 880, 860]]<|/det|> +For these experiments the donor animal was infected with a mixture of SARS- CoV- 2 lineage A and alpha variant. This opens the door the genesis of recombinant viruses in either the donor or recipient animals; coronaviruses, because of their "jumping polymerase" are notorious for their capacity to generate recombinants and have been referred to as viruses with "continuous segmented genomes". As it happened, the authors have guarded against this possible occurrence by doing complete genomic sequencing (using NGS) on most off the recovered isolates in recipient animals. However in 3 cases there was not enough RNA to do full sequencing and the identity of the isolate was inferred only through duplex qRT- PCR to detect a tell- tale mutation. Strictly speaking this would not rule out the presence of a recombinant virus in these 3 cases. I would suggest that the authors could + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 142, 881, 237]]<|/det|> +supplement the data with a SNP assay targeting another identifying mutation elsewhere in the genome (say in the ORF1a), which should be doable even with a very small amount of available RNA. Alternatively they could just modify their discussion and point out that in these 3 cases the mutation associated with B.1.1.7 was selected for and given the other results with complete sequencing it appears very likely that the variant, and not a recombinant, was selected. + +<|ref|>text<|/ref|><|det|>[[115, 237, 850, 290]]<|/det|> +Another point: I think that the 1:1 mix of the 2 lineages for inoculating the donor animal should be better explained; it is critical to make sure that approximately the same amount of TCID50s for each lineage be present. + +<|ref|>text<|/ref|><|det|>[[113, 300, 876, 481]]<|/det|> +We thank the reviewer for his comments. Given the sequencing technology used (Illumina Highseq) we would not be able to distinguish recombination events happening unless these viruses would be selected for (as it would then show in in figure 5 G&H). the reason for this is that the NGS typically sequences very small fragments of approximately 300nt which makes it hard to attribute them to any particular genomes. PACBio sequencing, which could generate read lengths of up to 10,000 nucleotides would be the best method to study recombination events. In addition, we are also hampered by the relatively limited number of SNPs occurring in the B.1.1.7 compared to the WA1 variant (see table with all the specific nt differences between lineage A and B.1.1.7, relative to a 30,000 nucleotide genome), because of this similarity it is difficult to recognize recombination events unless using very specific validated assays (like the PACBio). + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[114, 177, 629, 507]]<|/det|> + +
genenucleotideamino acid
ORF1abC3267TT1001I
C5388AA1708D
T6954CI2230T
11288-11296 deletionSGF 3675-3677 deletion
spike21765-21770 deletionHV 69-70 deletion
21991-21993 deletionY144 deletion
A23063TN501Y
C23271AA570D
C23604AP681H
C23709TT716I
T24506GS982A
G24914CD1118H
Orf8C27972TQ27stop
G28048TR52I
A28111GY73C
N28280 GAT->CTAD3L
C28977TS235F
+ +<|ref|>text<|/ref|><|det|>[[114, 565, 577, 578]]<|/det|> +We have addressed his comment by adding to the discussion: + +<|ref|>text<|/ref|><|det|>[[114, 594, 187, 606]]<|/det|> +Line 335: + +<|ref|>text<|/ref|><|det|>[[114, 622, 871, 708]]<|/det|> +“However, B.1.1.7 displayed an increased airborne transmission competitiveness over lineage A in a dual infection experiment both in the lower and upper respiratory tract. In three transmission events we could not confirm full viral sequences in oral swab samples. However, given all other events for which complete sequencing was done, it appears very likely that the variant, and not a recombinant, was selected.” + +<|ref|>text<|/ref|><|det|>[[114, 752, 852, 784]]<|/det|> +In addition, we have now added additional clarification of the composition of the inoculum for the competition experiment. + +<|ref|>text<|/ref|><|det|>[[114, 799, 187, 811]]<|/det|> +Line 517: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 875, 198]]<|/det|> +"Donor hamsters \((N = 8)\) were infected intranasally as described above with \(1 \times 10^{2}\) TCID50 SARS- CoV- 2 (as confirmed by back titration of the inoculum) at a 1:1 ratio of lineage A and B.1.1.7 mixture (54.7% B.1.1.7, as confirmed by full genome sequencing of the inoculum)." + +<|ref|>sub_title<|/ref|><|det|>[[116, 227, 320, 243]]<|/det|> +## 4) Discussion: lines 276-280 + +<|ref|>text<|/ref|><|det|>[[115, 245, 879, 372]]<|/det|> +Actually there are other type of evidence, not just long range transmission, to prove aerosol transmission (see eg Tellier et al BMJ Infect Dis 2019; 19(1): 101); as well aerosol transmission also readily occurs at short range and in fact more readily so, and some authors have argued that at short distance it was predominant compared to large droplet transmission ( Chen et al, Building and Environment 2020; 176: 106859); I would argue against using Brankston et al (ref 25) as a reference for this point as these authors understanding of virology is often inaccurate (as exemplified by their stamen that influenza A virus infects erythrocytes...). + +<|ref|>text<|/ref|><|det|>[[115, 383, 870, 419]]<|/det|> +We thank the reviewer for this important comment. We have removed the ref 25 and have modified the discussion and the result section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 431, 185, 447]]<|/det|> +## Line 291: + +<|ref|>text<|/ref|><|det|>[[114, 458, 880, 602]]<|/det|> +"Epidemiological studies in humans and experimental studies in ferrets strongly suggest that aerosol transmission occurs and plays a major role in driving the SARS- CoV- 2 pandemic 22- 26. Yet formal experimental proof of aerosol transmission with particle diameter \(< 5 \mu m\) 6 in the absence of other transmission routes of SARS- CoV- 2 has not been provided, which would further inform on the importance of this transmission route 27. Here we demonstrated efficient transmission of SARS- CoV- 2 between Syrian hamsters via particles \(< 5 \mu m\) over 200 cm distance. Additionally, we present first qualitative analyses of the efficiency of transmission, showing that even within one hour transmission can occur at a distance of 200 cm between Syrian hamsters. + +<|ref|>text<|/ref|><|det|>[[115, 614, 818, 668]]<|/det|> +Whereas several SARS- CoV- 2 airborne transmission studies in hamsters and ferrets have been performed, none of these studies were able to differentiate between large and small droplet transmission 14,15,25,28,29. " + +<|ref|>sub_title<|/ref|><|det|>[[115, 689, 212, 704]]<|/det|> +## 5) Discussion + +<|ref|>text<|/ref|><|det|>[[114, 706, 877, 833]]<|/det|> +It is not quite accurate that these results are the first "proof" of aerosol transmission of Covid as other lines of evidence have been published, including investigations of several outbreaks that would be essentially unexplainable without aerosols (see eg Katalaris et al EID 2021; 27: 6, June 2021); as well, the ferret transmission experiments of Kutter et al (ref 27) are compelling and although Kutter et al did not provide that calculation, based on the provided dimensions of the duct, the air flow and Stokes' law one can readily show that the maximum size of particles in their set up would be well within the aerosol range. + +<|ref|>text<|/ref|><|det|>[[112, 834, 830, 851]]<|/det|> +So I think that in their discussion the authors should instead insist on the main (and considerable) + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 288, 160]]<|/det|> +strengths of this study : + +<|ref|>text<|/ref|><|det|>[[113, 162, 879, 325]]<|/det|> +strengths of this study :i) actual measurement of the maximum size of aerosols in their set up ( \(< 10 \text{um}\) )ii) the demonstration that small aerosols can transmit SARS- CoV- 2 between hamstersiii) the demonstration that in mixed aerosol inocula the alpha variant out- compete the original lineage. The authors could with great benefits I think refer to an analogous result obtained with Influenza A virus by Koster et al (PLoS one 7(4): e33118), who showed than the pandemic strain of A(H1N1) was much more efficient at aerosol transmission than the seasonal A(H1N1) it replaced; this precedent with a different respiratory virus actually strengthen the plausibility of the results in this study and together they enhance our understanding of the pandemic potential of different respiratory viruses and the contribution of aerosol transmission to their pandemic potential. + +<|ref|>text<|/ref|><|det|>[[113, 364, 868, 473]]<|/det|> +We agree with the reviewer that various epidemiological and experimental studies have been published which very strongly suggest the large potential for SARS- CoV- 2 to be transmitted via aerosols. Coming more from an experimental background, the ongoing debate with animal transmission studies (since our work on influenza, Munster Science 2009, https://www.science.org/doi/full/10.1126/science.1177127), was that unless you show data on size exclusion towards small particles you need to refer to this as "Airborne" or "aerosol and droplet". + +<|ref|>text<|/ref|><|det|>[[115, 484, 841, 520]]<|/det|> +Obviously, the work by Kutter et al, did provide the first experimental evidence in a set- up which strongly suggest transmission of SARS- CoV- 2 by smaller particles. + +<|ref|>text<|/ref|><|det|>[[115, 531, 880, 603]]<|/det|> +We have modified the discussion to the reviewer's recommendations as listed above and have included the references as applicable. We have now modified, that this is the conclusive proof of aerosol transmission but have stressed that our experimental findings strengthen previous work, both experimental and epidemiological. + +<|ref|>text<|/ref|><|det|>[[115, 614, 879, 668]]<|/det|> +We have also included the newly published work by Adenaiye et al, in the discussion which observed a higher viral load in fine aerosol but not coarse aerosols confirming the selective advantage observed in the hamster competition studies. + +<|ref|>text<|/ref|><|det|>[[115, 680, 857, 715]]<|/det|> +Adenaiye, O. O. et al. Infectious SARS- CoV- 2 in Exhaled Aerosols and Efficacy of Masks During Early Mild Infection. Clin Infect Dis, doi:10.1093/cid/ciab797 (2021). + +<|ref|>sub_title<|/ref|><|det|>[[115, 745, 290, 761]]<|/det|> +## 6) Discussion: I 294-295 + +<|ref|>text<|/ref|><|det|>[[115, 763, 879, 853]]<|/det|> +6) Discussion: I 294-295For humans the threshold for effective penetration in the alveolar space has been shown to be < 5-6 um (Hinds WC Aerosol Technology 2nd ed0; but I am not aware of a similar determination of size cut off for other species including hamsters; and although it is difficult to believe that aerosols of < 5um would not reach the lower resp tract of hamsters the discussion must distinguishes between what is experimentally proven and what is plausible based on first principles. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 142, 877, 326]]<|/det|> +Whereas we have never performed complete size exclusion experiments, we have conducted several aerosol inoculation studies in hamsters using experimentally generated aerosols (ranging from \(1 - 5 \mu m\) in size) by a 3- jet collision nebulizer (Biaera technologies, USA). With SARS- CoV- 2 we see the infection is present in the lower respiratory tract starting at 1 day post inoculation (Port et al, Nature Communications, https://www.nature.com/articles/s41467- 021- 25156- 8), compared to intranasal inoculation. Especially, the extend of replication in the type I and II pneumocytes is striking this early in infection (as is the compete upper and lower respiratory tract deposition of SARS- CoV- 2 in hamsters). The extend of replication at 1 dpi in the aerosol exposed via the IN exposed animals directly suggest efficient deposition of aerosols in the \(< 5 \mu m\) size range (Figure taken from Port et al, Nature Communications showing replication of SARS- CoV- 2 at 1 dpi). + +<|ref|>text<|/ref|><|det|>[[115, 365, 194, 382]]<|/det|> +{redacted} + +<|ref|>sub_title<|/ref|><|det|>[[115, 421, 321, 438]]<|/det|> +## We have modified line 309: + +<|ref|>text<|/ref|><|det|>[[115, 449, 880, 504]]<|/det|> +While respirable aerosol (<2.5 \(\mu m\) ), thoracic aerosol (<10 \(\mu m\) ) and inhalable aerosol in general 29 all may be relevant to infection with SARS- CoV- 2 30, it has been suggested that direct deposition into the lower respiratory tract may decrease the necessary infectious dose in humans 32. + +<|ref|>text<|/ref|><|det|>[[115, 522, 880, 576]]<|/det|> +7) ref 4 has been much criticized in part for its methodology and for the point they want to make the authors could replace it with one of many other, for example Greenhaig et al Lancet 2021; 397: 10285, p 1603-1605) + +<|ref|>text<|/ref|><|det|>[[115, 587, 630, 605]]<|/det|> +Upon the suggestion of the reviewer we have replaced the reference + +<|ref|>text<|/ref|><|det|>[[115, 624, 812, 642]]<|/det|> +8) line 81: "... allowed for 30 cage changes per hour": presumably "cage air changes per hour"? + +<|ref|>text<|/ref|><|det|>[[115, 653, 275, 669]]<|/det|> +We have changed to: + +<|ref|>text<|/ref|><|det|>[[115, 681, 473, 698]]<|/det|> +"This allowed for 30 cage air changes per hour." + +<|ref|>text<|/ref|><|det|>[[115, 735, 393, 752]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 772, 872, 826]]<|/det|> +This manuscript describes a novel cage setup to study airborne transmission of SARS- CoV- 2 using the Syrian hamster model. The setup allows large droplets and aerosols to be tested and both B.1.1.7 and a lineage A variant have been studied. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 866, 179]]<|/det|> +I am commenting solely on the section of the paper that deals with the interaction of the RBD of these viruses with human and hamster ACE2. + +<|ref|>text<|/ref|><|det|>[[114, 198, 878, 344]]<|/det|> +It has previously been shown by several publications that the N501Y mutation in the RBD of B.1.1.7 leads to higher affinity for human ACE2. In this work, the authors state that they looked at the binding efficiency of the lineage A and B.1.1.7. RBDs to the hamster RBD in silico. This must be clarified. It seems that the authors have simply generated a figure showing the locations of the N501Y mutation and the relevant sites (H34Q and M82N) at which human and hamster ACE2 differ (with residues substituted in Coot - Figure 3). The word "efficiency" is unclear and suggests a deeper analysis. As far as I can tell, the authors have not performed any calculations to evaluate the relevant interaction energies (as might be expected of an in silico analysis). + +<|ref|>text<|/ref|><|det|>[[115, 363, 875, 416]]<|/det|> +At line 151, a VSV entry assay is introduced, and this shows that B.1.1.7 entry is increased for both human and hamster ACE2. From there, the authors conclude that B1.1.7 binds tighter to hamster ACE2: line 159: "We next investigated if the enhanced binding affinity of B1.1.7 to hamster ACE2 ..." + +<|ref|>text<|/ref|><|det|>[[115, 435, 878, 508]]<|/det|> +Given that human and hamster ACE2 do not differ in the region where RBD residue N501Y interacts with ACE2, it's not unreasonable to suggest that B.1.1.7 might also show higher affinity for hamster ACE2. However, neither the in silico work, nor the VSV assay (a binding studied would be required), establish that B.1.1.7 shows enhanced affinity for hamster ACE2 and the text should be qualified appropriately. + +<|ref|>text<|/ref|><|det|>[[115, 545, 879, 637]]<|/det|> +We thank the author for the comments and insight and fully agree that the text should be reworded to accurately reflect the analysis that was performed. We did not evaluate the relevant interaction energies or calculate in silico binding energies nor discern differences in binding. We have focused our in vitro work directly on entry studies where we show that the spike of B.1.1.7 has increased entry potential over the spike of WA1. We have therefor modified the results section to read as follows: + +<|ref|>sub_title<|/ref|><|det|>[[115, 667, 184, 682]]<|/det|> +## Line 137: + +<|ref|>text<|/ref|><|det|>[[115, 694, 714, 711]]<|/det|> +"Increased cellular entry and respiratory shedding of B.1.1.7 variant in hamsters + +<|ref|>text<|/ref|><|det|>[[115, 722, 875, 850]]<|/det|> +To investigate whether the increased transmission potential of B.1.1.7 on the population level is determined by changes in transmission potential at the individual level, we compared the airborne transmission kinetics of the B.1.1.7 with the prototype lineage A virus. First, we assessed the suitability of the Syrian hamster as a model to compare SARS- CoV- 2 variant transmission 19. Previous studies have demonstrated the B.1.1.7 spike binds with greater affinity to the human ACE2 than the lineage A spike, potentially explaining the increased transmission. Differences in the amino acid sequence were visualized by mapping onto a structure of the SARS- CoV- 2 spike protein in complex + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 141, 883, 473]]<|/det|> +with human ACE2 (PDB ID 6M0J). At position 501 of the B.1.1.7 spike RBD, the asparagine residue is substituted by tyrosine. This substitution has been proposed to increase binding affinity to (human) ACE2 via increased interactions with residues on ACE2 by stacking of aromatic sidechains and hydrogen bond interactions (19). A sequence alignment between human and hamster ACE2 reveals that two residues differ within the interface with SARS- CoV- 2 RBD. At positions 34 and 82, histidine and methionine are replaced by glutamine and asparagine, respectively, in the hamster ACE2 (Figure 3 A, B). It is possible that subtle changes resulting from these substitutions in hamster ACE2, not captured in this visualization, could affect the binding interactions with the B.1.1.7 variant. Interestingly, the substitution to asparagine at position 82 introduces an N- linked glycosylation sequon (NYS). This residue is located at the periphery of the interface and makes minor contributions in the human complex. The occupancy and biological relevance of this putative site requires further study. To evaluate whether these sequence differences in hamster ACE2 may affect viral entry, we also directly compared viral entry using a VSV pseudotype entry assay. No significant difference in entry between human and hamster ACE2 with either lineage A or B.1.1.7 was observed. For both human and hamster ACE2, B.1.1.7 demonstrated significantly increased entry compared to the lineage A variant (human ACE2 median lineage A/B.1.1.7 = 156.8/256 (relative entry to no spike), p <0.0001 and hamster ACE2 median lineage A/B.1.1.7 = 144.6/197.5 (relative entry to no spike), p = 0.003, N = 14, Mann- Whitney test) (Figure 3 C). + +<|ref|>text<|/ref|><|det|>[[115, 483, 875, 519]]<|/det|> +We next investigated if infection of hamsters with the B.1.1.7 variant translated to differences in viral replication and shedding dynamics in- vivo." + +<|ref|>sub_title<|/ref|><|det|>[[120, 605, 368, 620]]<|/det|> +## Decision Letter, second revision: + +<|ref|>text<|/ref|><|det|>[[119, 639, 253, 654]]<|/det|> +Dear Dr. Munster, + +<|ref|>text<|/ref|><|det|>[[115, 668, 880, 759]]<|/det|> +Thank you for submitting your revised manuscript "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" (NMICROBIOL- 21071818B). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Microbiology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[115, 771, 857, 804]]<|/det|> +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)- - we can not proceed with PDFs at this stage. + +<|ref|>text<|/ref|><|det|>[[115, 816, 857, 863]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 157, 860, 188]]<|/det|> +Thank you again for your interest in Nature Microbiology Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[116, 203, 199, 218]]<|/det|> +{redacted} + +<|ref|>text<|/ref|><|det|>[[116, 262, 404, 277]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 292, 639, 307]]<|/det|> +The authors have adequately addressed my comments in the revision. + +<|ref|>text<|/ref|><|det|>[[116, 336, 404, 351]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 366, 853, 381]]<|/det|> +My concerns have been addressed satisfactorily. This is an important study that advances the field. + +<|ref|>text<|/ref|><|det|>[[116, 410, 404, 424]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 440, 881, 530]]<|/det|> +Lines 42- 50: the authors are still too restrictive in their definition of respiratory aerosols (and so is WHO in the citation offered...)at a time when a consensus is emerging that respiratory aerosols include particles up to \(100\mu m\) ( aerodynamic diameter. The authors should note also that droplet nuclei arise after rapid dessication of aerosol droplets from the respiratory tract into dry air and this phenomenon affects also particles greater than \(5\mu m\) , see eg Nicas et al J Occ Environ Hyg 2005; 2: 143- 154; and Xie et al Indoor Air 2007; 17: 211- 225. + +<|ref|>text<|/ref|><|det|>[[115, 545, 870, 604]]<|/det|> +However this is essentially an editing problem for this manuscript because the authors' data are very robust to show transmission by particles \(< 5 - 10\mu m\) ( and mostly if not exclusively \(< 5\mu m\) ). And no one could rationally argue against transmission by aerosols under a broader definition if there is solid demonstration of transmission under a more restrictive definition of \(< 5\mu m\) . + +<|ref|>text<|/ref|><|det|>[[115, 604, 872, 695]]<|/det|> +Nonetheless I would suggest to the authors to replace lines 44- 47 by something like this: "Respiratory aerosols have been described as ranging from \(0.1\) to \(100\mu m\) ( aerodynamic diameter), with the fraction of particles \(< 5\mu m\) being referred to as "fine aerosols" ( Coleman et al Clin Infect. + +<|ref|>text<|/ref|><|det|>[[115, 725, 133, 738]]<|/det|> +2) + +<|ref|>text<|/ref|><|det|>[[116, 740, 370, 754]]<|/det|> +Aerodynamic vs physical diameter + +<|ref|>text<|/ref|><|det|>[[115, 755, 863, 858]]<|/det|> +This is still unclear in the text. If I understand correctly the experimental set up of the authors, they nebulized a solution of glycerin \(20\%\) into particles of up to \(20\mu m\) ; this is a measured physical diameter; their measurements of the diameter of particles that go through are a measurement of physical diameter (and not of aerodynamic diameter), please correct on lines 83 - 84 Owing to the density of glycerol \(20\%\) (approx. 1.05) the aerodynamic diameter will be greater (not smaller) by a factor of \(\sqrt{1.05} \approx 1.02\) (see Hinds pp 53- 55). Lines 85- 92 could be replaced by something much more succinct, I would suggest something along the lines of the following: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 157, 864, 188]]<|/det|> +"Owing to the greater density of glycerol \(20\%\) relative to water, the corresponding aerodynamic diameter can be obtained by applying a correction factor of 1.02, a minimal correction (ref 17, 18)" + +<|ref|>text<|/ref|><|det|>[[115, 202, 880, 248]]<|/det|> +This is much shorter but still makes the point that the conceptual difference between physical diameter and aerodynamic diameter has not escaped your attention and that the demonstration of the experimental set up as excluding non- aerosol particles is rigorous. + +<|ref|>sub_title<|/ref|><|det|>[[115, 263, 272, 277]]<|/det|> +## Recombinant viruses + +<|ref|>text<|/ref|><|det|>[[115, 278, 881, 368]]<|/det|> +I think that we are essentially in agreement. For samples where complete genomic sequences was feasible, the fact that only overlapping small fragments were sequenced is not a problem provided that only one genomic sequence ( alpha or original lineage) is obtained at all positions, which is the case here according to the data. Problems would arise if there was a mixture of signals from alpha and the original lineage at different positions, since then sequences of overlapping small fragments could not decide between a recombinant and a mixed infection. + +<|ref|>text<|/ref|><|det|>[[115, 368, 868, 442]]<|/det|> +For samples where only a SNP assay could be done because of a viral load too low for sequencing, in theory you could be facing a recombinant since you are scoring only one position in the genomic sequence. The discussion of this issue offered by the authors is satisfactory. For future work the authors may want to consider 2 or more SNP assays scattered throughout the genome, which would be doable even with a low viral load sample. + +<|ref|>text<|/ref|><|det|>[[116, 471, 404, 486]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 500, 877, 546]]<|/det|> +I have read the revised manuscript and the rebuttal provided by the authors. They have fully addressed the concerns that I raised in my initial review and I feel that the manuscript is now suitable for publication. + +<|ref|>sub_title<|/ref|><|det|>[[121, 620, 338, 635]]<|/det|> +## Decision Letter, final checks: + +<|ref|>text<|/ref|><|det|>[[115, 674, 250, 688]]<|/det|> +Dear Dr. Munster, + +<|ref|>text<|/ref|><|det|>[[115, 703, 866, 809]]<|/det|> +Thank you for your patience as we've prepared the guidelines for final submission of your Nature Microbiology manuscript, "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" (NMICROBIOL- 21071818B). Please carefully follow the step- by- step instructions provided in the attached file, and add a response in each row of the table to indicate the changes that you have made. Please also check and comment on any additional marked- up edits we have proposed within the text. Ensuring that each point is addressed will help to ensure that your revised manuscript can be swiftly handed over to our production team. + +<|ref|>text<|/ref|><|det|>[[115, 822, 844, 852]]<|/det|> +We would like to start working on your revised paper, with all of the requested files and forms, as soon as possible (preferably within a week). Due to the Christmas holidays our deadlines have + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 881, 189]]<|/det|> +unfortunately been brought forward, thus completing these revisions as soon as possible would ensure that your manuscript could be published within our January 2022 issue. Please get in contact with us if you anticipate delays. Please get in contact with us if you anticipate delays. + +<|ref|>text<|/ref|><|det|>[[115, 202, 840, 232]]<|/det|> +When you upload your final materials, please include a point- by- point response to any remaining reviewer comments. + +<|ref|>text<|/ref|><|det|>[[115, 247, 868, 308]]<|/det|> +If you have not done so already, please alert us to any related manuscripts from your group that are under consideration or in press at other journals, or are being written up for submission to other journals (see: https://www.nature.com/nature- research/editorial- policies/plagiarism#policy- on- duplicate- publication for details). + +<|ref|>text<|/ref|><|det|>[[115, 321, 872, 397]]<|/det|> +In recognition of the time and expertise our reviewers provide to Nature Microbiology's editorial process, we would like to formally acknowledge their contribution to the external peer review of your manuscript entitled "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2". For those reviewers who give their assent, we will be publishing their names alongside the published article. + +<|ref|>text<|/ref|><|det|>[[115, 410, 857, 516]]<|/det|> +Nature Microbiology offers a Transparent Peer Review option for new original research manuscripts submitted after December 1st, 2019. As part of this initiative, we encourage our authors to support increased transparency into the peer review process by agreeing to have the reviewer comments, author rebuttal letters, and editorial decision letters published as a Supplementary item. When you submit your final files please clearly state in your cover letter whether or not you would like to participate in this initiative. Please note that failure to state your preference will result in delays in accepting your manuscript for publication. + +<|ref|>text<|/ref|><|det|>[[118, 530, 325, 545]]<|/det|> +\(< b>\) Cover suggestions \(< /b>\) + +<|ref|>text<|/ref|><|det|>[[115, 559, 816, 590]]<|/det|> +As you prepare your final files we encourage you to consider whether you have any images or illustrations that may be appropriate for use on the cover of Nature Microbiology. + +<|ref|>text<|/ref|><|det|>[[115, 604, 880, 650]]<|/det|> +Covers should be both aesthetically appealing and scientifically relevant, and should be supplied at the best quality available. Due to the prominence of these images, we do not generally select images featuring faces, children, text, graphs, schematic drawings, or collages on our covers. + +<|ref|>text<|/ref|><|det|>[[115, 664, 844, 695]]<|/det|> +We accept TIFF, JPEG, PNG or PSD file formats (a layered PSD file would be ideal), and the image should be at least 300ppi resolution (preferably 600- 1200 ppi), in CMYK colour mode. + +<|ref|>text<|/ref|><|det|>[[115, 709, 875, 739]]<|/det|> +If your image is selected, we may also use it on the journal website as a banner image, and may need to make artistic alterations to fit our journal style. + +<|ref|>text<|/ref|><|det|>[[115, 752, 857, 783]]<|/det|> +Please submit your suggestions, clearly labeled, along with your final files. We'll be in touch if more information is needed. + +<|ref|>text<|/ref|><|det|>[[115, 812, 872, 858]]<|/det|> +Nature Microbiology has now transitioned to a unified Rights Collection system which will allow our Author Services team to quickly and easily collect the rights and permissions required to publish your work. Approximately 10 days after your paper is formally accepted, you will receive an email in + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 872, 189]]<|/det|> +providing you with a link to complete the grant of rights. If your paper is eligible for Open Access, our Author Services team will also be in touch regarding any additional information that may be required to arrange payment for your article. + +<|ref|>text<|/ref|><|det|>[[115, 202, 850, 233]]<|/det|> +Please note that you will not receive your proofs until the publishing agreement has been received through our system. + +<|ref|>text<|/ref|><|det|>[[115, 246, 868, 336]]<|/det|> +Please note that Nature Microbiology is a Transformative Journal (TJ). Authors may publish their research with us through the traditional subscription access route or make their paper immediately open access through payment of an article- processing charge (APC). Authors will not be required to make a final decision about access to their article until it has been accepted. Find out more about Transformative Journals + +<|ref|>text<|/ref|><|det|>[[115, 350, 876, 516]]<|/det|> +Authors may need to take specific actions to achieve compliance with funder and institutional open access mandates. For submissions from January 2021, if your research is supported by a funder that requires immediate open access (e.g. according to Plan S principles) then you should select the gold OA route, and we will direct you to the compliant route where possible. For authors selecting the subscription publication route our standard licensing terms will need to be accepted, including our self- archiving policies. Those standard licensing terms will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 544, 866, 604]]<|/det|> +For information regarding our different publishing models please see our Transformative Journals page. If you have any questions about costs, Open Access requirements, or our legal forms, please contact ASJournals@springernature.com. + +<|ref|>text<|/ref|><|det|>[[115, 618, 553, 649]]<|/det|> +Please use the following link for uploading these materials: {redacted} + +<|ref|>text<|/ref|><|det|>[[115, 663, 601, 679]]<|/det|> +If you have any further questions, please feel free to contact me. + +<|ref|>text<|/ref|><|det|>[[116, 709, 199, 724]]<|/det|> +{redacted} + +<|ref|>text<|/ref|><|det|>[[115, 769, 639, 813]]<|/det|> +Reviewer #1: Remarks to the Author: The authors have adequately addressed my comments in the revision. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 856, 189]]<|/det|> +Reviewer #2: Remarks to the Author: My concerns have been addressed satisfactorily. This is an important study that advances the field. + +<|ref|>text<|/ref|><|det|>[[115, 232, 293, 260]]<|/det|> +Reviewer #3: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 261, 880, 351]]<|/det|> +Lines 42- 50: the authors are still too restrictive in their definition of respiratory aerosols (and so is WHO in the citation offered...) at a time when a consensus is emerging that respiratory aerosols include particles up to \(100\mu m\) ( aerodynamic diameter. The authors should note also that droplet nuclei arise after rapid dessication of aerosol droplets from the respiratory tract into dry air and this phenomenon affects also particles greater than \(5\mu m\) , see eg Nicas et al J Occ Environ Hyg 2005; 2: 143- 154; and Xie et al Indoor Air 2007; 17: 211- 225. + +<|ref|>text<|/ref|><|det|>[[115, 366, 872, 428]]<|/det|> +However this is essentially an editing problem for this manuscript because the authors' data are very robust to show transmission by particles \(< 5 - 10\mu m\) ( and mostly if not exclusively \(< 5\mu m\) ). And no one could rationally argue against transmission by aerosols under a broader definition if there is solid demonstration of transmission under a more restrictive definition of \(< 5\mu m\) . + +<|ref|>text<|/ref|><|det|>[[115, 428, 872, 515]]<|/det|> +Nonetheless I would suggest to the authors to replace lines 44- 47 by something like this: "Respiratory aerosols have been described as ranging from 0.1 to \(100\mu m\) ( aerodynamic diameter), with the fraction of particles \(< 5\mu m\) being referred to as "fine aerosols" ( Coleman et al Clin Infect. Dise 2021; doi: 10.1093/cid/ciab691); fine aerosols remain suspended for longer periods and can penetrate all the way down into the alveolar space of the human respiratory tract ( ref: Hinds Aerosol Technology). For example influenza A... " + +<|ref|>text<|/ref|><|det|>[[115, 545, 135, 558]]<|/det|> +2) + +<|ref|>text<|/ref|><|det|>[[116, 560, 370, 574]]<|/det|> +Aerodynamic vs physical diameter + +<|ref|>text<|/ref|><|det|>[[115, 575, 863, 681]]<|/det|> +This is still unclear in the text. If I understand correctly the experimental set up of the authors, they nebulized a solution of glycerin \(20\%\) into particles of up to \(20\mu m\) ; this is a measured physical diameter; their measurements of the diameter of particles that go through are a measurement of physical diameter ( and not of aerodynamic diameter), please correct on lines 83 - 84 Owing to the density of glycerol \(20\%\) ( approx. 1.05) the aerodynamic diameter will be greater (not smaller) by a factor of \(\sqrt{1.05} \approx 1.02\) ( see Hinds pp 53- 55). Lines 85- 92 could be replaced by something much more succinct, I would suggest something along the lines of the following: + +<|ref|>text<|/ref|><|det|>[[115, 694, 863, 725]]<|/det|> +"Owing to the greater density of glycerol \(20\%\) relative to water, the corresponding aerodynamic diameter can be obtained by applying a correction factor of 1.02, a minimal correction ( ref 17, 18)" + +<|ref|>text<|/ref|><|det|>[[115, 739, 880, 784]]<|/det|> +This is much shorter but still makes the point that the conceptual difference between physical diameter and aerodynamic diameter has not escaped your attention and that the demonstration of the experimental set up as excluding non- aerosol particles is rigorous. + +<|ref|>text<|/ref|><|det|>[[115, 799, 271, 812]]<|/det|> +Recombinant viruses + +<|ref|>text<|/ref|><|det|>[[115, 813, 860, 858]]<|/det|> +I think that we are essentially in agreement. For samples where complete genomic sequences was feasible, the fact that only overlapping small fragments were sequenced is not a problem provided that only one genomic sequence ( alpha or original lineage) is obtained at all positions, which is the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 880, 188]]<|/det|> +case here according to the data. Problems would arise if there was a mixture of signals from alpha and the original lineage at different positions, since then sequences of overlapping small fragments could not decide between a recombinant and a mixed infection. + +<|ref|>text<|/ref|><|det|>[[115, 188, 868, 263]]<|/det|> +For samples where only a SNP assay could be done because of a viral load too low for sequencing, in theory you could be facing a recombinant since you are scoring only one position in the genomic sequence. The discussion of this issue offered by the authors is satisfactory. For future work the authors may want to consider 2 or more SNP assays scattered throughout the genome, which would be doable even with a low viral load sample. + +<|ref|>text<|/ref|><|det|>[[115, 308, 880, 383]]<|/det|> +Reviewer #4: Remarks to the Author: I have read the revised manuscript and the rebuttal provided by the authors. They have fully addressed the concerns that I raised in my initial review and I feel that the manuscript is now suitable for publication. + +<|ref|>sub_title<|/ref|><|det|>[[120, 420, 282, 435]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[115, 455, 250, 470]]<|/det|> +Dear Dr. Munster, + +<|ref|>text<|/ref|><|det|>[[115, 484, 874, 530]]<|/det|> +I am pleased to accept your Article "Increased aerosol transmission for B.1.1.7 (alpha variant) over lineage A variant of SARS- CoV- 2" for publication in Nature Microbiology. Thank you for having chosen to submit your work to us and many congratulations. + +<|ref|>text<|/ref|><|det|>[[115, 544, 840, 589]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Microbiology style. We look particularly carefully at the titles of all papers to ensure that they are relatively brief and understandable. + +<|ref|>text<|/ref|><|det|>[[115, 603, 869, 664]]<|/det|> +Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. Once your paper has been scheduled for online publication, the Nature press office will be in touch to confirm the details. + +<|ref|>text<|/ref|><|det|>[[115, 678, 878, 739]]<|/det|> +After the grant of rights is completed, you will receive a link to your electronic proof via email with a request to make any corrections within 48 hours. If, when you receive your proof, you cannot meet this deadline, please inform us at rjsproduction@springernature.com immediately. You will not receive your proofs until the publishing agreement has been received through our system + +<|ref|>text<|/ref|><|det|>[[115, 753, 880, 813]]<|/det|> +Due to the importance of these deadlines, we ask you please us know now whether you will be difficult to contact over the next month. If this is the case, we ask you provide us with the contact information (email, phone and fax) of someone who will be able to check the proofs on your behalf, and who will be available to address any last- minute problems. + +<|ref|>text<|/ref|><|det|>[[115, 827, 880, 858]]<|/det|> +Acceptance of your manuscript is conditional on all authors' agreement with our publication policies (see https://www.nature.com/nmicrobiol/editorial- policies). In particular your manuscript must not be + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 857, 174]]<|/det|> +published elsewhere and there must be no announcement of the work to any media outlet until the publication date (the day on which it is uploaded onto our website). + +<|ref|>text<|/ref|><|det|>[[115, 187, 868, 278]]<|/det|> +Please note that Nature Microbiology is a Transformative Journal (TJ). Authors may publish their research with us through the traditional subscription access route or make their paper immediately open access through payment of an article- processing charge (APC). Authors will not be required to make a final decision about access to their article until it has been accepted. Find out more about Transformative Journals + +<|ref|>text<|/ref|><|det|>[[115, 292, 877, 457]]<|/det|> +Authors may need to take specific actions to achieve compliance with funder and institutional open access mandates. For submissions from January 2021, if your research is supported by a funder that requires immediate open access (e.g. according to Plan S principles) then you should select the gold OA route, and we will direct you to the compliant route where possible. For authors selecting the subscription publication route our standard licensing terms will need to be accepted, including our self- archiving policies. Those standard licensing terms will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 485, 875, 516]]<|/det|> +If you have any questions about our publishing options, costs, Open Access requirements, or our legal forms, please contact ASJournals@springernature.com + +<|ref|>text<|/ref|><|det|>[[115, 530, 598, 546]]<|/det|> +An online order form for reprints of your paper is available at text<|/ref|><|det|>[[115, 546, 861, 606]]<|/det|> +href="https://www.nature.com/reprints/author- reprints.html">https://www.nature.com/reprints/author- reprints.html. All co- authors, authors' institutions and authors' funding agencies can order reprints using the form appropriate to their geographical region. + +<|ref|>text<|/ref|><|det|>[[115, 619, 875, 740]]<|/det|> +We welcome the submission of potential cover material (including a short caption of around 40 words) related to your manuscript; suggestions should be sent to Nature Microbiology as electronic files (the image should be 300 dpi at \(210 \times 297 \text{mm}\) in either TIFF or JPEG format). Please note that such pictures should be selected more for their aesthetic appeal than for their scientific content, and that colour images work better than black and white or grayscale images. Please do not try to design a cover with the Nature Microbiology logo etc., and please do not submit composites of images related to your work. I am sure you will understand that we cannot make any promise as to whether any of your suggestions might be selected for the cover of the journal. + +<|ref|>text<|/ref|><|det|>[[115, 753, 872, 800]]<|/det|> +You can now use a single sign- on for all your accounts, view the status of all your manuscript submissions and reviews, access usage statistics for your published articles and download a record of your refereeing activity for the Nature journals. + +<|ref|>text<|/ref|><|det|>[[115, 813, 877, 858]]<|/det|> +To assist our authors in disseminating their research to the broader community, our SharedIt initiative provides you with a unique shareable link that will allow anyone (with or without a subscription) to read the published article. Recipients of the link with a subscription will also be able to download and + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 220, 158]]<|/det|> +print the PDF. + +<|ref|>text<|/ref|><|det|>[[113, 187, 844, 203]]<|/det|> +As soon as your article is published, you will receive an automated email with your shareable link. + +<--- Page Split ---> diff --git a/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..1e9d7e5f50036a2e87c633b0a8ff6a8497524fc0 --- /dev/null +++ b/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,152 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure A. Distribution of AAV receptor mRNA expression in CNS models. (A,B) Violin plots showing the expression level of known AAV receptors on mixed CNS cultures at the end of the differentiation protocol (day 24) (A) as well as brain spheroids (day 150) (B). Plots contain pooled data from two biological replicates of mixed cultures or spheroids respectively, each performed in technical duplicate.", + "footnote": [], + "bbox": [ + [ + 130, + 98, + 896, + 558 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure B. GFP expression in mixed cultures and brain spheroids. FACS analysis of the percentage of GFP+ cells in mixed cultures and brain spheroids transduced with the indicated vectors.", + "footnote": [], + "bbox": [ + [ + 149, + 606, + 600, + 818 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure C. Time course of GFP expression. FACS analysis of GFP expression in iPSC-derived neurons transduced with the indicated serotypes at multiple time-points. Each dot corresponds to data from 1-3 independent transductions.", + "footnote": [], + "bbox": [ + [ + 128, + 283, + 653, + 491 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure D. Conditioned media transfer experiment in iPSC-derived neurons. iPSC-derived untransduced (UT) neurons were incubated for 48h with conditioned media (CM) from astrocytes previously transduced with AAV2 for 24h, washed with PBS following media replacement and cultured for another 48h before collecting the supernatant. Panels A and B show IF staining on neurons of yH2AX and cc3 respectively as markers of cell toxicity. Panels C and D show the analysis of GFP and p21 mRNA on untransduced neurons incubated with transduced astrocyte culture supernatants.", + "footnote": [], + "bbox": [ + [ + 130, + 103, + 865, + 336 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure E. Violin plots of common genes between human and murine datasets. Violin plot representation of example common genes significantly upregulated across human mixed cultures, brain spheroids and murine striatum datasets contributing to different pathways such as DNA stress response (yellow), pro-inflammatory signalling (purple), type I IFN signalling (green) and mitochondrial stress (orange).", + "footnote": [], + "bbox": [ + [ + 118, + 148, + 789, + 499 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Figure F. Analysis of selected p53-dependent genes (p21, TRIM22, APOBEC3H) and innate immunity markers (IL1b, CXCL8, ISG15) by qPCR in iNSCs transduced with full AAV9 for 6h or 24h.", + "footnote": [], + "bbox": [ + [ + 130, + 100, + 697, + 399 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Figure G. Measurement of GFP-expression levels in iPSC-derived neurons transduced with AAV9.", + "footnote": [], + "bbox": [ + [ + 125, + 465, + 264, + 617 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Figure H. Analysis of AAV-derived signalling in iPSC-derived neurons transduced with full and empty AAV9 at 24h and 48h post-transduction.", + "footnote": [], + "bbox": [ + [ + 128, + 660, + 870, + 789 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Figure I. cc3 staining in iPSC derived neurons. Quantification of cc3 staining by IF imaging in iPSC-derived neurons transduced with AAV9-CAG-GFP during 48 and 72h. Dots correspond to data from 3 pooled experiments.", + "footnote": [], + "bbox": [ + [ + 124, + 99, + 399, + 238 + ] + ], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Figure J. Phospho-TBK1 staining in iPSC-derived neurons. Representative IF images of phospho-TBK1 staining (red) in iPSC-derived neurons transduced with AAV9 at MOI 100,000 for 72 h. Images are from one experiment.", + "footnote": [], + "bbox": [ + [ + 173, + 348, + 725, + 601 + ] + ], + "page_idx": 27 + } +] \ No newline at end of file diff --git a/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e4b20125e2328c1086c3f7228ab5b10471fcb5cb --- /dev/null +++ b/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,743 @@ + +# nature portfolio + +Peer Review File + +# AAV vectors trigger DNA damage response-dependent pro-inflammatory signalling in human iPSC-derived CNS models and mouse brain + +Corresponding Author: Dr Anna Kajaste- Rudnitski + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In this study Costa- Verdera et al study the host transcriptome globally and at a single cell/nuclei level following AAV infection of neural cells and 3D organoids, as well as the mouse brain. The transcriptome is studied in vitro in human iPSC- derived neurons, astrocytes and oligodendrocytes, mixed neural cultures and 3D organoids, as well as in vivo in mouse striatum. Many interesting observations are made from a large dataset including: + +- Early activation of the p53 pathway and TNF/IL-1 signaling by AAV (genome-dependent)- Early activation of DNA damage responses by AAV (genome-dependent)- Delayed transgene expression-dependent/p53-independent/MAVS-dependent activation of ISGs by AAV- AAV causes p53-dependent apoptosis via cleaved Caspase-3- STING inhibition, p53 inhibition and IL-1Ra treatment block AAV IL-1b/CXCL8 activation but not ISG activation.- STING inhibition blocks AAV-mediated apoptosis + +This is a vast and complicated story and the authors simultaneously try to understand what appear to be many different but potentially interconnected pathways that are activated in different cell types and across different time points after AAV exposure. The authors should be commended for addressing the importance of host response to AAV in the brain in the context of neurotoxicity. However, their story is highly complex and as a result questions are left unanswered as the authors try to address several different observations across many experiments. This is an important topic and the scope and quality of the study is appropriate for Nature Communications, but several issues need to be addressed. + +Major points + +1. The relevance of the in vitro observations in terms of their in vivo significance need to be solidified, particularly in the context of antagonistic blockade of AAV-related toxicities. Since similar pathways are activated in human cells and mouse striatum, it is assumed that signaling blockade can translate to mouse brain but this should be validated. Effects of localized IL-1Ra, STING inhibition, MAVS inhibition and p53 inhibition should be studied in mouse brain. + +2. The title does not address all of the observations made in this study and also implies the observations were restricted to human cells. For example, STING is highlighted in the title but isn't mentioned in the story until the last experiment and is only one of several key players in all of the described pathways and responses. A more general or encompassing title should be considered. + +3. If STING and DNA damage responses are the focus of the paper as suggested by the title more exploration of them is required. For example, validation of the potential for STING antagonism should be performed in mouse striatum at a dose of AAV known to be neurotoxic. + +4. Lines 125-128 – The authors state “Of note, empty AAV9 capsid did not induce any significant transcriptional changes compared to untransduced controls, in contrast to the full AAV9 vector (Fig. 1E-H), suggesting that the vector genome is required for the detected signaling.”. Figures 1E-H support this statement. However, when you look globally across the entire + +<--- Page Split ---> + +dataset the AAV9 profile is more like the untransduced profile than the empty (AAV9) profile (Figure 1C, UT vs empty vs AAV9), contradicting this statement. This should be discussed further. + +5. Fig 1C/D – Why was empty AAV9 used as a control when 'full' AAV9 stimulated the lowest transcriptional response? Empty AAV2 which was more transcriptionally reactive should be compared? + +6. The reviewer appreciates that every experiment can't be performed with every dose, serotype, promoter, transgene combination, etc. However, there is a lot of back and forth between experimental (mainly AAV) details across different culture types and mice as the paper progresses. At some point in the paper, it is almost assumed that all serotypes are equivalent as the authors switch between AAV2, AAV6, Spark100 and AAV9, when the early experiments show there can be clear differences. The generalization that all responses are serotype independent are in places too presumptive and should be tempered. + +7. What is known about relative AAV receptor expression levels (HSPG, sialic acid, galactose, AAVR) in hiPSC-derived cells and organoids (neurons vs astrocytes vs oligodendrocytes), since signaling through different receptors may impact downstream transcriptional observations across the different serotypes studied? + +8. In Fig 6, snRNAseq is performed in mice given AAV9.CAG-EGFP via IPa then for some reason the DNA damage response observations in the striatum are validated in mice after ICV and not IPa delivery of AAV9.PGK-EF1a.Cre-EGFP. This validation should be performed after IPa delivery of the same vector. It is also not clear what AAV9.PGK-EF1a.Cre-GFP is. Is GFP expression conditional (Cre expressing mice were not used) or does it express 2 transgenes (Cre and GFP), which complicates observations made in Fig S8 in relation to Fig 6. + +## Minor points + +1. Lines 164-167 – The authors state “Overall, upregulation of signaling pathways was more significant in the 3D model compared to the 2D mixed cultures (Fig. 3E, Fig. 4E), suggesting active cross talk and paracrine effects of AAV signaling across cells of the human CNS.”, however, this could just be an MOI effect whereby cells on the outside of a 3D spheroid take up more AAV in culture, which in turn causes greater peak activation levels. Please discuss. + +2. Are different responses seen between ssAAV vs scAAV vectors? + +3. Table S1 reports the AAV ‘dose’ in v.p./cell but elsewhere vg/cell is used as the unit for infection. Are the reported MOI based on particles or genomes? + +4. No methods are provided for genome titer and/or AAV particle determination, please include. + +5. Details of the ICV injection procedure should be provided. + +6. Fig 1D – Why were Spark100, AAV1 and AAV6 omitted? + +7. Fig S3B – x-axis legend should read full and not AAV9 + +8. Fig 5B-D – The SPARK100-hAAT-GFP vector should be added to the right-hand ‘transgene minus’ panel for easier comparison since GFP isn’t expressed. + +9. mRNA is not expressed from the hAAT promoter in hiPSC-derived neurons. How would responses compare between the hAAT-GFP vector and a vector that produces an mRNA but is not translated (e.g. ATG deleted GFP)? + +10. Fig 6 – This study was performed at a single AAV dose. Why was this dose chosen? How representative is this dose per g of brain to those used in other animal studies where CNS toxicity has been observed? + +11. Fig S9B – MAVS blockade appears to accentuate AAV induction of IL-1 and CXCL8 substantially. This is not mentioned and should be discussed? + +12. FigS10 – legend says figure 10 + +13. Fig S9 legend – typo ‘signallig’ + +## Reviewer #2 + +(Remarks to the Author) + +The manuscript by Costa-Verdera and colleagues describes the transcriptional responses that arise in AAV- transduced cells of the CNS that were derived from hiPSC. The authors study 2d cultures of neurons, astrocytes and oligodendrocytes as well as brain spheroids tested after transduction by several different AAV capsids (AAV1, AAV2, AAV5, AAV6 AAV9 and Spk100). The authors determine the ability of these different capsids to transduce each cell type as well as the consequence of transduction on inflammatory signaling and DNA damage responses. They demonstrate that different capsid serotypes have varying abilities to transduce neurons and astrocytes (and in some cases oligodendrocytes). Furthermore, they + +<--- Page Split ---> + +demonstrate that AAV transduction correlates with activation of DNA damage repair pathways (p53 mediated) and activation of some inflammatory pathways. These two findings regarding the induction of p53 and inflammatory pathways are not completely novel, but the comprehensive approach being taken by the authors and the testing of many different CNS cell types against a large number of capsids is a strength of the paper. The authors also carry out in vivo experiments in mice by ICV injection and demonstrate the level of transduction of different cell types and some single cell gene expression data. + +The strengths of the manuscript include 1) the comprehensive testing of a variety of CNS cell types which demonstrates some consistent patterns of p53 induction and inflammatory signaling across different culture conditions (2D vs 3D), 3) the testing of many different AAV vector serotypes for their ability to transduce these various cell types and 3) numerous assessments of transcriptional changes that demonstrate inflammatory and DNA damage responses. The weaknesses of the manuscript are 1) some experiments are not well controlled, such as Fig. 5 where the authors use several promoters and transgenes in parallel but do not control for the CpG content of the vectors. These constructs will all have different risk factors for activating TLR9 signaling, which is activated within hours of transduction and has many cascading downstream effects; 2) the single cell data is not explored beyond identifying cell types and 3) the timepoints tested do not allow the authors to capture TLR signaling that occurs early after transduction (less than 12 hours post AAV transduction). Because they collected the samples so late after transduction, it becomes difficult to discriminate transgene induced TLR signaling vs capsid responses (such as in Fig. 5). The authors did a tremendous amount of work for this manuscript and it would be very difficult to repeat everything to obtain an early time point, but the authors do need to acknowledge that TLR signaling will influence downstream signaling. The specifics regarding Figure 5 are detailed below. Overall this is a strong manuscript that has a lot of important information that will be valuable to readers. + +Fig. 1A. Can the authors show examples of the FACS plots where they determined GFP+ cells and show the gating that was used to identify the positive cells. + +It would be good to show the vector copy number (currently in supplemental) in the main figures alongside the GFP+ mRNA. Figs 1E and F could be moved to the supplemental if space is needed. + +Supplementary Table 1: There seems to be information missing from the table. Also, could the authors state the titer in viral genomes, since it is the transgene that is inducing most of the response; thus, one would like to know the level of transgene instead of viral particles. + +Figure 3B: The authors should show how the frequency of their cell populations change with dosing between days 2 and 4. Can they show individual UMAPS and normalized cell numbers by time point? Also could the authors provide some of the top differentially expressed genes in addition to the pathways? + +Figure 3D: It would be best if the colors in Fig. 3D could match the colors for Figs 3B and 3C. + +Figure 5: In this figure the authors use different promoter and transgene constructs to transduce 3D spheroids, followed by isolation of transgene + and transgene - cells and subsequently compare the transcriptional patterns between the different cell types and between transgene + and transgene - cells. They also use two different capsids and use other promoter + transgene constructs. The vast diversity of constructs and cell types makes this figure very complicated to interpret. + +One main issue is that the authors do not consider how differences in CpG motifs (in each construct used) has the potential to impact TLR9 signaling. Thus, the experiment is very difficult to interpret. So while the authors used a control (Spark100 HAAT construct) that does not express protein, they did not take into consideration the fact that the presence of the viral genome will ALSO stimulate inflammatory signaling independent of protein expression. The experiment is not well controlled and therefore, conclusions are difficult to make. The interpretation of this experiment needs to be toned down considerably. + +1) Line 174: They are not able to state that different AAV serotypes induce different inflammatory signatures. The authors have proven that the AAV capsid determines whether the AAV particle can enter a cell but they have not proven that different signatures arise due to different capsids. + +2) Line 201: The authors cannot discriminate transgene specific responses due to lack of consideration for the differences in the different risk factor potentials to stimulate TLR9 signaling (formula published by J. Fraser Wright https://doi.org/10.1016/j.ymthe.2020.07.006), which is inherent to each transgene. So the comment that GAA stimulates more inflammatory signaling is likely due to a difference in the RF3. Furthermore, the idea of paracrine signaling (line 204) has not been proven. + +3) Line 207: The authors conclude that the vector genomes induce the p53 response, but this point is not proven at all. There are p53 responses in both transgene + and transgene - populations. It is recommended that the authors deconstruct this figure and parse out the points that they can make conclusively. + +4) Fig. S6: The authors do not control for the TLR risk factor here, which could be significantly different between the two promoters, so it is difficult to make any firm conclusions from this study. + +Line 246: The authors state that type I IFN signaling in AAV transduced human and mouse CNS cells triggers IFN1 signaling. This statement does not consider TLR9 signaling, which can trigger IFN1 signaling via CpG motifs in the transgene. + +Figure 6: The authors carry out ICV injections, isolate CNS cells after 28 days and carry out single cell sequencing. The authors do not see p53 dependent responses in vivo, which is hard to reconcile with their other studies. Is the mouse different than human, is it an in vivo vs in vitro issue or is it a timing problem? This figure could be the basis for a full paper + +<--- Page Split ---> + +that carefully assesses time points in the mouse and compares to the in vitro studies. If the authors want to include this study, I recommend that they extend their single cell data analysis and show in the figure how cell frequencies and phenotypes change with AAV dosing in vivo. In addition, they should demonstrate how those changes are similar and/or different from hiPSCs. I would recommend they show violin plots of individual genes and demonstrate how they are consistent or differ with observations made in the hiPSC- derived CNS cells. Since no violin plots are shown in the prior parts of the manuscript, they could show them here, so it is easy for the reader to compare across cell types vs the in vivo studies. + +Also, for this in vivo study, the authors should make comparisons of how AAV transduction of individual CNS cells compares to hiPSC derived CNS cells. Supplemental Fig. 8: In the figure legend the authors should state what is being stained and how the heat maps were obtained. + +Supplemental Figure 10: Why didn't the authors treat the cells with the inhibitors prior to transducing them? Since these signaling pathways are triggered upon AAV entry, the TLR pathway cannot be ruled out as upstream of some of the gene induction. + +## Reviewer #3 + +(Remarks to the Author) + +This is an interesting, informative, and timely study, addressing a major barrier in translating rAAV- based gene therapy to clinical application. Overall, the manuscript is well written, data thoughtfully analyzed and presented. However, the manuscript can be further strengthened if the authors can address the points below. + +1. In general, the time between AAV transduction and data collection seems to be longer than what is needed by the cells to initiate a DNA damage repair and innate immune responses. Could the authors explain clearly for the rationale to choose these timepoints? + +2. Also, it would be informative to study /compare the outcomes of transduction by single stranded and self-complementary rAAVs. + +3. For the data presented in Figure 1, in terms of transcriptomic changes with and without AAV vectors, those transduced by AAV9 appears to have milder changes compared to those transduced by AAV2 and AAV6, presumably due to less efficient transduction efficiency. Is there a way to first sort GFP+ cells, and then analyze transcriptomic changes in GFP+ cells alone? Alternatively, will it be a good idea to "normalize" transcriptomic changes based on GFP+ percentage? + +4. For the data described by Figure 2: Why did the authors chose 48 h post transduction as the time to assay caspase 3 cleavage? Would assaying an earlier time point (12h or 24h) give a more pronounced result? A general expectation would be that DNA damage response is induced much sooner than 48 h, especially for a flat-surface cell culture. + +5. After carefully reviewing the data presented in Figure 4, the p53 pathway in neurons seems to increase from day 2 to day 5. But by day 5, one would assume that the DNA cargo has already undergone ds synthesis and started episode formation. Why does the response appear to be delayed? Would simple transfection of episomes lead to p53 pathway activation? + +Please see a similar comments above. + +6. For the data presented in Figure 6, The author should explain better why the in vivo study was performed at day 28, which is very late for assaying innate immune responses against foreign DNA motifs. + +7. One major concern is the experiment described in Figure 8. There is evidence suggesting that STING inhibitor H151 only works for STING-HAQ mutation but not WT STING. Did the authors genotype the hiPSCs? Are they STING HAQ or WT STING? + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +## Reviewer #5 + +(Remarks to the Author) + +In this work Costa- Verdera et al have used iPSC- derived human brain cell/spheroid systems and mouse models to examine the hose immune response to AAV transduction in the brain. The authors report that AAV- induces p53- dependent DNA damage responses together with STING- and IL1R- dependent inflammatory responses. In addition, they report an involvement of MAVS in the host response evoked by AAV. Although the question under investigation is very timely, and many of the observations are intriguing, the work appears very descriptive at this stage and mechanistically rather underdeveloped. + +Major comments: + +1. Microglia expresses the highest levels of both cGAS and STING among brain-resident cells. The authors should include this cell type in the analysis. + +<--- Page Split ---> + +2. The data are mainly based on a transcriptional approach. For key activated pathways, e.g. IFN signaling, this should be complemented with protein data. + +3. CL-CASP3 does not equal apoptosis – in fact could drive GSDME-mediated pyroptosis. The modality of cell death should be further investigated, including the dependency on the innate immune signaling pathways studied. + +4. Brain infections with pathogenic viruses are well-described in lead to influx of immune cells from the periphery, most notably monocytes and T cells. The mouse work would gain a lot if the influx of at least these two cell types is evaluated. + +5. The conclusion that the innate immune response to AAV transduction is STING dependent is based only on the use of the STING inhibitor, which is not specific. Therefore, it should be tested whether the observed response is ablated in cGAS or STING-deficient mice. + +6. The mechanistic explanation for the reported phenomenon is under-developed. The authors should provide deeper explanation of the temporal, spatial, and cell-type-specific roles of the cGAS-STING, RLR-MAVS, and inflammasome pathways. + +7. The key question – and it can be claimed the motivation for the present study – is to understand mechanisms underlying "dose-dependent toxicities and severe adverse events" of AAV-based gene therapy. Therefore, the authors need to provide data demonstrating physiological importance of the identified innate immunological activities. + +Minor comments. + +8. This reviewer find that the term "cell-intrinsic innate immune mechanisms" is not correctly used in this work. Since, the data show upregulation of e.g. interferon pathways, which act in a paracrine manner, the activities discovered are not cell-intrinsic (although some of the effector mechanisms may be). I suggest that the authors simple use the term "innate immune mechanisms. + +9. The finding that virus infections in the brain and brain cells triggers apoptosis in a cGAS-STING dependent manner has been reported previously (e.g. PMID: 32990676), and should be cited. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +I want to thank the authors for doing such a good job of addressing my comments. Overall, I think that this is one of the best attempts that I have seen as a reviewer to address all reviewer comments in detail (and there were many comments). This is an excellent manuscript that was made even better with these revisions. I recommend immediate publication. + +Reviewer #2 + +(Remarks to the Author) + +The authors were responsive to the reviewer comments. The manuscript is easier to read and the figures are clearer. It is acceptable for publication. + +Reviewer #3 + +(Remarks to the Author) + +the authors have addressed this reviewer's comments clearly, in some cases, being supported by robust experimental data. I have no further concerns. + +Reviewer #5 + +(Remarks to the Author) + +The authors have greatly improved the work during the revision. However, I remain rather critical to conclusions drawn from the mechanistic work. The claim that the host response involves the cGAS-STING and the RLR-MAVS pathways is not based on data from KO mouse strains, which are readily available. In the absence of such data. I do not find the mechanistic claims well supported by the data. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +## Point-by- point reply to Reviewer Comments + +Reviewer #1 (Remarks to the Author): + +In this study Costa- Verdera et al study the host transcriptome globally and at a single cell/nuclei level following AAV infection of neural cells and 3D organoids, as well as the mouse brain. The transcriptome is studied in vitro in human iPSC- derived neurons, astrocytes and oligodendrocytes, mixed neural cultures and 3D organoids, as well as in vivo in mouse striatum. Many interesting observations are made from a large dataset including: + +- Early activation of the p53 pathway and TNF/IL-1 signaling by AAV (genome-dependent) + +- Early activation of DNA damage responses by AAV (genome-dependent) + +- Delayed transgene expression-dependent/p53-independent/MAVS-dependent activation of ISGs by AAV + +- AAV causes p53-dependent apoptosis via cleaved Caspase-3 + +- STING inhibition, p53 inhibition and IL-1Ra treatment block AAV IL-1b/CXCL8 activation but not ISG activation. + +- STING inhibition blocks AAV-mediated apoptosis + +This is a vast and complicated story and the authors simultaneously try to understand what appear to be many different but potentially interconnected pathways that are activated in different cell types and across different time points after AAV exposure. The authors should be commended for addressing the importance of host response to AAV in the brain in the context of neurotoxicity. However, their story is highly complex and as a result questions are left unanswered as the authors try to address several different observations across many experiments. This is an important topic and the scope and quality of the study is appropriate for Nature Communications, but several issues need to be addressed. + +We thank the Reviewer for appreciating our effort and for retaining this work of relevance for the field. + +Major points + +1. The relevance of the in vitro observations in terms of their in vivo significance need to be solidified, particularly in the context of antagonistic blockade of AAV-related toxicities. Since similar pathways are activated in human cells and mouse striatum, it is assumed that signaling blockade can translate to mouse brain but this should be validated. Effects of localized IL-1Ra, STING inhibition, MAVS inhibition and p53 inhibition should be studied in mouse brain. + +We thank the Reviewer for the suggestion. Although we were not able to perform localized inhibition of the mentioned pathways as suggested by the reviewer due to technical complexity and timing, we sought to further assess the impact of p53 signalling and downstream pathways on glial cell activation in vivo. For this purpose, we took advantage of a transgene-silent vector harbouring the coagulation factor IX (FIX) transgene under the control of the liver-specific hAAT promoter that activated mainly DNA damage- related responses in the human CNS spheroids (Fig. 5). Mice were injected with the vector in the striatum + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +with concomitant intraperitoneal administration of pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) or STING (H151), followed by assessment of gliosis on striatal sections. An increase in Iba1+ and GFAP+ cells was observed in mice having received the vector. Moreover, all three treatments decreased the presence of GFAP+ cells in the striata compared to mice injected with AAV only, while they had no effect on the Iba1+ population. NeuN staining indicated absence of neurotoxicity in terms of percentage of NeuN+ cells. These results suggest that, in mice, AAV- mediated CNS transduction can activate gliosis even in a context of low or absent transgene expression when using the hAAT promoter, and that these responses are not unique to the GFP transgene. These responses could be partially modulated through pharmacological inhibition of p53 or of the cGAS- STING pathway, highlighting that vector genome sensing contributes to the activation of local innate immune cells, particularly astrocytes. Results from this experiment are shown in Supplementary Figure 20 and described on lines 339- 356, pages 13- 14 of the revised manuscript. In addition, we wish to underscore that the human in vitro model used in the study, while presenting limitations, is unique in its ability to mimic the reality in the clinic. To this end, the mouse model is not perfect as it presents significant differences when it comes to innate immunity (Tathinen et al, 2022), and in AAV gene therapy they in fact fail to reproduce human findings. We also acknowledge that further studies should be performed to confirm the effect of these drugs on higher number of animals and performing side- by- side comparisons with transgene- expressing vectors in the future, but wish to mention here that due to recent reorganization within the collaborating biotech company that has performed these experiments, we will not be able to provide additional experiments for this part at this stage. + +2. The title does not address all of the observations made in this study and also implies the observations were restricted to human cells. For example, STING is highlighted in the title but isn't mentioned in the story until the last experiment and is only one of several key players in all of the described pathways and responses. A more general or encompassing title should be considered. + +We thank the Reviewer for the suggestion and agree that STING is not the main focus of our studies but rather the induction of the p53-associated DNA damage response pathway and its role in proinflammatory and stress signalling in CNS cells. We have now modified the title to better summarize the study findings as follows: + +AAV vectors trigger DNA damage response- dependent pro- inflammatory signalling in human iPSC- derived CNS models and mouse brain. + +3. If STING and DNA damage responses are the focus of the paper as suggested by the title more exploration of them is required. For example, validation of the potential for STING antagonism should be performed in mouse striatum at a dose of AAV known to be neurotoxic. + +We thank the Reviewer for this suggestion. In line with comments 1 and 2, we have modified the manuscript title to shift the focus away from the STING pathway but have also performed a first proof- concept in vivo study in Supplementary Figure 20, described above, to explore the effects of inhibiting the cGAS/STING and p53 pathways on local gliosis. Briefly, we observed that pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) or STING (H151) decreased the presence of GFAP+ cells in striatum compared to mice injected with AAV only, while they had no effect on the Iba1+ population, suggesting that pharmacological targeting of p53 or the cGAS- STING pathway can curb at least to some extent the vector- induced gliosis without overt toxicity on the CNS cell populations. The results from this experiment are described and discussed on lines 339- 356, pages 13- 14 and lines 480- 483, page 18, of the revised manuscript. + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +4. Lines 125-128 – The authors state “Of note, empty AAV9 capsid did not induce any significant transcriptional changes compared to untransduced controls, in contrast to the full AAV9 vector (Fig. 1E- H), suggesting that the vector genome is required for the detected signaling.” Figures 1E-H support this statement. However, when you look globally across the entire dataset the AAV9 profile is more like the untransduced profile than the empty (AAV9) profile (Figure 1C, UT vs empty vs AAV9), contradicting this statement. This should be discussed further. + +We appreciate the reviewer's observation regarding the global expression patterns seen in the heatmap shown in Fig. 1C. Indeed, on a global scale, the AAV9 profile appears more similar to the untransduced profile, reflecting the overall expression levels of differentially expressed genes across all conditions. However, it is important to note that this global view does not capture the specific biological processes driving the observed transcriptional differences in the full AAV9 condition. Our statement refers to genes significantly contributing to specific signalling pathways, as highlighted in Figures 1E-H. These analyses show that the few genes contributing to the differences in the full AAV9 vector are significantly enriched in signalling-related processes. In contrast, the empty AAV9 capsid does not induce significant transcriptional changes (Fig. 1E-H), indicating that the vector genome is required to trigger these pathways. Thus, while the heatmap provides an overview of overall gene expression, it does not reflect the specific pathway-level changes that are critical for interpreting the functional impact of the full AAV9 vector. To further clarify this point, we have now included Volcano plots showing the differentially expressed genes induced by the different vectors in Supplementary Figures 3 and 4 to better visualize differences in the level of signalling induced by each vector, including no significant induction of genes by the empty AAV9 vector, and describe this on lines 132- 137, page 6 of the revised manuscript. Moreover, we have included data in supplementary figures S5 and S16C and E showing the lack of induction of signalling by empty capsid of other serotypes (AAV1 and 6). + +5. Fig 1C/D – Why was empty AAV9 used as a control when 'full' AAV9 stimulated the lowest transcriptional response? Empty AAV2 which was more transcriptionally reactive should be compared? + +We thank the Reviewer for this observation. We focused on the comparison between empty and full AAV9 vectors given the clinical relevance and the CNS toxicities reported with this serotype. However, to confirm that the observed signalling is not capsid dependent in a more stringent condition, we have included a new experiment comparing the expression of selected genes from Figure 1H induced by empty vs. full AAV2. Results have been included in Supplementary Figure 5, confirming the lack of signalling in the absence of the genome also for this serotype. The following sentence has been added to the main text line 135- 137, page 6: “The same was confirmed for empty AAV2 capsid in hiPSC- derived astrocytes in terms of upregulation of selected genes (p21, CXCL8, IL- 18), chosen as representative from Figure 1H (Fig. S5).” + +6. The reviewer appreciates that every experiment can't be performed with every dose, serotype, promoter, transgene combination, etc. However, there is a lot of back and forth between experimental (mainly AAV) details across different culture types and mice as the paper progresses. At some point in the paper, it is almost assumed that all serotypes are equivalent as the authors switch between AAV2, AAV6, Spark100 and AAV9, when the early experiments show there can be clear differences. The generalization that all responses are serotype independent are in places too presumptive and should be tempered. + +Although we agree with the Reviewer that some serotype- specific responses cannot be excluded in this context, we did identify common genes for selected pathways in our RNAseq datasets upregulated across + +<--- Page Split ---> + +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +serotypes that can be used to assess common signalling by all used serotypes. Overall, we observe that the number of significantly upregulated genes contributing to a given pathway is dependent on the level of transduction by each serotype due to the delivery of higher vector genomes, rather than on capsid composition, given the absence of signalling by empty capsids (Fig S3, S4, S5, S16C, E). We have better clarified this in the revised manuscript, lines 394- 397, page 15 of the revised manuscript. + +7. What is known about relative AAV receptor expression levels (HSPG, sialic acid, galactose, AAVR) in hiPSC-derived cells and organoids (neurons vs astrocytes vs oligodendrocytes), since signaling through different receptors may impact downstream transcriptional observations across the different serotypes studied? + +We thank the Reviewer for this question. Firstly, we wish to emphasize that based on our observations it seems that the signalling is not different between serotypes but rather vary in magnitude according to the transduction efficiencies. Nevertheless, we took advantage of our single-cell RNAseq data from mixed cultures and brain spheroids to look at the pattern of expression of different known AAV receptor levels across cell types and have included the results below for the Reviewer (Figure A). We do not observe any significant differences in receptor expression across cell types, suggesting that differences in receptors do not explain the tropism and downstream transcriptional observations across the different serotypes. Given that this data does not add to the general message of this work, we would prefer not adding it to the manuscript that is already heavy in supplementary information. + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +![](images/Figure_unknown_0.jpg) + +
Figure A. Distribution of AAV receptor mRNA expression in CNS models. (A,B) Violin plots showing the expression level of known AAV receptors on mixed CNS cultures at the end of the differentiation protocol (day 24) (A) as well as brain spheroids (day 150) (B). Plots contain pooled data from two biological replicates of mixed cultures or spheroids respectively, each performed in technical duplicate.
+ +8. In Fig 6, snRNAseq is performed in mice given AAV9.CAG-EGFP via IPa then for some reason the DNA damage response observations in the striatum are validated in mice after ICV and not IPa delivery of AAV9.PGK-EF1a.Cre-EGFP. This validation should be performed after IPa delivery of the same vector. It is also not clear what AAV9.PGK-EF1a.Cre-GFP is. Is GFP expression conditional (Cre expressing mice were not used) or does it express 2 transgenes (Cre and GFP), which complicates observations made in Fig S8 in relation to Fig 6. + +We thank the Reviewer for this suggestion. The previous validation was performed on striatum of mice injected ICV due to tissue availability. We have now performed a new in vivo experiment replicating the experimental conditions of the snRNAseq experiment in Figure 6 (C57BL/6 mouse strain, IPa route of administration and AAV9-CAG-GFP vector at \(1 \times 10^{10} \mathrm{vg / side}\) ) to confirm local DNA damage responses in the striatum compared to vehicle injection (N=3 per group) and results are shown in Figure 7 and Supplementary figure 14 of the revised manuscript. Briefly, IF staining shows high colocalization of the neuron marker NeuN and the DNA- damage marker YH2AX in the striatum of injected animals (Fig. 7), as well as increased gliosis as shown by GFAP, Sox9 and Iba1 stainings (Fig. S14A- F). Moreover, Iba1+ cells + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +colocalized with Galectin- 3 staining, a marker for microglial activation (Ge et al, 2022) (Fig. S14D- F). Of note, we also observed increased GSDMD staining in Iba1+ cells, an indicator of microglial activation in this context (Pollock et al, 2024) (Fig. S14G and H). This new experiment is now described and discussed on lines 254- 268, pages 10- 11 and lines 425- 437, pages 16- 17 of the revised manuscript. + +## Minor points + +1. Lines 164-167 – The authors state “Overall, upregulation of signaling pathways was more significant in the 3D model compared to the 2D mixed cultures (Fig. 3E, Fig. 4E), suggesting active cross talk and paracrine effects of AAV signaling across cells of the human CNS.”, however, this could just be an MOI effect whereby cells on the outside of a 3D spheroid take up more AAV in culture, which in turn causes greater peak activation levels. Please discuss. + +We agree with the Reviewer that differences between 2D and 3D models can potentially be due to an MOI effect, or also to a longer transduction time of the 3D spheroids. Figures 3D and 4D show similar percentages of cells positive for GFP mRNA, suggesting that transduction rates are similar across the culture systems at least in terms of vector expression. In addition, FACS data from cells taken from transduced mixed cultures and homogenized organoids used for single-cell analyses show similar percentage of GFP+ cells across 2D and 3D cultures that we have included below for the Reviewers consideration (Figure B). These observations, together with an overall higher number of significantly upregulated pathways observed in Figure 4E compared to Figure 3E, and our results from Figure 5 in transgene-negative cells led us to hypothesize that the more complex 3D structures could contribute to the increased paracrine signalling. Of note, the higher % of GFP mRNA positive cells shown in Figures 3D and 4D of the manuscript compared to the % of GFP fluorescent cells measured by FACS shown below (Figure B) derive from the higher sensitivity of transcriptomics to detect low copies of transcript, and to the use of bulk cells for FACS vs. the cell-type specific analysis in scRNAseq. We have moved our statements regarding paracrine signalling to discussion and have added the Reviewer’s and other considerations to explain the differences in signalling between models, lines 397- 401, page 15 of the revised manuscript. + +![](images/Figure_unknown_1.jpg) + +
Figure B. GFP expression in mixed cultures and brain spheroids. FACS analysis of the percentage of GFP+ cells in mixed cultures and brain spheroids transduced with the indicated vectors.
+ +2. Are different responses seen between ssAAV vs scAAV vectors? + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +We thank the Reviewer for this relevant question. To try to answer it we have performed two independent transduction experiments to study differences between ssAAV9 and scAAV9 vectors. Results from both experiments have been pooled in Supplementary Figure 17 showing no significant differences between ss vs sc vectors despite the higher GFP expression derived from the scAAV9 vector (Fig. S17A). This result was somewhat unexpected as scAAV vectors are reported to be more immunogenic than ssAAV vectors in vivo due to higher stimulation of TLR9 receptors in plasmacytoid dendritic cells (pDCs) (Rogers et al, 2017). Our hypothesis is that the type of intrinsic signalling induced by AAV vectors and the relevance of TLR9 sensing is cell- type dependent, as was reported by Rogers et al., showing that TLR9 sensing was specific to pDCs and not conventional dendritic cells for instance. In agreement, additional experiments that we have performed and reported in Supplementary figure 16 further support the lack of involvement of TLR9 on neural cell signalling as we did not observe any major impact of TLR9 inhibition or the use of a TLR9 insensitive AAV2 vector (AAV2.io2, (Chan et al, 2021)) in terms of gene induction in hiPSC- derived astrocytes. We have described these results at lines 283- 293, page 11 of the revised manuscript. + +3. Table S1 reports the AAV 'dose' in v.p./cell but elsewhere vg/cell is used as the unit for infection. Are the reported MOI based on particles or genomes? + +We thank the Reviewer for this question. The term vector particles was previously used to refer to both capsid in case of empty vectors or genomes in case of full vector. To avoid confusion, the dose units on the table have been modified to MOI, and the use of vector particles or vector genomes has been specified in the table legend. Moreover, the text below has been included in the methods section, lines 621- 628, pages 23- 24 of the revised manuscript: "Full vector titers were determined by qPCR as vector genomes (vg) per mL using primers directed against the transgene poly- adenylation signal region. The AAV titer was calculated by averaging results from 2 qPCR rounds with 3 different dilutions tested for each sample in each round. The purity of vector preparations was evaluated by SDS- PAGE gel. Empty capsid titers were determined by Sypro Ruby staining following SDS- PAGE (Lock et al, 2010). Empty AAV9 and full AAV1, 2, 5, 6, 9 and Spk100 vector titers were simultaneously verified by side- by- side capsid imaging by western blot using an anti- AAV VP1/2/3 monoclonal antibody (Progen)". + +4. No methods are provided for genome titer and/or AAV particle determination, please include. + +We thank the Reviewer for pointing this out. Titration methods detailed above in comment 3 have been included in methods section, lines 623- 628, pages 23- 24 of the revised manuscript. + +5. Details of the ICV injection procedure should be provided. + +Following the Reviewer suggestion, we have now performed new in vivo experiment replicating the treatment conditions used in the snRNASeq study (C57BL/6 mouse strain, IPA route of administration and AAV9- CAG- GFP vector at \(1 \times 10^{10}\) vg/side) and the results from animals treated by ICV injection have been replaced by the new intraparenchymal study in Figure 7 and Supplementary Figure 14 of the revised manuscript and described in detail on lines 254- 268, pages 10- 11 of the revised manuscript. + +6. Fig 1D – Why were Spark100, AAV1 and AAV6 omitted? + +We thank the Reviewer for this observation. These serotypes were not used in the bulk RNAseq experiment shown in Fig. 1D, 1F and 1H because we chose to transduce cells with the three serotypes that showed different behaviour according to results in Fig. 1A, B in astrocytes. Specifically, AAV9 was + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +chosen as an example of low VGCN, low GFP expression and low signalling as well as due to clinical relevance, AAV5 for high VGCN in astrocytes compared to AAV9 but low GFP expression and low signalling, and AAV2 as high VGCN, high GFP expression and high signalling. We hypothesize that the discrepancy between the vector copies of AAV5 and the low GFP expression and signalling is due to a slower uncoating of this capsid, reported to be more stable compared to other serotypes (Bennett et al, 2017), confirming our hypothesis that vector genome sensing is needed to induce signalling. In agreement, we have performed preliminary time- course experiments showing delayed GFP expression observed for AAV5, included below for the Reviewer's consideration (Figure C). We have not specifically commented on the choice of the serotypes in the manuscript to avoid rendering the reading too heavy and hope the Reviewer agrees with this choice. + +![](images/Figure_unknown_2.jpg) + +
Figure C. Time course of GFP expression. FACS analysis of GFP expression in iPSC-derived neurons transduced with the indicated serotypes at multiple time-points. Each dot corresponds to data from 1-3 independent transductions.
+ +7. Fig S3B - x-axis legend should read full and not AAV9. + +We thank the Reviewer for pointing this out and have corrected the axes accordingly. This is now Fig. S6B. + +8. Fig 5B-D - The SPARK100-hAAT-GFP vector should be added to the right-hand 'transgene minus' panel for easier comparison since GFP isn't expressed. + +We thank the Reviewer for pointing this out. The figure has been modified accordingly. + +9. mRNA is not expressed from the hAAT promoter in hiPSC-derived neurons. How would responses compare between the hAAT-GFP vector and a vector that produces an mRNA but is not translated (e.g. ATG deleted GFP)? + +We thank the Reviewer for this suggestion and agree that this is a very interesting point to address. However, although we sought to obtain a non- translating vector, such as the suggested ATG- deleted version, to address the Reviewers' point, we have not been able to access such a vector yet. Therefore, while we agree that dissecting the role of transcription vs. translation is relevant, we hope that the Reviewer will understand that we have not been able to perform these experiments in the timeframe of this revision and will aim to do so in future studies. + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +10. Fig 6 – This study was performed at a single AAV dose. Why was this dose chosen? How representative is this dose per g of brain to those used in other animal studies where CNS toxicity has been observed? + +We thank the Reviewer for these questions. This vector dose was firstly chosen because it is a standard vector dose used for pre- clinical testing in several settings, independently of toxicity, and secondly because it has also been shown to induce glial cell activation and brain infiltration in previous mouse studies using the same route of administration (Guo et al, 2023; Hollidge et al, 2022; Ortinski et al, 2010). We have added an explanatory sentence in the revised manuscript, lines 800- 803, page 30. + +11. Fig S9B – MAVS blockade appears to accentuate AAV induction of IL-1 and CXCL8 substantially. This is not mentioned and should be discussed? + +We thank the Reviewer for pointing this out. Although this seems to be quite consistent, now in Fig. S17, we do not know yet the molecular basis on this observation. Because MAVS stays on the mitochondria, its depletion could potentially lead to some alterations affecting indirectly inflammation, or some sort of priming of the cells could occur in absence of physiological RNA sensing so that they will more readily react to incoming vectors. We have discussed this on lines 496- 499, page 19 of the revised manuscript. + +12. FigS10 – legend says figure 10. This has been corrected and is now Fig. S19 of the revised manuscript. + +13. Fig S9 legend – typo 'signallig' We have homogenized the text accordingly. This is now Fig. S18 of the revised manuscript. + +Reviewer #2 (Remarks to the Author): + +The manuscript by Costa- Verdera and colleagues describes the transcriptional responses that arise in AAV- transduced cells of the CNS that were derived from hIPSC. The authors study 2d cultures of neurons, astrocytes and oligodendrocytes as well as brain spheroids tested after transduction by several different AAV capsids (AAV1, AAV2, AAV5, AAV6 AAV9 and Spk100). The authors determine the ability of these different capsids to transduce each cell type as well as the consequence of transduction on inflammatory signaling and DNA damage responses. They demonstrate that different capsid serotypes have varying abilities to transduce neurons and astrocytes (and in some cases oligodendrocytes). Furthermore, they demonstrate that AAV transduction correlates with activation of DNA damage repair pathways (p53 mediated) and activation of some inflammatory pathways. These two findings regarding the induction of p53 and inflammatory pathways are not completely novel, but the comprehensive approach being taken by the authors and the testing of many different CNS cell types against a large number of capsids is a strength of the paper. The authors also carry out in vivo experiments in mice by ICV injection and demonstrate the level of transduction of different cell types and some single cell gene expression data. + +The strengths of the manuscript include 1) the comprehensive testing of a variety of CNS cell types which demonstrates some consistent patterns of p53 induction and inflammatory signaling across different culture conditions (2D vs 3D), 3) the testing of many different AAV vector serotypes for their ability to transduce these various cell types and 3) numerous assessments of transcriptional changes that demonstrate inflammatory and DNA damage responses. The weaknesses of the manuscript are 1) some experiments are not well controlled, such as Fig. 5 where the authors use several promoters and transgenes in parallel but do not control for the CpG content of the vectors. These constructs will all have + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +different risk factors for activating TLR9 signaling, which is activated within hours of transduction and has many cascading downstream effects; 2) the single cell data is not explored beyond identifying cell types? and 3) the timepoints tested do not allow the authors to capture TLR signaling that occurs early after transduction (less than 12 hours post AAV transduction. Because they collected the samples so late after transduction, it becomes difficult to discriminate transgene induced TLR signaling vs capsid responses (such as in Fig. 5). The authors did a tremendous amount of work for this manuscript and it would be very difficult to repeat everything to obtain an early time point, but the authors do need to acknowledge that TLR signaling will influence downstream signaling. The specifics regarding Figure 5 are detailed below. Overall this is a strong manuscript that has a lot of important information that will be valuable to readers. + +We thank the Reviewer for the overall positive feedback and constructive comments and agree that some of the experimental designs could have benefitted from earlier timepoints to more deeply investigate the involvement of TLR signalling in the downstream consequences of rAAV transduction. However, as this study aimed to broadly address rAAV impact on the target cells/tissue, we went for a compromise to address multiple pathways. + +Fig. 1A. Can the authors show examples of the FACS plots where they determined GFP+ cells and show the gating that was used to identify the positive cells. + +We thank the Reviewer for the question and have included representative FACS plots in Supplementary figure 2A of the revised manuscript. + +It would be good to show the vector copy number (currently in supplemental) in the main figures alongside the GFP+ mRNA. Figs 1E and F could be moved to the supplemental if space is needed. + +We thank the Reviewer for the suggestion. Vector genome copy number graphs have been moved from Supplementary figure 2 to main Figure 1B by plotting neuron and astrocyte data in the same graphs, same as for the GFP expression data. Regarding Figures 1E and F, we feel that pathway analysis is important and prefer to keep this information in the main Figure 1. + +Supplementary Table 1: There seems to be information missing from the table. Also, could the authors state the titer in viral genomes, since it is the transgene that is inducing most of the response; thus, one would like to know the level of transgene instead of viral particles. + +We thank the Reviewer for pointing this out. We have modified Supplementary Table 1 to clarify the units used and included the titration details in the methods section in lines 621- 628, pages 23- 24 as follows: "Full vector titers were determined by qPCR as vector genomes (vg) per mL using primers directed against the transgene poly- adenylation signal region. The AAV titer was calculated by averaging results from 2 qPCR rounds with 3 different dilutions tested for each sample in each round. The purity of vector preparations was evaluated by SDS- PAGE gel. Empty capsid titers were determined by Sypro Ruby staining following SDS- PAGE (Lock et al., 2010). Empty AAV9 and full AAV1, 2, 5, 6, 9 and Spk100 vector titers were simultaneously verified by side- by- side capsid imaging by western blot using an anti- AAV VP1/2/3 monoclonal antibody (Progen)". + +Figure 3B: The authors should show how the frequency of their cell populations change with dosing between days 2 and 4. Can they show individual UMAPS and normalized cell numbers by time point? + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +We thank the Reviewer for this question. Due to space limit, we are showing one representative UMAP and donut plot which contain clustered treated and untreated samples to show that populations cluster together independently of treatment. We have included individual plots from mixed cultures and brain spheroids in Supplementary figures 7 and 8A respectively. Overall, we do not observe consistent changes in the percentages of the different cell populations that could be related to treatment or the time- point after transduction. Differences are more likely due to sample- to- sample variability and sample handling and processing, and further experiments with larger numbers of organoids would be needed to confidently draw conclusions in terms of potential impact AAV transduction on the cell composition of these in vitro models. In addition, major signalling pathways and time- dependent increase in inflammatory signalling were confirmed by qPCR in 2D cultures (Figure S10 of the revised manuscript). + +Also could the authors provide some of the top differentially expressed genes in addition to the pathways? + +We thank the Reviewer for the suggestion and have now included Volcano plots with top altered genes in Supplementary figure 8B of the revised manuscript. + +3D: It would be best if the colors in Fig. 3D could match the colors for Figs 3B and 3C. + +We thank the Reviewer for the suggestion and have unified the colours between the panels. + +Figure 5: In this figure the authors use different promoter and transgene constructs to transduce 3D spheroids, followed by isolation of transgene + and transgene - cells and subsequently compare the transcriptional patterns between the different cell types and between transgene + and transgene - cells. They also use two different capsids and use other promoter + transgene constructs. The vast diversity of constructs and cell types makes this figure very complicated to interpret. + +One main issue is that the authors do not consider how differences in CpG motifs (in each construct used) has the potential to impact TLR9 signalling. Thus, the experiment is very difficult to interpret. So while the authors used a control (Spark100 HAAT construct) that does not express protein, they did not take into consideration the fact that the presence of the viral genome will ALSO stimulate inflammatory signalling independent of protein expression. The experiment is not well controlled and therefore, conclusions are difficult to make. The interpretation of this experiment needs to be toned down considerably. + +We thank the Reviewer for raising this point. We have better clarified, lines 189- 194, page 8 of the revised manuscript, that the Spark100 HAAT construct was used to assess the signalling coming from the viral genome only independently from transgene expression, given that this vector will bring the DNA genome into the cells but will not express the mRNA, and we have shown that empty capsids alone do not trigger significant signalling. Indeed, we agree with the reviewer that the presence of the viral genome will also stimulate inflammatory signalling independent of protein expression, as is also evidenced by our new in vivo experiments showing p53 and cGAS- STING- dependent gliosis using the Spk100 HAAT construct (Supplementary Figure 20), lines 339- 356, pages 13- 14 of the revised manuscript. These results are in agreement with an apical role of p53 in linking AAV genome sensing to inflammatory responses, similarly to what we observed in vitro using pathway- specific inhibitors and gene expression readouts (Figure 8). Nevertheless, while we agree that the different CpG content between constructs may play a role and have included a quantification of the CpG content of each construct in Supplementary figure 15 showing that the CAG- containing vectors do have higher CpG content compared to the hAAT promoter- containing vector, new experiments performed using a TLR9 specific inhibitor (A151) or a TLR9- stealth vector (io2 (Chan et al., 2021)) further suggest that TLR9 may not be involved in AAV sensing in CNS cells as no clear + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +benefit could be achieved in terms of gene activation in these contexts (Supplementary figures 16 and 17). We have discussed these observations on lines 277- 293, page 11 of the revised manuscript. + +1) Line 174: They are not able to state that different AAV serotypes induce different inflammatory signatures. The authors have proven that the AAV capsid determines whether the AAV particle can enter a cell but they have not proven that different signatures arise due to different capsids. + +We thank the Reviewers for pointing this out. We have rephrased the text to emphasize our hypothesis that the observed signalling is serotype-independent and rather depends on transduction levels, lines 394- 397, page 15 of the revised manuscript. + +2) Line 201: The authors cannot discriminate transgene specific responses due to lack of consideration for the differences in the different risk factor potentials to stimulate TLR9 signaling (formula published by J. Fraser Wright https://doi.org/10.1016/j.ymthe.2020.07.006), which is inherent to each transgene. So the comment that GAA stimulates more inflammatory signaling is likely due to a difference in the RF3. + +We thank the Reviewer for this comment. We have included this point and added the reference lines 280- 283, page 11 of the revised manuscript as follows: "As the CpG content of the AAV vector sequence has been shown to be an important modulator of cellular responses against transduced cells in vivo (Bertolini et al, 2021; Wright, 2020), this could contribute to the differences in signalling induced by the different expression cassettes through TLR9 sensing.". In addition, we have included a quantification of CpG motifs in our sequences in Supplementary figure 15. + +Furthermore, the idea of paracrine signaling (line 204) has not been proven. + +We agree with the Reviewer that formal proof of paracrine signalling is lacking and is based on observation of the GSEA results. In an attempt of studying potential paracrine signalling, we performed a conditioned media transfer experiment between transduced astrocytes to untransduced neurons to analyse toxicity markers potentially induced in neurons. However, our experiment was limited by the detection of GFP transcripts in the untransduced neurons, indicating the presence of contaminating AAV particles in the conditioned media that render interpretation of this data difficult as paracrine versus AAV- triggered changes cannot be discerned. We included the results of this experiment here for the Reviewers' consideration here below (Figure D). + +Due to this issue, we feel that we cannot include this experiment in the manuscript and have dampened our claims by moving our considerations to the discussion and including other potential explanations for the differences in signalling observed between 2D and 3D models: "Moreover, upregulation of signalling pathways seemed more significant in the 3D in vitro model compared to the 2D mixed cultures, suggesting potential cross talk and paracrine effects of AAV signalling across cells of the human CNS. However, these differences could also result from longer transduction time of brain spheroids or their longer differentiation yielding higher maturation stages. Alternatively, an MOI effect could also account for some of the differences as the outer cells in the spheroids are more highly transduced compared to the inner ones, although single- cell analyses showed similar percentage of GFP+ cells across 2D and 3D cultures", lines 397- 404, page 15 of the revised manuscript. + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Figure D. Conditioned media transfer experiment in iPSC-derived neurons. iPSC-derived untransduced (UT) neurons were incubated for 48h with conditioned media (CM) from astrocytes previously transduced with AAV2 for 24h, washed with PBS following media replacement and cultured for another 48h before collecting the supernatant. Panels A and B show IF staining on neurons of yH2AX and cc3 respectively as markers of cell toxicity. Panels C and D show the analysis of GFP and p21 mRNA on untransduced neurons incubated with transduced astrocyte culture supernatants.
+ +3) Line 207: The authors conclude that the vector genomes induce the p53 response, but this point is not proven at all. There are p53 responses in both transgene + and transgene - populations. It is recommended that the authors deconstruct this figure and parse out the points that they can make conclusively. + +We thank the Reviewer for pointing this out. Firstly, we wish to clarify that "transgene - " means that the transgene product is not expressed (mRNA and protein) while the vector genome is equally present in both conditions, as shown in terms of VGCN but no GFP signal in Fig. S11A, B. We have included an explanatory paragraph in the main text, lines 189-194, page 8 of the revised manuscript. We decided to use these two vectors to control for responses that are solely due to detection of the vector genome vs. effects associated with expression of the transgene as suggested by Hordeaix et. al in DRG neurons (Hordeaix et al, 2020b). Moreover, we show that empty capsids alone do not induce any significant responses in this experimental setting (Fig. 1E- H, Fig. S3, Fig. S4, Fig. S5, Fig. S16B- E). In addition to the DNA- damage foci that we detect by IF staining in our in vitro and in vivo models (Fig. 2, Fig. S6, Fig. 7), our hypothesis that vector genomes induce p53 responses is supported by the effect of inhibiting p53 with GSE56 or pharmacological inhibitors in preventing the upregulation of pro- inflammatory genes in vitro (Fig. 8) or the activation of GFAP+ cells in vivo (Fig. S14), even when using a transgene- silent vector (Figure S20). These observations are in line with previous reports showing that AAV vector genomes induce a p53 response (Cervelli et al, 2008; Hirsch et al, 2011), and observations linking DNA damage with increased inflammation in several contexts (Ghosh et al, 2023; Kay et al, 2019). We have better discussed the results obtained from "transgene +" and "transgene - " populations on lines 208- 215 pages 8- 9 of the revised manuscript. + +4) Fig. S6: The authors do not control for the TLR risk factor here, which could be significantly different between the two promoters, so it is difficult to make any firm conclusions from this study. + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +We thank the Reviewer for point this out. Following the Reviewers suggestion, we have included a quantification of the CpG content of the different sequences used in Supplementary figure 15 and acknowledge the potential influence of different CpG content in the observed responses, lines 277- 293, page 11 of the revised manuscript. However, our additional experiments included in Supplementary figures 16 and 17 using a TLR9 inhibitor or a TLR9- inhibitory AAV2 vector (AAV2.io2 (Chan et al., 2021)) do not provide any evidence of the role of CpGs and TLR9 in the sensing of AAV vectors by neural cell types. Instead, the main signalling in these cells seems to be p53- mediated, as shown by our results using a p53 inhibitor in vitro (Figure 8 of the revised manuscript) and in vivo (Figure S20 of the revised manuscript). We have further discussed these observations on lines 500- 509, pages 19 of the revised manuscript. + +Line 246: The authors state that type I IFN signaling in AAV transduced human and mouse CNS cells triggers IFN1 signaling. This statement does not consider TLR9 signaling, which can trigger IFN1 signaling via CpG motifs in the transgene. + +We agree with the Reviewer on the potential contribution TLR9 may have in activating type I responses upon AAV transduction and have included this consideration on lines 277- 293, page 11 and lines 500- 509, page 19 of the revised manuscript. However, as already discussed above, we wish to point out the several new experiments performed with TLR9 inhibitor or TLR9- stealth AAV seem to exclude a predominant role of this PRR in AAV sensing in CNS cells in our experiment setting (Fig. S16, S17). Moreover, our results in MAVS- depleted astrocytes (Supplementary Figure 18) together with the lack of altered ISG induction in presence of p53, STING or IL1R inhibitors (Figures 8 and 9) seem to point towards a type I IFN signature that is fuelled by cytosolic RNA sensing in this experimental context. We have better clarified this, lines 500- 509, page 19 of the revised manuscript. + +Figure 6: The authors carry out ICV injections, isolate CNS cells after 28 days and carry out single cell sequencing. The authors do not see p53 dependent responses in vivo, which is hard to reconcile with their other studies. Is the mouse different than human, is it an in vivo vs in vitro issue or is it a timing problem? + +We thank the Reviewer for this comment. In the first draft, ICV- injected animals were only used for histology and not for snRNAseq analysis. However, this question may not be relevant anymore as data from the ICV study has been replaced by data generated with intraparenchymal (IPa)- injected animals. In the new Figure 6E we did observe DNA repair and p53 response terms at the transcriptional level in some neuron subsets. This is in line with our histology findings in Figure 7, in which yH2AX foci mostly co- localize with neurons. The fact that results at the functional level are more robust than at the transcriptional level could be due to different expression kinetics in vivo vs. in vitro, or to dropout of cytoplasmic mRNA in snRNA sequencing compared to scRNAseq analysis, since our immunofluorescence staining confirms the functional formation of p- yH2AX- positive DDR foci in striatum sections of IPa- injected animals (Figure 7A, C). For side- by- side comparison of human and murine datasets, we generated a GSVA heatmap of common pathways enriched across our different in vitro models and murine datasets, showing that samples clustered together according to cell- type and treatment and independently of the species of origin, showing high clustering scores for pathways including IFN response, p53 pathway, inflammatory signalling, complement responses or apoptosis, now Supplementary Figure 13, lines 248- 253, page 10 of the revised manuscript. + +This figure could be the basis for a full paper that carefully assesses time points in the mouse and compares to the in vitro studies. If the authors want to include this study, I recommend that they extend + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +their single cell data analysis and show in the figure how cell frequencies and phenotypes change with AAV dosing in vivo. + +We thank the Reviewer for this suggestion and have included individual donut plots for plots for vehicle and AAV9- treated mice in Figure 6C of the revised manuscript. We did not observe important differences that could be associated to treatment, instead samples from untreated and treated mice cluster together as shown in Figure 6B. + +In addition, they should demonstrate how those changes are similar and/or different from hiPSCs. I would recommend they show violin plots of individual genes and demonstrate how they are consistent or differ with observations made in the hiPSC- derived CNS cells. Since no violin plots are shown in the prior parts of the manuscript, they could show them here, so it is easy for the reader to compare across cell types vs the in vivo studies. + +We have worked on generating a figure comparing pathways and single genes induced in murine vs. human cell datasets and the best way of representing the comparison. However, such comparison has a series of challenges: 1) the diversity of cell subsets found in vivo compared to in vitro models (i.e. neuron sub- types) and the maturation stage of the cells; 2) the techniques by which transcriptomes were analysed were different (snRNAseq in vivo which detects only nuclear mRNA vs. scRNAseq in vitro, for detection of cytosolic transcripts); and the individual genes that contribute to a specific pathway vary from mice to human (Fischer, 2019; Fischer, 2021), so we do not always expect the same genes to be upregulated across species. + +The main challenge we encountered when plotting murine and human genes on the same graph is that even though they were all significantly upregulated and contributed to same pathways, the folds were lower in mice. This can be due both to the fact that in mice we are only detecting nuclear transcripts, and that the percentage of transduced cells is lower in vivo compared to in vitro, so there is a vector dilution effect. For this reason, although we have generated a violin plot figure that we have added below for the reviewer's consideration (Figure E), showing examples of significantly induced genes that we found to be common in all datasets, we do not find this representation the most informative. + +Instead, given the high variation in the experimental context of the different human and mouse datasets, and in order to compare the in- vitro to in- vivo datasets, we performed a Gene Set Variation Analysis (GSVA) (Hanzelmann et al, 2013) to functionally integrate individual cell types and samples from the human 2D mixed neural- glial culture and 3D spheroids scRNAseq datasets with the mouse brain snRNAseq dataset (Supplementary Figure 13). GSVA is a particular type of gene set enrichment method that works at the single sample level and enables pathway- centric analyses of molecular data by performing functional analysis from genes to gene sets to detect subtle pathway activity changes over a sample population. Our results showed that the computed GSVA scores recovered cell type signatures that were previously analysed by GSEA in the different cell types from both the human and mouse datasets confirming that this approach captures transcriptionally encoded biological signals in scRNAseq and snRNAseq data. Notably, the k- means clustering of the different samples revealed an evident segregation based mainly on sample condition (AAV9 or UT) and cell type (astrocytes, oligodendrocytes or neurons), meaning that treated and untreated samples clustered together per cell- type independently of human or murine origin, indicating that treatment and cell- specific responses are the primary drivers of pathway activity. Interestingly, there was no clear clustering based on the different datasets (human- derived 2D and 3D cultures vs. mouse brain) or dataset type (in vitro vs. in vivo). Instead, we observed clustering of glial (left) and neuronal (right) cell populations respectively, showing that the three analysed dataset populations are comparable in their transcriptional profile at the functional level, suggesting highly similar pathway- level profiles between human and mouse. This indicates conserved biological + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +processes at the pathway level across species and experimental setups, despite differences in experimental context. We have included the details for the analysis in the methods section, lines 883- 896, page 33, and figure description in the main manuscript lines 248- 253, page 10 of the revised manuscript. + +![](images/Figure_unknown_4.jpg) + +
Figure E. Violin plots of common genes between human and murine datasets. Violin plot representation of example common genes significantly upregulated across human mixed cultures, brain spheroids and murine striatum datasets contributing to different pathways such as DNA stress response (yellow), pro-inflammatory signalling (purple), type I IFN signalling (green) and mitochondrial stress (orange).
+ +Also, for this in vivo study, the authors should make comparisons of how AAV transduction of individual CNS cells compares to hiPSC derived CNS cells. + +We thank the Reviewer for this suggestion and have address this point in the above- mentioned Figure E and new heatmap in Fig. S13, including the description of all the associated limitations of such comparisons. + +Supplemental Fig. 8: In the figure legend the authors should state what is being stained and how the heat maps were obtained. + +We thank the Reviewer for pointing this out. The figure and figure legend have been updated in the new main Figure 7. The heatmap was generated by Prism after introducing the results from quantifying the percentage of double- positive cells for each co- staining for the different tissue sections, obtained with the MACSima analysis software (MACS® iQ View), and data were plotted in a Grouped table format. Statistics were generated by multiple t- test, and a heatmap representation was selected to represent the results. We have detailed this information on the methods section lines 692- 694, page 26 of the revised manuscript. + +Supplemental Figure 10: Why didn't the authors treat the cells with the inhibitors prior to transducing + +<--- Page Split ---> + +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +them? Since these signalling pathways are triggered upon AAV entry, the TLR pathway cannot be ruled out as upstream of some of the gene induction. + +We thank the Reviewer for this question. As suggested, we repeated the experiment with the TLR9 inhibitor on iPSC- derived astrocytes including a 1- hour pre- treatment prior to AAV transduction (Fig. S16 of the revised manuscript). The inhibitor was maintained in the culture media after the end of the experiment. These new results, together with experiments performed with a TLR9- stealth AAV, suggest that TLR9 sensing does not play a major role in driving AAV signalling in this experimental setting. We have discussed these results on lines 277- 293, page 11 and lines 500- 509, page 19 of the revised manuscript. + +Reviewer #3 (Remarks to the Author): + +This is an interesting, informative, and timely study, addressing a major barrier in translating rAAV- based gene therapy to clinical application. Overall, the manuscript is well written, data thoughtfully analyzed and presented. However, the manuscript can be further strengthened if the authors can address the points below. + +We thank the Reviewer for appreciating our work and its relevance for the field. + +1. In general, the time between AAV transduction and data collection seems to be longer than what is needed by the cells to initiate a DNA damage repair and innate immune responses. Could the authors explain clearly for the rationale to choose these timepoints? + +We thank the Reviewer for this question. The choice of time- point is based on our preliminary tests at multiple time- points in neural stem cells (iNSCs, which are faster to generate compared to more differentiated cells) (Figure F below) showing that no responses are detected as early as 6h, and in iPSC- derived neurons (Figures G and H below) and previous observations in the context of HSPC (Piras et al, 2017) in which the 48h time- point was the first timepoint when robust GFP expression and induction of DNA- damage dependent genes (p21) at the transcriptional level were observed. For our single- cell experiments we chose to collect cells at 48h and at later timepoints days 4 and 5 after performing time- course experiments showing that this is the timepoint at which maximal transgene expression is obtained (Figure C above). + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +![](images/Figure_unknown_5.jpg) + +
Figure F. Analysis of selected p53-dependent genes (p21, TRIM22, APOBEC3H) and innate immunity markers (IL1b, CXCL8, ISG15) by qPCR in iNSCs transduced with full AAV9 for 6h or 24h.
+ +![](images/Figure_unknown_6.jpg) + +
Figure G. Measurement of GFP-expression levels in iPSC-derived neurons transduced with AAV9.
+ +![](images/Figure_unknown_7.jpg) + +
Figure H. Analysis of AAV-derived signalling in iPSC-derived neurons transduced with full and empty AAV9 at 24h and 48h post-transduction.
+ +2. Also, it would be informative to study /compare the outcomes of transduction by single stranded and self-complementary rAAVs. + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +We thank the Reviewer for raising this relevant point. We have now performed in vitro experiments to study differences between ssAAV9 and scAAV9 vectors. Results from these experiments have been pooled in Supplementary Figure 17 showing no significant differences between ss vs sc vectors despite the higher GFP expression derived from the scAAV9 vector (Fig. S17A). This result was somewhat unexpected as scAAV vectors are reported to be more immunogenic than ssAAV vectors in vivo due to higher stimulation of TLR9 receptors in plasmacytoid dendritic cells (pDCs) (Rogers et al., 2017). Our hypothesis is that the type of intrinsic signalling induced by AAV vectors and the relevance of TLR9 sensing is cell- type dependent, as was reported by Rogers et al., showing that TLR9 sensing was specific to pDCs and not conventional dendritic cells. In agreement, additional experiments that we have performed and reported in Supplementary figure 16 further support the lack of involvement of TLR9 on neural cell signalling as we did not observe any major impact of TLR9 inhibition or the use of a TLR9 insensitive AAV2 (io2 (Chan et al., 2021)) in terms of gene induction in hiPSC- derived astrocytes. We have described and discussed these results in lines 277- 293, page 11 and lines 500- 509, page 19 of the revised manuscript. + +3. For the data presented in Figure 1, in terms of transcriptomic changes with and without AAV vectors, those transduced by AAV9 appears to have milder changes compared to those transduced by AAV2 and AAV6, presumably due to less efficient transduction efficiency. Is there a way to first sort GFP+ cells, and then analyze transcriptomic changes in GFP+ cells alone? Alternatively, will it be a good idea to "normalize" transcriptomic changes based on GFP+ percentage? + +We thank the Reviewer for this question. Because this analysis was based on bulk RNAseq it is not possible to identify and focus on GFP+ cells, and from a bioinformatic point of view it is not feasible to perform a normalization as suggested by the Reviewer. Our observation is that higher VGCN will not only trigger higher fold changes of specific genes, but also induce changes in a higher number of genes involved in a particular pathway, which we would not be able to observe despite normalization. This type of analysis can instead be done on our single-cell RNAseq experiments in terms of transcript positive vs. negative cells. Indeed, we have reported similar transcriptional changes for both GFP+ and GFP- populations in Figure 5 of the revised manuscript, suggesting that some degree of paracrine activation occurs between the two populations. Nevertheless, it is not possible to normalize this analysis by the number of vector copies in each cell, for which we cannot rule out the presence of genome copies in cells in which GFP mRNA was not detected due to potential dropout effect, and VGCN is one of the main determinants of the signalling based on our observations. We have included this consideration on lines 219- 224, page 9 of the revised manuscript. + +4. For the data described by Figure 2: Why did the authors chose 48 h post transduction as the time to assay caspase 3 cleavage? Would assaying an earlier time point (12h or 24h) give a more pronounced result? A general expectation would be that DNA damage response is induced much sooner than 48 h, especially for a flat-surface cell culture. + +We thank the Reviewer for raising this point. We chose not to perform IF staining of toxicity markers earlier than 48h due to our preliminary tests showing that no transcriptomic changes could be detected in neurons before this timepoint, and that the response was limited to p53- dependent genes such as p21 (Figure H above), for which we did not expect to find changes at the protein level before that time- point. Moreover, we observed that the level of staining is maintained and even more significant at 72h compared to 48h, suggesting that transduction- derived stress may amplify over time and further supporting the rationale of looking for these responses at relatively late time- points after transduction (Fig. I below). + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +![](images/Figure_unknown_8.jpg) + +
Figure I. cc3 staining in iPSC derived neurons. Quantification of cc3 staining by IF imaging in iPSC-derived neurons transduced with AAV9-CAG-GFP during 48 and 72h. Dots correspond to data from 3 pooled experiments.
+ +After carefully reviewing the data presented in Figure 4, the p53 pathway in neurons seems to increase from day 2 to day 5. But by day 5, one would assume that the DNA cargo has already undergone ds synthesis and started episode formation. Why does the response appear to be delayed? Would simple transfection of episomes lead to p53 pathway activation? Please see a similar comments above. + +We thank the Reviewer for raising this interesting point. Indeed, as also mentioned above, the response to transduction seems somewhat delayed and persistent in these cells. It is possible that the kinetics of transduction are not synchronized in this setting, as shown for the different serotypes in neurons in Figure E above, and we can expect to find AAV genomes in different conformations in the nucleus with persistent detection of the ITRs. In addition, it is possible that DDR increases according to the kinetics of vector uncoating, and although AAV circularizes over time, ITRs are still recognized despite the episomal form as shown for transfected ITR sequences (Hirsch et al., 2011). We have discussed this point on lines 405- 413, page 16 of the revised manuscript. + +6. For the data presented in Figure 6, The author should explain better why the in vivo study was performed at day 28, which is very late for assaying innate immune responses against foreign DNA motifs. + +We thank the Reviewer for this question. As some of the AAV- induced responses were seen to be amplified upon transgene expression (Figure 5 of the revised manuscript), the day 28 time- point was chosen as one in which robust transgene expression in the CNS is expected (Hollidge et al., 2022; Mason et al, 2010). Moreover, we also considered that DRG toxicity is observed weeks after injection (Hordeaux et al, 2020a) and is reported to be transgene- expression dependent (Hordeaux et al., 2020b), so we reasoned that assessing this relatively late time point would give an appropriate readout of vector- induced signalling in vivo. We have specified the choice of the time- point in the revised manuscript, lines 234- 238, pages 9- 10 as follows: "Adult male mice were bilaterally injected into the striatum with AAV9- CAG- GFP or vehicle (N=2 mice/group respectively) and were sacrificed 28 days post- injection, a time- point at which robust transgene expression can be expected (Hollidge et al., 2022; Mason et al., 2010) and CNS toxicities have been reported (Golebiowski et al, 2017; Guo et al., 2023; Hordeaux et al., 2020a), which in the DRG context have been shown to be transgene expression- dependent (Hordeaux et al., 2020b)." + +7. One major concern is the experiment described in Figure 8. There is evidence suggesting that STING inhibitor H151 only works for STING-HAQ mutation but not WT STING. Did the authors genotype the hiPSCs? Are they STING HAQ or WT STING? + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +We thank the Reviewer for pointing this out and are aware of literature regarding potential functional differences in common STING variants. Nevertheless, we have successfully used this compound to inhibit STING mediated signalling in multiple types of cells from multiple sources across experiments (and projects (Valeri et al, 2024)), possibly because the HAQ allele is quite common in humans. Therefore, we have not performed sequencing of our hiPSCs to define specifically the STING sequence. + +Reviewer #4 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #5 (Remarks to the Author): + +In this work Costa- Verdera et al have used iPSC- derived human brain cell/spheroid systems and mouse models to examine the hose immune response to AAV transduction in the brain. The authors report that AAV- induces p53- dependent DNA damage responses together with STING- and IL1R- dependent inflammatory responses. In addition, they report an involvement of MAVS in the host response evoked by AAV. Although the question under investigation is very timely, and many of the observations are intriguing, the work appears very descriptive at this stage and mechanistically rather under- developed. + +We thank the Reviewer for reviewing the manuscript and helping us improving the quality of our work. While we agree that more work needs to be done to fully elucidate the mechanisms of innate sensing of AAV in the brain, we believe this manuscript is provide the first mechanistic evidence of this phenomenon in a human system. Furthermore, our molecular studies pinpoint distinct signalling pathways activated by the vector genome versus the expressed transgene that differentially contribute to downstream effects such as toxicity. These studies also provide a starting point for the development of tailored pharmacological approaches aimed at targeting the identified mechanisms of vector sensing and signalling and paves the way for further, more detailed mechanistic dissection of the different identified pathways. + +Major comments: + +1. Microglia expresses the highest levels of both cGAS and STING among brain-resident cells. The authors should include this cell type in the analysis. + +We thank the Reviewer for this suggestion and agree that studying the role of microglia in AAV- mediated signalling and functional consequences is highly relevant. However, we feel that investigating this aspect deserves a dedicated study, in particular regarding the mechanistic dissection of human microglia- specific alterations in vitro that require the set- up and validation of appropriate differentiation protocols and assays. In the present work, we have included data regarding the effect of AAV transduction on murine microglia in vivo (Figure 7 and S14 of the revised manuscript), that suggests that microglial activation together with a more generalized gliosis occurs upon local AAV administration, lines 244- 248, and 262- 266, pages 10- 11 of the revised manuscript, and have acknowledged the importance of pursuing more detailed mechanistic studies also in hiPSC- derived microglia- like cells in the future on lines 516- 517, page 20 of the revised manuscript. + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +2. The data are mainly based on a transcriptional approach. For key activated pathways, e.g. IFN signalling, this should be complemented with protein data. + +We thank the Reviewer for this suggestion. We have performed preliminary assays showing functional activation of IFN signalling, including phospho- TBK1 staining on iPSC- derived neurons (Fig. J) and ELISA for the cytokine IP- 10, which is dependent on IFNy activity, on pooled supernatants from 3 independent neuron transductions with AAV9 and AAV2, showing a tendency for induction on samples transduced with AAV2 (Fig. K). While these first results are encouraging and confirm activation of type I IFN and inflammatory pathways through protein- based assays, we have not been able to perform additional replicates to qualify them to be included in the manuscript due to logistical issues related to the on- going transfer of the PI lab from SR- Tiget in Milan, Italy to the University of Pavia Italy that is significantly slowing down experimental activities, in particular those related to hiPSC- derived cell cultures. We hope the Reviewer agrees to vision these data here and understands that we are not able to include them in the manuscript within a reasonable timeframe. + +![](images/Figure_unknown_9.jpg) + +
Figure J. Phospho-TBK1 staining in iPSC-derived neurons. Representative IF images of phospho-TBK1 staining (red) in iPSC-derived neurons transduced with AAV9 at MOI 100,000 for 72 h. Images are from one experiment.
+ +![PLACEHOLDER_27_1] + + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +Figure K. IP- 10 levels on iPSC- derived neuron supernatants. Quantification of IP- 10 concentration detected by MSD in supernatants from iPSC- derived neurons transduced with AAV9 and AAV2. Each dot corresponds to an independent experiment, each performed on pooled supernatants from technical replicates. + +3. CL-CASP3 does not equal apoptosis – in fact could drive GSDME-mediated pyroptosis. The modality of cell death should be further investigated, including the dependency on the innate immune signalling pathways studied. + +We thank the Reviewer for pointing this out and agree that cC3 could imply also other forms of cell death. For this reason, we have now rephrased our description replacing "apoptosis" with "cell death" across the revised manuscript where relevant. In addition, we have included GSDMD staining in murine sections, which we found to colocalize mainly with Iba1+ cells (Fig. S14G, H of the revised manuscript). Because of this co-localization, we interpret that in this context GSDMD is a marker of microglial activation (Pollock et al., 2024) rather than pyropototic cell death as we have no evidence of overt toxicity in our in vivo experiments, and wish to remain cautious in terms of our claims given the attention that gene therapy- related toxicities are receiving in the field in general. We have reported and discussed this additional in vivo data on lines 262- 268, pages 10- 11 of the revised manuscript. + +4. Brain infections with pathogenic viruses are well-described in lead to influx of immune cells from the periphery, most notably monocytes and T cells. The mouse work would gain a lot if the influx of at least these two cell types is evaluated. + +We thank the Reviewer for this suggestion. Although the effect of AAV transduction on adaptive responses is somewhat out of scope for this manuscript, we have included stainings for gliosis markers (GFAP, Iba1, Galectin 3) and T cells (CD45+CD3+) in Fig. S14 of the revised manuscript. Overall, these new results show increased presence of these markers in AAV- treated animals suggesting activation and recruitment of innate and adaptive immune cells within the transduced tissue in agreement with the Reviewers' suggestion. We have added the following sentence, lines 262- 268, pages 10- 11 of the revised manuscript to acknowledge this: "Injected animals also showed increased presence of GFAP+Sox9+ astrocytes (Fig. S14A- C) and Iba1+ microglia (Fig. 14D, E), in line with the induction of pro-inflammatory pathways detected by snRNAseq in these cell populations in injected animals. Stained Iba1+ cells expressed microglia activation markers such as Galectin- 3 (Fig. S14D, F) and Gasdermin D (GSDMD) (Fig. S14G, H). Finally, presence of infiltrating CD45+ and CD3+ cells was also detected by IF in injected striatum (Fig. S14I, J), altogether indicating the induction of gliosis and recruitment of immune cells". + +5. The conclusion that the innate immune response to AAV transduction is STING dependent is based only on the use of the STING inhibitor, which is not specific. Therefore, it should be tested whether the observed response is ablated in cGAS or STING-deficient mice. + +We thank the Reviewer for the suggestion and agree that performing experiments also in KO animals would be of interest. Unfortunately, however, we do not have access to such mice and are not able to perform these experiments in a reasonable timeframe. Instead, we have further assessed the impact of p53 signalling and downstream pathways on glial cell activation in vivo. For this purpose, we took advantage of a transgene- silent vector harbouring the coagulation factor IX (FIX) transgene under the control of the liver- specific hAAT promoter that activated mainly DNA damage- related responses in the human CNS spheroids (Fig. 5). Mice were injected with the vector in the striatum with concomitant intraperitoneal administration of pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) or STING + +<--- Page Split ---> + +Costa- Verdera et al., Point- by- point reply + +(H151), followed by assessment of gliosis on striatal sections. An increase in Iba1+ and GFAP+ cells was observed in mice having received the vector. Moreover, all three treatments decreased the presence of GFAP+ cells in the striata compared to mice injected with AAV only, while they had no effect on the Iba1+ population. NeuN staining indicated absence of neurotoxicity in terms of percentage of NeuN+ cells. These results suggest that, in mice, AAV- mediated CNS transduction can activate gliosis even in a context of low or absent transgene expression when using the hAAT promoter, and that these responses are not unique to the GFP transgene. These responses could be partially modulated through pharmacological inhibition of p53 or of the cGAS- STING pathway, highlighting that vector genome sensing contributes to the activation of local innate immune cells, particularly astrocytes. Results from this experiment are shown in Supplementary Figure 20 and described on lines 339- 356, pages 13- 14 of the revised manuscript. This data further supports the involvement of cGAS/STING signalling in AAV- mediated effects in the CNS and are described and discussed on lines 442- 446, page 17 and lines 480- 483, page 18 of the revised manuscript. In addition, as the focus of our work is not solely on STING- mediated effects, and in agreement with other Reviewer suggestions, we have also modified the title of our manuscript to better reflect the overall findings that are reported as follows: "AAV vectors trigger DNA damage responses and pro- inflammatory signalling in human iPSC- derived CNS models and mouse brain". + +6. The mechanistic explanation for the reported phenomenon is under-developed. The authors should provide deeper explanation of the temporal, spatial, and cell-type-specific roles of the cGAS-STING, RLR-MAVS, and inflammasome pathways. + +We thank the Reviewer for the suggestion and have better discussed this in the revised manuscript, lines 521- 527, page 20, as follows: "Mechanistically, we propose a working model in which the incoming vector DNA triggers a first p53- dependent DNA damage response that will subsequently activate the cGAS/STING mediated inflammatory signalling. Conversely, the type I IFN activation seems mainly driven by cytosolic RNA sensing that converges to the adaptor molecule MAVS in this context, potentially enhancing pro-inflammatory signalling as compared to conditions in which the transgene is not expressed". This working model is also summarized in the graphical abstract, pasted below. + +![PLACEHOLDER_29_0] + + +## Graphical abstract + +7. The key question – and it can be claimed the motivation for the present study – is to understand mechanisms underlying “dose-dependent toxicities and severe adverse events” of AAV-based gene + +<--- Page Split ---> + +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +therapy. Therefore, the authors need to provide data demonstrating physiological importance of the identified innate immunological activities. + +We thank the Reviewer for this comment. Our study links clinical findings with mechanistic insight (Bharucha- Goebel et al, 2024; Gougeon et al, 2021; Mueller et al, 2020; Sondhi et al, 2020) that may well be connected to our observations, as discussed lines 527- 536, page 20 of the revised manuscript. To further strengthen the physiological importance of our work, we have performed a proof- of- principle study showing that the use of inhibitors that target p53 or the cGAS/STING signalling axis can curb the AAV genome- triggered gliosis upon local AAV delivery in vivo. Briefly, mice were injected in the striatum with a transgene- silent AAV with concomitant intraperitoneal administration of identified pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) and STING (H151) and assessed their effect on gliosis on striatum sections. Although we acknowledge that the brain permeability and optimal dose of these drugs may remain limitations of this experimental approach, our analyses reveal that all three treatments decreased the presence of GFAP+ cells in striatum compared to mice injected with AAV only, while they had no effect on the lba1 population nor the NeuN positive cells, suggesting that pharmacological targeting of p53 or the cGAS- STING pathway can curb at least to some extent the vector- induced gliosis without overt toxicity on the CNS cell populations. Results from this experiment are shown in Supplementary Figure 20. We also acknowledge that further studies should be performed to confirm the effect of these drugs in the future including also transgene- expressing vectors for side- by- side comparison, lines 511- 516, pages 19- 20 of the revised manuscript, but wish to mention here that because of recent reorganization within the collaborating biotech company that has performed these experiments, we will not be able to provide additional experiments for this part at this stage. Together, these results further support physiological relevance for these signalling pathways in preventing inflammation in the CNS upon AAV injection. + +Minor comments. + +8. This reviewer find that the term "cell-intrinsic innate immune mechanisms" is not correctly used in this work. Since, the data show upregulation of e.g. interferon pathways, which act in a paracrine manner, the activities discovered are not cell-intrinsic (although some of the effector mechanisms may be). I suggest that the authors simple use the term "innate immune mechanisms. + +We thank the Reviewer for this suggestion and have applied it throughout the revised manuscript. + +9. The finding that virus infections in the brain and brain cells triggers apoptosis in a cGAS-STING dependent manner has been reported previously (e.g. PMID: 32990676) and should be cited. + +We thank the Reviewer for this suggestion and have referenced this work on line 463- 464, page 18 of the revised manuscript. + +## References: + +Bennett A, Patel S, Mietzsch M, Jose A, Lins- Austin B, Yu JC, Bothner B, McKenna R, Agbandje- McKenna M (2017) Thermal Stability as a Determinant of AAV Serotype Identity. Molecular Therapy Methods & Clinical Development 6: 171- 182 Bertolini TB, Shirley JL, Zolotukhin I, Li X, Kaisho T, Xiao W, Kumar SRP, Herzog RW (2021) Effect of CpG Depletion of Vector Genome on CD8(+) T Cell Responses in AAV Gene Therapy. Front Immunol 12: 672449 + +<--- Page Split ---> + +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +Bharucha- Goebel DX, Todd JJ, Saade D, Norato G, Jain M, Lehky T, Bailey RM, Chichester JA, Calcedo R, Armao D et al (2024) Intrathecal Gene Therapy for Giant Axonal Neuropathy. N Engl J Med 390: 1092- 1104 Cervelli T, Palacios JA, Zentilin L, Mano M, Schwartz RA, Weitzman MD, Giacca M (2008) Processing of recombinant AAV genomes occurs in specific nuclear structures that overlap with foci of DNA- damage- response proteins. Journal of cell science 121: 349- 357 Chan YK, Wang SK, Chu CJ, Copland DA, Letizia AJ, Costa Verdera H, Chiang JJ, Sethi M, Wang MK, Neidermyer WJ, Jr. et al (2021) Engineering adeno- associated viral vectors to evade innate immune and inflammatory responses. Sci Transl Med 13 Fischer M (2019) Conservation and divergence of the p53 gene regulatory network between mice and humans. Oncogene 38: 4095- 4109 Fischer M (2021) Mice Are Not Humans: The Case of p53. Trends Cancer 7: 12- 14 Ge MM, Chen N, Zhou YQ, Yang H, Tian YK, Ye DW (2022) Galectin- 3 in Microglia- Mediated Neuroinflammation: Implications for Central Nervous System Diseases. Curr Neuropharmacol 20: 2066- 2080 Ghosh M, Saha S, Li J, Montrose DC, Martinez LA (2023) p53 engages the cGAS/STING cytosolic DNA sensing pathway for tumor suppression. Mol Cell 83: 266- 280. e266 Golebiowski D, van der Bom IMJ, Kwon CS, Miller AD, Petrosky K, Bradbury AM, Maitland S, Kuhn AL, Bishop N, Curran E et al (2017) Direct Intracranial Injection of AAVrh8 Encoding Monkey beta- N- Acetylhexosaminidase Causes Neurotoxicity in the Primate Brain. Hum Gene Ther 28: 510- 522 Gougeon ML, Poirier- Beaudouin B, Ausseil J, Zerah M, Artaud C, Heard JM, Deiva K, Tardieu M (2021) Cell- Mediated Immunity to NAGLU Transgene Following Intracerebral Gene Therapy in Children With Mucopolysaccharidosis Type IIIB Syndrome. Front Immunol 12: 655478 Guo Y, Chen J, Ji W, Xu L, Xie Y, He S, Lai C, Hou K, Li Z, Chen G, Wu Z (2023) High- titer AAV disrupts cerebrovascular integrity and induces lymphocyte infiltration in adult mouse brain. Mol Ther Methods Clin Dev 31: 101102 Hanzelmann S, Castelo R, Guinney J (2013) GSVA: gene set variation analysis for microarray and RNA- seq data. BMC Bioinformatics 14: 7 Hirsch ML, Fagan BM, Dumitru R, Bower JJ, Yadav S, Porteus MH, Pevny LH, Samulski RJ (2011) Viral single- strand DNA induces p53- dependent apoptosis in human embryonic stem cells. PLoS One 6: e27520 Hollidge BS, Carroll HB, Qian R, Fuller ML, Giles AR, Mercer AC, Danos O, Liu Y, Bruder JT, Smith JB (2022) Kinetics and durability of transgene expression after intrastriatal injection of AAV9 vectors. Front Neurol 13: 1051559 Hordeaux J, Buza EL, Dyer C, Goode T, Mitchell TW, Richman L, Denton N, Hinderer C, Katz N, Schmid R et al (2020a) Adeno- Associated Virus- Induced Dorsal Root Ganglion Pathology. Hum Gene Ther 31: 808- 818 Hordeaux J, Buza EL, Jeffrey B, Song C, Jahan T, Yuan Y, Zhu Y, Bell P, Li M, Chichester JA et al (2020b) MicroRNA- mediated inhibition of transgene expression reduces dorsal root ganglion toxicity by AAV vectors in primates. Sci Transl Med 12 Kay J, Thadhani E, Samson L, Engelward B (2019) Inflammation- induced DNA damage, mutations and cancer. DNA Repair (Amst) 83: 102673 Lock M, McGorry S, Auricchio A, Ayuso E, Beecham EJ, Blouin- Tavel V, Bosch F, Bose M, Byrne BJ, Caton T et al (2010) Characterization of a recombinant adeno- associated virus type 2 Reference Standard Material. Hum Gene Ther 21: 1273- 1285 Mason MR, Ehlert EM, Eggers R, Pool CW, Hermening S, Huseinovic A, Timmermans E, Blits B, Verhaagen J (2010) Comparison of AAV serotypes for gene delivery to dorsal root ganglion neurons. Mol Ther 18: 715- 724 + +<--- Page Split ---> + +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS + +Mueller C, Berry JD, McKenna- Yasek DM, Gernoux G, Owegi MA, Pothier LM, Douthwright CL, Gelevski D, Luppino SD, Blackwood M et al (2020) SOD1 Suppression with Adeno- Associated Virus and MicroRNA in Familial ALS. N Engl J Med 383: 151- 158 + +Ortinski PI, Dong J, Mungenast A, Yue C, Takano H, Watson DJ, Haydon PG, Coulter DA (2010) Selective induction of astrocytic gliosis generates deficits in neuronal inhibition. Nature Neuroscience 13: 584- 591 + +Piras F, Riba M, Petrillo C, Lazarevic D, Cuccovillo I, Bartolaccini S, Stupka E, Gentner B, Cittaro D, Naldini L, Kajaste- Rudnitski A (2017) Lentiviral vectors escape innate sensing but trigger p53 in human + +hematopoietic stem and progenitor cells. EMBO Mol Med 9: 1198- 1211 + +Pollock NM, Fernandes JP, Woodfield J, Moussa E, Hlavay B, Branton WG, Wuest M, Mohammadzadeh N, Schmitt L, Plemel JR et al (2024) Gasdermin D activation in oligodendrocytes and microglia drives + +inflammatory demyelination in progressive multiple sclerosis. Brain Behav Immun 115: 374- 393 + +Rogers GL, Shirley JL, Zolotukhin I, Kumar SRP, Sherman A, Perrin GQ, Hoffman BE, Srivastava A, Basner- Tschakarjan E, Wallet MA et al (2017) Plasmacytoid and conventional dendritic cells cooperate in + +crosspriming AAV capsid- specific CD8(+) T cells. Blood 129: 3184- 3195 + +Sondhi D, Kaminsky SM, Hackett NR, Pagovich OE, Rosenberg JB, De BP, Chen A, Van de Graaf B, Mezey JG, Mammen GW et al (2020) Slowing late infantile Batten disease by direct brain parenchymal + +administration of a rh.10 adeno- associated virus expressing \(< \mathrm{i} > \mathrm{CLN}2< /\mathrm{i}>\) . Science Translational Medicine 12: eabb5413 + +Tahtinen S, Tong AJ, Himmels P, Oh J, Paler- Martinez A, Kim L, Wichner S, Oei Y, McCarron MJ, Freund EC et al (2022) IL- 1 and IL- 1ra are key regulators of the inflammatory response to RNA vaccines. Nat + +Immunol 23: 532- 542 + +Valeri E, Breggion S, Barzaghi F, Abou Alezz M, Crivicich G, Pagani I, Forneris F, Sartirana C, Costantini M, Costi S et al (2024) A novel STING variant triggers endothelial toxicity and SAVI disease. J Exp Med 221 + +Wright JF (2020) Quantification of CpG Motifs in rAAV Genomes: Avoiding the Toll. Mol Ther 28: 1756- + +1758 + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +I want to thank the authors for doing such a good job of addressing my comments. Overall, I think that this is one of the best attempts that I have seen as a reviewer to address all reviewer comments in detail (and there were many comments). This is an excellent manuscript that was made even better with these revisions. I recommend immediate publication. + +We thank the Reviewer for appreciating our efforts and for retaining our work much improved (thanks to the constructive comments) and of high relevance for the field. + +Reviewer #2 (Remarks to the Author): + +The authors were responsive to the reviewer comments. The manuscript is easier to read and the figures are clearer. It is acceptable for publication. + +We thank the Reviewer for the positive feedback and for retaining our work improved and ready for publication at this stage. + +Reviewer #3 (Remarks to the Author): + +the authors have addressed this reviewer's comments clearly, in some cases, being supported by robust experimental data. I have no further concerns. + +We thank the Reviewer for the positive feedback and for retaining our work ready for publication at this stage. + +Reviewer #5 (Remarks to the Author): + +The authors have greatly improved the work during the revision. However, I remain rather critical to conclusions drawn from the mechanistic work. The claim that the host response involves the cGAS- STING and the RLR- MAVS pathways is not based on data from KO mouse strains, which are readily available. In the absence of such data. I do not find the mechanistic claims well supported by the data. + +We thank the Reviewer for the overall positive feedback and agree that additional experimental validation of involved signalling pathways in genetic knockout models will further strengthen our observations in the future. We hope that the reviewer agrees that this work sets the stage for further molecular dissection of the vector signalling both in vitro and in vivo in relevant models, including the mentioned KO mice strains. We have included to following sentence: "Nevertheless, the contribution of cGAS/STING and MAVS pathways to vector sensing will benefit from further confirmations in genetic mouse models and further studies will help to elucidate the clinical impact of these molecular findings", lines 524- 527 of the revised manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6a580f215997a3ee224ae13ce3c8db86f077a623 --- /dev/null +++ b/peer_reviews/332eaef6f2a04a82806e5273dc5fd96e332fe6e034758ca6c3ddafef1041a5a5/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1023 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 161, 904, 234]]<|/det|> +# AAV vectors trigger DNA damage response-dependent pro-inflammatory signalling in human iPSC-derived CNS models and mouse brain + +<|ref|>text<|/ref|><|det|>[[73, 249, 501, 266]]<|/det|> +Corresponding Author: Dr Anna Kajaste- Rudnitski + +<|ref|>text<|/ref|><|det|>[[72, 299, 864, 314]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 352, 144, 365]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 378, 219, 391]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 404, 160, 417]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 430, 238, 443]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 443, 914, 495]]<|/det|> +In this study Costa- Verdera et al study the host transcriptome globally and at a single cell/nuclei level following AAV infection of neural cells and 3D organoids, as well as the mouse brain. The transcriptome is studied in vitro in human iPSC- derived neurons, astrocytes and oligodendrocytes, mixed neural cultures and 3D organoids, as well as in vivo in mouse striatum. Many interesting observations are made from a large dataset including: + +<|ref|>text<|/ref|><|det|>[[72, 507, 841, 586]]<|/det|> +- Early activation of the p53 pathway and TNF/IL-1 signaling by AAV (genome-dependent)- Early activation of DNA damage responses by AAV (genome-dependent)- Delayed transgene expression-dependent/p53-independent/MAVS-dependent activation of ISGs by AAV- AAV causes p53-dependent apoptosis via cleaved Caspase-3- STING inhibition, p53 inhibition and IL-1Ra treatment block AAV IL-1b/CXCL8 activation but not ISG activation.- STING inhibition blocks AAV-mediated apoptosis + +<|ref|>text<|/ref|><|det|>[[72, 597, 914, 677]]<|/det|> +This is a vast and complicated story and the authors simultaneously try to understand what appear to be many different but potentially interconnected pathways that are activated in different cell types and across different time points after AAV exposure. The authors should be commended for addressing the importance of host response to AAV in the brain in the context of neurotoxicity. However, their story is highly complex and as a result questions are left unanswered as the authors try to address several different observations across many experiments. This is an important topic and the scope and quality of the study is appropriate for Nature Communications, but several issues need to be addressed. + +<|ref|>text<|/ref|><|det|>[[73, 690, 159, 703]]<|/det|> +Major points + +<|ref|>text<|/ref|><|det|>[[72, 715, 916, 767]]<|/det|> +1. The relevance of the in vitro observations in terms of their in vivo significance need to be solidified, particularly in the context of antagonistic blockade of AAV-related toxicities. Since similar pathways are activated in human cells and mouse striatum, it is assumed that signaling blockade can translate to mouse brain but this should be validated. Effects of localized IL-1Ra, STING inhibition, MAVS inhibition and p53 inhibition should be studied in mouse brain. + +<|ref|>text<|/ref|><|det|>[[72, 780, 910, 832]]<|/det|> +2. The title does not address all of the observations made in this study and also implies the observations were restricted to human cells. For example, STING is highlighted in the title but isn't mentioned in the story until the last experiment and is only one of several key players in all of the described pathways and responses. A more general or encompassing title should be considered. + +<|ref|>text<|/ref|><|det|>[[72, 845, 919, 885]]<|/det|> +3. If STING and DNA damage responses are the focus of the paper as suggested by the title more exploration of them is required. For example, validation of the potential for STING antagonism should be performed in mouse striatum at a dose of AAV known to be neurotoxic. + +<|ref|>text<|/ref|><|det|>[[72, 898, 923, 939]]<|/det|> +4. Lines 125-128 – The authors state “Of note, empty AAV9 capsid did not induce any significant transcriptional changes compared to untransduced controls, in contrast to the full AAV9 vector (Fig. 1E-H), suggesting that the vector genome is required for the detected signaling.”. Figures 1E-H support this statement. However, when you look globally across the entire + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 890, 75]]<|/det|> +dataset the AAV9 profile is more like the untransduced profile than the empty (AAV9) profile (Figure 1C, UT vs empty vs AAV9), contradicting this statement. This should be discussed further. + +<|ref|>text<|/ref|><|det|>[[72, 86, 888, 114]]<|/det|> +5. Fig 1C/D – Why was empty AAV9 used as a control when 'full' AAV9 stimulated the lowest transcriptional response? Empty AAV2 which was more transcriptionally reactive should be compared? + +<|ref|>text<|/ref|><|det|>[[72, 125, 905, 205]]<|/det|> +6. The reviewer appreciates that every experiment can't be performed with every dose, serotype, promoter, transgene combination, etc. However, there is a lot of back and forth between experimental (mainly AAV) details across different culture types and mice as the paper progresses. At some point in the paper, it is almost assumed that all serotypes are equivalent as the authors switch between AAV2, AAV6, Spark100 and AAV9, when the early experiments show there can be clear differences. The generalization that all responses are serotype independent are in places too presumptive and should be tempered. + +<|ref|>text<|/ref|><|det|>[[72, 216, 901, 256]]<|/det|> +7. What is known about relative AAV receptor expression levels (HSPG, sialic acid, galactose, AAVR) in hiPSC-derived cells and organoids (neurons vs astrocytes vs oligodendrocytes), since signaling through different receptors may impact downstream transcriptional observations across the different serotypes studied? + +<|ref|>text<|/ref|><|det|>[[72, 267, 920, 335]]<|/det|> +8. In Fig 6, snRNAseq is performed in mice given AAV9.CAG-EGFP via IPa then for some reason the DNA damage response observations in the striatum are validated in mice after ICV and not IPa delivery of AAV9.PGK-EF1a.Cre-EGFP. This validation should be performed after IPa delivery of the same vector. It is also not clear what AAV9.PGK-EF1a.Cre-GFP is. Is GFP expression conditional (Cre expressing mice were not used) or does it express 2 transgenes (Cre and GFP), which complicates observations made in Fig S8 in relation to Fig 6. + +<|ref|>sub_title<|/ref|><|det|>[[72, 346, 159, 360]]<|/det|> +## Minor points + +<|ref|>text<|/ref|><|det|>[[72, 371, 899, 425]]<|/det|> +1. Lines 164-167 – The authors state “Overall, upregulation of signaling pathways was more significant in the 3D model compared to the 2D mixed cultures (Fig. 3E, Fig. 4E), suggesting active cross talk and paracrine effects of AAV signaling across cells of the human CNS.”, however, this could just be an MOI effect whereby cells on the outside of a 3D spheroid take up more AAV in culture, which in turn causes greater peak activation levels. Please discuss. + +<|ref|>text<|/ref|><|det|>[[72, 436, 535, 450]]<|/det|> +2. Are different responses seen between ssAAV vs scAAV vectors? + +<|ref|>text<|/ref|><|det|>[[70, 462, 899, 491]]<|/det|> +3. Table S1 reports the AAV ‘dose’ in v.p./cell but elsewhere vg/cell is used as the unit for infection. Are the reported MOI based on particles or genomes? + +<|ref|>text<|/ref|><|det|>[[72, 502, 722, 516]]<|/det|> +4. No methods are provided for genome titer and/or AAV particle determination, please include. + +<|ref|>text<|/ref|><|det|>[[72, 528, 488, 542]]<|/det|> +5. Details of the ICV injection procedure should be provided. + +<|ref|>text<|/ref|><|det|>[[72, 554, 480, 568]]<|/det|> +6. Fig 1D – Why were Spark100, AAV1 and AAV6 omitted? + +<|ref|>text<|/ref|><|det|>[[72, 580, 468, 593]]<|/det|> +7. Fig S3B – x-axis legend should read full and not AAV9 + +<|ref|>text<|/ref|><|det|>[[70, 605, 880, 633]]<|/det|> +8. Fig 5B-D – The SPARK100-hAAT-GFP vector should be added to the right-hand ‘transgene minus’ panel for easier comparison since GFP isn’t expressed. + +<|ref|>text<|/ref|><|det|>[[70, 644, 915, 672]]<|/det|> +9. mRNA is not expressed from the hAAT promoter in hiPSC-derived neurons. How would responses compare between the hAAT-GFP vector and a vector that produces an mRNA but is not translated (e.g. ATG deleted GFP)? + +<|ref|>text<|/ref|><|det|>[[70, 683, 920, 711]]<|/det|> +10. Fig 6 – This study was performed at a single AAV dose. Why was this dose chosen? How representative is this dose per g of brain to those used in other animal studies where CNS toxicity has been observed? + +<|ref|>text<|/ref|><|det|>[[70, 722, 920, 750]]<|/det|> +11. Fig S9B – MAVS blockade appears to accentuate AAV induction of IL-1 and CXCL8 substantially. This is not mentioned and should be discussed? + +<|ref|>text<|/ref|><|det|>[[73, 761, 314, 775]]<|/det|> +12. FigS10 – legend says figure 10 + +<|ref|>text<|/ref|><|det|>[[73, 787, 310, 801]]<|/det|> +13. Fig S9 legend – typo ‘signallig’ + +<|ref|>sub_title<|/ref|><|det|>[[72, 826, 162, 840]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 853, 238, 866]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 867, 920, 945]]<|/det|> +The manuscript by Costa-Verdera and colleagues describes the transcriptional responses that arise in AAV- transduced cells of the CNS that were derived from hiPSC. The authors study 2d cultures of neurons, astrocytes and oligodendrocytes as well as brain spheroids tested after transduction by several different AAV capsids (AAV1, AAV2, AAV5, AAV6 AAV9 and Spk100). The authors determine the ability of these different capsids to transduce each cell type as well as the consequence of transduction on inflammatory signaling and DNA damage responses. They demonstrate that different capsid serotypes have varying abilities to transduce neurons and astrocytes (and in some cases oligodendrocytes). Furthermore, they + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 112]]<|/det|> +demonstrate that AAV transduction correlates with activation of DNA damage repair pathways (p53 mediated) and activation of some inflammatory pathways. These two findings regarding the induction of p53 and inflammatory pathways are not completely novel, but the comprehensive approach being taken by the authors and the testing of many different CNS cell types against a large number of capsids is a strength of the paper. The authors also carry out in vivo experiments in mice by ICV injection and demonstrate the level of transduction of different cell types and some single cell gene expression data. + +<|ref|>text<|/ref|><|det|>[[72, 124, 924, 308]]<|/det|> +The strengths of the manuscript include 1) the comprehensive testing of a variety of CNS cell types which demonstrates some consistent patterns of p53 induction and inflammatory signaling across different culture conditions (2D vs 3D), 3) the testing of many different AAV vector serotypes for their ability to transduce these various cell types and 3) numerous assessments of transcriptional changes that demonstrate inflammatory and DNA damage responses. The weaknesses of the manuscript are 1) some experiments are not well controlled, such as Fig. 5 where the authors use several promoters and transgenes in parallel but do not control for the CpG content of the vectors. These constructs will all have different risk factors for activating TLR9 signaling, which is activated within hours of transduction and has many cascading downstream effects; 2) the single cell data is not explored beyond identifying cell types and 3) the timepoints tested do not allow the authors to capture TLR signaling that occurs early after transduction (less than 12 hours post AAV transduction). Because they collected the samples so late after transduction, it becomes difficult to discriminate transgene induced TLR signaling vs capsid responses (such as in Fig. 5). The authors did a tremendous amount of work for this manuscript and it would be very difficult to repeat everything to obtain an early time point, but the authors do need to acknowledge that TLR signaling will influence downstream signaling. The specifics regarding Figure 5 are detailed below. Overall this is a strong manuscript that has a lot of important information that will be valuable to readers. + +<|ref|>text<|/ref|><|det|>[[72, 320, 920, 346]]<|/det|> +Fig. 1A. Can the authors show examples of the FACS plots where they determined GFP+ cells and show the gating that was used to identify the positive cells. + +<|ref|>text<|/ref|><|det|>[[72, 346, 920, 373]]<|/det|> +It would be good to show the vector copy number (currently in supplemental) in the main figures alongside the GFP+ mRNA. Figs 1E and F could be moved to the supplemental if space is needed. + +<|ref|>text<|/ref|><|det|>[[72, 385, 916, 426]]<|/det|> +Supplementary Table 1: There seems to be information missing from the table. Also, could the authors state the titer in viral genomes, since it is the transgene that is inducing most of the response; thus, one would like to know the level of transgene instead of viral particles. + +<|ref|>text<|/ref|><|det|>[[72, 437, 912, 478]]<|/det|> +Figure 3B: The authors should show how the frequency of their cell populations change with dosing between days 2 and 4. Can they show individual UMAPS and normalized cell numbers by time point? Also could the authors provide some of the top differentially expressed genes in addition to the pathways? + +<|ref|>text<|/ref|><|det|>[[72, 478, 707, 491]]<|/det|> +Figure 3D: It would be best if the colors in Fig. 3D could match the colors for Figs 3B and 3C. + +<|ref|>text<|/ref|><|det|>[[72, 503, 911, 557]]<|/det|> +Figure 5: In this figure the authors use different promoter and transgene constructs to transduce 3D spheroids, followed by isolation of transgene + and transgene - cells and subsequently compare the transcriptional patterns between the different cell types and between transgene + and transgene - cells. They also use two different capsids and use other promoter + transgene constructs. The vast diversity of constructs and cell types makes this figure very complicated to interpret. + +<|ref|>text<|/ref|><|det|>[[72, 568, 914, 647]]<|/det|> +One main issue is that the authors do not consider how differences in CpG motifs (in each construct used) has the potential to impact TLR9 signaling. Thus, the experiment is very difficult to interpret. So while the authors used a control (Spark100 HAAT construct) that does not express protein, they did not take into consideration the fact that the presence of the viral genome will ALSO stimulate inflammatory signaling independent of protein expression. The experiment is not well controlled and therefore, conclusions are difficult to make. The interpretation of this experiment needs to be toned down considerably. + +<|ref|>text<|/ref|><|det|>[[72, 647, 923, 687]]<|/det|> +1) Line 174: They are not able to state that different AAV serotypes induce different inflammatory signatures. The authors have proven that the AAV capsid determines whether the AAV particle can enter a cell but they have not proven that different signatures arise due to different capsids. + +<|ref|>text<|/ref|><|det|>[[72, 698, 923, 764]]<|/det|> +2) Line 201: The authors cannot discriminate transgene specific responses due to lack of consideration for the differences in the different risk factor potentials to stimulate TLR9 signaling (formula published by J. Fraser Wright https://doi.org/10.1016/j.ymthe.2020.07.006), which is inherent to each transgene. So the comment that GAA stimulates more inflammatory signaling is likely due to a difference in the RF3. Furthermore, the idea of paracrine signaling (line 204) has not been proven. + +<|ref|>text<|/ref|><|det|>[[72, 776, 923, 817]]<|/det|> +3) Line 207: The authors conclude that the vector genomes induce the p53 response, but this point is not proven at all. There are p53 responses in both transgene + and transgene - populations. It is recommended that the authors deconstruct this figure and parse out the points that they can make conclusively. + +<|ref|>text<|/ref|><|det|>[[72, 828, 888, 855]]<|/det|> +4) Fig. S6: The authors do not control for the TLR risk factor here, which could be significantly different between the two promoters, so it is difficult to make any firm conclusions from this study. + +<|ref|>text<|/ref|><|det|>[[72, 866, 884, 907]]<|/det|> +Line 246: The authors state that type I IFN signaling in AAV transduced human and mouse CNS cells triggers IFN1 signaling. This statement does not consider TLR9 signaling, which can trigger IFN1 signaling via CpG motifs in the transgene. + +<|ref|>text<|/ref|><|det|>[[72, 907, 904, 948]]<|/det|> +Figure 6: The authors carry out ICV injections, isolate CNS cells after 28 days and carry out single cell sequencing. The authors do not see p53 dependent responses in vivo, which is hard to reconcile with their other studies. Is the mouse different than human, is it an in vivo vs in vitro issue or is it a timing problem? This figure could be the basis for a full paper + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 923, 127]]<|/det|> +that carefully assesses time points in the mouse and compares to the in vitro studies. If the authors want to include this study, I recommend that they extend their single cell data analysis and show in the figure how cell frequencies and phenotypes change with AAV dosing in vivo. In addition, they should demonstrate how those changes are similar and/or different from hiPSCs. I would recommend they show violin plots of individual genes and demonstrate how they are consistent or differ with observations made in the hiPSC- derived CNS cells. Since no violin plots are shown in the prior parts of the manuscript, they could show them here, so it is easy for the reader to compare across cell types vs the in vivo studies. + +<|ref|>text<|/ref|><|det|>[[70, 138, 923, 195]]<|/det|> +Also, for this in vivo study, the authors should make comparisons of how AAV transduction of individual CNS cells compares to hiPSC derived CNS cells. Supplemental Fig. 8: In the figure legend the authors should state what is being stained and how the heat maps were obtained. + +<|ref|>text<|/ref|><|det|>[[72, 203, 900, 244]]<|/det|> +Supplemental Figure 10: Why didn't the authors treat the cells with the inhibitors prior to transducing them? Since these signaling pathways are triggered upon AAV entry, the TLR pathway cannot be ruled out as upstream of some of the gene induction. + +<|ref|>sub_title<|/ref|><|det|>[[72, 307, 162, 320]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 334, 238, 347]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 347, 904, 386]]<|/det|> +This is an interesting, informative, and timely study, addressing a major barrier in translating rAAV- based gene therapy to clinical application. Overall, the manuscript is well written, data thoughtfully analyzed and presented. However, the manuscript can be further strengthened if the authors can address the points below. + +<|ref|>text<|/ref|><|det|>[[72, 385, 918, 424]]<|/det|> +1. In general, the time between AAV transduction and data collection seems to be longer than what is needed by the cells to initiate a DNA damage repair and innate immune responses. Could the authors explain clearly for the rationale to choose these timepoints? + +<|ref|>text<|/ref|><|det|>[[70, 423, 910, 450]]<|/det|> +2. Also, it would be informative to study /compare the outcomes of transduction by single stranded and self-complementary rAAVs. + +<|ref|>text<|/ref|><|det|>[[72, 450, 920, 503]]<|/det|> +3. For the data presented in Figure 1, in terms of transcriptomic changes with and without AAV vectors, those transduced by AAV9 appears to have milder changes compared to those transduced by AAV2 and AAV6, presumably due to less efficient transduction efficiency. Is there a way to first sort GFP+ cells, and then analyze transcriptomic changes in GFP+ cells alone? Alternatively, will it be a good idea to "normalize" transcriptomic changes based on GFP+ percentage? + +<|ref|>text<|/ref|><|det|>[[72, 503, 911, 542]]<|/det|> +4. For the data described by Figure 2: Why did the authors chose 48 h post transduction as the time to assay caspase 3 cleavage? Would assaying an earlier time point (12h or 24h) give a more pronounced result? A general expectation would be that DNA damage response is induced much sooner than 48 h, especially for a flat-surface cell culture. + +<|ref|>text<|/ref|><|det|>[[72, 542, 916, 581]]<|/det|> +5. After carefully reviewing the data presented in Figure 4, the p53 pathway in neurons seems to increase from day 2 to day 5. But by day 5, one would assume that the DNA cargo has already undergone ds synthesis and started episode formation. Why does the response appear to be delayed? Would simple transfection of episomes lead to p53 pathway activation? + +<|ref|>text<|/ref|><|det|>[[72, 581, 920, 607]]<|/det|> +Please see a similar comments above. + +<|ref|>text<|/ref|><|det|>[[72, 597, 920, 624]]<|/det|> +6. For the data presented in Figure 6, The author should explain better why the in vivo study was performed at day 28, which is very late for assaying innate immune responses against foreign DNA motifs. + +<|ref|>text<|/ref|><|det|>[[72, 623, 920, 662]]<|/det|> +7. One major concern is the experiment described in Figure 8. There is evidence suggesting that STING inhibitor H151 only works for STING-HAQ mutation but not WT STING. Did the authors genotype the hiPSCs? Are they STING HAQ or WT STING? + +<|ref|>sub_title<|/ref|><|det|>[[72, 687, 161, 700]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 712, 238, 725]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 725, 864, 764]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>sub_title<|/ref|><|det|>[[72, 777, 161, 789]]<|/det|> +## Reviewer #5 + +<|ref|>text<|/ref|><|det|>[[72, 803, 238, 816]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 816, 918, 895]]<|/det|> +In this work Costa- Verdera et al have used iPSC- derived human brain cell/spheroid systems and mouse models to examine the hose immune response to AAV transduction in the brain. The authors report that AAV- induces p53- dependent DNA damage responses together with STING- and IL1R- dependent inflammatory responses. In addition, they report an involvement of MAVS in the host response evoked by AAV. Although the question under investigation is very timely, and many of the observations are intriguing, the work appears very descriptive at this stage and mechanistically rather underdeveloped. + +<|ref|>text<|/ref|><|det|>[[72, 908, 192, 920]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[70, 920, 910, 946]]<|/det|> +1. Microglia expresses the highest levels of both cGAS and STING among brain-resident cells. The authors should include this cell type in the analysis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 60, 907, 88]]<|/det|> +2. The data are mainly based on a transcriptional approach. For key activated pathways, e.g. IFN signaling, this should be complemented with protein data. + +<|ref|>text<|/ref|><|det|>[[70, 99, 920, 127]]<|/det|> +3. CL-CASP3 does not equal apoptosis – in fact could drive GSDME-mediated pyroptosis. The modality of cell death should be further investigated, including the dependency on the innate immune signaling pathways studied. + +<|ref|>text<|/ref|><|det|>[[70, 138, 900, 166]]<|/det|> +4. Brain infections with pathogenic viruses are well-described in lead to influx of immune cells from the periphery, most notably monocytes and T cells. The mouse work would gain a lot if the influx of at least these two cell types is evaluated. + +<|ref|>text<|/ref|><|det|>[[70, 177, 920, 218]]<|/det|> +5. The conclusion that the innate immune response to AAV transduction is STING dependent is based only on the use of the STING inhibitor, which is not specific. Therefore, it should be tested whether the observed response is ablated in cGAS or STING-deficient mice. + +<|ref|>text<|/ref|><|det|>[[70, 230, 880, 270]]<|/det|> +6. The mechanistic explanation for the reported phenomenon is under-developed. The authors should provide deeper explanation of the temporal, spatial, and cell-type-specific roles of the cGAS-STING, RLR-MAVS, and inflammasome pathways. + +<|ref|>text<|/ref|><|det|>[[70, 281, 914, 322]]<|/det|> +7. The key question – and it can be claimed the motivation for the present study – is to understand mechanisms underlying "dose-dependent toxicities and severe adverse events" of AAV-based gene therapy. Therefore, the authors need to provide data demonstrating physiological importance of the identified innate immunological activities. + +<|ref|>text<|/ref|><|det|>[[72, 348, 191, 360]]<|/det|> +Minor comments. + +<|ref|>text<|/ref|><|det|>[[72, 360, 912, 412]]<|/det|> +8. This reviewer find that the term "cell-intrinsic innate immune mechanisms" is not correctly used in this work. Since, the data show upregulation of e.g. interferon pathways, which act in a paracrine manner, the activities discovered are not cell-intrinsic (although some of the effector mechanisms may be). I suggest that the authors simple use the term "innate immune mechanisms. + +<|ref|>text<|/ref|><|det|>[[70, 423, 905, 451]]<|/det|> +9. The finding that virus infections in the brain and brain cells triggers apoptosis in a cGAS-STING dependent manner has been reported previously (e.g. PMID: 32990676), and should be cited. + +<|ref|>text<|/ref|><|det|>[[72, 490, 144, 503]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 515, 219, 529]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 541, 160, 555]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 567, 238, 580]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 580, 918, 620]]<|/det|> +I want to thank the authors for doing such a good job of addressing my comments. Overall, I think that this is one of the best attempts that I have seen as a reviewer to address all reviewer comments in detail (and there were many comments). This is an excellent manuscript that was made even better with these revisions. I recommend immediate publication. + +<|ref|>text<|/ref|><|det|>[[72, 632, 161, 645]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 658, 238, 671]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 671, 900, 699]]<|/det|> +The authors were responsive to the reviewer comments. The manuscript is easier to read and the figures are clearer. It is acceptable for publication. + +<|ref|>text<|/ref|><|det|>[[72, 711, 161, 723]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 737, 238, 749]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 750, 923, 776]]<|/det|> +the authors have addressed this reviewer's comments clearly, in some cases, being supported by robust experimental data. I have no further concerns. + +<|ref|>text<|/ref|><|det|>[[72, 790, 161, 802]]<|/det|> +Reviewer #5 + +<|ref|>text<|/ref|><|det|>[[72, 816, 238, 828]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 828, 918, 881]]<|/det|> +The authors have greatly improved the work during the revision. However, I remain rather critical to conclusions drawn from the mechanistic work. The claim that the host response involves the cGAS-STING and the RLR-MAVS pathways is not based on data from KO mouse strains, which are readily available. In the absence of such data. I do not find the mechanistic claims well supported by the data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 46, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 450, 107]]<|/det|> +## Point-by- point reply to Reviewer Comments + +<|ref|>text<|/ref|><|det|>[[116, 124, 393, 140]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 157, 883, 243]]<|/det|> +In this study Costa- Verdera et al study the host transcriptome globally and at a single cell/nuclei level following AAV infection of neural cells and 3D organoids, as well as the mouse brain. The transcriptome is studied in vitro in human iPSC- derived neurons, astrocytes and oligodendrocytes, mixed neural cultures and 3D organoids, as well as in vivo in mouse striatum. Many interesting observations are made from a large dataset including: + +<|ref|>text<|/ref|><|det|>[[115, 275, 772, 293]]<|/det|> +- Early activation of the p53 pathway and TNF/IL-1 signaling by AAV (genome-dependent) + +<|ref|>text<|/ref|><|det|>[[115, 309, 656, 326]]<|/det|> +- Early activation of DNA damage responses by AAV (genome-dependent) + +<|ref|>text<|/ref|><|det|>[[115, 343, 883, 376]]<|/det|> +- Delayed transgene expression-dependent/p53-independent/MAVS-dependent activation of ISGs by AAV + +<|ref|>text<|/ref|><|det|>[[115, 378, 569, 395]]<|/det|> +- AAV causes p53-dependent apoptosis via cleaved Caspase-3 + +<|ref|>text<|/ref|><|det|>[[115, 411, 883, 445]]<|/det|> +- STING inhibition, p53 inhibition and IL-1Ra treatment block AAV IL-1b/CXCL8 activation but not ISG activation. + +<|ref|>text<|/ref|><|det|>[[115, 463, 483, 479]]<|/det|> +- STING inhibition blocks AAV-mediated apoptosis + +<|ref|>text<|/ref|><|det|>[[115, 496, 883, 615]]<|/det|> +This is a vast and complicated story and the authors simultaneously try to understand what appear to be many different but potentially interconnected pathways that are activated in different cell types and across different time points after AAV exposure. The authors should be commended for addressing the importance of host response to AAV in the brain in the context of neurotoxicity. However, their story is highly complex and as a result questions are left unanswered as the authors try to address several different observations across many experiments. This is an important topic and the scope and quality of the study is appropriate for Nature Communications, but several issues need to be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 632, 870, 649]]<|/det|> +We thank the Reviewer for appreciating our effort and for retaining this work of relevance for the field. + +<|ref|>text<|/ref|><|det|>[[115, 666, 210, 682]]<|/det|> +Major points + +<|ref|>text<|/ref|><|det|>[[115, 699, 882, 784]]<|/det|> +1. The relevance of the in vitro observations in terms of their in vivo significance need to be solidified, particularly in the context of antagonistic blockade of AAV-related toxicities. Since similar pathways are activated in human cells and mouse striatum, it is assumed that signaling blockade can translate to mouse brain but this should be validated. Effects of localized IL-1Ra, STING inhibition, MAVS inhibition and p53 inhibition should be studied in mouse brain. + +<|ref|>text<|/ref|><|det|>[[115, 802, 882, 902]]<|/det|> +We thank the Reviewer for the suggestion. Although we were not able to perform localized inhibition of the mentioned pathways as suggested by the reviewer due to technical complexity and timing, we sought to further assess the impact of p53 signalling and downstream pathways on glial cell activation in vivo. For this purpose, we took advantage of a transgene-silent vector harbouring the coagulation factor IX (FIX) transgene under the control of the liver-specific hAAT promoter that activated mainly DNA damage- related responses in the human CNS spheroids (Fig. 5). Mice were injected with the vector in the striatum + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 428]]<|/det|> +with concomitant intraperitoneal administration of pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) or STING (H151), followed by assessment of gliosis on striatal sections. An increase in Iba1+ and GFAP+ cells was observed in mice having received the vector. Moreover, all three treatments decreased the presence of GFAP+ cells in the striata compared to mice injected with AAV only, while they had no effect on the Iba1+ population. NeuN staining indicated absence of neurotoxicity in terms of percentage of NeuN+ cells. These results suggest that, in mice, AAV- mediated CNS transduction can activate gliosis even in a context of low or absent transgene expression when using the hAAT promoter, and that these responses are not unique to the GFP transgene. These responses could be partially modulated through pharmacological inhibition of p53 or of the cGAS- STING pathway, highlighting that vector genome sensing contributes to the activation of local innate immune cells, particularly astrocytes. Results from this experiment are shown in Supplementary Figure 20 and described on lines 339- 356, pages 13- 14 of the revised manuscript. In addition, we wish to underscore that the human in vitro model used in the study, while presenting limitations, is unique in its ability to mimic the reality in the clinic. To this end, the mouse model is not perfect as it presents significant differences when it comes to innate immunity (Tathinen et al, 2022), and in AAV gene therapy they in fact fail to reproduce human findings. We also acknowledge that further studies should be performed to confirm the effect of these drugs on higher number of animals and performing side- by- side comparisons with transgene- expressing vectors in the future, but wish to mention here that due to recent reorganization within the collaborating biotech company that has performed these experiments, we will not be able to provide additional experiments for this part at this stage. + +<|ref|>text<|/ref|><|det|>[[115, 444, 882, 512]]<|/det|> +2. The title does not address all of the observations made in this study and also implies the observations were restricted to human cells. For example, STING is highlighted in the title but isn't mentioned in the story until the last experiment and is only one of several key players in all of the described pathways and responses. A more general or encompassing title should be considered. + +<|ref|>text<|/ref|><|det|>[[115, 530, 882, 596]]<|/det|> +We thank the Reviewer for the suggestion and agree that STING is not the main focus of our studies but rather the induction of the p53-associated DNA damage response pathway and its role in proinflammatory and stress signalling in CNS cells. We have now modified the title to better summarize the study findings as follows: + +<|ref|>text<|/ref|><|det|>[[115, 614, 880, 647]]<|/det|> +AAV vectors trigger DNA damage response- dependent pro- inflammatory signalling in human iPSC- derived CNS models and mouse brain. + +<|ref|>text<|/ref|><|det|>[[115, 666, 882, 715]]<|/det|> +3. If STING and DNA damage responses are the focus of the paper as suggested by the title more exploration of them is required. For example, validation of the potential for STING antagonism should be performed in mouse striatum at a dose of AAV known to be neurotoxic. + +<|ref|>text<|/ref|><|det|>[[115, 733, 882, 902]]<|/det|> +We thank the Reviewer for this suggestion. In line with comments 1 and 2, we have modified the manuscript title to shift the focus away from the STING pathway but have also performed a first proof- concept in vivo study in Supplementary Figure 20, described above, to explore the effects of inhibiting the cGAS/STING and p53 pathways on local gliosis. Briefly, we observed that pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) or STING (H151) decreased the presence of GFAP+ cells in striatum compared to mice injected with AAV only, while they had no effect on the Iba1+ population, suggesting that pharmacological targeting of p53 or the cGAS- STING pathway can curb at least to some extent the vector- induced gliosis without overt toxicity on the CNS cell populations. The results from this experiment are described and discussed on lines 339- 356, pages 13- 14 and lines 480- 483, page 18, of the revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 106, 883, 209]]<|/det|> +4. Lines 125-128 – The authors state “Of note, empty AAV9 capsid did not induce any significant transcriptional changes compared to untransduced controls, in contrast to the full AAV9 vector (Fig. 1E- H), suggesting that the vector genome is required for the detected signaling.” Figures 1E-H support this statement. However, when you look globally across the entire dataset the AAV9 profile is more like the untransduced profile than the empty (AAV9) profile (Figure 1C, UT vs empty vs AAV9), contradicting this statement. This should be discussed further. + +<|ref|>text<|/ref|><|det|>[[114, 226, 883, 514]]<|/det|> +We appreciate the reviewer's observation regarding the global expression patterns seen in the heatmap shown in Fig. 1C. Indeed, on a global scale, the AAV9 profile appears more similar to the untransduced profile, reflecting the overall expression levels of differentially expressed genes across all conditions. However, it is important to note that this global view does not capture the specific biological processes driving the observed transcriptional differences in the full AAV9 condition. Our statement refers to genes significantly contributing to specific signalling pathways, as highlighted in Figures 1E-H. These analyses show that the few genes contributing to the differences in the full AAV9 vector are significantly enriched in signalling-related processes. In contrast, the empty AAV9 capsid does not induce significant transcriptional changes (Fig. 1E-H), indicating that the vector genome is required to trigger these pathways. Thus, while the heatmap provides an overview of overall gene expression, it does not reflect the specific pathway-level changes that are critical for interpreting the functional impact of the full AAV9 vector. To further clarify this point, we have now included Volcano plots showing the differentially expressed genes induced by the different vectors in Supplementary Figures 3 and 4 to better visualize differences in the level of signalling induced by each vector, including no significant induction of genes by the empty AAV9 vector, and describe this on lines 132- 137, page 6 of the revised manuscript. Moreover, we have included data in supplementary figures S5 and S16C and E showing the lack of induction of signalling by empty capsid of other serotypes (AAV1 and 6). + +<|ref|>text<|/ref|><|det|>[[115, 530, 883, 564]]<|/det|> +5. Fig 1C/D – Why was empty AAV9 used as a control when 'full' AAV9 stimulated the lowest transcriptional response? Empty AAV2 which was more transcriptionally reactive should be compared? + +<|ref|>text<|/ref|><|det|>[[114, 581, 883, 733]]<|/det|> +We thank the Reviewer for this observation. We focused on the comparison between empty and full AAV9 vectors given the clinical relevance and the CNS toxicities reported with this serotype. However, to confirm that the observed signalling is not capsid dependent in a more stringent condition, we have included a new experiment comparing the expression of selected genes from Figure 1H induced by empty vs. full AAV2. Results have been included in Supplementary Figure 5, confirming the lack of signalling in the absence of the genome also for this serotype. The following sentence has been added to the main text line 135- 137, page 6: “The same was confirmed for empty AAV2 capsid in hiPSC- derived astrocytes in terms of upregulation of selected genes (p21, CXCL8, IL- 18), chosen as representative from Figure 1H (Fig. S5).” + +<|ref|>text<|/ref|><|det|>[[115, 750, 883, 852]]<|/det|> +6. The reviewer appreciates that every experiment can't be performed with every dose, serotype, promoter, transgene combination, etc. However, there is a lot of back and forth between experimental (mainly AAV) details across different culture types and mice as the paper progresses. At some point in the paper, it is almost assumed that all serotypes are equivalent as the authors switch between AAV2, AAV6, Spark100 and AAV9, when the early experiments show there can be clear differences. The generalization that all responses are serotype independent are in places too presumptive and should be tempered. + +<|ref|>text<|/ref|><|det|>[[115, 870, 883, 903]]<|/det|> +Although we agree with the Reviewer that some serotype- specific responses cannot be excluded in this context, we did identify common genes for selected pathways in our RNAseq datasets upregulated across + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 863, 80]]<|/det|> +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 175]]<|/det|> +serotypes that can be used to assess common signalling by all used serotypes. Overall, we observe that the number of significantly upregulated genes contributing to a given pathway is dependent on the level of transduction by each serotype due to the delivery of higher vector genomes, rather than on capsid composition, given the absence of signalling by empty capsids (Fig S3, S4, S5, S16C, E). We have better clarified this in the revised manuscript, lines 394- 397, page 15 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 192, 883, 259]]<|/det|> +7. What is known about relative AAV receptor expression levels (HSPG, sialic acid, galactose, AAVR) in hiPSC-derived cells and organoids (neurons vs astrocytes vs oligodendrocytes), since signaling through different receptors may impact downstream transcriptional observations across the different serotypes studied? + +<|ref|>text<|/ref|><|det|>[[115, 276, 883, 428]]<|/det|> +We thank the Reviewer for this question. Firstly, we wish to emphasize that based on our observations it seems that the signalling is not different between serotypes but rather vary in magnitude according to the transduction efficiencies. Nevertheless, we took advantage of our single-cell RNAseq data from mixed cultures and brain spheroids to look at the pattern of expression of different known AAV receptor levels across cell types and have included the results below for the Reviewer (Figure A). We do not observe any significant differences in receptor expression across cell types, suggesting that differences in receptors do not explain the tropism and downstream transcriptional observations across the different serotypes. Given that this data does not add to the general message of this work, we would prefer not adding it to the manuscript that is already heavy in supplementary information. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 46, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>image<|/ref|><|det|>[[130, 98, 896, 558]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 564, 883, 633]]<|/det|> +
Figure A. Distribution of AAV receptor mRNA expression in CNS models. (A,B) Violin plots showing the expression level of known AAV receptors on mixed CNS cultures at the end of the differentiation protocol (day 24) (A) as well as brain spheroids (day 150) (B). Plots contain pooled data from two biological replicates of mixed cultures or spheroids respectively, each performed in technical duplicate.
+ +<|ref|>text<|/ref|><|det|>[[115, 649, 883, 752]]<|/det|> +8. In Fig 6, snRNAseq is performed in mice given AAV9.CAG-EGFP via IPa then for some reason the DNA damage response observations in the striatum are validated in mice after ICV and not IPa delivery of AAV9.PGK-EF1a.Cre-EGFP. This validation should be performed after IPa delivery of the same vector. It is also not clear what AAV9.PGK-EF1a.Cre-GFP is. Is GFP expression conditional (Cre expressing mice were not used) or does it express 2 transgenes (Cre and GFP), which complicates observations made in Fig S8 in relation to Fig 6. + +<|ref|>text<|/ref|><|det|>[[115, 769, 883, 904]]<|/det|> +We thank the Reviewer for this suggestion. The previous validation was performed on striatum of mice injected ICV due to tissue availability. We have now performed a new in vivo experiment replicating the experimental conditions of the snRNAseq experiment in Figure 6 (C57BL/6 mouse strain, IPa route of administration and AAV9-CAG-GFP vector at \(1 \times 10^{10} \mathrm{vg / side}\) ) to confirm local DNA damage responses in the striatum compared to vehicle injection (N=3 per group) and results are shown in Figure 7 and Supplementary figure 14 of the revised manuscript. Briefly, IF staining shows high colocalization of the neuron marker NeuN and the DNA- damage marker YH2AX in the striatum of injected animals (Fig. 7), as well as increased gliosis as shown by GFAP, Sox9 and Iba1 stainings (Fig. S14A- F). Moreover, Iba1+ cells + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 159]]<|/det|> +colocalized with Galectin- 3 staining, a marker for microglial activation (Ge et al, 2022) (Fig. S14D- F). Of note, we also observed increased GSDMD staining in Iba1+ cells, an indicator of microglial activation in this context (Pollock et al, 2024) (Fig. S14G and H). This new experiment is now described and discussed on lines 254- 268, pages 10- 11 and lines 425- 437, pages 16- 17 of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 176, 212, 192]]<|/det|> +## Minor points + +<|ref|>text<|/ref|><|det|>[[115, 209, 883, 293]]<|/det|> +1. Lines 164-167 – The authors state “Overall, upregulation of signaling pathways was more significant in the 3D model compared to the 2D mixed cultures (Fig. 3E, Fig. 4E), suggesting active cross talk and paracrine effects of AAV signaling across cells of the human CNS.”, however, this could just be an MOI effect whereby cells on the outside of a 3D spheroid take up more AAV in culture, which in turn causes greater peak activation levels. Please discuss. + +<|ref|>text<|/ref|><|det|>[[114, 310, 883, 582]]<|/det|> +We agree with the Reviewer that differences between 2D and 3D models can potentially be due to an MOI effect, or also to a longer transduction time of the 3D spheroids. Figures 3D and 4D show similar percentages of cells positive for GFP mRNA, suggesting that transduction rates are similar across the culture systems at least in terms of vector expression. In addition, FACS data from cells taken from transduced mixed cultures and homogenized organoids used for single-cell analyses show similar percentage of GFP+ cells across 2D and 3D cultures that we have included below for the Reviewers consideration (Figure B). These observations, together with an overall higher number of significantly upregulated pathways observed in Figure 4E compared to Figure 3E, and our results from Figure 5 in transgene-negative cells led us to hypothesize that the more complex 3D structures could contribute to the increased paracrine signalling. Of note, the higher % of GFP mRNA positive cells shown in Figures 3D and 4D of the manuscript compared to the % of GFP fluorescent cells measured by FACS shown below (Figure B) derive from the higher sensitivity of transcriptomics to detect low copies of transcript, and to the use of bulk cells for FACS vs. the cell-type specific analysis in scRNAseq. We have moved our statements regarding paracrine signalling to discussion and have added the Reviewer’s and other considerations to explain the differences in signalling between models, lines 397- 401, page 15 of the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[149, 606, 600, 818]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 825, 880, 860]]<|/det|> +
Figure B. GFP expression in mixed cultures and brain spheroids. FACS analysis of the percentage of GFP+ cells in mixed cultures and brain spheroids transduced with the indicated vectors.
+ +<|ref|>text<|/ref|><|det|>[[115, 877, 598, 893]]<|/det|> +2. Are different responses seen between ssAAV vs scAAV vectors? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 106, 883, 327]]<|/det|> +We thank the Reviewer for this relevant question. To try to answer it we have performed two independent transduction experiments to study differences between ssAAV9 and scAAV9 vectors. Results from both experiments have been pooled in Supplementary Figure 17 showing no significant differences between ss vs sc vectors despite the higher GFP expression derived from the scAAV9 vector (Fig. S17A). This result was somewhat unexpected as scAAV vectors are reported to be more immunogenic than ssAAV vectors in vivo due to higher stimulation of TLR9 receptors in plasmacytoid dendritic cells (pDCs) (Rogers et al, 2017). Our hypothesis is that the type of intrinsic signalling induced by AAV vectors and the relevance of TLR9 sensing is cell- type dependent, as was reported by Rogers et al., showing that TLR9 sensing was specific to pDCs and not conventional dendritic cells for instance. In agreement, additional experiments that we have performed and reported in Supplementary figure 16 further support the lack of involvement of TLR9 on neural cell signalling as we did not observe any major impact of TLR9 inhibition or the use of a TLR9 insensitive AAV2 vector (AAV2.io2, (Chan et al, 2021)) in terms of gene induction in hiPSC- derived astrocytes. We have described these results at lines 283- 293, page 11 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 344, 882, 378]]<|/det|> +3. Table S1 reports the AAV 'dose' in v.p./cell but elsewhere vg/cell is used as the unit for infection. Are the reported MOI based on particles or genomes? + +<|ref|>text<|/ref|><|det|>[[115, 394, 883, 580]]<|/det|> +We thank the Reviewer for this question. The term vector particles was previously used to refer to both capsid in case of empty vectors or genomes in case of full vector. To avoid confusion, the dose units on the table have been modified to MOI, and the use of vector particles or vector genomes has been specified in the table legend. Moreover, the text below has been included in the methods section, lines 621- 628, pages 23- 24 of the revised manuscript: "Full vector titers were determined by qPCR as vector genomes (vg) per mL using primers directed against the transgene poly- adenylation signal region. The AAV titer was calculated by averaging results from 2 qPCR rounds with 3 different dilutions tested for each sample in each round. The purity of vector preparations was evaluated by SDS- PAGE gel. Empty capsid titers were determined by Sypro Ruby staining following SDS- PAGE (Lock et al, 2010). Empty AAV9 and full AAV1, 2, 5, 6, 9 and Spk100 vector titers were simultaneously verified by side- by- side capsid imaging by western blot using an anti- AAV VP1/2/3 monoclonal antibody (Progen)". + +<|ref|>text<|/ref|><|det|>[[115, 597, 820, 614]]<|/det|> +4. No methods are provided for genome titer and/or AAV particle determination, please include. + +<|ref|>text<|/ref|><|det|>[[115, 631, 883, 666]]<|/det|> +We thank the Reviewer for pointing this out. Titration methods detailed above in comment 3 have been included in methods section, lines 623- 628, pages 23- 24 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 682, 557, 699]]<|/det|> +5. Details of the ICV injection procedure should be provided. + +<|ref|>text<|/ref|><|det|>[[115, 716, 883, 800]]<|/det|> +Following the Reviewer suggestion, we have now performed new in vivo experiment replicating the treatment conditions used in the snRNASeq study (C57BL/6 mouse strain, IPA route of administration and AAV9- CAG- GFP vector at \(1 \times 10^{10}\) vg/side) and the results from animals treated by ICV injection have been replaced by the new intraparenchymal study in Figure 7 and Supplementary Figure 14 of the revised manuscript and described in detail on lines 254- 268, pages 10- 11 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 818, 539, 835]]<|/det|> +6. Fig 1D – Why were Spark100, AAV1 and AAV6 omitted? + +<|ref|>text<|/ref|><|det|>[[115, 852, 883, 903]]<|/det|> +We thank the Reviewer for this observation. These serotypes were not used in the bulk RNAseq experiment shown in Fig. 1D, 1F and 1H because we chose to transduce cells with the three serotypes that showed different behaviour according to results in Fig. 1A, B in astrocytes. Specifically, AAV9 was + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 260]]<|/det|> +chosen as an example of low VGCN, low GFP expression and low signalling as well as due to clinical relevance, AAV5 for high VGCN in astrocytes compared to AAV9 but low GFP expression and low signalling, and AAV2 as high VGCN, high GFP expression and high signalling. We hypothesize that the discrepancy between the vector copies of AAV5 and the low GFP expression and signalling is due to a slower uncoating of this capsid, reported to be more stable compared to other serotypes (Bennett et al, 2017), confirming our hypothesis that vector genome sensing is needed to induce signalling. In agreement, we have performed preliminary time- course experiments showing delayed GFP expression observed for AAV5, included below for the Reviewer's consideration (Figure C). We have not specifically commented on the choice of the serotypes in the manuscript to avoid rendering the reading too heavy and hope the Reviewer agrees with this choice. + +<|ref|>image<|/ref|><|det|>[[128, 283, 653, 491]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 500, 883, 550]]<|/det|> +
Figure C. Time course of GFP expression. FACS analysis of GFP expression in iPSC-derived neurons transduced with the indicated serotypes at multiple time-points. Each dot corresponds to data from 1-3 independent transductions.
+ +<|ref|>text<|/ref|><|det|>[[115, 568, 525, 585]]<|/det|> +7. Fig S3B - x-axis legend should read full and not AAV9. + +<|ref|>text<|/ref|><|det|>[[115, 602, 880, 619]]<|/det|> +We thank the Reviewer for pointing this out and have corrected the axes accordingly. This is now Fig. S6B. + +<|ref|>text<|/ref|><|det|>[[115, 636, 883, 670]]<|/det|> +8. Fig 5B-D - The SPARK100-hAAT-GFP vector should be added to the right-hand 'transgene minus' panel for easier comparison since GFP isn't expressed. + +<|ref|>text<|/ref|><|det|>[[115, 687, 750, 704]]<|/det|> +We thank the Reviewer for pointing this out. The figure has been modified accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 721, 883, 772]]<|/det|> +9. mRNA is not expressed from the hAAT promoter in hiPSC-derived neurons. How would responses compare between the hAAT-GFP vector and a vector that produces an mRNA but is not translated (e.g. ATG deleted GFP)? + +<|ref|>text<|/ref|><|det|>[[115, 789, 883, 890]]<|/det|> +We thank the Reviewer for this suggestion and agree that this is a very interesting point to address. However, although we sought to obtain a non- translating vector, such as the suggested ATG- deleted version, to address the Reviewers' point, we have not been able to access such a vector yet. Therefore, while we agree that dissecting the role of transcription vs. translation is relevant, we hope that the Reviewer will understand that we have not been able to perform these experiments in the timeframe of this revision and will aim to do so in future studies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 106, 883, 140]]<|/det|> +10. Fig 6 – This study was performed at a single AAV dose. Why was this dose chosen? How representative is this dose per g of brain to those used in other animal studies where CNS toxicity has been observed? + +<|ref|>text<|/ref|><|det|>[[115, 157, 883, 243]]<|/det|> +We thank the Reviewer for these questions. This vector dose was firstly chosen because it is a standard vector dose used for pre- clinical testing in several settings, independently of toxicity, and secondly because it has also been shown to induce glial cell activation and brain infiltration in previous mouse studies using the same route of administration (Guo et al, 2023; Hollidge et al, 2022; Ortinski et al, 2010). We have added an explanatory sentence in the revised manuscript, lines 800- 803, page 30. + +<|ref|>text<|/ref|><|det|>[[115, 259, 883, 292]]<|/det|> +11. Fig S9B – MAVS blockade appears to accentuate AAV induction of IL-1 and CXCL8 substantially. This is not mentioned and should be discussed? + +<|ref|>text<|/ref|><|det|>[[115, 310, 883, 394]]<|/det|> +We thank the Reviewer for pointing this out. Although this seems to be quite consistent, now in Fig. S17, we do not know yet the molecular basis on this observation. Because MAVS stays on the mitochondria, its depletion could potentially lead to some alterations affecting indirectly inflammation, or some sort of priming of the cells could occur in absence of physiological RNA sensing so that they will more readily react to incoming vectors. We have discussed this on lines 496- 499, page 19 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 412, 630, 445]]<|/det|> +12. FigS10 – legend says figure 10. This has been corrected and is now Fig. S19 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 463, 778, 496]]<|/det|> +13. Fig S9 legend – typo 'signallig' We have homogenized the text accordingly. This is now Fig. S18 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 513, 393, 529]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 547, 883, 768]]<|/det|> +The manuscript by Costa- Verdera and colleagues describes the transcriptional responses that arise in AAV- transduced cells of the CNS that were derived from hIPSC. The authors study 2d cultures of neurons, astrocytes and oligodendrocytes as well as brain spheroids tested after transduction by several different AAV capsids (AAV1, AAV2, AAV5, AAV6 AAV9 and Spk100). The authors determine the ability of these different capsids to transduce each cell type as well as the consequence of transduction on inflammatory signaling and DNA damage responses. They demonstrate that different capsid serotypes have varying abilities to transduce neurons and astrocytes (and in some cases oligodendrocytes). Furthermore, they demonstrate that AAV transduction correlates with activation of DNA damage repair pathways (p53 mediated) and activation of some inflammatory pathways. These two findings regarding the induction of p53 and inflammatory pathways are not completely novel, but the comprehensive approach being taken by the authors and the testing of many different CNS cell types against a large number of capsids is a strength of the paper. The authors also carry out in vivo experiments in mice by ICV injection and demonstrate the level of transduction of different cell types and some single cell gene expression data. + +<|ref|>text<|/ref|><|det|>[[115, 785, 883, 903]]<|/det|> +The strengths of the manuscript include 1) the comprehensive testing of a variety of CNS cell types which demonstrates some consistent patterns of p53 induction and inflammatory signaling across different culture conditions (2D vs 3D), 3) the testing of many different AAV vector serotypes for their ability to transduce these various cell types and 3) numerous assessments of transcriptional changes that demonstrate inflammatory and DNA damage responses. The weaknesses of the manuscript are 1) some experiments are not well controlled, such as Fig. 5 where the authors use several promoters and transgenes in parallel but do not control for the CpG content of the vectors. These constructs will all have + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 243]]<|/det|> +different risk factors for activating TLR9 signaling, which is activated within hours of transduction and has many cascading downstream effects; 2) the single cell data is not explored beyond identifying cell types? and 3) the timepoints tested do not allow the authors to capture TLR signaling that occurs early after transduction (less than 12 hours post AAV transduction. Because they collected the samples so late after transduction, it becomes difficult to discriminate transgene induced TLR signaling vs capsid responses (such as in Fig. 5). The authors did a tremendous amount of work for this manuscript and it would be very difficult to repeat everything to obtain an early time point, but the authors do need to acknowledge that TLR signaling will influence downstream signaling. The specifics regarding Figure 5 are detailed below. Overall this is a strong manuscript that has a lot of important information that will be valuable to readers. + +<|ref|>text<|/ref|><|det|>[[115, 258, 883, 344]]<|/det|> +We thank the Reviewer for the overall positive feedback and constructive comments and agree that some of the experimental designs could have benefitted from earlier timepoints to more deeply investigate the involvement of TLR signalling in the downstream consequences of rAAV transduction. However, as this study aimed to broadly address rAAV impact on the target cells/tissue, we went for a compromise to address multiple pathways. + +<|ref|>text<|/ref|><|det|>[[115, 360, 883, 394]]<|/det|> +Fig. 1A. Can the authors show examples of the FACS plots where they determined GFP+ cells and show the gating that was used to identify the positive cells. + +<|ref|>text<|/ref|><|det|>[[115, 411, 883, 445]]<|/det|> +We thank the Reviewer for the question and have included representative FACS plots in Supplementary figure 2A of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 462, 883, 496]]<|/det|> +It would be good to show the vector copy number (currently in supplemental) in the main figures alongside the GFP+ mRNA. Figs 1E and F could be moved to the supplemental if space is needed. + +<|ref|>text<|/ref|><|det|>[[115, 513, 883, 581]]<|/det|> +We thank the Reviewer for the suggestion. Vector genome copy number graphs have been moved from Supplementary figure 2 to main Figure 1B by plotting neuron and astrocyte data in the same graphs, same as for the GFP expression data. Regarding Figures 1E and F, we feel that pathway analysis is important and prefer to keep this information in the main Figure 1. + +<|ref|>text<|/ref|><|det|>[[115, 597, 883, 649]]<|/det|> +Supplementary Table 1: There seems to be information missing from the table. Also, could the authors state the titer in viral genomes, since it is the transgene that is inducing most of the response; thus, one would like to know the level of transgene instead of viral particles. + +<|ref|>text<|/ref|><|det|>[[115, 666, 883, 819]]<|/det|> +We thank the Reviewer for pointing this out. We have modified Supplementary Table 1 to clarify the units used and included the titration details in the methods section in lines 621- 628, pages 23- 24 as follows: "Full vector titers were determined by qPCR as vector genomes (vg) per mL using primers directed against the transgene poly- adenylation signal region. The AAV titer was calculated by averaging results from 2 qPCR rounds with 3 different dilutions tested for each sample in each round. The purity of vector preparations was evaluated by SDS- PAGE gel. Empty capsid titers were determined by Sypro Ruby staining following SDS- PAGE (Lock et al., 2010). Empty AAV9 and full AAV1, 2, 5, 6, 9 and Spk100 vector titers were simultaneously verified by side- by- side capsid imaging by western blot using an anti- AAV VP1/2/3 monoclonal antibody (Progen)". + +<|ref|>text<|/ref|><|det|>[[115, 835, 883, 869]]<|/det|> +Figure 3B: The authors should show how the frequency of their cell populations change with dosing between days 2 and 4. Can they show individual UMAPS and normalized cell numbers by time point? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 260]]<|/det|> +We thank the Reviewer for this question. Due to space limit, we are showing one representative UMAP and donut plot which contain clustered treated and untreated samples to show that populations cluster together independently of treatment. We have included individual plots from mixed cultures and brain spheroids in Supplementary figures 7 and 8A respectively. Overall, we do not observe consistent changes in the percentages of the different cell populations that could be related to treatment or the time- point after transduction. Differences are more likely due to sample- to- sample variability and sample handling and processing, and further experiments with larger numbers of organoids would be needed to confidently draw conclusions in terms of potential impact AAV transduction on the cell composition of these in vitro models. In addition, major signalling pathways and time- dependent increase in inflammatory signalling were confirmed by qPCR in 2D cultures (Figure S10 of the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[115, 276, 881, 293]]<|/det|> +Also could the authors provide some of the top differentially expressed genes in addition to the pathways? + +<|ref|>text<|/ref|><|det|>[[115, 310, 883, 344]]<|/det|> +We thank the Reviewer for the suggestion and have now included Volcano plots with top altered genes in Supplementary figure 8B of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 360, 734, 377]]<|/det|> +3D: It would be best if the colors in Fig. 3D could match the colors for Figs 3B and 3C. + +<|ref|>text<|/ref|><|det|>[[115, 394, 789, 411]]<|/det|> +We thank the Reviewer for the suggestion and have unified the colours between the panels. + +<|ref|>text<|/ref|><|det|>[[115, 428, 883, 514]]<|/det|> +Figure 5: In this figure the authors use different promoter and transgene constructs to transduce 3D spheroids, followed by isolation of transgene + and transgene - cells and subsequently compare the transcriptional patterns between the different cell types and between transgene + and transgene - cells. They also use two different capsids and use other promoter + transgene constructs. The vast diversity of constructs and cell types makes this figure very complicated to interpret. + +<|ref|>text<|/ref|><|det|>[[115, 530, 883, 631]]<|/det|> +One main issue is that the authors do not consider how differences in CpG motifs (in each construct used) has the potential to impact TLR9 signalling. Thus, the experiment is very difficult to interpret. So while the authors used a control (Spark100 HAAT construct) that does not express protein, they did not take into consideration the fact that the presence of the viral genome will ALSO stimulate inflammatory signalling independent of protein expression. The experiment is not well controlled and therefore, conclusions are difficult to make. The interpretation of this experiment needs to be toned down considerably. + +<|ref|>text<|/ref|><|det|>[[115, 648, 883, 903]]<|/det|> +We thank the Reviewer for raising this point. We have better clarified, lines 189- 194, page 8 of the revised manuscript, that the Spark100 HAAT construct was used to assess the signalling coming from the viral genome only independently from transgene expression, given that this vector will bring the DNA genome into the cells but will not express the mRNA, and we have shown that empty capsids alone do not trigger significant signalling. Indeed, we agree with the reviewer that the presence of the viral genome will also stimulate inflammatory signalling independent of protein expression, as is also evidenced by our new in vivo experiments showing p53 and cGAS- STING- dependent gliosis using the Spk100 HAAT construct (Supplementary Figure 20), lines 339- 356, pages 13- 14 of the revised manuscript. These results are in agreement with an apical role of p53 in linking AAV genome sensing to inflammatory responses, similarly to what we observed in vitro using pathway- specific inhibitors and gene expression readouts (Figure 8). Nevertheless, while we agree that the different CpG content between constructs may play a role and have included a quantification of the CpG content of each construct in Supplementary figure 15 showing that the CAG- containing vectors do have higher CpG content compared to the hAAT promoter- containing vector, new experiments performed using a TLR9 specific inhibitor (A151) or a TLR9- stealth vector (io2 (Chan et al., 2021)) further suggest that TLR9 may not be involved in AAV sensing in CNS cells as no clear + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 124]]<|/det|> +benefit could be achieved in terms of gene activation in these contexts (Supplementary figures 16 and 17). We have discussed these observations on lines 277- 293, page 11 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 140, 882, 191]]<|/det|> +1) Line 174: They are not able to state that different AAV serotypes induce different inflammatory signatures. The authors have proven that the AAV capsid determines whether the AAV particle can enter a cell but they have not proven that different signatures arise due to different capsids. + +<|ref|>text<|/ref|><|det|>[[115, 209, 882, 259]]<|/det|> +We thank the Reviewers for pointing this out. We have rephrased the text to emphasize our hypothesis that the observed signalling is serotype-independent and rather depends on transduction levels, lines 394- 397, page 15 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 276, 882, 344]]<|/det|> +2) Line 201: The authors cannot discriminate transgene specific responses due to lack of consideration for the differences in the different risk factor potentials to stimulate TLR9 signaling (formula published by J. Fraser Wright https://doi.org/10.1016/j.ymthe.2020.07.006), which is inherent to each transgene. So the comment that GAA stimulates more inflammatory signaling is likely due to a difference in the RF3. + +<|ref|>text<|/ref|><|det|>[[115, 360, 882, 464]]<|/det|> +We thank the Reviewer for this comment. We have included this point and added the reference lines 280- 283, page 11 of the revised manuscript as follows: "As the CpG content of the AAV vector sequence has been shown to be an important modulator of cellular responses against transduced cells in vivo (Bertolini et al, 2021; Wright, 2020), this could contribute to the differences in signalling induced by the different expression cassettes through TLR9 sensing.". In addition, we have included a quantification of CpG motifs in our sequences in Supplementary figure 15. + +<|ref|>text<|/ref|><|det|>[[115, 480, 670, 497]]<|/det|> +Furthermore, the idea of paracrine signaling (line 204) has not been proven. + +<|ref|>text<|/ref|><|det|>[[115, 513, 882, 649]]<|/det|> +We agree with the Reviewer that formal proof of paracrine signalling is lacking and is based on observation of the GSEA results. In an attempt of studying potential paracrine signalling, we performed a conditioned media transfer experiment between transduced astrocytes to untransduced neurons to analyse toxicity markers potentially induced in neurons. However, our experiment was limited by the detection of GFP transcripts in the untransduced neurons, indicating the presence of contaminating AAV particles in the conditioned media that render interpretation of this data difficult as paracrine versus AAV- triggered changes cannot be discerned. We included the results of this experiment here for the Reviewers' consideration here below (Figure D). + +<|ref|>text<|/ref|><|det|>[[115, 650, 883, 819]]<|/det|> +Due to this issue, we feel that we cannot include this experiment in the manuscript and have dampened our claims by moving our considerations to the discussion and including other potential explanations for the differences in signalling observed between 2D and 3D models: "Moreover, upregulation of signalling pathways seemed more significant in the 3D in vitro model compared to the 2D mixed cultures, suggesting potential cross talk and paracrine effects of AAV signalling across cells of the human CNS. However, these differences could also result from longer transduction time of brain spheroids or their longer differentiation yielding higher maturation stages. Alternatively, an MOI effect could also account for some of the differences as the outer cells in the spheroids are more highly transduced compared to the inner ones, although single- cell analyses showed similar percentage of GFP+ cells across 2D and 3D cultures", lines 397- 404, page 15 of the revised manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[130, 103, 865, 336]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 346, 883, 447]]<|/det|> +
Figure D. Conditioned media transfer experiment in iPSC-derived neurons. iPSC-derived untransduced (UT) neurons were incubated for 48h with conditioned media (CM) from astrocytes previously transduced with AAV2 for 24h, washed with PBS following media replacement and cultured for another 48h before collecting the supernatant. Panels A and B show IF staining on neurons of yH2AX and cc3 respectively as markers of cell toxicity. Panels C and D show the analysis of GFP and p21 mRNA on untransduced neurons incubated with transduced astrocyte culture supernatants.
+ +<|ref|>text<|/ref|><|det|>[[115, 463, 883, 532]]<|/det|> +3) Line 207: The authors conclude that the vector genomes induce the p53 response, but this point is not proven at all. There are p53 responses in both transgene + and transgene - populations. It is recommended that the authors deconstruct this figure and parse out the points that they can make conclusively. + +<|ref|>text<|/ref|><|det|>[[114, 548, 883, 840]]<|/det|> +We thank the Reviewer for pointing this out. Firstly, we wish to clarify that "transgene - " means that the transgene product is not expressed (mRNA and protein) while the vector genome is equally present in both conditions, as shown in terms of VGCN but no GFP signal in Fig. S11A, B. We have included an explanatory paragraph in the main text, lines 189-194, page 8 of the revised manuscript. We decided to use these two vectors to control for responses that are solely due to detection of the vector genome vs. effects associated with expression of the transgene as suggested by Hordeaix et. al in DRG neurons (Hordeaix et al, 2020b). Moreover, we show that empty capsids alone do not induce any significant responses in this experimental setting (Fig. 1E- H, Fig. S3, Fig. S4, Fig. S5, Fig. S16B- E). In addition to the DNA- damage foci that we detect by IF staining in our in vitro and in vivo models (Fig. 2, Fig. S6, Fig. 7), our hypothesis that vector genomes induce p53 responses is supported by the effect of inhibiting p53 with GSE56 or pharmacological inhibitors in preventing the upregulation of pro- inflammatory genes in vitro (Fig. 8) or the activation of GFAP+ cells in vivo (Fig. S14), even when using a transgene- silent vector (Figure S20). These observations are in line with previous reports showing that AAV vector genomes induce a p53 response (Cervelli et al, 2008; Hirsch et al, 2011), and observations linking DNA damage with increased inflammation in several contexts (Ghosh et al, 2023; Kay et al, 2019). We have better discussed the results obtained from "transgene +" and "transgene - " populations on lines 208- 215 pages 8- 9 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[112, 854, 881, 888]]<|/det|> +4) Fig. S6: The authors do not control for the TLR risk factor here, which could be significantly different between the two promoters, so it is difficult to make any firm conclusions from this study. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 260]]<|/det|> +We thank the Reviewer for point this out. Following the Reviewers suggestion, we have included a quantification of the CpG content of the different sequences used in Supplementary figure 15 and acknowledge the potential influence of different CpG content in the observed responses, lines 277- 293, page 11 of the revised manuscript. However, our additional experiments included in Supplementary figures 16 and 17 using a TLR9 inhibitor or a TLR9- inhibitory AAV2 vector (AAV2.io2 (Chan et al., 2021)) do not provide any evidence of the role of CpGs and TLR9 in the sensing of AAV vectors by neural cell types. Instead, the main signalling in these cells seems to be p53- mediated, as shown by our results using a p53 inhibitor in vitro (Figure 8 of the revised manuscript) and in vivo (Figure S20 of the revised manuscript). We have further discussed these observations on lines 500- 509, pages 19 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 276, 882, 327]]<|/det|> +Line 246: The authors state that type I IFN signaling in AAV transduced human and mouse CNS cells triggers IFN1 signaling. This statement does not consider TLR9 signaling, which can trigger IFN1 signaling via CpG motifs in the transgene. + +<|ref|>text<|/ref|><|det|>[[115, 343, 883, 496]]<|/det|> +We agree with the Reviewer on the potential contribution TLR9 may have in activating type I responses upon AAV transduction and have included this consideration on lines 277- 293, page 11 and lines 500- 509, page 19 of the revised manuscript. However, as already discussed above, we wish to point out the several new experiments performed with TLR9 inhibitor or TLR9- stealth AAV seem to exclude a predominant role of this PRR in AAV sensing in CNS cells in our experiment setting (Fig. S16, S17). Moreover, our results in MAVS- depleted astrocytes (Supplementary Figure 18) together with the lack of altered ISG induction in presence of p53, STING or IL1R inhibitors (Figures 8 and 9) seem to point towards a type I IFN signature that is fuelled by cytosolic RNA sensing in this experimental context. We have better clarified this, lines 500- 509, page 19 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 512, 882, 564]]<|/det|> +Figure 6: The authors carry out ICV injections, isolate CNS cells after 28 days and carry out single cell sequencing. The authors do not see p53 dependent responses in vivo, which is hard to reconcile with their other studies. Is the mouse different than human, is it an in vivo vs in vitro issue or is it a timing problem? + +<|ref|>text<|/ref|><|det|>[[115, 580, 883, 835]]<|/det|> +We thank the Reviewer for this comment. In the first draft, ICV- injected animals were only used for histology and not for snRNAseq analysis. However, this question may not be relevant anymore as data from the ICV study has been replaced by data generated with intraparenchymal (IPa)- injected animals. In the new Figure 6E we did observe DNA repair and p53 response terms at the transcriptional level in some neuron subsets. This is in line with our histology findings in Figure 7, in which yH2AX foci mostly co- localize with neurons. The fact that results at the functional level are more robust than at the transcriptional level could be due to different expression kinetics in vivo vs. in vitro, or to dropout of cytoplasmic mRNA in snRNA sequencing compared to scRNAseq analysis, since our immunofluorescence staining confirms the functional formation of p- yH2AX- positive DDR foci in striatum sections of IPa- injected animals (Figure 7A, C). For side- by- side comparison of human and murine datasets, we generated a GSVA heatmap of common pathways enriched across our different in vitro models and murine datasets, showing that samples clustered together according to cell- type and treatment and independently of the species of origin, showing high clustering scores for pathways including IFN response, p53 pathway, inflammatory signalling, complement responses or apoptosis, now Supplementary Figure 13, lines 248- 253, page 10 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 852, 883, 886]]<|/det|> +This figure could be the basis for a full paper that carefully assesses time points in the mouse and compares to the in vitro studies. If the authors want to include this study, I recommend that they extend + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 267, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 125]]<|/det|> +their single cell data analysis and show in the figure how cell frequencies and phenotypes change with AAV dosing in vivo. + +<|ref|>text<|/ref|><|det|>[[115, 140, 882, 208]]<|/det|> +We thank the Reviewer for this suggestion and have included individual donut plots for plots for vehicle and AAV9- treated mice in Figure 6C of the revised manuscript. We did not observe important differences that could be associated to treatment, instead samples from untreated and treated mice cluster together as shown in Figure 6B. + +<|ref|>text<|/ref|><|det|>[[115, 225, 882, 309]]<|/det|> +In addition, they should demonstrate how those changes are similar and/or different from hiPSCs. I would recommend they show violin plots of individual genes and demonstrate how they are consistent or differ with observations made in the hiPSC- derived CNS cells. Since no violin plots are shown in the prior parts of the manuscript, they could show them here, so it is easy for the reader to compare across cell types vs the in vivo studies. + +<|ref|>text<|/ref|><|det|>[[115, 326, 882, 462]]<|/det|> +We have worked on generating a figure comparing pathways and single genes induced in murine vs. human cell datasets and the best way of representing the comparison. However, such comparison has a series of challenges: 1) the diversity of cell subsets found in vivo compared to in vitro models (i.e. neuron sub- types) and the maturation stage of the cells; 2) the techniques by which transcriptomes were analysed were different (snRNAseq in vivo which detects only nuclear mRNA vs. scRNAseq in vitro, for detection of cytosolic transcripts); and the individual genes that contribute to a specific pathway vary from mice to human (Fischer, 2019; Fischer, 2021), so we do not always expect the same genes to be upregulated across species. + +<|ref|>text<|/ref|><|det|>[[115, 463, 882, 580]]<|/det|> +The main challenge we encountered when plotting murine and human genes on the same graph is that even though they were all significantly upregulated and contributed to same pathways, the folds were lower in mice. This can be due both to the fact that in mice we are only detecting nuclear transcripts, and that the percentage of transduced cells is lower in vivo compared to in vitro, so there is a vector dilution effect. For this reason, although we have generated a violin plot figure that we have added below for the reviewer's consideration (Figure E), showing examples of significantly induced genes that we found to be common in all datasets, we do not find this representation the most informative. + +<|ref|>text<|/ref|><|det|>[[115, 581, 882, 903]]<|/det|> +Instead, given the high variation in the experimental context of the different human and mouse datasets, and in order to compare the in- vitro to in- vivo datasets, we performed a Gene Set Variation Analysis (GSVA) (Hanzelmann et al, 2013) to functionally integrate individual cell types and samples from the human 2D mixed neural- glial culture and 3D spheroids scRNAseq datasets with the mouse brain snRNAseq dataset (Supplementary Figure 13). GSVA is a particular type of gene set enrichment method that works at the single sample level and enables pathway- centric analyses of molecular data by performing functional analysis from genes to gene sets to detect subtle pathway activity changes over a sample population. Our results showed that the computed GSVA scores recovered cell type signatures that were previously analysed by GSEA in the different cell types from both the human and mouse datasets confirming that this approach captures transcriptionally encoded biological signals in scRNAseq and snRNAseq data. Notably, the k- means clustering of the different samples revealed an evident segregation based mainly on sample condition (AAV9 or UT) and cell type (astrocytes, oligodendrocytes or neurons), meaning that treated and untreated samples clustered together per cell- type independently of human or murine origin, indicating that treatment and cell- specific responses are the primary drivers of pathway activity. Interestingly, there was no clear clustering based on the different datasets (human- derived 2D and 3D cultures vs. mouse brain) or dataset type (in vitro vs. in vivo). Instead, we observed clustering of glial (left) and neuronal (right) cell populations respectively, showing that the three analysed dataset populations are comparable in their transcriptional profile at the functional level, suggesting highly similar pathway- level profiles between human and mouse. This indicates conserved biological + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 141]]<|/det|> +processes at the pathway level across species and experimental setups, despite differences in experimental context. We have included the details for the analysis in the methods section, lines 883- 896, page 33, and figure description in the main manuscript lines 248- 253, page 10 of the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[118, 148, 789, 499]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 500, 883, 569]]<|/det|> +
Figure E. Violin plots of common genes between human and murine datasets. Violin plot representation of example common genes significantly upregulated across human mixed cultures, brain spheroids and murine striatum datasets contributing to different pathways such as DNA stress response (yellow), pro-inflammatory signalling (purple), type I IFN signalling (green) and mitochondrial stress (orange).
+ +<|ref|>text<|/ref|><|det|>[[115, 585, 883, 619]]<|/det|> +Also, for this in vivo study, the authors should make comparisons of how AAV transduction of individual CNS cells compares to hiPSC derived CNS cells. + +<|ref|>text<|/ref|><|det|>[[115, 636, 882, 687]]<|/det|> +We thank the Reviewer for this suggestion and have address this point in the above- mentioned Figure E and new heatmap in Fig. S13, including the description of all the associated limitations of such comparisons. + +<|ref|>text<|/ref|><|det|>[[115, 704, 882, 737]]<|/det|> +Supplemental Fig. 8: In the figure legend the authors should state what is being stained and how the heat maps were obtained. + +<|ref|>text<|/ref|><|det|>[[115, 754, 882, 873]]<|/det|> +We thank the Reviewer for pointing this out. The figure and figure legend have been updated in the new main Figure 7. The heatmap was generated by Prism after introducing the results from quantifying the percentage of double- positive cells for each co- staining for the different tissue sections, obtained with the MACSima analysis software (MACS® iQ View), and data were plotted in a Grouped table format. Statistics were generated by multiple t- test, and a heatmap representation was selected to represent the results. We have detailed this information on the methods section lines 692- 694, page 26 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 891, 882, 907]]<|/det|> +Supplemental Figure 10: Why didn't the authors treat the cells with the inhibitors prior to transducing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 861, 80]]<|/det|> +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 125]]<|/det|> +them? Since these signalling pathways are triggered upon AAV entry, the TLR pathway cannot be ruled out as upstream of some of the gene induction. + +<|ref|>text<|/ref|><|det|>[[115, 140, 882, 243]]<|/det|> +We thank the Reviewer for this question. As suggested, we repeated the experiment with the TLR9 inhibitor on iPSC- derived astrocytes including a 1- hour pre- treatment prior to AAV transduction (Fig. S16 of the revised manuscript). The inhibitor was maintained in the culture media after the end of the experiment. These new results, together with experiments performed with a TLR9- stealth AAV, suggest that TLR9 sensing does not play a major role in driving AAV signalling in this experimental setting. We have discussed these results on lines 277- 293, page 11 and lines 500- 509, page 19 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 259, 393, 275]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 292, 882, 361]]<|/det|> +This is an interesting, informative, and timely study, addressing a major barrier in translating rAAV- based gene therapy to clinical application. Overall, the manuscript is well written, data thoughtfully analyzed and presented. However, the manuscript can be further strengthened if the authors can address the points below. + +<|ref|>text<|/ref|><|det|>[[115, 377, 700, 394]]<|/det|> +We thank the Reviewer for appreciating our work and its relevance for the field. + +<|ref|>text<|/ref|><|det|>[[115, 411, 882, 462]]<|/det|> +1. In general, the time between AAV transduction and data collection seems to be longer than what is needed by the cells to initiate a DNA damage repair and innate immune responses. Could the authors explain clearly for the rationale to choose these timepoints? + +<|ref|>text<|/ref|><|det|>[[115, 478, 882, 632]]<|/det|> +We thank the Reviewer for this question. The choice of time- point is based on our preliminary tests at multiple time- points in neural stem cells (iNSCs, which are faster to generate compared to more differentiated cells) (Figure F below) showing that no responses are detected as early as 6h, and in iPSC- derived neurons (Figures G and H below) and previous observations in the context of HSPC (Piras et al, 2017) in which the 48h time- point was the first timepoint when robust GFP expression and induction of DNA- damage dependent genes (p21) at the transcriptional level were observed. For our single- cell experiments we chose to collect cells at 48h and at later timepoints days 4 and 5 after performing time- course experiments showing that this is the timepoint at which maximal transgene expression is obtained (Figure C above). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 45, 267, 79]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>image<|/ref|><|det|>[[130, 100, 697, 399]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 410, 883, 446]]<|/det|> +
Figure F. Analysis of selected p53-dependent genes (p21, TRIM22, APOBEC3H) and innate immunity markers (IL1b, CXCL8, ISG15) by qPCR in iNSCs transduced with full AAV9 for 6h or 24h.
+ +<|ref|>image<|/ref|><|det|>[[125, 465, 264, 617]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 625, 821, 643]]<|/det|> +
Figure G. Measurement of GFP-expression levels in iPSC-derived neurons transduced with AAV9.
+ +<|ref|>image<|/ref|><|det|>[[128, 660, 870, 789]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 797, 881, 832]]<|/det|> +
Figure H. Analysis of AAV-derived signalling in iPSC-derived neurons transduced with full and empty AAV9 at 24h and 48h post-transduction.
+ +<|ref|>text<|/ref|><|det|>[[113, 865, 883, 900]]<|/det|> +2. Also, it would be informative to study /compare the outcomes of transduction by single stranded and self-complementary rAAVs. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 106, 883, 327]]<|/det|> +We thank the Reviewer for raising this relevant point. We have now performed in vitro experiments to study differences between ssAAV9 and scAAV9 vectors. Results from these experiments have been pooled in Supplementary Figure 17 showing no significant differences between ss vs sc vectors despite the higher GFP expression derived from the scAAV9 vector (Fig. S17A). This result was somewhat unexpected as scAAV vectors are reported to be more immunogenic than ssAAV vectors in vivo due to higher stimulation of TLR9 receptors in plasmacytoid dendritic cells (pDCs) (Rogers et al., 2017). Our hypothesis is that the type of intrinsic signalling induced by AAV vectors and the relevance of TLR9 sensing is cell- type dependent, as was reported by Rogers et al., showing that TLR9 sensing was specific to pDCs and not conventional dendritic cells. In agreement, additional experiments that we have performed and reported in Supplementary figure 16 further support the lack of involvement of TLR9 on neural cell signalling as we did not observe any major impact of TLR9 inhibition or the use of a TLR9 insensitive AAV2 (io2 (Chan et al., 2021)) in terms of gene induction in hiPSC- derived astrocytes. We have described and discussed these results in lines 277- 293, page 11 and lines 500- 509, page 19 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 344, 883, 428]]<|/det|> +3. For the data presented in Figure 1, in terms of transcriptomic changes with and without AAV vectors, those transduced by AAV9 appears to have milder changes compared to those transduced by AAV2 and AAV6, presumably due to less efficient transduction efficiency. Is there a way to first sort GFP+ cells, and then analyze transcriptomic changes in GFP+ cells alone? Alternatively, will it be a good idea to "normalize" transcriptomic changes based on GFP+ percentage? + +<|ref|>text<|/ref|><|det|>[[115, 444, 883, 666]]<|/det|> +We thank the Reviewer for this question. Because this analysis was based on bulk RNAseq it is not possible to identify and focus on GFP+ cells, and from a bioinformatic point of view it is not feasible to perform a normalization as suggested by the Reviewer. Our observation is that higher VGCN will not only trigger higher fold changes of specific genes, but also induce changes in a higher number of genes involved in a particular pathway, which we would not be able to observe despite normalization. This type of analysis can instead be done on our single-cell RNAseq experiments in terms of transcript positive vs. negative cells. Indeed, we have reported similar transcriptional changes for both GFP+ and GFP- populations in Figure 5 of the revised manuscript, suggesting that some degree of paracrine activation occurs between the two populations. Nevertheless, it is not possible to normalize this analysis by the number of vector copies in each cell, for which we cannot rule out the presence of genome copies in cells in which GFP mRNA was not detected due to potential dropout effect, and VGCN is one of the main determinants of the signalling based on our observations. We have included this consideration on lines 219- 224, page 9 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 682, 882, 750]]<|/det|> +4. For the data described by Figure 2: Why did the authors chose 48 h post transduction as the time to assay caspase 3 cleavage? Would assaying an earlier time point (12h or 24h) give a more pronounced result? A general expectation would be that DNA damage response is induced much sooner than 48 h, especially for a flat-surface cell culture. + +<|ref|>text<|/ref|><|det|>[[115, 767, 883, 886]]<|/det|> +We thank the Reviewer for raising this point. We chose not to perform IF staining of toxicity markers earlier than 48h due to our preliminary tests showing that no transcriptomic changes could be detected in neurons before this timepoint, and that the response was limited to p53- dependent genes such as p21 (Figure H above), for which we did not expect to find changes at the protein level before that time- point. Moreover, we observed that the level of staining is maintained and even more significant at 72h compared to 48h, suggesting that transduction- derived stress may amplify over time and further supporting the rationale of looking for these responses at relatively late time- points after transduction (Fig. I below). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 267, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>image<|/ref|><|det|>[[124, 99, 399, 238]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 244, 883, 295]]<|/det|> +
Figure I. cc3 staining in iPSC derived neurons. Quantification of cc3 staining by IF imaging in iPSC-derived neurons transduced with AAV9-CAG-GFP during 48 and 72h. Dots correspond to data from 3 pooled experiments.
+ +<|ref|>text<|/ref|><|det|>[[115, 310, 882, 379]]<|/det|> +After carefully reviewing the data presented in Figure 4, the p53 pathway in neurons seems to increase from day 2 to day 5. But by day 5, one would assume that the DNA cargo has already undergone ds synthesis and started episode formation. Why does the response appear to be delayed? Would simple transfection of episomes lead to p53 pathway activation? Please see a similar comments above. + +<|ref|>text<|/ref|><|det|>[[115, 395, 883, 532]]<|/det|> +We thank the Reviewer for raising this interesting point. Indeed, as also mentioned above, the response to transduction seems somewhat delayed and persistent in these cells. It is possible that the kinetics of transduction are not synchronized in this setting, as shown for the different serotypes in neurons in Figure E above, and we can expect to find AAV genomes in different conformations in the nucleus with persistent detection of the ITRs. In addition, it is possible that DDR increases according to the kinetics of vector uncoating, and although AAV circularizes over time, ITRs are still recognized despite the episomal form as shown for transfected ITR sequences (Hirsch et al., 2011). We have discussed this point on lines 405- 413, page 16 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 548, 882, 583]]<|/det|> +6. For the data presented in Figure 6, The author should explain better why the in vivo study was performed at day 28, which is very late for assaying innate immune responses against foreign DNA motifs. + +<|ref|>text<|/ref|><|det|>[[115, 599, 883, 803]]<|/det|> +We thank the Reviewer for this question. As some of the AAV- induced responses were seen to be amplified upon transgene expression (Figure 5 of the revised manuscript), the day 28 time- point was chosen as one in which robust transgene expression in the CNS is expected (Hollidge et al., 2022; Mason et al, 2010). Moreover, we also considered that DRG toxicity is observed weeks after injection (Hordeaux et al, 2020a) and is reported to be transgene- expression dependent (Hordeaux et al., 2020b), so we reasoned that assessing this relatively late time point would give an appropriate readout of vector- induced signalling in vivo. We have specified the choice of the time- point in the revised manuscript, lines 234- 238, pages 9- 10 as follows: "Adult male mice were bilaterally injected into the striatum with AAV9- CAG- GFP or vehicle (N=2 mice/group respectively) and were sacrificed 28 days post- injection, a time- point at which robust transgene expression can be expected (Hollidge et al., 2022; Mason et al., 2010) and CNS toxicities have been reported (Golebiowski et al, 2017; Guo et al., 2023; Hordeaux et al., 2020a), which in the DRG context have been shown to be transgene expression- dependent (Hordeaux et al., 2020b)." + +<|ref|>text<|/ref|><|det|>[[115, 819, 882, 870]]<|/det|> +7. One major concern is the experiment described in Figure 8. There is evidence suggesting that STING inhibitor H151 only works for STING-HAQ mutation but not WT STING. Did the authors genotype the hiPSCs? Are they STING HAQ or WT STING? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 175]]<|/det|> +We thank the Reviewer for pointing this out and are aware of literature regarding potential functional differences in common STING variants. Nevertheless, we have successfully used this compound to inhibit STING mediated signalling in multiple types of cells from multiple sources across experiments (and projects (Valeri et al, 2024)), possibly because the HAQ allele is quite common in humans. Therefore, we have not performed sequencing of our hiPSCs to define specifically the STING sequence. + +<|ref|>text<|/ref|><|det|>[[116, 192, 393, 208]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 226, 883, 275]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[116, 293, 393, 309]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 326, 883, 428]]<|/det|> +In this work Costa- Verdera et al have used iPSC- derived human brain cell/spheroid systems and mouse models to examine the hose immune response to AAV transduction in the brain. The authors report that AAV- induces p53- dependent DNA damage responses together with STING- and IL1R- dependent inflammatory responses. In addition, they report an involvement of MAVS in the host response evoked by AAV. Although the question under investigation is very timely, and many of the observations are intriguing, the work appears very descriptive at this stage and mechanistically rather under- developed. + +<|ref|>text<|/ref|><|det|>[[115, 445, 883, 597]]<|/det|> +We thank the Reviewer for reviewing the manuscript and helping us improving the quality of our work. While we agree that more work needs to be done to fully elucidate the mechanisms of innate sensing of AAV in the brain, we believe this manuscript is provide the first mechanistic evidence of this phenomenon in a human system. Furthermore, our molecular studies pinpoint distinct signalling pathways activated by the vector genome versus the expressed transgene that differentially contribute to downstream effects such as toxicity. These studies also provide a starting point for the development of tailored pharmacological approaches aimed at targeting the identified mechanisms of vector sensing and signalling and paves the way for further, more detailed mechanistic dissection of the different identified pathways. + +<|ref|>text<|/ref|><|det|>[[115, 615, 247, 630]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 648, 883, 682]]<|/det|> +1. Microglia expresses the highest levels of both cGAS and STING among brain-resident cells. The authors should include this cell type in the analysis. + +<|ref|>text<|/ref|><|det|>[[115, 699, 883, 867]]<|/det|> +We thank the Reviewer for this suggestion and agree that studying the role of microglia in AAV- mediated signalling and functional consequences is highly relevant. However, we feel that investigating this aspect deserves a dedicated study, in particular regarding the mechanistic dissection of human microglia- specific alterations in vitro that require the set- up and validation of appropriate differentiation protocols and assays. In the present work, we have included data regarding the effect of AAV transduction on murine microglia in vivo (Figure 7 and S14 of the revised manuscript), that suggests that microglial activation together with a more generalized gliosis occurs upon local AAV administration, lines 244- 248, and 262- 266, pages 10- 11 of the revised manuscript, and have acknowledged the importance of pursuing more detailed mechanistic studies also in hiPSC- derived microglia- like cells in the future on lines 516- 517, page 20 of the revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 106, 880, 141]]<|/det|> +2. The data are mainly based on a transcriptional approach. For key activated pathways, e.g. IFN signalling, this should be complemented with protein data. + +<|ref|>text<|/ref|><|det|>[[114, 157, 883, 344]]<|/det|> +We thank the Reviewer for this suggestion. We have performed preliminary assays showing functional activation of IFN signalling, including phospho- TBK1 staining on iPSC- derived neurons (Fig. J) and ELISA for the cytokine IP- 10, which is dependent on IFNy activity, on pooled supernatants from 3 independent neuron transductions with AAV9 and AAV2, showing a tendency for induction on samples transduced with AAV2 (Fig. K). While these first results are encouraging and confirm activation of type I IFN and inflammatory pathways through protein- based assays, we have not been able to perform additional replicates to qualify them to be included in the manuscript due to logistical issues related to the on- going transfer of the PI lab from SR- Tiget in Milan, Italy to the University of Pavia Italy that is significantly slowing down experimental activities, in particular those related to hiPSC- derived cell cultures. We hope the Reviewer agrees to vision these data here and understands that we are not able to include them in the manuscript within a reasonable timeframe. + +<|ref|>image<|/ref|><|det|>[[173, 348, 725, 601]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 618, 883, 668]]<|/det|> +
Figure J. Phospho-TBK1 staining in iPSC-derived neurons. Representative IF images of phospho-TBK1 staining (red) in iPSC-derived neurons transduced with AAV9 at MOI 100,000 for 72 h. Images are from one experiment.
+ +<|ref|>image<|/ref|><|det|>[[128, 690, 323, 900]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 158]]<|/det|> +Figure K. IP- 10 levels on iPSC- derived neuron supernatants. Quantification of IP- 10 concentration detected by MSD in supernatants from iPSC- derived neurons transduced with AAV9 and AAV2. Each dot corresponds to an independent experiment, each performed on pooled supernatants from technical replicates. + +<|ref|>text<|/ref|><|det|>[[115, 174, 883, 226]]<|/det|> +3. CL-CASP3 does not equal apoptosis – in fact could drive GSDME-mediated pyroptosis. The modality of cell death should be further investigated, including the dependency on the innate immune signalling pathways studied. + +<|ref|>text<|/ref|><|det|>[[115, 241, 883, 395]]<|/det|> +We thank the Reviewer for pointing this out and agree that cC3 could imply also other forms of cell death. For this reason, we have now rephrased our description replacing "apoptosis" with "cell death" across the revised manuscript where relevant. In addition, we have included GSDMD staining in murine sections, which we found to colocalize mainly with Iba1+ cells (Fig. S14G, H of the revised manuscript). Because of this co-localization, we interpret that in this context GSDMD is a marker of microglial activation (Pollock et al., 2024) rather than pyropototic cell death as we have no evidence of overt toxicity in our in vivo experiments, and wish to remain cautious in terms of our claims given the attention that gene therapy- related toxicities are receiving in the field in general. We have reported and discussed this additional in vivo data on lines 262- 268, pages 10- 11 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 411, 883, 462]]<|/det|> +4. Brain infections with pathogenic viruses are well-described in lead to influx of immune cells from the periphery, most notably monocytes and T cells. The mouse work would gain a lot if the influx of at least these two cell types is evaluated. + +<|ref|>text<|/ref|><|det|>[[115, 479, 883, 683]]<|/det|> +We thank the Reviewer for this suggestion. Although the effect of AAV transduction on adaptive responses is somewhat out of scope for this manuscript, we have included stainings for gliosis markers (GFAP, Iba1, Galectin 3) and T cells (CD45+CD3+) in Fig. S14 of the revised manuscript. Overall, these new results show increased presence of these markers in AAV- treated animals suggesting activation and recruitment of innate and adaptive immune cells within the transduced tissue in agreement with the Reviewers' suggestion. We have added the following sentence, lines 262- 268, pages 10- 11 of the revised manuscript to acknowledge this: "Injected animals also showed increased presence of GFAP+Sox9+ astrocytes (Fig. S14A- C) and Iba1+ microglia (Fig. 14D, E), in line with the induction of pro-inflammatory pathways detected by snRNAseq in these cell populations in injected animals. Stained Iba1+ cells expressed microglia activation markers such as Galectin- 3 (Fig. S14D, F) and Gasdermin D (GSDMD) (Fig. S14G, H). Finally, presence of infiltrating CD45+ and CD3+ cells was also detected by IF in injected striatum (Fig. S14I, J), altogether indicating the induction of gliosis and recruitment of immune cells". + +<|ref|>text<|/ref|><|det|>[[115, 699, 883, 750]]<|/det|> +5. The conclusion that the innate immune response to AAV transduction is STING dependent is based only on the use of the STING inhibitor, which is not specific. Therefore, it should be tested whether the observed response is ablated in cGAS or STING-deficient mice. + +<|ref|>text<|/ref|><|det|>[[115, 766, 883, 903]]<|/det|> +We thank the Reviewer for the suggestion and agree that performing experiments also in KO animals would be of interest. Unfortunately, however, we do not have access to such mice and are not able to perform these experiments in a reasonable timeframe. Instead, we have further assessed the impact of p53 signalling and downstream pathways on glial cell activation in vivo. For this purpose, we took advantage of a transgene- silent vector harbouring the coagulation factor IX (FIX) transgene under the control of the liver- specific hAAT promoter that activated mainly DNA damage- related responses in the human CNS spheroids (Fig. 5). Mice were injected with the vector in the striatum with concomitant intraperitoneal administration of pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) or STING + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 266, 78]]<|/det|> +Costa- Verdera et al., Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[113, 90, 883, 361]]<|/det|> +(H151), followed by assessment of gliosis on striatal sections. An increase in Iba1+ and GFAP+ cells was observed in mice having received the vector. Moreover, all three treatments decreased the presence of GFAP+ cells in the striata compared to mice injected with AAV only, while they had no effect on the Iba1+ population. NeuN staining indicated absence of neurotoxicity in terms of percentage of NeuN+ cells. These results suggest that, in mice, AAV- mediated CNS transduction can activate gliosis even in a context of low or absent transgene expression when using the hAAT promoter, and that these responses are not unique to the GFP transgene. These responses could be partially modulated through pharmacological inhibition of p53 or of the cGAS- STING pathway, highlighting that vector genome sensing contributes to the activation of local innate immune cells, particularly astrocytes. Results from this experiment are shown in Supplementary Figure 20 and described on lines 339- 356, pages 13- 14 of the revised manuscript. This data further supports the involvement of cGAS/STING signalling in AAV- mediated effects in the CNS and are described and discussed on lines 442- 446, page 17 and lines 480- 483, page 18 of the revised manuscript. In addition, as the focus of our work is not solely on STING- mediated effects, and in agreement with other Reviewer suggestions, we have also modified the title of our manuscript to better reflect the overall findings that are reported as follows: "AAV vectors trigger DNA damage responses and pro- inflammatory signalling in human iPSC- derived CNS models and mouse brain". + +<|ref|>text<|/ref|><|det|>[[115, 377, 882, 428]]<|/det|> +6. The mechanistic explanation for the reported phenomenon is under-developed. The authors should provide deeper explanation of the temporal, spatial, and cell-type-specific roles of the cGAS-STING, RLR-MAVS, and inflammasome pathways. + +<|ref|>text<|/ref|><|det|>[[115, 445, 883, 565]]<|/det|> +We thank the Reviewer for the suggestion and have better discussed this in the revised manuscript, lines 521- 527, page 20, as follows: "Mechanistically, we propose a working model in which the incoming vector DNA triggers a first p53- dependent DNA damage response that will subsequently activate the cGAS/STING mediated inflammatory signalling. Conversely, the type I IFN activation seems mainly driven by cytosolic RNA sensing that converges to the adaptor molecule MAVS in this context, potentially enhancing pro-inflammatory signalling as compared to conditions in which the transgene is not expressed". This working model is also summarized in the graphical abstract, pasted below. + +<|ref|>image<|/ref|><|det|>[[115, 581, 883, 825]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[115, 829, 254, 844]]<|/det|> +## Graphical abstract + +<|ref|>text<|/ref|><|det|>[[115, 861, 883, 895]]<|/det|> +7. The key question – and it can be claimed the motivation for the present study – is to understand mechanisms underlying “dose-dependent toxicities and severe adverse events” of AAV-based gene + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 866, 80]]<|/det|> +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 125]]<|/det|> +therapy. Therefore, the authors need to provide data demonstrating physiological importance of the identified innate immunological activities. + +<|ref|>text<|/ref|><|det|>[[114, 140, 883, 498]]<|/det|> +We thank the Reviewer for this comment. Our study links clinical findings with mechanistic insight (Bharucha- Goebel et al, 2024; Gougeon et al, 2021; Mueller et al, 2020; Sondhi et al, 2020) that may well be connected to our observations, as discussed lines 527- 536, page 20 of the revised manuscript. To further strengthen the physiological importance of our work, we have performed a proof- of- principle study showing that the use of inhibitors that target p53 or the cGAS/STING signalling axis can curb the AAV genome- triggered gliosis upon local AAV delivery in vivo. Briefly, mice were injected in the striatum with a transgene- silent AAV with concomitant intraperitoneal administration of identified pharmacological inhibitors for p53 (pifithrin- \(\alpha\) ), cGAS (RU.521) and STING (H151) and assessed their effect on gliosis on striatum sections. Although we acknowledge that the brain permeability and optimal dose of these drugs may remain limitations of this experimental approach, our analyses reveal that all three treatments decreased the presence of GFAP+ cells in striatum compared to mice injected with AAV only, while they had no effect on the lba1 population nor the NeuN positive cells, suggesting that pharmacological targeting of p53 or the cGAS- STING pathway can curb at least to some extent the vector- induced gliosis without overt toxicity on the CNS cell populations. Results from this experiment are shown in Supplementary Figure 20. We also acknowledge that further studies should be performed to confirm the effect of these drugs in the future including also transgene- expressing vectors for side- by- side comparison, lines 511- 516, pages 19- 20 of the revised manuscript, but wish to mention here that because of recent reorganization within the collaborating biotech company that has performed these experiments, we will not be able to provide additional experiments for this part at this stage. Together, these results further support physiological relevance for these signalling pathways in preventing inflammation in the CNS upon AAV injection. + +<|ref|>text<|/ref|><|det|>[[115, 514, 247, 529]]<|/det|> +Minor comments. + +<|ref|>text<|/ref|><|det|>[[115, 546, 883, 615]]<|/det|> +8. This reviewer find that the term "cell-intrinsic innate immune mechanisms" is not correctly used in this work. Since, the data show upregulation of e.g. interferon pathways, which act in a paracrine manner, the activities discovered are not cell-intrinsic (although some of the effector mechanisms may be). I suggest that the authors simple use the term "innate immune mechanisms. + +<|ref|>text<|/ref|><|det|>[[115, 632, 880, 649]]<|/det|> +We thank the Reviewer for this suggestion and have applied it throughout the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 666, 883, 700]]<|/det|> +9. The finding that virus infections in the brain and brain cells triggers apoptosis in a cGAS-STING dependent manner has been reported previously (e.g. PMID: 32990676) and should be cited. + +<|ref|>text<|/ref|><|det|>[[115, 716, 883, 750]]<|/det|> +We thank the Reviewer for this suggestion and have referenced this work on line 463- 464, page 18 of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 768, 204, 783]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[115, 801, 870, 903]]<|/det|> +Bennett A, Patel S, Mietzsch M, Jose A, Lins- Austin B, Yu JC, Bothner B, McKenna R, Agbandje- McKenna M (2017) Thermal Stability as a Determinant of AAV Serotype Identity. Molecular Therapy Methods & Clinical Development 6: 171- 182 Bertolini TB, Shirley JL, Zolotukhin I, Li X, Kaisho T, Xiao W, Kumar SRP, Herzog RW (2021) Effect of CpG Depletion of Vector Genome on CD8(+) T Cell Responses in AAV Gene Therapy. Front Immunol 12: 672449 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 44, 860, 90]]<|/det|> +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS Point- by- point reply + +<|ref|>text<|/ref|><|det|>[[110, 88, 884, 905]]<|/det|> +Bharucha- Goebel DX, Todd JJ, Saade D, Norato G, Jain M, Lehky T, Bailey RM, Chichester JA, Calcedo R, Armao D et al (2024) Intrathecal Gene Therapy for Giant Axonal Neuropathy. N Engl J Med 390: 1092- 1104 Cervelli T, Palacios JA, Zentilin L, Mano M, Schwartz RA, Weitzman MD, Giacca M (2008) Processing of recombinant AAV genomes occurs in specific nuclear structures that overlap with foci of DNA- damage- response proteins. Journal of cell science 121: 349- 357 Chan YK, Wang SK, Chu CJ, Copland DA, Letizia AJ, Costa Verdera H, Chiang JJ, Sethi M, Wang MK, Neidermyer WJ, Jr. et al (2021) Engineering adeno- associated viral vectors to evade innate immune and inflammatory responses. Sci Transl Med 13 Fischer M (2019) Conservation and divergence of the p53 gene regulatory network between mice and humans. Oncogene 38: 4095- 4109 Fischer M (2021) Mice Are Not Humans: The Case of p53. Trends Cancer 7: 12- 14 Ge MM, Chen N, Zhou YQ, Yang H, Tian YK, Ye DW (2022) Galectin- 3 in Microglia- Mediated Neuroinflammation: Implications for Central Nervous System Diseases. Curr Neuropharmacol 20: 2066- 2080 Ghosh M, Saha S, Li J, Montrose DC, Martinez LA (2023) p53 engages the cGAS/STING cytosolic DNA sensing pathway for tumor suppression. Mol Cell 83: 266- 280. e266 Golebiowski D, van der Bom IMJ, Kwon CS, Miller AD, Petrosky K, Bradbury AM, Maitland S, Kuhn AL, Bishop N, Curran E et al (2017) Direct Intracranial Injection of AAVrh8 Encoding Monkey beta- N- Acetylhexosaminidase Causes Neurotoxicity in the Primate Brain. Hum Gene Ther 28: 510- 522 Gougeon ML, Poirier- Beaudouin B, Ausseil J, Zerah M, Artaud C, Heard JM, Deiva K, Tardieu M (2021) Cell- Mediated Immunity to NAGLU Transgene Following Intracerebral Gene Therapy in Children With Mucopolysaccharidosis Type IIIB Syndrome. Front Immunol 12: 655478 Guo Y, Chen J, Ji W, Xu L, Xie Y, He S, Lai C, Hou K, Li Z, Chen G, Wu Z (2023) High- titer AAV disrupts cerebrovascular integrity and induces lymphocyte infiltration in adult mouse brain. Mol Ther Methods Clin Dev 31: 101102 Hanzelmann S, Castelo R, Guinney J (2013) GSVA: gene set variation analysis for microarray and RNA- seq data. BMC Bioinformatics 14: 7 Hirsch ML, Fagan BM, Dumitru R, Bower JJ, Yadav S, Porteus MH, Pevny LH, Samulski RJ (2011) Viral single- strand DNA induces p53- dependent apoptosis in human embryonic stem cells. PLoS One 6: e27520 Hollidge BS, Carroll HB, Qian R, Fuller ML, Giles AR, Mercer AC, Danos O, Liu Y, Bruder JT, Smith JB (2022) Kinetics and durability of transgene expression after intrastriatal injection of AAV9 vectors. Front Neurol 13: 1051559 Hordeaux J, Buza EL, Dyer C, Goode T, Mitchell TW, Richman L, Denton N, Hinderer C, Katz N, Schmid R et al (2020a) Adeno- Associated Virus- Induced Dorsal Root Ganglion Pathology. Hum Gene Ther 31: 808- 818 Hordeaux J, Buza EL, Jeffrey B, Song C, Jahan T, Yuan Y, Zhu Y, Bell P, Li M, Chichester JA et al (2020b) MicroRNA- mediated inhibition of transgene expression reduces dorsal root ganglion toxicity by AAV vectors in primates. Sci Transl Med 12 Kay J, Thadhani E, Samson L, Engelward B (2019) Inflammation- induced DNA damage, mutations and cancer. DNA Repair (Amst) 83: 102673 Lock M, McGorry S, Auricchio A, Ayuso E, Beecham EJ, Blouin- Tavel V, Bosch F, Bose M, Byrne BJ, Caton T et al (2010) Characterization of a recombinant adeno- associated virus type 2 Reference Standard Material. Hum Gene Ther 21: 1273- 1285 Mason MR, Ehlert EM, Eggers R, Pool CW, Hermening S, Huseinovic A, Timmermans E, Blits B, Verhaagen J (2010) Comparison of AAV serotypes for gene delivery to dorsal root ganglion neurons. Mol Ther 18: 715- 724 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 45, 856, 69]]<|/det|> +Costa- Verdera et al., AAV vectors trigger p53 and STING- mediated neurotoxicity in the CNS + +<|ref|>text<|/ref|><|det|>[[115, 88, 876, 114]]<|/det|> +Mueller C, Berry JD, McKenna- Yasek DM, Gernoux G, Owegi MA, Pothier LM, Douthwright CL, Gelevski D, Luppino SD, Blackwood M et al (2020) SOD1 Suppression with Adeno- Associated Virus and MicroRNA in Familial ALS. N Engl J Med 383: 151- 158 + +<|ref|>text<|/ref|><|det|>[[115, 115, 877, 163]]<|/det|> +Ortinski PI, Dong J, Mungenast A, Yue C, Takano H, Watson DJ, Haydon PG, Coulter DA (2010) Selective induction of astrocytic gliosis generates deficits in neuronal inhibition. Nature Neuroscience 13: 584- 591 + +<|ref|>text<|/ref|><|det|>[[115, 164, 875, 196]]<|/det|> +Piras F, Riba M, Petrillo C, Lazarevic D, Cuccovillo I, Bartolaccini S, Stupka E, Gentner B, Cittaro D, Naldini L, Kajaste- Rudnitski A (2017) Lentiviral vectors escape innate sensing but trigger p53 in human + +<|ref|>text<|/ref|><|det|>[[115, 197, 640, 213]]<|/det|> +hematopoietic stem and progenitor cells. EMBO Mol Med 9: 1198- 1211 + +<|ref|>text<|/ref|><|det|>[[115, 214, 875, 245]]<|/det|> +Pollock NM, Fernandes JP, Woodfield J, Moussa E, Hlavay B, Branton WG, Wuest M, Mohammadzadeh N, Schmitt L, Plemel JR et al (2024) Gasdermin D activation in oligodendrocytes and microglia drives + +<|ref|>text<|/ref|><|det|>[[115, 245, 875, 262]]<|/det|> +inflammatory demyelination in progressive multiple sclerosis. Brain Behav Immun 115: 374- 393 + +<|ref|>text<|/ref|><|det|>[[115, 263, 875, 295]]<|/det|> +Rogers GL, Shirley JL, Zolotukhin I, Kumar SRP, Sherman A, Perrin GQ, Hoffman BE, Srivastava A, Basner- Tschakarjan E, Wallet MA et al (2017) Plasmacytoid and conventional dendritic cells cooperate in + +<|ref|>text<|/ref|><|det|>[[115, 295, 630, 312]]<|/det|> +crosspriming AAV capsid- specific CD8(+) T cells. Blood 129: 3184- 3195 + +<|ref|>text<|/ref|><|det|>[[115, 313, 875, 345]]<|/det|> +Sondhi D, Kaminsky SM, Hackett NR, Pagovich OE, Rosenberg JB, De BP, Chen A, Van de Graaf B, Mezey JG, Mammen GW et al (2020) Slowing late infantile Batten disease by direct brain parenchymal + +<|ref|>text<|/ref|><|det|>[[115, 345, 875, 377]]<|/det|> +administration of a rh.10 adeno- associated virus expressing \(< \mathrm{i} > \mathrm{CLN}2< /\mathrm{i}>\) . Science Translational Medicine 12: eabb5413 + +<|ref|>text<|/ref|><|det|>[[115, 378, 865, 410]]<|/det|> +Tahtinen S, Tong AJ, Himmels P, Oh J, Paler- Martinez A, Kim L, Wichner S, Oei Y, McCarron MJ, Freund EC et al (2022) IL- 1 and IL- 1ra are key regulators of the inflammatory response to RNA vaccines. Nat + +<|ref|>text<|/ref|><|det|>[[115, 410, 275, 425]]<|/det|> +Immunol 23: 532- 542 + +<|ref|>text<|/ref|><|det|>[[115, 427, 875, 460]]<|/det|> +Valeri E, Breggion S, Barzaghi F, Abou Alezz M, Crivicich G, Pagani I, Forneris F, Sartirana C, Costantini M, Costi S et al (2024) A novel STING variant triggers endothelial toxicity and SAVI disease. J Exp Med 221 + +<|ref|>text<|/ref|><|det|>[[115, 460, 865, 475]]<|/det|> +Wright JF (2020) Quantification of CpG Motifs in rAAV Genomes: Avoiding the Toll. Mol Ther 28: 1756- + +<|ref|>text<|/ref|><|det|>[[115, 476, 155, 490]]<|/det|> +1758 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 348, 100]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 115, 433, 132]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 148, 872, 230]]<|/det|> +I want to thank the authors for doing such a good job of addressing my comments. Overall, I think that this is one of the best attempts that I have seen as a reviewer to address all reviewer comments in detail (and there were many comments). This is an excellent manuscript that was made even better with these revisions. I recommend immediate publication. + +<|ref|>text<|/ref|><|det|>[[118, 245, 876, 279]]<|/det|> +We thank the Reviewer for appreciating our efforts and for retaining our work much improved (thanks to the constructive comments) and of high relevance for the field. + +<|ref|>text<|/ref|><|det|>[[119, 303, 433, 320]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 336, 850, 370]]<|/det|> +The authors were responsive to the reviewer comments. The manuscript is easier to read and the figures are clearer. It is acceptable for publication. + +<|ref|>text<|/ref|><|det|>[[118, 394, 849, 428]]<|/det|> +We thank the Reviewer for the positive feedback and for retaining our work improved and ready for publication at this stage. + +<|ref|>text<|/ref|><|det|>[[119, 443, 433, 459]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 475, 803, 508]]<|/det|> +the authors have addressed this reviewer's comments clearly, in some cases, being supported by robust experimental data. I have no further concerns. + +<|ref|>text<|/ref|><|det|>[[118, 532, 810, 566]]<|/det|> +We thank the Reviewer for the positive feedback and for retaining our work ready for publication at this stage. + +<|ref|>text<|/ref|><|det|>[[119, 581, 430, 598]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 613, 850, 696]]<|/det|> +The authors have greatly improved the work during the revision. However, I remain rather critical to conclusions drawn from the mechanistic work. The claim that the host response involves the cGAS- STING and the RLR- MAVS pathways is not based on data from KO mouse strains, which are readily available. In the absence of such data. I do not find the mechanistic claims well supported by the data. + +<|ref|>text<|/ref|><|det|>[[117, 705, 881, 852]]<|/det|> +We thank the Reviewer for the overall positive feedback and agree that additional experimental validation of involved signalling pathways in genetic knockout models will further strengthen our observations in the future. We hope that the reviewer agrees that this work sets the stage for further molecular dissection of the vector signalling both in vitro and in vivo in relevant models, including the mentioned KO mice strains. We have included to following sentence: "Nevertheless, the contribution of cGAS/STING and MAVS pathways to vector sensing will benefit from further confirmations in genetic mouse models and further studies will help to elucidate the clinical impact of these molecular findings", lines 524- 527 of the revised manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/images_list.json b/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8a6f2d7359dfa32c7a94ef9fb9303c7028084cc4 --- /dev/null +++ b/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,336 @@ + +# nature portfolio + +Peer Review File + +Agnostic B cell selection approach identifies antibodies against K. pneumoniae that synergistically drive complement activation + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this study, van der Lans et. al have devised a new method to screen for antibodies that activate the complement cascade in an unbiased fashion by using whole- cell bacteria (Klebsiella pneumoniae). B cells able to bind whole bacteria were agnostically selected for after binding Klebsiella. Their B cell receptors were then sequenced (not a small task) and ultimately monoclonal antibodies were produced. The majority of these bound either O- antigen or capsule indicating that B cell receptors may not be able to access antigens beneath the surfaces on whole bacterial cells. Additionally, while antibodies against both O- antigen and capsule polysaccharide could both bind quite strongly, only those against O- antigen were able to activate the complement cascade, using their example strain. This manuscript was well- written and the use of Klebsiella as a target is important considering the global significance of this increasingly resistant and virulent pathogen. Overall this method is a powerful tool for finding highly avid antibodies in an unbiased way, although it may be a bit labor intensive upfront. Further, this reviewer has some specific questions about the human samples being used that, if further clarified, could strengthen this work: + +- Why did the authors choose to perform this analysis on healthy human serum, rather than choosing serum from patients that have survived a Klebsiella infection. One would expect these survivors to have larger memory B cell populations that were capable of binding (and potentially killing) Klebsiella. By using healthy human sera, aren't the authors selecting for antibodies that may not be as specific or functional? If healthy humans had a large array of pre-existing functional antibodies that bind Klebsiella already circulating, then we would rarely see Klebsiella infections. The authors should justify why they chose healthy subjects and how their results may have differed had they chosen Klebsiella-exposed individuals. + +- Despite the detailed description of bacterial dual-labeling with fluorophores (lines 180-195), it remains unclear why double labeling was required. Was this method initially performed with single-labeled bacteria but did not demonstrate good specificity for B cells capable of binding? Why was "no enrichment observed for the single-positive populations" of B cells? Shouldn't a B cell bound to a Klebsiella with even a single fluorophore suggest it may have relevant binding ability? Further, how does unlabeled bacteria "compete" with double-positive B cells? Wouldn't this just decrease the yield of truly relevant B cells capable of binding Klebsiella? + +- For the complement activation assays, the authors incubated bacteria, normal human serum (as a source of complement), with their specific antibody in question. However, wouldn't the normal human serum also potentially contain antibodies targeting Klebsiella? The authors discuss the creation of antibody-depleted NHS in the methods but fail to mention it in the results. Using bacteria as a method to deplete antibodies seems like it also may affect the complement components. Why not deplete antibodies another way (using anti-human IgG Abs)? + +- The authors include interesting studies looking at mutations in the Fc region that make the antibodies more likely to hexamerize. Interestingly the K-targeted monoclonal antibodies were less likely to hexamerize at baseline unless combined together. Do the authors think this would be the case in a patient that survived Klebsiella infection? Is this representative of the specific monoclonals studied here, or do the authors think this is a more universal phenomenon? + +Minor: + +- Line 110: 700.000 should be 700,000- Line 137: "in case of" should be "in the case of"- Line 183: please spell out STORM acronym- Line 197: "to proof" should be "to prove"- Line 203: Upon introduction of the clinical strains, the authors should give further description. What site of infection were they isolated from? Are they classical or hypervirulent strains? Etc.- Line 250: the authors demonstrate that capsule-targeting antibodies were all ineffective at activating complement. This contradicts much of the vaccine literature in which capsule-targeted antibodies are highly capable of killing most strains by SBA. Please discuss.- Figure S3d: quality needs to be improved for images of O2 and O2afg at the top + +<--- Page Split ---> + +- Line 282: "antibodies still bound" is confusing, reword- Line 287: "upon specific deletion" should be "upon specific deletion of"- Line 289: "suggesting suggests" should be reworded- Line 292: "other O1 strains than KpnO1" considering adding "besides"- Fig 5: why only neutrophils and no macrophages? (Figure 5)- Line 424: "motives" should probably be "motifs"- Line 482: "into pathway" should be "into the pathway"- Line 588: gentamicin is spelled wrong- Table 1 is called out in the methods but should be called out as Table S1 + +Reviewer #2 (Remarks to the Author): + +The manuscript by van der Lans et al. describes a method to identify and characterise in depth new antibodies directed against specific bacterial strains. The technology seems novel, versatile, elegant and efficient. Using this technology, the authors discover antibodies against different antigens on K. pneumoniae, and characterise their potential to drive complement activation and phagocytosis/killing by human neutrophils. The results and methodology are presented in a logical and accessible manner, and the conclusions drawn are fully supported by the data. As a non- subject expert, I cannot comment on other state- of- the- art studies in this field and the potential impact of this study. Instead my comments mainly focus on methodological aspects and some unexplained observations. + +Major points: + +1) The rationale behind only the double-positive B cells being enriched in memory B cells (Fig. 1b) is unclear. Theoretically, the two bacterial populations only differ in their staining (actually only in the fluorophore), not in any other aspect which might impact on their binding by B cells. Since the staining efficiency and fluorophore brightness and detector sensitivity might very well differ between the two stained strains, the detection efficiency and the relative brightness of the two populations might be different in absolute numbers but their behaviour should be qualitatively comparable. It appears that the double positive B cells are those who are stained brightest in each of the two channels. If the labeling of bacteria does not affect their binding by B cells, a similar enrichment in Memory B-cells should also be observed when gating for either KpnO2-Cy5 or KpnO2-Atto488 cells with very high fluorescence intensity (=many bacteria bound), e.g. by only analysing I(KpnO2-Cy5)>10,000 or I(KpnO2-Atto488) > 5,000. Is this the case? Otherwise, could the authors explain in more detail what distinguishes these double-positive B-cells from those only binding one stained strain? + +2) To understand the technology better, it would be helpful to know how many bacteria are typically bound by one B-cell. This could be estimated based on the fluorescence intensity of single bacteria in the flow cytometer, or visualised by an imaging flow cytometer or, alternatively, by normal fluorescence microscopy of pre-sorted B-cells. + +3) To exclude that the staining of the bacteria influenced the binding by antibodies (and thus the selection process), the data with 5x and 25x excess of unstained bacteria (Fig. S1d) could be reanalysed in terms of the gMFI of the stained populations (Q1 and Q3). If unstained bacteria have a similar binding affinity for the B cells as the stained bacteria, the gMFI should roughly reduce by a factor of 5x and 25x, respectively. If this is not the case, the authors should investigate and discuss the potential interference of the staining procedure on the selection process. + +4) Figure 5d showed a 100-fold lower survival of KpnO1 at 0.01 µg/mL UKpn72 compared to 10x and 100x higher antibody concentrations (0.1 and 1 µg/mL). This is surprising given that the same antibody at the same concentration hardly induced phagocytosis by neutrophils (Fig. 5b); it did however robustly induce C3b deposition at this concentration (Fig. 4c). Since the authors excluded a neutrophil-independent killing mechanism (Fig. 5Sc), they should discuss in more detail both, the proposed mechanism of action, and the peculiar dose-response behaviour. Was this behaviour also observed with other O1 antibodies? Would this have implications for possible applications in terms of a therapeutic window? + +5) Fig. 6e also shows enhanced binding of fluorescently labeled UKpn3 when competing against 1-10 µg/mL of unlabeled UKpn3. The same effect was seen for UKpn1 (Fig. S6d). What is the explanation for this finding? Shouldn't the same antibody compete for the same epitope and thus + +<--- Page Split ---> + +lead to a decrease in binding (as observed in Figure S6c for UKpn2)? + +6) The authors stress that (line 460ff) ,Indeed, most antibodies identified in this study could recognize the O1-polysaccharide exclusively in the context of whole bacterial cells and not in its isolated form.", which refers to Fig. 3h. Fig 3g shows that exactly those antibodies which also recognised the antigen in isolated form were those that also recognised other strains. Is there a scientific explanation for this coincidence? + +7) The synergism of anti-capsule antibodies is highly interesting, but the underlying mechanism remains mostly elusive, which calls for further investigations. Are capsule antigens more mobile on the bacterial surface than O2-antigen and O1-antigens? What is known about the relative surface concentrations or clustering of capsule proteins vs O2 and O1 glycans? Both, mobility and local clustering, could potentially influence hexamer formation (besides spacing/steric hindrance, as discussed by the authors). Any experiment and/or simulations that could provide more mechanistic insights into the observed synergism would be of high value. + +Minor points: + +8) Figure 1a: scale bars missing +9) Figure S1c, legend: what does ,MOI of 0.5 per fluorophore" mean? Is this referring to Multiplicity of Infection? Or related to the detection sensitivity (0.5 AU per fluorophore)? Please clarify and introduce abbreviation upon first usage. + +10) Figure S1 Legend: the last sentence of the legend is duplicate/unnecessary: ,(b) Fluorescent intensity (gMFI) and number of events normalized to mode are depicted on the X and Y-axis, respectively." + +11) Inconsistency between text and Figure 6a. Line 347f states that ,mixing two antibodies recognizing the O2 antigen (UKpn2 and UKpn6) did not affect their capacity to drive C3b deposition (Fig. 6a)." However, Fig. 6 a shows UKpn1+UKpn2. Probably there is a typo in the Figure? + +12) Methods: Line 549f: incomplete sentence/information: ,Lysis buffer consisted of." +13) Grammar: Line 117f: Clinically, the O1, O2 and O3 O-types are the most relevant as they [verb missing] over 80% of the clinical isolates. + +[verb missing] over 80% of the clinical isolates. + +14) Grammar: Line 287: missing ,Upon specific deletion [of] wbbY," + +15) Grammar: Line 289: duplicate ,suggesting suggests" should be ,suggesting" only + +Reviewer #3 (Remarks to the Author): + +The article "Agnostic B cell selection approach identifies antibodies against K. pneumoniae that synergistically drive complement activation" by van der Lans and Bardoei et al aims to describe antibody characteristics of human blood IgG memory B cells to the surface antigens of Klebsiella pneumoniae. Using an elegant dual staining approach, the authors isolate blood IgG memory B cells from healthy individuals bearing antibodies to K. pneumoniae prevalent O serotypes O1 and O2. Next, they generated monoclonal antibodies from those isolated B cells and showed that a small percentage binds to K. pneumoniae surface glycans. In total they identified 29 unique monoclonal antibodies. Next, they suggest that antibody binding intensity does not always correlate with the capability for C3b deposition, especially capsule, in contrast to O antigen antibodies, are incapable to activate complement. The authors showed that hexamer formation- enhancing Fc mutations allowed capsule antibodies to activate complement and that antibody- dependent bacterial killing did depend on the presence of neutrophils. Last, they show a synergistic binding and complement activation effect of two capsule antibodies. + +Novel, notable and interesting things about this paper: + +1) Using azide-KDO paired with click-chemistry to isolate memory B cells with specific BCRs is an elegant approach and likely suitable to isolate antibodies to other KDO-expressing bacteria +2) Data suggest that only glycan antigens are accessible on Kp surface +3) The authors show a synergistic binding and C3b deposition effect of two monoclonal antibodies targeting the capsule of Klebsiella pneumoniae + +<--- Page Split ---> + +Possible concerns: + +1) Fig 2a-d: It seems that O2 O antigen-reactive antibody binding levels do correlate with C3b deposition and only capsule-binders show no correlation. Please confirm. Fig. 2b could be plotted at higher antibody concentration to account for the differences between intermediate and negative binders. +2) The authors should proof that the O1 and O2 O antigen reactive antibodies directly target purified LPS of the respective O serotype (similar to Figure 3h). +3) Fig. 6e is not very intuitive. Why does Ukpn3 bind slightly better if more unlabelled Ukpn3 is added? The MFI should drop when more of the same unlabelled antibody is added. +4) Fig S6b: Please confirm that Ukpn1 and 3 do not deposit C3b on K00059 and add an isotype control. +5) The authors should show if the synergistic binding effect of Ukpn1 and 3 can be observed on isolated capsule glycan or it depends on the intact bacterium. +6) Fig 6g: Can Spa-B bind to Ukpn1 and Ukpn3 while they bind the surface of KpnO2? +7) The mechanism of Ukpn1 and 3 binding synergy is not resolved: Can the Fab fragments of Ukpn1 and 3 alone induce the synergistic binding effect? +8) Ultimately, an important question remains: Do Ukpn1 and 3 together are protective in an infection model? + +Minor comments: + +9) Axis labels/ units are frequently missing +10) The authors should change the wording for "active" and "inactive" antibodies. At the end these antibodies are not inactive. +11) Fig. S6b statistics missing +12) Line 340: Uptake by neutrophils was not addressed +13) Line 311: Please change wild-type to unmutated + +<--- Page Split ---> + +## Point-to-point reply (reference NCOMMS-24-14275) + +## Reviewer #1: + +In this study, van der Lans et. al have devised a new method to screen for antibodies that activate the complement cascade in an unbiased fashion by using whole- cell bacteria (Klebsiella pneumoniae). B cells able to bind whole bacteria were agnostically selected for after binding Klebsiella. Their B cell receptors were then sequenced (not a small task) and ultimately monoclonal antibodies were produced. The majority of these bound either O- antigen or capsule indicating that B cell receptors may not be able to access antigens beneath the surfaces on whole bacterial cells. Additionally, while antibodies against both O- antigen and capsule polysaccharide could both bind quite strongly, only those against O- antigen were able to activate the complement cascade, using their example strain. This manuscript was well- written and the use of Klebsiella as a target is important considering the global significance of this increasingly resistant and virulent pathogen. Overall this method is a powerful tool for finding highly avid antibodies in an unbiased way, although it may be a bit labor intensive upfront. Further, this reviewer has some specific questions about the human samples being used that, if further clarified, could strengthen this work: + +POINT 1: Why did the authors choose to perform this analysis on healthy human serum, rather than choosing serum from patients that have survived a Klebsiella infection. One would expect these survivors to have larger memory B cell populations that were capable of binding (and potentially killing) Klebsiella. By using healthy human sera, aren't the authors selecting for antibodies that may not be as specific or functional? If healthy humans had a large array of pre- existing functional antibodies that bind Klebsiella already circulating, then we would rarely see Klebsiella infections. The authors should justify why they chose healthy subjects and how their results may have differed had they chosen Klebsiella- exposed individuals. + +ANSWER 1: We focused on healthy donors since it was previously described that healthy individuals are exposed to Klebsiella and are an effective source for identifying memory B cells against purified antigens of Klebsiella. The referee is right that the levels of specific memory B cells in circulation are probably lower in healthy individuals. However, it is much easier to obtain large volumes of blood (and thus more B cells) from healthy donors than from patients. Especially, when using buffy coats derived from 500 ml healthy donor blood. In the revised manuscript, we now clarify our rationale for using healthy donors in (results section page 5, line 181- 182; discussion page 13, line 537- 540). + +We agree that employing a similar strategy on B cells from patients is an interesting follow- up study. Our study demonstrates that healthy donors have functional antibodies, but for patients this is not yet known. One could even argue that healthy individuals could potentially have better antibodies than patients, since they do not get disease. Indeed, there is literature suggesting that infected patients make non- functional antibodies that inhibit complement activation on Gram- negative bacteria. In the discussion, we now elaborate on how the results could have been different when choosing patients (page 13, line 542- 546). + +POINT 2: Despite the detailed description of bacterial dual- labeling with fluorophores (lines 180- 195), it remains unclear why double labeling was required. Was this method initially performed with single- labeled bacteria but did not demonstrate good specificity for B cells capable of binding? Why was "no enrichment observed for the single- positive populations" of B cells? Shouldn't a B cell bound to a Klebsiella with even a single fluorophore suggest it may have relevant binding ability? Further, how does unlabeled bacteria "compete" with double- positive + +<--- Page Split ---> + +B cells? Wouldn't this just decrease the yield of truly relevant B cells capable of binding Klebsiella? + +ANSWER 2: We used the dual- labeling technique to address the problem of false positive events in rare event sorting. We based this idea based on previous papers in which dual labeling of B cells with purified antigens was presented as a relatively simple method to enhance the signal to noise ratio and thus reduce the number of false positive events (PMID: 28111638). Although we think it would be possible to sort B cells based on fluorescence intensity with a single fluorophore, with one color it could be more difficult to eliminate false- positive events. The rationale for the dual labeling method is now clarified (Results, page 5, line 183- 184). + +In addition, we now performed fluorescence microscopy on the single and dual stained B cells to visualize our selection process (also see answer reviewer 2, point 2). While double- positive B cells indeed have multiple bacteria attached, \(95\%\) of single positive B cells have no bacteria bound indicating this signal is not specific (new Fig 1c, S1f & Results, page 5). When adding unlabeled bacteria there is competition between fluorescently labeled and unlabeled bacteria for binding to B cells (when the cells are saturated). Therefore, we observe a decrease of the double positive B cells when adding unlabeled bacteria in excess. In Fig S1e, we now also included gMFI of Fig S1d to show that when adding an excess of bacteria the specific signal (dual labeled B cells) disappears. + +POINT 3: For the complement activation assays, the authors incubated bacteria, normal human serum (as a source of complement), with their specific antibody in question. However, wouldn't the normal human serum also potentially contain antibodies targeting Klebsiella? The authors discuss the creation of antibody- depleted NHS in the methods but fail to mention it in the results. Using bacteria as a method to deplete antibodies seems like it also may affect the complement components. Why not deplete antibodies another way (using anti- human IgG Abs)? + +ANSWER 3: Normal human serum (NHS) can indeed contain antibodies against Klebsiella. To exclusively measure the effect of our monoclonal antibodies, we therefore often used serum that is depleted from pre- existing antibodies. This was mainly the case for assays with the \(KpnO1\) strain, since antibody levels against this strain are higher than for \(KpnO2\) . For the \(KpnO2\) strain, preexisting antibody levels are low and there is no difference between using NHS or pre- absorbed serum. Therefore, some experiments with \(KpnO2\) are performed with NHS. In the revised manuscript we have now stated more clearly when we used NHS versus depleted serum (Results and legends sections). + +Also, we have now clarified the use of our depletion method (Results, page 6, line 223- 225). We prefer depleting only bacteria- specific antibodies, since others have shown that total depletion of human IgG negatively affects complement activation (even after adding back polyclonal IgG and IgM (doi: 10.3389/fimmu.2018.02770). We previously showed that the depletion of bacterial antibodies alone specifically depletes strain- specific antibodies while keeping complement activity intact (doi: 10.1038/s41598- 023- 39613- 5). + +POINT 4: The authors include interesting studies looking at mutations in the Fc region that make the antibodies more likely to hexamerize. Interestingly the K- targeted monoclonal antibodies were less likely to hexamerize at baseline unless combined together. Do the authors think this would be the case in a patient that survived Klebsiella infection? Is this representative of the specific monoclonals studied here, or do the authors think this is a more universal phenomenon? + +<--- Page Split ---> + +ANSWER 4: The fact that the two synergistically acting antibodies (UKpn1 and 3) were isolated from the same healthy donor indeed suggests that cooperation between K- targeting antibodies could also occur in serum of an infected individual. Although future research is needed to determine whether other antibodies can do the same, our study indicates that collaboration between anti- capsular antibodies could be an important, but until now overlooked, mechanism by which antibodies protect against infections. We now elaborate on these points in the discussion section (page 12, line 506- 515). + +## POINT 5: + +POINT 5:Minor:- Line 110: 700.000 should be 700,000- Line 137: "in case of" should be "in the case of"- Line 183: please spell out STORM acronym- Line 197: "to proof" should be "to prove"- Figure S3d: quality needs to be improved for images of O2 and O2afg at the top- Line 282: "antibodies still bound" is confusing, reword- Line 287: "upon specific deletion" should be "upon specific deletion of"- Line 289: "suggesting suggests" should be reworded- Line 292: "other O1 strains than KpnO1" considering adding "besides"- Line 424: "motives" should probably be "motifs"- Line 482: "into pathway" should be "into the pathway"- Line 588: gentamicin is spelled wrong- Table 1 is called out in the methods but should be called out as Table S1 + +ANSWER 5: All points above are corrected in the revised manuscript. + +POINT 6: Line 203: Upon introduction of the clinical strains, the authors should give further description. What site of infection were they isolated from? Are they classical or hypervirulent strains? Etc. + +ANSWER 6: KpnO2 and KpnO1 are classical strains. Their sequence type and isolation site are now included in the manuscript (Results, page 5, line 204; and table S1). + +POINT 7: Line 250: the authors demonstrate that capsule- targeting antibodies were all ineffective at activating complement. This contradicts much of the vaccine literature in which capsule- targeted antibodies are highly capable of killing most strains by SBA. Please discuss. + +ANSWER 7: We believe that our findings do not contradict previous vaccine literature. Our monoclonal anti- KL110 antibodies were not able activate the complement system. However, as a polyclonal (or rather biclonal) mix, they did efficiently induce complement deposition and opsonophagocytosis. Since a capsule vaccine will induce a polyclonal response, an important aspect of the protective properties of the described capsule vaccines might be due to combined effects antibodies in the polyclonal response. We have now revised the discussion section to better reflect on previous vaccination studies (page 12, line 509- 515). + +POINT 8: Fig 5: why only neutrophils and no macrophages? (Figure 5) + +ANSWER 8: Although macrophages could also be used, we here focused on neutrophils since they are very effective in phagocytosis and killing of bacteria and therefore a relevant cell type to test the effector functions of the here identified antibodies. + +<--- Page Split ---> + +## Reviewer #2: + +Reviewer #2:The manuscript by van der Lans et al. describes a method to identify and characterise in depth new antibodies directed against specific bacterial strains. The technology seems novel, versatile, elegant and efficient. Using this technology, the authors discover antibodies against different antigens on K. pneumoniae, and characterise their potential to drive complement activation and phagocytosis/killing by human neutrophils. The results and methodology are presented in a logical and accessible manner, and the conclusions drawn are fully supported by the data. As a non- subject expert, I cannot comment on other state- of- the- art studies in this field and the potential impact of this study. Instead my comments mainly focus on methodological aspects and some unexplained observations. + +## Major points: + +Major points:POINT 1: The rationale behind only the double- positive B cells being enriched in memory B cells (Fig. 1b) is unclear. Theoretically, the two bacterial populations only differ in their staining (actually only in the fluorophore), not in any other aspect which might impact on their binding by B cells. Since the staining efficiency and fluorophore brightness and detector sensitivity might very well differ between the two stained strains, the detection efficiency and the relative brightness of the two populations might be different in absolute numbers but their behaviour should be qualitatively comparable. It appears that the double positive B cells are those who are stained brightest in each of the two channels. If the labeling of bacteria does not affect their binding by B cells, a similar enrichment in Memory B- cells should also be observed when gating for either KpnO2- Cy5 or KpnO2- Atto488 cells with very high fluorescence intensity (=many bacteria bound), e.g. by only analysing I(KpnO2- Cy5)>10,000 or I(KpnO2- Atto488) \(>5,000\) . Is this the case? Otherwise, could the authors explain in more detail what distinguishes these double- positive B- cells from those only binding one stained strain? + +## ANSWER 1: + +We used the dual- labeling technique to address the problem of false positive events in rare event sorting. We based this idea based on previous papers in which dual labeling of B cells with purified antigens was presented as a relatively simple method to enhance the signal to noise ratio and thus reduce the number of false positive events (PMID: 28111638). + +As suggested, we reanalyzed the geoMFI of the double stained bacteria for each fluorophore separately and observed that the levels were higher compared to the single stained bacteria (SFig 1f, right panel). In general, the dual stained B cells bind on average more bacteria (as discussed at point 2 below, new Fig S1f) resulting in higher fluorescence in Cy5 and Atto488 channel (as observed in Fig 1b, S1e). As suggested by the referee, this shows that it would be possible to sort B cells based on fluorescence intensity with a single fluorophore and obtain an enrichment in memory B cells. However, with two colors it is easier to eliminate false- positive events. + +As explained in answer 2 below, new microscopy experiments demonstrated that doublepositive B cells indeed have multiple bacteria attached. In contrast, single positive B cells have no bacteria bound indicating that this signal is not specific (new Fig 1c, S1f), + +POINT 2: To understand the technology better, it would be helpful to know how many bacteria are typically bound by one B- cell. This could be estimated based on the fluorescence intensity of single bacteria in the flow cytometer, or visualised by an imaging flow cytometer or, alternatively, by normal fluorescence microscopy of pre- sorted B- cells. + +<--- Page Split ---> + +ANSWER 2: As suggested, we sorted single and double positive B cells for KpnO2- Atto488 and KpnO2- Cy5 into poly- Lysine coated cell imaging chambers. Imaging revealed that most B cells that were sorted as double positive have multiple bacteria in the two different colors attached. For the B cells that stained single positive for KpnO2- Cy5 only some bacteria that were not attached to B cells were observed. We now included an image and quantification of single and double stained sorted cells as Fig 1c and Sfig1f and updated the results section. Based on the flow cytometry data, we determined that the gMFI of single versus double stained bacteria was 2- 3- fold higher (new Fig S1e and f – right panel) indicating that on average there are 5 times more bacteria associated with a B cell. With microscopy we observed that 47% of the double- positive- sorted cells have bacteria bound, indicating that on average around \(\sim 10\) bacteria bind to a bacterium specific B cell. We included this information as new figure 1c and S1f and described the experiment in the results section (page 5). + +POINT 3: To exclude that the staining of the bacteria influenced the binding by antibodies (and thus the selection process), the data with 5x and 25x excess of unstained bacteria (Fig. S1d) could be reanalysed in terms of the gMFI of the stained populations (Q1 and Q3). If unstained bacteria have a similar binding affinity for the B cells as the stained bacteria, the gMFI should roughly reduce by a factor of 5x and 25x, respectively. If this is not the case, the authors should investigate and discuss the potential interference of the staining procedure on the selection process. + +ANSWER 3: We reanalyzed the gMFI as suggested. The gMFI of cells in Q1 and Q3 were unaffected by addition of unlabeled bacteria as shown in the new Fig S1e. This indicates that this signal is not specific, which is confirmed with the new microscopy data (new Fig 1c, S1f) of single positive B cells that shows that 95% (S1f, right panel) of the cells have no bacteria bound. In contrast, in the double- positive population many B cells contain multiple bacteria, which explains why adding an excess of unlabeled bacteria results in competition and decrease of gMFI (Fig S1d and S1e). The decrease in fluorescent signal is 2.5- fold when adding 5x or 25x excess of unstained bacteria (Fig S1d). Due to the background signal, the specific signal is already lost at 5x excess of unlabeled bacteria. + +POINT 4: Figure 5d showed a 100- fold lower survival of KpnO1 at 0.01 \(\mu \mathrm{g / mL}\) UKpn72 compared to 10x and 100x higher antibody concentrations (0.1 and 1 \(\mu \mathrm{g / mL}\) ). This is surprising given that the same antibody at the same concentration hardly induced phagocytosis by neutrophils (Fig. 5b); it did however robustly induce C3b deposition at this concentration (Fig. 4c). Since the authors excluded a neutrophil- independent killing mechanism (Fig. S5c), they should discuss in more detail both, the proposed mechanism of action, and the peculiar dose- response behaviour. Was this behaviour also observed with other O1 antibodies? Would this have implications for possible applications in terms of a therapeutic window? + +ANSWER 4: In figure S5c we show that there is no major effect of UKpn72 on neutrophil- independent killing, however for UKpn72 there is a slight effect at 0.01 \(\mu \mathrm{g / mL}\) . At this concentration, a potential collaboration between MAC and neutrophils (10.1371/journal.ppat.1009227) could lead to better killing. We now better explain this in the results section (page 8, line 345- 346). We have also observed this behavior for other O1 antibodies (such as the previously described KPB202 antibody (Patent No.: US 11,117,956 B2)), but we don't know if this behavior is relevant in vivo, + +POINT 5: Fig. 6e also shows enhanced binding of fluorescently labeled UKpn3 when competing against 1- 10 \(\mu \mathrm{g / mL}\) of unlabeled UKpn3. The same effect was seen for UKpn1 (Fig. S6d). What is + +<--- Page Split ---> + +the explanation for this finding? Shouldn't the same antibody compete for the same epitope and thus lead to a decrease in binding (as observed in Figure S6c for UKpn2)? + +ANSWER 5: We suspect there is no saturation at this point since the capsule is a very abundant antigen on the bacterial surface and therefore there is no competition. In our paper, we focused on the increase in fluorescence when combining UKpn3- A647 with unlabeled UKpn1 since this effect is much stronger than for UKpn3- A647 with unlabeled UKpn3. For the slight increase with unlabeled UKpn3, we have no explanation at this moment. + +POINT 6: The authors stress that (line 460ff) „Indeed, most antibodies identified in this study could recognize the O1- polysaccharide exclusively in the context of whole bacterial cells and not in its isolated form.“, which refers to Fig. 3h. Fig 3g shows that exactly those antibodies which also recognised the antigen in isolated form were those that also recognised other strains. Is there a scientific explanation for this coincidence? + +ANSWER 6: We think this suggests that the antibodies that do not recognize their antigen in bacterial cell lysates recognize a configuration of the O1- antigen that is unique to the KpnO1 strain. Apparently, the epitope(s) that are recognized by these antibodies are affected by making bacterial lysates or recognition requires repetition of the epitope that is not available by western blot. That could be a reason to the impaired binding to other O1 strains that we observed. We now clarified this in the results section (page 8, line 304- 305). + +POINT 7: The synergism of anti- capsule antibodies is highly interesting, but the underlying mechanism remains mostly elusive, which calls for further investigations. Are capsule antigens more mobile on the bacterial surface than O2- antigen and O1- antigens? What is known about the relative surface concentrations or clustering of capsule proteins vs O2 and O1 glycans? Both, mobility and local clustering, could potentially influence hexamer formation (besides spacing/steric hindrance, as discussed by the authors). Any experiment and/or simulations that could provide more mechanistic insights into the observed synergism would be of high value. + +ANSWER 7: We have performed several new experiments to obtain more insights into the mechanism of synergism. Since it was suggested that synergistic binding would depend on Fc- mediated IgG hexamerization, we studied this question specifically. We generated both divalent F(ab')2 and monovalent Fab fragments from UKpn1 and UKpn3. To our surprise, we observed that synergistic binding between the two antibodies was independent of the IgG- Fc tail. Both F(ab')2 and Fab fragments of UKpn1 could strengthen the binding of full- length UKpn3 (and vice versa). Additionally, F(ab')2 fragments of UKpn1 also enhanced complement activation by full- length UKpn3 (and vice versa). Altogether, this new data set demonstrates that synergy between UKpn1 and UKpn3 occurs via a novel mechanism that is different from previously reported IgG hexamerization. In the revised manuscript, we included these 8 extra figures (Fig. 7b- d and SFig. 7c- f) and we made textual revisions of both the Results (page 9&10, line 389- 408) and Discussion (page 12, line 489- 505) sections to reflect on these new data. In addition, we have extensively revised our discussion section to better reflect on the existing knowledge concerning physical properties of both capsule and O antigen (page 11, line 462- 473). + +<--- Page Split ---> + +## Minor points + +POINT 8: Figure 1a: scale bars missing + +ANSWER 8: Scale bars were added to Fig 1a. + +POINT 9: Figure S1c, legend: what does „MOI of 0.5 per fluorophore“ mean? Is this referring to Multiplicity of Infection? Or related to the detection sensitivity (0.5 AU per fluorophore)? Please clarify and introduce abbreviation upon first usage. + +ANSWER 9: It refers to multiplicity of infection - per B cell 0.5 bacterium labeled with Cy5 and 0.5 bacterium labeled with ATTO488. Text was adjusted for clarification. + +POINT 10: Figure S1 Legend: the last sentence of the legend is duplicate/unnecessary: „(b) Fluorescent intensity (gMFI) and number of events normalized to mode are depicted on the X and Y- axis, respectively.“ + +ANSWER 10: Changed as suggested. + +POINT 11: Inconsistency between text and Figure 6a. Line 347f states that „mixing two antibodies recognizing the O2 antigen (UKpn2 and UKpn6) did not affect their capacity to drive C3b deposition (Fig. 6a).“ However, Fig. 6 a shows UKpn1+UKpn2. Probably there is a typo in the Figure? + +ANSWER 11: The wrong figure was shown as Fig 6a, this should be as mentioned in the text UKpn2 and UKpn6. We now corrected this in the revised manuscript. + +POINT 12: Methods: Line 549f: incomplete sentence/information: „Lysis buffer consisted of.“ ANSWER 12: Corrected in the revised manuscript. + +POINT 13: Grammar: Line 117f: Clinically, the O1, O2 and O3 O- types are the most relevant as they [verb missing] over \(80\%\) of the clinical isolates. + +ANSWER 13: Corrected in the revised manuscript. + +POINT 14: Grammar: Line 287: missing „Upon specific deletion [of] wbbY,“ ANSWER 14: Corrected in the revised manuscript. + +POINT 15: Grammar: Line 289: duplicate „suggesting suggests“ should be „suggesting“ only ANSWER 15: Corrected in the revised manuscript. + +<--- Page Split ---> + +## Reviewer #3 + +The article "Agnostic B cell selection approach identifies antibodies against K. pneumoniae that synergistically drive complement activation" by van der Lans and Bardoelet al aims to describe antibody characteristics of human blood IgG memory B cells to the surface antigens of Klebsiella pneumoniae. Using an elegant dual staining approach, the authors isolate blood IgG memory B cells from healthy individuals bearing antibodies to K. pneumoniae prevalent O serotypes O1 and O2. Next, they generated monoclonal antibodies from those isolated B cells and showed that a small percentage binds to K. pneumoniae surface glycans. In total they identified 29 unique monoclonal antibodies. Next, they suggest that antibody binding intensity does not always correlate with the capability for C3b deposition, especially capsule, in contrast to O antigen antibodies, are incapable to activate complement. The authors showed that hexamer formation- enhancing Fc mutations allowed capsule antibodies to activate complement and that antibody- dependent bacterial killing did depend on the presence of neutrophils. Last, they show a synergistic binding and complement activation effect of two capsule antibodies. + +Novel, notable and interesting things about this paper: + +1) Using azide-KDO paired with click-chemistry to isolate memory B cells with specific BCRs is an elegant approach and likely suitable to isolate antibodies to other KDO-expressing bacteria +2) Data suggest that only glycan antigens are accessible on Kp surface +3) The authors show a synergistic binding and C3b deposition effect of two monoclonal antibodies targeting the capsule of Klebsiella pneumoniae + +Possible concerns: + +POINT 1: Fig 2a- d: It seems that O2 O antigen- reactive antibody binding levels do correlate with C3b deposition and only capsule- binders show no correlation. Please confirm. Fig. 2b could be plotted at higher antibody concentration to account for the differences between intermediate and negative binders. + +ANSWER 1: Indeed, there is a correlation between antibody binding and C3b deposition for the mAbs targeting the O2 antigen. Since we did not identify the targets of the antibodies at this stage in the manuscript, we did not specify the different groups yet. We plotted fig 2b at the same concentration as the fig 2d to make a direct comparison. + +POINT 2: The authors should proof that the O1 and O2 O antigen reactive antibodies directly target purified LPS of the respective O serotype (similar to Figure 3h). + +ANSWER 2: We performed a western blot (as in Fig 3h for KpnO1) for some of the antibodies directed against KpnO2 on bacterial lysate of KpnO2. This shows that UKpn2, 6, 7 and 8 recognize the O- antigen as illustrated by the smear at around 50 kD indicative for the LPS O- antigen. Antibodies UKpn3 stains at a higher molecular weight, which probably indicate recognition of capsular polysaccharide. We now included the western blot as Fig S3d and included it to the text of the results section (Results, page, 7 line 258- 261). + +POINT 3: Fig. 6e is not very intuitive. Why does UKpn3 bind slightly better if more unlabelled UKpn3 is added? The MFI should drop when more of the same unlabelled antibody is added. + +<--- Page Split ---> + +ANSWER 3: We suspect there is no saturation at this point since the capsule is a very abundant antigen on the bacterial surface and therefore there is no competition. The slight increase we cannot explain at this moment. + +POINT 4: Fig S6b: Please confirm that UKpn1 and 3 do not deposit C3b on K00059 and add an isotype control. + +ANSWER 4: We repeated the experiment on 209S and SF0025 (K00059) with an isotype control (aDNP). For K00059 some C3b deposition by UKpn1 and UKpn3 only was observed at \(3\%\) , while absent at \(1\%\) NHS. We added the updated graphs to the revised manuscript (Fig S6b). + +POINT 5: The authors should show if the synergistic binding effect of UKpn1 and 3 can be observed on isolated capsule glycan or it depends on the intact bacterium. + +ANSWER 5: UKpn1 and 3 are directed against capsule type KL110. Since isolated glycans are not available for this capsule type, we focused on using whole bacteria. + +POINT 6: Fig 6g: Can Spa- B bind to UKpn1 and UKpn3 while they bind the surface of KpnO2? + +ANSWER 6: We have performed additional experiments to verify that Spa- B indeed binds to the combination of UKpn1 and UKpn3. We now included these new data as Figure S6c and describe the findings the text of the results section (page 9, line 371- 372). + +POINT 7: The mechanism of UKpn1 and 3 binding synergy is not resolved: Can the Fab fragments of UKpn1 and 3 alone induce the synergistic binding effect? + +ANSWER 7: We have now generated F(ab')2 and Fab fragments of UKpn1 and UKpn3 to study this question. Interestingly, the experiments reveal that the synergistic binding between UKpn1 and UKpn3 is also observed with F(ab')2 and Fab fragments. This shows that synergy between UKpn1 and UKpn3 is independent of the Fc tail. We added these new figures to the revised manuscript (Fig. 7b- d and Fig. S7c- f) and we made textual revisions of both the Results (page 9&10, line 389- 408) and Discussion (page 12, line 490- 505) sections to reflect on these new data + +POINT 8: Ultimately, an important question remains: Do UKpn1 and 3 together are protective in an infection model? + +ANSWER 8: Although we agree this would be an interesting study, we think it is outside the scope of the current manuscript. + +POINT 9: Minor comments: Axis labels/ units are frequently missing + +ANSWER 9: We tried to clarify this as much as possible in the revised manuscript. + +POINT 9: The authors should change the wording for "active" and "inactive" antibodies. At the end these antibodies are not inactive. + +ANSWER 10: We changed this or adjusted to complement- inactive. + +POINT 11: Fig. S6b statistics missing + +<--- Page Split ---> + +ANSWER 11: Statistics was added to Fig S6b + +POINT 12: Line 340: Uptake by neutrophils was not addressed + +ANSWER 12: In the results section we now clarified that we measured phagocytosis of bacteria by neutrophils + +POINT 13: Line 311: Please change wild- type to unmutated + +ANSWER 13: We changed this in the revised manuscript. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have done a commendable job addressing my previous concerns. I think the revised manuscript is significantly improved. + +Reviewer #2 (Remarks to the Author): + +Lans et al have submitted a revised version of their manuscript which includes several control experiments, new experiments exploring the mechanism of synergistic action, as well as edits to text and figures. The authors' detailed rebuttal in my opinion addresses the points raised by me and other reviewers in a comprehensive and thorough manner. The revision has clarified the rationale for using a dual- staining approach and substantially strengthened the main conclusions of the paper. While open questions remain about the mechanism of synergy as well as its effectiveness in an infection model, I deem these to be beyond the scope of this manuscript. I thus recommend this manuscript for publication without further request for changes and congratulate the authors on their excellent study. + +Reviewer #3 (Remarks to the Author): + +I do not have any further comments. Congratulations for the work. + +<--- Page Split ---> + +## Point-to-point reply + +Reviewer #2 raises one point: While open questions remain about the mechanism of synergy as well as its effectiveness in an infection model, I deem these to be beyond the scope of this manuscript. I thus recommend this manuscript for publication without further request for changes and congratulate the authors on their excellent study. + +Answer: In the discussion section of our revised paper, we now include the limitations mentioned by the reviewer: page 12, line 498: "Although open questions about the exact mechanism behind synergistic binding remain..." page 12, lines 511- 512: "Since our study is limited to in vitro experiments, it remains to be assessed whether the combination of two anti- capsule antibodies is effective in an in vivo infection model." + +<--- Page Split ---> diff --git a/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e0a466344725b02459ad5a683eeb3f9ecd326464 --- /dev/null +++ b/peer_reviews/33306b23e955a69377a2b9fd4a790f7b5a2a4b3873afaf51206bc0f2c5134481/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,459 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 360, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[68, 161, 895, 216]]<|/det|> +Agnostic B cell selection approach identifies antibodies against K. pneumoniae that synergistically drive complement activation + +<|ref|>image<|/ref|><|det|>[[56, 732, 239, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 802]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 295, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 111, 413, 125]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 140, 877, 323]]<|/det|> +In this study, van der Lans et. al have devised a new method to screen for antibodies that activate the complement cascade in an unbiased fashion by using whole- cell bacteria (Klebsiella pneumoniae). B cells able to bind whole bacteria were agnostically selected for after binding Klebsiella. Their B cell receptors were then sequenced (not a small task) and ultimately monoclonal antibodies were produced. The majority of these bound either O- antigen or capsule indicating that B cell receptors may not be able to access antigens beneath the surfaces on whole bacterial cells. Additionally, while antibodies against both O- antigen and capsule polysaccharide could both bind quite strongly, only those against O- antigen were able to activate the complement cascade, using their example strain. This manuscript was well- written and the use of Klebsiella as a target is important considering the global significance of this increasingly resistant and virulent pathogen. Overall this method is a powerful tool for finding highly avid antibodies in an unbiased way, although it may be a bit labor intensive upfront. Further, this reviewer has some specific questions about the human samples being used that, if further clarified, could strengthen this work: + +<|ref|>text<|/ref|><|det|>[[118, 336, 877, 448]]<|/det|> +- Why did the authors choose to perform this analysis on healthy human serum, rather than choosing serum from patients that have survived a Klebsiella infection. One would expect these survivors to have larger memory B cell populations that were capable of binding (and potentially killing) Klebsiella. By using healthy human sera, aren't the authors selecting for antibodies that may not be as specific or functional? If healthy humans had a large array of pre-existing functional antibodies that bind Klebsiella already circulating, then we would rarely see Klebsiella infections. The authors should justify why they chose healthy subjects and how their results may have differed had they chosen Klebsiella-exposed individuals. + +<|ref|>text<|/ref|><|det|>[[118, 461, 877, 560]]<|/det|> +- Despite the detailed description of bacterial dual-labeling with fluorophores (lines 180-195), it remains unclear why double labeling was required. Was this method initially performed with single-labeled bacteria but did not demonstrate good specificity for B cells capable of binding? Why was "no enrichment observed for the single-positive populations" of B cells? Shouldn't a B cell bound to a Klebsiella with even a single fluorophore suggest it may have relevant binding ability? Further, how does unlabeled bacteria "compete" with double-positive B cells? Wouldn't this just decrease the yield of truly relevant B cells capable of binding Klebsiella? + +<|ref|>text<|/ref|><|det|>[[118, 573, 878, 658]]<|/det|> +- For the complement activation assays, the authors incubated bacteria, normal human serum (as a source of complement), with their specific antibody in question. However, wouldn't the normal human serum also potentially contain antibodies targeting Klebsiella? The authors discuss the creation of antibody-depleted NHS in the methods but fail to mention it in the results. Using bacteria as a method to deplete antibodies seems like it also may affect the complement components. Why not deplete antibodies another way (using anti-human IgG Abs)? + +<|ref|>text<|/ref|><|det|>[[118, 672, 875, 742]]<|/det|> +- The authors include interesting studies looking at mutations in the Fc region that make the antibodies more likely to hexamerize. Interestingly the K-targeted monoclonal antibodies were less likely to hexamerize at baseline unless combined together. Do the authors think this would be the case in a patient that survived Klebsiella infection? Is this representative of the specific monoclonals studied here, or do the authors think this is a more universal phenomenon? + +<|ref|>text<|/ref|><|det|>[[118, 756, 168, 768]]<|/det|> +Minor: + +<|ref|>text<|/ref|><|det|>[[118, 770, 860, 910]]<|/det|> +- Line 110: 700.000 should be 700,000- Line 137: "in case of" should be "in the case of"- Line 183: please spell out STORM acronym- Line 197: "to proof" should be "to prove"- Line 203: Upon introduction of the clinical strains, the authors should give further description. What site of infection were they isolated from? Are they classical or hypervirulent strains? Etc.- Line 250: the authors demonstrate that capsule-targeting antibodies were all ineffective at activating complement. This contradicts much of the vaccine literature in which capsule-targeted antibodies are highly capable of killing most strains by SBA. Please discuss.- Figure S3d: quality needs to be improved for images of O2 and O2afg at the top + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 675, 210]]<|/det|> +- Line 282: "antibodies still bound" is confusing, reword- Line 287: "upon specific deletion" should be "upon specific deletion of"- Line 289: "suggesting suggests" should be reworded- Line 292: "other O1 strains than KpnO1" considering adding "besides"- Fig 5: why only neutrophils and no macrophages? (Figure 5)- Line 424: "motives" should probably be "motifs"- Line 482: "into pathway" should be "into the pathway"- Line 588: gentamicin is spelled wrong- Table 1 is called out in the methods but should be called out as Table S1 + +<|ref|>text<|/ref|><|det|>[[119, 264, 413, 279]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 292, 875, 419]]<|/det|> +The manuscript by van der Lans et al. describes a method to identify and characterise in depth new antibodies directed against specific bacterial strains. The technology seems novel, versatile, elegant and efficient. Using this technology, the authors discover antibodies against different antigens on K. pneumoniae, and characterise their potential to drive complement activation and phagocytosis/killing by human neutrophils. The results and methodology are presented in a logical and accessible manner, and the conclusions drawn are fully supported by the data. As a non- subject expert, I cannot comment on other state- of- the- art studies in this field and the potential impact of this study. Instead my comments mainly focus on methodological aspects and some unexplained observations. + +<|ref|>text<|/ref|><|det|>[[118, 420, 220, 433]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[117, 433, 876, 616]]<|/det|> +1) The rationale behind only the double-positive B cells being enriched in memory B cells (Fig. 1b) is unclear. Theoretically, the two bacterial populations only differ in their staining (actually only in the fluorophore), not in any other aspect which might impact on their binding by B cells. Since the staining efficiency and fluorophore brightness and detector sensitivity might very well differ between the two stained strains, the detection efficiency and the relative brightness of the two populations might be different in absolute numbers but their behaviour should be qualitatively comparable. It appears that the double positive B cells are those who are stained brightest in each of the two channels. If the labeling of bacteria does not affect their binding by B cells, a similar enrichment in Memory B-cells should also be observed when gating for either KpnO2-Cy5 or KpnO2-Atto488 cells with very high fluorescence intensity (=many bacteria bound), e.g. by only analysing I(KpnO2-Cy5)>10,000 or I(KpnO2-Atto488) > 5,000. Is this the case? Otherwise, could the authors explain in more detail what distinguishes these double-positive B-cells from those only binding one stained strain? + +<|ref|>text<|/ref|><|det|>[[117, 615, 876, 670]]<|/det|> +2) To understand the technology better, it would be helpful to know how many bacteria are typically bound by one B-cell. This could be estimated based on the fluorescence intensity of single bacteria in the flow cytometer, or visualised by an imaging flow cytometer or, alternatively, by normal fluorescence microscopy of pre-sorted B-cells. + +<|ref|>text<|/ref|><|det|>[[117, 670, 877, 755]]<|/det|> +3) To exclude that the staining of the bacteria influenced the binding by antibodies (and thus the selection process), the data with 5x and 25x excess of unstained bacteria (Fig. S1d) could be reanalysed in terms of the gMFI of the stained populations (Q1 and Q3). If unstained bacteria have a similar binding affinity for the B cells as the stained bacteria, the gMFI should roughly reduce by a factor of 5x and 25x, respectively. If this is not the case, the authors should investigate and discuss the potential interference of the staining procedure on the selection process. + +<|ref|>text<|/ref|><|det|>[[117, 755, 876, 867]]<|/det|> +4) Figure 5d showed a 100-fold lower survival of KpnO1 at 0.01 µg/mL UKpn72 compared to 10x and 100x higher antibody concentrations (0.1 and 1 µg/mL). This is surprising given that the same antibody at the same concentration hardly induced phagocytosis by neutrophils (Fig. 5b); it did however robustly induce C3b deposition at this concentration (Fig. 4c). Since the authors excluded a neutrophil-independent killing mechanism (Fig. 5Sc), they should discuss in more detail both, the proposed mechanism of action, and the peculiar dose-response behaviour. Was this behaviour also observed with other O1 antibodies? Would this have implications for possible applications in terms of a therapeutic window? + +<|ref|>text<|/ref|><|det|>[[117, 867, 870, 910]]<|/det|> +5) Fig. 6e also shows enhanced binding of fluorescently labeled UKpn3 when competing against 1-10 µg/mL of unlabeled UKpn3. The same effect was seen for UKpn1 (Fig. S6d). What is the explanation for this finding? Shouldn't the same antibody compete for the same epitope and thus + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 645, 98]]<|/det|> +lead to a decrease in binding (as observed in Figure S6c for UKpn2)? + +<|ref|>text<|/ref|><|det|>[[118, 99, 860, 168]]<|/det|> +6) The authors stress that (line 460ff) ,Indeed, most antibodies identified in this study could recognize the O1-polysaccharide exclusively in the context of whole bacterial cells and not in its isolated form.", which refers to Fig. 3h. Fig 3g shows that exactly those antibodies which also recognised the antigen in isolated form were those that also recognised other strains. Is there a scientific explanation for this coincidence? + +<|ref|>text<|/ref|><|det|>[[118, 169, 879, 272]]<|/det|> +7) The synergism of anti-capsule antibodies is highly interesting, but the underlying mechanism remains mostly elusive, which calls for further investigations. Are capsule antigens more mobile on the bacterial surface than O2-antigen and O1-antigens? What is known about the relative surface concentrations or clustering of capsule proteins vs O2 and O1 glycans? Both, mobility and local clustering, could potentially influence hexamer formation (besides spacing/steric hindrance, as discussed by the authors). Any experiment and/or simulations that could provide more mechanistic insights into the observed synergism would be of high value. + +<|ref|>text<|/ref|><|det|>[[119, 272, 220, 284]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[118, 285, 865, 339]]<|/det|> +8) Figure 1a: scale bars missing +9) Figure S1c, legend: what does ,MOI of 0.5 per fluorophore" mean? Is this referring to Multiplicity of Infection? Or related to the detection sensitivity (0.5 AU per fluorophore)? Please clarify and introduce abbreviation upon first usage. + +<|ref|>text<|/ref|><|det|>[[118, 339, 870, 380]]<|/det|> +10) Figure S1 Legend: the last sentence of the legend is duplicate/unnecessary: ,(b) Fluorescent intensity (gMFI) and number of events normalized to mode are depicted on the X and Y-axis, respectively." + +<|ref|>text<|/ref|><|det|>[[118, 380, 833, 435]]<|/det|> +11) Inconsistency between text and Figure 6a. Line 347f states that ,mixing two antibodies recognizing the O2 antigen (UKpn2 and UKpn6) did not affect their capacity to drive C3b deposition (Fig. 6a)." However, Fig. 6 a shows UKpn1+UKpn2. Probably there is a typo in the Figure? + +<|ref|>text<|/ref|><|det|>[[118, 435, 835, 463]]<|/det|> +12) Methods: Line 549f: incomplete sentence/information: ,Lysis buffer consisted of." +13) Grammar: Line 117f: Clinically, the O1, O2 and O3 O-types are the most relevant as they [verb missing] over 80% of the clinical isolates. + +<|ref|>text<|/ref|><|det|>[[118, 464, 640, 478]]<|/det|> +[verb missing] over 80% of the clinical isolates. + +<|ref|>text<|/ref|><|det|>[[118, 478, 640, 492]]<|/det|> +14) Grammar: Line 287: missing ,Upon specific deletion [of] wbbY," + +<|ref|>text<|/ref|><|det|>[[118, 492, 773, 507]]<|/det|> +15) Grammar: Line 289: duplicate ,suggesting suggests" should be ,suggesting" only + +<|ref|>text<|/ref|><|det|>[[120, 561, 413, 575]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 588, 860, 771]]<|/det|> +The article "Agnostic B cell selection approach identifies antibodies against K. pneumoniae that synergistically drive complement activation" by van der Lans and Bardoei et al aims to describe antibody characteristics of human blood IgG memory B cells to the surface antigens of Klebsiella pneumoniae. Using an elegant dual staining approach, the authors isolate blood IgG memory B cells from healthy individuals bearing antibodies to K. pneumoniae prevalent O serotypes O1 and O2. Next, they generated monoclonal antibodies from those isolated B cells and showed that a small percentage binds to K. pneumoniae surface glycans. In total they identified 29 unique monoclonal antibodies. Next, they suggest that antibody binding intensity does not always correlate with the capability for C3b deposition, especially capsule, in contrast to O antigen antibodies, are incapable to activate complement. The authors showed that hexamer formation- enhancing Fc mutations allowed capsule antibodies to activate complement and that antibody- dependent bacterial killing did depend on the presence of neutrophils. Last, they show a synergistic binding and complement activation effect of two capsule antibodies. + +<|ref|>text<|/ref|><|det|>[[118, 785, 536, 799]]<|/det|> +Novel, notable and interesting things about this paper: + +<|ref|>text<|/ref|><|det|>[[118, 812, 864, 882]]<|/det|> +1) Using azide-KDO paired with click-chemistry to isolate memory B cells with specific BCRs is an elegant approach and likely suitable to isolate antibodies to other KDO-expressing bacteria +2) Data suggest that only glycan antigens are accessible on Kp surface +3) The authors show a synergistic binding and C3b deposition effect of two monoclonal antibodies targeting the capsule of Klebsiella pneumoniae + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 258, 97]]<|/det|> +Possible concerns: + +<|ref|>text<|/ref|><|det|>[[115, 111, 875, 352]]<|/det|> +1) Fig 2a-d: It seems that O2 O antigen-reactive antibody binding levels do correlate with C3b deposition and only capsule-binders show no correlation. Please confirm. Fig. 2b could be plotted at higher antibody concentration to account for the differences between intermediate and negative binders. +2) The authors should proof that the O1 and O2 O antigen reactive antibodies directly target purified LPS of the respective O serotype (similar to Figure 3h). +3) Fig. 6e is not very intuitive. Why does Ukpn3 bind slightly better if more unlabelled Ukpn3 is added? The MFI should drop when more of the same unlabelled antibody is added. +4) Fig S6b: Please confirm that Ukpn1 and 3 do not deposit C3b on K00059 and add an isotype control. +5) The authors should show if the synergistic binding effect of Ukpn1 and 3 can be observed on isolated capsule glycan or it depends on the intact bacterium. +6) Fig 6g: Can Spa-B bind to Ukpn1 and Ukpn3 while they bind the surface of KpnO2? +7) The mechanism of Ukpn1 and 3 binding synergy is not resolved: Can the Fab fragments of Ukpn1 and 3 alone induce the synergistic binding effect? +8) Ultimately, an important question remains: Do Ukpn1 and 3 together are protective in an infection model? + +<|ref|>text<|/ref|><|det|>[[118, 378, 251, 391]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[118, 405, 875, 490]]<|/det|> +9) Axis labels/ units are frequently missing +10) The authors should change the wording for "active" and "inactive" antibodies. At the end these antibodies are not inactive. +11) Fig. S6b statistics missing +12) Line 340: Uptake by neutrophils was not addressed +13) Line 311: Please change wild-type to unmutated + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 84, 662, 103]]<|/det|> +## Point-to-point reply (reference NCOMMS-24-14275) + +<|ref|>sub_title<|/ref|><|det|>[[117, 125, 253, 141]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 144, 879, 366]]<|/det|> +In this study, van der Lans et. al have devised a new method to screen for antibodies that activate the complement cascade in an unbiased fashion by using whole- cell bacteria (Klebsiella pneumoniae). B cells able to bind whole bacteria were agnostically selected for after binding Klebsiella. Their B cell receptors were then sequenced (not a small task) and ultimately monoclonal antibodies were produced. The majority of these bound either O- antigen or capsule indicating that B cell receptors may not be able to access antigens beneath the surfaces on whole bacterial cells. Additionally, while antibodies against both O- antigen and capsule polysaccharide could both bind quite strongly, only those against O- antigen were able to activate the complement cascade, using their example strain. This manuscript was well- written and the use of Klebsiella as a target is important considering the global significance of this increasingly resistant and virulent pathogen. Overall this method is a powerful tool for finding highly avid antibodies in an unbiased way, although it may be a bit labor intensive upfront. Further, this reviewer has some specific questions about the human samples being used that, if further clarified, could strengthen this work: + +<|ref|>text<|/ref|><|det|>[[115, 389, 873, 518]]<|/det|> +POINT 1: Why did the authors choose to perform this analysis on healthy human serum, rather than choosing serum from patients that have survived a Klebsiella infection. One would expect these survivors to have larger memory B cell populations that were capable of binding (and potentially killing) Klebsiella. By using healthy human sera, aren't the authors selecting for antibodies that may not be as specific or functional? If healthy humans had a large array of pre- existing functional antibodies that bind Klebsiella already circulating, then we would rarely see Klebsiella infections. The authors should justify why they chose healthy subjects and how their results may have differed had they chosen Klebsiella- exposed individuals. + +<|ref|>text<|/ref|><|det|>[[115, 540, 874, 666]]<|/det|> +ANSWER 1: We focused on healthy donors since it was previously described that healthy individuals are exposed to Klebsiella and are an effective source for identifying memory B cells against purified antigens of Klebsiella. The referee is right that the levels of specific memory B cells in circulation are probably lower in healthy individuals. However, it is much easier to obtain large volumes of blood (and thus more B cells) from healthy donors than from patients. Especially, when using buffy coats derived from 500 ml healthy donor blood. In the revised manuscript, we now clarify our rationale for using healthy donors in (results section page 5, line 181- 182; discussion page 13, line 537- 540). + +<|ref|>text<|/ref|><|det|>[[115, 683, 871, 794]]<|/det|> +We agree that employing a similar strategy on B cells from patients is an interesting follow- up study. Our study demonstrates that healthy donors have functional antibodies, but for patients this is not yet known. One could even argue that healthy individuals could potentially have better antibodies than patients, since they do not get disease. Indeed, there is literature suggesting that infected patients make non- functional antibodies that inhibit complement activation on Gram- negative bacteria. In the discussion, we now elaborate on how the results could have been different when choosing patients (page 13, line 542- 546). + +<|ref|>text<|/ref|><|det|>[[115, 810, 880, 906]]<|/det|> +POINT 2: Despite the detailed description of bacterial dual- labeling with fluorophores (lines 180- 195), it remains unclear why double labeling was required. Was this method initially performed with single- labeled bacteria but did not demonstrate good specificity for B cells capable of binding? Why was "no enrichment observed for the single- positive populations" of B cells? Shouldn't a B cell bound to a Klebsiella with even a single fluorophore suggest it may have relevant binding ability? Further, how does unlabeled bacteria "compete" with double- positive + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 811, 113]]<|/det|> +B cells? Wouldn't this just decrease the yield of truly relevant B cells capable of binding Klebsiella? + +<|ref|>text<|/ref|><|det|>[[115, 130, 879, 242]]<|/det|> +ANSWER 2: We used the dual- labeling technique to address the problem of false positive events in rare event sorting. We based this idea based on previous papers in which dual labeling of B cells with purified antigens was presented as a relatively simple method to enhance the signal to noise ratio and thus reduce the number of false positive events (PMID: 28111638). Although we think it would be possible to sort B cells based on fluorescence intensity with a single fluorophore, with one color it could be more difficult to eliminate false- positive events. The rationale for the dual labeling method is now clarified (Results, page 5, line 183- 184). + +<|ref|>text<|/ref|><|det|>[[115, 258, 877, 402]]<|/det|> +In addition, we now performed fluorescence microscopy on the single and dual stained B cells to visualize our selection process (also see answer reviewer 2, point 2). While double- positive B cells indeed have multiple bacteria attached, \(95\%\) of single positive B cells have no bacteria bound indicating this signal is not specific (new Fig 1c, S1f & Results, page 5). When adding unlabeled bacteria there is competition between fluorescently labeled and unlabeled bacteria for binding to B cells (when the cells are saturated). Therefore, we observe a decrease of the double positive B cells when adding unlabeled bacteria in excess. In Fig S1e, we now also included gMFI of Fig S1d to show that when adding an excess of bacteria the specific signal (dual labeled B cells) disappears. + +<|ref|>text<|/ref|><|det|>[[115, 417, 880, 530]]<|/det|> +POINT 3: For the complement activation assays, the authors incubated bacteria, normal human serum (as a source of complement), with their specific antibody in question. However, wouldn't the normal human serum also potentially contain antibodies targeting Klebsiella? The authors discuss the creation of antibody- depleted NHS in the methods but fail to mention it in the results. Using bacteria as a method to deplete antibodies seems like it also may affect the complement components. Why not deplete antibodies another way (using anti- human IgG Abs)? + +<|ref|>text<|/ref|><|det|>[[115, 545, 879, 673]]<|/det|> +ANSWER 3: Normal human serum (NHS) can indeed contain antibodies against Klebsiella. To exclusively measure the effect of our monoclonal antibodies, we therefore often used serum that is depleted from pre- existing antibodies. This was mainly the case for assays with the \(KpnO1\) strain, since antibody levels against this strain are higher than for \(KpnO2\) . For the \(KpnO2\) strain, preexisting antibody levels are low and there is no difference between using NHS or pre- absorbed serum. Therefore, some experiments with \(KpnO2\) are performed with NHS. In the revised manuscript we have now stated more clearly when we used NHS versus depleted serum (Results and legends sections). + +<|ref|>text<|/ref|><|det|>[[115, 673, 880, 769]]<|/det|> +Also, we have now clarified the use of our depletion method (Results, page 6, line 223- 225). We prefer depleting only bacteria- specific antibodies, since others have shown that total depletion of human IgG negatively affects complement activation (even after adding back polyclonal IgG and IgM (doi: 10.3389/fimmu.2018.02770). We previously showed that the depletion of bacterial antibodies alone specifically depletes strain- specific antibodies while keeping complement activity intact (doi: 10.1038/s41598- 023- 39613- 5). + +<|ref|>text<|/ref|><|det|>[[115, 784, 880, 880]]<|/det|> +POINT 4: The authors include interesting studies looking at mutations in the Fc region that make the antibodies more likely to hexamerize. Interestingly the K- targeted monoclonal antibodies were less likely to hexamerize at baseline unless combined together. Do the authors think this would be the case in a patient that survived Klebsiella infection? Is this representative of the specific monoclonals studied here, or do the authors think this is a more universal phenomenon? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 875, 195]]<|/det|> +ANSWER 4: The fact that the two synergistically acting antibodies (UKpn1 and 3) were isolated from the same healthy donor indeed suggests that cooperation between K- targeting antibodies could also occur in serum of an infected individual. Although future research is needed to determine whether other antibodies can do the same, our study indicates that collaboration between anti- capsular antibodies could be an important, but until now overlooked, mechanism by which antibodies protect against infections. We now elaborate on these points in the discussion section (page 12, line 506- 515). + +<|ref|>sub_title<|/ref|><|det|>[[115, 210, 191, 223]]<|/det|> +## POINT 5: + +<|ref|>text<|/ref|><|det|>[[115, 227, 747, 450]]<|/det|> +POINT 5:Minor:- Line 110: 700.000 should be 700,000- Line 137: "in case of" should be "in the case of"- Line 183: please spell out STORM acronym- Line 197: "to proof" should be "to prove"- Figure S3d: quality needs to be improved for images of O2 and O2afg at the top- Line 282: "antibodies still bound" is confusing, reword- Line 287: "upon specific deletion" should be "upon specific deletion of"- Line 289: "suggesting suggests" should be reworded- Line 292: "other O1 strains than KpnO1" considering adding "besides"- Line 424: "motives" should probably be "motifs"- Line 482: "into pathway" should be "into the pathway"- Line 588: gentamicin is spelled wrong- Table 1 is called out in the methods but should be called out as Table S1 + +<|ref|>text<|/ref|><|det|>[[115, 465, 667, 481]]<|/det|> +ANSWER 5: All points above are corrected in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 497, 861, 544]]<|/det|> +POINT 6: Line 203: Upon introduction of the clinical strains, the authors should give further description. What site of infection were they isolated from? Are they classical or hypervirulent strains? Etc. + +<|ref|>text<|/ref|><|det|>[[115, 560, 866, 592]]<|/det|> +ANSWER 6: KpnO2 and KpnO1 are classical strains. Their sequence type and isolation site are now included in the manuscript (Results, page 5, line 204; and table S1). + +<|ref|>text<|/ref|><|det|>[[115, 608, 860, 655]]<|/det|> +POINT 7: Line 250: the authors demonstrate that capsule- targeting antibodies were all ineffective at activating complement. This contradicts much of the vaccine literature in which capsule- targeted antibodies are highly capable of killing most strains by SBA. Please discuss. + +<|ref|>text<|/ref|><|det|>[[115, 671, 883, 784]]<|/det|> +ANSWER 7: We believe that our findings do not contradict previous vaccine literature. Our monoclonal anti- KL110 antibodies were not able activate the complement system. However, as a polyclonal (or rather biclonal) mix, they did efficiently induce complement deposition and opsonophagocytosis. Since a capsule vaccine will induce a polyclonal response, an important aspect of the protective properties of the described capsule vaccines might be due to combined effects antibodies in the polyclonal response. We have now revised the discussion section to better reflect on previous vaccination studies (page 12, line 509- 515). + +<|ref|>text<|/ref|><|det|>[[115, 800, 666, 816]]<|/det|> +POINT 8: Fig 5: why only neutrophils and no macrophages? (Figure 5) + +<|ref|>text<|/ref|><|det|>[[115, 832, 878, 879]]<|/det|> +ANSWER 8: Although macrophages could also be used, we here focused on neutrophils since they are very effective in phagocytosis and killing of bacteria and therefore a relevant cell type to test the effector functions of the here identified antibodies. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 85, 253, 101]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 103, 880, 247]]<|/det|> +Reviewer #2:The manuscript by van der Lans et al. describes a method to identify and characterise in depth new antibodies directed against specific bacterial strains. The technology seems novel, versatile, elegant and efficient. Using this technology, the authors discover antibodies against different antigens on K. pneumoniae, and characterise their potential to drive complement activation and phagocytosis/killing by human neutrophils. The results and methodology are presented in a logical and accessible manner, and the conclusions drawn are fully supported by the data. As a non- subject expert, I cannot comment on other state- of- the- art studies in this field and the potential impact of this study. Instead my comments mainly focus on methodological aspects and some unexplained observations. + +<|ref|>sub_title<|/ref|><|det|>[[117, 263, 238, 280]]<|/det|> +## Major points: + +<|ref|>text<|/ref|><|det|>[[115, 295, 884, 504]]<|/det|> +Major points:POINT 1: The rationale behind only the double- positive B cells being enriched in memory B cells (Fig. 1b) is unclear. Theoretically, the two bacterial populations only differ in their staining (actually only in the fluorophore), not in any other aspect which might impact on their binding by B cells. Since the staining efficiency and fluorophore brightness and detector sensitivity might very well differ between the two stained strains, the detection efficiency and the relative brightness of the two populations might be different in absolute numbers but their behaviour should be qualitatively comparable. It appears that the double positive B cells are those who are stained brightest in each of the two channels. If the labeling of bacteria does not affect their binding by B cells, a similar enrichment in Memory B- cells should also be observed when gating for either KpnO2- Cy5 or KpnO2- Atto488 cells with very high fluorescence intensity (=many bacteria bound), e.g. by only analysing I(KpnO2- Cy5)>10,000 or I(KpnO2- Atto488) \(>5,000\) . Is this the case? Otherwise, could the authors explain in more detail what distinguishes these double- positive B- cells from those only binding one stained strain? + +<|ref|>sub_title<|/ref|><|det|>[[117, 520, 213, 534]]<|/det|> +## ANSWER 1: + +<|ref|>text<|/ref|><|det|>[[117, 536, 881, 598]]<|/det|> +We used the dual- labeling technique to address the problem of false positive events in rare event sorting. We based this idea based on previous papers in which dual labeling of B cells with purified antigens was presented as a relatively simple method to enhance the signal to noise ratio and thus reduce the number of false positive events (PMID: 28111638). + +<|ref|>text<|/ref|><|det|>[[115, 614, 870, 742]]<|/det|> +As suggested, we reanalyzed the geoMFI of the double stained bacteria for each fluorophore separately and observed that the levels were higher compared to the single stained bacteria (SFig 1f, right panel). In general, the dual stained B cells bind on average more bacteria (as discussed at point 2 below, new Fig S1f) resulting in higher fluorescence in Cy5 and Atto488 channel (as observed in Fig 1b, S1e). As suggested by the referee, this shows that it would be possible to sort B cells based on fluorescence intensity with a single fluorophore and obtain an enrichment in memory B cells. However, with two colors it is easier to eliminate false- positive events. + +<|ref|>text<|/ref|><|det|>[[117, 743, 870, 790]]<|/det|> +As explained in answer 2 below, new microscopy experiments demonstrated that doublepositive B cells indeed have multiple bacteria attached. In contrast, single positive B cells have no bacteria bound indicating that this signal is not specific (new Fig 1c, S1f), + +<|ref|>text<|/ref|><|det|>[[117, 821, 867, 886]]<|/det|> +POINT 2: To understand the technology better, it would be helpful to know how many bacteria are typically bound by one B- cell. This could be estimated based on the fluorescence intensity of single bacteria in the flow cytometer, or visualised by an imaging flow cytometer or, alternatively, by normal fluorescence microscopy of pre- sorted B- cells. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 875, 275]]<|/det|> +ANSWER 2: As suggested, we sorted single and double positive B cells for KpnO2- Atto488 and KpnO2- Cy5 into poly- Lysine coated cell imaging chambers. Imaging revealed that most B cells that were sorted as double positive have multiple bacteria in the two different colors attached. For the B cells that stained single positive for KpnO2- Cy5 only some bacteria that were not attached to B cells were observed. We now included an image and quantification of single and double stained sorted cells as Fig 1c and Sfig1f and updated the results section. Based on the flow cytometry data, we determined that the gMFI of single versus double stained bacteria was 2- 3- fold higher (new Fig S1e and f – right panel) indicating that on average there are 5 times more bacteria associated with a B cell. With microscopy we observed that 47% of the double- positive- sorted cells have bacteria bound, indicating that on average around \(\sim 10\) bacteria bind to a bacterium specific B cell. We included this information as new figure 1c and S1f and described the experiment in the results section (page 5). + +<|ref|>text<|/ref|><|det|>[[115, 305, 872, 416]]<|/det|> +POINT 3: To exclude that the staining of the bacteria influenced the binding by antibodies (and thus the selection process), the data with 5x and 25x excess of unstained bacteria (Fig. S1d) could be reanalysed in terms of the gMFI of the stained populations (Q1 and Q3). If unstained bacteria have a similar binding affinity for the B cells as the stained bacteria, the gMFI should roughly reduce by a factor of 5x and 25x, respectively. If this is not the case, the authors should investigate and discuss the potential interference of the staining procedure on the selection process. + +<|ref|>text<|/ref|><|det|>[[115, 432, 877, 576]]<|/det|> +ANSWER 3: We reanalyzed the gMFI as suggested. The gMFI of cells in Q1 and Q3 were unaffected by addition of unlabeled bacteria as shown in the new Fig S1e. This indicates that this signal is not specific, which is confirmed with the new microscopy data (new Fig 1c, S1f) of single positive B cells that shows that 95% (S1f, right panel) of the cells have no bacteria bound. In contrast, in the double- positive population many B cells contain multiple bacteria, which explains why adding an excess of unlabeled bacteria results in competition and decrease of gMFI (Fig S1d and S1e). The decrease in fluorescent signal is 2.5- fold when adding 5x or 25x excess of unstained bacteria (Fig S1d). Due to the background signal, the specific signal is already lost at 5x excess of unlabeled bacteria. + +<|ref|>text<|/ref|><|det|>[[115, 592, 880, 721]]<|/det|> +POINT 4: Figure 5d showed a 100- fold lower survival of KpnO1 at 0.01 \(\mu \mathrm{g / mL}\) UKpn72 compared to 10x and 100x higher antibody concentrations (0.1 and 1 \(\mu \mathrm{g / mL}\) ). This is surprising given that the same antibody at the same concentration hardly induced phagocytosis by neutrophils (Fig. 5b); it did however robustly induce C3b deposition at this concentration (Fig. 4c). Since the authors excluded a neutrophil- independent killing mechanism (Fig. S5c), they should discuss in more detail both, the proposed mechanism of action, and the peculiar dose- response behaviour. Was this behaviour also observed with other O1 antibodies? Would this have implications for possible applications in terms of a therapeutic window? + +<|ref|>text<|/ref|><|det|>[[115, 736, 875, 848]]<|/det|> +ANSWER 4: In figure S5c we show that there is no major effect of UKpn72 on neutrophil- independent killing, however for UKpn72 there is a slight effect at 0.01 \(\mu \mathrm{g / mL}\) . At this concentration, a potential collaboration between MAC and neutrophils (10.1371/journal.ppat.1009227) could lead to better killing. We now better explain this in the results section (page 8, line 345- 346). We have also observed this behavior for other O1 antibodies (such as the previously described KPB202 antibody (Patent No.: US 11,117,956 B2)), but we don't know if this behavior is relevant in vivo, + +<|ref|>text<|/ref|><|det|>[[115, 864, 875, 896]]<|/det|> +POINT 5: Fig. 6e also shows enhanced binding of fluorescently labeled UKpn3 when competing against 1- 10 \(\mu \mathrm{g / mL}\) of unlabeled UKpn3. The same effect was seen for UKpn1 (Fig. S6d). What is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 878, 115]]<|/det|> +the explanation for this finding? Shouldn't the same antibody compete for the same epitope and thus lead to a decrease in binding (as observed in Figure S6c for UKpn2)? + +<|ref|>text<|/ref|><|det|>[[115, 130, 878, 211]]<|/det|> +ANSWER 5: We suspect there is no saturation at this point since the capsule is a very abundant antigen on the bacterial surface and therefore there is no competition. In our paper, we focused on the increase in fluorescence when combining UKpn3- A647 with unlabeled UKpn1 since this effect is much stronger than for UKpn3- A647 with unlabeled UKpn3. For the slight increase with unlabeled UKpn3, we have no explanation at this moment. + +<|ref|>text<|/ref|><|det|>[[115, 226, 860, 306]]<|/det|> +POINT 6: The authors stress that (line 460ff) „Indeed, most antibodies identified in this study could recognize the O1- polysaccharide exclusively in the context of whole bacterial cells and not in its isolated form.“, which refers to Fig. 3h. Fig 3g shows that exactly those antibodies which also recognised the antigen in isolated form were those that also recognised other strains. Is there a scientific explanation for this coincidence? + +<|ref|>text<|/ref|><|det|>[[115, 321, 881, 418]]<|/det|> +ANSWER 6: We think this suggests that the antibodies that do not recognize their antigen in bacterial cell lysates recognize a configuration of the O1- antigen that is unique to the KpnO1 strain. Apparently, the epitope(s) that are recognized by these antibodies are affected by making bacterial lysates or recognition requires repetition of the epitope that is not available by western blot. That could be a reason to the impaired binding to other O1 strains that we observed. We now clarified this in the results section (page 8, line 304- 305). + +<|ref|>text<|/ref|><|det|>[[115, 433, 878, 546]]<|/det|> +POINT 7: The synergism of anti- capsule antibodies is highly interesting, but the underlying mechanism remains mostly elusive, which calls for further investigations. Are capsule antigens more mobile on the bacterial surface than O2- antigen and O1- antigens? What is known about the relative surface concentrations or clustering of capsule proteins vs O2 and O1 glycans? Both, mobility and local clustering, could potentially influence hexamer formation (besides spacing/steric hindrance, as discussed by the authors). Any experiment and/or simulations that could provide more mechanistic insights into the observed synergism would be of high value. + +<|ref|>text<|/ref|><|det|>[[114, 561, 880, 802]]<|/det|> +ANSWER 7: We have performed several new experiments to obtain more insights into the mechanism of synergism. Since it was suggested that synergistic binding would depend on Fc- mediated IgG hexamerization, we studied this question specifically. We generated both divalent F(ab')2 and monovalent Fab fragments from UKpn1 and UKpn3. To our surprise, we observed that synergistic binding between the two antibodies was independent of the IgG- Fc tail. Both F(ab')2 and Fab fragments of UKpn1 could strengthen the binding of full- length UKpn3 (and vice versa). Additionally, F(ab')2 fragments of UKpn1 also enhanced complement activation by full- length UKpn3 (and vice versa). Altogether, this new data set demonstrates that synergy between UKpn1 and UKpn3 occurs via a novel mechanism that is different from previously reported IgG hexamerization. In the revised manuscript, we included these 8 extra figures (Fig. 7b- d and SFig. 7c- f) and we made textual revisions of both the Results (page 9&10, line 389- 408) and Discussion (page 12, line 489- 505) sections to reflect on these new data. In addition, we have extensively revised our discussion section to better reflect on the existing knowledge concerning physical properties of both capsule and O antigen (page 11, line 462- 473). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 83, 224, 99]]<|/det|> +## Minor points + +<|ref|>text<|/ref|><|det|>[[116, 115, 434, 131]]<|/det|> +POINT 8: Figure 1a: scale bars missing + +<|ref|>text<|/ref|><|det|>[[116, 147, 480, 163]]<|/det|> +ANSWER 8: Scale bars were added to Fig 1a. + +<|ref|>text<|/ref|><|det|>[[116, 179, 870, 226]]<|/det|> +POINT 9: Figure S1c, legend: what does „MOI of 0.5 per fluorophore“ mean? Is this referring to Multiplicity of Infection? Or related to the detection sensitivity (0.5 AU per fluorophore)? Please clarify and introduce abbreviation upon first usage. + +<|ref|>text<|/ref|><|det|>[[116, 227, 866, 259]]<|/det|> +ANSWER 9: It refers to multiplicity of infection - per B cell 0.5 bacterium labeled with Cy5 and 0.5 bacterium labeled with ATTO488. Text was adjusted for clarification. + +<|ref|>text<|/ref|><|det|>[[116, 275, 857, 322]]<|/det|> +POINT 10: Figure S1 Legend: the last sentence of the legend is duplicate/unnecessary: „(b) Fluorescent intensity (gMFI) and number of events normalized to mode are depicted on the X and Y- axis, respectively.“ + +<|ref|>text<|/ref|><|det|>[[116, 323, 417, 338]]<|/det|> +ANSWER 10: Changed as suggested. + +<|ref|>text<|/ref|><|det|>[[116, 354, 880, 417]]<|/det|> +POINT 11: Inconsistency between text and Figure 6a. Line 347f states that „mixing two antibodies recognizing the O2 antigen (UKpn2 and UKpn6) did not affect their capacity to drive C3b deposition (Fig. 6a).“ However, Fig. 6 a shows UKpn1+UKpn2. Probably there is a typo in the Figure? + +<|ref|>text<|/ref|><|det|>[[116, 418, 850, 450]]<|/det|> +ANSWER 11: The wrong figure was shown as Fig 6a, this should be as mentioned in the text UKpn2 and UKpn6. We now corrected this in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 466, 870, 498]]<|/det|> +POINT 12: Methods: Line 549f: incomplete sentence/information: „Lysis buffer consisted of.“ ANSWER 12: Corrected in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 514, 880, 546]]<|/det|> +POINT 13: Grammar: Line 117f: Clinically, the O1, O2 and O3 O- types are the most relevant as they [verb missing] over \(80\%\) of the clinical isolates. + +<|ref|>text<|/ref|><|det|>[[116, 547, 525, 562]]<|/det|> +ANSWER 13: Corrected in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 578, 730, 610]]<|/det|> +POINT 14: Grammar: Line 287: missing „Upon specific deletion [of] wbbY,“ ANSWER 14: Corrected in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 626, 869, 658]]<|/det|> +POINT 15: Grammar: Line 289: duplicate „suggesting suggests“ should be „suggesting“ only ANSWER 15: Corrected in the revised manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 84, 248, 101]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[115, 102, 878, 327]]<|/det|> +The article "Agnostic B cell selection approach identifies antibodies against K. pneumoniae that synergistically drive complement activation" by van der Lans and Bardoelet al aims to describe antibody characteristics of human blood IgG memory B cells to the surface antigens of Klebsiella pneumoniae. Using an elegant dual staining approach, the authors isolate blood IgG memory B cells from healthy individuals bearing antibodies to K. pneumoniae prevalent O serotypes O1 and O2. Next, they generated monoclonal antibodies from those isolated B cells and showed that a small percentage binds to K. pneumoniae surface glycans. In total they identified 29 unique monoclonal antibodies. Next, they suggest that antibody binding intensity does not always correlate with the capability for C3b deposition, especially capsule, in contrast to O antigen antibodies, are incapable to activate complement. The authors showed that hexamer formation- enhancing Fc mutations allowed capsule antibodies to activate complement and that antibody- dependent bacterial killing did depend on the presence of neutrophils. Last, they show a synergistic binding and complement activation effect of two capsule antibodies. + +<|ref|>text<|/ref|><|det|>[[117, 343, 549, 359]]<|/det|> +Novel, notable and interesting things about this paper: + +<|ref|>text<|/ref|><|det|>[[116, 374, 866, 454]]<|/det|> +1) Using azide-KDO paired with click-chemistry to isolate memory B cells with specific BCRs is an elegant approach and likely suitable to isolate antibodies to other KDO-expressing bacteria +2) Data suggest that only glycan antigens are accessible on Kp surface +3) The authors show a synergistic binding and C3b deposition effect of two monoclonal antibodies targeting the capsule of Klebsiella pneumoniae + +<|ref|>text<|/ref|><|det|>[[117, 470, 270, 485]]<|/det|> +Possible concerns: + +<|ref|>text<|/ref|><|det|>[[116, 501, 880, 565]]<|/det|> +POINT 1: Fig 2a- d: It seems that O2 O antigen- reactive antibody binding levels do correlate with C3b deposition and only capsule- binders show no correlation. Please confirm. Fig. 2b could be plotted at higher antibody concentration to account for the differences between intermediate and negative binders. + +<|ref|>text<|/ref|><|det|>[[115, 581, 880, 644]]<|/det|> +ANSWER 1: Indeed, there is a correlation between antibody binding and C3b deposition for the mAbs targeting the O2 antigen. Since we did not identify the targets of the antibodies at this stage in the manuscript, we did not specify the different groups yet. We plotted fig 2b at the same concentration as the fig 2d to make a direct comparison. + +<|ref|>text<|/ref|><|det|>[[115, 660, 860, 693]]<|/det|> +POINT 2: The authors should proof that the O1 and O2 O antigen reactive antibodies directly target purified LPS of the respective O serotype (similar to Figure 3h). + +<|ref|>text<|/ref|><|det|>[[116, 708, 853, 805]]<|/det|> +ANSWER 2: We performed a western blot (as in Fig 3h for KpnO1) for some of the antibodies directed against KpnO2 on bacterial lysate of KpnO2. This shows that UKpn2, 6, 7 and 8 recognize the O- antigen as illustrated by the smear at around 50 kD indicative for the LPS O- antigen. Antibodies UKpn3 stains at a higher molecular weight, which probably indicate recognition of capsular polysaccharide. We now included the western blot as Fig S3d and included it to the text of the results section (Results, page, 7 line 258- 261). + +<|ref|>text<|/ref|><|det|>[[115, 821, 850, 853]]<|/det|> +POINT 3: Fig. 6e is not very intuitive. Why does UKpn3 bind slightly better if more unlabelled UKpn3 is added? The MFI should drop when more of the same unlabelled antibody is added. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 881, 130]]<|/det|> +ANSWER 3: We suspect there is no saturation at this point since the capsule is a very abundant antigen on the bacterial surface and therefore there is no competition. The slight increase we cannot explain at this moment. + +<|ref|>text<|/ref|><|det|>[[115, 146, 867, 179]]<|/det|> +POINT 4: Fig S6b: Please confirm that UKpn1 and 3 do not deposit C3b on K00059 and add an isotype control. + +<|ref|>text<|/ref|><|det|>[[115, 194, 875, 243]]<|/det|> +ANSWER 4: We repeated the experiment on 209S and SF0025 (K00059) with an isotype control (aDNP). For K00059 some C3b deposition by UKpn1 and UKpn3 only was observed at \(3\%\) , while absent at \(1\%\) NHS. We added the updated graphs to the revised manuscript (Fig S6b). + +<|ref|>text<|/ref|><|det|>[[115, 274, 835, 306]]<|/det|> +POINT 5: The authors should show if the synergistic binding effect of UKpn1 and 3 can be observed on isolated capsule glycan or it depends on the intact bacterium. + +<|ref|>text<|/ref|><|det|>[[115, 322, 866, 354]]<|/det|> +ANSWER 5: UKpn1 and 3 are directed against capsule type KL110. Since isolated glycans are not available for this capsule type, we focused on using whole bacteria. + +<|ref|>text<|/ref|><|det|>[[115, 370, 863, 387]]<|/det|> +POINT 6: Fig 6g: Can Spa- B bind to UKpn1 and UKpn3 while they bind the surface of KpnO2? + +<|ref|>text<|/ref|><|det|>[[115, 401, 878, 450]]<|/det|> +ANSWER 6: We have performed additional experiments to verify that Spa- B indeed binds to the combination of UKpn1 and UKpn3. We now included these new data as Figure S6c and describe the findings the text of the results section (page 9, line 371- 372). + +<|ref|>text<|/ref|><|det|>[[115, 465, 815, 498]]<|/det|> +POINT 7: The mechanism of UKpn1 and 3 binding synergy is not resolved: Can the Fab fragments of UKpn1 and 3 alone induce the synergistic binding effect? + +<|ref|>text<|/ref|><|det|>[[115, 513, 881, 609]]<|/det|> +ANSWER 7: We have now generated F(ab')2 and Fab fragments of UKpn1 and UKpn3 to study this question. Interestingly, the experiments reveal that the synergistic binding between UKpn1 and UKpn3 is also observed with F(ab')2 and Fab fragments. This shows that synergy between UKpn1 and UKpn3 is independent of the Fc tail. We added these new figures to the revised manuscript (Fig. 7b- d and Fig. S7c- f) and we made textual revisions of both the Results (page 9&10, line 389- 408) and Discussion (page 12, line 490- 505) sections to reflect on these new data + +<|ref|>text<|/ref|><|det|>[[115, 624, 866, 656]]<|/det|> +POINT 8: Ultimately, an important question remains: Do UKpn1 and 3 together are protective in an infection model? + +<|ref|>text<|/ref|><|det|>[[115, 672, 836, 704]]<|/det|> +ANSWER 8: Although we agree this would be an interesting study, we think it is outside the scope of the current manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 720, 435, 752]]<|/det|> +POINT 9: Minor comments: Axis labels/ units are frequently missing + +<|ref|>text<|/ref|><|det|>[[115, 767, 770, 784]]<|/det|> +ANSWER 9: We tried to clarify this as much as possible in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 800, 878, 832]]<|/det|> +POINT 9: The authors should change the wording for "active" and "inactive" antibodies. At the end these antibodies are not inactive. + +<|ref|>text<|/ref|><|det|>[[115, 848, 656, 864]]<|/det|> +ANSWER 10: We changed this or adjusted to complement- inactive. + +<|ref|>text<|/ref|><|det|>[[115, 879, 416, 895]]<|/det|> +POINT 11: Fig. S6b statistics missing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 83, 485, 99]]<|/det|> +ANSWER 11: Statistics was added to Fig S6b + +<|ref|>text<|/ref|><|det|>[[115, 115, 627, 131]]<|/det|> +POINT 12: Line 340: Uptake by neutrophils was not addressed + +<|ref|>text<|/ref|><|det|>[[115, 147, 877, 179]]<|/det|> +ANSWER 12: In the results section we now clarified that we measured phagocytosis of bacteria by neutrophils + +<|ref|>text<|/ref|><|det|>[[115, 195, 602, 210]]<|/det|> +POINT 13: Line 311: Please change wild- type to unmutated + +<|ref|>text<|/ref|><|det|>[[115, 227, 577, 243]]<|/det|> +ANSWER 13: We changed this in the revised manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 310, 97]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 111, 415, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 140, 860, 168]]<|/det|> +The authors have done a commendable job addressing my previous concerns. I think the revised manuscript is significantly improved. + +<|ref|>text<|/ref|><|det|>[[120, 210, 415, 224]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 238, 880, 365]]<|/det|> +Lans et al have submitted a revised version of their manuscript which includes several control experiments, new experiments exploring the mechanism of synergistic action, as well as edits to text and figures. The authors' detailed rebuttal in my opinion addresses the points raised by me and other reviewers in a comprehensive and thorough manner. The revision has clarified the rationale for using a dual- staining approach and substantially strengthened the main conclusions of the paper. While open questions remain about the mechanism of synergy as well as its effectiveness in an infection model, I deem these to be beyond the scope of this manuscript. I thus recommend this manuscript for publication without further request for changes and congratulate the authors on their excellent study. + +<|ref|>text<|/ref|><|det|>[[120, 405, 415, 419]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 433, 630, 448]]<|/det|> +I do not have any further comments. Congratulations for the work. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 463, 291, 480]]<|/det|> +## Point-to-point reply + +<|ref|>text<|/ref|><|det|>[[118, 498, 876, 568]]<|/det|> +Reviewer #2 raises one point: While open questions remain about the mechanism of synergy as well as its effectiveness in an infection model, I deem these to be beyond the scope of this manuscript. I thus recommend this manuscript for publication without further request for changes and congratulate the authors on their excellent study. + +<|ref|>text<|/ref|><|det|>[[115, 583, 870, 685]]<|/det|> +Answer: In the discussion section of our revised paper, we now include the limitations mentioned by the reviewer: page 12, line 498: "Although open questions about the exact mechanism behind synergistic binding remain..." page 12, lines 511- 512: "Since our study is limited to in vitro experiments, it remains to be assessed whether the combination of two anti- capsule antibodies is effective in an in vivo infection model." + +<--- Page Split ---> diff --git a/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/images_list.json b/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..88801fc99d90a9ea4403dbf4a6d7a8c6e02df624 --- /dev/null +++ b/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,48 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig. 1 Large range dl/dV spectra of D4 and D5.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Fig. 2 Large range dl/dV spectra of D6", + "footnote": [], + "bbox": [ + [ + 150, + 551, + 601, + 813 + ] + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig. 3 The dl/dV (top) and second dl/dV (bottom) spectra of D1 and D2.", + "footnote": [], + "bbox": [], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig. 4 The dl/dV spectra measured with different lock-in modulation voltages.", + "footnote": [], + "bbox": [ + [ + 122, + 600, + 637, + 765 + ] + ], + "page_idx": 5 + } +] \ No newline at end of file diff --git a/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d6719e3b5b2c627f4c500b1f3740385bb1423327 --- /dev/null +++ b/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,421 @@ + +# nature portfolio + +Peer Review File + +Orbital- Symmetry Effects on Magnetic Exchange in Open- Shell Nanographenes + +![](images/Figure_1.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +This manuscript by Q. Du, et al. reports a comprehensive investigation of the magnetic exchange coupling in a set of nanographene spin dimers and a spin trimer. The authors first used tight- binding calculation to formulate a hypothesis that the symmetry of the frontier orbital have a significant impact on the magnetic coupling. This hypothesis was then subjected to further analysis by DFT and CAS- CI. The on- surface synthesis and SPM experiments demonstrated different coupling strengths for different variations of the trimer molecule on Au(111) surface. Overall the manuscript is interesting but would require major revisions before it could be considered for publication. + +## Comments: + +a. The AFM result for the D6 molecule, as depicted in Figure 5a, exhibit equal brightness in the right sp3 carbon and the lower region, as opposed to the D1 molecule in the same figure. This observation is insufficient to determine if the sp3 carbon is the only atom passivated with two hydrogens, and thus cannot establish the origin of the Kondo peak at position 1. +b. The quality of the dI/dV maps Figure 6 e is inadequate to support the conclusions about the orbital and coupling information between positions 1 and 2. Additionally, the labels in Figure 6 are misplaced. +c. The large range of the dI/dV spectra with Au(111) background is not provided, which is not enough to prove the validity of the results. +d. The theoretical part of the study primarily relies on qualitative TB-MFH simulations, with the interpretation of the calculation results being largely guided by chemical intuition. We recommend this aspect of the study should get mostly revised with more robust and quantitative methods. Here are specific criticisms of the theoretical part: +i. The discussion of the t3 hopping term is unnecessary. There is no reason to fit the DFT results by considering the t3 hopping, and then derive a chemical intuition based on only four cases with qualitative results. +ii. Furthermore, Figure 3 depicts a case with \(\mathrm{U} = 0 \mathrm{eV}\) , which differs from the simulations of D1-D6 in Figure 1 and 2. It is therefore inaccurate to compare these results, draw conclusions, and make statements. +iii. In Figure 3, the explanation for why D1, D2 and D5 have different results with D4 when using the CAS-CI methods is inconsistent with the MFH results is unclear. The reason for larger CAS-CI gaps of is D1, D2, D5 is not well explained, especially with similar structure D4. This means that the MFH results can only be considered as a rough reference, rather than accurate scientific information. Further theoretical work is recommended to address this issue. +iv. The analysis of D1-D6 is mainly conducted using MFH and DFT, and there are no corresponding MFH and DFT results for the spin trimer T. +v. In Figure 6, the CAS-Hubbard model used to fit the experimental data of the spin trimer T employed \(\mathrm{U} = 4.1 \mathrm{eV}\) , which is not the same as \(\mathrm{U} = |2 \mathrm{t}|\) in the cited two paper for this method. As illustrate in the previous part of the paper, different U and t parameter significantly affect the simulation results. +e. The authors assert in the second sentence of paragraph 4, that the D3 and D6 configurations are well understood by theory and experiments, without providing a reference to support this claim. +f. The introduction and conclusion mention the potential for room-temperature spintronics, however, all the experiments were conducted at 4K. We suggest either remove this claim or try solution EPR at room temperature to validate the spin interaction. + +Reviewer #2: + +Remarks to the Author: + +The manuscript "Wide Tunning of Magnetic Exchange Coupling in Nanographenes through Orbital- Symmetry Engineering" by Du and his/her colleagues describe the magnetic exchange interaction in the on- surface synthesized (OSS) open- shell nanographenes with a combination of low- temperature scanning spectroscopy/inelastic tunneling spectroscopy and three- different theoretical + +<--- Page Split ---> + +calculations (DFT, MFH, and CAS). The authors found two different magnitudes of the exchange coupling, which was attributed to come from the different frontier orbital symmetries. In the last years, open- shell molecules, including triangulates, have attracted interests of researchers because the magnetic coupling can be tuned by OSS precursor molecules in a controlled way. This study can be categorized in this hot field. The topic described in this manuscript would be interesting, yet this reviewer feels that the quality of the work at present does not meet a standard of Nature Communications. Apparently, the theory part leads this study, yet the experimental results does not support the finding accordingly. First of all, the theory considered the dimer of the molecule but no experimental result. It is of importance to show the experimental results with the same system as the one described in the theory. In other word, it is mandatory that the authors measure the magnetic coupling of the compounds described in Figure 1. The theoretical work is based on three- different codes. However, there is no sufficient description why the authors used them. Besides these, all calculation seems to be conducted in gas phase. On surface, there must be a significant interaction between the metal substrate and the radical molecule. It would be very beneficial that the authors include it. Above the reasons, this reviewer feels that the present manuscript is not suitable for the publication. Several minor comments are described as below + +## 1. The title + +The authors did not tune the magnetic exchange coupling just gives a few examples of different coupling in the products + +2. Fig. 3bD1, D3, D2, and D5 are shown in this order. Yet, it is a bit confusing because Figure 3a is not. + +3. S=1 antiferromagnetic coupling in inelastic tunneling spectroscopy dataThe authors obtained the values of 20 mV and 160 mV. How did the authors get them?The AC voltages for the lock in measurement seems to be too large. + +4. Page 14, line 230, "... Consistent with experiments (Fig. 6g)." which is misleading. It is better to change the position of "(Fig. 6)". + +5. Page 12, line 199. By sharp contrast? + +6. Linker 1 and Linker 2It is shown in Figure 1 but is not clear enough in the text. + +<--- Page Split ---> + +## Response to Reviewer 1: + +Comments: This manuscript by Q. Du, et al. reports a comprehensive investigation of the magnetic exchange coupling in a set of nanographene spin dimers and a spin trimer. The authors first used tight- binding calculation to formulate a hypothesis that the symmetry of the frontier orbital have a significant impact on the magnetic coupling. This hypothesis was then subjected to further analysis by DFT and CAS- CI. The on- surface synthesis and SPM experiments demonstrated different coupling strengths for different variations of the trimer molecule on \(\mathrm{Au}(111)\) surface. Overall the manuscript is interesting but would require major revisions before it could be considered for publication. + +We thank the Reviewer for finding our work is interesting. We also appreciate the Reviewer's comments, which we have been fully addressed in the following and modified our manuscript accordingly. + +1. The AFM result for the D6 molecule, as depicted in Figure 5a, exhibit equal brightness in the right sp3 carbon and the lower region, as opposed to the D1 molecule in the same figure. This observation is insufficient to determine if the sp3 carbon is the only atom passivated with two hydrogens, and thus cannot establish the origin of the Kondo peak at position 1. + +We thank the reviewer's comments. The brightness in the lower region of the D6 molecule in Fig.5a is due to the tip creeping towards the sample which leads to more repulsive force detected in the AFM image. If there is additional hydrogen passivated in the lower part, the kondo peak can't be detected at position 1 due to the radical quenching. To avoid any confusion, we have exchanged this AFM image with the one measured in the stabilized tip- sample distance on the same D6 molecule. This AFM image clearly shows that only the sp3 carbon located at the top- right phenalenyl group exhibits bright contrast due to the additional hydrogen passivation. + +![](images/Figure_2.jpg) + + +<--- Page Split ---> + +**Modification:** The AFM image of the D6 molecule is exchanged in Fig.5a. + +2. The quality of the dl/dV maps Figure 6 e is inadequate to support the conclusions about the orbital and coupling information between positions 1 and 2. Additionally, the labels in Figure 6 are misplaced. + +We agree with the Reviewer that the features of dl/dV mappings in previous Fig.6e are not very pronounced. To improve it, we have exchanged these mappings with better quality as below. These dl/dV mappings clearly show that the electronic features at ±160 mV are mainly located at the top-right and bottom phenalenyl groups, while the electronic states measured at 1 mV are mainly located at the top-left phenalenyl group. These electronic state distributions are consistent with the dl/dV spectra measurements, corresponding to the spin excitation (±160 mV) and Kondo (1 mV) mappings respectively. + +We also thank the Reviewer to point out the error in the figure labels. We have checked all the figure labels, and they are all correct now. + +![](images/Figure_3.jpg) + + + +**Modification:** The dl/dV mappings are replaced with the ones with better quality in Fig.6e. The errors in the Figure captions are all corrected. + +3. The large range of the dl/dV spectra with Au(111) background is not provided, which is not enough to prove the validity of the results. + +We thank the Reviewer's comment. In the revised manuscript, we have included large range dl/dV spectra of molecules D4, D5, and D6 with Au(111) background in the supporting information. In the cases of molecules D4 and D5, the spectra are measured with the voltages from -1 V to 1.5 V. Because these two molecules have sp³ hydrogen passivation, the bias voltages are used smaller than 1.5 V to avoid hydrogen dissociation. In this range, the spin-flip feature can also be observed clearly at ±20 mV and ±160 mV for D4 and D5 respectively. Moreover, their singly unoccupied/occupied molecular orbital (SUMO/SOMO) can also be detected at 0.45 + +<--- Page Split ---> + +V/0.95 V and - 0.35 V/1.05 V for D4 and D5 respectively. The dl/dV mappings measured at the energies of SOMO/SUMO show similar features as the spin excitation mappings, which can further support the magnetic ground states of the molecules. Considering molecule D6 without any additional hydrogen passivation, the dl/dV spectra can be measured from - 2 V to 2 V. The molecular orbitals such as the SOMO/SUMO and the highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) can be all detected. The dl/dV mappings are also provided at these molecular orbital resonances in the supporting information for reference. + +![](images/Figure_4.jpg) + +
Fig. 1 Large range dl/dV spectra of D4 and D5.
+ +![PLACEHOLDER_5_1] + +
Fig. 2 Large range dl/dV spectra of D6
+ +<--- Page Split ---> + +Modifications: Large range dl/dV spectra with Au(111) background and the corresponding dl/dV mappings of D4, D5 and D6 are included in the supporting information. + +4. The theoretical part of the study primarily relies on qualitative TB-MFH simulations, with the interpretation of the calculation results being largely guided by chemical intuition. We recommend this aspect of the study should get mostly revised with more robust and quantitative methods. Here are specific criticisms of the theoretical part: + +We thank the Reviewer's comments, which help us to improve our manuscript. + +i. The discussion of the t3 hopping term is unnecessary. There is no reason to fit the DFT results by considering the t3 hopping, and then derive a chemical intuition based on only four cases with qualitative results. + +We apologize that the discussion on the t3 hopping term is not clear enough in the previous manuscript. Actually, we find that the strengths of exchange interaction have a remarkable difference between D4 and D5 molecules in the experiments first. And then, to understand this large difference, we have calculated the ground and first excited spin states of molecules D4 and D5 with different methods such as MFH, DFT, and CAS- Hubbard. All the calculation results show the same qualitative trend that the D5 molecule has a larger strength of magnetic exchange than that of D4, which is due to the frontier orbital symmetry affecting the singly occupied orbital density distribution. But for the quantitative values, only CAS- Hubbard method employing the t3 hopping term can best agree with the experimental values. Therefore, we suggest that the t3 hopping term also has a role in affecting the magnetic exchange coupling. But we agree that it is not necessary to fit the DFT results with the t3 hopping term. And we need a more robust and quantitative calculation method to compare. + +To avoid any confusion and improve the theoretical discussions, we have modified our manuscript structure by presenting the experimental results first and then explaining the mechanism with different calculation methods. In the revised manuscript, we only discuss the molecular structures the same as the experimental results, which have been renamed for phenalenyl diradicals (D1, D2) and triradical (D3). Since DFT and MFH methods are not precise enough to calculate the excitation energies quantitatively due to the spin contamination, we have moved these results to the supporting information only for identifying the ground magnetic states of the molecules. For comparison, we have performed additional calculations by using a robust quantum + +<--- Page Split ---> + +chemistry method NEVPT2, which has included the t3 hopping term spontaneously. Since the calculation results of NEVPT2 and CAS- Hubbard method including the t3 hopping term can best agree with the experimental values, we suggest that the t3 hopping term should have a role in affecting the values of exchange interaction. + +Modification: 1. We modified the manuscript structure by presenting the experimental results first and then discussed the theoretical mechanism. + +2. We included new calculation results by using a robust quantum chemistry method NEVPT2. + +3. The calculation results are replaced using the same molecular models as experiments labeled as D1, D2 and D3 for phenalenyl diradicals and triradical. + +4. We modified the discussion on the effect of the t3 hopping term at page 12. + +"As shown in Fig.4b, although the calculated exchange interaction of D1 is smaller than that of D2 by CAS-Hubbard only considering the \(t_1\) hopping term, the exchange interaction of D1 and D2 obtained by this method is remarkably different from the experimental values. To quantitatively explain the experiments, we find that upon employing the \(t_3\) hopping term in the CAS-Hubbard calculation, the calculated exchange interaction of D1 decreases, while increases for D2, both agreeing better with the experimental values. These results suggest that the \(t_3\) hopping term also has an impact on the exchange interaction, that is already included in the NEVPT2 calculation. (The next-nearest hopping \(t_2\) of graphene honeycomb lattice is less important in our case, cf. supplementary information)." + +ii. Furthermore, Figure 3 depicts a case with \(U = 0\) eV, which differs from the simulations of D1-D6 in Figure 1 and 2. It is therefore inaccurate to compare these results, draw conclusions, and make statements. + +We thank the Reviewer's comments. In Figure 3, the calculation is performed without considering the electron- electron interaction (U=0), just to easily compare the wave function symmetry on the molecular conjugation structures. If we include U values larger than 3.5 eV in the calculation, the molecules' ground state will turn from the closed shell to the open shell. And the linear combination of the HOMO and LUMO wavefunctions with U=0 can obtain the singly occupied and unoccupied molecular orbitals (SOMOs/SUMOS) in the case of U = 3.5 eV. We have added the low- lying orbitals with U=3.5 eV for comparison. It is shown that the SOMOs are exactly the same as the constructed orbitals using HOMO and LUMO with U=0. + +As the results shown in below, both for U=0 and U=3.5, the constructed wave function of SOMOs is likely to propagate in the branch of the molecular backbone along the + +<--- Page Split ---> + +mirror plane direction in D1, while the SOMOs wave function does not propagate along the mirror plane direction in D2. Since the magnetic exchange interaction depends on the orbital overlap of SOMOs at the connecting region (near the mirror plane), the D1 configuration has a much larger exchange coupling strength than D2 due to large orbital density. We have included results with \(\mathrm{U} = 3.5 \mathrm{eV}\) in the supporting information. + +Modification: We included the results of wave function distribution with \(\mathrm{U} = 0 \mathrm{eV}\) and \(\mathrm{U} = 3.5 \mathrm{eV}\) for comparison in the supporting information. + +![PLACEHOLDER_8_0] + + +<--- Page Split ---> + +iii. In Figure 3, the explanation for why D1, D2 and D5 have different results with D4 when using the CAS-Cl methods is inconsistent with the MFH results is unclear. The reason for larger CAS-Cl gaps of is D1, D2, D5 is not well explained, especially with similar structure D4. This means that the MFH results can only be considered as a rough reference, rather than accurate scientific information. Further theoretical work is recommended to address this issue. + +We agree with the Reviewer that MFH results can only be considered as a rough reference since DFT and MFH can't quantitatively calculate the excitation energy due to the spin contamination. In the revised manuscript, we have moved these results to the supporting information only for identifying the magnetic ground state. Moreover, a robust quantum chemistry method NEVPT2 was employed in the calculation. All the molecular models used for theoretical calculations are exchanged for complying with the experimental results, which have been labeled as D1 and D2 for two kinds of phenalenyl diradicals. + +Considering the experimental result that the spin excitation voltage of D1 (20 meV) is much smaller than that of D2 (160 meV), it mainly originated from the molecular orbital symmetry affecting the singly occupied orbital density distribution, which determines the strength of magnetic exchange interaction. In the case of D1, its HOMO wave function has an antisymmetric character exhibiting the opposite signs of wave functions corresponding to the middle mirror plane normal to the molecule backbone. And this antisymmetric wave function prefers to propagate along the mirror plane direction. Therefore, the singly occupied orbital density per site at the connection region is effectively reduced, which leads to a smaller strength of exchange interaction of D1. In contrast, D2 has symmetric wave functions of HOMO, which does not prefer to propagate in the mirror plane direction normal to the molecular backbone. Therefore, its singly occupied orbital density distribution is not reduced at the connection region. That's why the strength of the magnetic exchange of D1 is much smaller than that of D2. + +Modification: 1. The MFH calculation results are moved to the supporting information. 2. Additional theoretical works using NEVPT2 is employed. 3. Molecular models used for calculations are exchanged for complying with the experimental results. 4. The discussion on the reason of exchange interaction difference between D1 and D2 is modified at page 11 and 12. + +<--- Page Split ---> + +"As highlighted in Fig. 5b, for the molecular D1, the wave function of its HOMO has antisymmetric character showing the opposite sign of the wave function to the mirror plane perpendicular to the molecular backbone. This antisymmetric wave function is likely to propagate in the branch of the molecular backbone along the mirror plane direction. Thus, the singly occupied orbital density per site at the connecting region of D1 is effectively reduced, resulting in a smaller exchange interaction strength for D1. In contrast, D2 has a symmetric HOMO, whose wave function does not propagate in the branch of the molecular backbone along the mirror plane direction. Therefore, the singly occupied orbital density distribution is not reduced at the connecting region for D2. As a consequence, D1 has a smaller coupling strength than D2 due to the reduced orbital density overlap at the connecting region, originated from frontier orbital symmetry differences." + +iv. The analysis of D1- D6 is mainly conducted using MFH and DFT, and there are no corresponding MFH and DFT results for the spin trimer T. + +In the case of spin triradical T, there are three coupled spins. Because of the neglected spin- orbital coupling in the graphene system, the system can be simplified as a three- site Heisenberg quantum spin model. In the picture of mean- field approximation, the wave functions are not the eigenstates of the total spin operator \(\hat{S}\) , but of the \(\hat{S}z\) projection. So mean- field DFT and MFH calculations are not reliable for excitation energies calculation for multiple spin systems. We have performed DFT and MFH for the spin triradical T and found the obtained spin states greatly deviate from experiments. + +v. In Figure 6, the CAS-Hubbard model used to fit the experimental data of the spin trimer T employed \(U = 4.1 \text{eV}\) , which is not the same as \(U = |2t|\) in the cited two paper for this method. As illustrate in the previous part of the paper, different \(U\) and \(t\) parameter significantly affect the simulation results. + +We thank the reviewer's comments. The Hubbard model is used to qualitatively address the low- lying states of the system. We found the values of the chosen U inside a certain range (usually \(t< U< 2.2t\) ) give the same magnetic ground states. Therefore, it is not necessary to use exactly the same values as the cited two papers for this method. + +5. The authors assert in the second sentence of paragraph 4, that the D3 and D6 + +<--- Page Split ---> + +configurations are well understood by theory and experiments, without providing a reference to support this claim. + +We thank the Reviewer to point this out. D3 and D6 molecules are two conjugated phenalenyl groups in the way of hosting sublattice imbalance as suggested in Fig1. Therefore, they have the high spin ground state of \(\mathrm{S} = 1\) . The nanographene with a high spin ground state due to the sublattice imbalance has been investigated by several theoretical and experimental works. To make this point clear, we have modified this sentence and cited relative works on it. + +Modification: we modified the sentence on the magnetic state of D3 and added related references at page 9 and 10. + +"Since D3 hosting the high spin ground state, due to the sublattice imbalance, is well understood by theory \(^{25}\) and experiments \(^{41,42}\) , we focus on the competing cases of D1 and D2 as depicted in Fig. 4. " + +6. The introduction and conclusion mention the potential for room-temperature spintronics, however, all the experiments were conducted at 4K. We suggest either remove this claim or try solution EPR at room temperature to validate the spin interaction. + +We thank the reviewer's comment. Since one of our investigated molecules presents a large exchange interaction, which significantly exceeds the room- temperature thermal energy (25 meV), we suggest it has the potential to have applications at room temperature. Considering the reviewer's suggestion, we don't emphasize this point in the revised manuscript and removed the words "room- temperature". + +Modifications: We removed the words "room- temperature" in the introduction and conclusion parts. + +## Response to Reviewer 2: + +Comments: The manuscript "Wide Tunning of Magnetic Exchange Coupling in Nanographenes through Orbital- Symmetry Engineering" by Du and his/her colleagues describe the magnetic exchange interaction in the on- surface synthesized (OSS) open- shell nanographenes with a combination of low- temperature scanning spectroscopy/inelastic tunneling spectroscopy and three- different theoretical calculations (DFT, MFH, and CAS). The authors found two different magnitudes of the exchange coupling, which was attributed to come from the different frontier orbital + +<--- Page Split ---> + +symmetries. In the last years, open- shell molecules, including triangulates, have attracted interests of researchers because the magnetic coupling can be tuned by OSS precursor molecules in a controlled way. This study can be categorized in this hot field. The topic described in this manuscript would be interesting, yet this reviewer feels that the quality of the work at present does not meet a standard of Nature Communications. + +We thank the Reviewer finds the topic of our work is interesting. We have modified our manuscript according to both the reviewers' comments. We hope our revised manuscript can meet the standard of Nature Communications. + +Apparently, the theory part leads this study, yet the experimental results does not support the finding accordingly. First of all, the theory considered the dimer of the molecule but no experimental result. It is of importance to show the experimental results with the same system as the one described in the theory. In other word, it is mandatory that the authors measure the magnetic coupling of the compounds described in Figure 1. + +We apologize that we have not presented our work clearly in our previous manuscript. In fact, we first find interesting experimental evidence that just by tuning a little bit the conjugation symmetry, the strength of magnetic exchange interaction can be varied about one order of magnitude. To explain this experimental finding, we employed several calculation methods to find out the physical mechanism. + +To avoid any confusion, we have modified the structure of our manuscript. We first present the experimental results and then demonstrate the calculation results. Moreover, we agree with the reviewer that the molecular models used for calculation should be consistent with the experimental results. In the revised manuscript, all the calculation results presented are calculated with the molecular models complying with the experimental results. + +Modifications: 1. We modified the manuscript structure by presenting the experimental results first and then explained the mechanism with different calculation methods. + +2. The calculation results are presented with the same molecular models as the experiments. + +The theoretical work is based on three- different codes. However, there is no sufficient description why the authors used them. + +We thank the Reviewer's comments. DFT and MFH calculations are based on mean- field approximations, which normally underestimate the coulomb interactions. So we + +<--- Page Split ---> + +used high- level CAS- Hubbard and NEVPT2 calculations to better capture the many- body interactions. + +We realized that in our previous manuscript too many calculation models are presented, which may confuse the readers. Therefore, these calculation results are moved to the supporting information only for identifying the magnetic ground states in the revised manuscript. Now, we only use CAS- Hubbard and a more robust quantum chemistry method NEVPT2 for comparison. The corresponding discussions are also modified. + +Modifications: 1. The MFH and DFT calculation results are moved to the supporting information. + +2. Additional theoretical works using NEVPT2 are employed. + +3. The corresponding discussion is modified. + +Besides these, all calculation seems to be conducted in gas phase. On surface, there must be a significant interaction between the metal substrate and the radical molecule. It would be very beneficial that the authors include it. + +We thank the Reviewer's comments. Previous DFT calculations suggest the Au(111) substrate doesn't affect the magnetic ground states of magnetic triangulene systems, where the gas phase calculations agree well with experimental results (Physical Review B 104, 075404 (2021)). Considering our large system, a full quantum chemistry calculation including the substrate is too heavy to be realized. + +Above the reasons, this reviewer feels that the present manuscript is not suitable for the publication. Several minor comments are described as below + +With our responses and the corresponding modifications, we hope our revised manuscript can meet the criterion of publication in Nature Communications. For the other comments, we responded as below. + +## 1. The title + +The authors did not tune the magnetic exchange coupling just gives a few examples of different coupling in the products + +We agree that in the experiments we only observe two kinds of nanographenes with huge different strengths of exchange interaction determined by their wave function symmetries. To precisely present our work, we modified our manuscript title to "Orbital- Symmetry Effects on Magnetic Exchange in Open- Shell Nanographenes". + +<--- Page Split ---> + +Modification: The title is modified. + +2. Fig. 3b + +D1, D3, D2, and D5 are shown in this order. Yet, it is a bit confusing because Figure 3a is not. + +We agree with the reviewer that we have shown too many molecular models in Fig.1, which makes it difficult to understand our main experimental and theoretical results. To avoid any confusion, we have modified molecular models in Fig.1, which are consistent with the experimental results. In the revised manuscript, we only discuss two nanographene diradicals (D1, D2) and one nanographene triradical (D3), which have been investigated in the experiments. It should give a better understanding for both the experimental and theoretical results. + +Modifications: 1. Figure. 1 is modified. + +2. Only the molecular structures observed in the experiments are discussed in the revised manuscript, which have been labeled as D1, D2 and D3. + +3. S=1 antiferromagnetic coupling in inelastic tunneling spectroscopy data The authors obtained the values of \(20 \mathrm{mV}\) and \(160 \mathrm{mV}\) . How did the authors get them? The AC voltages for the lock in measurement seems to be too large. + +The values of \(20 \mathrm{meV}\) and \(160 \mathrm{meV}\) are obtained by measuring inelastic tunneling spectra. As shown below, the spin excitation threshold energies are about \(\pm 20 \mathrm{mV}\) and \(\pm 160 \mathrm{mV}\) at the step position in the dl/dV spectra for D1 and D2 respectively. To determine the excitation voltage, the second dl/dV spectra can also be used (the figures in the second row). The peak positions in the second dl/dV spectra correspond to the step position in the dl/dV spectra, which both give the spin excitation values of \(\pm 20 \mathrm{mV}\) and \(\pm 160 \mathrm{mV}\) for D1 and D2 respectively. We have included the second dl/dV spectra in the supporting information for reference. + +<--- Page Split ---> +![PLACEHOLDER_15_0] + +
Fig. 3 The dl/dV (top) and second dl/dV (bottom) spectra of D1 and D2.
+ +For the inelastic tunneling spectra measurements, we have tried different modulation voltages. As shown below, using \(5 \mathrm{mV}\) or \(1 \mathrm{mV}\) of modulation voltage both give similar spin- flip spectra. In the previous manuscript, \(20 \mathrm{mV}\) is a typo error for the excitation mapping measurement condition. This modulation voltage should also be \(5 \mathrm{mV}\) , which has been corrected in the revised manuscript. + +![PLACEHOLDER_15_1] + +
Fig. 4 The dl/dV spectra measured with different lock-in modulation voltages.
+ +Modifications: 1. The typo error is corrected. 2. The second dl/dV spectra are included in the supporting information. + +<--- Page Split ---> + +4. Page 14, line 230, + +4. Page 14, line 230, "... Consistent with experiments (Fig. 6g)." which is misleading. It is better to change the position of "(Fig. 6)". + +We thank the Reviewer's suggestion. We have modified this sentence. + +Modifications: This sentence at page 14 is modified. + +"To understand this system, a Heisenberg spin trimer model (Fig.6f) is solved, the calculation results shown in Fig.6g demonstrate that the ground state has \(\mathrm{S} = 1 / 2\) and the other six excited states are nearly degenerate with an excitation gap of \(\sim 160 \mathrm{meV}\) ." + +5. Page 12, line 199. By sharp contrast? + +We would like to emphasize the remarkable difference in magnetic exchange between molecules D1 and D2, which is about one order of magnitude. To avoid any confusion, this sentence has been modified. + +Modifications: The sentence at page 8 is modified. + +"In sharp contrast with the magnetic exchange of 20 meV observed on D1, the corresponding dl/dV spectra taken on D2 exhibit a substantially increased excitation threshold of 160 meV." + +## 6. Linker 1 and Linker 2 + +It is shown in Figure 1 but is not clear enough in the text. + +We thank the Reviewer's comment. We have realized that there are too many molecular models in the previous manuscript, which are difficult for the readers to catch the main experimental and theoretical results. In the revised manuscript, we have modified our molecular models for consistent with the experimental results and there is no need to introduce linker 1 and linker 2. + +Modification: We have modified Fig.1, the linkers 1 and 2 have been removed. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The manuscript has been significantly improved and the authors have addressed almost all the points raised as part of the review. In its current form the manuscript could be considered for publication in Nature Communications. + +Reviewer #2: + +Remarks to the Author: + +The authors changed the structure of the manuscript as showing the experimental data and subsequently explaining the possible mechanism with the theoretical calculation. Now, I think that the readability of the manuscript improves. However, this reviewer found it difficult to read the response letter. For instance, the authors states that "we have included large range dI/dV spectra of molecules D4, D5, and D6..." but no related data was shown in supporting information. The authors also replied as "which have been renamed for phenalenyl diradical (D1, D2) and triradical (D3)" but D3 seems to be a diradical. Most probably all would relate to typos but this reviewer is afraid that the intentions of the authors are really understood correctly. + +The new dI/dV data in Supplementary Figure 16 shows distinct different peak heights in second differential curves for D2 but not for D1. Why? Also, this reviewer could not find the zero line in the d2I/dV2 curves (btw, the authors described "dI2/dV2", which is incorrect.). The contrast of SOMO for D1 is almost identical with that of SUMO, but D2 shows distinct contrasts (Supplementary Figure 17). Why? These points relate to Comment 2 of Reviewer 1. The authors just replaced the dI/dV maps taken at +- 160 mV without any adequate explanation. For these reasons, this reviewer still feels that this contribution does not meet the standard for publication in Nature Communication. + +Minor: + +1. Chemical structures in Figure 4 should be revised. + +2. Bond-resolved AFM. Is that the topography? No information can be found in the figure. + +<--- Page Split ---> + +## Response to Reviewer 1: + +Comments: The manuscript has been significantly improved and the authors have addressed almost all the points raised as part of the review. In its current form the manuscript could be considered for publication in Nature Communications. + +We thank the Reviewer for his/her positive evaluation of our work. + +## Response to Reviewer 2: + +Comments: The authors changed the structure of the manuscript as showing the experimental data and subsequently explaining the possible mechanism with the theoretical calculation. Now, I think that the readability of the manuscript improves. + +We thank the Reviewer finds our revised manuscript has improved. + +However, this reviewer found it difficult to read the response letter. For instance, the authors states that "we have included large range dl/dV spectra of molecules D4, D5, and D6..." but no related data was shown in supporting information. + +These data have been included in the supporting information in Supplementary Figure 17 and Supplementary Figure 18 (p.14 and p.15 in the supporting information), but with the revised labels as D1, D2, and T instead of D4, D5, and D6. + +The authors also replied as ", which have been renamed for phenalenyl diradical (D1, D2) and triradical (D3)" but D3 seems to be a diradical. Most probably all would relate to typos but this reviewer is afraid that the intentions of the authors are really understood correctly. + +We apologize that this is the typo error in the previous response letter. As the reviewer's understanding, D1, D2, and D3 are phenaleny diradicals, while phenaleny triradical is labeled as T. We have checked through our revised manuscript, these labels should be correct and consistent. + +The new dl/dV data in Supplementary Figure 16 shows distinct different peak heights in second differential curves for D2 but not for D1. Why? + +We thank the Reviewer's comments. The bias- asymmetric peak heights are commonly observed in the experiments. The reason has been systematically investigated in theory (e.g. New J. Phys. 17, 63016 (2015)), which suggests that the high- order + +<--- Page Split ---> + +scattering process will result in the asymmetric peak heights in the IETS spectrum. And particularly, if there is a resonate state near the bias window of spin excitation, the high- order scattering process will be enhanced and produce a more pronounced asymmetric IETS line shape. As shown in the following figure, this is the case that we observed in our \(\mathrm{d}^2\mathrm{l} / \mathrm{d}\mathrm{V}^2\) . Since the spin excitation energies are very small for D1 \((\pm 20 \mathrm{mV})\) , which are both far away from its resonant orbital states of SOMO (- 450 mV) and SUMO (950 mV), the asymmetric peak heights of D1 \(\mathrm{d}^2\mathrm{l} / \mathrm{d}\mathrm{V}^2\) spectrum is not obvious. In contrast, the spin excitation energies of D2 are much larger \((\pm 160 \mathrm{mV})\) , which is close to its SOMO (- 350 mV) resonant orbital in the negative bias direction but far away from its SUMO orbital (1.05 V). Therefore, the peak height is more pronounced in the negative bias and results in a huge asymmetric IETS spectrum. This large asymmetric peak height behavior has also been observed recently in the \(\mathrm{d}^2\mathrm{l} / \mathrm{d}\mathrm{V}^2\) spectrum of a nanographene system with large exchange interaction, whose spin excitation energy is also close to one of the molecular resonant states (J. Am. Chem. Soc. 145, 2968- 2974 (2023)). To clarify this point, we have added some discussion on this asymmetric line shape in the manuscript. + +![PLACEHOLDER_19_0] + + +![PLACEHOLDER_19_1] + + +Modification: We added some discussion at page 8 and cited related theoretical and experimental works. + +"And a more pronounced asymmetric line shape of \(\mathrm{d} / \mathrm{d}\mathrm{V}\) spectra is observed on D2 compared to that of D1 since D2 has a high spin excitation energy which is close to its SOMO resonate state thus leading to a pronounced height in the negative bias. \(^{32,57*}\) + +Also, this reviewer could not find the zero line in the d2l/dV2 curves (btw, the authors described "dl2/dV2", which is incorrect.). + +We thank the reviewer's careful check. In the previous version, we shifted the spectra measured on the molecule and on Au(111) substrate vertically for clarity without + +<--- Page Split ---> + +indicating the zero line. In the revised version, we canceled the vertical shift (cf. the following figure). + +![PLACEHOLDER_20_0] + + +Modification: The vertical ordinates are added in the \(\mathrm{d}^2 /\mathrm{d}V^2\) spectra in Supplementary Fig.16. The typo error of \(\mathrm{d}^2 /\mathrm{d}V^2\) is also corrected. + +The contrast of SOMO for D1 is almost identical with that of SUMO, but D2 shows distinct contrasts (Supplementary Figure 17). Why? + +The SUMO contrast of D2 is distinct from its SOMO mainly due to their different tip- molecule separations when measuring the SOMO and SUMO \(\mathrm{d}l / \mathrm{d}V\) mappings. Since D1 and D2 have sp3 hydrogen passivation, the additional hydrogen will be dissociated if the tip is too close to the sample. And because the SUMO energy of D2 is about 1.05 eV while its SOMO energy is only 0.35 eV, the mappings of SUMO and SOMO are taken at different tunneling current set points of \(I = 400\) and \(500 \mathrm{pA}\) respectively to avoid hydrogen dissociation. Therefore, the tip- molecule separation at measuring the \(\mathrm{d}l / \mathrm{d}V\) mappings is much larger for SUMO than that of SOMO, which results in the fine structure of SUMO being different from SOMO. Additionally, we performed simulations considering such different tip- sample separation effect. As seen in the following simulated STS mappings, the fine structures of SOMO/SUMO orbitals depend sensitively on tip- sample separation, consistent with experimental observations. + +<--- Page Split ---> +![PLACEHOLDER_21_0] + + +Modification: The simulated dl/dV mappings of SOMO and SUMO at different tip- molecule distance have been included in the Supplementary Figure 17. + +These points relate to Comment 2 of Reviewer 1. The authors just replaced the dl/dV maps taken at \(+ - 160 \text{mV}\) without any adequate explanation. + +To detect the fine structures of molecular orbitals, we usually use CO functionalized tip since the p- wave orbitals of the CO molecule can enhance the lateral resolution compared with a bare metal tip (Phys. Rev. Lett. 107, 086101 (2011)). In experiments, the CO molecule is usually picked up to the tip by applying a short pulse, and its adsorption on the tip position sometimes is not perfect vertical and symmetric, which may not give the best spatial resolution as expected. The dl/dV mappings taken at \(\pm 160 \text{mV}\) in the revised manuscript is measured by a CO functionalized tip with a much higher spatial resolution of the orbital distribution than the previous images. + +For these reasons, this reviewer still feels that this contribution does not meet the standard for publication in Nature Communication. + +With our responses and the corresponding modifications, we hope our revised manuscript can meet the criterion of publication in Nature Communications. For the other comments, we responded as below. + +## Minor: + +1. Chemical structures in Figure 4 should be revised. We checked the chemical structures in Fig.4 and thought the reviewer might mean the chemical structure is not used the templates of ChemDraw. Therefore, we modified the chemical structure by using the ChemDraw template in Fig.4 + +<--- Page Split ---> +![PLACEHOLDER_22_0] + + +Modification: The chemical structure in Fig.4 is modified using the ChemDraw template. + +2. Bond-resolved AFM. Is that the topography? No information can be found in the figure. + +The bond- resolved AFM is measured by non- contact atomic force microscope with a qPlus sensor. The AFM images were recorded with the different shift frequency of the qPlus sensor in the constant height mode, whose contrasts reflect the topography of the molecules (Science 325,1110- 1114 (2009)). To make this point more clear, we have added grey scale bars of the shift frequency in all AFM images. + +Modification: The AFM images in Fig.2, Fig3, and Fig6 are added with the grey scale bars of the shift frequency. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #2: + +Remarks to the Author: + +The authors improved the manuscript a lot. Now, this reviewer feels more confident that this contribution deserves publication in Nature Communications. + +<--- Page Split ---> diff --git a/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d9d3a8417bfd3de7bd9c02a03e3b5a0e1ca85012 --- /dev/null +++ b/peer_reviews/3330d1cba317d38a3dbbbdfbc82ddb986482ff055a13daa4bcc89c14ef195f9c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,552 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 927, 212]]<|/det|> +Orbital- Symmetry Effects on Magnetic Exchange in Open- Shell Nanographenes + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 222, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 140, 878, 252]]<|/det|> +This manuscript by Q. Du, et al. reports a comprehensive investigation of the magnetic exchange coupling in a set of nanographene spin dimers and a spin trimer. The authors first used tight- binding calculation to formulate a hypothesis that the symmetry of the frontier orbital have a significant impact on the magnetic coupling. This hypothesis was then subjected to further analysis by DFT and CAS- CI. The on- surface synthesis and SPM experiments demonstrated different coupling strengths for different variations of the trimer molecule on Au(111) surface. Overall the manuscript is interesting but would require major revisions before it could be considered for publication. + +<|ref|>sub_title<|/ref|><|det|>[[119, 268, 207, 280]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[117, 280, 873, 781]]<|/det|> +a. The AFM result for the D6 molecule, as depicted in Figure 5a, exhibit equal brightness in the right sp3 carbon and the lower region, as opposed to the D1 molecule in the same figure. This observation is insufficient to determine if the sp3 carbon is the only atom passivated with two hydrogens, and thus cannot establish the origin of the Kondo peak at position 1. +b. The quality of the dI/dV maps Figure 6 e is inadequate to support the conclusions about the orbital and coupling information between positions 1 and 2. Additionally, the labels in Figure 6 are misplaced. +c. The large range of the dI/dV spectra with Au(111) background is not provided, which is not enough to prove the validity of the results. +d. The theoretical part of the study primarily relies on qualitative TB-MFH simulations, with the interpretation of the calculation results being largely guided by chemical intuition. We recommend this aspect of the study should get mostly revised with more robust and quantitative methods. Here are specific criticisms of the theoretical part: +i. The discussion of the t3 hopping term is unnecessary. There is no reason to fit the DFT results by considering the t3 hopping, and then derive a chemical intuition based on only four cases with qualitative results. +ii. Furthermore, Figure 3 depicts a case with \(\mathrm{U} = 0 \mathrm{eV}\) , which differs from the simulations of D1-D6 in Figure 1 and 2. It is therefore inaccurate to compare these results, draw conclusions, and make statements. +iii. In Figure 3, the explanation for why D1, D2 and D5 have different results with D4 when using the CAS-CI methods is inconsistent with the MFH results is unclear. The reason for larger CAS-CI gaps of is D1, D2, D5 is not well explained, especially with similar structure D4. This means that the MFH results can only be considered as a rough reference, rather than accurate scientific information. Further theoretical work is recommended to address this issue. +iv. The analysis of D1-D6 is mainly conducted using MFH and DFT, and there are no corresponding MFH and DFT results for the spin trimer T. +v. In Figure 6, the CAS-Hubbard model used to fit the experimental data of the spin trimer T employed \(\mathrm{U} = 4.1 \mathrm{eV}\) , which is not the same as \(\mathrm{U} = |2 \mathrm{t}|\) in the cited two paper for this method. As illustrate in the previous part of the paper, different U and t parameter significantly affect the simulation results. +e. The authors assert in the second sentence of paragraph 4, that the D3 and D6 configurations are well understood by theory and experiments, without providing a reference to support this claim. +f. The introduction and conclusion mention the potential for room-temperature spintronics, however, all the experiments were conducted at 4K. We suggest either remove this claim or try solution EPR at room temperature to validate the spin interaction. + +<|ref|>text<|/ref|><|det|>[[119, 825, 222, 839]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 840, 300, 853]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 854, 876, 911]]<|/det|> +The manuscript "Wide Tunning of Magnetic Exchange Coupling in Nanographenes through Orbital- Symmetry Engineering" by Du and his/her colleagues describe the magnetic exchange interaction in the on- surface synthesized (OSS) open- shell nanographenes with a combination of low- temperature scanning spectroscopy/inelastic tunneling spectroscopy and three- different theoretical + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 875, 323]]<|/det|> +calculations (DFT, MFH, and CAS). The authors found two different magnitudes of the exchange coupling, which was attributed to come from the different frontier orbital symmetries. In the last years, open- shell molecules, including triangulates, have attracted interests of researchers because the magnetic coupling can be tuned by OSS precursor molecules in a controlled way. This study can be categorized in this hot field. The topic described in this manuscript would be interesting, yet this reviewer feels that the quality of the work at present does not meet a standard of Nature Communications. Apparently, the theory part leads this study, yet the experimental results does not support the finding accordingly. First of all, the theory considered the dimer of the molecule but no experimental result. It is of importance to show the experimental results with the same system as the one described in the theory. In other word, it is mandatory that the authors measure the magnetic coupling of the compounds described in Figure 1. The theoretical work is based on three- different codes. However, there is no sufficient description why the authors used them. Besides these, all calculation seems to be conducted in gas phase. On surface, there must be a significant interaction between the metal substrate and the radical molecule. It would be very beneficial that the authors include it. Above the reasons, this reviewer feels that the present manuscript is not suitable for the publication. Several minor comments are described as below + +<|ref|>sub_title<|/ref|><|det|>[[119, 338, 204, 351]]<|/det|> +## 1. The title + +<|ref|>text<|/ref|><|det|>[[119, 352, 852, 380]]<|/det|> +The authors did not tune the magnetic exchange coupling just gives a few examples of different coupling in the products + +<|ref|>text<|/ref|><|det|>[[118, 393, 840, 422]]<|/det|> +2. Fig. 3bD1, D3, D2, and D5 are shown in this order. Yet, it is a bit confusing because Figure 3a is not. + +<|ref|>text<|/ref|><|det|>[[118, 434, 788, 476]]<|/det|> +3. S=1 antiferromagnetic coupling in inelastic tunneling spectroscopy dataThe authors obtained the values of 20 mV and 160 mV. How did the authors get them?The AC voltages for the lock in measurement seems to be too large. + +<|ref|>text<|/ref|><|det|>[[118, 490, 870, 532]]<|/det|> +4. Page 14, line 230, "... Consistent with experiments (Fig. 6g)." which is misleading. It is better to change the position of "(Fig. 6)". + +<|ref|>text<|/ref|><|det|>[[118, 545, 279, 573]]<|/det|> +5. Page 12, line 199. By sharp contrast? + +<|ref|>text<|/ref|><|det|>[[118, 587, 560, 615]]<|/det|> +6. Linker 1 and Linker 2It is shown in Figure 1 but is not clear enough in the text. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 115, 357, 132]]<|/det|> +## Response to Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[115, 136, 885, 325]]<|/det|> +Comments: This manuscript by Q. Du, et al. reports a comprehensive investigation of the magnetic exchange coupling in a set of nanographene spin dimers and a spin trimer. The authors first used tight- binding calculation to formulate a hypothesis that the symmetry of the frontier orbital have a significant impact on the magnetic coupling. This hypothesis was then subjected to further analysis by DFT and CAS- CI. The on- surface synthesis and SPM experiments demonstrated different coupling strengths for different variations of the trimer molecule on \(\mathrm{Au}(111)\) surface. Overall the manuscript is interesting but would require major revisions before it could be considered for publication. + +<|ref|>text<|/ref|><|det|>[[116, 348, 883, 412]]<|/det|> +We thank the Reviewer for finding our work is interesting. We also appreciate the Reviewer's comments, which we have been fully addressed in the following and modified our manuscript accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 434, 883, 540]]<|/det|> +1. The AFM result for the D6 molecule, as depicted in Figure 5a, exhibit equal brightness in the right sp3 carbon and the lower region, as opposed to the D1 molecule in the same figure. This observation is insufficient to determine if the sp3 carbon is the only atom passivated with two hydrogens, and thus cannot establish the origin of the Kondo peak at position 1. + +<|ref|>text<|/ref|><|det|>[[114, 562, 884, 733]]<|/det|> +We thank the reviewer's comments. The brightness in the lower region of the D6 molecule in Fig.5a is due to the tip creeping towards the sample which leads to more repulsive force detected in the AFM image. If there is additional hydrogen passivated in the lower part, the kondo peak can't be detected at position 1 due to the radical quenching. To avoid any confusion, we have exchanged this AFM image with the one measured in the stabilized tip- sample distance on the same D6 molecule. This AFM image clearly shows that only the sp3 carbon located at the top- right phenalenyl group exhibits bright contrast due to the additional hydrogen passivation. + +<|ref|>image<|/ref|><|det|>[[130, 745, 525, 884]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 93, 778, 112]]<|/det|> +**Modification:** The AFM image of the D6 molecule is exchanged in Fig.5a. + +<|ref|>text<|/ref|><|det|>[[115, 137, 884, 197]]<|/det|> +2. The quality of the dl/dV maps Figure 6 e is inadequate to support the conclusions about the orbital and coupling information between positions 1 and 2. Additionally, the labels in Figure 6 are misplaced. + +<|ref|>text<|/ref|><|det|>[[115, 223, 884, 389]]<|/det|> +We agree with the Reviewer that the features of dl/dV mappings in previous Fig.6e are not very pronounced. To improve it, we have exchanged these mappings with better quality as below. These dl/dV mappings clearly show that the electronic features at ±160 mV are mainly located at the top-right and bottom phenalenyl groups, while the electronic states measured at 1 mV are mainly located at the top-left phenalenyl group. These electronic state distributions are consistent with the dl/dV spectra measurements, corresponding to the spin excitation (±160 mV) and Kondo (1 mV) mappings respectively. + +<|ref|>text<|/ref|><|det|>[[115, 395, 884, 433]]<|/det|> +We also thank the Reviewer to point out the error in the figure labels. We have checked all the figure labels, and they are all correct now. + +<|ref|>image<|/ref|><|det|>[[128, 451, 737, 593]]<|/det|> + + +<|ref|>text<|/ref|><|det|>[[115, 608, 884, 646]]<|/det|> +**Modification:** The dl/dV mappings are replaced with the ones with better quality in Fig.6e. The errors in the Figure captions are all corrected. + +<|ref|>text<|/ref|><|det|>[[115, 672, 884, 710]]<|/det|> +3. The large range of the dl/dV spectra with Au(111) background is not provided, which is not enough to prove the validity of the results. + +<|ref|>text<|/ref|><|det|>[[115, 736, 884, 903]]<|/det|> +We thank the Reviewer's comment. In the revised manuscript, we have included large range dl/dV spectra of molecules D4, D5, and D6 with Au(111) background in the supporting information. In the cases of molecules D4 and D5, the spectra are measured with the voltages from -1 V to 1.5 V. Because these two molecules have sp³ hydrogen passivation, the bias voltages are used smaller than 1.5 V to avoid hydrogen dissociation. In this range, the spin-flip feature can also be observed clearly at ±20 mV and ±160 mV for D4 and D5 respectively. Moreover, their singly unoccupied/occupied molecular orbital (SUMO/SOMO) can also be detected at 0.45 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 884, 262]]<|/det|> +V/0.95 V and - 0.35 V/1.05 V for D4 and D5 respectively. The dl/dV mappings measured at the energies of SOMO/SUMO show similar features as the spin excitation mappings, which can further support the magnetic ground states of the molecules. Considering molecule D6 without any additional hydrogen passivation, the dl/dV spectra can be measured from - 2 V to 2 V. The molecular orbitals such as the SOMO/SUMO and the highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) can be all detected. The dl/dV mappings are also provided at these molecular orbital resonances in the supporting information for reference. + +<|ref|>image<|/ref|><|det|>[[120, 275, 605, 502]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 520, 538, 539]]<|/det|> +
Fig. 1 Large range dl/dV spectra of D4 and D5.
+ +<|ref|>image<|/ref|><|det|>[[150, 551, 601, 813]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 820, 463, 838]]<|/det|> +
Fig. 2 Large range dl/dV spectra of D6
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 93, 882, 155]]<|/det|> +Modifications: Large range dl/dV spectra with Au(111) background and the corresponding dl/dV mappings of D4, D5 and D6 are included in the supporting information. + +<|ref|>text<|/ref|><|det|>[[115, 179, 882, 262]]<|/det|> +4. The theoretical part of the study primarily relies on qualitative TB-MFH simulations, with the interpretation of the calculation results being largely guided by chemical intuition. We recommend this aspect of the study should get mostly revised with more robust and quantitative methods. Here are specific criticisms of the theoretical part: + +<|ref|>text<|/ref|><|det|>[[115, 285, 816, 304]]<|/det|> +We thank the Reviewer's comments, which help us to improve our manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 328, 882, 389]]<|/det|> +i. The discussion of the t3 hopping term is unnecessary. There is no reason to fit the DFT results by considering the t3 hopping, and then derive a chemical intuition based on only four cases with qualitative results. + +<|ref|>text<|/ref|><|det|>[[114, 412, 883, 689]]<|/det|> +We apologize that the discussion on the t3 hopping term is not clear enough in the previous manuscript. Actually, we find that the strengths of exchange interaction have a remarkable difference between D4 and D5 molecules in the experiments first. And then, to understand this large difference, we have calculated the ground and first excited spin states of molecules D4 and D5 with different methods such as MFH, DFT, and CAS- Hubbard. All the calculation results show the same qualitative trend that the D5 molecule has a larger strength of magnetic exchange than that of D4, which is due to the frontier orbital symmetry affecting the singly occupied orbital density distribution. But for the quantitative values, only CAS- Hubbard method employing the t3 hopping term can best agree with the experimental values. Therefore, we suggest that the t3 hopping term also has a role in affecting the magnetic exchange coupling. But we agree that it is not necessary to fit the DFT results with the t3 hopping term. And we need a more robust and quantitative calculation method to compare. + +<|ref|>text<|/ref|><|det|>[[115, 712, 883, 902]]<|/det|> +To avoid any confusion and improve the theoretical discussions, we have modified our manuscript structure by presenting the experimental results first and then explaining the mechanism with different calculation methods. In the revised manuscript, we only discuss the molecular structures the same as the experimental results, which have been renamed for phenalenyl diradicals (D1, D2) and triradical (D3). Since DFT and MFH methods are not precise enough to calculate the excitation energies quantitatively due to the spin contamination, we have moved these results to the supporting information only for identifying the ground magnetic states of the molecules. For comparison, we have performed additional calculations by using a robust quantum + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 883, 176]]<|/det|> +chemistry method NEVPT2, which has included the t3 hopping term spontaneously. Since the calculation results of NEVPT2 and CAS- Hubbard method including the t3 hopping term can best agree with the experimental values, we suggest that the t3 hopping term should have a role in affecting the values of exchange interaction. + +<|ref|>text<|/ref|><|det|>[[115, 200, 883, 240]]<|/det|> +Modification: 1. We modified the manuscript structure by presenting the experimental results first and then discussed the theoretical mechanism. + +<|ref|>text<|/ref|><|det|>[[115, 243, 883, 282]]<|/det|> +2. We included new calculation results by using a robust quantum chemistry method NEVPT2. + +<|ref|>text<|/ref|><|det|>[[115, 286, 883, 325]]<|/det|> +3. The calculation results are replaced using the same molecular models as experiments labeled as D1, D2 and D3 for phenalenyl diradicals and triradical. + +<|ref|>text<|/ref|><|det|>[[115, 328, 810, 347]]<|/det|> +4. We modified the discussion on the effect of the t3 hopping term at page 12. + +<|ref|>text<|/ref|><|det|>[[115, 350, 883, 560]]<|/det|> +"As shown in Fig.4b, although the calculated exchange interaction of D1 is smaller than that of D2 by CAS-Hubbard only considering the \(t_1\) hopping term, the exchange interaction of D1 and D2 obtained by this method is remarkably different from the experimental values. To quantitatively explain the experiments, we find that upon employing the \(t_3\) hopping term in the CAS-Hubbard calculation, the calculated exchange interaction of D1 decreases, while increases for D2, both agreeing better with the experimental values. These results suggest that the \(t_3\) hopping term also has an impact on the exchange interaction, that is already included in the NEVPT2 calculation. (The next-nearest hopping \(t_2\) of graphene honeycomb lattice is less important in our case, cf. supplementary information)." + +<|ref|>text<|/ref|><|det|>[[115, 584, 883, 645]]<|/det|> +ii. Furthermore, Figure 3 depicts a case with \(U = 0\) eV, which differs from the simulations of D1-D6 in Figure 1 and 2. It is therefore inaccurate to compare these results, draw conclusions, and make statements. + +<|ref|>text<|/ref|><|det|>[[115, 670, 883, 858]]<|/det|> +We thank the Reviewer's comments. In Figure 3, the calculation is performed without considering the electron- electron interaction (U=0), just to easily compare the wave function symmetry on the molecular conjugation structures. If we include U values larger than 3.5 eV in the calculation, the molecules' ground state will turn from the closed shell to the open shell. And the linear combination of the HOMO and LUMO wavefunctions with U=0 can obtain the singly occupied and unoccupied molecular orbitals (SOMOs/SUMOS) in the case of U = 3.5 eV. We have added the low- lying orbitals with U=3.5 eV for comparison. It is shown that the SOMOs are exactly the same as the constructed orbitals using HOMO and LUMO with U=0. + +<|ref|>text<|/ref|><|det|>[[115, 862, 883, 901]]<|/det|> +As the results shown in below, both for U=0 and U=3.5, the constructed wave function of SOMOs is likely to propagate in the branch of the molecular backbone along the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 884, 197]]<|/det|> +mirror plane direction in D1, while the SOMOs wave function does not propagate along the mirror plane direction in D2. Since the magnetic exchange interaction depends on the orbital overlap of SOMOs at the connecting region (near the mirror plane), the D1 configuration has a much larger exchange coupling strength than D2 due to large orbital density. We have included results with \(\mathrm{U} = 3.5 \mathrm{eV}\) in the supporting information. + +<|ref|>text<|/ref|><|det|>[[115, 241, 884, 282]]<|/det|> +Modification: We included the results of wave function distribution with \(\mathrm{U} = 0 \mathrm{eV}\) and \(\mathrm{U} = 3.5 \mathrm{eV}\) for comparison in the supporting information. + +<|ref|>image<|/ref|><|det|>[[66, 290, 950, 820]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 884, 219]]<|/det|> +iii. In Figure 3, the explanation for why D1, D2 and D5 have different results with D4 when using the CAS-Cl methods is inconsistent with the MFH results is unclear. The reason for larger CAS-Cl gaps of is D1, D2, D5 is not well explained, especially with similar structure D4. This means that the MFH results can only be considered as a rough reference, rather than accurate scientific information. Further theoretical work is recommended to address this issue. + +<|ref|>text<|/ref|><|det|>[[115, 242, 884, 410]]<|/det|> +We agree with the Reviewer that MFH results can only be considered as a rough reference since DFT and MFH can't quantitatively calculate the excitation energy due to the spin contamination. In the revised manuscript, we have moved these results to the supporting information only for identifying the magnetic ground state. Moreover, a robust quantum chemistry method NEVPT2 was employed in the calculation. All the molecular models used for theoretical calculations are exchanged for complying with the experimental results, which have been labeled as D1 and D2 for two kinds of phenalenyl diradicals. + +<|ref|>text<|/ref|><|det|>[[115, 433, 884, 732]]<|/det|> +Considering the experimental result that the spin excitation voltage of D1 (20 meV) is much smaller than that of D2 (160 meV), it mainly originated from the molecular orbital symmetry affecting the singly occupied orbital density distribution, which determines the strength of magnetic exchange interaction. In the case of D1, its HOMO wave function has an antisymmetric character exhibiting the opposite signs of wave functions corresponding to the middle mirror plane normal to the molecule backbone. And this antisymmetric wave function prefers to propagate along the mirror plane direction. Therefore, the singly occupied orbital density per site at the connection region is effectively reduced, which leads to a smaller strength of exchange interaction of D1. In contrast, D2 has symmetric wave functions of HOMO, which does not prefer to propagate in the mirror plane direction normal to the molecular backbone. Therefore, its singly occupied orbital density distribution is not reduced at the connection region. That's why the strength of the magnetic exchange of D1 is much smaller than that of D2. + +<|ref|>text<|/ref|><|det|>[[115, 755, 881, 884]]<|/det|> +Modification: 1. The MFH calculation results are moved to the supporting information. 2. Additional theoretical works using NEVPT2 is employed. 3. Molecular models used for calculations are exchanged for complying with the experimental results. 4. The discussion on the reason of exchange interaction difference between D1 and D2 is modified at page 11 and 12. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 92, 885, 346]]<|/det|> +"As highlighted in Fig. 5b, for the molecular D1, the wave function of its HOMO has antisymmetric character showing the opposite sign of the wave function to the mirror plane perpendicular to the molecular backbone. This antisymmetric wave function is likely to propagate in the branch of the molecular backbone along the mirror plane direction. Thus, the singly occupied orbital density per site at the connecting region of D1 is effectively reduced, resulting in a smaller exchange interaction strength for D1. In contrast, D2 has a symmetric HOMO, whose wave function does not propagate in the branch of the molecular backbone along the mirror plane direction. Therefore, the singly occupied orbital density distribution is not reduced at the connecting region for D2. As a consequence, D1 has a smaller coupling strength than D2 due to the reduced orbital density overlap at the connecting region, originated from frontier orbital symmetry differences." + +<|ref|>text<|/ref|><|det|>[[115, 377, 883, 418]]<|/det|> +iv. The analysis of D1- D6 is mainly conducted using MFH and DFT, and there are no corresponding MFH and DFT results for the spin trimer T. + +<|ref|>text<|/ref|><|det|>[[114, 441, 884, 610]]<|/det|> +In the case of spin triradical T, there are three coupled spins. Because of the neglected spin- orbital coupling in the graphene system, the system can be simplified as a three- site Heisenberg quantum spin model. In the picture of mean- field approximation, the wave functions are not the eigenstates of the total spin operator \(\hat{S}\) , but of the \(\hat{S}z\) projection. So mean- field DFT and MFH calculations are not reliable for excitation energies calculation for multiple spin systems. We have performed DFT and MFH for the spin triradical T and found the obtained spin states greatly deviate from experiments. + +<|ref|>text<|/ref|><|det|>[[115, 634, 884, 717]]<|/det|> +v. In Figure 6, the CAS-Hubbard model used to fit the experimental data of the spin trimer T employed \(U = 4.1 \text{eV}\) , which is not the same as \(U = |2t|\) in the cited two paper for this method. As illustrate in the previous part of the paper, different \(U\) and \(t\) parameter significantly affect the simulation results. + +<|ref|>text<|/ref|><|det|>[[115, 741, 885, 823]]<|/det|> +We thank the reviewer's comments. The Hubbard model is used to qualitatively address the low- lying states of the system. We found the values of the chosen U inside a certain range (usually \(t< U< 2.2t\) ) give the same magnetic ground states. Therefore, it is not necessary to use exactly the same values as the cited two papers for this method. + +<|ref|>text<|/ref|><|det|>[[115, 848, 883, 866]]<|/det|> +5. The authors assert in the second sentence of paragraph 4, that the D3 and D6 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 93, 883, 133]]<|/det|> +configurations are well understood by theory and experiments, without providing a reference to support this claim. + +<|ref|>text<|/ref|><|det|>[[115, 156, 883, 283]]<|/det|> +We thank the Reviewer to point this out. D3 and D6 molecules are two conjugated phenalenyl groups in the way of hosting sublattice imbalance as suggested in Fig1. Therefore, they have the high spin ground state of \(\mathrm{S} = 1\) . The nanographene with a high spin ground state due to the sublattice imbalance has been investigated by several theoretical and experimental works. To make this point clear, we have modified this sentence and cited relative works on it. + +<|ref|>text<|/ref|><|det|>[[115, 307, 883, 348]]<|/det|> +Modification: we modified the sentence on the magnetic state of D3 and added related references at page 9 and 10. + +<|ref|>text<|/ref|><|det|>[[115, 350, 883, 412]]<|/det|> +"Since D3 hosting the high spin ground state, due to the sublattice imbalance, is well understood by theory \(^{25}\) and experiments \(^{41,42}\) , we focus on the competing cases of D1 and D2 as depicted in Fig. 4. " + +<|ref|>text<|/ref|><|det|>[[115, 436, 883, 518]]<|/det|> +6. The introduction and conclusion mention the potential for room-temperature spintronics, however, all the experiments were conducted at 4K. We suggest either remove this claim or try solution EPR at room temperature to validate the spin interaction. + +<|ref|>text<|/ref|><|det|>[[115, 542, 883, 646]]<|/det|> +We thank the reviewer's comment. Since one of our investigated molecules presents a large exchange interaction, which significantly exceeds the room- temperature thermal energy (25 meV), we suggest it has the potential to have applications at room temperature. Considering the reviewer's suggestion, we don't emphasize this point in the revised manuscript and removed the words "room- temperature". + +<|ref|>text<|/ref|><|det|>[[115, 670, 883, 710]]<|/det|> +Modifications: We removed the words "room- temperature" in the introduction and conclusion parts. + +<|ref|>sub_title<|/ref|><|det|>[[117, 735, 356, 752]]<|/det|> +## Response to Reviewer 2: + +<|ref|>text<|/ref|><|det|>[[115, 756, 883, 902]]<|/det|> +Comments: The manuscript "Wide Tunning of Magnetic Exchange Coupling in Nanographenes through Orbital- Symmetry Engineering" by Du and his/her colleagues describe the magnetic exchange interaction in the on- surface synthesized (OSS) open- shell nanographenes with a combination of low- temperature scanning spectroscopy/inelastic tunneling spectroscopy and three- different theoretical calculations (DFT, MFH, and CAS). The authors found two different magnitudes of the exchange coupling, which was attributed to come from the different frontier orbital + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 93, 883, 198]]<|/det|> +symmetries. In the last years, open- shell molecules, including triangulates, have attracted interests of researchers because the magnetic coupling can be tuned by OSS precursor molecules in a controlled way. This study can be categorized in this hot field. The topic described in this manuscript would be interesting, yet this reviewer feels that the quality of the work at present does not meet a standard of Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 221, 883, 283]]<|/det|> +We thank the Reviewer finds the topic of our work is interesting. We have modified our manuscript according to both the reviewers' comments. We hope our revised manuscript can meet the standard of Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 306, 883, 433]]<|/det|> +Apparently, the theory part leads this study, yet the experimental results does not support the finding accordingly. First of all, the theory considered the dimer of the molecule but no experimental result. It is of importance to show the experimental results with the same system as the one described in the theory. In other word, it is mandatory that the authors measure the magnetic coupling of the compounds described in Figure 1. + +<|ref|>text<|/ref|><|det|>[[115, 456, 883, 561]]<|/det|> +We apologize that we have not presented our work clearly in our previous manuscript. In fact, we first find interesting experimental evidence that just by tuning a little bit the conjugation symmetry, the strength of magnetic exchange interaction can be varied about one order of magnitude. To explain this experimental finding, we employed several calculation methods to find out the physical mechanism. + +<|ref|>text<|/ref|><|det|>[[115, 563, 883, 689]]<|/det|> +To avoid any confusion, we have modified the structure of our manuscript. We first present the experimental results and then demonstrate the calculation results. Moreover, we agree with the reviewer that the molecular models used for calculation should be consistent with the experimental results. In the revised manuscript, all the calculation results presented are calculated with the molecular models complying with the experimental results. + +<|ref|>text<|/ref|><|det|>[[115, 712, 883, 752]]<|/det|> +Modifications: 1. We modified the manuscript structure by presenting the experimental results first and then explained the mechanism with different calculation methods. + +<|ref|>text<|/ref|><|det|>[[115, 755, 883, 795]]<|/det|> +2. The calculation results are presented with the same molecular models as the experiments. + +<|ref|>text<|/ref|><|det|>[[115, 799, 883, 839]]<|/det|> +The theoretical work is based on three- different codes. However, there is no sufficient description why the authors used them. + +<|ref|>text<|/ref|><|det|>[[115, 862, 883, 903]]<|/det|> +We thank the Reviewer's comments. DFT and MFH calculations are based on mean- field approximations, which normally underestimate the coulomb interactions. So we + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 93, 883, 133]]<|/det|> +used high- level CAS- Hubbard and NEVPT2 calculations to better capture the many- body interactions. + +<|ref|>text<|/ref|><|det|>[[115, 136, 885, 240]]<|/det|> +We realized that in our previous manuscript too many calculation models are presented, which may confuse the readers. Therefore, these calculation results are moved to the supporting information only for identifying the magnetic ground states in the revised manuscript. Now, we only use CAS- Hubbard and a more robust quantum chemistry method NEVPT2 for comparison. The corresponding discussions are also modified. + +<|ref|>text<|/ref|><|det|>[[115, 264, 883, 303]]<|/det|> +Modifications: 1. The MFH and DFT calculation results are moved to the supporting information. + +<|ref|>text<|/ref|><|det|>[[115, 306, 658, 325]]<|/det|> +2. Additional theoretical works using NEVPT2 are employed. + +<|ref|>text<|/ref|><|det|>[[115, 328, 515, 346]]<|/det|> +3. The corresponding discussion is modified. + +<|ref|>text<|/ref|><|det|>[[115, 370, 882, 432]]<|/det|> +Besides these, all calculation seems to be conducted in gas phase. On surface, there must be a significant interaction between the metal substrate and the radical molecule. It would be very beneficial that the authors include it. + +<|ref|>text<|/ref|><|det|>[[115, 455, 883, 560]]<|/det|> +We thank the Reviewer's comments. Previous DFT calculations suggest the Au(111) substrate doesn't affect the magnetic ground states of magnetic triangulene systems, where the gas phase calculations agree well with experimental results (Physical Review B 104, 075404 (2021)). Considering our large system, a full quantum chemistry calculation including the substrate is too heavy to be realized. + +<|ref|>text<|/ref|><|det|>[[115, 584, 882, 624]]<|/det|> +Above the reasons, this reviewer feels that the present manuscript is not suitable for the publication. Several minor comments are described as below + +<|ref|>text<|/ref|><|det|>[[115, 648, 882, 709]]<|/det|> +With our responses and the corresponding modifications, we hope our revised manuscript can meet the criterion of publication in Nature Communications. For the other comments, we responded as below. + +<|ref|>sub_title<|/ref|><|det|>[[117, 735, 208, 751]]<|/det|> +## 1. The title + +<|ref|>text<|/ref|><|det|>[[115, 756, 882, 795]]<|/det|> +The authors did not tune the magnetic exchange coupling just gives a few examples of different coupling in the products + +<|ref|>text<|/ref|><|det|>[[115, 819, 882, 901]]<|/det|> +We agree that in the experiments we only observe two kinds of nanographenes with huge different strengths of exchange interaction determined by their wave function symmetries. To precisely present our work, we modified our manuscript title to "Orbital- Symmetry Effects on Magnetic Exchange in Open- Shell Nanographenes". + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 115, 429, 133]]<|/det|> +Modification: The title is modified. + +<|ref|>text<|/ref|><|det|>[[115, 157, 198, 175]]<|/det|> +2. Fig. 3b + +<|ref|>text<|/ref|><|det|>[[115, 179, 881, 218]]<|/det|> +D1, D3, D2, and D5 are shown in this order. Yet, it is a bit confusing because Figure 3a is not. + +<|ref|>text<|/ref|><|det|>[[115, 242, 884, 390]]<|/det|> +We agree with the reviewer that we have shown too many molecular models in Fig.1, which makes it difficult to understand our main experimental and theoretical results. To avoid any confusion, we have modified molecular models in Fig.1, which are consistent with the experimental results. In the revised manuscript, we only discuss two nanographene diradicals (D1, D2) and one nanographene triradical (D3), which have been investigated in the experiments. It should give a better understanding for both the experimental and theoretical results. + +<|ref|>text<|/ref|><|det|>[[115, 413, 470, 431]]<|/det|> +Modifications: 1. Figure. 1 is modified. + +<|ref|>text<|/ref|><|det|>[[115, 435, 883, 475]]<|/det|> +2. Only the molecular structures observed in the experiments are discussed in the revised manuscript, which have been labeled as D1, D2 and D3. + +<|ref|>text<|/ref|><|det|>[[115, 499, 883, 560]]<|/det|> +3. S=1 antiferromagnetic coupling in inelastic tunneling spectroscopy data The authors obtained the values of \(20 \mathrm{mV}\) and \(160 \mathrm{mV}\) . How did the authors get them? The AC voltages for the lock in measurement seems to be too large. + +<|ref|>text<|/ref|><|det|>[[115, 583, 884, 753]]<|/det|> +The values of \(20 \mathrm{meV}\) and \(160 \mathrm{meV}\) are obtained by measuring inelastic tunneling spectra. As shown below, the spin excitation threshold energies are about \(\pm 20 \mathrm{mV}\) and \(\pm 160 \mathrm{mV}\) at the step position in the dl/dV spectra for D1 and D2 respectively. To determine the excitation voltage, the second dl/dV spectra can also be used (the figures in the second row). The peak positions in the second dl/dV spectra correspond to the step position in the dl/dV spectra, which both give the spin excitation values of \(\pm 20 \mathrm{mV}\) and \(\pm 160 \mathrm{mV}\) for D1 and D2 respectively. We have included the second dl/dV spectra in the supporting information for reference. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 595, 415]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 435, 754, 455]]<|/det|> +
Fig. 3 The dl/dV (top) and second dl/dV (bottom) spectra of D1 and D2.
+ +<|ref|>text<|/ref|><|det|>[[115, 477, 884, 583]]<|/det|> +For the inelastic tunneling spectra measurements, we have tried different modulation voltages. As shown below, using \(5 \mathrm{mV}\) or \(1 \mathrm{mV}\) of modulation voltage both give similar spin- flip spectra. In the previous manuscript, \(20 \mathrm{mV}\) is a typo error for the excitation mapping measurement condition. This modulation voltage should also be \(5 \mathrm{mV}\) , which has been corrected in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[122, 600, 637, 765]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 777, 802, 796]]<|/det|> +
Fig. 4 The dl/dV spectra measured with different lock-in modulation voltages.
+ +<|ref|>text<|/ref|><|det|>[[115, 819, 725, 860]]<|/det|> +Modifications: 1. The typo error is corrected. 2. The second dl/dV spectra are included in the supporting information. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 93, 303, 111]]<|/det|> +4. Page 14, line 230, + +<|ref|>text<|/ref|><|det|>[[115, 114, 883, 155]]<|/det|> +4. Page 14, line 230, "... Consistent with experiments (Fig. 6g)." which is misleading. It is better to change the position of "(Fig. 6)". + +<|ref|>text<|/ref|><|det|>[[115, 178, 747, 198]]<|/det|> +We thank the Reviewer's suggestion. We have modified this sentence. + +<|ref|>text<|/ref|><|det|>[[115, 221, 595, 240]]<|/det|> +Modifications: This sentence at page 14 is modified. + +<|ref|>text<|/ref|><|det|>[[115, 243, 883, 305]]<|/det|> +"To understand this system, a Heisenberg spin trimer model (Fig.6f) is solved, the calculation results shown in Fig.6g demonstrate that the ground state has \(\mathrm{S} = 1 / 2\) and the other six excited states are nearly degenerate with an excitation gap of \(\sim 160 \mathrm{meV}\) ." + +<|ref|>text<|/ref|><|det|>[[115, 328, 303, 368]]<|/det|> +5. Page 12, line 199. By sharp contrast? + +<|ref|>text<|/ref|><|det|>[[115, 391, 883, 454]]<|/det|> +We would like to emphasize the remarkable difference in magnetic exchange between molecules D1 and D2, which is about one order of magnitude. To avoid any confusion, this sentence has been modified. + +<|ref|>text<|/ref|><|det|>[[115, 477, 580, 497]]<|/det|> +Modifications: The sentence at page 8 is modified. + +<|ref|>text<|/ref|><|det|>[[115, 499, 883, 561]]<|/det|> +"In sharp contrast with the magnetic exchange of 20 meV observed on D1, the corresponding dl/dV spectra taken on D2 exhibit a substantially increased excitation threshold of 160 meV." + +<|ref|>sub_title<|/ref|><|det|>[[115, 585, 330, 602]]<|/det|> +## 6. Linker 1 and Linker 2 + +<|ref|>text<|/ref|><|det|>[[115, 606, 622, 625]]<|/det|> +It is shown in Figure 1 but is not clear enough in the text. + +<|ref|>text<|/ref|><|det|>[[115, 648, 883, 752]]<|/det|> +We thank the Reviewer's comment. We have realized that there are too many molecular models in the previous manuscript, which are difficult for the readers to catch the main experimental and theoretical results. In the revised manuscript, we have modified our molecular models for consistent with the experimental results and there is no need to introduce linker 1 and linker 2. + +<|ref|>text<|/ref|><|det|>[[115, 776, 826, 796]]<|/det|> +Modification: We have modified Fig.1, the linkers 1 and 2 have been removed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 225, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 140, 845, 182]]<|/det|> +The manuscript has been significantly improved and the authors have addressed almost all the points raised as part of the review. In its current form the manuscript could be considered for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[119, 225, 225, 238]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 240, 300, 252]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 253, 878, 365]]<|/det|> +The authors changed the structure of the manuscript as showing the experimental data and subsequently explaining the possible mechanism with the theoretical calculation. Now, I think that the readability of the manuscript improves. However, this reviewer found it difficult to read the response letter. For instance, the authors states that "we have included large range dI/dV spectra of molecules D4, D5, and D6..." but no related data was shown in supporting information. The authors also replied as "which have been renamed for phenalenyl diradical (D1, D2) and triradical (D3)" but D3 seems to be a diradical. Most probably all would relate to typos but this reviewer is afraid that the intentions of the authors are really understood correctly. + +<|ref|>text<|/ref|><|det|>[[118, 364, 875, 477]]<|/det|> +The new dI/dV data in Supplementary Figure 16 shows distinct different peak heights in second differential curves for D2 but not for D1. Why? Also, this reviewer could not find the zero line in the d2I/dV2 curves (btw, the authors described "dI2/dV2", which is incorrect.). The contrast of SOMO for D1 is almost identical with that of SUMO, but D2 shows distinct contrasts (Supplementary Figure 17). Why? These points relate to Comment 2 of Reviewer 1. The authors just replaced the dI/dV maps taken at +- 160 mV without any adequate explanation. For these reasons, this reviewer still feels that this contribution does not meet the standard for publication in Nature Communication. + +<|ref|>text<|/ref|><|det|>[[119, 492, 168, 504]]<|/det|> +Minor: + +<|ref|>text<|/ref|><|det|>[[118, 505, 520, 519]]<|/det|> +1. Chemical structures in Figure 4 should be revised. + +<|ref|>text<|/ref|><|det|>[[118, 519, 802, 534]]<|/det|> +2. Bond-resolved AFM. Is that the topography? No information can be found in the figure. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 94, 357, 111]]<|/det|> +## Response to Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[117, 115, 850, 176]]<|/det|> +Comments: The manuscript has been significantly improved and the authors have addressed almost all the points raised as part of the review. In its current form the manuscript could be considered for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[117, 200, 704, 218]]<|/det|> +We thank the Reviewer for his/her positive evaluation of our work. + +<|ref|>sub_title<|/ref|><|det|>[[117, 243, 357, 261]]<|/det|> +## Response to Reviewer 2: + +<|ref|>text<|/ref|><|det|>[[117, 265, 883, 325]]<|/det|> +Comments: The authors changed the structure of the manuscript as showing the experimental data and subsequently explaining the possible mechanism with the theoretical calculation. Now, I think that the readability of the manuscript improves. + +<|ref|>text<|/ref|><|det|>[[117, 349, 715, 367]]<|/det|> +We thank the Reviewer finds our revised manuscript has improved. + +<|ref|>text<|/ref|><|det|>[[116, 392, 882, 453]]<|/det|> +However, this reviewer found it difficult to read the response letter. For instance, the authors states that "we have included large range dl/dV spectra of molecules D4, D5, and D6..." but no related data was shown in supporting information. + +<|ref|>text<|/ref|><|det|>[[116, 477, 882, 539]]<|/det|> +These data have been included in the supporting information in Supplementary Figure 17 and Supplementary Figure 18 (p.14 and p.15 in the supporting information), but with the revised labels as D1, D2, and T instead of D4, D5, and D6. + +<|ref|>text<|/ref|><|det|>[[116, 562, 882, 645]]<|/det|> +The authors also replied as ", which have been renamed for phenalenyl diradical (D1, D2) and triradical (D3)" but D3 seems to be a diradical. Most probably all would relate to typos but this reviewer is afraid that the intentions of the authors are really understood correctly. + +<|ref|>text<|/ref|><|det|>[[116, 670, 882, 752]]<|/det|> +We apologize that this is the typo error in the previous response letter. As the reviewer's understanding, D1, D2, and D3 are phenaleny diradicals, while phenaleny triradical is labeled as T. We have checked through our revised manuscript, these labels should be correct and consistent. + +<|ref|>text<|/ref|><|det|>[[116, 777, 878, 816]]<|/det|> +The new dl/dV data in Supplementary Figure 16 shows distinct different peak heights in second differential curves for D2 but not for D1. Why? + +<|ref|>text<|/ref|><|det|>[[116, 841, 882, 902]]<|/det|> +We thank the Reviewer's comments. The bias- asymmetric peak heights are commonly observed in the experiments. The reason has been systematically investigated in theory (e.g. New J. Phys. 17, 63016 (2015)), which suggests that the high- order + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 92, 884, 432]]<|/det|> +scattering process will result in the asymmetric peak heights in the IETS spectrum. And particularly, if there is a resonate state near the bias window of spin excitation, the high- order scattering process will be enhanced and produce a more pronounced asymmetric IETS line shape. As shown in the following figure, this is the case that we observed in our \(\mathrm{d}^2\mathrm{l} / \mathrm{d}\mathrm{V}^2\) . Since the spin excitation energies are very small for D1 \((\pm 20 \mathrm{mV})\) , which are both far away from its resonant orbital states of SOMO (- 450 mV) and SUMO (950 mV), the asymmetric peak heights of D1 \(\mathrm{d}^2\mathrm{l} / \mathrm{d}\mathrm{V}^2\) spectrum is not obvious. In contrast, the spin excitation energies of D2 are much larger \((\pm 160 \mathrm{mV})\) , which is close to its SOMO (- 350 mV) resonant orbital in the negative bias direction but far away from its SUMO orbital (1.05 V). Therefore, the peak height is more pronounced in the negative bias and results in a huge asymmetric IETS spectrum. This large asymmetric peak height behavior has also been observed recently in the \(\mathrm{d}^2\mathrm{l} / \mathrm{d}\mathrm{V}^2\) spectrum of a nanographene system with large exchange interaction, whose spin excitation energy is also close to one of the molecular resonant states (J. Am. Chem. Soc. 145, 2968- 2974 (2023)). To clarify this point, we have added some discussion on this asymmetric line shape in the manuscript. + +<|ref|>image<|/ref|><|det|>[[117, 448, 470, 657]]<|/det|> + +<|ref|>image<|/ref|><|det|>[[524, 465, 868, 656]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 682, 884, 722]]<|/det|> +Modification: We added some discussion at page 8 and cited related theoretical and experimental works. + +<|ref|>text<|/ref|><|det|>[[115, 724, 883, 786]]<|/det|> +"And a more pronounced asymmetric line shape of \(\mathrm{d} / \mathrm{d}\mathrm{V}\) spectra is observed on D2 compared to that of D1 since D2 has a high spin excitation energy which is close to its SOMO resonate state thus leading to a pronounced height in the negative bias. \(^{32,57*}\) + +<|ref|>text<|/ref|><|det|>[[115, 810, 883, 850]]<|/det|> +Also, this reviewer could not find the zero line in the d2l/dV2 curves (btw, the authors described "dl2/dV2", which is incorrect.). + +<|ref|>text<|/ref|><|det|>[[115, 852, 884, 892]]<|/det|> +We thank the reviewer's careful check. In the previous version, we shifted the spectra measured on the molecule and on Au(111) substrate vertically for clarity without + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 883, 133]]<|/det|> +indicating the zero line. In the revised version, we canceled the vertical shift (cf. the following figure). + +<|ref|>image<|/ref|><|det|>[[150, 139, 785, 320]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 343, 881, 384]]<|/det|> +Modification: The vertical ordinates are added in the \(\mathrm{d}^2 /\mathrm{d}V^2\) spectra in Supplementary Fig.16. The typo error of \(\mathrm{d}^2 /\mathrm{d}V^2\) is also corrected. + +<|ref|>text<|/ref|><|det|>[[115, 406, 881, 448]]<|/det|> +The contrast of SOMO for D1 is almost identical with that of SUMO, but D2 shows distinct contrasts (Supplementary Figure 17). Why? + +<|ref|>text<|/ref|><|det|>[[115, 470, 883, 726]]<|/det|> +The SUMO contrast of D2 is distinct from its SOMO mainly due to their different tip- molecule separations when measuring the SOMO and SUMO \(\mathrm{d}l / \mathrm{d}V\) mappings. Since D1 and D2 have sp3 hydrogen passivation, the additional hydrogen will be dissociated if the tip is too close to the sample. And because the SUMO energy of D2 is about 1.05 eV while its SOMO energy is only 0.35 eV, the mappings of SUMO and SOMO are taken at different tunneling current set points of \(I = 400\) and \(500 \mathrm{pA}\) respectively to avoid hydrogen dissociation. Therefore, the tip- molecule separation at measuring the \(\mathrm{d}l / \mathrm{d}V\) mappings is much larger for SUMO than that of SOMO, which results in the fine structure of SUMO being different from SOMO. Additionally, we performed simulations considering such different tip- sample separation effect. As seen in the following simulated STS mappings, the fine structures of SOMO/SUMO orbitals depend sensitively on tip- sample separation, consistent with experimental observations. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[144, 91, 800, 305]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 328, 881, 368]]<|/det|> +Modification: The simulated dl/dV mappings of SOMO and SUMO at different tip- molecule distance have been included in the Supplementary Figure 17. + +<|ref|>text<|/ref|><|det|>[[115, 392, 881, 432]]<|/det|> +These points relate to Comment 2 of Reviewer 1. The authors just replaced the dl/dV maps taken at \(+ - 160 \text{mV}\) without any adequate explanation. + +<|ref|>text<|/ref|><|det|>[[115, 455, 883, 624]]<|/det|> +To detect the fine structures of molecular orbitals, we usually use CO functionalized tip since the p- wave orbitals of the CO molecule can enhance the lateral resolution compared with a bare metal tip (Phys. Rev. Lett. 107, 086101 (2011)). In experiments, the CO molecule is usually picked up to the tip by applying a short pulse, and its adsorption on the tip position sometimes is not perfect vertical and symmetric, which may not give the best spatial resolution as expected. The dl/dV mappings taken at \(\pm 160 \text{mV}\) in the revised manuscript is measured by a CO functionalized tip with a much higher spatial resolution of the orbital distribution than the previous images. + +<|ref|>text<|/ref|><|det|>[[115, 648, 881, 687]]<|/det|> +For these reasons, this reviewer still feels that this contribution does not meet the standard for publication in Nature Communication. + +<|ref|>text<|/ref|><|det|>[[115, 712, 881, 773]]<|/det|> +With our responses and the corresponding modifications, we hope our revised manuscript can meet the criterion of publication in Nature Communications. For the other comments, we responded as below. + +<|ref|>sub_title<|/ref|><|det|>[[115, 795, 175, 810]]<|/det|> +## Minor: + +<|ref|>text<|/ref|><|det|>[[115, 812, 881, 885]]<|/det|> +1. Chemical structures in Figure 4 should be revised. We checked the chemical structures in Fig.4 and thought the reviewer might mean the chemical structure is not used the templates of ChemDraw. Therefore, we modified the chemical structure by using the ChemDraw template in Fig.4 + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[172, 113, 721, 250]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 258, 825, 294]]<|/det|> +Modification: The chemical structure in Fig.4 is modified using the ChemDraw template. + +<|ref|>text<|/ref|><|det|>[[115, 330, 854, 367]]<|/det|> +2. Bond-resolved AFM. Is that the topography? No information can be found in the figure. + +<|ref|>text<|/ref|><|det|>[[115, 368, 883, 461]]<|/det|> +The bond- resolved AFM is measured by non- contact atomic force microscope with a qPlus sensor. The AFM images were recorded with the different shift frequency of the qPlus sensor in the constant height mode, whose contrasts reflect the topography of the molecules (Science 325,1110- 1114 (2009)). To make this point more clear, we have added grey scale bars of the shift frequency in all AFM images. + +<|ref|>text<|/ref|><|det|>[[115, 479, 881, 516]]<|/det|> +Modification: The AFM images in Fig.2, Fig3, and Fig6 are added with the grey scale bars of the shift frequency. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 294, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[118, 113, 225, 126]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 128, 300, 141]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 141, 830, 169]]<|/det|> +The authors improved the manuscript a lot. Now, this reviewer feels more confident that this contribution deserves publication in Nature Communications. + +<--- Page Split ---> diff --git a/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/images_list.json b/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..573a6d1e72c3a89bc6f43f606522b4217c260d0e --- /dev/null +++ b/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,277 @@ + +# nature portfolio + +Peer Review File + +Fibrocystin/Polyductin releases a C- terminal fragment that translocates into mitochondria and suppresses cystogenesis + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +This study presents an interesting story, which try to state that C- terminal fragments of FPC, \(\sim 15 \text{kDa}\) (ICD15), \(\sim 12 \text{kDa}\) (ICD12), and \(\sim 6 \text{kDa}\) (ICD6), translocate into mitochondria and have a prevent function from cytogenesis. Better support should be provided for the key conclusions "prevent cytogenesis" by the C- terminal fragments. There are some questions: + +1. PKHD1 has different isoforms. Cleaved fragments of FPC was found in this study. Were these proteins sequenced or, at part, has a same amino acid peptide as encoded in exon 67? +2. The authors found ICD15 translocated to mitochondria. Was mitochondrial biogenesis activated or mitochondrial structure or function altered when ICD15 translocated? +3. In the text, mitochondrial ultrastructure altered in Pkbd1 KO mice, compared to the Wt controls. To evaluate the ICD15 function or its impact on mitochondria, it is better to provide additional data of mitochondrial structure and function in vitro, compared with Pkbd1 KO, ICD15 transfected back, and Wt. +4. In line 375 "Both compound heterozygous Pkbd1Δ3-4/+;Pkbd1V/+ mutant mice...." Compound heterozygote is referred to two different mutations (or variants) in one same gene. As Pkbd1 and Pkd1 are two different genes, it should correct to be "digenic mutant mice". +5. The 5th result section (line 429-468) probably be better as a part of one result section or as a supplementary data. + +## Others: + +6. the cited refs37 in line138 and refs19 in line 354 should be confirmed (probably it should be corrected to 38 or 20 respectively). + +7. line 342-343, sentence "This result suggests that FPC may participate in regulating mitochondrial structure and function". However, no mitochondrial function has been provided in this section. + +8. Sentence in line 373-375, "The Pkbd1Δ3-4 allele has a deletion of exons 3-4....in the + +<--- Page Split ---> + +extracellular domain" is better to put in the place when Pkhd1Δ3- 4 first appeared. + +9. In Figure2,C)D)E)F)I) graphs should clearly shows the distribution of data and variation (as dot plot in the column), and the number of times of the experiments should be stated in figure legends. + +## Reviewer #2 (Remarks to the Author): + +The paper lacks sufficient novelty. All single mutant phenotypes were previously described. The genetic interaction between Pkd1 and Pkhd1 (double mutant phenotypes) was previously described by several groups, including this group. Pkhd1/FPC deficiency and mitochondrial defects were previously described. Cleavage of Pkhd1 protein FPC has been reported previously by other group and this group. This paper described a more detailed analysis of FPC CTT responsible for mitochondrial translocation. They found in Pkd1 and Pkhd1 double mutants develop embryonic pancreatic cysts that is present in Pkd1 null mutant. This finding is of some interest but of limited significance. The paper is too long: Introduction, 4 pages; Results, 12 pages; and Discussion is 6 pages, difficult to read. Nomenclature is confusing. What is Pkhd1- /-, Pkhd1 \(\Delta 3 - 4\) , Pkhd1 \(\Delta CT\) , Pkhd1 \(\Delta 67\) , KO. There are 2 Pkd1 lines (Pkd1RC, Pkd1V) and 5 Pkhd1 alleles used in the study or some of them are the same thing? In the methods, there is almost no information about all the mouse lines used in the study. The conclusion is not fully supported by the experimental data. + +## Reviewer #3 (Remarks to the Author): + +The authors describe that the type I transmembrane protein Fibrocystin/Polyductin (FPC), the main protein for autosomal recessive polycystic kidney disease (ARPKD) encoded by the large PKHD1 gene, undergoes complex proteolytic processing in vivo. This processing results in three small soluble C- terminal fragments with molecular weights ranging from 6- 15 kDa (termed ICD6, 12, and 15). At the N- terminus of ICD15 the authors identified a mitochondrial targeting sequence (MTS) that directs its mitochondrial localization. Walker et al. demonstrate convincing ultrastructural alterations of mitochondria of Pkhd1 KO mouse kidney tubules in contrast to wildtype controls. + +<--- Page Split ---> + +In addition, the authors performed comprehensive genetic epistasis studies in mice and could show that FPC inactivation aggravates renal cystogenesis in a Pkd1 mouse mutant (Pkd1v/v). Deletion of the final exon of Pkhd1 (exon 67) enhanced cystogenesis in the kidney, but not in the pancreas, of those Pkd1v/v mutant mice. Overall, the novel data generated by this study indicates that an important function of the ICD protein products within the mitochondria is to protect against cyst formation when the function of Polycystin- 1, the Pkd1 gene product and major ADPKD protein, is compromised. + +This is an excellent study that adds important knowledge to the pathophysiology of polycystic kidney disease. I have only minor comments that the authors are recommended to address: + +- A substantial amount of data has been generated by the authors, however, the manuscript and its readability would clearly benefit from some kind of shortening (e.g. in the introduction section). + +- Page 3: Please add the information that (while PKHD1 clearly defines the main ARPKD gene) pathogenic variants in various other genes may cause ARPKD or ARPKD-like phenotypes. + +<--- Page Split ---> + +## RESPONSE TO REFEREES + +We thank reviewers 1 and 3 for accepting the revised manuscript in its current form. Below, we present point- by- point responses to reviewer 2. + +## Reviewer #2 (Remarks to the Author) + +In this revised manuscript, the authors have improved the clarity of nomenclature and a table describing the mouse lines used in this study is helpful. However, several major points still warrant attention. + +"3) By utilizing the Pkd1V/V model in the genetic epistasis analyses, we have made the intriguing discovery that loss of FPC leads to a Pkd1 null-like cystic phenotype both in the kidney and pancreas. Moreover, unlike Pkd1RC used in Olson et al study, Pkd1V/V displayed impaired localization of PC1 to cilia, suggesting specific involvement of cilia in cyst progression as discussed and presented in our model (Figure 7)." + +The Pkd1 RC mutant was previously identified as having a maturation defect in PC1, leading to compromised cleavage, as documented by Hopp et al in 2012. Furthermore, research by Su et al in 2015 showed that the RC mutation hinders the proper localization of PC1 to cilia. Consequently, even though the Pkd1 V mutant carries a distinct genetic mutation compared to the Pkd1 RC mutant, which was formerly employed in Pkhd1- Pkd1 digenic study by Olsen et al, the observed distinction remains marginal, hence the novelty in this regard is inadequate. + +## Response: + +We appreciate the reviewer's recognition of the improved clarity in nomenclature in the revised manuscript. While we acknowledge the reviewer's concern regarding the distinction between the Pkhd1- Pkd1 interaction using the Pkd1V/V mutant versus the Pkd1 RC mutant, it's important to highlight that our study's main focus goes far beyond just the Pkhd1- Pkd1 interaction. + +The true novelty lies in the new insights derived from the utilization of the Pkd1V/V strain. As we outlined extensively in our prior response, our study introduces multiple noteworthy findings. These encompass the translocation of ICD15 into mitochondria, the identification of ultrastructural and functional mitochondrial abnormalities in Pkhd1 KO kidney tubules and renal epithelial cells, and the essential role of ICD15 in suppressing renal cyst development in mice. Consequently, our manuscript's contribution goes significantly beyond this single observation, offering novel perspectives on FPC's role in ARPKD and signifying a substantial advancement in the field. + +<--- Page Split ---> + +We had thoroughly discussed the rationale and advantages of utilizing the Pkd1V/V strain, particularly for assessing proximal tubules, in lines 358- 369, as provided in the previous revision. The results obtained through our utilization of the Pkd1V/V mutants offer valuable novel insights into the role of FPC in ARPKD and constitute a significant contribution to the current body of literature. + +## "Our discovery sheds light on a distinct mechanism of the ciliary function of FPC in pancreatic cystogenesis" + +Can the authors explain based on what evidence they connected the occurrence of pancreatic cysts with the ciliary function of FPC? + +## Response: + +Our identification of pancreatic cysts in the two digenic mutants ( \(\Delta 3 - 4 / V\) and KO/V) provides compelling evidence for the pivotal role of FPC in cystogenesis within the pancreas. Notably, our analysis of \(\Delta 67 / V\) digenic mutants revealed an intriguing pattern: while renal cystogenesis in \(\Delta 67 / V\) was enhanced compared to Pkd1V/V single mutants, no pancreatic cysts were observed. These results suggest that while FPC plays a crucial role in cystogenesis in the pancreas, its ICD15 component does not exert a substantial impact on this process when combined with the Pkd1V/V mutation. + +We have comprehensively discussed this intriguing finding in the revised manuscript in lines 583- 597 regarding the ciliary function of FPC in safeguarding the pancreas from cystogenesis through mechanisms extending beyond its C- terminal tail. This notion is based on the observation (shown in Figure 1G) that Pkhd1 \(\Delta 67 / \Delta 67\) expresses the FPC- \(\Delta CT\) protein. This variant lacks ICD15 but retains the intact ciliary targeting sequence, suggesting its likely localization to the cilia. Consequently, we hypothesize that this ciliary function could protect the pancreas from cystogenesis through the involvement of its ecto- and transmembrane domains. + +"We propose a molecular mechanism to explain the interaction between Pkhd1 and Pkd1 in cystogenesis through a cilia- mitochondria connection (Figure 7)." + +Please specify the experimental evidence that supports this model. Which experiments and figures are pertinent to establishing the cilia- mitochondria connection? + +Response: + +<--- Page Split ---> + +The proposed model is based on a synthesis of prior research and the results of this study. In our text, we reference prior studies that introduced the concept of the cilia- dependent cyst activation (CDCA) mechanism, which triggers cystogenesis upon the depletion of polycystins—integral ciliary membrane proteins, as outlined in lines 644- 649. + +Our model logically bridges the previously established ciliary roles of FPC and polycystins with FPC's mitochondrial function through ICD15 as revealed by our current study. The connection between cilia and mitochondria is explicitly articulated in the initial segment of the Discussion (lines 533- 535), following a concise overview of the pivotal discoveries of our study. Further elaboration on the model depicted in Figure 7 is provided in the concluding section of the Discussion. + +In our preceding round of revisions, we made extensive efforts to streamline the content, enhance clarity, and improve the manuscript's overall readability. The presentation logically follows from the progression of our presentation and is expounded upon in the preceding sections of the Discussion. Consequently, we have chosen to refrain from introducing supplementary elaboration or referencing specific experiments or figures in this section. Such additions might introduce redundancy and unnecessarily prolong the text—a situation we are keen to circumvent based on prior feedback. + +To amplify clarity, we have now added references to the pertinent figures (indicated in blue) that correspond to each of the key findings summarized in the initial section of the Discussion (lines 520- 532). + +Olsen et al conducted RNA- seq analysis on digenic and monogenic mouse models, highlighting the ciliary compartment as a commonly dysregulated target. This was underscored by enhanced ciliary expression and altered length in the digenic model. However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice. + +## Response: + +We acknowledge the alignment of our findings with those of Olsen et al., as noted in the manuscript (lines 133- 138). However, it is important to clarify that our study did not investigate the role of polycystin- 2. Therefore, the notion of the reviewer "However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice" is not directly applicable to our study. + +Are mitochondrial defects the sole abnormalities discovered in the Pkhd1 KO mice in the present study? Have any other ciliary defects been detected? Is PC1 ciliary localization normal across different Pkhd1 KO lines? Additionally, what impact does FPC KO have on PC1 C- tail cleavage? + +<--- Page Split ---> + +Notably, a decrease in mitochondrial mass and a PKD1- dose- dependent decline in mitochondrial membrane potential have been previously observed in renal tubular cells. Existing studies demonstrate that cleaved PC1 C- tail induces mitochondrial dysfunction, and mitochondrial abnormalities are evident in Pkd1 knockout mice. Have the authors investigated mitochondrial function in the digenic animals as well? This should be done. + +## Response: + +We appreciate the reviewer's thought- provoking new inquiries, which were not brought up in the previous critique. In our present study, we did not assert that mitochondrial defects are the sole abnormalities observed in Pkhd1 KO mice. Additionally, we recognize that inquiries, such as those regarding the cleaved PC1 C- tail, remain unexplored. However, we want to highlight that we did address the potential significance of FPC on the cleaved PC1 C- tail in our previous revision, as outlined in lines 564- 571. + +We concur that the questions related to the digenic animals indeed merit attention. Nevertheless, we view them as potential avenues for future investigations. + +In this study, the authors have identified mitochondrial defects in the kidneys of Pkhd1 knockout mice, despite the absence of cyst manifestation. The functional significance of these mitochondria defects in Pkhd1 KO mice raises pertinent questions. Does the lack of renal cysts in Pkhd1 KO mice suggest that mitochondrial abnormalities alone are insufficient to trigger cystogenesis? Alternatively, could it imply that the extent of mitochondrial defects in Pkhd1 mice is not substantial enough to drive cyst formation? Earlier research, notably the work of Nishio et al in 2010, has firmly established the absence of oriented cell division as a distinctive feature of Pkhd1 mutations. + +## Response: + +We appreciate the reviewer's recognition of our findings pertaining to the significance of mitochondrial defects in the kidneys of Pkhd1 knockout mice, even in the absence of observable cyst manifestation. This finding indeed stands as a noteworthy and innovative aspect of our study. It is indisputable that a multitude of dysregulated pathways contribute to a complex process such as cystogenesis, including a defect in oriented cell division. Our study raises important questions about whether mitochondrial abnormalities alone are insufficient to trigger cystogenesis or if other factors come into play, warranting further investigations. In its entirety, we believe that our study will make a significant and valuable addition to the existing literature. + +Overall, the mechanisms underlying the genetic epistasis analyses conducted in this + +<--- Page Split ---> + +study remain unclear. The model in Figure 7 is too hypothetic, which is not supported by data. + +## Response: + +We concur that although our study unveils a novel and critical mitochondrial role of FPC, a prominent cysteine, in cystogenesis, the precise mechanisms underlying the genetic epistasis analyses conducted in this study remain enigmatic. It is indeed a humbling realization that a study of this nature cannot comprehensively delve into the intricacies of the next- level mechanisms. + +Nonetheless, it's important to highlight that our current study has provided valuable insights into renal cystogenesis. These insights, while not exhaustive, have the potential to stimulate further exploration of these intricate questions by the research community. We therefore believe that our study would make a significant and valuable addition to the existing literature. + +While we acknowledge that our model in Figure 7 is hypothetical, as models inherently are, we respectfully disagree with the characterization of its level of hypothesis as being "TOO hypothetical." As previously discussed, the model is consistent with prior research and provides a coherent explanation for our current findings. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #1 (Remarks to the Author): + +I am happy that the authors have now addressed the concerns from the previous review. + +## Reviewer #2 (Remarks to the Author): + +In this revised manuscript, the authors have improved the clarity of nomenclature and a table describing the mouse lines used in this study is helpful. However, several major points still warrant attention. + +"3) By utilizing the Pkd1V/V model in the genetic epistasis analyses, we have made the intriguing discovery that loss of FPC leads to a Pkd1 null- like cystic phenotype both in the kidney and pancreas. Moreover, unlike Pkd1RC used in Olson et al study, Pkd1V/V displayed impaired localization of PC1 to cilia, suggesting specific involvement of cilia in cyst progression as discussed and presented in our model (Figure 7)." + +The Pkd1 RC mutant was previously identified as having a maturation defect in PC1, leading to compromised cleavage, as documented by Hopp et al in 2012. Furthermore, research by Su et al in 2015 showed that the RC mutation hinders the proper localization of PC1 to cilia. Consequently, even though the Pkd1 V mutant carries a distinct genetic mutation compared to the Pkd1 RC mutant, which was formerly employed in Pkhd1- Pkd1 digenic study by Olsen et al, the observed distinction remains marginal, hence the novelty in this regard is inadequate. + +"Our discovery sheds light on a distinct mechanism of the ciliary function of FPC in pancreatic cystogenesis" + +Can the authors explain based on what evidence they connected the occurrence of pancreatic cysts with the ciliary function of FPC? + +"We propose a molecular mechanism to explain the interaction between Pkhd1 and Pkd1 in cystogenesis through a cilia- mitochondria connection (Figure 7)." + +<--- Page Split ---> + +Please specify the experimental evidence that supports this model. Which experiments and figures are pertinent to establishing the cilia- mitochondria connection? + +Olsen et al conducted RNA- seq analysis on digenic and monogenic mouse models, highlighting the ciliary compartment as a commonly dysregulated target. This was underscored by enhanced ciliary expression and altered length in the digenic model. However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice. + +Are mitochondrial defects the sole abnormalities discovered in the Pkhd1 KO mice in the present study? Have any other ciliary defects been detected? Is PC1 ciliary localization normal across different Pkhd1 KO lines? Additionally, what impact does FPC KO have on PC1 C- tail cleavage? + +Notably, a decrease in mitochondrial mass and a PKD1- dose- dependent decline in mitochondrial membrane potential have been previously observed in renal tubular cells. Existing studies demonstrate that cleaved PC1 C- tail induces mitochondrial dysfunction, and mitochondrial abnormalities are evident in Pkd1 knockout mice. Have the authors investigated mitochondrial function in the digenic animals as well? This should be done. + +In this study, the authors have identified mitochondrial defects in the kidneys of Pkhd1 knockout mice, despite the absence of cyst manifestation. The functional significance of these mitochondria defects in Pkhd1 KO mice raises pertinent questions. Does the lack of renal cysts in Pkhd1 KO mice suggest that mitochondrial abnormalities alone are insufficient to trigger cystogenesis? Alternatively, could it imply that the extent of mitochondrial defects in Pkhd1 mice is not substantial enough to drive cyst formation? + +Earlier research, notably the work of Nishio et al in 2010, has firmly established the absence of oriented cell division as a distinctive feature of Pkhd1 mutations. Overall, the mechanisms underlying the genetic epistasis analyses conducted in this study remain unclear. The model in Figure 7 is too hypothetic, which is not supported by data. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +Congratulations to this wonderful study, I have no further comments. + +<--- Page Split ---> + +## RESPONSE TO REFEREES + +We thank reviewers 1 and 3 for accepting the revised manuscript in its current form. Below, we present point- by- point responses to reviewer 2 for the final version (NCOMMS- 22- 35324B). + +## Reviewer #2 (Remarks to the Author) + +In this revised manuscript, the authors have improved the clarity of nomenclature and a table describing the mouse lines used in this study is helpful. However, several major points still warrant attention. + +"3) By utilizing the Pkd1V/V model in the genetic epistasis analyses, we have made the intriguing discovery that loss of FPC leads to a Pkd1 null- like cystic phenotype both in the kidney and pancreas. Moreover, unlike Pkd1RC used in Olson et al study, Pkd1V/V displayed impaired localization of PC1 to cilia, suggesting specific involvement of cilia in cyst progression as discussed and presented in our model (Figure 7)." + +The Pkd1 RC mutant was previously identified as having a maturation defect in PC1, leading to compromised cleavage, as documented by Hopp et al in 2012. Furthermore, research by Su et al in 2015 showed that the RC mutation hinders the proper localization of PC1 to cilia. Consequently, even though the Pkd1 V mutant carries a distinct genetic mutation compared to the Pkd1 RC mutant, which was formerly employed in Pkhd1- Pkd1 digenic study by Olsen et al, the observed distinction remains marginal, hence the novelty in this regard is inadequate. + +## Response: + +We appreciate the reviewer's recognition of the improved clarity in nomenclature in the revised manuscript. While we acknowledge the reviewer's concern regarding the distinction between the Pkhd1- Pkd1 interaction using the Pkd1V/V mutant versus the Pkd1 RC mutant, it's important to highlight that our study's main focus goes far beyond just the Pkhd1- Pkd1 interaction. + +The true novelty lies in the new insights derived from the utilization of the Pkd1V/V strain. As we outlined extensively in our prior response, our study introduces multiple noteworthy findings. These encompass the translocation of ICD15 into mitochondria, the identification of ultrastructural and functional mitochondrial abnormalities in Pkhd1 KO kidney tubules and renal epithelial cells, and the essential role of ICD15 in suppressing renal cyst development in mice. Consequently, our manuscript's contribution goes significantly beyond this single observation, offering novel perspectives on FPC's role in ARPKD and signifying a substantial advancement in the field. + +<--- Page Split ---> + +We had thoroughly discussed the rationale and advantages of utilizing the Pkd1V/V strain, particularly for assessing proximal tubules, in lines 354- 365 (of the final version), as provided in the previous revision. The results obtained through our utilization of the Pkd1V/V mutants offer valuable novel insights into the role of FPC in ARPKD and constitute a significant contribution to the current body of literature. + +## "Our discovery sheds light on a distinct mechanism of the ciliary function of FPC in pancreatic cystogenesis" + +Can the authors explain based on what evidence they connected the occurrence of pancreatic cysts with the ciliary function of FPC? + +## Response: + +Our identification of pancreatic cysts in the two digenic mutants (Δ3- 4/V and KO/V) provides compelling evidence for the pivotal role of FPC in cystogenesis within the pancreas. Notably, our analysis of Δ67/V digenic mutants revealed an intriguing pattern: while renal cystogenesis in Δ67/V was enhanced compared to Pkd1V/V single mutants, no pancreatic cysts were observed. These results suggest that while FPC plays a crucial role in cystogenesis in the pancreas, its ICD15 component does not exert a substantial impact on this process when combined with the Pkd1V/V mutation. + +We have comprehensively discussed this intriguing finding in the revised manuscript in lines 578- 592 regarding the ciliary function of FPC in safeguarding the pancreas from cystogenesis through mechanisms extending beyond its C- terminal tail. This notion is based on the observation (shown in Figure 1g) that Pkhd1Δ67/Δ67 expresses the FPC- ΔCT protein. This variant lacks ICD15 but retains the intact ciliary targeting sequence, suggesting its likely localization to the cilia. Consequently, we hypothesize that this ciliary function could protect the pancreas from cystogenesis through the involvement of its ecto- and transmembrane domains. + +"We propose a molecular mechanism to explain the interaction between Pkhd1 and Pkd1 in cystogenesis through a cilia- mitochondria connection (Figure 7)." + +Please specify the experimental evidence that supports this model. Which experiments and figures are pertinent to establishing the cilia- mitochondria connection? + +Response: + +<--- Page Split ---> + +The proposed model is based on a synthesis of prior research and the results of this study. In our text, we reference prior studies that introduced the concept of the cilia- dependent cyst activation (CDCA) mechanism, which triggers cystogenesis upon the depletion of polycystins—integral ciliary membrane proteins, as outlined in lines 639- 644. + +Our model logically bridges the previously established ciliary roles of FPC and polycystins with FPC's mitochondrial function through ICD15 as revealed by our current study. The connection between cilia and mitochondria is explicitly articulated in the initial segment of the Discussion (lines 528- 531), following a concise overview of the pivotal discoveries of our study. Further elaboration on the model depicted in Figure 7 is provided in the concluding section of the Discussion. + +In our preceding round of revisions, we made extensive efforts to streamline the content, enhance clarity, and improve the manuscript's overall readability. The presentation logically follows from the progression of our presentation and is expounded upon in the preceding sections of the Discussion. Consequently, we have chosen to refrain from introducing supplementary elaboration or referencing specific experiments or figures in this section. Such additions might introduce redundancy and unnecessarily prolong the text—a situation we are keen to circumvent based on prior feedback. + +To amplify clarity, we have now added references to the pertinent figures that correspond to each of the key findings summarized in the initial section of the Discussion (lines 515- 531). + +Olsen et al conducted RNA- seq analysis on digenic and monogenic mouse models, highlighting the ciliary compartment as a commonly dysregulated target. This was underscored by enhanced ciliary expression and altered length in the digenic model. However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice. + +## Response: + +We acknowledge the alignment of our findings with those of Olsen et al., as noted in the manuscript (lines 131- 136). However, it is important to clarify that our study did not investigate the role of polycystin- 2. Therefore, the notion of the reviewer "However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice" is not directly applicable to our study. + +Are mitochondrial defects the sole abnormalities discovered in the Pkhd1 KO mice in the present study? Have any other ciliary defects been detected? Is PC1 ciliary localization normal across different Pkhd1 KO lines? Additionally, what impact does FPC KO have on PC1 C- tail cleavage? + +<--- Page Split ---> + +Notably, a decrease in mitochondrial mass and a PKD1- dose- dependent decline in mitochondrial membrane potential have been previously observed in renal tubular cells. Existing studies demonstrate that cleaved PC1 C- tail induces mitochondrial dysfunction, and mitochondrial abnormalities are evident in Pkd1 knockout mice. Have the authors investigated mitochondrial function in the digenic animals as well? This should be done. + +## Response: + +We appreciate the reviewer's thought- provoking new inquiries, which were not brought up in the previous critique. In our present study, we did not assert that mitochondrial defects are the sole abnormalities observed in Pkhd1 KO mice. Additionally, we recognize that inquiries, such as those regarding the cleaved PC1 C- tail, remain unexplored. However, we want to highlight that we did address the potential significance of FPC on the cleaved PC1 C- tail in our previous revision, as outlined in lines 559- 566. + +We concur that the questions related to the digenic animals indeed merit attention. Nevertheless, we view them as potential avenues for future investigations. + +In this study, the authors have identified mitochondrial defects in the kidneys of Pkhd1 knockout mice, despite the absence of cyst manifestation. The functional significance of these mitochondria defects in Pkhd1 KO mice raises pertinent questions. Does the lack of renal cysts in Pkhd1 KO mice suggest that mitochondrial abnormalities alone are insufficient to trigger cystogenesis? Alternatively, could it imply that the extent of mitochondrial defects in Pkhd1 mice is not substantial enough to drive cyst formation? Earlier research, notably the work of Nishio et al in 2010, has firmly established the absence of oriented cell division as a distinctive feature of Pkhd1 mutations. + +## Response: + +We appreciate the reviewer's recognition of our findings pertaining to the significance of mitochondrial defects in the kidneys of Pkhd1 knockout mice, even in the absence of observable cyst manifestation. This finding indeed stands as a noteworthy and innovative aspect of our study. It is indisputable that a multitude of dysregulated pathways contribute to a complex process such as cystogenesis, including a defect in oriented cell division. Our study raises important questions about whether mitochondrial abnormalities alone are insufficient to trigger cystogenesis or if other factors come into play, warranting further investigations. In its entirety, we believe that our study will make a significant and valuable addition to the existing literature. + +Overall, the mechanisms underlying the genetic epistasis analyses conducted in this + +<--- Page Split ---> + +study remain unclear. The model in Figure 7 is too hypothetic, which is not supported by data. + +## Response: + +We concur that although our study unveils a novel and critical mitochondrial role of FPC, a prominent cysteine, in cystogenesis, the precise mechanisms underlying the genetic epistasis analyses conducted in this study remain enigmatic. It is indeed a humbling realization that a study of this nature cannot comprehensively delve into the intricacies of the next- level mechanisms. + +Nonetheless, it's important to highlight that our current study has provided valuable insights into renal cystogenesis. These insights, while not exhaustive, have the potential to stimulate further exploration of these intricate questions by the research community. We therefore believe that our study would make a significant and valuable addition to the existing literature. + +While we acknowledge that our model in Figure 7 is hypothetical, as models inherently are, we respectfully disagree with the characterization of its level of hypothesis as being "TOO hypothetical." As previously discussed, the model is consistent with prior research and provides a coherent explanation for our current findings. + +<--- Page Split ---> diff --git a/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..468265b1152cf653a98148eb33599258d9a7b5ce --- /dev/null +++ b/peer_reviews/3336aba4117893c109b0f4991fea84ae9b3245765bc747b80f5a2a0196585fde/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,377 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[66, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[86, 154, 911, 211]]<|/det|> +Fibrocystin/Polyductin releases a C- terminal fragment that translocates into mitochondria and suppresses cystogenesis + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 316, 101]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[118, 136, 438, 153]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 162, 878, 261]]<|/det|> +This study presents an interesting story, which try to state that C- terminal fragments of FPC, \(\sim 15 \text{kDa}\) (ICD15), \(\sim 12 \text{kDa}\) (ICD12), and \(\sim 6 \text{kDa}\) (ICD6), translocate into mitochondria and have a prevent function from cytogenesis. Better support should be provided for the key conclusions "prevent cytogenesis" by the C- terminal fragments. There are some questions: + +<|ref|>text<|/ref|><|det|>[[115, 291, 880, 655]]<|/det|> +1. PKHD1 has different isoforms. Cleaved fragments of FPC was found in this study. Were these proteins sequenced or, at part, has a same amino acid peptide as encoded in exon 67? +2. The authors found ICD15 translocated to mitochondria. Was mitochondrial biogenesis activated or mitochondrial structure or function altered when ICD15 translocated? +3. In the text, mitochondrial ultrastructure altered in Pkbd1 KO mice, compared to the Wt controls. To evaluate the ICD15 function or its impact on mitochondria, it is better to provide additional data of mitochondrial structure and function in vitro, compared with Pkbd1 KO, ICD15 transfected back, and Wt. +4. In line 375 "Both compound heterozygous Pkbd1Δ3-4/+;Pkbd1V/+ mutant mice...." Compound heterozygote is referred to two different mutations (or variants) in one same gene. As Pkbd1 and Pkd1 are two different genes, it should correct to be "digenic mutant mice". +5. The 5th result section (line 429-468) probably be better as a part of one result section or as a supplementary data. + +<|ref|>sub_title<|/ref|><|det|>[[118, 686, 182, 701]]<|/det|> +## Others: + +<|ref|>text<|/ref|><|det|>[[118, 710, 869, 755]]<|/det|> +6. the cited refs37 in line138 and refs19 in line 354 should be confirmed (probably it should be corrected to 38 or 20 respectively). + +<|ref|>text<|/ref|><|det|>[[118, 788, 820, 858]]<|/det|> +7. line 342-343, sentence "This result suggests that FPC may participate in regulating mitochondrial structure and function". However, no mitochondrial function has been provided in this section. + +<|ref|>text<|/ref|><|det|>[[115, 892, 833, 910]]<|/det|> +8. Sentence in line 373-375, "The Pkbd1Δ3-4 allele has a deletion of exons 3-4....in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 792, 102]]<|/det|> +extracellular domain" is better to put in the place when Pkhd1Δ3- 4 first appeared. + +<|ref|>text<|/ref|><|det|>[[117, 136, 875, 207]]<|/det|> +9. In Figure2,C)D)E)F)I) graphs should clearly shows the distribution of data and variation (as dot plot in the column), and the number of times of the experiments should be stated in figure legends. + +<|ref|>sub_title<|/ref|><|det|>[[118, 267, 438, 284]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 291, 870, 626]]<|/det|> +The paper lacks sufficient novelty. All single mutant phenotypes were previously described. The genetic interaction between Pkd1 and Pkhd1 (double mutant phenotypes) was previously described by several groups, including this group. Pkhd1/FPC deficiency and mitochondrial defects were previously described. Cleavage of Pkhd1 protein FPC has been reported previously by other group and this group. This paper described a more detailed analysis of FPC CTT responsible for mitochondrial translocation. They found in Pkd1 and Pkhd1 double mutants develop embryonic pancreatic cysts that is present in Pkd1 null mutant. This finding is of some interest but of limited significance. The paper is too long: Introduction, 4 pages; Results, 12 pages; and Discussion is 6 pages, difficult to read. Nomenclature is confusing. What is Pkhd1- /-, Pkhd1 \(\Delta 3 - 4\) , Pkhd1 \(\Delta CT\) , Pkhd1 \(\Delta 67\) , KO. There are 2 Pkd1 lines (Pkd1RC, Pkd1V) and 5 Pkhd1 alleles used in the study or some of them are the same thing? In the methods, there is almost no information about all the mouse lines used in the study. The conclusion is not fully supported by the experimental data. + +<|ref|>sub_title<|/ref|><|det|>[[118, 685, 438, 702]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 710, 877, 911]]<|/det|> +The authors describe that the type I transmembrane protein Fibrocystin/Polyductin (FPC), the main protein for autosomal recessive polycystic kidney disease (ARPKD) encoded by the large PKHD1 gene, undergoes complex proteolytic processing in vivo. This processing results in three small soluble C- terminal fragments with molecular weights ranging from 6- 15 kDa (termed ICD6, 12, and 15). At the N- terminus of ICD15 the authors identified a mitochondrial targeting sequence (MTS) that directs its mitochondrial localization. Walker et al. demonstrate convincing ultrastructural alterations of mitochondria of Pkhd1 KO mouse kidney tubules in contrast to wildtype controls. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 846, 261]]<|/det|> +In addition, the authors performed comprehensive genetic epistasis studies in mice and could show that FPC inactivation aggravates renal cystogenesis in a Pkd1 mouse mutant (Pkd1v/v). Deletion of the final exon of Pkhd1 (exon 67) enhanced cystogenesis in the kidney, but not in the pancreas, of those Pkd1v/v mutant mice. Overall, the novel data generated by this study indicates that an important function of the ICD protein products within the mitochondria is to protect against cyst formation when the function of Polycystin- 1, the Pkd1 gene product and major ADPKD protein, is compromised. + +<|ref|>text<|/ref|><|det|>[[118, 292, 866, 363]]<|/det|> +This is an excellent study that adds important knowledge to the pathophysiology of polycystic kidney disease. I have only minor comments that the authors are recommended to address: + +<|ref|>text<|/ref|><|det|>[[118, 396, 875, 468]]<|/det|> +- A substantial amount of data has been generated by the authors, however, the manuscript and its readability would clearly benefit from some kind of shortening (e.g. in the introduction section). + +<|ref|>text<|/ref|><|det|>[[118, 500, 835, 571]]<|/det|> +- Page 3: Please add the information that (while PKHD1 clearly defines the main ARPKD gene) pathogenic variants in various other genes may cause ARPKD or ARPKD-like phenotypes. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[104, 89, 358, 108]]<|/det|> +## RESPONSE TO REFEREES + +<|ref|>text<|/ref|><|det|>[[102, 121, 895, 158]]<|/det|> +We thank reviewers 1 and 3 for accepting the revised manuscript in its current form. Below, we present point- by- point responses to reviewer 2. + +<|ref|>sub_title<|/ref|><|det|>[[104, 204, 448, 222]]<|/det|> +## Reviewer #2 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[104, 236, 894, 290]]<|/det|> +In this revised manuscript, the authors have improved the clarity of nomenclature and a table describing the mouse lines used in this study is helpful. However, several major points still warrant attention. + +<|ref|>text<|/ref|><|det|>[[103, 321, 894, 428]]<|/det|> +"3) By utilizing the Pkd1V/V model in the genetic epistasis analyses, we have made the intriguing discovery that loss of FPC leads to a Pkd1 null-like cystic phenotype both in the kidney and pancreas. Moreover, unlike Pkd1RC used in Olson et al study, Pkd1V/V displayed impaired localization of PC1 to cilia, suggesting specific involvement of cilia in cyst progression as discussed and presented in our model (Figure 7)." + +<|ref|>text<|/ref|><|det|>[[103, 458, 894, 582]]<|/det|> +The Pkd1 RC mutant was previously identified as having a maturation defect in PC1, leading to compromised cleavage, as documented by Hopp et al in 2012. Furthermore, research by Su et al in 2015 showed that the RC mutation hinders the proper localization of PC1 to cilia. Consequently, even though the Pkd1 V mutant carries a distinct genetic mutation compared to the Pkd1 RC mutant, which was formerly employed in Pkhd1- Pkd1 digenic study by Olsen et al, the observed distinction remains marginal, hence the novelty in this regard is inadequate. + +<|ref|>sub_title<|/ref|><|det|>[[104, 596, 205, 614]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[103, 628, 894, 715]]<|/det|> +We appreciate the reviewer's recognition of the improved clarity in nomenclature in the revised manuscript. While we acknowledge the reviewer's concern regarding the distinction between the Pkhd1- Pkd1 interaction using the Pkd1V/V mutant versus the Pkd1 RC mutant, it's important to highlight that our study's main focus goes far beyond just the Pkhd1- Pkd1 interaction. + +<|ref|>text<|/ref|><|det|>[[103, 730, 894, 869]]<|/det|> +The true novelty lies in the new insights derived from the utilization of the Pkd1V/V strain. As we outlined extensively in our prior response, our study introduces multiple noteworthy findings. These encompass the translocation of ICD15 into mitochondria, the identification of ultrastructural and functional mitochondrial abnormalities in Pkhd1 KO kidney tubules and renal epithelial cells, and the essential role of ICD15 in suppressing renal cyst development in mice. Consequently, our manuscript's contribution goes significantly beyond this single observation, offering novel perspectives on FPC's role in ARPKD and signifying a substantial advancement in the field. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[103, 89, 894, 177]]<|/det|> +We had thoroughly discussed the rationale and advantages of utilizing the Pkd1V/V strain, particularly for assessing proximal tubules, in lines 358- 369, as provided in the previous revision. The results obtained through our utilization of the Pkd1V/V mutants offer valuable novel insights into the role of FPC in ARPKD and constitute a significant contribution to the current body of literature. + +<|ref|>sub_title<|/ref|><|det|>[[103, 226, 894, 263]]<|/det|> +## "Our discovery sheds light on a distinct mechanism of the ciliary function of FPC in pancreatic cystogenesis" + +<|ref|>text<|/ref|><|det|>[[103, 276, 894, 313]]<|/det|> +Can the authors explain based on what evidence they connected the occurrence of pancreatic cysts with the ciliary function of FPC? + +<|ref|>sub_title<|/ref|><|det|>[[104, 326, 206, 345]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[103, 358, 894, 489]]<|/det|> +Our identification of pancreatic cysts in the two digenic mutants ( \(\Delta 3 - 4 / V\) and KO/V) provides compelling evidence for the pivotal role of FPC in cystogenesis within the pancreas. Notably, our analysis of \(\Delta 67 / V\) digenic mutants revealed an intriguing pattern: while renal cystogenesis in \(\Delta 67 / V\) was enhanced compared to Pkd1V/V single mutants, no pancreatic cysts were observed. These results suggest that while FPC plays a crucial role in cystogenesis in the pancreas, its ICD15 component does not exert a substantial impact on this process when combined with the Pkd1V/V mutation. + +<|ref|>text<|/ref|><|det|>[[103, 507, 894, 656]]<|/det|> +We have comprehensively discussed this intriguing finding in the revised manuscript in lines 583- 597 regarding the ciliary function of FPC in safeguarding the pancreas from cystogenesis through mechanisms extending beyond its C- terminal tail. This notion is based on the observation (shown in Figure 1G) that Pkhd1 \(\Delta 67 / \Delta 67\) expresses the FPC- \(\Delta CT\) protein. This variant lacks ICD15 but retains the intact ciliary targeting sequence, suggesting its likely localization to the cilia. Consequently, we hypothesize that this ciliary function could protect the pancreas from cystogenesis through the involvement of its ecto- and transmembrane domains. + +<|ref|>text<|/ref|><|det|>[[103, 707, 894, 744]]<|/det|> +"We propose a molecular mechanism to explain the interaction between Pkhd1 and Pkd1 in cystogenesis through a cilia- mitochondria connection (Figure 7)." + +<|ref|>text<|/ref|><|det|>[[103, 775, 894, 828]]<|/det|> +Please specify the experimental evidence that supports this model. Which experiments and figures are pertinent to establishing the cilia- mitochondria connection? + +<|ref|>text<|/ref|><|det|>[[104, 842, 206, 860]]<|/det|> +Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 89, 895, 160]]<|/det|> +The proposed model is based on a synthesis of prior research and the results of this study. In our text, we reference prior studies that introduced the concept of the cilia- dependent cyst activation (CDCA) mechanism, which triggers cystogenesis upon the depletion of polycystins—integral ciliary membrane proteins, as outlined in lines 644- 649. + +<|ref|>text<|/ref|><|det|>[[104, 175, 895, 280]]<|/det|> +Our model logically bridges the previously established ciliary roles of FPC and polycystins with FPC's mitochondrial function through ICD15 as revealed by our current study. The connection between cilia and mitochondria is explicitly articulated in the initial segment of the Discussion (lines 533- 535), following a concise overview of the pivotal discoveries of our study. Further elaboration on the model depicted in Figure 7 is provided in the concluding section of the Discussion. + +<|ref|>text<|/ref|><|det|>[[104, 294, 895, 416]]<|/det|> +In our preceding round of revisions, we made extensive efforts to streamline the content, enhance clarity, and improve the manuscript's overall readability. The presentation logically follows from the progression of our presentation and is expounded upon in the preceding sections of the Discussion. Consequently, we have chosen to refrain from introducing supplementary elaboration or referencing specific experiments or figures in this section. Such additions might introduce redundancy and unnecessarily prolong the text—a situation we are keen to circumvent based on prior feedback. + +<|ref|>text<|/ref|><|det|>[[104, 431, 894, 485]]<|/det|> +To amplify clarity, we have now added references to the pertinent figures (indicated in blue) that correspond to each of the key findings summarized in the initial section of the Discussion (lines 520- 532). + +<|ref|>text<|/ref|><|det|>[[104, 533, 894, 621]]<|/det|> +Olsen et al conducted RNA- seq analysis on digenic and monogenic mouse models, highlighting the ciliary compartment as a commonly dysregulated target. This was underscored by enhanced ciliary expression and altered length in the digenic model. However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice. + +<|ref|>sub_title<|/ref|><|det|>[[104, 636, 206, 654]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[104, 668, 895, 757]]<|/det|> +We acknowledge the alignment of our findings with those of Olsen et al., as noted in the manuscript (lines 133- 138). However, it is important to clarify that our study did not investigate the role of polycystin- 2. Therefore, the notion of the reviewer "However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice" is not directly applicable to our study. + +<|ref|>text<|/ref|><|det|>[[104, 820, 895, 891]]<|/det|> +Are mitochondrial defects the sole abnormalities discovered in the Pkhd1 KO mice in the present study? Have any other ciliary defects been detected? Is PC1 ciliary localization normal across different Pkhd1 KO lines? Additionally, what impact does FPC KO have on PC1 C- tail cleavage? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 106, 894, 213]]<|/det|> +Notably, a decrease in mitochondrial mass and a PKD1- dose- dependent decline in mitochondrial membrane potential have been previously observed in renal tubular cells. Existing studies demonstrate that cleaved PC1 C- tail induces mitochondrial dysfunction, and mitochondrial abnormalities are evident in Pkd1 knockout mice. Have the authors investigated mitochondrial function in the digenic animals as well? This should be done. + +<|ref|>sub_title<|/ref|><|det|>[[104, 228, 205, 246]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[103, 259, 894, 365]]<|/det|> +We appreciate the reviewer's thought- provoking new inquiries, which were not brought up in the previous critique. In our present study, we did not assert that mitochondrial defects are the sole abnormalities observed in Pkhd1 KO mice. Additionally, we recognize that inquiries, such as those regarding the cleaved PC1 C- tail, remain unexplored. However, we want to highlight that we did address the potential significance of FPC on the cleaved PC1 C- tail in our previous revision, as outlined in lines 564- 571. + +<|ref|>text<|/ref|><|det|>[[103, 379, 893, 415]]<|/det|> +We concur that the questions related to the digenic animals indeed merit attention. Nevertheless, we view them as potential avenues for future investigations. + +<|ref|>text<|/ref|><|det|>[[102, 462, 894, 621]]<|/det|> +In this study, the authors have identified mitochondrial defects in the kidneys of Pkhd1 knockout mice, despite the absence of cyst manifestation. The functional significance of these mitochondria defects in Pkhd1 KO mice raises pertinent questions. Does the lack of renal cysts in Pkhd1 KO mice suggest that mitochondrial abnormalities alone are insufficient to trigger cystogenesis? Alternatively, could it imply that the extent of mitochondrial defects in Pkhd1 mice is not substantial enough to drive cyst formation? Earlier research, notably the work of Nishio et al in 2010, has firmly established the absence of oriented cell division as a distinctive feature of Pkhd1 mutations. + +<|ref|>sub_title<|/ref|><|det|>[[104, 636, 205, 653]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[102, 667, 894, 825]]<|/det|> +We appreciate the reviewer's recognition of our findings pertaining to the significance of mitochondrial defects in the kidneys of Pkhd1 knockout mice, even in the absence of observable cyst manifestation. This finding indeed stands as a noteworthy and innovative aspect of our study. It is indisputable that a multitude of dysregulated pathways contribute to a complex process such as cystogenesis, including a defect in oriented cell division. Our study raises important questions about whether mitochondrial abnormalities alone are insufficient to trigger cystogenesis or if other factors come into play, warranting further investigations. In its entirety, we believe that our study will make a significant and valuable addition to the existing literature. + +<|ref|>text<|/ref|><|det|>[[102, 874, 893, 894]]<|/det|> +Overall, the mechanisms underlying the genetic epistasis analyses conducted in this + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 89, 894, 125]]<|/det|> +study remain unclear. The model in Figure 7 is too hypothetic, which is not supported by data. + +<|ref|>sub_title<|/ref|><|det|>[[104, 140, 205, 158]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[104, 171, 894, 260]]<|/det|> +We concur that although our study unveils a novel and critical mitochondrial role of FPC, a prominent cysteine, in cystogenesis, the precise mechanisms underlying the genetic epistasis analyses conducted in this study remain enigmatic. It is indeed a humbling realization that a study of this nature cannot comprehensively delve into the intricacies of the next- level mechanisms. + +<|ref|>text<|/ref|><|det|>[[104, 273, 895, 344]]<|/det|> +Nonetheless, it's important to highlight that our current study has provided valuable insights into renal cystogenesis. These insights, while not exhaustive, have the potential to stimulate further exploration of these intricate questions by the research community. We therefore believe that our study would make a significant and valuable addition to the existing literature. + +<|ref|>text<|/ref|><|det|>[[104, 358, 894, 429]]<|/det|> +While we acknowledge that our model in Figure 7 is hypothetical, as models inherently are, we respectfully disagree with the characterization of its level of hypothesis as being "TOO hypothetical." As previously discussed, the model is consistent with prior research and provides a coherent explanation for our current findings. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 330, 101]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[118, 137, 437, 154]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 163, 848, 181]]<|/det|> +I am happy that the authors have now addressed the concerns from the previous review. + +<|ref|>sub_title<|/ref|><|det|>[[118, 241, 437, 258]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 266, 874, 336]]<|/det|> +In this revised manuscript, the authors have improved the clarity of nomenclature and a table describing the mouse lines used in this study is helpful. However, several major points still warrant attention. + +<|ref|>text<|/ref|><|det|>[[117, 370, 877, 495]]<|/det|> +"3) By utilizing the Pkd1V/V model in the genetic epistasis analyses, we have made the intriguing discovery that loss of FPC leads to a Pkd1 null- like cystic phenotype both in the kidney and pancreas. Moreover, unlike Pkd1RC used in Olson et al study, Pkd1V/V displayed impaired localization of PC1 to cilia, suggesting specific involvement of cilia in cyst progression as discussed and presented in our model (Figure 7)." + +<|ref|>text<|/ref|><|det|>[[117, 527, 877, 701]]<|/det|> +The Pkd1 RC mutant was previously identified as having a maturation defect in PC1, leading to compromised cleavage, as documented by Hopp et al in 2012. Furthermore, research by Su et al in 2015 showed that the RC mutation hinders the proper localization of PC1 to cilia. Consequently, even though the Pkd1 V mutant carries a distinct genetic mutation compared to the Pkd1 RC mutant, which was formerly employed in Pkhd1- Pkd1 digenic study by Olsen et al, the observed distinction remains marginal, hence the novelty in this regard is inadequate. + +<|ref|>text<|/ref|><|det|>[[118, 736, 795, 780]]<|/det|> +"Our discovery sheds light on a distinct mechanism of the ciliary function of FPC in pancreatic cystogenesis" + +<|ref|>text<|/ref|><|det|>[[118, 814, 802, 859]]<|/det|> +Can the authors explain based on what evidence they connected the occurrence of pancreatic cysts with the ciliary function of FPC? + +<|ref|>text<|/ref|><|det|>[[118, 867, 874, 911]]<|/det|> +"We propose a molecular mechanism to explain the interaction between Pkhd1 and Pkd1 in cystogenesis through a cilia- mitochondria connection (Figure 7)." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 870, 129]]<|/det|> +Please specify the experimental evidence that supports this model. Which experiments and figures are pertinent to establishing the cilia- mitochondria connection? + +<|ref|>text<|/ref|><|det|>[[117, 162, 847, 285]]<|/det|> +Olsen et al conducted RNA- seq analysis on digenic and monogenic mouse models, highlighting the ciliary compartment as a commonly dysregulated target. This was underscored by enhanced ciliary expression and altered length in the digenic model. However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice. + +<|ref|>text<|/ref|><|det|>[[117, 318, 876, 416]]<|/det|> +Are mitochondrial defects the sole abnormalities discovered in the Pkhd1 KO mice in the present study? Have any other ciliary defects been detected? Is PC1 ciliary localization normal across different Pkhd1 KO lines? Additionally, what impact does FPC KO have on PC1 C- tail cleavage? + +<|ref|>text<|/ref|><|det|>[[117, 448, 877, 574]]<|/det|> +Notably, a decrease in mitochondrial mass and a PKD1- dose- dependent decline in mitochondrial membrane potential have been previously observed in renal tubular cells. Existing studies demonstrate that cleaved PC1 C- tail induces mitochondrial dysfunction, and mitochondrial abnormalities are evident in Pkd1 knockout mice. Have the authors investigated mitochondrial function in the digenic animals as well? This should be done. + +<|ref|>text<|/ref|><|det|>[[117, 606, 880, 756]]<|/det|> +In this study, the authors have identified mitochondrial defects in the kidneys of Pkhd1 knockout mice, despite the absence of cyst manifestation. The functional significance of these mitochondria defects in Pkhd1 KO mice raises pertinent questions. Does the lack of renal cysts in Pkhd1 KO mice suggest that mitochondrial abnormalities alone are insufficient to trigger cystogenesis? Alternatively, could it imply that the extent of mitochondrial defects in Pkhd1 mice is not substantial enough to drive cyst formation? + +<|ref|>text<|/ref|><|det|>[[117, 789, 874, 885]]<|/det|> +Earlier research, notably the work of Nishio et al in 2010, has firmly established the absence of oriented cell division as a distinctive feature of Pkhd1 mutations. Overall, the mechanisms underlying the genetic epistasis analyses conducted in this study remain unclear. The model in Figure 7 is too hypothetic, which is not supported by data. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 438, 102]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 111, 690, 128]]<|/det|> +Congratulations to this wonderful study, I have no further comments. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[104, 89, 358, 108]]<|/det|> +## RESPONSE TO REFEREES + +<|ref|>text<|/ref|><|det|>[[104, 122, 894, 175]]<|/det|> +We thank reviewers 1 and 3 for accepting the revised manuscript in its current form. Below, we present point- by- point responses to reviewer 2 for the final version (NCOMMS- 22- 35324B). + +<|ref|>sub_title<|/ref|><|det|>[[104, 221, 449, 240]]<|/det|> +## Reviewer #2 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[104, 254, 894, 307]]<|/det|> +In this revised manuscript, the authors have improved the clarity of nomenclature and a table describing the mouse lines used in this study is helpful. However, several major points still warrant attention. + +<|ref|>text<|/ref|><|det|>[[104, 339, 894, 445]]<|/det|> +"3) By utilizing the Pkd1V/V model in the genetic epistasis analyses, we have made the intriguing discovery that loss of FPC leads to a Pkd1 null- like cystic phenotype both in the kidney and pancreas. Moreover, unlike Pkd1RC used in Olson et al study, Pkd1V/V displayed impaired localization of PC1 to cilia, suggesting specific involvement of cilia in cyst progression as discussed and presented in our model (Figure 7)." + +<|ref|>text<|/ref|><|det|>[[104, 475, 894, 600]]<|/det|> +The Pkd1 RC mutant was previously identified as having a maturation defect in PC1, leading to compromised cleavage, as documented by Hopp et al in 2012. Furthermore, research by Su et al in 2015 showed that the RC mutation hinders the proper localization of PC1 to cilia. Consequently, even though the Pkd1 V mutant carries a distinct genetic mutation compared to the Pkd1 RC mutant, which was formerly employed in Pkhd1- Pkd1 digenic study by Olsen et al, the observed distinction remains marginal, hence the novelty in this regard is inadequate. + +<|ref|>sub_title<|/ref|><|det|>[[104, 614, 205, 632]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[104, 646, 894, 733]]<|/det|> +We appreciate the reviewer's recognition of the improved clarity in nomenclature in the revised manuscript. While we acknowledge the reviewer's concern regarding the distinction between the Pkhd1- Pkd1 interaction using the Pkd1V/V mutant versus the Pkd1 RC mutant, it's important to highlight that our study's main focus goes far beyond just the Pkhd1- Pkd1 interaction. + +<|ref|>text<|/ref|><|det|>[[104, 747, 894, 888]]<|/det|> +The true novelty lies in the new insights derived from the utilization of the Pkd1V/V strain. As we outlined extensively in our prior response, our study introduces multiple noteworthy findings. These encompass the translocation of ICD15 into mitochondria, the identification of ultrastructural and functional mitochondrial abnormalities in Pkhd1 KO kidney tubules and renal epithelial cells, and the essential role of ICD15 in suppressing renal cyst development in mice. Consequently, our manuscript's contribution goes significantly beyond this single observation, offering novel perspectives on FPC's role in ARPKD and signifying a substantial advancement in the field. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[103, 89, 894, 177]]<|/det|> +We had thoroughly discussed the rationale and advantages of utilizing the Pkd1V/V strain, particularly for assessing proximal tubules, in lines 354- 365 (of the final version), as provided in the previous revision. The results obtained through our utilization of the Pkd1V/V mutants offer valuable novel insights into the role of FPC in ARPKD and constitute a significant contribution to the current body of literature. + +<|ref|>sub_title<|/ref|><|det|>[[103, 226, 894, 263]]<|/det|> +## "Our discovery sheds light on a distinct mechanism of the ciliary function of FPC in pancreatic cystogenesis" + +<|ref|>text<|/ref|><|det|>[[103, 276, 894, 313]]<|/det|> +Can the authors explain based on what evidence they connected the occurrence of pancreatic cysts with the ciliary function of FPC? + +<|ref|>sub_title<|/ref|><|det|>[[104, 326, 205, 345]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[103, 358, 894, 488]]<|/det|> +Our identification of pancreatic cysts in the two digenic mutants (Δ3- 4/V and KO/V) provides compelling evidence for the pivotal role of FPC in cystogenesis within the pancreas. Notably, our analysis of Δ67/V digenic mutants revealed an intriguing pattern: while renal cystogenesis in Δ67/V was enhanced compared to Pkd1V/V single mutants, no pancreatic cysts were observed. These results suggest that while FPC plays a crucial role in cystogenesis in the pancreas, its ICD15 component does not exert a substantial impact on this process when combined with the Pkd1V/V mutation. + +<|ref|>text<|/ref|><|det|>[[103, 506, 894, 655]]<|/det|> +We have comprehensively discussed this intriguing finding in the revised manuscript in lines 578- 592 regarding the ciliary function of FPC in safeguarding the pancreas from cystogenesis through mechanisms extending beyond its C- terminal tail. This notion is based on the observation (shown in Figure 1g) that Pkhd1Δ67/Δ67 expresses the FPC- ΔCT protein. This variant lacks ICD15 but retains the intact ciliary targeting sequence, suggesting its likely localization to the cilia. Consequently, we hypothesize that this ciliary function could protect the pancreas from cystogenesis through the involvement of its ecto- and transmembrane domains. + +<|ref|>text<|/ref|><|det|>[[103, 707, 894, 744]]<|/det|> +"We propose a molecular mechanism to explain the interaction between Pkhd1 and Pkd1 in cystogenesis through a cilia- mitochondria connection (Figure 7)." + +<|ref|>text<|/ref|><|det|>[[103, 774, 894, 828]]<|/det|> +Please specify the experimental evidence that supports this model. Which experiments and figures are pertinent to establishing the cilia- mitochondria connection? + +<|ref|>text<|/ref|><|det|>[[104, 842, 205, 860]]<|/det|> +Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 90, 894, 160]]<|/det|> +The proposed model is based on a synthesis of prior research and the results of this study. In our text, we reference prior studies that introduced the concept of the cilia- dependent cyst activation (CDCA) mechanism, which triggers cystogenesis upon the depletion of polycystins—integral ciliary membrane proteins, as outlined in lines 639- 644. + +<|ref|>text<|/ref|><|det|>[[104, 175, 894, 280]]<|/det|> +Our model logically bridges the previously established ciliary roles of FPC and polycystins with FPC's mitochondrial function through ICD15 as revealed by our current study. The connection between cilia and mitochondria is explicitly articulated in the initial segment of the Discussion (lines 528- 531), following a concise overview of the pivotal discoveries of our study. Further elaboration on the model depicted in Figure 7 is provided in the concluding section of the Discussion. + +<|ref|>text<|/ref|><|det|>[[104, 294, 894, 416]]<|/det|> +In our preceding round of revisions, we made extensive efforts to streamline the content, enhance clarity, and improve the manuscript's overall readability. The presentation logically follows from the progression of our presentation and is expounded upon in the preceding sections of the Discussion. Consequently, we have chosen to refrain from introducing supplementary elaboration or referencing specific experiments or figures in this section. Such additions might introduce redundancy and unnecessarily prolong the text—a situation we are keen to circumvent based on prior feedback. + +<|ref|>text<|/ref|><|det|>[[104, 431, 894, 467]]<|/det|> +To amplify clarity, we have now added references to the pertinent figures that correspond to each of the key findings summarized in the initial section of the Discussion (lines 515- 531). + +<|ref|>text<|/ref|><|det|>[[104, 515, 894, 604]]<|/det|> +Olsen et al conducted RNA- seq analysis on digenic and monogenic mouse models, highlighting the ciliary compartment as a commonly dysregulated target. This was underscored by enhanced ciliary expression and altered length in the digenic model. However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice. + +<|ref|>sub_title<|/ref|><|det|>[[104, 618, 205, 636]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[104, 650, 894, 738]]<|/det|> +We acknowledge the alignment of our findings with those of Olsen et al., as noted in the manuscript (lines 131- 136). However, it is important to clarify that our study did not investigate the role of polycystin- 2. Therefore, the notion of the reviewer "However, they did not identify any defects in polycystin- 2 ciliary localization within their Pkhd1 KO mice" is not directly applicable to our study. + +<|ref|>text<|/ref|><|det|>[[104, 802, 894, 873]]<|/det|> +Are mitochondrial defects the sole abnormalities discovered in the Pkhd1 KO mice in the present study? Have any other ciliary defects been detected? Is PC1 ciliary localization normal across different Pkhd1 KO lines? Additionally, what impact does FPC KO have on PC1 C- tail cleavage? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[103, 106, 895, 213]]<|/det|> +Notably, a decrease in mitochondrial mass and a PKD1- dose- dependent decline in mitochondrial membrane potential have been previously observed in renal tubular cells. Existing studies demonstrate that cleaved PC1 C- tail induces mitochondrial dysfunction, and mitochondrial abnormalities are evident in Pkd1 knockout mice. Have the authors investigated mitochondrial function in the digenic animals as well? This should be done. + +<|ref|>sub_title<|/ref|><|det|>[[104, 228, 205, 246]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[103, 259, 894, 365]]<|/det|> +We appreciate the reviewer's thought- provoking new inquiries, which were not brought up in the previous critique. In our present study, we did not assert that mitochondrial defects are the sole abnormalities observed in Pkhd1 KO mice. Additionally, we recognize that inquiries, such as those regarding the cleaved PC1 C- tail, remain unexplored. However, we want to highlight that we did address the potential significance of FPC on the cleaved PC1 C- tail in our previous revision, as outlined in lines 559- 566. + +<|ref|>text<|/ref|><|det|>[[103, 379, 894, 415]]<|/det|> +We concur that the questions related to the digenic animals indeed merit attention. Nevertheless, we view them as potential avenues for future investigations. + +<|ref|>text<|/ref|><|det|>[[103, 462, 895, 621]]<|/det|> +In this study, the authors have identified mitochondrial defects in the kidneys of Pkhd1 knockout mice, despite the absence of cyst manifestation. The functional significance of these mitochondria defects in Pkhd1 KO mice raises pertinent questions. Does the lack of renal cysts in Pkhd1 KO mice suggest that mitochondrial abnormalities alone are insufficient to trigger cystogenesis? Alternatively, could it imply that the extent of mitochondrial defects in Pkhd1 mice is not substantial enough to drive cyst formation? Earlier research, notably the work of Nishio et al in 2010, has firmly established the absence of oriented cell division as a distinctive feature of Pkhd1 mutations. + +<|ref|>sub_title<|/ref|><|det|>[[104, 636, 205, 654]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[103, 667, 895, 825]]<|/det|> +We appreciate the reviewer's recognition of our findings pertaining to the significance of mitochondrial defects in the kidneys of Pkhd1 knockout mice, even in the absence of observable cyst manifestation. This finding indeed stands as a noteworthy and innovative aspect of our study. It is indisputable that a multitude of dysregulated pathways contribute to a complex process such as cystogenesis, including a defect in oriented cell division. Our study raises important questions about whether mitochondrial abnormalities alone are insufficient to trigger cystogenesis or if other factors come into play, warranting further investigations. In its entirety, we believe that our study will make a significant and valuable addition to the existing literature. + +<|ref|>text<|/ref|><|det|>[[101, 874, 894, 894]]<|/det|> +Overall, the mechanisms underlying the genetic epistasis analyses conducted in this + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[102, 89, 894, 125]]<|/det|> +study remain unclear. The model in Figure 7 is too hypothetic, which is not supported by data. + +<|ref|>sub_title<|/ref|><|det|>[[104, 140, 205, 158]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[104, 171, 894, 260]]<|/det|> +We concur that although our study unveils a novel and critical mitochondrial role of FPC, a prominent cysteine, in cystogenesis, the precise mechanisms underlying the genetic epistasis analyses conducted in this study remain enigmatic. It is indeed a humbling realization that a study of this nature cannot comprehensively delve into the intricacies of the next- level mechanisms. + +<|ref|>text<|/ref|><|det|>[[104, 273, 895, 344]]<|/det|> +Nonetheless, it's important to highlight that our current study has provided valuable insights into renal cystogenesis. These insights, while not exhaustive, have the potential to stimulate further exploration of these intricate questions by the research community. We therefore believe that our study would make a significant and valuable addition to the existing literature. + +<|ref|>text<|/ref|><|det|>[[104, 358, 894, 429]]<|/det|> +While we acknowledge that our model in Figure 7 is hypothetical, as models inherently are, we respectfully disagree with the characterization of its level of hypothesis as being "TOO hypothetical." As previously discussed, the model is consistent with prior research and provides a coherent explanation for our current findings. + +<--- Page Split ---> diff --git a/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/images_list.json b/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..3943ffac071d49dc42ce010325ef3c1c1660099f --- /dev/null +++ b/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,215 @@ + +# nature portfolio + +Peer Review File + +Electrochemical meta- C- H Sulfonylation of Pyridines with Nucleophilic Sulfinates + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +meta- C- H functionalization of pyridines is of paramount importance but remain quite challenging. Established methods for such selective functionalization mostly rely on the use of electrophilic reagents to demand the intrinsic polarity match. The manuscript from Zeng et al. reported a complementary electrochemical method in which a wide variety of nucleophilic sulfinates allow metasulfonylation of pyridines. This method is impressive and uniquely facilitated by electrochemistry, as well as features excellent functional group tolerance and late- stage modification. Hence, I would suggest that it would publish on Nature Communications after addressing the following concerns. + +1. This reaction seems uniquely promoted by electrochemistry. Did the authors test more other oxidant sources to support this conclusion? These additional experiments should be added in supporting information. + +2. In addition to sulfonation, thiolation was also demonstrated. The authors may test other electrophilic radical precursors. I would highly recommend placing these negative results in supporting information for readers' better understanding. + +3. The authors have demonstrated some product derivatizations. One more interesting transformation would be introducing a sulfonyl fluoride (-SO2F) unit at pyridine meta-position since this group can be used as for sulfur(VI) fluoride exchange (SuFEx) click chemistry. + +4. Representative bioactive molecules featuring meta-sulfonated pyridines are provided in Fig 1c. Can the authors show that their method allows access to some these drug molecules? + +5. Regarding the mechanism, clarification is required from the author on the potential involvement of intermediate state II', which remains inert to the structure of the final product. In Fig 6, please provide the life of persistent radical I and II. It would be beneficial for reader to have a better understanding of this electro mechanism. + +7. There are quite a few grammatical/typographical errors. For example, in SI, page S4, S6 and S8, the ChemDraw Scheme exhibits a disordered layout. + +8. In SI, several product NMR spectra seem to be impure, such as compound 7, 8, 10, 12, 13, 14, 16, 19, 20, 21, 23, 24, 25, 26, 28, 31, 35, 39, 42, 43, 45, 47, 51, and 54. It is imperative to repurify these compounds and recalculate their yields to ensure the accuracy and reliability of the experimental data. Moreover, the melting points of some new compounds are missing. + +Reviewer #2: Remarks to the Author: + +Hashmi, Yi, Zeng, and coworkers reported the selective C3 sulfonylation with sulfinates by using a dearomative activation mode. The reaction showed a remarkable functional group tolerance both with regards to pyridines and sulfinates. The reaction was selectively giving the desired C3 monosubstituted adduct. The mechanistic studies supported the proposed mechanism. Indeed, the selective C3 functionalization of pyridines is quite challenging and of high importance thus I suggest the publication of this manuscript in Nature Communications after some major issues are addressed. 1. The authors should comment on the reason for the change on the anode material when benzannulated pyridines were used (examples 46, 47). 2. The authors should demonstrate the position of the attack on the 1'. The sequential functionalization (synthesis of 57) implies that the functionalization of 1' is selective. But in the SI page 16 the authors report a mixture of isomers (before hydrolysis). This needs to be clarified. For that reason the authors should separate and characterize the products. 3. The authors should cite a related work: G.- Q. Sun, P. Yu, W. Zhang, W. Zhang, Y. Wang, L.- L. Liao, Z. Zhang, L. Li, Z. Lu, D.- G. Yu, S. Lin, Nature 2023, 615, 67- 72. 4. Concerning the Supplementary Information the spectra of some compounds, such as 19, 21, 23, + +<--- Page Split ---> + +14, 15, 31, 42, 51 among others are not sufficiently pure. Thus, the authors must repurify the compounds that are not pure enough and re- evaluate the reported yields. + +Reviewer #3: + +Remarks to the Author: + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #4: + +Remarks to the Author: + +Hashmi, Yi, Zeng and coworkers reported here an electrochemical meta- sulfonylation of pyridine derivatives via a dearomatization/rearomatization strategy that has been demonstrated previously by Studer and others. The key design is to convert nucleophilic sulfinate anion to electrophilic sulfonyl radical via anodic oxidation. The authors have demonstrated the synthetic potential of this method by providing a broad scope of both sulfinates and pyridine substrates, potential derivatization of the products and large- scale synthesis. I recommend publication of this manuscript with minor revision. The authors should address the following questions: + +1. In the optimization Table 1, the authors found that the sodium sulfinate is more effective than the other base metal and the organic soluble tetrabutyl ammonium salts (entries 9 and 11), which indicates that the sodium cation plays some critical roles in the observed reactivity besides solubility. The authors should provide some explanations about why the sodium salt is the most effective. +2. In the mechanistic studies, the authors observed suppressed reactivity in the presence of TEMPO. Based on which, the authors concluded a radical-based mechanism. TEMPO is known to undergo oxidation under mild electrochemical potentials (Phys. Chem. Chem. Phys., 2021,23, 10205-10217). So the low reactivity in the presence of TEMPO could be resulting from its lower oxidation potential than the sulfinate salt. CV should be performed to compare redox potentials of TEMPO and sulfinate. If that is the case, this experiment cannot be used to prove the radical mechanism of the sulfonylation reaction. + +3. I found several subjective, exaggerated description in the manuscript unnecessary and lacks literatur support. The authors should revise and avoid those expressions. For example, in the abstract, the authors stated, "a direct meta-selective C-H functionalization of pyridines is of paramount importance, but such reactions remain extremely limited and highly challenging.". The authors may consider remove "extremely", as references 15-25 are all about meta-selective C-H functionalizations. On page 3, the authors mentioned "Using a nucleophilic partner to fulfill such transformations still remains unexplored, presumably due to the inherent polarity mismatch, although it is attractive since most reagents are nucleophilic." I found the general statement about most reagents are nucleophilic lacks context and is doubtful. The authors should revise and avoid those claims. + +<--- Page Split ---> + +## Dear Reviewers, + +Dear Reviewers,We are very grateful for the careful evaluation of our manuscript by the reviewers and the editorial office for the constructive criticism. We have thoroughly revised the manuscript following the reviewer's and the editor's comment. Manuscript files with and without highlighted changes have been uploaded as requested. Please find below the point- by- point response to these comments. Your comments are in black, and our responses are in blue. + +## Response to Reviewer #1: + +## Recommendation: Revisions required + +Comment 1: meta- C- H functionalization of pyridines is of paramount importance but remain quite challenging. Established methods for such selective functionalization mostly rely on the use of electrophilic reagents to demand the intrinsic polarity match. The manuscript from Zeng et al. reported a complementary electrochemical method in which a wide variety of nucleophilic sulfinates allow meta- sulfonylation of pyridines. This method is impressive and uniquely facilitated by electrochemistry, as well as features excellent functional group tolerance and late- stage modification. Hence, I would suggest that it would publish on Nature Communications after addressing the following concerns. + +Response: We thank the reviewer for his/her kind recommendation. + +Comment 2: This reaction seems uniquely promoted by electrochemistry. Did the authors test more other oxidant sources to support this conclusion? These additional experiments should be added in supporting information. + +Response: We tested additional several common chemical oxidants, including \(\mathrm{PhI(OAc)_2}\) , \(\mathrm{Cu(OAc)_2}\) , \(\mathrm{Mn(OAc)_3\cdot 2H_2O}\) as well as \(\mathrm{O_2}\) (entries 17and 18 in Table 1 and entries 31- 34, Table S1 in SI), but none of them gave the product more than \(20\%\) yield. These results highlight the unique of electrochemistry for the target transformation. Accordingly, we updated the comment regarding this in the revised manuscript: "...no or much lower efficiency was observed with conventional chemical oxidizing agents such as 1,4- benzoquinone (BQ), \(\mathrm{K_2S_2O_8}\) , \(\mathrm{I_2}\) , \(\mathrm{Ag_2CO_3}\) , \(\mathrm{Cu(OAc)_2}\) , and \(\mathrm{Mn(OAc)_3\cdot 2H_2O}\) " + +Comment 3: In addition to sulfonation, thiolation was also demonstrated. The authors may test other electrophilic radical precursors. I would highly recommend placing these negative results in supporting information for readers' better understanding. + +Response: Indeed, we tested numerous radical precursors listed below which so far were found not amenable under the standard electrochemical conditions and have been provided in the supporting information (see Figures S11 and S12 in SI). + +<--- Page Split ---> +![PLACEHOLDER_4_0] + + +Comment 4: The authors have demonstrated some product derivatizations. One more interesting transformation would be introducing a sulfonyl fluoride (- SO₂F) unit at pyridine meta- position since this group can be used as for sulfur(VI) fluoride exchange (SuFEx) click chemistry. + +Response: This is an interesting point. To realize transformation into sulfonyl fluorides, the most common method is to access sulfinate salts which then react with electrophilic fluorinating reagents. Unfortunately, attempt to incorporate several masked SO₂⁻ anion equivalents (e.g., 2ah, 2ai, 2aj, 2ak) was unsuccessful under the standard electrochemical condition. These negative results have been included in Figure S10 in the Supporting Information. In addition, our newly developed electrochemical method allows facile access to 3-(methylsulfonyl)pyridine 50, whose follow- up demethylation to generate pyridyl sulfinates proved so far unfeasible. Nevertheless, translation of such methylsulfonyl handle into valuable ether and thioether groups (59, 60) was demonstrated. + +<--- Page Split ---> +![PLACEHOLDER_5_0] + + +Comment 5: Representative bioactive molecules featuring meta- sulfonated pyridines are provided in Fig 1c. Can the authors show that their method allows access to some these drug molecules? + +Response: Formal synthesis of Intepidine, a potential Alzheimer's disease drug, was demonstrated by a two- pot procedure (Fig 2). This sequence includes facile access key intermediate 8- chloro- 3- (phenylsulfonyl)quinoline (48) by our newly developed electrochemical method and follow- up palladium- catalyzed C- N cross- coupling known from the literature (Angew. Chem. Int. Ed. 2013, 52, 12679). For better understanding, the yield of this known animation procedure was added in the revised manuscript. + +Comment 6: Regarding the mechanism, clarification is required from the author on the potential involvement of intermediate state II', which remains inert to the structure of the final product. In Fig 6, please provide the life of persistent radical I and II. It would be beneficial for reader to have a better understanding of this electro mechanism. + +Response: We guess this intermediate state II' mentioned by the reviewer might be I (now named as I- δ in the revised manuscript and used as I'- δ for the following discussion) in the initial manuscript. If this is the case, I'- δ is proposed as a resonance form of I- δ, and would lose an electron at the anode similar to I- δ to deliver the final product through iminium- type species II- δ (initially III). Following the suggestion of the Reviewer#2, we isolated the electrochemical C- H sulfonated products of 1a' before hydrolysis, which proved to be a mixture of β- and δ- regioisomers. We accordingly modified the proposed mechanism, specifically added the β- radical adduct (I- β) and follow- up intermediates (II- β and III- β), although both regioisomers uniformly give the final product 3. For details, please see our reply to the Comment#3 of the Review#2 below. + +Based on the definitions of Griller and Ingold, radicals I and II in this case were believed to be resonance stabilized radicals, which belong to "transient" radicals (Acc. + +<--- Page Split ---> + +Chem. Res. 1976, 9, 13). In general, a transient species has a life- time of less than 1 ms (Angew. Chem. Int. Ed. 2020, 59, 74). + +Comment 7: There are quite a few grammatical/typographical errors. For example, in SI, page S4, S6 and S8, the ChemDraw Scheme exhibits a disordered layout. + +Response: The schemes in page S4, S6 and S8 in SI have been improved for a better layout. + +Comment 8: In SI, several product NMR spectra seem to be impure, such as compound 7, 8, 10, 12, 13, 14, 16, 19, 20, 21, 23, 24, 25, 26, 28, 31, 35, 39, 42, 43, 45, 47, 51, and 54. It is imperative to repurify these compounds and recalculate their yields to ensure the accuracy and reliability of the experimental data. Moreover, the melting points of some new compounds are missing. + +Response: Thanks for pointing out this issue. We have repurified all these aforementioned compounds to ensure their NMR spectra suitable for publication, and accordingly recalculated their chemical yields. In addition, we placed the melting points of all new solid compounds (except \(3^{\circ}\) and \(1\mathrm{m}^{\circ}\) which are inseparable diastereo-/regioisomers). + +## Response to Reviewer #2: + +## Recommendation: Revisions required + +Comment 1: Hashmi, Yi, Zeng, and coworkers reported the selective C3 sulfonylation with sulfinates by using a dearomatic activation mode. The reaction showed a remarkable functional group tolerance both with regards to pyridines and sulfinates. The reaction was selectively giving the desired C3 monosubstituted adduct. The mechanistic studies supported the proposed mechanism. Indeed, the selective C3 functionalization of pyridines is quite challenging and of high importance thus I suggest the publication of this manuscript in Nature Communications after some major issues are addressed. + +Response: We appreciate for the reviewer's supportive comments. + +Comment 2: The authors should comment on the reason for the change on the anode material when benzannulated pyridines were used (examples 46, 47). + +Response: For these benzannulated pyridines (46- 48), the use of GF as the anode led to a low yield of less than \(25\%\) under the standard conditions. Preliminary reaction optimization reveals that switching GF anode to C (graphite) electrode gives the target meta- sulfonylated products with decent yields (see below). Thus, we rephrased the related discussion in the revised manuscript: "...to prepare the sulfonated heteroarenes complete meta- selectivity, although switching to C anode sees required to ensure decent efficiency." + +<--- Page Split ---> +![PLACEHOLDER_7_0] + + +Comment 3: The authors should demonstrate the position of the attack on the 1'. The sequential functionalization (synthesis of 57) implies that the functionalization of 1' is selective. But in the SI page 16 the authors report a mixture of isomers (before hydrolysis). This needs to be clarified. For that reason the authors should separate and characterize the products. + +Response: We thank the reviewer for this insightful suggestion. Before that, please allow us to correct a minor mistake that may cause misunderstanding. In fact, 3' used for streamlined synthesis of 57 should be consistent with that in SI, which is an inseparable mixture of regioisomers and diastereomers generated via redox- neutral dearmative cycloaddition instead of electrochemical C- H functionalization of 1a before hydrolysis. For clear clarification, we indicated that which general procedure was followed for the substrate/product synthesis in Section 8 in SI. + +Nevertheless, we attempted to isolate the electrochemical C- H sulfonated products of 1a' before hydrolysis, which also proved to be a mixture of \(\beta\) - and \(\delta\) - regioisomers. This result clearly indicates the sulfonyl radical addition onto both \(\beta\) - and \(\delta\) - positions of oxazino- pyridine 1a'. Thus, a brief comment was added in the revised manuscript as the following: "Isolation of the electrochemical process before hydrolysis proved to be an inseparable mixture of \(\beta\) - and \(\delta\) - sulfonated regioisomers, which clearly indicates the sulfonyl radical addition onto both sites of oxazino- pyridine 1a'." + +Nevertheless, for oxazino- pyridines bearing a substituent at the \(\alpha\) - site, the final \(\delta\) - regioisomer was identified as a single isomer (36, 37, 53), which could be rationalized by the steric effect. Thus, we have added the regioselective ratios and a brief comment: "It is worth noting that oxazino- pyridines bearing a substituent at the \(\alpha\) - site delivered the \(\delta\) - sulfonated product as a single isomer (36, 37, 53), which could be rationalized by the steric effect." + +![PLACEHOLDER_7_1] + + +Comment 4: The authors should cite a related work: G.- Q. Sun, P. Yu, W. Zhang, W. Zhang, Y. Wang, L.- L. Liao, Z. Zhang, L. Li, Z. Lu, D.- G. Yu, S. Lin, Nature 2023, 615, 67- 72. + +<--- Page Split ---> + +Response: This reference has been added as requested (see ref. 17 in the revised manuscript). + +Comment 5: Concerning the Supplementary Information the spectra of some compounds, such as 19, 21, 23, 14, 15, 31, 42, 51 among others are not sufficiently pure. Thus, the authors must repurify the compounds that are not pure enough and re- evaluate the reported yields. + +Response: As replied to the Reviewer #1, we have repurified all the mentioned, and recalculated the yields, and accordingly re- recorded the NMR spectra. + +## Response to Reviewer #3: + +Comments: I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Response: We are very supportive of this new co- reviewing pattern which we believe can facilitate training in peer review for early career researchers. + +## Response to Reviewer #4: + +## Recommendation: Revisions required + +Comment 1: Hashmi, Yi, Zeng and coworkers reported here an electrochemical meta- sulfonylation of pyridine derivatives via a dearomatization/rearomatization strategy that has been demonstrated previously by Studer and others. The key design is to convert nucleophilic sulfinate anion to electrophilic sulfonyl radical via anodic oxidation. The authors have demonstrated the synthetic potential of this method by providing a broad scope of both sulfinates and pyridine substrates, potential derivatization of the products and large- scale synthesis. I recommend publication of this manuscript with minor revision. The authors should address the following questions: + +Response: We thank the Reviewer for their appreciation. + +Comment 2: In the optimization Table 1, the authors found that the sodium sulfinate is more effective than the other base metal and the organic soluble tetrabutyl ammonium salts (entries 9 and 11), which indicates that the sodium cation plays some critical roles in the observed reactivity besides solubility. The authors should provide some explanations about why the sodium salt is the most effective. + +Response: This is indeed an interesting phenomenon. In their Perspective (Chem Catal. 2022, 2, 1267- 1276), Li and Wang mentioned: "The electrical double layer (EDL) formed at the interface between the electrode and electrolyte has significant impacts on electrochemical reactions... The Gouy- Chapman- Stern (GCS) model provides a classic description of the EDL structure (shown below). As schematically illustrated in the figure below, it consists—with increasing distance away from the electrode surface—of an inner Helmholtz layer (IHP, where ions are chemisorbed on + +<--- Page Split ---> + +the electrode surface), an outer Helmholtz layer (OHP, where ions are mainly bound by electrostatic attraction and not specifically adsorbed), and a diffuse layer (where ions have an increasingly disordered and loose arrangement). It is the interactions among electrodes, electrolytes, and reactants in the EDL that dictate the reaction energetics." + +As for our case, the reactivity difference of these sulfinate reactants seems to result from the identity of their cations. The cations from both sulfinates and electrolyte ("Bu4NBF4) should competitively approach toward the cathode electrodes to form solvated cations. We speculated that the size of these cations might influence the surface charge density, availability of methanol molecules (related to hydrogen evolution), and stability of reaction intermediates, although the detailed mechanism remains unclear due to the difficulty in providing direct experimental evidence. + +Thus, a brief comment was added in the revised manuscript as the following: "the reactivity difference of these sulfinate salts might be rationalized by the interplays among the cathode electrode, electrolyte, the cation of sulfinates, and methanol solvent (related to hydrogen evolution), although the detailed mechanism remains unclear at this stage." + +<--- Page Split ---> +![PLACEHOLDER_10_0] + + +Comment 3: In the mechanistic studies, the authors observed suppressed reactivity in the presence of TEMPO. Based on which, the authors concluded a radical- based mechanism. TEMPO is known to undergo oxidation under mild electrochemical potentials (Phys. Chem. Chem. Phys., 2021,23, 10205- 10217). So the low reactivity in the presence of TEMPO could be resulting from its lower oxidation potential than the sulfinate salt. CV should be performed to compare redox potentials of TEMPO and sulfinate. If that is the case, this experiment cannot be used to prove the radical mechanism of the sulfonylation reaction. + +Response: As suggested by the reviewer, we conducted cyclic voltammetry (CV) of TEMPO and 1,1- diphenylethene. It shows that TEMPO has a slightly higher oxidation potential (+1.43 V, Figure S16 in SI) than \(\mathrm{PhSO_2Na}\) (+0.94 V). Since the potential applied for the reaction is ca. +2 V, the competitive oxidation of TEMPO at the anode might also be feasible. Thus, we agreed that no formation of 3 in the presence of TEMPO cannot prove the radical pathway. This radical- trapping reaction has been shifted to SI and related comment has been removed. Nevertheless, the + +<--- Page Split ---> + +inhibition of 1,1- diphenylethylene which exhibits one weak oxidative peak at \(+2.33\mathrm{V}\) (Figure S17 in SI) seems supportive of a radical pathway. + +Comment 4: I found several subjective, exaggerated description in the manuscript unnecessary and lacks literature support. The authors should revise and avoid those expressions. For example, in the abstract, the authors stated, "a direct meta- selective C- H functionalization of pyridines is of paramount importance, but such reactions remain extremely limited and highly challenging.". The authors may consider remove "extremely", as references 15- 25 are all about meta- selective C- H functionalizations. On page 3, the authors mentioned "Using a nucleophilic partner to fulfill such transformations still remains unexplored, presumably due to the inherent polarity mismatch, although it is attractive since most reagents are nucleophilic." I found the general statement about most reagents are nucleophilic lacks context and is doubtful. The authors should revise and avoid those claims. + +Response: The "extremely" has been removed as suggested. Also, we rephrased the second sentence, which now reads as "Using a nucleophilic partner to fulfill such transformations still remains unexplored, presumably due to the inherent polarity mismatch, although it is attractive since most reagents natively exists as their nucleophilic." Furthermore, we re- checked the whole manuscript to avoid such subjective description. + +Finally, we have uploaded all proper files and made the appropriate changes according to the requirement from the editorial office and the reviewers. + +We again want to thank you for your efforts in handling our manuscript and the reviewers for their very insightful comments, which have helped us to improve the manuscript. We hope you will find the revised manuscript suitable for publication in Nature Communications. + +With best regards, Sincerely yours, Prof. Dr. Zhongyi Zeng & Prof. Dr. Wei Yi & Prof. Dr. A. Stephen K. Hashmi E- mail: zzeng@gzhm.edu.cn (Z. Zeng); yiwei@gzhm.edu.cn (W. Y.); hashmi@hashmi.de (A. S. K. H.) + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: The authors have carefully revised the ms. I am satisfied with the revisions. Publication in NC is recommended. + +Reviewer #2: Remarks to the Author: I believe that all the issues with the Supporting information have been properly addressed and thus the paper is for me ready to be accepted. + +Reviewer #3: Remarks to the Author: I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #4: Remarks to the Author: After reviewing the response letter, the revised manuscript and SI, I am glad to find out that the authors have addressed all my concerns and suggestions about this work. Therefore, I recommend publication of this paper as it is. + +<--- Page Split ---> diff --git a/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f8503a1fae8b7627df36a4f7516dacf96a78b868 --- /dev/null +++ b/peer_reviews/3350c78b4eb169bea49203388d0b2681cbd879d99c6337177411401aa8c19d75/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,287 @@ +<|ref|>title<|/ref|><|det|>[[99, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[108, 154, 830, 211]]<|/det|> +Electrochemical meta- C- H Sulfonylation of Pyridines with Nucleophilic Sulfinates + +<|ref|>image<|/ref|><|det|>[[95, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 285, 103]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[116, 120, 216, 133]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[116, 136, 291, 149]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 150, 866, 253]]<|/det|> +meta- C- H functionalization of pyridines is of paramount importance but remain quite challenging. Established methods for such selective functionalization mostly rely on the use of electrophilic reagents to demand the intrinsic polarity match. The manuscript from Zeng et al. reported a complementary electrochemical method in which a wide variety of nucleophilic sulfinates allow metasulfonylation of pyridines. This method is impressive and uniquely facilitated by electrochemistry, as well as features excellent functional group tolerance and late- stage modification. Hence, I would suggest that it would publish on Nature Communications after addressing the following concerns. + +<|ref|>text<|/ref|><|det|>[[116, 268, 829, 312]]<|/det|> +1. This reaction seems uniquely promoted by electrochemistry. Did the authors test more other oxidant sources to support this conclusion? These additional experiments should be added in supporting information. + +<|ref|>text<|/ref|><|det|>[[116, 313, 878, 357]]<|/det|> +2. In addition to sulfonation, thiolation was also demonstrated. The authors may test other electrophilic radical precursors. I would highly recommend placing these negative results in supporting information for readers' better understanding. + +<|ref|>text<|/ref|><|det|>[[116, 358, 876, 402]]<|/det|> +3. The authors have demonstrated some product derivatizations. One more interesting transformation would be introducing a sulfonyl fluoride (-SO2F) unit at pyridine meta-position since this group can be used as for sulfur(VI) fluoride exchange (SuFEx) click chemistry. + +<|ref|>text<|/ref|><|det|>[[116, 403, 872, 432]]<|/det|> +4. Representative bioactive molecules featuring meta-sulfonated pyridines are provided in Fig 1c. Can the authors show that their method allows access to some these drug molecules? + +<|ref|>text<|/ref|><|det|>[[116, 433, 872, 491]]<|/det|> +5. Regarding the mechanism, clarification is required from the author on the potential involvement of intermediate state II', which remains inert to the structure of the final product. In Fig 6, please provide the life of persistent radical I and II. It would be beneficial for reader to have a better understanding of this electro mechanism. + +<|ref|>text<|/ref|><|det|>[[116, 492, 870, 521]]<|/det|> +7. There are quite a few grammatical/typographical errors. For example, in SI, page S4, S6 and S8, the ChemDraw Scheme exhibits a disordered layout. + +<|ref|>text<|/ref|><|det|>[[116, 522, 880, 581]]<|/det|> +8. In SI, several product NMR spectra seem to be impure, such as compound 7, 8, 10, 12, 13, 14, 16, 19, 20, 21, 23, 24, 25, 26, 28, 31, 35, 39, 42, 43, 45, 47, 51, and 54. It is imperative to repurify these compounds and recalculate their yields to ensure the accuracy and reliability of the experimental data. Moreover, the melting points of some new compounds are missing. + +<|ref|>text<|/ref|><|det|>[[116, 625, 291, 655]]<|/det|> +Reviewer #2: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 670, 875, 900]]<|/det|> +Hashmi, Yi, Zeng, and coworkers reported the selective C3 sulfonylation with sulfinates by using a dearomative activation mode. The reaction showed a remarkable functional group tolerance both with regards to pyridines and sulfinates. The reaction was selectively giving the desired C3 monosubstituted adduct. The mechanistic studies supported the proposed mechanism. Indeed, the selective C3 functionalization of pyridines is quite challenging and of high importance thus I suggest the publication of this manuscript in Nature Communications after some major issues are addressed. 1. The authors should comment on the reason for the change on the anode material when benzannulated pyridines were used (examples 46, 47). 2. The authors should demonstrate the position of the attack on the 1'. The sequential functionalization (synthesis of 57) implies that the functionalization of 1' is selective. But in the SI page 16 the authors report a mixture of isomers (before hydrolysis). This needs to be clarified. For that reason the authors should separate and characterize the products. 3. The authors should cite a related work: G.- Q. Sun, P. Yu, W. Zhang, W. Zhang, Y. Wang, L.- L. Liao, Z. Zhang, L. Li, Z. Lu, D.- G. Yu, S. Lin, Nature 2023, 615, 67- 72. 4. Concerning the Supplementary Information the spectra of some compounds, such as 19, 21, 23, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 820, 120]]<|/det|> +14, 15, 31, 42, 51 among others are not sufficiently pure. Thus, the authors must repurify the compounds that are not pure enough and re- evaluate the reported yields. + +<|ref|>text<|/ref|><|det|>[[115, 163, 216, 177]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 180, 291, 193]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 194, 880, 238]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 283, 216, 297]]<|/det|> +Reviewer #4: + +<|ref|>text<|/ref|><|det|>[[115, 300, 291, 313]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 314, 875, 416]]<|/det|> +Hashmi, Yi, Zeng and coworkers reported here an electrochemical meta- sulfonylation of pyridine derivatives via a dearomatization/rearomatization strategy that has been demonstrated previously by Studer and others. The key design is to convert nucleophilic sulfinate anion to electrophilic sulfonyl radical via anodic oxidation. The authors have demonstrated the synthetic potential of this method by providing a broad scope of both sulfinates and pyridine substrates, potential derivatization of the products and large- scale synthesis. I recommend publication of this manuscript with minor revision. The authors should address the following questions: + +<|ref|>text<|/ref|><|det|>[[113, 431, 880, 596]]<|/det|> +1. In the optimization Table 1, the authors found that the sodium sulfinate is more effective than the other base metal and the organic soluble tetrabutyl ammonium salts (entries 9 and 11), which indicates that the sodium cation plays some critical roles in the observed reactivity besides solubility. The authors should provide some explanations about why the sodium salt is the most effective. +2. In the mechanistic studies, the authors observed suppressed reactivity in the presence of TEMPO. Based on which, the authors concluded a radical-based mechanism. TEMPO is known to undergo oxidation under mild electrochemical potentials (Phys. Chem. Chem. Phys., 2021,23, 10205-10217). So the low reactivity in the presence of TEMPO could be resulting from its lower oxidation potential than the sulfinate salt. CV should be performed to compare redox potentials of TEMPO and sulfinate. If that is the case, this experiment cannot be used to prove the radical mechanism of the sulfonylation reaction. + +<|ref|>text<|/ref|><|det|>[[115, 596, 880, 729]]<|/det|> +3. I found several subjective, exaggerated description in the manuscript unnecessary and lacks literatur support. The authors should revise and avoid those expressions. For example, in the abstract, the authors stated, "a direct meta-selective C-H functionalization of pyridines is of paramount importance, but such reactions remain extremely limited and highly challenging.". The authors may consider remove "extremely", as references 15-25 are all about meta-selective C-H functionalizations. On page 3, the authors mentioned "Using a nucleophilic partner to fulfill such transformations still remains unexplored, presumably due to the inherent polarity mismatch, although it is attractive since most reagents are nucleophilic." I found the general statement about most reagents are nucleophilic lacks context and is doubtful. The authors should revise and avoid those claims. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 118, 290, 134]]<|/det|> +## Dear Reviewers, + +<|ref|>text<|/ref|><|det|>[[148, 151, 850, 261]]<|/det|> +Dear Reviewers,We are very grateful for the careful evaluation of our manuscript by the reviewers and the editorial office for the constructive criticism. We have thoroughly revised the manuscript following the reviewer's and the editor's comment. Manuscript files with and without highlighted changes have been uploaded as requested. Please find below the point- by- point response to these comments. Your comments are in black, and our responses are in blue. + +<|ref|>sub_title<|/ref|><|det|>[[149, 293, 370, 309]]<|/det|> +## Response to Reviewer #1: + +<|ref|>sub_title<|/ref|><|det|>[[149, 311, 475, 327]]<|/det|> +## Recommendation: Revisions required + +<|ref|>text<|/ref|><|det|>[[148, 329, 850, 493]]<|/det|> +Comment 1: meta- C- H functionalization of pyridines is of paramount importance but remain quite challenging. Established methods for such selective functionalization mostly rely on the use of electrophilic reagents to demand the intrinsic polarity match. The manuscript from Zeng et al. reported a complementary electrochemical method in which a wide variety of nucleophilic sulfinates allow meta- sulfonylation of pyridines. This method is impressive and uniquely facilitated by electrochemistry, as well as features excellent functional group tolerance and late- stage modification. Hence, I would suggest that it would publish on Nature Communications after addressing the following concerns. + +<|ref|>text<|/ref|><|det|>[[149, 495, 698, 511]]<|/det|> +Response: We thank the reviewer for his/her kind recommendation. + +<|ref|>text<|/ref|><|det|>[[148, 531, 850, 586]]<|/det|> +Comment 2: This reaction seems uniquely promoted by electrochemistry. Did the authors test more other oxidant sources to support this conclusion? These additional experiments should be added in supporting information. + +<|ref|>text<|/ref|><|det|>[[148, 588, 850, 735]]<|/det|> +Response: We tested additional several common chemical oxidants, including \(\mathrm{PhI(OAc)_2}\) , \(\mathrm{Cu(OAc)_2}\) , \(\mathrm{Mn(OAc)_3\cdot 2H_2O}\) as well as \(\mathrm{O_2}\) (entries 17and 18 in Table 1 and entries 31- 34, Table S1 in SI), but none of them gave the product more than \(20\%\) yield. These results highlight the unique of electrochemistry for the target transformation. Accordingly, we updated the comment regarding this in the revised manuscript: "...no or much lower efficiency was observed with conventional chemical oxidizing agents such as 1,4- benzoquinone (BQ), \(\mathrm{K_2S_2O_8}\) , \(\mathrm{I_2}\) , \(\mathrm{Ag_2CO_3}\) , \(\mathrm{Cu(OAc)_2}\) , and \(\mathrm{Mn(OAc)_3\cdot 2H_2O}\) " + +<|ref|>text<|/ref|><|det|>[[148, 754, 850, 808]]<|/det|> +Comment 3: In addition to sulfonation, thiolation was also demonstrated. The authors may test other electrophilic radical precursors. I would highly recommend placing these negative results in supporting information for readers' better understanding. + +<|ref|>text<|/ref|><|det|>[[149, 810, 850, 864]]<|/det|> +Response: Indeed, we tested numerous radical precursors listed below which so far were found not amenable under the standard electrochemical conditions and have been provided in the supporting information (see Figures S11 and S12 in SI). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 88, 850, 451]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 473, 850, 548]]<|/det|> +Comment 4: The authors have demonstrated some product derivatizations. One more interesting transformation would be introducing a sulfonyl fluoride (- SO₂F) unit at pyridine meta- position since this group can be used as for sulfur(VI) fluoride exchange (SuFEx) click chemistry. + +<|ref|>text<|/ref|><|det|>[[148, 549, 851, 733]]<|/det|> +Response: This is an interesting point. To realize transformation into sulfonyl fluorides, the most common method is to access sulfinate salts which then react with electrophilic fluorinating reagents. Unfortunately, attempt to incorporate several masked SO₂⁻ anion equivalents (e.g., 2ah, 2ai, 2aj, 2ak) was unsuccessful under the standard electrochemical condition. These negative results have been included in Figure S10 in the Supporting Information. In addition, our newly developed electrochemical method allows facile access to 3-(methylsulfonyl)pyridine 50, whose follow- up demethylation to generate pyridyl sulfinates proved so far unfeasible. Nevertheless, translation of such methylsulfonyl handle into valuable ether and thioether groups (59, 60) was demonstrated. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[157, 98, 840, 320]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[149, 345, 850, 400]]<|/det|> +Comment 5: Representative bioactive molecules featuring meta- sulfonated pyridines are provided in Fig 1c. Can the authors show that their method allows access to some these drug molecules? + +<|ref|>text<|/ref|><|det|>[[148, 400, 850, 530]]<|/det|> +Response: Formal synthesis of Intepidine, a potential Alzheimer's disease drug, was demonstrated by a two- pot procedure (Fig 2). This sequence includes facile access key intermediate 8- chloro- 3- (phenylsulfonyl)quinoline (48) by our newly developed electrochemical method and follow- up palladium- catalyzed C- N cross- coupling known from the literature (Angew. Chem. Int. Ed. 2013, 52, 12679). For better understanding, the yield of this known animation procedure was added in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 548, 850, 640]]<|/det|> +Comment 6: Regarding the mechanism, clarification is required from the author on the potential involvement of intermediate state II', which remains inert to the structure of the final product. In Fig 6, please provide the life of persistent radical I and II. It would be beneficial for reader to have a better understanding of this electro mechanism. + +<|ref|>text<|/ref|><|det|>[[148, 641, 850, 842]]<|/det|> +Response: We guess this intermediate state II' mentioned by the reviewer might be I (now named as I- δ in the revised manuscript and used as I'- δ for the following discussion) in the initial manuscript. If this is the case, I'- δ is proposed as a resonance form of I- δ, and would lose an electron at the anode similar to I- δ to deliver the final product through iminium- type species II- δ (initially III). Following the suggestion of the Reviewer#2, we isolated the electrochemical C- H sulfonated products of 1a' before hydrolysis, which proved to be a mixture of β- and δ- regioisomers. We accordingly modified the proposed mechanism, specifically added the β- radical adduct (I- β) and follow- up intermediates (II- β and III- β), although both regioisomers uniformly give the final product 3. For details, please see our reply to the Comment#3 of the Review#2 below. + +<|ref|>text<|/ref|><|det|>[[148, 844, 848, 880]]<|/det|> +Based on the definitions of Griller and Ingold, radicals I and II in this case were believed to be resonance stabilized radicals, which belong to "transient" radicals (Acc. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 848, 120]]<|/det|> +Chem. Res. 1976, 9, 13). In general, a transient species has a life- time of less than 1 ms (Angew. Chem. Int. Ed. 2020, 59, 74). + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 175]]<|/det|> +Comment 7: There are quite a few grammatical/typographical errors. For example, in SI, page S4, S6 and S8, the ChemDraw Scheme exhibits a disordered layout. + +<|ref|>text<|/ref|><|det|>[[148, 177, 850, 213]]<|/det|> +Response: The schemes in page S4, S6 and S8 in SI have been improved for a better layout. + +<|ref|>text<|/ref|><|det|>[[148, 232, 852, 325]]<|/det|> +Comment 8: In SI, several product NMR spectra seem to be impure, such as compound 7, 8, 10, 12, 13, 14, 16, 19, 20, 21, 23, 24, 25, 26, 28, 31, 35, 39, 42, 43, 45, 47, 51, and 54. It is imperative to repurify these compounds and recalculate their yields to ensure the accuracy and reliability of the experimental data. Moreover, the melting points of some new compounds are missing. + +<|ref|>text<|/ref|><|det|>[[148, 326, 850, 417]]<|/det|> +Response: Thanks for pointing out this issue. We have repurified all these aforementioned compounds to ensure their NMR spectra suitable for publication, and accordingly recalculated their chemical yields. In addition, we placed the melting points of all new solid compounds (except \(3^{\circ}\) and \(1\mathrm{m}^{\circ}\) which are inseparable diastereo-/regioisomers). + +<|ref|>sub_title<|/ref|><|det|>[[149, 455, 370, 471]]<|/det|> +## Response to Reviewer #2: + +<|ref|>sub_title<|/ref|><|det|>[[149, 474, 475, 490]]<|/det|> +## Recommendation: Revisions required + +<|ref|>text<|/ref|><|det|>[[148, 491, 850, 638]]<|/det|> +Comment 1: Hashmi, Yi, Zeng, and coworkers reported the selective C3 sulfonylation with sulfinates by using a dearomatic activation mode. The reaction showed a remarkable functional group tolerance both with regards to pyridines and sulfinates. The reaction was selectively giving the desired C3 monosubstituted adduct. The mechanistic studies supported the proposed mechanism. Indeed, the selective C3 functionalization of pyridines is quite challenging and of high importance thus I suggest the publication of this manuscript in Nature Communications after some major issues are addressed. + +<|ref|>text<|/ref|><|det|>[[149, 640, 688, 657]]<|/det|> +Response: We appreciate for the reviewer's supportive comments. + +<|ref|>text<|/ref|><|det|>[[148, 676, 850, 711]]<|/det|> +Comment 2: The authors should comment on the reason for the change on the anode material when benzannulated pyridines were used (examples 46, 47). + +<|ref|>text<|/ref|><|det|>[[148, 713, 850, 841]]<|/det|> +Response: For these benzannulated pyridines (46- 48), the use of GF as the anode led to a low yield of less than \(25\%\) under the standard conditions. Preliminary reaction optimization reveals that switching GF anode to C (graphite) electrode gives the target meta- sulfonylated products with decent yields (see below). Thus, we rephrased the related discussion in the revised manuscript: "...to prepare the sulfonated heteroarenes complete meta- selectivity, although switching to C anode sees required to ensure decent efficiency." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[293, 90, 702, 170]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 195, 850, 288]]<|/det|> +Comment 3: The authors should demonstrate the position of the attack on the 1'. The sequential functionalization (synthesis of 57) implies that the functionalization of 1' is selective. But in the SI page 16 the authors report a mixture of isomers (before hydrolysis). This needs to be clarified. For that reason the authors should separate and characterize the products. + +<|ref|>text<|/ref|><|det|>[[147, 289, 850, 417]]<|/det|> +Response: We thank the reviewer for this insightful suggestion. Before that, please allow us to correct a minor mistake that may cause misunderstanding. In fact, 3' used for streamlined synthesis of 57 should be consistent with that in SI, which is an inseparable mixture of regioisomers and diastereomers generated via redox- neutral dearmative cycloaddition instead of electrochemical C- H functionalization of 1a before hydrolysis. For clear clarification, we indicated that which general procedure was followed for the substrate/product synthesis in Section 8 in SI. + +<|ref|>text<|/ref|><|det|>[[147, 418, 850, 548]]<|/det|> +Nevertheless, we attempted to isolate the electrochemical C- H sulfonated products of 1a' before hydrolysis, which also proved to be a mixture of \(\beta\) - and \(\delta\) - regioisomers. This result clearly indicates the sulfonyl radical addition onto both \(\beta\) - and \(\delta\) - positions of oxazino- pyridine 1a'. Thus, a brief comment was added in the revised manuscript as the following: "Isolation of the electrochemical process before hydrolysis proved to be an inseparable mixture of \(\beta\) - and \(\delta\) - sulfonated regioisomers, which clearly indicates the sulfonyl radical addition onto both sites of oxazino- pyridine 1a'." + +<|ref|>text<|/ref|><|det|>[[147, 549, 852, 658]]<|/det|> +Nevertheless, for oxazino- pyridines bearing a substituent at the \(\alpha\) - site, the final \(\delta\) - regioisomer was identified as a single isomer (36, 37, 53), which could be rationalized by the steric effect. Thus, we have added the regioselective ratios and a brief comment: "It is worth noting that oxazino- pyridines bearing a substituent at the \(\alpha\) - site delivered the \(\delta\) - sulfonated product as a single isomer (36, 37, 53), which could be rationalized by the steric effect." + +<|ref|>image<|/ref|><|det|>[[232, 661, 765, 824]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 845, 850, 899]]<|/det|> +Comment 4: The authors should cite a related work: G.- Q. Sun, P. Yu, W. Zhang, W. Zhang, Y. Wang, L.- L. Liao, Z. Zhang, L. Li, Z. Lu, D.- G. Yu, S. Lin, Nature 2023, 615, 67- 72. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 848, 120]]<|/det|> +Response: This reference has been added as requested (see ref. 17 in the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[149, 141, 849, 213]]<|/det|> +Comment 5: Concerning the Supplementary Information the spectra of some compounds, such as 19, 21, 23, 14, 15, 31, 42, 51 among others are not sufficiently pure. Thus, the authors must repurify the compounds that are not pure enough and re- evaluate the reported yields. + +<|ref|>text<|/ref|><|det|>[[149, 216, 848, 251]]<|/det|> +Response: As replied to the Reviewer #1, we have repurified all the mentioned, and recalculated the yields, and accordingly re- recorded the NMR spectra. + +<|ref|>sub_title<|/ref|><|det|>[[150, 272, 370, 288]]<|/det|> +## Response to Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[149, 291, 850, 362]]<|/det|> +Comments: I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[149, 364, 848, 399]]<|/det|> +Response: We are very supportive of this new co- reviewing pattern which we believe can facilitate training in peer review for early career researchers. + +<|ref|>sub_title<|/ref|><|det|>[[149, 437, 370, 453]]<|/det|> +## Response to Reviewer #4: + +<|ref|>sub_title<|/ref|><|det|>[[149, 456, 475, 471]]<|/det|> +## Recommendation: Revisions required + +<|ref|>text<|/ref|><|det|>[[148, 473, 850, 638]]<|/det|> +Comment 1: Hashmi, Yi, Zeng and coworkers reported here an electrochemical meta- sulfonylation of pyridine derivatives via a dearomatization/rearomatization strategy that has been demonstrated previously by Studer and others. The key design is to convert nucleophilic sulfinate anion to electrophilic sulfonyl radical via anodic oxidation. The authors have demonstrated the synthetic potential of this method by providing a broad scope of both sulfinates and pyridine substrates, potential derivatization of the products and large- scale synthesis. I recommend publication of this manuscript with minor revision. The authors should address the following questions: + +<|ref|>text<|/ref|><|det|>[[148, 640, 610, 656]]<|/det|> +Response: We thank the Reviewer for their appreciation. + +<|ref|>text<|/ref|><|det|>[[148, 676, 850, 766]]<|/det|> +Comment 2: In the optimization Table 1, the authors found that the sodium sulfinate is more effective than the other base metal and the organic soluble tetrabutyl ammonium salts (entries 9 and 11), which indicates that the sodium cation plays some critical roles in the observed reactivity besides solubility. The authors should provide some explanations about why the sodium salt is the most effective. + +<|ref|>text<|/ref|><|det|>[[148, 769, 850, 896]]<|/det|> +Response: This is indeed an interesting phenomenon. In their Perspective (Chem Catal. 2022, 2, 1267- 1276), Li and Wang mentioned: "The electrical double layer (EDL) formed at the interface between the electrode and electrolyte has significant impacts on electrochemical reactions... The Gouy- Chapman- Stern (GCS) model provides a classic description of the EDL structure (shown below). As schematically illustrated in the figure below, it consists—with increasing distance away from the electrode surface—of an inner Helmholtz layer (IHP, where ions are chemisorbed on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 177]]<|/det|> +the electrode surface), an outer Helmholtz layer (OHP, where ions are mainly bound by electrostatic attraction and not specifically adsorbed), and a diffuse layer (where ions have an increasingly disordered and loose arrangement). It is the interactions among electrodes, electrolytes, and reactants in the EDL that dictate the reaction energetics." + +<|ref|>text<|/ref|><|det|>[[148, 179, 850, 308]]<|/det|> +As for our case, the reactivity difference of these sulfinate reactants seems to result from the identity of their cations. The cations from both sulfinates and electrolyte ("Bu4NBF4) should competitively approach toward the cathode electrodes to form solvated cations. We speculated that the size of these cations might influence the surface charge density, availability of methanol molecules (related to hydrogen evolution), and stability of reaction intermediates, although the detailed mechanism remains unclear due to the difficulty in providing direct experimental evidence. + +<|ref|>text<|/ref|><|det|>[[148, 308, 850, 400]]<|/det|> +Thus, a brief comment was added in the revised manuscript as the following: "the reactivity difference of these sulfinate salts might be rationalized by the interplays among the cathode electrode, electrolyte, the cation of sulfinates, and methanol solvent (related to hydrogen evolution), although the detailed mechanism remains unclear at this stage." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 88, 850, 595]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 621, 850, 770]]<|/det|> +Comment 3: In the mechanistic studies, the authors observed suppressed reactivity in the presence of TEMPO. Based on which, the authors concluded a radical- based mechanism. TEMPO is known to undergo oxidation under mild electrochemical potentials (Phys. Chem. Chem. Phys., 2021,23, 10205- 10217). So the low reactivity in the presence of TEMPO could be resulting from its lower oxidation potential than the sulfinate salt. CV should be performed to compare redox potentials of TEMPO and sulfinate. If that is the case, this experiment cannot be used to prove the radical mechanism of the sulfonylation reaction. + +<|ref|>text<|/ref|><|det|>[[147, 770, 850, 900]]<|/det|> +Response: As suggested by the reviewer, we conducted cyclic voltammetry (CV) of TEMPO and 1,1- diphenylethene. It shows that TEMPO has a slightly higher oxidation potential (+1.43 V, Figure S16 in SI) than \(\mathrm{PhSO_2Na}\) (+0.94 V). Since the potential applied for the reaction is ca. +2 V, the competitive oxidation of TEMPO at the anode might also be feasible. Thus, we agreed that no formation of 3 in the presence of TEMPO cannot prove the radical pathway. This radical- trapping reaction has been shifted to SI and related comment has been removed. Nevertheless, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 848, 121]]<|/det|> +inhibition of 1,1- diphenylethylene which exhibits one weak oxidative peak at \(+2.33\mathrm{V}\) (Figure S17 in SI) seems supportive of a radical pathway. + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 344]]<|/det|> +Comment 4: I found several subjective, exaggerated description in the manuscript unnecessary and lacks literature support. The authors should revise and avoid those expressions. For example, in the abstract, the authors stated, "a direct meta- selective C- H functionalization of pyridines is of paramount importance, but such reactions remain extremely limited and highly challenging.". The authors may consider remove "extremely", as references 15- 25 are all about meta- selective C- H functionalizations. On page 3, the authors mentioned "Using a nucleophilic partner to fulfill such transformations still remains unexplored, presumably due to the inherent polarity mismatch, although it is attractive since most reagents are nucleophilic." I found the general statement about most reagents are nucleophilic lacks context and is doubtful. The authors should revise and avoid those claims. + +<|ref|>text<|/ref|><|det|>[[148, 345, 850, 454]]<|/det|> +Response: The "extremely" has been removed as suggested. Also, we rephrased the second sentence, which now reads as "Using a nucleophilic partner to fulfill such transformations still remains unexplored, presumably due to the inherent polarity mismatch, although it is attractive since most reagents natively exists as their nucleophilic." Furthermore, we re- checked the whole manuscript to avoid such subjective description. + +<|ref|>text<|/ref|><|det|>[[148, 488, 850, 523]]<|/det|> +Finally, we have uploaded all proper files and made the appropriate changes according to the requirement from the editorial office and the reviewers. + +<|ref|>text<|/ref|><|det|>[[148, 525, 850, 597]]<|/det|> +We again want to thank you for your efforts in handling our manuscript and the reviewers for their very insightful comments, which have helped us to improve the manuscript. We hope you will find the revised manuscript suitable for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[148, 613, 850, 696]]<|/det|> +With best regards, Sincerely yours, Prof. Dr. Zhongyi Zeng & Prof. Dr. Wei Yi & Prof. Dr. A. Stephen K. Hashmi E- mail: zzeng@gzhm.edu.cn (Z. Zeng); yiwei@gzhm.edu.cn (W. Y.); hashmi@hashmi.de (A. S. K. H.) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 285, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 120, 681, 180]]<|/det|> +Reviewer #1: Remarks to the Author: The authors have carefully revised the ms. I am satisfied with the revisions. Publication in NC is recommended. + +<|ref|>text<|/ref|><|det|>[[115, 223, 851, 283]]<|/det|> +Reviewer #2: Remarks to the Author: I believe that all the issues with the Supporting information have been properly addressed and thus the paper is for me ready to be accepted. + +<|ref|>text<|/ref|><|det|>[[115, 328, 851, 402]]<|/det|> +Reviewer #3: Remarks to the Author: I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 447, 852, 522]]<|/det|> +Reviewer #4: Remarks to the Author: After reviewing the response letter, the revised manuscript and SI, I am glad to find out that the authors have addressed all my concerns and suggestions about this work. Therefore, I recommend publication of this paper as it is. + +<--- Page Split ---> diff --git a/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/images_list.json b/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f05643248b75e5b1f0302c4c05e08ed1b9e9707d --- /dev/null +++ b/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,329 @@ + +# nature portfolio + +Peer Review File + +ATF3 Induction Prevents Precocious Activation of Skeletal Muscle Stem Cell by Regulating H2B Expression + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The manuscript brings highly interesting new insight into the control of muscle stem cells quiescence and senescence, with extensive experimental data. The finding that ATF3 controls H2B expression thus preventing genome instability and replicative senescence + +in SCs is unexpected, novel and important. + +Has requested, I did especially look at the cut & run data. The signal to noise ratio appears to be the problem. The image in Fig 6n has low resolution, but the image in Fig 6s on the Eln gene doesn't really show peaks consistent with nucleosomes. Just a lot of noise across the gene. This makes me wonder about the quality of the data set. That being said, the cumulative data shows there is a decrease at the 5' end of the gene around the TSS (Fig 6q). This is the one thing I would say is true on the Eln gene in Figure 6S. + +So, overall, I would recommend that ideally the experiment should be repeated to get better signal to noise ratio before being able to state there is a loss of H2B at specific areas of the genome. + +Reviewer #2 (Remarks to the Author): + +Skeletal muscles have the remarkable capacity to undergo regenerative growth in response to injury or other external stimuli. Muscle regeneration relies on activation and expansion of skeletal muscle stem cells, also known as satellite cells (SCs), residing beneath the basal lamina of myofibers, followed by differentiation into multinucleated myotubes. The mechanism for preserving the SCs population has become an attractive avenue of research for the discovery of possible therapeutic interventions for many muscle degeneration disorders. The manuscript by Zhang et al. provides some interesting aspects for SCs area. The study put multiple sets of data in mice and cells together into a story. However, the reviewer found numerous issues in the logic, data quality and conceptual novelty. + +First, I have a hard time reckoning with the main conclusion "ATF3 preserves skeletal muscle stem cell quiescence". What the authors showed in this paper was that ATF3 was not expressed/or expressed at very low levels in SCs at quiescence state (QSC), and ATF3 is only rapidly induced upon SCs activation, even though the authors showed some data suggesting that deletion of ATF3 in SCs accelerates acute injury- induced regeneration. The authors also showed many difference phenotypes between the "Shortterm" and "long- term" ATF3 iKO, this could be due to many reasons, either experimental systems (such as Tamoxifen system) or chronic secondary compensation. Moreover, the authors claimed that ATF3 is induced upon SCs activation and ATF3 prevents SCs activation. However, no data to demonstrate that ATF3 overexpression is sufficient to inhibit SCs activation. In this reviewer's view, no data support the concept in this paper. + +<--- Page Split ---> + +The second issue is the link to H2B. If the authors claim the liner link between ATF3 and H2B, the critical experiment would be to demonstrate that ATF3 overexpression sufficiently prevents SCs activation, and genetic loss of H2B blocks the process. + +The third issue is about data figures: there are many data provided; however there are several shortcomings in the presentation of the data, data interpretation, and importantly, the lack of high quality data. + +Indeed, the conceptual advance that this manuscript will bring forward is also being questioned. + +## Major Points: + +1. As discuss above, the authors concluded that ATF3 preserves muscle stem cell quiescence. However, in this reviewer's view, the data did not support this concept in this paper. What the authors showed in this paper was that ATF3 was not expressed/or expressed at very low levels in SCs at quiescence state (QSC), and ATF3 is only rapidly induced upon SCs activation, even though the authors show some data suggesting that deletion of ATF3 in SCs accelerates acute injury-induced regeneration. The authors also showed many difference phenotypes between the "Short-term" and "long-term" ATF3 iKO, this could be due to many reasons, either experimental systems (such as Tamoxifen system) or chronic secondary compensation. + +2. The authors claimed that ATF3 is induced upon SCs activation, and ATF3 prevents SCs activation. However, no data to demonstrate that ATF3 overexpression is sufficient to inhibit SCs activation. + +3. Although the author did some interesting experiment to suggest that H2B loss in SCs results in increased genome instability and cellular senescence. In this reviewer's view, if the authors claim the liner link between ATF3 and H2B, the critical experiment would be to demonstrate that ATF3 overexpression sufficiently prevents SCs activation, and genetic loss of H2B blocks the process. + +4. There are several short-comings in the presentation of the data and data interpretation, and importantly, the lack of high quality data. For example, all IF staining data (multiple replicates of the experiment) need quantification to show statistical significance; very poor quality images in Fig. 2e, Fig. 2g, Fig. 2n and Fig. 3g....., and all the poor quality laminin stainings; the Reviewer is confusing, In Fig.1f, why the Pax7 staining is so low in QSC compare to others in the same panel? In Fig. 4d, the image suggests increased Pax7 levels in iKO at 5dpi, but the quantification data show decreased in iKO at 5dpi. + +5. Furthermore, \(\mathsf{N} = 3\) throughout the paper, with such a small sample size for mice studies, how can the authors be certain their data is reproducible? + +6. The study follows work previously published by the same group, using the same dataset, the authors describe that ATF3 was induced in FISC compared to QSCs, but indeed this is also known and reported previously by other group (Machado L, et al., Cell Rep. 2017;21(7):1982-1993.). Moreover, previously study has also reported that ATF3 regulates stem cells self-renewal (Liu Y, et al., Front Cell Dev Biol. 2020;8:585771), a paper that the authors have cited. Thus, the conceptual novelty is marginal in this journal. + +<--- Page Split ---> + +7. By comparing the pre-fixed and non-fixed SCs (indeed quite an artificial system), the authors claimed that ATF3 is induced upon SCs activation. But as the authors said, AP-1 family members are very sensitive to a variety of cellular stresses and quickly induced by even slight disturbance. Therefore, it would be very important to examine whether ATF3 is induced in SCs during injury induced muscle regeneration in vivo. + +8. The authors used the term "resistance exercise" to study the SCs activation. However, in page 12, the authors described a typical endurance exercise protocol that uses a treadmill set at a \(5^{\circ}\) incline and a speed of \(20 \text{cm/sec}\) . This protocol is not resistance exercise. The reviewer is very confusing, since endurance exercise do not trigger SC activation and muscle hypertrophy. It would be much better to study the SCs activation of these mice with a protocol of real resistance exercise (Cui D, et al., FASEB J. 2020;34(6):7330-7344.). + +9. SCs undergo a self-renewal process and returns to the quiescent stage to replenish the SC pool. The authors found that deletion of ATF3 in SCs increased muscle weight and fiber size during 1st, 2nd and 3rd injury. They also showed that Pax7+ cells were decreased in ATF3 KO after 3rd injury. If the authors claim that ATF3 KO exhausts SC pool, it would be at very least to examine the SC pool (Pax7+ cells) after 1st injury and 2nd injury as well. + +10. The similar engraftment assay (Fig. 2l,m) need to be done to examine the regenerative ability of the iKO SCs in the "long-term" iKO mouse models. + +11. Figure S7. The authors performed some functional screening using the Pax7 Cas9/AAV-sgRNA mediated in vivo genome editing system. Although there are many data provided, the data do not support authors claim due to the low editing efficiency and the none-inducible SC specific deletion. + +## Minor: + +1. The authors mislabel The Fig.1e, 1d in the text. page 6: "this was also confirmed by RT-qPCR (Fig.1e)", Fig.1e not RT-PCR. + +2. Many errors in the text. e.g. page 6: "which was also n confirmed by RT-qPCR (Fig. S1a)." + +Reviewer #3 (Remarks to the Author): + +This manuscript describes a novel role of the activating transcriptional factor 3 (ATF3) in muscle stem cells called satellite cells. The authors first used RNA-seq to show and immunostaining to confirm that Atf3 expression is transiently elevated in activated satellite cells (Fig. 1). They then generated conditional KO mice to delete Atf3 gene in quiescent satellite cells using the Pax7-CreER driver. They show that the cKO exhibited accelerated regeneration initially but regeneration declines upon repeated injury at the 3rd injury, associated with reduced myogenic cells. These results suggest a defect in self-renewal that sequentially reduces satellite cell number and regenerative capacity. Figure 3 use single fiber culture and in vivo regeneration model to confirm there is a defect in self-renewal of Atf4 KO cells as manifested by reduced Pax7+/Myod- cells, even though the cell proliferation is elevated. They then + +<--- Page Split ---> + +show in figure 4 a regenerative effect in response to a single bout of injury 6 months after Atf3 deletion. In Figure 5 they show that Atf3 KO satellite cells activate more readily in response to exercise. In figure 6, they use RNA- seq, CUT&RUN and ChIP- seq to bring about the idea that loss of ATF3 suppress transcription of the H2b clusters. Figure 7 demonstrate that the Atf3 null satellite cells display aggravated stress- induced DNA damage and accelerated aging phenotypes. Together, the study uses a number of omics, conditional KO, in vivo injury and exercise models to demonstrate for the first time a key role of ATF3 in satellite cells and muscle regeneration. The results are striking and based on large amount of solid data. + +I only have a main concern, which is related to the interpretation of the results that can be fixed by rewording. The title (ATF3 Preserves Skeletal Muscle Stem Cell Quiescence by Preventing Precocious Activation), the abstract, results all indicate that ATF plays a role in quiescent cells but the data appear to suggest a role of ATF3 in self- renewal (i.e. it is elevated in activated cells to force the cell back to a quiescent state). I think this concept must be clarified throughout the manuscript. + +Related to the previous point on ATF3 expression: Fig 1g showing expression of ATF3 in satellite cells on fresh isolated myofiber suggesting its expression in quiescent cells (even though fiber isolation takes 1- 2 hours that could activate cells, it takes more than two hours for a gene to be transcribed and then made into proteins). Therefore, my worry is that in situ fixation may induce artifacts in gene expression. It would have been nice if sections of non- injured and injured muscles can be used to validate or reject the conclusion that ATF3 expression is only induced by activation. + +Still related to data interpretation: If as the authors concluded, ATF3 is not expressed in quiescent satellite cells (Fig 1b, c, d, f), then why would knock out of a non- expressed gene affect satellite cells over time? This does not make sense. It only makes sense if ATF3 is indeed expressed in the quiescent satellite cells. The authors argue that there are various stress conditions that induce activation of satellite cells but what is the threshold of such stress? Why would normal use (movements) does not induce the (activation) stress whereas exercise induce stress? Again, if ATF3 function to push stress activated satellite cells back to a quiescent state, then its function is more in line with the self- renewal function in HSC. You cannot declare that a protein function to enforce quiescence while it is not expressed in the quiescent satellite cells. + +Minor: + +Subtitles of the results section do not effectively capture the results. + +In Figure 5l, H2B is completely lost in the iKO. It is intriguing that the phenotype is so "mild" given the complete loss of H2B. On another note, the histone proteins are thought to be very stable, even a + +<--- Page Split ---> + +complete shutdown of H2b transcription should not deplete all H2B proteins without extensive cell division. Please clarify. + +Abstract: "Here we report that AP- 1 family member ATF3 preserves the SC quiescence by preventing their premature activation. Atf3 is rapidly and transiently induced in SCs upon activation." Without any context the two sentences appear to contradict. If ATF3 preserves quiescence then induction of Atf3 should enforce quiescence but not lead to activation. I suggest that these should be rewritten. + +Similarly, the ending sentence of the first paragraph in Results: "Taken together, our findings show that ATF3 and several other AP- 1 family members are rapidly and transiently induced during early SC activation, suggesting the potential roles of ATF3 and other family members in the regulation of SC quiescence or early activation." Without reading discussion this sentence does not make sense at all. + +As satellite cells were increased by \(80\%\) in the Pax7- Cre KO in embryonic myoblasts, is the muscle hypertrophic in the young mice? + +Also in p12: "Altogether the above results suggest an essential role of ATF3 induction in preventing precocious SC activation,.." So far the study has never shown that ATF3 induction prevents precocious activation. + +P13: "These results demonstrate that the ATF3 loss decreases H2b gene expression". This is counterintuitive as Atf3 KO leads to activation and proliferation, which require generation of new histone protein. + +Full name of ATF3 should be provided at the first occurrence. ATF3 is known to activate gene expression and it is puzzling why most genes are upregulated in Atf3 KO satellite cells. Some discussion might be helpful. + +Abstract: "which reduction accelerates nucleosome displacement and gene transcription required for SC activation". This sentence appears to have grammar issue. Change to "whose reduction" + +The Atf3 KO phenotype is very similar to, but milder then, Pten KO phenotypes (PMID: 27880908, PMID: 28094257). In discussion, the authors discussed other quiescent regulators and PTEN should be included. Also, there are reports that ATF3 and PTEN may phenocopy and regulate each other (PMID: 25531328, PMID: 27308526). These should also be discussed. + +<--- Page Split ---> + +## Point by point responses + +## Reviewer #1: + +The manuscript brings highly interesting new insight into the control of muscle stem cells quiescence and senescence, with extensive experimental data. The finding that ATF3 controls H2B expression thus preventing genome instability and replicative senescence in SCs is unexpected, novel and important. + +1.1. Has requested, I did especially look at the cut & run data. The signal to noise ratio appears to be the problem. The image in Fig 6n has low resolution, but the image in Fig 6s on the Eln gene doesn't really show peaks consistent with nucleosomes. Just a lot of noise across the gene. This makes me wonder about the quality of the data set. That being said, the cumulative data shows there is a decrease at the 5' end of the gene around the TSS (Fig 6q). This is the one thing I would say is true on the Eln gene in Figure 6S. So, overall, I would recommend that ideally the experiment should be repeated to get better signal to noise ratio before being able to state there is a loss of H2B at specific areas of the genome. + +A: We thank the reviewer for the constructive comment. We agree that the CUT&RUN experiment should be repeated to improve the signal to noise ratio. We have now repeated the experiment in FISCs from Ctrl and Atf3 iKO mice and provided data from three replicates. This time, we set a more stringent cutoff to remove low bin signals to improve the signal to noise ratio. The findings from analyzing the new datasets remain largely the same as our original one. The average H2B CUT&RUN signals were largely unaltered in the iKO vs. Ctrl. but \(93.9\%\) of the altered bins showed decreased H2B enrichment (Fig. m). When intersecting with the original RNA-Seq data, this time 137 up-regulated genes showed decreased H2B signals on their promoters or gene bodies and are known to be associated with SC activation and differentiation (Fig. r). These newly added results can be found on page 14- 15 of the revised text. + +## Reviewer #2: + +Skeletal muscles have the remarkable capacity to undergo regenerative growth in response to injury or other external stimuli. Muscle regeneration relies on activation and expansion of skeletal muscle stem cells, also known as satellite cells (SCs), residing beneath the basal lamina of myofibers, followed by differentiation into multinucleated myotubes. The mechanism for preserving the SCs population has become an attractive avenue of research for the discovery of possible therapeutic interventions for many muscle degeneration disorders. The manuscript by Zhang et al. provides some interesting aspects for SCs area. The study put multiple sets of data in mice and cells together into a story. However, the reviewer found numerous issues in the logic, data quality and conceptual novelty. + +<--- Page Split ---> + +2.1 As discuss above, the authors concluded that ATF3 preserves muscle stem cell quiescence. However, in this reviewer's view, the data did not support this concept in this paper. What the authors showed in this paper was that ATF3 was not expressed/or expressed at very low levels in SCs at quiescence state (QSC), and ATF3 is only rapidly induced upon SCs activation, even though the authors show some data suggesting that deletion of ATF3 in SCs accelerates acute injury-induced regeneration. The authors also showed many difference phenotypes between the "Short-term" and "long-term" ATF3 iKO, this could be due to many reasons, either experimental systems (such as Tamoxifen system) or chronic secondary compensation. + +A: Thanks for the critical comment. The reviewer 3 raised a similar question in his/her comment 3.1 regarding the use of "preserves quiescence" to describe ATF3 function in SCs. We now agree that it may not be accurate to describe its function as quiescence maintenance. We agree that actively maintaining the quiescence can only be executed by factors that are expressed in quiescent stage such as PTEN, Notch, FoxO and Rac. In the case of ATF3, its direct function is to suppress early activation and indirectly preserves SC quiescence. We have now revised throughout the text accordingly. + +Additionally, we don't think the observed phenotypes from our ATF3 iKO mice arise from experimental errors. As shown in Fig. 2c and Fig S4e, ATF3 protein is completely depleted in both short- term and long- term settings. + +2.2 The authors claimed that ATF3 is induced upon SCs activation, and ATF3 prevents SCs activation. However, no data to demonstrate that ATF3 overexpression is sufficient to inhibit SCs activation. + +A: Thanks for the constructive comment. We agree that is it critical to show gain of function evidence to provide solid evidence to support our argument that ATF3 actively suppresses SC activation. As suggested, we have now performed the ATF3 overexpression both in vitro and in vivo. In vitro we over- expressed ATF3 by a lentivirus in FISC. Both EdU assay and Pax7/Mydo double staining were then performed to demonstrate that indeed SC activation was inhibited by ATF3 over- expression (Fig. 3j- k). In vivo, we over- expressed ATF3 by intramuscular injection of the lentivirus at 1 dpi in both Ctrl and iKO mice and found the overexpression obviously delayed regeneration in Ctrl mice and also blunted the accelerated muscle regeneration in iKO mice. (Fig. 3l- q and Fig. S3c- e). The above findings thus strengthened our claim that ATF3 prevents SC activation. The newly added results can be found on page 10 of the revised text. + +2.3 Although the author did some interesting experiment to suggest that H2B loss in SCs results in increased genome instability and cellular senescence. In this reviewer's view, if the authors claim the liner link between ATF3 and H2B, the critical experiment would be to demonstrate that ATF3 overexpression sufficiently prevents SCs activation, and genetic loss of H2B blocks the process. + +<--- Page Split ---> + +A: Thanks for the great suggestion. We agree that it is necessary to demonstrate the functional link between ATF3 and H2B by rescue experiment. As described above in 2.2, we have now performed ATF3 over- expression to demonstrate it can prevent SC activation. We also made attempts to knockdown H2B in vitro or in vivo only to realize this is not possible because of the large quantify of H2B produced in cells. As shown in Fig. S6c, histone encoding genes are typically organized into multigene clusters and H2B protein is encoded by 2 gene clusters with 15 on Chr13 forming a Hist1h2b cluster and 2 on Chr3 forming a Hist2h2b cluster. It is thus impossible to decrease histone levels by siRNA knockdown1. In fact, it is also rare to find studies using siRNAs to knockdown H2B. To circumvent the difficulty, we instead over- expressed H2B in vitro and in vivo. In vitro we found that over- expressing H2B by a transfecting a pcDNA- H2B plasmid in FISCs indeed repressed accelerated activation of Atf3 iKO cells but no impact on Ctrl cells (Fig. 7a- b). And in vivo, we also over- expressed H2B by intramuscular injection of H2B expressing lentivirus and found that H2B overexpression indeed blunted the accelerated regeneration in Atf3- iKO mice (Fig. 7c- g). Altogether these findings validate that H2B loss indeed mediates the precocious SC activation and enhanced muscle regeneration. The newly added results can be found on page 15 of the revised text. + +2.4 There are several short- comings in the presentation of the data and data interpretation, and importantly, the lack of high quality data. For example, all IF staining data (multiple replicates of the experiment) need quantification to show statistical significance; very poor quality images in Fig. 2e, Fig. 2g, Fig. 2n and Fig. 3g......, and all the poor quality laminin stainings; the Reviewer is confusing, In Fig.1f, why the Pax7 staining is so low in QSC compare to others in the same panel? In Fig. 4d, the image suggests increased Pax7 levels in iKO at 5dpi, but the quantification data show decreased in iKO at 5dpi. + +A: Thanks for the critical comment. We apologize for the poor quality of some IF images in our original submission. We have now provided high quality images in Fig. 2e, Fig. 4c, Fig. 4f. To better show the laminin staining, we have now provided separate images in Fig. S2i, Fig. S2j, Fig. S3a, Fig. S4a, Fig. S4b, Fig. S5h, Fig. S5i, Fig. S5j and Fig. S5k. We apologize for the low Pax7 staining on QSC in Fig. 1f and have now repeated the experiment to provide images with high quality. In the original Fig.4d we apologize for using the non- representative images and have now replaced it to be consistent with the quantification data in Fig. S4a. + +2.5 Furthermore, \(N = 3\) throughout the paper, with such a small sample size for mice studies, how can the authors be certain their data is reproducible? + +A: Thanks for the critical comment. We agree that \(N = 3\) is a small number for animal experiments. Still we argue that we performed multiple sets of experiments to support each conclusion. For example, to demonstrate the defect of Atf3 iKO in SC activation, we not only used in vitro cultured SCs but also single myofibers as well as in vivo muscle sections to conduct the EdU assay; our conclusions were therefore drawn from more than 3 mice. Nevertheless, to solidify our conclusions, following the suggestion, we have now increased the sample size to five mice for experiments + +<--- Page Split ---> + +described in Fig. 2d- f, Fig. 2k, Fig. 2m, Fig. 2n, Fig. 3a- h, Fig. 4b- g, Fig. 5b- g, Fig. 5i- n, Fig. S2c- h, Fig. S3g and Fig. S5a- b. With the newly added mice, all our original conclusions remain unaltered. The corresponding figure legends have also been changed accordingly. + +2.6 The study follows work previously published by the same group, using the same dataset, the authors describe that ATF3 was induced in FISC compared to QSCs, but indeed this is also known and reported previously by other group (Machado L, et al., Cell Rep. 2017;21(7):1982-1993.). Moreover, previously study has also reported that ATF3 regulates stem cells self-renewal (Liu Y, et al., Front Cell Dev Biol. 2020;8:585771), a paper that the authors have cited. Thus, the conceptual novelty is marginal in this journal. + +A: Thanks for the critical comment but we have to disagree with the reviewer's opinion. Yes, we acknowledge that the induction of ATF3 in FISC compared to QSC has been noticed and reported by several groups (Almada AE, et al., Nat Rev Mol Cell Biol. 2016;17(5):267- 79; Machado L, et al., Cell Rep. 2017;21(7):1982- 1993; van Velthoven CTJ, et al., Cell Rep. 2017;21(7):1994- 2004; van den Brink SC, et al., Nat Methods. 2017;14(10):935- 6; Almada AE, et al., Cell Rep. 2021;34(4):108656; Barutcu, A.R., et al., Skelet Muscle. 2022;12(1):20).2- 7. However, none of these reports investigated the function of ATF3 induction in detail. We are the first one to dive in and provide a functional and mechanistic investigation of ATF3 in SCs. We also acknowledge that a prior study has reported that ATF3 regulates stem cells self-renewal (Liu Y, et al., Front Cell Dev Biol. 2020;8:585771), however, this study was performed in HSCs and the findings are different from ours. For example, the study shows that ATF3 is down- regulated after stress stimulation while in our case it is induced in FISC. ATF3 deficiency leads to enhanced proliferation and expansion of long- term repopulating hematopoietic stem cells (LT- HSCs) upon short- term chemotherapy or irradiation. The long- term reconstitution capability of LT- HSCs is dramatically impaired after a series of bone marrow transplantations, indicating that ATF3 plays a protective role in stress hematopoiesis to maintain HSC self- renewal8. These are completely different aspects of stem cell activities compared to our study. Moreover, this study provides no mechanistic insights into how ATF3 functions in HSCs while ours thoroughly elucidates the underlying mechanism of how ATF3 regulates H2B expression to function in SC activation. Therefore, we argue that our findings provide sufficient conceptual novelty not only for the field of skeletal muscle regeneration but also the stem cell field in general considering this is the first study showing an induced protein can function to actively prevent not promote stem cell activation. The above points have been included in the revised text on page 18 and page 20. + +2.7 By comparing the pre- fixed and non- fixed SCs (indeed quite an artificial system), the authors claimed that ATF3 is induced upon SCs activation. But as the authors said, AP-1 family members are very sensitive to a variety of cellular stresses and quickly induced by even slight disturbance. Therefore, it would be very important to examine whether ATF3 is induced in SCs during injury induced muscle regeneration in vivo. + +<--- Page Split ---> + +A: Thanks for the great suggestion. We agree it is important to show ATF3 induction in vivo. We have now performed IF staining on both uninjured and injured TA muscle (at various time after injury) sections. Expectedly, our data (Fig. 1h) demonstrated that ATF3 is not expressed in uninjured muscles. At 1dpi we observed increased ATF3 expression and some staining did not merge with \(\mathrm{Pa x}7+\) cell, which is in line with its ubiquitous expression in multiple cells \(^{9}\) induced by injury \(^{10}\) . At 2dpi ATF3 expression was highly increased from \(\mathrm{Pa x}7+\) cells, concomitant with the activation stage of the SCs. These results thus provide solid evidence to support ATF3 is induced upon SC activation during muscle regeneration. The newly added results can be found on page 6- 7 of the revised manuscript. + +2.8 The authors used the term "resistance exercise" to study the SCs activation. However, in page 12, the authors described a typical endurance exercise protocol that uses a treadmill set at a \(5^{\circ}\) incline and a speed of \(20 \mathrm{cm / sec}\) . This protocol is not resistance exercise. The reviewer is very confusing, since endurance exercise do not trigger SC activation and muscle hypertrophy. It would be much better to study the SCs activation of these mice with a protocol of real resistance exercise (Cui D, et al., FASEB J. 2020;34(6):7330- 7344. ). + +A: Thanks for the critical comment. We agree that the described exercise protocol should be called "endurance exercise". We are very sorry for the mistake and have now made changes in the manuscript. However, we would like to point out that endurance exercise does trigger SC activation and muscle hypertrophy according to previous reports. For example, Cisterna B. et. al showed that, endurance training of mice on a treadmill increases the activation of SCs as well as their capability to differentiate into myotubes \(^{11}\) . Fry CS. et.al; Macaluso F. et.al. Joanisse S. et.al and Mackey AL et.al all demonstrated that after different types of aerobic exercises, human muscle also showed increased SC activation, myonuclear content and fiber diameter \(^{12- 15}\) . Therefore, we think it is reasonable to use the endurance exercise in our study to demonstrate the enhanced activating ability of ATF3- iKO cells in an exercise setting. Switching to a resistance training model may take extra time which may delay the publication of the study. We hope the reviewer will find this acceptable. + +2.9 SCs undergo a self- renewal process and returns to the quiescent stage to replenish the SC pool. The authors found that deletion of ATF3 in SCs increased muscle weight and fiber size during 1st, 2nd and 3rd injury. They also showed that \(\mathrm{Pa x}7+\) cells were decreased in ATF3 KO after 3rd injury. If the authors claim that ATF3 KO exhausts SC pool, it would be at very least to examine the SC pool ( \(\mathrm{Pa x}7+\) cells) after 1st injury and 2nd injury as well. + +A: Thanks for the great suggestion. We have now examined \(\mathrm{Pa x}7+\) cell numbers after the \(1^{\mathrm{st}}\) , \(2^{\mathrm{nd}}\) and \(3^{\mathrm{rd}}\) round of injury and found that SC numbers were indeed decreased after each round of injury (Fig.2k), supporting our conclusion that ATF3 deletion leads to the exhaustion of SC pool during injury induced muscle regeneration. The newly added results can be found on page 10 of the revised text. + +<--- Page Split ---> + +2.10 The similar engraftment assay (Fig. 2l,m) need to be done to examine the regenerative ability of the iKO SCs in the "long- term" iKO mouse models. + +A: Thanks for the suggestion. We have now performed the engraftment assay after the long term ATF3 deletion. As illustrated in Fig. 4h, 4 months after TMX injection, \(\mathrm{YFP + }\) donor SCs were collected from the Ctrl or iKO mice and injected into the recipient nude mice which were pre- injured 1 day before the engraftment. 21 days later, the injected TA muscles were harvested for IF staining. A higher number of \(\mathrm{YFP + }\) myofibers were observed in the mice transplanted with the iKO vs. Ctrl SCs (Fig. 4i), ), suggesting that enhanced regenerative ability of the iKO cells persists after long term ATF3 loss and the impaired muscle regeneration indeed arises from the reduced cell pool. The newly added results are included on page 11 of the revised text. + +2.11 Figure S7. The authors performed some functional screening using the Pax7 Cas9/AAV- sgRNA mediated in vivo genome editing system. Although there are many data provided, the data do not support authors claim due to the low editing efficiency and the none- inducible SC specific deletion. + +A: Thanks for the comment. The purpose of the functional screening in Fig. S7 is to provide initial evidence for the differential roles that AP- 1 family members may play in muscle regeneration. The Pax7 Cas9/AAV- sgRNA mediated in vivo genome editing system permits efficient gene editing in quiescent SCs and was used in many of our prior publications16- 20, it is thus an acceptable approach for such screening. In Fig. S8 we demonstrate that the editing efficiency is in fact very good, 84% for ATF4, 52% for FOS, 67% for FOSB and 64% for JUNB. We acknowledge that this is not an inducible SC specific deletion which will provide more solid evidence for their roles in SCs. We have now revised the text on page 21 to point out this only serves as an initial screening and further investigation can be performed using an inducible genetic mouse model. + +2.12 The authors mislabel The Fig.1e, 1d in the text. page 6: "this was also confirmed by RT- qPCR (Fig.1e)", Fig.1e not RT- PCR. + +A: Thanks for the comment and we apologize for the mistake. We have now corrected the labeling in Fig. 1e. + +2.13 Many errors in the text. e.g. page 6: "which was also n confirmed by RT- qPCR (Fig. S1a)." + +A: Thanks for the comment. We have now gone through the entire text and corrected the errors. + +## Reviewer #3: + +This manuscript describes a novel role of the activating transcriptional factor 3 (ATF3) in muscle stem cells called satellite cells. The authors first used RNA- seq to show and immunostaining to + +<--- Page Split ---> + +confirm that Atf3 expression is transiently elevated in activated satellite cells (Fig. 1). They then generated conditional KO mice to delete Atf3 gene in quiescent satellite cells using the Pax7- CreER driver. They show that the cKO exhibited accelerated regeneration initially but regeneration declines upon repeated injury at the 3rd injury, associated with reduced myogenic cells. These results suggest a defect in self- renewal that sequentially reduces satellite cell number and regenerative capacity. Figure 3 use single fiber culture and in vivo regeneration model to confirm there is a defect in self- renewal of Atf4 KO cells as manifested by reduced Pax7+/Myod- cells, even though the cell proliferation is elevated. They then show in figure 4 a regenerative effect in response to a single bout of injury 6 months after Atf3 deletion. In Figure 5 they show that Atf3 KO satellite cells activate more readily in response to exercise. In figure 6, they use RNA- seq, CUT&RUN and ChIP- seq to bring about the idea that loss of ATF3 suppress transcription of the H2b clusters. Figure 7 demonstrate that the Atf3 null satellite cells display aggravated stress- induced DNA damage and accelerated aging phenotypes. Together, the study uses a number of omics, conditional KO, in vivo injury and exercise models to demonstrate for the first time a key role of ATF3 in satellite cells and muscle regeneration. The results are striking and based on large amount of solid data. + +3.1 I only have a main concern, which is related to the interpretation of the results that can be fixed by rewording. The title (ATF3 Preserves Skeletal Muscle Stem Cell Quiescence by Preventing Precocious Activation), the abstract, results all indicate that ATF plays a role in quiescent cells but the data appear to suggest a role of ATF3 in self- renewal (i.e. it is elevated in activated cells to force the cell back to a quiescent state). I think this concept must be clarified throughout the manuscript. + +A: Thanks for the great comment. The Reviewer 2 raised a similar concern in his/her comment 2.1. We now agree that it may not be accurate to describe ATF3 function as quiescence maintenance. We agree that actively maintaining quiescence can only be executed by factors that are expressed in quiescent stage such as PTEN, Notch, FoxO and Rac. In the case of ATF3, its direct function is to suppress early activation and indirectly preserves SC quiescence as a consequence. We have not changed the title to "ATF3 Induction Prevents Precocious Activation of Skeletal Muscle Stem Cell by Regulating H2B Expression" and revised several places throughout the text accordingly. As for its role in SC self- renewal, we did observe reduced Pax7+ cells after each of the three rounds of injuries which hinted a possible function in self- renewal upon acute regeneration. This is included on page 10 of the text. + +3.2 Related to the previous point on ATF3 expression: Fig 1g showing expression of ATF3 in satellite cells on fresh isolated myofiber suggesting its expression in quiescent cells (even though fiber isolation takes 1-2 hours that could activate cells, it takes more than two hours for a gene to be transcribed and then made into proteins). Therefore, my worry is that in situ fixation may induce artifacts in gene expression. It would have been nice if sections of non- injured and injured muscles can be used to validate or reject the conclusion that ATF3 expression is only induced by activation. + +<--- Page Split ---> + +A: Thanks for the great suggestion. This comment is also raised by reviewer 2 (comment 2.7). As stated above in our answer, we agree it is important to show ATF3 induction in vivo. We have now performed IF staining on both uninjured and injured TA muscle (at various time after injury) (Fig. 1h). Expectedly, our data indeed demonstrated that ATF3 is not expressed on uninjured muscle. At 1dpi we observed increased ATF3 expression and some staining did not merge with Pax7+ cell, which is in line with its ubiquitous expression in multiple cells 9. At 2dpi ATF3 expression was highly increased from Pax7+ cells, concomitant with the activation stage of the SCs. These results thus provide solid evidence to support ATF3 is induced upon SC activation during muscle regeneration. The newly added results can be found on page 6- 7 of the revised text. + +3.3 Still related to data interpretation: If as the authors concluded, ATF3 is not expressed in quiescent satellite cells (Fig 1b, c, d, f), then why would knock out of a non- expressed gene affect satellite cells over time? This does not make sense. It only makes sense if ATF3 is indeed expressed in the quiescent satellite cells. The authors argue that there are various stress conditions that induce activation of satellite cells but what is the threshold of such stress? Why would normal use (movements) does not induce the (activation) stress whereas exercise induce stress? Again, if ATF3 function to push stress activated satellite cells back to a quiescent state, then its function is more in line with the self- renewal function in HSC. You cannot declare that a protein function to enforce quiescence while it is not expressed in the quiescent satellite cells. + +A: Thanks for the great comment. As stated in the answer to your comment 3.1, we now agree that it may not be accurate to describe its function as quiescence maintenance. We agree that the direct function in actively maintaining the quiescence can only be executed by factors that are expressed in quiescent stage such as PTEN, Notch, FoxO and Rac. In the case of ATF3, its direct function is to suppress early activation and consequently preserves SC quiescence. We have not changed the title and revised several places throughout the text. + +Secondly, it is a great question as what kind of stress would induce activation of SCs. There is an increasing body of literature on the association of exercise and SC activation. It is now clear that short- term, non- strenuous, voluntary exercise does not disturb SC quiescence but resistance training or more intense endurance exercise can induce SC activation. It is believed that endurance exercises and strength training cause muscle fiber micro- damage thus SC activation to repair damaged fiber 21. In homeostasis, it is believed that SCs can also activate and proliferate sporadically to replace myofibres damaged by normal use of muscle e.g. daily movements or activities 22. In our next chapter of the investigation, it will be interesting to further test how and what kind of stress signaling from daily movement or normal exercise triggers SC activation via ATF3 or other early response genes. We have now added the above points on page 19- 20 of the revised text. We thank the reviewer for all these thought- provoking comments. + +3.4 Subtitles of the results section do not effectively capture the results. + +<--- Page Split ---> + +Thanks for the comment. We only made a slight change on the first subtitle on page 6 as we feel the original subtitles are OK to recapitulate the results. We are open to further suggestions from the reviewer. + +3.5 In Figure 5l, H2B is completely lost in the iKO. It is intriguing that the phenotype is so "mild" given the complete loss of H2B. On another note, the histone proteins are thought to be very stable, even a complete shutdown of H2b transcription should not deplete all H2B proteins without extensive cell division. Please clarify. + +A: Thanks for the questions. In fact, we have discussed this in the original submission. We believe proper histone gene expression and histone protein synthesis are key to nucleosome assembly and composition which in turn governs chromatin structure and gene transcription. Loss of ATF3 expectedly caused an obvious loss of H2B protein in SCs, which interestingly did not result in genome- wide decrease of H2B enrichment by CUT&RUN, suggesting genome- wide nucleosome occupancy may not be largely impacted. It is likely the reduced amount of H2B may lead to formation of non- canonical nucleosomes, for example, so called half- nucleosomes consisting of one copy of each of the four core histones or hexasomes with two copies of H3/H4 and one copy of H2A/H2B. The function of these sub- nucleosomes in transcription is still unclear, it is possible that they prevalently exist in the iKO cells and alter the overall nucleosome structure and chromatin properties, therefore explaining the overall transcriptional activation occurring in the cell. In addition, the existence of these sub- nucleosomes may also affect genomic stability and increase the propensity for DNA damage thus cellular senescence, which was indeed observed in the iKO cells. The above points can be found on page 20- 21 of the revised text. + +3.6 Abstract: "Here we report that AP- 1 family member ATF3 preserves the SC quiescence by preventing their premature activation. Atf3 is rapidly and transiently induced in SCs upon activation." Without any context the two sentences appear to contradict. If ATF3 preserves quiescence, then induction of Atf3 should enforce quiescence but not lead to activation. I suggest that these should be rewritten. + +A: Thanks for the suggestion. As stated earlier, we agree it is not accurate to describe ATF3 function as quiescence maintenance, we have revised the abstract to better summarize our findings. + +3.7 Similarly, the ending sentence of the first paragraph in Results: "Taken together, our findings show that ATF3 and several other AP- 1 family members are rapidly and transiently induced during early SC activation, suggesting the potential roles of ATF3 and other family members in the regulation of SC quiescence or early activation." Without reading discussion this sentence does not make sense at all. + +A: Thanks for the comment, we have revised this sentence on page 7 of the revised text. + +3.8 As satellite cells were increased by \(80\%\) in the Pax7- Cre KO in embryonic myoblasts, is the muscle hypertrophic in the young mice? + +<--- Page Split ---> + +A: Thanks for the great question. We have now measured the TA muscle weight of the 1-month-old mice to show that there was a decrease in cKO compared with control (Fig. S4h). We have also quantified the fiber size but found no significant difference (Fig. S4i). It is thus hard to conclude that muscle hypertrophy occurs in the young cKO mice. The results are included on page 11 of the revised manuscript. + +3.9 Also in p12: "Altogether the above results suggest an essential role of ATF3 induction in preventing precocious SC activation,.." So far the study has never shown that ATF3 induction prevents precocious activation. + +A: Thanks for the critical comment. as shown in our answer to above comment 2.2, we agree that it is necessary to show overexpressing ATF3 can repress SC activation. As suggested, we have now performed the ATF3 overexpression both in vitro and in vivo. In vitro we over- expressed ATF3 by a lentivirus in FISC. Both EdU assay and Pax7/Myod double staining were then performed to demonstrate that indeed SC activation was inhibited by ATF3 over- expression (Fig. 3j- k). In vivo, we over- expressed ATF3 by intramuscular injection of the lentivirus at 1 dpi in both Ctrl and iKO mice and found the overexpression obviously delayed regeneration in Ctrl mice and also blunted the accelerated muscle regeneration in iKO mice. (Fig. 3l- q and Fig. S3c- e). The above findings thus strengthened our claim that ATF3 prevents SC activation. The newly added results can be found on Page 10 of the revised manuscript. We also over- expressed H2B in vitro and in vivo. In vitro we found that over- expressing H2B by a transfecting a pcDNA- H2B plasmid in FISCs indeed repressed accelerated activation of Atf3 iKO cells but had no impact on Ctrl cells (Fig. 7a- b). And in vivo, we also over- expressed H2B by intramuscular injection of H2B expressing lentivirus and found that H2B overexpression indeed blunted the accelerated regeneration in Atf3- iKO mice (Fig. 7c- g). Altogether these findings validate that H2B loss indeed mediates the precocious SC activation and enhanced muscle regeneration. The newly added results can be found on Page 15 of the revised manuscript. + +3.10 P13: "These results demonstrate that the ATF3 loss decreases H2b gene expression". This is counter- intuitive as Atf3 KO leads to activation and proliferation, which require generation of new histone protein. + +A: Thanks for the critical question. As answered in comment 3.5, it is likely the reduced amount of H2B may lead to formation of non- canonical nucleosomes, for example, so called half- nucleosomes consisting of one copy of each of the four core histones or hexasomes with two copies of H3/H4 and one copy of H2A/H2B. The existence of half- nucleosomes in fact facilitates the transcription of activation/differentiation genes thus promotes SC activation. + +3.11 Full name of ATF3 should be provided at the first occurrence. ATF3 is known to activate gene expression and it is puzzling why most genes are upregulated in Atf3 KO satellite cells. Some discussion might be helpful. + +<--- Page Split ---> + +A: Thanks for the great suggestion. We have now added the full name on page 2 of the revised text. ATF3 is known to play both activating and repressing functions in cell dependent manner. ATF3 homodimers and heterodimers (with other bZip proteins) repress and induce gene expression, respectively23. For example, ATF3 can repress the expression of proinflammatory cytokines induced by the toll-like receptor 4 in the immune response24. ATF3 is induced during the early stage of paligenosis to transcriptionally activate the lysosomal trafficking gene Rab7b25. We have added the above discussion on page 4 of the revised text. + +3.12 Abstract: "which reduction accelerates nucleosome displacement and gene transcription required for SC activation". This sentence appears to have grammar issue. Change to "whose reduction" + +A: Thanks for the comment and we apologize for the mistake. We have made the change on page 2 of the revised abstract. + +3.13 The Atf3 KO phenotype is very similar to, but milder then, Pten KO phenotypes (PMID: 27880908, PMID: 28094257). In discussion, the authors discussed other quiescent regulators and PTEN should be included. Also, there are reports that ATF3 and PTEN may phenocopy and regulate each other (PMID: 25531328, PMID: 27308526). These should also be discussed. + +A: Thanks for the great suggestion. We have now included Pten in the list of SC quiescence maintenance factors on Page 19 of the revised Discussion. Nevertheless, we feel elaborated discussion on PTEN and ATF3 connection may break the logical flow of the context. + +1. Marzluff WF, Gongidi P, Woods KR, Jin J, Maltais LJ. The Human and Mouse Replication-Dependent Histone Genes. Genomics. 2002/11/01/ 2002;80(5):487-498. +2. Almada AE, Wagers AJ. Molecular circuitry of stem cell fate in skeletal muscle regeneration, ageing and disease. Nat Rev Mol Cell Biol. May 2016;17(5):267-279. +3. Machado L, Esteves de Lima J, Fabre O, et al. In Situ Fixation Redefines Quiescence and Early Activation of Skeletal Muscle Stem Cells. Cell Rep. Nov 14 2017;21(7):1982-1993. +4. van Velthoven CTJ, de Morree A, Egner IM, Brett JO, Rando TA. Transcriptional Profiling of Quiescent Muscle Stem Cells In Vivo. Cell Rep. Nov 14 2017;21(7):1994-2004. +5. van den Brink SC, Sage F, Vertesy A, et al. Single-cell sequencing reveals dissociation-induced gene expression in tissue subpopulations. Nat Methods. Sep 29 2017;14(10):935-936. +6. Almada AE, Horwitz N, Price FD, et al. FOS licenses early events in stem cell activation driving skeletal muscle regeneration. Cell Rep. Jan 26 2021;34(4):108656. +7. Barutcu AR, Elizalde G, Gonzalez AE, et al. Prolonged FOS activity disrupts a global myogenic transcriptional program by altering 3D chromatin architecture in primary muscle progenitor cells. Skeletal Muscle. 2022/08/15 2022;12(1):20. + +<--- Page Split ---> + +8. Liu Y, Chen Y, Deng X, Zhou J. ATF3 Prevents Stress-Induced Hematopoietic Stem Cell Exhaustion. Frontiers in cell and developmental biology. 2020;8:585771. + +9. Tsujino H, Kondo E, Fukuoka T, et al. Activating transcription factor 3 (ATF3) induction by axotomy in sensory and motoneurons: A novel neuronal marker of nerve injury. Mol Cell Neurosci. Feb 2000;15(2):170-182. + +10. Wanner R, Knöll B. Interference with SRF expression in skeletal muscles reduces peripheral nerve regeneration in mice. Sci Rep. Mar 24 2020;10(1):5281. + +11. Cisterna B, Giagnacovo M, Costanzo M, et al. Adapted physical exercise enhances activation and differentiation potential of satellite cells in the skeletal muscle of old mice. Journal of anatomy. May 2016;228(5):771-783. + +12. Fry CS, Noehren B, Mula J, et al. Fibre type-specific satellite cell response to aerobic training in sedentary adults. The Journal of physiology. Jun 15 2014;592(12):2625-2635. + +13. Macaluso F, Brooks NE, van de Vyver M, Van Tubbergh K, Niesler CU, Myburgh KH. Satellite cell count, VO(2max), and p38 MAPK in inactive to moderately active young men. Scandinavian journal of medicine & science in sports. Aug 2012;22(4):e38-44. + +14. Joanisse S, McKay BR, Nederveen JP, et al. Satellite cell activity, without expansion, after nonhyperprothic stimuli. American journal of physiology. Regulatory, integrative and comparative physiology. Nov 1 2015;309(9):R1101-1111. + +15. Mackey AL, Karlsen A, Coupé C, et al. Differential satellite cell density of type I and II fibres with lifelong endurance running in old men. Acta physiologica (Oxford, England). Mar 2014;210(3):612-627. + +16. He L, Ding Y, Zhao Y, et al. CRISPR/Cas9/AAV9-mediated in vivo editing identifies MYC regulation of 3D genome in skeletal muscle stem cell. Stem Cell Reports. Oct 12 2021;16(10):2442-2458. + +17. Chen X, Xue G, Zhao J, et al. Lockd promotes myoblast proliferation and muscle regeneration via binding with DHX36 to facilitate 5' UTR rG4 unwinding and Anp32e translation. Cell Reports. 2022/06/07/ 2022;39(10):110927. + +18. So KKH, Huang Y, Zhang S, et al. seRNA PAM controls skeletal muscle satellite cell proliferation and aging through trans regulation of Timp2 expression synergistically with Ddx5. Aging Cell. 2022;21(8):e13673. + +19. Zhao Y, Ding Y, He L, et al. Multiscale 3D genome reorganization during skeletal muscle stem cell lineage progression and aging. Science Advances. 2023;9(7):eab01360. + +20. Qiao Y, Sun Q, Chen X, et al. Nuclear m6A reader YTHDC1 promotes muscle stem cell activation/proliferation by regulating mRNA splicing and nuclear export. eLife. 2023/03/09 2023;12:e82703. + +21. Proske U, Morgan DL. Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications. J Physiol. Dec 1 2001;537(Pt 2):333-345. + +22. Sousa-Victor P, Garcia-Prat L, Muñoz-Canovés P. Control of satellite cell function in muscle regeneration and its disruption in ageing. Nature Reviews Molecular Cell Biology. 2022/03/01 2022;23(3):204-226. + +23. Hai T, Wolfgang CD, Marsee DK, Allen AE, Sivaprasad U. ATF3 and stress responses. Gene Expr. 1999;7(4-6):321-335. + +24. Gilchrist M, Thorsson V, Li B, et al. Systems biology approaches identify ATF3 as a negative regulator of Toll-like receptor 4. Nature. May 11 2006;441(7090):173-178. + +<--- Page Split ---> + +25. Radyk MD, Spatz LB, Peña BL, et al. ATF3 induces RAB7 to govern autodegradation in paligenosis, a conserved cell plasticity program. EMBO Rep. Sep 6 2021;22(9):e51806. + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +Cut & Run experiments have been improved as requested. + +I have no further questions. + +Reviewer #2 (Remarks to the Author): + +The authors have made a strong effort to address all of the points raised in my initial review. Their manuscript is acceptable for your journal. + +Reviewer #3 (Remarks to the Author): + +The authors did a great job addressing my concerns + +<--- Page Split ---> diff --git a/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..35518c2e2d0fc6d69e1924adbf69e0f60742de28 --- /dev/null +++ b/peer_reviews/335f0963cb80c7128945ab73d09895a86d23ca1644dcb07bab2c97a17dfd8457/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,448 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 162, 861, 220]]<|/det|> +ATF3 Induction Prevents Precocious Activation of Skeletal Muscle Stem Cell by Regulating H2B Expression + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 393, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 867, 256]]<|/det|> +The manuscript brings highly interesting new insight into the control of muscle stem cells quiescence and senescence, with extensive experimental data. The finding that ATF3 controls H2B expression thus preventing genome instability and replicative senescence + +<|ref|>text<|/ref|><|det|>[[115, 268, 428, 285]]<|/det|> +in SCs is unexpected, novel and important. + +<|ref|>text<|/ref|><|det|>[[115, 296, 867, 404]]<|/det|> +Has requested, I did especially look at the cut & run data. The signal to noise ratio appears to be the problem. The image in Fig 6n has low resolution, but the image in Fig 6s on the Eln gene doesn't really show peaks consistent with nucleosomes. Just a lot of noise across the gene. This makes me wonder about the quality of the data set. That being said, the cumulative data shows there is a decrease at the 5' end of the gene around the TSS (Fig 6q). This is the one thing I would say is true on the Eln gene in Figure 6S. + +<|ref|>text<|/ref|><|det|>[[115, 416, 861, 452]]<|/det|> +So, overall, I would recommend that ideally the experiment should be repeated to get better signal to noise ratio before being able to state there is a loss of H2B at specific areas of the genome. + +<|ref|>text<|/ref|><|det|>[[115, 492, 393, 508]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 547, 875, 693]]<|/det|> +Skeletal muscles have the remarkable capacity to undergo regenerative growth in response to injury or other external stimuli. Muscle regeneration relies on activation and expansion of skeletal muscle stem cells, also known as satellite cells (SCs), residing beneath the basal lamina of myofibers, followed by differentiation into multinucleated myotubes. The mechanism for preserving the SCs population has become an attractive avenue of research for the discovery of possible therapeutic interventions for many muscle degeneration disorders. The manuscript by Zhang et al. provides some interesting aspects for SCs area. The study put multiple sets of data in mice and cells together into a story. However, the reviewer found numerous issues in the logic, data quality and conceptual novelty. + +<|ref|>text<|/ref|><|det|>[[114, 704, 880, 886]]<|/det|> +First, I have a hard time reckoning with the main conclusion "ATF3 preserves skeletal muscle stem cell quiescence". What the authors showed in this paper was that ATF3 was not expressed/or expressed at very low levels in SCs at quiescence state (QSC), and ATF3 is only rapidly induced upon SCs activation, even though the authors showed some data suggesting that deletion of ATF3 in SCs accelerates acute injury- induced regeneration. The authors also showed many difference phenotypes between the "Shortterm" and "long- term" ATF3 iKO, this could be due to many reasons, either experimental systems (such as Tamoxifen system) or chronic secondary compensation. Moreover, the authors claimed that ATF3 is induced upon SCs activation and ATF3 prevents SCs activation. However, no data to demonstrate that ATF3 overexpression is sufficient to inhibit SCs activation. In this reviewer's view, no data support the concept in this paper. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 877, 143]]<|/det|> +The second issue is the link to H2B. If the authors claim the liner link between ATF3 and H2B, the critical experiment would be to demonstrate that ATF3 overexpression sufficiently prevents SCs activation, and genetic loss of H2B blocks the process. + +<|ref|>text<|/ref|><|det|>[[115, 155, 860, 208]]<|/det|> +The third issue is about data figures: there are many data provided; however there are several shortcomings in the presentation of the data, data interpretation, and importantly, the lack of high quality data. + +<|ref|>text<|/ref|><|det|>[[115, 220, 819, 237]]<|/det|> +Indeed, the conceptual advance that this manuscript will bring forward is also being questioned. + +<|ref|>sub_title<|/ref|><|det|>[[115, 277, 215, 293]]<|/det|> +## Major Points: + +<|ref|>text<|/ref|><|det|>[[114, 305, 881, 450]]<|/det|> +1. As discuss above, the authors concluded that ATF3 preserves muscle stem cell quiescence. However, in this reviewer's view, the data did not support this concept in this paper. What the authors showed in this paper was that ATF3 was not expressed/or expressed at very low levels in SCs at quiescence state (QSC), and ATF3 is only rapidly induced upon SCs activation, even though the authors show some data suggesting that deletion of ATF3 in SCs accelerates acute injury-induced regeneration. The authors also showed many difference phenotypes between the "Short-term" and "long-term" ATF3 iKO, this could be due to many reasons, either experimental systems (such as Tamoxifen system) or chronic secondary compensation. + +<|ref|>text<|/ref|><|det|>[[115, 461, 840, 497]]<|/det|> +2. The authors claimed that ATF3 is induced upon SCs activation, and ATF3 prevents SCs activation. However, no data to demonstrate that ATF3 overexpression is sufficient to inhibit SCs activation. + +<|ref|>text<|/ref|><|det|>[[115, 508, 856, 580]]<|/det|> +3. Although the author did some interesting experiment to suggest that H2B loss in SCs results in increased genome instability and cellular senescence. In this reviewer's view, if the authors claim the liner link between ATF3 and H2B, the critical experiment would be to demonstrate that ATF3 overexpression sufficiently prevents SCs activation, and genetic loss of H2B blocks the process. + +<|ref|>text<|/ref|><|det|>[[114, 592, 874, 700]]<|/det|> +4. There are several short-comings in the presentation of the data and data interpretation, and importantly, the lack of high quality data. For example, all IF staining data (multiple replicates of the experiment) need quantification to show statistical significance; very poor quality images in Fig. 2e, Fig. 2g, Fig. 2n and Fig. 3g....., and all the poor quality laminin stainings; the Reviewer is confusing, In Fig.1f, why the Pax7 staining is so low in QSC compare to others in the same panel? In Fig. 4d, the image suggests increased Pax7 levels in iKO at 5dpi, but the quantification data show decreased in iKO at 5dpi. + +<|ref|>text<|/ref|><|det|>[[115, 712, 876, 746]]<|/det|> +5. Furthermore, \(\mathsf{N} = 3\) throughout the paper, with such a small sample size for mice studies, how can the authors be certain their data is reproducible? + +<|ref|>text<|/ref|><|det|>[[114, 757, 868, 866]]<|/det|> +6. The study follows work previously published by the same group, using the same dataset, the authors describe that ATF3 was induced in FISC compared to QSCs, but indeed this is also known and reported previously by other group (Machado L, et al., Cell Rep. 2017;21(7):1982-1993.). Moreover, previously study has also reported that ATF3 regulates stem cells self-renewal (Liu Y, et al., Front Cell Dev Biol. 2020;8:585771), a paper that the authors have cited. Thus, the conceptual novelty is marginal in this journal. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 872, 180]]<|/det|> +7. By comparing the pre-fixed and non-fixed SCs (indeed quite an artificial system), the authors claimed that ATF3 is induced upon SCs activation. But as the authors said, AP-1 family members are very sensitive to a variety of cellular stresses and quickly induced by even slight disturbance. Therefore, it would be very important to examine whether ATF3 is induced in SCs during injury induced muscle regeneration in vivo. + +<|ref|>text<|/ref|><|det|>[[114, 191, 875, 300]]<|/det|> +8. The authors used the term "resistance exercise" to study the SCs activation. However, in page 12, the authors described a typical endurance exercise protocol that uses a treadmill set at a \(5^{\circ}\) incline and a speed of \(20 \text{cm/sec}\) . This protocol is not resistance exercise. The reviewer is very confusing, since endurance exercise do not trigger SC activation and muscle hypertrophy. It would be much better to study the SCs activation of these mice with a protocol of real resistance exercise (Cui D, et al., FASEB J. 2020;34(6):7330-7344.). + +<|ref|>text<|/ref|><|det|>[[114, 311, 875, 402]]<|/det|> +9. SCs undergo a self-renewal process and returns to the quiescent stage to replenish the SC pool. The authors found that deletion of ATF3 in SCs increased muscle weight and fiber size during 1st, 2nd and 3rd injury. They also showed that Pax7+ cells were decreased in ATF3 KO after 3rd injury. If the authors claim that ATF3 KO exhausts SC pool, it would be at very least to examine the SC pool (Pax7+ cells) after 1st injury and 2nd injury as well. + +<|ref|>text<|/ref|><|det|>[[114, 413, 872, 448]]<|/det|> +10. The similar engraftment assay (Fig. 2l,m) need to be done to examine the regenerative ability of the iKO SCs in the "long-term" iKO mouse models. + +<|ref|>text<|/ref|><|det|>[[115, 459, 840, 513]]<|/det|> +11. Figure S7. The authors performed some functional screening using the Pax7 Cas9/AAV-sgRNA mediated in vivo genome editing system. Although there are many data provided, the data do not support authors claim due to the low editing efficiency and the none-inducible SC specific deletion. + +<|ref|>sub_title<|/ref|><|det|>[[115, 555, 166, 569]]<|/det|> +## Minor: + +<|ref|>text<|/ref|><|det|>[[115, 581, 875, 616]]<|/det|> +1. The authors mislabel The Fig.1e, 1d in the text. page 6: "this was also confirmed by RT-qPCR (Fig.1e)", Fig.1e not RT-PCR. + +<|ref|>text<|/ref|><|det|>[[115, 628, 780, 645]]<|/det|> +2. Many errors in the text. e.g. page 6: "which was also n confirmed by RT-qPCR (Fig. S1a)." + +<|ref|>text<|/ref|><|det|>[[115, 684, 393, 700]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 740, 875, 904]]<|/det|> +This manuscript describes a novel role of the activating transcriptional factor 3 (ATF3) in muscle stem cells called satellite cells. The authors first used RNA-seq to show and immunostaining to confirm that Atf3 expression is transiently elevated in activated satellite cells (Fig. 1). They then generated conditional KO mice to delete Atf3 gene in quiescent satellite cells using the Pax7-CreER driver. They show that the cKO exhibited accelerated regeneration initially but regeneration declines upon repeated injury at the 3rd injury, associated with reduced myogenic cells. These results suggest a defect in self-renewal that sequentially reduces satellite cell number and regenerative capacity. Figure 3 use single fiber culture and in vivo regeneration model to confirm there is a defect in self-renewal of Atf4 KO cells as manifested by reduced Pax7+/Myod- cells, even though the cell proliferation is elevated. They then + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 875, 234]]<|/det|> +show in figure 4 a regenerative effect in response to a single bout of injury 6 months after Atf3 deletion. In Figure 5 they show that Atf3 KO satellite cells activate more readily in response to exercise. In figure 6, they use RNA- seq, CUT&RUN and ChIP- seq to bring about the idea that loss of ATF3 suppress transcription of the H2b clusters. Figure 7 demonstrate that the Atf3 null satellite cells display aggravated stress- induced DNA damage and accelerated aging phenotypes. Together, the study uses a number of omics, conditional KO, in vivo injury and exercise models to demonstrate for the first time a key role of ATF3 in satellite cells and muscle regeneration. The results are striking and based on large amount of solid data. + +<|ref|>text<|/ref|><|det|>[[114, 273, 869, 365]]<|/det|> +I only have a main concern, which is related to the interpretation of the results that can be fixed by rewording. The title (ATF3 Preserves Skeletal Muscle Stem Cell Quiescence by Preventing Precocious Activation), the abstract, results all indicate that ATF plays a role in quiescent cells but the data appear to suggest a role of ATF3 in self- renewal (i.e. it is elevated in activated cells to force the cell back to a quiescent state). I think this concept must be clarified throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 403, 881, 514]]<|/det|> +Related to the previous point on ATF3 expression: Fig 1g showing expression of ATF3 in satellite cells on fresh isolated myofiber suggesting its expression in quiescent cells (even though fiber isolation takes 1- 2 hours that could activate cells, it takes more than two hours for a gene to be transcribed and then made into proteins). Therefore, my worry is that in situ fixation may induce artifacts in gene expression. It would have been nice if sections of non- injured and injured muscles can be used to validate or reject the conclusion that ATF3 expression is only induced by activation. + +<|ref|>text<|/ref|><|det|>[[114, 552, 866, 717]]<|/det|> +Still related to data interpretation: If as the authors concluded, ATF3 is not expressed in quiescent satellite cells (Fig 1b, c, d, f), then why would knock out of a non- expressed gene affect satellite cells over time? This does not make sense. It only makes sense if ATF3 is indeed expressed in the quiescent satellite cells. The authors argue that there are various stress conditions that induce activation of satellite cells but what is the threshold of such stress? Why would normal use (movements) does not induce the (activation) stress whereas exercise induce stress? Again, if ATF3 function to push stress activated satellite cells back to a quiescent state, then its function is more in line with the self- renewal function in HSC. You cannot declare that a protein function to enforce quiescence while it is not expressed in the quiescent satellite cells. + +<|ref|>text<|/ref|><|det|>[[115, 756, 166, 771]]<|/det|> +Minor: + +<|ref|>text<|/ref|><|det|>[[115, 783, 615, 800]]<|/det|> +Subtitles of the results section do not effectively capture the results. + +<|ref|>text<|/ref|><|det|>[[115, 839, 860, 876]]<|/det|> +In Figure 5l, H2B is completely lost in the iKO. It is intriguing that the phenotype is so "mild" given the complete loss of H2B. On another note, the histone proteins are thought to be very stable, even a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 841, 125]]<|/det|> +complete shutdown of H2b transcription should not deplete all H2B proteins without extensive cell division. Please clarify. + +<|ref|>text<|/ref|><|det|>[[115, 164, 870, 237]]<|/det|> +Abstract: "Here we report that AP- 1 family member ATF3 preserves the SC quiescence by preventing their premature activation. Atf3 is rapidly and transiently induced in SCs upon activation." Without any context the two sentences appear to contradict. If ATF3 preserves quiescence then induction of Atf3 should enforce quiescence but not lead to activation. I suggest that these should be rewritten. + +<|ref|>text<|/ref|><|det|>[[115, 276, 872, 349]]<|/det|> +Similarly, the ending sentence of the first paragraph in Results: "Taken together, our findings show that ATF3 and several other AP- 1 family members are rapidly and transiently induced during early SC activation, suggesting the potential roles of ATF3 and other family members in the regulation of SC quiescence or early activation." Without reading discussion this sentence does not make sense at all. + +<|ref|>text<|/ref|><|det|>[[115, 387, 830, 423]]<|/det|> +As satellite cells were increased by \(80\%\) in the Pax7- Cre KO in embryonic myoblasts, is the muscle hypertrophic in the young mice? + +<|ref|>text<|/ref|><|det|>[[115, 462, 864, 515]]<|/det|> +Also in p12: "Altogether the above results suggest an essential role of ATF3 induction in preventing precocious SC activation,.." So far the study has never shown that ATF3 induction prevents precocious activation. + +<|ref|>text<|/ref|><|det|>[[115, 555, 855, 609]]<|/det|> +P13: "These results demonstrate that the ATF3 loss decreases H2b gene expression". This is counterintuitive as Atf3 KO leads to activation and proliferation, which require generation of new histone protein. + +<|ref|>text<|/ref|><|det|>[[115, 649, 877, 702]]<|/det|> +Full name of ATF3 should be provided at the first occurrence. ATF3 is known to activate gene expression and it is puzzling why most genes are upregulated in Atf3 KO satellite cells. Some discussion might be helpful. + +<|ref|>text<|/ref|><|det|>[[115, 742, 879, 778]]<|/det|> +Abstract: "which reduction accelerates nucleosome displacement and gene transcription required for SC activation". This sentence appears to have grammar issue. Change to "whose reduction" + +<|ref|>text<|/ref|><|det|>[[115, 817, 876, 889]]<|/det|> +The Atf3 KO phenotype is very similar to, but milder then, Pten KO phenotypes (PMID: 27880908, PMID: 28094257). In discussion, the authors discussed other quiescent regulators and PTEN should be included. Also, there are reports that ATF3 and PTEN may phenocopy and regulate each other (PMID: 25531328, PMID: 27308526). These should also be discussed. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[124, 86, 346, 103]]<|/det|> +## Point by point responses + +<|ref|>sub_title<|/ref|><|det|>[[124, 122, 230, 138]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[123, 149, 877, 228]]<|/det|> +The manuscript brings highly interesting new insight into the control of muscle stem cells quiescence and senescence, with extensive experimental data. The finding that ATF3 controls H2B expression thus preventing genome instability and replicative senescence in SCs is unexpected, novel and important. + +<|ref|>text<|/ref|><|det|>[[122, 239, 879, 397]]<|/det|> +1.1. Has requested, I did especially look at the cut & run data. The signal to noise ratio appears to be the problem. The image in Fig 6n has low resolution, but the image in Fig 6s on the Eln gene doesn't really show peaks consistent with nucleosomes. Just a lot of noise across the gene. This makes me wonder about the quality of the data set. That being said, the cumulative data shows there is a decrease at the 5' end of the gene around the TSS (Fig 6q). This is the one thing I would say is true on the Eln gene in Figure 6S. So, overall, I would recommend that ideally the experiment should be repeated to get better signal to noise ratio before being able to state there is a loss of H2B at specific areas of the genome. + +<|ref|>text<|/ref|><|det|>[[121, 408, 878, 607]]<|/det|> +A: We thank the reviewer for the constructive comment. We agree that the CUT&RUN experiment should be repeated to improve the signal to noise ratio. We have now repeated the experiment in FISCs from Ctrl and Atf3 iKO mice and provided data from three replicates. This time, we set a more stringent cutoff to remove low bin signals to improve the signal to noise ratio. The findings from analyzing the new datasets remain largely the same as our original one. The average H2B CUT&RUN signals were largely unaltered in the iKO vs. Ctrl. but \(93.9\%\) of the altered bins showed decreased H2B enrichment (Fig. m). When intersecting with the original RNA-Seq data, this time 137 up-regulated genes showed decreased H2B signals on their promoters or gene bodies and are known to be associated with SC activation and differentiation (Fig. r). These newly added results can be found on page 14- 15 of the revised text. + +<|ref|>sub_title<|/ref|><|det|>[[123, 650, 228, 666]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[122, 677, 878, 855]]<|/det|> +Skeletal muscles have the remarkable capacity to undergo regenerative growth in response to injury or other external stimuli. Muscle regeneration relies on activation and expansion of skeletal muscle stem cells, also known as satellite cells (SCs), residing beneath the basal lamina of myofibers, followed by differentiation into multinucleated myotubes. The mechanism for preserving the SCs population has become an attractive avenue of research for the discovery of possible therapeutic interventions for many muscle degeneration disorders. The manuscript by Zhang et al. provides some interesting aspects for SCs area. The study put multiple sets of data in mice and cells together into a story. However, the reviewer found numerous issues in the logic, data quality and conceptual novelty. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 85, 877, 244]]<|/det|> +2.1 As discuss above, the authors concluded that ATF3 preserves muscle stem cell quiescence. However, in this reviewer's view, the data did not support this concept in this paper. What the authors showed in this paper was that ATF3 was not expressed/or expressed at very low levels in SCs at quiescence state (QSC), and ATF3 is only rapidly induced upon SCs activation, even though the authors show some data suggesting that deletion of ATF3 in SCs accelerates acute injury-induced regeneration. The authors also showed many difference phenotypes between the "Short-term" and "long-term" ATF3 iKO, this could be due to many reasons, either experimental systems (such as Tamoxifen system) or chronic secondary compensation. + +<|ref|>text<|/ref|><|det|>[[122, 255, 875, 393]]<|/det|> +A: Thanks for the critical comment. The reviewer 3 raised a similar question in his/her comment 3.1 regarding the use of "preserves quiescence" to describe ATF3 function in SCs. We now agree that it may not be accurate to describe its function as quiescence maintenance. We agree that actively maintaining the quiescence can only be executed by factors that are expressed in quiescent stage such as PTEN, Notch, FoxO and Rac. In the case of ATF3, its direct function is to suppress early activation and indirectly preserves SC quiescence. We have now revised throughout the text accordingly. + +<|ref|>text<|/ref|><|det|>[[123, 414, 860, 472]]<|/det|> +Additionally, we don't think the observed phenotypes from our ATF3 iKO mice arise from experimental errors. As shown in Fig. 2c and Fig S4e, ATF3 protein is completely depleted in both short- term and long- term settings. + +<|ref|>text<|/ref|><|det|>[[123, 495, 852, 552]]<|/det|> +2.2 The authors claimed that ATF3 is induced upon SCs activation, and ATF3 prevents SCs activation. However, no data to demonstrate that ATF3 overexpression is sufficient to inhibit SCs activation. + +<|ref|>text<|/ref|><|det|>[[121, 564, 879, 761]]<|/det|> +A: Thanks for the constructive comment. We agree that is it critical to show gain of function evidence to provide solid evidence to support our argument that ATF3 actively suppresses SC activation. As suggested, we have now performed the ATF3 overexpression both in vitro and in vivo. In vitro we over- expressed ATF3 by a lentivirus in FISC. Both EdU assay and Pax7/Mydo double staining were then performed to demonstrate that indeed SC activation was inhibited by ATF3 over- expression (Fig. 3j- k). In vivo, we over- expressed ATF3 by intramuscular injection of the lentivirus at 1 dpi in both Ctrl and iKO mice and found the overexpression obviously delayed regeneration in Ctrl mice and also blunted the accelerated muscle regeneration in iKO mice. (Fig. 3l- q and Fig. S3c- e). The above findings thus strengthened our claim that ATF3 prevents SC activation. The newly added results can be found on page 10 of the revised text. + +<|ref|>text<|/ref|><|det|>[[123, 793, 877, 871]]<|/det|> +2.3 Although the author did some interesting experiment to suggest that H2B loss in SCs results in increased genome instability and cellular senescence. In this reviewer's view, if the authors claim the liner link between ATF3 and H2B, the critical experiment would be to demonstrate that ATF3 overexpression sufficiently prevents SCs activation, and genetic loss of H2B blocks the process. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[121, 84, 876, 384]]<|/det|> +A: Thanks for the great suggestion. We agree that it is necessary to demonstrate the functional link between ATF3 and H2B by rescue experiment. As described above in 2.2, we have now performed ATF3 over- expression to demonstrate it can prevent SC activation. We also made attempts to knockdown H2B in vitro or in vivo only to realize this is not possible because of the large quantify of H2B produced in cells. As shown in Fig. S6c, histone encoding genes are typically organized into multigene clusters and H2B protein is encoded by 2 gene clusters with 15 on Chr13 forming a Hist1h2b cluster and 2 on Chr3 forming a Hist2h2b cluster. It is thus impossible to decrease histone levels by siRNA knockdown1. In fact, it is also rare to find studies using siRNAs to knockdown H2B. To circumvent the difficulty, we instead over- expressed H2B in vitro and in vivo. In vitro we found that over- expressing H2B by a transfecting a pcDNA- H2B plasmid in FISCs indeed repressed accelerated activation of Atf3 iKO cells but no impact on Ctrl cells (Fig. 7a- b). And in vivo, we also over- expressed H2B by intramuscular injection of H2B expressing lentivirus and found that H2B overexpression indeed blunted the accelerated regeneration in Atf3- iKO mice (Fig. 7c- g). Altogether these findings validate that H2B loss indeed mediates the precocious SC activation and enhanced muscle regeneration. The newly added results can be found on page 15 of the revised text. + +<|ref|>text<|/ref|><|det|>[[121, 413, 878, 554]]<|/det|> +2.4 There are several short- comings in the presentation of the data and data interpretation, and importantly, the lack of high quality data. For example, all IF staining data (multiple replicates of the experiment) need quantification to show statistical significance; very poor quality images in Fig. 2e, Fig. 2g, Fig. 2n and Fig. 3g......, and all the poor quality laminin stainings; the Reviewer is confusing, In Fig.1f, why the Pax7 staining is so low in QSC compare to others in the same panel? In Fig. 4d, the image suggests increased Pax7 levels in iKO at 5dpi, but the quantification data show decreased in iKO at 5dpi. + +<|ref|>text<|/ref|><|det|>[[121, 564, 877, 702]]<|/det|> +A: Thanks for the critical comment. We apologize for the poor quality of some IF images in our original submission. We have now provided high quality images in Fig. 2e, Fig. 4c, Fig. 4f. To better show the laminin staining, we have now provided separate images in Fig. S2i, Fig. S2j, Fig. S3a, Fig. S4a, Fig. S4b, Fig. S5h, Fig. S5i, Fig. S5j and Fig. S5k. We apologize for the low Pax7 staining on QSC in Fig. 1f and have now repeated the experiment to provide images with high quality. In the original Fig.4d we apologize for using the non- representative images and have now replaced it to be consistent with the quantification data in Fig. S4a. + +<|ref|>text<|/ref|><|det|>[[122, 733, 857, 772]]<|/det|> +2.5 Furthermore, \(N = 3\) throughout the paper, with such a small sample size for mice studies, how can the authors be certain their data is reproducible? + +<|ref|>text<|/ref|><|det|>[[121, 782, 868, 901]]<|/det|> +A: Thanks for the critical comment. We agree that \(N = 3\) is a small number for animal experiments. Still we argue that we performed multiple sets of experiments to support each conclusion. For example, to demonstrate the defect of Atf3 iKO in SC activation, we not only used in vitro cultured SCs but also single myofibers as well as in vivo muscle sections to conduct the EdU assay; our conclusions were therefore drawn from more than 3 mice. Nevertheless, to solidify our conclusions, following the suggestion, we have now increased the sample size to five mice for experiments + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[123, 85, 861, 144]]<|/det|> +described in Fig. 2d- f, Fig. 2k, Fig. 2m, Fig. 2n, Fig. 3a- h, Fig. 4b- g, Fig. 5b- g, Fig. 5i- n, Fig. S2c- h, Fig. S3g and Fig. S5a- b. With the newly added mice, all our original conclusions remain unaltered. The corresponding figure legends have also been changed accordingly. + +<|ref|>text<|/ref|><|det|>[[123, 175, 869, 292]]<|/det|> +2.6 The study follows work previously published by the same group, using the same dataset, the authors describe that ATF3 was induced in FISC compared to QSCs, but indeed this is also known and reported previously by other group (Machado L, et al., Cell Rep. 2017;21(7):1982-1993.). Moreover, previously study has also reported that ATF3 regulates stem cells self-renewal (Liu Y, et al., Front Cell Dev Biol. 2020;8:585771), a paper that the authors have cited. Thus, the conceptual novelty is marginal in this journal. + +<|ref|>text<|/ref|><|det|>[[121, 303, 877, 744]]<|/det|> +A: Thanks for the critical comment but we have to disagree with the reviewer's opinion. Yes, we acknowledge that the induction of ATF3 in FISC compared to QSC has been noticed and reported by several groups (Almada AE, et al., Nat Rev Mol Cell Biol. 2016;17(5):267- 79; Machado L, et al., Cell Rep. 2017;21(7):1982- 1993; van Velthoven CTJ, et al., Cell Rep. 2017;21(7):1994- 2004; van den Brink SC, et al., Nat Methods. 2017;14(10):935- 6; Almada AE, et al., Cell Rep. 2021;34(4):108656; Barutcu, A.R., et al., Skelet Muscle. 2022;12(1):20).2- 7. However, none of these reports investigated the function of ATF3 induction in detail. We are the first one to dive in and provide a functional and mechanistic investigation of ATF3 in SCs. We also acknowledge that a prior study has reported that ATF3 regulates stem cells self-renewal (Liu Y, et al., Front Cell Dev Biol. 2020;8:585771), however, this study was performed in HSCs and the findings are different from ours. For example, the study shows that ATF3 is down- regulated after stress stimulation while in our case it is induced in FISC. ATF3 deficiency leads to enhanced proliferation and expansion of long- term repopulating hematopoietic stem cells (LT- HSCs) upon short- term chemotherapy or irradiation. The long- term reconstitution capability of LT- HSCs is dramatically impaired after a series of bone marrow transplantations, indicating that ATF3 plays a protective role in stress hematopoiesis to maintain HSC self- renewal8. These are completely different aspects of stem cell activities compared to our study. Moreover, this study provides no mechanistic insights into how ATF3 functions in HSCs while ours thoroughly elucidates the underlying mechanism of how ATF3 regulates H2B expression to function in SC activation. Therefore, we argue that our findings provide sufficient conceptual novelty not only for the field of skeletal muscle regeneration but also the stem cell field in general considering this is the first study showing an induced protein can function to actively prevent not promote stem cell activation. The above points have been included in the revised text on page 18 and page 20. + +<|ref|>text<|/ref|><|det|>[[123, 773, 877, 872]]<|/det|> +2.7 By comparing the pre- fixed and non- fixed SCs (indeed quite an artificial system), the authors claimed that ATF3 is induced upon SCs activation. But as the authors said, AP-1 family members are very sensitive to a variety of cellular stresses and quickly induced by even slight disturbance. Therefore, it would be very important to examine whether ATF3 is induced in SCs during injury induced muscle regeneration in vivo. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 84, 877, 265]]<|/det|> +A: Thanks for the great suggestion. We agree it is important to show ATF3 induction in vivo. We have now performed IF staining on both uninjured and injured TA muscle (at various time after injury) sections. Expectedly, our data (Fig. 1h) demonstrated that ATF3 is not expressed in uninjured muscles. At 1dpi we observed increased ATF3 expression and some staining did not merge with \(\mathrm{Pa x}7+\) cell, which is in line with its ubiquitous expression in multiple cells \(^{9}\) induced by injury \(^{10}\) . At 2dpi ATF3 expression was highly increased from \(\mathrm{Pa x}7+\) cells, concomitant with the activation stage of the SCs. These results thus provide solid evidence to support ATF3 is induced upon SC activation during muscle regeneration. The newly added results can be found on page 6- 7 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[123, 294, 866, 413]]<|/det|> +2.8 The authors used the term "resistance exercise" to study the SCs activation. However, in page 12, the authors described a typical endurance exercise protocol that uses a treadmill set at a \(5^{\circ}\) incline and a speed of \(20 \mathrm{cm / sec}\) . This protocol is not resistance exercise. The reviewer is very confusing, since endurance exercise do not trigger SC activation and muscle hypertrophy. It would be much better to study the SCs activation of these mice with a protocol of real resistance exercise (Cui D, et al., FASEB J. 2020;34(6):7330- 7344. ). + +<|ref|>text<|/ref|><|det|>[[121, 424, 875, 662]]<|/det|> +A: Thanks for the critical comment. We agree that the described exercise protocol should be called "endurance exercise". We are very sorry for the mistake and have now made changes in the manuscript. However, we would like to point out that endurance exercise does trigger SC activation and muscle hypertrophy according to previous reports. For example, Cisterna B. et. al showed that, endurance training of mice on a treadmill increases the activation of SCs as well as their capability to differentiate into myotubes \(^{11}\) . Fry CS. et.al; Macaluso F. et.al. Joanisse S. et.al and Mackey AL et.al all demonstrated that after different types of aerobic exercises, human muscle also showed increased SC activation, myonuclear content and fiber diameter \(^{12- 15}\) . Therefore, we think it is reasonable to use the endurance exercise in our study to demonstrate the enhanced activating ability of ATF3- iKO cells in an exercise setting. Switching to a resistance training model may take extra time which may delay the publication of the study. We hope the reviewer will find this acceptable. + +<|ref|>text<|/ref|><|det|>[[122, 694, 877, 790]]<|/det|> +2.9 SCs undergo a self- renewal process and returns to the quiescent stage to replenish the SC pool. The authors found that deletion of ATF3 in SCs increased muscle weight and fiber size during 1st, 2nd and 3rd injury. They also showed that \(\mathrm{Pa x}7+\) cells were decreased in ATF3 KO after 3rd injury. If the authors claim that ATF3 KO exhausts SC pool, it would be at very least to examine the SC pool ( \(\mathrm{Pa x}7+\) cells) after 1st injury and 2nd injury as well. + +<|ref|>text<|/ref|><|det|>[[121, 802, 877, 900]]<|/det|> +A: Thanks for the great suggestion. We have now examined \(\mathrm{Pa x}7+\) cell numbers after the \(1^{\mathrm{st}}\) , \(2^{\mathrm{nd}}\) and \(3^{\mathrm{rd}}\) round of injury and found that SC numbers were indeed decreased after each round of injury (Fig.2k), supporting our conclusion that ATF3 deletion leads to the exhaustion of SC pool during injury induced muscle regeneration. The newly added results can be found on page 10 of the revised text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[123, 105, 876, 144]]<|/det|> +2.10 The similar engraftment assay (Fig. 2l,m) need to be done to examine the regenerative ability of the iKO SCs in the "long- term" iKO mouse models. + +<|ref|>text<|/ref|><|det|>[[122, 154, 876, 313]]<|/det|> +A: Thanks for the suggestion. We have now performed the engraftment assay after the long term ATF3 deletion. As illustrated in Fig. 4h, 4 months after TMX injection, \(\mathrm{YFP + }\) donor SCs were collected from the Ctrl or iKO mice and injected into the recipient nude mice which were pre- injured 1 day before the engraftment. 21 days later, the injected TA muscles were harvested for IF staining. A higher number of \(\mathrm{YFP + }\) myofibers were observed in the mice transplanted with the iKO vs. Ctrl SCs (Fig. 4i), ), suggesting that enhanced regenerative ability of the iKO cells persists after long term ATF3 loss and the impaired muscle regeneration indeed arises from the reduced cell pool. The newly added results are included on page 11 of the revised text. + +<|ref|>text<|/ref|><|det|>[[123, 343, 875, 403]]<|/det|> +2.11 Figure S7. The authors performed some functional screening using the Pax7 Cas9/AAV- sgRNA mediated in vivo genome editing system. Although there are many data provided, the data do not support authors claim due to the low editing efficiency and the none- inducible SC specific deletion. + +<|ref|>text<|/ref|><|det|>[[122, 411, 877, 592]]<|/det|> +A: Thanks for the comment. The purpose of the functional screening in Fig. S7 is to provide initial evidence for the differential roles that AP- 1 family members may play in muscle regeneration. The Pax7 Cas9/AAV- sgRNA mediated in vivo genome editing system permits efficient gene editing in quiescent SCs and was used in many of our prior publications16- 20, it is thus an acceptable approach for such screening. In Fig. S8 we demonstrate that the editing efficiency is in fact very good, 84% for ATF4, 52% for FOS, 67% for FOSB and 64% for JUNB. We acknowledge that this is not an inducible SC specific deletion which will provide more solid evidence for their roles in SCs. We have now revised the text on page 21 to point out this only serves as an initial screening and further investigation can be performed using an inducible genetic mouse model. + +<|ref|>text<|/ref|><|det|>[[123, 622, 868, 661]]<|/det|> +2.12 The authors mislabel The Fig.1e, 1d in the text. page 6: "this was also confirmed by RT- qPCR (Fig.1e)", Fig.1e not RT- PCR. + +<|ref|>text<|/ref|><|det|>[[123, 671, 875, 710]]<|/det|> +A: Thanks for the comment and we apologize for the mistake. We have now corrected the labeling in Fig. 1e. + +<|ref|>text<|/ref|><|det|>[[123, 741, 840, 760]]<|/det|> +2.13 Many errors in the text. e.g. page 6: "which was also n confirmed by RT- qPCR (Fig. S1a)." + +<|ref|>text<|/ref|><|det|>[[123, 771, 842, 789]]<|/det|> +A: Thanks for the comment. We have now gone through the entire text and corrected the errors. + +<|ref|>sub_title<|/ref|><|det|>[[123, 831, 229, 848]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[123, 859, 844, 898]]<|/det|> +This manuscript describes a novel role of the activating transcriptional factor 3 (ATF3) in muscle stem cells called satellite cells. The authors first used RNA- seq to show and immunostaining to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 85, 880, 384]]<|/det|> +confirm that Atf3 expression is transiently elevated in activated satellite cells (Fig. 1). They then generated conditional KO mice to delete Atf3 gene in quiescent satellite cells using the Pax7- CreER driver. They show that the cKO exhibited accelerated regeneration initially but regeneration declines upon repeated injury at the 3rd injury, associated with reduced myogenic cells. These results suggest a defect in self- renewal that sequentially reduces satellite cell number and regenerative capacity. Figure 3 use single fiber culture and in vivo regeneration model to confirm there is a defect in self- renewal of Atf4 KO cells as manifested by reduced Pax7+/Myod- cells, even though the cell proliferation is elevated. They then show in figure 4 a regenerative effect in response to a single bout of injury 6 months after Atf3 deletion. In Figure 5 they show that Atf3 KO satellite cells activate more readily in response to exercise. In figure 6, they use RNA- seq, CUT&RUN and ChIP- seq to bring about the idea that loss of ATF3 suppress transcription of the H2b clusters. Figure 7 demonstrate that the Atf3 null satellite cells display aggravated stress- induced DNA damage and accelerated aging phenotypes. Together, the study uses a number of omics, conditional KO, in vivo injury and exercise models to demonstrate for the first time a key role of ATF3 in satellite cells and muscle regeneration. The results are striking and based on large amount of solid data. + +<|ref|>text<|/ref|><|det|>[[123, 424, 876, 523]]<|/det|> +3.1 I only have a main concern, which is related to the interpretation of the results that can be fixed by rewording. The title (ATF3 Preserves Skeletal Muscle Stem Cell Quiescence by Preventing Precocious Activation), the abstract, results all indicate that ATF plays a role in quiescent cells but the data appear to suggest a role of ATF3 in self- renewal (i.e. it is elevated in activated cells to force the cell back to a quiescent state). I think this concept must be clarified throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[122, 533, 879, 731]]<|/det|> +A: Thanks for the great comment. The Reviewer 2 raised a similar concern in his/her comment 2.1. We now agree that it may not be accurate to describe ATF3 function as quiescence maintenance. We agree that actively maintaining quiescence can only be executed by factors that are expressed in quiescent stage such as PTEN, Notch, FoxO and Rac. In the case of ATF3, its direct function is to suppress early activation and indirectly preserves SC quiescence as a consequence. We have not changed the title to "ATF3 Induction Prevents Precocious Activation of Skeletal Muscle Stem Cell by Regulating H2B Expression" and revised several places throughout the text accordingly. As for its role in SC self- renewal, we did observe reduced Pax7+ cells after each of the three rounds of injuries which hinted a possible function in self- renewal upon acute regeneration. This is included on page 10 of the text. + +<|ref|>text<|/ref|><|det|>[[123, 772, 876, 890]]<|/det|> +3.2 Related to the previous point on ATF3 expression: Fig 1g showing expression of ATF3 in satellite cells on fresh isolated myofiber suggesting its expression in quiescent cells (even though fiber isolation takes 1-2 hours that could activate cells, it takes more than two hours for a gene to be transcribed and then made into proteins). Therefore, my worry is that in situ fixation may induce artifacts in gene expression. It would have been nice if sections of non- injured and injured muscles can be used to validate or reject the conclusion that ATF3 expression is only induced by activation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 84, 877, 264]]<|/det|> +A: Thanks for the great suggestion. This comment is also raised by reviewer 2 (comment 2.7). As stated above in our answer, we agree it is important to show ATF3 induction in vivo. We have now performed IF staining on both uninjured and injured TA muscle (at various time after injury) (Fig. 1h). Expectedly, our data indeed demonstrated that ATF3 is not expressed on uninjured muscle. At 1dpi we observed increased ATF3 expression and some staining did not merge with Pax7+ cell, which is in line with its ubiquitous expression in multiple cells 9. At 2dpi ATF3 expression was highly increased from Pax7+ cells, concomitant with the activation stage of the SCs. These results thus provide solid evidence to support ATF3 is induced upon SC activation during muscle regeneration. The newly added results can be found on page 6- 7 of the revised text. + +<|ref|>text<|/ref|><|det|>[[122, 275, 880, 453]]<|/det|> +3.3 Still related to data interpretation: If as the authors concluded, ATF3 is not expressed in quiescent satellite cells (Fig 1b, c, d, f), then why would knock out of a non- expressed gene affect satellite cells over time? This does not make sense. It only makes sense if ATF3 is indeed expressed in the quiescent satellite cells. The authors argue that there are various stress conditions that induce activation of satellite cells but what is the threshold of such stress? Why would normal use (movements) does not induce the (activation) stress whereas exercise induce stress? Again, if ATF3 function to push stress activated satellite cells back to a quiescent state, then its function is more in line with the self- renewal function in HSC. You cannot declare that a protein function to enforce quiescence while it is not expressed in the quiescent satellite cells. + +<|ref|>text<|/ref|><|det|>[[122, 464, 878, 582]]<|/det|> +A: Thanks for the great comment. As stated in the answer to your comment 3.1, we now agree that it may not be accurate to describe its function as quiescence maintenance. We agree that the direct function in actively maintaining the quiescence can only be executed by factors that are expressed in quiescent stage such as PTEN, Notch, FoxO and Rac. In the case of ATF3, its direct function is to suppress early activation and consequently preserves SC quiescence. We have not changed the title and revised several places throughout the text. + +<|ref|>text<|/ref|><|det|>[[122, 593, 876, 812]]<|/det|> +Secondly, it is a great question as what kind of stress would induce activation of SCs. There is an increasing body of literature on the association of exercise and SC activation. It is now clear that short- term, non- strenuous, voluntary exercise does not disturb SC quiescence but resistance training or more intense endurance exercise can induce SC activation. It is believed that endurance exercises and strength training cause muscle fiber micro- damage thus SC activation to repair damaged fiber 21. In homeostasis, it is believed that SCs can also activate and proliferate sporadically to replace myofibres damaged by normal use of muscle e.g. daily movements or activities 22. In our next chapter of the investigation, it will be interesting to further test how and what kind of stress signaling from daily movement or normal exercise triggers SC activation via ATF3 or other early response genes. We have now added the above points on page 19- 20 of the revised text. We thank the reviewer for all these thought- provoking comments. + +<|ref|>text<|/ref|><|det|>[[123, 854, 657, 872]]<|/det|> +3.4 Subtitles of the results section do not effectively capture the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[123, 85, 875, 143]]<|/det|> +Thanks for the comment. We only made a slight change on the first subtitle on page 6 as we feel the original subtitles are OK to recapitulate the results. We are open to further suggestions from the reviewer. + +<|ref|>text<|/ref|><|det|>[[123, 175, 877, 253]]<|/det|> +3.5 In Figure 5l, H2B is completely lost in the iKO. It is intriguing that the phenotype is so "mild" given the complete loss of H2B. On another note, the histone proteins are thought to be very stable, even a complete shutdown of H2b transcription should not deplete all H2B proteins without extensive cell division. Please clarify. + +<|ref|>text<|/ref|><|det|>[[121, 264, 877, 543]]<|/det|> +A: Thanks for the questions. In fact, we have discussed this in the original submission. We believe proper histone gene expression and histone protein synthesis are key to nucleosome assembly and composition which in turn governs chromatin structure and gene transcription. Loss of ATF3 expectedly caused an obvious loss of H2B protein in SCs, which interestingly did not result in genome- wide decrease of H2B enrichment by CUT&RUN, suggesting genome- wide nucleosome occupancy may not be largely impacted. It is likely the reduced amount of H2B may lead to formation of non- canonical nucleosomes, for example, so called half- nucleosomes consisting of one copy of each of the four core histones or hexasomes with two copies of H3/H4 and one copy of H2A/H2B. The function of these sub- nucleosomes in transcription is still unclear, it is possible that they prevalently exist in the iKO cells and alter the overall nucleosome structure and chromatin properties, therefore explaining the overall transcriptional activation occurring in the cell. In addition, the existence of these sub- nucleosomes may also affect genomic stability and increase the propensity for DNA damage thus cellular senescence, which was indeed observed in the iKO cells. The above points can be found on page 20- 21 of the revised text. + +<|ref|>text<|/ref|><|det|>[[122, 564, 877, 661]]<|/det|> +3.6 Abstract: "Here we report that AP- 1 family member ATF3 preserves the SC quiescence by preventing their premature activation. Atf3 is rapidly and transiently induced in SCs upon activation." Without any context the two sentences appear to contradict. If ATF3 preserves quiescence, then induction of Atf3 should enforce quiescence but not lead to activation. I suggest that these should be rewritten. + +<|ref|>text<|/ref|><|det|>[[122, 665, 875, 702]]<|/det|> +A: Thanks for the suggestion. As stated earlier, we agree it is not accurate to describe ATF3 function as quiescence maintenance, we have revised the abstract to better summarize our findings. + +<|ref|>text<|/ref|><|det|>[[122, 725, 870, 821]]<|/det|> +3.7 Similarly, the ending sentence of the first paragraph in Results: "Taken together, our findings show that ATF3 and several other AP- 1 family members are rapidly and transiently induced during early SC activation, suggesting the potential roles of ATF3 and other family members in the regulation of SC quiescence or early activation." Without reading discussion this sentence does not make sense at all. + +<|ref|>text<|/ref|><|det|>[[120, 834, 787, 852]]<|/det|> +A: Thanks for the comment, we have revised this sentence on page 7 of the revised text. + +<|ref|>text<|/ref|><|det|>[[122, 875, 839, 911]]<|/det|> +3.8 As satellite cells were increased by \(80\%\) in the Pax7- Cre KO in embryonic myoblasts, is the muscle hypertrophic in the young mice? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 85, 870, 183]]<|/det|> +A: Thanks for the great question. We have now measured the TA muscle weight of the 1-month-old mice to show that there was a decrease in cKO compared with control (Fig. S4h). We have also quantified the fiber size but found no significant difference (Fig. S4i). It is thus hard to conclude that muscle hypertrophy occurs in the young cKO mice. The results are included on page 11 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[123, 205, 822, 263]]<|/det|> +3.9 Also in p12: "Altogether the above results suggest an essential role of ATF3 induction in preventing precocious SC activation,.." So far the study has never shown that ATF3 induction prevents precocious activation. + +<|ref|>text<|/ref|><|det|>[[121, 275, 877, 593]]<|/det|> +A: Thanks for the critical comment. as shown in our answer to above comment 2.2, we agree that it is necessary to show overexpressing ATF3 can repress SC activation. As suggested, we have now performed the ATF3 overexpression both in vitro and in vivo. In vitro we over- expressed ATF3 by a lentivirus in FISC. Both EdU assay and Pax7/Myod double staining were then performed to demonstrate that indeed SC activation was inhibited by ATF3 over- expression (Fig. 3j- k). In vivo, we over- expressed ATF3 by intramuscular injection of the lentivirus at 1 dpi in both Ctrl and iKO mice and found the overexpression obviously delayed regeneration in Ctrl mice and also blunted the accelerated muscle regeneration in iKO mice. (Fig. 3l- q and Fig. S3c- e). The above findings thus strengthened our claim that ATF3 prevents SC activation. The newly added results can be found on Page 10 of the revised manuscript. We also over- expressed H2B in vitro and in vivo. In vitro we found that over- expressing H2B by a transfecting a pcDNA- H2B plasmid in FISCs indeed repressed accelerated activation of Atf3 iKO cells but had no impact on Ctrl cells (Fig. 7a- b). And in vivo, we also over- expressed H2B by intramuscular injection of H2B expressing lentivirus and found that H2B overexpression indeed blunted the accelerated regeneration in Atf3- iKO mice (Fig. 7c- g). Altogether these findings validate that H2B loss indeed mediates the precocious SC activation and enhanced muscle regeneration. The newly added results can be found on Page 15 of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[123, 614, 866, 672]]<|/det|> +3.10 P13: "These results demonstrate that the ATF3 loss decreases H2b gene expression". This is counter- intuitive as Atf3 KO leads to activation and proliferation, which require generation of new histone protein. + +<|ref|>text<|/ref|><|det|>[[122, 684, 875, 782]]<|/det|> +A: Thanks for the critical question. As answered in comment 3.5, it is likely the reduced amount of H2B may lead to formation of non- canonical nucleosomes, for example, so called half- nucleosomes consisting of one copy of each of the four core histones or hexasomes with two copies of H3/H4 and one copy of H2A/H2B. The existence of half- nucleosomes in fact facilitates the transcription of activation/differentiation genes thus promotes SC activation. + +<|ref|>text<|/ref|><|det|>[[123, 814, 865, 872]]<|/det|> +3.11 Full name of ATF3 should be provided at the first occurrence. ATF3 is known to activate gene expression and it is puzzling why most genes are upregulated in Atf3 KO satellite cells. Some discussion might be helpful. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 84, 875, 223]]<|/det|> +A: Thanks for the great suggestion. We have now added the full name on page 2 of the revised text. ATF3 is known to play both activating and repressing functions in cell dependent manner. ATF3 homodimers and heterodimers (with other bZip proteins) repress and induce gene expression, respectively23. For example, ATF3 can repress the expression of proinflammatory cytokines induced by the toll-like receptor 4 in the immune response24. ATF3 is induced during the early stage of paligenosis to transcriptionally activate the lysosomal trafficking gene Rab7b25. We have added the above discussion on page 4 of the revised text. + +<|ref|>text<|/ref|><|det|>[[123, 244, 830, 302]]<|/det|> +3.12 Abstract: "which reduction accelerates nucleosome displacement and gene transcription required for SC activation". This sentence appears to have grammar issue. Change to "whose reduction" + +<|ref|>text<|/ref|><|det|>[[123, 314, 872, 351]]<|/det|> +A: Thanks for the comment and we apologize for the mistake. We have made the change on page 2 of the revised abstract. + +<|ref|>text<|/ref|><|det|>[[123, 373, 877, 451]]<|/det|> +3.13 The Atf3 KO phenotype is very similar to, but milder then, Pten KO phenotypes (PMID: 27880908, PMID: 28094257). In discussion, the authors discussed other quiescent regulators and PTEN should be included. Also, there are reports that ATF3 and PTEN may phenocopy and regulate each other (PMID: 25531328, PMID: 27308526). These should also be discussed. + +<|ref|>text<|/ref|><|det|>[[123, 463, 820, 521]]<|/det|> +A: Thanks for the great suggestion. We have now included Pten in the list of SC quiescence maintenance factors on Page 19 of the revised Discussion. Nevertheless, we feel elaborated discussion on PTEN and ATF3 connection may break the logical flow of the context. + +<|ref|>text<|/ref|><|det|>[[120, 561, 877, 875]]<|/det|> +1. Marzluff WF, Gongidi P, Woods KR, Jin J, Maltais LJ. The Human and Mouse Replication-Dependent Histone Genes. Genomics. 2002/11/01/ 2002;80(5):487-498. +2. Almada AE, Wagers AJ. Molecular circuitry of stem cell fate in skeletal muscle regeneration, ageing and disease. Nat Rev Mol Cell Biol. May 2016;17(5):267-279. +3. Machado L, Esteves de Lima J, Fabre O, et al. In Situ Fixation Redefines Quiescence and Early Activation of Skeletal Muscle Stem Cells. Cell Rep. Nov 14 2017;21(7):1982-1993. +4. van Velthoven CTJ, de Morree A, Egner IM, Brett JO, Rando TA. Transcriptional Profiling of Quiescent Muscle Stem Cells In Vivo. Cell Rep. Nov 14 2017;21(7):1994-2004. +5. van den Brink SC, Sage F, Vertesy A, et al. Single-cell sequencing reveals dissociation-induced gene expression in tissue subpopulations. Nat Methods. Sep 29 2017;14(10):935-936. +6. Almada AE, Horwitz N, Price FD, et al. FOS licenses early events in stem cell activation driving skeletal muscle regeneration. Cell Rep. Jan 26 2021;34(4):108656. +7. Barutcu AR, Elizalde G, Gonzalez AE, et al. Prolonged FOS activity disrupts a global myogenic transcriptional program by altering 3D chromatin architecture in primary muscle progenitor cells. Skeletal Muscle. 2022/08/15 2022;12(1):20. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[120, 85, 875, 120]]<|/det|> +8. Liu Y, Chen Y, Deng X, Zhou J. ATF3 Prevents Stress-Induced Hematopoietic Stem Cell Exhaustion. Frontiers in cell and developmental biology. 2020;8:585771. + +<|ref|>text<|/ref|><|det|>[[120, 123, 875, 175]]<|/det|> +9. Tsujino H, Kondo E, Fukuoka T, et al. Activating transcription factor 3 (ATF3) induction by axotomy in sensory and motoneurons: A novel neuronal marker of nerve injury. Mol Cell Neurosci. Feb 2000;15(2):170-182. + +<|ref|>text<|/ref|><|det|>[[120, 179, 850, 213]]<|/det|> +10. Wanner R, Knöll B. Interference with SRF expression in skeletal muscles reduces peripheral nerve regeneration in mice. Sci Rep. Mar 24 2020;10(1):5281. + +<|ref|>text<|/ref|><|det|>[[120, 216, 875, 268]]<|/det|> +11. Cisterna B, Giagnacovo M, Costanzo M, et al. Adapted physical exercise enhances activation and differentiation potential of satellite cells in the skeletal muscle of old mice. Journal of anatomy. May 2016;228(5):771-783. + +<|ref|>text<|/ref|><|det|>[[120, 272, 875, 305]]<|/det|> +12. Fry CS, Noehren B, Mula J, et al. Fibre type-specific satellite cell response to aerobic training in sedentary adults. The Journal of physiology. Jun 15 2014;592(12):2625-2635. + +<|ref|>text<|/ref|><|det|>[[120, 309, 875, 360]]<|/det|> +13. Macaluso F, Brooks NE, van de Vyver M, Van Tubbergh K, Niesler CU, Myburgh KH. Satellite cell count, VO(2max), and p38 MAPK in inactive to moderately active young men. Scandinavian journal of medicine & science in sports. Aug 2012;22(4):e38-44. + +<|ref|>text<|/ref|><|det|>[[120, 364, 875, 416]]<|/det|> +14. Joanisse S, McKay BR, Nederveen JP, et al. Satellite cell activity, without expansion, after nonhyperprothic stimuli. American journal of physiology. Regulatory, integrative and comparative physiology. Nov 1 2015;309(9):R1101-1111. + +<|ref|>text<|/ref|><|det|>[[120, 420, 875, 471]]<|/det|> +15. Mackey AL, Karlsen A, Coupé C, et al. Differential satellite cell density of type I and II fibres with lifelong endurance running in old men. Acta physiologica (Oxford, England). Mar 2014;210(3):612-627. + +<|ref|>text<|/ref|><|det|>[[120, 475, 875, 527]]<|/det|> +16. He L, Ding Y, Zhao Y, et al. CRISPR/Cas9/AAV9-mediated in vivo editing identifies MYC regulation of 3D genome in skeletal muscle stem cell. Stem Cell Reports. Oct 12 2021;16(10):2442-2458. + +<|ref|>text<|/ref|><|det|>[[120, 531, 875, 583]]<|/det|> +17. Chen X, Xue G, Zhao J, et al. Lockd promotes myoblast proliferation and muscle regeneration via binding with DHX36 to facilitate 5' UTR rG4 unwinding and Anp32e translation. Cell Reports. 2022/06/07/ 2022;39(10):110927. + +<|ref|>text<|/ref|><|det|>[[120, 586, 875, 638]]<|/det|> +18. So KKH, Huang Y, Zhang S, et al. seRNA PAM controls skeletal muscle satellite cell proliferation and aging through trans regulation of Timp2 expression synergistically with Ddx5. Aging Cell. 2022;21(8):e13673. + +<|ref|>text<|/ref|><|det|>[[120, 642, 875, 675]]<|/det|> +19. Zhao Y, Ding Y, He L, et al. Multiscale 3D genome reorganization during skeletal muscle stem cell lineage progression and aging. Science Advances. 2023;9(7):eab01360. + +<|ref|>text<|/ref|><|det|>[[120, 679, 866, 730]]<|/det|> +20. Qiao Y, Sun Q, Chen X, et al. Nuclear m6A reader YTHDC1 promotes muscle stem cell activation/proliferation by regulating mRNA splicing and nuclear export. eLife. 2023/03/09 2023;12:e82703. + +<|ref|>text<|/ref|><|det|>[[120, 734, 875, 768]]<|/det|> +21. Proske U, Morgan DL. Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications. J Physiol. Dec 1 2001;537(Pt 2):333-345. + +<|ref|>text<|/ref|><|det|>[[120, 772, 877, 823]]<|/det|> +22. Sousa-Victor P, Garcia-Prat L, Muñoz-Canovés P. Control of satellite cell function in muscle regeneration and its disruption in ageing. Nature Reviews Molecular Cell Biology. 2022/03/01 2022;23(3):204-226. + +<|ref|>text<|/ref|><|det|>[[120, 828, 875, 861]]<|/det|> +23. Hai T, Wolfgang CD, Marsee DK, Allen AE, Sivaprasad U. ATF3 and stress responses. Gene Expr. 1999;7(4-6):321-335. + +<|ref|>text<|/ref|><|det|>[[120, 865, 875, 899]]<|/det|> +24. Gilchrist M, Thorsson V, Li B, et al. Systems biology approaches identify ATF3 as a negative regulator of Toll-like receptor 4. Nature. May 11 2006;441(7090):173-178. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[121, 87, 872, 120]]<|/det|> +25. Radyk MD, Spatz LB, Peña BL, et al. ATF3 induces RAB7 to govern autodegradation in paligenosis, a conserved cell plasticity program. EMBO Rep. Sep 6 2021;22(9):e51806. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 300, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 146, 394, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 203, 544, 220]]<|/det|> +Cut & Run experiments have been improved as requested. + +<|ref|>text<|/ref|><|det|>[[115, 232, 320, 248]]<|/det|> +I have no further questions. + +<|ref|>text<|/ref|><|det|>[[115, 317, 394, 333]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 373, 835, 409]]<|/det|> +The authors have made a strong effort to address all of the points raised in my initial review. Their manuscript is acceptable for your journal. + +<|ref|>text<|/ref|><|det|>[[115, 478, 394, 494]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 534, 494, 551]]<|/det|> +The authors did a great job addressing my concerns + +<--- Page Split ---> diff --git a/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/images_list.json b/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..cffb8b9d9cf2c92aff85d9be6793b5b4d751b55d --- /dev/null +++ b/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,396 @@ + +# nature portfolio + +Peer Review File + +# MRI-Based Microthrombi Detection in Stroke with Polydopamine Iron Oxide + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +This manuscript evaluates a unique MRI based contrast agent (PHYSIOMIC) for detection of microthrombi in the brain during experimental stroke. + +I have a number of questions/concerns/suggestions about the experiments performed. + +Page 20, paragraph 2: etiology is misspelled. + +Was the parent vessel still occluded at the time hypointense signal was seen after PHYSIOMIC injection? 3D TOF MRI should be able to confirm such? Could PHYSIOMIC being simply measuring poor cerebral blood flow from a proximal occlusion rather than true microthrombi? + +Please provide more details in the pathologic analysis of how the PHYSIOMIC is aggregating with microthrombi? Figure 2g. Magnified images of the clusters of iron oxide and their association with microthrombi (stained by specific immunostains to confirm such). + +Please show some electron microscopic evidence of PHYSIOMIC/iron oxide particles in proximity to microthrombi from brain samples at the location of the infarct where microthrombi seen. EM was performed for spleen and liver deposition of PHYSIOMIC so could also be done for brain samples. + +Why does the AICI3 model (Figure 3) not produce microthrombi? + +Figure 6 is assessing Melamine and Melamine- Carboxylic not PHYSIOMIC? + +Supplemental Figure 4 raises major concerns about the MR contrast agent slowing the effects of clot lysis with TPA with longer clot lysis times. Please discuss in Discussion section. + +<--- Page Split ---> + +Supplemental Figure 5: Authors should speculate whether the disappearance of PHYSIOMIC with time is a product of the half life/metabolism properties of the agent or that microthrombi clear over time? + +Supplemental Figure 6d: The Time of Flight image provided offers no compelling evidence of recanalization. The wrong side of the brain has an arrow? + +Please orient the reader to which side of the brain we are seeing for each Figure of the manuscript. Is Left on left and right on right consistently for the various imaging figures provided throughout the manuscript? + +Please consider showing a more representative example of persistent occlusion versus recanalization at 6 hours. + +Reviewer #2 (Remarks to the Author): + +This manuscript describes a new MRI contrast agent, PHYSIOMIC, which is intended to allow MR imaging of thrombi and microthrombi in a mouse model of thromboembolic ischemic stroke. Currently there is no accurate way of imaging thrombi and microthrombi in the brain. Being able to do so, would have tremendous value in both detecting such lesions during stroke, and also monitoring the response of individual sites following standard of care treatments. The significance of this work is therefore very high. Detection of both thrombi and microthrombi and monitoring of thrombolytic treatment was demonstrated in this mouse model. The authors present very well- designed experiments to assess the targeting and MR imaging characteristics, biologic mechanism of action, degradation, and clearance pathways, as well as the ability of the agent to monitor the efficacy of response in near real time which is imperative in stroke patients. The approach was very thorough, and data provided strongly supported the conclusions. Statistical support is appropriate. Supplementary materials all appear to be important for supporting conclusions. There are only a few questions or comments that would improve the paper which follow. + +1. It is stated in the methods section on p26 that either "PHYSIOMIC or SPIO particles with concentrations of 4 mg [FE]/kg were administered to naïve male Swiss mice. Please clarify this dosing + +<--- Page Split ---> + +nomenclature and provide a total mass dose and volume of each agent administered per mouse. Please provide clear dosing masses and volumes when agents are injected. Although assessing safety and tolerance of the agent was not an aim of this paper, it will be necessary to clearly understand the dosing especially since large volumes of particles greater than \(500~\mathrm{nm}\) in diameter have proven problematic in early human studies [Ivancev, et al. (1989) Effect of Intravenously Injected Iodinated Lipid Emulsions on the Liver, Acta Radiologica, 30:3, 291- 298, DOI: 10.3109/02841858909174683] where it was found that the sinusoids in the liver became bloated ultimately blocking the flow of bile causing significant lower back pain and ultimately precluding the use of these particulates in humans. + +2. Page 6: line 4, change "...phantoms using a 7T..." to "phantoms using 7T..." and line 28, change "...major risk associated..." to "...major risks associated...). + +3. A burning question is whether or not these 750 nm particles would be rapidly sequestered by the RE cells in the liver and if MRI of the liver would show significant uptake. This question was beautifully addressed on p 16. It may be prudent to add a sentence or two on the potential impact of significant first pass liver clearance on the amount of agent ultimately reaching the micro-thrombi in the brain and whether or not alternative injection sites might allow more efficient targeting. + +4. Page 22, Transmission Electron Microscopy section: line 1: change dry to dried. Line 7: change ultrahion to ultrathin. + +5. Page 24 Exclusion criteria section: line 1, change MIE to Mice + +6. Page 26: Please justify why only male mice were used in this study. If it is because of their large size in this strain, then say this. + +Reviewer #3 (Remarks to the Author): + +The paper describes the development of magnetic material based on iron oxide and polydopamine that enables the non- invasive in vivo diagnosis and monitoring of microthrombi using MRI and during acute ischemic strokes. The ability of the material was assessed on a mouse model by identifying differences in MRI response and by confirming them by histological analysis. The results were associated with a study of the protein corona, which indicated the key role of fibrinogen in the corona in the targeting to microthrombi. Finally, the authors studied the fate of the injected contrast agent, which is degraded in the liver and spleen. The relevance of the work is that the described methodology allows the identification of microvascular thrombosis through non- invasive methods, which is a challenging and important task because the microthrombi are associated with poorer clinical outcomes. + +<--- Page Split ---> + +As for the specific part associated with my expertise, the corona appears to have a fundamental role in targeting. Indeed, the authors characterize the corona because no active targeting by ligands is present on the material. Fibrinogen is used to explain the targeting. + +1) The authors could add a brief explanation as to why fibrinogen in the corona can target clots. + +2) A brief discussion on the role of other major proteins in the corona can also be added, to elucidate possible interactions with the immune system. Please focus on the PhySIOMIC particles rather than melamine particles. + +3) A quantitative analysis of fibrinogen in PhySIOMIC and melamine particles could also be included, to support the results with the commercial fluorescent particles. + +4) In the methods section, please add a sentence on the type of processing used for proteomic analysis, with a reference to the protocol. + +5) Figure 7 in supplementary material is difficult to read, please improve size and font. In addition, please provide the corona composition as an Excel file with matched protein groups and associated information for identification. + +6) Deposit in a public repository of raw LC/MS data and protein identifications could be done. + +Reviewer #4 (Remarks to the Author): + +In this study, the authors have developed a contrast agent of MRI called PhySIOMIC, synthesized through a self- assembly process of SPIO within a polydopamine matrix. This approach has enabled us to combine the advantages of clinically approved SPIO, which possesses good \(\mathsf{T2}^*\) relaxivity in MRI, with those of micro- sized particles. These micro- sized particles enhance \(\mathsf{T2}^*\) contrast and enable rapid absorption for fast molecular imaging. Additionally, the polydopamine matrix conferred thrombosis targeting properties that enabled molecular MRI of microthrombi in a thrombo- embolic ischemic stroke murine model. Overall, this design is very intriguing. However, there are a few concerns that need to be clarified before consideration for publication. + +1. The authors found that PhySIOMIC without any ligands targeted microthrombi through the formation of the protein corona. However, the effect of the particle size and zeta potential of PhySIOMIC on the microthrombi targeting was not well revealed. In addition, the composition and the underlying mechanism of the protein corona to facilitate PhySIOMIC's microthrombi targeting were not well discovered. + +<--- Page Split ---> + +2. Figure 2b demonstrated that the imaging effect of PhySIOMIC was significantly superior to that of SPIO. It was proven that the protein corona of PhySIOMIC could enhance its microthrombi-targeting. However, there is no additional analysis of SPIO to illustrate the unique composition of the protein corona of PhySIOMIC. Please provide further evidence. + +3. The formation of the protein corona on nanoparticles could accelerate the removal of particles from the bloodstream, thereby reducing the amount of PhySIOMIC reaching the microvasculature. It was also evident that the half-life of PhySIOMIC was much shorter than that of SPIO. Why did PhySIOMIC have a superior targeting to microthrombi? Please discuss the results. + +4. Figure 7a illustrated that both PhySIOMIC and SPIO particles induced a significant decrease in signal intensity in the liver and spleen, indicating rapid clearance of the particles from the body. Additionally, in Fig. 7b, it is noteworthy that the signal intensity after injection is considerably lower than before, and it gradually increases with time. Can you explain the underlying cause of this phenomenon? + +5. The administration of thrombolysis with rtPA results in increased permeability of the blood-brain barrier. However, using PhySIOMIC at this stage is associated with an elevated risk of the contrast agent crossing the blood-brain barrier, which can potentially cause severe brain injury. Please discuss the advantages and disadvantages of PhySIOMIC as an MRI contrast agent. + +6. It is advisable to carefully proofread the manuscript for any errors in grammar and typos. + +<--- Page Split ---> + +Dear Reviewers + +# Title: MRI-Based Microthrombi Detection in Stroke with Polydopamine Iron Oxide + +Manuscript - NCOMMS- 23- 56845- T + +We would like to thank the reviewers for their recommendations. + +In response to the comments, we have enriched the manuscript following the suggestions of the 4 reviewers. + +In total, we have modified 8 figures (Figures 2, 3, 4, 5, 6, S7, S8, and S9), added 2 supplementary figures (Figures S5 and S6) and 2 other supplementary materials; a video file (supplementary material 1) and the detailed analysis of raw data (supplementary material 2). We enriched the introduction, method, results, and discussion sections to answer the different comments. We also shortened the abstract to respect the 150- word limit and shortened the subheadings as requested. + +All modifications are listed below and new text is highlighted in blue. Additionally, a version of the manuscript with all modifications identified via the tracking mode is provided; it shows in red the modifications. A clean final version of the revised manuscript is also provided. + +We hope the modifications will meet the requirements of the editor and the different reviewers. + +With best regards, + +Corresponding Author + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +This manuscript evaluates a unique MRI- based contrast agent (PHySIOMIC) for detection of microthrombi in the brain during experimental stroke. + +I have a number of questions/concerns/suggestions about the experiments performed. + +Page 20, paragraph 2: etiology is misspelled. + +We have corrected this error, thank you for spotting it. + +Was the parent vessel still occluded at the time hypointense signal was seen after PHySIOMIC injection? 3D TOF MRI should be able to confirm such? Could PHySIOMIC being simply measuring poor cerebral blood flow from a proximal occlusion rather than true microthrombi? + +In both ischemic stroke models presented in Figure 3, we confirm that the parent vessel is still occluded at the time of the injection as confirmed by the TOF as well as perfusion MRI (Figure 3d). We also confirm that this blood flow deficit induces tissue injury as we detect the formation of a brain infarct via diffusion- weighted MRI. In both models, the consequences in terms of blood flow reduction are similar. Yet, the results are radically different between the two models; in the thrombin model we observe a strong signal corresponding to PHySIOMIC accumulation and we can observe microthrombi in histology sections, while in the AICl3 model, we have no signal and no microthrombi in histology (figure 3d). If the PHySIOMIC were measuring poor cerebral blood flow, a similar signal would have been obtained in both models. Moreover, in every observation of histology sections (TEM, immuno- histology, or PERLS staining) or two- photon microscopy, we found the PHySIOMIC exclusively where thrombi were found. We now provide more data in terms of histology and added TEM observations in order to clarify this point (Supplementary Figures 5 and 6, more details are provided in the following questions). + +However, it is not to be excluded that the slower blood flow downstream of the proximal clot contributes to the effective binding of our particles to the microthrombi. The decrease in blood flow might enhance the contact between the particles and the microthrombi, thereby facilitating binding. + +Please provide more details in the pathologic analysis of how the PHySIOMIC is aggregating with microthrombi? Figure 2g. Magnified images of the clusters of iron oxide and their association with microthrombi (stained by specific immunostains to confirm such). + +Regarding the analysis of how the PHySIOMIC is binding to the microthrombi, we hypothesize that the fibrinogen content from the protein corona confers affinity to activated platelets. We now have a whole set data presented in Figure 6 further supporting this hypothesis. Accordingly, we added several sentences to the revised version of the manuscript. We discussed this hypothesis in the discussion section, p 19- 20: + +"we notably investigated the composition of the PC of PHySIOMIC particles and pursued the hypothesis that its fibrinogen composition could contribute to the targeting process to microthrombi. However, it remains plausible that other PC components might contribute to the thrombosis targeting phenomenon. In such conditions, it should be noted that the presence of a higher concentration of fibrinogen in the protein corona on the PHySIOMIC particles could also have prothrombotic consequences. At this stage, we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin αIIbβ3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations as the PHySIOMIC were found attached to activated platelets." + +<--- Page Split ---> + +Regarding Figure 2g, we removed the histology observations to put forward the TEM observations (explained in the next question). We also added a supplementary figure exclusively dedicated to histology and immune- staining of microthrombi. We now provide images from histology sections of a brain harvested after the intravenous injection of PHySIOMIC, just after the MRI procedure, where the microthrombi were revealed via CD41 and where the PHySIOMIC could be detected by light reflection on the surrounding of the microthrombi. The Perls' staining also supports the fact that the iron oxide clusters are localized around the microthrombi. + +We added an explanation of this additional observation in the method section, p 27: + +"The specificity of immunostainings was checked by showing the absence of staining when primary antibodies were omitted. The PHySIOMIC could also be revealed via reflection of the polydopamine, using \(488\mathrm{nm}\) laser as emission and setting both, the excitation and the emission filter around the laser wavelength ( \(480\mathrm{nm}\) to \(495\mathrm{nm}\) ) in order to detect reflection of the laser." + +We completed the results p 7: + +"We can conclude that, in this model, PHySIOMIC particles constitute a diagnosis tool to reveal microthrombi and to predict the size of the ischemic lesions. Microthrombi could be identified via platelet marker CD41 immunolabelling in the ischemic area on histological analysis of brains harvested just after the MRI acquisition, 1 hour after the stroke induction. The PHySIOMIC particles could be detected via light reflection from polydopamine positioned around thrombi and the microthrombi, on the luminal side of blood vessels (Supplementary Fig. 5a,b). Perls staining confirmed this specific localization of the particles, stained blue due to their iron oxide composition (Supplementary Fig. 5c)." + +See below the added Figure S5: + +![PLACEHOLDER_8_0] + + +<--- Page Split ---> + +Please show some electron microscopic evidence of PhySIOMIC/iron oxide particles in proximity to microthrombi from brain samples at the location of the infarct where microthrombi seen. TEM was performed for spleen and liver deposition of PhySIOMIC so could also be done for brain samples. + +We would like to thank the reviewer for this interesting suggestion. The requested experiments were performed with the help of the electron microscopy imaging facility MicroEleCS from the INSERM UMR- S1255 Unit in Strasbourg. The images obtained following the processing of the samples are presented in the new Supplementary Figure 6 + +We added the description of the experiment in the method section p 23: + +"Microthrombi in brain section were observed at the electron microscopy imaging facility MicroEleCS (INSERM UMR- S1255 Unit, Strasbourg, France). Brain tissue was fixed with \(2.5\%\) glutaraldehyde in \(0.1\mathrm{M}\) sodium cacodylate buffer containing \(2\%\) sucrose, previously warmed to \(37^{\circ}\mathrm{C}\) (305 mOsm, pH 7.3) for 1 hour. The samples were then rinsed and postfixed with \(1\%\) osmium tetroxide in \(0.1\mathrm{M}\) sodium cacodylate buffer for 1 hour at \(4^{\circ}\mathrm{C}\) . After additional washing in the \(0.1\mathrm{M}\) sodium cacodylate buffer, the samples were dehydrated in successively increasing ethanol concentrations before embedding in epoxy. The resin was polymerized for 2 days at \(50^{\circ}\mathrm{C}\) . Ultrathin sections (100 nm) were stained with lead citrate and uranyl acetate, and examined under a Jeol 2100- plus (120 kV)." + +In the result section p 8: + +"To further investigate the localization of the PhySIOMIC within the microthrombi, we performed transmission electronic microscopy (TEM) of the brain sections and we observed the iron oxide clusters close to degranulated platelets (Fig. 2g and Supplementary Fig 6). In all observations of the histological sections, the PhySIOMIC particles were identified inside or at the surface of microthrombi, without noticeable accumulation in other parts of the brain." + +See below the added Figure S6: + +![PLACEHOLDER_9_0] + + +<--- Page Split ---> + +## Why does the AlCl3 model (Figure 3) not produce microthrombi? + +AlCl3 is deposited locally over the MCA bifurcation and enables thrombosis formation restricted to the vessel exposed to AlCl3. In contrast, in the thrombin model, recombinant murine thrombin is infused intra- arterially and reach not only the main artery where the pipet tip is located, but also the whole downstream microcirculation, thereby leading to microthrombi formation. We completed the result part with more description of the model and an explanation of this specific difference, p10: + +"We further compared the results obtained after PhySIOMIC injection in this first ischemic stroke model induced via thrombin injection in the MCA (referred to as 'thrombin model'), to a second ischemic stroke model in which thrombosis was induced in situ via local deposition on the MCA of a filter paper soaked with aluminum chloride (Fig 3). In this second model (referred to as the 'AlCl3 model'), a unique clot is formed precisely at the area in contact with AlCl3 and no embolization in the microcirculation occurs." + +## Figure 6 is assessing Melamine and Melamine-Carboxylic not PhySIOMIC? + +Indeed, in Figure 6, we focused mainly on fluorescent particles of Melamine and Melamine- Carboxylic except for the results from the mass spectrometry for the analysis of the plasma protein corona where we also performed the experiment on the PhySIOMIC. The reason we could not perform the same experiments on the PhySIOMIC is that we were not able to label them with fluorescent dye as the polydopamine modifies optic properties. + +We explain this in the discussion section, p 21: + +"Due to the light- absorbing properties of polydopamine, it was not possible to obtain fluorescently labeled polydopamine particles without surface modification for in vitro experiments. Therefore, to delve deeper into the thrombosis targeting mechanism identified with PhySIOMIC particles, we opted to use commercially available fluorescent particles composed of melamine resin. This choice was motivated by the presence of amine groups on the surface of melamine resin, which is akin to polydopamine. Furthermore, it has been reported that modifying the external layer of nanomedicines with carboxylate groups significantly influences the profile of adsorbed proteins compared to bare particles with amine groups36. Consequently, we also used melamine functionalized with carboxylic termination (melamine-COOH). Thanks to the strong fluorescent labeling of melamine and melamine-COOH, we were able to track them in vitro through a microfluidic study and in vivo with two- photon microscopy." + +## Supplemental Figure 4 raises major concerns about the MR contrast agent slowing the effects of clot lysis with TPA with longer clot lysis times. Please discuss in Discussion section. + +The supplementary figure 4 indicates that the presence of the MR contrast agent might slightly slow the clot lysis with tPA. Although this difference is not significant for both the tPA concentrations tested, we agree that this is an important risk to consider for future development. In addition, the thrombosis targeting mechanism that we elucidated in this study involves the presence of fibrinogen in higher concentration in the protein corona of the particles adhering to thrombosis which in itself may carry prothrombotic risk. We propose to raise this aspect in the discussion p19- 20: + +"In such conditions, it should be noted that the presence of a higher concentration of fibrinogen in the protein corona on the PhySIOMIC particles could also have prothrombotic consequences. At this stage, we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin αIIbβ3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations, where the PhySIOMIC were found attached to activated platelets. So, in addition to bringing some fibrinogen to the edge of the clot and thus possibly enhancing fibrin + +<--- Page Split ---> + +polymerization, the PhySIOMIC covered with fibrinogen could also increase platelet aggregation. Besides, although the clot lysis assay did not show a significant difference in the tPA- induced clot lysis time in the presence of PhySIOMIC, the mean value of lysis time was numerically higher. Overall, the putative risk of prothrombotic effect should be monitored for further developments of the PhySIOMIC particles." + +## Supplemental Figure 5: Authors should speculate whether the disappearance of PhySIOMIC with time is a product of the half life/metabolism properties of the agent or that microthrombi clear over time? + +The disappearance of the signal coincides with recalculation time and for this reason, we attribute the loss of signal to microthrombi clearance rather than proper half- life/metabolism of the PhySIOMIC. Indeed, we observe disappearance of PhySIOMIC on MRI over a few hours, whereas usually the metabolism of iron oxide nanoparticles requires a few weeks to reverse the MRI signal (Martinez de Lizarondo et al., Science Advances 2022). We added a sentence to precise this hypothesis, p12: + +While the signal void was consistent with previous observations when measured at early time points after stroke onset (30 minutes and 2 hours post- occlusion), it almost completely disappears at 6 hours post- occlusion (Supplementary Fig. 8c). These events coincide with cerebral reperfusion, as indicated by the increase in the angiographic score (Supplementary Fig. 8d,e) which supports that this slow progressive signal disappearance is caused by the clearance of the microthrombi rather than in situ metabolization of the PhySIOMIC." + +Supplemental Figure 6d: The Time of Flight image provided offers no compelling evidence of recalculation. The wrong side of the brain has an arrow? Please orient the reader to which side of the brain we are seeing for each Figure of the manuscript. Is Left on left and right on right consistently for the various imaging figures provided throughout the manuscript? + +Time- of- flight images are presented along the axial axis, viewed from above. In this representation, the MCA was observed on the right of the images (where was the arrow). To ensure better comprehension, we changed the visualization of the TOF images to place the MCA on the left in all images. The TOF images are seen now from below. We also added left and right indications on the images (noted L & R). + +Please consider showing a more representative example of persistent occlusion versus recalculation at 6 hours. + +The images used as examples to demonstrate recalculation are not the most representative; they have been modified to better match the average of the data presented in the recalculation graph. These modifications also led us to change the orientation of the images in Figure 3 (perfusion imaging and angiography) to correspond. + +## Reviewer #2 (Remarks to the Author): + +This manuscript describes a new MRI contrast agent, PhySIOMIC, which is intended to allow MR imaging of thrombi and microthrombi in a mouse model of thromboembolic ischemic stroke. Currently there is no accurate way of imaging thrombi and microthrombi in the brain. Being able to do so, would have tremendous value in both detecting such lesions during stroke, and also monitoring the response of individual sites following standard of care treatments. The significance of this work is therefore + +<--- Page Split ---> + +very high. Detection of both thrombi and microthrombi and monitoring of thrombolytic treatment was demonstrated in this mouse model. The authors present very well- designed experiments to assess the targeting and MR imaging characteristics, biologic mechanism of action, degradation, and clearance pathways, as well as the ability of the agent to monitor the efficacy of response in near real time which is imperative in stroke patients. The approach was very thorough, and data provided strongly supported the conclusions. Statistical support is appropriate. Supplementary materials all appear to be important for supporting conclusions. There are only a few questions or comments that would improve the paper which follow. + +1. It is stated in the methods section on p26 that either "PhYSIOMIC or SPIO particles with concentrations of \(4\mathrm{mg}\) [FE]/kg were administered to naive male Swiss mice. Please clarify this dosing nomenclature and provide a total mass dose and volume of each agent administered per mouse. Please provide clear dosing masses and volumes when agents are injected. Although assessing safety and tolerance of the agent was not an aim of this paper, it will be necessary to clearly understand the dosing especially since large volumes of particles greater than \(500\mathrm{nm}\) in diameter have proven problematic in early human studies [Ivancev, et al. (1989) Effect of Intravenously Injected iodinated Lipid Emulsions on the Liver, Acta Radiologica, 30:3, 291-298, DOI: 10.3109/02841858909174683] where it was found that the sinusoids in the liver became bloated ultimately blocking the flow of bile causing significant lower back pain and ultimately precluding the use of these particulates in humans. + +The sentence in the Materials and Methods indicating the dose administered to mice was changed for a better understanding of the injected dose, p29: + +The PhYSIOMIC and SPIO particles were individually reconcentrated to a concentration of \(0.8\mathrm{mg}[\mathrm{Fe}].\mathrm{mL}^{- 1}\) using a magnet. They were then intravenously injected to attain a final iron concentration of \(4\mathrm{mg}.\mathrm{kg}^{- 1}\) , with approximately \(200\mu \mathrm{L}\) of solution administered to each naive male Swiss mouse (8 weeks, \(\mathrm{n} = 5\) per group). The ratio polydopamine to iron is of 3.2 so an iron dose of \(4\mathrm{mg}.\mathrm{kg}^{- 1}\) correspond to a \(16.8\mathrm{mg}\) dose of particles injected per kg. + +Concerning the risks associated with particles larger than \(500\mathrm{nm}\) , we thank the reviewer for pointing us to this study and the specific risks of large particles. We agree that it will be crucial to conduct further stability/toxicity studies before advancing these particles to clinical trials to ensure their safety. Knowing this specific risk of liver sinusoid embolization will be useful at this point and we will certainly add it to the list of risk to be considered. + +From our side, we performed a more comprehensive toxicity study regarding the risk in the liver with similar particles in a study we published recently (Sara Martinez de Lizarondo et al., Tracking the immune response by MRI using biodegradable and ultrasensitive microprobes.Sci. Adv.8,ebm3596(2022).DOI:10.1126/sciadv.ebm3596). We verified the non- toxicity of other submicrometric iron oxide- based particles, with a 6- month follow- up on animals. We observed hepatic biodegradation of the particles, assessed the condition of the liver, kidneys, lungs, and spleen via histology, and verified the absence of ASAT and ALAT or pro- inflammatory cytokines generated. With this data, we are confident that iron oxide polydopamine particles with a diameter between \(500\mathrm{nm}\) and \(1\mu \mathrm{m}\) do not induce toxic side effects if injected at reasonable dose. It should however be acknowledged that preclinical studies cannot reveal every side effects and that consequences of intravenous injection of such particles in human remain largely unknown. + +2. Page 6: line 4, change "...phantoms using a 7T..." to "phantoms using 7T..." and line 28, change "...major risk associated..." to "...major risks associated...). + +Thank you for spotting these mistakes, we corrected them. + +<--- Page Split ---> + +3. A burning question is whether or not these 750 nm particles would be rapidly sequestered by the RE cells in the liver and if MRI of the liver would show significant uptake. This question was beautifully addressed on p 16. It may be prudent to add a sentence or two on the potential impact of significant first pass liver clearance on the amount of agent ultimately reaching the micro-thrombi in the brain and whether or not alternative injection sites might allow more efficient targeting. + +We added a specific paragraph in the revised version of the discussion to discuss the potential negative impact of the short half- life. We agree that the number of particles reaching the target is most likely very low (probably around \(0.5\%\) ). However, it should also be noted that if the particles were decorated with PEG chains to decrease the RE sequestration, for example, the targeting would not be effective anymore because of a perturbed protein corona. Regarding the injection route, it is indeed possible that intra- arterial injection would increase the targeting ratio as the particles would pass through the brain before being filtered by the liver. + +We now discuss this aspect in the discussion: + +It is also interesting to note that the PhYSIOMIC provided strong imaging signal detection although they exhibited an extremely short half- life (less than a minute) compared to the SPIO which typically circulates much longer (over 10 minutes) but was not able to reveal the microthrombi. This might appear surprising as the field of nanomedicine usually supports long circulation half- life as a positive feature for molecular imaging applications as longer exposure time should logically result in increased targeting35. However, this study provides evidence that this reasoning is not always true and that, at least in some contexts, modifying the surface to improve the targeting properties can be more valuable than to increase the circulation time. + +## 4. Page 22, Transmission Electron Microscopy section: line 1: change dry to dried. Line 7: change ultrathion to ultrathin. + +Thank you for spotting these mistakes, we corrected them. + +## 5. Page 24 Exclusion criteria section: line 1, change MIE to Mice + +Thank you for spotting this mistake, we corrected it. + +## 6. Page 26: Please justify why only male mice were used in this study. If it is because of their large size in this strain, then say this. + +We generally use exclusively male mice because we encounter more reproducibility as we avoid the potential impact of the estrous cycle. This is a general habit of preclinical research and animal experiments that we are aware is not ideal, as we might miss an effect related to sex. For this reason, in this study, we have now included a study on female mice to study the potential effect of sex (cf described in the answer to editor comments). In summary, we do not observe any significant differences between male and female mice for microthrombi imaging using PhYSIOMIC. + +## Reviewer #3 (Remarks to the Author): + +The paper describes the development of magnetic material based on iron oxide and polydopamine that enables the non- invasive in vivo diagnosis and monitoring of microthrombi using MRI and during acute ischemic strokes. The ability of the material was assessed on a mouse model by identifying differences in MRI response and by confirming them by histological analysis. The results were associated with a study of the protein corona, which indicated the key role of fibrinogen in the corona in the targeting to microthrombi. Finally, the authors studied the fate of the injected contrast + +<--- Page Split ---> + +agent, which is degraded in the liver and spleen. The relevance of the work is that the described methodology allows the identification of microvascular thrombosis through non- invasive methods, which is a challenging and important task because the microthrombi are associated with poorer clinical outcomes. As for the specific part associated with my expertise, the corona appears to have a fundamental role in targeting. Indeed, the authors characterize the corona because no active targeting by ligands is present on the material. Fibrinogen is used to explain the targeting. + +We added a hypothesis on this explanation in the discussion section p 19- 20: + +"At this stage, we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin aIIbB3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations, where the PhySIOMIC were found attached to activated platelets." + +2) A brief discussion on the role of other major proteins in the corona can also be added, to elucidate possible interactions with the immune system. Please focus on the PhySIOMIC particles rather than melamine particles. + +To enrich the discussion, we have incorporated a paragraph in the Discussion section addressing the proteins found in the protein corona and their potential influence on PhySIOMIC particles' biodistribution, blood half-life, and immune response, p19: + +"It is noteworthy that the protein corona plays a significant role in the biodistribution, blood circulation time, and immune response to particles. Thus, the presence of opsonins within this protein corona facilitates rapid recognition by the complement system and the clearance of particles from circulation by macrophages." + +## 3) A quantitative analysis of fibrinogen in PhySIOMIC and melamine particles could also be included, to support the results with the commercial fluorescent particles. + +To address this question, we conducted an additional experiment, as depicted in the new Supplementary Figure 7, to measure fibrinogen adsorption on melamine and PhySIOMIC particles using a Nanodrop spectrophotometer (Implen). A fibrinogen solution (1 mg/mL) was exposed to the different particles, and after centrifugation, the particles were separated from the solution, allowing us to measure the fibrinogen content in the supernatant. The results support our hypothesis that fibrinogen adsorption is more pronounced in PhySIOMIC and melamine particles targeting microthrombi. In contrast, fibrinogen absorption was found to be negligeable on melamine- COOH particles. Unfortunately, it was not possible to measure PhySIOMIC- BSA's fibrinogen adsorption using this technique due to interference between BSA and fibrinogen spectra on the nano spectrophotometer. We have included this experiment in the Results section, along with the technique in the Methods section. + +Results section, p 16: "Remarkably, we noticed an augmentation in the number of particles adhering to thrombi when the particles were suspended in fibrinogen- rich plasma (Fig. 6f). Hence, the fibrinogen integrated into the PCs of PhySIOMIC while in circulation plays a pivotal role in their passive targeting to thrombi and microthrombi. To measure the adsorption of fibrinogen onto the surface of particles, we exposed the particles to a fibrinogen solution (1 mg.mL- 1) during 30 minutes at 37°C. The particles were then centrifuged, and the fibrinogen remaining in the supernatant was measured using a nano spectrophotometer. Fibrinogen adsorption is greater on melamine and PhySIOMIC particles, with mean + +<--- Page Split ---> + +values of \(50 \mu \mathrm{g}\) and \(75 \mu \mathrm{g}\) , respectively, per \(250 \mu \mathrm{l}\) of particles (Figure 6g).” + +Methods section, p26: + +## “Fibrinogen adsorption quantification + +Melamine (diluted at 1:5), Melamine- COOH (diluted at 1:50) and PHySIOMIC particles were incubated with a fibrinogen solution (1 mg.mL- 1) at a 1:1 ratio during 30 minutes at \(37^{\circ}\mathrm{C}\) . The particles were then centrifuged (3 minutes, 10000 rpm) and the supernatant was measured with a nano spectrophotometer (Nanodrop, Implen) with a molar extinction coefficient of 1,51. The amount of fibrinogen adsorbed onto the surface of the particles is measured by subtracting the fibrinogen value measured in the supernatant from the control fibrinogen value (incubation of fibrinogen and mannitol buffer of the particles).” + +See below the modified Figure 6: + +![PLACEHOLDER_15_0] + + +<--- Page Split ---> + +## 4) In the methods section, please add a sentence on the type of processing used for proteomic analysis, with a reference to the protocol. + +The proteomic protocol conducted by the Proteogen platform has been added to the "Methods" section, \(p 24 - 25\) : + +"Five \(\mu \mathrm{g}\) of each protein extract were prepared using a modified Gel- aided Sample Preparation protocol51. Samples were digested with trypsin/Lys- C overnight at \(37^{\circ}\mathrm{C}\) . For nano- LC fragmentation, protein or peptide samples were first desalted and concentrated onto a \(\mu \mathrm{C18}\) OmiX (Agilent) before analysis. The chromatography step was performed on a NanoElute (Bruker Daltonics) ultra- high- pressure nano flow chromatography system. Approximately \(200\mathrm{ng}\) of each peptide sample were concentrated onto a C18 pepmap 100 (5mm x \(300\mu \mathrm{m}\) i.d.) precolumn (Thermo Scientific) and separated at \(50^{\circ}\mathrm{C}\) onto a reversed phase Reprosil column (25cm x \(75\mu \mathrm{m}\) i.d.) packed with \(1.6\mu \mathrm{m}\) C18 coated porous silica beads (Ionopticks). Mobile phases consisted of \(0.1\%\) formic acid, \(99.9\%\) water (v/v) (A) and \(0.1\%\) formic acid in \(99.9\%\) ACN (v/v) (B). The nanoflow rate was set at \(300\mathrm{nl / min}\) , and the gradient profile was as follows: from 2 to \(15\%\) B within \(15\mathrm{min}\) , followed by an increase to \(25\%\) B within \(10\mathrm{min}\) and to \(37\%\) B within \(12\mathrm{min}\) and further to \(9\%\) within \(7\mathrm{min}\) and reequilibration. Mass Spectrometry (MS) experiments were carried out on an TIMS- TOF pro mass spectrometer (Bruker Daltonics) with a modified nano electrospray ion source (CaptiveSpray, Bruker Daltonics). A 1400 spray voltage with a capillary temperature of \(180^{\circ}\mathrm{C}\) was typically employed for ionizing. MS spectra were acquired in the positive mode in the mass range from \(100\) to \(1700\mathrm{m / z}\) and \(0.75\) to \(1.30\mathrm{1 / k0}\) window. In the experiments described here, the mass spectrometer was operated in PASEF DIA mode with exclusion of single charged peptides. The DIA acquisition scheme consisted of 24 variable windows ranging from 300 to \(1000\mathrm{m / z}\) . + +5) Figure 7 in supplementary material is difficult to read, please improve size and font. In addition, please provide the corona composition as an Excel file with matched protein groups and associated information for identification. + +Thank you for your feedback. The layout of the graphs has been adjusted, and their sizes have been increased to enhance clarity in reading the figure. The composition of the protein corona is provided in the Excel file of the Raw data. In this file, we have listed the proteins, their affiliations with a biological cluster, as well as the measurements by mass spectrometry. + +6) Deposit in a public repository of raw LC/MS data and protein identifications could be done. + +According to your recommendations, the mass spectrometry data has been added to a repository on the iProX website, under the number: IPX0008212001. + +## Reviewer #4 (Remarks to the Author): + +In this study, the authors have developed a contrast agent of MRI called PhySIOMIC, synthesized through a self- assembly process of SPIO within a polydopamine matrix. This approach has enabled us to combine the advantages of clinically approved SPIO, which possesses good \(\mathrm{T2^*}\) relaxivity in MRI, with those of micro- sized particles. These micro- sized particles enhance \(\mathrm{T2^*}\) contrast and enable rapid absorption for fast molecular imaging. Additionally, the polydopamine matrix conferred thrombosis targeting properties that enabled molecular MRI of microthrombi in a thrombo- embolic ischemic stroke murine model. Overall, this design is very intriguing. However, there are a few concerns that need to be clarified before consideration for publication. + +1. The authors found that PhySIOMIC without any ligands targeted microthrombi through the formation of the protein corona. However, the effect of the particle size and zeta potential of PhySIOMIC on the microthrombi targeting was not well revealed. In + +<--- Page Split ---> + +## addition, the composition and the underlying mechanism of the protein corona to facilitate PhySIOMIC's microthrombi targeting were not well discovered. + +While the mechanism involved in targeting microthrombi through protein corona formation has yet to be investigated, we demonstrate the importance of fibrinogen in this mechanism using microfluidic experiments. We proposed in a paragraph added to the Discussion Section that PhySIOMIC, with fibrinogen adsorbed on its surface, may bind to platelet integrin aIIbB3 in microthrombi: + +"Thus, we notably investigated the composition of the PC of PhySIOMIC particles and pursued the hypothesis that its fibrinogen composition could contribute to the targeting process to microthrombi. However, it remains plausible that other PC components might contribute to the thrombosis targeting phenomenon. In such condition, it should be noted that the presence of a higher concentration of fibrinogen in the protein corona on the PhySIOMIC particles could also have prothrombotic consequences. At this stage we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin aIIbB3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations as the PhySIOMIC were found attached to activated platelets." + +Regarding the particle size and zeta potential, we agree that they are important parameters with an impact on targeting via the circulation time and via the influence on the protein corona. We provide a table to list these different parameters for the SPIO and the PhySIOMIC (table 1) and we added a paragraph in the discussion section, p21: + +"These micro- sized particles enhance \(\mathrm{T}_2^*\) contrast and enable rapid absorption for fast molecular imaging. Additionally, the polydopamine matrix conferred thrombosis targeting properties that enabled molecular MRI of microthrombi in a thrombo- embolic ischemic stroke murine model. It is also interesting to note that the PhySIOMIC provided strong imaging signal detection although they exhibited an extremely short half- life (less than a minute) compared to the SPIO which typically circulates much longer (over 10 minutes) but was not able to reveal the microthrombi. This might appear surprising as the field of nanomedicine usually supports long circulation half- life as a positive feature for molecular imaging applications as longer exposure time should logically result in increased targeting35. However, this study provides evidence that this reasoning is not always true and that, at least in some contexts, modifying the surface to improve the targeting properties can be more valuable than to increase the circulation time." + +2. Figure 2b demonstrated that the imaging effect of PhySIOMIC was significantly superior to that of SPIO. It was proven that the protein corona of PhySIOMIC could enhance its microthrombi-targeting. However, there is no additional analysis of SPIO to illustrate the unique composition of the protein corona of PhySIOMIC. Please provide further evidence. + +We have added the proteomic analysis of SPIO in the supplementary Figure S9. It shows that the amount of fibrinogen with the protein corona is lower that for the particles that bind to microthrombi (i.e. PhySIOMIC and melamine). + +3. The formation of the protein corona on nanoparticles could accelerate the removal of particles from the bloodstream, thereby reducing the amount of PhySIOMIC reaching the microvasculature. It was also evident that the half-life of PhySIOMIC was much shorter than that of SPIO. Why did PhySIOMIC have a superior targeting to microthrombi? Please discuss the results. + +Efficient targeting is indeed more important than long half- life to perform efficient molecular imaging and this study perfectly illustrates this fact. We believe that the composition of the protein corona and the size of the particles are two key aspects to target microthrombi. Moreover, the shorter half- life allows to perform imaging only a couple of minutes after intravenous injection, since plasma clearance + +<--- Page Split ---> + +is very fast. We now raise this aspect in the discussion p 19: + +It is also interesting to note that the PhySIOMIC provided a strong imaging signal detection although they exhibit an extremely short half- life (less than a minute) compared to the SPIO that typically circulate much longer (over 10 minutes) but were not able to reveal the microthrombi. This might appear surprising as the field of nanomedicine usually supports long circulation half- life as a positive feature for molecular imaging applications as longer exposure time should logically result in increased targeting35. However, this study provides evidence that this reasoning is not always true and that, at least in some contexts, modifying the surface to improve the targeting properties can be more valuable than to increase the circulation time. + +4. Figure 7a illustrated that both PhySIOMIC and SPIO particles induced a significant decrease in signal intensity in the liver and spleen, indicating rapid clearance of the particles from the body. Additionally, in Fig. 7b, it is noteworthy that the signal intensity after injection is considerably lower than before, and it gradually increases with time. Can you explain the underlying cause of this phenomenon? + +We indeed attribute the strong signal decrease to rapid sequestration of the particles in the macrophages of the liver and the spleen. The iron oxide particles accumulate and confer negative signal. Then, the signal gradually increases with time once the iron oxide has been degraded and the iron incorporated into the iron pool of the organism. In the liver, it goes back to baseline at day 7 post injection. + +We completed the result section p16: + +"Signal enhancement was monitored in the liver, spleen and kidney at 2, 7 and 31 days after injection. Both PhySIOMIC and SPIO particles induced a strong hyposignal within the liver and the spleen (Fig. 7a) which is in line with a rapid elimination of particles from the bloodstream and uptake by the mononuclear phagocyte system; in the Kupffer cells of the liver and resident macrophages of the spleen.21 This hyposignal gradually fade out in time ending at baseline level at 31 days post injection. This observation was attributed to gradual biodegradation of the iron oxide particles within the lysosomal compartment of the macrophages; a mechanism well described in literature for inorganic nanoparticles, including iron oxide33." + +5. The administration of thrombolysis with rtPA results in increased permeability of the blood-brain barrier. However, using PhySIOMIC at this stage is associated with an elevated risk of the contrast agent crossing the blood-brain barrier, which can potentially cause severe brain injury. Please discuss the advantages and disadvantages of PhySIOMIC as an MRI contrast agent. + +We agree that this is another potential risk to consider in future developments. We added a paragraph in the discussion on that specific topic: + +"Another risk to consider is the potential toxicity induced by PhySIOMIC particles that would eventually cross into the brain tissue, especially in the context of severe hemorrhagic transformation post- stroke. Although none of the current data did reveal PhySIOMIC retention other than the one bound to thrombi (due to their submicrometric size that prevents their passage through the blood- brain barrier (BBB)), the fate of the PhySIOMIC would need to be closely monitored for future development. Notably, a clear asset of this contrast agent is that it is fully made from biocompatible materials (iron oxide and polydopamine) that lack neurotoxic side effects. Accordingly, SPIO that can cross the injured BBB has been injected in humans at the subacute phase of ischemic stroke, without worrying signals for toxicity39. Moreover, polydopamine nanoparticles exhibit strong antioxidant properties and were shown to result in a neuroprotective effect in an ischemic stroke model for this specific reason40. These data are reinsuring for the clinical translation of PhySIOMIC." + +6. It is advisable to carefully proofread the manuscript for any errors in grammar and typos. + +We thoroughly proofread the manuscript, corrected errors and typos and hope we did not miss any. + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +All concerns/suggestions addressed in a complete and detailed way. + +No further concerns. + +Reviewer #2 (Remarks to the Author): + +It appears that the authors thoroughly addressed the vast majority of the reviewers comments resulting in a much stronger and highly impactful manuscript. + +Reviewer #3 (Remarks to the Author): + +My remarks were adequately addressed, the manuscript can be accepted. + +Reviewer #4 (Remarks to the Author): + +The authors have addressed the reviewer comments well and the manuscript is recommended for publication after careful checking of spelling and clarity of language in the text and captions. + +<--- Page Split ---> diff --git a/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e26d7a98d978b8f4cd3136d0aeda5aabbe5361aa --- /dev/null +++ b/peer_reviews/337e571503b28d15abdfc4ba75ff294d568592c2aadf53eb1abf668f2ed15f8a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,544 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[66, 111, 362, 140]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[87, 152, 933, 220]]<|/det|> +# MRI-Based Microthrombi Detection in Stroke with Polydopamine Iron Oxide + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 145, 404, 160]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 204, 803, 239]]<|/det|> +This manuscript evaluates a unique MRI based contrast agent (PHYSIOMIC) for detection of microthrombi in the brain during experimental stroke. + +<|ref|>text<|/ref|><|det|>[[118, 283, 770, 300]]<|/det|> +I have a number of questions/concerns/suggestions about the experiments performed. + +<|ref|>text<|/ref|><|det|>[[118, 344, 451, 360]]<|/det|> +Page 20, paragraph 2: etiology is misspelled. + +<|ref|>text<|/ref|><|det|>[[118, 404, 852, 456]]<|/det|> +Was the parent vessel still occluded at the time hypointense signal was seen after PHYSIOMIC injection? 3D TOF MRI should be able to confirm such? Could PHYSIOMIC being simply measuring poor cerebral blood flow from a proximal occlusion rather than true microthrombi? + +<|ref|>text<|/ref|><|det|>[[118, 500, 856, 554]]<|/det|> +Please provide more details in the pathologic analysis of how the PHYSIOMIC is aggregating with microthrombi? Figure 2g. Magnified images of the clusters of iron oxide and their association with microthrombi (stained by specific immunostains to confirm such). + +<|ref|>text<|/ref|><|det|>[[118, 598, 861, 652]]<|/det|> +Please show some electron microscopic evidence of PHYSIOMIC/iron oxide particles in proximity to microthrombi from brain samples at the location of the infarct where microthrombi seen. EM was performed for spleen and liver deposition of PHYSIOMIC so could also be done for brain samples. + +<|ref|>text<|/ref|><|det|>[[118, 695, 607, 712]]<|/det|> +Why does the AICI3 model (Figure 3) not produce microthrombi? + +<|ref|>text<|/ref|><|det|>[[118, 756, 673, 772]]<|/det|> +Figure 6 is assessing Melamine and Melamine- Carboxylic not PHYSIOMIC? + +<|ref|>text<|/ref|><|det|>[[118, 816, 872, 851]]<|/det|> +Supplemental Figure 4 raises major concerns about the MR contrast agent slowing the effects of clot lysis with TPA with longer clot lysis times. Please discuss in Discussion section. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 870, 137]]<|/det|> +Supplemental Figure 5: Authors should speculate whether the disappearance of PHYSIOMIC with time is a product of the half life/metabolism properties of the agent or that microthrombi clear over time? + +<|ref|>text<|/ref|><|det|>[[118, 181, 812, 216]]<|/det|> +Supplemental Figure 6d: The Time of Flight image provided offers no compelling evidence of recanalization. The wrong side of the brain has an arrow? + +<|ref|>text<|/ref|><|det|>[[118, 259, 878, 312]]<|/det|> +Please orient the reader to which side of the brain we are seeing for each Figure of the manuscript. Is Left on left and right on right consistently for the various imaging figures provided throughout the manuscript? + +<|ref|>text<|/ref|><|det|>[[118, 356, 875, 391]]<|/det|> +Please consider showing a more representative example of persistent occlusion versus recanalization at 6 hours. + +<|ref|>text<|/ref|><|det|>[[119, 527, 403, 543]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 586, 878, 824]]<|/det|> +This manuscript describes a new MRI contrast agent, PHYSIOMIC, which is intended to allow MR imaging of thrombi and microthrombi in a mouse model of thromboembolic ischemic stroke. Currently there is no accurate way of imaging thrombi and microthrombi in the brain. Being able to do so, would have tremendous value in both detecting such lesions during stroke, and also monitoring the response of individual sites following standard of care treatments. The significance of this work is therefore very high. Detection of both thrombi and microthrombi and monitoring of thrombolytic treatment was demonstrated in this mouse model. The authors present very well- designed experiments to assess the targeting and MR imaging characteristics, biologic mechanism of action, degradation, and clearance pathways, as well as the ability of the agent to monitor the efficacy of response in near real time which is imperative in stroke patients. The approach was very thorough, and data provided strongly supported the conclusions. Statistical support is appropriate. Supplementary materials all appear to be important for supporting conclusions. There are only a few questions or comments that would improve the paper which follow. + +<|ref|>text<|/ref|><|det|>[[118, 867, 878, 902]]<|/det|> +1. It is stated in the methods section on p26 that either "PHYSIOMIC or SPIO particles with concentrations of 4 mg [FE]/kg were administered to naïve male Swiss mice. Please clarify this dosing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 247]]<|/det|> +nomenclature and provide a total mass dose and volume of each agent administered per mouse. Please provide clear dosing masses and volumes when agents are injected. Although assessing safety and tolerance of the agent was not an aim of this paper, it will be necessary to clearly understand the dosing especially since large volumes of particles greater than \(500~\mathrm{nm}\) in diameter have proven problematic in early human studies [Ivancev, et al. (1989) Effect of Intravenously Injected Iodinated Lipid Emulsions on the Liver, Acta Radiologica, 30:3, 291- 298, DOI: 10.3109/02841858909174683] where it was found that the sinusoids in the liver became bloated ultimately blocking the flow of bile causing significant lower back pain and ultimately precluding the use of these particulates in humans. + +<|ref|>text<|/ref|><|det|>[[118, 261, 848, 296]]<|/det|> +2. Page 6: line 4, change "...phantoms using a 7T..." to "phantoms using 7T..." and line 28, change "...major risk associated..." to "...major risks associated...). + +<|ref|>text<|/ref|><|det|>[[117, 310, 880, 399]]<|/det|> +3. A burning question is whether or not these 750 nm particles would be rapidly sequestered by the RE cells in the liver and if MRI of the liver would show significant uptake. This question was beautifully addressed on p 16. It may be prudent to add a sentence or two on the potential impact of significant first pass liver clearance on the amount of agent ultimately reaching the micro-thrombi in the brain and whether or not alternative injection sites might allow more efficient targeting. + +<|ref|>text<|/ref|><|det|>[[117, 413, 840, 447]]<|/det|> +4. Page 22, Transmission Electron Microscopy section: line 1: change dry to dried. Line 7: change ultrahion to ultrathin. + +<|ref|>text<|/ref|><|det|>[[117, 462, 595, 478]]<|/det|> +5. Page 24 Exclusion criteria section: line 1, change MIE to Mice + +<|ref|>text<|/ref|><|det|>[[117, 492, 850, 527]]<|/det|> +6. Page 26: Please justify why only male mice were used in this study. If it is because of their large size in this strain, then say this. + +<|ref|>text<|/ref|><|det|>[[119, 631, 403, 646]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 691, 880, 872]]<|/det|> +The paper describes the development of magnetic material based on iron oxide and polydopamine that enables the non- invasive in vivo diagnosis and monitoring of microthrombi using MRI and during acute ischemic strokes. The ability of the material was assessed on a mouse model by identifying differences in MRI response and by confirming them by histological analysis. The results were associated with a study of the protein corona, which indicated the key role of fibrinogen in the corona in the targeting to microthrombi. Finally, the authors studied the fate of the injected contrast agent, which is degraded in the liver and spleen. The relevance of the work is that the described methodology allows the identification of microvascular thrombosis through non- invasive methods, which is a challenging and important task because the microthrombi are associated with poorer clinical outcomes. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 872, 138]]<|/det|> +As for the specific part associated with my expertise, the corona appears to have a fundamental role in targeting. Indeed, the authors characterize the corona because no active targeting by ligands is present on the material. Fibrinogen is used to explain the targeting. + +<|ref|>text<|/ref|><|det|>[[115, 150, 837, 168]]<|/det|> +1) The authors could add a brief explanation as to why fibrinogen in the corona can target clots. + +<|ref|>text<|/ref|><|det|>[[118, 180, 877, 234]]<|/det|> +2) A brief discussion on the role of other major proteins in the corona can also be added, to elucidate possible interactions with the immune system. Please focus on the PhySIOMIC particles rather than melamine particles. + +<|ref|>text<|/ref|><|det|>[[115, 247, 872, 283]]<|/det|> +3) A quantitative analysis of fibrinogen in PhySIOMIC and melamine particles could also be included, to support the results with the commercial fluorescent particles. + +<|ref|>text<|/ref|><|det|>[[115, 296, 833, 332]]<|/det|> +4) In the methods section, please add a sentence on the type of processing used for proteomic analysis, with a reference to the protocol. + +<|ref|>text<|/ref|><|det|>[[118, 344, 864, 399]]<|/det|> +5) Figure 7 in supplementary material is difficult to read, please improve size and font. In addition, please provide the corona composition as an Excel file with matched protein groups and associated information for identification. + +<|ref|>text<|/ref|><|det|>[[115, 411, 819, 429]]<|/det|> +6) Deposit in a public repository of raw LC/MS data and protein identifications could be done. + +<|ref|>text<|/ref|><|det|>[[118, 593, 403, 608]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 653, 880, 799]]<|/det|> +In this study, the authors have developed a contrast agent of MRI called PhySIOMIC, synthesized through a self- assembly process of SPIO within a polydopamine matrix. This approach has enabled us to combine the advantages of clinically approved SPIO, which possesses good \(\mathsf{T2}^*\) relaxivity in MRI, with those of micro- sized particles. These micro- sized particles enhance \(\mathsf{T2}^*\) contrast and enable rapid absorption for fast molecular imaging. Additionally, the polydopamine matrix conferred thrombosis targeting properties that enabled molecular MRI of microthrombi in a thrombo- embolic ischemic stroke murine model. Overall, this design is very intriguing. However, there are a few concerns that need to be clarified before consideration for publication. + +<|ref|>text<|/ref|><|det|>[[118, 811, 860, 902]]<|/det|> +1. The authors found that PhySIOMIC without any ligands targeted microthrombi through the formation of the protein corona. However, the effect of the particle size and zeta potential of PhySIOMIC on the microthrombi targeting was not well revealed. In addition, the composition and the underlying mechanism of the protein corona to facilitate PhySIOMIC's microthrombi targeting were not well discovered. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 875, 156]]<|/det|> +2. Figure 2b demonstrated that the imaging effect of PhySIOMIC was significantly superior to that of SPIO. It was proven that the protein corona of PhySIOMIC could enhance its microthrombi-targeting. However, there is no additional analysis of SPIO to illustrate the unique composition of the protein corona of PhySIOMIC. Please provide further evidence. + +<|ref|>text<|/ref|><|det|>[[118, 169, 875, 241]]<|/det|> +3. The formation of the protein corona on nanoparticles could accelerate the removal of particles from the bloodstream, thereby reducing the amount of PhySIOMIC reaching the microvasculature. It was also evident that the half-life of PhySIOMIC was much shorter than that of SPIO. Why did PhySIOMIC have a superior targeting to microthrombi? Please discuss the results. + +<|ref|>text<|/ref|><|det|>[[118, 254, 866, 344]]<|/det|> +4. Figure 7a illustrated that both PhySIOMIC and SPIO particles induced a significant decrease in signal intensity in the liver and spleen, indicating rapid clearance of the particles from the body. Additionally, in Fig. 7b, it is noteworthy that the signal intensity after injection is considerably lower than before, and it gradually increases with time. Can you explain the underlying cause of this phenomenon? + +<|ref|>text<|/ref|><|det|>[[118, 358, 864, 429]]<|/det|> +5. The administration of thrombolysis with rtPA results in increased permeability of the blood-brain barrier. However, using PhySIOMIC at this stage is associated with an elevated risk of the contrast agent crossing the blood-brain barrier, which can potentially cause severe brain injury. Please discuss the advantages and disadvantages of PhySIOMIC as an MRI contrast agent. + +<|ref|>text<|/ref|><|det|>[[115, 443, 803, 460]]<|/det|> +6. It is advisable to carefully proofread the manuscript for any errors in grammar and typos. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 135, 250, 149]]<|/det|> +Dear Reviewers + +<|ref|>title<|/ref|><|det|>[[117, 168, 830, 186]]<|/det|> +# Title: MRI-Based Microthrombi Detection in Stroke with Polydopamine Iron Oxide + +<|ref|>text<|/ref|><|det|>[[117, 203, 425, 219]]<|/det|> +Manuscript - NCOMMS- 23- 56845- T + +<|ref|>text<|/ref|><|det|>[[117, 237, 642, 253]]<|/det|> +We would like to thank the reviewers for their recommendations. + +<|ref|>text<|/ref|><|det|>[[115, 255, 881, 288]]<|/det|> +In response to the comments, we have enriched the manuscript following the suggestions of the 4 reviewers. + +<|ref|>text<|/ref|><|det|>[[115, 289, 881, 392]]<|/det|> +In total, we have modified 8 figures (Figures 2, 3, 4, 5, 6, S7, S8, and S9), added 2 supplementary figures (Figures S5 and S6) and 2 other supplementary materials; a video file (supplementary material 1) and the detailed analysis of raw data (supplementary material 2). We enriched the introduction, method, results, and discussion sections to answer the different comments. We also shortened the abstract to respect the 150- word limit and shortened the subheadings as requested. + +<|ref|>text<|/ref|><|det|>[[117, 409, 881, 460]]<|/det|> +All modifications are listed below and new text is highlighted in blue. Additionally, a version of the manuscript with all modifications identified via the tracking mode is provided; it shows in red the modifications. A clean final version of the revised manuscript is also provided. + +<|ref|>text<|/ref|><|det|>[[115, 478, 878, 495]]<|/det|> +We hope the modifications will meet the requirements of the editor and the different reviewers. + +<|ref|>text<|/ref|><|det|>[[117, 531, 267, 547]]<|/det|> +With best regards, + +<|ref|>text<|/ref|><|det|>[[117, 565, 299, 581]]<|/det|> +Corresponding Author + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 447, 98]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 112, 880, 144]]<|/det|> +This manuscript evaluates a unique MRI- based contrast agent (PHySIOMIC) for detection of microthrombi in the brain during experimental stroke. + +<|ref|>text<|/ref|><|det|>[[117, 157, 878, 174]]<|/det|> +I have a number of questions/concerns/suggestions about the experiments performed. + +<|ref|>text<|/ref|><|det|>[[117, 187, 512, 203]]<|/det|> +Page 20, paragraph 2: etiology is misspelled. + +<|ref|>text<|/ref|><|det|>[[117, 218, 521, 233]]<|/det|> +We have corrected this error, thank you for spotting it. + +<|ref|>text<|/ref|><|det|>[[116, 247, 880, 309]]<|/det|> +Was the parent vessel still occluded at the time hypointense signal was seen after PHySIOMIC injection? 3D TOF MRI should be able to confirm such? Could PHySIOMIC being simply measuring poor cerebral blood flow from a proximal occlusion rather than true microthrombi? + +<|ref|>text<|/ref|><|det|>[[115, 323, 881, 504]]<|/det|> +In both ischemic stroke models presented in Figure 3, we confirm that the parent vessel is still occluded at the time of the injection as confirmed by the TOF as well as perfusion MRI (Figure 3d). We also confirm that this blood flow deficit induces tissue injury as we detect the formation of a brain infarct via diffusion- weighted MRI. In both models, the consequences in terms of blood flow reduction are similar. Yet, the results are radically different between the two models; in the thrombin model we observe a strong signal corresponding to PHySIOMIC accumulation and we can observe microthrombi in histology sections, while in the AICl3 model, we have no signal and no microthrombi in histology (figure 3d). If the PHySIOMIC were measuring poor cerebral blood flow, a similar signal would have been obtained in both models. Moreover, in every observation of histology sections (TEM, immuno- histology, or PERLS staining) or two- photon microscopy, we found the PHySIOMIC exclusively where thrombi were found. We now provide more data in terms of histology and added TEM observations in order to clarify this point (Supplementary Figures 5 and 6, more details are provided in the following questions). + +<|ref|>text<|/ref|><|det|>[[116, 519, 880, 565]]<|/det|> +However, it is not to be excluded that the slower blood flow downstream of the proximal clot contributes to the effective binding of our particles to the microthrombi. The decrease in blood flow might enhance the contact between the particles and the microthrombi, thereby facilitating binding. + +<|ref|>text<|/ref|><|det|>[[116, 593, 880, 655]]<|/det|> +Please provide more details in the pathologic analysis of how the PHySIOMIC is aggregating with microthrombi? Figure 2g. Magnified images of the clusters of iron oxide and their association with microthrombi (stained by specific immunostains to confirm such). + +<|ref|>text<|/ref|><|det|>[[115, 669, 880, 745]]<|/det|> +Regarding the analysis of how the PHySIOMIC is binding to the microthrombi, we hypothesize that the fibrinogen content from the protein corona confers affinity to activated platelets. We now have a whole set data presented in Figure 6 further supporting this hypothesis. Accordingly, we added several sentences to the revised version of the manuscript. We discussed this hypothesis in the discussion section, p 19- 20: + +<|ref|>text<|/ref|><|det|>[[115, 758, 881, 895]]<|/det|> +"we notably investigated the composition of the PC of PHySIOMIC particles and pursued the hypothesis that its fibrinogen composition could contribute to the targeting process to microthrombi. However, it remains plausible that other PC components might contribute to the thrombosis targeting phenomenon. In such conditions, it should be noted that the presence of a higher concentration of fibrinogen in the protein corona on the PHySIOMIC particles could also have prothrombotic consequences. At this stage, we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin αIIbβ3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations as the PHySIOMIC were found attached to activated platelets." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 881, 188]]<|/det|> +Regarding Figure 2g, we removed the histology observations to put forward the TEM observations (explained in the next question). We also added a supplementary figure exclusively dedicated to histology and immune- staining of microthrombi. We now provide images from histology sections of a brain harvested after the intravenous injection of PHySIOMIC, just after the MRI procedure, where the microthrombi were revealed via CD41 and where the PHySIOMIC could be detected by light reflection on the surrounding of the microthrombi. The Perls' staining also supports the fact that the iron oxide clusters are localized around the microthrombi. + +<|ref|>text<|/ref|><|det|>[[118, 194, 739, 210]]<|/det|> +We added an explanation of this additional observation in the method section, p 27: + +<|ref|>text<|/ref|><|det|>[[117, 216, 880, 277]]<|/det|> +"The specificity of immunostainings was checked by showing the absence of staining when primary antibodies were omitted. The PHySIOMIC could also be revealed via reflection of the polydopamine, using \(488\mathrm{nm}\) laser as emission and setting both, the excitation and the emission filter around the laser wavelength ( \(480\mathrm{nm}\) to \(495\mathrm{nm}\) ) in order to detect reflection of the laser." + +<|ref|>text<|/ref|><|det|>[[118, 284, 337, 300]]<|/det|> +We completed the results p 7: + +<|ref|>text<|/ref|><|det|>[[115, 306, 881, 412]]<|/det|> +"We can conclude that, in this model, PHySIOMIC particles constitute a diagnosis tool to reveal microthrombi and to predict the size of the ischemic lesions. Microthrombi could be identified via platelet marker CD41 immunolabelling in the ischemic area on histological analysis of brains harvested just after the MRI acquisition, 1 hour after the stroke induction. The PHySIOMIC particles could be detected via light reflection from polydopamine positioned around thrombi and the microthrombi, on the luminal side of blood vessels (Supplementary Fig. 5a,b). Perls staining confirmed this specific localization of the particles, stained blue due to their iron oxide composition (Supplementary Fig. 5c)." + +<|ref|>text<|/ref|><|det|>[[117, 418, 353, 433]]<|/det|> +See below the added Figure S5: + +<|ref|>image<|/ref|><|det|>[[118, 440, 740, 870]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 81, 880, 144]]<|/det|> +Please show some electron microscopic evidence of PhySIOMIC/iron oxide particles in proximity to microthrombi from brain samples at the location of the infarct where microthrombi seen. TEM was performed for spleen and liver deposition of PhySIOMIC so could also be done for brain samples. + +<|ref|>text<|/ref|><|det|>[[116, 158, 880, 219]]<|/det|> +We would like to thank the reviewer for this interesting suggestion. The requested experiments were performed with the help of the electron microscopy imaging facility MicroEleCS from the INSERM UMR- S1255 Unit in Strasbourg. The images obtained following the processing of the samples are presented in the new Supplementary Figure 6 + +<|ref|>text<|/ref|><|det|>[[117, 233, 644, 249]]<|/det|> +We added the description of the experiment in the method section p 23: + +<|ref|>text<|/ref|><|det|>[[116, 263, 881, 385]]<|/det|> +"Microthrombi in brain section were observed at the electron microscopy imaging facility MicroEleCS (INSERM UMR- S1255 Unit, Strasbourg, France). Brain tissue was fixed with \(2.5\%\) glutaraldehyde in \(0.1\mathrm{M}\) sodium cacodylate buffer containing \(2\%\) sucrose, previously warmed to \(37^{\circ}\mathrm{C}\) (305 mOsm, pH 7.3) for 1 hour. The samples were then rinsed and postfixed with \(1\%\) osmium tetroxide in \(0.1\mathrm{M}\) sodium cacodylate buffer for 1 hour at \(4^{\circ}\mathrm{C}\) . After additional washing in the \(0.1\mathrm{M}\) sodium cacodylate buffer, the samples were dehydrated in successively increasing ethanol concentrations before embedding in epoxy. The resin was polymerized for 2 days at \(50^{\circ}\mathrm{C}\) . Ultrathin sections (100 nm) were stained with lead citrate and uranyl acetate, and examined under a Jeol 2100- plus (120 kV)." + +<|ref|>text<|/ref|><|det|>[[117, 399, 297, 414]]<|/det|> +In the result section p 8: + +<|ref|>text<|/ref|><|det|>[[116, 428, 880, 504]]<|/det|> +"To further investigate the localization of the PhySIOMIC within the microthrombi, we performed transmission electronic microscopy (TEM) of the brain sections and we observed the iron oxide clusters close to degranulated platelets (Fig. 2g and Supplementary Fig 6). In all observations of the histological sections, the PhySIOMIC particles were identified inside or at the surface of microthrombi, without noticeable accumulation in other parts of the brain." + +<|ref|>text<|/ref|><|det|>[[117, 526, 353, 541]]<|/det|> +See below the added Figure S6: + +<|ref|>image<|/ref|><|det|>[[120, 545, 737, 911]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 97, 686, 115]]<|/det|> +## Why does the AlCl3 model (Figure 3) not produce microthrombi? + +<|ref|>text<|/ref|><|det|>[[116, 127, 881, 204]]<|/det|> +AlCl3 is deposited locally over the MCA bifurcation and enables thrombosis formation restricted to the vessel exposed to AlCl3. In contrast, in the thrombin model, recombinant murine thrombin is infused intra- arterially and reach not only the main artery where the pipet tip is located, but also the whole downstream microcirculation, thereby leading to microthrombi formation. We completed the result part with more description of the model and an explanation of this specific difference, p10: + +<|ref|>text<|/ref|><|det|>[[116, 209, 881, 300]]<|/det|> +"We further compared the results obtained after PhySIOMIC injection in this first ischemic stroke model induced via thrombin injection in the MCA (referred to as 'thrombin model'), to a second ischemic stroke model in which thrombosis was induced in situ via local deposition on the MCA of a filter paper soaked with aluminum chloride (Fig 3). In this second model (referred to as the 'AlCl3 model'), a unique clot is formed precisely at the area in contact with AlCl3 and no embolization in the microcirculation occurs." + +<|ref|>sub_title<|/ref|><|det|>[[116, 321, 773, 339]]<|/det|> +## Figure 6 is assessing Melamine and Melamine-Carboxylic not PhySIOMIC? + +<|ref|>text<|/ref|><|det|>[[116, 344, 881, 421]]<|/det|> +Indeed, in Figure 6, we focused mainly on fluorescent particles of Melamine and Melamine- Carboxylic except for the results from the mass spectrometry for the analysis of the plasma protein corona where we also performed the experiment on the PhySIOMIC. The reason we could not perform the same experiments on the PhySIOMIC is that we were not able to label them with fluorescent dye as the polydopamine modifies optic properties. + +<|ref|>text<|/ref|><|det|>[[118, 427, 463, 442]]<|/det|> +We explain this in the discussion section, p 21: + +<|ref|>text<|/ref|><|det|>[[116, 463, 881, 630]]<|/det|> +"Due to the light- absorbing properties of polydopamine, it was not possible to obtain fluorescently labeled polydopamine particles without surface modification for in vitro experiments. Therefore, to delve deeper into the thrombosis targeting mechanism identified with PhySIOMIC particles, we opted to use commercially available fluorescent particles composed of melamine resin. This choice was motivated by the presence of amine groups on the surface of melamine resin, which is akin to polydopamine. Furthermore, it has been reported that modifying the external layer of nanomedicines with carboxylate groups significantly influences the profile of adsorbed proteins compared to bare particles with amine groups36. Consequently, we also used melamine functionalized with carboxylic termination (melamine-COOH). Thanks to the strong fluorescent labeling of melamine and melamine-COOH, we were able to track them in vitro through a microfluidic study and in vivo with two- photon microscopy." + +<|ref|>sub_title<|/ref|><|det|>[[116, 652, 880, 700]]<|/det|> +## Supplemental Figure 4 raises major concerns about the MR contrast agent slowing the effects of clot lysis with TPA with longer clot lysis times. Please discuss in Discussion section. + +<|ref|>text<|/ref|><|det|>[[116, 705, 881, 798]]<|/det|> +The supplementary figure 4 indicates that the presence of the MR contrast agent might slightly slow the clot lysis with tPA. Although this difference is not significant for both the tPA concentrations tested, we agree that this is an important risk to consider for future development. In addition, the thrombosis targeting mechanism that we elucidated in this study involves the presence of fibrinogen in higher concentration in the protein corona of the particles adhering to thrombosis which in itself may carry prothrombotic risk. We propose to raise this aspect in the discussion p19- 20: + +<|ref|>text<|/ref|><|det|>[[116, 803, 881, 910]]<|/det|> +"In such conditions, it should be noted that the presence of a higher concentration of fibrinogen in the protein corona on the PhySIOMIC particles could also have prothrombotic consequences. At this stage, we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin αIIbβ3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations, where the PhySIOMIC were found attached to activated platelets. So, in addition to bringing some fibrinogen to the edge of the clot and thus possibly enhancing fibrin + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 82, 880, 158]]<|/det|> +polymerization, the PhySIOMIC covered with fibrinogen could also increase platelet aggregation. Besides, although the clot lysis assay did not show a significant difference in the tPA- induced clot lysis time in the presence of PhySIOMIC, the mean value of lysis time was numerically higher. Overall, the putative risk of prothrombotic effect should be monitored for further developments of the PhySIOMIC particles." + +<|ref|>sub_title<|/ref|><|det|>[[116, 194, 880, 241]]<|/det|> +## Supplemental Figure 5: Authors should speculate whether the disappearance of PhySIOMIC with time is a product of the half life/metabolism properties of the agent or that microthrombi clear over time? + +<|ref|>text<|/ref|><|det|>[[116, 255, 880, 331]]<|/det|> +The disappearance of the signal coincides with recalculation time and for this reason, we attribute the loss of signal to microthrombi clearance rather than proper half- life/metabolism of the PhySIOMIC. Indeed, we observe disappearance of PhySIOMIC on MRI over a few hours, whereas usually the metabolism of iron oxide nanoparticles requires a few weeks to reverse the MRI signal (Martinez de Lizarondo et al., Science Advances 2022). We added a sentence to precise this hypothesis, p12: + +<|ref|>text<|/ref|><|det|>[[116, 345, 880, 436]]<|/det|> +While the signal void was consistent with previous observations when measured at early time points after stroke onset (30 minutes and 2 hours post- occlusion), it almost completely disappears at 6 hours post- occlusion (Supplementary Fig. 8c). These events coincide with cerebral reperfusion, as indicated by the increase in the angiographic score (Supplementary Fig. 8d,e) which supports that this slow progressive signal disappearance is caused by the clearance of the microthrombi rather than in situ metabolization of the PhySIOMIC." + +<|ref|>text<|/ref|><|det|>[[116, 465, 880, 542]]<|/det|> +Supplemental Figure 6d: The Time of Flight image provided offers no compelling evidence of recalculation. The wrong side of the brain has an arrow? Please orient the reader to which side of the brain we are seeing for each Figure of the manuscript. Is Left on left and right on right consistently for the various imaging figures provided throughout the manuscript? + +<|ref|>text<|/ref|><|det|>[[116, 556, 880, 616]]<|/det|> +Time- of- flight images are presented along the axial axis, viewed from above. In this representation, the MCA was observed on the right of the images (where was the arrow). To ensure better comprehension, we changed the visualization of the TOF images to place the MCA on the left in all images. The TOF images are seen now from below. We also added left and right indications on the images (noted L & R). + +<|ref|>text<|/ref|><|det|>[[116, 644, 880, 677]]<|/det|> +Please consider showing a more representative example of persistent occlusion versus recalculation at 6 hours. + +<|ref|>text<|/ref|><|det|>[[116, 691, 880, 752]]<|/det|> +The images used as examples to demonstrate recalculation are not the most representative; they have been modified to better match the average of the data presented in the recalculation graph. These modifications also led us to change the orientation of the images in Figure 3 (perfusion imaging and angiography) to correspond. + +<|ref|>sub_title<|/ref|><|det|>[[117, 780, 447, 796]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 810, 880, 901]]<|/det|> +This manuscript describes a new MRI contrast agent, PhySIOMIC, which is intended to allow MR imaging of thrombi and microthrombi in a mouse model of thromboembolic ischemic stroke. Currently there is no accurate way of imaging thrombi and microthrombi in the brain. Being able to do so, would have tremendous value in both detecting such lesions during stroke, and also monitoring the response of individual sites following standard of care treatments. The significance of this work is therefore + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 82, 880, 219]]<|/det|> +very high. Detection of both thrombi and microthrombi and monitoring of thrombolytic treatment was demonstrated in this mouse model. The authors present very well- designed experiments to assess the targeting and MR imaging characteristics, biologic mechanism of action, degradation, and clearance pathways, as well as the ability of the agent to monitor the efficacy of response in near real time which is imperative in stroke patients. The approach was very thorough, and data provided strongly supported the conclusions. Statistical support is appropriate. Supplementary materials all appear to be important for supporting conclusions. There are only a few questions or comments that would improve the paper which follow. + +<|ref|>text<|/ref|><|det|>[[116, 232, 881, 414]]<|/det|> +1. It is stated in the methods section on p26 that either "PhYSIOMIC or SPIO particles with concentrations of \(4\mathrm{mg}\) [FE]/kg were administered to naive male Swiss mice. Please clarify this dosing nomenclature and provide a total mass dose and volume of each agent administered per mouse. Please provide clear dosing masses and volumes when agents are injected. Although assessing safety and tolerance of the agent was not an aim of this paper, it will be necessary to clearly understand the dosing especially since large volumes of particles greater than \(500\mathrm{nm}\) in diameter have proven problematic in early human studies [Ivancev, et al. (1989) Effect of Intravenously Injected iodinated Lipid Emulsions on the Liver, Acta Radiologica, 30:3, 291-298, DOI: 10.3109/02841858909174683] where it was found that the sinusoids in the liver became bloated ultimately blocking the flow of bile causing significant lower back pain and ultimately precluding the use of these particulates in humans. + +<|ref|>text<|/ref|><|det|>[[117, 428, 880, 458]]<|/det|> +The sentence in the Materials and Methods indicating the dose administered to mice was changed for a better understanding of the injected dose, p29: + +<|ref|>text<|/ref|><|det|>[[116, 473, 880, 549]]<|/det|> +The PhYSIOMIC and SPIO particles were individually reconcentrated to a concentration of \(0.8\mathrm{mg}[\mathrm{Fe}].\mathrm{mL}^{- 1}\) using a magnet. They were then intravenously injected to attain a final iron concentration of \(4\mathrm{mg}.\mathrm{kg}^{- 1}\) , with approximately \(200\mu \mathrm{L}\) of solution administered to each naive male Swiss mouse (8 weeks, \(\mathrm{n} = 5\) per group). The ratio polydopamine to iron is of 3.2 so an iron dose of \(4\mathrm{mg}.\mathrm{kg}^{- 1}\) correspond to a \(16.8\mathrm{mg}\) dose of particles injected per kg. + +<|ref|>text<|/ref|><|det|>[[116, 563, 880, 638]]<|/det|> +Concerning the risks associated with particles larger than \(500\mathrm{nm}\) , we thank the reviewer for pointing us to this study and the specific risks of large particles. We agree that it will be crucial to conduct further stability/toxicity studies before advancing these particles to clinical trials to ensure their safety. Knowing this specific risk of liver sinusoid embolization will be useful at this point and we will certainly add it to the list of risk to be considered. + +<|ref|>text<|/ref|><|det|>[[116, 639, 881, 804]]<|/det|> +From our side, we performed a more comprehensive toxicity study regarding the risk in the liver with similar particles in a study we published recently (Sara Martinez de Lizarondo et al., Tracking the immune response by MRI using biodegradable and ultrasensitive microprobes.Sci. Adv.8,ebm3596(2022).DOI:10.1126/sciadv.ebm3596). We verified the non- toxicity of other submicrometric iron oxide- based particles, with a 6- month follow- up on animals. We observed hepatic biodegradation of the particles, assessed the condition of the liver, kidneys, lungs, and spleen via histology, and verified the absence of ASAT and ALAT or pro- inflammatory cytokines generated. With this data, we are confident that iron oxide polydopamine particles with a diameter between \(500\mathrm{nm}\) and \(1\mu \mathrm{m}\) do not induce toxic side effects if injected at reasonable dose. It should however be acknowledged that preclinical studies cannot reveal every side effects and that consequences of intravenous injection of such particles in human remain largely unknown. + +<|ref|>text<|/ref|><|det|>[[115, 833, 880, 865]]<|/det|> +2. Page 6: line 4, change "...phantoms using a 7T..." to "phantoms using 7T..." and line 28, change "...major risk associated..." to "...major risks associated...). + +<|ref|>text<|/ref|><|det|>[[117, 879, 546, 894]]<|/det|> +Thank you for spotting these mistakes, we corrected them. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 880, 174]]<|/det|> +3. A burning question is whether or not these 750 nm particles would be rapidly sequestered by the RE cells in the liver and if MRI of the liver would show significant uptake. This question was beautifully addressed on p 16. It may be prudent to add a sentence or two on the potential impact of significant first pass liver clearance on the amount of agent ultimately reaching the micro-thrombi in the brain and whether or not alternative injection sites might allow more efficient targeting. + +<|ref|>text<|/ref|><|det|>[[115, 188, 880, 293]]<|/det|> +We added a specific paragraph in the revised version of the discussion to discuss the potential negative impact of the short half- life. We agree that the number of particles reaching the target is most likely very low (probably around \(0.5\%\) ). However, it should also be noted that if the particles were decorated with PEG chains to decrease the RE sequestration, for example, the targeting would not be effective anymore because of a perturbed protein corona. Regarding the injection route, it is indeed possible that intra- arterial injection would increase the targeting ratio as the particles would pass through the brain before being filtered by the liver. + +<|ref|>text<|/ref|><|det|>[[118, 293, 450, 307]]<|/det|> +We now discuss this aspect in the discussion: + +<|ref|>text<|/ref|><|det|>[[115, 323, 880, 444]]<|/det|> +It is also interesting to note that the PhYSIOMIC provided strong imaging signal detection although they exhibited an extremely short half- life (less than a minute) compared to the SPIO which typically circulates much longer (over 10 minutes) but was not able to reveal the microthrombi. This might appear surprising as the field of nanomedicine usually supports long circulation half- life as a positive feature for molecular imaging applications as longer exposure time should logically result in increased targeting35. However, this study provides evidence that this reasoning is not always true and that, at least in some contexts, modifying the surface to improve the targeting properties can be more valuable than to increase the circulation time. + +<|ref|>sub_title<|/ref|><|det|>[[115, 467, 880, 499]]<|/det|> +## 4. Page 22, Transmission Electron Microscopy section: line 1: change dry to dried. Line 7: change ultrathion to ultrathin. + +<|ref|>text<|/ref|><|det|>[[117, 513, 545, 528]]<|/det|> +Thank you for spotting these mistakes, we corrected them. + +<|ref|>sub_title<|/ref|><|det|>[[115, 542, 678, 558]]<|/det|> +## 5. Page 24 Exclusion criteria section: line 1, change MIE to Mice + +<|ref|>text<|/ref|><|det|>[[117, 573, 501, 588]]<|/det|> +Thank you for spotting this mistake, we corrected it. + +<|ref|>sub_title<|/ref|><|det|>[[115, 602, 880, 634]]<|/det|> +## 6. Page 26: Please justify why only male mice were used in this study. If it is because of their large size in this strain, then say this. + +<|ref|>text<|/ref|><|det|>[[115, 648, 881, 739]]<|/det|> +We generally use exclusively male mice because we encounter more reproducibility as we avoid the potential impact of the estrous cycle. This is a general habit of preclinical research and animal experiments that we are aware is not ideal, as we might miss an effect related to sex. For this reason, in this study, we have now included a study on female mice to study the potential effect of sex (cf described in the answer to editor comments). In summary, we do not observe any significant differences between male and female mice for microthrombi imaging using PhYSIOMIC. + +<|ref|>sub_title<|/ref|><|det|>[[117, 767, 446, 783]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 797, 880, 904]]<|/det|> +The paper describes the development of magnetic material based on iron oxide and polydopamine that enables the non- invasive in vivo diagnosis and monitoring of microthrombi using MRI and during acute ischemic strokes. The ability of the material was assessed on a mouse model by identifying differences in MRI response and by confirming them by histological analysis. The results were associated with a study of the protein corona, which indicated the key role of fibrinogen in the corona in the targeting to microthrombi. Finally, the authors studied the fate of the injected contrast + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 880, 242]]<|/det|> +agent, which is degraded in the liver and spleen. The relevance of the work is that the described methodology allows the identification of microvascular thrombosis through non- invasive methods, which is a challenging and important task because the microthrombi are associated with poorer clinical outcomes. As for the specific part associated with my expertise, the corona appears to have a fundamental role in targeting. Indeed, the authors characterize the corona because no active targeting by ligands is present on the material. Fibrinogen is used to explain the targeting. + +<|ref|>text<|/ref|><|det|>[[117, 255, 686, 271]]<|/det|> +We added a hypothesis on this explanation in the discussion section p 19- 20: + +<|ref|>text<|/ref|><|det|>[[116, 289, 880, 368]]<|/det|> +"At this stage, we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin aIIbB3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations, where the PhySIOMIC were found attached to activated platelets." + +<|ref|>text<|/ref|><|det|>[[116, 382, 880, 430]]<|/det|> +2) A brief discussion on the role of other major proteins in the corona can also be added, to elucidate possible interactions with the immune system. Please focus on the PhySIOMIC particles rather than melamine particles. + +<|ref|>text<|/ref|><|det|>[[116, 443, 880, 489]]<|/det|> +To enrich the discussion, we have incorporated a paragraph in the Discussion section addressing the proteins found in the protein corona and their potential influence on PhySIOMIC particles' biodistribution, blood half-life, and immune response, p19: + +<|ref|>text<|/ref|><|det|>[[116, 503, 880, 564]]<|/det|> +"It is noteworthy that the protein corona plays a significant role in the biodistribution, blood circulation time, and immune response to particles. Thus, the presence of opsonins within this protein corona facilitates rapid recognition by the complement system and the clearance of particles from circulation by macrophages." + +<|ref|>sub_title<|/ref|><|det|>[[115, 577, 880, 609]]<|/det|> +## 3) A quantitative analysis of fibrinogen in PhySIOMIC and melamine particles could also be included, to support the results with the commercial fluorescent particles. + +<|ref|>text<|/ref|><|det|>[[115, 622, 881, 775]]<|/det|> +To address this question, we conducted an additional experiment, as depicted in the new Supplementary Figure 7, to measure fibrinogen adsorption on melamine and PhySIOMIC particles using a Nanodrop spectrophotometer (Implen). A fibrinogen solution (1 mg/mL) was exposed to the different particles, and after centrifugation, the particles were separated from the solution, allowing us to measure the fibrinogen content in the supernatant. The results support our hypothesis that fibrinogen adsorption is more pronounced in PhySIOMIC and melamine particles targeting microthrombi. In contrast, fibrinogen absorption was found to be negligeable on melamine- COOH particles. Unfortunately, it was not possible to measure PhySIOMIC- BSA's fibrinogen adsorption using this technique due to interference between BSA and fibrinogen spectra on the nano spectrophotometer. We have included this experiment in the Results section, along with the technique in the Methods section. + +<|ref|>text<|/ref|><|det|>[[115, 802, 880, 910]]<|/det|> +Results section, p 16: "Remarkably, we noticed an augmentation in the number of particles adhering to thrombi when the particles were suspended in fibrinogen- rich plasma (Fig. 6f). Hence, the fibrinogen integrated into the PCs of PhySIOMIC while in circulation plays a pivotal role in their passive targeting to thrombi and microthrombi. To measure the adsorption of fibrinogen onto the surface of particles, we exposed the particles to a fibrinogen solution (1 mg.mL- 1) during 30 minutes at 37°C. The particles were then centrifuged, and the fibrinogen remaining in the supernatant was measured using a nano spectrophotometer. Fibrinogen adsorption is greater on melamine and PhySIOMIC particles, with mean + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 682, 99]]<|/det|> +values of \(50 \mu \mathrm{g}\) and \(75 \mu \mathrm{g}\) , respectively, per \(250 \mu \mathrm{l}\) of particles (Figure 6g).” + +<|ref|>text<|/ref|><|det|>[[117, 113, 281, 128]]<|/det|> +Methods section, p26: + +<|ref|>sub_title<|/ref|><|det|>[[117, 152, 404, 167]]<|/det|> +## “Fibrinogen adsorption quantification + +<|ref|>text<|/ref|><|det|>[[115, 177, 881, 268]]<|/det|> +Melamine (diluted at 1:5), Melamine- COOH (diluted at 1:50) and PHySIOMIC particles were incubated with a fibrinogen solution (1 mg.mL- 1) at a 1:1 ratio during 30 minutes at \(37^{\circ}\mathrm{C}\) . The particles were then centrifuged (3 minutes, 10000 rpm) and the supernatant was measured with a nano spectrophotometer (Nanodrop, Implen) with a molar extinction coefficient of 1,51. The amount of fibrinogen adsorbed onto the surface of the particles is measured by subtracting the fibrinogen value measured in the supernatant from the control fibrinogen value (incubation of fibrinogen and mannitol buffer of the particles).” + +<|ref|>text<|/ref|><|det|>[[117, 276, 364, 291]]<|/det|> +See below the modified Figure 6: + +<|ref|>image<|/ref|><|det|>[[117, 299, 768, 875]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 82, 880, 114]]<|/det|> +## 4) In the methods section, please add a sentence on the type of processing used for proteomic analysis, with a reference to the protocol. + +<|ref|>text<|/ref|><|det|>[[115, 128, 880, 158]]<|/det|> +The proteomic protocol conducted by the Proteogen platform has been added to the "Methods" section, \(p 24 - 25\) : + +<|ref|>text<|/ref|><|det|>[[115, 159, 881, 435]]<|/det|> +"Five \(\mu \mathrm{g}\) of each protein extract were prepared using a modified Gel- aided Sample Preparation protocol51. Samples were digested with trypsin/Lys- C overnight at \(37^{\circ}\mathrm{C}\) . For nano- LC fragmentation, protein or peptide samples were first desalted and concentrated onto a \(\mu \mathrm{C18}\) OmiX (Agilent) before analysis. The chromatography step was performed on a NanoElute (Bruker Daltonics) ultra- high- pressure nano flow chromatography system. Approximately \(200\mathrm{ng}\) of each peptide sample were concentrated onto a C18 pepmap 100 (5mm x \(300\mu \mathrm{m}\) i.d.) precolumn (Thermo Scientific) and separated at \(50^{\circ}\mathrm{C}\) onto a reversed phase Reprosil column (25cm x \(75\mu \mathrm{m}\) i.d.) packed with \(1.6\mu \mathrm{m}\) C18 coated porous silica beads (Ionopticks). Mobile phases consisted of \(0.1\%\) formic acid, \(99.9\%\) water (v/v) (A) and \(0.1\%\) formic acid in \(99.9\%\) ACN (v/v) (B). The nanoflow rate was set at \(300\mathrm{nl / min}\) , and the gradient profile was as follows: from 2 to \(15\%\) B within \(15\mathrm{min}\) , followed by an increase to \(25\%\) B within \(10\mathrm{min}\) and to \(37\%\) B within \(12\mathrm{min}\) and further to \(9\%\) within \(7\mathrm{min}\) and reequilibration. Mass Spectrometry (MS) experiments were carried out on an TIMS- TOF pro mass spectrometer (Bruker Daltonics) with a modified nano electrospray ion source (CaptiveSpray, Bruker Daltonics). A 1400 spray voltage with a capillary temperature of \(180^{\circ}\mathrm{C}\) was typically employed for ionizing. MS spectra were acquired in the positive mode in the mass range from \(100\) to \(1700\mathrm{m / z}\) and \(0.75\) to \(1.30\mathrm{1 / k0}\) window. In the experiments described here, the mass spectrometer was operated in PASEF DIA mode with exclusion of single charged peptides. The DIA acquisition scheme consisted of 24 variable windows ranging from 300 to \(1000\mathrm{m / z}\) . + +<|ref|>text<|/ref|><|det|>[[117, 450, 880, 497]]<|/det|> +5) Figure 7 in supplementary material is difficult to read, please improve size and font. In addition, please provide the corona composition as an Excel file with matched protein groups and associated information for identification. + +<|ref|>text<|/ref|><|det|>[[117, 511, 880, 572]]<|/det|> +Thank you for your feedback. The layout of the graphs has been adjusted, and their sizes have been increased to enhance clarity in reading the figure. The composition of the protein corona is provided in the Excel file of the Raw data. In this file, we have listed the proteins, their affiliations with a biological cluster, as well as the measurements by mass spectrometry. + +<|ref|>text<|/ref|><|det|>[[115, 586, 880, 616]]<|/det|> +6) Deposit in a public repository of raw LC/MS data and protein identifications could be done. + +<|ref|>text<|/ref|><|det|>[[115, 632, 880, 661]]<|/det|> +According to your recommendations, the mass spectrometry data has been added to a repository on the iProX website, under the number: IPX0008212001. + +<|ref|>sub_title<|/ref|><|det|>[[118, 684, 447, 700]]<|/det|> +## Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 713, 881, 849]]<|/det|> +In this study, the authors have developed a contrast agent of MRI called PhySIOMIC, synthesized through a self- assembly process of SPIO within a polydopamine matrix. This approach has enabled us to combine the advantages of clinically approved SPIO, which possesses good \(\mathrm{T2^*}\) relaxivity in MRI, with those of micro- sized particles. These micro- sized particles enhance \(\mathrm{T2^*}\) contrast and enable rapid absorption for fast molecular imaging. Additionally, the polydopamine matrix conferred thrombosis targeting properties that enabled molecular MRI of microthrombi in a thrombo- embolic ischemic stroke murine model. Overall, this design is very intriguing. However, there are a few concerns that need to be clarified before consideration for publication. + +<|ref|>text<|/ref|><|det|>[[117, 863, 880, 909]]<|/det|> +1. The authors found that PhySIOMIC without any ligands targeted microthrombi through the formation of the protein corona. However, the effect of the particle size and zeta potential of PhySIOMIC on the microthrombi targeting was not well revealed. In + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 81, 880, 115]]<|/det|> +## addition, the composition and the underlying mechanism of the protein corona to facilitate PhySIOMIC's microthrombi targeting were not well discovered. + +<|ref|>text<|/ref|><|det|>[[116, 134, 880, 196]]<|/det|> +While the mechanism involved in targeting microthrombi through protein corona formation has yet to be investigated, we demonstrate the importance of fibrinogen in this mechanism using microfluidic experiments. We proposed in a paragraph added to the Discussion Section that PhySIOMIC, with fibrinogen adsorbed on its surface, may bind to platelet integrin aIIbB3 in microthrombi: + +<|ref|>text<|/ref|><|det|>[[115, 209, 881, 362]]<|/det|> +"Thus, we notably investigated the composition of the PC of PhySIOMIC particles and pursued the hypothesis that its fibrinogen composition could contribute to the targeting process to microthrombi. However, it remains plausible that other PC components might contribute to the thrombosis targeting phenomenon. In such condition, it should be noted that the presence of a higher concentration of fibrinogen in the protein corona on the PhySIOMIC particles could also have prothrombotic consequences. At this stage we did not completely elucidate to which specific thrombosis component or protein the protein corona confer adhesion, but one possible target could be the activated form of platelet integrin aIIbB3 which is known to specifically recognize fibrinogen38. This hypothesis is in accordance with the transmission electronic microscopy observations as the PhySIOMIC were found attached to activated platelets." + +<|ref|>text<|/ref|><|det|>[[116, 375, 880, 437]]<|/det|> +Regarding the particle size and zeta potential, we agree that they are important parameters with an impact on targeting via the circulation time and via the influence on the protein corona. We provide a table to list these different parameters for the SPIO and the PhySIOMIC (table 1) and we added a paragraph in the discussion section, p21: + +<|ref|>text<|/ref|><|det|>[[115, 441, 881, 608]]<|/det|> +"These micro- sized particles enhance \(\mathrm{T}_2^*\) contrast and enable rapid absorption for fast molecular imaging. Additionally, the polydopamine matrix conferred thrombosis targeting properties that enabled molecular MRI of microthrombi in a thrombo- embolic ischemic stroke murine model. It is also interesting to note that the PhySIOMIC provided strong imaging signal detection although they exhibited an extremely short half- life (less than a minute) compared to the SPIO which typically circulates much longer (over 10 minutes) but was not able to reveal the microthrombi. This might appear surprising as the field of nanomedicine usually supports long circulation half- life as a positive feature for molecular imaging applications as longer exposure time should logically result in increased targeting35. However, this study provides evidence that this reasoning is not always true and that, at least in some contexts, modifying the surface to improve the targeting properties can be more valuable than to increase the circulation time." + +<|ref|>text<|/ref|><|det|>[[115, 621, 880, 698]]<|/det|> +2. Figure 2b demonstrated that the imaging effect of PhySIOMIC was significantly superior to that of SPIO. It was proven that the protein corona of PhySIOMIC could enhance its microthrombi-targeting. However, there is no additional analysis of SPIO to illustrate the unique composition of the protein corona of PhySIOMIC. Please provide further evidence. + +<|ref|>text<|/ref|><|det|>[[116, 704, 880, 750]]<|/det|> +We have added the proteomic analysis of SPIO in the supplementary Figure S9. It shows that the amount of fibrinogen with the protein corona is lower that for the particles that bind to microthrombi (i.e. PhySIOMIC and melamine). + +<|ref|>text<|/ref|><|det|>[[115, 763, 880, 841]]<|/det|> +3. The formation of the protein corona on nanoparticles could accelerate the removal of particles from the bloodstream, thereby reducing the amount of PhySIOMIC reaching the microvasculature. It was also evident that the half-life of PhySIOMIC was much shorter than that of SPIO. Why did PhySIOMIC have a superior targeting to microthrombi? Please discuss the results. + +<|ref|>text<|/ref|><|det|>[[116, 847, 880, 909]]<|/det|> +Efficient targeting is indeed more important than long half- life to perform efficient molecular imaging and this study perfectly illustrates this fact. We believe that the composition of the protein corona and the size of the particles are two key aspects to target microthrombi. Moreover, the shorter half- life allows to perform imaging only a couple of minutes after intravenous injection, since plasma clearance + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 562, 98]]<|/det|> +is very fast. We now raise this aspect in the discussion p 19: + +<|ref|>text<|/ref|><|det|>[[116, 104, 881, 226]]<|/det|> +It is also interesting to note that the PhySIOMIC provided a strong imaging signal detection although they exhibit an extremely short half- life (less than a minute) compared to the SPIO that typically circulate much longer (over 10 minutes) but were not able to reveal the microthrombi. This might appear surprising as the field of nanomedicine usually supports long circulation half- life as a positive feature for molecular imaging applications as longer exposure time should logically result in increased targeting35. However, this study provides evidence that this reasoning is not always true and that, at least in some contexts, modifying the surface to improve the targeting properties can be more valuable than to increase the circulation time. + +<|ref|>text<|/ref|><|det|>[[116, 239, 881, 315]]<|/det|> +4. Figure 7a illustrated that both PhySIOMIC and SPIO particles induced a significant decrease in signal intensity in the liver and spleen, indicating rapid clearance of the particles from the body. Additionally, in Fig. 7b, it is noteworthy that the signal intensity after injection is considerably lower than before, and it gradually increases with time. Can you explain the underlying cause of this phenomenon? + +<|ref|>text<|/ref|><|det|>[[117, 322, 881, 384]]<|/det|> +We indeed attribute the strong signal decrease to rapid sequestration of the particles in the macrophages of the liver and the spleen. The iron oxide particles accumulate and confer negative signal. Then, the signal gradually increases with time once the iron oxide has been degraded and the iron incorporated into the iron pool of the organism. In the liver, it goes back to baseline at day 7 post injection. + +<|ref|>text<|/ref|><|det|>[[118, 390, 390, 405]]<|/det|> +We completed the result section p16: + +<|ref|>text<|/ref|><|det|>[[116, 411, 881, 533]]<|/det|> +"Signal enhancement was monitored in the liver, spleen and kidney at 2, 7 and 31 days after injection. Both PhySIOMIC and SPIO particles induced a strong hyposignal within the liver and the spleen (Fig. 7a) which is in line with a rapid elimination of particles from the bloodstream and uptake by the mononuclear phagocyte system; in the Kupffer cells of the liver and resident macrophages of the spleen.21 This hyposignal gradually fade out in time ending at baseline level at 31 days post injection. This observation was attributed to gradual biodegradation of the iron oxide particles within the lysosomal compartment of the macrophages; a mechanism well described in literature for inorganic nanoparticles, including iron oxide33." + +<|ref|>text<|/ref|><|det|>[[116, 546, 881, 622]]<|/det|> +5. The administration of thrombolysis with rtPA results in increased permeability of the blood-brain barrier. However, using PhySIOMIC at this stage is associated with an elevated risk of the contrast agent crossing the blood-brain barrier, which can potentially cause severe brain injury. Please discuss the advantages and disadvantages of PhySIOMIC as an MRI contrast agent. + +<|ref|>text<|/ref|><|det|>[[116, 629, 880, 660]]<|/det|> +We agree that this is another potential risk to consider in future developments. We added a paragraph in the discussion on that specific topic: + +<|ref|>text<|/ref|><|det|>[[116, 666, 881, 832]]<|/det|> +"Another risk to consider is the potential toxicity induced by PhySIOMIC particles that would eventually cross into the brain tissue, especially in the context of severe hemorrhagic transformation post- stroke. Although none of the current data did reveal PhySIOMIC retention other than the one bound to thrombi (due to their submicrometric size that prevents their passage through the blood- brain barrier (BBB)), the fate of the PhySIOMIC would need to be closely monitored for future development. Notably, a clear asset of this contrast agent is that it is fully made from biocompatible materials (iron oxide and polydopamine) that lack neurotoxic side effects. Accordingly, SPIO that can cross the injured BBB has been injected in humans at the subacute phase of ischemic stroke, without worrying signals for toxicity39. Moreover, polydopamine nanoparticles exhibit strong antioxidant properties and were shown to result in a neuroprotective effect in an ischemic stroke model for this specific reason40. These data are reinsuring for the clinical translation of PhySIOMIC." + +<|ref|>text<|/ref|><|det|>[[115, 846, 880, 878]]<|/det|> +6. It is advisable to carefully proofread the manuscript for any errors in grammar and typos. + +<|ref|>text<|/ref|><|det|>[[116, 886, 855, 902]]<|/det|> +We thoroughly proofread the manuscript, corrected errors and typos and hope we did not miss any. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 308, 100]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 145, 404, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 204, 628, 220]]<|/det|> +All concerns/suggestions addressed in a complete and detailed way. + +<|ref|>text<|/ref|><|det|>[[118, 265, 275, 280]]<|/det|> +No further concerns. + +<|ref|>text<|/ref|><|det|>[[118, 355, 404, 371]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 415, 830, 451]]<|/det|> +It appears that the authors thoroughly addressed the vast majority of the reviewers comments resulting in a much stronger and highly impactful manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 525, 404, 541]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 585, 673, 602]]<|/det|> +My remarks were adequately addressed, the manuscript can be accepted. + +<|ref|>text<|/ref|><|det|>[[118, 676, 404, 692]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 736, 856, 771]]<|/det|> +The authors have addressed the reviewer comments well and the manuscript is recommended for publication after careful checking of spelling and clarity of language in the text and captions. + +<--- Page Split ---> diff --git a/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8f9c8dfb73e3cb897c4fa9cd4a1b22f898ec5d02 --- /dev/null +++ b/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,1930 @@ + +# nature portfolio + +Peer Review File + +# Base editing HbS to HbG-Makassar improves hemoglobin function, supporting its use in sickle cell disease + +Corresponding Author: Dr Vivien Sheehan + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Attachments originally included by the reviewers as part of their assessment can be found at the end of this file. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In this study "Installation of HbG- Makassar by base editing restores hemoglobin function: a transformative therapy for sickle cell disease" the authors describe their work to characterize mice that have been genetically modified to harbor the Makassar variant of adult beta globin, which can be efficiently introduced using adenine base editing in cells harboring the sickle cell disease genetic variant. + +This Makassar variant is extremely rare in the natural human population, so this study is extremely valuable to characterize what the potential outcomes would be in erythroid cells differentiated from homozygous or heterozygous HSCs. The authors make many important findings, including the similarity in phenotype between mice with an AA genotype and GG genotype, and interesting differences between GS and AS phenotypes. In particular, the white blood cell and reticulocyte counts of GS mice are similar to SS mice. The structure of Makassar globin is described here for the first time to my knowledge. + +The methodology of this manuscript appears sound and it is well- written and illustrated. I am enthusiastic about this study recommend acceptance of this manuscript pending three relatively small comments. + +1. The structure of the original and modified beta globin locus in the newly established mouse haplotype is not shown or described in detail. I believe that this mouse also includes human gamma globin genes, but these are not expressed at high levels. Since fetal hemoglobin is a particularly strong modifier of the described phenotypes, it would be helpful to show a quantification of fetal hemoglobin in each mouse genotype to ensure that fetal hemoglobin expression was not modified in the new established Makassar haplotype and did not confound any of these results. + +2. The paragraph on dense red blood cells is particularly sparse with only one mouse genotype detailed and minimal reference to what is normal and what dysfunction may indicate here. Hematocrit and density appear to be the main parameters where AA differs from GG, so discussing this in more detail is warranted. Furthermore, the reference appears incorrect since the panel that describes density is Fig 4H, not Fig 4E. + +3. The axis text in Figure 7 relating to the genome editing experiment is too small to readily interpret. The methods section is also lacking in detail about exactly which editor variant and sgRNA was used in this experiment. It references a different journal for the electroporation conditions - it would be better to state the methods explicitly here. + +## Reviewer #2 + +(Remarks to the Author) + +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBS) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including + +<--- Page Split ---> + +deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question, and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +## Major comments: + +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta\) EA mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerase. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G 3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +a. Figure 3 + +i. Are pairwise comparisons being made between all samples? + +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +iii. Why is the order of genotypes/color scheme different between panels? + +iv. Why is \(n\) so dramatically different between panels/assays? + +v. In particular, Figure 3C is confusing in that the absolute recytocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" - why does HbG heterozygous state not have any effect on baseline ARC? + +b. Figure 4 + +i. For Figure 4A, the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +ii. For Figure 4C, the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of pO2 >15% in the bone marrow reference (Figure 4)" - this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than 15 mmHg (overlapping with HbSS samples) and half less than 15 mmHg. The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (maybe Figure 4E?) + +iv. The relevance of Hematocrit-Viscocity Ratio (HVR) is not explained in any way for Figure 4D. + +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with \(n = 3\) or alternatively removed. + +c. Figure 5 + +i. For Figure 5A-B - the statement is made that "RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA", but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<--- Page Split ---> + +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +d. Figure 6 + +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +e. Figure 7 + +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G - numerous additional replicates would be necessary to be able to make this claim. + +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as \(2\%\) metabisulfite, but the figure legend states that \(2\%\) oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C. + +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by any of the data in the manuscript. + +Minor comments: + +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate - there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. These need to be cited and the language of this sentence toned down to be reflective of the literature. + +4. Haploidentical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa-cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the βE6A mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +9. Towns mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +10. "Zombie dye" is not standard terminology and needs to be clarified. + +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +12. All figures in Figure 1 are very difficult to read/interpret - would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +<--- Page Split ---> + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +## Reviewer #4 + +(Remarks to the Author) + +Generating the Makassar hemoglobin variant is a promising therapeutic strategy to correct the sickle cell disease- causing mutation. In this work, Kostamo and colleagues generated a mouse model harboring the Makassar mutation and evaluated in vitro properties of the Makassar hemoglobin as well as hematological and organ parameters in vivo. Furthermore, they evaluated the effect of mono and bi- allelic editing in clonal culture of control and edited erythroid cells from patients with sickle cell disease. Although interesting, we have some important remarks. + +- The Authors should mitigate the conclusions of the study (in the title, abstract, intro and discussion) as mono allelic editing will likely not lead to a major clinical benefit and mouse models are not always predictive of the results observed in patients. Furthermore, this study demonstrates that HbG-Makassar does not behave like HbA + +- Introduction: some references regarding the other ABE-approaches developed to induce HbF are missing: Ravi et al 2022, Han et al 2023, Antoniou et al 2022, ... + +- The Authors generate the Makassar mutation together with a silent mutation. It would be interesting to evaluate if this silent mutation affects beta-globin expression at transcriptional or translational level. To this aim, the Authors could compare + +HPLC profiles in AS and GS mice (to complete Figure 4G if this panel is showing HPLC data, the Authors should specify it) + +- Figure 1: Previous polymerization studies using recombinant Hb (Pagnier et al 1993) have demonstrated that HbG-Makassar solutions show a sudden increase in turbidity in 2.2M phosphate buffer following temperature increase while HbG-Makassar behaves similarly to HbA in a 1.8M phosphate buffer solution. It would have been interesting to consider reproducing these data (by including the 2.2M condition) to better understand the biochemical properties of HbG variant. Moreover, since these results (Pagnier et al 1993) using recombinant Hb suggested that HbG has a lower solubility as compared to HbA, experiments evaluating this parameter would have been of interest. + +- Figure 2: the Authors should also compare the crystal structure of HbS, superimpose the structures of the different hemoglobins and analyze the lateral contacts + +- Overall, since some hematological parameters were found to be affected in GG and SG mice models (clearly demonstrating that HbG does not behave like HbA) further functional characterization of the purified proteins should be performed to provide potential explanations for these observations (inflammation in GS not in GA, lower deformability of GG vs AA, sickling of GS RBCs vs no sickling of AS RBCs; ...). In other words, are there any experiments that could be performed to reconcile in vitro and in vivo data? + +- Figure 1: Since it is known that blood of patients with SCD exhibits decreased affinity for oxygen, although the oxygen affinity of HbS is the same as that of HbA (Figure 1), oxygen binding studies could also be performed in whole blood of transgenic mice since HbG containing RBCs seem to be affected. + +- Figure 4H: The observed increase in DRBC in GG and GS condition is not further commented: could it have any clinical impact? + +- It is not clear which conditions have been tested for Pair comparisons across histograms of Figures 3-6. All the conditions should be compared to draw proper conclusions. For example, for the liver weight (Figure 6A), only SS mice seem to be different from the others. In Figure 6B, spleen size looks much bigger (and not "comparable" as mentioned in the text) in SS than in GS mice + +- Figure 6B: the % of Ter119 should be evaluated in the spleen + +- Figure 7A: It is not clear which engineered ABE has been used. The editing efficiency looks higher to the one reported in Chu et al 2021, it should be explicit whether it is the same strategy or if a new editing strategy has been developed + +Minor comments: + +- Some references to the Figures are missing in the text or misplaced (Figure 1G, Figure 4) +- Some Figures are not commented (Figure 4D, 4G...) or commented later. All the panels of Figure 4 should be discussed (and in the right order) +- Some Legends are missing (colors of Figure 5C) or incorrect (Figure 6A-B mismatched) +- Figure 1G is not clear. It is mentioned in the Mat&Met that 5 different % of AS and GS Hb mixtures were tested. Which ones are depicted here? +- Some Main Figures are blurry or difficult to read (Figure 1, Figure 5D, Figure 7) +- Figure 3: colors are confusing since they are not consistently associated to the same genotype +- Figure 5A: the difference mitochondrial retention % between AS and GS is still present in the graph, were the data normalized for retic count or not? The Authors should better explain how (and if) they perform normalization and show the proportion of reticulocytes in the different mouse groups +- Figure 5C: the assumption that HbGG and HbAA show a similar distribution of erythroid states should be confirmed by performing statistical analysis. +- Figure 6C: why the sclerosis score was not evaluated in all 5/6 mice per group?As mice are sometimes only 2, the Authors cannot discuss about "significant difference" +- Figure 7F/Figure S3: a quantitative graph of % of sickle cells would be more informative than representative pictures. AS samples should also be analyzed. +- Discussion: The Authors should compare the proposed approach with currently available strategies and other approaches in development (mutation correction by prime editing) + +in development (mutation correction by prime editing) + +<--- Page Split ---> + +- Discussion: Overall, in vitro and in vivo results are contradictory (normal properties of the purified Hb in vitro and altered hematological parameters observed in vivo): which protein parameters could explain these in vivo alterations? The Authors could also discuss the potential causes of RBC dehydration in GG mice. +- Discussion: It would be interesting to discuss the results obtained in the GG mouse model with data collected from the homozygous HbG patient in Sangkitporn et al 2002 + +## Reviewer #5 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In their resubmitted manuscript, the authors have addressed all of my concerns. This work constitutes a useful comparison of the properties of HbAA, HbAS, HbGG, HbGS, and HbSS mice and red blood cells. + +Reviewer #2 + +(Remarks to the Author) + +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments; thus, the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBs) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +Major comments: + +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta \in \mathrm{6A}\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +Authors' response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected p50 range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +Reviewer's Response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the Authors could explain this discrepancy/change to the Reviewer would be very helpful. + +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is + +<--- Page Split ---> + +unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +Authors' response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +Reviewer's Response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artefactual effects of high temperatures on hemoglobin integrity. + +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +Authors' response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +Reviewer's Response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +Authors' response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures \((p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +Reviewer's Response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include p- value in graph to emphasize that there is no difference between the trendlines. + +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +Authors' response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +Reviewer's Response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +a. Figure 3 (now figure 4) i. Are pairwise comparisons being made between all samples? + +Authors' response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann- Whitney test when the distribution of the + +<--- Page Split ---> + +groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (SI, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +Reviewer's Response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +Authors' response. Statistics were performed and shown for the pairwise comparisons where their difference appeared to be significant. P values were reported in the main text. Samples whose statistics are not shown are because their difference was not significant. In both cases significance and lack of significance was addressed in the main text in the original submission. To make this observation more accessible to the general reader, P value descriptors have been added to the figure legend and the statistical analysis method section was expanded as well (lines 193- 202). + +Reviewer's Response. Authors' response noted and accepted. + +iii. Why is the order of genotypes/color scheme different between panels? + +Color in figure 3 (now figure 4, page 21) panels and in all of the other figures have been standardized to match color and genotype across panels. + +Reviewer's Response. The newly plotted graphs in new Figure 4 are now much easier to read/interpret. + +iv. Why is n so dramatically different between panels/assays? + +Authors' response. Thanks for pointing out this observation. The number of mice from each genotype varies from assay to assay primarily due to blood volume limitations of the mouse model. We have summarized the number of mice used in each analysis in the supplementary information, supplementary table 5 (SI, page 6). + +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 is a welcome addition to clarify these differences. + +v. In particular, Figure 3C is confusing in that the absolute reticulocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +Authors' response. Thank you for your observation. Additional mice were analyzed, and Figure 3 (now Figure 4, page 21) is updated. Reticulocyte count requires very large blood volumes, so it was only possible to measure it in those mice where the blood drawn met the assay volume requirements. Supplementary Table 5 (SI, page 6) contains all the sample sizes and comparisons performed in the manuscript. We have now assured that a minimum of \(n = 3\) mice from each genotype were used in every test. + +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 as well as at least \(n = 3\) for each genotype is appreciated. + +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +Authors' response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +Reviewer's Response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the health of this mouse that could be provided to the Reviewer would be useful, as would be expected to be quite different physiologically with over a \(50\%\) reduction in hemoglobin; Authors (and Editors) should decide whether this + +<--- Page Split ---> + +mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse. + +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +Authors' response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +Reviewer's Response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +b. Figure 4 (now figure 5) + +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +Authors' response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a p-value of <0.0001. + +Reviewer's Response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A – the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y-axis should be set to zero as the adjusted Y-axis (0.35 to 0.65) exaggerates the biological differences here. + +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(pO2 > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15 \text{mmHg}\) (overlapping with HbSS samples) and half less than \(15 \text{mmHg}\). The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +Authors' response. Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\). + +Reviewer's Response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +Authors' response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +Reviewer's Response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS %sickled RBCs do not appear statistically different. This statement needs to be changed to "HbGS shows a trend toward decreased sickling as compared to HbSS" or similar. + +iv. The relevance of Hematocrit-Viscosity Ratio (HVR) is not explained in any way for Figure 4D (now figure 5e). + +Authors' response. An additional discussion of viscosity and HVR has been added to the text (lines 166- 171, 337- 340). + +Reviewer's Response. This additional discussion of HVR in the text is appreciated by the Reviewer and acceptable. + +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure + +<--- Page Split ---> + +functionally irrelevant. + +Authors' response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +Reviewer's Response. The Reviewer appreciates this addition of n for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with \(n = 3\) or alternatively removed. + +Authors' response. Thanks for bringing this observation to our attention. Panel g from the original submission was moved to the supplementary information as supplementary figure 7 (SI, page 13) with proper reference calling in the main text (line 397- 398). An additional description was added to show the data refers to protein expression abundance (line 395). The data being presented has an \(n = 4\) for each genotype (supplementary figure 7, SI page 13). + +Reviewer's Response. This change is appreciated and acceptable. + +c. Figure 5 (now figure 6) + +i. For Figure 5A-B - the statement is made that "RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA", but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +Authors' response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +Reviewer's Response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement "retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis") as this will not be evident to the general Nature Communications readership. + +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +Authors' response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +Reviewer's Response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However, given the ineffective erythropoiesis seen in Figure 6D with increased HbGS, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +Authors' response. We have moved the gating strategy to the supplementary information (SI Figure 5, page 11). + +Reviewer's Response. This is an acceptable alternative and works well as in supplementary figure section. + +d. Figure 6 (now figure 7) + +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +Authors' response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +<--- Page Split ---> + +Reviewer's Response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and any potential implications on therapeutic applications. + +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +Authors' response. Figure legends have been corrected (lines 365,369), thank you (now figures 7a and 7b) + +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +e. Figure 7(Now Figure 8) + +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. + +Thanks for the feedback. The figure was replotted with appropriate font sizes (page 25). + +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. + +Authors' response. We appreciate the reviewer's comment. The approach described in this manuscript, specifically in Figure 8 for editing of human mPB CD34s, is using a highly engineered inlaid base editor with NGC PAM tolerance that converts the sickle allele to a Makassar allele that was developed by Beam that was previously published (Chu et al 2021). This is different from the Newby approach which uses a NRCH- PAM tolerant guide. The functional result is the same, installation of the Makassar variant but the editor and guide sequences are different. We refer to this in the section describing the data (lines 388- 390) and we believe that these data are complimentary and orthogonal and give further confidence that the deployment of ABEs, even with slightly different features, give similar outcomes. + +Reviewer's Response. These clarifications and additional text additions are appreciated. + +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +Authors' response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +Reviewer's Response. The Reviewer appreciates this revision and clarification and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common terminology) and also contains jargon not generally accessible ("bulk d18 IVED" – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is rather generic. + +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as 2% metabisulfite, but the figure legend states that 2% oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +Authors' response. We completely agree with the reviewer's comments around quantitation of sickling events in these images. Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. To that end, we have removed these figures and tempered any conclusions that were drawn from this data. + +Reviewer's Response. The Reviewer appreciates the Authors' candor on this point, removal of this figure, and tempering of conclusions drawn from it. + +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, + +<--- Page Split ---> + +Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +Authors' response. Our text in the discussion was modified to align with the current data presented. Figures 1G (now 2e, page 19) and 4C (now 5c, page 22), the reminder of Figure 4 (now 5, page 22), Figure 3 (now 4, page 21), Figure 5A (now 6a, page 23), Figure 6 (now 7, page 24) and Figure 7 (now 8, page 25) have been replotted and presented in a more accessible and concise way. In addition, our new text in the discussion acknowledges the difference between the results obtained studying the purified protein and those obtained when studying it in the context of RBCs (lines 403- 486). The impact of dehydration on a similar compound heterozygote, HbSC, and the impact of RBC dehydration mediated by HbG on the red cell has been expanded in the introduction and discussion sections (lines 81- 91 and 443- 475). Ex vivo analysis of HbG does not show sickling, even as a HbG/HbS mixture. It is only when in the confines of a dehydrated mature red cell that the HbS in a 60:40 mixture with HbG where sickling becomes possible. + +Reviewer's Response. The new tempered statement in lines 434- 441 is appreciated and more reflective of the data presented, as well as the context present regarding ex vivo vs intracellular HbS/HbG mixtures in lines 443- 475. + +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C (now figure 7). + +Authors' response. HbSS mice had significantly heavier liver per body weight compared to HbGS mice (median 8.75 vs 6.44, \(p = 0.002\) ) while the liver weights/body weight of HbAA and HbAS were comparable with HbGG and HbGS, respectively. (now figure 7a, page 22). Although the sclerosis scores were different across the genotypes, they did not rise to the level of statistical significance. The manuscript has been modified to include this information (Lines 362- 372, 455- 459). + +Reviewer's Response. The modified verbiage in lines 362- 372 and 455- 460 much more accurately reflect the data presented in the manuscript. + +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by any of the data in the manuscript. + +Authors' response. Thank you for your feedback. Concluding statement was modified to highlight the importance of assessing red cell function of any novel hemoglobin editing strategy (lines 477- 486). While HbGG is the most likely editing outcome, and HbGS is in most domains superior to HbSS, one must consider the imperfect quality of HbGS when contemplating the Makassar strategy for base editing in SCD. + +Reviewer's Response. This new concluding paragraph is acceptable. + +Minor comments: + +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +Authors' response. The word transformative has been removed from the manuscript. + +Reviewer's Response. The Reviewers appreciate removal of this terminology from the manuscript. + +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +Authors' response. The abstract was edited for clarity and consistency (lines 23- 33). + +Reviewer's Response. The revised abstract is much clearer and more precise. + +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate - there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. These need to be cited and the language of this sentence toned down to be reflective of the literature. + +Authors' response. We agree with the reviewer that these therapies have modified the clinical severity for many individuals and have altered this section accordingly and added citations (lines 40- 42). + +Reviewer's Response. This new sentence and citations are accurate and reflect the current state of the field. + +4. Haploidetical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the + +<--- Page Split ---> + +best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +Authors' response. We now discuss haploidential transplantation as an option as well (lines 44- 46). + +Reviewer's Response. This addition is acceptable. + +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa-cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +Authors' response. We have eliminated this comment, as it is not integral to the discussion of base editing in the context of the larger transplant field. + +Reviewer's Response. Removal of this comment is appreciated. + +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the βE6A mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +Authors' response. Authors' response. Sentence was rewritten to remove technical jargon (lines 77- 79). + +Reviewer's Response. This revision is acceptable. + +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +Authors' response. This statement has been revised, and no longer comments on HbSC to HbSS relative severity. + +Reviewer's Response. This change is appreciated. + +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +Authors' response. The main text was modified to remove this confusing statement. We would like to clarify that HbG behaves normally in vitro but appears to dehydrate the red cell in vivo. There are some aspects of the HbGG red cell or of organ function of a HbGG mouse that are not statistically different from HbAA, as outlined in the text. + +Reviewer's Response. This clarification is acceptable. + +9. Townes mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +Authors' response. The genotype of the Townes mice, its stock number, as well as a description of the model is now present in the methods section (lines 108- 109) as well as in a new figure 1 (page 19). The new figure shows the humanized beta globin locus present in the Townes mice RBC. + +Reviewer's Response. The addition of this new Figure 1 is greatly appreciated by the Reviewer and provides a key foundation for the studies done in the remainder of the manuscript. + +10. "Zombie dye" is not standard terminology and needs to be clarified. + +Authors' response. "Zombie dye" was replaced with the commercial name utilized by Life Technologies (line 182). + +Reviewer's Response. This clarification is appreciated. + +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +Authors' response. Relevance of the p50 values, Hill coefficients and polymerization data of purified HbG in relationship to hemoglobin function and benefit to SCD is now expanded in the discussion section (lines 427- 441). + +Reviewer's Response. This clarification and addition of text to the discussion is appreciated. + +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate + +<--- Page Split ---> + +(particularly in Figure 1G). + +Authors' response. Figure 1 (now figure 2, page 19) was replotted to make it more accessible to the general audience. + +Reviewer's Response. Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +Authors' response. Figure calling has been corrected in the text (line 283) + +Reviewer's Response. This correction is appreciated. + +Reviewer #3 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #4 + +(Remarks to the Author) + +The manuscript was improved in terms of clarity, however some important comments have not been addressed: + +1. The title should be tempered since data do not support a proper restoration of Hb function and its use in sickle cell disease compared to other developed approaches reactivating HbF +2. G and S can be distinguished via HPLC as shown by Newby et al Nature 2021. However, for proper technical comparison of globin expression, beta globin abundance should be evaluated as well in the AS genotype. Ratio of the different beta globins over alpha globin expression would also be informative. Alternatively, to precisely answer this point the authors could insert the silent mutation in HD HSPCs and compare beta-globin expression at mRNA and protein level in the erythroid progeny. + +3. It would be relevant to reproduce the comparison of solubility with proteins purified in the frame of this study (HbA, HbG, HbS and maybe HbC) and discuss it as an altered property of HbG that could further explain the alteration of HbG-containing RBCs. Furthermore, the comment regarding the increased turbidity observed in 2.2M phosphate buffer with HbG purified in this study has not been addressed. This point should be discussed in the manuscript since it was described as a specific feature of HbG (Pagnier et al 1993). + +4. Hb tetramers fiber lateral contacts between beta2 Val/Ala6 and beta1 Phe85 and Leu88, if solved, should be discussed. +5. RBC dehydration is probably not the root of the HbGS/HbGG associated phenotypes but is likely a consequence of an Hb characterized by altered physicochemical properties. The statement that in vitro characteristics of HbG are normal is not correct since it has been shown to be altered in previous studies using recombinant proteins (turbidity in 2.2M phosphate buffer, altered solubility), validation of these observations in the protein purified in this study and discussion on these altered properties would give a better overview of the description of the Hb variant of interest. + +6. Reference to the CRISPR Journal 2021 paper should be added line 204-205 when mentioning the IBE12.2. + +7. While Sup Table 5 indicates that statistical analyses have been performed in Figure 7c, it is not clear which conditions have been compared (as well as in other figures) + +8. It would be interesting to comment on the osmotic fragility test that results positive in the homozygous HbG patient, could it be linked to the high % of dense cells? + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #5 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 2: + +Reviewer comments: + +<--- Page Split ---> + +Reviewer #2 + +(Remarks to the Author) The Authors have responded well to the critiques and concerns, and have incorporated suggested changes. + +Only two suggestions remain, and pertain to the SDS- Page gel with aberrant size marker, and the proper y- axis for Figure 5A. + +Reviewer #3 + +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #4 + +(Remarks to the Author) We thank the authors for answering our questions We have a last comment to address: Supplementary Figure 7c should include AA and AS data for proper technical comparison. + +Reviewer #5 + +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Point by Point Response to reviewer comments + +Authors comments are in italics. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this study "Installation of HbG- Makassar by base editing restores hemoglobin function: a transformative therapy for sickle cell disease" the authors describe their work to characterize mice that have been genetically modified to harbor the Makassar variant of adult beta globin, which can be efficiently introduced using adenine base editing in cells harboring the sickle cell disease genetic variant. + +This Makassar variant is extremely rare in the natural human population, so this study is extremely valuable to characterize what the potential outcomes would be in erythroid cells differentiated from homozygous or heterozygous edited HSCs. The authors make many important findings, including the similarity in phenotype between mice with an AA genotype and GG genotype, and interesting differences between GS and AS phenotypes. In particular, the white blood cell and reticulocyte counts of GS mice are similar to SS mice. The structure of Makassar globin is described here for the first time to my knowledge. + +The methodology of this manuscript appears sound and it is well- written and illustrated. I am enthusiastic about this study recommend acceptance of this manuscript pending three relatively small comments. + +1. The structure of the original and modified beta globin locus in the newly established mouse haplotype is not shown or described in detail. I believe that this mouse also includes human gamma globin genes, but these are not expressed at high levels. Since fetal hemoglobin is a particularly strong modifier of the described phenotypes, it would be helpful to show a quantification of fetal hemoglobin in each mouse genotype to ensure that fetal hemoglobin expression was not modified in the new established Makassar haplotype and did not confound any of these results. + +We appreciate the reviewer's comments. We have added Figure 1 (page 18), which details the changes made to the beta globin locus in the Townes mice model. UPLC analysis of the Townes mice HbGG and HbSG RBCs did not detect HbF (data included in the Supplementary Fig 7, page 13). + +2. The paragraph on dense red blood cells is particularly sparse with only one mouse genotype detailed and minimal reference to what is normal and what dysfunction may indicate. Hematocrit and density appear to be the main parameters where AA differs from GG, so discussing this in more detail is warranted. Furthermore, the reference appears incorrect since the panel that describes density is Fig 4H, not Fig 4E. + +We have expanded this topic in the manuscript, in the introduction (lines81- 89), in the results (lines 333- 339), in the methods section (lines 166- 171) and in the discussion (lines 448- 449, 461- 471). Figures have been renumbered and the references to panels corrected (line 348). + +<--- Page Split ---> + +3. The axis text in Figure 7 relating to the genome editing experiment is too small to readily interpret. The methods section is also lacking in detail about exactly which editor variant and sgRNA was used in this experiment. It references a different journal for the electroporation conditions - it would be better to state the methods explicitly here. + +Figure 7 (now figure 8, page 25) has been revised for clarity and legibility. We have included in the revised manuscript (lines 204- 205) the identity of the inlaid base editor which was used from the CRISPR Journal 2021 paper (IBE12.2). Additionally, we have included additional experimental details (lines 215- 216) which were left off the initial submission due to length restrictions. Further details can be found in the supplementary methods section. + +Reviewer #2 (Remarks to the Author): + +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBs) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +Major comments: + +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta \in \mathrm{6A}\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadrupulicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected \(p50\) range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}\mathrm{C}\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +<--- Page Split ---> + +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures ( \(p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +a. Figure 3 (now figure 4) +i. Are pairwise comparisons being made between all samples? + +<--- Page Split ---> + +Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann - Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (SI, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +Statistics were performed and shown for the pairwise comparisons where their difference appeared to be significant. P values were reported in the main text. Samples whose statistics are not shown are because their difference was not significant. In both cases significance and lack of significance was addressed in the main text in the original submission. To make this observation more accessible to the general reader, P value descriptors have been added to the figure legend and the statistical analysis method section was expanded as well (lines 193- 202). + +iii. Why is the order of genotypes/color scheme different between panels? + +Color in figure 3 (now figure 4, page 21) panels and in all of the other figures have been standardized to match color and genotype across panels. + +iv. Why is \(n\) so dramatically different between panels/assays? + +Thanks for pointing out this observation. The number of mice from each genotype varies from assay to assay primarily due to blood volume limitations of the mouse model. We have summarized the number of mice used in each analysis in the supplementary information, supplementary table 5 (SI, page 6). + +v. In particular, Figure 3C is confusing in that the absolute reticulocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +Thank you for your observation. Additional mice were analyzed, and Figure 3 (now Figure 4, page 21) is updated. Reticulocyte count requires very large blood volumes, so it was only possible to measure it in those mice where the blood drawn met the assay volume requirements. Supplementary Table 5 (SI, page 6) contains all the sample sizes and comparisons performed in the manuscript. We have now assured that a minimum of \(n = 3\) mice from each genotype were used in every test. + +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and + +<--- Page Split ---> + +HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +b. Figure 4 (now figure 5) + +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a \(p\) - value of \(< 0.0001\) . + +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(pO2 > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15 \text{mmHg}\) (overlapping with HbSS samples) and half less than \(15 \text{mmHg}\) . The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +<--- Page Split ---> + +iv. The relevance of Hematocrit-Viscosity Ratio (HVR) is not explained in any way for Figure 4D (now figure 5e). + +An additional discussion of viscosity and HVR has been added to the text (lines 166- 171, 337- 340). + +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with n=3 or alternatively removed. + +Thanks for bringing this observation to our attention. Panel g from the original submission was moved to the supplementary information as supplementary figure 7 (Sl, page 13) with proper reference calling in the main text (line 397- 398). An additional description was added to show the data refers to protein expression abundance (line 395). The data being presented has an n =4 for each genotype (supplementary figure 7, Sl page 13). + +c. Figure 5 (now figure 6) + +i. For Figure 5A-B – the statement is made that "RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA", but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +<--- Page Split ---> + +We have moved the gating strategy to the supplementary information (SI Figure 5, page 11). + +d. Figure 6 (now figure 7) + +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +Figure legends have been corrected (lines 365,369), thank you (now figures 7a and 7b) + +e. Figure 7(Now Figure 8) + +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. + +Thanks for the feedback. The figure was replotted with appropriate font sizes (page 25). + +ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. + +We appreciate the reviewer's comment. The approach described in this manuscript, specifically in Figure 8 for editing of human mpB CD34s, is using a highly engineered inlaid base editor with NGC PAM tolerance that converts the sickle allele to a Makassar allele that was developed by Beam that was previously published (Chu et al 2021). This is different from the Newby approach which uses a NRCH- PAM tolerant guide. The functional result is the same, installation of the Makassar variant but the editor and guide sequences are different. We refer to this in the section describing the data (lines 388- 390) and we believe that these data are complimentary and orthogonal and give further confidence that the deployment of ABEs, even with slightly different features, give similar outcomes. + +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +<--- Page Split ---> + +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as \(2\%\) metabisulfite, but the figure legend states that \(2\%\) oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +We completely agree with the reviewer's comments around quantitation of sickling events in these images. Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. To that end, we have removed these figures and tempered any conclusions that were drawn from this data. + +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +Our text in the discussion was modified to align with the current data presented. Figures 1G (now 2e, page 19) and 4C (now 5c, page 22), the reminder of Figure 4 (now 5, page 22), Figure 3 (now 4, page 21), Figure 5A (now 6a, page 23), Figure 6 (now 7, page 24) and Figure 7 (now 8, page 25) have been replotted and presented in a more accessible and concise way. In addition, our new text in the discussion acknowledges the difference between the results obtained studying the purified protein and those obtained when studying it in the context of RBCs (lines 403- 486). The impact of dehydration on a similar compound heterozygote, HbSC, and the impact of RBC dehydration mediated by HbG on the red cell has been expanded in the introduction and discussion sections (lines 81- 91 and 443- 475). Ex vivo analysis of HbG does not show sickling, even as a HbG/HbS mixture. It is only when in the confines of a dehydrated mature red cell that the HbS in a 60:40 mixture with HbG where sickling becomes possible. + +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C (now figure 7). + +HbSS mice had significantly heavier liver per body weight compared to HbGS mice (median 8.75 vs 6.44, \(p = 0.002\) ) while the liver weights/body weight of HbAA and HbAS were comparable with HbGG and HbGS, respectively. (now figure 7a, page 22). Although the sclerosis scores were different across the genotypes, they did not rise to the level of statistical significance. The manuscript has been modified to include this information (Lines 362- 372, 455- 459). + +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by + +<--- Page Split ---> + +any of the data in the manuscript. + +Thank you for your feedback. Concluding statement was modified to highlight the importance of assessing red cell function of any novel hemoglobin editing strategy (lines 477- 486). While HbGG is the most likely editing outcome, and HbGS is in most domains superior to HbSS, one must consider the imperfect quality of HbGS when contemplating the Makassar strategy for base editing in SCD. + +Minor comments: + +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +The word transformative has been removed from the manuscript. + +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +The abstract was edited for clarity and consistency (lines 23- 33). + +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate - there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. These need to be cited and the language of this sentence toned down to be reflective of the literature. + +We agree with the reviewer that these therapies have modified the clinical severity for many individuals and have altered this section accordingly and added citations (lines 40- 42). + +4. Haploidentical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +We now discuss haploidentical transplantation as an option as well (lines 44- 46). + +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa-cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +We have eliminated this comment, as it is not integral to the discussion of base editing in the context of the larger transplant field. + +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the \(\beta \in 6A\) mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +<--- Page Split ---> + +Sentence was rewritten to remove technical jargon (lines 77- 79). + +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +This statement has been revised, and no longer comments on HbSC to HbSS relative severity. + +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +The main text was modified to remove this confusing statement. We would like to clarify that HbG behaves normally in vitro but appears to dehydrate the red cell in vivo. There are some aspects of the HbGG red cell or of organ function of a HbGG mouse that are not statistically different from HbAA, as outlined in the text. + +9. Townes mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +The genotype of the Townes mice, its stock number, as well as a description of the model is now present in the methods section (lines 108- 109) as well as in a new figure 1 (page 19). The new figure shows the humanized beta globin locus present in the Townes mice RBC. + +10. "Zombie dye" is not standard terminology and needs to be clarified. + +"Zombie dye" was replaced with the commercial name utilized by Life Technologies (line 182). + +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +Relevance of the p50 values, Hill coefficients and polymerization data of purified HbG in relationship to hemoglobin function and benefit to SCD is now expanded in the discussion section (lines 427- 441). + +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +Figure 1 (now figure 2, page 19) was replotted to make it more accessible to the general audience. + +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +Figure calling has been corrected in the text (line 283) + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #4 (Remarks to the Author): + +Generating the Makassar hemoglobin variant is a promising therapeutic strategy to correct the sickle cell disease- causing mutation. In this work, Kostamo and colleagues generated a mouse model harboring the Makassar mutation and evaluated in vitro properties of the Makassar hemoglobin as well as hematological and organ parameters in vivo. Furthermore, they evaluated the effect of mono and bi- allelic editing in clonal culture of control and edited erythroid cells from patients with sickle cell disease. Although interesting, we have some important remarks. + +- The Authors should mitigate the conclusions of the study (in the title, abstract, intro and discussion) as mono allelic editing will likely not lead to a major clinical benefit and mouse models are not always predictive of the results observed in patients. Furthermore, this study demonstrates that HbG-Makassar does not behave like HbA. + +Thanks for your feedback. The manuscript has been revised to make sure conclusions align with the reported data. We discuss the biochemical characterization of HbG and present it in light with our findings pertaining to the differences observed in HbG when present in an HbGG and HbGS mature RBC environment. + +- Introduction: some references regarding the other ABE-approaches developed to induce HbF are missing: Ravi et al 2022, Han et al 2023, Antoniou et al 2022, ... + +The manuscript was not intended to be an exhausted review of ABE based approaches for inducing HbF; we had previously included Mayaurnanthan et al (2023) that captures several different HBG1/2 promoter sites using ABEs and additionally argues the potency and durability of ABE-based editing over other nuclease based strategies. We would be happy to add additional references but were at the 70 citation limit as per Nature Comms guidance. + +- The Authors generate the Makassar mutation together with a silent mutation. It would be interesting to evaluate if this silent mutation affects beta-globin expression at transcriptional or translational level. To this aim, the Authors could compare HPLC profiles in AS and GS mice (to complete Figure 4G if this panel is showing HPLC data, the Authors should specify it) + +G and S cannot be distinguished via HPLC; supplemental information shows a 60:40 ratio of G:S; in the Townes mouse, HbA: HbS is 60:40 (Wang et al, Journal of Gene Medicine, 2023) suggesting that the silent mutation does not impair transcription or translation. + +- Figure 1: Previous polymerization studies using recombinant Hb (Pagnier et al 1993) have demonstrated that HbG-Makassar solutions show a sudden increase in turbidity in 2.2M phosphate buffer following temperature increase while HbG-Makassar behaves similarly to HbA in a 1.8M phosphate buffer solution. It would have been interesting to consider reproducing these data (by including the 2.2M condition) to better understand the biochemical properties of HbG variant. Moreover, since these results (Pagnier et al 1993) using recombinant Hb + +<--- Page Split ---> + +suggested that HbG has a lower solubility as compared to HbA, experiments evaluating this parameter would have been of interest. + +Thanks for providing this suggestion. The effect of \(\beta 6\) amino acid hydrophobicity on the solubility of hemoglobins was assessed in Adachi et.al., 1993 (J. Biol. Chem. 1993 268:29 21650- 21656). Using recombinant material and substituting the \(\beta 6E\) for \(A\) , \(I\) , \(L\) , \(V\) , \(W\) , \(Q\) , their work along with others showed that hemoglobin solubility increased in the order of \(I < L < V < W < Q < A < E\) in high phosphate buffers. At 2.1 M phosphate HbG had a solubility of greater than 150 mg/dL while HbA was 350 mg/dL. + +- Figure 2: the Authors should also compare the crystal structure of HbS, superimpose the structures of the different hemoglobins and analyze the lateral contacts + +Thanks for the feedback. A new figure comparing the HbG structure with that to HbS was added in the Supplementary Information (SI figure 4, page 10). We analyzed the lateral contacts between at the \(\alpha\) and \(\beta\) interface as well as the \(\alpha \beta\) dimer interface, but no apparent changes were observed. This could be explained by the high RMSD found between HbG and HbA/HbS. To have a streamlined story we decided not to include lateral contact information in the manuscript. + +- Overall, since some hematological parameters were found to be affected in GG and SG mice models (clearly demonstrating that HbG does not behave like HbA) further functional characterization of the purified proteins should be performed to provide potential explanations for these observations (inflammation in GS not in GA, lower deformability of GG vs AA, sickling of GS RBCs vs no sickling of AS RBCs; ...). In other words, are there any experiments that could be performed to reconciliate in vitro and in vivo data? + +Thanks for your feedback. Based on our current body of work we believe the reason for the apparent discrepancy is possibly due the effect HbG has in red blood cell dehydration. This phenomenon could only be identified when studying HbG in the context of an RBC environment and not in isolation as is the case with purified protein. Our text has been modified to make this conclusion more accessible to the general reader. We consider the in vivo and ex vivo differences to be explained by red cell dehydration, analogous to "The paradox of HbSC", in which a compound heterozygous state containing a non-sickling Hb and HbS results in a disease state rather than a carrier state due to activation of the Gardos channel (Nagel et al, Blood Reviews 2003). + +- Figure 1: Since it is known that blood of patients with SCD exhibits decreased affinity for oxygen, although the oxygen affinity of HbS is the same as that of HbA (Figure 1), oxygen binding studies could also be performed in whole blood of transgenic mice since HbG containing RBCs seem to be affected. + +Previous work has shown that the discrepancy in oxygen binding affinity between HbS and HbA within an RBC is not an intrinsic protein property but instead is due to different levels of 2,3- DPG among these cells (J Clin Invest. 1970 Apr; 49(4): 806- 812). + +<--- Page Split ---> + +- Figure 4H: The observed increase in DRBC in GG and GS condition is not further commented: could it have any clinical impact? + +We have significantly expanded this discussion (lines 444- 471), as we consider this to have significant impact on the red cell quality, which correlates with risk of SCD complications in other human studies. + +- It is not clear which conditions have been tested for Pair comparisons across histograms of Figures 3-6. All the conditions should be compared to draw proper conclusions. For example, for the liver weight (Figure 6A), only SS mice seem to be different from the others. In Figure 6B, spleen size looks much bigger (and not "comparable" as mentioned in the text) in SS than in GS mice + +Additional details are now included in the methods section on how pairwise comparisons were made (lines 193- 202). In addition, p values for all statistically significant comparisons are now included in the figure legends. The supplementary information contains a table describing the statistical test performed on each comparison (Supplementary table 5, SI, page 6). + +- Figure 6B: the % of Ter119 should be evaluated in the spleen + +Our intent is to assess for ineffective erythropoiesis, which we have done indirectly through spleen weights, and directly through assessment of erythroid precursors in the mouse bone marrow. + +- Figure 7 + +A: It is not clear which engineered ABE has been used. The editing efficiency looks higher to the one reported in Chu et al 2021, it should be explicit whether it is the same strategy or if a new editing strategy has been developed + +We have included in the revised manuscript the identity of the inlaid base editor which was used from the CRISPR Journal 2021 paper (IBE12.2) (line 204). While the editing reagents were identical, the editing conditions (e.g concentration of editor and guide) were slightly different than those in the previous paper to achieve saturating editing conditions in these HbSS CD34s. We have included additional experimental details (lines 215- 216) which were left off the initial submission due to length restrictions to reflect this in the methods section along with further experimental details in the supplemental methods section + +Minor comments: + +- Some references to the Figures are missing in the text or misplaced (Figure 1G, Figure 4) + +Text was revised and missing figure references were added. + +- Some Figures are not commented (Figure 4D, 4G...) or commented later. All the panels of Figure 4 should be discussed (and in the right order) + +All panels in figures are now being referenced in the text in sequential order + +- Some Legends are missing (colors of Figure 5C) or incorrect (Figure 6A-B mismatched) + +Legends have been added that were missing and all the figures are now properly labeled. + +<--- Page Split ---> + +- Figure 1G is not clear. It is mentioned in the Mat&Met that 5 different % of AS and GS Hb mixtures were tested. Which ones are depicted here? + +Figure 1G (now 2e, page 19) was replotted to make it more accessible to the reader. HbS percentages used are now labeled in the figure. + +- Some Main Figures are blurry or difficult to read (Figure 1, Figure 5D, Figure 7) + +Figures are now at high resolutions + +- Figure 3: colors are confusing since they are not consistently associated to the same genotype + +Figures containing panels depicting various genotypes have been standardized to use the same color for genotypes across panels. + +- Figure 5A: the difference mitochondrial retention % between AS and GS is still present in the graph, were the data normalized for retic count or not? The Authors should better explain how (and if) they perform normalization and show the proportion of reticulocytes in the different mouse groups + +Thank you for the comment. While the text commented on normalization, the data shown was in fact not normalized. We have corrected the text (lines 350- 352); the data in Figure 6a (page 23) shows % of cells with mitochondrial retention for each genotype. + +- Figure 5C: the assumption that HbGG and HbAA show a similar distribution of erythroid states should be confirmed by performing statistical analysis. + +We understand that the reviewer is asking about erythroid precursor levels; this figure and the analysis have been revised to improve clarity; see Figures 6c- e (page 23). + +- Figure 6C: why the sclerosis score was not evaluated in all 5/6 mice per group? As mice are sometimes only 2, the Authors cannot discuss about "significant difference" + +We have further analyzed sclerosis scores, and there are now at least 3 mice from each genotype. Difficulties with sample processing reduced the numbers of animals available for analysis (now figure 7c, page 24). + +- Figure 7F/Figure S3: a quantitative graph of % of sickle cells would be more informative than representative pictures. AS samples should also be analyzed. + +Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. As a result, we have removed these figures and tempered any conclusions that were drawn from this data. + +- Discussion: The Authors should compare the proposed approach with currently available strategies and other approaches in development (mutation correction by prime editing) + +We appreciate the reviewer's comments and have included language in the discussion around complementary approaches (lines 403- 411). While we believe each of these approaches have + +<--- Page Split ---> + +advantages and pitfalls, we don't want to overstate therapeutic potential in the clinic as that can only be determined once in the clinic. We have attempted to stick to the facts and state that these other strategies lead to expression of HbA and HbF whereas a direct editing strategy like Makassar can lead to the complete replacement/elimination of HbS. While Makassar hemoglobin can be found in nature, careful characterization of hemoglobin properties sheds light on the nuances of the normal hematological parameters that have thus far been described in relation to Makassar hemoglobin, precisely why we believe this manuscript adds novel understanding to the field. Additionally, bluebird bio and CRISPR/Vertex clinical trials did not include red cell function testing, so this comparison is not possible. + +- Discussion: Overall, in vitro and in vivo results are contradictory (normal properties of the purified Hb in vitro and altered hematological parameters observed in vivo): which protein parameters could explain these in vivo alterations? The Authors could also discuss the potential causes of RBC dehydration in GG mice. + +Thanks for the feedback. Based on our current data we believe the reason for the observed differences between the in vitro data showing normal functional properties of HbG when compared to HbA but altered hematological parameters in the context of HbGS in RBCs is due to RBC dehydration. We have included language in the manuscript to better discuss this conclusion (lines 427- 486). + +- Discussion: It would be interesting to discuss the results obtained in the GG mouse model with data collected from the homozygous HbG patient in Sangkitporn et al 2002 + +Very limited data was provided in that paper; without normal ranges for the particular analyzer used, the MCHC, a commonly available value similar to percent dense red blood cells, is difficult to interpret. It is interesting that osmotic fragility test was positive; HbCC red cells are also fragile and prone to hemolysis. Additional text in the discussion was added discussing this observation (lines 419- 425) + +Reviewer #5 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Author's comments in italics + +Reviewer #1 (Remarks to the Author): + +In their resubmitted manuscript, the authors have addressed all of my concerns. This work constitutes a useful comparison of the properties of HbAA, HbAS, HbGG, HbGS, and HbSS mice and red blood cells. + +Author's response, second revision. Thank you so much for your interest in our work. + +Reviewer #2 (Remarks to the Author): + +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments; thus, the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBS) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +Major comments: + +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta\) E6A mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is + +<--- Page Split ---> + +expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +Authors' response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected p50 range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +Reviewer's Response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the Authors could explain this discrepancy/change to the Reviewer would be very helpful. + +Author's response, second revision. Apologies for the confusion. No additional replicates have been added to the data. The means being compared are for HbG and HbA/HbS isolated from human RBC. The 24.8 value reported for HbA is for the sample isolated from Townes mice. + +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +Authors' response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +Reviewer's Response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artefactual effects of high temperatures on hemoglobin integrity. + +Author's response, second revision. Thank you for sharing your concerns around artefactual effects of high temperatures on hemoglobin integrity. + +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It + +<--- Page Split ---> + +would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +Authors' response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +Reviewer's Response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +Author's response, second revision. Thank you for your feedback. Labels for figure 2c and 2d have been inverted. Curve for 100% HbS in panel 2c has been replaced for a more representative curve taken from the data sets acquired in replicates. + +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +Authors' response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures (p=0.51, lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +Reviewer's Response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should + +<--- Page Split ---> + +specifically label that in the graph. Authors should also include p- value in graph to emphasize that there is no difference between the trendlines. + +Author's response, second revision. Thank you for your feedback. Requested additions to figure 2g have been added. + +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA – this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +Authors' response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +Reviewer's Response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +Author's response, second revision. Thank you for your feedback. A key main result of our manuscript is the identification that the βE6A mutation does not alter the hemoglobin protein fold. The manuscript has been revised to make sure this point is accessible to the general Nature's communication audience. We do agree with the reviewer to move this figure to the Supplementary information if the Editor believes this is too technical for the general readership. + +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +a. Figure 3 (now figure 4) +i. Are pairwise comparisons being made between all samples? + +Authors' response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann- Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs + +<--- Page Split ---> + +HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (Sl, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +Reviewer's Response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +Author's response, second revision. We reported comparison for three biologically relevant groups (HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS) in the revised manuscript as mentioned in the statistical analysis section (lines 193- 194). Thus, GG and GS were not compared and reported. The initial submission had a discrepancy in which HbGG data was in the usual location of HbAS and was therefore missed by the statistical comparison process. This does not change the interpretation of the data (lines 319- 324). + +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +Authors' response. Statistics were performed and shown for the pairwise comparisons where their difference appeared to be significant. P values were reported in the main text. Samples whose statistics are not shown are because their difference was not significant. In both cases significance and lack of significance was addressed in the main text in the original submission. To make this observation more accessible to the general reader, P value descriptors have been added to the figure legend and the statistical analysis method section was expanded as well (lines 193- 202). + +Reviewer's Response. Authors' response noted and accepted. + +iii. Why is the order of genotypes/color scheme different between panels? + +Color in figure 3 (now figure 4, page 21) panels and in all of the other figures have been standardized to match color and genotype across panels. + +Reviewer's Response. The newly plotted graphs in new Figure 4 are now much easier to read/interpret. + +iv. Why is n so dramatically different between panels/assays? + +<--- Page Split ---> + +Authors' response. Thanks for pointing out this observation. The number of mice from each genotype varies from assay to assay primarily due to blood volume limitations of the mouse model. We have summarized the number of mice used in each analysis in the supplementary information, supplementary table 5 (SI, page 6). + +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 is a welcome addition to clarify these differences. + +v. In particular, Figure 3C is confusing in that the absolute reticulocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +Authors' response. Thank you for your observation. Additional mice were analyzed, and Figure 3 (now Figure 4, page 21) is updated. Reticulocyte count requires very large blood volumes, so it was only possible to measure it in those mice where the blood drawn met the assay volume requirements. Supplementary Table 5 (SI, page 6) contains all the sample sizes and comparisons performed in the manuscript. We have now assured that a minimum of \(n = 3\) mice from each genotype were used in every test. + +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 as well as at least \(n = 3\) for each genotype is appreciated. + +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +Authors' response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +Reviewer's Response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the + +<--- Page Split ---> + +health of this mouse that could be provided to the Reviewer would be useful, as would be expected to be quite different physiologically with over a \(50\%\) reduction in hemoglobin; Authors (and Editors) should decide whether this mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse. + +Author's response, second revision. We performed statistical analyses after excluding the HbAA mouse with Hb of \(5.5g / dL\) and did not observe significant changes in the statistical output that altered any inferences. We decided to leave this outlier as a way to be transparent and rigorous by presenting the data as was collected. The mouse was sacrificed in a good state of health per experimental design at 23 weeks, which is considered "middle- aged" for this mouse model. + +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +Authors' response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +Reviewer's Response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +Author's response, second revision. Author's response. Thank you for the suggestion. We have altered the text accordingly (lines 319- 324). + +b. Figure 4 (now figure 5) + +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +Authors' response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically + +<--- Page Split ---> + +significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a p- value of <0.0001. + +Reviewer's Response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A – the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y- axis should be set to zero as the adjusted Y- axis (0.35 to 0.65) exaggerates the biological differences here. + +Author's response, second revision. An earlier cohort of mice were used only for deformability measurements. In reviewing our data to make revisions and addition of animals for a more consistent number per assessment, this was noted. We replaced this cohort with data from the animals used in other analyses, such as CBC. This changed the Elmin significantly, although not the overall conclusions. The dramatic difference seen between the data sets is due to the variability within the sickle mouse model, which is not congenic. The correct data set is now being used for the elongation minimum (5A), elongation maximum (5B) and PoS (5C). This is also reflected within the sample size change for the data from 10 points to 12. The data sets for the remaining genotypes remain the same as their respective data sets were correct. We apologize for the initial error. + +GraphPad Prism software automatically adjusted the Y- axis to fit between 0.35 to 0.65. We understand the reviewer has concerns, so we have included both figures below—the original, and the readjusted Y- axis version to compare. The graph with the Y- axis from 0 to 0.6 is difficult to read due to overlapping individual observations. We believe that the inclusion of p- values does not allow for exaggeration to take place and prefer the original. + +![PLACEHOLDER_36_0] + + +ii. For Figure 4C (now figure 5c), the statement “HbGS mice had very low point of sickling + +<--- Page Split ---> + +compared to HbSS, typically below a physiologic threshold of \(\mathsf{pO2} > 15\%\) in the bone marrow reference (Figure 4)" - this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15~\mathrm{mmHg}\) (overlapping with HbSS samples) and half less than \(15~\mathrm{mmHg}\) . The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +Authors' response. Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +Reviewer's Response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +Author's response, second revision. The histograms of the previous data (panel A) and the current data (panel B) are shown below. Both panels show non- normal distribution with the mode for panel A at the fourth bar (midpoint of 22.5) and the mode for panel B at the third bar (midpoint 17) using the strict definition- the value with the highest frequency. We are aware that the first column of panel A may quality as a second mode using the less strict definition. We also created histograms using different numbers of bins, as suggested in the literature, to confirm our findings. The Mann- Whitney test that we used to analysis is appropriate for data with non- normal distribution irrespective of the number of modes. The initial data showed low end points for the HbGG group due to the Point of Sickling (PoS) cut off of \(97.5\%\) oxygenation. PoS is typically defined as oxygen level at which \(95\%\) of the previous deformability is noted, thus the newer data reflects the correct standard removing values that did not have a greater than \(5\%\) difference between their elongation maximum and minimum. The values of the remaining data points reflect their Elongation Index at \(95\%\) oxygenation pressure. + +<--- Page Split ---> +![PLACEHOLDER_38_0] + + +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +Authors' response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +Reviewer's Response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS %sickled RBCs do not appear statistically different. This statement needs to be changed to "HbGS shows a trend toward + +<--- Page Split ---> + +decreased sickling as compared to HbSS" or similar. + +Author's response, second revision. As reviewer requests changes have been made (lines 341- 342). + +iv. The relevance of Hematocrit-Viscosity Ratio (HVR) is not explained in any way for Figure 4D (now figure 5e). + +Authors' response. An additional discussion of viscosity and HVR has been added to the text (lines 166- 171, 337- 340). + +Reviewer's Response. This additional discussion of HVR in the text is appreciated by the Reviewer and acceptable. + +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +Authors' response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +Reviewer's Response. The Reviewer appreciates this addition of n for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +Author's response, second revision. Thank you for the suggestion to clarify; it is a challenging observation that in the mouse model, HbSS RBC are so abnormal and easily hemolyzed that they do not remain in circulation long enough to dehydrate and become dense, as in humans. The milder phenotype of HbGS and HbGG permits this observation (lines 458- 464). Additionally, humans with HbSC demonstrate greater RBC density than HbSS. + +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with n=3 or alternatively removed. + +Authors' response. Thanks for bringing this observation to our attention. Panel g from the original submission was moved to the supplementary information as supplementary figure 7 (Sl, page 13) with proper reference calling in the main text (line 397- 398). An additional description was added to show the data refers to protein expression abundance (line 395). The data being presented has an n = 4 for each genotype (supplementary figure 7, Sl page + +<--- Page Split ---> + +13). + +Reviewer's Response. This change is appreciated and acceptable. + +c. Figure 5 (now figure 6) + +i. For Figure 5A-B – the statement is made that “RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA”, but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +Authors' response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +Reviewer's Response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement “retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis”) as this will not be evident to the general Nature Communications readership. + +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 357- 358). + +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +Authors' response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +Reviewer's Response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However, given the ineffective erythropoiesis seen in Figure 6D with increased + +<--- Page Split ---> + +HbGS, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 366- 370). + +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +Authors' response. We have moved the gating strategy to the supplementary information (SI Figure 5, page 11). + +Reviewer's Response. This is an acceptable alternative and works well as in supplementary figure section. + +d. Figure 6 (now figure 7) + +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +Authors' response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +Reviewer's Response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and any potential implications on therapeutic applications. + +Author's response, second revision. In SCD, ineffective erythropoiesis is driven by apoptosis of erythroid precursors in the BM; this occurs under normoxia, so HbS polymerization is not required. It is likely that this occurs in HbGS mice as well, based on spleen and erythroid maturation findings. Clinical implications include exacerbation of anemia and iron overload. We discuss the clinical implications of ineffective erythropoiesis in lines 366- 370. + +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +Authors' response. Figure legends have been corrected (lines 365, 369), thank you (now + +<--- Page Split ---> + +figures 7a and 7b) + +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +e. Figure 7(Now Figure 8) + +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. + +Thanks for the feedback. The figure was replotted with appropriate font sizes (page 25). + +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. + +Authors' response. We appreciate the reviewer's comment. The approach described in this manuscript, specifically in Figure 8 for editing of human mPB CD34s, is using a highly engineered inlaid base editor with NGC PAM tolerance that converts the sickle allele to a Makassar allele that was developed by Beam that was previously published (Chu et al 2021). This is different from the Newby approach which uses a NRCH- PAM tolerant guide. The functional result is the same, installation of the Makassar variant but the editor and guide sequences are different. We refer to this in the section describing the data (lines 388- 390) and we believe that these data are complimentary and orthogonal and give further confidence that the deployment of ABEs, even with slightly different features, give similar outcomes. + +Reviewer's Response. These clarifications and additional text additions are appreciated. + +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +Authors' response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +Reviewer's Response. The Reviewer appreciates this revision and clarification and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common + +<--- Page Split ---> + +terminology) and also contains jargon not generally accessible ("bulk d18 IVED" – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +Author's response, second revision. Thank you for your feedback. Abbreviations used in figure 8e are now defined in the figure legend. + +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is rather generic. + +Author's response, second revision. Thank you for your feedback. The SDS- PAGE is being used as a relative method to assess the purity of the proteins being used in the biochemical characterization and not for MW estimation. Given the purified material has a relative migration distance similar to the one observed for a commercially available HbA standard (lane 2, Sigma, H7379) and following the observation that MS analyses (panel b) confirm the correct expected MW for the isolated hemoglobins, we speculate the observed discrepancy between the ladder and observed migration could be due to an SDS- PAGE artifact or the improper MW estimation of the ladder by the vendor in the conditions used for running the aforementioned gel. Representative chromatograms from the globin chain analyses shown in Supplementary Figure 7a/b are now shown in SI Figure 7c. The method utilized for separation is cited in the materials and methods (line 231). + +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as \(2\%\) metabisulfite, but the figure legend states that \(2\%\) oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +Authors' response. We completely agree with the reviewer's comments around quantitation of sickling events in these images. Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. To that end, we have removed these figures and tempered any conclusions that were drawn from this data. + +<--- Page Split ---> + +Reviewer's Response. The Reviewer appreciates the Authors' candor on this point, removal of this figure, and tempering of conclusions drawn from it. + +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +Authors' response. Our text in the discussion was modified to align with the current data presented. Figures 1G (now 2e, page 19) and 4C (now 5c, page 22), the reminder of Figure 4 (now 5, page 22), Figure 3 (now 4, page 21), Figure 5A (now 6a, page 23), Figure 6 (now 7, page 24) and Figure 7 (now 8, page 25) have been replotted and presented in a more accessible and concise way. In addition, our new text in the discussion acknowledges the difference between the results obtained studying the purified protein and those obtained when studying it in the context of RBCs (lines 403- 486). The impact of dehydration on a similar compound heterozygote, HbSC, and the impact of RBC dehydration mediated by HbG on the red cell has been expanded in the introduction and discussion sections (lines 81- 91 and 443- 475). Ex vivo analysis of HbG does not show sickling, even as a HbG/HbS mixture. It is only when in the confines of a dehydrated mature red cell that the HbS in a 60:40 mixture with HbG where sickling becomes possible. + +Reviewer's Response. The new tempered statement in lines 434- 441 is appreciated and more reflective of the data presented, as well as the context present regarding ex vivo vs intracellular HbS/HbG mixtures in lines 443- 475. + +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C (now figure 7). + +Authors' response. HbSS mice had significantly heavier liver per body weight compared to HbGS mice (median 8.75 vs 6.44, \(p = 0.002\) ) while the liver weights/body weight of HbAA and HbAS were comparable with HbGG and HbGS, respectively. (now figure 7a, page 22). Although the sclerosis scores were different across the genotypes, they did not rise to the level of statistical significance. The manuscript has been modified to include this information (Lines 362- 372, 455- 459). + +<--- Page Split ---> + +Reviewer's Response. The modified verbiage in lines 362- 372 and 455- 460 much more accurately reflect the data presented in the manuscript. + +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by any of the data in the manuscript. + +Authors' response. Thank you for your feedback. Concluding statement was modified to highlight the importance of assessing red cell function of any novel hemoglobin editing strategy (lines 477- 486). While HbGG is the most likely editing outcome, and HbGS is in most domains superior to HbSS, one must consider the imperfect quality of HbGS when contemplating the Makassar strategy for base editing in SCD. + +Reviewer's Response. This new concluding paragraph is acceptable. + +Minor comments: + +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +Authors' response. The word transformative has been removed from the manuscript. + +Reviewer's Response. The Reviewers appreciate removal of this terminology from the manuscript. + +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +Authors' response. The abstract was edited for clarity and consistency (lines 23- 33). + +Reviewer's Response. The revised abstract is much clearer and more precise. + +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate – there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. + +<--- Page Split ---> + +These need to be cited and the language of this sentence toned down to be reflective of the literature. + +Authors' response. We agree with the reviewer that these therapies have modified the clinical severity for many individuals and have altered this section accordingly and added citations (lines 40- 42). + +Reviewer's Response. This new sentence and citations are accurate and reflect the current state of the field. + +4. Haploidentical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +Authors' response. We now discuss haploidentical transplantation as an option as well (lines 44- 46). + +Reviewer's Response. This addition is acceptable. + +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa- cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +Authors' response. We have eliminated this comment, as it is not integral to the discussion of base editing in the context of the larger transplant field. + +Reviewer's Response. Removal of this comment is appreciated. + +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the \(\beta \in \mathrm{6A}\) mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +Authors' response. Authors' response. Sentence was rewritten to remove technical jargon (lines 77- 79). + +Reviewer's Response. This revision is acceptable. + +<--- Page Split ---> + +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +Authors' response. This statement has been revised, and no longer comments on HbSC to HbSS relative severity. + +Reviewer's Response. This change is appreciated. + +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +Authors' response. The main text was modified to remove this confusing statement. We would like to clarify that HbG behaves normally in vitro but appears to dehydrate the red cell in vivo. There are some aspects of the HbGG red cell or of organ function of a HbGG mouse that are not statistically different from HbAA, as outlined in the text. + +Reviewer's Response. This clarification is acceptable. + +9. Townes mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +Authors' response. The genotype of the Townes mice, its stock number, as well as a description of the model is now present in the methods section (lines 108- 109) as well as in a new figure 1 (page 19). The new figure shows the humanized beta globin locus present in the Townes mice RBC. + +Reviewer's Response. The addition of this new Figure 1 is greatly appreciated by the Reviewer and provides a key foundation for the studies done in the remainder of the manuscript. + +10. "Zombie dye" is not standard terminology and needs to be clarified. + +Authors' response. "Zombie dye" was replaced with the commercial name utilized by Life Technologies (line 182). + +<--- Page Split ---> + +Reviewer's Response. This clarification is appreciated. + +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +Authors' response. Relevance of the p50 values, Hill coefficients and polymerization data of purified HbG in relationship to hemoglobin function and benefit to SCD is now expanded in the discussion section (lines 427- 441). + +Reviewer's Response. This clarification and addition of text to the discussion is appreciated. + +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +Authors' response. Figure 1(now figure 2, page 19) was replotted to make it more accessible to the general audience. + +Reviewer's Response. Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA – so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +Author's response, second revision. Thank you for your feedback. Requested changes have been made to figure 2e. + +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +Authors' response. Figure calling has been corrected in the text (line 283) + +Reviewer's Response. This correction is appreciated. + +Reviewer #3 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review + +<--- Page Split ---> + +manuscripts. + +Reviewer #4 (Remarks to the Author): + +The manuscript was improved in terms of clarity, however some important comments have not been addressed: + +1. The title should be tempered since data do not support a proper restoration of Hb function and its use in sickle cell disease compared to other developed approaches reactivating HbF + +Author's response, second revision. Thank you for your feedback. We have replaced the word "restores" with "improves" in the title. HbGG is the most likely editing outcome; HbG significantly improves RBC function compared to HbS. We do not want to speculate on efficacy of this strategy; the clinical outcome comparison of this strategy to induction of HbF is beyond the scope of this manuscript + +2. G and S can be distinguished via HPLC as shown by Newby et al Nature 2021. However, for proper technical comparison of globin expression, beta globin abundance should be evaluated as well in the AS genotype. Ratio of the different beta globins over alpha globin expression would also be informative. Alternatively, to precisely answer this point the authors could insert the silent mutation in HD HSPCs and compare beta-globin expression at mRNA and protein level in the erythroid progeny. + +Author's response, second revision. Apologies for the confusion. We intended to write \(\beta \mathsf{EGA}\) and \(\beta \mathsf{EGV}\) globins cannot be baseline separated. Supplementary Figure 7c now include representative chromatograms used to calculate the abundance of beta globins in the Makassar RBC. Our observations show a 60:40 ratio of G to S similar to the 60:40 A:S split observed in Townes HbA:HbS het mice. When comparing with previous quantifications done for the HbAS Townes mice (Wang et al, Journal of Gene Medicine, 2023) our data suggest that the silent mutation does not impair globin abundance. + +We can further demonstrate that globin protein abundance itself isn't impaired by the silent mutation by looking, as the reviewer suggests, at the alpha to beta globin protein abundance from uHPLC. Across several genotypes, in the same uHPLC run containing samples with the Makassar variant, peak areas consistent with the retention time of beta globin species and alpha show similar relative protein abundances compared to WT genotypes. This uHPLC raw data was included in the original source data that was part of the submission. + +
total betatotal alphabeta/alpha
WT111.15710.5841.05413832
WT213.26112.171.08964667
M83-1-B111.0510.1221.09168149
+ +<--- Page Split ---> + + +
M83-2-B28.9958.3291.07996158
M83-3-B311.20810.2481.09367681
M83-4-B410.5389.7611.0796025
M83-5-B510.45910.0761.03801112
M83-6-B612.0219.7431.23380889
M85-1-C111.69410.9921.06386463
M85-2-C214.14913.0241.08637899
M85-3-C314.5313.8751.04720721
M85-4-C414.28713.3151.07300038
M85-5-C515.96915.0491.06113363
M85-7-C714.17813.0371.08752014
M85-8-C812.49811.9841.04289052
M85-9-C913.52712.5561.0773355
+ +M83-HbAG + +M85-HbGS + +Total beta = Makassar + WT Beta or Makassar + sickle globin + +3. It would be relevant to reproduce the comparison of solubility with proteins purified in the frame of this study (HbA, HbG, HbS and maybe HbC) and discuss it as an altered + +property of HbG that could further explain the alteration of HbG-containing RBCs. + +Furthermore, the comment regarding the increased turbidity observed in 2.2M phosphate buffer with HbG purified in this study has not been addressed. This point should be discussed in the manuscript since it was described as a specific feature of HbG (Pagnier et al 1993). + +Author's response, second revision. Thank you for your feedback. The solubility work has been published (Adachi et.al., J. Biol. Chem. 1993 268:29 21650-21656 and Adachi et al.1993 FEBS 315:147-50), and thus it is not clear what new additional information we would contribute by repeating the experiment. In the published work the βE6 position was replaced for A (HbG), I, L, V (HbS), W, Q and it was found that HbA was more soluble than HbG which was more soluble than HbS. In addition, the authors found that HbG had a solubility greater than 150 mg/dL while that of HbA was of 350 mg/dL in a 2.1 M phosphate buffer solution. The increased turbidity observed at 2.2 M phosphate buffer reported in Pagnier et al. 1993 for HbG could be attributed to the decreased solubility of HbG at this buffer concentration. A statement of HbG solubility has been included in the manuscript (lines 478-488) and how,similarly to HbC, might be involved in the observed red cell dehydration. + +4. Hb tetramers fiber lateral contacts between beta2 Val/Ala6 and beta1 Phe85 and Leu88,if solved, should be discussed. + +<--- Page Split ---> + +Author's response, second revision. Apologies for the confusion. The contacts you are referring to are not observed in our HbG structure. We speculate the reason being due to differences in the crystal packing between our HbG structure and the HbS structure where these contacts were described (Harrington D.J. et al. 1997 J. Mol. Biol. 272 398- 407). The inability of HbG to polymerize in vitro would suggest that the nucleation in HbG crystals is different from the hemoglobin double strand helix that is formed in HbS which presumably helped in nucleating HbS crystals. + +5. RBC dehydration is probably not the root of the HbGS/HbGG associated phenotypes but is likely a consequence of an Hb characterized by altered physicochemical properties. The statement that in vitro characteristics of HbG are normal is not correct since it has been shown to be altered in previous studies using recombinant proteins (turbidity in 2.2M phosphate buffer, altered solubility), validation of these observations in the protein purified in this study and discussion on these altered properties would give a better overview of the description of the Hb variant of interest. + +Author's response, second revision. Apologies for the confusion. From our data, the only parameters where HbGG differed from HbAA were in metrics affected by dehydration. As a result, our data suggests that RBC dehydration is playing a major role in the observed HbGS/HbGG phenotypes akin to HbC (lines 453- 465, and 480- 488). The authors would like to emphasize that the main objective of this work is to characterize RBCs containing HbG. Ongoing work aimed to identify the root mechanism of dehydration caused by HbG is currently being pursued and it is intended to be published as a follow up to the current manuscript. + +6. Reference to the CRISPR Journal 2021 paper should be added line 204-205 when mentioning the IBE12.2. + +Author's response, second revision. Reference was added as suggested. Thank you. + +7. While Sup Table 5 indicates that statistical analyses have been performed in Figure 7c, it is not clear which conditions have been compared (as well as in other figures) + +Author's response, second revision. Apologies for the confusion. As stated in our revised manuscript in lines 193- 194, we compared the following three groups: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS. + +8. It would be interesting to comment on the osmotic fragility test that results positive in the homozygous HbG patient, could it be linked to the high % of dense cells? + +Author's response, second revision. Increased osmotic fragility is not characteristic of dense red blood cells; however, we hesitate to draw conclusions from a single individual who was pregnant at the time of assessment, which impacts RBC, for whom the primary + +<--- Page Split ---> + +data is not provided, and nutritional status such as iron levels that may impact the assay is unknown. + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #5 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> + +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments, thus the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +## REVIEWER COMMENTS + +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +Reviewer #2 (Remarks to the Author): + +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBS) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +## Major comments: + +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta E6A\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +Author's response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected \(p50\) range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +Reviewer's response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the authors could explain this discrepancy/change to the Reviewer would be very helpful. + +Author's response, second revision. Apologies for the confusion. No additional replicates have been added to the data. The means being compared are for HbG and HbA/HbS isolated + +<--- Page Split ---> + +from human RBC. The 24.8 value reported for HbA is for the sample isolated from Townes mice. + +This is an acceptable response. The Authors should also specifically clarify what "h blood" means in the Figure 1A legend as this is not a standard abbreviation. + +Thanks for your suggestion. Suggested clarification was added to the figure 2 legend. + +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +Author's response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +Reviewer's response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artifactual effects of high temperatures on hemoglobin integrity. + +Author's response, second revision. Thank you for sharing your concerns around artefactual effects of high temperatures on hemoglobin integrity. + +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +Author's response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +Reviewer's response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures, and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +Author's response, second revision. Thank you for your feedback. Labels for figure 2c and 2d have been inverted. Curve for 100% HbS in panel 2c has been replaced for a more representative curve taken from the data sets acquired in replicates. + +<--- Page Split ---> + +This is now acceptable. + +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +Author's response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures \((p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +Reviewer's response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include p- value in graph to emphasize that there is no difference between the trendlines. + +Author's response, second revision. Thank you for your feedback. Requested additions to figure 2g have been added. + +## This is now acceptable. + +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +Author's response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +Reviewer's response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +Author's response, second revision. Thank you for your feedback. A key main result of our + +<--- Page Split ---> + +manuscript is the identification that the \(\beta E6A\) mutation does not alter the hemoglobin protein fold. The manuscript has been revised to make sure this point is accessible to the general Nature's communication audience. We do agree with the reviewer to move this figure to the Supplementary information if the Editor believes this is too technical for the general readership. + +## This is an acceptable response and will defer to Editorial staff on this point. + +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +### a. Figure 3 (now figure 4) + +### i. Are pairwise comparisons being made between all samples? + +Author's response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann - Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (SI, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +Reviewer's response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +Author's response, second revision. We reported comparison for three biologically relevant groups (HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS) in the revised manuscript as mentioned in the statistical analysis section (lines 193- 194). Thus, GG and GS were not compared and reported. The initial submission had a discrepancy in which HbGG data was in the usual location of HbAS and was therefore missed by the statistical comparison process. This does not change the interpretation of the data (lines 319- 324). + +The Reviewer appreciates the detailed description of this issue and is now acceptable. + +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<--- Page Split ---> + +Author's response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +Reviewer's response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the health of this mouse that could be provided to the reviewer would be useful (as would be expected to be quite different physiologically with over a 50% reduction in hemoglobin; will defer to Editors as to whether this mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse). + +Author's response, second revision. We performed statistical analyses after excluding the HbAA mouse with Hb of 5.5 g/dL and did not observe significant changes in the statistical output that altered any inferences. We decided to leave this outlier as a way to be transparent and rigorous by presenting the data as was collected. The mouse was sacrificed in a good state of health per experimental design at 23 weeks, which is considered "middle- aged" for this mouse model. + +## Authors' response noted and accepted. + +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +Author's response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +Reviewer's response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +Author's response, second revision. Author's response. Thank you for the suggestion. We have altered the text accordingly (lines 319- 324). + +<--- Page Split ---> + +Authors' response noted and accepted. + +### b. Figure 4 (now figure 5) + +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +Author's response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a \(p\) - value of \(< 0.0001\) . + +Reviewer's response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A - the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y- axis should be set to zero as the adjusted Y- axis (0.35 to 0.65) exaggerates the biological differences here. + +Author's response, second revision. An earlier cohort of mice were used only for deformability measurements. In reviewing our data to make revisions and addition of animals for a more consistent number per assessment, this was noted. We replaced this cohort with data from the animals used in other analyses, such as CBC. This changed the Elmin significantly, although not the overall conclusions. The dramatic difference seen between the data sets is due to the variability within the sickle mouse model, which is not congenic. The correct data set is now being used for the elongation minimum (5A), elongation maximum (5B) and PoS (5C). This is also reflected within the sample size change for the data from 10 points to 12. The data sets for the remaining genotypes remain the same as their respective data sets were correct. We apologize for the initial error. + +GraphPad Prism software automatically adjusted the Y- axis to fit between 0.35 to 0.65. We understand the reviewer has concerns, so we have included both figures below—the original, and the readjusted Y- axis version to compare. The graph with the Y- axis from 0 to 0.6 is difficult to read due to overlapping individual observations. We believe that the inclusion of \(p\) - values does not allow for exaggeration to take place and prefer the original. + +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure. Will defer to the editors on the final decision on Y- axis trimming, but the Reviewer believes that the full Y- axis graph on the left emphasizes key differences without overexaggerating findings, and strongly prefer the Y- axis 0- 0.6 version on the left below. + +Thank you for your suggestion. A new figure displaying a full Y- axis version has been added to the manuscript. + +<--- Page Split ---> +![PLACEHOLDER_59_0] + + +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(\mathsf{pO2} > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15 \mathrm{mmHg}\) (overlapping with HbSS samples) and half less than \(15 \mathrm{mmHg}\) . The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +Author's response Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +Reviewer's response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +Author's response, second revision. The histograms of the previous data (panel A) and the current data (panel B) are shown below. Both panels show non- normal distribution with the mode for panel A at the fourth bar (midpoint of 22.5) and the mode for panel B at the third bar (midpoint 17) using the strict definition- the value with the highest frequency. We are aware that the first column of panel A may qualify as a second mode using the less strict definition. We also created histograms using different numbers of bins, as suggested in the literature, to confirm our findings. The Mann- Whitney test that we used to analysis is appropriate for data with non- normal distribution irrespective of the number of modes. The initial data showed low end points for the HbGG group due to the Point of Sickling (PoS) cut off of \(97.5\%\) oxygenation. PoS is typically defined as oxygen level at which \(95\%\) of the previous deformability is noted, thus the newer data reflects the correct standard removing values that did not have a greater than \(5\%\) difference between their elongation maximum + +<--- Page Split ---> + +and minimum. The values of the remaining data points reflect their Elongation Index at \(95\%\) oxygenation pressure. + +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure, and response is acceptable. + +![PLACEHOLDER_60_0] + + +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +Author's response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +Reviewer's response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS %sickled RBC do not appear not statistically different. This statement needs to be changed to "HbGS shows a trend toward decreased sickling as compared to HbSS" or similar. + +Author's response, second revision. As reviewer requests changes have been made (lines 341- 342). + +Authors' response noted and accepted. + +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +Author's response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +<--- Page Split ---> + +Reviewer's response. The Reviewer appreciates this addition of \(n\) for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +Author's response, second revision. Thank you for the suggestion to clarify; it is a challenging observation that in the mouse model, HbSS RBC are so abnormal and easily hemolyzed that they do not remain in circulation long enough to dehydrate and become dense, as in humans. The milder phenotype of HbGS and HbGG permits this observation (lines 458- 464). Additionally, humans with HbSC demonstrate greater RBC density than HbSS. + +This addition to the text is appreciated by the Reviewer; Authors' response noted and accepted. + +### c. Figure 5 (now figure 6) + +i. For Figure 5A-B – the statement is made that “RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA”, but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +Author's response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +Reviewer's response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement “retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis”) as this will not be evident to the general Nature Communications readership. + +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 357- 358). + +## Authors' response noted and accepted. + +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +Author's response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +<--- Page Split ---> + +Reviewer's response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However given the increased HbGS ineffective erythropoiesis seen in Figure 6D, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 366- 370). + +Authors' response noted and accepted. + +## d. Figure 6 (now figure 7) + +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +Author's response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +Reviewer's response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and implications on therapeutic applications. + +Author's response, second revision. In SCD, ineffective erythropoiesis is driven by apoptosis of erythroid precursors in the BM; this occurs under normoxia, so HbS polymerization is not required. It is likely that this occurs in HbGS mice as well, based on spleen and erythroid maturation findings. Clinical implications include exacerbation of anemia and iron overload. We discuss the clinical implications of ineffective erythropoiesis in lines 366- 370. + +This addition to the text is appreciated by the Reviewer and provides important context for the reader; Authors' response noted and accepted. + +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +Author's response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +Reviewer's response. The Reviewer appreciates this revision and clarification, and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on + +<--- Page Split ---> + +Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common terminology) and also contains jargon not generally accessible (“bulk d18 IVED” – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +Author's response, second revision. Thank you for your feedback. Abbreviations used in figure 8e are now defined in the figure legend. + +Authors' response noted and accepted. + +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is generic. + +Author's response, second revision. Thank you for your feedback. The SDS- PAGE is being used as a relative method to assess the purity of the proteins being used in the biochemical characterization and not for MW estimation. Given the purified material has a relative migration distance similar to the one observed for a commercially available HbA standard (lane 2, Sigma, H7379) and following the observation that MS analyses (panel b) confirm the correct expected MW for the isolated hemoglobins, we speculate the observed discrepancy between the ladder and observed migration could be due to an SDS- PAGE artifact or the improper MW estimation of the ladder by the vendor in the conditions used for running the aforementioned gel. Representative chromatograms from the globin chain analyses shown in Supplementary Figure 7a/b are now shown in SI Figure 7c. The method utilized for separation is cited in the materials and methods (line 231). + +This addition to the text for uHPLC is appreciated by the Reviewer. It is reasonable to use the MS in Supp. Figure 1a and the chromatogram as shown in Supp. Figure 7c as the definitive test for correct globin identification. However, given the Authors think that this discrepancy may be due to an issue with the SDS- PAGE gel or a manufacturer ladder error, would recommend either repeating this blot to see if a more concordant result can be obtained, or alternatively to remove Supp. Figure 1A completely. + +We have run the SDS- PAGE of hemoglobins multiple times and in all occasions we have observed the hemoglobins migrate faster (apparent smaller size) when compared to the protein standard being used. To avoid confusions and given we confirmed the identity of the proteins via MS we have removed the Supp. Figure 1A as suggested by the reviewer. + +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +Figure 1(now figure 2, page 19) was replotted to make it more accessible to the general audience. + +<--- Page Split ---> + +Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA – so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +Author's response, second revision. Thank you for your feedback. Requested changes have been made to figure 2e. + +## Authors' response noted and accepted. + +Reviewer #3 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #4 (Remarks to the Author): + +We thank the authors for answering our questions We have a last comment to address: Supplementary Figure 7c should include AA and AS data for proper technical comparison. + +Thank you for your suggestion. Figure 7c (now 6d and e) are the requested chromatograms for AA and AS requested by the reviewer for proper technical comparison. + +Reviewer #5 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> + +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments, thus the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +## REVIEWER COMMENTS + +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +Reviewer #2 (Remarks to the Author): + +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBs) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +## Major comments: + +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta E6A\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +Author's response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected \(p50\) range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +Reviewer's response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the authors could explain this discrepancy/change to the Reviewer would be very helpful. + +Author's response, second revision. Apologies for the confusion. No additional replicates have been added to the data. The means being compared are for HbG and HbA/HbS isolated + +<--- Page Split ---> + +from human RBC. The 24.8 value reported for HbA is for the sample isolated from Townes mice. + +This is an acceptable response. The Authors should also specifically clarify what "h blood" means in the Figure 1A legend as this is not a standard abbreviation. + +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +Author's response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +Reviewer's response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artifactual effects of high temperatures on hemoglobin integrity. + +Author's response, second revision. Thank you for sharing your concerns around artefactual effects of high temperatures on hemoglobin integrity. + +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +Author's response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +Reviewer's response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures, and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +Author's response, second revision. Thank you for your feedback. Labels for figure 2c and 2d have been inverted. Curve for 100% HbS in panel 2c has been replaced for a more representative curve taken from the data sets acquired in replicates. + +This is now acceptable. + +<--- Page Split ---> + +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +Author's response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures \((p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +Reviewer's response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include \(p\) - value in graph to emphasize that there is no difference between the trendlines. + +Author's response, second revision. Thank you for your feedback. Requested additions to figure 2g have been added. + +## This is now acceptable. + +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +Author's response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +Reviewer's response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +Author's response, second revision. Thank you for your feedback. A key main result of our manuscript is the identification that the \(\beta E6A\) mutation does not alter the hemoglobin protein fold. The manuscript has been revised to make sure this point is accessible to the + +<--- Page Split ---> + +general Nature's communication audience. We do agree with the reviewer to move this figure to the Supplementary information if the Editor believes this is too technical for the general readership. + +## This is an acceptable response and will defer to Editorial staff on this point. + +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +### a. Figure 3 (now figure 4) +i. Are pairwise comparisons being made between all samples? + +Author's response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann - Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (Sl, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +Reviewer's response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +Author's response, second revision. We reported comparison for three biologically relevant groups (HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS) in the revised manuscript as mentioned in the statistical analysis section (lines 193- 194). Thus, GG and GS were not compared and reported. The initial submission had a discrepancy in which HbGG data was in the usual location of HbAS and was therefore missed by the statistical comparison process. This does not change the interpretation of the data (lines 319- 324). + +The Reviewer appreciates the detailed description of this issue and is now acceptable. + +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +Author's response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin + +<--- Page Split ---> + +values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +Reviewer's response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the health of this mouse that could be provided to the reviewer would be useful (as would be expected to be quite different physiologically with over a 50% reduction in hemoglobin; will defer to Editors as to whether this mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse). + +Author's response, second revision. We performed statistical analyses after excluding the HbAA mouse with Hb of 5.5 g/dL and did not observe significant changes in the statistical output that altered any inferences. We decided to leave this outlier as a way to be transparent and rigorous by presenting the data as was collected. The mouse was sacrificed in a good state of health per experimental design at 23 weeks, which is considered "middle- aged" for this mouse model. + +## Authors' response noted and accepted. + +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +Author's response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +Reviewer's response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +Author's response, second revision. Author's response. Thank you for the suggestion. We have altered the text accordingly (lines 319- 324). + +Authors' response noted and accepted. + +## b. Figure 4 (now figure 5) + +<--- Page Split ---> + +## i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +Author's response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a \(p\) - value of \(< 0.0001\) . + +Reviewer's response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A – the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y- axis should be set to zero as the adjusted Y- axis (0.35 to 0.65) exaggerates the biological differences here. + +Author's response, second revision. An earlier cohort of mice were used only for deformability measurements. In reviewing our data to make revisions and addition of animals for a more consistent number per assessment, this was noted. We replaced this cohort with data from the animals used in other analyses, such as CBC. This changed the Elmin significantly, although not the overall conclusions. The dramatic difference seen between the data sets is due to the variability within the sickle mouse model, which is not congenic. The correct data set is now being used for the elongation minimum (5A), elongation maximum (5B) and PoS (5C). This is also reflected within the sample size change for the data from 10 points to 12. The data sets for the remaining genotypes remain the same as their respective data sets were correct. We apologize for the initial error. + +GraphPad Prism software automatically adjusted the Y- axis to fit between 0.35 to 0.65. We understand the reviewer has concerns, so we have included both figures below—the original, and the readjusted Y- axis version to compare. The graph with the Y- axis from 0 to 0.6 is difficult to read due to overlapping individual observations. We believe that the inclusion of \(p\) - values does not allow for exaggeration to take place and prefer the original. + +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure. Will defer to the editors on the final decision on Y- axis trimming, but the Reviewer believes that the full Y- axis graph on the left emphasizes key differences without overexaggerating findings, and strongly prefer the Y- axis 0- 0.6 version on the left below. + +![PLACEHOLDER_70_0] + + +<--- Page Split ---> + +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(\mathsf{pO2} > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than 15 mmHg (overlapping with HbSS samples) and half less than 15 mmHg. The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +Author's response Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +Reviewer's response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +Author's response, second revision. The histograms of the previous data (panel A) and the current data (panel B) are shown below. Both panels show non- normal distribution with the mode for panel A at the fourth bar (midpoint of 22.5) and the mode for panel B at the third bar (midpoint 17) using the strict definition- the value with the highest frequency. We are aware that the first column of panel A may qualify as a second mode using the less strict definition. We also created histograms using different numbers of bins, as suggested in the literature, to confirm our findings. The Mann- Whitney test that we used to analysis is appropriate for data with non- normal distribution irrespective of the number of modes. The initial data showed low end points for the HbGG group due to the Point of Sickling (PoS) cut off of 97.5% oxygenation. PoS is typically defined as oxygen level at which 95% of the previous deformability is noted, thus the newer data reflects the correct standard removing values that did not have a greater than 5% difference between their elongation maximum and minimum. The values of the remaining data points reflect their Elongation Index at 95% oxygenation pressure. + +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure, and response is acceptable. + +<--- Page Split ---> +![PLACEHOLDER_72_0] + + +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +Author's response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +Reviewer's response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS \(\%\) sickled RBC do not appear not statistically different. This statement needs to be changed to "HbGS shows a trend toward decreased sickling as compared to HbSS" or similar. + +Author's response, second revision. As reviewer requests changes have been made (lines 341- 342). + +Authors' response noted and accepted. + +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +Author's response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +Reviewer's response. The Reviewer appreciates this addition of n for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +Author's response, second revision. Thank you for the suggestion to clarify; it is a challenging observation that in the mouse model, HbSS RBC are so abnormal and easily + +<--- Page Split ---> + +hemolyzed that they do not remain in circulation long enough to dehydrate and become dense, as in humans. The milder phenotype of HbGS and HbGG permits this observation (lines 458- 464). Additionally, humans with HbSC demonstrate greater RBC density than HbSS. + +This addition to the text is appreciated by the Reviewer; Authors' response noted and accepted. + +### c. Figure 5 (now figure 6) + +i. For Figure 5A-B – the statement is made that “RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA”, but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +Author's response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +Reviewer's response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement “retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis”) as this will not be evident to the general Nature Communications readership. + +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 357- 358). + +## Authors' response noted and accepted. + +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +Author's response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +Reviewer's response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However given the increased HbGS ineffective erythropoiesis seen in Figure 6D, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 366- 370). + +<--- Page Split ---> + +Authors' response noted and accepted. + +## d. Figure 6 (now figure 7) + +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +Author's response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +Reviewer's response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and implications on therapeutic applications. + +Author's response, second revision. In SCD, ineffective erythropoiesis is driven by apoptosis of erythroid precursors in the BM; this occurs under normoxia, so HbS polymerization is not required. It is likely that this occurs in HbGS mice as well, based on spleen and erythroid maturation findings. Clinical implications include exacerbation of anemia and iron overload. We discuss the clinical implications of ineffective erythropoiesis in lines 366- 370. + +This addition to the text is appreciated by the Reviewer and provides important context for the reader; Authors' response noted and accepted. + +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +Author's response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +Reviewer's response. The Reviewer appreciates this revision and clarification, and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common terminology) and also contains jargon not generally accessible ("bulk d18 IVED" – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +<--- Page Split ---> + +Author's response, second revision. Thank you for your feedback. Abbreviations used in figure 8e are now defined in the figure legend. + +## Authors' response noted and accepted. + +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is generic. + +Author's response, second revision. Thank you for your feedback. The SDS- PAGE is being used as a relative method to assess the purity of the proteins being used in the biochemical characterization and not for MW estimation. Given the purified material has a relative migration distance similar to the one observed for a commercially available HbA standard (lane 2, Sigma, H7379) and following the observation that MS analyses (panel b) confirm the correct expected MW for the isolated hemoglobins, we speculate the observed discrepancy between the ladder and observed migration could be due to an SDS- PAGE artifact or the improper MW estimation of the ladder by the vendor in the conditions used for running the aforementioned gel. Representative chromatograms from the globin chain analyses shown in Supplementary Figure 7a/b are now shown in SI Figure 7c. The method utilized for separation is cited in the materials and methods (line 231). + +This addition to the text for uHPLC is appreciated by the Reviewer. It is reasonable to use the MS in Supp. Figure 1a and the chromatogram as shown in Supp. Figure 7c as the definitive test for correct globin identification. However, given the Authors think that this discrepancy may be due to an issue with the SDS- PAGE gel or a manufacturer ladder error, would recommend either repeating this blot to see if a more concordant result can be obtained, or alternatively to remove Supp. Figure 1A completely. + +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +Figure 1(now figure 2, page 19) was replotted to make it more accessible to the general audience. + +Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA – so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +Author's response, second revision. Thank you for your feedback. Requested changes have been made to figure 2e. + +Authors' response noted and accepted. + +<--- Page Split ---> diff --git a/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..753a54e1daad74a563540e89a8d6563d412e0d7d --- /dev/null +++ b/peer_reviews/3383aaa8a05a08da7b9953db445c0c9f532033ec36caa6219ff87f74b7081a8f/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,2725 @@ +<|ref|>title<|/ref|><|det|>[[73, 50, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 296, 120]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[74, 161, 870, 211]]<|/det|> +# Base editing HbS to HbG-Makassar improves hemoglobin function, supporting its use in sickle cell disease + +<|ref|>text<|/ref|><|det|>[[74, 224, 435, 241]]<|/det|> +Corresponding Author: Dr Vivien Sheehan + +<|ref|>text<|/ref|><|det|>[[72, 274, 866, 290]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[72, 301, 890, 316]]<|/det|> +Attachments originally included by the reviewers as part of their assessment can be found at the end of this file. + +<|ref|>text<|/ref|><|det|>[[73, 353, 144, 367]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 379, 219, 393]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 404, 160, 418]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 431, 238, 444]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 444, 915, 496]]<|/det|> +In this study "Installation of HbG- Makassar by base editing restores hemoglobin function: a transformative therapy for sickle cell disease" the authors describe their work to characterize mice that have been genetically modified to harbor the Makassar variant of adult beta globin, which can be efficiently introduced using adenine base editing in cells harboring the sickle cell disease genetic variant. + +<|ref|>text<|/ref|><|det|>[[72, 508, 911, 588]]<|/det|> +This Makassar variant is extremely rare in the natural human population, so this study is extremely valuable to characterize what the potential outcomes would be in erythroid cells differentiated from homozygous or heterozygous HSCs. The authors make many important findings, including the similarity in phenotype between mice with an AA genotype and GG genotype, and interesting differences between GS and AS phenotypes. In particular, the white blood cell and reticulocyte counts of GS mice are similar to SS mice. The structure of Makassar globin is described here for the first time to my knowledge. + +<|ref|>text<|/ref|><|det|>[[72, 599, 900, 627]]<|/det|> +The methodology of this manuscript appears sound and it is well- written and illustrated. I am enthusiastic about this study recommend acceptance of this manuscript pending three relatively small comments. + +<|ref|>text<|/ref|><|det|>[[72, 638, 916, 705]]<|/det|> +1. The structure of the original and modified beta globin locus in the newly established mouse haplotype is not shown or described in detail. I believe that this mouse also includes human gamma globin genes, but these are not expressed at high levels. Since fetal hemoglobin is a particularly strong modifier of the described phenotypes, it would be helpful to show a quantification of fetal hemoglobin in each mouse genotype to ensure that fetal hemoglobin expression was not modified in the new established Makassar haplotype and did not confound any of these results. + +<|ref|>text<|/ref|><|det|>[[72, 716, 897, 770]]<|/det|> +2. The paragraph on dense red blood cells is particularly sparse with only one mouse genotype detailed and minimal reference to what is normal and what dysfunction may indicate here. Hematocrit and density appear to be the main parameters where AA differs from GG, so discussing this in more detail is warranted. Furthermore, the reference appears incorrect since the panel that describes density is Fig 4H, not Fig 4E. + +<|ref|>text<|/ref|><|det|>[[72, 781, 918, 822]]<|/det|> +3. The axis text in Figure 7 relating to the genome editing experiment is too small to readily interpret. The methods section is also lacking in detail about exactly which editor variant and sgRNA was used in this experiment. It references a different journal for the electroporation conditions - it would be better to state the methods explicitly here. + +<|ref|>sub_title<|/ref|><|det|>[[73, 834, 161, 848]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 861, 237, 874]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 874, 919, 941]]<|/det|> +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBS) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 910, 112]]<|/det|> +deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question, and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +<|ref|>sub_title<|/ref|><|det|>[[73, 127, 193, 139]]<|/det|> +## Major comments: + +<|ref|>text<|/ref|><|det|>[[72, 139, 921, 230]]<|/det|> +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta\) EA mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +<|ref|>text<|/ref|><|det|>[[72, 230, 920, 332]]<|/det|> +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerase. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G 3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +<|ref|>text<|/ref|><|det|>[[72, 332, 904, 373]]<|/det|> +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +<|ref|>text<|/ref|><|det|>[[70, 372, 920, 399]]<|/det|> +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +<|ref|>text<|/ref|><|det|>[[72, 400, 150, 412]]<|/det|> +a. Figure 3 + +<|ref|>text<|/ref|><|det|>[[72, 412, 504, 425]]<|/det|> +i. Are pairwise comparisons being made between all samples? + +<|ref|>text<|/ref|><|det|>[[72, 425, 815, 439]]<|/det|> +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +<|ref|>text<|/ref|><|det|>[[72, 439, 580, 451]]<|/det|> +iii. Why is the order of genotypes/color scheme different between panels? + +<|ref|>text<|/ref|><|det|>[[72, 451, 501, 464]]<|/det|> +iv. Why is \(n\) so dramatically different between panels/assays? + +<|ref|>text<|/ref|><|det|>[[72, 464, 904, 491]]<|/det|> +v. In particular, Figure 3C is confusing in that the absolute recytocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +<|ref|>text<|/ref|><|det|>[[72, 491, 920, 555]]<|/det|> +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<|ref|>text<|/ref|><|det|>[[72, 555, 920, 607]]<|/det|> +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" - why does HbG heterozygous state not have any effect on baseline ARC? + +<|ref|>text<|/ref|><|det|>[[72, 608, 149, 620]]<|/det|> +b. Figure 4 + +<|ref|>text<|/ref|><|det|>[[72, 620, 920, 647]]<|/det|> +i. For Figure 4A, the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +<|ref|>text<|/ref|><|det|>[[72, 647, 920, 712]]<|/det|> +ii. For Figure 4C, the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of pO2 >15% in the bone marrow reference (Figure 4)" - this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than 15 mmHg (overlapping with HbSS samples) and half less than 15 mmHg. The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +<|ref|>text<|/ref|><|det|>[[72, 712, 904, 752]]<|/det|> +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (maybe Figure 4E?) + +<|ref|>text<|/ref|><|det|>[[72, 752, 730, 765]]<|/det|> +iv. The relevance of Hematocrit-Viscocity Ratio (HVR) is not explained in any way for Figure 4D. + +<|ref|>text<|/ref|><|det|>[[72, 765, 884, 805]]<|/det|> +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +<|ref|>text<|/ref|><|det|>[[72, 805, 920, 845]]<|/det|> +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with \(n = 3\) or alternatively removed. + +<|ref|>text<|/ref|><|det|>[[72, 845, 149, 857]]<|/det|> +c. Figure 5 + +<|ref|>text<|/ref|><|det|>[[72, 857, 916, 922]]<|/det|> +i. For Figure 5A-B - the statement is made that "RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA", but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +<|ref|>text<|/ref|><|det|>[[70, 921, 920, 948]]<|/det|> +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 666, 61]]<|/det|> +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +<|ref|>text<|/ref|><|det|>[[72, 60, 150, 72]]<|/det|> +d. Figure 6 + +<|ref|>text<|/ref|><|det|>[[72, 72, 916, 112]]<|/det|> +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +<|ref|>text<|/ref|><|det|>[[72, 112, 465, 125]]<|/det|> +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +<|ref|>text<|/ref|><|det|>[[72, 126, 150, 138]]<|/det|> +e. Figure 7 + +<|ref|>text<|/ref|><|det|>[[72, 138, 920, 220]]<|/det|> +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G - numerous additional replicates would be necessary to be able to make this claim. + +<|ref|>text<|/ref|><|det|>[[72, 218, 914, 283]]<|/det|> +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as \(2\%\) metabisulfite, but the figure legend states that \(2\%\) oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +<|ref|>text<|/ref|><|det|>[[72, 282, 914, 360]]<|/det|> +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +<|ref|>text<|/ref|><|det|>[[72, 359, 884, 386]]<|/det|> +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C. + +<|ref|>text<|/ref|><|det|>[[72, 385, 913, 438]]<|/det|> +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by any of the data in the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 451, 193, 464]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 464, 904, 504]]<|/det|> +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +<|ref|>text<|/ref|><|det|>[[72, 503, 900, 530]]<|/det|> +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +<|ref|>text<|/ref|><|det|>[[72, 529, 914, 582]]<|/det|> +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate - there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. These need to be cited and the language of this sentence toned down to be reflective of the literature. + +<|ref|>text<|/ref|><|det|>[[72, 581, 914, 621]]<|/det|> +4. Haploidentical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +<|ref|>text<|/ref|><|det|>[[72, 620, 911, 660]]<|/det|> +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa-cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +<|ref|>text<|/ref|><|det|>[[72, 659, 900, 699]]<|/det|> +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the βE6A mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +<|ref|>text<|/ref|><|det|>[[72, 698, 920, 738]]<|/det|> +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +<|ref|>text<|/ref|><|det|>[[72, 737, 900, 778]]<|/det|> +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +<|ref|>text<|/ref|><|det|>[[72, 777, 901, 829]]<|/det|> +9. Towns mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +<|ref|>text<|/ref|><|det|>[[72, 828, 556, 842]]<|/det|> +10. "Zombie dye" is not standard terminology and needs to be clarified. + +<|ref|>text<|/ref|><|det|>[[72, 841, 916, 881]]<|/det|> +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +<|ref|>text<|/ref|><|det|>[[72, 880, 888, 909]]<|/det|> +12. All figures in Figure 1 are very difficult to read/interpret - would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +<|ref|>text<|/ref|><|det|>[[72, 908, 513, 922]]<|/det|> +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 61, 238, 74]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 74, 864, 115]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>sub_title<|/ref|><|det|>[[73, 127, 161, 140]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 153, 238, 165]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 166, 914, 231]]<|/det|> +Generating the Makassar hemoglobin variant is a promising therapeutic strategy to correct the sickle cell disease- causing mutation. In this work, Kostamo and colleagues generated a mouse model harboring the Makassar mutation and evaluated in vitro properties of the Makassar hemoglobin as well as hematological and organ parameters in vivo. Furthermore, they evaluated the effect of mono and bi- allelic editing in clonal culture of control and edited erythroid cells from patients with sickle cell disease. Although interesting, we have some important remarks. + +<|ref|>text<|/ref|><|det|>[[72, 242, 920, 283]]<|/det|> +- The Authors should mitigate the conclusions of the study (in the title, abstract, intro and discussion) as mono allelic editing will likely not lead to a major clinical benefit and mouse models are not always predictive of the results observed in patients. Furthermore, this study demonstrates that HbG-Makassar does not behave like HbA + +<|ref|>text<|/ref|><|det|>[[72, 282, 920, 309]]<|/det|> +- Introduction: some references regarding the other ABE-approaches developed to induce HbF are missing: Ravi et al 2022, Han et al 2023, Antoniou et al 2022, ... + +<|ref|>text<|/ref|><|det|>[[72, 308, 920, 335]]<|/det|> +- The Authors generate the Makassar mutation together with a silent mutation. It would be interesting to evaluate if this silent mutation affects beta-globin expression at transcriptional or translational level. To this aim, the Authors could compare + +<|ref|>text<|/ref|><|det|>[[72, 335, 920, 356]]<|/det|> +HPLC profiles in AS and GS mice (to complete Figure 4G if this panel is showing HPLC data, the Authors should specify it) + +<|ref|>text<|/ref|><|det|>[[72, 355, 920, 421]]<|/det|> +- Figure 1: Previous polymerization studies using recombinant Hb (Pagnier et al 1993) have demonstrated that HbG-Makassar solutions show a sudden increase in turbidity in 2.2M phosphate buffer following temperature increase while HbG-Makassar behaves similarly to HbA in a 1.8M phosphate buffer solution. It would have been interesting to consider reproducing these data (by including the 2.2M condition) to better understand the biochemical properties of HbG variant. Moreover, since these results (Pagnier et al 1993) using recombinant Hb suggested that HbG has a lower solubility as compared to HbA, experiments evaluating this parameter would have been of interest. + +<|ref|>text<|/ref|><|det|>[[72, 421, 860, 448]]<|/det|> +- Figure 2: the Authors should also compare the crystal structure of HbS, superimpose the structures of the different hemoglobins and analyze the lateral contacts + +<|ref|>text<|/ref|><|det|>[[72, 448, 920, 515]]<|/det|> +- Overall, since some hematological parameters were found to be affected in GG and SG mice models (clearly demonstrating that HbG does not behave like HbA) further functional characterization of the purified proteins should be performed to provide potential explanations for these observations (inflammation in GS not in GA, lower deformability of GG vs AA, sickling of GS RBCs vs no sickling of AS RBCs; ...). In other words, are there any experiments that could be performed to reconcile in vitro and in vivo data? + +<|ref|>text<|/ref|><|det|>[[72, 515, 890, 555]]<|/det|> +- Figure 1: Since it is known that blood of patients with SCD exhibits decreased affinity for oxygen, although the oxygen affinity of HbS is the same as that of HbA (Figure 1), oxygen binding studies could also be performed in whole blood of transgenic mice since HbG containing RBCs seem to be affected. + +<|ref|>text<|/ref|><|det|>[[72, 554, 900, 580]]<|/det|> +- Figure 4H: The observed increase in DRBC in GG and GS condition is not further commented: could it have any clinical impact? + +<|ref|>text<|/ref|><|det|>[[72, 580, 914, 634]]<|/det|> +- It is not clear which conditions have been tested for Pair comparisons across histograms of Figures 3-6. All the conditions should be compared to draw proper conclusions. For example, for the liver weight (Figure 6A), only SS mice seem to be different from the others. In Figure 6B, spleen size looks much bigger (and not "comparable" as mentioned in the text) in SS than in GS mice + +<|ref|>text<|/ref|><|det|>[[72, 633, 504, 647]]<|/det|> +- Figure 6B: the % of Ter119 should be evaluated in the spleen + +<|ref|>text<|/ref|><|det|>[[72, 647, 910, 673]]<|/det|> +- Figure 7A: It is not clear which engineered ABE has been used. The editing efficiency looks higher to the one reported in Chu et al 2021, it should be explicit whether it is the same strategy or if a new editing strategy has been developed + +<|ref|>text<|/ref|><|det|>[[72, 686, 192, 698]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 698, 916, 925]]<|/det|> +- Some references to the Figures are missing in the text or misplaced (Figure 1G, Figure 4) +- Some Figures are not commented (Figure 4D, 4G...) or commented later. All the panels of Figure 4 should be discussed (and in the right order) +- Some Legends are missing (colors of Figure 5C) or incorrect (Figure 6A-B mismatched) +- Figure 1G is not clear. It is mentioned in the Mat&Met that 5 different % of AS and GS Hb mixtures were tested. Which ones are depicted here? +- Some Main Figures are blurry or difficult to read (Figure 1, Figure 5D, Figure 7) +- Figure 3: colors are confusing since they are not consistently associated to the same genotype +- Figure 5A: the difference mitochondrial retention % between AS and GS is still present in the graph, were the data normalized for retic count or not? The Authors should better explain how (and if) they perform normalization and show the proportion of reticulocytes in the different mouse groups +- Figure 5C: the assumption that HbGG and HbAA show a similar distribution of erythroid states should be confirmed by performing statistical analysis. +- Figure 6C: why the sclerosis score was not evaluated in all 5/6 mice per group?As mice are sometimes only 2, the Authors cannot discuss about "significant difference" +- Figure 7F/Figure S3: a quantitative graph of % of sickle cells would be more informative than representative pictures. AS samples should also be analyzed. +- Discussion: The Authors should compare the proposed approach with currently available strategies and other approaches in development (mutation correction by prime editing) + +<|ref|>text<|/ref|><|det|>[[72, 920, 916, 946]]<|/det|> +in development (mutation correction by prime editing) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 915, 112]]<|/det|> +- Discussion: Overall, in vitro and in vivo results are contradictory (normal properties of the purified Hb in vitro and altered hematological parameters observed in vivo): which protein parameters could explain these in vivo alterations? The Authors could also discuss the potential causes of RBC dehydration in GG mice. +- Discussion: It would be interesting to discuss the results obtained in the GG mouse model with data collected from the homozygous HbG patient in Sangkitporn et al 2002 + +<|ref|>sub_title<|/ref|><|det|>[[73, 138, 162, 151]]<|/det|> +## Reviewer #5 + +<|ref|>text<|/ref|><|det|>[[73, 164, 237, 178]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 178, 864, 219]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 230, 144, 244]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 256, 219, 270]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 282, 160, 296]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 308, 238, 321]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 321, 923, 349]]<|/det|> +In their resubmitted manuscript, the authors have addressed all of my concerns. This work constitutes a useful comparison of the properties of HbAA, HbAS, HbGG, HbGS, and HbSS mice and red blood cells. + +<|ref|>text<|/ref|><|det|>[[73, 360, 162, 373]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 386, 238, 400]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 399, 917, 490]]<|/det|> +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments; thus, the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +<|ref|>text<|/ref|><|det|>[[73, 501, 680, 516]]<|/det|> +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +<|ref|>text<|/ref|><|det|>[[72, 540, 920, 673]]<|/det|> +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBs) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +<|ref|>text<|/ref|><|det|>[[73, 685, 192, 698]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[72, 697, 923, 763]]<|/det|> +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta \in \mathrm{6A}\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +<|ref|>text<|/ref|><|det|>[[72, 775, 923, 840]]<|/det|> +Authors' response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected p50 range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +<|ref|>text<|/ref|><|det|>[[72, 852, 923, 920]]<|/det|> +Reviewer's Response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the Authors could explain this discrepancy/change to the Reviewer would be very helpful. + +<|ref|>text<|/ref|><|det|>[[70, 931, 884, 946]]<|/det|> +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 896, 74]]<|/det|> +unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +<|ref|>text<|/ref|><|det|>[[72, 85, 891, 153]]<|/det|> +Authors' response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +<|ref|>text<|/ref|><|det|>[[72, 164, 890, 192]]<|/det|> +Reviewer's Response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artefactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[72, 202, 912, 244]]<|/det|> +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +<|ref|>text<|/ref|><|det|>[[72, 254, 911, 321]]<|/det|> +Authors' response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +<|ref|>text<|/ref|><|det|>[[72, 332, 920, 399]]<|/det|> +Reviewer's Response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +<|ref|>text<|/ref|><|det|>[[72, 410, 914, 478]]<|/det|> +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +<|ref|>text<|/ref|><|det|>[[72, 488, 920, 569]]<|/det|> +Authors' response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures \((p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +<|ref|>text<|/ref|><|det|>[[72, 579, 915, 620]]<|/det|> +Reviewer's Response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include p- value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[72, 631, 901, 672]]<|/det|> +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +<|ref|>text<|/ref|><|det|>[[72, 683, 918, 752]]<|/det|> +Authors' response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +<|ref|>text<|/ref|><|det|>[[72, 762, 911, 816]]<|/det|> +Reviewer's Response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +<|ref|>text<|/ref|><|det|>[[70, 840, 920, 869]]<|/det|> +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +<|ref|>text<|/ref|><|det|>[[72, 880, 504, 908]]<|/det|> +a. Figure 3 (now figure 4) i. Are pairwise comparisons being made between all samples? + +<|ref|>text<|/ref|><|det|>[[70, 918, 920, 946]]<|/det|> +Authors' response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann- Whitney test when the distribution of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 888, 100]]<|/det|> +groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (SI, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +<|ref|>text<|/ref|><|det|>[[73, 111, 920, 153]]<|/det|> +Reviewer's Response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +<|ref|>text<|/ref|><|det|>[[73, 164, 920, 205]]<|/det|> +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +<|ref|>text<|/ref|><|det|>[[70, 215, 815, 230]]<|/det|> +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +<|ref|>text<|/ref|><|det|>[[73, 241, 920, 309]]<|/det|> +Authors' response. Statistics were performed and shown for the pairwise comparisons where their difference appeared to be significant. P values were reported in the main text. Samples whose statistics are not shown are because their difference was not significant. In both cases significance and lack of significance was addressed in the main text in the original submission. To make this observation more accessible to the general reader, P value descriptors have been added to the figure legend and the statistical analysis method section was expanded as well (lines 193- 202). + +<|ref|>text<|/ref|><|det|>[[73, 320, 500, 334]]<|/det|> +Reviewer's Response. Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[73, 346, 575, 360]]<|/det|> +iii. Why is the order of genotypes/color scheme different between panels? + +<|ref|>text<|/ref|><|det|>[[73, 371, 896, 399]]<|/det|> +Color in figure 3 (now figure 4, page 21) panels and in all of the other figures have been standardized to match color and genotype across panels. + +<|ref|>text<|/ref|><|det|>[[73, 410, 780, 425]]<|/det|> +Reviewer's Response. The newly plotted graphs in new Figure 4 are now much easier to read/interpret. + +<|ref|>text<|/ref|><|det|>[[73, 436, 495, 450]]<|/det|> +iv. Why is n so dramatically different between panels/assays? + +<|ref|>text<|/ref|><|det|>[[73, 462, 918, 503]]<|/det|> +Authors' response. Thanks for pointing out this observation. The number of mice from each genotype varies from assay to assay primarily due to blood volume limitations of the mouse model. We have summarized the number of mice used in each analysis in the supplementary information, supplementary table 5 (SI, page 6). + +<|ref|>text<|/ref|><|det|>[[73, 514, 905, 542]]<|/det|> +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 is a welcome addition to clarify these differences. + +<|ref|>text<|/ref|><|det|>[[73, 553, 901, 594]]<|/det|> +v. In particular, Figure 3C is confusing in that the absolute reticulocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +<|ref|>text<|/ref|><|det|>[[73, 605, 923, 673]]<|/det|> +Authors' response. Thank you for your observation. Additional mice were analyzed, and Figure 3 (now Figure 4, page 21) is updated. Reticulocyte count requires very large blood volumes, so it was only possible to measure it in those mice where the blood drawn met the assay volume requirements. Supplementary Table 5 (SI, page 6) contains all the sample sizes and comparisons performed in the manuscript. We have now assured that a minimum of \(n = 3\) mice from each genotype were used in every test. + +<|ref|>text<|/ref|><|det|>[[73, 684, 911, 712]]<|/det|> +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 as well as at least \(n = 3\) for each genotype is appreciated. + +<|ref|>text<|/ref|><|det|>[[73, 723, 923, 777]]<|/det|> +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<|ref|>text<|/ref|><|det|>[[73, 787, 924, 880]]<|/det|> +Authors' response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +<|ref|>text<|/ref|><|det|>[[73, 891, 914, 946]]<|/det|> +Reviewer's Response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the health of this mouse that could be provided to the Reviewer would be useful, as would be expected to be quite different physiologically with over a \(50\%\) reduction in hemoglobin; Authors (and Editors) should decide whether this + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 816, 61]]<|/det|> +mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse. + +<|ref|>text<|/ref|><|det|>[[72, 72, 921, 125]]<|/det|> +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +<|ref|>text<|/ref|><|det|>[[72, 137, 920, 203]]<|/det|> +Authors' response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +<|ref|>text<|/ref|><|det|>[[72, 215, 914, 282]]<|/det|> +Reviewer's Response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +<|ref|>text<|/ref|><|det|>[[72, 294, 247, 308]]<|/det|> +b. Figure 4 (now figure 5) + +<|ref|>text<|/ref|><|det|>[[72, 306, 911, 335]]<|/det|> +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +<|ref|>text<|/ref|><|det|>[[72, 345, 920, 386]]<|/det|> +Authors' response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a p-value of <0.0001. + +<|ref|>text<|/ref|><|det|>[[72, 397, 921, 450]]<|/det|> +Reviewer's Response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A – the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y-axis should be set to zero as the adjusted Y-axis (0.35 to 0.65) exaggerates the biological differences here. + +<|ref|>text<|/ref|><|det|>[[72, 462, 920, 529]]<|/det|> +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(pO2 > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15 \text{mmHg}\) (overlapping with HbSS samples) and half less than \(15 \text{mmHg}\). The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +<|ref|>text<|/ref|><|det|>[[72, 540, 920, 606]]<|/det|> +Authors' response. Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\). + +<|ref|>text<|/ref|><|det|>[[72, 618, 923, 685]]<|/det|> +Reviewer's Response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +<|ref|>text<|/ref|><|det|>[[72, 696, 900, 737]]<|/det|> +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +<|ref|>text<|/ref|><|det|>[[72, 748, 781, 763]]<|/det|> +Authors' response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +<|ref|>text<|/ref|><|det|>[[72, 774, 905, 829]]<|/det|> +Reviewer's Response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS %sickled RBCs do not appear statistically different. This statement needs to be changed to "HbGS shows a trend toward decreased sickling as compared to HbSS" or similar. + +<|ref|>text<|/ref|><|det|>[[70, 840, 837, 855]]<|/det|> +iv. The relevance of Hematocrit-Viscosity Ratio (HVR) is not explained in any way for Figure 4D (now figure 5e). + +<|ref|>text<|/ref|><|det|>[[70, 866, 884, 880]]<|/det|> +Authors' response. An additional discussion of viscosity and HVR has been added to the text (lines 166- 171, 337- 340). + +<|ref|>text<|/ref|><|det|>[[70, 892, 866, 907]]<|/det|> +Reviewer's Response. This additional discussion of HVR in the text is appreciated by the Reviewer and acceptable. + +<|ref|>text<|/ref|><|det|>[[70, 918, 880, 946]]<|/det|> +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 48, 223, 61]]<|/det|> +functionally irrelevant. + +<|ref|>text<|/ref|><|det|>[[72, 72, 917, 101]]<|/det|> +Authors' response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +<|ref|>text<|/ref|><|det|>[[72, 111, 918, 167]]<|/det|> +Reviewer's Response. The Reviewer appreciates this addition of n for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +<|ref|>text<|/ref|><|det|>[[72, 177, 919, 219]]<|/det|> +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with \(n = 3\) or alternatively removed. + +<|ref|>text<|/ref|><|det|>[[72, 229, 919, 284]]<|/det|> +Authors' response. Thanks for bringing this observation to our attention. Panel g from the original submission was moved to the supplementary information as supplementary figure 7 (SI, page 13) with proper reference calling in the main text (line 397- 398). An additional description was added to show the data refers to protein expression abundance (line 395). The data being presented has an \(n = 4\) for each genotype (supplementary figure 7, SI page 13). + +<|ref|>text<|/ref|><|det|>[[73, 294, 533, 309]]<|/det|> +Reviewer's Response. This change is appreciated and acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 334, 245, 348]]<|/det|> +c. Figure 5 (now figure 6) + +<|ref|>text<|/ref|><|det|>[[72, 347, 912, 412]]<|/det|> +i. For Figure 5A-B - the statement is made that "RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA", but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +<|ref|>text<|/ref|><|det|>[[72, 422, 920, 504]]<|/det|> +Authors' response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +<|ref|>text<|/ref|><|det|>[[72, 514, 911, 556]]<|/det|> +Reviewer's Response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement "retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis") as this will not be evident to the general Nature Communications readership. + +<|ref|>text<|/ref|><|det|>[[70, 566, 920, 595]]<|/det|> +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<|ref|>text<|/ref|><|det|>[[72, 605, 900, 647]]<|/det|> +Authors' response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +<|ref|>text<|/ref|><|det|>[[72, 657, 920, 699]]<|/det|> +Reviewer's Response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However, given the ineffective erythropoiesis seen in Figure 6D with increased HbGS, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +<|ref|>text<|/ref|><|det|>[[72, 709, 666, 724]]<|/det|> +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +<|ref|>text<|/ref|><|det|>[[72, 735, 832, 750]]<|/det|> +Authors' response. We have moved the gating strategy to the supplementary information (SI Figure 5, page 11). + +<|ref|>text<|/ref|><|det|>[[72, 760, 805, 775]]<|/det|> +Reviewer's Response. This is an acceptable alternative and works well as in supplementary figure section. + +<|ref|>text<|/ref|><|det|>[[72, 787, 246, 801]]<|/det|> +d. Figure 6 (now figure 7) + +<|ref|>text<|/ref|><|det|>[[72, 801, 917, 841]]<|/det|> +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +<|ref|>text<|/ref|><|det|>[[72, 853, 923, 932]]<|/det|> +Authors' response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 884, 75]]<|/det|> +Reviewer's Response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and any potential implications on therapeutic applications. + +<|ref|>text<|/ref|><|det|>[[72, 86, 468, 100]]<|/det|> +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +<|ref|>text<|/ref|><|det|>[[72, 112, 802, 127]]<|/det|> +Authors' response. Figure legends have been corrected (lines 365,369), thank you (now figures 7a and 7b) + +<|ref|>text<|/ref|><|det|>[[72, 139, 660, 153]]<|/det|> +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 165, 252, 179]]<|/det|> +e. Figure 7(Now Figure 8) + +<|ref|>text<|/ref|><|det|>[[72, 178, 768, 192]]<|/det|> +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. + +<|ref|>text<|/ref|><|det|>[[73, 203, 668, 217]]<|/det|> +Thanks for the feedback. The figure was replotted with appropriate font sizes (page 25). + +<|ref|>text<|/ref|><|det|>[[72, 229, 660, 243]]<|/det|> +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 255, 875, 269]]<|/det|> +ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. + +<|ref|>text<|/ref|><|det|>[[72, 281, 920, 372]]<|/det|> +Authors' response. We appreciate the reviewer's comment. The approach described in this manuscript, specifically in Figure 8 for editing of human mPB CD34s, is using a highly engineered inlaid base editor with NGC PAM tolerance that converts the sickle allele to a Makassar allele that was developed by Beam that was previously published (Chu et al 2021). This is different from the Newby approach which uses a NRCH- PAM tolerant guide. The functional result is the same, installation of the Makassar variant but the editor and guide sequences are different. We refer to this in the section describing the data (lines 388- 390) and we believe that these data are complimentary and orthogonal and give further confidence that the deployment of ABEs, even with slightly different features, give similar outcomes. + +<|ref|>text<|/ref|><|det|>[[73, 384, 679, 398]]<|/det|> +Reviewer's Response. These clarifications and additional text additions are appreciated. + +<|ref|>text<|/ref|><|det|>[[72, 410, 919, 463]]<|/det|> +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +<|ref|>text<|/ref|><|det|>[[72, 475, 911, 515]]<|/det|> +Authors' response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +<|ref|>text<|/ref|><|det|>[[72, 527, 920, 620]]<|/det|> +Reviewer's Response. The Reviewer appreciates this revision and clarification and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common terminology) and also contains jargon not generally accessible ("bulk d18 IVED" – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +<|ref|>text<|/ref|><|det|>[[72, 620, 920, 686]]<|/det|> +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is rather generic. + +<|ref|>text<|/ref|><|det|>[[72, 697, 911, 763]]<|/det|> +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as 2% metabisulfite, but the figure legend states that 2% oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +<|ref|>text<|/ref|><|det|>[[72, 775, 920, 828]]<|/det|> +Authors' response. We completely agree with the reviewer's comments around quantitation of sickling events in these images. Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. To that end, we have removed these figures and tempered any conclusions that were drawn from this data. + +<|ref|>text<|/ref|><|det|>[[70, 840, 914, 867]]<|/det|> +Reviewer's Response. The Reviewer appreciates the Authors' candor on this point, removal of this figure, and tempering of conclusions drawn from it. + +<|ref|>text<|/ref|><|det|>[[72, 879, 911, 946]]<|/det|> +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 750, 61]]<|/det|> +Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +<|ref|>text<|/ref|><|det|>[[72, 72, 921, 192]]<|/det|> +Authors' response. Our text in the discussion was modified to align with the current data presented. Figures 1G (now 2e, page 19) and 4C (now 5c, page 22), the reminder of Figure 4 (now 5, page 22), Figure 3 (now 4, page 21), Figure 5A (now 6a, page 23), Figure 6 (now 7, page 24) and Figure 7 (now 8, page 25) have been replotted and presented in a more accessible and concise way. In addition, our new text in the discussion acknowledges the difference between the results obtained studying the purified protein and those obtained when studying it in the context of RBCs (lines 403- 486). The impact of dehydration on a similar compound heterozygote, HbSC, and the impact of RBC dehydration mediated by HbG on the red cell has been expanded in the introduction and discussion sections (lines 81- 91 and 443- 475). Ex vivo analysis of HbG does not show sickling, even as a HbG/HbS mixture. It is only when in the confines of a dehydrated mature red cell that the HbS in a 60:40 mixture with HbG where sickling becomes possible. + +<|ref|>text<|/ref|><|det|>[[72, 203, 864, 231]]<|/det|> +Reviewer's Response. The new tempered statement in lines 434- 441 is appreciated and more reflective of the data presented, as well as the context present regarding ex vivo vs intracellular HbS/HbG mixtures in lines 443- 475. + +<|ref|>text<|/ref|><|det|>[[72, 243, 910, 284]]<|/det|> +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C (now figure 7). + +<|ref|>text<|/ref|><|det|>[[72, 294, 917, 348]]<|/det|> +Authors' response. HbSS mice had significantly heavier liver per body weight compared to HbGS mice (median 8.75 vs 6.44, \(p = 0.002\) ) while the liver weights/body weight of HbAA and HbAS were comparable with HbGG and HbGS, respectively. (now figure 7a, page 22). Although the sclerosis scores were different across the genotypes, they did not rise to the level of statistical significance. The manuscript has been modified to include this information (Lines 362- 372, 455- 459). + +<|ref|>text<|/ref|><|det|>[[72, 359, 857, 387]]<|/det|> +Reviewer's Response. The modified verbiage in lines 362- 372 and 455- 460 much more accurately reflect the data presented in the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 410, 911, 464]]<|/det|> +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by any of the data in the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 475, 910, 530]]<|/det|> +Authors' response. Thank you for your feedback. Concluding statement was modified to highlight the importance of assessing red cell function of any novel hemoglobin editing strategy (lines 477- 486). While HbGG is the most likely editing outcome, and HbGS is in most domains superior to HbSS, one must consider the imperfect quality of HbGS when contemplating the Makassar strategy for base editing in SCD. + +<|ref|>text<|/ref|><|det|>[[72, 542, 550, 556]]<|/det|> +Reviewer's Response. This new concluding paragraph is acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 568, 193, 580]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 581, 904, 621]]<|/det|> +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +<|ref|>text<|/ref|><|det|>[[72, 632, 646, 646]]<|/det|> +Authors' response. The word transformative has been removed from the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 658, 745, 672]]<|/det|> +Reviewer's Response. The Reviewers appreciate removal of this terminology from the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 684, 895, 711]]<|/det|> +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +<|ref|>text<|/ref|><|det|>[[72, 723, 646, 737]]<|/det|> +Authors' response. The abstract was edited for clarity and consistency (lines 23- 33). + +<|ref|>text<|/ref|><|det|>[[72, 749, 608, 763]]<|/det|> +Reviewer's Response. The revised abstract is much clearer and more precise. + +<|ref|>text<|/ref|><|det|>[[72, 788, 913, 841]]<|/det|> +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate - there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. These need to be cited and the language of this sentence toned down to be reflective of the literature. + +<|ref|>text<|/ref|><|det|>[[72, 853, 910, 880]]<|/det|> +Authors' response. We agree with the reviewer that these therapies have modified the clinical severity for many individuals and have altered this section accordingly and added citations (lines 40- 42). + +<|ref|>text<|/ref|><|det|>[[72, 892, 810, 906]]<|/det|> +Reviewer's Response. This new sentence and citations are accurate and reflect the current state of the field. + +<|ref|>text<|/ref|><|det|>[[72, 918, 913, 945]]<|/det|> +4. Haploidetical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 535, 62]]<|/det|> +best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +<|ref|>text<|/ref|><|det|>[[72, 73, 760, 88]]<|/det|> +Authors' response. We now discuss haploidential transplantation as an option as well (lines 44- 46). + +<|ref|>text<|/ref|><|det|>[[73, 99, 421, 114]]<|/det|> +Reviewer's Response. This addition is acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 125, 910, 167]]<|/det|> +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa-cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +<|ref|>text<|/ref|><|det|>[[72, 177, 905, 205]]<|/det|> +Authors' response. We have eliminated this comment, as it is not integral to the discussion of base editing in the context of the larger transplant field. + +<|ref|>text<|/ref|><|det|>[[72, 216, 512, 231]]<|/det|> +Reviewer's Response. Removal of this comment is appreciated. + +<|ref|>text<|/ref|><|det|>[[72, 242, 901, 283]]<|/det|> +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the βE6A mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +<|ref|>text<|/ref|><|det|>[[70, 293, 779, 309]]<|/det|> +Authors' response. Authors' response. Sentence was rewritten to remove technical jargon (lines 77- 79). + +<|ref|>text<|/ref|><|det|>[[73, 320, 421, 334]]<|/det|> +Reviewer's Response. This revision is acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 346, 921, 387]]<|/det|> +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +<|ref|>text<|/ref|><|det|>[[70, 397, 853, 413]]<|/det|> +Authors' response. This statement has been revised, and no longer comments on HbSC to HbSS relative severity. + +<|ref|>text<|/ref|><|det|>[[73, 424, 422, 439]]<|/det|> +Reviewer's Response. This change is appreciated. + +<|ref|>text<|/ref|><|det|>[[72, 450, 901, 491]]<|/det|> +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +<|ref|>text<|/ref|><|det|>[[72, 502, 901, 543]]<|/det|> +Authors' response. The main text was modified to remove this confusing statement. We would like to clarify that HbG behaves normally in vitro but appears to dehydrate the red cell in vivo. There are some aspects of the HbGG red cell or of organ function of a HbGG mouse that are not statistically different from HbAA, as outlined in the text. + +<|ref|>text<|/ref|><|det|>[[72, 554, 444, 568]]<|/det|> +Reviewer's Response. This clarification is acceptable. + +<|ref|>text<|/ref|><|det|>[[72, 580, 900, 634]]<|/det|> +9. Townes mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +<|ref|>text<|/ref|><|det|>[[72, 645, 920, 686]]<|/det|> +Authors' response. The genotype of the Townes mice, its stock number, as well as a description of the model is now present in the methods section (lines 108- 109) as well as in a new figure 1 (page 19). The new figure shows the humanized beta globin locus present in the Townes mice RBC. + +<|ref|>text<|/ref|><|det|>[[72, 697, 861, 725]]<|/det|> +Reviewer's Response. The addition of this new Figure 1 is greatly appreciated by the Reviewer and provides a key foundation for the studies done in the remainder of the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 736, 556, 751]]<|/det|> +10. "Zombie dye" is not standard terminology and needs to be clarified. + +<|ref|>text<|/ref|><|det|>[[70, 762, 850, 777]]<|/det|> +Authors' response. "Zombie dye" was replaced with the commercial name utilized by Life Technologies (line 182). + +<|ref|>text<|/ref|><|det|>[[72, 788, 451, 802]]<|/det|> +Reviewer's Response. This clarification is appreciated. + +<|ref|>text<|/ref|><|det|>[[72, 814, 916, 855]]<|/det|> +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +<|ref|>text<|/ref|><|det|>[[70, 866, 910, 894]]<|/det|> +Authors' response. Relevance of the p50 values, Hill coefficients and polymerization data of purified HbG in relationship to hemoglobin function and benefit to SCD is now expanded in the discussion section (lines 427- 441). + +<|ref|>text<|/ref|><|det|>[[72, 905, 704, 920]]<|/det|> +Reviewer's Response. This clarification and addition of text to the discussion is appreciated. + +<|ref|>text<|/ref|><|det|>[[70, 931, 886, 947]]<|/det|> +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 252, 61]]<|/det|> +(particularly in Figure 1G). + +<|ref|>text<|/ref|><|det|>[[72, 72, 875, 88]]<|/det|> +Authors' response. Figure 1 (now figure 2, page 19) was replotted to make it more accessible to the general audience. + +<|ref|>text<|/ref|><|det|>[[73, 99, 914, 153]]<|/det|> +Reviewer's Response. Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[73, 164, 515, 179]]<|/det|> +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +<|ref|>text<|/ref|><|det|>[[73, 190, 576, 204]]<|/det|> +Authors' response. Figure calling has been corrected in the text (line 283) + +<|ref|>text<|/ref|><|det|>[[73, 216, 440, 230]]<|/det|> +Reviewer's Response. This correction is appreciated. + +<|ref|>text<|/ref|><|det|>[[73, 242, 163, 256]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 269, 238, 282]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 282, 864, 321]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 333, 163, 347]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 359, 238, 372]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 372, 866, 399]]<|/det|> +The manuscript was improved in terms of clarity, however some important comments have not been addressed: + +<|ref|>text<|/ref|><|det|>[[72, 399, 920, 476]]<|/det|> +1. The title should be tempered since data do not support a proper restoration of Hb function and its use in sickle cell disease compared to other developed approaches reactivating HbF +2. G and S can be distinguished via HPLC as shown by Newby et al Nature 2021. However, for proper technical comparison of globin expression, beta globin abundance should be evaluated as well in the AS genotype. Ratio of the different beta globins over alpha globin expression would also be informative. Alternatively, to precisely answer this point the authors could insert the silent mutation in HD HSPCs and compare beta-globin expression at mRNA and protein level in the erythroid progeny. + +<|ref|>text<|/ref|><|det|>[[72, 475, 916, 542]]<|/det|> +3. It would be relevant to reproduce the comparison of solubility with proteins purified in the frame of this study (HbA, HbG, HbS and maybe HbC) and discuss it as an altered property of HbG that could further explain the alteration of HbG-containing RBCs. Furthermore, the comment regarding the increased turbidity observed in 2.2M phosphate buffer with HbG purified in this study has not been addressed. This point should be discussed in the manuscript since it was described as a specific feature of HbG (Pagnier et al 1993). + +<|ref|>text<|/ref|><|det|>[[72, 541, 920, 620]]<|/det|> +4. Hb tetramers fiber lateral contacts between beta2 Val/Ala6 and beta1 Phe85 and Leu88, if solved, should be discussed. +5. RBC dehydration is probably not the root of the HbGS/HbGG associated phenotypes but is likely a consequence of an Hb characterized by altered physicochemical properties. The statement that in vitro characteristics of HbG are normal is not correct since it has been shown to be altered in previous studies using recombinant proteins (turbidity in 2.2M phosphate buffer, altered solubility), validation of these observations in the protein purified in this study and discussion on these altered properties would give a better overview of the description of the Hb variant of interest. + +<|ref|>text<|/ref|><|det|>[[72, 619, 840, 633]]<|/det|> +6. Reference to the CRISPR Journal 2021 paper should be added line 204-205 when mentioning the IBE12.2. + +<|ref|>text<|/ref|><|det|>[[72, 632, 900, 658]]<|/det|> +7. While Sup Table 5 indicates that statistical analyses have been performed in Figure 7c, it is not clear which conditions have been compared (as well as in other figures) + +<|ref|>text<|/ref|><|det|>[[72, 658, 923, 684]]<|/det|> +8. It would be interesting to comment on the osmotic fragility test that results positive in the homozygous HbG patient, could it be linked to the high % of dense cells? + +<|ref|>text<|/ref|><|det|>[[72, 696, 866, 737]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 801, 163, 815]]<|/det|> +Reviewer #5 + +<|ref|>text<|/ref|><|det|>[[73, 827, 238, 840]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 840, 864, 879]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 891, 144, 904]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 917, 219, 930]]<|/det|> +Reviewer comments: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 163, 60]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 73, 812, 101]]<|/det|> +(Remarks to the Author) The Authors have responded well to the critiques and concerns, and have incorporated suggested changes. + +<|ref|>text<|/ref|><|det|>[[70, 111, 904, 140]]<|/det|> +Only two suggestions remain, and pertain to the SDS- Page gel with aberrant size marker, and the proper y- axis for Figure 5A. + +<|ref|>text<|/ref|><|det|>[[73, 190, 163, 204]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 217, 863, 270]]<|/det|> +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 281, 163, 295]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 307, 690, 360]]<|/det|> +(Remarks to the Author) We thank the authors for answering our questions We have a last comment to address: Supplementary Figure 7c should include AA and AS data for proper technical comparison. + +<|ref|>text<|/ref|><|det|>[[73, 372, 163, 385]]<|/det|> +Reviewer #5 + +<|ref|>text<|/ref|><|det|>[[73, 398, 864, 451]]<|/det|> +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 790, 916, 844]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 844, 916, 910]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[73, 909, 618, 923]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 523, 107]]<|/det|> +## Point by Point Response to reviewer comments + +<|ref|>text<|/ref|><|det|>[[117, 122, 370, 138]]<|/det|> +Authors comments are in italics. + +<|ref|>sub_title<|/ref|><|det|>[[116, 168, 323, 186]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 201, 418, 217]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 232, 864, 314]]<|/det|> +In this study "Installation of HbG- Makassar by base editing restores hemoglobin function: a transformative therapy for sickle cell disease" the authors describe their work to characterize mice that have been genetically modified to harbor the Makassar variant of adult beta globin, which can be efficiently introduced using adenine base editing in cells harboring the sickle cell disease genetic variant. + +<|ref|>text<|/ref|><|det|>[[115, 329, 876, 442]]<|/det|> +This Makassar variant is extremely rare in the natural human population, so this study is extremely valuable to characterize what the potential outcomes would be in erythroid cells differentiated from homozygous or heterozygous edited HSCs. The authors make many important findings, including the similarity in phenotype between mice with an AA genotype and GG genotype, and interesting differences between GS and AS phenotypes. In particular, the white blood cell and reticulocyte counts of GS mice are similar to SS mice. The structure of Makassar globin is described here for the first time to my knowledge. + +<|ref|>text<|/ref|><|det|>[[115, 456, 876, 506]]<|/det|> +The methodology of this manuscript appears sound and it is well- written and illustrated. I am enthusiastic about this study recommend acceptance of this manuscript pending three relatively small comments. + +<|ref|>text<|/ref|><|det|>[[115, 520, 867, 633]]<|/det|> +1. The structure of the original and modified beta globin locus in the newly established mouse haplotype is not shown or described in detail. I believe that this mouse also includes human gamma globin genes, but these are not expressed at high levels. Since fetal hemoglobin is a particularly strong modifier of the described phenotypes, it would be helpful to show a quantification of fetal hemoglobin in each mouse genotype to ensure that fetal hemoglobin expression was not modified in the new established Makassar haplotype and did not confound any of these results. + +<|ref|>text<|/ref|><|det|>[[115, 648, 872, 717]]<|/det|> +We appreciate the reviewer's comments. We have added Figure 1 (page 18), which details the changes made to the beta globin locus in the Townes mice model. UPLC analysis of the Townes mice HbGG and HbSG RBCs did not detect HbF (data included in the Supplementary Fig 7, page 13). + +<|ref|>text<|/ref|><|det|>[[115, 733, 880, 820]]<|/det|> +2. The paragraph on dense red blood cells is particularly sparse with only one mouse genotype detailed and minimal reference to what is normal and what dysfunction may indicate. Hematocrit and density appear to be the main parameters where AA differs from GG, so discussing this in more detail is warranted. Furthermore, the reference appears incorrect since the panel that describes density is Fig 4H, not Fig 4E. + +<|ref|>text<|/ref|><|det|>[[116, 836, 856, 886]]<|/det|> +We have expanded this topic in the manuscript, in the introduction (lines81- 89), in the results (lines 333- 339), in the methods section (lines 166- 171) and in the discussion (lines 448- 449, 461- 471). Figures have been renumbered and the references to panels corrected (line 348). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 852, 154]]<|/det|> +3. The axis text in Figure 7 relating to the genome editing experiment is too small to readily interpret. The methods section is also lacking in detail about exactly which editor variant and sgRNA was used in this experiment. It references a different journal for the electroporation conditions - it would be better to state the methods explicitly here. + +<|ref|>text<|/ref|><|det|>[[116, 169, 880, 250]]<|/det|> +Figure 7 (now figure 8, page 25) has been revised for clarity and legibility. We have included in the revised manuscript (lines 204- 205) the identity of the inlaid base editor which was used from the CRISPR Journal 2021 paper (IBE12.2). Additionally, we have included additional experimental details (lines 215- 216) which were left off the initial submission due to length restrictions. Further details can be found in the supplementary methods section. + +<|ref|>text<|/ref|><|det|>[[116, 280, 419, 297]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 312, 880, 504]]<|/det|> +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBs) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +<|ref|>text<|/ref|><|det|>[[116, 520, 255, 536]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[116, 536, 880, 633]]<|/det|> +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta \in \mathrm{6A}\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +<|ref|>text<|/ref|><|det|>[[116, 648, 881, 728]]<|/det|> +Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadrupulicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected \(p50\) range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +<|ref|>text<|/ref|><|det|>[[116, 744, 861, 792]]<|/det|> +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +<|ref|>text<|/ref|><|det|>[[116, 807, 870, 904]]<|/det|> +Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}\mathrm{C}\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 872, 171]]<|/det|> +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +<|ref|>text<|/ref|><|det|>[[115, 185, 875, 283]]<|/det|> +Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +<|ref|>text<|/ref|><|det|>[[115, 296, 879, 395]]<|/det|> +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +<|ref|>text<|/ref|><|det|>[[115, 408, 872, 538]]<|/det|> +Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures ( \(p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +<|ref|>text<|/ref|><|det|>[[115, 552, 875, 617]]<|/det|> +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +<|ref|>text<|/ref|><|det|>[[115, 632, 879, 745]]<|/det|> +The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +<|ref|>text<|/ref|><|det|>[[115, 775, 835, 825]]<|/det|> +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +<|ref|>text<|/ref|><|det|>[[115, 839, 614, 874]]<|/det|> +a. Figure 3 (now figure 4) +i. Are pairwise comparisons being made between all samples? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 875, 202]]<|/det|> +Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann - Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (SI, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +<|ref|>text<|/ref|><|det|>[[115, 216, 861, 250]]<|/det|> +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +<|ref|>text<|/ref|><|det|>[[115, 265, 874, 362]]<|/det|> +Statistics were performed and shown for the pairwise comparisons where their difference appeared to be significant. P values were reported in the main text. Samples whose statistics are not shown are because their difference was not significant. In both cases significance and lack of significance was addressed in the main text in the original submission. To make this observation more accessible to the general reader, P value descriptors have been added to the figure legend and the statistical analysis method section was expanded as well (lines 193- 202). + +<|ref|>text<|/ref|><|det|>[[115, 376, 700, 394]]<|/det|> +iii. Why is the order of genotypes/color scheme different between panels? + +<|ref|>text<|/ref|><|det|>[[115, 408, 815, 441]]<|/det|> +Color in figure 3 (now figure 4, page 21) panels and in all of the other figures have been standardized to match color and genotype across panels. + +<|ref|>text<|/ref|><|det|>[[115, 456, 605, 473]]<|/det|> +iv. Why is \(n\) so dramatically different between panels/assays? + +<|ref|>text<|/ref|><|det|>[[116, 488, 861, 553]]<|/det|> +Thanks for pointing out this observation. The number of mice from each genotype varies from assay to assay primarily due to blood volume limitations of the mouse model. We have summarized the number of mice used in each analysis in the supplementary information, supplementary table 5 (SI, page 6). + +<|ref|>text<|/ref|><|det|>[[115, 567, 878, 633]]<|/det|> +v. In particular, Figure 3C is confusing in that the absolute reticulocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +<|ref|>text<|/ref|><|det|>[[115, 648, 865, 745]]<|/det|> +Thank you for your observation. Additional mice were analyzed, and Figure 3 (now Figure 4, page 21) is updated. Reticulocyte count requires very large blood volumes, so it was only possible to measure it in those mice where the blood drawn met the assay volume requirements. Supplementary Table 5 (SI, page 6) contains all the sample sizes and comparisons performed in the manuscript. We have now assured that a minimum of \(n = 3\) mice from each genotype were used in every test. + +<|ref|>text<|/ref|><|det|>[[115, 760, 876, 840]]<|/det|> +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<|ref|>text<|/ref|><|det|>[[116, 855, 868, 904]]<|/det|> +Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 187]]<|/det|> +HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +<|ref|>text<|/ref|><|det|>[[115, 201, 882, 281]]<|/det|> +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +<|ref|>text<|/ref|><|det|>[[115, 296, 879, 394]]<|/det|> +One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +<|ref|>text<|/ref|><|det|>[[115, 409, 317, 425]]<|/det|> +b. Figure 4 (now figure 5) + +<|ref|>text<|/ref|><|det|>[[115, 425, 881, 473]]<|/det|> +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +<|ref|>text<|/ref|><|det|>[[115, 488, 880, 537]]<|/det|> +Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a \(p\) - value of \(< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 552, 870, 666]]<|/det|> +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(pO2 > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15 \text{mmHg}\) (overlapping with HbSS samples) and half less than \(15 \text{mmHg}\) . The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +<|ref|>text<|/ref|><|det|>[[115, 680, 877, 792]]<|/det|> +Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 808, 866, 856]]<|/det|> +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +<|ref|>text<|/ref|><|det|>[[115, 871, 785, 889]]<|/det|> +The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 874, 123]]<|/det|> +iv. The relevance of Hematocrit-Viscosity Ratio (HVR) is not explained in any way for Figure 4D (now figure 5e). + +<|ref|>text<|/ref|><|det|>[[115, 136, 868, 170]]<|/det|> +An additional discussion of viscosity and HVR has been added to the text (lines 166- 171, 337- 340). + +<|ref|>text<|/ref|><|det|>[[115, 185, 879, 234]]<|/det|> +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +<|ref|>text<|/ref|><|det|>[[115, 249, 870, 282]]<|/det|> +Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +<|ref|>text<|/ref|><|det|>[[115, 296, 880, 361]]<|/det|> +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with n=3 or alternatively removed. + +<|ref|>text<|/ref|><|det|>[[115, 376, 870, 458]]<|/det|> +Thanks for bringing this observation to our attention. Panel g from the original submission was moved to the supplementary information as supplementary figure 7 (Sl, page 13) with proper reference calling in the main text (line 397- 398). An additional description was added to show the data refers to protein expression abundance (line 395). The data being presented has an n =4 for each genotype (supplementary figure 7, Sl page 13). + +<|ref|>text<|/ref|><|det|>[[115, 490, 317, 505]]<|/det|> +c. Figure 5 (now figure 6) + +<|ref|>text<|/ref|><|det|>[[115, 505, 870, 601]]<|/det|> +i. For Figure 5A-B – the statement is made that "RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA", but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +<|ref|>text<|/ref|><|det|>[[115, 615, 875, 744]]<|/det|> +Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +<|ref|>text<|/ref|><|det|>[[115, 760, 872, 809]]<|/det|> +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<|ref|>text<|/ref|><|det|>[[115, 823, 852, 872]]<|/det|> +We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +<|ref|>text<|/ref|><|det|>[[112, 887, 806, 904]]<|/det|> +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 850, 123]]<|/det|> +We have moved the gating strategy to the supplementary information (SI Figure 5, page 11). + +<|ref|>text<|/ref|><|det|>[[115, 137, 318, 154]]<|/det|> +d. Figure 6 (now figure 7) + +<|ref|>text<|/ref|><|det|>[[115, 154, 870, 218]]<|/det|> +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +<|ref|>text<|/ref|><|det|>[[115, 232, 877, 346]]<|/det|> +We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +<|ref|>text<|/ref|><|det|>[[115, 360, 575, 378]]<|/det|> +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +<|ref|>text<|/ref|><|det|>[[115, 392, 812, 410]]<|/det|> +Figure legends have been corrected (lines 365,369), thank you (now figures 7a and 7b) + +<|ref|>text<|/ref|><|det|>[[115, 424, 322, 440]]<|/det|> +e. Figure 7(Now Figure 8) + +<|ref|>text<|/ref|><|det|>[[115, 440, 848, 472]]<|/det|> +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. + +<|ref|>text<|/ref|><|det|>[[115, 487, 812, 505]]<|/det|> +Thanks for the feedback. The figure was replotted with appropriate font sizes (page 25). + +<|ref|>text<|/ref|><|det|>[[115, 519, 840, 552]]<|/det|> +ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. + +<|ref|>text<|/ref|><|det|>[[115, 566, 882, 712]]<|/det|> +We appreciate the reviewer's comment. The approach described in this manuscript, specifically in Figure 8 for editing of human mpB CD34s, is using a highly engineered inlaid base editor with NGC PAM tolerance that converts the sickle allele to a Makassar allele that was developed by Beam that was previously published (Chu et al 2021). This is different from the Newby approach which uses a NRCH- PAM tolerant guide. The functional result is the same, installation of the Makassar variant but the editor and guide sequences are different. We refer to this in the section describing the data (lines 388- 390) and we believe that these data are complimentary and orthogonal and give further confidence that the deployment of ABEs, even with slightly different features, give similar outcomes. + +<|ref|>text<|/ref|><|det|>[[115, 726, 876, 807]]<|/det|> +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +<|ref|>text<|/ref|><|det|>[[115, 822, 881, 888]]<|/det|> +The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 105, 875, 219]]<|/det|> +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as \(2\%\) metabisulfite, but the figure legend states that \(2\%\) oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +<|ref|>text<|/ref|><|det|>[[115, 232, 870, 313]]<|/det|> +We completely agree with the reviewer's comments around quantitation of sickling events in these images. Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. To that end, we have removed these figures and tempered any conclusions that were drawn from this data. + +<|ref|>text<|/ref|><|det|>[[115, 328, 874, 457]]<|/det|> +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +<|ref|>text<|/ref|><|det|>[[115, 471, 877, 650]]<|/det|> +Our text in the discussion was modified to align with the current data presented. Figures 1G (now 2e, page 19) and 4C (now 5c, page 22), the reminder of Figure 4 (now 5, page 22), Figure 3 (now 4, page 21), Figure 5A (now 6a, page 23), Figure 6 (now 7, page 24) and Figure 7 (now 8, page 25) have been replotted and presented in a more accessible and concise way. In addition, our new text in the discussion acknowledges the difference between the results obtained studying the purified protein and those obtained when studying it in the context of RBCs (lines 403- 486). The impact of dehydration on a similar compound heterozygote, HbSC, and the impact of RBC dehydration mediated by HbG on the red cell has been expanded in the introduction and discussion sections (lines 81- 91 and 443- 475). Ex vivo analysis of HbG does not show sickling, even as a HbG/HbS mixture. It is only when in the confines of a dehydrated mature red cell that the HbS in a 60:40 mixture with HbG where sickling becomes possible. + +<|ref|>text<|/ref|><|det|>[[116, 664, 870, 714]]<|/det|> +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C (now figure 7). + +<|ref|>text<|/ref|><|det|>[[116, 728, 879, 809]]<|/det|> +HbSS mice had significantly heavier liver per body weight compared to HbGS mice (median 8.75 vs 6.44, \(p = 0.002\) ) while the liver weights/body weight of HbAA and HbAS were comparable with HbGG and HbGS, respectively. (now figure 7a, page 22). Although the sclerosis scores were different across the genotypes, they did not rise to the level of statistical significance. The manuscript has been modified to include this information (Lines 362- 372, 455- 459). + +<|ref|>text<|/ref|><|det|>[[115, 840, 879, 905]]<|/det|> +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 381, 106]]<|/det|> +any of the data in the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 121, 877, 202]]<|/det|> +Thank you for your feedback. Concluding statement was modified to highlight the importance of assessing red cell function of any novel hemoglobin editing strategy (lines 477- 486). While HbGG is the most likely editing outcome, and HbGS is in most domains superior to HbSS, one must consider the imperfect quality of HbGS when contemplating the Makassar strategy for base editing in SCD. + +<|ref|>text<|/ref|><|det|>[[116, 218, 254, 233]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[116, 234, 847, 298]]<|/det|> +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +<|ref|>text<|/ref|><|det|>[[118, 312, 632, 329]]<|/det|> +The word transformative has been removed from the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 344, 870, 378]]<|/det|> +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +<|ref|>text<|/ref|><|det|>[[118, 392, 629, 409]]<|/det|> +The abstract was edited for clarity and consistency (lines 23- 33). + +<|ref|>text<|/ref|><|det|>[[115, 440, 875, 521]]<|/det|> +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate - there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. These need to be cited and the language of this sentence toned down to be reflective of the literature. + +<|ref|>text<|/ref|><|det|>[[116, 536, 848, 569]]<|/det|> +We agree with the reviewer that these therapies have modified the clinical severity for many individuals and have altered this section accordingly and added citations (lines 40- 42). + +<|ref|>text<|/ref|><|det|>[[115, 584, 877, 649]]<|/det|> +4. Haploidentical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +<|ref|>text<|/ref|><|det|>[[116, 663, 757, 681]]<|/det|> +We now discuss haploidentical transplantation as an option as well (lines 44- 46). + +<|ref|>text<|/ref|><|det|>[[115, 696, 870, 761]]<|/det|> +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa-cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +<|ref|>text<|/ref|><|det|>[[116, 775, 855, 809]]<|/det|> +We have eliminated this comment, as it is not integral to the discussion of base editing in the context of the larger transplant field. + +<|ref|>text<|/ref|><|det|>[[115, 823, 866, 888]]<|/det|> +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the \(\beta \in 6A\) mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 629, 107]]<|/det|> +Sentence was rewritten to remove technical jargon (lines 77- 79). + +<|ref|>text<|/ref|><|det|>[[116, 121, 868, 170]]<|/det|> +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +<|ref|>text<|/ref|><|det|>[[116, 184, 868, 201]]<|/det|> +This statement has been revised, and no longer comments on HbSC to HbSS relative severity. + +<|ref|>text<|/ref|><|det|>[[116, 216, 846, 281]]<|/det|> +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +<|ref|>text<|/ref|><|det|>[[116, 295, 852, 361]]<|/det|> +The main text was modified to remove this confusing statement. We would like to clarify that HbG behaves normally in vitro but appears to dehydrate the red cell in vivo. There are some aspects of the HbGG red cell or of organ function of a HbGG mouse that are not statistically different from HbAA, as outlined in the text. + +<|ref|>text<|/ref|><|det|>[[115, 375, 881, 457]]<|/det|> +9. Townes mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +<|ref|>text<|/ref|><|det|>[[116, 472, 872, 521]]<|/det|> +The genotype of the Townes mice, its stock number, as well as a description of the model is now present in the methods section (lines 108- 109) as well as in a new figure 1 (page 19). The new figure shows the humanized beta globin locus present in the Townes mice RBC. + +<|ref|>text<|/ref|><|det|>[[116, 535, 678, 552]]<|/det|> +10. "Zombie dye" is not standard terminology and needs to be clarified. + +<|ref|>text<|/ref|><|det|>[[116, 567, 863, 584]]<|/det|> +"Zombie dye" was replaced with the commercial name utilized by Life Technologies (line 182). + +<|ref|>text<|/ref|><|det|>[[116, 599, 881, 648]]<|/det|> +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +<|ref|>text<|/ref|><|det|>[[116, 662, 832, 711]]<|/det|> +Relevance of the p50 values, Hill coefficients and polymerization data of purified HbG in relationship to hemoglobin function and benefit to SCD is now expanded in the discussion section (lines 427- 441). + +<|ref|>text<|/ref|><|det|>[[112, 726, 870, 760]]<|/det|> +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +<|ref|>text<|/ref|><|det|>[[116, 774, 816, 807]]<|/det|> +Figure 1 (now figure 2, page 19) was replotted to make it more accessible to the general audience. + +<|ref|>text<|/ref|><|det|>[[116, 822, 629, 840]]<|/det|> +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +<|ref|>text<|/ref|><|det|>[[116, 854, 548, 872]]<|/det|> +Figure calling has been corrected in the text (line 283) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 89, 419, 105]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 121, 866, 170]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[116, 201, 419, 217]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 232, 871, 346]]<|/det|> +Generating the Makassar hemoglobin variant is a promising therapeutic strategy to correct the sickle cell disease- causing mutation. In this work, Kostamo and colleagues generated a mouse model harboring the Makassar mutation and evaluated in vitro properties of the Makassar hemoglobin as well as hematological and organ parameters in vivo. Furthermore, they evaluated the effect of mono and bi- allelic editing in clonal culture of control and edited erythroid cells from patients with sickle cell disease. Although interesting, we have some important remarks. + +<|ref|>text<|/ref|><|det|>[[116, 361, 850, 425]]<|/det|> +- The Authors should mitigate the conclusions of the study (in the title, abstract, intro and discussion) as mono allelic editing will likely not lead to a major clinical benefit and mouse models are not always predictive of the results observed in patients. Furthermore, this study demonstrates that HbG-Makassar does not behave like HbA. + +<|ref|>text<|/ref|><|det|>[[116, 440, 867, 505]]<|/det|> +Thanks for your feedback. The manuscript has been revised to make sure conclusions align with the reported data. We discuss the biochemical characterization of HbG and present it in light with our findings pertaining to the differences observed in HbG when present in an HbGG and HbGS mature RBC environment. + +<|ref|>text<|/ref|><|det|>[[116, 520, 867, 553]]<|/det|> +- Introduction: some references regarding the other ABE-approaches developed to induce HbF are missing: Ravi et al 2022, Han et al 2023, Antoniou et al 2022, ... + +<|ref|>text<|/ref|><|det|>[[116, 568, 870, 649]]<|/det|> +The manuscript was not intended to be an exhausted review of ABE based approaches for inducing HbF; we had previously included Mayaurnanthan et al (2023) that captures several different HBG1/2 promoter sites using ABEs and additionally argues the potency and durability of ABE-based editing over other nuclease based strategies. We would be happy to add additional references but were at the 70 citation limit as per Nature Comms guidance. + +<|ref|>text<|/ref|><|det|>[[116, 664, 877, 729]]<|/det|> +- The Authors generate the Makassar mutation together with a silent mutation. It would be interesting to evaluate if this silent mutation affects beta-globin expression at transcriptional or translational level. To this aim, the Authors could compare HPLC profiles in AS and GS mice (to complete Figure 4G if this panel is showing HPLC data, the Authors should specify it) + +<|ref|>text<|/ref|><|det|>[[116, 744, 860, 792]]<|/det|> +G and S cannot be distinguished via HPLC; supplemental information shows a 60:40 ratio of G:S; in the Townes mouse, HbA: HbS is 60:40 (Wang et al, Journal of Gene Medicine, 2023) suggesting that the silent mutation does not impair transcription or translation. + +<|ref|>text<|/ref|><|det|>[[115, 807, 876, 903]]<|/det|> +- Figure 1: Previous polymerization studies using recombinant Hb (Pagnier et al 1993) have demonstrated that HbG-Makassar solutions show a sudden increase in turbidity in 2.2M phosphate buffer following temperature increase while HbG-Makassar behaves similarly to HbA in a 1.8M phosphate buffer solution. It would have been interesting to consider reproducing these data (by including the 2.2M condition) to better understand the biochemical properties of HbG variant. Moreover, since these results (Pagnier et al 1993) using recombinant Hb + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 847, 123]]<|/det|> +suggested that HbG has a lower solubility as compared to HbA, experiments evaluating this parameter would have been of interest. + +<|ref|>text<|/ref|><|det|>[[115, 136, 884, 234]]<|/det|> +Thanks for providing this suggestion. The effect of \(\beta 6\) amino acid hydrophobicity on the solubility of hemoglobins was assessed in Adachi et.al., 1993 (J. Biol. Chem. 1993 268:29 21650- 21656). Using recombinant material and substituting the \(\beta 6E\) for \(A\) , \(I\) , \(L\) , \(V\) , \(W\) , \(Q\) , their work along with others showed that hemoglobin solubility increased in the order of \(I < L < V < W < Q < A < E\) in high phosphate buffers. At 2.1 M phosphate HbG had a solubility of greater than 150 mg/dL while HbA was 350 mg/dL. + +<|ref|>text<|/ref|><|det|>[[115, 248, 833, 282]]<|/det|> +- Figure 2: the Authors should also compare the crystal structure of HbS, superimpose the structures of the different hemoglobins and analyze the lateral contacts + +<|ref|>text<|/ref|><|det|>[[115, 295, 881, 394]]<|/det|> +Thanks for the feedback. A new figure comparing the HbG structure with that to HbS was added in the Supplementary Information (SI figure 4, page 10). We analyzed the lateral contacts between at the \(\alpha\) and \(\beta\) interface as well as the \(\alpha \beta\) dimer interface, but no apparent changes were observed. This could be explained by the high RMSD found between HbG and HbA/HbS. To have a streamlined story we decided not to include lateral contact information in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 407, 872, 506]]<|/det|> +- Overall, since some hematological parameters were found to be affected in GG and SG mice models (clearly demonstrating that HbG does not behave like HbA) further functional characterization of the purified proteins should be performed to provide potential explanations for these observations (inflammation in GS not in GA, lower deformability of GG vs AA, sickling of GS RBCs vs no sickling of AS RBCs; ...). In other words, are there any experiments that could be performed to reconciliate in vitro and in vivo data? + +<|ref|>text<|/ref|><|det|>[[115, 520, 879, 666]]<|/det|> +Thanks for your feedback. Based on our current body of work we believe the reason for the apparent discrepancy is possibly due the effect HbG has in red blood cell dehydration. This phenomenon could only be identified when studying HbG in the context of an RBC environment and not in isolation as is the case with purified protein. Our text has been modified to make this conclusion more accessible to the general reader. We consider the in vivo and ex vivo differences to be explained by red cell dehydration, analogous to "The paradox of HbSC", in which a compound heterozygous state containing a non-sickling Hb and HbS results in a disease state rather than a carrier state due to activation of the Gardos channel (Nagel et al, Blood Reviews 2003). + +<|ref|>text<|/ref|><|det|>[[115, 679, 881, 744]]<|/det|> +- Figure 1: Since it is known that blood of patients with SCD exhibits decreased affinity for oxygen, although the oxygen affinity of HbS is the same as that of HbA (Figure 1), oxygen binding studies could also be performed in whole blood of transgenic mice since HbG containing RBCs seem to be affected. + +<|ref|>text<|/ref|><|det|>[[115, 758, 877, 809]]<|/det|> +Previous work has shown that the discrepancy in oxygen binding affinity between HbS and HbA within an RBC is not an intrinsic protein property but instead is due to different levels of 2,3- DPG among these cells (J Clin Invest. 1970 Apr; 49(4): 806- 812). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 877, 122]]<|/det|> +- Figure 4H: The observed increase in DRBC in GG and GS condition is not further commented: could it have any clinical impact? + +<|ref|>text<|/ref|><|det|>[[116, 136, 883, 186]]<|/det|> +We have significantly expanded this discussion (lines 444- 471), as we consider this to have significant impact on the red cell quality, which correlates with risk of SCD complications in other human studies. + +<|ref|>text<|/ref|><|det|>[[115, 201, 880, 281]]<|/det|> +- It is not clear which conditions have been tested for Pair comparisons across histograms of Figures 3-6. All the conditions should be compared to draw proper conclusions. For example, for the liver weight (Figure 6A), only SS mice seem to be different from the others. In Figure 6B, spleen size looks much bigger (and not "comparable" as mentioned in the text) in SS than in GS mice + +<|ref|>text<|/ref|><|det|>[[116, 296, 865, 362]]<|/det|> +Additional details are now included in the methods section on how pairwise comparisons were made (lines 193- 202). In addition, p values for all statistically significant comparisons are now included in the figure legends. The supplementary information contains a table describing the statistical test performed on each comparison (Supplementary table 5, SI, page 6). + +<|ref|>text<|/ref|><|det|>[[116, 392, 616, 409]]<|/det|> +- Figure 6B: the % of Ter119 should be evaluated in the spleen + +<|ref|>text<|/ref|><|det|>[[116, 424, 844, 473]]<|/det|> +Our intent is to assess for ineffective erythropoiesis, which we have done indirectly through spleen weights, and directly through assessment of erythroid precursors in the mouse bone marrow. + +<|ref|>text<|/ref|><|det|>[[116, 490, 194, 504]]<|/det|> +- Figure 7 + +<|ref|>text<|/ref|><|det|>[[116, 504, 881, 553]]<|/det|> +A: It is not clear which engineered ABE has been used. The editing efficiency looks higher to the one reported in Chu et al 2021, it should be explicit whether it is the same strategy or if a new editing strategy has been developed + +<|ref|>text<|/ref|><|det|>[[115, 567, 881, 682]]<|/det|> +We have included in the revised manuscript the identity of the inlaid base editor which was used from the CRISPR Journal 2021 paper (IBE12.2) (line 204). While the editing reagents were identical, the editing conditions (e.g concentration of editor and guide) were slightly different than those in the previous paper to achieve saturating editing conditions in these HbSS CD34s. We have included additional experimental details (lines 215- 216) which were left off the initial submission due to length restrictions to reflect this in the methods section along with further experimental details in the supplemental methods section + +<|ref|>text<|/ref|><|det|>[[116, 697, 255, 712]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 712, 840, 729]]<|/det|> +- Some references to the Figures are missing in the text or misplaced (Figure 1G, Figure 4) + +<|ref|>text<|/ref|><|det|>[[116, 744, 595, 761]]<|/det|> +Text was revised and missing figure references were added. + +<|ref|>text<|/ref|><|det|>[[115, 775, 848, 809]]<|/det|> +- Some Figures are not commented (Figure 4D, 4G...) or commented later. All the panels of Figure 4 should be discussed (and in the right order) + +<|ref|>text<|/ref|><|det|>[[115, 823, 720, 840]]<|/det|> +All panels in figures are now being referenced in the text in sequential order + +<|ref|>text<|/ref|><|det|>[[115, 855, 825, 872]]<|/det|> +- Some Legends are missing (colors of Figure 5C) or incorrect (Figure 6A-B mismatched) + +<|ref|>text<|/ref|><|det|>[[115, 887, 828, 904]]<|/det|> +Legends have been added that were missing and all the figures are now properly labeled. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 839, 138]]<|/det|> +- Figure 1G is not clear. It is mentioned in the Mat&Met that 5 different % of AS and GS Hb mixtures were tested. Which ones are depicted here? + +<|ref|>text<|/ref|><|det|>[[115, 153, 833, 187]]<|/det|> +Figure 1G (now 2e, page 19) was replotted to make it more accessible to the reader. HbS percentages used are now labeled in the figure. + +<|ref|>text<|/ref|><|det|>[[115, 201, 755, 219]]<|/det|> +- Some Main Figures are blurry or difficult to read (Figure 1, Figure 5D, Figure 7) + +<|ref|>text<|/ref|><|det|>[[117, 233, 399, 250]]<|/det|> +Figures are now at high resolutions + +<|ref|>text<|/ref|><|det|>[[115, 265, 879, 282]]<|/det|> +- Figure 3: colors are confusing since they are not consistently associated to the same genotype + +<|ref|>text<|/ref|><|det|>[[115, 296, 880, 330]]<|/det|> +Figures containing panels depicting various genotypes have been standardized to use the same color for genotypes across panels. + +<|ref|>text<|/ref|><|det|>[[115, 344, 866, 409]]<|/det|> +- Figure 5A: the difference mitochondrial retention % between AS and GS is still present in the graph, were the data normalized for retic count or not? The Authors should better explain how (and if) they perform normalization and show the proportion of reticulocytes in the different mouse groups + +<|ref|>text<|/ref|><|det|>[[115, 423, 879, 473]]<|/det|> +Thank you for the comment. While the text commented on normalization, the data shown was in fact not normalized. We have corrected the text (lines 350- 352); the data in Figure 6a (page 23) shows % of cells with mitochondrial retention for each genotype. + +<|ref|>text<|/ref|><|det|>[[115, 488, 875, 521]]<|/det|> +- Figure 5C: the assumption that HbGG and HbAA show a similar distribution of erythroid states should be confirmed by performing statistical analysis. + +<|ref|>text<|/ref|><|det|>[[115, 536, 865, 569]]<|/det|> +We understand that the reviewer is asking about erythroid precursor levels; this figure and the analysis have been revised to improve clarity; see Figures 6c- e (page 23). + +<|ref|>text<|/ref|><|det|>[[115, 584, 861, 616]]<|/det|> +- Figure 6C: why the sclerosis score was not evaluated in all 5/6 mice per group? As mice are sometimes only 2, the Authors cannot discuss about "significant difference" + +<|ref|>text<|/ref|><|det|>[[115, 631, 843, 680]]<|/det|> +We have further analyzed sclerosis scores, and there are now at least 3 mice from each genotype. Difficulties with sample processing reduced the numbers of animals available for analysis (now figure 7c, page 24). + +<|ref|>text<|/ref|><|det|>[[115, 695, 864, 728]]<|/det|> +- Figure 7F/Figure S3: a quantitative graph of % of sickle cells would be more informative than representative pictures. AS samples should also be analyzed. + +<|ref|>text<|/ref|><|det|>[[115, 743, 855, 808]]<|/det|> +Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. As a result, we have removed these figures and tempered any conclusions that were drawn from this data. + +<|ref|>text<|/ref|><|det|>[[115, 823, 833, 856]]<|/det|> +- Discussion: The Authors should compare the proposed approach with currently available strategies and other approaches in development (mutation correction by prime editing) + +<|ref|>text<|/ref|><|det|>[[115, 871, 868, 904]]<|/det|> +We appreciate the reviewer's comments and have included language in the discussion around complementary approaches (lines 403- 411). While we believe each of these approaches have + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 876, 234]]<|/det|> +advantages and pitfalls, we don't want to overstate therapeutic potential in the clinic as that can only be determined once in the clinic. We have attempted to stick to the facts and state that these other strategies lead to expression of HbA and HbF whereas a direct editing strategy like Makassar can lead to the complete replacement/elimination of HbS. While Makassar hemoglobin can be found in nature, careful characterization of hemoglobin properties sheds light on the nuances of the normal hematological parameters that have thus far been described in relation to Makassar hemoglobin, precisely why we believe this manuscript adds novel understanding to the field. Additionally, bluebird bio and CRISPR/Vertex clinical trials did not include red cell function testing, so this comparison is not possible. + +<|ref|>text<|/ref|><|det|>[[115, 248, 877, 313]]<|/det|> +- Discussion: Overall, in vitro and in vivo results are contradictory (normal properties of the purified Hb in vitro and altered hematological parameters observed in vivo): which protein parameters could explain these in vivo alterations? The Authors could also discuss the potential causes of RBC dehydration in GG mice. + +<|ref|>text<|/ref|><|det|>[[115, 328, 870, 409]]<|/det|> +Thanks for the feedback. Based on our current data we believe the reason for the observed differences between the in vitro data showing normal functional properties of HbG when compared to HbA but altered hematological parameters in the context of HbGS in RBCs is due to RBC dehydration. We have included language in the manuscript to better discuss this conclusion (lines 427- 486). + +<|ref|>text<|/ref|><|det|>[[115, 440, 877, 474]]<|/det|> +- Discussion: It would be interesting to discuss the results obtained in the GG mouse model with data collected from the homozygous HbG patient in Sangkitporn et al 2002 + +<|ref|>text<|/ref|><|det|>[[115, 488, 884, 569]]<|/det|> +Very limited data was provided in that paper; without normal ranges for the particular analyzer used, the MCHC, a commonly available value similar to percent dense red blood cells, is difficult to interpret. It is interesting that osmotic fragility test was positive; HbCC red cells are also fragile and prone to hemolysis. Additional text in the discussion was added discussing this observation (lines 419- 425) + +<|ref|>text<|/ref|><|det|>[[116, 600, 419, 616]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 632, 867, 682]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 325, 108]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 110, 358, 126]]<|/det|> +Author's comments in italics + +<|ref|>text<|/ref|><|det|>[[115, 145, 429, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 182, 879, 237]]<|/det|> +In their resubmitted manuscript, the authors have addressed all of my concerns. This work constitutes a useful comparison of the properties of HbAA, HbAS, HbGG, HbGS, and HbSS mice and red blood cells. + +<|ref|>text<|/ref|><|det|>[[115, 256, 822, 274]]<|/det|> +Author's response, second revision. Thank you so much for your interest in our work. + +<|ref|>text<|/ref|><|det|>[[115, 293, 429, 310]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 330, 880, 496]]<|/det|> +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments; thus, the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +<|ref|>text<|/ref|><|det|>[[115, 515, 868, 533]]<|/det|> +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +<|ref|>text<|/ref|><|det|>[[114, 570, 880, 811]]<|/det|> +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBS) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +<|ref|>text<|/ref|><|det|>[[115, 831, 266, 848]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 850, 861, 904]]<|/det|> +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta\) E6A mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 876, 145]]<|/det|> +expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +<|ref|>text<|/ref|><|det|>[[115, 164, 867, 275]]<|/det|> +Authors' response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected p50 range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +<|ref|>text<|/ref|><|det|>[[115, 293, 867, 404]]<|/det|> +Reviewer's Response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the Authors could explain this discrepancy/change to the Reviewer would be very helpful. + +<|ref|>text<|/ref|><|det|>[[115, 422, 883, 496]]<|/det|> +Author's response, second revision. Apologies for the confusion. No additional replicates have been added to the data. The means being compared are for HbG and HbA/HbS isolated from human RBC. The 24.8 value reported for HbA is for the sample isolated from Townes mice. + +<|ref|>text<|/ref|><|det|>[[115, 515, 872, 570]]<|/det|> +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +<|ref|>text<|/ref|><|det|>[[115, 588, 881, 718]]<|/det|> +Authors' response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +<|ref|>text<|/ref|><|det|>[[115, 737, 842, 792]]<|/det|> +Reviewer's Response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artefactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[115, 811, 792, 847]]<|/det|> +Author's response, second revision. Thank you for sharing your concerns around artefactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[115, 866, 881, 903]]<|/det|> +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 866, 127]]<|/det|> +would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +<|ref|>text<|/ref|><|det|>[[114, 144, 878, 275]]<|/det|> +Authors' response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +<|ref|>text<|/ref|><|det|>[[114, 292, 878, 422]]<|/det|> +Reviewer's Response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +<|ref|>text<|/ref|><|det|>[[115, 440, 868, 496]]<|/det|> +Author's response, second revision. Thank you for your feedback. Labels for figure 2c and 2d have been inverted. Curve for 100% HbS in panel 2c has been replaced for a more representative curve taken from the data sets acquired in replicates. + +<|ref|>text<|/ref|><|det|>[[114, 533, 875, 663]]<|/det|> +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +<|ref|>text<|/ref|><|det|>[[114, 681, 875, 829]]<|/det|> +Authors' response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures (p=0.51, lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +<|ref|>text<|/ref|><|det|>[[115, 848, 843, 884]]<|/det|> +Reviewer's Response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 808, 127]]<|/det|> +specifically label that in the graph. Authors should also include p- value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[115, 144, 866, 182]]<|/det|> +Author's response, second revision. Thank you for your feedback. Requested additions to figure 2g have been added. + +<|ref|>text<|/ref|><|det|>[[115, 199, 816, 293]]<|/det|> +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA – this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +<|ref|>text<|/ref|><|det|>[[114, 311, 877, 441]]<|/det|> +Authors' response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +<|ref|>text<|/ref|><|det|>[[114, 459, 880, 553]]<|/det|> +Reviewer's Response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +<|ref|>text<|/ref|><|det|>[[114, 570, 868, 682]]<|/det|> +Author's response, second revision. Thank you for your feedback. A key main result of our manuscript is the identification that the βE6A mutation does not alter the hemoglobin protein fold. The manuscript has been revised to make sure this point is accessible to the general Nature's communication audience. We do agree with the reviewer to move this figure to the Supplementary information if the Editor believes this is too technical for the general readership. + +<|ref|>text<|/ref|><|det|>[[115, 700, 852, 756]]<|/det|> +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +<|ref|>text<|/ref|><|det|>[[114, 774, 642, 811]]<|/det|> +a. Figure 3 (now figure 4) +i. Are pairwise comparisons being made between all samples? + +<|ref|>text<|/ref|><|det|>[[115, 829, 863, 904]]<|/det|> +Authors' response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann- Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 872, 163]]<|/det|> +HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (Sl, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +<|ref|>text<|/ref|><|det|>[[115, 182, 877, 256]]<|/det|> +Reviewer's Response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +<|ref|>text<|/ref|><|det|>[[115, 275, 880, 349]]<|/det|> +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +<|ref|>text<|/ref|><|det|>[[115, 367, 883, 479]]<|/det|> +Author's response, second revision. We reported comparison for three biologically relevant groups (HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS) in the revised manuscript as mentioned in the statistical analysis section (lines 193- 194). Thus, GG and GS were not compared and reported. The initial submission had a discrepancy in which HbGG data was in the usual location of HbAS and was therefore missed by the statistical comparison process. This does not change the interpretation of the data (lines 319- 324). + +<|ref|>text<|/ref|><|det|>[[115, 497, 852, 534]]<|/det|> +ii. If statistics are not shown, does that imply lack of significance, or that statistics were simply not performed? + +<|ref|>text<|/ref|><|det|>[[115, 552, 877, 682]]<|/det|> +Authors' response. Statistics were performed and shown for the pairwise comparisons where their difference appeared to be significant. P values were reported in the main text. Samples whose statistics are not shown are because their difference was not significant. In both cases significance and lack of significance was addressed in the main text in the original submission. To make this observation more accessible to the general reader, P value descriptors have been added to the figure legend and the statistical analysis method section was expanded as well (lines 193- 202). + +<|ref|>text<|/ref|><|det|>[[115, 700, 640, 718]]<|/det|> +Reviewer's Response. Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 737, 736, 755]]<|/det|> +iii. Why is the order of genotypes/color scheme different between panels? + +<|ref|>text<|/ref|><|det|>[[115, 774, 840, 810]]<|/det|> +Color in figure 3 (now figure 4, page 21) panels and in all of the other figures have been standardized to match color and genotype across panels. + +<|ref|>text<|/ref|><|det|>[[115, 830, 848, 866]]<|/det|> +Reviewer's Response. The newly plotted graphs in new Figure 4 are now much easier to read/interpret. + +<|ref|>text<|/ref|><|det|>[[115, 886, 635, 903]]<|/det|> +iv. Why is n so dramatically different between panels/assays? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 880, 183]]<|/det|> +Authors' response. Thanks for pointing out this observation. The number of mice from each genotype varies from assay to assay primarily due to blood volume limitations of the mouse model. We have summarized the number of mice used in each analysis in the supplementary information, supplementary table 5 (SI, page 6). + +<|ref|>text<|/ref|><|det|>[[115, 200, 864, 238]]<|/det|> +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 is a welcome addition to clarify these differences. + +<|ref|>text<|/ref|><|det|>[[115, 255, 882, 330]]<|/det|> +v. In particular, Figure 3C is confusing in that the absolute reticulocyte count for HbAS mice is clearly different from HbGS mice, but not labeled as statistically significant given \(n = 1\) for ARC of HbAS mice. More mice (at least \(n = 3\) ) need to be analyzed for HbAS mice and statistics performed comparing HbAS to HbGS mice for all parameters listed in Figure 3. + +<|ref|>text<|/ref|><|det|>[[115, 348, 872, 460]]<|/det|> +Authors' response. Thank you for your observation. Additional mice were analyzed, and Figure 3 (now Figure 4, page 21) is updated. Reticulocyte count requires very large blood volumes, so it was only possible to measure it in those mice where the blood drawn met the assay volume requirements. Supplementary Table 5 (SI, page 6) contains all the sample sizes and comparisons performed in the manuscript. We have now assured that a minimum of \(n = 3\) mice from each genotype were used in every test. + +<|ref|>text<|/ref|><|det|>[[115, 478, 864, 515]]<|/det|> +Reviewer's Response. This is an acceptable response and the addition of supplementary table 5 as well as at least \(n = 3\) for each genotype is appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 533, 880, 626]]<|/det|> +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<|ref|>text<|/ref|><|det|>[[115, 644, 881, 829]]<|/det|> +Authors' response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +<|ref|>text<|/ref|><|det|>[[115, 848, 868, 904]]<|/det|> +Reviewer's Response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 868, 163]]<|/det|> +health of this mouse that could be provided to the Reviewer would be useful, as would be expected to be quite different physiologically with over a \(50\%\) reduction in hemoglobin; Authors (and Editors) should decide whether this mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse. + +<|ref|>text<|/ref|><|det|>[[115, 182, 872, 294]]<|/det|> +Author's response, second revision. We performed statistical analyses after excluding the HbAA mouse with Hb of \(5.5g / dL\) and did not observe significant changes in the statistical output that altered any inferences. We decided to leave this outlier as a way to be transparent and rigorous by presenting the data as was collected. The mouse was sacrificed in a good state of health per experimental design at 23 weeks, which is considered "middle- aged" for this mouse model. + +<|ref|>text<|/ref|><|det|>[[115, 311, 870, 404]]<|/det|> +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +<|ref|>text<|/ref|><|det|>[[115, 422, 879, 533]]<|/det|> +Authors' response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +<|ref|>text<|/ref|><|det|>[[115, 551, 881, 682]]<|/det|> +Reviewer's Response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +<|ref|>text<|/ref|><|det|>[[115, 700, 866, 737]]<|/det|> +Author's response, second revision. Author's response. Thank you for the suggestion. We have altered the text accordingly (lines 319- 324). + +<|ref|>text<|/ref|><|det|>[[115, 775, 323, 792]]<|/det|> +b. Figure 4 (now figure 5) + +<|ref|>text<|/ref|><|det|>[[115, 793, 879, 848]]<|/det|> +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +<|ref|>text<|/ref|><|det|>[[115, 867, 825, 904]]<|/det|> +Authors' response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 880, 127]]<|/det|> +significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a p- value of <0.0001. + +<|ref|>text<|/ref|><|det|>[[115, 144, 880, 238]]<|/det|> +Reviewer's Response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A – the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y- axis should be set to zero as the adjusted Y- axis (0.35 to 0.65) exaggerates the biological differences here. + +<|ref|>text<|/ref|><|det|>[[114, 255, 875, 441]]<|/det|> +Author's response, second revision. An earlier cohort of mice were used only for deformability measurements. In reviewing our data to make revisions and addition of animals for a more consistent number per assessment, this was noted. We replaced this cohort with data from the animals used in other analyses, such as CBC. This changed the Elmin significantly, although not the overall conclusions. The dramatic difference seen between the data sets is due to the variability within the sickle mouse model, which is not congenic. The correct data set is now being used for the elongation minimum (5A), elongation maximum (5B) and PoS (5C). This is also reflected within the sample size change for the data from 10 points to 12. The data sets for the remaining genotypes remain the same as their respective data sets were correct. We apologize for the initial error. + +<|ref|>text<|/ref|><|det|>[[114, 459, 877, 554]]<|/det|> +GraphPad Prism software automatically adjusted the Y- axis to fit between 0.35 to 0.65. We understand the reviewer has concerns, so we have included both figures below—the original, and the readjusted Y- axis version to compare. The graph with the Y- axis from 0 to 0.6 is difficult to read due to overlapping individual observations. We believe that the inclusion of p- values does not allow for exaggeration to take place and prefer the original. + +<|ref|>image<|/ref|><|det|>[[177, 597, 780, 814]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[112, 876, 861, 896]]<|/det|> +ii. For Figure 4C (now figure 5c), the statement “HbGS mice had very low point of sickling + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 880, 201]]<|/det|> +compared to HbSS, typically below a physiologic threshold of \(\mathsf{pO2} > 15\%\) in the bone marrow reference (Figure 4)" - this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15~\mathrm{mmHg}\) (overlapping with HbSS samples) and half less than \(15~\mathrm{mmHg}\) . The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +<|ref|>text<|/ref|><|det|>[[115, 220, 881, 349]]<|/det|> +Authors' response. Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 367, 883, 498]]<|/det|> +Reviewer's Response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +<|ref|>text<|/ref|><|det|>[[114, 515, 883, 794]]<|/det|> +Author's response, second revision. The histograms of the previous data (panel A) and the current data (panel B) are shown below. Both panels show non- normal distribution with the mode for panel A at the fourth bar (midpoint of 22.5) and the mode for panel B at the third bar (midpoint 17) using the strict definition- the value with the highest frequency. We are aware that the first column of panel A may quality as a second mode using the less strict definition. We also created histograms using different numbers of bins, as suggested in the literature, to confirm our findings. The Mann- Whitney test that we used to analysis is appropriate for data with non- normal distribution irrespective of the number of modes. The initial data showed low end points for the HbGG group due to the Point of Sickling (PoS) cut off of \(97.5\%\) oxygenation. PoS is typically defined as oxygen level at which \(95\%\) of the previous deformability is noted, thus the newer data reflects the correct standard removing values that did not have a greater than \(5\%\) difference between their elongation maximum and minimum. The values of the remaining data points reflect their Elongation Index at \(95\%\) oxygenation pressure. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[125, 95, 660, 465]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 678, 840, 735]]<|/det|> +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +<|ref|>text<|/ref|><|det|>[[114, 752, 861, 790]]<|/det|> +Authors' response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +<|ref|>text<|/ref|><|det|>[[114, 807, 875, 882]]<|/det|> +Reviewer's Response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS %sickled RBCs do not appear statistically different. This statement needs to be changed to "HbGS shows a trend toward + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 559, 108]]<|/det|> +decreased sickling as compared to HbSS" or similar. + +<|ref|>text<|/ref|><|det|>[[115, 127, 870, 165]]<|/det|> +Author's response, second revision. As reviewer requests changes have been made (lines 341- 342). + +<|ref|>text<|/ref|><|det|>[[115, 185, 872, 222]]<|/det|> +iv. The relevance of Hematocrit-Viscosity Ratio (HVR) is not explained in any way for Figure 4D (now figure 5e). + +<|ref|>text<|/ref|><|det|>[[115, 241, 860, 277]]<|/det|> +Authors' response. An additional discussion of viscosity and HVR has been added to the text (lines 166- 171, 337- 340). + +<|ref|>text<|/ref|><|det|>[[115, 296, 860, 333]]<|/det|> +Reviewer's Response. This additional discussion of HVR in the text is appreciated by the Reviewer and acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 352, 853, 407]]<|/det|> +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +<|ref|>text<|/ref|><|det|>[[115, 425, 852, 462]]<|/det|> +Authors' response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +<|ref|>text<|/ref|><|det|>[[115, 481, 879, 573]]<|/det|> +Reviewer's Response. The Reviewer appreciates this addition of n for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +<|ref|>text<|/ref|><|det|>[[115, 592, 863, 702]]<|/det|> +Author's response, second revision. Thank you for the suggestion to clarify; it is a challenging observation that in the mouse model, HbSS RBC are so abnormal and easily hemolyzed that they do not remain in circulation long enough to dehydrate and become dense, as in humans. The milder phenotype of HbGS and HbGG permits this observation (lines 458- 464). Additionally, humans with HbSC demonstrate greater RBC density than HbSS. + +<|ref|>text<|/ref|><|det|>[[115, 722, 868, 794]]<|/det|> +vi. Figure 4G is not referenced until end of article, is not relevant here, and is completely unclear as to how many samples this represents, what assay was used, or even if this represents transcript vs protein abundance, and needs to be significant clarified with n=3 or alternatively removed. + +<|ref|>text<|/ref|><|det|>[[115, 813, 877, 906]]<|/det|> +Authors' response. Thanks for bringing this observation to our attention. Panel g from the original submission was moved to the supplementary information as supplementary figure 7 (Sl, page 13) with proper reference calling in the main text (line 397- 398). An additional description was added to show the data refers to protein expression abundance (line 395). The data being presented has an n = 4 for each genotype (supplementary figure 7, Sl page + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 92, 149, 107]]<|/det|> +13). + +<|ref|>text<|/ref|><|det|>[[115, 127, 672, 145]]<|/det|> +Reviewer's Response. This change is appreciated and acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 183, 322, 200]]<|/det|> +c. Figure 5 (now figure 6) + +<|ref|>text<|/ref|><|det|>[[114, 201, 870, 330]]<|/det|> +i. For Figure 5A-B – the statement is made that “RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA”, but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +<|ref|>text<|/ref|><|det|>[[114, 349, 872, 515]]<|/det|> +Authors' response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +<|ref|>text<|/ref|><|det|>[[114, 533, 874, 626]]<|/det|> +Reviewer's Response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement “retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis”) as this will not be evident to the general Nature Communications readership. + +<|ref|>text<|/ref|><|det|>[[115, 645, 870, 682]]<|/det|> +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 357- 358). + +<|ref|>text<|/ref|><|det|>[[115, 700, 870, 756]]<|/det|> +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<|ref|>text<|/ref|><|det|>[[115, 774, 866, 848]]<|/det|> +Authors' response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +<|ref|>text<|/ref|><|det|>[[115, 866, 872, 904]]<|/det|> +Reviewer's Response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However, given the ineffective erythropoiesis seen in Figure 6D with increased + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 802, 127]]<|/det|> +HbGS, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +<|ref|>text<|/ref|><|det|>[[115, 144, 869, 183]]<|/det|> +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 366- 370). + +<|ref|>text<|/ref|><|det|>[[115, 219, 833, 238]]<|/det|> +iii. Figure 5D is a gating strategy for HbAA only and is not appropriate for a main figure. + +<|ref|>text<|/ref|><|det|>[[115, 256, 863, 294]]<|/det|> +Authors' response. We have moved the gating strategy to the supplementary information (SI Figure 5, page 11). + +<|ref|>text<|/ref|><|det|>[[115, 312, 752, 349]]<|/det|> +Reviewer's Response. This is an acceptable alternative and works well as in supplementary figure section. + +<|ref|>text<|/ref|><|det|>[[115, 367, 323, 385]]<|/det|> +d. Figure 6 (now figure 7) + +<|ref|>text<|/ref|><|det|>[[115, 386, 875, 460]]<|/det|> +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +<|ref|>text<|/ref|><|det|>[[114, 478, 872, 626]]<|/det|> +Authors' response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +<|ref|>text<|/ref|><|det|>[[115, 644, 867, 700]]<|/det|> +Reviewer's Response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and any potential implications on therapeutic applications. + +<|ref|>text<|/ref|><|det|>[[114, 718, 880, 829]]<|/det|> +Author's response, second revision. In SCD, ineffective erythropoiesis is driven by apoptosis of erythroid precursors in the BM; this occurs under normoxia, so HbS polymerization is not required. It is likely that this occurs in HbGS mice as well, based on spleen and erythroid maturation findings. Clinical implications include exacerbation of anemia and iron overload. We discuss the clinical implications of ineffective erythropoiesis in lines 366- 370. + +<|ref|>text<|/ref|><|det|>[[114, 848, 591, 866]]<|/det|> +ii. Figures 6A and 6B are mis-referenced (spleen vs liver). + +<|ref|>text<|/ref|><|det|>[[112, 885, 848, 904]]<|/det|> +Authors' response. Figure legends have been corrected (lines 365, 369), thank you (now + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 267, 108]]<|/det|> +figures 7a and 7b) + +<|ref|>text<|/ref|><|det|>[[115, 127, 824, 145]]<|/det|> +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 164, 327, 182]]<|/det|> +e. Figure 7(Now Figure 8) + +<|ref|>text<|/ref|><|det|>[[115, 183, 875, 219]]<|/det|> +i. Fonts in Figure 7A-D are nearly illegible in regard font size and resolution and needs to be resolved. + +<|ref|>text<|/ref|><|det|>[[115, 238, 844, 257]]<|/det|> +Thanks for the feedback. The figure was replotted with appropriate font sizes (page 25). + +<|ref|>text<|/ref|><|det|>[[115, 275, 824, 294]]<|/det|> +Reviewer's Response. The Reviewer appreciates this change and is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 311, 876, 349]]<|/det|> +ii. It is unclear how Figure 7A-D are any different than the previously published approach in Newby et al. Nature 2021. + +<|ref|>text<|/ref|><|det|>[[114, 366, 881, 551]]<|/det|> +Authors' response. We appreciate the reviewer's comment. The approach described in this manuscript, specifically in Figure 8 for editing of human mPB CD34s, is using a highly engineered inlaid base editor with NGC PAM tolerance that converts the sickle allele to a Makassar allele that was developed by Beam that was previously published (Chu et al 2021). This is different from the Newby approach which uses a NRCH- PAM tolerant guide. The functional result is the same, installation of the Makassar variant but the editor and guide sequences are different. We refer to this in the section describing the data (lines 388- 390) and we believe that these data are complimentary and orthogonal and give further confidence that the deployment of ABEs, even with slightly different features, give similar outcomes. + +<|ref|>text<|/ref|><|det|>[[115, 570, 858, 588]]<|/det|> +Reviewer's Response. These clarifications and additional text additions are appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 607, 881, 699]]<|/det|> +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +<|ref|>text<|/ref|><|det|>[[115, 718, 879, 792]]<|/det|> +Authors' response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +<|ref|>text<|/ref|><|det|>[[115, 810, 869, 903]]<|/det|> +Reviewer's Response. The Reviewer appreciates this revision and clarification and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 183]]<|/det|> +terminology) and also contains jargon not generally accessible ("bulk d18 IVED" – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +<|ref|>text<|/ref|><|det|>[[115, 201, 852, 238]]<|/det|> +Author's response, second revision. Thank you for your feedback. Abbreviations used in figure 8e are now defined in the figure legend. + +<|ref|>text<|/ref|><|det|>[[115, 255, 870, 386]]<|/det|> +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is rather generic. + +<|ref|>text<|/ref|><|det|>[[114, 404, 884, 607]]<|/det|> +Author's response, second revision. Thank you for your feedback. The SDS- PAGE is being used as a relative method to assess the purity of the proteins being used in the biochemical characterization and not for MW estimation. Given the purified material has a relative migration distance similar to the one observed for a commercially available HbA standard (lane 2, Sigma, H7379) and following the observation that MS analyses (panel b) confirm the correct expected MW for the isolated hemoglobins, we speculate the observed discrepancy between the ladder and observed migration could be due to an SDS- PAGE artifact or the improper MW estimation of the ladder by the vendor in the conditions used for running the aforementioned gel. Representative chromatograms from the globin chain analyses shown in Supplementary Figure 7a/b are now shown in SI Figure 7c. The method utilized for separation is cited in the materials and methods (line 231). + +<|ref|>text<|/ref|><|det|>[[114, 626, 875, 765]]<|/det|> +iv. The sickling assays displayed in Figure 7 are of insufficient quality to be published, show low baseline sickling even in HbSS clones to be uninterpretable, and show no quantification or statistical analysis, making these studies uninterpretable in their current form. Additionally, the Methods section refers to deoxygenation method as \(2\%\) metabisulfite, but the figure legend states that \(2\%\) oxygen gas was used. Authors need to be clearer. Moreover, 96 hours of deoxygenation, with such unacceptably low rates of baseline sickling suggest a flaw with the assay. + +<|ref|>text<|/ref|><|det|>[[115, 787, 860, 885]]<|/det|> +Authors' response. We completely agree with the reviewer's comments around quantitation of sickling events in these images. Due to rarity of HbSS CD34+ cells, we do not have the ability to regenerate the IVED cells to allow for sufficient, unbiased sickling assessments either with image analysis or blinded pathology. To that end, we have removed these figures and tempered any conclusions that were drawn from this data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 129]]<|/det|> +Reviewer's Response. The Reviewer appreciates the Authors' candor on this point, removal of this figure, and tempering of conclusions drawn from it. + +<|ref|>text<|/ref|><|det|>[[114, 149, 878, 328]]<|/det|> +6. In the Discussion section, the statement "Considering the functional similarities between HbG-Makassar and HbA, it was anticipated that HbGS mixtures would polymerize to the same extent as HbAS in vitro, and our functional characterization indeed demonstrated HbG-Makassar behaves like a wild-type hemoglobin in heterozygous conditions in vitro" implies that HbGS is equivalent to HbAS, which may be shown but not in a significant manner in Figure 1G and shown in a statistically significant manner (but bimodal) in Figure 4C, but is contradicted by the data in the remainder of Figure 4, all of Figure 3, Figure 5A, and all of Figure 6 (hard to interpret Figure 7 due to lack of quantification and replicates). + +<|ref|>text<|/ref|><|det|>[[114, 348, 878, 589]]<|/det|> +Authors' response. Our text in the discussion was modified to align with the current data presented. Figures 1G (now 2e, page 19) and 4C (now 5c, page 22), the reminder of Figure 4 (now 5, page 22), Figure 3 (now 4, page 21), Figure 5A (now 6a, page 23), Figure 6 (now 7, page 24) and Figure 7 (now 8, page 25) have been replotted and presented in a more accessible and concise way. In addition, our new text in the discussion acknowledges the difference between the results obtained studying the purified protein and those obtained when studying it in the context of RBCs (lines 403- 486). The impact of dehydration on a similar compound heterozygote, HbSC, and the impact of RBC dehydration mediated by HbG on the red cell has been expanded in the introduction and discussion sections (lines 81- 91 and 443- 475). Ex vivo analysis of HbG does not show sickling, even as a HbG/HbS mixture. It is only when in the confines of a dehydrated mature red cell that the HbS in a 60:40 mixture with HbG where sickling becomes possible. + +<|ref|>text<|/ref|><|det|>[[115, 608, 858, 667]]<|/det|> +Reviewer's Response. The new tempered statement in lines 434- 441 is appreciated and more reflective of the data presented, as well as the context present regarding ex vivo vs intracellular HbS/HbG mixtures in lines 443- 475. + +<|ref|>text<|/ref|><|det|>[[115, 688, 875, 747]]<|/det|> +7. The statement "HbSS mice exhibited typical pathology of liver enlargement and glomerular sclerosis; there was no significant difference between HbAA, HbAS, HbGS and HbGG mice" is directly contradicted by the data in Figure 6C (now figure 7). + +<|ref|>text<|/ref|><|det|>[[114, 767, 880, 887]]<|/det|> +Authors' response. HbSS mice had significantly heavier liver per body weight compared to HbGS mice (median 8.75 vs 6.44, \(p = 0.002\) ) while the liver weights/body weight of HbAA and HbAS were comparable with HbGG and HbGS, respectively. (now figure 7a, page 22). Although the sclerosis scores were different across the genotypes, they did not rise to the level of statistical significance. The manuscript has been modified to include this information (Lines 362- 372, 455- 459). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 842, 128]]<|/det|> +Reviewer's Response. The modified verbiage in lines 362- 372 and 455- 460 much more accurately reflect the data presented in the manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 169, 877, 269]]<|/det|> +8. The concluding statement "By directly replacing, and thereby eliminating, in edited cells the pathogenic HbS from red blood cells with a normally functioning, naturally occurring and benign hemoglobin variant, adenine base editing strategies that install HbG-Makassar have the potential to provide life-long transformative therapy for individuals with SCD" is not supported by any of the data in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 289, 860, 388]]<|/det|> +Authors' response. Thank you for your feedback. Concluding statement was modified to highlight the importance of assessing red cell function of any novel hemoglobin editing strategy (lines 477- 486). While HbGG is the most likely editing outcome, and HbGS is in most domains superior to HbSS, one must consider the imperfect quality of HbGS when contemplating the Makassar strategy for base editing in SCD. + +<|ref|>text<|/ref|><|det|>[[115, 410, 692, 428]]<|/det|> +Reviewer's Response. This new concluding paragraph is acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 450, 266, 466]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 469, 872, 547]]<|/det|> +1. While direct correction of HbS to HbG-Makassar may serve as a future therapy in the treatment of SCD, the terminology "transformative" should be removed from the text (and particularly the abstract), as this is overly optimistic of the impact of this approach, given the reported data. + +<|ref|>text<|/ref|><|det|>[[115, 569, 828, 587]]<|/det|> +Authors' response. The word transformative has been removed from the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 609, 835, 646]]<|/det|> +Reviewer's Response. The Reviewers appreciate removal of this terminology from the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 668, 857, 706]]<|/det|> +2. The abstract needs to be edited for grammatical/syntax errors (word count limitations should help overcome confusing sentence structure). + +<|ref|>text<|/ref|><|det|>[[115, 728, 822, 746]]<|/det|> +Authors' response. The abstract was edited for clarity and consistency (lines 23- 33). + +<|ref|>text<|/ref|><|det|>[[115, 768, 768, 786]]<|/det|> +Reviewer's Response. The revised abstract is much clearer and more precise. + +<|ref|>text<|/ref|><|det|>[[115, 828, 867, 906]]<|/det|> +3. The statement "All pharmacologic therapies, including hydroxyurea and newer second line therapies, are palliative, as is chronic transfusion therapy" is not accurate – there are numerous reports of both hydroxyurea and red cell exchange improving organ function (particularly risk of renal dysfunction and CKD) and improved overall survival. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 880, 127]]<|/det|> +These need to be cited and the language of this sentence toned down to be reflective of the literature. + +<|ref|>text<|/ref|><|det|>[[115, 149, 867, 208]]<|/det|> +Authors' response. We agree with the reviewer that these therapies have modified the clinical severity for many individuals and have altered this section accordingly and added citations (lines 40- 42). + +<|ref|>text<|/ref|><|det|>[[115, 230, 881, 267]]<|/det|> +Reviewer's Response. This new sentence and citations are accurate and reflect the current state of the field. + +<|ref|>text<|/ref|><|det|>[[115, 289, 868, 368]]<|/det|> +4. Haploidentical transplant approaches and ongoing trials should be briefly mentioned after the sentence "Allogenic hematopoietic cell transplantation may be curative for individuals with SCD; but matched sibling donors, which produce the best outcomes, are available to only \(\sim 10\%\) of individuals with SCD" + +<|ref|>text<|/ref|><|det|>[[115, 389, 852, 427]]<|/det|> +Authors' response. We now discuss haploidentical transplantation as an option as well (lines 44- 46). + +<|ref|>text<|/ref|><|det|>[[115, 449, 537, 467]]<|/det|> +Reviewer's Response. This addition is acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 489, 880, 587]]<|/det|> +5. For the statement "Most study participants achieved the clinical endpoint, \(80\%\) reduction of vaso-occlusive crisis (VOC)", this is a very minor endpoint for exa- cel and not an endpoint for lovo-cel, so should remove reference to \(80\%\) and state specific percentage of patients that met primary endpoint as presented at ASH 2023 and in FDA approval documents. + +<|ref|>text<|/ref|><|det|>[[115, 609, 880, 647]]<|/det|> +Authors' response. We have eliminated this comment, as it is not integral to the discussion of base editing in the context of the larger transplant field. + +<|ref|>text<|/ref|><|det|>[[115, 668, 653, 687]]<|/det|> +Reviewer's Response. Removal of this comment is appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 708, 877, 787]]<|/det|> +6. The statement "Furthermore, the lack of structural studies on HbG-Makassar prevents assessing the impact the \(\beta \in \mathrm{6A}\) mutation has on the hemoglobin fold and consequently, on its function" is confusing and technical jargon. Authors should specifically clarify what is meant by "hemoglobin fold" and how this would be beneficial to the field. + +<|ref|>text<|/ref|><|det|>[[115, 809, 872, 846]]<|/det|> +Authors' response. Authors' response. Sentence was rewritten to remove technical jargon (lines 77- 79). + +<|ref|>text<|/ref|><|det|>[[115, 868, 535, 886]]<|/det|> +Reviewer's Response. This revision is acceptable. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 168]]<|/det|> +7. The statement "HbC produces a milder disease state with an abnormal red blood cell due to the impact of HbC on hydration" is not entirely accurate, as SCD-HbSC patients can show a wide variety of clinical severity up to and including the severity seen in SCD-HbSS patients. + +<|ref|>text<|/ref|><|det|>[[115, 190, 875, 228]]<|/det|> +Authors' response. This statement has been revised, and no longer comments on HbSC to HbSS relative severity. + +<|ref|>text<|/ref|><|det|>[[115, 249, 536, 268]]<|/det|> +Reviewer's Response. This change is appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 289, 868, 368]]<|/det|> +8. Unclear what is meant by "HbG-Makassar is indeed a functional hemoglobin variant with normal characteristics when compared to HbS" when elsewhere stated that HbG-Makassar shows an intermediate phenotype between HbS and HbA. What do the Authors consider as "normal characteristics"? Oxygen delivery, or phenotype? + +<|ref|>text<|/ref|><|det|>[[115, 389, 857, 467]]<|/det|> +Authors' response. The main text was modified to remove this confusing statement. We would like to clarify that HbG behaves normally in vitro but appears to dehydrate the red cell in vivo. There are some aspects of the HbGG red cell or of organ function of a HbGG mouse that are not statistically different from HbAA, as outlined in the text. + +<|ref|>text<|/ref|><|det|>[[115, 489, 568, 507]]<|/det|> +Reviewer's Response. This clarification is acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 529, 867, 627]]<|/det|> +9. Townes mice need to be introduced properly before utilizing terminology (either in the Introduction or in the Methods section). Authors could use something similar to the statement in the Results section "utilizing the Townes mice that carry several human hemoglobin genes, replacing the endogenous mouse hemoglobin genes" but need to use more precise wording and come earlier in the text. + +<|ref|>text<|/ref|><|det|>[[115, 649, 872, 727]]<|/det|> +Authors' response. The genotype of the Townes mice, its stock number, as well as a description of the model is now present in the methods section (lines 108- 109) as well as in a new figure 1 (page 19). The new figure shows the humanized beta globin locus present in the Townes mice RBC. + +<|ref|>text<|/ref|><|det|>[[115, 748, 820, 806]]<|/det|> +Reviewer's Response. The addition of this new Figure 1 is greatly appreciated by the Reviewer and provides a key foundation for the studies done in the remainder of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 828, 714, 846]]<|/det|> +10. "Zombie dye" is not standard terminology and needs to be clarified. + +<|ref|>text<|/ref|><|det|>[[115, 868, 868, 906]]<|/det|> +Authors' response. "Zombie dye" was replaced with the commercial name utilized by Life Technologies (line 182). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 110, 576, 127]]<|/det|> +Reviewer's Response. This clarification is appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 149, 825, 227]]<|/det|> +11. For Figure 1, and Results text, the relevance of p50 values, Hill coefficients, and hemoglobin polymerization delay times in relationship to hemoglobin function and potential benefit to SCD patients needs to be highlighted here for the general Nature Communications audience. + +<|ref|>text<|/ref|><|det|>[[115, 249, 880, 308]]<|/det|> +Authors' response. Relevance of the p50 values, Hill coefficients and polymerization data of purified HbG in relationship to hemoglobin function and benefit to SCD is now expanded in the discussion section (lines 427- 441). + +<|ref|>text<|/ref|><|det|>[[115, 329, 780, 367]]<|/det|> +Reviewer's Response. This clarification and addition of text to the discussion is appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 389, 833, 428]]<|/det|> +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +<|ref|>text<|/ref|><|det|>[[115, 449, 794, 487]]<|/det|> +Authors' response. Figure 1(now figure 2, page 19) was replotted to make it more accessible to the general audience. + +<|ref|>text<|/ref|><|det|>[[115, 508, 880, 607]]<|/det|> +Reviewer's Response. Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA – so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[115, 628, 881, 665]]<|/det|> +Author's response, second revision. Thank you for your feedback. Requested changes have been made to figure 2e. + +<|ref|>text<|/ref|><|det|>[[115, 684, 648, 701]]<|/det|> +13. Figure 2C is mis-referenced as Figure 3C in the Results text. + +<|ref|>text<|/ref|><|det|>[[115, 721, 730, 738]]<|/det|> +Authors' response. Figure calling has been corrected in the text (line 283) + +<|ref|>text<|/ref|><|det|>[[115, 757, 562, 774]]<|/det|> +Reviewer's Response. This correction is appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 812, 429, 829]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 850, 875, 905]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 228, 106]]<|/det|> +manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 145, 429, 162]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 183, 881, 218]]<|/det|> +The manuscript was improved in terms of clarity, however some important comments have not been addressed: + +<|ref|>text<|/ref|><|det|>[[115, 220, 822, 274]]<|/det|> +1. The title should be tempered since data do not support a proper restoration of Hb function and its use in sickle cell disease compared to other developed approaches reactivating HbF + +<|ref|>text<|/ref|><|det|>[[115, 293, 883, 391]]<|/det|> +Author's response, second revision. Thank you for your feedback. We have replaced the word "restores" with "improves" in the title. HbGG is the most likely editing outcome; HbG significantly improves RBC function compared to HbS. We do not want to speculate on efficacy of this strategy; the clinical outcome comparison of this strategy to induction of HbF is beyond the scope of this manuscript + +<|ref|>text<|/ref|><|det|>[[115, 410, 883, 522]]<|/det|> +2. G and S can be distinguished via HPLC as shown by Newby et al Nature 2021. However, for proper technical comparison of globin expression, beta globin abundance should be evaluated as well in the AS genotype. Ratio of the different beta globins over alpha globin expression would also be informative. Alternatively, to precisely answer this point the authors could insert the silent mutation in HD HSPCs and compare beta-globin expression at mRNA and protein level in the erythroid progeny. + +<|ref|>text<|/ref|><|det|>[[115, 540, 883, 670]]<|/det|> +Author's response, second revision. Apologies for the confusion. We intended to write \(\beta \mathsf{EGA}\) and \(\beta \mathsf{EGV}\) globins cannot be baseline separated. Supplementary Figure 7c now include representative chromatograms used to calculate the abundance of beta globins in the Makassar RBC. Our observations show a 60:40 ratio of G to S similar to the 60:40 A:S split observed in Townes HbA:HbS het mice. When comparing with previous quantifications done for the HbAS Townes mice (Wang et al, Journal of Gene Medicine, 2023) our data suggest that the silent mutation does not impair globin abundance. + +<|ref|>text<|/ref|><|det|>[[115, 689, 866, 816]]<|/det|> +We can further demonstrate that globin protein abundance itself isn't impaired by the silent mutation by looking, as the reviewer suggests, at the alpha to beta globin protein abundance from uHPLC. Across several genotypes, in the same uHPLC run containing samples with the Makassar variant, peak areas consistent with the retention time of beta globin species and alpha show similar relative protein abundances compared to WT genotypes. This uHPLC raw data was included in the original source data that was part of the submission. + +<|ref|>table<|/ref|><|det|>[[115, 816, 549, 902]]<|/det|> + +
total betatotal alphabeta/alpha
WT111.15710.5841.05413832
WT213.26112.171.08964667
M83-1-B111.0510.1221.09168149
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[113, 88, 550, 363]]<|/det|> + +
M83-2-B28.9958.3291.07996158
M83-3-B311.20810.2481.09367681
M83-4-B410.5389.7611.0796025
M83-5-B510.45910.0761.03801112
M83-6-B612.0219.7431.23380889
M85-1-C111.69410.9921.06386463
M85-2-C214.14913.0241.08637899
M85-3-C314.5313.8751.04720721
M85-4-C414.28713.3151.07300038
M85-5-C515.96915.0491.06113363
M85-7-C714.17813.0371.08752014
M85-8-C812.49811.9841.04289052
M85-9-C913.52712.5561.0773355
+ +<|ref|>text<|/ref|><|det|>[[114, 381, 222, 395]]<|/det|> +M83-HbAG + +<|ref|>text<|/ref|><|det|>[[114, 400, 223, 413]]<|/det|> +M85-HbGS + +<|ref|>text<|/ref|><|det|>[[114, 419, 622, 433]]<|/det|> +Total beta = Makassar + WT Beta or Makassar + sickle globin + +<|ref|>text<|/ref|><|det|>[[114, 492, 870, 520]]<|/det|> +3. It would be relevant to reproduce the comparison of solubility with proteins purified in the frame of this study (HbA, HbG, HbS and maybe HbC) and discuss it as an altered + +<|ref|>text<|/ref|><|det|>[[114, 525, 820, 539]]<|/det|> +property of HbG that could further explain the alteration of HbG-containing RBCs. + +<|ref|>text<|/ref|><|det|>[[114, 544, 875, 615]]<|/det|> +Furthermore, the comment regarding the increased turbidity observed in 2.2M phosphate buffer with HbG purified in this study has not been addressed. This point should be discussed in the manuscript since it was described as a specific feature of HbG (Pagnier et al 1993). + +<|ref|>text<|/ref|><|det|>[[114, 639, 884, 840]]<|/det|> +Author's response, second revision. Thank you for your feedback. The solubility work has been published (Adachi et.al., J. Biol. Chem. 1993 268:29 21650-21656 and Adachi et al.1993 FEBS 315:147-50), and thus it is not clear what new additional information we would contribute by repeating the experiment. In the published work the βE6 position was replaced for A (HbG), I, L, V (HbS), W, Q and it was found that HbA was more soluble than HbG which was more soluble than HbS. In addition, the authors found that HbG had a solubility greater than 150 mg/dL while that of HbA was of 350 mg/dL in a 2.1 M phosphate buffer solution. The increased turbidity observed at 2.2 M phosphate buffer reported in Pagnier et al. 1993 for HbG could be attributed to the decreased solubility of HbG at this buffer concentration. A statement of HbG solubility has been included in the manuscript (lines 478-488) and how,similarly to HbC, might be involved in the observed red cell dehydration. + +<|ref|>text<|/ref|><|det|>[[114, 863, 877, 895]]<|/det|> +4. Hb tetramers fiber lateral contacts between beta2 Val/Ala6 and beta1 Phe85 and Leu88,if solved, should be discussed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 108, 877, 238]]<|/det|> +Author's response, second revision. Apologies for the confusion. The contacts you are referring to are not observed in our HbG structure. We speculate the reason being due to differences in the crystal packing between our HbG structure and the HbS structure where these contacts were described (Harrington D.J. et al. 1997 J. Mol. Biol. 272 398- 407). The inability of HbG to polymerize in vitro would suggest that the nucleation in HbG crystals is different from the hemoglobin double strand helix that is formed in HbS which presumably helped in nucleating HbS crystals. + +<|ref|>text<|/ref|><|det|>[[114, 255, 880, 385]]<|/det|> +5. RBC dehydration is probably not the root of the HbGS/HbGG associated phenotypes but is likely a consequence of an Hb characterized by altered physicochemical properties. The statement that in vitro characteristics of HbG are normal is not correct since it has been shown to be altered in previous studies using recombinant proteins (turbidity in 2.2M phosphate buffer, altered solubility), validation of these observations in the protein purified in this study and discussion on these altered properties would give a better overview of the description of the Hb variant of interest. + +<|ref|>text<|/ref|><|det|>[[114, 404, 878, 552]]<|/det|> +Author's response, second revision. Apologies for the confusion. From our data, the only parameters where HbGG differed from HbAA were in metrics affected by dehydration. As a result, our data suggests that RBC dehydration is playing a major role in the observed HbGS/HbGG phenotypes akin to HbC (lines 453- 465, and 480- 488). The authors would like to emphasize that the main objective of this work is to characterize RBCs containing HbG. Ongoing work aimed to identify the root mechanism of dehydration caused by HbG is currently being pursued and it is intended to be published as a follow up to the current manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 570, 815, 607]]<|/det|> +6. Reference to the CRISPR Journal 2021 paper should be added line 204-205 when mentioning the IBE12.2. + +<|ref|>text<|/ref|><|det|>[[115, 626, 820, 644]]<|/det|> +Author's response, second revision. Reference was added as suggested. Thank you. + +<|ref|>text<|/ref|><|det|>[[115, 664, 880, 700]]<|/det|> +7. While Sup Table 5 indicates that statistical analyses have been performed in Figure 7c, it is not clear which conditions have been compared (as well as in other figures) + +<|ref|>text<|/ref|><|det|>[[115, 719, 860, 774]]<|/det|> +Author's response, second revision. Apologies for the confusion. As stated in our revised manuscript in lines 193- 194, we compared the following three groups: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS. + +<|ref|>text<|/ref|><|det|>[[115, 793, 856, 829]]<|/det|> +8. It would be interesting to comment on the osmotic fragility test that results positive in the homozygous HbG patient, could it be linked to the high % of dense cells? + +<|ref|>text<|/ref|><|det|>[[115, 848, 857, 904]]<|/det|> +Author's response, second revision. Increased osmotic fragility is not characteristic of dense red blood cells; however, we hesitate to draw conclusions from a single individual who was pregnant at the time of assessment, which impacts RBC, for whom the primary + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 875, 126]]<|/det|> +data is not provided, and nutritional status such as iron levels that may impact the assay is unknown. + +<|ref|>text<|/ref|><|det|>[[115, 144, 875, 219]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 275, 429, 293]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 311, 875, 386]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 219]]<|/det|> +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments, thus the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +<|ref|>sub_title<|/ref|><|det|>[[116, 233, 323, 249]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 250, 820, 267]]<|/det|> +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +<|ref|>text<|/ref|><|det|>[[116, 281, 419, 298]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 313, 879, 507]]<|/det|> +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBS) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +<|ref|>sub_title<|/ref|><|det|>[[116, 522, 265, 538]]<|/det|> +## Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 538, 872, 634]]<|/det|> +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta E6A\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +<|ref|>text<|/ref|><|det|>[[115, 649, 881, 746]]<|/det|> +Author's response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected \(p50\) range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +<|ref|>text<|/ref|><|det|>[[115, 760, 876, 857]]<|/det|> +Reviewer's response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the authors could explain this discrepancy/change to the Reviewer would be very helpful. + +<|ref|>text<|/ref|><|det|>[[115, 871, 864, 905]]<|/det|> +Author's response, second revision. Apologies for the confusion. No additional replicates have been added to the data. The means being compared are for HbG and HbA/HbS isolated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 836, 122]]<|/det|> +from human RBC. The 24.8 value reported for HbA is for the sample isolated from Townes mice. + +<|ref|>text<|/ref|><|det|>[[115, 137, 839, 170]]<|/det|> +This is an acceptable response. The Authors should also specifically clarify what "h blood" means in the Figure 1A legend as this is not a standard abbreviation. + +<|ref|>text<|/ref|><|det|>[[115, 185, 850, 202]]<|/det|> +Thanks for your suggestion. Suggested clarification was added to the figure 2 legend. + +<|ref|>text<|/ref|><|det|>[[115, 217, 881, 266]]<|/det|> +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +<|ref|>text<|/ref|><|det|>[[115, 281, 870, 393]]<|/det|> +Author's response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +<|ref|>text<|/ref|><|det|>[[115, 408, 870, 457]]<|/det|> +Reviewer's response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artifactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[115, 473, 760, 505]]<|/det|> +Author's response, second revision. Thank you for sharing your concerns around artefactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[115, 520, 877, 600]]<|/det|> +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +<|ref|>text<|/ref|><|det|>[[115, 615, 877, 712]]<|/det|> +Author's response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +<|ref|>text<|/ref|><|det|>[[115, 727, 863, 840]]<|/det|> +Reviewer's response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures, and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +<|ref|>text<|/ref|><|det|>[[115, 856, 835, 904]]<|/det|> +Author's response, second revision. Thank you for your feedback. Labels for figure 2c and 2d have been inverted. Curve for 100% HbS in panel 2c has been replaced for a more representative curve taken from the data sets acquired in replicates. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 105, 316, 121]]<|/det|> +This is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 136, 876, 250]]<|/det|> +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +<|ref|>text<|/ref|><|det|>[[115, 265, 877, 394]]<|/det|> +Author's response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures \((p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +<|ref|>text<|/ref|><|det|>[[116, 408, 881, 473]]<|/det|> +Reviewer's response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include p- value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[116, 488, 830, 521]]<|/det|> +Author's response, second revision. Thank you for your feedback. Requested additions to figure 2g have been added. + +<|ref|>sub_title<|/ref|><|det|>[[118, 536, 317, 553]]<|/det|> +## This is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 567, 830, 649]]<|/det|> +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +<|ref|>text<|/ref|><|det|>[[115, 663, 882, 777]]<|/det|> +Author's response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +<|ref|>text<|/ref|><|det|>[[115, 791, 874, 872]]<|/det|> +Reviewer's response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +<|ref|>text<|/ref|><|det|>[[115, 887, 835, 904]]<|/det|> +Author's response, second revision. Thank you for your feedback. A key main result of our + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 826, 170]]<|/det|> +manuscript is the identification that the \(\beta E6A\) mutation does not alter the hemoglobin protein fold. The manuscript has been revised to make sure this point is accessible to the general Nature's communication audience. We do agree with the reviewer to move this figure to the Supplementary information if the Editor believes this is too technical for the general readership. + +<|ref|>sub_title<|/ref|><|det|>[[116, 184, 761, 202]]<|/det|> +## This is an acceptable response and will defer to Editorial staff on this point. + +<|ref|>text<|/ref|><|det|>[[115, 216, 835, 265]]<|/det|> +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +<|ref|>sub_title<|/ref|><|det|>[[115, 281, 350, 297]]<|/det|> +### a. Figure 3 (now figure 4) + +<|ref|>sub_title<|/ref|><|det|>[[115, 297, 650, 314]]<|/det|> +### i. Are pairwise comparisons being made between all samples? + +<|ref|>text<|/ref|><|det|>[[115, 328, 872, 457]]<|/det|> +Author's response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann - Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (SI, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +<|ref|>text<|/ref|><|det|>[[115, 473, 852, 536]]<|/det|> +Reviewer's response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +<|ref|>text<|/ref|><|det|>[[115, 551, 881, 616]]<|/det|> +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +<|ref|>text<|/ref|><|det|>[[115, 631, 850, 728]]<|/det|> +Author's response, second revision. We reported comparison for three biologically relevant groups (HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS) in the revised manuscript as mentioned in the statistical analysis section (lines 193- 194). Thus, GG and GS were not compared and reported. The initial submission had a discrepancy in which HbGG data was in the usual location of HbAS and was therefore missed by the statistical comparison process. This does not change the interpretation of the data (lines 319- 324). + +<|ref|>text<|/ref|><|det|>[[115, 743, 853, 760]]<|/det|> +The Reviewer appreciates the detailed description of this issue and is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 774, 867, 872]]<|/det|> +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 235]]<|/det|> +Author's response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +<|ref|>text<|/ref|><|det|>[[115, 250, 881, 362]]<|/det|> +Reviewer's response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the health of this mouse that could be provided to the reviewer would be useful (as would be expected to be quite different physiologically with over a 50% reduction in hemoglobin; will defer to Editors as to whether this mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse). + +<|ref|>text<|/ref|><|det|>[[116, 377, 830, 474]]<|/det|> +Author's response, second revision. We performed statistical analyses after excluding the HbAA mouse with Hb of 5.5 g/dL and did not observe significant changes in the statistical output that altered any inferences. We decided to leave this outlier as a way to be transparent and rigorous by presenting the data as was collected. The mouse was sacrificed in a good state of health per experimental design at 23 weeks, which is considered "middle- aged" for this mouse model. + +<|ref|>sub_title<|/ref|><|det|>[[116, 489, 453, 505]]<|/det|> +## Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 520, 861, 601]]<|/det|> +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +<|ref|>text<|/ref|><|det|>[[115, 616, 879, 713]]<|/det|> +Author's response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +<|ref|>text<|/ref|><|det|>[[115, 728, 880, 841]]<|/det|> +Reviewer's response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +<|ref|>text<|/ref|><|det|>[[115, 856, 833, 889]]<|/det|> +Author's response, second revision. Author's response. Thank you for the suggestion. We have altered the text accordingly (lines 319- 324). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 454, 106]]<|/det|> +Authors' response noted and accepted. + +<|ref|>sub_title<|/ref|><|det|>[[115, 121, 333, 138]]<|/det|> +### b. Figure 4 (now figure 5) + +<|ref|>text<|/ref|><|det|>[[115, 137, 864, 187]]<|/det|> +i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +<|ref|>text<|/ref|><|det|>[[115, 202, 872, 250]]<|/det|> +Author's response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a \(p\) - value of \(< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 265, 872, 345]]<|/det|> +Reviewer's response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A - the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y- axis should be set to zero as the adjusted Y- axis (0.35 to 0.65) exaggerates the biological differences here. + +<|ref|>text<|/ref|><|det|>[[115, 360, 845, 519]]<|/det|> +Author's response, second revision. An earlier cohort of mice were used only for deformability measurements. In reviewing our data to make revisions and addition of animals for a more consistent number per assessment, this was noted. We replaced this cohort with data from the animals used in other analyses, such as CBC. This changed the Elmin significantly, although not the overall conclusions. The dramatic difference seen between the data sets is due to the variability within the sickle mouse model, which is not congenic. The correct data set is now being used for the elongation minimum (5A), elongation maximum (5B) and PoS (5C). This is also reflected within the sample size change for the data from 10 points to 12. The data sets for the remaining genotypes remain the same as their respective data sets were correct. We apologize for the initial error. + +<|ref|>text<|/ref|><|det|>[[116, 534, 842, 616]]<|/det|> +GraphPad Prism software automatically adjusted the Y- axis to fit between 0.35 to 0.65. We understand the reviewer has concerns, so we have included both figures below—the original, and the readjusted Y- axis version to compare. The graph with the Y- axis from 0 to 0.6 is difficult to read due to overlapping individual observations. We believe that the inclusion of \(p\) - values does not allow for exaggeration to take place and prefer the original. + +<|ref|>text<|/ref|><|det|>[[116, 631, 877, 696]]<|/det|> +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure. Will defer to the editors on the final decision on Y- axis trimming, but the Reviewer believes that the full Y- axis graph on the left emphasizes key differences without overexaggerating findings, and strongly prefer the Y- axis 0- 0.6 version on the left below. + +<|ref|>text<|/ref|><|det|>[[116, 711, 852, 744]]<|/det|> +Thank you for your suggestion. A new figure displaying a full Y- axis version has been added to the manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 92, 710, 290]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 323, 880, 439]]<|/det|> +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(\mathsf{pO2} > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than \(15 \mathrm{mmHg}\) (overlapping with HbSS samples) and half less than \(15 \mathrm{mmHg}\) . The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +<|ref|>text<|/ref|><|det|>[[115, 451, 879, 565]]<|/det|> +Author's response Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 579, 880, 693]]<|/det|> +Reviewer's response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +<|ref|>text<|/ref|><|det|>[[115, 707, 852, 900]]<|/det|> +Author's response, second revision. The histograms of the previous data (panel A) and the current data (panel B) are shown below. Both panels show non- normal distribution with the mode for panel A at the fourth bar (midpoint of 22.5) and the mode for panel B at the third bar (midpoint 17) using the strict definition- the value with the highest frequency. We are aware that the first column of panel A may qualify as a second mode using the less strict definition. We also created histograms using different numbers of bins, as suggested in the literature, to confirm our findings. The Mann- Whitney test that we used to analysis is appropriate for data with non- normal distribution irrespective of the number of modes. The initial data showed low end points for the HbGG group due to the Point of Sickling (PoS) cut off of \(97.5\%\) oxygenation. PoS is typically defined as oxygen level at which \(95\%\) of the previous deformability is noted, thus the newer data reflects the correct standard removing values that did not have a greater than \(5\%\) difference between their elongation maximum + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 846, 123]]<|/det|> +and minimum. The values of the remaining data points reflect their Elongation Index at \(95\%\) oxygenation pressure. + +<|ref|>text<|/ref|><|det|>[[115, 137, 875, 171]]<|/det|> +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure, and response is acceptable. + +<|ref|>image<|/ref|><|det|>[[120, 201, 491, 458]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 486, 861, 536]]<|/det|> +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +<|ref|>text<|/ref|><|det|>[[115, 550, 861, 583]]<|/det|> +Author's response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +<|ref|>text<|/ref|><|det|>[[115, 598, 874, 679]]<|/det|> +Reviewer's response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS %sickled RBC do not appear not statistically different. This statement needs to be changed to "HbGS shows a trend toward decreased sickling as compared to HbSS" or similar. + +<|ref|>text<|/ref|><|det|>[[115, 694, 837, 727]]<|/det|> +Author's response, second revision. As reviewer requests changes have been made (lines 341- 342). + +<|ref|>text<|/ref|><|det|>[[115, 742, 454, 758]]<|/det|> +Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 774, 870, 823]]<|/det|> +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +<|ref|>text<|/ref|><|det|>[[115, 839, 819, 872]]<|/det|> +Author's response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 871, 155]]<|/det|> +Reviewer's response. The Reviewer appreciates this addition of \(n\) for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +<|ref|>text<|/ref|><|det|>[[115, 169, 830, 266]]<|/det|> +Author's response, second revision. Thank you for the suggestion to clarify; it is a challenging observation that in the mouse model, HbSS RBC are so abnormal and easily hemolyzed that they do not remain in circulation long enough to dehydrate and become dense, as in humans. The milder phenotype of HbGS and HbGG permits this observation (lines 458- 464). Additionally, humans with HbSC demonstrate greater RBC density than HbSS. + +<|ref|>text<|/ref|><|det|>[[115, 281, 850, 315]]<|/det|> +This addition to the text is appreciated by the Reviewer; Authors' response noted and accepted. + +<|ref|>sub_title<|/ref|><|det|>[[115, 330, 330, 346]]<|/det|> +### c. Figure 5 (now figure 6) + +<|ref|>text<|/ref|><|det|>[[115, 345, 880, 459]]<|/det|> +i. For Figure 5A-B – the statement is made that “RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA”, but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +<|ref|>text<|/ref|><|det|>[[115, 472, 872, 601]]<|/det|> +Author's response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +<|ref|>text<|/ref|><|det|>[[115, 615, 852, 681]]<|/det|> +Reviewer's response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement “retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis”) as this will not be evident to the general Nature Communications readership. + +<|ref|>text<|/ref|><|det|>[[115, 695, 835, 728]]<|/det|> +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 357- 358). + +<|ref|>sub_title<|/ref|><|det|>[[115, 743, 455, 760]]<|/det|> +## Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 774, 870, 825]]<|/det|> +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<|ref|>text<|/ref|><|det|>[[115, 840, 874, 889]]<|/det|> +Author's response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 89, 868, 138]]<|/det|> +Reviewer's response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However given the increased HbGS ineffective erythropoiesis seen in Figure 6D, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +<|ref|>text<|/ref|><|det|>[[116, 153, 835, 186]]<|/det|> +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 366- 370). + +<|ref|>text<|/ref|><|det|>[[116, 202, 454, 218]]<|/det|> +Authors' response noted and accepted. + +<|ref|>sub_title<|/ref|><|det|>[[116, 234, 331, 250]]<|/det|> +## d. Figure 6 (now figure 7) + +<|ref|>text<|/ref|><|det|>[[115, 250, 867, 314]]<|/det|> +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +<|ref|>text<|/ref|><|det|>[[115, 329, 875, 442]]<|/det|> +Author's response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +<|ref|>text<|/ref|><|det|>[[116, 457, 870, 506]]<|/det|> +Reviewer's response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and implications on therapeutic applications. + +<|ref|>text<|/ref|><|det|>[[115, 521, 835, 617]]<|/det|> +Author's response, second revision. In SCD, ineffective erythropoiesis is driven by apoptosis of erythroid precursors in the BM; this occurs under normoxia, so HbS polymerization is not required. It is likely that this occurs in HbGS mice as well, based on spleen and erythroid maturation findings. Clinical implications include exacerbation of anemia and iron overload. We discuss the clinical implications of ineffective erythropoiesis in lines 366- 370. + +<|ref|>text<|/ref|><|det|>[[116, 633, 864, 666]]<|/det|> +This addition to the text is appreciated by the Reviewer and provides important context for the reader; Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 696, 872, 777]]<|/det|> +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +<|ref|>text<|/ref|><|det|>[[115, 792, 875, 857]]<|/det|> +Author's response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +<|ref|>text<|/ref|><|det|>[[115, 872, 870, 905]]<|/det|> +Reviewer's response. The Reviewer appreciates this revision and clarification, and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 203]]<|/det|> +Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common terminology) and also contains jargon not generally accessible (“bulk d18 IVED” – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +<|ref|>text<|/ref|><|det|>[[115, 217, 818, 250]]<|/det|> +Author's response, second revision. Thank you for your feedback. Abbreviations used in figure 8e are now defined in the figure legend. + +<|ref|>text<|/ref|><|det|>[[116, 265, 454, 282]]<|/det|> +Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 296, 872, 410]]<|/det|> +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is generic. + +<|ref|>text<|/ref|><|det|>[[115, 424, 856, 600]]<|/det|> +Author's response, second revision. Thank you for your feedback. The SDS- PAGE is being used as a relative method to assess the purity of the proteins being used in the biochemical characterization and not for MW estimation. Given the purified material has a relative migration distance similar to the one observed for a commercially available HbA standard (lane 2, Sigma, H7379) and following the observation that MS analyses (panel b) confirm the correct expected MW for the isolated hemoglobins, we speculate the observed discrepancy between the ladder and observed migration could be due to an SDS- PAGE artifact or the improper MW estimation of the ladder by the vendor in the conditions used for running the aforementioned gel. Representative chromatograms from the globin chain analyses shown in Supplementary Figure 7a/b are now shown in SI Figure 7c. The method utilized for separation is cited in the materials and methods (line 231). + +<|ref|>text<|/ref|><|det|>[[115, 615, 881, 713]]<|/det|> +This addition to the text for uHPLC is appreciated by the Reviewer. It is reasonable to use the MS in Supp. Figure 1a and the chromatogram as shown in Supp. Figure 7c as the definitive test for correct globin identification. However, given the Authors think that this discrepancy may be due to an issue with the SDS- PAGE gel or a manufacturer ladder error, would recommend either repeating this blot to see if a more concordant result can be obtained, or alternatively to remove Supp. Figure 1A completely. + +<|ref|>text<|/ref|><|det|>[[116, 727, 878, 792]]<|/det|> +We have run the SDS- PAGE of hemoglobins multiple times and in all occasions we have observed the hemoglobins migrate faster (apparent smaller size) when compared to the protein standard being used. To avoid confusions and given we confirmed the identity of the proteins via MS we have removed the Supp. Figure 1A as suggested by the reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 807, 852, 841]]<|/det|> +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +<|ref|>text<|/ref|><|det|>[[115, 855, 815, 888]]<|/det|> +Figure 1(now figure 2, page 19) was replotted to make it more accessible to the general audience. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 170]]<|/det|> +Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA – so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[115, 185, 850, 219]]<|/det|> +Author's response, second revision. Thank you for your feedback. Requested changes have been made to figure 2e. + +<|ref|>sub_title<|/ref|><|det|>[[116, 233, 454, 250]]<|/det|> +## Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[117, 265, 420, 282]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 296, 867, 346]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[117, 376, 420, 393]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 408, 833, 457]]<|/det|> +We thank the authors for answering our questions We have a last comment to address: Supplementary Figure 7c should include AA and AS data for proper technical comparison. + +<|ref|>text<|/ref|><|det|>[[116, 472, 784, 520]]<|/det|> +Thank you for your suggestion. Figure 7c (now 6d and e) are the requested chromatograms for AA and AS requested by the reviewer for proper technical comparison. + +<|ref|>text<|/ref|><|det|>[[117, 551, 420, 568]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 584, 867, 633]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 219]]<|/det|> +The Authors have made considerable revisions and changes to the manuscript and have comprehensively addressed nearly all major and minor comments, thus the Reviewers feel that no further experiments are required in subsequent revisions. However, as described below, additional minor revisions are required to address discrepancies between original and new figures that need to be clarified (particularly Figure 2A, Figure 4B, Figure 4D, and Figure 5C); sickling data in Figure 5D whose conclusions in the text remain unsupported by the data; further clarification in the Results or Discussion section as to how increased RBC density may be detrimental or worsen phenotype; and additional minor figure revisions as outlined below. + +<|ref|>sub_title<|/ref|><|det|>[[116, 233, 323, 249]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 250, 820, 267]]<|/det|> +Original comments, followed by Authors' responses and Reviewer's follow- up comments. + +<|ref|>text<|/ref|><|det|>[[116, 281, 419, 297]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 312, 879, 507]]<|/det|> +Recent studies performed by Newby et al. (Nature 2021 Jul; 595(7866): 295- 302) indicate that adenine base editing approaches converting the pathogenic sickle cell mutation (HBBs) to the Makassar \(\beta\) - globin mutation (HBBG) could represent a therapeutic approach to significantly reduce cellular sickling in vivo that minimizes the undesired consequences of double- strand DNA breaks inherent to CRISPR- Cas9- based therapies currently approved for treatment of SCD. In the current manuscript, the Authors utilize in vitro and in vivo models to better characterize the biophysical properties, including deformability and sickling, of mature RBCs containing HbGS and HbGG, with the goal of providing evidence that the direct correction of HbS to HbG- Makassar using base editing is a feasible approach to treat SCD. While the study addresses an important question and utilizes detailed approaches which are important to further understand the implications of the Makassar \(\beta\) - globin mutation in both the homozygous and heterozygous states, there are important concerns detailed as major and minor comments. + +<|ref|>sub_title<|/ref|><|det|>[[116, 521, 265, 537]]<|/det|> +## Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 537, 872, 635]]<|/det|> +1. The Authors state that "Oxygen equilibrium curves show HbG-Makassar has similar functional parameters as HbA, indicating that the \(\beta E6A\) mutation has a negligible impact on the ability of HbG-Makassar to bind and release oxygen (Figure 1C)". While this is expected (and reflected in the data), the representative curves shown indicates that in this study, the curves for HbS and HbG are overlapping whereas the HbA curve is distinct. This needs to be reworded to reflect the data presented. + +<|ref|>text<|/ref|><|det|>[[115, 649, 881, 746]]<|/det|> +Author's response. Thank you for bringing this to our attention. The curves shown are a single representative curve of data taken in quadruplicates. While there is indeed a difference between the mean values of HbG and HbA both values are within the expected \(p50\) range for purified hemoglobins and differ by \(5\%\) which is within the expected experimental error of the instrument. The text and figures for Figure 1 (now figure 2, page 19) have been modified to reflect this observation (lines 255- 256). + +<|ref|>text<|/ref|><|det|>[[115, 760, 876, 857]]<|/det|> +Reviewer's response. This is a reasonable response, as new curves are now more representative with different data plotted and enumerated (former Figure 1C HbA 24.8, HbS 20.9, HbG 21.6; new Figure 2A HbG 21.6, HbS 21.3, HbA 22.8). However, the original means were not within the expected \(5\%\) error, whereas the new means seem to be. Were more replicates added here to change this data? If the authors could explain this discrepancy/change to the Reviewer would be very helpful. + +<|ref|>text<|/ref|><|det|>[[115, 871, 864, 905]]<|/det|> +Author's response, second revision. Apologies for the confusion. No additional replicates have been added to the data. The means being compared are for HbG and HbA/HbS isolated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 839, 122]]<|/det|> +from human RBC. The 24.8 value reported for HbA is for the sample isolated from Townes mice. + +<|ref|>text<|/ref|><|det|>[[115, 137, 839, 170]]<|/det|> +This is an acceptable response. The Authors should also specifically clarify what "h blood" means in the Figure 1A legend as this is not a standard abbreviation. + +<|ref|>text<|/ref|><|det|>[[115, 185, 880, 234]]<|/det|> +Besides, the details of the study are not reported, not even in the supplemental data. Specifically, naked hemoglobin is unstable at 37 deg Celsius, so at what temperature was the study conducted? 25 degrees is standard for hemolysates or purified Hb. + +<|ref|>text<|/ref|><|det|>[[115, 249, 870, 362]]<|/det|> +Author's response. Apologies for the confusion. Experimental details for the oxygen binding studies were provided and shared in the supplementary information on the original submission (SI, page 14). A statement on the contents of the supplementary information was added to the text (lines 517- 520). The study was conducted at \(37^{\circ}C\) following published conditions (J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Jan;879(2) 131- 138, Drug Des Devel Ther. 2018; 12: 1599- 1607). Methods have been modified to provide additional details (lines 126- 127). + +<|ref|>text<|/ref|><|det|>[[115, 377, 870, 426]]<|/det|> +Reviewer's response. Thanks for this response and references, which are acceptable. Authors should however remain mindful of artifactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[115, 441, 761, 474]]<|/det|> +Author's response, second revision. Thank you for sharing your concerns around artefactual effects of high temperatures on hemoglobin integrity. + +<|ref|>text<|/ref|><|det|>[[115, 488, 878, 568]]<|/det|> +2. Figures 1D and 1E are not useful, neither as experimental findings nor as controls, as under no circumstances would either of the hemoglobin species HbA or HbG polymerize. It would have been clearly more important to show the polymerization curves for HbAS and HbAG here, and especially Hb S titrated with varying concentrations of Hb A and Hb G + +<|ref|>text<|/ref|><|det|>[[115, 584, 878, 681]]<|/det|> +Author's response. Thanks for sharing your constructive feedback. Panels E and F were moved to the supplementary information (SI figure 3). We decided to still present the polymerization of HbA and HbS in the SI (Supplementary Figure 3, page 9) as reference for the reader. New panels have been added showing the polymerization curves for HbA+HbS, HbG+HbS mixtures. (figure 2c- d, page 19) which was the data used to plot figure 1G (now figure 2e, page 19). We do not show HbA+HbG polymerization, as HbAG is not a possible gene therapy outcome. + +<|ref|>text<|/ref|><|det|>[[115, 696, 861, 808]]<|/det|> +Reviewer's response. The Reviewer appreciates the addition of HbA/HbS and HbG/HbS mixtures, and agree that HbA/HbG would not be useful. The trends with titration look appropriate for both Figure 2C and 2D. It would be helpful to label Figure 2C and 2D with inverse labels (100% HbS on top, 75% HbS, etc. so that the order aligns with the graph vertically). In Figure 2C, it appears the total Hb concentration in the 100% HbS sample is only half, based on the magnitude on the y- axis. If the study was conducted in replicates, a more representative curve should be used. + +<|ref|>text<|/ref|><|det|>[[115, 824, 835, 872]]<|/det|> +Author's response, second revision. Thank you for your feedback. Labels for figure 2c and 2d have been inverted. Curve for 100% HbS in panel 2c has been replaced for a more representative curve taken from the data sets acquired in replicates. + +<|ref|>text<|/ref|><|det|>[[118, 888, 316, 904]]<|/det|> +This is now acceptable. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 104, 875, 219]]<|/det|> +3. Figure 1G is not referenced in the text and it is unclear to the general Reader what this represents. Perhaps the plot summarizes data not shown that would be the equivalent of 1D-1F conducted using HbAS and HbGS? This further confounds as to why the Authors chose to show delay time polymerization curves for Hb A and HbG. Additionally, statistics need to be performed on Figure 1G polymerization delay data, as change appears minimal among HbS (should be labeled as HbSS to be accurate/consistent), HbAS, and HbGS samples. + +<|ref|>text<|/ref|><|det|>[[115, 232, 876, 363]]<|/det|> +Author's response. Apologies for this omission. Figure 1G (now Figure 2e, page 19) is referenced now in the main text (line 270). The meaning and interpretation of the graph 2e has been expanded in the main text to make sure it is accessible to the general reader (lines 267- 270). HbS was not named HbSS given that we are working with protein mixtures. To avoid confusion protein mixtures labels have been changed. Statistics were performed on curves in panel 2e to assess if the trend was different; Polymerization of HbG and HbS protein mixtures was not significantly different when compared to HbAS mixtures \((p = 0.51\) , lines 270- 272). Figure 2e was replotted to make it more accessible to the general reader. + +<|ref|>text<|/ref|><|det|>[[116, 376, 881, 442]]<|/det|> +Reviewer's response. This is a reasonable new figure, although from the figure it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA - so Authors should specifically label that in the graph. Authors should also include \(p\) - value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[116, 456, 830, 490]]<|/det|> +Author's response, second revision. Thank you for your feedback. Requested additions to figure 2g have been added. + +<|ref|>sub_title<|/ref|><|det|>[[118, 504, 317, 521]]<|/det|> +## This is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 535, 830, 617]]<|/det|> +4. It is not at all clear to the general Reader how the structural and biochemical characterization presented in Figure 2 suggests HbG-Makassar would function analogously to HbA - this needs to be explicitly stated as to why this is the case. Comparative studies alongside HbS and HbA would be extremely beneficial for this argument. + +<|ref|>text<|/ref|><|det|>[[115, 631, 883, 745]]<|/det|> +Author's response. The authors like to emphasize that Figure 1 (now figure 2, page 19) and Figure 2 (now figure 3, page 20) are comparative study results (figure 2 biochemical parameters, and figure 3 structural parameters) between HbA, HbS, and HbG. Given there were no significant deviations in HbG biochemical and structural data we infer it should function analogously to HbA. Results (lines 288- 291) and discussion (lines 427- 441) sections have been expanded to make it clear to the general reader how the structural and biochemical results of HbG suggest it will function analogously to HbA in vitro. + +<|ref|>text<|/ref|><|det|>[[115, 758, 874, 841]]<|/det|> +Reviewer's response. Although the Reviewer feels that Figure 3 is a bit technical for the average Nature Communications reader, this is a reasonable response and agree with the Author's additions to the text to clarify this point. Will defer to the Editors as to whether this degree of technical data is appropriate for the general readership as a main figure or should be moved to supplementary. + +<|ref|>text<|/ref|><|det|>[[116, 855, 836, 905]]<|/det|> +Author's response, second revision. Thank you for your feedback. A key main result of our manuscript is the identification that the \(\beta E6A\) mutation does not alter the hemoglobin protein fold. The manuscript has been revised to make sure this point is accessible to the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 815, 138]]<|/det|> +general Nature's communication audience. We do agree with the reviewer to move this figure to the Supplementary information if the Editor believes this is too technical for the general readership. + +<|ref|>sub_title<|/ref|><|det|>[[116, 153, 761, 171]]<|/det|> +## This is an acceptable response and will defer to Editorial staff on this point. + +<|ref|>text<|/ref|><|det|>[[115, 185, 835, 234]]<|/det|> +5. Overall Figures 3,4,5, and 7 need to be significantly reworked and reanalyzed with appropriate n and biologically relevant comparisons to be acceptable for publication in any journal: + +<|ref|>sub_title<|/ref|><|det|>[[115, 249, 650, 283]]<|/det|> +### a. Figure 3 (now figure 4) +i. Are pairwise comparisons being made between all samples? + +<|ref|>text<|/ref|><|det|>[[115, 297, 872, 425]]<|/det|> +Author's response. Kruskal- Wallis test was performed to compare more than two groups and Mann- Whitney test was used to compare two groups. The median test was used instead of Kruskal- Wallis or Mann - Whitney test when the distribution of the groups was unequal as per Kolmogorov- Smirnov test. The following groups were compared: HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS (lines 193- 202). P values were adjusted for multiple comparisons and values have been reported in the main text and their respective figure legend. Table 5 (Sl, page 6) has been added to the supplementary information that lists all the statistical tests and sample sizes. + +<|ref|>text<|/ref|><|det|>[[115, 440, 852, 504]]<|/det|> +Reviewer's response. This is reasonable, although some of the statistical analyses seem different between the original and revised. The difference in old Figure 3C vs new Figure 4C (statistical difference between AS and GS) seems to be due to increased n, which is reasonable. + +<|ref|>text<|/ref|><|det|>[[115, 519, 881, 585]]<|/det|> +However, old Figure 3B (GG and GS statistically different) is different vs new Figure 4B (AS and GS statistically different), as well as old Figure 3D vs new Figure 4D (addition of statistical significance between GS and SS, not present in original) Can the Authors explain this discrepancy and whether it changed interpretation of the data? + +<|ref|>text<|/ref|><|det|>[[115, 599, 850, 696]]<|/det|> +Author's response, second revision. We reported comparison for three biologically relevant groups (HbAA vs HbGG, HbAS vs HbGS, and HbGS vs HbSS) in the revised manuscript as mentioned in the statistical analysis section (lines 193- 194). Thus, GG and GS were not compared and reported. The initial submission had a discrepancy in which HbGG data was in the usual location of HbAS and was therefore missed by the statistical comparison process. This does not change the interpretation of the data (lines 319- 324). + +<|ref|>text<|/ref|><|det|>[[115, 710, 855, 728]]<|/det|> +The Reviewer appreciates the detailed description of this issue and is now acceptable. + +<|ref|>text<|/ref|><|det|>[[115, 742, 868, 841]]<|/det|> +vi. Authors wrote "Mice with HbGG had hemoglobin levels of 2.8 to 12.5 g/dL, compared to HbAA mice with hemoglobin levels of 5.5 to 12.6 g/dL and HbAS with hemoglobin levels of 10.9 to 15.7 g/dL." Unclear why an Hb AA mouse had an Hb count of 5.5 g/dL, and why HbAS mice had higher hemoglobin levels than HbAA and Hb GG. Perhaps the single mouse with Hb 5.5 g/dL should have been flagged and reanalyzed, and genotype confirmed. + +<|ref|>text<|/ref|><|det|>[[115, 856, 865, 905]]<|/det|> +Author's response. Apologies for the confusion. Hemoglobin levels (lines 297- 302) are now presented as medians for comparison purposes. HbAS mice typically have significantly higher median hemoglobin values compared to HbGS (11.7 vs 8.5 g/dL, \(p = 0.0003\) ). The hemoglobin + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 188]]<|/det|> +values of HbAA and HbSS were not statistically significantly different from that of HbGG and HbGS, respectively (median values of 12.2 g/dL (HbAA), 6.9 g/dL (HbSS), 11.3 g/dL (HbGG), and 8.5 g/dL (HbGS)). The p values did not change significantly when analyses were performed excluding the outlier values obtained. HbAS mice did not have higher hemoglobin than HbAA mice (11.7 vs 12.2 g/dL). The manuscript has been updated with this information (Lines 297- 302). The HbAA genotype of the mouse with Hb of 5.5 g/dL was confirmed. + +<|ref|>text<|/ref|><|det|>[[115, 201, 883, 315]]<|/det|> +Reviewer's response. The Reviewer appreciates the clarity on these points, and the median values are much more in line with what would be expected from these genotypes. It remains quite unusual that a HbAA mouse had a hemoglobin of 5.5; any details on the health of this mouse that could be provided to the reviewer would be useful (as would be expected to be quite different physiologically with over a 50% reduction in hemoglobin; will defer to Editors as to whether this mouse should be kept in analysis, or omitted and reanalyzed with point in text as to one outlier HbAA mouse). + +<|ref|>text<|/ref|><|det|>[[115, 329, 830, 426]]<|/det|> +Author's response, second revision. We performed statistical analyses after excluding the HbAA mouse with Hb of 5.5 g/dL and did not observe significant changes in the statistical output that altered any inferences. We decided to leave this outlier as a way to be transparent and rigorous by presenting the data as was collected. The mouse was sacrificed in a good state of health per experimental design at 23 weeks, which is considered "middle- aged" for this mouse model. + +<|ref|>sub_title<|/ref|><|det|>[[116, 441, 454, 458]]<|/det|> +## Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 472, 861, 555]]<|/det|> +vii. The statement "HbAA and HbGG mice had similar absolute reticulocyte counts (ARC), suggesting that the RBC of HbGG mice had similar lifespans and rates of hemolysis as of HbAA mice" needs to be reconciled with the statement "The ARC from HbGS and HbSS mice were not significantly different (Figure 3C)" – why does HbG heterozygous state not have any effect on baseline ARC? + +<|ref|>text<|/ref|><|det|>[[115, 568, 880, 666]]<|/det|> +Author's response. One of the major findings of this research is that HbG appears to cause red cell dehydration, similar to another non- sickling variant, HbC. This impacts HbGS red cells, as the dehydration of the red cell in the presence of HbS causes cell quality to be intermediate between HbSS and HbAS. In the case of ARC, the HbGS phenotype was indistinguishable from HbSS. In the absence of HbS, HbG driven red cell dehydration has a trivial impact on ARC; therefore, HbGG ARC is not significantly different from that of HbAA. + +<|ref|>text<|/ref|><|det|>[[115, 680, 880, 793]]<|/det|> +Reviewer's response. This is acceptable, but this point should be made in this section of the results – potentially after the statement "HbG contributes to red cell dehydration" (lines 317- 318), making clear that lifespans and hemolysis are similar between HbAA and HbGG at steady state but may be differ in a dehydrated state. This is important to note here as patients with HbGG who have mild otherwise benign concomitant heterozygous conditions (i.e. PIEZO1 mutations) could dehydrate the cell and worsen HbGG lifespan leading to ineffective erythropoiesis. + +<|ref|>text<|/ref|><|det|>[[115, 807, 833, 841]]<|/det|> +Author's response, second revision. Author's response. Thank you for the suggestion. We have altered the text accordingly (lines 319- 324). + +<|ref|>text<|/ref|><|det|>[[116, 855, 454, 872]]<|/det|> +Authors' response noted and accepted. + +<|ref|>sub_title<|/ref|><|det|>[[115, 887, 332, 905]]<|/det|> +## b. Figure 4 (now figure 5) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 89, 864, 138]]<|/det|> +## i. For Figure 4A (now figure 5a), the statement "HbGS RBC deformability under hypoxia was better than that of HbSS RBC" seems to not be supported by the data as the difference between HbGS and HbSS is not statistically significant. + +<|ref|>text<|/ref|><|det|>[[115, 153, 872, 202]]<|/det|> +Author's response. Thank you for this observation. We have reanalyzed the data and updated Figure 4 (Now figure 5a, page 22); the Median test identifies a statistically significant difference between the Elmin of HbGS and HbSS mouse RBCs, with a \(p\) - value of \(< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 217, 872, 297]]<|/det|> +Reviewer's response. The new Figure 5A shows a dramatic difference in elongation index minimum for HbSS as compared to the old Figure 4A – the Authors should explain in detail this discrepancy, as the other genotypes remain relatively similar. In addition, for Figure 5B the Y- axis should be set to zero as the adjusted Y- axis (0.35 to 0.65) exaggerates the biological differences here. + +<|ref|>text<|/ref|><|det|>[[115, 313, 844, 474]]<|/det|> +Author's response, second revision. An earlier cohort of mice were used only for deformability measurements. In reviewing our data to make revisions and addition of animals for a more consistent number per assessment, this was noted. We replaced this cohort with data from the animals used in other analyses, such as CBC. This changed the Elmin significantly, although not the overall conclusions. The dramatic difference seen between the data sets is due to the variability within the sickle mouse model, which is not congenic. The correct data set is now being used for the elongation minimum (5A), elongation maximum (5B) and PoS (5C). This is also reflected within the sample size change for the data from 10 points to 12. The data sets for the remaining genotypes remain the same as their respective data sets were correct. We apologize for the initial error. + +<|ref|>text<|/ref|><|det|>[[115, 488, 843, 569]]<|/det|> +GraphPad Prism software automatically adjusted the Y- axis to fit between 0.35 to 0.65. We understand the reviewer has concerns, so we have included both figures below—the original, and the readjusted Y- axis version to compare. The graph with the Y- axis from 0 to 0.6 is difficult to read due to overlapping individual observations. We believe that the inclusion of \(p\) - values does not allow for exaggeration to take place and prefer the original. + +<|ref|>text<|/ref|><|det|>[[115, 584, 878, 650]]<|/det|> +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure. Will defer to the editors on the final decision on Y- axis trimming, but the Reviewer believes that the full Y- axis graph on the left emphasizes key differences without overexaggerating findings, and strongly prefer the Y- axis 0- 0.6 version on the left below. + +<|ref|>image<|/ref|><|det|>[[149, 667, 710, 864]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 880, 203]]<|/det|> +ii. For Figure 4C (now figure 5c), the statement "HbGS mice had very low point of sickling compared to HbSS, typically below a physiologic threshold of \(\mathsf{pO2} > 15\%\) in the bone marrow reference (Figure 4)" – this is not labeled correctly (Figure 4 instead of 4C), and also does not seem to be reflected by the data, which shows an almost bimodal population, half greater than 15 mmHg (overlapping with HbSS samples) and half less than 15 mmHg. The authors need to explain this discrepancy and speculate on the potential biological significance and apparent heterogeneity. + +<|ref|>text<|/ref|><|det|>[[115, 217, 880, 330]]<|/det|> +Author's response Thanks for pointing out this observation. Histograms of the data do not support bimodal distribution. Default jittering, in which the software shifts the overlapping observations so that each observation is visible, produces the bimodal effect reflected in the old figure. To eliminate this artifact, bar graphs in the manuscript have been substituted for box plots which we believe is a better way to represent the data. In addition, we corrected the figure calling error in the text (line 334). The Dunn test identifies a significant difference between HbGS and HbSS RBC point of sickling, \(p< 0.0001\) . + +<|ref|>text<|/ref|><|det|>[[115, 344, 880, 459]]<|/det|> +Reviewer's response. If the histograms of the data do not support bimodal distribution, the authors should provide examples of this, and also explain why the point of sickling data is so dramatically different between old Figure 4C and new Figure 5C (much fewer N in new figure, and most of data points in low end of apparent bimodal distribution are now missing from the new figure). It is not clear from the authors' response what is meant by "default jittering" and how the new data plotted reflects (or does not reflect) this data. Please clarify these points more specifically in the response. + +<|ref|>text<|/ref|><|det|>[[115, 473, 857, 699]]<|/det|> +Author's response, second revision. The histograms of the previous data (panel A) and the current data (panel B) are shown below. Both panels show non- normal distribution with the mode for panel A at the fourth bar (midpoint of 22.5) and the mode for panel B at the third bar (midpoint 17) using the strict definition- the value with the highest frequency. We are aware that the first column of panel A may qualify as a second mode using the less strict definition. We also created histograms using different numbers of bins, as suggested in the literature, to confirm our findings. The Mann- Whitney test that we used to analysis is appropriate for data with non- normal distribution irrespective of the number of modes. The initial data showed low end points for the HbGG group due to the Point of Sickling (PoS) cut off of 97.5% oxygenation. PoS is typically defined as oxygen level at which 95% of the previous deformability is noted, thus the newer data reflects the correct standard removing values that did not have a greater than 5% difference between their elongation maximum and minimum. The values of the remaining data points reflect their Elongation Index at 95% oxygenation pressure. + +<|ref|>text<|/ref|><|det|>[[115, 712, 875, 746]]<|/det|> +The Reviewer appreciates the detailed description of the Authors' response/edits for this figure, and response is acceptable. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[122, 105, 490, 360]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 390, 861, 442]]<|/det|> +iii. There is no data shown or referenced for the statement "Visualized sickling under chemical hypoxia was similar to the PoS using oxygen gradient ektacytometry, with no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs" (Figure 4E) + +<|ref|>text<|/ref|><|det|>[[115, 454, 864, 489]]<|/det|> +Author's response. The sickling assay results are now shown in figure 5d (formerly Figure 4E, page 22). + +<|ref|>text<|/ref|><|det|>[[115, 502, 875, 585]]<|/det|> +Reviewer's response. The statement "visualized sickling under chemical hypoxia produced...no sickling in HbGG RBCs, and minimal sickling in HbGS RBCs 336 (Figure 5d)." remains unsupported by the data as HbGS and HbSS \(\%\) sickled RBC do not appear not statistically different. This statement needs to be changed to "HbGS shows a trend toward decreased sickling as compared to HbSS" or similar. + +<|ref|>text<|/ref|><|det|>[[115, 599, 836, 632]]<|/det|> +Author's response, second revision. As reviewer requests changes have been made (lines 341- 342). + +<|ref|>text<|/ref|><|det|>[[115, 647, 455, 664]]<|/det|> +Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 677, 872, 728]]<|/det|> +v. Dense red blood cell analysis is mislabeled as Figure 4E instead of Figure 4H, and the lack of adequate samples in HbAS (n=1 similar to Figure 3C) in the critical comparison between HbAS and HbGS and HbSS makes this figure functionally irrelevant. + +<|ref|>text<|/ref|><|det|>[[115, 742, 820, 776]]<|/det|> +Author's response. Five additional HbAS mice were analyzed, and the figure calling was corrected (line 348) (now figure 5f, page 22) + +<|ref|>text<|/ref|><|det|>[[115, 790, 872, 856]]<|/det|> +Reviewer's response. The Reviewer appreciates this addition of n for these experiments; however, as HbGS and HbGG show increased density as compared to HbAS, HbAA, or HbSS, the Authors need to elaborate more specifically in the Results or Discussion section as to how increased RBC density may be detrimental/worsen phenotype (this is glossed over in the text). + +<|ref|>text<|/ref|><|det|>[[115, 870, 825, 903]]<|/det|> +Author's response, second revision. Thank you for the suggestion to clarify; it is a challenging observation that in the mouse model, HbSS RBC are so abnormal and easily + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 830, 155]]<|/det|> +hemolyzed that they do not remain in circulation long enough to dehydrate and become dense, as in humans. The milder phenotype of HbGS and HbGG permits this observation (lines 458- 464). Additionally, humans with HbSC demonstrate greater RBC density than HbSS. + +<|ref|>text<|/ref|><|det|>[[115, 169, 850, 203]]<|/det|> +This addition to the text is appreciated by the Reviewer; Authors' response noted and accepted. + +<|ref|>sub_title<|/ref|><|det|>[[115, 218, 330, 234]]<|/det|> +### c. Figure 5 (now figure 6) + +<|ref|>text<|/ref|><|det|>[[115, 234, 880, 346]]<|/det|> +i. For Figure 5A-B – the statement is made that “RBCs from mice with the HbGG genotype had significantly more mitochondrial retention compared to the RBCs of HbAA mice; however, this difference was eliminated when corrected for the higher level of reticulocytes found in HbGG compared to HbAA”, but this comparison is not made in the data presented, and it is unclear overall what the Authors imply with this statement. Does this make the data more or less biologically relevant and in what way? Why does this matter here? + +<|ref|>text<|/ref|><|det|>[[115, 360, 872, 490]]<|/det|> +Author's response. Thank you for the comment. We did not normalize the data as described in the original text. We present mitochondrial retention without correcting for reticulocyte count in figure 6a (page 23). As for biological relevance, retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis; Our HbAA to HbGG erythroid maturation shows a trend toward maturation delay, and a statistically significant maturation delay in HbGS compared to HbAS. Taken together, these findings support an aspect of ineffective erythropoiesis in HbGS animals intermediate between HbAS and HbSS. This finding is presented in the main manuscript (lines 350- 360) + +<|ref|>text<|/ref|><|det|>[[115, 504, 857, 569]]<|/det|> +Reviewer's response. The Authors need to provide specific context as to why mitochondrial retention was examined (perhaps leading the paragraph with the statement “retention of mitochondria is seen in immature erythroid precursors and ineffective erythropoiesis”) as this will not be evident to the general Nature Communications readership. + +<|ref|>text<|/ref|><|det|>[[115, 584, 836, 617]]<|/det|> +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 357- 358). + +<|ref|>sub_title<|/ref|><|det|>[[116, 632, 454, 649]]<|/det|> +## Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 664, 870, 714]]<|/det|> +ii. Figure 5C has no labels and it is not clear what the asterisk and pound sign represent or how this in any way assesses for ineffective erythropoiesis (would at best show erythroid maturation if labeled properly) + +<|ref|>text<|/ref|><|det|>[[115, 728, 874, 777]]<|/det|> +Author's response. We have revised this figure extensively (now figure 6c 6d 6e, page 23), and the maturation arrest with HbGS compared to HbAS is apparent. Ineffective erythropoiesis is defined as the expansion of early- stage erythroid precursors in the bone marrow. + +<|ref|>text<|/ref|><|det|>[[115, 792, 868, 841]]<|/det|> +Reviewer's response. The revised Figures 6C, 6D, and 6E are now far clearer and easier to interpret. However given the increased HbGS ineffective erythropoiesis seen in Figure 6D, the Authors must explicitly speculate as to why this might be and potential implications for therapy. + +<|ref|>text<|/ref|><|det|>[[115, 856, 836, 889]]<|/det|> +Author's response, second revision. Thank you for this suggestion; this has been added to the results section (lines 366- 370). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 454, 106]]<|/det|> +Authors' response noted and accepted. + +<|ref|>sub_title<|/ref|><|det|>[[115, 121, 332, 138]]<|/det|> +## d. Figure 6 (now figure 7) + +<|ref|>text<|/ref|><|det|>[[115, 138, 868, 202]]<|/det|> +i. Given spleen size is comparable between HbGS and HbSS mice (and greater in HbGS vs HbAS or HbAA mice) in Figure 6, why do the Authors not comment that this may contradict the data from Figure 5 implying that ineffective erythropoiesis is not an issue in these mice or in Makassar models? The data seems to suggest otherwise. + +<|ref|>text<|/ref|><|det|>[[115, 217, 876, 330]]<|/det|> +Author's response. We appreciate this advice; a revised analysis indicates that there is ineffective erythropoiesis as demonstrated by maturation arrest in HbGS compared to HbAS, in agreement with spleen findings. Results and discussion have been revised to reflect new analysis (lines 365- 372 and 450- 455). Spleen weight per total mass was comparable between HbAA and HbGG mice (median 0.51 and 1.07, respectively, \(p = 0.24\) ); the mass ratio of HbGS spleens was significantly larger than HbAS (median 1.57 and 0.69, respectively, \(p = 0.012\) ), but smaller when compared to HbSS (median 1.57 and 4.78, respectively, \(p = 0.01\) ). + +<|ref|>text<|/ref|><|det|>[[116, 345, 870, 394]]<|/det|> +Reviewer's response. This is appreciated, but as above the Authors must speculate as to the mechanistic reason why HbGS shows aspects of ineffective erythropoiesis and implications on therapeutic applications. + +<|ref|>text<|/ref|><|det|>[[115, 409, 835, 504]]<|/det|> +Author's response, second revision. In SCD, ineffective erythropoiesis is driven by apoptosis of erythroid precursors in the BM; this occurs under normoxia, so HbS polymerization is not required. It is likely that this occurs in HbGS mice as well, based on spleen and erythroid maturation findings. Clinical implications include exacerbation of anemia and iron overload. We discuss the clinical implications of ineffective erythropoiesis in lines 366- 370. + +<|ref|>text<|/ref|><|det|>[[115, 520, 866, 553]]<|/det|> +This addition to the text is appreciated by the Reviewer and provides important context for the reader; Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 583, 874, 666]]<|/det|> +iii. The statement "The percent globin expression detected by UHPLC in these HbGS cells displayed a similar 60:40 ratio of HbG-Makassar globin to HbS globin seen in HbGS Townes mice (Figure 4G), and to individuals with sickle trait (HbAS) (Figure 7E)" is not supported by the data presented in either Figure 7E or Figure 4G – numerous additional replicates would be necessary to be able to make this claim. + +<|ref|>text<|/ref|><|det|>[[115, 681, 875, 746]]<|/det|> +Author's response. The data being compared has an \(n = 14\) for the IVED clones and \(n = 15\) for the Makassar Townes whole blood (Figure 8e, page 25 supplementary figure 7, SI page 13). We believe our statement is supported by the present data. To make this point more accessible Figure 8e (page 25) was replotted and panel 4G was moved to the SI (page 13). + +<|ref|>text<|/ref|><|det|>[[115, 760, 880, 905]]<|/det|> +Reviewer's response. The Reviewer appreciates this revision and clarification, and agrees that the data now more clearly show the intended point made here. However, the X- axis labels on Figure 8E remain very difficult to decipher for the general readership and further more contain relatively reserved terminology (SC – unclear what this represents and also confusing with HbSC disease which is not studied in this manuscript but is a common terminology) and also contains jargon not generally accessible ("bulk d18 IVED" – assuming d14 is used for editing for gDNA extraction whereas d18 used for UPLC as mature globin tetramers, but this is not explained. These labels should be clarified/simplified to eliminate confusion/jargon, or at the very least defined specifically in the Figure 8E legend. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 105, 819, 138]]<|/det|> +Author's response, second revision. Thank you for your feedback. Abbreviations used in figure 8e are now defined in the figure legend. + +<|ref|>sub_title<|/ref|><|det|>[[116, 153, 455, 170]]<|/det|> +## Authors' response noted and accepted. + +<|ref|>text<|/ref|><|det|>[[115, 184, 870, 300]]<|/det|> +Additional comments pertain to Supplementary Figures 1 and 7. Figure 1A (SDS- Page) the globin chains run around 13Kda. Any explanation, given that they should run closer to 16kDa? Are the molecular weight markers/ladders mislabeled? Additionally, Authors should include representative uHPLC chromatograms from globin chain analyses that were used to generate Figure 7A, as they did for Figure 7B. Additional details on uHPLC system (manufacturer/model) and the columns utilized should be provided, as C18 is generic. + +<|ref|>text<|/ref|><|det|>[[115, 313, 857, 490]]<|/det|> +Author's response, second revision. Thank you for your feedback. The SDS- PAGE is being used as a relative method to assess the purity of the proteins being used in the biochemical characterization and not for MW estimation. Given the purified material has a relative migration distance similar to the one observed for a commercially available HbA standard (lane 2, Sigma, H7379) and following the observation that MS analyses (panel b) confirm the correct expected MW for the isolated hemoglobins, we speculate the observed discrepancy between the ladder and observed migration could be due to an SDS- PAGE artifact or the improper MW estimation of the ladder by the vendor in the conditions used for running the aforementioned gel. Representative chromatograms from the globin chain analyses shown in Supplementary Figure 7a/b are now shown in SI Figure 7c. The method utilized for separation is cited in the materials and methods (line 231). + +<|ref|>text<|/ref|><|det|>[[115, 504, 880, 602]]<|/det|> +This addition to the text for uHPLC is appreciated by the Reviewer. It is reasonable to use the MS in Supp. Figure 1a and the chromatogram as shown in Supp. Figure 7c as the definitive test for correct globin identification. However, given the Authors think that this discrepancy may be due to an issue with the SDS- PAGE gel or a manufacturer ladder error, would recommend either repeating this blot to see if a more concordant result can be obtained, or alternatively to remove Supp. Figure 1A completely. + +<|ref|>text<|/ref|><|det|>[[115, 616, 853, 650]]<|/det|> +12. All figures in Figure 1 are very difficult to read/interpret – would use different color schemes to more clearly illustrate (particularly in Figure 1G). + +<|ref|>text<|/ref|><|det|>[[115, 664, 816, 697]]<|/det|> +Figure 1(now figure 2, page 19) was replotted to make it more accessible to the general audience. + +<|ref|>text<|/ref|><|det|>[[115, 711, 881, 792]]<|/det|> +Revised Figure 1 (now Figure 2) is much clearer, particularly old Figure 1G/new Figure 2E, with the exception of the comment by the Reviewer above that in new Figure 2E it is not clear immediately if the 25/50/75% represents HbS or HbG/HbA – so Authors should specifically label that in the graph. Authors should also include p-value in graph to emphasize that there is no difference between the trendlines. + +<|ref|>text<|/ref|><|det|>[[115, 807, 850, 840]]<|/det|> +Author's response, second revision. Thank you for your feedback. Requested changes have been made to figure 2e. + +<|ref|>text<|/ref|><|det|>[[115, 855, 455, 872]]<|/det|> +Authors' response noted and accepted. + +<--- Page Split ---> diff --git a/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/images_list.json b/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..045774c676dbd2da9aabff1247e7bcd49d4ec09d --- /dev/null +++ b/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1,170 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_8.jpg", + "caption": "Supplementary fig. 8 Exemplary temporal waveform-shape features. Different characteristics of band-pass filtered oscillations or raw-signal can be extracted: peak and troughs amplitudes, prominence of troughs to peaks, intervals between troughs or peaks, sharpness, decay and rise times of identified peaks and troughs, and the 5 ms width of peaks and troughs.", + "footnote": [], + "bbox": [ + [ + 245, + 140, + 777, + 560 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure from Köhler et al. Dopamine and DBS accelerate the neural dynamics of volitional action in Parkinson's disease. bioRxiv (Cold Spring Harbor Laboratory) (2023). doi:10.1101/2023.10.30.564700. Under review. (A) Features of a single motor cortex channel averaged across trials. (B) Classifier outputs averaged across subjects. Classifier outputs of electrocorticography (ECoG) and subthalamic local field potentials (STN-LFP) differed between \\(-2.2\\) to \\(1.7\\) s (OFF therapy), \\(-1.6\\) to \\(1.6\\) s (ON levodopa) and \\(-1.0\\) to \\(0.9\\) s (ON subthalamic deep brain stimulation [STN-DBS]; all \\(P\\leq 0.05\\) , cluster corrected). Data are represented as mean \\(\\pm\\) SEM. (C) Time of motor intention of single subjects derived from ECoG classifier outputs. (D) Time of motor intention derived from single-channel ECoG classifier outputs. Left hemispheric channels were flipped onto the right hemisphere. \\(*P\\leq 0.05\\) ; \\(**P\\leq 0.01\\) ; \\(***P\\leq 0.001\\)", + "footnote": [], + "bbox": [], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_1.jpg", + "caption": "Supplementary fig. 1: Individual differences in ECoG electrode contact localizations across cohorts.", + "footnote": [], + "bbox": [ + [ + 120, + 315, + 878, + 481 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R1: Real-time single trial decoding is shown using true analog rotameter movements, classification probability predictions and binary classification outputs.", + "footnote": [], + "bbox": [ + [ + 118, + 420, + 575, + 711 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure R2: Movement label transformation. Raw movement traces (a) were transformed by investigating visually the EMG movement onset and offset, which resulted (b) in a binary movement vector. For contrastive learning, the binary movement was filtered using a Gaussian window. This function was beneficial for training the non-linear embedding layer and subsequent movement classification. The Gaussian filtered movement signal closely resembles the movement characteristics of the acquired raw signal.", + "footnote": [], + "bbox": [ + [ + 120, + 430, + 872, + 664 + ] + ], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_3.jpg", + "caption": "Supplementary fig. 3 Stimulation ON/OFF power spectra and cross-prediction movement decoding performances for different stimulation artifact rejection methods. (a) Exemplary power spectra of a single subject without stimulation artifact rejection, and for two artifact rejection methods: PARRM (Period-based", + "footnote": [], + "bbox": [ + [ + 184, + 380, + 808, + 844 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure R3: (a) New classification results on sensory cortex signals for which the positive movement intention (positive) class was defined as the time-period -2 s prior to movement onset, and the rest (negative) class was defined as -4 till -2 s before movement onset. We excluded the movement period for classifier training, to investigate the single effect of somatosensory cortex related decoding for movement intention. We tested the movement intention decoding using a class-weight balanced and lasso-regularized logistic regression model within a three-fold non-shuffled cross-validation. Sensory cortex prediction performances rose above chance level as early as 2 seconds before motor onset (b) leading to a total balanced accuracy of movement intention classification of \\(0.6 \\pm 0.05\\) (c).", + "footnote": [], + "bbox": [ + [ + 120, + 525, + 880, + 700 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_5.jpg", + "caption": "Supplementary fig. 5 Connectomics-based neural decoding without patient-individual training. (a) Estimation of a patient-individual \"fingerprint\". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called \"fingerprint\" and represents the brain-wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the \"fingerprint\" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity", + "footnote": [], + "bbox": [], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_4.jpg", + "caption": "Supplementary fig. 4 Comparison of different approaches for neural decoding without patient-individual training. (a) Grid-point interpolation: Individual recording contact locations are estimated in a standardized", + "footnote": [], + "bbox": [], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_2.jpg", + "caption": "Supplementary fig. 2 Sum of linear model absolute value coefficients shows feature importances for all movement decoding patients.", + "footnote": [], + "bbox": [], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_9.jpg", + "caption": "Supplementary fig. 9 Responsive Neurostimulation (RNS) device artifact annotations and corresponding features. (a) Raw time-series including annotated stimulation and clipping artifacts and (b) corresponding FFT features. The RNS does not allow for simultaneous stimulation and recording. The device parameters allow for specifying a \"gain\" setting that can omit the clipping artifact.", + "footnote": [], + "bbox": [ + [ + 131, + 281, + 880, + 580 + ] + ], + "page_idx": 38 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Revision Figure 1: Correlation of decoding performances and embedding consistencies. a) Optimal functional connectivity is shown computed based on training data subjects. b) For an exemplar patient (Berlin subject 008), leave-one-patient out cross validation performances were computed. For each test-subject channel, the embeddings were computed given the training data CEBRA non-linear encoding model. The embedding correlations of each channel and the training data is color-coded for the test patients' channels. The embedding consistencies were computed by correlating the training data embedding by other patients' optimal decoding connectivity channels and the left-out test patient embeddings. c) A significant correlation could be found between left-out decoding performances and channel-individual embedding correlations.", + "footnote": [], + "bbox": [], + "page_idx": 43 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Revision Figure 3: Electrode localizations color-coded by patient ID.", + "footnote": [], + "bbox": [], + "page_idx": 46 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Revision Figure 4: Optimal structural seizure decoding network (a) predicts seizure detection performance in leave one subject out cross-validation (b).", + "footnote": [], + "bbox": [ + [ + 122, + 170, + 925, + 444 + ] + ], + "page_idx": 54 + } +] \ No newline at end of file diff --git a/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..efcdf45e98f9b9a500d1c2e241aa834ba922cf81 --- /dev/null +++ b/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,1622 @@ + +# nature portfolio + +Peer Review File + +# Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants + +Corresponding Author: Dr Timon Merk + +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Biomedical Engineering. + +Version 0: + +Decision Letter: + +Dear Prof Neumann and Mr Merk, + +Thank you again for submitting to Nature Biomedical Engineering your manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants". The manuscript has been seen by 3 experts; however, despite our chasing efforts one reviewer has yet to provide a report (should the reviewer provide it, we will send it to you in due course). You will find the reports of 2 reviewers at the end of this message. + +You will see that the reviewers appreciate aspects of the work. However, they articulate concerns about the degree of support for some of the claims and about the advance that the work represents over relevant published studies also from your group, and provide useful suggestions for improvement. We hope that with significant further effort you can address the criticisms, increase the level of significance of the study, and convince the reviewers of its merits. In particular, we would expect that a revised version of the manuscript provides: + +\* Extended discussion about the the novelty of the work respect to previously published manuscripts + +\* Clarification about the use of both terms BCI and closed loop neuromodulation, as highlighted by Reviewer #2 + +\* Thorough methodological reporting, with emphasis on facilitating reproducibility as per many points of all the Reviewers + +When you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that explains the main improvements included in the revision and responds to any points highlighted in this decision. + +Please follow the following recommendations: + +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +\* If you and your co- authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the reason(s). + +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +<--- Page Split ---> + +We hope that you will be able to resubmit the manuscript within 25 weeks from the receipt of this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +We hope that you will find the referee reports helpful when revising the work. Please do not hesitate to contact me should you have any questions. + +Best wishes, + +Valeria + +Dr Valeria Caprettini Associate Editor, Nature Biomedical Engineering + +Reviewer #2 (Report for the authors (Required)): + +This manuscript describes the use of a Python toolbox for decoding brain signals for the purposes of neuromodulation. The basic idea is to bring together multiple existing methods for feature extraction, dimensionality reduction, and decoding to try to improve on methods that are currently in clinical use or in clinical trials. It also describes some methods to use structural connectivity to help perform decoding across patients without having to obtain new training data. This is all useful; however, it is not clear how much of this is actually new. They do here show more examples of potential use cases in large datasets (DBS in patients with PD and depression, RNS in epilepsy patients), and this is useful to show the potential of using more techniques to optimize closed- loop neuromodulation. However, the authors have shown the connectivity "fingerprint", and many of their other methods (and ability to decode force in PD patients) in their prior eLife paper, and it appears that the toolbox was also created for that paper, since it cites that paper. None of the techniques in the toolbox are novel, though it is certainly helpful to have them all in one place and open- source (which is a strength). Further, many of the techniques are not clearly described, so it is difficult to assess their importance and, since the paper's main theme appears to be the toolbox itself, it seems to fall short of its main purpose- to make these techniques more user- friendly and widely used. Overall, this seems to be an incremental advance. More specific concerns follow below. + +Major concerns: + +1. It is not clear why the manuscript starts out talking about BCIs but then switches to closed loop neuromodulation. These are not the same thing, and there is enough confusion in the literature about what constitutes a BCI. The widely accepted definition involves some volitional modulation, which is not what is being described here. It would be preferable to not call this a BCI, but rather other methods of closed-loop neuromodulation. + +2. Multiple other open-source toolboxes exist that have brain signal feature extraction, selection, and decoding algorithms included (e.g., FieldTrip). These are not even mentioned in this paper, and they clearly should be discussed and the advantages of this toolbox described clearly. + +3. The introduction could be clearer as to exactly what problem is being solved with these techniques. It keeps talking about BCIs and decoding, but the problem envisioned seems to be closed-loop neuromodulation. But this works fairly well. For example, the sentence (in Results) "A key problem for invasive brain signal decoding is the individualized localization of brain implants + +4. across patients, which significantly complicates the development of large-scale models..." What does localization of implants have to do with decoding? Decoding does not depend on location in any BCI literature. What type of large-scale models are being referred to here? Models across patients? This all needs more explanation. + +5. To say that calibrating a move vs rest decoder in each patient is a serious limitation and would hinder broad clinical adoption seems a bit exaggerated, given the time it takes to do the DBS implant itself. Calibration could easily be done intraoperatively, or in already scheduled calibration sessions in clinic, within each patient in a few minutes for this simple of a decoding measure. + +6. The Results and Methods need much clearer explanations of what was being done and decoded. It is not meaningful to say "balanced accuracy of \(0.8 / 0.98 \pm 0.07 / 0.04\) for single sample/movement detection..." without explaining what is "single sample" (or "sample-wise") decoding, what movements are being detected, and how many classes are being decoded among. The tasks seem highly disparate among these datasets, so combining results across them does not make much sense. The tasks are not even described in any detail, nor what is being decoded. It is also not clear exactly what features are being used to decode (e.g., how many time bins were used in each decoder? Were they causal-only bins?) nor how much data (trials) were used to train and test in each case. Since the whole point of the study is to show how this toolbox enables decoding, and the methods are not described in enough detail to understand the task, it is very difficult to ascertain the impact of the innovation. In addition, if the goal is to show that these techniques allow better decoding of movement vs + +<--- Page Split ---> + +rest (which I am inferring, since this is never stated clearly), then the results here should be compared to prior studies in closed- loop DBS using simpler methods. + +7. Line 121: "0.88 ± 0.17 movement detection rate across movements" – unclear how this number was derived, as Fig 2g does not seem to show this high of accuracy averaged across all boxes. + +8. In Table 1, what is the difference between "sample" vs "movement" columns? Is movement detection the same as sensitivity? If so, then state this. + +9. "To approximate the movement kinematics..." What movement kinematics? Were these recorded? It's not even stated how movement times were recorded. + +10. How were stimulation artifacts dealt with, given that the high gamma range includes the stimulation frequency used? + +11. It seems that many ECoG electrodes with high decoding accuracy were in primary somatosensory cortex, which begs the question if these were really sensing sensory feedback, as opposed to motor intent. Sensory feedback would not be useful for controlling DBS, since it could be causing a positive feedback loop. + +12. Another central theme of the paper is not clearly explained. The idea of using connectivity as a way to decode across patients is very interesting and potentially useful. However, the methods are not explained clearly enough. What does "voxel-wise correlation of connectivity profiles with decoding performances from offline training" mean (lines 548-49)? How does one correlate a connectivity profile with an R2 value? What exactly is meant by a "connectivity profile"? Just a pairwise correlation matrix? Other graph theoretic measures? There are many types of connectivity that can be calculated, and this needs to be explained. The cited reference likewise does not explain this sufficiently clearly, but in any case, this is a central theme of this paper and should be explained here, not delegated to a reference. Without this, "prospective channel selection" is not easily understood, because "optimal connectomic decoding map" is not clear at all. + +13. It's not clear what the clinical relevance of training on a single subject to predict other subject's data, given that one would not know in practice who the "best" subject is without training on a group of subjects and testing on all of them anyway. + +14. Authors seem to claim that CEBRA performs better than 2nd method, but do not provide statistical testing evidence to back this up (a p-value is presented, but how was this tested?). Similarly, it mentions several times that a given performance is above chance, but never states how chance is computed for any case. It is also not true that accuracy of \(\sim 60\%\) is "high above" chance when chance is likely \(50\%\) . Also, not clear what is being shown in Fig 2o -there are no y axis labels, and not clear if these are averages, single trials, or other. + +15. More details should be provided about the DBS trial for depression. Without these, it is difficult to evaluate the phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." (line 244). Were all DBS leads used for stimulation? If not, how did those leads used for stimulation relate to the leads in the decoder? The clinical trials registry number should also be included for all of these trials. + +16. More information is required about the "additional fiber filtering approach recently introduced..." (line 246). The method should be described clearly. Again, the term connectivity fingerprint is not explained. The phrase "estimated best therapeutic stimulation target from Fox et al 2014" is also not explained at all. Why is this important and what does it have to do with the results presented here? This needs explanation for a broad audience. + +17. It's not clear whether the optimization of RNS parameters using a grid search is feasible or helpful for an actual clinical use case in individual patients. Was this optimized over all patients with holding patients out? Or by doing cross-validation with data from all patients together? + +Minor concerns: + +Please type out all acronyms used for those not familiar (e.g., CEBRA). + +Methods mentions multiple terms that could mean similar things. What are data "batches" vs "segments"? FFTs were computed at 100 ms resolution – does this mean 100 ms windows, or longer windows overlapped by 100 ms? Fig 4 labels are too small to be legible. + +Supplementary video is not explained clearly. What are the different decoding/prediction windows showing? The prediction output looks very noisy during movements. + +Reviewer #3 (Report for the authors (Required)): + +This is a very interesting and ambitious paper describing an open source software system, py_neuromodulation, for "decoding" of behavioral states, including disease specific states, from invasive intracranial recording. It is designed for field potential (LFP and electrocorticography) approaches. At a time of great excitement in human invasive neurophysiology and its application in neural engineering, authors are to be applauded for developing a comprehensive analytic system that is + +<--- Page Split ---> + +accessible to all and that begins to standardize brain decoding across applications. A strength of the system is that it is designed to combine physiological recordings with connectomics, the merger of which can lead to new neuroscience insights. A strength of the paper is the illustration of the system in three different scenarios: decoding of movement (move vs rest, I believe, but see below) from motor system recordings in a variety of tasks in patients with movement disorders, decoding of emotional state from area 25 limbic implants, and decoding of pre- ictal or ictal activity in epilepsy. + +Some general points for improvement: + +1) The paper is quite dense. It assumes a high level of expertise form the reader, who would need to have fluency in neurophysiology of LFPs, advanced imaging methods especially merging imaging imaging sets across individuals, and machine learning, to fully grasp it. Below are specific areas where the authors could give a bit more information or clarification to help readers who don't already have expertise in all three of these. +2) Its not very clear how the system handles electrical recordings with lots of artifacts. There is one statement in methods on movement decoding that alludes to an answer "All 606 features were z-score normalized across the past 30 s and clipped at minus and plus three.." perhaps the "clipping" is their answer. More on how the system handles noisy data would be appreciated. + +3) Authors should be more specific about what the system does NOT do, perhaps in discussion. At times the text seems to imply that the system can simulate closed loop stimulation for design of closed loop algorithms. For example this sentence in the abstract: "Our platform provides rapid, high-accuracy decoding for precision medicine approaches that can dynamically adapt neuromodulation therapies in response to the individual needs of patients" - is a DBS prototyping really part of py_neuromodulation? This should be clarified. + +4) A description somewhere of what data or tools the user actually needs, to utilize this system, would be helpful. For example, how are electrode locations input into the system? Is a DICOM formatted image set of the whole brain needed? CT only or is MRI needed? Or does py_neuromodulation require Some sort of output from other software packages such as LeadDBS? Also how are the specific machine learning algorithms implemented.? Does the user make a simple selection like "support vector machine" and then is able to input hyperparameters? Or does py_neuromodulation require specific outputs from other machine learning packages? + +5) One of the three big problems the authors hope to address is "Machine learning can capitalize on large datasets but current brain signal decoding approaches for BCI still commonly rely on individual patient training sets of short duration". It is never really clear to me how the authors solve this - is there a particular method they introduce to solve it? Or are they just trying to show that in fact you don't need large data sets of long duration, even though other researchers try to use those? More clarity in discussion on this would help. + +Specific comments to improve readability: + +Early in results or in intro, authors should say that their system is called "py_neuromodulation" When they began to use this term in results, I did not perceive that it is actually the name of their software pipeline. + +Results section 1: "To address this, we developed dedicated approaches for patient decoding based on normative MRI connectomics and latent embeddings from contrastive learning with CEBRA13. " - this sentence will be opaque to a number of readers who are unfamiliar with contrastive learning and the acronym CEBRA. + +Figure 1, Part D is not completely clear as it is first presented, and it seems to be a major part of the author's pipeline. Especially this statement: "Features can be mapped in space (d) for patient individual or across- patient decoding and consecutive adjustment of therapeutic delivery." Its not clear here how mapping features in space specifically contributes to decoding of dynamic patient states like movement, emotion, or seizure occurrence. Mapping the relevant activities would certainly contribute to a better understanding of anatomic localization or network involvement of recording sites that are relevant to decoding, and that contributes to understanding which brain networks are most relevant for the decoded brain state. But it is not clear at this point in the manuscript how the spatial mapping contributes to the process of decoding or to its accuracy. At line 89- 91, and later in the text, they imply that accounting for the variable localization of implants would be a contributor to generalized cross- subjects decoding, which seems true, but how would anatomic localization contribute to individual decoding performance as is stated in the figure legend? + +## Results section 2 + +"at the single sample level (100 ms precision indicating presence or absence of movement) and at the individual movement level (300 ms or more movement time decoded consecutively)" - this sentence is not clear + +it is not quite spelled out what movement decoding really means - are the brain states that are decoded "not moving" versus "moving"? this should be more clearly stated. + +Figure 2 - Panels j, k - the term "embedding" is not clear here. Panel o - the meaning of the y axis is not clear in these plots. For example for "true movement" is the y axis displacement? Force? + +"To investigate the individual variability of trainer vs. learner performance" - not sure what this means + +In general for this section: what signal features contributed to movement decoding? In the following section on emotion decoding, the features used are stated more explicitly, and that would help here in this section. + +<--- Page Split ---> + +Results section 3 + +"To investigate a potential relationship with clinical scores, we correlated decoding performances from the most predictive channel contrasting neutral vs. positive/negative per patient with Beck's Depression Inventory (BDI) at time of recording and after six months of chronic DBS. Decoding performance correlated with DBS induced improvement in BDI scores (rho=0.79, p=0.01), but not + +with concurrent symptom severity (Fig. 3f)." + +- this is tough to follow - why would the decoding performance in emotional task be expected to correlate with depression severity? Is the hypothesis that the more depressed one is, the more task related emotional valence is "decodable"? the opposite seems more likely, that is depression would blunt ones ability to distinguish emotional valences. + +"... connectivity fingerprints seeded from LFP channel locations were correlated with channel specific decoder test-set performance". - for a nonexpert - how are connectivity fingerprints quantified so as to feed into a correlation? A sentence on this would help. + +Figure 3e - even zooming in, its hard to read the feature labels or understand what they mean. Legend refers to a part "I" but don't see that panel in the figure. + +Results section 4 briefly explain what an F1 score is + +Discussion: + +"Nevertheless, decoding performances were investigated in the presence of clinical brain stimulation in two out of three use cases, namely STN- DBS for PD and responsive neurostimulation for epilepsy" - is this actually true for RNS? My understanding is that RNS is a "half duplex" device, that is it senses, provides preprogrammed stimulation train when an event is detected, then returns to sensing mode. It does not actually sense during stimulation. + +"The network description however, is static in nature, while symptoms wax and wane. Brain signal decoding may help these networks to come to life in a dynamic closed- loop neurostimulation approach by informing both decoding and stimulation models of symptom specific circuits to optimize symptom decoding and adaptation of stimulation right at the time they occur" - not sure I get the meaning here. This seems to be a discussion of the advantage of combining connectomics (static) with brain signal decoding (dynamic) to produce something that hasn't been done before, but the sentence is lofty enough that it loses the reader. + +Version 1: + +Decision Letter: + +Dear Dr Merk and Prof Neumann, + +Thank you for your revised manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants", which has been seen by the original reviewers. Please apologise for the slow turnaround time, that is related to a combination of event among which the team being severely understaffed for several months, making hard to be efficient in processing all the files, and the need to chase reviewers or recruit new ones. In their reports, which you will find at the end of this message, you will see that the reviewers acknowledge the improvements to the work but one of them raises additional criticisms that we hope you will be able to address. + +In particular, we would expect that the next version of the manuscript provides clear and complete methodological reporting, and convincing discussion about the advancement provided by the proposed toolbox. + +As before, when you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that explains the main improvements included in the revision and responds to any points highlighted in this decision. + +As a reminder, please follow the following recommendations: + +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +\* If you and your co- authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the + +<--- Page Split ---> + +reason(s). + +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +We hope that you will be able to resubmit the manuscript within 15 weeks from the receipt of this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +We look forward to receive a further revised version of the work. Please do not hesitate to contact me should you have any questions. + +Best wishes, + +Valeria + +Dr Valeria Caprettini Associate Editor, Nature Biomedical Engineering + +Reviewer #2 (Report for the authors (Required)): + +The goal of having "plug and play" decoding algorithms for closed loop DBS is an important one. Likewise, having a toolbox that can implement these algorithms and distribute open- source would be valuable. However, the paper does not give enough information as to how this toolbox implements a plug and play algorithm. Multiple steps still seem to be involved, including coregistering individual's imaging to MNI space, and placing the electrodes in this coordinate space. This, as mentioned by the authors in their rebuttal, is not trivial, especially when taking into account brain shifts due to opening the dura. No mention of how this substantial shift would be accounted for. The authors state that one of their goals is to "facilitate multicenter clinical trials ...and democratization of the methodological approach." Yet, the descriptions in this paper are far too vague and lacking in specific methods for even those engineers familiar with BCIs to be able to implement, let alone for clinicians to be able to even comprehend the basics. And importantly, this procedure of coregistering would take significant time - indeed, in our experience, much more time than building a very simple decoder of movement vs. rest for an individual, which could be done in less than 5 min (including recording and automated decoder building). Either way, this will require some time for the clinician or a technologist. Since this (across- patient decoding) appears to be the biggest goal of this paper, the authors need to make a much stronger case (including empiric evidence of time to perform and compute the different steps for a given patient, as a clinician would do it, and showing this is truly less than recording move vs rest for 3- 5 min and building a very simple individualized decoder, rather than vague estimates as in the rebuttal) for why this is better than individual decoders. Overall, the paper still assumes too high of an expertise in many disparate and specific domains to be applicable to a broad audience. + +## Major issues + +1. The central theme of the paper, the connectivity-based decoding, is still not explained clearly enough to understand. The additional supplementary figures help slightly, but they still dance around, and gloss over, the main concerns I had previously - the "connectivity values", correlation of them with "decoding performance (what is this??)", and "optimal decoding map" are not clearly defined. SF4 shows correlations with 1000 functional connections - does this mean they are averaged over all participants? What does decoding performance for a single electrode mean? Does that mean you're building single-channel decoders? If not, this does not make sense. And how are you correlating one value with a connectivity map (which is a whole vector for a single electrode)? SF5.c similarly needs much clearer explanation. (What is a connectivity template? What are R1-R6? What is being correlated with what?) This needs much better explanation if you want people to understand how to use it. Examples would help. + +2. The performance, especially across cohorts, and ability to extrapolate to new patients, is somewhat oversold in this paper, even if this performance is substantially better than previous studies. In particular, when the leave-one-cohort-out accuracy is barely above chance (~0.6), it suggests that even subtle differences in movement types will lead to poor decoder performance across patients. That would seem to not be very practical for a patient wanting to do many different types of movement, and thus "plug & play" would not work very well. Even ~80% accuracy is highly unlikely to be good enough for most patients - think about how frustrated you would be if your computer cursor did not work correctly 2/10 times. + +3. The revised paper still leans too heavily on the term BCI. The BCI society's working definition was not intended to include + +<--- Page Split ---> + +closed- loop DBS as a BCI. While philosophically cDBS could fit in this definition, the vast majority of BCI researchers do not consider it to be a BCI, and doing so could cause a host of logistical issues. Not to mention confusing many non- experts. + +4. Methods are still incomplete. The description of movement detection is better, but the performance description:". balanced accuracy of \(0.8 / 0.98\pm 0.07 / 0.04\) for single sample/movement detection" still could be clearer. Is the second value for the 300 ms consecutive "rate?" If so, then state that more clearly. Also the following sentences are unclear: "A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block. It's important to note, however, that this measure addresses only the movement class and has no predictive value of rest segments." What does it mean to only "address the movement class"? It's a binary classification, so how is it not predicting rest vs movement? Or does this have something to do with the fact that there are now 3 bins and not all of them may be movement at that same time? Also is this balanced accuracy or not? If not, it should be, to make fair comparisons between 1 and 3-bin decoders and to avoid biases of too many false positives. Introducing a 300 ms delay (effectively) to movement is also not trivial and is long enough that it could impair movement precision (due to feedback delays) for patients. This should be discussed. + +5. "processing steps to mitigate DBS artifacts including bandpass filtering and period-based DBS artifact removal did not improve, but instead aggravated this deterioration" The fact that artifact removal significantly worsened decoding accuracy is a potentially significant issue. The point was not to improve accuracy; the point was to see that accuracy did not worsen with removal of artifacts, but in fact it did worsen in most cases. That is concerning that a good portion of your "movement" decoding was really artifact decoding. This could lead to false positives. This deserves much more discussion and tempering of conclusions than is currently in the paper. + +6. The sensory cortex issue is insufficiently addressed in the manuscript. This needs to be acknowledged in the discussion more clearly than talking about interplay of motor and sensory information vaguely. + +7. Statistical rigor (at least in reporting) is still lacking. Many results are still described as "above chance", sometimes with p values, without statistical methods described. + +8. The phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." is still opaque. What does this mean? + +Minor issues: + +Regarding differentiating from other toolboxes - the first point about offline and online using the same routines is not unique - FieldTrip also enables this. + +"Neuromedicine" is not a word. The more appropriate term seems to be neurology. + +Reviewer #3 (Report for the authors (Required)): + +the authors have responded quite thoroughly to reviewer comments and improved the manuscript. my summary of the results is part of my initial review so is not reproduced here. + +Version 2: + +Decision Letter: + +Dear Dr Merk, + +Thank you for your revised manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants". I went back to Reviewer #2 for them to review your point- by- point rebuttal, but at this time they were unavailable for reviewing. I found another reviewer with expertise in computational neuroscience and surgical experience in brain implants, and I provided them with the previous review reports as well as your point- by- point answers. You can find their report at the end of this message, and you will see that the reviewer acknowledges the value of the work, provides useful suggestions of how to make the story more appealing and raises a few additional technical criticisms that we hope you will be able to address. In particular, we would expect that the next version of the manuscript provides further analysis of some of your data to strengthen the evidence in support of the possibilities that your approach offers, as per the many suggestions of this new report. + +As before, when you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that + +<--- Page Split ---> + +explains the main improvements included in the revision and responds to any points highlighted in this decision. + +As a reminder, please follow the following recommendations: + +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +\* If you and your co- authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the reason(s). + +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +We expect that you will be able to resubmit the manuscript within 15 weeks of receiving this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +We look forward to receive a further revised version of the work. Please do not hesitate to contact me should you have any questions. + +Best wishes, + +Valeria + +Dr Valeria Caprettini Senior Editor, Nature Biomedical Engineering + +Reviewer #4 (Report for the authors (Required)): + +I begin by paraphrasing the authors' problem statement. Problem 1: modern approaches to neural decoding use modern ML algorithms, which are data hungry. Collecting enough data in patients is hard, and there is a dearth of frameworks to facilitate transfer learning between patients in low- data regimes. Problem 2: the authors want a framework to extract neural signals. Problem 3: most experiments record data from only small areas of the brain and fail to incorporate networks of neural activity that give rise to signals. To address all three issues, the authors describe a new software package. The claims are that the software package is (i) a real- time BCI platform, that (ii) implements multiple novel signal analysis processing methods, and (iii) implements a method for transfer- learning using anatomical and connectome data. They further motivate how their software package is useful with three real- world examples: transfer learning with ECoG recordings in patients undergoing DBS (and epilepsy monitoring, Fig 2); retrospective analysis of intracranial signals to predict findings in a study of DBS for depression (Fig 3); and retrospective analysis of data collected from RNS recordings (Fig 4). + +I am a neurosurgeon and I have previously published software packages in BCI methods, analysis of intracortical signals, and articles on RNS signal analysis. I am familiar with Dr. Horn's Lead DBS platform and have examined some of its methods in detail. In summary of my review to follow, I think this paper's broad appeal is the method that combines connectome information to assist with neural decoding in a low- data regime. As with many scientific ideas, it is both elegant and profound. By contrast, I think the framing of this paper through the lens of a software platform is a distraction. Below, I comment extensively on the framing of the authors' results and provide suggestions for further analyses that would further highlight the excitement and broad- scientific appeal. + +1) A new method of transfer learning that uses imaging data (resting state fMRI and anatomical MRI) to boost intracranial neural decoding performance in low data regimes is compelling. To that end, I found Table 1, Fig 2l, and Fig 2m cool. I can record data from patients in the EMU and/or previous patients in the OR, and then use those recordings to learn hyperparameters for my decoder for a movement task in the OR for a new patient. By using CEBRA, you have now taught me that there exists a cross-person neural manifold for movement, informed by where I am physically recording on the brain (and how this part of the brain is connected to other parts, over multiple participants). + +<--- Page Split ---> + +But - the whole point of transfer learning in a neural decoding framework is to save time by priming a decoder with hyperparameters in a low- data regime. For instance, isn't the value of the approach obviated if it only takes two exemplars of movement (and movement onset) to get comparable decoding? Show us this is useful by plotting performance as a function of time for the participants, and especially the "real- time decoding" PD patient, to point out that decoding performance happens out of the box with your new method. In fact, the most compelling demonstration of the method would be to show that leveraging your approach would improve decoding further beyond what you would have achieved from just the data from that patient. In other words, demonstrate evidence that "For a real- world clinical application this means that every implant would need to undergo tedious model training sessions, which could be a burden to both patients and medical staff and may hinder a broad clinical adoption." + +2) Here's another way you could convince me this approach works: suppose that one of the PD patients implanted had abnormal cortical anatomy (which happens not infrequently). For this patient, supposed that I had an ECoG strip where I thought the contacts were on the pre- and post-central gyri (based on imaging), but using your transfer-learning approach I had missed by a gyrus, and had landed on the MFG and the pre-central gyrus instead. Could your approach convince me that I've made a mistake in identifying the anatomy? Placing ECoG strips in the OR through a burr-hole during DBS is a blind procedure and needs to be confirmed with an intra-operative spin (at least in my hands), which is time-consuming and exposes the patient to radiation (which is challenging to justify if the research program itself is motivated through a non-significant-risk patient consent). Can your system save time for optimizing ECoG placement by providing an ongoing estimate of where the ECoG is likely located on the brain? + +3) The most compelling part of Fig. 3 is the utilization of the image-registration method incorporating connectome information that allows you to perform out-of-patient prediction for optimal electrode selection, which in turn has direct clinical relevance. This is a beautiful story. You showed me that the connectome method was predictive of decoding performance. This story could perhaps culminate in you telling the reader that this post-hoc information predicted that the contacts were correctly or incorrectly chosen for each patient, and then making suggestions that correctly choosing the right electrode would have had a tangible clinical impact. Also, the "sweet spot" in Fig 3h is covered by the left hemisphere, and I can't see the cingulate (unless I misunderstood, and Fox 2014 stimulated the DLPFC?). + +4) Describing this paper as a real-time BCI platform is a distraction. To start, I'm not sure we agree as to what real-time means. Most people think that real-time means that there are deterministic bounds on program cycle execution and OS context switches. So, to make the claim that this system is real-time, you must do the following: (1) put bounds of performance by examining jitter and latency - I suspect this will be hard, because I assume the platform is designed to run in Windows (since I find .bat files in the github code) and as far as I know, Windows doesn't provide soft real-time guarantees; (2) characterize how long the system can run before you run out of memory (unless you've solved this issue by writing drivers that move data from memory to disk in a way that doesn't interrupt data flow); and (3) characterize real-time performance as a function of algorithm complexity and channel count (i.e., beyond a handful of channels and a binary classification problem). These would be the minimum requirements before I would re-engage with this claim. + +However, I would further argue that if you now want to sell a real- time software package as a high- impact publication in 2024, then you're obliged to do much more: (1) ensure that it works in multiple operating systems, (2) account for multiple languages (python is exciting right now, but matlab was exciting a decade ago), (3) have hooks to plug into multiple open source frameworks (like neurodata without borders), (4) have plans for long- term maintenance and naming conventions for code, (5) demonstrate that the system works outside of a small group of collaborating neuroscience labs, etc. In summary, I strongly disagree with your claim that py_neuromodulation is a "...toolkit for invasive brain signal decoding for closed- loop neuromodulation that emphasizes rigorous real- time compatibility and reproducibility." This is an unsubstantiated claim. Please de- emphasize this claim in the paper. + +5) I find this sentence problematic: "... a unique and novel feature set that included temporal waveform features, such as discharge prominence, sharpness, decay and rise time, and peak and trough interval in addition to traditional oscillatory FFT features." Is the authors' claim that the peak and troughs-based analysis of local field potentials has never been described before? If you believe this is true, then how have you yourselves characterized these features? What's the electrophysiological relevance of these features that teaches us something new about the brain? Why would these metrics have broad appeal, and why would I as a biomedical engineer know which to pick? In summary, if the main claim of the paper is that these spike wave forms are novel and interesting and useful, then they have been insufficiently characterized to be relevant to a broad scientific audience. In my opinion, characterizing these in detail is a paper into itself, and shouldn't be conflated with the main compelling scientific idea. + +6) I don't understand how Figure 4 addresses the problem statements of your paper. The motivation for the analysis is "... to inspire new ways to improve seizure detection accuracy by constraining the decoding platforms to the specifications of clinical brain implants and suggesting improved parameters from offline predictions that are implementable and testable through the clinical patient data management systems (PDMS) provided by Neuropace." Returning to the problems you're solving, as introduced by the introduction of the paper, this figure does not (Problem 1) incorporate data between patients to solve a low-data regime problem, nor (Problem 3) incorporate connectome information between patients. While it does (Problem 2) apply ML algorithms to different a cornucopia of uncharacterized electrophysiologic features, it feels like a fishing expedition. Further, the per-day limitations of data collection with RNS are substantial, as the PDMS available is necessarily biased by whatever the clinician has previously identified to be a seizure (unless I missed somewhere that you're doing long-term data streaming) – I am highly skeptical of the consequence of the findings without seeing the impact (neurophysiologic or clinical). I'm happy to be convinced otherwise, but right now Fig. 4 doesn't prove your paper's point. + +<--- Page Split ---> + +Here's one way that would make the presentation more compelling to the reader. Hopefully, the leads in patients with epilepsy are placed in critical parts of the seizure network. Surely, across 9 patients, some networks have been sampled more than once. Hence, here is a wonderful opportunity to showcase the connectome approach to decoding. Can your approach leverage connectome data to assist with seizure prediction? Can you tell me which network I'm in, to help me with optimal lead selection? Or, can you tell me that a set of parameters determined offline for person A will likely work for person B, because they're targeting the same seizure network? + +Minor points: + +7) The authors have told me that Lead DBS was, "optimized in Lead-DBS for subcortical structures." This matches my experience as well – the default settings (which again, the authors recommend) have both whole-brain and sub-cortical masks that are applied in series to emphasize this fact. Have they quantified the performance of LeadDBS on non-linear deformations of cortical anatomy, in the same way that Dice coefficients have been computed for subcortical structures? If so, can you point me in the direction of a paper that validates cortical anatomy between patients? If not, then can you comment about why not validating the default settings of the program do not impact the quality of your transfer learning approaches? If this question isn't relevant, please explain why (because this point isn't clear to me). + +8) "In brief, Lead-DBS uses preoperative MRI and postoperative CT scans for co-registration and normalization to MNI 2009b NLIN ASYM space." This is incorrect, though I am happy to be corrected by Dr. Horn. There are many options available for using standard spaces. That's one of the really nice things about the software. In fact, Fig 4a proves my point! + +9) On 23 May 2024, the BCI Society voted to accept this definition of a BCI (https://bcisociety.org/bci-definition/): A brain-computer interface is a system that measures brain activity and converts it in (nearly) real-time into functionally useful outputs to replace, restore, enhance, supplement, and/or improve the natural outputs of the brain, thereby changing the ongoing interactions between the brain and its external or internal environments. It may additionally modify brain activity using targeted delivery of stimuli to create functionally useful inputs to the brain. Most people I know consider a BCI as the first sentence. To my chagrin, neuroprosthetics that meet the definition of the second sentence are now part of the story, so arguably, closed-loop DBS and RNS systems are now under the umbrella of what makes up a BCI. Nevertheless, approach with caution, as you will aggravate some readers with this word choice. For context, neither FDA leadership nor the iBCI-CC consider closed-loop DBS/RNS systems to be BCIs. + +10) Perhaps you meant, "closed loop" rather than "real-time" in the paper? + +11) Why is it so necessary to be so deprecating to the clinical hardware that we have, when the paper itself hasn't created new hardware? Said another way: this is unnecessarily grandiose and sets a weird tone for the paper: "The clinical neurosciences stand at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology." + +12) Consider switching Supplementary Figure 5 and Figure 1. + +13) The newly added text that goes into tremendous (and important) detail about data analysis describing Figure 2 should go to the Methods. + +14) "We may speculate that neurodegeneration in PD may impact neural encoding of movement, which may also impede machine learning based decoding performance". Patients with worse UPDRS scales may have less brain. Is your decoding performance related to the ECoG strips not actually sitting on the brain, or perhaps have much more air than snuck in during the case? + +15) "Divining appropriate settings" in describing RNS programming is unnecessarily pessimistic. The very fact that patients often do get better, either tells us that clinical heuristics are useful, or a significant subset of the high-dimensional parameter space is useful. + +Reviewer #4 (Remarks on code availability): + +The code documentation is variable. Some parts hand- hold the user through the process and are easy to follow, and others are slapped together to make a point in OS- specific configuration files. I didn't try running the code. + +Version 3: + +Decision Letter: + +Dear Dr Merk, + +<--- Page Split ---> + +Thank you for your revised manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants". Having consulted with Reviewers #4 (whose comment you will find at the end of this message), I am pleased to write that we shall be happy to publish the manuscript in Nature Biomedical Engineering. + +We will be performing detailed checks on your manuscript, and in due course will send you a checklist detailing our editorial and formatting requirements. You will need to follow these instructions before you upload the final manuscript files. + +Please do not hesitate to contact me if you have any questions. + +Best wishes, + +Valeria + +Dr Valeria Caprettini Senior Editor, Nature Biomedical Engineering + +Reviewer #4 (Report for the authors (Required)): + +Please see attached PDF document. + +Reviewer #4 (Remarks on code availability): + +I have partially reviewed the updated code base. Did not try installing or running it. + +Version 4: + +Decision Letter: + +Dear Dr Merk, + +I am happy to inform you that your manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants", has now been accepted for publication in Nature Biomedical Engineering. + +Over the next few weeks, the figures will be checked for production quality, the text edited to ensure that it conforms to house style, and the manuscript typeset. + +Our Articles are published about 40 days after the acceptance date (we recommend that you inform your institutional press office of this timeframe), and you will be notified of the actual publication date a few days in advance. Articles can be published any working day of the week, and are pushed live shortly after 10 am London time. + +Publishing agreement. You will be asked to digitally sign a publishing agreement (grant of rights). 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Recipients of the link who are subscribers will also be able to download and print the PDF. + +Thank you for having submitted this work to Nature Biomedical Engineering. + +Best wishes, + +Barbara Cheifet Editor Nature Biomedical Engineering + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Reviewer comments were appended in black, author replies to the reviewers were made in blue and changes in the manuscript were highlighted in green font color. + +Reviewer #2: + +This manuscript describes the use of a Python toolbox for decoding brain signals for the purposes of neuromodulation. The basic idea is to bring together multiple existing methods for feature extraction, dimensionality reduction, and decoding to try to improve on methods that are currently in clinical use or in clinical trials. It also describes some methods to use structural connectivity to help perform decoding across patients without having to obtain new training data. This is all useful; however, it is not clear how much of this is actually new. They do here show more examples of potential use cases in large datasets (DBS in patients with PD and depression, RNS in epilepsy patients), and this is useful to show the potential of using more techniques to optimize closed- loop neuromodulation. However, the authors have shown the connectivity "fingerprint", and many of their other methods (and ability to decode force in PD patients) in their prior eLife paper, and it appears that the toolbox was also created for that paper, since it cites that paper. None of the techniques in the toolbox are novel, though it is certainly helpful to have them all in one place and open- source (which is a strength). Further, many of the techniques are not clearly described, so it is difficult to assess their importance and, since the paper's main theme appears to be the toolbox itself, it seems to fall short of its main purpose- to make these techniques more user- friendly and widely used. Overall, this seems to be an incremental advance. More specific concerns follow below. + +We thank the reviewer for their valuable feedback. Through this, we have more clearly identified the critical points that we hope to convey with the present manuscript. We would like to highlight three key aims as follows: + +Aim 1. First and foremost the aim of the manuscript is to highlight advances that brain signal decoders can provide for invasive neurotechnology across disciplines of neuromedicine. Aim 2. We formalize and describe the methodology to achieve those advances in an open- source toolbox py_neuromodulation. Aim 3. We illustrate how the two biggest innovations in deep brain stimulation research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility. + +This is now clarified in the last sentence of the introduction: + +"In this paper, we aimed to a) highlight the clinical utility of brain signal decoding advances in a large cohort of patients across thousands of recording sources from invasive brain implants within three key areas of clinical neurotechnology innovation: movement disorders, psychiatry, and epilepsy; b) formalize and describe the methodology to achieve those advances in an open- source python software called py_neuromodulation; c) illustrate how the two biggest innovations in deep brain stimulation research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility." + +In the following we would like to elaborate on these aims: + +<--- Page Split ---> + +For aim 1, we have chosen three critical frontiers of brain health and key areas of neurotechnological innovation, namely: movement disorders, depression and epilepsy. In these, areas we show a series of previously unattained achievements, including the first description of a generalizable movement decoder (for discussion on clinical relevance see our reply to comment 4), the characterization of temporal dynamics of emotion decoding and its' relationship to brain circuits underlying good DBS response in depression and finally the demonstration that offline optimization can be used to improve detector parameters for embedded devices for seizure decoding in epilepsy. Despite the fact that invasive neurotechnology such as deep brain stimulation is now being used for decades, there are still no clinical devices that capitalize on the use of machine learning and brain signal decoding. To clarify the intellectual merit with respect to the referenced eLife paper, we would like to point out that in the present manuscript we did not decode grip- force from motor cortex in 11 patients with PD, but instead decoded general presence of movement across 56 patients from multiple cohorts including both Parkinson's disease and epilepsy patients, performing different movement tasks, with brain activity recorded from different brain areas. Through this, we demonstrate for the first time that decoding movement across cohorts and brain areas is possible and showcase the superiority of a novel contrastive learning based decoding algorithm CEBRA that has gained widespread attention in animal studies but was never used in humans. And we investigate to what degree high- frequency DBS can impair decoding. All of these aspects have not been addressed in the eLife paper, and as pointed out by the reviewer, the movement decoding is only one use- case described. Importantly, through the revision and in response to the valuable feedback from the reviewers, we have now added an additional case where pretrained models were used to adjust stimulation delivery in real- time, again a methodological advance that was not reported before. + +For aim 2, as pointed out by the informed reviewer, we formalize and describe the methodology to achieve those results in the open- source toolbox py_neuromodulation, which we have developed through a transatlantic US- German collaborative funding initiative by the National Science Foundation and the German Ministry of Education and Research in 2018- 2024. Similar to the development of other toolboxes, such as Lead- DBS (www.lead- dbs.org), which the (co- ) authors have lead and contributed to, we have first focused on the implementation of a useful set of tools that supports our research, such as described in the eLife paper, that was kindly read and cited by the reviewer. We are truly thankful for the time the reviewer has taken to scrutinize and support the improvement of our manuscript and we hope that we can make our case, that indeed, major milestones have been met in the further development process of this toolbox and we believe that it is now mature enough to deserve a dedicated publication. To be specific, we have vastly extended the feature extraction algorithms in the toolbox to modalities inspired by basic science, such as waveform shape parameters, that can significantly contribute to emotion decoding as shown in use- case 2. The importance of temporal characteristics of electrophysiological brain data was previously described (Voytek et al 2017) but never used for brain signal decoding before. The following graphic illustrates the precision of our temporal waveform shape characterization for brain signal decoding: + +<--- Page Split ---> +![](images/Supplementary_Figure_8.jpg) + +
Supplementary fig. 8 Exemplary temporal waveform-shape features. Different characteristics of band-pass filtered oscillations or raw-signal can be extracted: peak and troughs amplitudes, prominence of troughs to peaks, intervals between troughs or peaks, sharpness, decay and rise times of identified peaks and troughs, and the 5 ms width of peaks and troughs.
+ +But our extensions since the eLife paper go far beyond this, as we have developed entirely new aspects, including methods for preprocessing, different artifact rejection methods, additional feature modalities and post- processing methods. In the current version fourteen different feature modalities, including Hjorth parameters, temporal waveform shape, characterization of periodic and aperiodic components with FOOOF (fitting oscillations & 1 over f toolbox; https://fooof- tools.github.io/fooof/; Donoghue et al. 2020, Parameterizing neural power spectra into periodic and aperiodic components. Nature Neuroscience, 23, 1655- 1665. DOI: 10.1038/s41593- 020- 00744- x), oscillatory burst dynamics, line length, coherence non- linear dynamical features and bispectrum based features were additionally implemented. This culminated in hundreds of pull requests, more than a thousand commits and novel developments from multiple international internal and external contributors. The toolbox now standardizes and simplifies electrophysiological signal processing by a parametrization file, providing an end- to- end pipeline parametrization without the need to adapt any programming code. This is all embedded in a real- time compatible framework that interfaces with electrophysiology and brain stimulation hardware. Importantly, we have further interfaced our toolbox with one of the most advanced decoding + +<--- Page Split ---> + +algorithms in basic neuroscience that builds on contrastive learning (Schneider, S., Lee, J.H. & Mathis, M.W. Learnable latent embeddings for joint behavioral and neural analysis. Nature 617, 360–368 (2023). https://doi.org/10.1038/s41586-023-06031-6). Our paper indeed, is the first to report the use of this algorithm for a human application. Finally, we believe that the best evidence for the relevance and novelty of this toolbox is the fact, that since the upload of this preprint alongside the review process, first external contributors have already started to co- develop this open- source endeavor with relevant extensions such as improved computational performance for bursts (pull request #286), temporal waveform shape analysis (pull request #288), and parallelized multiprocessing of features (pull request #290). + +For aim 3, we illustrate how the two biggest innovations in DBS research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility. The reviewer is correct that we have indeed applied retrospective connectomic analyses in our previous paper. This has laid the foundation to pursue the concept that this could be a fruitful approach for prospective channel identification and general brain circuit discovery. Within the toolbox we have since added modules for cross- validation using pre- computed whole- brain connectivity. With the present manuscript, we demonstrate for the first time, that combining neurophysiology with connectomics enables the development of generalizable plug & play decoders across patients. Moreover, we highlight how the brain network associated with optimal emotion decoding relates to brain networks with optimal treatment. In the future, we envision a real- time adaptation of brain stimulation algorithms to precisely defined response networks with relation to the presence of symptoms. Recently, co- authors of this study have demonstrated that optimal stimulation networks can vary for disease and symptoms (e.g. see Hollunder, B., Ostrem, J.L., Sahin, I.A. et al. Mapping dysfunctional circuits in the frontal cortex using deep brain stimulation. Nat Neurosci (2024). https://doi.org/10.1038/s41593-024-01570-1). In the future, the work presented in this manuscript may inspire a closed- loop neuromodulation strategy at the brain network level, where connectomics informed brain signal decoders indicate symptom presence that orchestrate control policies for algorithmic current steering to target the optimal symptom network in real- time. To further illustrate the methodological framework, we have now added a methods figure to help guide the reader: + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + + +Supplementary fig. 5 Connectomics- based neural decoding without patient- individual training. (a) Estimation of a patient- individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain- wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template + +<--- Page Split ---> + +associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. + +Moreover, we have added an API example in the methods section: + +For applying the optimal connectivity decoding without patient- individual training, the electrode contact MNI coordinates need to obtained beforehand (Randazzo et al 2016, Soper et al 2023), and then utilized for obtaining the corresponding connectivity fingerprints from either the Lead- DBS Lead- Mapper toolbox (Neudorfer et al 2023), or by a pre- defined grid. Py_neuromodulation provides a method for obtaining matching points from a pre- defined cortical hull grid (n=1025 points) or whole- brain grid (1236 points). The computed grids can be downloaded from a public repository (https://doi.org/10.5281/zenodo.10805915) and utilized through the following API: + +from py_neuromodulation import nm_RMAP import numpy as np + +mni_coords = [[10, 40, 20], [50, 14, 12]] # definition of MNI contacts + +ch_sel = nm_RMAP.ConnectivityChannelSelector( whole_brain_connectome=True, func_connectivity=True + +1 + +# retrieve connectivity fingerprints for passed MNI coordinates fps, grid_idx = ch_sel.get_closest_node (mni_coords) + +# computation of optimal connectivity correlations corrs = ch_sel.get_rmap_correlations (fps) + +recording_contact_use = np.argmax(corrs) + +The added pre- computed functional and structural connectivity profiles are further referenced to in the methods section: + +Alternatively, single ECoG or depth electrode channels can be selected through optimal connectivity. Functional and structural connectivity measures can for example be calculated within the Lead- Mapper tool of the Lead- DBS toolbox (Neudorfer et al. 2023) or via pre- computed connectivity profiles based on a cortical hull or whole- brain grid (DOI: 10.5281/zenodo.3814723). + +We hope that this clarification and our detailed replies below will alleviate some of the general concerns the expert reviewer has raised and note that we have also taken their criticism with regard to the lack of clarity of the methods description very seriously. We worked very hard to further improve upon this aspect of the manuscript, by adding supportive information in main text, methods and extended data, including new figures such as the ones highlighted above. Beyond these direct changes in the submission, we have further significantly improved the documentation page that accompanies our toolbox (https://py- neuromodulation.readthedocs.io/) including tutorials on all critical points mentioned in this paper, including advanced feature analyses and connectomic applications. + +Major concerns: + +<--- Page Split ---> + +1. It is not clear why the manuscript starts out talking about BCIs but then switches to closed loop neuromodulation. These are not the same thing, and there is enough confusion in the literature about what constitutes a BCI. The widely accepted definition involves some volitional modulation, which is not what is being described here. It would be preferable to not call this a BCI, but rather other methods of closed-loop neuromodulation. + +We thank the reviewer for this valuable comment and agree that our previous manuscript had shortcomings in the precise definition between closed- loop neuromodulation and brain computer interface approaches. Through this revision, we would like to take the opportunity to elaborate our viewpoint further as this comment of the reviewer touched upon a pivotal issue that is currently at the forefront of global discourse in the field. As noted by the reviewer, the precise definition of BCI is a subject of ongoing debate among experts, which has most recently inspired a community driven open innovation in science approach by the international BCI society, to which we contribute (see https://bit.ly/BCI- Definition). + +The foundation for this redefinition is laid based on a thoughtful and widely accepted precedent by Wolpaw & Wolpaw 2012: "A BCI is a system that measures CNS activity and converts it into artificial output that replaces, restores, enhances, supplements, or improves natural CNS output and thereby changes the ongoing interactions between the CNS and its external or internal environment." + +The current initiative proposes a slightly adapted redefinition that opens the doors for wider applications. In the following, we will cite a paragraph from the information of the BCI society as referenced above: + +"The definition of Wolpaw and Wolpaw, as well as the suggested alternative definitions, do not require the measured brain activity to contain information about the ongoing intention of the user, because this would exclude technologies referred to as passive BCIs from the definition. The consequence of this is that technologies such as closed- loop neuromodulation (e.g., responsive DBS) may fall under the definition of a BCI. Suggestions on the need to distinguish between these types of technologies, and how to differentiate between them, are welcomed." + +This does not mean that the reviewer is not right in their definition, as they have pointed out, there are many different valid opinions present. Nevertheless, we would like to present a case for keeping the term, even when applying the more strict definition of BCI that the reviewer favors including volitional modulation. In a different study, (Köhler et al. 2023, under review) we have investigated to what extent the most common neurotherapies for Parkinson's disease, dopamine replacement and DBS, can modulate the initiation of volitional action. In brief, we trained decoders with the py_neuromodulation toolbox described in this paper, to quantify latencies from movement intention to motor execution. We found that both dopamine and DBS can shorten these latencies, providing the foundation for a closed- loop neuromodulation therapy for the support of volitional action initiation based on brain signal decoding. In this example the volitional modulation, the intention to act, would activate the neurotransmitter implant to support the patient to perform their movement. We believe that this closed- loop neuromodulation application could be considered to lie within the BCI definition that the reviewer favors. + +<--- Page Split ---> +![](images/Supplementary_Figure_1.jpg) + +
Figure from Köhler et al. Dopamine and DBS accelerate the neural dynamics of volitional action in Parkinson's disease. bioRxiv (Cold Spring Harbor Laboratory) (2023). doi:10.1101/2023.10.30.564700. Under review. (A) Features of a single motor cortex channel averaged across trials. (B) Classifier outputs averaged across subjects. Classifier outputs of electrocorticography (ECoG) and subthalamic local field potentials (STN-LFP) differed between \(-2.2\) to \(1.7\) s (OFF therapy), \(-1.6\) to \(1.6\) s (ON levodopa) and \(-1.0\) to \(0.9\) s (ON subthalamic deep brain stimulation [STN-DBS]; all \(P\leq 0.05\) , cluster corrected). Data are represented as mean \(\pm\) SEM. (C) Time of motor intention of single subjects derived from ECoG classifier outputs. (D) Time of motor intention derived from single-channel ECoG classifier outputs. Left hemispheric channels were flipped onto the right hemisphere. \(*P\leq 0.05\) ; \(**P\leq 0.01\) ; \(***P\leq 0.001\)
+ +Back to our current submission, as stated in our new introductory paragraph, we want to point out that we are at the brink of a new era in the treatment of brain disorders, where previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology, that can deliver closed- loop neurostimulation while adjusting to the individual symptoms of our patients in real time. We hope that the reviewer can see why some people would define this technology as brain computer interfaces. Certainly, we ourselves believe that the reviewers comment and the cited discussion can be understood as a supportive factor of the novelty and importance of our work. Hoping that the reviewer accepts our proposal to clarify that our approach combines both closed- loop neuromodulation and clinical brain computer interfaces, we have now adapted abstract and introduction of our manuscript as outlined below. However, given that the reviewer clearly is a more experienced expert in the field than we are, we are open to revise and exclude the term BCI in a further revision, should the reviewer remain doubtful that our approach is sufficiently clear or sensible. + +Highlighted changes to the manuscript: + +Abstract: + +"Advances in neurotechnology that combine closed- loop neuromodulation with brain computer interfaces promise an unprecedented spatiotemporal precision for the treatment of brain disorders. Decoding dynamic patient states from brain signals with machine learning is required + +<--- Page Split ---> + +to leverage this precision, but a standardized framework for invasive brain signal decoding from neural implants does not exist." + +## Introduction: + +"Neuromedicine stands at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology. Advanced neurotechnology has the potential to combine the unprecedented temporal precision of closed- loop neuromodulation with accurate decoding of patient states achieved through clinical brain computer interfaces (BCI). This provides the foundation for revolutionary neurotherapies that can adapt therapy to the individual situation and symptoms that patients are facing." + +"To overcome these roadblocks, we developed a modularized open- source software platform for invasive brain signal decoding in neurotechnology, bridging the gap between closed- loop neuromodulation and clinical brain computer interface approaches." + +2. Multiple other open-source toolboxes exist that have brain signal feature extraction, selection, and decoding algorithms included (e.g., FieldTrip). These are not even mentioned in this paper, and they clearly should be discussed and the advantages of this toolbox described clearly. + +We thank the reviewer for this valuable feedback and apologize for this lapse. We absolutely agree that acknowledgement of these important open- source initiatives that inspired and in part enable our toolbox is very important. In fact, the authors of the present paper have actively contributed to FieldTrip (Jonathan Vanhocke), MNE (Timon Merk, Victoria Peterson, Thomas S. Binns, Richard M. Köhler) and CEBRA (Timon Merk). Timon Merk participated in the 2021 MNE code sprint and made contributions to the MNE, MNE- Realtime and MNE- QT- Browser package. Furthermore, some of the authors organized a hackathon within the Transregional Collaborative Research Center TRR- 295, to further improve the useability of the recently presented CEBRA package, which resulted in multiple pull requests. Additionally, Thomas S. Binns and Richard M. Köhler added many of the MNE- connectivity core modules throughout multiple pull requests. Unlike these toolboxes, py_neuromodulation is specifically designed to enable invasive brain signal decoding from neural implants for real- time adaptation of therapeutic delivery. + +We now highlight these alternatives in the discussion and provide a comparison to the presented toolbox: + +## Discussion: + +"Several widely- used open- source toolboxes, such as Fieldtrip (Oostenveld et al 2011), MNE (Gramfort et al 2013), Brainstorm (Tadel et al 2011,) and BrainDecode (Schirrmeister et al 2017), exist for signal processing and brain state decoding. While all these tools contain valuable and extensive methods for electrophysiological data analysis, we would like to point out multiple key aspects of py_neuromodulation that uniquely positions it as a toolkit for invasive brain signal decoding for closed- loop neuromodulation that emphasizes rigorous real- time compatibility and reproducibility. Most importantly, all processing is optimized for invasive brain data and developed with the target of adapting therapeutic brain stimulation algorithms in mind. Therefore, offline and online signal processing are conducted using the exact same routines, by only replacing the data stream. Thus, any analysis performed based on py_neuromodulation features is real- time + +<--- Page Split ---> + +compatible. Second, all pipeline parametrization is conducted through shareable files, that eases comparison across processing workflows and allows for effortless reproduction of established parameter specifications. Feature extraction is standardized and contains predefined feature modalities that extend far beyond what is available in other toolboxes. Finally, our toolbox implements several methods that enable neural decoding without patient- individual training. For that reason, we implemented cortical and subcortical spatial interpolation methods, and whole- brain connectivity estimation in combination with electrophysiological decoding." + +3. The introduction could be clearer as to exactly what problem is being solved with these techniques. It keeps talking about BCIs and decoding, but the problem envisioned seems to be closed-loop neuromodulation. But this works fairly well. For example, the sentence (in Results) "A key problem for invasive brain signal decoding is the individualized localization of brain implants across patients, which significantly complicates the development of large-scale models..." What does localization of implants have to do with decoding? Decoding does not depend on location in any BCI literature. What type of large-scale models are being referred to here? Models across patients? This all needs more explanation. + +We would like to excuse the lack of clarity in the previous iteration of this manuscript, which we hope to alleviate with the present explanation and the corresponding changes in text. Yes, this sentence primarily refers to across- patient decoding. Overall, only a handful of studies have ever applied brain signal decoding in the context of invasive neuromodulation (see comprehensive review on all studies in our recent review article: Merk et al., 2022 https://doi.org/10.1016/j.expenurol.2022.113993). None of these studies report across- patient decoding approaches and most did not consider the relevance of electrode placement for decoding performance. In our previous publication in eLife however, that the reviewer mentioned above, we demonstrated for the first time, that grip- force decoding performance both on the level of cortex and the STN correlates negatively with anatomical landmarks of the recording location. + +This is not unexpected, as the expert reviewer is aware, the human brain exhibits considerable anatomical and functional variability across brain regions and individual subjects. What is important to consider in this regard is that unlike with EEG or MEG, the brain regions that are covered with invasive neurophysiology methods differ across subjects and used electrode types, leading to the following constraints: + +- Every patient's brain has unique anatomical features, including variations in the size, shape, and positioning of gyri and sulci. These differences necessitate individualized planning for electrode placement to ensure optimal coverage of the targeted brain areas while avoiding critical regions that could impact essential functions.- The brain's vascular anatomy is another critical consideration. Avoiding major blood vessels is paramount to reducing the risk of hemorrhage during electrode placement. This constraint can limit the possible trajectories for implanting electrodes, especially when targeting deep or hard-to-reach areas.- Variations in skull thickness and shape can also impact the approach and trajectory for placing ECoG and stereoelectrophagrapy electrodes. Accessing certain areas of the brain may be more challenging in individuals with thicker or thinner skulls or unusual skull shapes, requiring adjustments to the surgical plan. + +<--- Page Split ---> + +- Other patient-specific factors, including previous surgeries, co-existing medical conditions, and the patient's overall health status, can influence surgical planning. For example, a patient with a history of multiple brain surgeries may have scar tissue that complicates electrode placement.- Finally, there is surgical imprecision related to other factors such as movement artifacts in neuroimaging, brain shift through leakage of spinal fluid after opening the dura and mechanical alterations in surgical hardware, often related to sterilization, that can lead to deviations in the final surgical outcome from the planned/intended trajectory. + +To further demonstrate variability in ECoG implant locations across subjects in the use- case of the movement decoders, we created a new supplementary figure: + +![](images/Figure_unknown_1.jpg) + +
Supplementary fig. 1: Individual differences in ECoG electrode contact localizations across cohorts.
+ +The relevance of implant location for machine learning based brain signal decoding is further corroborated by a literal citation of an impactful publication in our field (Opri et al., Science Translational Medicine, 2019 https://doi.org/10.1126/scitranslmed.aay7680): "We observed that cortical placement was an important factor in our paradigm. Hence, we assumed that ET02 had the worst performance ... of the three subjects because of a less than optimal cortical placement. ... The cause behind the suboptimal placement can be found in the surgical avoidance of conspicuous blood vessels." + +The advanced neuroimaging approach to across- patient generalization that we present in this manuscript solves most of these aspects while having an additional major advantage. They work across all invasive neurophysiology recording approaches, including the complex differences arising from electrode architecture. When comparing subdural surface electrocorticography (ECoG) and stereoelectrophagaphy (SEEG), ECoG provides high spatial resolution over a broad area of the cortex but lacks access to deep brain structures. In contrast, SEEG provides three- dimensional sampling of brain activity, including deep structures, but with more localized coverage. + +The accuracy and generalizability of decoding algorithms depend on a thorough understanding of how implant localization interacts with signal patterns. This understanding is crucial for the development of large- scale models that can adapt to or accommodate the anatomical and functional diversity of the human brain across different individuals. + +<--- Page Split ---> + +This variability means that the optimal implantation sites for capturing high- quality signals that can be decoded into specific commands or responses may differ significantly from one patient to another. Therefore, understanding the precise location of these implants in relation to the functional areas of the brain is essential for interpreting the signals they capture. + +This variability means that the optimal implantation sites for capturing high- quality signals that can be decoded into specific commands or responses may differ significantly from one patient to another. Therefore, understanding the precise location of these implants in relation to the functional areas of the brain is essential for interpreting the signals they capture.Thus, our toolbox combines invasive signal processing and feature estimation for the use of machine learning for neural decoding while also providing a clear approach for neuroimaging- based consideration of individual electrode locations. Since invasive human recordings are rare, and commonly acquired with limited time duration, aggregating data across subjects through multi- center collaborations can enable the development and training of large- scale machine learning models that can generalize well across subjects. It is therefore necessary to standardize signal- preprocessing and feature estimation. Currently, different laboratories use different processing parametrization of invasive recordings. By standardizing real- time and offline analyses, results are made comparable across studies and centers, and could be utilized for building powerful generalizable neural decoding models. The individualized localization of brain implants constitutes one of the reasons why machine learning based brain signal decoding performances are not generalizable across subjects and centers. In addition, we aimed to extend electrophysiological feature domains by the use of whole- brain connectomics, which we show to be beneficial for decoding without patient- individual data. The reviewer states, that closed- loop neuromodulation works fairly well, which can be true on a single subject level, even though evidence that it does work is generally sparse, reported in a handful of papers often reporting results for as few as three subjects. As clinician scientists we are aware of the amount of time and refinement such successful reports on very few subjects require, which is way beyond what the clinical routine would allow for. Therefore, we are convinced that for broad clinical adoption of brain signal decoding in closed- loop neuromodulation, across- patient generalization will be a critical economic and ergonomic factor. Indeed, to the best of our knowledge, not a single report exists with respect to successful across- patient decoding in the context of closed- loop neuromodulation. We believe that providing rigorously reproducible methods to achieve this will be a critical cornerstone of future multicenter clinical trials on closed- loop neurotherapies. Such multicenter trials will bring entirely new challenges unforeseen by single center examples of brain signal decoders and BCIs in individual subjects that have never been scrutinized in a way that live up to the present standards of evidence- based medicine including double- blind randomized controlled trials with patient centered primary outcomes, such as quality of life. Our toolbox provides an early but impactful step towards this vision. + +We have now clarified the specific relationship of location and decoding accuracy in the introduction as follows: + +"Invasive recordings are commonly acquired from varying electrode locations. While non- invasive recordings can rely on standardized positions, placement of invasive electrodes is currently guided by clinical surgical needs. This point requires an algorithmic solution to include data for neural decoding from varying localizations." + +4. To say that calibrating a move vs rest decoder in each patient is a serious limitation and would hinder broad clinical adoption seems a bit exaggerated, given the time it takes to do the DBS implant itself. Calibration could easily be done intraoperatively, or in already scheduled calibration sessions in clinic, within each patient in a few minutes for this simple of a decoding measure. + +<--- Page Split ---> + +While the scientists in us sympathize with this statement, our own clinical experience tells us that that the difference in burden to adoption is economically and ergonomically relevant. Moreover, we provide movement decoding as a simple first proof- of- concept that will become more important when multiple dimensions of symptoms, side- effects and behaviors are to be decoded in our future vision of intelligent closed- loop neuromodulation. But to address the comment, we would like to discuss the most simple account suggested by the reviewer in the context of our movement decoding problem first. Starting with the potential opportunity to calibrate intraoperatively, we would first focus our argument on cost factors. A ten- minute block in a neurosurgical operation theatre requiring presence of a specialized team can very roughly be estimated to cost \(\) 3,000- \\(10,000\). This is why the current trend to perform DBS surgeries under general anesthesia (asleep DBS) without microelectrode mapping is not solely motivated by patient preference. Microelectrode mapping refers to the recording of multiunit activity for the neurophysiological identification of the target trajectory. A previous cost analysis of microelectrode mapping for DBS, which could be similarly time consuming as calibration of machine learning models, estimates the specific cost of microelectrode recording to \(\) 20,535.98\(, increasing the total cost of the surgery by\) 159\%\$ . Overall, microelectrode recording was estimated to more than double the cost of subthalamic nucleus deep brain stimulation for Parkinson's disease and more than triple the cost for unilateral and staged bilateral procedures simply because of the extension of surgery time (https://doi.org/10.1002/mds.23787). Even if the process would be shorter, it would require specialized equipment, trained staff and operation theatre time that are all excessively cost- intensive. These costs would burden healthcare systems and patients. Moreover, patient preference does lean towards asleep DBS and indeed in many instances awake DBS surgery is prohibited by cardiovascular risk factors or anxiety, rendering a potential intraoperative calibration session impossible, even if short and cheap solutions could be found. When it comes to scheduled postoperative sessions, we agree that this could be a potentially more viable solution, e.g. with a very rough estimable cost of \(\) 500\$ per session. For a research project with few subjects, this would not be a relevant barrier, but to a widely adopted therapy that could benefit more than 200,000 people already implanted with DBS devices, this cost could quickly scale to \(\) 100,000,000\$ excess cost. This cost could be avoided, if devices or approaches could be developed that patients can mostly handle on their own. This however, would burden patients and could be arguably deemed an even more difficult problem than the one we are aiming to solve. Having to deal with extensive training of devices would overwhelm many patients suffering from dementia in the context of their neurodegenerative disease, and we hope that the reviewer shares our intuition that if they had the choice, they would likely prefer a solution that does not require calibration. In summary, we believe that being able to provide pretrained models to a neurostimulator that may be implanted in thousands of patients, would have significant economical impact on healthcare costs and patient satisfaction, even for a simple movement decoder. Therefore, we are proud that our study provides the first open movement decoding model, which is published and openly available under a CC- BY license for precisely this purpose - alongside a rigorously reproducible methodological pipeline to implement it (DOI: 10.5281/zenodo.10794370). In the future, we envision to train and publish many other models that can decode brain states and symptoms of neuropsychiatric disorders, such sleep stages, tremor, dyskinesia, freezing of gait, tics, dystonic muscle contractions and more. If successful, this would revolutionize the democratization of machine learning for neurotechnology as I hope we can convince the reviewer, capturing these diverse patient states in individual training sessions will not be easy to achieve. + +<--- Page Split ---> + +We have now clarified the motivation behind developing and implementing the methods for decoding without patient- individual training in the discussion section: + +"The presented methods for decoding without patient- individual training may catalyze the adoption of brain signal decoders for closed- loop neuromodulation by curbing healthcare costs and improving patient satisfaction. This will be especially relevant for future approaches that implement decoding of multiple brain states related to circadian rhythms, sleep and diverse symptoms such as tremor, freezing of gait, dyskinesia, dystonic muscle contractions, tics and more. Our study entails a first step in this direction by describing different methods that allow for transfer- learning and decoding without requiring individual training and providing the first generalizable movement decoder for invasive neurophysiology as a digital resource (DOI: 10.5281/zenodo.10794369)." + +5. The Results and Methods need much clearer explanations of what was being done and decoded. It is not meaningful to say "balanced accuracy of 0.8/0.98 ± 0.07/0.04 for single sample/movement detection..." without explaining what is "single sample" (or "sample-wise") decoding, what movements are being detected, and how many classes are being decoded among. The tasks seem highly disparate among these datasets, so combining results across them does not make much sense. The tasks are not even described in any detail, nor what is being decoded. It is also not clear exactly what features are being used to decode (e.g., how many time bins were used in each decoder? Were they causal-only bins?) nor how much data (trials) were used to train and test in each case. Since the whole point of the study is to show how this toolbox enables decoding, and the methods are not described in enough detail to understand the task, it is very difficult to ascertain the impact of the innovation. In addition, if the goal is to show that these techniques allow better decoding of movement vs rest (which I am inferring, since this is never stated clearly), then the results here should be compared to prior studies in closed-loop DBS using simpler methods. + +We thank the reviewer for identifying our lack of clarity with regard to these important depictions. The movement decoder solves a classification problem with two- classes with either rest or movement present. Balanced accuracy at the single- sample level is the correct classification of a 100 ms time- step of model output vs. target, while ensuring that equal numbers of samples of each class were present in the test set. This is a very conservative measure, as the temporal resolution is ten times higher than in most comparable previous studies (e.g. one of the most highly cited movement decoding papers by Gerwin Schalk and the team of Jonathan Wolpaw https://doi.org/10.1088/1741- 2560/4/3/012, which commonly used 1 second time resolutions). Indeed, many movement classification papers, do not decode movements continuously but describe accuracies at the trial level (e.g. if 90/100 trials are classified correctly, this would yield 90% accuracy without providing any detail on the temporal precision of the classification). In addition to this very conservative measure, we have added a second performance metric, which focused on the correct identification of a movement entity, which we defined as the correct continuous classification of over 300 ms of movement time. This is still more conservative than many other studies, but we felt that for the application of closed- loop neuromodulation it yields sufficient precision while providing higher stability. We believe the expert reviewer has understood this, but we used balanced accuracy, because in the context of movement tasks, the rest condition typically outscales the movement condition in time, leading to biased accuracy estimates if not + +<--- Page Split ---> + +balanced (e.g. if \(90\%\) is rest and \(10\%\) is movement, a decoder could simply always predict rest and have an accuracy of \(90\%\) without predicting a single movement sample correctly). + +For the movement decoding analysis we used FFT features in eight different frequency bands: \(θ\) (4- 8 Hz), \(\alpha\) (8- 12 Hz), low \(\beta\) (13- 20 Hz), high \(\beta\) (20- 35 Hz), low \(\gamma\) (60- 80 Hz), high \(\gamma\) (90- 200 Hz), and high- frequency activity (200- 400 Hz) at a temporal resolution of 100 ms. All features were z- score normalized across the past 30 s and clipped at minus and plus three, allowing for a causal real- time normalization of the feature range across subjects and cohorts. Only one causal time- bin was used in each decoder and generally every single aspect of any of the decoding work in the entire paper was done in a causal only way, rendering the analysis directly transferable to a real- time application (as shown for the prospectively recruited patients in the supplementary videos). + +We show that our classifier performed well, despite variability in the movement tasks. We agree with the reviewer that the movement tasks are disparate and we have now improved the description of this aspect and all other points above in the manuscript. With relation to our reply to comment 4, we believe that the generalizability of our decoders across tasks is an asset instead of a limitation. Our results indicate that the model that we provide as an open- source resource, can classify movements with meaningful accuracy independent of the specific motor task. Finally, to address the last comment, which relates to the comparability or superiority of our observed performance to previous publications, it is precisely this nature of the challenge that we have set ourselves to address, that is entirely novel to the field and therefore no benchmark exists. Indeed, very few studies exist that report movement decoding in Parkinson's disease patients (again details can be found in our review article on the topic: https://doi.org/10.1016/j.expneurol.2022.113993), none of them report across patient or across task decoding. One study used subthalamic local field potentials and reported a maximum performance of 0.74 (https://doi.org/10.3389/fnhum.2023.1111590) and another combined MEG and LFP and reports a mean balanced accuracy at 0.38 for the distinction of tremor and voluntary movement at the single- subject level for a temporal resolution of 1 second (https://doi.org/10.1016/j.clinph.2023.10.018), which despite being not entirely comparable, our paper relevantly outperformed. Indeed, our results reach an average performance above 0.8 across patients for the more comparable temporal resolution of the movement detection rate (0.74 at a temporal resolution of 100 ms). Our prospective out- of- cohort validation of the patient naive model resulted in a sample- wise balanced accuracy: 0.71 and a respective movement detection rate of 0.97. Notably, these performances would likely not be possible without the use of an ECoG strip, a technique that is not routinely performed in DBS patients. The Berlin team leading this study is the first to establish ECoG in PD patients undergoing DBS in Europe, for the precise reason of improving brain signal decoding for DBS. In addition to the abovementioned results from Parkinson's disease, we would like to highlight two studies that indeed did use ECoG strips for movement classification, but in a different brain disorder, namely essential tremor. Both studies had low n and only reported individually optimized decoders. The first reported a balanced accuracy of 0.532 across two subjects at a temporal resolution of 200 Hz (https://doi.org/10.1088/1741- 2552/abb416). The second, from a leading neural engineering team, yielded higher performances of 0.92 (https://doi.org/10.1126/scitranslmed.aay7680), which are comparable to the within subject performances of the Berlin cohort and outperformed by the Pittsburgh cohort in our study with three key differences: a) our results have ten times higher temporal resolution at a 100 ms vs. 1 s in the abovementioned paper, b) the decoders for the abovementioned paper were individually and repeatedly optimized in dedicated calibration + +<--- Page Split ---> + +sessions and c) our results stem from Parkinson's disease patients, which as we show in our paper, is associated with deteriorated decoding performances in advanced disease stages. In summary, our study demonstrates the only across- subject movement decoder in the field of DBS, performs at comparable accuracy as previous within- subject approaches that required calibration sessions and operates at higher temporal resolution than most previous reports. We hope that clarifying this now further highlights the relevance and novelty of our report. + +We have made an effort to address all the abovementioned points with a specific focus on explaining the performance metrics in detail in the methods section: + +Results: + +"We implemented py_neuromodulation for electrocorticography (ECoG) based movement decoding as a two- class classification problem (rest vs. movement present) without individual training ..." + +"We computed FFT features in eight frequency bands from 4 to 400 Hz with a temporal resolution of 100 ms. All features were z- score normalized across the past 30 s and clipped at minus and plus three for artifact mitigation. Normalization was performed to ensure comparable feature values across subjects. Feature contributions were observed in each frequency band but highest importance was identified in the theta, high beta and high gamma frequency bands (see supplementary fig. 2)." + +"We trained ridge regularized logistic regression classifiers and evaluated their performance using the balanced accuracy metric with 3- fold cross- validation on consecutive data segments, yielding sample wise performances indicating presence or absence of movement at 100 ms resolution. Sample- wise performances were concatenated to establish a more coarse metric that allowed for detection of individual movement entities, termed movement detection rate and defined as 300 ms of consecutive movement classification." + +## Methods: + +"The aim of the first use case was the two- class classification problem of movement vs. rest for different cohorts including different movement types across four cohorts from different neuromedicine centers (Berlin, Beijing, Pittsburgh, Washington). Berlin subjects performed a rotational handle task. Patients were instructed as follows: 'Perform 50 wrist rotations with your left hand with an interval of about 10 seconds. Do not count in between rotations'. The self- paced wrist rotations were performed on a custom- built analog rotameter, which translates the degree of rotation into a voltage. This task was previously utilized and described in different studies (Lofredi et al 2018, eLife; Brücke et al 2012, Journal of Neuroscience). Beijing subjects engaged in a voluntary button press task and were instructed to press the button with their left index finger every 10 s while avoiding to count in between the button presses. Pittsburgh subjects performed a gripping hand movement contralateral to the implanted cortical electrode. The visually cued handgrip was temporally adjusted in a Go/No- Go task, and previously described in different publications (Merk et al 2022, eLife, Peterson et al 2022 Exp. Neur., Kondylis et al 2016, Brain). Furthermore, we used invasive recordings from epilepsy patients undergoing seizure monitoring from a publicly available dataset (Miller et al 2019). The patients engaged in a hand clench and + +<--- Page Split ---> + +release task. The original publication described the 'motor_basic' tasks as follows. Direct quote (Miller et al. 2019): + +"Cue- based movement task": Patients performed simple, repetitive, motor tasks of hand (synchronous flexion and extension of all fingers, i.e., clenching and releasing a fist at a self- paced rate of \(\sim 1 - 2 \mathrm{~Hz}\) ) or tongue (opening of mouth with protrusion and retraction of the tongue, i.e., sticking the tongue in and out, also at \(\sim 1 - 2 \mathrm{~Hz}\) ). These movements were performed in an interval- based manner, alternating between movement and rest, and the side of movement was always contralateral to the side of cortical grid placement. There were between 30 and 75 cue presentations for each movement modality. Cues for motor movement were delivered visually in a \(10 \times 10 \mathrm{~cm}\) presentation window at a distance of \(75 - 100 \mathrm{~cm}\) from patient. Visual cues were presented using the BCI 2000 program with a written word indicating the specific body part to be moved (typically, multiple movement types were interleaved in each experimental run). Stimuli were presented for 2 s or 3 s cue blocks, followed by rest intervals (indicated by a blank screen) of the same length. The patients were instructed to perform repetitive, self- paced motor movement, alternating with rest intervals of the same length (indicated by the absence of the cuing target). Repetitive motion, rather than tonic contraction, was intended to accentuate the spectral shift during each interval. (Miller et al, 2019) + +In this analysis we excluded the tongue movement to unify the movement effector across cohorts. We specifically included multiple cohorts and tasks to investigate and develop decoding models that can generalize across recorded brain regions, tasks, recording equipment, surgical approach and electrode models. The primary performance metric was defined as sample- wise balanced accuracy at a temporal resolution of \(100 \mathrm{~ms}\) for each prediction. The used time- duration for feature computation was specified to be 1 s, only preceding the current target sample, therefore all feature computation including pre- and post- processing were applied in a causal manner. For the practical application of adaptive invasive neuromodulation, the measure of sample- wise decoding is of limited importance. In addition to reporting the sample- wise classification performances, we therefore report the accuracy of correct predicted movement blocks termed "movement detection rate". If the classifier's output probability is above 0.5 for three consecutive samples (300 ms) the present movement is classified to be detected. A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block. It's important to note, however, that this measure addresses only the movement class and has no predictive value of rest segments." + +Additionally, we extended the supplementary tables 2 and 3 to display the total recording and movement duration times in minutes for each subject. Supplementary Table Y showing the recording durations of the Washington cohort was uploaded separately as an excel file. + +
Total recording duration [min]Movement recording duration [min]Rest recording duration [min]N samples at 10 Hz for decoding
Cohort-IDAgeGenderUPDRS
Berlin-00150fn.a.7.912.85.114737
Berlin-00262m2115.782.213.589459
Berlin-00356f3113.562.56118127
Berlin-00445f3626.427.8518.5815843
Berlin-00543f3195.321.4473.8657171
+ +<--- Page Split ---> + + +
Berlin-00657m3640.913.1537.7624537
Berlin-00755m5927.464.5522.9116467
Berlin-00866m2440.974.6436.3424573
Berlin-00959m2730.122.3627.7618063
Berlin-01066f3010.771.88.976453
Berlin-01167m3917.513.1414.3710497
Berlin-01254m3119.312.2517.0611577
Beijing-00166f6110.921.749.186543
Beijing-00270m7016.190.4115.789705
Beijing-00373f519.910.719.195937
Beijing-00467f526.990.746.244185
Beijing-00559f5823.891.0822.8214325
Beijing-00776m4121.770.7920.9813053
Beijing-00866f5522.691.2421.4513605
Beijing-00966f3918.621.4117.2111163
Beijing-01067f2711.582.848.746939
Beijing-01172f4710.620.6110.026363
Pittsburgh-00160.3m2812.620.9311.77563
Pittsburgh-00251.2m2719.461.0318.4311667
Pittsburgh-00363.8m4018.931.9816.9511349
Pittsburgh-00454.7fn.a.10.550.4210.136321
Pittsburgh-00553.8m337.60.567.044551
Pittsburgh-00644.2m3116.240.8615.389735
Pittsburgh-00763.6m3217.931.4716.4610749
Pittsburgh-00859.6m525.780.395.43459
Pittsburgh-00971.6m5510.80.310.56471
Pittsburgh-01052.5m5012.990.8812.127785
Pittsburgh-01166.8f6222.991.6821.3113785
Pittsburgh-01265.2f5417.750.751710641
Pittsburgh-01354.4m3427.611.5226.0916557
Pittsburgh-01467.9m488.220.477.754923
Pittsburgh-01569f3112.31.6310.677371
Pittsburgh-01667m4215.251.7113.559141
+ +Supplementary table 2: Parkinson's disease cohort information + +We further show in an added supplementary table the mean number of training samples for each cross- validation method. Due to the subject and cohort- specific recording durations, this number varies for each cross- validation split. + +
Cross validation typeNumber of samples Mean ± Std [a.u.]Duration Mean ± Std [min]
Within subjects11616 ± 910119.37 ± 15.18
Leave one subject out within cohorts137991± 41745230 ± 69.6
Leave one subject out across cohort430017 ± 9213716,71 ± 15.4
+ +<--- Page Split ---> + +7. Line 121: "0.88 ± 0.17 movement detection rate across movements" – unclear how this number was derived, as Fig 2g does not seem to show this high of accuracy averaged across all boxes. + +Figure 2g shows sample- wise movement classification performances. We now report the average movement classification performance as balanced accuracy \((0.79 \pm 0.13)\) in text in addition to the movement detection rate \((0.88 \pm 0.17)\) . The Figure legend was also adapted to state that the movement classification metric is the sample- wise balanced accuracy. Note that now the figure 2 panel o was adapted to also show the adaptive stimulation decoding and stimulation single trial time traces for the additional subject. + +The new figure and corresponding figure legend is shown below. We adapted the legend labels of the upper label panel to specify "Hand movement [a.u.]", additionally the y- axes were added for each subplot. + +![](images/Figure_unknown_2.jpg) + +
Figure R1: Real-time single trial decoding is shown using true analog rotameter movements, classification probability predictions and binary classification outputs.
+ +8. In Table 1, what is the difference between "sample" vs "movement" columns? Is movement detection the same as sensitivity? If so, then state this. + +In response to comment 6 above we addressed the motivation between sample- wise classification and movement detection rate and added further clarification about the sample- wise and movement detection performance in the methods and results sections. + +<--- Page Split ---> + +We further added the following information to the table legend: + +"Decoding performance is depicted as balanced accuracy, which accounts for class imbalances. Single sample estimates provide performance metrics at 100 ms precision. Movement detection estimates were defined as the rate of movements in which the classifier's movement class predictions exceeded a 300 ms time window". + +9. "To approximate the movement kinematics..." What movement kinematics? Were these recorded? It's not even stated how movement times were recorded. + +The movement kinematics for certain tasks (e.g. Berlin rotational handle and Pittsburgh hand gripping force) were recorded. To standardize the decoding problem to be a rest-vs-movement classification problem, the kinematic time traces were transformed into a binary movement representation. The embedding training using contrastive learning (using the CEBRA) required application of a Gaussian filter to the binary movement trace, as extracted for the two-class classification problem. The following Figure demonstrates how the raw movement trace signal was transformed to a binary signal, and further transformed using the gaussian filter, for training the CEBRA embedding layer using contrastive learning, to a continuous signal. + +![](images/Supplementary_Figure_3.jpg) + +
Figure R2: Movement label transformation. Raw movement traces (a) were transformed by investigating visually the EMG movement onset and offset, which resulted (b) in a binary movement vector. For contrastive learning, the binary movement was filtered using a Gaussian window. This function was beneficial for training the non-linear embedding layer and subsequent movement classification. The Gaussian filtered movement signal closely resembles the movement characteristics of the acquired raw signal.
+ +We have now clarified this further in the respective paragraph of the methods section: + +"The Gaussian filter transformed the binary classification labels into a continuous label vector, which empirically improved performance. For the Berlin and Pittsburgh cohorts, which included continuous movement recordings, the Gaussian filter convolution resulted in unvaried continuous movement traces compared to the original recorded signals." + +<--- Page Split ---> + +10. How were stimulation artifacts dealt with, given that the high gamma range includes the stimulation frequency used? + +We thank the reviewer for raising this important point. In the reported analysis, we did not explore the effect of different stimulation artifact rejection methods. To address this comment more thoroughly, we now investigated if bandpass-filtering in a frequency range of 100 to \(160\mathrm{Hz}\) around the \(130\mathrm{Hz}\) stimulation frequency yields improved performances. Additionally, we implemented the recently presented "Period-based Artifact Reconstruction and Removal Method" (PARRM) (Dastin- van Rijn et al 2021, Cell Reports Methods) method for calculating a recording stimulation artifact template which is subsequently removed for each artifact occurrence. Both have become additions to the toolbox through the revision, now openly available to the scientific community in response to this comment. However, neither of the methods resulted in movement decoding performance improvement: + +Empirically, the filtering techniques interact with the stimulation artifact leading to shifts in feature magnitudes that were relatively unaffected by the original DBS artifact. This is now described through a new supplementary figure and cited in the main results section as follows: + +![](images/Figure_unknown_3.jpg) + +
Supplementary fig. 3 Stimulation ON/OFF power spectra and cross-prediction movement decoding performances for different stimulation artifact rejection methods. (a) Exemplary power spectra of a single subject without stimulation artifact rejection, and for two artifact rejection methods: PARRM (Period-based
+ +<--- Page Split ---> + +Artifact Reconstruction and Removal Method) and bandstop filtering (100- 160 Hz). Both methods can be selected within py_neuromodulation. PARRM requires, however, computation of a filter before real- time application. (b) Logistic regression performances for stimulation ON/OFF cross- predictions show that the utilized artifact rejection methods did not improve but deteriorate movement decoding performances. + +## Results: + +"Importantly, processing steps to mitigate DBS artifacts including bandpass filtering and period- based DBS artifact removal did not improve, but instead aggravated this deterioration (see supplementary fig. 3)." + +11. It seems that many ECoG electrodes with high decoding accuracy were in primary somatosensory cortex, which begs the question if these were really sensing sensory feedback, as opposed to motor intent. Sensory feedback would not be useful for controlling DBS, since it could be causing a positive feedback loop. + +This is a relevant point that we cannot fully rule out with the data at hand. However, to address it analytically, we reanalyzed data from the Berlin cohort. As described above, this includes self- initiated movements without visual or other sensory cues. Patients held the rotational handle in their hands across the entire recording period. Despite some limitations on the assumptions we argue that if sensory cortex holds information on future movement prior to motor execution, this would hint that indeed even sensory cortex can be used for decoding of motor output independent of sensory input. Therefore, to reply to the reviewer more thoroughly we trained a new causal movement initiation classifier (Figure R3) below. + +![](images/Supplementary_Figure_5.jpg) + +
Figure R3: (a) New classification results on sensory cortex signals for which the positive movement intention (positive) class was defined as the time-period -2 s prior to movement onset, and the rest (negative) class was defined as -4 till -2 s before movement onset. We excluded the movement period for classifier training, to investigate the single effect of somatosensory cortex related decoding for movement intention. We tested the movement intention decoding using a class-weight balanced and lasso-regularized logistic regression model within a three-fold non-shuffled cross-validation. Sensory cortex prediction performances rose above chance level as early as 2 seconds before motor onset (b) leading to a total balanced accuracy of movement intention classification of \(0.6 \pm 0.05\) (c).
+ +However, some of these results could still be the result of sensory prediction or miniscule adjustments to hand pressure that we did not control for. Therefore, we decided not to include + +<--- Page Split ---> + +these results in the manuscript and instead acknowledge the potential influence of sensory input in the main results text as follows: + +"Performance was significantly above chance in every subject, with an average balanced accuracy of \(0.8 / 0.98 \pm 0.07 / 0.04\) for single sample/movement detection in the best channel per subject, spatially peaking in sensorimotor cortex indicative of a potential interplay of motor and sensory information predictive for movement output (Fig. 2b- d)." + +12. Another central theme of the paper is not clearly explained. The idea of using connectivity as a way to decode across patients is very interesting and potentially useful. However, the methods are not explained clearly enough. What does "voxel-wise correlation of connectivity profiles with decoding performances from offline training" mean (lines 548-49)? How does one correlate a connectivity profile with an R2 value? What exactly is meant by a "connectivity profile"? Just a pairwise correlation matrix? Other graph theoretic measures? There are many types of connectivity that can be calculated, and this needs to be explained. The cited reference likewise does not explain this sufficiently clearly, but in any case, this is a central theme of this paper and should be explained here, not delegated to a reference. Without this, "prospective channel selection" is not easily understood, because "optimal connectomic decoding map" is not clear at all. + +We thank the reviewer for that suggestion and now added a new methods figure explaining the connectomic decoding. We have added two supplementary figures to clarify the respective methods. First, we highlight the differences of the tested approaches to account for individual electrode localizations in a schematic overview: + +<--- Page Split ---> +![](images/Supplementary_Figure_4.jpg) + + +Supplementary fig. 4 Comparison of different approaches for neural decoding without patient- individual training. (a) Grid- point interpolation: Individual recording contact locations are estimated in a standardized space. Features are separately computed for each recording contact. Data is then mapped to a pre- defined cortical or subcortical grid in MNI coordinates. This mapping ensures a correct sorting of activity sources stemming from similar brain regions. In this manner, feature vectors are mapped to a common grid defined in space (similar to EEG montages), which then lay the foundation to train models on grid- points instead of recording channels for neural decoding without patient individual training. (b) Connectomic channel selection: An optimal decoding whole- brain connectivity map is computed based on training data. This step requires the computation of contact- specific neural decoding performances and whole- brain connectivity estimates. The connectivity profiles and decoding performances are correlated in a voxel- wise manner to estimate a connectivity map associated with optimal decoding performance. For a test subject, the connectivity map of each channel is spatially correlated with the optimal decoding map and the one with the highest similarity is selected and used for testing of a pre- trained machine learning model. (c) The connectomics- based channel selection approach is further extended by transforming individual channel features using an embedding layer. This layer is computed through contrastive learning and auxiliary variables. Here we utilized the CEBRA package (Schneider et al 2023, Nature). + +In the present manuscript, the Pearson correlation coefficient was utilized for the connectomics based approach. We note, however, that this approach can be extended by different correlation + +<--- Page Split ---> + +metrics. In the following, we added another more detailed figure explaining the connectomic channel selection approach, including a definition of connectivity profile, correlations of connectivity profiles and the optimal connectomics derived decoding map: + +![](images/Supplementary_Figure_2.jpg) + +
Supplementary fig. 5 Connectomics-based neural decoding without patient-individual training. (a) Estimation of a patient-individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain-wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity
+ +<--- Page Split ---> + +template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. + +13. It's not clear what the clinical relevance of training on a single subject to predict other subject's data, given that one would not know in practice who the "best" subject is without training on a group of subjects and testing on all of them anyway. + +We thank the reviewer for this relevant point. We agree with the statement, but would like to argue that it is still interesting to show this as a) in a post- hoc analysis of a cohort it is possible to know which subject is good for training and which isn't; That means that selectively curating a database of good training subjects could further enhance across patient decoding performance. b) it should motivate us to explore across patient decoding methods even in cases where data from only few subjects is available. E.g. in rare forms of child dystonia, opportunities to record invasive data may be very sparse. Being able to train generalizable models in single subject data could have important implications in such instances. We now clarify this further in the manuscript: + +## Discussion: + +"Moreover, we show that training data from an individual subject can generalize to other subjects, which holds promise for across- patient decoding applications even in rare diseases, where only few datasets may be available." + +14. Authors seem to claim that CEBRA performs better than 2nd method, but do not provide statistical testing evidence to back this up (a p-value is presented, but how was this tested?). Similarly, it mentions several times that a given performance is above chance, but never states how chance is computed for any case. It is also not true that accuracy of \(\sim 60\%\) is "high above" chance when chance is likely \(50\%\) . Also, not clear what is being shown in Fig 2o - - there are no y axis labels, and not clear if these are averages, single trials, or other. + +We thank the reviewer for this remark. We have now directly performed a statistical comparison for the decoding performances without patient- individual training between the CEBRA model performances and the grid point and connectomic channel selection methods. We used a paired permutation test and found that CEBRA outperformed both other methods for all cross- validation approaches. We defined statistical significance \((p = 0.05)\) to be corrected by Bonferroni correction \((n = 12\) tests, \(p = 0.05 / 12 = 0.004\) ). Significant balanced accuracy performance differences were observed for all comparisons except CEBRA vs grid points \((p = 0.03)\) . For movement detection rates, none of the performance differences were significant, mainly due to the already high movement detection rates present in all predictions. + +<--- Page Split ---> + + +
Within cohorts
CEBRA vs Grid
Points
Within cohorts
CEBRA vs
Connectomics
Across cohorts
CEBRA vs Grid
Points
Across cohorts
CEBRA vs
Connectomics
Balanced
accuracy
0.02 (p=0.03)0.02 (p=0.003)0.02 (p<10-5)0.02 (p<10-5)
Movement
detection rate
0.01 (p=0.69)0.01 (p=0.7)0.03 (p=0.04)0.03 (p=0.04)
+ +Table R1: Mean differences of leave one subject out cross validation approaches of CEBRA against grid point and connectomics channel selection methods. P-values are shown for paired permutation test comparison. + +
CEBRA vs Grid PointsLOCO within cohorts
CEBRA vs Connectomics
Balanced
accuracy
0.03 (p=0.0002)0.03 (p<10-5)
Movement
detection rate
0.02 (p=0.33)0.02 (p=0.35)
+ +Table R2: Mean differences of leave one cohort out cross validation of CEBRA against grid point and connectomics channel selection methods. P-values are shown for paired permutation test comparison. + +We furthermore added in Figure 2l,m the individual patient lines and highlight statistical significance: + +![](images/Supplementary_Figure_9.jpg) + + +<--- Page Split ---> + +The Figure 2l,m figure legend now reads: + +"CEBRA outperformed other methods as indicated by Bonferroni- corrected paired permutation tests." + +Additionally, we described the statistical analysis now in the Results section: + +In addition to the conceptual advantage to account for specific recording location and underlying brain network affiliation, the connectomic approach with contrastive learning (CEBRA) outperformed the other two methods for each cross validation approach in sample- wise balanced accuracy (see Table 1 for performances, paired permutation test leave one subject out within cohort CEBRA vs grid points: \(\mathsf{p} = 0.03\) , CEBRA vs connectomics: \(\mathsf{p} = 0.003\) ; leave one subject out across cohorts CEBRA vs grid points: \(\mathsf{p}< 10^{- 5}\) , CEBRA vs connectomics \(\mathsf{p}< 10^{- 5}\) ; leave one cohort out CEBRA vs grid points: \(\mathsf{p} = 0.0002\) , CEBRA vs connectomics: \(\mathsf{p}< 10^{- 5}\) ). + +With regard to the following comment, the reviewer was right that the two- class classification problem of rest vs. movement, the chance level is \(50\%\) . In response to the reviewers criticism we discuss some of the results more cautiously and specifically replaced the "high above chance" phrasing. The reviewer points out that in some instances the reported sample- wise performance can be as low as \(60\%\) . However, we would like to highlight again, that the performance for a subject that was newly and prospectively recruited after model training was never seen by any of the models reached a sample- wise balanced accuracy of 0.71 at the very high 100 ms temporal resolution and a movement detection rate of 0.97, meaning that almost every movement was correctly classified. To the best of our knowledge, no previous report exists of a prospective model validation of a newly recruited patient for any movement decoder while our performance is in the range of previous post- hoc offline study results. We computed p- values using non- parametric Monte- Carlo sampled permutation tests with a significance value of \(\mathsf{p}< 0.05\) . + +We updated in the publication the text "high above" chance to "above" chance. The statistical test is now further annotated in the manuscript. + +15. More details should be provided about the DBS trial for depression. Without these, it is difficult to evaluate the phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." (line 244). Were all DBS leads used for stimulation? If not, how did those leads used for stimulation relate to the leads in the decoder? The clinical trials registry number should also be included for all of these trials. + +We thank the reviewer for this important remark. We would like to note that the present study did not aim to present the clinical evaluation of the DBS for depression trial, which were previously published in a series of papers that we cited (Merkl A et al., Deep brain stimulation of the subcallosal cingulate gyrus in patients with treatment-resistant depression: A double- blinded randomized controlled study and long- term follow- up in eight patients. J Affect Disord. 2018 Feb;227:521- 529. doi: 10.1016/j.jad.2017.11.024. Epub 2017 Nov 8. PMID: 29161674.). The clinical trial registration number NCT00531726, registered at clinicaltrial.gov, was now added in the manuscript and in the Nature Portfolio reporting summary and in the methods section. Nevertheless, we agree that some clarification was required in our manuscript. For the reviewers convenience we cite the full methods paragraph from the clinical manuscript in the following: + +<--- Page Split ---> + +"For parameter settings we used a monopolar configuration (contact cathode and case anode; contacts 0,1,2,3 being right hemisphere and contacts 4,5,6,7 being left hemisphere electrodes, contact 0 and 3 being the lowermost and uppermost contacts, respectively). Given the scarce empirical evidence about optimal stimulation parameters, we adopted the same approach as in previous partially successful open- label trials (Holtzheimer et al., 2012; Lozano et al., 2012). Pulse width and frequency were set to \(90\mu \mathrm{s}\) and \(130\mathrm{Hz}\) respectively. For all contacts, the amplitude was raised up to \(10\mathrm{V}\) in 2.5 steps, remaining on each level for \(10\mathrm{min}\) in order to assess acute side effects due to voltage increase, and was subsequently set constant between 5 and \(7\mathrm{V}\) . During the eight- week blinded- phase, no modifications in frequency, amplitude or in pulse width were allowed. During the open- label phase beyond eight weeks, amplitude changes were allowed." + +To summarize briefly, one contact was activated for stimulation per hemisphere (as depicted in Figure 3b). Contrary to the monopolar stimulation, all channels were recorded bipolarly (channels 0- 1, 1- 2, 2- 3 and 3- 0). Therefore, a direct comparison of recording and stimulation channel is not possible, because each stimulation channel occurs in two recording channels. To still give a direct reply to the reviewer's question, we investigated if the stimulation contacts were present in the best bipolar recording channels. Indeed, in all eight patients the stimulation contact matched at least for one hemisphere with the channel of highest decoding performance, with only 4/16 electrodes presenting without overlap. Given the uncertain relationship of monopolar stimulation and bipolar recording electrodes we however believe that this is not easily interpretable which is why we have decided not to include this result in the main text and instead discuss our interpretation more cautiously. The following changes have been made to the manuscript: + +## Results: + +"Machine learning decoders were trained on local field potential signals from the DBS electrodes in SCC in eight patients undergoing DBS for treatment resistant major depressive disorder as part of a clinical trial (mean age: \(48 \pm 11.4\) , 4 females; Supplementary table 6; ClinicalTrials.gov registration number: NCT00531726)." + +"The correlation could potentially be driven by optimal targeting rather than by depressive symptoms themselves, which inspired us to explore the underlying whole- brain networks." + +16. More information is required about the "additional fiber filtering approach recently introduced..."(line 246). The method should be described clearly. Again, the term connectivity fingerprint is not explained. The phrase "estimated best therapeutic stimulation target from Fox et al 2014" is also not explained at all. Why is this important and what does it have to do with the results presented here? This needs explanation for a broad audience. + +We agree with the reviewer that while the method has been used in many previous publications (most recently in Hollunder, B., Ostrern, J.L., Sahin, I.A. et al. Mapping dysfunctional circuits in the frontal cortex using deep brain stimulation. Nat Neurosci 27, 573- 586 (2024). https://doi.org/10.1038/s41593- 024- 01570- 1), it may not have been introduced in sufficient detail with the present submission. In brief, the employed fiber tract method can indicate fiber tracts associated with high decoding performance through a statistical procedure in which a normative fiber tract connectome (or wiring diagram of streamlines of white matter) is used to determine the + +<--- Page Split ---> + +fibers that are connected to a certain region of interest, in our case the location of the recording channels. Each fiber streamline is then weighted by its relationship to decoding performance. Streamlines in proximity to recording contacts associated with high decoding performance received high positive weights whereas those associated with low decoding performances were attributed high negative weights. A t- statistic was computed for each respective fiber tract that was corrected for multiple comparisons using the false discovery rate with \(\alpha = 0.05\) . The approach is validated to predict decoding performance from a recording channel solely based on fiber connectivity in held out subjects. This revealed left prefrontal fibers that were associated with emotion decoding performance. This lateralization was previously described for major depressive disorder and is in clinical practice also used for treatment using transcranial magnetic stimulation, which is highlighted by showing the TMS target for depression described in the Fox et al., 2014 publication (DOI: 10.1073/pnas.1405003111). + +We have now further clarified this in the methods section: + +"Structural connectivity was estimated between recording contacts region of interest (ROI) with a spherical seed (4 mm radius) and all other brain regions. We utilized the multi- shell diffusion- weighted imaging data acquired within the Human Connectome Project (Van Essen et al 2013, n=985 subjects). For each subject, fibers were normalized into ICBM 2009b Nonlinear Asymmetric ("MNI") standard space using Advanced Normalization Tools (ANTs, http://stnava.github.io/ANTs/, Avants et al 2009) within Lead- DBS (Neudorfer et al 2023). For each tract, a two- sample t- test was calculated between the associated decoding performances of connected and unconnected recording contact ROIs. The t- value was then used to color- code each fiber tract. Positive significant fiber tracts were thus connected to many recording contacts with high decoding performance. Negative fiber tracts on the contrary were connected to many poor performance recording contacts. To account for multiple- comparison tests, a False- Discovery- Rate with \(\alpha = 0.05\) was defined for defining statistical significance." + +17. It's not clear whether the optimization of RNS parameters using a grid search is feasible or helpful for an actual clinical use case in individual patients. Was this optimized over all patients with holding patients out? Or by doing cross-validation with data from all patients together? + +Thank you for the relevant comment. We would like to admit that it is hard to see a scenario where this would not be helpful or feasible but it is obvious that we have not made this point clear enough. To support this notion further, we would like to first state that RNS data are continuously recorded and streamed over months of therapy. Right now, only a few seconds of recording can be selected to estimate the detection parameters in the implant, despite the patients having weeks worth of data. In the future, it would be more sensible to continuously update and improve the detector using all available data on the single subject or across- subject level. Given the limited number of subjects, we have focused on within patient predictions with models trained on expert annotations. In the future, automated seizure detectors could be used offline to continuously update the seizure detectors, even across patients. First models for automated annotation were described in one of our previous publications (Peterson V, et al. Deep net detection and onset prediction of electrographic seizure patterns in responsive neurostimulation. Epilepsia. 2023 Aug;64(8):2056- 2069. doi: 10.1111/epi.17666. ). + +We have now made the following adaptation to the manuscript: + +<--- Page Split ---> + +"In the future, it would thus be sensible to continuously update and improve brain signal decoders using all available data on the single subject or across- subject level." + +Minor concerns: + +Please type out all acronyms used for those not familiar (e.g., CEBRA). + +We are sorry for the lapse and have now typed out all acronyms. + +Methods mentions multiple terms that could mean similar things. What are data "batches" vs "segments"? FFTs were computed at 100 ms resolution – does this mean 100 ms windows, or longer windows overlapped by 100 ms? + +Thank you for pointing us to this lack of clarity in our manuscript. Batches are data packets including any number of channels and samples that are streamed as input for py_neuromodulation, either through a simulated datastream from an offline dataset or through the API of an electrophysiology processor for real- time application. Segments are parametrized window sizes for feature estimation of a predefined length, in the use cases of this manuscript this length is 1000 ms. The segments can be updated at a predefined update rate, in the present manuscript this rate was set to 10 Hz. This leads to a temporal resolution of the decoder of 100 ms with feature windows using data from the past 1000 ms. For offline processing where we simulate batch streaming, and thus batch size equals the number of samples required for maintain the predefined update rate, e.g. 100 ms for 10 Hz as described above. For real- time interfacing with electrophysiological processors however, it is typically required to query data batches sequentially, sometimes without control over which channels and how many samples will be transmitted. Then the batch size and the update rate can differ. Py_neuromodulation would then query as many batches that are required to maintain the update rate and generate the full segment according to the chosen settings defined in the nm_settings.json file. + +We have now clarified this in the results and methods section: + +Methods: + +"The abovementioned batches are analyzed in segments of a defined window length and sampled at a predefined update rate, that can, depending on the amount of desired segment overlap be shorter or equal to the segment length." + +Fig 4 labels are too small to be legible. + +Thank you we have now adapted the font size of the respective labels: + +<--- Page Split ---> +![](images/Figure_1.jpg) + + +Supplementary video is not explained clearly. What are the different decoding/prediction windows showing? The prediction output looks very noisy during movements. + +We thank the reviewer for this important remark and adapted the Supplementary video legend: + +Supplementary video 1: Real- time movement decoding with py_neuromodulation using a pretrained model in a newly recruited patient with Parkinson's disease at Charité – Universitätsmedizin Berlin. The patient performed hand rotation movements using a rotational handle. On the top left the real- time feature visualization and decoding is shown. On the top right the Timeflux browser window (https://timeflux.io/) shows the true movement- induced analog voltage trace (top), movement classifier probability predictions (middle) and binary predictions (bottom). On the top right panel, the raw channel time series is visualized using BrainStreamingLayer (https://github.com/bsl- tools/bsl). Decoding was significantly above chance for decoding without patient- individual training (balanced accuracy: 0.71, movement detection rate: 97 %). + +Reviewer #3 (Report for the authors (Required)): + +This is a very interesting and ambitious paper describing an open source software system, py_neuromodulation, for “decoding” of behavioral states, including disease specific states, from invasive intracranial recording. It is designed for field potential (LFP and electrocorticography) approaches. At a time of great excitement in human invasive neurophysiology and its application in neural engineering, authors are to be applauded for developing a comprehensive analytic system that is accessible to all and that begins to standardize brain decoding across applications. A strength of the system is that it is designed to combine physiological recordings with connectomics, the merger of which can lead to new neuroscience insights. A strength of the paper is the illustration of the system in three different scenarios: decoding of movement (move vs rest, I believe, but see below) from motor system recordings in a variety of tasks in patients with movement disorders, decoding of emotional state from area 25 limbic implants, and decoding of pre- ictal or ictal activity in epilepsy. + +<--- Page Split ---> + +We thank the reviewer for highlighting the timeliness and ambition of our work. We have made a sincere effort to further improve the manuscript based on the expert review of the referee. + +Some general points for improvement: + +1) The paper is quite dense. It assumes a high level of expertise from the reader, who would need to have fluency in neurophysiology of LFPs, advanced imaging methods especially merging imaging sets across individuals, and machine learning, to fully grasp it. Below are specific areas where the authors could give a bit more information or clarification to help readers who don't already have expertise in all three of these. + +We agree with this statement and have thoroughly revised the manuscript to improve the clarity of both the methods and results. Specifically, we added exemplary API sections describing the toolbox feature estimation and decoding setup. Additionally, we added a section on how to make use of the connectomic decoding pipeline. We also provide the required code to utilize the movement decoding model without patient-individual training. + +2) Its not very clear how the system handles electrical recordings with lots of artifacts. There is one statement in methods on movement decoding that alludes to an answer "All 606 features were z-score normalized across the past 30 s and clipped at minus and plus three.." perhaps the "clipping" is their answer. More on how the system handles noisy data would be appreciated. + +We thank the reviewer for this valuable suggestion and added a section on artifact handling to the methods section: + +"Electrophysiological recordings can be affected by multiple artifact sources. We accounted for different artifact types within py_neuromodulation and describe the parametrization methods in the following. First, notch filtering to remove power line noise can be applied with parameters specific in the nm_settings file. Next, raw data and computed features can be clipped to limit the effect of outliers for decoding and normalization. To specifically account for artifacts resulting from neurostimulation, the "Period-based Artifact Reconstruction and Removal Method (PARRM)" (Dastin- van Rijn et al 2021, Cell Reports Methods) was implemented by the authors in Python (https://github.com/neuromodulation/PyPARRM). This allows for offline filter estimation and online application to clean signals contaminated by stimulation artifacts. Additionally, for offline data, artifact annotations can be provided in a .tsv file, e.g. through visual detection for which a wrapper of the mne- qt- browser GUI (https://github.com/mne- tools/mne- qt- browser) is provided." + +3) Authors should be more specific about what the system does NOT do, perhaps in discussion. At times the text seems to imply that the system can simulate closed loop stimulation for design of closed loop algorithms. For example this sentence in the abstract: "Our platform provides rapid, high-accuracy decoding for precision medicine approaches that can dynamically adapt neuromodulation therapies in response to the individual needs of patients" – is a DBS prototyping really part of py_neuromodulation? This should be clarified. + +We thank the reviewer for this important remark. The intention of py_neuromodulation is indeed to provide decision support for adaptive neuromodulation based on machine learning. However, we recognize that the application of invasive brain stimulation per se is not something that a software toolbox can offer. Specialized medical devices are required to actually apply the + +<--- Page Split ---> + +stimulation, that will often have additional proprietary software that are less standardized than neurophysiological processors for recording of brain activity. In our specific laboratory, we interface py_neuromodulation with a TMSi SAGA neurophysiology processor for brain signal recording and an Alpha Omega NeuroOmega for stimulation. This setup allows for brain signal decoding- based closed- loop invasive neurostimulation paradigms, which we are actively investigating. To demonstrate the capability of py_neuromodulation in the realm of closed- loop neuromodulation in reply to this comment we have now recruited an additional patient, in whom we performed movement triggered closed- loop DBS based on a pretrained movement decoder model. We obtained stable decoding and consequently stimulation results without any requirement for individual calibration. The results are now integrated in figure 2 and the case is added to the methods and results sections and a new video of the performance was added to the supplements. + +## Methods: + +In addition to decoding movement in real- time, we further recruited a second exemplar patient with early onset Parkinson's disease (age: 32, male). ECoG recordings were acquired from an Ad- Tech electrode (1x6 contact layout, contact area: \(12.56 \text{mm}^2\) ) and a SAGA (TMSi) amplifier. The Alpha Omega NeuroOmega was used for movement triggered stimulation. The movement decoding model was a linear model trained on all other Berlin subjects, that is also made publicly available (DOI: 10.5281/zenodo.10794370). To mitigate the stimulation artifact contribution, the ECoG channel used for feature estimation was bipolarly referenced to the adjacent channels, and in py_neuromodulation common average re- referenced. Features were z- score normalized within a time range of 30 s and clipped at plus and minus three standard deviations. Once the movement decoder probability output exceeded a pre- defined threshold (0.25), stimulation was triggered through the Alpha Omega NeuroOmega API for a duration of 1 s. Stimulation was enabled only on the clinically effective contralateral DBS contact (stimulation frequency=130 Hz, amplitude=1.5 mA). + +## Results: + +As the next step, to demonstrate the full automatized brain signal decoding based closed- loop neuromodulation capabilities of our platform, we recruited a new patient for a closed- loop neurostimulation paradigm. Here, we used our pretrained model without any calibration or individual training to trigger subthalamic high- frequency stimulation when movement was detected. The decoding performance remained stable (Fig. 2o, with stimulation- based sample- wise balanced accuracy: 0.66, rate of movements stimulated with at least 300 ms: 0.91), despite the presence of intermittent closed- loop DBS. + +We added, in addition, supplementaary video 2, which presents movement decoding triggered adaptive deep brain stimulation: + +Supplementary video 2: Real- time movement triggered subthalamic deep brain stimulation based on movement decoding without patient individual training. A Parkinson's disease patient performed hand rotation movements which were decoded by a movement decoding classifier. py_neuromodulation computed features are visualized on the lower panel in addition to the movement classifier prediction probabilities. When the movement classification probability passed a specified threshold, stimulation was switched on for a duration of 1 s. Overall, stimulation resulted in 0.62 balanced accuracy and a movement stimulation rate with at least 300 ms of 0.91. + +<--- Page Split ---> + +We also adapted Figure 2 legend where the stimulation- based changes are incorporated: + +To demonstrate the ability to decode movements without patient individual training, we prospectively recruited one subject in Berlin and decoded movements using pretrained models based on all previous subjects of the Berlin cohort (o). Real- time single trial decoding is shown for out- of- cohort patient 1 with y- axes depicting true measured analog rotameter movement amplitude (top), classification probability predictions without patient- individual training (middle) and predictions with training (bottom). For a second patient we tested movement- triggered stimulation and show the true movement traces (top), single trial movement predictions without patient- individual training (middle) and movement- triggered stimulation time (bottom). (p) Real- time performances are shown for both patients for decoding and stimulation. Above chance sample- wise balanced accuracy and movement detection rates were obtained despite presence of closed- loop neurostimulation and without model calibration. + +Here the adapted Figure 2 o and p including the movement- triggered adaptive stimulation results: + +![](images/Figure_3.jpg) + + +Despite these major efforts, we also recognize that the neurostimulation aspect is less clearly fleshed out in our manuscript and remains in an earlier stage with respect to presentable results. A reason why we believe it is still important to mention this ambition in the manuscript is that the entire decoding pipeline is optimized to be sufficiently fast and accurate for real- time implementation of adaptive neurostimulation. To provide an example, a pipeline comprising FFT feature computation, common- average- rereferencing and feature normalization is conducted within 1 millisecond for a single channel (4 milliseconds for 6 channels). We foresee real- world use cases of machine learning based adaptive DBS, such as freezing of gait for PD, tremor decoding for essential tremor, tic decoding for Tourette- syndrome and many more. The presented parameter optimization for responsive neurostimulation illustrates an application how the computed features could be used in an offline- analysis to optimize current available closed- loop + +<--- Page Split ---> + +neurostimulation implants, e.g. also for finding optimal parameters for sensing enabled devices. A missing development step that is planned however, is the direct implementation of stimulation parameter adjustment within py_neuromodulation. At this stage of development, the definition of stimulation parameters still resides outside of our software framework, e.g. in our use case through additional code addressing the NeuroOmega API. + +We have now clarified the discussion: + +Discussion: + +"The toolbox is designed with closed- loop neurostimulation in mind, but at this stage primarily streamlines the decoding aspect. Nevertheless, interfacing neurostimulation hardware APIs such as the Alpha Omega NeuroOmega or other neurostimulation systems is straightforward and provides a comprehensive solution to using machine learning models for therapeutic real- time adaptation. Moreover, we will continuously update and extend the capabilities for stimulation parameter adaptation for emerging technologies." + +4) A description somewhere of what data or tools the user actually needs, to utilize this system, would be helpful. For example, how are electrode locations input into the system? Is a DICOM formatted image set of the whole brain needed? CT only or is MRI needed? Or does py_neuromodulation require some sort of output from other software packages such as LeadDBS? Also how are the specific machine learning algorithms implemented? Does the user make a simple selection like "support vector machine" and then is able to input hyperparameters? Or does py_neuromodulation require specific outputs from other machine learning packages? + +We thank the reviewer for motivating us to clarify the specifics with regard to the implemented workflows. Py_neuromodulation automatically reads coordinates stored in metadata as part of the BIDS iEEG standard (Holdgraf et al., 2019). This is relevant for feature visualization in 3D space, connectomics based brain circuit analysis and across- patient decoding. By default, py_neuromodulation expects coordinates to be in MNI standard space that correspond with the mesh and connectomes provided with py_neuromodulation, but practically any coordinate system can be used if a corresponding mesh or connectome is available. Thus, electrode localization must be performed outside of py_neuromodulation. In the most simple approach, the coordinates can be extracted based on visual inspection of a CT or MRI scan after normalization to MNI space. Given that there are potential errors that can result from suboptimal coregistration and normalization, many different toolboxes have been developed to optimize this process, often specialized to the specific electrode type and research field. Consequently, py_neuromodulation does not require any neuroimaging data, but depending on the electrode localization approach and pipeline, CT, MRI, both or even intraoperative fluoroscopy can be used to determine electrode coordinates as input for py_neuromodulation (Randazzo et al 2015, Soper et al 2023). In fact, we believe that requiring coordinates over requiring individual neuroimaging data is advantageous, as neurophysiology datasets are commonly shared with coordinates but without individual imaging data available. For example, the open epilepsy dataset used for the movement decoding use- case provided electrode locations which were readily usable within py_neuromodulation. In our lab and more generally in the context of DBS, we take advantage of the sophisticated semi- automatized electrode localization pipeline provided by LeadDBS v3.0, which is built around a refined protocol using Advanced Normalization Tools combined with visual inspection of coregistration, normalization and artifact localization. For this we use preoperative + +<--- Page Split ---> + +3T T1 and T2 MRI imaging combined with postoperative CT. Connectivity profiles from the given coordinates can then be extracted with py_neuromodulation from pre- constructed connectivity matrices that have been made openly available via Zenodo (https://doi.org/10.5281/zenodo.10805915). Alternatively, Lead Connectome Mapper can be used to get more refined estimates based on patient specific or disease specific connectomes. The saved Lead- Mapper output represents connectivity estimates in whole- brain NIfTI format (.nii) which can then be processed using py_neuromodulation for computation of the optimal decoding connectivity map and subsequent connectomic channel selection with different cross- validation approaches. + +The heart of the py_neuromodulation package is the data stream with the extensive preprocessing and feature estimation module that generates interpretable neurophysiological features in a way that is directly transferrable form offline to real- time. This feature estimation module interfaces the machine learning module, which leverages the many advanced and actively maintained and developed machine learning packages in Python. In fact, the availability of cutting- edge machine learning packages was together with the open- source nature of Python, a key reason for us to decide against an implementation of py_neuromodulation in Matlab. The key design principle for this aspect is that we wanted to provide an easy interface for simple and straightforward decoding approaches including optimized default parameters, while also making it as straightforward as possible to plug in new model architectures, given the rapid development of ever improving machine learning methods. As a consequence, py_neuromodulation provides default parameters for simple linear models alongside options to plugin any other model. Additionally, py_neuromodulation defines and supports different dimensionality reduction methods, such as Principal Component Analysis (PCA) or Canonical Correlation Analysis (CCA) and validation strategies and metrics building on the widely- used scikit- learn package (Pedregosa et al 2011) and pre- calibrated based on default parameters as established in this study. Additional features within the py_neuromodulation workflow include feature selection using the Minimum- Redundancy- Maximum- Relevance method based on the mrmr Python package (https://github.com/smazzanti/mrmr), random over- and undersampling based on the imbalanced- learn python package (Lemaitre et al 2017) and Bayesian hyperparameter optimization through the skopt package (https://github.com/scikit- optimize/scikit- optimize). Importantly, all these dependencies are already solved through installation of py_neuromodulation as described in the documentation (https://py- neuromodulation.readthedocs.io/en/latest/installation.html). The novel cross- validation approaches for across- patient and across- cohort decoding were developed within py_neuromodulation itself, providing modules for storing and validation of the computed features in a defined standardized data structure. Realistically, we believe that py_neuromodulation provides the necessary framework to bridge the gap between neuroscience, clinical neurology and machine learning communities by handling complex workflows for which extensive domain knowledge is required. + +To clarify these aspects for the reader, we have made the following adjustments to the manuscript: + +## Methods: + +"py_neuromodulation reads electrode localization from BIDS iEEG metadata files, including referencing information and electrode locations, which is necessary for across patient decoding described below. Here, it is important to note that py_neuromodulation does not provide a workflow for performing the localization of invasive electrodes, but expects electrode locations to be predefined using one of the many workflows that are available in the literature (Randazzo et + +<--- Page Split ---> + +al. 2016, Soper et al. 2023, Neudorfer et al. 2023). We recommend the advanced neuroimaging pipeline defined by Lead- DBS with default settings (Neudorfer et al. 2023). In brief, Lead- DBS uses preoperative MRI and postoperative CT scans for co- registration and normalization to MNI 2009b NLIN ASYM space. Electrode artefacts of both DBS and ECoG electrodes can then be visually identified and marked to obtain MNI coordinates of electrode contacts." + +"py_neuromodulation provides optimized default parameters for straightforward invasive brain signal decoding approaches, while also allowing to seamlessly plug in new and alternative machine learning models directly in the Python code." + +We have further included example code within the methods to make the utility of the software easier to follow: "Py_neuromodulation API and example usage": + +"The general goal of the presented package is to simplify analysis of invasive electrophysiological data. For a minimal example for offline analysis, the recording in a form of a numpy array or pandas dataframe needs to be supplied in the shape (n_channels, n_time) with a respective sampling frequency. Subsequently, features are computed with a feature interval given the sampling_rate_features_hz. The following code shows the "stream" initialization and call of the "run" function: + +import py_neuromodulation as nm import numpy as np NUM_CHANNELS = 5 NUM_DATA = 10000 sfreq = 1000 # Hz sampling_rate_features_hz = 10 # Hz data = np.random.random([NUM_CHANNELS, NUM_DATA]) stream = nm.Stream( sfreq=sfreq, data=data, sampling_rate_features_hz=sampling_rate_features_hz ) features = stream.run() + +The returned "feature" object is a dictionary containing each feature name - value pair. The general convention is that the feature names are given in the nomenclature "channel name" "feature_name" "feature_name_subgroup". It is important to note that in the upper example the settings and channel- specific information were automatically defined given default parameters. Given a BIDS- data path the respective information can be queried: + +from py_neuromodulation import nm_IO ( raw, data, sfreq, line_noise, coord_list, coord_names, ) = nm_IO.read_BIDS_data( PATH_RUN=PATH_RUN, BIDS_PATH=PATH_BIDS, datatype=datatype ) + +The nm_channel dataframe can then be initialized given different parameters: + +<--- Page Split ---> + +from py_neuromodulation import nm_define_nmchannels + +nm_channels = nm_define_nmchannels.set_channels( + +ch_names=raw.ch_names, ch_types=raw.get_channel_types(), reference="default", bads=raw.info["bads"], new_names="default", used_types=("ecog", "dbs", "seeg"), target_keywords=["MOV_RIGHT"], + +The pre- processing and feature computation settings can be modified using a dictionary (software version tag 0.02). Therefore, the default settings can be obtained and modified: + +from py_neuromodulation import nm_settings + +settings = nm_settings.get_default_settings() settings = nm_settings.set_settings_fast_compute(settings) + +settings["features"]["fft"] = True settings["features"]["bursts"] = True settings["features"]["sharpwave_analysis"] = True settings["sharpwave_analysis_settings"]["estimator"]["mean"] = [] for sw_feature in list( settings["sharpwave_analysis_settings"]["sharpwave_features"].keys() ): settings["sharpwave_analysis_settings"]["sharpwave_features"][ sw_feature ] = True settings["sharpwave_analysis_settings"]["estimator"]["mean"].append( sw_feature ) + +After feature computation using the "run" method, a decoder module can be used to evaluate a scikit- learn model: + +from py_neuromodulation import nm_analysis, nm_decoder from sklearn import metrics, model_selection, linear_model + +feature_reader = nm_analysis.Feature_Reader( feature_dir=PATH_OUT, feature_file=RUN_NAME, ) + +model = linear_model.LinearRegression() + +feature_reader.decoder = nm_decoder.Decoder( features=feature_reader.feature_arr, label=feature_reader.label, label_name=feature_reader.label_name, used_chs=feature_reader.used_chs, model=model, eval_method=metrics.r2_score, cv_method=model_selection.KFold(n_splits=3, shuffle=True), + +<--- Page Split ---> + +) + +performances \(=\) feature_reader.run_ML_model( estimate_channels \(=\) True, estimate_gridpoints \(=\) False, estimate_all_channels_combined \(=\) True, save_results \(=\) True, ) + +Based on the used scikit- learn metric and cross- validation strategy, the performances are estimated. Multiple additional arguments can further be supplied to adapt the feature estimation and decoding pipeline. + +For applying the optimal connectivity decoding without patient- individual training, the electrode contact MNI coordinates need to be obtained beforehand (Randazzo et al 2016, Soper et al 2023), and then utilized for obtaining the corresponding connectivity fingerprints from either the Lead- DBS Lead- Mapper toolbox (Neudorfer et al 2023), or by a pre- defined grid. py_neuromodulation provides a method for obtaining matching points from a pre- defined cortical hull grid (n=1025 points) or whole- brain grid (1236 points). The computed grids can be downloaded from a public repository (https://doi.org/10.5281/zenodo.10805915) and utilized through the following API: + +from py_neuromodulation import nm_RMAP import numpy as np + +mni_coords \(=\) [[10, 40, 20], [50, 14, 12]] # definition of MNI contacts + +ch_sel \(=\) nm_RMAP.ConnectivityChannelSelector( whole_brain_connectome \(=\) True, func_connectivity \(=\) True ) + +# retrieve connectivity fingerprints for passed MNI coordinates fps, grid_idx \(=\) ch_sel.get_closest_node(mni_coords) + +# computation of optimal connectivity correlations corrs \(=\) ch_sel.get_rmap_correlations(fps) + +recording_contact_use \(=\) np.argmax(corrs) + +For the movement decoding use- case, a movement decoding model was trained that could significantly predict movement without patient- individual training. The model can be accessed through a Zenodo archive and the required code is made publicly available through a GitHub repository (https://github.com/neuromodulation/AcrossPatientDecodingModel). The following exemplary code illustrates how the model can be loaded and directly be utilized in the py_neuromodulation API: + +import py_neuromodulation as nm from py_neuromodulation import nm_settings import skops model \(=\) skops.io.load("movement_decoder.skops") settings \(=\) nm_settings.get_default_settings() settings \(=\) nm_settings.set_settings_fast_compute(settings) stream \(=\) nm.Stream(settings \(=\) settings) + +<--- Page Split ---> + +# definition of nm_channels and exemplary data features = stream.run(data) model.predict(features.to_numpy()) + +5) One of the three big problems the authors hope to address is "Machine learning can capitalize on large datasets but current brain signal decoding approaches for BCI still commonly rely on individual patient training sets of short duration". It is never really clear to me how the authors solve this – is there a particular method they introduce to solve it? Or are they just trying to show that in fact you don't need large data sets of long duration, even though other researchers try to use those? More clarity in discussion on this would help. + +We thank the reviewer for this important question. Most of the invasive recordings are acquired within an intra-operative setting or using "externalized" electrodes that allow recordings in the clinics outside of the operating room. This inherently limits the recording durations. The key point that we are trying to make in our manuscript is that developing across- patient decoding approaches could not only be more convenient and cheaper for clinical applications, but could also lead to improved decoding performances because more complex models can be trained on the larger datasets after merging data from multiple subjects and cohorts. Thus, since the performance of machine learning and especially deep learning models was shown to be highly dependent on dataset size (Sarker et al 2021, SN Computer Science), we believe that it becomes necessary to develop machine learning models that utilize datasets from multiple subjects and cohorts. Evidence for this is provided in our study through the validation of the pretrained model performance vs. the model trained on individual data. We found that the model that was trained on all other subjects of the cohort performed better than the model trained on the relatively short individual recording duration. + +Part of the motivation of the design of py_neuromodulation stems from the concern that a lot of brain signal decoding studies are practically not reproducible. With this we do not intend to say that the science or results are manufactured or wrong. Instead, we mean that the approaches that are reported are so individualized and require so much domain knowledge and resources that it is hard to envision how other labs could actually perform the same task, even if given the same data. On the other hand, we are convinced that the future of clinical neurotechnology will use machine learning methods, requiring multicenter validations of specific approaches that should be easily implementable by different teams and highly standardized. We have searched for software solutions that provide standardized means to implement and validate machine learning models for invasive brain data that can be directly translated into real- time applications and were not satisfied with what we found. Therefore, we aimed to address this problem by ourselves, by implementing standardized tools for preprocessing, feature estimation and across center decoding. Since the pipeline parametrization in py_neuromodulation is implemented within a single file, all settings can be shared and implemented without the need to change programming code. In this manner the utilized parameters and models are easily implementable, transparent and reproducible, greatly facilitating multicenter collaborations and clinical trials. In addition to the democratization of the methodological approach, this also allows for a direct sharing of models, as we have done for the generalizable movement decoder that is now available via a DOI (https://doi.org/10.5281/zenodo.10794370) and can be plugged into py_neuromodulation anywhere in the world for out- of- the- box plug&play invasive brain signal decoding. We hope that in the future, we can create a model database that contains usable models for decoding of + +<--- Page Split ---> + +symptom and behavior for open- source development of the next- generation of machine learning powered neurotechnology. Through across patient decoding more and more refined models based on larger multicenter datasets can build the foundation for an ever- expanding complexity of the most cutting edge machine learning approaches. + +We have now clarified this further in the methods: + +"By standardizing feature estimation and brain signal decoding we aim to enable machine learning decoding to make use of many datasets from different patients and centers. The implemented pipeline provides, therefore, a method for unifying features and decoding across different acquisition methods. To enable generalized future movement decoding, we provide the validated across- patient machine learning model with the required pre- processing and feature computation modules as an openly available resource (https://doi.org/10.5281/zenodo.10794370)." + +Specific comments to improve readability: + +Early in results or in intro, authors should say that their system is called "py_neuromodulation" When they began to use this term in results, I did not perceive that it is actually the name of their software pipeline. + +Thank you for pointing this out, the introduction now reads: + +"We developed an open, integrative and modularized platform (Fig. 1), for standardized and reproducible implementation of machine learning based brain signal decoding algorithms called py_neuromodulation (https://github.com/neuromodulation/py_neuromodulation)." + +Results section 1: "To address this, we developed dedicated approaches for patient decoding based on normative MRI connectomics and latent embeddings from contrastive learning with CEBRA13. " – this sentence will be opaque to a number of readers who are unfamiliar with contrastive learning and the acronym CEBRA. + +We have now simplified the phrasing to make it more generally understandable: + +"To address this, we developed dedicated approaches for across- patient decoding based on advanced machine learning algorithms that can account for variability in electrode localization." + +Figure 1, Part D is not completely clear as it is first presented, and it seems to be a major part of the author's pipeline. Especially this statement: "Features can be mapped in space (d) for patient individual or across- patient decoding and consecutive adjustment of therapeutic delivery." Its not clear here how mapping features in space specifically contributes to decoding of dynamic patient states like movement, emotion, or seizure occurrence. Mapping the relevant activities would certainly contribute to a better understanding of anatomic localization or network involvement of recording sites that are relevant to decoding, and that contributes to understanding which brain networks are most relevant for the decoded brain state. But it is not clear at this point in the manuscript how the spatial mapping contributes to the process of decoding or to its accuracy. At line 89- 91, and later in the text, they imply that accounting for the variable localization of implants + +<--- Page Split ---> + +would be a contributor to generalized cross- subjects decoding, which seems true, but how would anatomic localization contribute to individual decoding performance as is stated in the figure legend? + +We thank the reviewer for this important remark. Indeed, the spatial raw data or feature mapping to a standardized space is only a requirement for decoding without patient- individual training. + +We adapted the Figure 1 legend to delete the phrase of feature mapping for patient individual decoding: + +"Features can be mapped in space (d) for across- patient decoding and consecutive adjustment of therapeutic delivery." + +Finally, we have introduced two new supplementary figures that explain the process in more detail, also in response to reviewer #2: + +![](images/Figure_4.jpg) + +
Supplementary fig. 4 Comparison of different approaches for neural decoding without patient-individual training. (a) Grid-point interpolation: Individual recording contact locations are estimated in a standardized
+ +<--- Page Split ---> + +space. Features are separately computed for each recording contact. Data is then mapped to a pre- defined cortical or subcortical grid in MNI coordinates. This mapping ensures a correct sorting of activity sources stemming from similar brain regions. In this manner, feature vectors are mapped to a common grid defined in space (similar to EEG montages), which then lay the foundation to train models on grid- points instead of recording channels for neural decoding without patient individual training. (b) Connectomic channel selection: An optimal decoding whole- brain connectivity map is computed based on training data. This step requires the computation of contact- specific neural decoding performances and whole- brain connectivity estimates. The connectivity profiles and decoding performances are correlated in a voxel- wise manner to estimate a connectivity map associated with optimal decoding performance. For a test subject, the connectivity map of each channel is spatially correlated with the optimal decoding map and the one with the highest similarity is selected and used for testing of a pre- trained machine learning model. (c) The connectomics- based channel selection approach is further extended by transforming individual channel features using an embedding layer. This layer is computed through contrastive learning and auxiliary variables. Here we utilized the CEBRA package (Schneider et al 2023, Nature). + +In the present manuscript, the Pearson correlation coefficient was utilized for the connectomics based approach. We note, however, that this approach can be extended by different correlation metrics. In the following we added another more detailed figure explaining the connectomic channel selection approach, including a definition of connectivity profile, correlations of connectivity profiles and the optimal connectomics derived decoding map: + +<--- Page Split ---> +![PLACEHOLDER_56_0] + + +Supplementary fig. 5 Connectomics- based neural decoding without patient- individual training. (a) Estimation of a patient- individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain- wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template + +<--- Page Split ---> + +associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. + +## Results section 2 + +"at the single sample level (100 ms precision indicating presence or absence of movement) and at the individual movement level (300 ms or more movement time decoded consecutively)" – this sentence is not clear + +Also in response to reviewer #2 we have further clarified the sample- wise performance vs. the movement detection rate. + +We adapted the sentence to read: + +"We trained ridge regularized logistic regression classifiers and evaluated their performance using the balanced accuracy metric with 3- fold cross- validation on consecutive data segments, yielding sample- wise performances indicating presence or absence of movement at 100 ms resolution. Sample- wise performances were concatenated to establish a more coarse metric that allowed for detection of individual movement entities, termed movement detection rate and defined as 300 ms of consecutive movement classification." + +and added the following to the methods: + +"In addition to reporting the sample- wise classification performances, we therefore report the accuracy of correct predicted movement blocks termed "movement detection rate". If the classifier's output probability is above 0.5 for three consecutive samples (300 ms) the present movement is classified to be detected. A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block." + +it is not quite spelled out what movement decoding really means – are the brain states that are decoded "not moving" versus "moving"? this should be more clearly stated. + +Also in response to reviewer #2 this has now been clarified and the respective results sections reads: + +"We implemented py_neuromodulation for electrocorticography (ECoG) based movement decoding as a two- class classification problem (rest vs. movement present) without individual training ..." + +Figure 2 –Panels j, k – the term "embedding" is not clear here. + +Thank you for pointing us to this lack of clarity. Through the application of the non- linear encoder as part of the contrastive learning approach (Consistent EmBeddings of high- dimensional Recordings using Auxiliary variables - CEBRA), we transform, multi- dimensional invasive brain signal features into a lower- dimensional, yet highly informative "embedding space" using a five- layer convolutional neural network with the InfoNCE (Noise- Contrastive Estimation) contrastive loss. When data is input into the network, it passes through various layers, each performing different transformations guided by the weights (and biases) of the network. The specific layer from which we extract the embedding is a non- linear encoder. The resulting embeddings showed + +<--- Page Split ---> + +exceptionally high consistency across subjects as investigated with linear identifiability in our study, which facilitates the discernment of neural patterns associated with motor output across subjects. The exceptional utility of the embedding in our study lies in its ability to convert the vast, high- dimensional invasive brain signal recordings with different number of channels, locations and durations into a more tractable, simplified form without significant loss of critical information that is comparable across subjects. By doing so, we can compare the similarity of the embedding and use that for across- patient decoding. + +We now added a short clarification to the figure and the figure legend: + +![PLACEHOLDER_58_0] + + +"... (j) low- dimensional embedding (exemplar subject shown) derived from the model weights of non- linear decoder using contrastive learning with a convolutional neural network with CEBRA. Comparison of embeddings provides the foundation of across- patient decoding. (k) shows the embedding consistency from each to every other patient via linear identifiability. ..." + +Panel o – the meaning of the y axis is not clear in these plots. For example for “true movement” is the y axis displacement? Force? + +<--- Page Split ---> + +This was not sufficiently clear. The movements shown in this plot are the single- trial movement amplitudes recorded from an electrical rotational handle coupled to a potentiometer. It is therefore a kinematic representation of the hand movement. + +We adapted the Figure 2o "y axis" label: "Hand movement [a.u.]" (see above) and added in the Figure legend: "Real- time single trial decoding is shown for out- of- cohort patient 1 with y- axes depicting true measured analog rotameter movement amplitude (top), classification probability predictions without patient- individual training (middle) and predictions with training (bottom)." + +"To investigate the individual variability of trainer vs. learner performance" – not sure what this means + +We agree that this sentence did not make sense, we have now clarified this as follows: + +"We next established a subject- to- subject decoding matrix, which provides information on the performance of each subject when trained on a single other subject from the cohort. This reveals, which subjects brain signals are well- suited to serve as training data leading to decoders on other subjects perform well (good trainer) and which subjects brain data have generalizable qualities that allow them to train from a variety of subjects yielding high performances independent of the training data (good learner)." + +In general for this section: what signal features contributed to movement decoding? In the following section on emotion decoding, the features used are stated more explicitly, and that would help here in this section. + +We thank the reviewer for this important remark. For the movement decoding model, there were slight variations to what degree the oscillatory features contributed for each cohort and model. Overall, all frequency bands had high contributions to the decoders with theta, high- beta and high- gamma yielding the strongest relationships. + +We have now clarified this in text and through an additional Supplementary figure showing the sum of the absolute value linear model coefficients from the patient- individual movement decoding models of all patients. + +<--- Page Split ---> +![PLACEHOLDER_60_0] + +
Supplementary fig. 2 Sum of linear model absolute value coefficients shows feature importances for all movement decoding patients.
+ +Results: "Feature contributions were observed in each frequency band but highest importance was identified in the theta, high beta and high gamma frequency bands (see supplementary fig. 2)." + +"To investigate a potential relationship with clinical scores, we correlated decoding performances from the most predictive channel contrasting neutral vs. positive/negative per patient with Beck's Depression Inventory (BDI) at time of recording and after six months of chronic DBS. Decoding performance correlated with DBS induced improvement in BDI scores (rho=0.79, p=0.01), but not with concurrent symptom severity (Fig. 3f)." - this is tough to follow - why would the decoding performance in emotional task be expected to correlate with depression severity? Is the hypothesis that the more depressed one is, the more task related emotional valence is "decodable"? the opposite seems more likely, that is depression would blunt ones ability to distinguish emotional valences. + +We agree with the reviewer, that indeed we sought a negative relationship, given the impairment in emotion regulation that is associated with depression. + +We have now clarified this in the respective sentence: + +"Decoding performance correlated with DBS induced improvement in BDI scores (rho=0.79, p=0.01), but concurrent symptom severity did not reflect in lower decoding performances (Fig. 3f)." + +"... connectivity fingerprints seeded from LFP channel locations were correlated with channel specific decoder test- set performance". - for a nonexpert - how are connectivity fingerprints quantified so as to feed into a correlation? A sentence on this would help. + +<--- Page Split ---> + +We have now extended the description of the methodological approach with new figures and text. In addition, we have extended the phrasing to make it more intuitively comprehensible: + +"In all cases connectivity fingerprints seeded from LFP channel locations were correlated with channel specific decoder test- set performance, by vectorizing or reducing spatial information and deriving similarity estimates to the optimal fingerprint (see supplementary figure 6)." + +Figure 3e – even zooming in, its hard to read the feature labels or understand what they mean. Legend refers to a part “I” but don’t see that panel in the figure. + +We thank the reviewer for this comment and updated the feature label font size in Figure 3e, and corrected the panel labelling. + +Results section 4, briefly explain what an F1 score is + +The results section now reads: + +“We optimized these parameters for sample- wise seizure classification to maximize the F1- score, which depicts the harmonic mean between precision (the model's ability to identify only true seizure instances) and recall (the model's ability to find all seizure instances).” + +## Discussion: + +“Nevertheless, decoding performances were investigated in the presence of clinical brain + +<--- Page Split ---> + +stimulation in two out of three use cases, namely STN- DBS for PD and responsive neurostimulation for epilepsy" – is this actually true for RNS? My understanding is that RNS is a "half duplex" device, that is it senses, provides preprogrammed stimulation train when an event is detected, then returns to sensing mode. It does not actually sense during stimulation. + +We thank the reviewer for this expert remark. The RNS device indeed does blank during stimulation, but this does not render the recordings free from the consequences of acute stimulation, which are very visible, both through physiological changes as described in Kokkinos et al. JAMA Neurol 2019 https://doi.org/10.1001/jamaneurol.2019.0658 and through artifacts even though recordings were blanked for the brief periods of stimulation, as shown in an added supplementary figure: + +![PLACEHOLDER_62_0] + +
Supplementary fig. 9 Responsive Neurostimulation (RNS) device artifact annotations and corresponding features. (a) Raw time-series including annotated stimulation and clipping artifacts and (b) corresponding FFT features. The RNS does not allow for simultaneous stimulation and recording. The device parameters allow for specifying a "gain" setting that can omit the clipping artifact.
+ +We further referenced this artifact annotation within the methods section: + +"Both artifact types and their corresponding annotations in the raw signal and FFT features are visualized in supplementary fig. 9." + +We hope that the reviewer agrees that these recordings are clearly influenced by stimulation. We have still tried to adapt the phrasing to make it more precise, but the changes we came up with all lead to a more convoluted and less easily understandable discussion, which is why we hope that the reviewer accepts that we keep the phrasing as is. However, we would be happy to accommodate any suggestions the reviewer may have to make this more clear. + +"The network description however, is static in nature, while symptoms wax and wane. Brain signal decoding may help these networks to come to life in a dynamic closed- loop neurostimulation approach by informing both decoding and stimulation models of symptom specific circuits to + +<--- Page Split ---> + +optimize symptom decoding and adaptation of stimulation right at the time they occur" – not sure I get the meaning here. This seems to be a discussion of the advantage of combining connectomics (static) with brain signal decoding (dynamic) to produce something that hasn't been done before, but the sentence is lofty enough that it loses the reader. + +We are truly thankful that the reviewer has taken the time to help us improve our manuscript so constructively. The reviewer is right that we were a bit ambitious in the phrasing here. Practically, we believe that in the future, adaptive DBS will be tuned to disease specific connectomic targets and we will use connectomic information to a) decode symptom presence and b) define the optimal stimulation parameters and location to hit the right target in a dynamic manner. + +We have now adapted the phrasing accordingly: + +"The network description however, is static in nature, while symptoms wax and wane. Brain signal decoding may help these networks to come to life in a dynamic closed- loop neurostimulation approach. Invasive multisite recordings can be used to monitor the presence of symptoms in specific brain networks and advanced control algorithms can tune stimulation parameters in real- time to stimulate precisely the networks of symptoms that are present." + +## Notes by the authors: + +In the previous manuscript version we reported in the statistics section, we reported: "All statistical tests were computed using non- parametric Monte- Carlo sampled permutation tests with a significance value of \(\alpha = 0.5\) ". We corrected the \(\alpha\) value now to be 0.05. + +<--- Page Split ---> + +Reviewer #2 (Report for the authors (Required)): + +The goal of having "plug and play" decoding algorithms for closed loop DBS is an important one. Likewise, having a toolbox that can implement these algorithms and distribute open- source would be valuable. However, the paper does not give enough information as to how this toolbox implements a plug and play algorithm. Multiple steps still seem to be involved, including co- registering individual's imaging to MNI space, and placing the electrodes in this coordinate space. This, as mentioned by the authors in their rebuttal, is not trivial, especially when taking into account brain shifts due to opening the dura. No mention of how this substantial shift would be accounted for. The authors state that one of their goals is to "facilitate multicenter clinical trials ...and democratization of the methodological approach." Yet, the descriptions in this paper are far too vague and lacking in specific methods for even those engineers familiar with BCIs to be able to implement, let alone for clinicians to be able to even comprehend the basics. And importantly, this procedure of co- registering would take significant time - indeed, in our experience, much more time than building a very simple decoder of movement vs. rest for an individual, which could be done in less than 5 min (including recording and automated decoder building). Either way, this will require some time for the clinician or a technologist. Since this (across- patient decoding) appears to be the biggest goal of this paper, the authors need to make a much stronger case (including empiric evidence of time to perform and compute the different steps for a given patient, as a clinician would do it, and showing this is truly less than recording move vs rest for 3- 5 min and building a very simple individualized decoder, rather than vague estimates as in the rebuttal) for why this is better than individual decoders. Overall, the paper still assumes too high of an expertise in many disparate and specific domains to be applicable to a broad audience. + +We are truly thankful for the expert assessment of our manuscript by the insightful reviewer. We agree with the reviewer that methodological clarity is important, even if the procedures are complex. We have now added additional information and new supplementary figures in the hope to address this point. To further improve the methodological clarity of our manuscript, we have now adapted the methods section to include a dedicated imaging chapter to include further information regarding normalization, co- registration and accounting for brain shifts. We acknowledge this requirement and provide necessary instructions to obtain electrode localization in a standard image space. However, we would like to emphasize that in our view not time saving but the ability to leverage larger dataset sizes, with the potential to scale performances of complex machine learning algorithms beyond what is recordable at the single subject level, will be the key benefit, and we provide a specific example for this point. In context of current AI breakthroughs, our thought process is that a brain signal decoder that can use all available brain signals from different subjects, will be more powerful than a decoder that can only use individual subject data, just as large language models that can use all text available will be more powerful than models that can only learn from text of individual subjects. + +<--- Page Split ---> + +Nevertheless, our approach does save time, because image acquisition, processing and localization is done routinely in the hospital and therefore does not require additional time or expertise beyond what is expected by a multidisciplinary DBS board that consists of neurosurgeons, neurologists and neuroradiologists. MRI and CT scans, as well as coregistration are critical steps of the implant procedure that is performed by the neurosurgeon, in order to translate stereotactic coordinates. Postoperative imaging is performed to rule out complications and perform electrode localization that is critical for surgical decision making, typically performed by neuroradiologists. Patients with electrodes outside the target area will be considered for a revision in case of unsatisfactory clinical results. This electrode localization is performed by clinical staff and the output is used in our toolbox without requiring further processing. Thus, no additional time is required for image processing. + +In theory, many different approaches using different tools could be used for electrode localization and our toolbox is agnostic to which tool was used. However, given that we have substantial expertise in this matter and have contributed to some of the used tools, we propose a pipeline that is based on the Lead- DBS toolbox (Neudorfer et al 2023). Notably, all image co- registration, normalization and brain- shift correction was performed as performed as clinical routine in our center. Our center co- develops and uses Lead- DBS that builds on the ANTs toolbox (Avants et al 2008, Symmetric diffeomorphic image registration with cross- correlation: evaluating automated labeling of elderly and neurodegenerative brain) for co- registration and normalization of image patient space to MNI nonlinear 2009b standard space. This process was optimized in Lead- DBS for subcortical structures (Ewert et al 2009). In addition, brain- shift correction induced by dura opening is implemented in Lead- DBS through a linear transformation refined to a subcortical region (Schönecker et al 2009, Automated Optimization of Subcortical Cerebral MR Imaging- Atlas Coregistration for Improved Postoperative Electrode Localization in Deep Brain Stimulation). The Lead- DBS Volume Registration documentation describes this method in further detail: https://netstim.gitbook.io/leaddbs/lead- dbs/step3- volume- registrations. Since these steps are required for connectivity- based neural decoding, we now added them to the "Electrode Information and imaging" methods section in the main manuscript: + +"py_neuromodulation reads electrode localization from BIDS iEEG metadata files, including referencing information and electrode locations, which is necessary for across patient decoding described below. We recommend the advanced neuroimaging pipeline defined by Lead- DBS with default settings36. In brief, Lead- DBS uses preoperative MRI and postoperative CT scans for co- registration and normalization to MNI 2009b NLIN ASYM space. Electrode artefacts of both DBS and ECoG electrodes can then be visually identified and marked to obtain MNI coordinates of electrode contacts. Image co- registration, normalization and brain- shift correction are thus automatically obtained through Lead- DBS. Localization of subcortical lead electrodes requires a post- operative CT or MRI image, which needs to contain the electrode contact artifacts. Lead- DBS uses internally the ANTs toolbox (Avants et al 2008, Symmetric diffeomorphic image registration with + +<--- Page Split ---> + +cross- correlation: evaluating automated labeling of elderly and neurodegenerative brain) for co- registration and normalization of image patient space to MNI nonlinear 2009b standard space. This process was optimized in Lead- DBS for subcortical structures (Ewert et al 2009). In addition, brain- shift correction induced by dura opening is implemented in Lead- DBS through a linear transformation refined to a subcortical region (Schonecker et al 2009, Automated Optimization of Subcortical Cerebral MR Imaging- Atlas Coregistration for Improved Postoperative Electrode Localization in Deep Brain Stimulation). The Lead- DBS Volume Registration documentation describes this method in further detail: https://netstim.gitbook.io/leaddbs/lead- dbs/step3- volume- registrations. + +We want to highlight the following advantages of our decoding approach without patient individual training in contrast to a patient- individual training decoder with a short 3- 5 min training duration: + +1. Our proposed connectivity-based decoding makes use of the precise localization and connectivity profile of the implanted electrodes. +2. Training data from all previous training-cohort patients related to this connectivity profile are utilized. +3. Any setup required for electrophysiological signal acquisition and model training could be omitted. + +Beyond these points that the reviewer picked up, we would also like to highlight other aspects of novelty in the present article: + +We have extended the combined neurophysiology and connectomics approach beyond the motor domain, applying it to patients undergoing deep brain stimulation (DBS) for major depressive disorder. We show that in these patients, perceived emotions can be decoded within 600 milliseconds from cortical regions targeted by neuromodulation, using brain signal waveform shape features that have never before been utilized for decoding. This underscores the value of linking novel neurophysiological measures and connectomics for brain circuit discovery, as we identify the optimal decoding network in the left prefrontal cortex, a region previously recognized as crucial for successful depression treatment with neuromodulation. Additionally, we demonstrate that our approach can directly suggest device parameters to optimize seizure detection in currently available implantable responsive neurostimulators for epilepsy. The key advancement here is the use of machine learning algorithms that simulate an implantable device by constraining model parameters to the specific capabilities of the implant. Thus, we show that our innovations can propose targeted improvements for patients already equipped with invasive brain stimulation devices. This bridges the gap between experimental breakthroughs and real- world clinical treatments, highlighting the applicability of our approach to routine clinical care. + +Major issues + +<--- Page Split ---> + +1. The central theme of the paper, the connectivity-based decoding, is still not explained clearly enough to understand. The additional supplementary figures help slightly, but they still dance around, and gloss over, the main concerns I had previously – the "connectivity values", correlation of them with "decoding performance (what is this??)", and "optimal decoding map" are not clearly defined. SF4 shows correlations with 1000 functional connections – does this mean they are averaged over all participants? What does decoding performance for a single electrode mean? Does that mean you're building single-channel decoders? If not, this does not make sense. And how are you correlating one value with a connectivity map (which is a whole vector for a single electrode)? SF5.c similarly needs much clearer explanation. (What is a connectivity template? What are R1-R6? What is being correlated with what?) This needs much better explanation if you want people to understand how to use it. Examples would help. + +We are very thankful for this important point. We have now significantly improved the description of this complex approach, now listing all required steps in sequence and explaining each term in detail in the "Connectomics- based neural decoding section" of the methods. We also want to highlight that all the required steps can be reproduced computationally through provided tutorials on the GitHub documentation page: https://neuromodulation.github.io/py_neuromodulation/index.html, which we also list in the respective methods section: + +1. A connectome is required that contains resting state fMRI recordings (time-series of whole-brain blood oxygenation dependent [BOLD] activation). This connectome should be registered to a standard space such as MNI nonlinear 2009b. +2. For invasive electrophysiological recordings, the recording contact locations need to be estimated in the same space (MNI). This requires normalization to an imaging standard space, co-registration of pre-operative MRI and post-operative CT images, brain-shift correction and subsequent annotation of the recording contact artifacts to obtain the standardized recording contact locations. +3. The location of each recording contact is then used as a region-of-interest (ROI), for which traditional resting state fMRI connectivity (Pearson correlation of BOLD time – series) is computed to all voxels in the brain, repeated for each of the subjects in the connectome (for example \(n = 1000\) in the Human Connectome Project data) and then averaged. +4. This results in a normative "whole-brain connectivity fingerprint" (Supplementary Figure 5a) for each recording contact, with each voxel indicating how strongly connected (or temporally correlated as defined for resting state fMRI connectivity) it is on average to the location of the recording contact. E.g. if the recording contact is residing over the right motor cortex, typically the left motor cortex will show high connectivity values, while other regions, such as the + +<--- Page Split ---> + +occipital cortex, will show lower connectivity values, because their BOLD time- series are on average less correlated. + +5. These "whole-brain connectivity fingerprints" can then be subjected to voxel-wise correlations with the single-channel decoding performance across all available recording contacts to identify the "optimal connectivity map". E.g. if one recording location is in motor cortex and has a high movement decoding performance while other recording locations are scattered in different areas with lower decoding performances, subjecting these to voxel-wise correlations will yield a whole-brain map of correlation values that resembles the connectivity profile of the motor cortex. The "optimal connectivity map" is thus defined as the map derived from voxel-wise correlations of resting-state fMRI connectivity with single-channel decoding performance across all "whole-brain connectivity fingerprints". + +6. Finally, when aiming to estimate the decoding performance of a specific recording location, it is now possible to assess the spatial similarity (mathematically defined as vectorized correlation across voxels) between the "whole-brain connectivity fingerprint" of the respective location, with the "optimal decoding map". A fingerprint that has a spatial pattern similar to the "optimal decoding map", will likely provide good decoding results, while a spatially dissimilar fingerprint will likely indicate that the recording contact location does not yield high decoding performance. + +7. For the purpose of selecting the best available recording contact location available within a set of contacts for each subject, these estimated performances can be compared ((termed R1 to R6 in Supplementary Figure 5c) and the one with the highest performance can be chosen for across-patient decoding. Signals or features are therefore not projected or altered and only a single channel is selected for decoding based on the connectivity performance estimation. + +8. Importantly, when using this approach for across-patient decoding in previously recorded subjects, the true test-set performance must be void of circularities and thus the subject/recording contact to be tested must be left out of the definition of the "optimal decoding map". Once, the "optimal decoding map" is defined from a cohort, it can be prospectively applied for channel selection in a new subject, as performed in prospective validation cases in the present manuscript. + +We want to highlight in addition that the required steps can be reproduced computationally according to the provided tutorials on the GitHub documentation page: https://neuromodulation.github.io/py_neuromodulation/index.html. + +<--- Page Split ---> +![PLACEHOLDER_69_0] + + +Supplementary fig. 5 Connectomics- based neural decoding without patient- individual training. (a) Estimation of a patient- individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain- wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. Nomenclature: "Whole- brain connectivity fingerprint": Time- series correlation of a specific recording contact location to all other brain voxels in a fMRI resting state connectome. "Machine learning decoding performances": Single- channel machine learning performances from a supervised neural decoding problem such as movement classification. "Optimal decoding map": Correlation map computed from voxel- wise whole- brain connectivity fingerprints and machine learning decoding performances. Each voxel therefore represents the correlation between fMRI resting state connectivity for this specific region and the respective neural decoding performances. + +<--- Page Split ---> + +2. The performance, especially across cohorts, and ability to extrapolate to new patients, is somewhat oversold in this paper, even if this performance is substantially better than previous studies. In particular, when the leave-one-cohort-out accuracy is barely above chance ( \(\sim 0.6\) ), it suggests that even subtle differences in movement types will lead to poor decoder performance across patients. That would seem to not be very practical for a patient wanting to do many different types of movement, and thus "plug & play" would not work very well. Even \(\sim 80\%\) accuracy is highly unlikely to be good enough for most patients – think about how frustrated you would be if your computer cursor did not work correctly 2/10 times. + +We agree with the reviewer that we should aim to further increase all performances, which is our primary research mission for the coming years. However, we would like to comment in a bit more detail on the specific points the reviewer raises. The reviewer mentions that low across- cohort performance could reflect low generalization across movement types. However, the deterioration of across- cohort- performance is in our view not solely attributable to differences in movement task. In addition, entirely different hardware, including implantation procedure, implanted electrodes, patient states, neurological disorders may contribute to relatively lower decoding performance. As it stands, our report remains the first to ever demonstrate that decoding across- patients with such widely varying factors is possible at above- chance level. Nevertheless, the reviewer is absolutely right that this performance is low. With regard to the second point, that \(80\%\) performance may not be sufficient, we believe that it strongly depends on the purpose. Yes, not being able to move a cursor 2/10 times would be frustrating but we would like to provide a scenario more closely linked to the study at hand. E.g. for the treatment of essential tremor (ET) patients deep brain stimulation is only required during voluntary movement, because ET is defined by action tremor. Currently, DBS is always turned on, even if the patient doesn't move, because closed- loop therapies do not exist yet. Meanwhile, it is well- known that overstimulation leads to side- effects such as ataxia and gait impairment. Thus, for this purpose a classifier with \(80\%\) accuracy, biased to a high true- negative rate, while accepting a high false- positive rate, will significantly improve the treatment, leading to less overstimulation and consequently less side- effects. Thus, such a low- accuracy decoder could clinically meaningfully benefit more than 50,000 people implanted with DBS for essential tremor. This demonstrates how fruitful the merging of closed- loop neuromodulation and BCI research could be. Nevertheless, we agree with the reviewer that we should remind the readers that there is a lot of room for improvement and that our current results will not stand as the highest- ranking performance. Indeed, it is our aim to inspire more BCI experts to help improve the clinical realm of closed- loop neuromodulation. We now discuss the point of low decoding performances in the manuscript: + +We specifically want to highlight here also the limitation that the presented leave one subject out and leave one cohort out performances motivate the investigation of neural decoding improvements. + +<--- Page Split ---> + +Clinical implementation for closed- loop neuromodulation would require higher decoding accuracies to reliably address current neural states and symptoms. + +3. The revised paper still leans too heavily on the term BCI. The BCI society's working definition was not intended to include closed-loop DBS as a BCI. While philosophically clDBS could fit in this definition, the vast majority of BCI researchers do not consider it to be a BCI, and doing so could cause a host of logistical issues. Not to mention confusing many non-experts. + +The reviewer is clearly a BCI expert and our research team is predominantly working in the field of neuromodulation, rather new to the BCI community. We believe that the many relevant comments from the reviewer demonstrate the mutual interest in each others research and that there is increasing overlap in the questions we aim to address. Our research is very strongly inspired by all the important pioneering work of BCI engineers in the past decades. Indeed, without it, we would be very unlikely to even come up with the idea of using brain signal decoders to advance closed- loop neuromodulation. We believe that the merging of these two fields is a very exciting development, which has cast enthusiasm in recent articles. In fact, that this BCI expert reviewer was chosen to scrutinize our paper is indeed a hint that we are working in a field that now strongly overlaps. This development was recently formalized in an impactful review article titled "The convergence of neuromodulation and brain- computer interfaces" (Herron et al 2024, Nature Reviews Bioengineering). The authors stated that the neuromodulation and BCI fields "[...] can inform each other, and as the technological overlap increases, the distinction between neuromodulation and BCI becomes increasingly irrelevant" (Herron et al 2024). Instead of confusing people, we would like to invite BCI experts and curious students to the opportunities that closed- loop neuromodulation provides for improving patient lives using approaches that have been pioneered by BCI researchers. With the present article it is our dedicated wish to introduce BCI methodology for clinical neuromodulation research. We are not alone with this. In fact, previous research already used the term BCI to describe a closed- loop DBS system: "Cortical brain- computer interface for closed- loop deep brain stimulation" (Herron et al 2017, IEEE Transactions on Neural Systems and Rehabilitation Engineering). We personally build on these examples that invite experts from different fields to work together and that have inspired us to follow this path. Nevertheless, we respect the reviewers opinion and thus have now removed or rephrased paragraphs that mention brain computer interfaces without explicitly stating that this merging of fields is a new development. Most prominently, the first sentence of the abstract now reads: + +"Brain computer interface research can inspire closed- loop neuromodulation therapies, promising an unprecedented spatiotemporal precision for the treatment of brain disorders." + +<--- Page Split ---> + +4. Methods are still incomplete. The description of movement detection is better, but the performance description: "... balanced accuracy of \(0.8 / 0.98 \pm 0.07 / 0.04\) for single sample/movement detection" still could be clearer. Is the second value for the \(300 \text{ms consecutive "rate?"}\) If so, then state that more clearly. Also the following sentences are unclear: "A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block. It's important to note, however, that this measure addresses only the movement class and has no predictive value of rest segments." What does it mean to only "address the movement class"? It's a binary classification, so how is it not predicting rest vs movement? Or does this have something to do with the fact that there are now 3 bins and not all of them may be movement at that same time? Also is this balanced accuracy or not? If not, it should be, to make fair comparisons between 1 and 3-bin decoders and to avoid biases of too many false positives. Introducing a \(300 \text{ms delay (effectively)}\) to movement is also not trivial and is long enough that it could impair movement precision (due to feedback delays) for patients. This should be discussed. + +We thank the reviewer for helping us to further improve the manuscript and pointing us to this inaccuracy. The reviewer did understand correctly and we have rephrased this sentence to make it more clear. It now reads: + +"... balanced accuracy of \(0.8 \pm 0.07\) for single sample and a movement detection rate of \(0.98 \pm 0.04\) " + +We believe that the reviewer has also understood the movement detection rate correctly. It is positive if 300 consecutive ms are predicted to be movement class, so in a way this is a 3- bin based classification within the movement class. The \(300 \text{ms delay}\) is a relevant limitation, which we now mention in the definition of the movement detection rate, which we have also further improved. + +"Sample- wise performances were concatenated to establish a more coarse metric that allowed for detection of individual movement entities, termed movement detection rate and defined as \(300 \text{ms}\) of consecutive movement classification during actual motor performance. Note, that this movement detection rate measure has the significant limitation of requiring at least \(300 \text{ms}\) of time passing during the movement, before it can be positive, leading to potential delays for real- time applications." + +5. "processing steps to mitigate DBS artifacts including bandpass filtering and period-based DBS artifact removal did not improve, but instead aggravated this deterioration" The fact that artifact removal significantly worsened decoding accuracy is a potentially significant issue. The point was not to improve accuracy; the point was to see that accuracy did not worsen with removal of artifacts, but in fact it did worsen in most cases. That is concerning that a good portion of your "movement" decoding was really artifact decoding. This could lead to false positives. This deserves much more discussion and tempering of conclusions than is currently in the paper. + +<--- Page Split ---> + +We thank the reviewer for this remark. We have to clarify during the presented stimulation ON recordings for the artifact analysis shown in Figure 2 f+g, stimulation was switched on continuously as is clinical routine in all DBS patients. Traditionally DBS is turned on all the time at high frequencies. Thus, stimulation was in this artifact analysis not triggered based on movement decoding, but applied to investigate the potentially detrimental effect to signal quality without it having any temporal relationship to motor performance. We tested if movement classification performance increases when the continuous stimulation artifact was removed. We observed that by removing frequency bands affected by stimulation, or designing a filter that is intended to remove the time- series artifact (PARRM, Dastin- van Rijn et al 2023), movement- related electrophysiological characteristics are also removed and classification accuracy was reduced. In the following analysis (Figure 2 o+p) stimulation was indeed triggered by movement decoding. But stimulation was only switched on for a duration of 1 s after movement classification. For the subsequent samples stimulation could have triggered stimulation through a positive feedback loop. Nonetheless we did not observe that stimulation resulted in false positive movement classification. We have now further clarified this in the figure legend and results sections: + +"Next and equally important, we show that continuous therapeutic electrical stimulation (130 Hz STNDBS) can significantly deteriorate sample- wise decoding in some but not all patients and that models trained separately for OFF and ON stimulation conditions outperform models trained on both conditions together." + +"(g) Sample- wise performances OFF and ON chronic clinically effective subthalamic 130 Hz DBS in six PD patients from Berlin (all above 0.5 balanced accuracy chance; all p<0.05 for one- sample permutation tests)." + +6. The sensory cortex issue is insufficiently addressed in the manuscript. This needs to be acknowledged in the discussion more clearly than talking about interplay of motor and sensory information vaguely. + +We thank the reviewer for this suggestion and added now a section discussing the motor and sensory cortices: + +"Electrode localizations were also spanning many cortical brain regions including sensory areas. Relatively high movement decoding performances were observed not only for motor, but also sensory cortex. There is potential that these performances are in part augmented through sensory information, which could be detrimental to closed- loop applications. Notably, the Berlin cohort performed self- initiated movements without sensory cues and yielded high decoding accuracies. + +<--- Page Split ---> + +Nevertheless, it is important to note that not only motor but also sensory prediction or even sensory information stemming from adjustments to hand pressure may have affected the performances." + +7. Statistical rigor (at least in reporting) is still lacking. Many results are still described as "above chance", sometimes with p values, without statistical methods described. + +We thank the reviewer for this remark and added in addition to mentioning statistical significance also the permutation test described in the methods and 0.5 chance level: + +"All statistical tests were computed using non- parametric Monte- Carlo sampled permutation tests with a significance value of \(\alpha = 0.05\) " + +"Performance was above 0.5 chance level in every subject [...] (p<0.05, across subject one- sample permutation test)." + +Figure 2g legend: "Sample- wise performances OFF and ON clinically effective subthalamic 130 Hz DBS in six PD patients from Berlin (all above 0.5 balanced accuracy; all p<0.05 for one- sample permutation tests)." + +"Sample- wise performances were above 0.5 chance- level for all classifications [...] (all p<0.05 for one- sample permutation tests; Fig. 3d)." + +Best channel performances showed above 0.5 chance classification emotion decoding across subjects (p<0.05 for one- sample permutation test). + +8. The phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." is still opaque. What does this mean? + +We thank the reviewer for pointing us to this lack of clarity. The correlation states that DBS was more effective in patients that had higher decoding performances. This more direct interpretation of this observation would be that patients in which decoding worked better, may have higher capacity for improvement, speculatively because their ability to perceive emotions is less impaired. With this interpretation the variability of therapeutic outcome and decoding performance is attributed to some inherent disease related factors of the patient. However, this interpretation disregards the fact that electrode location as a result of variance in "surgical" targeting can have significant impact on both therapeutic outcome and decoding performance. Thus, perhaps the electrode was not optimally placed in patients with worse outcome, and this coincides with worse decoding performances. Here, + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026A + +the variance is attributed to the surgical targeting. This second hypothesis is the one we favor. We have now adapted the text to make this more clear: + +"The correlation could potentially be driven by differences in electrode localization stemming from natural variance in surgical targeting rather than by disease related factors, which inspired us to explore the underlying whole- brain networks." + +Minor issues: + +Regarding differentiating from other toolboxes – the first point about offline and online using the same routines is not unique – FieldTrip also enables this. + +We thank the reviewer for this remark. We added the following section to the discussion section: + +Therefore, offline and online signal processing are conducted using the exact same routines, by only replacing the data stream, similar to the Buffer implemented for FieldTrip in Matlab. + +"Neuromedicine" is not a word. The more appropriate term seems to be neurology. + +This now reads: + +"The clinical neurosciences stand at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology." + +Reviewer #3 (Report for the authors (Required)): + +the authors have responded quite thoroughly to reviewer comments and improved the manuscript. my summary of the results is part of my initial review so is not reproduced here. + +We thank the reviewer for their helpful and constructive feedback that substantially improved this manuscript. + +<--- Page Split ---> + +## Reviewer #3: + +Reviewer #3:Reviewer: I begin by paraphrasing the authors' problem statement. Problem 1: modern approaches to neural decoding use modern ML algorithms, which are data hungry. Collecting enough data in patients is hard, and there is a dearth of frameworks to facilitate transfer learning between patients in low- data regimes. Problem 2: the authors want a framework to extract neural signals. Problem 3: most experiments record data from only small areas of the brain and fail to incorporate networks of neural activity that give rise to signals. To address all three issues, the authors describe a new software package. The claims are that the software package is (i) a real- time BCI platform, that (ii) implements multiple novel signal analysis processing methods, and (iii) implements a method for transfer- learning using anatomical and connectome data. They further motivate how their software package is useful with three real- world examples: transfer learning with ECoG recordings in patients undergoing DBS (and epilepsy monitoring, Fig 2); retrospective analysis of intracranial signals to predict findings in a study of DBS for depression (Fig 3); and retrospective analysis of data collected from RNS recordings (Fig 4). + +Reply: We thank the reviewer for their expert assessment and the time they have taken to formulate constructive feedback while taking the aims of our study into account. Upon reflection of the reviewers' comments, we would formulate the key problem of our study as follows: Neuromodulation combined with machine learning offers a whole new world of possibilities for the treatment of brain disorders, but their joint application remains under- researched. We believe that this can in- part be attributed to the lack of demonstration of utility from researchers and lack of standardized tools to explore them. To address this, we demonstrate the clinical utility of machine learning based brain signal decoding for deep brain stimulation applications addressing multiple sub- aims, including the ones the reviewer has correctly identified. + +We would like to point out that while the theoretical utility for machine learning in neuromodulation may be obvious, so far only very few studies have used brain signal decoding in the context of deep brain stimulation, all with varying methodologies, often requiring proprietary hardware that are not open to other researchers (for an overview see our review article on the topic https://doi.org/10.1016/j.expneurol.2022.113993). Most prominently, the Medtronic Nexus system and the Medtronic RC+S Summit, as well as the RNS Neuropace devices come to mind, which have facilitated the use of neural data for advanced control algorithms. But these devices and algorithms are entirely inaccessible outside of specific industry collaborations which are almost if not entirely inaccessible to centers outside the US. + +We hope that the expert reviewer agrees with our vision and may even find it trivial to state that machine learning based brain signal decoding may prove useful and requires complex tools to advance invasive neurostimulation. We believe that our study provides novel and innovative analytic and methodological guidance as well as empirical evidence for the utility of machine learning based brain signal decoding to advance future closed- loop stimulation approaches, beyond the use of connectomes. We hope that the reviewer is equally excited about the unprecedented opportunities that arise from the combination of machine learning with closed- loop neurostimulation and that they can see the merit of our study for stakeholders such as DBS researchers, patients, neurotechnology companies and regulatory bodies beyond the more specific problem statements that the reviewer has identified above. An example that we are particularly proud of is the use of contrastive learning algorithms that our paper pioneers for the first time in human brain data, and for which it has been cited in the last issue of the journal Cell with the title "Decoding the Brain: From neural representations to mechanistic models" (Mathis MM et al., 2024 https://doi.org/10.1016/j.cell.2024.08.051). + +Changes in manuscript: We have now tried to emphasize and clarify the overarching aim further through edits in the introduction: "However, to date only few studies have investigated the clinical utility of machine learning based brain signal decoding, especially in the field of invasive neuromodulation. ... In this paper, we aimed to a) highlight the clinical utility of brain signal decoding + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +advances in a large cohort of patients across thousands of recording sources from invasive brain implants within three key areas of clinical neurotechnology innovation: movement disorders, psychiatry, and epilepsy; b) formalize and describe the methodology to achieve those advances in an open- source python software platform called py_neuromodulation; c) illustrate how the two biggest innovations in deep brain stimulation research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility." + +Reviewer: I am a neurosurgeon and I have previously published software packages in BCI methods, analysis of intracortical signals, and articles on RNS signal analysis. I am familiar with Dr. Horn's Lead DBS platform and have examined some of its methods in detail. In summary of my review to follow, I think this paper's broad appeal is the method that combines connectome information to assist with neural decoding in a low- data regime. As with many scientific ideas, it is both elegant and profound. By contrast, I think the framing of this paper through the lens of a software platform is a distraction. Below, I comment extensively on the framing of the authors' results and provide suggestions for further analyses that would further highlight the excitement and broad- scientific appeal. + +Reply: We are very thankful that the editorial team has found an expert, who understands both the clinical and methodological challenges that we are trying to address. We take their suggestions for improvement very seriously and have now adapted the narrative of our paper according to their excellent remarks. We agree that the dichotomy of describing a toolbox vs. describing the utility through novel insights that can be gained, can be distracting. For reference, we have tried to take inspiration from similar descriptions that have achieved this, such as FOOOF (Donoghue, T., Haller, M., Peterson, E.J. et al. Parameterizing neural power spectra into periodic and aperiodic components. Nat Neurosci 23, 1655- 1665 (2020) https://doi.org/10.1038/s41593- 020- 00744- x). To address this point, we have now shifted the narrative to highlight the Toolbox aspect of our paper less and try to focus more on the conceptual advances. + +1) Reviewer: A new method of transfer learning that uses imaging data (resting state fMRI and anatomical MRI) to boost intracranial neural decoding performance in low data regimes is compelling. To that end, I found Table 1, Fig 2l, and Fig 2m cool. I can record data from patients in the EMU and/or previous patients in the OR, and then use those recordings to learn hyperparameters for my decoder for a movement task in the OR for a new patient. By using CEBRA, you have now taught me that there exists a cross-person neural manifold for movement, informed by where I am physically recording on the brain (and how this part of the brain is connected to other parts, over multiple participants). But - the whole point of transfer learning in a neural decoding framework is to save time by priming a decoder with hyperparameters in a low-data regime. For instance, isn't the value of the approach obviated if it only takes two exemplars of movement (and movement onset) to get comparable decoding? Show us this is useful by plotting performance as a function of time for the participants, and especially the "real-time decoding" PD patient, to point out that decoding performance happens out of the box with your new method. + +Reply: We are grateful and excited that the reviewer highlights the merit of combining connectomics with neural decoding. We now provide the suggested analysis, highlighting the relationship of saved recording time with number of subjects. Before delving into more detail, we would argue that not only patient recording time, but also expertise in neurophysiological recordings, machine learning engineering and clinical handling are significant barriers that would be surpassed by a plug & play decoder that does not require individual training. Thus, we believe that providing an open- source decoding model (which we publish openly for anyone to use: 10.5281/zenodo.10794370) provides a no- data solution that is conceptually far ahead of any approach that does require individual training, regardless of how short the training is. + +Reviewer: In fact, the most compelling demonstration of the method would be to show that leveraging your approach would improve decoding further beyond what you would have achieved from just the data from that patient. In other words, demonstrate evidence that "For a real- world + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +clinical application this means that every implant would need to undergo tedious model training sessions, which could be a burden to both patients and medical staff and may hinder a broad clinical adoption." + +Reply: We are thankful for the enthusiasm and the excellent suggestion of the reviewer. The potential for superiority of pretrained models vs. individual training is exactly what we can show in the prospectively recruited patient, where the individual training session led to balanced accuracy performances of 0.67, while our generalizable model achieved 0.71. We have now followed the excellent suggestions and added a more specific analysis to further corroborate this by a) objectifying the amount of training data required to reach the same performance that our pretrained model reaches across all subjects using an iterative train- test split for each recording. In brief, the total recording time that can be saved with our model in our cohort was over 3 hours and 47 minutes. More importantly, upon further inspection of individual performances, we found that for 32% of the patients, our across- patient model performance surpassed the individual performance. This information is now added to the text and figure as follows. + +Changes in manuscript: We have now replaced the previous panels (n) and (o) of Figure 2 (see below) and mentioned the findings in the main results section, which now reads: "We further tested for the time improvement of decoding without patient- individual training compared to individual training. Here, the cumulative individual training time reached 3 h 47min to reach leave one subject out performance across patients (Fig. 2n). For a subset of those patients (n=8) the individual training performance could not reach the across- patient decoding performance (Fig 2o)." + +![PLACEHOLDER_78_0] + + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +Fig. 2: Movement decoding across patients, cohorts, diseases, movement types, and stimulation conditions. (a) Data from four cohorts with different diseases and movement types were used for decoding (1480 channels, 56 patients). (b) Individual recording locations with color- coded movement decoding classification performances. (c) Performances from patient individual 3- fold cross- validation. (d) Movement detection rates are defined as 300 ms consecutively correct classification during movement ( \(98 \pm 4\%\) for best channels across all patients). (e) In PD, mean channel performances negatively correlated with motor sign severity (UPDRS- III). (f) Exemplar time- series with DBS on ECoG raw data in a representative subject from the Berlin cohort. (g) Sample- wise performances OFF and ON chronic clinically effective subthalamic 130 Hz DBS in six PD patients from Berlin (all above 0.5 balanced accuracy; all \(p< 0.05\) for one- sample permutation tests). To demonstrate the utility of py_neuromodulation for across- patient decoding, three alternative pipelines integrate channel selection and neural signals: (h) Spatial interpolation to a common grid in MNI space; (i) channel selection based on normative fMRI connectivity correlation to a predefined optimal decoding network; (j) low- dimensional embedding (exemplar subject shown) derived from the model weights of non- linear decoder using contrastive learning with a convolutional neural network with CEBRA. (k) shows embedding consistency from each to every other patient via linear identifiability. All three methods achieved high decoding accuracies within and across cohorts for sample- wise balanced accuracy (l) and movement detection rates (m). CEBRA outperformed other methods as indicated by Bonferroni- corrected paired permutation tests. (n) Individual recording times shown as distinct colors of a bar plot indicating the cumulative invasive recording time of 3 h 47 min made obsolete by the generalizable movement decoder. o) For eight patients leave one subject out performances exceeded individual training performances shown as line plots indicating the relationship of recording time and final performance normalized to the generalizable across- patient decoder result (dashed vertical line). The color- coded learning curves show individual patient performances that never reached the across- patient result. To demonstrate the ability to decode movements without patient individual training, we prospectively recruited two subjects in Berlin and decoded movements using pretrained models based on all previous subjects of the Berlin cohort. (p) Real- time single trial decoding is shown for out- of- cohort patient 1 with y- axes depicting true measured analog rotameter movement amplitude (top), classification probability predictions without patient- individual training (middle) and predictions with training (bottom). For the second patient we tested movement- triggered stimulation and show the true movement traces (top), single trial movement predictions without patient- individual training (middle) and movement- triggered stimulation time (bottom). (q) Real- time performances are shown for both patients for decoding and stimulation. Above 0.5 chance balanced accuracy and movement detection rates were obtained despite presence of closed- loop neurostimulation and without model calibration. + +2) Reviewer: Here's another way you could convince me this approach works: suppose that one of the PD patients implanted had abnormal cortical anatomy (which happens not infrequently). For this patient, supposed that I had an ECoG strip where I thought the contacts were on the pre- and post- central gyri (based on imaging), but using your transfer-learning approach I had missed by a gyrus, and had landed on the MFG and the pre-central gyrus instead. Could your approach convince me that I've made a mistake in identifying the anatomy? Placing ECoG strips in the OR through a burr-hole during DBS is a blind procedure and needs to be confirmed with an intra-operative spin (at least in my hands), which is time-consuming and exposes the patient to radiation (which is challenging to justify if the research program itself is motivated through a non-significant-risk patient consent). Can your system save time for optimizing ECoG placement by providing an ongoing estimate of where the ECoG is likely located on the brain? + +Reply: The reviewer makes an excellent and creative point, that we did even consider before. Indeed, the alignment of the embedding could be used to verify "network affiliation" with the optimal decoding network at the individual level. We demonstrate how performance and embedding consistency relate to anatomy and optimal decoding network in an exemplar patient: + +<--- Page Split ---> +![PLACEHOLDER_80_0] + +
Revision Figure 1: Correlation of decoding performances and embedding consistencies. a) Optimal functional connectivity is shown computed based on training data subjects. b) For an exemplar patient (Berlin subject 008), leave-one-patient out cross validation performances were computed. For each test-subject channel, the embeddings were computed given the training data CEBRA non-linear encoding model. The embedding correlations of each channel and the training data is color-coded for the test patients' channels. The embedding consistencies were computed by correlating the training data embedding by other patients' optimal decoding connectivity channels and the left-out test patient embeddings. c) A significant correlation could be found between left-out decoding performances and channel-individual embedding correlations.
+ +However, to truly demonstrate that this could serve for anomaly detection, we would have to verify that in cases where anomalies are present, optimally imaging the individual fMRI networks. We will definitely study this, when the opportunity arises. In the given cohorts however, there were no such anomalies and thus, we decided to provide this concept as an outlook instead of taking it into the results section. + +Changes in manuscript: The discussion now reads: "An additional use- case for this approach in the future, could be to use the embedding consistency as an anatomical circuit verification, which could help identify anatomical anomalies and locate the correct optimal localization for decoding." + +3) Reviewer: The most compelling part of Fig. 3 is the utilization of the image-registration method incorporating connectome information that allows you to perform out-of-patient prediction for optimal electrode selection, which in turn has direct clinical relevance. This is a beautiful story. You showed me that the connectome method was predictive of decoding performance. This story could perhaps culminate in you telling the reader that this post-hoc information predicted that the contacts were correctly or incorrectly chosen for each patient, and then making suggestions that correctly choosing the right electrode would have had a tangible clinical impact. Also, the "sweet spot" in Fig 3h is covered by the left hemisphere, and I can't see the cingulate (unless I misunderstood, and Fox 2014 stimulated the DLPFC?). + +Reply: We thank the reviewer for this important remark. To address this comment thoroughly, we should note that stimulation was applied in a monopolar fashion, bilaterally (as depicted in Figure 3b). Contrary to this monopolar stimulation, all channels were recorded in a hardware bipolar montage (channels 0- 1, 1- 2, 2- 3 and 3- 0), a choice made at the time- point of experiment, which prioritizes signal fidelity over flexibility in post- hoc localization. Therefore, a direct comparison of recording and stimulation channel is not straightforward, as each stimulation channel occurs in two recording channels. To still give a direct reply to the reviewers question, we investigated if the stimulation contacts were present in the best bipolar recording channels. Indeed, in all eight patients + +<--- Page Split ---> + +the stimulation contact matched at least one channel of highest decoding performance (Chi- Square Test \(p< 0.05\) ). Given the uncertain relationship of monopolar stimulation and bipolar recording electrodes we however believe that this is not easily interpretable which is why we have decided not to include this result in the main text. Similarly, we felt that making any unsubstantiated claims about contacts being chosen wrongly in the clinical trial is beyond our comfort zone given the data at hand. Instead, we have added this notion to the discussion. To add to the last point, the noted "sweet spot" is indeed a cortical transcranial magnetic stimulation "sweet spot" in the dorsolateral prefrontal cortex, we are sorry for not making this more clear. We have now completely reworked that part of the figure, also fixing a visualization issue of panel h that we noticed through the revision. We further extended this depiction and now added all dorsolateral prefrontal cortex targets identified in Fox et al 2012 "Efficacy of transcranial magnetic stimulation targets for depression is related to intrinsic functional connectivity with the subgenual cingulate": EEG F3 Herwig et al 2003, Average 5cm Herbsman 2009, Rajkowska et al 1995 BA9, Paus et al 2001 / Cho et al 2009, Rusjan et al 2010, Fitzgerald et al 2009. + +Changes in manuscript: The revised figure is shown below: + +Fig. 3: Emotion decoding using LFP signals from subgenual cingulate cortex in patients with treatment- resistant depression. Eight subjects undergoing DBS surgery performed an emotion task (a) with visual stimuli of negative, neutral, and positive valence. Electrode locations are visualized alongside the anterior- (red and light blue) and subcallosal cingulate cortex (white and dark blue, Harvard- Oxford atlas28). Balanced decoding accuracies (c) rose from 150 ms after onset, peaked at 600 ms and decayed until 1600 ms post stimulus. Best channel performances showed above 0.5 chance (permutation test) emotion decoding across subjects (all \(p< 0.05\) ). (e) Best performance channels revealed highest feature importances for FFT gamma features followed by different temporal waveform shape features. (f) Best performances correlated with DBS induced Beck Depression Inventory (BDI) changes 24 months following DBS implantation (rho=0.79, \(p = 0.01\) ). Performances were, however, not significantly correlated to baseline BDI scores. (g) Significant fiber- tracks, FDR (False Discovery Rate) corrected with \(\alpha = 0.05\) , predicting emotional state decoding performances showed a clear relation to the left prefrontal cortex. This is reflected in functional and structural connectivity for all patient channels and particularly visible for fiber filtering (g) and fMRI maps (h). Transcranial magnetic stimulation targets from Fox et al 2014 are additionally displayed29: EEG F3 Herwig 200330, Average 5cm + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +Herbsman \(2009^{31}\) , Rajkowska 1995 BA \(9^{32}\) , Paus 2001 / Cho \(2009^{33,34}\) , Rusjan \(2010^{35}\) , Fitzgerald \(2009^{36}\) , Rajkowska 1995 BA \(46^{32}\) . All three connectivity models (fMRI, dMRI, fiber filtering) could cross- predict left out channel decoding performances (supplementary fig. 6,7). + +The discussion now reads: "In the future, clinical testing in patients with major depressive disorder could aim to confirm the left centric network by comparing clinical efficacy of right vs. left contacts and their relationship to the prefrontal network." + +4) Reviewer: Describing this paper as a real-time BCI platform is a distraction. To start, I'm not sure we agree as to what real-time means. Most people think that real-time means that there are deterministic bounds on program cycle execution and OS context switches. So, to make the claim that this system is real-time, you must do the following: (1) put bounds of performance by examining jitter and latency - I suspect this will be hard, because I assume the platform is designed to run in Windows (since I find .bat files in the github code) and as far as I know, Windows doesn't provide soft real-time guarantees; (2) characterize how long the system can run before you run out of memory (unless you've solved this issue by writing drivers that move data from memory to disk in a way that doesn't interrupt data flow); and (3) characterize real-time performance as a function of algorithm complexity and channel count (i.e., beyond a handful of channels and a binary classification problem). These would be the minimum requirements before I would re-engage with this claim. However, I would further argue that if you now want to sell a real-time software package as a high-impact publication in 2024, then you're obliged to do much more: (1) ensure that it works in multiple operating systems, (2) account for multiple languages (python is exciting right now, but matlab was exciting a decade ago), (3) have hooks to plug into multiple open source frameworks (like neurodata without borders), (4) have plans for long-term maintenance and naming conventions for code, (5) demonstrate that the system works outside of a small group of collaborating neuroscience labs, etc. In summary, I strongly disagree with your claim that py_neuromodulation is a "...toolkit for invasive brain signal decoding for closed-loop neuromodulation that emphasizes rigorous real-time compatibility and reproducibility." This is an unsubstantiated claim. Please deemphasize this claim in the paper. + +Reply: We thank the reviewer for this important point. We understand that our use of the wording was inaccurate. We aimed to describe that previously recorded datasets are handled in precisely the same way as data that are live- streamed from a neural signal processor. In many previous "offline" decoding studies, pre- processing steps are performed which are not compatible with prospective decoding, such as artifact rejection, non- causal filtering, time- frequency transformation and z- score normalization across a whole recording. This can lead to data- leakage and inflated signal to noise ratio estimates that overestimate machine learning performance evaluation for real world applications. By using the same data processing routines and only exchanging the data source, we circumvent this problem and process the data in an "online compatible" manner. Before going into more detail about performance and testing below, we understand the confusion that arose from this phrase and exchanged the "real- time" with "online" further explaining that we mean that the data are decoded as they are streamed from a patients' brain. We remain open to alternative suggestions by the expert reviewer. + +Regarding the other more specific points, we would like to highlight that py_neuromodulation implements a dataflow that builds on top of Python's multiprocessing module, where raw data acquisition, feature computation, decoding and visualization are parallelized and multiprocessing queues used for inter- process communication. We continuously tested the integration of data streams using LabStreamingLayer and the required feature computation time on latest Windows, MacOS and Ubuntu operating systems using GitHub's automatic workflow testing. Given the basic GitHub Workflow Linux runners (4 CPU's, 16 GB RAM, https://docs.github.com/en/actions/using- github- hosted- runners/using- github- hosted- runners/about- github- hosted- runners, state October 2024) hardware, the documentation hosts automatic timing estimation (https://neuromodulation.github.io/py_neuromodulation/auto_examples/plot 6 real time demo.ht ml). We found that the FFT feature estimation including common- average re- referencing and + +<--- Page Split ---> + +standard- scale feature normalization could be achieved for a six channel data batch in 1 ms. When more complex features are included, such as temporal waveform shape and burst features, the computation time is 3 ms for a single channel. In our experience, those timings are sufficient for many decoding applications, such as movement or tremor classification. This information is now added to the methods section. Notably, timing jitters for adaptive deep brain stimulation can additionally be dependent on external stimulator communication. For example, the neurostimulator used in our setup can cause a delay of approximately 10 ms to activate stimulation via an API call. + +For py_neuromodulation we emphasize computation speed and continuously optimize preprocessing and feature estimation routines. We already perform multiple experiments relying on its' online feature estimation and decoding capabilities. On our hardware (TMSi SAGA amplifier, AlphaOmega NeuroOmega stimulator, Lenovo Thinkpad T14 Gen3 with Windows 11) we robustly run decoding and adaptive stimulation applications with a stimulation update rate of 100 ms. As a reference, we would like to highlight that the fastest update rate used in the arguably most cutting edge aDBS paper (Oehrn et al., Nature medicine 2024) was as slow as 10,000 ms, with the average update rate reported to be 21,250 ms. + +With regard to maintenance of the code, we are lucky to have dedicated development funding that allows us to invest time and effort into continuous improvement and support for at least another four years. + +In reply to the notion that a tool published in a high- impact paper should not rely solely on python, we believe that we should simply work with what works. Apart from that we would like to point out that many of the highest impact toolkits are published as solely available in Python (e.g. Deep Lab Cut Lauer, J., Zhou, M., Ye, S. et al. Multi- animal pose estimation, identification and tracking with DeepLabCut. Nat Methods 19, 496- 504 (2022). https://doi.org/10.1038/s41592- 022- 01443- 0, FOOOF Donoghue, T., Haller, M., Peterson, E.J. et al. Parameterizing neural power spectra into periodic and aperiodic components. Nat Neurosci 23, 1655- 1665 (2020). https://doi.org/10.1038/s41593- 020- 00744- x and DPAD Sani, O.G., Abbaspourazad, H., Wong, Y.T. et al. Modeling behaviorally relevant neural dynamics enabled by preferential subspace identification. Nat Neurosci 24, 140- 149 (2021). https://doi.org/10.1038/s41593- 020- 00733- 0) + +Nevertheless, we fully agree that despite five years of joint NIH/BMBF funding and dedicated development, there is still a lot of room for development of the toolbox, which is why we have decided to de- emphasize the toolbox aspect throughout the narrative of the paper. In fact, emphasizing the toolbox was one of the previous reviewers' suggestions. We hope that we have now struck a middle ground that provides both conceptual advances and how they are integrated in the code that we provide, as we still believe that sharing the methods in an open manner is a positive aspect of our paper. + +Changes in manuscript: In addition to many smaller edits and changes throughout the text, we have removed the cited claim "While all these tools contain valuable and extensive methods for electrophysiological data analysis, we would like to point out key aspects of py_neuromodulation that uniquely positions it as a toolkit for invasive brain signal decoding for closed- loop neuromodulation that emphasizes rigorous real- time compatibility and reproducibility." from the text. + +Additionally, we added a "Feature computation using multiprocessing" section to the methods highlighting the feature estimation speed of py_neuromodulation: + +"Py_neuromodulation implements a dataflow that builds on top of Python's multiprocessing module, where raw data acquisition, feature computation, decoding and visualization are parallelized and multiprocessing queues used for inter- process communication. The integration of data streams using LabStreamingLayer and the required feature computation time was tested on Windows, MacOS and Ubuntu operating systems using GitHub automatic workflow testing. Given the basic GitHub Workflow Linux runners (4 CPU's, 16 GB RAM, https://docs.github.com/en/actions/using- github- hosted- runners/using- github- hosted- runners/about- github- hosted- runners, state October 2024) + +<--- Page Split ---> + +hardware, the documentation hosts automatic timing estimation (https://neuromodulation.github.io/py_neuromodulation/auto_examples/plot_6_real_time_demo.html). We found that the FFT feature estimation including common-average re-referencing and standard-scale feature normalization could be achieved for a six channel data batch in 1 ms. When more complex features are included, such as temporal waveform shape and burst features, the computation time is 3 ms for a single channel. Notably, timing jitters for adaptive deep brain stimulation can additionally be dependent on external stimulator communication." + +5) Reviewer: I find this sentence problematic: "... a unique and novel feature set that included temporal waveform features, such as discharge prominence, sharpness, decay and rise time, and peak and trough interval in addition to traditional oscillatory FFT features." Is the authors' claim that the peak and troughs-based analysis of local field potentials has never been described before? If you believe this is true, then how have you yourselves characterized these features? + +Reply: We are sorry for the confusion and want to be clear that we absolutely do not claim that these analyses have not been described before. We are sorry this was not clearly communicated in our manuscript. The neurophysiological importance of these features has been studied intensively, most prominently by the group of Bradley Voytek who provide an excellent and highly cited review article on their origin and relevance (Scott R. Cole, Bradley Voytek, Brain Oscillations and the Importance of Waveform Shape, Trends in Cognitive Sciences, Volume 21, Issue 2, 2017, Pages 137- 149, https://doi.org/10.1016/j.tics.2016.12.008). + +What we do claim is that these analyses have not been used for machine learning based brain signal decoding before and that no toolkit for decoding offers the usage of these important neurophysiological features. We now make this clearer in the manuscript. We also would like to point out that this is indeed another novelty beyond the use of contrastive learning and connectomics. + +Reviewer: What's the electrophysiological relevance of these features that teaches us something new about the brain? + +Reply: The abovementioned review article on the importance of waveform shape offers a fresh perspective in neurophysiology by capturing nuanced aspects of neural oscillations that traditional measures often overlook (https://doi.org/10.1016/j.tics.2016.12.008). Typically, neural oscillations are analyzed by examining their frequency, power, and phase. However, waveform shape features—like asymmetry, steepness, and sharpness—add an extra layer of information that reveals underlying neurophysiological processes with greater specificity. + +Waveform shape features can reflect underlying synaptic and cellular dynamics that frequency or power alone cannot capture. For example, the sharpness or steepness of oscillatory peaks may indicate synaptic synchrony or the dynamics of inhibitory versus excitatory activity within a network at millisecond temporal scale. These features can also reveal the balance of cortical excitability and inhibition, potentially offering insights into disease states. In disorders like epilepsy or Parkinson's disease, waveform shape deviations could signal pathophysiological changes, providing novel pathways for neurophysiological monitoring (e.g. see https://doi.org/10.1523/JNEUROSCI.2208- 16.2017, https://doi.org/10.1523/JNEURO.0151- 19.2019, https://doi.org/10.1523/JNEUROSCI.1996- 19.2020 and https://doi.org/10.1016/j.expneurol.2022.114089). + +Reviewer: Why would these metrics have broad appeal, and why would I as a biomedical engineer know which to pick? In summary, if the main claim of the paper is that these spike wave forms are novel and interesting and useful, then they have been insufficiently characterized to be relevant to a broad scientific audience. In my opinion, characterizing these in detail is a paper into itself, and shouldn't be conflated with the main compelling scientific idea. + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +Reply: As highlighted above, we believe that the notion that these features have not been studied or are insufficiently characterized is a misunderstanding. Many more basic neuroscience investigations and some clinical studies (of which we cited four on PD alone above) have indeed reported the relevance of these metrics, with some of them even discussing their potential utility for disease monitoring. However, they have never been used for brain signal decoding in the context of invasive neuromodulation, despite having broad appeal, as they offer a way to quantify subtle changes in brain states with sensitivity to cellular and circuit- level dynamics while being extracted from the same recordings that we use to extract oscillations, meaning they are directly accessible. + +What we aim to communicate with our application of these waveform features is that they may prove useful for biomedical engineers the design and optimization of brain- machine interfaces or neural signal processing algorithms used in invasive neuromodulation. Knowing which features to select depends on the specific brain states or disorders you're studying and the type of signals you're working with. For example: Peak Sharpness can be important for detecting seizure onsets or assessing synaptic excitability. Symmetry can be relevant for tracking oscillatory dynamics in sleep or anesthesia, as well as disease conditions affecting cortical oscillations, such as Parkinson's disease. In many other use- cases or conditions, these features have not yet been explored, and we believe that providing biomedical engineers with a data- driven way to discover their utility is exactly what is required at this point and what we achieve with the present publication. + +Changes in manuscript: We added the following in the Introduction section: "Current advances in basic neuroscience have revealed the presence of complex brain signal features such as waveform shape and aperiodic activity as markers of synaptic synchrony and balance of excitatory and inhibitory modulation (Cole and Voytek 2017, Donoghue et al 2020), but standardized methods to extract them for machine learning applications are lacking." Furthermore, we described the relevance of waveform- shape features in the discussion: "Here, we additionally demonstrated the predictive relevance of feature sets beyond oscillatory activity such as waveform shape for emotion decoding. Waveform shape features can reflect underlying synaptic and cellular dynamics that frequency or power alone cannot capture. For example, the sharpness or steepness of oscillatory peaks may indicate synaptic synchrony or the dynamics of inhibitory versus excitatory activity within a network. These features can also reveal the balance of cortical excitability and inhibition, potentially offering insights into disease states. A systematic data- driven approach to neural decoding based on waveform features can result in higher accuracy and identification of new biological insights into the importance of these measures. Our results indicate that both the amplitude and rise time of neural discharges can reflect information on the computation of emotional valence in the human limbic system. This could be attributed to valence specific changes in synaptic synchrony and afferent excitatory drive." + +6) Reviewer: I don't understand how Figure 4 addresses the problem statements of your paper. The motivation for the analysis is "... to inspire new ways to improve seizure detection accuracy by constraining the decoding platforms to the specifications of clinical brain implants and suggesting improved parameters from offline predictions that are implementable and testable through the clinical patient data management systems (PDMS) provided by Neuropace." Returning to the problems you're solving, as introduced by the introduction of the paper, this figure does not (Problem 1) incorporate data between patients to solve a low-data regime problem, nor (Problem 3) incorporate connectome information between patients. While it does (Problem 2) apply ML algorithms to different a cornucopia of uncharacterized electrophysiologic features, it feels like a fishing expedition. Further, the per-day limitations of data collection with RNS are substantial, as the PDMS available is necessarily biased by whatever the clinician has previously identified to be a seizure (unless I missed somewhere that you're doing long-term data streaming) – I am highly skeptical of the consequence of the findings without seeing the impact (neurophysiologic or clinical). + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +Reply: We would like to jump in here, just to state that there have been daily "scheduled" recordings that were not triggered by a seizure. Within the PDMS, recording triggers can be set to capture scheduled recording at pre- defined start times: + +![PLACEHOLDER_86_0] + + +Revision Figure 2: Patient Data Management System (PDMS) recording parametrizations. + +The reserved programming triggers were reserved for scheduled recordings, magnet swipes, long episode detections or amplitude saturation events. The scheduled recordings have the same duration as the long- episode seizure events, saturation or magnetic recordings, and sum up in typical patients to a substantial amount of saved recordings. In our cohort at least two recordings per day were reserved for scheduled recordings. Taking this into account, together with the use of the seizure triggered data, we believe that our approach provides the solution to what the reviewer cites as a problem, which is the arbitrary selection made by a clinical tech or MD based on a single event. Instead, our approach uses all available data to come up with an optimized detector setting. + +Reviewer: I'm happy to be convinced otherwise, but right now Fig. 4 doesn't prove your paper's point. + +Reply: We may not have done the best job doing so, but we aimed to make the main point that machine learning based brain signal decoding can aid the optimization of invasive neuromodulation applications, while offering an open- source platform that provides the necessary tools for implementation. Therefore, we do think that the use- case does aid us in making this point. Notwithstanding this, we are thankful for the excellent suggestion made by the reviewer below, which we have fully adopted in our revision. + +Reviewer: Here's one way that would make the presentation more compelling to the reader. Hopefully, the leads in patients with epilepsy are placed in critical parts of the seizure network. Surely, across 9 patients, some networks have been sampled more than once. Hence, here is a wonderful opportunity to showcase the connectome approach to decoding. Can your approach leverage connectome data to assist with seizure prediction? Can you tell me which network I'm in, to help me with optimal lead selection? Or, can you tell me that a set of parameters determined offline for person A will likely work for person B, because they're targeting the same seizure network? + +Reply: We thank the reviewer for adding this valuable suggestion. While we agree to disagree that the presentation of our third use- case was not on- topic to the paper, we enthusiastically agree that it does provide another opportunity to showcase the connectomic approach. The key reason we have not tackled this with the initial version of the article was that imaging was not readily available in these cases. The many replies and a boatload of work that already went into the previous and present revision sparked a sunken cost fallacy and led us to believe that we should now really make the effort, obtain and perform electrode localizations and run the connectome analysis, which accounted for the lion share of the time required for this third revision of our manuscript. And we are thankful for it, as a) obtaining the electrode localizations in all cases can be seen as critical quality control for the neurophysiology and b) the connectome analysis did indeed spark some very interesting results. In this plot we show the electrode localizations of the analyzed subjects: + +<--- Page Split ---> +![PLACEHOLDER_87_0] + +
Revision Figure 3: Electrode localizations color-coded by patient ID.
+ +For the reviewers' convenience, we summarize the patient information in the following table: + +
Patient RNS IDGroupLocation (lead 1)Location (lead 2)Months postopNumber RecordingIctal recordi ng duration [min]Total recordi ng duration [min]SexAge
RNS1529Hippo-campusLeft Hippo-campusRight Hippo-campus11676131.38754.89F22.7
RNS1603NeocortexRight premotor areaRight primary motor area1154538.97747.49F34.5
RNS1836Migrational DysplasiaLeft heterotopiaRight heterotopia101059258.63956.8F39.2
RNS1090Migrational DysplasiaRight heterotopiaRight heterotopia23590132.22575.25M21.8
RNS9536Migrational DysplasiaLeft heterotopiaRight heterotopia2635665.16431.73F46.4
RNS1440NeocortexBasal temporal (depth)Temporo occipital (strip)351058195.211215.61F41.4
RNS1534Hippo-campusLeft Hippo-campusRight Hippocampus722823.46301.04F39.5
+ +To address the key question, whether connectomic network affiliation can predict seizure decoding performance, we followed the same analytic approach as in the other use- cases. In brief, we computed for each RNS recording channel a whole- brain connectivity network map from the seed region. Each recording contact was paired with an optimal seizure detection F1- score. We then computed in a leave- one- subject out cross- validation the optimal seizure decoding connectivity map and estimated the predicted seizure decoding performances by correlating the optimal decoding map with the left- out channel- individual connectivity maps. The approach was also described in the methods section (Supplementary Fig. 5). First, we tested optimal connectivity computation based on the Human Connectome Project fMRI data (Van Essen et al 2013, n=985 subjects), and did not obtain significant results (leave one channel out cross- validation rho=- 0.06, p=0.36; leave one subject out cross- validation rho=0.25, p=0.1). Next, we tested the same pipeline for the HCP diffusion + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +weighted structural MRI data (Setsompop et al 2013, adapted by Li et al 2020, \(n = 985\) ), which resulted in significant predictions (leave one channel out cross- validation \(r h o = 0.44\) \(p = 0.01\) ; leave one subject out cross- validation \(r h o = 0.42\) , \(p = 0.02\) ). Thus, we identified a structural whole- brain network, predictive of seizure decoding performance, characterized by dominant positive correlations to bilateral temporal lobe, hippocampus, cingulate and occipital cortex. + +![PLACEHOLDER_88_0] + +
Revision Figure 4: Optimal structural seizure decoding network (a) predicts seizure detection performance in leave one subject out cross-validation (b).
+ +To represent this major point adequately in the manuscript while also taking the "fishing expedition" criticism into account, we have now removed the "unconstrained" machine learning results and replaced them with this connectome analysis. + +Changes in manuscript: To include the connectomics- based seizure decoding results, adapted Figure 4 as displayed below: + +![PLACEHOLDER_88_1] + + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +Fig. 4: Predictive parameter identification for seizure detection in responsive neurostimulation (RNS). (a) RNS data was either acquired from two lead depth electrodes (eight patients) or a cortical electrode in addition to a depth electrode (one patient). Two lead depth electrodes are visualized using Lead- DBS44 for an exemplar patient. The Harvard- Oxford atlas28 parcellation shows the lingual gyrus (white) and the left lateral occipital cortex superior division (red) that are penetrated by the electrodes. (b) In an exemplary recording, from a baseline programming epoch without stimulation artifacts, ictal onset characteristics across the four recording channels are displayed (top). RNS detectors can produce false positive seizure detections even in the absence of seizure activity (bottom) that can occur so frequently that no further therapy is provided (maximum stimulation number reached), even though no ictal activity is present (as defined by the epileptologist annotation). (c) FFT and line- length features were computed similar to the embedded RNS algorithm with py_neuromodulation. The exemplary ictal recording shows clear seizure induced changes. (d) By combining these features with expert seizure annotations, optimal detection parameters were extracted in a grid- search to optimize the F1 score for seizure detection. (e) The RNS patient data management system (PDMS) provides the "SimpleStart" algorithm, in which detection programming settings are automatically inferred based on a single ictal event. Instead, we propose seizure detection using data- driven parameters based on grid- search optimization that builds on expert annotations across hundreds or thousands of events. This approach may hold the potential for improved true negative predictions and increased F1 scores (f). Finally, we use connectomics to reveal a structural network associated with seizure detection performances across subjects. To this end, electrode localizations (g) for seven subjects (color coded) were obtained subjected to a structural connectome analysis to determine an optimal seizure decoding network. Affiliation with this network (h), that spanned bilateral temporal lobe, hippocampus, cingulate and occipital cortex, allowed for significant prediction of seizure detection performance with leave- one- subject out cross- validation (i). + +The new supplementary figure 8 shows axial and sagittal planes. + +Additionally, we added the following to the results section: "Next, we used the optimized seizure detection performances of all RNS channels combined with their specific localization (supplementary table 8) to identify a whole- brain network associated with optimal seizure detection, following the same connectomics approach described for movement and emotion decoding. To this end, we computed structural connectivity fingerprints from each recording channel using the HCP dataset (Setsompop et al 2013, adapted by Li et al 2020, n=985), and correlated seizure detection performances with voxel- wise connectivity. We identified a structural connectivity network (Fig 4h), predictive of seizure decoding performance, characterized by dominant positive correlations to the bilateral temporal lobes, hippocampus, cingulate and occipital cortex, which could significantly predict seizure detection performances in a leave one subject out cross- validation (rho=0.42, p=0.02) (Fig. 4i)." + +Furthermore, we described the approach in the methods section: "For a subset of the cohort (n=7) electrode localizations were obtained either through the Lead- DBS pipeline or through co- registration in Brainstorm (Tadel et al 2011) and manual annotation of electrode contacts. Since each RNS electrode contains four recording contacts and bipolar referencing is applied between contact pairs, the midpoint between the coordinates of contact pairs was estimated. Subsequently, structural connectivity was computed with the Lead Connectome Mapper in Lead- DBS (Neudorfer et al 2023) using diffusion MRI data from the Human Connectome Project (Setsompop et al 2013) adapted by Li et al 2020 (n=985). Here, a spherical seed was used for each recording channel with a radius of 4 mm to estimate connectivity maps. Next, leave- one- patient out cross- validation optimal structural seizure detection connectivity profiles were estimated. The optimal seizure detection connectivity map was thus repetitively estimated by correlating individual channel connectivity voxel values with the RNS channel- specific seizure detection performances. This approach is equivalent to the described connectomics approach for movement and depression above but diffusion MRI images were used instead of functional MRI." + +Finally, we added an additional supplementary Table with the exact electrode MNI coordinates: + +Supplementary Table 8: Electrode localizations of RNS subjects utilized for connectivity- based seizure decoding. + +<--- Page Split ---> + + +Revision of manuscript NBME-23-2026B + +
Patient RNS IDchMni-xMni-yMni-z
RNS1090052.21-16.727.4
160.52-17.18.5
251.99-33.8820.04
359.98-31.4422.27
RNS14400-36.28-33.73-12.62
1-57.77-39.8-11.08
2-49.65-78.967.2
3-57.8-59.93-2
RNS1529026.78-9.03-3.15
130.4-31.5-7.3
2-27.2-5.3-5.27
3-33.37-25.71-2.56
RNS15340-24.88-27.1-20.72
1-29.12-26.11-0.61
225.5-32.13-15.17
328.27-29.485.27
RNS160306.94-27.6141.9
112.39-20.9964.41
23.15-21.4538.83
34.77-19.2162.13
RNS18360-30.2529.2325.37
1-33.16.4527.23
2-40.77-12.1627.73
3-42.18-35.0431.49
RNS95360-26.55-12.51-27.03
1-30.04-30.35-18.61
224.19-34.09-14.51
329.47-52.34-9.33
+ +## Minor points: + +7) Reviewer: The authors have told me that Lead DBS was, "optimized in Lead-DBS for subcortical structures." This matches my experience as well – the default settings (which again, the authors recommend) have both whole-brain and sub-cortical masks that are applied in series to emphasize this fact. Have they quantified the performance of LeadDBS on non-linear deformations of cortical anatomy, in the same way that Dice coefficients have been computed for subcortical structures? If so, can you point me in the direction of a paper that validates cortical anatomy between patients? If not, then can you comment about why not validating the default settings of the program do not impact the quality of your transfer learning approaches? If this question isn't relevant, please explain why (because this point isn't clear to me). + +Reply: Indeed, ANTs has been celebrated as the best method for volumetric registrations of the cortex, for instance in the large- scale comparative study by Arno Klein (10.1016/j.neuroimage.2008.12.037). While DICE- coefficients are less suitable for cortical comparisons, this paper evaluated ANTs based on surface distance metrics. The Lead- DBS team (in part co- authors of this work) have evaluated performance of ANTs for subcortical structures and came up with presets that also optimize this region (especially large scale comparative work by Siobhán Ewert; 10.1016/j.neuroimage.2018.09.061, also replicated by Dorian Vogel: 10.1016/j.nicl.2020.102271). While some studies that exclusively focus on cortical regions choose surface based registrations (e.g. using freesurfer), this format is not automatically suitable when analyzing both subcortical and cortical data that are connected to one another in the same subjects. Hence, in summary, we chose an algorithm that is widely used and has been evaluated for both cortical (Klein et al.) and subcortical (Vogel et al.) registrations. Since ANTs has been the default in many fMRI studies that focus on cortical activity, we for now refrain from adding these points to the discussion, but would be happy to do so in case the reviewer sees the necessity of clarifying this further. + +Changes in manuscript: The methods section now reads: "We utilized ANTs for volumetric registration within LeadDBS since it was previously shown as the best metric for cortical regions + +<--- Page Split ---> + +(Klein et al 2008) and separately subcortical regions for deep brain stimulation in movement disorders (Vogel et al 2020)." + +8) Reviewer: "In brief, Lead-DBS uses preoperative MRI and postoperative CT scans for co-registration and normalization to MNI 2009b NLIN ASYM space." This is incorrect, though I am happy to be corrected by Dr. Horn. There are many options available for using standard spaces. That's one of the really nice things about the software. In fact, Fig 4a proves my point! + +Changes in manuscript: We thank the reviewer for addressing this point, and corrected the sentence with input from Dr. Horn in the manuscript as follows: "In brief, Lead-DBS uses preoperative MRI and postoperative CT scans for co-registration and normalization by default to MNI 2009b NLIN ASYM space." + +9) Reviewer: On 23 May 2024, the BCI Society voted to accept this definition of a BCI (https://bcisociety.org/bci-definition/): A brain-computer interface is a system that measures brain activity and converts it in (nearly) real-time into functionally useful outputs to replace, restore, enhance, supplement, and/or improve the natural outputs of the brain, thereby changing the ongoing interactions between the brain and its external or internal environments. It may additionally modify brain activity using targeted delivery of stimuli to create functionally useful inputs to the brain. Most people I know consider a BCI as the first sentence. To my chagrin, neuroprosthetics that meet the definition of the second sentence are now part of the story, so arguably, closed-loop DBS and RNS systems are now under the umbrella of what makes up a BCI. Nevertheless, approach with caution, as you will aggravate some readers with this word choice. For context, neither FDA leadership nor the iBCI-CC consider closed-loop DBS/RNS systems to be BCIs. + +Reply: We thank the reviewer for their expert input. We have followed this discussion closely and believe that the comment by Robinson et al., published in December 2024 in the present Journal provides us with some guidance on the taxonomy that we believe is useful (Robinson, J.T., Norman, S.L., Angle, M.R. et al. An application- based taxonomy for brain- computer interfaces. Nat. Biomed. Eng (2024). https://doi.org/10.1038/s41551-024-01326-z). We now adhere to this taxonomy and explicitly reference it to avoid any confusion. + +Changes in manuscript: "The presented approaches for intelligent adaptive deep brain stimulation could be categorized by the recently published taxonomy for brain- computer interfaces by Robinson et al (Robinson et al 2024) as therapeutic BCI's in the fields of movement disorders, depression and epilepsy." + +10) Reviewer: Perhaps you meant, "closed loop" rather than "real-time" in the paper? + +Reply: We appreciate the feedback and acknowledge the potential confusion surrounding our use of the term "real- time." As laid out in response to major comment 4, for our initial description, we did not mean "real- time" in the strict sense of deterministic execution with bounded latency and jitter, as used in control systems or systems with hard real- time requirements. Instead, we intended to convey that our platform operates in an "online" manner, where data is processed continuously and promptly as it is acquired, enabling rapid interaction or feedback. We have now updated the terminology to "online" to better reflect this intended meaning and avoid misinterpretation, as described in more detail in response to major comment 4. + +11) Reviewer: Why is it so necessary to be so deprecating to the clinical hardware that we have, when the paper itself hasn't created new hardware? Said another way: this is unnecessarily grandiose and sets a weird tone for the paper: "The clinical neurosciences stand at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology." + +<--- Page Split ---> + +## Revision of manuscript NBME-23-2026B + +Changes in manuscript: We thank the reviewer for their input and have now rephrased the sentence to "The clinical neurosciences are undergoing a transformative period in the treatment of brain disorders, with neuromodulation therapies like deep brain stimulation (DBS) evolving from their initial designs into advanced computer- powered neurotechnologies." + +12) Reviewer: Consider switching Supplementary Figure 5 and Figure 1. + +Reply: We have considered this suggestion and believe that it would likely overwhelm most of the readers as a first introductory figure, which is why we have respectfully decided to leave it as a supplement. + +13) Reviewer: The newly added text that goes into tremendous (and important) detail about data analysis describing Figure 2 should go to the Methods. + +Reply: Thank you for this helpful suggestion, we have followed the advice. + +14) Reviewer: "We may speculate that neurodegeneration in PD may impact neural encoding of movement, which may also impede machine learning based decoding performance". Patients with worse UPDRS scales may have less brain. Is your decoding performance related to the ECoG strips not actually sitting on the brain, or perhaps have much more air that snuck in during the case? + +Reply: We have assessed this and found no example of any distance between electrode contacts and brain tissue. + +15) Reviewer: "Divining appropriate settings" in describing RNS programming is unnecessarily pessimistic. The very fact that patients often do get better, either tells us that clinical heuristics are useful, or a significant subset of the high-dimensional parameter space is useful. + +Changes in manuscript: Thank you for pointing this out, we have rephrased the sentence as follows: "Defining appropriate settings from this vast parameter space is a largely manual process that has potential for significant acceleration through data-driven methods". + +## Reviewer #4 (Remarks on code availability): + +Reviewer: The code documentation is variable. Some parts hand- hold the user through the process and are easy to follow, and others are slapped together to make a point in OS- specific configuration files. I didn't try running the code. + +Reply: We thank the reviewer for their feedback. With the present revision we have significantly improved the code documentation across all domains. The main code documentation is hosted through GitHub pages https://neuromodulation.github.io/py_neuromodulation/ and presents the overall toolbox usage with examples. The online implementation provides support for replacing the offline data generator by an LSL stream. In a single branch ("online_decode") we include hardware specific files for the used amplifier (TMSi SAGA and NeuroOmega). We did not merge this branch into the main branch to keep the code and documentation general for multiple acquisition systems and use- cases. + +<--- Page Split ---> + +Thanks to the authors who have considered my criticisms and recommendations thoroughly. My major concerns have been addressed. My comments are now minor and focus on how the novel results are presented in Figure 2. I also make ancillary editorial comments responding to the authors' questions that do not need to be addressed in a future round of revisions. + +I don't know what this means: "Here, the cumulative individual training time reached 3 h 47min to reach leave one subject out performance across patients (Fig. 2n)." I think what you're saying is that you can use data between participants to help minimize decoder training time. More precisely, are you saying that on average you can drop about 4 hours of neural data collection from your decoder and still achieve the same decoding performance. I think this is awkwardly worded. Also, what do the different colors mean in 2n? + +I also don't know what this means: "For a subset of those patients (n=8) the individual training performance could not reach the across- patient decoding performance (Fig 2o)." I think what this means is that for eight patients, you didn't save time by using data from other participants. Is this correct? What do the different colors mean? Are they patients? + +Before going into more detail about performance and testing below, we understand the confusion that arose from this phrase and exchanged the "real- time" with "online" further explaining that we mean that the data are decoded as they are streamed from a patients' brain. We remain open to alternative suggestions by the expert reviewer. + +As long as you're not making the claim that this is a real- time system, there's no further work needed here. + +In reply to the notion that a tool published in a high- impact paper should not rely solely on python, we believe that we should simply work with what works. + +We all agree python is great and it's the modern lingua franca for neuroscience. The examples y'all have provided are important contributions to the field of neuroscience, but they're not real- time platforms. Please find me a real- time BCI platform that relies exclusively on non- compiled python in Windows and has physiologically- relevant bounds on jitter. The only ones I know that fit the bill are Timeflux and LabGraph. The former uses Cython to achieve timing goals, and the latter uses a custom- written C++ middleware for IPC. + +We hope that we have now struck a middle ground that provides both conceptual advances and how they are integrated in the code that we provide, as we still believe that sharing the methods in an open manner is a positive aspect of our paper. + +No further concerns here. + +While we agree to disagree that the presentation of our third use- case was not on- topic to the paper, we enthusiastically agree that it does provide another opportunity to showcase the + +<--- Page Split ---> + +connectomic approach. The key reason we have not tackled this with the initial version of the article was that imaging was not readily available in these cases. The many replies and a boatload of work that already went into the previous and present revision sparked a sunken cost fallacy and led us to believe that we should now really make the effort, obtain and perform electrode localizations and run the connectome analysis, which accounted for the lion share of the time required for this third revision of our manuscript. And we are thankful for it, as a) obtaining the electrode localizations in all cases can be seen as critical quality control for the neurophysiology and b) the connectome analysis did indeed spark some very interesting results. In this plot we show the electrode localizations of the analyzed subjects: + +Cool. Thanks for doing the work – Figure 4 is now congruent with the rest of the paper, demonstrates the utility of the across brain normalization. + +Since ANTs has been the default in many fMRI studies that focus on cortical activity, we for now refrain from adding these points to the discussion, but would be happy to do so in case the reviewer sees the necessity of clarifying this further. + +No, that's fine as is. + +Finally, quick note to the authors. Documentation of github greatly improved. Here are some broken links: "Usage" and "First examples" on the introductory REAMDE.md. Please clarify if your system works on Linux or Mac. + +<--- Page Split ---> diff --git a/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..626a69367fecf9f2a97a380b37969d802c160340 --- /dev/null +++ b/peer_reviews/34886832d0d7cf637d11a7dc2250cbcb4f811480e8274314d4fd82662a5cd1e0/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,2201 @@ +<|ref|>title<|/ref|><|det|>[[72, 50, 296, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 297, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 907, 211]]<|/det|> +# Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants + +<|ref|>text<|/ref|><|det|>[[74, 224, 404, 241]]<|/det|> +Corresponding Author: Dr Timon Merk + +<|ref|>text<|/ref|><|det|>[[72, 274, 875, 302]]<|/det|> +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[73, 339, 145, 353]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 365, 183, 379]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[73, 391, 305, 405]]<|/det|> +Dear Prof Neumann and Mr Merk, + +<|ref|>text<|/ref|><|det|>[[73, 416, 914, 472]]<|/det|> +Thank you again for submitting to Nature Biomedical Engineering your manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants". The manuscript has been seen by 3 experts; however, despite our chasing efforts one reviewer has yet to provide a report (should the reviewer provide it, we will send it to you in due course). You will find the reports of 2 reviewers at the end of this message. + +<|ref|>text<|/ref|><|det|>[[73, 482, 916, 550]]<|/det|> +You will see that the reviewers appreciate aspects of the work. However, they articulate concerns about the degree of support for some of the claims and about the advance that the work represents over relevant published studies also from your group, and provide useful suggestions for improvement. We hope that with significant further effort you can address the criticisms, increase the level of significance of the study, and convince the reviewers of its merits. In particular, we would expect that a revised version of the manuscript provides: + +<|ref|>text<|/ref|><|det|>[[73, 560, 757, 576]]<|/det|> +\* Extended discussion about the the novelty of the work respect to previously published manuscripts + +<|ref|>text<|/ref|><|det|>[[73, 586, 835, 602]]<|/det|> +\* Clarification about the use of both terms BCI and closed loop neuromodulation, as highlighted by Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 612, 904, 629]]<|/det|> +\* Thorough methodological reporting, with emphasis on facilitating reproducibility as per many points of all the Reviewers + +<|ref|>text<|/ref|><|det|>[[73, 638, 911, 694]]<|/det|> +When you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that explains the main improvements included in the revision and responds to any points highlighted in this decision. + +<|ref|>text<|/ref|><|det|>[[73, 704, 390, 718]]<|/det|> +Please follow the following recommendations: + +<|ref|>text<|/ref|><|det|>[[72, 729, 864, 758]]<|/det|> +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +<|ref|>text<|/ref|><|det|>[[72, 767, 918, 797]]<|/det|> +\* If you and your co- authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +<|ref|>text<|/ref|><|det|>[[72, 807, 900, 836]]<|/det|> +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the reason(s). + +<|ref|>text<|/ref|><|det|>[[72, 847, 884, 875]]<|/det|> +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +<|ref|>text<|/ref|><|det|>[[72, 886, 910, 914]]<|/det|> +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +<|ref|>text<|/ref|><|det|>[[72, 924, 652, 940]]<|/det|> +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 58, 920, 112]]<|/det|> +We hope that you will be able to resubmit the manuscript within 25 weeks from the receipt of this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[70, 124, 900, 152]]<|/det|> +We hope that you will find the referee reports helpful when revising the work. Please do not hesitate to contact me should you have any questions. + +<|ref|>text<|/ref|><|det|>[[72, 164, 161, 177]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[72, 190, 125, 202]]<|/det|> +Valeria + +<|ref|>text<|/ref|><|det|>[[72, 228, 712, 257]]<|/det|> +Dr Valeria Caprettini Associate Editor, Nature Biomedical Engineering + +<|ref|>text<|/ref|><|det|>[[72, 318, 405, 332]]<|/det|> +Reviewer #2 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[70, 344, 920, 520]]<|/det|> +This manuscript describes the use of a Python toolbox for decoding brain signals for the purposes of neuromodulation. The basic idea is to bring together multiple existing methods for feature extraction, dimensionality reduction, and decoding to try to improve on methods that are currently in clinical use or in clinical trials. It also describes some methods to use structural connectivity to help perform decoding across patients without having to obtain new training data. This is all useful; however, it is not clear how much of this is actually new. They do here show more examples of potential use cases in large datasets (DBS in patients with PD and depression, RNS in epilepsy patients), and this is useful to show the potential of using more techniques to optimize closed- loop neuromodulation. However, the authors have shown the connectivity "fingerprint", and many of their other methods (and ability to decode force in PD patients) in their prior eLife paper, and it appears that the toolbox was also created for that paper, since it cites that paper. None of the techniques in the toolbox are novel, though it is certainly helpful to have them all in one place and open- source (which is a strength). Further, many of the techniques are not clearly described, so it is difficult to assess their importance and, since the paper's main theme appears to be the toolbox itself, it seems to fall short of its main purpose- to make these techniques more user- friendly and widely used. Overall, this seems to be an incremental advance. More specific concerns follow below. + +<|ref|>text<|/ref|><|det|>[[72, 520, 185, 531]]<|/det|> +Major concerns: + +<|ref|>text<|/ref|><|det|>[[72, 531, 906, 580]]<|/det|> +1. It is not clear why the manuscript starts out talking about BCIs but then switches to closed loop neuromodulation. These are not the same thing, and there is enough confusion in the literature about what constitutes a BCI. The widely accepted definition involves some volitional modulation, which is not what is being described here. It would be preferable to not call this a BCI, but rather other methods of closed-loop neuromodulation. + +<|ref|>text<|/ref|><|det|>[[72, 593, 904, 633]]<|/det|> +2. Multiple other open-source toolboxes exist that have brain signal feature extraction, selection, and decoding algorithms included (e.g., FieldTrip). These are not even mentioned in this paper, and they clearly should be discussed and the advantages of this toolbox described clearly. + +<|ref|>text<|/ref|><|det|>[[72, 645, 916, 698]]<|/det|> +3. The introduction could be clearer as to exactly what problem is being solved with these techniques. It keeps talking about BCIs and decoding, but the problem envisioned seems to be closed-loop neuromodulation. But this works fairly well. For example, the sentence (in Results) "A key problem for invasive brain signal decoding is the individualized localization of brain implants + +<|ref|>text<|/ref|><|det|>[[72, 710, 901, 750]]<|/det|> +4. across patients, which significantly complicates the development of large-scale models..." What does localization of implants have to do with decoding? Decoding does not depend on location in any BCI literature. What type of large-scale models are being referred to here? Models across patients? This all needs more explanation. + +<|ref|>text<|/ref|><|det|>[[72, 762, 914, 815]]<|/det|> +5. To say that calibrating a move vs rest decoder in each patient is a serious limitation and would hinder broad clinical adoption seems a bit exaggerated, given the time it takes to do the DBS implant itself. Calibration could easily be done intraoperatively, or in already scheduled calibration sessions in clinic, within each patient in a few minutes for this simple of a decoding measure. + +<|ref|>text<|/ref|><|det|>[[70, 827, 913, 945]]<|/det|> +6. The Results and Methods need much clearer explanations of what was being done and decoded. It is not meaningful to say "balanced accuracy of \(0.8 / 0.98 \pm 0.07 / 0.04\) for single sample/movement detection..." without explaining what is "single sample" (or "sample-wise") decoding, what movements are being detected, and how many classes are being decoded among. The tasks seem highly disparate among these datasets, so combining results across them does not make much sense. The tasks are not even described in any detail, nor what is being decoded. It is also not clear exactly what features are being used to decode (e.g., how many time bins were used in each decoder? Were they causal-only bins?) nor how much data (trials) were used to train and test in each case. Since the whole point of the study is to show how this toolbox enables decoding, and the methods are not described in enough detail to understand the task, it is very difficult to ascertain the impact of the innovation. In addition, if the goal is to show that these techniques allow better decoding of movement vs + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 888, 75]]<|/det|> +rest (which I am inferring, since this is never stated clearly), then the results here should be compared to prior studies in closed- loop DBS using simpler methods. + +<|ref|>text<|/ref|><|det|>[[70, 85, 896, 114]]<|/det|> +7. Line 121: "0.88 ± 0.17 movement detection rate across movements" – unclear how this number was derived, as Fig 2g does not seem to show this high of accuracy averaged across all boxes. + +<|ref|>text<|/ref|><|det|>[[70, 125, 864, 153]]<|/det|> +8. In Table 1, what is the difference between "sample" vs "movement" columns? Is movement detection the same as sensitivity? If so, then state this. + +<|ref|>text<|/ref|><|det|>[[70, 164, 891, 191]]<|/det|> +9. "To approximate the movement kinematics..." What movement kinematics? Were these recorded? It's not even stated how movement times were recorded. + +<|ref|>text<|/ref|><|det|>[[70, 202, 890, 217]]<|/det|> +10. How were stimulation artifacts dealt with, given that the high gamma range includes the stimulation frequency used? + +<|ref|>text<|/ref|><|det|>[[72, 228, 902, 269]]<|/det|> +11. It seems that many ECoG electrodes with high decoding accuracy were in primary somatosensory cortex, which begs the question if these were really sensing sensory feedback, as opposed to motor intent. Sensory feedback would not be useful for controlling DBS, since it could be causing a positive feedback loop. + +<|ref|>text<|/ref|><|det|>[[72, 280, 920, 386]]<|/det|> +12. Another central theme of the paper is not clearly explained. The idea of using connectivity as a way to decode across patients is very interesting and potentially useful. However, the methods are not explained clearly enough. What does "voxel-wise correlation of connectivity profiles with decoding performances from offline training" mean (lines 548-49)? How does one correlate a connectivity profile with an R2 value? What exactly is meant by a "connectivity profile"? Just a pairwise correlation matrix? Other graph theoretic measures? There are many types of connectivity that can be calculated, and this needs to be explained. The cited reference likewise does not explain this sufficiently clearly, but in any case, this is a central theme of this paper and should be explained here, not delegated to a reference. Without this, "prospective channel selection" is not easily understood, because "optimal connectomic decoding map" is not clear at all. + +<|ref|>text<|/ref|><|det|>[[72, 397, 888, 438]]<|/det|> +13. It's not clear what the clinical relevance of training on a single subject to predict other subject's data, given that one would not know in practice who the "best" subject is without training on a group of subjects and testing on all of them anyway. + +<|ref|>text<|/ref|><|det|>[[72, 448, 920, 516]]<|/det|> +14. Authors seem to claim that CEBRA performs better than 2nd method, but do not provide statistical testing evidence to back this up (a p-value is presented, but how was this tested?). Similarly, it mentions several times that a given performance is above chance, but never states how chance is computed for any case. It is also not true that accuracy of \(\sim 60\%\) is "high above" chance when chance is likely \(50\%\) . Also, not clear what is being shown in Fig 2o -there are no y axis labels, and not clear if these are averages, single trials, or other. + +<|ref|>text<|/ref|><|det|>[[72, 527, 910, 594]]<|/det|> +15. More details should be provided about the DBS trial for depression. Without these, it is difficult to evaluate the phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." (line 244). Were all DBS leads used for stimulation? If not, how did those leads used for stimulation relate to the leads in the decoder? The clinical trials registry number should also be included for all of these trials. + +<|ref|>text<|/ref|><|det|>[[72, 605, 920, 660]]<|/det|> +16. More information is required about the "additional fiber filtering approach recently introduced..." (line 246). The method should be described clearly. Again, the term connectivity fingerprint is not explained. The phrase "estimated best therapeutic stimulation target from Fox et al 2014" is also not explained at all. Why is this important and what does it have to do with the results presented here? This needs explanation for a broad audience. + +<|ref|>text<|/ref|><|det|>[[72, 671, 910, 712]]<|/det|> +17. It's not clear whether the optimization of RNS parameters using a grid search is feasible or helpful for an actual clinical use case in individual patients. Was this optimized over all patients with holding patients out? Or by doing cross-validation with data from all patients together? + +<|ref|>text<|/ref|><|det|>[[72, 737, 185, 749]]<|/det|> +Minor concerns: + +<|ref|>text<|/ref|><|det|>[[72, 750, 558, 763]]<|/det|> +Please type out all acronyms used for those not familiar (e.g., CEBRA). + +<|ref|>text<|/ref|><|det|>[[72, 763, 870, 803]]<|/det|> +Methods mentions multiple terms that could mean similar things. What are data "batches" vs "segments"? FFTs were computed at 100 ms resolution – does this mean 100 ms windows, or longer windows overlapped by 100 ms? Fig 4 labels are too small to be legible. + +<|ref|>text<|/ref|><|det|>[[72, 802, 914, 829]]<|/det|> +Supplementary video is not explained clearly. What are the different decoding/prediction windows showing? The prediction output looks very noisy during movements. + +<|ref|>text<|/ref|><|det|>[[72, 866, 405, 880]]<|/det|> +Reviewer #3 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[72, 892, 916, 946]]<|/det|> +This is a very interesting and ambitious paper describing an open source software system, py_neuromodulation, for "decoding" of behavioral states, including disease specific states, from invasive intracranial recording. It is designed for field potential (LFP and electrocorticography) approaches. At a time of great excitement in human invasive neurophysiology and its application in neural engineering, authors are to be applauded for developing a comprehensive analytic system that is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 917, 112]]<|/det|> +accessible to all and that begins to standardize brain decoding across applications. A strength of the system is that it is designed to combine physiological recordings with connectomics, the merger of which can lead to new neuroscience insights. A strength of the paper is the illustration of the system in three different scenarios: decoding of movement (move vs rest, I believe, but see below) from motor system recordings in a variety of tasks in patients with movement disorders, decoding of emotional state from area 25 limbic implants, and decoding of pre- ictal or ictal activity in epilepsy. + +<|ref|>text<|/ref|><|det|>[[73, 125, 335, 138]]<|/det|> +Some general points for improvement: + +<|ref|>text<|/ref|><|det|>[[72, 138, 921, 240]]<|/det|> +1) The paper is quite dense. It assumes a high level of expertise form the reader, who would need to have fluency in neurophysiology of LFPs, advanced imaging methods especially merging imaging imaging sets across individuals, and machine learning, to fully grasp it. Below are specific areas where the authors could give a bit more information or clarification to help readers who don't already have expertise in all three of these. +2) Its not very clear how the system handles electrical recordings with lots of artifacts. There is one statement in methods on movement decoding that alludes to an answer "All 606 features were z-score normalized across the past 30 s and clipped at minus and plus three.." perhaps the "clipping" is their answer. More on how the system handles noisy data would be appreciated. + +<|ref|>text<|/ref|><|det|>[[72, 240, 924, 308]]<|/det|> +3) Authors should be more specific about what the system does NOT do, perhaps in discussion. At times the text seems to imply that the system can simulate closed loop stimulation for design of closed loop algorithms. For example this sentence in the abstract: "Our platform provides rapid, high-accuracy decoding for precision medicine approaches that can dynamically adapt neuromodulation therapies in response to the individual needs of patients" - is a DBS prototyping really part of py_neuromodulation? This should be clarified. + +<|ref|>text<|/ref|><|det|>[[72, 308, 923, 385]]<|/det|> +4) A description somewhere of what data or tools the user actually needs, to utilize this system, would be helpful. For example, how are electrode locations input into the system? Is a DICOM formatted image set of the whole brain needed? CT only or is MRI needed? Or does py_neuromodulation require Some sort of output from other software packages such as LeadDBS? Also how are the specific machine learning algorithms implemented.? Does the user make a simple selection like "support vector machine" and then is able to input hyperparameters? Or does py_neuromodulation require specific outputs from other machine learning packages? + +<|ref|>text<|/ref|><|det|>[[72, 385, 923, 450]]<|/det|> +5) One of the three big problems the authors hope to address is "Machine learning can capitalize on large datasets but current brain signal decoding approaches for BCI still commonly rely on individual patient training sets of short duration". It is never really clear to me how the authors solve this - is there a particular method they introduce to solve it? Or are they just trying to show that in fact you don't need large data sets of long duration, even though other researchers try to use those? More clarity in discussion on this would help. + +<|ref|>text<|/ref|><|det|>[[73, 475, 359, 490]]<|/det|> +Specific comments to improve readability: + +<|ref|>text<|/ref|><|det|>[[72, 501, 911, 529]]<|/det|> +Early in results or in intro, authors should say that their system is called "py_neuromodulation" When they began to use this term in results, I did not perceive that it is actually the name of their software pipeline. + +<|ref|>text<|/ref|><|det|>[[72, 541, 921, 580]]<|/det|> +Results section 1: "To address this, we developed dedicated approaches for patient decoding based on normative MRI connectomics and latent embeddings from contrastive learning with CEBRA13. " - this sentence will be opaque to a number of readers who are unfamiliar with contrastive learning and the acronym CEBRA. + +<|ref|>text<|/ref|><|det|>[[72, 592, 917, 724]]<|/det|> +Figure 1, Part D is not completely clear as it is first presented, and it seems to be a major part of the author's pipeline. Especially this statement: "Features can be mapped in space (d) for patient individual or across- patient decoding and consecutive adjustment of therapeutic delivery." Its not clear here how mapping features in space specifically contributes to decoding of dynamic patient states like movement, emotion, or seizure occurrence. Mapping the relevant activities would certainly contribute to a better understanding of anatomic localization or network involvement of recording sites that are relevant to decoding, and that contributes to understanding which brain networks are most relevant for the decoded brain state. But it is not clear at this point in the manuscript how the spatial mapping contributes to the process of decoding or to its accuracy. At line 89- 91, and later in the text, they imply that accounting for the variable localization of implants would be a contributor to generalized cross- subjects decoding, which seems true, but how would anatomic localization contribute to individual decoding performance as is stated in the figure legend? + +<|ref|>sub_title<|/ref|><|det|>[[72, 749, 193, 761]]<|/det|> +## Results section 2 + +<|ref|>text<|/ref|><|det|>[[72, 761, 914, 789]]<|/det|> +"at the single sample level (100 ms precision indicating presence or absence of movement) and at the individual movement level (300 ms or more movement time decoded consecutively)" - this sentence is not clear + +<|ref|>text<|/ref|><|det|>[[72, 801, 916, 828]]<|/det|> +it is not quite spelled out what movement decoding really means - are the brain states that are decoded "not moving" versus "moving"? this should be more clearly stated. + +<|ref|>text<|/ref|><|det|>[[72, 840, 910, 880]]<|/det|> +Figure 2 - Panels j, k - the term "embedding" is not clear here. Panel o - the meaning of the y axis is not clear in these plots. For example for "true movement" is the y axis displacement? Force? + +<|ref|>text<|/ref|><|det|>[[72, 892, 763, 906]]<|/det|> +"To investigate the individual variability of trainer vs. learner performance" - not sure what this means + +<|ref|>text<|/ref|><|det|>[[72, 917, 884, 944]]<|/det|> +In general for this section: what signal features contributed to movement decoding? In the following section on emotion decoding, the features used are stated more explicitly, and that would help here in this section. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 60, 193, 72]]<|/det|> +Results section 3 + +<|ref|>text<|/ref|><|det|>[[72, 73, 919, 125]]<|/det|> +"To investigate a potential relationship with clinical scores, we correlated decoding performances from the most predictive channel contrasting neutral vs. positive/negative per patient with Beck's Depression Inventory (BDI) at time of recording and after six months of chronic DBS. Decoding performance correlated with DBS induced improvement in BDI scores (rho=0.79, p=0.01), but not + +<|ref|>text<|/ref|><|det|>[[72, 125, 365, 139]]<|/det|> +with concurrent symptom severity (Fig. 3f)." + +<|ref|>text<|/ref|><|det|>[[72, 139, 901, 180]]<|/det|> +- this is tough to follow - why would the decoding performance in emotional task be expected to correlate with depression severity? Is the hypothesis that the more depressed one is, the more task related emotional valence is "decodable"? the opposite seems more likely, that is depression would blunt ones ability to distinguish emotional valences. + +<|ref|>text<|/ref|><|det|>[[72, 191, 920, 231]]<|/det|> +"... connectivity fingerprints seeded from LFP channel locations were correlated with channel specific decoder test-set performance". - for a nonexpert - how are connectivity fingerprints quantified so as to feed into a correlation? A sentence on this would help. + +<|ref|>text<|/ref|><|det|>[[72, 243, 920, 271]]<|/det|> +Figure 3e - even zooming in, its hard to read the feature labels or understand what they mean. Legend refers to a part "I" but don't see that panel in the figure. + +<|ref|>text<|/ref|><|det|>[[72, 282, 308, 309]]<|/det|> +Results section 4 briefly explain what an F1 score is + +<|ref|>text<|/ref|><|det|>[[72, 321, 155, 334]]<|/det|> +Discussion: + +<|ref|>text<|/ref|><|det|>[[72, 346, 916, 399]]<|/det|> +"Nevertheless, decoding performances were investigated in the presence of clinical brain stimulation in two out of three use cases, namely STN- DBS for PD and responsive neurostimulation for epilepsy" - is this actually true for RNS? My understanding is that RNS is a "half duplex" device, that is it senses, provides preprogrammed stimulation train when an event is detected, then returns to sensing mode. It does not actually sense during stimulation. + +<|ref|>text<|/ref|><|det|>[[72, 410, 920, 490]]<|/det|> +"The network description however, is static in nature, while symptoms wax and wane. Brain signal decoding may help these networks to come to life in a dynamic closed- loop neurostimulation approach by informing both decoding and stimulation models of symptom specific circuits to optimize symptom decoding and adaptation of stimulation right at the time they occur" - not sure I get the meaning here. This seems to be a discussion of the advantage of combining connectomics (static) with brain signal decoding (dynamic) to produce something that hasn't been done before, but the sentence is lofty enough that it loses the reader. + +<|ref|>text<|/ref|><|det|>[[72, 567, 144, 580]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 593, 181, 606]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 618, 303, 632]]<|/det|> +Dear Dr Merk and Prof Neumann, + +<|ref|>text<|/ref|><|det|>[[72, 644, 920, 723]]<|/det|> +Thank you for your revised manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants", which has been seen by the original reviewers. Please apologise for the slow turnaround time, that is related to a combination of event among which the team being severely understaffed for several months, making hard to be efficient in processing all the files, and the need to chase reviewers or recruit new ones. In their reports, which you will find at the end of this message, you will see that the reviewers acknowledge the improvements to the work but one of them raises additional criticisms that we hope you will be able to address. + +<|ref|>text<|/ref|><|det|>[[72, 722, 916, 750]]<|/det|> +In particular, we would expect that the next version of the manuscript provides clear and complete methodological reporting, and convincing discussion about the advancement provided by the proposed toolbox. + +<|ref|>text<|/ref|><|det|>[[72, 762, 920, 816]]<|/det|> +As before, when you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that explains the main improvements included in the revision and responds to any points highlighted in this decision. + +<|ref|>text<|/ref|><|det|>[[72, 826, 491, 840]]<|/det|> +As a reminder, please follow the following recommendations: + +<|ref|>text<|/ref|><|det|>[[72, 852, 863, 880]]<|/det|> +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +<|ref|>text<|/ref|><|det|>[[72, 892, 920, 919]]<|/det|> +\* If you and your co- authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +<|ref|>text<|/ref|><|det|>[[70, 931, 900, 946]]<|/det|> +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 142, 60]]<|/det|> +reason(s). + +<|ref|>text<|/ref|><|det|>[[72, 72, 884, 100]]<|/det|> +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +<|ref|>text<|/ref|><|det|>[[72, 111, 910, 140]]<|/det|> +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +<|ref|>text<|/ref|><|det|>[[72, 151, 651, 166]]<|/det|> +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +<|ref|>text<|/ref|><|det|>[[72, 177, 920, 231]]<|/det|> +We hope that you will be able to resubmit the manuscript within 15 weeks from the receipt of this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[70, 242, 907, 271]]<|/det|> +We look forward to receive a further revised version of the work. Please do not hesitate to contact me should you have any questions. + +<|ref|>text<|/ref|><|det|>[[72, 282, 161, 295]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[72, 308, 124, 321]]<|/det|> +Valeria + +<|ref|>text<|/ref|><|det|>[[72, 345, 712, 374]]<|/det|> +Dr Valeria Caprettini Associate Editor, Nature Biomedical Engineering + +<|ref|>text<|/ref|><|det|>[[72, 437, 405, 451]]<|/det|> +Reviewer #2 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[70, 462, 923, 686]]<|/det|> +The goal of having "plug and play" decoding algorithms for closed loop DBS is an important one. Likewise, having a toolbox that can implement these algorithms and distribute open- source would be valuable. However, the paper does not give enough information as to how this toolbox implements a plug and play algorithm. Multiple steps still seem to be involved, including coregistering individual's imaging to MNI space, and placing the electrodes in this coordinate space. This, as mentioned by the authors in their rebuttal, is not trivial, especially when taking into account brain shifts due to opening the dura. No mention of how this substantial shift would be accounted for. The authors state that one of their goals is to "facilitate multicenter clinical trials ...and democratization of the methodological approach." Yet, the descriptions in this paper are far too vague and lacking in specific methods for even those engineers familiar with BCIs to be able to implement, let alone for clinicians to be able to even comprehend the basics. And importantly, this procedure of coregistering would take significant time - indeed, in our experience, much more time than building a very simple decoder of movement vs. rest for an individual, which could be done in less than 5 min (including recording and automated decoder building). Either way, this will require some time for the clinician or a technologist. Since this (across- patient decoding) appears to be the biggest goal of this paper, the authors need to make a much stronger case (including empiric evidence of time to perform and compute the different steps for a given patient, as a clinician would do it, and showing this is truly less than recording move vs rest for 3- 5 min and building a very simple individualized decoder, rather than vague estimates as in the rebuttal) for why this is better than individual decoders. Overall, the paper still assumes too high of an expertise in many disparate and specific domains to be applicable to a broad audience. + +<|ref|>sub_title<|/ref|><|det|>[[72, 699, 161, 711]]<|/det|> +## Major issues + +<|ref|>text<|/ref|><|det|>[[70, 710, 916, 829]]<|/det|> +1. The central theme of the paper, the connectivity-based decoding, is still not explained clearly enough to understand. The additional supplementary figures help slightly, but they still dance around, and gloss over, the main concerns I had previously - the "connectivity values", correlation of them with "decoding performance (what is this??)", and "optimal decoding map" are not clearly defined. SF4 shows correlations with 1000 functional connections - does this mean they are averaged over all participants? What does decoding performance for a single electrode mean? Does that mean you're building single-channel decoders? If not, this does not make sense. And how are you correlating one value with a connectivity map (which is a whole vector for a single electrode)? SF5.c similarly needs much clearer explanation. (What is a connectivity template? What are R1-R6? What is being correlated with what?) This needs much better explanation if you want people to understand how to use it. Examples would help. + +<|ref|>text<|/ref|><|det|>[[70, 840, 923, 920]]<|/det|> +2. The performance, especially across cohorts, and ability to extrapolate to new patients, is somewhat oversold in this paper, even if this performance is substantially better than previous studies. In particular, when the leave-one-cohort-out accuracy is barely above chance (~0.6), it suggests that even subtle differences in movement types will lead to poor decoder performance across patients. That would seem to not be very practical for a patient wanting to do many different types of movement, and thus "plug & play" would not work very well. Even ~80% accuracy is highly unlikely to be good enough for most patients - think about how frustrated you would be if your computer cursor did not work correctly 2/10 times. + +<|ref|>text<|/ref|><|det|>[[70, 931, 920, 946]]<|/det|> +3. The revised paper still leans too heavily on the term BCI. The BCI society's working definition was not intended to include + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 918, 73]]<|/det|> +closed- loop DBS as a BCI. While philosophically cDBS could fit in this definition, the vast majority of BCI researchers do not consider it to be a BCI, and doing so could cause a host of logistical issues. Not to mention confusing many non- experts. + +<|ref|>text<|/ref|><|det|>[[72, 85, 920, 218]]<|/det|> +4. Methods are still incomplete. The description of movement detection is better, but the performance description:". balanced accuracy of \(0.8 / 0.98\pm 0.07 / 0.04\) for single sample/movement detection" still could be clearer. Is the second value for the 300 ms consecutive "rate?" If so, then state that more clearly. Also the following sentences are unclear: "A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block. It's important to note, however, that this measure addresses only the movement class and has no predictive value of rest segments." What does it mean to only "address the movement class"? It's a binary classification, so how is it not predicting rest vs movement? Or does this have something to do with the fact that there are now 3 bins and not all of them may be movement at that same time? Also is this balanced accuracy or not? If not, it should be, to make fair comparisons between 1 and 3-bin decoders and to avoid biases of too many false positives. Introducing a 300 ms delay (effectively) to movement is also not trivial and is long enough that it could impair movement precision (due to feedback delays) for patients. This should be discussed. + +<|ref|>text<|/ref|><|det|>[[72, 243, 920, 321]]<|/det|> +5. "processing steps to mitigate DBS artifacts including bandpass filtering and period-based DBS artifact removal did not improve, but instead aggravated this deterioration" The fact that artifact removal significantly worsened decoding accuracy is a potentially significant issue. The point was not to improve accuracy; the point was to see that accuracy did not worsen with removal of artifacts, but in fact it did worsen in most cases. That is concerning that a good portion of your "movement" decoding was really artifact decoding. This could lead to false positives. This deserves much more discussion and tempering of conclusions than is currently in the paper. + +<|ref|>text<|/ref|><|det|>[[70, 333, 910, 361]]<|/det|> +6. The sensory cortex issue is insufficiently addressed in the manuscript. This needs to be acknowledged in the discussion more clearly than talking about interplay of motor and sensory information vaguely. + +<|ref|>text<|/ref|><|det|>[[70, 372, 910, 399]]<|/det|> +7. Statistical rigor (at least in reporting) is still lacking. Many results are still described as "above chance", sometimes with p values, without statistical methods described. + +<|ref|>text<|/ref|><|det|>[[70, 411, 866, 439]]<|/det|> +8. The phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." is still opaque. What does this mean? + +<|ref|>text<|/ref|><|det|>[[72, 465, 165, 478]]<|/det|> +Minor issues: + +<|ref|>text<|/ref|><|det|>[[70, 490, 914, 517]]<|/det|> +Regarding differentiating from other toolboxes - the first point about offline and online using the same routines is not unique - FieldTrip also enables this. + +<|ref|>text<|/ref|><|det|>[[72, 529, 634, 544]]<|/det|> +"Neuromedicine" is not a word. The more appropriate term seems to be neurology. + +<|ref|>text<|/ref|><|det|>[[72, 580, 405, 594]]<|/det|> +Reviewer #3 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[70, 606, 923, 633]]<|/det|> +the authors have responded quite thoroughly to reviewer comments and improved the manuscript. my summary of the results is part of my initial review so is not reproduced here. + +<|ref|>text<|/ref|><|det|>[[72, 699, 144, 711]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[72, 724, 183, 737]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 750, 170, 763]]<|/det|> +Dear Dr Merk, + +<|ref|>text<|/ref|><|det|>[[72, 776, 923, 894]]<|/det|> +Thank you for your revised manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants". I went back to Reviewer #2 for them to review your point- by- point rebuttal, but at this time they were unavailable for reviewing. I found another reviewer with expertise in computational neuroscience and surgical experience in brain implants, and I provided them with the previous review reports as well as your point- by- point answers. You can find their report at the end of this message, and you will see that the reviewer acknowledges the value of the work, provides useful suggestions of how to make the story more appealing and raises a few additional technical criticisms that we hope you will be able to address. In particular, we would expect that the next version of the manuscript provides further analysis of some of your data to strengthen the evidence in support of the possibilities that your approach offers, as per the many suggestions of this new report. + +<|ref|>text<|/ref|><|det|>[[70, 906, 916, 948]]<|/det|> +As before, when you are ready to resubmit your manuscript, please upload the revised files, a point- by- point rebuttal to the comments from all reviewers, the reporting summary, and a cover letter that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 839, 62]]<|/det|> +explains the main improvements included in the revision and responds to any points highlighted in this decision. + +<|ref|>text<|/ref|><|det|>[[72, 72, 491, 87]]<|/det|> +As a reminder, please follow the following recommendations: + +<|ref|>text<|/ref|><|det|>[[70, 98, 864, 128]]<|/det|> +\* Clearly highlight any amendments to the text and figures to help the reviewers and editors find and understand the changes (yet keep in mind that excessive marking can hinder readability). + +<|ref|>text<|/ref|><|det|>[[70, 138, 920, 167]]<|/det|> +\* If you and your co- authors disagree with a criticism, provide the arguments to the reviewer (optionally, indicate the relevant points in the cover letter). + +<|ref|>text<|/ref|><|det|>[[70, 177, 900, 206]]<|/det|> +\* If a criticism or suggestion is not addressed, please indicate so in the rebuttal to the reviewer comments and explain the reason(s). + +<|ref|>text<|/ref|><|det|>[[70, 216, 885, 245]]<|/det|> +\* Consider including responses to any criticisms raised by more than one reviewer at the beginning of the rebuttal, in a section addressed to all reviewers. + +<|ref|>text<|/ref|><|det|>[[70, 255, 910, 284]]<|/det|> +\* The rebuttal should include the reviewer comments in point- by- point format (please note that we provide all reviewers will the reports as they appear at the end of this message). + +<|ref|>text<|/ref|><|det|>[[72, 294, 652, 309]]<|/det|> +\* Provide the rebuttal to the reviewer comments and the cover letter as separate files. + +<|ref|>text<|/ref|><|det|>[[72, 319, 917, 375]]<|/det|> +We expect that you will be able to resubmit the manuscript within 15 weeks of receiving this message. If this is the case, you will be protected against potential scooping. Otherwise, we will be happy to consider a revised manuscript as long as the significance of the work is not compromised by work published elsewhere or accepted for publication at Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[70, 384, 907, 413]]<|/det|> +We look forward to receive a further revised version of the work. Please do not hesitate to contact me should you have any questions. + +<|ref|>text<|/ref|><|det|>[[72, 424, 161, 438]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[72, 450, 125, 463]]<|/det|> +Valeria + +<|ref|>text<|/ref|><|det|>[[72, 488, 690, 517]]<|/det|> +Dr Valeria Caprettini Senior Editor, Nature Biomedical Engineering + +<|ref|>text<|/ref|><|det|>[[72, 576, 405, 591]]<|/det|> +Reviewer #4 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[72, 602, 923, 740]]<|/det|> +I begin by paraphrasing the authors' problem statement. Problem 1: modern approaches to neural decoding use modern ML algorithms, which are data hungry. Collecting enough data in patients is hard, and there is a dearth of frameworks to facilitate transfer learning between patients in low- data regimes. Problem 2: the authors want a framework to extract neural signals. Problem 3: most experiments record data from only small areas of the brain and fail to incorporate networks of neural activity that give rise to signals. To address all three issues, the authors describe a new software package. The claims are that the software package is (i) a real- time BCI platform, that (ii) implements multiple novel signal analysis processing methods, and (iii) implements a method for transfer- learning using anatomical and connectome data. They further motivate how their software package is useful with three real- world examples: transfer learning with ECoG recordings in patients undergoing DBS (and epilepsy monitoring, Fig 2); retrospective analysis of intracranial signals to predict findings in a study of DBS for depression (Fig 3); and retrospective analysis of data collected from RNS recordings (Fig 4). + +<|ref|>text<|/ref|><|det|>[[72, 749, 918, 841]]<|/det|> +I am a neurosurgeon and I have previously published software packages in BCI methods, analysis of intracortical signals, and articles on RNS signal analysis. I am familiar with Dr. Horn's Lead DBS platform and have examined some of its methods in detail. In summary of my review to follow, I think this paper's broad appeal is the method that combines connectome information to assist with neural decoding in a low- data regime. As with many scientific ideas, it is both elegant and profound. By contrast, I think the framing of this paper through the lens of a software platform is a distraction. Below, I comment extensively on the framing of the authors' results and provide suggestions for further analyses that would further highlight the excitement and broad- scientific appeal. + +<|ref|>text<|/ref|><|det|>[[72, 852, 915, 933]]<|/det|> +1) A new method of transfer learning that uses imaging data (resting state fMRI and anatomical MRI) to boost intracranial neural decoding performance in low data regimes is compelling. To that end, I found Table 1, Fig 2l, and Fig 2m cool. I can record data from patients in the EMU and/or previous patients in the OR, and then use those recordings to learn hyperparameters for my decoder for a movement task in the OR for a new patient. By using CEBRA, you have now taught me that there exists a cross-person neural manifold for movement, informed by where I am physically recording on the brain (and how this part of the brain is connected to other parts, over multiple participants). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 166]]<|/det|> +But - the whole point of transfer learning in a neural decoding framework is to save time by priming a decoder with hyperparameters in a low- data regime. For instance, isn't the value of the approach obviated if it only takes two exemplars of movement (and movement onset) to get comparable decoding? Show us this is useful by plotting performance as a function of time for the participants, and especially the "real- time decoding" PD patient, to point out that decoding performance happens out of the box with your new method. In fact, the most compelling demonstration of the method would be to show that leveraging your approach would improve decoding further beyond what you would have achieved from just the data from that patient. In other words, demonstrate evidence that "For a real- world clinical application this means that every implant would need to undergo tedious model training sessions, which could be a burden to both patients and medical staff and may hinder a broad clinical adoption." + +<|ref|>text<|/ref|><|det|>[[72, 176, 917, 296]]<|/det|> +2) Here's another way you could convince me this approach works: suppose that one of the PD patients implanted had abnormal cortical anatomy (which happens not infrequently). For this patient, supposed that I had an ECoG strip where I thought the contacts were on the pre- and post-central gyri (based on imaging), but using your transfer-learning approach I had missed by a gyrus, and had landed on the MFG and the pre-central gyrus instead. Could your approach convince me that I've made a mistake in identifying the anatomy? Placing ECoG strips in the OR through a burr-hole during DBS is a blind procedure and needs to be confirmed with an intra-operative spin (at least in my hands), which is time-consuming and exposes the patient to radiation (which is challenging to justify if the research program itself is motivated through a non-significant-risk patient consent). Can your system save time for optimizing ECoG placement by providing an ongoing estimate of where the ECoG is likely located on the brain? + +<|ref|>text<|/ref|><|det|>[[72, 306, 920, 399]]<|/det|> +3) The most compelling part of Fig. 3 is the utilization of the image-registration method incorporating connectome information that allows you to perform out-of-patient prediction for optimal electrode selection, which in turn has direct clinical relevance. This is a beautiful story. You showed me that the connectome method was predictive of decoding performance. This story could perhaps culminate in you telling the reader that this post-hoc information predicted that the contacts were correctly or incorrectly chosen for each patient, and then making suggestions that correctly choosing the right electrode would have had a tangible clinical impact. Also, the "sweet spot" in Fig 3h is covered by the left hemisphere, and I can't see the cingulate (unless I misunderstood, and Fox 2014 stimulated the DLPFC?). + +<|ref|>text<|/ref|><|det|>[[72, 410, 923, 530]]<|/det|> +4) Describing this paper as a real-time BCI platform is a distraction. To start, I'm not sure we agree as to what real-time means. Most people think that real-time means that there are deterministic bounds on program cycle execution and OS context switches. So, to make the claim that this system is real-time, you must do the following: (1) put bounds of performance by examining jitter and latency - I suspect this will be hard, because I assume the platform is designed to run in Windows (since I find .bat files in the github code) and as far as I know, Windows doesn't provide soft real-time guarantees; (2) characterize how long the system can run before you run out of memory (unless you've solved this issue by writing drivers that move data from memory to disk in a way that doesn't interrupt data flow); and (3) characterize real-time performance as a function of algorithm complexity and channel count (i.e., beyond a handful of channels and a binary classification problem). These would be the minimum requirements before I would re-engage with this claim. + +<|ref|>text<|/ref|><|det|>[[72, 540, 911, 646]]<|/det|> +However, I would further argue that if you now want to sell a real- time software package as a high- impact publication in 2024, then you're obliged to do much more: (1) ensure that it works in multiple operating systems, (2) account for multiple languages (python is exciting right now, but matlab was exciting a decade ago), (3) have hooks to plug into multiple open source frameworks (like neurodata without borders), (4) have plans for long- term maintenance and naming conventions for code, (5) demonstrate that the system works outside of a small group of collaborating neuroscience labs, etc. In summary, I strongly disagree with your claim that py_neuromodulation is a "...toolkit for invasive brain signal decoding for closed- loop neuromodulation that emphasizes rigorous real- time compatibility and reproducibility." This is an unsubstantiated claim. Please de- emphasize this claim in the paper. + +<|ref|>text<|/ref|><|det|>[[72, 657, 923, 776]]<|/det|> +5) I find this sentence problematic: "... a unique and novel feature set that included temporal waveform features, such as discharge prominence, sharpness, decay and rise time, and peak and trough interval in addition to traditional oscillatory FFT features." Is the authors' claim that the peak and troughs-based analysis of local field potentials has never been described before? If you believe this is true, then how have you yourselves characterized these features? What's the electrophysiological relevance of these features that teaches us something new about the brain? Why would these metrics have broad appeal, and why would I as a biomedical engineer know which to pick? In summary, if the main claim of the paper is that these spike wave forms are novel and interesting and useful, then they have been insufficiently characterized to be relevant to a broad scientific audience. In my opinion, characterizing these in detail is a paper into itself, and shouldn't be conflated with the main compelling scientific idea. + +<|ref|>text<|/ref|><|det|>[[72, 787, 917, 933]]<|/det|> +6) I don't understand how Figure 4 addresses the problem statements of your paper. The motivation for the analysis is "... to inspire new ways to improve seizure detection accuracy by constraining the decoding platforms to the specifications of clinical brain implants and suggesting improved parameters from offline predictions that are implementable and testable through the clinical patient data management systems (PDMS) provided by Neuropace." Returning to the problems you're solving, as introduced by the introduction of the paper, this figure does not (Problem 1) incorporate data between patients to solve a low-data regime problem, nor (Problem 3) incorporate connectome information between patients. While it does (Problem 2) apply ML algorithms to different a cornucopia of uncharacterized electrophysiologic features, it feels like a fishing expedition. Further, the per-day limitations of data collection with RNS are substantial, as the PDMS available is necessarily biased by whatever the clinician has previously identified to be a seizure (unless I missed somewhere that you're doing long-term data streaming) – I am highly skeptical of the consequence of the findings without seeing the impact (neurophysiologic or clinical). I'm happy to be convinced otherwise, but right now Fig. 4 doesn't prove your paper's point. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 127]]<|/det|> +Here's one way that would make the presentation more compelling to the reader. Hopefully, the leads in patients with epilepsy are placed in critical parts of the seizure network. Surely, across 9 patients, some networks have been sampled more than once. Hence, here is a wonderful opportunity to showcase the connectome approach to decoding. Can your approach leverage connectome data to assist with seizure prediction? Can you tell me which network I'm in, to help me with optimal lead selection? Or, can you tell me that a set of parameters determined offline for person A will likely work for person B, because they're targeting the same seizure network? + +<|ref|>text<|/ref|><|det|>[[72, 152, 161, 165]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[72, 177, 905, 270]]<|/det|> +7) The authors have told me that Lead DBS was, "optimized in Lead-DBS for subcortical structures." This matches my experience as well – the default settings (which again, the authors recommend) have both whole-brain and sub-cortical masks that are applied in series to emphasize this fact. Have they quantified the performance of LeadDBS on non-linear deformations of cortical anatomy, in the same way that Dice coefficients have been computed for subcortical structures? If so, can you point me in the direction of a paper that validates cortical anatomy between patients? If not, then can you comment about why not validating the default settings of the program do not impact the quality of your transfer learning approaches? If this question isn't relevant, please explain why (because this point isn't clear to me). + +<|ref|>text<|/ref|><|det|>[[72, 281, 910, 322]]<|/det|> +8) "In brief, Lead-DBS uses preoperative MRI and postoperative CT scans for co-registration and normalization to MNI 2009b NLIN ASYM space." This is incorrect, though I am happy to be corrected by Dr. Horn. There are many options available for using standard spaces. That's one of the really nice things about the software. In fact, Fig 4a proves my point! + +<|ref|>text<|/ref|><|det|>[[72, 332, 920, 450]]<|/det|> +9) On 23 May 2024, the BCI Society voted to accept this definition of a BCI (https://bcisociety.org/bci-definition/): A brain-computer interface is a system that measures brain activity and converts it in (nearly) real-time into functionally useful outputs to replace, restore, enhance, supplement, and/or improve the natural outputs of the brain, thereby changing the ongoing interactions between the brain and its external or internal environments. It may additionally modify brain activity using targeted delivery of stimuli to create functionally useful inputs to the brain. Most people I know consider a BCI as the first sentence. To my chagrin, neuroprosthetics that meet the definition of the second sentence are now part of the story, so arguably, closed-loop DBS and RNS systems are now under the umbrella of what makes up a BCI. Nevertheless, approach with caution, as you will aggravate some readers with this word choice. For context, neither FDA leadership nor the iBCI-CC consider closed-loop DBS/RNS systems to be BCIs. + +<|ref|>text<|/ref|><|det|>[[73, 462, 576, 477]]<|/det|> +10) Perhaps you meant, "closed loop" rather than "real-time" in the paper? + +<|ref|>text<|/ref|><|det|>[[72, 489, 921, 556]]<|/det|> +11) Why is it so necessary to be so deprecating to the clinical hardware that we have, when the paper itself hasn't created new hardware? Said another way: this is unnecessarily grandiose and sets a weird tone for the paper: "The clinical neurosciences stand at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology." + +<|ref|>text<|/ref|><|det|>[[72, 567, 496, 581]]<|/det|> +12) Consider switching Supplementary Figure 5 and Figure 1. + +<|ref|>text<|/ref|><|det|>[[72, 593, 905, 620]]<|/det|> +13) The newly added text that goes into tremendous (and important) detail about data analysis describing Figure 2 should go to the Methods. + +<|ref|>text<|/ref|><|det|>[[72, 632, 915, 686]]<|/det|> +14) "We may speculate that neurodegeneration in PD may impact neural encoding of movement, which may also impede machine learning based decoding performance". Patients with worse UPDRS scales may have less brain. Is your decoding performance related to the ECoG strips not actually sitting on the brain, or perhaps have much more air than snuck in during the case? + +<|ref|>text<|/ref|><|det|>[[72, 698, 915, 738]]<|/det|> +15) "Divining appropriate settings" in describing RNS programming is unnecessarily pessimistic. The very fact that patients often do get better, either tells us that clinical heuristics are useful, or a significant subset of the high-dimensional parameter space is useful. + +<|ref|>text<|/ref|><|det|>[[73, 763, 377, 777]]<|/det|> +Reviewer #4 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[72, 789, 911, 816]]<|/det|> +The code documentation is variable. Some parts hand- hold the user through the process and are easy to follow, and others are slapped together to make a point in OS- specific configuration files. I didn't try running the code. + +<|ref|>text<|/ref|><|det|>[[72, 880, 144, 892]]<|/det|> +Version 3: + +<|ref|>text<|/ref|><|det|>[[72, 906, 181, 918]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 932, 170, 944]]<|/det|> +Dear Dr Merk, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 59, 895, 100]]<|/det|> +Thank you for your revised manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants". Having consulted with Reviewers #4 (whose comment you will find at the end of this message), I am pleased to write that we shall be happy to publish the manuscript in Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[70, 111, 920, 140]]<|/det|> +We will be performing detailed checks on your manuscript, and in due course will send you a checklist detailing our editorial and formatting requirements. You will need to follow these instructions before you upload the final manuscript files. + +<|ref|>text<|/ref|><|det|>[[72, 151, 504, 166]]<|/det|> +Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[72, 178, 161, 191]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[72, 204, 124, 217]]<|/det|> +Valeria + +<|ref|>text<|/ref|><|det|>[[72, 242, 690, 270]]<|/det|> +Dr Valeria Caprettini Senior Editor, Nature Biomedical Engineering + +<|ref|>text<|/ref|><|det|>[[72, 333, 406, 347]]<|/det|> +Reviewer #4 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[73, 359, 325, 373]]<|/det|> +Please see attached PDF document. + +<|ref|>text<|/ref|><|det|>[[73, 385, 378, 399]]<|/det|> +Reviewer #4 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[72, 411, 634, 425]]<|/det|> +I have partially reviewed the updated code base. Did not try installing or running it. + +<|ref|>text<|/ref|><|det|>[[72, 488, 145, 501]]<|/det|> +Version 4: + +<|ref|>text<|/ref|><|det|>[[72, 514, 183, 527]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 540, 170, 554]]<|/det|> +Dear Dr Merk, + +<|ref|>text<|/ref|><|det|>[[70, 566, 923, 595]]<|/det|> +I am happy to inform you that your manuscript, "Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants", has now been accepted for publication in Nature Biomedical Engineering. + +<|ref|>text<|/ref|><|det|>[[70, 606, 921, 634]]<|/det|> +Over the next few weeks, the figures will be checked for production quality, the text edited to ensure that it conforms to house style, and the manuscript typeset. + +<|ref|>text<|/ref|><|det|>[[72, 646, 911, 687]]<|/det|> +Our Articles are published about 40 days after the acceptance date (we recommend that you inform your institutional press office of this timeframe), and you will be notified of the actual publication date a few days in advance. 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The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 755, 620, 768]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 124]]<|/det|> +Reviewer comments were appended in black, author replies to the reviewers were made in blue and changes in the manuscript were highlighted in green font color. + +<|ref|>text<|/ref|><|det|>[[115, 134, 221, 150]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[114, 160, 882, 454]]<|/det|> +This manuscript describes the use of a Python toolbox for decoding brain signals for the purposes of neuromodulation. The basic idea is to bring together multiple existing methods for feature extraction, dimensionality reduction, and decoding to try to improve on methods that are currently in clinical use or in clinical trials. It also describes some methods to use structural connectivity to help perform decoding across patients without having to obtain new training data. This is all useful; however, it is not clear how much of this is actually new. They do here show more examples of potential use cases in large datasets (DBS in patients with PD and depression, RNS in epilepsy patients), and this is useful to show the potential of using more techniques to optimize closed- loop neuromodulation. However, the authors have shown the connectivity "fingerprint", and many of their other methods (and ability to decode force in PD patients) in their prior eLife paper, and it appears that the toolbox was also created for that paper, since it cites that paper. None of the techniques in the toolbox are novel, though it is certainly helpful to have them all in one place and open- source (which is a strength). Further, many of the techniques are not clearly described, so it is difficult to assess their importance and, since the paper's main theme appears to be the toolbox itself, it seems to fall short of its main purpose- to make these techniques more user- friendly and widely used. Overall, this seems to be an incremental advance. More specific concerns follow below. + +<|ref|>text<|/ref|><|det|>[[115, 464, 882, 515]]<|/det|> +We thank the reviewer for their valuable feedback. Through this, we have more clearly identified the critical points that we hope to convey with the present manuscript. We would like to highlight three key aims as follows: + +<|ref|>text<|/ref|><|det|>[[160, 525, 884, 664]]<|/det|> +Aim 1. First and foremost the aim of the manuscript is to highlight advances that brain signal decoders can provide for invasive neurotechnology across disciplines of neuromedicine. Aim 2. We formalize and describe the methodology to achieve those advances in an open- source toolbox py_neuromodulation. Aim 3. We illustrate how the two biggest innovations in deep brain stimulation research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility. + +<|ref|>text<|/ref|><|det|>[[115, 680, 586, 697]]<|/det|> +This is now clarified in the last sentence of the introduction: + +<|ref|>text<|/ref|><|det|>[[115, 715, 882, 835]]<|/det|> +"In this paper, we aimed to a) highlight the clinical utility of brain signal decoding advances in a large cohort of patients across thousands of recording sources from invasive brain implants within three key areas of clinical neurotechnology innovation: movement disorders, psychiatry, and epilepsy; b) formalize and describe the methodology to achieve those advances in an open- source python software called py_neuromodulation; c) illustrate how the two biggest innovations in deep brain stimulation research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility." + +<|ref|>text<|/ref|><|det|>[[115, 853, 570, 870]]<|/det|> +In the following we would like to elaborate on these aims: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 486]]<|/det|> +For aim 1, we have chosen three critical frontiers of brain health and key areas of neurotechnological innovation, namely: movement disorders, depression and epilepsy. In these, areas we show a series of previously unattained achievements, including the first description of a generalizable movement decoder (for discussion on clinical relevance see our reply to comment 4), the characterization of temporal dynamics of emotion decoding and its' relationship to brain circuits underlying good DBS response in depression and finally the demonstration that offline optimization can be used to improve detector parameters for embedded devices for seizure decoding in epilepsy. Despite the fact that invasive neurotechnology such as deep brain stimulation is now being used for decades, there are still no clinical devices that capitalize on the use of machine learning and brain signal decoding. To clarify the intellectual merit with respect to the referenced eLife paper, we would like to point out that in the present manuscript we did not decode grip- force from motor cortex in 11 patients with PD, but instead decoded general presence of movement across 56 patients from multiple cohorts including both Parkinson's disease and epilepsy patients, performing different movement tasks, with brain activity recorded from different brain areas. Through this, we demonstrate for the first time that decoding movement across cohorts and brain areas is possible and showcase the superiority of a novel contrastive learning based decoding algorithm CEBRA that has gained widespread attention in animal studies but was never used in humans. And we investigate to what degree high- frequency DBS can impair decoding. All of these aspects have not been addressed in the eLife paper, and as pointed out by the reviewer, the movement decoding is only one use- case described. Importantly, through the revision and in response to the valuable feedback from the reviewers, we have now added an additional case where pretrained models were used to adjust stimulation delivery in real- time, again a methodological advance that was not reported before. + +<|ref|>text<|/ref|><|det|>[[114, 502, 883, 795]]<|/det|> +For aim 2, as pointed out by the informed reviewer, we formalize and describe the methodology to achieve those results in the open- source toolbox py_neuromodulation, which we have developed through a transatlantic US- German collaborative funding initiative by the National Science Foundation and the German Ministry of Education and Research in 2018- 2024. Similar to the development of other toolboxes, such as Lead- DBS (www.lead- dbs.org), which the (co- ) authors have lead and contributed to, we have first focused on the implementation of a useful set of tools that supports our research, such as described in the eLife paper, that was kindly read and cited by the reviewer. We are truly thankful for the time the reviewer has taken to scrutinize and support the improvement of our manuscript and we hope that we can make our case, that indeed, major milestones have been met in the further development process of this toolbox and we believe that it is now mature enough to deserve a dedicated publication. To be specific, we have vastly extended the feature extraction algorithms in the toolbox to modalities inspired by basic science, such as waveform shape parameters, that can significantly contribute to emotion decoding as shown in use- case 2. The importance of temporal characteristics of electrophysiological brain data was previously described (Voytek et al 2017) but never used for brain signal decoding before. The following graphic illustrates the precision of our temporal waveform shape characterization for brain signal decoding: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[245, 140, 777, 560]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 572, 884, 637]]<|/det|> +
Supplementary fig. 8 Exemplary temporal waveform-shape features. Different characteristics of band-pass filtered oscillations or raw-signal can be extracted: peak and troughs amplitudes, prominence of troughs to peaks, intervals between troughs or peaks, sharpness, decay and rise times of identified peaks and troughs, and the 5 ms width of peaks and troughs.
+ +<|ref|>text<|/ref|><|det|>[[114, 644, 883, 904]]<|/det|> +But our extensions since the eLife paper go far beyond this, as we have developed entirely new aspects, including methods for preprocessing, different artifact rejection methods, additional feature modalities and post- processing methods. In the current version fourteen different feature modalities, including Hjorth parameters, temporal waveform shape, characterization of periodic and aperiodic components with FOOOF (fitting oscillations & 1 over f toolbox; https://fooof- tools.github.io/fooof/; Donoghue et al. 2020, Parameterizing neural power spectra into periodic and aperiodic components. Nature Neuroscience, 23, 1655- 1665. DOI: 10.1038/s41593- 020- 00744- x), oscillatory burst dynamics, line length, coherence non- linear dynamical features and bispectrum based features were additionally implemented. This culminated in hundreds of pull requests, more than a thousand commits and novel developments from multiple international internal and external contributors. The toolbox now standardizes and simplifies electrophysiological signal processing by a parametrization file, providing an end- to- end pipeline parametrization without the need to adapt any programming code. This is all embedded in a real- time compatible framework that interfaces with electrophysiology and brain stimulation hardware. Importantly, we have further interfaced our toolbox with one of the most advanced decoding + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 245]]<|/det|> +algorithms in basic neuroscience that builds on contrastive learning (Schneider, S., Lee, J.H. & Mathis, M.W. Learnable latent embeddings for joint behavioral and neural analysis. Nature 617, 360–368 (2023). https://doi.org/10.1038/s41586-023-06031-6). Our paper indeed, is the first to report the use of this algorithm for a human application. Finally, we believe that the best evidence for the relevance and novelty of this toolbox is the fact, that since the upload of this preprint alongside the review process, first external contributors have already started to co- develop this open- source endeavor with relevant extensions such as improved computational performance for bursts (pull request #286), temporal waveform shape analysis (pull request #288), and parallelized multiprocessing of features (pull request #290). + +<|ref|>text<|/ref|><|det|>[[114, 253, 883, 600]]<|/det|> +For aim 3, we illustrate how the two biggest innovations in DBS research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility. The reviewer is correct that we have indeed applied retrospective connectomic analyses in our previous paper. This has laid the foundation to pursue the concept that this could be a fruitful approach for prospective channel identification and general brain circuit discovery. Within the toolbox we have since added modules for cross- validation using pre- computed whole- brain connectivity. With the present manuscript, we demonstrate for the first time, that combining neurophysiology with connectomics enables the development of generalizable plug & play decoders across patients. Moreover, we highlight how the brain network associated with optimal emotion decoding relates to brain networks with optimal treatment. In the future, we envision a real- time adaptation of brain stimulation algorithms to precisely defined response networks with relation to the presence of symptoms. Recently, co- authors of this study have demonstrated that optimal stimulation networks can vary for disease and symptoms (e.g. see Hollunder, B., Ostrem, J.L., Sahin, I.A. et al. Mapping dysfunctional circuits in the frontal cortex using deep brain stimulation. Nat Neurosci (2024). https://doi.org/10.1038/s41593-024-01570-1). In the future, the work presented in this manuscript may inspire a closed- loop neuromodulation strategy at the brain network level, where connectomics informed brain signal decoders indicate symptom presence that orchestrate control policies for algorithmic current steering to target the optimal symptom network in real- time. To further illustrate the methodological framework, we have now added a methods figure to help guide the reader: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 90, 884, 728]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 733, 884, 892]]<|/det|> +Supplementary fig. 5 Connectomics- based neural decoding without patient- individual training. (a) Estimation of a patient- individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain- wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 121]]<|/det|> +associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. + +<|ref|>text<|/ref|><|det|>[[115, 131, 647, 148]]<|/det|> +Moreover, we have added an API example in the methods section: + +<|ref|>text<|/ref|><|det|>[[115, 156, 882, 270]]<|/det|> +For applying the optimal connectivity decoding without patient- individual training, the electrode contact MNI coordinates need to obtained beforehand (Randazzo et al 2016, Soper et al 2023), and then utilized for obtaining the corresponding connectivity fingerprints from either the Lead- DBS Lead- Mapper toolbox (Neudorfer et al 2023), or by a pre- defined grid. Py_neuromodulation provides a method for obtaining matching points from a pre- defined cortical hull grid (n=1025 points) or whole- brain grid (1236 points). The computed grids can be downloaded from a public repository (https://doi.org/10.5281/zenodo.10805915) and utilized through the following API: + +<|ref|>text<|/ref|><|det|>[[115, 305, 490, 335]]<|/det|> +from py_neuromodulation import nm_RMAP import numpy as np + +<|ref|>text<|/ref|><|det|>[[115, 348, 803, 364]]<|/det|> +mni_coords = [[10, 40, 20], [50, 14, 12]] # definition of MNI contacts + +<|ref|>text<|/ref|><|det|>[[115, 378, 556, 420]]<|/det|> +ch_sel = nm_RMAP.ConnectivityChannelSelector( whole_brain_connectome=True, func_connectivity=True + +<|ref|>text<|/ref|><|det|>[[115, 420, 123, 430]]<|/det|> +1 + +<|ref|>text<|/ref|><|det|>[[115, 448, 735, 479]]<|/det|> +# retrieve connectivity fingerprints for passed MNI coordinates fps, grid_idx = ch_sel.get_closest_node (mni_coords) + +<|ref|>text<|/ref|><|det|>[[115, 492, 608, 521]]<|/det|> +# computation of optimal connectivity correlations corrs = ch_sel.get_rmap_correlations (fps) + +<|ref|>text<|/ref|><|det|>[[115, 535, 508, 551]]<|/det|> +recording_contact_use = np.argmax(corrs) + +<|ref|>text<|/ref|><|det|>[[115, 566, 882, 600]]<|/det|> +The added pre- computed functional and structural connectivity profiles are further referenced to in the methods section: + +<|ref|>text<|/ref|><|det|>[[115, 610, 882, 679]]<|/det|> +Alternatively, single ECoG or depth electrode channels can be selected through optimal connectivity. Functional and structural connectivity measures can for example be calculated within the Lead- Mapper tool of the Lead- DBS toolbox (Neudorfer et al. 2023) or via pre- computed connectivity profiles based on a cortical hull or whole- brain grid (DOI: 10.5281/zenodo.3814723). + +<|ref|>text<|/ref|><|det|>[[115, 689, 882, 844]]<|/det|> +We hope that this clarification and our detailed replies below will alleviate some of the general concerns the expert reviewer has raised and note that we have also taken their criticism with regard to the lack of clarity of the methods description very seriously. We worked very hard to further improve upon this aspect of the manuscript, by adding supportive information in main text, methods and extended data, including new figures such as the ones highlighted above. Beyond these direct changes in the submission, we have further significantly improved the documentation page that accompanies our toolbox (https://py- neuromodulation.readthedocs.io/) including tutorials on all critical points mentioned in this paper, including advanced feature analyses and connectomic applications. + +<|ref|>text<|/ref|><|det|>[[115, 873, 245, 889]]<|/det|> +Major concerns: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 175]]<|/det|> +1. It is not clear why the manuscript starts out talking about BCIs but then switches to closed loop neuromodulation. These are not the same thing, and there is enough confusion in the literature about what constitutes a BCI. The widely accepted definition involves some volitional modulation, which is not what is being described here. It would be preferable to not call this a BCI, but rather other methods of closed-loop neuromodulation. + +<|ref|>text<|/ref|><|det|>[[115, 185, 882, 324]]<|/det|> +We thank the reviewer for this valuable comment and agree that our previous manuscript had shortcomings in the precise definition between closed- loop neuromodulation and brain computer interface approaches. Through this revision, we would like to take the opportunity to elaborate our viewpoint further as this comment of the reviewer touched upon a pivotal issue that is currently at the forefront of global discourse in the field. As noted by the reviewer, the precise definition of BCI is a subject of ongoing debate among experts, which has most recently inspired a community driven open innovation in science approach by the international BCI society, to which we contribute (see https://bit.ly/BCI- Definition). + +<|ref|>text<|/ref|><|det|>[[115, 333, 882, 419]]<|/det|> +The foundation for this redefinition is laid based on a thoughtful and widely accepted precedent by Wolpaw & Wolpaw 2012: "A BCI is a system that measures CNS activity and converts it into artificial output that replaces, restores, enhances, supplements, or improves natural CNS output and thereby changes the ongoing interactions between the CNS and its external or internal environment." + +<|ref|>text<|/ref|><|det|>[[115, 429, 882, 480]]<|/det|> +The current initiative proposes a slightly adapted redefinition that opens the doors for wider applications. In the following, we will cite a paragraph from the information of the BCI society as referenced above: + +<|ref|>text<|/ref|><|det|>[[115, 491, 882, 594]]<|/det|> +"The definition of Wolpaw and Wolpaw, as well as the suggested alternative definitions, do not require the measured brain activity to contain information about the ongoing intention of the user, because this would exclude technologies referred to as passive BCIs from the definition. The consequence of this is that technologies such as closed- loop neuromodulation (e.g., responsive DBS) may fall under the definition of a BCI. Suggestions on the need to distinguish between these types of technologies, and how to differentiate between them, are welcomed." + +<|ref|>text<|/ref|><|det|>[[115, 612, 882, 820]]<|/det|> +This does not mean that the reviewer is not right in their definition, as they have pointed out, there are many different valid opinions present. Nevertheless, we would like to present a case for keeping the term, even when applying the more strict definition of BCI that the reviewer favors including volitional modulation. In a different study, (Köhler et al. 2023, under review) we have investigated to what extent the most common neurotherapies for Parkinson's disease, dopamine replacement and DBS, can modulate the initiation of volitional action. In brief, we trained decoders with the py_neuromodulation toolbox described in this paper, to quantify latencies from movement intention to motor execution. We found that both dopamine and DBS can shorten these latencies, providing the foundation for a closed- loop neuromodulation therapy for the support of volitional action initiation based on brain signal decoding. In this example the volitional modulation, the intention to act, would activate the neurotransmitter implant to support the patient to perform their movement. We believe that this closed- loop neuromodulation application could be considered to lie within the BCI definition that the reviewer favors. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 85, 884, 358]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 373, 884, 515]]<|/det|> +
Figure from Köhler et al. Dopamine and DBS accelerate the neural dynamics of volitional action in Parkinson's disease. bioRxiv (Cold Spring Harbor Laboratory) (2023). doi:10.1101/2023.10.30.564700. Under review. (A) Features of a single motor cortex channel averaged across trials. (B) Classifier outputs averaged across subjects. Classifier outputs of electrocorticography (ECoG) and subthalamic local field potentials (STN-LFP) differed between \(-2.2\) to \(1.7\) s (OFF therapy), \(-1.6\) to \(1.6\) s (ON levodopa) and \(-1.0\) to \(0.9\) s (ON subthalamic deep brain stimulation [STN-DBS]; all \(P\leq 0.05\) , cluster corrected). Data are represented as mean \(\pm\) SEM. (C) Time of motor intention of single subjects derived from ECoG classifier outputs. (D) Time of motor intention derived from single-channel ECoG classifier outputs. Left hemispheric channels were flipped onto the right hemisphere. \(*P\leq 0.05\) ; \(**P\leq 0.01\) ; \(***P\leq 0.001\)
+ +<|ref|>text<|/ref|><|det|>[[115, 525, 883, 766]]<|/det|> +Back to our current submission, as stated in our new introductory paragraph, we want to point out that we are at the brink of a new era in the treatment of brain disorders, where previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology, that can deliver closed- loop neurostimulation while adjusting to the individual symptoms of our patients in real time. We hope that the reviewer can see why some people would define this technology as brain computer interfaces. Certainly, we ourselves believe that the reviewers comment and the cited discussion can be understood as a supportive factor of the novelty and importance of our work. Hoping that the reviewer accepts our proposal to clarify that our approach combines both closed- loop neuromodulation and clinical brain computer interfaces, we have now adapted abstract and introduction of our manuscript as outlined below. However, given that the reviewer clearly is a more experienced expert in the field than we are, we are open to revise and exclude the term BCI in a further revision, should the reviewer remain doubtful that our approach is sufficiently clear or sensible. + +<|ref|>text<|/ref|><|det|>[[117, 775, 428, 792]]<|/det|> +Highlighted changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[116, 803, 188, 818]]<|/det|> +Abstract: + +<|ref|>text<|/ref|><|det|>[[116, 830, 882, 881]]<|/det|> +"Advances in neurotechnology that combine closed- loop neuromodulation with brain computer interfaces promise an unprecedented spatiotemporal precision for the treatment of brain disorders. Decoding dynamic patient states from brain signals with machine learning is required + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 123]]<|/det|> +to leverage this precision, but a standardized framework for invasive brain signal decoding from neural implants does not exist." + +<|ref|>sub_title<|/ref|><|det|>[[115, 134, 215, 150]]<|/det|> +## Introduction: + +<|ref|>text<|/ref|><|det|>[[115, 160, 882, 282]]<|/det|> +"Neuromedicine stands at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology. Advanced neurotechnology has the potential to combine the unprecedented temporal precision of closed- loop neuromodulation with accurate decoding of patient states achieved through clinical brain computer interfaces (BCI). This provides the foundation for revolutionary neurotherapies that can adapt therapy to the individual situation and symptoms that patients are facing." + +<|ref|>text<|/ref|><|det|>[[115, 291, 882, 343]]<|/det|> +"To overcome these roadblocks, we developed a modularized open- source software platform for invasive brain signal decoding in neurotechnology, bridging the gap between closed- loop neuromodulation and clinical brain computer interface approaches." + +<|ref|>text<|/ref|><|det|>[[115, 370, 881, 422]]<|/det|> +2. Multiple other open-source toolboxes exist that have brain signal feature extraction, selection, and decoding algorithms included (e.g., FieldTrip). These are not even mentioned in this paper, and they clearly should be discussed and the advantages of this toolbox described clearly. + +<|ref|>text<|/ref|><|det|>[[114, 431, 882, 640]]<|/det|> +We thank the reviewer for this valuable feedback and apologize for this lapse. We absolutely agree that acknowledgement of these important open- source initiatives that inspired and in part enable our toolbox is very important. In fact, the authors of the present paper have actively contributed to FieldTrip (Jonathan Vanhocke), MNE (Timon Merk, Victoria Peterson, Thomas S. Binns, Richard M. Köhler) and CEBRA (Timon Merk). Timon Merk participated in the 2021 MNE code sprint and made contributions to the MNE, MNE- Realtime and MNE- QT- Browser package. Furthermore, some of the authors organized a hackathon within the Transregional Collaborative Research Center TRR- 295, to further improve the useability of the recently presented CEBRA package, which resulted in multiple pull requests. Additionally, Thomas S. Binns and Richard M. Köhler added many of the MNE- connectivity core modules throughout multiple pull requests. Unlike these toolboxes, py_neuromodulation is specifically designed to enable invasive brain signal decoding from neural implants for real- time adaptation of therapeutic delivery. + +<|ref|>text<|/ref|><|det|>[[115, 649, 881, 683]]<|/det|> +We now highlight these alternatives in the discussion and provide a comparison to the presented toolbox: + +<|ref|>sub_title<|/ref|><|det|>[[115, 695, 208, 711]]<|/det|> +## Discussion: + +<|ref|>text<|/ref|><|det|>[[115, 721, 882, 893]]<|/det|> +"Several widely- used open- source toolboxes, such as Fieldtrip (Oostenveld et al 2011), MNE (Gramfort et al 2013), Brainstorm (Tadel et al 2011,) and BrainDecode (Schirrmeister et al 2017), exist for signal processing and brain state decoding. While all these tools contain valuable and extensive methods for electrophysiological data analysis, we would like to point out multiple key aspects of py_neuromodulation that uniquely positions it as a toolkit for invasive brain signal decoding for closed- loop neuromodulation that emphasizes rigorous real- time compatibility and reproducibility. Most importantly, all processing is optimized for invasive brain data and developed with the target of adapting therapeutic brain stimulation algorithms in mind. Therefore, offline and online signal processing are conducted using the exact same routines, by only replacing the data stream. Thus, any analysis performed based on py_neuromodulation features is real- time + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 210]]<|/det|> +compatible. Second, all pipeline parametrization is conducted through shareable files, that eases comparison across processing workflows and allows for effortless reproduction of established parameter specifications. Feature extraction is standardized and contains predefined feature modalities that extend far beyond what is available in other toolboxes. Finally, our toolbox implements several methods that enable neural decoding without patient- individual training. For that reason, we implemented cortical and subcortical spatial interpolation methods, and whole- brain connectivity estimation in combination with electrophysiological decoding." + +<|ref|>text<|/ref|><|det|>[[115, 237, 882, 375]]<|/det|> +3. The introduction could be clearer as to exactly what problem is being solved with these techniques. It keeps talking about BCIs and decoding, but the problem envisioned seems to be closed-loop neuromodulation. But this works fairly well. For example, the sentence (in Results) "A key problem for invasive brain signal decoding is the individualized localization of brain implants across patients, which significantly complicates the development of large-scale models..." What does localization of implants have to do with decoding? Decoding does not depend on location in any BCI literature. What type of large-scale models are being referred to here? Models across patients? This all needs more explanation. + +<|ref|>text<|/ref|><|det|>[[115, 384, 882, 558]]<|/det|> +We would like to excuse the lack of clarity in the previous iteration of this manuscript, which we hope to alleviate with the present explanation and the corresponding changes in text. Yes, this sentence primarily refers to across- patient decoding. Overall, only a handful of studies have ever applied brain signal decoding in the context of invasive neuromodulation (see comprehensive review on all studies in our recent review article: Merk et al., 2022 https://doi.org/10.1016/j.expenurol.2022.113993). None of these studies report across- patient decoding approaches and most did not consider the relevance of electrode placement for decoding performance. In our previous publication in eLife however, that the reviewer mentioned above, we demonstrated for the first time, that grip- force decoding performance both on the level of cortex and the STN correlates negatively with anatomical landmarks of the recording location. + +<|ref|>text<|/ref|><|det|>[[115, 567, 882, 653]]<|/det|> +This is not unexpected, as the expert reviewer is aware, the human brain exhibits considerable anatomical and functional variability across brain regions and individual subjects. What is important to consider in this regard is that unlike with EEG or MEG, the brain regions that are covered with invasive neurophysiology methods differ across subjects and used electrode types, leading to the following constraints: + +<|ref|>text<|/ref|><|det|>[[142, 664, 883, 872]]<|/det|> +- Every patient's brain has unique anatomical features, including variations in the size, shape, and positioning of gyri and sulci. These differences necessitate individualized planning for electrode placement to ensure optimal coverage of the targeted brain areas while avoiding critical regions that could impact essential functions.- The brain's vascular anatomy is another critical consideration. Avoiding major blood vessels is paramount to reducing the risk of hemorrhage during electrode placement. This constraint can limit the possible trajectories for implanting electrodes, especially when targeting deep or hard-to-reach areas.- Variations in skull thickness and shape can also impact the approach and trajectory for placing ECoG and stereoelectrophagrapy electrodes. Accessing certain areas of the brain may be more challenging in individuals with thicker or thinner skulls or unusual skull shapes, requiring adjustments to the surgical plan. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[142, 90, 884, 230]]<|/det|> +- Other patient-specific factors, including previous surgeries, co-existing medical conditions, and the patient's overall health status, can influence surgical planning. For example, a patient with a history of multiple brain surgeries may have scar tissue that complicates electrode placement.- Finally, there is surgical imprecision related to other factors such as movement artifacts in neuroimaging, brain shift through leakage of spinal fluid after opening the dura and mechanical alterations in surgical hardware, often related to sterilization, that can lead to deviations in the final surgical outcome from the planned/intended trajectory. + +<|ref|>text<|/ref|><|det|>[[115, 245, 883, 281]]<|/det|> +To further demonstrate variability in ECoG implant locations across subjects in the use- case of the movement decoders, we created a new supplementary figure: + +<|ref|>image<|/ref|><|det|>[[120, 315, 878, 481]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[133, 493, 864, 510]]<|/det|> +
Supplementary fig. 1: Individual differences in ECoG electrode contact localizations across cohorts.
+ +<|ref|>text<|/ref|><|det|>[[115, 518, 883, 640]]<|/det|> +The relevance of implant location for machine learning based brain signal decoding is further corroborated by a literal citation of an impactful publication in our field (Opri et al., Science Translational Medicine, 2019 https://doi.org/10.1126/scitranslmed.aay7680): "We observed that cortical placement was an important factor in our paradigm. Hence, we assumed that ET02 had the worst performance ... of the three subjects because of a less than optimal cortical placement. ... The cause behind the suboptimal placement can be found in the surgical avoidance of conspicuous blood vessels." + +<|ref|>text<|/ref|><|det|>[[115, 657, 882, 796]]<|/det|> +The advanced neuroimaging approach to across- patient generalization that we present in this manuscript solves most of these aspects while having an additional major advantage. They work across all invasive neurophysiology recording approaches, including the complex differences arising from electrode architecture. When comparing subdural surface electrocorticography (ECoG) and stereoelectrophagaphy (SEEG), ECoG provides high spatial resolution over a broad area of the cortex but lacks access to deep brain structures. In contrast, SEEG provides three- dimensional sampling of brain activity, including deep structures, but with more localized coverage. + +<|ref|>text<|/ref|><|det|>[[115, 805, 882, 874]]<|/det|> +The accuracy and generalizability of decoding algorithms depend on a thorough understanding of how implant localization interacts with signal patterns. This understanding is crucial for the development of large- scale models that can adapt to or accommodate the anatomical and functional diversity of the human brain across different individuals. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 158]]<|/det|> +This variability means that the optimal implantation sites for capturing high- quality signals that can be decoded into specific commands or responses may differ significantly from one patient to another. Therefore, understanding the precise location of these implants in relation to the functional areas of the brain is essential for interpreting the signals they capture. + +<|ref|>text<|/ref|><|det|>[[114, 168, 882, 669]]<|/det|> +This variability means that the optimal implantation sites for capturing high- quality signals that can be decoded into specific commands or responses may differ significantly from one patient to another. Therefore, understanding the precise location of these implants in relation to the functional areas of the brain is essential for interpreting the signals they capture.Thus, our toolbox combines invasive signal processing and feature estimation for the use of machine learning for neural decoding while also providing a clear approach for neuroimaging- based consideration of individual electrode locations. Since invasive human recordings are rare, and commonly acquired with limited time duration, aggregating data across subjects through multi- center collaborations can enable the development and training of large- scale machine learning models that can generalize well across subjects. It is therefore necessary to standardize signal- preprocessing and feature estimation. Currently, different laboratories use different processing parametrization of invasive recordings. By standardizing real- time and offline analyses, results are made comparable across studies and centers, and could be utilized for building powerful generalizable neural decoding models. The individualized localization of brain implants constitutes one of the reasons why machine learning based brain signal decoding performances are not generalizable across subjects and centers. In addition, we aimed to extend electrophysiological feature domains by the use of whole- brain connectomics, which we show to be beneficial for decoding without patient- individual data. The reviewer states, that closed- loop neuromodulation works fairly well, which can be true on a single subject level, even though evidence that it does work is generally sparse, reported in a handful of papers often reporting results for as few as three subjects. As clinician scientists we are aware of the amount of time and refinement such successful reports on very few subjects require, which is way beyond what the clinical routine would allow for. Therefore, we are convinced that for broad clinical adoption of brain signal decoding in closed- loop neuromodulation, across- patient generalization will be a critical economic and ergonomic factor. Indeed, to the best of our knowledge, not a single report exists with respect to successful across- patient decoding in the context of closed- loop neuromodulation. We believe that providing rigorously reproducible methods to achieve this will be a critical cornerstone of future multicenter clinical trials on closed- loop neurotherapies. Such multicenter trials will bring entirely new challenges unforeseen by single center examples of brain signal decoders and BCIs in individual subjects that have never been scrutinized in a way that live up to the present standards of evidence- based medicine including double- blind randomized controlled trials with patient centered primary outcomes, such as quality of life. Our toolbox provides an early but impactful step towards this vision. + +<|ref|>text<|/ref|><|det|>[[115, 678, 881, 712]]<|/det|> +We have now clarified the specific relationship of location and decoding accuracy in the introduction as follows: + +<|ref|>text<|/ref|><|det|>[[115, 722, 881, 790]]<|/det|> +"Invasive recordings are commonly acquired from varying electrode locations. While non- invasive recordings can rely on standardized positions, placement of invasive electrodes is currently guided by clinical surgical needs. This point requires an algorithmic solution to include data for neural decoding from varying localizations." + +<|ref|>text<|/ref|><|det|>[[115, 819, 881, 887]]<|/det|> +4. To say that calibrating a move vs rest decoder in each patient is a serious limitation and would hinder broad clinical adoption seems a bit exaggerated, given the time it takes to do the DBS implant itself. Calibration could easily be done intraoperatively, or in already scheduled calibration sessions in clinic, within each patient in a few minutes for this simple of a decoding measure. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 85, 883, 884]]<|/det|> +While the scientists in us sympathize with this statement, our own clinical experience tells us that that the difference in burden to adoption is economically and ergonomically relevant. Moreover, we provide movement decoding as a simple first proof- of- concept that will become more important when multiple dimensions of symptoms, side- effects and behaviors are to be decoded in our future vision of intelligent closed- loop neuromodulation. But to address the comment, we would like to discuss the most simple account suggested by the reviewer in the context of our movement decoding problem first. Starting with the potential opportunity to calibrate intraoperatively, we would first focus our argument on cost factors. A ten- minute block in a neurosurgical operation theatre requiring presence of a specialized team can very roughly be estimated to cost \(\) 3,000- \\(10,000\). This is why the current trend to perform DBS surgeries under general anesthesia (asleep DBS) without microelectrode mapping is not solely motivated by patient preference. Microelectrode mapping refers to the recording of multiunit activity for the neurophysiological identification of the target trajectory. A previous cost analysis of microelectrode mapping for DBS, which could be similarly time consuming as calibration of machine learning models, estimates the specific cost of microelectrode recording to \(\) 20,535.98\(, increasing the total cost of the surgery by\) 159\%\$ . Overall, microelectrode recording was estimated to more than double the cost of subthalamic nucleus deep brain stimulation for Parkinson's disease and more than triple the cost for unilateral and staged bilateral procedures simply because of the extension of surgery time (https://doi.org/10.1002/mds.23787). Even if the process would be shorter, it would require specialized equipment, trained staff and operation theatre time that are all excessively cost- intensive. These costs would burden healthcare systems and patients. Moreover, patient preference does lean towards asleep DBS and indeed in many instances awake DBS surgery is prohibited by cardiovascular risk factors or anxiety, rendering a potential intraoperative calibration session impossible, even if short and cheap solutions could be found. When it comes to scheduled postoperative sessions, we agree that this could be a potentially more viable solution, e.g. with a very rough estimable cost of \(\) 500\$ per session. For a research project with few subjects, this would not be a relevant barrier, but to a widely adopted therapy that could benefit more than 200,000 people already implanted with DBS devices, this cost could quickly scale to \(\) 100,000,000\$ excess cost. This cost could be avoided, if devices or approaches could be developed that patients can mostly handle on their own. This however, would burden patients and could be arguably deemed an even more difficult problem than the one we are aiming to solve. Having to deal with extensive training of devices would overwhelm many patients suffering from dementia in the context of their neurodegenerative disease, and we hope that the reviewer shares our intuition that if they had the choice, they would likely prefer a solution that does not require calibration. In summary, we believe that being able to provide pretrained models to a neurostimulator that may be implanted in thousands of patients, would have significant economical impact on healthcare costs and patient satisfaction, even for a simple movement decoder. Therefore, we are proud that our study provides the first open movement decoding model, which is published and openly available under a CC- BY license for precisely this purpose - alongside a rigorously reproducible methodological pipeline to implement it (DOI: 10.5281/zenodo.10794370). In the future, we envision to train and publish many other models that can decode brain states and symptoms of neuropsychiatric disorders, such sleep stages, tremor, dyskinesia, freezing of gait, tics, dystonic muscle contractions and more. If successful, this would revolutionize the democratization of machine learning for neurotechnology as I hope we can convince the reviewer, capturing these diverse patient states in individual training sessions will not be easy to achieve. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 106, 881, 140]]<|/det|> +We have now clarified the motivation behind developing and implementing the methods for decoding without patient- individual training in the discussion section: + +<|ref|>text<|/ref|><|det|>[[115, 150, 882, 307]]<|/det|> +"The presented methods for decoding without patient- individual training may catalyze the adoption of brain signal decoders for closed- loop neuromodulation by curbing healthcare costs and improving patient satisfaction. This will be especially relevant for future approaches that implement decoding of multiple brain states related to circadian rhythms, sleep and diverse symptoms such as tremor, freezing of gait, dyskinesia, dystonic muscle contractions, tics and more. Our study entails a first step in this direction by describing different methods that allow for transfer- learning and decoding without requiring individual training and providing the first generalizable movement decoder for invasive neurophysiology as a digital resource (DOI: 10.5281/zenodo.10794369)." + +<|ref|>text<|/ref|><|det|>[[114, 343, 882, 585]]<|/det|> +5. The Results and Methods need much clearer explanations of what was being done and decoded. It is not meaningful to say "balanced accuracy of 0.8/0.98 ± 0.07/0.04 for single sample/movement detection..." without explaining what is "single sample" (or "sample-wise") decoding, what movements are being detected, and how many classes are being decoded among. The tasks seem highly disparate among these datasets, so combining results across them does not make much sense. The tasks are not even described in any detail, nor what is being decoded. It is also not clear exactly what features are being used to decode (e.g., how many time bins were used in each decoder? Were they causal-only bins?) nor how much data (trials) were used to train and test in each case. Since the whole point of the study is to show how this toolbox enables decoding, and the methods are not described in enough detail to understand the task, it is very difficult to ascertain the impact of the innovation. In addition, if the goal is to show that these techniques allow better decoding of movement vs rest (which I am inferring, since this is never stated clearly), then the results here should be compared to prior studies in closed-loop DBS using simpler methods. + +<|ref|>text<|/ref|><|det|>[[114, 594, 882, 905]]<|/det|> +We thank the reviewer for identifying our lack of clarity with regard to these important depictions. The movement decoder solves a classification problem with two- classes with either rest or movement present. Balanced accuracy at the single- sample level is the correct classification of a 100 ms time- step of model output vs. target, while ensuring that equal numbers of samples of each class were present in the test set. This is a very conservative measure, as the temporal resolution is ten times higher than in most comparable previous studies (e.g. one of the most highly cited movement decoding papers by Gerwin Schalk and the team of Jonathan Wolpaw https://doi.org/10.1088/1741- 2560/4/3/012, which commonly used 1 second time resolutions). Indeed, many movement classification papers, do not decode movements continuously but describe accuracies at the trial level (e.g. if 90/100 trials are classified correctly, this would yield 90% accuracy without providing any detail on the temporal precision of the classification). In addition to this very conservative measure, we have added a second performance metric, which focused on the correct identification of a movement entity, which we defined as the correct continuous classification of over 300 ms of movement time. This is still more conservative than many other studies, but we felt that for the application of closed- loop neuromodulation it yields sufficient precision while providing higher stability. We believe the expert reviewer has understood this, but we used balanced accuracy, because in the context of movement tasks, the rest condition typically outscales the movement condition in time, leading to biased accuracy estimates if not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 124]]<|/det|> +balanced (e.g. if \(90\%\) is rest and \(10\%\) is movement, a decoder could simply always predict rest and have an accuracy of \(90\%\) without predicting a single movement sample correctly). + +<|ref|>text<|/ref|><|det|>[[114, 133, 883, 289]]<|/det|> +For the movement decoding analysis we used FFT features in eight different frequency bands: \(θ\) (4- 8 Hz), \(\alpha\) (8- 12 Hz), low \(\beta\) (13- 20 Hz), high \(\beta\) (20- 35 Hz), low \(\gamma\) (60- 80 Hz), high \(\gamma\) (90- 200 Hz), and high- frequency activity (200- 400 Hz) at a temporal resolution of 100 ms. All features were z- score normalized across the past 30 s and clipped at minus and plus three, allowing for a causal real- time normalization of the feature range across subjects and cohorts. Only one causal time- bin was used in each decoder and generally every single aspect of any of the decoding work in the entire paper was done in a causal only way, rendering the analysis directly transferable to a real- time application (as shown for the prospectively recruited patients in the supplementary videos). + +<|ref|>text<|/ref|><|det|>[[114, 295, 883, 905]]<|/det|> +We show that our classifier performed well, despite variability in the movement tasks. We agree with the reviewer that the movement tasks are disparate and we have now improved the description of this aspect and all other points above in the manuscript. With relation to our reply to comment 4, we believe that the generalizability of our decoders across tasks is an asset instead of a limitation. Our results indicate that the model that we provide as an open- source resource, can classify movements with meaningful accuracy independent of the specific motor task. Finally, to address the last comment, which relates to the comparability or superiority of our observed performance to previous publications, it is precisely this nature of the challenge that we have set ourselves to address, that is entirely novel to the field and therefore no benchmark exists. Indeed, very few studies exist that report movement decoding in Parkinson's disease patients (again details can be found in our review article on the topic: https://doi.org/10.1016/j.expneurol.2022.113993), none of them report across patient or across task decoding. One study used subthalamic local field potentials and reported a maximum performance of 0.74 (https://doi.org/10.3389/fnhum.2023.1111590) and another combined MEG and LFP and reports a mean balanced accuracy at 0.38 for the distinction of tremor and voluntary movement at the single- subject level for a temporal resolution of 1 second (https://doi.org/10.1016/j.clinph.2023.10.018), which despite being not entirely comparable, our paper relevantly outperformed. Indeed, our results reach an average performance above 0.8 across patients for the more comparable temporal resolution of the movement detection rate (0.74 at a temporal resolution of 100 ms). Our prospective out- of- cohort validation of the patient naive model resulted in a sample- wise balanced accuracy: 0.71 and a respective movement detection rate of 0.97. Notably, these performances would likely not be possible without the use of an ECoG strip, a technique that is not routinely performed in DBS patients. The Berlin team leading this study is the first to establish ECoG in PD patients undergoing DBS in Europe, for the precise reason of improving brain signal decoding for DBS. In addition to the abovementioned results from Parkinson's disease, we would like to highlight two studies that indeed did use ECoG strips for movement classification, but in a different brain disorder, namely essential tremor. Both studies had low n and only reported individually optimized decoders. The first reported a balanced accuracy of 0.532 across two subjects at a temporal resolution of 200 Hz (https://doi.org/10.1088/1741- 2552/abb416). The second, from a leading neural engineering team, yielded higher performances of 0.92 (https://doi.org/10.1126/scitranslmed.aay7680), which are comparable to the within subject performances of the Berlin cohort and outperformed by the Pittsburgh cohort in our study with three key differences: a) our results have ten times higher temporal resolution at a 100 ms vs. 1 s in the abovementioned paper, b) the decoders for the abovementioned paper were individually and repeatedly optimized in dedicated calibration + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 193]]<|/det|> +sessions and c) our results stem from Parkinson's disease patients, which as we show in our paper, is associated with deteriorated decoding performances in advanced disease stages. In summary, our study demonstrates the only across- subject movement decoder in the field of DBS, performs at comparable accuracy as previous within- subject approaches that required calibration sessions and operates at higher temporal resolution than most previous reports. We hope that clarifying this now further highlights the relevance and novelty of our report. + +<|ref|>text<|/ref|><|det|>[[115, 202, 882, 238]]<|/det|> +We have made an effort to address all the abovementioned points with a specific focus on explaining the performance metrics in detail in the methods section: + +<|ref|>text<|/ref|><|det|>[[115, 247, 182, 264]]<|/det|> +Results: + +<|ref|>text<|/ref|><|det|>[[115, 274, 882, 327]]<|/det|> +"We implemented py_neuromodulation for electrocorticography (ECoG) based movement decoding as a two- class classification problem (rest vs. movement present) without individual training ..." + +<|ref|>text<|/ref|><|det|>[[115, 336, 882, 441]]<|/det|> +"We computed FFT features in eight frequency bands from 4 to 400 Hz with a temporal resolution of 100 ms. All features were z- score normalized across the past 30 s and clipped at minus and plus three for artifact mitigation. Normalization was performed to ensure comparable feature values across subjects. Feature contributions were observed in each frequency band but highest importance was identified in the theta, high beta and high gamma frequency bands (see supplementary fig. 2)." + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 553]]<|/det|> +"We trained ridge regularized logistic regression classifiers and evaluated their performance using the balanced accuracy metric with 3- fold cross- validation on consecutive data segments, yielding sample wise performances indicating presence or absence of movement at 100 ms resolution. Sample- wise performances were concatenated to establish a more coarse metric that allowed for detection of individual movement entities, termed movement detection rate and defined as 300 ms of consecutive movement classification." + +<|ref|>sub_title<|/ref|><|det|>[[115, 590, 191, 606]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[114, 616, 882, 876]]<|/det|> +"The aim of the first use case was the two- class classification problem of movement vs. rest for different cohorts including different movement types across four cohorts from different neuromedicine centers (Berlin, Beijing, Pittsburgh, Washington). Berlin subjects performed a rotational handle task. Patients were instructed as follows: 'Perform 50 wrist rotations with your left hand with an interval of about 10 seconds. Do not count in between rotations'. The self- paced wrist rotations were performed on a custom- built analog rotameter, which translates the degree of rotation into a voltage. This task was previously utilized and described in different studies (Lofredi et al 2018, eLife; Brücke et al 2012, Journal of Neuroscience). Beijing subjects engaged in a voluntary button press task and were instructed to press the button with their left index finger every 10 s while avoiding to count in between the button presses. Pittsburgh subjects performed a gripping hand movement contralateral to the implanted cortical electrode. The visually cued handgrip was temporally adjusted in a Go/No- Go task, and previously described in different publications (Merk et al 2022, eLife, Peterson et al 2022 Exp. Neur., Kondylis et al 2016, Brain). Furthermore, we used invasive recordings from epilepsy patients undergoing seizure monitoring from a publicly available dataset (Miller et al 2019). The patients engaged in a hand clench and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 123]]<|/det|> +release task. The original publication described the 'motor_basic' tasks as follows. Direct quote (Miller et al. 2019): + +<|ref|>text<|/ref|><|det|>[[114, 133, 882, 392]]<|/det|> +"Cue- based movement task": Patients performed simple, repetitive, motor tasks of hand (synchronous flexion and extension of all fingers, i.e., clenching and releasing a fist at a self- paced rate of \(\sim 1 - 2 \mathrm{~Hz}\) ) or tongue (opening of mouth with protrusion and retraction of the tongue, i.e., sticking the tongue in and out, also at \(\sim 1 - 2 \mathrm{~Hz}\) ). These movements were performed in an interval- based manner, alternating between movement and rest, and the side of movement was always contralateral to the side of cortical grid placement. There were between 30 and 75 cue presentations for each movement modality. Cues for motor movement were delivered visually in a \(10 \times 10 \mathrm{~cm}\) presentation window at a distance of \(75 - 100 \mathrm{~cm}\) from patient. Visual cues were presented using the BCI 2000 program with a written word indicating the specific body part to be moved (typically, multiple movement types were interleaved in each experimental run). Stimuli were presented for 2 s or 3 s cue blocks, followed by rest intervals (indicated by a blank screen) of the same length. The patients were instructed to perform repetitive, self- paced motor movement, alternating with rest intervals of the same length (indicated by the absence of the cuing target). Repetitive motion, rather than tonic contraction, was intended to accentuate the spectral shift during each interval. (Miller et al, 2019) + +<|ref|>text<|/ref|><|det|>[[114, 402, 882, 643]]<|/det|> +In this analysis we excluded the tongue movement to unify the movement effector across cohorts. We specifically included multiple cohorts and tasks to investigate and develop decoding models that can generalize across recorded brain regions, tasks, recording equipment, surgical approach and electrode models. The primary performance metric was defined as sample- wise balanced accuracy at a temporal resolution of \(100 \mathrm{~ms}\) for each prediction. The used time- duration for feature computation was specified to be 1 s, only preceding the current target sample, therefore all feature computation including pre- and post- processing were applied in a causal manner. For the practical application of adaptive invasive neuromodulation, the measure of sample- wise decoding is of limited importance. In addition to reporting the sample- wise classification performances, we therefore report the accuracy of correct predicted movement blocks termed "movement detection rate". If the classifier's output probability is above 0.5 for three consecutive samples (300 ms) the present movement is classified to be detected. A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block. It's important to note, however, that this measure addresses only the movement class and has no predictive value of rest segments." + +<|ref|>text<|/ref|><|det|>[[115, 653, 882, 704]]<|/det|> +Additionally, we extended the supplementary tables 2 and 3 to display the total recording and movement duration times in minutes for each subject. Supplementary Table Y showing the recording durations of the Washington cohort was uploaded separately as an excel file. + +<|ref|>table<|/ref|><|det|>[[114, 739, 890, 896]]<|/det|> + +
Total recording duration [min]Movement recording duration [min]Rest recording duration [min]N samples at 10 Hz for decoding
Cohort-IDAgeGenderUPDRS
Berlin-00150fn.a.7.912.85.114737
Berlin-00262m2115.782.213.589459
Berlin-00356f3113.562.56118127
Berlin-00445f3626.427.8518.5815843
Berlin-00543f3195.321.4473.8657171
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[117, 88, 884, 696]]<|/det|> + +
Berlin-00657m3640.913.1537.7624537
Berlin-00755m5927.464.5522.9116467
Berlin-00866m2440.974.6436.3424573
Berlin-00959m2730.122.3627.7618063
Berlin-01066f3010.771.88.976453
Berlin-01167m3917.513.1414.3710497
Berlin-01254m3119.312.2517.0611577
Beijing-00166f6110.921.749.186543
Beijing-00270m7016.190.4115.789705
Beijing-00373f519.910.719.195937
Beijing-00467f526.990.746.244185
Beijing-00559f5823.891.0822.8214325
Beijing-00776m4121.770.7920.9813053
Beijing-00866f5522.691.2421.4513605
Beijing-00966f3918.621.4117.2111163
Beijing-01067f2711.582.848.746939
Beijing-01172f4710.620.6110.026363
Pittsburgh-00160.3m2812.620.9311.77563
Pittsburgh-00251.2m2719.461.0318.4311667
Pittsburgh-00363.8m4018.931.9816.9511349
Pittsburgh-00454.7fn.a.10.550.4210.136321
Pittsburgh-00553.8m337.60.567.044551
Pittsburgh-00644.2m3116.240.8615.389735
Pittsburgh-00763.6m3217.931.4716.4610749
Pittsburgh-00859.6m525.780.395.43459
Pittsburgh-00971.6m5510.80.310.56471
Pittsburgh-01052.5m5012.990.8812.127785
Pittsburgh-01166.8f6222.991.6821.3113785
Pittsburgh-01265.2f5417.750.751710641
Pittsburgh-01354.4m3427.611.5226.0916557
Pittsburgh-01467.9m488.220.477.754923
Pittsburgh-01569f3112.31.6310.677371
Pittsburgh-01667m4215.251.7113.559141
+ +<|ref|>table_footnote<|/ref|><|det|>[[115, 693, 572, 708]]<|/det|> +Supplementary table 2: Parkinson's disease cohort information + +<|ref|>text<|/ref|><|det|>[[115, 745, 883, 799]]<|/det|> +We further show in an added supplementary table the mean number of training samples for each cross- validation method. Due to the subject and cohort- specific recording durations, this number varies for each cross- validation split. + +<|ref|>table<|/ref|><|det|>[[115, 807, 780, 901]]<|/det|> + +
Cross validation typeNumber of samples Mean ± Std [a.u.]Duration Mean ± Std [min]
Within subjects11616 ± 910119.37 ± 15.18
Leave one subject out within cohorts137991± 41745230 ± 69.6
Leave one subject out across cohort430017 ± 9213716,71 ± 15.4
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 152, 882, 188]]<|/det|> +7. Line 121: "0.88 ± 0.17 movement detection rate across movements" – unclear how this number was derived, as Fig 2g does not seem to show this high of accuracy averaged across all boxes. + +<|ref|>text<|/ref|><|det|>[[115, 214, 882, 319]]<|/det|> +Figure 2g shows sample- wise movement classification performances. We now report the average movement classification performance as balanced accuracy \((0.79 \pm 0.13)\) in text in addition to the movement detection rate \((0.88 \pm 0.17)\) . The Figure legend was also adapted to state that the movement classification metric is the sample- wise balanced accuracy. Note that now the figure 2 panel o was adapted to also show the adaptive stimulation decoding and stimulation single trial time traces for the additional subject. + +<|ref|>text<|/ref|><|det|>[[115, 327, 882, 380]]<|/det|> +The new figure and corresponding figure legend is shown below. We adapted the legend labels of the upper label panel to specify "Hand movement [a.u.]", additionally the y- axes were added for each subplot. + +<|ref|>image<|/ref|><|det|>[[118, 420, 575, 711]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 728, 882, 760]]<|/det|> +
Figure R1: Real-time single trial decoding is shown using true analog rotameter movements, classification probability predictions and binary classification outputs.
+ +<|ref|>text<|/ref|><|det|>[[115, 785, 882, 820]]<|/det|> +8. In Table 1, what is the difference between "sample" vs "movement" columns? Is movement detection the same as sensitivity? If so, then state this. + +<|ref|>text<|/ref|><|det|>[[115, 830, 882, 883]]<|/det|> +In response to comment 6 above we addressed the motivation between sample- wise classification and movement detection rate and added further clarification about the sample- wise and movement detection performance in the methods and results sections. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 106, 612, 123]]<|/det|> +We further added the following information to the table legend: + +<|ref|>text<|/ref|><|det|>[[115, 133, 881, 202]]<|/det|> +"Decoding performance is depicted as balanced accuracy, which accounts for class imbalances. Single sample estimates provide performance metrics at 100 ms precision. Movement detection estimates were defined as the rate of movements in which the classifier's movement class predictions exceeded a 300 ms time window". + +<|ref|>text<|/ref|><|det|>[[115, 230, 881, 264]]<|/det|> +9. "To approximate the movement kinematics..." What movement kinematics? Were these recorded? It's not even stated how movement times were recorded. + +<|ref|>text<|/ref|><|det|>[[114, 274, 882, 412]]<|/det|> +The movement kinematics for certain tasks (e.g. Berlin rotational handle and Pittsburgh hand gripping force) were recorded. To standardize the decoding problem to be a rest-vs-movement classification problem, the kinematic time traces were transformed into a binary movement representation. The embedding training using contrastive learning (using the CEBRA) required application of a Gaussian filter to the binary movement trace, as extracted for the two-class classification problem. The following Figure demonstrates how the raw movement trace signal was transformed to a binary signal, and further transformed using the gaussian filter, for training the CEBRA embedding layer using contrastive learning, to a continuous signal. + +<|ref|>image<|/ref|><|det|>[[120, 430, 872, 664]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 678, 884, 772]]<|/det|> +
Figure R2: Movement label transformation. Raw movement traces (a) were transformed by investigating visually the EMG movement onset and offset, which resulted (b) in a binary movement vector. For contrastive learning, the binary movement was filtered using a Gaussian window. This function was beneficial for training the non-linear embedding layer and subsequent movement classification. The Gaussian filtered movement signal closely resembles the movement characteristics of the acquired raw signal.
+ +<|ref|>text<|/ref|><|det|>[[115, 782, 796, 799]]<|/det|> +We have now clarified this further in the respective paragraph of the methods section: + +<|ref|>text<|/ref|><|det|>[[115, 809, 882, 877]]<|/det|> +"The Gaussian filter transformed the binary classification labels into a continuous label vector, which empirically improved performance. For the Berlin and Pittsburgh cohorts, which included continuous movement recordings, the Gaussian filter convolution resulted in unvaried continuous movement traces compared to the original recorded signals." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 881, 125]]<|/det|> +10. How were stimulation artifacts dealt with, given that the high gamma range includes the stimulation frequency used? + +<|ref|>text<|/ref|><|det|>[[114, 133, 882, 306]]<|/det|> +We thank the reviewer for raising this important point. In the reported analysis, we did not explore the effect of different stimulation artifact rejection methods. To address this comment more thoroughly, we now investigated if bandpass-filtering in a frequency range of 100 to \(160\mathrm{Hz}\) around the \(130\mathrm{Hz}\) stimulation frequency yields improved performances. Additionally, we implemented the recently presented "Period-based Artifact Reconstruction and Removal Method" (PARRM) (Dastin- van Rijn et al 2021, Cell Reports Methods) method for calculating a recording stimulation artifact template which is subsequently removed for each artifact occurrence. Both have become additions to the toolbox through the revision, now openly available to the scientific community in response to this comment. However, neither of the methods resulted in movement decoding performance improvement: + +<|ref|>text<|/ref|><|det|>[[115, 315, 882, 368]]<|/det|> +Empirically, the filtering techniques interact with the stimulation artifact leading to shifts in feature magnitudes that were relatively unaffected by the original DBS artifact. This is now described through a new supplementary figure and cited in the main results section as follows: + +<|ref|>image<|/ref|><|det|>[[184, 380, 808, 844]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 856, 884, 905]]<|/det|> +
Supplementary fig. 3 Stimulation ON/OFF power spectra and cross-prediction movement decoding performances for different stimulation artifact rejection methods. (a) Exemplary power spectra of a single subject without stimulation artifact rejection, and for two artifact rejection methods: PARRM (Period-based
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 153]]<|/det|> +Artifact Reconstruction and Removal Method) and bandstop filtering (100- 160 Hz). Both methods can be selected within py_neuromodulation. PARRM requires, however, computation of a filter before real- time application. (b) Logistic regression performances for stimulation ON/OFF cross- predictions show that the utilized artifact rejection methods did not improve but deteriorate movement decoding performances. + +<|ref|>sub_title<|/ref|><|det|>[[115, 163, 182, 179]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[115, 189, 882, 242]]<|/det|> +"Importantly, processing steps to mitigate DBS artifacts including bandpass filtering and period- based DBS artifact removal did not improve, but instead aggravated this deterioration (see supplementary fig. 3)." + +<|ref|>text<|/ref|><|det|>[[115, 267, 882, 337]]<|/det|> +11. It seems that many ECoG electrodes with high decoding accuracy were in primary somatosensory cortex, which begs the question if these were really sensing sensory feedback, as opposed to motor intent. Sensory feedback would not be useful for controlling DBS, since it could be causing a positive feedback loop. + +<|ref|>text<|/ref|><|det|>[[114, 346, 883, 486]]<|/det|> +This is a relevant point that we cannot fully rule out with the data at hand. However, to address it analytically, we reanalyzed data from the Berlin cohort. As described above, this includes self- initiated movements without visual or other sensory cues. Patients held the rotational handle in their hands across the entire recording period. Despite some limitations on the assumptions we argue that if sensory cortex holds information on future movement prior to motor execution, this would hint that indeed even sensory cortex can be used for decoding of motor output independent of sensory input. Therefore, to reply to the reviewer more thoroughly we trained a new causal movement initiation classifier (Figure R3) below. + +<|ref|>image<|/ref|><|det|>[[120, 525, 880, 700]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 720, 884, 847]]<|/det|> +
Figure R3: (a) New classification results on sensory cortex signals for which the positive movement intention (positive) class was defined as the time-period -2 s prior to movement onset, and the rest (negative) class was defined as -4 till -2 s before movement onset. We excluded the movement period for classifier training, to investigate the single effect of somatosensory cortex related decoding for movement intention. We tested the movement intention decoding using a class-weight balanced and lasso-regularized logistic regression model within a three-fold non-shuffled cross-validation. Sensory cortex prediction performances rose above chance level as early as 2 seconds before motor onset (b) leading to a total balanced accuracy of movement intention classification of \(0.6 \pm 0.05\) (c).
+ +<|ref|>text<|/ref|><|det|>[[115, 857, 882, 891]]<|/det|> +However, some of these results could still be the result of sensory prediction or miniscule adjustments to hand pressure that we did not control for. Therefore, we decided not to include + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 123]]<|/det|> +these results in the manuscript and instead acknowledge the potential influence of sensory input in the main results text as follows: + +<|ref|>text<|/ref|><|det|>[[115, 133, 882, 203]]<|/det|> +"Performance was significantly above chance in every subject, with an average balanced accuracy of \(0.8 / 0.98 \pm 0.07 / 0.04\) for single sample/movement detection in the best channel per subject, spatially peaking in sensorimotor cortex indicative of a potential interplay of motor and sensory information predictive for movement output (Fig. 2b- d)." + +<|ref|>text<|/ref|><|det|>[[114, 230, 882, 419]]<|/det|> +12. Another central theme of the paper is not clearly explained. The idea of using connectivity as a way to decode across patients is very interesting and potentially useful. However, the methods are not explained clearly enough. What does "voxel-wise correlation of connectivity profiles with decoding performances from offline training" mean (lines 548-49)? How does one correlate a connectivity profile with an R2 value? What exactly is meant by a "connectivity profile"? Just a pairwise correlation matrix? Other graph theoretic measures? There are many types of connectivity that can be calculated, and this needs to be explained. The cited reference likewise does not explain this sufficiently clearly, but in any case, this is a central theme of this paper and should be explained here, not delegated to a reference. Without this, "prospective channel selection" is not easily understood, because "optimal connectomic decoding map" is not clear at all. + +<|ref|>text<|/ref|><|det|>[[115, 429, 882, 498]]<|/det|> +We thank the reviewer for that suggestion and now added a new methods figure explaining the connectomic decoding. We have added two supplementary figures to clarify the respective methods. First, we highlight the differences of the tested approaches to account for individual electrode localizations in a schematic overview: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 95, 872, 595]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 606, 884, 858]]<|/det|> +Supplementary fig. 4 Comparison of different approaches for neural decoding without patient- individual training. (a) Grid- point interpolation: Individual recording contact locations are estimated in a standardized space. Features are separately computed for each recording contact. Data is then mapped to a pre- defined cortical or subcortical grid in MNI coordinates. This mapping ensures a correct sorting of activity sources stemming from similar brain regions. In this manner, feature vectors are mapped to a common grid defined in space (similar to EEG montages), which then lay the foundation to train models on grid- points instead of recording channels for neural decoding without patient individual training. (b) Connectomic channel selection: An optimal decoding whole- brain connectivity map is computed based on training data. This step requires the computation of contact- specific neural decoding performances and whole- brain connectivity estimates. The connectivity profiles and decoding performances are correlated in a voxel- wise manner to estimate a connectivity map associated with optimal decoding performance. For a test subject, the connectivity map of each channel is spatially correlated with the optimal decoding map and the one with the highest similarity is selected and used for testing of a pre- trained machine learning model. (c) The connectomics- based channel selection approach is further extended by transforming individual channel features using an embedding layer. This layer is computed through contrastive learning and auxiliary variables. Here we utilized the CEBRA package (Schneider et al 2023, Nature). + +<|ref|>text<|/ref|><|det|>[[114, 868, 883, 902]]<|/det|> +In the present manuscript, the Pearson correlation coefficient was utilized for the connectomics based approach. We note, however, that this approach can be extended by different correlation + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 142]]<|/det|> +metrics. In the following, we added another more detailed figure explaining the connectomic channel selection approach, including a definition of connectivity profile, correlations of connectivity profiles and the optimal connectomics derived decoding map: + +<|ref|>image<|/ref|><|det|>[[115, 150, 884, 789]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 795, 884, 906]]<|/det|> +
Supplementary fig. 5 Connectomics-based neural decoding without patient-individual training. (a) Estimation of a patient-individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain-wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 89, 883, 169]]<|/det|> +template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. + +<|ref|>text<|/ref|><|det|>[[116, 195, 882, 247]]<|/det|> +13. It's not clear what the clinical relevance of training on a single subject to predict other subject's data, given that one would not know in practice who the "best" subject is without training on a group of subjects and testing on all of them anyway. + +<|ref|>text<|/ref|><|det|>[[115, 257, 882, 395]]<|/det|> +We thank the reviewer for this relevant point. We agree with the statement, but would like to argue that it is still interesting to show this as a) in a post- hoc analysis of a cohort it is possible to know which subject is good for training and which isn't; That means that selectively curating a database of good training subjects could further enhance across patient decoding performance. b) it should motivate us to explore across patient decoding methods even in cases where data from only few subjects is available. E.g. in rare forms of child dystonia, opportunities to record invasive data may be very sparse. Being able to train generalizable models in single subject data could have important implications in such instances. We now clarify this further in the manuscript: + +<|ref|>sub_title<|/ref|><|det|>[[116, 405, 209, 420]]<|/det|> +## Discussion: + +<|ref|>text<|/ref|><|det|>[[116, 421, 882, 473]]<|/det|> +"Moreover, we show that training data from an individual subject can generalize to other subjects, which holds promise for across- patient decoding applications even in rare diseases, where only few datasets may be available." + +<|ref|>text<|/ref|><|det|>[[115, 500, 882, 604]]<|/det|> +14. Authors seem to claim that CEBRA performs better than 2nd method, but do not provide statistical testing evidence to back this up (a p-value is presented, but how was this tested?). Similarly, it mentions several times that a given performance is above chance, but never states how chance is computed for any case. It is also not true that accuracy of \(\sim 60\%\) is "high above" chance when chance is likely \(50\%\) . Also, not clear what is being shown in Fig 2o - - there are no y axis labels, and not clear if these are averages, single trials, or other. + +<|ref|>text<|/ref|><|det|>[[115, 630, 882, 787]]<|/det|> +We thank the reviewer for this remark. We have now directly performed a statistical comparison for the decoding performances without patient- individual training between the CEBRA model performances and the grid point and connectomic channel selection methods. We used a paired permutation test and found that CEBRA outperformed both other methods for all cross- validation approaches. We defined statistical significance \((p = 0.05)\) to be corrected by Bonferroni correction \((n = 12\) tests, \(p = 0.05 / 12 = 0.004\) ). Significant balanced accuracy performance differences were observed for all comparisons except CEBRA vs grid points \((p = 0.03)\) . For movement detection rates, none of the performance differences were significant, mainly due to the already high movement detection rates present in all predictions. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[114, 87, 890, 222]]<|/det|> + +
Within cohorts
CEBRA vs Grid
Points
Within cohorts
CEBRA vs
Connectomics
Across cohorts
CEBRA vs Grid
Points
Across cohorts
CEBRA vs
Connectomics
Balanced
accuracy
0.02 (p=0.03)0.02 (p=0.003)0.02 (p<10-5)0.02 (p<10-5)
Movement
detection rate
0.01 (p=0.69)0.01 (p=0.7)0.03 (p=0.04)0.03 (p=0.04)
+ +<|ref|>table_caption<|/ref|><|det|>[[113, 234, 884, 284]]<|/det|> +Table R1: Mean differences of leave one subject out cross validation approaches of CEBRA against grid point and connectomics channel selection methods. P-values are shown for paired permutation test comparison. + +<|ref|>table<|/ref|><|det|>[[114, 317, 884, 435]]<|/det|> + +
CEBRA vs Grid PointsLOCO within cohorts
CEBRA vs Connectomics
Balanced
accuracy
0.03 (p=0.0002)0.03 (p<10-5)
Movement
detection rate
0.02 (p=0.33)0.02 (p=0.35)
+ +<|ref|>table_caption<|/ref|><|det|>[[113, 450, 884, 500]]<|/det|> +Table R2: Mean differences of leave one cohort out cross validation of CEBRA against grid point and connectomics channel selection methods. P-values are shown for paired permutation test comparison. + +<|ref|>text<|/ref|><|det|>[[113, 512, 884, 544]]<|/det|> +We furthermore added in Figure 2l,m the individual patient lines and highlight statistical significance: + +<|ref|>image<|/ref|><|det|>[[115, 558, 652, 904]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 445, 108]]<|/det|> +The Figure 2l,m figure legend now reads: + +<|ref|>text<|/ref|><|det|>[[115, 117, 881, 153]]<|/det|> +"CEBRA outperformed other methods as indicated by Bonferroni- corrected paired permutation tests." + +<|ref|>text<|/ref|><|det|>[[115, 161, 723, 180]]<|/det|> +Additionally, we described the statistical analysis now in the Results section: + +<|ref|>text<|/ref|><|det|>[[115, 189, 882, 311]]<|/det|> +In addition to the conceptual advantage to account for specific recording location and underlying brain network affiliation, the connectomic approach with contrastive learning (CEBRA) outperformed the other two methods for each cross validation approach in sample- wise balanced accuracy (see Table 1 for performances, paired permutation test leave one subject out within cohort CEBRA vs grid points: \(\mathsf{p} = 0.03\) , CEBRA vs connectomics: \(\mathsf{p} = 0.003\) ; leave one subject out across cohorts CEBRA vs grid points: \(\mathsf{p}< 10^{- 5}\) , CEBRA vs connectomics \(\mathsf{p}< 10^{- 5}\) ; leave one cohort out CEBRA vs grid points: \(\mathsf{p} = 0.0002\) , CEBRA vs connectomics: \(\mathsf{p}< 10^{- 5}\) ). + +<|ref|>text<|/ref|><|det|>[[115, 320, 882, 529]]<|/det|> +With regard to the following comment, the reviewer was right that the two- class classification problem of rest vs. movement, the chance level is \(50\%\) . In response to the reviewers criticism we discuss some of the results more cautiously and specifically replaced the "high above chance" phrasing. The reviewer points out that in some instances the reported sample- wise performance can be as low as \(60\%\) . However, we would like to highlight again, that the performance for a subject that was newly and prospectively recruited after model training was never seen by any of the models reached a sample- wise balanced accuracy of 0.71 at the very high 100 ms temporal resolution and a movement detection rate of 0.97, meaning that almost every movement was correctly classified. To the best of our knowledge, no previous report exists of a prospective model validation of a newly recruited patient for any movement decoder while our performance is in the range of previous post- hoc offline study results. We computed p- values using non- parametric Monte- Carlo sampled permutation tests with a significance value of \(\mathsf{p}< 0.05\) . + +<|ref|>text<|/ref|><|det|>[[115, 537, 882, 573]]<|/det|> +We updated in the publication the text "high above" chance to "above" chance. The statistical test is now further annotated in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 598, 882, 704]]<|/det|> +15. More details should be provided about the DBS trial for depression. Without these, it is difficult to evaluate the phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." (line 244). Were all DBS leads used for stimulation? If not, how did those leads used for stimulation relate to the leads in the decoder? The clinical trials registry number should also be included for all of these trials. + +<|ref|>text<|/ref|><|det|>[[115, 712, 882, 886]]<|/det|> +We thank the reviewer for this important remark. We would like to note that the present study did not aim to present the clinical evaluation of the DBS for depression trial, which were previously published in a series of papers that we cited (Merkl A et al., Deep brain stimulation of the subcallosal cingulate gyrus in patients with treatment-resistant depression: A double- blinded randomized controlled study and long- term follow- up in eight patients. J Affect Disord. 2018 Feb;227:521- 529. doi: 10.1016/j.jad.2017.11.024. Epub 2017 Nov 8. PMID: 29161674.). The clinical trial registration number NCT00531726, registered at clinicaltrial.gov, was now added in the manuscript and in the Nature Portfolio reporting summary and in the methods section. Nevertheless, we agree that some clarification was required in our manuscript. For the reviewers convenience we cite the full methods paragraph from the clinical manuscript in the following: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 882, 278]]<|/det|> +"For parameter settings we used a monopolar configuration (contact cathode and case anode; contacts 0,1,2,3 being right hemisphere and contacts 4,5,6,7 being left hemisphere electrodes, contact 0 and 3 being the lowermost and uppermost contacts, respectively). Given the scarce empirical evidence about optimal stimulation parameters, we adopted the same approach as in previous partially successful open- label trials (Holtzheimer et al., 2012; Lozano et al., 2012). Pulse width and frequency were set to \(90\mu \mathrm{s}\) and \(130\mathrm{Hz}\) respectively. For all contacts, the amplitude was raised up to \(10\mathrm{V}\) in 2.5 steps, remaining on each level for \(10\mathrm{min}\) in order to assess acute side effects due to voltage increase, and was subsequently set constant between 5 and \(7\mathrm{V}\) . During the eight- week blinded- phase, no modifications in frequency, amplitude or in pulse width were allowed. During the open- label phase beyond eight weeks, amplitude changes were allowed." + +<|ref|>text<|/ref|><|det|>[[114, 288, 882, 479]]<|/det|> +To summarize briefly, one contact was activated for stimulation per hemisphere (as depicted in Figure 3b). Contrary to the monopolar stimulation, all channels were recorded bipolarly (channels 0- 1, 1- 2, 2- 3 and 3- 0). Therefore, a direct comparison of recording and stimulation channel is not possible, because each stimulation channel occurs in two recording channels. To still give a direct reply to the reviewer's question, we investigated if the stimulation contacts were present in the best bipolar recording channels. Indeed, in all eight patients the stimulation contact matched at least for one hemisphere with the channel of highest decoding performance, with only 4/16 electrodes presenting without overlap. Given the uncertain relationship of monopolar stimulation and bipolar recording electrodes we however believe that this is not easily interpretable which is why we have decided not to include this result in the main text and instead discuss our interpretation more cautiously. The following changes have been made to the manuscript: + +<|ref|>sub_title<|/ref|><|det|>[[115, 505, 182, 520]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[115, 522, 882, 591]]<|/det|> +"Machine learning decoders were trained on local field potential signals from the DBS electrodes in SCC in eight patients undergoing DBS for treatment resistant major depressive disorder as part of a clinical trial (mean age: \(48 \pm 11.4\) , 4 females; Supplementary table 6; ClinicalTrials.gov registration number: NCT00531726)." + +<|ref|>text<|/ref|><|det|>[[115, 601, 881, 636]]<|/det|> +"The correlation could potentially be driven by optimal targeting rather than by depressive symptoms themselves, which inspired us to explore the underlying whole- brain networks." + +<|ref|>text<|/ref|><|det|>[[115, 662, 882, 750]]<|/det|> +16. More information is required about the "additional fiber filtering approach recently introduced..."(line 246). The method should be described clearly. Again, the term connectivity fingerprint is not explained. The phrase "estimated best therapeutic stimulation target from Fox et al 2014" is also not explained at all. Why is this important and what does it have to do with the results presented here? This needs explanation for a broad audience. + +<|ref|>text<|/ref|><|det|>[[115, 776, 882, 897]]<|/det|> +We agree with the reviewer that while the method has been used in many previous publications (most recently in Hollunder, B., Ostrern, J.L., Sahin, I.A. et al. Mapping dysfunctional circuits in the frontal cortex using deep brain stimulation. Nat Neurosci 27, 573- 586 (2024). https://doi.org/10.1038/s41593- 024- 01570- 1), it may not have been introduced in sufficient detail with the present submission. In brief, the employed fiber tract method can indicate fiber tracts associated with high decoding performance through a statistical procedure in which a normative fiber tract connectome (or wiring diagram of streamlines of white matter) is used to determine the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 296]]<|/det|> +fibers that are connected to a certain region of interest, in our case the location of the recording channels. Each fiber streamline is then weighted by its relationship to decoding performance. Streamlines in proximity to recording contacts associated with high decoding performance received high positive weights whereas those associated with low decoding performances were attributed high negative weights. A t- statistic was computed for each respective fiber tract that was corrected for multiple comparisons using the false discovery rate with \(\alpha = 0.05\) . The approach is validated to predict decoding performance from a recording channel solely based on fiber connectivity in held out subjects. This revealed left prefrontal fibers that were associated with emotion decoding performance. This lateralization was previously described for major depressive disorder and is in clinical practice also used for treatment using transcranial magnetic stimulation, which is highlighted by showing the TMS target for depression described in the Fox et al., 2014 publication (DOI: 10.1073/pnas.1405003111). + +<|ref|>text<|/ref|><|det|>[[115, 306, 572, 322]]<|/det|> +We have now further clarified this in the methods section: + +<|ref|>text<|/ref|><|det|>[[114, 333, 883, 541]]<|/det|> +"Structural connectivity was estimated between recording contacts region of interest (ROI) with a spherical seed (4 mm radius) and all other brain regions. We utilized the multi- shell diffusion- weighted imaging data acquired within the Human Connectome Project (Van Essen et al 2013, n=985 subjects). For each subject, fibers were normalized into ICBM 2009b Nonlinear Asymmetric ("MNI") standard space using Advanced Normalization Tools (ANTs, http://stnava.github.io/ANTs/, Avants et al 2009) within Lead- DBS (Neudorfer et al 2023). For each tract, a two- sample t- test was calculated between the associated decoding performances of connected and unconnected recording contact ROIs. The t- value was then used to color- code each fiber tract. Positive significant fiber tracts were thus connected to many recording contacts with high decoding performance. Negative fiber tracts on the contrary were connected to many poor performance recording contacts. To account for multiple- comparison tests, a False- Discovery- Rate with \(\alpha = 0.05\) was defined for defining statistical significance." + +<|ref|>text<|/ref|><|det|>[[115, 576, 882, 629]]<|/det|> +17. It's not clear whether the optimization of RNS parameters using a grid search is feasible or helpful for an actual clinical use case in individual patients. Was this optimized over all patients with holding patients out? Or by doing cross-validation with data from all patients together? + +<|ref|>text<|/ref|><|det|>[[114, 656, 883, 880]]<|/det|> +Thank you for the relevant comment. We would like to admit that it is hard to see a scenario where this would not be helpful or feasible but it is obvious that we have not made this point clear enough. To support this notion further, we would like to first state that RNS data are continuously recorded and streamed over months of therapy. Right now, only a few seconds of recording can be selected to estimate the detection parameters in the implant, despite the patients having weeks worth of data. In the future, it would be more sensible to continuously update and improve the detector using all available data on the single subject or across- subject level. Given the limited number of subjects, we have focused on within patient predictions with models trained on expert annotations. In the future, automated seizure detectors could be used offline to continuously update the seizure detectors, even across patients. First models for automated annotation were described in one of our previous publications (Peterson V, et al. Deep net detection and onset prediction of electrographic seizure patterns in responsive neurostimulation. Epilepsia. 2023 Aug;64(8):2056- 2069. doi: 10.1111/epi.17666. ). + +<|ref|>text<|/ref|><|det|>[[115, 890, 617, 907]]<|/det|> +We have now made the following adaptation to the manuscript: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 124]]<|/det|> +"In the future, it would thus be sensible to continuously update and improve brain signal decoders using all available data on the single subject or across- subject level." + +<|ref|>text<|/ref|><|det|>[[115, 151, 245, 167]]<|/det|> +Minor concerns: + +<|ref|>text<|/ref|><|det|>[[115, 178, 681, 196]]<|/det|> +Please type out all acronyms used for those not familiar (e.g., CEBRA). + +<|ref|>text<|/ref|><|det|>[[115, 206, 630, 223]]<|/det|> +We are sorry for the lapse and have now typed out all acronyms. + +<|ref|>text<|/ref|><|det|>[[115, 250, 882, 302]]<|/det|> +Methods mentions multiple terms that could mean similar things. What are data "batches" vs "segments"? FFTs were computed at 100 ms resolution – does this mean 100 ms windows, or longer windows overlapped by 100 ms? + +<|ref|>text<|/ref|><|det|>[[114, 311, 882, 570]]<|/det|> +Thank you for pointing us to this lack of clarity in our manuscript. Batches are data packets including any number of channels and samples that are streamed as input for py_neuromodulation, either through a simulated datastream from an offline dataset or through the API of an electrophysiology processor for real- time application. Segments are parametrized window sizes for feature estimation of a predefined length, in the use cases of this manuscript this length is 1000 ms. The segments can be updated at a predefined update rate, in the present manuscript this rate was set to 10 Hz. This leads to a temporal resolution of the decoder of 100 ms with feature windows using data from the past 1000 ms. For offline processing where we simulate batch streaming, and thus batch size equals the number of samples required for maintain the predefined update rate, e.g. 100 ms for 10 Hz as described above. For real- time interfacing with electrophysiological processors however, it is typically required to query data batches sequentially, sometimes without control over which channels and how many samples will be transmitted. Then the batch size and the update rate can differ. Py_neuromodulation would then query as many batches that are required to maintain the update rate and generate the full segment according to the chosen settings defined in the nm_settings.json file. + +<|ref|>text<|/ref|><|det|>[[115, 580, 608, 597]]<|/det|> +We have now clarified this in the results and methods section: + +<|ref|>text<|/ref|><|det|>[[115, 608, 191, 624]]<|/det|> +Methods: + +<|ref|>text<|/ref|><|det|>[[115, 635, 882, 686]]<|/det|> +"The abovementioned batches are analyzed in segments of a defined window length and sampled at a predefined update rate, that can, depending on the amount of desired segment overlap be shorter or equal to the segment length." + +<|ref|>text<|/ref|><|det|>[[115, 714, 424, 731]]<|/det|> +Fig 4 labels are too small to be legible. + +<|ref|>text<|/ref|><|det|>[[115, 741, 676, 758]]<|/det|> +Thank you we have now adapted the font size of the respective labels: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 880, 380]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 412, 881, 448]]<|/det|> +Supplementary video is not explained clearly. What are the different decoding/prediction windows showing? The prediction output looks very noisy during movements. + +<|ref|>text<|/ref|><|det|>[[115, 457, 870, 475]]<|/det|> +We thank the reviewer for this important remark and adapted the Supplementary video legend: + +<|ref|>text<|/ref|><|det|>[[115, 484, 884, 619]]<|/det|> +Supplementary video 1: Real- time movement decoding with py_neuromodulation using a pretrained model in a newly recruited patient with Parkinson's disease at Charité – Universitätsmedizin Berlin. The patient performed hand rotation movements using a rotational handle. On the top left the real- time feature visualization and decoding is shown. On the top right the Timeflux browser window (https://timeflux.io/) shows the true movement- induced analog voltage trace (top), movement classifier probability predictions (middle) and binary predictions (bottom). On the top right panel, the raw channel time series is visualized using BrainStreamingLayer (https://github.com/bsl- tools/bsl). Decoding was significantly above chance for decoding without patient- individual training (balanced accuracy: 0.71, movement detection rate: 97 %). + +<|ref|>text<|/ref|><|det|>[[115, 646, 504, 664]]<|/det|> +Reviewer #3 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[114, 673, 883, 880]]<|/det|> +This is a very interesting and ambitious paper describing an open source software system, py_neuromodulation, for “decoding” of behavioral states, including disease specific states, from invasive intracranial recording. It is designed for field potential (LFP and electrocorticography) approaches. At a time of great excitement in human invasive neurophysiology and its application in neural engineering, authors are to be applauded for developing a comprehensive analytic system that is accessible to all and that begins to standardize brain decoding across applications. A strength of the system is that it is designed to combine physiological recordings with connectomics, the merger of which can lead to new neuroscience insights. A strength of the paper is the illustration of the system in three different scenarios: decoding of movement (move vs rest, I believe, but see below) from motor system recordings in a variety of tasks in patients with movement disorders, decoding of emotional state from area 25 limbic implants, and decoding of pre- ictal or ictal activity in epilepsy. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 123]]<|/det|> +We thank the reviewer for highlighting the timeliness and ambition of our work. We have made a sincere effort to further improve the manuscript based on the expert review of the referee. + +<|ref|>text<|/ref|><|det|>[[116, 150, 421, 167]]<|/det|> +Some general points for improvement: + +<|ref|>text<|/ref|><|det|>[[115, 178, 882, 264]]<|/det|> +1) The paper is quite dense. It assumes a high level of expertise from the reader, who would need to have fluency in neurophysiology of LFPs, advanced imaging methods especially merging imaging sets across individuals, and machine learning, to fully grasp it. Below are specific areas where the authors could give a bit more information or clarification to help readers who don't already have expertise in all three of these. + +<|ref|>text<|/ref|><|det|>[[115, 274, 882, 360]]<|/det|> +We agree with this statement and have thoroughly revised the manuscript to improve the clarity of both the methods and results. Specifically, we added exemplary API sections describing the toolbox feature estimation and decoding setup. Additionally, we added a section on how to make use of the connectomic decoding pipeline. We also provide the required code to utilize the movement decoding model without patient-individual training. + +<|ref|>text<|/ref|><|det|>[[115, 370, 882, 439]]<|/det|> +2) Its not very clear how the system handles electrical recordings with lots of artifacts. There is one statement in methods on movement decoding that alludes to an answer "All 606 features were z-score normalized across the past 30 s and clipped at minus and plus three.." perhaps the "clipping" is their answer. More on how the system handles noisy data would be appreciated. + +<|ref|>text<|/ref|><|det|>[[115, 449, 880, 483]]<|/det|> +We thank the reviewer for this valuable suggestion and added a section on artifact handling to the methods section: + +<|ref|>text<|/ref|><|det|>[[114, 493, 882, 685]]<|/det|> +"Electrophysiological recordings can be affected by multiple artifact sources. We accounted for different artifact types within py_neuromodulation and describe the parametrization methods in the following. First, notch filtering to remove power line noise can be applied with parameters specific in the nm_settings file. Next, raw data and computed features can be clipped to limit the effect of outliers for decoding and normalization. To specifically account for artifacts resulting from neurostimulation, the "Period-based Artifact Reconstruction and Removal Method (PARRM)" (Dastin- van Rijn et al 2021, Cell Reports Methods) was implemented by the authors in Python (https://github.com/neuromodulation/PyPARRM). This allows for offline filter estimation and online application to clean signals contaminated by stimulation artifacts. Additionally, for offline data, artifact annotations can be provided in a .tsv file, e.g. through visual detection for which a wrapper of the mne- qt- browser GUI (https://github.com/mne- tools/mne- qt- browser) is provided." + +<|ref|>text<|/ref|><|det|>[[114, 712, 882, 816]]<|/det|> +3) Authors should be more specific about what the system does NOT do, perhaps in discussion. At times the text seems to imply that the system can simulate closed loop stimulation for design of closed loop algorithms. For example this sentence in the abstract: "Our platform provides rapid, high-accuracy decoding for precision medicine approaches that can dynamically adapt neuromodulation therapies in response to the individual needs of patients" – is a DBS prototyping really part of py_neuromodulation? This should be clarified. + +<|ref|>text<|/ref|><|det|>[[115, 826, 882, 894]]<|/det|> +We thank the reviewer for this important remark. The intention of py_neuromodulation is indeed to provide decision support for adaptive neuromodulation based on machine learning. However, we recognize that the application of invasive brain stimulation per se is not something that a software toolbox can offer. Specialized medical devices are required to actually apply the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 882, 295]]<|/det|> +stimulation, that will often have additional proprietary software that are less standardized than neurophysiological processors for recording of brain activity. In our specific laboratory, we interface py_neuromodulation with a TMSi SAGA neurophysiology processor for brain signal recording and an Alpha Omega NeuroOmega for stimulation. This setup allows for brain signal decoding- based closed- loop invasive neurostimulation paradigms, which we are actively investigating. To demonstrate the capability of py_neuromodulation in the realm of closed- loop neuromodulation in reply to this comment we have now recruited an additional patient, in whom we performed movement triggered closed- loop DBS based on a pretrained movement decoder model. We obtained stable decoding and consequently stimulation results without any requirement for individual calibration. The results are now integrated in figure 2 and the case is added to the methods and results sections and a new video of the performance was added to the supplements. + +<|ref|>sub_title<|/ref|><|det|>[[115, 313, 191, 329]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[114, 340, 882, 565]]<|/det|> +In addition to decoding movement in real- time, we further recruited a second exemplar patient with early onset Parkinson's disease (age: 32, male). ECoG recordings were acquired from an Ad- Tech electrode (1x6 contact layout, contact area: \(12.56 \text{mm}^2\) ) and a SAGA (TMSi) amplifier. The Alpha Omega NeuroOmega was used for movement triggered stimulation. The movement decoding model was a linear model trained on all other Berlin subjects, that is also made publicly available (DOI: 10.5281/zenodo.10794370). To mitigate the stimulation artifact contribution, the ECoG channel used for feature estimation was bipolarly referenced to the adjacent channels, and in py_neuromodulation common average re- referenced. Features were z- score normalized within a time range of 30 s and clipped at plus and minus three standard deviations. Once the movement decoder probability output exceeded a pre- defined threshold (0.25), stimulation was triggered through the Alpha Omega NeuroOmega API for a duration of 1 s. Stimulation was enabled only on the clinically effective contralateral DBS contact (stimulation frequency=130 Hz, amplitude=1.5 mA). + +<|ref|>sub_title<|/ref|><|det|>[[115, 575, 181, 591]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[115, 601, 882, 723]]<|/det|> +As the next step, to demonstrate the full automatized brain signal decoding based closed- loop neuromodulation capabilities of our platform, we recruited a new patient for a closed- loop neurostimulation paradigm. Here, we used our pretrained model without any calibration or individual training to trigger subthalamic high- frequency stimulation when movement was detected. The decoding performance remained stable (Fig. 2o, with stimulation- based sample- wise balanced accuracy: 0.66, rate of movements stimulated with at least 300 ms: 0.91), despite the presence of intermittent closed- loop DBS. + +<|ref|>text<|/ref|><|det|>[[115, 732, 880, 766]]<|/det|> +We added, in addition, supplementaary video 2, which presents movement decoding triggered adaptive deep brain stimulation: + +<|ref|>text<|/ref|><|det|>[[115, 777, 882, 897]]<|/det|> +Supplementary video 2: Real- time movement triggered subthalamic deep brain stimulation based on movement decoding without patient individual training. A Parkinson's disease patient performed hand rotation movements which were decoded by a movement decoding classifier. py_neuromodulation computed features are visualized on the lower panel in addition to the movement classifier prediction probabilities. When the movement classification probability passed a specified threshold, stimulation was switched on for a duration of 1 s. Overall, stimulation resulted in 0.62 balanced accuracy and a movement stimulation rate with at least 300 ms of 0.91. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 825, 106]]<|/det|> +We also adapted Figure 2 legend where the stimulation- based changes are incorporated: + +<|ref|>text<|/ref|><|det|>[[114, 115, 883, 306]]<|/det|> +To demonstrate the ability to decode movements without patient individual training, we prospectively recruited one subject in Berlin and decoded movements using pretrained models based on all previous subjects of the Berlin cohort (o). Real- time single trial decoding is shown for out- of- cohort patient 1 with y- axes depicting true measured analog rotameter movement amplitude (top), classification probability predictions without patient- individual training (middle) and predictions with training (bottom). For a second patient we tested movement- triggered stimulation and show the true movement traces (top), single trial movement predictions without patient- individual training (middle) and movement- triggered stimulation time (bottom). (p) Real- time performances are shown for both patients for decoding and stimulation. Above chance sample- wise balanced accuracy and movement detection rates were obtained despite presence of closed- loop neurostimulation and without model calibration. + +<|ref|>text<|/ref|><|det|>[[115, 315, 881, 334]]<|/det|> +Here the adapted Figure 2 o and p including the movement- triggered adaptive stimulation results: + +<|ref|>image<|/ref|><|det|>[[116, 360, 777, 675]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 705, 883, 894]]<|/det|> +Despite these major efforts, we also recognize that the neurostimulation aspect is less clearly fleshed out in our manuscript and remains in an earlier stage with respect to presentable results. A reason why we believe it is still important to mention this ambition in the manuscript is that the entire decoding pipeline is optimized to be sufficiently fast and accurate for real- time implementation of adaptive neurostimulation. To provide an example, a pipeline comprising FFT feature computation, common- average- rereferencing and feature normalization is conducted within 1 millisecond for a single channel (4 milliseconds for 6 channels). We foresee real- world use cases of machine learning based adaptive DBS, such as freezing of gait for PD, tremor decoding for essential tremor, tic decoding for Tourette- syndrome and many more. The presented parameter optimization for responsive neurostimulation illustrates an application how the computed features could be used in an offline- analysis to optimize current available closed- loop + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 175]]<|/det|> +neurostimulation implants, e.g. also for finding optimal parameters for sensing enabled devices. A missing development step that is planned however, is the direct implementation of stimulation parameter adjustment within py_neuromodulation. At this stage of development, the definition of stimulation parameters still resides outside of our software framework, e.g. in our use case through additional code addressing the NeuroOmega API. + +<|ref|>text<|/ref|><|det|>[[116, 185, 416, 201]]<|/det|> +We have now clarified the discussion: + +<|ref|>text<|/ref|><|det|>[[116, 213, 208, 229]]<|/det|> +Discussion: + +<|ref|>text<|/ref|><|det|>[[115, 240, 882, 344]]<|/det|> +"The toolbox is designed with closed- loop neurostimulation in mind, but at this stage primarily streamlines the decoding aspect. Nevertheless, interfacing neurostimulation hardware APIs such as the Alpha Omega NeuroOmega or other neurostimulation systems is straightforward and provides a comprehensive solution to using machine learning models for therapeutic real- time adaptation. Moreover, we will continuously update and extend the capabilities for stimulation parameter adaptation for emerging technologies." + +<|ref|>text<|/ref|><|det|>[[115, 370, 882, 491]]<|/det|> +4) A description somewhere of what data or tools the user actually needs, to utilize this system, would be helpful. For example, how are electrode locations input into the system? Is a DICOM formatted image set of the whole brain needed? CT only or is MRI needed? Or does py_neuromodulation require some sort of output from other software packages such as LeadDBS? Also how are the specific machine learning algorithms implemented? Does the user make a simple selection like "support vector machine" and then is able to input hyperparameters? Or does py_neuromodulation require specific outputs from other machine learning packages? + +<|ref|>text<|/ref|><|det|>[[114, 501, 882, 899]]<|/det|> +We thank the reviewer for motivating us to clarify the specifics with regard to the implemented workflows. Py_neuromodulation automatically reads coordinates stored in metadata as part of the BIDS iEEG standard (Holdgraf et al., 2019). This is relevant for feature visualization in 3D space, connectomics based brain circuit analysis and across- patient decoding. By default, py_neuromodulation expects coordinates to be in MNI standard space that correspond with the mesh and connectomes provided with py_neuromodulation, but practically any coordinate system can be used if a corresponding mesh or connectome is available. Thus, electrode localization must be performed outside of py_neuromodulation. In the most simple approach, the coordinates can be extracted based on visual inspection of a CT or MRI scan after normalization to MNI space. Given that there are potential errors that can result from suboptimal coregistration and normalization, many different toolboxes have been developed to optimize this process, often specialized to the specific electrode type and research field. Consequently, py_neuromodulation does not require any neuroimaging data, but depending on the electrode localization approach and pipeline, CT, MRI, both or even intraoperative fluoroscopy can be used to determine electrode coordinates as input for py_neuromodulation (Randazzo et al 2015, Soper et al 2023). In fact, we believe that requiring coordinates over requiring individual neuroimaging data is advantageous, as neurophysiology datasets are commonly shared with coordinates but without individual imaging data available. For example, the open epilepsy dataset used for the movement decoding use- case provided electrode locations which were readily usable within py_neuromodulation. In our lab and more generally in the context of DBS, we take advantage of the sophisticated semi- automatized electrode localization pipeline provided by LeadDBS v3.0, which is built around a refined protocol using Advanced Normalization Tools combined with visual inspection of coregistration, normalization and artifact localization. For this we use preoperative + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 882, 245]]<|/det|> +3T T1 and T2 MRI imaging combined with postoperative CT. Connectivity profiles from the given coordinates can then be extracted with py_neuromodulation from pre- constructed connectivity matrices that have been made openly available via Zenodo (https://doi.org/10.5281/zenodo.10805915). Alternatively, Lead Connectome Mapper can be used to get more refined estimates based on patient specific or disease specific connectomes. The saved Lead- Mapper output represents connectivity estimates in whole- brain NIfTI format (.nii) which can then be processed using py_neuromodulation for computation of the optimal decoding connectivity map and subsequent connectomic channel selection with different cross- validation approaches. + +<|ref|>text<|/ref|><|det|>[[114, 253, 882, 755]]<|/det|> +The heart of the py_neuromodulation package is the data stream with the extensive preprocessing and feature estimation module that generates interpretable neurophysiological features in a way that is directly transferrable form offline to real- time. This feature estimation module interfaces the machine learning module, which leverages the many advanced and actively maintained and developed machine learning packages in Python. In fact, the availability of cutting- edge machine learning packages was together with the open- source nature of Python, a key reason for us to decide against an implementation of py_neuromodulation in Matlab. The key design principle for this aspect is that we wanted to provide an easy interface for simple and straightforward decoding approaches including optimized default parameters, while also making it as straightforward as possible to plug in new model architectures, given the rapid development of ever improving machine learning methods. As a consequence, py_neuromodulation provides default parameters for simple linear models alongside options to plugin any other model. Additionally, py_neuromodulation defines and supports different dimensionality reduction methods, such as Principal Component Analysis (PCA) or Canonical Correlation Analysis (CCA) and validation strategies and metrics building on the widely- used scikit- learn package (Pedregosa et al 2011) and pre- calibrated based on default parameters as established in this study. Additional features within the py_neuromodulation workflow include feature selection using the Minimum- Redundancy- Maximum- Relevance method based on the mrmr Python package (https://github.com/smazzanti/mrmr), random over- and undersampling based on the imbalanced- learn python package (Lemaitre et al 2017) and Bayesian hyperparameter optimization through the skopt package (https://github.com/scikit- optimize/scikit- optimize). Importantly, all these dependencies are already solved through installation of py_neuromodulation as described in the documentation (https://py- neuromodulation.readthedocs.io/en/latest/installation.html). The novel cross- validation approaches for across- patient and across- cohort decoding were developed within py_neuromodulation itself, providing modules for storing and validation of the computed features in a defined standardized data structure. Realistically, we believe that py_neuromodulation provides the necessary framework to bridge the gap between neuroscience, clinical neurology and machine learning communities by handling complex workflows for which extensive domain knowledge is required. + +<|ref|>text<|/ref|><|det|>[[116, 763, 880, 781]]<|/det|> +To clarify these aspects for the reader, we have made the following adjustments to the manuscript: + +<|ref|>sub_title<|/ref|><|det|>[[116, 792, 191, 807]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[116, 818, 882, 900]]<|/det|> +"py_neuromodulation reads electrode localization from BIDS iEEG metadata files, including referencing information and electrode locations, which is necessary for across patient decoding described below. Here, it is important to note that py_neuromodulation does not provide a workflow for performing the localization of invasive electrodes, but expects electrode locations to be predefined using one of the many workflows that are available in the literature (Randazzo et + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 882, 170]]<|/det|> +al. 2016, Soper et al. 2023, Neudorfer et al. 2023). We recommend the advanced neuroimaging pipeline defined by Lead- DBS with default settings (Neudorfer et al. 2023). In brief, Lead- DBS uses preoperative MRI and postoperative CT scans for co- registration and normalization to MNI 2009b NLIN ASYM space. Electrode artefacts of both DBS and ECoG electrodes can then be visually identified and marked to obtain MNI coordinates of electrode contacts." + +<|ref|>text<|/ref|><|det|>[[115, 179, 882, 229]]<|/det|> +"py_neuromodulation provides optimized default parameters for straightforward invasive brain signal decoding approaches, while also allowing to seamlessly plug in new and alternative machine learning models directly in the Python code." + +<|ref|>text<|/ref|><|det|>[[115, 237, 880, 271]]<|/det|> +We have further included example code within the methods to make the utility of the software easier to follow: "Py_neuromodulation API and example usage": + +<|ref|>text<|/ref|><|det|>[[115, 279, 882, 375]]<|/det|> +"The general goal of the presented package is to simplify analysis of invasive electrophysiological data. For a minimal example for offline analysis, the recording in a form of a numpy array or pandas dataframe needs to be supplied in the shape (n_channels, n_time) with a respective sampling frequency. Subsequently, features are computed with a feature interval given the sampling_rate_features_hz. The following code shows the "stream" initialization and call of the "run" function: + +<|ref|>text<|/ref|><|det|>[[114, 410, 677, 585]]<|/det|> +import py_neuromodulation as nm import numpy as np NUM_CHANNELS = 5 NUM_DATA = 10000 sfreq = 1000 # Hz sampling_rate_features_hz = 10 # Hz data = np.random.random([NUM_CHANNELS, NUM_DATA]) stream = nm.Stream( sfreq=sfreq, data=data, sampling_rate_features_hz=sampling_rate_features_hz ) features = stream.run() + +<|ref|>text<|/ref|><|det|>[[114, 609, 882, 689]]<|/det|> +The returned "feature" object is a dictionary containing each feature name - value pair. The general convention is that the feature names are given in the nomenclature "channel name" "feature_name" "feature_name_subgroup". It is important to note that in the upper example the settings and channel- specific information were automatically defined given default parameters. Given a BIDS- data path the respective information can be queried: + +<|ref|>text<|/ref|><|det|>[[114, 697, 716, 858]]<|/det|> +from py_neuromodulation import nm_IO ( raw, data, sfreq, line_noise, coord_list, coord_names, ) = nm_IO.read_BIDS_data( PATH_RUN=PATH_RUN, BIDS_PATH=PATH_BIDS, datatype=datatype ) + +<|ref|>text<|/ref|><|det|>[[114, 874, 734, 891]]<|/det|> +The nm_channel dataframe can then be initialized given different parameters: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 106, 617, 123]]<|/det|> +from py_neuromodulation import nm_define_nmchannels + +<|ref|>text<|/ref|><|det|>[[115, 134, 585, 149]]<|/det|> +nm_channels = nm_define_nmchannels.set_channels( + +<|ref|>text<|/ref|><|det|>[[115, 150, 540, 264]]<|/det|> +ch_names=raw.ch_names, ch_types=raw.get_channel_types(), reference="default", bads=raw.info["bads"], new_names="default", used_types=("ecog", "dbs", "seeg"), target_keywords=["MOV_RIGHT"], + +<|ref|>text<|/ref|><|det|>[[115, 290, 881, 325]]<|/det|> +The pre- processing and feature computation settings can be modified using a dictionary (software version tag 0.02). Therefore, the default settings can be obtained and modified: + +<|ref|>text<|/ref|><|det|>[[115, 333, 522, 349]]<|/det|> +from py_neuromodulation import nm_settings + +<|ref|>text<|/ref|><|det|>[[115, 360, 684, 390]]<|/det|> +settings = nm_settings.get_default_settings() settings = nm_settings.set_settings_fast_compute(settings) + +<|ref|>text<|/ref|><|det|>[[115, 402, 820, 593]]<|/det|> +settings["features"]["fft"] = True settings["features"]["bursts"] = True settings["features"]["sharpwave_analysis"] = True settings["sharpwave_analysis_settings"]["estimator"]["mean"] = [] for sw_feature in list( settings["sharpwave_analysis_settings"]["sharpwave_features"].keys() ): settings["sharpwave_analysis_settings"]["sharpwave_features"][ sw_feature ] = True settings["sharpwave_analysis_settings"]["estimator"]["mean"].append( sw_feature ) + +<|ref|>text<|/ref|><|det|>[[115, 604, 883, 638]]<|/det|> +After feature computation using the "run" method, a decoder module can be used to evaluate a scikit- learn model: + +<|ref|>text<|/ref|><|det|>[[115, 646, 686, 678]]<|/det|> +from py_neuromodulation import nm_analysis, nm_decoder from sklearn import metrics, model_selection, linear_model + +<|ref|>text<|/ref|><|det|>[[115, 690, 549, 750]]<|/det|> +feature_reader = nm_analysis.Feature_Reader( feature_dir=PATH_OUT, feature_file=RUN_NAME, ) + +<|ref|>text<|/ref|><|det|>[[115, 761, 494, 777]]<|/det|> +model = linear_model.LinearRegression() + +<|ref|>text<|/ref|><|det|>[[115, 789, 722, 904]]<|/det|> +feature_reader.decoder = nm_decoder.Decoder( features=feature_reader.feature_arr, label=feature_reader.label, label_name=feature_reader.label_name, used_chs=feature_reader.used_chs, model=model, eval_method=metrics.r2_score, cv_method=model_selection.KFold(n_splits=3, shuffle=True), + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 125, 103]]<|/det|> +) + +<|ref|>text<|/ref|><|det|>[[123, 118, 546, 202]]<|/det|> +performances \(=\) feature_reader.run_ML_model( estimate_channels \(=\) True, estimate_gridpoints \(=\) False, estimate_all_channels_combined \(=\) True, save_results \(=\) True, ) + +<|ref|>text<|/ref|><|det|>[[115, 230, 882, 280]]<|/det|> +Based on the used scikit- learn metric and cross- validation strategy, the performances are estimated. Multiple additional arguments can further be supplied to adapt the feature estimation and decoding pipeline. + +<|ref|>text<|/ref|><|det|>[[115, 288, 882, 401]]<|/det|> +For applying the optimal connectivity decoding without patient- individual training, the electrode contact MNI coordinates need to be obtained beforehand (Randazzo et al 2016, Soper et al 2023), and then utilized for obtaining the corresponding connectivity fingerprints from either the Lead- DBS Lead- Mapper toolbox (Neudorfer et al 2023), or by a pre- defined grid. py_neuromodulation provides a method for obtaining matching points from a pre- defined cortical hull grid (n=1025 points) or whole- brain grid (1236 points). The computed grids can be downloaded from a public repository (https://doi.org/10.5281/zenodo.10805915) and utilized through the following API: + +<|ref|>text<|/ref|><|det|>[[115, 410, 492, 440]]<|/det|> +from py_neuromodulation import nm_RMAP import numpy as np + +<|ref|>text<|/ref|><|det|>[[115, 452, 803, 469]]<|/det|> +mni_coords \(=\) [[10, 40, 20], [50, 14, 12]] # definition of MNI contacts + +<|ref|>text<|/ref|><|det|>[[115, 481, 557, 540]]<|/det|> +ch_sel \(=\) nm_RMAP.ConnectivityChannelSelector( whole_brain_connectome \(=\) True, func_connectivity \(=\) True ) + +<|ref|>text<|/ref|><|det|>[[115, 553, 735, 583]]<|/det|> +# retrieve connectivity fingerprints for passed MNI coordinates fps, grid_idx \(=\) ch_sel.get_closest_node(mni_coords) + +<|ref|>text<|/ref|><|det|>[[115, 596, 608, 626]]<|/det|> +# computation of optimal connectivity correlations corrs \(=\) ch_sel.get_rmap_correlations(fps) + +<|ref|>text<|/ref|><|det|>[[115, 640, 515, 655]]<|/det|> +recording_contact_use \(=\) np.argmax(corrs) + +<|ref|>text<|/ref|><|det|>[[115, 668, 882, 766]]<|/det|> +For the movement decoding use- case, a movement decoding model was trained that could significantly predict movement without patient- individual training. The model can be accessed through a Zenodo archive and the required code is made publicly available through a GitHub repository (https://github.com/neuromodulation/AcrossPatientDecodingModel). The following exemplary code illustrates how the model can be loaded and directly be utilized in the py_neuromodulation API: + +<|ref|>text<|/ref|><|det|>[[115, 776, 682, 905]]<|/det|> +import py_neuromodulation as nm from py_neuromodulation import nm_settings import skops model \(=\) skops.io.load("movement_decoder.skops") settings \(=\) nm_settings.get_default_settings() settings \(=\) nm_settings.set_settings_fast_compute(settings) stream \(=\) nm.Stream(settings \(=\) settings) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 567, 134]]<|/det|> +# definition of nm_channels and exemplary data features = stream.run(data) model.predict(features.to_numpy()) + +<|ref|>text<|/ref|><|det|>[[115, 168, 882, 272]]<|/det|> +5) One of the three big problems the authors hope to address is "Machine learning can capitalize on large datasets but current brain signal decoding approaches for BCI still commonly rely on individual patient training sets of short duration". It is never really clear to me how the authors solve this – is there a particular method they introduce to solve it? Or are they just trying to show that in fact you don't need large data sets of long duration, even though other researchers try to use those? More clarity in discussion on this would help. + +<|ref|>text<|/ref|><|det|>[[115, 282, 882, 523]]<|/det|> +We thank the reviewer for this important question. Most of the invasive recordings are acquired within an intra-operative setting or using "externalized" electrodes that allow recordings in the clinics outside of the operating room. This inherently limits the recording durations. The key point that we are trying to make in our manuscript is that developing across- patient decoding approaches could not only be more convenient and cheaper for clinical applications, but could also lead to improved decoding performances because more complex models can be trained on the larger datasets after merging data from multiple subjects and cohorts. Thus, since the performance of machine learning and especially deep learning models was shown to be highly dependent on dataset size (Sarker et al 2021, SN Computer Science), we believe that it becomes necessary to develop machine learning models that utilize datasets from multiple subjects and cohorts. Evidence for this is provided in our study through the validation of the pretrained model performance vs. the model trained on individual data. We found that the model that was trained on all other subjects of the cohort performed better than the model trained on the relatively short individual recording duration. + +<|ref|>text<|/ref|><|det|>[[115, 533, 882, 895]]<|/det|> +Part of the motivation of the design of py_neuromodulation stems from the concern that a lot of brain signal decoding studies are practically not reproducible. With this we do not intend to say that the science or results are manufactured or wrong. Instead, we mean that the approaches that are reported are so individualized and require so much domain knowledge and resources that it is hard to envision how other labs could actually perform the same task, even if given the same data. On the other hand, we are convinced that the future of clinical neurotechnology will use machine learning methods, requiring multicenter validations of specific approaches that should be easily implementable by different teams and highly standardized. We have searched for software solutions that provide standardized means to implement and validate machine learning models for invasive brain data that can be directly translated into real- time applications and were not satisfied with what we found. Therefore, we aimed to address this problem by ourselves, by implementing standardized tools for preprocessing, feature estimation and across center decoding. Since the pipeline parametrization in py_neuromodulation is implemented within a single file, all settings can be shared and implemented without the need to change programming code. In this manner the utilized parameters and models are easily implementable, transparent and reproducible, greatly facilitating multicenter collaborations and clinical trials. In addition to the democratization of the methodological approach, this also allows for a direct sharing of models, as we have done for the generalizable movement decoder that is now available via a DOI (https://doi.org/10.5281/zenodo.10794370) and can be plugged into py_neuromodulation anywhere in the world for out- of- the- box plug&play invasive brain signal decoding. We hope that in the future, we can create a model database that contains usable models for decoding of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 158]]<|/det|> +symptom and behavior for open- source development of the next- generation of machine learning powered neurotechnology. Through across patient decoding more and more refined models based on larger multicenter datasets can build the foundation for an ever- expanding complexity of the most cutting edge machine learning approaches. + +<|ref|>text<|/ref|><|det|>[[115, 168, 512, 185]]<|/det|> +We have now clarified this further in the methods: + +<|ref|>text<|/ref|><|det|>[[115, 195, 882, 299]]<|/det|> +"By standardizing feature estimation and brain signal decoding we aim to enable machine learning decoding to make use of many datasets from different patients and centers. The implemented pipeline provides, therefore, a method for unifying features and decoding across different acquisition methods. To enable generalized future movement decoding, we provide the validated across- patient machine learning model with the required pre- processing and feature computation modules as an openly available resource (https://doi.org/10.5281/zenodo.10794370)." + +<|ref|>text<|/ref|><|det|>[[115, 326, 448, 343]]<|/det|> +Specific comments to improve readability: + +<|ref|>text<|/ref|><|det|>[[115, 370, 882, 422]]<|/det|> +Early in results or in intro, authors should say that their system is called "py_neuromodulation" When they began to use this term in results, I did not perceive that it is actually the name of their software pipeline. + +<|ref|>text<|/ref|><|det|>[[115, 460, 584, 477]]<|/det|> +Thank you for pointing this out, the introduction now reads: + +<|ref|>text<|/ref|><|det|>[[115, 487, 882, 539]]<|/det|> +"We developed an open, integrative and modularized platform (Fig. 1), for standardized and reproducible implementation of machine learning based brain signal decoding algorithms called py_neuromodulation (https://github.com/neuromodulation/py_neuromodulation)." + +<|ref|>text<|/ref|><|det|>[[115, 565, 882, 635]]<|/det|> +Results section 1: "To address this, we developed dedicated approaches for patient decoding based on normative MRI connectomics and latent embeddings from contrastive learning with CEBRA13. " – this sentence will be opaque to a number of readers who are unfamiliar with contrastive learning and the acronym CEBRA. + +<|ref|>text<|/ref|><|det|>[[115, 645, 750, 663]]<|/det|> +We have now simplified the phrasing to make it more generally understandable: + +<|ref|>text<|/ref|><|det|>[[115, 672, 882, 707]]<|/det|> +"To address this, we developed dedicated approaches for across- patient decoding based on advanced machine learning algorithms that can account for variability in electrode localization." + +<|ref|>text<|/ref|><|det|>[[115, 734, 882, 906]]<|/det|> +Figure 1, Part D is not completely clear as it is first presented, and it seems to be a major part of the author's pipeline. Especially this statement: "Features can be mapped in space (d) for patient individual or across- patient decoding and consecutive adjustment of therapeutic delivery." Its not clear here how mapping features in space specifically contributes to decoding of dynamic patient states like movement, emotion, or seizure occurrence. Mapping the relevant activities would certainly contribute to a better understanding of anatomic localization or network involvement of recording sites that are relevant to decoding, and that contributes to understanding which brain networks are most relevant for the decoded brain state. But it is not clear at this point in the manuscript how the spatial mapping contributes to the process of decoding or to its accuracy. At line 89- 91, and later in the text, they imply that accounting for the variable localization of implants + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 882, 141]]<|/det|> +would be a contributor to generalized cross- subjects decoding, which seems true, but how would anatomic localization contribute to individual decoding performance as is stated in the figure legend? + +<|ref|>text<|/ref|><|det|>[[114, 167, 882, 202]]<|/det|> +We thank the reviewer for this important remark. Indeed, the spatial raw data or feature mapping to a standardized space is only a requirement for decoding without patient- individual training. + +<|ref|>text<|/ref|><|det|>[[114, 212, 882, 247]]<|/det|> +We adapted the Figure 1 legend to delete the phrase of feature mapping for patient individual decoding: + +<|ref|>text<|/ref|><|det|>[[114, 256, 882, 291]]<|/det|> +"Features can be mapped in space (d) for across- patient decoding and consecutive adjustment of therapeutic delivery." + +<|ref|>text<|/ref|><|det|>[[114, 301, 882, 336]]<|/det|> +Finally, we have introduced two new supplementary figures that explain the process in more detail, also in response to reviewer #2: + +<|ref|>image<|/ref|><|det|>[[120, 350, 872, 852]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 864, 884, 897]]<|/det|> +
Supplementary fig. 4 Comparison of different approaches for neural decoding without patient-individual training. (a) Grid-point interpolation: Individual recording contact locations are estimated in a standardized
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 309]]<|/det|> +space. Features are separately computed for each recording contact. Data is then mapped to a pre- defined cortical or subcortical grid in MNI coordinates. This mapping ensures a correct sorting of activity sources stemming from similar brain regions. In this manner, feature vectors are mapped to a common grid defined in space (similar to EEG montages), which then lay the foundation to train models on grid- points instead of recording channels for neural decoding without patient individual training. (b) Connectomic channel selection: An optimal decoding whole- brain connectivity map is computed based on training data. This step requires the computation of contact- specific neural decoding performances and whole- brain connectivity estimates. The connectivity profiles and decoding performances are correlated in a voxel- wise manner to estimate a connectivity map associated with optimal decoding performance. For a test subject, the connectivity map of each channel is spatially correlated with the optimal decoding map and the one with the highest similarity is selected and used for testing of a pre- trained machine learning model. (c) The connectomics- based channel selection approach is further extended by transforming individual channel features using an embedding layer. This layer is computed through contrastive learning and auxiliary variables. Here we utilized the CEBRA package (Schneider et al 2023, Nature). + +<|ref|>text<|/ref|><|det|>[[115, 345, 883, 432]]<|/det|> +In the present manuscript, the Pearson correlation coefficient was utilized for the connectomics based approach. We note, however, that this approach can be extended by different correlation metrics. In the following we added another more detailed figure explaining the connectomic channel selection approach, including a definition of connectivity profile, correlations of connectivity profiles and the optimal connectomics derived decoding map: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 90, 884, 728]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 732, 884, 892]]<|/det|> +Supplementary fig. 5 Connectomics- based neural decoding without patient- individual training. (a) Estimation of a patient- individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain- wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 121]]<|/det|> +associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. + +<|ref|>sub_title<|/ref|><|det|>[[115, 148, 254, 164]]<|/det|> +## Results section 2 + +<|ref|>text<|/ref|><|det|>[[115, 175, 882, 226]]<|/det|> +"at the single sample level (100 ms precision indicating presence or absence of movement) and at the individual movement level (300 ms or more movement time decoded consecutively)" – this sentence is not clear + +<|ref|>text<|/ref|><|det|>[[115, 237, 882, 270]]<|/det|> +Also in response to reviewer #2 we have further clarified the sample- wise performance vs. the movement detection rate. + +<|ref|>text<|/ref|><|det|>[[116, 282, 388, 298]]<|/det|> +We adapted the sentence to read: + +<|ref|>text<|/ref|><|det|>[[115, 309, 882, 411]]<|/det|> +"We trained ridge regularized logistic regression classifiers and evaluated their performance using the balanced accuracy metric with 3- fold cross- validation on consecutive data segments, yielding sample- wise performances indicating presence or absence of movement at 100 ms resolution. Sample- wise performances were concatenated to establish a more coarse metric that allowed for detection of individual movement entities, termed movement detection rate and defined as 300 ms of consecutive movement classification." + +<|ref|>text<|/ref|><|det|>[[115, 422, 436, 438]]<|/det|> +and added the following to the methods: + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 535]]<|/det|> +"In addition to reporting the sample- wise classification performances, we therefore report the accuracy of correct predicted movement blocks termed "movement detection rate". If the classifier's output probability is above 0.5 for three consecutive samples (300 ms) the present movement is classified to be detected. A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block." + +<|ref|>text<|/ref|><|det|>[[115, 562, 882, 596]]<|/det|> +it is not quite spelled out what movement decoding really means – are the brain states that are decoded "not moving" versus "moving"? this should be more clearly stated. + +<|ref|>text<|/ref|><|det|>[[115, 607, 882, 640]]<|/det|> +Also in response to reviewer #2 this has now been clarified and the respective results sections reads: + +<|ref|>text<|/ref|><|det|>[[115, 652, 882, 703]]<|/det|> +"We implemented py_neuromodulation for electrocorticography (ECoG) based movement decoding as a two- class classification problem (rest vs. movement present) without individual training ..." + +<|ref|>text<|/ref|><|det|>[[115, 731, 609, 748]]<|/det|> +Figure 2 –Panels j, k – the term "embedding" is not clear here. + +<|ref|>text<|/ref|><|det|>[[115, 758, 882, 896]]<|/det|> +Thank you for pointing us to this lack of clarity. Through the application of the non- linear encoder as part of the contrastive learning approach (Consistent EmBeddings of high- dimensional Recordings using Auxiliary variables - CEBRA), we transform, multi- dimensional invasive brain signal features into a lower- dimensional, yet highly informative "embedding space" using a five- layer convolutional neural network with the InfoNCE (Noise- Contrastive Estimation) contrastive loss. When data is input into the network, it passes through various layers, each performing different transformations guided by the weights (and biases) of the network. The specific layer from which we extract the embedding is a non- linear encoder. The resulting embeddings showed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 209]]<|/det|> +exceptionally high consistency across subjects as investigated with linear identifiability in our study, which facilitates the discernment of neural patterns associated with motor output across subjects. The exceptional utility of the embedding in our study lies in its ability to convert the vast, high- dimensional invasive brain signal recordings with different number of channels, locations and durations into a more tractable, simplified form without significant loss of critical information that is comparable across subjects. By doing so, we can compare the similarity of the embedding and use that for across- patient decoding. + +<|ref|>text<|/ref|><|det|>[[114, 219, 671, 236]]<|/det|> +We now added a short clarification to the figure and the figure legend: + +<|ref|>image<|/ref|><|det|>[[115, 247, 857, 753]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 765, 883, 834]]<|/det|> +"... (j) low- dimensional embedding (exemplar subject shown) derived from the model weights of non- linear decoder using contrastive learning with a convolutional neural network with CEBRA. Comparison of embeddings provides the foundation of across- patient decoding. (k) shows the embedding consistency from each to every other patient via linear identifiability. ..." + +<|ref|>text<|/ref|><|det|>[[113, 861, 881, 896]]<|/det|> +Panel o – the meaning of the y axis is not clear in these plots. For example for “true movement” is the y axis displacement? Force? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 140]]<|/det|> +This was not sufficiently clear. The movements shown in this plot are the single- trial movement amplitudes recorded from an electrical rotational handle coupled to a potentiometer. It is therefore a kinematic representation of the hand movement. + +<|ref|>text<|/ref|><|det|>[[115, 150, 882, 220]]<|/det|> +We adapted the Figure 2o "y axis" label: "Hand movement [a.u.]" (see above) and added in the Figure legend: "Real- time single trial decoding is shown for out- of- cohort patient 1 with y- axes depicting true measured analog rotameter movement amplitude (top), classification probability predictions without patient- individual training (middle) and predictions with training (bottom)." + +<|ref|>text<|/ref|><|det|>[[115, 247, 882, 281]]<|/det|> +"To investigate the individual variability of trainer vs. learner performance" – not sure what this means + +<|ref|>text<|/ref|><|det|>[[115, 291, 805, 308]]<|/det|> +We agree that this sentence did not make sense, we have now clarified this as follows: + +<|ref|>text<|/ref|><|det|>[[115, 319, 882, 423]]<|/det|> +"We next established a subject- to- subject decoding matrix, which provides information on the performance of each subject when trained on a single other subject from the cohort. This reveals, which subjects brain signals are well- suited to serve as training data leading to decoders on other subjects perform well (good trainer) and which subjects brain data have generalizable qualities that allow them to train from a variety of subjects yielding high performances independent of the training data (good learner)." + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 502]]<|/det|> +In general for this section: what signal features contributed to movement decoding? In the following section on emotion decoding, the features used are stated more explicitly, and that would help here in this section. + +<|ref|>text<|/ref|><|det|>[[115, 511, 882, 581]]<|/det|> +We thank the reviewer for this important remark. For the movement decoding model, there were slight variations to what degree the oscillatory features contributed for each cohort and model. Overall, all frequency bands had high contributions to the decoders with theta, high- beta and high- gamma yielding the strongest relationships. + +<|ref|>text<|/ref|><|det|>[[115, 590, 882, 642]]<|/det|> +We have now clarified this in text and through an additional Supplementary figure showing the sum of the absolute value linear model coefficients from the patient- individual movement decoding models of all patients. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 94, 655, 345]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 361, 884, 394]]<|/det|> +
Supplementary fig. 2 Sum of linear model absolute value coefficients shows feature importances for all movement decoding patients.
+ +<|ref|>text<|/ref|><|det|>[[115, 419, 882, 473]]<|/det|> +Results: "Feature contributions were observed in each frequency band but highest importance was identified in the theta, high beta and high gamma frequency bands (see supplementary fig. 2)." + +<|ref|>text<|/ref|><|det|>[[114, 499, 882, 655]]<|/det|> +"To investigate a potential relationship with clinical scores, we correlated decoding performances from the most predictive channel contrasting neutral vs. positive/negative per patient with Beck's Depression Inventory (BDI) at time of recording and after six months of chronic DBS. Decoding performance correlated with DBS induced improvement in BDI scores (rho=0.79, p=0.01), but not with concurrent symptom severity (Fig. 3f)." - this is tough to follow - why would the decoding performance in emotional task be expected to correlate with depression severity? Is the hypothesis that the more depressed one is, the more task related emotional valence is "decodable"? the opposite seems more likely, that is depression would blunt ones ability to distinguish emotional valences. + +<|ref|>text<|/ref|><|det|>[[115, 665, 882, 700]]<|/det|> +We agree with the reviewer, that indeed we sought a negative relationship, given the impairment in emotion regulation that is associated with depression. + +<|ref|>text<|/ref|><|det|>[[115, 710, 545, 727]]<|/det|> +We have now clarified this in the respective sentence: + +<|ref|>text<|/ref|><|det|>[[115, 737, 881, 789]]<|/det|> +"Decoding performance correlated with DBS induced improvement in BDI scores (rho=0.79, p=0.01), but concurrent symptom severity did not reflect in lower decoding performances (Fig. 3f)." + +<|ref|>text<|/ref|><|det|>[[115, 816, 881, 869]]<|/det|> +"... connectivity fingerprints seeded from LFP channel locations were correlated with channel specific decoder test- set performance". - for a nonexpert - how are connectivity fingerprints quantified so as to feed into a correlation? A sentence on this would help. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 881, 125]]<|/det|> +We have now extended the description of the methodological approach with new figures and text. In addition, we have extended the phrasing to make it more intuitively comprehensible: + +<|ref|>text<|/ref|><|det|>[[115, 133, 882, 187]]<|/det|> +"In all cases connectivity fingerprints seeded from LFP channel locations were correlated with channel specific decoder test- set performance, by vectorizing or reducing spatial information and deriving similarity estimates to the optimal fingerprint (see supplementary figure 6)." + +<|ref|>text<|/ref|><|det|>[[115, 212, 881, 248]]<|/det|> +Figure 3e – even zooming in, its hard to read the feature labels or understand what they mean. Legend refers to a part “I” but don’t see that panel in the figure. + +<|ref|>text<|/ref|><|det|>[[115, 257, 882, 292]]<|/det|> +We thank the reviewer for this comment and updated the feature label font size in Figure 3e, and corrected the panel labelling. + +<|ref|>text<|/ref|><|det|>[[115, 721, 535, 738]]<|/det|> +Results section 4, briefly explain what an F1 score is + +<|ref|>text<|/ref|><|det|>[[117, 748, 361, 764]]<|/det|> +The results section now reads: + +<|ref|>text<|/ref|><|det|>[[115, 775, 882, 827]]<|/det|> +“We optimized these parameters for sample- wise seizure classification to maximize the F1- score, which depicts the harmonic mean between precision (the model's ability to identify only true seizure instances) and recall (the model's ability to find all seizure instances).” + +<|ref|>sub_title<|/ref|><|det|>[[115, 854, 209, 870]]<|/det|> +## Discussion: + +<|ref|>text<|/ref|><|det|>[[115, 887, 882, 905]]<|/det|> +“Nevertheless, decoding performances were investigated in the presence of clinical brain + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 158]]<|/det|> +stimulation in two out of three use cases, namely STN- DBS for PD and responsive neurostimulation for epilepsy" – is this actually true for RNS? My understanding is that RNS is a "half duplex" device, that is it senses, provides preprogrammed stimulation train when an event is detected, then returns to sensing mode. It does not actually sense during stimulation. + +<|ref|>text<|/ref|><|det|>[[115, 167, 882, 272]]<|/det|> +We thank the reviewer for this expert remark. The RNS device indeed does blank during stimulation, but this does not render the recordings free from the consequences of acute stimulation, which are very visible, both through physiological changes as described in Kokkinos et al. JAMA Neurol 2019 https://doi.org/10.1001/jamaneurol.2019.0658 and through artifacts even though recordings were blanked for the brief periods of stimulation, as shown in an added supplementary figure: + +<|ref|>image<|/ref|><|det|>[[131, 281, 880, 580]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 592, 883, 656]]<|/det|> +
Supplementary fig. 9 Responsive Neurostimulation (RNS) device artifact annotations and corresponding features. (a) Raw time-series including annotated stimulation and clipping artifacts and (b) corresponding FFT features. The RNS does not allow for simultaneous stimulation and recording. The device parameters allow for specifying a "gain" setting that can omit the clipping artifact.
+ +<|ref|>text<|/ref|><|det|>[[115, 665, 694, 682]]<|/det|> +We further referenced this artifact annotation within the methods section: + +<|ref|>text<|/ref|><|det|>[[115, 692, 882, 727]]<|/det|> +"Both artifact types and their corresponding annotations in the raw signal and FFT features are visualized in supplementary fig. 9." + +<|ref|>text<|/ref|><|det|>[[115, 736, 882, 822]]<|/det|> +We hope that the reviewer agrees that these recordings are clearly influenced by stimulation. We have still tried to adapt the phrasing to make it more precise, but the changes we came up with all lead to a more convoluted and less easily understandable discussion, which is why we hope that the reviewer accepts that we keep the phrasing as is. However, we would be happy to accommodate any suggestions the reviewer may have to make this more clear. + +<|ref|>text<|/ref|><|det|>[[115, 850, 882, 902]]<|/det|> +"The network description however, is static in nature, while symptoms wax and wane. Brain signal decoding may help these networks to come to life in a dynamic closed- loop neurostimulation approach by informing both decoding and stimulation models of symptom specific circuits to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 157]]<|/det|> +optimize symptom decoding and adaptation of stimulation right at the time they occur" – not sure I get the meaning here. This seems to be a discussion of the advantage of combining connectomics (static) with brain signal decoding (dynamic) to produce something that hasn't been done before, but the sentence is lofty enough that it loses the reader. + +<|ref|>text<|/ref|><|det|>[[115, 167, 882, 254]]<|/det|> +We are truly thankful that the reviewer has taken the time to help us improve our manuscript so constructively. The reviewer is right that we were a bit ambitious in the phrasing here. Practically, we believe that in the future, adaptive DBS will be tuned to disease specific connectomic targets and we will use connectomic information to a) decode symptom presence and b) define the optimal stimulation parameters and location to hit the right target in a dynamic manner. + +<|ref|>text<|/ref|><|det|>[[115, 264, 501, 281]]<|/det|> +We have now adapted the phrasing accordingly: + +<|ref|>text<|/ref|><|det|>[[115, 291, 882, 377]]<|/det|> +"The network description however, is static in nature, while symptoms wax and wane. Brain signal decoding may help these networks to come to life in a dynamic closed- loop neurostimulation approach. Invasive multisite recordings can be used to monitor the presence of symptoms in specific brain networks and advanced control algorithms can tune stimulation parameters in real- time to stimulate precisely the networks of symptoms that are present." + +<|ref|>sub_title<|/ref|><|det|>[[115, 415, 300, 432]]<|/det|> +## Notes by the authors: + +<|ref|>text<|/ref|><|det|>[[115, 443, 882, 493]]<|/det|> +In the previous manuscript version we reported in the statistics section, we reported: "All statistical tests were computed using non- parametric Monte- Carlo sampled permutation tests with a significance value of \(\alpha = 0.5\) ". We corrected the \(\alpha\) value now to be 0.05. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 68, 517, 85]]<|/det|> +Reviewer #2 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[114, 111, 930, 583]]<|/det|> +The goal of having "plug and play" decoding algorithms for closed loop DBS is an important one. Likewise, having a toolbox that can implement these algorithms and distribute open- source would be valuable. However, the paper does not give enough information as to how this toolbox implements a plug and play algorithm. Multiple steps still seem to be involved, including co- registering individual's imaging to MNI space, and placing the electrodes in this coordinate space. This, as mentioned by the authors in their rebuttal, is not trivial, especially when taking into account brain shifts due to opening the dura. No mention of how this substantial shift would be accounted for. The authors state that one of their goals is to "facilitate multicenter clinical trials ...and democratization of the methodological approach." Yet, the descriptions in this paper are far too vague and lacking in specific methods for even those engineers familiar with BCIs to be able to implement, let alone for clinicians to be able to even comprehend the basics. And importantly, this procedure of co- registering would take significant time - indeed, in our experience, much more time than building a very simple decoder of movement vs. rest for an individual, which could be done in less than 5 min (including recording and automated decoder building). Either way, this will require some time for the clinician or a technologist. Since this (across- patient decoding) appears to be the biggest goal of this paper, the authors need to make a much stronger case (including empiric evidence of time to perform and compute the different steps for a given patient, as a clinician would do it, and showing this is truly less than recording move vs rest for 3- 5 min and building a very simple individualized decoder, rather than vague estimates as in the rebuttal) for why this is better than individual decoders. Overall, the paper still assumes too high of an expertise in many disparate and specific domains to be applicable to a broad audience. + +<|ref|>text<|/ref|><|det|>[[114, 606, 930, 919]]<|/det|> +We are truly thankful for the expert assessment of our manuscript by the insightful reviewer. We agree with the reviewer that methodological clarity is important, even if the procedures are complex. We have now added additional information and new supplementary figures in the hope to address this point. To further improve the methodological clarity of our manuscript, we have now adapted the methods section to include a dedicated imaging chapter to include further information regarding normalization, co- registration and accounting for brain shifts. We acknowledge this requirement and provide necessary instructions to obtain electrode localization in a standard image space. However, we would like to emphasize that in our view not time saving but the ability to leverage larger dataset sizes, with the potential to scale performances of complex machine learning algorithms beyond what is recordable at the single subject level, will be the key benefit, and we provide a specific example for this point. In context of current AI breakthroughs, our thought process is that a brain signal decoder that can use all available brain signals from different subjects, will be more powerful than a decoder that can only use individual subject data, just as large language models that can use all text available will be more powerful than models that can only learn from text of individual subjects. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 67, 931, 290]]<|/det|> +Nevertheless, our approach does save time, because image acquisition, processing and localization is done routinely in the hospital and therefore does not require additional time or expertise beyond what is expected by a multidisciplinary DBS board that consists of neurosurgeons, neurologists and neuroradiologists. MRI and CT scans, as well as coregistration are critical steps of the implant procedure that is performed by the neurosurgeon, in order to translate stereotactic coordinates. Postoperative imaging is performed to rule out complications and perform electrode localization that is critical for surgical decision making, typically performed by neuroradiologists. Patients with electrodes outside the target area will be considered for a revision in case of unsatisfactory clinical results. This electrode localization is performed by clinical staff and the output is used in our toolbox without requiring further processing. Thus, no additional time is required for image processing. + +<|ref|>text<|/ref|><|det|>[[113, 293, 931, 671]]<|/det|> +In theory, many different approaches using different tools could be used for electrode localization and our toolbox is agnostic to which tool was used. However, given that we have substantial expertise in this matter and have contributed to some of the used tools, we propose a pipeline that is based on the Lead- DBS toolbox (Neudorfer et al 2023). Notably, all image co- registration, normalization and brain- shift correction was performed as performed as clinical routine in our center. Our center co- develops and uses Lead- DBS that builds on the ANTs toolbox (Avants et al 2008, Symmetric diffeomorphic image registration with cross- correlation: evaluating automated labeling of elderly and neurodegenerative brain) for co- registration and normalization of image patient space to MNI nonlinear 2009b standard space. This process was optimized in Lead- DBS for subcortical structures (Ewert et al 2009). In addition, brain- shift correction induced by dura opening is implemented in Lead- DBS through a linear transformation refined to a subcortical region (Schönecker et al 2009, Automated Optimization of Subcortical Cerebral MR Imaging- Atlas Coregistration for Improved Postoperative Electrode Localization in Deep Brain Stimulation). The Lead- DBS Volume Registration documentation describes this method in further detail: https://netstim.gitbook.io/leaddbs/lead- dbs/step3- volume- registrations. Since these steps are required for connectivity- based neural decoding, we now added them to the "Electrode Information and imaging" methods section in the main manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 697, 931, 920]]<|/det|> +"py_neuromodulation reads electrode localization from BIDS iEEG metadata files, including referencing information and electrode locations, which is necessary for across patient decoding described below. We recommend the advanced neuroimaging pipeline defined by Lead- DBS with default settings36. In brief, Lead- DBS uses preoperative MRI and postoperative CT scans for co- registration and normalization to MNI 2009b NLIN ASYM space. Electrode artefacts of both DBS and ECoG electrodes can then be visually identified and marked to obtain MNI coordinates of electrode contacts. Image co- registration, normalization and brain- shift correction are thus automatically obtained through Lead- DBS. Localization of subcortical lead electrodes requires a post- operative CT or MRI image, which needs to contain the electrode contact artifacts. Lead- DBS uses internally the ANTs toolbox (Avants et al 2008, Symmetric diffeomorphic image registration with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 67, 930, 245]]<|/det|> +cross- correlation: evaluating automated labeling of elderly and neurodegenerative brain) for co- registration and normalization of image patient space to MNI nonlinear 2009b standard space. This process was optimized in Lead- DBS for subcortical structures (Ewert et al 2009). In addition, brain- shift correction induced by dura opening is implemented in Lead- DBS through a linear transformation refined to a subcortical region (Schonecker et al 2009, Automated Optimization of Subcortical Cerebral MR Imaging- Atlas Coregistration for Improved Postoperative Electrode Localization in Deep Brain Stimulation). The Lead- DBS Volume Registration documentation describes this method in further detail: https://netstim.gitbook.io/leaddbs/lead- dbs/step3- volume- registrations. + +<|ref|>text<|/ref|><|det|>[[115, 280, 930, 320]]<|/det|> +We want to highlight the following advantages of our decoding approach without patient individual training in contrast to a patient- individual training decoder with a short 3- 5 min training duration: + +<|ref|>text<|/ref|><|det|>[[144, 325, 930, 455]]<|/det|> +1. Our proposed connectivity-based decoding makes use of the precise localization and connectivity profile of the implanted electrodes. +2. Training data from all previous training-cohort patients related to this connectivity profile are utilized. +3. Any setup required for electrophysiological signal acquisition and model training could be omitted. + +<|ref|>text<|/ref|><|det|>[[115, 483, 930, 523]]<|/det|> +Beyond these points that the reviewer picked up, we would also like to highlight other aspects of novelty in the present article: + +<|ref|>text<|/ref|><|det|>[[114, 550, 930, 884]]<|/det|> +We have extended the combined neurophysiology and connectomics approach beyond the motor domain, applying it to patients undergoing deep brain stimulation (DBS) for major depressive disorder. We show that in these patients, perceived emotions can be decoded within 600 milliseconds from cortical regions targeted by neuromodulation, using brain signal waveform shape features that have never before been utilized for decoding. This underscores the value of linking novel neurophysiological measures and connectomics for brain circuit discovery, as we identify the optimal decoding network in the left prefrontal cortex, a region previously recognized as crucial for successful depression treatment with neuromodulation. Additionally, we demonstrate that our approach can directly suggest device parameters to optimize seizure detection in currently available implantable responsive neurostimulators for epilepsy. The key advancement here is the use of machine learning algorithms that simulate an implantable device by constraining model parameters to the specific capabilities of the implant. Thus, we show that our innovations can propose targeted improvements for patients already equipped with invasive brain stimulation devices. This bridges the gap between experimental breakthroughs and real- world clinical treatments, highlighting the applicability of our approach to routine clinical care. + +<|ref|>text<|/ref|><|det|>[[115, 912, 222, 928]]<|/det|> +Major issues + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 931, 334]]<|/det|> +1. The central theme of the paper, the connectivity-based decoding, is still not explained clearly enough to understand. The additional supplementary figures help slightly, but they still dance around, and gloss over, the main concerns I had previously – the "connectivity values", correlation of them with "decoding performance (what is this??)", and "optimal decoding map" are not clearly defined. SF4 shows correlations with 1000 functional connections – does this mean they are averaged over all participants? What does decoding performance for a single electrode mean? Does that mean you're building single-channel decoders? If not, this does not make sense. And how are you correlating one value with a connectivity map (which is a whole vector for a single electrode)? SF5.c similarly needs much clearer explanation. (What is a connectivity template? What are R1-R6? What is being correlated with what?) This needs much better explanation if you want people to understand how to use it. Examples would help. + +<|ref|>text<|/ref|><|det|>[[114, 359, 931, 491]]<|/det|> +We are very thankful for this important point. We have now significantly improved the description of this complex approach, now listing all required steps in sequence and explaining each term in detail in the "Connectomics- based neural decoding section" of the methods. We also want to highlight that all the required steps can be reproduced computationally through provided tutorials on the GitHub documentation page: https://neuromodulation.github.io/py_neuromodulation/index.html, which we also list in the respective methods section: + +<|ref|>text<|/ref|><|det|>[[144, 517, 930, 900]]<|/det|> +1. A connectome is required that contains resting state fMRI recordings (time-series of whole-brain blood oxygenation dependent [BOLD] activation). This connectome should be registered to a standard space such as MNI nonlinear 2009b. +2. For invasive electrophysiological recordings, the recording contact locations need to be estimated in the same space (MNI). This requires normalization to an imaging standard space, co-registration of pre-operative MRI and post-operative CT images, brain-shift correction and subsequent annotation of the recording contact artifacts to obtain the standardized recording contact locations. +3. The location of each recording contact is then used as a region-of-interest (ROI), for which traditional resting state fMRI connectivity (Pearson correlation of BOLD time – series) is computed to all voxels in the brain, repeated for each of the subjects in the connectome (for example \(n = 1000\) in the Human Connectome Project data) and then averaged. +4. This results in a normative "whole-brain connectivity fingerprint" (Supplementary Figure 5a) for each recording contact, with each voxel indicating how strongly connected (or temporally correlated as defined for resting state fMRI connectivity) it is on average to the location of the recording contact. E.g. if the recording contact is residing over the right motor cortex, typically the left motor cortex will show high connectivity values, while other regions, such as the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 68, 930, 107]]<|/det|> +occipital cortex, will show lower connectivity values, because their BOLD time- series are on average less correlated. + +<|ref|>text<|/ref|><|det|>[[146, 113, 932, 310]]<|/det|> +5. These "whole-brain connectivity fingerprints" can then be subjected to voxel-wise correlations with the single-channel decoding performance across all available recording contacts to identify the "optimal connectivity map". E.g. if one recording location is in motor cortex and has a high movement decoding performance while other recording locations are scattered in different areas with lower decoding performances, subjecting these to voxel-wise correlations will yield a whole-brain map of correlation values that resembles the connectivity profile of the motor cortex. The "optimal connectivity map" is thus defined as the map derived from voxel-wise correlations of resting-state fMRI connectivity with single-channel decoding performance across all "whole-brain connectivity fingerprints". + +<|ref|>text<|/ref|><|det|>[[146, 315, 932, 468]]<|/det|> +6. Finally, when aiming to estimate the decoding performance of a specific recording location, it is now possible to assess the spatial similarity (mathematically defined as vectorized correlation across voxels) between the "whole-brain connectivity fingerprint" of the respective location, with the "optimal decoding map". A fingerprint that has a spatial pattern similar to the "optimal decoding map", will likely provide good decoding results, while a spatially dissimilar fingerprint will likely indicate that the recording contact location does not yield high decoding performance. + +<|ref|>text<|/ref|><|det|>[[146, 473, 932, 602]]<|/det|> +7. For the purpose of selecting the best available recording contact location available within a set of contacts for each subject, these estimated performances can be compared ((termed R1 to R6 in Supplementary Figure 5c) and the one with the highest performance can be chosen for across-patient decoding. Signals or features are therefore not projected or altered and only a single channel is selected for decoding based on the connectivity performance estimation. + +<|ref|>text<|/ref|><|det|>[[146, 608, 932, 738]]<|/det|> +8. Importantly, when using this approach for across-patient decoding in previously recorded subjects, the true test-set performance must be void of circularities and thus the subject/recording contact to be tested must be left out of the definition of the "optimal decoding map". Once, the "optimal decoding map" is defined from a cohort, it can be prospectively applied for channel selection in a new subject, as performed in prospective validation cases in the present manuscript. + +<|ref|>text<|/ref|><|det|>[[146, 766, 930, 829]]<|/det|> +We want to highlight in addition that the required steps can be reproduced computationally according to the provided tutorials on the GitHub documentation page: https://neuromodulation.github.io/py_neuromodulation/index.html. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 70, 880, 655]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 657, 930, 924]]<|/det|> +Supplementary fig. 5 Connectomics- based neural decoding without patient- individual training. (a) Estimation of a patient- individual "fingerprint". For each electrode location, the Region of Interest (ROI) is estimated to identify voxels surrounding the location of the recording contact. The connectivity (e.g. fMRI BOLD correlation) between the ROI voxels to all other voxels is estimated. This correlation brain map is called "fingerprint" and represents the brain- wide connectivity of that recording contact. (b) Construction of the neural decoding connectivity map: Connectivity values of the "fingerprint" profiles are correlated for each voxel with the machine learning based brain signal decoding performances, resulting in a connectivity template associated with optimal decoding performance. (c) For neural decoding of a novel out- of- cohort subject, the connectivity "fingerprint" of each recording contact is retrieved based on its' MNI coordinates and the contact fingerprint that shows the highest spatial correlation with the connectivity template associated with optimal decoding performance, is then selected for machine learning (d) model prediction without patient- individual training. Nomenclature: "Whole- brain connectivity fingerprint": Time- series correlation of a specific recording contact location to all other brain voxels in a fMRI resting state connectome. "Machine learning decoding performances": Single- channel machine learning performances from a supervised neural decoding problem such as movement classification. "Optimal decoding map": Correlation map computed from voxel- wise whole- brain connectivity fingerprints and machine learning decoding performances. Each voxel therefore represents the correlation between fMRI resting state connectivity for this specific region and the respective neural decoding performances. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[120, 90, 931, 266]]<|/det|> +2. The performance, especially across cohorts, and ability to extrapolate to new patients, is somewhat oversold in this paper, even if this performance is substantially better than previous studies. In particular, when the leave-one-cohort-out accuracy is barely above chance ( \(\sim 0.6\) ), it suggests that even subtle differences in movement types will lead to poor decoder performance across patients. That would seem to not be very practical for a patient wanting to do many different types of movement, and thus "plug & play" would not work very well. Even \(\sim 80\%\) accuracy is highly unlikely to be good enough for most patients – think about how frustrated you would be if your computer cursor did not work correctly 2/10 times. + +<|ref|>text<|/ref|><|det|>[[113, 288, 931, 855]]<|/det|> +We agree with the reviewer that we should aim to further increase all performances, which is our primary research mission for the coming years. However, we would like to comment in a bit more detail on the specific points the reviewer raises. The reviewer mentions that low across- cohort performance could reflect low generalization across movement types. However, the deterioration of across- cohort- performance is in our view not solely attributable to differences in movement task. In addition, entirely different hardware, including implantation procedure, implanted electrodes, patient states, neurological disorders may contribute to relatively lower decoding performance. As it stands, our report remains the first to ever demonstrate that decoding across- patients with such widely varying factors is possible at above- chance level. Nevertheless, the reviewer is absolutely right that this performance is low. With regard to the second point, that \(80\%\) performance may not be sufficient, we believe that it strongly depends on the purpose. Yes, not being able to move a cursor 2/10 times would be frustrating but we would like to provide a scenario more closely linked to the study at hand. E.g. for the treatment of essential tremor (ET) patients deep brain stimulation is only required during voluntary movement, because ET is defined by action tremor. Currently, DBS is always turned on, even if the patient doesn't move, because closed- loop therapies do not exist yet. Meanwhile, it is well- known that overstimulation leads to side- effects such as ataxia and gait impairment. Thus, for this purpose a classifier with \(80\%\) accuracy, biased to a high true- negative rate, while accepting a high false- positive rate, will significantly improve the treatment, leading to less overstimulation and consequently less side- effects. Thus, such a low- accuracy decoder could clinically meaningfully benefit more than 50,000 people implanted with DBS for essential tremor. This demonstrates how fruitful the merging of closed- loop neuromodulation and BCI research could be. Nevertheless, we agree with the reviewer that we should remind the readers that there is a lot of room for improvement and that our current results will not stand as the highest- ranking performance. Indeed, it is our aim to inspire more BCI experts to help improve the clinical realm of closed- loop neuromodulation. We now discuss the point of low decoding performances in the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 878, 929, 919]]<|/det|> +We specifically want to highlight here also the limitation that the presented leave one subject out and leave one cohort out performances motivate the investigation of neural decoding improvements. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 68, 928, 108]]<|/det|> +Clinical implementation for closed- loop neuromodulation would require higher decoding accuracies to reliably address current neural states and symptoms. + +<|ref|>text<|/ref|><|det|>[[115, 134, 930, 221]]<|/det|> +3. The revised paper still leans too heavily on the term BCI. The BCI society's working definition was not intended to include closed-loop DBS as a BCI. While philosophically clDBS could fit in this definition, the vast majority of BCI researchers do not consider it to be a BCI, and doing so could cause a host of logistical issues. Not to mention confusing many non-experts. + +<|ref|>text<|/ref|><|det|>[[114, 245, 931, 808]]<|/det|> +The reviewer is clearly a BCI expert and our research team is predominantly working in the field of neuromodulation, rather new to the BCI community. We believe that the many relevant comments from the reviewer demonstrate the mutual interest in each others research and that there is increasing overlap in the questions we aim to address. Our research is very strongly inspired by all the important pioneering work of BCI engineers in the past decades. Indeed, without it, we would be very unlikely to even come up with the idea of using brain signal decoders to advance closed- loop neuromodulation. We believe that the merging of these two fields is a very exciting development, which has cast enthusiasm in recent articles. In fact, that this BCI expert reviewer was chosen to scrutinize our paper is indeed a hint that we are working in a field that now strongly overlaps. This development was recently formalized in an impactful review article titled "The convergence of neuromodulation and brain- computer interfaces" (Herron et al 2024, Nature Reviews Bioengineering). The authors stated that the neuromodulation and BCI fields "[...] can inform each other, and as the technological overlap increases, the distinction between neuromodulation and BCI becomes increasingly irrelevant" (Herron et al 2024). Instead of confusing people, we would like to invite BCI experts and curious students to the opportunities that closed- loop neuromodulation provides for improving patient lives using approaches that have been pioneered by BCI researchers. With the present article it is our dedicated wish to introduce BCI methodology for clinical neuromodulation research. We are not alone with this. In fact, previous research already used the term BCI to describe a closed- loop DBS system: "Cortical brain- computer interface for closed- loop deep brain stimulation" (Herron et al 2017, IEEE Transactions on Neural Systems and Rehabilitation Engineering). We personally build on these examples that invite experts from different fields to work together and that have inspired us to follow this path. Nevertheless, we respect the reviewers opinion and thus have now removed or rephrased paragraphs that mention brain computer interfaces without explicitly stating that this merging of fields is a new development. Most prominently, the first sentence of the abstract now reads: + +<|ref|>text<|/ref|><|det|>[[115, 834, 930, 874]]<|/det|> +"Brain computer interface research can inspire closed- loop neuromodulation therapies, promising an unprecedented spatiotemporal precision for the treatment of brain disorders." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 68, 931, 355]]<|/det|> +4. Methods are still incomplete. The description of movement detection is better, but the performance description: "... balanced accuracy of \(0.8 / 0.98 \pm 0.07 / 0.04\) for single sample/movement detection" still could be clearer. Is the second value for the \(300 \text{ms consecutive "rate?"}\) If so, then state that more clearly. Also the following sentences are unclear: "A movement detection rate of 1 is achieved if this criterion is fulfilled within every movement block. It's important to note, however, that this measure addresses only the movement class and has no predictive value of rest segments." What does it mean to only "address the movement class"? It's a binary classification, so how is it not predicting rest vs movement? Or does this have something to do with the fact that there are now 3 bins and not all of them may be movement at that same time? Also is this balanced accuracy or not? If not, it should be, to make fair comparisons between 1 and 3-bin decoders and to avoid biases of too many false positives. Introducing a \(300 \text{ms delay (effectively)}\) to movement is also not trivial and is long enough that it could impair movement precision (due to feedback delays) for patients. This should be discussed. + +<|ref|>text<|/ref|><|det|>[[115, 383, 930, 446]]<|/det|> +We thank the reviewer for helping us to further improve the manuscript and pointing us to this inaccuracy. The reviewer did understand correctly and we have rephrased this sentence to make it more clear. It now reads: + +<|ref|>text<|/ref|><|det|>[[115, 473, 928, 491]]<|/det|> +"... balanced accuracy of \(0.8 \pm 0.07\) for single sample and a movement detection rate of \(0.98 \pm 0.04\) " + +<|ref|>text<|/ref|><|det|>[[115, 517, 930, 602]]<|/det|> +We believe that the reviewer has also understood the movement detection rate correctly. It is positive if 300 consecutive ms are predicted to be movement class, so in a way this is a 3- bin based classification within the movement class. The \(300 \text{ms delay}\) is a relevant limitation, which we now mention in the definition of the movement detection rate, which we have also further improved. + +<|ref|>text<|/ref|><|det|>[[115, 630, 930, 738]]<|/det|> +"Sample- wise performances were concatenated to establish a more coarse metric that allowed for detection of individual movement entities, termed movement detection rate and defined as \(300 \text{ms}\) of consecutive movement classification during actual motor performance. Note, that this movement detection rate measure has the significant limitation of requiring at least \(300 \text{ms}\) of time passing during the movement, before it can be positive, leading to potential delays for real- time applications." + +<|ref|>text<|/ref|><|det|>[[115, 765, 930, 920]]<|/det|> +5. "processing steps to mitigate DBS artifacts including bandpass filtering and period-based DBS artifact removal did not improve, but instead aggravated this deterioration" The fact that artifact removal significantly worsened decoding accuracy is a potentially significant issue. The point was not to improve accuracy; the point was to see that accuracy did not worsen with removal of artifacts, but in fact it did worsen in most cases. That is concerning that a good portion of your "movement" decoding was really artifact decoding. This could lead to false positives. This deserves much more discussion and tempering of conclusions than is currently in the paper. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 931, 424]]<|/det|> +We thank the reviewer for this remark. We have to clarify during the presented stimulation ON recordings for the artifact analysis shown in Figure 2 f+g, stimulation was switched on continuously as is clinical routine in all DBS patients. Traditionally DBS is turned on all the time at high frequencies. Thus, stimulation was in this artifact analysis not triggered based on movement decoding, but applied to investigate the potentially detrimental effect to signal quality without it having any temporal relationship to motor performance. We tested if movement classification performance increases when the continuous stimulation artifact was removed. We observed that by removing frequency bands affected by stimulation, or designing a filter that is intended to remove the time- series artifact (PARRM, Dastin- van Rijn et al 2023), movement- related electrophysiological characteristics are also removed and classification accuracy was reduced. In the following analysis (Figure 2 o+p) stimulation was indeed triggered by movement decoding. But stimulation was only switched on for a duration of 1 s after movement classification. For the subsequent samples stimulation could have triggered stimulation through a positive feedback loop. Nonetheless we did not observe that stimulation resulted in false positive movement classification. We have now further clarified this in the figure legend and results sections: + +<|ref|>text<|/ref|><|det|>[[115, 450, 930, 536]]<|/det|> +"Next and equally important, we show that continuous therapeutic electrical stimulation (130 Hz STNDBS) can significantly deteriorate sample- wise decoding in some but not all patients and that models trained separately for OFF and ON stimulation conditions outperform models trained on both conditions together." + +<|ref|>text<|/ref|><|det|>[[115, 541, 930, 604]]<|/det|> +"(g) Sample- wise performances OFF and ON chronic clinically effective subthalamic 130 Hz DBS in six PD patients from Berlin (all above 0.5 balanced accuracy chance; all p<0.05 for one- sample permutation tests)." + +<|ref|>text<|/ref|><|det|>[[115, 630, 930, 694]]<|/det|> +6. The sensory cortex issue is insufficiently addressed in the manuscript. This needs to be acknowledged in the discussion more clearly than talking about interplay of motor and sensory information vaguely. + +<|ref|>text<|/ref|><|det|>[[115, 720, 930, 760]]<|/det|> +We thank the reviewer for this suggestion and added now a section discussing the motor and sensory cortices: + +<|ref|>text<|/ref|><|det|>[[115, 788, 930, 896]]<|/det|> +"Electrode localizations were also spanning many cortical brain regions including sensory areas. Relatively high movement decoding performances were observed not only for motor, but also sensory cortex. There is potential that these performances are in part augmented through sensory information, which could be detrimental to closed- loop applications. Notably, the Berlin cohort performed self- initiated movements without sensory cues and yielded high decoding accuracies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 68, 930, 108]]<|/det|> +Nevertheless, it is important to note that not only motor but also sensory prediction or even sensory information stemming from adjustments to hand pressure may have affected the performances." + +<|ref|>text<|/ref|><|det|>[[115, 134, 930, 175]]<|/det|> +7. Statistical rigor (at least in reporting) is still lacking. Many results are still described as "above chance", sometimes with p values, without statistical methods described. + +<|ref|>text<|/ref|><|det|>[[115, 202, 930, 243]]<|/det|> +We thank the reviewer for this remark and added in addition to mentioning statistical significance also the permutation test described in the methods and 0.5 chance level: + +<|ref|>text<|/ref|><|det|>[[115, 270, 930, 310]]<|/det|> +"All statistical tests were computed using non- parametric Monte- Carlo sampled permutation tests with a significance value of \(\alpha = 0.05\) " + +<|ref|>text<|/ref|><|det|>[[115, 337, 930, 377]]<|/det|> +"Performance was above 0.5 chance level in every subject [...] (p<0.05, across subject one- sample permutation test)." + +<|ref|>text<|/ref|><|det|>[[115, 404, 930, 467]]<|/det|> +Figure 2g legend: "Sample- wise performances OFF and ON clinically effective subthalamic 130 Hz DBS in six PD patients from Berlin (all above 0.5 balanced accuracy; all p<0.05 for one- sample permutation tests)." + +<|ref|>text<|/ref|><|det|>[[115, 495, 930, 535]]<|/det|> +"Sample- wise performances were above 0.5 chance- level for all classifications [...] (all p<0.05 for one- sample permutation tests; Fig. 3d)." + +<|ref|>text<|/ref|><|det|>[[115, 562, 930, 602]]<|/det|> +Best channel performances showed above 0.5 chance classification emotion decoding across subjects (p<0.05 for one- sample permutation test). + +<|ref|>text<|/ref|><|det|>[[115, 629, 930, 692]]<|/det|> +8. The phrase that the correlation between decoding performance and BDI improvement "could be driven by optimal targeting rather than by depressive symptoms themselves..." is still opaque. What does this mean? + +<|ref|>text<|/ref|><|det|>[[115, 720, 931, 918]]<|/det|> +We thank the reviewer for pointing us to this lack of clarity. The correlation states that DBS was more effective in patients that had higher decoding performances. This more direct interpretation of this observation would be that patients in which decoding worked better, may have higher capacity for improvement, speculatively because their ability to perceive emotions is less impaired. With this interpretation the variability of therapeutic outcome and decoding performance is attributed to some inherent disease related factors of the patient. However, this interpretation disregards the fact that electrode location as a result of variance in "surgical" targeting can have significant impact on both therapeutic outcome and decoding performance. Thus, perhaps the electrode was not optimally placed in patients with worse outcome, and this coincides with worse decoding performances. Here, + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 37, 503, 55]]<|/det|> +## Revision of manuscript NBME-23-2026A + +<|ref|>text<|/ref|><|det|>[[116, 68, 930, 108]]<|/det|> +the variance is attributed to the surgical targeting. This second hypothesis is the one we favor. We have now adapted the text to make this more clear: + +<|ref|>text<|/ref|><|det|>[[116, 135, 930, 199]]<|/det|> +"The correlation could potentially be driven by differences in electrode localization stemming from natural variance in surgical targeting rather than by disease related factors, which inspired us to explore the underlying whole- brain networks." + +<|ref|>text<|/ref|><|det|>[[116, 248, 228, 265]]<|/det|> +Minor issues: + +<|ref|>text<|/ref|><|det|>[[116, 292, 930, 333]]<|/det|> +Regarding differentiating from other toolboxes – the first point about offline and online using the same routines is not unique – FieldTrip also enables this. + +<|ref|>text<|/ref|><|det|>[[116, 360, 904, 378]]<|/det|> +We thank the reviewer for this remark. We added the following section to the discussion section: + +<|ref|>text<|/ref|><|det|>[[116, 405, 930, 446]]<|/det|> +Therefore, offline and online signal processing are conducted using the exact same routines, by only replacing the data stream, similar to the Buffer implemented for FieldTrip in Matlab. + +<|ref|>text<|/ref|><|det|>[[116, 473, 928, 491]]<|/det|> +"Neuromedicine" is not a word. The more appropriate term seems to be neurology. + +<|ref|>text<|/ref|><|det|>[[116, 519, 250, 535]]<|/det|> +This now reads: + +<|ref|>text<|/ref|><|det|>[[116, 541, 930, 604]]<|/det|> +"The clinical neurosciences stand at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology." + +<|ref|>text<|/ref|><|det|>[[116, 631, 517, 649]]<|/det|> +Reviewer #3 (Report for the authors (Required)): + +<|ref|>text<|/ref|><|det|>[[116, 697, 928, 738]]<|/det|> +the authors have responded quite thoroughly to reviewer comments and improved the manuscript. my summary of the results is part of my initial review so is not reproduced here. + +<|ref|>text<|/ref|><|det|>[[116, 765, 911, 806]]<|/det|> +We thank the reviewer for their helpful and constructive feedback that substantially improved this manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 66, 230, 81]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 95, 930, 308]]<|/det|> +Reviewer #3:Reviewer: I begin by paraphrasing the authors' problem statement. Problem 1: modern approaches to neural decoding use modern ML algorithms, which are data hungry. Collecting enough data in patients is hard, and there is a dearth of frameworks to facilitate transfer learning between patients in low- data regimes. Problem 2: the authors want a framework to extract neural signals. Problem 3: most experiments record data from only small areas of the brain and fail to incorporate networks of neural activity that give rise to signals. To address all three issues, the authors describe a new software package. The claims are that the software package is (i) a real- time BCI platform, that (ii) implements multiple novel signal analysis processing methods, and (iii) implements a method for transfer- learning using anatomical and connectome data. They further motivate how their software package is useful with three real- world examples: transfer learning with ECoG recordings in patients undergoing DBS (and epilepsy monitoring, Fig 2); retrospective analysis of intracranial signals to predict findings in a study of DBS for depression (Fig 3); and retrospective analysis of data collected from RNS recordings (Fig 4). + +<|ref|>text<|/ref|><|det|>[[115, 315, 930, 462]]<|/det|> +Reply: We thank the reviewer for their expert assessment and the time they have taken to formulate constructive feedback while taking the aims of our study into account. Upon reflection of the reviewers' comments, we would formulate the key problem of our study as follows: Neuromodulation combined with machine learning offers a whole new world of possibilities for the treatment of brain disorders, but their joint application remains under- researched. We believe that this can in- part be attributed to the lack of demonstration of utility from researchers and lack of standardized tools to explore them. To address this, we demonstrate the clinical utility of machine learning based brain signal decoding for deep brain stimulation applications addressing multiple sub- aims, including the ones the reviewer has correctly identified. + +<|ref|>text<|/ref|><|det|>[[115, 470, 930, 617]]<|/det|> +We would like to point out that while the theoretical utility for machine learning in neuromodulation may be obvious, so far only very few studies have used brain signal decoding in the context of deep brain stimulation, all with varying methodologies, often requiring proprietary hardware that are not open to other researchers (for an overview see our review article on the topic https://doi.org/10.1016/j.expneurol.2022.113993). Most prominently, the Medtronic Nexus system and the Medtronic RC+S Summit, as well as the RNS Neuropace devices come to mind, which have facilitated the use of neural data for advanced control algorithms. But these devices and algorithms are entirely inaccessible outside of specific industry collaborations which are almost if not entirely inaccessible to centers outside the US. + +<|ref|>text<|/ref|><|det|>[[115, 625, 930, 854]]<|/det|> +We hope that the expert reviewer agrees with our vision and may even find it trivial to state that machine learning based brain signal decoding may prove useful and requires complex tools to advance invasive neurostimulation. We believe that our study provides novel and innovative analytic and methodological guidance as well as empirical evidence for the utility of machine learning based brain signal decoding to advance future closed- loop stimulation approaches, beyond the use of connectomes. We hope that the reviewer is equally excited about the unprecedented opportunities that arise from the combination of machine learning with closed- loop neurostimulation and that they can see the merit of our study for stakeholders such as DBS researchers, patients, neurotechnology companies and regulatory bodies beyond the more specific problem statements that the reviewer has identified above. An example that we are particularly proud of is the use of contrastive learning algorithms that our paper pioneers for the first time in human brain data, and for which it has been cited in the last issue of the journal Cell with the title "Decoding the Brain: From neural representations to mechanistic models" (Mathis MM et al., 2024 https://doi.org/10.1016/j.cell.2024.08.051). + +<|ref|>text<|/ref|><|det|>[[117, 863, 930, 928]]<|/det|> +Changes in manuscript: We have now tried to emphasize and clarify the overarching aim further through edits in the introduction: "However, to date only few studies have investigated the clinical utility of machine learning based brain signal decoding, especially in the field of invasive neuromodulation. ... In this paper, we aimed to a) highlight the clinical utility of brain signal decoding + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 38, 565, 58]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[115, 65, 928, 163]]<|/det|> +advances in a large cohort of patients across thousands of recording sources from invasive brain implants within three key areas of clinical neurotechnology innovation: movement disorders, psychiatry, and epilepsy; b) formalize and describe the methodology to achieve those advances in an open- source python software platform called py_neuromodulation; c) illustrate how the two biggest innovations in deep brain stimulation research of the past decade, namely DBS connectomics and adaptive DBS, can be combined to extend their clinical utility." + +<|ref|>text<|/ref|><|det|>[[115, 172, 928, 319]]<|/det|> +Reviewer: I am a neurosurgeon and I have previously published software packages in BCI methods, analysis of intracortical signals, and articles on RNS signal analysis. I am familiar with Dr. Horn's Lead DBS platform and have examined some of its methods in detail. In summary of my review to follow, I think this paper's broad appeal is the method that combines connectome information to assist with neural decoding in a low- data regime. As with many scientific ideas, it is both elegant and profound. By contrast, I think the framing of this paper through the lens of a software platform is a distraction. Below, I comment extensively on the framing of the authors' results and provide suggestions for further analyses that would further highlight the excitement and broad- scientific appeal. + +<|ref|>text<|/ref|><|det|>[[115, 327, 928, 490]]<|/det|> +Reply: We are very thankful that the editorial team has found an expert, who understands both the clinical and methodological challenges that we are trying to address. We take their suggestions for improvement very seriously and have now adapted the narrative of our paper according to their excellent remarks. We agree that the dichotomy of describing a toolbox vs. describing the utility through novel insights that can be gained, can be distracting. For reference, we have tried to take inspiration from similar descriptions that have achieved this, such as FOOOF (Donoghue, T., Haller, M., Peterson, E.J. et al. Parameterizing neural power spectra into periodic and aperiodic components. Nat Neurosci 23, 1655- 1665 (2020) https://doi.org/10.1038/s41593- 020- 00744- x). To address this point, we have now shifted the narrative to highlight the Toolbox aspect of our paper less and try to focus more on the conceptual advances. + +<|ref|>text<|/ref|><|det|>[[115, 498, 928, 710]]<|/det|> +1) Reviewer: A new method of transfer learning that uses imaging data (resting state fMRI and anatomical MRI) to boost intracranial neural decoding performance in low data regimes is compelling. To that end, I found Table 1, Fig 2l, and Fig 2m cool. I can record data from patients in the EMU and/or previous patients in the OR, and then use those recordings to learn hyperparameters for my decoder for a movement task in the OR for a new patient. By using CEBRA, you have now taught me that there exists a cross-person neural manifold for movement, informed by where I am physically recording on the brain (and how this part of the brain is connected to other parts, over multiple participants). But - the whole point of transfer learning in a neural decoding framework is to save time by priming a decoder with hyperparameters in a low-data regime. For instance, isn't the value of the approach obviated if it only takes two exemplars of movement (and movement onset) to get comparable decoding? Show us this is useful by plotting performance as a function of time for the participants, and especially the "real-time decoding" PD patient, to point out that decoding performance happens out of the box with your new method. + +<|ref|>text<|/ref|><|det|>[[115, 719, 928, 865]]<|/det|> +Reply: We are grateful and excited that the reviewer highlights the merit of combining connectomics with neural decoding. We now provide the suggested analysis, highlighting the relationship of saved recording time with number of subjects. Before delving into more detail, we would argue that not only patient recording time, but also expertise in neurophysiological recordings, machine learning engineering and clinical handling are significant barriers that would be surpassed by a plug & play decoder that does not require individual training. Thus, we believe that providing an open- source decoding model (which we publish openly for anyone to use: 10.5281/zenodo.10794370) provides a no- data solution that is conceptually far ahead of any approach that does require individual training, regardless of how short the training is. + +<|ref|>text<|/ref|><|det|>[[115, 874, 928, 923]]<|/det|> +Reviewer: In fact, the most compelling demonstration of the method would be to show that leveraging your approach would improve decoding further beyond what you would have achieved from just the data from that patient. In other words, demonstrate evidence that "For a real- world + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 38, 565, 57]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[116, 66, 928, 114]]<|/det|> +clinical application this means that every implant would need to undergo tedious model training sessions, which could be a burden to both patients and medical staff and may hinder a broad clinical adoption." + +<|ref|>text<|/ref|><|det|>[[115, 123, 928, 303]]<|/det|> +Reply: We are thankful for the enthusiasm and the excellent suggestion of the reviewer. The potential for superiority of pretrained models vs. individual training is exactly what we can show in the prospectively recruited patient, where the individual training session led to balanced accuracy performances of 0.67, while our generalizable model achieved 0.71. We have now followed the excellent suggestions and added a more specific analysis to further corroborate this by a) objectifying the amount of training data required to reach the same performance that our pretrained model reaches across all subjects using an iterative train- test split for each recording. In brief, the total recording time that can be saved with our model in our cohort was over 3 hours and 47 minutes. More importantly, upon further inspection of individual performances, we found that for 32% of the patients, our across- patient model performance surpassed the individual performance. This information is now added to the text and figure as follows. + +<|ref|>text<|/ref|><|det|>[[115, 312, 930, 410]]<|/det|> +Changes in manuscript: We have now replaced the previous panels (n) and (o) of Figure 2 (see below) and mentioned the findings in the main results section, which now reads: "We further tested for the time improvement of decoding without patient- individual training compared to individual training. Here, the cumulative individual training time reached 3 h 47min to reach leave one subject out performance across patients (Fig. 2n). For a subset of those patients (n=8) the individual training performance could not reach the across- patient decoding performance (Fig 2o)." + +<|ref|>image<|/ref|><|det|>[[115, 444, 890, 930]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 37, 565, 57]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[115, 65, 930, 540]]<|/det|> +Fig. 2: Movement decoding across patients, cohorts, diseases, movement types, and stimulation conditions. (a) Data from four cohorts with different diseases and movement types were used for decoding (1480 channels, 56 patients). (b) Individual recording locations with color- coded movement decoding classification performances. (c) Performances from patient individual 3- fold cross- validation. (d) Movement detection rates are defined as 300 ms consecutively correct classification during movement ( \(98 \pm 4\%\) for best channels across all patients). (e) In PD, mean channel performances negatively correlated with motor sign severity (UPDRS- III). (f) Exemplar time- series with DBS on ECoG raw data in a representative subject from the Berlin cohort. (g) Sample- wise performances OFF and ON chronic clinically effective subthalamic 130 Hz DBS in six PD patients from Berlin (all above 0.5 balanced accuracy; all \(p< 0.05\) for one- sample permutation tests). To demonstrate the utility of py_neuromodulation for across- patient decoding, three alternative pipelines integrate channel selection and neural signals: (h) Spatial interpolation to a common grid in MNI space; (i) channel selection based on normative fMRI connectivity correlation to a predefined optimal decoding network; (j) low- dimensional embedding (exemplar subject shown) derived from the model weights of non- linear decoder using contrastive learning with a convolutional neural network with CEBRA. (k) shows embedding consistency from each to every other patient via linear identifiability. All three methods achieved high decoding accuracies within and across cohorts for sample- wise balanced accuracy (l) and movement detection rates (m). CEBRA outperformed other methods as indicated by Bonferroni- corrected paired permutation tests. (n) Individual recording times shown as distinct colors of a bar plot indicating the cumulative invasive recording time of 3 h 47 min made obsolete by the generalizable movement decoder. o) For eight patients leave one subject out performances exceeded individual training performances shown as line plots indicating the relationship of recording time and final performance normalized to the generalizable across- patient decoder result (dashed vertical line). The color- coded learning curves show individual patient performances that never reached the across- patient result. To demonstrate the ability to decode movements without patient individual training, we prospectively recruited two subjects in Berlin and decoded movements using pretrained models based on all previous subjects of the Berlin cohort. (p) Real- time single trial decoding is shown for out- of- cohort patient 1 with y- axes depicting true measured analog rotameter movement amplitude (top), classification probability predictions without patient- individual training (middle) and predictions with training (bottom). For the second patient we tested movement- triggered stimulation and show the true movement traces (top), single trial movement predictions without patient- individual training (middle) and movement- triggered stimulation time (bottom). (q) Real- time performances are shown for both patients for decoding and stimulation. Above 0.5 chance balanced accuracy and movement detection rates were obtained despite presence of closed- loop neurostimulation and without model calibration. + +<|ref|>text<|/ref|><|det|>[[115, 547, 930, 725]]<|/det|> +2) Reviewer: Here's another way you could convince me this approach works: suppose that one of the PD patients implanted had abnormal cortical anatomy (which happens not infrequently). For this patient, supposed that I had an ECoG strip where I thought the contacts were on the pre- and post- central gyri (based on imaging), but using your transfer-learning approach I had missed by a gyrus, and had landed on the MFG and the pre-central gyrus instead. Could your approach convince me that I've made a mistake in identifying the anatomy? Placing ECoG strips in the OR through a burr-hole during DBS is a blind procedure and needs to be confirmed with an intra-operative spin (at least in my hands), which is time-consuming and exposes the patient to radiation (which is challenging to justify if the research program itself is motivated through a non-significant-risk patient consent). Can your system save time for optimizing ECoG placement by providing an ongoing estimate of where the ECoG is likely located on the brain? + +<|ref|>text<|/ref|><|det|>[[117, 733, 928, 799]]<|/det|> +Reply: The reviewer makes an excellent and creative point, that we did even consider before. Indeed, the alignment of the embedding could be used to verify "network affiliation" with the optimal decoding network at the individual level. We demonstrate how performance and embedding consistency relate to anatomy and optimal decoding network in an exemplar patient: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 66, 911, 350]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 359, 930, 477]]<|/det|> +
Revision Figure 1: Correlation of decoding performances and embedding consistencies. a) Optimal functional connectivity is shown computed based on training data subjects. b) For an exemplar patient (Berlin subject 008), leave-one-patient out cross validation performances were computed. For each test-subject channel, the embeddings were computed given the training data CEBRA non-linear encoding model. The embedding correlations of each channel and the training data is color-coded for the test patients' channels. The embedding consistencies were computed by correlating the training data embedding by other patients' optimal decoding connectivity channels and the left-out test patient embeddings. c) A significant correlation could be found between left-out decoding performances and channel-individual embedding correlations.
+ +<|ref|>text<|/ref|><|det|>[[115, 486, 930, 566]]<|/det|> +However, to truly demonstrate that this could serve for anomaly detection, we would have to verify that in cases where anomalies are present, optimally imaging the individual fMRI networks. We will definitely study this, when the opportunity arises. In the given cohorts however, there were no such anomalies and thus, we decided to provide this concept as an outlook instead of taking it into the results section. + +<|ref|>text<|/ref|><|det|>[[115, 576, 930, 625]]<|/det|> +Changes in manuscript: The discussion now reads: "An additional use- case for this approach in the future, could be to use the embedding consistency as an anatomical circuit verification, which could help identify anatomical anomalies and locate the correct optimal localization for decoding." + +<|ref|>text<|/ref|><|det|>[[115, 634, 930, 780]]<|/det|> +3) Reviewer: The most compelling part of Fig. 3 is the utilization of the image-registration method incorporating connectome information that allows you to perform out-of-patient prediction for optimal electrode selection, which in turn has direct clinical relevance. This is a beautiful story. You showed me that the connectome method was predictive of decoding performance. This story could perhaps culminate in you telling the reader that this post-hoc information predicted that the contacts were correctly or incorrectly chosen for each patient, and then making suggestions that correctly choosing the right electrode would have had a tangible clinical impact. Also, the "sweet spot" in Fig 3h is covered by the left hemisphere, and I can't see the cingulate (unless I misunderstood, and Fox 2014 stimulated the DLPFC?). + +<|ref|>text<|/ref|><|det|>[[115, 790, 930, 919]]<|/det|> +Reply: We thank the reviewer for this important remark. To address this comment thoroughly, we should note that stimulation was applied in a monopolar fashion, bilaterally (as depicted in Figure 3b). Contrary to this monopolar stimulation, all channels were recorded in a hardware bipolar montage (channels 0- 1, 1- 2, 2- 3 and 3- 0), a choice made at the time- point of experiment, which prioritizes signal fidelity over flexibility in post- hoc localization. Therefore, a direct comparison of recording and stimulation channel is not straightforward, as each stimulation channel occurs in two recording channels. To still give a direct reply to the reviewers question, we investigated if the stimulation contacts were present in the best bipolar recording channels. Indeed, in all eight patients + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 66, 930, 294]]<|/det|> +the stimulation contact matched at least one channel of highest decoding performance (Chi- Square Test \(p< 0.05\) ). Given the uncertain relationship of monopolar stimulation and bipolar recording electrodes we however believe that this is not easily interpretable which is why we have decided not to include this result in the main text. Similarly, we felt that making any unsubstantiated claims about contacts being chosen wrongly in the clinical trial is beyond our comfort zone given the data at hand. Instead, we have added this notion to the discussion. To add to the last point, the noted "sweet spot" is indeed a cortical transcranial magnetic stimulation "sweet spot" in the dorsolateral prefrontal cortex, we are sorry for not making this more clear. We have now completely reworked that part of the figure, also fixing a visualization issue of panel h that we noticed through the revision. We further extended this depiction and now added all dorsolateral prefrontal cortex targets identified in Fox et al 2012 "Efficacy of transcranial magnetic stimulation targets for depression is related to intrinsic functional connectivity with the subgenual cingulate": EEG F3 Herwig et al 2003, Average 5cm Herbsman 2009, Rajkowska et al 1995 BA9, Paus et al 2001 / Cho et al 2009, Rusjan et al 2010, Fitzgerald et al 2009. + +<|ref|>text<|/ref|><|det|>[[117, 303, 617, 320]]<|/det|> +Changes in manuscript: The revised figure is shown below: + +<|ref|>text<|/ref|><|det|>[[115, 715, 930, 923]]<|/det|> +Fig. 3: Emotion decoding using LFP signals from subgenual cingulate cortex in patients with treatment- resistant depression. Eight subjects undergoing DBS surgery performed an emotion task (a) with visual stimuli of negative, neutral, and positive valence. Electrode locations are visualized alongside the anterior- (red and light blue) and subcallosal cingulate cortex (white and dark blue, Harvard- Oxford atlas28). Balanced decoding accuracies (c) rose from 150 ms after onset, peaked at 600 ms and decayed until 1600 ms post stimulus. Best channel performances showed above 0.5 chance (permutation test) emotion decoding across subjects (all \(p< 0.05\) ). (e) Best performance channels revealed highest feature importances for FFT gamma features followed by different temporal waveform shape features. (f) Best performances correlated with DBS induced Beck Depression Inventory (BDI) changes 24 months following DBS implantation (rho=0.79, \(p = 0.01\) ). Performances were, however, not significantly correlated to baseline BDI scores. (g) Significant fiber- tracks, FDR (False Discovery Rate) corrected with \(\alpha = 0.05\) , predicting emotional state decoding performances showed a clear relation to the left prefrontal cortex. This is reflected in functional and structural connectivity for all patient channels and particularly visible for fiber filtering (g) and fMRI maps (h). Transcranial magnetic stimulation targets from Fox et al 2014 are additionally displayed29: EEG F3 Herwig 200330, Average 5cm + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 38, 565, 58]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[117, 64, 930, 111]]<|/det|> +Herbsman \(2009^{31}\) , Rajkowska 1995 BA \(9^{32}\) , Paus 2001 / Cho \(2009^{33,34}\) , Rusjan \(2010^{35}\) , Fitzgerald \(2009^{36}\) , Rajkowska 1995 BA \(46^{32}\) . All three connectivity models (fMRI, dMRI, fiber filtering) could cross- predict left out channel decoding performances (supplementary fig. 6,7). + +<|ref|>text<|/ref|><|det|>[[117, 120, 930, 168]]<|/det|> +The discussion now reads: "In the future, clinical testing in patients with major depressive disorder could aim to confirm the left centric network by comparing clinical efficacy of right vs. left contacts and their relationship to the prefrontal network." + +<|ref|>text<|/ref|><|det|>[[115, 178, 930, 518]]<|/det|> +4) Reviewer: Describing this paper as a real-time BCI platform is a distraction. To start, I'm not sure we agree as to what real-time means. Most people think that real-time means that there are deterministic bounds on program cycle execution and OS context switches. So, to make the claim that this system is real-time, you must do the following: (1) put bounds of performance by examining jitter and latency - I suspect this will be hard, because I assume the platform is designed to run in Windows (since I find .bat files in the github code) and as far as I know, Windows doesn't provide soft real-time guarantees; (2) characterize how long the system can run before you run out of memory (unless you've solved this issue by writing drivers that move data from memory to disk in a way that doesn't interrupt data flow); and (3) characterize real-time performance as a function of algorithm complexity and channel count (i.e., beyond a handful of channels and a binary classification problem). These would be the minimum requirements before I would re-engage with this claim. However, I would further argue that if you now want to sell a real-time software package as a high-impact publication in 2024, then you're obliged to do much more: (1) ensure that it works in multiple operating systems, (2) account for multiple languages (python is exciting right now, but matlab was exciting a decade ago), (3) have hooks to plug into multiple open source frameworks (like neurodata without borders), (4) have plans for long-term maintenance and naming conventions for code, (5) demonstrate that the system works outside of a small group of collaborating neuroscience labs, etc. In summary, I strongly disagree with your claim that py_neuromodulation is a "...toolkit for invasive brain signal decoding for closed-loop neuromodulation that emphasizes rigorous real-time compatibility and reproducibility." This is an unsubstantiated claim. Please deemphasize this claim in the paper. + +<|ref|>text<|/ref|><|det|>[[115, 527, 930, 737]]<|/det|> +Reply: We thank the reviewer for this important point. We understand that our use of the wording was inaccurate. We aimed to describe that previously recorded datasets are handled in precisely the same way as data that are live- streamed from a neural signal processor. In many previous "offline" decoding studies, pre- processing steps are performed which are not compatible with prospective decoding, such as artifact rejection, non- causal filtering, time- frequency transformation and z- score normalization across a whole recording. This can lead to data- leakage and inflated signal to noise ratio estimates that overestimate machine learning performance evaluation for real world applications. By using the same data processing routines and only exchanging the data source, we circumvent this problem and process the data in an "online compatible" manner. Before going into more detail about performance and testing below, we understand the confusion that arose from this phrase and exchanged the "real- time" with "online" further explaining that we mean that the data are decoded as they are streamed from a patients' brain. We remain open to alternative suggestions by the expert reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 747, 930, 925]]<|/det|> +Regarding the other more specific points, we would like to highlight that py_neuromodulation implements a dataflow that builds on top of Python's multiprocessing module, where raw data acquisition, feature computation, decoding and visualization are parallelized and multiprocessing queues used for inter- process communication. We continuously tested the integration of data streams using LabStreamingLayer and the required feature computation time on latest Windows, MacOS and Ubuntu operating systems using GitHub's automatic workflow testing. Given the basic GitHub Workflow Linux runners (4 CPU's, 16 GB RAM, https://docs.github.com/en/actions/using- github- hosted- runners/using- github- hosted- runners/about- github- hosted- runners, state October 2024) hardware, the documentation hosts automatic timing estimation (https://neuromodulation.github.io/py_neuromodulation/auto_examples/plot 6 real time demo.ht ml). We found that the FFT feature estimation including common- average re- referencing and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 65, 930, 180]]<|/det|> +standard- scale feature normalization could be achieved for a six channel data batch in 1 ms. When more complex features are included, such as temporal waveform shape and burst features, the computation time is 3 ms for a single channel. In our experience, those timings are sufficient for many decoding applications, such as movement or tremor classification. This information is now added to the methods section. Notably, timing jitters for adaptive deep brain stimulation can additionally be dependent on external stimulator communication. For example, the neurostimulator used in our setup can cause a delay of approximately 10 ms to activate stimulation via an API call. + +<|ref|>text<|/ref|><|det|>[[115, 189, 930, 319]]<|/det|> +For py_neuromodulation we emphasize computation speed and continuously optimize preprocessing and feature estimation routines. We already perform multiple experiments relying on its' online feature estimation and decoding capabilities. On our hardware (TMSi SAGA amplifier, AlphaOmega NeuroOmega stimulator, Lenovo Thinkpad T14 Gen3 with Windows 11) we robustly run decoding and adaptive stimulation applications with a stimulation update rate of 100 ms. As a reference, we would like to highlight that the fastest update rate used in the arguably most cutting edge aDBS paper (Oehrn et al., Nature medicine 2024) was as slow as 10,000 ms, with the average update rate reported to be 21,250 ms. + +<|ref|>text<|/ref|><|det|>[[115, 328, 930, 377]]<|/det|> +With regard to maintenance of the code, we are lucky to have dedicated development funding that allows us to invest time and effort into continuous improvement and support for at least another four years. + +<|ref|>text<|/ref|><|det|>[[115, 385, 930, 550]]<|/det|> +In reply to the notion that a tool published in a high- impact paper should not rely solely on python, we believe that we should simply work with what works. Apart from that we would like to point out that many of the highest impact toolkits are published as solely available in Python (e.g. Deep Lab Cut Lauer, J., Zhou, M., Ye, S. et al. Multi- animal pose estimation, identification and tracking with DeepLabCut. Nat Methods 19, 496- 504 (2022). https://doi.org/10.1038/s41592- 022- 01443- 0, FOOOF Donoghue, T., Haller, M., Peterson, E.J. et al. Parameterizing neural power spectra into periodic and aperiodic components. Nat Neurosci 23, 1655- 1665 (2020). https://doi.org/10.1038/s41593- 020- 00744- x and DPAD Sani, O.G., Abbaspourazad, H., Wong, Y.T. et al. Modeling behaviorally relevant neural dynamics enabled by preferential subspace identification. Nat Neurosci 24, 140- 149 (2021). https://doi.org/10.1038/s41593- 020- 00733- 0) + +<|ref|>text<|/ref|><|det|>[[115, 558, 930, 672]]<|/det|> +Nevertheless, we fully agree that despite five years of joint NIH/BMBF funding and dedicated development, there is still a lot of room for development of the toolbox, which is why we have decided to de- emphasize the toolbox aspect throughout the narrative of the paper. In fact, emphasizing the toolbox was one of the previous reviewers' suggestions. We hope that we have now struck a middle ground that provides both conceptual advances and how they are integrated in the code that we provide, as we still believe that sharing the methods in an open manner is a positive aspect of our paper. + +<|ref|>text<|/ref|><|det|>[[115, 680, 930, 763]]<|/det|> +Changes in manuscript: In addition to many smaller edits and changes throughout the text, we have removed the cited claim "While all these tools contain valuable and extensive methods for electrophysiological data analysis, we would like to point out key aspects of py_neuromodulation that uniquely positions it as a toolkit for invasive brain signal decoding for closed- loop neuromodulation that emphasizes rigorous real- time compatibility and reproducibility." from the text. + +<|ref|>text<|/ref|><|det|>[[115, 771, 930, 804]]<|/det|> +Additionally, we added a "Feature computation using multiprocessing" section to the methods highlighting the feature estimation speed of py_neuromodulation: + +<|ref|>text<|/ref|><|det|>[[115, 812, 930, 928]]<|/det|> +"Py_neuromodulation implements a dataflow that builds on top of Python's multiprocessing module, where raw data acquisition, feature computation, decoding and visualization are parallelized and multiprocessing queues used for inter- process communication. The integration of data streams using LabStreamingLayer and the required feature computation time was tested on Windows, MacOS and Ubuntu operating systems using GitHub automatic workflow testing. Given the basic GitHub Workflow Linux runners (4 CPU's, 16 GB RAM, https://docs.github.com/en/actions/using- github- hosted- runners/using- github- hosted- runners/about- github- hosted- runners, state October 2024) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 66, 930, 179]]<|/det|> +hardware, the documentation hosts automatic timing estimation (https://neuromodulation.github.io/py_neuromodulation/auto_examples/plot_6_real_time_demo.html). We found that the FFT feature estimation including common-average re-referencing and standard-scale feature normalization could be achieved for a six channel data batch in 1 ms. When more complex features are included, such as temporal waveform shape and burst features, the computation time is 3 ms for a single channel. Notably, timing jitters for adaptive deep brain stimulation can additionally be dependent on external stimulator communication." + +<|ref|>text<|/ref|><|det|>[[115, 213, 930, 295]]<|/det|> +5) Reviewer: I find this sentence problematic: "... a unique and novel feature set that included temporal waveform features, such as discharge prominence, sharpness, decay and rise time, and peak and trough interval in addition to traditional oscillatory FFT features." Is the authors' claim that the peak and troughs-based analysis of local field potentials has never been described before? If you believe this is true, then how have you yourselves characterized these features? + +<|ref|>text<|/ref|><|det|>[[115, 304, 930, 418]]<|/det|> +Reply: We are sorry for the confusion and want to be clear that we absolutely do not claim that these analyses have not been described before. We are sorry this was not clearly communicated in our manuscript. The neurophysiological importance of these features has been studied intensively, most prominently by the group of Bradley Voytek who provide an excellent and highly cited review article on their origin and relevance (Scott R. Cole, Bradley Voytek, Brain Oscillations and the Importance of Waveform Shape, Trends in Cognitive Sciences, Volume 21, Issue 2, 2017, Pages 137- 149, https://doi.org/10.1016/j.tics.2016.12.008). + +<|ref|>text<|/ref|><|det|>[[115, 427, 930, 494]]<|/det|> +What we do claim is that these analyses have not been used for machine learning based brain signal decoding before and that no toolkit for decoding offers the usage of these important neurophysiological features. We now make this clearer in the manuscript. We also would like to point out that this is indeed another novelty beyond the use of contrastive learning and connectomics. + +<|ref|>text<|/ref|><|det|>[[115, 502, 928, 535]]<|/det|> +Reviewer: What's the electrophysiological relevance of these features that teaches us something new about the brain? + +<|ref|>text<|/ref|><|det|>[[115, 544, 930, 641]]<|/det|> +Reply: The abovementioned review article on the importance of waveform shape offers a fresh perspective in neurophysiology by capturing nuanced aspects of neural oscillations that traditional measures often overlook (https://doi.org/10.1016/j.tics.2016.12.008). Typically, neural oscillations are analyzed by examining their frequency, power, and phase. However, waveform shape features—like asymmetry, steepness, and sharpness—add an extra layer of information that reveals underlying neurophysiological processes with greater specificity. + +<|ref|>text<|/ref|><|det|>[[115, 650, 930, 814]]<|/det|> +Waveform shape features can reflect underlying synaptic and cellular dynamics that frequency or power alone cannot capture. For example, the sharpness or steepness of oscillatory peaks may indicate synaptic synchrony or the dynamics of inhibitory versus excitatory activity within a network at millisecond temporal scale. These features can also reveal the balance of cortical excitability and inhibition, potentially offering insights into disease states. In disorders like epilepsy or Parkinson's disease, waveform shape deviations could signal pathophysiological changes, providing novel pathways for neurophysiological monitoring (e.g. see https://doi.org/10.1523/JNEUROSCI.2208- 16.2017, https://doi.org/10.1523/JNEURO.0151- 19.2019, https://doi.org/10.1523/JNEUROSCI.1996- 19.2020 and https://doi.org/10.1016/j.expneurol.2022.114089). + +<|ref|>text<|/ref|><|det|>[[115, 823, 930, 903]]<|/det|> +Reviewer: Why would these metrics have broad appeal, and why would I as a biomedical engineer know which to pick? In summary, if the main claim of the paper is that these spike wave forms are novel and interesting and useful, then they have been insufficiently characterized to be relevant to a broad scientific audience. In my opinion, characterizing these in detail is a paper into itself, and shouldn't be conflated with the main compelling scientific idea. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 38, 565, 58]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[116, 65, 930, 196]]<|/det|> +Reply: As highlighted above, we believe that the notion that these features have not been studied or are insufficiently characterized is a misunderstanding. Many more basic neuroscience investigations and some clinical studies (of which we cited four on PD alone above) have indeed reported the relevance of these metrics, with some of them even discussing their potential utility for disease monitoring. However, they have never been used for brain signal decoding in the context of invasive neuromodulation, despite having broad appeal, as they offer a way to quantify subtle changes in brain states with sensitivity to cellular and circuit- level dynamics while being extracted from the same recordings that we use to extract oscillations, meaning they are directly accessible. + +<|ref|>text<|/ref|><|det|>[[116, 206, 930, 368]]<|/det|> +What we aim to communicate with our application of these waveform features is that they may prove useful for biomedical engineers the design and optimization of brain- machine interfaces or neural signal processing algorithms used in invasive neuromodulation. Knowing which features to select depends on the specific brain states or disorders you're studying and the type of signals you're working with. For example: Peak Sharpness can be important for detecting seizure onsets or assessing synaptic excitability. Symmetry can be relevant for tracking oscillatory dynamics in sleep or anesthesia, as well as disease conditions affecting cortical oscillations, such as Parkinson's disease. In many other use- cases or conditions, these features have not yet been explored, and we believe that providing biomedical engineers with a data- driven way to discover their utility is exactly what is required at this point and what we achieve with the present publication. + +<|ref|>text<|/ref|><|det|>[[116, 377, 930, 652]]<|/det|> +Changes in manuscript: We added the following in the Introduction section: "Current advances in basic neuroscience have revealed the presence of complex brain signal features such as waveform shape and aperiodic activity as markers of synaptic synchrony and balance of excitatory and inhibitory modulation (Cole and Voytek 2017, Donoghue et al 2020), but standardized methods to extract them for machine learning applications are lacking." Furthermore, we described the relevance of waveform- shape features in the discussion: "Here, we additionally demonstrated the predictive relevance of feature sets beyond oscillatory activity such as waveform shape for emotion decoding. Waveform shape features can reflect underlying synaptic and cellular dynamics that frequency or power alone cannot capture. For example, the sharpness or steepness of oscillatory peaks may indicate synaptic synchrony or the dynamics of inhibitory versus excitatory activity within a network. These features can also reveal the balance of cortical excitability and inhibition, potentially offering insights into disease states. A systematic data- driven approach to neural decoding based on waveform features can result in higher accuracy and identification of new biological insights into the importance of these measures. Our results indicate that both the amplitude and rise time of neural discharges can reflect information on the computation of emotional valence in the human limbic system. This could be attributed to valence specific changes in synaptic synchrony and afferent excitatory drive." + +<|ref|>text<|/ref|><|det|>[[116, 686, 930, 899]]<|/det|> +6) Reviewer: I don't understand how Figure 4 addresses the problem statements of your paper. The motivation for the analysis is "... to inspire new ways to improve seizure detection accuracy by constraining the decoding platforms to the specifications of clinical brain implants and suggesting improved parameters from offline predictions that are implementable and testable through the clinical patient data management systems (PDMS) provided by Neuropace." Returning to the problems you're solving, as introduced by the introduction of the paper, this figure does not (Problem 1) incorporate data between patients to solve a low-data regime problem, nor (Problem 3) incorporate connectome information between patients. While it does (Problem 2) apply ML algorithms to different a cornucopia of uncharacterized electrophysiologic features, it feels like a fishing expedition. Further, the per-day limitations of data collection with RNS are substantial, as the PDMS available is necessarily biased by whatever the clinician has previously identified to be a seizure (unless I missed somewhere that you're doing long-term data streaming) – I am highly skeptical of the consequence of the findings without seeing the impact (neurophysiologic or clinical). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 38, 565, 58]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[115, 65, 930, 114]]<|/det|> +Reply: We would like to jump in here, just to state that there have been daily "scheduled" recordings that were not triggered by a seizure. Within the PDMS, recording triggers can be set to capture scheduled recording at pre- defined start times: + +<|ref|>image<|/ref|><|det|>[[115, 123, 916, 268]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 280, 864, 298]]<|/det|> +Revision Figure 2: Patient Data Management System (PDMS) recording parametrizations. + +<|ref|>text<|/ref|><|det|>[[115, 306, 930, 437]]<|/det|> +The reserved programming triggers were reserved for scheduled recordings, magnet swipes, long episode detections or amplitude saturation events. The scheduled recordings have the same duration as the long- episode seizure events, saturation or magnetic recordings, and sum up in typical patients to a substantial amount of saved recordings. In our cohort at least two recordings per day were reserved for scheduled recordings. Taking this into account, together with the use of the seizure triggered data, we believe that our approach provides the solution to what the reviewer cites as a problem, which is the arbitrary selection made by a clinical tech or MD based on a single event. Instead, our approach uses all available data to come up with an optimized detector setting. + +<|ref|>text<|/ref|><|det|>[[115, 444, 928, 477]]<|/det|> +Reviewer: I'm happy to be convinced otherwise, but right now Fig. 4 doesn't prove your paper's point. + +<|ref|>text<|/ref|><|det|>[[115, 486, 930, 584]]<|/det|> +Reply: We may not have done the best job doing so, but we aimed to make the main point that machine learning based brain signal decoding can aid the optimization of invasive neuromodulation applications, while offering an open- source platform that provides the necessary tools for implementation. Therefore, we do think that the use- case does aid us in making this point. Notwithstanding this, we are thankful for the excellent suggestion made by the reviewer below, which we have fully adopted in our revision. + +<|ref|>text<|/ref|><|det|>[[115, 592, 930, 708]]<|/det|> +Reviewer: Here's one way that would make the presentation more compelling to the reader. Hopefully, the leads in patients with epilepsy are placed in critical parts of the seizure network. Surely, across 9 patients, some networks have been sampled more than once. Hence, here is a wonderful opportunity to showcase the connectome approach to decoding. Can your approach leverage connectome data to assist with seizure prediction? Can you tell me which network I'm in, to help me with optimal lead selection? Or, can you tell me that a set of parameters determined offline for person A will likely work for person B, because they're targeting the same seizure network? + +<|ref|>text<|/ref|><|det|>[[115, 716, 930, 896]]<|/det|> +Reply: We thank the reviewer for adding this valuable suggestion. While we agree to disagree that the presentation of our third use- case was not on- topic to the paper, we enthusiastically agree that it does provide another opportunity to showcase the connectomic approach. The key reason we have not tackled this with the initial version of the article was that imaging was not readily available in these cases. The many replies and a boatload of work that already went into the previous and present revision sparked a sunken cost fallacy and led us to believe that we should now really make the effort, obtain and perform electrode localizations and run the connectome analysis, which accounted for the lion share of the time required for this third revision of our manuscript. And we are thankful for it, as a) obtaining the electrode localizations in all cases can be seen as critical quality control for the neurophysiology and b) the connectome analysis did indeed spark some very interesting results. In this plot we show the electrode localizations of the analyzed subjects: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[277, 75, 766, 343]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 360, 632, 374]]<|/det|> +
Revision Figure 3: Electrode localizations color-coded by patient ID.
+ +<|ref|>text<|/ref|><|det|>[[117, 384, 870, 399]]<|/det|> +For the reviewers' convenience, we summarize the patient information in the following table: + +<|ref|>table<|/ref|><|det|>[[115, 408, 855, 720]]<|/det|> + +
Patient RNS IDGroupLocation (lead 1)Location (lead 2)Months postopNumber RecordingIctal recordi ng duration [min]Total recordi ng duration [min]SexAge
RNS1529Hippo-campusLeft Hippo-campusRight Hippo-campus11676131.38754.89F22.7
RNS1603NeocortexRight premotor areaRight primary motor area1154538.97747.49F34.5
RNS1836Migrational DysplasiaLeft heterotopiaRight heterotopia101059258.63956.8F39.2
RNS1090Migrational DysplasiaRight heterotopiaRight heterotopia23590132.22575.25M21.8
RNS9536Migrational DysplasiaLeft heterotopiaRight heterotopia2635665.16431.73F46.4
RNS1440NeocortexBasal temporal (depth)Temporo occipital (strip)351058195.211215.61F41.4
RNS1534Hippo-campusLeft Hippo-campusRight Hippocampus722823.46301.04F39.5
+ +<|ref|>text<|/ref|><|det|>[[115, 744, 930, 922]]<|/det|> +To address the key question, whether connectomic network affiliation can predict seizure decoding performance, we followed the same analytic approach as in the other use- cases. In brief, we computed for each RNS recording channel a whole- brain connectivity network map from the seed region. Each recording contact was paired with an optimal seizure detection F1- score. We then computed in a leave- one- subject out cross- validation the optimal seizure decoding connectivity map and estimated the predicted seizure decoding performances by correlating the optimal decoding map with the left- out channel- individual connectivity maps. The approach was also described in the methods section (Supplementary Fig. 5). First, we tested optimal connectivity computation based on the Human Connectome Project fMRI data (Van Essen et al 2013, n=985 subjects), and did not obtain significant results (leave one channel out cross- validation rho=- 0.06, p=0.36; leave one subject out cross- validation rho=0.25, p=0.1). Next, we tested the same pipeline for the HCP diffusion + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 38, 565, 57]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[115, 65, 930, 146]]<|/det|> +weighted structural MRI data (Setsompop et al 2013, adapted by Li et al 2020, \(n = 985\) ), which resulted in significant predictions (leave one channel out cross- validation \(r h o = 0.44\) \(p = 0.01\) ; leave one subject out cross- validation \(r h o = 0.42\) , \(p = 0.02\) ). Thus, we identified a structural whole- brain network, predictive of seizure decoding performance, characterized by dominant positive correlations to bilateral temporal lobe, hippocampus, cingulate and occipital cortex. + +<|ref|>image<|/ref|><|det|>[[122, 170, 925, 444]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 467, 918, 498]]<|/det|> +
Revision Figure 4: Optimal structural seizure decoding network (a) predicts seizure detection performance in leave one subject out cross-validation (b).
+ +<|ref|>text<|/ref|><|det|>[[115, 506, 930, 555]]<|/det|> +To represent this major point adequately in the manuscript while also taking the "fishing expedition" criticism into account, we have now removed the "unconstrained" machine learning results and replaced them with this connectome analysis. + +<|ref|>text<|/ref|><|det|>[[115, 564, 930, 596]]<|/det|> +Changes in manuscript: To include the connectomics- based seizure decoding results, adapted Figure 4 as displayed below: + +<|ref|>image<|/ref|><|det|>[[123, 610, 920, 900]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 37, 565, 57]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[115, 65, 930, 402]]<|/det|> +Fig. 4: Predictive parameter identification for seizure detection in responsive neurostimulation (RNS). (a) RNS data was either acquired from two lead depth electrodes (eight patients) or a cortical electrode in addition to a depth electrode (one patient). Two lead depth electrodes are visualized using Lead- DBS44 for an exemplar patient. The Harvard- Oxford atlas28 parcellation shows the lingual gyrus (white) and the left lateral occipital cortex superior division (red) that are penetrated by the electrodes. (b) In an exemplary recording, from a baseline programming epoch without stimulation artifacts, ictal onset characteristics across the four recording channels are displayed (top). RNS detectors can produce false positive seizure detections even in the absence of seizure activity (bottom) that can occur so frequently that no further therapy is provided (maximum stimulation number reached), even though no ictal activity is present (as defined by the epileptologist annotation). (c) FFT and line- length features were computed similar to the embedded RNS algorithm with py_neuromodulation. The exemplary ictal recording shows clear seizure induced changes. (d) By combining these features with expert seizure annotations, optimal detection parameters were extracted in a grid- search to optimize the F1 score for seizure detection. (e) The RNS patient data management system (PDMS) provides the "SimpleStart" algorithm, in which detection programming settings are automatically inferred based on a single ictal event. Instead, we propose seizure detection using data- driven parameters based on grid- search optimization that builds on expert annotations across hundreds or thousands of events. This approach may hold the potential for improved true negative predictions and increased F1 scores (f). Finally, we use connectomics to reveal a structural network associated with seizure detection performances across subjects. To this end, electrode localizations (g) for seven subjects (color coded) were obtained subjected to a structural connectome analysis to determine an optimal seizure decoding network. Affiliation with this network (h), that spanned bilateral temporal lobe, hippocampus, cingulate and occipital cortex, allowed for significant prediction of seizure detection performance with leave- one- subject out cross- validation (i). + +<|ref|>text<|/ref|><|det|>[[118, 412, 652, 429]]<|/det|> +The new supplementary figure 8 shows axial and sagittal planes. + +<|ref|>text<|/ref|><|det|>[[115, 437, 930, 618]]<|/det|> +Additionally, we added the following to the results section: "Next, we used the optimized seizure detection performances of all RNS channels combined with their specific localization (supplementary table 8) to identify a whole- brain network associated with optimal seizure detection, following the same connectomics approach described for movement and emotion decoding. To this end, we computed structural connectivity fingerprints from each recording channel using the HCP dataset (Setsompop et al 2013, adapted by Li et al 2020, n=985), and correlated seizure detection performances with voxel- wise connectivity. We identified a structural connectivity network (Fig 4h), predictive of seizure decoding performance, characterized by dominant positive correlations to the bilateral temporal lobes, hippocampus, cingulate and occipital cortex, which could significantly predict seizure detection performances in a leave one subject out cross- validation (rho=0.42, p=0.02) (Fig. 4i)." + +<|ref|>text<|/ref|><|det|>[[115, 626, 930, 853]]<|/det|> +Furthermore, we described the approach in the methods section: "For a subset of the cohort (n=7) electrode localizations were obtained either through the Lead- DBS pipeline or through co- registration in Brainstorm (Tadel et al 2011) and manual annotation of electrode contacts. Since each RNS electrode contains four recording contacts and bipolar referencing is applied between contact pairs, the midpoint between the coordinates of contact pairs was estimated. Subsequently, structural connectivity was computed with the Lead Connectome Mapper in Lead- DBS (Neudorfer et al 2023) using diffusion MRI data from the Human Connectome Project (Setsompop et al 2013) adapted by Li et al 2020 (n=985). Here, a spherical seed was used for each recording channel with a radius of 4 mm to estimate connectivity maps. Next, leave- one- patient out cross- validation optimal structural seizure detection connectivity profiles were estimated. The optimal seizure detection connectivity map was thus repetitively estimated by correlating individual channel connectivity voxel values with the RNS channel- specific seizure detection performances. This approach is equivalent to the described connectomics approach for movement and depression above but diffusion MRI images were used instead of functional MRI." + +<|ref|>text<|/ref|><|det|>[[115, 862, 890, 879]]<|/det|> +Finally, we added an additional supplementary Table with the exact electrode MNI coordinates: + +<|ref|>text<|/ref|><|det|>[[115, 888, 890, 919]]<|/det|> +Supplementary Table 8: Electrode localizations of RNS subjects utilized for connectivity- based seizure decoding. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[348, 61, 696, 440]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[116, 38, 565, 57]]<|/det|> +Revision of manuscript NBME-23-2026B + +
Patient RNS IDchMni-xMni-yMni-z
RNS1090052.21-16.727.4
160.52-17.18.5
251.99-33.8820.04
359.98-31.4422.27
RNS14400-36.28-33.73-12.62
1-57.77-39.8-11.08
2-49.65-78.967.2
3-57.8-59.93-2
RNS1529026.78-9.03-3.15
130.4-31.5-7.3
2-27.2-5.3-5.27
3-33.37-25.71-2.56
RNS15340-24.88-27.1-20.72
1-29.12-26.11-0.61
225.5-32.13-15.17
328.27-29.485.27
RNS160306.94-27.6141.9
112.39-20.9964.41
23.15-21.4538.83
34.77-19.2162.13
RNS18360-30.2529.2325.37
1-33.16.4527.23
2-40.77-12.1627.73
3-42.18-35.0431.49
RNS95360-26.55-12.51-27.03
1-30.04-30.35-18.61
224.19-34.09-14.51
329.47-52.34-9.33
+ +<|ref|>sub_title<|/ref|><|det|>[[116, 465, 234, 480]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 488, 930, 635]]<|/det|> +7) Reviewer: The authors have told me that Lead DBS was, "optimized in Lead-DBS for subcortical structures." This matches my experience as well – the default settings (which again, the authors recommend) have both whole-brain and sub-cortical masks that are applied in series to emphasize this fact. Have they quantified the performance of LeadDBS on non-linear deformations of cortical anatomy, in the same way that Dice coefficients have been computed for subcortical structures? If so, can you point me in the direction of a paper that validates cortical anatomy between patients? If not, then can you comment about why not validating the default settings of the program do not impact the quality of your transfer learning approaches? If this question isn't relevant, please explain why (because this point isn't clear to me). + +<|ref|>text<|/ref|><|det|>[[115, 643, 930, 888]]<|/det|> +Reply: Indeed, ANTs has been celebrated as the best method for volumetric registrations of the cortex, for instance in the large- scale comparative study by Arno Klein (10.1016/j.neuroimage.2008.12.037). While DICE- coefficients are less suitable for cortical comparisons, this paper evaluated ANTs based on surface distance metrics. The Lead- DBS team (in part co- authors of this work) have evaluated performance of ANTs for subcortical structures and came up with presets that also optimize this region (especially large scale comparative work by Siobhán Ewert; 10.1016/j.neuroimage.2018.09.061, also replicated by Dorian Vogel: 10.1016/j.nicl.2020.102271). While some studies that exclusively focus on cortical regions choose surface based registrations (e.g. using freesurfer), this format is not automatically suitable when analyzing both subcortical and cortical data that are connected to one another in the same subjects. Hence, in summary, we chose an algorithm that is widely used and has been evaluated for both cortical (Klein et al.) and subcortical (Vogel et al.) registrations. Since ANTs has been the default in many fMRI studies that focus on cortical activity, we for now refrain from adding these points to the discussion, but would be happy to do so in case the reviewer sees the necessity of clarifying this further. + +<|ref|>text<|/ref|><|det|>[[115, 897, 930, 928]]<|/det|> +Changes in manuscript: The methods section now reads: "We utilized ANTs for volumetric registration within LeadDBS since it was previously shown as the best metric for cortical regions + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 66, 928, 98]]<|/det|> +(Klein et al 2008) and separately subcortical regions for deep brain stimulation in movement disorders (Vogel et al 2020)." + +<|ref|>text<|/ref|><|det|>[[115, 123, 928, 189]]<|/det|> +8) Reviewer: "In brief, Lead-DBS uses preoperative MRI and postoperative CT scans for co-registration and normalization to MNI 2009b NLIN ASYM space." This is incorrect, though I am happy to be corrected by Dr. Horn. There are many options available for using standard spaces. That's one of the really nice things about the software. In fact, Fig 4a proves my point! + +<|ref|>text<|/ref|><|det|>[[115, 198, 928, 262]]<|/det|> +Changes in manuscript: We thank the reviewer for addressing this point, and corrected the sentence with input from Dr. Horn in the manuscript as follows: "In brief, Lead-DBS uses preoperative MRI and postoperative CT scans for co-registration and normalization by default to MNI 2009b NLIN ASYM space." + +<|ref|>text<|/ref|><|det|>[[115, 272, 929, 450]]<|/det|> +9) Reviewer: On 23 May 2024, the BCI Society voted to accept this definition of a BCI (https://bcisociety.org/bci-definition/): A brain-computer interface is a system that measures brain activity and converts it in (nearly) real-time into functionally useful outputs to replace, restore, enhance, supplement, and/or improve the natural outputs of the brain, thereby changing the ongoing interactions between the brain and its external or internal environments. It may additionally modify brain activity using targeted delivery of stimuli to create functionally useful inputs to the brain. Most people I know consider a BCI as the first sentence. To my chagrin, neuroprosthetics that meet the definition of the second sentence are now part of the story, so arguably, closed-loop DBS and RNS systems are now under the umbrella of what makes up a BCI. Nevertheless, approach with caution, as you will aggravate some readers with this word choice. For context, neither FDA leadership nor the iBCI-CC consider closed-loop DBS/RNS systems to be BCIs. + +<|ref|>text<|/ref|><|det|>[[115, 460, 929, 556]]<|/det|> +Reply: We thank the reviewer for their expert input. We have followed this discussion closely and believe that the comment by Robinson et al., published in December 2024 in the present Journal provides us with some guidance on the taxonomy that we believe is useful (Robinson, J.T., Norman, S.L., Angle, M.R. et al. An application- based taxonomy for brain- computer interfaces. Nat. Biomed. Eng (2024). https://doi.org/10.1038/s41551-024-01326-z). We now adhere to this taxonomy and explicitly reference it to avoid any confusion. + +<|ref|>text<|/ref|><|det|>[[115, 565, 928, 630]]<|/det|> +Changes in manuscript: "The presented approaches for intelligent adaptive deep brain stimulation could be categorized by the recently published taxonomy for brain- computer interfaces by Robinson et al (Robinson et al 2024) as therapeutic BCI's in the fields of movement disorders, depression and epilepsy." + +<|ref|>text<|/ref|><|det|>[[115, 640, 816, 657]]<|/det|> +10) Reviewer: Perhaps you meant, "closed loop" rather than "real-time" in the paper? + +<|ref|>text<|/ref|><|det|>[[115, 666, 929, 797]]<|/det|> +Reply: We appreciate the feedback and acknowledge the potential confusion surrounding our use of the term "real- time." As laid out in response to major comment 4, for our initial description, we did not mean "real- time" in the strict sense of deterministic execution with bounded latency and jitter, as used in control systems or systems with hard real- time requirements. Instead, we intended to convey that our platform operates in an "online" manner, where data is processed continuously and promptly as it is acquired, enabling rapid interaction or feedback. We have now updated the terminology to "online" to better reflect this intended meaning and avoid misinterpretation, as described in more detail in response to major comment 4. + +<|ref|>text<|/ref|><|det|>[[115, 806, 929, 903]]<|/det|> +11) Reviewer: Why is it so necessary to be so deprecating to the clinical hardware that we have, when the paper itself hasn't created new hardware? Said another way: this is unnecessarily grandiose and sets a weird tone for the paper: "The clinical neurosciences stand at the brink of a transformative time in the treatment of brain disorders, as previously primitive electrically active implants for deep brain stimulation (DBS) and other neuromodulation therapies have evolved into complex computer powered neurotechnology." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 38, 565, 58]]<|/det|> +## Revision of manuscript NBME-23-2026B + +<|ref|>text<|/ref|><|det|>[[116, 65, 930, 131]]<|/det|> +Changes in manuscript: We thank the reviewer for their input and have now rephrased the sentence to "The clinical neurosciences are undergoing a transformative period in the treatment of brain disorders, with neuromodulation therapies like deep brain stimulation (DBS) evolving from their initial designs into advanced computer- powered neurotechnologies." + +<|ref|>text<|/ref|><|det|>[[117, 139, 714, 157]]<|/det|> +12) Reviewer: Consider switching Supplementary Figure 5 and Figure 1. + +<|ref|>text<|/ref|><|det|>[[116, 165, 930, 215]]<|/det|> +Reply: We have considered this suggestion and believe that it would likely overwhelm most of the readers as a first introductory figure, which is why we have respectfully decided to leave it as a supplement. + +<|ref|>text<|/ref|><|det|>[[116, 223, 930, 257]]<|/det|> +13) Reviewer: The newly added text that goes into tremendous (and important) detail about data analysis describing Figure 2 should go to the Methods. + +<|ref|>text<|/ref|><|det|>[[116, 265, 727, 282]]<|/det|> +Reply: Thank you for this helpful suggestion, we have followed the advice. + +<|ref|>text<|/ref|><|det|>[[116, 291, 930, 357]]<|/det|> +14) Reviewer: "We may speculate that neurodegeneration in PD may impact neural encoding of movement, which may also impede machine learning based decoding performance". Patients with worse UPDRS scales may have less brain. Is your decoding performance related to the ECoG strips not actually sitting on the brain, or perhaps have much more air that snuck in during the case? + +<|ref|>text<|/ref|><|det|>[[116, 365, 930, 398]]<|/det|> +Reply: We have assessed this and found no example of any distance between electrode contacts and brain tissue. + +<|ref|>text<|/ref|><|det|>[[116, 422, 930, 473]]<|/det|> +15) Reviewer: "Divining appropriate settings" in describing RNS programming is unnecessarily pessimistic. The very fact that patients often do get better, either tells us that clinical heuristics are useful, or a significant subset of the high-dimensional parameter space is useful. + +<|ref|>text<|/ref|><|det|>[[116, 481, 930, 531]]<|/det|> +Changes in manuscript: Thank you for pointing this out, we have rephrased the sentence as follows: "Defining appropriate settings from this vast parameter space is a largely manual process that has potential for significant acceleration through data-driven methods". + +<|ref|>sub_title<|/ref|><|det|>[[116, 565, 503, 581]]<|/det|> +## Reviewer #4 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[116, 591, 930, 640]]<|/det|> +Reviewer: The code documentation is variable. Some parts hand- hold the user through the process and are easy to follow, and others are slapped together to make a point in OS- specific configuration files. I didn't try running the code. + +<|ref|>text<|/ref|><|det|>[[116, 650, 930, 780]]<|/det|> +Reply: We thank the reviewer for their feedback. With the present revision we have significantly improved the code documentation across all domains. The main code documentation is hosted through GitHub pages https://neuromodulation.github.io/py_neuromodulation/ and presents the overall toolbox usage with examples. The online implementation provides support for replacing the offline data generator by an LSL stream. In a single branch ("online_decode") we include hardware specific files for the used amplifier (TMSi SAGA and NeuroOmega). We did not merge this branch into the main branch to keep the code and documentation general for multiple acquisition systems and use- cases. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 883, 165]]<|/det|> +Thanks to the authors who have considered my criticisms and recommendations thoroughly. My major concerns have been addressed. My comments are now minor and focus on how the novel results are presented in Figure 2. I also make ancillary editorial comments responding to the authors' questions that do not need to be addressed in a future round of revisions. + +<|ref|>text<|/ref|><|det|>[[115, 183, 879, 294]]<|/det|> +I don't know what this means: "Here, the cumulative individual training time reached 3 h 47min to reach leave one subject out performance across patients (Fig. 2n)." I think what you're saying is that you can use data between participants to help minimize decoder training time. More precisely, are you saying that on average you can drop about 4 hours of neural data collection from your decoder and still achieve the same decoding performance. I think this is awkwardly worded. Also, what do the different colors mean in 2n? + +<|ref|>text<|/ref|><|det|>[[115, 313, 874, 388]]<|/det|> +I also don't know what this means: "For a subset of those patients (n=8) the individual training performance could not reach the across- patient decoding performance (Fig 2o)." I think what this means is that for eight patients, you didn't save time by using data from other participants. Is this correct? What do the different colors mean? Are they patients? + +<|ref|>text<|/ref|><|det|>[[115, 425, 877, 500]]<|/det|> +Before going into more detail about performance and testing below, we understand the confusion that arose from this phrase and exchanged the "real- time" with "online" further explaining that we mean that the data are decoded as they are streamed from a patients' brain. We remain open to alternative suggestions by the expert reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 518, 860, 555]]<|/det|> +As long as you're not making the claim that this is a real- time system, there's no further work needed here. + +<|ref|>text<|/ref|><|det|>[[115, 574, 840, 611]]<|/det|> +In reply to the notion that a tool published in a high- impact paper should not rely solely on python, we believe that we should simply work with what works. + +<|ref|>text<|/ref|><|det|>[[115, 629, 867, 741]]<|/det|> +We all agree python is great and it's the modern lingua franca for neuroscience. The examples y'all have provided are important contributions to the field of neuroscience, but they're not real- time platforms. Please find me a real- time BCI platform that relies exclusively on non- compiled python in Windows and has physiologically- relevant bounds on jitter. The only ones I know that fit the bill are Timeflux and LabGraph. The former uses Cython to achieve timing goals, and the latter uses a custom- written C++ middleware for IPC. + +<|ref|>text<|/ref|><|det|>[[115, 759, 880, 814]]<|/det|> +We hope that we have now struck a middle ground that provides both conceptual advances and how they are integrated in the code that we provide, as we still believe that sharing the methods in an open manner is a positive aspect of our paper. + +<|ref|>text<|/ref|><|det|>[[116, 834, 323, 851]]<|/det|> +No further concerns here. + +<|ref|>text<|/ref|><|det|>[[115, 870, 868, 907]]<|/det|> +While we agree to disagree that the presentation of our third use- case was not on- topic to the paper, we enthusiastically agree that it does provide another opportunity to showcase the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 879, 257]]<|/det|> +connectomic approach. The key reason we have not tackled this with the initial version of the article was that imaging was not readily available in these cases. The many replies and a boatload of work that already went into the previous and present revision sparked a sunken cost fallacy and led us to believe that we should now really make the effort, obtain and perform electrode localizations and run the connectome analysis, which accounted for the lion share of the time required for this third revision of our manuscript. And we are thankful for it, as a) obtaining the electrode localizations in all cases can be seen as critical quality control for the neurophysiology and b) the connectome analysis did indeed spark some very interesting results. In this plot we show the electrode localizations of the analyzed subjects: + +<|ref|>text<|/ref|><|det|>[[115, 276, 808, 312]]<|/det|> +Cool. Thanks for doing the work – Figure 4 is now congruent with the rest of the paper, demonstrates the utility of the across brain normalization. + +<|ref|>text<|/ref|><|det|>[[115, 331, 875, 386]]<|/det|> +Since ANTs has been the default in many fMRI studies that focus on cortical activity, we for now refrain from adding these points to the discussion, but would be happy to do so in case the reviewer sees the necessity of clarifying this further. + +<|ref|>text<|/ref|><|det|>[[116, 405, 272, 422]]<|/det|> +No, that's fine as is. + +<|ref|>text<|/ref|><|det|>[[116, 442, 855, 496]]<|/det|> +Finally, quick note to the authors. Documentation of github greatly improved. Here are some broken links: "Usage" and "First examples" on the introductory REAMDE.md. Please clarify if your system works on Linux or Mac. + +<--- Page Split ---> diff --git a/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/images_list.json b/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..41f19d7aa267c2c5c77add9506dc455dd7fec16d --- /dev/null +++ b/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/images_list.json @@ -0,0 +1,79 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_21.jpg", + "caption": "Supplementary Fig. 21 | PL and TOF-SIMS map of pristine \\((\\mathbf{FA}_{1 - x}\\mathbf{MA}_x)\\mathbf{Pb}(\\mathbf{I}_{1 - y}\\mathbf{Br}_y)_3\\) perovskite film. a PL intensity map (750 nm) for perovskite composition \\(\\{x / y\\} = 0.75\\colon 0.50\\) Dashed square represents sample area was used for TOF-SIMS measurement. b Corresponding TOF-SIMS map of \\(\\Gamma /\\mathrm{Br}^{-}\\) ratio.", + "footnote": [], + "bbox": [], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Fig. 5 | Heterogeneity in photoluminescence emission. Hyperspectral luminescence of perovskite thin films with compositions. \\(\\mathbf{a} - \\mathbf{d}\\{x / y\\} = 0.25[0.40. \\mathbf{e} - \\mathbf{h}\\{x / y\\} = 0.75;0.40. \\mathbf{i} - \\mathbf{l}\\{x / y\\} = 0.75;0.50\\) . Here, 2D emission maps in panels a, e, and i represent the wavelength at emission maximum for pristine films. 2D maps in panels b, f, and j show the wavelength change \\((\\Delta \\lambda)\\) upon continuous illumination (450 nm, 5 min.). Spectra in panels c, g, and k are averaged over the scanned area of pristine (red line) and illuminated (blue shaded) films. Panels d, h, and l show histogram of maximum emission wavelengths in pristine (red) and illuminated (blue) thin films. The maps show that emission heterogeneity increases with increasing MA and Br content and that", + "footnote": [], + "bbox": [], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_6.jpg", + "caption": "Supplementary Fig. 6 | Three-dimensional atomic force microscopy height profiles of \\((\\mathbf{FA}_{1 - x}\\mathbf{MA}_x)\\mathbf{Pb}(\\mathbf{I}_{1 - y}\\mathbf{Br}_y)_3\\) perovskite thin films. a \\(\\{x / y\\} = 0.25|0.40\\) . b \\(\\{x / y\\} = 0.50|0.40\\) . c \\(\\{x / y\\} = 0.75|0.40\\) . d \\(\\{x / y\\} = 0.25|0.50\\) . e \\(\\{x / y\\} = 0.50|0.50\\) . f \\(\\{x / y\\} = 0.75|0.50\\) . g \\(\\{x / y\\} = 0.25|0.60\\) . h \\(\\{x / y\\} = 0.50|0.60\\) . i \\(\\{x / y\\} = 0.75|0.60\\) .", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_2.jpg", + "caption": "Supplementary Fig. 2 | Surface SEM images of \\((\\mathrm{FA}_{1 - x}\\mathrm{MA}_x)\\mathrm{Pb}(\\mathrm{I}_{1 - y}\\mathrm{Br}_y)_3\\) perovskite films with \\(50\\%\\) Br content and different MA contents. \\(a x = 0.25\\) . \\(b.x = 0.50\\) . \\(c.x = 0.75\\)", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_5.jpg", + "caption": "Supplementary Fig. 5 | Atomic force microscopy height profiles of \\((\\mathrm{FA}_{1 - x}\\mathrm{MA}_x)\\mathrm{Pb}(\\mathrm{I}_{1 - y}\\mathrm{Br}_y)_3\\) perovskite thin films. a \\(\\{x / y\\} = 0.25 / 0.40\\) . b \\(\\{x / y\\} = 0.50 / 0.40\\) . c \\(\\{x / y\\} = 0.75 / 0.40\\) . d \\(\\{x / y\\} = 0.25 / 0.50\\) . e \\(\\{x / y\\} = 0.50 / 0.50\\) . f \\(\\{x / y\\} = 0.75 / 0.50\\) . g \\(\\{x / y\\} = 0.25 / 0.60\\) . h \\(\\{x / y\\} = 0.50 / 0.60\\) . i \\(\\{x / y\\} = 0.75 / 0.60\\) . Scale bars are \\(10\\mu \\mathrm{m}\\) . Height range is from \\(0 - 2.0\\mu \\mathrm{m}\\) .", + "footnote": [], + "bbox": [ + [ + 141, + 383, + 863, + 629 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_6.jpg", + "caption": "Supplementary Fig. 6 | Three-dimensional atomic force microscopy height profiles of \\((\\mathbf{FA}_{1 - x}\\mathbf{MA}_x)\\mathbf{Pb}(\\mathbf{I}_{1 - y}\\mathbf{Br}_y)_3\\) perovskite thin films. a \\(\\{x / y\\} = 0.25|0.40\\) . b \\(\\{x / y\\} = 0.50|0.40\\) . c \\(\\{x / y\\} = 0.75|0.40\\) . d \\(\\{x / y\\} = 0.25|0.50\\) . e \\(\\{x / y\\} = 0.50|0.50\\) . f \\(\\{x / y\\} = 0.75|0.50\\) . g \\(\\{x / y\\} = 0.25|0.60\\) . h \\(\\{x / y\\} = 0.50|0.60\\) . i \\(\\{x / y\\} = 0.75|0.60\\) .", + "footnote": [], + "bbox": [ + [ + 127, + 132, + 856, + 462 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_7.jpg", + "caption": "Supplementary Fig. 7 | Film roughness as a function of \\((\\mathbf{FA}_{1 - x}\\mathbf{MA}_x)\\mathbf{Pb}(\\mathbf{I}_{1 - y}\\mathbf{Br}_y)_3\\) perovskite composition. a Average maximum peak profile height. b Root mean square average roughness.", + "footnote": [], + "bbox": [ + [ + 200, + 556, + 787, + 711 + ] + ], + "page_idx": 14 + } +] \ No newline at end of file diff --git a/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd b/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..774dca533f49eace641f4b79e7d94e29737b3b28 --- /dev/null +++ b/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd @@ -0,0 +1,511 @@ + +# nature portfolio + +Peer Review File + +# Local halide heterogeneity drives surface wrinkling in mixed-halide wide-bandgap perovskites + +Corresponding Author: Professor René Janssen + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +"Local halide heterogeneity drives surface wrinkling in mixed- halide wide- bandgap perovskites" by Kunal Datta et al. discusses that wrinkling in (FA1- xMAx)Pb(11- yBry)3 perovskites is compositionally driven, requiring high concentrations of MA, and found that the peaks of these wrinkles are iodide- rich while the troughs are bromide- rich. This conclusion is interesting and well- supported by the experimental results. There are a few lingering questions remaining that should be addressed before this manuscript is published, though. + +1. One general comment given how many compositions the authors tested was that it was hard to keep straight which compositions were wrinkled and which weren't as I was reading. Perhaps there could be some sort of additional designator in addition to the x/y to help out people like me from having to refer back to figure 1 all the time? + +2. It is difficult to tell if the PbI2 peak is unchanged in the GlWAXS as stated by the authors. There appears to be an orientational change depending on the composition. + +3. Also in the GlWAXS, the authors refer to "Fig. 2f, 2h, 2i, 2j and 2l" when discussing intense spots on the ring at \(q = 1.0\) A-1, but it does not seem like all of these figures align with what is written. + +4. The correlation between the PL and TOF-SIMS is not presented in a particularly conclusive way. I can maybe see what the authors are stating if I squint, but I could just be seeing what the authors want me to see. Is there a better way to present this information? + +5. A key question remaining in this work is are these wrinkles due to film compression and subsequent delamination? If so, what mechanism would be driving volumetric expansion of the film as it is drying? Is it possible that the wrinkles occur where the perovskite is iodide-rich due to the larger size of iodide forcing the perovskite to distort out-of-plane to relax stresses? + +## Reviewer #2 + +(Remarks to the Author) + +Data et al. reported an in- depth analysis of compositional heterogeneity in wide bandgap perovskites and its impact on their structural and optoelectronic properties. Authors analyzed different set of samples (varying the A- site cation and halides, respectively) to investigate the wrinkle formation on the surface of the films. The local inhomogeneities (morphological and compositional) were identified as key contributors to film degradation under continuous light exposure. The findings of the significant and timely for research on mixed cation mixed halide perovskites. + +1. Page 4: Authors used different FA and MA ratios for A-site cation, and different bromide and iodide ratios for X-site halide effects. In sample labeling, denoting as x/y was hard to follow in the main text. Directly MA/Br percentages would be easier to follow as in figure insets. + +2. Is the process tuned for each perovskite composition? For example, is the antisolvent quenching time optimized? The ink formation influences the crystallization process, which is likely to impact wrinkle formation and the overall film quality. Is there a relationship between the pH of the precursor and the film crystallization? + +<--- Page Split ---> + +3. Page 13: Authors discuss the "illuminated" samples to investigate the halide segregation in the films. The stated that the samples were continuously illuminated for 5 min. The details of the illumination condition comes in page 15. Please consider to move the details in page 13 where the first time the experiment mentioned. This would be easier for the readers. + +4. In Figure 5, for the PL redshift images, please consider adjusting the resolution of the scale bar. The 3 different color scale represents a nearly 40 nm shift, which corresponds to a significant change in bandgap. A higher resolution PL peak wavelength image after 5 min of illumination would more effectively highlight the differences although I believe the histograms already show the differences before and after continuous illumination. + +5. How long did the PL mapping measurement take? The experimental section mentions an exposure time of 1 minute 15 seconds per frame. Did the authors test whether this exposure time initiates halide segregation in samples with high Br content? + +6. I understand why authors did not discuss the device parameters in the main text. However, the quantification of these losses is missing. They demonstrated that Urbach energy increases in samples with greater heterogeneity. Including a Urbach energy vs. Woc graph (Fig 3 in the following paper: https://pubs.acs.org/doi/full/10.1021/acs.jpclett.2c01812) for these samples would better correlate the defects with device performance. Additionally, in Figure 6c, higher Br content increases the Urbach energy rather than decreasing it. Lower Urbach energy indicates better electronic quality, so please correct the figure accordingly. + +## Reviewer #3 + +(Remarks to the Author) + +Comments + +The manuscript on the whole looks well- organized and thorough. The results showcased in the manuscript are mostly straightforward to understand and complement each other along with validating the conclusions. The manuscript needs some edits and refinement to better present the results. + +## Introduction + +Page 3, Line 2 Introducing mixed- halide wide- bandgap perovskites as only APbX3 might not be the right way as there are wide bandgap perovskites reported with no Pb and only Sn in them - https://pubs.acs.org/doi/10.1021/acsenerglyett.4c00796, So a generic representation as ABX3 might be better suited. The introduction section is well ordered explaining the reason for looking into wide bandgap perovskites and the reasons for having compositional and morphological heterogeneity. It then explains why a correlation between compositional and morphological heterogeneity in wide band- gap compositions is needed and how this work achieves that. + +## Results + +Figure 1h - can't say if the color in the figure matches the color scale of the image or not. The color in the figure looks a bit greenish. + +Three- dimensional AFM profiles for the compositions look great but these profiles can be included for all the compositions for better visualization to the audience and better consistency in the supplementary information. + +Page 6, Line 25 - Instead of mentioning the feature size of the smooth films to be around 100 nm it would be better if mentioned in um, this would distinguish the feature sizes from smooth to rough films along with easy comparison Page 6, Line 26 - It is confusing if different names are used for the rough films, such as heterogeneous films, a common representation can be used. + +Page 6, Line 28 - A description can be added for the increase in average roughness with the increase in MA and Br content as seen in Fig.1 and Supplementary Fig.4 + +Why was the compositional study not performed with MA content of \(0\%\) and \(100\%\) ? Even though they do not fall in the desired bandgap of the perovskite top won't the insights be helpful to check if the trend of large feature sizes continues with more MA content? + +Page 8, Line 14 - Roughness information for \(50\%\) Br compositions i.e. 0.25/0.50, 0.50/0.50, 0.75/0.50 can be added to supplementary as it is not present in either Fig.1 or the supplementary figures. + +Page 8, Line 18 - A reference to Fig.2c, 2e, 2g is missing in the main text + +Supplementary Fig.6c is labeled wrong in the caption as 0.25/0.40, it should be 0.25/0.50 + +Figure 3 - check the spin coating timing in methods + +Page 9, Line 11 - Is there a reason why the time stamp between 25s and 31s is different for Fig.3 (29s) and Supplementary Fig.7 (27s)? + +Supplementary Fig.7 - 0.75/0.50 does not show similar features (as in the yellow shading) as Fig.3 for the antisolvent drop at 25s. This figure needs to be checked if the images are misplaced or if there is an actual difference. + +Also, there is a discrepancy in the labeling of Supplementary Fig.7 and its captions. + +Fig.3 - It is evident from the figure but it is better to mention that Fig.3a, c, e, g are of 0.25/0.60, and Fig.3b, d, f, g are of 0.75/0.60 in the caption. + +Explanation and reference for Fig. 3i and 3j are missing in the main text. + +Page 11, Line 3 - The sentence on the elemental map of Pb is confusing, can be simplified + +Page 11, Line 13 - It would be better to mention it as homogeneous distribution of Pb, Br, and I instead of homogeneous distribution of ions + +Fig.4 - Line cuts can be elaborated in a better way in the main text, what are the dotted lines in those figures? + +<--- Page Split ---> + +Supplementary figure 12 - homogeneous distribution of ions? 12a - has more iodine rich regions, 12b more equal variation, 12c much smoother variation + +Supplementary figure 13 - Instead of homogeneous and heterogeneous distribution can this be called clustered distribution vs unclustered distribution? + +Page 15, Line 10 - Hyperspectral PL study on composition 0.75/0.60 can be included to make a stronger claim on the statement about an increase in PL heterogeneity with an increase in bromide content. The same study can be included for composition 0.25/0.60 to rule out the possibility of PL heterogeneity increase with Br at lower MA content. + +Fig.6 - In the figure caption the continuous illumination is mentioned as 10 minutes but in the main text it is mentioned as 5 minutes - check this discrepancy + +The claims over increased photostability based on the inclusion of MA without any device or accelerated testing under light + heat is a bit concerning, especially due to the well- characterized instability challenges of MA inclusion. How can the authors be sure that the improvements in morphology from crystallization control with larger MA fractions will not lead to degradation in devices? + +There is a discussion of relevance to tandems and multi- junctions in the work- such as claiming the wrinkled surface is not amenable to multijunction processing- - but there are reports of high- efficiency tandems on textured Si with a similar profile to the wrinkled films (https://www.sciencedirect.com/science/article/pii/S2542435120300350). Can the authors comment on why they expect this to be different than in the case of Si? + +The results section has the required details, which are well- elaborated. The hypothesis observed is well- explained and well- validated by relevant tests. However, the results section still needs some refinement to put forth the best representation. + +Summary This section is well- explained. + +Materials and Methods Well- elaborated. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) I thank the reviewers for addressing my comments. One lingering question remains, though. The authors' explanation of wrinkle formation due to the instability of the elastic/viscoelastic bilayer is reasonable. However, what remains unexplained is the relative richness of the peaks/ridges in iodide and the troughs/valleys in bromide. + +Reviewer #2 + +(Remarks to the Author) + +The authors have responded to the reviewers' comments and revised the manuscript accordingly. I have no additional remarks. + +Reviewer #3 + +(Remarks to the Author) + +The comments and the suggestions were addressed adequately. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS + +We thank the reviewers for their careful consideration of our work and their constructive feedback. We have addressed the comments and questions in our responses below. The comments/questions from reviewers are marked in BLUE, the authors' responses are marked in BLACK and any references to the Main Text or Supplementary Information are marked in RED. Changes in the Main Text and Supplementary Information files are highlighted in yellow. We note that since several Supplementary Figs. have been changed in sequence, they have also been highlighted. + +## Reviewer #1 (Remarks to the Author): + +"Local halide heterogeneity drives surface wrinkling in mixed- halide wide- bandgap perovskites" by Kunal Datta et al. discusses that wrinkling in (FA1- xMAx)Pb(11- yBry)3 perovskite is compositionally driven, requiring high concentrations of MA, and found that the peaks of these wrinkles are iodide- rich while the troughs are bromide- rich. This conclusion is interesting and well- supported by the experimental results. There are a few lingering questions remaining that should be addressed before this manuscript is published, though. + +We thank the reviewer for their positive evaluation. + +1. One general comment given how many compositions the authors tested was that it was hard to keep straight which compositions were wrinkled and which weren't as I was reading. Perhaps there could be some sort of additional designator in addition to the x/y to help out people like me from having to refer back to figure 1 all the time? + +Thank you for raising this very important issue. We have considered the feedback and have changed the way we designate the different compositions in the body of the text and in figure captions both in the main text file and the Supplementary Information. We now indicate smooth samples as \(x|y\) and wrinkled samples as \(x|y\) and an intermediate roughness as \(x|y\) . For example, the \(0.25|0.40\) composition yields a smooth film, the \(0.75|0.60\) composition yields a wrinkled film and the \(0.25|0.60\) film has an intermediate behavior. We hope this change helps readability. We have also added a piece of text in the main body to explain this nomenclature (see below). + +Page 6: "Hereafter, we refer to these compositions as \(\{x|y\}\) for smooth films, \(\{x|y\}\) for rough films, and \(\{x|y\}\) for films with intermediate morphology. For example, \(\{x|y\} = 0.25|0.40\) forms a smooth film, \(\{x|y\} = 0.75|0.60\) forms a rough film, and \(\{x|y\} = 0.25|0.60\) has an intermediate behavior." + +2. It is difficult to tell if the PbI2 peak is unchanged in the GIWAXS as stated by the authors. There appears to be an orientational change depending on the composition. + +Thank you for this interesting question. For the PbI2 peak, we can see from the 2D GIWAXS images that the position \((q \sim 0.9 \text{Å}^{-1})\) is unchanged irrespective of film composition. We have also analyzed the orientation through azimuthal integration of the diffraction feature. As can be seen (figure below), the preferential orientation undergoes some changes in different compositions. In particular, the MA content seems to have a noticeable impact on the orientation wherein increasing the MA content increases preferential orientation. In contrast, however, the Br content does not + +<--- Page Split ---> + +have a strong influence on the orientation even though the Br content has a stronger impact on the wrinkling behavior than the MA content. Therefore, although there are some changes in the orientation, we conclude that they may not be completely related to the wrinkling behavior we report in this manuscript. The main text has been edited to note the change in orientation. + +Page 7: "The peak position corresponding to unreacted \(\mathrm{PbI}_2\) \((q \approx 0.9 \mathrm{\AA}^{- 1})\) remains unchanged across compositions, albeit with an increase in preferential orientation with increasing MA content (Supplementary Fig. 9)." + +![](images/Supplementary_Figure_21.jpg) + + +Supplementary Fig. 9 | Orientation of \(\mathrm{PbI}_2\) from GIWAXS patterns of \((\mathrm{FA}_{1 - x}\mathrm{MA}_x)\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_y)\) perovskites. Azimuthal intensity profiles of the Debye- Scherrer ring associated to \(\mathrm{PbI}_2\) \((q = 0.9 \mathrm{\AA}^{- 1})\) as a function of \(\chi\) angle from GIWAXS for perovskite compositions with Br content a \(40\%\) , b \(50\%\) , and c \(60\%\) . The MA content is varied between \(25\%\) , \(50\%\) , and \(75\%\) . + +3. Also in the GIWAXS, the authors refer to "Fig. 2f, 2h, 2i, 2j and 2l" when discussing intense spots on the ring at \(q = 1.0 \mathrm{\AA}^{-1}\) , but it does not seem like all of these figures align with what is written. + +Thank you for pointing it out. It was a typo and has been corrected to exclude 2j and 2l. Please see below for the modified text. + +Page 9: "the appearance of intense spots on the ring at \(q \approx 1.0 \mathrm{\AA}^{- 1}\) (Fig. 2f, 2h, and 2i), especially in the out- of- plane" + +4. The correlation between the PL and TOF-SIMS is not presented in a particularly conclusive way. I can maybe see what the authors are stating if I squint, but I could just be seeing what the authors want me to see. Is there a better way to present this information? + +Thank you for this question. We have processed the TOF- SIMS data in Supplementary Fig. 21 (previously Supplementary Fig. 17) further using Gaussian smoothening that has reduced the amount of detail and helped make the data easier to understand (see new figure below). We have also marked two other locations in the frame where we can find an association between the PL emission and the halide composition. We hope the correlation is easier to perceive now. + +<--- Page Split ---> +![](images/Figure_5.jpg) + +
Supplementary Fig. 21 | PL and TOF-SIMS map of pristine \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite film. a PL intensity map (750 nm) for perovskite composition \(\{x / y\} = 0.75\colon 0.50\) Dashed square represents sample area was used for TOF-SIMS measurement. b Corresponding TOF-SIMS map of \(\Gamma /\mathrm{Br}^{-}\) ratio.
+ +5. A key question remaining in this work is are these wrinkles due to film compression and subsequent delamination? If so, what mechanism would be driving volumetric expansion of the film as it is drying? Is it possible that the wrinkles occur where the perovskite is iodide-rich due to the larger size of iodide forcing the perovskite to distort out-of-plane to relax stresses? + +Thank you for raising this question. Isotropic wavy pattern wrinkles similar to those described in the manuscript have been observed in several thin films, e.g., sol-gel derived zinc oxide (Phys. Rev. E 2005, 71, 011604 and Colloids Surf., A 2023, 658, 130628) and alumina (Appl. Phys. Lett. 2016, 108, 151601), in \(\mathrm{YBa_2Cu_3O_{7 - x}}\) (Appl. Surf. Sci. 2015, 355, 736- 742), and perovskites (ACS Energy Lett. 2018, 3, 1225- 1232; Nat. Commun. 2021, 12, 1554). Their formation has been described theoretically (J. Appl. Mech. 2004, 72, 955- 961) in terms of a bilayer system consisting of an elastic layer, on top of a viscoelastic layer, on top of a rigid substrate. Our findings agree with the proposed mechanism and we explain the wrinkle formation as follows. The perovskite precursor solution is initially present as a homogeneous elastic layer. Immediately after the antisolvent is cast, a Br- rich perovskite phase in the presence of higher MA concentrations, forming a skin layer with a higher elastic modulus than the wet film below. As the remaining more I- rich film below dries and shrinks it exerts a compressive stress on the top layer. The wrinkling is then a consequence of a spinodal- like decomposition which creates a pattern of ridges and valleys (Phys. Rev. Lett. 2003, 91, 154502). The valleys are mainly rich in bromide and the ridges are rich in iodide. This entire process sets in within approx. the first 5 s of film crystallization (immediately after antisolvent cast) while the film is still wet. While subsequent annealing promotes crystallization, the orientation and wrinkling has largely occurred already (Supplementary Fig. 13). + +Page 21- 22: "Isotropic wavy pattern wrinkles similar to those described in the manuscript have been observed in several thin films, e.g., sol- gel derived zinc oxide and alumina, in \(\mathrm{YBa_2Cu_3O_{7 - x}}\) , and perovskites16,18,59- 61. Their formation has been described theoretically in terms of a bilayer system consisting of an elastic layer, on top of a viscoelastic layer, on top of a rigid substrate62. + +<--- Page Split ---> + +Our findings agree with the proposed mechanism and we rationalize the wrinkle formation as follows. The perovskite precursor solution is initially present as a homogenous elastic layer. Immediately after the antisolvent is cast a Br- rich perovskite phase crystallizes in the presence of higher MA concentrations, forming a skin layer with a higher elastic modulus than the wet film below. As the remaining more I- rich film below dries and shrinks it exerts a compressive stress on the top layer. The wrinkling is then a consequence of a spinodal- like decomposition which creates a pattern of ridges and valleys63. The valleys are mainly rich in bromide and the ridges are rich in iodide. This entire process sets in within approx. the first 5 s of film crystallization (immediately after antisolvent cast) while the film is still wet. While subsequent annealing promotes crystallization, the orientation and wrinkling has largely occurred already (Supplementary Fig. 13)." + +## Reviewer #2 (Remarks to the Author): + +Datta et al. reported an in- depth analysis of compositional heterogeneity in wide bandgap perovskites and its impact on their structural and optoelectronic properties. Authors analyzed different set of samples (varying the A- site cation and halides, respectively) to investigate the wrinkle formation on the surface of the films. The local inhomogeneities (morphological and compositional) were identified as key contributors to film degradation under continuous light exposure. The findings of the significant and timely for research on mixed cation mixed halide perovskites. + +We thank the reviewer for their positive evaluation and for recognizing the relevance of this work in the current context of the field. + +1. Page 4: Authors used different FA and MA ratios for A-site cation, and different bromide and iodide ratios for X-site halide effects. In sample labeling, denoting as x/y was hard to follow in the main text. Directly MA/Br percentages would be easier to follow as in figure insets. + +Thank you for pointing this out. We have added a small piece of text (see below) at the beginning of the results section to explain what \(x\) and \(y\) represent. Additionally, as also suggested by Reviewer #1, we have changed the way we designate compositions. We now indicate smooth samples as \(x|y\) and wrinkled samples as \(x|y\) and an intermediate roughness as \(x|y\) . For example, the 0.25|0.40 composition yields a smooth film, the 0.75|0.60 composition yields a wrinkled film and the 0.25|0.60 film has an intermediate behavior. This change has been made throughout the main text and supplementary information text and figure captions and we hope it helps readability. We have also added a piece of text in the main body to explain this nomenclature. + +Page 4: "where \(x\) refers to MA content and \(y\) refers to Br content" + +Page 6: "Hereafter, we refer to these compositions as \(\{x|y\}\) for smooth films, \(\{x|y\}\) for rough films, and \(\{x|y\}\) for films with intermediate morphology. For example, \(\{x / y\} = 0.25|0.40\) forms a smooth film, \(\{x / y\} = 0.75|0.60\) forms a rough film, and \(\{x / y\} = 0.25|0.60\) has an intermediate behavior." + +2. Is the process tuned for each perovskite composition? For example, is the antisolvent quenching + +<--- Page Split ---> + +time optimized? The ink formation influences the crystallization process, which is likely to impact wrinkle formation and the overall film quality. Is there a relationship between the pH of the precursor and the film crystallization? + +Processing variables are not tuned for each film since we wanted to study the direct impact of the perovskite composition. We have now clearly stated this in the Methods section (see text below). During this study, however, we studied the impact of some variables on wrinkling behavior but found no significant differences. For example, we have studied the impact of surface hydrophobicity by depositing the perovskite on a hydrophobic PTAA layer (Nat. Commun. 2015, 6, 7747). However, wrinkling behavior was unchanged (see figure below). Furthermore, we have studied the impact of annealing conditions ranging from no annealing to 5 min annealing. In all cases, the wrinkling behavior was unchanged (see figure below), further supporting our hypothesis that wrinkle formation starts to occur during spin- coating and is largely unaffected by annealing conditions. + +The pH of the precursor solution has previously been studied in relation to effect of the acidic hydrolysis and thermal decomposition of DMF on the crystallization and optoelectronic properties of perovskite films (Joule 2017, 1, 2, 328 - 343). Formamidinium is only slightly less acidic than \(\mathrm{(pKa(FA^{+})}\approx 11.5)\) than methylammonium \(\mathrm{(pKa(MA^{+})}\approx 10.6)\) (Nat. Energy 2023, 8, 1229 - 1239, J. Phys. Chem. C 2021, 125, 21851 - 21861). Hence, the acidities of the precursor solutions are very similar and an effect on wrinkling is not expected. + +![](images/Supplementary_Figure_6.jpg) + + +Impact of surface hydrophobicity on wrinkling | Surface SEM images of perovskite thin films with \(50\%\) MA content and \(60\%\) Br content deposited on a glass and b PTAA. + +![](images/Supplementary_Figure_2.jpg) + + +Impact of annealing time on wrinkling | Surface SEM images of perovskite thin films with \(50\%\) MA content and \(60\%\) Br content annealed for a 0 s, b 10 s, c 1 min and d 5 min. + +Page 23: "It must be noted that processing methods are unchanged across all compositions." + +<--- Page Split ---> + +3. Page 13: Authors discuss the "illuminated" samples to investigate the halide segregation in the films. The stated that the samples were continuously illuminated for 5 min. The details of the illumination condition comes in page 15. Please consider to move the details in page 13 where the first time the experiment mentioned. This would be easier for the readers. + +We thank the reviewer for this comment. We have added the experimental conditions (wavelength, intensity) for illumination to an earlier part of the text (see below). + +Page 14: "We then continuously illuminated the film for another 5 min. (450 nm, 130 mW cm \(^{- 2}\) ), and measured again with a 1 min. acquisition time (referred to as "illuminated")." + +4. In Figure 5, for the PL redshift images, please consider adjusting the resolution of the scale bar. The 3 different color scale represents a nearly 40 nm shift, which corresponds to a significant change in bandgap. A higher resolution PL peak wavelength image after 5 min of illumination would more effectively highlight the differences although I believe the histograms already show the differences before and after continuous illumination. + +Thank you for this suggestion. We have changed the scale bars in Figs. 5b, 5f and 5j and used a more appropriate color scale to better highlight the local differences in PL redshift. Please see figure below. + +<--- Page Split ---> +![](images/Supplementary_Figure_5.jpg) + +
Fig. 5 | Heterogeneity in photoluminescence emission. Hyperspectral luminescence of perovskite thin films with compositions. \(\mathbf{a} - \mathbf{d}\{x / y\} = 0.25[0.40. \mathbf{e} - \mathbf{h}\{x / y\} = 0.75;0.40. \mathbf{i} - \mathbf{l}\{x / y\} = 0.75;0.50\) . Here, 2D emission maps in panels a, e, and i represent the wavelength at emission maximum for pristine films. 2D maps in panels b, f, and j show the wavelength change \((\Delta \lambda)\) upon continuous illumination (450 nm, 5 min.). Spectra in panels c, g, and k are averaged over the scanned area of pristine (red line) and illuminated (blue shaded) films. Panels d, h, and l show histogram of maximum emission wavelengths in pristine (red) and illuminated (blue) thin films. The maps show that emission heterogeneity increases with increasing MA and Br content and that
+ +<--- Page Split ---> + +in rough films, regions of low- energy emission undergo a smaller redshift after continuous illumination. Note the different color scales in panels b, f and j. + +5. How long did the PL mapping measurement take? The experimental section mentions an exposure time of 1 minute 15 seconds per frame. Did the authors test whether this exposure time initiates halide segregation in samples with high Br content? + +One limitation of the PL acquisition technique was that the minimum acquisition time (1 min) restricts our ability to capture events occurring on a shorter timescale. Therefore, in order to observe larger changes, we conducted the 5 min light exposure stress experiment and observe the progression of halide segregation over a longer period. We cannot exclude that in some cases, for compositions with high Br content, some ion migration may have happened within the 1 min acquisition time. + +6. I understand why authors did not discuss the device parameters in the main text. However, the quantification of these losses is missing. They demonstrated that Urbach energy increases in samples with greater heterogeneity. Including a Urbach energy vs. Woc graph (Fig 3 in the following paper: https://pubs.acs.org/doi/full/10.1021/acs.jpclett.2c01812) for these samples would better correlate the defects with device performance. Additionally, in Figure 6c, higher Br content increases the Urbach energy rather than decreasing it. Lower Urbach energy indicates better electronic quality, so please correct the figure accordingly. + +Thank you for this suggestion. We have considered this representation (Urbach energy vs \(V_{\mathrm{oc}}\) loss) as well for this work. However, a key issue in calculating the Urbach energy here is that halide heterogeneity in wrinkled perovskites introduces additional features in the band tail (Fig. 6c). This means that the commonly used method of fitting the exponential tail (Nat. Commun. 2017, 8, 590, Adv. Energy Mater. 2020, 10, 1902573) is no longer applicable due to the presence of several absorbing species and instead of one Urbach energy, the film has a distribution of Urbach energies (similar to Fig. 2b in Nat. Nanotechnol. 2022, 17, 190- 196) which cannot be estimated at the cell level using the photocurrent spectroscopy method we are using. As a result, while our current methods are designed to provide an understanding of average band- edge disorder, microscopy techniques would be needed to precisely associate local changes of Urbach energy to local \(V_{\mathrm{oc}}\) losses. We have mentioned the relevance of such methods in the main text (see text below). Also, thank you for pointing out the typo in Fig. 6c, we have corrected it. + +Page 18: "Increasing variations in local bandgap- edge have also been related to non- radiative recombination driven by sub- bandgap defects32." + +## Reviewer #3 (Remarks to the Author): + +## Comments: + +The manuscript on the whole looks well- organized and thorough. The results showcased in the manuscript are mostly straightforward to understand and complement each other along with validating the conclusions. The manuscript needs some edits and refinement to better present the results. + +<--- Page Split ---> + +We thank the reviewer for their positive feedback on our work. + +## Introduction + +Page 3, Line 2 Introducing mixed- halide wide- bandgap perovskites as only APbX3 might not be the right way as there are wide bandgap perovskites reported with no Pb and only Sn in them - https://pubs.acs.org/doi/10.1021/acsenergylett.4c00796, So a generic representation as ABX3 might be better suited. + +Thank you for pointing that out. We have changed this in the Introduction (see below). + +Page 3: "Mixed- halide wide- bandgap ABX3 (A is a monovalent cation, B is lead or tin, and X is a halide ion (iodide or bromide)) perovskite semiconductors are promising candidates for use in monolithic multijunction photovoltaic devices where the use of complementary absorber layers enables an increase in photovoltaic performance". + +The introduction section is well ordered explaining the reason for looking into wide bandgap perovskites and the reasons for having compositional and morphological heterogeneity. It then explains why a correlation between compositional and morphological heterogeneity in wide bandgap compositions is needed and how this work achieves that. + +We thank the reviewer for their positive evaluation of the Introduction section and how it lays out the background for this research. + +## Results + +Figure 1h - can't say if the color in the figure matches the color scale of the image or not. The color in the figure looks a bit greenish. + +Thank you for pointing that out. We have corrected the 3D AFM figure panels (see figure below). We have also recalculated the Rp values based on the 2D images (Supplementary Fig. 5) and the new values are reflected in panels j, k, l, m, n and o of Fig. 1. The trends are the same as before. + +<--- Page Split ---> +![](images/Supplementary_Figure_6.jpg) + + +Three- dimensional AFM profiles for the compositions look great but these profiles can be included for all the compositions for better visualization to the audience and better consistency in the supplementary information. + +Thank you for the suggestion. We have added the 3D AFM maps (see below) for all nine compositions in the Supplementary Information (Supplementary Fig. 6). + +<--- Page Split ---> +![](images/Supplementary_Figure_7.jpg) + +
Supplementary Fig. 6 | Three-dimensional atomic force microscopy height profiles of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite thin films. a \(\{x / y\} = 0.25|0.40\) . b \(\{x / y\} = 0.50|0.40\) . c \(\{x / y\} = 0.75|0.40\) . d \(\{x / y\} = 0.25|0.50\) . e \(\{x / y\} = 0.50|0.50\) . f \(\{x / y\} = 0.75|0.50\) . g \(\{x / y\} = 0.25|0.60\) . h \(\{x / y\} = 0.50|0.60\) . i \(\{x / y\} = 0.75|0.60\) .
+ +Page 6, Line 25 – Instead of mentioning the feature size of the smooth films to be around \(100 \mathrm{nm}\) it would be better if mentioned in \(\mu \mathrm{m}\) , this would distinguish the feature sizes from smooth to rough films along with easy comparison + +We have changed the units from \(\mathrm{nm}\) to \(\mu \mathrm{m}\) when discussing feature sizes observed in AFM measurements (see below). + +Page 7: “The feature sizes in the smooth films \((\{x / y\} = 0.25|0.40, 0.50|0.40, \text{and} 0.25|0.60)\) are on the order of \(0.10 \mu \mathrm{m}\) whereas compositions that yield rough films \((\{x / y\} = 0.75|0.40, 0.50|0.60, \text{and} 0.75|0.60)\) exhibit feature sizes as large as \(1.5 - 2.0 \mu \mathrm{m}\) .” + +Page 6, Line 26 – It is confusing if different names are used for the rough films, such as heterogeneous films, a common representation can be used. + +Thank you for this suggestion. We’ve made changes to the text to distinguish between morphological behavior and compositional/photoluminescence properties. We have now used the words “smooth” and “rough” when discussing morphology and we use “homogeneous” and “heterogeneous” when describing other forms of disorder such as for the XRF, PL and TOF- SIMS data. + +<--- Page Split ---> + +Page 6, Line 28 – A description can be added for the increase in average roughness with the increase in MA and Br content as seen in Fig.1 and Supplementary Fig.4 Why was the compositional study not performed with MA content of \(0\%\) and \(100\%\) ? Even though they do not fall in the desired bandgap of the perovskite top won’t the insights be helpful to check if the trend of large feature sizes continues with more MA content? + +To address the first part of this comment, we have edited the main text (page 6) to describe the increase in roughness parameters \(R_{\mathrm{p}}\) and \(R_{\mathrm{q}}\) . + +Page 7: “This results in an increase in the average maximum profile height \((R_{\mathrm{p}})\) and root mean square average roughness \((R_{\mathrm{q}})\) as a function of increasing MA and Br contents (Supplementary Fig. 7).” + +We have also studied a wider range of MA- contents for Br- contents \(40\%\) and \(60\%\) . SEM images (see below) show that the trends are similar; lower MA content films are smooth while high MA content films are rough. The figure has been added to the Supplementary Figures and the main text has been edited to refer to it (see text below). + +Page 6: “We note that the behavior is also consistent at lower \((0\%)\) and higher \((100\%)\) MA contents (Supplementary Fig. 3) and that the appearance of morphological disorder does not significantly affect SEM features at \(1 - 2\mu \mathrm{m}\) size or create voids in the film surface (Supplementary Fig. 4).” + +![PLACEHOLDER_15_0] + + +Supplementary Fig. 3 | Surface SEM images of \((\mathrm{FA}_{1 - x}\mathrm{MA}_{x})\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_{y})_{3}\) perovskite thin films for different compositions. a \(\{x / y\} = 0|0.40\) . b. \(\{x / y\} = 1.0\dot{0}.40\) . c. \(\{x / y\} = 0|0.60\) . d. \(\{x / y\} = 1.0\dot{0}.60\) . + +Page 8, Line 14 – Roughness information for \(50\%\) Br compositions i.e. \(0.25 / 0.50\) , \(0.50 / 0.50\) , \(0.75 / 0.50\) can be added to supplementary as it is not present in either Fig.1 or the supplementary figures. + +<--- Page Split ---> + +We have added SEM and AFM data for \(50\%\) Br series to the Supplementary Information (Supplementary Figs. 2. 5 and 6) along with values for \(R_{\mathrm{p}}\) and \(R_{\mathrm{q}}\) (Supplementary Fig. 7) (see figures below). + +![PLACEHOLDER_16_0] + +
Supplementary Fig. 2 | Surface SEM images of \((\mathrm{FA}_{1 - x}\mathrm{MA}_x)\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_y)_3\) perovskite films with \(50\%\) Br content and different MA contents. \(a x = 0.25\) . \(b.x = 0.50\) . \(c.x = 0.75\)
+ +![PLACEHOLDER_16_1] + +
Supplementary Fig. 5 | Atomic force microscopy height profiles of \((\mathrm{FA}_{1 - x}\mathrm{MA}_x)\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_y)_3\) perovskite thin films. a \(\{x / y\} = 0.25 / 0.40\) . b \(\{x / y\} = 0.50 / 0.40\) . c \(\{x / y\} = 0.75 / 0.40\) . d \(\{x / y\} = 0.25 / 0.50\) . e \(\{x / y\} = 0.50 / 0.50\) . f \(\{x / y\} = 0.75 / 0.50\) . g \(\{x / y\} = 0.25 / 0.60\) . h \(\{x / y\} = 0.50 / 0.60\) . i \(\{x / y\} = 0.75 / 0.60\) . Scale bars are \(10\mu \mathrm{m}\) . Height range is from \(0 - 2.0\mu \mathrm{m}\) .
+ +<--- Page Split ---> +![PLACEHOLDER_17_0] + +
Supplementary Fig. 6 | Three-dimensional atomic force microscopy height profiles of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite thin films. a \(\{x / y\} = 0.25|0.40\) . b \(\{x / y\} = 0.50|0.40\) . c \(\{x / y\} = 0.75|0.40\) . d \(\{x / y\} = 0.25|0.50\) . e \(\{x / y\} = 0.50|0.50\) . f \(\{x / y\} = 0.75|0.50\) . g \(\{x / y\} = 0.25|0.60\) . h \(\{x / y\} = 0.50|0.60\) . i \(\{x / y\} = 0.75|0.60\) .
+ +![PLACEHOLDER_17_1] + +
Supplementary Fig. 7 | Film roughness as a function of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite composition. a Average maximum peak profile height. b Root mean square average roughness.
+ +Page 8, Line 18 – A reference to Fig.2c, 2e, 2g is missing in the main text Supplementary Fig.6c is labeled wrong in the caption as 0.25/0.40, it should be 0.25/0.50 + +Thank you for pointing that out. We have made the corrections (see below). + +<--- Page Split ---> + +Page 9: “smooth films \((\{x / y\} = 0.25|0.40, 0.50|0.40, 0.25|0.50, 0.50|0.50, \text{and} 0.25|0.60)\) show GIWAXS patterns (Fig. 2a, 2b, 2d, 2e, and 2g)” + +Page 9: “roughness \(> 1 \mu \mathrm{m}\) with composition \((\{x / y\} = 0.75|0.40, 0.75|0.50, 0.50|0.60, \text{and} 0.75|0.60)\) show GIWAXS patterns” + +Figure 3 – check the spin coating timing in methods + +We have confirmed the spin- coating time. To clarify, the data presented in Figure 3 shows a small section (between 21 s and 31 s) of the overall 40 s spin- coating period. The structural evolution during the entire process can be seen in Supplementary Fig. 13. + +Page 9, Line 11 – Is there a reason why the time stamp between 25s and 31s is different for Fig.3 (29s) and Supplementary Fig.7 (27s)? + +Thank you for pointing this out. We have now made the two figures uniform, including the frame at 29 s in the Supplementary Figure (see below). The structural behavior is similar to what we had previously reported at 27 s. + +![PLACEHOLDER_18_0] + + +<--- Page Split ---> + +Supplementary Fig. 11 | In situ GIWAXS patterns acquired at different times during spin- coating of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite films. a, c, e and g \(\{x / y\} = 0.25|0.50\) . b, d, f and h and \(0.75\dot{0}.50\) . The anti- solvent is applied after 25 s (panels c and d). + +Supplementary Fig.7- 0.75/0.50 does not show similar features (as in the yellow shading) as Fig.3 for the antisolvent drop at 25s, This figure needs to be checked if the images are misplaced or if there is an actual difference. + +The yellow shaded region in Supplementary Fig. 11 is related to scattering observed when the antisolvent is cast onto the film but disappears immediately after casting. Similar increases in intensity in the \(q\approx 1 - 1.2\mathrm{\AA}^{- 1}\) range has previously been reported in other studies using in- situ GIWAXS measurements (for example Fig. 3 in Adv Energy Mater. 2017, 7, 1602600, Figs. 2b and 2f in Adv. Mater. 2019, 31, 1901284). A likely explanation for its absence in the \(\{x / y\} = 0.75 / 0.50\) measurement is the ms- scale mismatch in the antisolvent drip timing and the frame acquisition which likely causes this feature to not appear prominently in the 25 s frame. + +Also, there is a discrepancy in the labeling of Supplementary Fig.7 and its captions. + +There was an error in the panel labels in the caption, it has been rectified (see below). Thank you for pointing it out. + +Page S8: "Supplementary Fig. 11 | In situ GIWAXS patterns acquired at different times during spin- coating of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite films. a, c, e, and g \(\{x / y\} = 0.25|0.50\) . b, d, f, and h and \(0.75\dot{0}.50\) . The anti- solvent is applied after 25 s (panels c and d)." + +Fig.3 - It is evident from the figure but it is better to mention that Fig.3a, c, e, g are of \(0.25 / 0.60\) and Fig.3b, d, f, g are of \(0.75 / 0.60\) in the caption. + +Thank you for the suggestion, we have made the suggested change in the figure caption. + +Page 11: "Fig. 3 | Crystallization dynamics of mixed- halide perovskite thin films. In situ GIWAXS patterns of perovskites with compositions \(\{x / y\} = 0.25|0.60\) and \(\{x / y\} = 0.75\dot{0}.60\) during spin- coating. Panels mark time stamps during the spin coating process. a, b 21 s. c, d 25 s. e, f 29 s. g, h 31 s. The frame at 25 s represents the casting of the antisolvent onto the substrate. Azimuthal intensity profiles of the main Debye- Scherrer ring (100) as a function of \(\chi\) angle from GIWAXS for different perovskite compositions acquired in the \(20 - 40\) s period of spin- coating. i \(\{x / y\} = 0.25|0.60\) . j \(\{x / y\} = 0.75\dot{0}.60\) . Panels a, c, e, g, and i refer to \(\{x / y\} = 0.25|0.60\) and panels b, d, f, h, and j refer to \(\{x / y\} = 0.75\dot{0}.60\) . The data in panels i and j have been vertically offset for clarity." + +Explanation and reference for Fig. 3i and 3j are missing in the main text. + +Thank you for pointing that out, we have referred to it in the main text. The explanation was already written (referring to Supplementary Fig. 9) in the original version of the text. Now it also refers to Fig. 3i and 3j (see below). + +<--- Page Split ---> + +Page 10: "we propose that in an MA- rich environment, heterogeneous crystal nucleation leads to the formation of oriented bromide- rich perovskites immediately after antisolvent casting (Fig. 3i, 3j and Supplementary Fig. 13) followed by the incorporation of iodide- containing phases18" + +Page 11, Line 3 – The sentence on the elemental map of Pb is confusing, can be simplified + +Thank you for the suggestion. We have added a sentence to explain the relationship between Pb content and film thickness (see below). + +Page 11- 12: "As a result, regions with higher Pb content refer to the peak- like regions of wrinkles whereas lower Pb content corresponds to valley- like regions." + +Page 11, Line 13 – It would be better to mention it as homogeneous distribution of Pb, Br, and I instead of homogeneous distribution of ions + +Thank you for the suggestion, the text has been changed (see below) to be more specific to the elements being discussed. + +Page 12: "Similar homogeneous distribution of iodide- to- bromide ratio is observed for other smooth films" + +Fig.4 – Line cuts can be elaborated in a better way in the main text, what are the dotted lines in those figures? + +Thank you for the suggestion. We have marked the lines as solid and dashed for iodide- to- bromide ratio and Pb- content respectively in the figure caption (see below). We have also emphasized in the main text that the correlation being drawn is between the local increase in layer thickness (Pb content) and higher iodide concentration. + +Page 13: "Fig. 4 | Compositional heterogeneity in mixed- halide perovskite thin films from nano- XRF. a Normalized elemental maps of Pb, I, and Br of perovskite thin film with \(\{x / y\} = 0.25|0.40\) . b Map of iodide- to- bromide ratio in shaded region of panel a. Sub- panels A, B, C, and D represent the normalized Pb elemental map in regions highlighted (dashed squares) in the iodide- to- bromide map. c Line cuts of iodide- to- bromide ratios (solid) overlapped with local Pb content line cuts (dashed) marked with (1) and (2) in panel b. d Normalized elemental maps of Pb, I, and Br of perovskite thin film with \(\{x / y\} = 0.50|0.60\) . e Map of iodide- to- bromide ratio in shaded region of panel d. Sub- panels E, F, G, and H represent the normalized Pb elemental map in regions highlighted in the iodide- to- bromide map. f, g Line cuts of iodide- to- bromide ratios (solid) overlapped with local Pb content line cuts (dashed) at points marked with (1), (2), (3), and (4) in panel e. Maps show that smooth films yield homogeneous halide distribution across the film thickness and wrinkled films have iodide- rich domains concentrated at peak- like regions. All scale bars are \(10 \mu \mathrm{m}\) ." + +Page 12: "Line cuts at four distinct locations of the film and two- dimensional maps (Fig. 4f, 4g, and Supplementary Fig. 18) further confirm the positive correlation between the local increase in layer thickness (Pb content) and higher iodide concentration." + +<--- Page Split ---> + +Supplementary figure 12 – homogeneous distribution of ions? 12a – has more iodine rich regions, 12b more equal variation, 12c much smoother variation + +Thank you for this comment. We would like to clarify that the three compositions in Supplementary Fig. 16 \(\{x / y\} = 0.50|0.40, 0.50|0.50\) and \(0.25|0.60\) have different halide contents as a result of which the overall iodide/bromide content is different in each case. There is also a stochastic distribution of halides which may result in nanometer- scale domains rich in either iodide/bromide as has also been observed by others (J. Am. Chem. Soc. 2016, 138, 15821 – 15824 and ACS Energy Lett. 2022, 7, 471 – 480). What we would like to emphasize in this work though that in these compositions, the large micrometer- scale domains related to wrinkling are absent. We have clarified this in the main text now (see text below) and thank you for raising this issue. + +Page12: "We note here that the stochastic distribution of ions causes local nanometer- scale domains to develop that are rich in iodide or bromide ions \(^{26,28}\) ." + +Supplementary figure 13 – Instead of homogeneous and heterogeneous distribution can this be called clustered distribution vs unclustered distribution? + +Thank you for this suggestion. Indeed the nomenclature referring to this behavior can use several combination of words such as homogeneous/heterogeneous, homogeneous/inhomogeneous, mixed/unmixed, segregated/non- segregated, aggregated/disaggregated and clustered/unclustered. And although we understand the motivation to use "clustered/unclustered" instead of "homogeneous/heterogeneous", we find ourselves very much within the currently used nomenclature in the field, as demonstrated by other publications (Nat. Rev. Mater. 2019, 4, 573 – 587, Nat. Nanotechnol. 2022, 17, 190–196, Matter 2024, 7, 1054 – 1070, Science 2019, 363, 627 – 631, Chem. Mater. 2016, 28, 6536 – 6543, Science 2022, 378, 747 – 754). As a result, we have continued using homogeneous/heterogeneous to refer to this behavior in order to be consistent with published works. We have nevertheless now made a clear distinction (based on input from Reviewer #2) between homogeneous/heterogeneous for variations related to composition and luminescence and smooth/rough describe morphological properties. + +Page 15, Line 10 – Hyperspectral PL study on composition 0.75/0.60 can be included to make a stronger claim on the statement about an increase in PL heterogeneity with an increase in bromide content. The same study can be included for composition 0.25/0.60 to rule out the possibility of PL heterogeneity increase with Br at lower MA content. + +We have considered expanding our compositional space further (75% MA, 60% Br) for local PL measurements. However, we found that these compositions are very sensitive to visible illumination required for the PL measurement such that within the acquisition time, ion migration occurs causing a red- shift in the PL. As a result, measurements that use lower light intensity such as the sensitive EQE measurements (Fig. 6) are more suitable for such compositions. + +Fig.6 – In the figure caption the continuous illumination is mentioned as 10 minutes but in the main text it is mentioned as 5 minutes – check this discrepancy + +<--- Page Split ---> + +Thank you for pointing out this typo. We have corrected it in the main text. The correct duration is 10 min (see below). + +Page 20: "We used continuous illumination (532 nm, 1- Sun equivalent intensity, 10 min.) to induce defect migration and drive halide segregation in the solar cells58." + +The claims over increased photostability based on the inclusion of MA without any device or accelerated testing under light + heat is a bit concerning, especially due to the well- characterized instability challenges of MA inclusion. How can the authors be sure that the improvements in morphology from crystallization control with larger MA fractions will not lead to degradation in devices? + +Thanks for this interesting question. Indeed, MA has been linked to degradation in previous studies (for example Energy Environ. Sci. 2016, 9, 1655 - 1660). However, the wrinkling behavior we describe in this work is not limited to MA- containing perovskites and has been observed in MA- free perovskites in several prior publications (Nature Communications 2021, 12, 1554, ACS Energy Letters 2018, 3, 6, 1225- 1232, J. Phys. Chem. C 2018, 122, 30, 17123- 17135, J. Phys. Chem. Lett. 2024, 15, 36, 9255- 9262, ACS Energy Lett. 2023, 9, 75- 84, J. Appl. Phys. 2018, 123, 175302, Matter 2020, 2, 207- 219). The precise role of the cation in this process needs further examination although there is one report in triple- cation (Cs, FA, MA) perovskites that describes Cs heterogeneity in wrinkled films (J. Phys. Chem. C 2018, 122, 23345- 23351). It is therefore possible that ionic (cation and halide) heterogeneity also occurs in MA- free materials, similar to what we report in our work. As a result, we speculate that in a MA- free wrinkled film with ionic heterogeneity, the halide migration processes discussed in our work also occur and drive degradation. Therefore, while it is entirely possible that degradation due to MA dissociation is suppressed in MA- free films, degradation due to wrinkling will likely still persist. We have added some text (see below) to the Summary section to highlight the ubiquity of this behavior irrespective of MA content. + +Page 22: "We also note previous works that report similar morphological behavior in methylammonium- free perovskite compositions, emphasizing possible limits to charge- carrier dynamics and stability11,12,14- 16,18." + +There is a discussion of relevance to tandems and multi- junctions in the work—such as claiming the wrinkled surface is not amenable to multijunction processing—but there are reports of high- efficiency tandems on textured Si with a similar profile to the wrinkled films (https://www.sciencedirect.com/science/article/pii/S2542435120300350). Can the authors comment on why they expect this to be different than in the case of Si? + +Thank you for raising this interesting issue. Indeed, there are reports of tandem devices that successfully incorporate texturing. Devices using thermal evaporation to coat the perovskite and charge transport layers certainly don't face these processing challenges when depositing on textured surfaces (Nature Materials 2018, 17, 820). There are other reports of solution- processed perovskite sub- cells on top of textured silicon sub- cells with varying degrees of texturing. Here, to our knowledge, only blade coating (Joule 2020, 4, 5, 850) has been reported for coating on top of textures in the range of \(>1\) um. The texture heights must be lower for spin- coating to be + +<--- Page Split ---> + +applicable (Nature Nanotechnology 2022, 17, 1214 and Science 2020, 367, 6482, 1135). Furthermore, in this work, we are trying to address challenges for devices that are beyond tandem solar cells (triple- junctions and quadruple- junctions, for example), motivating our choice to study perovskite compositions with high bromide contents. There, irrespective of the overall configuration (perovskite- perovskite- silicon or all- perovskite), there is a perovskite- perovskite "sub- tandem" in the stack. To our knowledge, no reports are currently available where a textured perovskite sub- cell has been used in a multijunction device. Finally, another important challenge to consider, in addition to the perovskite deposition, is the conformal coating of a series of thin ( \(< 50 \mathrm{nm}\) ), optically benign charge transport and interfacial layers in complex multijunction stacks using solution- processing. And while several layers are deposited using evaporation, sputtering or atomic layer deposition ( \(C_{60}\) , \(\mathrm{SnO_x}\) , TCO, anti- reflection coatings), spin- coating and other solution- based methods are common for other layers. For example, commonly used self- assembled monolayers ( \(< 5 \mathrm{nm}\) ) are very sensitive to the surface (Nature 2023, 624, 289- 294, ACS Appl. Mater. Interfaces 2022, 14, 1, 2166- 2176). Solution- processed interfacial layers in devices are also very thin. So, taken together, we strongly believe that overcoming challenges related to wrinkling is extremely relevant to the development of multijunction device stacks where solution- processing is involved in the series of fabrication steps. + +The results section has the required details, which are well- elaborated. The hypothesis observed is well- explained and well- validated by relevant tests. However, the results section still needs some refinement to put forth the best representation. + +Thank you for the overall positive view of our results. We hope that the changes we have described above have addressed your comments/questions appropriately. + +Summary This section is well- explained. + +Thank you for the positive comment. + +Materials and Methods + +Well- elaborated + +Thank you for the positive comment. + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS + +We thank the reviewers for their positive evaluation of our work. We have addressed the comment from Reviewer #1 below. The comment is marked in BLUE and the authors' response is marked in BLACK. + +## Reviewer #1 (Remarks to the Author): + +I thank the reviewers for addressing my comments. One lingering question remains, though. The authors' explanation of wrinkle formation due to the instability of the elastic/viscoelastic bilayer is reasonable. However, what remains unexplained is the relative richness of the peaks/ridges in iodide and the troughs/valleys in bromide. + +We thank the reviewer for their positive evaluation and for this question. The relative richness in iodide of the peaks compared to the valleys in the XRF measurements is related to the overall volume fractions that the iodide- rich (viscoelastic) and iodide- poor (elastic) layers represent in those regions. In the peak- like region, the iodide- rich viscoelastic layer is thicker than in the valley- like region. As a result, in the XRF measurement that probes the bulk composition, the iodide- rich viscoelastic layer represents a larger volume fraction at the peaks and a relatively smaller volume fraction in the valley. As a result, the peaks show an overall richness in iodide compared to the valley. + +## Reviewer #2 (Remarks to the Author): + +The authors have responded to the reviewers' comments and revised the manuscript accordingly. I have no additional remarks. + +We thank the reviewer for their positive evaluation. + +## Reviewer #3 (Remarks to the Author): + +The comments and the suggestions were addressed adequately. + +We thank the reviewer for their positive evaluation. + +<--- Page Split ---> diff --git a/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd b/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..430a6ce9f3e23b0f4b0721e92a79b4f408205257 --- /dev/null +++ b/peer_reviews/34f7befbd20dae5c695338ff41653b8cd42a39e97aca4a39019001bb2d49d423/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd @@ -0,0 +1,695 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 297, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 914, 209]]<|/det|> +# Local halide heterogeneity drives surface wrinkling in mixed-halide wide-bandgap perovskites + +<|ref|>text<|/ref|><|det|>[[73, 224, 488, 240]]<|/det|> +Corresponding Author: Professor René Janssen + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 339]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 220, 366]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 419, 911, 483]]<|/det|> +"Local halide heterogeneity drives surface wrinkling in mixed- halide wide- bandgap perovskites" by Kunal Datta et al. discusses that wrinkling in (FA1- xMAx)Pb(11- yBry)3 perovskites is compositionally driven, requiring high concentrations of MA, and found that the peaks of these wrinkles are iodide- rich while the troughs are bromide- rich. This conclusion is interesting and well- supported by the experimental results. There are a few lingering questions remaining that should be addressed before this manuscript is published, though. + +<|ref|>text<|/ref|><|det|>[[72, 484, 914, 523]]<|/det|> +1. One general comment given how many compositions the authors tested was that it was hard to keep straight which compositions were wrinkled and which weren't as I was reading. Perhaps there could be some sort of additional designator in addition to the x/y to help out people like me from having to refer back to figure 1 all the time? + +<|ref|>text<|/ref|><|det|>[[70, 534, 860, 562]]<|/det|> +2. It is difficult to tell if the PbI2 peak is unchanged in the GlWAXS as stated by the authors. There appears to be an orientational change depending on the composition. + +<|ref|>text<|/ref|><|det|>[[70, 574, 895, 601]]<|/det|> +3. Also in the GlWAXS, the authors refer to "Fig. 2f, 2h, 2i, 2j and 2l" when discussing intense spots on the ring at \(q = 1.0\) A-1, but it does not seem like all of these figures align with what is written. + +<|ref|>text<|/ref|><|det|>[[72, 613, 912, 653]]<|/det|> +4. The correlation between the PL and TOF-SIMS is not presented in a particularly conclusive way. I can maybe see what the authors are stating if I squint, but I could just be seeing what the authors want me to see. Is there a better way to present this information? + +<|ref|>text<|/ref|><|det|>[[72, 665, 921, 705]]<|/det|> +5. A key question remaining in this work is are these wrinkles due to film compression and subsequent delamination? If so, what mechanism would be driving volumetric expansion of the film as it is drying? Is it possible that the wrinkles occur where the perovskite is iodide-rich due to the larger size of iodide forcing the perovskite to distort out-of-plane to relax stresses? + +<|ref|>sub_title<|/ref|><|det|>[[73, 730, 162, 743]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 757, 237, 770]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 770, 920, 836]]<|/det|> +Data et al. reported an in- depth analysis of compositional heterogeneity in wide bandgap perovskites and its impact on their structural and optoelectronic properties. Authors analyzed different set of samples (varying the A- site cation and halides, respectively) to investigate the wrinkle formation on the surface of the films. The local inhomogeneities (morphological and compositional) were identified as key contributors to film degradation under continuous light exposure. The findings of the significant and timely for research on mixed cation mixed halide perovskites. + +<|ref|>text<|/ref|><|det|>[[72, 848, 914, 887]]<|/det|> +1. Page 4: Authors used different FA and MA ratios for A-site cation, and different bromide and iodide ratios for X-site halide effects. In sample labeling, denoting as x/y was hard to follow in the main text. Directly MA/Br percentages would be easier to follow as in figure insets. + +<|ref|>text<|/ref|><|det|>[[72, 899, 915, 939]]<|/det|> +2. Is the process tuned for each perovskite composition? For example, is the antisolvent quenching time optimized? The ink formation influences the crystallization process, which is likely to impact wrinkle formation and the overall film quality. Is there a relationship between the pH of the precursor and the film crystallization? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 60, 916, 101]]<|/det|> +3. Page 13: Authors discuss the "illuminated" samples to investigate the halide segregation in the films. The stated that the samples were continuously illuminated for 5 min. The details of the illumination condition comes in page 15. Please consider to move the details in page 13 where the first time the experiment mentioned. This would be easier for the readers. + +<|ref|>text<|/ref|><|det|>[[72, 111, 921, 165]]<|/det|> +4. In Figure 5, for the PL redshift images, please consider adjusting the resolution of the scale bar. The 3 different color scale represents a nearly 40 nm shift, which corresponds to a significant change in bandgap. A higher resolution PL peak wavelength image after 5 min of illumination would more effectively highlight the differences although I believe the histograms already show the differences before and after continuous illumination. + +<|ref|>text<|/ref|><|det|>[[72, 176, 905, 217]]<|/det|> +5. How long did the PL mapping measurement take? The experimental section mentions an exposure time of 1 minute 15 seconds per frame. Did the authors test whether this exposure time initiates halide segregation in samples with high Br content? + +<|ref|>text<|/ref|><|det|>[[72, 228, 904, 310]]<|/det|> +6. I understand why authors did not discuss the device parameters in the main text. However, the quantification of these losses is missing. They demonstrated that Urbach energy increases in samples with greater heterogeneity. Including a Urbach energy vs. Woc graph (Fig 3 in the following paper: https://pubs.acs.org/doi/full/10.1021/acs.jpclett.2c01812) for these samples would better correlate the defects with device performance. Additionally, in Figure 6c, higher Br content increases the Urbach energy rather than decreasing it. Lower Urbach energy indicates better electronic quality, so please correct the figure accordingly. + +<|ref|>sub_title<|/ref|><|det|>[[73, 333, 162, 347]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 360, 238, 373]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 374, 150, 386]]<|/det|> +Comments + +<|ref|>text<|/ref|><|det|>[[73, 386, 889, 426]]<|/det|> +The manuscript on the whole looks well- organized and thorough. The results showcased in the manuscript are mostly straightforward to understand and complement each other along with validating the conclusions. The manuscript needs some edits and refinement to better present the results. + +<|ref|>sub_title<|/ref|><|det|>[[73, 439, 156, 451]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[72, 451, 916, 530]]<|/det|> +Page 3, Line 2 Introducing mixed- halide wide- bandgap perovskites as only APbX3 might not be the right way as there are wide bandgap perovskites reported with no Pb and only Sn in them - https://pubs.acs.org/doi/10.1021/acsenerglyett.4c00796, So a generic representation as ABX3 might be better suited. The introduction section is well ordered explaining the reason for looking into wide bandgap perovskites and the reasons for having compositional and morphological heterogeneity. It then explains why a correlation between compositional and morphological heterogeneity in wide band- gap compositions is needed and how this work achieves that. + +<|ref|>sub_title<|/ref|><|det|>[[73, 543, 127, 555]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[72, 555, 905, 581]]<|/det|> +Figure 1h - can't say if the color in the figure matches the color scale of the image or not. The color in the figure looks a bit greenish. + +<|ref|>text<|/ref|><|det|>[[72, 581, 905, 608]]<|/det|> +Three- dimensional AFM profiles for the compositions look great but these profiles can be included for all the compositions for better visualization to the audience and better consistency in the supplementary information. + +<|ref|>text<|/ref|><|det|>[[72, 608, 900, 660]]<|/det|> +Page 6, Line 25 - Instead of mentioning the feature size of the smooth films to be around 100 nm it would be better if mentioned in um, this would distinguish the feature sizes from smooth to rough films along with easy comparison Page 6, Line 26 - It is confusing if different names are used for the rough films, such as heterogeneous films, a common representation can be used. + +<|ref|>text<|/ref|><|det|>[[72, 660, 916, 687]]<|/det|> +Page 6, Line 28 - A description can be added for the increase in average roughness with the increase in MA and Br content as seen in Fig.1 and Supplementary Fig.4 + +<|ref|>text<|/ref|><|det|>[[72, 687, 911, 725]]<|/det|> +Why was the compositional study not performed with MA content of \(0\%\) and \(100\%\) ? Even though they do not fall in the desired bandgap of the perovskite top won't the insights be helpful to check if the trend of large feature sizes continues with more MA content? + +<|ref|>text<|/ref|><|det|>[[72, 725, 884, 752]]<|/det|> +Page 8, Line 14 - Roughness information for \(50\%\) Br compositions i.e. 0.25/0.50, 0.50/0.50, 0.75/0.50 can be added to supplementary as it is not present in either Fig.1 or the supplementary figures. + +<|ref|>text<|/ref|><|det|>[[72, 752, 576, 765]]<|/det|> +Page 8, Line 18 - A reference to Fig.2c, 2e, 2g is missing in the main text + +<|ref|>text<|/ref|><|det|>[[72, 765, 682, 778]]<|/det|> +Supplementary Fig.6c is labeled wrong in the caption as 0.25/0.40, it should be 0.25/0.50 + +<|ref|>text<|/ref|><|det|>[[72, 778, 427, 791]]<|/det|> +Figure 3 - check the spin coating timing in methods + +<|ref|>text<|/ref|><|det|>[[72, 791, 911, 817]]<|/det|> +Page 9, Line 11 - Is there a reason why the time stamp between 25s and 31s is different for Fig.3 (29s) and Supplementary Fig.7 (27s)? + +<|ref|>text<|/ref|><|det|>[[72, 817, 911, 844]]<|/det|> +Supplementary Fig.7 - 0.75/0.50 does not show similar features (as in the yellow shading) as Fig.3 for the antisolvent drop at 25s. This figure needs to be checked if the images are misplaced or if there is an actual difference. + +<|ref|>text<|/ref|><|det|>[[72, 844, 644, 857]]<|/det|> +Also, there is a discrepancy in the labeling of Supplementary Fig.7 and its captions. + +<|ref|>text<|/ref|><|det|>[[72, 857, 884, 882]]<|/det|> +Fig.3 - It is evident from the figure but it is better to mention that Fig.3a, c, e, g are of 0.25/0.60, and Fig.3b, d, f, g are of 0.75/0.60 in the caption. + +<|ref|>text<|/ref|><|det|>[[72, 883, 565, 896]]<|/det|> +Explanation and reference for Fig. 3i and 3j are missing in the main text. + +<|ref|>text<|/ref|><|det|>[[72, 896, 700, 909]]<|/det|> +Page 11, Line 3 - The sentence on the elemental map of Pb is confusing, can be simplified + +<|ref|>text<|/ref|><|det|>[[72, 909, 895, 934]]<|/det|> +Page 11, Line 13 - It would be better to mention it as homogeneous distribution of Pb, Br, and I instead of homogeneous distribution of ions + +<|ref|>text<|/ref|><|det|>[[72, 934, 820, 948]]<|/det|> +Fig.4 - Line cuts can be elaborated in a better way in the main text, what are the dotted lines in those figures? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 75]]<|/det|> +Supplementary figure 12 - homogeneous distribution of ions? 12a - has more iodine rich regions, 12b more equal variation, 12c much smoother variation + +<|ref|>text<|/ref|><|det|>[[72, 74, 918, 100]]<|/det|> +Supplementary figure 13 - Instead of homogeneous and heterogeneous distribution can this be called clustered distribution vs unclustered distribution? + +<|ref|>text<|/ref|><|det|>[[72, 100, 914, 140]]<|/det|> +Page 15, Line 10 - Hyperspectral PL study on composition 0.75/0.60 can be included to make a stronger claim on the statement about an increase in PL heterogeneity with an increase in bromide content. The same study can be included for composition 0.25/0.60 to rule out the possibility of PL heterogeneity increase with Br at lower MA content. + +<|ref|>text<|/ref|><|det|>[[72, 140, 911, 166]]<|/det|> +Fig.6 - In the figure caption the continuous illumination is mentioned as 10 minutes but in the main text it is mentioned as 5 minutes - check this discrepancy + +<|ref|>text<|/ref|><|det|>[[72, 166, 917, 218]]<|/det|> +The claims over increased photostability based on the inclusion of MA without any device or accelerated testing under light + heat is a bit concerning, especially due to the well- characterized instability challenges of MA inclusion. How can the authors be sure that the improvements in morphology from crystallization control with larger MA fractions will not lead to degradation in devices? + +<|ref|>text<|/ref|><|det|>[[72, 217, 921, 270]]<|/det|> +There is a discussion of relevance to tandems and multi- junctions in the work- such as claiming the wrinkled surface is not amenable to multijunction processing- - but there are reports of high- efficiency tandems on textured Si with a similar profile to the wrinkled films (https://www.sciencedirect.com/science/article/pii/S2542435120300350). Can the authors comment on why they expect this to be different than in the case of Si? + +<|ref|>text<|/ref|><|det|>[[72, 269, 920, 297]]<|/det|> +The results section has the required details, which are well- elaborated. The hypothesis observed is well- explained and well- validated by relevant tests. However, the results section still needs some refinement to put forth the best representation. + +<|ref|>text<|/ref|><|det|>[[72, 310, 280, 336]]<|/det|> +Summary This section is well- explained. + +<|ref|>text<|/ref|><|det|>[[72, 349, 230, 375]]<|/det|> +Materials and Methods Well- elaborated. + +<|ref|>text<|/ref|><|det|>[[72, 400, 144, 413]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 426, 219, 439]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 451, 160, 464]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 477, 922, 529]]<|/det|> +(Remarks to the Author) I thank the reviewers for addressing my comments. One lingering question remains, though. The authors' explanation of wrinkle formation due to the instability of the elastic/viscoelastic bilayer is reasonable. However, what remains unexplained is the relative richness of the peaks/ridges in iodide and the troughs/valleys in bromide. + +<|ref|>text<|/ref|><|det|>[[72, 541, 160, 554]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 567, 238, 580]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 580, 877, 606]]<|/det|> +The authors have responded to the reviewers' comments and revised the manuscript accordingly. I have no additional remarks. + +<|ref|>text<|/ref|><|det|>[[72, 620, 160, 633]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 646, 238, 659]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 660, 518, 673]]<|/det|> +The comments and the suggestions were addressed adequately. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 916, 100]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 910, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 124, 378, 141]]<|/det|> +## RESPONSE TO REVIEWERS + +<|ref|>text<|/ref|><|det|>[[115, 155, 883, 253]]<|/det|> +We thank the reviewers for their careful consideration of our work and their constructive feedback. We have addressed the comments and questions in our responses below. The comments/questions from reviewers are marked in BLUE, the authors' responses are marked in BLACK and any references to the Main Text or Supplementary Information are marked in RED. Changes in the Main Text and Supplementary Information files are highlighted in yellow. We note that since several Supplementary Figs. have been changed in sequence, they have also been highlighted. + +<|ref|>sub_title<|/ref|><|det|>[[115, 268, 436, 285]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 300, 883, 395]]<|/det|> +"Local halide heterogeneity drives surface wrinkling in mixed- halide wide- bandgap perovskites" by Kunal Datta et al. discusses that wrinkling in (FA1- xMAx)Pb(11- yBry)3 perovskite is compositionally driven, requiring high concentrations of MA, and found that the peaks of these wrinkles are iodide- rich while the troughs are bromide- rich. This conclusion is interesting and well- supported by the experimental results. There are a few lingering questions remaining that should be addressed before this manuscript is published, though. + +<|ref|>text<|/ref|><|det|>[[115, 411, 520, 427]]<|/det|> +We thank the reviewer for their positive evaluation. + +<|ref|>text<|/ref|><|det|>[[115, 443, 883, 507]]<|/det|> +1. One general comment given how many compositions the authors tested was that it was hard to keep straight which compositions were wrinkled and which weren't as I was reading. Perhaps there could be some sort of additional designator in addition to the x/y to help out people like me from having to refer back to figure 1 all the time? + +<|ref|>text<|/ref|><|det|>[[115, 522, 883, 635]]<|/det|> +Thank you for raising this very important issue. We have considered the feedback and have changed the way we designate the different compositions in the body of the text and in figure captions both in the main text file and the Supplementary Information. We now indicate smooth samples as \(x|y\) and wrinkled samples as \(x|y\) and an intermediate roughness as \(x|y\) . For example, the \(0.25|0.40\) composition yields a smooth film, the \(0.75|0.60\) composition yields a wrinkled film and the \(0.25|0.60\) film has an intermediate behavior. We hope this change helps readability. We have also added a piece of text in the main body to explain this nomenclature (see below). + +<|ref|>text<|/ref|><|det|>[[115, 650, 883, 699]]<|/det|> +Page 6: "Hereafter, we refer to these compositions as \(\{x|y\}\) for smooth films, \(\{x|y\}\) for rough films, and \(\{x|y\}\) for films with intermediate morphology. For example, \(\{x|y\} = 0.25|0.40\) forms a smooth film, \(\{x|y\} = 0.75|0.60\) forms a rough film, and \(\{x|y\} = 0.25|0.60\) has an intermediate behavior." + +<|ref|>text<|/ref|><|det|>[[115, 714, 881, 746]]<|/det|> +2. It is difficult to tell if the PbI2 peak is unchanged in the GIWAXS as stated by the authors. There appears to be an orientational change depending on the composition. + +<|ref|>text<|/ref|><|det|>[[115, 761, 883, 857]]<|/det|> +Thank you for this interesting question. For the PbI2 peak, we can see from the 2D GIWAXS images that the position \((q \sim 0.9 \text{Å}^{-1})\) is unchanged irrespective of film composition. We have also analyzed the orientation through azimuthal integration of the diffraction feature. As can be seen (figure below), the preferential orientation undergoes some changes in different compositions. In particular, the MA content seems to have a noticeable impact on the orientation wherein increasing the MA content increases preferential orientation. In contrast, however, the Br content does not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 884, 190]]<|/det|> +have a strong influence on the orientation even though the Br content has a stronger impact on the wrinkling behavior than the MA content. Therefore, although there are some changes in the orientation, we conclude that they may not be completely related to the wrinkling behavior we report in this manuscript. The main text has been edited to note the change in orientation. + +<|ref|>text<|/ref|><|det|>[[115, 202, 884, 253]]<|/det|> +Page 7: "The peak position corresponding to unreacted \(\mathrm{PbI}_2\) \((q \approx 0.9 \mathrm{\AA}^{- 1})\) remains unchanged across compositions, albeit with an increase in preferential orientation with increasing MA content (Supplementary Fig. 9)." + +<|ref|>image<|/ref|><|det|>[[152, 272, 833, 418]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 425, 884, 514]]<|/det|> +Supplementary Fig. 9 | Orientation of \(\mathrm{PbI}_2\) from GIWAXS patterns of \((\mathrm{FA}_{1 - x}\mathrm{MA}_x)\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_y)\) perovskites. Azimuthal intensity profiles of the Debye- Scherrer ring associated to \(\mathrm{PbI}_2\) \((q = 0.9 \mathrm{\AA}^{- 1})\) as a function of \(\chi\) angle from GIWAXS for perovskite compositions with Br content a \(40\%\) , b \(50\%\) , and c \(60\%\) . The MA content is varied between \(25\%\) , \(50\%\) , and \(75\%\) . + +<|ref|>text<|/ref|><|det|>[[115, 539, 884, 588]]<|/det|> +3. Also in the GIWAXS, the authors refer to "Fig. 2f, 2h, 2i, 2j and 2l" when discussing intense spots on the ring at \(q = 1.0 \mathrm{\AA}^{-1}\) , but it does not seem like all of these figures align with what is written. + +<|ref|>text<|/ref|><|det|>[[115, 603, 884, 636]]<|/det|> +Thank you for pointing it out. It was a typo and has been corrected to exclude 2j and 2l. Please see below for the modified text. + +<|ref|>text<|/ref|><|det|>[[115, 650, 884, 684]]<|/det|> +Page 9: "the appearance of intense spots on the ring at \(q \approx 1.0 \mathrm{\AA}^{- 1}\) (Fig. 2f, 2h, and 2i), especially in the out- of- plane" + +<|ref|>text<|/ref|><|det|>[[115, 699, 884, 747]]<|/det|> +4. The correlation between the PL and TOF-SIMS is not presented in a particularly conclusive way. I can maybe see what the authors are stating if I squint, but I could just be seeing what the authors want me to see. Is there a better way to present this information? + +<|ref|>text<|/ref|><|det|>[[115, 762, 884, 842]]<|/det|> +Thank you for this question. We have processed the TOF- SIMS data in Supplementary Fig. 21 (previously Supplementary Fig. 17) further using Gaussian smoothening that has reduced the amount of detail and helped make the data easier to understand (see new figure below). We have also marked two other locations in the frame where we can find an association between the PL emission and the halide composition. We hope the correlation is easier to perceive now. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[296, 140, 700, 329]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 342, 884, 414]]<|/det|> +
Supplementary Fig. 21 | PL and TOF-SIMS map of pristine \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite film. a PL intensity map (750 nm) for perovskite composition \(\{x / y\} = 0.75\colon 0.50\) Dashed square represents sample area was used for TOF-SIMS measurement. b Corresponding TOF-SIMS map of \(\Gamma /\mathrm{Br}^{-}\) ratio.
+ +<|ref|>text<|/ref|><|det|>[[115, 436, 883, 503]]<|/det|> +5. A key question remaining in this work is are these wrinkles due to film compression and subsequent delamination? If so, what mechanism would be driving volumetric expansion of the film as it is drying? Is it possible that the wrinkles occur where the perovskite is iodide-rich due to the larger size of iodide forcing the perovskite to distort out-of-plane to relax stresses? + +<|ref|>text<|/ref|><|det|>[[114, 516, 884, 790]]<|/det|> +Thank you for raising this question. Isotropic wavy pattern wrinkles similar to those described in the manuscript have been observed in several thin films, e.g., sol-gel derived zinc oxide (Phys. Rev. E 2005, 71, 011604 and Colloids Surf., A 2023, 658, 130628) and alumina (Appl. Phys. Lett. 2016, 108, 151601), in \(\mathrm{YBa_2Cu_3O_{7 - x}}\) (Appl. Surf. Sci. 2015, 355, 736- 742), and perovskites (ACS Energy Lett. 2018, 3, 1225- 1232; Nat. Commun. 2021, 12, 1554). Their formation has been described theoretically (J. Appl. Mech. 2004, 72, 955- 961) in terms of a bilayer system consisting of an elastic layer, on top of a viscoelastic layer, on top of a rigid substrate. Our findings agree with the proposed mechanism and we explain the wrinkle formation as follows. The perovskite precursor solution is initially present as a homogeneous elastic layer. Immediately after the antisolvent is cast, a Br- rich perovskite phase in the presence of higher MA concentrations, forming a skin layer with a higher elastic modulus than the wet film below. As the remaining more I- rich film below dries and shrinks it exerts a compressive stress on the top layer. The wrinkling is then a consequence of a spinodal- like decomposition which creates a pattern of ridges and valleys (Phys. Rev. Lett. 2003, 91, 154502). The valleys are mainly rich in bromide and the ridges are rich in iodide. This entire process sets in within approx. the first 5 s of film crystallization (immediately after antisolvent cast) while the film is still wet. While subsequent annealing promotes crystallization, the orientation and wrinkling has largely occurred already (Supplementary Fig. 13). + +<|ref|>text<|/ref|><|det|>[[115, 803, 883, 870]]<|/det|> +Page 21- 22: "Isotropic wavy pattern wrinkles similar to those described in the manuscript have been observed in several thin films, e.g., sol- gel derived zinc oxide and alumina, in \(\mathrm{YBa_2Cu_3O_{7 - x}}\) , and perovskites16,18,59- 61. Their formation has been described theoretically in terms of a bilayer system consisting of an elastic layer, on top of a viscoelastic layer, on top of a rigid substrate62. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 883, 300]]<|/det|> +Our findings agree with the proposed mechanism and we rationalize the wrinkle formation as follows. The perovskite precursor solution is initially present as a homogenous elastic layer. Immediately after the antisolvent is cast a Br- rich perovskite phase crystallizes in the presence of higher MA concentrations, forming a skin layer with a higher elastic modulus than the wet film below. As the remaining more I- rich film below dries and shrinks it exerts a compressive stress on the top layer. The wrinkling is then a consequence of a spinodal- like decomposition which creates a pattern of ridges and valleys63. The valleys are mainly rich in bromide and the ridges are rich in iodide. This entire process sets in within approx. the first 5 s of film crystallization (immediately after antisolvent cast) while the film is still wet. While subsequent annealing promotes crystallization, the orientation and wrinkling has largely occurred already (Supplementary Fig. 13)." + +<|ref|>sub_title<|/ref|><|det|>[[116, 332, 437, 348]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 363, 883, 476]]<|/det|> +Datta et al. reported an in- depth analysis of compositional heterogeneity in wide bandgap perovskites and its impact on their structural and optoelectronic properties. Authors analyzed different set of samples (varying the A- site cation and halides, respectively) to investigate the wrinkle formation on the surface of the films. The local inhomogeneities (morphological and compositional) were identified as key contributors to film degradation under continuous light exposure. The findings of the significant and timely for research on mixed cation mixed halide perovskites. + +<|ref|>text<|/ref|><|det|>[[115, 491, 883, 523]]<|/det|> +We thank the reviewer for their positive evaluation and for recognizing the relevance of this work in the current context of the field. + +<|ref|>text<|/ref|><|det|>[[115, 539, 883, 587]]<|/det|> +1. Page 4: Authors used different FA and MA ratios for A-site cation, and different bromide and iodide ratios for X-site halide effects. In sample labeling, denoting as x/y was hard to follow in the main text. Directly MA/Br percentages would be easier to follow as in figure insets. + +<|ref|>text<|/ref|><|det|>[[115, 602, 883, 731]]<|/det|> +Thank you for pointing this out. We have added a small piece of text (see below) at the beginning of the results section to explain what \(x\) and \(y\) represent. Additionally, as also suggested by Reviewer #1, we have changed the way we designate compositions. We now indicate smooth samples as \(x|y\) and wrinkled samples as \(x|y\) and an intermediate roughness as \(x|y\) . For example, the 0.25|0.40 composition yields a smooth film, the 0.75|0.60 composition yields a wrinkled film and the 0.25|0.60 film has an intermediate behavior. This change has been made throughout the main text and supplementary information text and figure captions and we hope it helps readability. We have also added a piece of text in the main body to explain this nomenclature. + +<|ref|>text<|/ref|><|det|>[[115, 746, 630, 762]]<|/det|> +Page 4: "where \(x\) refers to MA content and \(y\) refers to Br content" + +<|ref|>text<|/ref|><|det|>[[115, 778, 883, 826]]<|/det|> +Page 6: "Hereafter, we refer to these compositions as \(\{x|y\}\) for smooth films, \(\{x|y\}\) for rough films, and \(\{x|y\}\) for films with intermediate morphology. For example, \(\{x / y\} = 0.25|0.40\) forms a smooth film, \(\{x / y\} = 0.75|0.60\) forms a rough film, and \(\{x / y\} = 0.25|0.60\) has an intermediate behavior." + +<|ref|>text<|/ref|><|det|>[[111, 841, 883, 858]]<|/det|> +2. Is the process tuned for each perovskite composition? For example, is the antisolvent quenching + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 883, 172]]<|/det|> +time optimized? The ink formation influences the crystallization process, which is likely to impact wrinkle formation and the overall film quality. Is there a relationship between the pH of the precursor and the film crystallization? + +<|ref|>text<|/ref|><|det|>[[114, 188, 883, 348]]<|/det|> +Processing variables are not tuned for each film since we wanted to study the direct impact of the perovskite composition. We have now clearly stated this in the Methods section (see text below). During this study, however, we studied the impact of some variables on wrinkling behavior but found no significant differences. For example, we have studied the impact of surface hydrophobicity by depositing the perovskite on a hydrophobic PTAA layer (Nat. Commun. 2015, 6, 7747). However, wrinkling behavior was unchanged (see figure below). Furthermore, we have studied the impact of annealing conditions ranging from no annealing to 5 min annealing. In all cases, the wrinkling behavior was unchanged (see figure below), further supporting our hypothesis that wrinkle formation starts to occur during spin- coating and is largely unaffected by annealing conditions. + +<|ref|>text<|/ref|><|det|>[[114, 363, 883, 459]]<|/det|> +The pH of the precursor solution has previously been studied in relation to effect of the acidic hydrolysis and thermal decomposition of DMF on the crystallization and optoelectronic properties of perovskite films (Joule 2017, 1, 2, 328 - 343). Formamidinium is only slightly less acidic than \(\mathrm{(pKa(FA^{+})}\approx 11.5)\) than methylammonium \(\mathrm{(pKa(MA^{+})}\approx 10.6)\) (Nat. Energy 2023, 8, 1229 - 1239, J. Phys. Chem. C 2021, 125, 21851 - 21861). Hence, the acidities of the precursor solutions are very similar and an effect on wrinkling is not expected. + +<|ref|>image<|/ref|><|det|>[[283, 480, 700, 612]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 624, 883, 657]]<|/det|> +Impact of surface hydrophobicity on wrinkling | Surface SEM images of perovskite thin films with \(50\%\) MA content and \(60\%\) Br content deposited on a glass and b PTAA. + +<|ref|>image<|/ref|><|det|>[[120, 678, 863, 797]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 809, 883, 842]]<|/det|> +Impact of annealing time on wrinkling | Surface SEM images of perovskite thin films with \(50\%\) MA content and \(60\%\) Br content annealed for a 0 s, b 10 s, c 1 min and d 5 min. + +<|ref|>text<|/ref|><|det|>[[113, 857, 841, 874]]<|/det|> +Page 23: "It must be noted that processing methods are unchanged across all compositions." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 140, 883, 204]]<|/det|> +3. Page 13: Authors discuss the "illuminated" samples to investigate the halide segregation in the films. The stated that the samples were continuously illuminated for 5 min. The details of the illumination condition comes in page 15. Please consider to move the details in page 13 where the first time the experiment mentioned. This would be easier for the readers. + +<|ref|>text<|/ref|><|det|>[[115, 220, 881, 252]]<|/det|> +We thank the reviewer for this comment. We have added the experimental conditions (wavelength, intensity) for illumination to an earlier part of the text (see below). + +<|ref|>text<|/ref|><|det|>[[115, 267, 881, 300]]<|/det|> +Page 14: "We then continuously illuminated the film for another 5 min. (450 nm, 130 mW cm \(^{- 2}\) ), and measured again with a 1 min. acquisition time (referred to as "illuminated")." + +<|ref|>text<|/ref|><|det|>[[115, 315, 883, 394]]<|/det|> +4. In Figure 5, for the PL redshift images, please consider adjusting the resolution of the scale bar. The 3 different color scale represents a nearly 40 nm shift, which corresponds to a significant change in bandgap. A higher resolution PL peak wavelength image after 5 min of illumination would more effectively highlight the differences although I believe the histograms already show the differences before and after continuous illumination. + +<|ref|>text<|/ref|><|det|>[[115, 410, 883, 458]]<|/det|> +Thank you for this suggestion. We have changed the scale bars in Figs. 5b, 5f and 5j and used a more appropriate color scale to better highlight the local differences in PL redshift. Please see figure below. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[202, 125, 792, 728]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 729, 885, 858]]<|/det|> +
Fig. 5 | Heterogeneity in photoluminescence emission. Hyperspectral luminescence of perovskite thin films with compositions. \(\mathbf{a} - \mathbf{d}\{x / y\} = 0.25[0.40. \mathbf{e} - \mathbf{h}\{x / y\} = 0.75;0.40. \mathbf{i} - \mathbf{l}\{x / y\} = 0.75;0.50\) . Here, 2D emission maps in panels a, e, and i represent the wavelength at emission maximum for pristine films. 2D maps in panels b, f, and j show the wavelength change \((\Delta \lambda)\) upon continuous illumination (450 nm, 5 min.). Spectra in panels c, g, and k are averaged over the scanned area of pristine (red line) and illuminated (blue shaded) films. Panels d, h, and l show histogram of maximum emission wavelengths in pristine (red) and illuminated (blue) thin films. The maps show that emission heterogeneity increases with increasing MA and Br content and that
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 882, 157]]<|/det|> +in rough films, regions of low- energy emission undergo a smaller redshift after continuous illumination. Note the different color scales in panels b, f and j. + +<|ref|>text<|/ref|><|det|>[[115, 173, 882, 221]]<|/det|> +5. How long did the PL mapping measurement take? The experimental section mentions an exposure time of 1 minute 15 seconds per frame. Did the authors test whether this exposure time initiates halide segregation in samples with high Br content? + +<|ref|>text<|/ref|><|det|>[[115, 236, 883, 333]]<|/det|> +One limitation of the PL acquisition technique was that the minimum acquisition time (1 min) restricts our ability to capture events occurring on a shorter timescale. Therefore, in order to observe larger changes, we conducted the 5 min light exposure stress experiment and observe the progression of halide segregation over a longer period. We cannot exclude that in some cases, for compositions with high Br content, some ion migration may have happened within the 1 min acquisition time. + +<|ref|>text<|/ref|><|det|>[[115, 348, 883, 460]]<|/det|> +6. I understand why authors did not discuss the device parameters in the main text. However, the quantification of these losses is missing. They demonstrated that Urbach energy increases in samples with greater heterogeneity. Including a Urbach energy vs. Woc graph (Fig 3 in the following paper: https://pubs.acs.org/doi/full/10.1021/acs.jpclett.2c01812) for these samples would better correlate the defects with device performance. Additionally, in Figure 6c, higher Br content increases the Urbach energy rather than decreasing it. Lower Urbach energy indicates better electronic quality, so please correct the figure accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 475, 883, 666]]<|/det|> +Thank you for this suggestion. We have considered this representation (Urbach energy vs \(V_{\mathrm{oc}}\) loss) as well for this work. However, a key issue in calculating the Urbach energy here is that halide heterogeneity in wrinkled perovskites introduces additional features in the band tail (Fig. 6c). This means that the commonly used method of fitting the exponential tail (Nat. Commun. 2017, 8, 590, Adv. Energy Mater. 2020, 10, 1902573) is no longer applicable due to the presence of several absorbing species and instead of one Urbach energy, the film has a distribution of Urbach energies (similar to Fig. 2b in Nat. Nanotechnol. 2022, 17, 190- 196) which cannot be estimated at the cell level using the photocurrent spectroscopy method we are using. As a result, while our current methods are designed to provide an understanding of average band- edge disorder, microscopy techniques would be needed to precisely associate local changes of Urbach energy to local \(V_{\mathrm{oc}}\) losses. We have mentioned the relevance of such methods in the main text (see text below). Also, thank you for pointing out the typo in Fig. 6c, we have corrected it. + +<|ref|>text<|/ref|><|det|>[[115, 682, 882, 714]]<|/det|> +Page 18: "Increasing variations in local bandgap- edge have also been related to non- radiative recombination driven by sub- bandgap defects32." + +<|ref|>sub_title<|/ref|><|det|>[[116, 746, 436, 762]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[116, 780, 207, 793]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[116, 795, 883, 857]]<|/det|> +The manuscript on the whole looks well- organized and thorough. The results showcased in the manuscript are mostly straightforward to understand and complement each other along with validating the conclusions. The manuscript needs some edits and refinement to better present the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 140, 610, 157]]<|/det|> +We thank the reviewer for their positive feedback on our work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 173, 215, 187]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[115, 188, 883, 251]]<|/det|> +Page 3, Line 2 Introducing mixed- halide wide- bandgap perovskites as only APbX3 might not be the right way as there are wide bandgap perovskites reported with no Pb and only Sn in them - https://pubs.acs.org/doi/10.1021/acsenergylett.4c00796, So a generic representation as ABX3 might be better suited. + +<|ref|>text<|/ref|><|det|>[[115, 268, 795, 285]]<|/det|> +Thank you for pointing that out. We have changed this in the Introduction (see below). + +<|ref|>text<|/ref|><|det|>[[115, 300, 883, 365]]<|/det|> +Page 3: "Mixed- halide wide- bandgap ABX3 (A is a monovalent cation, B is lead or tin, and X is a halide ion (iodide or bromide)) perovskite semiconductors are promising candidates for use in monolithic multijunction photovoltaic devices where the use of complementary absorber layers enables an increase in photovoltaic performance". + +<|ref|>text<|/ref|><|det|>[[115, 380, 883, 444]]<|/det|> +The introduction section is well ordered explaining the reason for looking into wide bandgap perovskites and the reasons for having compositional and morphological heterogeneity. It then explains why a correlation between compositional and morphological heterogeneity in wide bandgap compositions is needed and how this work achieves that. + +<|ref|>text<|/ref|><|det|>[[115, 460, 883, 492]]<|/det|> +We thank the reviewer for their positive evaluation of the Introduction section and how it lays out the background for this research. + +<|ref|>sub_title<|/ref|><|det|>[[115, 508, 176, 522]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[115, 523, 883, 555]]<|/det|> +Figure 1h - can't say if the color in the figure matches the color scale of the image or not. The color in the figure looks a bit greenish. + +<|ref|>text<|/ref|><|det|>[[115, 571, 883, 619]]<|/det|> +Thank you for pointing that out. We have corrected the 3D AFM figure panels (see figure below). We have also recalculated the Rp values based on the 2D images (Supplementary Fig. 5) and the new values are reflected in panels j, k, l, m, n and o of Fig. 1. The trends are the same as before. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 130, 870, 680]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 697, 883, 746]]<|/det|> +Three- dimensional AFM profiles for the compositions look great but these profiles can be included for all the compositions for better visualization to the audience and better consistency in the supplementary information. + +<|ref|>text<|/ref|><|det|>[[115, 760, 883, 794]]<|/det|> +Thank you for the suggestion. We have added the 3D AFM maps (see below) for all nine compositions in the Supplementary Information (Supplementary Fig. 6). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[125, 130, 856, 465]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 470, 884, 536]]<|/det|> +
Supplementary Fig. 6 | Three-dimensional atomic force microscopy height profiles of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite thin films. a \(\{x / y\} = 0.25|0.40\) . b \(\{x / y\} = 0.50|0.40\) . c \(\{x / y\} = 0.75|0.40\) . d \(\{x / y\} = 0.25|0.50\) . e \(\{x / y\} = 0.50|0.50\) . f \(\{x / y\} = 0.75|0.50\) . g \(\{x / y\} = 0.25|0.60\) . h \(\{x / y\} = 0.50|0.60\) . i \(\{x / y\} = 0.75|0.60\) .
+ +<|ref|>text<|/ref|><|det|>[[114, 565, 883, 614]]<|/det|> +Page 6, Line 25 – Instead of mentioning the feature size of the smooth films to be around \(100 \mathrm{nm}\) it would be better if mentioned in \(\mu \mathrm{m}\) , this would distinguish the feature sizes from smooth to rough films along with easy comparison + +<|ref|>text<|/ref|><|det|>[[114, 629, 883, 662]]<|/det|> +We have changed the units from \(\mathrm{nm}\) to \(\mu \mathrm{m}\) when discussing feature sizes observed in AFM measurements (see below). + +<|ref|>text<|/ref|><|det|>[[114, 677, 883, 726]]<|/det|> +Page 7: “The feature sizes in the smooth films \((\{x / y\} = 0.25|0.40, 0.50|0.40, \text{and} 0.25|0.60)\) are on the order of \(0.10 \mu \mathrm{m}\) whereas compositions that yield rough films \((\{x / y\} = 0.75|0.40, 0.50|0.60, \text{and} 0.75|0.60)\) exhibit feature sizes as large as \(1.5 - 2.0 \mu \mathrm{m}\) .” + +<|ref|>text<|/ref|><|det|>[[114, 741, 883, 774]]<|/det|> +Page 6, Line 26 – It is confusing if different names are used for the rough films, such as heterogeneous films, a common representation can be used. + +<|ref|>text<|/ref|><|det|>[[114, 789, 883, 870]]<|/det|> +Thank you for this suggestion. We’ve made changes to the text to distinguish between morphological behavior and compositional/photoluminescence properties. We have now used the words “smooth” and “rough” when discussing morphology and we use “homogeneous” and “heterogeneous” when describing other forms of disorder such as for the XRF, PL and TOF- SIMS data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 140, 883, 220]]<|/det|> +Page 6, Line 28 – A description can be added for the increase in average roughness with the increase in MA and Br content as seen in Fig.1 and Supplementary Fig.4 Why was the compositional study not performed with MA content of \(0\%\) and \(100\%\) ? Even though they do not fall in the desired bandgap of the perovskite top won’t the insights be helpful to check if the trend of large feature sizes continues with more MA content? + +<|ref|>text<|/ref|><|det|>[[115, 235, 883, 269]]<|/det|> +To address the first part of this comment, we have edited the main text (page 6) to describe the increase in roughness parameters \(R_{\mathrm{p}}\) and \(R_{\mathrm{q}}\) . + +<|ref|>text<|/ref|><|det|>[[115, 283, 883, 333]]<|/det|> +Page 7: “This results in an increase in the average maximum profile height \((R_{\mathrm{p}})\) and root mean square average roughness \((R_{\mathrm{q}})\) as a function of increasing MA and Br contents (Supplementary Fig. 7).” + +<|ref|>text<|/ref|><|det|>[[115, 347, 883, 412]]<|/det|> +We have also studied a wider range of MA- contents for Br- contents \(40\%\) and \(60\%\) . SEM images (see below) show that the trends are similar; lower MA content films are smooth while high MA content films are rough. The figure has been added to the Supplementary Figures and the main text has been edited to refer to it (see text below). + +<|ref|>text<|/ref|><|det|>[[115, 427, 883, 476]]<|/det|> +Page 6: “We note that the behavior is also consistent at lower \((0\%)\) and higher \((100\%)\) MA contents (Supplementary Fig. 3) and that the appearance of morphological disorder does not significantly affect SEM features at \(1 - 2\mu \mathrm{m}\) size or create voids in the film surface (Supplementary Fig. 4).” + +<|ref|>image<|/ref|><|det|>[[315, 514, 680, 740]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 746, 883, 794]]<|/det|> +Supplementary Fig. 3 | Surface SEM images of \((\mathrm{FA}_{1 - x}\mathrm{MA}_{x})\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_{y})_{3}\) perovskite thin films for different compositions. a \(\{x / y\} = 0|0.40\) . b. \(\{x / y\} = 1.0\dot{0}.40\) . c. \(\{x / y\} = 0|0.60\) . d. \(\{x / y\} = 1.0\dot{0}.60\) . + +<|ref|>text<|/ref|><|det|>[[115, 809, 883, 857]]<|/det|> +Page 8, Line 14 – Roughness information for \(50\%\) Br compositions i.e. \(0.25 / 0.50\) , \(0.50 / 0.50\) , \(0.75 / 0.50\) can be added to supplementary as it is not present in either Fig.1 or the supplementary figures. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 140, 883, 189]]<|/det|> +We have added SEM and AFM data for \(50\%\) Br series to the Supplementary Information (Supplementary Figs. 2. 5 and 6) along with values for \(R_{\mathrm{p}}\) and \(R_{\mathrm{q}}\) (Supplementary Fig. 7) (see figures below). + +<|ref|>image<|/ref|><|det|>[[241, 211, 752, 320]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 330, 883, 364]]<|/det|> +
Supplementary Fig. 2 | Surface SEM images of \((\mathrm{FA}_{1 - x}\mathrm{MA}_x)\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_y)_3\) perovskite films with \(50\%\) Br content and different MA contents. \(a x = 0.25\) . \(b.x = 0.50\) . \(c.x = 0.75\)
+ +<|ref|>image<|/ref|><|det|>[[141, 383, 863, 629]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 637, 883, 702]]<|/det|> +
Supplementary Fig. 5 | Atomic force microscopy height profiles of \((\mathrm{FA}_{1 - x}\mathrm{MA}_x)\mathrm{Pb}(\mathrm{I}_{1 - y}\mathrm{Br}_y)_3\) perovskite thin films. a \(\{x / y\} = 0.25 / 0.40\) . b \(\{x / y\} = 0.50 / 0.40\) . c \(\{x / y\} = 0.75 / 0.40\) . d \(\{x / y\} = 0.25 / 0.50\) . e \(\{x / y\} = 0.50 / 0.50\) . f \(\{x / y\} = 0.75 / 0.50\) . g \(\{x / y\} = 0.25 / 0.60\) . h \(\{x / y\} = 0.50 / 0.60\) . i \(\{x / y\} = 0.75 / 0.60\) . Scale bars are \(10\mu \mathrm{m}\) . Height range is from \(0 - 2.0\mu \mathrm{m}\) .
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[127, 132, 856, 462]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 469, 884, 536]]<|/det|> +
Supplementary Fig. 6 | Three-dimensional atomic force microscopy height profiles of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite thin films. a \(\{x / y\} = 0.25|0.40\) . b \(\{x / y\} = 0.50|0.40\) . c \(\{x / y\} = 0.75|0.40\) . d \(\{x / y\} = 0.25|0.50\) . e \(\{x / y\} = 0.50|0.50\) . f \(\{x / y\} = 0.75|0.50\) . g \(\{x / y\} = 0.25|0.60\) . h \(\{x / y\} = 0.50|0.60\) . i \(\{x / y\} = 0.75|0.60\) .
+ +<|ref|>image<|/ref|><|det|>[[200, 556, 787, 711]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 718, 884, 754]]<|/det|> +
Supplementary Fig. 7 | Film roughness as a function of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite composition. a Average maximum peak profile height. b Root mean square average roughness.
+ +<|ref|>text<|/ref|><|det|>[[113, 766, 884, 800]]<|/det|> +Page 8, Line 18 – A reference to Fig.2c, 2e, 2g is missing in the main text Supplementary Fig.6c is labeled wrong in the caption as 0.25/0.40, it should be 0.25/0.50 + +<|ref|>text<|/ref|><|det|>[[115, 814, 710, 832]]<|/det|> +Thank you for pointing that out. We have made the corrections (see below). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 124, 884, 159]]<|/det|> +Page 9: “smooth films \((\{x / y\} = 0.25|0.40, 0.50|0.40, 0.25|0.50, 0.50|0.50, \text{and} 0.25|0.60)\) show GIWAXS patterns (Fig. 2a, 2b, 2d, 2e, and 2g)” + +<|ref|>text<|/ref|><|det|>[[113, 172, 884, 206]]<|/det|> +Page 9: “roughness \(> 1 \mu \mathrm{m}\) with composition \((\{x / y\} = 0.75|0.40, 0.75|0.50, 0.50|0.60, \text{and} 0.75|0.60)\) show GIWAXS patterns” + +<|ref|>text<|/ref|><|det|>[[115, 220, 527, 238]]<|/det|> +Figure 3 – check the spin coating timing in methods + +<|ref|>text<|/ref|><|det|>[[115, 250, 884, 302]]<|/det|> +We have confirmed the spin- coating time. To clarify, the data presented in Figure 3 shows a small section (between 21 s and 31 s) of the overall 40 s spin- coating period. The structural evolution during the entire process can be seen in Supplementary Fig. 13. + +<|ref|>text<|/ref|><|det|>[[115, 315, 884, 350]]<|/det|> +Page 9, Line 11 – Is there a reason why the time stamp between 25s and 31s is different for Fig.3 (29s) and Supplementary Fig.7 (27s)? + +<|ref|>text<|/ref|><|det|>[[115, 363, 884, 414]]<|/det|> +Thank you for pointing this out. We have now made the two figures uniform, including the frame at 29 s in the Supplementary Figure (see below). The structural behavior is similar to what we had previously reported at 27 s. + +<|ref|>image<|/ref|><|det|>[[240, 430, 748, 835]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 883, 173]]<|/det|> +Supplementary Fig. 11 | In situ GIWAXS patterns acquired at different times during spin- coating of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite films. a, c, e and g \(\{x / y\} = 0.25|0.50\) . b, d, f and h and \(0.75\dot{0}.50\) . The anti- solvent is applied after 25 s (panels c and d). + +<|ref|>text<|/ref|><|det|>[[115, 203, 884, 251]]<|/det|> +Supplementary Fig.7- 0.75/0.50 does not show similar features (as in the yellow shading) as Fig.3 for the antisolvent drop at 25s, This figure needs to be checked if the images are misplaced or if there is an actual difference. + +<|ref|>text<|/ref|><|det|>[[115, 268, 883, 380]]<|/det|> +The yellow shaded region in Supplementary Fig. 11 is related to scattering observed when the antisolvent is cast onto the film but disappears immediately after casting. Similar increases in intensity in the \(q\approx 1 - 1.2\mathrm{\AA}^{- 1}\) range has previously been reported in other studies using in- situ GIWAXS measurements (for example Fig. 3 in Adv Energy Mater. 2017, 7, 1602600, Figs. 2b and 2f in Adv. Mater. 2019, 31, 1901284). A likely explanation for its absence in the \(\{x / y\} = 0.75 / 0.50\) measurement is the ms- scale mismatch in the antisolvent drip timing and the frame acquisition which likely causes this feature to not appear prominently in the 25 s frame. + +<|ref|>text<|/ref|><|det|>[[115, 395, 771, 412]]<|/det|> +Also, there is a discrepancy in the labeling of Supplementary Fig.7 and its captions. + +<|ref|>text<|/ref|><|det|>[[115, 427, 883, 460]]<|/det|> +There was an error in the panel labels in the caption, it has been rectified (see below). Thank you for pointing it out. + +<|ref|>text<|/ref|><|det|>[[115, 475, 883, 523]]<|/det|> +Page S8: "Supplementary Fig. 11 | In situ GIWAXS patterns acquired at different times during spin- coating of \((\mathbf{FA}_{1 - x}\mathbf{MA}_x)\mathbf{Pb}(\mathbf{I}_{1 - y}\mathbf{Br}_y)_3\) perovskite films. a, c, e, and g \(\{x / y\} = 0.25|0.50\) . b, d, f, and h and \(0.75\dot{0}.50\) . The anti- solvent is applied after 25 s (panels c and d)." + +<|ref|>text<|/ref|><|det|>[[115, 539, 883, 571]]<|/det|> +Fig.3 - It is evident from the figure but it is better to mention that Fig.3a, c, e, g are of \(0.25 / 0.60\) and Fig.3b, d, f, g are of \(0.75 / 0.60\) in the caption. + +<|ref|>text<|/ref|><|det|>[[115, 587, 808, 604]]<|/det|> +Thank you for the suggestion, we have made the suggested change in the figure caption. + +<|ref|>text<|/ref|><|det|>[[115, 618, 883, 749]]<|/det|> +Page 11: "Fig. 3 | Crystallization dynamics of mixed- halide perovskite thin films. In situ GIWAXS patterns of perovskites with compositions \(\{x / y\} = 0.25|0.60\) and \(\{x / y\} = 0.75\dot{0}.60\) during spin- coating. Panels mark time stamps during the spin coating process. a, b 21 s. c, d 25 s. e, f 29 s. g, h 31 s. The frame at 25 s represents the casting of the antisolvent onto the substrate. Azimuthal intensity profiles of the main Debye- Scherrer ring (100) as a function of \(\chi\) angle from GIWAXS for different perovskite compositions acquired in the \(20 - 40\) s period of spin- coating. i \(\{x / y\} = 0.25|0.60\) . j \(\{x / y\} = 0.75\dot{0}.60\) . Panels a, c, e, g, and i refer to \(\{x / y\} = 0.25|0.60\) and panels b, d, f, h, and j refer to \(\{x / y\} = 0.75\dot{0}.60\) . The data in panels i and j have been vertically offset for clarity." + +<|ref|>text<|/ref|><|det|>[[115, 763, 686, 780]]<|/det|> +Explanation and reference for Fig. 3i and 3j are missing in the main text. + +<|ref|>text<|/ref|><|det|>[[115, 794, 883, 843]]<|/det|> +Thank you for pointing that out, we have referred to it in the main text. The explanation was already written (referring to Supplementary Fig. 9) in the original version of the text. Now it also refers to Fig. 3i and 3j (see below). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 883, 174]]<|/det|> +Page 10: "we propose that in an MA- rich environment, heterogeneous crystal nucleation leads to the formation of oriented bromide- rich perovskites immediately after antisolvent casting (Fig. 3i, 3j and Supplementary Fig. 13) followed by the incorporation of iodide- containing phases18" + +<|ref|>text<|/ref|><|det|>[[115, 188, 883, 205]]<|/det|> +Page 11, Line 3 – The sentence on the elemental map of Pb is confusing, can be simplified + +<|ref|>text<|/ref|><|det|>[[115, 220, 883, 252]]<|/det|> +Thank you for the suggestion. We have added a sentence to explain the relationship between Pb content and film thickness (see below). + +<|ref|>text<|/ref|><|det|>[[115, 267, 883, 300]]<|/det|> +Page 11- 12: "As a result, regions with higher Pb content refer to the peak- like regions of wrinkles whereas lower Pb content corresponds to valley- like regions." + +<|ref|>text<|/ref|><|det|>[[115, 315, 883, 348]]<|/det|> +Page 11, Line 13 – It would be better to mention it as homogeneous distribution of Pb, Br, and I instead of homogeneous distribution of ions + +<|ref|>text<|/ref|><|det|>[[115, 363, 883, 395]]<|/det|> +Thank you for the suggestion, the text has been changed (see below) to be more specific to the elements being discussed. + +<|ref|>text<|/ref|><|det|>[[115, 410, 883, 442]]<|/det|> +Page 12: "Similar homogeneous distribution of iodide- to- bromide ratio is observed for other smooth films" + +<|ref|>text<|/ref|><|det|>[[115, 458, 883, 491]]<|/det|> +Fig.4 – Line cuts can be elaborated in a better way in the main text, what are the dotted lines in those figures? + +<|ref|>text<|/ref|><|det|>[[115, 506, 883, 571]]<|/det|> +Thank you for the suggestion. We have marked the lines as solid and dashed for iodide- to- bromide ratio and Pb- content respectively in the figure caption (see below). We have also emphasized in the main text that the correlation being drawn is between the local increase in layer thickness (Pb content) and higher iodide concentration. + +<|ref|>text<|/ref|><|det|>[[115, 586, 883, 795]]<|/det|> +Page 13: "Fig. 4 | Compositional heterogeneity in mixed- halide perovskite thin films from nano- XRF. a Normalized elemental maps of Pb, I, and Br of perovskite thin film with \(\{x / y\} = 0.25|0.40\) . b Map of iodide- to- bromide ratio in shaded region of panel a. Sub- panels A, B, C, and D represent the normalized Pb elemental map in regions highlighted (dashed squares) in the iodide- to- bromide map. c Line cuts of iodide- to- bromide ratios (solid) overlapped with local Pb content line cuts (dashed) marked with (1) and (2) in panel b. d Normalized elemental maps of Pb, I, and Br of perovskite thin film with \(\{x / y\} = 0.50|0.60\) . e Map of iodide- to- bromide ratio in shaded region of panel d. Sub- panels E, F, G, and H represent the normalized Pb elemental map in regions highlighted in the iodide- to- bromide map. f, g Line cuts of iodide- to- bromide ratios (solid) overlapped with local Pb content line cuts (dashed) at points marked with (1), (2), (3), and (4) in panel e. Maps show that smooth films yield homogeneous halide distribution across the film thickness and wrinkled films have iodide- rich domains concentrated at peak- like regions. All scale bars are \(10 \mu \mathrm{m}\) ." + +<|ref|>text<|/ref|><|det|>[[115, 810, 883, 858]]<|/det|> +Page 12: "Line cuts at four distinct locations of the film and two- dimensional maps (Fig. 4f, 4g, and Supplementary Fig. 18) further confirm the positive correlation between the local increase in layer thickness (Pb content) and higher iodide concentration." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 140, 881, 172]]<|/det|> +Supplementary figure 12 – homogeneous distribution of ions? 12a – has more iodine rich regions, 12b more equal variation, 12c much smoother variation + +<|ref|>text<|/ref|><|det|>[[115, 189, 883, 317]]<|/det|> +Thank you for this comment. We would like to clarify that the three compositions in Supplementary Fig. 16 \(\{x / y\} = 0.50|0.40, 0.50|0.50\) and \(0.25|0.60\) have different halide contents as a result of which the overall iodide/bromide content is different in each case. There is also a stochastic distribution of halides which may result in nanometer- scale domains rich in either iodide/bromide as has also been observed by others (J. Am. Chem. Soc. 2016, 138, 15821 – 15824 and ACS Energy Lett. 2022, 7, 471 – 480). What we would like to emphasize in this work though that in these compositions, the large micrometer- scale domains related to wrinkling are absent. We have clarified this in the main text now (see text below) and thank you for raising this issue. + +<|ref|>text<|/ref|><|det|>[[115, 333, 881, 365]]<|/det|> +Page12: "We note here that the stochastic distribution of ions causes local nanometer- scale domains to develop that are rich in iodide or bromide ions \(^{26,28}\) ." + +<|ref|>text<|/ref|><|det|>[[115, 380, 881, 412]]<|/det|> +Supplementary figure 13 – Instead of homogeneous and heterogeneous distribution can this be called clustered distribution vs unclustered distribution? + +<|ref|>text<|/ref|><|det|>[[115, 428, 883, 619]]<|/det|> +Thank you for this suggestion. Indeed the nomenclature referring to this behavior can use several combination of words such as homogeneous/heterogeneous, homogeneous/inhomogeneous, mixed/unmixed, segregated/non- segregated, aggregated/disaggregated and clustered/unclustered. And although we understand the motivation to use "clustered/unclustered" instead of "homogeneous/heterogeneous", we find ourselves very much within the currently used nomenclature in the field, as demonstrated by other publications (Nat. Rev. Mater. 2019, 4, 573 – 587, Nat. Nanotechnol. 2022, 17, 190–196, Matter 2024, 7, 1054 – 1070, Science 2019, 363, 627 – 631, Chem. Mater. 2016, 28, 6536 – 6543, Science 2022, 378, 747 – 754). As a result, we have continued using homogeneous/heterogeneous to refer to this behavior in order to be consistent with published works. We have nevertheless now made a clear distinction (based on input from Reviewer #2) between homogeneous/heterogeneous for variations related to composition and luminescence and smooth/rough describe morphological properties. + +<|ref|>text<|/ref|><|det|>[[115, 635, 883, 699]]<|/det|> +Page 15, Line 10 – Hyperspectral PL study on composition 0.75/0.60 can be included to make a stronger claim on the statement about an increase in PL heterogeneity with an increase in bromide content. The same study can be included for composition 0.25/0.60 to rule out the possibility of PL heterogeneity increase with Br at lower MA content. + +<|ref|>text<|/ref|><|det|>[[115, 714, 883, 795]]<|/det|> +We have considered expanding our compositional space further (75% MA, 60% Br) for local PL measurements. However, we found that these compositions are very sensitive to visible illumination required for the PL measurement such that within the acquisition time, ion migration occurs causing a red- shift in the PL. As a result, measurements that use lower light intensity such as the sensitive EQE measurements (Fig. 6) are more suitable for such compositions. + +<|ref|>text<|/ref|><|det|>[[115, 811, 883, 842]]<|/det|> +Fig.6 – In the figure caption the continuous illumination is mentioned as 10 minutes but in the main text it is mentioned as 5 minutes – check this discrepancy + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 883, 157]]<|/det|> +Thank you for pointing out this typo. We have corrected it in the main text. The correct duration is 10 min (see below). + +<|ref|>text<|/ref|><|det|>[[115, 172, 881, 205]]<|/det|> +Page 20: "We used continuous illumination (532 nm, 1- Sun equivalent intensity, 10 min.) to induce defect migration and drive halide segregation in the solar cells58." + +<|ref|>text<|/ref|><|det|>[[115, 220, 883, 300]]<|/det|> +The claims over increased photostability based on the inclusion of MA without any device or accelerated testing under light + heat is a bit concerning, especially due to the well- characterized instability challenges of MA inclusion. How can the authors be sure that the improvements in morphology from crystallization control with larger MA fractions will not lead to degradation in devices? + +<|ref|>text<|/ref|><|det|>[[115, 316, 883, 571]]<|/det|> +Thanks for this interesting question. Indeed, MA has been linked to degradation in previous studies (for example Energy Environ. Sci. 2016, 9, 1655 - 1660). However, the wrinkling behavior we describe in this work is not limited to MA- containing perovskites and has been observed in MA- free perovskites in several prior publications (Nature Communications 2021, 12, 1554, ACS Energy Letters 2018, 3, 6, 1225- 1232, J. Phys. Chem. C 2018, 122, 30, 17123- 17135, J. Phys. Chem. Lett. 2024, 15, 36, 9255- 9262, ACS Energy Lett. 2023, 9, 75- 84, J. Appl. Phys. 2018, 123, 175302, Matter 2020, 2, 207- 219). The precise role of the cation in this process needs further examination although there is one report in triple- cation (Cs, FA, MA) perovskites that describes Cs heterogeneity in wrinkled films (J. Phys. Chem. C 2018, 122, 23345- 23351). It is therefore possible that ionic (cation and halide) heterogeneity also occurs in MA- free materials, similar to what we report in our work. As a result, we speculate that in a MA- free wrinkled film with ionic heterogeneity, the halide migration processes discussed in our work also occur and drive degradation. Therefore, while it is entirely possible that degradation due to MA dissociation is suppressed in MA- free films, degradation due to wrinkling will likely still persist. We have added some text (see below) to the Summary section to highlight the ubiquity of this behavior irrespective of MA content. + +<|ref|>text<|/ref|><|det|>[[115, 587, 881, 634]]<|/det|> +Page 22: "We also note previous works that report similar morphological behavior in methylammonium- free perovskite compositions, emphasizing possible limits to charge- carrier dynamics and stability11,12,14- 16,18." + +<|ref|>text<|/ref|><|det|>[[115, 651, 881, 730]]<|/det|> +There is a discussion of relevance to tandems and multi- junctions in the work—such as claiming the wrinkled surface is not amenable to multijunction processing—but there are reports of high- efficiency tandems on textured Si with a similar profile to the wrinkled films (https://www.sciencedirect.com/science/article/pii/S2542435120300350). Can the authors comment on why they expect this to be different than in the case of Si? + +<|ref|>text<|/ref|><|det|>[[115, 746, 883, 857]]<|/det|> +Thank you for raising this interesting issue. Indeed, there are reports of tandem devices that successfully incorporate texturing. Devices using thermal evaporation to coat the perovskite and charge transport layers certainly don't face these processing challenges when depositing on textured surfaces (Nature Materials 2018, 17, 820). There are other reports of solution- processed perovskite sub- cells on top of textured silicon sub- cells with varying degrees of texturing. Here, to our knowledge, only blade coating (Joule 2020, 4, 5, 850) has been reported for coating on top of textures in the range of \(>1\) um. The texture heights must be lower for spin- coating to be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 123, 883, 395]]<|/det|> +applicable (Nature Nanotechnology 2022, 17, 1214 and Science 2020, 367, 6482, 1135). Furthermore, in this work, we are trying to address challenges for devices that are beyond tandem solar cells (triple- junctions and quadruple- junctions, for example), motivating our choice to study perovskite compositions with high bromide contents. There, irrespective of the overall configuration (perovskite- perovskite- silicon or all- perovskite), there is a perovskite- perovskite "sub- tandem" in the stack. To our knowledge, no reports are currently available where a textured perovskite sub- cell has been used in a multijunction device. Finally, another important challenge to consider, in addition to the perovskite deposition, is the conformal coating of a series of thin ( \(< 50 \mathrm{nm}\) ), optically benign charge transport and interfacial layers in complex multijunction stacks using solution- processing. And while several layers are deposited using evaporation, sputtering or atomic layer deposition ( \(C_{60}\) , \(\mathrm{SnO_x}\) , TCO, anti- reflection coatings), spin- coating and other solution- based methods are common for other layers. For example, commonly used self- assembled monolayers ( \(< 5 \mathrm{nm}\) ) are very sensitive to the surface (Nature 2023, 624, 289- 294, ACS Appl. Mater. Interfaces 2022, 14, 1, 2166- 2176). Solution- processed interfacial layers in devices are also very thin. So, taken together, we strongly believe that overcoming challenges related to wrinkling is extremely relevant to the development of multijunction device stacks where solution- processing is involved in the series of fabrication steps. + +<|ref|>text<|/ref|><|det|>[[115, 410, 883, 460]]<|/det|> +The results section has the required details, which are well- elaborated. The hypothesis observed is well- explained and well- validated by relevant tests. However, the results section still needs some refinement to put forth the best representation. + +<|ref|>text<|/ref|><|det|>[[115, 474, 883, 508]]<|/det|> +Thank you for the overall positive view of our results. We hope that the changes we have described above have addressed your comments/questions appropriately. + +<|ref|>text<|/ref|><|det|>[[115, 523, 355, 555]]<|/det|> +Summary This section is well- explained. + +<|ref|>text<|/ref|><|det|>[[116, 571, 407, 587]]<|/det|> +Thank you for the positive comment. + +<|ref|>text<|/ref|><|det|>[[116, 602, 298, 618]]<|/det|> +Materials and Methods + +<|ref|>text<|/ref|><|det|>[[116, 634, 243, 650]]<|/det|> +Well- elaborated + +<|ref|>text<|/ref|><|det|>[[116, 666, 407, 683]]<|/det|> +Thank you for the positive comment. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 89, 378, 108]]<|/det|> +## RESPONSE TO REVIEWERS + +<|ref|>text<|/ref|><|det|>[[115, 123, 882, 177]]<|/det|> +We thank the reviewers for their positive evaluation of our work. We have addressed the comment from Reviewer #1 below. The comment is marked in BLUE and the authors' response is marked in BLACK. + +<|ref|>sub_title<|/ref|><|det|>[[115, 194, 437, 212]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 229, 882, 298]]<|/det|> +I thank the reviewers for addressing my comments. One lingering question remains, though. The authors' explanation of wrinkle formation due to the instability of the elastic/viscoelastic bilayer is reasonable. However, what remains unexplained is the relative richness of the peaks/ridges in iodide and the troughs/valleys in bromide. + +<|ref|>text<|/ref|><|det|>[[115, 315, 882, 456]]<|/det|> +We thank the reviewer for their positive evaluation and for this question. The relative richness in iodide of the peaks compared to the valleys in the XRF measurements is related to the overall volume fractions that the iodide- rich (viscoelastic) and iodide- poor (elastic) layers represent in those regions. In the peak- like region, the iodide- rich viscoelastic layer is thicker than in the valley- like region. As a result, in the XRF measurement that probes the bulk composition, the iodide- rich viscoelastic layer represents a larger volume fraction at the peaks and a relatively smaller volume fraction in the valley. As a result, the peaks show an overall richness in iodide compared to the valley. + +<|ref|>sub_title<|/ref|><|det|>[[115, 473, 437, 490]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 491, 882, 525]]<|/det|> +The authors have responded to the reviewers' comments and revised the manuscript accordingly. I have no additional remarks. + +<|ref|>text<|/ref|><|det|>[[115, 543, 520, 560]]<|/det|> +We thank the reviewer for their positive evaluation. + +<|ref|>sub_title<|/ref|><|det|>[[115, 578, 437, 595]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 596, 610, 613]]<|/det|> +The comments and the suggestions were addressed adequately. + +<|ref|>text<|/ref|><|det|>[[115, 630, 520, 648]]<|/det|> +We thank the reviewer for their positive evaluation. + +<--- Page Split ---> diff --git a/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/images_list.json b/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/supplementary_1_Peer Review file.mmd b/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/supplementary_1_Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d1d190eee42b81ac83b3b4587311d2db2609b7d1 --- /dev/null +++ b/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/supplementary_1_Peer Review file.mmd @@ -0,0 +1,366 @@ + +# nature portfolio + +Peer Review File + +# Sde Proteins Coordinate Ubiquitin Utilization and Phosphoribosylation to Establish and Maintain the Legionella Replication Vacuole + +Corresponding Author: Dr Ralph Isberg + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) In this manuscript, Kotewicz, Zhang, and Kim et al. examined the roles of both the DUB and PR- ubiquitination activities of Sde proteins from Legionella. Based on their observations, the authors proposed that the DUB domain is responsible for ER rearrangement, and PR- ubiquitination on the ubiquitin chain on the LCV prevents the interaction with autophagic adaptors such as p62, allowing the evasion of host autophagy. + +Overall, this is an interesting story, but there are several points that are not clear enough to support the conclusion. Authors should address these concerns to strengthen their findings, and I do not recommend the current version of the manuscript for publication in Nature Communications. + +[Specific comments] + +1. (Lines 175-184) Authors intended to test the hypothesis that the DUB domain of Sde is linked with pR-modification. However, the designed experiment shown in Fig. 1L should be redesigned to properly examine this hypothesis. I would prepare another set of cells transfected with HA-Ub R42A to block PR-ubiquitination. The current bands from cells with pSdeA can be either canonical ubiquitination or pR-ubiquitination. + +2. (Lines 197-199) Data shown in Fig. 1 do not provide direct evidence to support the likely role of pR-modification in stabilizing polyUb. + +3. (Fig. 2A) Several points: (1) Authors should explain why there are no ubiquitin signals detected under ART-conditions. (2) Why doesn't the DUB domain of WT SdeC cleave K63-Ub? Is ART and PDE working faster than DUB? Even if that is the case, there is no evidence that the ubiquitin chains shown here are pR-modified. Based on the structure of mART and PDE in complex with ubiquitin, it will be very difficult for the internal ubiquitin moieties within the poly-Ub molecule to be located in the active site. (3) (Lines 199-202) There is no direct evidence that the poly-Ub chain is modified by PR- or ADPR-. The cited reference (Puvar et al.) used di-ubiquitin, where both ubiquitin moieties are exposed and accessible to mART and PDE. Therefore, authors should provide more direct evidence that internal ubiquitin is modified by PR- or ADPR-. (4) The Ub7 band from both K48 and K63 becomes faint after incubation with DUBs. Please provide an explanation for this. + +4. (Fig. 3) Similar to the above points, incubating polyubiquitin with Sde enzymes does not guarantee PR- or ADPR- modifications. Authors should provide clear biochemical evidence to support the entire data shown in Fig. 3. + +5. (Figs. 4, 5) I agree that delta Sde affects the localization of p62 on LCV and that it is linked to the activity of the ART and PDE domains, promoting PR-ubiquitination. However, without direct biochemical evidence from Fig. 2 and Fig. 3, one cannot conclude that the polyubiquitin chains on the LCV are PR- or ADPR-modified. + +6. Authors conducted many SPR experiments. Providing kinetic values would be more insightful than showing sensorsgrams. + +(Minor comments) + +Fig. 1J: pSdec -> pSdeC Fig. 2A: Out-1 -> OTU1 Fig. S1 and line 172: Is it C293A or C293S? + +<--- Page Split ---> + +Font size in Fig S1 differs from each other. + +Reviewer #2 + +(Remarks to the Author) + +In this work Kotewicz and colleagues dissect the role of the Sde protein family in the establishment of the Legionella containing vacuole in host cells. Using molecular, biochemical and cell biology approaches the authors propose that the Sde protein family transiently (first 20 min of infection disappearing within 1h of infection) block p62 accumulation on the polyubiquitinated vacuole. This is achieved by firstly using the DUB domain of the Sde proteins that deubiquitinates K63 linked ubiquitin to provide Ub to the mART domain of Sde proteins that catalyzes pr- Ub conjugation on e.g. Rtn4 that accumulates on the LCV. This, pr- modification of ubiquitin blocks the association with the autophagy adaptor p62 with the vacuole and thereby protects the LCV against autophagy. + +This very detailed dissection of the function of the Sde family proteins and their different domains in the establishment of the Legionella containing vacuole and some of their results contradict previously published work. + +It is very interesting that the Sde protein family camouflages the LCV and blocks p62 accumulation and thereby autophagy in the first 20min. Indeed, the first minutes of infection are without doubt very important to survive or surrender, but it is known that Legionella blocks/retards autophagy much longer than the first 20 min of infection. How is this process thus maintained when the Sde proteins are not active anymore? Is there a timely difference in the secretion e.g. of the Sde proteins and RavZ or LpSpl or others? + +Line 108- 109 several effectors/systems are described that Legionella employs to block autophagy. Please add the effector LpSpl (PMID: 26831115) + +Lines 113- 114 and elsewhere in the manuscript "... ADPribosylation or phosphoribosylation of Ub interferes with autophagy by causing an absolute physical block on binding of polyUb to anautophagy adaptor, primarily by phosphoribosylation of target Ub chains about the LCV... What is an "absolute physical block"? + +The authors present many convincing results, however in all different experiments the L. pneumophila WT strain was used without empty vector. Legionella is very sensitive to carrying vectors and intra and extracellular replication changes when adding vector. Thus, the control should be not only the sde mutant \(^+\) empty vector but also the WT \(^+\) empty vector to have the correct comparison when strains carrying plasmids are analyzed. This is the case for the entire Figure 1, Figure 2 D- H, Figure 4 A- H, and Figure 5. Please repeat at least the most important experiments with a correct WT vector control. + +Figure 2A - please provide a better explanation what exactly one can see in this panel Figure 2B - which strain is pSdeC WT? Figure 2D- H - please quantify the images + +Line 180 it reads... To test this hypothesis, HEK293T cells transfected with HA- Ub were challenged by L. pneumophila harboring either WT or DUB defective (C118S) derivatives as the only active Sde family members... The HEK293T cells were challenged with Legionella at an MOI of 10. HEK293T cells are very poorly infected, I am surprised that an MOI=10 was sufficient? Did you check how many bacteria were internalized before continuing this experiment were HEK293T cells expressing the Fc - RII receptor used? In this case please specify in the M&M section + +Lines 275- 276 where are the quantifications? Should eb shown + +Throughout the manuscript one can read ... " about the LCV..." I don't think that the use of "about" is correct in this context + +Line 33. . please correct to "The Legionella pneumophila Sde family of translocated proteins promotes host tubular > + +Author Rebuttal letter: + +Editor and Referees: Please note that major changes are noted in the manuscript by vertical lines in left margins. + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Kotewicz, Zhang, and Kim et al. examined the roles of both the DUB and PR- ubiquitination activities of Sde proteins from Legionella. Based on their observations, the authors proposed that the DUB domain is responsible for ER rearrangement, and PR- ubiquitination on the ubiquitin chain on the LCV prevents the interaction with autophagic adaptors such as p62, allowing the evasion of host autophagy. + +Overall, this is an interesting story, but there are several points that are not clear enough to support + +<--- Page Split ---> + +the conclusion. Authors should address these concerns to strengthen their findings, and I do not recommend the current version of the manuscript for publication in Nature Communications. + +Related points 1 and 2. + +1 (Lines 175- 184) Authors intended to test the hypothesis that the DUB domain of Sde is linked with pR- modification. However, the designed experiment shown in Fig. 1L should be redesigned to properly examine this hypothesis. I would prepare another set of cells transfected with HA- Ub R42A to block PR- ubiquitination. The current bands from cells with SdeA can be either canonical ubiquitination or pR- ubiquitination. + +2. (Lines 197-199) Data shown in Fig. 1 do not provide direct evidence to support the likely role of pR- modification in stabilizing polyUb + +We thank the referee for the positive critique of the manuscript. Regarding points 1 and 2, we appreciate the suggestion for this experiment, but there is no evidence that SdeA can promote canonical ubiquitination. The active site shows no ability to act as an E3 ligase, as documented by the Luo lab. We concentrated on utilizing resources to directly address the other critiques of the Referee, which were answered largely by biochemical experiments coupled to LC/MS (described below). 3. (Fig. 2A) Several points: (1) Authors should explain why there are no ubiquitin signals detected under ART- conditions. + +Thank you for making this point, our previous draft was terribly confusing regarding this panel. As stated in our response to Referee 2 below, who was similarly confused by our narrative on this figure, we did a very poor job of explaining the experiments in Fig. 2A, and this section has been totally rewritten. To specifically answer Referee point 3, the loss of K63- linked ubiquitin signals in the ART(- ) is because the protein loses the ability to block its own DUB activity, which is further demonstration that the ART activity is required to block the Sde DUB activity. The reason that mono- Ub cannot be detected is that the Western was probed with the FK1 antibody, which shows very low affinity for monoUb. You will also note that there is some remaining K48 Ub, because the Sde DUB shows K63 preference. These phenomena were largely documented in our previous 2017 manuscript (PMID: 28041930). The text was modified on lines 209- 212 (but also note that this entire paragraph was rewritten to answer Referee 2 criticism, as well): + +aAs observed previously, the absence of the ART domain resulted in quantitative hydrolysis of the K63 polyUb chain by the SdeC DUB domain, leaving monomeric Ub that was poorly resolved after probing with a poly- UB specific antibody (Fig. 2A, ART- ) 22. As predicted, this hydrolysis in the absence of ART activity was less efficient with the K48- linked substrate 42. a (2) Why doesn't the DUB domain of WT SdeC cleave K63- Ub? Is ART and PDE working faster than DUB? + +Yes, this is one of the many amazing things about this enzyme. Both the ART and PDE domains are extremely efficient, as demonstrated in our previous paper (PMID: 28041930). In order to see ADPribosylation of Ub by the WT SdeC, the reaction has to be incubated on ice! If the modified protein is then shifted to 37C, the modification largely converts to pR- Ub within 1 minute. The original demonstration of a blockade of the DUB activity was seen in Fig 4E of that paper, and you can see that even after one hour, the total hydrolysis of unmodified poly- Ub by the DUB was not complete. So the kinetics of each of the activities is vastly different, with modification taking place rapidly and DUB hydrolysis taking place slowly. + +Even if that is the case, there is no evidence that the ubiquitin chains shown here are pR- modified. Based on the structure of mART and PDE in complex with ubiquitin, it will be very difficult for the internal ubiquitin moieties within the poly- Ub molecule to be located in the active site. + +See answer to comment below, which includes new experiments and a new multipanel figure to demonstrate the ability of SdeC to target internal residues. + +(3) (Lines 199-202) There is no direct evidence that the poly-Ub chain is modified by PR- or ADPR-. The cited reference (Puvar et al.) used di-ubiquitin, where both ubiquitin moieties are exposed and accessible to mART and PDE. Therefore, authors should provide more direct evidence that internal ubiquitin is modified by PR- or ADPR-. + +To answer this question, we used the same substrate as used in Fig. 4 (new numbering in the resubmitted manuscript) to demonstrate that all the internal R42 sidechains are modified to pR by WT protein. In new Figure 3, we performed the critical experiment to demonstrate quantitative modification of internal R42 residues. + +<--- Page Split ---> + +The WT SdeC protein was incubated with Ub4 at a ratio of 1 SdeC : 750 Ub4 molecules. That comes out to a ratio of 3000 R42 targets for each SdeC enzyme. After allowing 1 hr reaction at 37C, the Ub4 preparation was compared to an untreated sample. After MS and EIC analysis, we could easily demonstrate that the treated sample had greater than \(96\%\) modification of all four R42 targets in Ub4, as there was an increase in MW of 848.21 AMU, corresponding to four pR modifications. This was clearly quantitative, as there was no evidence of smaller forms having 3,2 or 1 modifications. If it were true that only the R42 residues located near the N or C terminal should be accessible, then we would see an accumulation of di- modified Ub4: this clearly was not the case. To demonstrate that R42 and only R42 were modified, peptides were scanned for ones that were not found in the unmodified control. We found only one peptide that was unique to the treated sample and had endpoints predicted for trypsin cleavage. This was a Z=3 peptide that was the 10 amino acid ion expected for Arg42 modification. No other modifications were found. On MS/MS analysis of the peptide, the modification was clearly on Arg42. We conclude that internal Arg42 residues are super- efficiently targeted by SdeC and are quantitatively modified even when there is great excess of substrate to enzyme. This work was performed by Ms. Meghan Martin in the lab of Dr. Rebecca Scheck, my long- time collaborator, using material prepared by Dr. Atish RoyChowdhury, a fellow in my lab. These three scientists have been added as authors on the manuscript. This work is now described on lines 235- 270, with experimental procedures included in the Materials and Methods section. + +(4) The Ub7 band from both K48 and K63 becomes faint after incubation with DUBs. Please provide an explanation for this. + +In Figure 2, this is not true for every sample and is dependent on the particular substrate/enzyme derivatives used. For instance, for USP2, this phenomenon is only seen with the ART \((+)\) PDE \((- )\) mutant. For OUT1, this is not seen with any derivative. It is most obvious for K48 linked Ub, which may indicate that modification works with lower efficiency on K48 relative to K63 (similar to the DUB) domain, but even with K48, the phenomenon pointed out by the referee is not uniform. It should be noted that we are performing the modification reaction in conditions that we have shown are suboptimal, in which SdeC is immobilized on beads, as described in our previous publication (PMID: 34704056). The lowered activity on beads could mean that with some samples there was incomplete modification using immobilized SdeC. There is also another confounding issue that has been pointed out by some manufacturers of Ub4 on data sheets, which is that heating the tetramer in SDS- PAGE buffer can lead to unexpected banding or smearing. In any case, we clearly showed in new Figures 3 and 4, that using very small amounts of SdeC relative to tetra- Ub results in quantitative modification. We do not think that these results argue in any way against the ability to totally modify the tetramer, when reaction conditions involve a simple aqueous mixture of components. + +4. (Fig. 3) Similar to the above points, incubating polyubiquitin with Sde enzymes does not guarantee PR- or ADPR-modifications. Authors should provide clear biochemical evidence to support the entire data shown in Fig. 3. + +See above response. We think the new Fig. 3 answers this criticism. + +5. (Figs. 4, 5) I agree that delta Sde affects the localization of p62 on LCV and that it is linked to the activity of the ART and PDE domains, promoting PR-ubiquitination. However, without direct biochemical evidence from Fig. 2 and Fig. 3, one cannot conclude that the polyubiquitin chains on the LCV are PR- or ADPR-modified + +We believe that new Fig. 3 is the biochemical evidence for modification occurring. In addition, in a simultaneously submitted manuscript, the laboratory of Yuxin Mao has performed similar experiments showing that internal UB moieties can be modified by Sde proteins. In their case, they synthesized tri- UB chains in which only one of the monomers had the WT Arg42 residue. They showed that modification occurred wherever the Arg42 was found. Arg42 internal to the trimer was modified as efficiently as the Arg42 that was found either in the N- terminal or C- terminal copy Ub. Therefore, phosphoribosylation is independent of the location of the UB monomer, which is consistent with our data in Fig. 3. + +6. Authors conducted many SPR experiments. Providing kinetic values would be more insightful than showing sensorsgrams. + +We have added more detail to the kinetic data for unmodified where relevant in the results (varies between Kd=6.2 x10e- 8 a 1.6X1- e- 7), but we disagree with the concept that modified Ub should have a different Kd than unmodified. The kinetic + +<--- Page Split ---> + +data for the modified Ub simply cannot be determined with any measure of confidence. Firstly, in the case of the modified Ub, the amount of binding is close to unmeasurable, making a kinetic determination of binding between p62 and modified Ub unreliable. In fact, the BiaCore provides a warning that the akinetic constants ka and kd are approaching the limits that can be measured by the instrument and kinetic constants cannot be uniquely determined. A Secondly, the miniscule amount of binding that can be detected is presumably due to the small amount of unmodified Ub. The prediction is that the binding kinetics of this small fraction of unmodified Ub should be identical to what is seen in the absence of Sde activity. We do, however, include kinetic data for the untreated Ub which has some level of reliability. To provide more accurate description of the experiments, we now put in the text (lines 289- 299): + +aln the absence of SdeC, Ub4 bound His- p62 with apparent \(\mathrm{KD} = 1.2\times 10 - 7\) to \(6.2\times 10 - 8M\) , indicating that binding affinity was at least as efficient as previous SPR studies using diUb as a substrate \((\mathrm{KD} = 9.3\times 10 - 8M;54)\) (Fig. 4F). Binding of p62 to mono- Ub was very poor, consistent with DUB activity interfering with recognition of p62, with binding constants that could not be reliably determined by SPR (Fig. 4G, Fig. S2C). ... In all cases in which modification blocked p62 recognition, the binding constants could not be reliably determined by SPR. + +(Minor comments) + +Fig. 1J: pSdec -> pSdeC + +Changed Fig. 2A: Out- 1 -> OTU1 + +Changed Fig. S1 and line 172: Is it C293A or C293S? + +The Figure is correct. It is C293A. Thank you for identifying this. Font size in Fig S1 differs from each other. + +The figure was carefully recomposed and then converted to PDF. We think this may have fixed the problem, although we suspect the change in font size may be associated with the conversion to pdf. + +Reviewer #2 (Remarks to the Author): + +In this work Kotevicz and colleagues dissect the role of the Sde protein family in the establishment of the Legionella containing vacuole in host cells. Using molecular, biochemical and cell biology approaches the authors propose that the Sde protein family transiently (first 20 min of infection disappearing within 1h of infection) block p62 accumulation on the polyubiquitinated vacuole. This is achieved by firstly using the DUB domain of the Sde proteins that deubiquitinates K63 linked ubiquitin to provide Ub to the mART domain of Sde proteins that catalyzes pr- Ub conjugation on e.g. Rtn4 that accumulates on the LCV. This, pr- modification of ubiquitin blocks the association with the autophagy adaptor p62 with the vacuole and thereby protects the LCV against autophagy. + +This very detailed dissection of the function of the Sde family proteins and their different domains in the establishment of the Legionella containing vacuole and some of their results contradict previously published work. + +It is very interesting that the Sde protein family camouflages the LCV and blocks p62 accumulation and thereby autophagy in the first 20min. Indeed, the first minutes of infection are without doubt very important to survive or surrender, but it is known that Legionella blocks/retards autophagy much longer than the first 20 min of infection. How is this process thus maintained when the Sde proteins are not active anymore? Is there a timely difference in the secretion e.g. of the Sde proteins and RavZ or LpSpl or others? + +Thank you for the comments and the downstream requests for changes that we think strengthened the manuscript and eliminated some confusion. + +From Fig. 4L, we clearly show that there must be at least one uncharacterized activity that accumulates over time and interferes with p62 recruitment, because other known activities (such as RavZ) do not interfere with the accumulation of p62. The presence of this hypothetical activity was similarly noted in the referenced Omodate and Roy manuscript (PMID: 32482642). This activity could either directly target autophagy adapters or the replication vacuole. No matter the nature of the + +<--- Page Split ---> + +activity, at least one additional activity must exist based on our data. + +Line 108- 109 several effectors/systems are described that Legionella employs to block autophagy. Please add the effector LpSpl (PMID: 26831115) + +Now noted in resubmission, line 109. + +Lines 113- 114 and elsewhere in the manuscript a... ADPribosylation or phosphoribosylation of Ub interferes with autophagy by causing an absolute physical block on binding of polyUb to an autophagy adaptor, primarily by phosphoribosylation of target Ub chains about the LCVa; What is an aabsolute physical blocka? + +That was poor wording in the previous manuscript. Changed to ainterferes with autophagy by blocking binding of polyUb + +The authors present many convincing results, however in all different experiments the L. pneumophila WT strain was used without empty vector. Legionella is very sensitive to carrying vectors and intra and extracellular replication changes when adding vector. Thus, the control should be not only the sde mutant \(^+\) empty vector but also the WT \(^+\) empty vector to have the correct comparison when strains carrying plasmids are analyzed. This is the case for the entire Figure 1, Figure 2 D- H, Figure 4 A- H, and Figure 5. Please repeat at least the most important experiments with a correct WT vector control. + +We went back to the original data and all the images associated with former Figs. 1, 4 and 5 (now Figs. 1,5, and 6) to determine if the experiments were carried out with strains that had empty vector. All the images that were grabbed to generate these figures were carefully annotated in our original datasets, and all clearly note that the WT and LP03(T4SS(- )) strains used to infect macrophages had the empty vector pJB908att- empty. We edited the figures accordingly, and the figures are now consistent with our laboratory records. + +Because these missed annotations raised questions regarding whether empty vector altered the observed phenotypes, we performed side- by- side comparisons in the presence and absence of the pJB908att- empty vector and now include these results in the new Supplemental Data (Supplemental Figs. S1 and S5). In Figure S1, Rtn4 staining is interrogated, while in Figure S5, p62 staining is imaged. In both cases, the presence or absence of empty vector makes little difference, although for Rtn4 staining the absence of vector provides a somewhat more robust difference compared to the sde deletion control. We used empty vector throughout, so it's clear vector is not interfering with the result. + +Figure 2A a please provide a better explanation what exactly one can see in this panel + +Thank you very much for this comment. Referee 1 had similar problems with our description of this panel. The previous version was very poorly written, and we did not describe the experiment in Fig. 2A. We have now totally rewritten the section from lines 198- 215, clearly stating the experiment and describing the results. This much improves the manuscript. + +Figure 2B a which strain is pSdeC WT? + +The panel detailed the behavior of pSdeC(WT) compared to that of three plasmidborne SdeC point mutations. The manner that we displayed the panel probably didn't have consistent nomenclature. I think if we had put nothing for this panel it would have been even more confusing, and implied there was no plasmid. To try to clarify this, we put parentheses around WT, which we think makes sense, and added apa in front of complementing plasmids to make it look more uniform in nomenclature. + +Figure 2D- H a please quantify the images + +The 20 minute timepoint for the three point mutations was quantified in panel B. The iSidE data was quantified extensively in Fig. 1 at multiple timepoints as was the C118S data. The images show very little ubiquitin recruitment with WT at 5 min post- infection (the point of the figures) which was quantified in Fig. 1. The main point of the panel display was to display the morphology of serpentine localization, when the text referred to it (panels F and H). + +Line 180 it readsa; To test this hypothesis, HEK293T cells transfected with HA- Ub were challenged by L. pneumophila harboring either WT or DUB defective (C118S) derivatives as the only active Sde family membersa; The HEK293T cells were challenged with Legionella at an MOI of 10. HEK293T + +<--- Page Split ---> + +cells are very poorly infected, I am surprised that an MOI=10 was sufficient? Did you check how many bacteria were internalized before continuing this experiment were HEK293T cells expressing the Fcgr- RII receptor used? In this case please specify in the M&M section + +We followed protocols described in our previous manuscript, Losick, et al (2010) PMID: 20148897. This is now referenced in Materials and Methods, lines 527- 528. As can be seen in Figure 2 of that publication, MOI = 10 gave us high levels of NFkB induction in transfected cells, and even at an MOI = 1 in a 96 well dish we observed uptake of 2 X 104 bacteria (this was approximately \(30\%\) of cells infected). We did not go higher than 10 based on the idea that in an NFkB induction system, increasing the MOI to 100 only resulted in about a 2x increase in NFkB induction. We repeated these infection conditions in Lipo, et al. (2022) PMID: 6321832, which used MOI=5,15, 25 and 50, then used MOI=25 to maximize NFkB induction. Based on this previous work, we went ahead with MOI=10 and it was clear that it was sufficient to get a response. It's possible that going higher with MOI may have helped, but we got a response at MOI = 10 so we stuck with it. Lines 275- 276 where are the quantifications? Should be shown. Quantification of p62 puncta at the 0 min timepoint is now displayed in new Supplemental Fig. S4. As pointed out in manuscript, distinguishing puncta that are LCV associated from those free in cytoplasm was difficult, so we focused on enveloped LCVs. + +Throughout the manuscript one can read a; a about the LCV. a I donat think that the use of aabout is correct in this context + +This was changed to ain the vicinity of the LCV, a the aLCV vicinity, a or in the Discussion when a model was proposed aassociated with the LCV a + +Line 33. . please correct to aThe Legionella pneumophila Sde family of translocated proteins promotes host tubular A> + +Changed. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Kotewicz, Zhang, and Kim et al. have addressed the raised points. My major concern was the finest explanation of the biochemical data in Figure 2A and the evidence of PRibosylation on the internal ubiquitin within the poly- Ub molecule. In the revised manuscript, the authors added a new figure (Figure 3) that supports internal PRibosylation on ubiquitin, and I am glad to see this clear MS data. The authors also rewrote their findings on Fig. 2A, and it is now much better than the previous version, and I am satisfied to recommend the publication of this manuscript in Nature Communications. + +However, I still would like to ask the authors to put some effort into the figures to meet the quality of other articles published in Nature Communications. + +For example, the points below need to be corrected. I do not want to be too picky, but there are too many issues, and I hope this correction will help the authors be more professional. + +Fig 1B, D: The size of the y- axis label is different from each other. Fig 1M: mock font? Fig 1B, C, D, E: Numbers on the y- axis are not aligned. Fig 1C: C118S -> subscript? + +Fig 2A: There are at least four different font styles used. It would be much better if authors use a single font so that readers won't be distracted by looking at different fonts. + +AlphaUb is too big, K48/K63 Ub is too small. + +Please be kind to readers. + +Fig 3 is an excellent example of data presentation. + +Fig 4: Again, there are cartoons with small letters, and I do not get the point of using this small font. Also, different font sizes and styles. + +<--- Page Split ---> + +Reviewer #2 + +(Remarks to the Author) The authors have answered all my comments satisfactory, I have no further comments + +Author Rebuttal letter: + +Editor and Referees: Please note that major changes are noted in the manuscript by vertical lines in left margins. + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Kotewicz, Zhang, and Kim et al. examined the roles of both the DUB and PR- ubiquitination activities of Sde proteins from Legionella. Based on their observations, the authors proposed that the DUB domain is responsible for ER rearrangement, and PR- ubiquitination on the ubiquitin chain on the LCV prevents the interaction with autophagic adaptors such as p62, allowing the evasion of host autophagy. + +Overall, this is an interesting story, but there are several points that are not clear enough to support the conclusion. Authors should address these concerns to strengthen their findings, and I do not recommend the current version of the manuscript for publication in Nature Communications. + +Related points 1 and 2. + +1 (Lines 175- 184) Authors intended to test the hypothesis that the DUB domain of Sde is linked with pR- modification. However, the designed experiment shown in Fig. 1L should be redesigned to properly examine this hypothesis. I would prepare another set of cells transfected with HA- Ub R42A to block PR- ubiquitination. The current bands from cells with SdeA can be either canonical ubiquitination or pR- ubiquitination. + +2. (Lines 197-199) Data shown in Fig. 1 do not provide direct evidence to support the likely role of pR- modification in stabilizing polyUb + +We thank the referee for the positive critique of the manuscript. Regarding points 1 and 2, we appreciate the suggestion for this experiment, but there is no evidence that SdeA can promote canonical ubiquitination. The active site shows no ability to act as an E3 ligase, as documented by the Luo lab. We concentrated on utilizing resources to directly address the other critiques of the Referee, which were answered largely by biochemical experiments coupled to LC/MS (described below). 3. (Fig. 2A) Several points: (1) Authors should explain why there are no ubiquitin signals detected under ART- conditions. + +Thank you for making this point, our previous draft was terribly confusing regarding this panel. As stated in our response to Referee 2 below, who was similarly confused by our narrative on this figure, we did a very poor job of explaining the experiments in Fig. 2A, and this section has been totally rewritten. To specifically answer Referee point 3, the loss of K63- linked ubiquitin signals in the ART(- ) is because the protein loses the ability to block its own DUB activity, which is further demonstration that the ART activity is required to block the Sde DUB activity. The reason that mono- Ub cannot be detected is that the Western was probed with the FK1 antibody, which shows very low affinity for monoUb. You will also note that there is some remaining K48 Ub, because the Sde DUB shows K63 preference. These phenomena were largely documented in our previous 2017 manuscript (PMID: 28041930). The text was modified on lines 209- 212 (but also note that this entire paragraph was rewritten to answer Referee 2 criticism, as well): + +aAs observed previously, the absence of the ART domain resulted in quantitative hydrolysis of the K63 polyUB chain by the SdeC DUB domain, leaving monomeric Ub that was poorly resolved after probing with a poly- UB specific antibody (Fig. 2A, ART- ) 22. As predicted, this hydrolysis in the absence of ART activity was less efficient with the K48- linked substrate 42. a (2) Why doesn't the DUB domain of WT SdeC cleave K63- Ub? Is ART and PDE working faster than DUB? + +Yes, this is one of the many amazing things about this enzyme. Both the ART and PDE domains are extremely efficient, as demonstrated in our previous paper (PMID: 28041930). In order to see ADPribosylation of Ub by the WT SdeC, the reaction has to be incubated on ice! If the modified protein is then shifted to 37C, the modification largely converts to pR- Ub within 1 minute. The original demonstration of a blockade of the DUB activity was seen in Fig 4E of that paper, and you can see that even after one hour, the total hydrolysis of unmodified poly- Ub by the DUB was not complete. + +<--- Page Split ---> + +So the kinetics of each of the activities is vastly different, with modification taking place rapidly and DUB hydrolysis taking place slowly. + +Even if that is the case, there is no evidence that the ubiquitin chains shown here are pR- modified. Based on the structure of mART and PDE in complex with ubiquitin, it will be very difficult for the internal ubiquitin moieties within the poly- Ub molecule to be located in the active site. + +See answer to comment below, which includes new experiments and a new multipanel figure to demonstrate the ability of SdeC to target internal residues. + +(3) (Lines 199-202) There is no direct evidence that the poly-Ub chain is modified by PR- or ADPR-. The cited reference (Puvar et al.) used di-ubiquitin, where both ubiquitin moieties are exposed and accessible to mART and PDE. Therefore, authors should provide more direct evidence that internal ubiquitin is modified by PR- or ADPR-. + +To answer this question, we used the same substrate as used in Fig. 4 (new numbering in the resubmitted manuscript) to demonstrate that all the internal R42 sidechains are modified to pR by WT protein. In new Figure 3, we performed the critical experiment to demonstrate quantitative modification of internal R42 residues. The WT SdeC protein was incubated with Ub4 at a ratio of 1 SdeC : 750 Ub4 molecules. That comes out to a ratio of 3000 R42 targets for each SdeC enzyme. After allowing 1 hr reaction at 37C, the Ub4 preparation was compared to an untreated sample. After MS and EIC analysis, we could easily demonstrate that the treated sample had greater than 96% modification of all four R42 targets in Ub4, as there was an increase in MW of 848.21 AMU, corresponding to four pR modifications. This was clearly quantitative, as there was no evidence of smaller forms having 3.2 or 1 modifications. If it were true that only the R42 residues located near the N or C terminal should be accessible, then we would see an accumulation of di- modified Ub4: this clearly was not the case. To demonstrate that R42 and only R42 were modified, peptides were scanned for ones that were not found in the unmodified control. We found only one peptide that was unique to the treated sample and had endpoints predicted for trypsin cleavage. This was a Z=3 peptide that was the 10 amino acid ion expected for Arg42 modification. No other modifications were found. On MS/MS analysis of the peptide, the modification was clearly on Arg42. We conclude that internal Arg42 residues are super- efficiently targeted by SdeC and are quantitatively modified even when there is great excess of substrate to enzyme. This work was performed by Ms. Meghan Martin in the lab of Dr. Rebecca Scheck, my long- time collaborator, using material prepared by Dr. Atish RoyChowdhury, a fellow in my lab. These three scientists have been added as authors on the manuscript. This work is now described on lines 235- 270, with experimental procedures included in the Materials and Methods section. + +(4) The Ub7 band from both K48 and K63 becomes faint after incubation with DUBs. Please provide an explanation for this. + +In Figure 2, this is not true for every sample and is dependent on the particular substrate/enzyme derivatives used. For instance, for USP2, this phenomenon is only seen with the ART \((+)\) PDE \((-)\) mutant. For OUT1, this is not seen with any derivative. It is most obvious for K48 linked Ub, which may indicate that modification works with lower efficiency on K48 relative to K63 (similar to the DUB) domain, but even with K48, the phenomenon pointed out by the referee is not uniform. It should be noted that we are performing the modification reaction in conditions that we have shown are suboptimal, in which SdeC is immobilized on beads, as described in our previous publication (PMID: 34704056). The lowered activity on beads could mean that with some samples there was incomplete modification using immobilized SdeC. There is also another confounding issue that has been pointed out by some manufacturers of Ub4 on data sheets, which is that heating the tetramer in SDS- PAGE buffer can lead to unexpected banding or smearing. In any case, we clearly showed in new Figures 3 and 4, that using very small amounts of SdeC relative to tetra- Ub results in quantitative modification. We do not think that these results argue in any way against the ability to totally modify the tetramer, when reaction conditions involve a simple aqueous mixture of components. + +4. (Fig. 3) Similar to the above points, incubating polyubiquitin with Sde enzymes does not guarantee PR- or ADPR-modifications. Authors should provide clear biochemical evidence to support the entire data shown in Fig. 3. + +See above response. We think the new Fig. 3 answers this criticism. + +5. (Figs. 4, 5) I agree that delta Sde affects the localization of p62 on LCV and that it is linked to the activity of the ART and PDE domains, promoting PR-ubiquitination. + +<--- Page Split ---> + +However, without direct biochemical evidence from Fig. 2 and Fig. 3, one cannot conclude that the polyubiquitin chains on the LCV are PR- or ADPR- modified + +We believe that new Fig. 3 is the biochemical evidence for modification occurring. In addition, in a simultaneously submitted manuscript, the laboratory of Yuxin Mao has performed similar experiments showing that internal UB moieties can be modified by Sde proteins. In their case, they synthesized tri- UB chains in which only one of the monomers had the WT Arg42 residue. They showed that modification occurred wherever the Arg42 was found. Arg42 internal to the trimer was modified as efficiently as the Arg42 that was found either in the N- terminal or C- terminal copy Ub. Therefore, phosphoribosylation is independent of the location of the UB monomer, which is consistent with our data in Fig. 3. + +6. Authors conducted many SPR experiments. Providing kinetic values would be more insightful than showing sensorsgrams. + +We have added more detail to the kinetic data for unmodified where relevant in the results (varies between Kd=6.2 x10e- 8 a 1.6X1- e- 7), but we disagree with the concept that modified Ub should have a different Kd than unmodified. The kinetic data for the modified Ub simply cannot be determined with any measure of confidence. Firstly, in the case of the modified Ub, the amount of binding is close to unmeasurable, making a kinetic determination of binding between p62 and modified Ub unreliable. In fact, the BiaCore provides a warning that the akinetic constants ka and kd are approaching the limits that can be measured by the instrument and kinetic constants cannot be uniquely determined. A Secondly, the miniscule amount of binding that can be detected is presumably due to the small amount of unmodified Ub. The prediction is that the binding kinetics of this small fraction of unmodified Ub should be identical to what is seen in the absence of Sde activity. We do, however, include kinetic data for the untreated Ub which has some level of reliability. To provide more accurate description of the experiments, we now put in the text (lines 289- 299): + +In the absence of SdeC, Ub4 bound His- p62 with apparent KD = 1.2 X 10- 7 to 6.2 X 10- 8 M, indicating that binding affinity was at least as efficient as previous SPR studies using diUb as a substrate (KD = 9.3 X 10- 8 M; 54) (Fig. 4F). Binding of p62 to mono- Ub was very poor, consistent with DUB activity interfering with recognition of p62, with binding constants that could not be reliably determined by SPR (Fig. 4G, Fig. S2C). ... In all cases in which modification blocked p62 recognition, the binding constants could not be reliably determined by SPR. + +(Minor comments) + +Fig. 1J: pSdec - > pSdeC + +Changed Fig. 2A: Out- 1 - > OTU1 + +Changed Fig. S1 and line 172: Is it C293A or C293S? + +The Figure is correct. It is C293A. Thank you for identifying this. Font size in Fig S1 differs from each other. + +The figure was carefully recomposed and then converted to PDF. We think this may have fixed the problem, although we suspect the change in font size may be associated with the conversion to pdf. + +Reviewer #2 (Remarks to the Author): + +In this work Kotewicz and colleagues dissect the role of the Sde protein family in the establishment of the Legionella containing vacuole in host cells. Using molecular, biochemical and cell biology approaches the authors propose that the Sde protein family transiently (first 20 min of infection disappearing within 1h of infection) block p62 accumulation on the polyubiquitinated vacuole. This is achieved by firstly using the DUB domain of the Sde proteins that deubiquitinates K63 linked ubiquitin to provide Ub to the mART domain of Sde proteins that catalyzes pr- Ub conjugation on e.g. Rtn4 that accumulates on the LCV. This, pr- modification of ubiquitin blocks the association with the autophagy adaptor p62 with the vacuole and thereby protects the LCV against autophagy. + +<--- Page Split ---> + +This very detailed dissection of the function of the Sde family proteins and their different domains in the establishment of the Legionella containing vacuole and some of their results contradict previously published work. + +It is very interesting that the Sde protein family camouflages the LCV and blocks p62 accumulation and thereby autophagy in the first 20min. Indeed, the first minutes of infection are without doubt very important to survive or surrender, but it is known that Legionella blocks/retards autophagy much longer than the first 20 min of infection. How is this process thus maintained when the Sde proteins are not active anymore? Is there a timely difference in the secretion e.g. of the Sde proteins and RavZ or LpSpl or others? + +Thank you for the comments and the downstream requests for changes that we think strengthened the manuscript and eliminated some confusion. + +From Fig. 4L, we clearly show that there must be at least one uncharacterized activity that accumulates over time and interferes with p62 recruitment, because other known activities (such as RavZ) do not interfere with the accumulation of p62. The presence of this hypothetical activity was similarly noted in the referenced Omatode and Roy manuscript (PMID: 32482642). This activity could either directly target autophagy adapters or the replication vacuole. No matter the nature of the activity, at least one additional activity must exist based on our data. + +Line 108- 109 several effectors/systems are described that Legionella employs to block autophagy. Please add the effector LpSpl (PMID: 26831115) + +Now noted in resubmission, line 109. + +Lines 113- 114 and elsewhere in the manuscript a.. ADPribosylation or phosphoribosylation of Ub interferes with autophagy by causing an absolute physical block on binding of polyUb to anautophagy adaptor, primarily by phosphoribosylation of target Ub chains about the LCVa; What is an aabsolute physical blocka? + +That was poor wording in the previous manuscript. Changed to ainterferes with autophagy by blocking binding of polyUba + +The authors present many convincing results, however in all different experiments the L. pneumophila WT strain was used without empty vector. Legionella is very sensitive to carrying vectors and intra and extracellular replication changes when adding vector. Thus, the control should be not only the sde mutant \(^+\) empty vector but also the WT \(^+\) empty vector to have the correct comparison when strains carrying plasmids are analyzed. This is the case for the entire Figure 1, Figure 2 D- H, Figure 4 A- H, and Figure 5. Please repeat at least the most important experiments with a correct WT vector control. + +We went back to the original data and all the images associated with former Figs. 1, 4 and 5 (now Figs. 1.5, and 6) to determine if the experiments were carried out with strains that had empty vector. All the images that were grabbed to generate these figures were carefully annotated in our original datasets, and all clearly note that the WT and LP03(T4SS(- )) strains used to infect macrophages had the empty vector pJB908att- empty. We edited the figures accordingly, and the figures are now consistent with our laboratory records. + +Because these missed annotations raised questions regarding whether empty vector altered the observed phenotypes, we performed side- by- side comparisons in the presence and absence of the pJB908att- empty vector and now include these results in the new Supplemental Data (Supplemental Figs. S1 and S5). In Figure S1, Rtn4 staining is interrogated, while in Figure S5, p62 staining is imaged. In both cases, the presence or absence of empty vector makes little difference, although for Rtn4 staining the absence of vector provides a somewhat more robust difference compared to the sde deletion control. We used empty vector throughout, so it's clear vector is not interfering with the result. + +Figure 2A a please provide a better explanation what exactly one can see in this panel + +Thank you very much for this comment. Referee 1 had similar problems with our description of this panel. The previous version was very poorly written, and we did not describe the experiment in Fig. 2A. We have now totally rewritten the section from lines 198- 215, clearly stating the experiment and describing the results. This much improves the manuscript. + +Figure 2B a which strain is pSdeC WT? + +<--- Page Split ---> + +The panel detailed the behavior of pSdeC(WT) compared to that of three plasmidborne SdeC point mutations. The manner that we displayed the panel probably didn't have consistent nomenclature. I think if we had put nothing for this panel it would have been even more confusing, and implied there was no plasmid. To try to clarify this, we put parentheses around WT, which we think makes sense, and added apá in front of complementing plasmids to make it look more uniform in nomenclature. + +Figure 2D- H á please quantify the images + +The 20 minute timepoint for the three point mutations was quantified in panel B. The iSidE data was quantified extensively in Fig. 1 at multiple timepoints as was the C118S data. The images show very little ubiquitin recruitment with WT at 5 min post- infection (the point of the figures) which was quantified in Fig. 1. The main point of the panel display was to display the morphology of serpentine localization, when the text referred to it (panels F and H). + +Line 180 it readsá! To test this hypothesis, HEK293T cells transfected with HA- Ub were challenged by L. pneumophila harboring either WT or DUB defective (C118S) derivatives as the only active Sde family membersá! The HEK293T cells were challenged with Legionella at an MOI of 10. HEK293T cells are very poorly infected, I am surprised that an MOI=10 was sufficient? Did you check how many bacteria were internalized before continuing this experiment were HEK293T cells expressing the FcgrIII receptor used? In this case please specify in the M&M section + +We followed protocols described in our previous manuscript, Losick, et al (2010) PMID: 20148897. This is now referenced in Materials and Methods, lines 527- 528. As can be seen in Figure 2 of that publication, MOI = 10 gave us high levels of NFkB induction in transfected cells, and even at an MOI = 1 in a 96 well dish we observed uptake of 2 X 104 bacteria (this was approximately 30% of cells infected). We did not go higher than 10 based on the idea that in an NFkB induction system, increasing the MOI to 100 only resulted in about a 2x increase in NFkB induction. We repeated these infection conditions in Lipo, et al. (2022) PMID: 6321832, which used MOI=5,15, 25 and 50, then used MOI=25 to maximize NFkB induction. Based on this previous work, we went ahead with MOI=10 and it was clear that it was sufficient to get a response. Itás possible that going higher with MOI may have helped, but we got a response at MOI = 10 so we stuck with it. Lines 275- 276 where are the quantifications? Should be shown. Quantification of p62 puncta at the 0 min timepoint is now displayed in new Supplemental Fig. S4. As pointed out in manuscript, distinguishing puncta that are LCV associated from those free in cytoplasm was difficult, so we focused on enveloped LCVs. + +Throughout the manuscript one can read á! á about the LCV. á I donât think that the use of áaboutá is correct in this context + +This was changed to áin the vicinity of the LCV, á the áLCV vicinity, á or in the Discussion when a model was proposed áassociated with the LCV. á + +Line 33. . please correct to áThe Legionella pneumophila Sde family of translocated proteins promotes host tubular Á» + +Changed. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> diff --git a/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/supplementary_1_Peer Review file_det.mmd b/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/supplementary_1_Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a0e564b0703ce4e957705edb7aa0b0f1d1b0c4cd --- /dev/null +++ b/peer_reviews/3db86c9de8c0ea8d5ba691fd0777866ea460796c4debd704a55fc39d3ba4383d/supplementary_1_Peer Review file/supplementary_1_Peer Review file_det.mmd @@ -0,0 +1,523 @@ +<|ref|>title<|/ref|><|det|>[[73, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 97, 295, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 160, 920, 234]]<|/det|> +# Sde Proteins Coordinate Ubiquitin Utilization and Phosphoribosylation to Establish and Maintain the Legionella Replication Vacuole + +<|ref|>text<|/ref|><|det|>[[73, 248, 411, 265]]<|/det|> +Corresponding Author: Dr Ralph Isberg + +<|ref|>text<|/ref|><|det|>[[73, 300, 144, 313]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 326, 217, 340]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 352, 159, 365]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 378, 922, 444]]<|/det|> +(Remarks to the Author) In this manuscript, Kotewicz, Zhang, and Kim et al. examined the roles of both the DUB and PR- ubiquitination activities of Sde proteins from Legionella. Based on their observations, the authors proposed that the DUB domain is responsible for ER rearrangement, and PR- ubiquitination on the ubiquitin chain on the LCV prevents the interaction with autophagic adaptors such as p62, allowing the evasion of host autophagy. + +<|ref|>text<|/ref|><|det|>[[72, 456, 920, 497]]<|/det|> +Overall, this is an interesting story, but there are several points that are not clear enough to support the conclusion. Authors should address these concerns to strengthen their findings, and I do not recommend the current version of the manuscript for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 509, 212, 523]]<|/det|> +[Specific comments] + +<|ref|>text<|/ref|><|det|>[[72, 534, 888, 587]]<|/det|> +1. (Lines 175-184) Authors intended to test the hypothesis that the DUB domain of Sde is linked with pR-modification. However, the designed experiment shown in Fig. 1L should be redesigned to properly examine this hypothesis. I would prepare another set of cells transfected with HA-Ub R42A to block PR-ubiquitination. The current bands from cells with pSdeA can be either canonical ubiquitination or pR-ubiquitination. + +<|ref|>text<|/ref|><|det|>[[70, 597, 870, 626]]<|/det|> +2. (Lines 197-199) Data shown in Fig. 1 do not provide direct evidence to support the likely role of pR-modification in stabilizing polyUb. + +<|ref|>text<|/ref|><|det|>[[71, 636, 925, 742]]<|/det|> +3. (Fig. 2A) Several points: (1) Authors should explain why there are no ubiquitin signals detected under ART-conditions. (2) Why doesn't the DUB domain of WT SdeC cleave K63-Ub? Is ART and PDE working faster than DUB? Even if that is the case, there is no evidence that the ubiquitin chains shown here are pR-modified. Based on the structure of mART and PDE in complex with ubiquitin, it will be very difficult for the internal ubiquitin moieties within the poly-Ub molecule to be located in the active site. (3) (Lines 199-202) There is no direct evidence that the poly-Ub chain is modified by PR- or ADPR-. The cited reference (Puvar et al.) used di-ubiquitin, where both ubiquitin moieties are exposed and accessible to mART and PDE. Therefore, authors should provide more direct evidence that internal ubiquitin is modified by PR- or ADPR-. (4) The Ub7 band from both K48 and K63 becomes faint after incubation with DUBs. Please provide an explanation for this. + +<|ref|>text<|/ref|><|det|>[[70, 753, 866, 781]]<|/det|> +4. (Fig. 3) Similar to the above points, incubating polyubiquitin with Sde enzymes does not guarantee PR- or ADPR- modifications. Authors should provide clear biochemical evidence to support the entire data shown in Fig. 3. + +<|ref|>text<|/ref|><|det|>[[71, 793, 907, 834]]<|/det|> +5. (Figs. 4, 5) I agree that delta Sde affects the localization of p62 on LCV and that it is linked to the activity of the ART and PDE domains, promoting PR-ubiquitination. However, without direct biochemical evidence from Fig. 2 and Fig. 3, one cannot conclude that the polyubiquitin chains on the LCV are PR- or ADPR-modified. + +<|ref|>text<|/ref|><|det|>[[70, 845, 920, 860]]<|/det|> +6. Authors conducted many SPR experiments. Providing kinetic values would be more insightful than showing sensorsgrams. + +<|ref|>text<|/ref|><|det|>[[73, 872, 197, 885]]<|/det|> +(Minor comments) + +<|ref|>text<|/ref|><|det|>[[71, 897, 375, 937]]<|/det|> +Fig. 1J: pSdec -> pSdeC Fig. 2A: Out-1 -> OTU1 Fig. S1 and line 172: Is it C293A or C293S? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 362, 61]]<|/det|> +Font size in Fig S1 differs from each other. + +<|ref|>text<|/ref|><|det|>[[73, 73, 162, 86]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 99, 238, 112]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 112, 910, 203]]<|/det|> +In this work Kotewicz and colleagues dissect the role of the Sde protein family in the establishment of the Legionella containing vacuole in host cells. Using molecular, biochemical and cell biology approaches the authors propose that the Sde protein family transiently (first 20 min of infection disappearing within 1h of infection) block p62 accumulation on the polyubiquitinated vacuole. This is achieved by firstly using the DUB domain of the Sde proteins that deubiquitinates K63 linked ubiquitin to provide Ub to the mART domain of Sde proteins that catalyzes pr- Ub conjugation on e.g. Rtn4 that accumulates on the LCV. This, pr- modification of ubiquitin blocks the association with the autophagy adaptor p62 with the vacuole and thereby protects the LCV against autophagy. + +<|ref|>text<|/ref|><|det|>[[73, 215, 918, 243]]<|/det|> +This very detailed dissection of the function of the Sde family proteins and their different domains in the establishment of the Legionella containing vacuole and some of their results contradict previously published work. + +<|ref|>text<|/ref|><|det|>[[73, 254, 923, 320]]<|/det|> +It is very interesting that the Sde protein family camouflages the LCV and blocks p62 accumulation and thereby autophagy in the first 20min. Indeed, the first minutes of infection are without doubt very important to survive or surrender, but it is known that Legionella blocks/retards autophagy much longer than the first 20 min of infection. How is this process thus maintained when the Sde proteins are not active anymore? Is there a timely difference in the secretion e.g. of the Sde proteins and RavZ or LpSpl or others? + +<|ref|>text<|/ref|><|det|>[[73, 332, 910, 360]]<|/det|> +Line 108- 109 several effectors/systems are described that Legionella employs to block autophagy. Please add the effector LpSpl (PMID: 26831115) + +<|ref|>text<|/ref|><|det|>[[73, 371, 913, 425]]<|/det|> +Lines 113- 114 and elsewhere in the manuscript "... ADPribosylation or phosphoribosylation of Ub interferes with autophagy by causing an absolute physical block on binding of polyUb to anautophagy adaptor, primarily by phosphoribosylation of target Ub chains about the LCV... What is an "absolute physical block"? + +<|ref|>text<|/ref|><|det|>[[73, 436, 923, 503]]<|/det|> +The authors present many convincing results, however in all different experiments the L. pneumophila WT strain was used without empty vector. Legionella is very sensitive to carrying vectors and intra and extracellular replication changes when adding vector. Thus, the control should be not only the sde mutant \(^+\) empty vector but also the WT \(^+\) empty vector to have the correct comparison when strains carrying plasmids are analyzed. This is the case for the entire Figure 1, Figure 2 D- H, Figure 4 A- H, and Figure 5. Please repeat at least the most important experiments with a correct WT vector control. + +<|ref|>text<|/ref|><|det|>[[73, 515, 664, 555]]<|/det|> +Figure 2A - please provide a better explanation what exactly one can see in this panel Figure 2B - which strain is pSdeC WT? Figure 2D- H - please quantify the images + +<|ref|>text<|/ref|><|det|>[[73, 566, 913, 633]]<|/det|> +Line 180 it reads... To test this hypothesis, HEK293T cells transfected with HA- Ub were challenged by L. pneumophila harboring either WT or DUB defective (C118S) derivatives as the only active Sde family members... The HEK293T cells were challenged with Legionella at an MOI of 10. HEK293T cells are very poorly infected, I am surprised that an MOI=10 was sufficient? Did you check how many bacteria were internalized before continuing this experiment were HEK293T cells expressing the Fc - RII receptor used? In this case please specify in the M&M section + +<|ref|>text<|/ref|><|det|>[[73, 656, 512, 671]]<|/det|> +Lines 275- 276 where are the quantifications? Should eb shown + +<|ref|>text<|/ref|><|det|>[[73, 683, 899, 698]]<|/det|> +Throughout the manuscript one can read ... " about the LCV..." I don't think that the use of "about" is correct in this context + +<|ref|>text<|/ref|><|det|>[[73, 709, 860, 724]]<|/det|> +Line 33. . please correct to "The Legionella pneumophila Sde family of translocated proteins promotes host tubular > + +<|ref|>text<|/ref|><|det|>[[73, 761, 223, 775]]<|/det|> +Author Rebuttal letter: + +<|ref|>text<|/ref|><|det|>[[73, 787, 647, 815]]<|/det|> +Editor and Referees: Please note that major changes are noted in the manuscript by vertical lines in left margins. + +<|ref|>text<|/ref|><|det|>[[73, 826, 333, 840]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[73, 852, 750, 920]]<|/det|> +In this manuscript, Kotewicz, Zhang, and Kim et al. examined the roles of both the DUB and PR- ubiquitination activities of Sde proteins from Legionella. Based on their observations, the authors proposed that the DUB domain is responsible for ER rearrangement, and PR- ubiquitination on the ubiquitin chain on the LCV prevents the interaction with autophagic adaptors such as p62, allowing the evasion of host autophagy. + +<|ref|>text<|/ref|><|det|>[[70, 931, 746, 946]]<|/det|> +Overall, this is an interesting story, but there are several points that are not clear enough to support + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 728, 75]]<|/det|> +the conclusion. Authors should address these concerns to strengthen their findings, and I do not recommend the current version of the manuscript for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 87, 232, 100]]<|/det|> +Related points 1 and 2. + +<|ref|>text<|/ref|><|det|>[[72, 100, 760, 178]]<|/det|> +1 (Lines 175- 184) Authors intended to test the hypothesis that the DUB domain of Sde is linked with pR- modification. However, the designed experiment shown in Fig. 1L should be redesigned to properly examine this hypothesis. I would prepare another set of cells transfected with HA- Ub R42A to block PR- ubiquitination. The current bands from cells with SdeA can be either canonical ubiquitination or pR- ubiquitination. + +<|ref|>text<|/ref|><|det|>[[72, 168, 767, 194]]<|/det|> +2. (Lines 197-199) Data shown in Fig. 1 do not provide direct evidence to support the likely role of pR- modification in stabilizing polyUb + +<|ref|>text<|/ref|><|det|>[[72, 205, 740, 308]]<|/det|> +We thank the referee for the positive critique of the manuscript. Regarding points 1 and 2, we appreciate the suggestion for this experiment, but there is no evidence that SdeA can promote canonical ubiquitination. The active site shows no ability to act as an E3 ligase, as documented by the Luo lab. We concentrated on utilizing resources to directly address the other critiques of the Referee, which were answered largely by biochemical experiments coupled to LC/MS (described below). 3. (Fig. 2A) Several points: (1) Authors should explain why there are no ubiquitin signals detected under ART- conditions. + +<|ref|>text<|/ref|><|det|>[[72, 320, 636, 491]]<|/det|> +Thank you for making this point, our previous draft was terribly confusing regarding this panel. As stated in our response to Referee 2 below, who was similarly confused by our narrative on this figure, we did a very poor job of explaining the experiments in Fig. 2A, and this section has been totally rewritten. To specifically answer Referee point 3, the loss of K63- linked ubiquitin signals in the ART(- ) is because the protein loses the ability to block its own DUB activity, which is further demonstration that the ART activity is required to block the Sde DUB activity. The reason that mono- Ub cannot be detected is that the Western was probed with the FK1 antibody, which shows very low affinity for monoUb. You will also note that there is some remaining K48 Ub, because the Sde DUB shows K63 preference. These phenomena were largely documented in our previous 2017 manuscript (PMID: 28041930). The text was modified on lines 209- 212 (but also note that this entire paragraph was rewritten to answer Referee 2 criticism, as well): + +<|ref|>text<|/ref|><|det|>[[72, 502, 756, 594]]<|/det|> +aAs observed previously, the absence of the ART domain resulted in quantitative hydrolysis of the K63 polyUb chain by the SdeC DUB domain, leaving monomeric Ub that was poorly resolved after probing with a poly- UB specific antibody (Fig. 2A, ART- ) 22. As predicted, this hydrolysis in the absence of ART activity was less efficient with the K48- linked substrate 42. a (2) Why doesn't the DUB domain of WT SdeC cleave K63- Ub? Is ART and PDE working faster than DUB? + +<|ref|>text<|/ref|><|det|>[[72, 606, 648, 725]]<|/det|> +Yes, this is one of the many amazing things about this enzyme. Both the ART and PDE domains are extremely efficient, as demonstrated in our previous paper (PMID: 28041930). In order to see ADPribosylation of Ub by the WT SdeC, the reaction has to be incubated on ice! If the modified protein is then shifted to 37C, the modification largely converts to pR- Ub within 1 minute. The original demonstration of a blockade of the DUB activity was seen in Fig 4E of that paper, and you can see that even after one hour, the total hydrolysis of unmodified poly- Ub by the DUB was not complete. So the kinetics of each of the activities is vastly different, with modification taking place rapidly and DUB hydrolysis taking place slowly. + +<|ref|>text<|/ref|><|det|>[[72, 736, 744, 777]]<|/det|> +Even if that is the case, there is no evidence that the ubiquitin chains shown here are pR- modified. Based on the structure of mART and PDE in complex with ubiquitin, it will be very difficult for the internal ubiquitin moieties within the poly- Ub molecule to be located in the active site. + +<|ref|>text<|/ref|><|det|>[[72, 788, 605, 816]]<|/det|> +See answer to comment below, which includes new experiments and a new multipanel figure to demonstrate the ability of SdeC to target internal residues. + +<|ref|>text<|/ref|><|det|>[[72, 827, 752, 881]]<|/det|> +(3) (Lines 199-202) There is no direct evidence that the poly-Ub chain is modified by PR- or ADPR-. The cited reference (Puvar et al.) used di-ubiquitin, where both ubiquitin moieties are exposed and accessible to mART and PDE. Therefore, authors should provide more direct evidence that internal ubiquitin is modified by PR- or ADPR-. + +<|ref|>text<|/ref|><|det|>[[72, 892, 647, 946]]<|/det|> +To answer this question, we used the same substrate as used in Fig. 4 (new numbering in the resubmitted manuscript) to demonstrate that all the internal R42 sidechains are modified to pR by WT protein. In new Figure 3, we performed the critical experiment to demonstrate quantitative modification of internal R42 residues. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 654, 350]]<|/det|> +The WT SdeC protein was incubated with Ub4 at a ratio of 1 SdeC : 750 Ub4 molecules. That comes out to a ratio of 3000 R42 targets for each SdeC enzyme. After allowing 1 hr reaction at 37C, the Ub4 preparation was compared to an untreated sample. After MS and EIC analysis, we could easily demonstrate that the treated sample had greater than \(96\%\) modification of all four R42 targets in Ub4, as there was an increase in MW of 848.21 AMU, corresponding to four pR modifications. This was clearly quantitative, as there was no evidence of smaller forms having 3,2 or 1 modifications. If it were true that only the R42 residues located near the N or C terminal should be accessible, then we would see an accumulation of di- modified Ub4: this clearly was not the case. To demonstrate that R42 and only R42 were modified, peptides were scanned for ones that were not found in the unmodified control. We found only one peptide that was unique to the treated sample and had endpoints predicted for trypsin cleavage. This was a Z=3 peptide that was the 10 amino acid ion expected for Arg42 modification. No other modifications were found. On MS/MS analysis of the peptide, the modification was clearly on Arg42. We conclude that internal Arg42 residues are super- efficiently targeted by SdeC and are quantitatively modified even when there is great excess of substrate to enzyme. This work was performed by Ms. Meghan Martin in the lab of Dr. Rebecca Scheck, my long- time collaborator, using material prepared by Dr. Atish RoyChowdhury, a fellow in my lab. These three scientists have been added as authors on the manuscript. This work is now described on lines 235- 270, with experimental procedures included in the Materials and Methods section. + +<|ref|>text<|/ref|><|det|>[[72, 330, 756, 360]]<|/det|> +(4) The Ub7 band from both K48 and K63 becomes faint after incubation with DUBs. Please provide an explanation for this. + +<|ref|>text<|/ref|><|det|>[[72, 372, 650, 595]]<|/det|> +In Figure 2, this is not true for every sample and is dependent on the particular substrate/enzyme derivatives used. For instance, for USP2, this phenomenon is only seen with the ART \((+)\) PDE \((- )\) mutant. For OUT1, this is not seen with any derivative. It is most obvious for K48 linked Ub, which may indicate that modification works with lower efficiency on K48 relative to K63 (similar to the DUB) domain, but even with K48, the phenomenon pointed out by the referee is not uniform. It should be noted that we are performing the modification reaction in conditions that we have shown are suboptimal, in which SdeC is immobilized on beads, as described in our previous publication (PMID: 34704056). The lowered activity on beads could mean that with some samples there was incomplete modification using immobilized SdeC. There is also another confounding issue that has been pointed out by some manufacturers of Ub4 on data sheets, which is that heating the tetramer in SDS- PAGE buffer can lead to unexpected banding or smearing. In any case, we clearly showed in new Figures 3 and 4, that using very small amounts of SdeC relative to tetra- Ub results in quantitative modification. We do not think that these results argue in any way against the ability to totally modify the tetramer, when reaction conditions involve a simple aqueous mixture of components. + +<|ref|>text<|/ref|><|det|>[[72, 594, 763, 634]]<|/det|> +4. (Fig. 3) Similar to the above points, incubating polyubiquitin with Sde enzymes does not guarantee PR- or ADPR-modifications. Authors should provide clear biochemical evidence to support the entire data shown in Fig. 3. + +<|ref|>text<|/ref|><|det|>[[72, 645, 538, 659]]<|/det|> +See above response. We think the new Fig. 3 answers this criticism. + +<|ref|>text<|/ref|><|det|>[[72, 671, 645, 724]]<|/det|> +5. (Figs. 4, 5) I agree that delta Sde affects the localization of p62 on LCV and that it is linked to the activity of the ART and PDE domains, promoting PR-ubiquitination. However, without direct biochemical evidence from Fig. 2 and Fig. 3, one cannot conclude that the polyubiquitin chains on the LCV are PR- or ADPR-modified + +<|ref|>text<|/ref|><|det|>[[72, 736, 650, 854]]<|/det|> +We believe that new Fig. 3 is the biochemical evidence for modification occurring. In addition, in a simultaneously submitted manuscript, the laboratory of Yuxin Mao has performed similar experiments showing that internal UB moieties can be modified by Sde proteins. In their case, they synthesized tri- UB chains in which only one of the monomers had the WT Arg42 residue. They showed that modification occurred wherever the Arg42 was found. Arg42 internal to the trimer was modified as efficiently as the Arg42 that was found either in the N- terminal or C- terminal copy Ub. Therefore, phosphoribosylation is independent of the location of the UB monomer, which is consistent with our data in Fig. 3. + +<|ref|>text<|/ref|><|det|>[[70, 866, 763, 894]]<|/det|> +6. Authors conducted many SPR experiments. Providing kinetic values would be more insightful than showing sensorsgrams. + +<|ref|>text<|/ref|><|det|>[[72, 906, 633, 946]]<|/det|> +We have added more detail to the kinetic data for unmodified where relevant in the results (varies between Kd=6.2 x10e- 8 a 1.6X1- e- 7), but we disagree with the concept that modified Ub should have a different Kd than unmodified. The kinetic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 658, 204]]<|/det|> +data for the modified Ub simply cannot be determined with any measure of confidence. Firstly, in the case of the modified Ub, the amount of binding is close to unmeasurable, making a kinetic determination of binding between p62 and modified Ub unreliable. In fact, the BiaCore provides a warning that the akinetic constants ka and kd are approaching the limits that can be measured by the instrument and kinetic constants cannot be uniquely determined. A Secondly, the miniscule amount of binding that can be detected is presumably due to the small amount of unmodified Ub. The prediction is that the binding kinetics of this small fraction of unmodified Ub should be identical to what is seen in the absence of Sde activity. We do, however, include kinetic data for the untreated Ub which has some level of reliability. To provide more accurate description of the experiments, we now put in the text (lines 289- 299): + +<|ref|>text<|/ref|><|det|>[[72, 216, 608, 320]]<|/det|> +aln the absence of SdeC, Ub4 bound His- p62 with apparent \(\mathrm{KD} = 1.2\times 10 - 7\) to \(6.2\times 10 - 8M\) , indicating that binding affinity was at least as efficient as previous SPR studies using diUb as a substrate \((\mathrm{KD} = 9.3\times 10 - 8M;54)\) (Fig. 4F). Binding of p62 to mono- Ub was very poor, consistent with DUB activity interfering with recognition of p62, with binding constants that could not be reliably determined by SPR (Fig. 4G, Fig. S2C). ... In all cases in which modification blocked p62 recognition, the binding constants could not be reliably determined by SPR. + +<|ref|>text<|/ref|><|det|>[[73, 334, 198, 348]]<|/det|> +(Minor comments) + +<|ref|>text<|/ref|><|det|>[[73, 360, 243, 374]]<|/det|> +Fig. 1J: pSdec -> pSdeC + +<|ref|>text<|/ref|><|det|>[[73, 386, 231, 412]]<|/det|> +Changed Fig. 2A: Out- 1 -> OTU1 + +<|ref|>text<|/ref|><|det|>[[73, 424, 375, 451]]<|/det|> +Changed Fig. S1 and line 172: Is it C293A or C293S? + +<|ref|>text<|/ref|><|det|>[[73, 463, 507, 490]]<|/det|> +The Figure is correct. It is C293A. Thank you for identifying this. Font size in Fig S1 differs from each other. + +<|ref|>text<|/ref|><|det|>[[73, 502, 644, 542]]<|/det|> +The figure was carefully recomposed and then converted to PDF. We think this may have fixed the problem, although we suspect the change in font size may be associated with the conversion to pdf. + +<|ref|>text<|/ref|><|det|>[[74, 554, 332, 568]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[73, 580, 768, 686]]<|/det|> +In this work Kotevicz and colleagues dissect the role of the Sde protein family in the establishment of the Legionella containing vacuole in host cells. Using molecular, biochemical and cell biology approaches the authors propose that the Sde protein family transiently (first 20 min of infection disappearing within 1h of infection) block p62 accumulation on the polyubiquitinated vacuole. This is achieved by firstly using the DUB domain of the Sde proteins that deubiquitinates K63 linked ubiquitin to provide Ub to the mART domain of Sde proteins that catalyzes pr- Ub conjugation on e.g. Rtn4 that accumulates on the LCV. This, pr- modification of ubiquitin blocks the association with the autophagy adaptor p62 with the vacuole and thereby protects the LCV against autophagy. + +<|ref|>text<|/ref|><|det|>[[73, 697, 766, 736]]<|/det|> +This very detailed dissection of the function of the Sde family proteins and their different domains in the establishment of the Legionella containing vacuole and some of their results contradict previously published work. + +<|ref|>text<|/ref|><|det|>[[73, 736, 766, 816]]<|/det|> +It is very interesting that the Sde protein family camouflages the LCV and blocks p62 accumulation and thereby autophagy in the first 20min. Indeed, the first minutes of infection are without doubt very important to survive or surrender, but it is known that Legionella blocks/retards autophagy much longer than the first 20 min of infection. How is this process thus maintained when the Sde proteins are not active anymore? Is there a timely difference in the secretion e.g. of the Sde proteins and RavZ or LpSpl or others? + +<|ref|>text<|/ref|><|det|>[[73, 828, 649, 855]]<|/det|> +Thank you for the comments and the downstream requests for changes that we think strengthened the manuscript and eliminated some confusion. + +<|ref|>text<|/ref|><|det|>[[73, 867, 641, 947]]<|/det|> +From Fig. 4L, we clearly show that there must be at least one uncharacterized activity that accumulates over time and interferes with p62 recruitment, because other known activities (such as RavZ) do not interfere with the accumulation of p62. The presence of this hypothetical activity was similarly noted in the referenced Omodate and Roy manuscript (PMID: 32482642). This activity could either directly target autophagy adapters or the replication vacuole. No matter the nature of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 48, 535, 61]]<|/det|> +activity, at least one additional activity must exist based on our data. + +<|ref|>text<|/ref|><|det|>[[73, 73, 666, 100]]<|/det|> +Line 108- 109 several effectors/systems are described that Legionella employs to block autophagy. Please add the effector LpSpl (PMID: 26831115) + +<|ref|>text<|/ref|><|det|>[[74, 113, 327, 126]]<|/det|> +Now noted in resubmission, line 109. + +<|ref|>text<|/ref|><|det|>[[73, 139, 770, 191]]<|/det|> +Lines 113- 114 and elsewhere in the manuscript a... ADPribosylation or phosphoribosylation of Ub interferes with autophagy by causing an absolute physical block on binding of polyUb to an autophagy adaptor, primarily by phosphoribosylation of target Ub chains about the LCVa; What is an aabsolute physical blocka? + +<|ref|>text<|/ref|><|det|>[[73, 204, 611, 231]]<|/det|> +That was poor wording in the previous manuscript. Changed to ainterferes with autophagy by blocking binding of polyUb + +<|ref|>text<|/ref|><|det|>[[73, 243, 770, 333]]<|/det|> +The authors present many convincing results, however in all different experiments the L. pneumophila WT strain was used without empty vector. Legionella is very sensitive to carrying vectors and intra and extracellular replication changes when adding vector. Thus, the control should be not only the sde mutant \(^+\) empty vector but also the WT \(^+\) empty vector to have the correct comparison when strains carrying plasmids are analyzed. This is the case for the entire Figure 1, Figure 2 D- H, Figure 4 A- H, and Figure 5. Please repeat at least the most important experiments with a correct WT vector control. + +<|ref|>text<|/ref|><|det|>[[73, 346, 647, 437]]<|/det|> +We went back to the original data and all the images associated with former Figs. 1, 4 and 5 (now Figs. 1,5, and 6) to determine if the experiments were carried out with strains that had empty vector. All the images that were grabbed to generate these figures were carefully annotated in our original datasets, and all clearly note that the WT and LP03(T4SS(- )) strains used to infect macrophages had the empty vector pJB908att- empty. We edited the figures accordingly, and the figures are now consistent with our laboratory records. + +<|ref|>text<|/ref|><|det|>[[73, 450, 652, 567]]<|/det|> +Because these missed annotations raised questions regarding whether empty vector altered the observed phenotypes, we performed side- by- side comparisons in the presence and absence of the pJB908att- empty vector and now include these results in the new Supplemental Data (Supplemental Figs. S1 and S5). In Figure S1, Rtn4 staining is interrogated, while in Figure S5, p62 staining is imaged. In both cases, the presence or absence of empty vector makes little difference, although for Rtn4 staining the absence of vector provides a somewhat more robust difference compared to the sde deletion control. We used empty vector throughout, so it's clear vector is not interfering with the result. + +<|ref|>text<|/ref|><|det|>[[73, 580, 662, 593]]<|/det|> +Figure 2A a please provide a better explanation what exactly one can see in this panel + +<|ref|>text<|/ref|><|det|>[[73, 606, 636, 672]]<|/det|> +Thank you very much for this comment. Referee 1 had similar problems with our description of this panel. The previous version was very poorly written, and we did not describe the experiment in Fig. 2A. We have now totally rewritten the section from lines 198- 215, clearly stating the experiment and describing the results. This much improves the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 672, 345, 684]]<|/det|> +Figure 2B a which strain is pSdeC WT? + +<|ref|>text<|/ref|><|det|>[[73, 697, 655, 775]]<|/det|> +The panel detailed the behavior of pSdeC(WT) compared to that of three plasmidborne SdeC point mutations. The manner that we displayed the panel probably didn't have consistent nomenclature. I think if we had put nothing for this panel it would have been even more confusing, and implied there was no plasmid. To try to clarify this, we put parentheses around WT, which we think makes sense, and added apa in front of complementing plasmids to make it look more uniform in nomenclature. + +<|ref|>text<|/ref|><|det|>[[73, 789, 360, 802]]<|/det|> +Figure 2D- H a please quantify the images + +<|ref|>text<|/ref|><|det|>[[73, 815, 650, 893]]<|/det|> +The 20 minute timepoint for the three point mutations was quantified in panel B. The iSidE data was quantified extensively in Fig. 1 at multiple timepoints as was the C118S data. The images show very little ubiquitin recruitment with WT at 5 min post- infection (the point of the figures) which was quantified in Fig. 1. The main point of the panel display was to display the morphology of serpentine localization, when the text referred to it (panels F and H). + +<|ref|>text<|/ref|><|det|>[[73, 906, 758, 946]]<|/det|> +Line 180 it readsa; To test this hypothesis, HEK293T cells transfected with HA- Ub were challenged by L. pneumophila harboring either WT or DUB defective (C118S) derivatives as the only active Sde family membersa; The HEK293T cells were challenged with Legionella at an MOI of 10. HEK293T + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 770, 88]]<|/det|> +cells are very poorly infected, I am surprised that an MOI=10 was sufficient? Did you check how many bacteria were internalized before continuing this experiment were HEK293T cells expressing the Fcgr- RII receptor used? In this case please specify in the M&M section + +<|ref|>text<|/ref|><|det|>[[72, 100, 650, 320]]<|/det|> +We followed protocols described in our previous manuscript, Losick, et al (2010) PMID: 20148897. This is now referenced in Materials and Methods, lines 527- 528. As can be seen in Figure 2 of that publication, MOI = 10 gave us high levels of NFkB induction in transfected cells, and even at an MOI = 1 in a 96 well dish we observed uptake of 2 X 104 bacteria (this was approximately \(30\%\) of cells infected). We did not go higher than 10 based on the idea that in an NFkB induction system, increasing the MOI to 100 only resulted in about a 2x increase in NFkB induction. We repeated these infection conditions in Lipo, et al. (2022) PMID: 6321832, which used MOI=5,15, 25 and 50, then used MOI=25 to maximize NFkB induction. Based on this previous work, we went ahead with MOI=10 and it was clear that it was sufficient to get a response. It's possible that going higher with MOI may have helped, but we got a response at MOI = 10 so we stuck with it. Lines 275- 276 where are the quantifications? Should be shown. Quantification of p62 puncta at the 0 min timepoint is now displayed in new Supplemental Fig. S4. As pointed out in manuscript, distinguishing puncta that are LCV associated from those free in cytoplasm was difficult, so we focused on enveloped LCVs. + +<|ref|>text<|/ref|><|det|>[[72, 333, 763, 360]]<|/det|> +Throughout the manuscript one can read a; a about the LCV. a I donat think that the use of aabout is correct in this context + +<|ref|>text<|/ref|><|det|>[[72, 371, 600, 398]]<|/det|> +This was changed to ain the vicinity of the LCV, a the aLCV vicinity, a or in the Discussion when a model was proposed aassociated with the LCV a + +<|ref|>text<|/ref|><|det|>[[72, 410, 770, 437]]<|/det|> +Line 33. . please correct to aThe Legionella pneumophila Sde family of translocated proteins promotes host tubular A> + +<|ref|>text<|/ref|><|det|>[[72, 450, 140, 463]]<|/det|> +Changed. + +<|ref|>text<|/ref|><|det|>[[72, 490, 144, 502]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 515, 219, 528]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 541, 160, 554]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 567, 238, 580]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 580, 921, 646]]<|/det|> +Kotewicz, Zhang, and Kim et al. have addressed the raised points. My major concern was the finest explanation of the biochemical data in Figure 2A and the evidence of PRibosylation on the internal ubiquitin within the poly- Ub molecule. In the revised manuscript, the authors added a new figure (Figure 3) that supports internal PRibosylation on ubiquitin, and I am glad to see this clear MS data. The authors also rewrote their findings on Fig. 2A, and it is now much better than the previous version, and I am satisfied to recommend the publication of this manuscript in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[70, 658, 911, 685]]<|/det|> +However, I still would like to ask the authors to put some effort into the figures to meet the quality of other articles published in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[70, 697, 914, 725]]<|/det|> +For example, the points below need to be corrected. I do not want to be too picky, but there are too many issues, and I hope this correction will help the authors be more professional. + +<|ref|>text<|/ref|><|det|>[[72, 737, 653, 777]]<|/det|> +Fig 1B, D: The size of the y- axis label is different from each other. Fig 1M: mock font? Fig 1B, C, D, E: Numbers on the y- axis are not aligned. Fig 1C: C118S -> subscript? + +<|ref|>text<|/ref|><|det|>[[70, 789, 904, 816]]<|/det|> +Fig 2A: There are at least four different font styles used. It would be much better if authors use a single font so that readers won't be distracted by looking at different fonts. + +<|ref|>text<|/ref|><|det|>[[72, 828, 378, 842]]<|/det|> +AlphaUb is too big, K48/K63 Ub is too small. + +<|ref|>text<|/ref|><|det|>[[72, 855, 253, 867]]<|/det|> +Please be kind to readers. + +<|ref|>text<|/ref|><|det|>[[72, 880, 418, 894]]<|/det|> +Fig 3 is an excellent example of data presentation. + +<|ref|>text<|/ref|><|det|>[[70, 906, 911, 933]]<|/det|> +Fig 4: Again, there are cartoons with small letters, and I do not get the point of using this small font. Also, different font sizes and styles. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 163, 60]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 73, 660, 100]]<|/det|> +(Remarks to the Author) The authors have answered all my comments satisfactory, I have no further comments + +<|ref|>text<|/ref|><|det|>[[73, 112, 223, 126]]<|/det|> +Author Rebuttal letter: + +<|ref|>text<|/ref|><|det|>[[73, 138, 647, 166]]<|/det|> +Editor and Referees: Please note that major changes are noted in the manuscript by vertical lines in left margins. + +<|ref|>text<|/ref|><|det|>[[73, 177, 332, 191]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[73, 203, 750, 269]]<|/det|> +In this manuscript, Kotewicz, Zhang, and Kim et al. examined the roles of both the DUB and PR- ubiquitination activities of Sde proteins from Legionella. Based on their observations, the authors proposed that the DUB domain is responsible for ER rearrangement, and PR- ubiquitination on the ubiquitin chain on the LCV prevents the interaction with autophagic adaptors such as p62, allowing the evasion of host autophagy. + +<|ref|>text<|/ref|><|det|>[[73, 281, 748, 321]]<|/det|> +Overall, this is an interesting story, but there are several points that are not clear enough to support the conclusion. Authors should address these concerns to strengthen their findings, and I do not recommend the current version of the manuscript for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 333, 232, 346]]<|/det|> +Related points 1 and 2. + +<|ref|>text<|/ref|><|det|>[[73, 346, 760, 412]]<|/det|> +1 (Lines 175- 184) Authors intended to test the hypothesis that the DUB domain of Sde is linked with pR- modification. However, the designed experiment shown in Fig. 1L should be redesigned to properly examine this hypothesis. I would prepare another set of cells transfected with HA- Ub R42A to block PR- ubiquitination. The current bands from cells with SdeA can be either canonical ubiquitination or pR- ubiquitination. + +<|ref|>text<|/ref|><|det|>[[73, 412, 765, 440]]<|/det|> +2. (Lines 197-199) Data shown in Fig. 1 do not provide direct evidence to support the likely role of pR- modification in stabilizing polyUb + +<|ref|>text<|/ref|><|det|>[[72, 451, 740, 555]]<|/det|> +We thank the referee for the positive critique of the manuscript. Regarding points 1 and 2, we appreciate the suggestion for this experiment, but there is no evidence that SdeA can promote canonical ubiquitination. The active site shows no ability to act as an E3 ligase, as documented by the Luo lab. We concentrated on utilizing resources to directly address the other critiques of the Referee, which were answered largely by biochemical experiments coupled to LC/MS (described below). 3. (Fig. 2A) Several points: (1) Authors should explain why there are no ubiquitin signals detected under ART- conditions. + +<|ref|>text<|/ref|><|det|>[[72, 567, 636, 737]]<|/det|> +Thank you for making this point, our previous draft was terribly confusing regarding this panel. As stated in our response to Referee 2 below, who was similarly confused by our narrative on this figure, we did a very poor job of explaining the experiments in Fig. 2A, and this section has been totally rewritten. To specifically answer Referee point 3, the loss of K63- linked ubiquitin signals in the ART(- ) is because the protein loses the ability to block its own DUB activity, which is further demonstration that the ART activity is required to block the Sde DUB activity. The reason that mono- Ub cannot be detected is that the Western was probed with the FK1 antibody, which shows very low affinity for monoUb. You will also note that there is some remaining K48 Ub, because the Sde DUB shows K63 preference. These phenomena were largely documented in our previous 2017 manuscript (PMID: 28041930). The text was modified on lines 209- 212 (but also note that this entire paragraph was rewritten to answer Referee 2 criticism, as well): + +<|ref|>text<|/ref|><|det|>[[72, 749, 755, 840]]<|/det|> +aAs observed previously, the absence of the ART domain resulted in quantitative hydrolysis of the K63 polyUB chain by the SdeC DUB domain, leaving monomeric Ub that was poorly resolved after probing with a poly- UB specific antibody (Fig. 2A, ART- ) 22. As predicted, this hydrolysis in the absence of ART activity was less efficient with the K48- linked substrate 42. a (2) Why doesn't the DUB domain of WT SdeC cleave K63- Ub? Is ART and PDE working faster than DUB? + +<|ref|>text<|/ref|><|det|>[[72, 853, 648, 945]]<|/det|> +Yes, this is one of the many amazing things about this enzyme. Both the ART and PDE domains are extremely efficient, as demonstrated in our previous paper (PMID: 28041930). In order to see ADPribosylation of Ub by the WT SdeC, the reaction has to be incubated on ice! If the modified protein is then shifted to 37C, the modification largely converts to pR- Ub within 1 minute. The original demonstration of a blockade of the DUB activity was seen in Fig 4E of that paper, and you can see that even after one hour, the total hydrolysis of unmodified poly- Ub by the DUB was not complete. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 622, 75]]<|/det|> +So the kinetics of each of the activities is vastly different, with modification taking place rapidly and DUB hydrolysis taking place slowly. + +<|ref|>text<|/ref|><|det|>[[73, 86, 744, 126]]<|/det|> +Even if that is the case, there is no evidence that the ubiquitin chains shown here are pR- modified. Based on the structure of mART and PDE in complex with ubiquitin, it will be very difficult for the internal ubiquitin moieties within the poly- Ub molecule to be located in the active site. + +<|ref|>text<|/ref|><|det|>[[73, 138, 605, 165]]<|/det|> +See answer to comment below, which includes new experiments and a new multipanel figure to demonstrate the ability of SdeC to target internal residues. + +<|ref|>text<|/ref|><|det|>[[73, 177, 752, 230]]<|/det|> +(3) (Lines 199-202) There is no direct evidence that the poly-Ub chain is modified by PR- or ADPR-. The cited reference (Puvar et al.) used di-ubiquitin, where both ubiquitin moieties are exposed and accessible to mART and PDE. Therefore, authors should provide more direct evidence that internal ubiquitin is modified by PR- or ADPR-. + +<|ref|>text<|/ref|><|det|>[[72, 241, 655, 588]]<|/det|> +To answer this question, we used the same substrate as used in Fig. 4 (new numbering in the resubmitted manuscript) to demonstrate that all the internal R42 sidechains are modified to pR by WT protein. In new Figure 3, we performed the critical experiment to demonstrate quantitative modification of internal R42 residues. The WT SdeC protein was incubated with Ub4 at a ratio of 1 SdeC : 750 Ub4 molecules. That comes out to a ratio of 3000 R42 targets for each SdeC enzyme. After allowing 1 hr reaction at 37C, the Ub4 preparation was compared to an untreated sample. After MS and EIC analysis, we could easily demonstrate that the treated sample had greater than 96% modification of all four R42 targets in Ub4, as there was an increase in MW of 848.21 AMU, corresponding to four pR modifications. This was clearly quantitative, as there was no evidence of smaller forms having 3.2 or 1 modifications. If it were true that only the R42 residues located near the N or C terminal should be accessible, then we would see an accumulation of di- modified Ub4: this clearly was not the case. To demonstrate that R42 and only R42 were modified, peptides were scanned for ones that were not found in the unmodified control. We found only one peptide that was unique to the treated sample and had endpoints predicted for trypsin cleavage. This was a Z=3 peptide that was the 10 amino acid ion expected for Arg42 modification. No other modifications were found. On MS/MS analysis of the peptide, the modification was clearly on Arg42. We conclude that internal Arg42 residues are super- efficiently targeted by SdeC and are quantitatively modified even when there is great excess of substrate to enzyme. This work was performed by Ms. Meghan Martin in the lab of Dr. Rebecca Scheck, my long- time collaborator, using material prepared by Dr. Atish RoyChowdhury, a fellow in my lab. These three scientists have been added as authors on the manuscript. This work is now described on lines 235- 270, with experimental procedures included in the Materials and Methods section. + +<|ref|>text<|/ref|><|det|>[[72, 584, 755, 609]]<|/det|> +(4) The Ub7 band from both K48 and K63 becomes faint after incubation with DUBs. Please provide an explanation for this. + +<|ref|>text<|/ref|><|det|>[[72, 620, 650, 844]]<|/det|> +In Figure 2, this is not true for every sample and is dependent on the particular substrate/enzyme derivatives used. For instance, for USP2, this phenomenon is only seen with the ART \((+)\) PDE \((-)\) mutant. For OUT1, this is not seen with any derivative. It is most obvious for K48 linked Ub, which may indicate that modification works with lower efficiency on K48 relative to K63 (similar to the DUB) domain, but even with K48, the phenomenon pointed out by the referee is not uniform. It should be noted that we are performing the modification reaction in conditions that we have shown are suboptimal, in which SdeC is immobilized on beads, as described in our previous publication (PMID: 34704056). The lowered activity on beads could mean that with some samples there was incomplete modification using immobilized SdeC. There is also another confounding issue that has been pointed out by some manufacturers of Ub4 on data sheets, which is that heating the tetramer in SDS- PAGE buffer can lead to unexpected banding or smearing. In any case, we clearly showed in new Figures 3 and 4, that using very small amounts of SdeC relative to tetra- Ub results in quantitative modification. We do not think that these results argue in any way against the ability to totally modify the tetramer, when reaction conditions involve a simple aqueous mixture of components. + +<|ref|>text<|/ref|><|det|>[[72, 843, 763, 881]]<|/det|> +4. (Fig. 3) Similar to the above points, incubating polyubiquitin with Sde enzymes does not guarantee PR- or ADPR-modifications. Authors should provide clear biochemical evidence to support the entire data shown in Fig. 3. + +<|ref|>text<|/ref|><|det|>[[72, 893, 540, 907]]<|/det|> +See above response. We think the new Fig. 3 answers this criticism. + +<|ref|>text<|/ref|><|det|>[[70, 919, 645, 945]]<|/det|> +5. (Figs. 4, 5) I agree that delta Sde affects the localization of p62 on LCV and that it is linked to the activity of the ART and PDE domains, promoting PR-ubiquitination. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 624, 72]]<|/det|> +However, without direct biochemical evidence from Fig. 2 and Fig. 3, one cannot conclude that the polyubiquitin chains on the LCV are PR- or ADPR- modified + +<|ref|>text<|/ref|><|det|>[[72, 85, 651, 203]]<|/det|> +We believe that new Fig. 3 is the biochemical evidence for modification occurring. In addition, in a simultaneously submitted manuscript, the laboratory of Yuxin Mao has performed similar experiments showing that internal UB moieties can be modified by Sde proteins. In their case, they synthesized tri- UB chains in which only one of the monomers had the WT Arg42 residue. They showed that modification occurred wherever the Arg42 was found. Arg42 internal to the trimer was modified as efficiently as the Arg42 that was found either in the N- terminal or C- terminal copy Ub. Therefore, phosphoribosylation is independent of the location of the UB monomer, which is consistent with our data in Fig. 3. + +<|ref|>text<|/ref|><|det|>[[72, 216, 763, 243]]<|/det|> +6. Authors conducted many SPR experiments. Providing kinetic values would be more insightful than showing sensorsgrams. + +<|ref|>text<|/ref|><|det|>[[72, 255, 660, 450]]<|/det|> +We have added more detail to the kinetic data for unmodified where relevant in the results (varies between Kd=6.2 x10e- 8 a 1.6X1- e- 7), but we disagree with the concept that modified Ub should have a different Kd than unmodified. The kinetic data for the modified Ub simply cannot be determined with any measure of confidence. Firstly, in the case of the modified Ub, the amount of binding is close to unmeasurable, making a kinetic determination of binding between p62 and modified Ub unreliable. In fact, the BiaCore provides a warning that the akinetic constants ka and kd are approaching the limits that can be measured by the instrument and kinetic constants cannot be uniquely determined. A Secondly, the miniscule amount of binding that can be detected is presumably due to the small amount of unmodified Ub. The prediction is that the binding kinetics of this small fraction of unmodified Ub should be identical to what is seen in the absence of Sde activity. We do, however, include kinetic data for the untreated Ub which has some level of reliability. To provide more accurate description of the experiments, we now put in the text (lines 289- 299): + +<|ref|>text<|/ref|><|det|>[[72, 462, 614, 567]]<|/det|> +In the absence of SdeC, Ub4 bound His- p62 with apparent KD = 1.2 X 10- 7 to 6.2 X 10- 8 M, indicating that binding affinity was at least as efficient as previous SPR studies using diUb as a substrate (KD = 9.3 X 10- 8 M; 54) (Fig. 4F). Binding of p62 to mono- Ub was very poor, consistent with DUB activity interfering with recognition of p62, with binding constants that could not be reliably determined by SPR (Fig. 4G, Fig. S2C). ... In all cases in which modification blocked p62 recognition, the binding constants could not be reliably determined by SPR. + +<|ref|>text<|/ref|><|det|>[[73, 580, 198, 593]]<|/det|> +(Minor comments) + +<|ref|>text<|/ref|><|det|>[[73, 606, 243, 620]]<|/det|> +Fig. 1J: pSdec - > pSdeC + +<|ref|>text<|/ref|><|det|>[[73, 633, 230, 658]]<|/det|> +Changed Fig. 2A: Out- 1 - > OTU1 + +<|ref|>text<|/ref|><|det|>[[73, 671, 375, 697]]<|/det|> +Changed Fig. S1 and line 172: Is it C293A or C293S? + +<|ref|>text<|/ref|><|det|>[[73, 710, 507, 737]]<|/det|> +The Figure is correct. It is C293A. Thank you for identifying this. Font size in Fig S1 differs from each other. + +<|ref|>text<|/ref|><|det|>[[73, 750, 644, 789]]<|/det|> +The figure was carefully recomposed and then converted to PDF. We think this may have fixed the problem, although we suspect the change in font size may be associated with the conversion to pdf. + +<|ref|>text<|/ref|><|det|>[[73, 802, 332, 815]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[73, 828, 768, 933]]<|/det|> +In this work Kotewicz and colleagues dissect the role of the Sde protein family in the establishment of the Legionella containing vacuole in host cells. Using molecular, biochemical and cell biology approaches the authors propose that the Sde protein family transiently (first 20 min of infection disappearing within 1h of infection) block p62 accumulation on the polyubiquitinated vacuole. This is achieved by firstly using the DUB domain of the Sde proteins that deubiquitinates K63 linked ubiquitin to provide Ub to the mART domain of Sde proteins that catalyzes pr- Ub conjugation on e.g. Rtn4 that accumulates on the LCV. This, pr- modification of ubiquitin blocks the association with the autophagy adaptor p62 with the vacuole and thereby protects the LCV against autophagy. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 764, 85]]<|/det|> +This very detailed dissection of the function of the Sde family proteins and their different domains in the establishment of the Legionella containing vacuole and some of their results contradict previously published work. + +<|ref|>text<|/ref|><|det|>[[72, 85, 764, 166]]<|/det|> +It is very interesting that the Sde protein family camouflages the LCV and blocks p62 accumulation and thereby autophagy in the first 20min. Indeed, the first minutes of infection are without doubt very important to survive or surrender, but it is known that Legionella blocks/retards autophagy much longer than the first 20 min of infection. How is this process thus maintained when the Sde proteins are not active anymore? Is there a timely difference in the secretion e.g. of the Sde proteins and RavZ or LpSpl or others? + +<|ref|>text<|/ref|><|det|>[[72, 177, 650, 203]]<|/det|> +Thank you for the comments and the downstream requests for changes that we think strengthened the manuscript and eliminated some confusion. + +<|ref|>text<|/ref|><|det|>[[72, 216, 640, 308]]<|/det|> +From Fig. 4L, we clearly show that there must be at least one uncharacterized activity that accumulates over time and interferes with p62 recruitment, because other known activities (such as RavZ) do not interfere with the accumulation of p62. The presence of this hypothetical activity was similarly noted in the referenced Omatode and Roy manuscript (PMID: 32482642). This activity could either directly target autophagy adapters or the replication vacuole. No matter the nature of the activity, at least one additional activity must exist based on our data. + +<|ref|>text<|/ref|><|det|>[[72, 320, 664, 347]]<|/det|> +Line 108- 109 several effectors/systems are described that Legionella employs to block autophagy. Please add the effector LpSpl (PMID: 26831115) + +<|ref|>text<|/ref|><|det|>[[73, 359, 327, 372]]<|/det|> +Now noted in resubmission, line 109. + +<|ref|>text<|/ref|><|det|>[[72, 385, 768, 438]]<|/det|> +Lines 113- 114 and elsewhere in the manuscript a.. ADPribosylation or phosphoribosylation of Ub interferes with autophagy by causing an absolute physical block on binding of polyUb to anautophagy adaptor, primarily by phosphoribosylation of target Ub chains about the LCVa; What is an aabsolute physical blocka? + +<|ref|>text<|/ref|><|det|>[[72, 450, 612, 477]]<|/det|> +That was poor wording in the previous manuscript. Changed to ainterferes with autophagy by blocking binding of polyUba + +<|ref|>text<|/ref|><|det|>[[72, 489, 768, 580]]<|/det|> +The authors present many convincing results, however in all different experiments the L. pneumophila WT strain was used without empty vector. Legionella is very sensitive to carrying vectors and intra and extracellular replication changes when adding vector. Thus, the control should be not only the sde mutant \(^+\) empty vector but also the WT \(^+\) empty vector to have the correct comparison when strains carrying plasmids are analyzed. This is the case for the entire Figure 1, Figure 2 D- H, Figure 4 A- H, and Figure 5. Please repeat at least the most important experiments with a correct WT vector control. + +<|ref|>text<|/ref|><|det|>[[72, 592, 645, 685]]<|/det|> +We went back to the original data and all the images associated with former Figs. 1, 4 and 5 (now Figs. 1.5, and 6) to determine if the experiments were carried out with strains that had empty vector. All the images that were grabbed to generate these figures were carefully annotated in our original datasets, and all clearly note that the WT and LP03(T4SS(- )) strains used to infect macrophages had the empty vector pJB908att- empty. We edited the figures accordingly, and the figures are now consistent with our laboratory records. + +<|ref|>text<|/ref|><|det|>[[72, 697, 652, 815]]<|/det|> +Because these missed annotations raised questions regarding whether empty vector altered the observed phenotypes, we performed side- by- side comparisons in the presence and absence of the pJB908att- empty vector and now include these results in the new Supplemental Data (Supplemental Figs. S1 and S5). In Figure S1, Rtn4 staining is interrogated, while in Figure S5, p62 staining is imaged. In both cases, the presence or absence of empty vector makes little difference, although for Rtn4 staining the absence of vector provides a somewhat more robust difference compared to the sde deletion control. We used empty vector throughout, so it's clear vector is not interfering with the result. + +<|ref|>text<|/ref|><|det|>[[72, 827, 664, 841]]<|/det|> +Figure 2A a please provide a better explanation what exactly one can see in this panel + +<|ref|>text<|/ref|><|det|>[[72, 853, 634, 921]]<|/det|> +Thank you very much for this comment. Referee 1 had similar problems with our description of this panel. The previous version was very poorly written, and we did not describe the experiment in Fig. 2A. We have now totally rewritten the section from lines 198- 215, clearly stating the experiment and describing the results. This much improves the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 920, 345, 933]]<|/det|> +Figure 2B a which strain is pSdeC WT? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 656, 127]]<|/det|> +The panel detailed the behavior of pSdeC(WT) compared to that of three plasmidborne SdeC point mutations. The manner that we displayed the panel probably didn't have consistent nomenclature. I think if we had put nothing for this panel it would have been even more confusing, and implied there was no plasmid. To try to clarify this, we put parentheses around WT, which we think makes sense, and added apá in front of complementing plasmids to make it look more uniform in nomenclature. + +<|ref|>text<|/ref|><|det|>[[73, 139, 360, 153]]<|/det|> +Figure 2D- H á please quantify the images + +<|ref|>text<|/ref|><|det|>[[73, 164, 652, 244]]<|/det|> +The 20 minute timepoint for the three point mutations was quantified in panel B. The iSidE data was quantified extensively in Fig. 1 at multiple timepoints as was the C118S data. The images show very little ubiquitin recruitment with WT at 5 min post- infection (the point of the figures) which was quantified in Fig. 1. The main point of the panel display was to display the morphology of serpentine localization, when the text referred to it (panels F and H). + +<|ref|>text<|/ref|><|det|>[[73, 255, 770, 333]]<|/det|> +Line 180 it readsá! To test this hypothesis, HEK293T cells transfected with HA- Ub were challenged by L. pneumophila harboring either WT or DUB defective (C118S) derivatives as the only active Sde family membersá! The HEK293T cells were challenged with Legionella at an MOI of 10. HEK293T cells are very poorly infected, I am surprised that an MOI=10 was sufficient? Did you check how many bacteria were internalized before continuing this experiment were HEK293T cells expressing the FcgrIII receptor used? In this case please specify in the M&M section + +<|ref|>text<|/ref|><|det|>[[72, 345, 648, 562]]<|/det|> +We followed protocols described in our previous manuscript, Losick, et al (2010) PMID: 20148897. This is now referenced in Materials and Methods, lines 527- 528. As can be seen in Figure 2 of that publication, MOI = 10 gave us high levels of NFkB induction in transfected cells, and even at an MOI = 1 in a 96 well dish we observed uptake of 2 X 104 bacteria (this was approximately 30% of cells infected). We did not go higher than 10 based on the idea that in an NFkB induction system, increasing the MOI to 100 only resulted in about a 2x increase in NFkB induction. We repeated these infection conditions in Lipo, et al. (2022) PMID: 6321832, which used MOI=5,15, 25 and 50, then used MOI=25 to maximize NFkB induction. Based on this previous work, we went ahead with MOI=10 and it was clear that it was sufficient to get a response. Itás possible that going higher with MOI may have helped, but we got a response at MOI = 10 so we stuck with it. Lines 275- 276 where are the quantifications? Should be shown. Quantification of p62 puncta at the 0 min timepoint is now displayed in new Supplemental Fig. S4. As pointed out in manuscript, distinguishing puncta that are LCV associated from those free in cytoplasm was difficult, so we focused on enveloped LCVs. + +<|ref|>text<|/ref|><|det|>[[72, 577, 763, 605]]<|/det|> +Throughout the manuscript one can read á! á about the LCV. á I donât think that the use of áaboutá is correct in this context + +<|ref|>text<|/ref|><|det|>[[73, 618, 600, 646]]<|/det|> +This was changed to áin the vicinity of the LCV, á the áLCV vicinity, á or in the Discussion when a model was proposed áassociated with the LCV. á + +<|ref|>text<|/ref|><|det|>[[72, 658, 768, 686]]<|/det|> +Line 33. . please correct to áThe Legionella pneumophila Sde family of translocated proteins promotes host tubular Á» + +<|ref|>text<|/ref|><|det|>[[73, 698, 142, 712]]<|/det|> +Changed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> diff --git a/peer_reviews/464166c7614ce71840865ad4fdf5ff6fab4d616871595069cfe6aee6eb009000/supplementary_1_Peer review file/images_list.json b/peer_reviews/464166c7614ce71840865ad4fdf5ff6fab4d616871595069cfe6aee6eb009000/supplementary_1_Peer review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2830ce084e9eaa80ba1cf5d551b420417c9941b2 --- /dev/null +++ b/peer_reviews/464166c7614ce71840865ad4fdf5ff6fab4d616871595069cfe6aee6eb009000/supplementary_1_Peer review file/images_list.json @@ -0,0 +1,33 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. F2. Time-series – fit and out-of-sample projection", + "footnote": [], + "bbox": [], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. E3. Overlaid vaccinations, cases and deaths", + "footnote": [], + "bbox": [ + [ + 125, + 643, + 868, + 833 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. F4. Placebo announcement dates", + "footnote": [], + "bbox": [], + "page_idx": 16 + } +] \ No newline at end of file diff --git a/peer_reviews/464166c7614ce71840865ad4fdf5ff6fab4d616871595069cfe6aee6eb009000/supplementary_1_Peer review file/supplementary_1_Peer review file.mmd b/peer_reviews/464166c7614ce71840865ad4fdf5ff6fab4d616871595069cfe6aee6eb009000/supplementary_1_Peer review file/supplementary_1_Peer review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a7000f490c2e1b1a2f0d215ad46d3e6d6673e0bb --- /dev/null +++ b/peer_reviews/464166c7614ce71840865ad4fdf5ff6fab4d616871595069cfe6aee6eb009000/supplementary_1_Peer review file/supplementary_1_Peer review file.mmd @@ -0,0 +1,510 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Human Behaviour Manuscript Title: COVID- 19 Vaccination Mandates and Vaccine Uptake Corresponding author name(s): Alexander Karainov + +## Reviewer Comments & Decisions: + +Decision Letter, initial version: + +17th February 2022 + +Dear Professor Karainov, + +Thank you once again for your manuscript, entitled "COVID- 19 Vaccination Mandates and Vaccine Uptake," and for your patience during the peer review process. + +Your manuscript has now been evaluated by 2 reviewers, whose comments are included at the end of this letter. A third reviewer agreed to review the work but was unable to submit their review; if they do send us their review, we will also forward their comments to you. Although the reviewers find your work to be of interest, they also raise some important concerns. We are very interested in the possibility of publishing your study in Nature Human Behaviour, but would like to consider your response to these concerns in the form of a revised manuscript before we make a decision on publication. + +As you will see, both of our reviewers raise a number of concerns about the strength of evidence for the central claim of your paper, of a causal relationship between vaccination mandates and vaccine uptake. They offer recommendations for additional analyses to strengthen the technical approach, and we ask that you respond to all of their recommendations in full, incorporating new analyses into the main text as appropriate. While Reviewer 1 is hesitant about the significance of the advance your paper represents in its current form, we feel that the advance here will be sufficient for us if the technical issues raised are satisfactorily addressed. + +Finally, your revised manuscript must comply fully with our editorial policies and formatting requirements. Failure to do so will result in your manuscript being returned to you, which will delay its consideration. To assist you in this process, I have attached a checklist that lists all of our + +<--- Page Split ---> + +# natureresearch + +requirements. If you have any questions about any of our policies or formatting, please don't hesitate to contact me. + +In sum, we invite you to revise your manuscript taking into account all reviewer and editor comments. We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +We hope to receive your revised manuscript within four weeks. We understand that the COVID- 19 pandemic is causing significant disruption for many of our authors and reviewers. If you cannot send your revised manuscript within this time, please let us know - we will be happy to extend the submission date to enable you to complete your work on the revision. + +With your revision, please: + +- Include a "Response to the editors and reviewers" document detailing, point-by-point, how you addressed each editor and referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be used by the editors to evaluate your revision and sent back to the reviewers along with the revised manuscript. + +- Highlight all changes made to your manuscript or provide us with a version that tracks changes. + +Please use the link below to submit your revised manuscript and related files: + +## [REDACTED] + +\(< \mathsf{strong} >\) Note: \(< /strong>\) This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. + +Sincerely, + +Charlotte Payne + +Charlotte Payne, PhD Senior Editor Nature Human Behaviour + +Reviewer expertise: + +<--- Page Split ---> + +# natureresearch + +Reviewer #1: epidemiology; health economics + +Reviewer #2: health economics; vaccination policies + +## REVIEWER COMMENTS: + +Reviewer #1: Remarks to the Author: + +In this study, the authors used several statistical methods and vaccination data from multiple countries to estimate the effect of COVID- 19 vaccination mandates on vaccine update. This is certainly an important topic during the pandemic. As the authors indicated in the paper, currently there are a large body of works focusing on the effect of various incentives on vaccination, including mandate orders (Mills and Ruttenauer 2021). This paper adds another evidence along this line of research. Overall, this is a solid study with careful analysis and robust results. However, I feel it lacks a significant advance that supersedes existing literature in scale or methodological novelty and rigor. Below I have a few comments on the analysis and presentation. + +1. The DID analysis relies on a key assumption of parallel trends among the treatment and control groups. Could the authors use the data before mandates to validate this assumption? + +2. Is there a spillover effect of mandate on vaccination in other locations? In Fig. 1, it seems after the mandate announcement of Quebec, there is a small increase of vaccination in British Columbia. This phenomenon also appears in Ontario after mandate in British Columbia and seems more pronounced. Since no spillover effect is an important assumption in DID analysis, it would be good to discuss about it. + +3. Equation 1 only controlled the mandate announcement and epidemiological information (case and death). Other covariates were represented in the time and location fixed effects. I think some other important factors should also be considered and tested if they are available, e.g., age-structure, socioeconomic status, education, political alignment, etc. These factors have been shown to affect vaccination and should be included and tested in the analysis if possible. + +4. Vit in Equation 1 could have spatiotemporal autocorrelation. Neglecting it in regression could lead to overconfidence in the effect size. Could the authors do a residual analysis and check if there exist spatial and temporal autocorrelations in the residuals? + +5. The time series analysis requires a strong assumption that the pattern was only affected by vaccination mandate. Equation 2 used two time trends to represent the change rates of Vt before and after mandate. Have the authors tested other functional forms of Equation 2? How well does Equation + +<--- Page Split ---> + +# natureresearch + +2 fit the data? To validate Equation 2, authors could perform out- of- sample predictions using Equation 2. This analysis could also provide a stronger support to the validity of the counterfactual analysis. + +6. Some explanations on statistical details should be provided for a better readability. For instance, what does each column represent in Table 1? What's the statistics in Fig. 3 and how to interpret it? The current presentation of the Sun-Abraham DID analysis is a bit difficult to comprehend for readers who are not familiar with this particular method. + +7. A minor issue. In the first paragraph in introduction, "... at about \(60\%\) of the population,...". Which country do the authors refer to here? The worldwide vaccination rate is way lower than this number. + +Reviewer #2: Remarks to the Author: + +Report on "COVID- 19 Vaccination Mandates and Vaccine Uptake" (NATHUMBEHAV- 220117753) This paper examines the impact of government- mandated proof of vaccination requirements for entering specific venues on receipt of first doses of the COVID- 19 vaccine. The authors implement a within- Canada difference- in- difference approach that leverages province- level variation in mandate adoption, and also estimate time series analyses to examine country- level policy adoption in France, Italy, and Germany. Estimates show that the mandates resulted in significant increases in COVID- 19 vaccination initiation, with estimates ranging from 5 to 12 percentage points. Overall, I found the paper to be very thorough, and I commend the authors for the substantial work they have done to demonstrate the robustness of their estimates. + +1. The clearest potential threat to the identification strategies used in this article is that rising COVID cases cause policy makers to adopt the vaccine mandates and also cause people to choose to be vaccinated. While the authors do a couple of things to address this (e.g. showing results are robust to controlling for various lags of log cases and deaths), there are several additional things that I think would be useful to include. + +a. It would be helpful to show figures overlaying vaccination rates/cases/deaths for each location, to allow for direct visual inspection of these relationships. + +b. Although the authors include cases and deaths as control variables, it would be more convincing to examine the relationship between policy adoption and these variables by running the event study, difference-in-differences, interrupted time series specifications with cases/hospitalizations/deaths as the outcome variables (Pei et al., 2019). + +c. There is good evidence that increased disease incidence causes vaccination rates to increase (Oster, 2018; Schaller et al., 2019). This evidence should be cited and discussed. Secondary comments + +2. The discussion on the literature on the determinants of vaccination would benefit from further development. The existing discussion is brief and not well integrated into the article. Additionally, + +<--- Page Split ---> + +# natureresearch + +there is a large pre- Covid literature that should be referenced. For example: Churchill (2021), Jin & Koch (2021), Lawler (2017), and White (2021). + +3. How were the set of countries chosen, both with regards to treatment countries and falsification countries? For example, Mills and Ruttenauer (2021) also looks at Israel, which seems to adopt during this time period. Are there other non-adopters, besides Spain, that can also be looked at as falsifications? + +4. Similar to the randomization inference exercise, it would also be useful to conduct placebo structural break/ time series estimation using never adopting countries. + +5. This is addressed somewhat in the notes to an appendix table, but I think it would be useful to have information in the main text about the extent to which 1 vs. 2 doses of the vaccine were required to satisfy the mandates. If 2 doses are required, more direct discussion of why do we not see a (lagged 3-4 week) effect on 2nd doses would be helpful. + +Minor comments + +6. The policy studied by Mills and Ruttenauer (2021) is referred to as "certification mandates" (page 6) - are these the same as the policies studied in this paper? Please just clarify. + +7. I thought many of the footnotes were sufficiently important to put in main text. For example, FN 6, 14, 16, 29, etc. + +## References + +Churchill, B. F. (2021). How Important is the Structure of School Vaccine Requirement Opt- Out Provisions? Evidence from Washington, DC's HPV Vaccine Requirement. Journal of Health Economics, 102480. + +Jin, G. Z., & Koch, T. G. (2021). Learning By Suffering? Patterns in Flu Vaccination Take- Up. American Journal of Health Economics, 7(1), 68- 94. + +Lawler, E. C. (2017). Effectiveness of vaccination recommendations versus mandates: evidence from the hepatitis A vaccine. Journal of health economics, 52, 45- 62. + +Zhuan Pei, Jörn- Steffen Pischke & Hannes Schwandt (2019) Poorly Measured Confounders are More Useful on the Left than on the Right, Journal of Business & Economic Statistics, 37:2, 205- 216, DOI: 10.1080/07350015.2018.1462710 + +White, C. (2021). Measuring social and externality benefits of influenza vaccination. Journal of Human Resources, 56(3), 749- 785. + +<--- Page Split ---> + +# natureresearch + +## Response to Reviewer 1, the report beginning: "In this study, the authors used several statistical methods..." + +Thank you very much for your valuable and constructive comments. We appreciate your time and detailed feedback. We have addressed all the Reviewers' concerns and editorial formatting requirements, and we believe that the paper is improved as a result. We follow up by responses to your specific comments (reproduced in italics). + +In this study, the authors used several statistical methods and vaccination data from multiple countries to estimate the effect of COVID- 19 vaccination mandates on vaccine update. This is certainly an important topic during the pandemic. As the authors indicated in the paper, currently there are a large body of works focusing on the effect of various incentives on vaccination, including mandate orders (Mills and Rutterauer 2021). This paper adds another evidence along this line of research. Overall, this is a solid study with careful analysis and robust results. However, I feel it lacks a significant advance that supersedes existing literature in scale or methodological novelty and rigor. Below I have a few comments on the analysis and presentation. + +1. The DID analysis relies on a key assumption of parallel trends among the treatment and control groups. Could the authors use the data before mandates to validate this assumption? + +We use data from before the mandate announcements in the event- study analysis in Fig. 3 on p. 5 and the underlying difference- in- differences (DID) regressions. We find no mandate associated pre- trend in the data – the DID estimates before the announcements (T = - 6 to T = - 2 on the figure) are statistically indistinguishable from zero. This indicates that the provinces that announced a mandate and provinces that did not announce a mandate by a given date have similar pre- trends in first- dose vaccinations. While, as known in the literature, there is no way to directly test the parallel trends assumption, that is, the provinces that announced a mandate would have the same trend in the outcomes as provinces that did not announce a mandate, it is reassuring that these two sets of provinces have the same trend before the mandate. Examining the pre- trend using event- study analysis, as we do, follows a + +<--- Page Split ---> + +# natureresearch + +conventional statistical method to gather evidence on the parallel trend assumption (e.g., Currie et al., 2020). + +We explain this on p. 6, second complete paragraph: + +Fig. 3 shows a lack of mandate- associated pre- trend in the data – the DID estimates before the mandate announcement are statistically indistinguishable from zero. This addresses the potential endogeneity concern (parallel trends assumption) that provinces that announced a mandate may have had a different trend in first- dose vaccinations than provinces that did not announce a mandate. + +2. Is there a spillover effect of mandate on vaccination in other locations? In Fig. 1, it seems after the mandate announcement of Quebec, there is a small increase of vaccination in British Columbia. This phenomenon also appears in Ontario after mandate in British Columbia and seems more pronounced. Since no spillover effect is an important assumption in DID analysis, it would be good to discuss about it. + +Thank you for this observation and question. We first did a visual inspection by 'zooming into' the data around the dates you suggest as shown below on Fig. F1; however, we do not see an obvious increase in the first dose vaccination rate around these dates. + +Fig. F1. Checking for spillovers + +<--- Page Split ---> + +# natureresearch + +![](images/Figure_unknown_0.jpg) + + +While there is no way to directly check for such spillover effects in the DID analysis, we are able to check via our time- series (TS) approach. Specifically, we ran the TS regressions for Ontario and British Columbia assuming (counterfactual) announcement dates from the provinces which announced a mandate earlier. The TS regression for Ontario, using the British Columbia announcement date (Aug. 23) instead of the actual announcement date (Sep. 1), yields a statistically insignificantly different from zero policy effect estimate, \(\pi\) in eq. (2), equal to 0.106 (p- value 0.451); similarly, the TS regression for British Columbia with the Quebec announcement date (Aug. 5) yields 0.182 (p- value 0.263). The TS regression for Ontario with the Quebec announcement date yields a negative policy effect estimate of - 0.451 (p- value 0.019). + +In addition, while the above evidence does not indicate so, if such spillover effects did exist across some provinces or dates, i.e., if some people received their first dose in advance of their provincial announcement because of a mandate in another province, then we can interpret our estimates as a lower bound of the full policy effect, since a fraction of people would have been vaccinated before the announcement. + +We have added a discussion regarding the above on p. 31 in the Supplementary Information section. + +<--- Page Split ---> + +# natureresearch + +1. Equation 1 only controlled the mandate announcement and epidemiological information (case and death). Other covariates were represented in the time and location fixed effects. I think some other important factors should also be considered and tested if they are available, e.g., age-structure, socioeconomic status, education, political alignment, etc. These factors have been shown to affect vaccination and should be included and tested in the analysis if possible. + +Thank you for this suggestion. Factors such as age structure, socioeconomic status, education, political alignment, however, do not vary over time given the short period we study. Therefore, these time- invariant factors are fully captured and subsumed in the province (location) fixed effects. We state this on p. 16, under "Other controls": + +The province fixed effects account for any time- invariant province characteristics such as sentiment towards vaccination, age structure, education, political alignment, etc. + +As an alternative, to address your suggestion, we re- ran the diff- in- diff specification by replacing the province fixed effects with time- invariant province characteristics (we used GDP per capita, % rural population, population density, unemployment rate, ICU beds per capita, % of population of age \(65+\) , full- time university students per capita and political alignment). The results are reported in Table R1 below. It is reassuring that the estimated effect of the mandate announcements on vaccine uptake remains very similar in magnitude and significance in this specification (columns 3 and 4) as in our main specification with province fixed effects (columns 1 and 2), see Table R1 below. + +We have added discussion about this robustness exercise on p. 30, middle. + +We also ran a specification replacing the province fixed effects with time- invariant + +Table R1. Canadian provinces – difference- in- differences estimates + +<--- Page Split ---> + +# natureresearch + +
Outcome: log weekly vaccine first doses, V<sub>it</sub>
p-values in [ ](1)(2)(3)(4)
mandate announced, P<sub>it</sub>0.506 ***
[0.001]
0.505 ***
[0.001]
week 00.359 ***
[0.005]
0.377 ***
[0.003]
week 10.543 ***
[0.001]
0.557 ***
[0.001]
week 20.498 **
[0.010]
0.476 ***
[0.007]
week 30.705 ***
[0.001]
0.681 ***
[0.001]
week 40.713 **
[0.018]
0.677 ***
[0.005]
week 5+0.651 *
[0.056]
0.591 **
[0.019]
log weekly cases, C<sub>it</sub>0.002
[0.967]
0.002
[0.958]
-0.010
[0.816]
-0.010
[0.814]
log weekly deaths, D<sub>it</sub>0.048
[0.365]
0.046
[0.415]
0.085
[0.100]
0.085
[0.116]
R-squared0.8200.8210.8080.809
sample size, N920920920920
province fixed effectsXX
province characteristicsXX
date fixed effectsXXXX
+ +province characteristics (GDP per capita, \(\%\) rural population, population density, unemployment rate, ICU beds per capita, \(\%\) of population of age 65 or older, full- time university students per capita, and political alignment). The estimated effect of the mandate announcements on vaccine uptake in this specification is very similar in magnitude and significance to our main estimates in Table 1. + +4. \(V_{it}\) in Equation 1 could have spatiotemporal autocorrelation. Neglecting it in regression could lead to overconfidence in the effect size. Could the authors do a residual analysis and check if there exist spatial and temporal autocorrelations in the residuals? + +<--- Page Split ---> + +We use cluster- robust standard errors and wild bootstrap. In our main results, the standard errors are clustered at the province level, so that the error terms are allowed to be serially correlated within each province. We also report wild bootstrap two- way clustered stan- dard errors, by province and date, which account for within- day spatial correlation across provinces, in Table S6. Both the one- way and two- way clustered standard errors are very similar to each other, so we do not suspect that spatiotemporal correlation leads to overconfidence in the effect size (an excerpt from Table S6 is replicated below; please see the full table for more details). + +Table R2. Robustness - standard errors (excerpt) + +
Outcome: log weekly first doses, Vk
mandate announced0.506
clustered SE (asymptotic)(0.001) ***
wild bootstrap one-way clustered SE[0.001] ***
wild bootstrap two-way clustered SE{0.000} ***
+ +We have added a clarification about this on p. 16, bottom: + +The use of clustered standard errors allows the error terms to be to be serially correlated within each province. Alternative methods for computing the standard errors are explored in Table S6 - clustering at the province level (Stata command "cluster"), wild bootstrap standard errors clustered at the province level and wild bootstrap standard errors two- way clustered by province and date allowing for spatio- temporal correlation (Stata command "bootstrap"). + +5. The time series analysis requires a strong assumption that the pattern was only affected by vaccination mandate. Equation 2 used two time trends to represent the change rates of \(Vt\) before and after mandate. Have the authors tested other functional forms of Equation 2? How well does Equation 2 fit the data? To validate Equation 2, authors could perform out-of-sample predictions using Equation 2. This analysis could also provide a stronger support to the validity of the counterfactual analysis. + +<--- Page Split ---> + +# natureresearch + +Thank you for these helpful suggestions. We did check alternative specifications for the time- series regressions at the working paper stage: additional lags, no time trend, or one time trend and chose the current specification as providing the best fit and consistent with the existing interrupted time- series analysis literature. + +Following your specific suggestions, we have added Fig. S1 in the Supplementary Information section, p. 34 (reproduced as Fig. F2 below), which displays the time- series model fit with the data until Oct. 31, 2021. In addition, the figure plots out- of- sample predictions obtained using equation (2) and our time- series estimates from Table 2 and using the actual weekly cases and deaths data for these out- of- sample dates. The figure shows that the time- series specification fits the weekly first dose vaccine data very well (e.g., the adjusted R- squared is 0.997 for France, 0.940 for Italy and 0.990 for Germany). + +In addition, the out- of- sample projections (dotted red line) are close to the observed vaccine first- dose data (black circles) in November in most locations, with the exception of Germany, where the COVID- 19 certificate became more restrictive in that period ("3G" to "2G"), excluding unvaccinated people, who were previously able to supply a negative test, from indoor dining, bars and hairdressers, etc. The fact that the tightening of the certification requirements in Germany (that we do not model, however) is accompanied by a increase in first- dose vaccinations in November 2021 is consistent with our main findings. + +A constraining factor for the out- of- sample projections is that first doses for the 5 to 11 age group were approved in November (Nov. 19 in Canada and Nov. 25 in the EU) and, for many jurisdictions in our sample, we cannot distinguish these doses from adult first doses in the vaccinations data. Hence, we only show out- of- sample projections for three additional weeks beyond our sample end date, until Nov. 21, 2021. + +We summarize the above discussion on p. 31, bottom in the Supplementary Information section and refer to it in the main text on p. 10, third paragraph. + +<--- Page Split ---> + +# natureresearch + +6. Some explanations on statistical details should be provided for a better readability. For instance, what does each column represent in Table 1? What's the statistics in Fig. 3 and how to interpret it? The current presentation of the Sun-Abraham DID analysis is a bit difficult to comprehend for readers who are not familiar with this particular method. + +Thank you – we agree and have added more details as follows. + +![](images/Figure_unknown_1.jpg) + +
Fig. F2. Time-series – fit and out-of-sample projection
+ +Notes: The black circles are log weekly first doses per 100,000 people. The red solid line is the fitted value from the time- series regression, equation (2). The dotted line is the out- of- sample extrapolation of the fitted value line for three + +<--- Page Split ---> + +additional weeks, using cases and deaths data until Nov. 21, 2021. Germany introduced a stricter version of their COVID certificate in November 2021. + +We have added explanations about the specification of each column of Table 1 in the table notes (p. 7), reproduced below: + +Columns (1) and (2) report the average mandate effect estimate over the postannouncement period, without and with controlling for weekly cases and deaths. Column (3) decomposes the effect by post- announcement week. + +as well as in the last complete paragraph on p. 6: + +Table 1 displays DID estimates of the mandate effect on first- dose uptake, relative to the pre- mandate period, controlling for information (cases and deaths) and time and location fixed effects. Columns (1) and (2) show that the mandate announcement is associated with an average increase of about 66 percent (50.6 log points, 95% CI 25- 77 in column 2) in weekly first doses. In column (3), we report estimates where the mandate policy variable is decomposed into six binary variables (one for each week after the announcement date) to account for dynamic effects. + +We also explain the results and statistics in Fig. 3 in the figure notes (p. 5) and in the main text (p. 6), reproduced below: + +The figure plots the estimates from a variant of equation (1) where the man- date announcement variable \(P_{ii}\) is replaced by the interaction of being in the 'treatment' group (announced mandate) with a series of dummies for each week ranging from 6 weeks before \((T = - 6)\) to 5 or more weeks after the announcement \((T = 5)\) , where \(T = 0\) denotes the week starting at the announcement date. The reference point is one week before the announcement \((T = - 1)\) . The dotted lines correspond to 95% confidence intervals. + +[p. 6, main text]. In Fig. 3, we plot results from an event study analysis of weekly first doses administered in the ten Canadian provinces, from six weeks prior to five or more weeks after the announcement of a mandate. + +The interpretation of Fig. 3 is on p. 6, reproduced below: + +<--- Page Split ---> + +# natureresearch + +Fig. 3 shows lack of mandate- associated pre- trend in the data – the DID estimates before the mandate announcement are statistically indistinguishable from zero. This addresses the potential endogeneity concern (parallel trends assumption) that provinces that announced a mandate may have had a different trend in first- dose vaccinations than provinces that did not announce a mandate. Second, the impact of the mandate announcement on first- dose vaccine uptake is realized relatively quickly and is large in magnitude – an increase of \(42\%\) (35 log points, \(95\%\) CI 9–62) in new weekly doses in the first post- announcement week and \(71\%\) (54 log points, 21–86) in the second week, each relative to one week before the announcement. The observed quick increase in uptake mitigates possible concerns that vaccine supply or scheduling constraints may be affecting our results. Third, the policy effect persists over time over the 6- week post- announcement period we analyze \((T = 0\) to \(T = 5\) ). Unfortunately, data limitations (the timing of the announcements) and the need for a not- yet- treated control group in the DID method do not allow us to investigate longer horizons. + +We have also added detailed explanations on the Sun and Abraham estimator in the Methods section; please see p. 17 (replicated below): + +In particular, Sun and Abraham sun develop a difference- in- differences estimator valid under these conditions, which we use to estimate (1). The Sun and Abra- ham estimator uses never- treated or last- treated units as the control group and is constructed as weighted average of treatment effects for each cohort (by date of mandate announcement) and each relative time after or before the announce- ment (we use the Stata function eventstudyinteract provided by the authors). Specifically, to calculate the average treatment effect \(\alpha\) in (1), we replace \(aP_{ii}\) with + +\[\underbrace{\mathbf{L}\cdot\mathbf{L}}_{\substack{\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots}}a_{i,i}(1.[\hat{i}=g]D_{i t}^{i})\] + +where \(C\) is the set of never- treated or last- treated provinces (control group), + +<--- Page Split ---> + +# natureresearch + +\(\mathrm{D}_{l} = \mathrm{\Omega}_{1}[\mathrm{\Omega}_{l} - \mathrm{\Omega}_{l} = \mathrm{\Omega}_{l}]\) is a "relative time" indicator, and \(l^{\wedge}i\) is the date of treatment for province \(i\) . Under parallel trends and no anticipation, Sun and Abraham (2021) show that \(\alpha_{i,l}\) is consistent for the province- time specific treatment effect. Then, the average treatment effect for each relative- time period, \(\alpha_{i}\) , is the appropriately weighted (by the sample share of each treated province in relative time \(l\) ) average of \(\alpha_{i,l}\) across the units \(i\) , and \(\alpha\) in (1) is computed as the simple average of \(\alpha_{i}\) across \(l\) . + +7. A minor issue. In the first paragraph in introduction, "... at about \(60\%\) of the population...". Which country do the authors refer to here? The worldwide vaccination rate is way lower than this number. + +Thank you, we have edited the text to eliminate this potential confusion. Please see p. 2, the first paragraph: + +...Yet, following a rapid uptake in early 2021, vaccinations in many countries (see Fig. E1) slowed down significantly in the summer months. + +## Response to Reviewer 2, the report beginning: "This paper examines the im- pact..." + +Thank you very much for your valuable and constructive comments. We appreciate your time and detailed feedback. We have addressed all the Reviewers' concerns and editorial formatting requirements, and we believe that the paper is improved as a result. We follow up by responses to your specific comments (reproduced in italics). + +This paper examines the impact of government- mandated proof of vaccination requirements for entering specific venues on receipt of first doses of the COVID- 19 vaccine. The authors implement a within- Canada difference- in- difference approach that leverages province- level variation in mandate adoption, and also estimate time series analyses to examine country- level policy adoption in France, Italy, and Germany. Estimates show that the mandates resulted in + +<--- Page Split ---> + +# natureresearch + +significant increases in COVID- 19 vaccination initiation, with estimates ranging from 5 to 12 percentage points. Overall, I found the paper to be very thorough, and I commend the authors for the substantial work they have done to demonstrate the robustness of their estimates. + +1. The clearest potential threat to the identification strategies used in this article is that rising COVID cases cause policy makers to adopt the vaccine mandates and also cause people to choose to be vaccinated. While the authors do a couple of things to address this (e.g. showing results are robust to controlling for various lags of log cases and deaths), there are several additional things that I think would be useful to include. + +Thank you for these helpful comments. We have addressed them in the revised version of the paper. Please see our detailed responses below. + +a. It would be helpful to show figures overlaying vaccination rates/cases/deaths for each location, to allow for direct visual inspection of these relationships. + +Thank you for this suggestion. While we control for weekly cases and deaths in both the difference- in- differences (DID) and time- series regressions, we agree that visually illustrating the evolution of cases and deaths together with vaccine uptake can be useful in interpreting our results. We have followed your suggestion and overlaid the cases and death counts on Extended Data Fig. E3 (reproduced below). + +![](images/Figure_unknown_2.jpg) + +
Fig. E3. Overlaid vaccinations, cases and deaths
+ +<--- Page Split ---> + +# natureresearch + +![PLACEHOLDER_17_0] + + +Notes: The figure plots the weekly administered COVID- 19 vaccine first doses per 100,000 people for dates \(t - 6\) to \(t\) where \(t\) is the date on the horizontal axis (solid black line). The dashed red lines denote the proof of vaccination mandate announcement date for each province. The dotted green lines denote the mandate implementation (enforcement) date for each province (see Table S1). The thin blue line is weekly cases per 100,000 (right axis); the thin magenta line is the number of weekly deaths (right axis). + +a. Although the authors include cases and deaths as control variables, it would be more convincing to examine the relationship between policy adoption and these variables by running the event study, difference-in-differences, interrupted time series specifications with cases/hospitalizations/deaths as the outcome variables (Pei et al., 2019). + +Thank you. In this paper, we made the deliberate choice to put the focus on quantifying, as precisely as we can and using both Canadian provincial data and country- level data, the direct effect of proof of vaccination mandates on first dose vaccine uptake. One can then use vaccine + +<--- Page Split ---> + +# natureresearch + +effectiveness estimates from the medical literature (in which we are not experts) to map the gains in vaccinations we estimate into averted cases, hospitalizations or deaths. + +While the impact on health outcomes is beyond the scope of our paper, we agree that it definitely remains an important topic for further research, ideally controlling for both the direct effect through vaccine effectiveness and also possible indirect effects through changes in behaviour. We have added a sentence in the Discussion section (p. 14) clarifying this, along with other limitations of our study: + +We have abstracted from assessing the mandates' impact on health outcomes (cases, hospitalizations or deaths). However, vaccine effectiveness estimates from the medical literature can be used to study this further, ideally controlling for possible changes in behaviour. + +Nevertheless, following your suggestion, we also ran a DID regression analogous to equation (1), but where we replace the outcome variable with weekly cases or deaths and lag the policy variable (mandate announced) by two weeks, see Table R3 below. We do not find statistically significant results related to the mandate announcements. However, one may not expect health outcome metrics to change quickly after the mandate announcements because the gains in vaccinations accumulate over time and because of the time lag between vaccination and its impact on the health outcome for an individual. + +Table R3. Cases or deaths as outcome variable + +
Outcome:log weekly caseslog weekly deaths
mandate announced (lagged)-0.2020.408
[0.315][0.184]
R-squared0.9370.864
sample size780780
province fixed effectsXX
date fixed effectsXX
+ +<--- Page Split ---> + +# natureresearch + +a. There is good evidence that increased disease incidence causes vaccination rates to increase (Oster, 2018; Schaller et al., 2019). This evidence should be cited and discussed. + +Thank you for these helpful references. We have now cited them, and we also discuss briefly the importance of disease incidence (as controlled for by log weekly cases and deaths in our empirical analysis); see p. 15, under "Information". + +We include variables related to the concurrent COVID- 19 epidemiological situation, specifically log of weekly cases, \(\mathrm{C_{it}}\) , and log of weekly deaths, \(\mathrm{D_{it}}\) , for the week ending at date t (dates t - 6 to t). We refer to these variables jointly as 'information', \(\mathrm{I_{it}}\) , see [33, 34], since they can inform a person's COVID- 19 exposure risk assessment and/or decision to be vaccinated, e.g., as shown in [21, 22]. + +## Secondary comments + +2. The discussion on the literature on the determinants of vaccination would benefit from further development. The existing discussion is brief and not well integrated into the article. Additionally, there is a large pre-Covid literature that should be referenced. For example: Churchill (2021), Jin & Koch (2021), Lawler (2017), and White (2021). + +Thank you for suggesting these valuable references that we have now included early on in the paper's introduction - please see p.2, bottom and p. 14, third complete paragraph. We have also re- organized the paper's introduction and discussion sections to integrate better all the relevant literature while conforming to the journal requirements. Additional details on the related literature are included in the Supplementary Information, p. 32-33. + +3. How were the set of countries chosen, both with regards to treatment countries and falsification countries? For example, Mills and Rutenauer (2021) also looks at Israel, which seems to adopt during this time period. Are there other non-adopters, besides Spain, that can also be looked at as falsifications? + +We have added a brief discussion regarding the countries chosen. Please see p. 2, the fourth complete paragraph, reproduced below: + +<--- Page Split ---> + +# natureresearch + +We chose these locations since they have similar economies, demographics and vaccine access and all announced and implemented mandates in July- October 2021, a period with minimal binding vaccine supply or access constraints and a high base first- dose vaccination rate (above \(60\%\) of those eligible in the three countries and above \(80\%\) in Canada at the time of the mandate announcements). + +Unlike Mills and Ruttenauer (2021), we do not use the synthetic control method which requires data from non- adopters, and hence we only show an example of a country without national mandate in the studied period (Spain), purely for visual illustration. We do not study Israel, as it introduced a very early certification requirement (Green Pass), in Feb. 2021, which was removed in early June, and then re- imposed again in July 2021. Israel's vaccination campaign also proceeded on a different (earlier) schedule compared to the other countries we study. + +4. Similar to the randomization inference exercise, it would also be useful to conduct placebo structural break/ time series estimation using never adopting countries. + +Thank you for your suggestion. Similar to the DID randomization inference robustness exercise (Fig. E6 and p. 30 in the paper), we used our time- series model and estimated the mandate policy effect (the parameter \(\pi\) in equation (2) on p. 17) for a range of placebo announcement dates (132 unique dates in total including the true announcement date), from Jun. 17 to Oct. 24 for each of France, Italy and Germany. Fig. F4 below displays the results. There is only a small number of placebo dates (mostly in a close neighbourhood of the true announcement date) for which the time- series regression yields a larger policy estimate that that for the true date. Specifically, there are 12 dates (9.1%) with estimate larger than that for the true announcement date for France, 14 dates (10.6%) for Italy and only 5 such dates (3.8%) for Germany. While the results for France and Italy are noisier than that of the DID randomization inference exercise (Fig. E6 in the paper), these results are not directly comparable since the DID results use data from several treated provinces to estimate the policy effect. + +<--- Page Split ---> + +# natureresearch + +The time- series approach and specification we use relies on a known date for the policy regime change. We thus cannot apply it to never adopting countries as we have no way of interpreting such results. + +We have added discussion regarding the above on p. 32 and added Supplementary Fig. S2 on p. 34. + +![PLACEHOLDER_21_0] + +
Fig. F4. Placebo announcement dates
+ +Notes: The figure reports time- series estimates from 132 runs with all possible placebo announcement dates between June 17 and Oct 24. The dashed red line is the main estimate from Table 2 using the actual announcement date. + +1. This is addressed somewhat in the notes to an appendix table, but I think it would be useful to have information in the main text about the extent to which 1 vs. 2 doses of the vaccine were required to satisfy the mandates. If 2 doses are required, more direct discussion of why do we not see a (lagged 3-4 week) effect on 2nd doses would be helpful. + +Thank you for this comment. We now specify in the text (p. 7, bottom) that: + +Most provincial proof of vaccination mandates required two doses to be considered adequately vaccinated with a vaccine offered in Canada during the study period (Pfizer (Comirnaty), Moderna (SpikeVax) or AstraZeneca (Vaxzevria)); there were limited exceptions in Quebec (a prior infection could count as first + +<--- Page Split ---> + +# natureresearch + +dose) and British Columbia (only one dose was required between Sep. 13 and Oct. 23, 2021). + +We also checked for a second- dose effect after excluding British Columbia (BC) from the sample, and we find weak evidence for a positive post- mandate announcement impact on second doses – the average estimate analogous to Table 1, column 2 is 0.227 (p- value 0.053). This is consistent with an impact on second doses becoming more apparent after excluding BC since it differs from the rest of the provinces with its phased implementation. + +We offer the following possible explanation (see p. 8, top) for why we do not find robust statistically significant effect on second doses: + +One possible explanation for the lack of large increases in second doses a few weeks after the spikes in first doses is that mandates may have encouraged some people that already had their first doses to obtain their second dose sooner, thus shifting some second doses forward and dampening the lagged effect. + +Minor comments + +6. The policy studied by Mills and Ruttenaver (2021) is referred to as "certification mandates" (page 6) – are these the same as the policies studied in this paper? Please just clarify. + +Thank you. Yes, both we and Mills and Ruttenaver study policy requirements regarding access to non- essential settings or services. We now clearly refer to "proof of vaccination mandates" or "certificates" in the introduction (p. 2, third paragraph) and at the beginning of the discussion section (p. 12, bottom) where we discuss Mills and Ruttenaver (2021). We do the same in the data description (see p. 14-15) and several other places in the main text. + +7. I thought many of the footnotes were sufficiently important to put in main text. For example, FN 6, 14, 16, 29, etc. + +<--- Page Split ---> + +# natureresearch + +Thank you. To comply with the journal formatting requirements, we have incorporated all former footnotes in the main text and in the table/figures notes or deleted a few peripheral notes. All the former footnotes you list have been incorporated in the text. + +## Decision Letter, first revision: + +Our ref: NATHUMBEHAV- 220117753A + +25th March 2022 + +Dear Dr. Karaivanov, + +Thank you for submitting your revised manuscript "COVID- 19 Vaccination Mandates and Vaccine Uptake" (NATHUMBEHAV- 220117753A). It has now been seen by the original referees and their comments are below. As you can see, the reviewers find that the paper has improved in revision. We will therefore be happy in principle to publish it in Nature Human Behaviour, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements within a week. 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I apologize for the confusion with regards to my main comment 1b in the previous report. What I think needs to be examined more carefully is the possibility that case and death rates predict policy adoption, while also independently predicting vaccination. The trends in Figure E3 show that this is potentially true. + +## Final Decision Letter: + +Dear Professor Karaivanov, + +We are pleased to inform you that your Article "COVID- 19 Vaccination Mandates and Vaccine Uptake", has now been accepted for publication in Nature Human Behaviour. + +Please note that Nature Human Behaviour is a Transformative Journal (TJ). Authors whose manuscript was submitted on or after January 1st, 2021, may publish their research with us through the traditional subscription access route or make their paper immediately open access through payment of an article- processing charge (APC). Authors will not be required to make a final decision about access to their article until it has been accepted. 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A third reviewer agreed to review the work but was unable to submit their review; if they do send us their review, we will also forward their comments to you. Although the reviewers find your work to be of interest, they also raise some important concerns. We are very interested in the possibility of publishing your study in Nature Human Behaviour, but would like to consider your response to these concerns in the form of a revised manuscript before we make a decision on publication. + +<|ref|>text<|/ref|><|det|>[[115, 672, 879, 779]]<|/det|> +As you will see, both of our reviewers raise a number of concerns about the strength of evidence for the central claim of your paper, of a causal relationship between vaccination mandates and vaccine uptake. They offer recommendations for additional analyses to strengthen the technical approach, and we ask that you respond to all of their recommendations in full, incorporating new analyses into the main text as appropriate. While Reviewer 1 is hesitant about the significance of the advance your paper represents in its current form, we feel that the advance here will be sufficient for us if the technical issues raised are satisfactorily addressed. + +<|ref|>text<|/ref|><|det|>[[115, 796, 877, 842]]<|/det|> +Finally, your revised manuscript must comply fully with our editorial policies and formatting requirements. Failure to do so will result in your manuscript being returned to you, which will delay its consideration. To assist you in this process, I have attached a checklist that lists all of our + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 51, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 148, 872, 179]]<|/det|> +requirements. If you have any questions about any of our policies or formatting, please don't hesitate to contact me. + +<|ref|>text<|/ref|><|det|>[[115, 196, 877, 257]]<|/det|> +In sum, we invite you to revise your manuscript taking into account all reviewer and editor comments. We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[115, 275, 868, 336]]<|/det|> +We hope to receive your revised manuscript within four weeks. We understand that the COVID- 19 pandemic is causing significant disruption for many of our authors and reviewers. If you cannot send your revised manuscript within this time, please let us know - we will be happy to extend the submission date to enable you to complete your work on the revision. + +<|ref|>text<|/ref|><|det|>[[116, 354, 315, 368]]<|/det|> +With your revision, please: + +<|ref|>text<|/ref|><|det|>[[115, 386, 883, 447]]<|/det|> +- Include a "Response to the editors and reviewers" document detailing, point-by-point, how you addressed each editor and referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be used by the editors to evaluate your revision and sent back to the reviewers along with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 465, 842, 481]]<|/det|> +- Highlight all changes made to your manuscript or provide us with a version that tracks changes. + +<|ref|>text<|/ref|><|det|>[[115, 498, 692, 513]]<|/det|> +Please use the link below to submit your revised manuscript and related files: + +<|ref|>sub_title<|/ref|><|det|>[[116, 530, 221, 546]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[116, 563, 863, 609]]<|/det|> +\(< \mathsf{strong} >\) Note: \(< /strong>\) This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[116, 627, 857, 672]]<|/det|> +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. + +<|ref|>text<|/ref|><|det|>[[116, 692, 188, 706]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[116, 724, 235, 738]]<|/det|> +Charlotte Payne + +<|ref|>text<|/ref|><|det|>[[116, 757, 305, 802]]<|/det|> +Charlotte Payne, PhD Senior Editor Nature Human Behaviour + +<|ref|>text<|/ref|><|det|>[[116, 840, 262, 854]]<|/det|> +Reviewer expertise: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 52, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 165, 463, 181]]<|/det|> +Reviewer #1: epidemiology; health economics + +<|ref|>text<|/ref|><|det|>[[115, 199, 506, 214]]<|/det|> +Reviewer #2: health economics; vaccination policies + +<|ref|>sub_title<|/ref|><|det|>[[115, 286, 293, 301]]<|/det|> +## REVIEWER COMMENTS: + +<|ref|>text<|/ref|><|det|>[[115, 319, 291, 349]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 364, 880, 486]]<|/det|> +In this study, the authors used several statistical methods and vaccination data from multiple countries to estimate the effect of COVID- 19 vaccination mandates on vaccine update. This is certainly an important topic during the pandemic. As the authors indicated in the paper, currently there are a large body of works focusing on the effect of various incentives on vaccination, including mandate orders (Mills and Ruttenauer 2021). This paper adds another evidence along this line of research. Overall, this is a solid study with careful analysis and robust results. However, I feel it lacks a significant advance that supersedes existing literature in scale or methodological novelty and rigor. Below I have a few comments on the analysis and presentation. + +<|ref|>text<|/ref|><|det|>[[115, 504, 850, 535]]<|/det|> +1. The DID analysis relies on a key assumption of parallel trends among the treatment and control groups. Could the authors use the data before mandates to validate this assumption? + +<|ref|>text<|/ref|><|det|>[[115, 551, 878, 628]]<|/det|> +2. Is there a spillover effect of mandate on vaccination in other locations? In Fig. 1, it seems after the mandate announcement of Quebec, there is a small increase of vaccination in British Columbia. This phenomenon also appears in Ontario after mandate in British Columbia and seems more pronounced. Since no spillover effect is an important assumption in DID analysis, it would be good to discuss about it. + +<|ref|>text<|/ref|><|det|>[[115, 645, 866, 722]]<|/det|> +3. Equation 1 only controlled the mandate announcement and epidemiological information (case and death). Other covariates were represented in the time and location fixed effects. I think some other important factors should also be considered and tested if they are available, e.g., age-structure, socioeconomic status, education, political alignment, etc. These factors have been shown to affect vaccination and should be included and tested in the analysis if possible. + +<|ref|>text<|/ref|><|det|>[[115, 739, 880, 785]]<|/det|> +4. Vit in Equation 1 could have spatiotemporal autocorrelation. Neglecting it in regression could lead to overconfidence in the effect size. Could the authors do a residual analysis and check if there exist spatial and temporal autocorrelations in the residuals? + +<|ref|>text<|/ref|><|det|>[[115, 803, 875, 849]]<|/det|> +5. The time series analysis requires a strong assumption that the pattern was only affected by vaccination mandate. Equation 2 used two time trends to represent the change rates of Vt before and after mandate. Have the authors tested other functional forms of Equation 2? How well does Equation + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 148, 874, 180]]<|/det|> +2 fit the data? To validate Equation 2, authors could perform out- of- sample predictions using Equation 2. This analysis could also provide a stronger support to the validity of the counterfactual analysis. + +<|ref|>text<|/ref|><|det|>[[115, 196, 873, 258]]<|/det|> +6. Some explanations on statistical details should be provided for a better readability. For instance, what does each column represent in Table 1? What's the statistics in Fig. 3 and how to interpret it? The current presentation of the Sun-Abraham DID analysis is a bit difficult to comprehend for readers who are not familiar with this particular method. + +<|ref|>text<|/ref|><|det|>[[115, 275, 870, 307]]<|/det|> +7. A minor issue. In the first paragraph in introduction, "... at about \(60\%\) of the population,...". Which country do the authors refer to here? The worldwide vaccination rate is way lower than this number. + +<|ref|>text<|/ref|><|det|>[[115, 360, 291, 390]]<|/det|> +Reviewer #2: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 404, 865, 541]]<|/det|> +Report on "COVID- 19 Vaccination Mandates and Vaccine Uptake" (NATHUMBEHAV- 220117753) This paper examines the impact of government- mandated proof of vaccination requirements for entering specific venues on receipt of first doses of the COVID- 19 vaccine. The authors implement a within- Canada difference- in- difference approach that leverages province- level variation in mandate adoption, and also estimate time series analyses to examine country- level policy adoption in France, Italy, and Germany. Estimates show that the mandates resulted in significant increases in COVID- 19 vaccination initiation, with estimates ranging from 5 to 12 percentage points. Overall, I found the paper to be very thorough, and I commend the authors for the substantial work they have done to demonstrate the robustness of their estimates. + +<|ref|>text<|/ref|><|det|>[[115, 556, 874, 632]]<|/det|> +1. The clearest potential threat to the identification strategies used in this article is that rising COVID cases cause policy makers to adopt the vaccine mandates and also cause people to choose to be vaccinated. While the authors do a couple of things to address this (e.g. showing results are robust to controlling for various lags of log cases and deaths), there are several additional things that I think would be useful to include. + +<|ref|>text<|/ref|><|det|>[[115, 647, 866, 678]]<|/det|> +a. It would be helpful to show figures overlaying vaccination rates/cases/deaths for each location, to allow for direct visual inspection of these relationships. + +<|ref|>text<|/ref|><|det|>[[115, 693, 872, 753]]<|/det|> +b. Although the authors include cases and deaths as control variables, it would be more convincing to examine the relationship between policy adoption and these variables by running the event study, difference-in-differences, interrupted time series specifications with cases/hospitalizations/deaths as the outcome variables (Pei et al., 2019). + +<|ref|>text<|/ref|><|det|>[[115, 768, 875, 814]]<|/det|> +c. There is good evidence that increased disease incidence causes vaccination rates to increase (Oster, 2018; Schaller et al., 2019). This evidence should be cited and discussed. Secondary comments + +<|ref|>text<|/ref|><|det|>[[112, 830, 840, 860]]<|/det|> +2. The discussion on the literature on the determinants of vaccination would benefit from further development. The existing discussion is brief and not well integrated into the article. Additionally, + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 50, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 147, 857, 179]]<|/det|> +there is a large pre- Covid literature that should be referenced. For example: Churchill (2021), Jin & Koch (2021), Lawler (2017), and White (2021). + +<|ref|>text<|/ref|><|det|>[[115, 193, 877, 255]]<|/det|> +3. How were the set of countries chosen, both with regards to treatment countries and falsification countries? For example, Mills and Ruttenauer (2021) also looks at Israel, which seems to adopt during this time period. Are there other non-adopters, besides Spain, that can also be looked at as falsifications? + +<|ref|>text<|/ref|><|det|>[[115, 269, 808, 300]]<|/det|> +4. Similar to the randomization inference exercise, it would also be useful to conduct placebo structural break/ time series estimation using never adopting countries. + +<|ref|>text<|/ref|><|det|>[[115, 314, 881, 377]]<|/det|> +5. This is addressed somewhat in the notes to an appendix table, but I think it would be useful to have information in the main text about the extent to which 1 vs. 2 doses of the vaccine were required to satisfy the mandates. If 2 doses are required, more direct discussion of why do we not see a (lagged 3-4 week) effect on 2nd doses would be helpful. + +<|ref|>text<|/ref|><|det|>[[115, 377, 241, 390]]<|/det|> +Minor comments + +<|ref|>text<|/ref|><|det|>[[115, 405, 880, 437]]<|/det|> +6. The policy studied by Mills and Ruttenauer (2021) is referred to as "certification mandates" (page 6) - are these the same as the policies studied in this paper? Please just clarify. + +<|ref|>text<|/ref|><|det|>[[115, 436, 875, 467]]<|/det|> +7. I thought many of the footnotes were sufficiently important to put in main text. For example, FN 6, 14, 16, 29, etc. + +<|ref|>sub_title<|/ref|><|det|>[[115, 484, 199, 499]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 513, 867, 559]]<|/det|> +Churchill, B. F. (2021). How Important is the Structure of School Vaccine Requirement Opt- Out Provisions? Evidence from Washington, DC's HPV Vaccine Requirement. Journal of Health Economics, 102480. + +<|ref|>text<|/ref|><|det|>[[115, 574, 870, 605]]<|/det|> +Jin, G. Z., & Koch, T. G. (2021). Learning By Suffering? Patterns in Flu Vaccination Take- Up. American Journal of Health Economics, 7(1), 68- 94. + +<|ref|>text<|/ref|><|det|>[[115, 620, 866, 651]]<|/det|> +Lawler, E. C. (2017). Effectiveness of vaccination recommendations versus mandates: evidence from the hepatitis A vaccine. Journal of health economics, 52, 45- 62. + +<|ref|>text<|/ref|><|det|>[[115, 665, 865, 711]]<|/det|> +Zhuan Pei, Jörn- Steffen Pischke & Hannes Schwandt (2019) Poorly Measured Confounders are More Useful on the Left than on the Right, Journal of Business & Economic Statistics, 37:2, 205- 216, DOI: 10.1080/07350015.2018.1462710 + +<|ref|>text<|/ref|><|det|>[[115, 726, 875, 757]]<|/det|> +White, C. (2021). Measuring social and externality benefits of influenza vaccination. Journal of Human Resources, 56(3), 749- 785. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[114, 180, 850, 218]]<|/det|> +## Response to Reviewer 1, the report beginning: "In this study, the authors used several statistical methods..." + +<|ref|>text<|/ref|><|det|>[[124, 223, 873, 307]]<|/det|> +Thank you very much for your valuable and constructive comments. We appreciate your time and detailed feedback. We have addressed all the Reviewers' concerns and editorial formatting requirements, and we believe that the paper is improved as a result. We follow up by responses to your specific comments (reproduced in italics). + +<|ref|>text<|/ref|><|det|>[[123, 331, 875, 533]]<|/det|> +In this study, the authors used several statistical methods and vaccination data from multiple countries to estimate the effect of COVID- 19 vaccination mandates on vaccine update. This is certainly an important topic during the pandemic. As the authors indicated in the paper, currently there are a large body of works focusing on the effect of various incentives on vaccination, including mandate orders (Mills and Rutterauer 2021). This paper adds another evidence along this line of research. Overall, this is a solid study with careful analysis and robust results. However, I feel it lacks a significant advance that supersedes existing literature in scale or methodological novelty and rigor. Below I have a few comments on the analysis and presentation. + +<|ref|>text<|/ref|><|det|>[[115, 551, 843, 592]]<|/det|> +1. The DID analysis relies on a key assumption of parallel trends among the treatment and control groups. Could the authors use the data before mandates to validate this assumption? + +<|ref|>text<|/ref|><|det|>[[123, 609, 875, 826]]<|/det|> +We use data from before the mandate announcements in the event- study analysis in Fig. 3 on p. 5 and the underlying difference- in- differences (DID) regressions. We find no mandate associated pre- trend in the data – the DID estimates before the announcements (T = - 6 to T = - 2 on the figure) are statistically indistinguishable from zero. This indicates that the provinces that announced a mandate and provinces that did not announce a mandate by a given date have similar pre- trends in first- dose vaccinations. While, as known in the literature, there is no way to directly test the parallel trends assumption, that is, the provinces that announced a mandate would have the same trend in the outcomes as provinces that did not announce a mandate, it is reassuring that these two sets of provinces have the same trend before the mandate. Examining the pre- trend using event- study analysis, as we do, follows a + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[125, 148, 871, 190]]<|/det|> +conventional statistical method to gather evidence on the parallel trend assumption (e.g., Currie et al., 2020). + +<|ref|>text<|/ref|><|det|>[[124, 207, 542, 226]]<|/det|> +We explain this on p. 6, second complete paragraph: + +<|ref|>text<|/ref|><|det|>[[170, 243, 816, 350]]<|/det|> +Fig. 3 shows a lack of mandate- associated pre- trend in the data – the DID estimates before the mandate announcement are statistically indistinguishable from zero. This addresses the potential endogeneity concern (parallel trends assumption) that provinces that announced a mandate may have had a different trend in first- dose vaccinations than provinces that did not announce a mandate. + +<|ref|>text<|/ref|><|det|>[[113, 367, 860, 479]]<|/det|> +2. Is there a spillover effect of mandate on vaccination in other locations? In Fig. 1, it seems after the mandate announcement of Quebec, there is a small increase of vaccination in British Columbia. This phenomenon also appears in Ontario after mandate in British Columbia and seems more pronounced. Since no spillover effect is an important assumption in DID analysis, it would be good to discuss about it. + +<|ref|>text<|/ref|><|det|>[[123, 495, 872, 560]]<|/det|> +Thank you for this observation and question. We first did a visual inspection by 'zooming into' the data around the dates you suggest as shown below on Fig. F1; however, we do not see an obvious increase in the first dose vaccination rate around these dates. + +<|ref|>text<|/ref|><|det|>[[373, 573, 621, 592]]<|/det|> +Fig. F1. Checking for spillovers + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>image<|/ref|><|det|>[[115, 163, 808, 410]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[123, 417, 875, 633]]<|/det|> +While there is no way to directly check for such spillover effects in the DID analysis, we are able to check via our time- series (TS) approach. Specifically, we ran the TS regressions for Ontario and British Columbia assuming (counterfactual) announcement dates from the provinces which announced a mandate earlier. The TS regression for Ontario, using the British Columbia announcement date (Aug. 23) instead of the actual announcement date (Sep. 1), yields a statistically insignificantly different from zero policy effect estimate, \(\pi\) in eq. (2), equal to 0.106 (p- value 0.451); similarly, the TS regression for British Columbia with the Quebec announcement date (Aug. 5) yields 0.182 (p- value 0.263). The TS regression for Ontario with the Quebec announcement date yields a negative policy effect estimate of - 0.451 (p- value 0.019). + +<|ref|>text<|/ref|><|det|>[[123, 634, 875, 742]]<|/det|> +In addition, while the above evidence does not indicate so, if such spillover effects did exist across some provinces or dates, i.e., if some people received their first dose in advance of their provincial announcement because of a mandate in another province, then we can interpret our estimates as a lower bound of the full policy effect, since a fraction of people would have been vaccinated before the announcement. + +<|ref|>text<|/ref|><|det|>[[123, 759, 880, 799]]<|/det|> +We have added a discussion regarding the above on p. 31 in the Supplementary Information section. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 148, 852, 282]]<|/det|> +1. Equation 1 only controlled the mandate announcement and epidemiological information (case and death). Other covariates were represented in the time and location fixed effects. I think some other important factors should also be considered and tested if they are available, e.g., age-structure, socioeconomic status, education, political alignment, etc. These factors have been shown to affect vaccination and should be included and tested in the analysis if possible. + +<|ref|>text<|/ref|><|det|>[[123, 300, 872, 383]]<|/det|> +Thank you for this suggestion. Factors such as age structure, socioeconomic status, education, political alignment, however, do not vary over time given the short period we study. Therefore, these time- invariant factors are fully captured and subsumed in the province (location) fixed effects. We state this on p. 16, under "Other controls": + +<|ref|>text<|/ref|><|det|>[[171, 395, 825, 457]]<|/det|> +The province fixed effects account for any time- invariant province characteristics such as sentiment towards vaccination, age structure, education, political alignment, etc. + +<|ref|>text<|/ref|><|det|>[[123, 470, 874, 643]]<|/det|> +As an alternative, to address your suggestion, we re- ran the diff- in- diff specification by replacing the province fixed effects with time- invariant province characteristics (we used GDP per capita, % rural population, population density, unemployment rate, ICU beds per capita, % of population of age \(65+\) , full- time university students per capita and political alignment). The results are reported in Table R1 below. It is reassuring that the estimated effect of the mandate announcements on vaccine uptake remains very similar in magnitude and significance in this specification (columns 3 and 4) as in our main specification with province fixed effects (columns 1 and 2), see Table R1 below. + +<|ref|>text<|/ref|><|det|>[[125, 660, 715, 680]]<|/det|> +We have added discussion about this robustness exercise on p. 30, middle. + +<|ref|>text<|/ref|><|det|>[[170, 697, 825, 717]]<|/det|> +We also ran a specification replacing the province fixed effects with time- invariant + +<|ref|>text<|/ref|><|det|>[[230, 752, 765, 771]]<|/det|> +Table R1. Canadian provinces – difference- in- differences estimates + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>table<|/ref|><|det|>[[212, 153, 728, 636]]<|/det|> + +
Outcome: log weekly vaccine first doses, V<sub>it</sub>
p-values in [ ](1)(2)(3)(4)
mandate announced, P<sub>it</sub>0.506 ***
[0.001]
0.505 ***
[0.001]
week 00.359 ***
[0.005]
0.377 ***
[0.003]
week 10.543 ***
[0.001]
0.557 ***
[0.001]
week 20.498 **
[0.010]
0.476 ***
[0.007]
week 30.705 ***
[0.001]
0.681 ***
[0.001]
week 40.713 **
[0.018]
0.677 ***
[0.005]
week 5+0.651 *
[0.056]
0.591 **
[0.019]
log weekly cases, C<sub>it</sub>0.002
[0.967]
0.002
[0.958]
-0.010
[0.816]
-0.010
[0.814]
log weekly deaths, D<sub>it</sub>0.048
[0.365]
0.046
[0.415]
0.085
[0.100]
0.085
[0.116]
R-squared0.8200.8210.8080.809
sample size, N920920920920
province fixed effectsXX
province characteristicsXX
date fixed effectsXXXX
+ +<|ref|>text<|/ref|><|det|>[[170, 648, 825, 755]]<|/det|> +province characteristics (GDP per capita, \(\%\) rural population, population density, unemployment rate, ICU beds per capita, \(\%\) of population of age 65 or older, full- time university students per capita, and political alignment). The estimated effect of the mandate announcements on vaccine uptake in this specification is very similar in magnitude and significance to our main estimates in Table 1. + +<|ref|>text<|/ref|><|det|>[[113, 780, 875, 848]]<|/det|> +4. \(V_{it}\) in Equation 1 could have spatiotemporal autocorrelation. Neglecting it in regression could lead to overconfidence in the effect size. Could the authors do a residual analysis and check if there exist spatial and temporal autocorrelations in the residuals? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[123, 171, 874, 343]]<|/det|> +We use cluster- robust standard errors and wild bootstrap. In our main results, the standard errors are clustered at the province level, so that the error terms are allowed to be serially correlated within each province. We also report wild bootstrap two- way clustered stan- dard errors, by province and date, which account for within- day spatial correlation across provinces, in Table S6. Both the one- way and two- way clustered standard errors are very similar to each other, so we do not suspect that spatiotemporal correlation leads to overconfidence in the effect size (an excerpt from Table S6 is replicated below; please see the full table for more details). + +<|ref|>table<|/ref|><|det|>[[228, 383, 710, 518]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[300, 346, 696, 365]]<|/det|> +Table R2. Robustness - standard errors (excerpt) + +
Outcome: log weekly first doses, Vk
mandate announced0.506
clustered SE (asymptotic)(0.001) ***
wild bootstrap one-way clustered SE[0.001] ***
wild bootstrap two-way clustered SE{0.000} ***
+ +<|ref|>text<|/ref|><|det|>[[124, 525, 583, 544]]<|/det|> +We have added a clarification about this on p. 16, bottom: + +<|ref|>text<|/ref|><|det|>[[170, 548, 826, 677]]<|/det|> +The use of clustered standard errors allows the error terms to be to be serially correlated within each province. Alternative methods for computing the standard errors are explored in Table S6 - clustering at the province level (Stata command "cluster"), wild bootstrap standard errors clustered at the province level and wild bootstrap standard errors two- way clustered by province and date allowing for spatio- temporal correlation (Stata command "bootstrap"). + +<|ref|>text<|/ref|><|det|>[[123, 689, 870, 823]]<|/det|> +5. The time series analysis requires a strong assumption that the pattern was only affected by vaccination mandate. Equation 2 used two time trends to represent the change rates of \(Vt\) before and after mandate. Have the authors tested other functional forms of Equation 2? How well does Equation 2 fit the data? To validate Equation 2, authors could perform out-of-sample predictions using Equation 2. This analysis could also provide a stronger support to the validity of the counterfactual analysis. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[124, 150, 873, 237]]<|/det|> +Thank you for these helpful suggestions. We did check alternative specifications for the time- series regressions at the working paper stage: additional lags, no time trend, or one time trend and chose the current specification as providing the best fit and consistent with the existing interrupted time- series analysis literature. + +<|ref|>text<|/ref|><|det|>[[123, 262, 874, 414]]<|/det|> +Following your specific suggestions, we have added Fig. S1 in the Supplementary Information section, p. 34 (reproduced as Fig. F2 below), which displays the time- series model fit with the data until Oct. 31, 2021. In addition, the figure plots out- of- sample predictions obtained using equation (2) and our time- series estimates from Table 2 and using the actual weekly cases and deaths data for these out- of- sample dates. The figure shows that the time- series specification fits the weekly first dose vaccine data very well (e.g., the adjusted R- squared is 0.997 for France, 0.940 for Italy and 0.990 for Germany). + +<|ref|>text<|/ref|><|det|>[[123, 435, 874, 587]]<|/det|> +In addition, the out- of- sample projections (dotted red line) are close to the observed vaccine first- dose data (black circles) in November in most locations, with the exception of Germany, where the COVID- 19 certificate became more restrictive in that period ("3G" to "2G"), excluding unvaccinated people, who were previously able to supply a negative test, from indoor dining, bars and hairdressers, etc. The fact that the tightening of the certification requirements in Germany (that we do not model, however) is accompanied by a increase in first- dose vaccinations in November 2021 is consistent with our main findings. + +<|ref|>text<|/ref|><|det|>[[123, 610, 873, 717]]<|/det|> +A constraining factor for the out- of- sample projections is that first doses for the 5 to 11 age group were approved in November (Nov. 19 in Canada and Nov. 25 in the EU) and, for many jurisdictions in our sample, we cannot distinguish these doses from adult first doses in the vaccinations data. Hence, we only show out- of- sample projections for three additional weeks beyond our sample end date, until Nov. 21, 2021. + +<|ref|>text<|/ref|><|det|>[[123, 741, 872, 783]]<|/det|> +We summarize the above discussion on p. 31, bottom in the Supplementary Information section and refer to it in the main text on p. 10, third paragraph. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 52, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 163, 872, 253]]<|/det|> +6. Some explanations on statistical details should be provided for a better readability. For instance, what does each column represent in Table 1? What's the statistics in Fig. 3 and how to interpret it? The current presentation of the Sun-Abraham DID analysis is a bit difficult to comprehend for readers who are not familiar with this particular method. + +<|ref|>text<|/ref|><|det|>[[123, 270, 618, 289]]<|/det|> +Thank you – we agree and have added more details as follows. + +<|ref|>image<|/ref|><|det|>[[123, 339, 875, 775]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[279, 306, 715, 325]]<|/det|> +
Fig. F2. Time-series – fit and out-of-sample projection
+ +<|ref|>text<|/ref|><|det|>[[123, 794, 855, 832]]<|/det|> +Notes: The black circles are log weekly first doses per 100,000 people. The red solid line is the fitted value from the time- series regression, equation (2). The dotted line is the out- of- sample extrapolation of the fitted value line for three + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[123, 149, 820, 185]]<|/det|> +additional weeks, using cases and deaths data until Nov. 21, 2021. Germany introduced a stricter version of their COVID certificate in November 2021. + +<|ref|>text<|/ref|><|det|>[[124, 209, 872, 251]]<|/det|> +We have added explanations about the specification of each column of Table 1 in the table notes (p. 7), reproduced below: + +<|ref|>text<|/ref|><|det|>[[171, 263, 825, 327]]<|/det|> +Columns (1) and (2) report the average mandate effect estimate over the postannouncement period, without and with controlling for weekly cases and deaths. Column (3) decomposes the effect by post- announcement week. + +<|ref|>text<|/ref|><|det|>[[124, 339, 512, 358]]<|/det|> +as well as in the last complete paragraph on p. 6: + +<|ref|>text<|/ref|><|det|>[[171, 361, 827, 533]]<|/det|> +Table 1 displays DID estimates of the mandate effect on first- dose uptake, relative to the pre- mandate period, controlling for information (cases and deaths) and time and location fixed effects. Columns (1) and (2) show that the mandate announcement is associated with an average increase of about 66 percent (50.6 log points, 95% CI 25- 77 in column 2) in weekly first doses. In column (3), we report estimates where the mandate policy variable is decomposed into six binary variables (one for each week after the announcement date) to account for dynamic effects. + +<|ref|>text<|/ref|><|det|>[[124, 544, 872, 585]]<|/det|> +We also explain the results and statistics in Fig. 3 in the figure notes (p. 5) and in the main text (p. 6), reproduced below: + +<|ref|>text<|/ref|><|det|>[[171, 594, 827, 744]]<|/det|> +The figure plots the estimates from a variant of equation (1) where the man- date announcement variable \(P_{ii}\) is replaced by the interaction of being in the 'treatment' group (announced mandate) with a series of dummies for each week ranging from 6 weeks before \((T = - 6)\) to 5 or more weeks after the announcement \((T = 5)\) , where \(T = 0\) denotes the week starting at the announcement date. The reference point is one week before the announcement \((T = - 1)\) . The dotted lines correspond to 95% confidence intervals. + +<|ref|>text<|/ref|><|det|>[[172, 747, 825, 809]]<|/det|> +[p. 6, main text]. In Fig. 3, we plot results from an event study analysis of weekly first doses administered in the ten Canadian provinces, from six weeks prior to five or more weeks after the announcement of a mandate. + +<|ref|>text<|/ref|><|det|>[[124, 821, 575, 840]]<|/det|> +The interpretation of Fig. 3 is on p. 6, reproduced below: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[171, 159, 827, 485]]<|/det|> +Fig. 3 shows lack of mandate- associated pre- trend in the data – the DID estimates before the mandate announcement are statistically indistinguishable from zero. This addresses the potential endogeneity concern (parallel trends assumption) that provinces that announced a mandate may have had a different trend in first- dose vaccinations than provinces that did not announce a mandate. Second, the impact of the mandate announcement on first- dose vaccine uptake is realized relatively quickly and is large in magnitude – an increase of \(42\%\) (35 log points, \(95\%\) CI 9–62) in new weekly doses in the first post- announcement week and \(71\%\) (54 log points, 21–86) in the second week, each relative to one week before the announcement. The observed quick increase in uptake mitigates possible concerns that vaccine supply or scheduling constraints may be affecting our results. Third, the policy effect persists over time over the 6- week post- announcement period we analyze \((T = 0\) to \(T = 5\) ). Unfortunately, data limitations (the timing of the announcements) and the need for a not- yet- treated control group in the DID method do not allow us to investigate longer horizons. + +<|ref|>text<|/ref|><|det|>[[124, 533, 870, 575]]<|/det|> +We have also added detailed explanations on the Sun and Abraham estimator in the Methods section; please see p. 17 (replicated below): + +<|ref|>text<|/ref|><|det|>[[171, 580, 827, 750]]<|/det|> +In particular, Sun and Abraham sun develop a difference- in- differences estimator valid under these conditions, which we use to estimate (1). The Sun and Abra- ham estimator uses never- treated or last- treated units as the control group and is constructed as weighted average of treatment effects for each cohort (by date of mandate announcement) and each relative time after or before the announce- ment (we use the Stata function eventstudyinteract provided by the authors). Specifically, to calculate the average treatment effect \(\alpha\) in (1), we replace \(aP_{ii}\) with + +<|ref|>equation<|/ref|><|det|>[[425, 754, 624, 806]]<|/det|> +\[\underbrace{\mathbf{L}\cdot\mathbf{L}}_{\substack{\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots}}a_{i,i}(1.[\hat{i}=g]D_{i t}^{i})\] + +<|ref|>text<|/ref|><|det|>[[171, 816, 774, 836]]<|/det|> +where \(C\) is the set of never- treated or last- treated provinces (control group), + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[170, 152, 828, 300]]<|/det|> +\(\mathrm{D}_{l} = \mathrm{\Omega}_{1}[\mathrm{\Omega}_{l} - \mathrm{\Omega}_{l} = \mathrm{\Omega}_{l}]\) is a "relative time" indicator, and \(l^{\wedge}i\) is the date of treatment for province \(i\) . Under parallel trends and no anticipation, Sun and Abraham (2021) show that \(\alpha_{i,l}\) is consistent for the province- time specific treatment effect. Then, the average treatment effect for each relative- time period, \(\alpha_{i}\) , is the appropriately weighted (by the sample share of each treated province in relative time \(l\) ) average of \(\alpha_{i,l}\) across the units \(i\) , and \(\alpha\) in (1) is computed as the simple average of \(\alpha_{i}\) across \(l\) . + +<|ref|>text<|/ref|><|det|>[[125, 314, 868, 379]]<|/det|> +7. A minor issue. In the first paragraph in introduction, "... at about \(60\%\) of the population...". Which country do the authors refer to here? The worldwide vaccination rate is way lower than this number. + +<|ref|>text<|/ref|><|det|>[[123, 396, 852, 438]]<|/det|> +Thank you, we have edited the text to eliminate this potential confusion. Please see p. 2, the first paragraph: + +<|ref|>text<|/ref|><|det|>[[170, 455, 825, 497]]<|/det|> +...Yet, following a rapid uptake in early 2021, vaccinations in many countries (see Fig. E1) slowed down significantly in the summer months. + +<|ref|>sub_title<|/ref|><|det|>[[114, 561, 872, 605]]<|/det|> +## Response to Reviewer 2, the report beginning: "This paper examines the im- pact..." + +<|ref|>text<|/ref|><|det|>[[122, 615, 874, 701]]<|/det|> +Thank you very much for your valuable and constructive comments. We appreciate your time and detailed feedback. We have addressed all the Reviewers' concerns and editorial formatting requirements, and we believe that the paper is improved as a result. We follow up by responses to your specific comments (reproduced in italics). + +<|ref|>text<|/ref|><|det|>[[113, 726, 874, 838]]<|/det|> +This paper examines the impact of government- mandated proof of vaccination requirements for entering specific venues on receipt of first doses of the COVID- 19 vaccine. The authors implement a within- Canada difference- in- difference approach that leverages province- level variation in mandate adoption, and also estimate time series analyses to examine country- level policy adoption in France, Italy, and Germany. Estimates show that the mandates resulted in + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 51, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 149, 872, 215]]<|/det|> +significant increases in COVID- 19 vaccination initiation, with estimates ranging from 5 to 12 percentage points. Overall, I found the paper to be very thorough, and I commend the authors for the substantial work they have done to demonstrate the robustness of their estimates. + +<|ref|>text<|/ref|><|det|>[[114, 240, 873, 351]]<|/det|> +1. The clearest potential threat to the identification strategies used in this article is that rising COVID cases cause policy makers to adopt the vaccine mandates and also cause people to choose to be vaccinated. While the authors do a couple of things to address this (e.g. showing results are robust to controlling for various lags of log cases and deaths), there are several additional things that I think would be useful to include. + +<|ref|>text<|/ref|><|det|>[[123, 380, 872, 422]]<|/det|> +Thank you for these helpful comments. We have addressed them in the revised version of the paper. Please see our detailed responses below. + +<|ref|>text<|/ref|><|det|>[[115, 440, 844, 483]]<|/det|> +a. It would be helpful to show figures overlaying vaccination rates/cases/deaths for each location, to allow for direct visual inspection of these relationships. + +<|ref|>text<|/ref|><|det|>[[123, 499, 875, 606]]<|/det|> +Thank you for this suggestion. While we control for weekly cases and deaths in both the difference- in- differences (DID) and time- series regressions, we agree that visually illustrating the evolution of cases and deaths together with vaccine uptake can be useful in interpreting our results. We have followed your suggestion and overlaid the cases and death counts on Extended Data Fig. E3 (reproduced below). + +<|ref|>image<|/ref|><|det|>[[125, 643, 868, 833]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[306, 613, 690, 632]]<|/det|> +
Fig. E3. Overlaid vaccinations, cases and deaths
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>image<|/ref|><|det|>[[123, 150, 873, 536]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[123, 553, 872, 648]]<|/det|> +Notes: The figure plots the weekly administered COVID- 19 vaccine first doses per 100,000 people for dates \(t - 6\) to \(t\) where \(t\) is the date on the horizontal axis (solid black line). The dashed red lines denote the proof of vaccination mandate announcement date for each province. The dotted green lines denote the mandate implementation (enforcement) date for each province (see Table S1). The thin blue line is weekly cases per 100,000 (right axis); the thin magenta line is the number of weekly deaths (right axis). + +<|ref|>text<|/ref|><|det|>[[123, 659, 850, 748]]<|/det|> +a. Although the authors include cases and deaths as control variables, it would be more convincing to examine the relationship between policy adoption and these variables by running the event study, difference-in-differences, interrupted time series specifications with cases/hospitalizations/deaths as the outcome variables (Pei et al., 2019). + +<|ref|>text<|/ref|><|det|>[[123, 785, 874, 849]]<|/det|> +Thank you. In this paper, we made the deliberate choice to put the focus on quantifying, as precisely as we can and using both Canadian provincial data and country- level data, the direct effect of proof of vaccination mandates on first dose vaccine uptake. One can then use vaccine + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[124, 148, 872, 190]]<|/det|> +effectiveness estimates from the medical literature (in which we are not experts) to map the gains in vaccinations we estimate into averted cases, hospitalizations or deaths. + +<|ref|>text<|/ref|><|det|>[[124, 213, 874, 320]]<|/det|> +While the impact on health outcomes is beyond the scope of our paper, we agree that it definitely remains an important topic for further research, ideally controlling for both the direct effect through vaccine effectiveness and also possible indirect effects through changes in behaviour. We have added a sentence in the Discussion section (p. 14) clarifying this, along with other limitations of our study: + +<|ref|>text<|/ref|><|det|>[[171, 349, 827, 436]]<|/det|> +We have abstracted from assessing the mandates' impact on health outcomes (cases, hospitalizations or deaths). However, vaccine effectiveness estimates from the medical literature can be used to study this further, ideally controlling for possible changes in behaviour. + +<|ref|>text<|/ref|><|det|>[[123, 458, 874, 608]]<|/det|> +Nevertheless, following your suggestion, we also ran a DID regression analogous to equation (1), but where we replace the outcome variable with weekly cases or deaths and lag the policy variable (mandate announced) by two weeks, see Table R3 below. We do not find statistically significant results related to the mandate announcements. However, one may not expect health outcome metrics to change quickly after the mandate announcements because the gains in vaccinations accumulate over time and because of the time lag between vaccination and its impact on the health outcome for an individual. + +<|ref|>table<|/ref|><|det|>[[272, 660, 727, 805]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[309, 621, 679, 640]]<|/det|> +Table R3. Cases or deaths as outcome variable + +
Outcome:log weekly caseslog weekly deaths
mandate announced (lagged)-0.2020.408
[0.315][0.184]
R-squared0.9370.864
sample size780780
province fixed effectsXX
date fixed effectsXX
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 52, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 164, 875, 206]]<|/det|> +a. There is good evidence that increased disease incidence causes vaccination rates to increase (Oster, 2018; Schaller et al., 2019). This evidence should be cited and discussed. + +<|ref|>text<|/ref|><|det|>[[123, 223, 874, 287]]<|/det|> +Thank you for these helpful references. We have now cited them, and we also discuss briefly the importance of disease incidence (as controlled for by log weekly cases and deaths in our empirical analysis); see p. 15, under "Information". + +<|ref|>text<|/ref|><|det|>[[171, 295, 827, 399]]<|/det|> +We include variables related to the concurrent COVID- 19 epidemiological situation, specifically log of weekly cases, \(\mathrm{C_{it}}\) , and log of weekly deaths, \(\mathrm{D_{it}}\) , for the week ending at date t (dates t - 6 to t). We refer to these variables jointly as 'information', \(\mathrm{I_{it}}\) , see [33, 34], since they can inform a person's COVID- 19 exposure risk assessment and/or decision to be vaccinated, e.g., as shown in [21, 22]. + +<|ref|>sub_title<|/ref|><|det|>[[125, 424, 293, 442]]<|/det|> +## Secondary comments + +<|ref|>text<|/ref|><|det|>[[112, 460, 840, 550]]<|/det|> +2. The discussion on the literature on the determinants of vaccination would benefit from further development. The existing discussion is brief and not well integrated into the article. Additionally, there is a large pre-Covid literature that should be referenced. For example: Churchill (2021), Jin & Koch (2021), Lawler (2017), and White (2021). + +<|ref|>text<|/ref|><|det|>[[122, 566, 875, 674]]<|/det|> +Thank you for suggesting these valuable references that we have now included early on in the paper's introduction - please see p.2, bottom and p. 14, third complete paragraph. We have also re- organized the paper's introduction and discussion sections to integrate better all the relevant literature while conforming to the journal requirements. Additional details on the related literature are included in the Supplementary Information, p. 32-33. + +<|ref|>text<|/ref|><|det|>[[113, 690, 850, 779]]<|/det|> +3. How were the set of countries chosen, both with regards to treatment countries and falsification countries? For example, Mills and Rutenauer (2021) also looks at Israel, which seems to adopt during this time period. Are there other non-adopters, besides Spain, that can also be looked at as falsifications? + +<|ref|>text<|/ref|><|det|>[[123, 796, 872, 838]]<|/det|> +We have added a brief discussion regarding the countries chosen. Please see p. 2, the fourth complete paragraph, reproduced below: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[172, 153, 827, 261]]<|/det|> +We chose these locations since they have similar economies, demographics and vaccine access and all announced and implemented mandates in July- October 2021, a period with minimal binding vaccine supply or access constraints and a high base first- dose vaccination rate (above \(60\%\) of those eligible in the three countries and above \(80\%\) in Canada at the time of the mandate announcements). + +<|ref|>text<|/ref|><|det|>[[123, 291, 874, 443]]<|/det|> +Unlike Mills and Ruttenauer (2021), we do not use the synthetic control method which requires data from non- adopters, and hence we only show an example of a country without national mandate in the studied period (Spain), purely for visual illustration. We do not study Israel, as it introduced a very early certification requirement (Green Pass), in Feb. 2021, which was removed in early June, and then re- imposed again in July 2021. Israel's vaccination campaign also proceeded on a different (earlier) schedule compared to the other countries we study. + +<|ref|>text<|/ref|><|det|>[[115, 460, 866, 504]]<|/det|> +4. Similar to the randomization inference exercise, it would also be useful to conduct placebo structural break/ time series estimation using never adopting countries. + +<|ref|>text<|/ref|><|det|>[[123, 519, 875, 802]]<|/det|> +Thank you for your suggestion. Similar to the DID randomization inference robustness exercise (Fig. E6 and p. 30 in the paper), we used our time- series model and estimated the mandate policy effect (the parameter \(\pi\) in equation (2) on p. 17) for a range of placebo announcement dates (132 unique dates in total including the true announcement date), from Jun. 17 to Oct. 24 for each of France, Italy and Germany. Fig. F4 below displays the results. There is only a small number of placebo dates (mostly in a close neighbourhood of the true announcement date) for which the time- series regression yields a larger policy estimate that that for the true date. Specifically, there are 12 dates (9.1%) with estimate larger than that for the true announcement date for France, 14 dates (10.6%) for Italy and only 5 such dates (3.8%) for Germany. While the results for France and Italy are noisier than that of the DID randomization inference exercise (Fig. E6 in the paper), these results are not directly comparable since the DID results use data from several treated provinces to estimate the policy effect. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 50, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[124, 148, 874, 212]]<|/det|> +The time- series approach and specification we use relies on a known date for the policy regime change. We thus cannot apply it to never adopting countries as we have no way of interpreting such results. + +<|ref|>text<|/ref|><|det|>[[123, 235, 872, 278]]<|/det|> +We have added discussion regarding the above on p. 32 and added Supplementary Fig. S2 on p. 34. + +<|ref|>image<|/ref|><|det|>[[123, 325, 880, 550]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[348, 283, 648, 302]]<|/det|> +
Fig. F4. Placebo announcement dates
+ +<|ref|>text<|/ref|><|det|>[[123, 574, 866, 611]]<|/det|> +Notes: The figure reports time- series estimates from 132 runs with all possible placebo announcement dates between June 17 and Oct 24. The dashed red line is the main estimate from Table 2 using the actual announcement date. + +<|ref|>text<|/ref|><|det|>[[113, 629, 878, 720]]<|/det|> +1. This is addressed somewhat in the notes to an appendix table, but I think it would be useful to have information in the main text about the extent to which 1 vs. 2 doses of the vaccine were required to satisfy the mandates. If 2 doses are required, more direct discussion of why do we not see a (lagged 3-4 week) effect on 2nd doses would be helpful. + +<|ref|>text<|/ref|><|det|>[[124, 735, 723, 755]]<|/det|> +Thank you for this comment. We now specify in the text (p. 7, bottom) that: + +<|ref|>text<|/ref|><|det|>[[171, 772, 825, 857]]<|/det|> +Most provincial proof of vaccination mandates required two doses to be considered adequately vaccinated with a vaccine offered in Canada during the study period (Pfizer (Comirnaty), Moderna (SpikeVax) or AstraZeneca (Vaxzevria)); there were limited exceptions in Quebec (a prior infection could count as first + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 50, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[171, 148, 824, 190]]<|/det|> +dose) and British Columbia (only one dose was required between Sep. 13 and Oct. 23, 2021). + +<|ref|>text<|/ref|><|det|>[[124, 201, 874, 309]]<|/det|> +We also checked for a second- dose effect after excluding British Columbia (BC) from the sample, and we find weak evidence for a positive post- mandate announcement impact on second doses – the average estimate analogous to Table 1, column 2 is 0.227 (p- value 0.053). This is consistent with an impact on second doses becoming more apparent after excluding BC since it differs from the rest of the provinces with its phased implementation. + +<|ref|>text<|/ref|><|det|>[[124, 342, 872, 385]]<|/det|> +We offer the following possible explanation (see p. 8, top) for why we do not find robust statistically significant effect on second doses: + +<|ref|>text<|/ref|><|det|>[[171, 410, 827, 496]]<|/det|> +One possible explanation for the lack of large increases in second doses a few weeks after the spikes in first doses is that mandates may have encouraged some people that already had their first doses to obtain their second dose sooner, thus shifting some second doses forward and dampening the lagged effect. + +<|ref|>text<|/ref|><|det|>[[125, 510, 260, 527]]<|/det|> +Minor comments + +<|ref|>text<|/ref|><|det|>[[125, 546, 855, 590]]<|/det|> +6. The policy studied by Mills and Ruttenaver (2021) is referred to as "certification mandates" (page 6) – are these the same as the policies studied in this paper? Please just clarify. + +<|ref|>text<|/ref|><|det|>[[124, 606, 875, 715]]<|/det|> +Thank you. Yes, both we and Mills and Ruttenaver study policy requirements regarding access to non- essential settings or services. We now clearly refer to "proof of vaccination mandates" or "certificates" in the introduction (p. 2, third paragraph) and at the beginning of the discussion section (p. 12, bottom) where we discuss Mills and Ruttenaver (2021). We do the same in the data description (see p. 14-15) and several other places in the main text. + +<|ref|>text<|/ref|><|det|>[[125, 751, 825, 794]]<|/det|> +7. I thought many of the footnotes were sufficiently important to put in main text. For example, FN 6, 14, 16, 29, etc. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[546, 51, 870, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[123, 148, 873, 211]]<|/det|> +Thank you. To comply with the journal formatting requirements, we have incorporated all former footnotes in the main text and in the table/figures notes or deleted a few peripheral notes. All the former footnotes you list have been incorporated in the text. + +<|ref|>sub_title<|/ref|><|det|>[[111, 234, 333, 250]]<|/det|> +## Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[118, 270, 400, 286]]<|/det|> +Our ref: NATHUMBEHAV- 220117753A + +<|ref|>text<|/ref|><|det|>[[116, 304, 244, 319]]<|/det|> +25th March 2022 + +<|ref|>text<|/ref|><|det|>[[116, 338, 269, 353]]<|/det|> +Dear Dr. Karaivanov, + +<|ref|>text<|/ref|><|det|>[[115, 370, 868, 447]]<|/det|> +Thank you for submitting your revised manuscript "COVID- 19 Vaccination Mandates and Vaccine Uptake" (NATHUMBEHAV- 220117753A). It has now been seen by the original referees and their comments are below. As you can see, the reviewers find that the paper has improved in revision. We will therefore be happy in principle to publish it in Nature Human Behaviour, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[116, 464, 841, 510]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements within a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[115, 527, 586, 543]]<|/det|> +Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[115, 561, 188, 576]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[115, 594, 235, 609]]<|/det|> +Charlotte Payne + +<|ref|>text<|/ref|><|det|>[[115, 627, 303, 673]]<|/det|> +Charlotte Payne, PhD Senior Editor Nature Human Behaviour + +<|ref|>text<|/ref|><|det|>[[115, 708, 404, 724]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[112, 741, 866, 773]]<|/det|> +I appreciate the authors' efforts in revising the manuscript. The additional analyses and clarifications have addressed my questions. + +<|ref|>text<|/ref|><|det|>[[115, 808, 404, 824]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[545, 52, 870, 88]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 148, 695, 180]]<|/det|> +Report on revision 1 of "COVID- 19 Vaccination Mandates and Vaccine Uptake" (NATHUMBEHAV- 220117753A) + +<|ref|>text<|/ref|><|det|>[[115, 193, 800, 225]]<|/det|> +I would like to thank the authors for the clear and comprehensive responses to my previous comments. I have only a few additional comments. + +<|ref|>text<|/ref|><|det|>[[115, 239, 857, 271]]<|/det|> +1. For Figure E3 (showing vaccinations, cases, and deaths), please also show this figure for France, Italy, Germany, and Spain. + +<|ref|>text<|/ref|><|det|>[[115, 285, 860, 348]]<|/det|> +2. I apologize for the confusion with regards to my main comment 1b in the previous report. What I think needs to be examined more carefully is the possibility that case and death rates predict policy adoption, while also independently predicting vaccination. The trends in Figure E3 show that this is potentially true. + +<|ref|>sub_title<|/ref|><|det|>[[115, 402, 272, 417]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[116, 438, 335, 456]]<|/det|> +Dear Professor Karaivanov, + +<|ref|>text<|/ref|><|det|>[[116, 477, 863, 515]]<|/det|> +We are pleased to inform you that your Article "COVID- 19 Vaccination Mandates and Vaccine Uptake", has now been accepted for publication in Nature Human Behaviour. + +<|ref|>text<|/ref|><|det|>[[114, 535, 866, 675]]<|/det|> +Please note that Nature Human Behaviour is a Transformative Journal (TJ). 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(a) Observed and theoretically predicted vibrational features of UN@ \\(C_2(5) - C_{82}\\) . The lower curve (black) presents the observed infrared absorption (IR) spectrum vs. wavenumber from 1600 to \\(600~\\mathrm{cm^{-1}}\\) , with quantum-chemical density-functional simulation upper (in blue).", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Response Fig. 5. (a) Isotopic distribution of UC@C82 from theoretical simulations. (b) Isotopic distribution of UN@C82 from theoretical simulations. (c) Isotopic distribution of UO@C82 from theoretical simulations.", + "footnote": [], + "bbox": [ + [ + 147, + 506, + 843, + 660 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_7.jpg", + "caption": "Response Fig. 7. Isotopic distribution of \\(\\mathrm{UN@C}_{82}\\) from theoretical simulations and the masses", + "footnote": [], + "bbox": [], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_8.jpg", + "caption": "Response Fig. 8. (a) Observed and theoretically predicted vibrational features of UN@C2(5)-C82.", + "footnote": [], + "bbox": [ + [ + 343, + 688, + 655, + 888 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_9.jpg", + "caption": "Response Fig. 9. X-Band EPR spectrum of UN@C2(5)-C82. It is recorded in a toluene glass tube at 4 K and 10 K.", + "footnote": [], + "bbox": [ + [ + 339, + 530, + 668, + 730 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_12.jpg", + "caption": "Response Fig. 12. X-Band EPR spectrum of UN@C \\(_{2}(5)\\) -C \\(_{82}\\) . It is recorded in a toluene glass tube at 4 K and 10 K.", + "footnote": [], + "bbox": [], + "page_idx": 15 + } +] \ No newline at end of file diff --git a/peer_reviews/53b312065a46a22c9efb5be896a397d500703899f16c61630ebab85e62a61df4/supplementary_0_Peer Review File - updated/supplementary_0_Peer Review File - updated.mmd b/peer_reviews/53b312065a46a22c9efb5be896a397d500703899f16c61630ebab85e62a61df4/supplementary_0_Peer Review File - updated/supplementary_0_Peer Review File - updated.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d97cb93d0c050a6852e3cb78edb86759433ae176 --- /dev/null +++ b/peer_reviews/53b312065a46a22c9efb5be896a397d500703899f16c61630ebab85e62a61df4/supplementary_0_Peer Review File - updated/supplementary_0_Peer Review File - updated.mmd @@ -0,0 +1,740 @@ + +# nature portfolio + +Peer Review File + +A charged diatomic triple- bonded U=N species trapped in C82 fullerene cages + +![](images/Figure_4.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +EDITORIAL NOTE: Parts of this peer review file have been redacted at the author's request. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors report on the synthesis of two UN@C82 isomers. The compounds are characterized by X- ray diffraction, optical, Raman, and quantum chemical calculations. The techniques have been done competently. The computational analysis is excellent, and most of the experimental analysis is well done, except a fairly important point below. References are appropriate. + +The authors have demonstrated some considerable synthetic skill to make these systems. But in the end from grams of starting materials and 800 carbon rods they isolate 0.2 mg of the title complexes (each or total I was not entirely clear on). Isolating UN inside these fullerenes is neat, but it has to be acknowledged that the incredibly low yields and scale, which limits the number of techniques that can be brought to bear, very much degrades the impact of this work, especially when isolable molecular analogs have been made on gram scales. + +So it is then a reasonable question to ask what the novelty is given it is arguably easier to make regular coordination complexes since they can be made on gram scales and examined fully with a wider range of techniques than here. The authors make a variety of claims or novelty statements, but not many stand up to scrutiny, in particular the shortest UN distance claim is factually incorrect (see below). As I read through the computational analysis whilst I thought that it was a professional write- up I did not come across a new electronic structure for UN. The orbitals all look to be arranged very much as has been shown elsewhere before, comparison to which seems to be missing from the UN bonding discussion - sure some \(\%\) shift around but it all looks very similar to me. + +This is a really nice and mostly solid study in many regards, but I was left with the impression that using a synthetically arduous approach the authors made a system that looks largely the same as already reported UN bonds and were unable to characterize it as much as in other studies because of the sub- mg yields. If there were no regular coordination complexes of UN then I would say this would be an advance over inert gas matrices, but that is not the case, so I do not see the novelty or new conceptual insight that I'd expect to see in a Nature family journal. I therefore have to conclude that I am unable to support publication in Nature Communications. + +Specific issues to address before publication anywhere: + +The first sentence of the abstract is ambiguous. It can be read as the authors saying that all actinide multiple bonds are elusive and only found in gas matrices, which is clearly not the case. + +The second sentence of the abstract is worded poorly as it says that UN is unpredented, but it would seem that Andrews has isolated it in gas matrices - the authors then go on to contradict themselves (line 69) by acknowledging the work of Andrews. + +The penultimate sentence of the abstract is not worded precisely enough so could be debated. There are around 20 UN triple bonds now, is that still rare? + +The last sentence is imprecise, since it implies that a UN triple bond is still elusive, but they have been made. I don't think this is what the authors meant but it is how it reads. + +Introduction, Cummins made U2C2, there are now many UNU, and Ephritkhine made UCN, so how can the authors refer to those linkages as unprecedented? + +Line 65, TrenTIPSUN should be mentioned overtly here. + +The authors use the phrase cluster a lot, the phrase 'diatomic cluster' is a contradiction in terms and is an inappropriate description. + +<--- Page Split ---> + +Lines 133- 152, the authors present crystallographic bond metrics without standard uncertainties, which makes the values and statements associated with them meaningless, and in one case certainly factually incorrect. A bond distance is only fair game to refer to as shorter or longer than another bond distance if they do not overlap by the 3sigma rule. The UN distance they quote is 1.760 angstroms, undoubtedly short, however the UN distance of Mazzanti's complex is 1.769 angstroms, but her bond length has a standard uncertainty of 2, so her UN distance could be as small as 1.763 angstroms. In the 100 K cif file the UN distance is given as 1.760(9) angstroms, so the UN distance could be as long as 1.787 angstroms (it could also be shorter but that is not the point here), which also falls within the lower range of Liddle's uranium +6 nitride (1.778- 1.820 angstroms by 3sigma). So the author's and Mazzanti's UN distances are statistically indistinguishable, therefore the authors cannot lay claim to have the shortest UN bond characterized by crystallography. + +Did the authors observe any absorptions characteristic of the uranium +5 oxidation state in the nIR region? Whilst I am mostly convinced that they have made UN@C82 I don't think the possibility of UO@C82 being present in variable proportions can be considered to be completely excluded given the extensive crystallographic disorder and [understandable] absence of magnetic data. The optical spectrum is really the only way of the data provided to probe if it is all uranium +5 or whether there is any +4 present but this key aspect is not covered in the discussion. This would not affect the computational analysis, but purity really is an issue when only making 0.2 mg. + +Line 273, as written I found this confusing. The authors say the two optical spectra of the two UN fullerene isomers are different then seem to say this shows their electronic structures are the same. If the spectra are different their electronic structures are not the same. + +Raman, what do the spectra look like above 600 cm- 1? The authors found the UN wagging mode but what about the UN stretch? I would expect this aspect to be probed and discussed as a bare minimum. + +Line 400, delete fully, that is subjective and these compounds aren't fully characterized when thinking about the range of techniques available. + +Lines 405- 407, the mistake of claiming the shortest UN distance is repeated, so then saying it is notably shorter is also incorrect. + +Reviewer #2 (Remarks to the Author): + +The manuscript is very well written and easy to read. The Experimental part is good and state- of- the- art. I am no expert for quantum- chemical calculations but they look reasonable to me, especially the agreement of the observed and simulated Raman band positions is nice. + +In my opinion the manuscript is unclear when it comes to the differentiation of the encaged species, if it is "UN", "UO", or "UC" as during the synthesis also a lot of O and C atoms have been present. Maybe the authors could explicitly state if/that the mass spectroscopic analysis is evidence enough to exclude UO and UC species? + +For the mass specs I miss simulations, especially for the isotopic distributions (13C, ...) and if the resolution was high enough to discriminate the species. With some many C atoms the 13C signal should superpose with the one from 12C, a high- res MS should however be able to discriminate the species. The authors should comment on this. + +Regarding the crystal structures: That the N atom is completely ordered and the heavy U atom not is peculiar? Is that really plausible? Are there proofer examples for such a observation? + +Is there no O/C/N mixed site occupancy possible? + +Are the electron densities of the less occupied U atom positions similar to N/O/C electron density? The absolute densities should be given in the SI. + +The authors should investigate and comment, if structure models in subgroup C2 give better results, i.e. resolution of the disorder by twinning. That would be something reasonable to expect for the + +<--- Page Split ---> + +models in C2/m and should be commented. + +All bond lengths and atom distances in the manuscript and the SI should be reported with their respective standard uncertainties as only these will allow for a proper comparison with other species, especially when it comes to the discussion of the UN bond lengths and its comparison with compounds from the literature. + +The U- N bond length is a value that is surely biased by the disorder and should only be used with the necessary care. + +How far is the residual electron density away from the U atom? Can it be clearly discriminated from a N atom? + +Where would one expect the UN stretch vibration? These should be given. Can an isotope effect be observed? + +The observed and calculated Raman bands should be assigned more clearly in the manuscript as well as in the SI as the arrows in Supp. Fig. 22 and 23 are simply to small. + +Discrimination from UO and UC species: Where would those show bands? Have the respective UO and UC species been calculated? + +Overall, I recommend revision of the manuscript. I think that if the issues can be sorted out it would be a fine contribution. + +Reviewer #3 (Remarks to the Author): + +In this article, Chen presents a UN triple bond captured inside fullerene cages. The isolation of uranium nitride species is of great importance because this material has been proposed as possible uranium- based nuclear fuel. Understanding, the fundamentals of its bonding is thus rather useful. The results presented in this article are interesting but I disagree with most comments on the fact that they are unique opportunities to study the UN bond. Coordination compounds are now known and accessible on a larger scale, which allowed various characterization and computations. This article is following with a new type of UN terminal bond since I would argue that the U coordination to the fullerene mimics well what is observed with a classical coordination compound. If most characterizations are fair (see below), the technique only provides crystals and the compounds remain rather elusive. Considering that molecular compounds with similar bonding exist, I would state that this study merits publication in a more specialized journal provided that my few technical comments are sorted out. + +1. The crystallographic disorder is large and the esd on the distance must be large as well. I have seen no mention of esd in the main text or SI. I would argue that Table S14 and the R1/wR2 give an idea of the large esd that should be associated with these distances. Without these esd comparing distances is pointless, especially if the authors want to convince us that the UN bond of this work is the shortest one reported to date! On this matter, I would be very cautious since the molecular UN bond distances are very close to that one if not identical. + +2. Both crystallographic positions of the U are true. The fact that there is a minor one does not mean the distance argument can only be made from the major one. An average would be more accurate for the discussion. + +3. I would agree with the authors with the hypothesis stating that UN species are formed during the arc discharging process but not that it can be related to similar distances observed in unstable gas molecules, this is too speculative. + +<--- Page Split ---> + +4. The strong interaction of U with the C-skeleton of the fullerene is shown by the calculated spin doublet ground-state being the most stable one. Would it be possible to confirm this by EPR spectroscopy? Since the EPR is a sensitive technique, few crystals should be enough. + +5. The VT-XRD studies are nice and interesting but do not bring much to the bonding analysis. + +6. The UV-Vis-NIR data is provided without informing the reader of the nature of the bands reported. + +7. I wonder if the use of the term somewhat twice to define the UN bonding nature is not too much. I would say, the bond is polarized. How does it compare with molecular coordination compounds? + +8. The comparison of the NU and UN2- electronic structure by ab initio methods is also interesting but the conclusion of this interesting comparison full of information is elaborated, neither in the conclusion nor in the discussion. Were these computations done only to mention that WFT and DFT produce similar results? Could these be gathered and compared on a table? + +Reviewer #4 (Remarks to the Author): + +This is another paper in the series of the synthesis of clusterfullerenes containing simple, and now characterizable, f-block diatomics with multiple metal-element bonding. This time UEN in two different fullerene symmetries. + +The driver for the work is understanding covalent bonding with the 5f and 6d orbitals in An- ligand multiple bonds. The authors are able to slow the rotation of the diatom at low temperatures, enabling them to achieve this aim, since they can quantify the contributions of the C cage. + +The very short 1.760 Å UN bond is the same as the UO bond in the simplest U(VI) uranyl complexes, yet this is U(V). I think this comparison is worthy of comment. In addition to this, there is a list of points to address below. The most important being to present fully the characterizing data for the compounds. + +I think this is a really elegant piece of work and look forward to reading the finished article. + +Other, more detailed points to address: + +1. Line 42- describe more carefully stable with respect to what. + +2. Line 104. Describe the physical nature of the products. Yield. Colour (I assume they're black or very dark brown). Air-sensitivity? Include more characterizing data here, especially the Raman spec.. The synthetic description in the SI should contain pictures of the Raman spectra and as full synthetic details as the authors can manage. + +3. Line 106. Please explain the reason for co-crystallization with Ni(OEP). I would also like to see use of spectroscopic characterizing data (Raman spec.?) that confirms the electronic structure of the fullerene complex is not disturbed by the presence of the Ni complex. It is known from magnetic studies that the magnetic field of paramagnetic f-block complexes can easily extend 20 Å through space. Maybe the Ni complex is actually useful in isolating the U spins from each other to give better data? Some of this should/could also go in the SI. + +4. Line 133. All the bonds discussed in the paragraph should have esds. + +5. Line 152. I don't understand the link between a bond length in an isolated molecule and the mechanism by which it was made. + +6. Line 212. The contributions from the cage are clearly very important in stabilising, ligating, the U; this should be emphasized in the abstract. Here also, draw comparisons on U-C distances with literature organometallics U-C5 and U-C6 systems, ideally with U in the same formal oxidation state for comparison. For example U(IV) Cp4 https://www.degruyter.com/document/doi/10.1515/znb-1962-0410/html and U(IV) arene in https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.1c03365. + +7. Line 238. I'm not sure the retention of order of the NiOEP is interesting. + +8. Line 242. Is it helpful to describe the N atom as stationary and U as disordered? The description on + +<--- Page Split ---> + +252 is more useful, as there is still significant order in the U's position, and the cage bonding9. Line 293. Please define the ratio of d:f in this orbital. How does it compare to the other U-E multiple bonds? + +10. Line 313 5f rather than 6d backdonation? Again, please compare the size of the U contributions (4-10 %) to that found in other uranium organometallics such as the Cp and COT sandwiches. + +11. Line 354 – this is the first time that UC is described as having a genuine triple bond, which I agree with, but which also undermines the statements made in the introduction about the absence of U-E triple bonds in the literature. + +12. Line 417 please replace 'spins' with a more precise description, including the axis. + +<--- Page Split ---> + +## Response to reviewer's comments: + +Reviewer #1 (Remarks to the Author): + +The authors report on the synthesis of two UN@C82 isomers. The compounds are characterized by X- ray diffraction, optical, Raman, and quantum chemical calculations. The techniques have been done competently. The computational analysis is excellent, and most of the experimental analysis is well done, except a fairly important point below. References are appropriate. + +The authors have demonstrated some considerable synthetic skill to make these systems. But in the end from grams of starting materials and 800 carbon rods they isolate \(0.2\mathrm{mg}\) of the title complexes (each or total I was not entirely clear on). Isolating UN inside these fullerenes is neat, but it has to be acknowledged that the incredibly low yields and scale, which limits the number of techniques that can be brought to bear, very much degrades the impact of this work, especially when isolable molecular analogs have been made on gram scales. + +So it is then a reasonable question to ask what the novelty is given it is arguably easier to make regular coordination complexes since they can be made on gram scales and examined fully with a wider range of techniques than here. The authors make a variety of claims or novelty statements, but not many stand up to scrutiny, in particular the shortest UN distance claim is factually incorrect (see below). As I read through the computational analysis whilst I thought that it was a professional write- up I did not come across a new electronic structure for UN. The orbitals all look to be arranged very much as has been shown elsewhere before, comparison to which seems to be missing from the UN bonding discussion - sure some \(\%\) shift around but it all looks very similar to me. + +This is a really nice and mostly solid study in many regards, but I was left with the + +<--- Page Split ---> + +impression that using a synthetically arduous approach the authors made a system that looks largely the same as already reported UN bonds and were unable to characterize it as much as in other studies because of the sub- mg yields. If there were no regular coordination complexes of UN then I would say this would be an advance over inert gas matrices, but that is not the case, so I do not see the novelty or new conceptual insight that I'd expect to see in a Nature family journal. I therefore have to conclude that I am unable to support publication in Nature Communications. + +Specific issues to address before publication anywhere: + +1. The first sentence of the abstract is ambiguous. It can be read as the authors saying that all actinide multiple bonds are elusive and only found in gas matrices, which is clearly not the case. + +Response: We thank the reviewer for the comments. In the first sentence, we in fact intend to imply that 'actinide diatomic molecules' rather than 'actinide multiple bonds' have only been found in the gas matrices. The original writing caused some confusion for the reviewer. Accordingly, we revised the first sentence as follows: 'Actinide diatomic molecules are ideal models to study elusive actinide multiple bonds, but most of these diatomic molecules have only been studied in solid inert gas matrices to date.' We hope this revised sentence can convey our point without confusion. + +2. The second sentence of the abstract is worded poorly as it says that UN is unpredented, but it would seem that Andrews has isolated it in gas matrices - the authors then go on to contradict themselves (line 69) by acknowledging the work of Andrews. Response: We have deleted the word 'unprecedented'. + +3. The penultimate sentence of the abstract is not worded precisely enough so could be debated. There are around 20 UN triple bonds now, is that still rare? + +Response: We have deleted the word 'rare'. + +<--- Page Split ---> + +4. The last sentence is imprecise, since it implies that a UN triple bond is still elusive, but they have been made. I don't think this is what the authors meant but it is how it reads. + +Response: Here, we made this statement mainly referring to the other elusive and yet to be found multiple bonded species, i.e., \(\mathrm{U} \equiv \mathrm{C}\) . We thought this method could be utilized to stabilize them in the molecular compound. To address the reviewer's concern and make it clearer, we replaced this sentence with 'Ongoing studies are underway to extend the paradigm to capture other currently elusive but fundamentally important actinide bonding motifs, i.e., \(\mathrm{U} \equiv \mathrm{C}\) , by the fullerene cages.' + +5. Introduction, Cummins made U2C2, there are now many UNU, and Ephritikhine made UCN, so how can the authors refer to those linkages as unprecedented? + +Response: The \(\mathrm{U}_2\mathrm{C}_2\) and UCN in endohedral fullerenes, i.e., \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{78}\) , \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{80}\) and UCN@ \(\mathrm{C}_{82}\) have unique bonding structures. \(\mathrm{U}_2\mathrm{C}_2\) in \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{78}\) and \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{80}\) demonstrates a unique bonding motif with two U bridged by a \(\mathrm{C} \equiv \mathrm{C}\) triple bond (J. Am. Chem. Soc., 141, 20249- 20260 (2019)), which, to the best of our knowledge, has not been reported by Cummins (Dalton Trans., 39, 6632- 6634 (2010)). UCN in UCN@ \(\mathrm{C}_{82}\) features a triangular cluster configuration with \(\eta^2\) (side- on) coordination of U by a cyanide (J. Am. Chem. Soc., 143, 16226- 16234 (2021)), which is different from those reported by Ephrikhine (Dalton Trans., 44, 7727- 7742 (2015)). For UNU in \(\mathrm{C}_{80}\) , we agree that the bonding structures are not substantially different from the UNU reported before and should not be mentioned here. To make this introduction more accurate, we modified the corresponding text as follows: 'The encapsulated \(\mathrm{U}_2\mathrm{C}_2\) , which presents two U bridged by \(\mathrm{C} \equiv \mathrm{C}\) triple bond, and triangular UCN cluster, which features \(\eta^2\) (side- on) coordination of U by a cyanide, show novel bonding motifs for U, broadening our understanding of the bonding properties of the actinide elements.' For details please see the first paragraph of Introduction. + +6. Line 65, TrenTIPsUN should be mentioned overtly here. + +Response: We thank the reviewer for the kind suggestion. In the revised manuscript, in + +<--- Page Split ---> + +Line 65, we have added a description of [UN(TrenTIPS)] (the second paragraph of Introduction). + +7. The authors use the phrase cluster a lot, the phrase 'diatomic cluster' is a contradiction in terms and is an inappropriate description. + +Response: In endohedral fullerene studies, these encapsulated species are commonly referred to as 'clusters', and clusterfullerenes specifically refer to fullerenes encapsulating species formed by two or more atoms. For details please see references (Chem. Rev. 113, 5989- 6113 (2013)). Here, to avoid disputes, we replaced 'diatomic cluster' with 'diatomic species' in the corresponding text. + +8. Lines 133-152, the authors present crystallographic bond metrics without standard uncertainties, which makes the values and statements associated with them meaningless, and in one case certainly factually incorrect. A bond distance is only fair game to refer to as shorter or longer than another bond distance if they do not overlap by the 3sigma rule. The UN distance they quote is 1.760 angstroms, undoubtedly short, however the UN distance of Mazzanti's complex is 1.769 angstroms, but her bond length has a standard uncertainty of 2, so her UN distance could be as small as 1.763 angstroms. In the 100 K cif file the UN distance is given as 1.760(9) angstroms, so the UN distance could be as long as 1.787 angstroms (it could also be shorter but that is not the point here), which also falls within the lower range of Liddle's uranium +6 nitride (1.778-1.820 angstroms by 3sigma). So the author's and Mazzanti's UN distances are statistically indistinguishable, therefore the authors cannot lay claim to have the shortest UN bond characterized by crystallography. + +Response: Many thanks to the reviewers for their corrections. In the revised manuscript, we have added standard uncertainties to the bond length and distances involved in the work. Considering standard uncertainties, the UN bond in UN@C82, as the reviewer pointed out, is still very short. However, compared to the UN bond in Mazzanti's complex, it is indeed true that we cannot determine that the UN bond in UN@C82 is the shortest. Thus, to avoid misstatement, we revised the corresponding text to + +<--- Page Split ---> + +' Crystallographic analysis reveals very short U- N bond lengths of 1.760(7) and 1.760(20) Å in UN@Cs(6)- C82 and UN@C2(5)- C82.' in the abstract and revised/deleted the corresponding discussion in the main text to avoid the statement of 'the shortest'. + +9. Did the authors observe any absorptions characteristic of the uranium +5 oxidation state in the nIR region? Whilst I am mostly convinced that they have made UN@C82 I don't think the possibility of UO@C82 being present in variable proportions can be considered to be completely excluded given the extensive crystallographic disorder and [understandable] absence of magnetic data. The optical spectrum is really the only way of the data provided to probe if it is all uranium +5 or whether there is any +4 present but this key aspect is not covered in the discussion. This would not affect the computational analysis, but purity really is an issue when only making 0.2 mg. + +Response: We have checked the literature and found that U(V) compounds usually have characteristic absorption bands at approximately 6700, 10000, and 12000 cm- 1 (Chem. Rev. 69, 657- 671 (1969); Inorg. Chem. 44, 6211- 6218 (2005); Nat. Commun. 12, 4832 (2021)). As shown in Response Fig. 1, we changed the horizontal coordinate of the UV- vis- NIR absorption spectrum to the wavenumber and could not find the corresponding characteristic peaks for U(V) compounds in the near- IR region of UN@C82. In fact, in the study of endohedral fullerenes, the characteristic absorption of the encaged metal ion is hardly visible in the absorption spectra because the absorption spectra of endohedral fullerenes are generally dominated by the \(\pi \rightarrow \pi^{*}\) excitation of their carbon cage \(\pi\) system, and the absorption of metals mostly overlap and become invisible. (Chem. Rev. 113, 5989- 6113 (2013)). + +The UV- vis- NIR spectra in this work also assisted us in determining the cage structure of the two isomers and the electron transfer between the clusters and the carbon cage. Although we did not observe the absorptions characteristic of the uranium +5 oxidation state, by comparing the UV- vis- NIR spectra of UN@C82 with the previously reported TbCN@C82 (J. Am. Chem. Soc. 138, 14764- 14771(2016)), which is almost identical to those of UN@C82, we can deduce that the electron transfer between the cluster and carbon cages is the same in UN@C82 and TbCN@C82, i.e., both + +<--- Page Split ---> + +are two- electron transfers, which also helps us determine that the formal oxidation state of U in UN@C \(_{82}\) is \(+5\) . + +![](images/Figure_5.jpg) + + +Response Fig. 1. (a) UV- vis- NIR spectra of UN@ \(C_{2}(5)\) - C \(_{82}\) (left) and UN@ \(C_{4}(6)\) - C \(_{82}\) (right) dissolved in CS \(_{2}\) . + +On the other hand, the exclusion of the presence of UO@C \(_{82}\) in the sample was determined by high- resolution matrix- assisted laser desorption/ionization time- offlight (MALDI- TOF) mass spectrometry. Response Fig. 2 shows the theoretically calculated isotopic distributions of UN@C \(_{82}\) and UO@C \(_{82}\) . + +![](images/Figure_7.jpg) + + +Response Fig. 2. (a) Isotopic distribution of UN@C \(_{82}\) from theoretical simulations. (b) Isotopic distribution of UO@C \(_{82}\) from theoretical simulations. + +In the separation processes of UN@ \(C_{4}(6)\) - C \(_{82}\) (Supplementary Fig. 1), the sixth stage of HPLC separation was performed by recycling on a Buckyprep column. In this HPLC profile of this stage, the fraction that contains UN@ \(C_{4}(6)\) - C \(_{82}\) is labelled in green (Response Fig. 3a). The mass spectra obtained from this fraction in front of the UN@ \(C_{4}(6)\) - C \(_{82}\) fraction are presented in Response Fig. 3b. In this mass spectrum, in + +<--- Page Split ---> + +addition to the mass signal of UN@ \(C_{s}(6) - C_{82}\) and other fullerenes, the isotopic distribution assigned to UO@ \(C_{82}\) (1237.951) can be clearly seen. This result suggests that UO@ \(C_{82}\) was also generated during the arcing process along with UN@ \(C_{82}\) . However, after further purification processes, the mass spectrum of the final purified sample (Supplementary Fig. 1- 2) only shows the isotopic distribution of UN@ \(C_{82}\) , and the peak of UO@ \(C_{82}\) (1237.951) is absent, which indicates that UO@ \(C_{82}\) has been successfully removed by recycling HPLC operations. + +![](images/Figure_8.jpg) + + +Response Fig. 3. (a) Partial magnification of the sixth step of chromatographic separation of UN@ \(C_{s}(6) - C_{82}\) . The fractions marked in green are UN@ \(C_{s}(6) - C_{82}\) . (b) Mass spectra of the previous fraction of UN@ \(C_{s}(6) - C_{82}\) (marked by the yellow box). The inset is an enlarged view of the mass spectra at the position marked by the blue box. The complete chromatographic separation is shown in Supplementary Fig. 1. + +10. Line 273, as written I found this confusing. The authors say the two optical spectra of the two UN fullerene isomers are different then seem to say this shows their electronic structures are the same. If the spectra are different, their electronic structures are not the same. + +Response: We thank the reviewers for pointing out the ambiguity in our presentation with respect to the absorption spectroscopic analysis. In fact, the two UN@ \(C_{82}\) isomers have different spectra because of their different isomeric cage structures. On the other + +<--- Page Split ---> + +hand, both isomers have the same two- electron cluster- to- cage charge transfer. Accordingly, we revised \(\mathrm{^1UN@C_2(5) - C_{82}}\) shows a different absorption pattern with two well- defined peaks at 772 and \(1050\mathrm{nm}\) , resembling that of \(\mathrm{TbCN@C_2(5) - C_{82}}\) . This indicates similar isomeric and electronic structures, respectively, which are consistent with crystallographic assignments of their molecular structures and the computational results for \([\mathrm{UN}]^{2 + }@\mathrm{C_{82}}^{2 - }\) as 'On the other hand, \(\mathrm{UN@C_2(5) - C_{82}}\) shows a different absorption pattern from \(\mathrm{UN@C_5(6) - C_{82}}\) , with two well- defined peaks at 772 and \(1050\mathrm{nm}\) , but resembles that of \(\mathrm{TbCN@C_2(5) - C_{82}}\) . This indicates similar isomeric structures and electronic transfer between \(\mathrm{UN@C_2(5) - C_{82}}\) and \(\mathrm{TbCN@C_2(5) - C_{82}}\) and between \(\mathrm{UN@C_5(6) - C_{82}}\) and \(\mathrm{TbCN@C_5(6) - C_{82}}\) . These results are consistent with the computational results for \([\mathrm{UN}]^{2 + }@\mathrm{C_{82}}^{2 - }\) (both \(\mathrm{TbCN@C_2(5) - C_{82}}\) and \(\mathrm{TbCN@C_5(6) - C_{82}}\) have two electron cluster- to- cage electron transfer) and the crystallographic assignments of their different isomeric structures of \(\mathrm{C_2(5) - C_{82}}\) and \(\mathrm{C_5(6) - C_{82}}\) .' in the Spectroscopic Characterization of the revised manuscript. + +11. Raman, what do the spectra look like above \(600\mathrm{cm}^{-1}\) ? The authors found the UN wagging mode but what about the UN stretch? I would expect this aspect to be probed and discussed as a bare minimum. + +Response: We thank the reviewer for the kind suggestion. Following this suggestion, we obtained the FTIR spectrum of one of the two \(\mathrm{UN@C_{82}}\) isomers, \(\mathrm{UN@C_2(5) - C_{82}}\) , and the experimental and simulated spectra are shown below in Response Fig. 4. The peak at \(924\mathrm{cm}^{-1}\) can be assigned to the stretching vibration of \(\mathrm{U} \equiv \mathrm{N}\) , which is close to the vibration of the \(\mathrm{U} \equiv \mathrm{N}\) triple bond in the FTIR spectrum of \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})][\mathrm{Na}(12\mathrm{C4})_2]\) at \(936\mathrm{cm}^{-1}\) (Science 337, 717- 720 (2012)). The spectrum above \(1000\mathrm{cm}^{-1}\) corresponds to the vibrations of the carbon cage, reproduced well by the theoretical calculation. We added the corresponding discussion of FTIR spectra and figures after the Raman section in the revised manuscript (Spectroscopic Characterizations and Supplementary Fig. 25). + +<--- Page Split ---> +![](images/Figure_9.jpg) + +
Response Fig. 4. (a) Observed and theoretically predicted vibrational features of UN@ \(C_2(5) - C_{82}\) . The lower curve (black) presents the observed infrared absorption (IR) spectrum vs. wavenumber from 1600 to \(600~\mathrm{cm^{-1}}\) , with quantum-chemical density-functional simulation upper (in blue).
+ +12. Line 400, delete fully, that is subjective and these compounds aren't fully characterized when thinking about the range of techniques available. + +Response: We have deleted this sentence in the revised manuscript. + +13. Lines 405-407, the mistake of claiming the shortest UN distance is repeated, so then saying it is notably shorter is also incorrect. + +Response: We deleted 'The bond length of 1.760 Å is, to the best of our knowledge, the shortest U-N bond length, characterized by crystallography, notably shorter than those discovered in coordination compounds but comparable to the calculated bond lengths for gas-phase molecules previously studied by matrix isolation.' in the revised manuscript. + +Reviewer #2 (Remarks to the Author): + +The manuscript is very well written and easy to read. The Experimental part is good and state- of- the- art. I am no expert for quantum- chemical calculations but they look reasonable to me, especially the agreement of the observed and simulated Raman band + +<--- Page Split ---> + +positions is nice. + +1. In my opinion the manuscript is unclear when it comes to the differentiation of the encaged species, if it is "UN", "UO", or "UC" as during the synthesis also a lot of O and C atoms have been present. + +Maybe the authors could explicitly state if/that the mass spectroscopic analysis is evidence enough to exclude UO and UC species? + +Response: We did only give a brief discussion about the purification process and mass spectra of UN@C82, which did not elaborate them in detail. In fact, high- resolution mass spectra can unambiguously differentiate UN@C82, UO@C82 and UC@C82. UO@C82 was generated during the arcing process and was removed during the purification process. However, there is no evidence that UC@C82 was generated during the arcing process in this work. + +Response Fig. 5 shows the theoretically calculated isotopic distributions of UC@C82, UN@C82 and UO@C82, which are distinguishable in the high- resolution mass spectra. + +![](images/Figure_12.jpg) + +
Response Fig. 5. (a) Isotopic distribution of UC@C82 from theoretical simulations. (b) Isotopic distribution of UN@C82 from theoretical simulations. (c) Isotopic distribution of UO@C82 from theoretical simulations.
+ +For UC@C82, the mass spectral signal of 1234.042 was not observed throughout the entire HPLC separation process. + +For UO@C82, in the separation of UN@C4(6)- C82 (Supplementary Fig. 1), the sixth HPLC stage, which was performed on a Buckyprep column, the mass signal of UO@C82 can be observed in fraction 6- 1, while UN@C4(6)- C82 was found mainly in + +<--- Page Split ---> + +fraction 6- 2 labelled in green. As shown in Response Fig. 6, the isotopic distribution of 1237.951 can be assigned to \(\mathrm{UO@C_{82}}\) , which overlaps with a minor isotopic distribution of 1235.962, mass signal of \(\mathrm{UN@C_{s}(6) - C_{82}}\) . In addition, no mass signal of \(\mathrm{UO@C_{82}}\) was observed in any of the HPLC fractions after this separation process of \(\mathrm{UN@C_{2}(5) - C_{82}}\) (Supplementary Fig. 2), which indicates that \(\mathrm{UO@C_{82}}\) was removed in the fourth step (Buckyprep column recycling). + +![PLACEHOLDER_16_0] + + +Response Fig. 6. (a) The HPLC profile of the sixth step of the \(\mathrm{UN@C_{s}(6) - C_{82}}\) chromatographic separation. The fractions marked in green mainly contain \(\mathrm{UN@C_{s}(6) - C_{82}}\) . (b) Mass spectra of fraction 6- 2. The inset is an enlarged view of the mass spectra at the position marked by the blue square. The complete chromatographic separation HPLC profiles and corresponding mass spectra are shown in Supplementary Fig. 2. + +Accordingly, we revised the 'Synthesis and Isolation of \(\mathrm{UN@C_{s}(6) - C_{82}}\) and \(\mathrm{UN@C_{2}(5) - C_{82}}\) ' section and added the following sentences: 'It is noteworthy that \(\mathrm{UO@C_{82}}\) is also observed during the HPLC separation process, possibly due to the leak of air into the arcing chamber, but was removed during the purification processes (Supplementary Fig. 3a- b). The purity of the samples was confirmed by single peak HPLC chromatography. Furthermore, the high- resolution mass spectrum of the final purified sample also shows that the isotopic distribution of the samples obtained experimentally is consistent with the theoretical isotopic distribution of \(\mathrm{UN@C_{82}}\) , excluding the existence of \(\mathrm{UC@C_{82}}\) or \(\mathrm{UO@C_{82}}\) (see Supplementary Fig. 3c- d).' + +<--- Page Split ---> +![PLACEHOLDER_17_0] + + +Supplementary Fig. 3c- d. HPLC chromatograms of purified \(\mathrm{UN@C}_s(6)\) - \(\mathrm{C}_{82}\) and \(\mathrm{UN@C}_2(5)\) - \(\mathrm{C}_{82}\) . (c) \(\mathrm{UN@C}_s(6)\) - \(\mathrm{C}_{82}\) on a Buckyprep column and (d) \(\mathrm{UN@C}_2(5)\) - \(\mathrm{C}_{82}\) on a 5PBB column with toluene as the eluent. HPLC conditions, \(\lambda = 310 \mathrm{nm}\) ; flow rate, \(4 \mathrm{mL / min}\) . The insets show the positive- ion mode MALDI- TOF mass spectra and expansions of the corresponding experimental isotopic distributions of the compound in comparison with their calculated values. + +2. For the mass specs I miss simulations, especially for the isotopic distributions (13C...) and if the resolution was high enough to discriminate the species. With some many C atoms the 13C signal should superpose with the one from 12C, a high-res MS should however be able to discriminate the species. The authors should comment on this. + +Response: We thank the reviewer for the kind suggestion. As commented by the reviewer, in the mass spectrum of the \(\mathrm{UN@C}_{82}\) molecule, we observed the \(^{13}\mathrm{C}\) signal superposed with the signal from \(^{12}\mathrm{C}\) . + +![PLACEHOLDER_17_1] + +
Response Fig. 7. Isotopic distribution of \(\mathrm{UN@C}_{82}\) from theoretical simulations and the masses
+ +<--- Page Split ---> + +corresponding to the major isotopic peaks. + +Response Fig. 7 shows the mass spectrum and data of the isotopic distribution of the theoretical calculated \(\mathrm{UN@C_{82}}\) . In the following discussion, only the isotopic distribution of C is considered, assuming that only \(^{238}\mathrm{U}\) and \(^{14}\mathrm{N}\) are in the molecule, to reduce the complexity of the discussion. We can see that the first distinct peak (near 1236) corresponds to \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{82}\) , and the subsequent peaks are \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{81}^{13}\mathrm{C}\) (near 1237), \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{80}^{13}\mathrm{C}_{2}\) (near 1238).... + +The abundances of \(^{13}\mathrm{C}\) and \(^{12}\mathrm{C}\) in nature are \(98.93\%\) and \(1.07\%\) , respectively. Then, the probability of having only \(^{12}\mathrm{C}\) in \(\mathrm{UN@C_{82}}\) ( \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{82}\) ) is given as + +\[P_{1} = (0.9893)^{82}\] + +The probability of having exactly one \(13\mathrm{C}\) atom in \(\mathrm{UN@C_{82}}\) ( \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{81}^{13}\mathrm{C}\) ) is therefore + +\[P_{2} = 82\times (0.9893)^{81}\times 0.0107\] + +and the ratio \(\mathrm{P_2 / P_1}\) is given as + +\[\frac{P_2}{P_1} = \frac{82\times(0.9893)^{81}\times0.0107}{(0.9893)^{82}} = 0.8869\] + +If the monoisotopic peak at 1236 assigned to \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{82}\) is regarded as \(100\%\) , the 1237 peak assigned to \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{81}^{13}\mathrm{C}\) will have \(88.69\%\) relative intensity. (Gross, J. H. In Mass Spectrometry: A Textbook; Gross, J. H., Ed.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2011; pp 67- 116. ) The relative intensity of the peak of \(\mathrm{UN@C_{82}}\) at 1237 is \(89\%\) , as shown in the above figure. If we consider the effect of the isotopes of U and N, the result should be corrected to \(89\%\) . The relative intensities of the peaks of other isotopic distributions of \(\mathrm{UN@C_{82}}\) can be calculated according to this method as well. + +Response Table 1. Experimental and theoretical isotopic distribution of \(\mathrm{UN@C_{82}}\) and its relative intensity. + +
Isotopic distribution for UN@C82
Theoretical simulationUN@C2(5)-C82UN@C8(6)-C82
+ +<--- Page Split ---> + + +
Neutral MassIntensitym/zIntensitym/zIntensity
1233.0450.73
1234.0450.65
1235.0450.28
1236.045100.001236.160939 (100.00%)1236.3347936 (100.00%)
1237.04589.001237.161818 (87.11%)1237.3346488 (81.75%)
1238.04539.151238.170335 (35.68%)1238.3382759 (34.76%)
1239.04511.341239.18039 (4.15%)1239.348602 (7.59%)
1240.0452.431240.34378 (0.98%)
1241.0450.41
1242.0450.06
+ +As shown in Supplementary Fig. 1, the isotopic distribution of UN@C82 obtained by MALDI- TOF mass spectrometry is almost identical to that of the theoretical simulation. The values and relative intensities of each peak in the isotopic distributions of UN@ \(C_2(5) - C_{82}\) and UN@ \(C_4(6) - C_{82}\) are listed in Response Table 1. Thus, the purity of UN@ \(C_{82}\) can be determined by high- resolution mass spectrometry. + +3. Regarding the crystal structures: That the N atom is completely ordered and the heavy U atom not is peculiar? Is that really plausible? Are there proof examples for such an observation? + +Response: The problem of disordered metal sites is commonly reported in the studies of endohedral metallofullerenes. In the majority of nitride clusterfullerenes, the N atom of the nitride cluster is generally fully ordered and located in the center of the fullerene cage. In contrast, in many cases, the metal sites inside the carbon cage are disordered, which is partially caused by the thermal vibration and partially related to the interaction between the metal and the neighboring carbon- cage moiety (Chem. Rev. 113, 5989- 6113 (2013)). + +The energy barriers of endohedral fullerenes with metal located near different carbon cage moieties are generally not high, and thus, the metal ions can overcome the + +<--- Page Split ---> + +energy barriers, resulting in the motion of the metal ion and disordered metal sides in different positions inside fullerene cages, as commonly seen in EMF crystals. However, in some cases, when the metal atoms have a strong enough interaction with a particular moiety of the carbon cage, the metal atoms can remain fully ordered. For example, in the crystal of \(\mathrm{Sc}_2@C_{2v}(4059) - \mathrm{C}_{66}\) , the two Sc atoms are fully ordered and located over the pair of doubly fused- pentagon moieties of the \(C_{2v}(4395) - C_{66}\) cage because the interaction between the Sc atoms and such a fused- pentagon moiety is much stronger than others (J. Am. Chem. Soc. 2014, 136, 21, 7611- 7614). + +In this work, although the cages of \(\mathrm{UN}@C_2(5) - \mathrm{C}_{82}\) and \(\mathrm{UN}@C_4(6) - \mathrm{C}_{82}\) do not have fused- pentagon moieties, the major U sites show much higher occupancies than the other minor sites, suggesting that the U sites in these two cages are largely ordered and that the U ions and neighboring carbon cage moieties have relatively strong interactions. However, when temperatures increase, as we see in the VT- crystallography, U ions can overcome the energy barriers, and the U sites become disordered. + +4. Is there no O/C/N mixed site occupancy possible? + +Response: Indeed, it is difficult to distinguish the case of O/C/N mixed sites in the crystal. However, in this work, the possibility of the central O/C can be excluded by high- resolution mass spectrometry, and the purities of the two \(\mathrm{UN}@\mathrm{C}_{82}\) isomers have been confirmed by the single HPLC peak, as we have answered in detail in response to question 1. + +5. Are the electron densities of the less occupied U atom positions similar to the N/O/C electron density? + +The absolute densities should be given in the SI. + +Response: (1) All studies thus far have shown that when clusters are embedded in the carbon cage, the nonmetallic atoms are located at the center of the carbon cage. Therefore, the low- occupancy sites close to the side of the carbon cage are reasonably determined to be disordered metal sites, as the metal ion needs to be close to cage carbon to maintain the interaction between them, which is essential to the stabilization + +<--- Page Split ---> + +of the endohedral fullerene molecular structure (Chem. Rev. 113, 5989- 6113 (2013)). + +(2) We thank the reviewer for the suggestions. However, after careful analysis, we can only provide the absolute density of the U site with the lowest occupancy in the crystal of UN@ \(C_{s}(6) - C_{82}\) , i.e., U4 (0.0566), with an absolute density of 6.21. These data were added as a footnote to Supplementary Table S6. The reason for this is because the electron density of U is much heavier than those of N/O/C, and even the U4 site in the crystal of UN@ \(C_{s}(6) - C_{82}\) , with the lowest occupancy, is still heavier than a complete carbon atom (with an average density of \(\sim 3\) ). Thus, we could not provide the electron densities of the other U sites because when we removed these U sites, the structural model collapsed, and the refinement process was unable to converge. + +The occupancies of all the U sites in the two crystals are shown in Response Table 2 for reference. + +Response Table 2. Metal site occupancy in UN@ \(C_{82}\) + +
UN@C2(5)-C82UN@C8(6)-C82
siteoccupancysiteoccupancy
U10.312U10.6442
U20.188U20.1903
U30.1087
U40.0566
+ +6. The authors should investigate and comment, if structure models in subgroup C2 give better results, i.e., resolution of the disorder by twinning. That would be something reasonable to expect for the models in C2/m and should be commented. + +Response: As we answered in response to question 3, the disorder of encapsulated metal is partially caused by the thermal vibration and partially related to the interaction between the metal and the neighboring carbon- cage moiety, instead of being caused by twinning. The space group of \(C2 / m\) is very commonly seen in the EMF- Ni(OEP) cocrystal system (Chem. Rev. 113, 5989- 6113 (2013)). The removal of the mirror to subgroup \(C_{2}\) does not help solve the disorder problem but instead increases the + +<--- Page Split ---> + +difficulty of refining the structure. Therefore, it is more reasonable to solve and refine the crystal in the higher \(C2 / m\) space group, which is also the reason why the \(C2 / m\) space group, rather than \(C2\) , is much more commonly seen in the EMF- Ni(OEP) cocrystal system. + +7. All bond lengths and atom distances in the manuscript and the SI should be reported with their respective standard uncertainties as only these will allow for a proper comparison with other species, especially when it comes to the discussion of the UN bond lengths and its comparison with compounds from the literature. + +Response: We thank the reviewers for this suggestion. We have added the corresponding standard uncertainties to the bond lengths and atomic distances involved in this work. Please see the revised manuscript. + +8. The U-N bond length is a value that is surely biased by the disorder and should only be used with the necessary care. + +How far is the residual electron density away from the U atom? Can it be clearly discriminated from a N atom? + +Response: We thank the reviewer for the kind suggestion. (1) As replied in point 3, in the crystal of endohedral fullerenes, the metal disorder is mainly related to the interaction between the metal and the neighboring carbon- cage moiety, especially when the crystal is measured at low temperature (Chem. Rev. 113, 5989- 6113 (2013)). Therefore, the metal disorder generally reflects different conformations of the molecule with small energy barriers. In this work, we focus on the major site because it represents the most stable conformation. Thus, we discuss the UN bond length with the major U site. In the process of solving the two crystals, we found that the major U sites are completely fixed and are little affected by the disordered sites. In addition to the determined U disordered sites with small atomic displacement parameters, we did not observe a large residual electron density around U and the central N, and the top ten residual electron densities are all distributed on the fullerene cage. Therefore, we think the U- N bond lengths determined by the major U sites are accurate for the most stable + +<--- Page Split ---> + +conformations of these two compounds. It is also a commonly accepted method in the studies of endohedral fullerenes. + +(2) In this work, the U atom can be easily discriminated from the central N atom. In response to question 3, the metal atoms are located on one side of the carbon cage, while the nonmetal atoms are normally located at the center of the carbon cage. In addition to the determined U disordered sites with small atomic displacement parameters, we did not observe large residual electron density around U and the central N, and the top ten residual electron densities are all distributed on the fullerene cage. + +9. Where would one expect the UN stretch vibration? These should be given. Can an isotope effect be observed? + +Response: We thank the reviewer for the kind suggestion. Following this suggestion, we obtained the FTIR spectrum of one of the two UN@C82 isomers, UN@C2(5)- C82, and the experimental and simulated spectra are shown below in Response Fig. 8. The peak at \(924~\mathrm{cm^{-1}}\) can be assigned to the stretching vibration of \(\mathrm{U}\equiv \mathrm{N}\) , which is close to the vibration of the \(\mathrm{U}\equiv \mathrm{N}\) triple bond in the FTIR spectrum of \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})][\mathrm{Na}(12\mathrm{C4})_2]\) at \(936~\mathrm{cm^{-1}}\) (Science 337, 717- 720 (2012)). The spectrum above \(1000~\mathrm{cm^{-1}}\) corresponds to the vibrations of the carbon cage, reproduced well by the theoretical calculation. We added the corresponding discussion of FTIR spectra and figures after the Raman section in the revised manuscript (Spectroscopic Characterizations and Supplementary Fig. 25). + +![PLACEHOLDER_23_0] + +
Response Fig. 8. (a) Observed and theoretically predicted vibrational features of UN@C2(5)-C82.
+ +<--- Page Split ---> + +The lower curve (black) presents the observed infrared absorption (IR) spectrum vs. wavenumber from 1600 to \(600~\mathrm{cm^{- 1}}\) , with quantum- chemical density- functional simulation upper (in blue). + +We note that in the previous report by Liddle et al., the \(^{15}\mathrm{N}\) isotope was used in the synthesis of \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})][\mathrm{Na}(12\mathrm{C4})_2]\) and \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})]\) to study the isotopic effect of the vibrational band of the U- N triple bond, in which isotopic effects cause the peaks to shift to lower wavenumbers. (Science 337, 717- 720 (2012); Nat. Chem. 12, 962- 967 (2020)). However, in this work, we cannot expect the observation of a similar isotopic effect because we used regular \(^{14}\mathrm{N}_2\) in the synthesis of \(\mathrm{UN@C_{82}}\) . In addition, the very limited amount of sample also made it very difficult to observe such an isotopic effect. + +10. The observed and calculated Raman bands should be assigned more clearly in the manuscript as well as in the SI as the arrows in Supp. Fig. 22 and 23 are simply to small. Response: We thank the reviewer for the kind suggestion. In the revised Supplementary Information, we have replaced Supp. Fig. 22 and 23 with improved figures, which hopefully will help the reader to better understand the Raman vibration modes in \(\mathrm{UN@C_{82}}\) . + +11. Discrimination from UO and UC species: Where would those show bands? Have the respective UO and UC species been calculated? + +Response: As we explained in our response to the reviewer's first question, the characterization of the fractions obtained by chromatographic separation by matrix- assisted laser desorption/ionization time- of- flight (MALDI- TOF) mass spectrometry allowed us to determine that we obtained \(\mathrm{UN@C_{82}}\) without the mixture of \(\mathrm{UO@C_{82}}\) and \(\mathrm{UC@C_{82}}\) , and therefore, we did not consider these substances in our theoretical calculations. + +Overall, I recommend revision of the manuscript. I think that if the issues can be sorted out it would be a fine contribution. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +In this article, Chen presents a UN triple bond captured inside fullerene cages. The isolation of uranium nitride species is of great importance because this material has been proposed as possible uranium- based nuclear fuel. Understanding the fundamentals of its bonding is thus rather useful. The results presented in this article are interesting but I disagree with most comments on the fact that they are unique opportunities to study the UN bond. Coordination compounds are now known and accessible on a larger scale, which allowed various characterization and computations. This article is following with a new type of UN terminal bond since I would argue that the U coordination to the fullerene mimics well what is observed with a classical coordination compound. If most characterizations are fair (see below), the technique only provides crystals, and the compounds remain rather elusive. Considering that molecular compounds with similar bonding exist, I would state that this study merits publication in a more specialized journal provided that my few technical comments are sorted out. + +1. The crystallographic disorder is large and the esd on the distance must be large as well. I have seen no mention of esd in the main text or SI. I would argue that Table S14 and the R1/wR2 give an idea of the large esd that should be associated with these distances. Without these esd comparing distances is pointless, especially if the authors want to convince us that the UN bond of this work is the shortest one reported to date! On this matter, I would be very cautious since the molecular UN bond distances are very close to that one if not identical. + +Response: Many thanks to the reviewers for their corrections. In the revised manuscript, we have added standard uncertainties to the bond length reported in the work. In addition, to avoid misstatement, we have changed the expression 'shortest' to more precise 'one of the shortest bond lengths' or 'very short' for the description of the UN triple bond in the corresponding text. + +<--- Page Split ---> + +2. Both crystallographic positions of the U are true. The fact that there is a minor one does not mean the distance argument can only be made from the major one. An average would be more accurate for the discussion. + +Response: In the crystal of endohedral fullerenes, the metal disorder is mainly related to the interaction between the metal ions and the neighboring carbon- cage moieties, especially when the crystal is measured at low temperature (Chem. Rev. 113, 5989- 6113 (2013)). Therefore, the metal disorder generally reflects the different conformations of the molecule with small energy barriers. In this work, we focus on the major site because it represents the most stable conformation and thus show the UN bond using the major U site. In addition, in the process of solving the two crystals, we found that the major U sites are completely fixed and are little affected by the disordered sites. In addition, in addition to the determined U disordered sites with small atomic displacement parameters, we did not observe a large residual electron density around U and the central N, and the top ten residual electron densities are all distributed on the fullerene cage. Therefore, we believe that the U- N bond lengths determined by the major U sites are accurate for the most stable conformations of these two compounds. It is also a commonly accepted method in the studies of endohedral fullerenes (J. Am. Chem. Soc., 137, 10116- 10119 (2015), J. Am. Chem. Soc., 138, 13030- 13037 (2016), Nat Commun 5, 3568 (2014)). Nevertheless, we also add bond lengths measured with minor U sites in the SI. + +3. I would agree with the authors with the hypothesis stating that UN species are formed during the arc discharging process but not that it can be related to similar distances observed in unstable gas molecules, this is too speculative. + +Response: To address this concern, we deleted the corresponding text ‘The similarity of the bond lengths of encaged UN to those of isolated molecules might indicate that the isolated UN species were formed during the arc discharging process and then the nanocavity of the fullerene cage captured and stabilized them in the form of endohedral fullerenes.’ We hope in this way, we have deleted the speculative discussion. + +<--- Page Split ---> + +4. The strong interaction of U with the C skeleton of the fullerene is shown by the calculated spin doublet ground state being the most stable one. Would it be possible to confirm this by EPR spectroscopy? Since the EPR is a sensitive technique, few crystals should be enough. + +Response: We thank the reviewers for this suggestion. Following this suggestion, we carried out an EPR test of UN@C82 at low temperature. However, this attempt to further resolve the electronic structure using EPR spectroscopy was unsuccessful, as no clearly defined signal was observed even at 4 K. A similar situation occurred when we investigated the ESR signal corresponding to U(V) in our study of U2C@C80 (Nat. Commun. 9, 2753-2760). The reason for the absence of the EPR signal is yet to be understood. Nevertheless, we added the sentence 'Attempts to further resolve the electronic structure using EPR spectroscopy were unsuccessful, as no clearly defined signal was observed at 4 K (Supplementary Fig. 26). The ESR signal corresponding to U(V) was also not observed in U2C@C80, probably due to the shielding effect of the carbon cage.' in the section 'Spectroscopic Characterizations' as well as Supplementary Fig. 26 in the Supporting Information. + +![PLACEHOLDER_27_0] + +
Response Fig. 9. X-Band EPR spectrum of UN@C2(5)-C82. It is recorded in a toluene glass tube at 4 K and 10 K.
+ +5. The VT-XRD studies are nice and interesting but do not bring much to the bonding analysis. + +Response: It is true that the VT-XRD study did not help us to study the nature of the + +<--- Page Split ---> + +UN triple bond, but variable- temperature XRD is a powerful tool to unravel the temperature- dependent dynamics of endohedral metallofullerenes in the crystal lattice. In this work, the VT- XRD study of UN@ \(C_{s}(6) - C_{82}\) revealed a rare phase transition process and thus gives important insight into the problem of disorder impeding metallofullerene crystallography. UN@ \(C_{82}\) is the simplest endohedral clusterfullerenes found to date, and its cluster contains only one UN triple bond. The VT- XRD study of UN@ \(C_{s}(6) - C_{82}\) and UN@ \(C_{2}(5) - C_{82}\) helped us to study the movement of the UN bonding motif within the carbon cage. The U ion appears to “rotate” around the Ni···N axis, thus making the movement of the UN cluster look like a spinning top with N atoms as the apex. Therefore, VT- XRD helped us recognize the temperature- dependent dynamics of UN@ \(C_{82}\) . However, the reviewer's comment made us realize that the VT- XRD maybe too extensive. Thus, in the revised manuscript, we deleted the discussion of the phase transition, which is not related to the bonding analysis. + +6. The UV-Vis-NIR data is provided without informing the reader of the nature of the bands reported? + +Response: We thank the reviewer for the kind suggestion. The absorption spectra of fullerene are dominated by the \(\pi \rightarrow \pi^{*}\) excitation of their carbon \(\pi\) - system. When the number of carbon atoms on the fullerene cage (e.g., \(C_{80}\) and \(C_{82}\) ) or the symmetry of the carbon cage (e.g., \(C_{s}(6) - C_{82}\) and \(C_{2}(5) - C_{82}\) in this work) changes, a change in the absorption spectrum can be clearly observed (Chem. Rev. 113, 5989-6113 (2013)). In this work, the absorption spectra obtained from experimental tests are consistent with those previously reported for \(\mathrm{TbCN@C_{82}}\) [REDACTED] (J. Am. Chem. Soc. 138, 14 764-14771 (2016))), suggesting that the carbon cage structures of the two UN@ \(C_{82}\) isomers are \(C_{s}(6) - C_{82}\) and \(C_{2}(5) - C_{82}\) , respectively. It can also be deduced that their electronic structures are similar to those of \(\mathrm{TbCN@C_{82}}\) , as clusters transfer two electron on to the carbon cage: [UN] \(^{2 + }@[C_{82}]^{2 - }\) . + +Considering all this information, we did not carry out calculations on the electronic spectra. Nevertheless, following this comment, we added ‘The absorption features of the two isomers of UN@ \(C_{82}\) are dominated by the \(\pi \rightarrow \pi^{*}\) excitation of their carbon \(\pi\) - system, as commonly known for other reported endohedral fullerenes.’ in the + +<--- Page Split ---> + +first paragraph of the 'Spectroscopic Characterizations' section. We hope in this way that the readers can better understand the nature of these absorption bands. + +7. I wonder if the use of the term somewhat twice to define the UN bonding nature is not too much. I would say, the bond is polarized. How does it compare with molecular coordination compounds? + +Response: We thank the reviewer for the kind suggestion. We revised the manuscript in lines 294 and 295 to avoid vague language. + +For bond comparisons, there are works by Liddle with \(^{15}\mathrm{N}\) NMR (Nat Commun. 12, 5649(2021)), Hayton and some of us on the \(^{15}\mathrm{N}\) bonds with thorium (Chem. Sci., 12, 14383- 14388(2021), Chem. Sci., 10, 6431- 6436(2019)), and related systems that one of us studied with Hayton and Neidig with U- C bonds (Inorg. Chem. 60, 20, 15413- 15420(2021), Inorg. Chem. 60, 16, 12436- 12444(2021), Chem. Eur. J. 27, 5885(2021), Angew. Chem. Int. Ed. 59, 13586(2020), Angew. Chem. Int. Ed. 58, 10266(2019)). Comparing our system to what was reported in the literature in other complexes, the UN bond appears remarkably unpolarized. We have included a comment about it in the manuscript, along with relevant references. + +8. The comparison of the NU and UN \(^{2 - }\) electronic structure by ab initio methods is also + +<--- Page Split ---> + +interesting but the conclusion of this interesting comparison full of information is elaborated, neither in the conclusion nor in the discussion. Were these computations done only to mention that WFT and DFT produce similar results? Could these be gathered and compared on a table? + +Response: The comparison of the electronic structure between UN and \(\mathrm{UN}^{2 - }\) by density functional theory (DFT) and ab initio wavefunction (WFT) was indeed performed to ensure that the results derived from the DFT calculations are reliable. We edited and clarified the text and moved most of the discussion of the WFT calculations to the Supporting Information because the additional WFT results appear to have distracted the Reviewer from the main message, which is that UN in the clusterfullerenes and in the gas phase unambiguously can be assigned a triple bond. The main results from the WFT calculations are reported in Figure 5 and the Tables that were moved to the SI, and therefore we deem it unnecessary to create an additional Table. + +Reviewer #4 (Remarks to the Author): + +This is another paper in the series of the synthesis of clusterfullerenes containing simple, and now characterizable, f- block diatomics with multiple metal- element bonding. This time \(\mathrm{U} \equiv \mathrm{N}\) in two different fullerene symmetries. + +The driver for the work is understanding covalent bonding with the 5f and 6d orbitals in An- ligand multiple bonds. The authors are able to slow the rotation of the diatom at low temperatures, enabling them to achieve this aim, since they can quantify the contributions of the C cage. + +The very short 1.760 Å UN bond is the same as the UO bond in the simplest U(VI) uranyl complexes, yet this is U(V). I think this comparison is worthy of comment. In addition to this, there is a list of points to address below. The most important being to present fully the characterizing data for the compounds. + +I think this is a really elegant piece of work and look forward to reading the finished article. + +<--- Page Split ---> + +Response: We thank the reviewer for this comment. In the revised manuscript, we added the comment 'These short UN bonds are similar to the situation of the short UO bond in the simplest U(VI) uranyl complexes, such as \(\mathrm{U(VI)O_2(^{Bu}acnac)_2}\) which has a UO bond with bond length of 1.770(3) Å. + +Other, more detailed points to address: + +1. Line 42- describe more carefully stable with respect to what. + +Response: We thank the reviewer for the kind suggestion. We have added a description of "stable" in Line 42. The corresponding sentence has been changed from 'Our recent studies showed that very diverse actinide clusters containing important new actinide bonding motifs can be formed and stabilized inside the fullerene cages and can thus be systematically characterized in the form of molecular compounds.' to 'Our recent studies showed that very diverse actinide clusters containing important new actinide bonding motifs can be formed and stabilized inside the fullerene cages by electron transfer between the cluster and carbon cage and by the U- fullerene coordination. They can thus be systematically characterized in the form of molecular compounds.' + +2. Line 104. Describe the physical nature of the products. Yield. Colour (I assume they're black or very dark brown). Air sensitivity? Include more characterizing data here, especially the Raman spec. The synthetic description in the SI should contain pictures of the Raman spectra and as full synthetic details as the authors can manage. Response: We thank the reviewer for this kind suggestion. Accordingly, we added a detailed description of the physical nature of the products in SI (page 5) as follows: In total, 2.02 g of graphite powder and 1.58 g of \(\mathrm{U_3O_8}\) (molar ratio of \(\mathrm{C:U = 30:1}\) ) were packed in each rod. On average, ca. 40 mg of crude fullerene mixture per rod was obtained, and 800 carbon rods were vaporized in this work. After HPLC isolation and purification, ca. Purified \(\mathrm{UN@C_8(6) - C_{82}}\) and \(\mathrm{UN@C_2(5) - C_{82}}\) (0.2 mg) were obtained. The obtained samples show a brown color in toluene and carbon disulfide solutions, + +<--- Page Split ---> + +and the color in carbon disulfide is illustrated in Supplementary Fig. 20. The sample was stable in air, and no decomposition was detected after 3 months of storage in the air. + +The Raman spectra of the samples can be seen in Supplementary Fig. 21a- b, and we have also added pictures (Supplementary Fig. 21f) of the morphology of the samples made during the Raman characterization, which we hope will help readers better understand our work. + +![PLACEHOLDER_32_0] + + +Response Fig. 11. Shape of the sample during Raman testing. + +3. Line 106. Please explain the reason for co-crystallization with Ni(OEP). I would also like to see use of spectroscopic characterizing data (Raman spec.?) that confirms the electronic structure of the fullerene complex is not disturbed by the presence of the Ni complex. It is known from magnetic studies that the magnetic field of paramagnetic f-block complexes can easily extend \(20 \mathrm{\AA}\) through space. Maybe the Ni complex is actually useful in isolating the U spins from each other to give better data? Some of this should/could also go in the SI. + +Response: We thank the reviewer for the question. The reason for using Ni(OEP) for co- crystallization is to prevent the rotation of the fullerene cage, which has long been a great challenge for solving the crystal structures of these compounds. Ni(OEP), which has a noncovalent \(\pi - \pi\) interaction with endohedral fullerenes when forming a cocrystal, + +<--- Page Split ---> + +was utilized in the crystal growth process to hinder the rotation of the fullerene cage. + +Except for the single crystal characterization where Ni(OEP) is used as a eutectic agent, the rest of the characterizations in this work are all performed on the pristine UN@C \(_{82}\) molecule. Thus, there is no influence of Ni(OEP) on the determination of their electronic structures. In the revised manuscript, we also carried out an EPR test of UN@C \(_{82}\) at low temperature. However, this attempt to further resolve the electronic structure using EPR spectroscopy was unsuccessful, as no clearly defined signal was observed even at 4 K. A similar situation occurred when we investigated the ESR signal corresponding to U(V) in our study of U \(_{2}\) C@C \(_{80}\) (Nat. Commun. 9, 2753- 2760). The reason for the absence of the EPR signal is yet to be understood. Nevertheless, we added the sentence 'Attempts to further resolve the electronic structure using EPR spectroscopy were unsuccessful, as no clearly defined signal was observed at 4 K (Supplementary Fig. 26). The ESR signal corresponding to U(V) was also not observed in U \(_{2}\) C@C \(_{80}\) , probably due to the shielding effect of the carbon cage.' in the section 'Spectroscopic Characterizations' as well as Supplementary Fig. 26 in the Supporting Information. + +![PLACEHOLDER_33_0] + +
Response Fig. 12. X-Band EPR spectrum of UN@C \(_{2}(5)\) -C \(_{82}\) . It is recorded in a toluene glass tube at 4 K and 10 K.
+ +4. Line 133. All the bonds discussed in the paragraph should have esds. + +Response: We thank the reviewers for this suggestion. We have added the corresponding standard uncertainties to all the bond lengths reported in this work in the + +<--- Page Split ---> + +revised manuscript. + +5. Line 152. I don't understand the link between a bond length in an isolated molecule and the mechanism by which it was made. + +Response: We thank the reviewer for the comment. Reviewer 3 raised similar questions and pointed out that this link seems to be too speculative. Thus, to make a fact- based statement and remove the speculative mechanism, we deleted the speculative discussion about this link. + +6. Line 212. The contributions from the cage are clearly very important in stabilising, ligating, the U; this should be emphasized in the abstract. Here also, draw comparisons on U-C distances with literature organometallics U-C5 and U-C6 systems, ideally with U in the same formal oxidation state for comparison. For example, U(IV) Cp4 https://www.degruyter.com/document/doi/10.1515/znb-1962-0410/html and U(IV) arene in https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.1c03365. + +Response: We thank the reviewer for the kind suggestion. (1) Following this suggestion, we revised the second sentence of the abstract as follows: 'Herein, we report that the U \(\equiv\) N diatomic species captured in two different fullerene cages and stabilized by the U- fullerene coordination.' + +(2) Following the reviewer's comments, we checked the relevant data for or g anometallic compounds of U(V). [REDACTED] In (CpiPr4)2U(μ-N)B(C6F5)3 (Chem. Commun. 56, 4535-4538 (2020)), the U-Cp distances are in the range of 2.723(3)- 2.830(3) Å, and the distances of U-Cp(cent) are 2.511(1) and 2.520(1) Å. In {U[η8- C8H6(1,4-Si(Pr)3)]Cp8)(NSiMe3)} [REDACTED] (J. Organomet. Chem. 857, 25-33 (2018)), the U-Cp distance is between 2.718(7)- 2.866(7), the U-COT distance is between 2.687(6)- 2.747(7) Å, and the distances of U-Cp(cent) are 2.500(1). + +<--- Page Split ---> + +The shortest U- \(C_{\mathrm{cage}}\) distances in UN@ \(C_{s}(6) - C_{82}\) and UN@ \(C_{2}(5) - C_{82}\) are 2.487(15) and 2.503(7) A, respectively, similar to the U- \(C_{\mathrm{p(cent)}}\) distances mentioned above. The distances between the metal and the six closest carbons on the fullerene cage are 2.478(15)- 2.861(22) A and 2.503(7)- 2.785(7) A, respectively, which are also close to the U- Cp distances in the abovementioned organometallic compounds. This indicates that the interaction between the fullerene cage and U is likely similar to the coordination between the metal and the cyclopentadienyl group in the organometallic compounds. + +In the revised manuscript, we added a comparison with the metal- cyclopentadienyl ligand distances in organometallic compounds after the description of the metal- cage distances in the section 'Molecular and Electronic Structures of UN@ \(C_{82}\) '. + +7. Line 238. I'm not sure the retention of order of the NiOEP is interesting. + +Response: We thank the reviewer for the comments. We revised the sentence as follows: 'the \(\mathrm{Ni}^{\mathrm{II}}(\mathrm{OEP})\) molecule remained completely ordered as the temperature increased from 100 to 273 K' and deleted 'interestingly'. + +8. Line 242. Is it helpful to describe the N atom as stationary and U as disordered? The + +<--- Page Split ---> + +description on 252 is more useful, as there is still significant order in the U's position and the cage bonding. + +Response: We thank the reviewer for this comment. In endohedral metallofullerenes, the nonmetallic atoms tend to be completely ordered, while the metal atoms in many cases are disordered. We note, however, that describing such a sentence here is not significantly helpful for the analysis of the data, so we have removed the corresponding text in Line 242 in the revised manuscript. + +9. Line 293. Please define the ratio of d:f in this orbital. How does it compare to the other U-E multiple bonds? + +Response: We have added the corresponding ratio of d:f in the text, which was already defined in Figure 4. The d:f ratio is not discussed other than in the context of the selfcontained comparison of UN, UN(2+), and the UN clusterfullerenes, and it is not relevant for the bond order analysis provided in the manuscript. The same comment also applies to point 10. By the Reviewer. We added some context and references regarding the bond polarity in response to point 7 of Reviewer #3. + +10. Line 313 5f rather than 6d backdonation? Again, please compare the size of the U contributions (4-10 %) to that found in other uranium organometallics such as the Cp and COT sandwiches. + +Response: Please see our response to point 9. + +11. Line 354 – this is the first time that UC is described as having a genuine triple bond, which I agree with, but which also undermines the statements made in the introduction about the absence of U-E triple bonds in the literature. + +Response: We thank the reviewer for this comment. In the introduction we wrote: 'Covalent bonding with the 5f and 6d orbitals in actinide-ligand multiple bonds has been intensively studied, but remains incompletely understood both experimentally and + +<--- Page Split ---> + +theoretically'. We assume that the reviewer is referring to this sentence. In this place, we intend to say that the U- E triple bond has been intensively studied but is not fully understood. Ref 60 (J. Am. Chem. Soc. 132, 8484- 8488 (2010)) is a combined spectroscopic and theoretical study of UC and CUC, in which the U- C was defined as a well- developed triple bond. However, this U- C triple band has never been discovered in the condensed- phase molecular compound to date. Thus, we think mentioning this work does not seem to contradict the description of the U- E triple bond, which has been intensively studied but is not fully understood. + +12. Line 417 please replace 'spins' with a more precise description, including the axis. Response: We thank the reviewer for the kind suggestion. In the revised version, we revised "the UN spins inside the fullerene cages" to "UN is more mobile and rotates inside the fullerene cage" in the corresponding text. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have revised their manuscript and resubmitted. + +In the abstract the authors state that actinide diatomics are elusive and only studied in solid inert matices. They then go on to say they have a diatomic in a fullerene, but it is not a neutral diatomic, it carries a \(2+\) charge. This is then no different to a coordination complex with a \((\mathrm{UN})2+\) coordinated by one or more ligands. In effect the fullerene is just another ligand (as highlighted by the analogy to Cp and arene binding). It is certainly not the same as a neutral diatomic in a matrix. Given that there are many coordination complexes with diatomic actinide units carrying a variety of charges, since being neutral is obviously not a defining caveat, then it is not objectively credible to say they are only studied in inert matices. The authors would have a case if the UN were neutral but it is not, they cannot then have their argument both ways. What this then reduces to is that this is the third class of terminal uranium nitride outside of inert matrices. + +The authors concede the point that they cannot claim the shortest UN distance. Then they have amended the statement in the abstract to address that point and state that they amended the discussion to "avoid the statement of 'the shortest'". However, despite conceding the point around lines 153- 156 the authors persist in making shortest statements "Moreover, these UN bonds are shorter than most of the observed UN bond lengths for...". The first two examples are complexes with UN distances that overlap with the UN fullerene one by the 3sigma criteria. + +The authors have provided a range of clarifying statements and extra analysis. I stated before that I was largely convinced of the formulations, details not withstanding, but my central concerns have not actually been resolved. The authors have made a system in incredibly low yield and quantities, there is limited analysis compared to other systems, in contrast to coordination complexes that are made on higher yields with much more analysis. The authors persist in claiming a shorter/shortest bond when they concede they should not, and they continue to push their novelty arguments too far. + +The technical clarifications are appreciated, but a central claim has been conceded and I do not see the novelty or new conceptual insight I expect in a Nature journal so I am unable to support publication here. + +Reviewer #2 (Remarks to the Author): + +From my point of view all is sorted out now and I recommend publication. + +Reviewer #3 (Remarks to the Author): + +The article of Chen et al. has been modified after the comments of 4 reviewers and most questions raised were answered. However, in several cases - and with different reviewers, the authors refrained from their original statement of a singular case of UN since many molecular UN features now exist. Thus, I prefer staying on my original statement, which would make this article worthy of publication but in a more specialized journal. + +Additionally, on two specific points that were addressed by the authors, I would have more comments: + +I am sorry, I am not sure I am satisfied with the answer of the authors on my original point on the different crystallographic positions of the metal center. I agree with the definition, which is made of a disorder as it "reflects the different conformations of the molecule with small energy barriers" but yet the other configuration is still present and thus shall be discussed. Even if the position is "fixed", meaning that the ellipsoid is of fair size, the second configuration, although minor, should be + +<--- Page Split ---> + +considered. I understand that the major is the shortest UN distance but then all following characterization, especially Raman (see comments of Reviewers 1 and 2) should point to both configurations with two distinct UN sets of bands. Is it the case? Although it is a common method used in this peculiar chemistry, I wonder how one can just ignore an existing configuration. + +Thanks to the authors for attempting ERP spectroscopy. There are many reasons for having a silent EPR spectrum: the ligand field shall be studied. I wonder if the "shielding effect of the carbon cage" is not a little too vague. + +Reviewer #4 (Remarks to the Author): + +Overall, I am satisfied with the corrections the authors have made. I am not sure what they can learn from the EPR studies though. + +I don't understand why a carbon cage shields an EPR resonance. + +The lack of signal could actually tell us about a high symmetry at the U(V) site - If the symmetry is high enough at the \(\cup 5+\) site, then the lack of an epr signal can indicate that the ground state of the \(\cup 5+\) ion does not contain a \(\mathrm{Jz = + / - 1 / 2}\) component, g(perp) can be zero, and thus we get information about the ground state. See the C3v symmetric molecule in https://escholarship.org/uc/item/6v96t1kb + +Please could the authors discuss. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors have revised their manuscript and resubmitted. + +In the abstract the authors state that actinide diatomics are elusive and only studied in solid inert matices. They then go on to say they have a diatomic in a fullerene, but it is not a neutral diatomic, it carries a \(2+\) charge. This is then no different to a coordination complex with a (UN) \(2+\) coordinated by one or more ligands. In effect the fullerene is just another ligand (as highlighted by the analogy to Cp and arene binding). It is certainly not the same as a neutral diatomic in a matrix. Given that there are many coordination complexes with diatomic actinide units carrying a variety of charges, since being neutral is obviously not a defining caveat, then it is not objectively credible to say they are only studied in inert matices. The authors would have a case if the UN were neutral but it is not, they cannot then have their argument both ways. What this then reduces to is that this is the third class of terminal uranium nitride outside of inert matrices. + +## Response : + +(1) We intend to have it “both ways”, in fact. We agree that the interaction between U and fullerene cage can be considered as a kind of coordination, as we already wrote in the manuscript. However, this interaction is notably different from what we know from conventional coordination complexes. The encapsulated UN unit, analogous to many other endohedral fullerenes (Chem. Rev. 113, 5989–6113(2013); Chem. Commun., 55, 13000–13003(2019)), has a quite unique interaction with the fullerene cages and can rotate inside the cage at higher temperatures. It is a much ‘softer’ interaction than the coordination between other diatomic units and ligands. Given the strong back-donation from the fullerene cage identified in the computations, the charged species vs. neutral species distinction becomes much less defined than the Reviewer seems to think. Many previous studies, including some of ours, have shown that, due to the unique interactions between the encaged species and fullerene cages, bonding motifs which + +<--- Page Split ---> + +have never been observed in conventional coordination complexes can be stabilized inside fullerene cages, which indicates that the fullerene is not just another ligand (e.g., Nat. Commun. 9, 2753 (2018); J. Am. Chem. Soc. 141, 20249- 20260 (2019)). Thus, even if the system were considered to be a third class of terminal Uranium nitride, it is very different from the previously reported ones. Therefore, this does not undermine the novelty of this work. + +(2) The charged UN unit has similar bonding to the neutral UN, as we already discussed in the manuscript. + +(3) To differential the 'neutral' and 'charged' UN units and highlight the unique interaction between fullerene cage and UN unit, we modified the second sentence of the abstract as 'we report a charged U=N diatomic species captured in fullerene cages and stabilized by the unique U-fullerene coordination.' + +The authors concede the point that they cannot claim the shortest UN distance. Then they have amended the statement in the abstract to address that point and state that they amended the discussion to "avoid the statement of 'the shortest'". However, despite conceding the point around lines 153- 156 the authors persist in making shortest statements "Moreover, these UN bonds are shorter than most of the observed UN bond lengths for...". The first two examples are complexes with UN distances that overlap with the UN fullerene one by the 3sigma criteria. + +Response : To render the statement more precise, we revised the abovementioned text as' Moreover, these U=N bonds are relatively short compared to the observed U=N bond lengths for molecular compounds, such as..... + +The authors have provided a range of clarifying statements and extra analysis. I stated before that I was largely convinced of the formulations, details not withstanding, but my central concerns have not actually been resolved. The authors have made a system in incredibly low yield and quantities, there is limited analysis compared to other systems, in contrast to coordination complexes that are made on higher yields with + +<--- Page Split ---> + +much more analysis. The authors persist in claiming a shorter/shortest bond when they concede they should not, and they continue to push their novelty arguments too far. + +Response : We did not intent to state that the novelty of this work is the short/shortest U- N bond, which accordingly is not highlighted in the abstract and conclusion in the revised manuscript. Instead, what we would like to highlight is that such a simple diatomic species can be captured and stabilized inside fullerene cages, forming a new fullerene family with an encaged triple bond. This is a quite unique host- guest molecular structure and indeed unexpected for endohedral fullerene studies. From the perspective of actinide chemistry, the capture of this charged diatomic species in a stable molecular compound provides an unconventional way to study elusive \(\mathrm{Ac} \equiv \mathrm{E}\) bonds, not just limited to \(\mathrm{U} \equiv \mathrm{N}\) . We have tried to extend this paradigm to capture other currently elusive but fundamentally important actinide bonding motifs, i.e. \(\mathrm{U} \equiv \mathrm{C}\) , by the fullerene cages and preliminary results show that fullerene cages have similar stabilization effect on the elusive \(\mathrm{U} \equiv \mathrm{C}\) bonding motif. We have emphasized this point in the last sentence of abstract and conclusions. + +The technical clarifications are appreciated, but a central claim has been conceded and I do not see the novelty or new conceptual insight I expect in a Nature journal so I am unable to support publication here. + +Response : It is unfortunate that the Reviewer is so focused on the charged vs. neutral aspect. As already stated, we consider it inappropriate to lump the fullerene cage together with all other ligands, because it offers a unique environment for encapsulated species. + +Reviewer #2 (Remarks to the Author): + +From my point of view all is sorted out now and I recommend publication. + +<--- Page Split ---> + +Response : We thank the Reviewer for the positive evaluation of our work. + +Reviewer #3 (Remarks to the Author): + +The article of Chen et al. has been modified after the comments of 4 reviewers and most questions raised were answered. However, in several cases – and with different reviewers, the authors refrained from their original statement of a singular case of UN since many molecular UN features now exist. Thus, I prefer staying on my original statement, which would make this article worthy of publication but in a more specialized journal. + +Additionally, on two specific points that were addressed by the authors, I would have more comments: + +I am sorry, I am not sure I am satisfied with the answer of the authors on my original point on the different crystallographic positions of the metal center. I agree with the definition, which is made of a disorder as it “reflects the different conformations of the molecule with small energy barriers” but yet the other configuration is still present and thus shall be discussed. Even if the position is “fixed”, meaning that the ellipsoid is of fair size, the second configuration, although minor, should be considered. I understand that the major is the shortest UN distance but then all following characterization, especially Raman (see comments of Reviewers 1 and 2) should point to both configurations with two distinct UN sets of bands. Is it the case? Although it is a common method used in this peculiar chemistry, I wonder how one can just ignore an existing configuration. + +Response: We thank the reviewer for this suggestion. To address the other configurations corresponds to the minor U sites, in the revised manuscript, we added “On the other hand, the U- N distances in the other configuration corresponding to its minor U sites are 1.681(7)- 1.820(9) Å (U2 (0.1903), U3 (0.1087) and U4 (0.0566) + +<--- Page Split ---> + +for UN@ \(C_{s}(6) - C_{82}\) ) and 1.705(20) Å (U2 (0.188) for UN@ \(C_{2}(5) - C_{82}\) ) (Supplementary Fig. 4 and 6 and Supplementary Table 14- 15), all of which are within the bond length range of a U≡N triple bond. ” in the crystal analysis section. + +Thanks to the authors for attempting ERP spectroscopy. There are many reasons for having a silent EPR spectrum: the ligand field shall be studied. I wonder if the “shielding effect of the carbon cage” is not a little too vague. + +Response: This remark is also raised by Reviewer #4 (see below), who pointed us to check whether the silent EPR feature is due to a ground state Kramers doublet with \(\mathrm{g}_{\perp}\) \(= \mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . Analyzing in more detail the electronic structure of UN \(^{2 + }\) and UN isolated diatomics obtained from the wavefunction theory calculations, we can confirm that both systems exhibit GS Kramers doublets with axial \(\mathrm{g}\) tensor and \(\mathrm{g}_{\perp} = \mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . The main manuscript was amended with the following paragraph: “This behavior is supported by wavefunction theory (WFT) calculations (see Computational Details) on an isolated UN \(^{2 + }\) diatomic, \(d(\mathrm{U - N}) = 1.707 \mathrm{\AA}\) , which predict a \(j_{z} = 5 / 2\) ground state Kramers doublet (see Supplementary Table 17) characterized by an axial \(g\) tensor with \(\mathrm{g}_{\parallel} = \mathrm{g}_{z} = 4.19\) and \(\mathrm{g}_{\perp} = \mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . These values resemble those calculated for a UN \(^{2 + }\) diatomic with \(\mathrm{d}(\mathrm{U - N}) = 1.84 \mathrm{\AA}\) ( \(\mathrm{g}_{z} = 4.20\) , \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) ), and both are very close to the expected values for a \(|\mathrm{j}, \mathrm{j}_{z} > = |5 / 2, \pm 5 / 2>\) , namely \(\mathrm{g}_{z} = 4.29\) and \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . Similar WFT calculations for an isolated UN diatomic predicted a GS Kramers doublet with \(j_{z} = 7 / 2\) (see Supplementary Table 16) and axial \(\mathrm{g}\) tensor with \(\mathrm{g}_{z} = 3.99\) and \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) , which is an example case for a crystal field GS with \(l_{z} = \pm 5\) , \(s_{z} = \mp 3 / 2\) , and \(\mathrm{j}_{z} = \mp 5 / 2\) characterized by \(\mathrm{g}_{z} = 4.00\) and \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . Absence of EPR signals were also reported for \((\mathrm{MeC}_{5}\mathrm{H}_{4})_{3}\mathrm{UNR}\) compounds where the local \(\mathrm{C}_{3\mathrm{v}}\) symmetry around the metal center renders nil values for \(\mathrm{g}_{\mathrm{x}}\) and \(\mathrm{g}_{\mathrm{y}}\) .” + +Reviewer #4 (Remarks to the Author): + +<--- Page Split ---> + +Overall, I am satisfied with the corrections the authors have made. I am not sure what they can learn from the EPR studies though. + +I don't understand why a carbon cage shields an EPR resonance. The lack of signal could actually tell us about a high symmetry at the U(V) site – If the symmetry is high enough at the U5+ site, then the lack of an epr signal can indicate that the ground state of the U5+ ion does not contain a \(\mathrm{Jz} = + / - 1 / 2\) component, g(perp) can be zero, and thus we get information about the ground state. See the C3v symmetric molecule in https://escholarship.org/uc/item/6v96t1kb + +Please could the authors discuss. + +Response: The reviewer is correct! Please see our response to the last remark of Reviewer #3. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have presented a revised manuscript. Ignoring shifting priority claims and judging the manuscript in isolation my assessment is that in its current form it is much improved and now strikes the right balance being more precisely worded. It's unfortunate that EPR data are not forthcoming, since they would resolve the fullerene ligand question one way or another since variance, or not, of the gz value from 4.2 would clarify the 'ligand' effect. + +I have only one remaining question, which in the new portion of EPR text the authors state "These values resemble those calculated for a UN2+ diatomic with \(\mathsf{d}(\mathsf{U} - \mathsf{N}) = 1.84\mathsf{\AA}\) (gz = 4.20, gx = gy = 0),". What are they referring to, a prior study? + +Reviewer #2 (Remarks to the Author): + +After carefully reading and considering the comments of the other reviewers, I recommend publication in a more specialized journal. + +Reviewer #3 (Remarks to the Author): + +I sincerely appreciate the efforts made by the authors to answer all my technical comments during this review process. Although I am satisfied with these, I am still finding that the work presented herein is not suitable for Nature Communications because I don't see the findings of exceptional novelty. As stated in my two previous reviews, I'll find the work more suitable for a more specialized journal. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors have presented a revised manuscript. Ignoring shifting priority claims and judging the manuscript in isolation my assessment is that in its current form it is much improved and now strikes the right balance being more precisely worded. It's unfortunate that EPR data are not forthcoming, since they would resolve the fullerene ligand question one way or another since variance, or not, of the gz value from 4.2 would clarify the 'ligand' effect. + +I have only one remaining question, which in the new portion of EPR text the authors state "These values resemble those calculated for a UN2+ diatomic with \(\mathrm{d(U - N)} = 1.84\) \(\mathrm{\AA} (\mathrm{gz} = 4.20, \mathrm{gx} = \mathrm{gy} = 0)\) ." What are they referring to, a prior study? + +Response: We thank the reviewer for this question. Here we missed a citation and have added it in the corresponding text (Nat. Commun. 7, 13773 (2016)). It has been cited elsewhere as ref. 22. For details please see the revised manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/53b312065a46a22c9efb5be896a397d500703899f16c61630ebab85e62a61df4/supplementary_0_Peer Review File - updated/supplementary_0_Peer Review File - updated_det.mmd b/peer_reviews/53b312065a46a22c9efb5be896a397d500703899f16c61630ebab85e62a61df4/supplementary_0_Peer Review File - updated/supplementary_0_Peer Review File - updated_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..14f44d4c585e4c96f86f92d33407ccf7200100d2 --- /dev/null +++ b/peer_reviews/53b312065a46a22c9efb5be896a397d500703899f16c61630ebab85e62a61df4/supplementary_0_Peer Review File - updated/supplementary_0_Peer Review File - updated_det.mmd @@ -0,0 +1,988 @@ +<|ref|>title<|/ref|><|det|>[[60, 38, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[67, 110, 362, 138]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[133, 154, 923, 210]]<|/det|> +A charged diatomic triple- bonded U=N species trapped in C82 fullerene cages + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[122, 47, 743, 61]]<|/det|> +EDITORIAL NOTE: Parts of this peer review file have been redacted at the author's request. + +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 312, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 112, 402, 127]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 142, 864, 202]]<|/det|> +The authors report on the synthesis of two UN@C82 isomers. The compounds are characterized by X- ray diffraction, optical, Raman, and quantum chemical calculations. The techniques have been done competently. The computational analysis is excellent, and most of the experimental analysis is well done, except a fairly important point below. References are appropriate. + +<|ref|>text<|/ref|><|det|>[[118, 216, 871, 305]]<|/det|> +The authors have demonstrated some considerable synthetic skill to make these systems. But in the end from grams of starting materials and 800 carbon rods they isolate 0.2 mg of the title complexes (each or total I was not entirely clear on). Isolating UN inside these fullerenes is neat, but it has to be acknowledged that the incredibly low yields and scale, which limits the number of techniques that can be brought to bear, very much degrades the impact of this work, especially when isolable molecular analogs have been made on gram scales. + +<|ref|>text<|/ref|><|det|>[[118, 319, 871, 438]]<|/det|> +So it is then a reasonable question to ask what the novelty is given it is arguably easier to make regular coordination complexes since they can be made on gram scales and examined fully with a wider range of techniques than here. The authors make a variety of claims or novelty statements, but not many stand up to scrutiny, in particular the shortest UN distance claim is factually incorrect (see below). As I read through the computational analysis whilst I thought that it was a professional write- up I did not come across a new electronic structure for UN. The orbitals all look to be arranged very much as has been shown elsewhere before, comparison to which seems to be missing from the UN bonding discussion - sure some \(\%\) shift around but it all looks very similar to me. + +<|ref|>text<|/ref|><|det|>[[118, 452, 875, 556]]<|/det|> +This is a really nice and mostly solid study in many regards, but I was left with the impression that using a synthetically arduous approach the authors made a system that looks largely the same as already reported UN bonds and were unable to characterize it as much as in other studies because of the sub- mg yields. If there were no regular coordination complexes of UN then I would say this would be an advance over inert gas matrices, but that is not the case, so I do not see the novelty or new conceptual insight that I'd expect to see in a Nature family journal. I therefore have to conclude that I am unable to support publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[119, 570, 534, 585]]<|/det|> +Specific issues to address before publication anywhere: + +<|ref|>text<|/ref|><|det|>[[120, 599, 864, 629]]<|/det|> +The first sentence of the abstract is ambiguous. It can be read as the authors saying that all actinide multiple bonds are elusive and only found in gas matrices, which is clearly not the case. + +<|ref|>text<|/ref|><|det|>[[119, 643, 866, 688]]<|/det|> +The second sentence of the abstract is worded poorly as it says that UN is unpredented, but it would seem that Andrews has isolated it in gas matrices - the authors then go on to contradict themselves (line 69) by acknowledging the work of Andrews. + +<|ref|>text<|/ref|><|det|>[[118, 702, 870, 732]]<|/det|> +The penultimate sentence of the abstract is not worded precisely enough so could be debated. There are around 20 UN triple bonds now, is that still rare? + +<|ref|>text<|/ref|><|det|>[[118, 746, 839, 776]]<|/det|> +The last sentence is imprecise, since it implies that a UN triple bond is still elusive, but they have been made. I don't think this is what the authors meant but it is how it reads. + +<|ref|>text<|/ref|><|det|>[[118, 791, 860, 821]]<|/det|> +Introduction, Cummins made U2C2, there are now many UNU, and Ephritkhine made UCN, so how can the authors refer to those linkages as unprecedented? + +<|ref|>text<|/ref|><|det|>[[118, 835, 538, 850]]<|/det|> +Line 65, TrenTIPSUN should be mentioned overtly here. + +<|ref|>text<|/ref|><|det|>[[115, 864, 864, 894]]<|/det|> +The authors use the phrase cluster a lot, the phrase 'diatomic cluster' is a contradiction in terms and is an inappropriate description. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 878, 247]]<|/det|> +Lines 133- 152, the authors present crystallographic bond metrics without standard uncertainties, which makes the values and statements associated with them meaningless, and in one case certainly factually incorrect. A bond distance is only fair game to refer to as shorter or longer than another bond distance if they do not overlap by the 3sigma rule. The UN distance they quote is 1.760 angstroms, undoubtedly short, however the UN distance of Mazzanti's complex is 1.769 angstroms, but her bond length has a standard uncertainty of 2, so her UN distance could be as small as 1.763 angstroms. In the 100 K cif file the UN distance is given as 1.760(9) angstroms, so the UN distance could be as long as 1.787 angstroms (it could also be shorter but that is not the point here), which also falls within the lower range of Liddle's uranium +6 nitride (1.778- 1.820 angstroms by 3sigma). So the author's and Mazzanti's UN distances are statistically indistinguishable, therefore the authors cannot lay claim to have the shortest UN bond characterized by crystallography. + +<|ref|>text<|/ref|><|det|>[[118, 260, 870, 364]]<|/det|> +Did the authors observe any absorptions characteristic of the uranium +5 oxidation state in the nIR region? Whilst I am mostly convinced that they have made UN@C82 I don't think the possibility of UO@C82 being present in variable proportions can be considered to be completely excluded given the extensive crystallographic disorder and [understandable] absence of magnetic data. The optical spectrum is really the only way of the data provided to probe if it is all uranium +5 or whether there is any +4 present but this key aspect is not covered in the discussion. This would not affect the computational analysis, but purity really is an issue when only making 0.2 mg. + +<|ref|>text<|/ref|><|det|>[[118, 377, 875, 421]]<|/det|> +Line 273, as written I found this confusing. The authors say the two optical spectra of the two UN fullerene isomers are different then seem to say this shows their electronic structures are the same. If the spectra are different their electronic structures are not the same. + +<|ref|>text<|/ref|><|det|>[[118, 435, 872, 480]]<|/det|> +Raman, what do the spectra look like above 600 cm- 1? The authors found the UN wagging mode but what about the UN stretch? I would expect this aspect to be probed and discussed as a bare minimum. + +<|ref|>text<|/ref|><|det|>[[118, 495, 872, 525]]<|/det|> +Line 400, delete fully, that is subjective and these compounds aren't fully characterized when thinking about the range of techniques available. + +<|ref|>text<|/ref|><|det|>[[118, 540, 833, 570]]<|/det|> +Lines 405- 407, the mistake of claiming the shortest UN distance is repeated, so then saying it is notably shorter is also incorrect. + +<|ref|>text<|/ref|><|det|>[[120, 598, 402, 613]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 628, 868, 672]]<|/det|> +The manuscript is very well written and easy to read. The Experimental part is good and state- of- the- art. I am no expert for quantum- chemical calculations but they look reasonable to me, especially the agreement of the observed and simulated Raman band positions is nice. + +<|ref|>text<|/ref|><|det|>[[118, 687, 875, 746]]<|/det|> +In my opinion the manuscript is unclear when it comes to the differentiation of the encaged species, if it is "UN", "UO", or "UC" as during the synthesis also a lot of O and C atoms have been present. Maybe the authors could explicitly state if/that the mass spectroscopic analysis is evidence enough to exclude UO and UC species? + +<|ref|>text<|/ref|><|det|>[[118, 747, 864, 806]]<|/det|> +For the mass specs I miss simulations, especially for the isotopic distributions (13C, ...) and if the resolution was high enough to discriminate the species. With some many C atoms the 13C signal should superpose with the one from 12C, a high- res MS should however be able to discriminate the species. The authors should comment on this. + +<|ref|>text<|/ref|><|det|>[[118, 807, 866, 837]]<|/det|> +Regarding the crystal structures: That the N atom is completely ordered and the heavy U atom not is peculiar? Is that really plausible? Are there proofer examples for such a observation? + +<|ref|>text<|/ref|><|det|>[[118, 837, 490, 851]]<|/det|> +Is there no O/C/N mixed site occupancy possible? + +<|ref|>text<|/ref|><|det|>[[118, 851, 848, 880]]<|/det|> +Are the electron densities of the less occupied U atom positions similar to N/O/C electron density? The absolute densities should be given in the SI. + +<|ref|>text<|/ref|><|det|>[[118, 881, 864, 910]]<|/det|> +The authors should investigate and comment, if structure models in subgroup C2 give better results, i.e. resolution of the disorder by twinning. That would be something reasonable to expect for the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 83, 443, 97]]<|/det|> +models in C2/m and should be commented. + +<|ref|>text<|/ref|><|det|>[[119, 112, 877, 172]]<|/det|> +All bond lengths and atom distances in the manuscript and the SI should be reported with their respective standard uncertainties as only these will allow for a proper comparison with other species, especially when it comes to the discussion of the UN bond lengths and its comparison with compounds from the literature. + +<|ref|>text<|/ref|><|det|>[[118, 186, 872, 215]]<|/det|> +The U- N bond length is a value that is surely biased by the disorder and should only be used with the necessary care. + +<|ref|>text<|/ref|><|det|>[[118, 216, 870, 245]]<|/det|> +How far is the residual electron density away from the U atom? Can it be clearly discriminated from a N atom? + +<|ref|>text<|/ref|><|det|>[[118, 260, 864, 290]]<|/det|> +Where would one expect the UN stretch vibration? These should be given. Can an isotope effect be observed? + +<|ref|>text<|/ref|><|det|>[[118, 290, 870, 320]]<|/det|> +The observed and calculated Raman bands should be assigned more clearly in the manuscript as well as in the SI as the arrows in Supp. Fig. 22 and 23 are simply to small. + +<|ref|>text<|/ref|><|det|>[[118, 320, 875, 349]]<|/det|> +Discrimination from UO and UC species: Where would those show bands? Have the respective UO and UC species been calculated? + +<|ref|>text<|/ref|><|det|>[[118, 378, 875, 408]]<|/det|> +Overall, I recommend revision of the manuscript. I think that if the issues can be sorted out it would be a fine contribution. + +<|ref|>text<|/ref|><|det|>[[120, 481, 402, 495]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 510, 875, 686]]<|/det|> +In this article, Chen presents a UN triple bond captured inside fullerene cages. The isolation of uranium nitride species is of great importance because this material has been proposed as possible uranium- based nuclear fuel. Understanding, the fundamentals of its bonding is thus rather useful. The results presented in this article are interesting but I disagree with most comments on the fact that they are unique opportunities to study the UN bond. Coordination compounds are now known and accessible on a larger scale, which allowed various characterization and computations. This article is following with a new type of UN terminal bond since I would argue that the U coordination to the fullerene mimics well what is observed with a classical coordination compound. If most characterizations are fair (see below), the technique only provides crystals and the compounds remain rather elusive. Considering that molecular compounds with similar bonding exist, I would state that this study merits publication in a more specialized journal provided that my few technical comments are sorted out. + +<|ref|>text<|/ref|><|det|>[[118, 701, 864, 790]]<|/det|> +1. The crystallographic disorder is large and the esd on the distance must be large as well. I have seen no mention of esd in the main text or SI. I would argue that Table S14 and the R1/wR2 give an idea of the large esd that should be associated with these distances. Without these esd comparing distances is pointless, especially if the authors want to convince us that the UN bond of this work is the shortest one reported to date! On this matter, I would be very cautious since the molecular UN bond distances are very close to that one if not identical. + +<|ref|>text<|/ref|><|det|>[[118, 805, 872, 849]]<|/det|> +2. Both crystallographic positions of the U are true. The fact that there is a minor one does not mean the distance argument can only be made from the major one. An average would be more accurate for the discussion. + +<|ref|>text<|/ref|><|det|>[[118, 864, 855, 908]]<|/det|> +3. I would agree with the authors with the hypothesis stating that UN species are formed during the arc discharging process but not that it can be related to similar distances observed in unstable gas molecules, this is too speculative. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 97, 839, 142]]<|/det|> +4. The strong interaction of U with the C-skeleton of the fullerene is shown by the calculated spin doublet ground-state being the most stable one. Would it be possible to confirm this by EPR spectroscopy? Since the EPR is a sensitive technique, few crystals should be enough. + +<|ref|>text<|/ref|><|det|>[[118, 156, 820, 172]]<|/det|> +5. The VT-XRD studies are nice and interesting but do not bring much to the bonding analysis. + +<|ref|>text<|/ref|><|det|>[[118, 185, 864, 201]]<|/det|> +6. The UV-Vis-NIR data is provided without informing the reader of the nature of the bands reported. + +<|ref|>text<|/ref|><|det|>[[118, 215, 864, 245]]<|/det|> +7. I wonder if the use of the term somewhat twice to define the UN bonding nature is not too much. I would say, the bond is polarized. How does it compare with molecular coordination compounds? + +<|ref|>text<|/ref|><|det|>[[118, 259, 876, 319]]<|/det|> +8. The comparison of the NU and UN2- electronic structure by ab initio methods is also interesting but the conclusion of this interesting comparison full of information is elaborated, neither in the conclusion nor in the discussion. Were these computations done only to mention that WFT and DFT produce similar results? Could these be gathered and compared on a table? + +<|ref|>text<|/ref|><|det|>[[120, 348, 402, 363]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 377, 875, 421]]<|/det|> +This is another paper in the series of the synthesis of clusterfullerenes containing simple, and now characterizable, f-block diatomics with multiple metal-element bonding. This time UEN in two different fullerene symmetries. + +<|ref|>text<|/ref|><|det|>[[118, 421, 872, 465]]<|/det|> +The driver for the work is understanding covalent bonding with the 5f and 6d orbitals in An- ligand multiple bonds. The authors are able to slow the rotation of the diatom at low temperatures, enabling them to achieve this aim, since they can quantify the contributions of the C cage. + +<|ref|>text<|/ref|><|det|>[[118, 465, 877, 524]]<|/det|> +The very short 1.760 Å UN bond is the same as the UO bond in the simplest U(VI) uranyl complexes, yet this is U(V). I think this comparison is worthy of comment. In addition to this, there is a list of points to address below. The most important being to present fully the characterizing data for the compounds. + +<|ref|>text<|/ref|><|det|>[[118, 539, 787, 555]]<|/det|> +I think this is a really elegant piece of work and look forward to reading the finished article. + +<|ref|>text<|/ref|><|det|>[[120, 585, 410, 599]]<|/det|> +Other, more detailed points to address: + +<|ref|>text<|/ref|><|det|>[[118, 600, 585, 614]]<|/det|> +1. Line 42- describe more carefully stable with respect to what. + +<|ref|>text<|/ref|><|det|>[[118, 615, 870, 673]]<|/det|> +2. Line 104. Describe the physical nature of the products. Yield. Colour (I assume they're black or very dark brown). Air-sensitivity? Include more characterizing data here, especially the Raman spec.. The synthetic description in the SI should contain pictures of the Raman spectra and as full synthetic details as the authors can manage. + +<|ref|>text<|/ref|><|det|>[[118, 674, 872, 761]]<|/det|> +3. Line 106. Please explain the reason for co-crystallization with Ni(OEP). I would also like to see use of spectroscopic characterizing data (Raman spec.?) that confirms the electronic structure of the fullerene complex is not disturbed by the presence of the Ni complex. It is known from magnetic studies that the magnetic field of paramagnetic f-block complexes can easily extend 20 Å through space. Maybe the Ni complex is actually useful in isolating the U spins from each other to give better data? Some of this should/could also go in the SI. + +<|ref|>text<|/ref|><|det|>[[118, 761, 655, 775]]<|/det|> +4. Line 133. All the bonds discussed in the paragraph should have esds. + +<|ref|>text<|/ref|><|det|>[[118, 776, 820, 805]]<|/det|> +5. Line 152. I don't understand the link between a bond length in an isolated molecule and the mechanism by which it was made. + +<|ref|>text<|/ref|><|det|>[[118, 806, 866, 880]]<|/det|> +6. Line 212. The contributions from the cage are clearly very important in stabilising, ligating, the U; this should be emphasized in the abstract. Here also, draw comparisons on U-C distances with literature organometallics U-C5 and U-C6 systems, ideally with U in the same formal oxidation state for comparison. For example U(IV) Cp4 https://www.degruyter.com/document/doi/10.1515/znb-1962-0410/html and U(IV) arene in https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.1c03365. + +<|ref|>text<|/ref|><|det|>[[118, 880, 666, 894]]<|/det|> +7. Line 238. I'm not sure the retention of order of the NiOEP is interesting. + +<|ref|>text<|/ref|><|det|>[[115, 895, 875, 910]]<|/det|> +8. Line 242. Is it helpful to describe the N atom as stationary and U as disordered? The description on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 875, 118]]<|/det|> +252 is more useful, as there is still significant order in the U's position, and the cage bonding9. Line 293. Please define the ratio of d:f in this orbital. How does it compare to the other U-E multiple bonds? + +<|ref|>text<|/ref|><|det|>[[117, 127, 870, 160]]<|/det|> +10. Line 313 5f rather than 6d backdonation? Again, please compare the size of the U contributions (4-10 %) to that found in other uranium organometallics such as the Cp and COT sandwiches. + +<|ref|>text<|/ref|><|det|>[[117, 160, 875, 204]]<|/det|> +11. Line 354 – this is the first time that UC is described as having a genuine triple bond, which I agree with, but which also undermines the statements made in the introduction about the absence of U-E triple bonds in the literature. + +<|ref|>text<|/ref|><|det|>[[117, 203, 757, 219]]<|/det|> +12. Line 417 please replace 'spins' with a more precise description, including the axis. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 87, 446, 104]]<|/det|> +## Response to reviewer's comments: + +<|ref|>text<|/ref|><|det|>[[149, 139, 460, 156]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 193, 852, 323]]<|/det|> +The authors report on the synthesis of two UN@C82 isomers. The compounds are characterized by X- ray diffraction, optical, Raman, and quantum chemical calculations. The techniques have been done competently. The computational analysis is excellent, and most of the experimental analysis is well done, except a fairly important point below. References are appropriate. + +<|ref|>text<|/ref|><|det|>[[147, 359, 853, 546]]<|/det|> +The authors have demonstrated some considerable synthetic skill to make these systems. But in the end from grams of starting materials and 800 carbon rods they isolate \(0.2\mathrm{mg}\) of the title complexes (each or total I was not entirely clear on). Isolating UN inside these fullerenes is neat, but it has to be acknowledged that the incredibly low yields and scale, which limits the number of techniques that can be brought to bear, very much degrades the impact of this work, especially when isolable molecular analogs have been made on gram scales. + +<|ref|>text<|/ref|><|det|>[[147, 582, 853, 851]]<|/det|> +So it is then a reasonable question to ask what the novelty is given it is arguably easier to make regular coordination complexes since they can be made on gram scales and examined fully with a wider range of techniques than here. The authors make a variety of claims or novelty statements, but not many stand up to scrutiny, in particular the shortest UN distance claim is factually incorrect (see below). As I read through the computational analysis whilst I thought that it was a professional write- up I did not come across a new electronic structure for UN. The orbitals all look to be arranged very much as has been shown elsewhere before, comparison to which seems to be missing from the UN bonding discussion - sure some \(\%\) shift around but it all looks very similar to me. + +<|ref|>text<|/ref|><|det|>[[147, 888, 848, 907]]<|/det|> +This is a really nice and mostly solid study in many regards, but I was left with the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 852, 275]]<|/det|> +impression that using a synthetically arduous approach the authors made a system that looks largely the same as already reported UN bonds and were unable to characterize it as much as in other studies because of the sub- mg yields. If there were no regular coordination complexes of UN then I would say this would be an advance over inert gas matrices, but that is not the case, so I do not see the novelty or new conceptual insight that I'd expect to see in a Nature family journal. I therefore have to conclude that I am unable to support publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[148, 312, 597, 330]]<|/det|> +Specific issues to address before publication anywhere: + +<|ref|>text<|/ref|><|det|>[[148, 366, 851, 440]]<|/det|> +1. The first sentence of the abstract is ambiguous. It can be read as the authors saying that all actinide multiple bonds are elusive and only found in gas matrices, which is clearly not the case. + +<|ref|>text<|/ref|><|det|>[[147, 450, 852, 635]]<|/det|> +Response: We thank the reviewer for the comments. In the first sentence, we in fact intend to imply that 'actinide diatomic molecules' rather than 'actinide multiple bonds' have only been found in the gas matrices. The original writing caused some confusion for the reviewer. Accordingly, we revised the first sentence as follows: 'Actinide diatomic molecules are ideal models to study elusive actinide multiple bonds, but most of these diatomic molecules have only been studied in solid inert gas matrices to date.' We hope this revised sentence can convey our point without confusion. + +<|ref|>text<|/ref|><|det|>[[147, 672, 851, 771]]<|/det|> +2. The second sentence of the abstract is worded poorly as it says that UN is unpredented, but it would seem that Andrews has isolated it in gas matrices - the authors then go on to contradict themselves (line 69) by acknowledging the work of Andrews. Response: We have deleted the word 'unprecedented'. + +<|ref|>text<|/ref|><|det|>[[147, 812, 851, 858]]<|/det|> +3. The penultimate sentence of the abstract is not worded precisely enough so could be debated. There are around 20 UN triple bonds now, is that still rare? + +<|ref|>text<|/ref|><|det|>[[148, 868, 505, 885]]<|/det|> +Response: We have deleted the word 'rare'. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 851, 163]]<|/det|> +4. The last sentence is imprecise, since it implies that a UN triple bond is still elusive, but they have been made. I don't think this is what the authors meant but it is how it reads. + +<|ref|>text<|/ref|><|det|>[[147, 172, 852, 332]]<|/det|> +Response: Here, we made this statement mainly referring to the other elusive and yet to be found multiple bonded species, i.e., \(\mathrm{U} \equiv \mathrm{C}\) . We thought this method could be utilized to stabilize them in the molecular compound. To address the reviewer's concern and make it clearer, we replaced this sentence with 'Ongoing studies are underway to extend the paradigm to capture other currently elusive but fundamentally important actinide bonding motifs, i.e., \(\mathrm{U} \equiv \mathrm{C}\) , by the fullerene cages.' + +<|ref|>text<|/ref|><|det|>[[147, 366, 851, 413]]<|/det|> +5. Introduction, Cummins made U2C2, there are now many UNU, and Ephritikhine made UCN, so how can the authors refer to those linkages as unprecedented? + +<|ref|>text<|/ref|><|det|>[[146, 420, 853, 832]]<|/det|> +Response: The \(\mathrm{U}_2\mathrm{C}_2\) and UCN in endohedral fullerenes, i.e., \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{78}\) , \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{80}\) and UCN@ \(\mathrm{C}_{82}\) have unique bonding structures. \(\mathrm{U}_2\mathrm{C}_2\) in \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{78}\) and \(\mathrm{U}_2\mathrm{C}_2@\mathrm{C}_{80}\) demonstrates a unique bonding motif with two U bridged by a \(\mathrm{C} \equiv \mathrm{C}\) triple bond (J. Am. Chem. Soc., 141, 20249- 20260 (2019)), which, to the best of our knowledge, has not been reported by Cummins (Dalton Trans., 39, 6632- 6634 (2010)). UCN in UCN@ \(\mathrm{C}_{82}\) features a triangular cluster configuration with \(\eta^2\) (side- on) coordination of U by a cyanide (J. Am. Chem. Soc., 143, 16226- 16234 (2021)), which is different from those reported by Ephrikhine (Dalton Trans., 44, 7727- 7742 (2015)). For UNU in \(\mathrm{C}_{80}\) , we agree that the bonding structures are not substantially different from the UNU reported before and should not be mentioned here. To make this introduction more accurate, we modified the corresponding text as follows: 'The encapsulated \(\mathrm{U}_2\mathrm{C}_2\) , which presents two U bridged by \(\mathrm{C} \equiv \mathrm{C}\) triple bond, and triangular UCN cluster, which features \(\eta^2\) (side- on) coordination of U by a cyanide, show novel bonding motifs for U, broadening our understanding of the bonding properties of the actinide elements.' For details please see the first paragraph of Introduction. + +<|ref|>text<|/ref|><|det|>[[147, 865, 632, 884]]<|/det|> +6. Line 65, TrenTIPsUN should be mentioned overtly here. + +<|ref|>text<|/ref|><|det|>[[147, 894, 850, 913]]<|/det|> +Response: We thank the reviewer for the kind suggestion. In the revised manuscript, in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 850, 135]]<|/det|> +Line 65, we have added a description of [UN(TrenTIPS)] (the second paragraph of Introduction). + +<|ref|>text<|/ref|><|det|>[[147, 172, 850, 219]]<|/det|> +7. The authors use the phrase cluster a lot, the phrase 'diatomic cluster' is a contradiction in terms and is an inappropriate description. + +<|ref|>text<|/ref|><|det|>[[147, 227, 852, 358]]<|/det|> +Response: In endohedral fullerene studies, these encapsulated species are commonly referred to as 'clusters', and clusterfullerenes specifically refer to fullerenes encapsulating species formed by two or more atoms. For details please see references (Chem. Rev. 113, 5989- 6113 (2013)). Here, to avoid disputes, we replaced 'diatomic cluster' with 'diatomic species' in the corresponding text. + +<|ref|>text<|/ref|><|det|>[[147, 394, 853, 748]]<|/det|> +8. Lines 133-152, the authors present crystallographic bond metrics without standard uncertainties, which makes the values and statements associated with them meaningless, and in one case certainly factually incorrect. A bond distance is only fair game to refer to as shorter or longer than another bond distance if they do not overlap by the 3sigma rule. The UN distance they quote is 1.760 angstroms, undoubtedly short, however the UN distance of Mazzanti's complex is 1.769 angstroms, but her bond length has a standard uncertainty of 2, so her UN distance could be as small as 1.763 angstroms. In the 100 K cif file the UN distance is given as 1.760(9) angstroms, so the UN distance could be as long as 1.787 angstroms (it could also be shorter but that is not the point here), which also falls within the lower range of Liddle's uranium +6 nitride (1.778-1.820 angstroms by 3sigma). So the author's and Mazzanti's UN distances are statistically indistinguishable, therefore the authors cannot lay claim to have the shortest UN bond characterized by crystallography. + +<|ref|>text<|/ref|><|det|>[[147, 755, 853, 913]]<|/det|> +Response: Many thanks to the reviewers for their corrections. In the revised manuscript, we have added standard uncertainties to the bond length and distances involved in the work. Considering standard uncertainties, the UN bond in UN@C82, as the reviewer pointed out, is still very short. However, compared to the UN bond in Mazzanti's complex, it is indeed true that we cannot determine that the UN bond in UN@C82 is the shortest. Thus, to avoid misstatement, we revised the corresponding text to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 88, 850, 164]]<|/det|> +' Crystallographic analysis reveals very short U- N bond lengths of 1.760(7) and 1.760(20) Å in UN@Cs(6)- C82 and UN@C2(5)- C82.' in the abstract and revised/deleted the corresponding discussion in the main text to avoid the statement of 'the shortest'. + +<|ref|>text<|/ref|><|det|>[[147, 199, 852, 413]]<|/det|> +9. Did the authors observe any absorptions characteristic of the uranium +5 oxidation state in the nIR region? Whilst I am mostly convinced that they have made UN@C82 I don't think the possibility of UO@C82 being present in variable proportions can be considered to be completely excluded given the extensive crystallographic disorder and [understandable] absence of magnetic data. The optical spectrum is really the only way of the data provided to probe if it is all uranium +5 or whether there is any +4 present but this key aspect is not covered in the discussion. This would not affect the computational analysis, but purity really is an issue when only making 0.2 mg. + +<|ref|>text<|/ref|><|det|>[[147, 421, 852, 720]]<|/det|> +Response: We have checked the literature and found that U(V) compounds usually have characteristic absorption bands at approximately 6700, 10000, and 12000 cm- 1 (Chem. Rev. 69, 657- 671 (1969); Inorg. Chem. 44, 6211- 6218 (2005); Nat. Commun. 12, 4832 (2021)). As shown in Response Fig. 1, we changed the horizontal coordinate of the UV- vis- NIR absorption spectrum to the wavenumber and could not find the corresponding characteristic peaks for U(V) compounds in the near- IR region of UN@C82. In fact, in the study of endohedral fullerenes, the characteristic absorption of the encaged metal ion is hardly visible in the absorption spectra because the absorption spectra of endohedral fullerenes are generally dominated by the \(\pi \rightarrow \pi^{*}\) excitation of their carbon cage \(\pi\) system, and the absorption of metals mostly overlap and become invisible. (Chem. Rev. 113, 5989- 6113 (2013)). + +<|ref|>text<|/ref|><|det|>[[147, 728, 852, 914]]<|/det|> +The UV- vis- NIR spectra in this work also assisted us in determining the cage structure of the two isomers and the electron transfer between the clusters and the carbon cage. Although we did not observe the absorptions characteristic of the uranium +5 oxidation state, by comparing the UV- vis- NIR spectra of UN@C82 with the previously reported TbCN@C82 (J. Am. Chem. Soc. 138, 14764- 14771(2016)), which is almost identical to those of UN@C82, we can deduce that the electron transfer between the cluster and carbon cages is the same in UN@C82 and TbCN@C82, i.e., both + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 135]]<|/det|> +are two- electron transfers, which also helps us determine that the formal oxidation state of U in UN@C \(_{82}\) is \(+5\) . + +<|ref|>image<|/ref|><|det|>[[200, 150, 785, 319]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 330, 850, 376]]<|/det|> +Response Fig. 1. (a) UV- vis- NIR spectra of UN@ \(C_{2}(5)\) - C \(_{82}\) (left) and UN@ \(C_{4}(6)\) - C \(_{82}\) (right) dissolved in CS \(_{2}\) . + +<|ref|>text<|/ref|><|det|>[[147, 403, 851, 506]]<|/det|> +On the other hand, the exclusion of the presence of UO@C \(_{82}\) in the sample was determined by high- resolution matrix- assisted laser desorption/ionization time- offlight (MALDI- TOF) mass spectrometry. Response Fig. 2 shows the theoretically calculated isotopic distributions of UN@C \(_{82}\) and UO@C \(_{82}\) . + +<|ref|>image<|/ref|><|det|>[[252, 516, 736, 683]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 700, 850, 745]]<|/det|> +Response Fig. 2. (a) Isotopic distribution of UN@C \(_{82}\) from theoretical simulations. (b) Isotopic distribution of UO@C \(_{82}\) from theoretical simulations. + +<|ref|>text<|/ref|><|det|>[[147, 774, 852, 905]]<|/det|> +In the separation processes of UN@ \(C_{4}(6)\) - C \(_{82}\) (Supplementary Fig. 1), the sixth stage of HPLC separation was performed by recycling on a Buckyprep column. In this HPLC profile of this stage, the fraction that contains UN@ \(C_{4}(6)\) - C \(_{82}\) is labelled in green (Response Fig. 3a). The mass spectra obtained from this fraction in front of the UN@ \(C_{4}(6)\) - C \(_{82}\) fraction are presented in Response Fig. 3b. In this mass spectrum, in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 275]]<|/det|> +addition to the mass signal of UN@ \(C_{s}(6) - C_{82}\) and other fullerenes, the isotopic distribution assigned to UO@ \(C_{82}\) (1237.951) can be clearly seen. This result suggests that UO@ \(C_{82}\) was also generated during the arcing process along with UN@ \(C_{82}\) . However, after further purification processes, the mass spectrum of the final purified sample (Supplementary Fig. 1- 2) only shows the isotopic distribution of UN@ \(C_{82}\) , and the peak of UO@ \(C_{82}\) (1237.951) is absent, which indicates that UO@ \(C_{82}\) has been successfully removed by recycling HPLC operations. + +<|ref|>image<|/ref|><|det|>[[145, 290, 844, 523]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 544, 852, 672]]<|/det|> +Response Fig. 3. (a) Partial magnification of the sixth step of chromatographic separation of UN@ \(C_{s}(6) - C_{82}\) . The fractions marked in green are UN@ \(C_{s}(6) - C_{82}\) . (b) Mass spectra of the previous fraction of UN@ \(C_{s}(6) - C_{82}\) (marked by the yellow box). The inset is an enlarged view of the mass spectra at the position marked by the blue box. The complete chromatographic separation is shown in Supplementary Fig. 1. + +<|ref|>text<|/ref|><|det|>[[147, 727, 852, 830]]<|/det|> +10. Line 273, as written I found this confusing. The authors say the two optical spectra of the two UN fullerene isomers are different then seem to say this shows their electronic structures are the same. If the spectra are different, their electronic structures are not the same. + +<|ref|>text<|/ref|><|det|>[[147, 840, 851, 913]]<|/det|> +Response: We thank the reviewers for pointing out the ambiguity in our presentation with respect to the absorption spectroscopic analysis. In fact, the two UN@ \(C_{82}\) isomers have different spectra because of their different isomeric cage structures. On the other + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 88, 853, 470]]<|/det|> +hand, both isomers have the same two- electron cluster- to- cage charge transfer. Accordingly, we revised \(\mathrm{^1UN@C_2(5) - C_{82}}\) shows a different absorption pattern with two well- defined peaks at 772 and \(1050\mathrm{nm}\) , resembling that of \(\mathrm{TbCN@C_2(5) - C_{82}}\) . This indicates similar isomeric and electronic structures, respectively, which are consistent with crystallographic assignments of their molecular structures and the computational results for \([\mathrm{UN}]^{2 + }@\mathrm{C_{82}}^{2 - }\) as 'On the other hand, \(\mathrm{UN@C_2(5) - C_{82}}\) shows a different absorption pattern from \(\mathrm{UN@C_5(6) - C_{82}}\) , with two well- defined peaks at 772 and \(1050\mathrm{nm}\) , but resembles that of \(\mathrm{TbCN@C_2(5) - C_{82}}\) . This indicates similar isomeric structures and electronic transfer between \(\mathrm{UN@C_2(5) - C_{82}}\) and \(\mathrm{TbCN@C_2(5) - C_{82}}\) and between \(\mathrm{UN@C_5(6) - C_{82}}\) and \(\mathrm{TbCN@C_5(6) - C_{82}}\) . These results are consistent with the computational results for \([\mathrm{UN}]^{2 + }@\mathrm{C_{82}}^{2 - }\) (both \(\mathrm{TbCN@C_2(5) - C_{82}}\) and \(\mathrm{TbCN@C_5(6) - C_{82}}\) have two electron cluster- to- cage electron transfer) and the crystallographic assignments of their different isomeric structures of \(\mathrm{C_2(5) - C_{82}}\) and \(\mathrm{C_5(6) - C_{82}}\) .' in the Spectroscopic Characterization of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 504, 851, 580]]<|/det|> +11. Raman, what do the spectra look like above \(600\mathrm{cm}^{-1}\) ? The authors found the UN wagging mode but what about the UN stretch? I would expect this aspect to be probed and discussed as a bare minimum. + +<|ref|>text<|/ref|><|det|>[[146, 588, 855, 860]]<|/det|> +Response: We thank the reviewer for the kind suggestion. Following this suggestion, we obtained the FTIR spectrum of one of the two \(\mathrm{UN@C_{82}}\) isomers, \(\mathrm{UN@C_2(5) - C_{82}}\) , and the experimental and simulated spectra are shown below in Response Fig. 4. The peak at \(924\mathrm{cm}^{-1}\) can be assigned to the stretching vibration of \(\mathrm{U} \equiv \mathrm{N}\) , which is close to the vibration of the \(\mathrm{U} \equiv \mathrm{N}\) triple bond in the FTIR spectrum of \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})][\mathrm{Na}(12\mathrm{C4})_2]\) at \(936\mathrm{cm}^{-1}\) (Science 337, 717- 720 (2012)). The spectrum above \(1000\mathrm{cm}^{-1}\) corresponds to the vibrations of the carbon cage, reproduced well by the theoretical calculation. We added the corresponding discussion of FTIR spectra and figures after the Raman section in the revised manuscript (Spectroscopic Characterizations and Supplementary Fig. 25). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[340, 85, 656, 288]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 294, 850, 366]]<|/det|> +
Response Fig. 4. (a) Observed and theoretically predicted vibrational features of UN@ \(C_2(5) - C_{82}\) . The lower curve (black) presents the observed infrared absorption (IR) spectrum vs. wavenumber from 1600 to \(600~\mathrm{cm^{-1}}\) , with quantum-chemical density-functional simulation upper (in blue).
+ +<|ref|>text<|/ref|><|det|>[[148, 402, 850, 450]]<|/det|> +12. Line 400, delete fully, that is subjective and these compounds aren't fully characterized when thinking about the range of techniques available. + +<|ref|>text<|/ref|><|det|>[[148, 459, 697, 478]]<|/det|> +Response: We have deleted this sentence in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 515, 850, 561]]<|/det|> +13. Lines 405-407, the mistake of claiming the shortest UN distance is repeated, so then saying it is notably shorter is also incorrect. + +<|ref|>text<|/ref|><|det|>[[147, 570, 851, 700]]<|/det|> +Response: We deleted 'The bond length of 1.760 Å is, to the best of our knowledge, the shortest U-N bond length, characterized by crystallography, notably shorter than those discovered in coordination compounds but comparable to the calculated bond lengths for gas-phase molecules previously studied by matrix isolation.' in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 766, 460, 783]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 820, 851, 895]]<|/det|> +The manuscript is very well written and easy to read. The Experimental part is good and state- of- the- art. I am no expert for quantum- chemical calculations but they look reasonable to me, especially the agreement of the observed and simulated Raman band + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 91, 285, 107]]<|/det|> +positions is nice. + +<|ref|>text<|/ref|><|det|>[[147, 144, 851, 217]]<|/det|> +1. In my opinion the manuscript is unclear when it comes to the differentiation of the encaged species, if it is "UN", "UO", or "UC" as during the synthesis also a lot of O and C atoms have been present. + +<|ref|>text<|/ref|><|det|>[[147, 228, 850, 274]]<|/det|> +Maybe the authors could explicitly state if/that the mass spectroscopic analysis is evidence enough to exclude UO and UC species? + +<|ref|>text<|/ref|><|det|>[[147, 283, 852, 441]]<|/det|> +Response: We did only give a brief discussion about the purification process and mass spectra of UN@C82, which did not elaborate them in detail. In fact, high- resolution mass spectra can unambiguously differentiate UN@C82, UO@C82 and UC@C82. UO@C82 was generated during the arcing process and was removed during the purification process. However, there is no evidence that UC@C82 was generated during the arcing process in this work. + +<|ref|>text<|/ref|><|det|>[[147, 450, 855, 496]]<|/det|> +Response Fig. 5 shows the theoretically calculated isotopic distributions of UC@C82, UN@C82 and UO@C82, which are distinguishable in the high- resolution mass spectra. + +<|ref|>image<|/ref|><|det|>[[147, 506, 843, 660]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 673, 851, 744]]<|/det|> +
Response Fig. 5. (a) Isotopic distribution of UC@C82 from theoretical simulations. (b) Isotopic distribution of UN@C82 from theoretical simulations. (c) Isotopic distribution of UO@C82 from theoretical simulations.
+ +<|ref|>text<|/ref|><|det|>[[148, 774, 850, 820]]<|/det|> +For UC@C82, the mass spectral signal of 1234.042 was not observed throughout the entire HPLC separation process. + +<|ref|>text<|/ref|><|det|>[[147, 830, 851, 904]]<|/det|> +For UO@C82, in the separation of UN@C4(6)- C82 (Supplementary Fig. 1), the sixth HPLC stage, which was performed on a Buckyprep column, the mass signal of UO@C82 can be observed in fraction 6- 1, while UN@C4(6)- C82 was found mainly in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 247]]<|/det|> +fraction 6- 2 labelled in green. As shown in Response Fig. 6, the isotopic distribution of 1237.951 can be assigned to \(\mathrm{UO@C_{82}}\) , which overlaps with a minor isotopic distribution of 1235.962, mass signal of \(\mathrm{UN@C_{s}(6) - C_{82}}\) . In addition, no mass signal of \(\mathrm{UO@C_{82}}\) was observed in any of the HPLC fractions after this separation process of \(\mathrm{UN@C_{2}(5) - C_{82}}\) (Supplementary Fig. 2), which indicates that \(\mathrm{UO@C_{82}}\) was removed in the fourth step (Buckyprep column recycling). + +<|ref|>image<|/ref|><|det|>[[147, 262, 844, 494]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 515, 852, 644]]<|/det|> +Response Fig. 6. (a) The HPLC profile of the sixth step of the \(\mathrm{UN@C_{s}(6) - C_{82}}\) chromatographic separation. The fractions marked in green mainly contain \(\mathrm{UN@C_{s}(6) - C_{82}}\) . (b) Mass spectra of fraction 6- 2. The inset is an enlarged view of the mass spectra at the position marked by the blue square. The complete chromatographic separation HPLC profiles and corresponding mass spectra are shown in Supplementary Fig. 2. + +<|ref|>text<|/ref|><|det|>[[147, 672, 852, 914]]<|/det|> +Accordingly, we revised the 'Synthesis and Isolation of \(\mathrm{UN@C_{s}(6) - C_{82}}\) and \(\mathrm{UN@C_{2}(5) - C_{82}}\) ' section and added the following sentences: 'It is noteworthy that \(\mathrm{UO@C_{82}}\) is also observed during the HPLC separation process, possibly due to the leak of air into the arcing chamber, but was removed during the purification processes (Supplementary Fig. 3a- b). The purity of the samples was confirmed by single peak HPLC chromatography. Furthermore, the high- resolution mass spectrum of the final purified sample also shows that the isotopic distribution of the samples obtained experimentally is consistent with the theoretical isotopic distribution of \(\mathrm{UN@C_{82}}\) , excluding the existence of \(\mathrm{UC@C_{82}}\) or \(\mathrm{UO@C_{82}}\) (see Supplementary Fig. 3c- d).' + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[166, 95, 828, 311]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[146, 330, 852, 460]]<|/det|> +Supplementary Fig. 3c- d. HPLC chromatograms of purified \(\mathrm{UN@C}_s(6)\) - \(\mathrm{C}_{82}\) and \(\mathrm{UN@C}_2(5)\) - \(\mathrm{C}_{82}\) . (c) \(\mathrm{UN@C}_s(6)\) - \(\mathrm{C}_{82}\) on a Buckyprep column and (d) \(\mathrm{UN@C}_2(5)\) - \(\mathrm{C}_{82}\) on a 5PBB column with toluene as the eluent. HPLC conditions, \(\lambda = 310 \mathrm{nm}\) ; flow rate, \(4 \mathrm{mL / min}\) . The insets show the positive- ion mode MALDI- TOF mass spectra and expansions of the corresponding experimental isotopic distributions of the compound in comparison with their calculated values. + +<|ref|>text<|/ref|><|det|>[[147, 495, 856, 599]]<|/det|> +2. For the mass specs I miss simulations, especially for the isotopic distributions (13C...) and if the resolution was high enough to discriminate the species. With some many C atoms the 13C signal should superpose with the one from 12C, a high-res MS should however be able to discriminate the species. The authors should comment on this. + +<|ref|>text<|/ref|><|det|>[[147, 607, 852, 682]]<|/det|> +Response: We thank the reviewer for the kind suggestion. As commented by the reviewer, in the mass spectrum of the \(\mathrm{UN@C}_{82}\) molecule, we observed the \(^{13}\mathrm{C}\) signal superposed with the signal from \(^{12}\mathrm{C}\) . + +<|ref|>image<|/ref|><|det|>[[337, 697, 660, 868]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[146, 877, 850, 894]]<|/det|> +
Response Fig. 7. Isotopic distribution of \(\mathrm{UN@C}_{82}\) from theoretical simulations and the masses
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 91, 450, 106]]<|/det|> +corresponding to the major isotopic peaks. + +<|ref|>text<|/ref|><|det|>[[147, 135, 852, 295]]<|/det|> +Response Fig. 7 shows the mass spectrum and data of the isotopic distribution of the theoretical calculated \(\mathrm{UN@C_{82}}\) . In the following discussion, only the isotopic distribution of C is considered, assuming that only \(^{238}\mathrm{U}\) and \(^{14}\mathrm{N}\) are in the molecule, to reduce the complexity of the discussion. We can see that the first distinct peak (near 1236) corresponds to \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{82}\) , and the subsequent peaks are \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{81}^{13}\mathrm{C}\) (near 1237), \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{80}^{13}\mathrm{C}_{2}\) (near 1238).... + +<|ref|>text<|/ref|><|det|>[[147, 302, 850, 350]]<|/det|> +The abundances of \(^{13}\mathrm{C}\) and \(^{12}\mathrm{C}\) in nature are \(98.93\%\) and \(1.07\%\) , respectively. Then, the probability of having only \(^{12}\mathrm{C}\) in \(\mathrm{UN@C_{82}}\) ( \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{82}\) ) is given as + +<|ref|>equation<|/ref|><|det|>[[426, 357, 570, 377]]<|/det|> +\[P_{1} = (0.9893)^{82}\] + +<|ref|>text<|/ref|><|det|>[[147, 384, 850, 431]]<|/det|> +The probability of having exactly one \(13\mathrm{C}\) atom in \(\mathrm{UN@C_{82}}\) ( \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{81}^{13}\mathrm{C}\) ) is therefore + +<|ref|>equation<|/ref|><|det|>[[360, 440, 635, 460]]<|/det|> +\[P_{2} = 82\times (0.9893)^{81}\times 0.0107\] + +<|ref|>text<|/ref|><|det|>[[167, 468, 410, 486]]<|/det|> +and the ratio \(\mathrm{P_2 / P_1}\) is given as + +<|ref|>equation<|/ref|><|det|>[[315, 490, 678, 530]]<|/det|> +\[\frac{P_2}{P_1} = \frac{82\times(0.9893)^{81}\times0.0107}{(0.9893)^{82}} = 0.8869\] + +<|ref|>text<|/ref|><|det|>[[146, 532, 853, 746]]<|/det|> +If the monoisotopic peak at 1236 assigned to \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{82}\) is regarded as \(100\%\) , the 1237 peak assigned to \(^{238}\mathrm{U}^{14}\mathrm{N}@^{12}\mathrm{C}_{81}^{13}\mathrm{C}\) will have \(88.69\%\) relative intensity. (Gross, J. H. In Mass Spectrometry: A Textbook; Gross, J. H., Ed.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2011; pp 67- 116. ) The relative intensity of the peak of \(\mathrm{UN@C_{82}}\) at 1237 is \(89\%\) , as shown in the above figure. If we consider the effect of the isotopes of U and N, the result should be corrected to \(89\%\) . The relative intensities of the peaks of other isotopic distributions of \(\mathrm{UN@C_{82}}\) can be calculated according to this method as well. + +<|ref|>text<|/ref|><|det|>[[147, 774, 850, 820]]<|/det|> +Response Table 1. Experimental and theoretical isotopic distribution of \(\mathrm{UN@C_{82}}\) and its relative intensity. + +<|ref|>table<|/ref|><|det|>[[147, 828, 852, 885]]<|/det|> + +
Isotopic distribution for UN@C82
Theoretical simulationUN@C2(5)-C82UN@C8(6)-C82
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 81, 852, 395]]<|/det|> + +
Neutral MassIntensitym/zIntensitym/zIntensity
1233.0450.73
1234.0450.65
1235.0450.28
1236.045100.001236.160939 (100.00%)1236.3347936 (100.00%)
1237.04589.001237.161818 (87.11%)1237.3346488 (81.75%)
1238.04539.151238.170335 (35.68%)1238.3382759 (34.76%)
1239.04511.341239.18039 (4.15%)1239.348602 (7.59%)
1240.0452.431240.34378 (0.98%)
1241.0450.41
1242.0450.06
+ +<|ref|>text<|/ref|><|det|>[[147, 416, 852, 548]]<|/det|> +As shown in Supplementary Fig. 1, the isotopic distribution of UN@C82 obtained by MALDI- TOF mass spectrometry is almost identical to that of the theoretical simulation. The values and relative intensities of each peak in the isotopic distributions of UN@ \(C_2(5) - C_{82}\) and UN@ \(C_4(6) - C_{82}\) are listed in Response Table 1. Thus, the purity of UN@ \(C_{82}\) can be determined by high- resolution mass spectrometry. + +<|ref|>text<|/ref|><|det|>[[147, 583, 851, 657]]<|/det|> +3. Regarding the crystal structures: That the N atom is completely ordered and the heavy U atom not is peculiar? Is that really plausible? Are there proof examples for such an observation? + +<|ref|>text<|/ref|><|det|>[[147, 666, 852, 852]]<|/det|> +Response: The problem of disordered metal sites is commonly reported in the studies of endohedral metallofullerenes. In the majority of nitride clusterfullerenes, the N atom of the nitride cluster is generally fully ordered and located in the center of the fullerene cage. In contrast, in many cases, the metal sites inside the carbon cage are disordered, which is partially caused by the thermal vibration and partially related to the interaction between the metal and the neighboring carbon- cage moiety (Chem. Rev. 113, 5989- 6113 (2013)). + +<|ref|>text<|/ref|><|det|>[[148, 862, 851, 908]]<|/det|> +The energy barriers of endohedral fullerenes with metal located near different carbon cage moieties are generally not high, and thus, the metal ions can overcome the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 303]]<|/det|> +energy barriers, resulting in the motion of the metal ion and disordered metal sides in different positions inside fullerene cages, as commonly seen in EMF crystals. However, in some cases, when the metal atoms have a strong enough interaction with a particular moiety of the carbon cage, the metal atoms can remain fully ordered. For example, in the crystal of \(\mathrm{Sc}_2@C_{2v}(4059) - \mathrm{C}_{66}\) , the two Sc atoms are fully ordered and located over the pair of doubly fused- pentagon moieties of the \(C_{2v}(4395) - C_{66}\) cage because the interaction between the Sc atoms and such a fused- pentagon moiety is much stronger than others (J. Am. Chem. Soc. 2014, 136, 21, 7611- 7614). + +<|ref|>text<|/ref|><|det|>[[147, 311, 853, 469]]<|/det|> +In this work, although the cages of \(\mathrm{UN}@C_2(5) - \mathrm{C}_{82}\) and \(\mathrm{UN}@C_4(6) - \mathrm{C}_{82}\) do not have fused- pentagon moieties, the major U sites show much higher occupancies than the other minor sites, suggesting that the U sites in these two cages are largely ordered and that the U ions and neighboring carbon cage moieties have relatively strong interactions. However, when temperatures increase, as we see in the VT- crystallography, U ions can overcome the energy barriers, and the U sites become disordered. + +<|ref|>text<|/ref|><|det|>[[147, 506, 576, 525]]<|/det|> +4. Is there no O/C/N mixed site occupancy possible? + +<|ref|>text<|/ref|><|det|>[[147, 533, 852, 664]]<|/det|> +Response: Indeed, it is difficult to distinguish the case of O/C/N mixed sites in the crystal. However, in this work, the possibility of the central O/C can be excluded by high- resolution mass spectrometry, and the purities of the two \(\mathrm{UN}@\mathrm{C}_{82}\) isomers have been confirmed by the single HPLC peak, as we have answered in detail in response to question 1. + +<|ref|>text<|/ref|><|det|>[[147, 700, 850, 746]]<|/det|> +5. Are the electron densities of the less occupied U atom positions similar to the N/O/C electron density? + +<|ref|>text<|/ref|><|det|>[[148, 755, 542, 774]]<|/det|> +The absolute densities should be given in the SI. + +<|ref|>text<|/ref|><|det|>[[147, 783, 852, 914]]<|/det|> +Response: (1) All studies thus far have shown that when clusters are embedded in the carbon cage, the nonmetallic atoms are located at the center of the carbon cage. Therefore, the low- occupancy sites close to the side of the carbon cage are reasonably determined to be disordered metal sites, as the metal ion needs to be close to cage carbon to maintain the interaction between them, which is essential to the stabilization + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 835, 108]]<|/det|> +of the endohedral fullerene molecular structure (Chem. Rev. 113, 5989- 6113 (2013)). + +<|ref|>text<|/ref|><|det|>[[147, 117, 852, 359]]<|/det|> +(2) We thank the reviewer for the suggestions. However, after careful analysis, we can only provide the absolute density of the U site with the lowest occupancy in the crystal of UN@ \(C_{s}(6) - C_{82}\) , i.e., U4 (0.0566), with an absolute density of 6.21. These data were added as a footnote to Supplementary Table S6. The reason for this is because the electron density of U is much heavier than those of N/O/C, and even the U4 site in the crystal of UN@ \(C_{s}(6) - C_{82}\) , with the lowest occupancy, is still heavier than a complete carbon atom (with an average density of \(\sim 3\) ). Thus, we could not provide the electron densities of the other U sites because when we removed these U sites, the structural model collapsed, and the refinement process was unable to converge. + +<|ref|>text<|/ref|><|det|>[[148, 367, 850, 413]]<|/det|> +The occupancies of all the U sites in the two crystals are shown in Response Table 2 for reference. + +<|ref|>table<|/ref|><|det|>[[255, 465, 739, 636]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[147, 441, 585, 460]]<|/det|> +Response Table 2. Metal site occupancy in UN@ \(C_{82}\) + +
UN@C2(5)-C82UN@C8(6)-C82
siteoccupancysiteoccupancy
U10.312U10.6442
U20.188U20.1903
U30.1087
U40.0566
+ +<|ref|>text<|/ref|><|det|>[[147, 669, 851, 743]]<|/det|> +6. The authors should investigate and comment, if structure models in subgroup C2 give better results, i.e., resolution of the disorder by twinning. That would be something reasonable to expect for the models in C2/m and should be commented. + +<|ref|>text<|/ref|><|det|>[[147, 752, 852, 911]]<|/det|> +Response: As we answered in response to question 3, the disorder of encapsulated metal is partially caused by the thermal vibration and partially related to the interaction between the metal and the neighboring carbon- cage moiety, instead of being caused by twinning. The space group of \(C2 / m\) is very commonly seen in the EMF- Ni(OEP) cocrystal system (Chem. Rev. 113, 5989- 6113 (2013)). The removal of the mirror to subgroup \(C_{2}\) does not help solve the disorder problem but instead increases the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 851, 191]]<|/det|> +difficulty of refining the structure. Therefore, it is more reasonable to solve and refine the crystal in the higher \(C2 / m\) space group, which is also the reason why the \(C2 / m\) space group, rather than \(C2\) , is much more commonly seen in the EMF- Ni(OEP) cocrystal system. + +<|ref|>text<|/ref|><|det|>[[147, 228, 851, 329]]<|/det|> +7. All bond lengths and atom distances in the manuscript and the SI should be reported with their respective standard uncertainties as only these will allow for a proper comparison with other species, especially when it comes to the discussion of the UN bond lengths and its comparison with compounds from the literature. + +<|ref|>text<|/ref|><|det|>[[147, 339, 851, 413]]<|/det|> +Response: We thank the reviewers for this suggestion. We have added the corresponding standard uncertainties to the bond lengths and atomic distances involved in this work. Please see the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 450, 850, 496]]<|/det|> +8. The U-N bond length is a value that is surely biased by the disorder and should only be used with the necessary care. + +<|ref|>text<|/ref|><|det|>[[147, 505, 850, 551]]<|/det|> +How far is the residual electron density away from the U atom? Can it be clearly discriminated from a N atom? + +<|ref|>text<|/ref|><|det|>[[147, 561, 852, 914]]<|/det|> +Response: We thank the reviewer for the kind suggestion. (1) As replied in point 3, in the crystal of endohedral fullerenes, the metal disorder is mainly related to the interaction between the metal and the neighboring carbon- cage moiety, especially when the crystal is measured at low temperature (Chem. Rev. 113, 5989- 6113 (2013)). Therefore, the metal disorder generally reflects different conformations of the molecule with small energy barriers. In this work, we focus on the major site because it represents the most stable conformation. Thus, we discuss the UN bond length with the major U site. In the process of solving the two crystals, we found that the major U sites are completely fixed and are little affected by the disordered sites. In addition to the determined U disordered sites with small atomic displacement parameters, we did not observe a large residual electron density around U and the central N, and the top ten residual electron densities are all distributed on the fullerene cage. Therefore, we think the U- N bond lengths determined by the major U sites are accurate for the most stable + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 850, 135]]<|/det|> +conformations of these two compounds. It is also a commonly accepted method in the studies of endohedral fullerenes. + +<|ref|>text<|/ref|><|det|>[[147, 145, 852, 303]]<|/det|> +(2) In this work, the U atom can be easily discriminated from the central N atom. In response to question 3, the metal atoms are located on one side of the carbon cage, while the nonmetal atoms are normally located at the center of the carbon cage. In addition to the determined U disordered sites with small atomic displacement parameters, we did not observe large residual electron density around U and the central N, and the top ten residual electron densities are all distributed on the fullerene cage. + +<|ref|>text<|/ref|><|det|>[[147, 339, 850, 385]]<|/det|> +9. Where would one expect the UN stretch vibration? These should be given. Can an isotope effect be observed? + +<|ref|>text<|/ref|><|det|>[[146, 394, 855, 664]]<|/det|> +Response: We thank the reviewer for the kind suggestion. Following this suggestion, we obtained the FTIR spectrum of one of the two UN@C82 isomers, UN@C2(5)- C82, and the experimental and simulated spectra are shown below in Response Fig. 8. The peak at \(924~\mathrm{cm^{-1}}\) can be assigned to the stretching vibration of \(\mathrm{U}\equiv \mathrm{N}\) , which is close to the vibration of the \(\mathrm{U}\equiv \mathrm{N}\) triple bond in the FTIR spectrum of \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})][\mathrm{Na}(12\mathrm{C4})_2]\) at \(936~\mathrm{cm^{-1}}\) (Science 337, 717- 720 (2012)). The spectrum above \(1000~\mathrm{cm^{-1}}\) corresponds to the vibrations of the carbon cage, reproduced well by the theoretical calculation. We added the corresponding discussion of FTIR spectra and figures after the Raman section in the revised manuscript (Spectroscopic Characterizations and Supplementary Fig. 25). + +<|ref|>image<|/ref|><|det|>[[343, 688, 655, 888]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 896, 848, 913]]<|/det|> +
Response Fig. 8. (a) Observed and theoretically predicted vibrational features of UN@C2(5)-C82.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 135]]<|/det|> +The lower curve (black) presents the observed infrared absorption (IR) spectrum vs. wavenumber from 1600 to \(600~\mathrm{cm^{- 1}}\) , with quantum- chemical density- functional simulation upper (in blue). + +<|ref|>text<|/ref|><|det|>[[147, 163, 852, 349]]<|/det|> +We note that in the previous report by Liddle et al., the \(^{15}\mathrm{N}\) isotope was used in the synthesis of \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})][\mathrm{Na}(12\mathrm{C4})_2]\) and \([\mathrm{UN}(\mathrm{Tren}^{\mathrm{TIPS}})]\) to study the isotopic effect of the vibrational band of the U- N triple bond, in which isotopic effects cause the peaks to shift to lower wavenumbers. (Science 337, 717- 720 (2012); Nat. Chem. 12, 962- 967 (2020)). However, in this work, we cannot expect the observation of a similar isotopic effect because we used regular \(^{14}\mathrm{N}_2\) in the synthesis of \(\mathrm{UN@C_{82}}\) . In addition, the very limited amount of sample also made it very difficult to observe such an isotopic effect. + +<|ref|>text<|/ref|><|det|>[[147, 384, 852, 543]]<|/det|> +10. The observed and calculated Raman bands should be assigned more clearly in the manuscript as well as in the SI as the arrows in Supp. Fig. 22 and 23 are simply to small. Response: We thank the reviewer for the kind suggestion. In the revised Supplementary Information, we have replaced Supp. Fig. 22 and 23 with improved figures, which hopefully will help the reader to better understand the Raman vibration modes in \(\mathrm{UN@C_{82}}\) . + +<|ref|>text<|/ref|><|det|>[[148, 580, 850, 626]]<|/det|> +11. Discrimination from UO and UC species: Where would those show bands? Have the respective UO and UC species been calculated? + +<|ref|>text<|/ref|><|det|>[[147, 636, 852, 792]]<|/det|> +Response: As we explained in our response to the reviewer's first question, the characterization of the fractions obtained by chromatographic separation by matrix- assisted laser desorption/ionization time- of- flight (MALDI- TOF) mass spectrometry allowed us to determine that we obtained \(\mathrm{UN@C_{82}}\) without the mixture of \(\mathrm{UO@C_{82}}\) and \(\mathrm{UC@C_{82}}\) , and therefore, we did not consider these substances in our theoretical calculations. + +<|ref|>text<|/ref|><|det|>[[147, 829, 850, 875]]<|/det|> +Overall, I recommend revision of the manuscript. I think that if the issues can be sorted out it would be a fine contribution. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 115, 460, 132]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 171, 852, 526]]<|/det|> +In this article, Chen presents a UN triple bond captured inside fullerene cages. The isolation of uranium nitride species is of great importance because this material has been proposed as possible uranium- based nuclear fuel. Understanding the fundamentals of its bonding is thus rather useful. The results presented in this article are interesting but I disagree with most comments on the fact that they are unique opportunities to study the UN bond. Coordination compounds are now known and accessible on a larger scale, which allowed various characterization and computations. This article is following with a new type of UN terminal bond since I would argue that the U coordination to the fullerene mimics well what is observed with a classical coordination compound. If most characterizations are fair (see below), the technique only provides crystals, and the compounds remain rather elusive. Considering that molecular compounds with similar bonding exist, I would state that this study merits publication in a more specialized journal provided that my few technical comments are sorted out. + +<|ref|>text<|/ref|><|det|>[[147, 560, 852, 747]]<|/det|> +1. The crystallographic disorder is large and the esd on the distance must be large as well. I have seen no mention of esd in the main text or SI. I would argue that Table S14 and the R1/wR2 give an idea of the large esd that should be associated with these distances. Without these esd comparing distances is pointless, especially if the authors want to convince us that the UN bond of this work is the shortest one reported to date! On this matter, I would be very cautious since the molecular UN bond distances are very close to that one if not identical. + +<|ref|>text<|/ref|><|det|>[[147, 756, 852, 886]]<|/det|> +Response: Many thanks to the reviewers for their corrections. In the revised manuscript, we have added standard uncertainties to the bond length reported in the work. In addition, to avoid misstatement, we have changed the expression 'shortest' to more precise 'one of the shortest bond lengths' or 'very short' for the description of the UN triple bond in the corresponding text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 163]]<|/det|> +2. Both crystallographic positions of the U are true. The fact that there is a minor one does not mean the distance argument can only be made from the major one. An average would be more accurate for the discussion. + +<|ref|>text<|/ref|><|det|>[[146, 172, 852, 636]]<|/det|> +Response: In the crystal of endohedral fullerenes, the metal disorder is mainly related to the interaction between the metal ions and the neighboring carbon- cage moieties, especially when the crystal is measured at low temperature (Chem. Rev. 113, 5989- 6113 (2013)). Therefore, the metal disorder generally reflects the different conformations of the molecule with small energy barriers. In this work, we focus on the major site because it represents the most stable conformation and thus show the UN bond using the major U site. In addition, in the process of solving the two crystals, we found that the major U sites are completely fixed and are little affected by the disordered sites. In addition, in addition to the determined U disordered sites with small atomic displacement parameters, we did not observe a large residual electron density around U and the central N, and the top ten residual electron densities are all distributed on the fullerene cage. Therefore, we believe that the U- N bond lengths determined by the major U sites are accurate for the most stable conformations of these two compounds. It is also a commonly accepted method in the studies of endohedral fullerenes (J. Am. Chem. Soc., 137, 10116- 10119 (2015), J. Am. Chem. Soc., 138, 13030- 13037 (2016), Nat Commun 5, 3568 (2014)). Nevertheless, we also add bond lengths measured with minor U sites in the SI. + +<|ref|>text<|/ref|><|det|>[[147, 672, 850, 746]]<|/det|> +3. I would agree with the authors with the hypothesis stating that UN species are formed during the arc discharging process but not that it can be related to similar distances observed in unstable gas molecules, this is too speculative. + +<|ref|>text<|/ref|><|det|>[[147, 755, 851, 885]]<|/det|> +Response: To address this concern, we deleted the corresponding text ‘The similarity of the bond lengths of encaged UN to those of isolated molecules might indicate that the isolated UN species were formed during the arc discharging process and then the nanocavity of the fullerene cage captured and stabilized them in the form of endohedral fullerenes.’ We hope in this way, we have deleted the speculative discussion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 191]]<|/det|> +4. The strong interaction of U with the C skeleton of the fullerene is shown by the calculated spin doublet ground state being the most stable one. Would it be possible to confirm this by EPR spectroscopy? Since the EPR is a sensitive technique, few crystals should be enough. + +<|ref|>text<|/ref|><|det|>[[147, 199, 853, 526]]<|/det|> +Response: We thank the reviewers for this suggestion. Following this suggestion, we carried out an EPR test of UN@C82 at low temperature. However, this attempt to further resolve the electronic structure using EPR spectroscopy was unsuccessful, as no clearly defined signal was observed even at 4 K. A similar situation occurred when we investigated the ESR signal corresponding to U(V) in our study of U2C@C80 (Nat. Commun. 9, 2753-2760). The reason for the absence of the EPR signal is yet to be understood. Nevertheless, we added the sentence 'Attempts to further resolve the electronic structure using EPR spectroscopy were unsuccessful, as no clearly defined signal was observed at 4 K (Supplementary Fig. 26). The ESR signal corresponding to U(V) was also not observed in U2C@C80, probably due to the shielding effect of the carbon cage.' in the section 'Spectroscopic Characterizations' as well as Supplementary Fig. 26 in the Supporting Information. + +<|ref|>image<|/ref|><|det|>[[339, 530, 668, 730]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 737, 850, 781]]<|/det|> +
Response Fig. 9. X-Band EPR spectrum of UN@C2(5)-C82. It is recorded in a toluene glass tube at 4 K and 10 K.
+ +<|ref|>text<|/ref|><|det|>[[147, 820, 850, 866]]<|/det|> +5. The VT-XRD studies are nice and interesting but do not bring much to the bonding analysis. + +<|ref|>text<|/ref|><|det|>[[147, 875, 850, 895]]<|/det|> +Response: It is true that the VT-XRD study did not help us to study the nature of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 88, 852, 444]]<|/det|> +UN triple bond, but variable- temperature XRD is a powerful tool to unravel the temperature- dependent dynamics of endohedral metallofullerenes in the crystal lattice. In this work, the VT- XRD study of UN@ \(C_{s}(6) - C_{82}\) revealed a rare phase transition process and thus gives important insight into the problem of disorder impeding metallofullerene crystallography. UN@ \(C_{82}\) is the simplest endohedral clusterfullerenes found to date, and its cluster contains only one UN triple bond. The VT- XRD study of UN@ \(C_{s}(6) - C_{82}\) and UN@ \(C_{2}(5) - C_{82}\) helped us to study the movement of the UN bonding motif within the carbon cage. The U ion appears to “rotate” around the Ni···N axis, thus making the movement of the UN cluster look like a spinning top with N atoms as the apex. Therefore, VT- XRD helped us recognize the temperature- dependent dynamics of UN@ \(C_{82}\) . However, the reviewer's comment made us realize that the VT- XRD maybe too extensive. Thus, in the revised manuscript, we deleted the discussion of the phase transition, which is not related to the bonding analysis. + +<|ref|>text<|/ref|><|det|>[[147, 477, 850, 524]]<|/det|> +6. The UV-Vis-NIR data is provided without informing the reader of the nature of the bands reported? + +<|ref|>text<|/ref|><|det|>[[146, 533, 853, 833]]<|/det|> +Response: We thank the reviewer for the kind suggestion. The absorption spectra of fullerene are dominated by the \(\pi \rightarrow \pi^{*}\) excitation of their carbon \(\pi\) - system. When the number of carbon atoms on the fullerene cage (e.g., \(C_{80}\) and \(C_{82}\) ) or the symmetry of the carbon cage (e.g., \(C_{s}(6) - C_{82}\) and \(C_{2}(5) - C_{82}\) in this work) changes, a change in the absorption spectrum can be clearly observed (Chem. Rev. 113, 5989-6113 (2013)). In this work, the absorption spectra obtained from experimental tests are consistent with those previously reported for \(\mathrm{TbCN@C_{82}}\) [REDACTED] (J. Am. Chem. Soc. 138, 14 764-14771 (2016))), suggesting that the carbon cage structures of the two UN@ \(C_{82}\) isomers are \(C_{s}(6) - C_{82}\) and \(C_{2}(5) - C_{82}\) , respectively. It can also be deduced that their electronic structures are similar to those of \(\mathrm{TbCN@C_{82}}\) , as clusters transfer two electron on to the carbon cage: [UN] \(^{2 + }@[C_{82}]^{2 - }\) . + +<|ref|>text<|/ref|><|det|>[[147, 841, 852, 944]]<|/det|> +Considering all this information, we did not carry out calculations on the electronic spectra. Nevertheless, following this comment, we added ‘The absorption features of the two isomers of UN@ \(C_{82}\) are dominated by the \(\pi \rightarrow \pi^{*}\) excitation of their carbon \(\pi\) - system, as commonly known for other reported endohedral fullerenes.’ in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 135]]<|/det|> +first paragraph of the 'Spectroscopic Characterizations' section. We hope in this way that the readers can better understand the nature of these absorption bands. + +<|ref|>text<|/ref|><|det|>[[147, 460, 851, 534]]<|/det|> +7. I wonder if the use of the term somewhat twice to define the UN bonding nature is not too much. I would say, the bond is polarized. How does it compare with molecular coordination compounds? + +<|ref|>text<|/ref|><|det|>[[147, 544, 850, 590]]<|/det|> +Response: We thank the reviewer for the kind suggestion. We revised the manuscript in lines 294 and 295 to avoid vague language. + +<|ref|>text<|/ref|><|det|>[[147, 598, 852, 839]]<|/det|> +For bond comparisons, there are works by Liddle with \(^{15}\mathrm{N}\) NMR (Nat Commun. 12, 5649(2021)), Hayton and some of us on the \(^{15}\mathrm{N}\) bonds with thorium (Chem. Sci., 12, 14383- 14388(2021), Chem. Sci., 10, 6431- 6436(2019)), and related systems that one of us studied with Hayton and Neidig with U- C bonds (Inorg. Chem. 60, 20, 15413- 15420(2021), Inorg. Chem. 60, 16, 12436- 12444(2021), Chem. Eur. J. 27, 5885(2021), Angew. Chem. Int. Ed. 59, 13586(2020), Angew. Chem. Int. Ed. 58, 10266(2019)). Comparing our system to what was reported in the literature in other complexes, the UN bond appears remarkably unpolarized. We have included a comment about it in the manuscript, along with relevant references. + +<|ref|>text<|/ref|><|det|>[[145, 876, 850, 895]]<|/det|> +8. The comparison of the NU and UN \(^{2 - }\) electronic structure by ab initio methods is also + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 191]]<|/det|> +interesting but the conclusion of this interesting comparison full of information is elaborated, neither in the conclusion nor in the discussion. Were these computations done only to mention that WFT and DFT produce similar results? Could these be gathered and compared on a table? + +<|ref|>text<|/ref|><|det|>[[147, 199, 853, 442]]<|/det|> +Response: The comparison of the electronic structure between UN and \(\mathrm{UN}^{2 - }\) by density functional theory (DFT) and ab initio wavefunction (WFT) was indeed performed to ensure that the results derived from the DFT calculations are reliable. We edited and clarified the text and moved most of the discussion of the WFT calculations to the Supporting Information because the additional WFT results appear to have distracted the Reviewer from the main message, which is that UN in the clusterfullerenes and in the gas phase unambiguously can be assigned a triple bond. The main results from the WFT calculations are reported in Figure 5 and the Tables that were moved to the SI, and therefore we deem it unnecessary to create an additional Table. + +<|ref|>text<|/ref|><|det|>[[148, 507, 460, 524]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 561, 854, 660]]<|/det|> +This is another paper in the series of the synthesis of clusterfullerenes containing simple, and now characterizable, f- block diatomics with multiple metal- element bonding. This time \(\mathrm{U} \equiv \mathrm{N}\) in two different fullerene symmetries. + +<|ref|>text<|/ref|><|det|>[[147, 643, 852, 747]]<|/det|> +The driver for the work is understanding covalent bonding with the 5f and 6d orbitals in An- ligand multiple bonds. The authors are able to slow the rotation of the diatom at low temperatures, enabling them to achieve this aim, since they can quantify the contributions of the C cage. + +<|ref|>text<|/ref|><|det|>[[147, 754, 852, 858]]<|/det|> +The very short 1.760 Å UN bond is the same as the UO bond in the simplest U(VI) uranyl complexes, yet this is U(V). I think this comparison is worthy of comment. In addition to this, there is a list of points to address below. The most important being to present fully the characterizing data for the compounds. + +<|ref|>text<|/ref|><|det|>[[147, 866, 850, 912]]<|/det|> +I think this is a really elegant piece of work and look forward to reading the finished article. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 852, 192]]<|/det|> +Response: We thank the reviewer for this comment. In the revised manuscript, we added the comment 'These short UN bonds are similar to the situation of the short UO bond in the simplest U(VI) uranyl complexes, such as \(\mathrm{U(VI)O_2(^{Bu}acnac)_2}\) which has a UO bond with bond length of 1.770(3) Å. + +<|ref|>text<|/ref|><|det|>[[148, 228, 462, 246]]<|/det|> +Other, more detailed points to address: + +<|ref|>text<|/ref|><|det|>[[148, 255, 660, 274]]<|/det|> +1. Line 42- describe more carefully stable with respect to what. + +<|ref|>text<|/ref|><|det|>[[147, 283, 852, 553]]<|/det|> +Response: We thank the reviewer for the kind suggestion. We have added a description of "stable" in Line 42. The corresponding sentence has been changed from 'Our recent studies showed that very diverse actinide clusters containing important new actinide bonding motifs can be formed and stabilized inside the fullerene cages and can thus be systematically characterized in the form of molecular compounds.' to 'Our recent studies showed that very diverse actinide clusters containing important new actinide bonding motifs can be formed and stabilized inside the fullerene cages by electron transfer between the cluster and carbon cage and by the U- fullerene coordination. They can thus be systematically characterized in the form of molecular compounds.' + +<|ref|>text<|/ref|><|det|>[[147, 606, 852, 905]]<|/det|> +2. Line 104. Describe the physical nature of the products. Yield. Colour (I assume they're black or very dark brown). Air sensitivity? Include more characterizing data here, especially the Raman spec. The synthetic description in the SI should contain pictures of the Raman spectra and as full synthetic details as the authors can manage. Response: We thank the reviewer for this kind suggestion. Accordingly, we added a detailed description of the physical nature of the products in SI (page 5) as follows: In total, 2.02 g of graphite powder and 1.58 g of \(\mathrm{U_3O_8}\) (molar ratio of \(\mathrm{C:U = 30:1}\) ) were packed in each rod. On average, ca. 40 mg of crude fullerene mixture per rod was obtained, and 800 carbon rods were vaporized in this work. After HPLC isolation and purification, ca. Purified \(\mathrm{UN@C_8(6) - C_{82}}\) and \(\mathrm{UN@C_2(5) - C_{82}}\) (0.2 mg) were obtained. The obtained samples show a brown color in toluene and carbon disulfide solutions, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 163]]<|/det|> +and the color in carbon disulfide is illustrated in Supplementary Fig. 20. The sample was stable in air, and no decomposition was detected after 3 months of storage in the air. + +<|ref|>text<|/ref|><|det|>[[147, 173, 850, 275]]<|/det|> +The Raman spectra of the samples can be seen in Supplementary Fig. 21a- b, and we have also added pictures (Supplementary Fig. 21f) of the morphology of the samples made during the Raman characterization, which we hope will help readers better understand our work. + +<|ref|>image<|/ref|><|det|>[[285, 303, 710, 530]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 562, 588, 579]]<|/det|> +Response Fig. 11. Shape of the sample during Raman testing. + +<|ref|>text<|/ref|><|det|>[[147, 606, 852, 793]]<|/det|> +3. Line 106. Please explain the reason for co-crystallization with Ni(OEP). I would also like to see use of spectroscopic characterizing data (Raman spec.?) that confirms the electronic structure of the fullerene complex is not disturbed by the presence of the Ni complex. It is known from magnetic studies that the magnetic field of paramagnetic f-block complexes can easily extend \(20 \mathrm{\AA}\) through space. Maybe the Ni complex is actually useful in isolating the U spins from each other to give better data? Some of this should/could also go in the SI. + +<|ref|>text<|/ref|><|det|>[[147, 802, 850, 904]]<|/det|> +Response: We thank the reviewer for the question. The reason for using Ni(OEP) for co- crystallization is to prevent the rotation of the fullerene cage, which has long been a great challenge for solving the crystal structures of these compounds. Ni(OEP), which has a noncovalent \(\pi - \pi\) interaction with endohedral fullerenes when forming a cocrystal, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 835, 108]]<|/det|> +was utilized in the crystal growth process to hinder the rotation of the fullerene cage. + +<|ref|>text<|/ref|><|det|>[[147, 116, 853, 527]]<|/det|> +Except for the single crystal characterization where Ni(OEP) is used as a eutectic agent, the rest of the characterizations in this work are all performed on the pristine UN@C \(_{82}\) molecule. Thus, there is no influence of Ni(OEP) on the determination of their electronic structures. In the revised manuscript, we also carried out an EPR test of UN@C \(_{82}\) at low temperature. However, this attempt to further resolve the electronic structure using EPR spectroscopy was unsuccessful, as no clearly defined signal was observed even at 4 K. A similar situation occurred when we investigated the ESR signal corresponding to U(V) in our study of U \(_{2}\) C@C \(_{80}\) (Nat. Commun. 9, 2753- 2760). The reason for the absence of the EPR signal is yet to be understood. Nevertheless, we added the sentence 'Attempts to further resolve the electronic structure using EPR spectroscopy were unsuccessful, as no clearly defined signal was observed at 4 K (Supplementary Fig. 26). The ESR signal corresponding to U(V) was also not observed in U \(_{2}\) C@C \(_{80}\) , probably due to the shielding effect of the carbon cage.' in the section 'Spectroscopic Characterizations' as well as Supplementary Fig. 26 in the Supporting Information. + +<|ref|>image<|/ref|><|det|>[[338, 530, 668, 730]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 738, 850, 782]]<|/det|> +
Response Fig. 12. X-Band EPR spectrum of UN@C \(_{2}(5)\) -C \(_{82}\) . It is recorded in a toluene glass tube at 4 K and 10 K.
+ +<|ref|>text<|/ref|><|det|>[[147, 820, 725, 839]]<|/det|> +4. Line 133. All the bonds discussed in the paragraph should have esds. + +<|ref|>text<|/ref|><|det|>[[147, 848, 850, 894]]<|/det|> +Response: We thank the reviewers for this suggestion. We have added the corresponding standard uncertainties to all the bond lengths reported in this work in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 92, 308, 107]]<|/det|> +revised manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 163, 850, 209]]<|/det|> +5. Line 152. I don't understand the link between a bond length in an isolated molecule and the mechanism by which it was made. + +<|ref|>text<|/ref|><|det|>[[147, 219, 851, 320]]<|/det|> +Response: We thank the reviewer for the comment. Reviewer 3 raised similar questions and pointed out that this link seems to be too speculative. Thus, to make a fact- based statement and remove the speculative mechanism, we deleted the speculative discussion about this link. + +<|ref|>text<|/ref|><|det|>[[147, 375, 852, 535]]<|/det|> +6. Line 212. The contributions from the cage are clearly very important in stabilising, ligating, the U; this should be emphasized in the abstract. Here also, draw comparisons on U-C distances with literature organometallics U-C5 and U-C6 systems, ideally with U in the same formal oxidation state for comparison. For example, U(IV) Cp4 https://www.degruyter.com/document/doi/10.1515/znb-1962-0410/html and U(IV) arene in https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.1c03365. + +<|ref|>text<|/ref|><|det|>[[147, 544, 853, 645]]<|/det|> +Response: We thank the reviewer for the kind suggestion. (1) Following this suggestion, we revised the second sentence of the abstract as follows: 'Herein, we report that the U \(\equiv\) N diatomic species captured in two different fullerene cages and stabilized by the U- fullerene coordination.' + +<|ref|>text<|/ref|><|det|>[[147, 655, 855, 873]]<|/det|> +(2) Following the reviewer's comments, we checked the relevant data for or g anometallic compounds of U(V). [REDACTED] In (CpiPr4)2U(μ-N)B(C6F5)3 (Chem. Commun. 56, 4535-4538 (2020)), the U-Cp distances are in the range of 2.723(3)- 2.830(3) Å, and the distances of U-Cp(cent) are 2.511(1) and 2.520(1) Å. In {U[η8- C8H6(1,4-Si(Pr)3)]Cp8)(NSiMe3)} [REDACTED] (J. Organomet. Chem. 857, 25-33 (2018)), the U-Cp distance is between 2.718(7)- 2.866(7), the U-COT distance is between 2.687(6)- 2.747(7) Å, and the distances of U-Cp(cent) are 2.500(1). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 412, 852, 600]]<|/det|> +The shortest U- \(C_{\mathrm{cage}}\) distances in UN@ \(C_{s}(6) - C_{82}\) and UN@ \(C_{2}(5) - C_{82}\) are 2.487(15) and 2.503(7) A, respectively, similar to the U- \(C_{\mathrm{p(cent)}}\) distances mentioned above. The distances between the metal and the six closest carbons on the fullerene cage are 2.478(15)- 2.861(22) A and 2.503(7)- 2.785(7) A, respectively, which are also close to the U- Cp distances in the abovementioned organometallic compounds. This indicates that the interaction between the fullerene cage and U is likely similar to the coordination between the metal and the cyclopentadienyl group in the organometallic compounds. + +<|ref|>text<|/ref|><|det|>[[148, 608, 850, 682]]<|/det|> +In the revised manuscript, we added a comparison with the metal- cyclopentadienyl ligand distances in organometallic compounds after the description of the metal- cage distances in the section 'Molecular and Electronic Structures of UN@ \(C_{82}\) '. + +<|ref|>text<|/ref|><|det|>[[148, 736, 756, 755]]<|/det|> +7. Line 238. I'm not sure the retention of order of the NiOEP is interesting. + +<|ref|>text<|/ref|><|det|>[[148, 765, 855, 839]]<|/det|> +Response: We thank the reviewer for the comments. We revised the sentence as follows: 'the \(\mathrm{Ni}^{\mathrm{II}}(\mathrm{OEP})\) molecule remained completely ordered as the temperature increased from 100 to 273 K' and deleted 'interestingly'. + +<|ref|>text<|/ref|><|det|>[[147, 894, 850, 913]]<|/det|> +8. Line 242. Is it helpful to describe the N atom as stationary and U as disordered? The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 850, 136]]<|/det|> +description on 252 is more useful, as there is still significant order in the U's position and the cage bonding. + +<|ref|>text<|/ref|><|det|>[[147, 145, 852, 275]]<|/det|> +Response: We thank the reviewer for this comment. In endohedral metallofullerenes, the nonmetallic atoms tend to be completely ordered, while the metal atoms in many cases are disordered. We note, however, that describing such a sentence here is not significantly helpful for the analysis of the data, so we have removed the corresponding text in Line 242 in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 329, 850, 375]]<|/det|> +9. Line 293. Please define the ratio of d:f in this orbital. How does it compare to the other U-E multiple bonds? + +<|ref|>text<|/ref|><|det|>[[147, 385, 852, 544]]<|/det|> +Response: We have added the corresponding ratio of d:f in the text, which was already defined in Figure 4. The d:f ratio is not discussed other than in the context of the selfcontained comparison of UN, UN(2+), and the UN clusterfullerenes, and it is not relevant for the bond order analysis provided in the manuscript. The same comment also applies to point 10. By the Reviewer. We added some context and references regarding the bond polarity in response to point 7 of Reviewer #3. + +<|ref|>text<|/ref|><|det|>[[148, 598, 850, 672]]<|/det|> +10. Line 313 5f rather than 6d backdonation? Again, please compare the size of the U contributions (4-10 %) to that found in other uranium organometallics such as the Cp and COT sandwiches. + +<|ref|>text<|/ref|><|det|>[[148, 683, 520, 700]]<|/det|> +Response: Please see our response to point 9. + +<|ref|>text<|/ref|><|det|>[[148, 755, 850, 829]]<|/det|> +11. Line 354 – this is the first time that UC is described as having a genuine triple bond, which I agree with, but which also undermines the statements made in the introduction about the absence of U-E triple bonds in the literature. + +<|ref|>text<|/ref|><|det|>[[148, 839, 850, 913]]<|/det|> +Response: We thank the reviewer for this comment. In the introduction we wrote: 'Covalent bonding with the 5f and 6d orbitals in actinide-ligand multiple bonds has been intensively studied, but remains incompletely understood both experimentally and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 853, 303]]<|/det|> +theoretically'. We assume that the reviewer is referring to this sentence. In this place, we intend to say that the U- E triple bond has been intensively studied but is not fully understood. Ref 60 (J. Am. Chem. Soc. 132, 8484- 8488 (2010)) is a combined spectroscopic and theoretical study of UC and CUC, in which the U- C was defined as a well- developed triple bond. However, this U- C triple band has never been discovered in the condensed- phase molecular compound to date. Thus, we think mentioning this work does not seem to contradict the description of the U- E triple bond, which has been intensively studied but is not fully understood. + +<|ref|>text<|/ref|><|det|>[[147, 375, 851, 479]]<|/det|> +12. Line 417 please replace 'spins' with a more precise description, including the axis. Response: We thank the reviewer for the kind suggestion. In the revised version, we revised "the UN spins inside the fullerene cages" to "UN is more mobile and rotates inside the fullerene cage" in the corresponding text. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 312, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 113, 402, 128]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[120, 142, 562, 157]]<|/det|> +The authors have revised their manuscript and resubmitted. + +<|ref|>text<|/ref|><|det|>[[118, 171, 868, 319]]<|/det|> +In the abstract the authors state that actinide diatomics are elusive and only studied in solid inert matices. They then go on to say they have a diatomic in a fullerene, but it is not a neutral diatomic, it carries a \(2+\) charge. This is then no different to a coordination complex with a \((\mathrm{UN})2+\) coordinated by one or more ligands. In effect the fullerene is just another ligand (as highlighted by the analogy to Cp and arene binding). It is certainly not the same as a neutral diatomic in a matrix. Given that there are many coordination complexes with diatomic actinide units carrying a variety of charges, since being neutral is obviously not a defining caveat, then it is not objectively credible to say they are only studied in inert matices. The authors would have a case if the UN were neutral but it is not, they cannot then have their argument both ways. What this then reduces to is that this is the third class of terminal uranium nitride outside of inert matrices. + +<|ref|>text<|/ref|><|det|>[[118, 333, 874, 422]]<|/det|> +The authors concede the point that they cannot claim the shortest UN distance. Then they have amended the statement in the abstract to address that point and state that they amended the discussion to "avoid the statement of 'the shortest'". However, despite conceding the point around lines 153- 156 the authors persist in making shortest statements "Moreover, these UN bonds are shorter than most of the observed UN bond lengths for...". The first two examples are complexes with UN distances that overlap with the UN fullerene one by the 3sigma criteria. + +<|ref|>text<|/ref|><|det|>[[118, 436, 876, 527]]<|/det|> +The authors have provided a range of clarifying statements and extra analysis. I stated before that I was largely convinced of the formulations, details not withstanding, but my central concerns have not actually been resolved. The authors have made a system in incredibly low yield and quantities, there is limited analysis compared to other systems, in contrast to coordination complexes that are made on higher yields with much more analysis. The authors persist in claiming a shorter/shortest bond when they concede they should not, and they continue to push their novelty arguments too far. + +<|ref|>text<|/ref|><|det|>[[118, 541, 863, 586]]<|/det|> +The technical clarifications are appreciated, but a central claim has been conceded and I do not see the novelty or new conceptual insight I expect in a Nature journal so I am unable to support publication here. + +<|ref|>text<|/ref|><|det|>[[120, 613, 402, 628]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[120, 643, 660, 658]]<|/det|> +From my point of view all is sorted out now and I recommend publication. + +<|ref|>text<|/ref|><|det|>[[120, 687, 402, 702]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 716, 878, 791]]<|/det|> +The article of Chen et al. has been modified after the comments of 4 reviewers and most questions raised were answered. However, in several cases - and with different reviewers, the authors refrained from their original statement of a singular case of UN since many molecular UN features now exist. Thus, I prefer staying on my original statement, which would make this article worthy of publication but in a more specialized journal. + +<|ref|>text<|/ref|><|det|>[[118, 805, 876, 821]]<|/det|> +Additionally, on two specific points that were addressed by the authors, I would have more comments: + +<|ref|>text<|/ref|><|det|>[[118, 834, 864, 909]]<|/det|> +I am sorry, I am not sure I am satisfied with the answer of the authors on my original point on the different crystallographic positions of the metal center. I agree with the definition, which is made of a disorder as it "reflects the different conformations of the molecule with small energy barriers" but yet the other configuration is still present and thus shall be discussed. Even if the position is "fixed", meaning that the ellipsoid is of fair size, the second configuration, although minor, should be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 841, 142]]<|/det|> +considered. I understand that the major is the shortest UN distance but then all following characterization, especially Raman (see comments of Reviewers 1 and 2) should point to both configurations with two distinct UN sets of bands. Is it the case? Although it is a common method used in this peculiar chemistry, I wonder how one can just ignore an existing configuration. + +<|ref|>text<|/ref|><|det|>[[118, 157, 870, 202]]<|/det|> +Thanks to the authors for attempting ERP spectroscopy. There are many reasons for having a silent EPR spectrum: the ligand field shall be studied. I wonder if the "shielding effect of the carbon cage" is not a little too vague. + +<|ref|>text<|/ref|><|det|>[[119, 231, 402, 245]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 260, 866, 291]]<|/det|> +Overall, I am satisfied with the corrections the authors have made. I am not sure what they can learn from the EPR studies though. + +<|ref|>text<|/ref|><|det|>[[118, 291, 608, 305]]<|/det|> +I don't understand why a carbon cage shields an EPR resonance. + +<|ref|>text<|/ref|><|det|>[[118, 306, 860, 385]]<|/det|> +The lack of signal could actually tell us about a high symmetry at the U(V) site - If the symmetry is high enough at the \(\cup 5+\) site, then the lack of an epr signal can indicate that the ground state of the \(\cup 5+\) ion does not contain a \(\mathrm{Jz = + / - 1 / 2}\) component, g(perp) can be zero, and thus we get information about the ground state. See the C3v symmetric molecule in https://escholarship.org/uc/item/6v96t1kb + +<|ref|>text<|/ref|><|det|>[[119, 380, 370, 393]]<|/det|> +Please could the authors discuss. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 460, 107]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 145, 628, 163]]<|/det|> +The authors have revised their manuscript and resubmitted. + +<|ref|>text<|/ref|><|det|>[[146, 199, 852, 525]]<|/det|> +In the abstract the authors state that actinide diatomics are elusive and only studied in solid inert matices. They then go on to say they have a diatomic in a fullerene, but it is not a neutral diatomic, it carries a \(2+\) charge. This is then no different to a coordination complex with a (UN) \(2+\) coordinated by one or more ligands. In effect the fullerene is just another ligand (as highlighted by the analogy to Cp and arene binding). It is certainly not the same as a neutral diatomic in a matrix. Given that there are many coordination complexes with diatomic actinide units carrying a variety of charges, since being neutral is obviously not a defining caveat, then it is not objectively credible to say they are only studied in inert matices. The authors would have a case if the UN were neutral but it is not, they cannot then have their argument both ways. What this then reduces to is that this is the third class of terminal uranium nitride outside of inert matrices. + +<|ref|>sub_title<|/ref|><|det|>[[148, 563, 248, 579]]<|/det|> +## Response : + +<|ref|>text<|/ref|><|det|>[[146, 588, 852, 914]]<|/det|> +(1) We intend to have it “both ways”, in fact. We agree that the interaction between U and fullerene cage can be considered as a kind of coordination, as we already wrote in the manuscript. However, this interaction is notably different from what we know from conventional coordination complexes. The encapsulated UN unit, analogous to many other endohedral fullerenes (Chem. Rev. 113, 5989–6113(2013); Chem. Commun., 55, 13000–13003(2019)), has a quite unique interaction with the fullerene cages and can rotate inside the cage at higher temperatures. It is a much ‘softer’ interaction than the coordination between other diatomic units and ligands. Given the strong back-donation from the fullerene cage identified in the computations, the charged species vs. neutral species distinction becomes much less defined than the Reviewer seems to think. Many previous studies, including some of ours, have shown that, due to the unique interactions between the encaged species and fullerene cages, bonding motifs which + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 852, 247]]<|/det|> +have never been observed in conventional coordination complexes can be stabilized inside fullerene cages, which indicates that the fullerene is not just another ligand (e.g., Nat. Commun. 9, 2753 (2018); J. Am. Chem. Soc. 141, 20249- 20260 (2019)). Thus, even if the system were considered to be a third class of terminal Uranium nitride, it is very different from the previously reported ones. Therefore, this does not undermine the novelty of this work. + +<|ref|>text<|/ref|><|det|>[[147, 256, 850, 303]]<|/det|> +(2) The charged UN unit has similar bonding to the neutral UN, as we already discussed in the manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 311, 852, 414]]<|/det|> +(3) To differential the 'neutral' and 'charged' UN units and highlight the unique interaction between fullerene cage and UN unit, we modified the second sentence of the abstract as 'we report a charged U=N diatomic species captured in fullerene cages and stabilized by the unique U-fullerene coordination.' + +<|ref|>text<|/ref|><|det|>[[147, 449, 852, 636]]<|/det|> +The authors concede the point that they cannot claim the shortest UN distance. Then they have amended the statement in the abstract to address that point and state that they amended the discussion to "avoid the statement of 'the shortest'". However, despite conceding the point around lines 153- 156 the authors persist in making shortest statements "Moreover, these UN bonds are shorter than most of the observed UN bond lengths for...". The first two examples are complexes with UN distances that overlap with the UN fullerene one by the 3sigma criteria. + +<|ref|>text<|/ref|><|det|>[[147, 672, 850, 746]]<|/det|> +Response : To render the statement more precise, we revised the abovementioned text as' Moreover, these U=N bonds are relatively short compared to the observed U=N bond lengths for molecular compounds, such as..... + +<|ref|>text<|/ref|><|det|>[[147, 783, 852, 914]]<|/det|> +The authors have provided a range of clarifying statements and extra analysis. I stated before that I was largely convinced of the formulations, details not withstanding, but my central concerns have not actually been resolved. The authors have made a system in incredibly low yield and quantities, there is limited analysis compared to other systems, in contrast to coordination complexes that are made on higher yields with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 850, 136]]<|/det|> +much more analysis. The authors persist in claiming a shorter/shortest bond when they concede they should not, and they continue to push their novelty arguments too far. + +<|ref|>text<|/ref|><|det|>[[147, 172, 852, 527]]<|/det|> +Response : We did not intent to state that the novelty of this work is the short/shortest U- N bond, which accordingly is not highlighted in the abstract and conclusion in the revised manuscript. Instead, what we would like to highlight is that such a simple diatomic species can be captured and stabilized inside fullerene cages, forming a new fullerene family with an encaged triple bond. This is a quite unique host- guest molecular structure and indeed unexpected for endohedral fullerene studies. From the perspective of actinide chemistry, the capture of this charged diatomic species in a stable molecular compound provides an unconventional way to study elusive \(\mathrm{Ac} \equiv \mathrm{E}\) bonds, not just limited to \(\mathrm{U} \equiv \mathrm{N}\) . We have tried to extend this paradigm to capture other currently elusive but fundamentally important actinide bonding motifs, i.e. \(\mathrm{U} \equiv \mathrm{C}\) , by the fullerene cages and preliminary results show that fullerene cages have similar stabilization effect on the elusive \(\mathrm{U} \equiv \mathrm{C}\) bonding motif. We have emphasized this point in the last sentence of abstract and conclusions. + +<|ref|>text<|/ref|><|det|>[[148, 561, 850, 635]]<|/det|> +The technical clarifications are appreciated, but a central claim has been conceded and I do not see the novelty or new conceptual insight I expect in a Nature journal so I am unable to support publication here. + +<|ref|>text<|/ref|><|det|>[[147, 672, 850, 775]]<|/det|> +Response : It is unfortunate that the Reviewer is so focused on the charged vs. neutral aspect. As already stated, we consider it inappropriate to lump the fullerene cage together with all other ligands, because it offers a unique environment for encapsulated species. + +<|ref|>text<|/ref|><|det|>[[148, 812, 461, 829]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 867, 752, 885]]<|/det|> +From my point of view all is sorted out now and I recommend publication. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 771, 108]]<|/det|> +Response : We thank the Reviewer for the positive evaluation of our work. + +<|ref|>text<|/ref|><|det|>[[148, 145, 460, 163]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 199, 852, 358]]<|/det|> +The article of Chen et al. has been modified after the comments of 4 reviewers and most questions raised were answered. However, in several cases – and with different reviewers, the authors refrained from their original statement of a singular case of UN since many molecular UN features now exist. Thus, I prefer staying on my original statement, which would make this article worthy of publication but in a more specialized journal. + +<|ref|>text<|/ref|><|det|>[[148, 394, 850, 440]]<|/det|> +Additionally, on two specific points that were addressed by the authors, I would have more comments: + +<|ref|>text<|/ref|><|det|>[[147, 477, 852, 775]]<|/det|> +I am sorry, I am not sure I am satisfied with the answer of the authors on my original point on the different crystallographic positions of the metal center. I agree with the definition, which is made of a disorder as it “reflects the different conformations of the molecule with small energy barriers” but yet the other configuration is still present and thus shall be discussed. Even if the position is “fixed”, meaning that the ellipsoid is of fair size, the second configuration, although minor, should be considered. I understand that the major is the shortest UN distance but then all following characterization, especially Raman (see comments of Reviewers 1 and 2) should point to both configurations with two distinct UN sets of bands. Is it the case? Although it is a common method used in this peculiar chemistry, I wonder how one can just ignore an existing configuration. + +<|ref|>text<|/ref|><|det|>[[147, 811, 850, 913]]<|/det|> +Response: We thank the reviewer for this suggestion. To address the other configurations corresponds to the minor U sites, in the revised manuscript, we added “On the other hand, the U- N distances in the other configuration corresponding to its minor U sites are 1.681(7)- 1.820(9) Å (U2 (0.1903), U3 (0.1087) and U4 (0.0566) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 849, 163]]<|/det|> +for UN@ \(C_{s}(6) - C_{82}\) ) and 1.705(20) Å (U2 (0.188) for UN@ \(C_{2}(5) - C_{82}\) ) (Supplementary Fig. 4 and 6 and Supplementary Table 14- 15), all of which are within the bond length range of a U≡N triple bond. ” in the crystal analysis section. + +<|ref|>text<|/ref|><|det|>[[147, 200, 851, 275]]<|/det|> +Thanks to the authors for attempting ERP spectroscopy. There are many reasons for having a silent EPR spectrum: the ligand field shall be studied. I wonder if the “shielding effect of the carbon cage” is not a little too vague. + +<|ref|>text<|/ref|><|det|>[[146, 310, 852, 805]]<|/det|> +Response: This remark is also raised by Reviewer #4 (see below), who pointed us to check whether the silent EPR feature is due to a ground state Kramers doublet with \(\mathrm{g}_{\perp}\) \(= \mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . Analyzing in more detail the electronic structure of UN \(^{2 + }\) and UN isolated diatomics obtained from the wavefunction theory calculations, we can confirm that both systems exhibit GS Kramers doublets with axial \(\mathrm{g}\) tensor and \(\mathrm{g}_{\perp} = \mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . The main manuscript was amended with the following paragraph: “This behavior is supported by wavefunction theory (WFT) calculations (see Computational Details) on an isolated UN \(^{2 + }\) diatomic, \(d(\mathrm{U - N}) = 1.707 \mathrm{\AA}\) , which predict a \(j_{z} = 5 / 2\) ground state Kramers doublet (see Supplementary Table 17) characterized by an axial \(g\) tensor with \(\mathrm{g}_{\parallel} = \mathrm{g}_{z} = 4.19\) and \(\mathrm{g}_{\perp} = \mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . These values resemble those calculated for a UN \(^{2 + }\) diatomic with \(\mathrm{d}(\mathrm{U - N}) = 1.84 \mathrm{\AA}\) ( \(\mathrm{g}_{z} = 4.20\) , \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) ), and both are very close to the expected values for a \(|\mathrm{j}, \mathrm{j}_{z} > = |5 / 2, \pm 5 / 2>\) , namely \(\mathrm{g}_{z} = 4.29\) and \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . Similar WFT calculations for an isolated UN diatomic predicted a GS Kramers doublet with \(j_{z} = 7 / 2\) (see Supplementary Table 16) and axial \(\mathrm{g}\) tensor with \(\mathrm{g}_{z} = 3.99\) and \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) , which is an example case for a crystal field GS with \(l_{z} = \pm 5\) , \(s_{z} = \mp 3 / 2\) , and \(\mathrm{j}_{z} = \mp 5 / 2\) characterized by \(\mathrm{g}_{z} = 4.00\) and \(\mathrm{g}_{\mathrm{x}} = \mathrm{g}_{\mathrm{y}} = 0\) . Absence of EPR signals were also reported for \((\mathrm{MeC}_{5}\mathrm{H}_{4})_{3}\mathrm{UNR}\) compounds where the local \(\mathrm{C}_{3\mathrm{v}}\) symmetry around the metal center renders nil values for \(\mathrm{g}_{\mathrm{x}}\) and \(\mathrm{g}_{\mathrm{y}}\) .” + +<|ref|>text<|/ref|><|det|>[[148, 867, 460, 884]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 136]]<|/det|> +Overall, I am satisfied with the corrections the authors have made. I am not sure what they can learn from the EPR studies though. + +<|ref|>text<|/ref|><|det|>[[147, 144, 852, 303]]<|/det|> +I don't understand why a carbon cage shields an EPR resonance. The lack of signal could actually tell us about a high symmetry at the U(V) site – If the symmetry is high enough at the U5+ site, then the lack of an epr signal can indicate that the ground state of the U5+ ion does not contain a \(\mathrm{Jz} = + / - 1 / 2\) component, g(perp) can be zero, and thus we get information about the ground state. See the C3v symmetric molecule in https://escholarship.org/uc/item/6v96t1kb + +<|ref|>text<|/ref|><|det|>[[149, 312, 415, 329]]<|/det|> +Please could the authors discuss. + +<|ref|>text<|/ref|><|det|>[[147, 366, 850, 412]]<|/det|> +Response: The reviewer is correct! Please see our response to the last remark of Reviewer #3. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 82, 328, 97]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 112, 402, 127]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 142, 864, 217]]<|/det|> +The authors have presented a revised manuscript. Ignoring shifting priority claims and judging the manuscript in isolation my assessment is that in its current form it is much improved and now strikes the right balance being more precisely worded. It's unfortunate that EPR data are not forthcoming, since they would resolve the fullerene ligand question one way or another since variance, or not, of the gz value from 4.2 would clarify the 'ligand' effect. + +<|ref|>text<|/ref|><|det|>[[118, 231, 872, 276]]<|/det|> +I have only one remaining question, which in the new portion of EPR text the authors state "These values resemble those calculated for a UN2+ diatomic with \(\mathsf{d}(\mathsf{U} - \mathsf{N}) = 1.84\mathsf{\AA}\) (gz = 4.20, gx = gy = 0),". What are they referring to, a prior study? + +<|ref|>text<|/ref|><|det|>[[119, 319, 402, 334]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 348, 875, 378]]<|/det|> +After carefully reading and considering the comments of the other reviewers, I recommend publication in a more specialized journal. + +<|ref|>text<|/ref|><|det|>[[119, 407, 402, 422]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 437, 878, 496]]<|/det|> +I sincerely appreciate the efforts made by the authors to answer all my technical comments during this review process. Although I am satisfied with these, I am still finding that the work presented herein is not suitable for Nature Communications because I don't see the findings of exceptional novelty. As stated in my two previous reviews, I'll find the work more suitable for a more specialized journal. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 460, 107]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 144, 852, 303]]<|/det|> +The authors have presented a revised manuscript. Ignoring shifting priority claims and judging the manuscript in isolation my assessment is that in its current form it is much improved and now strikes the right balance being more precisely worded. It's unfortunate that EPR data are not forthcoming, since they would resolve the fullerene ligand question one way or another since variance, or not, of the gz value from 4.2 would clarify the 'ligand' effect. + +<|ref|>text<|/ref|><|det|>[[147, 339, 850, 415]]<|/det|> +I have only one remaining question, which in the new portion of EPR text the authors state "These values resemble those calculated for a UN2+ diatomic with \(\mathrm{d(U - N)} = 1.84\) \(\mathrm{\AA} (\mathrm{gz} = 4.20, \mathrm{gx} = \mathrm{gy} = 0)\) ." What are they referring to, a prior study? + +<|ref|>text<|/ref|><|det|>[[147, 450, 850, 525]]<|/det|> +Response: We thank the reviewer for this question. Here we missed a citation and have added it in the corresponding text (Nat. Commun. 7, 13773 (2016)). It has been cited elsewhere as ref. 22. For details please see the revised manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/images_list.json b/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..1c12e746c07cc4d901d3cf28ad8528fe0f81f141 --- /dev/null +++ b/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_2.jpg", + "caption": "**Supplementary Figure 2. Varying intra-individual and inter-individual standard deviations (SD). (A)** The ratios of overlap between the genes with high intra-individual SDs and high inter-individual SDs, with intra-individual SDs varying from 0.5 to 3. **(B)** The ratios of overlap between the genes with high inter-individual SDs and high intra-individual SDs, with inter-individual SDs varying from 0.5 to 3.", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..2702c6ead2b1839767e88e8ad67e9010c447249f --- /dev/null +++ b/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,596 @@ + +# nature portfolio + +Peer Review File + +Orgo- Seq integrates single- cell and bulk transcriptomic data to identify cell type specific- driver genes associated with autism spectrum disorder + +![](images/Supplementary_Figure_2.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +## Reviewers' comments: + +Reviewer #2 (Remarks to the Author): + +To the authors, I wish you and your families health, happiness, and some semblance of stability during these trying times. + +In their manuscript now titled "Data integration of bulk and single- cell transcriptomics from cerebral organoids and post- mortem brains to identify cell types and cell type specific driver genes in autism" Lim et al identify the cell type(s) and driver gene(s) in 16p11.2 deletion and 15q11- 13 duplications using patient- derived human brain organoids. The conducted RNAseq on 1,420 organoids from 25 individuals, and developed "Orgo- Seq" to systematically quantify and identify the inherent variability in whole- transcriptome bulk RNA sequence data derived from the organoids. Their primary findings are the identification of neuroepithelial cells as a critical cell type for 16p11.2 deletions, the prioritization of KCTD13 as a cell type specific driver gene, and the validation of KCTD13 using CRISPR/Cas9- edited KCTD13 mosaic organoids. Since the original revision, the authors have clarified their methods and conclusions, and done a great job addressing concerns from my previous review. I am happy to now recommend this publication for publication in Nature Communications. + +Reviewer #3 (Remarks to the Author): + +This manuscript is a revision of a manuscript previously submitted to Nature Genetics. The paper analyzes two genomic copy number variations (CNVs), 16p11.2 deletion and 15q11- 13 duplication, for their role in autism spectrum disorders (ASD). Using cerebral organoids grown from iPSCs of control donors and patients carrying said CNVs, the authors try to identify disease driving genes within the affected regions and find cell types driving the disease. The paper focusses on a candidate gene KCTD13 found in the 16p11.2 deletion, which the authors verify with a pooled knockout experiment. In the current version of the manuscript, the authors have moved the focus towards their data analysis platform Orgo- Seq that allows to identify both driver genes and cell types causative for ASD based on bulk RNAseq from patient- derived cerebral organoids when compared to published reference scRNAseq and post- mortem brain control datasets. + +The authors address an interesting problem of high relevance to the field, namely that driving genes and cells are not easily identified in ASD patients with CNVs. Cerebral organoids grown from patient iPSCs are a potential surrogate for patient phenotypes. Thus, their phenotype needs to be compared to control data and the authors' Orgo- Seq pipeline is suggested to provide a platform to solve this problem. + +Unfortunately, though, the paper has only been slightly changed and my initial concerns have been barely addressed. Clearly, one strength of the paper is the large amount of bulk RNAseq generated from cerebral organoids grown from multiple donor iPSCs. Unfortunately, however, the analysis of those data by Orgo- Seq is not really convincing. I feel there is still insufficient support to unequivocally demonstrate that Orgo- Seq allows for identification of ASD driver genes and cell types in patients with CNVs by way of analyzing cerebral organoids grown from their iPSCs. Below, I will point out some concerns about serious logical weaknesses that remain. + +<--- Page Split ---> + +Major points: + +1. The new focus of the paper is on the Orgo-Seq data integration framework. The major claim is that Orgo-Seq can identify driver genes and cell types causal for ASD based on cerebral organoids grown from patient iPSCs. To support this claim, the authors should reanalyze organoids on an individual donor basis. The assumption would be that one can identify genes and cell types based on their references. + +2. To bolster their reference input wildtype basis, I want to once again point to state-of-the-art scRNAseq reference data from the Arlotta, Kriegstein and Treutlein labs among others. It may well be that these reference datasets improve the Orgo-seq basis to a point where better phenotyping may be possible. + +3. To verify their driver gene identification, the authors perform a chimeric organoid experiment knocking out KCTD13. The authors provide FACS plots for their markers TRA1-60, Nestin and NeuN but unfortunately, only 3.88, 11.3 and \(4.46\%\) of cells are positive for any of the markers used. In my view, this raises serious concerns about the method used. Even assuming each cell is only positive for one of the markers, what are the remaining \(80\%\) of cells? How can the authors conclude that Nestin-positive neural progenitor cells are driving the phenotype if they only make up \(11.3\%\) of cells in their organoids? + +4. The authors claim KCTD13 to be the gene causative for ASD in the 16p11.2 deletion. This is primarily based on published data and they cite very recent papers. They also performed the verification experiment targeting KCTD (see point 3). However, based on a revised Orgo-Seq analysis they also prioritize two additional genes, YPEL3 and INO80E, in the 16p11.2 deletion. Do these genes also hold up to their verification assay? As it stands, the authors turn their argument on their head with published data verifying their chimeric organoid model while Orgo-Seq predicts additional genes. + +Reviewer #4 (Remarks to the Author): + +While the authors have made some changes to the paper, much still remains to be done before this paper would be suitable for publication at this journal. + +In general, the flow and framing of the paper are still very much unclear. There are many tangential topics in the text making the paper hard to understand. It is unclear why some of the analyses were performed (especially regarding the DE of the different 16p11 groups, but not limited to this). Additionally, while the authors state that they highlight the development of a framework most of the paper is not about this development and it still remains unclear + +The following major changes are still required (organized by numbers of original critiques). + +1. The comparison of CellScore to CIBERSORTx seems insufficient to prove this is a useful novel method. While CIBERSORTx is a deconvolution method CellScore doesn't aim to deconvolute the data (as the authors state). Rather, CellScore is a method to test for enrichment of cell types using cell-specific genes and would therefore benefit from comparisons to similar enrichment tests. If the paper is a methods development paper there needs to be some conceptual schema of why this method works better than existing methods in a main figure. + +2. The figures are still not at all sufficient. The authors state they have checked the figures but there are still figures lacking y-axis labels. The legends need to be re-written as well to much more detailed results/statistics. Many supplementary figures should be included as panels in the main figures - there + +<--- Page Split ---> + +is very little substance in the main figures. It is very hard to understand what the results are by looking at the figures. + +3. It is still unclear why the authors used different thresholds for the most variable genes. The fact they yield the same number of genes is irrelevant and should not be a consideration as this will change from experiment to experiment. Rather the authors should use statistical justification for a cutoff and use it in both instances. If the genes are variable because they show low expression, use a RPKM cutoff instead of a variability cutoff. If the genes are highly expressed and variable, they should be included in the analysis. + +4. While the authors state that they have modified the text to clarify the differential expression much of the text presented as new, it is essential the same text from the original submission and the authors did not respond to our comment. - is there any overlap between the different sets (here we only see SetA compared with the 15q11-13 deletion). Are the logFC similar? + +5. In this paper, organoids were grown for 46 days, while the cell types derived from single cell RNAseq were ascertained from 3 and 6 month-old organoids. The authors claim that their method is tolerant to these time differences, but in order to make this claim they need to show much more data, as this comprises very large differences in developmental stage and cell composition. + +a. The authors do not show any evidence that the cell types that they are using in the analysis are even found at this early stage. For example - cluster c4 "cells with forebrain markers" - are these cells/markers present in the organoid data? + +b. One alternative hypothesis is that a difference in the cell specific markers could mean a developmental shift in the treated vs. control and not a cell enrichment shift. Can the authors show data for the cell specific markers across development to rule out this hypothesis or at least discuss this in interpreting their data? + +6. The authors did not address the misclassification and while they claim that it was validated in another data set (from thelsame lab) there are many published single cell data sets and the authors should really validate their methods using many of these data sets. + +7. (Additional comment). For the odds ratio statistics comparing the isogenic with the patient-derived lines, is this statistic (page 9 of the response to reviewers) comparing the overlap in DEGs between the neural stem cells vs. the iNeurons? Or is this showing that the neural stem cell/patient derived cerebral organoid overlap is more significant than would be expected by chance? Make it clear what statistical comparisons are being done in the text and figure legends. + +Minor issues not addressed (from critiques): + +10. Using all samples, even those from the same individual, as independent samples in the linear model falsely inflates the number of DEG (see Germain and Testa 2017 Stem Cell Reports). Instead, a mixed linear model should be used to account for multiple samples coming from the same individual. - this was not addressed. The assumption of independence even if it was used to increase the number of permutations is wrong. + +15. There are still more sections in the results that need to be moved to the discussion. + +<--- Page Split ---> + +We thank all the reviewers for taking the time to provide detailed and insightful comments that have greatly improved our revised manuscript. We summarize a few key revisions to our manuscript, and provide a detailed point- by- point response below. + +## Emphasizing the focus of the Orgo-Seq framework + +We apologize that our previous manuscript did not sufficiently highlight the novelty and focus of the Orgo- Seq framework. We have now rewritten our manuscript and the new title of our manuscript is "Multi- transcriptomics data integration of cerebral organoids and post- mortem brains to identify cell type specific co- expressed driver genes in autism". + +Briefly, we emphasized that the goal of Orgo- Seq is not simply to perform cell type deconvolution or enrichment (which can be performed using existing tools such as CIBERSORT, CIBERSORTx and xCell). Instead, Orgo- Seq is a framework to enable the discovery of cell type specific co- expression (such as cell type specific co- expressed driver genes). By performing data integration of single- cell RNA sequence (scRNA- seq) and bulk RNA sequence (bRNA- seq) data, we can leverage on the strengths of performing unbiased critical cell type discovery from scRNA- seq data, but also overcome weaknesses in current scRNA- seq technologies for the discovery of cell type specific co- expressed genes. We had also clarified that in order to achieve the identification of critical cell type co- expressed driver genes, we took a 2- step approach with Orgo- Seq: to first identify the critical cell types (CellScore), and next to identify cell type specific driver genes (GeneScore). To improve readability of our manuscript, we have removed several tangential parts of the manuscript and cited prior literature instead, or moved sections into our supplementary methods. + +## Integration of additional large-scale single-cell RNA seq data + +As Reviewers 3 and 4 had pointed out, there are several state- of- the- art, large- scale single- cell RNA sequence (scRNA- seq) datasets that had been generated and published from several groups. There is a recent paper by Tanaka Y et al. (Cell Reports 2020) that aggregated all the scRNA- seq datasets from 8 different brain organoid protocols and fetal brains that were previously published by multiple groups, comprising of \(\sim 190,000\) single cells. We used their aggregated scRNA- seq dataset to identify 11 unique cell type clusters, and have now included analyses on this larger- scale scRNA- seq using the Orgo- Seq framework. Our previous results were based on the scRNA- seq dataset by Quadrato G et al. (Nature 2017) comprising of \(\sim 67,000\) single cells, so the Tanaka dataset has \(\sim 3\) times more single cells. + +## Replication of critical cell types using the Tanaka scRNA-seq data + +Previously by using the Orgo- Seq framework, we identified that the c9 (neuroepithelial cell) cluster and c6 (unknown) cluster from the Quadrato dataset were critical cell types for the 16p11.2 locus. In our updated analyses using the Orgo- Seq framework with the Tanaka dataset, we found that there was only 1 critical cell type cluster (CC3 comprising of cortical excitatory neurons) for the 16p11.2 locus. We also found that there were strong correlations between the c9 cluster from the Quadrato study and the CC3 cluster from the Tanaka study. + +## Fine-mapping of cell type cluster identities using reconstituted neurodevelopmental maps + +Reviewer 4 had raised concerns about potential inconsistencies in cell type cluster identification from different groups/studies generating scRNA- seq data from brain organoids. Velasco S et al. (Nature 2019) and Eze UC et al. (Nature Neuroscience 2021) had generated detailed neurodevelopmental maps reconstituted from large- scale scRNA- seq data from brain organoids and fetal brains. We have now performed systematic comparisons between cell type clusters identified from different studies (the Quadrato and Tanaka studies), with the cell type clusters in + +<--- Page Split ---> + +both neurodevelopmental maps, and found that both the c9 cluster and CC3 cluster map to the same critical cell types implicating immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +## Replication of candidate driver genes using the Tanaka scRNA-seq data + +We used the Orgo- Seq framework with the Tanaka dataset to identify candidate driver genes using the CC3 cluster, and identified \(Y P E L3\) with \(\mathsf{FDR}< = 0.05\) , and both KCTD13 and INO80E with \(\mathsf{FDR}< = 0.1\) . We had also identified CDIPT with \(\mathsf{FDR}< = 0.1\) . Thus, across both datasets and analyses, we replicated our results that \(Y P E L3\) , \(K C T D13\) and INO80E are likely to be bona fide candidate driver genes impacting immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +Our point- by- point responses (in blue text) to the reviewers' comments (in black text) is as follow. References to updated text in the revised manuscript are highlighted in red text. + +## Point-by-point response + +## Reviewer #2 (Remarks to the Author): + +To the authors, I wish you and your families health, happiness, and some semblance of stability during these trying times. In their manuscript now titled "Data integration of bulk and single- cell transcriptomics from cerebral organoids and post- mortem brains to identify cell types and cell type specific driver genes in autism" Lim et al identify the cell type(s) and driver gene(s) in 16p11.2 deletion and 15q11- 13 duplications using patient- derived human brain organoids. The conducted RNAseq on 1,420 organoids from 25 individuals, and developed "Orgo- Seq" to systematically quantify and identify the inherent variability in whole- transcriptome bulk RNA sequence data derived from the organoids. Their primary findings are the identification of neuroepithelial cells as a critical cell type for 16p11.2 deletions, the prioritization of KCTD13 as a cell type specific driver gene, and the validation of KCTD13 using CRISPR/Cas9- edited KCTD13 mosaic organoids. Since the original revision, the authors have clarified their methods and conclusions, and done a great job addressing concerns from my previous review. I am happy to now recommend this publication for publication in Nature Communications. + +We sincerely thank the reviewer for her/his positive comments and well wishes, and we are very grateful to all reviewers for their very fast and thorough reviews, especially during these times. + +## Reviewer #3 (Remarks to the Author): + +This manuscript is a revision of a manuscript previously submitted to Nature Genetics. The paper analyzes two genomic copy number variations (CNVs), 16p11.2 deletion and 15q11- 13 duplication, for their role in autism spectrum disorders (ASD). Using cerebral organoids grown from iPSCs of control donors and patients carrying said CNVs, the authors try to identify disease driving genes within the affected regions and find cell types driving the disease. The paper focusses on a candidate gene KCTD13 found in the 16p11.2 deletion, which the authors verify with a pooled knockout experiment. In the current version of the manuscript, the authors have moved the focus towards their data analysis platform Orgo- Seq that allows to identify both driver genes and cell types causative for ASD based on bulk RNAseq from patient- derived cerebral organoids when compared to published reference scRNAseq and post- mortem brain control datasets. + +The authors address an interesting problem of high relevance to the field, namely that driving genes and cells are not easily identified in ASD patients with CNVs. Cerebral organoids grown from patient iPSCs are a potential surrogate for patient phenotypes. Thus, their phenotype + +<--- Page Split ---> + +needs to be compared to control data and the authors' Orgo- Seq pipeline is suggested to provide a platform to solve this problem. + +We thank the reviewer for highlighting the importance of the biological questions that we are addressing with our current manuscript, which were not easily addressable by using blood or brain samples from ASD patients, or by using animal models. + +Unfortunately, though, the paper has only been slightly changed and my initial concerns have been barely addressed. Clearly, one strength of the paper is the large amount of bulk RNAseq generated from cerebral organoids grown from multiple donor iPSCs. Unfortunately, however, the analysis of those data by Orgo- Seq is not really convincing. I feel there is still insufficient support to unequivocally demonstrate that Orgo- Seq allows for identification of ASD driver genes and cell types in patients with CNVs by way of analyzing cerebral organoids grown from their iPSCs. Below, I will point out some concerns about serious logical weaknesses that remain. + +## Reviewer 3 Major points: + +1. The new focus of the paper is on the Orgo-Seq data integration framework. The major claim is that Orgo-Seq can identify driver genes and cell types causal for ASD based on cerebral organoids grown from patient iPSCs. To support this claim, the authors should reanalyze organoids on an individual donor basis. The assumption would be that one can identify genes and cell types based on their references. + +The reviewer has raised an interesting new angle about analyzing the organoids on an individual donor basis, and we agree that the development of new methods for analyzing cerebral organoids from individual donors for identifying cell types and driver genes in an individual patient, is of great significance for diagnosing disease subtypes or personalized genetic causes of the disease (precision medicine). + +However, the reviewer is asking a different question from what our current manuscript and Orgo- Seq aims to address. Orgo- Seq compares donor- derived cerebral organoids from many individuals with the same genetic risk loci, to enable the discovery of novel critical cell type(s) and cell type specific driver genes. The development of methods for personalized diagnostics will require previously identified critical cell type(s) and cell type specific driver genes. + +We are really excited about the reviewer's question if we can eventually achieve personalized diagnoses of individuals using cerebral organoids, and have also added the following text to conclude our discussion: + +"As a future direction, it will be exciting to explore the possibility of developing a precision medicine framework to rapidly identify critical cell types and cell type specific driver genes in individual donors, and the framework can complement DNA sequencing to enable the identification of putative causal cell types and cell type specific genes and gene networks in an individual patient for personalized diagnostics." + +## Reviewer 3 Major points: + +2. To bolster their reference input wildtype basis, I want to once again point to state-of-the-art scRNAseq reference data from the Arlotta, Kriegstein and Treutlein labs among others. It may well be that these reference datasets improve the Orgo-seq basis to a point where better phenotyping may be possible. + +<--- Page Split ---> + +We thank the reviewer for pointing out these additional high- quality datasets. We found that Yoshiaki Tanaka and In- Hyun Park had harmonized and projected a total of 190,022 single cells post- quality control, across 8 different scRNA- seq datasets generated from brain organoids and fetal brains (including the datasets mentioned by the reviewer). Our updated manuscript now includes analyses using the Tanaka harmonized scRNA- seq data, and as mentioned in our summary above, our results for the critical cell types and candidate driver genes in the 16p11.2 locus have been replicated, and we believe that our manuscript is much stronger now because of the reviewer's suggestion. + +The new sections in our updated manuscript are as follow: + +## Introduction + +"We applied Orgo- Seq for two ASD- associated copy number variants (CNVs) in the 16p11.2 and 15q11- 13 loci16- 18, by integrating 3 sets of transcriptomics datasets: bRNA- seq data that we generated from donor- derived cerebral organoids, previously published scRNA- seq data from cerebral organoids and fetal brains1,13,19,20, and previously published bRNA- seq data from human post- mortem brain samples in the BrainSpan Project21. Using an initial scRNA- seq dataset from 66,889 single cells1, we initially observed that neuroepithelial cells are perturbed in donor- derived cerebral organoids from individuals with deletions in 16p11.2 compared to individuals without the deletions, and that 3 of the genes in the locus (YPEL3, KCTD13 and INO80E) are likely to be candidate driver genes functioning in neuroepithelial cells. Using a larger scRNA- seq dataset comprising of 190,022 cells19 from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and two neurodevelopmental maps constructed from scRNA- seq on brain organoids and fetal brains to fine- map the critical cell types13,20, we replicated the critical cell type that was initially discovered, and were able to pinpoint the identity of the critical cell type more precisely during neurodevelopment to immature neurons and intermediate progenitor cells for the 16p11.2 locus. We also replicated our initial results that YPEL3, KCTD13 and INO80E are cell type specific candidate driver genes." + +## Results + +## "Fine-mapping of cell type identities using large-scale neurodevelopmental maps point to the role of immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +A recent study by Tanaka Y et al. had re- analyzed 190,022 cells from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and identified 24 cell type clusters19. We systematically compared the percentage overlaps among genes across the 24 cell type clusters to identify 11 unique clusters (CC1- 11; Supplementary Table 13). We calculated CellScores using the 11 cell type clusters for 16p11.2, and found that there was only the cell type cluster comprising of cortical excitatory neurons (CC3) that had an FWER \(\leq 0.05\) (P(CellScore) = \(3.6 \times 10^{- 4}\), Fig. 3C). Interestingly, we did not observe any association for 16p11.2 with the neuroepithelial cell cluster (CC7) in the Tanaka study (P(CellScore) = 0.11). + +To ensure consistencies in assigning cell type identities across different studies, and to fine- map the critical cell types more precisely during neurodevelopment, we used two neurodevelopmental maps that were reconstituted from scRNA- seq data on brain organoids and fetal brains. The first neurodevelopmental map by Velasco S et al. comprised of 12 cell types13, and we calculated the percentage overlap among genes from each cell type cluster reported by Quadrato G et al. and Tanaka Y et al.1,19 (Supplementary Table 14). We found that the neuroepithelial cell cluster (c9) from the Quadrato study overlapped most closely with immature projection neurons (mean overlap = 0.37%), and that the unknown cell type (c6) from the Quadrato study overlapped most closely with outer radial glia cells (mean overlap = 0.29%). The CC3 cluster from the Tanaka study overlapped most closely with immature projection neurons in the neurodevelopmental map (mean overlap = 1.14%), similar to the c9 cluster from the Quadrato study. + +<--- Page Split ---> + +We used a second neurodevelopmental map by Eze UC et al. that comprised of 6 cell types20, and calculated the percentage overlap among the genes from each cell type cluster reported by the Quadrato and Tanaka studies (Supplementary Table 14). We found that the c9 cluster from the Quadrato study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 8.1\%\) and \(5.4\%\) respectively). Similarly, the CC3 cluster from the Tanaka study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 19.8\%\) and \(11.1\%\) respectively). These results suggest that the critical cell types for the 16p11.2 locus are likely to be immature neurons and intermediate progenitor cells. + +To evaluate the degree of independence among the genes in the c9 cluster from the Quadrato study and the CC3 cluster from the Tanaka study, we calculated the correlations between the mean overlaps across the two neurodevelopmental maps for both the c9 and CC3 clusters (Supplementary Table 15). We observed high correlations between both the c9 and CC3 clusters using both neurodevelopmental maps \((r = 0.71\) , \(P = 9.1 \times 10^{- 3}\) ; \(r = 0.95\) , \(P = 3.6 \times 10^{- 3}\) ). However, there were stronger correlations between the CC3 and c5 clusters \((r = 0.96\) , \(P = 8.7 \times 10^{- 7}\) ; \(r = 0.98\) , \(P = 6.3 \times 10^{- 4}\) ), even though the c5 cluster was not implicated as the critical cell type from the 16p11.2 donor- derived organoids. This indicates that there is likely to be independence among the genes implicating the c9 and CC3 clusters as critical cell types in the 16p11.2 locus. + +## Replication of driver gene results for the 16p11.2 locus by integrating a large-scale scRNA-seq dataset + +To replicate our results for the 16p11.2 locus, we calculated GeneScores using the cell type specific genes in the CC3 cluster from the Tanaka study. YPEL3 was similarly prioritized as a high- confidence candidate driver gene at FDR \(\leq 0.05\) , and both KCTD13 and INO80E were prioritized at FDR \(\leq 0.1\) (Fig. 3F, Supplementary Tables 18- 19). Another gene (CDIPT) was also prioritized at FDR \(\leq 0.1\) ." + +## Reviewer 3 Major points: + +3. To verify their driver gene identification, the authors perform a chimeric organoid experiment knocking out KCTD13. The authors provide FACS plots for their markers TRA1-60, Nestin and NeuN but unfortunately, only 3.88, 11.3 and 4.46% of cells are positive for any of the markers used. In my view, this raises serious concerns about the method used. Even assuming each cell is only positive for one of the markers, what are the remaining 80% of cells? + +Based on the scRNA- seq data from brain organoids that had been published, there are additional cell types within the cerebral organoids that will not be positive for TRA- 1- 60, Nestin or NeuN. For instance, glia cells such as microglia and mature astrocytes will not be positive for any of the 3 markers. + +In addition, we had used a highly stringent approach to gating the cells during FACS sorting, resulting in smaller fractions of positive cells for TRA- 1- 60, Nestin or NeuN. If we use less stringent gating, there will be greater fractions of positive cells for the 3 markers. + +We updated our main text to clarify that we had focused on 3 groups of well- validated cell types in the mosaic organoid experiments: + +"We focused on a subset of three groups of well- validated cell types to validate our results from Orgo- Seq, and selected four antibody markers for FACS - NeuN for neuronal cells, Nestin for neural progenitor cells, TRA- 1- 60 for stem cells and mouse IgG2A as a negative control (Supplementary Fig. 10)." + +<--- Page Split ---> + +## Reviewer 3 Major points: + +3. (cont). How can the authors conclude that Nestin-positive neural progenitor cells are driving the phenotype if they only make up \(11.3\%\) of cells in their organoids? + +We will like to clarify that FACS sorting is a selection assay, and the mosaic organoid validation system that we used is adapted from a similar system that our group and other groups had reported using yeast and bacteria (FlowSeq by Kosuri S et al. PNAS 2013; Raveh-Sadka T et al., Nature Genetics 2012; Sharon E et al., Nature Biotech 2012). We have now named the method as oFlowSeq for "organoid FlowSeq", and cited our previous publication describing the system (Kosuri S et al.). + +We have also provided a schematic to provide more clarity to the oFlowSeq system in the supplementary methods section. + +## "Schematic of sequencing results from oFlowSeq using mosaic cerebral organoids + +![PLACEHOLDER_9_0] + + +The figure on the left illustrates an example where we dissociate the CRISPR- edited organoids and FACS sort equal numbers of cells for 3 sets of genotypes: 1) control cells with no edits in the KCTD13 gene, 2) cells with a deleterious mutation in KCTD13 that impacts protein function (red triangles), and 3) cells with a benign mutation in KCTD13 that does not impact protein function (blue triangles). + +In this example, there are 11 control unedited cells used for sorting (3 TRA- 1- 60+ cells, 3 Nestin+ cells and 5 NeuN+ cells). + +Similarly, 11 edited cells that are heterozygous for a deleterious mutation in KCTD13 were used for sorting (2 TRA- 1- 60+ cells, 5 Nestin+ cells and 4 NeuN+ cells). If the deleterious mutation in KCTD13 results in increased numbers of Nestin+ cells, there will be an increased proportion of Nestin+ cells with the deleterious mutation, compared to TRA- 1- 60+ or NeuN+ cells with the deleterious mutation. + +Another 11 edited cells that are heterozygous for a benign mutation in KCTD13 were used for sorting, and we expect the proportions of cell types with the benign mutation to be similar to the proportions of cell types for the control unedited cells. + +In this example, after FACS sorting using TRA- 1- 60 as a marker, followed by targeted sequencing of the TRA- 1- 60+ cells, we expect to count 33 reads without any mutations in KCTD13 (66% of all reads), 9 reads with the deleterious mutation in KCTD13 (18% of all reads), and 8 reads with the benign mutation in KCTD13 (16% of all reads). For the TRA- 1- 60+ cells, we expect to count 11 reads without any mutations in the gene (69%), 2 reads with the deleterious mutation (13%), and 3 reads with the benign mutation (19%). + +Similarly, the expected numbers and percentages of reads for the Nestin+ versus Nestin+ cells, and NeuN+ versus NeuN+ cells, are illustrated in the example. If the deleterious mutation in KCTD13 results in increased numbers of Nestin+ cells, then we expect the Nestin+ cells to harbor + +<--- Page Split ---> + +a higher percentage of the deleterious mutation compared to the percentage of the mutation in Nestin cells. + +Based on the results, we calculated an odds ratio for each mutation in each sorted cell population. If there are benign mutations in KCTD13 that are not differentially represented in a cell type (such as Nestin+ cells), then the distribution of odds ratios for these benign mutations will center around a mean odds ratio of 1, illustrated by the blue distribution in the figure on the right. However, if some of the mutations in KCTD13 are deleterious and do affect the proportions of cell types, then these deleterious mutations will show a distribution of odds ratios that center around a mean odds ratio of greater than 1, illustrated by the pink distribution in the figure on the right." + +![PLACEHOLDER_10_0] + + +## Reviewer 3 Major points: + +4. The authors claim KCTD13 to be the gene causative for ASD in the 16p11.2 deletion. This is primarily based on published data and they cite very recent papers. + +We will like to clarify that because we are developing a novel data integration framework, we are primarily using published data to benchmark and validate our results and framework. The papers that we cite are recent because relatively new technologies and tools, as well as new resources, have enabled these studies to be conducted. The generation of most of the donor- derived iPSCs with 16p11.2 deletions was only reported only recently by Theo Palmer's group (Roth JG, eLife 2020). Some of the iPSCs in our work were also from an earlier publication by Lauren Weiss' group (Deshpande A, Cell Reports 2017). We obtained the donor iPSCs from both recent studies, and our manuscript is the first (or among the first) to report results from 16p11.2 deletion donor-derived cerebral organoids. + +## Reviewer 3 Major points: + +4. (cont) They also performed the verification experiment targeting KCTD (see point 3). However, based on a revised Orgo-Seq analysis they also prioritize two additional genes, YPEL3 and INO80E, in the 16p11.2 deletion. Do these genes also hold up to their verification assay? As it stands, the authors turn their argument on their head with published data verifying their chimeric organoid model while Orgo-Seq predicts additional genes. + +We will like to clarify that the version of our manuscript prior to the initial submission had already prioritized YPEL3 and INO80E as driver genes (besides KCTD13) using the Orgo- Seq framework. In this current revised manuscript, we included more scRNA- seq data from additional publications, and have now replicated the results for all 3 genes (YPEL3, INO80E and KCTD13) as cell type specific driver genes in immature neurons and intermediate progenitor cells for the 16p11.2 locus in our new analyses. + +The reviewer had raised a question that is of great interest in the field, and Reviewer 2 had similarly asked about this in the previous review. In the zebrafish study by Golzio C et al., the authors found that KCTD13 is the only driver gene in the 16p11.2 deletion locus modulating the proportions of neural progenitor cells (or head sizes) in zebrafish. While our Orgo- Seq results found that KCTD13 is a driver gene in the locus using patient- derived cerebral organoids, we did not find that there was a clear transcriptomic co- expression signature pointing to only KCTD13 and not the other genes in the 16p11.2 locus. Reviewer 2 had asked if KCTD13 is sufficient and necessary for driving the 16p11.2 phenotype, i.e. if KCTD13 is the only driver + +<--- Page Split ---> + +gene in the 16p11.2 locus. Since the publication by Golzio C et al., there have been supporting evidence for the role of other driver genes in the 16p11.2 locus, and our results similarly support evidence for the role of multiple driver genes in the 16p11.2 locus. + +In our previous response letter to address Reviewer 2's question, we had also elaborated on additional supporting evidence from our work that do not support the result that KCTD13 is the only driver gene in the locus (shown below in green text). + +While we provide direct evidence for the role of KCTD13 affecting the proportions of neuroepithelial cells, Orgo- Seq also prioritizes 2 other genes in the 16p11.2 locus with FDR \(< = 0.05\) . These 2 genes are less well- studied and more research is needed in the future to understand the role of these genes in the locus, and the interactions of these genes with KCTD13. + +Kizner V et al. had also reported a list of 13 cell cycle associated genes that were expressed at significantly lower levels in the KCTD13- deficient NPCs compared to wildtype. None of these 13 genes are expressed at significantly lower levels in the patient organoids with 16p11.2 deletions. This suggests that deletions in KCTD13 in human NPCs is insufficient to recapitulate the transcriptomic perturbations identified in the patient organoids with 16p11.2 deletions. We have added a new section on these results supporting the role of multiple driver genes in the 16p11.2 locus. + +The goal of comparing the Orgo- Seq results with published results on KCTD13 is to validate our multi- transcriptomics data integration approach (Orgo- Seq), and not to validate the mosaic organoid experiments (oFlowSeq). We had optimized methods for the mosaic organoid experiments, but we did not develop new methods. Similar methods had been developed previously by our group and other groups using yeast and bacteria (Kosuri S et al., PNAS 2013; Raveh- Sadka T et al., Nature Genetics 2012; Sharon E et al., Nature Biotech 2012). + +We thank the reviewer for raising this question, which led us to realize that we should have cited the previous papers. Our group had published previously using a similar FACS- based method, which was termed "FlowSeq" (Kosuri S et al., PNAS 2013). However, the application using FlowSeq was for bacteria instead of human cerebral organoids, and addressed a different set of questions. We adapted an approach similar to FlowSeq for application to human mosaic cerebral organoids, and to address a different set of questions in ASD genetics, so we did not use the term FlowSeq to refer to our mosaic organoid experiments. For clarity, we have now termed the mosaic cerebral organoid approach as oFlowSeq for "organoid FlowSeq". + +We have now updated our manuscript to provide citations to the previous publications on FlowSeq and similar approaches: + +## Introduction + +"Given that immature neurons are enriched for Nestin\* cells \(^{23 - 25}\) , we adapted a previous framework (FlowSeq) \(^{26}\) to create a mosaic cerebral organoid framework using CRISPR/Cas9 editing (termed oFlowSeq for "organoid FlowSeq") to validate one of our key findings from OrgoSeq for the 16p11.2 locus, that KCTD13 is one of the driver genes in the locus modulating the proportions of Nestin\* cells in cerebral organoids. Our work presents a quantitative framework to identify cell types and cell type specific driver genes in a complex disease by integrating bRNA-seq and scRNA-seq from donor- derived cerebral organoids and human post- mortem brains (Orgo- Seq) and a CRISPR/Cas9 based mosaic cerebral organoid system (oFlowSeq) to validate the findings from the donor- derived cerebral organoids." + +<--- Page Split ---> + +## Results + +"To provide further validation that KCTD13 is one of the driver genes in the 16p11.2 locus modulating the proportions of immature neurons in the patient- derived organoids, and to resolve prior conflicting results from KCTD13- deficient animal models39- 41, we used a CRISPR- based approach61- 64 to directly measure the effects of knockouts in cerebral organoids, and adapted a fluorescence activated cell sorting (FACS) based approach that our group and other groups had previously described using bacteria and yeast26,65,66. We termed the adapted approach as oFlowSeq for "organoid FlowSeq". + +## Reviewer #4 (Remarks to the Author): + +While the authors have made some changes to the paper, much still remains to be done before this paper would be suitable for publication at this journal. + +In general, the flow and framing of the paper are still very much unclear. There are many tangential topics in the text making the paper hard to understand. It is unclear why some of the analyses were performed (especially regarding the DE of the different 16p11 groups, but not limited to this). Additionally, while the authors state that they highlight the development of a framework most of the paper is not about this development and it still remains unclear. + +We have now substantially rewritten our manuscript to emphasize the goal of Orgo- Seq, and have removed much of the tangential topics in the text, as well as cited published literature for clarification. + +## Reviewer 4: + +The following major changes are still required (organized by numbers of original critiques). + +1. The comparison of CellScore to CIBERSORTx seems insufficient to prove this is a useful novel method. While CIBERSORTx is a deconvolution method CellScore doesn't aim to deconvolute the data (as the authors state). Rather, CellScore is a method to test for enrichment of cell types using cell-specific genes and would therefore benefit from comparisons to similar enrichment tests. If the paper is a methods development paper there needs to be some conceptual schema of why this method works better than existing methods in a main figure. + +We apologize that the goal of Orgo- Seq was not articulately clearly previously, and we have rewritten the manuscript to clarify this. As explained in our summary, Orgo- Seq is not an approach to simply identify critical cell types. The reviewer correctly stated that there are several existing methods for doing so, such as CIBERSORTx, CIBERSORT and xCell. In the xCell paper (Aran D et al., Genome Biology 2017), the authors had extensively compared a cell type enrichment approach (xCell) to a deconvolution approach (CIBERSORT). Both xCell and CIBERSORT used bRNA-seq data from homogeneous cell populations as a reference panel, and not scRNA-seq data. However, the comparisons between a cell type enrichment approach versus a deconvolution approach is beyond the scope and aim of our manuscript, so we referenced the xCell paper instead. + +We will also like to further emphasize the novelty and motivation behind Orgo- Seq. Ideally, scRNA- seq can be performed directly on the donor- derived cerebral organoids to identify cell type specific co- expressed driver genes, i.e. which of the genes in the 16p11.2 locus are co- expressed in specific cell types associated with ASD. However, the limited capture efficiencies of current high- throughput scRNA- seq technologies do not allow for these analyses to be + +<--- Page Split ---> + +performed using scRNA- seq data alone. So Orgo- Seq was developed to address this limitation, by integrating bulk and scRNA- seq data from brain organoids to identify cell type specific co- expression such as cell type specific driver genes. Orgo- Seq is not just conceptually different from deconvolution/enrichment methods, but also, Orgo- Seq is addressing a different issue that is not addressed by deconvolution/enrichment methods. The more accurate comparison is between the Orgo- Seq results and analyses with what we could achieve using scRNA- seq alone or bulk RNA sequencing alone. + +We have now rewritten our manuscript to emphasize this, as well as updated Figure 1 in our main text to illustrate that Orgo- Seq is an integrative platform to combine the strengths of bRNA- seq and scRNA- seq for cell type specific co- expression discovery. + +Figure 1: Orgo- Seq framework to identify cell type specific co- expressed driver genes. (A) Figure illustrating the strengths and weaknesses of bRNA- seq and scRNA- seq, and what + +Orgo- Seq can achieve by integrating both types of datasets. (B) A schematic of the Orgo- Seq framework to integrate bRNA- seq data from patient- derived brain organoids with scRNA- seq data from control brain organoids and bRNA- seq data from post- mortem human brains (BrainSpan), for the discovery of critical cell types and cell type specific driver genes. + +![PLACEHOLDER_13_0] + + +# "Data integration of bRNA-seq data from donor-derived cerebral organoids and scRNA-seq data from control organoids identifies critical cell types for 16p11.2 deletions and 15q11-13 duplications + +Deletions in 16p11.2 are significantly associated with ASD but not with schizophrenia, whereas duplications in 16p11.2 are associated with both ASD and schizophrenia6,32,33. Clinical studies have shown that individuals with 16p11.2 deletions have increased brain sizes, and individuals with duplications in the same locus have decreased brain sizes32,34,35. Mouse models with 16p11.2 deletions or duplications similarly show an increase or reduction in brain sizes and in the proportions of neural progenitor cells36- 38. A systematic perturbation of all genes in the 16p11.2 locus using head sizes as the phenotypic readout in zebrafish identified KCTD13 as the only driver gene in the locus modulating the proportion of neural progenitor cells39. However, recent studies in mice and zebrafish with deleted KCTD13 did not observe increased brain sizes + +<--- Page Split ---> + +or neurogenesis in these mutant animal models40,41. In the absence of human fetal brains with 16p11.2 deletions that could be used to resolve these conflicting results from animal models42, the use of donor- derived cerebral organoids could be good models to provide supporting results. + +To accomplish this, we would have to identify which cell type specific co- expressed gene(s) from the donor- derived cerebral organoids are misregulating the proportions of critical cell types in cases versus controls (Fig. 1B). We developed a two- step solution where we first identified the critical cell types that were disproportionately affected in cases versus controls using mRNA- seq data from the donor- derived cerebral organoids, and a second step where we identified which of the genes in the CNV loci were disproportionately misregulating cell type specific expression of genes outside the CNV loci between cases versus controls. + +There are two general approaches to identify critical cell types from mRNA- seq data: deconvolution methods such as CIBERSORT and CIBERSORTx, or cell type enrichment methods such as xCell43,44. Previously, when using mRNA- seq data from pure cell types as a reference panel43, it was shown that a cell type enrichment approach (xCell) outperforms a deconvolution approach (CIBERSORT). We sought to develop a cell type enrichment based approach for mRNA- seq data from cerebral organoids, by using scRNA- seq data from brain organoids and fetal brains as a reference panel." + +## Reviewer 4 Major issues: + +2. The figures are still not at all sufficient. The authors state they have checked the figures but there are still figures lacking y-axis labels. The legends need to be re-written as well to much more detailed results/statistics. Many supplementary figures should be included as panels in the main figures - there is very little substance in the main figures. It is very hard to understand what the results are by looking at the figures. + +We apologize for the confusion and have checked all the figures to ensure that they all have y- axis labels. We have also shortened all the legends to remove detailed results/statistics. We have gone through all the supplementary figures and felt that while the supplementary figures were important for quality control, demonstrating the validity of the data or conceptualization of our methods, they were not directly contributing to visualizing the results of the main text (unlike our main figures). + +## Reviewer 4 Major issues: + +3. It is still unclear why the authors used different thresholds for the most variable genes. The fact they yield the same number of genes is irrelevant and should not be a consideration as this will change from experiment to experiment. Rather the authors should use statistical justification for a cutoff and use it in both instances. If the genes are variable because they show low expression, use a RPKM cutoff instead of a variability cutoff. If the genes are highly expressed and variable, they should be included in the analysis. + +We will like to clarify that we did use an expression cutoff (FPKM \(> = 2\) ). However, a single dimension by using a FPKM cutoff alone is insufficient. Using a variance cutoff or developing statistical models for identifying highly variable genes had been used in prior publications, especially for small sample sizes and for scRNA-seq, to account for technical variability in library preparation and low read counts per cell (e.g. Law CW et al., Genome Biology 2014; Chen HH et al., BMC Genomics 2016). + +We thank the reviewer for the clarification and we understand that the reviewer's concern also stems from having a standardized statistical justification across different studies. We had systematically compared the percentage of genes that overlap between the lists of genes with + +<--- Page Split ---> + +high intra-individual variability and genes with high inter-individual variability. The thresholds that we used were selected based on the points of inflection for both intra-individual variability (SD=2) and inter-individual variability (SD=1.5), and we have now included the data in Supplementary Table 5 and plotted the results in the updated Supplementary Fig. 2. + +![PLACEHOLDER_15_0] + + + +
**Supplementary Figure 2. Varying intra-individual and inter-individual standard deviations (SD). (A)** The ratios of overlap between the genes with high intra-individual SDs and high inter-individual SDs, with intra-individual SDs varying from 0.5 to 3. **(B)** The ratios of overlap between the genes with high inter-individual SDs and high intra-individual SDs, with inter-individual SDs varying from 0.5 to 3.
+ +## Reviewer 4 Major issues: + +4. While the authors state that they have modified the text to clarify the differential expression much of the text presented as new, it is essential the same text from the original submission and the authors did not respond to our comment. - is there any overlap between the different sets (here we only see SetA compared with the 15q11-13 deletion). Are the logFC similar? + +We thank the reviewer for raising this point. Actually there is a high correlation between the fold changes of 8 out of 9 genes in common between Set A of the 16p11.2 and 15q11-13 (Pearson’s \(r = 0.92\), \(P = 0.0014\)). + +We moved all these analyses in the updated Supplementary Materials section, and expanded on the analyses: + +**“Comparison of differentially expressed genes from 16p11.2 deletion and 15q11-13 duplication cerebral organoids reveals 9 genes in common** + +We compared the differentially expressed genes with FDR≤0.05 between the 16p11.2 deletion SetA and 15q11-13 duplication results, and observed that there were 8 genes that were differentially expressed in the same direction for 16p11.2 deletions (SetA) and 15q11-13 duplications (RPS14, PCDHGB6, TUBGCP5, CYFIP1, ELAVL2, SNHG5, NAP1L5 and MYL6B). There was a high correlation between the fold changes of these 8 genes between 16p11.2 deletions and 15q11-13 duplications (Pearson’s \(r = 0.92\), \(P = 0.0014\)). + +
GeneFold change in 16p11.2Fold change in 15q11-13
RPS141.091.11
PCDHGB60.540.54
TUBGCP51.181.72
CYFIP11.051.35
ELAVL20.680.52
+ +<--- Page Split ---> + + +
SNHG51.151.3
NAP1L50.750.53
MYL6B0.970.92
+ +Another gene (HERC2) was also differentially expressed for 16p11.2 deletions (SetA) and 15q11- 13 duplications but in opposite directions. HERC2 was over- expressed in 15q11- 13 duplications cases compared to controls (fold change \(= 1.48\) ), whereas HERC2 was under- expressed in 16p11.2 deletion cases compared to controls (fold change \(= 0.9\) ). Of the 9 genes that were differentially expressed, 3 of them (TUBGCP5, CYFIP1 and HERC2) were found in the 15q11- 13 locus. These results suggest that there are shared key genes that are perturbed by 16p11.2 deletions and 15q11- 13 duplications. + +There were 6 genes that were differentially expressed in the same direction for 16p11.2 deletions (SetP) and 15q11- 13 duplications (RPS14, PCDHGB6, ELAVL2, SNHG5, CTNNA2 and NAP1L5). There was a moderate correlation between the fold changes of these 6 genes between 16p11.2 deletions (SetP) and 15q11- 13 duplications (Pearson's \(r = 0.73\) , \(P = 0.064\) ). + +
GeneFold change in 16p11.2Fold change in 15q11-13
RPS141.091.11
PCDHGB60.520.54
ELAVL20.720.52
SNHG51.151.3
CTNNA20.590.58
NAP1L50.690.53
+ +HERC2 was also differentially expressed for 16p11.2 deletions (SetP) and 15q11- 13 duplications but in opposite directions (fold change \(= 0.8\) in 16p11.2 SetP and fold change \(= 1.48\) in 15q11- 13). + +There were no significantly differentially expressed genes with FDR≤0.05 from the 16p11.2 deletion (SetD) analyses." + +## Reviewer 4 Major issues: + +5. In this paper, organoids were grown for 46 days, while the cell types derived from single cell RNAseq were ascertained from 3 and 6 month-old organoids. The authors claim that their method is tolerant to these time differences, but in order to make this claim they need to show much more data, as this comprises very large differences in developmental stage and cell composition. + +We agree with the reviewer that it is interesting to understand the transcriptomic differences during neurodevelopment and cell type composition between brain organoids with different ages. There are several scRNA- seq papers that have been published on brain organoids and fetal brains addressing these questions, and these questions are beyond the scope of our manuscript, so we did not specifically address them. We had also removed the comparisons between 3- month and 6- month organoids as they had been systematically compared in prior publications. + +However, for the purpose of our manuscript, which is to identify cell type specific co- expressed driver genes in ASD, we demonstrate that our Orgo- Seq framework is robust in integrating scRNA- seq data from organoids with different ages (e.g. 3 and 6 month organoids), and bRNA- seq from 46- day old organoids in a few ways: + +<--- Page Split ---> + +1. We integrated scRNA-seq data from the Tanaka study, which is an aggregated scRNA-seq dataset from 8 different brain organoid protocols and fetal brains across different developmental timepoints, and replicated our initial results when using scRNA-seq data from the Quadrato study (please see point 6 below). + +2. We performed validation of one of the key findings to identify cell type specific co-expressed driver genes (KCTD13) using the mosaic organoid oFlowSeq framework. + +3. We performed multiple analyses to compare our results with results reported by other studies (published and unpublished). + +## Reviewer 4 Major issues: + +a. The authors do not show any evidence that the cell types that they are using in the analysis are even found at this early stage. For example - cluster c4 "cells with forebrain markers" - are these cells/markers present in the organoid data? + +Yes, all the genes in each cell type cluster are expressed in bRNA-seq data from our 46-day old cerebral organoids. We had performed quality control to remove genes that are not expressed in the 46-day old cerebral organoids from all downstream analyses. For each of the cell type clusters, the genes that were found in the cell type cluster, and were expressed in our donor-derived cerebral organoids were reported in Supplementary Table 11. All the 10 cell type clusters from the Quadrato study were represented by multiple cell type specific genes (ranging from 47 to 266). All the 11 cell type clusters from the Tanaka study were represented by multiple cell type specific genes (ranging from 12 to 421). + +## Reviewer 4 Major issues: + +b. One alternative hypothesis is that a difference in the cell specific markers could mean a developmental shift in the treated vs. control and not a cell enrichment shift. Can the authors show data for the cell specific markers across development to rule out this hypothesis or at least discuss this in interpreting their data? + +Yes, we thank the reviewer for pointing this out, and we apologize that we did not articulate these hypotheses more clearly in our previous manuscript. We were also curious about these two alternative hypotheses, and our mosaic cerebral organoid experiments (oFlowSeq) served 2 main purposes: + +1) to validate the critical cell type specific driver gene (KCTD13) based on our results from Orgo-Seq +2) to evaluate if there is a distortion in the proportion of Nestin+ cells due to KCTD13 mutations. + +If we did not identify differences in the proportions of Nestin+ cells for all deleterious mutations in KCTD13, then the results will suggest a developmental shift in transcriptomic differences within the cells and not differences in the proportions of cell types. However, we did observe a difference in the proportions of Nestin+ cells with KCTD13 deleterious mutations, so we can rule out that the first hypothesis (intrinsic developmental shift). In addition, the distortion in cell type proportions is in concordance with prior literature on KCTD13 deficiency (Kizner V et al, 2019), and might explain for the increased head sizes observed in patients with 16p11.2 deletions. + +## Our updated text reads: + +"This validation approach provides an orthogonal approach to validate our observed results from Orgo-Seq, and also serves to test the two hypotheses generated from the Orgo-Seq results: if there is a distortion in the proportions of cell types between the cerebral organoids from cases + +<--- Page Split ---> + +versus controls, or if there is an intrinsic developmental shift resulting in transcriptomic differences within the cells, but not a distortion in the proportions of cell types. If KCTD13 mutations do not affect the proportions of a specific cell type population, we expect to observe that the mutations are not significantly enriched in cells that are positive or negative for that cell type marker (Fig. 4A, Supplementary Materials). However, if KCTD13 mutations affect the proportions of a specific cell type population, we expect to observe that the mutations are significantly enriched in the cells that are positive for that cell type marker." + +## Reviewer 4 Major issues: + +6. The authors did not address the misclassification and while they claim that it was validated in another data set (from the same lab) there are many published single cell data sets and the authors should really validate their methods using many of these data sets. + +We have now addressed the reviewer's concerns about misclassification in 2 ways. Firstly, we have now re- done our Orgo- Seq analyses using a larger- scale aggregated dataset published by Tanaka et al., and validated our initial results identifying YPEL3, INO80E and KCTD13 as critical cell type specific driver genes for 16p11.2 deletions. + +In addition, we revisited the reviewer's comment about potential misclassification of the identities of cell type clusters from different scRNA- seq studies by different labs, and we developed an approach to enable consistent cell type identification across different studies, by using 2 neurodevelopmental reference maps to fine- map the cell type identities from different studies. + +Our updated text is as follow: + +## Introduction + +"We applied Orgo- Seq for two ASD- associated copy number variants (CNVs) in the 16p11.2 and 15q11- 13 loci16- 18, by integrating 3 sets of transcriptomics datasets: bRNA- seq data that we generated from donor- derived cerebral organoids, previously published scRNA- seq data from cerebral organoids and fetal brains1,13,19,20, and previously published bRNA- seq data from human post- mortem brain samples in the BrainSpan Project21. Using an initial scRNA- seq dataset from 66,889 single cells1, we initially observed that neuroepithelial cells are perturbed in donor- derived cerebral organoids from individuals with deletions in 16p11.2 compared to individuals without the deletions, and that 3 of the genes in the locus (YPEL3, KCTD13 and INO80E) are likely to be candidate driver genes functioning in neuroepithelial cells. Using a larger scRNA- seq dataset comprising of 190,022 cells19 from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and two neurodevelopmental maps constructed from scRNA- seq on brain organoids and fetal brains to fine- map the critical cell types13,20, we replicated the critical cell type that was initially discovered, and were able to pinpoint the identity of the critical cell type more precisely during neurodevelopment to immature neurons and intermediate progenitor cells for the 16p11.2 locus. We also replicated our initial results that YPEL3, KCTD13 and INO80E are cell type specific candidate driver genes." + +## Results + +"Fine- mapping of cell type identities using large- scale neurodevelopmental maps point to the role of immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +A recent study by Tanaka Y et al. had re- analyzed 190,022 cells from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and identified 24 cell type clusters19. We systematically compared the percentage overlaps among genes across the 24 cell type clusters to identify 11 unique clusters (CC1- 11; Supplementary Table 13). We calculated CellScores using the 11 cell type clusters for 16p11.2, and found that there was only + +<--- Page Split ---> + +the cell type cluster comprising of cortical excitatory neurons (CC3) that had an FWER \(\leq 0.05\) \((P(CellScore) = 3.6 \times 10^{- 4}\) , Fig. 3C). Interestingly, we did not observe any association for 16p11.2 with the neuroepithelial cell cluster (CC7) in the Tanaka study \((P(CellScore) = 0.11)\) . + +To ensure consistencies in assigning cell type identities across different studies, and to fine- map the critical cell types more precisely during neurodevelopment, we used two neurodevelopmental maps that were reconstituted from scRNA- seq data on brain organoids and fetal brains. The first neurodevelopmental map by Velasco S et al. comprised of 12 cell types \(^{13}\) , and we calculated the percentage overlap among genes from each cell type cluster reported by Quadrato G et al. and Tanaka Y et al. \(^{1,19}\) (Supplementary Table 14). We found that the neuroepithelial cell cluster (c9) from the Quadrato study overlapped most closely with immature projection neurons (mean overlap \(= 0.37\%\) ), and that the unknown cell type (c6) from the Quadrato study overlapped most closely with outer radial glia cells (mean overlap \(= 0.29\%\) ). The CC3 cluster from the Tanaka study overlapped most closely with immature projection neurons in the neurodevelopmental map (mean overlap \(= 1.14\%\) ), similar to the c9 cluster from the Quadrato study. + +We used a second neurodevelopmental map by Eze UC et al. that comprised of 6 cell types \(^{20}\) , and calculated the percentage overlap among the genes from each cell type cluster reported by the Quadrato and Tanaka studies (Supplementary Table 14). We found that the c9 cluster from the Quadrato study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 8.1\%\) and \(5.4\%\) respectively). Similarly, the CC3 cluster from the Tanaka study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 19.8\%\) and \(11.1\%\) respectively). These results suggest that the critical cell types for the 16p11.2 locus are likely to be immature neurons and intermediate progenitor cells. + +To evaluate the degree of independence among the genes in the c9 cluster from the Quadrato study and the CC3 cluster from the Tanaka study, we calculated the correlations between the mean overlaps across the two neurodevelopmental maps for both the c9 and CC3 clusters (Supplementary Table 15). We observed high correlations between both the c9 and CC3 clusters using both neurodevelopmental maps \((r = 0.71, P = 9.1 \times 10^{- 3}; r = 0.95, P = 3.6 \times 10^{- 3})\) . However, there were stronger correlations between the CC3 and c5 clusters \((r = 0.96, P = 8.7 \times 10^{- 7}; r = 0.98, P = 6.3 \times 10^{- 4})\) , even though the c5 cluster was not implicated as the critical cell type from the 16p11.2 donor- derived organoids. This indicates that there is likely to be independence among the genes implicating the c9 and CC3 clusters as critical cell types in the 16p11.2 locus." + +## Reviewer 4 Major issues: + +7. (Additional comment). For the odds ratio statistics comparing the isogenic with the patient-derived lines, is this statistic (page 9 of the response to reviewers) comparing the overlap in DEGs between the neural stem cells vs. the iNeurons? Or is this showing that the neural stem cell/patient derived cerebral organoid overlap is more significant than would be expected by chance? Make it clear what statistical comparisons are being done in the text and figure legends. + +Yes, the odds ratios are comparing the overlaps in DEGs between the organoids and the NSCs versus iNs. We had also reported the \(95\%\) confidence intervals and Fisher's Exact Test P- values to evaluate if the overlaps were more significant than would be expected by chance (that is, the overlap in DEGs between donor- derived cerebral organoids with iNs is assumed to be the baseline null). + +We have updated the text to clarify this: + +<--- Page Split ---> + +These observations provide further evidence that the differentially expressed genes from the patient- derived cerebral organoids are significantly more similar to the differentially expressed genes from the isogenic NSCs than the isogenic iNs with the same 16p11.2 deletion or duplication than by chance. + +We have also made a figure in the Supplementary Methods section to provide clarity to the results: + +![PLACEHOLDER_20_0] + + +## Reviewer 4 Minor issues not addressed (from critiques): + +10. Using all samples, even those from the same individual, as independent samples in the linear model falsely inflates the number of DEG (see Germain and Testa 2017 Stem Cell Reports). Instead, a mixed linear model should be used to account for multiple samples coming from the same individual. - this was not addressed. The assumption of independence even if it was used to increase the number of permutations is wrong. + +We have now performed a DEG analysis for 16p11.2 SetA using EdgeR with a linear mixed effects model and accounting for multiple replicates from the same individual. The histograms of the p-value and FDR distributions are shown below. + +![PLACEHOLDER_20_1] + + +For each gene, we calculated a ratio, which gives us an estimate of the degree of inflation or deflation in the P- value distributions. Ratio = - log10(P- value from linear regression) divided by - log10(P- value from EdgeR) + +We plotted the log10(Ratio) histogram below: + +<--- Page Split ---> +![PLACEHOLDER_21_0] + + +As the reviewer correctly pointed out, there is an inflation and the median \(\log 10(\text{Ratio})\) is 0.4156586 (indicated by the red line), and \(10^{\wedge}0.4156586 = 2.604106\) . + +Our GeneScore statistic is: + +\[G e n e S c o r e(x) = \frac{1}{l o g_{10}\lambda}\sum_{a l l y}\frac{-l o g_{10}P_{y}\times r_{x,y}^{2}}{N u m_{y}}\] + +We had used the \(\lambda\) term in GeneScore to correct for any potential inflation in the p- value distributions. From the 16p11.2 SetA data, the calculated \(\lambda\) was 5.60565, which is higher than the median inflation calculated from comparing the two different DEG analyses (2.604106). As such, the test statistics that we had used were even more stringent than accounting for multiple replicates from the same individual alone. + +We did not include these analyses mentioned above in our revised manuscript as we felt that these were tangential points that would cause confusion to the readers. However, we reiterate that we had used highly conservative statistics and analyses in our current Orgo- Seq manuscript as our initial manuscript is to evaluate if we can detect cell type specific co- expressed driver genes by integrating bRNA- seq and scRNA- seq data from multiple brain organoid studies, and we wanted to ensure that our results were robust and were likely to replicate (using the mosaic organoid oFlowSeq approach and when integrating additional scRNA- seq data). + +## Reviewer 4 Minor issues: + +15. There are still more sections in the results that need to be moved to the discussion. We have revised the manuscript substantially and moved several sections into the supplementary materials. Also, we had removed several sections that rehashed the results from prior publications, and instead, we cited these prior publications instead. + +<--- Page Split ---> + +## Reviewers' comments: + +Reviewer #3 (Remarks to the Author): + +The revised manuscript, now called "Multi- transcriptomics data integration of cerebral organoids and post- mortem brains to identify cell type specific co- expressed driver genes in autism" has been considerably improved by the authors. The text and logic flow is improved to gain clarity. Inclusion of a new reference scRNAseq dataset, a combination of several recent datasets from multiple labs performed by Tanaka et al. is very valuable and firmly grounds Orgo- Seq within a variety of protocols and organoids. The authors have performed several additional computational analyses and controls bolstering their claims. I remain skeptical of the FACS- based verification, which still raises a lot of questions. Given that the paper's increased focus on the computational Orgo- Seq pipeline, the FACS- based assay seems dispensable and, in my mind, might be removed from the ms entirely. Given the extensive bulk RNA- Seq provided and more importantly the Orgo- Seq pipeline, which constitutes a valuable contribution in this very exciting, important and ongoing research area, I would recommend publication upon some editorial changes. + +Major points: + +1. The text still would benefit from further streamlining. As an example, there is a lengthy passage on the initial use of the Quadrato et al dataset as the scRNAseq reference for Orgo-Seq. Given that the authors have repeated this analysis using the much better Tanaka et al combined reference dataset, this should be the focus of the text. + +2. Like before, the figures need some improvement. Font sizes are too small to read at times (ie figure 3, axis labelling, multiple supplementary figures). + +3. As explained above, I would propose to remove the FACS data. However, if the authors insist to keep them, they need to explain their approach. a) As mentioned before, why are so few cells positive for the markers used? This is inconsistent with other lab's data on progenitor and neuron percentages in organoids. b) In the FACS plots (Supplementary figure 10), why is IgG2A used as a control, even though the antibodies are of a different antibody class? c) Why are the forward scatter plots so different? These are antibody independent and should be equal. d) All gates used are equal and presumably set on the incorrect IgG2A isotype control. The increased rates of positive cells for all the markers could be simply explained by the different antibody conditions used. In fact, the entire population (including negative cells, easily seen by the red mark in the heat map plots) is shifted to the right by about 0.5 logs on the x-axis. e) Were similar FACS settings used? + +Reviewer #4 (Remarks to the Author): + +The overall goals of this work are laudable and a lot has been done. There were serious critiques to the previous version and authors have done a good job of answering concerns especially regarding some of the more technical issues that concerned me and other reviewers. The paper is much better put together and clearer to follow. The major issue is whether the major claims vis a vis driver genes is convincing and whether Orgo- seq is itself an advanced and widely useful framework for integration of multi- transcriptomics data sets as claimed --- I am not entirely convinced, but the work is very good, and I also think that the authors have done a reasonable job responding (and this is a nice data set), so that this should be published. These issues will be decided by the readers and the community once the work is published, and as the field moves forward with larger, additional samples as suggested. + +<--- Page Split ---> + +My minor comments are below: + +The high reproducibility and demonstration that genes within the CNVs study change as would be expected from the dosage changes are important strengths of the work. + +Other published work shows similar high correlation between organoids from controls and should be cited. + +I do wonder whether pairwise correlations used to identify co- expression are nearly as robust as graph theoretical measures such as topological overlap (T0). It has been shown that TO removes spurious correlations and reduces noise, compared with standard pairwise correlation measures. In this case, TO would remove noisy genes or spuriously correlated genes - conversely this weakness with pairwise correlation may underlie the initial negative results with 15q. Perhaps applying these methods (see also recent Nature Genetics paper integrating single cell and bulk tissue- PMID: 34239132) using this more robust framework would yield stronger putative drivers at the 15q11- 13 locus. + +One issue that I had which is likely out of the scope of the paper is that there seems to be very low mean overlap between the clusters in the Quadrato and Tanaka studies with the Velasco neurodevelopmental maps (ranging from \(0.37\% = 1.14\%\) ). It is also unclear from the methods how this mean overlap was calculated. + +Another issue is the interpretation of the integration of the bulk RNAseq from the postmortem brains. While the method developed in the paper allows to integrate the organoid single cell and post mortem bulk RNAseq the two tissues have different cell types or at the very least different levels of maturation. To make this point even more apparent the top cell type cluster identified was the stem cell cluster which is massively depleted in the adult brain. + +<--- Page Split ---> + +We thank both reviewers for their comments, and we summarize a few key revisions to our manuscript. + +## Orgo-Seq package and documentation + +We have now re- implemented Orgo- Seq as an R package, provided the source codes, and wrote detailed documentation for running the package on our GitHub site (https://gitlab.com/elimlab/orgo- seq). As part of the re- implementation, we have also worked on optimizing the codes, parallelization and improving runtimes. Given the more efficient codes, we have now performed 1 million permutations for our 16p11.2 CellScore results, instead of the initial 100,000 permutations. We have also calculated CellScores for the 15q11- 13 data using the Tanaka dataset, but similar to the Quadrato dataset, we did not observe any cell type clusters with FWER \(< = 0.1\) for the 15q11- 13 data. + +## Figures + +We have re- done most of the figures in the manuscript and the supplementary materials, and re- organized panels within the figures to improve readability. + +## oFlowSeq (FACS based system) + +We have removed this section from our revised manuscript. + +## 15q11-13 results + +We re- ran our analyses for critical cell types using both the Quadrato and Tanaka datasets for the 15q11- 13 locus (100,000 permutations). We did not observed any significant critical cell type using both datasets. To avoid confusion, we have revised our manuscript to focus only on the 16p11.2 driver gene results in the critical cell type identified, and removed the 15q11- 13 putative driver gene results. + +Our point- by- point responses (in blue text) to the reviewers' comments (in black text) is as follow. References to updated text in the revised manuscript are highlighted in red text. + +Reviewer #3 (Remarks to the Author): + +The revised manuscript, now called "Multi- transcriptomics data integration of cerebral organoids and post- mortem brains to identify cell type specific co- expressed driver genes in autism" has been considerably improved by the authors. The text and logic flow is improved to gain clarity. Inclusion of a new reference scRNASeq dataset, a combination of several recent datasets from multiple labs performed by Tanaka et al. is very valuable and firmly grounds Orgo- Seq within a variety of protocols and organoids. The authors have performed several additional computational analyses and controls bolstering their claims. I remain skeptical of the FACS- based verification, which still raises a lot of questions. Given that the paper's increased focus on the computational Orgo- Seq pipeline, the FACS- based assay seems dispensable and, in my mind, might be removed from the ms entirely. Given the extensive bulk RNA- Seq provided and more importantly the Orgo- Seq pipeline, which constitutes a valuable contribution in this very exciting, important and ongoing research area, I would recommend publication upon some editorial changes. + +<--- Page Split ---> + +We thank the reviewer for his/her suggestions, and have now removed the FACS- based assay from the manuscript. + +1. The text still would benefit from further streamlining. As an example, there is a lengthy passage on the initial use of the Quadrato et al dataset as the scRNAseq reference for Orgo-Seq. Given that the authors have repeated this analysis using the much better Tanaka et al combined reference dataset, this should be the focus of the text. + +We thank the reviewer and have rewritten the text to state that we used the Quadrato and Tanaka datasets, and replicated our findings with both datasets. + +2. Like before, the figures need some improvement. Font sizes are too small to read at times (ie figure 3, axis labelling, multiple supplementary figures). + +We apologize and have re- done most of the figures to ensure that all axes are labeled, and re- organized the figures within multiple larger figures to provide better clarity. + +3. As explained above, I would propose to remove the FACS data. However, if the authors insist to keep them, they need to explain their approach. a) As mentioned before, why are so few cells positive for the markers used? This is inconsistent with other lab's data on progenitor and neuron percentages in organoids. b) In the FACS plots (Supplementary figure 10), why is IgG2A used as a control, even though the antibodies are of a different antibody class? c) Why are the forward scatter plots so different? These are antibody independent and should be equal. d) All gates used are equal and presumably set on the incorrect IgG2A isotype control. The increased rates of positive cells for all the markers could be simply explained by the different antibody conditions used. In fact, the entire population (including negative cells, easily seen by the red mark in the heat map plots) is shifted to the right by about 0.5 logs on the x-axis. e) Were similar FACS settings used? + +We have removed the FACS data from our current manuscript. We sincerely thank the reviewer for these helpful comments. + +Reviewer #4 (Remarks to the Author): + +The overall goals of this work are laudable and a lot has been done. There were serious critiques to the previous version and authors have done a good job of answering concerns especially regarding some of the more technical issues that concerned me and other reviewers. The paper is much better put together and clearer to follow. The major issue is whether the major claims vis a vis driver genes is convincing and whether Orgo- seq is itself an advanced and widely useful framework for integration of multi- transcriptomics data sets as claimed --- I am not entirely convinced, but the work is very good, and I also think that the authors have done a reasonable job responding (and this is a nice data set), so that this should be published. These issues will be decided by the readers and the community once the work is published, and as the field moves forward with larger, additional samples as suggested. + +<--- Page Split ---> + +The high reproducibility and demonstration that genes within the CNVs study change as would be expected from the dosage changes are important strengths of the work. + +We thank the reviewer for his/her encouragement. + +Other published work shows similar high correlation between organoids from controls and should be cited. + +We have included an additional reference comparing organoids from different donors. + +I do wonder whether pairwise correlations used to identify co- expression are nearly as robust as graph theoretical measures such as topological overlap (TO). It has been shown that TO removes spurious correlations and reduces noise, compared with standard pairwise correlation measures. In this case, TO would remove noisy genes or spuriously correlated genes - conversely this weakness with pairwise correlation may underlie the initial negative results with 15q. Perhaps applying these methods (see also recent Nature Genetics paper integrating single cell and bulk tissue- PMID: 34239132) using this more robust framework would yield stronger putative drivers at the 15q11- 13 locus. + +We thank the reviewer for the interesting suggestion, and we are currently working on generating additional datasets to evaluate this question with different approaches. We have removed the section of putative cell type specific driver genes in the 15q11- 13 locus, given that there was no critical cell type identified for the 15q11- 13 locus. + +One issue that I had which is likely out of the scope of the paper is that there seems to be very low mean overlap between the clusters in the Quadrato and Tanaka studies with the Velasco neurodevelopmental maps (ranging from \(0.37\% = 1.14\%\) ). It is also unclear from the methods how this mean overlap was calculated. + +We agree with the reviewer that additional research and investigation into datasets from scRNA- seq technologies will be needed. We have also updated our revised manuscript to clarify how we calculated the mean overlap. + +## Calculation of overlaps and correlations with neurodevelopmental maps + +We used the cell type clusters from two large- scale scRNA- seq studies on brain organoids and fetal brains as neurodevelopmental maps \(^{13,20}\) , and calculated the percentage overlaps between the genes found in each cell type cluster from the Quadrato and Tanaka studies, and each cell type cluster from both neurodevelopmental maps (Supplementary Table 14). Using these percentage overlaps, we calculated the Pearson's correlations between each cell type cluster from both the Quadrato and Tanaka studies (Supplementary Table 15). + +Another issue is the interpretation of the integration of the bulk RNAseq from the postmortem brains. While the method developed in the paper allows to integrate the organoid single cell + +<--- Page Split ---> + +and post mortem bulk RNAseq the two tissues have different cell types or at the very least different levels of maturation. To make this point even more apparent the top cell type cluster identified was the stem cell cluster which is massively depleted in the adult brain. + +We agree with the reviewer that additional research into the integration of bulk RNA- seq data from brain organoids and postmortem brains, will be needed. We have rewritten the section to emphasize that we did not detect any critical cell type through integration of bulk RNA- seq data from brain organoids and postmortem brains for the 15q11- 13 locus. + +## Data integration of bRNA-seq data from post-mortem brain samples and scRNA-seq data from control cerebral organoids to identify critical cell types + +A prior publication had performed RNA sequencing on post- mortem brain samples of the cortex that were obtained from 9 individuals with 15q11- 13 duplications and 49 control individuals39. We calculated CellScores for each of the 10 cell type clusters in the Quadrato study using the differential expression results from the post- mortem brain samples, and calculated a weighted average P(CellScore) using the results from the patient- derived cerebral organoids and post- mortem brain samples with 15q11- 13 duplications (Supplementary Table 16). Similar to our results from the patient- derived cerebral organoids, there were no cell type clusters identified from the post- mortem brain samples that was significantly perturbed. + +<--- Page Split ---> diff --git a/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..55e84d9f4bb810ec8fc561052c1b507ecc372229 --- /dev/null +++ b/peer_reviews/55089d778af4643241ef9d798cf099653dee91ac67a1152fc04a903fc177206b/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,819 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[72, 154, 928, 241]]<|/det|> +Orgo- Seq integrates single- cell and bulk transcriptomic data to identify cell type specific- driver genes associated with autism spectrum disorder + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 825, 125]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[119, 167, 300, 182]]<|/det|> +## Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[120, 199, 402, 214]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 230, 830, 261]]<|/det|> +To the authors, I wish you and your families health, happiness, and some semblance of stability during these trying times. + +<|ref|>text<|/ref|><|det|>[[117, 262, 878, 434]]<|/det|> +In their manuscript now titled "Data integration of bulk and single- cell transcriptomics from cerebral organoids and post- mortem brains to identify cell types and cell type specific driver genes in autism" Lim et al identify the cell type(s) and driver gene(s) in 16p11.2 deletion and 15q11- 13 duplications using patient- derived human brain organoids. The conducted RNAseq on 1,420 organoids from 25 individuals, and developed "Orgo- Seq" to systematically quantify and identify the inherent variability in whole- transcriptome bulk RNA sequence data derived from the organoids. Their primary findings are the identification of neuroepithelial cells as a critical cell type for 16p11.2 deletions, the prioritization of KCTD13 as a cell type specific driver gene, and the validation of KCTD13 using CRISPR/Cas9- edited KCTD13 mosaic organoids. Since the original revision, the authors have clarified their methods and conclusions, and done a great job addressing concerns from my previous review. I am happy to now recommend this publication for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[120, 481, 402, 496]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 528, 873, 685]]<|/det|> +This manuscript is a revision of a manuscript previously submitted to Nature Genetics. The paper analyzes two genomic copy number variations (CNVs), 16p11.2 deletion and 15q11- 13 duplication, for their role in autism spectrum disorders (ASD). Using cerebral organoids grown from iPSCs of control donors and patients carrying said CNVs, the authors try to identify disease driving genes within the affected regions and find cell types driving the disease. The paper focusses on a candidate gene KCTD13 found in the 16p11.2 deletion, which the authors verify with a pooled knockout experiment. In the current version of the manuscript, the authors have moved the focus towards their data analysis platform Orgo- Seq that allows to identify both driver genes and cell types causative for ASD based on bulk RNAseq from patient- derived cerebral organoids when compared to published reference scRNAseq and post- mortem brain control datasets. + +<|ref|>text<|/ref|><|det|>[[118, 701, 870, 779]]<|/det|> +The authors address an interesting problem of high relevance to the field, namely that driving genes and cells are not easily identified in ASD patients with CNVs. Cerebral organoids grown from patient iPSCs are a potential surrogate for patient phenotypes. Thus, their phenotype needs to be compared to control data and the authors' Orgo- Seq pipeline is suggested to provide a platform to solve this problem. + +<|ref|>text<|/ref|><|det|>[[117, 795, 878, 905]]<|/det|> +Unfortunately, though, the paper has only been slightly changed and my initial concerns have been barely addressed. Clearly, one strength of the paper is the large amount of bulk RNAseq generated from cerebral organoids grown from multiple donor iPSCs. Unfortunately, however, the analysis of those data by Orgo- Seq is not really convincing. I feel there is still insufficient support to unequivocally demonstrate that Orgo- Seq allows for identification of ASD driver genes and cell types in patients with CNVs by way of analyzing cerebral organoids grown from their iPSCs. Below, I will point out some concerns about serious logical weaknesses that remain. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 216, 98]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[118, 99, 875, 177]]<|/det|> +1. The new focus of the paper is on the Orgo-Seq data integration framework. The major claim is that Orgo-Seq can identify driver genes and cell types causal for ASD based on cerebral organoids grown from patient iPSCs. To support this claim, the authors should reanalyze organoids on an individual donor basis. The assumption would be that one can identify genes and cell types based on their references. + +<|ref|>text<|/ref|><|det|>[[118, 193, 878, 256]]<|/det|> +2. To bolster their reference input wildtype basis, I want to once again point to state-of-the-art scRNAseq reference data from the Arlotta, Kriegstein and Treutlein labs among others. It may well be that these reference datasets improve the Orgo-seq basis to a point where better phenotyping may be possible. + +<|ref|>text<|/ref|><|det|>[[118, 272, 877, 381]]<|/det|> +3. To verify their driver gene identification, the authors perform a chimeric organoid experiment knocking out KCTD13. The authors provide FACS plots for their markers TRA1-60, Nestin and NeuN but unfortunately, only 3.88, 11.3 and \(4.46\%\) of cells are positive for any of the markers used. In my view, this raises serious concerns about the method used. Even assuming each cell is only positive for one of the markers, what are the remaining \(80\%\) of cells? How can the authors conclude that Nestin-positive neural progenitor cells are driving the phenotype if they only make up \(11.3\%\) of cells in their organoids? + +<|ref|>text<|/ref|><|det|>[[118, 397, 877, 507]]<|/det|> +4. The authors claim KCTD13 to be the gene causative for ASD in the 16p11.2 deletion. This is primarily based on published data and they cite very recent papers. They also performed the verification experiment targeting KCTD (see point 3). However, based on a revised Orgo-Seq analysis they also prioritize two additional genes, YPEL3 and INO80E, in the 16p11.2 deletion. Do these genes also hold up to their verification assay? As it stands, the authors turn their argument on their head with published data verifying their chimeric organoid model while Orgo-Seq predicts additional genes. + +<|ref|>text<|/ref|><|det|>[[120, 554, 402, 569]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 585, 860, 616]]<|/det|> +While the authors have made some changes to the paper, much still remains to be done before this paper would be suitable for publication at this journal. + +<|ref|>text<|/ref|><|det|>[[118, 632, 857, 710]]<|/det|> +In general, the flow and framing of the paper are still very much unclear. There are many tangential topics in the text making the paper hard to understand. It is unclear why some of the analyses were performed (especially regarding the DE of the different 16p11 groups, but not limited to this). Additionally, while the authors state that they highlight the development of a framework most of the paper is not about this development and it still remains unclear + +<|ref|>text<|/ref|><|det|>[[118, 727, 788, 742]]<|/det|> +The following major changes are still required (organized by numbers of original critiques). + +<|ref|>text<|/ref|><|det|>[[118, 758, 855, 852]]<|/det|> +1. The comparison of CellScore to CIBERSORTx seems insufficient to prove this is a useful novel method. While CIBERSORTx is a deconvolution method CellScore doesn't aim to deconvolute the data (as the authors state). Rather, CellScore is a method to test for enrichment of cell types using cell-specific genes and would therefore benefit from comparisons to similar enrichment tests. If the paper is a methods development paper there needs to be some conceptual schema of why this method works better than existing methods in a main figure. + +<|ref|>text<|/ref|><|det|>[[118, 853, 875, 900]]<|/det|> +2. The figures are still not at all sufficient. The authors state they have checked the figures but there are still figures lacking y-axis labels. The legends need to be re-written as well to much more detailed results/statistics. Many supplementary figures should be included as panels in the main figures - there + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 83, 875, 115]]<|/det|> +is very little substance in the main figures. It is very hard to understand what the results are by looking at the figures. + +<|ref|>text<|/ref|><|det|>[[117, 115, 877, 210]]<|/det|> +3. It is still unclear why the authors used different thresholds for the most variable genes. The fact they yield the same number of genes is irrelevant and should not be a consideration as this will change from experiment to experiment. Rather the authors should use statistical justification for a cutoff and use it in both instances. If the genes are variable because they show low expression, use a RPKM cutoff instead of a variability cutoff. If the genes are highly expressed and variable, they should be included in the analysis. + +<|ref|>text<|/ref|><|det|>[[117, 225, 878, 288]]<|/det|> +4. While the authors state that they have modified the text to clarify the differential expression much of the text presented as new, it is essential the same text from the original submission and the authors did not respond to our comment. - is there any overlap between the different sets (here we only see SetA compared with the 15q11-13 deletion). Are the logFC similar? + +<|ref|>text<|/ref|><|det|>[[117, 289, 874, 350]]<|/det|> +5. In this paper, organoids were grown for 46 days, while the cell types derived from single cell RNAseq were ascertained from 3 and 6 month-old organoids. The authors claim that their method is tolerant to these time differences, but in order to make this claim they need to show much more data, as this comprises very large differences in developmental stage and cell composition. + +<|ref|>text<|/ref|><|det|>[[117, 350, 850, 397]]<|/det|> +a. The authors do not show any evidence that the cell types that they are using in the analysis are even found at this early stage. For example - cluster c4 "cells with forebrain markers" - are these cells/markers present in the organoid data? + +<|ref|>text<|/ref|><|det|>[[117, 398, 853, 460]]<|/det|> +b. One alternative hypothesis is that a difference in the cell specific markers could mean a developmental shift in the treated vs. control and not a cell enrichment shift. Can the authors show data for the cell specific markers across development to rule out this hypothesis or at least discuss this in interpreting their data? + +<|ref|>text<|/ref|><|det|>[[117, 461, 861, 508]]<|/det|> +6. The authors did not address the misclassification and while they claim that it was validated in another data set (from thelsame lab) there are many published single cell data sets and the authors should really validate their methods using many of these data sets. + +<|ref|>text<|/ref|><|det|>[[117, 508, 866, 586]]<|/det|> +7. (Additional comment). For the odds ratio statistics comparing the isogenic with the patient-derived lines, is this statistic (page 9 of the response to reviewers) comparing the overlap in DEGs between the neural stem cells vs. the iNeurons? Or is this showing that the neural stem cell/patient derived cerebral organoid overlap is more significant than would be expected by chance? Make it clear what statistical comparisons are being done in the text and figure legends. + +<|ref|>text<|/ref|><|det|>[[119, 617, 447, 632]]<|/det|> +Minor issues not addressed (from critiques): + +<|ref|>text<|/ref|><|det|>[[118, 633, 870, 711]]<|/det|> +10. Using all samples, even those from the same individual, as independent samples in the linear model falsely inflates the number of DEG (see Germain and Testa 2017 Stem Cell Reports). Instead, a mixed linear model should be used to account for multiple samples coming from the same individual. - this was not addressed. The assumption of independence even if it was used to increase the number of permutations is wrong. + +<|ref|>text<|/ref|><|det|>[[118, 712, 764, 728]]<|/det|> +15. There are still more sections in the results that need to be moved to the discussion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 864, 168]]<|/det|> +We thank all the reviewers for taking the time to provide detailed and insightful comments that have greatly improved our revised manuscript. We summarize a few key revisions to our manuscript, and provide a detailed point- by- point response below. + +<|ref|>sub_title<|/ref|><|det|>[[115, 182, 550, 197]]<|/det|> +## Emphasizing the focus of the Orgo-Seq framework + +<|ref|>text<|/ref|><|det|>[[115, 198, 875, 255]]<|/det|> +We apologize that our previous manuscript did not sufficiently highlight the novelty and focus of the Orgo- Seq framework. We have now rewritten our manuscript and the new title of our manuscript is "Multi- transcriptomics data integration of cerebral organoids and post- mortem brains to identify cell type specific co- expressed driver genes in autism". + +<|ref|>text<|/ref|><|det|>[[114, 269, 880, 460]]<|/det|> +Briefly, we emphasized that the goal of Orgo- Seq is not simply to perform cell type deconvolution or enrichment (which can be performed using existing tools such as CIBERSORT, CIBERSORTx and xCell). Instead, Orgo- Seq is a framework to enable the discovery of cell type specific co- expression (such as cell type specific co- expressed driver genes). By performing data integration of single- cell RNA sequence (scRNA- seq) and bulk RNA sequence (bRNA- seq) data, we can leverage on the strengths of performing unbiased critical cell type discovery from scRNA- seq data, but also overcome weaknesses in current scRNA- seq technologies for the discovery of cell type specific co- expressed genes. We had also clarified that in order to achieve the identification of critical cell type co- expressed driver genes, we took a 2- step approach with Orgo- Seq: to first identify the critical cell types (CellScore), and next to identify cell type specific driver genes (GeneScore). To improve readability of our manuscript, we have removed several tangential parts of the manuscript and cited prior literature instead, or moved sections into our supplementary methods. + +<|ref|>sub_title<|/ref|><|det|>[[115, 474, 637, 489]]<|/det|> +## Integration of additional large-scale single-cell RNA seq data + +<|ref|>text<|/ref|><|det|>[[114, 489, 874, 620]]<|/det|> +As Reviewers 3 and 4 had pointed out, there are several state- of- the- art, large- scale single- cell RNA sequence (scRNA- seq) datasets that had been generated and published from several groups. There is a recent paper by Tanaka Y et al. (Cell Reports 2020) that aggregated all the scRNA- seq datasets from 8 different brain organoid protocols and fetal brains that were previously published by multiple groups, comprising of \(\sim 190,000\) single cells. We used their aggregated scRNA- seq dataset to identify 11 unique cell type clusters, and have now included analyses on this larger- scale scRNA- seq using the Orgo- Seq framework. Our previous results were based on the scRNA- seq dataset by Quadrato G et al. (Nature 2017) comprising of \(\sim 67,000\) single cells, so the Tanaka dataset has \(\sim 3\) times more single cells. + +<|ref|>sub_title<|/ref|><|det|>[[115, 635, 681, 650]]<|/det|> +## Replication of critical cell types using the Tanaka scRNA-seq data + +<|ref|>text<|/ref|><|det|>[[115, 650, 882, 737]]<|/det|> +Previously by using the Orgo- Seq framework, we identified that the c9 (neuroepithelial cell) cluster and c6 (unknown) cluster from the Quadrato dataset were critical cell types for the 16p11.2 locus. In our updated analyses using the Orgo- Seq framework with the Tanaka dataset, we found that there was only 1 critical cell type cluster (CC3 comprising of cortical excitatory neurons) for the 16p11.2 locus. We also found that there were strong correlations between the c9 cluster from the Quadrato study and the CC3 cluster from the Tanaka study. + +<|ref|>sub_title<|/ref|><|det|>[[115, 752, 835, 782]]<|/det|> +## Fine-mapping of cell type cluster identities using reconstituted neurodevelopmental maps + +<|ref|>text<|/ref|><|det|>[[115, 782, 880, 869]]<|/det|> +Reviewer 4 had raised concerns about potential inconsistencies in cell type cluster identification from different groups/studies generating scRNA- seq data from brain organoids. Velasco S et al. (Nature 2019) and Eze UC et al. (Nature Neuroscience 2021) had generated detailed neurodevelopmental maps reconstituted from large- scale scRNA- seq data from brain organoids and fetal brains. We have now performed systematic comparisons between cell type clusters identified from different studies (the Quadrato and Tanaka studies), with the cell type clusters in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 870, 168]]<|/det|> +both neurodevelopmental maps, and found that both the c9 cluster and CC3 cluster map to the same critical cell types implicating immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +<|ref|>sub_title<|/ref|><|det|>[[115, 182, 732, 197]]<|/det|> +## Replication of candidate driver genes using the Tanaka scRNA-seq data + +<|ref|>text<|/ref|><|det|>[[115, 198, 872, 285]]<|/det|> +We used the Orgo- Seq framework with the Tanaka dataset to identify candidate driver genes using the CC3 cluster, and identified \(Y P E L3\) with \(\mathsf{FDR}< = 0.05\) , and both KCTD13 and INO80E with \(\mathsf{FDR}< = 0.1\) . We had also identified CDIPT with \(\mathsf{FDR}< = 0.1\) . Thus, across both datasets and analyses, we replicated our results that \(Y P E L3\) , \(K C T D13\) and INO80E are likely to be bona fide candidate driver genes impacting immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +<|ref|>text<|/ref|><|det|>[[115, 300, 833, 330]]<|/det|> +Our point- by- point responses (in blue text) to the reviewers' comments (in black text) is as follow. References to updated text in the revised manuscript are highlighted in red text. + +<|ref|>sub_title<|/ref|><|det|>[[116, 344, 323, 359]]<|/det|> +## Point-by-point response + +<|ref|>sub_title<|/ref|><|det|>[[116, 372, 437, 387]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 387, 876, 577]]<|/det|> +To the authors, I wish you and your families health, happiness, and some semblance of stability during these trying times. In their manuscript now titled "Data integration of bulk and single- cell transcriptomics from cerebral organoids and post- mortem brains to identify cell types and cell type specific driver genes in autism" Lim et al identify the cell type(s) and driver gene(s) in 16p11.2 deletion and 15q11- 13 duplications using patient- derived human brain organoids. The conducted RNAseq on 1,420 organoids from 25 individuals, and developed "Orgo- Seq" to systematically quantify and identify the inherent variability in whole- transcriptome bulk RNA sequence data derived from the organoids. Their primary findings are the identification of neuroepithelial cells as a critical cell type for 16p11.2 deletions, the prioritization of KCTD13 as a cell type specific driver gene, and the validation of KCTD13 using CRISPR/Cas9- edited KCTD13 mosaic organoids. Since the original revision, the authors have clarified their methods and conclusions, and done a great job addressing concerns from my previous review. I am happy to now recommend this publication for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 592, 880, 621]]<|/det|> +We sincerely thank the reviewer for her/his positive comments and well wishes, and we are very grateful to all reviewers for their very fast and thorough reviews, especially during these times. + +<|ref|>sub_title<|/ref|><|det|>[[116, 636, 437, 650]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 652, 875, 810]]<|/det|> +This manuscript is a revision of a manuscript previously submitted to Nature Genetics. The paper analyzes two genomic copy number variations (CNVs), 16p11.2 deletion and 15q11- 13 duplication, for their role in autism spectrum disorders (ASD). Using cerebral organoids grown from iPSCs of control donors and patients carrying said CNVs, the authors try to identify disease driving genes within the affected regions and find cell types driving the disease. The paper focusses on a candidate gene KCTD13 found in the 16p11.2 deletion, which the authors verify with a pooled knockout experiment. In the current version of the manuscript, the authors have moved the focus towards their data analysis platform Orgo- Seq that allows to identify both driver genes and cell types causative for ASD based on bulk RNAseq from patient- derived cerebral organoids when compared to published reference scRNAseq and post- mortem brain control datasets. + +<|ref|>text<|/ref|><|det|>[[116, 825, 867, 870]]<|/det|> +The authors address an interesting problem of high relevance to the field, namely that driving genes and cells are not easily identified in ASD patients with CNVs. Cerebral organoids grown from patient iPSCs are a potential surrogate for patient phenotypes. Thus, their phenotype + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 825, 155]]<|/det|> +needs to be compared to control data and the authors' Orgo- Seq pipeline is suggested to provide a platform to solve this problem. + +<|ref|>text<|/ref|><|det|>[[115, 167, 856, 213]]<|/det|> +We thank the reviewer for highlighting the importance of the biological questions that we are addressing with our current manuscript, which were not easily addressable by using blood or brain samples from ASD patients, or by using animal models. + +<|ref|>text<|/ref|><|det|>[[115, 225, 870, 345]]<|/det|> +Unfortunately, though, the paper has only been slightly changed and my initial concerns have been barely addressed. Clearly, one strength of the paper is the large amount of bulk RNAseq generated from cerebral organoids grown from multiple donor iPSCs. Unfortunately, however, the analysis of those data by Orgo- Seq is not really convincing. I feel there is still insufficient support to unequivocally demonstrate that Orgo- Seq allows for identification of ASD driver genes and cell types in patients with CNVs by way of analyzing cerebral organoids grown from their iPSCs. Below, I will point out some concerns about serious logical weaknesses that remain. + +<|ref|>sub_title<|/ref|><|det|>[[116, 358, 328, 373]]<|/det|> +## Reviewer 3 Major points: + +<|ref|>text<|/ref|><|det|>[[115, 373, 867, 447]]<|/det|> +1. The new focus of the paper is on the Orgo-Seq data integration framework. The major claim is that Orgo-Seq can identify driver genes and cell types causal for ASD based on cerebral organoids grown from patient iPSCs. To support this claim, the authors should reanalyze organoids on an individual donor basis. The assumption would be that one can identify genes and cell types based on their references. + +<|ref|>text<|/ref|><|det|>[[115, 460, 831, 535]]<|/det|> +The reviewer has raised an interesting new angle about analyzing the organoids on an individual donor basis, and we agree that the development of new methods for analyzing cerebral organoids from individual donors for identifying cell types and driver genes in an individual patient, is of great significance for diagnosing disease subtypes or personalized genetic causes of the disease (precision medicine). + +<|ref|>text<|/ref|><|det|>[[115, 547, 860, 622]]<|/det|> +However, the reviewer is asking a different question from what our current manuscript and Orgo- Seq aims to address. Orgo- Seq compares donor- derived cerebral organoids from many individuals with the same genetic risk loci, to enable the discovery of novel critical cell type(s) and cell type specific driver genes. The development of methods for personalized diagnostics will require previously identified critical cell type(s) and cell type specific driver genes. + +<|ref|>text<|/ref|><|det|>[[115, 635, 863, 680]]<|/det|> +We are really excited about the reviewer's question if we can eventually achieve personalized diagnoses of individuals using cerebral organoids, and have also added the following text to conclude our discussion: + +<|ref|>text<|/ref|><|det|>[[115, 680, 868, 755]]<|/det|> +"As a future direction, it will be exciting to explore the possibility of developing a precision medicine framework to rapidly identify critical cell types and cell type specific driver genes in individual donors, and the framework can complement DNA sequencing to enable the identification of putative causal cell types and cell type specific genes and gene networks in an individual patient for personalized diagnostics." + +<|ref|>sub_title<|/ref|><|det|>[[116, 768, 328, 783]]<|/det|> +## Reviewer 3 Major points: + +<|ref|>text<|/ref|><|det|>[[115, 783, 864, 842]]<|/det|> +2. To bolster their reference input wildtype basis, I want to once again point to state-of-the-art scRNAseq reference data from the Arlotta, Kriegstein and Treutlein labs among others. It may well be that these reference datasets improve the Orgo-seq basis to a point where better phenotyping may be possible. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 880, 243]]<|/det|> +We thank the reviewer for pointing out these additional high- quality datasets. We found that Yoshiaki Tanaka and In- Hyun Park had harmonized and projected a total of 190,022 single cells post- quality control, across 8 different scRNA- seq datasets generated from brain organoids and fetal brains (including the datasets mentioned by the reviewer). Our updated manuscript now includes analyses using the Tanaka harmonized scRNA- seq data, and as mentioned in our summary above, our results for the critical cell types and candidate driver genes in the 16p11.2 locus have been replicated, and we believe that our manuscript is much stronger now because of the reviewer's suggestion. + +<|ref|>text<|/ref|><|det|>[[115, 255, 581, 270]]<|/det|> +The new sections in our updated manuscript are as follow: + +<|ref|>sub_title<|/ref|><|det|>[[115, 271, 212, 284]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[114, 284, 881, 520]]<|/det|> +"We applied Orgo- Seq for two ASD- associated copy number variants (CNVs) in the 16p11.2 and 15q11- 13 loci16- 18, by integrating 3 sets of transcriptomics datasets: bRNA- seq data that we generated from donor- derived cerebral organoids, previously published scRNA- seq data from cerebral organoids and fetal brains1,13,19,20, and previously published bRNA- seq data from human post- mortem brain samples in the BrainSpan Project21. Using an initial scRNA- seq dataset from 66,889 single cells1, we initially observed that neuroepithelial cells are perturbed in donor- derived cerebral organoids from individuals with deletions in 16p11.2 compared to individuals without the deletions, and that 3 of the genes in the locus (YPEL3, KCTD13 and INO80E) are likely to be candidate driver genes functioning in neuroepithelial cells. Using a larger scRNA- seq dataset comprising of 190,022 cells19 from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and two neurodevelopmental maps constructed from scRNA- seq on brain organoids and fetal brains to fine- map the critical cell types13,20, we replicated the critical cell type that was initially discovered, and were able to pinpoint the identity of the critical cell type more precisely during neurodevelopment to immature neurons and intermediate progenitor cells for the 16p11.2 locus. We also replicated our initial results that YPEL3, KCTD13 and INO80E are cell type specific candidate driver genes." + +<|ref|>sub_title<|/ref|><|det|>[[115, 533, 178, 547]]<|/det|> +## Results + +<|ref|>sub_title<|/ref|><|det|>[[115, 547, 864, 577]]<|/det|> +## "Fine-mapping of cell type identities using large-scale neurodevelopmental maps point to the role of immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +<|ref|>text<|/ref|><|det|>[[115, 577, 878, 698]]<|/det|> +A recent study by Tanaka Y et al. had re- analyzed 190,022 cells from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and identified 24 cell type clusters19. We systematically compared the percentage overlaps among genes across the 24 cell type clusters to identify 11 unique clusters (CC1- 11; Supplementary Table 13). We calculated CellScores using the 11 cell type clusters for 16p11.2, and found that there was only the cell type cluster comprising of cortical excitatory neurons (CC3) that had an FWER \(\leq 0.05\) (P(CellScore) = \(3.6 \times 10^{- 4}\), Fig. 3C). Interestingly, we did not observe any association for 16p11.2 with the neuroepithelial cell cluster (CC7) in the Tanaka study (P(CellScore) = 0.11). + +<|ref|>text<|/ref|><|det|>[[115, 698, 881, 870]]<|/det|> +To ensure consistencies in assigning cell type identities across different studies, and to fine- map the critical cell types more precisely during neurodevelopment, we used two neurodevelopmental maps that were reconstituted from scRNA- seq data on brain organoids and fetal brains. The first neurodevelopmental map by Velasco S et al. comprised of 12 cell types13, and we calculated the percentage overlap among genes from each cell type cluster reported by Quadrato G et al. and Tanaka Y et al.1,19 (Supplementary Table 14). We found that the neuroepithelial cell cluster (c9) from the Quadrato study overlapped most closely with immature projection neurons (mean overlap = 0.37%), and that the unknown cell type (c6) from the Quadrato study overlapped most closely with outer radial glia cells (mean overlap = 0.29%). The CC3 cluster from the Tanaka study overlapped most closely with immature projection neurons in the neurodevelopmental map (mean overlap = 1.14%), similar to the c9 cluster from the Quadrato study. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 122, 880, 256]]<|/det|> +We used a second neurodevelopmental map by Eze UC et al. that comprised of 6 cell types20, and calculated the percentage overlap among the genes from each cell type cluster reported by the Quadrato and Tanaka studies (Supplementary Table 14). We found that the c9 cluster from the Quadrato study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 8.1\%\) and \(5.4\%\) respectively). Similarly, the CC3 cluster from the Tanaka study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 19.8\%\) and \(11.1\%\) respectively). These results suggest that the critical cell types for the 16p11.2 locus are likely to be immature neurons and intermediate progenitor cells. + +<|ref|>text<|/ref|><|det|>[[115, 256, 880, 392]]<|/det|> +To evaluate the degree of independence among the genes in the c9 cluster from the Quadrato study and the CC3 cluster from the Tanaka study, we calculated the correlations between the mean overlaps across the two neurodevelopmental maps for both the c9 and CC3 clusters (Supplementary Table 15). We observed high correlations between both the c9 and CC3 clusters using both neurodevelopmental maps \((r = 0.71\) , \(P = 9.1 \times 10^{- 3}\) ; \(r = 0.95\) , \(P = 3.6 \times 10^{- 3}\) ). However, there were stronger correlations between the CC3 and c5 clusters \((r = 0.96\) , \(P = 8.7 \times 10^{- 7}\) ; \(r = 0.98\) , \(P = 6.3 \times 10^{- 4}\) ), even though the c5 cluster was not implicated as the critical cell type from the 16p11.2 donor- derived organoids. This indicates that there is likely to be independence among the genes implicating the c9 and CC3 clusters as critical cell types in the 16p11.2 locus. + +<|ref|>sub_title<|/ref|><|det|>[[115, 404, 825, 435]]<|/det|> +## Replication of driver gene results for the 16p11.2 locus by integrating a large-scale scRNA-seq dataset + +<|ref|>text<|/ref|><|det|>[[115, 435, 883, 511]]<|/det|> +To replicate our results for the 16p11.2 locus, we calculated GeneScores using the cell type specific genes in the CC3 cluster from the Tanaka study. YPEL3 was similarly prioritized as a high- confidence candidate driver gene at FDR \(\leq 0.05\) , and both KCTD13 and INO80E were prioritized at FDR \(\leq 0.1\) (Fig. 3F, Supplementary Tables 18- 19). Another gene (CDIPT) was also prioritized at FDR \(\leq 0.1\) ." + +<|ref|>sub_title<|/ref|><|det|>[[116, 524, 328, 539]]<|/det|> +## Reviewer 3 Major points: + +<|ref|>text<|/ref|><|det|>[[115, 540, 882, 613]]<|/det|> +3. To verify their driver gene identification, the authors perform a chimeric organoid experiment knocking out KCTD13. The authors provide FACS plots for their markers TRA1-60, Nestin and NeuN but unfortunately, only 3.88, 11.3 and 4.46% of cells are positive for any of the markers used. In my view, this raises serious concerns about the method used. Even assuming each cell is only positive for one of the markers, what are the remaining 80% of cells? + +<|ref|>text<|/ref|><|det|>[[115, 626, 878, 686]]<|/det|> +Based on the scRNA- seq data from brain organoids that had been published, there are additional cell types within the cerebral organoids that will not be positive for TRA- 1- 60, Nestin or NeuN. For instance, glia cells such as microglia and mature astrocytes will not be positive for any of the 3 markers. + +<|ref|>text<|/ref|><|det|>[[115, 700, 852, 745]]<|/det|> +In addition, we had used a highly stringent approach to gating the cells during FACS sorting, resulting in smaller fractions of positive cells for TRA- 1- 60, Nestin or NeuN. If we use less stringent gating, there will be greater fractions of positive cells for the 3 markers. + +<|ref|>text<|/ref|><|det|>[[115, 758, 875, 789]]<|/det|> +We updated our main text to clarify that we had focused on 3 groups of well- validated cell types in the mosaic organoid experiments: + +<|ref|>text<|/ref|><|det|>[[115, 789, 875, 848]]<|/det|> +"We focused on a subset of three groups of well- validated cell types to validate our results from Orgo- Seq, and selected four antibody markers for FACS - NeuN for neuronal cells, Nestin for neural progenitor cells, TRA- 1- 60 for stem cells and mouse IgG2A as a negative control (Supplementary Fig. 10)." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 124, 330, 139]]<|/det|> +## Reviewer 3 Major points: + +<|ref|>text<|/ref|><|det|>[[115, 138, 868, 169]]<|/det|> +3. (cont). How can the authors conclude that Nestin-positive neural progenitor cells are driving the phenotype if they only make up \(11.3\%\) of cells in their organoids? + +<|ref|>text<|/ref|><|det|>[[115, 181, 875, 272]]<|/det|> +We will like to clarify that FACS sorting is a selection assay, and the mosaic organoid validation system that we used is adapted from a similar system that our group and other groups had reported using yeast and bacteria (FlowSeq by Kosuri S et al. PNAS 2013; Raveh-Sadka T et al., Nature Genetics 2012; Sharon E et al., Nature Biotech 2012). We have now named the method as oFlowSeq for "organoid FlowSeq", and cited our previous publication describing the system (Kosuri S et al.). + +<|ref|>text<|/ref|><|det|>[[115, 284, 832, 315]]<|/det|> +We have also provided a schematic to provide more clarity to the oFlowSeq system in the supplementary methods section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 328, 828, 344]]<|/det|> +## "Schematic of sequencing results from oFlowSeq using mosaic cerebral organoids + +<|ref|>image<|/ref|><|det|>[[115, 345, 440, 660]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[456, 344, 884, 461]]<|/det|> +The figure on the left illustrates an example where we dissociate the CRISPR- edited organoids and FACS sort equal numbers of cells for 3 sets of genotypes: 1) control cells with no edits in the KCTD13 gene, 2) cells with a deleterious mutation in KCTD13 that impacts protein function (red triangles), and 3) cells with a benign mutation in KCTD13 that does not impact protein function (blue triangles). + +<|ref|>text<|/ref|><|det|>[[456, 475, 883, 520]]<|/det|> +In this example, there are 11 control unedited cells used for sorting (3 TRA- 1- 60+ cells, 3 Nestin+ cells and 5 NeuN+ cells). + +<|ref|>text<|/ref|><|det|>[[456, 533, 884, 651]]<|/det|> +Similarly, 11 edited cells that are heterozygous for a deleterious mutation in KCTD13 were used for sorting (2 TRA- 1- 60+ cells, 5 Nestin+ cells and 4 NeuN+ cells). If the deleterious mutation in KCTD13 results in increased numbers of Nestin+ cells, there will be an increased proportion of Nestin+ cells with the deleterious mutation, compared to TRA- 1- 60+ or NeuN+ cells with the deleterious mutation. + +<|ref|>text<|/ref|><|det|>[[115, 665, 884, 711]]<|/det|> +Another 11 edited cells that are heterozygous for a benign mutation in KCTD13 were used for sorting, and we expect the proportions of cell types with the benign mutation to be similar to the proportions of cell types for the control unedited cells. + +<|ref|>text<|/ref|><|det|>[[115, 723, 884, 813]]<|/det|> +In this example, after FACS sorting using TRA- 1- 60 as a marker, followed by targeted sequencing of the TRA- 1- 60+ cells, we expect to count 33 reads without any mutations in KCTD13 (66% of all reads), 9 reads with the deleterious mutation in KCTD13 (18% of all reads), and 8 reads with the benign mutation in KCTD13 (16% of all reads). For the TRA- 1- 60+ cells, we expect to count 11 reads without any mutations in the gene (69%), 2 reads with the deleterious mutation (13%), and 3 reads with the benign mutation (19%). + +<|ref|>text<|/ref|><|det|>[[115, 825, 884, 870]]<|/det|> +Similarly, the expected numbers and percentages of reads for the Nestin+ versus Nestin+ cells, and NeuN+ versus NeuN+ cells, are illustrated in the example. If the deleterious mutation in KCTD13 results in increased numbers of Nestin+ cells, then we expect the Nestin+ cells to harbor + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 883, 154]]<|/det|> +a higher percentage of the deleterious mutation compared to the percentage of the mutation in Nestin cells. + +<|ref|>text<|/ref|><|det|>[[115, 167, 620, 331]]<|/det|> +Based on the results, we calculated an odds ratio for each mutation in each sorted cell population. If there are benign mutations in KCTD13 that are not differentially represented in a cell type (such as Nestin+ cells), then the distribution of odds ratios for these benign mutations will center around a mean odds ratio of 1, illustrated by the blue distribution in the figure on the right. However, if some of the mutations in KCTD13 are deleterious and do affect the proportions of cell types, then these deleterious mutations will show a distribution of odds ratios that center around a mean odds ratio of greater than 1, illustrated by the pink distribution in the figure on the right." + +<|ref|>image<|/ref|><|det|>[[632, 169, 880, 325]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[116, 344, 328, 360]]<|/det|> +## Reviewer 3 Major points: + +<|ref|>text<|/ref|><|det|>[[115, 359, 875, 389]]<|/det|> +4. The authors claim KCTD13 to be the gene causative for ASD in the 16p11.2 deletion. This is primarily based on published data and they cite very recent papers. + +<|ref|>text<|/ref|><|det|>[[115, 401, 881, 535]]<|/det|> +We will like to clarify that because we are developing a novel data integration framework, we are primarily using published data to benchmark and validate our results and framework. The papers that we cite are recent because relatively new technologies and tools, as well as new resources, have enabled these studies to be conducted. The generation of most of the donor- derived iPSCs with 16p11.2 deletions was only reported only recently by Theo Palmer's group (Roth JG, eLife 2020). Some of the iPSCs in our work were also from an earlier publication by Lauren Weiss' group (Deshpande A, Cell Reports 2017). We obtained the donor iPSCs from both recent studies, and our manuscript is the first (or among the first) to report results from 16p11.2 deletion donor-derived cerebral organoids. + +<|ref|>sub_title<|/ref|><|det|>[[116, 548, 328, 563]]<|/det|> +## Reviewer 3 Major points: + +<|ref|>text<|/ref|><|det|>[[115, 562, 872, 637]]<|/det|> +4. (cont) They also performed the verification experiment targeting KCTD (see point 3). However, based on a revised Orgo-Seq analysis they also prioritize two additional genes, YPEL3 and INO80E, in the 16p11.2 deletion. Do these genes also hold up to their verification assay? As it stands, the authors turn their argument on their head with published data verifying their chimeric organoid model while Orgo-Seq predicts additional genes. + +<|ref|>text<|/ref|><|det|>[[115, 649, 884, 739]]<|/det|> +We will like to clarify that the version of our manuscript prior to the initial submission had already prioritized YPEL3 and INO80E as driver genes (besides KCTD13) using the Orgo- Seq framework. In this current revised manuscript, we included more scRNA- seq data from additional publications, and have now replicated the results for all 3 genes (YPEL3, INO80E and KCTD13) as cell type specific driver genes in immature neurons and intermediate progenitor cells for the 16p11.2 locus in our new analyses. + +<|ref|>text<|/ref|><|det|>[[115, 752, 875, 870]]<|/det|> +The reviewer had raised a question that is of great interest in the field, and Reviewer 2 had similarly asked about this in the previous review. In the zebrafish study by Golzio C et al., the authors found that KCTD13 is the only driver gene in the 16p11.2 deletion locus modulating the proportions of neural progenitor cells (or head sizes) in zebrafish. While our Orgo- Seq results found that KCTD13 is a driver gene in the locus using patient- derived cerebral organoids, we did not find that there was a clear transcriptomic co- expression signature pointing to only KCTD13 and not the other genes in the 16p11.2 locus. Reviewer 2 had asked if KCTD13 is sufficient and necessary for driving the 16p11.2 phenotype, i.e. if KCTD13 is the only driver + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 880, 169]]<|/det|> +gene in the 16p11.2 locus. Since the publication by Golzio C et al., there have been supporting evidence for the role of other driver genes in the 16p11.2 locus, and our results similarly support evidence for the role of multiple driver genes in the 16p11.2 locus. + +<|ref|>text<|/ref|><|det|>[[115, 182, 870, 227]]<|/det|> +In our previous response letter to address Reviewer 2's question, we had also elaborated on additional supporting evidence from our work that do not support the result that KCTD13 is the only driver gene in the locus (shown below in green text). + +<|ref|>text<|/ref|><|det|>[[115, 240, 870, 315]]<|/det|> +While we provide direct evidence for the role of KCTD13 affecting the proportions of neuroepithelial cells, Orgo- Seq also prioritizes 2 other genes in the 16p11.2 locus with FDR \(< = 0.05\) . These 2 genes are less well- studied and more research is needed in the future to understand the role of these genes in the locus, and the interactions of these genes with KCTD13. + +<|ref|>text<|/ref|><|det|>[[115, 328, 880, 431]]<|/det|> +Kizner V et al. had also reported a list of 13 cell cycle associated genes that were expressed at significantly lower levels in the KCTD13- deficient NPCs compared to wildtype. None of these 13 genes are expressed at significantly lower levels in the patient organoids with 16p11.2 deletions. This suggests that deletions in KCTD13 in human NPCs is insufficient to recapitulate the transcriptomic perturbations identified in the patient organoids with 16p11.2 deletions. We have added a new section on these results supporting the role of multiple driver genes in the 16p11.2 locus. + +<|ref|>text<|/ref|><|det|>[[115, 444, 880, 533]]<|/det|> +The goal of comparing the Orgo- Seq results with published results on KCTD13 is to validate our multi- transcriptomics data integration approach (Orgo- Seq), and not to validate the mosaic organoid experiments (oFlowSeq). We had optimized methods for the mosaic organoid experiments, but we did not develop new methods. Similar methods had been developed previously by our group and other groups using yeast and bacteria (Kosuri S et al., PNAS 2013; Raveh- Sadka T et al., Nature Genetics 2012; Sharon E et al., Nature Biotech 2012). + +<|ref|>text<|/ref|><|det|>[[115, 547, 881, 666]]<|/det|> +We thank the reviewer for raising this question, which led us to realize that we should have cited the previous papers. Our group had published previously using a similar FACS- based method, which was termed "FlowSeq" (Kosuri S et al., PNAS 2013). However, the application using FlowSeq was for bacteria instead of human cerebral organoids, and addressed a different set of questions. We adapted an approach similar to FlowSeq for application to human mosaic cerebral organoids, and to address a different set of questions in ASD genetics, so we did not use the term FlowSeq to refer to our mosaic organoid experiments. For clarity, we have now termed the mosaic cerebral organoid approach as oFlowSeq for "organoid FlowSeq". + +<|ref|>text<|/ref|><|det|>[[115, 679, 825, 710]]<|/det|> +We have now updated our manuscript to provide citations to the previous publications on FlowSeq and similar approaches: + +<|ref|>sub_title<|/ref|><|det|>[[115, 724, 212, 738]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[115, 738, 883, 870]]<|/det|> +"Given that immature neurons are enriched for Nestin\* cells \(^{23 - 25}\) , we adapted a previous framework (FlowSeq) \(^{26}\) to create a mosaic cerebral organoid framework using CRISPR/Cas9 editing (termed oFlowSeq for "organoid FlowSeq") to validate one of our key findings from OrgoSeq for the 16p11.2 locus, that KCTD13 is one of the driver genes in the locus modulating the proportions of Nestin\* cells in cerebral organoids. Our work presents a quantitative framework to identify cell types and cell type specific driver genes in a complex disease by integrating bRNA-seq and scRNA-seq from donor- derived cerebral organoids and human post- mortem brains (Orgo- Seq) and a CRISPR/Cas9 based mosaic cerebral organoid system (oFlowSeq) to validate the findings from the donor- derived cerebral organoids." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 140, 178, 153]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[115, 153, 881, 257]]<|/det|> +"To provide further validation that KCTD13 is one of the driver genes in the 16p11.2 locus modulating the proportions of immature neurons in the patient- derived organoids, and to resolve prior conflicting results from KCTD13- deficient animal models39- 41, we used a CRISPR- based approach61- 64 to directly measure the effects of knockouts in cerebral organoids, and adapted a fluorescence activated cell sorting (FACS) based approach that our group and other groups had previously described using bacteria and yeast26,65,66. We termed the adapted approach as oFlowSeq for "organoid FlowSeq". + +<|ref|>sub_title<|/ref|><|det|>[[115, 271, 437, 285]]<|/det|> +## Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 285, 875, 315]]<|/det|> +While the authors have made some changes to the paper, much still remains to be done before this paper would be suitable for publication at this journal. + +<|ref|>text<|/ref|><|det|>[[115, 328, 870, 402]]<|/det|> +In general, the flow and framing of the paper are still very much unclear. There are many tangential topics in the text making the paper hard to understand. It is unclear why some of the analyses were performed (especially regarding the DE of the different 16p11 groups, but not limited to this). Additionally, while the authors state that they highlight the development of a framework most of the paper is not about this development and it still remains unclear. + +<|ref|>text<|/ref|><|det|>[[115, 415, 866, 460]]<|/det|> +We have now substantially rewritten our manuscript to emphasize the goal of Orgo- Seq, and have removed much of the tangential topics in the text, as well as cited published literature for clarification. + +<|ref|>sub_title<|/ref|><|det|>[[115, 475, 217, 489]]<|/det|> +## Reviewer 4: + +<|ref|>text<|/ref|><|det|>[[115, 489, 833, 505]]<|/det|> +The following major changes are still required (organized by numbers of original critiques). + +<|ref|>text<|/ref|><|det|>[[115, 517, 880, 621]]<|/det|> +1. The comparison of CellScore to CIBERSORTx seems insufficient to prove this is a useful novel method. While CIBERSORTx is a deconvolution method CellScore doesn't aim to deconvolute the data (as the authors state). Rather, CellScore is a method to test for enrichment of cell types using cell-specific genes and would therefore benefit from comparisons to similar enrichment tests. If the paper is a methods development paper there needs to be some conceptual schema of why this method works better than existing methods in a main figure. + +<|ref|>text<|/ref|><|det|>[[115, 634, 884, 783]]<|/det|> +We apologize that the goal of Orgo- Seq was not articulately clearly previously, and we have rewritten the manuscript to clarify this. As explained in our summary, Orgo- Seq is not an approach to simply identify critical cell types. The reviewer correctly stated that there are several existing methods for doing so, such as CIBERSORTx, CIBERSORT and xCell. In the xCell paper (Aran D et al., Genome Biology 2017), the authors had extensively compared a cell type enrichment approach (xCell) to a deconvolution approach (CIBERSORT). Both xCell and CIBERSORT used bRNA-seq data from homogeneous cell populations as a reference panel, and not scRNA-seq data. However, the comparisons between a cell type enrichment approach versus a deconvolution approach is beyond the scope and aim of our manuscript, so we referenced the xCell paper instead. + +<|ref|>text<|/ref|><|det|>[[115, 796, 867, 870]]<|/det|> +We will also like to further emphasize the novelty and motivation behind Orgo- Seq. Ideally, scRNA- seq can be performed directly on the donor- derived cerebral organoids to identify cell type specific co- expressed driver genes, i.e. which of the genes in the 16p11.2 locus are co- expressed in specific cell types associated with ASD. However, the limited capture efficiencies of current high- throughput scRNA- seq technologies do not allow for these analyses to be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 879, 227]]<|/det|> +performed using scRNA- seq data alone. So Orgo- Seq was developed to address this limitation, by integrating bulk and scRNA- seq data from brain organoids to identify cell type specific co- expression such as cell type specific driver genes. Orgo- Seq is not just conceptually different from deconvolution/enrichment methods, but also, Orgo- Seq is addressing a different issue that is not addressed by deconvolution/enrichment methods. The more accurate comparison is between the Orgo- Seq results and analyses with what we could achieve using scRNA- seq alone or bulk RNA sequencing alone. + +<|ref|>text<|/ref|><|det|>[[115, 241, 883, 286]]<|/det|> +We have now rewritten our manuscript to emphasize this, as well as updated Figure 1 in our main text to illustrate that Orgo- Seq is an integrative platform to combine the strengths of bRNA- seq and scRNA- seq for cell type specific co- expression discovery. + +<|ref|>text<|/ref|><|det|>[[115, 299, 857, 333]]<|/det|> +Figure 1: Orgo- Seq framework to identify cell type specific co- expressed driver genes. (A) Figure illustrating the strengths and weaknesses of bRNA- seq and scRNA- seq, and what + +<|ref|>text<|/ref|><|det|>[[115, 333, 857, 402]]<|/det|> +Orgo- Seq can achieve by integrating both types of datasets. (B) A schematic of the Orgo- Seq framework to integrate bRNA- seq data from patient- derived brain organoids with scRNA- seq data from control brain organoids and bRNA- seq data from post- mortem human brains (BrainSpan), for the discovery of critical cell types and cell type specific driver genes. + +<|ref|>image<|/ref|><|det|>[[120, 402, 870, 678]]<|/det|> + +<|ref|>title<|/ref|><|det|>[[115, 693, 865, 738]]<|/det|> +# "Data integration of bRNA-seq data from donor-derived cerebral organoids and scRNA-seq data from control organoids identifies critical cell types for 16p11.2 deletions and 15q11-13 duplications + +<|ref|>text<|/ref|><|det|>[[115, 737, 883, 869]]<|/det|> +Deletions in 16p11.2 are significantly associated with ASD but not with schizophrenia, whereas duplications in 16p11.2 are associated with both ASD and schizophrenia6,32,33. Clinical studies have shown that individuals with 16p11.2 deletions have increased brain sizes, and individuals with duplications in the same locus have decreased brain sizes32,34,35. Mouse models with 16p11.2 deletions or duplications similarly show an increase or reduction in brain sizes and in the proportions of neural progenitor cells36- 38. A systematic perturbation of all genes in the 16p11.2 locus using head sizes as the phenotypic readout in zebrafish identified KCTD13 as the only driver gene in the locus modulating the proportion of neural progenitor cells39. However, recent studies in mice and zebrafish with deleted KCTD13 did not observe increased brain sizes + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 866, 183]]<|/det|> +or neurogenesis in these mutant animal models40,41. In the absence of human fetal brains with 16p11.2 deletions that could be used to resolve these conflicting results from animal models42, the use of donor- derived cerebral organoids could be good models to provide supporting results. + +<|ref|>text<|/ref|><|det|>[[115, 182, 870, 285]]<|/det|> +To accomplish this, we would have to identify which cell type specific co- expressed gene(s) from the donor- derived cerebral organoids are misregulating the proportions of critical cell types in cases versus controls (Fig. 1B). We developed a two- step solution where we first identified the critical cell types that were disproportionately affected in cases versus controls using mRNA- seq data from the donor- derived cerebral organoids, and a second step where we identified which of the genes in the CNV loci were disproportionately misregulating cell type specific expression of genes outside the CNV loci between cases versus controls. + +<|ref|>text<|/ref|><|det|>[[115, 284, 868, 388]]<|/det|> +There are two general approaches to identify critical cell types from mRNA- seq data: deconvolution methods such as CIBERSORT and CIBERSORTx, or cell type enrichment methods such as xCell43,44. Previously, when using mRNA- seq data from pure cell types as a reference panel43, it was shown that a cell type enrichment approach (xCell) outperforms a deconvolution approach (CIBERSORT). We sought to develop a cell type enrichment based approach for mRNA- seq data from cerebral organoids, by using scRNA- seq data from brain organoids and fetal brains as a reference panel." + +<|ref|>sub_title<|/ref|><|det|>[[115, 401, 330, 416]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 416, 881, 490]]<|/det|> +2. The figures are still not at all sufficient. The authors state they have checked the figures but there are still figures lacking y-axis labels. The legends need to be re-written as well to much more detailed results/statistics. Many supplementary figures should be included as panels in the main figures - there is very little substance in the main figures. It is very hard to understand what the results are by looking at the figures. + +<|ref|>text<|/ref|><|det|>[[115, 503, 878, 592]]<|/det|> +We apologize for the confusion and have checked all the figures to ensure that they all have y- axis labels. We have also shortened all the legends to remove detailed results/statistics. We have gone through all the supplementary figures and felt that while the supplementary figures were important for quality control, demonstrating the validity of the data or conceptualization of our methods, they were not directly contributing to visualizing the results of the main text (unlike our main figures). + +<|ref|>sub_title<|/ref|><|det|>[[115, 606, 330, 620]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 621, 878, 710]]<|/det|> +3. It is still unclear why the authors used different thresholds for the most variable genes. The fact they yield the same number of genes is irrelevant and should not be a consideration as this will change from experiment to experiment. Rather the authors should use statistical justification for a cutoff and use it in both instances. If the genes are variable because they show low expression, use a RPKM cutoff instead of a variability cutoff. If the genes are highly expressed and variable, they should be included in the analysis. + +<|ref|>text<|/ref|><|det|>[[115, 723, 856, 811]]<|/det|> +We will like to clarify that we did use an expression cutoff (FPKM \(> = 2\) ). However, a single dimension by using a FPKM cutoff alone is insufficient. Using a variance cutoff or developing statistical models for identifying highly variable genes had been used in prior publications, especially for small sample sizes and for scRNA-seq, to account for technical variability in library preparation and low read counts per cell (e.g. Law CW et al., Genome Biology 2014; Chen HH et al., BMC Genomics 2016). + +<|ref|>text<|/ref|><|det|>[[115, 825, 864, 870]]<|/det|> +We thank the reviewer for the clarification and we understand that the reviewer's concern also stems from having a standardized statistical justification across different studies. We had systematically compared the percentage of genes that overlap between the lists of genes with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 884, 185]]<|/det|> +high intra-individual variability and genes with high inter-individual variability. The thresholds that we used were selected based on the points of inflection for both intra-individual variability (SD=2) and inter-individual variability (SD=1.5), and we have now included the data in Supplementary Table 5 and plotted the results in the updated Supplementary Fig. 2. + +<|ref|>image<|/ref|><|det|>[[117, 199, 625, 373]]<|/det|> + + +<|ref|>image_caption<|/ref|><|det|>[[115, 379, 880, 455]]<|/det|> +
**Supplementary Figure 2. Varying intra-individual and inter-individual standard deviations (SD). (A)** The ratios of overlap between the genes with high intra-individual SDs and high inter-individual SDs, with intra-individual SDs varying from 0.5 to 3. **(B)** The ratios of overlap between the genes with high inter-individual SDs and high intra-individual SDs, with inter-individual SDs varying from 0.5 to 3.
+ +<|ref|>sub_title<|/ref|><|det|>[[115, 468, 335, 483]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 483, 884, 543]]<|/det|> +4. While the authors state that they have modified the text to clarify the differential expression much of the text presented as new, it is essential the same text from the original submission and the authors did not respond to our comment. - is there any overlap between the different sets (here we only see SetA compared with the 15q11-13 deletion). Are the logFC similar? + +<|ref|>text<|/ref|><|det|>[[115, 556, 884, 601]]<|/det|> +We thank the reviewer for raising this point. Actually there is a high correlation between the fold changes of 8 out of 9 genes in common between Set A of the 16p11.2 and 15q11-13 (Pearson’s \(r = 0.92\), \(P = 0.0014\)). + +<|ref|>text<|/ref|><|det|>[[115, 615, 864, 644]]<|/det|> +We moved all these analyses in the updated Supplementary Materials section, and expanded on the analyses: + +<|ref|>text<|/ref|><|det|>[[115, 644, 884, 673]]<|/det|> +**“Comparison of differentially expressed genes from 16p11.2 deletion and 15q11-13 duplication cerebral organoids reveals 9 genes in common** + +<|ref|>text<|/ref|><|det|>[[115, 673, 884, 763]]<|/det|> +We compared the differentially expressed genes with FDR≤0.05 between the 16p11.2 deletion SetA and 15q11-13 duplication results, and observed that there were 8 genes that were differentially expressed in the same direction for 16p11.2 deletions (SetA) and 15q11-13 duplications (RPS14, PCDHGB6, TUBGCP5, CYFIP1, ELAVL2, SNHG5, NAP1L5 and MYL6B). There was a high correlation between the fold changes of these 8 genes between 16p11.2 deletions and 15q11-13 duplications (Pearson’s \(r = 0.92\), \(P = 0.0014\)). + +<|ref|>table<|/ref|><|det|>[[216, 775, 780, 870]]<|/det|> +
GeneFold change in 16p11.2Fold change in 15q11-13
RPS141.091.11
PCDHGB60.540.54
TUBGCP51.181.72
CYFIP11.051.35
ELAVL20.680.52
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[216, 123, 780, 173]]<|/det|> + +
SNHG51.151.3
NAP1L50.750.53
MYL6B0.970.92
+ +<|ref|>text<|/ref|><|det|>[[115, 185, 884, 290]]<|/det|> +Another gene (HERC2) was also differentially expressed for 16p11.2 deletions (SetA) and 15q11- 13 duplications but in opposite directions. HERC2 was over- expressed in 15q11- 13 duplications cases compared to controls (fold change \(= 1.48\) ), whereas HERC2 was under- expressed in 16p11.2 deletion cases compared to controls (fold change \(= 0.9\) ). Of the 9 genes that were differentially expressed, 3 of them (TUBGCP5, CYFIP1 and HERC2) were found in the 15q11- 13 locus. These results suggest that there are shared key genes that are perturbed by 16p11.2 deletions and 15q11- 13 duplications. + +<|ref|>text<|/ref|><|det|>[[115, 302, 884, 362]]<|/det|> +There were 6 genes that were differentially expressed in the same direction for 16p11.2 deletions (SetP) and 15q11- 13 duplications (RPS14, PCDHGB6, ELAVL2, SNHG5, CTNNA2 and NAP1L5). There was a moderate correlation between the fold changes of these 6 genes between 16p11.2 deletions (SetP) and 15q11- 13 duplications (Pearson's \(r = 0.73\) , \(P = 0.064\) ). + +<|ref|>table<|/ref|><|det|>[[216, 361, 780, 469]]<|/det|> + +
GeneFold change in 16p11.2Fold change in 15q11-13
RPS141.091.11
PCDHGB60.520.54
ELAVL20.720.52
SNHG51.151.3
CTNNA20.590.58
NAP1L50.690.53
+ +<|ref|>text<|/ref|><|det|>[[115, 468, 884, 512]]<|/det|> +HERC2 was also differentially expressed for 16p11.2 deletions (SetP) and 15q11- 13 duplications but in opposite directions (fold change \(= 0.8\) in 16p11.2 SetP and fold change \(= 1.48\) in 15q11- 13). + +<|ref|>text<|/ref|><|det|>[[115, 526, 884, 558]]<|/det|> +There were no significantly differentially expressed genes with FDR≤0.05 from the 16p11.2 deletion (SetD) analyses." + +<|ref|>sub_title<|/ref|><|det|>[[115, 571, 330, 586]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 586, 869, 660]]<|/det|> +5. In this paper, organoids were grown for 46 days, while the cell types derived from single cell RNAseq were ascertained from 3 and 6 month-old organoids. The authors claim that their method is tolerant to these time differences, but in order to make this claim they need to show much more data, as this comprises very large differences in developmental stage and cell composition. + +<|ref|>text<|/ref|><|det|>[[115, 673, 861, 777]]<|/det|> +We agree with the reviewer that it is interesting to understand the transcriptomic differences during neurodevelopment and cell type composition between brain organoids with different ages. There are several scRNA- seq papers that have been published on brain organoids and fetal brains addressing these questions, and these questions are beyond the scope of our manuscript, so we did not specifically address them. We had also removed the comparisons between 3- month and 6- month organoids as they had been systematically compared in prior publications. + +<|ref|>text<|/ref|><|det|>[[115, 789, 872, 849]]<|/det|> +However, for the purpose of our manuscript, which is to identify cell type specific co- expressed driver genes in ASD, we demonstrate that our Orgo- Seq framework is robust in integrating scRNA- seq data from organoids with different ages (e.g. 3 and 6 month organoids), and bRNA- seq from 46- day old organoids in a few ways: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 880, 184]]<|/det|> +1. We integrated scRNA-seq data from the Tanaka study, which is an aggregated scRNA-seq dataset from 8 different brain organoid protocols and fetal brains across different developmental timepoints, and replicated our initial results when using scRNA-seq data from the Quadrato study (please see point 6 below). + +<|ref|>text<|/ref|><|det|>[[115, 196, 870, 227]]<|/det|> +2. We performed validation of one of the key findings to identify cell type specific co-expressed driver genes (KCTD13) using the mosaic organoid oFlowSeq framework. + +<|ref|>text<|/ref|><|det|>[[115, 240, 875, 271]]<|/det|> +3. We performed multiple analyses to compare our results with results reported by other studies (published and unpublished). + +<|ref|>sub_title<|/ref|><|det|>[[115, 284, 331, 300]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 300, 867, 344]]<|/det|> +a. The authors do not show any evidence that the cell types that they are using in the analysis are even found at this early stage. For example - cluster c4 "cells with forebrain markers" - are these cells/markers present in the organoid data? + +<|ref|>text<|/ref|><|det|>[[114, 358, 882, 476]]<|/det|> +Yes, all the genes in each cell type cluster are expressed in bRNA-seq data from our 46-day old cerebral organoids. We had performed quality control to remove genes that are not expressed in the 46-day old cerebral organoids from all downstream analyses. For each of the cell type clusters, the genes that were found in the cell type cluster, and were expressed in our donor-derived cerebral organoids were reported in Supplementary Table 11. All the 10 cell type clusters from the Quadrato study were represented by multiple cell type specific genes (ranging from 47 to 266). All the 11 cell type clusters from the Tanaka study were represented by multiple cell type specific genes (ranging from 12 to 421). + +<|ref|>sub_title<|/ref|><|det|>[[115, 489, 331, 504]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 504, 882, 563]]<|/det|> +b. One alternative hypothesis is that a difference in the cell specific markers could mean a developmental shift in the treated vs. control and not a cell enrichment shift. Can the authors show data for the cell specific markers across development to rule out this hypothesis or at least discuss this in interpreting their data? + +<|ref|>text<|/ref|><|det|>[[115, 576, 884, 633]]<|/det|> +Yes, we thank the reviewer for pointing this out, and we apologize that we did not articulate these hypotheses more clearly in our previous manuscript. We were also curious about these two alternative hypotheses, and our mosaic cerebral organoid experiments (oFlowSeq) served 2 main purposes: + +<|ref|>text<|/ref|><|det|>[[115, 633, 880, 680]]<|/det|> +1) to validate the critical cell type specific driver gene (KCTD13) based on our results from Orgo-Seq +2) to evaluate if there is a distortion in the proportion of Nestin+ cells due to KCTD13 mutations. + +<|ref|>text<|/ref|><|det|>[[115, 693, 881, 797]]<|/det|> +If we did not identify differences in the proportions of Nestin+ cells for all deleterious mutations in KCTD13, then the results will suggest a developmental shift in transcriptomic differences within the cells and not differences in the proportions of cell types. However, we did observe a difference in the proportions of Nestin+ cells with KCTD13 deleterious mutations, so we can rule out that the first hypothesis (intrinsic developmental shift). In addition, the distortion in cell type proportions is in concordance with prior literature on KCTD13 deficiency (Kizner V et al, 2019), and might explain for the increased head sizes observed in patients with 16p11.2 deletions. + +<|ref|>sub_title<|/ref|><|det|>[[115, 811, 305, 825]]<|/det|> +## Our updated text reads: + +<|ref|>text<|/ref|><|det|>[[115, 826, 881, 870]]<|/det|> +"This validation approach provides an orthogonal approach to validate our observed results from Orgo-Seq, and also serves to test the two hypotheses generated from the Orgo-Seq results: if there is a distortion in the proportions of cell types between the cerebral organoids from cases + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 875, 228]]<|/det|> +versus controls, or if there is an intrinsic developmental shift resulting in transcriptomic differences within the cells, but not a distortion in the proportions of cell types. If KCTD13 mutations do not affect the proportions of a specific cell type population, we expect to observe that the mutations are not significantly enriched in cells that are positive or negative for that cell type marker (Fig. 4A, Supplementary Materials). However, if KCTD13 mutations affect the proportions of a specific cell type population, we expect to observe that the mutations are significantly enriched in the cells that are positive for that cell type marker." + +<|ref|>sub_title<|/ref|><|det|>[[116, 241, 331, 256]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 256, 876, 300]]<|/det|> +6. The authors did not address the misclassification and while they claim that it was validated in another data set (from the same lab) there are many published single cell data sets and the authors should really validate their methods using many of these data sets. + +<|ref|>text<|/ref|><|det|>[[115, 314, 880, 374]]<|/det|> +We have now addressed the reviewer's concerns about misclassification in 2 ways. Firstly, we have now re- done our Orgo- Seq analyses using a larger- scale aggregated dataset published by Tanaka et al., and validated our initial results identifying YPEL3, INO80E and KCTD13 as critical cell type specific driver genes for 16p11.2 deletions. + +<|ref|>text<|/ref|><|det|>[[115, 387, 868, 461]]<|/det|> +In addition, we revisited the reviewer's comment about potential misclassification of the identities of cell type clusters from different scRNA- seq studies by different labs, and we developed an approach to enable consistent cell type identification across different studies, by using 2 neurodevelopmental reference maps to fine- map the cell type identities from different studies. + +<|ref|>text<|/ref|><|det|>[[116, 475, 350, 490]]<|/det|> +Our updated text is as follow: + +<|ref|>sub_title<|/ref|><|det|>[[116, 491, 213, 504]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[114, 504, 880, 740]]<|/det|> +"We applied Orgo- Seq for two ASD- associated copy number variants (CNVs) in the 16p11.2 and 15q11- 13 loci16- 18, by integrating 3 sets of transcriptomics datasets: bRNA- seq data that we generated from donor- derived cerebral organoids, previously published scRNA- seq data from cerebral organoids and fetal brains1,13,19,20, and previously published bRNA- seq data from human post- mortem brain samples in the BrainSpan Project21. Using an initial scRNA- seq dataset from 66,889 single cells1, we initially observed that neuroepithelial cells are perturbed in donor- derived cerebral organoids from individuals with deletions in 16p11.2 compared to individuals without the deletions, and that 3 of the genes in the locus (YPEL3, KCTD13 and INO80E) are likely to be candidate driver genes functioning in neuroepithelial cells. Using a larger scRNA- seq dataset comprising of 190,022 cells19 from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and two neurodevelopmental maps constructed from scRNA- seq on brain organoids and fetal brains to fine- map the critical cell types13,20, we replicated the critical cell type that was initially discovered, and were able to pinpoint the identity of the critical cell type more precisely during neurodevelopment to immature neurons and intermediate progenitor cells for the 16p11.2 locus. We also replicated our initial results that YPEL3, KCTD13 and INO80E are cell type specific candidate driver genes." + +<|ref|>sub_title<|/ref|><|det|>[[115, 754, 178, 767]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[115, 768, 866, 798]]<|/det|> +"Fine- mapping of cell type identities using large- scale neurodevelopmental maps point to the role of immature neurons and intermediate progenitor cells for the 16p11.2 locus. + +<|ref|>text<|/ref|><|det|>[[115, 798, 872, 872]]<|/det|> +A recent study by Tanaka Y et al. had re- analyzed 190,022 cells from brain organoids differentiated using 8 different protocols and fetal brains1,7- 13,22, and identified 24 cell type clusters19. We systematically compared the percentage overlaps among genes across the 24 cell type clusters to identify 11 unique clusters (CC1- 11; Supplementary Table 13). We calculated CellScores using the 11 cell type clusters for 16p11.2, and found that there was only + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 879, 170]]<|/det|> +the cell type cluster comprising of cortical excitatory neurons (CC3) that had an FWER \(\leq 0.05\) \((P(CellScore) = 3.6 \times 10^{- 4}\) , Fig. 3C). Interestingly, we did not observe any association for 16p11.2 with the neuroepithelial cell cluster (CC7) in the Tanaka study \((P(CellScore) = 0.11)\) . + +<|ref|>text<|/ref|><|det|>[[114, 170, 880, 345]]<|/det|> +To ensure consistencies in assigning cell type identities across different studies, and to fine- map the critical cell types more precisely during neurodevelopment, we used two neurodevelopmental maps that were reconstituted from scRNA- seq data on brain organoids and fetal brains. The first neurodevelopmental map by Velasco S et al. comprised of 12 cell types \(^{13}\) , and we calculated the percentage overlap among genes from each cell type cluster reported by Quadrato G et al. and Tanaka Y et al. \(^{1,19}\) (Supplementary Table 14). We found that the neuroepithelial cell cluster (c9) from the Quadrato study overlapped most closely with immature projection neurons (mean overlap \(= 0.37\%\) ), and that the unknown cell type (c6) from the Quadrato study overlapped most closely with outer radial glia cells (mean overlap \(= 0.29\%\) ). The CC3 cluster from the Tanaka study overlapped most closely with immature projection neurons in the neurodevelopmental map (mean overlap \(= 1.14\%\) ), similar to the c9 cluster from the Quadrato study. + +<|ref|>text<|/ref|><|det|>[[114, 345, 880, 477]]<|/det|> +We used a second neurodevelopmental map by Eze UC et al. that comprised of 6 cell types \(^{20}\) , and calculated the percentage overlap among the genes from each cell type cluster reported by the Quadrato and Tanaka studies (Supplementary Table 14). We found that the c9 cluster from the Quadrato study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 8.1\%\) and \(5.4\%\) respectively). Similarly, the CC3 cluster from the Tanaka study overlapped most closely with the neuronal and intermediate progenitor cell clusters (mean overlaps \(= 19.8\%\) and \(11.1\%\) respectively). These results suggest that the critical cell types for the 16p11.2 locus are likely to be immature neurons and intermediate progenitor cells. + +<|ref|>text<|/ref|><|det|>[[114, 477, 881, 612]]<|/det|> +To evaluate the degree of independence among the genes in the c9 cluster from the Quadrato study and the CC3 cluster from the Tanaka study, we calculated the correlations between the mean overlaps across the two neurodevelopmental maps for both the c9 and CC3 clusters (Supplementary Table 15). We observed high correlations between both the c9 and CC3 clusters using both neurodevelopmental maps \((r = 0.71, P = 9.1 \times 10^{- 3}; r = 0.95, P = 3.6 \times 10^{- 3})\) . However, there were stronger correlations between the CC3 and c5 clusters \((r = 0.96, P = 8.7 \times 10^{- 7}; r = 0.98, P = 6.3 \times 10^{- 4})\) , even though the c5 cluster was not implicated as the critical cell type from the 16p11.2 donor- derived organoids. This indicates that there is likely to be independence among the genes implicating the c9 and CC3 clusters as critical cell types in the 16p11.2 locus." + +<|ref|>sub_title<|/ref|><|det|>[[115, 625, 330, 640]]<|/det|> +## Reviewer 4 Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 640, 867, 730]]<|/det|> +7. (Additional comment). For the odds ratio statistics comparing the isogenic with the patient-derived lines, is this statistic (page 9 of the response to reviewers) comparing the overlap in DEGs between the neural stem cells vs. the iNeurons? Or is this showing that the neural stem cell/patient derived cerebral organoid overlap is more significant than would be expected by chance? Make it clear what statistical comparisons are being done in the text and figure legends. + +<|ref|>text<|/ref|><|det|>[[115, 743, 878, 817]]<|/det|> +Yes, the odds ratios are comparing the overlaps in DEGs between the organoids and the NSCs versus iNs. We had also reported the \(95\%\) confidence intervals and Fisher's Exact Test P- values to evaluate if the overlaps were more significant than would be expected by chance (that is, the overlap in DEGs between donor- derived cerebral organoids with iNs is assumed to be the baseline null). + +<|ref|>text<|/ref|><|det|>[[115, 831, 432, 846]]<|/det|> +We have updated the text to clarify this: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 863, 185]]<|/det|> +These observations provide further evidence that the differentially expressed genes from the patient- derived cerebral organoids are significantly more similar to the differentially expressed genes from the isogenic NSCs than the isogenic iNs with the same 16p11.2 deletion or duplication than by chance. + +<|ref|>text<|/ref|><|det|>[[115, 198, 840, 228]]<|/det|> +We have also made a figure in the Supplementary Methods section to provide clarity to the results: + +<|ref|>image<|/ref|><|det|>[[120, 230, 400, 412]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[115, 426, 598, 442]]<|/det|> +## Reviewer 4 Minor issues not addressed (from critiques): + +<|ref|>text<|/ref|><|det|>[[115, 442, 878, 516]]<|/det|> +10. Using all samples, even those from the same individual, as independent samples in the linear model falsely inflates the number of DEG (see Germain and Testa 2017 Stem Cell Reports). Instead, a mixed linear model should be used to account for multiple samples coming from the same individual. - this was not addressed. The assumption of independence even if it was used to increase the number of permutations is wrong. + +<|ref|>text<|/ref|><|det|>[[115, 530, 881, 574]]<|/det|> +We have now performed a DEG analysis for 16p11.2 SetA using EdgeR with a linear mixed effects model and accounting for multiple replicates from the same individual. The histograms of the p-value and FDR distributions are shown below. + +<|ref|>image<|/ref|><|det|>[[115, 579, 535, 721]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 725, 852, 770]]<|/det|> +For each gene, we calculated a ratio, which gives us an estimate of the degree of inflation or deflation in the P- value distributions. Ratio = - log10(P- value from linear regression) divided by - log10(P- value from EdgeR) + +<|ref|>text<|/ref|><|det|>[[115, 783, 478, 799]]<|/det|> +We plotted the log10(Ratio) histogram below: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 130, 405, 333]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 339, 820, 370]]<|/det|> +As the reviewer correctly pointed out, there is an inflation and the median \(\log 10(\text{Ratio})\) is 0.4156586 (indicated by the red line), and \(10^{\wedge}0.4156586 = 2.604106\) . + +<|ref|>text<|/ref|><|det|>[[115, 382, 333, 397]]<|/det|> +Our GeneScore statistic is: + +<|ref|>equation<|/ref|><|det|>[[325, 397, 671, 440]]<|/det|> +\[G e n e S c o r e(x) = \frac{1}{l o g_{10}\lambda}\sum_{a l l y}\frac{-l o g_{10}P_{y}\times r_{x,y}^{2}}{N u m_{y}}\] + +<|ref|>text<|/ref|><|det|>[[115, 452, 872, 528]]<|/det|> +We had used the \(\lambda\) term in GeneScore to correct for any potential inflation in the p- value distributions. From the 16p11.2 SetA data, the calculated \(\lambda\) was 5.60565, which is higher than the median inflation calculated from comparing the two different DEG analyses (2.604106). As such, the test statistics that we had used were even more stringent than accounting for multiple replicates from the same individual alone. + +<|ref|>text<|/ref|><|det|>[[115, 541, 866, 660]]<|/det|> +We did not include these analyses mentioned above in our revised manuscript as we felt that these were tangential points that would cause confusion to the readers. However, we reiterate that we had used highly conservative statistics and analyses in our current Orgo- Seq manuscript as our initial manuscript is to evaluate if we can detect cell type specific co- expressed driver genes by integrating bRNA- seq and scRNA- seq data from multiple brain organoid studies, and we wanted to ensure that our results were robust and were likely to replicate (using the mosaic organoid oFlowSeq approach and when integrating additional scRNA- seq data). + +<|ref|>sub_title<|/ref|><|det|>[[115, 673, 333, 688]]<|/det|> +## Reviewer 4 Minor issues: + +<|ref|>text<|/ref|><|det|>[[115, 688, 879, 746]]<|/det|> +15. There are still more sections in the results that need to be moved to the discussion. We have revised the manuscript substantially and moved several sections into the supplementary materials. Also, we had removed several sections that rehashed the results from prior publications, and instead, we cited these prior publications instead. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 300, 97]]<|/det|> +## Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[120, 114, 402, 129]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 145, 875, 334]]<|/det|> +The revised manuscript, now called "Multi- transcriptomics data integration of cerebral organoids and post- mortem brains to identify cell type specific co- expressed driver genes in autism" has been considerably improved by the authors. The text and logic flow is improved to gain clarity. Inclusion of a new reference scRNAseq dataset, a combination of several recent datasets from multiple labs performed by Tanaka et al. is very valuable and firmly grounds Orgo- Seq within a variety of protocols and organoids. The authors have performed several additional computational analyses and controls bolstering their claims. I remain skeptical of the FACS- based verification, which still raises a lot of questions. Given that the paper's increased focus on the computational Orgo- Seq pipeline, the FACS- based assay seems dispensable and, in my mind, might be removed from the ms entirely. Given the extensive bulk RNA- Seq provided and more importantly the Orgo- Seq pipeline, which constitutes a valuable contribution in this very exciting, important and ongoing research area, I would recommend publication upon some editorial changes. + +<|ref|>text<|/ref|><|det|>[[118, 351, 216, 365]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[118, 366, 870, 428]]<|/det|> +1. The text still would benefit from further streamlining. As an example, there is a lengthy passage on the initial use of the Quadrato et al dataset as the scRNAseq reference for Orgo-Seq. Given that the authors have repeated this analysis using the much better Tanaka et al combined reference dataset, this should be the focus of the text. + +<|ref|>text<|/ref|><|det|>[[116, 444, 875, 476]]<|/det|> +2. Like before, the figures need some improvement. Font sizes are too small to read at times (ie figure 3, axis labelling, multiple supplementary figures). + +<|ref|>text<|/ref|><|det|>[[117, 491, 877, 648]]<|/det|> +3. As explained above, I would propose to remove the FACS data. However, if the authors insist to keep them, they need to explain their approach. a) As mentioned before, why are so few cells positive for the markers used? This is inconsistent with other lab's data on progenitor and neuron percentages in organoids. b) In the FACS plots (Supplementary figure 10), why is IgG2A used as a control, even though the antibodies are of a different antibody class? c) Why are the forward scatter plots so different? These are antibody independent and should be equal. d) All gates used are equal and presumably set on the incorrect IgG2A isotype control. The increased rates of positive cells for all the markers could be simply explained by the different antibody conditions used. In fact, the entire population (including negative cells, easily seen by the red mark in the heat map plots) is shifted to the right by about 0.5 logs on the x-axis. e) Were similar FACS settings used? + +<|ref|>text<|/ref|><|det|>[[120, 696, 402, 710]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 727, 878, 884]]<|/det|> +The overall goals of this work are laudable and a lot has been done. There were serious critiques to the previous version and authors have done a good job of answering concerns especially regarding some of the more technical issues that concerned me and other reviewers. The paper is much better put together and clearer to follow. The major issue is whether the major claims vis a vis driver genes is convincing and whether Orgo- seq is itself an advanced and widely useful framework for integration of multi- transcriptomics data sets as claimed --- I am not entirely convinced, but the work is very good, and I also think that the authors have done a reasonable job responding (and this is a nice data set), so that this should be published. These issues will be decided by the readers and the community once the work is published, and as the field moves forward with larger, additional samples as suggested. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 353, 98]]<|/det|> +My minor comments are below: + +<|ref|>text<|/ref|><|det|>[[118, 115, 848, 146]]<|/det|> +The high reproducibility and demonstration that genes within the CNVs study change as would be expected from the dosage changes are important strengths of the work. + +<|ref|>text<|/ref|><|det|>[[118, 162, 863, 193]]<|/det|> +Other published work shows similar high correlation between organoids from controls and should be cited. + +<|ref|>text<|/ref|><|det|>[[118, 209, 860, 334]]<|/det|> +I do wonder whether pairwise correlations used to identify co- expression are nearly as robust as graph theoretical measures such as topological overlap (T0). It has been shown that TO removes spurious correlations and reduces noise, compared with standard pairwise correlation measures. In this case, TO would remove noisy genes or spuriously correlated genes - conversely this weakness with pairwise correlation may underlie the initial negative results with 15q. Perhaps applying these methods (see also recent Nature Genetics paper integrating single cell and bulk tissue- PMID: 34239132) using this more robust framework would yield stronger putative drivers at the 15q11- 13 locus. + +<|ref|>text<|/ref|><|det|>[[118, 350, 872, 412]]<|/det|> +One issue that I had which is likely out of the scope of the paper is that there seems to be very low mean overlap between the clusters in the Quadrato and Tanaka studies with the Velasco neurodevelopmental maps (ranging from \(0.37\% = 1.14\%\) ). It is also unclear from the methods how this mean overlap was calculated. + +<|ref|>text<|/ref|><|det|>[[118, 427, 875, 507]]<|/det|> +Another issue is the interpretation of the integration of the bulk RNAseq from the postmortem brains. While the method developed in the paper allows to integrate the organoid single cell and post mortem bulk RNAseq the two tissues have different cell types or at the very least different levels of maturation. To make this point even more apparent the top cell type cluster identified was the stem cell cluster which is massively depleted in the adult brain. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 848, 127]]<|/det|> +We thank both reviewers for their comments, and we summarize a few key revisions to our manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 147, 430, 164]]<|/det|> +## Orgo-Seq package and documentation + +<|ref|>text<|/ref|><|det|>[[114, 165, 880, 312]]<|/det|> +We have now re- implemented Orgo- Seq as an R package, provided the source codes, and wrote detailed documentation for running the package on our GitHub site (https://gitlab.com/elimlab/orgo- seq). As part of the re- implementation, we have also worked on optimizing the codes, parallelization and improving runtimes. Given the more efficient codes, we have now performed 1 million permutations for our 16p11.2 CellScore results, instead of the initial 100,000 permutations. We have also calculated CellScores for the 15q11- 13 data using the Tanaka dataset, but similar to the Quadrato dataset, we did not observe any cell type clusters with FWER \(< = 0.1\) for the 15q11- 13 data. + +<|ref|>sub_title<|/ref|><|det|>[[115, 332, 177, 348]]<|/det|> +## Figures + +<|ref|>text<|/ref|><|det|>[[115, 349, 866, 386]]<|/det|> +We have re- done most of the figures in the manuscript and the supplementary materials, and re- organized panels within the figures to improve readability. + +<|ref|>sub_title<|/ref|><|det|>[[115, 404, 370, 421]]<|/det|> +## oFlowSeq (FACS based system) + +<|ref|>text<|/ref|><|det|>[[115, 423, 594, 440]]<|/det|> +We have removed this section from our revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 460, 253, 476]]<|/det|> +## 15q11-13 results + +<|ref|>text<|/ref|><|det|>[[115, 478, 870, 570]]<|/det|> +We re- ran our analyses for critical cell types using both the Quadrato and Tanaka datasets for the 15q11- 13 locus (100,000 permutations). We did not observed any significant critical cell type using both datasets. To avoid confusion, we have revised our manuscript to focus only on the 16p11.2 driver gene results in the critical cell type identified, and removed the 15q11- 13 putative driver gene results. + +<|ref|>text<|/ref|><|det|>[[115, 587, 833, 621]]<|/det|> +Our point- by- point responses (in blue text) to the reviewers' comments (in black text) is as follow. References to updated text in the revised manuscript are highlighted in red text. + +<|ref|>text<|/ref|><|det|>[[115, 641, 420, 658]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 659, 881, 899]]<|/det|> +The revised manuscript, now called "Multi- transcriptomics data integration of cerebral organoids and post- mortem brains to identify cell type specific co- expressed driver genes in autism" has been considerably improved by the authors. The text and logic flow is improved to gain clarity. Inclusion of a new reference scRNASeq dataset, a combination of several recent datasets from multiple labs performed by Tanaka et al. is very valuable and firmly grounds Orgo- Seq within a variety of protocols and organoids. The authors have performed several additional computational analyses and controls bolstering their claims. I remain skeptical of the FACS- based verification, which still raises a lot of questions. Given that the paper's increased focus on the computational Orgo- Seq pipeline, the FACS- based assay seems dispensable and, in my mind, might be removed from the ms entirely. Given the extensive bulk RNA- Seq provided and more importantly the Orgo- Seq pipeline, which constitutes a valuable contribution in this very exciting, important and ongoing research area, I would recommend publication upon some editorial changes. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 863, 145]]<|/det|> +We thank the reviewer for his/her suggestions, and have now removed the FACS- based assay from the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 163, 881, 238]]<|/det|> +1. The text still would benefit from further streamlining. As an example, there is a lengthy passage on the initial use of the Quadrato et al dataset as the scRNAseq reference for Orgo-Seq. Given that the authors have repeated this analysis using the much better Tanaka et al combined reference dataset, this should be the focus of the text. + +<|ref|>text<|/ref|><|det|>[[115, 256, 846, 293]]<|/det|> +We thank the reviewer and have rewritten the text to state that we used the Quadrato and Tanaka datasets, and replicated our findings with both datasets. + +<|ref|>text<|/ref|><|det|>[[115, 311, 846, 349]]<|/det|> +2. Like before, the figures need some improvement. Font sizes are too small to read at times (ie figure 3, axis labelling, multiple supplementary figures). + +<|ref|>text<|/ref|><|det|>[[115, 367, 866, 404]]<|/det|> +We apologize and have re- done most of the figures to ensure that all axes are labeled, and re- organized the figures within multiple larger figures to provide better clarity. + +<|ref|>text<|/ref|><|det|>[[114, 422, 879, 625]]<|/det|> +3. As explained above, I would propose to remove the FACS data. However, if the authors insist to keep them, they need to explain their approach. a) As mentioned before, why are so few cells positive for the markers used? This is inconsistent with other lab's data on progenitor and neuron percentages in organoids. b) In the FACS plots (Supplementary figure 10), why is IgG2A used as a control, even though the antibodies are of a different antibody class? c) Why are the forward scatter plots so different? These are antibody independent and should be equal. d) All gates used are equal and presumably set on the incorrect IgG2A isotype control. The increased rates of positive cells for all the markers could be simply explained by the different antibody conditions used. In fact, the entire population (including negative cells, easily seen by the red mark in the heat map plots) is shifted to the right by about 0.5 logs on the x-axis. e) Were similar FACS settings used? + +<|ref|>text<|/ref|><|det|>[[115, 644, 879, 680]]<|/det|> +We have removed the FACS data from our current manuscript. We sincerely thank the reviewer for these helpful comments. + +<|ref|>text<|/ref|><|det|>[[115, 700, 420, 717]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 718, 880, 903]]<|/det|> +The overall goals of this work are laudable and a lot has been done. There were serious critiques to the previous version and authors have done a good job of answering concerns especially regarding some of the more technical issues that concerned me and other reviewers. The paper is much better put together and clearer to follow. The major issue is whether the major claims vis a vis driver genes is convincing and whether Orgo- seq is itself an advanced and widely useful framework for integration of multi- transcriptomics data sets as claimed --- I am not entirely convinced, but the work is very good, and I also think that the authors have done a reasonable job responding (and this is a nice data set), so that this should be published. These issues will be decided by the readers and the community once the work is published, and as the field moves forward with larger, additional samples as suggested. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 870, 145]]<|/det|> +The high reproducibility and demonstration that genes within the CNVs study change as would be expected from the dosage changes are important strengths of the work. + +<|ref|>text<|/ref|><|det|>[[115, 164, 525, 181]]<|/det|> +We thank the reviewer for his/her encouragement. + +<|ref|>text<|/ref|><|det|>[[115, 201, 840, 236]]<|/det|> +Other published work shows similar high correlation between organoids from controls and should be cited. + +<|ref|>text<|/ref|><|det|>[[115, 256, 804, 274]]<|/det|> +We have included an additional reference comparing organoids from different donors. + +<|ref|>text<|/ref|><|det|>[[114, 293, 883, 441]]<|/det|> +I do wonder whether pairwise correlations used to identify co- expression are nearly as robust as graph theoretical measures such as topological overlap (TO). It has been shown that TO removes spurious correlations and reduces noise, compared with standard pairwise correlation measures. In this case, TO would remove noisy genes or spuriously correlated genes - conversely this weakness with pairwise correlation may underlie the initial negative results with 15q. Perhaps applying these methods (see also recent Nature Genetics paper integrating single cell and bulk tissue- PMID: 34239132) using this more robust framework would yield stronger putative drivers at the 15q11- 13 locus. + +<|ref|>text<|/ref|><|det|>[[115, 460, 878, 533]]<|/det|> +We thank the reviewer for the interesting suggestion, and we are currently working on generating additional datasets to evaluate this question with different approaches. We have removed the section of putative cell type specific driver genes in the 15q11- 13 locus, given that there was no critical cell type identified for the 15q11- 13 locus. + +<|ref|>text<|/ref|><|det|>[[115, 552, 870, 625]]<|/det|> +One issue that I had which is likely out of the scope of the paper is that there seems to be very low mean overlap between the clusters in the Quadrato and Tanaka studies with the Velasco neurodevelopmental maps (ranging from \(0.37\% = 1.14\%\) ). It is also unclear from the methods how this mean overlap was calculated. + +<|ref|>text<|/ref|><|det|>[[115, 644, 878, 699]]<|/det|> +We agree with the reviewer that additional research and investigation into datasets from scRNA- seq technologies will be needed. We have also updated our revised manuscript to clarify how we calculated the mean overlap. + +<|ref|>sub_title<|/ref|><|det|>[[115, 719, 707, 736]]<|/det|> +## Calculation of overlaps and correlations with neurodevelopmental maps + +<|ref|>text<|/ref|><|det|>[[115, 737, 872, 847]]<|/det|> +We used the cell type clusters from two large- scale scRNA- seq studies on brain organoids and fetal brains as neurodevelopmental maps \(^{13,20}\) , and calculated the percentage overlaps between the genes found in each cell type cluster from the Quadrato and Tanaka studies, and each cell type cluster from both neurodevelopmental maps (Supplementary Table 14). Using these percentage overlaps, we calculated the Pearson's correlations between each cell type cluster from both the Quadrato and Tanaka studies (Supplementary Table 15). + +<|ref|>text<|/ref|><|det|>[[115, 866, 872, 902]]<|/det|> +Another issue is the interpretation of the integration of the bulk RNAseq from the postmortem brains. While the method developed in the paper allows to integrate the organoid single cell + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 145]]<|/det|> +and post mortem bulk RNAseq the two tissues have different cell types or at the very least different levels of maturation. To make this point even more apparent the top cell type cluster identified was the stem cell cluster which is massively depleted in the adult brain. + +<|ref|>text<|/ref|><|det|>[[115, 164, 880, 237]]<|/det|> +We agree with the reviewer that additional research into the integration of bulk RNA- seq data from brain organoids and postmortem brains, will be needed. We have rewritten the section to emphasize that we did not detect any critical cell type through integration of bulk RNA- seq data from brain organoids and postmortem brains for the 15q11- 13 locus. + +<|ref|>sub_title<|/ref|><|det|>[[115, 256, 840, 292]]<|/det|> +## Data integration of bRNA-seq data from post-mortem brain samples and scRNA-seq data from control cerebral organoids to identify critical cell types + +<|ref|>text<|/ref|><|det|>[[114, 293, 870, 441]]<|/det|> +A prior publication had performed RNA sequencing on post- mortem brain samples of the cortex that were obtained from 9 individuals with 15q11- 13 duplications and 49 control individuals39. We calculated CellScores for each of the 10 cell type clusters in the Quadrato study using the differential expression results from the post- mortem brain samples, and calculated a weighted average P(CellScore) using the results from the patient- derived cerebral organoids and post- mortem brain samples with 15q11- 13 duplications (Supplementary Table 16). Similar to our results from the patient- derived cerebral organoids, there were no cell type clusters identified from the post- mortem brain samples that was significantly perturbed. + +<--- Page Split ---> diff --git a/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/images_list.json b/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c6b051c0598bbfd54e51858883cedfbba5656705 --- /dev/null +++ b/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,305 @@ + +# nature portfolio + +Peer Review File + +Molecular mechanism of parental H3/H4 recycling at a replication fork + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +## Summary: + +This research conducted molecular dynamics (MD) simulations of a yeast replication machinery, including Mcm2- 7, Cdc45, GINS, Pol \(\epsilon\) , and H3/H4 tetramer, along with replicated DNA. It was found that the H3/H4 tetramer initially bound to Mcm2 is transferred onto the replicated strands, a process termed recycling. The study demonstrates that the H3/H4 tetramer can be deposited on either the leading or lagging strand via a pathway mediated by Cdc45 or one not involving Cdc45. Specifically, in the Cdc45- mediated pathway, the H3/H4 tetramer tends to be deposited on the leading strand. Furthermore, the presence of RPA (Replication Protein A) restricts the migration area of histone recycling, although recycling of histones was observed even in the presence of two RPA molecules. Additionally, it was observed that Pol \(\epsilon\) orients the leading strand in a suboptimal direction for recycling purposes. The research question appears intriguing as it seeks to comprehend the molecular mechanism underlying the recycling of the H3/H4 tetramer during replication. However, I have few comments and suggestions. + +1. The study performed coarse-grained simulations of a very large system. This is very timely to push the boundaries of molecular simulations to address complex biological problems. While the study provides molecular mechanism its linkage with experimental studies should be strengthen beyond providing testable hypotheses. + +2. In their model, they considered only electrostatic interactions and excluded volume interactions. Despite experimental examination of the binding affinity between cdc45 and the H3/H4 tetramer, they noted that the stable association could be attributed to hydrophobic interactions. The model could have been enhanced and made less dependable by incorporating these hydrophobic interactions. + +3. What is the initial structure of the replication machinery? Is it based on experimental observations? For example, in the initial conformation, the H3/H4 tetramer was already bound to Mcm-2, does the initial conformation bias the observations obtained in the study, can authors comment on that? For example, they comment that in \(100\%\) of the simulation trajectories they obtained H3/H4 tetramer bound to Mcm2 associated with cdc45 at least once. Is not it based on the initial conformation? + +4. In \(20\%\) of the simulation runs, Mcm2 placed H3/H4 on the replicated strands, while in the rest, it put H3/H4 on the parental strand. However, the main focus of the paper is on depositing H3/H4 on the replicated strand. Additionally, they noted that in 3 out of 100 simulation runs, H3/H4 didn't bind to cdc45, suggesting a pathway not involving cdc45. In both cases, I wonder how statistically significant these observations are. Could the lack of interaction in those three simulations be due to random chance? + +5. The remarks about changes in azimuthal and elevation angles supporting this bias might not be easily understood by all readers. Could the schematic in Figure 3, which explains these angles, be simplified further? Even in the text, the discussion about these angles could be made easier to understand, in my opinion. + +6. The section titled "Modelling of replicated-DNA-engaged replisome binding to H3/H4 tetramer" in the results (page 3, lines 83-158) provides detailed methods and would be better suited for inclusion in the methods section. Additionally, I think the discussion could be improved and condensed. + +7. The manuscript should better cite studies of coarse-grained model of protein-DNA systems. + +Reviewer #2 (Remarks to the Author): + +This study presents a novel understanding of the molecular mechanism of histone recycling at a replication fork. The simulation study reveals two distinct recycling pathways: Cdc45- mediated and unmediated pathways. Moreover, the study uncovers the regulatory role of RPA binding to the + +<--- Page Split ---> + +ssDNA in the ratio recycled to each strand. The proposed mechanism awaits experimental validation. The simulation study, employing a set of finely calibrated force fields, demonstrates the H3/H4 tetramer transition to the parental, leading, or lagging strand. This transition will occur when the binding free energy of the H3/H4 tetramer and MCM2 is designed to be higher than that of H3/H4 and dsDNA. Thus, the transition is coordinated in advance. However, the study also reveals unexpected, insightful events. The simulations show that the Cdc45 acidic loop, previously invisible in cryo- EM structural analysis due to its flexibility, plays a crucial role in histone recycling and regulates the transition ratio to the lagging or leading strand. The study shows that the spatial distribution of H3/H4 tetramers changes depending on the interaction with cdc45, determining to which strand the tetramer moves. In addition, the impact of RPA and Pol eta is discussed. + +Before accepting the paper, several points should be clarified. + +The authors discussed the length of the ssDNA gap on the leading strand, which can take a variety of lengths. The authors should clarify why 33 nt was used in their molecular configuration (Figure 1). The length will affect the ratio of the H3/H4 tetramer transition to the leading or lagging strand. + +Line 111. Supplementary Figure 1 does not have the binding free energy of the Mcm2 and H3/H4 tetramer. It seems Figure 21. The binding free energy calculated from the coarse- grained simulation highly depends on the definition. The authors need to clarify why the bound state is the state with \(Q > 0\) . In addition, the figure denotes the H3/H4 dimer- Mcm2 interaction, not the tetramer. In addition, it is helpful to understand the simulation results if the binding free energy of H3/H4 tetramer and dsDNA obtained by the simulation is provided. + +Line 135. The authors used 1KX5 as the reference structure in which the histones are from Xenopus laevis. It is not clear if the histones used in the simulation are from budding yeast as used in their experiment. + +Figure 21 legend does not match the figure. + +Line 166- 171. The current estimate of the H3/H4 tetramer association time to the dsDNA, derived from a fitting, is considered unreliable. The authors must re- evaluate the fitting error to ensure a more accurate estimation of the validity of the study's conclusions. This is particularly important as the coarse- grained simulation may overestimate the real recycling time. If this is the case, the authors are encouraged to rationalize why the time is estimated. + +L 263. No definition for the coordinate system is provided. The x- axis is defined as the vector from the center of mass of Mcm2- 7 to that of Mcm2, but how is the y- axis or z- axis defined? + +Line 263. The DNA persistent length is typically around 500 bp but is described as 150 bp. Is this length specific to this coarse- grained simulation? + +Line 385. Figure 5 shows the distance between the junction and the H3/H4 tetramer, but the text says the distance between the junction and Cdc45. It seems that the figure is wrong. + +Lines 389- 408 and Fig.6 This paragraph does not strengthen the authors' argument and can be excluded from the paper, though I guess the authors might start to study this molecular configuration. + +In the figure legends, the authors should explain what the error bars denote wherever they appear (e.g., Figs. 2I and 4G, I). + +<--- Page Split ---> + +## Responses to Reviewer #1 + +## Comment 1: + +This research conducted molecular dynamics (MD) simulations of a yeast replication machinery, including Mcm2- 7, Cdc45, GINS, Pol \(\epsilon\) , and H3/H4 tetramer, along with replicated DNA. It was found that the H3/H4 tetramer initially bound to Mcm2 is transferred onto the replicated strands, a process termed recycling. The study demonstrates that the H3/H4 tetramer can be deposited on either the leading or lagging strand via a pathway mediated by Cdc45 or one not involving Cdc45. Specifically, in the Cdc45- mediated pathway, the H3/H4 tetramer tends to be deposited on the leading strand. Furthermore, the presence of RPA (Replication Protein A) restricts the migration area of histone recycling, although recycling of histones was observed even in the presence of two RPA molecules. Additionally, it was observed that Pol \(\epsilon\) orients the leading strand in a suboptimal direction for recycling purposes. The research question appears intriguing as it seeks to comprehend the molecular mechanism underlying the recycling of the H3/H4 tetramer during replication. However, I have few comments and suggestions. + +## Response 1: + +We would like to thank Reviewer 1 for carefully reviewing this manuscript and for being interested in reading it. We revised the manuscript in response to the comments and the suggestions below. We firmly believe that the revised manuscript is of quality worth being published in Nature Communications. + +## Comment 2: + +The study performed coarse- grained simulations of a very large system. This is very timely to push the boundaries of molecular simulations to address complex biological problems. While the study provides molecular mechanism its linkage with experimental studies should be strengthen beyond providing testable hypotheses. + +## Response 2: + +The reviewer correctly pointed out the need to strengthen the linkage between our simulation findings and experimental studies. Recent experimental studies using deep sequencing techniques + +<--- Page Split ---> + +such as SCAR- seq [Petryk et al. (2018) Science 361:1389] and eSPAN [Gan et al. (2018) Mol Cell 72:140] have demonstrated the involvement of Mcm2 N- tail in histone recycling to lagging strand. Consistent with these findings, our simulations reproduced the direct handover of H3/H4 from Mcm2 N- tail to the lagging strand. This point should have been emphasized in the manuscript. Therefore, we revised the sentences in the Discussion section to "The previous studies using deep sequencing techniques such as SCAR- seq14 and eSPAN22 demonstrated that Mcm2 N- tail contributes to recycling, especially on the lagging strand, in the cellular condition. Consistent with these findings, our simulations reproduced the direct handover of the H3/H4 tetramer from the Mcm2 N- tail to the lagging strand. However, the current study also showed that the Mcm2 N- tail deposits the H3/H4 tetramer predominantly to the leading strand via the Cdc45- mediated pathway. This result indicates that the factors missing in the current simulation setup regulate the predominant pathway in cellular conditions." Furthermore, a new electron microscopy structure of the intermediate state of histone recycling supported that a histone hexamer is captured by FACT bound to the N- terminal side of Mcm2- 7. Future electron microscopy structures may reveal that Cdc45 captures a histone hexamer (or tetramer) as the simulations suggested. To emphasize this point, we added the new sentence, "Interestingly, recently solved electron microscopy structure of the intermediate state of histone recycling supported that a histone hexamer is captured by FACT bound to the N- terminal side of Mcm2- 748, indicating that FACT may bias the predominant pathway to the lagging strand. Future studies should address the mechanisms of strand bias determination." and "Future electron microscopy structures of the intermediate of histone recycling may prove that Cdc45 can capture a histone hexamer (or tetramer)." to the Discussion section. The most powerful method to test the hypothesis obtained from the simulations in this study is to reconstitute histone recycling in vitro and measure its recycling frequency and strand bias. We added the sentence, "The most direct procedure to test this prediction is to reconstitute histone recycling in vitro19 and measure the recycling frequency and strand bias. It is highly hoped that such a method will be established." to the Discussion section to emphasize the importance of establishing such procedures. The changes here will enrich the discussion and enhance the manuscript's impact. + +## Comment 3: + +In their model, they considered only electrostatic interactions and excluded volume interactions. Despite experimental examination of the binding affinity between cdc45 and the H3/H4 tetramer, they noted that the stable association could be attributed to hydrophobic interactions. The model + +<--- Page Split ---> + +could have been enhanced and made less dependable by incorporating these hydrophobic interactions. + +## Response 3: + +Incorporating hydrophobic interactions into the model would likely lead to a more accurate representation. However, it should be noted that while the HPS model [Dignon et al. (2018) \(PLoS\) Comput. Biol. 14(1): e1005941] is currently one of the most reliable coarse- grained models for representing hydrophobic interactions, it has limitations in representing hydrophobic interactions within folded regions of Cdc45. Additionally, as evident from the new supplementary figure (Supplementary Figure S4) added to the revised manuscript, the surface of Cdc45 is predominantly filled with hydrophilic residues. This suggests that the contribution of hydrophobic interactions in the interaction with histones is limited. We believe that these facts justify not incorporating hydrophobic interactions into our coarse- grained model at this stage. To clarify this point, we have modified the sentence in the revised manuscript: "However, as evident from Supplementary Figure S4, the surface of Cdc45 is predominantly filled with hydrophilic residues, supporting that the contribution of hydrophobic interaction is not dominant, if any, and justifying not incorporating the interactions into our coarse- grained model." + +## Comment 4: + +What is the initial structure of the replication machinery? Is it based on experimental observations? For example, in the initial conformation, the H3/H4 tetramer was already bound to Mcm- 2, does the initial conformation bias the observations obtained in the study, can authors comment on that? For example, they comment that in \(100\%\) of the simulation trajectories they obtained H3/H4 tetramer bound to Mcm2 associated with cdc45 at least once. Is not it based on the initial conformation? + +## Response 4: + +We want to clarify that all initial structures used in our simulations are based on experimental data, specifically X- ray crystallography and cryo- electron microscopy structures, as thoroughly explained in the Method section. These experimental structures include the structure of the H3/H4 tetramer binding to the Mcm2 N- tail, which has been observed in both gel electrophoresis [Foltman et al. (2013) Cell Reports 3:892] and cryo- electron microscopy [Li et al. (2024) Nature 627:890] + +<--- Page Split ---> + +studies. Notably, the cryo- electron microscopy structure we refer to depicted the architecture of endogenous replisomes. This suggests the relevance of interactions between the H3/H4 tetramer and the Mcm2 N- tail as intermediate structures in histone- recycling reactions within cells. Of course, other pathways are possible but they were not considered here. In the revised manuscript, we commented on this by adding the sentence, "The recent cryo- EM structure of an endogenous replisome48 suggested the relevance of interactions between the H3/H4 tetramer and the Mcm2 N- tail as intermediate structures in histone recycling reactions within cells. Here, we focused on the recycling pathways in which the H3/H4 tetramer binds to the Mcm2 N- tail, although other pathways may also be possible." to the Result section. + +We acknowledge that the initial conformation may influence subsequent dynamics in molecular simulations. However, our simulations showed that H3/H4 underwent repeated association to and dissociation from Cdc45 (Supplementary Figure S2E & S6C), suggesting structural relaxation from the initial state occurs significantly faster than the timescale of histone recycling reactions. Furthermore, H3/H4 demonstrates extensive sampling across spatial domains in our simulations (Figure 3I- 3L). Based on these points, our simulation results are robust with respect to the initial structures. To clarify this point, we added the sentence "The repeated dissociation from and association with Cdc45 suggested that the simulation result is robust to the initial structure." to the Result section. + +## Comment 5: + +In \(20\%\) of the simulation runs, Mcm2 placed H3/H4 on the replicated strands, while in the rest, it put H3/H4 on the parental strand. However, the main focus of the paper is on depositing H3/H4 on the replicated strand. Additionally, they noted that in 3 out of 100 simulation runs, H3/H4 didn't bind to cdc45, suggesting a pathway not involving cdc45. In both cases, I wonder how statistically significant these observations are. Could the lack of interaction in those three simulations be due to random chance? + +## Response 5: + +As indicated in Supplementary Figure S2B, our simulation results, while constrained by current computational limits, suggested that extending simulation durations could increase the number of recycling trajectories. Moreover, we hypothesized that mechanisms within cells, such as + +<--- Page Split ---> + +downstream nucleosomes or histone chaperones, likely accelerate recycling. Despite these limitations in our simulation length and setups, we obtained 20 recycling trajectories, enough to statistically analyze the pathways to the replicated strands. Regarding the simulations where H3/H4 did not bind to Cdc45, these instances might reflect random occurrences rather than a dominant pathway. Nevertheless, the simulation results suggested that the Cdc45 unmediated pathway is statistically rare but is physically feasible. To clarify these points, we added the sentences "Below, we focused on the 20 recycling trajectories to statistically analyze the molecular pathway of histone recycling." and "The rare occurrence of the Cdc45-unmediated pathway suggested that the path is physically feasible but is statistically rare." to the Result section. + +## Comment 6: + +The remarks about changes in azimuthal and elevation angles supporting this bias might not be easily understood by all readers. Could the schematic in Figure 3, which explains these angles, be simplified further? Even in the text, the discussion about these angles could be made easier to understand, in my opinion. + +## Response 6: + +We appreciate the suggestion to simplify the explanation of azimuthal and elevation angles in Figure 3 and the text. We have revised Figure 3A to include a more precise depiction of the Z- axis and the X- axis. Additionally, we have provided a more precise explanation of these angles in the revised manuscript, aiming to improve accessibility for all readers: "The Z- axis is aligned with the direction of the rotation axis of Mcm2- 7, and the X- axis is perpendicular to the Z- axis, passing through the COM of Mcm2 (Figure 3A). The Y- axis is perpendicular to both X- and Z- axes. The angle between the vectors and the X- axis on the X- Z plane is defined as the elevation angle \(\phi\) , and the angle between the vectors and the X- axis on the X- Y plane is defined as the azimuthal angle \(\theta\) (Figure 3B &C)." We believe these changes have significantly enhanced the clarity of our discussion regarding azimuthal and elevation angles. + +## Comment 7: + +<--- Page Split ---> + +The section titled "Modelling of replicated- DNA- engaged replisome binding to H3/H4 tetramer" in the results (page 3, lines 83- 158) provides detailed methods and would be better suited for inclusion in the methods section. Additionally, I think the discussion could be improved and condensed. + +## Response 7: + +We have relocated the detailed methods described in the Result section to the Methods section. Also, we have condensed the Discussion section from 9 to 5 paragraphs to improve clarity and conciseness. We would like to thank Reviewer 1 for the valuable feedback, which helped us enhance the quality of our manuscript. + +## Comment 8: + +The manuscript should better cite studies of coarse- grained model of protein- DNA systems. + +## Response 8: + +We agree on citing previous studies applying coarse- grained models for protein- DNA systems to highlight that our computational approach is intended to visualize the molecular trajectories of H3/H4 recycling. To clarify these points, we added the sentence with citations, "Coarse- grained molecular dynamics simulations have successfully visualized the dynamics of protein- DNA complexes in long- time scale, providing insights into molecular mechanisms31- 35." + +## Responses to Reviewer #2 + +## Comment 1: + +This study presents a novel understanding of the molecular mechanism of histone recycling at a replication fork. The simulation study reveals two distinct recycling pathways: Cdc45- mediated and unmediated pathways. Moreover, the study uncovers the regulatory role of RPA binding to the ssDNA in the ratio recycled to each strand. The proposed mechanism awaits experimental validation. The simulation study, employing a set of finely calibrated force fields, demonstrates the H3/H4 tetramer transition to the parental, leading, or lagging strand. This transition will occur + +<--- Page Split ---> + +when the binding free energy of the H3/H4 tetramer and MCM2 is designed to be higher than that of H3/H4 and dsDNA. Thus, the transition is coordinated in advance. However, the study also reveals unexpected, insightful events. The simulations show that the Cdc45 acidic loop, previously invisible in cryo- EM structural analysis due to its flexibility, plays a crucial role in histone recycling and regulates the transition ratio to the lagging or leading strand. The study shows that the spatial distribution of H3/H4 tetramers changes depending on the interaction with cdc45, determining to which strand the tetramer moves. In addition, the impact of RPA and Pol eta is discussed. Before accepting the paper, several points should be clarified. + +## Response 1: + +We would like to thank Reviewer 2 for carefully reading and reviewing the manuscript. We revised the manuscript in responses to the comments below. We firmly believe that the revised manuscript is ready to be published in Nature Communications. + +## Comment 2: + +The authors discussed the length of the ssDNA gap on the leading strand, which can take a variety of lengths. The authors should clarify why 33 nt was used in their molecular configuration (Figure 1). The length will affect the ratio of the H3/H4 tetramer transition to the leading or lagging strand. + +## Response 2: + +We chose to use 33 nt in our study based on the minimum length required for the single- strand DNA region to traverse the Mcm2- 7 channel and reach the active center of Pol \(\epsilon\) . Pol \(\epsilon\) fixes the orientation of the leading strand dsDNA. Thus the gap size appears to have little, if any, effect on strand bias in histone recycling. To clarify this point, we added the sentence, "The length of the ssDNA gap on the leading strand was 33 nt and passed through the central channel of Mcm2- 7 and the catalytic subunit of Pol \(\epsilon\) . Pol \(\epsilon\) fixes the orientation of the leading strand dsDNA. Thus, the gap size appears to have little, if any, effect on strand bias in histone recycling." to the Method section. + +## Comment 3: + +<--- Page Split ---> + +Line 111. Supplementary Figure 1 does not have the binding free energy of the Mcm2 and H3/H4 tetramer. It seems Figure 21. The binding free energy calculated from the coarse- grained simulation highly depends on the definition. The authors need to clarify why the bound state is the state with \(Q > 0\) . In addition, the figure denotes the H3/H4 dimer- Mcm2 interaction, not the tetramer. In addition, it is helpful to understand the simulation results if the binding free energy of H3/H4 tetramer and dsDNA obtained by the simulation is provided. + +## Response 3: + +We have revised the text to specify that Supplementary Figure 1 does not depict the binding free energy but rather illustrates the results of our temperature replica exchange simulations of Mcm2 and the H3/H4 dimer (revised text: "Therefore, in this study, we performed temperature replica exchange simulations of Mcm2 and an H3/H4 dimer associating to and dissociating from each other with varying parameters (Supplementary Figure 1) and selected the one that reproduced the experimental binding free energy (Simulation: \(- 10.00 \pm 0.26\) kcal/mol, Experiment: \(- 10.45 \pm 0.04\) kcal/mol \(^{15}\) )." + +Regarding the definition of the bound state with \(Q > 0\) , we utilized this criterion because even partial formation of native contacts can imply binding in the experimental setup. Even when a cutoff of \(10 \text{Å}\) was used for the minimum distance between Mcm2 and the H3/H4 dimer, the binding free energy was \(- 10.1 \pm 0.3\) kcal/mol, suggesting that our simulation results are robust to the cutoff definition. To clarify this point, we added the sentence, "Then, we defined the bound state as the state with \(Q > 0\) because even partial formation of native contacts can imply binding in the experimental setup. Even when a cutoff of \(10 \text{Å}\) was used for the minimum distance between Mcm2 and the H3/H4 dimer, the binding free energy was \(- 10.1 \pm 0.3\) kcal/mol, suggesting that our simulation results are robust to the cutoff definition." to the Methods section. + +The main text incorrectly stated that this was a replica exchange simulation of the Mcm2 N- tail and H3/H4 tetramer, which has been corrected in the revised manuscript as above. In reality, Mcm2 N- tail and H3/H4 dimer interact with each other, so the simulation results were compared with the experimental binding free energy of Mcm2 N- tail and H3/H4 dimer. We would like to express our apologies to the reviewers for the confusion caused by this error. + +As for the binding free energy between the H3/H4 tetramer and dsDNA, while direct calculation from simulations remains challenging due to multiple binding sites of the tetramer on dsDNA, we note that the previous experiment suggested binding energy around - 12 kcal/mol [Andrews et al. + +<--- Page Split ---> + +(2010) Mol Cell 37:834], consistent with our simulation findings that Mcm2 N- tail directly hand over the H3/H4 tetramer to the replicated strands. To clarify this point, we added the sentence, "The previous experiment suggested a binding free energy between the H3/H4 tetramer and dsDNA of around - 12 kcal/mol79, in line with the direct handover of the H3/H4 tetramer from the Mcm2 N- tail to the replicated strands." to the Methods section. + +## Comment 4: + +Line 135. The authors used 1KX5 as the reference structure in which the histones are from Xenopus laevis. It is not clear if the histones used in the simulation are from budding yeast as used in their experiment. + +## Response 4: + +Reviewer 2 correctly pointed out that the histone sequence used in the simulation is from Xenopus laevis. Past studies used this sequence to calibrate parameters to match experimental results [Niina et al. (2017) PLoS Comput. Biol. 13(12): e1005880, Brandani et al. (2021) PLoS Comput. Biol. 17(7):e1009253]. It is not straightforward to perform a similar calibration for Saccharomyces cerevisiae histones, as several corresponding experiments have yet to be performed. However, the sequence of H3 and H4 in Xenopus laevis and Saccharomyces cerevisiae is highly conserved at 97.1% and 99.0% similarity, respectively, and it is thought that the effect of sequence changes on intermolecular interactions is small. In particular, the impact on conclusions obtained from the simulations with the coarse- grained resolution should be minimal. We clarified this point by adding the sentence, "The amino acid sequence was taken from Xenopus laevis for parameter calibration purposes. However, because of the high degree of sequence similarity in histones (97.1% for H3 and 99.0% for H4), the impact of the sequence on conclusions obtained from the coarse- grained simulations should be minimal." to the Methods section. + +## Comment 5: + +Figure 2I legend does not match the figure. + +## Response 5: + +<--- Page Split ---> + +We fixed this error. We would like to express our apologies to the reviewers for the confusion caused by this error. + +## Comment 6: + +Line 166- 171. The current estimate of the H3/H4 tetramer association time to the dsDNA, derived from a fitting, is considered unreliable. The authors must re- evaluate the fitting error to ensure a more accurate estimation of the validity of the study's conclusions. This is particularly important as the coarse- grained simulation may overestimate the real recycling time. If this is the case, the authors are encouraged to rationalize why the time is estimated. + +## Response 6: + +We have removed the statement "roughly corresponding to \(\sim 1.5\) microseconds" to avoid implying a precise mapping to real- world time from coarse- grained molecular dynamics simulations. We acknowledge that accurately estimating such timescales is challenging, as Reviewer 2 stated in the comment. + +Additionally, we have modified the sentence to read: "We estimated that it would take \(>1 \times 10^{9}\) steps for the H3/H4 tetramer to associate with the parental, leading, or lagging strand in all the trajectories (Supplementary Figure 2B)." This change emphasizes that our conclusions are not critically dependent on precise time scale estimation. + +## Comment 7: + +L 263. No definition for the coordinate system is provided. The x- axis is defined as the vector from the center of mass of Mcm2- 7 to that of Mcm2, but how is the y- axis or z- axis defined? + +## Response 7: + +We would like to express our apology for this ambiguity. We added the sentence, "The Z- axis is aligned with the direction of the rotation axis of Mcm2- 7, and the X- axis is perpendicular to the + +<--- Page Split ---> + +Z-axis, passing through the COM of Mcm2 (Figure 3A). The Y-axis is perpendicular to both X- and Z-axes." to the Result section. + +## Comment 8: + +Comment 8:Line 263. The DNA persistent length is typically around 500 bp but is described as 150 bp. Is this length specific to this coarse- grained simulation? + +## Response 8: + +Response 8:Under typical conditions, the persistence length of dsDNA is 50 nm [e.g., Geggier et al. (2010) PNAS 107:15421], equivalent to approximately 150 base pairs. + +## Comment 9: + +Comment 9:Line 385. Figure 5 shows the distance between the junction and the H3/H4 tetramer, but the text says the distance between the junction and Cdc45. It seems that the figure is wrong. + +## Response 9: + +Response 9:We fixed this error by changing the figure representation. We would like to express our apologies to the reviewers for the confusion caused by this error. + +## Comment 10: + +Comment 10:Lines 389- 408 and Fig.6. This paragraph does not strengthen the authors' argument and can be excluded from the paper, though I guess the authors might start to study this molecular configuration. + +## Response 10: + +<--- Page Split ---> + +As Reviewer 2 correctly pointed out, we have removed the paragraph and Fig. 6 as they do not strengthen the main argument of the paper. We deeply appreciate the suggestion, and this molecular configuration could be explored in future studies in different contexts. + +## Comment 11: + +In the figure legends, the authors should explain what the error bars denote wherever they appear (e.g., Figs. 2I and 4G, I). + +## Response 11: + +We would like to express our apology for the lack of information. The error bars represent mean \(\pm\) standard deviation. The figure legends were revised accordingly. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +All my comments are adequately addressed in the revised manuscript + +Reviewer #2 (Remarks to the Author): + +The authors have satisfactorily addressed all the concerns raised by the reviewers. However, the numbering for supplementary figures is not consistent. Some are referred to as S5, while others are referred to as 5. Please ensure consistent numbering throughout the document. + +<--- Page Split ---> + +## Responses to Reviewer #1 + +## Comment 1: + +All my comments are adequately addressed in the revised manuscript. + +## Response 1: + +We would like to thank Reviewer 1 again for carefully reviewing this manuscript. + +## Responses to Reviewer #2 + +## Comment 1: + +The authors have satisfactorily addressed all the concerns raised by the reviewers. However, the numbering for supplementary figures is not consistent. Some are referred to as S5, while others are referred to as 5. Please ensure consistent numbering throughout the document. + +## Response 1: + +We also would like to thank Reviewer 2 for carefully reviewing the manuscript. We unified the notation. + +<--- Page Split ---> diff --git a/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..fc5df47c27b1e773553cc8576819ee3b3eef921e --- /dev/null +++ b/peer_reviews/5530b4bee05af274b4f8de0870c601caa1e23cb2bb6ea921d4fe9fac20dcb9f6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,421 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 111, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 162, 820, 218]]<|/det|> +Molecular mechanism of parental H3/H4 recycling at a replication fork + +<|ref|>image<|/ref|><|det|>[[56, 732, 239, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 923]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 66, 295, 80]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 93, 414, 107]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[119, 122, 200, 135]]<|/det|> +## Summary: + +<|ref|>text<|/ref|><|det|>[[118, 136, 875, 305]]<|/det|> +This research conducted molecular dynamics (MD) simulations of a yeast replication machinery, including Mcm2- 7, Cdc45, GINS, Pol \(\epsilon\) , and H3/H4 tetramer, along with replicated DNA. It was found that the H3/H4 tetramer initially bound to Mcm2 is transferred onto the replicated strands, a process termed recycling. The study demonstrates that the H3/H4 tetramer can be deposited on either the leading or lagging strand via a pathway mediated by Cdc45 or one not involving Cdc45. Specifically, in the Cdc45- mediated pathway, the H3/H4 tetramer tends to be deposited on the leading strand. Furthermore, the presence of RPA (Replication Protein A) restricts the migration area of histone recycling, although recycling of histones was observed even in the presence of two RPA molecules. Additionally, it was observed that Pol \(\epsilon\) orients the leading strand in a suboptimal direction for recycling purposes. The research question appears intriguing as it seeks to comprehend the molecular mechanism underlying the recycling of the H3/H4 tetramer during replication. However, I have few comments and suggestions. + +<|ref|>text<|/ref|><|det|>[[118, 305, 861, 360]]<|/det|> +1. The study performed coarse-grained simulations of a very large system. This is very timely to push the boundaries of molecular simulations to address complex biological problems. While the study provides molecular mechanism its linkage with experimental studies should be strengthen beyond providing testable hypotheses. + +<|ref|>text<|/ref|><|det|>[[118, 360, 872, 430]]<|/det|> +2. In their model, they considered only electrostatic interactions and excluded volume interactions. Despite experimental examination of the binding affinity between cdc45 and the H3/H4 tetramer, they noted that the stable association could be attributed to hydrophobic interactions. The model could have been enhanced and made less dependable by incorporating these hydrophobic interactions. + +<|ref|>text<|/ref|><|det|>[[118, 443, 863, 528]]<|/det|> +3. What is the initial structure of the replication machinery? Is it based on experimental observations? For example, in the initial conformation, the H3/H4 tetramer was already bound to Mcm-2, does the initial conformation bias the observations obtained in the study, can authors comment on that? For example, they comment that in \(100\%\) of the simulation trajectories they obtained H3/H4 tetramer bound to Mcm2 associated with cdc45 at least once. Is not it based on the initial conformation? + +<|ref|>text<|/ref|><|det|>[[118, 541, 876, 625]]<|/det|> +4. In \(20\%\) of the simulation runs, Mcm2 placed H3/H4 on the replicated strands, while in the rest, it put H3/H4 on the parental strand. However, the main focus of the paper is on depositing H3/H4 on the replicated strand. Additionally, they noted that in 3 out of 100 simulation runs, H3/H4 didn't bind to cdc45, suggesting a pathway not involving cdc45. In both cases, I wonder how statistically significant these observations are. Could the lack of interaction in those three simulations be due to random chance? + +<|ref|>text<|/ref|><|det|>[[118, 639, 872, 695]]<|/det|> +5. The remarks about changes in azimuthal and elevation angles supporting this bias might not be easily understood by all readers. Could the schematic in Figure 3, which explains these angles, be simplified further? Even in the text, the discussion about these angles could be made easier to understand, in my opinion. + +<|ref|>text<|/ref|><|det|>[[118, 710, 860, 765]]<|/det|> +6. The section titled "Modelling of replicated-DNA-engaged replisome binding to H3/H4 tetramer" in the results (page 3, lines 83-158) provides detailed methods and would be better suited for inclusion in the methods section. Additionally, I think the discussion could be improved and condensed. + +<|ref|>text<|/ref|><|det|>[[118, 780, 836, 795]]<|/det|> +7. The manuscript should better cite studies of coarse-grained model of protein-DNA systems. + +<|ref|>text<|/ref|><|det|>[[119, 850, 414, 864]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 878, 877, 920]]<|/det|> +This study presents a novel understanding of the molecular mechanism of histone recycling at a replication fork. The simulation study reveals two distinct recycling pathways: Cdc45- mediated and unmediated pathways. Moreover, the study uncovers the regulatory role of RPA binding to the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 66, 875, 206]]<|/det|> +ssDNA in the ratio recycled to each strand. The proposed mechanism awaits experimental validation. The simulation study, employing a set of finely calibrated force fields, demonstrates the H3/H4 tetramer transition to the parental, leading, or lagging strand. This transition will occur when the binding free energy of the H3/H4 tetramer and MCM2 is designed to be higher than that of H3/H4 and dsDNA. Thus, the transition is coordinated in advance. However, the study also reveals unexpected, insightful events. The simulations show that the Cdc45 acidic loop, previously invisible in cryo- EM structural analysis due to its flexibility, plays a crucial role in histone recycling and regulates the transition ratio to the lagging or leading strand. The study shows that the spatial distribution of H3/H4 tetramers changes depending on the interaction with cdc45, determining to which strand the tetramer moves. In addition, the impact of RPA and Pol eta is discussed. + +<|ref|>text<|/ref|><|det|>[[120, 219, 588, 233]]<|/det|> +Before accepting the paper, several points should be clarified. + +<|ref|>text<|/ref|><|det|>[[119, 247, 874, 303]]<|/det|> +The authors discussed the length of the ssDNA gap on the leading strand, which can take a variety of lengths. The authors should clarify why 33 nt was used in their molecular configuration (Figure 1). The length will affect the ratio of the H3/H4 tetramer transition to the leading or lagging strand. + +<|ref|>text<|/ref|><|det|>[[118, 317, 875, 402]]<|/det|> +Line 111. Supplementary Figure 1 does not have the binding free energy of the Mcm2 and H3/H4 tetramer. It seems Figure 21. The binding free energy calculated from the coarse- grained simulation highly depends on the definition. The authors need to clarify why the bound state is the state with \(Q > 0\) . In addition, the figure denotes the H3/H4 dimer- Mcm2 interaction, not the tetramer. In addition, it is helpful to understand the simulation results if the binding free energy of H3/H4 tetramer and dsDNA obtained by the simulation is provided. + +<|ref|>text<|/ref|><|det|>[[119, 415, 840, 457]]<|/det|> +Line 135. The authors used 1KX5 as the reference structure in which the histones are from Xenopus laevis. It is not clear if the histones used in the simulation are from budding yeast as used in their experiment. + +<|ref|>text<|/ref|><|det|>[[120, 472, 451, 486]]<|/det|> +Figure 21 legend does not match the figure. + +<|ref|>text<|/ref|><|det|>[[118, 500, 877, 570]]<|/det|> +Line 166- 171. The current estimate of the H3/H4 tetramer association time to the dsDNA, derived from a fitting, is considered unreliable. The authors must re- evaluate the fitting error to ensure a more accurate estimation of the validity of the study's conclusions. This is particularly important as the coarse- grained simulation may overestimate the real recycling time. If this is the case, the authors are encouraged to rationalize why the time is estimated. + +<|ref|>text<|/ref|><|det|>[[118, 584, 874, 612]]<|/det|> +L 263. No definition for the coordinate system is provided. The x- axis is defined as the vector from the center of mass of Mcm2- 7 to that of Mcm2, but how is the y- axis or z- axis defined? + +<|ref|>text<|/ref|><|det|>[[118, 626, 809, 654]]<|/det|> +Line 263. The DNA persistent length is typically around 500 bp but is described as 150 bp. Is this length specific to this coarse- grained simulation? + +<|ref|>text<|/ref|><|det|>[[118, 668, 872, 697]]<|/det|> +Line 385. Figure 5 shows the distance between the junction and the H3/H4 tetramer, but the text says the distance between the junction and Cdc45. It seems that the figure is wrong. + +<|ref|>text<|/ref|><|det|>[[118, 711, 855, 753]]<|/det|> +Lines 389- 408 and Fig.6 This paragraph does not strengthen the authors' argument and can be excluded from the paper, though I guess the authors might start to study this molecular configuration. + +<|ref|>text<|/ref|><|det|>[[115, 767, 874, 795]]<|/det|> +In the figure legends, the authors should explain what the error bars denote wherever they appear (e.g., Figs. 2I and 4G, I). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 93, 363, 111]]<|/det|> +## Responses to Reviewer #1 + +<|ref|>sub_title<|/ref|><|det|>[[115, 136, 229, 153]]<|/det|> +## Comment 1: + +<|ref|>text<|/ref|><|det|>[[113, 175, 884, 444]]<|/det|> +This research conducted molecular dynamics (MD) simulations of a yeast replication machinery, including Mcm2- 7, Cdc45, GINS, Pol \(\epsilon\) , and H3/H4 tetramer, along with replicated DNA. It was found that the H3/H4 tetramer initially bound to Mcm2 is transferred onto the replicated strands, a process termed recycling. The study demonstrates that the H3/H4 tetramer can be deposited on either the leading or lagging strand via a pathway mediated by Cdc45 or one not involving Cdc45. Specifically, in the Cdc45- mediated pathway, the H3/H4 tetramer tends to be deposited on the leading strand. Furthermore, the presence of RPA (Replication Protein A) restricts the migration area of histone recycling, although recycling of histones was observed even in the presence of two RPA molecules. Additionally, it was observed that Pol \(\epsilon\) orients the leading strand in a suboptimal direction for recycling purposes. The research question appears intriguing as it seeks to comprehend the molecular mechanism underlying the recycling of the H3/H4 tetramer during replication. However, I have few comments and suggestions. + +<|ref|>sub_title<|/ref|><|det|>[[115, 471, 232, 489]]<|/det|> +## Response 1: + +<|ref|>text<|/ref|><|det|>[[114, 510, 884, 598]]<|/det|> +We would like to thank Reviewer 1 for carefully reviewing this manuscript and for being interested in reading it. We revised the manuscript in response to the comments and the suggestions below. We firmly believe that the revised manuscript is of quality worth being published in Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[115, 666, 230, 682]]<|/det|> +## Comment 2: + +<|ref|>text<|/ref|><|det|>[[114, 705, 883, 792]]<|/det|> +The study performed coarse- grained simulations of a very large system. This is very timely to push the boundaries of molecular simulations to address complex biological problems. While the study provides molecular mechanism its linkage with experimental studies should be strengthen beyond providing testable hypotheses. + +<|ref|>sub_title<|/ref|><|det|>[[115, 820, 232, 838]]<|/det|> +## Response 2: + +<|ref|>text<|/ref|><|det|>[[115, 860, 883, 901]]<|/det|> +The reviewer correctly pointed out the need to strengthen the linkage between our simulation findings and experimental studies. Recent experimental studies using deep sequencing techniques + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 87, 884, 728]]<|/det|> +such as SCAR- seq [Petryk et al. (2018) Science 361:1389] and eSPAN [Gan et al. (2018) Mol Cell 72:140] have demonstrated the involvement of Mcm2 N- tail in histone recycling to lagging strand. Consistent with these findings, our simulations reproduced the direct handover of H3/H4 from Mcm2 N- tail to the lagging strand. This point should have been emphasized in the manuscript. Therefore, we revised the sentences in the Discussion section to "The previous studies using deep sequencing techniques such as SCAR- seq14 and eSPAN22 demonstrated that Mcm2 N- tail contributes to recycling, especially on the lagging strand, in the cellular condition. Consistent with these findings, our simulations reproduced the direct handover of the H3/H4 tetramer from the Mcm2 N- tail to the lagging strand. However, the current study also showed that the Mcm2 N- tail deposits the H3/H4 tetramer predominantly to the leading strand via the Cdc45- mediated pathway. This result indicates that the factors missing in the current simulation setup regulate the predominant pathway in cellular conditions." Furthermore, a new electron microscopy structure of the intermediate state of histone recycling supported that a histone hexamer is captured by FACT bound to the N- terminal side of Mcm2- 7. Future electron microscopy structures may reveal that Cdc45 captures a histone hexamer (or tetramer) as the simulations suggested. To emphasize this point, we added the new sentence, "Interestingly, recently solved electron microscopy structure of the intermediate state of histone recycling supported that a histone hexamer is captured by FACT bound to the N- terminal side of Mcm2- 748, indicating that FACT may bias the predominant pathway to the lagging strand. Future studies should address the mechanisms of strand bias determination." and "Future electron microscopy structures of the intermediate of histone recycling may prove that Cdc45 can capture a histone hexamer (or tetramer)." to the Discussion section. The most powerful method to test the hypothesis obtained from the simulations in this study is to reconstitute histone recycling in vitro and measure its recycling frequency and strand bias. We added the sentence, "The most direct procedure to test this prediction is to reconstitute histone recycling in vitro19 and measure the recycling frequency and strand bias. It is highly hoped that such a method will be established." to the Discussion section to emphasize the importance of establishing such procedures. The changes here will enrich the discussion and enhance the manuscript's impact. + +<|ref|>sub_title<|/ref|><|det|>[[116, 791, 230, 809]]<|/det|> +## Comment 3: + +<|ref|>text<|/ref|><|det|>[[115, 830, 883, 896]]<|/det|> +In their model, they considered only electrostatic interactions and excluded volume interactions. Despite experimental examination of the binding affinity between cdc45 and the H3/H4 tetramer, they noted that the stable association could be attributed to hydrophobic interactions. The model + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 92, 883, 133]]<|/det|> +could have been enhanced and made less dependable by incorporating these hydrophobic interactions. + +<|ref|>sub_title<|/ref|><|det|>[[114, 161, 232, 180]]<|/det|> +## Response 3: + +<|ref|>text<|/ref|><|det|>[[113, 200, 884, 493]]<|/det|> +Incorporating hydrophobic interactions into the model would likely lead to a more accurate representation. However, it should be noted that while the HPS model [Dignon et al. (2018) \(PLoS\) Comput. Biol. 14(1): e1005941] is currently one of the most reliable coarse- grained models for representing hydrophobic interactions, it has limitations in representing hydrophobic interactions within folded regions of Cdc45. Additionally, as evident from the new supplementary figure (Supplementary Figure S4) added to the revised manuscript, the surface of Cdc45 is predominantly filled with hydrophilic residues. This suggests that the contribution of hydrophobic interactions in the interaction with histones is limited. We believe that these facts justify not incorporating hydrophobic interactions into our coarse- grained model at this stage. To clarify this point, we have modified the sentence in the revised manuscript: "However, as evident from Supplementary Figure S4, the surface of Cdc45 is predominantly filled with hydrophilic residues, supporting that the contribution of hydrophobic interaction is not dominant, if any, and justifying not incorporating the interactions into our coarse- grained model." + +<|ref|>sub_title<|/ref|><|det|>[[114, 560, 230, 577]]<|/det|> +## Comment 4: + +<|ref|>text<|/ref|><|det|>[[114, 598, 884, 731]]<|/det|> +What is the initial structure of the replication machinery? Is it based on experimental observations? For example, in the initial conformation, the H3/H4 tetramer was already bound to Mcm- 2, does the initial conformation bias the observations obtained in the study, can authors comment on that? For example, they comment that in \(100\%\) of the simulation trajectories they obtained H3/H4 tetramer bound to Mcm2 associated with cdc45 at least once. Is not it based on the initial conformation? + +<|ref|>sub_title<|/ref|><|det|>[[114, 759, 232, 777]]<|/det|> +## Response 4: + +<|ref|>text<|/ref|><|det|>[[114, 798, 884, 910]]<|/det|> +We want to clarify that all initial structures used in our simulations are based on experimental data, specifically X- ray crystallography and cryo- electron microscopy structures, as thoroughly explained in the Method section. These experimental structures include the structure of the H3/H4 tetramer binding to the Mcm2 N- tail, which has been observed in both gel electrophoresis [Foltman et al. (2013) Cell Reports 3:892] and cryo- electron microscopy [Li et al. (2024) Nature 627:890] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 91, 884, 294]]<|/det|> +studies. Notably, the cryo- electron microscopy structure we refer to depicted the architecture of endogenous replisomes. This suggests the relevance of interactions between the H3/H4 tetramer and the Mcm2 N- tail as intermediate structures in histone- recycling reactions within cells. Of course, other pathways are possible but they were not considered here. In the revised manuscript, we commented on this by adding the sentence, "The recent cryo- EM structure of an endogenous replisome48 suggested the relevance of interactions between the H3/H4 tetramer and the Mcm2 N- tail as intermediate structures in histone recycling reactions within cells. Here, we focused on the recycling pathways in which the H3/H4 tetramer binds to the Mcm2 N- tail, although other pathways may also be possible." to the Result section. + +<|ref|>text<|/ref|><|det|>[[114, 314, 884, 516]]<|/det|> +We acknowledge that the initial conformation may influence subsequent dynamics in molecular simulations. However, our simulations showed that H3/H4 underwent repeated association to and dissociation from Cdc45 (Supplementary Figure S2E & S6C), suggesting structural relaxation from the initial state occurs significantly faster than the timescale of histone recycling reactions. Furthermore, H3/H4 demonstrates extensive sampling across spatial domains in our simulations (Figure 3I- 3L). Based on these points, our simulation results are robust with respect to the initial structures. To clarify this point, we added the sentence "The repeated dissociation from and association with Cdc45 suggested that the simulation result is robust to the initial structure." to the Result section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 582, 230, 600]]<|/det|> +## Comment 5: + +<|ref|>text<|/ref|><|det|>[[114, 621, 884, 755]]<|/det|> +In \(20\%\) of the simulation runs, Mcm2 placed H3/H4 on the replicated strands, while in the rest, it put H3/H4 on the parental strand. However, the main focus of the paper is on depositing H3/H4 on the replicated strand. Additionally, they noted that in 3 out of 100 simulation runs, H3/H4 didn't bind to cdc45, suggesting a pathway not involving cdc45. In both cases, I wonder how statistically significant these observations are. Could the lack of interaction in those three simulations be due to random chance? + +<|ref|>sub_title<|/ref|><|det|>[[115, 782, 232, 800]]<|/det|> +## Response 5: + +<|ref|>text<|/ref|><|det|>[[115, 821, 884, 888]]<|/det|> +As indicated in Supplementary Figure S2B, our simulation results, while constrained by current computational limits, suggested that extending simulation durations could increase the number of recycling trajectories. Moreover, we hypothesized that mechanisms within cells, such as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 884, 294]]<|/det|> +downstream nucleosomes or histone chaperones, likely accelerate recycling. Despite these limitations in our simulation length and setups, we obtained 20 recycling trajectories, enough to statistically analyze the pathways to the replicated strands. Regarding the simulations where H3/H4 did not bind to Cdc45, these instances might reflect random occurrences rather than a dominant pathway. Nevertheless, the simulation results suggested that the Cdc45 unmediated pathway is statistically rare but is physically feasible. To clarify these points, we added the sentences "Below, we focused on the 20 recycling trajectories to statistically analyze the molecular pathway of histone recycling." and "The rare occurrence of the Cdc45-unmediated pathway suggested that the path is physically feasible but is statistically rare." to the Result section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 360, 230, 377]]<|/det|> +## Comment 6: + +<|ref|>text<|/ref|><|det|>[[115, 399, 884, 488]]<|/det|> +The remarks about changes in azimuthal and elevation angles supporting this bias might not be easily understood by all readers. Could the schematic in Figure 3, which explains these angles, be simplified further? Even in the text, the discussion about these angles could be made easier to understand, in my opinion. + +<|ref|>sub_title<|/ref|><|det|>[[115, 514, 232, 532]]<|/det|> +## Response 6: + +<|ref|>text<|/ref|><|det|>[[113, 553, 884, 779]]<|/det|> +We appreciate the suggestion to simplify the explanation of azimuthal and elevation angles in Figure 3 and the text. We have revised Figure 3A to include a more precise depiction of the Z- axis and the X- axis. Additionally, we have provided a more precise explanation of these angles in the revised manuscript, aiming to improve accessibility for all readers: "The Z- axis is aligned with the direction of the rotation axis of Mcm2- 7, and the X- axis is perpendicular to the Z- axis, passing through the COM of Mcm2 (Figure 3A). The Y- axis is perpendicular to both X- and Z- axes. The angle between the vectors and the X- axis on the X- Z plane is defined as the elevation angle \(\phi\) , and the angle between the vectors and the X- axis on the X- Y plane is defined as the azimuthal angle \(\theta\) (Figure 3B &C)." We believe these changes have significantly enhanced the clarity of our discussion regarding azimuthal and elevation angles. + +<|ref|>sub_title<|/ref|><|det|>[[115, 845, 230, 862]]<|/det|> +## Comment 7: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 92, 883, 179]]<|/det|> +The section titled "Modelling of replicated- DNA- engaged replisome binding to H3/H4 tetramer" in the results (page 3, lines 83- 158) provides detailed methods and would be better suited for inclusion in the methods section. Additionally, I think the discussion could be improved and condensed. + +<|ref|>sub_title<|/ref|><|det|>[[115, 206, 233, 224]]<|/det|> +## Response 7: + +<|ref|>text<|/ref|><|det|>[[114, 245, 883, 334]]<|/det|> +We have relocated the detailed methods described in the Result section to the Methods section. Also, we have condensed the Discussion section from 9 to 5 paragraphs to improve clarity and conciseness. We would like to thank Reviewer 1 for the valuable feedback, which helped us enhance the quality of our manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 400, 230, 417]]<|/det|> +## Comment 8: + +<|ref|>text<|/ref|><|det|>[[115, 440, 837, 459]]<|/det|> +The manuscript should better cite studies of coarse- grained model of protein- DNA systems. + +<|ref|>sub_title<|/ref|><|det|>[[115, 486, 233, 504]]<|/det|> +## Response 8: + +<|ref|>text<|/ref|><|det|>[[114, 525, 884, 637]]<|/det|> +We agree on citing previous studies applying coarse- grained models for protein- DNA systems to highlight that our computational approach is intended to visualize the molecular trajectories of H3/H4 recycling. To clarify these points, we added the sentence with citations, "Coarse- grained molecular dynamics simulations have successfully visualized the dynamics of protein- DNA complexes in long- time scale, providing insights into molecular mechanisms31- 35." + +<|ref|>sub_title<|/ref|><|det|>[[115, 683, 365, 701]]<|/det|> +## Responses to Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[115, 726, 230, 744]]<|/det|> +## Comment 1: + +<|ref|>text<|/ref|><|det|>[[114, 765, 884, 899]]<|/det|> +This study presents a novel understanding of the molecular mechanism of histone recycling at a replication fork. The simulation study reveals two distinct recycling pathways: Cdc45- mediated and unmediated pathways. Moreover, the study uncovers the regulatory role of RPA binding to the ssDNA in the ratio recycled to each strand. The proposed mechanism awaits experimental validation. The simulation study, employing a set of finely calibrated force fields, demonstrates the H3/H4 tetramer transition to the parental, leading, or lagging strand. This transition will occur + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 91, 884, 271]]<|/det|> +when the binding free energy of the H3/H4 tetramer and MCM2 is designed to be higher than that of H3/H4 and dsDNA. Thus, the transition is coordinated in advance. However, the study also reveals unexpected, insightful events. The simulations show that the Cdc45 acidic loop, previously invisible in cryo- EM structural analysis due to its flexibility, plays a crucial role in histone recycling and regulates the transition ratio to the lagging or leading strand. The study shows that the spatial distribution of H3/H4 tetramers changes depending on the interaction with cdc45, determining to which strand the tetramer moves. In addition, the impact of RPA and Pol eta is discussed. Before accepting the paper, several points should be clarified. + +<|ref|>sub_title<|/ref|><|det|>[[115, 297, 232, 315]]<|/det|> +## Response 1: + +<|ref|>text<|/ref|><|det|>[[114, 336, 883, 402]]<|/det|> +We would like to thank Reviewer 2 for carefully reading and reviewing the manuscript. We revised the manuscript in responses to the comments below. We firmly believe that the revised manuscript is ready to be published in Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[115, 468, 230, 486]]<|/det|> +## Comment 2: + +<|ref|>text<|/ref|><|det|>[[115, 507, 883, 573]]<|/det|> +The authors discussed the length of the ssDNA gap on the leading strand, which can take a variety of lengths. The authors should clarify why 33 nt was used in their molecular configuration (Figure 1). The length will affect the ratio of the H3/H4 tetramer transition to the leading or lagging strand. + +<|ref|>sub_title<|/ref|><|det|>[[115, 599, 232, 618]]<|/det|> +## Response 2: + +<|ref|>text<|/ref|><|det|>[[114, 638, 884, 818]]<|/det|> +We chose to use 33 nt in our study based on the minimum length required for the single- strand DNA region to traverse the Mcm2- 7 channel and reach the active center of Pol \(\epsilon\) . Pol \(\epsilon\) fixes the orientation of the leading strand dsDNA. Thus the gap size appears to have little, if any, effect on strand bias in histone recycling. To clarify this point, we added the sentence, "The length of the ssDNA gap on the leading strand was 33 nt and passed through the central channel of Mcm2- 7 and the catalytic subunit of Pol \(\epsilon\) . Pol \(\epsilon\) fixes the orientation of the leading strand dsDNA. Thus, the gap size appears to have little, if any, effect on strand bias in histone recycling." to the Method section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 885, 230, 902]]<|/det|> +## Comment 3: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 91, 884, 225]]<|/det|> +Line 111. Supplementary Figure 1 does not have the binding free energy of the Mcm2 and H3/H4 tetramer. It seems Figure 21. The binding free energy calculated from the coarse- grained simulation highly depends on the definition. The authors need to clarify why the bound state is the state with \(Q > 0\) . In addition, the figure denotes the H3/H4 dimer- Mcm2 interaction, not the tetramer. In addition, it is helpful to understand the simulation results if the binding free energy of H3/H4 tetramer and dsDNA obtained by the simulation is provided. + +<|ref|>sub_title<|/ref|><|det|>[[115, 251, 233, 270]]<|/det|> +## Response 3: + +<|ref|>text<|/ref|><|det|>[[114, 290, 884, 448]]<|/det|> +We have revised the text to specify that Supplementary Figure 1 does not depict the binding free energy but rather illustrates the results of our temperature replica exchange simulations of Mcm2 and the H3/H4 dimer (revised text: "Therefore, in this study, we performed temperature replica exchange simulations of Mcm2 and an H3/H4 dimer associating to and dissociating from each other with varying parameters (Supplementary Figure 1) and selected the one that reproduced the experimental binding free energy (Simulation: \(- 10.00 \pm 0.26\) kcal/mol, Experiment: \(- 10.45 \pm 0.04\) kcal/mol \(^{15}\) )." + +<|ref|>text<|/ref|><|det|>[[114, 467, 884, 670]]<|/det|> +Regarding the definition of the bound state with \(Q > 0\) , we utilized this criterion because even partial formation of native contacts can imply binding in the experimental setup. Even when a cutoff of \(10 \text{Å}\) was used for the minimum distance between Mcm2 and the H3/H4 dimer, the binding free energy was \(- 10.1 \pm 0.3\) kcal/mol, suggesting that our simulation results are robust to the cutoff definition. To clarify this point, we added the sentence, "Then, we defined the bound state as the state with \(Q > 0\) because even partial formation of native contacts can imply binding in the experimental setup. Even when a cutoff of \(10 \text{Å}\) was used for the minimum distance between Mcm2 and the H3/H4 dimer, the binding free energy was \(- 10.1 \pm 0.3\) kcal/mol, suggesting that our simulation results are robust to the cutoff definition." to the Methods section. + +<|ref|>text<|/ref|><|det|>[[114, 690, 884, 800]]<|/det|> +The main text incorrectly stated that this was a replica exchange simulation of the Mcm2 N- tail and H3/H4 tetramer, which has been corrected in the revised manuscript as above. In reality, Mcm2 N- tail and H3/H4 dimer interact with each other, so the simulation results were compared with the experimental binding free energy of Mcm2 N- tail and H3/H4 dimer. We would like to express our apologies to the reviewers for the confusion caused by this error. + +<|ref|>text<|/ref|><|det|>[[115, 820, 883, 886]]<|/det|> +As for the binding free energy between the H3/H4 tetramer and dsDNA, while direct calculation from simulations remains challenging due to multiple binding sites of the tetramer on dsDNA, we note that the previous experiment suggested binding energy around - 12 kcal/mol [Andrews et al. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 91, 884, 202]]<|/det|> +(2010) Mol Cell 37:834], consistent with our simulation findings that Mcm2 N- tail directly hand over the H3/H4 tetramer to the replicated strands. To clarify this point, we added the sentence, "The previous experiment suggested a binding free energy between the H3/H4 tetramer and dsDNA of around - 12 kcal/mol79, in line with the direct handover of the H3/H4 tetramer from the Mcm2 N- tail to the replicated strands." to the Methods section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 269, 230, 287]]<|/det|> +## Comment 4: + +<|ref|>text<|/ref|><|det|>[[114, 308, 883, 373]]<|/det|> +Line 135. The authors used 1KX5 as the reference structure in which the histones are from Xenopus laevis. It is not clear if the histones used in the simulation are from budding yeast as used in their experiment. + +<|ref|>sub_title<|/ref|><|det|>[[115, 400, 232, 419]]<|/det|> +## Response 4: + +<|ref|>text<|/ref|><|det|>[[113, 439, 884, 733]]<|/det|> +Reviewer 2 correctly pointed out that the histone sequence used in the simulation is from Xenopus laevis. Past studies used this sequence to calibrate parameters to match experimental results [Niina et al. (2017) PLoS Comput. Biol. 13(12): e1005880, Brandani et al. (2021) PLoS Comput. Biol. 17(7):e1009253]. It is not straightforward to perform a similar calibration for Saccharomyces cerevisiae histones, as several corresponding experiments have yet to be performed. However, the sequence of H3 and H4 in Xenopus laevis and Saccharomyces cerevisiae is highly conserved at 97.1% and 99.0% similarity, respectively, and it is thought that the effect of sequence changes on intermolecular interactions is small. In particular, the impact on conclusions obtained from the simulations with the coarse- grained resolution should be minimal. We clarified this point by adding the sentence, "The amino acid sequence was taken from Xenopus laevis for parameter calibration purposes. However, because of the high degree of sequence similarity in histones (97.1% for H3 and 99.0% for H4), the impact of the sequence on conclusions obtained from the coarse- grained simulations should be minimal." to the Methods section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 799, 230, 816]]<|/det|> +## Comment 5: + +<|ref|>text<|/ref|><|det|>[[115, 840, 456, 858]]<|/det|> +Figure 2I legend does not match the figure. + +<|ref|>sub_title<|/ref|><|det|>[[115, 885, 232, 903]]<|/det|> +## Response 5: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 92, 883, 133]]<|/det|> +We fixed this error. We would like to express our apologies to the reviewers for the confusion caused by this error. + +<|ref|>sub_title<|/ref|><|det|>[[114, 201, 230, 218]]<|/det|> +## Comment 6: + +<|ref|>text<|/ref|><|det|>[[114, 240, 884, 351]]<|/det|> +Line 166- 171. The current estimate of the H3/H4 tetramer association time to the dsDNA, derived from a fitting, is considered unreliable. The authors must re- evaluate the fitting error to ensure a more accurate estimation of the validity of the study's conclusions. This is particularly important as the coarse- grained simulation may overestimate the real recycling time. If this is the case, the authors are encouraged to rationalize why the time is estimated. + +<|ref|>sub_title<|/ref|><|det|>[[114, 378, 232, 396]]<|/det|> +## Response 6: + +<|ref|>text<|/ref|><|det|>[[114, 417, 884, 505]]<|/det|> +We have removed the statement "roughly corresponding to \(\sim 1.5\) microseconds" to avoid implying a precise mapping to real- world time from coarse- grained molecular dynamics simulations. We acknowledge that accurately estimating such timescales is challenging, as Reviewer 2 stated in the comment. + +<|ref|>text<|/ref|><|det|>[[114, 526, 884, 614]]<|/det|> +Additionally, we have modified the sentence to read: "We estimated that it would take \(>1 \times 10^{9}\) steps for the H3/H4 tetramer to associate with the parental, leading, or lagging strand in all the trajectories (Supplementary Figure 2B)." This change emphasizes that our conclusions are not critically dependent on precise time scale estimation. + +<|ref|>sub_title<|/ref|><|det|>[[114, 680, 230, 698]]<|/det|> +## Comment 7: + +<|ref|>text<|/ref|><|det|>[[114, 720, 883, 761]]<|/det|> +L 263. No definition for the coordinate system is provided. The x- axis is defined as the vector from the center of mass of Mcm2- 7 to that of Mcm2, but how is the y- axis or z- axis defined? + +<|ref|>sub_title<|/ref|><|det|>[[114, 789, 232, 807]]<|/det|> +## Response 7: + +<|ref|>text<|/ref|><|det|>[[114, 829, 884, 871]]<|/det|> +We would like to express our apology for this ambiguity. We added the sentence, "The Z- axis is aligned with the direction of the rotation axis of Mcm2- 7, and the X- axis is perpendicular to the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 92, 882, 134]]<|/det|> +Z-axis, passing through the COM of Mcm2 (Figure 3A). The Y-axis is perpendicular to both X- and Z-axes." to the Result section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 202, 230, 219]]<|/det|> +## Comment 8: + +<|ref|>text<|/ref|><|det|>[[115, 241, 883, 283]]<|/det|> +Comment 8:Line 263. The DNA persistent length is typically around 500 bp but is described as 150 bp. Is this length specific to this coarse- grained simulation? + +<|ref|>sub_title<|/ref|><|det|>[[115, 310, 233, 328]]<|/det|> +## Response 8: + +<|ref|>text<|/ref|><|det|>[[115, 350, 883, 392]]<|/det|> +Response 8:Under typical conditions, the persistence length of dsDNA is 50 nm [e.g., Geggier et al. (2010) PNAS 107:15421], equivalent to approximately 150 base pairs. + +<|ref|>sub_title<|/ref|><|det|>[[115, 458, 230, 475]]<|/det|> +## Comment 9: + +<|ref|>text<|/ref|><|det|>[[115, 498, 883, 540]]<|/det|> +Comment 9:Line 385. Figure 5 shows the distance between the junction and the H3/H4 tetramer, but the text says the distance between the junction and Cdc45. It seems that the figure is wrong. + +<|ref|>sub_title<|/ref|><|det|>[[115, 567, 232, 585]]<|/det|> +## Response 9: + +<|ref|>text<|/ref|><|det|>[[115, 607, 883, 649]]<|/det|> +Response 9:We fixed this error by changing the figure representation. We would like to express our apologies to the reviewers for the confusion caused by this error. + +<|ref|>sub_title<|/ref|><|det|>[[115, 715, 240, 732]]<|/det|> +## Comment 10: + +<|ref|>text<|/ref|><|det|>[[115, 755, 883, 819]]<|/det|> +Comment 10:Lines 389- 408 and Fig.6. This paragraph does not strengthen the authors' argument and can be excluded from the paper, though I guess the authors might start to study this molecular configuration. + +<|ref|>sub_title<|/ref|><|det|>[[115, 847, 244, 865]]<|/det|> +## Response 10: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 91, 883, 157]]<|/det|> +As Reviewer 2 correctly pointed out, we have removed the paragraph and Fig. 6 as they do not strengthen the main argument of the paper. We deeply appreciate the suggestion, and this molecular configuration could be explored in future studies in different contexts. + +<|ref|>sub_title<|/ref|><|det|>[[114, 222, 241, 240]]<|/det|> +## Comment 11: + +<|ref|>text<|/ref|><|det|>[[114, 262, 883, 306]]<|/det|> +In the figure legends, the authors should explain what the error bars denote wherever they appear (e.g., Figs. 2I and 4G, I). + +<|ref|>sub_title<|/ref|><|det|>[[114, 331, 245, 350]]<|/det|> +## Response 11: + +<|ref|>text<|/ref|><|det|>[[114, 371, 883, 414]]<|/det|> +We would like to express our apology for the lack of information. The error bars represent mean \(\pm\) standard deviation. The figure legends were revised accordingly. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 310, 97]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 111, 415, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 140, 653, 155]]<|/det|> +All my comments are adequately addressed in the revised manuscript + +<|ref|>text<|/ref|><|det|>[[119, 196, 415, 210]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 224, 863, 266]]<|/det|> +The authors have satisfactorily addressed all the concerns raised by the reviewers. However, the numbering for supplementary figures is not consistent. Some are referred to as S5, while others are referred to as 5. Please ensure consistent numbering throughout the document. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 93, 364, 111]]<|/det|> +## Responses to Reviewer #1 + +<|ref|>sub_title<|/ref|><|det|>[[115, 136, 230, 153]]<|/det|> +## Comment 1: + +<|ref|>text<|/ref|><|det|>[[115, 177, 666, 195]]<|/det|> +All my comments are adequately addressed in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 221, 234, 239]]<|/det|> +## Response 1: + +<|ref|>text<|/ref|><|det|>[[115, 261, 758, 280]]<|/det|> +We would like to thank Reviewer 1 again for carefully reviewing this manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 350, 365, 368]]<|/det|> +## Responses to Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[115, 393, 230, 410]]<|/det|> +## Comment 1: + +<|ref|>text<|/ref|><|det|>[[115, 433, 883, 497]]<|/det|> +The authors have satisfactorily addressed all the concerns raised by the reviewers. However, the numbering for supplementary figures is not consistent. Some are referred to as S5, while others are referred to as 5. Please ensure consistent numbering throughout the document. + +<|ref|>sub_title<|/ref|><|det|>[[115, 523, 234, 541]]<|/det|> +## Response 1: + +<|ref|>text<|/ref|><|det|>[[115, 563, 883, 605]]<|/det|> +We also would like to thank Reviewer 2 for carefully reviewing the manuscript. We unified the notation. + +<--- Page Split ---> diff --git a/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/images_list.json b/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd b/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a794a936c642e86600377d0c496c22ca94525ae8 --- /dev/null +++ b/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd @@ -0,0 +1,349 @@ + +# Potent AMA1-specific human monoclonal antibody against P. vivax Pre-erythrocytic and Blood Stages + +Corresponding Author: Professor Christopher King + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) Summary: + +This manuscript reports the isolation of a monoclonal antibody that inhibits binding of Plasmodium vivax (Pv) Apical Membrane Antigen 1 (AMA- 1). Neutralization of this antigen has been reported to neutralize both blood stages as well as stopping sporozoite invasion of hepatocytes, thereby, neutralizing the develop of liver- stages. The latter is essential to prevent the formation of hypnozoites, which are the prime drivers of infections and transmission of Pv in endemic areas. Thus, there is significant interest in identifying monoclonal antibodies that could be used to reduce the hypnozoite reservoir and reduce disease and transmission. This antibody, in principle, could reduce hypnozoite burden and may have the added benefit of neutralizing blood- stage parasites if used in vivo. Together, these make the work presented here important to the field of Pv research. + +In the manuscript, the authors detail the isolation of the antibody through standard monoclonal methods, assessment of neutralization of blood and liver- stages, and also perform structural analysis to propose mechanisms that result in the best antibody's ability to neutralize. The latter is particular useful for the field as PvAMA- 1 has been a vaccine candidate, but due to its polymorphic nature has not provided significant protection from blood- stage infection. Thus, the structural analyses provide some insights into how antibodies targeting these regions can be evaded, which may lead to improvement of AMA- 1 immunogen design. While this work is important, there are a number of concerns that reduce the impact of the manuscript. + +The major weaknesses are as follows: + +1. The authors provide no data on how well this antibody will perform in vivo, which the authors indicate could be tested using humanized mice with Pv or potentially P. cynomolg. Given the IC50 values reported in the paper, this would be needed to truly assess the impact and therapeutic potential of this antibody. + +2. Representative data demonstrating the isolation of the Pv AMA-1 + memory B cells is not presented for assessment in the manuscript. This is standard in most manuscripts assessing or creating monoclonal antibodies. This is more important here because there is some concern that the antibodies used in the panel may have interfered with the binding of the B cell receptor to the antigen due to steric hindrance, thereby, reducing the number of clones identified. + +3. The clonal analysis is not consistent with field standards. Generally, to be considered a clone, a B cell must have the same VDJ segment usage, have the same CDR3 length, and 85% AA identity across heavy and light chains. The rationale for using the term clonal group is unclear in the manuscript, and there are also standards for tracing lineages of B cells. Additionally, it seems that not many high-quality sequences were obtained. An example of a suite of software the authors might find useful for better assessing this information is Immacntation, which can be found here https://immcanton.readthedocs.io/en/stable/index.html + +4. There are significant discrepancies between the authors use of terms, language, and numbers in the main text, figure legends, and methods. For example, the authors indicate in the abstract that they isolated antibodies from the plasma, but their methods describe isolation from peripheral blood mononuclear cells. Additionally, the text says that Anopheles dirus were fed directly on patients to generate Pv sporozoites in Thailand while the methods indicate the mosquitoes were fed blood from infected patients. These inconsistencies should be reviewed and fixed. + +<--- Page Split ---> + +## Minor Weaknesses + +1. The authors indicate in their results that they may have a strain transcending antibody, but then, they state it is strain- transcending in the discussion. One phrase should be selected. Also, strains are typically associated with the laboratory and continuous maintenance of a parasite versus what was assessed here is Pv isolates/variants since these are circulating parasites that cannot be obtained again. + +2. It should be made clear the parasitemia and liver-stage form cut-offs used to assess if the data from the neutralization experiments were valid. Currently, there is information suggesting there were assessments, but it is important to state what the experiment had to be for you to include the data in the analysis (i.e. what were the lower limits of quantitation). + +3. In the legend for Figure 1 and elsewhere, the authors should consider using the field-standard abbreviations/capitalizations for antibody chains and Kd. Additionally, it would be helpful to indicate whether the number of SHM indicated in Fig. 1A are amino acid or nucleotide mutations. + +4. In the legend for Figure 3B, the lowest IC50 measured is listed as \(0.07 \mu \mathrm{g / mL}\) . This does not match the text, which lists the lowest IC50 measured as \(0.01 \mu \mathrm{g / mL}\) . + +5. In Figure 4B, it would be helpful and improve ease of understanding to shade the buried surface area on the structure model. Similarly, changing the legend labels from the PDB IDs to the protein names used elsewhere in the text would improve clarity for the reader. + +6. Generally speaking, it would improve clarity if the numerical orientation of the x-axis were kept constant between figures. + +## Reviewer #2 + +(Remarks to the Author) + +Winnicki and colleagues report on the isolation and characterization of human monoclonal antibodies (mAbs) against Plasmodium vivax (Pv) AMA1. AMA1 has a somewhat spotty record historically in vaccine development for P. falciparum (Pf), thought to be inhibited by the extensive polymorphisms among circulating strains. Here the authors evaluate mAbs to Pv, which historically is less studied for vaccine development. After screening serum from infected subjects, they isolated B cells reactive to PvAMA1. They evaluated their ability to bind to AMA1 from other strains, observing extensive cross- reactivity to another Pv strain and to PkAMA1, and some limited cross- reactivity to PAMA1. The leading antibody, 826827, showed inhibitory activity against both blood and pre- erythrocytic stages, across multiple clinical isolates. Potency against field isolates for hepatocyte invasion was similar to that of the prototype anti- CSP mAb 2F2. Structural studies revealed that the antibody binds to the protein element that interacts with RON2, a part of AMA1 that is less polymorphic. Thus, mechanistically, the antibody likely inhibits invasion of Hepatocytes or RBCs by occupying the hydrophobic groove that would normally be occupied by RON2 during invasion. + +As a whole, this is a well- presented study, with data that strongly support their overall conclusions. Strain transcendency is an important aspect, which is highly relevant to vaccine design. The blocking of both PE and BS invasion is highly interesting, and the potency with which it blocks is extraordinary (in fact, perhaps under sold in the manuscript). In fact, the potential broader impact of this finding is also a bit undersold and could be hyped a bit more. This study also touches upon the importance of affinity in mediating potent blocking activity, a feature that is becoming more and more clear to be critical for functional blocking. Overall, despite the conventional wisdom that AMA1 is not a great vaccine target for Pf, this study highlights that there are elements within the protein that could be highly effective vaccine targets. As such, this study may guide structure- based design toward a vaccine candidate focused on the RON2 binding groove, perhaps in combination with other potent targets, that ultimately may be able to reduce or eliminate transmission of P. vivax. + +Some minor comments: + +- Fig 2A seems unnecessary. It is in a highly contrived model, and IC50 values were more potent in the biologically relevant reticulocyte invasion assay anyway. + +- There is some mixing of equivalent units, ng/ul and ug/ml. I'd pick one and unify for readability. + +- Some grammatical errors need to be fixed throughout. + +- A little more experimental detail on binding would be useful in the results. The assay used in binding studies does not appear to be noted in the text (results section 1, paragraph 2). + +- Similar to previous, a touch more info on the assays in the body of the text would go a long way for broad readership. + +- Other than antigen binding, is the epitope specificity known for any other clones? It would be interesting to understand the antibody within the context of the rest of the anti-AMA1 response. E.g., is it a rare target or immunodominant, etc. + +Reviewer #3 + +<--- Page Split ---> + +(Remarks to the Author) + +In this manuscript, Winnicki et al. isolate human mAbs that target the Plasmodium vivax protein AMA1, a protein important for invasion of the parasite into hepatocytes and reticulocytes. They show that one antibody, 826827, performed better than others at blocking erythrocytes using a chimeric P. falciparum line expressing PvAMA1. 826827 was also able to inhibit hepatocyte invasions at lower IC50 than all others tested in vitro. A crystal structure of the 826927 Fab was solved bound to PvAMA1 and showed that the heavy chain of 826827 has an extended CDRH3 that binds in a hydrophobic groove that serves as the binding site of RON2, providing a mechanism for 826927's inhibition. The interaction of AMA1 and RON2 is important for both sporozoite and merozoite invasion. They further show that the key interactions in the 826827- PvAMA1 have low polymorphisms among clinical isolates. In all, this study provides important biological and structural information for P. vivax immunology and could be useful for vaccine design. + +Major comments: + +In the intro the authors mention that "we have identified a potent, strain- transcending humAb that blocks RON2- loop binding and can inhibit both blood stage and sporozoite infection." I believe this manuscript would benefit from an in vivo experiment for liver burden, either using the human liver chimeric mouse model or with a chimeric P. berghei expressing PvCSP since they mention the humAb also inhibit sporozoite infection. Have the authors tested 826827 binding to PbAMA1? The authors specifically looked for "PvRON2- binding- inhibition" huMabs but it is possible that there are huMabs that will prevent AMA- 1 action by not blocking RON2. Have the authors looked at this at all? I think it should be added to the discussion. This recent paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10475129/) showed that antibodies that do not inhibit AMA1- RON2 interaction are highly protective. + +Minor comments: + +In the introduction, the term humAbs is used multiple times before it is defined in the last paragraph and on one occasion "human humAbs" is used. However, it is clearly defined in the abstract. Maybe revise the intro. + +It is not clear from the beginning what the naming convention of the humAbs is. I was initially confused when the heavy chain was referred to as 826. This should be clarified. It seems indeed that 826827 comes from 826HC and 827LC but this is not mentioned in the results. Usually one refers to the Mab 826827 HC and LC otherwise it seems they come from a different antibody. + +The buried surface area of 826827 is stated twice (page 8 and page 10 in the PDF) in the text and with different significant figures. In general, buried surface area are approximate - at place the authors mention 1392.5 A2 and other 1392 A2. Maybe just change to "- 1392 A2." + +Rewrite this sentence: "The combined buried surface area is 1392.5 A2 large, while the major contribution of 70% is provided by the heavy chain 826." To something like "The major contribution of humAb 826827 is through its heavy chain (- 70% of the - 1392 A2 buried surface area)." Also that sentence can be moved when describing the interactions first. It seems a bit out of place to have a repeat of this information in another paragraph. + +Suggestion: "Figure 5A shows that the contact residues between PvAMA1 and RON2- loop overlap with the residues of PvAMA1 that contact humAb 826827 CDR- H3 residues, which contributes to \(\sim X\%\) of the total buried surface area of 826827 interaction with PvAMA1". (it is actually unclear what is the CDRH3 only contribution to the interaction the way it is currently written). + +Same here " Comparing the RON2 and 826 CDR3 binding site to other available Plasmodium species and model systems reveals that P..." Since CDRL3 is not involved at all in the interaction specify CDRH3. + +Rewrite sentence: "They are also exhibit similar potency compared to a PfAMA1 humAb that was previously produced based on an IgG" + +Figure 1 - is the number of SHM amino acid or nucleotide based? + +Figure 2A, 2C, and 3B, error bars should be added to show distribution of the replicates. + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +## Reviewer #5 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The revised manuscript is much improved, and the results are interesting. Importantly, I think that the comparison of the different assays helps to start defining an appropriate pipeline for testing monoclonal antibodies for Pv. + +Fig 3A and 3B - Why are the data shown differently in these panels? They are generally the same assay, albeit with different hepatocytes. However, IC50 should be able to be calculated for either or inhibition to show consistency. It would also help compare the assays head- to- head for determining appropriate pipelines for monoclonal antibodies in the future. + +Fig 3 - The liver stages still leaves a few behind based on supplementary data in Figure s6. Can you comment directly in discussion how this may impact the utility or if alternative approaches could be used? + +Line 194 - says 'reticulates' instead of reticulocytes + +Reviewer #2 + +(Remarks to the Author) + +This reviewer had few major criticisms, all of which have been responded to, if not fully addressed. Other reviewer comments have been addressed, and the authors added a major new experiment in FRG mice to assess blocking activity in vivo against field isolates. This experiment shows blocking activity of the mAb in vivo against the sporozoite, and represents a major investment for this study, since infected mosquitoes are shipped from Thailand and each mouse is nearly the cost of a non- human primate. The data support the overall conclusions and have strengthened the manuscript. + +Reviewer #3 + +(Remarks to the Author) The authors have addressed the reviewers' comments. + +Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Below is a point- by- point response to the reviewers: + +Reviewer #1 + +1. The authors provide no data on how well this antibody will perform in vivo, which the authors indicate could be tested using humanized mice with Pv or potentially P. cynomolg. Given the IC50 values reported in the paper, this would be needed to truly assess the impact and therapeutic potential of this antibody. + +Response: We agree that data from animal models may help further understand the efficacy and potential prophylaxis and therapeutic potential of the monoclonal antibodies. The availability of animal models for P. vivax is extremely limited. Evaluating the MAb in primate models will need to be a long-term goal and is not possible within the scope and timeframe of this paper; access to primate models is limited and their use is ethically complex and costly. However, we have been able to conduct experiments using human liver chimeric mice (FRGhuHep), which have been transplanted with human hepatocytes and support P. vivax sporozoite infection and liver-stage development, (Mikolajczak et al., 2015). Using this model we found that administration of humAb 826827 prior to infection challenge markedly reduced the liver burden of P. vivax infection, as shown in our revised Figure 4 and Supplemental Figure S5. This is consistent with our in vitro data showing that humAb 826827 inhibited infection of hepatocytes by P. vivax sporozoites. Results are shown Figure 4 and Supplemental Figure 6. New sections describing these results are detailed in lines 210- 227. + +2. Representative data demonstrating the isolation of the Pv AMA-1 + memory B cells is not presented for assessment in the manuscript. This is standard in most manuscripts assessing or creating monoclonal antibodies. This is more important here because there is some concern that the antibodies used in the panel may have interfered with the binding of the B cell receptor to the antigen due to steric hinderance, thereby, reducing the number of clones identified. + +Response: We show flow panels from which the PvAMA1- specific B cells were isolated in supplemental Figure S2. The PvAMA1- specific B cells were tightly clustered and well separated from the non- antigen- specific B cells, suggesting strong binding of the PvAMA1- specific tetramers. + +3. The clonal analysis is not consistent with field standards. Generally, to be considered a clone, a B cell must have the same VDJ segment usage, have the same CDR3 length, and \(85\%\) AA identity across heavy and light chains. The rationale for using the term clonal group is unclear in the manuscript, and there are also standards for tracing lineages of B cells. Additionally, it seems that not many high-quality sequences were obtained. + +Response: We appreciate this comment from the reviewer and as suggested we have redefined the clonal groups to have the same VDJ segment and CDR3 length and \(85\%\) or greater amino acid similarity for CDR3. With this modified criterion, we now have 67 clonal groups, and the number of B cells identified in each clonal group has changed for some clonal groups, as shown in Figure 1A, Supplemental Figure 2 and detailed in lines 141- 146. We provide the VDJ usage and CDR3 sequences for all 158 isolated B cells in Supplemental Table 1. In terms of the lower number of high- quality sequences, due to the primer set used for single- cell sorting of antigen- specific B cells, obtaining high- quality sequences across the entire + +<--- Page Split ---> + +heavy and light chains is at times challenging. Nonetheless, CDR3 sequences consistently maintain high quality. + +4. There are significant discrepancies between the authors use of terms, language, and numbers in the main text, figure legends, and methods. For example, the authors indicate in the abstract that they isolated antibodies from the plasma, but their methods describe isolation from peripheral blood mononuclear cells. Additionally, the text says that Anopheles dirus were fed directly on patients to generate Pv sporozoites in Thailand while the methods indicate the mosquitoes were fed blood from infected patients. These inconsistencies should be reviewed and fixed. + +Response: Thank you for pointing out these inconsistencies. The abstract has been changed to PBMC, and the text has been changed to designate that mosquitoes were fed on human blood, not directly on humans. This is consistent with the methods sections. Some other discrepancies have been identified and corrected. + +## Minor Weaknesses + +1. The authors indicate in their results that they 'may have a strain transcending antibody', but then, they state it is strain-transcending in the discussion. One phrase should be selected. Also, strains are typically associated with the laboratory and continuous maintenance of a parasite versus what was assessed here is Pv isolates/variants since these are circulating parasites that cannot be obtained again. + +Response: We now say recognizing and active against multiple clinical isolates, rather than strain-transcending. + +2. It should be made clear the parasitemia and liver-stage form cut-offs used to assess if the data from the neutralization experiments were valid. Currently, there is information suggesting there were assessments, but it is important to state what the experiment had to be for you to include the data in the analysis (i.e. what were the lower limits of quantitation). + +Response: The threshold for P. vivax invasion of reticulocytes in controls is \(0.2\%\) parasitemia (detailed in lines 666- 667). This clearly separates new invasion events from uninfected reticulocytes on FACS analysis. For the experiments performed with AMA1 humAbs, invasion rates in controls varied from 0.24 to \(0.7\%\) (detailed in lines 733- 735). For the liver stage assay, 60 liver stage parasites/well in controls are used as cut-offs for a valid experiment. The mean of invasion controls varied from 72 to 904 for experiments using humAbs to PvAMA1. + +3. In the legend for Figure 1 and elsewhere, the authors should consider using the field-standard abbreviations/capitalizations for antibody chains and Kd. Additionally, it would be helpful to indicate whether the number of SHM indicated in Fig. 1A are amino acid or nucleotide mutations. + +Response: As shown in figure 1A, we have used the standard nomenclature in the legend for antibody chains. We now designate SHM as nucleotide mutations, detailed in lines 1118- 1119. + +4. In the legend for Figure 3B, the lowest IC50 measured is listed as \(0.07 \mu \mathrm{g} / \mathrm{mL}\). This does not match the text, which lists the lowest IC50 measured as \(0.01 \mu \mathrm{g} / \mathrm{mL}\). + +<--- Page Split ---> + +Response: In Figure 3A, one isolate's IC50 is measured as \(0.01 \mu g / mL\) . However, 3B shows 3 additional isolates with detailed IC50 curves, and the lowest is \(0.07 \mu g / mL\) . The text (lines 1160- 1163) has been corrected to reflect the lowest IC50 in 3B as \(0.07 \mu g / mL\) . + +5. In Figure 4B, it would be helpful and improve ease of understanding to shade the buried surface area on the structure model. Similarly, changing the legend labels from the PDB IDs to the protein names used elsewhere in the text would improve clarity for the reader. + +Response: We appreciate the suggestion of the reviewer but found that shading the epitope made panel B busier and more confusing. We also tried to highlight the epitope with an outline instead (please, see comparisons below) but still think that the original panel B shows best what we want to show. We changed the legends in the Figure and included the protein names as suggested by the reviewer. In addition we included a new Supplementary Figure 10 where the epitope and paratopes are shaded on the protein surfaces. + +![PLACEHOLDER_7_0] + + +6. Generally speaking, keeping the numerical orientation of the x-axis constant between figures would improve clarity. + +Response: All x- axes on the graphs are oriented similarly, with the largest concentration starting on the left side and decreasing in concentration as it moves to the right. Some graphs start at 1000 \(\mu g / mL\) of humAb, whereas others start at 100 \(\mu g / mL\) , reflecting different experimental conditions with different assays. + +<--- Page Split ---> + +## Reviewer #2 + +Overall Response: Thank you for your overall positive response to the manuscript and constructive comments. + +Some minor comments: + +- Fig 2A seems unnecessary. It is in a highly contrived model, and IC50 values were more potent in the biologically relevant reticulocyte invasion assay anyway. + +Response: We prefer to retain Figure 2A as valuable data and complements data generated using P. vivax isolates; the other reviewers have not requested removal of that figure. The advantage of the Pf- PvAMA1 transgenic parasite model is that it expresses the Palo Alto variant of PvAMA1, which is the same PvAMA1 allele that was used to isolate the humAbs. Therefore, we could evaluate the activity of the humAbs without the potential confounding effect of polymorphisms in PvAMA1 that occur in clinical isolates. + +- There is some mixing of equivalent units, ng/ul and ug/ml. I'd pick one and unify for readability. + +Response: ng/ml is used only in Figure 1 because reactivity to recombinant protein is much more sensitive compared to the amount of antibody required for invasion assays. We changed this to \(\mu \mathrm{g / mL}\) in Figure 1 legend. + +- Some grammatical errors need to be fixed throughout. + +Response: Thank you. We edited the text more carefully. + +- A little more experimental detail on binding would be useful in the results. The assay used in binding studies does not appear to be noted in the text (results section 1, paragraph 2). + +- Similar to previous, a touch more info on the assays in the body of the text would go a long way for broad readership. + +Response: We have further described key assay methods in the result sections + +- Other than antigen binding, is the epitope specificity known for any other clones? It would be interesting to understand the antibody within the context of the rest of the anti-AMA1 response. E.g., is it a rare target or immunodominant, etc. + +Response: This is an interesting point. A future goal will be to co- crystallize other human monoclonal antibodies. We will use the RON2—PvAMA1 binding assay to identify Pv- exposed individuals with blocking activity, like the individual from whom we isolated the most inhibitory monoclonal antibody in the present study. We will then use our different monoclonals to see if they compete with the inhibitory activity in sera. This will determine whether this response is rare or immunodominant. These experiments will be part of a future project, which we plan to publish as a separate manuscript. + +Reviewer # 3 + +<--- Page Split ---> + +Major comments: + +Major comments:In the intro the authors mention that "we have identified a potent, strain- transcending humAb that blocks RON2- loop binding and can inhibit both blood stage and sporozoite infection." I believe this manuscript would benefit from an in vivo experiment for liver burden, either using the human liver chimeric mouse model or with a chimeric P. berghei expressing PvCSP since they mention the humAb also inhibit sporozoite infection. Have the authors tested 826827 binding to PbAMA1? + +Response: We have shown humAb 826827 inhibits sporozoite invasion in the human liver chimeric mouse model, which is now included in the manuscript. However, based on structural and sequence analysis, we suspect that 826827 would not show as potent inhibition of P. berghei parasites. There is \(45\%\) identity for amino acids in the PvAMA1 epitope recognized by 826827 between Pb and Pv. The amino acid identity for Pv and PfAMA1 (31.5%), and 826827 does not bind to PfAMA1. Thus, 826827 is unlikely to recognize PbAMA1, although we have not tested it. Results for in vivo data are shown Figure 4 and Supplemental Figure 6. New sections describing these results are detailed in lines 210- 227. + +The authors specifically looked for "PvRON2- binding- inhibition" huMabs but it is possible that there are huMabs that will prevent AMA- 1 action by not blocking RON2. Have the authors looked at this at all? I think it should be added to the discussion. This recent paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10475129/) showed that antibodies that do not inhibit AMA1- RON2 interaction are highly protective. + +Responses: This is an interesting point, and we have considered it. Most of the humAbs generated from this donor appear to have some blocking activity in PvAMA1- RON2 assay. No humAbs antibodies that do not block or weakly block PvAMA1- RON2 demonstrate potent invasion inhibition in vitro using clinical isolates. We may have biased selection of PvAMA1- RON2 blocking Abs because this individual had potent blocking activity in serum. To address this question, we are isolating humAbs to PvAMA1 from other individuals, some without detectable PvAMA1- RON2 blocking activity. We address this point briefly in the discussion. + +Minor comments: + +In the introduction, the term humAbs is used multiple times before it is defined in the last paragraph and on one occasion "human humAbs" is used. However, it is clearly defined in the abstract. Maybe revise the intro. + +Response: Corrected + +It is not clear from the beginning what the naming convention of the humAbs is. I was initially confused when the heavy chain was referred to as 826. This should be clarified. It seems indeed that 826827 comes from 826HC and 827LC but this is not mentioned in the results. Usually one refers to the Mab 826827 HC and LC otherwise it seems they come from a different antibody. + +Response: This humAb numbering is now described at the binding of the results section (lines 151- 152). + +<--- Page Split ---> + +The buried surface area of 826827 is stated twice (page 8 and page 10 in the PDF) in the text and with different significant figures. In general, buried surface area are approximate - at place the authors mention 1392.5 A2 and other 1392 A2. Maybe just change to "\\~1392 A2." + +Rewrite this sentence: "The combined buried surface area is 1392.5 A2 large, while the major contribution of \(70\%\) is provided by the heavy chain \(826\) ." To something like "The major contribution of humAb 826827 is through its heavy chain ( \(\sim 70\%\) of the \(\sim 1392\) A2 buried surface area)." Also that sentence can be moved when describing the interactions first. It seems a bit out of place to have a repeat of this information in another paragraph. + +Suggestion: "Figure 5A shows that the contact residues between PvAMA1 and RON2- loop overlap with the residues of PvAMA1 that contact humAb 826827 CDR- H3 residues, which contributes to \(\sim X\%\) of the total buried surface area of 826827 interaction with PvAMA1". (it is actually unclear what is the CDRH3 only contribution to the interaction the way it is currently written). + +Same here " Comparing the RON2 and 826 CDR3 binding site to other available Plasmodium species and model systems reveals that P..." Since CDRL3 is not involved at all in the interaction specify CDRH3. + +Rewrite sentence: "They are also exhibit similar potency compared to a PfAMA1 humAb that was previously produced based on an IgG" + +Response: We agree with the reviewer and now only mention the buried surface area once as an approximate and have moved the information of the CDR- H3 contribution to the section when first describing the interaction. + +In line 236- 238, we changed the sentence "Five of the six complementarity- determining regions (CDR, namely: L1, L2, H1, H2, and H3) form direct contacts with PvAMA1 with a buried interaction surface of 1392 A2, with the light chain contributing 432 A2 and the heavy chain contributing 959 A2" to "Five of the six complementarity- determining regions (CDR, namely: L1, L2, H1, H2, and H3) form direct contacts with PvAMA1 with a buried interaction surface of \(\sim 1392\) A2, with the CDR- H3 loop of 826827 contributing \(70\%\) of the buried surface area (Figure 5B). + +As suggested by the reviewer we changed the sentence in line 281- 285 to specify CDR- H3. It reads now: "Comparing the RON2 and CDR- H3 binding site of 826827 to other available Plasmodium species and model systems reveals that P. cynomolgi AMA1 is \(100\%\) conserved and would therefore serve as a predictive non- human primate model for Pv challenge infections to evaluate humAb 826827 (Figure 6A, Supplemental Figure 8). + +Line 341- 343: We rewrote the sentence "They are also exhibit similar potency compared to a PfAMA1 humAb that was previously produced based on an IgG...", to "They exhibit similar potency to a PfAMA1 humAb produced from an IgG sequence isolated from a Ghanaian with an \(IC_{50}\) of 35 \(\mu g / mL\) against the Pf 3D7 variant in vitro." + +Figure 1 - is the number of SHM amino acid or nucleotide based? + +Response: Addressed in figure legend (lines 1118- 1119). + +Figure 2A, 2C, and 3B, error bars should be added to show distribution of the replicates. + +<--- Page Split ---> + +Response: Corrected, however the graph in Figure 2C is displaying the dose curve for each replicate that was performed. Therefore, this graph represents the distribution of replicates without the need for error bars. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The revised manuscript is much improved, and the results are interesting. Importantly, I think that the comparison of the different assays helps to start defining an appropriate pipeline for testing monoclonal antibodies for Pv. + +Fig 3A and 3B – Why are the data shown differently in these panels? They are generally the same assay, albeit with different hepatocytes. However, IC50 should be able to be calculated for either or inhibition to show consistency. It would also help compare the assays head- to- head for determining appropriate pipelines for monoclonal antibodies in the future. + +## Authors Response: + +We have removed Figure 3B as suggested by the reviewer. + +Fig 3 – The liver stages still leaves a few behind based on supplementary data in Figure s6. Can you comment directly in discussion how this may impact the utility or if alternative approaches could be used? + +## Authors Response: + +We have added a few lines of clarifications and explanation in the text to help explain why there is signal in the qPCR results for the in vivo experiments as well as added one more reference demonstrating the same finding with Pf in this model system. + +Line 194 – says ‘reticulates’ instead of reticulocytes + +## Authors Response: + +This spelling error has been fixed and we thank the reviewer for catching our error. + +Reviewer #2 (Remarks to the Author): + +This reviewer had few major criticisms, all of which have been responded to, if not fully addressed. Other reviewer comments have been addressed, and the authors added a major new experiment in FRG mice to assess blocking activity in vivo against field isolates. This experiment shows blocking activity of the mAb in vivo against the sporozoite, and represents a major investment for this study, since infected mosquitos are shipped from Thailand and each mouse is nearly the cost of a non- human primate. The data support the overall conclusions and have strengthened the manuscript. + +## Authors Response: + +We thank the reviewer for helping us improve the manuscript. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The authors have addressed the reviewers' comments. + +## Authors Response: + +We thank the reviewer for helping us improve the manuscript. + +Reviewer #4 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +## Authors Response: + +We thank the reviewer for helping us improve the manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd b/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1ea90edcfa17fba3ef16f39bd3c57b3ec0082394 --- /dev/null +++ b/peer_reviews/554382dc59986cda1be72afba8c2ba55cf52fcd1b48c8110487238b155ebb86d/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd @@ -0,0 +1,493 @@ +<|ref|>title<|/ref|><|det|>[[73, 161, 919, 211]]<|/det|> +# Potent AMA1-specific human monoclonal antibody against P. vivax Pre-erythrocytic and Blood Stages + +<|ref|>text<|/ref|><|det|>[[73, 224, 508, 241]]<|/det|> +Corresponding Author: Professor Christopher King + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 220, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 432]]<|/det|> +(Remarks to the Author) Summary: + +<|ref|>text<|/ref|><|det|>[[72, 432, 920, 537]]<|/det|> +This manuscript reports the isolation of a monoclonal antibody that inhibits binding of Plasmodium vivax (Pv) Apical Membrane Antigen 1 (AMA- 1). Neutralization of this antigen has been reported to neutralize both blood stages as well as stopping sporozoite invasion of hepatocytes, thereby, neutralizing the develop of liver- stages. The latter is essential to prevent the formation of hypnozoites, which are the prime drivers of infections and transmission of Pv in endemic areas. Thus, there is significant interest in identifying monoclonal antibodies that could be used to reduce the hypnozoite reservoir and reduce disease and transmission. This antibody, in principle, could reduce hypnozoite burden and may have the added benefit of neutralizing blood- stage parasites if used in vivo. Together, these make the work presented here important to the field of Pv research. + +<|ref|>text<|/ref|><|det|>[[72, 536, 922, 614]]<|/det|> +In the manuscript, the authors detail the isolation of the antibody through standard monoclonal methods, assessment of neutralization of blood and liver- stages, and also perform structural analysis to propose mechanisms that result in the best antibody's ability to neutralize. The latter is particular useful for the field as PvAMA- 1 has been a vaccine candidate, but due to its polymorphic nature has not provided significant protection from blood- stage infection. Thus, the structural analyses provide some insights into how antibodies targeting these regions can be evaded, which may lead to improvement of AMA- 1 immunogen design. While this work is important, there are a number of concerns that reduce the impact of the manuscript. + +<|ref|>text<|/ref|><|det|>[[74, 626, 337, 640]]<|/det|> +The major weaknesses are as follows: + +<|ref|>text<|/ref|><|det|>[[72, 652, 890, 693]]<|/det|> +1. The authors provide no data on how well this antibody will perform in vivo, which the authors indicate could be tested using humanized mice with Pv or potentially P. cynomolg. Given the IC50 values reported in the paper, this would be needed to truly assess the impact and therapeutic potential of this antibody. + +<|ref|>text<|/ref|><|det|>[[72, 704, 920, 758]]<|/det|> +2. Representative data demonstrating the isolation of the Pv AMA-1 + memory B cells is not presented for assessment in the manuscript. This is standard in most manuscripts assessing or creating monoclonal antibodies. This is more important here because there is some concern that the antibodies used in the panel may have interfered with the binding of the B cell receptor to the antigen due to steric hindrance, thereby, reducing the number of clones identified. + +<|ref|>text<|/ref|><|det|>[[72, 769, 914, 848]]<|/det|> +3. The clonal analysis is not consistent with field standards. Generally, to be considered a clone, a B cell must have the same VDJ segment usage, have the same CDR3 length, and 85% AA identity across heavy and light chains. The rationale for using the term clonal group is unclear in the manuscript, and there are also standards for tracing lineages of B cells. Additionally, it seems that not many high-quality sequences were obtained. An example of a suite of software the authors might find useful for better assessing this information is Immacntation, which can be found here https://immcanton.readthedocs.io/en/stable/index.html + +<|ref|>text<|/ref|><|det|>[[72, 860, 904, 925]]<|/det|> +4. There are significant discrepancies between the authors use of terms, language, and numbers in the main text, figure legends, and methods. For example, the authors indicate in the abstract that they isolated antibodies from the plasma, but their methods describe isolation from peripheral blood mononuclear cells. Additionally, the text says that Anopheles dirus were fed directly on patients to generate Pv sporozoites in Thailand while the methods indicate the mosquitoes were fed blood from infected patients. These inconsistencies should be reviewed and fixed. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[73, 47, 206, 60]]<|/det|> +## Minor Weaknesses + +<|ref|>text<|/ref|><|det|>[[73, 73, 922, 125]]<|/det|> +1. The authors indicate in their results that they may have a strain transcending antibody, but then, they state it is strain- transcending in the discussion. One phrase should be selected. Also, strains are typically associated with the laboratory and continuous maintenance of a parasite versus what was assessed here is Pv isolates/variants since these are circulating parasites that cannot be obtained again. + +<|ref|>text<|/ref|><|det|>[[73, 138, 912, 179]]<|/det|> +2. It should be made clear the parasitemia and liver-stage form cut-offs used to assess if the data from the neutralization experiments were valid. Currently, there is information suggesting there were assessments, but it is important to state what the experiment had to be for you to include the data in the analysis (i.e. what were the lower limits of quantitation). + +<|ref|>text<|/ref|><|det|>[[73, 190, 914, 230]]<|/det|> +3. In the legend for Figure 1 and elsewhere, the authors should consider using the field-standard abbreviations/capitalizations for antibody chains and Kd. Additionally, it would be helpful to indicate whether the number of SHM indicated in Fig. 1A are amino acid or nucleotide mutations. + +<|ref|>text<|/ref|><|det|>[[70, 242, 920, 270]]<|/det|> +4. In the legend for Figure 3B, the lowest IC50 measured is listed as \(0.07 \mu \mathrm{g / mL}\) . This does not match the text, which lists the lowest IC50 measured as \(0.01 \mu \mathrm{g / mL}\) . + +<|ref|>text<|/ref|><|det|>[[73, 281, 891, 321]]<|/det|> +5. In Figure 4B, it would be helpful and improve ease of understanding to shade the buried surface area on the structure model. Similarly, changing the legend labels from the PDB IDs to the protein names used elsewhere in the text would improve clarity for the reader. + +<|ref|>text<|/ref|><|det|>[[70, 333, 910, 348]]<|/det|> +6. Generally speaking, it would improve clarity if the numerical orientation of the x-axis were kept constant between figures. + +<|ref|>sub_title<|/ref|><|det|>[[73, 373, 162, 386]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 399, 238, 412]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 412, 915, 555]]<|/det|> +Winnicki and colleagues report on the isolation and characterization of human monoclonal antibodies (mAbs) against Plasmodium vivax (Pv) AMA1. AMA1 has a somewhat spotty record historically in vaccine development for P. falciparum (Pf), thought to be inhibited by the extensive polymorphisms among circulating strains. Here the authors evaluate mAbs to Pv, which historically is less studied for vaccine development. After screening serum from infected subjects, they isolated B cells reactive to PvAMA1. They evaluated their ability to bind to AMA1 from other strains, observing extensive cross- reactivity to another Pv strain and to PkAMA1, and some limited cross- reactivity to PAMA1. The leading antibody, 826827, showed inhibitory activity against both blood and pre- erythrocytic stages, across multiple clinical isolates. Potency against field isolates for hepatocyte invasion was similar to that of the prototype anti- CSP mAb 2F2. Structural studies revealed that the antibody binds to the protein element that interacts with RON2, a part of AMA1 that is less polymorphic. Thus, mechanistically, the antibody likely inhibits invasion of Hepatocytes or RBCs by occupying the hydrophobic groove that would normally be occupied by RON2 during invasion. + +<|ref|>text<|/ref|><|det|>[[72, 555, 912, 671]]<|/det|> +As a whole, this is a well- presented study, with data that strongly support their overall conclusions. Strain transcendency is an important aspect, which is highly relevant to vaccine design. The blocking of both PE and BS invasion is highly interesting, and the potency with which it blocks is extraordinary (in fact, perhaps under sold in the manuscript). In fact, the potential broader impact of this finding is also a bit undersold and could be hyped a bit more. This study also touches upon the importance of affinity in mediating potent blocking activity, a feature that is becoming more and more clear to be critical for functional blocking. Overall, despite the conventional wisdom that AMA1 is not a great vaccine target for Pf, this study highlights that there are elements within the protein that could be highly effective vaccine targets. As such, this study may guide structure- based design toward a vaccine candidate focused on the RON2 binding groove, perhaps in combination with other potent targets, that ultimately may be able to reduce or eliminate transmission of P. vivax. + +<|ref|>text<|/ref|><|det|>[[73, 685, 237, 697]]<|/det|> +Some minor comments: + +<|ref|>text<|/ref|><|det|>[[70, 697, 916, 725]]<|/det|> +- Fig 2A seems unnecessary. It is in a highly contrived model, and IC50 values were more potent in the biologically relevant reticulocyte invasion assay anyway. + +<|ref|>text<|/ref|><|det|>[[73, 736, 725, 750]]<|/det|> +- There is some mixing of equivalent units, ng/ul and ug/ml. I'd pick one and unify for readability. + +<|ref|>text<|/ref|><|det|>[[73, 763, 450, 776]]<|/det|> +- Some grammatical errors need to be fixed throughout. + +<|ref|>text<|/ref|><|det|>[[72, 788, 888, 828]]<|/det|> +- A little more experimental detail on binding would be useful in the results. The assay used in binding studies does not appear to be noted in the text (results section 1, paragraph 2). + +<|ref|>text<|/ref|><|det|>[[70, 840, 876, 854]]<|/det|> +- Similar to previous, a touch more info on the assays in the body of the text would go a long way for broad readership. + +<|ref|>text<|/ref|><|det|>[[70, 866, 910, 893]]<|/det|> +- Other than antigen binding, is the epitope specificity known for any other clones? It would be interesting to understand the antibody within the context of the rest of the anti-AMA1 response. E.g., is it a rare target or immunodominant, etc. + +<|ref|>text<|/ref|><|det|>[[73, 919, 162, 931]]<|/det|> +Reviewer #3 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 48, 238, 60]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 60, 920, 180]]<|/det|> +In this manuscript, Winnicki et al. isolate human mAbs that target the Plasmodium vivax protein AMA1, a protein important for invasion of the parasite into hepatocytes and reticulocytes. They show that one antibody, 826827, performed better than others at blocking erythrocytes using a chimeric P. falciparum line expressing PvAMA1. 826827 was also able to inhibit hepatocyte invasions at lower IC50 than all others tested in vitro. A crystal structure of the 826927 Fab was solved bound to PvAMA1 and showed that the heavy chain of 826827 has an extended CDRH3 that binds in a hydrophobic groove that serves as the binding site of RON2, providing a mechanism for 826927's inhibition. The interaction of AMA1 and RON2 is important for both sporozoite and merozoite invasion. They further show that the key interactions in the 826827- PvAMA1 have low polymorphisms among clinical isolates. In all, this study provides important biological and structural information for P. vivax immunology and could be useful for vaccine design. + +<|ref|>text<|/ref|><|det|>[[72, 192, 192, 204]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[72, 204, 923, 310]]<|/det|> +In the intro the authors mention that "we have identified a potent, strain- transcending humAb that blocks RON2- loop binding and can inhibit both blood stage and sporozoite infection." I believe this manuscript would benefit from an in vivo experiment for liver burden, either using the human liver chimeric mouse model or with a chimeric P. berghei expressing PvCSP since they mention the humAb also inhibit sporozoite infection. Have the authors tested 826827 binding to PbAMA1? The authors specifically looked for "PvRON2- binding- inhibition" huMabs but it is possible that there are huMabs that will prevent AMA- 1 action by not blocking RON2. Have the authors looked at this at all? I think it should be added to the discussion. This recent paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10475129/) showed that antibodies that do not inhibit AMA1- RON2 interaction are highly protective. + +<|ref|>text<|/ref|><|det|>[[72, 322, 192, 334]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 334, 920, 373]]<|/det|> +In the introduction, the term humAbs is used multiple times before it is defined in the last paragraph and on one occasion "human humAbs" is used. However, it is clearly defined in the abstract. Maybe revise the intro. + +<|ref|>text<|/ref|><|det|>[[72, 363, 925, 414]]<|/det|> +It is not clear from the beginning what the naming convention of the humAbs is. I was initially confused when the heavy chain was referred to as 826. This should be clarified. It seems indeed that 826827 comes from 826HC and 827LC but this is not mentioned in the results. Usually one refers to the Mab 826827 HC and LC otherwise it seems they come from a different antibody. + +<|ref|>text<|/ref|><|det|>[[72, 412, 925, 451]]<|/det|> +The buried surface area of 826827 is stated twice (page 8 and page 10 in the PDF) in the text and with different significant figures. In general, buried surface area are approximate - at place the authors mention 1392.5 A2 and other 1392 A2. Maybe just change to "- 1392 A2." + +<|ref|>text<|/ref|><|det|>[[72, 450, 925, 502]]<|/det|> +Rewrite this sentence: "The combined buried surface area is 1392.5 A2 large, while the major contribution of 70% is provided by the heavy chain 826." To something like "The major contribution of humAb 826827 is through its heavy chain (- 70% of the - 1392 A2 buried surface area)." Also that sentence can be moved when describing the interactions first. It seems a bit out of place to have a repeat of this information in another paragraph. + +<|ref|>text<|/ref|><|det|>[[72, 500, 925, 553]]<|/det|> +Suggestion: "Figure 5A shows that the contact residues between PvAMA1 and RON2- loop overlap with the residues of PvAMA1 that contact humAb 826827 CDR- H3 residues, which contributes to \(\sim X\%\) of the total buried surface area of 826827 interaction with PvAMA1". (it is actually unclear what is the CDRH3 only contribution to the interaction the way it is currently written). + +<|ref|>text<|/ref|><|det|>[[72, 553, 911, 580]]<|/det|> +Same here " Comparing the RON2 and 826 CDR3 binding site to other available Plasmodium species and model systems reveals that P..." Since CDRL3 is not involved at all in the interaction specify CDRH3. + +<|ref|>text<|/ref|><|det|>[[72, 580, 884, 606]]<|/det|> +Rewrite sentence: "They are also exhibit similar potency compared to a PfAMA1 humAb that was previously produced based on an IgG" + +<|ref|>text<|/ref|><|det|>[[72, 606, 525, 619]]<|/det|> +Figure 1 - is the number of SHM amino acid or nucleotide based? + +<|ref|>text<|/ref|><|det|>[[72, 619, 672, 633]]<|/det|> +Figure 2A, 2C, and 3B, error bars should be added to show distribution of the replicates. + +<|ref|>sub_title<|/ref|><|det|>[[72, 736, 161, 749]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 763, 238, 776]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 777, 864, 816]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>sub_title<|/ref|><|det|>[[72, 828, 161, 841]]<|/det|> +## Reviewer #5 + +<|ref|>text<|/ref|><|det|>[[72, 855, 238, 867]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 868, 864, 907]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 145, 60]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 73, 220, 87]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 99, 160, 113]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 125, 238, 139]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 139, 884, 167]]<|/det|> +The revised manuscript is much improved, and the results are interesting. Importantly, I think that the comparison of the different assays helps to start defining an appropriate pipeline for testing monoclonal antibodies for Pv. + +<|ref|>text<|/ref|><|det|>[[73, 177, 900, 219]]<|/det|> +Fig 3A and 3B - Why are the data shown differently in these panels? They are generally the same assay, albeit with different hepatocytes. However, IC50 should be able to be calculated for either or inhibition to show consistency. It would also help compare the assays head- to- head for determining appropriate pipelines for monoclonal antibodies in the future. + +<|ref|>text<|/ref|><|det|>[[73, 230, 900, 258]]<|/det|> +Fig 3 - The liver stages still leaves a few behind based on supplementary data in Figure s6. Can you comment directly in discussion how this may impact the utility or if alternative approaches could be used? + +<|ref|>text<|/ref|><|det|>[[73, 269, 427, 283]]<|/det|> +Line 194 - says 'reticulates' instead of reticulocytes + +<|ref|>text<|/ref|><|det|>[[73, 307, 161, 321]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 334, 238, 347]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 347, 922, 412]]<|/det|> +This reviewer had few major criticisms, all of which have been responded to, if not fully addressed. Other reviewer comments have been addressed, and the authors added a major new experiment in FRG mice to assess blocking activity in vivo against field isolates. This experiment shows blocking activity of the mAb in vivo against the sporozoite, and represents a major investment for this study, since infected mosquitoes are shipped from Thailand and each mouse is nearly the cost of a non- human primate. The data support the overall conclusions and have strengthened the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 424, 161, 437]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 450, 448, 476]]<|/det|> +(Remarks to the Author) The authors have addressed the reviewers' comments. + +<|ref|>text<|/ref|><|det|>[[73, 502, 161, 515]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 529, 238, 542]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 543, 864, 582]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 528, 106]]<|/det|> +Below is a point- by- point response to the reviewers: + +<|ref|>text<|/ref|><|det|>[[115, 122, 215, 137]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[145, 153, 856, 219]]<|/det|> +1. The authors provide no data on how well this antibody will perform in vivo, which the authors indicate could be tested using humanized mice with Pv or potentially P. cynomolg. Given the IC50 values reported in the paper, this would be needed to truly assess the impact and therapeutic potential of this antibody. + +<|ref|>text<|/ref|><|det|>[[114, 233, 879, 441]]<|/det|> +Response: We agree that data from animal models may help further understand the efficacy and potential prophylaxis and therapeutic potential of the monoclonal antibodies. The availability of animal models for P. vivax is extremely limited. Evaluating the MAb in primate models will need to be a long-term goal and is not possible within the scope and timeframe of this paper; access to primate models is limited and their use is ethically complex and costly. However, we have been able to conduct experiments using human liver chimeric mice (FRGhuHep), which have been transplanted with human hepatocytes and support P. vivax sporozoite infection and liver-stage development, (Mikolajczak et al., 2015). Using this model we found that administration of humAb 826827 prior to infection challenge markedly reduced the liver burden of P. vivax infection, as shown in our revised Figure 4 and Supplemental Figure S5. This is consistent with our in vitro data showing that humAb 826827 inhibited infection of hepatocytes by P. vivax sporozoites. Results are shown Figure 4 and Supplemental Figure 6. New sections describing these results are detailed in lines 210- 227. + +<|ref|>text<|/ref|><|det|>[[144, 456, 877, 553]]<|/det|> +2. Representative data demonstrating the isolation of the Pv AMA-1 + memory B cells is not presented for assessment in the manuscript. This is standard in most manuscripts assessing or creating monoclonal antibodies. This is more important here because there is some concern that the antibodies used in the panel may have interfered with the binding of the B cell receptor to the antigen due to steric hinderance, thereby, reducing the number of clones identified. + +<|ref|>text<|/ref|><|det|>[[116, 568, 840, 633]]<|/det|> +Response: We show flow panels from which the PvAMA1- specific B cells were isolated in supplemental Figure S2. The PvAMA1- specific B cells were tightly clustered and well separated from the non- antigen- specific B cells, suggesting strong binding of the PvAMA1- specific tetramers. + +<|ref|>text<|/ref|><|det|>[[144, 664, 867, 760]]<|/det|> +3. The clonal analysis is not consistent with field standards. Generally, to be considered a clone, a B cell must have the same VDJ segment usage, have the same CDR3 length, and \(85\%\) AA identity across heavy and light chains. The rationale for using the term clonal group is unclear in the manuscript, and there are also standards for tracing lineages of B cells. Additionally, it seems that not many high-quality sequences were obtained. + +<|ref|>text<|/ref|><|det|>[[115, 775, 875, 905]]<|/det|> +Response: We appreciate this comment from the reviewer and as suggested we have redefined the clonal groups to have the same VDJ segment and CDR3 length and \(85\%\) or greater amino acid similarity for CDR3. With this modified criterion, we now have 67 clonal groups, and the number of B cells identified in each clonal group has changed for some clonal groups, as shown in Figure 1A, Supplemental Figure 2 and detailed in lines 141- 146. We provide the VDJ usage and CDR3 sequences for all 158 isolated B cells in Supplemental Table 1. In terms of the lower number of high- quality sequences, due to the primer set used for single- cell sorting of antigen- specific B cells, obtaining high- quality sequences across the entire + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 839, 123]]<|/det|> +heavy and light chains is at times challenging. Nonetheless, CDR3 sequences consistently maintain high quality. + +<|ref|>text<|/ref|><|det|>[[144, 137, 880, 250]]<|/det|> +4. There are significant discrepancies between the authors use of terms, language, and numbers in the main text, figure legends, and methods. For example, the authors indicate in the abstract that they isolated antibodies from the plasma, but their methods describe isolation from peripheral blood mononuclear cells. Additionally, the text says that Anopheles dirus were fed directly on patients to generate Pv sporozoites in Thailand while the methods indicate the mosquitoes were fed blood from infected patients. These inconsistencies should be reviewed and fixed. + +<|ref|>text<|/ref|><|det|>[[115, 265, 877, 330]]<|/det|> +Response: Thank you for pointing out these inconsistencies. The abstract has been changed to PBMC, and the text has been changed to designate that mosquitoes were fed on human blood, not directly on humans. This is consistent with the methods sections. Some other discrepancies have been identified and corrected. + +<|ref|>sub_title<|/ref|><|det|>[[115, 344, 270, 361]]<|/det|> +## Minor Weaknesses + +<|ref|>text<|/ref|><|det|>[[115, 376, 877, 457]]<|/det|> +1. The authors indicate in their results that they 'may have a strain transcending antibody', but then, they state it is strain-transcending in the discussion. One phrase should be selected. Also, strains are typically associated with the laboratory and continuous maintenance of a parasite versus what was assessed here is Pv isolates/variants since these are circulating parasites that cannot be obtained again. + +<|ref|>text<|/ref|><|det|>[[115, 472, 843, 505]]<|/det|> +Response: We now say recognizing and active against multiple clinical isolates, rather than strain-transcending. + +<|ref|>text<|/ref|><|det|>[[115, 520, 863, 585]]<|/det|> +2. It should be made clear the parasitemia and liver-stage form cut-offs used to assess if the data from the neutralization experiments were valid. Currently, there is information suggesting there were assessments, but it is important to state what the experiment had to be for you to include the data in the analysis (i.e. what were the lower limits of quantitation). + +<|ref|>text<|/ref|><|det|>[[115, 599, 878, 696]]<|/det|> +Response: The threshold for P. vivax invasion of reticulocytes in controls is \(0.2\%\) parasitemia (detailed in lines 666- 667). This clearly separates new invasion events from uninfected reticulocytes on FACS analysis. For the experiments performed with AMA1 humAbs, invasion rates in controls varied from 0.24 to \(0.7\%\) (detailed in lines 733- 735). For the liver stage assay, 60 liver stage parasites/well in controls are used as cut-offs for a valid experiment. The mean of invasion controls varied from 72 to 904 for experiments using humAbs to PvAMA1. + +<|ref|>text<|/ref|><|det|>[[115, 727, 877, 792]]<|/det|> +3. In the legend for Figure 1 and elsewhere, the authors should consider using the field-standard abbreviations/capitalizations for antibody chains and Kd. Additionally, it would be helpful to indicate whether the number of SHM indicated in Fig. 1A are amino acid or nucleotide mutations. + +<|ref|>text<|/ref|><|det|>[[115, 807, 877, 840]]<|/det|> +Response: As shown in figure 1A, we have used the standard nomenclature in the legend for antibody chains. We now designate SHM as nucleotide mutations, detailed in lines 1118- 1119. + +<|ref|>text<|/ref|><|det|>[[112, 855, 872, 888]]<|/det|> +4. In the legend for Figure 3B, the lowest IC50 measured is listed as \(0.07 \mu \mathrm{g} / \mathrm{mL}\). This does not match the text, which lists the lowest IC50 measured as \(0.01 \mu \mathrm{g} / \mathrm{mL}\). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 88, 872, 138]]<|/det|> +Response: In Figure 3A, one isolate's IC50 is measured as \(0.01 \mu g / mL\) . However, 3B shows 3 additional isolates with detailed IC50 curves, and the lowest is \(0.07 \mu g / mL\) . The text (lines 1160- 1163) has been corrected to reflect the lowest IC50 in 3B as \(0.07 \mu g / mL\) . + +<|ref|>text<|/ref|><|det|>[[115, 152, 870, 202]]<|/det|> +5. In Figure 4B, it would be helpful and improve ease of understanding to shade the buried surface area on the structure model. Similarly, changing the legend labels from the PDB IDs to the protein names used elsewhere in the text would improve clarity for the reader. + +<|ref|>text<|/ref|><|det|>[[115, 216, 880, 314]]<|/det|> +Response: We appreciate the suggestion of the reviewer but found that shading the epitope made panel B busier and more confusing. We also tried to highlight the epitope with an outline instead (please, see comparisons below) but still think that the original panel B shows best what we want to show. We changed the legends in the Figure and included the protein names as suggested by the reviewer. In addition we included a new Supplementary Figure 10 where the epitope and paratopes are shaded on the protein surfaces. + +<|ref|>image<|/ref|><|det|>[[115, 325, 883, 720]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 749, 872, 783]]<|/det|> +6. Generally speaking, keeping the numerical orientation of the x-axis constant between figures would improve clarity. + +<|ref|>text<|/ref|><|det|>[[115, 797, 880, 863]]<|/det|> +Response: All x- axes on the graphs are oriented similarly, with the largest concentration starting on the left side and decreasing in concentration as it moves to the right. Some graphs start at 1000 \(\mu g / mL\) of humAb, whereas others start at 100 \(\mu g / mL\) , reflecting different experimental conditions with different assays. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 217, 105]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[115, 121, 808, 154]]<|/det|> +Overall Response: Thank you for your overall positive response to the manuscript and constructive comments. + +<|ref|>text<|/ref|><|det|>[[115, 170, 306, 186]]<|/det|> +Some minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 186, 832, 219]]<|/det|> +- Fig 2A seems unnecessary. It is in a highly contrived model, and IC50 values were more potent in the biologically relevant reticulocyte invasion assay anyway. + +<|ref|>text<|/ref|><|det|>[[115, 233, 880, 330]]<|/det|> +Response: We prefer to retain Figure 2A as valuable data and complements data generated using P. vivax isolates; the other reviewers have not requested removal of that figure. The advantage of the Pf- PvAMA1 transgenic parasite model is that it expresses the Palo Alto variant of PvAMA1, which is the same PvAMA1 allele that was used to isolate the humAbs. Therefore, we could evaluate the activity of the humAbs without the potential confounding effect of polymorphisms in PvAMA1 that occur in clinical isolates. + +<|ref|>text<|/ref|><|det|>[[115, 344, 875, 362]]<|/det|> +- There is some mixing of equivalent units, ng/ul and ug/ml. I'd pick one and unify for readability. + +<|ref|>text<|/ref|><|det|>[[115, 376, 870, 425]]<|/det|> +Response: ng/ml is used only in Figure 1 because reactivity to recombinant protein is much more sensitive compared to the amount of antibody required for invasion assays. We changed this to \(\mu \mathrm{g / mL}\) in Figure 1 legend. + +<|ref|>text<|/ref|><|det|>[[115, 440, 558, 457]]<|/det|> +- Some grammatical errors need to be fixed throughout. + +<|ref|>text<|/ref|><|det|>[[115, 472, 570, 489]]<|/det|> +Response: Thank you. We edited the text more carefully. + +<|ref|>text<|/ref|><|det|>[[115, 503, 861, 552]]<|/det|> +- A little more experimental detail on binding would be useful in the results. The assay used in binding studies does not appear to be noted in the text (results section 1, paragraph 2). + +<|ref|>text<|/ref|><|det|>[[115, 567, 851, 601]]<|/det|> +- Similar to previous, a touch more info on the assays in the body of the text would go a long way for broad readership. + +<|ref|>text<|/ref|><|det|>[[115, 615, 748, 632]]<|/det|> +Response: We have further described key assay methods in the result sections + +<|ref|>text<|/ref|><|det|>[[115, 647, 868, 696]]<|/det|> +- Other than antigen binding, is the epitope specificity known for any other clones? It would be interesting to understand the antibody within the context of the rest of the anti-AMA1 response. E.g., is it a rare target or immunodominant, etc. + +<|ref|>text<|/ref|><|det|>[[115, 711, 868, 824]]<|/det|> +Response: This is an interesting point. A future goal will be to co- crystallize other human monoclonal antibodies. We will use the RON2—PvAMA1 binding assay to identify Pv- exposed individuals with blocking activity, like the individual from whom we isolated the most inhibitory monoclonal antibody in the present study. We will then use our different monoclonals to see if they compete with the inhibitory activity in sera. This will determine whether this response is rare or immunodominant. These experiments will be part of a future project, which we plan to publish as a separate manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 856, 222, 872]]<|/det|> +Reviewer # 3 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 254, 105]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 106, 860, 202]]<|/det|> +Major comments:In the intro the authors mention that "we have identified a potent, strain- transcending humAb that blocks RON2- loop binding and can inhibit both blood stage and sporozoite infection." I believe this manuscript would benefit from an in vivo experiment for liver burden, either using the human liver chimeric mouse model or with a chimeric P. berghei expressing PvCSP since they mention the humAb also inhibit sporozoite infection. Have the authors tested 826827 binding to PbAMA1? + +<|ref|>text<|/ref|><|det|>[[115, 217, 880, 346]]<|/det|> +Response: We have shown humAb 826827 inhibits sporozoite invasion in the human liver chimeric mouse model, which is now included in the manuscript. However, based on structural and sequence analysis, we suspect that 826827 would not show as potent inhibition of P. berghei parasites. There is \(45\%\) identity for amino acids in the PvAMA1 epitope recognized by 826827 between Pb and Pv. The amino acid identity for Pv and PfAMA1 (31.5%), and 826827 does not bind to PfAMA1. Thus, 826827 is unlikely to recognize PbAMA1, although we have not tested it. Results for in vivo data are shown Figure 4 and Supplemental Figure 6. New sections describing these results are detailed in lines 210- 227. + +<|ref|>text<|/ref|><|det|>[[115, 376, 868, 457]]<|/det|> +The authors specifically looked for "PvRON2- binding- inhibition" huMabs but it is possible that there are huMabs that will prevent AMA- 1 action by not blocking RON2. Have the authors looked at this at all? I think it should be added to the discussion. This recent paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10475129/) showed that antibodies that do not inhibit AMA1- RON2 interaction are highly protective. + +<|ref|>text<|/ref|><|det|>[[115, 472, 865, 586]]<|/det|> +Responses: This is an interesting point, and we have considered it. Most of the humAbs generated from this donor appear to have some blocking activity in PvAMA1- RON2 assay. No humAbs antibodies that do not block or weakly block PvAMA1- RON2 demonstrate potent invasion inhibition in vitro using clinical isolates. We may have biased selection of PvAMA1- RON2 blocking Abs because this individual had potent blocking activity in serum. To address this question, we are isolating humAbs to PvAMA1 from other individuals, some without detectable PvAMA1- RON2 blocking activity. We address this point briefly in the discussion. + +<|ref|>text<|/ref|><|det|>[[115, 633, 255, 648]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 649, 863, 697]]<|/det|> +In the introduction, the term humAbs is used multiple times before it is defined in the last paragraph and on one occasion "human humAbs" is used. However, it is clearly defined in the abstract. Maybe revise the intro. + +<|ref|>text<|/ref|><|det|>[[116, 712, 293, 728]]<|/det|> +Response: Corrected + +<|ref|>text<|/ref|><|det|>[[115, 744, 878, 825]]<|/det|> +It is not clear from the beginning what the naming convention of the humAbs is. I was initially confused when the heavy chain was referred to as 826. This should be clarified. It seems indeed that 826827 comes from 826HC and 827LC but this is not mentioned in the results. Usually one refers to the Mab 826827 HC and LC otherwise it seems they come from a different antibody. + +<|ref|>text<|/ref|><|det|>[[115, 840, 872, 872]]<|/det|> +Response: This humAb numbering is now described at the binding of the results section (lines 151- 152). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 105, 875, 150]]<|/det|> +The buried surface area of 826827 is stated twice (page 8 and page 10 in the PDF) in the text and with different significant figures. In general, buried surface area are approximate - at place the authors mention 1392.5 A2 and other 1392 A2. Maybe just change to "\\~1392 A2." + +<|ref|>text<|/ref|><|det|>[[115, 151, 875, 233]]<|/det|> +Rewrite this sentence: "The combined buried surface area is 1392.5 A2 large, while the major contribution of \(70\%\) is provided by the heavy chain \(826\) ." To something like "The major contribution of humAb 826827 is through its heavy chain ( \(\sim 70\%\) of the \(\sim 1392\) A2 buried surface area)." Also that sentence can be moved when describing the interactions first. It seems a bit out of place to have a repeat of this information in another paragraph. + +<|ref|>text<|/ref|><|det|>[[115, 233, 860, 312]]<|/det|> +Suggestion: "Figure 5A shows that the contact residues between PvAMA1 and RON2- loop overlap with the residues of PvAMA1 that contact humAb 826827 CDR- H3 residues, which contributes to \(\sim X\%\) of the total buried surface area of 826827 interaction with PvAMA1". (it is actually unclear what is the CDRH3 only contribution to the interaction the way it is currently written). + +<|ref|>text<|/ref|><|det|>[[115, 313, 863, 360]]<|/det|> +Same here " Comparing the RON2 and 826 CDR3 binding site to other available Plasmodium species and model systems reveals that P..." Since CDRL3 is not involved at all in the interaction specify CDRH3. + +<|ref|>text<|/ref|><|det|>[[115, 361, 854, 394]]<|/det|> +Rewrite sentence: "They are also exhibit similar potency compared to a PfAMA1 humAb that was previously produced based on an IgG" + +<|ref|>text<|/ref|><|det|>[[116, 408, 870, 456]]<|/det|> +Response: We agree with the reviewer and now only mention the buried surface area once as an approximate and have moved the information of the CDR- H3 contribution to the section when first describing the interaction. + +<|ref|>text<|/ref|><|det|>[[115, 472, 878, 585]]<|/det|> +In line 236- 238, we changed the sentence "Five of the six complementarity- determining regions (CDR, namely: L1, L2, H1, H2, and H3) form direct contacts with PvAMA1 with a buried interaction surface of 1392 A2, with the light chain contributing 432 A2 and the heavy chain contributing 959 A2" to "Five of the six complementarity- determining regions (CDR, namely: L1, L2, H1, H2, and H3) form direct contacts with PvAMA1 with a buried interaction surface of \(\sim 1392\) A2, with the CDR- H3 loop of 826827 contributing \(70\%\) of the buried surface area (Figure 5B). + +<|ref|>text<|/ref|><|det|>[[115, 600, 876, 681]]<|/det|> +As suggested by the reviewer we changed the sentence in line 281- 285 to specify CDR- H3. It reads now: "Comparing the RON2 and CDR- H3 binding site of 826827 to other available Plasmodium species and model systems reveals that P. cynomolgi AMA1 is \(100\%\) conserved and would therefore serve as a predictive non- human primate model for Pv challenge infections to evaluate humAb 826827 (Figure 6A, Supplemental Figure 8). + +<|ref|>text<|/ref|><|det|>[[115, 696, 880, 760]]<|/det|> +Line 341- 343: We rewrote the sentence "They are also exhibit similar potency compared to a PfAMA1 humAb that was previously produced based on an IgG...", to "They exhibit similar potency to a PfAMA1 humAb produced from an IgG sequence isolated from a Ghanaian with an \(IC_{50}\) of 35 \(\mu g / mL\) against the Pf 3D7 variant in vitro." + +<|ref|>text<|/ref|><|det|>[[115, 775, 641, 792]]<|/det|> +Figure 1 - is the number of SHM amino acid or nucleotide based? + +<|ref|>text<|/ref|><|det|>[[115, 807, 580, 825]]<|/det|> +Response: Addressed in figure legend (lines 1118- 1119). + +<|ref|>text<|/ref|><|det|>[[115, 839, 815, 857]]<|/det|> +Figure 2A, 2C, and 3B, error bars should be added to show distribution of the replicates. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 856, 138]]<|/det|> +Response: Corrected, however the graph in Figure 2C is displaying the dose curve for each replicate that was performed. Therefore, this graph represents the distribution of replicates without the need for error bars. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 316, 108]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 416, 145]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 164, 859, 219]]<|/det|> +The revised manuscript is much improved, and the results are interesting. Importantly, I think that the comparison of the different assays helps to start defining an appropriate pipeline for testing monoclonal antibodies for Pv. + +<|ref|>text<|/ref|><|det|>[[115, 238, 880, 312]]<|/det|> +Fig 3A and 3B – Why are the data shown differently in these panels? They are generally the same assay, albeit with different hepatocytes. However, IC50 should be able to be calculated for either or inhibition to show consistency. It would also help compare the assays head- to- head for determining appropriate pipelines for monoclonal antibodies in the future. + +<|ref|>sub_title<|/ref|><|det|>[[116, 332, 270, 348]]<|/det|> +## Authors Response: + +<|ref|>text<|/ref|><|det|>[[116, 350, 577, 367]]<|/det|> +We have removed Figure 3B as suggested by the reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 386, 872, 440]]<|/det|> +Fig 3 – The liver stages still leaves a few behind based on supplementary data in Figure s6. Can you comment directly in discussion how this may impact the utility or if alternative approaches could be used? + +<|ref|>sub_title<|/ref|><|det|>[[116, 461, 270, 477]]<|/det|> +## Authors Response: + +<|ref|>text<|/ref|><|det|>[[116, 479, 879, 533]]<|/det|> +We have added a few lines of clarifications and explanation in the text to help explain why there is signal in the qPCR results for the in vivo experiments as well as added one more reference demonstrating the same finding with Pf in this model system. + +<|ref|>text<|/ref|><|det|>[[115, 552, 523, 569]]<|/det|> +Line 194 – says ‘reticulates’ instead of reticulocytes + +<|ref|>sub_title<|/ref|><|det|>[[116, 590, 270, 606]]<|/det|> +## Authors Response: + +<|ref|>text<|/ref|><|det|>[[116, 608, 772, 626]]<|/det|> +This spelling error has been fixed and we thank the reviewer for catching our error. + +<|ref|>text<|/ref|><|det|>[[116, 682, 416, 699]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 718, 875, 848]]<|/det|> +This reviewer had few major criticisms, all of which have been responded to, if not fully addressed. Other reviewer comments have been addressed, and the authors added a major new experiment in FRG mice to assess blocking activity in vivo against field isolates. This experiment shows blocking activity of the mAb in vivo against the sporozoite, and represents a major investment for this study, since infected mosquitos are shipped from Thailand and each mouse is nearly the cost of a non- human primate. The data support the overall conclusions and have strengthened the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 867, 270, 883]]<|/det|> +## Authors Response: + +<|ref|>text<|/ref|><|det|>[[116, 886, 611, 903]]<|/det|> +We thank the reviewer for helping us improve the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 417, 125]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 145, 550, 163]]<|/det|> +The authors have addressed the reviewers' comments. + +<|ref|>sub_title<|/ref|><|det|>[[115, 183, 270, 199]]<|/det|> +## Authors Response: + +<|ref|>text<|/ref|><|det|>[[115, 201, 611, 219]]<|/det|> +We thank the reviewer for helping us improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 256, 417, 274]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 293, 874, 349]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>sub_title<|/ref|><|det|>[[115, 368, 270, 384]]<|/det|> +## Authors Response: + +<|ref|>text<|/ref|><|det|>[[115, 386, 611, 404]]<|/det|> +We thank the reviewer for helping us improve the manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/images_list.json b/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..fa16f06614c9d87e62566472fd17cf5012b25bda --- /dev/null +++ b/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,123 @@ + +# nature portfolio + +Peer Review File + +# Machine Learning the Metastable Phase Diagram of Covalently Bonded Carbon + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +I appreciate that the authors have carefully answered all my concerns in their revision and reply letter. After the revision, I believe the authors have greatly improved the presentation regarding the computational methodologies and impacts on carbon research. That said, I would like to reserve my opinion on the use of DL approach. According to the results as shown in their reply letter, it seems that DL does not significantly improve the accuracy with respect the relative simple GPR model. If the authors is concerned about the large volume of data, a shallow NN with properly engineered descriptor (not deep NN) may behave equally better. In fact, I am also a bit worried that the improvement from DL is due to overfitting. At this stage, I won't suggest the authors to try any other new approach since they have already spent enormous time on it. However, the author would be better neutral about the use of DL. Don't leave the readers an impression that DL is a must- go approach and mention that there may exist alternative approaches with simpler framework. + +From computational point of view, my judgement is that the paper is well written and can be considered for a publication in Nature Comm. + +Reviewer #5 (Remarks to the Author): + +The paper introduces the idea of a metastable "phase diagram" and charts out the possible "phases" which might exist there. They are characterised by differences in free energy from the stable state at a given P,T condition. This is a very valuable and worthwhile thing to try to do. + +Temperature dependence is determined by the harmonic phonon method, which appears to preclude a very wide range of high- T phases - anything which is dynamically stabilised, anything involving molecular rotations, melting, and (probably) amorphous materials etc. They apply the + +<--- Page Split ---> + +method to carbon, excluding the fullerene phases ostensibly by cutoff in deltaG They hypothesize, that this "should be large enough to include the thermodynamically relevant metastable structures". This is a bizarre claim given the known existence of fullerene crystals. They also exclude fullerenes also by not searching for large enough unit cells, because they test DFT only up to 20 atoms per cell. + +I appreciate that large scale structure searches are expensive, and fullerenes may be troublesome for their method - but why then choose carbon in the first place if you know you won't scan the whole range of possibilities? + +They cite as a reason for choosing carbon that "Importantly, these allotropes have wide- ranging properties, from metals [4- 7], semiconductors [8], topological insulators [9- 11], to wide band gap insulators [12]". It's an excellent reason. Unfortunately, after this sentence in the introduction no further mention of metals, semiconductors or topological insulators is made. + +The fact that the method is so limited in scope is not necessarily a block on publication, but it does mean the title "Machine Learning the Metastable Phase Diagram of Materials" misleadingly over claims what they have done. "Machine Learning the Metastable Phase Diagram of Covalently bonded Carbon" would be more accurate and honest. + +I don't see amorphous carbon on the phase diagram. There is a sentence + +"For disordered and amorphous systems exhibiting non- negligible degree of anharmonicity, their free energy contribution should be included using an appropriate method [33]". But there's no further mention of ref [33] (a review) or an "appropriate method". So while I agree that it should be done, I strongly suspect that they haven't done it. + +They explain, correctly, that G depends on both T and P. But when they actually apply the workflow: "for computational cost efficiency, we only include the effect of finite pressure in the selection". And no discussion of how this could be included in the paper. + +Overall, there is plenty of interesting work here relevant to the low temperature- high pressure phases of carbon. The method may be applicable more generally, but since they chose carbon, and then molten, amorphous, fullerene and metallic carbon at extreme pressures are all omitted, this is not convincingly demonstrated. I think it could be published in Nature Communications if the excessive claims of generality of the method were removed. + +<--- Page Split ---> + +# Responses to Referees' Report for Machine Learning the Metastable Phase Diagram of Materials + +April 15, 2022 + +## Reviewer #1: + +I appreciate that the authors have carefully answered all my concerns in their revision and reply letter. After the revision, I believe the authors have greatly improved the presentation regarding the computational methodologies and impacts on carbon research. That said, I would like to reserve my opinion on the use of DL approach. According to the results as shown in their reply letter, it seems that DL does not significantly improve the accuracy with respect the relative simple GPR model. If the authors is concerned about the large volume of data, a shallow NN with properly engineered descriptor (not deep NN) may behave equally better. In fact, I am also a bit worried that the improvement from DL is due to overfitting. At this stage, I won't suggest the authors to try any other new approach since they have already spent enormous time on it. However, the author would be better neutral about the use of DL. Don't leave the readers an impression that DL is a must- go approach and mention that there may exist alternative approaches with simpler framework. From computational point of view, my judgement is that the paper is well written and can be considered for a publication in Nature Comm. + +Author reply: We agree with reviewers' opinion that more rigorous comparison between different ML strategies and input structure fingerprint is required to confidently find the best ML approach for this learning problem. Accordingly we have modified the main manuscript. Moreover, we believe that the presented NN models do not have an overfitting issue because of the following two reasons: 1) we adopted several established techniques to avoid over- fitting such as dropout, validation set, etc. 2) the good predictions achieved on the SACADA dataset (which was not part of the NN model training exercise) is indicative of the high quality of the models trained. This would not be the case if the NN models were overfit. + +Changes: We have added the following sentences in the revised manuscript: + +- In Discussion, line 346, "Inspired by the success of deep neural networks in achieving good performance on DFT datasets related to atomic energies and forces, we use a similar ML strategy in this work."- In Discussion, line 362, "While the performance of DNN seems satisfactory, more rigorous work should be done in the future to find more suitable ML methods and the input structure fingerprints that improves the model performance further." + +## Reviewer #5: + +The paper introduces the idea of a metastable "phase diagram" and charts out the possible "phases" which might exist there. They are characterised by differences in free energy from the stable state at a given P,T condition. This is a very valuable and worthwhile thing to try to do. Temperature dependence is determined by the harmonic phonon method, which appears to preclude a very wide range of high- T phases - anything which is dynamically stabilised, anything involving molecular rotations, melting, and (probably) amorphous materials etc. They apply the method to carbon, excluding the fullerene phases ostensibly by cutoff in deltaG. They hypothesize, that this "should be large enough to include the thermodynamically relevant metastable structures". This is a bizarre claim given the known existence of fullerene crystals. They also exclude fullerenes also by not searching for large enough unit cells, because they test DFT only up to 20 atoms per cell. + +<--- Page Split ---> + +Author reply: In this work, we have mainly considered bulk carbon phases and excluded nanoscale metastable structures such as fullerenes ( \(\mathrm{C}_{60}\) ) or their ordered 3D configurations. These were mainly due to the computational cost associated with much larger simulation cells needed to model such metastable structures within the density functional theory (DFT) framework. Also, considering the computational expense of free energy calculations using first principles DFT, it was necessary to choose an enthalpy cutoff to keep the number of calculations tractable. Moreover, the computational complexity of the DFT calculation also increases with the size of the unit cell making the calculations further difficult to perform in a high throughput settings. While the phase with large unit cells (e.g. 3D fullerene configurations) are not considered in our calculations, we believe the main contribution of this work is conceptualize a "metastable phase diagram" as a tool to accelerate discovery of novel materials with desired properties + +Changes: We have added the following sentence to clarify this + +In Results, line 120, "In this work, we focus on the bulk phases of carbon and exclude nanoscale clusters, such as fullerene C60, their ordered 3D configurations, amorphous or molten carbon phases, and metallic carbon at extreme pressures due to the prohibitively high computational cost required to estimate their free energies." + +I appreciate that large scale structure searches are expensive, and fullerenes may be troublesome for their method - but why then choose carbon in the first place if you know you won't scan the whole range of possibilities? + +They cite as a reason for choosing carbon that "Importantly, these allotropes have wide- ranging properties, from metals [4- 7], semiconductors [8], topological insulators [9- 11], to wide band gap insulators [12]". It's an excellent reason. Unfortunately, after this sentence in the introduction no further mention of metals, semiconductors or topological insulators is made. + +Author reply: Carbon has a multitude of metastable structures with interesting properties and hence was chosen for this study. For reasons stated in the previous comment, we excluded 3D fullerene arrangements but consider \(\sim 1000\) other metastable configurations. In principle, one can never be certain if we have scanned all possible metastable structures and they will continue to be discovered both experimentally and theoretically. Our framework, however, allows for inclusion of such metastable configurations. In future, as computations become more efficient, we should be able to include fullerenes as well and identify their phase space (T,P) in the metastable phase diagram of carbon. We have added a few sentences in the manuscript to address this. Regarding the second statement in this comment, we have added more sentences in the revised manuscript to clarify that the metastable configurations of carbon have interesting electronic properties that range from metallic to semiconducting to insulating - which can be exploited if we can understand the thermodynamic landscape of such phases and the barriers to transform from one metastable phase (eg. metallic) to another (e.g. insulating). + +Changes: We have added the following sentences + +In Results, line 271, "We note that while our framework does not guarantee an exhaustive search of all possible metastable structures, it allows for the inclusion of a new metastable phases when encountered experimentally or theoretically." In Discussion, line 308, "It is worth pointing out that metastable configurations of carbon have interesting electronic properties that range from metallic to semiconducting to insulating - which can be exploited if we can understand the thermodynamic landscape of such phases and the barriers to transform from one metastable phase (eg. metallic) to another (e.g. insulating). For example, graphite is electrically conducting whereas Z- carbon is insulating [1]. Similarly, diamond is insulating while bct- C carbon is predicted to be metallic [2, 3]." + +The fact that the method is so limited in scope is not necessarily a block on publication, but it does mean the title "Machine Learning the Metastable Phase Diagram of Materials" misleadingly over claims what they have done. "Machine Learning the Metastable Phase Diagram of Covalently bonded Carbon" would be more accurate and honest. + +Author reply: We thank the reviewer for their suggestion. We have now changed the title of the manuscript + +Changes: The title has been changed to "Machine Learning the Metastable Phase Diagram of Covalently bonded Carbon" + +<--- Page Split ---> + +I don't see amorphous carbon on the phase diagram. There is a sentence "For disordered and amorphous systems exhibiting non- negligible degree of anharmonicity, their free energy contribution should be included using an appropriate method [33]". But there's no further mention of ref [33] (a review) or an "appropriate method". So while I agree that it should be done, I strongly suspect that they haven't done it. + +Author reply: Since the free energies were computed from a periodic model, to reliably calculate free energies for amorphous phase, we require (i) a large unit cell to ensure there are no short range order and (b) sampling over several different configurations. Both of these factors make the free energy calculation of amorphous system using DFT prohibitively expensive. So we have not performed those calculations here and would be considered in future work to account for crystalline (metastable) to amorphous transformations + +They explain, correctly, that G depends on both T and P. But when they actually apply the workflow: "for computational cost efficiency, we only include the effect of finite pressure in the selection". And no discussion of how this could be included in the paper. + +Author reply: The above statement is true for the selection of candidate phases from evolutionary structure search since we are minimizing enthalpy. We would like to clarify that both the temperature effects and the entropic contributions are accounted for in the harmonic model for Gibbs free energy. Also, pressure effects are considered in the free energy calculations since we explicitly consider the pressure induced volume and configurational change in our free energy calculations. We have clarified this in the revised manuscript. + +Changes: We have added the following sentence in the revised manuscript + +- In Results, line 136, "The Gibbs free energy of each candidate screened from the previous step is computed across the temperature and pressure range of interest, and by including the temperature and entropic contributions of free energy to the enthalpy" + +Overall, there is plenty of interesting work here relevant to the low temperature- high pressure phases of carbon. The method may be applicable more generally, but since they chose carbon, and then molten, amorphous, fullerene and metallic carbon at extreme pressures are all omitted, this is not convincingly demonstrated. I think it could be published in Nature Communications if the excessive claims of generality of the method were removed + +Author reply: We thank the reviewer for their nice words about our work and for recommending publication in Nature Communications. We agree with the reviewer and have changed the title as per the reviewer suggestion and also explicitly stated in the revised manuscript that molten, amorphous, fullerene and metallic carbon at extreme pressures are not considered in our current metastable phase diagram workflow. + +Changes: As pointed out by the reviewer, due to the computational challenges that remains to be addressed, we removed the following statement from the abstract and conclusion respectively + +- The workflow presented here is general and broadly applicable to single and multi-component systems.- Our data-driven approach is fairly general and applicable to other chemical systems systems with negligible configurational entropy and weak anharmonicity + +## References + +[1] C. He, L. Sun, C. Zhang, X. Peng, K. Zhang, and J. Zhong, "New superhard carbon phases between graphite and diamond," Solid State Communications, vol. 152, no. 16, pp. 1560- 1563, 2012. [Online]. Available: https://www.sciencedirect.com/science/article/pii/S0038109812003432 + +[2] C. He, L. Sun, C. Zhang, and J. Zhong, "Two viable three- dimensional carbon semiconductors with an entirely sp2 configuration," Phys. Chem. Chem. Phys., vol. 15, pp. 680- 684, 2013. [Online]. Available: http://dx.doi.org/10.1039/C2CP43221H + +[3] Z. Zhao, B. Xu, X.- F. Zhou, L.- M. Wang, B. Wen, J. He, Z. Liu, H.- T. Wang, and Y. Tian, "Novel superhard carbon: C- centered orthorhombic \(\mathrm{c_{8}}\) ," Phys. Rev. Lett., vol. 107, p. 215502, Nov 2011. [Online]. Available: https://link.aps.org/doi/10.1103/PhysRevLett.107.215502 + +<--- Page Split ---> diff --git a/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0036d3f7ed34121eae1a2a8574e23aeddbe109ec --- /dev/null +++ b/peer_reviews/554bad3e1df6c0cbb4d69083f40241980dfeb04a06aab68b363d5b6d0b6c3ca1/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,170 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 111, 362, 140]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[80, 157, 936, 225]]<|/det|> +# Machine Learning the Metastable Phase Diagram of Covalently Bonded Carbon + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 867, 138]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[118, 211, 308, 226]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 272, 404, 287]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 332, 877, 532]]<|/det|> +I appreciate that the authors have carefully answered all my concerns in their revision and reply letter. After the revision, I believe the authors have greatly improved the presentation regarding the computational methodologies and impacts on carbon research. That said, I would like to reserve my opinion on the use of DL approach. According to the results as shown in their reply letter, it seems that DL does not significantly improve the accuracy with respect the relative simple GPR model. If the authors is concerned about the large volume of data, a shallow NN with properly engineered descriptor (not deep NN) may behave equally better. In fact, I am also a bit worried that the improvement from DL is due to overfitting. At this stage, I won't suggest the authors to try any other new approach since they have already spent enormous time on it. However, the author would be better neutral about the use of DL. Don't leave the readers an impression that DL is a must- go approach and mention that there may exist alternative approaches with simpler framework. + +<|ref|>text<|/ref|><|det|>[[118, 576, 819, 610]]<|/det|> +From computational point of view, my judgement is that the paper is well written and can be considered for a publication in Nature Comm. + +<|ref|>text<|/ref|><|det|>[[118, 686, 404, 701]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 745, 877, 799]]<|/det|> +The paper introduces the idea of a metastable "phase diagram" and charts out the possible "phases" which might exist there. They are characterised by differences in free energy from the stable state at a given P,T condition. This is a very valuable and worthwhile thing to try to do. + +<|ref|>text<|/ref|><|det|>[[118, 842, 839, 896]]<|/det|> +Temperature dependence is determined by the harmonic phonon method, which appears to preclude a very wide range of high- T phases - anything which is dynamically stabilised, anything involving molecular rotations, melting, and (probably) amorphous materials etc. They apply the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 875, 157]]<|/det|> +method to carbon, excluding the fullerene phases ostensibly by cutoff in deltaG They hypothesize, that this "should be large enough to include the thermodynamically relevant metastable structures". This is a bizarre claim given the known existence of fullerene crystals. They also exclude fullerenes also by not searching for large enough unit cells, because they test DFT only up to 20 atoms per cell. + +<|ref|>text<|/ref|><|det|>[[118, 199, 857, 252]]<|/det|> +I appreciate that large scale structure searches are expensive, and fullerenes may be troublesome for their method - but why then choose carbon in the first place if you know you won't scan the whole range of possibilities? + +<|ref|>text<|/ref|><|det|>[[118, 296, 858, 368]]<|/det|> +They cite as a reason for choosing carbon that "Importantly, these allotropes have wide- ranging properties, from metals [4- 7], semiconductors [8], topological insulators [9- 11], to wide band gap insulators [12]". It's an excellent reason. Unfortunately, after this sentence in the introduction no further mention of metals, semiconductors or topological insulators is made. + +<|ref|>text<|/ref|><|det|>[[118, 382, 861, 453]]<|/det|> +The fact that the method is so limited in scope is not necessarily a block on publication, but it does mean the title "Machine Learning the Metastable Phase Diagram of Materials" misleadingly over claims what they have done. "Machine Learning the Metastable Phase Diagram of Covalently bonded Carbon" would be more accurate and honest. + +<|ref|>text<|/ref|><|det|>[[118, 497, 666, 514]]<|/det|> +I don't see amorphous carbon on the phase diagram. There is a sentence + +<|ref|>text<|/ref|><|det|>[[118, 527, 870, 599]]<|/det|> +"For disordered and amorphous systems exhibiting non- negligible degree of anharmonicity, their free energy contribution should be included using an appropriate method [33]". But there's no further mention of ref [33] (a review) or an "appropriate method". So while I agree that it should be done, I strongly suspect that they haven't done it. + +<|ref|>text<|/ref|><|det|>[[118, 642, 875, 696]]<|/det|> +They explain, correctly, that G depends on both T and P. But when they actually apply the workflow: "for computational cost efficiency, we only include the effect of finite pressure in the selection". And no discussion of how this could be included in the paper. + +<|ref|>text<|/ref|><|det|>[[118, 739, 870, 829]]<|/det|> +Overall, there is plenty of interesting work here relevant to the low temperature- high pressure phases of carbon. The method may be applicable more generally, but since they chose carbon, and then molten, amorphous, fullerene and metallic carbon at extreme pressures are all omitted, this is not convincingly demonstrated. I think it could be published in Nature Communications if the excessive claims of generality of the method were removed. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[135, 108, 863, 159]]<|/det|> +# Responses to Referees' Report for Machine Learning the Metastable Phase Diagram of Materials + +<|ref|>text<|/ref|><|det|>[[437, 200, 560, 216]]<|/det|> +April 15, 2022 + +<|ref|>sub_title<|/ref|><|det|>[[93, 248, 255, 268]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[92, 277, 905, 465]]<|/det|> +I appreciate that the authors have carefully answered all my concerns in their revision and reply letter. After the revision, I believe the authors have greatly improved the presentation regarding the computational methodologies and impacts on carbon research. That said, I would like to reserve my opinion on the use of DL approach. According to the results as shown in their reply letter, it seems that DL does not significantly improve the accuracy with respect the relative simple GPR model. If the authors is concerned about the large volume of data, a shallow NN with properly engineered descriptor (not deep NN) may behave equally better. In fact, I am also a bit worried that the improvement from DL is due to overfitting. At this stage, I won't suggest the authors to try any other new approach since they have already spent enormous time on it. However, the author would be better neutral about the use of DL. Don't leave the readers an impression that DL is a must- go approach and mention that there may exist alternative approaches with simpler framework. From computational point of view, my judgement is that the paper is well written and can be considered for a publication in Nature Comm. + +<|ref|>text<|/ref|><|det|>[[92, 477, 905, 578]]<|/det|> +Author reply: We agree with reviewers' opinion that more rigorous comparison between different ML strategies and input structure fingerprint is required to confidently find the best ML approach for this learning problem. Accordingly we have modified the main manuscript. Moreover, we believe that the presented NN models do not have an overfitting issue because of the following two reasons: 1) we adopted several established techniques to avoid over- fitting such as dropout, validation set, etc. 2) the good predictions achieved on the SACADA dataset (which was not part of the NN model training exercise) is indicative of the high quality of the models trained. This would not be the case if the NN models were overfit. + +<|ref|>text<|/ref|><|det|>[[119, 591, 684, 606]]<|/det|> +Changes: We have added the following sentences in the revised manuscript: + +<|ref|>text<|/ref|><|det|>[[113, 614, 905, 696]]<|/det|> +- In Discussion, line 346, "Inspired by the success of deep neural networks in achieving good performance on DFT datasets related to atomic energies and forces, we use a similar ML strategy in this work."- In Discussion, line 362, "While the performance of DNN seems satisfactory, more rigorous work should be done in the future to find more suitable ML methods and the input structure fingerprints that improves the model performance further." + +<|ref|>sub_title<|/ref|><|det|>[[93, 725, 255, 745]]<|/det|> +## Reviewer #5: + +<|ref|>text<|/ref|><|det|>[[92, 755, 905, 914]]<|/det|> +The paper introduces the idea of a metastable "phase diagram" and charts out the possible "phases" which might exist there. They are characterised by differences in free energy from the stable state at a given P,T condition. This is a very valuable and worthwhile thing to try to do. Temperature dependence is determined by the harmonic phonon method, which appears to preclude a very wide range of high- T phases - anything which is dynamically stabilised, anything involving molecular rotations, melting, and (probably) amorphous materials etc. They apply the method to carbon, excluding the fullerene phases ostensibly by cutoff in deltaG. They hypothesize, that this "should be large enough to include the thermodynamically relevant metastable structures". This is a bizarre claim given the known existence of fullerene crystals. They also exclude fullerenes also by not searching for large enough unit cells, because they test DFT only up to 20 atoms per cell. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 65, 905, 210]]<|/det|> +Author reply: In this work, we have mainly considered bulk carbon phases and excluded nanoscale metastable structures such as fullerenes ( \(\mathrm{C}_{60}\) ) or their ordered 3D configurations. These were mainly due to the computational cost associated with much larger simulation cells needed to model such metastable structures within the density functional theory (DFT) framework. Also, considering the computational expense of free energy calculations using first principles DFT, it was necessary to choose an enthalpy cutoff to keep the number of calculations tractable. Moreover, the computational complexity of the DFT calculation also increases with the size of the unit cell making the calculations further difficult to perform in a high throughput settings. While the phase with large unit cells (e.g. 3D fullerene configurations) are not considered in our calculations, we believe the main contribution of this work is conceptualize a "metastable phase diagram" as a tool to accelerate discovery of novel materials with desired properties + +<|ref|>text<|/ref|><|det|>[[120, 222, 587, 237]]<|/det|> +Changes: We have added the following sentence to clarify this + +<|ref|>text<|/ref|><|det|>[[119, 245, 905, 304]]<|/det|> +In Results, line 120, "In this work, we focus on the bulk phases of carbon and exclude nanoscale clusters, such as fullerene C60, their ordered 3D configurations, amorphous or molten carbon phases, and metallic carbon at extreme pressures due to the prohibitively high computational cost required to estimate their free energies." + +<|ref|>text<|/ref|><|det|>[[92, 313, 904, 355]]<|/det|> +I appreciate that large scale structure searches are expensive, and fullerenes may be troublesome for their method - but why then choose carbon in the first place if you know you won't scan the whole range of possibilities? + +<|ref|>text<|/ref|><|det|>[[92, 355, 904, 413]]<|/det|> +They cite as a reason for choosing carbon that "Importantly, these allotropes have wide- ranging properties, from metals [4- 7], semiconductors [8], topological insulators [9- 11], to wide band gap insulators [12]". It's an excellent reason. Unfortunately, after this sentence in the introduction no further mention of metals, semiconductors or topological insulators is made. + +<|ref|>text<|/ref|><|det|>[[92, 425, 905, 596]]<|/det|> +Author reply: Carbon has a multitude of metastable structures with interesting properties and hence was chosen for this study. For reasons stated in the previous comment, we excluded 3D fullerene arrangements but consider \(\sim 1000\) other metastable configurations. In principle, one can never be certain if we have scanned all possible metastable structures and they will continue to be discovered both experimentally and theoretically. Our framework, however, allows for inclusion of such metastable configurations. In future, as computations become more efficient, we should be able to include fullerenes as well and identify their phase space (T,P) in the metastable phase diagram of carbon. We have added a few sentences in the manuscript to address this. Regarding the second statement in this comment, we have added more sentences in the revised manuscript to clarify that the metastable configurations of carbon have interesting electronic properties that range from metallic to semiconducting to insulating - which can be exploited if we can understand the thermodynamic landscape of such phases and the barriers to transform from one metastable phase (eg. metallic) to another (e.g. insulating). + +<|ref|>text<|/ref|><|det|>[[120, 609, 489, 624]]<|/det|> +Changes: We have added the following sentences + +<|ref|>text<|/ref|><|det|>[[118, 633, 905, 771]]<|/det|> +In Results, line 271, "We note that while our framework does not guarantee an exhaustive search of all possible metastable structures, it allows for the inclusion of a new metastable phases when encountered experimentally or theoretically." In Discussion, line 308, "It is worth pointing out that metastable configurations of carbon have interesting electronic properties that range from metallic to semiconducting to insulating - which can be exploited if we can understand the thermodynamic landscape of such phases and the barriers to transform from one metastable phase (eg. metallic) to another (e.g. insulating). For example, graphite is electrically conducting whereas Z- carbon is insulating [1]. Similarly, diamond is insulating while bct- C carbon is predicted to be metallic [2, 3]." + +<|ref|>text<|/ref|><|det|>[[92, 780, 905, 838]]<|/det|> +The fact that the method is so limited in scope is not necessarily a block on publication, but it does mean the title "Machine Learning the Metastable Phase Diagram of Materials" misleadingly over claims what they have done. "Machine Learning the Metastable Phase Diagram of Covalently bonded Carbon" would be more accurate and honest. + +<|ref|>text<|/ref|><|det|>[[115, 851, 900, 866]]<|/det|> +Author reply: We thank the reviewer for their suggestion. We have now changed the title of the manuscript + +<|ref|>text<|/ref|><|det|>[[92, 880, 904, 909]]<|/det|> +Changes: The title has been changed to "Machine Learning the Metastable Phase Diagram of Covalently bonded Carbon" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 66, 904, 138]]<|/det|> +I don't see amorphous carbon on the phase diagram. There is a sentence "For disordered and amorphous systems exhibiting non- negligible degree of anharmonicity, their free energy contribution should be included using an appropriate method [33]". But there's no further mention of ref [33] (a review) or an "appropriate method". So while I agree that it should be done, I strongly suspect that they haven't done it. + +<|ref|>text<|/ref|><|det|>[[92, 151, 904, 223]]<|/det|> +Author reply: Since the free energies were computed from a periodic model, to reliably calculate free energies for amorphous phase, we require (i) a large unit cell to ensure there are no short range order and (b) sampling over several different configurations. Both of these factors make the free energy calculation of amorphous system using DFT prohibitively expensive. So we have not performed those calculations here and would be considered in future work to account for crystalline (metastable) to amorphous transformations + +<|ref|>text<|/ref|><|det|>[[92, 237, 904, 281]]<|/det|> +They explain, correctly, that G depends on both T and P. But when they actually apply the workflow: "for computational cost efficiency, we only include the effect of finite pressure in the selection". And no discussion of how this could be included in the paper. + +<|ref|>text<|/ref|><|det|>[[92, 294, 904, 366]]<|/det|> +Author reply: The above statement is true for the selection of candidate phases from evolutionary structure search since we are minimizing enthalpy. We would like to clarify that both the temperature effects and the entropic contributions are accounted for in the harmonic model for Gibbs free energy. Also, pressure effects are considered in the free energy calculations since we explicitly consider the pressure induced volume and configurational change in our free energy calculations. We have clarified this in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[119, 378, 673, 394]]<|/det|> +Changes: We have added the following sentence in the revised manuscript + +<|ref|>text<|/ref|><|det|>[[118, 402, 904, 447]]<|/det|> +- In Results, line 136, "The Gibbs free energy of each candidate screened from the previous step is computed across the temperature and pressure range of interest, and by including the temperature and entropic contributions of free energy to the enthalpy" + +<|ref|>text<|/ref|><|det|>[[92, 455, 904, 528]]<|/det|> +Overall, there is plenty of interesting work here relevant to the low temperature- high pressure phases of carbon. The method may be applicable more generally, but since they chose carbon, and then molten, amorphous, fullerene and metallic carbon at extreme pressures are all omitted, this is not convincingly demonstrated. I think it could be published in Nature Communications if the excessive claims of generality of the method were removed + +<|ref|>text<|/ref|><|det|>[[92, 540, 904, 598]]<|/det|> +Author reply: We thank the reviewer for their nice words about our work and for recommending publication in Nature Communications. We agree with the reviewer and have changed the title as per the reviewer suggestion and also explicitly stated in the revised manuscript that molten, amorphous, fullerene and metallic carbon at extreme pressures are not considered in our current metastable phase diagram workflow. + +<|ref|>text<|/ref|><|det|>[[92, 611, 904, 640]]<|/det|> +Changes: As pointed out by the reviewer, due to the computational challenges that remains to be addressed, we removed the following statement from the abstract and conclusion respectively + +<|ref|>text<|/ref|><|det|>[[115, 649, 904, 700]]<|/det|> +- The workflow presented here is general and broadly applicable to single and multi-component systems.- Our data-driven approach is fairly general and applicable to other chemical systems systems with negligible configurational entropy and weak anharmonicity + +<|ref|>sub_title<|/ref|><|det|>[[92, 732, 221, 750]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[92, 761, 904, 804]]<|/det|> +[1] C. He, L. Sun, C. Zhang, X. Peng, K. Zhang, and J. Zhong, "New superhard carbon phases between graphite and diamond," Solid State Communications, vol. 152, no. 16, pp. 1560- 1563, 2012. [Online]. Available: https://www.sciencedirect.com/science/article/pii/S0038109812003432 + +<|ref|>text<|/ref|><|det|>[[92, 814, 904, 857]]<|/det|> +[2] C. He, L. Sun, C. Zhang, and J. Zhong, "Two viable three- dimensional carbon semiconductors with an entirely sp2 configuration," Phys. Chem. Chem. Phys., vol. 15, pp. 680- 684, 2013. [Online]. Available: http://dx.doi.org/10.1039/C2CP43221H + +<|ref|>text<|/ref|><|det|>[[92, 865, 904, 908]]<|/det|> +[3] Z. Zhao, B. Xu, X.- F. Zhou, L.- M. Wang, B. Wen, J. He, Z. Liu, H.- T. Wang, and Y. Tian, "Novel superhard carbon: C- centered orthorhombic \(\mathrm{c_{8}}\) ," Phys. Rev. Lett., vol. 107, p. 215502, Nov 2011. [Online]. Available: https://link.aps.org/doi/10.1103/PhysRevLett.107.215502 + +<--- Page Split ---> diff --git a/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..60a773975a500006c94a925663e05cc7d201851e --- /dev/null +++ b/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,40 @@ +[ + { + "type": "image", + "img_path": "images/Figure_7.jpg", + "caption": "Fig. 7 | Workflow of PMM. a, Obtain CMM validated experimental metal sites. b, Predict metal binding sites.", + "footnote": [], + "bbox": [ + [ + 278, + 265, + 840, + 850 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_8.jpg", + "caption": "Supplementary Figure 8. Distribution of transition metal coordination motifs. CH0, CH1, CH2, CH3, and CH4 represent combinations of metal coordination sites where ligands contain 0, 1, 2, 3, 4 C and/or H ligands; \"Unclassified\" denotes other uncategorized ligand combinations.", + "footnote": [], + "bbox": [ + [ + 186, + 88, + 945, + 412 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_4.jpg", + "caption": "Supplementary Figure 4. Examples of redundant or incorrect metal binding site identifications in Metal3D. The figure shows examples where Metal3D misidentified or duplicated metal binding sites. Metal3D, a recently developed metal site prediction tool based on 3D convolutional neural networks, is currently the most accurate predictor of metal ion positions. The dataset reported in Metal3D includes 189 zinc binding sites from 59 structures, none of which overlap with the training set used by PMM. However, since Metal3D uses Biopython to retrieve metal sites, some redundancies and errors were identified among the 189 sites. After removing these redundant and erroneous sites, 178 valid zinc binding sites remained. a, In 2akf, multiple conformations (A1, B3, B4) were treated as separate sites. b, In 3q1d, two actual zinc sites (A20, A202) were counted as four. c, In 4a7k, three sites (A950, A951, A952) were recognized as six. d, e, Free metal ions, such as A402 in 4l99 and B4 in 3e7l, were incorrectly labeled as binding sites—each with only one ligand within 5 Å, which are not listed as metal binding in LINK, positioned too far from the zinc. f, In 2a0s, B381 was generated due to crystal symmetry. The magenta sticks represent ligand amino acids coordinating the metal ions. These errors were removed in the final dataset.", + "footnote": [], + "bbox": [], + "page_idx": 14 + } +] \ No newline at end of file diff --git a/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f3ec06a100cc30db256ff39bf4fe595d5fed9ff2 --- /dev/null +++ b/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,603 @@ + +# nature portfolio + +Peer Review File + +# PinMyMetal: A hybrid learning system to accurately model transition metal binding sites in macromolecules + +Corresponding Author: Dr Heping Zheng + +This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. The manuscript was considered suitable for publication without further review at Nature Communications. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The manuscript reports a new machine learning- based method for predicting Zinc metal binding sites. + +Comments: + +The beginning of the results section is confusing, particularly regarding the validation module. Generating a benchmark dataset does not seem to be part of the actual prediction process, i.e. it is not part of PMM. + +This continues in the second paragraph - the first sentence does not make sense. The first sentence of the next paragraph is also very difficult to follow. + +In fact the beginning of this results section does not read like a typical results section at all. This continue in section 2.2 with "Subsequently, the binding positions of zinc ions are deduced based on the ligand residues of the candidate zinc binding sites". + +Figure 1 - Bar chart has text that is not legible + +It seems odd to have named the methods PinMyMetal and then refer to it as PMM throughout. + +Section 2.4 does not read like a results section, more like an advert for the method. + +There are many different metal binding site predictors but there is limited comparison to only one other methods Metal3D. + +Methods - refers to checking quality of zinc binding site using CMM in a modified way. How was it modified? + +I may have missed it but the methods appear to be missing important information. There are no details on the machine learning methods and how they were trained and tested, the different parameters used. Further, was redundancy removed from the dataset i.e. proteins with high levels of sequence identity removed. + +Webserver - quick to run but does not provide users with predicted accuracy of each prediction, this really limits how the user can interpret the predictions made. + +(Remarks on code availability) + +Reviewer #2 + +<--- Page Split ---> + +(Remarks to the Author) + +In this article, the authors present a fast and accurate method (available as webserver and as standalone tool) to predict 2-, 3- and 4- fold coordinated zinc sites in proteins using a scoring function to place candidate binding sites and then ranking those binding sites using an ensemble ML model and/or hydrophobicity profiles. By design, the tool requires that the binding site is composed of at least two residues that are either cysteine or histidine (HC). This approach is of potential interest for a wide community but prior to publication, several issues should be clarified: + +Clearer definition of the scope: + +The algorithm and workflow that is presented is highly tailored to zinc sites but the title, abstract, introduction and other parts of the manuscript present the findings as a universal metal ion finder. Although the authors claim that an extension to other metal ions such as transition metals and alkali as well as alkali- earth ions is straightforward, this remains to be proven. In fact, the entire current algorithm is heavily tuned to the case of zinc, hardcoding the properties of existing zinc sites into the algorithm (taking HC residues as primary and ED as secondary target and using specific classifications and adapted workflows for 2-, 3- respectively 4- fold coordinated zinc sites). Other methods such as Metal3D make no such choices and learn all these properties from the structure alone. This contradicts the claim that the algorithm can be easily adapted to all other metals since it requires to develop the scoring criteria for each metal instead of just changing the dataset. In fact, it is not clear how the current approach can easily be extended to other metals with high coordination numbers and a wider and less specific spectrum of binding partners (including e.g. binding to amino acid back bones etc..). Therefore, the title should reflect the current specialization for zinc and the abstract and other parts of the text should be adapted accordingly. + +Clarifications about the workflow in the case of zinc: + +- Do the authors use the asymmetric unit or the biological assembly? Since zinc ions are often located at crystal interfaces, this is an important difference. + +- L.243: it is unclear how the auxiliary ED criterion works. ED is also not present in Figure 1. + +- Why was a cutoff of 0.5 used in the end? + +- L.553: Please describe the scoring function. + +- The algorithm only detects 2-, 3-, or 4-fold coordinated sites. What about 5- and 6- fold coordination that can be fairly abundant, especially for catalytically active sites, with varying percentages cited in the literature of up to 30% for 5-fold and roughly 10% for 6-fold. + +- Several of the coordination spheres may contain one or even several water molecules. How are these handled? +- The authors claim that they developed a hybrid algorithm based on geometric, physicochemical as well as ML selection but it seems that the primary selection of all zinc sites is based solely on amino acid type (HC&DE) plus geometric (and solvation) considerations. Only in the case of 2-fold 'regulatory' sites, do the authors also invoke an ensemble method with different ML models. Is there any ML part in the detection of the 3- and 4-fold coordinated sites? What is the additional impact of the ML model? + +Comparison with other methods: + +- The restriction to HD sites that pinMyMetal (PMM) is based on, can be restrictive, in fact some well-defined Zn sites cannot be located (e.g. in 4HTM). These limitations should be discussed. + +- While comparing accuracy differences in metal ion detection (in terms of predicted versus experimental position), the (in)accuracy of the experimental structures should be kept in mind. In fact, is the difference in accuracy between Metal3D 0.52±0.45A and PMM 0.257±?? (standard deviation should be given!), statistically significant considering the fact that typical x-ray structures with 1.5-3A resolution have typical average atomic coordinate errors of the order of 0.2-0.6A (according to the DPI database http://pranag.physics.iisc.ac.in/dpi_db/ using e.g. the Luzzati equation) and this does not even take low-resolution cryo-EM structures into account. Some illustrative examples of pdb structures that the authors discuss in the text: 1bc2 (resolution 1.9A): average positional error 0.25-0.29A, estimated accuracy for the zinc positions 0.17-0.23A or, an extreme case, 1thj (resolution 2.8A), experimental uncertainty for zinc positions 1.28-1.32A. + +- Explicit comparison with Metal3D: + +oFor a fair comparison, the same data should be tested. Why are there 205 zinc sites for PMM and 189 for Metal3D? The number for the transition metal test cases also do not match. + +oThe values for TP, FP and FN for Metal3D that the authors cite in Suppl. Table S5 (and that are used to calculated Precision and Recall values that are discussed in the main text) are not correct. In fact, the cited numbers 78, 47, 111 for TP, FP and FN refer to Metal1D results (also given in the Metal3D paper) while the results for Metal3D (with the recommended probability threshold of \(p = 0.75\) ) are 85, 9, 104. + +oHowever, Metal3D predicts two additional zinc locations in the same structure, where no electron density is observed, indicating a higher rate of false positive hits of Metal3D when compared with PMM': The additional sites predicted with Metal3D have much lower probability \((p = 0.5)\) than the C4 sites in the structure. The probability of 0.5 is below the recommended probability threshold of Metal3D of 0.75 so these predictions should not be categorized as false positives by the authors. + +oL. 519: 'While Metal3D uses 5A to determine the presence of occupancy redundancy, we disagree with their threshold since the dinuclear zinc binding site would be mislabeled in Metal3D (Fig. S7b)' + +It would be good to discuss this better. Metal3D does not mislabel such sites since the predicted density correctly contains both binding sites. However, the current placement algorithm might sometimes not be able to place two separate zincs into the predicted density. In fact for the given example 6jkw, Metal3D does correctly predict and place two zinc ions. + +oComparison of timings: deep learning networks like Metal3D that are trained on GPUs are very slow on 1 or 2 CPU cores. Metal3D surely is slower than PMM but for a fair comparison it should be stated that GPU acceleration is available. It should also be mentioned on what hardware the timing for PMM is computed. + +<--- Page Split ---> + +Minor corrections: + +Minor corrections:- Typo "check my metal" in Figure 6.- It would be nice if the webserver would show the certainty score in the webviewer.- The standard deviations should be reported for all means (as required by Nature Comm.).- In 1.280 the standard deviation for Metal3D is reported using just a plus sign, should be \(\pm\) .- Figure 4: 2z9p should be 2zp9. + +Simon Durr and Ursula Rothlisberger + +(Remarks on code availability) + +Software&data availability: + +- Nature Communications requires authors to deposit all data. Authors should therefore make available all predicted locations for the reported structures. In case, the authors only used the asymmetric units, the results should be rerun for the biological assemblies. This also concerns the deposited data for Figure 4. The supplementary data (e.g figure4a.csv) only contains aggregated numbers. + +- It is great that the code of the standalone tool is available and it seems the authors have already made some improvements judging by recent commit history. We tried installing the program on 13.3.2024 in a fresh Debian bookworm Docker container but still some packages were missing and there are errors in the log file produced such as "KeyError: 'None of [0] are in the columns'. No predictions are output currently. Some paths also seem hardcoded inside the program e.g the name of the input file if providing PDB input). It would be advisable to make available an apptiner or a Docker container with all requirements already installed in the correct version. Especially so since postgresql is used which normally cannot be installed by users in normal computing environments such as HPC machines because users lack root privileges to run e.g apt-get. + +- The xlsx supplementary files contain PDB names formatted as scientific numbers e.g 2E26 is formatted as \(2^{*}10^{*}26\) . Please use plaintext csv like for some of the other supplementary files. + +- The source files of some plot scripts are also not available. E.g figure1.R contains a reference to transition_metal_type.csv that is not in the supplementary folder. + +## Reviewer #3 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +(Remarks on code availability) + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The revised manuscript addresses the comments made in my original review + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +The revised version of the manuscript has clearly improved and most of the issues that we have raised have now been answered satisfactorily. However, there are few points that should be further clarified: + +The authors have now better defined the scope of the paper and even extended it from a zinc- only predictor restricted to HC- based tetrahedral sites to a general predictor for transition metal ions including also octahedral sites with EDH motif. The scope of the paper is now correctly reflected in the title as well as in the abstract of the paper. However, the introduction still makes some claims about possible extensions to alkali and alkaline earth metal ions that seem not justified: + +'Extending PMM to include alkali and alkaline earth metals requires the use of carboxyl side chains from Glutamic acid and Aspartic acid (ED) as the primary measure, and hydroxyl side chains from Serine and Threonine (ST) as the auxiliary measures, along with new feature descriptors to account for their unique coordination properties, and a corresponding training set.' + +<--- Page Split ---> + +This statement is not correct because an extension to alkaline earth ions also requires the inclusion of protein backbone oxygens as binding sites, which does not seem straightforward in the sidechain- based approach that PMM uses. It would be best if the authors remove this paragraph and do not make any claims beyond the defined scope. + +In the methods section the authors also cite a reference stating 'that for less than \(1\%\) of all metal ions coordination with mainchain is observed'. However, the quoted paper only describes zinc proteins. Many alkaline earth binding sites include main chain coordination (e.g the EF- hand motif for calcium). + +The answer of the authors to the issue we raised about the significance of the accuracy differences between various metal ion location predictors in view of the typical uncertainties in the experimental protein structures seems unclear: 'It is important to pay attention to the distinction between absolute accuracy and relative accuracy when evaluating the precision of predicted metal coordinates. In low- resolution structures, even if both the ligand and metal ion positions are subject to error, as long as the predicted relative position of the metal ion with respect to the ligand is accurate, this relative accuracy remains valuable in practical applications.' + +Do the authors want to say that relative accuracies might be better than absolute ones? But if the experimental position uncertainty is sigma, the uncertainty for the distance d between two atoms A and B is according to error propagation \(\mathrm{Sqr}(2)^*\) sigma. Since the location accuracy is measured as deviation from the experimental position and typical positional uncertainties in protein structures are easily 0.1- 0.2A, performance differences in the hundredths of angstrom seem hardly significant. + +This revised paper contains many new results and the structure is very hard to follow. For example the new model apparently includes a way to predict the identity of metal ions in 4 different classes. However, this is only described in the discussion section and not in the results. The authors should improve the flow of the paper to make it easier to read. + +(Remarks on code availability) Regarding code availability and building of a container for the app: + +Exactly because it is difficult to setup PostgreSQL the authors should make it available as a container since there it will always be in the same environment with the same configurations options used by the authors. We tried setting up a local postgresql server and were unsuccessful. Data persistence is not a problem as far as I understand it because the postgresql database is only used to save data for one run. And port forwarding is easily accomplished in the Dockerfile. Especially in a few years from now the authors might have moved institutions etc. and therefore it is likely that the web server no longer works because no support can be provided. This is very common for most web servers in the field that they are unavailable after some point. + +Reviewer #3 + +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +(Remarks on code availability) + +Version 2: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) I think the manuscript is suitable for publication. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) Authors have now addressed all the raised issues. + +(Remarks on code availability) + +Reviewer #3 + +<--- Page Split ---> + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +(Remarks on code availability) + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Response to reviewers' comments + +Reviewer #1's comments and responses: + +The manuscript reports a new machine learning- based method for predicting Zinc metal binding sites. + +1. The beginning of the results section is confusing, particularly regarding the validation module. Generating a benchmark dataset does not seem to be part of the actual prediction process, i.e. it is not part of PMM. + +We agree with the reviewer's comment that generating a benchmark dataset is not part of the actual prediction process, and that including the validation process in the results figure is indeed misleading. The description of validation process has been moved to the methods section for improved clarity, specifically under subsection 4.2.1, titled 'Data acquisition, validation, and redundancy elimination. + +2. This continues in the second paragraph – the first sentence does not make sense. The first sentence of the next paragraph is also very difficult to follow. In fact the beginning of this results section does not read like a typical results section at all. This continue in section 2.2 with "Subsequently, the binding positions of zinc ions are deduced based on the ligand residues of the candidate zinc binding sites". + +Thanks for pointing out the problems in our writing. We agree that section 2.1 and the first paragraph of 2.2 focuses on the methodological steps and are not suitable for the results section. Therefore, we moved the flowchart to the methods section and rewrote both the result and the method sections with the updated methodology and improved clarity. The problematic descriptions raised by the reviewer in 2.1 and 2.2 of the result sections from the original manuscript have been reflected in the method sections 4.2.1 and 4.2.3 after revision, respectively. + +<--- Page Split ---> + +## 3. Figure 1 - Bar chart has text that is not legible. + +Thank you for pointing out this issue. We have gone through all figures in our manuscript, improved the resolution wherever appropriate, and ensured that all the fonts within every Figure is legible. We have relocated Figure 1 from the original manuscript to Figure 7 in the updated manuscript. The bar chart has been deemed unnecessary and therefore was eliminated. The updated Figure is provided below for the reviewer's convenience. + +![](images/Figure_7.jpg) + +
Fig. 7 | Workflow of PMM. a, Obtain CMM validated experimental metal sites. b, Predict metal binding sites.
+ +<--- Page Split ---> + +## 4. It seems odd to have named the methods PinMyMetal and then refer to it as PMM throughout. + +Thank you for your feedback on the naming and abbreviation of our method, PinMyMetal (PMM). The term "pin" in PinMyMetal reflects our aim to precisely identify the metal type, localization, and environment. This naming follows our previous web server, CheckMyMetal, which was used for validating metal binding sites. The revised version submitted herein addressed the characterization of metal binding sites for most common transition metals such as Mn, Fe, Co, Ni, and Cu. We believe that the name PinMyMetal is appropriate, and the abbreviation PMM is used consistently throughout the manuscript. + +## 5. Section 2.4 does not read like a results section, more like an advert for the method. + +Thank you for pointing out the inappropriate tone used in the manuscript. We have revised the section to present a more balanced description for comparison of PMM amongst other predictors. The manuscript text has been majorly revised and the content has been moved from Section 2.4 to Section 2.5, while retains its title as "Comparison with other predictors." + +## 6. There are many different metal binding site predictors but there is limited comparison to only one other methods Metal3D. + +We have indeed provided a detailed comparison of the PMM with multiple methods in the manuscript, summarized in Table 1, titled "Comparison with Other Metal Predictors." This section emphasizes key features such as input data requirements, prediction methods, output data, and response times for multiple other predictors. + +We have performed in- depth comparison not only between PMM and Metal3D, but also between PMM and various other methods. PMM is compared with representative predictors other than Metal3D in more detail, including Category I predictors ZincBindDB, CHED; Category II predictors AlphaFill; and Category III predictors GRE4Zn, TEMSP. PMM was compared with several Category I and III predictors that have shown good performance in predicting zinc binding sites, including ZincBindDB, GRE4Zn, TEMSP, and CHED using a dataset comprising 136 experimentally determined zinc binding sites derived from 100 protein structures. PMM was also + +<--- Page Split ---> + +compared with AlphaFill using 2zp9 structure as an example to illustrate that AlphaFill use structural homology to transplant metals from similar PDB structures to the predicted structure and have limited ability to predict novel metal binding sites. + +Since other methods are majorly used for the prediction of zinc binding sites, for the comparison of transition metals other than zinc, Metal3D is the only tool that evaluate a benchmark dataset of 503 PDB structures that contain the most common transition metals. Therefore, we compared PMM to Metal3D to evaluate the performance of PMM on all transition metals. + +## 7. Methods – refers to checking quality of zinc binding site using CMM in a modified way. How was it modified? + +The original paper describing CMM was published in 2014 and used 8 parameters to described a wealth of features of different metal ions. These 8 parameters belong to three categories of features: 1) valence for coordinating ligand (ligand composition, valence); 2) deviation from ideal geometry (nVECSUM, geometry, gRMSD, vacancy); 3) experimental agreement (occupancy, B factor). Later on, the quality of each metal binding site was assessed using an algorithm for validating magnesium ions in nucleic acid structures (Zheng et al., 2015) \(^{1}\) . The quality measured was abbreviated into 3 parameters to account for all three categories of features: Qv (to account for valence for coordinating ligands), Qc (to account for deviation from ideal geometry), and Qe (to account for experimental agreement). The work submitted herein further extends the method described in the 2015 work. + +While the algorithm described in the 2015 work was designed only for magnesium ions, the current work involves transition metal binding sites and requires modification of the validation parameters. Specifically, we tailored the formulas for the three quality parameters \(Q_{v}\) , \(Q_{c}\) , and \(Q_{e}\) with the aim that higher values represent better quality and normalized them within the range of 0 and 1. The modification used in the current work are described in details in the method section 4.2.1 of the submitted manuscript, for comparison with the formulas described in the 2015 work. + +## Reference: + +1. Zheng H, Shabalin IG, Handing KB, Bujnicki JM, Minor W. Magnesium-binding architectures in RNA crystal structures: validation, binding preferences, classification and motif detection. Nucleic Acids Res. 43, 3789-3801 (2015). + +<--- Page Split ---> + +8. I may have missed it but the methods appear to be missing important information. There are no details on the machine learning methods and how they were trained and tested, the different parameters used. Further, was redundancy removed from the dataset i.e. proteins with high levels of sequence identity removed. + +Thank you for noting the lack of clarity in the methods section regarding the details on the machine learning methods. We bear your criticism in mind when revising the methods related to the part of machine learning, which we described in detail throughout the methods section. To improve the readability, we have also included the concept and strategy of the hybrid learning system in the section 4.1.2. Specifically: + +a. Machine Learning Methods: The methods for determining metal binding site probability are now described in detail in Section 4.2.6, titled "Determine metal binding site probability." Here, we outline the ensemble model employed in our analysis, including the specific machine learning techniques, including details in the training, validation, and test procedures. Additionally, Section 4.2.7, "Metal type identification for confirmed metal binding sites," provides comprehensive information on how we identify the types of metals at confirmed binding sites. + +b. Machine Learning Parameters: The parameters for the machine learning models are now listed in Supplemental Table 7 and Supplemental Table 9. The sizes of the datasets used in our analysis are provided in Supplemental Table 8 and Supplemental Table 10. + +c. Redundancy Removal: We have addressed the redundancy issue by applying MMseqs2 with a sequence identity threshold of \(30\%\) and a coverage threshold of \(80\%\) to remove redundant sequences from the dataset. This process is detailed in Section 4.2.1, "Data acquisition, validation, and redundancy elimination." + +## 9. Webserver – quick to run but does not provide users with predicted accuracy of each prediction, this really limits how the user can interpret the predictions made. + +The version of webserver after revision features certainty scores as a measure of the predicted accuracy. The certainty score is implemented for each predicted metal site to indicate the likelihood that the site is a metal binding site. Additionally, users can use the provided CheckMyMetal link to evaluate the predicted metal sites (this applies only to structures from the PDB database). The + +<--- Page Split ---> + +certainty score reflects the model's confidence in each prediction. + +## Reviewer #2's comments and responses: + +In this article, the authors present a fast and accurate method (available as webserver and as standalone tool) to predict 2-, 3- and 4- fold coordinated zinc sites in proteins using a scoring function to place candidate binding sites and then ranking those binding sites using an ensemble ML model and/or hydrophobicity profiles. By design, the tool requires that the binding site is composed of at least two residues that are either cysteine or histidine (HC). This approach is of potential interest for a wide community but prior to publication, several issues should be clarified: + +## 1. Clearer definition of the scope: + +The algorithm and workflow that is presented is highly tailored to zinc sites but the title, abstract, introduction and other parts of the manuscript present the findings as a universal metal ion finder. Although the authors claim that an extension to other metal ions such as transition metals and alkali as well as alkali- earth ions is straightforward, this remains to be proven. In fact, the entire current algorithm is heavily tuned to the case of zinc, hardcoding the properties of existing zinc sites into the algorithm (taking HC residues as primary and ED as secondary target and using specific classifications and adapted workflows for 2-, 3- respectively 4- fold coordinated zinc sites). Other methods such as Metal3D make no such choices and learn all these properties from the structure alone. This contradicts the claim that the algorithm can be easily adapted to all other metals since it requires to develop the scoring criteria for each metal instead of just changing the dataset. In fact, it is not clear how the current approach can easily be extended to other metals with high coordination numbers and a wider and less specific spectrum of binding partners (including e.g. binding to amino acid back bones etc.). Therefore, the title should reflect the current specialization for zinc and the abstract and other parts of the text should be adapted accordingly. + +Thank you for raising this important point about the original algorithm's generality to be applied to metals other than zinc. In the first version of the paper, the algorithm was designed + +<--- Page Split ---> + +specifically based on the properties unique to zinc, which limited its application to other metals. According to the reviewer's comments, we have revised the algorithm and dataset to account for transition metals other than zinc. To improve the clarity of our description in terms of scope, we have updated the title, abstract, introduction and other parts of the manuscript to account for only transition metals. + +The original version of the PMM algorithm indeed considered only the case of zinc in tetrahedral geometry, hardcoding the properties of existing zinc sites into the algorithm (taking HC residues as primary and ED as secondary target and using specific classifications and adapted workflows for 2-, 3- respectively 4- fold coordinated zinc sites). This is suitable for metals like zinc and copper, which predominantly coordinate with sulfur atoms of cysteine or nitrogen atoms of histidine. However, other transition metals like manganese, iron, cobalt, and nickel, which are mainly coordinated by carboxyl oxygen atoms and nitrogen atoms in histidine (Fig. S8), the use of solely CH ligands would significantly lower the recall rate if the initial step of the PMM algorithm does not consider E and D amino acids as ligands. To this end, we have revised the PMM algorithm to include EDH ligands as an additional criterion. The use of EDH ligands is typically correlated with six- coordinated octahedral metal binding sites that represent not only the predominant coordination geometry for transition metals other than zinc and copper, but also a minor fraction of coordination geometry for zinc and copper sites. Therefore, the inclusion of EDH strategy as part of the updated PMM algorithm signifies its applicability to all transition metals. + +<--- Page Split ---> +![](images/Supplementary_Figure_8.jpg) + +
Supplementary Figure 8. Distribution of transition metal coordination motifs. CH0, CH1, CH2, CH3, and CH4 represent combinations of metal coordination sites where ligands contain 0, 1, 2, 3, 4 C and/or H ligands; "Unclassified" denotes other uncategorized ligand combinations.
+ +In the updated PMM system, we employ customized methods to predict transition metal binding sites based on different coordination geometries. For tetrahedral coordination, the algorithm uses a CH- based approach, focusing on combinations of C and H residues, while for octahedral coordination, the EDH- based approach is applied, considering E, D, and H residues. This strategy, tailored to specific coordination geometries and supported by dedicated training datasets, significantly enhances the accuracy of identifying metal binding sites. The detailed concepts and methods are described thoroughly in the Methods section 4.1.1. + +The PMM algorithm is currently trained only on common transition metal binding sites, relying on CH (tetrahedral) and EDH (octahedral) geometries to predict transition metal sites. In macromolecular structures with biological functions, distinguishing and identifying different transition metals is crucial. These metals play specific roles in biological systems, such as participating in catalytic reactions, regulating physiological processes, and maintaining structural stability. Accurately identifying transition metals can enhance our understanding of their biological functions and their impact on health and disease, thus guiding drug development and biotechnology. However, alkali and alkaline- earth metals present challenges for accurate predictions due to their + +<--- Page Split ---> + +simpler chemical properties (such as fixed \(+1\) or \(+2\) oxidation states), weaker ligand binding capacities, and greater mobility. These elements primarily bind to ligands through weaker ionic interactions, and their coordination structures are more flexible. Therefore, specialized algorithms needed to address these unique characteristics effectively and predict binding sites for alkali and alkaline- earth metals are beyond the scope of this study. + +## 2. Clarifications about the workflow in the case of zinc: + +(1). Do the authors use the asymmetric unit or the biological assembly? Since zinc ions are often located at crystal interfaces, this is an important difference. + +In our study, we used the asymmetric unit structures (.ent files) downloaded from the PDB database. These files are obtained directly from crystallographic experiments and represent the asymmetric unit. + +We recognize that zinc ions are often located at crystal interfaces. To identify metal binding sites located at these interfaces, we incorporated a step in our updated PMM algorithm where we apply symmetry operations to the asymmetric unit using the CCP4 contact tool during data processing. This allows us to identify metal binding sites that may exist at the interfaces between asymmetric units. + +We chose not to use the biological assembly directly because, for structures with multiple biological assemblies, the use of all biological assemblies would introduce additional redundancy, while the use of only the first biological assembly could result in not considering some metal binding sites, as not all metal sites may be present in the first biological assembly. By applying symmetry operations to the asymmetric unit, we can assure that we identify all potential metal binding sites with full completeness and no redundancy. + +## (2). L.243: it is unclear how the auxiliary ED criterion works. ED is also not present in Figure 1. + +We apologize for any confusion. In the initial version of the PMM algorithm, the ED criterion was not used in predicting zinc binding sites and was only applied after prediction. We have revised the PMM algorithm to include an EDH criterion, mainly to predict transition metals other than zinc. However, we found that the application of EDH criterion on top of CH algorithm also improves + +<--- Page Split ---> + +the recall rate for the prediction of zinc binding sites. Therefore, PMM uses a CH ligand- based algorithm for tetrahedral coordination structures and an EDH algorithm for octahedral coordination structures. + +To present a realistic coordination scenario, the auxiliary ED criterion is recognized in the displayed metal site structures on the webpage include ligands within a \(4\mathrm{\AA}\) radius after the predictions are made. The webpage show all ligands that bind to metals, which may also involve amino acids other than CHED residues or small molecules. For example, the structure of metallopeptidase (PDB code: 2qvp) contains a CH site (B498) coordinated by two histidine residues, and after predicting the metal ion position, a third and fourth coordinating ligand—glutamate and water—were also identified (Fig. S6). A clearer methodology explanation is provided in Section 4.1 Concept and strategy of the revised manuscript. + +![](images/Supplementary_Figure_4.jpg) + + +Supplementary Figure 6. The prediction results for the B chain of 2qvp on the PMM web server are shown. In this structure, the CH algorithm predicts a tetrahedral magnesium binding site at B498, where PMM identifies additional ligands—glutamate and water—beyond C and H at this site. Non- experimental sites: metal binding sites with unknown functions predicted by PMM. The coloring of ligands at metal binding sites is as follows: green represents the initially identified ligands (C or H ligands in the CH algorithm, and E, D, or H ligands in the EDH algorithm), while gray indicates other ligands identified within a \(4\mathrm{\AA}\) radius of the metal coordinates after their determination. + +## (3). Why was a cutoff of 0.5 used in the end? + +Thank you for the question that led to the screening of the optimal cutoff for certainty score to achieve a balance between sensitivity and specificity. The certainty score ranges from 0 to 1, and the cutoff of 0.5 is chosen using different strategies depending on the coordination number of the + +<--- Page Split ---> + +metal binding sites being low- coordination sites (LCS) or high- coordination sites (HCS). + +For low- coordination sites, the cutoff of 0.5 is chosen to achieve the optimal performance metrics (Recall, Precision, F1- Score, and Accuracy) on the test dataset across different thresholds (Table S3). Candidates with a score greater than 0.5 are considered verified sites. At this threshold, the F1- Score for CH sites is 0.924, with high precision (0.958) and recall (0.893), resulting in an overall accuracy of 0.941. For EDH sites, the F1- Score at 0.5 is 0.848, with no improvement at a threshold of 0.55. + +For high- coordination sites, we calculate the similarity between predicted binding sites and the standard curve (representing known metal binding site characteristics) using Pearson correlation coefficients. The cutoff of 0.5 was chosen because it indicates a moderate to strong positive correlation, suggesting that the predicted metal binding sites are similar to known binding features (Fig. S2). + +## (4). L.553: Please describe the scoring function. + +Thank you for your inquiry about the scoring function. The scoring function evaluates the deviation of each point on the circle from the expected Zn- Sγ- Cβ angle of \(109^{\circ}\) . Specifically, the final Zn coordinate (f1\*) is determined by summing the deviations of the angles between two sets of coordinates (f1a1c1 and f1b1d1) from this expected angle. The position with the minimum score is selected as the optimal Zn location, ensuring that the identified Zn position closely aligns with the ideal geometric configuration. Further details can be found in section 4.2.3, "Determination of Metal Ion Location," particularly in the (a) C2 sites coordinate prediction subsection. + +\[\mathrm{f_{1}^{*} = \arg \min_{f_{1}}\left(|\theta_{\mathrm{f_{1a1c1}}} - 109^{\circ}| + |\theta_{\mathrm{f_{1b1d1}}} - 109^{\circ}|\right)} \quad (7)\] + +(5). The algorithm only detects 2-, 3-, or 4-fold coordinated sites. What about 5- and 6- fold coordination that can be fairly abundant, especially for catalytically active sites, with varying percentages cited in the literature of up to \(30\%\) for 5- fold and roughly \(10\%\) for 6- fold. + +Thank you for pointing out that 5- and 6- fold coordination that can be fairly abundant. We have updated our PMM algorithm to be compatible with octahedral geometry and include 5- and 6- fold coordinated sites (details in 4.1.2). + +<--- Page Split ---> + +## (6). Several of the coordination spheres may contain one or even several water molecules. How are these handled? + +Water molecules are excluded during the feature summarization and prediction processes. This exclusion applies to the calculation of hydrophobicity values and any other subsequently added chemical feature parameters. However, after the site prediction, water molecules are included when completing the site ligands within a \(4\mathrm{\AA}\) distance, where they are presented as ligands. + +(7). The authors claim that they developed a hybrid algorithm based on geometric, physicochemical as well as ML selection but it seems that the primary selection of all zinc sites is based solely on amino acid type (HC&DE) plus geometric (and solvation) considerations. Only in the case of 2-fold 'regulatory' sites, do the authors also invoke an ensemble method with different ML models. Is there any ML part in the detection of the 3- and 4-fold coordinated sites? What is the additional impact of the ML model? + +Thank you for your question. In identifying 3- and 4- fold coordinated sites (i.e., high- coordination tetrahedral sites), we did not employ machine learning methods. Instead, we employed the Pearson correlation coefficient to evaluate the similarity of hydrophobic features between predicted and experimentally determined binding sites to determine if a site is a metal binding site. + +The hybrid algorithm of PMM involves three key steps. First, geometric and physicochemical properties are used to predict candidate metal binding sites. Next, the predicted sites are validated to determine whether they are metal binding sites. Finally, after confirming that a site is indeed a metal binding site, the type of metal that is most likely to bind at the site is determined. + +ML is used in the second and the third steps. In the second step, for low- coordination sites (2 ligands in CH and 2 or 3 ligands in EDH), two ensemble learning models are invoked, one for CH- based tetrahedral algorithm and the other for EDH- based octahedral algorithm. In the third step of characterizing the type of metal, a classification ensemble learning model is invoked using additional chemical parameters. The use of multiple ML models in different steps of the metal localization and identity prediction process constitutes a hybrid learning system. We have formulated the concept as an introductory "Concept and Strategy" section for additional clarity + +<--- Page Split ---> + +(see details in 4.1.2). + +The additional impact of the ML models are: + +a. For the Low-coordination sites in the second step, relying solely on hydrophobicity curves may not yield accurate predictions due to having fewer ligands, exhibiting more flexible and irregular geometries, resulting in less distinct hydrophobic patterns. Using ensemble learning models can enhance the predictive accuracy for low-coordinate sites by incorporating additional geometric features, such as ligand distances and ligand-metal angle. + +b. For the High-coordination sites in the second step, the certainty score is derived by calculating Pearson correlation coefficients between the predicted sites and experimental data for C and \(\Delta \sigma\) value curves. The increase in coordination number enhances geometric stability and makes hydrophobic patterns more pronounced, achieving high predictive accuracy without reliance on machine learning algorithms. As the number of ligands increases in high-coordination sites, the combinations of geometric features grow exponentially, complicating the feature space and posing challenges for machine learning model training. This complexity may lead to redundancy and an increased risk of overfitting. + +c. For characterization of different type of metal in the third step, the use of classification ensemble learning model ensure the consideration of a multitude of relevant parameters to differentiate the metal type. These parameters include a hydrophobicity profile and seven chemical features, along with the 27 features implemented in the NEIGHBORHOOD database (Table S9). The seven chemical features include aromaticity, hydrophobicity, positive ionizable, negative ionizable, hydrogen bond donor, hydrogen bond acceptor, and MBS chain (see details in 4.2.7). + +## 3. Comparison with other methods: + +(1). The restriction to HD sites that PinMyMetal (PMM) is based on, can be restrictive, in fact some well-defined Zn sites cannot be located (e.g. in 4HTM). These limitations should be discussed. + +Thank you for pointing out the problem, which led to an improved design in experiment, algorithm, and interface. As mentioned in the response to Comment 1, in the step of predicting potential metal binding sites using geometric constraints, we have added the EDH combination in + +<--- Page Split ---> + +addition to the previous CH combinations. This update allows for the prediction of sites that do not contain C or H but are coordinated by two or more ED ligands. With the updated algorithm, zinc sites in 4HTM that are coordinated solely by two ED ligands can now be predicted. + +![PLACEHOLDER_18_0] + + +(2). While comparing accuracy differences in metal ion detection (in terms of predicted versus experimental position), the (in)accuracy of the experimental structures should be kept in mind. In fact, is the difference in accuracy between Metal3D \(0.52\pm 0.45\mathrm{A}\) and PMM \(0.257\pm ?\) (standard deviation should be given!), statistically significant considering the fact that typical x- ray structures with 1.5- 3A resolution have typical average atomic coordinate errors of the order of \(0.2 - 0.6\mathrm{A}\) (according to the DPI database http://pranag.physics.iisc.ac.in/dpi_db/ using e.g. the Luzzati equation) and this does not even take low- resolution cryo- EM structures into account. Some illustrative examples of pdb structures that the authors discuss in the text: 1bc2 (resolution 1.9A): average positional error \(0.25 - 0.29\mathrm{A}\) , estimated accuracy for the zinc positions 0.17- 0.23A or, an extreme case, 1thj (resolution 2.8A), experimental uncertainty for zinc positions 1.28- 1.32A. + +Thank you for pointing out the need to provide the standard deviation for the accuracy of PMM predictions compared to experimental positions. We have now included the standard deviation for PMM. For example, in the CH- based method, Zn shows the highest prediction accuracy, with a mean deviation of \(0.279\pm 0.29\mathrm{\AA}\) . Detailed information can be found in Section 2.1 of the results. + +The reviewer has also raised a very good point regarding the impact of experimental structure inaccuracies on the comparison of predicted metal ion positions. It is important to pay attention to the distinction between absolute accuracy and relative accuracy when evaluating the precision of + +<--- Page Split ---> + +predicted metal coordinates. In low- resolution structures, even if both the ligand and metal ion positions are subject to error, as long as the predicted relative position of the metal ion with respect to the ligand is accurate, this relative accuracy remains valuable in practical applications. + +## 4. Explicit comparison with Metal3D: + +Thank you for your detailed review and valuable feedback on our work. We apologize for any confusion caused by our oversight. + +(1). For a fair comparison, the same data should be tested. Why are there 205 zinc sites for PMM and 189 for Metal3D? The number for the transition metal test cases also do not match. + +We acknowledge that our initial data did not use the first biological assembly files provided in the Metal3D paper, but rather used .ent files directly obtained from the PDB database, which correspond to the asymmetric unit structures and possess 205 zinc sites. We have corrected this issue by now using the first biological assembly files as specified in the Metal3D paper. This adjustment ensures a fair comparison between the two methods. + +Additionally, upon analyzing the Metal3D dataset, we identified redundancies and errors among the 189 reported zinc binding sites, primarily due to Biopython's recognition process. For instance, multiple conformations in structures such as 2akf were counted as separate sites, and misidentified sites were observed in cases like 3q1d and 4a7k. Furthermore, free metal ions were mistakenly recognized as binding sites (e.g., A402 in 4199 and B4 in 3e7l), and site 381 in 2a0s was identified due to crystal symmetry (Fig. S4). After removal of these sites, we identified 178 valid metal binding sites in the Metal3D dataset. + +<--- Page Split ---> +![PLACEHOLDER_20_0] + +
Supplementary Figure 4. Examples of redundant or incorrect metal binding site identifications in Metal3D. The figure shows examples where Metal3D misidentified or duplicated metal binding sites. Metal3D, a recently developed metal site prediction tool based on 3D convolutional neural networks, is currently the most accurate predictor of metal ion positions. The dataset reported in Metal3D includes 189 zinc binding sites from 59 structures, none of which overlap with the training set used by PMM. However, since Metal3D uses Biopython to retrieve metal sites, some redundancies and errors were identified among the 189 sites. After removing these redundant and erroneous sites, 178 valid zinc binding sites remained. a, In 2akf, multiple conformations (A1, B3, B4) were treated as separate sites. b, In 3q1d, two actual zinc sites (A20, A202) were counted as four. c, In 4a7k, three sites (A950, A951, A952) were recognized as six. d, e, Free metal ions, such as A402 in 4l99 and B4 in 3e7l, were incorrectly labeled as binding sites—each with only one ligand within 5 Å, which are not listed as metal binding in LINK, positioned too far from the zinc. f, In 2a0s, B381 was generated due to crystal symmetry. The magenta sticks represent ligand amino acids coordinating the metal ions. These errors were removed in the final dataset.
+ +(2). The values for TP, FP and FN for Metal3D that the authors cite in Suppl. Table S5 (and that are used to calculated Precision and Recall values that are discussed in the main text) are not correct. In fact, the cited numbers 78, 47, 111 for TP, FP and FN refer to Metal1D results (also given in the Metal3D paper) while the results for Metal3D (with the recommended probability threshold of \(p = 0.75\) ) are 85, 9, 104. + +This issue was due to an oversight on our part when referencing the Metal3D paper, as we inadvertently used incorrect data. The revised data and analysis results have been incorporated into the revised manuscript, specifically in Table S5 and in the third paragraph of Section 2.5. + +(3). 'However, Metal3D predicts two additional zinc locations in the same structure, where no electron density is observed, indicating a higher rate of false positive hits of Metal3D when compared with PMM': The additional sites predicted with Metal3D have much lower probability ( \(p = 0.5\) ) than the C4 sites in the structure. The probability of 0.5 is + +<--- Page Split ---> + +## below the recommended probability threshold of Metal3D of 0.75 so these predictions should not be categorized as false positives by the authors. + +Regarding the additional zinc sites predicted by Metal3D and their false positive rate, we acknowledge that the predicted sites with a probability of \(\mathrm{p = 0.5}\) are below the Metal3D- recommended threshold of \(\mathrm{p = 0.75}\) . Therefore, these predictions should not be classified as false positives. We have updated the relevant analysis in the revised manuscript and corrected this misunderstanding, specifically in Figures 3d and 3e, as well as in the last paragraph of Section 2.5. + +(4). L. 519: 'While Metal3D uses 5Å to determine the presence of occupancy redundancy, we disagree with their threshold since the dinuclear zinc binding site would be mislabeled in Metal3D (Fig. S7b)': It would be good to discuss this better. Metal3D does not mislabel such sites since the predicted density correctly contains both binding sites. However, the current placement algorithm might sometimes not be able to place two separate zincs into the predicted density. In fact for the given example 6jkw, Metal3D does correctly predict and place two zinc ions. + +Regarding the 5Å threshold used by Metal3D and the labeling of dinuclear zinc binding sites, we have confirmed that Metal3D correctly predicts and places the dinuclear zinc ions in the example of 6jkw. Our statement that "the dinuclear zinc binding site would be mislabeled in Metal3D" was incorrect. We have revised the discussion on this issue and updated the figure to Fig S12. In Section 4.2.4, we have included an explanation of how Metal3D handles such sites to avoid confusion. + +(5). Comparison of timings: deep learning networks like Metal3D that are trained on GPUs are very slow on 1 or 2 CPU cores. Metal3D surely is slower than PMM but for a fair comparison it should be stated that GPU acceleration is available. It should also be mentioned on what hardware the timing for PMM is computed. + +Regarding the comparison of performance timings, we acknowledge that failure to mention the availability of GPU acceleration for Metal3D may lead to misunderstandings. We have removed the specific timing comparisons with Metal3D from the manuscript, retaining only a general comparison of run times in Table 1, with a note indicating that the Metal3D predictor benefits from + +<--- Page Split ---> + +GPU acceleration during its operation. + +In a virtual machine configured with an AMD EPYC 7551 CPU (32 cores, 1 thread per core, approximately 2000 MHz base clock, 8 MB L3 cache, and a total of 64 CPUs), the PMM predictor took 23 seconds to run the 2zp9 structure (a complex consisting of 6 chains of 81 amino acids and 9 chains of 53 amino acids), while Metal3D required 5 minutes and 51 seconds. For the 2y42 structure (comprising four chains of 350 amino acids), PMM took 28 seconds, whereas Metal3D took 13 minutes and 45 seconds. + +Additionally, PMM provides a web service hosted on a Tencent Cloud server. The resource configuration of the Tencent Cloud server differs from that of the local virtual machine, particularly regarding core count and performance, which may impact the run times of the different predictors. + +## 5. Minor corrections: + +-Typo "check my metal" in Figure 6. + +-It would be nice if the webserver would show the certainty score in the webviewer. + +-The standard deviations should be reported for all means (as required by Nature Comm.). + +-In 1.280 the standard deviation for Metal3D is reported using just a plus sign, should be ±. + +-Figure 4: 2z9p should be 2zp9. + +Thank you for pointing out these minor corrections. We have made the following adjustments based on your feedback: + +Corrected the typo "check my metal" in Figure 6 (now Figure 5). + +Added the certainty score display in the webviewer of the webserver. + +Reported the standard deviations for PMM, in accordance with the requirements of Nature Comm. + +We have removed the line regarding the standard deviation for Metal3D in the new version of the manuscript. Instead, we have included the standard deviation in the Deviation (A) column of + +<--- Page Split ---> + +Table S5, using the correct symbol \(\pm\) to represent it. + +Corrected the label in Figure 4 (now Figure 3) from "2z9p" to "2zp9." + +We appreciate your attention to detail, and these changes have been incorporated into the revised manuscript. + +Reviewer #2 (Remarks on code availability): + +## 6. Software&data availability: + +- Nature Communications requires authors to deposit all data. Authors should therefore make available all predicted locations for the reported structures. In case, the authors only used the asymmetric units, the results should be rerun for the biological assemblies. This also concerns the deposited data for Figure 4. The supplementary data (e.g figure4a.csv) only contains aggregated numbers. + +Thank you for your suggestions. We have ensured that detailed prediction data is provided for all reported structures. Additionally, in the section evaluating PMM prediction accuracy using the Metal3D test set, we reran the results using the biological assemblies. We have updated the deposited data for Figure 4 (now Figure 3 in the revised manuscript), providing more detailed information, including the prediction results for each metal site in the structures, rather than just aggregated data. + +- It is great that the code of the standalone tool is available and it seems the authors have already made some improvements judging by recent commit history. We tried installing the program on 13.3.2024 in a fresh Debian bookworm Docker container but still some packages were missing and there are errors in the log file produced such as "KeyError: 'None of [0] are in the columns'. No predictions are output currently. Some paths also seem hardcoded inside the program e.g the name of the input file if providing PDB input). It would be advisable to make available an apptainer or a Docker container with all requirements already installed in the correct version. Especially so since postgresql is used which normally cannot be installed by users in normal computing environments such as HPC machines because users + +<--- Page Split ---> + +## lack root privileges to run e.g apt-get. + +We appreciate your detailed feedback. Building an Apptainer or Docker container that includes PostgreSQL is a reasonable solution. However, constructing and deploying such a container involves certain technical complexities, including: + +Database Configuration: PostgreSQL has numerous configuration options, such as memory management, connection limits, and concurrency handling. Ensuring that PostgreSQL operates effectively across different environments requires additional setup. + +Data Persistence: Running a database in a container necessitates managing persistent storage to ensure that data is retained even if the container is restarted or removed. This typically involves managing and configuring external volumes for secure data storage. + +Network Configuration: Correctly handling network requests within the container, including external access and communication with other containers, may require port mapping and network settings to allow users seamless access to the database. + +Performance Optimization: Performance tuning for different environments may require adjustments based on available resources to ensure PostgreSQL runs efficiently in a containerized setting. + +Security: Special attention must be paid to database security settings to ensure proper access controls and authentication mechanisms are in place to mitigate potential security risks. + +The current version manages all dependencies except PostgreSQL through Conda and provides an environment.yml file to facilitate code execution in supported environments. For users unable to run PostgreSQL locally, while we cannot guarantee complete code execution, predictions can be performed via the provided web service. + +We will consider exploring the option of providing a container with PostgreSQL in future versions. Regarding the errors in the log files during operation, due to updates in the PMM algorithm, the corresponding code has been revised and re- tested to ensure proper functionality. + +-The xlsx supplementary files contain PDB names formatted as scientific numbers e.g 2E26 is formatted as \(2^{*}10^{*}26\) . Please use plaintext csv like for some of the other supplementary files. + +Thank you for your suggestion. We have converted all XLSX files in the supplementary + +<--- Page Split ---> + +materials to plain text CSV format to ensure that the data is displayed correctly and is not affected by data type errors. + +-The source files of some plot scripts are also not available. E.g figure1.R contains a reference to transition_metal_type.csv that is not in the supplementary folder. + +Thank you for pointing out this issue. We have reviewed and included all missing files, and we have modified and tested the plotting scripts to ensure that they run correctly and generate the relevant result data. + +Reviewer #3 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> + +## Response to reviewers' comments + +Reviewer #1's comments and responses: + +The revised manuscript addresses the comments made in my original review. + +Reviewer #2's comments and responses: + +The revised version of the manuscript has clearly improved and most of the issues that we have raised have now been answered satisfactorily. However, there are few points that should be further clarified: + +1. The authors have now better defined the scope of the paper and even extended it from a zinc-only predictor restricted to HC-based tetrahedral sites to a general predictor for transition metal ions including also octahedral sites with EDH motif. The scope of the paper is now correctly reflected in the title as well as in the abstract of the paper. However, the introduction still makes some claims about possible extensions to alkali and alkaline earth metal ions that seem not justified: + +'Extending PMM to include alkali and alkaline earth metals requires the use of carboxyl side chains from Glutamic acid and Aspartic acid (ED) as the primary measure, and hydroxyl side chains from Serine and Threonine (ST) as the auxiliary measures, along with new feature descriptors to account for their unique coordination properties, and a corresponding training set.' + +This statement is not correct because an extension to alkaline earth ions also requires the inclusion of protein backbone oxygens as binding sites, which does not seem straightforward in the sidechain-based approach that PMM uses. It would be best if the authors remove this paragraph and do not make any claims beyond the defined scope. + +Thank you for your insightful feedback. As per your suggestion, we have removed the statement in the introduction regarding the extension of PMM to alkali and alkaline earth metals. The revised text now focuses solely on the scope of the current study, ensuring accuracy and consistency throughout the manuscript. + +<--- Page Split ---> + +2. In the methods section the authors also cite a reference stating 'that for less than \(1\%\) of all metal ions coordination with mainchain is observed'. However, the quoted paper only describes zinc proteins. Many alkaline earth binding sites include main chain coordination (e.g the EF-hand motif for calcium). + +Thank you for your comment. We have revised the content accordingly. "The CHED residues are the most common ligands for transition metal ions. In contrast, donor atoms from other amino acids, such as mainchain oxygen, serine, threonine, or lysine, are much less frequent and account for only a small fraction of transition metal-ligand interactions (Section 4.1.1)." We have also updated the citation to reflect this distinction appropriately. + +3. The answer of the authors to the issue we raised about the significance of the accuracy differences between various metal ion location predictors in view of the typical uncertainties in the experimental protein structures seems unclear: + +'It is important to pay attention to the distinction between absolute accuracy and relative accuracy when evaluating the precision of predicted metal coordinates. In low-resolution structures, even if both the ligand and metal ion positions are subject to error, as long as the predicted relative position of the metal ion with respect to the ligand is accurate, this relative accuracy remains valuable in practical applications.' + +Do the authors want to say that relative accuracies might be better than absolute ones? But if the experimental position uncertainty is sigma, the uncertainty for the distance d between two atoms A and B is according to error propagation \(\mathrm{Sqr}(2)*\mathrm{sigma}\) . Since the location accuracy is measured as deviation from the experimental position and typical positional uncertainties in protein structures are easily 0.1- 0.2A, performance differences in the hundredths of angstrom seem hardly significant. + +Thank you for your valuable feedback. We agree that typical positional uncertainties in protein structures are around 0.1- 0.2 Å, and performance differences in the hundredths of an angstrom may not be statistically significant when considering experimental error margins. + +As a result, we have updated the Section 3.3 Innovation and validation of the PMM algorithm to reflect this point, acknowledging that: "However, it is important to consider the inherent + +<--- Page Split ---> + +uncertainties in experimental structures when interpreting these results. Typical positional uncertainties in protein structures range from 0.1- 0.2 Å, and metal location accuracy is measured as the deviation from these experimental positions. Given this, performance differences in the hundredths of an angstrom may not be statistically significant, especially when accounting for the experimental error margins." + +4. This revised paper contains many new results and the structure is very hard to follow. For example, the new model apparently includes a way to predict the identity of metal ions in 4 different classes. However, this is only described in the discussion section and not in the results. The authors should improve the flow of the paper to make it easier to read. + +Thank you for your constructive feedback on our manuscript. We have made the following revisions to improve its clarity, structure, and readability: + +A new section, 2.4 Identification of metal types, has been added to the Results section, clearly describing the model's ability to predict four different metal types. This analysis was relocated from the original Discussion section to enhance logical flow. + +The previous 3.2 Identifying metal types: the predictive power of PMM section has been streamlined. Results related to the prediction of four metal types are now concisely presented in the revised 3.2. Content unrelated to the section title has been moved to a new section, 3.3 Innovation and validation of the PMM algorithm. + +In 4.1 Concept and strategy, we refined the description of the hybrid learning system, outlining its three- step process: + +Step 1: Geometric constraints are used to predict candidate metal- binding sites (corresponding to 2.1). + +Step 2: Predicted sites are validated to determine whether they are true metal- binding sites, with validation for low- coordination sites (LCS) discussed in 2.2 and high- coordination sites (HCS) in 2.3. + +Step 3: For sites with certainty scores above 0.5, a single ensemble learning model is used to predict the most probable metal type for each site (corresponding to 2.4). + +We also revised the introductory paragraph of the Results section to align with the updated + +<--- Page Split ---> + +description in 4.1 Concept and Strategy, ensuring a clearer presentation of results and steps. + +Further revisions were made to improve clarity in description and consistency in terminology. More specifically, we enhanced figure legends (Figure 2, Figure 7, and Supplementary Figure 2) and section titles (2.1, 2.7, and 4.2.7), ensuring that they reflect the content more accurately. + +## Reviewer #2 (Remarks on code availability): + +5. Regarding code availability and building of a container for the app: + +Exactly because it is difficult to setup PostgreSQL the authors should make it available as a container since there it will always be in the same environment with the same configurations options used by the authors. We tried setting up a local postgresql server and were unsuccessful. Data persistence is not a problem as far as I understand it because the postgresql database is only used to save data for one run. And port forwarding is easily accomplished in the Dockerfile. Especially in a few years from now the authors might have moved institutions etc. and therefore it is likely that the web server no longer works because no support can be provided. This is very common for most web servers in the field that they are unavailable after some point. + +Thank you for your suggestion. We recognize the importance of containerizing PostgreSQL with Docker to ensure consistency in version and configuration, which is crucial for users to replicate the project environment. To this end, we have provided a PostgreSQL database container (from the official Docker image) and a container for running the project code in a Conda environment we built. These two containers are managed through Docker Compose and are seamlessly connected via a shared network. + +Additionally, we support data persistence through Docker Volumes to cater to diverse user requirements. The container ports are clearly mapped, allowing users to access the database service from the host machine directly. We provide comprehensive documentation that guides users on how to directly pull the images or manually build them, and deploy the containers locally, ensuring the project remains accessible and operational in the long term. The relevant instructions have been uploaded to GitHub for user reference and implementation. + +The authors also make a long- term commitment to maintaining the web service using an + +<--- Page Split ---> + +institution- independent domain name (i.e., biocloud.top). This will give the authors the possibility to continue maintenance of the PMM web service even after the change of institutions. + +## Reviewer #3 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> diff --git a/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..42abbbe6ef176fef75dfa0d927737a6c5c66249f --- /dev/null +++ b/peer_reviews/55576b4c738507347dde4644bafc5034d1053aff215e7d5dca64f2e96a29a671/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,834 @@ +<|ref|>title<|/ref|><|det|>[[73, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 297, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 881, 210]]<|/det|> +# PinMyMetal: A hybrid learning system to accurately model transition metal binding sites in macromolecules + +<|ref|>text<|/ref|><|det|>[[74, 224, 422, 241]]<|/det|> +Corresponding Author: Dr Heping Zheng + +<|ref|>text<|/ref|><|det|>[[73, 275, 896, 303]]<|/det|> +This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. The manuscript was considered suitable for publication without further review at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[72, 313, 866, 329]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 366, 145, 380]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 392, 220, 406]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 418, 161, 432]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 444, 768, 472]]<|/det|> +(Remarks to the Author) The manuscript reports a new machine learning- based method for predicting Zinc metal binding sites. + +<|ref|>text<|/ref|><|det|>[[73, 484, 152, 497]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[72, 509, 890, 536]]<|/det|> +The beginning of the results section is confusing, particularly regarding the validation module. Generating a benchmark dataset does not seem to be part of the actual prediction process, i.e. it is not part of PMM. + +<|ref|>text<|/ref|><|det|>[[72, 547, 922, 575]]<|/det|> +This continues in the second paragraph - the first sentence does not make sense. The first sentence of the next paragraph is also very difficult to follow. + +<|ref|>text<|/ref|><|det|>[[72, 586, 919, 627]]<|/det|> +In fact the beginning of this results section does not read like a typical results section at all. This continue in section 2.2 with "Subsequently, the binding positions of zinc ions are deduced based on the ligand residues of the candidate zinc binding sites". + +<|ref|>text<|/ref|><|det|>[[73, 638, 388, 653]]<|/det|> +Figure 1 - Bar chart has text that is not legible + +<|ref|>text<|/ref|><|det|>[[72, 664, 710, 680]]<|/det|> +It seems odd to have named the methods PinMyMetal and then refer to it as PMM throughout. + +<|ref|>text<|/ref|><|det|>[[72, 691, 637, 706]]<|/det|> +Section 2.4 does not read like a results section, more like an advert for the method. + +<|ref|>text<|/ref|><|det|>[[72, 717, 900, 732]]<|/det|> +There are many different metal binding site predictors but there is limited comparison to only one other methods Metal3D. + +<|ref|>text<|/ref|><|det|>[[72, 743, 815, 758]]<|/det|> +Methods - refers to checking quality of zinc binding site using CMM in a modified way. How was it modified? + +<|ref|>text<|/ref|><|det|>[[72, 769, 904, 811]]<|/det|> +I may have missed it but the methods appear to be missing important information. There are no details on the machine learning methods and how they were trained and tested, the different parameters used. Further, was redundancy removed from the dataset i.e. proteins with high levels of sequence identity removed. + +<|ref|>text<|/ref|><|det|>[[70, 821, 896, 850]]<|/det|> +Webserver - quick to run but does not provide users with predicted accuracy of each prediction, this really limits how the user can interpret the predictions made. + +<|ref|>text<|/ref|><|det|>[[73, 874, 283, 888]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 912, 161, 925]]<|/det|> +Reviewer #2 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 48, 238, 60]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 61, 920, 125]]<|/det|> +In this article, the authors present a fast and accurate method (available as webserver and as standalone tool) to predict 2-, 3- and 4- fold coordinated zinc sites in proteins using a scoring function to place candidate binding sites and then ranking those binding sites using an ensemble ML model and/or hydrophobicity profiles. By design, the tool requires that the binding site is composed of at least two residues that are either cysteine or histidine (HC). This approach is of potential interest for a wide community but prior to publication, several issues should be clarified: + +<|ref|>text<|/ref|><|det|>[[73, 139, 285, 152]]<|/det|> +Clearer definition of the scope: + +<|ref|>text<|/ref|><|det|>[[72, 152, 916, 296]]<|/det|> +The algorithm and workflow that is presented is highly tailored to zinc sites but the title, abstract, introduction and other parts of the manuscript present the findings as a universal metal ion finder. Although the authors claim that an extension to other metal ions such as transition metals and alkali as well as alkali- earth ions is straightforward, this remains to be proven. In fact, the entire current algorithm is heavily tuned to the case of zinc, hardcoding the properties of existing zinc sites into the algorithm (taking HC residues as primary and ED as secondary target and using specific classifications and adapted workflows for 2-, 3- respectively 4- fold coordinated zinc sites). Other methods such as Metal3D make no such choices and learn all these properties from the structure alone. This contradicts the claim that the algorithm can be easily adapted to all other metals since it requires to develop the scoring criteria for each metal instead of just changing the dataset. In fact, it is not clear how the current approach can easily be extended to other metals with high coordination numbers and a wider and less specific spectrum of binding partners (including e.g. binding to amino acid back bones etc..). Therefore, the title should reflect the current specialization for zinc and the abstract and other parts of the text should be adapted accordingly. + +<|ref|>text<|/ref|><|det|>[[73, 308, 428, 321]]<|/det|> +Clarifications about the workflow in the case of zinc: + +<|ref|>text<|/ref|><|det|>[[72, 321, 905, 348]]<|/det|> +- Do the authors use the asymmetric unit or the biological assembly? Since zinc ions are often located at crystal interfaces, this is an important difference. + +<|ref|>text<|/ref|><|det|>[[72, 348, 694, 362]]<|/det|> +- L.243: it is unclear how the auxiliary ED criterion works. ED is also not present in Figure 1. + +<|ref|>text<|/ref|><|det|>[[73, 362, 350, 374]]<|/det|> +- Why was a cutoff of 0.5 used in the end? + +<|ref|>text<|/ref|><|det|>[[73, 375, 377, 387]]<|/det|> +- L.553: Please describe the scoring function. + +<|ref|>text<|/ref|><|det|>[[72, 387, 911, 426]]<|/det|> +- The algorithm only detects 2-, 3-, or 4-fold coordinated sites. What about 5- and 6- fold coordination that can be fairly abundant, especially for catalytically active sites, with varying percentages cited in the literature of up to 30% for 5-fold and roughly 10% for 6-fold. + +<|ref|>text<|/ref|><|det|>[[72, 426, 920, 505]]<|/det|> +- Several of the coordination spheres may contain one or even several water molecules. How are these handled? +- The authors claim that they developed a hybrid algorithm based on geometric, physicochemical as well as ML selection but it seems that the primary selection of all zinc sites is based solely on amino acid type (HC&DE) plus geometric (and solvation) considerations. Only in the case of 2-fold 'regulatory' sites, do the authors also invoke an ensemble method with different ML models. Is there any ML part in the detection of the 3- and 4-fold coordinated sites? What is the additional impact of the ML model? + +<|ref|>text<|/ref|><|det|>[[73, 518, 295, 530]]<|/det|> +Comparison with other methods: + +<|ref|>text<|/ref|><|det|>[[72, 530, 920, 560]]<|/det|> +- The restriction to HD sites that pinMyMetal (PMM) is based on, can be restrictive, in fact some well-defined Zn sites cannot be located (e.g. in 4HTM). These limitations should be discussed. + +<|ref|>text<|/ref|><|det|>[[72, 559, 920, 660]]<|/det|> +- While comparing accuracy differences in metal ion detection (in terms of predicted versus experimental position), the (in)accuracy of the experimental structures should be kept in mind. In fact, is the difference in accuracy between Metal3D 0.52±0.45A and PMM 0.257±?? (standard deviation should be given!), statistically significant considering the fact that typical x-ray structures with 1.5-3A resolution have typical average atomic coordinate errors of the order of 0.2-0.6A (according to the DPI database http://pranag.physics.iisc.ac.in/dpi_db/ using e.g. the Luzzati equation) and this does not even take low-resolution cryo-EM structures into account. Some illustrative examples of pdb structures that the authors discuss in the text: 1bc2 (resolution 1.9A): average positional error 0.25-0.29A, estimated accuracy for the zinc positions 0.17-0.23A or, an extreme case, 1thj (resolution 2.8A), experimental uncertainty for zinc positions 1.28-1.32A. + +<|ref|>text<|/ref|><|det|>[[72, 660, 310, 672]]<|/det|> +- Explicit comparison with Metal3D: + +<|ref|>text<|/ref|><|det|>[[72, 672, 900, 698]]<|/det|> +oFor a fair comparison, the same data should be tested. Why are there 205 zinc sites for PMM and 189 for Metal3D? The number for the transition metal test cases also do not match. + +<|ref|>text<|/ref|><|det|>[[72, 699, 920, 750]]<|/det|> +oThe values for TP, FP and FN for Metal3D that the authors cite in Suppl. Table S5 (and that are used to calculated Precision and Recall values that are discussed in the main text) are not correct. In fact, the cited numbers 78, 47, 111 for TP, FP and FN refer to Metal1D results (also given in the Metal3D paper) while the results for Metal3D (with the recommended probability threshold of \(p = 0.75\) ) are 85, 9, 104. + +<|ref|>text<|/ref|><|det|>[[72, 750, 916, 815]]<|/det|> +oHowever, Metal3D predicts two additional zinc locations in the same structure, where no electron density is observed, indicating a higher rate of false positive hits of Metal3D when compared with PMM': The additional sites predicted with Metal3D have much lower probability \((p = 0.5)\) than the C4 sites in the structure. The probability of 0.5 is below the recommended probability threshold of Metal3D of 0.75 so these predictions should not be categorized as false positives by the authors. + +<|ref|>text<|/ref|><|det|>[[72, 816, 900, 842]]<|/det|> +oL. 519: 'While Metal3D uses 5A to determine the presence of occupancy redundancy, we disagree with their threshold since the dinuclear zinc binding site would be mislabeled in Metal3D (Fig. S7b)' + +<|ref|>text<|/ref|><|det|>[[72, 842, 911, 881]]<|/det|> +It would be good to discuss this better. Metal3D does not mislabel such sites since the predicted density correctly contains both binding sites. However, the current placement algorithm might sometimes not be able to place two separate zincs into the predicted density. In fact for the given example 6jkw, Metal3D does correctly predict and place two zinc ions. + +<|ref|>text<|/ref|><|det|>[[72, 893, 918, 933]]<|/det|> +oComparison of timings: deep learning networks like Metal3D that are trained on GPUs are very slow on 1 or 2 CPU cores. Metal3D surely is slower than PMM but for a fair comparison it should be stated that GPU acceleration is available. It should also be mentioned on what hardware the timing for PMM is computed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 48, 198, 60]]<|/det|> +Minor corrections: + +<|ref|>text<|/ref|><|det|>[[72, 60, 688, 125]]<|/det|> +Minor corrections:- Typo "check my metal" in Figure 6.- It would be nice if the webserver would show the certainty score in the webviewer.- The standard deviations should be reported for all means (as required by Nature Comm.).- In 1.280 the standard deviation for Metal3D is reported using just a plus sign, should be \(\pm\) .- Figure 4: 2z9p should be 2zp9. + +<|ref|>text<|/ref|><|det|>[[73, 138, 330, 152]]<|/det|> +Simon Durr and Ursula Rothlisberger + +<|ref|>text<|/ref|><|det|>[[72, 191, 281, 204]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 205, 260, 217]]<|/det|> +Software&data availability: + +<|ref|>text<|/ref|><|det|>[[72, 217, 915, 270]]<|/det|> +- Nature Communications requires authors to deposit all data. Authors should therefore make available all predicted locations for the reported structures. In case, the authors only used the asymmetric units, the results should be rerun for the biological assemblies. This also concerns the deposited data for Figure 4. The supplementary data (e.g figure4a.csv) only contains aggregated numbers. + +<|ref|>text<|/ref|><|det|>[[72, 270, 918, 373]]<|/det|> +- It is great that the code of the standalone tool is available and it seems the authors have already made some improvements judging by recent commit history. We tried installing the program on 13.3.2024 in a fresh Debian bookworm Docker container but still some packages were missing and there are errors in the log file produced such as "KeyError: 'None of [0] are in the columns'. No predictions are output currently. Some paths also seem hardcoded inside the program e.g the name of the input file if providing PDB input). It would be advisable to make available an apptiner or a Docker container with all requirements already installed in the correct version. Especially so since postgresql is used which normally cannot be installed by users in normal computing environments such as HPC machines because users lack root privileges to run e.g apt-get. + +<|ref|>text<|/ref|><|det|>[[72, 373, 918, 399]]<|/det|> +- The xlsx supplementary files contain PDB names formatted as scientific numbers e.g 2E26 is formatted as \(2^{*}10^{*}26\) . Please use plaintext csv like for some of the other supplementary files. + +<|ref|>text<|/ref|><|det|>[[72, 399, 914, 425]]<|/det|> +- The source files of some plot scripts are also not available. E.g figure1.R contains a reference to transition_metal_type.csv that is not in the supplementary folder. + +<|ref|>sub_title<|/ref|><|det|>[[73, 450, 162, 463]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 476, 238, 489]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 490, 864, 530]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 542, 281, 555]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 580, 144, 592]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 606, 219, 619]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 632, 160, 645]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 658, 600, 685]]<|/det|> +(Remarks to the Author) The revised manuscript addresses the comments made in my original review + +<|ref|>text<|/ref|><|det|>[[73, 697, 281, 710]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 735, 162, 748]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 762, 238, 775]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 775, 881, 802]]<|/det|> +The revised version of the manuscript has clearly improved and most of the issues that we have raised have now been answered satisfactorily. However, there are few points that should be further clarified: + +<|ref|>text<|/ref|><|det|>[[72, 814, 919, 867]]<|/det|> +The authors have now better defined the scope of the paper and even extended it from a zinc- only predictor restricted to HC- based tetrahedral sites to a general predictor for transition metal ions including also octahedral sites with EDH motif. The scope of the paper is now correctly reflected in the title as well as in the abstract of the paper. However, the introduction still makes some claims about possible extensions to alkali and alkaline earth metal ions that seem not justified: + +<|ref|>text<|/ref|><|det|>[[72, 879, 914, 932]]<|/det|> +'Extending PMM to include alkali and alkaline earth metals requires the use of carboxyl side chains from Glutamic acid and Aspartic acid (ED) as the primary measure, and hydroxyl side chains from Serine and Threonine (ST) as the auxiliary measures, along with new feature descriptors to account for their unique coordination properties, and a corresponding training set.' + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 90]]<|/det|> +This statement is not correct because an extension to alkaline earth ions also requires the inclusion of protein backbone oxygens as binding sites, which does not seem straightforward in the sidechain- based approach that PMM uses. It would be best if the authors remove this paragraph and do not make any claims beyond the defined scope. + +<|ref|>text<|/ref|><|det|>[[72, 88, 914, 128]]<|/det|> +In the methods section the authors also cite a reference stating 'that for less than \(1\%\) of all metal ions coordination with mainchain is observed'. However, the quoted paper only describes zinc proteins. Many alkaline earth binding sites include main chain coordination (e.g the EF- hand motif for calcium). + +<|ref|>text<|/ref|><|det|>[[72, 138, 911, 220]]<|/det|> +The answer of the authors to the issue we raised about the significance of the accuracy differences between various metal ion location predictors in view of the typical uncertainties in the experimental protein structures seems unclear: 'It is important to pay attention to the distinction between absolute accuracy and relative accuracy when evaluating the precision of predicted metal coordinates. In low- resolution structures, even if both the ligand and metal ion positions are subject to error, as long as the predicted relative position of the metal ion with respect to the ligand is accurate, this relative accuracy remains valuable in practical applications.' + +<|ref|>text<|/ref|><|det|>[[72, 218, 905, 284]]<|/det|> +Do the authors want to say that relative accuracies might be better than absolute ones? But if the experimental position uncertainty is sigma, the uncertainty for the distance d between two atoms A and B is according to error propagation \(\mathrm{Sqr}(2)^*\) sigma. Since the location accuracy is measured as deviation from the experimental position and typical positional uncertainties in protein structures are easily 0.1- 0.2A, performance differences in the hundredths of angstrom seem hardly significant. + +<|ref|>text<|/ref|><|det|>[[72, 295, 900, 336]]<|/det|> +This revised paper contains many new results and the structure is very hard to follow. For example the new model apparently includes a way to predict the identity of metal ions in 4 different classes. However, this is only described in the discussion section and not in the results. The authors should improve the flow of the paper to make it easier to read. + +<|ref|>text<|/ref|><|det|>[[72, 384, 530, 412]]<|/det|> +(Remarks on code availability) Regarding code availability and building of a container for the app: + +<|ref|>text<|/ref|><|det|>[[72, 424, 919, 516]]<|/det|> +Exactly because it is difficult to setup PostgreSQL the authors should make it available as a container since there it will always be in the same environment with the same configurations options used by the authors. We tried setting up a local postgresql server and were unsuccessful. Data persistence is not a problem as far as I understand it because the postgresql database is only used to save data for one run. And port forwarding is easily accomplished in the Dockerfile. Especially in a few years from now the authors might have moved institutions etc. and therefore it is likely that the web server no longer works because no support can be provided. This is very common for most web servers in the field that they are unavailable after some point. + +<|ref|>text<|/ref|><|det|>[[72, 528, 161, 541]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 554, 861, 608]]<|/det|> +(Remarks to the Author) I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 620, 282, 634]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 660, 144, 673]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[72, 686, 219, 699]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 711, 161, 724]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 737, 398, 764]]<|/det|> +(Remarks to the Author) I think the manuscript is suitable for publication. + +<|ref|>text<|/ref|><|det|>[[72, 776, 282, 789]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 815, 161, 828]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 841, 419, 867]]<|/det|> +(Remarks to the Author) Authors have now addressed all the raised issues. + +<|ref|>text<|/ref|><|det|>[[72, 879, 282, 893]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 917, 161, 930]]<|/det|> +Reviewer #3 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 237, 60]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 60, 864, 101]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 113, 283, 127]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 490, 916, 545]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 545, 796, 559]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 559, 910, 611]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 610, 618, 624]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[398, 102, 737, 122]]<|/det|> +## Response to reviewers' comments + +<|ref|>text<|/ref|><|det|>[[188, 145, 535, 163]]<|/det|> +Reviewer #1's comments and responses: + +<|ref|>text<|/ref|><|det|>[[148, 182, 941, 228]]<|/det|> +The manuscript reports a new machine learning- based method for predicting Zinc metal binding sites. + +<|ref|>text<|/ref|><|det|>[[148, 258, 941, 333]]<|/det|> +1. The beginning of the results section is confusing, particularly regarding the validation module. Generating a benchmark dataset does not seem to be part of the actual prediction process, i.e. it is not part of PMM. + +<|ref|>text<|/ref|><|det|>[[147, 351, 943, 483]]<|/det|> +We agree with the reviewer's comment that generating a benchmark dataset is not part of the actual prediction process, and that including the validation process in the results figure is indeed misleading. The description of validation process has been moved to the methods section for improved clarity, specifically under subsection 4.2.1, titled 'Data acquisition, validation, and redundancy elimination. + +<|ref|>text<|/ref|><|det|>[[147, 511, 943, 642]]<|/det|> +2. This continues in the second paragraph – the first sentence does not make sense. The first sentence of the next paragraph is also very difficult to follow. In fact the beginning of this results section does not read like a typical results section at all. This continue in section 2.2 with "Subsequently, the binding positions of zinc ions are deduced based on the ligand residues of the candidate zinc binding sites". + +<|ref|>text<|/ref|><|det|>[[147, 660, 943, 818]]<|/det|> +Thanks for pointing out the problems in our writing. We agree that section 2.1 and the first paragraph of 2.2 focuses on the methodological steps and are not suitable for the results section. Therefore, we moved the flowchart to the methods section and rewrote both the result and the method sections with the updated methodology and improved clarity. The problematic descriptions raised by the reviewer in 2.1 and 2.2 of the result sections from the original manuscript have been reflected in the method sections 4.2.1 and 4.2.3 after revision, respectively. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 90, 575, 108]]<|/det|> +## 3. Figure 1 - Bar chart has text that is not legible. + +<|ref|>text<|/ref|><|det|>[[147, 126, 943, 256]]<|/det|> +Thank you for pointing out this issue. We have gone through all figures in our manuscript, improved the resolution wherever appropriate, and ensured that all the fonts within every Figure is legible. We have relocated Figure 1 from the original manuscript to Figure 7 in the updated manuscript. The bar chart has been deemed unnecessary and therefore was eliminated. The updated Figure is provided below for the reviewer's convenience. + +<|ref|>image<|/ref|><|det|>[[278, 265, 840, 850]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[180, 875, 912, 891]]<|/det|> +
Fig. 7 | Workflow of PMM. a, Obtain CMM validated experimental metal sites. b, Predict metal binding sites.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 89, 940, 136]]<|/det|> +## 4. It seems odd to have named the methods PinMyMetal and then refer to it as PMM throughout. + +<|ref|>text<|/ref|><|det|>[[147, 153, 944, 341]]<|/det|> +Thank you for your feedback on the naming and abbreviation of our method, PinMyMetal (PMM). The term "pin" in PinMyMetal reflects our aim to precisely identify the metal type, localization, and environment. This naming follows our previous web server, CheckMyMetal, which was used for validating metal binding sites. The revised version submitted herein addressed the characterization of metal binding sites for most common transition metals such as Mn, Fe, Co, Ni, and Cu. We believe that the name PinMyMetal is appropriate, and the abbreviation PMM is used consistently throughout the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[147, 370, 877, 389]]<|/det|> +## 5. Section 2.4 does not read like a results section, more like an advert for the method. + +<|ref|>text<|/ref|><|det|>[[147, 407, 943, 509]]<|/det|> +Thank you for pointing out the inappropriate tone used in the manuscript. We have revised the section to present a more balanced description for comparison of PMM amongst other predictors. The manuscript text has been majorly revised and the content has been moved from Section 2.4 to Section 2.5, while retains its title as "Comparison with other predictors." + +<|ref|>sub_title<|/ref|><|det|>[[147, 539, 941, 585]]<|/det|> +## 6. There are many different metal binding site predictors but there is limited comparison to only one other methods Metal3D. + +<|ref|>text<|/ref|><|det|>[[147, 603, 943, 707]]<|/det|> +We have indeed provided a detailed comparison of the PMM with multiple methods in the manuscript, summarized in Table 1, titled "Comparison with Other Metal Predictors." This section emphasizes key features such as input data requirements, prediction methods, output data, and response times for multiple other predictors. + +<|ref|>text<|/ref|><|det|>[[147, 715, 944, 901]]<|/det|> +We have performed in- depth comparison not only between PMM and Metal3D, but also between PMM and various other methods. PMM is compared with representative predictors other than Metal3D in more detail, including Category I predictors ZincBindDB, CHED; Category II predictors AlphaFill; and Category III predictors GRE4Zn, TEMSP. PMM was compared with several Category I and III predictors that have shown good performance in predicting zinc binding sites, including ZincBindDB, GRE4Zn, TEMSP, and CHED using a dataset comprising 136 experimentally determined zinc binding sites derived from 100 protein structures. PMM was also + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 942, 164]]<|/det|> +compared with AlphaFill using 2zp9 structure as an example to illustrate that AlphaFill use structural homology to transplant metals from similar PDB structures to the predicted structure and have limited ability to predict novel metal binding sites. + +<|ref|>text<|/ref|><|det|>[[148, 172, 943, 275]]<|/det|> +Since other methods are majorly used for the prediction of zinc binding sites, for the comparison of transition metals other than zinc, Metal3D is the only tool that evaluate a benchmark dataset of 503 PDB structures that contain the most common transition metals. Therefore, we compared PMM to Metal3D to evaluate the performance of PMM on all transition metals. + +<|ref|>sub_title<|/ref|><|det|>[[148, 305, 941, 351]]<|/det|> +## 7. Methods – refers to checking quality of zinc binding site using CMM in a modified way. How was it modified? + +<|ref|>text<|/ref|><|det|>[[147, 369, 944, 638]]<|/det|> +The original paper describing CMM was published in 2014 and used 8 parameters to described a wealth of features of different metal ions. These 8 parameters belong to three categories of features: 1) valence for coordinating ligand (ligand composition, valence); 2) deviation from ideal geometry (nVECSUM, geometry, gRMSD, vacancy); 3) experimental agreement (occupancy, B factor). Later on, the quality of each metal binding site was assessed using an algorithm for validating magnesium ions in nucleic acid structures (Zheng et al., 2015) \(^{1}\) . The quality measured was abbreviated into 3 parameters to account for all three categories of features: Qv (to account for valence for coordinating ligands), Qc (to account for deviation from ideal geometry), and Qe (to account for experimental agreement). The work submitted herein further extends the method described in the 2015 work. + +<|ref|>text<|/ref|><|det|>[[147, 647, 944, 805]]<|/det|> +While the algorithm described in the 2015 work was designed only for magnesium ions, the current work involves transition metal binding sites and requires modification of the validation parameters. Specifically, we tailored the formulas for the three quality parameters \(Q_{v}\) , \(Q_{c}\) , and \(Q_{e}\) with the aim that higher values represent better quality and normalized them within the range of 0 and 1. The modification used in the current work are described in details in the method section 4.2.1 of the submitted manuscript, for comparison with the formulas described in the 2015 work. + +<|ref|>sub_title<|/ref|><|det|>[[148, 816, 244, 832]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 838, 941, 894]]<|/det|> +1. Zheng H, Shabalin IG, Handing KB, Bujnicki JM, Minor W. Magnesium-binding architectures in RNA crystal structures: validation, binding preferences, classification and motif detection. Nucleic Acids Res. 43, 3789-3801 (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 943, 191]]<|/det|> +8. I may have missed it but the methods appear to be missing important information. There are no details on the machine learning methods and how they were trained and tested, the different parameters used. Further, was redundancy removed from the dataset i.e. proteins with high levels of sequence identity removed. + +<|ref|>text<|/ref|><|det|>[[147, 209, 944, 340]]<|/det|> +Thank you for noting the lack of clarity in the methods section regarding the details on the machine learning methods. We bear your criticism in mind when revising the methods related to the part of machine learning, which we described in detail throughout the methods section. To improve the readability, we have also included the concept and strategy of the hybrid learning system in the section 4.1.2. Specifically: + +<|ref|>text<|/ref|><|det|>[[147, 348, 944, 506]]<|/det|> +a. Machine Learning Methods: The methods for determining metal binding site probability are now described in detail in Section 4.2.6, titled "Determine metal binding site probability." Here, we outline the ensemble model employed in our analysis, including the specific machine learning techniques, including details in the training, validation, and test procedures. Additionally, Section 4.2.7, "Metal type identification for confirmed metal binding sites," provides comprehensive information on how we identify the types of metals at confirmed binding sites. + +<|ref|>text<|/ref|><|det|>[[147, 515, 943, 589]]<|/det|> +b. Machine Learning Parameters: The parameters for the machine learning models are now listed in Supplemental Table 7 and Supplemental Table 9. The sizes of the datasets used in our analysis are provided in Supplemental Table 8 and Supplemental Table 10. + +<|ref|>text<|/ref|><|det|>[[147, 598, 944, 701]]<|/det|> +c. Redundancy Removal: We have addressed the redundancy issue by applying MMseqs2 with a sequence identity threshold of \(30\%\) and a coverage threshold of \(80\%\) to remove redundant sequences from the dataset. This process is detailed in Section 4.2.1, "Data acquisition, validation, and redundancy elimination." + +<|ref|>sub_title<|/ref|><|det|>[[147, 731, 941, 778]]<|/det|> +## 9. Webserver – quick to run but does not provide users with predicted accuracy of each prediction, this really limits how the user can interpret the predictions made. + +<|ref|>text<|/ref|><|det|>[[147, 795, 944, 898]]<|/det|> +The version of webserver after revision features certainty scores as a measure of the predicted accuracy. The certainty score is implemented for each predicted metal site to indicate the likelihood that the site is a metal binding site. Additionally, users can use the provided CheckMyMetal link to evaluate the predicted metal sites (this applies only to structures from the PDB database). The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 677, 108]]<|/det|> +certainty score reflects the model's confidence in each prediction. + +<|ref|>sub_title<|/ref|><|det|>[[149, 139, 494, 157]]<|/det|> +## Reviewer #2's comments and responses: + +<|ref|>text<|/ref|><|det|>[[147, 175, 944, 361]]<|/det|> +In this article, the authors present a fast and accurate method (available as webserver and as standalone tool) to predict 2-, 3- and 4- fold coordinated zinc sites in proteins using a scoring function to place candidate binding sites and then ranking those binding sites using an ensemble ML model and/or hydrophobicity profiles. By design, the tool requires that the binding site is composed of at least two residues that are either cysteine or histidine (HC). This approach is of potential interest for a wide community but prior to publication, several issues should be clarified: + +<|ref|>sub_title<|/ref|><|det|>[[150, 392, 436, 410]]<|/det|> +## 1. Clearer definition of the scope: + +<|ref|>text<|/ref|><|det|>[[147, 427, 944, 838]]<|/det|> +The algorithm and workflow that is presented is highly tailored to zinc sites but the title, abstract, introduction and other parts of the manuscript present the findings as a universal metal ion finder. Although the authors claim that an extension to other metal ions such as transition metals and alkali as well as alkali- earth ions is straightforward, this remains to be proven. In fact, the entire current algorithm is heavily tuned to the case of zinc, hardcoding the properties of existing zinc sites into the algorithm (taking HC residues as primary and ED as secondary target and using specific classifications and adapted workflows for 2-, 3- respectively 4- fold coordinated zinc sites). Other methods such as Metal3D make no such choices and learn all these properties from the structure alone. This contradicts the claim that the algorithm can be easily adapted to all other metals since it requires to develop the scoring criteria for each metal instead of just changing the dataset. In fact, it is not clear how the current approach can easily be extended to other metals with high coordination numbers and a wider and less specific spectrum of binding partners (including e.g. binding to amino acid back bones etc.). Therefore, the title should reflect the current specialization for zinc and the abstract and other parts of the text should be adapted accordingly. + +<|ref|>text<|/ref|><|det|>[[148, 853, 942, 899]]<|/det|> +Thank you for raising this important point about the original algorithm's generality to be applied to metals other than zinc. In the first version of the paper, the algorithm was designed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 943, 218]]<|/det|> +specifically based on the properties unique to zinc, which limited its application to other metals. According to the reviewer's comments, we have revised the algorithm and dataset to account for transition metals other than zinc. To improve the clarity of our description in terms of scope, we have updated the title, abstract, introduction and other parts of the manuscript to account for only transition metals. + +<|ref|>text<|/ref|><|det|>[[147, 227, 944, 609]]<|/det|> +The original version of the PMM algorithm indeed considered only the case of zinc in tetrahedral geometry, hardcoding the properties of existing zinc sites into the algorithm (taking HC residues as primary and ED as secondary target and using specific classifications and adapted workflows for 2-, 3- respectively 4- fold coordinated zinc sites). This is suitable for metals like zinc and copper, which predominantly coordinate with sulfur atoms of cysteine or nitrogen atoms of histidine. However, other transition metals like manganese, iron, cobalt, and nickel, which are mainly coordinated by carboxyl oxygen atoms and nitrogen atoms in histidine (Fig. S8), the use of solely CH ligands would significantly lower the recall rate if the initial step of the PMM algorithm does not consider E and D amino acids as ligands. To this end, we have revised the PMM algorithm to include EDH ligands as an additional criterion. The use of EDH ligands is typically correlated with six- coordinated octahedral metal binding sites that represent not only the predominant coordination geometry for transition metals other than zinc and copper, but also a minor fraction of coordination geometry for zinc and copper sites. Therefore, the inclusion of EDH strategy as part of the updated PMM algorithm signifies its applicability to all transition metals. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[186, 88, 945, 412]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 420, 941, 472]]<|/det|> +
Supplementary Figure 8. Distribution of transition metal coordination motifs. CH0, CH1, CH2, CH3, and CH4 represent combinations of metal coordination sites where ligands contain 0, 1, 2, 3, 4 C and/or H ligands; "Unclassified" denotes other uncategorized ligand combinations.
+ +<|ref|>text<|/ref|><|det|>[[147, 496, 943, 682]]<|/det|> +In the updated PMM system, we employ customized methods to predict transition metal binding sites based on different coordination geometries. For tetrahedral coordination, the algorithm uses a CH- based approach, focusing on combinations of C and H residues, while for octahedral coordination, the EDH- based approach is applied, considering E, D, and H residues. This strategy, tailored to specific coordination geometries and supported by dedicated training datasets, significantly enhances the accuracy of identifying metal binding sites. The detailed concepts and methods are described thoroughly in the Methods section 4.1.1. + +<|ref|>text<|/ref|><|det|>[[147, 691, 944, 905]]<|/det|> +The PMM algorithm is currently trained only on common transition metal binding sites, relying on CH (tetrahedral) and EDH (octahedral) geometries to predict transition metal sites. In macromolecular structures with biological functions, distinguishing and identifying different transition metals is crucial. These metals play specific roles in biological systems, such as participating in catalytic reactions, regulating physiological processes, and maintaining structural stability. Accurately identifying transition metals can enhance our understanding of their biological functions and their impact on health and disease, thus guiding drug development and biotechnology. However, alkali and alkaline- earth metals present challenges for accurate predictions due to their + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 943, 219]]<|/det|> +simpler chemical properties (such as fixed \(+1\) or \(+2\) oxidation states), weaker ligand binding capacities, and greater mobility. These elements primarily bind to ligands through weaker ionic interactions, and their coordination structures are more flexible. Therefore, specialized algorithms needed to address these unique characteristics effectively and predict binding sites for alkali and alkaline- earth metals are beyond the scope of this study. + +<|ref|>sub_title<|/ref|><|det|>[[157, 249, 634, 267]]<|/det|> +## 2. Clarifications about the workflow in the case of zinc: + +<|ref|>text<|/ref|><|det|>[[147, 286, 941, 332]]<|/det|> +(1). Do the authors use the asymmetric unit or the biological assembly? Since zinc ions are often located at crystal interfaces, this is an important difference. + +<|ref|>text<|/ref|><|det|>[[147, 349, 942, 423]]<|/det|> +In our study, we used the asymmetric unit structures (.ent files) downloaded from the PDB database. These files are obtained directly from crystallographic experiments and represent the asymmetric unit. + +<|ref|>text<|/ref|><|det|>[[147, 432, 943, 562]]<|/det|> +We recognize that zinc ions are often located at crystal interfaces. To identify metal binding sites located at these interfaces, we incorporated a step in our updated PMM algorithm where we apply symmetry operations to the asymmetric unit using the CCP4 contact tool during data processing. This allows us to identify metal binding sites that may exist at the interfaces between asymmetric units. + +<|ref|>text<|/ref|><|det|>[[147, 572, 943, 729]]<|/det|> +We chose not to use the biological assembly directly because, for structures with multiple biological assemblies, the use of all biological assemblies would introduce additional redundancy, while the use of only the first biological assembly could result in not considering some metal binding sites, as not all metal sites may be present in the first biological assembly. By applying symmetry operations to the asymmetric unit, we can assure that we identify all potential metal binding sites with full completeness and no redundancy. + +<|ref|>sub_title<|/ref|><|det|>[[147, 746, 941, 791]]<|/det|> +## (2). L.243: it is unclear how the auxiliary ED criterion works. ED is also not present in Figure 1. + +<|ref|>text<|/ref|><|det|>[[147, 808, 943, 910]]<|/det|> +We apologize for any confusion. In the initial version of the PMM algorithm, the ED criterion was not used in predicting zinc binding sites and was only applied after prediction. We have revised the PMM algorithm to include an EDH criterion, mainly to predict transition metals other than zinc. However, we found that the application of EDH criterion on top of CH algorithm also improves + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 942, 163]]<|/det|> +the recall rate for the prediction of zinc binding sites. Therefore, PMM uses a CH ligand- based algorithm for tetrahedral coordination structures and an EDH algorithm for octahedral coordination structures. + +<|ref|>text<|/ref|><|det|>[[147, 173, 944, 388]]<|/det|> +To present a realistic coordination scenario, the auxiliary ED criterion is recognized in the displayed metal site structures on the webpage include ligands within a \(4\mathrm{\AA}\) radius after the predictions are made. The webpage show all ligands that bind to metals, which may also involve amino acids other than CHED residues or small molecules. For example, the structure of metallopeptidase (PDB code: 2qvp) contains a CH site (B498) coordinated by two histidine residues, and after predicting the metal ion position, a third and fourth coordinating ligand—glutamate and water—were also identified (Fig. S6). A clearer methodology explanation is provided in Section 4.1 Concept and strategy of the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[331, 396, 790, 640]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 656, 944, 765]]<|/det|> +Supplementary Figure 6. The prediction results for the B chain of 2qvp on the PMM web server are shown. In this structure, the CH algorithm predicts a tetrahedral magnesium binding site at B498, where PMM identifies additional ligands—glutamate and water—beyond C and H at this site. Non- experimental sites: metal binding sites with unknown functions predicted by PMM. The coloring of ligands at metal binding sites is as follows: green represents the initially identified ligands (C or H ligands in the CH algorithm, and E, D, or H ligands in the EDH algorithm), while gray indicates other ligands identified within a \(4\mathrm{\AA}\) radius of the metal coordinates after their determination. + +<|ref|>sub_title<|/ref|><|det|>[[188, 790, 571, 808]]<|/det|> +## (3). Why was a cutoff of 0.5 used in the end? + +<|ref|>text<|/ref|><|det|>[[147, 825, 943, 898]]<|/det|> +Thank you for the question that led to the screening of the optimal cutoff for certainty score to achieve a balance between sensitivity and specificity. The certainty score ranges from 0 to 1, and the cutoff of 0.5 is chosen using different strategies depending on the coordination number of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 868, 109]]<|/det|> +metal binding sites being low- coordination sites (LCS) or high- coordination sites (HCS). + +<|ref|>text<|/ref|><|det|>[[147, 117, 944, 275]]<|/det|> +For low- coordination sites, the cutoff of 0.5 is chosen to achieve the optimal performance metrics (Recall, Precision, F1- Score, and Accuracy) on the test dataset across different thresholds (Table S3). Candidates with a score greater than 0.5 are considered verified sites. At this threshold, the F1- Score for CH sites is 0.924, with high precision (0.958) and recall (0.893), resulting in an overall accuracy of 0.941. For EDH sites, the F1- Score at 0.5 is 0.848, with no improvement at a threshold of 0.55. + +<|ref|>text<|/ref|><|det|>[[147, 283, 944, 415]]<|/det|> +For high- coordination sites, we calculate the similarity between predicted binding sites and the standard curve (representing known metal binding site characteristics) using Pearson correlation coefficients. The cutoff of 0.5 was chosen because it indicates a moderate to strong positive correlation, suggesting that the predicted metal binding sites are similar to known binding features (Fig. S2). + +<|ref|>sub_title<|/ref|><|det|>[[188, 430, 598, 449]]<|/det|> +## (4). L.553: Please describe the scoring function. + +<|ref|>text<|/ref|><|det|>[[147, 464, 944, 650]]<|/det|> +Thank you for your inquiry about the scoring function. The scoring function evaluates the deviation of each point on the circle from the expected Zn- Sγ- Cβ angle of \(109^{\circ}\) . Specifically, the final Zn coordinate (f1\*) is determined by summing the deviations of the angles between two sets of coordinates (f1a1c1 and f1b1d1) from this expected angle. The position with the minimum score is selected as the optimal Zn location, ensuring that the identified Zn position closely aligns with the ideal geometric configuration. Further details can be found in section 4.2.3, "Determination of Metal Ion Location," particularly in the (a) C2 sites coordinate prediction subsection. + +<|ref|>equation<|/ref|><|det|>[[290, 657, 795, 689]]<|/det|> +\[\mathrm{f_{1}^{*} = \arg \min_{f_{1}}\left(|\theta_{\mathrm{f_{1a1c1}}} - 109^{\circ}| + |\theta_{\mathrm{f_{1b1d1}}} - 109^{\circ}|\right)} \quad (7)\] + +<|ref|>text<|/ref|><|det|>[[147, 703, 942, 806]]<|/det|> +(5). The algorithm only detects 2-, 3-, or 4-fold coordinated sites. What about 5- and 6- fold coordination that can be fairly abundant, especially for catalytically active sites, with varying percentages cited in the literature of up to \(30\%\) for 5- fold and roughly \(10\%\) for 6- fold. + +<|ref|>text<|/ref|><|det|>[[147, 821, 942, 895]]<|/det|> +Thank you for pointing out that 5- and 6- fold coordination that can be fairly abundant. We have updated our PMM algorithm to be compatible with octahedral geometry and include 5- and 6- fold coordinated sites (details in 4.1.2). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 90, 940, 135]]<|/det|> +## (6). Several of the coordination spheres may contain one or even several water molecules. How are these handled? + +<|ref|>text<|/ref|><|det|>[[147, 152, 942, 281]]<|/det|> +Water molecules are excluded during the feature summarization and prediction processes. This exclusion applies to the calculation of hydrophobicity values and any other subsequently added chemical feature parameters. However, after the site prediction, water molecules are included when completing the site ligands within a \(4\mathrm{\AA}\) distance, where they are presented as ligands. + +<|ref|>text<|/ref|><|det|>[[147, 298, 943, 456]]<|/det|> +(7). The authors claim that they developed a hybrid algorithm based on geometric, physicochemical as well as ML selection but it seems that the primary selection of all zinc sites is based solely on amino acid type (HC&DE) plus geometric (and solvation) considerations. Only in the case of 2-fold 'regulatory' sites, do the authors also invoke an ensemble method with different ML models. Is there any ML part in the detection of the 3- and 4-fold coordinated sites? What is the additional impact of the ML model? + +<|ref|>text<|/ref|><|det|>[[147, 472, 943, 601]]<|/det|> +Thank you for your question. In identifying 3- and 4- fold coordinated sites (i.e., high- coordination tetrahedral sites), we did not employ machine learning methods. Instead, we employed the Pearson correlation coefficient to evaluate the similarity of hydrophobic features between predicted and experimentally determined binding sites to determine if a site is a metal binding site. + +<|ref|>text<|/ref|><|det|>[[147, 610, 943, 712]]<|/det|> +The hybrid algorithm of PMM involves three key steps. First, geometric and physicochemical properties are used to predict candidate metal binding sites. Next, the predicted sites are validated to determine whether they are metal binding sites. Finally, after confirming that a site is indeed a metal binding site, the type of metal that is most likely to bind at the site is determined. + +<|ref|>text<|/ref|><|det|>[[147, 722, 943, 907]]<|/det|> +ML is used in the second and the third steps. In the second step, for low- coordination sites (2 ligands in CH and 2 or 3 ligands in EDH), two ensemble learning models are invoked, one for CH- based tetrahedral algorithm and the other for EDH- based octahedral algorithm. In the third step of characterizing the type of metal, a classification ensemble learning model is invoked using additional chemical parameters. The use of multiple ML models in different steps of the metal localization and identity prediction process constitutes a hybrid learning system. We have formulated the concept as an introductory "Concept and Strategy" section for additional clarity + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 319, 107]]<|/det|> +(see details in 4.1.2). + +<|ref|>text<|/ref|><|det|>[[187, 117, 552, 135]]<|/det|> +The additional impact of the ML models are: + +<|ref|>text<|/ref|><|det|>[[147, 145, 943, 275]]<|/det|> +a. For the Low-coordination sites in the second step, relying solely on hydrophobicity curves may not yield accurate predictions due to having fewer ligands, exhibiting more flexible and irregular geometries, resulting in less distinct hydrophobic patterns. Using ensemble learning models can enhance the predictive accuracy for low-coordinate sites by incorporating additional geometric features, such as ligand distances and ligand-metal angle. + +<|ref|>text<|/ref|><|det|>[[147, 284, 944, 496]]<|/det|> +b. For the High-coordination sites in the second step, the certainty score is derived by calculating Pearson correlation coefficients between the predicted sites and experimental data for C and \(\Delta \sigma\) value curves. The increase in coordination number enhances geometric stability and makes hydrophobic patterns more pronounced, achieving high predictive accuracy without reliance on machine learning algorithms. As the number of ligands increases in high-coordination sites, the combinations of geometric features grow exponentially, complicating the feature space and posing challenges for machine learning model training. This complexity may lead to redundancy and an increased risk of overfitting. + +<|ref|>text<|/ref|><|det|>[[147, 506, 944, 664]]<|/det|> +c. For characterization of different type of metal in the third step, the use of classification ensemble learning model ensure the consideration of a multitude of relevant parameters to differentiate the metal type. These parameters include a hydrophobicity profile and seven chemical features, along with the 27 features implemented in the NEIGHBORHOOD database (Table S9). The seven chemical features include aromaticity, hydrophobicity, positive ionizable, negative ionizable, hydrogen bond donor, hydrogen bond acceptor, and MBS chain (see details in 4.2.7). + +<|ref|>sub_title<|/ref|><|det|>[[149, 694, 456, 711]]<|/det|> +## 3. Comparison with other methods: + +<|ref|>text<|/ref|><|det|>[[147, 730, 942, 805]]<|/det|> +(1). The restriction to HD sites that PinMyMetal (PMM) is based on, can be restrictive, in fact some well-defined Zn sites cannot be located (e.g. in 4HTM). These limitations should be discussed. + +<|ref|>text<|/ref|><|det|>[[148, 822, 942, 895]]<|/det|> +Thank you for pointing out the problem, which led to an improved design in experiment, algorithm, and interface. As mentioned in the response to Comment 1, in the step of predicting potential metal binding sites using geometric constraints, we have added the EDH combination in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 943, 164]]<|/det|> +addition to the previous CH combinations. This update allows for the prediction of sites that do not contain C or H but are coordinated by two or more ED ligands. With the updated algorithm, zinc sites in 4HTM that are coordinated solely by two ED ligands can now be predicted. + +<|ref|>image<|/ref|><|det|>[[375, 175, 710, 364]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[146, 383, 949, 682]]<|/det|> +(2). While comparing accuracy differences in metal ion detection (in terms of predicted versus experimental position), the (in)accuracy of the experimental structures should be kept in mind. In fact, is the difference in accuracy between Metal3D \(0.52\pm 0.45\mathrm{A}\) and PMM \(0.257\pm ?\) (standard deviation should be given!), statistically significant considering the fact that typical x- ray structures with 1.5- 3A resolution have typical average atomic coordinate errors of the order of \(0.2 - 0.6\mathrm{A}\) (according to the DPI database http://pranag.physics.iisc.ac.in/dpi_db/ using e.g. the Luzzati equation) and this does not even take low- resolution cryo- EM structures into account. Some illustrative examples of pdb structures that the authors discuss in the text: 1bc2 (resolution 1.9A): average positional error \(0.25 - 0.29\mathrm{A}\) , estimated accuracy for the zinc positions 0.17- 0.23A or, an extreme case, 1thj (resolution 2.8A), experimental uncertainty for zinc positions 1.28- 1.32A. + +<|ref|>text<|/ref|><|det|>[[147, 696, 944, 826]]<|/det|> +Thank you for pointing out the need to provide the standard deviation for the accuracy of PMM predictions compared to experimental positions. We have now included the standard deviation for PMM. For example, in the CH- based method, Zn shows the highest prediction accuracy, with a mean deviation of \(0.279\pm 0.29\mathrm{\AA}\) . Detailed information can be found in Section 2.1 of the results. + +<|ref|>text<|/ref|><|det|>[[147, 835, 943, 910]]<|/det|> +The reviewer has also raised a very good point regarding the impact of experimental structure inaccuracies on the comparison of predicted metal ion positions. It is important to pay attention to the distinction between absolute accuracy and relative accuracy when evaluating the precision of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 942, 164]]<|/det|> +predicted metal coordinates. In low- resolution structures, even if both the ligand and metal ion positions are subject to error, as long as the predicted relative position of the metal ion with respect to the ligand is accurate, this relative accuracy remains valuable in practical applications. + +<|ref|>sub_title<|/ref|><|det|>[[148, 194, 473, 212]]<|/det|> +## 4. Explicit comparison with Metal3D: + +<|ref|>text<|/ref|><|det|>[[148, 231, 940, 277]]<|/det|> +Thank you for your detailed review and valuable feedback on our work. We apologize for any confusion caused by our oversight. + +<|ref|>text<|/ref|><|det|>[[147, 293, 942, 367]]<|/det|> +(1). For a fair comparison, the same data should be tested. Why are there 205 zinc sites for PMM and 189 for Metal3D? The number for the transition metal test cases also do not match. + +<|ref|>text<|/ref|><|det|>[[147, 384, 943, 514]]<|/det|> +We acknowledge that our initial data did not use the first biological assembly files provided in the Metal3D paper, but rather used .ent files directly obtained from the PDB database, which correspond to the asymmetric unit structures and possess 205 zinc sites. We have corrected this issue by now using the first biological assembly files as specified in the Metal3D paper. This adjustment ensures a fair comparison between the two methods. + +<|ref|>text<|/ref|><|det|>[[147, 523, 944, 708]]<|/det|> +Additionally, upon analyzing the Metal3D dataset, we identified redundancies and errors among the 189 reported zinc binding sites, primarily due to Biopython's recognition process. For instance, multiple conformations in structures such as 2akf were counted as separate sites, and misidentified sites were observed in cases like 3q1d and 4a7k. Furthermore, free metal ions were mistakenly recognized as binding sites (e.g., A402 in 4199 and B4 in 3e7l), and site 381 in 2a0s was identified due to crystal symmetry (Fig. S4). After removal of these sites, we identified 178 valid metal binding sites in the Metal3D dataset. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[295, 82, 830, 318]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 327, 943, 548]]<|/det|> +
Supplementary Figure 4. Examples of redundant or incorrect metal binding site identifications in Metal3D. The figure shows examples where Metal3D misidentified or duplicated metal binding sites. Metal3D, a recently developed metal site prediction tool based on 3D convolutional neural networks, is currently the most accurate predictor of metal ion positions. The dataset reported in Metal3D includes 189 zinc binding sites from 59 structures, none of which overlap with the training set used by PMM. However, since Metal3D uses Biopython to retrieve metal sites, some redundancies and errors were identified among the 189 sites. After removing these redundant and erroneous sites, 178 valid zinc binding sites remained. a, In 2akf, multiple conformations (A1, B3, B4) were treated as separate sites. b, In 3q1d, two actual zinc sites (A20, A202) were counted as four. c, In 4a7k, three sites (A950, A951, A952) were recognized as six. d, e, Free metal ions, such as A402 in 4l99 and B4 in 3e7l, were incorrectly labeled as binding sites—each with only one ligand within 5 Å, which are not listed as metal binding in LINK, positioned too far from the zinc. f, In 2a0s, B381 was generated due to crystal symmetry. The magenta sticks represent ligand amino acids coordinating the metal ions. These errors were removed in the final dataset.
+ +<|ref|>text<|/ref|><|det|>[[147, 560, 943, 690]]<|/det|> +(2). The values for TP, FP and FN for Metal3D that the authors cite in Suppl. Table S5 (and that are used to calculated Precision and Recall values that are discussed in the main text) are not correct. In fact, the cited numbers 78, 47, 111 for TP, FP and FN refer to Metal1D results (also given in the Metal3D paper) while the results for Metal3D (with the recommended probability threshold of \(p = 0.75\) ) are 85, 9, 104. + +<|ref|>text<|/ref|><|det|>[[147, 705, 943, 780]]<|/det|> +This issue was due to an oversight on our part when referencing the Metal3D paper, as we inadvertently used incorrect data. The revised data and analysis results have been incorporated into the revised manuscript, specifically in Table S5 and in the third paragraph of Section 2.5. + +<|ref|>text<|/ref|><|det|>[[147, 795, 943, 899]]<|/det|> +(3). 'However, Metal3D predicts two additional zinc locations in the same structure, where no electron density is observed, indicating a higher rate of false positive hits of Metal3D when compared with PMM': The additional sites predicted with Metal3D have much lower probability ( \(p = 0.5\) ) than the C4 sites in the structure. The probability of 0.5 is + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 89, 941, 137]]<|/det|> +## below the recommended probability threshold of Metal3D of 0.75 so these predictions should not be categorized as false positives by the authors. + +<|ref|>text<|/ref|><|det|>[[147, 152, 943, 283]]<|/det|> +Regarding the additional zinc sites predicted by Metal3D and their false positive rate, we acknowledge that the predicted sites with a probability of \(\mathrm{p = 0.5}\) are below the Metal3D- recommended threshold of \(\mathrm{p = 0.75}\) . Therefore, these predictions should not be classified as false positives. We have updated the relevant analysis in the revised manuscript and corrected this misunderstanding, specifically in Figures 3d and 3e, as well as in the last paragraph of Section 2.5. + +<|ref|>text<|/ref|><|det|>[[146, 298, 944, 483]]<|/det|> +(4). L. 519: 'While Metal3D uses 5Å to determine the presence of occupancy redundancy, we disagree with their threshold since the dinuclear zinc binding site would be mislabeled in Metal3D (Fig. S7b)': It would be good to discuss this better. Metal3D does not mislabel such sites since the predicted density correctly contains both binding sites. However, the current placement algorithm might sometimes not be able to place two separate zincs into the predicted density. In fact for the given example 6jkw, Metal3D does correctly predict and place two zinc ions. + +<|ref|>text<|/ref|><|det|>[[147, 498, 944, 656]]<|/det|> +Regarding the 5Å threshold used by Metal3D and the labeling of dinuclear zinc binding sites, we have confirmed that Metal3D correctly predicts and places the dinuclear zinc ions in the example of 6jkw. Our statement that "the dinuclear zinc binding site would be mislabeled in Metal3D" was incorrect. We have revised the discussion on this issue and updated the figure to Fig S12. In Section 4.2.4, we have included an explanation of how Metal3D handles such sites to avoid confusion. + +<|ref|>text<|/ref|><|det|>[[147, 672, 943, 775]]<|/det|> +(5). Comparison of timings: deep learning networks like Metal3D that are trained on GPUs are very slow on 1 or 2 CPU cores. Metal3D surely is slower than PMM but for a fair comparison it should be stated that GPU acceleration is available. It should also be mentioned on what hardware the timing for PMM is computed. + +<|ref|>text<|/ref|><|det|>[[147, 791, 943, 894]]<|/det|> +Regarding the comparison of performance timings, we acknowledge that failure to mention the availability of GPU acceleration for Metal3D may lead to misunderstandings. We have removed the specific timing comparisons with Metal3D from the manuscript, retaining only a general comparison of run times in Table 1, with a note indicating that the Metal3D predictor benefits from + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 460, 107]]<|/det|> +GPU acceleration during its operation. + +<|ref|>text<|/ref|><|det|>[[147, 117, 944, 275]]<|/det|> +In a virtual machine configured with an AMD EPYC 7551 CPU (32 cores, 1 thread per core, approximately 2000 MHz base clock, 8 MB L3 cache, and a total of 64 CPUs), the PMM predictor took 23 seconds to run the 2zp9 structure (a complex consisting of 6 chains of 81 amino acids and 9 chains of 53 amino acids), while Metal3D required 5 minutes and 51 seconds. For the 2y42 structure (comprising four chains of 350 amino acids), PMM took 28 seconds, whereas Metal3D took 13 minutes and 45 seconds. + +<|ref|>text<|/ref|><|det|>[[148, 284, 943, 359]]<|/det|> +Additionally, PMM provides a web service hosted on a Tencent Cloud server. The resource configuration of the Tencent Cloud server differs from that of the local virtual machine, particularly regarding core count and performance, which may impact the run times of the different predictors. + +<|ref|>sub_title<|/ref|><|det|>[[148, 389, 333, 406]]<|/det|> +## 5. Minor corrections: + +<|ref|>text<|/ref|><|det|>[[188, 425, 509, 444]]<|/det|> +-Typo "check my metal" in Figure 6. + +<|ref|>text<|/ref|><|det|>[[188, 460, 904, 479]]<|/det|> +-It would be nice if the webserver would show the certainty score in the webviewer. + +<|ref|>text<|/ref|><|det|>[[148, 495, 942, 541]]<|/det|> +-The standard deviations should be reported for all means (as required by Nature Comm.). + +<|ref|>text<|/ref|><|det|>[[148, 558, 942, 603]]<|/det|> +-In 1.280 the standard deviation for Metal3D is reported using just a plus sign, should be ±. + +<|ref|>text<|/ref|><|det|>[[188, 620, 460, 639]]<|/det|> +-Figure 4: 2z9p should be 2zp9. + +<|ref|>text<|/ref|><|det|>[[148, 658, 941, 703]]<|/det|> +Thank you for pointing out these minor corrections. We have made the following adjustments based on your feedback: + +<|ref|>text<|/ref|><|det|>[[187, 722, 715, 741]]<|/det|> +Corrected the typo "check my metal" in Figure 6 (now Figure 5). + +<|ref|>text<|/ref|><|det|>[[188, 759, 748, 777]]<|/det|> +Added the certainty score display in the webviewer of the webserver. + +<|ref|>text<|/ref|><|det|>[[148, 796, 941, 841]]<|/det|> +Reported the standard deviations for PMM, in accordance with the requirements of Nature Comm. + +<|ref|>text<|/ref|><|det|>[[148, 861, 943, 907]]<|/det|> +We have removed the line regarding the standard deviation for Metal3D in the new version of the manuscript. Instead, we have included the standard deviation in the Deviation (A) column of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 567, 108]]<|/det|> +Table S5, using the correct symbol \(\pm\) to represent it. + +<|ref|>text<|/ref|><|det|>[[186, 126, 755, 145]]<|/det|> +Corrected the label in Figure 4 (now Figure 3) from "2z9p" to "2zp9." + +<|ref|>text<|/ref|><|det|>[[148, 164, 941, 210]]<|/det|> +We appreciate your attention to detail, and these changes have been incorporated into the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 240, 531, 258]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>sub_title<|/ref|><|det|>[[148, 290, 410, 307]]<|/det|> +## 6. Software&data availability: + +<|ref|>text<|/ref|><|det|>[[147, 326, 942, 457]]<|/det|> +- Nature Communications requires authors to deposit all data. Authors should therefore make available all predicted locations for the reported structures. In case, the authors only used the asymmetric units, the results should be rerun for the biological assemblies. This also concerns the deposited data for Figure 4. The supplementary data (e.g figure4a.csv) only contains aggregated numbers. + +<|ref|>text<|/ref|><|det|>[[147, 473, 943, 630]]<|/det|> +Thank you for your suggestions. We have ensured that detailed prediction data is provided for all reported structures. Additionally, in the section evaluating PMM prediction accuracy using the Metal3D test set, we reran the results using the biological assemblies. We have updated the deposited data for Figure 4 (now Figure 3 in the revised manuscript), providing more detailed information, including the prediction results for each metal site in the structures, rather than just aggregated data. + +<|ref|>text<|/ref|><|det|>[[147, 646, 944, 888]]<|/det|> +- It is great that the code of the standalone tool is available and it seems the authors have already made some improvements judging by recent commit history. We tried installing the program on 13.3.2024 in a fresh Debian bookworm Docker container but still some packages were missing and there are errors in the log file produced such as "KeyError: 'None of [0] are in the columns'. No predictions are output currently. Some paths also seem hardcoded inside the program e.g the name of the input file if providing PDB input). It would be advisable to make available an apptainer or a Docker container with all requirements already installed in the correct version. Especially so since postgresql is used which normally cannot be installed by users in normal computing environments such as HPC machines because users + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 90, 472, 108]]<|/det|> +## lack root privileges to run e.g apt-get. + +<|ref|>text<|/ref|><|det|>[[148, 124, 942, 199]]<|/det|> +We appreciate your detailed feedback. Building an Apptainer or Docker container that includes PostgreSQL is a reasonable solution. However, constructing and deploying such a container involves certain technical complexities, including: + +<|ref|>text<|/ref|><|det|>[[148, 208, 942, 283]]<|/det|> +Database Configuration: PostgreSQL has numerous configuration options, such as memory management, connection limits, and concurrency handling. Ensuring that PostgreSQL operates effectively across different environments requires additional setup. + +<|ref|>text<|/ref|><|det|>[[148, 292, 942, 365]]<|/det|> +Data Persistence: Running a database in a container necessitates managing persistent storage to ensure that data is retained even if the container is restarted or removed. This typically involves managing and configuring external volumes for secure data storage. + +<|ref|>text<|/ref|><|det|>[[148, 374, 942, 448]]<|/det|> +Network Configuration: Correctly handling network requests within the container, including external access and communication with other containers, may require port mapping and network settings to allow users seamless access to the database. + +<|ref|>text<|/ref|><|det|>[[148, 457, 942, 532]]<|/det|> +Performance Optimization: Performance tuning for different environments may require adjustments based on available resources to ensure PostgreSQL runs efficiently in a containerized setting. + +<|ref|>text<|/ref|><|det|>[[148, 541, 942, 588]]<|/det|> +Security: Special attention must be paid to database security settings to ensure proper access controls and authentication mechanisms are in place to mitigate potential security risks. + +<|ref|>text<|/ref|><|det|>[[148, 596, 942, 699]]<|/det|> +The current version manages all dependencies except PostgreSQL through Conda and provides an environment.yml file to facilitate code execution in supported environments. For users unable to run PostgreSQL locally, while we cannot guarantee complete code execution, predictions can be performed via the provided web service. + +<|ref|>text<|/ref|><|det|>[[148, 708, 942, 782]]<|/det|> +We will consider exploring the option of providing a container with PostgreSQL in future versions. Regarding the errors in the log files during operation, due to updates in the PMM algorithm, the corresponding code has been revised and re- tested to ensure proper functionality. + +<|ref|>text<|/ref|><|det|>[[148, 798, 942, 872]]<|/det|> +-The xlsx supplementary files contain PDB names formatted as scientific numbers e.g 2E26 is formatted as \(2^{*}10^{*}26\) . Please use plaintext csv like for some of the other supplementary files. + +<|ref|>text<|/ref|><|det|>[[186, 888, 940, 907]]<|/det|> +Thank you for your suggestion. We have converted all XLSX files in the supplementary + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 941, 135]]<|/det|> +materials to plain text CSV format to ensure that the data is displayed correctly and is not affected by data type errors. + +<|ref|>text<|/ref|><|det|>[[147, 151, 941, 198]]<|/det|> +-The source files of some plot scripts are also not available. E.g figure1.R contains a reference to transition_metal_type.csv that is not in the supplementary folder. + +<|ref|>text<|/ref|><|det|>[[147, 217, 942, 290]]<|/det|> +Thank you for pointing out this issue. We have reviewed and included all missing files, and we have modified and tested the plotting scripts to ensure that they run correctly and generate the relevant result data. + +<|ref|>text<|/ref|><|det|>[[148, 321, 480, 339]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 358, 942, 431]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[398, 102, 737, 122]]<|/det|> +## Response to reviewers' comments + +<|ref|>text<|/ref|><|det|>[[149, 157, 495, 174]]<|/det|> +Reviewer #1's comments and responses: + +<|ref|>text<|/ref|><|det|>[[186, 194, 850, 211]]<|/det|> +The revised manuscript addresses the comments made in my original review. + +<|ref|>text<|/ref|><|det|>[[149, 242, 495, 260]]<|/det|> +Reviewer #2's comments and responses: + +<|ref|>text<|/ref|><|det|>[[148, 280, 943, 354]]<|/det|> +The revised version of the manuscript has clearly improved and most of the issues that we have raised have now been answered satisfactorily. However, there are few points that should be further clarified: + +<|ref|>text<|/ref|><|det|>[[147, 372, 944, 530]]<|/det|> +1. The authors have now better defined the scope of the paper and even extended it from a zinc-only predictor restricted to HC-based tetrahedral sites to a general predictor for transition metal ions including also octahedral sites with EDH motif. The scope of the paper is now correctly reflected in the title as well as in the abstract of the paper. However, the introduction still makes some claims about possible extensions to alkali and alkaline earth metal ions that seem not justified: + +<|ref|>text<|/ref|><|det|>[[147, 539, 944, 668]]<|/det|> +'Extending PMM to include alkali and alkaline earth metals requires the use of carboxyl side chains from Glutamic acid and Aspartic acid (ED) as the primary measure, and hydroxyl side chains from Serine and Threonine (ST) as the auxiliary measures, along with new feature descriptors to account for their unique coordination properties, and a corresponding training set.' + +<|ref|>text<|/ref|><|det|>[[147, 678, 943, 781]]<|/det|> +This statement is not correct because an extension to alkaline earth ions also requires the inclusion of protein backbone oxygens as binding sites, which does not seem straightforward in the sidechain-based approach that PMM uses. It would be best if the authors remove this paragraph and do not make any claims beyond the defined scope. + +<|ref|>text<|/ref|><|det|>[[148, 808, 943, 910]]<|/det|> +Thank you for your insightful feedback. As per your suggestion, we have removed the statement in the introduction regarding the extension of PMM to alkali and alkaline earth metals. The revised text now focuses solely on the scope of the current study, ensuring accuracy and consistency throughout the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 942, 192]]<|/det|> +2. In the methods section the authors also cite a reference stating 'that for less than \(1\%\) of all metal ions coordination with mainchain is observed'. However, the quoted paper only describes zinc proteins. Many alkaline earth binding sites include main chain coordination (e.g the EF-hand motif for calcium). + +<|ref|>text<|/ref|><|det|>[[147, 218, 944, 350]]<|/det|> +Thank you for your comment. We have revised the content accordingly. "The CHED residues are the most common ligands for transition metal ions. In contrast, donor atoms from other amino acids, such as mainchain oxygen, serine, threonine, or lysine, are much less frequent and account for only a small fraction of transition metal-ligand interactions (Section 4.1.1)." We have also updated the citation to reflect this distinction appropriately. + +<|ref|>text<|/ref|><|det|>[[147, 376, 942, 450]]<|/det|> +3. The answer of the authors to the issue we raised about the significance of the accuracy differences between various metal ion location predictors in view of the typical uncertainties in the experimental protein structures seems unclear: + +<|ref|>text<|/ref|><|det|>[[147, 459, 944, 590]]<|/det|> +'It is important to pay attention to the distinction between absolute accuracy and relative accuracy when evaluating the precision of predicted metal coordinates. In low-resolution structures, even if both the ligand and metal ion positions are subject to error, as long as the predicted relative position of the metal ion with respect to the ligand is accurate, this relative accuracy remains valuable in practical applications.' + +<|ref|>text<|/ref|><|det|>[[147, 598, 944, 757]]<|/det|> +Do the authors want to say that relative accuracies might be better than absolute ones? But if the experimental position uncertainty is sigma, the uncertainty for the distance d between two atoms A and B is according to error propagation \(\mathrm{Sqr}(2)*\mathrm{sigma}\) . Since the location accuracy is measured as deviation from the experimental position and typical positional uncertainties in protein structures are easily 0.1- 0.2A, performance differences in the hundredths of angstrom seem hardly significant. + +<|ref|>text<|/ref|><|det|>[[147, 784, 942, 858]]<|/det|> +Thank you for your valuable feedback. We agree that typical positional uncertainties in protein structures are around 0.1- 0.2 Å, and performance differences in the hundredths of an angstrom may not be statistically significant when considering experimental error margins. + +<|ref|>text<|/ref|><|det|>[[148, 867, 942, 913]]<|/det|> +As a result, we have updated the Section 3.3 Innovation and validation of the PMM algorithm to reflect this point, acknowledging that: "However, it is important to consider the inherent + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 943, 219]]<|/det|> +uncertainties in experimental structures when interpreting these results. Typical positional uncertainties in protein structures range from 0.1- 0.2 Å, and metal location accuracy is measured as the deviation from these experimental positions. Given this, performance differences in the hundredths of an angstrom may not be statistically significant, especially when accounting for the experimental error margins." + +<|ref|>text<|/ref|><|det|>[[147, 245, 943, 349]]<|/det|> +4. This revised paper contains many new results and the structure is very hard to follow. For example, the new model apparently includes a way to predict the identity of metal ions in 4 different classes. However, this is only described in the discussion section and not in the results. The authors should improve the flow of the paper to make it easier to read. + +<|ref|>text<|/ref|><|det|>[[148, 376, 942, 421]]<|/det|> +Thank you for your constructive feedback on our manuscript. We have made the following revisions to improve its clarity, structure, and readability: + +<|ref|>text<|/ref|><|det|>[[148, 431, 942, 505]]<|/det|> +A new section, 2.4 Identification of metal types, has been added to the Results section, clearly describing the model's ability to predict four different metal types. This analysis was relocated from the original Discussion section to enhance logical flow. + +<|ref|>text<|/ref|><|det|>[[147, 515, 943, 616]]<|/det|> +The previous 3.2 Identifying metal types: the predictive power of PMM section has been streamlined. Results related to the prediction of four metal types are now concisely presented in the revised 3.2. Content unrelated to the section title has been moved to a new section, 3.3 Innovation and validation of the PMM algorithm. + +<|ref|>text<|/ref|><|det|>[[148, 626, 942, 672]]<|/det|> +In 4.1 Concept and strategy, we refined the description of the hybrid learning system, outlining its three- step process: + +<|ref|>text<|/ref|><|det|>[[148, 682, 942, 727]]<|/det|> +Step 1: Geometric constraints are used to predict candidate metal- binding sites (corresponding to 2.1). + +<|ref|>text<|/ref|><|det|>[[147, 737, 947, 810]]<|/det|> +Step 2: Predicted sites are validated to determine whether they are true metal- binding sites, with validation for low- coordination sites (LCS) discussed in 2.2 and high- coordination sites (HCS) in 2.3. + +<|ref|>text<|/ref|><|det|>[[148, 821, 943, 867]]<|/det|> +Step 3: For sites with certainty scores above 0.5, a single ensemble learning model is used to predict the most probable metal type for each site (corresponding to 2.4). + +<|ref|>text<|/ref|><|det|>[[184, 876, 942, 895]]<|/det|> +We also revised the introductory paragraph of the Results section to align with the updated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 891, 108]]<|/det|> +description in 4.1 Concept and Strategy, ensuring a clearer presentation of results and steps. + +<|ref|>text<|/ref|><|det|>[[147, 118, 942, 191]]<|/det|> +Further revisions were made to improve clarity in description and consistency in terminology. More specifically, we enhanced figure legends (Figure 2, Figure 7, and Supplementary Figure 2) and section titles (2.1, 2.7, and 4.2.7), ensuring that they reflect the content more accurately. + +<|ref|>sub_title<|/ref|><|det|>[[148, 222, 531, 240]]<|/det|> +## Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[186, 259, 792, 278]]<|/det|> +5. Regarding code availability and building of a container for the app: + +<|ref|>text<|/ref|><|det|>[[146, 286, 944, 529]]<|/det|> +Exactly because it is difficult to setup PostgreSQL the authors should make it available as a container since there it will always be in the same environment with the same configurations options used by the authors. We tried setting up a local postgresql server and were unsuccessful. Data persistence is not a problem as far as I understand it because the postgresql database is only used to save data for one run. And port forwarding is easily accomplished in the Dockerfile. Especially in a few years from now the authors might have moved institutions etc. and therefore it is likely that the web server no longer works because no support can be provided. This is very common for most web servers in the field that they are unavailable after some point. + +<|ref|>text<|/ref|><|det|>[[147, 556, 944, 712]]<|/det|> +Thank you for your suggestion. We recognize the importance of containerizing PostgreSQL with Docker to ensure consistency in version and configuration, which is crucial for users to replicate the project environment. To this end, we have provided a PostgreSQL database container (from the official Docker image) and a container for running the project code in a Conda environment we built. These two containers are managed through Docker Compose and are seamlessly connected via a shared network. + +<|ref|>text<|/ref|><|det|>[[147, 722, 944, 880]]<|/det|> +Additionally, we support data persistence through Docker Volumes to cater to diverse user requirements. The container ports are clearly mapped, allowing users to access the database service from the host machine directly. We provide comprehensive documentation that guides users on how to directly pull the images or manually build them, and deploy the containers locally, ensuring the project remains accessible and operational in the long term. The relevant instructions have been uploaded to GitHub for user reference and implementation. + +<|ref|>text<|/ref|><|det|>[[183, 890, 941, 908]]<|/det|> +The authors also make a long- term commitment to maintaining the web service using an + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 940, 135]]<|/det|> +institution- independent domain name (i.e., biocloud.top). This will give the authors the possibility to continue maintenance of the PMM web service even after the change of institutions. + +<|ref|>sub_title<|/ref|><|det|>[[148, 166, 480, 184]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 203, 941, 277]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<--- Page Split ---> diff --git a/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/images_list.json b/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/supplementary_0_Peer review file.mmd b/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/supplementary_0_Peer review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a7957d35f65fa84dd7a06ac82d2a4037bed31246 --- /dev/null +++ b/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/supplementary_0_Peer review file.mmd @@ -0,0 +1,263 @@ + +# nature portfolio + +Peer Review File + +Complex regulation of Gephyrin splicing is a determinant of inhibitory postsynaptic diversity + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors combine targeted gene approach and long read sequencing to uncover the GPHN isoforms and their differential functions when interaction with inhibitory Glycine and GABA- A receptors. The study shows the relevance of isoform level studies, and how the combinatorial expression pool of the different isoforms of GPHN affects the inhibitory synapses in the cerebellum during mouse brain development and human tissue. The authors identify + +The study shows the relevance in the isoform level studies instead of gene level focus uncovering a new catalog of GPHN isoforms and unannotated EEJ, with different expression patterns along development and in different tissues. Moreover, some of these different isoforms are translated in different isoform protein with different function and location in inhibitory synapses. The results are validated in vivo and show evidence in human samples. + +It is also interesting to see that all the internal exons from GPHN/Gphn appear as alternative exons. There is some controversy in the field on how to define a constitutive exon, and with more and more data including now the long read technologies is getting more clear that alternative exons are even more abundant than it was thought. Which makes even more difficult to find a truly always constitutive exon. + +## Comments: + +The authors use Gphn targeted approach with PAC- BIO technology to identify all the isoforms on the gene. To validate and compare their sequencing results they authors use a database of published sequencing datasets and find that their approach is able to identify unannotated EEJ. There is currently a quite extensive curated database for EEJ from thousands of datasets, intropolis https://github.com/nellore/intropolis. Mainly in human but also has the mouse version of it in snaptron. It would be interesting to compare to this database and recalculate the number of known and novel EEJ recovered with the Gphn targeted approach. + +There is an updated database of alternative splicing events that uses public datasets, Vast- db https://vastdb.crg.eu/wiki/Main_Page. Authors should compare non annotated EEJ and alternative exon to the database entries. It would be helpful for to provide the new isoforms and EEJ to public repository and/or provide the annotations the be able to expand the catalog of isoforms in future studies. + +<--- Page Split ---> + +The authors mention that Gphn is the first gene with more than 10 exons for which all internal exons can be alternatively spliced. Looking to the isoforms recovered in Fig. S1B seems that for some of the exons are skipped only in 1 out of the 277 isoforms. If the authors look for the expression of those specific isoforms like the case of E2 which is included included in one isoform. Does this isoform have enough coverage on E2 and significant number of EEJ? + +On the other hand, some exons are included in almost all isoforms the case of E36 for instance. How is the expression of those specific isoforms? Do they have enough coverage. I am guessing that isoforms excluding E36 are very low expressed or/and very specific to a celltype or/and tissue. + +Would the authors consider all these very lowly present isoforms as real, leading to a protein or as nuclear noise, or part of the technical limitations of the long- reads technologies, which can lead to noise? Many studies combine bulk sequencing together with long- read to avoid false positives. + +All the processing pipeline of the isoform detection is mentioned in the methods, but it should include more details and include the code used. The authors write is a custom pipeline, for that reason I find it more important that this is included in more detail and with the code used. It should include threshold used to consider a significant EEJ and expression levels thresholds to consider a lowly or highly expressed isoform. + +In Page 4 authors mention Fig.2D while they are referring to Fig.1D. + +In Fig1. F the heatmap shows highly and lowly expressed exons in different celltypes. What is the threshold for defining a high or a low expressed exon? A heatmap showing the actual expression ( as a log) of the exon in each celltype will help to show the real expression differences between celltypes. + +As I have mentioned before, the authors identify 277 different isoforms. Could be that not all the isoforms are truly expressed in any celltype, and isoform level expression heatmap per celltype and developmental stage will help to clarify if all the detected isoforms are true, at least for these celltypes and developmental stages. + +By using a new reference built from the PAC- BIO detected isoforms it would be interesting to look further of the differential isoform usage and differentially spliced events between celltypes using methods like tappAS, https://app.tappas.org. Instead of only looking to whole differential expression of general coverage differences between exons. + +<--- Page Split ---> + +Since the interest of the study is focus in inhibitory synapses, would be of interest to look differences in different types of neurons at least inhibitory and excitatory. There are available datasets on single cell which classify different neuronal types it would be of interest to see changes in expression of the different isoforms and alternative exons in different types of neurons. + +Do the authors have any hint on how these isoforms are conserved in human? With the huge catalog of Gphn isoforms and the functional relevance on synapses connections one could also expect to find a highly alternative spliced and maybe conserved GPHN transcriptome in human. The human GPHN gene already shows many alternative exons as comparison to the mouse Gphn when looking to the datasets in UCSC. In the final part of the manuscript the authors show the detected isoforms in human tissues, which shows many alternative isoforms but less than in mouse. Are any of these isoforms conserved between mouse and human? + +In Fig3 C, I am missing the quantification values on the pie- charts. Pie charts are usually confusing to interpret due to the non scaled sizes. Authors should add the proportion for each epitope in the figure. Which will also help to see which ones are the most prevalent combinations, which I cannot clearly see from the pie- charts. + +In page 9, cannot find the referred fig.8F + +Is it possible to look for known risk SNPs in their PAC- BIO data of each specific, or the validated isoforms? Long reads should give SNP resolution. This would provide more relevance on human disorders and their link to different isoforms. + +Authors should include a data availability section with access to the raw sequencing data and processed data used in the study. In the reporting list the ENA accession are included but these should be added to main manuscript. The authors should make a reviewers token to be able to browse the raw and processed data from the study. It would be of huge interest to have the newly annotated reference isoforms and EEJ of GPHN in mouse and human for future studies and increase knowledge. + +Authors mentions several RBPs in their conclusions and how they can be regulators of GPHN. There is available data on splicing factors mice KOs and the effect on specific alternative splicing. Considering the isoforms that were validated and follow up in the manuscript, the authors could look for binding of the most typical factors as for instance NOVA, PTBP1/2 around the identified novel EEJ and 3'splice sites and also if there is any effect after KO from published datasets. The results from the manuscript open many + +<--- Page Split ---> + +venues on trying to identify the regulators of these specific isoforms and how this affect the final isoform combination in inhibitory synapses diversity and specialization. + +Reviewer #2 (Remarks to the Author): + +This is an excellent paper of very high quality that provides a comprehensive understanding of Gephryn molecular and synaptic diversity. Of particular merit is the general systematic nature of the work, the corroboration of mRNA and protein data, the studies of subcellular distribution, the functional consequences of misexpression and the addition of the human studies. This paper makes a significant contribution to our understanding of synapses diversity and the molecular mechanisms underpinning it. + +One minor point: the developmental study in figure 1D points to changes in synapse composition and diversity during development and the authors may wish to cite that this has been reported in excitatory synapses using scaffold protein markers using single- synapse resolution data (Cizeron et al, Science 2020 DOI: 10.1126/science.aba3163). + +Reviewer #3 (Remarks to the Author): + +The enclosed paper does a remarkably thorough analysis of gephrin isoforms across the CNS and associated non- neural tissue. Their results, which is among the first to so fully document the splice forms of a single protein revealed diversity far beyond that was anticipated with an additional undocumented 10 exons being identified. In addition they found large numbers of unexpected forms of gephrin, over half based on Mass Spec appear to actually be produced. Next they study both the cellular and intracellular distributions of these forms and find strong correlations between the distribution both across cell types and within specific cellular compartments (dendrite vs axon). As gephrin exists as a multimeric protein comprised of hetromers of different isoforms they use antibodies against specific epitopes to examine the co- distribution of these four epitopes and find they have different combinations with specific stochiometry combinations of isomers. While these combinations are not random with regards to compartments or cell types neither are they absolute. Similarly they find the + +<--- Page Split ---> + +surprising presence of isoforms thought to be associated with neuropsychiatric conditions are found normally within wild type neurons. One one hand this is a wonderful tout de force analysis but on the other the reader is left short of knowing how isoforms relate to function with suggestions but no spoking gun to indicate that these alternatively splice forms have an impact on actual postsynaptic function of inhibitory synapses. What seemed obviously missing was an attempt to relate isoform prevalent to postsynaptic inhibitory function. While reading this paper I continually puzzled with how such a connection could be made and the best I could come up with was to use GOF of some of the novel isoforms (particularly those that might be associated with neurological disfunction) to see if they in this context could disrupt inhibitory signaling. Given that they likely do normally in affected patients, this is in part a circular argument, although still GOF disruption would extend causation beyond correlation. All that said the authors have one a truly insane amount of work here and their findings will be of interest to the general public as an exemplar of the need for such analysis to truly understand the impact of isoforms on protein function in general and peghrin in particular. On balance I think this paper stands on its own and while I would encourage them to include some discussion of the need to causal experiments with GOF in the future, I do feel this is too high a bar to demand of them after their already admittedly Herculean efforts. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors combine targeted gene approach and long read sequencing to uncover the GPHN isoforms and their differential functions when interaction with inhibitory Glycine and GABA- A receptors. The study shows the relevance of isoform level studies, and how the combinatorial expression pool of the different isoforms of GPHN affects the inhibitory synapses in the cerebellum during mouse brain development and human tissue. The authors identify + +The study shows the relevance in the isoform level studies instead of gene level focus uncovering a new catalog of GPHN isoforms and unannotated EEJ, with different expression patterns along development and in different tissues. Moreover, some of these different isoforms are translated in different isoform protein with different function and location in inhibitory synapses. The results are validated in vivo and show evidence in human samples. + +It is also interesting to see that all the internal exons from GPHN/Gphn appear as alternative exons. There is some controversy in the field on how to define a constitutive exon, and with more and more data including now the long read technologies is getting more clear that alternative exons are even more abundant than it was thought. Which makes even more difficult to find a truly always constitutive exon. + +## Comments: + +The authors use Gphn targeted approach with PAC- BIO technology to identify all the isoforms on the gene. To validate and compare their sequencing results they authors use a database of published sequencing datasets and find that their approach is able to identify unannotated EEJ. There is currently a quite extensive curated database for EEJ from thousands of datasets, intropolis https://github.com/nellore/intropolis. Mainly in human but also has the mouse version of it in snaptron. It would be interesting to compare to this database and recalculate the number of known and novel EEJ recovered with the Gphn targeted approach. + +## Point 1 + +We would like to thank the reviewer for her/his suggestion. We have now used the mouse version of intropolis to validate new EEJs and the analysis was added to the Fig. 1C and Table S2 of the manuscript. Using intropolis database, we confirmed 11 new EEJs compared to Ensembl database EEJs, however the intropolis database provides less coverage than the dataset of short reads (2,872.109 short sequences) that we used by compiling public RNAseq projects (Table S2). + +The manuscript was modified to incorporate analysis of Gphn expression by using Snaptron. Overall, we observe that our Gphn targeted analysis using PAC- BIO technology far exceeds previous analysis, and therefore promotes a better understanding of the Gphn expression diversity. Not only do we provide a broader description of the multiple EEJs, but we also identify the different transcripts that carry these specific EEJs. Multiple data sets obtained by short- read sequencing technologies are not able to provide such information. + +<--- Page Split ---> + +There is an updated database of alternative splicing events that uses public datasets, Vast- db https://vastdb.crg.eu/wiki/Main Page. Authors should compare non annotated EEJ and alternative exon to the database entries. It would be helpful for to provide the new isoforms and EEJ to public repository and/or provide the annotations the be able to expand the catalog of isoforms in future studies. + +## Point 2 + +Thank you for this suggestion, we have used VastDB and incorporated in Fig.S1C the alternative exons annotated in Vasdb for Gphn expression in mouse. Furthermore, Fig.S1C also shows the number of transcripts carrying each alternative exon referenced in VastDB. Concerning the submission of mouse Gphn transcripts to Vastdb, we have contacted the administrator of this database and it is currently not possible to submit full length transcripts because they are specialized in event- level information. + +We agree with the reviewer's point regarding the importance of providing this information to the public. All new Gphn transcripts are referenced in Table S1 and S6 for mouse and human respectively, in addition we now provide BAM and BED files in supplemental information. + +The authors mention that Gphn is the first gene with more than 10 exons for which all internal exons can be alternatively spliced. Looking to the isoforms recovered in Fig. S1B seems that for some of the exons are skipped only in 1 out of the 277 isoforms. If the authors look for the expression of those specific isoforms like the case of E2 which is included included in one isoform. Does this isoform have enough coverage on E2 and significant number of EEJ? + +## Point 3 + +Thank you for pointing this out. + +We performed several tests to confirm that transcripts covered with one read were biologically significant. We performed a manual clearance step of sequences by visual inspection of long read clusters that led to removing one third of CCS. In addition, we show in Fig.S1E, S1F, S1I and S2A that multiple transcripts covered with a single read (Gphn- 244, - 192, - 203) were efficiently validated by RT- PCR. One can note that Gphn- 244 expression is restricted to specific tissues (see Fig. 1E), demonstrating that even weakly expressed transcripts are subjected to specific regulation between different mouse tissues. Furthermore, our mass spectrometry analysis validated GPHN protein isoforms translated from transcripts covered with a single sequencing read, for instance GPHN- 226, - 235, - 269 (Table S5). Overall we can conclude that transcripts covered with one single read are sustained by biological evidence and validates our claim about GPHN splicing regulation. + +On the other hand, some exons are included in almost all isoforms the case of E36 for instance. How is the expression of those specific isoforms? Do they have enough coverage. I am guessing that isoforms excluding E36 are very low expressed or/and very specific to a celltype or/and tissue. + +## Point 4 + +We found seven transcripts without E36 and they are weakly represented in our analysis (Gphn- 152, Gphn- 193, Gphn- 198, Gphn- 230, Gphn- 232, Gphn- 240, Gphn- 246). We show below the architecture of these transcripts and their regulations in different developmental stages and brain tissues. One can note that their expression is restricted to specific developmental points, suggesting fine tuning of alternative splicing during development. We + +<--- Page Split ---> + +would also like to point out that experiments were performed with bulk samples, so it is possible that the expression of these transcripts is much higher in specific subpopulations of neuronal cells as pointed out by the reviewer. + +![PLACEHOLDER_8_0] + + +Would the authors consider all these very lowly present isoforms as real, leading to a protein or as nuclear noise, or part of the technical limitations of the long- reads technologies, which can lead to noise? Many studies combine bulk sequencing together with long- read to avoid false positives. + +## Point 5 + +This point is reminiscent of point 3, and all our data sustain that diversity of Gphn expression does not result from transcriptional/splicing noise. Following the suggestion of the reviewer in point 1, 2 and 3, we have already compared our data to a large database of bulk sequencing dataset provided by many laboratories around the world. However, such a comparative approach remains poorly efficient because these data were generated by global assessment of gene expression in contrast to our targeted approach. The depth obtained from global gene expression analysis fails to detect under- represented EEJs. In addition, short read sequencing is unable to provide the exonic architecture composing full length transcripts, since GPHN exons and/or EEJs are used by multiple isoforms, as we show in Fig. 1C and 8C for mouse and human respectively. + +All the processing pipeline of the isoform detection is mentioned in the methods, but it should include more details and include the code used. The authors write is a custom pipeline, for that reason I find it more important that this is included in more detail and with the code used. It should include threshold used to consider a significant EEJ and expression levels thresholds to consider a lowly or highly expressed isoform. + +## Point 6 + +We completely agree with the point raised by the reviewer and therefore we have updated the methods section with more details and especially specified some missing parameters/threshold (see section "PacBio, ONT and short reads analysis" of the revised manuscript). It should be noted that our analysis includes several steps that were handled + +<--- Page Split ---> + +manually (Fig.S1A), such as the annotation of exons, and we were not able to automate these steps. + +Regarding the question about "threshold used to consider a significant EEJ", we add additional information in the Material and Methods section and answer in Point 3. + +In Page 4 authors mention Fig.2D while they are referring to Fig.1D. + +Point 7 + +Thanks to the reviewer, this was corrected in the revised version of the manuscript. + +In Fig1. F the heatmap shows highly and lowly expressed exons in different celltypes. What is the threshold for defining a high or a low expressed exon? A heatmap showing the actual expression ( as a log) of the exon in each celltype will help to show the real expression differences between celltypes. + +Point 8 + +We would like to thank the reviewer for this suggestion. We added a new heatmap version of the Fig1. F in which each exon relative expression in each cell- type is displayed. + +As I have mentioned before, the authors identify 277 different isoforms. Could be that not all the isoforms are truly expressed in any celltype, and isoform level expression heatmap per celltype and developmental stage will help to clarify if all the detected isoforms are true, at least for these celltypes and developmental stages. + +## Point 9 + +Some of the information requested by the reviewer was already present in the manuscript. We now update the Fig.1D by providing a heatmap of the expression of all isoforms during 4 developmental time points in the cerebellum and the cortex. + +Regarding the expression of individual isoforms in different neuronal cell types, we cannot provide this information because the public data used in Fig.1F are from short- read sequencing that ignores exon architecture of individual full- length isoforms. Nevertheless Fig.1F shows that the expression level of individual exons across cell- type is different, which suggests a cell- type dependent regulation of their alternative splicing. Furthermore, this is in agreement with our finding that all internal exons of Gphn are regulated by alternative splicing. + +A methodological approach that combines long- read sequencing and single cell analysis will require significant development, and we believe that it is out of the scope of our manuscript. + +By using a new reference built from the PAC- BIO detected isoforms it would be interesting to look further of the differential isoform usage and differentially spliced events between celltypes using methods like tappAS, https://app.tappas.org. Instead of only looking to whole differential expression of general coverage differences between exons. + +<--- Page Split ---> + +Following the reviewer's suggestion, we invested a lot of time and energy to get tappAS working with our data. We provide below to the attention of the reviewer the few results that we succeed to generate with tappAS: + +![PLACEHOLDER_10_0] + + +We believe that these data do not make critical changes to the message and analysis that we have already included in the manuscript. + +Since the interest of the study is focus in inhibitory synapses, would be of interest to look differences in different types of neurons at least inhibitory and excitatory. There are available datasets on single cell which classify different neuronal types it would be of interest to see changes in expression of the different isoforms and alternative exons in different types of neurons. + +## Point 11 + +This point is similar to point 9. Most studies use methods such as "drop seq" or "10x genomics" coupled to short read sequencing, which enable high throughput with a relatively shallow sequencing depth, thus global RNA expression in individual cells is only acquired for most expressed genes making a deep analysis of Gphn splicing regulation rediitory. Supporting our conclusion, the use of a large sequencing dataset corresponding to global gene expression analysis is not sufficient to reveal a lot of EEJ Gphn as indicated in point 1, either with the public databases selected by us or using intropolis. + +Do the authors have any hint on how these isoforms are conserved in human? With the huge catalog of Gphn isoforms and the functional relevance on synapses connections one could also expect to find a highly alternative spliced and maybe conserved GPHN transcriptome in human. The human GPHN gene already shows many alternative exons as comparison to the mouse Gphn when looking to the datasets in UCSC. In the final part of the manuscript the authors show the detected isoforms in human tissues, which shows many alternative isoforms but less than in mouse. Are any of these isoforms conserved between mouse and human? + +Point 12 + +<--- Page Split ---> + +We agree with the reviewer that making a comparison between human and mouse is informative, this was already provided in Fig.5SC and commented in the text. To make this point more clear, we added the following text in the manuscript: "Our analysis showed that 28 exons with more than \(95\%\) homology are shared between mouse and Human. It is interesting to note that most of the nearly identical exons are the ones that are overrepresented in the transcriptome (Fig.5B). This observation highly suggests that a significant proportion of mouse and human GPHN isoforms shared the same core protein domains. However, 12 and 14 dissimilar exons are also present in mouse and human respectively, indicating that significant differences also exist." + +Regarding the number of alternative transcripts in mouse and human, the reviewer might have missed in the Fig.7C that the GPHN alternative transcripts are far more numerous in any human tissues than in the mouse brain. + +In Fig3 C, I am missing the quantification values on the pie- charts. Pie charts are usually confusing to interpret due to the non scaled sizes. Authors should add the proportion for each epitope in the figure. Which will also help to see which ones are the most prevalent combinations, which I cannot clearly see from the pie- charts. + +Point 13 + +Thank you for this suggestion. We have added the proportion of each epitope in the revised Fig.3C. + +In page 9, cannot find the referred fig.8F + +Point 14 + +We apologize for this error and this was corrected by replacing Fig.8F with Fig.8A in the revised manuscript. + +Is it possible to look for known risk SNPs in their PAC- BIO data of each specific, or the validated isoforms? Long reads should give SNP resolution. This would provide more relevance on human disorders and their link to different isoforms. + +Point 15 + +Human RNA samples used to sequence GPHN transcriptomes were prepared by pooling together 1 to 64 samples and were performed with Oxford Nanopore technologies; we were not able to identify SNPs properly with such a variety of samples and with the error rate of the sequencing technology at the time we engaged these experiments. Moreover, none of the individuals included in these cohorts were diagnosed for neuronal disorders, so in our condition it is not possible to identify SNP that will be relevant in human disorders. + +Authors should include a data availability section with access to the raw sequencing data and processed data used in the study. In the reporting list the ENA accession are included but these should be added to main manuscript. The authors should make a reviewers token to be able to browse the raw and processed data from the study. It would be of huge interest to have the newly annotated reference isoforms and EEJ of GPHN in mouse and human for future studies and increase knowledge. + +Point 16 + +A chapter "Raw sequencing data, BAM and BED files" are available in the revised manuscript at the section Materials and Methods. + +<--- Page Split ---> + +Authors mentions several RBPs in their conclusions and how they can be regulators of GPHN. There is available data on splicing factors mice KOs and the effect on specific alternative splicing. Considering the isoforms that were validated and follow up in the manuscript, the authors could look for binding of the most typical factors as for instance NOVA, PTBP1/2 around the identified novel EEJ and 3'splice sites and also if there is any effect after KO from published datasets. The results from the manuscript open many venues on trying to identify the regulators of these specific isoforms and how this affect the final isoform combination in inhibitory synapses diversity and specialization. + +## Point 17 + +In published datasets, the authors have essentially examined the seven gephyrin exons reported to be alternatively spliced. For example, in NOVA knockout mice, they found that only exon 9 was significantly regulated. Based on our study, the exon 9 (exon 17 in the new annotation) is included in 230 transcripts (check the Fig.S1C), it is therefore not possible to identify isoforms regulation with these data sets. To address this question, one will need to perform a new study by combining Gphn- targeted long read sequencing in different mutant mouse models such as Nova or PTBP1/2 mouse models. Nevertheless, we agree with the reviewer that it is an important issue that will need to be addressed in the future, as we noted in our conclusion. + +Reviewer #2 (Remarks to the Author): + +This is an excellent paper of very high quality that provides a comprehensive understanding of Gephryn molecular and synaptic diversity. Of particular merit is the general systematic nature of the work, the corroboration of mRNA and protein data, the studies of subcellular distribution, the functional consequences of misexpression and the addition of the human studies. This paper makes a significant contribution to our understanding of synapses diversity and the molecular mechanisms underpinning it. + +One minor point: the developmental study in figure 1D points to changes in synapse composition and diversity during development and the authors may wish to cite that this has been reported in excitatory synapses using scaffold protein markers using single- synapse resolution data (Cizeron et al, Science 2020 DOI: 10.1126/science.aba3163). + +## Point 18 + +We would like to thank the reviewer for the glowing superlatives he wrote about our manuscript and our study. We agree that this work is important for the field of inhibitory synapse diversity and we thank him/her for the kind comments. We really appreciate it. The reference is now added in the text page 4 - line 28 + +Reviewer #3 (Remarks to the Author): + +The enclosed paper does a remarkably thorough analysis of gephrin isoforms across the CNS and associated non- neural tissue. Their results, which is among the first to so fully document the splice forms of a single protein revealed diversity far beyond that was anticipated with an additional undocumented 10 exons being identified. In addition they found large numbers of unexpected forms of gephrin, over half based on Mass Spec appear + +<--- Page Split ---> + +to actually be produced. Next they study both the cellular and intracellular distributions of these forms and find strong correlations between the distribution both across cell types and within specific cellular compartments (dendrite vs axon). As peghrin exists as a multimeric protein comprised of hetromers of different isoforms they use antibodies against specific epitopes to examine the co- distribution of these four epitopes and find they have different combinations with specific stochiometry combinations of isomers. While these combinations are not random with regards to compartments or cell types neither are they absolute. Similarly they find the surprising presence of isoforms thought to be associated with neuropsychiatric conditions are found normally within wild type neurons. One one hand this is a wonderful tout de force analysis but on the other the reader is left short of knowing how isoforms relate to function with suggestions but no spoking gun to indicate that these alternatively splice forms have an impact on actual postsynaptic function of inhibitory synapses. What seemed obviously missing was an attempt to relate isoform prevalent to postsynaptic inhibitory function. While reading this paper I continually puzzled with how such a connection could be made and the best I could come up with was to use GOF of some of the novel isoforms (particularly those that might be associated with neurological disfunction) to see if they in this context could disrupt inhibitory signaling. Given that they likely do normally in affected patients, this is in part a circular argument, although still GOF disruption would extend causation beyond correlation. All that said the authors have one a truly insane amount of work here and their findings will be of interest to the general public as an exemplar of the need for such analysis to truly understand the impact of isoforms on protein function in general and peghrin in particular. On balance I think this paper stands on its own and while I would encourage them to include some discussion of the need to causal experiments with GOF in the future, I do feel this is too high a bar to demand of them after their already admittedly Herculean efforts. + +## Point 19 + +First, we would like to thank the reviewer for finding our work of interest for the general public and we appreciate his/her kind words about our work. We completely agree that in the future, we will need to assess in more detail the role of GPHN variants in inhibitory synapse signaling. Maybe the reviewer miss this part in our manuscript but we performed several isoforms GOF in cerebellum and observed important effects on inhibitory synapse formation/stabilization (Fig.5) Following his/her recommendation, we added a new paragraph in the discussion to highlight the need of causal experiments with GOF in the future. + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +Thanks to the authors for considering my comments. I see the changes and additions have increased the value of the study, which already showed good quality and insights. I find it a great paper that shows the effort and good work of the authors. I am totally satisfied with the revisions and I would recommend it for acceptance. + +<--- Page Split ---> diff --git a/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/supplementary_0_Peer review file_det.mmd b/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/supplementary_0_Peer review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8cb49dc31c1d8a9c88f97c5670fff0f780361dfb --- /dev/null +++ b/peer_reviews/55628abcce4b0a0912eaf92b6c58d5f993fc1b370d3d9ad17d61c8b1c9406bf0/supplementary_0_Peer review file/supplementary_0_Peer review file_det.mmd @@ -0,0 +1,357 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[69, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 889, 212]]<|/det|> +Complex regulation of Gephyrin splicing is a determinant of inhibitory postsynaptic diversity + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 394, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 201, 870, 294]]<|/det|> +The authors combine targeted gene approach and long read sequencing to uncover the GPHN isoforms and their differential functions when interaction with inhibitory Glycine and GABA- A receptors. The study shows the relevance of isoform level studies, and how the combinatorial expression pool of the different isoforms of GPHN affects the inhibitory synapses in the cerebellum during mouse brain development and human tissue. The authors identify + +<|ref|>text<|/ref|><|det|>[[115, 333, 874, 424]]<|/det|> +The study shows the relevance in the isoform level studies instead of gene level focus uncovering a new catalog of GPHN isoforms and unannotated EEJ, with different expression patterns along development and in different tissues. Moreover, some of these different isoforms are translated in different isoform protein with different function and location in inhibitory synapses. The results are validated in vivo and show evidence in human samples. + +<|ref|>text<|/ref|><|det|>[[115, 462, 865, 554]]<|/det|> +It is also interesting to see that all the internal exons from GPHN/Gphn appear as alternative exons. There is some controversy in the field on how to define a constitutive exon, and with more and more data including now the long read technologies is getting more clear that alternative exons are even more abundant than it was thought. Which makes even more difficult to find a truly always constitutive exon. + +<|ref|>sub_title<|/ref|><|det|>[[115, 594, 201, 610]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[113, 648, 883, 777]]<|/det|> +The authors use Gphn targeted approach with PAC- BIO technology to identify all the isoforms on the gene. To validate and compare their sequencing results they authors use a database of published sequencing datasets and find that their approach is able to identify unannotated EEJ. There is currently a quite extensive curated database for EEJ from thousands of datasets, intropolis https://github.com/nellore/intropolis. Mainly in human but also has the mouse version of it in snaptron. It would be interesting to compare to this database and recalculate the number of known and novel EEJ recovered with the Gphn targeted approach. + +<|ref|>text<|/ref|><|det|>[[115, 816, 881, 888]]<|/det|> +There is an updated database of alternative splicing events that uses public datasets, Vast- db https://vastdb.crg.eu/wiki/Main_Page. Authors should compare non annotated EEJ and alternative exon to the database entries. It would be helpful for to provide the new isoforms and EEJ to public repository and/or provide the annotations the be able to expand the catalog of isoforms in future studies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 116, 857, 208]]<|/det|> +The authors mention that Gphn is the first gene with more than 10 exons for which all internal exons can be alternatively spliced. Looking to the isoforms recovered in Fig. S1B seems that for some of the exons are skipped only in 1 out of the 277 isoforms. If the authors look for the expression of those specific isoforms like the case of E2 which is included included in one isoform. Does this isoform have enough coverage on E2 and significant number of EEJ? + +<|ref|>text<|/ref|><|det|>[[115, 247, 865, 302]]<|/det|> +On the other hand, some exons are included in almost all isoforms the case of E36 for instance. How is the expression of those specific isoforms? Do they have enough coverage. I am guessing that isoforms excluding E36 are very low expressed or/and very specific to a celltype or/and tissue. + +<|ref|>text<|/ref|><|det|>[[115, 340, 839, 395]]<|/det|> +Would the authors consider all these very lowly present isoforms as real, leading to a protein or as nuclear noise, or part of the technical limitations of the long- reads technologies, which can lead to noise? Many studies combine bulk sequencing together with long- read to avoid false positives. + +<|ref|>text<|/ref|><|det|>[[115, 433, 867, 525]]<|/det|> +All the processing pipeline of the isoform detection is mentioned in the methods, but it should include more details and include the code used. The authors write is a custom pipeline, for that reason I find it more important that this is included in more detail and with the code used. It should include threshold used to consider a significant EEJ and expression levels thresholds to consider a lowly or highly expressed isoform. + +<|ref|>text<|/ref|><|det|>[[115, 564, 609, 582]]<|/det|> +In Page 4 authors mention Fig.2D while they are referring to Fig.1D. + +<|ref|>text<|/ref|><|det|>[[115, 620, 866, 676]]<|/det|> +In Fig1. F the heatmap shows highly and lowly expressed exons in different celltypes. What is the threshold for defining a high or a low expressed exon? A heatmap showing the actual expression ( as a log) of the exon in each celltype will help to show the real expression differences between celltypes. + +<|ref|>text<|/ref|><|det|>[[115, 714, 867, 787]]<|/det|> +As I have mentioned before, the authors identify 277 different isoforms. Could be that not all the isoforms are truly expressed in any celltype, and isoform level expression heatmap per celltype and developmental stage will help to clarify if all the detected isoforms are true, at least for these celltypes and developmental stages. + +<|ref|>text<|/ref|><|det|>[[115, 825, 874, 899]]<|/det|> +By using a new reference built from the PAC- BIO detected isoforms it would be interesting to look further of the differential isoform usage and differentially spliced events between celltypes using methods like tappAS, https://app.tappas.org. Instead of only looking to whole differential expression of general coverage differences between exons. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 117, 874, 191]]<|/det|> +Since the interest of the study is focus in inhibitory synapses, would be of interest to look differences in different types of neurons at least inhibitory and excitatory. There are available datasets on single cell which classify different neuronal types it would be of interest to see changes in expression of the different isoforms and alternative exons in different types of neurons. + +<|ref|>text<|/ref|><|det|>[[114, 229, 875, 357]]<|/det|> +Do the authors have any hint on how these isoforms are conserved in human? With the huge catalog of Gphn isoforms and the functional relevance on synapses connections one could also expect to find a highly alternative spliced and maybe conserved GPHN transcriptome in human. The human GPHN gene already shows many alternative exons as comparison to the mouse Gphn when looking to the datasets in UCSC. In the final part of the manuscript the authors show the detected isoforms in human tissues, which shows many alternative isoforms but less than in mouse. Are any of these isoforms conserved between mouse and human? + +<|ref|>text<|/ref|><|det|>[[115, 395, 870, 469]]<|/det|> +In Fig3 C, I am missing the quantification values on the pie- charts. Pie charts are usually confusing to interpret due to the non scaled sizes. Authors should add the proportion for each epitope in the figure. Which will also help to see which ones are the most prevalent combinations, which I cannot clearly see from the pie- charts. + +<|ref|>text<|/ref|><|det|>[[115, 508, 413, 524]]<|/det|> +In page 9, cannot find the referred fig.8F + +<|ref|>text<|/ref|><|det|>[[115, 564, 816, 618]]<|/det|> +Is it possible to look for known risk SNPs in their PAC- BIO data of each specific, or the validated isoforms? Long reads should give SNP resolution. This would provide more relevance on human disorders and their link to different isoforms. + +<|ref|>text<|/ref|><|det|>[[115, 657, 879, 749]]<|/det|> +Authors should include a data availability section with access to the raw sequencing data and processed data used in the study. In the reporting list the ENA accession are included but these should be added to main manuscript. The authors should make a reviewers token to be able to browse the raw and processed data from the study. It would be of huge interest to have the newly annotated reference isoforms and EEJ of GPHN in mouse and human for future studies and increase knowledge. + +<|ref|>text<|/ref|><|det|>[[115, 787, 880, 878]]<|/det|> +Authors mentions several RBPs in their conclusions and how they can be regulators of GPHN. There is available data on splicing factors mice KOs and the effect on specific alternative splicing. Considering the isoforms that were validated and follow up in the manuscript, the authors could look for binding of the most typical factors as for instance NOVA, PTBP1/2 around the identified novel EEJ and 3'splice sites and also if there is any effect after KO from published datasets. The results from the manuscript open many + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 825, 125]]<|/det|> +venues on trying to identify the regulators of these specific isoforms and how this affect the final isoform combination in inhibitory synapses diversity and specialization. + +<|ref|>text<|/ref|><|det|>[[115, 277, 393, 293]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 335, 875, 426]]<|/det|> +This is an excellent paper of very high quality that provides a comprehensive understanding of Gephryn molecular and synaptic diversity. Of particular merit is the general systematic nature of the work, the corroboration of mRNA and protein data, the studies of subcellular distribution, the functional consequences of misexpression and the addition of the human studies. This paper makes a significant contribution to our understanding of synapses diversity and the molecular mechanisms underpinning it. + +<|ref|>text<|/ref|><|det|>[[115, 465, 881, 537]]<|/det|> +One minor point: the developmental study in figure 1D points to changes in synapse composition and diversity during development and the authors may wish to cite that this has been reported in excitatory synapses using scaffold protein markers using single- synapse resolution data (Cizeron et al, Science 2020 DOI: 10.1126/science.aba3163). + +<|ref|>text<|/ref|><|det|>[[115, 633, 393, 649]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 689, 880, 890]]<|/det|> +The enclosed paper does a remarkably thorough analysis of gephrin isoforms across the CNS and associated non- neural tissue. Their results, which is among the first to so fully document the splice forms of a single protein revealed diversity far beyond that was anticipated with an additional undocumented 10 exons being identified. In addition they found large numbers of unexpected forms of gephrin, over half based on Mass Spec appear to actually be produced. Next they study both the cellular and intracellular distributions of these forms and find strong correlations between the distribution both across cell types and within specific cellular compartments (dendrite vs axon). As gephrin exists as a multimeric protein comprised of hetromers of different isoforms they use antibodies against specific epitopes to examine the co- distribution of these four epitopes and find they have different combinations with specific stochiometry combinations of isomers. While these combinations are not random with regards to compartments or cell types neither are they absolute. Similarly they find the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 879, 382]]<|/det|> +surprising presence of isoforms thought to be associated with neuropsychiatric conditions are found normally within wild type neurons. One one hand this is a wonderful tout de force analysis but on the other the reader is left short of knowing how isoforms relate to function with suggestions but no spoking gun to indicate that these alternatively splice forms have an impact on actual postsynaptic function of inhibitory synapses. What seemed obviously missing was an attempt to relate isoform prevalent to postsynaptic inhibitory function. While reading this paper I continually puzzled with how such a connection could be made and the best I could come up with was to use GOF of some of the novel isoforms (particularly those that might be associated with neurological disfunction) to see if they in this context could disrupt inhibitory signaling. Given that they likely do normally in affected patients, this is in part a circular argument, although still GOF disruption would extend causation beyond correlation. All that said the authors have one a truly insane amount of work here and their findings will be of interest to the general public as an exemplar of the need for such analysis to truly understand the impact of isoforms on protein function in general and peghrin in particular. On balance I think this paper stands on its own and while I would encourage them to include some discussion of the need to causal experiments with GOF in the future, I do feel this is too high a bar to demand of them after their already admittedly Herculean efforts. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 331, 100]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 118, 429, 135]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 152, 879, 256]]<|/det|> +The authors combine targeted gene approach and long read sequencing to uncover the GPHN isoforms and their differential functions when interaction with inhibitory Glycine and GABA- A receptors. The study shows the relevance of isoform level studies, and how the combinatorial expression pool of the different isoforms of GPHN affects the inhibitory synapses in the cerebellum during mouse brain development and human tissue. The authors identify + +<|ref|>text<|/ref|><|det|>[[118, 273, 879, 360]]<|/det|> +The study shows the relevance in the isoform level studies instead of gene level focus uncovering a new catalog of GPHN isoforms and unannotated EEJ, with different expression patterns along development and in different tissues. Moreover, some of these different isoforms are translated in different isoform protein with different function and location in inhibitory synapses. The results are validated in vivo and show evidence in human samples. + +<|ref|>text<|/ref|><|det|>[[118, 376, 879, 464]]<|/det|> +It is also interesting to see that all the internal exons from GPHN/Gphn appear as alternative exons. There is some controversy in the field on how to define a constitutive exon, and with more and more data including now the long read technologies is getting more clear that alternative exons are even more abundant than it was thought. Which makes even more difficult to find a truly always constitutive exon. + +<|ref|>sub_title<|/ref|><|det|>[[118, 481, 213, 497]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[117, 514, 879, 653]]<|/det|> +The authors use Gphn targeted approach with PAC- BIO technology to identify all the isoforms on the gene. To validate and compare their sequencing results they authors use a database of published sequencing datasets and find that their approach is able to identify unannotated EEJ. There is currently a quite extensive curated database for EEJ from thousands of datasets, intropolis https://github.com/nellore/intropolis. Mainly in human but also has the mouse version of it in snaptron. It would be interesting to compare to this database and recalculate the number of known and novel EEJ recovered with the Gphn targeted approach. + +<|ref|>sub_title<|/ref|><|det|>[[118, 671, 179, 686]]<|/det|> +## Point 1 + +<|ref|>text<|/ref|><|det|>[[118, 688, 880, 791]]<|/det|> +We would like to thank the reviewer for her/his suggestion. We have now used the mouse version of intropolis to validate new EEJs and the analysis was added to the Fig. 1C and Table S2 of the manuscript. Using intropolis database, we confirmed 11 new EEJs compared to Ensembl database EEJs, however the intropolis database provides less coverage than the dataset of short reads (2,872.109 short sequences) that we used by compiling public RNAseq projects (Table S2). + +<|ref|>text<|/ref|><|det|>[[118, 791, 880, 895]]<|/det|> +The manuscript was modified to incorporate analysis of Gphn expression by using Snaptron. Overall, we observe that our Gphn targeted analysis using PAC- BIO technology far exceeds previous analysis, and therefore promotes a better understanding of the Gphn expression diversity. Not only do we provide a broader description of the multiple EEJs, but we also identify the different transcripts that carry these specific EEJs. Multiple data sets obtained by short- read sequencing technologies are not able to provide such information. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 879, 170]]<|/det|> +There is an updated database of alternative splicing events that uses public datasets, Vast- db https://vastdb.crg.eu/wiki/Main Page. Authors should compare non annotated EEJ and alternative exon to the database entries. It would be helpful for to provide the new isoforms and EEJ to public repository and/or provide the annotations the be able to expand the catalog of isoforms in future studies. + +<|ref|>sub_title<|/ref|><|det|>[[119, 171, 179, 186]]<|/det|> +## Point 2 + +<|ref|>text<|/ref|><|det|>[[118, 187, 880, 330]]<|/det|> +Thank you for this suggestion, we have used VastDB and incorporated in Fig.S1C the alternative exons annotated in Vasdb for Gphn expression in mouse. Furthermore, Fig.S1C also shows the number of transcripts carrying each alternative exon referenced in VastDB. Concerning the submission of mouse Gphn transcripts to Vastdb, we have contacted the administrator of this database and it is currently not possible to submit full length transcripts because they are specialized in event- level information. + +<|ref|>text<|/ref|><|det|>[[118, 328, 879, 380]]<|/det|> +We agree with the reviewer's point regarding the importance of providing this information to the public. All new Gphn transcripts are referenced in Table S1 and S6 for mouse and human respectively, in addition we now provide BAM and BED files in supplemental information. + +<|ref|>text<|/ref|><|det|>[[118, 377, 879, 483]]<|/det|> +The authors mention that Gphn is the first gene with more than 10 exons for which all internal exons can be alternatively spliced. Looking to the isoforms recovered in Fig. S1B seems that for some of the exons are skipped only in 1 out of the 277 isoforms. If the authors look for the expression of those specific isoforms like the case of E2 which is included included in one isoform. Does this isoform have enough coverage on E2 and significant number of EEJ? + +<|ref|>sub_title<|/ref|><|det|>[[118, 500, 179, 515]]<|/det|> +## Point 3 + +<|ref|>text<|/ref|><|det|>[[120, 517, 371, 533]]<|/det|> +Thank you for pointing this out. + +<|ref|>text<|/ref|><|det|>[[117, 533, 880, 725]]<|/det|> +We performed several tests to confirm that transcripts covered with one read were biologically significant. We performed a manual clearance step of sequences by visual inspection of long read clusters that led to removing one third of CCS. In addition, we show in Fig.S1E, S1F, S1I and S2A that multiple transcripts covered with a single read (Gphn- 244, - 192, - 203) were efficiently validated by RT- PCR. One can note that Gphn- 244 expression is restricted to specific tissues (see Fig. 1E), demonstrating that even weakly expressed transcripts are subjected to specific regulation between different mouse tissues. Furthermore, our mass spectrometry analysis validated GPHN protein isoforms translated from transcripts covered with a single sequencing read, for instance GPHN- 226, - 235, - 269 (Table S5). Overall we can conclude that transcripts covered with one single read are sustained by biological evidence and validates our claim about GPHN splicing regulation. + +<|ref|>text<|/ref|><|det|>[[118, 741, 879, 810]]<|/det|> +On the other hand, some exons are included in almost all isoforms the case of E36 for instance. How is the expression of those specific isoforms? Do they have enough coverage. I am guessing that isoforms excluding E36 are very low expressed or/and very specific to a celltype or/and tissue. + +<|ref|>sub_title<|/ref|><|det|>[[118, 811, 179, 825]]<|/det|> +## Point 4 + +<|ref|>text<|/ref|><|det|>[[118, 827, 879, 914]]<|/det|> +We found seven transcripts without E36 and they are weakly represented in our analysis (Gphn- 152, Gphn- 193, Gphn- 198, Gphn- 230, Gphn- 232, Gphn- 240, Gphn- 246). We show below the architecture of these transcripts and their regulations in different developmental stages and brain tissues. One can note that their expression is restricted to specific developmental points, suggesting fine tuning of alternative splicing during development. We + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 136]]<|/det|> +would also like to point out that experiments were performed with bulk samples, so it is possible that the expression of these transcripts is much higher in specific subpopulations of neuronal cells as pointed out by the reviewer. + +<|ref|>image<|/ref|><|det|>[[130, 150, 866, 391]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 410, 880, 480]]<|/det|> +Would the authors consider all these very lowly present isoforms as real, leading to a protein or as nuclear noise, or part of the technical limitations of the long- reads technologies, which can lead to noise? Many studies combine bulk sequencing together with long- read to avoid false positives. + +<|ref|>sub_title<|/ref|><|det|>[[119, 482, 180, 497]]<|/det|> +## Point 5 + +<|ref|>text<|/ref|><|det|>[[118, 514, 880, 689]]<|/det|> +This point is reminiscent of point 3, and all our data sustain that diversity of Gphn expression does not result from transcriptional/splicing noise. Following the suggestion of the reviewer in point 1, 2 and 3, we have already compared our data to a large database of bulk sequencing dataset provided by many laboratories around the world. However, such a comparative approach remains poorly efficient because these data were generated by global assessment of gene expression in contrast to our targeted approach. The depth obtained from global gene expression analysis fails to detect under- represented EEJs. In addition, short read sequencing is unable to provide the exonic architecture composing full length transcripts, since GPHN exons and/or EEJs are used by multiple isoforms, as we show in Fig. 1C and 8C for mouse and human respectively. + +<|ref|>text<|/ref|><|det|>[[118, 739, 880, 826]]<|/det|> +All the processing pipeline of the isoform detection is mentioned in the methods, but it should include more details and include the code used. The authors write is a custom pipeline, for that reason I find it more important that this is included in more detail and with the code used. It should include threshold used to consider a significant EEJ and expression levels thresholds to consider a lowly or highly expressed isoform. + +<|ref|>sub_title<|/ref|><|det|>[[119, 828, 180, 842]]<|/det|> +## Point 6 + +<|ref|>text<|/ref|><|det|>[[118, 844, 880, 912]]<|/det|> +We completely agree with the point raised by the reviewer and therefore we have updated the methods section with more details and especially specified some missing parameters/threshold (see section "PacBio, ONT and short reads analysis" of the revised manuscript). It should be noted that our analysis includes several steps that were handled + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 878, 118]]<|/det|> +manually (Fig.S1A), such as the annotation of exons, and we were not able to automate these steps. + +<|ref|>text<|/ref|><|det|>[[118, 134, 880, 170]]<|/det|> +Regarding the question about "threshold used to consider a significant EEJ", we add additional information in the Material and Methods section and answer in Point 3. + +<|ref|>text<|/ref|><|det|>[[118, 186, 675, 204]]<|/det|> +In Page 4 authors mention Fig.2D while they are referring to Fig.1D. + +<|ref|>text<|/ref|><|det|>[[119, 205, 179, 220]]<|/det|> +Point 7 + +<|ref|>text<|/ref|><|det|>[[120, 220, 794, 238]]<|/det|> +Thanks to the reviewer, this was corrected in the revised version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 255, 880, 327]]<|/det|> +In Fig1. F the heatmap shows highly and lowly expressed exons in different celltypes. What is the threshold for defining a high or a low expressed exon? A heatmap showing the actual expression ( as a log) of the exon in each celltype will help to show the real expression differences between celltypes. + +<|ref|>text<|/ref|><|det|>[[119, 327, 180, 341]]<|/det|> +Point 8 + +<|ref|>text<|/ref|><|det|>[[118, 342, 880, 378]]<|/det|> +We would like to thank the reviewer for this suggestion. We added a new heatmap version of the Fig1. F in which each exon relative expression in each cell- type is displayed. + +<|ref|>text<|/ref|><|det|>[[118, 393, 880, 465]]<|/det|> +As I have mentioned before, the authors identify 277 different isoforms. Could be that not all the isoforms are truly expressed in any celltype, and isoform level expression heatmap per celltype and developmental stage will help to clarify if all the detected isoforms are true, at least for these celltypes and developmental stages. + +<|ref|>sub_title<|/ref|><|det|>[[119, 515, 179, 531]]<|/det|> +## Point 9 + +<|ref|>text<|/ref|><|det|>[[119, 548, 879, 601]]<|/det|> +Some of the information requested by the reviewer was already present in the manuscript. We now update the Fig.1D by providing a heatmap of the expression of all isoforms during 4 developmental time points in the cerebellum and the cortex. + +<|ref|>text<|/ref|><|det|>[[118, 617, 880, 740]]<|/det|> +Regarding the expression of individual isoforms in different neuronal cell types, we cannot provide this information because the public data used in Fig.1F are from short- read sequencing that ignores exon architecture of individual full- length isoforms. Nevertheless Fig.1F shows that the expression level of individual exons across cell- type is different, which suggests a cell- type dependent regulation of their alternative splicing. Furthermore, this is in agreement with our finding that all internal exons of Gphn are regulated by alternative splicing. + +<|ref|>text<|/ref|><|det|>[[118, 739, 879, 775]]<|/det|> +A methodological approach that combines long- read sequencing and single cell analysis will require significant development, and we believe that it is out of the scope of our manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 790, 879, 861]]<|/det|> +By using a new reference built from the PAC- BIO detected isoforms it would be interesting to look further of the differential isoform usage and differentially spliced events between celltypes using methods like tappAS, https://app.tappas.org. Instead of only looking to whole differential expression of general coverage differences between exons. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 880, 136]]<|/det|> +Following the reviewer's suggestion, we invested a lot of time and energy to get tappAS working with our data. We provide below to the attention of the reviewer the few results that we succeed to generate with tappAS: + +<|ref|>image<|/ref|><|det|>[[120, 138, 880, 437]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 444, 880, 479]]<|/det|> +We believe that these data do not make critical changes to the message and analysis that we have already included in the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 495, 880, 583]]<|/det|> +Since the interest of the study is focus in inhibitory synapses, would be of interest to look differences in different types of neurons at least inhibitory and excitatory. There are available datasets on single cell which classify different neuronal types it would be of interest to see changes in expression of the different isoforms and alternative exons in different types of neurons. + +<|ref|>sub_title<|/ref|><|det|>[[119, 584, 188, 599]]<|/det|> +## Point 11 + +<|ref|>text<|/ref|><|det|>[[118, 599, 880, 721]]<|/det|> +This point is similar to point 9. Most studies use methods such as "drop seq" or "10x genomics" coupled to short read sequencing, which enable high throughput with a relatively shallow sequencing depth, thus global RNA expression in individual cells is only acquired for most expressed genes making a deep analysis of Gphn splicing regulation rediitory. Supporting our conclusion, the use of a large sequencing dataset corresponding to global gene expression analysis is not sufficient to reveal a lot of EEJ Gphn as indicated in point 1, either with the public databases selected by us or using intropolis. + +<|ref|>text<|/ref|><|det|>[[118, 737, 880, 875]]<|/det|> +Do the authors have any hint on how these isoforms are conserved in human? With the huge catalog of Gphn isoforms and the functional relevance on synapses connections one could also expect to find a highly alternative spliced and maybe conserved GPHN transcriptome in human. The human GPHN gene already shows many alternative exons as comparison to the mouse Gphn when looking to the datasets in UCSC. In the final part of the manuscript the authors show the detected isoforms in human tissues, which shows many alternative isoforms but less than in mouse. Are any of these isoforms conserved between mouse and human? + +<|ref|>text<|/ref|><|det|>[[118, 876, 190, 891]]<|/det|> +Point 12 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 880, 239]]<|/det|> +We agree with the reviewer that making a comparison between human and mouse is informative, this was already provided in Fig.5SC and commented in the text. To make this point more clear, we added the following text in the manuscript: "Our analysis showed that 28 exons with more than \(95\%\) homology are shared between mouse and Human. It is interesting to note that most of the nearly identical exons are the ones that are overrepresented in the transcriptome (Fig.5B). This observation highly suggests that a significant proportion of mouse and human GPHN isoforms shared the same core protein domains. However, 12 and 14 dissimilar exons are also present in mouse and human respectively, indicating that significant differences also exist." + +<|ref|>text<|/ref|><|det|>[[118, 239, 879, 291]]<|/det|> +Regarding the number of alternative transcripts in mouse and human, the reviewer might have missed in the Fig.7C that the GPHN alternative transcripts are far more numerous in any human tissues than in the mouse brain. + +<|ref|>text<|/ref|><|det|>[[118, 309, 879, 378]]<|/det|> +In Fig3 C, I am missing the quantification values on the pie- charts. Pie charts are usually confusing to interpret due to the non scaled sizes. Authors should add the proportion for each epitope in the figure. Which will also help to see which ones are the most prevalent combinations, which I cannot clearly see from the pie- charts. + +<|ref|>text<|/ref|><|det|>[[118, 378, 191, 393]]<|/det|> +Point 13 + +<|ref|>text<|/ref|><|det|>[[118, 395, 878, 429]]<|/det|> +Thank you for this suggestion. We have added the proportion of each epitope in the revised Fig.3C. + +<|ref|>text<|/ref|><|det|>[[118, 447, 449, 464]]<|/det|> +In page 9, cannot find the referred fig.8F + +<|ref|>text<|/ref|><|det|>[[118, 465, 191, 480]]<|/det|> +Point 14 + +<|ref|>text<|/ref|><|det|>[[118, 481, 878, 515]]<|/det|> +We apologize for this error and this was corrected by replacing Fig.8F with Fig.8A in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 532, 879, 585]]<|/det|> +Is it possible to look for known risk SNPs in their PAC- BIO data of each specific, or the validated isoforms? Long reads should give SNP resolution. This would provide more relevance on human disorders and their link to different isoforms. + +<|ref|>text<|/ref|><|det|>[[118, 586, 191, 601]]<|/det|> +Point 15 + +<|ref|>text<|/ref|><|det|>[[118, 602, 880, 705]]<|/det|> +Human RNA samples used to sequence GPHN transcriptomes were prepared by pooling together 1 to 64 samples and were performed with Oxford Nanopore technologies; we were not able to identify SNPs properly with such a variety of samples and with the error rate of the sequencing technology at the time we engaged these experiments. Moreover, none of the individuals included in these cohorts were diagnosed for neuronal disorders, so in our condition it is not possible to identify SNP that will be relevant in human disorders. + +<|ref|>text<|/ref|><|det|>[[118, 722, 879, 826]]<|/det|> +Authors should include a data availability section with access to the raw sequencing data and processed data used in the study. In the reporting list the ENA accession are included but these should be added to main manuscript. The authors should make a reviewers token to be able to browse the raw and processed data from the study. It would be of huge interest to have the newly annotated reference isoforms and EEJ of GPHN in mouse and human for future studies and increase knowledge. + +<|ref|>text<|/ref|><|det|>[[118, 828, 191, 842]]<|/det|> +Point 16 + +<|ref|>text<|/ref|><|det|>[[118, 844, 878, 877]]<|/det|> +A chapter "Raw sequencing data, BAM and BED files" are available in the revised manuscript at the section Materials and Methods. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 879, 221]]<|/det|> +Authors mentions several RBPs in their conclusions and how they can be regulators of GPHN. There is available data on splicing factors mice KOs and the effect on specific alternative splicing. Considering the isoforms that were validated and follow up in the manuscript, the authors could look for binding of the most typical factors as for instance NOVA, PTBP1/2 around the identified novel EEJ and 3'splice sites and also if there is any effect after KO from published datasets. The results from the manuscript open many venues on trying to identify the regulators of these specific isoforms and how this affect the final isoform combination in inhibitory synapses diversity and specialization. + +<|ref|>sub_title<|/ref|><|det|>[[119, 240, 190, 255]]<|/det|> +## Point 17 + +<|ref|>text<|/ref|><|det|>[[118, 256, 880, 410]]<|/det|> +In published datasets, the authors have essentially examined the seven gephyrin exons reported to be alternatively spliced. For example, in NOVA knockout mice, they found that only exon 9 was significantly regulated. Based on our study, the exon 9 (exon 17 in the new annotation) is included in 230 transcripts (check the Fig.S1C), it is therefore not possible to identify isoforms regulation with these data sets. To address this question, one will need to perform a new study by combining Gphn- targeted long read sequencing in different mutant mouse models such as Nova or PTBP1/2 mouse models. Nevertheless, we agree with the reviewer that it is an important issue that will need to be addressed in the future, as we noted in our conclusion. + +<|ref|>text<|/ref|><|det|>[[120, 463, 428, 480]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 498, 879, 601]]<|/det|> +This is an excellent paper of very high quality that provides a comprehensive understanding of Gephryn molecular and synaptic diversity. Of particular merit is the general systematic nature of the work, the corroboration of mRNA and protein data, the studies of subcellular distribution, the functional consequences of misexpression and the addition of the human studies. This paper makes a significant contribution to our understanding of synapses diversity and the molecular mechanisms underpinning it. + +<|ref|>text<|/ref|><|det|>[[118, 619, 879, 688]]<|/det|> +One minor point: the developmental study in figure 1D points to changes in synapse composition and diversity during development and the authors may wish to cite that this has been reported in excitatory synapses using scaffold protein markers using single- synapse resolution data (Cizeron et al, Science 2020 DOI: 10.1126/science.aba3163). + +<|ref|>sub_title<|/ref|><|det|>[[119, 689, 190, 704]]<|/det|> +## Point 18 + +<|ref|>text<|/ref|><|det|>[[118, 706, 879, 774]]<|/det|> +We would like to thank the reviewer for the glowing superlatives he wrote about our manuscript and our study. We agree that this work is important for the field of inhibitory synapse diversity and we thank him/her for the kind comments. We really appreciate it. The reference is now added in the text page 4 - line 28 + +<|ref|>text<|/ref|><|det|>[[119, 792, 428, 808]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 826, 879, 912]]<|/det|> +The enclosed paper does a remarkably thorough analysis of gephrin isoforms across the CNS and associated non- neural tissue. Their results, which is among the first to so fully document the splice forms of a single protein revealed diversity far beyond that was anticipated with an additional undocumented 10 exons being identified. In addition they found large numbers of unexpected forms of gephrin, over half based on Mass Spec appear + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 82, 880, 500]]<|/det|> +to actually be produced. Next they study both the cellular and intracellular distributions of these forms and find strong correlations between the distribution both across cell types and within specific cellular compartments (dendrite vs axon). As peghrin exists as a multimeric protein comprised of hetromers of different isoforms they use antibodies against specific epitopes to examine the co- distribution of these four epitopes and find they have different combinations with specific stochiometry combinations of isomers. While these combinations are not random with regards to compartments or cell types neither are they absolute. Similarly they find the surprising presence of isoforms thought to be associated with neuropsychiatric conditions are found normally within wild type neurons. One one hand this is a wonderful tout de force analysis but on the other the reader is left short of knowing how isoforms relate to function with suggestions but no spoking gun to indicate that these alternatively splice forms have an impact on actual postsynaptic function of inhibitory synapses. What seemed obviously missing was an attempt to relate isoform prevalent to postsynaptic inhibitory function. While reading this paper I continually puzzled with how such a connection could be made and the best I could come up with was to use GOF of some of the novel isoforms (particularly those that might be associated with neurological disfunction) to see if they in this context could disrupt inhibitory signaling. Given that they likely do normally in affected patients, this is in part a circular argument, although still GOF disruption would extend causation beyond correlation. All that said the authors have one a truly insane amount of work here and their findings will be of interest to the general public as an exemplar of the need for such analysis to truly understand the impact of isoforms on protein function in general and peghrin in particular. On balance I think this paper stands on its own and while I would encourage them to include some discussion of the need to causal experiments with GOF in the future, I do feel this is too high a bar to demand of them after their already admittedly Herculean efforts. + +<|ref|>sub_title<|/ref|><|det|>[[118, 516, 189, 530]]<|/det|> +## Point 19 + +<|ref|>text<|/ref|><|det|>[[118, 531, 880, 653]]<|/det|> +First, we would like to thank the reviewer for finding our work of interest for the general public and we appreciate his/her kind words about our work. We completely agree that in the future, we will need to assess in more detail the role of GPHN variants in inhibitory synapse signaling. Maybe the reviewer miss this part in our manuscript but we performed several isoforms GOF in cerebellum and observed important effects on inhibitory synapse formation/stabilization (Fig.5) Following his/her recommendation, we added a new paragraph in the discussion to highlight the need of causal experiments with GOF in the future. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 300, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 147, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 880, 275]]<|/det|> +Thanks to the authors for considering my comments. I see the changes and additions have increased the value of the study, which already showed good quality and insights. I find it a great paper that shows the effort and good work of the authors. I am totally satisfied with the revisions and I would recommend it for acceptance. + +<--- Page Split ---> diff --git a/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/images_list.json b/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..78cb13cfc3659a0a1b72ebc5d0010fd2b463f280 --- /dev/null +++ b/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,368 @@ + +# nature portfolio + +Peer Review File + +Shared neutrophil and T cell dysfunction is accompanied by a distinct interferon signature during severe febrile illnesses in children + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +Major comments: + +1. In their analysis of gene expression, the authors attribute a limited number of changes in mass cytometry to highly specific cellular states. However, these few proteins are not sufficiently specific for the authors' claims: + +- For example, they use CD279 as a marker for exhausted T cells, but this gene is also upregulated on T cells in response to Type II IFNs, which does not necessarily imply exhaustion. Additionally, CD279 is upregulated on recently activated T cells and on specific subsets of T cells (eg CD4+ T follicular helper cells). Similar findings and the limitations of using CD279 as a sole marker of exhaustion have been noted in patients with MIS-C (Vella, L. et al. Sci Immunol., 2021). + +- The authors state that "Factor 2 represented restoration of innate and adaptive immune cell homeostasis, with a decrease in the proportion of immature neutrophils and increased CD11b and CD16 on myeloid cells" (lines 218 - 220). Additionally biologic proof is needed to support these statements, as these two markers are not sufficient to indicate "restoration of innate and adaptive immune cell homeostasis" + +- Similarly, the author note upregulation of "genes associated with formation of NETS31,32: ELANE (neutrophil elastase) and MPO (myeloperoxidase) were elevated in MIS-C in comparison with viral infection (ELANE only) and KD (Figure 5b)" (lines 341-343). Similarly, the discussion, they state: Our gene expression analysis showed increased expression of markers related to NETS in acute MIS-C, bacterial infections and KD compared with viral infections and HPC (lines 390 - 391). These genes are upregulated with neutrophil activation and are not necessarily markers of NETS. To support this statement, multiple assays (eg bisulfite sequencing of cell-free DNA to determine cell origins, quantification of intact nucleosomes containing histone 3.1, or citrullinated histone H3R8, among others) would need to be done. + +2. For the T cell stimulation assays, the percentages of antigen-specific T cells (eg through an AIM assay) are important for understanding the data, as this may vary greatly among the cohorts and may contribute assessments of differences in cytokine production. Intracellular staining for key cytokines (eg IFN-g) in SARS-CoV-2-specific T cells would be more convincing evidence of the attenuated response to spike antigen that the authors report. These data are also complicated by the fact that for some of the patients with MIS-C, there was little response to mitogen stimulation (which is typically used as a positive control to indicate overall cell function despite a lack of specific Ag response). + +3. The manuscript describes findings, but unfortunately cannot identify underlying mechanisms. a. For example, the authors state that: "Taken together, MOFA showed differences in myeloid cell and T cell activation markers predominate differences between groups of patients with severe febrile illnesses and innate and adaptive immune cell function is restored by convalescence in MIS + +<--- Page Split ---> + +C and SBI." (lines 227 – 230). What are the mechanisms underlying these differences? b. Similarly, the differences in gene expression are described without additional context or follow- up investigations, as line lines 366 – 370 presented increased expression of IFNAR1, IFNGR1/2 in patients with MIS- C, SBI, and KD compared to those with SVI) and increased TLR3 in patients with SVI and KD compared to MIS- C and SBI. What is the significance of these findings? + +4. This claim needs additional clarification: "Further experiments to define the mechanism of NET production in severe febrile illness in children may be useful, particularly since polyspecific intravenous immunoglobulins are used as treatment in MIS-C, KD, and toxic shock syndrome" (lines 392 – 394). Are the authors implying that IVIG influences NETs? + +5. Additional support is needed to support the authors' statement that: "More generally, this characterization suggests a key signaling role for neutrophils." Additional studies are needed to prove that neutrophils have a key signaling role in the pathogenesis of MIS-C. How do the authors differentiate between bystander activation/apoptosis of neutrophils from a driver effect of neutrophil activation? + +6. Please justify why for the human adult controls all were vaccinated but for human pediatric controls almost none were vaccinated. It is unclear to me why the healthy adult controls (HAC) were chosen as the rest of the cohorts are pediatric. It is not surprising that there are differences immunologically between non-ill vaccinated adults and severely ill febrile children. Some of the differences were between MIS-C and HAC only and not with healthy pediatric controls (HPC) eg. lines 280-283. So if HPC and MIS-C are different than HAC, would it infer that it is an age-related difference given the immune systems of adults are different than children? + +7. There are no details given in the table of patients about the HAC but the age differences in the pediatric cohorts is large. For example, KD median age is 1.4 years and there are only 8 KD patients. SVI 2.9 years median age. Whereas MIS-C, SBI and other inflammatory conditions median age is 9-10 years. Age alone may explain differences. + +8. The authors do not note that MIS-C overlaps with KD and many MIS-C patients meet KD criteria. Sub-phenotypes within MIS-C are also important to evaluate. + +9. The authors repeatedly mention "sepsis" and note a paper by Menon showing overlap of critical illness phenotypes. The relationship of the authors work to reference is not clear to me. MIS-C is a post-infectious inflammatory process that looks like sepsis. The patients with SBI likely many have sepsis and some of the SVI. The paper by Menon compared TBI, sepsis, ARDS and other critical illness phenotypes and showed overlap of these phenotypes. The authors are trying to show differences and are not emphasizing similarities. + +Minor comments + +1. In the introduction, you state with certainty why the incidence of MIS-C has decreased. But it is not certain, and the authors may want to insert the word "likely" before the word "because". + +<--- Page Split ---> + +2. Expressing the cytokine concentration in pg/mL or ng/mL is standard convention. The baseline units in Supplemental Table 5 are not defined. + +## Reviewer #2 (Remarks to the Author): + +Patel et al. presented a study on the immunology of severe febrile illness. The results are well presented however they are preliminary compared to other studies published in Nature Communications which generally takes studies that generate in depth results leading to deeper insights of the disease. Therefore, the current manuscript is well suited in other journals such as Immunology or Frontiers in Immunology or similar. + +Having said that the authors can improve the study to make it more fit with Nature Comm requirements by adding the following additional work to the study: + +1) In immunophenotyping the authors used GLM (lines 171 - 230) to identify the themes distinct to MIS-C however their results are subjective nad the validation was supported by hierarchical clustering which is not ideal. It would be better if the authors carry out deeper analysis of the RNAseq data and apply GSEA on the DEG especially the C7 geneset which has over 4000 immune related pathways then filter based on p-value and FDR and validated the top 3-5 pathways. If the top 3 pathways are activated innate immune cells then dysregulated T-cell function then mature and activated myeloid DC they can use the data they have to show that the validation is correct, but if not they should carry out additional validation on whatever the GSEA brings. This will provide deeper insights into some of the mechanisms involved in MIS in children + +2) The authors need to carry out additional analysis using other software to show the role of the different immune cells. For example they can use CIBERSORT. This can be done on the targeted or the RNAseq from the blood but will provide better insights into the immune response in MIS + +3) in line 638 the authors NF-kB but which part of the NF-kB they are looking for when they say activation e.g. is it p65, p50, p52 or RelA ..etc. They need to investigate this further as they may provide more interesting results because many immune cell types activate NFkB in different ways. For example recent publications showed that in pooled purified NK-T-like and NK cells (CD3+CD56+ and CD3-CD56+, respectively) the expression of mRNA coding for TLR1 to TLR9 was observed: https://onlinelibrary.wiley.com/doi/full/10.1038/icb.2013.99 + +Since TLRs are upstream of the NFkB pathway concentrating on some of the relevant NFkB molecules can provide insights into the existing findings the authors presented in this manuscript. + +<--- Page Split ---> + +# Re: NCOMMS-23-44279-R1 Title: Immunology of severe febrile illness in children in the COVID-19 era + +## Reviewer #1 + +We thank the reviewer for taking time to critically appraise our work and providing constructive critique to improve our manuscript. We hope that our responses have addressed your concerns. We wish to note that revisions based on your comments have strengthened our work. + +## Major comments: + +1. In their analysis of gene expression, the authors attribute a limited number of changes in mass cytometry to highly specific cellular states. However, these few proteins are not sufficiently specific for the authors' claims: + +<--- Page Split ---> + +a. For example, they use CD279 as a marker for exhausted T cells, but this gene is also upregulated on T cells in response to Type II IFNs, which does not necessarily imply exhaustion. Additionally, CD279 is upregulated on recently activated T cells and on specific subsets of T cells (eg CD4+ T follicular helper cells). Similar findings and the limitations of using CD279 as a sole marker of exhaustion have been noted in patients with MIS-C (Vella, L. et al. Sci Immunol., 2021). + +Response: Correlates of T cell activation, exhaustion, and apoptosisWe have run regression analyses of the co-expression of CD279 PD1 with important markers of T cell activation, exhaustion and apoptosis (HLA-DR, CD38, CD152 CTLA4, CD278 ICOS, CD134 OX40, CD95 Fas), and with intracellular IFNγ concentrations in CD4 memory T cells, CD8 memory T cells and memory regulatory T (Treg) cells (Supplementary Figure 9). There was a pronounced increase in expression of CD279 PD1 in CD4 memory T cells from patients with MIS-C in comparison to other cell populations, and CD4 memory T cells from patients with other illnesses. + +In general, markers of activation, exhaustion and apoptosis were highly associated \((p< 0.001\) and \(\mathsf{R}^2 >0.20)\) with CD279 PD- 1 in memory CD4 T cells. In general, markers of activation, exhaustion and apoptosis had lower p values and co- efficients of determination in memory CD8 T cells. Markers of activation and exhaustion were associated with CD279 PD- 1 in memory \(\mathsf{T}_{\mathrm{reg}}\) cells, but this was less so for CD95 Fas (used as a marker of apoptosis, \(p = 0.027\) and \(\mathsf{R}^2 = 0.029\) ) and CD223 LAG3 (used as a marker of T cell exhaustion \((p = 0.647\) \(\mathsf{R}^2 = 0\) ). Thus, CD4 memory T cells co- express markers of T cell activation, exhaustion and apoptosis in severe febrile illness in children (particularly MIS- C), but this is less prominent in CD8 T cells and memory \(\mathsf{T}_{\mathrm{reg}}\) cells. + +We now illustrate the co- expression of CD279 PD1 with markers of activation, exhaustion and apoptosis in CD4 memory and naive/effector T cells from a representative child with MIS- C, in comparison with a representative healthy pediatric control child (Supplementary Figure 10). + +Using cell stimulation / cytokine release assays, we show that there is a lower upregulation of IFNγ and other pro- inflammatory cytokines in response to SARS- CoV- 2 Ag1 stimulation in children with MIS- C at T1 in comparison to vaccinated healthy adult controls, suggesting a differential T cell response to the same antigen stimulus (submitted manuscript Figure 3b). We subsequently showed that there was also a lower upregulation of IFNγ and other pro- inflammatory cytokines in response to mitogen in children with MIS- C, SBI and SVI at T1 in comparison with healthy pediatric controls and vaccinated healthy adult controls (submitted manuscript Figure 3c). These cell stimulation data support the mass cytometry data that show the co- existence of T cell activation and exhaustion in children with MIS- C and SBI. + +We then analysed differential gene expression in children with MIS- C, SBI and other severe febrile illnesses (submitted manuscript Figure 5). These differential gene expression data also support the mass cytometry and cell stimulation data that show the co- existence of T cell activation and exhaustion in children with MIS- C and SBI. + +<--- Page Split ---> + +We believe that our findings are in accordance with previous work describing the immunology of MIS- C1 and with data on the immunology of adult sepsis2. Vella and co-authors describe both a CD4 and CD8 T cell response in MIS- C, and use CD279 PD1 and CD39 as markers of T cell exhaustion in activated T cells. They describe a population of CX3CR1+ CD8 T cells that correlate with the use of vasoactive medication as the primary population of interest, in contrast to our data that emphasize CD4 T cells as the primary population of interest. This may represent sample timing, since Vella and co-authors sampled patients for lymphocyte cytometry typically several (≥5) days following presentation to hospital, in contrast to our earlier sampling (median 1.6, IQR 0.7–3.2, days for T1) and note that the CX3CR1+ CD8 T cells occur in patients with prolonged vasoactive therapy. + +b. The authors state that "Factor 2 represented restoration of innate and adaptive immune cell homeostasis, with a decrease in the proportion of immature neutrophils and increased CD11b and CD16 on myeloid cells" (lines 218 – 220). Additionally biologic proof is needed to support these statements, as these two markers are not sufficient to indicate "restoration of innate and adaptive immune cell homeostasis" + +## Response: + +We have changed the text to include a number of other markers and changed the term for Factor 2 from "restoration of innate and adaptive immune cell homeostasis" to "restoration of innate and adaptive immune cells to baseline". The use of MOFA reflects our wish to approach the data in an agnostic manner. However, to illustrate the additional markers used to support this statement, we have directly analysed important markers of innate and adaptive immune cell activation in patients with MIS- C and SBI at T1, T2 and T3 (Supplementary Figure 8). Data shown in these figures support the (admittedly broad) statement of restoration of innate and adaptive immune cell responses over time, features that are identified in Factor 2 in the agnostic analysis of these data. + +The paragraph now reads: + +Factor 2 represented restoration of innate and adaptive immune cells to baseline, with a decrease in the proportion of immature neutrophils, increased CD11b and CD16 expression and decreased phosphorylation of NFκB in myeloid cells, and increased CD28 changes in T cells, among other changes (Supplementary Figure 8). + +c. Similarly, the author note upregulation of "genes associated with formation of NETS31,32: ELANE (neutrophil elastase) and MPO (myeloperoxidase) were elevated in MIS-C in comparison with viral infection (ELANE only) and KD (Figure 5b)" (lines 341-343). Similarly, the discussion, they state: Our gene expression analysis showed increased expression of markers related to NETS in acute MIS-C, bacterial infections and KD compared with viral infections and HPC (lines 390 - 391). These genes are upregulated with neutrophil activation and are not necessarily markers of NETS. To support this statement, multiple assays (eg + +<--- Page Split ---> + +bisulfite sequencing of cell- free DNA to determine cell origins, quantification of intact nucleosomes containing histone 3.1, or citrullinated histone H3R8, among others) would need to be done. + +## Response + +We used a series of genes that have been associated with NETosis in children with MIS- C and other severe infections in adults and children3. However, we have rephrased the paragraph noted above to reflect the uncertainty of whether upregulation of these genes represents formation of NETs, or simply upregulation of activation markers in neutrophils. We have added a small section on possible NETosis in MIS- C, SBI and KD to the Discussion, particularly in the light of work by Boribong and co- authors3. The relevant paragraph now reads (n.b. reference numbers correspond to this document, not the submitted manuscript): + +In accordance with previous work, we observed highly activated neutrophils and other innate immune cells in MIS- C and SBI1,4,5, and in KD. Neutrophil expression of FcγRs enables neutrophil phagocytosis in SBI. However, neutrophils from children with MIS- C had a distinct immune signature with extremely high expression of FcγRI and CD95/Fas. Upregulation of FcγR expression through IFNγ signaling may predispose neutrophil degranulation. Our gene expression analysis showed increased expression of genes associated with neutrophil activation, degranulation and production of NETs in acute MIS- C, bacterial infections and KD compared with viral infections and HPC. We did not, however, directly measure NET formation with microscopy and measurements of cell free DNA. However, other groups have shown extensive NET formation in MIS- C3. Formation of NETs by activated and apoptotic neutrophils may induce endothelial damage and thrombosis in MIS- C3, COVID- 19 and acute respiratory distress syndrome6, and KD7. Further experiments to measure the extent of NETosis in severe febrile illness in children and to define the mechanism of NET production in severe febrile illness in children may be useful. + +2. For the T cell stimulation assays, the percentages of antigen-specific T cells (eg through an AIM assay) are important for understanding the data, as this may vary greatly among the cohorts and may contribute assessments of differences in cytokine production. Intracellular staining for key cytokines (eg IFN-g) in SARS-CoV-2-specific T cells would be more convincing evidence of the attenuated response to spike antigen that the authors report. These data are also complicated by the fact that for some of the patients with MIS-C, there was little response to mitogen stimulation (which is typically used as a positive control to indicate overall cell function despite a lack of specific Ag response). + +Response: We agree that there is an attenuated response to spike antigen (SARS- CoV- 2 Ag1) in the cell stimulation assays (see above) in children with MIS- C, in comparison to vaccinated healthy adult controls (note, the healthy pediatric controls were seronegative for SARS- CoV- 2 IgG/IgM). However, more generally, we hypothesized that children with severe febrile illness would have a lower ability to upregulate cytokine production in response to pathogen antigen due to T cell exhaustion. The data that show little response to mitogen + +<--- Page Split ---> + +stimulation in children with MIS- C, and also in children with SBI, are supportive of this hypothesis. + +We have measured intracellular IFNy in the mass cytometry experiments. We were unable to stain for T cells with the reported T cell receptor expansion (described as \(\mathsf{V}\beta 21.3^{8}\) or \(\mathsf{V}\beta 11.2^{9,10}\) ) because the metal- conjugated antibodies to this region did not (and do not to our knowledge) exist. Such an approach would also limit the applicability of the experiment to children with MIS- C, rather than the comparative immunological approach to severe febrile illnesses (including severe bacterial infection and severe viral infection from several different pathogens) in children that we have taken. + +3. The manuscript describes findings, but unfortunately cannot identify underlying mechanisms. + +a. For example, the authors state that: "Taken together, MOFA showed differences in myeloid cell and T cell activation markers predominate differences between groups of patients with severe febrile illnesses and innate and adaptive immune cell function is restored by convalescence in MIS-C and SBI." (lines 227 - 230). What are the mechanisms underlying these differences? + +## Response: + +We were not able to test children before they become unwell, and without adequate models of disease, we are unable to accurately discriminate between pathways that are pathological or pathways that represent a beneficial host response to severe inflammation. We have extended the Discussion to highlight these limitations and areas for future research. We also hope that the reviewer agrees with us that testing children before they become unwell with acute febrile illnesses is not feasible. + +The sentences of relevance now read: + +A key limitation to many observational studies of childhood disease is the lack of sampling prior to illness. This limits our ability to infer differences between causal pathways to disease, and "bystander" inflammation. Further ex vivo experiments may be useful, particularly regarding modulation of neutrophil activation. + +b. Similarly, the differences in gene expression are described without additional context or follow-up investigations, as line lines 366 - 370 presented increased expression of IFNAR1, IFNGR1/2 in patients with MIS-C, SBI, and KD compared to those with SVI) and increased TLR3 in patients with SVI and KD compared to MIS-C and SBI. What is the significance of these findings? + +## Response: + +We have extended the Discussion accordingly, noting that decreased IFNα, IFNγ1/2 receptor expression has been previously noted in severe viral infection. It is unclear whether this represents a pathological response to viral disease or whether this is a beneficial downregulation of IFN signalling for these children to limit inflammatory damage. Similarly, we have expanded the Discussion section to note the significance of upregulated TLR- 3 expression in viral infection. The sentences now read: + +<--- Page Split ---> + +In the whole blood differential gene expression analysis we noted increased expression of receptors for IFNa/β and for IFNγ in children with MIS- C, bacterial illness and KD in comparison with viral illness, implying continued upregulation of inflammatory responses in these illnesses. It is unclear if the relative downregulation of IFNAR1/IFNAR2/IFNGR1/IFNGR2 in SVI is a physiological response to limit over- exuberant inflammation or is a pathological process. Conversely, TLR3 is required for clearance of herpes simplex virus11, but implicated its upregulation is implicated in damaging innate and adaptive immune responses in respiratory infection12. Future work should explore the association of IFNγ signaling with T cell exhaustion in severe febrile illnesses in children. + +4. This claim needs additional clarification: "Further experiments to define the mechanism of NET production in severe febrile illness in children may be useful, particularly since polyspecific intravenous immunoglobulin are used as treatment in MIS-C, KD, and toxic shock syndrome" (lines 392 – 394). Are the authors implying that IVIG influences NETs? + +## Response: + +There is reasonable evidence that NETs are produced in MIS- C3 and SBI2, and our data here do not contradict this. We consider there to be reasonable evidence from other studies that IVIG modulates the formation of NETs that are induced by application of plasma from patients with severe COVID- 19 to ex vivo healthy donor neutrophils6,13,14. Given that IVIG is widely used for the treatment of MIS- C15 and some SBI (particularly streptococcal toxic shock syndrome)16, we believe that further experiments to define the mechanism of NET production may be useful. However, we have become more circumspect in the manuscript. The relevant sentence now reads: + +Further experiments to measure, define mechanisms and explore immunomodulation of NETosis in severe febrile illness in may be useful. + +5. Additional support is needed to support the authors' statement that: "More generally, this characterization suggests a key signaling role for neutrophils." Additional studies are needed to prove that neutrophils have a key signaling role in the pathogenesis of MIS-C. How do the authors differentiate between bystander activation/apoptosis of neutrophils from a driver effect of neutrophil activation? + +Response: We have removed the "signalling" component of this sentence, since we are unable to differentiate between neutrophils as primary drivers of disease in comparison to a bystander effect. The sentence, "More generally, this characterization..." has now been removed entirely. + +6. Please justify why for the human adult controls all were vaccinated but for human pediatric controls almost none were vaccinated. It is unclear to me why the healthy adult controls (HAC) were chosen as the rest of the cohorts are pediatric. It is not surprising that there are differences immunologically between non-ill vaccinated adults and severely ill febrile children. Some of the differences were between MIS-C and HAC + +<--- Page Split ---> + +only and not with healthy pediatric controls (HPC) eg. lines 280- 283. So if HPC and MIS- C are different than HAC, would it infer that it is an age- related difference given the immune systems of adults are different than children? + +## Response: + +We agree that differences in T cell response to antigen between infants and older children have been well described. However, by the age of approximately 2- 3 years children appear to produce robust antibody responses to protein and polysaccharide antigens in vaccines and pathogens20,21. More specifically, as noted above, recent data have shown that SARS- CoV- 2 mRNA vaccines elicit a robust antibody response in children aged 6 months to 5 years, similar to that of mRNA vaccination in adults19. The median age of children with MIS- C in the cohort was 9.6 years (IQR 5.4- 13.2 years), an age when one might expect mature memory T cell responses following immunisation either by infection or vaccination18. + +Furthermore, at the time of study recruitment there was a small unrepresentative cohort of vaccinated children in the United Kingdom due to a focus of vaccination campaigns on older adults. By the time of vaccine rollout for children in the UK a large proportion of children had been exposed to SARS- CoV- 2 (and therefore the risk of developing MIS- C)17. We have captured this point in the discussion. + +7. There are no details given in the table of patients about the HAC but the age differences in the paediatric cohorts is large. For example, KD median age is 1.4 years and there are only 8 KD patients. SVI 2.9 years median age. Whereas MIS-C, SBI and other inflammatory conditions median age is 9-10 years. Age alone may explain differences. + +## Response + +We have now added citations to Table 1 and Supplementary Table 1 in the text of the Results about the HPC and the HAC respectively. + +We agree that age may explain some of the differences between the severe febrile illnesses in the cohorts (but see above with a view on the development of T cell responses over the first 2- 3 years of life). However, this does not make the comparisons less valid: severe viral infections and Kawasaki disease are typically syndromes of early childhood. Indeed, we sought to recruit children at the age where they commonly present with the range of severe febrile illnesses studied in the cohort - rather than seeking to recruit non- typical cases. + +8. The authors do not note that MIS-C overlaps with KD and many MIS-C patients meet KD criteria. Sub-phenotypes within MIS-C are also important to evaluate. + +## Response + +We agree that the clinical overlap between KD and MIS- C has been highlighted since the early case series of MIS- C (e.g.22- 24). There is also considerable clinical overlap between MIS- C and toxic shock syndrome22,25. + +We have noted this in the Introduction: Clinically, MIS- C shares similarities with severe bacterial infection (SBI) including toxic shock syndrome (TSS), and Kawasaki disease (KD)25. Both MIS- C and KD can also cause coronary artery aneurysms (CAA). MIS- C may + +<--- Page Split ---> + +share immunological features with SBI and KD including a skew towards activated immature neutrophil populations, markers of neutrophil extracellular trap (NET) production, and reduced markers for antigen presentation. + +We agree that sub- phenotypes within MIS- C may be important, and that these phenotypes may also be shared across diseases. Using cell population and cell expression markers we identified two distinct clusters ("sub- phenotypes") in children with severe febrile illness (Cluster 1 and Cluster 2; Figure 2c). Children in Cluster 1 were more likely to receive vasoactive infusions than children with Cluster 2. We have also added the hierarchical clustering in children in whom no immunomodulation was given (Supplementary Figure 4) which supports the existence of sub- phenotypes in severe febrile illnesses in children, and MIS- C specifically. + +9. The authors repeatedly mention "sepsis" and note a paper by Menon showing overlap of critical illness phenotypes. The relationship of the authors work to reference is not clear to me. MIS-C is a post-infectious inflammatory process that looks like sepsis. The patients with SBI likely many have sepsis and some of the SVI. The paper by Menon compared TBI, sepsis, ARDS and other critical illness phenotypes and showed overlap of these phenotypes. The authors are trying to show differences and are not emphasizing similarities. + +## Response: + +We agree that this manuscript should be balancing a description of the similarities across severe febrile illness in children as well as the differences between them. We checked and can confirm that we do not have a reference with Menon as a first or senior co-author in the References. We have, however, taken the opportunity to add a reference to a recent paper by Schlapbach and colleagues32 that operationalizes the diagnosis of "sepsis" in children – that emphasizes the similarities between diagnoses that are conceptualized as "sepsis". + +We mention "sepsis" in the start of the Introduction: + +Severe febrile illnesses in children requiring hospitalization and organ support, arise from diverse infections or inflammatory triggers, and overlap with the dysregulated host response that characterizes sepsis32- 34. + +And the start of the Discussion: + +We compared the immunology of severe febrile illnesses in children over the trajectory of illnesses2,33,35. This approach is supported by the framing of sepsis as a dysfunctional host response to infection34, the successful use of immunomodulator therapies during the COVID- 19 pandemic36, and ongoing trials in sepsis2,33. Using mass cytometry for peripheral blood immunophenotyping, cell stimulation assays and gene expression data with supervised, and unsupervised analytic approaches, we identified several shared and distinct immunological pathways in MIS- C, SBI, SVI and KD. + +## Minor comments + +<--- Page Split ---> + +1. In the introduction, you state with certainty why the incidence of MIS-C has decreased. But it is not certain, and the authors may want to insert the word "likely" before the word "because". + +## Response + +The sentence now reads: + +Although the incidence of MIS- C has now declined, likely because of natural and vaccine- induced population immunity against SARS- CoV- 2... + +2. Expressing the cytokine concentration in pg/mL or ng/mL is standard convention. The baseline units in Supplemental Table 5 are not defined. Response: The units have now been added as appropriate. + +## Reviewer #2 + +We thank the reviewer for taking time to critically appraise our work and providing constructive critique to improve our manuscript with validation using a different approach. Again, we wish to note that revisions based on your comments have strengthened our work considerably. Thank you. + +Patel et al. presented a study on the immunology of severe febrile illness. The results are well presented however they are preliminary compared to other studies published in Nature Communications which generally takes studies that generate in depth results leading to deeper insights of the disease. Therefore, the current manuscript is well suited in other journals such as Immunology or Frontiers in Immunology or similar. + +Having said that the authors can improve the study to make it more fit with Nature Comm requirements by adding the following additional work to the study: + +1. In immunophenotyping the authors used GLM (lines 171 - 230) to identify the themes distinct to MIS-C however their results are subjective and the validation was supported by hierarchical clustering which is not ideal. It would be better if the authors carry out deeper analysis of the RNAseq data and apply GSEA on the DEG especially the C7 geneset which has over 4000 immune related pathways then filter based on p-value and FDR and validated the top 3-5 pathways. If the top 3 pathways are activated innate immune cells then dysregulated T-cell function then mature and activated myeloid DC they can use the data they have to show that the validation is correct, but if not they should carry out additional validation on whatever the GSEA brings. This will provide deeper insights into some of the mechanisms involved in MIS in children + +## Response + +Thank you for highlighting the use of GSEA to infer immune pathways that are upregulated based on differential gene expression analysis in MIS- C (and other severe febrile illnesses in children). + +We have directly measured immune cell populations, their expression of markers of activation, exhaustion and apoptosis, and their function (in cell stimulation assays). Further, + +<--- Page Split ---> + +we explored the key themes in the data using multi- omic factor analysis (Supplementary Figure 5). The dimensionality reduction inherent to factor analyses are of use given we might anticipate several variables to be closely correlated. The factor analysis also combines data on the proportions of cell populations, and the expression of markers in cell populations. As discussed in the manuscript, Factor 1 represented myeloid cell activation and T cell activation, and Factor 2 represented restoration of innate and adaptive immune cells to baseline, and Factor 3 represented decreased phosphorylation of the cell signaling molecules STAT1 and STAT5 and NFkB. + +As suggested we undertook GSEA, as implemented by the R packages fgsea, using the C7 geneset (https://bioinf.wehi.edu.au/software/MSigDB/) and interpreted by the Gene Ontology database (https://geneontology.org/docs/go- enrichment- analysis/). Supplementary Figure 16 now describes the GSEA for the following comparisons. + +The top three pathways by \(\%\) hits were: + +a, MIS- C versus pHC: 1. Myeloid leukocyte activation, \(82.2\%\) 2. T cell differentiation, \(81.6\%\) 3. T cell activation, \(80.1\%\) + +b, DB infection versus pHC: 1. Myeloid leukocyte activation, \(88.0\%\) 2. T cell activation, \(84.4\%\) 3. Regulation of defense response, \(83.4\%\) + +c, DV infection versus pHC: 1. Innate immune response, \(66.1\%\) 2. Response to cytokine, \(63.5\%\) 3. Defence response to other organism, \(63.4\%\) + +As predicted by Reviewer 2, these are highly similar to themes identified from the directly measured immune cell proportions and cell activation, exhaustion and apoptotic markers. + +2. The authors need to carry out additional analysis using other software to show the role of the different immune cells. For example they can use CIBERSORT. This can be done on the targeted or the RNAseq from the blood but will provide better insights into the immune response in MIS. + +## Response + +In this manuscript we have directly measured, using standard markers, the major immune cell populations found in peripheral blood in the Derivation (mass cytometry) cohort. We have used the whole blood transcriptomic data to explore the features of neutrophil activation and apoptosis, T cell activation, and cytokine signalling. As suggested, we have now analyzed bulk whole blood transcriptomic data described in the manuscript in CIBERSORT (https://cibersortx.stanford.edu). We used the LM22 dataset + +<--- Page Split ---> + +as the reference dataset, which is a signature matrix containing 22 functionally defined human immune cell subsets derived from fresh, frozen and fixed tissues and profiled by microarrays. There are no immune cell populations from children with MIS- C or other severe febrile illnesses in these data. We used 100 permutations to measure p- values associated with each population described in the reference dataset to the bulk transcriptomic data described in this manuscript. + +The data are shown in Appendix 1. Following the removal of 3 outlying samples that had p values of \(\geq 0.05\) , we had patients in the following groups, MIS- C \((n = 38)\) , definite bacterial infection (DB, \(n = 186\) ), definite viral infection (DV, \(n = 137\) ), Kawasaki disease (KD, \(n = 136\) ) and paediatric healthy controls (HC, \(n = 134\) ). The data show median correlations of MIS- C 0.73, DB 0.68, DV 0.62, DV 0.60, KD 0.71, HC 0.65. + +Children with any severe febrile illness had lower CD8 T cells. Children with any severe febrile illness had resting CD4 T cells than healthy controls \((p< 0.05\) for all groups versus healthy controls), and MIS- C, DB and DV had the lower proportions than DV. In contrast, any severe febrile illness had higher memory activated CD4 T cells than healthy controls. + +Children with MIS- C had lower proportions of macrophages than other severe febrile illnesses or healthy controls. Children with MIS- C and SBI had higher proportions of M0 (non- activated) and M2 (anti- inflammatory) macrophages, than children with other severe febrile illnesses and healthy controls. M1 (pro- inflammatory) macrophages were generally not identified by CIBERSORT in the blood of any children. This may be due to genuine absence, or limitations of inferring rare immune cell subsets from bulk transcriptomic data with reference to a mixed adult cell reference population. + +Resting dendritic cells were also generally not identified in the blood of children with severe febrile illness or controls. Activated dendritic cells were a greater proportion of immune cell populations identified in children with SV in comparison with other severe febrile illnesses, which in turn may indicate altered cytokine signalling in children with SV. However, without single cell data that includes relatively rare populations such as dendritic cells, we cannot show this – this is a major reason why we have preferred to derive our immunological data from single cell (cytometry) methods and use gene expression analysis to explore our findings further. + +As anticipated, following review of the cytometry data, inferred neutrophil proportions were higher in children with MIS- C than any other severe febrile illness or healthy controls, and higher in DB and KD than both SV and healthy controls. + +3. in line 638 the authors NF-kB but which part of the NF-kB they are looking for when they say activation e.g. is it p65, p50, p52 or RelA ..etc. They need to investigate this further as they may provide more interesting results because many immune cell types activate NFkB in different ways. For example recent publications showed that in pooled purified NK-T-like and NK cells (CD3+CD56+ and CD3-CD56+, respectively) the expression of mRNA coding for TLR1 to TLR9 was observed: https://onlinelibrary.wiley.com/doi/full/10.1038/icb.2013.99 + +<--- Page Split ---> + +## Response + +Since TLRs are upstream of the NFkB pathway concentrating on some of the relevant NFkB molecules can provide insights into the existing findings the authors presented in this manuscript. + +We directly measured the phosphorylation status of the p65 subunit of NFkB and have now changed this in the manuscript, e.g. "and phosphorylated nuclear factor kappa B p65 (NFkB) expression in mature neutrophils" to emphasise the subunit specificity. + +Appendix 1. Proportions of cells in the bulk transcriptomic data, as inferred by CIBERSORT, in whole blood from children with MIS- C, definite bacterial infection (DB), definite viral infection (DV), Kawasaki disease (KD) and pediatric healthy controls (HC). 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Methylprednisolone versus intravenous immunoglobulins in children with paediatric inflammatory multisystem syndrome temporally associated with SARS- CoV- 2 (PIMS- TS): an open- label, multicentre, randomised trial. Lancet Child Adolesc Health 7, 238- 248, doi:10.1016/s2352- 4642(23)00020- 2 (2023).31 Recovery Trial Group. Immunomodulatory therapy in children with paediatric inflammatory multisystem syndrome temporally associated with SARS- CoV- 2 (PIMS- TS, MIS- C; RECOVERY): a randomised, controlled, open- label, platform trial. Lancet Child Adolesc Health 8, 190- 200, doi:10.1016/s2352- 4642(23)00316- 4 (2024).32 Schlapbach, L. J. et al. International Consensus Criteria for Pediatric Sepsis and Septic Shock. JAMA 331, 665- 674, doi:10.1001/jama.2024.0179 (2024).33 Maslove, D. M. et al. Redefining critical illness. Nat Med 28, 1141- 1148, doi:10.1038/s41591- 022- 01843- x (2022). + +<--- Page Split ---> + +34 Singer, M. et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis- 3). JAMA 315, 801- 810, doi:10.1001/jama.2016.0287 (2016).35 DeMerle, K. M. et al. Sepsis Subclasses: A Framework for Development and Interpretation. Crit Care Med 49, 748- 759, doi:10.1097/ccm.0000000000004842 (2021).36 Lamontagne, F. et al. A living WHO guideline on drugs for covid- 19. BMJ 370, m3379, doi:10.1136/bmj.m3379 (2020). + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #2 (Remarks to the Author): + +Patel et al. addressed the concerns I had regarding the manuscript and the additional analysis provided further credence of the results. + +One minor point is for the authors to insert the additional methods into the revised manuscript. For example the GSEA was only mentioned in the results section lines 339- 340 but no mention at all in the methods section. It is advisable they add a paragraph in the "Whole blood RNA Sequencing" section starting at line 631 mentioning the source of the tool used and if they used the R version list the version. Also mention which gene sets were screened e.g. I believe they only used C7 in this case. + +They should put any additional methods they applied in the methods section of the revised version. Other than that, I believe the concerns were addressed sufficiently for the manuscript to be accepted for publication. + +## Reviewer #3 (Remarks to the Author): + +The authors have addressed the reviewers' comment with appropriate changes to the text and additional data provided. The findings and impact of the data are thoughtfully discussed within the complexities of the field and the additional details support their conclusions well. Thank you for your thorough revision. + +<--- Page Split ---> + +# Re: NCOMMS-23-44279-B Title: Immunology of severe febrile illness in children in the COVID-19 era + +## Summary of changes to manuscript + +Materials and Methods + +- Addition of the methodology for the gene-set enrichment analysis contained in Supplementary Figure 16 as requested by Reviewer #2. + +## Reviewer #1 + +[No further comments.] + +Response: Thank you for your previous review. + +## Reviewer #2 + +Patel et al. addressed the concerns I had regarding the manuscript and the additional analysis provided further credence of the results. + +One minor point is for the authors to insert the additional methods into the revised manuscript. For example the GSEA was only mentioned in the results section lines 339- 340 but no mention at all in the methods section. It is advisable they add a paragraph in the "Whole blood RNA Sequencing" section starting at line 631 mentioning the source of the tool used and if they used the R version list the version. Also mention which gene sets were screened e.g. I believe they only used C7 in this case. + +They should put any additional methods they applied in the methods section of the revised version. Other than that, I believe the concerns were addressed sufficiently for the manuscript to be accepted for publication. + +## Response: + +We have added details of gene- set enrichment analysis (GSEA), at the suggested section of the Methods. We have also included the source of the tool (including references), the version of the tool, R version, and the signature gene set (C7) and its source. The data for the GSEA are available now online and this is shown. The R code for the analysis (and its source) is included on Dr Carter's GitHub page. The relevant section now reads: + +Gene- set enrichment analysis (GSEA)33 (Supplementary Figure 16) was undertaken on previously published data from Jackson et al.29 that are available at ArrayExpress under accession E- MTAB- 11671 and E- MTAB- 12793. We used the R (version 4.4) implementation of gene- set enrichment analysis (fgsea, version 1.3)42, the C7 immunologic signature gene sets available from as part of the Human MSigDB Collections (https://www.gseamsigdb.org/gsea/msigdb/collections.jsp), and Gene Ontology (GO) enrichment analysis. We compared gene enrichment between children with MIS- C and healthy controls, with definite bacterial infection and healthy controls, definite viral infection and healthy controls and children with MIS- C and definite bacterial infection. Code for the GSEA is available here: https://github.com/michaeljamescarter/SIFIC. + +## Reviewer #3 + +The authors have addressed the reviewers' comment with appropriate changes to the text and additional data provided. The findings and impact of the data are thoughtfully discussed within the complexities of the field and the additional details support their conclusions well. Thank you for your thorough revision. + +<--- Page Split ---> + +ResponseThank you for your review. + +<--- Page Split ---> diff --git a/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9540b813f1c7ba2e6e016d22696d20e9aa7817c6 --- /dev/null +++ b/peer_reviews/556692f14e8b0d1e0cf19cca609439b17ce6f4e0a85c3d1540b0262cd8f1a22d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,503 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 910, 240]]<|/det|> +Shared neutrophil and T cell dysfunction is accompanied by a distinct interferon signature during severe febrile illnesses in children + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 98, 323, 115]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[116, 164, 416, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 220, 253, 235]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[115, 238, 881, 290]]<|/det|> +1. In their analysis of gene expression, the authors attribute a limited number of changes in mass cytometry to highly specific cellular states. However, these few proteins are not sufficiently specific for the authors' claims: + +<|ref|>text<|/ref|><|det|>[[115, 292, 872, 382]]<|/det|> +- For example, they use CD279 as a marker for exhausted T cells, but this gene is also upregulated on T cells in response to Type II IFNs, which does not necessarily imply exhaustion. Additionally, CD279 is upregulated on recently activated T cells and on specific subsets of T cells (eg CD4+ T follicular helper cells). Similar findings and the limitations of using CD279 as a sole marker of exhaustion have been noted in patients with MIS-C (Vella, L. et al. Sci Immunol., 2021). + +<|ref|>text<|/ref|><|det|>[[115, 384, 876, 473]]<|/det|> +- The authors state that "Factor 2 represented restoration of innate and adaptive immune cell homeostasis, with a decrease in the proportion of immature neutrophils and increased CD11b and CD16 on myeloid cells" (lines 218 - 220). Additionally biologic proof is needed to support these statements, as these two markers are not sufficient to indicate "restoration of innate and adaptive immune cell homeostasis" + +<|ref|>text<|/ref|><|det|>[[114, 475, 879, 638]]<|/det|> +- Similarly, the author note upregulation of "genes associated with formation of NETS31,32: ELANE (neutrophil elastase) and MPO (myeloperoxidase) were elevated in MIS-C in comparison with viral infection (ELANE only) and KD (Figure 5b)" (lines 341-343). Similarly, the discussion, they state: Our gene expression analysis showed increased expression of markers related to NETS in acute MIS-C, bacterial infections and KD compared with viral infections and HPC (lines 390 - 391). These genes are upregulated with neutrophil activation and are not necessarily markers of NETS. To support this statement, multiple assays (eg bisulfite sequencing of cell-free DNA to determine cell origins, quantification of intact nucleosomes containing histone 3.1, or citrullinated histone H3R8, among others) would need to be done. + +<|ref|>text<|/ref|><|det|>[[114, 658, 866, 802]]<|/det|> +2. For the T cell stimulation assays, the percentages of antigen-specific T cells (eg through an AIM assay) are important for understanding the data, as this may vary greatly among the cohorts and may contribute assessments of differences in cytokine production. Intracellular staining for key cytokines (eg IFN-g) in SARS-CoV-2-specific T cells would be more convincing evidence of the attenuated response to spike antigen that the authors report. These data are also complicated by the fact that for some of the patients with MIS-C, there was little response to mitogen stimulation (which is typically used as a positive control to indicate overall cell function despite a lack of specific Ag response). + +<|ref|>text<|/ref|><|det|>[[114, 822, 879, 894]]<|/det|> +3. The manuscript describes findings, but unfortunately cannot identify underlying mechanisms. a. For example, the authors state that: "Taken together, MOFA showed differences in myeloid cell and T cell activation markers predominate differences between groups of patients with severe febrile illnesses and innate and adaptive immune cell function is restored by convalescence in MIS + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 95, 868, 188]]<|/det|> +C and SBI." (lines 227 – 230). What are the mechanisms underlying these differences? b. Similarly, the differences in gene expression are described without additional context or follow- up investigations, as line lines 366 – 370 presented increased expression of IFNAR1, IFNGR1/2 in patients with MIS- C, SBI, and KD compared to those with SVI) and increased TLR3 in patients with SVI and KD compared to MIS- C and SBI. What is the significance of these findings? + +<|ref|>text<|/ref|><|det|>[[115, 206, 866, 279]]<|/det|> +4. This claim needs additional clarification: "Further experiments to define the mechanism of NET production in severe febrile illness in children may be useful, particularly since polyspecific intravenous immunoglobulins are used as treatment in MIS-C, KD, and toxic shock syndrome" (lines 392 – 394). Are the authors implying that IVIG influences NETs? + +<|ref|>text<|/ref|><|det|>[[115, 297, 864, 388]]<|/det|> +5. Additional support is needed to support the authors' statement that: "More generally, this characterization suggests a key signaling role for neutrophils." Additional studies are needed to prove that neutrophils have a key signaling role in the pathogenesis of MIS-C. How do the authors differentiate between bystander activation/apoptosis of neutrophils from a driver effect of neutrophil activation? + +<|ref|>text<|/ref|><|det|>[[115, 425, 857, 553]]<|/det|> +6. Please justify why for the human adult controls all were vaccinated but for human pediatric controls almost none were vaccinated. It is unclear to me why the healthy adult controls (HAC) were chosen as the rest of the cohorts are pediatric. It is not surprising that there are differences immunologically between non-ill vaccinated adults and severely ill febrile children. Some of the differences were between MIS-C and HAC only and not with healthy pediatric controls (HPC) eg. lines 280-283. So if HPC and MIS-C are different than HAC, would it infer that it is an age-related difference given the immune systems of adults are different than children? + +<|ref|>text<|/ref|><|det|>[[115, 572, 877, 645]]<|/det|> +7. There are no details given in the table of patients about the HAC but the age differences in the pediatric cohorts is large. For example, KD median age is 1.4 years and there are only 8 KD patients. SVI 2.9 years median age. Whereas MIS-C, SBI and other inflammatory conditions median age is 9-10 years. Age alone may explain differences. + +<|ref|>text<|/ref|><|det|>[[115, 664, 870, 700]]<|/det|> +8. The authors do not note that MIS-C overlaps with KD and many MIS-C patients meet KD criteria. Sub-phenotypes within MIS-C are also important to evaluate. + +<|ref|>text<|/ref|><|det|>[[115, 718, 872, 826]]<|/det|> +9. The authors repeatedly mention "sepsis" and note a paper by Menon showing overlap of critical illness phenotypes. The relationship of the authors work to reference is not clear to me. MIS-C is a post-infectious inflammatory process that looks like sepsis. The patients with SBI likely many have sepsis and some of the SVI. The paper by Menon compared TBI, sepsis, ARDS and other critical illness phenotypes and showed overlap of these phenotypes. The authors are trying to show differences and are not emphasizing similarities. + +<|ref|>text<|/ref|><|det|>[[116, 829, 250, 844]]<|/det|> +Minor comments + +<|ref|>text<|/ref|><|det|>[[115, 847, 865, 882]]<|/det|> +1. In the introduction, you state with certainty why the incidence of MIS-C has decreased. But it is not certain, and the authors may want to insert the word "likely" before the word "because". + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 97, 860, 133]]<|/det|> +2. Expressing the cytokine concentration in pg/mL or ng/mL is standard convention. The baseline units in Supplemental Table 5 are not defined. + +<|ref|>sub_title<|/ref|><|det|>[[116, 135, 417, 151]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 171, 857, 262]]<|/det|> +Patel et al. presented a study on the immunology of severe febrile illness. The results are well presented however they are preliminary compared to other studies published in Nature Communications which generally takes studies that generate in depth results leading to deeper insights of the disease. Therefore, the current manuscript is well suited in other journals such as Immunology or Frontiers in Immunology or similar. + +<|ref|>text<|/ref|><|det|>[[115, 280, 802, 316]]<|/det|> +Having said that the authors can improve the study to make it more fit with Nature Comm requirements by adding the following additional work to the study: + +<|ref|>text<|/ref|><|det|>[[114, 334, 881, 499]]<|/det|> +1) In immunophenotyping the authors used GLM (lines 171 - 230) to identify the themes distinct to MIS-C however their results are subjective nad the validation was supported by hierarchical clustering which is not ideal. It would be better if the authors carry out deeper analysis of the RNAseq data and apply GSEA on the DEG especially the C7 geneset which has over 4000 immune related pathways then filter based on p-value and FDR and validated the top 3-5 pathways. If the top 3 pathways are activated innate immune cells then dysregulated T-cell function then mature and activated myeloid DC they can use the data they have to show that the validation is correct, but if not they should carry out additional validation on whatever the GSEA brings. This will provide deeper insights into some of the mechanisms involved in MIS in children + +<|ref|>text<|/ref|><|det|>[[115, 517, 872, 571]]<|/det|> +2) The authors need to carry out additional analysis using other software to show the role of the different immune cells. For example they can use CIBERSORT. This can be done on the targeted or the RNAseq from the blood but will provide better insights into the immune response in MIS + +<|ref|>text<|/ref|><|det|>[[115, 590, 883, 700]]<|/det|> +3) in line 638 the authors NF-kB but which part of the NF-kB they are looking for when they say activation e.g. is it p65, p50, p52 or RelA ..etc. They need to investigate this further as they may provide more interesting results because many immune cell types activate NFkB in different ways. For example recent publications showed that in pooled purified NK-T-like and NK cells (CD3+CD56+ and CD3-CD56+, respectively) the expression of mRNA coding for TLR1 to TLR9 was observed: https://onlinelibrary.wiley.com/doi/full/10.1038/icb.2013.99 + +<|ref|>text<|/ref|><|det|>[[115, 719, 870, 755]]<|/det|> +Since TLRs are upstream of the NFkB pathway concentrating on some of the relevant NFkB molecules can provide insights into the existing findings the authors presented in this manuscript. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[115, 443, 765, 479]]<|/det|> +# Re: NCOMMS-23-44279-R1 Title: Immunology of severe febrile illness in children in the COVID-19 era + +<|ref|>sub_title<|/ref|><|det|>[[118, 640, 228, 655]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[118, 657, 853, 727]]<|/det|> +We thank the reviewer for taking time to critically appraise our work and providing constructive critique to improve our manuscript. We hope that our responses have addressed your concerns. We wish to note that revisions based on your comments have strengthened our work. + +<|ref|>sub_title<|/ref|><|det|>[[118, 747, 274, 762]]<|/det|> +## Major comments: + +<|ref|>text<|/ref|><|det|>[[125, 789, 888, 846]]<|/det|> +1. In their analysis of gene expression, the authors attribute a limited number of changes in mass cytometry to highly specific cellular states. However, these few proteins are not sufficiently specific for the authors' claims: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 874, 208]]<|/det|> +a. For example, they use CD279 as a marker for exhausted T cells, but this gene is also upregulated on T cells in response to Type II IFNs, which does not necessarily imply exhaustion. Additionally, CD279 is upregulated on recently activated T cells and on specific subsets of T cells (eg CD4+ T follicular helper cells). Similar findings and the limitations of using CD279 as a sole marker of exhaustion have been noted in patients with MIS-C (Vella, L. et al. Sci Immunol., 2021). + +<|ref|>text<|/ref|><|det|>[[118, 228, 875, 369]]<|/det|> +Response: Correlates of T cell activation, exhaustion, and apoptosisWe have run regression analyses of the co-expression of CD279 PD1 with important markers of T cell activation, exhaustion and apoptosis (HLA-DR, CD38, CD152 CTLA4, CD278 ICOS, CD134 OX40, CD95 Fas), and with intracellular IFNγ concentrations in CD4 memory T cells, CD8 memory T cells and memory regulatory T (Treg) cells (Supplementary Figure 9). There was a pronounced increase in expression of CD279 PD1 in CD4 memory T cells from patients with MIS-C in comparison to other cell populations, and CD4 memory T cells from patients with other illnesses. + +<|ref|>text<|/ref|><|det|>[[117, 388, 873, 550]]<|/det|> +In general, markers of activation, exhaustion and apoptosis were highly associated \((p< 0.001\) and \(\mathsf{R}^2 >0.20)\) with CD279 PD- 1 in memory CD4 T cells. In general, markers of activation, exhaustion and apoptosis had lower p values and co- efficients of determination in memory CD8 T cells. Markers of activation and exhaustion were associated with CD279 PD- 1 in memory \(\mathsf{T}_{\mathrm{reg}}\) cells, but this was less so for CD95 Fas (used as a marker of apoptosis, \(p = 0.027\) and \(\mathsf{R}^2 = 0.029\) ) and CD223 LAG3 (used as a marker of T cell exhaustion \((p = 0.647\) \(\mathsf{R}^2 = 0\) ). Thus, CD4 memory T cells co- express markers of T cell activation, exhaustion and apoptosis in severe febrile illness in children (particularly MIS- C), but this is less prominent in CD8 T cells and memory \(\mathsf{T}_{\mathrm{reg}}\) cells. + +<|ref|>text<|/ref|><|det|>[[118, 568, 864, 639]]<|/det|> +We now illustrate the co- expression of CD279 PD1 with markers of activation, exhaustion and apoptosis in CD4 memory and naive/effector T cells from a representative child with MIS- C, in comparison with a representative healthy pediatric control child (Supplementary Figure 10). + +<|ref|>text<|/ref|><|det|>[[117, 657, 880, 818]]<|/det|> +Using cell stimulation / cytokine release assays, we show that there is a lower upregulation of IFNγ and other pro- inflammatory cytokines in response to SARS- CoV- 2 Ag1 stimulation in children with MIS- C at T1 in comparison to vaccinated healthy adult controls, suggesting a differential T cell response to the same antigen stimulus (submitted manuscript Figure 3b). We subsequently showed that there was also a lower upregulation of IFNγ and other pro- inflammatory cytokines in response to mitogen in children with MIS- C, SBI and SVI at T1 in comparison with healthy pediatric controls and vaccinated healthy adult controls (submitted manuscript Figure 3c). These cell stimulation data support the mass cytometry data that show the co- existence of T cell activation and exhaustion in children with MIS- C and SBI. + +<|ref|>text<|/ref|><|det|>[[118, 836, 873, 907]]<|/det|> +We then analysed differential gene expression in children with MIS- C, SBI and other severe febrile illnesses (submitted manuscript Figure 5). These differential gene expression data also support the mass cytometry and cell stimulation data that show the co- existence of T cell activation and exhaustion in children with MIS- C and SBI. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 101, 870, 299]]<|/det|> +We believe that our findings are in accordance with previous work describing the immunology of MIS- C1 and with data on the immunology of adult sepsis2. Vella and co-authors describe both a CD4 and CD8 T cell response in MIS- C, and use CD279 PD1 and CD39 as markers of T cell exhaustion in activated T cells. They describe a population of CX3CR1+ CD8 T cells that correlate with the use of vasoactive medication as the primary population of interest, in contrast to our data that emphasize CD4 T cells as the primary population of interest. This may represent sample timing, since Vella and co-authors sampled patients for lymphocyte cytometry typically several (≥5) days following presentation to hospital, in contrast to our earlier sampling (median 1.6, IQR 0.7–3.2, days for T1) and note that the CX3CR1+ CD8 T cells occur in patients with prolonged vasoactive therapy. + +<|ref|>text<|/ref|><|det|>[[177, 316, 875, 423]]<|/det|> +b. The authors state that "Factor 2 represented restoration of innate and adaptive immune cell homeostasis, with a decrease in the proportion of immature neutrophils and increased CD11b and CD16 on myeloid cells" (lines 218 – 220). Additionally biologic proof is needed to support these statements, as these two markers are not sufficient to indicate "restoration of innate and adaptive immune cell homeostasis" + +<|ref|>sub_title<|/ref|><|det|>[[118, 443, 208, 458]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 460, 870, 620]]<|/det|> +We have changed the text to include a number of other markers and changed the term for Factor 2 from "restoration of innate and adaptive immune cell homeostasis" to "restoration of innate and adaptive immune cells to baseline". The use of MOFA reflects our wish to approach the data in an agnostic manner. However, to illustrate the additional markers used to support this statement, we have directly analysed important markers of innate and adaptive immune cell activation in patients with MIS- C and SBI at T1, T2 and T3 (Supplementary Figure 8). Data shown in these figures support the (admittedly broad) statement of restoration of innate and adaptive immune cell responses over time, features that are identified in Factor 2 in the agnostic analysis of these data. + +<|ref|>text<|/ref|><|det|>[[119, 640, 338, 656]]<|/det|> +The paragraph now reads: + +<|ref|>text<|/ref|><|det|>[[118, 675, 879, 746]]<|/det|> +Factor 2 represented restoration of innate and adaptive immune cells to baseline, with a decrease in the proportion of immature neutrophils, increased CD11b and CD16 expression and decreased phosphorylation of NFκB in myeloid cells, and increased CD28 changes in T cells, among other changes (Supplementary Figure 8). + +<|ref|>text<|/ref|><|det|>[[178, 763, 878, 907]]<|/det|> +c. Similarly, the author note upregulation of "genes associated with formation of NETS31,32: ELANE (neutrophil elastase) and MPO (myeloperoxidase) were elevated in MIS-C in comparison with viral infection (ELANE only) and KD (Figure 5b)" (lines 341-343). Similarly, the discussion, they state: Our gene expression analysis showed increased expression of markers related to NETS in acute MIS-C, bacterial infections and KD compared with viral infections and HPC (lines 390 - 391). These genes are upregulated with neutrophil activation and are not necessarily markers of NETS. To support this statement, multiple assays (eg + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[208, 84, 877, 137]]<|/det|> +bisulfite sequencing of cell- free DNA to determine cell origins, quantification of intact nucleosomes containing histone 3.1, or citrullinated histone H3R8, among others) would need to be done. + +<|ref|>sub_title<|/ref|><|det|>[[118, 157, 204, 172]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[117, 174, 864, 317]]<|/det|> +We used a series of genes that have been associated with NETosis in children with MIS- C and other severe infections in adults and children3. However, we have rephrased the paragraph noted above to reflect the uncertainty of whether upregulation of these genes represents formation of NETs, or simply upregulation of activation markers in neutrophils. We have added a small section on possible NETosis in MIS- C, SBI and KD to the Discussion, particularly in the light of work by Boribong and co- authors3. The relevant paragraph now reads (n.b. reference numbers correspond to this document, not the submitted manuscript): + +<|ref|>text<|/ref|><|det|>[[115, 335, 875, 602]]<|/det|> +In accordance with previous work, we observed highly activated neutrophils and other innate immune cells in MIS- C and SBI1,4,5, and in KD. Neutrophil expression of FcγRs enables neutrophil phagocytosis in SBI. However, neutrophils from children with MIS- C had a distinct immune signature with extremely high expression of FcγRI and CD95/Fas. Upregulation of FcγR expression through IFNγ signaling may predispose neutrophil degranulation. Our gene expression analysis showed increased expression of genes associated with neutrophil activation, degranulation and production of NETs in acute MIS- C, bacterial infections and KD compared with viral infections and HPC. We did not, however, directly measure NET formation with microscopy and measurements of cell free DNA. However, other groups have shown extensive NET formation in MIS- C3. Formation of NETs by activated and apoptotic neutrophils may induce endothelial damage and thrombosis in MIS- C3, COVID- 19 and acute respiratory distress syndrome6, and KD7. Further experiments to measure the extent of NETosis in severe febrile illness in children and to define the mechanism of NET production in severe febrile illness in children may be useful. + +<|ref|>text<|/ref|><|det|>[[117, 620, 880, 764]]<|/det|> +2. For the T cell stimulation assays, the percentages of antigen-specific T cells (eg through an AIM assay) are important for understanding the data, as this may vary greatly among the cohorts and may contribute assessments of differences in cytokine production. Intracellular staining for key cytokines (eg IFN-g) in SARS-CoV-2-specific T cells would be more convincing evidence of the attenuated response to spike antigen that the authors report. These data are also complicated by the fact that for some of the patients with MIS-C, there was little response to mitogen stimulation (which is typically used as a positive control to indicate overall cell function despite a lack of specific Ag response). + +<|ref|>text<|/ref|><|det|>[[117, 782, 880, 890]]<|/det|> +Response: We agree that there is an attenuated response to spike antigen (SARS- CoV- 2 Ag1) in the cell stimulation assays (see above) in children with MIS- C, in comparison to vaccinated healthy adult controls (note, the healthy pediatric controls were seronegative for SARS- CoV- 2 IgG/IgM). However, more generally, we hypothesized that children with severe febrile illness would have a lower ability to upregulate cytokine production in response to pathogen antigen due to T cell exhaustion. The data that show little response to mitogen + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 830, 119]]<|/det|> +stimulation in children with MIS- C, and also in children with SBI, are supportive of this hypothesis. + +<|ref|>text<|/ref|><|det|>[[117, 137, 873, 262]]<|/det|> +We have measured intracellular IFNy in the mass cytometry experiments. We were unable to stain for T cells with the reported T cell receptor expansion (described as \(\mathsf{V}\beta 21.3^{8}\) or \(\mathsf{V}\beta 11.2^{9,10}\) ) because the metal- conjugated antibodies to this region did not (and do not to our knowledge) exist. Such an approach would also limit the applicability of the experiment to children with MIS- C, rather than the comparative immunological approach to severe febrile illnesses (including severe bacterial infection and severe viral infection from several different pathogens) in children that we have taken. + +<|ref|>text<|/ref|><|det|>[[118, 281, 805, 316]]<|/det|> +3. The manuscript describes findings, but unfortunately cannot identify underlying mechanisms. + +<|ref|>text<|/ref|><|det|>[[177, 317, 874, 406]]<|/det|> +a. For example, the authors state that: "Taken together, MOFA showed differences in myeloid cell and T cell activation markers predominate differences between groups of patients with severe febrile illnesses and innate and adaptive immune cell function is restored by convalescence in MIS-C and SBI." (lines 227 - 230). What are the mechanisms underlying these differences? + +<|ref|>sub_title<|/ref|><|det|>[[118, 425, 208, 440]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 442, 877, 550]]<|/det|> +We were not able to test children before they become unwell, and without adequate models of disease, we are unable to accurately discriminate between pathways that are pathological or pathways that represent a beneficial host response to severe inflammation. We have extended the Discussion to highlight these limitations and areas for future research. We also hope that the reviewer agrees with us that testing children before they become unwell with acute febrile illnesses is not feasible. + +<|ref|>text<|/ref|><|det|>[[120, 569, 433, 584]]<|/det|> +The sentences of relevance now read: + +<|ref|>text<|/ref|><|det|>[[118, 586, 867, 657]]<|/det|> +A key limitation to many observational studies of childhood disease is the lack of sampling prior to illness. This limits our ability to infer differences between causal pathways to disease, and "bystander" inflammation. Further ex vivo experiments may be useful, particularly regarding modulation of neutrophil activation. + +<|ref|>text<|/ref|><|det|>[[177, 675, 875, 765]]<|/det|> +b. Similarly, the differences in gene expression are described without additional context or follow-up investigations, as line lines 366 - 370 presented increased expression of IFNAR1, IFNGR1/2 in patients with MIS-C, SBI, and KD compared to those with SVI) and increased TLR3 in patients with SVI and KD compared to MIS-C and SBI. What is the significance of these findings? + +<|ref|>sub_title<|/ref|><|det|>[[118, 784, 208, 799]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[118, 801, 878, 907]]<|/det|> +We have extended the Discussion accordingly, noting that decreased IFNα, IFNγ1/2 receptor expression has been previously noted in severe viral infection. It is unclear whether this represents a pathological response to viral disease or whether this is a beneficial downregulation of IFN signalling for these children to limit inflammatory damage. Similarly, we have expanded the Discussion section to note the significance of upregulated TLR- 3 expression in viral infection. The sentences now read: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 100, 875, 263]]<|/det|> +In the whole blood differential gene expression analysis we noted increased expression of receptors for IFNa/β and for IFNγ in children with MIS- C, bacterial illness and KD in comparison with viral illness, implying continued upregulation of inflammatory responses in these illnesses. It is unclear if the relative downregulation of IFNAR1/IFNAR2/IFNGR1/IFNGR2 in SVI is a physiological response to limit over- exuberant inflammation or is a pathological process. Conversely, TLR3 is required for clearance of herpes simplex virus11, but implicated its upregulation is implicated in damaging innate and adaptive immune responses in respiratory infection12. Future work should explore the association of IFNγ signaling with T cell exhaustion in severe febrile illnesses in children. + +<|ref|>text<|/ref|><|det|>[[118, 281, 870, 370]]<|/det|> +4. This claim needs additional clarification: "Further experiments to define the mechanism of NET production in severe febrile illness in children may be useful, particularly since polyspecific intravenous immunoglobulin are used as treatment in MIS-C, KD, and toxic shock syndrome" (lines 392 – 394). Are the authors implying that IVIG influences NETs? + +<|ref|>sub_title<|/ref|><|det|>[[118, 390, 208, 405]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 406, 880, 550]]<|/det|> +There is reasonable evidence that NETs are produced in MIS- C3 and SBI2, and our data here do not contradict this. We consider there to be reasonable evidence from other studies that IVIG modulates the formation of NETs that are induced by application of plasma from patients with severe COVID- 19 to ex vivo healthy donor neutrophils6,13,14. Given that IVIG is widely used for the treatment of MIS- C15 and some SBI (particularly streptococcal toxic shock syndrome)16, we believe that further experiments to define the mechanism of NET production may be useful. However, we have become more circumspect in the manuscript. The relevant sentence now reads: + +<|ref|>text<|/ref|><|det|>[[118, 568, 847, 603]]<|/det|> +Further experiments to measure, define mechanisms and explore immunomodulation of NETosis in severe febrile illness in may be useful. + +<|ref|>text<|/ref|><|det|>[[118, 621, 855, 711]]<|/det|> +5. Additional support is needed to support the authors' statement that: "More generally, this characterization suggests a key signaling role for neutrophils." Additional studies are needed to prove that neutrophils have a key signaling role in the pathogenesis of MIS-C. How do the authors differentiate between bystander activation/apoptosis of neutrophils from a driver effect of neutrophil activation? + +<|ref|>text<|/ref|><|det|>[[118, 728, 876, 800]]<|/det|> +Response: We have removed the "signalling" component of this sentence, since we are unable to differentiate between neutrophils as primary drivers of disease in comparison to a bystander effect. The sentence, "More generally, this characterization..." has now been removed entirely. + +<|ref|>text<|/ref|><|det|>[[118, 818, 870, 908]]<|/det|> +6. Please justify why for the human adult controls all were vaccinated but for human pediatric controls almost none were vaccinated. It is unclear to me why the healthy adult controls (HAC) were chosen as the rest of the cohorts are pediatric. It is not surprising that there are differences immunologically between non-ill vaccinated adults and severely ill febrile children. Some of the differences were between MIS-C and HAC + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 875, 137]]<|/det|> +only and not with healthy pediatric controls (HPC) eg. lines 280- 283. So if HPC and MIS- C are different than HAC, would it infer that it is an age- related difference given the immune systems of adults are different than children? + +<|ref|>sub_title<|/ref|><|det|>[[118, 157, 208, 172]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 174, 875, 316]]<|/det|> +We agree that differences in T cell response to antigen between infants and older children have been well described. However, by the age of approximately 2- 3 years children appear to produce robust antibody responses to protein and polysaccharide antigens in vaccines and pathogens20,21. More specifically, as noted above, recent data have shown that SARS- CoV- 2 mRNA vaccines elicit a robust antibody response in children aged 6 months to 5 years, similar to that of mRNA vaccination in adults19. The median age of children with MIS- C in the cohort was 9.6 years (IQR 5.4- 13.2 years), an age when one might expect mature memory T cell responses following immunisation either by infection or vaccination18. + +<|ref|>text<|/ref|><|det|>[[118, 335, 866, 424]]<|/det|> +Furthermore, at the time of study recruitment there was a small unrepresentative cohort of vaccinated children in the United Kingdom due to a focus of vaccination campaigns on older adults. By the time of vaccine rollout for children in the UK a large proportion of children had been exposed to SARS- CoV- 2 (and therefore the risk of developing MIS- C)17. We have captured this point in the discussion. + +<|ref|>text<|/ref|><|det|>[[118, 442, 875, 514]]<|/det|> +7. There are no details given in the table of patients about the HAC but the age differences in the paediatric cohorts is large. For example, KD median age is 1.4 years and there are only 8 KD patients. SVI 2.9 years median age. Whereas MIS-C, SBI and other inflammatory conditions median age is 9-10 years. Age alone may explain differences. + +<|ref|>sub_title<|/ref|><|det|>[[118, 533, 204, 548]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[118, 550, 827, 585]]<|/det|> +We have now added citations to Table 1 and Supplementary Table 1 in the text of the Results about the HPC and the HAC respectively. + +<|ref|>text<|/ref|><|det|>[[117, 604, 875, 710]]<|/det|> +We agree that age may explain some of the differences between the severe febrile illnesses in the cohorts (but see above with a view on the development of T cell responses over the first 2- 3 years of life). However, this does not make the comparisons less valid: severe viral infections and Kawasaki disease are typically syndromes of early childhood. Indeed, we sought to recruit children at the age where they commonly present with the range of severe febrile illnesses studied in the cohort - rather than seeking to recruit non- typical cases. + +<|ref|>text<|/ref|><|det|>[[117, 729, 856, 764]]<|/det|> +8. The authors do not note that MIS-C overlaps with KD and many MIS-C patients meet KD criteria. Sub-phenotypes within MIS-C are also important to evaluate. + +<|ref|>sub_title<|/ref|><|det|>[[118, 784, 204, 799]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[118, 801, 856, 852]]<|/det|> +We agree that the clinical overlap between KD and MIS- C has been highlighted since the early case series of MIS- C (e.g.22- 24). There is also considerable clinical overlap between MIS- C and toxic shock syndrome22,25. + +<|ref|>text<|/ref|><|det|>[[118, 855, 855, 907]]<|/det|> +We have noted this in the Introduction: Clinically, MIS- C shares similarities with severe bacterial infection (SBI) including toxic shock syndrome (TSS), and Kawasaki disease (KD)25. Both MIS- C and KD can also cause coronary artery aneurysms (CAA). MIS- C may + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 868, 137]]<|/det|> +share immunological features with SBI and KD including a skew towards activated immature neutrophil populations, markers of neutrophil extracellular trap (NET) production, and reduced markers for antigen presentation. + +<|ref|>text<|/ref|><|det|>[[117, 156, 872, 300]]<|/det|> +We agree that sub- phenotypes within MIS- C may be important, and that these phenotypes may also be shared across diseases. Using cell population and cell expression markers we identified two distinct clusters ("sub- phenotypes") in children with severe febrile illness (Cluster 1 and Cluster 2; Figure 2c). Children in Cluster 1 were more likely to receive vasoactive infusions than children with Cluster 2. We have also added the hierarchical clustering in children in whom no immunomodulation was given (Supplementary Figure 4) which supports the existence of sub- phenotypes in severe febrile illnesses in children, and MIS- C specifically. + +<|ref|>text<|/ref|><|det|>[[118, 317, 872, 441]]<|/det|> +9. The authors repeatedly mention "sepsis" and note a paper by Menon showing overlap of critical illness phenotypes. The relationship of the authors work to reference is not clear to me. MIS-C is a post-infectious inflammatory process that looks like sepsis. The patients with SBI likely many have sepsis and some of the SVI. The paper by Menon compared TBI, sepsis, ARDS and other critical illness phenotypes and showed overlap of these phenotypes. The authors are trying to show differences and are not emphasizing similarities. + +<|ref|>sub_title<|/ref|><|det|>[[118, 461, 208, 476]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 478, 877, 585]]<|/det|> +We agree that this manuscript should be balancing a description of the similarities across severe febrile illness in children as well as the differences between them. We checked and can confirm that we do not have a reference with Menon as a first or senior co-author in the References. We have, however, taken the opportunity to add a reference to a recent paper by Schlapbach and colleagues32 that operationalizes the diagnosis of "sepsis" in children – that emphasizes the similarities between diagnoses that are conceptualized as "sepsis". + +<|ref|>text<|/ref|><|det|>[[117, 604, 549, 620]]<|/det|> +We mention "sepsis" in the start of the Introduction: + +<|ref|>text<|/ref|><|det|>[[118, 622, 853, 674]]<|/det|> +Severe febrile illnesses in children requiring hospitalization and organ support, arise from diverse infections or inflammatory triggers, and overlap with the dysregulated host response that characterizes sepsis32- 34. + +<|ref|>text<|/ref|><|det|>[[118, 694, 380, 709]]<|/det|> +And the start of the Discussion: + +<|ref|>text<|/ref|><|det|>[[117, 711, 872, 835]]<|/det|> +We compared the immunology of severe febrile illnesses in children over the trajectory of illnesses2,33,35. This approach is supported by the framing of sepsis as a dysfunctional host response to infection34, the successful use of immunomodulator therapies during the COVID- 19 pandemic36, and ongoing trials in sepsis2,33. Using mass cytometry for peripheral blood immunophenotyping, cell stimulation assays and gene expression data with supervised, and unsupervised analytic approaches, we identified several shared and distinct immunological pathways in MIS- C, SBI, SVI and KD. + +<|ref|>sub_title<|/ref|><|det|>[[118, 855, 269, 870]]<|/det|> +## Minor comments + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 868, 137]]<|/det|> +1. In the introduction, you state with certainty why the incidence of MIS-C has decreased. But it is not certain, and the authors may want to insert the word "likely" before the word "because". + +<|ref|>sub_title<|/ref|><|det|>[[119, 157, 205, 172]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[119, 175, 330, 189]]<|/det|> +The sentence now reads: + +<|ref|>text<|/ref|><|det|>[[119, 192, 861, 226]]<|/det|> +Although the incidence of MIS- C has now declined, likely because of natural and vaccine- induced population immunity against SARS- CoV- 2... + +<|ref|>text<|/ref|><|det|>[[118, 245, 861, 300]]<|/det|> +2. Expressing the cytokine concentration in pg/mL or ng/mL is standard convention. The baseline units in Supplemental Table 5 are not defined. Response: The units have now been added as appropriate. + +<|ref|>sub_title<|/ref|><|det|>[[119, 357, 230, 372]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[118, 374, 876, 446]]<|/det|> +We thank the reviewer for taking time to critically appraise our work and providing constructive critique to improve our manuscript with validation using a different approach. Again, we wish to note that revisions based on your comments have strengthened our work considerably. Thank you. + +<|ref|>text<|/ref|><|det|>[[117, 464, 875, 555]]<|/det|> +Patel et al. presented a study on the immunology of severe febrile illness. The results are well presented however they are preliminary compared to other studies published in Nature Communications which generally takes studies that generate in depth results leading to deeper insights of the disease. Therefore, the current manuscript is well suited in other journals such as Immunology or Frontiers in Immunology or similar. + +<|ref|>text<|/ref|><|det|>[[118, 555, 860, 590]]<|/det|> +Having said that the authors can improve the study to make it more fit with Nature Comm requirements by adding the following additional work to the study: + +<|ref|>text<|/ref|><|det|>[[119, 591, 878, 768]]<|/det|> +1. In immunophenotyping the authors used GLM (lines 171 - 230) to identify the themes distinct to MIS-C however their results are subjective and the validation was supported by hierarchical clustering which is not ideal. It would be better if the authors carry out deeper analysis of the RNAseq data and apply GSEA on the DEG especially the C7 geneset which has over 4000 immune related pathways then filter based on p-value and FDR and validated the top 3-5 pathways. If the top 3 pathways are activated innate immune cells then dysregulated T-cell function then mature and activated myeloid DC they can use the data they have to show that the validation is correct, but if not they should carry out additional validation on whatever the GSEA brings. This will provide deeper insights into some of the mechanisms involved in MIS in children + +<|ref|>sub_title<|/ref|><|det|>[[118, 788, 204, 802]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[118, 805, 878, 857]]<|/det|> +Thank you for highlighting the use of GSEA to infer immune pathways that are upregulated based on differential gene expression analysis in MIS- C (and other severe febrile illnesses in children). + +<|ref|>text<|/ref|><|det|>[[118, 876, 872, 911]]<|/det|> +We have directly measured immune cell populations, their expression of markers of activation, exhaustion and apoptosis, and their function (in cell stimulation assays). Further, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 874, 227]]<|/det|> +we explored the key themes in the data using multi- omic factor analysis (Supplementary Figure 5). The dimensionality reduction inherent to factor analyses are of use given we might anticipate several variables to be closely correlated. The factor analysis also combines data on the proportions of cell populations, and the expression of markers in cell populations. As discussed in the manuscript, Factor 1 represented myeloid cell activation and T cell activation, and Factor 2 represented restoration of innate and adaptive immune cells to baseline, and Factor 3 represented decreased phosphorylation of the cell signaling molecules STAT1 and STAT5 and NFkB. + +<|ref|>text<|/ref|><|det|>[[118, 245, 875, 316]]<|/det|> +As suggested we undertook GSEA, as implemented by the R packages fgsea, using the C7 geneset (https://bioinf.wehi.edu.au/software/MSigDB/) and interpreted by the Gene Ontology database (https://geneontology.org/docs/go- enrichment- analysis/). Supplementary Figure 16 now describes the GSEA for the following comparisons. + +<|ref|>text<|/ref|><|det|>[[120, 335, 450, 351]]<|/det|> +The top three pathways by \(\%\) hits were: + +<|ref|>text<|/ref|><|det|>[[118, 370, 441, 440]]<|/det|> +a, MIS- C versus pHC: 1. Myeloid leukocyte activation, \(82.2\%\) 2. T cell differentiation, \(81.6\%\) 3. T cell activation, \(80.1\%\) + +<|ref|>text<|/ref|><|det|>[[118, 460, 468, 531]]<|/det|> +b, DB infection versus pHC: 1. Myeloid leukocyte activation, \(88.0\%\) 2. T cell activation, \(84.4\%\) 3. Regulation of defense response, \(83.4\%\) + +<|ref|>text<|/ref|><|det|>[[118, 550, 508, 619]]<|/det|> +c, DV infection versus pHC: 1. Innate immune response, \(66.1\%\) 2. Response to cytokine, \(63.5\%\) 3. Defence response to other organism, \(63.4\%\) + +<|ref|>text<|/ref|><|det|>[[118, 639, 860, 674]]<|/det|> +As predicted by Reviewer 2, these are highly similar to themes identified from the directly measured immune cell proportions and cell activation, exhaustion and apoptotic markers. + +<|ref|>text<|/ref|><|det|>[[118, 693, 872, 764]]<|/det|> +2. The authors need to carry out additional analysis using other software to show the role of the different immune cells. For example they can use CIBERSORT. This can be done on the targeted or the RNAseq from the blood but will provide better insights into the immune response in MIS. + +<|ref|>sub_title<|/ref|><|det|>[[118, 784, 204, 799]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[117, 801, 872, 908]]<|/det|> +In this manuscript we have directly measured, using standard markers, the major immune cell populations found in peripheral blood in the Derivation (mass cytometry) cohort. We have used the whole blood transcriptomic data to explore the features of neutrophil activation and apoptosis, T cell activation, and cytokine signalling. As suggested, we have now analyzed bulk whole blood transcriptomic data described in the manuscript in CIBERSORT (https://cibersortx.stanford.edu). We used the LM22 dataset + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 845, 190]]<|/det|> +as the reference dataset, which is a signature matrix containing 22 functionally defined human immune cell subsets derived from fresh, frozen and fixed tissues and profiled by microarrays. There are no immune cell populations from children with MIS- C or other severe febrile illnesses in these data. We used 100 permutations to measure p- values associated with each population described in the reference dataset to the bulk transcriptomic data described in this manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 192, 878, 280]]<|/det|> +The data are shown in Appendix 1. Following the removal of 3 outlying samples that had p values of \(\geq 0.05\) , we had patients in the following groups, MIS- C \((n = 38)\) , definite bacterial infection (DB, \(n = 186\) ), definite viral infection (DV, \(n = 137\) ), Kawasaki disease (KD, \(n = 136\) ) and paediatric healthy controls (HC, \(n = 134\) ). The data show median correlations of MIS- C 0.73, DB 0.68, DV 0.62, DV 0.60, KD 0.71, HC 0.65. + +<|ref|>text<|/ref|><|det|>[[118, 299, 853, 369]]<|/det|> +Children with any severe febrile illness had lower CD8 T cells. Children with any severe febrile illness had resting CD4 T cells than healthy controls \((p< 0.05\) for all groups versus healthy controls), and MIS- C, DB and DV had the lower proportions than DV. In contrast, any severe febrile illness had higher memory activated CD4 T cells than healthy controls. + +<|ref|>text<|/ref|><|det|>[[117, 388, 860, 514]]<|/det|> +Children with MIS- C had lower proportions of macrophages than other severe febrile illnesses or healthy controls. Children with MIS- C and SBI had higher proportions of M0 (non- activated) and M2 (anti- inflammatory) macrophages, than children with other severe febrile illnesses and healthy controls. M1 (pro- inflammatory) macrophages were generally not identified by CIBERSORT in the blood of any children. This may be due to genuine absence, or limitations of inferring rare immune cell subsets from bulk transcriptomic data with reference to a mixed adult cell reference population. + +<|ref|>text<|/ref|><|det|>[[117, 532, 874, 675]]<|/det|> +Resting dendritic cells were also generally not identified in the blood of children with severe febrile illness or controls. Activated dendritic cells were a greater proportion of immune cell populations identified in children with SV in comparison with other severe febrile illnesses, which in turn may indicate altered cytokine signalling in children with SV. However, without single cell data that includes relatively rare populations such as dendritic cells, we cannot show this – this is a major reason why we have preferred to derive our immunological data from single cell (cytometry) methods and use gene expression analysis to explore our findings further. + +<|ref|>text<|/ref|><|det|>[[118, 694, 870, 746]]<|/det|> +As anticipated, following review of the cytometry data, inferred neutrophil proportions were higher in children with MIS- C than any other severe febrile illness or healthy controls, and higher in DB and KD than both SV and healthy controls. + +<|ref|>text<|/ref|><|det|>[[118, 765, 875, 890]]<|/det|> +3. in line 638 the authors NF-kB but which part of the NF-kB they are looking for when they say activation e.g. is it p65, p50, p52 or RelA ..etc. They need to investigate this further as they may provide more interesting results because many immune cell types activate NFkB in different ways. For example recent publications showed that in pooled purified NK-T-like and NK cells (CD3+CD56+ and CD3-CD56+, respectively) the expression of mRNA coding for TLR1 to TLR9 was observed: https://onlinelibrary.wiley.com/doi/full/10.1038/icb.2013.99 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 86, 204, 100]]<|/det|> +## Response + +<|ref|>text<|/ref|><|det|>[[118, 102, 878, 155]]<|/det|> +Since TLRs are upstream of the NFkB pathway concentrating on some of the relevant NFkB molecules can provide insights into the existing findings the authors presented in this manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 157, 875, 210]]<|/det|> +We directly measured the phosphorylation status of the p65 subunit of NFkB and have now changed this in the manuscript, e.g. "and phosphorylated nuclear factor kappa B p65 (NFkB) expression in mature neutrophils" to emphasise the subunit specificity. + +<|ref|>text<|/ref|><|det|>[[118, 227, 878, 300]]<|/det|> +Appendix 1. Proportions of cells in the bulk transcriptomic data, as inferred by CIBERSORT, in whole blood from children with MIS- C, definite bacterial infection (DB), definite viral infection (DV), Kawasaki disease (KD) and pediatric healthy controls (HC). P values for pairwise- comparisons across time are using Wilcoxon rank sum testing. + +<|ref|>image<|/ref|><|det|>[[118, 315, 666, 777]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 799, 342, 815]]<|/det|> +On behalf of all co- authors + +<|ref|>text<|/ref|><|det|>[[118, 835, 252, 850]]<|/det|> +Yours sincerely, + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 84, 247, 100]]<|/det|> +## REFERENCES + +<|ref|>text<|/ref|><|det|>[[113, 99, 875, 895]]<|/det|> +1 Carter, M. J. et al. Peripheral immunophenotypes in children with multisystem inflammatory syndrome associated with SARS- CoV- 2 infection. Nat Med 26, 1701- 1707, doi:10.1038/s41591- 020- 1054- 6 (2020).2 van der Poll, T., Shankar- Hari, M. & Wiersinga, W. J. 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Abrogation of neutrophil inflammatory pathways and potential reduction of neutrophil- related factors in COVID- 19 by intravenous immunoglobulin. Front Immunol 13, 993720, doi:10.3389/fimmu.2022.993720 (2022).14 Uozumi, R. et al. Pharmaceutical immunoglobulins reduce neutrophil extracellular trap formation and ameliorate the development of MPO- ANCA- associated vasculitis. Mod Rheumatol 30, 544- 550, doi:10.1080/14397595.2019.1602292 (2020).15 Channon- Wells, S. et al. Immunoglobulin, glucocorticoid, or combination therapy for multisystem inflammatory syndrome in children: a propensity- weighted cohort study. Lancet Rheumatol 5, e184- e199, doi:10.1016/s2665- 9913(23)00029- 2 (2023).16 Parks, T., Wilson, C., Curtis, N., Norrby- Teglund, A. & Sriskandan, S. Polyspecific Intravenous Immunoglobulin in Clindamycin- treated Patients With Streptococcal Toxic Shock Syndrome: A Systematic Review and Meta- analysis. Clin Infect Dis 67, 1434- 1436, doi:10.1093/cid/ciy401 (2018). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 78, 881, 899]]<|/det|> +17 Aldridge, S. J. et al. Uptake of COVID- 19 vaccinations amongst 3,433,483 children and young people: meta- analysis of UK prospective cohorts. Nature Communications 15, 2363, doi:10.1038/s41467- 024- 46451- 0 (2024).18 Carter, M. J., Blohmke, C. J. & Pollard, A. J. in The Vaccine Book, Second Edition (eds B. R. Bloom & P. H. Lambert) (Elsevier, 2016).19 Nziza, N. et al. Humoral profiles of toddlers and young children following SARS-CoV- 2 mRNA vaccination. Nat Commun 15, 905, doi:10.1038/s41467- 024- 45181- 7 (2024).20 Zhang, X., Zhivaki, D. & Lo- Man, R. Unique aspects of the perinatal immune system. Nat Rev Immunol 17, 495- 507, doi:10.1038/nri.2017.54 (2017).21 Knolle, J. et al. Children From the Age of Three Show a Developmental Switch in T- Cell Differentiation. Front Immunol 11, 1640, doi:10.3389/fimmu.2020.01640 (2020).22 Whittaker, E. et al. Clinical Characteristics of 58 Children With a Pediatric Inflammatory Multisystem Syndrome Temporally Associated With SARS- CoV- 2. JAMA 324, 259- 269, doi:10.1001/jama.2020.10369 (2020).23 Verdoni, L. et al. An outbreak of severe Kawasaki- like disease at the Italian epicentre of the SARS- CoV- 2 epidemic: an observational cohort study. Lancet 395, 1771- 1778, doi:10.1016/s0140- 6736(20)31103- x (2020).24 Feldstein, L. R. et al. Multisystem Inflammatory Syndrome in U.S. Children and Adolescents. N Engl J Med 383, 334- 346, doi:10.1056/NEJMoa2021680 (2020).25 Carter, M. J., Shankar- Hari, M. & Tibby, S. M. Paediatric Inflammatory Multisystem Syndrome Temporally- Associated with SARS- CoV- 2 Infection: An Overview. Intensive Care Med 47, 90- 93, doi:10.1007/s00134- 020- 06273- 2 (2021).26 McArdle, A. J. et al. Treatment of Multisystem Inflammatory Syndrome in Children. N Engl J Med 385, 11- 22, doi:10.1056/NEJMoa2102968 (2021).27 Son, M. B. F. et al. Multisystem Inflammatory Syndrome in Children - Initial Therapy and Outcomes. New England Journal of Medicine 385, 23- 34, doi:10.1056/NEJMoa2102605 (2021).28 Ouldali, N. et al. Association of Intravenous Immunoglobulinus Plus Methylprednisolone vs Immunoglobulinus Alone With Course of Fever in Multisystem Inflammatory Syndrome in Children. JAMA 325, 855- 864, doi:10.1001/jama.2021.0694 (2021).29 Ouldali, N. et al. Immunomodulatory Therapy for MIS- C. Pediatrics 152, doi:10.1542/peds.2022- 061173 (2023).30 Welzel, T. et al. Methylprednisolone versus intravenous immunoglobulins in children with paediatric inflammatory multisystem syndrome temporally associated with SARS- CoV- 2 (PIMS- TS): an open- label, multicentre, randomised trial. Lancet Child Adolesc Health 7, 238- 248, doi:10.1016/s2352- 4642(23)00020- 2 (2023).31 Recovery Trial Group. Immunomodulatory therapy in children with paediatric inflammatory multisystem syndrome temporally associated with SARS- CoV- 2 (PIMS- TS, MIS- C; RECOVERY): a randomised, controlled, open- label, platform trial. Lancet Child Adolesc Health 8, 190- 200, doi:10.1016/s2352- 4642(23)00316- 4 (2024).32 Schlapbach, L. J. et al. International Consensus Criteria for Pediatric Sepsis and Septic Shock. JAMA 331, 665- 674, doi:10.1001/jama.2024.0179 (2024).33 Maslove, D. M. et al. Redefining critical illness. Nat Med 28, 1141- 1148, doi:10.1038/s41591- 022- 01843- x (2022). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 83, 875, 193]]<|/det|> +34 Singer, M. et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis- 3). JAMA 315, 801- 810, doi:10.1001/jama.2016.0287 (2016).35 DeMerle, K. M. et al. Sepsis Subclasses: A Framework for Development and Interpretation. Crit Care Med 49, 748- 759, doi:10.1097/ccm.0000000000004842 (2021).36 Lamontagne, F. et al. A living WHO guideline on drugs for covid- 19. BMJ 370, m3379, doi:10.1136/bmj.m3379 (2020). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 97, 340, 115]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[116, 163, 417, 180]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 200, 840, 235]]<|/det|> +Patel et al. addressed the concerns I had regarding the manuscript and the additional analysis provided further credence of the results. + +<|ref|>text<|/ref|><|det|>[[114, 254, 879, 364]]<|/det|> +One minor point is for the authors to insert the additional methods into the revised manuscript. For example the GSEA was only mentioned in the results section lines 339- 340 but no mention at all in the methods section. It is advisable they add a paragraph in the "Whole blood RNA Sequencing" section starting at line 631 mentioning the source of the tool used and if they used the R version list the version. Also mention which gene sets were screened e.g. I believe they only used C7 in this case. + +<|ref|>text<|/ref|><|det|>[[116, 382, 876, 437]]<|/det|> +They should put any additional methods they applied in the methods section of the revised version. Other than that, I believe the concerns were addressed sufficiently for the manuscript to be accepted for publication. + +<|ref|>sub_title<|/ref|><|det|>[[116, 493, 417, 510]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 529, 873, 602]]<|/det|> +The authors have addressed the reviewers' comment with appropriate changes to the text and additional data provided. The findings and impact of the data are thoughtfully discussed within the complexities of the field and the additional details support their conclusions well. Thank you for your thorough revision. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 90, 768, 123]]<|/det|> +# Re: NCOMMS-23-44279-B Title: Immunology of severe febrile illness in children in the COVID-19 era + +<|ref|>sub_title<|/ref|><|det|>[[120, 138, 435, 154]]<|/det|> +## Summary of changes to manuscript + +<|ref|>text<|/ref|><|det|>[[120, 170, 308, 184]]<|/det|> +Materials and Methods + +<|ref|>text<|/ref|><|det|>[[147, 186, 819, 216]]<|/det|> +- Addition of the methodology for the gene-set enrichment analysis contained in Supplementary Figure 16 as requested by Reviewer #2. + +<|ref|>sub_title<|/ref|><|det|>[[118, 231, 226, 246]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[118, 260, 309, 275]]<|/det|> +[No further comments.] + +<|ref|>text<|/ref|><|det|>[[118, 291, 411, 320]]<|/det|> +Response: Thank you for your previous review. + +<|ref|>sub_title<|/ref|><|det|>[[118, 336, 226, 351]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[118, 365, 816, 395]]<|/det|> +Patel et al. addressed the concerns I had regarding the manuscript and the additional analysis provided further credence of the results. + +<|ref|>text<|/ref|><|det|>[[118, 410, 874, 500]]<|/det|> +One minor point is for the authors to insert the additional methods into the revised manuscript. For example the GSEA was only mentioned in the results section lines 339- 340 but no mention at all in the methods section. It is advisable they add a paragraph in the "Whole blood RNA Sequencing" section starting at line 631 mentioning the source of the tool used and if they used the R version list the version. Also mention which gene sets were screened e.g. I believe they only used C7 in this case. + +<|ref|>text<|/ref|><|det|>[[118, 515, 860, 560]]<|/det|> +They should put any additional methods they applied in the methods section of the revised version. Other than that, I believe the concerns were addressed sufficiently for the manuscript to be accepted for publication. + +<|ref|>sub_title<|/ref|><|det|>[[118, 577, 207, 590]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[118, 590, 875, 666]]<|/det|> +We have added details of gene- set enrichment analysis (GSEA), at the suggested section of the Methods. We have also included the source of the tool (including references), the version of the tool, R version, and the signature gene set (C7) and its source. The data for the GSEA are available now online and this is shown. The R code for the analysis (and its source) is included on Dr Carter's GitHub page. The relevant section now reads: + +<|ref|>text<|/ref|><|det|>[[179, 680, 865, 817]]<|/det|> +Gene- set enrichment analysis (GSEA)33 (Supplementary Figure 16) was undertaken on previously published data from Jackson et al.29 that are available at ArrayExpress under accession E- MTAB- 11671 and E- MTAB- 12793. We used the R (version 4.4) implementation of gene- set enrichment analysis (fgsea, version 1.3)42, the C7 immunologic signature gene sets available from as part of the Human MSigDB Collections (https://www.gseamsigdb.org/gsea/msigdb/collections.jsp), and Gene Ontology (GO) enrichment analysis. We compared gene enrichment between children with MIS- C and healthy controls, with definite bacterial infection and healthy controls, definite viral infection and healthy controls and children with MIS- C and definite bacterial infection. Code for the GSEA is available here: https://github.com/michaeljamescarter/SIFIC. + +<|ref|>sub_title<|/ref|><|det|>[[118, 833, 227, 847]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[118, 848, 870, 907]]<|/det|> +The authors have addressed the reviewers' comment with appropriate changes to the text and additional data provided. The findings and impact of the data are thoughtfully discussed within the complexities of the field and the additional details support their conclusions well. Thank you for your thorough revision. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 108, 338, 138]]<|/det|> +ResponseThank you for your review. + +<--- Page Split ---> diff --git a/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/images_list.json b/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..736092df49a85f03ce5c75450c3a8c85d4b78100 --- /dev/null +++ b/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,33 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "S 2 Raman spectra of pure potassium bicarbonate and of the cathode catalyst layer after cell operation. The spectra were recorded at different positions of the cathode GDE catalyst layer surface after carefully removing the membrane. The phenyl group signal results from the Sustainion cathode catalyst binder \\(^{18,19}\\) . Raman spectra were obtained using a WITec alpha 300 confocal Raman microscope with a 532 nm laser operated at \\(10 \\pm 1 \\text{mW}\\) as the excitation source. Average spectra of the samples were produced by averaging five single spectra from each respective sample. All single spectra were integrated for 0.5 s and accumulated ten times. Background subtraction and fitting was done using WITec project.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1 Transport processes and cell components. a) water management highlighted in schematic of reactions and transport processes during operation, b) enlarged section of a normalized neutron radiographic image of the \\(\\mathrm{CO_2}\\) electrolysis cell, c) idealized cathode processes, and d) influence of precipitates on the cathode processes.", + "footnote": [], + "bbox": [ + [ + 147, + 330, + 875, + 735 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "S 4 Calculated neutron transmission for different compounds and sample thicknesses calculated with the online calculator from \"NIST Center for Neutron Research\" [https://www.ncnr.nist.gov/resources/activation/, Date: 02.2022]. The wavelength was set to 3 Å.", + "footnote": [], + "bbox": [], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..fe97580e528b47867d743f3657badd329731e83e --- /dev/null +++ b/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,355 @@ + +# nature portfolio + +Peer Review File + +High- resolution neutron imaging of salt precipitation and water transport in zero- gap CO2 electrolysis + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' comments: + +Reviewer #1 (Remarks to the Author): + +The Authors present an insight in a zero- gap CO2 electrolyzer cell under operation, which is clearly a nice piece of work. The application of neutron imaging is well presented, but the conclusions drawn are not very new or convincing. The precipitate formation during operation was witnessed by several groups earlier, and the details of water management in the cell are not revealed here in details. Therefore, I feel that these achievements are more technical than novel, and hence I do not think that this paper belongs to Nature Communications. I believe it would be more suitable for more technical journals, such as ACS AMI, Applied Catalysis B, etc. + +Some comments regarding the details of the manuscript: + +Neutron imaging is a nice tool for visualizing the inner structure of the cell. Identifying precipitate, dry regions or bubbles is however very questionable, if not impossible. In Fig. S6 it is seen that K2CO3 is almost transparent for neutrons, and therefore its formation might result in the exact same image as a completely dry region. Assuming that the precipitate is hydrated is completely unfounded. If the water transport within the cell is to be described, other techniques should be applied to support these findings. + +Regarding Fig. 1a, the followings are written: "As the cathode GDE is brighter in the land area of the cathode flow field even at 0 mA cm- 2, it can be assumed, that less precipitates are located in that area". Is there really any precipitate in the GDE at 0 current? + +At higher current densities the membrane seems to be fairly dry. This would suggest a lower water concentration at the cathode surface, but we still see and increased HER at higher current densities. I find this a little contradictory. + +"Going from 200 mA cm- 2 to 300 mA cm- 2 this trend for the cathode GDE is coming to halt and some regions of the GDE seem to get even slightly wetter again." - Why would the water content of the cathode GDE increase at higher current densities? + +<--- Page Split ---> + +Instead of the Ti frit typically applied in zero gap cells, the authors used a carbon paper as anode support. Isn't this too hydrophobic to allow the proper wetting of the catalyst surface? + +Reviewer #2 (Remarks to the Author): + +The manuscript "High- resolution neutron imaging of carbonate precipitation and water transport in zero- gap CO2 electrolysis" by J. Disch et al. is an interesting experimental attempt to vizualize the transport of ions and molecules in a CO2 electrolyzer by state- of- the- art neutron imaging, + +which is of utmost importance for the further optimization of such cells. + +Thus, the topic and aims are relevant and of interest to the specialists working in CO2- electrolysis as well as to the neutron imaging community. The research is well performed, and the research results justified (details follow later). Thus I have no problem in recommending publication of this nice piece of work. However, the appetite comes with eating. Roughly speaking, the authors discuss one "beamtime experiment", which should be elaborated and be put in perspective of the science and technology needed in CO2 electrolysis, in particular the importance of mass transport. Adding a discussion around this may make this paper a cornerstone in CO2 electrolysis. Concretely: + +- A figure of the CO2 electrolyzer showing the electrodes and membrane geometry and what the neutrons probe, and highlighting the processes taking place. For understanding it is helpful to pinpoint, where water and CO2 is consumed, where a pH gradient builds up, where the gases evolve, etc., and how potential precipitations may perturb the overall process. I have the impression that the authors involved have some background in water electrolysis, where similar processes such as water management are relevant. However, CO2 electrolysis is more complex simply because CO2 is involved (see, e.g., Ref. 37; and Nesbitt et al., ACS Catal. 10, 14093-14106 (2020); Lu et al., + +J. Am. Chem. Soc. 142, 15438-15444 (2020); Borgschulte et al., Front. Energy Res. 9:784082 (2022)). Figure 1 gives some of the aforementioned reactions, but it may be split in two figures one only showing the sketch (and critical phenomena). Also, to generalize the findings. The authors correctly mention that the findings may not be applicable to other electrolyzer setups (line 77 ff). Here, discussion/explanations are most important (e.g., what are the differences). + +- The attribution of the neutron contrast to K(H)CO3 is the most important finding, but also the most critical one. It is based on a kind of of handwaving arguments, but this is for sure not a chemical identification. Spatially resolved spectroscopy methods such as Raman spectroscopy (Lu et al., J. Am. Chem. Soc. 142, 15438-15444 (2020)) could provide evidence for this argumentation. I recommend to apply this (I do not know whether possible in this short time). + +<--- Page Split ---> + +## Response to referees + +Dear Sir or Madam, + +We thank the editor for considering our manuscript for review and the referees for their comments. The questions and comments from the referees lead to fruitful discussions and helped to improve the manuscript. Below, we address each comment separately and highlight the changes we made to the manuscript. + +## Reviewer #1 + +## Comment 1: + +The Authors present an insight in a zero- gap CO2 electrolyzer cell under operation, which is clearly a nice piece of work. The application of neutron imaging is well presented, but the conclusions drawn are not very new or convincing. The precipitate formation during operation was witnessed by several groups earlier, and the details of water management in the cell are not revealed here in details. Therefore, I feel that these achievements are more technical than novel, and hence I do not think that this paper belongs to Nature Communications. I believe it would be more suitable for more technical journals, such as ACS AMI, Applied Catalysis B, etc. + +## Response: + +We thank the reviewer for the profound feedback. We tried to significantly work on our manuscript, including new ex- situ characterization results which hopefully back up our findings in a convincing way (see below). + +## Comment 2: + +Neutron imaging is a nice tool for visualizing the inner structure of the cell. Identifying precipitate, dry regions or bubbles is however very questionable, if not impossible. + +## Response: + +The reviewer is right, that neutron imaging is a complex method, and any results need to be interpreted with care. However, it was repeatedly proven over more than a decade now that neutron imaging is especially suitable for the in- situ investigation of water distribution and bubble formation in electrochemical devices, what has been proven in a multitude of publications \(^{1 - 7}\) . The identification of precipitates by neutron imaging is less explored and therefore discussed in detail in the comments following below. + +## Comment 3: + +In Fig. S6 it is seen that K2CO3 is almost transparent for neutrons, and therefore its formation might result in the exact same image as a completely dry region. + +## Response: + +<--- Page Split ---> + +Yes, this is right. This is why we did not claim that \(\mathsf{K}_2\mathsf{CO}_3\) is imaged directly in the neutron radiography. In fact, we stated that \(\mathsf{K}_2\mathsf{CO}_3\) can only be imaged indirectly by imaging the retained water (original manuscript line 172ff) and specifically added the mentioned Fig. S6 to illustrate that. However, Fig. S6 also shows that \(\mathsf{KHCO}_3\) can significantly contribute to the neutron attenuation, which makes imaging of \(\mathsf{KHCO}_3\) possible (see comment 7 and comment 4 of Reviewer #2). + +Considering the reviewer's comment, we concluded that the wording in the manuscript and its title could be more precise to not be misunderstood. We therefore changed the title and some expressions in the manuscript. + +## Changes to the manuscript: + +Title, line 1f: High- resolution neutron imaging of salt precipitation and water transport in zero- gap \(\mathbf{CO}_2\) electrolysis + +Line 22f: Neutron imaging further shows higher salt accumulation under the cathode channel of the flow field compared to the land. + +Line 31f: Salt precipitation and associated electrode flooding are observed in neutron images visualizing the cause of commonly observed decreasing Faraday efficiency. + +Line 333ff: Although precipitates and associated electrode flooding are visible in the neutron images over the entire current range (precipitates potentially already formed during pretests), the cell is demonstrating good cell performance with \(\mathrm{FE_{CO}}\) above \(90\%\) for current densities below \(300~\mathrm{mA~cm^{- 2}}\) . + +## Comment 4: + +Assuming that the precipitate is hydrated is completely unfounded. If the water transport within the cell is to be described, other techniques should be applied to support these findings. + +## Response: + +Carbonate precipitates are normally porous and hydrophilic and hence increase the capillary pressure. Considering the deliquescent properties of carbonates and the moist reaction environment (humidified cathode gas stream, aqueous anolyte, a membrane with a high water uptake and ambient temperature) carbonates are very likely hydrated. This should be the case, especially in the zero current state, where no water is consumed by the electrode reactions. Fig. S6 also shows that already small amounts of water have a significant effect on the neutron transmission. However, the cathode GDE land region stays significantly brighter than the channel region at \(0~\mathrm{mA / cm^2}\) . It has been shown in literature, that the relative humidity is quite high in the cathode compartment even at higher current densities. Particularly the publication of Wheeler et al. is to mention in this context, + +<--- Page Split ---> + +in which the humidity in the cathode flow field is measured at 4 different positions, with and without humidification of the gas feed9. They show that without prior gas humidification the gas stream is humidified inside the cell, even at 200 mA / cm2 (RH of 79% at the outlet, also using similar Sustainion membranes). + +We now address the humid environment in the manuscript. + +## Changes to the manuscript: + +Line 195ff: \(\mathsf{K}_2\mathsf{CO}_3\) shows significantly lower neutron absorption and scattering rates than water (see SI Figure S6 for neutron transmission rates). Due to its low neutron attenuation, \(\mathsf{K}_2\mathsf{CO}_3\) can only be observed indirectly, by imaging the retained water. Considering the deliquescent properties of \(\mathsf{K}_2\mathsf{CO}_3\) and the moist reaction environment (humidified cathode gas stream, aqueous anolyte, a membrane with a high water uptake10 and ambient temperature) carbonates inside the cell are very likely hydrated8. This should be the case, especially in the zero current state, when no water is consumed by the cathode reactions and condensing water in the cathode flow field is observed. \(\mathsf{KHCO}_3\) instead contains a hydrogen atom in its structure, yielding higher interactions with neutrons than \(\mathsf{K}_2\mathsf{CO}_3\) . + +## Comment 5: + +Regarding Fig. 1a, the followings are written: "As the cathode GDE is brighter in the land area of the cathode flow field even at 0 mA cm- 2, it can be assumed, that less precipitates are located in that area". Is there really any precipitate in the GDE at 0 current? + +## Response: + +As described in detail in the SI (line 69ff) and mentioned in the manuscript (line 265f), there have been preceding electrochemical measurements to the experiments reported in the manuscript. Therefore, we see no contradiction with precipitates or highly saturated solution in the cathode GDE at zero current. We now do also mention it in that section. + +## Changes to the manuscript: + +Line 214ff: For example, as the cathode GDE is brighter in the land area of the cathode flow field even at 0 mA cm2, it can be assumed, that less precipitates are located in that area (note that \(\mathsf{KHCO}_3\) and \(\mathsf{K}_2\mathsf{CO}_3\) might have accumulated in the cathode GDE already in the preceding electrochemical measurements described in the SI). + +## Comment 6: + +At higher current densities the membrane seems to be fairly dry. This would suggest a lower water concentration at the cathode surface, but we still see and increased HER at higher current densities. I find this a little contradictory. + +## Response: + +The reviewer is right, that this might at first seem counterintuitive. Nonetheless, several points have to be considered: + +<--- Page Split ---> + +- Figure 5 shows that the membrane is getting slightly dryer with rising current density compared to the 0 current image. The change in water content, however, is not as drastic as in other regions in the cell (see e.g. cathode GDE, condensate in cathode flow field channels). This is a reasonable result, as the utilized Sustainion membrane was reported to have a very high water uptake ( \(\sim 80\%\) reported by Lindquist et al.)10,11. Thereby it provides liquid water to the cathode catalyst layer as it is in direct contact with it. Moreover, in dry cathode AEM water electrolysis, significantly higher HER current densities are achieved, only providing water from the anode side through the membrane12,13. + +- Further, as Reviewer #2 mentioned, mass transport plays an important role in \(\mathrm{CO_2}\) electrolysis. Most likely, more limiting than water availability is the availability of \(\mathrm{CO_2}\) at the cathode. \(\mathrm{CO_2}\) has to reach the active sites of the cathode catalyst layer by diffusing from the cathode flow field channel through the gas diffusion layer, the micro porous layer and finally the pores of the catalyst layer. With rising current density more \(\mathrm{CO_2}\) is consumed by the \(\mathrm{CO_2}\) reduction reaction and the carbonation reaction, lowering the \(\mathrm{CO_2}\) concentration at the electrode surface, while there is still enough water to maintain the HER (concentration of \(\mathrm{CO_2}\) in a humidified gas stream \(\mathrm{C_{CO2} = 0.041 M}\) compared to concentration of pure liquid water \(\mathrm{C_{H2O} = 55.5 M}\)14). Precipitates in the electrode add an additional diffusion barrier for \(\mathrm{CO_2}\) . + +## Changes to the manuscript: + +Line 289ff: While this might be surprising, one has to consider that a region depleted of \(\mathrm{CO_2}\) might still have a sufficiently high water content for the hydrogen evolution reaction. The utilized Sustainion® membranes were reported to have a very high water uptake of \(\sim 80\%\) 10,11 and are only getting slightly drier during cell operation (see Figure 5), directly providing water to cathode catalyst layer. \(\mathrm{CO_2}\) , however, has to reach the active sites of the cathode catalyst layer by diffusing from the cathode flow field channel through the gas diffusion layer, the micro porous layer and finally the pores of the catalyst layer. With rising current density more \(\mathrm{CO_2}\) is consumed by the \(\mathrm{CO_2}\) reduction reaction and the carbonation reaction, lowering the \(\mathrm{CO_2}\) concentration at the electrode surface. Precipitates in the electrode add an additional diffusion barrier for \(\mathrm{CO_2}\) (see Figure 1d). Thus the reaction shifts to the HER resulting in lower faradaic efficiency of the \(\mathrm{CO_2}\) reduction at high current densities (Figure 2c) instead of increasing the overpotential. + +## Comment 7: + +"Going from 200 mA cm- 2 to 300 mA cm- 2 this trend for the cathode GDE is coming to halt and some regions of the GDE seem to get even slightly wetter again." – Why would the water content of the cathode GDE increase at higher current densities? + +## Response: + +We agree with the reviewer that this observation is not very intuitive, as the water consumption on the cathode side rises with increasing current density. Nonetheless, we observed this behavior (also in other measurements). In our manuscript we explain + +<--- Page Split ---> + +possible reasons for this observation (line 223ff). The intensity decrease is mainly observed in the cathode gas diffusion layer and more pronounced in the channel region of the cathode flow field (see Figure 4 and 5). As this is a continuous process (see Figure 5) we conclude that this intensity decrease is most probably caused by \(\mathrm{KHCO_3}\) precipitates (and water retained by the precipitates) accumulating in that area. + +To additionally support this statement, we conducted SEM/EDX measurements of a cross- section of the cathode GDE and Raman measurements of the silver catalyst layer after cell operation and added them to the Supplementary Information (see below). The SEM/EDX measurements clearly show potassium containing precipitates in the silver catalyst layer, the micro porous layer and in the gas diffusion layer of the cathode. The Raman measurements further confirm the presence of \(\mathrm{KHCO_3}\) in the silver catalyst layer. The spectrum does not show the typical bands for \(\mathrm{K_2CO_3}\) . + +Different publications concluded from post- experiment analysis that the precipitates consist of a mixture of different carbonic salts: + +E.g. Endrödi et al. conducted XRD measurements and concluded that the precipitated salts consist of a mixture of \(\mathrm{KHCO_3}\) and \(\mathrm{K_4H_2(CO_3)_3\cdot 1.5H_2O}\) , with an approximate 1:3 weight ratio15. Xu et al. showed with Raman measurements that in their case, the precipitates consist of a mixture of \(\mathrm{K_2CO_3}\) and \(\mathrm{KHCO_3}\) with more \(\mathrm{K_2CO_3}\) than \(\mathrm{KHCO_3}^{16}\) . All studies report species containing hydrogen atoms in the precipitates (thus, species yielding significant neutron interaction). The ratio of the different species might strongly differ in different cells, depending on material properties and operating conditions. + +## Changes to the manuscript: + +Line 205ff: Nonetheless, \(\mathrm{KHCO_3}\) is also strongly hygroscopic and retains water, which might more drastically affect its neutron opacity in a humid environment. Scanning electron microscopy and energy dispersive X- ray spectroscopy (SEM/EDX) measurements of a cathode cross section further show precipitates containing potassium in the silver catalyst layer, the micro porous layer and in the gas diffusion layer (see SI Figure S7). The presence of \(\mathrm{KHCO_3}\) in the catalyst layer was additionally verified by post- operation Raman measurements (see SI Figure S8). Considering those results and the mentioned observations made by other groups15,17, it can be assumed that the dark dents originate from precipitated \(\mathrm{KHCO_3}\) and water retained by the precipitates in that area. + +By that, the intensity differences alongside the cathode GDE allow to deduce where precipitates are mainly located in the electrode. For example, as the cathode GDE is brighter in the land area of the cathode flow field even at \(0 \mathrm{mA} \mathrm{cm}^{- 2}\) , it can be assumed, that less precipitates are located in that area. + +Line 237ff: Going from \(200 \mathrm{mA} \mathrm{cm}^{- 2}\) to \(300 \mathrm{mA} \mathrm{cm}^{- 2}\) this trend for the cathode GDE is coming to halt and the intensity in some regions of the cathode gas diffusion layer even decreases. + +<--- Page Split ---> + +Line 252ff: However, considering the afore- mentioned points and the post- operation Raman and SEM/EDX measurements (see SI Figure S7 and S8), it is most probable that the accumulation of KHCO₃ causes the observed drop in intensity. + +Line 272ff: Again, if the change in intensity would only account for water content, this observation would be counterintuitive, as the increased reaction rate leads to higher water consumption and electro- osmotic drag from cathode to anode (see Figure 1a). This observation in the cathode GDL suggest that KHCO₃ is continuously accumulating during cell operation. The different slopes of the cathode GDL intensity curve translate to KHCO₃ accumulation already starting at 100 mA cm⁻² and significantly increasing at 300 mA cm⁻². + +Changes to the Supplementary Information: + +<--- Page Split ---> +![](images/Figure_1.jpg) + + +S 1 Scanning electron micrographs and energy dispersive X- ray spectroscopies of the cathode electrode cross section after cell operation. a) electron micrograph and elemental maps of carbon, fluorine, oxygen, silver, potassium and iridium, b) a layered image of the electron micrograph and the elemental map of potassium, c) an electron micrograph layered with the elemental maps of iridium, silver and fluorine, identifying the catalyst layers and the hydrophobic microporous layer, and d) spectrum obtained from the energy dispersive X- ray spectroscopy. The cross section was prepared by cryo- cutting. + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
S 2 Raman spectra of pure potassium bicarbonate and of the cathode catalyst layer after cell operation. The spectra were recorded at different positions of the cathode GDE catalyst layer surface after carefully removing the membrane. The phenyl group signal results from the Sustainion cathode catalyst binder \(^{18,19}\) . Raman spectra were obtained using a WITec alpha 300 confocal Raman microscope with a 532 nm laser operated at \(10 \pm 1 \text{mW}\) as the excitation source. Average spectra of the samples were produced by averaging five single spectra from each respective sample. All single spectra were integrated for 0.5 s and accumulated ten times. Background subtraction and fitting was done using WITec project.
+ +## Comment 8: + +Instead of the Ti rift typically applied in zero gap cells, the authors used a carbon paper as anode support. Isn't this too hydrophobic to allow the proper wetting of the catalyst surface? + +## Response: + +We decided to use this anode as it is a commercially available state- of- the- art electrode and has been proven to be suitable for this application in several studies \(^{19,20,21}\) . By choosing commercially available materials, we try to make our results reproducible for other groups. As the neutron radiographic images show electrolyte fully enters the anode GDE. Thus, the carbon paper works well as a substrate despite its wettability. + +## Reviewer #2: + +## Comment 1: + +The manuscript "High- resolution neutron imaging of carbonate precipitation and water transport in zero- gap CO2 electrolysis" by J. Disch et al. is an interesting experimental attempt to vizualize the transport of ions and molecules in a CO2 electrolyzer by state- of- the- art neutron imaging, which is of utmost importance for the further optimization of such cells. + +<--- Page Split ---> + +Thus, the topic and aims are relevant and of interest to the specialists working in CO2- electrolysis as well as to the neutron imaging community. The research is well performed, and the research results justified (details follow later). Thus I have no problem in recommending publication of this nice piece of work. However, the appetite comes with eating. Roughly speaking, the authors discuss one "beamtime experiment", which should be elaborated and be put in perspective of the science and technology needed in CO2 electrolysis, in particular the importance of mass transport. Adding a discussion around this may make this paper a cornerstone in CO2 electrolysis. + +## Response: + +We thank the reviewer for the very positive evaluation or our manuscript. Within the restricted time budget of a revision process, we tried our best to further back up our statements following the reviewer's recommendations. Therefore, we included now further post- mortem microanalysis of the MEAs by SEM/EDX and Raman. The measurements clearly confirm the presence of potassium accumulations in the cathode. + +## Comment 2: + +Concretely: + +- A figure of the CO2 electrolyzer showing the electrodes and membrane geometry and what the neutrons probe, and highlighting the processes taking place. For understanding it is helpful to pinpoint, where water and CO2 is consumed, where a pH gradient builds up, where the gases evolve, etc., and how potential precipitations may perturb the overall process. I have the impression that the authors involved have some background in water electrolysis, where similar processes such as water management are relevant. However, CO2 electrolysis is more complex simply because CO2 is involved (see, e.g., Ref. 37; and Nesbitt et al., ACS Catal. 10, 14093-14106 (2020); Lu et al., J. Am. Chem. Soc. 142, 15438-15444 (2020); Borgschulte et al., Front. Energy Res. 9:784082 (2022)). + +Figure 1 gives some of the aforementioned reactions, but it may be split in two figures one only showing the sketch (and critical phenomena). Also, to generalize the findings. + +## Response: + +We thank the reviewer for the feedback and the proposed amendments. Considering the propositions we revised Figure 1. We added a Figure 1c and 1d, illustrating the idealized processes at the cathode GDE and the influence of carbonates on the \(\mathrm{CO_2}\) mass transport. Additionally, we added Figure S1b to the supplementary information, showing a rendering of the neutron detector and a cross section of the cell fixture, to provide a better understanding what the neutrons probe. + +## Changes to the manuscript: + +Line 63ff: Although the AEM hinders potassium cations from crossing the membrane in bigger quantities by Donnan exclusion, a small amount of cations is still migrating through the membrane. As cations move from the anode to the cathode side, they drag water in their hydration shell with them. Over time potassium, carbonate and bicarbonate ions can accumulate at the cathode. When exceeding the solubility limit, by increasing ion concentration or by consumption of water, salt crystallites can precipitate on the cathode + +<--- Page Split ---> + +side. Figures 1c and 1d illustrate how precipitates supposedly influence the processes in the cathode gas diffusion electrode (GDE). Carbonate precipitates are normally porous and hydrophilic, increasing the capillary pressure inside the cathode GDE8. Hence, the precipitates make the GDE prone to electrode flooding. Liquids and precipitates can clog pores in the catalyst layer, micro porous layer and the gas diffusion layer of the cathode GDE, and thereby impede the gas transport22. With an increasing amount of precipitates, the mass transport resistance for the \(\mathrm{CO_2}\) to reach the active sites of the catalyst layer increases and the \(\mathrm{CO_2}\) concentration at the catalyst surface will eventually decrease. The lower \(\mathrm{CO_2}\) concentration may cause a selectivity shift towards the HER, as water can still be sufficiently supplied from the anode side through the membrane. + +![PLACEHOLDER_12_0] + +
Figure 1 Transport processes and cell components. a) water management highlighted in schematic of reactions and transport processes during operation, b) enlarged section of a normalized neutron radiographic image of the \(\mathrm{CO_2}\) electrolysis cell, c) idealized cathode processes, and d) influence of precipitates on the cathode processes.
+ +Changes to the Supplementary Information: + +<--- Page Split ---> +![PLACEHOLDER_13_0] + + +S 3 Cell fixture and neutron detector/cell alignment. a) an explosion view of the custom- built electrolysis cell (End plates: Stainless steel, flow fields: Au coated Ti grade 2, gaskets: PTFE), and b) a rendering of the neutron detector and of the cell fixture cross section in alignment to the incident neutron beam. The scintillator sits in the neutron detector head close to the cell fixture. The emitted scintillation light is reflected to the detector, which is orientated perpendicular to the incident neutron beam. + +## Comment 3: + +The authors correctly mention that the findings may not be applicable to other electrolyzer setups (line 77 ff). Here, discussion/explanations are most important (e.g., what are the differences). + +## Response: + +The reviewer raised a fair point and we therefore added that discussion to the manuscript. + +## Changes to the manuscript: + +Line 83ff: The technological advances of neutron imaging detectors significantly improved the resolution of neutron radiography in recent years. Nonetheless, only two neutron- imaging studies investigating \(\mathrm{CO_2}\) electrolyzers have been published up to now. The first study investigated bubble formation in a liquid buffer layer on the cathode side3. Besides high cell potentials, cells with a liquid catholyte between the membrane and cathode GDE + +<--- Page Split ---> + +often exhibit fast electrode flooding, as the cathode is in direct contact with the liquid electrolyte. The circulating electrolyte, however, can wash away precipitates and depending on its chemical composition change the ion concentration at the cathode side compared to a zero- gap cell. The second study conducted neutron imaging of a zero- gap cell with a cation exchange membrane23. Zero- gap cells using cation exchange membranes show significantly lower CO selectivity compared to cells using AEMs, as they provide an acidic reaction environments to the cathode, facilitating the competing HER24. Furthermore, protons moving from the anode to the cathode are responsible for the ionic charge transfer between the anode and cathode. The ionic transport and the electroosmotic drag are directed in the opposite direction compared to cells using AEMs, drastically changing the water balance. As the water balance and flooding behavior in the above- mentioned studies strongly differ, their results cannot be applied to AEM- based zero- gap \(\mathrm{CO_2}\) electrolyzers. Etzold et al. have recently highlighted this lack of neutron studies for zero- gap \(\mathrm{CO_2}\) electrolysis in a review25. + +## Comment 4: + +The attribution of the neutron contrast to \(\mathrm{K(H)CO_3}\) is the most important finding, but also the most critical one. It is based on a kind of of handwaving arguments, but this is for sure not a chemical identification. Spatially resolved spectroscopy methods such as Raman spectroscopy (Lu et al., J. Am. Chem. Soc. 142, 15438- 15444 (2020)) could provide evidence for this argumentation. I recommend to apply this (I do not know whether possible in this short time). + +## Response: + +The reviewer is right, that it is not possible to quantitatively deconvolute the contribution of \(\mathrm{KHCO_3}\) and water to the neutron attenuation with our method. Unfortunately, the proposed in situ Raman spectroscopy is not only impossible in this short time, but is not possible at all, as we investigate a zero- gap cell architecture (membranes and electrodes are not transparent for the Raman laser). Lu et al. only investigate the concentration gradients inside the liquid catholyte and cannot analyze the gradients inside the cathode GDE. The liquid catholyte renders the results not applicable to a zero- gap cell (also see comment 3, different cell architectures). + +However, we followed the reviewer's recommendation to employ Raman spectroscopy as method of choice, and backed the findings up with additional SEM/EDX measurements of the cathode electrode to further investigate the distribution and the composition of the precipitates (see comment 7 of Reviewer #1). + +The SEM/EDX measurements clearly show potassium containing precipitates in the silver catalyst layer, the micro porous layer and in the gas diffusion layer. The Raman measurements further prove the presence of \(\mathrm{KHCO_3}\) in the cathode. + +Considering the above- mentioned, a closer look at Figure S6 can help to further clarify the interpretation of the neutron radiography data. As Reviewer #1 correctly stated, the contribution of \(\mathrm{K_2CO_3}\) to the neutron attenuation can be neglected, whereas \(\mathrm{KHCO_3}\) shows significant neutron attenuation: + +<--- Page Split ---> +![PLACEHOLDER_15_0] + +
S 4 Calculated neutron transmission for different compounds and sample thicknesses calculated with the online calculator from "NIST Center for Neutron Research" [https://www.ncnr.nist.gov/resources/activation/, Date: 02.2022]. The wavelength was set to 3 Å.
+ +The neutron attenuation of water is still significantly higher than that of \(\mathrm{KHCO_3}\) . In the zero current state and at low current densities (low water consumption) the neutron attenuation might be dominated by water. At higher current densities (increased water consumption and electroosmotic drag) the contribution of \(\mathrm{KHCO_3}\) to the neutron attenuation in the cathode GDE gets more significant. At \(200 \mathrm{mA cm^{- 2}}\) the liquid water in the cathode flow field has already fully dried off, however, the precipitates are clearly visible. + +All information we gained from the Raman measurements, SEM/EDX measurements and literature (see comment 7 of Reviewer #1 and line 191ff in the manuscript) supports the claim that \(\mathrm{KHCO_3}\) contributes to the neutron attenuation in the presented radiographic images. + +## Changes to the manuscript: + +Line 188ff: Nevertheless, at \(300 \mathrm{mA cm^{- 2}}\) these bulges are still clearly visible, whereas the liquid condensate in the channel has fully dried off. Even though the images are averaged over several minutes, the bulges show sharp contours, indicating an immobile solid phase. + +All other related changes are listed in the response to comment 7 of Reviewer #1. + +## Concluding remarks + +Further minor changes to the manuscript that are not mentioned in this letter are highlighted in the newly submitted manuscript file. We appreciate the detailed revision of our manuscript. We hope that we could answer all questions to the satisfaction of the referees. Furthermore, we are open to discuss any further questions. + +Sincerely yours, + +<--- Page Split ---> + +## Severin Vierrath + +## References + +1. Kardjilov, N., Manke, I., Woracek, R., Hilger, A. & Banhart, J. Advances in neutron imaging. Materials Today 21, 652–672; 10.1016/j.mattod.2018.03.001 (2018). +2. Boillat, P., Frei, G., Lehmann, E. H., Scherer, G. G. & Wokaun, A. Neutron Imaging Resolution Improvements Optimized for Fuel Cell Applications. Electrochem. Solid-State Lett. 13, B25; 10.1149/1.3279636 (2010). +3. Krause, K. et al. Electrolyte layer gas triggers cathode potential instability in CO2 electrolyzers. Journal of Power Sources 520, 230879; 10.1016/j.jpowsour.2021.230879 (2022). +4. Lehmann, E. H. & Wagner, W. Neutron imaging at PSI. A promising tool in materials science and technology. Appl. Phys. A 99, 627–634; 10.1007/s00339-010-5606-3 (2010). +5. Hoeh, M. A. et al. In-Operando Neutron Radiography Studies of Polymer Electrolyte Membrane Water Electrolyzers. ECS Trans. 69, 1135–1140; 10.1149/06917.1135ecst (2015). +6. Omasta, T. J. et al. Beyond catalysis and membranes. Visualizing and solving the challenge of electrode water accumulation and flooding in AEMFCs. Energy Environ. Sci. 11, 551–558; 10.1039/C8EE00122G (2018). +7. Zlobinski, M., Schuler, T., Büchi, F. N., Schmidt, T. J. & Boillat, P. Transient and Steady State Two-Phase Flow in Anodic Porous Transport Layer of Proton Exchange Membrane Water Electrolyzer. J. Electrochem. Soc. 167, 84509; 10.1149/1945-7111/ab8c89 (2020). +8. Li, M. et al. The role of electrode wettability in electrochemical reduction of carbon dioxide. J. Mater. Chem. A 9, 19369–19409; 10.1039/d1ta03636j (2021). +9. Wheeler, D. G. et al. Quantification of water transport in a CO 2 electrolyzer. Energy Environ. Sci. 13, 5126–5134; 10.1039/d0ee02219e (2020). +10. Kaczur, J. J., Yang, H., Liu, Z., Sajjad, S. D. & Masel, R. I. Carbon Dioxide and Water Electrolysis Using New Alkaline Stable Anion Membranes. Frontiers in chemistry 6, 263; 10.3389/fchem.2018.00263 (2018). +11. Lindquist, G. A. et al. Performance and Durability of Pure-Water-Fed Anion Exchange Membrane Electrolyzers Using Baseline Materials and Operation. ACS applied materials & interfaces; 10.1021/acsami.1c06053 (2021). +12. Cho, M. K. et al. Alkaline anion exchange membrane water electrolysis. Effects of electrolyte feed method and electrode binder content. Journal of Power Sources 382, 22–29; 10.1016/j.jpowsour.2018.02.025 (2018). +13. Parrondo, J., George, M., Capuano, C., Ayers, K. E. & Ramani, V. Pyrochlore electrocatalysts for efficient alkaline water electrolysis. J. Mater. Chem. A 3, 10819–10828; 10.1039/C5TA01771H (2015). + +<--- Page Split ---> + +14. Weekes, D. M., Salvatore, D. A., Reyes, A., Huang, A. & Berlinguette, C. P. Electrolytic CO2 Reduction in a Flow Cell. Accounts of chemical research 51, 910–918; 10.1021/acs.accounts.8b00010 (2018). + +15. Endrődi, B. et al. Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolyzers. Nature energy 6, 439–448; 10.1038/s41560-021-00813-w (2021). + +16. Xu, Y. et al. Self-Cleaning CO 2 Reduction Systems. Unsteady Electrochemical Forcing Enables Stability. ACS Energy Lett., 809–815; 10.1021/acsenergylett.0c02401 (2021). + +17. Kong, Y. et al. Visualisation and quantification of flooding phenomena in gas diffusion electrodes (GDEs) used for electrochemical CO2 reduction. A combined EDX/ICP-MS approach (2022). + +18. Nwabara, U. O. et al. Binder-Focused Approaches to Improve the Stability of Cathodes for CO 2 Electroreduction. ACS Appl. Energy Mater. 4, 5175–5186; 10.1021/acsaeam.1c00715 (2021). + +19. Kutz, R. B. et al. Sustainion Imidazolium-Functionalized Polymers for Carbon Dioxide Electrolysis. Energy Technol. 5, 929–936; 10.1002/ente.201600636 (2017). + +20. Larrazabal, G. O. et al. Analysis of Mass Flows and Membrane Cross-over in CO2 Reduction at High Current Densities in an MEA-Type Electrolyzer. ACS applied materials & interfaces 11, 41281–41288; 10.1021/acsami.9b13081 (2019). + +21. Liu, Z., Yang, H., Kutz, R. & Masel, R. I. CO 2 Electrolysis to CO and O 2 at High Selectivity, Stability and Efficiency Using Sustainion Membranes. J. Electrochem. Soc. 165, J3371-J3377; 10.1149/2.0501815jes (2018). + +22. Leonard, M. E., Clarke, L. E., Forner-Cuenca, A., Brown, S. M. & Brushett, F. R. Investigating Electrode Flooding in a Flowing Electrolyte, Gas-Fed Carbon Dioxide Electrolyzer. ChemSuscChem; 10.1002/cssc.201902547 (2019). + +23. Shafaque, H. W. et al. Boosting Membrane Hydration for High Current Densities in Membrane Electrode Assembly CO2 Electrolysis. ACS applied materials & interfaces; 10.1021/acsami.0c14832 (2020). + +24. Delacourt, C., Ridgway, P. L., Kerr, J. B. & Newman, J. Design of an Electrochemical Cell Making Syngas (CO+H[sub 2]) from CO[sub 2] and H[sub 2]O Reduction at Room Temperature. J. Electrochem. Soc. 155, B42; 10.1149/1.2801871 (2008). + +25. Etzold, B. J.M. et al. Understanding the activity transport nexus in water and CO2 electrolysis. State of the art, challenges and perspectives. Chemical Engineering Journal 424, 130501; 10.1016/j.cej.2021.130501 (2021). + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +It is clear, that the Authors worked a lot on the manuscript, that is now much more clear. Reading it again I accept the novelty in the neutron imaging and in the spatial resolution of precipitate formation and water transport. There are still some open questions, that will hopefully be addressed in the follow- up studies from the authors. + +All things considered, I suggest the publication of the manuscript in its current form. As my questions were fully addressed, I do not have any questions/comments. + +Reviewer #2 (Remarks to the Author): + +My first review was already quite positive, with the only major concern about the chemical identification by neutrons. This is now supported by Raman spectroscopy, unfortunately not operando, but I think the results are sound nevertheless. I am happy! If I my help countering the first reviewer: he is of course right that the precipitation was already observed before. You might stress the point that in- situ imaging is very good tool in optimizing cell geometry and operation conditions ("an image is worth 1000 words, and a movie..."), less so in finding a new effect. This was also my intention of the suggestion to add a scheme of the processes involved. On the images one gets the feeling what to improve (e.g., the land/free space ratio). + +<--- Page Split ---> diff --git a/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6c01e1581fb85864a2ddf1ed93d3bfadbe61b1a6 --- /dev/null +++ b/peer_reviews/5569c3b9ac9d3d651019baf72550198b13563b1b4fee92de8445815738db29db/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,481 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 855, 215]]<|/det|> +High- resolution neutron imaging of salt precipitation and water transport in zero- gap CO2 electrolysis + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 281, 106]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[115, 147, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 202, 884, 330]]<|/det|> +The Authors present an insight in a zero- gap CO2 electrolyzer cell under operation, which is clearly a nice piece of work. The application of neutron imaging is well presented, but the conclusions drawn are not very new or convincing. The precipitate formation during operation was witnessed by several groups earlier, and the details of water management in the cell are not revealed here in details. Therefore, I feel that these achievements are more technical than novel, and hence I do not think that this paper belongs to Nature Communications. I believe it would be more suitable for more technical journals, such as ACS AMI, Applied Catalysis B, etc. + +<|ref|>text<|/ref|><|det|>[[115, 369, 533, 386]]<|/det|> +Some comments regarding the details of the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 425, 870, 536]]<|/det|> +Neutron imaging is a nice tool for visualizing the inner structure of the cell. Identifying precipitate, dry regions or bubbles is however very questionable, if not impossible. In Fig. S6 it is seen that K2CO3 is almost transparent for neutrons, and therefore its formation might result in the exact same image as a completely dry region. Assuming that the precipitate is hydrated is completely unfounded. If the water transport within the cell is to be described, other techniques should be applied to support these findings. + +<|ref|>text<|/ref|><|det|>[[115, 575, 876, 629]]<|/det|> +Regarding Fig. 1a, the followings are written: "As the cathode GDE is brighter in the land area of the cathode flow field even at 0 mA cm- 2, it can be assumed, that less precipitates are located in that area". Is there really any precipitate in the GDE at 0 current? + +<|ref|>text<|/ref|><|det|>[[115, 667, 857, 721]]<|/det|> +At higher current densities the membrane seems to be fairly dry. This would suggest a lower water concentration at the cathode surface, but we still see and increased HER at higher current densities. I find this a little contradictory. + +<|ref|>text<|/ref|><|det|>[[115, 760, 857, 814]]<|/det|> +"Going from 200 mA cm- 2 to 300 mA cm- 2 this trend for the cathode GDE is coming to halt and some regions of the GDE seem to get even slightly wetter again." - Why would the water content of the cathode GDE increase at higher current densities? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 822, 125]]<|/det|> +Instead of the Ti frit typically applied in zero gap cells, the authors used a carbon paper as anode support. Isn't this too hydrophobic to allow the proper wetting of the catalyst surface? + +<|ref|>text<|/ref|><|det|>[[116, 221, 393, 237]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 278, 844, 333]]<|/det|> +The manuscript "High- resolution neutron imaging of carbonate precipitation and water transport in zero- gap CO2 electrolysis" by J. Disch et al. is an interesting experimental attempt to vizualize the transport of ions and molecules in a CO2 electrolyzer by state- of- the- art neutron imaging, + +<|ref|>text<|/ref|><|det|>[[115, 343, 641, 360]]<|/det|> +which is of utmost importance for the further optimization of such cells. + +<|ref|>text<|/ref|><|det|>[[114, 400, 877, 528]]<|/det|> +Thus, the topic and aims are relevant and of interest to the specialists working in CO2- electrolysis as well as to the neutron imaging community. The research is well performed, and the research results justified (details follow later). Thus I have no problem in recommending publication of this nice piece of work. However, the appetite comes with eating. Roughly speaking, the authors discuss one "beamtime experiment", which should be elaborated and be put in perspective of the science and technology needed in CO2 electrolysis, in particular the importance of mass transport. Adding a discussion around this may make this paper a cornerstone in CO2 electrolysis. Concretely: + +<|ref|>text<|/ref|><|det|>[[114, 566, 872, 694]]<|/det|> +- A figure of the CO2 electrolyzer showing the electrodes and membrane geometry and what the neutrons probe, and highlighting the processes taking place. For understanding it is helpful to pinpoint, where water and CO2 is consumed, where a pH gradient builds up, where the gases evolve, etc., and how potential precipitations may perturb the overall process. I have the impression that the authors involved have some background in water electrolysis, where similar processes such as water management are relevant. However, CO2 electrolysis is more complex simply because CO2 is involved (see, e.g., Ref. 37; and Nesbitt et al., ACS Catal. 10, 14093-14106 (2020); Lu et al., + +<|ref|>text<|/ref|><|det|>[[114, 704, 881, 795]]<|/det|> +J. Am. Chem. Soc. 142, 15438-15444 (2020); Borgschulte et al., Front. Energy Res. 9:784082 (2022)). Figure 1 gives some of the aforementioned reactions, but it may be split in two figures one only showing the sketch (and critical phenomena). Also, to generalize the findings. The authors correctly mention that the findings may not be applicable to other electrolyzer setups (line 77 ff). Here, discussion/explanations are most important (e.g., what are the differences). + +<|ref|>text<|/ref|><|det|>[[114, 805, 866, 897]]<|/det|> +- The attribution of the neutron contrast to K(H)CO3 is the most important finding, but also the most critical one. It is based on a kind of of handwaving arguments, but this is for sure not a chemical identification. Spatially resolved spectroscopy methods such as Raman spectroscopy (Lu et al., J. Am. Chem. Soc. 142, 15438-15444 (2020)) could provide evidence for this argumentation. I recommend to apply this (I do not know whether possible in this short time). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[145, 152, 411, 175]]<|/det|> +## Response to referees + +<|ref|>text<|/ref|><|det|>[[145, 191, 306, 207]]<|/det|> +Dear Sir or Madam, + +<|ref|>text<|/ref|><|det|>[[145, 223, 875, 290]]<|/det|> +We thank the editor for considering our manuscript for review and the referees for their comments. The questions and comments from the referees lead to fruitful discussions and helped to improve the manuscript. Below, we address each comment separately and highlight the changes we made to the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[145, 306, 281, 326]]<|/det|> +## Reviewer #1 + +<|ref|>sub_title<|/ref|><|det|>[[145, 343, 253, 358]]<|/det|> +## Comment 1: + +<|ref|>text<|/ref|><|det|>[[144, 359, 875, 490]]<|/det|> +The Authors present an insight in a zero- gap CO2 electrolyzer cell under operation, which is clearly a nice piece of work. The application of neutron imaging is well presented, but the conclusions drawn are not very new or convincing. The precipitate formation during operation was witnessed by several groups earlier, and the details of water management in the cell are not revealed here in details. Therefore, I feel that these achievements are more technical than novel, and hence I do not think that this paper belongs to Nature Communications. I believe it would be more suitable for more technical journals, such as ACS AMI, Applied Catalysis B, etc. + +<|ref|>sub_title<|/ref|><|det|>[[145, 504, 240, 519]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 520, 875, 569]]<|/det|> +We thank the reviewer for the profound feedback. We tried to significantly work on our manuscript, including new ex- situ characterization results which hopefully back up our findings in a convincing way (see below). + +<|ref|>sub_title<|/ref|><|det|>[[145, 600, 253, 615]]<|/det|> +## Comment 2: + +<|ref|>text<|/ref|><|det|>[[145, 616, 875, 650]]<|/det|> +Neutron imaging is a nice tool for visualizing the inner structure of the cell. Identifying precipitate, dry regions or bubbles is however very questionable, if not impossible. + +<|ref|>sub_title<|/ref|><|det|>[[145, 666, 240, 681]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 682, 875, 780]]<|/det|> +The reviewer is right, that neutron imaging is a complex method, and any results need to be interpreted with care. However, it was repeatedly proven over more than a decade now that neutron imaging is especially suitable for the in- situ investigation of water distribution and bubble formation in electrochemical devices, what has been proven in a multitude of publications \(^{1 - 7}\) . The identification of precipitates by neutron imaging is less explored and therefore discussed in detail in the comments following below. + +<|ref|>sub_title<|/ref|><|det|>[[145, 811, 253, 826]]<|/det|> +## Comment 3: + +<|ref|>text<|/ref|><|det|>[[144, 827, 875, 860]]<|/det|> +In Fig. S6 it is seen that K2CO3 is almost transparent for neutrons, and therefore its formation might result in the exact same image as a completely dry region. + +<|ref|>sub_title<|/ref|><|det|>[[145, 874, 240, 890]]<|/det|> +## Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 150, 875, 250]]<|/det|> +Yes, this is right. This is why we did not claim that \(\mathsf{K}_2\mathsf{CO}_3\) is imaged directly in the neutron radiography. In fact, we stated that \(\mathsf{K}_2\mathsf{CO}_3\) can only be imaged indirectly by imaging the retained water (original manuscript line 172ff) and specifically added the mentioned Fig. S6 to illustrate that. However, Fig. S6 also shows that \(\mathsf{KHCO}_3\) can significantly contribute to the neutron attenuation, which makes imaging of \(\mathsf{KHCO}_3\) possible (see comment 7 and comment 4 of Reviewer #2). + +<|ref|>text<|/ref|><|det|>[[145, 263, 875, 312]]<|/det|> +Considering the reviewer's comment, we concluded that the wording in the manuscript and its title could be more precise to not be misunderstood. We therefore changed the title and some expressions in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[146, 326, 390, 343]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 363, 874, 400]]<|/det|> +Title, line 1f: High- resolution neutron imaging of salt precipitation and water transport in zero- gap \(\mathbf{CO}_2\) electrolysis + +<|ref|>text<|/ref|><|det|>[[144, 419, 875, 455]]<|/det|> +Line 22f: Neutron imaging further shows higher salt accumulation under the cathode channel of the flow field compared to the land. + +<|ref|>text<|/ref|><|det|>[[144, 475, 875, 512]]<|/det|> +Line 31f: Salt precipitation and associated electrode flooding are observed in neutron images visualizing the cause of commonly observed decreasing Faraday efficiency. + +<|ref|>text<|/ref|><|det|>[[144, 532, 875, 604]]<|/det|> +Line 333ff: Although precipitates and associated electrode flooding are visible in the neutron images over the entire current range (precipitates potentially already formed during pretests), the cell is demonstrating good cell performance with \(\mathrm{FE_{CO}}\) above \(90\%\) for current densities below \(300~\mathrm{mA~cm^{- 2}}\) . + +<|ref|>sub_title<|/ref|><|det|>[[145, 639, 253, 655]]<|/det|> +## Comment 4: + +<|ref|>text<|/ref|><|det|>[[145, 655, 875, 704]]<|/det|> +Assuming that the precipitate is hydrated is completely unfounded. If the water transport within the cell is to be described, other techniques should be applied to support these findings. + +<|ref|>sub_title<|/ref|><|det|>[[145, 720, 240, 735]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[144, 736, 875, 899]]<|/det|> +Carbonate precipitates are normally porous and hydrophilic and hence increase the capillary pressure. Considering the deliquescent properties of carbonates and the moist reaction environment (humidified cathode gas stream, aqueous anolyte, a membrane with a high water uptake and ambient temperature) carbonates are very likely hydrated. This should be the case, especially in the zero current state, where no water is consumed by the electrode reactions. Fig. S6 also shows that already small amounts of water have a significant effect on the neutron transmission. However, the cathode GDE land region stays significantly brighter than the channel region at \(0~\mathrm{mA / cm^2}\) . It has been shown in literature, that the relative humidity is quite high in the cathode compartment even at higher current densities. Particularly the publication of Wheeler et al. is to mention in this context, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 150, 875, 217]]<|/det|> +in which the humidity in the cathode flow field is measured at 4 different positions, with and without humidification of the gas feed9. They show that without prior gas humidification the gas stream is humidified inside the cell, even at 200 mA / cm2 (RH of 79% at the outlet, also using similar Sustainion membranes). + +<|ref|>text<|/ref|><|det|>[[144, 230, 626, 247]]<|/det|> +We now address the humid environment in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[145, 260, 391, 277]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 279, 875, 448]]<|/det|> +Line 195ff: \(\mathsf{K}_2\mathsf{CO}_3\) shows significantly lower neutron absorption and scattering rates than water (see SI Figure S6 for neutron transmission rates). Due to its low neutron attenuation, \(\mathsf{K}_2\mathsf{CO}_3\) can only be observed indirectly, by imaging the retained water. Considering the deliquescent properties of \(\mathsf{K}_2\mathsf{CO}_3\) and the moist reaction environment (humidified cathode gas stream, aqueous anolyte, a membrane with a high water uptake10 and ambient temperature) carbonates inside the cell are very likely hydrated8. This should be the case, especially in the zero current state, when no water is consumed by the cathode reactions and condensing water in the cathode flow field is observed. \(\mathsf{KHCO}_3\) instead contains a hydrogen atom in its structure, yielding higher interactions with neutrons than \(\mathsf{K}_2\mathsf{CO}_3\) . + +<|ref|>sub_title<|/ref|><|det|>[[144, 484, 253, 500]]<|/det|> +## Comment 5: + +<|ref|>text<|/ref|><|det|>[[145, 500, 875, 550]]<|/det|> +Regarding Fig. 1a, the followings are written: "As the cathode GDE is brighter in the land area of the cathode flow field even at 0 mA cm- 2, it can be assumed, that less precipitates are located in that area". Is there really any precipitate in the GDE at 0 current? + +<|ref|>sub_title<|/ref|><|det|>[[145, 564, 241, 579]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 580, 875, 646]]<|/det|> +As described in detail in the SI (line 69ff) and mentioned in the manuscript (line 265f), there have been preceding electrochemical measurements to the experiments reported in the manuscript. Therefore, we see no contradiction with precipitates or highly saturated solution in the cathode GDE at zero current. We now do also mention it in that section. + +<|ref|>sub_title<|/ref|><|det|>[[145, 660, 390, 676]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[145, 677, 875, 743]]<|/det|> +Line 214ff: For example, as the cathode GDE is brighter in the land area of the cathode flow field even at 0 mA cm2, it can be assumed, that less precipitates are located in that area (note that \(\mathsf{KHCO}_3\) and \(\mathsf{K}_2\mathsf{CO}_3\) might have accumulated in the cathode GDE already in the preceding electrochemical measurements described in the SI). + +<|ref|>sub_title<|/ref|><|det|>[[145, 773, 253, 788]]<|/det|> +## Comment 6: + +<|ref|>text<|/ref|><|det|>[[145, 789, 875, 838]]<|/det|> +At higher current densities the membrane seems to be fairly dry. This would suggest a lower water concentration at the cathode surface, but we still see and increased HER at higher current densities. I find this a little contradictory. + +<|ref|>sub_title<|/ref|><|det|>[[145, 853, 240, 868]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[144, 869, 875, 901]]<|/det|> +The reviewer is right, that this might at first seem counterintuitive. Nonetheless, several points have to be considered: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 151, 875, 300]]<|/det|> +- Figure 5 shows that the membrane is getting slightly dryer with rising current density compared to the 0 current image. The change in water content, however, is not as drastic as in other regions in the cell (see e.g. cathode GDE, condensate in cathode flow field channels). This is a reasonable result, as the utilized Sustainion membrane was reported to have a very high water uptake ( \(\sim 80\%\) reported by Lindquist et al.)10,11. Thereby it provides liquid water to the cathode catalyst layer as it is in direct contact with it. Moreover, in dry cathode AEM water electrolysis, significantly higher HER current densities are achieved, only providing water from the anode side through the membrane12,13. + +<|ref|>text<|/ref|><|det|>[[172, 313, 875, 479]]<|/det|> +- Further, as Reviewer #2 mentioned, mass transport plays an important role in \(\mathrm{CO_2}\) electrolysis. Most likely, more limiting than water availability is the availability of \(\mathrm{CO_2}\) at the cathode. \(\mathrm{CO_2}\) has to reach the active sites of the cathode catalyst layer by diffusing from the cathode flow field channel through the gas diffusion layer, the micro porous layer and finally the pores of the catalyst layer. With rising current density more \(\mathrm{CO_2}\) is consumed by the \(\mathrm{CO_2}\) reduction reaction and the carbonation reaction, lowering the \(\mathrm{CO_2}\) concentration at the electrode surface, while there is still enough water to maintain the HER (concentration of \(\mathrm{CO_2}\) in a humidified gas stream \(\mathrm{C_{CO2} = 0.041 M}\) compared to concentration of pure liquid water \(\mathrm{C_{H2O} = 55.5 M}\)14). Precipitates in the electrode add an additional diffusion barrier for \(\mathrm{CO_2}\) . + +<|ref|>sub_title<|/ref|><|det|>[[146, 492, 390, 509]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 521, 875, 720]]<|/det|> +Line 289ff: While this might be surprising, one has to consider that a region depleted of \(\mathrm{CO_2}\) might still have a sufficiently high water content for the hydrogen evolution reaction. The utilized Sustainion® membranes were reported to have a very high water uptake of \(\sim 80\%\) 10,11 and are only getting slightly drier during cell operation (see Figure 5), directly providing water to cathode catalyst layer. \(\mathrm{CO_2}\) , however, has to reach the active sites of the cathode catalyst layer by diffusing from the cathode flow field channel through the gas diffusion layer, the micro porous layer and finally the pores of the catalyst layer. With rising current density more \(\mathrm{CO_2}\) is consumed by the \(\mathrm{CO_2}\) reduction reaction and the carbonation reaction, lowering the \(\mathrm{CO_2}\) concentration at the electrode surface. Precipitates in the electrode add an additional diffusion barrier for \(\mathrm{CO_2}\) (see Figure 1d). Thus the reaction shifts to the HER resulting in lower faradaic efficiency of the \(\mathrm{CO_2}\) reduction at high current densities (Figure 2c) instead of increasing the overpotential. + +<|ref|>sub_title<|/ref|><|det|>[[145, 750, 253, 765]]<|/det|> +## Comment 7: + +<|ref|>text<|/ref|><|det|>[[145, 765, 874, 815]]<|/det|> +"Going from 200 mA cm- 2 to 300 mA cm- 2 this trend for the cathode GDE is coming to halt and some regions of the GDE seem to get even slightly wetter again." – Why would the water content of the cathode GDE increase at higher current densities? + +<|ref|>sub_title<|/ref|><|det|>[[145, 832, 240, 847]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 848, 874, 897]]<|/det|> +We agree with the reviewer that this observation is not very intuitive, as the water consumption on the cathode side rises with increasing current density. Nonetheless, we observed this behavior (also in other measurements). In our manuscript we explain + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 150, 875, 233]]<|/det|> +possible reasons for this observation (line 223ff). The intensity decrease is mainly observed in the cathode gas diffusion layer and more pronounced in the channel region of the cathode flow field (see Figure 4 and 5). As this is a continuous process (see Figure 5) we conclude that this intensity decrease is most probably caused by \(\mathrm{KHCO_3}\) precipitates (and water retained by the precipitates) accumulating in that area. + +<|ref|>text<|/ref|><|det|>[[144, 247, 875, 360]]<|/det|> +To additionally support this statement, we conducted SEM/EDX measurements of a cross- section of the cathode GDE and Raman measurements of the silver catalyst layer after cell operation and added them to the Supplementary Information (see below). The SEM/EDX measurements clearly show potassium containing precipitates in the silver catalyst layer, the micro porous layer and in the gas diffusion layer of the cathode. The Raman measurements further confirm the presence of \(\mathrm{KHCO_3}\) in the silver catalyst layer. The spectrum does not show the typical bands for \(\mathrm{K_2CO_3}\) . + +<|ref|>text<|/ref|><|det|>[[144, 375, 872, 408]]<|/det|> +Different publications concluded from post- experiment analysis that the precipitates consist of a mixture of different carbonic salts: + +<|ref|>text<|/ref|><|det|>[[145, 422, 875, 540]]<|/det|> +E.g. Endrödi et al. conducted XRD measurements and concluded that the precipitated salts consist of a mixture of \(\mathrm{KHCO_3}\) and \(\mathrm{K_4H_2(CO_3)_3\cdot 1.5H_2O}\) , with an approximate 1:3 weight ratio15. Xu et al. showed with Raman measurements that in their case, the precipitates consist of a mixture of \(\mathrm{K_2CO_3}\) and \(\mathrm{KHCO_3}\) with more \(\mathrm{K_2CO_3}\) than \(\mathrm{KHCO_3}^{16}\) . All studies report species containing hydrogen atoms in the precipitates (thus, species yielding significant neutron interaction). The ratio of the different species might strongly differ in different cells, depending on material properties and operating conditions. + +<|ref|>sub_title<|/ref|><|det|>[[146, 553, 390, 570]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 572, 875, 740]]<|/det|> +Line 205ff: Nonetheless, \(\mathrm{KHCO_3}\) is also strongly hygroscopic and retains water, which might more drastically affect its neutron opacity in a humid environment. Scanning electron microscopy and energy dispersive X- ray spectroscopy (SEM/EDX) measurements of a cathode cross section further show precipitates containing potassium in the silver catalyst layer, the micro porous layer and in the gas diffusion layer (see SI Figure S7). The presence of \(\mathrm{KHCO_3}\) in the catalyst layer was additionally verified by post- operation Raman measurements (see SI Figure S8). Considering those results and the mentioned observations made by other groups15,17, it can be assumed that the dark dents originate from precipitated \(\mathrm{KHCO_3}\) and water retained by the precipitates in that area. + +<|ref|>text<|/ref|><|det|>[[145, 720, 875, 787]]<|/det|> +By that, the intensity differences alongside the cathode GDE allow to deduce where precipitates are mainly located in the electrode. For example, as the cathode GDE is brighter in the land area of the cathode flow field even at \(0 \mathrm{mA} \mathrm{cm}^{- 2}\) , it can be assumed, that less precipitates are located in that area. + +<|ref|>text<|/ref|><|det|>[[145, 800, 875, 850]]<|/det|> +Line 237ff: Going from \(200 \mathrm{mA} \mathrm{cm}^{- 2}\) to \(300 \mathrm{mA} \mathrm{cm}^{- 2}\) this trend for the cathode GDE is coming to halt and the intensity in some regions of the cathode gas diffusion layer even decreases. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 150, 875, 201]]<|/det|> +Line 252ff: However, considering the afore- mentioned points and the post- operation Raman and SEM/EDX measurements (see SI Figure S7 and S8), it is most probable that the accumulation of KHCO₃ causes the observed drop in intensity. + +<|ref|>text<|/ref|><|det|>[[144, 215, 875, 315]]<|/det|> +Line 272ff: Again, if the change in intensity would only account for water content, this observation would be counterintuitive, as the increased reaction rate leads to higher water consumption and electro- osmotic drag from cathode to anode (see Figure 1a). This observation in the cathode GDL suggest that KHCO₃ is continuously accumulating during cell operation. The different slopes of the cathode GDL intensity curve translate to KHCO₃ accumulation already starting at 100 mA cm⁻² and significantly increasing at 300 mA cm⁻². + +<|ref|>text<|/ref|><|det|>[[144, 346, 530, 364]]<|/det|> +Changes to the Supplementary Information: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[213, 150, 803, 789]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[143, 801, 877, 870]]<|/det|> +S 1 Scanning electron micrographs and energy dispersive X- ray spectroscopies of the cathode electrode cross section after cell operation. a) electron micrograph and elemental maps of carbon, fluorine, oxygen, silver, potassium and iridium, b) a layered image of the electron micrograph and the elemental map of potassium, c) an electron micrograph layered with the elemental maps of iridium, silver and fluorine, identifying the catalyst layers and the hydrophobic microporous layer, and d) spectrum obtained from the energy dispersive X- ray spectroscopy. The cross section was prepared by cryo- cutting. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[260, 159, 752, 420]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[144, 426, 876, 517]]<|/det|> +
S 2 Raman spectra of pure potassium bicarbonate and of the cathode catalyst layer after cell operation. The spectra were recorded at different positions of the cathode GDE catalyst layer surface after carefully removing the membrane. The phenyl group signal results from the Sustainion cathode catalyst binder \(^{18,19}\) . Raman spectra were obtained using a WITec alpha 300 confocal Raman microscope with a 532 nm laser operated at \(10 \pm 1 \text{mW}\) as the excitation source. Average spectra of the samples were produced by averaging five single spectra from each respective sample. All single spectra were integrated for 0.5 s and accumulated ten times. Background subtraction and fitting was done using WITec project.
+ +<|ref|>sub_title<|/ref|><|det|>[[145, 548, 253, 563]]<|/det|> +## Comment 8: + +<|ref|>text<|/ref|><|det|>[[145, 563, 875, 612]]<|/det|> +Instead of the Ti rift typically applied in zero gap cells, the authors used a carbon paper as anode support. Isn't this too hydrophobic to allow the proper wetting of the catalyst surface? + +<|ref|>sub_title<|/ref|><|det|>[[145, 630, 240, 645]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 645, 875, 727]]<|/det|> +We decided to use this anode as it is a commercially available state- of- the- art electrode and has been proven to be suitable for this application in several studies \(^{19,20,21}\) . By choosing commercially available materials, we try to make our results reproducible for other groups. As the neutron radiographic images show electrolyte fully enters the anode GDE. Thus, the carbon paper works well as a substrate despite its wettability. + +<|ref|>sub_title<|/ref|><|det|>[[145, 760, 290, 780]]<|/det|> +## Reviewer #2: + +<|ref|>sub_title<|/ref|><|det|>[[145, 797, 253, 812]]<|/det|> +## Comment 1: + +<|ref|>text<|/ref|><|det|>[[145, 812, 875, 893]]<|/det|> +The manuscript "High- resolution neutron imaging of carbonate precipitation and water transport in zero- gap CO2 electrolysis" by J. Disch et al. is an interesting experimental attempt to vizualize the transport of ions and molecules in a CO2 electrolyzer by state- of- the- art neutron imaging, which is of utmost importance for the further optimization of such cells. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 150, 875, 281]]<|/det|> +Thus, the topic and aims are relevant and of interest to the specialists working in CO2- electrolysis as well as to the neutron imaging community. The research is well performed, and the research results justified (details follow later). Thus I have no problem in recommending publication of this nice piece of work. However, the appetite comes with eating. Roughly speaking, the authors discuss one "beamtime experiment", which should be elaborated and be put in perspective of the science and technology needed in CO2 electrolysis, in particular the importance of mass transport. Adding a discussion around this may make this paper a cornerstone in CO2 electrolysis. + +<|ref|>sub_title<|/ref|><|det|>[[145, 298, 241, 313]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 314, 875, 397]]<|/det|> +We thank the reviewer for the very positive evaluation or our manuscript. Within the restricted time budget of a revision process, we tried our best to further back up our statements following the reviewer's recommendations. Therefore, we included now further post- mortem microanalysis of the MEAs by SEM/EDX and Raman. The measurements clearly confirm the presence of potassium accumulations in the cathode. + +<|ref|>sub_title<|/ref|><|det|>[[145, 411, 253, 427]]<|/det|> +## Comment 2: + +<|ref|>text<|/ref|><|det|>[[145, 428, 243, 443]]<|/det|> +Concretely: + +<|ref|>text<|/ref|><|det|>[[144, 443, 875, 592]]<|/det|> +- A figure of the CO2 electrolyzer showing the electrodes and membrane geometry and what the neutrons probe, and highlighting the processes taking place. For understanding it is helpful to pinpoint, where water and CO2 is consumed, where a pH gradient builds up, where the gases evolve, etc., and how potential precipitations may perturb the overall process. I have the impression that the authors involved have some background in water electrolysis, where similar processes such as water management are relevant. However, CO2 electrolysis is more complex simply because CO2 is involved (see, e.g., Ref. 37; and Nesbitt et al., ACS Catal. 10, 14093-14106 (2020); Lu et al., J. Am. Chem. Soc. 142, 15438-15444 (2020); Borgschulte et al., Front. Energy Res. 9:784082 (2022)). + +<|ref|>text<|/ref|><|det|>[[144, 604, 875, 638]]<|/det|> +Figure 1 gives some of the aforementioned reactions, but it may be split in two figures one only showing the sketch (and critical phenomena). Also, to generalize the findings. + +<|ref|>sub_title<|/ref|><|det|>[[145, 653, 241, 668]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 669, 875, 767]]<|/det|> +We thank the reviewer for the feedback and the proposed amendments. Considering the propositions we revised Figure 1. We added a Figure 1c and 1d, illustrating the idealized processes at the cathode GDE and the influence of carbonates on the \(\mathrm{CO_2}\) mass transport. Additionally, we added Figure S1b to the supplementary information, showing a rendering of the neutron detector and a cross section of the cell fixture, to provide a better understanding what the neutrons probe. + +<|ref|>sub_title<|/ref|><|det|>[[146, 781, 390, 797]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[145, 797, 875, 896]]<|/det|> +Line 63ff: Although the AEM hinders potassium cations from crossing the membrane in bigger quantities by Donnan exclusion, a small amount of cations is still migrating through the membrane. As cations move from the anode to the cathode side, they drag water in their hydration shell with them. Over time potassium, carbonate and bicarbonate ions can accumulate at the cathode. When exceeding the solubility limit, by increasing ion concentration or by consumption of water, salt crystallites can precipitate on the cathode + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 150, 875, 316]]<|/det|> +side. Figures 1c and 1d illustrate how precipitates supposedly influence the processes in the cathode gas diffusion electrode (GDE). Carbonate precipitates are normally porous and hydrophilic, increasing the capillary pressure inside the cathode GDE8. Hence, the precipitates make the GDE prone to electrode flooding. Liquids and precipitates can clog pores in the catalyst layer, micro porous layer and the gas diffusion layer of the cathode GDE, and thereby impede the gas transport22. With an increasing amount of precipitates, the mass transport resistance for the \(\mathrm{CO_2}\) to reach the active sites of the catalyst layer increases and the \(\mathrm{CO_2}\) concentration at the catalyst surface will eventually decrease. The lower \(\mathrm{CO_2}\) concentration may cause a selectivity shift towards the HER, as water can still be sufficiently supplied from the anode side through the membrane. + +<|ref|>image<|/ref|><|det|>[[147, 330, 875, 735]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[144, 736, 877, 802]]<|/det|> +
Figure 1 Transport processes and cell components. a) water management highlighted in schematic of reactions and transport processes during operation, b) enlarged section of a normalized neutron radiographic image of the \(\mathrm{CO_2}\) electrolysis cell, c) idealized cathode processes, and d) influence of precipitates on the cathode processes.
+ +<|ref|>text<|/ref|><|det|>[[144, 839, 531, 858]]<|/det|> +Changes to the Supplementary Information: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[291, 150, 731, 536]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 550, 877, 650]]<|/det|> +S 3 Cell fixture and neutron detector/cell alignment. a) an explosion view of the custom- built electrolysis cell (End plates: Stainless steel, flow fields: Au coated Ti grade 2, gaskets: PTFE), and b) a rendering of the neutron detector and of the cell fixture cross section in alignment to the incident neutron beam. The scintillator sits in the neutron detector head close to the cell fixture. The emitted scintillation light is reflected to the detector, which is orientated perpendicular to the incident neutron beam. + +<|ref|>sub_title<|/ref|><|det|>[[145, 677, 253, 693]]<|/det|> +## Comment 3: + +<|ref|>text<|/ref|><|det|>[[145, 694, 875, 744]]<|/det|> +The authors correctly mention that the findings may not be applicable to other electrolyzer setups (line 77 ff). Here, discussion/explanations are most important (e.g., what are the differences). + +<|ref|>sub_title<|/ref|><|det|>[[145, 757, 240, 772]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[144, 773, 872, 789]]<|/det|> +The reviewer raised a fair point and we therefore added that discussion to the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[145, 804, 390, 820]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 821, 875, 903]]<|/det|> +Line 83ff: The technological advances of neutron imaging detectors significantly improved the resolution of neutron radiography in recent years. Nonetheless, only two neutron- imaging studies investigating \(\mathrm{CO_2}\) electrolyzers have been published up to now. The first study investigated bubble formation in a liquid buffer layer on the cathode side3. Besides high cell potentials, cells with a liquid catholyte between the membrane and cathode GDE + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 150, 875, 380]]<|/det|> +often exhibit fast electrode flooding, as the cathode is in direct contact with the liquid electrolyte. The circulating electrolyte, however, can wash away precipitates and depending on its chemical composition change the ion concentration at the cathode side compared to a zero- gap cell. The second study conducted neutron imaging of a zero- gap cell with a cation exchange membrane23. Zero- gap cells using cation exchange membranes show significantly lower CO selectivity compared to cells using AEMs, as they provide an acidic reaction environments to the cathode, facilitating the competing HER24. Furthermore, protons moving from the anode to the cathode are responsible for the ionic charge transfer between the anode and cathode. The ionic transport and the electroosmotic drag are directed in the opposite direction compared to cells using AEMs, drastically changing the water balance. As the water balance and flooding behavior in the above- mentioned studies strongly differ, their results cannot be applied to AEM- based zero- gap \(\mathrm{CO_2}\) electrolyzers. Etzold et al. have recently highlighted this lack of neutron studies for zero- gap \(\mathrm{CO_2}\) electrolysis in a review25. + +<|ref|>sub_title<|/ref|><|det|>[[145, 397, 253, 413]]<|/det|> +## Comment 4: + +<|ref|>text<|/ref|><|det|>[[145, 413, 875, 510]]<|/det|> +The attribution of the neutron contrast to \(\mathrm{K(H)CO_3}\) is the most important finding, but also the most critical one. It is based on a kind of of handwaving arguments, but this is for sure not a chemical identification. Spatially resolved spectroscopy methods such as Raman spectroscopy (Lu et al., J. Am. Chem. Soc. 142, 15438- 15444 (2020)) could provide evidence for this argumentation. I recommend to apply this (I do not know whether possible in this short time). + +<|ref|>sub_title<|/ref|><|det|>[[145, 525, 241, 540]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[145, 540, 875, 672]]<|/det|> +The reviewer is right, that it is not possible to quantitatively deconvolute the contribution of \(\mathrm{KHCO_3}\) and water to the neutron attenuation with our method. Unfortunately, the proposed in situ Raman spectroscopy is not only impossible in this short time, but is not possible at all, as we investigate a zero- gap cell architecture (membranes and electrodes are not transparent for the Raman laser). Lu et al. only investigate the concentration gradients inside the liquid catholyte and cannot analyze the gradients inside the cathode GDE. The liquid catholyte renders the results not applicable to a zero- gap cell (also see comment 3, different cell architectures). + +<|ref|>text<|/ref|><|det|>[[145, 686, 875, 752]]<|/det|> +However, we followed the reviewer's recommendation to employ Raman spectroscopy as method of choice, and backed the findings up with additional SEM/EDX measurements of the cathode electrode to further investigate the distribution and the composition of the precipitates (see comment 7 of Reviewer #1). + +<|ref|>text<|/ref|><|det|>[[145, 766, 875, 814]]<|/det|> +The SEM/EDX measurements clearly show potassium containing precipitates in the silver catalyst layer, the micro porous layer and in the gas diffusion layer. The Raman measurements further prove the presence of \(\mathrm{KHCO_3}\) in the cathode. + +<|ref|>text<|/ref|><|det|>[[145, 815, 875, 880]]<|/det|> +Considering the above- mentioned, a closer look at Figure S6 can help to further clarify the interpretation of the neutron radiography data. As Reviewer #1 correctly stated, the contribution of \(\mathrm{K_2CO_3}\) to the neutron attenuation can be neglected, whereas \(\mathrm{KHCO_3}\) shows significant neutron attenuation: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[310, 156, 705, 394]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[144, 412, 875, 451]]<|/det|> +
S 4 Calculated neutron transmission for different compounds and sample thicknesses calculated with the online calculator from "NIST Center for Neutron Research" [https://www.ncnr.nist.gov/resources/activation/, Date: 02.2022]. The wavelength was set to 3 Å.
+ +<|ref|>text<|/ref|><|det|>[[144, 463, 875, 563]]<|/det|> +The neutron attenuation of water is still significantly higher than that of \(\mathrm{KHCO_3}\) . In the zero current state and at low current densities (low water consumption) the neutron attenuation might be dominated by water. At higher current densities (increased water consumption and electroosmotic drag) the contribution of \(\mathrm{KHCO_3}\) to the neutron attenuation in the cathode GDE gets more significant. At \(200 \mathrm{mA cm^{- 2}}\) the liquid water in the cathode flow field has already fully dried off, however, the precipitates are clearly visible. + +<|ref|>text<|/ref|><|det|>[[145, 562, 875, 628]]<|/det|> +All information we gained from the Raman measurements, SEM/EDX measurements and literature (see comment 7 of Reviewer #1 and line 191ff in the manuscript) supports the claim that \(\mathrm{KHCO_3}\) contributes to the neutron attenuation in the presented radiographic images. + +<|ref|>sub_title<|/ref|><|det|>[[146, 644, 390, 660]]<|/det|> +## Changes to the manuscript: + +<|ref|>text<|/ref|><|det|>[[145, 660, 875, 709]]<|/det|> +Line 188ff: Nevertheless, at \(300 \mathrm{mA cm^{- 2}}\) these bulges are still clearly visible, whereas the liquid condensate in the channel has fully dried off. Even though the images are averaged over several minutes, the bulges show sharp contours, indicating an immobile solid phase. + +<|ref|>text<|/ref|><|det|>[[144, 729, 810, 746]]<|/det|> +All other related changes are listed in the response to comment 7 of Reviewer #1. + +<|ref|>sub_title<|/ref|><|det|>[[145, 767, 385, 787]]<|/det|> +## Concluding remarks + +<|ref|>text<|/ref|><|det|>[[145, 788, 875, 853]]<|/det|> +Further minor changes to the manuscript that are not mentioned in this letter are highlighted in the newly submitted manuscript file. We appreciate the detailed revision of our manuscript. We hope that we could answer all questions to the satisfaction of the referees. Furthermore, we are open to discuss any further questions. + +<|ref|>text<|/ref|><|det|>[[145, 870, 277, 886]]<|/det|> +Sincerely yours, + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[144, 150, 279, 167]]<|/det|> +## Severin Vierrath + +<|ref|>sub_title<|/ref|><|det|>[[144, 193, 229, 208]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[140, 204, 875, 880]]<|/det|> +1. Kardjilov, N., Manke, I., Woracek, R., Hilger, A. & Banhart, J. Advances in neutron imaging. Materials Today 21, 652–672; 10.1016/j.mattod.2018.03.001 (2018). +2. Boillat, P., Frei, G., Lehmann, E. H., Scherer, G. G. & Wokaun, A. Neutron Imaging Resolution Improvements Optimized for Fuel Cell Applications. Electrochem. Solid-State Lett. 13, B25; 10.1149/1.3279636 (2010). +3. Krause, K. et al. Electrolyte layer gas triggers cathode potential instability in CO2 electrolyzers. Journal of Power Sources 520, 230879; 10.1016/j.jpowsour.2021.230879 (2022). +4. Lehmann, E. H. & Wagner, W. Neutron imaging at PSI. A promising tool in materials science and technology. Appl. Phys. A 99, 627–634; 10.1007/s00339-010-5606-3 (2010). +5. Hoeh, M. A. et al. In-Operando Neutron Radiography Studies of Polymer Electrolyte Membrane Water Electrolyzers. ECS Trans. 69, 1135–1140; 10.1149/06917.1135ecst (2015). +6. Omasta, T. J. et al. Beyond catalysis and membranes. Visualizing and solving the challenge of electrode water accumulation and flooding in AEMFCs. Energy Environ. Sci. 11, 551–558; 10.1039/C8EE00122G (2018). +7. Zlobinski, M., Schuler, T., Büchi, F. N., Schmidt, T. J. & Boillat, P. Transient and Steady State Two-Phase Flow in Anodic Porous Transport Layer of Proton Exchange Membrane Water Electrolyzer. J. Electrochem. Soc. 167, 84509; 10.1149/1945-7111/ab8c89 (2020). +8. Li, M. et al. The role of electrode wettability in electrochemical reduction of carbon dioxide. J. Mater. Chem. A 9, 19369–19409; 10.1039/d1ta03636j (2021). +9. Wheeler, D. G. et al. Quantification of water transport in a CO 2 electrolyzer. Energy Environ. Sci. 13, 5126–5134; 10.1039/d0ee02219e (2020). +10. Kaczur, J. J., Yang, H., Liu, Z., Sajjad, S. D. & Masel, R. I. Carbon Dioxide and Water Electrolysis Using New Alkaline Stable Anion Membranes. Frontiers in chemistry 6, 263; 10.3389/fchem.2018.00263 (2018). +11. Lindquist, G. A. et al. Performance and Durability of Pure-Water-Fed Anion Exchange Membrane Electrolyzers Using Baseline Materials and Operation. ACS applied materials & interfaces; 10.1021/acsami.1c06053 (2021). +12. Cho, M. K. et al. Alkaline anion exchange membrane water electrolysis. Effects of electrolyte feed method and electrode binder content. Journal of Power Sources 382, 22–29; 10.1016/j.jpowsour.2018.02.025 (2018). +13. Parrondo, J., George, M., Capuano, C., Ayers, K. E. & Ramani, V. Pyrochlore electrocatalysts for efficient alkaline water electrolysis. J. Mater. Chem. A 3, 10819–10828; 10.1039/C5TA01771H (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[140, 150, 864, 186]]<|/det|> +14. Weekes, D. M., Salvatore, D. A., Reyes, A., Huang, A. & Berlinguette, C. P. Electrolytic CO2 Reduction in a Flow Cell. Accounts of chemical research 51, 910–918; 10.1021/acs.accounts.8b00010 (2018). + +<|ref|>text<|/ref|><|det|>[[144, 193, 830, 247]]<|/det|> +15. Endrődi, B. et al. Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolyzers. Nature energy 6, 439–448; 10.1038/s41560-021-00813-w (2021). + +<|ref|>text<|/ref|><|det|>[[144, 255, 872, 291]]<|/det|> +16. Xu, Y. et al. Self-Cleaning CO 2 Reduction Systems. Unsteady Electrochemical Forcing Enables Stability. ACS Energy Lett., 809–815; 10.1021/acsenergylett.0c02401 (2021). + +<|ref|>text<|/ref|><|det|>[[144, 299, 835, 335]]<|/det|> +17. Kong, Y. et al. Visualisation and quantification of flooding phenomena in gas diffusion electrodes (GDEs) used for electrochemical CO2 reduction. A combined EDX/ICP-MS approach (2022). + +<|ref|>text<|/ref|><|det|>[[144, 343, 825, 379]]<|/det|> +18. Nwabara, U. O. et al. Binder-Focused Approaches to Improve the Stability of Cathodes for CO 2 Electroreduction. ACS Appl. Energy Mater. 4, 5175–5186; 10.1021/acsaeam.1c00715 (2021). + +<|ref|>text<|/ref|><|det|>[[144, 387, 835, 423]]<|/det|> +19. Kutz, R. B. et al. Sustainion Imidazolium-Functionalized Polymers for Carbon Dioxide Electrolysis. Energy Technol. 5, 929–936; 10.1002/ente.201600636 (2017). + +<|ref|>text<|/ref|><|det|>[[144, 430, 864, 485]]<|/det|> +20. Larrazabal, G. O. et al. Analysis of Mass Flows and Membrane Cross-over in CO2 Reduction at High Current Densities in an MEA-Type Electrolyzer. ACS applied materials & interfaces 11, 41281–41288; 10.1021/acsami.9b13081 (2019). + +<|ref|>text<|/ref|><|det|>[[144, 493, 870, 546]]<|/det|> +21. Liu, Z., Yang, H., Kutz, R. & Masel, R. I. CO 2 Electrolysis to CO and O 2 at High Selectivity, Stability and Efficiency Using Sustainion Membranes. J. Electrochem. Soc. 165, J3371-J3377; 10.1149/2.0501815jes (2018). + +<|ref|>text<|/ref|><|det|>[[144, 555, 864, 608]]<|/det|> +22. Leonard, M. E., Clarke, L. E., Forner-Cuenca, A., Brown, S. M. & Brushett, F. R. Investigating Electrode Flooding in a Flowing Electrolyte, Gas-Fed Carbon Dioxide Electrolyzer. ChemSuscChem; 10.1002/cssc.201902547 (2019). + +<|ref|>text<|/ref|><|det|>[[144, 617, 848, 671]]<|/det|> +23. Shafaque, H. W. et al. Boosting Membrane Hydration for High Current Densities in Membrane Electrode Assembly CO2 Electrolysis. ACS applied materials & interfaces; 10.1021/acsami.0c14832 (2020). + +<|ref|>text<|/ref|><|det|>[[144, 679, 870, 732]]<|/det|> +24. Delacourt, C., Ridgway, P. L., Kerr, J. B. & Newman, J. Design of an Electrochemical Cell Making Syngas (CO+H[sub 2]) from CO[sub 2] and H[sub 2]O Reduction at Room Temperature. J. Electrochem. Soc. 155, B42; 10.1149/1.2801871 (2008). + +<|ref|>text<|/ref|><|det|>[[144, 741, 872, 795]]<|/det|> +25. Etzold, B. J.M. et al. Understanding the activity transport nexus in water and CO2 electrolysis. State of the art, challenges and perspectives. Chemical Engineering Journal 424, 130501; 10.1016/j.cej.2021.130501 (2021). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 300, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 147, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 875, 275]]<|/det|> +It is clear, that the Authors worked a lot on the manuscript, that is now much more clear. Reading it again I accept the novelty in the neutron imaging and in the spatial resolution of precipitate formation and water transport. There are still some open questions, that will hopefully be addressed in the follow- up studies from the authors. + +<|ref|>text<|/ref|><|det|>[[115, 287, 857, 322]]<|/det|> +All things considered, I suggest the publication of the manuscript in its current form. As my questions were fully addressed, I do not have any questions/comments. + +<|ref|>text<|/ref|><|det|>[[115, 390, 393, 406]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 445, 881, 592]]<|/det|> +My first review was already quite positive, with the only major concern about the chemical identification by neutrons. This is now supported by Raman spectroscopy, unfortunately not operando, but I think the results are sound nevertheless. I am happy! If I my help countering the first reviewer: he is of course right that the precipitation was already observed before. You might stress the point that in- situ imaging is very good tool in optimizing cell geometry and operation conditions ("an image is worth 1000 words, and a movie..."), less so in finding a new effect. This was also my intention of the suggestion to add a scheme of the processes involved. On the images one gets the feeling what to improve (e.g., the land/free space ratio). + +<--- Page Split ---> diff --git a/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/images_list.json b/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..4e61ace9911e502a5070b530dcef8421ef5f8e39 --- /dev/null +++ b/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,78 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. rf The features of bubbles did not change during the x-tilt operation.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. r2 The magnetic \\(\\mathbf{R}+\\) configuration of \\(2\\#\\) bubble. a Distribution of in-plane magnetizations in 3D feature of the \\(\\mathbf{R}+\\) model. b In-plane induction components computed from \\(\\mathbf{R}+\\) model. c In-plane induction components reconstructed from the tilted LTEM images simulated based on \\(\\mathbf{R}+\\) model. d In-plane induction components recovered from the experimental data of \\(2\\#\\) bubble. The box frames in a)-c) indicate the physical size of \\(\\mathbf{R}+\\) model. Only the pixels with values larger than \\(20\\%\\) of the maximum intensity are rendered in b)-d) to depress the artifacts from regularization parameter and missing-wedge effect.", + "footnote": [], + "bbox": [ + [ + 180, + 157, + 816, + 518 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. r3 The simulated LTEM images for a \\(\\mathrm{R}+\\) skyrmion. a) and b) under-focus and over-focus without tilting; c) and d) under-focus and over-focus with tilting \\(-30^{\\circ}\\) around x axis.", + "footnote": [], + "bbox": [ + [ + 275, + 323, + 719, + 610 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. r4 The in-plane components of induction retrieved with a) \\(\\mathrm{q_0 = 5\\times 10^{-3}nm^{-1}}\\) and b) \\(\\mathrm{q_0 = 7.5\\times 10^{-3}}\\) \\(\\mathrm{nm^{-1}}\\) , respectively.", + "footnote": [], + "bbox": [ + [ + 241, + 88, + 757, + 262 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. r5 Diffractogram of the merged phase image, where the dash denotes the orientation of tilt axis.", + "footnote": [], + "bbox": [ + [ + 366, + 86, + 629, + 265 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig. 4 The magnetic spin transition of bubble #5. The \\(\\mathrm{B}_{\\mathrm{x}}\\) (a) and \\(\\mathrm{B}_{\\mathrm{y}}\\) (b) features in the top, middle and bottom x-y sections. The solid arrows indicate the direction of the corresponding component, while the dashed arrows indicate the speculative direction of the orthogonal component based on prior knowledge of Bloch skyrmion bubbles. The color legend indicates the magnitude of induction components in x or y direction, which corresponds the magnetization between \\(-6.5\\times 10^{5}\\sim 7\\times 10^{5}\\mathrm{A / m}\\) and well agrees with the measured value of \\(8\\times 10^{5}\\mathrm{A / m}\\) .42", + "footnote": [], + "bbox": [], + "page_idx": 14 + } +] \ No newline at end of file diff --git a/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..2940dfc78aba476ea206c0ffa35edb669faf3b6a --- /dev/null +++ b/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,417 @@ + +# nature portfolio + +Peer Review File + +Chirality flips of skyrmion bubbles + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: + +This manuscript reports on dynamic chirality flips of skyrmion bubbles found in a thin plate cut from a bulk sample of (Mn(1- x)Nix)65Ga35 (x = 0.45). Magnetic skyrmions have been found in chiral non- centrosymmetric crystals such as MnSi, FeGe, Cu2OSeO3, CoZnMn, GaV4S8 etc. MnNiGa is centrosymmetric and hence cannot host conventional magnetic skyrmions. The authors have undertaken Lorentz transmission electron microscopy studies to investigate the structure of the magnetic objects found in MnNiGa. Using vector field tomography they have demonstrated that the objects are in fact skyrmion bubbles. They also demonstrate that these skyrmion bubbles can be observed to flip their chirality and transform their vorticity whilst retaining their positive polarity. + +Unfortunately, nearly all of the conclusions they report in this paper have been reported, and published, before, and in papers not referenced by the authors. Loudon et al (Advanced Materials 31 (16) 1806598 2019) have previously reported a very similar study using Lorentz TEM on the same material and found both type I and type II bubbles and that the previously reported biskyrmions were in fact type II bubbles. They also demonstrated the internal structure of these objects using both x- ray holography and Lorentz TEM. Micromagnetic simulations and quantitative transport of intensity equation were used to determine the magnetisation of the objects. Figure 4 of their paper also shows the transformation, chirality flips, of individual bubbles in MnNiGa. I note that Loudon et al include a reference in their paper to an arXiv paper published by Y. Yao et al and including four of the manuscript authors. I am surprised that the authors of this manuscript have not found it worthwhile referencing the paper by Loudon et al. + +This manuscript would be greatly improved by the authors referencing previous relevant studies and restricting their manuscript to the novel aspects which have not been published. The use of vector field tomography via LTEM is a wonderful demonstration and does have advantages over the earlier study by Loudon. However, the authors are not able to explain these advantages without referencing the earlier studies. I also note a later paper published by Turnbull et al (ACS NANO 15 (1) 387 2021) reporting on tilting x- ray holography of magnetic bubbles in the same material, which is a technique making progress towards vector tomography. The authors should also consider the arXiv paper published by Nakajima "Two types of magnetic bubbles in MnNiGa observed via Lorentz microscopy" arXiv:2110.15507 (2021) and also S.L. Zuo et al., Nanoscale 10, 2260 (2018). + +I believe this manuscript is not worthy of publication in Nature Communications and should be rejected. The authors should in future take more care to adequately reference papers published by others in the field and to give suitable credit to them. The current manuscript certainly does contain novel and interesting results but is not worthy of publication in its present form. + +Reviewer #2: Remarks to the Author: Review of manuscript NCOMMS- 21- 41870 entitled „The dynamic chirality flips of Skyrmion bubbles“ by Yuan Yao, Bei Ding, Jinjing Liang, Hang Li, Xi Shen, Richeng Yu, Wenhong Wang + +Yuan Yao, Bei Ding and coworkers report on the tomographic 3D reconstruction of skyrmion bubbles in Mn- Ni- Ga from tilt series of Lorentz transmission electron micrographs. The goal of these investigations is to determine the 3D magnetic spin structure of different types of bubbles in terms of chirality, polarity and topology that is not possible from single L- TEM images. As a result, they found that bubbles switched their chirality (between reconstructions of two different Cartesian B- field components) but still keep the polarity to remain the singularity of the bubbles within the material. + +I find the approach very appealing and suited to be published in Nature Communications. However, the paper in its current stage lacks from numerous experimental uncertainties, logical + +<--- Page Split ---> + +and theoretical inconsistencies, and physical flaws and hence I can only recommend it for publication after a careful and major revision considering the points below. + +The major points of criticism which have to be addressed are the following: + +1. The magnetic states of the Skyrmion bubbles seem to be very unstable (metastable) at RT and therefore susceptible to be modified by small magnetic fields (compare e.g. in Fig.2a left and right column). The authors observe this problem by comparing the 3D induction maps of Bx and By (e.g. Fig.4 and Table 1). Since Bx and By belong only to the same magnetic state in bubble #2 only, they could only be combined in this case to obtain the full 3D vector-field by solving \(\mathrm{divB} = 0\) . Could it be that the residual magnetic field of the Lorentz lens (how large?) has changed the magnetic states of the bubbles when the sample was retracted and inserted in the TEM in-plane rotation? Even worse, did the authors has detected some changes within tilt series acquisition, i.e. when going to higher tilt angles due to the changed orientation of the residual field with respect to the specimen? To avoid this unintended flipping of the magnetic states, it would have been more favorable to cool the sample during acquisition or to use an in-plane rotation holder. + +2. The four magnetic states of the type I bubbles were computed by micromagnetic simulations as shown in Fig. 1. The Neel twisting at their surfaces leads to magnetic charges, i.e. a high contribution of H, but a low one of B. Since, L-TEM is only sensitive to B not M, it is worthwhile to know how the simulated B-field looks like especially at the surface. In this context, it is also interesting to know how extended in z-direction these Neel twists are and whether they can be resolved by VFET. + +3. The experimental tilt range is quite low: ca. \(+55^{\circ}\) instead of \(+90^{\circ}\) . Therefore the tomograms suffer from a large missing wedge, not discussed in the manuscript at all. I suppose, one problem is the slab geometry of the (FIB?) lamella, which is disadvantageous at high tilts, when new object information appears in the field-of-view and the projected thickness becomes thicker and thicker. How the authors tackled this issue especially when using a SIRT algorithm for reconstruction, where the reconstructed volume must be limited? Why the authors have not tried to prepare a needle-shaped sample much more suitable for tomography? + +4. To judge the fidelity of the tomograms, it is also important to know how the applied focus of \(300\mu m\) determines the lateral resolution of the L-TEM images described by the spatial envelope. Also the regularization (not regularity as written in the paper) parameter q0 (line 272) determines on a certain way the fidelity of the 3D data. In best case, the authors should check by a simulated tilt series using same parameters (tilt range, defocus, q0), whether the tomogram reveals the original magnetic structure? + +5. With respect to the resolution limitations mentioned in points 3 and 4, the observation of a very localized Bloch line in Figs. 3c,d is really questionable. The authors should check the reliability of this feature. + +6. Why the authors do not provide the reconstructed 3D B-fields in Tesla. E.g., in Fig.4 the values range from \(+ - 10^{\circ}6\) (A/m?). They must not be denoted Mx and My, because these are B-fields. Minor comments + +1. Can the authors give more information/data about the experiment and data treatment (at least in the Suppl. Mat.), such as + +- TEM lamella preparation (by FIB?) +- Field cooling procedure +- Lorentz TEM tilt series (to be shown in supplement?) +- TIE reconstruction (influence of regularization) +- phase tilt series (to be shown in supplement?) +- Image alignment (line 275) +- W-SIRT parameters (influence of regularization) + +2. Mathematics: + +Could the authors more clearly describe the mathematics of TIE? - As shown by Lubk et al. (PRL 111, 173902 (2013)) Eq. 1 is only valid, if a) the object is a pure phase object, or b) the current density is conservative. What is valid here? - What is the meaning of symbol \(\nabla < \mathrm{sup} > - 2< /\mathrm{sup} > ?\) Isn't it the inversion of Laplacian, \(1 / \mathrm{q} < \mathrm{sup} > 2< /\mathrm{sup} >\) in Fourier space to be inserted in line 271 on the LHS instead \(\nabla \mathrm{xy}\) ? - Inconsistencies of notation, in Eq. (1) reciprocal vector is q, whereas in Eq. (2) reciprocal vector is k + +<--- Page Split ---> + +3. English writing and wording. + +- there are numerous typos and sometimes inadequate choice of words, e.g. line 20: "magnetic moment" is misleading here, line 40 "need", line 48 "turns into" not appropriate in this context, line 64 "charity", line 116 "configuraton", line 232, 238 "configure", line 263 "3D structure reconstruction" not the right term The text needs very much polishing in general. 4. Fig.1b: Why there is a threshold in the simulated induction maps (black mask)? 5. Line 273: Please provide the value of q0 in "1/nm" not pixels. + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +This manuscript reports on dynamic chirality flips of skyrmion bubbles found in a thin plate cut from a bulk sample of \((\mathrm{Mn}(1 - x)\mathrm{Nix})65\mathrm{Ga}35\) \(\mathrm{(x = 0.45)}\) . Magnetic skyrmions have been found in chiral non- centrosymmetric crystals such as MnSi, FeGe, \(\mathrm{Cu2OSeO3}\) , \(\mathrm{CoZnMn}\) , GaV4S8 etc. MnNiGa is centrosymmetric and hence cannot host conventional magnetic skyrmions. The authors have undertaken Lorentz transmission electron microscopy studies to investigate the structure of the magnetic objects found in MnNiGa. Using vector field tomography they have demonstrated that the objects are in fact skyrmion bubbles. They also demonstrate that these skyrmion bubbles can be observed to flip their chirality and transform their vorticity whilst retaining their positive polarity. + +Unfortunately, nearly all of the conclusions they report in this paper have been reported, and published, before, and in papers not referenced by the authors. Loudon et al (Advanced Materials 31 (16) 1806598 2019) have previously reported a very similar study using Lorentz TEM on the same material and found both type I and type II bubbles and that the previously reported biskyrmions were in fact type II bubbles. They also demonstrated the internal structure of these objects using both x- ray holography and Lorentz TEM. Micromagnetic simulations and quantitative transport of intensity equation were used to determine the magnetisation of the objects. Figure 4 of their paper also shows the transformation, chirality flips, of individual bubbles in MnNiGa. I note that Loudon et al include a reference in their paper to an arXiv paper published by Y. Yao et al and including four of the manuscript authors. I am surprised that the authors of this manuscript have not found it worthwhile referencing the paper by Loudon et al. + +This manuscript would be greatly improved by the authors referencing previous relevant studies and restricting their manuscript to the novel aspects which have not been published. The use of vector field tomography via LTEM is a wonderful demonstration and does have advantages over the earlier study by Loudon. However, the authors are not able to explain these advantages without referencing the earlier studies. I also note a later paper published by Turnbull et al (ACS NANO 15 (1) 387 2021) reporting on tilting x- ray holography of magnetic bubbles in the same material, which is a technique making progress towards vector tomography. The authors should also consider the arXiv paper published by Nakajima "Two types of magnetic bubbles in MnNiGa observed via Lorentz microscopy" arXiv:2110.15507 (2021) and also S.L. Zuo et al., Nanoscale 10, 2260 (2018). + +I believe this manuscript is not worthy of publication in Nature Communications and should be rejected. The authors should in future take more care to adequately reference papers published by + +<--- Page Split ---> + +others in the field and to give suitable credit to them. The current manuscript certainly does contain novel and interesting results but is not worthy of publication in its present form. + +R: We totally refuse the comments from the referee. We are familiar with Loudon's paper in Advanced Materials (31 (16) 1806598 2019) which also cited the arXiv version of our previous paper (the published version is Applied Physics Letters, 114, 102404, 2019). Both his AM paper and our previous APL paper claimed that the biskyrmions should be interpreted as the Type II bubbles. We appreciate the experimental design of combining the X- ray holography and LTEM imaging techniques to illuminate the magnetic detail of Type I and Type II bubbles. They also found that the structure changes from Type I to Type II bubbles under applying external magnetic field. + +1. However, Loudon's work used X-ray to characterize the out-plane component (Bz) of the Type I bubbles but LTEM to observe the in-plane component (Bx-By) of the bubbles. Obviously, the combination of these two sets of data cannot confirm the chirality of individual bubble, whatever the Type I or Type II because the in-plane components of the moments are lost in X-ray experiments and the polarity of each bubble disappears in LTEM images. Although the polarity (Bz) may be confirmed in X-ray investigation, the actual chirality of bubbles in LTEM could not be directly determined from their swirling style of in-plane components unless they pre-specified the Bz direction of each bubble in LTEM (of cause they cannot), which is indicated clearly in fig. 1 of our submitted manuscript. Indeed based on Loudon's data, it is difficult to build the real 3D magnetic structure of bubbles and hard to claim that "demonstrated the internal structure of these objects" as referee said. Loudon et al employed micromagnetic simulation, a conventional method, to illustrate the 3D structure of the bubbles in their paper but it does not mean that they really observed the entire configurations in the 3D space. Compared with them, we did reconstruct the entire structure of bubbles in MnNiGa including the internal and surface moment orientation and this is exactly the novelty of our manuscript. We also indicated that based on the reconstructed 3D feature of the Bx or By component, the chirality of bubbles can be clarified qualitatively, which is another important contribution of our work. It seems like a natural anticipation from the simulation but cannot be revealed by Loudon's work or other literature listed by the referee. The referee's conclusion that Loudon et al have reconstructed the magnetic structure of the bubbles in MnNiGa is a misleading statement. + +2. The referee said that the fig. 4 in Loudon's AM paper displayed the helical reversal of the bubbles and he concluded Loudon et al also confirmed the chirality changes as our reported. But referee forgets that there was an external out-plane field of 233 mT applied on the sample! (First sentence in second-to-last paragraph, page 4 of Loudon's paper.) Based on this condition, one can suppose that the Bz of bubbles were fixed and the reversal of the in-plane components implied the change of the chirality. However, without this assumption + +<--- Page Split ---> + +or in a field free situation as described in our experiments, Bx- By changes could not infer whether the polarity varies simultaneously. If both vorticity (what can be seen in Loudon's work) and polarity (what cannot be seen in Loudon's work) change, the chirality maintains unchanged! Clearly, distinguishing what happens cannot be achieved by the traditional LTEM images in Loudon's paper or other's. The referee may skip the fig1 in our manuscript which demonstrates the importance of the real 3D exploration for spiral magnetic structures. We denoted this point and realized this discrimination in MnNiGa system for the more general case, which was impossible to be accomplished in Loudon's AM paper or other literature mentioned by the referee since the features in several tilted LTEM images cannot supply enough information to determine the detail of the magnetic structures. Actually, those papers did not show the conclusion that they really detected the chirality of studied bubbles at a field free condition. + +3. Turnbull's paper (ACS NANO 15 (1) 387 2021, from the same research group with Loudon) described the progress in detecting the Type I and Type II bubbles by X-ray holography and an approach using two projection images at different angles to judge the type of bubbles. However, the vorticity of the in-plane components cannot be explored because X-ray is only sensitive to the components parallel the propagating direction. Tilting the sample also impossibly supplies the rotation manner of the in-plane features. This method cannot even demonstrate the swirling style of the bubble, let along the chirality! The highlights of our work are to draw the 3D configuration of the magnetic bubbles and clarify their topological characteristics, but are not to prove the existence of type-I or type-II bubbles in MnNiGa alloy. The arXiv paper of Nakajima 2110.15507 (2021) found there may be two kinds of Type II bubbles in MnNiGa, characterized by LTEM images. Zuo's paper studied the so-called "biskyrminons" in MnNiGaY. Both of two literatures did not mention the 3D structure or the chirality of the magnetic bubbles. We cannot understand why the referee mentioned these literatures as the evidence to debase the novelty of our work. + +We respect Loudon's beautiful works and other related outstanding researches. Since we focused on the 3D structure recovery of the magnetic structure, their papers were not referenced in our manuscript. We can give more comparison with their reports in our work but cannot accept referee's misleading and biased comments. Some literature have been appended in the revised manuscript. Thus, we strongly appeal to editor to reconsider our modified manuscript. + +## Reviewer #2 (Remarks to the Author): + +Review of manuscript NCOMMS- 21- 41870 entitled „The dynamic chirality flips of Skyrmion bubbles“ by Yuan Yao, Bei Ding, Jinjing Liang, Hang Li, Xi Shen, Richeng Yu, Wenhong Wang + +<--- Page Split ---> + +Yuan Yao, Bei Ding and coworkers report on the tomographic 3D reconstruction of skyrmion bubbles in Mn- Ni- Ga from tilt series of Lorentz transmission electron micrographs. The goal of these investigations is to determine the 3D magnetic spin structure of different types of bubbles in terms of chirality, polarity and topology that is not possible from single L- TEM images. As a result, they found that bubbles switched their chirality (between reconstructions of two different Cartesian B- field components) but still keep the polarity to remain the singularity of the bubbles within the material. + +I find the approach very appealing and suited to be published in Nature Communications. However, the paper in its current stage lacks from numerous experimental uncertainties, logical and theoretical inconsistencies, and physical flaws and hence I can only recommend it for publication after a careful and major revision considering the points below. + +The major points of criticism which have to be addressed are the following: + +1. The magnetic states of the Skyrmion bubbles seem to be very unstable (metastable) at RT and therefore susceptible to be modified by small magnetic fields (compare e.g. in Fig.2a left and right column). The authors observe this problem by comparing the 3D induction maps of Bx and By (e.g. Fig.4 and Table 1). Since Bx and By belong only to the same magnetic state in bubble #2 only, they could only be combined in this case to obtain the full 3D vector-field by solving \(\mathrm{divB = 0}\) . Could it be that the residual magnetic field of the Lorentz lens (how large?) has changed the magnetic states of the bubbles when the sample was retracted and inserted in the TEM for in-plane rotation? Even worse, did the authors has detected some changes within tilt series acquisition, i.e. when going to higher tilt angles due to the changed orientation of the residual field with respect to the specimen? To avoid this unintended flipping of the magnetic states, it would have been more favorable to cool the sample during acquisition or to use an in-plane rotation holder. + +R: The residual magnetic field in LTEM JEOL 2100F- LM is below 10 Oe since it is a special designed instrument for the magnetic object characterization. So the residual field should not be a reasonable influence to the observed feature changes of the bubbles. The appearance of the bubbles varied little during the sample tilting, which has been testified by the images before and after tilting (fig. s14 in supplemental information or fig. r1 here). Indeed, the reconstruction of each Bx or By may include the tolerance of these possible distortion and strictly speaking the results were semi- quantitative to illuminate the moments behavior within the bubbles. We also avoid the quantificational description for the magnetic moment because of the regularization + +<--- Page Split ---> + +parameter, the missing- wedge effect and the uncertain in Bz calculation. Fortunately, these semi- quantitative features containing some details can supply enough information to investigate the type or the chirality of the bubbles. Unfortunately, the features of some bubbles changed obviously when sample rotated 90 degrees for acquisition in another tilting axis. The environment changes during operation MAY be considered but we have to say that the exact reason is not clear right now. One confirmation is that the configuration of the bubbles in MnNiGa is not stable. Cooling down the sample is a good suggestion to avoid some unknown effects but the tomography experiment needs a high- tilting holder, which excludes the possibility of the cooling holders in present study. In- plane 90 degrees rotation holder is not a general available apparatus for the tomography exploration now, but it is a valuable direction to be developed. + +![](images/Figure_unknown_1.jpg) + +
Fig. rf The features of bubbles did not change during the x-tilt operation.
+ +2. The four magnetic states of the type I bubbles were computed by micromagnetic simulations as shown in Fig. 1. The Neel twisting at their surfaces leads to magnetic charges, i.e. a high contribution of H, but a low one of B. Since, L-TEM is only sensitive to B not M, it is worthwhile to know how the simulated B-field looks like especially at the surface. In this context, it is also interesting to know how extended in z-direction these Neel twists are and whether they can be resolved by VFET. + +R: Yes, the LTEM only detect the magnetic induction B, not the magnetization M or magnetic field strength H. Following the suggestion, we computed the induction B in 3D space from the type I magnetic bubble with R+ configuration and verify the similar Neel features existing in both surfaces of the bubble, as the surface features in M cylinder. Of cause the size of B cylinder is + +<--- Page Split ---> + +slightly larger than the M configuration and there are some differences resulted from the demagnetization in the simulation. These contents are added in the modified manuscript (fig. 3 and related discussion in manuscript, and fig. r2 here). + +![](images/Figure_unknown_2.jpg) + +
Fig. r2 The magnetic \(\mathbf{R}+\) configuration of \(2\#\) bubble. a Distribution of in-plane magnetizations in 3D feature of the \(\mathbf{R}+\) model. b In-plane induction components computed from \(\mathbf{R}+\) model. c In-plane induction components reconstructed from the tilted LTEM images simulated based on \(\mathbf{R}+\) model. d In-plane induction components recovered from the experimental data of \(2\#\) bubble. The box frames in a)-c) indicate the physical size of \(\mathbf{R}+\) model. Only the pixels with values larger than \(20\%\) of the maximum intensity are rendered in b)-d) to depress the artifacts from regularization parameter and missing-wedge effect.
+ +"Fig. 3a interprets the rendered orientation of in- plane magnetization components within simulated \(\mathbf{R}+\) model in three dimensions, demonstrating the surface convergent or divergent features, while Fig. 3b shows the calculated in- plane inductions. The induction field involving stray strength in Fig. 3b replicates the moment style of the \(\mathbf{R}+\) bubble. In order to testify the fidelity of the reconstruction, serial tilting LTEM images were simulated from \(\mathbf{R}+\) model with same experimental conditions to rebuild the induction shape with those processing parameters for experimental task. The product in Fig. 3c demonstrates the reliable recovery of the \(\mathbf{R}+\) bubble but bears some artifacts from the TIE parameters and missing- wedge effect (the weak extension along z direction owing to the limited tilting range in data acquisition). Fig. 3d outlines the in- plane induction retrieved for \(2\#\) bubble, which appears similar contour in Fig. 3c and confirms the \(\mathbf{R}+\) type." + +<--- Page Split ---> + +3. The experimental tilt range is quite low: ca. \(+55^{\circ}\) instead of \(+90^{\circ}\) . Therefore the tomograms suffer from a large missing wedge, not discussed in the manuscript at all. I suppose, one problem is the slab geometry of the (FIB?) lamella, which is disadvantageous at high tilts, when new object information appears in the field-of-view and the projected thickness becomes thicker and thicker. How the authors tackled this issue especially when using a SIRT algorithm for reconstruction, where the reconstructed volume must be limited? Why the authors have not tried to prepare a needle-shaped sample much more suitable for tomography? + +R: Yes, the limited tilting range is the intrinsic shortage of present tomography in TEM. Frankly speaking, the missing- wedge is the problem difficult to be solved in TEM tomography because of the narrow space between the pole pieces. FIB prepared needle is more suitable for scalar field tomography since it can be tilted along the long axis of the cylinder to increase the tilt range. But for vector field reconstruction, the sample should be tilted along the short axis for second component reconstruction and eventually the tilt angle is also limited by its cylinder shape. At last the available common range for two tilting axes is not as large as expected. A wider region can be investigated in \(\mathrm{Ar + }\) ion milling sample (not FIB prepared sample) used in our experiment, which favors the discovery of the bubbles. The prolonged features along z- axis are observed in our reconstructed 3D features of Bx or By component. It deteriorates the resolution in z direction and carried out worse spatial resolution for Bz component. We depressed the data below \(20\%\) of maximum value of the corresponding components in our work to remove the missing- wedge effect. Although it is not a good choice for accuracy, it is an effective approach to remove the attenuate extension part and to recognize the contour of magnetic microstructure. Both simulations and practices verified the validation of this method. Conquering this difficulty needs more technical improvement in data acquisition or data processing but it is out the scope of present work. We add some discussions about this issue in the modified manuscript and emphasize that the retrieved moment figuration is a semi- quantitative result in order to avoid misleading the readers. It should be denoted that the relative strength of B vector, although less spatial resolution and data accuracy, could believably depict the chirality of the bubbles. They are contained in the modified version. + +4. To judge the fidelity of the tomograms, it is also important to know how the applied focus of \(300 \mu \mathrm{m}\) determines the lateral resolution of the L-TEM images described by the spatial envelope. Also the regularization (not regularity as written in the paper) parameter \(q0\) (line 272) determines on a certain way the fidelity of the 3D data. In best case, the authors should check by a simulated tilt series using same parameters (tilt range, defocus, \(q0\) ), whether the tomogram reveals the original magnetic structure? + +<--- Page Split ---> + +R: The lateral spatial resolution of the LTEM under large defocus (such as \(300 \mu \mathrm{m}\) ) is about \(5 \mathrm{~nm}\) , a coarse estimation. We try to use the simulated images with different tilting to reconstruct the entire virtue bubble to testify the validation of the method and parameters. We also tilted the simulated B configuration (R+) from \(- 50^{\circ}\) to \(50^{\circ}\) with \(2^{\circ}\) internal along tow orthogonal axes, generated the Fresnel images at each angle, retrieve each phase image with regularization parameter \(\mathrm{q}_{0} = 5 \times 10^{- 3} \mathrm{~nm}^{- 1}\) and reconstructed the entire induction matrix, as same as the experimental pipeline. Fig. s5 in supplemental information or fig. r3 here displays some simulated Fresnel images for different angles. The virtual operation demonstrated the parameters in experiment can ensure the recovery of the magnetic induction, while \(\mathrm{q}_{0} = 5 \times 10^{- 3} \mathrm{~nm}^{- 1}\) may enhance the extra artificial structure in the simulated structure than in the experimental data because of the low noise in the simulated images. This information has been appended in the revised manuscript. + +![](images/Figure_unknown_3.jpg) + +
Fig. r3 The simulated LTEM images for a \(\mathrm{R}+\) skyrmion. a) and b) under-focus and over-focus without tilting; c) and d) under-focus and over-focus with tilting \(-30^{\circ}\) around x axis.
+ +5. With respect to the resolution limitations mentioned in points 3 and 4, the observation of a very localized Bloch line in Figs. 3c,d is really questionable. The authors should check the reliability of this feature. + +R: We understand the concern from the reviewer. The approximate location of the Bloch line could be estimated by the orientation change of the inductions although the resolution is not perfect for present results. We removed that statement in the manuscript to avoid the confusing presentation. + +<--- Page Split ---> + +6. Why the authors do not provide the reconstructed 3D B-fields in Tesla. E.g., in Fig.4 the values range from \(+ - 10^{6}\) (A/m?). They must not be denoted Mx and My, because these are B-fields. + +R: Actually, the initial motivation of this study is to obtain the qualitative field of the bubble. But we found that the TIE method employed here can unavoidably distort the absolute value of the retrieved field because of the regularization parameter \(q_{0}\) though the relative value may be credible. Therefore, we abandoned to evaluate the real value of B or M. The used calculated value at each pixel from the reconstruction algorithm is to illustrate the relative changes of B components. It is correct true that the LTEM investigates the B-field, not M. We have modified the figures and added more pictures about the computed B field and recovered B field retrieved from the simulated tilting images. Please see Fig. 3 and related discussion in manuscript, or fig. r2 here. + +## Minor comments + +1. Can the authors give more information/data about the experiment and data treatment (at least in the Suppl. Mat.), such as + +- TEM lamella preparation (by FIB?) + +R: The Ar+ ion milling process was added in the Method section. + +- Field cooling procedure + +R: The specific FC manipulation was performed in the Physical Property Measurement System (PPMS). The sample was fixed in the puck and put into the cavity. It was heated to \(380\mathrm{K}\) , which is higher than the Curie temperature ( \(\mathrm{T_{C} \sim 345K}\) ). Then a small magnetic field of \(500\mathrm{Oe}\) was applied and the sample was cooled gradually to \(300\mathrm{K}\) at which the field turned off. It was added in Method section. + +- Lorentz TEM tilt series (to be shown in supplement?) + +R: The some images in the experimental tilting series were shown in the supplement file. + +- TIE reconstruction (influence of regularization) + +R: The affect from the regularization \(q_{0}\) on retrieved phase images are shown in supplement for the experiment data. + +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
Fig. r4 The in-plane components of induction retrieved with a) \(\mathrm{q_0 = 5\times 10^{-3}nm^{-1}}\) and b) \(\mathrm{q_0 = 7.5\times 10^{-3}}\) \(\mathrm{nm^{-1}}\) , respectively.
+ +- phase tilt series (to be shown in supplement?) + +R: Due to limitations on space, some phase images from the tilting phase series are shown in Fig. s9 and s10 in supplement. We add the movie files of the phase stacks. + +- Image alignment (line 275) + +R: The phase images, such as for x-tilting, were formed to one stack file and aligned with the "Image Alignment" function in Gatan Microscopy Suite (GMS). A "bandpass filter" with default mode was employed to "automatic" register the images, followed by forward and backward corrections. After alignment, all phase images were merged into one image and that image were transformed to Fourier space. The prolonging diffuse background of the auto-correlation region (center part) in diffractogram indicated the tilt axis orientation, as shown in fig. r5. After the ailment, all phase images were rotated to make the tilting axis vertical or horizontal to the image boundary, facilitating the followed calculation of Bx or By components. It is denoted in the manuscript and some details are demonstrated in supplement. + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Fig. r5 Diffractogram of the merged phase image, where the dash denotes the orientation of tilt axis.
+ +- W-SIRT parameters (influence of regularization) + +R: The parameter in GUI of reconstruction plugin is added in the supplements. We think the referee wants to check whether different \(\mathrm{q}_0\) can make a significant change in the reconstructed 3D features. We added the investigation for reconstruction of the \(\mathrm{R + }\) model skyrmion in supplement to show this influence. + +## 2. Mathematics: + +Could the authors more clearly describe the mathematics of TIE? + +- As shown by Lubk et al. (PRL 111, 173902 (2013)) Eq. 1 is only valid, if a) the object is a pure phase object, or b) the current density is conservative. What is valid here? + +- What is the meaning of symbol \(\overline{V_{x,y}^2}\) ? Isn't it the inversion of Laplacian, \(1 / \mathrm{q}^2\) in Fourier space to be inserted in line 271 on the LHS instead \(\overline{V_{x,y}^2}\) ? + +- Inconsistencies of notation, in Eq. (1) reciprocal vector is \(\mathrm{q}\) , whereas in Eq. (2) reciprocal vector is \(\mathrm{k}\) + +R: The principle of TIE is added in Supplement file. TIE is used to recover the phase of a wave, exactly the wave exiting the object in TEM experiments. Interpreting the physical meaning of the phase is not the responsibility of TIE, so actually it needn't any assumption for the wave characteristics. Eq. 1 only requires a conservation of Poynting current, described by the original Paganin's paper (D. Paganin and K. A. Nugent, Noninterferometric Phase Imaging with Partially Coherent Light, Phys. Rev. Lett., 80, 2586, 1998). Because the scattering ability of the specimen + +<--- Page Split ---> + +is very weak so most features in images satisfy the conservation except the image boundaries which is out the interesting range in our studies. Eq. 1 is valid for most parts of the processed images. Lubk's paper proposed a method to deal with the vortex beam containing the phase singularity. The phase of the electron beam exiting the skyrmions does not have such singular portion - although the in-plane magnetic inductions show the singular point in bubble center the phase of exit wave is continue. Pure phase object assumption that was cited by Lubk is another literature (T. E. Gureyev and S.W. Wilkins, J. Opt. Soc. Am. A, 15, 579, 1998). Gureyev et al just used the phase contrast concept to introduce the image mode but not as the premise of deduction. In principle, the differential operation and the normalization by \(\mathrm{I}(z = z0)\) in Eq. 1 remove the influence from the amplitude of the wave since the intensity of in- focus image presents the amplitude of the wave. Therefore Eq. 1 can give the proper phase solution. + +\(\overline{V_{x,y}^{2,2}}\) is the inverse Laplacian operator, and it can be substituted by \(- 1 / \mathrm{q}^2\) in Fourier transform. Allen's paper gave a deduction about this point. (Eq. 8- 10 in "L. J. Allen, M. P. Oxley, Phase retrieval from series of images obtained by defocus variation. Opt. Commu., 199, 65- 75, 2001 ") The errors and inconsistence about \(\mathrm{q}\) and \(\mathrm{k}\) have been corrected. + +3. English writing and wording. + +- there are numerous typos and sometimes inadequate choice of words, e.g. line 20: "magnetic moment" is misleading here, line 40 "need", line 48 "turns into" not appropriate in this context, line 64 "charity", line 116 "configuraiton", line 232, 238 "configure", line 263 "3D structure reconstruction" not the right term The text needs very much polishing in general. + +R: We carefully modified the manuscript and tried our best to correct the typo and grammar errors. + +4. Fig.1b: Why there is a threshold in the simulated induction maps (black mask)? + +R: The color maps in Fig. 1b is the TIE retrieved induction maps which are influenced by the regularization parameter \(\mathrm{q}_0\) . Thus a threshold, \(5\%\) of the maximum induction, is used to get rid of that effect. + +5. Line 273: Please provide the value of \(\mathrm{q0}\) in "1/nm" not pixels. + +R: It was changed to \(5 \times 10^{- 3} \mathrm{~nm}^{- 1}\) . + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +This is a much improved manuscript that now makes clear what has been done by the authors and by others in the past, and what is new. The major novelty of the paper is the three dimensional reconstruction of the magnetic induction. The authors have utilised the method of Wolf (reference 30) which first demonstrated how to accomplish the 3D magnetic texture of a Bloch skyrmion in FeGe using holographic vector tomography. That means that the authors can measure not just the vorticity of the skyrmion bubble but also its polarity and hence the chirality. This means that when a magnetic bubble switches its circular direction, they can say whether its chirality also changes. This is a degree of freedom which is not available to a skyrmion and its chirality is fixed by the Dzyaloshinskii- Moriya interaction and the orientation of the applied magnetic field. + +The editor should decide whether this observed chirality switch in a skyrmion bubble in centrosymmetric MnNiGa is of sufficiently wide interest to a journal such as Nature Communications, or is more suited to a more specialist condensed matter or magnetism journal. + +The few remaining comments about the revised manuscript are: + +Fig 1a Why does the magnetization go to zero at a given radius? Are they magnetic disks? What model was used to generate the skyrmions? Fig 1b Why was the contrast below \(5\%\) of maximum magnitude masked in the magnetization mapping to filter the artifacts induced by the regularisation parameter in TIE? Fig 4 There is a confusion of B and M between the figures and the caption. + +Reviewer #2: + +Remarks to the Author: + +First of all, I appreciate that the authors have addressed all of my concerns and in general I am satisfied with their detailed reply and corresponding modifications of the main text. I do not doubt that the major findings namely the identification of the chirality and polarity of the type I bubble as well as the discrimination to the type II bubble is possible by inspecting the upper and lower surface of one component of the magnetic induction reconstructed by tomography. I also do not doubt the 3D reconstruction of the in- plane vector- field of one bubble (#2), one of the few which seemed to be stable for both tilt series. + +However, by reading the revised text I identified remaining problems (in particular with respect to the papers' impact for the community): + +1. The reason for the dynamic chirality flips (content of title!) is not resolved, because they were unintended. Maybe one reason could be a small in-plane field. This must be investigated further. For example, the authors mention in the last sentence of the abstract: "Our results offer valuable insights into the fundamental dynamics to understand the chirality behavior of skyrmion bubbles". But I miss exactly this understanding although it is extensive observation. Maybe also a micromagnetic simulation and corresponding energies could give more insight. + +2. A way how to use the chirality (switching) information (e.g., as read-out for memory devices) and make it useful for technological applications is not discussed. As the authors mentioned the polarity (which could be easily read out) was not changed. + +3. The central theme through the entire manuscript is not consistent. The title promises to study the reason for the chirality flips but it is not done. The abstract promises the 3D vector-field reconstruction of magnetic induction, i.e., all three components of all bubbles but in fact only two components of one bubble or one component of the other bubbles with two different states are presented. + +4. Still the writing (wording) and presentation has serious flaws. In the following I mention only a few examples, but there are much more: + +- the term Skyrmion bubble in general is questionable- sentence line 20: "The induction configuration of the bubbles was determined from investigating + +<--- Page Split ---> + +the magnetic vectors in entire space." contains strange combinations: "induction configuration" should be either "magnetic configuration" or "magnetic induction" One suggestion: "The magnetic configuration of the bubbles was determined from the reconstructed magnetic induction (B- field) at their surfaces and their center." - in Fig. 2 tilt axes should be indicated - line 134 Bx matrix wrong term better Bx array, By array - in Fig. 3 sub panel label must be in the upper corner - line 153 "serial tilting" wrong term, just say tilt series - line 157 "extension" must read: elongation (see for example Midgley and Weyland, Ultramicroscopy 96 (2003) 413, https://doi.org/10.1016/S0304- 3991(03)00105- 0 - line 165 "out- plane" must be out- of plane - line 168 "thickness measurement error" minor comment regarding content: thickness measurement should not influence the tomographic reconstruction - in Fig. 4: What is shown in a and b upper left panel labeled with Mx, My - line 219: "That is to say, they cannot reveal the dynamic behavior of the bubbles in a field free condition." Bad English - line 221 "be against" should be "anti- parallel" - line 236 "always fabricated by focus ion beam (FIB)" not always, self- grown NWs are also possible - line 240: "is tilted around its short axis." One way out is to orient the needle- axis \(+ - 45^{\circ}\) to the tilt axis. (e.g. see Wolf et al., Commun. Phys. 2 (2019) 87 https://doi.org/10.1038/s42005- 019- 0187- 8 ) - line 242 "prolongs" better "elongates" - lines 311,313, 314 "mappings" must read in these contexts "maps" - actually the whole sentence from lines 311- 315 is very badly written. There are much more issues like these, also in the supplement. + +In its current form I still cannot recommend the paper to be published in Nature Communications. In my opinion, it needs a second major revision. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +This is a much improved manuscript that now makes clear what has been done by the authors and by others in the past, and what is new. The major novelty of the paper is the three dimensional reconstruction of the magnetic induction. The authors have utilised the method of Wolf (reference 30) which first demonstrated how to accomplish the 3D magnetic texture of a Bloch skyrmion in FeGe using holographic vector tomography. That means that the authors can measure not just the vorticity of the skyrmion bubble but also its polarity and hence the chirality. This means that when a magnetic bubble switches its circular direction, they can say whether its chirality also changes. This is a degree of freedom which is not available to a skyrmion and its chirality is fixed by the Dzyaloshinskii- Moriya interaction and the orientation of the applied magnetic field. + +The editor should decide whether this observed chirality switch in a skyrmion bubble in centrosymmetric MnNiGa is of sufficiently wide interest to a journal such as Nature Communications, or is more suited to a more specialist condensed matter or magnetism journal. + +R: We sincerely thank the referee for carefully reading our manuscript and noting that the major novelty of our paper is the three- dimensional reconstruction of the magnetic induction. Following the referee's comments and suggestions, we carried out additional experiments and analyses. Moreover, we carefully and thoroughly revised the language in the manuscript. Below, we address the referee's comments and questions on a point- by- point basis. We hope the referee is satisfied with the revised manuscript and our response. + +Fig 1a Why does the magnetization go to zero at a given radius? Are they magnetic disks? + +R: Yes, we use a disk model to simulate the magnetic features of the bubbles. In general, DDI skyrmions can be stabilized by a sixfold symmetric array. To simplify the simulation, a single bubble was generated by the OOMMF code with a disk- shaped boundary. + +Fig 1b Why was the contrast below \(5\%\) of maximum magnitude masked in the magnetization mapping to filter the artifacts induced by the regularisation parameter in + +<--- Page Split ---> + +TIE? + +R: In the TIE method, the regularization parameter \(q_{0}\) is used to replace \(\frac{- 1}{|q|^{2}}\) with \(\frac{- |q|^{2}}{(|q|^{2} + q_{0}^{2})^{2}}\) to prevent the divergence of \(\mathcal{F}^{- 1}\left\{\frac{-\mathcal{F}[.]}{|q|^{2}}\right\}\) ; however, this parameter suppresses the low- frequency part of the original data. For example, if \(q_{0} = 2\) , the strength of information for \(q = 2\) may be 4 times smaller than the original value (1/4 vs. 1/16). However, for high- frequency information, such as \(q = 10\) , the influence is minimal (1/100 vs. 1/108.08). Thus, \(q_{0}\) exaggerates high- frequency information. As described in our previous papers [Cui, J. et al. Artifacts in magnetic spirals retrieved by transport of intensity equation (TIE). J. Magn. Magn. Mater. 454, 304- 313, (2018); Yao, Y et al. Magnetic hard nanobubble: A possible magnetization structure behind the bi- skyrmion. Appl. Phys. Lett. 114, 102404, (2019)], this distortion can lead to some artifacts in the results. Considering the noise in the experimental data, this distortion may also cause high- frequency noise. Therefore, a contrast threshold of \(5\%\) was employed to address this disturbance with a proper \(q_{0}\) . + +Fig 4 There is a confusion of B and M between the figures and the caption. R: Thank you. This error has been corrected. + +Reviewer #2 (Remarks to the Author): + +First of all, I appreciate that the authors have addressed all of my concerns and in general I am satisfied with their detailed reply and corresponding modifications of the main text. I do not doubt that the major findings namely the identification of the chirality and polarity of the type I bubble as well as the discrimination to the type II bubble is possible by inspecting the upper and lower surface of one component of the magnetic induction reconstructed by tomography. I also do not doubt the 3D reconstruction of the in- plane vector- field of one bubble (#2), one of the few which seemed to be stable for both tilt series. + +R: We thank the reviewer for his previous comments, which helped us to improve the presentation of the manuscript. + +However, by reading the revised text I identified remaining problems (in particular with respect to the papers' impact for the community): + +1. The reason for the dynamic chirality flips (content of title!) is not resolved, because they were unintended. Maybe one reason could be a small in-plane field. This must be investigated further. For example, the authors mention in the last sentence of the + +<--- Page Split ---> + +abstract: "Our results offer valuable insights into the fundamental dynamics to understand the chirality behavior of skyrmion bubbles". But I miss exactly this understanding although it is extensive observation. Maybe also a micromagnetic simulation and corresponding energies could give more insight. + +R: Thank you for your helpful comments. As we mentioned in the manuscript, the field- free bubbles, which were obtained via the field cooling method, are in metastable states and can thus be manipulated by external stimulation. In practice, the electron beam can flip the bubbles during the initial observation; however, the bubbles were gradually stabilized after a shower period. We selected a region containing stable bubbles to acquire our data. During the data acquisition process, the investigated bubbles maintained their features, as shown in the SI. However, when the sample was removed from the LTEM for the 90- degree rotation for the next acquisition, the new beam illumination may change the configuration of some bubbles in the observation area. We assessed the influence of the electron beam the in SI to elucidate this effect. We believe that the electron beam may induce a local temperature increase that may be responsible for this dynamic flipping; this result was also verified in the temperature control experiment. The sample was initially balanced during the first characterization; however, when the sample was removed from the TEM and rotated for the next observation, a new balance must be established during the second beam irradiation, as some bubbles may have different configurations. Unfortunately, because we lack additional evidence to explain the detailed process, we modified the title of the manuscript to "Chirality flips of skyrmion bubbles" to prevent confusion. + +2. A way how to use the chirality (switching) information (e.g., as read-out for memory devices) and make it useful for technological applications is not discussed. As the authors mentioned the polarity (which could be easily read out) was not changed. + +R: We thank the referee for raising this interesting question. To date, the key operation of skyrmion racetrack memory is to assist the DMI skyrmion in reading/writing with electrical currents. Inspired by this method, we propose a new mechanism that uses the spin transfer torque technique to select different chiral DDI bubbles. A constant current carries bubbles with uniform chirality and polarity passing through an electron beam, and the beam can only determine whether the chirality of individual bubbles is flipped and does not change the orientation of the polarity. Then, the bubbles enter different branches due to the Magnus effect. The sensors in each branch detect only the existence of the bubbles (whatever their polarity) when recording the information state. The electron beam can easily be shrunk to tens of nanometers to manipulate individual DDI bubbles rather than changing the entire spin configuration of DMI skyrmions. + +<--- Page Split ---> +![PLACEHOLDER_21_0] + + +3. The central theme through the entire manuscript is not consistent. The title promises to study the reason for the chirality flips but it is not done. The abstract promises the 3D vector-field reconstruction of magnetic induction, i.e., all three components of all bubbles but in fact only two components of one bubble or one component of the other bubbles with two different states are presented. + +R: We apologize for the confusion. We understand the concerns of the reviewer. We evaluated chirality flipping by analyzing the 3D magnetic feature of the bubbles. After careful analyses, we recognized that it was not necessary to know all information about the bubble components to distinguish the type of bubble. Therefore, we focused on evaluating the 3D spin configurations of the bubbles after their chirality flipped. To clarify this point, the title has been changed to "Chirality flips of skyrmion bubbles". In addition, we added new experimental data to provide a possible explanation for the flip; however, this topic should be studied further in future work. + +4. Still the writing (wording) and presentation has serious flaws. In the following I mention only a few examples, but there are much more: + +- the term Skyrmion bubble in general is questionable- sentence line 20: "The induction configuration of the bubbles was determined from investigating the magnetic vectors in entire space." contains strange combinations: "induction configuration" should be either "magnetic configuration" or "magnetic induction" + +One suggestion: "The magnetic configuration of the bubbles was determined from the reconstructed magnetic induction (B-field) at their surfaces and their center." + +- in Fig. 2 tilt axes should be indicated- line 134 Bx matrix wrong term better Bx array, By array- in Fig. 3 sub panel label must be in the upper corner- line 153 "serial tilting" wrong term, just say tilt series- line 157 "extension" must read: elongation (see for example Midgley and Weyland, Ultramicroscopy 96 (2003) 413, https://doi.org/10.1016/S0304- 3991(03)00105- 0 + +<--- Page Split ---> + +- line 165 "out-plane" must be out-of plane- line 168 "thickness measurement error" minor comment regarding content: thickness measurement should not influence the tomographic reconstruction- in Fig. 4: What is shown in a and b upper left panel labeled with Mx, My- line 219: "That is to say, they cannot reveal the dynamic behavior of the bubbles in a field free condition." Bad English- line 221 "be against" should be "anti-parallel"- line 236 "always fabricated by focus ion beam (FIB)" not always, self-grown NWs are also possible- line 240: "is tilted around its short axis." One way out is to orient the needle-axis \(+\) \(45^{\circ}\) to the tilt axis. (e.g. see Wolf et al., Commun. Phys. 2 (2019) 87 https://doi.org/10.1038/s42005-019-0187-8)- line 242 "prolongs" better "elongates"- lines 311,313, 314 "mappings" must read in these contexts "maps"- actually the whole sentence from lines 311-315 is very badly written. There are much more issues like these, also in the supplement. + +R: To address the language issues, the manuscript and the supporting information have been revised by one or more highly qualified native English-speaking editors at AJE. If the referee has additional sentences that they believe require revision, we would be happy to incorporate any suggestions. + +In its current form I still cannot recommend the paper to be published in Nature Communications. In my opinion, it needs a second major revision. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: + +I am now content with the paper to be published. The paper reports noteworthy results and hopefully will be a significant paper in the field. The authors have acted upon the comments from the referees and as a result the manuscript is much improved. + +Reviewer #2: + +Remarks to the Author: + +The authors have severely revised and improved the manuscript further. I have only a few remarks left: + +1. ) I find the proposed concept of race track memory using DDI skyrmions interesting (new Fig. 5 and corresponding text), but I cannot judge the validity of it, because this topic exceeds my expertise. + +2. ) There are still some minor issues: + +What are the units of the colorbar in Fig. 4? If the values are in A/m, then they are with \(\sim 4*10^{-6}\) too high, because they correspond to \(\sim 5\) Tesla! + +Line 287: "spin transfer torch" must read "spin- transfer torque" + +Line 358: I suggest to write: "Bx map was computed from the derivative of the phase in y direction." + +Line 363: q is the coordinate or variable or spatial frequency in Fourier space, not the grid. + +After especially my point 2) is addressed, I can recommend the paper for publication. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +I am now content with the paper to be published. The paper reports noteworthy results and hopefully will be a significant paper in the field. The authors have acted upon the comments from the referees and as a result the manuscript is much improved. + +R: Thank you for recommending our manuscript to be published in Nature Communications + +Reviewer #2 (Remarks to the Author): + +The authors have severely revised and improved the manuscript further. I have only a few remarks left: + +1. ) I find the proposed concept of race track memory using DDI skyrmions interesting (new Fig. 5 and corresponding text), but I cannot judge the validity of it, because this topic exceeds my expertise. + +R: We sincerely thank the referee for careful reading of our manuscript, and for pointing out that race track memory using DDI skyrmions are intriguing. In fact, the race track memory using DMI skyrmions are extendedly studied by the theoretical and experimental group [Zhou Y, Ezawa M. A reversible conversion between a skyrmion and a domain-wall pair in a junction geometry. Nature communications, 2014, 5(1): 1- 8; Zhang X, Ezawa M, Zhou Y. Magnetic skyrmion logic gates: conversion, duplication and merging of skyrmions. Scientific reports, 2015, 5(1): 1- 8. ], but it's rare for the DDI skyrmions. We hope our work might evoke more theoretical studies on the race track memory using DDI skyrmions and may also lead to the realization of skyrmion- based spintronic devices. + +2. ) There are still some minor issues: What are the units of the colorbar in Fig. 4? If the values are in A/m, then they are with + +<--- Page Split ---> + +\(\sim 4*10^{6}\) too high, because they correspond to \(\sim 5\) Tesla! + +R: The resolution of Fig. 4 in the PDF file is not good. The order of the value is \(10^{\wedge}(- 6)\) , not \(10^{\wedge}6\) which represents the relative strength of magnetic induction deduced from the phase differential, but not the absolute value of the induction. However, in the revised manuscript, it has been changed to the absolute induction now. And the corresponding calculated magnetization is about \(7\times 10^{5}\mathrm{A / m}\) , which agrees well with the measured value of \(8\times 10^{5}\mathrm{A / m}\) [Bei Ding et al, Manipulating Spin Chirality of Magnetic Skyrmion Bubbles by In- Plane Reversed Magnetic Fields in (Mn1- xNix)65Ga35 (x =0.45) Magnet, Physical Review Applied, vol. 12, 054060 (2019)]. + +![PLACEHOLDER_25_0] + +
Fig. 4 The magnetic spin transition of bubble #5. The \(\mathrm{B}_{\mathrm{x}}\) (a) and \(\mathrm{B}_{\mathrm{y}}\) (b) features in the top, middle and bottom x-y sections. The solid arrows indicate the direction of the corresponding component, while the dashed arrows indicate the speculative direction of the orthogonal component based on prior knowledge of Bloch skyrmion bubbles. The color legend indicates the magnitude of induction components in x or y direction, which corresponds the magnetization between \(-6.5\times 10^{5}\sim 7\times 10^{5}\mathrm{A / m}\) and well agrees with the measured value of \(8\times 10^{5}\mathrm{A / m}\) .42
+ +Line 287: "spin transfer torch" must read "spin- transfer torque" + +<--- Page Split ---> + +Line 358: I suggest to write: "Bx map was computed from the derivative of the phase in y direction." + +Line 363: q is the coordinate or variable or spatial frequency in Fourier space, not the grid. + +After especially my point 2) is addressed, I can recommend the paper for publication. + +R: We sincerely thank the referee for recommending our manuscript to be published in Nature Communications. In the revised version, we have modified above issues. + +<--- Page Split ---> diff --git a/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..44b335315a7c91c86b386c9e5405cff77f9e3e0d --- /dev/null +++ b/peer_reviews/557334dc3f69418a2739ccee8b566bdde24767da828a685039f007fbe132eebc/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,556 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 505, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 537, 180]]<|/det|> +Chirality flips of skyrmion bubbles + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 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To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 293, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 113, 300, 140]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 141, 870, 268]]<|/det|> +This manuscript reports on dynamic chirality flips of skyrmion bubbles found in a thin plate cut from a bulk sample of (Mn(1- x)Nix)65Ga35 (x = 0.45). Magnetic skyrmions have been found in chiral non- centrosymmetric crystals such as MnSi, FeGe, Cu2OSeO3, CoZnMn, GaV4S8 etc. MnNiGa is centrosymmetric and hence cannot host conventional magnetic skyrmions. The authors have undertaken Lorentz transmission electron microscopy studies to investigate the structure of the magnetic objects found in MnNiGa. Using vector field tomography they have demonstrated that the objects are in fact skyrmion bubbles. They also demonstrate that these skyrmion bubbles can be observed to flip their chirality and transform their vorticity whilst retaining their positive polarity. + +<|ref|>text<|/ref|><|det|>[[118, 280, 874, 434]]<|/det|> +Unfortunately, nearly all of the conclusions they report in this paper have been reported, and published, before, and in papers not referenced by the authors. Loudon et al (Advanced Materials 31 (16) 1806598 2019) have previously reported a very similar study using Lorentz TEM on the same material and found both type I and type II bubbles and that the previously reported biskyrmions were in fact type II bubbles. They also demonstrated the internal structure of these objects using both x- ray holography and Lorentz TEM. Micromagnetic simulations and quantitative transport of intensity equation were used to determine the magnetisation of the objects. Figure 4 of their paper also shows the transformation, chirality flips, of individual bubbles in MnNiGa. I note that Loudon et al include a reference in their paper to an arXiv paper published by Y. Yao et al and including four of the manuscript authors. I am surprised that the authors of this manuscript have not found it worthwhile referencing the paper by Loudon et al. + +<|ref|>text<|/ref|><|det|>[[118, 447, 860, 589]]<|/det|> +This manuscript would be greatly improved by the authors referencing previous relevant studies and restricting their manuscript to the novel aspects which have not been published. The use of vector field tomography via LTEM is a wonderful demonstration and does have advantages over the earlier study by Loudon. However, the authors are not able to explain these advantages without referencing the earlier studies. I also note a later paper published by Turnbull et al (ACS NANO 15 (1) 387 2021) reporting on tilting x- ray holography of magnetic bubbles in the same material, which is a technique making progress towards vector tomography. The authors should also consider the arXiv paper published by Nakajima "Two types of magnetic bubbles in MnNiGa observed via Lorentz microscopy" arXiv:2110.15507 (2021) and also S.L. Zuo et al., Nanoscale 10, 2260 (2018). + +<|ref|>text<|/ref|><|det|>[[118, 602, 875, 658]]<|/det|> +I believe this manuscript is not worthy of publication in Nature Communications and should be rejected. The authors should in future take more care to adequately reference papers published by others in the field and to give suitable credit to them. The current manuscript certainly does contain novel and interesting results but is not worthy of publication in its present form. + +<|ref|>text<|/ref|><|det|>[[118, 700, 830, 757]]<|/det|> +Reviewer #2: Remarks to the Author: Review of manuscript NCOMMS- 21- 41870 entitled „The dynamic chirality flips of Skyrmion bubbles“ by Yuan Yao, Bei Ding, Jinjing Liang, Hang Li, Xi Shen, Richeng Yu, Wenhong Wang + +<|ref|>text<|/ref|><|det|>[[118, 770, 877, 868]]<|/det|> +Yuan Yao, Bei Ding and coworkers report on the tomographic 3D reconstruction of skyrmion bubbles in Mn- Ni- Ga from tilt series of Lorentz transmission electron micrographs. The goal of these investigations is to determine the 3D magnetic spin structure of different types of bubbles in terms of chirality, polarity and topology that is not possible from single L- TEM images. As a result, they found that bubbles switched their chirality (between reconstructions of two different Cartesian B- field components) but still keep the polarity to remain the singularity of the bubbles within the material. + +<|ref|>text<|/ref|><|det|>[[118, 882, 855, 910]]<|/det|> +I find the approach very appealing and suited to be published in Nature Communications. However, the paper in its current stage lacks from numerous experimental uncertainties, logical + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 805, 112]]<|/det|> +and theoretical inconsistencies, and physical flaws and hence I can only recommend it for publication after a careful and major revision considering the points below. + +<|ref|>text<|/ref|><|det|>[[120, 125, 694, 140]]<|/det|> +The major points of criticism which have to be addressed are the following: + +<|ref|>text<|/ref|><|det|>[[117, 153, 877, 320]]<|/det|> +1. The magnetic states of the Skyrmion bubbles seem to be very unstable (metastable) at RT and therefore susceptible to be modified by small magnetic fields (compare e.g. in Fig.2a left and right column). The authors observe this problem by comparing the 3D induction maps of Bx and By (e.g. Fig.4 and Table 1). Since Bx and By belong only to the same magnetic state in bubble #2 only, they could only be combined in this case to obtain the full 3D vector-field by solving \(\mathrm{divB} = 0\) . Could it be that the residual magnetic field of the Lorentz lens (how large?) has changed the magnetic states of the bubbles when the sample was retracted and inserted in the TEM in-plane rotation? Even worse, did the authors has detected some changes within tilt series acquisition, i.e. when going to higher tilt angles due to the changed orientation of the residual field with respect to the specimen? To avoid this unintended flipping of the magnetic states, it would have been more favorable to cool the sample during acquisition or to use an in-plane rotation holder. + +<|ref|>text<|/ref|><|det|>[[118, 321, 874, 405]]<|/det|> +2. The four magnetic states of the type I bubbles were computed by micromagnetic simulations as shown in Fig. 1. The Neel twisting at their surfaces leads to magnetic charges, i.e. a high contribution of H, but a low one of B. Since, L-TEM is only sensitive to B not M, it is worthwhile to know how the simulated B-field looks like especially at the surface. In this context, it is also interesting to know how extended in z-direction these Neel twists are and whether they can be resolved by VFET. + +<|ref|>text<|/ref|><|det|>[[118, 405, 875, 505]]<|/det|> +3. The experimental tilt range is quite low: ca. \(+55^{\circ}\) instead of \(+90^{\circ}\) . Therefore the tomograms suffer from a large missing wedge, not discussed in the manuscript at all. I suppose, one problem is the slab geometry of the (FIB?) lamella, which is disadvantageous at high tilts, when new object information appears in the field-of-view and the projected thickness becomes thicker and thicker. How the authors tackled this issue especially when using a SIRT algorithm for reconstruction, where the reconstructed volume must be limited? Why the authors have not tried to prepare a needle-shaped sample much more suitable for tomography? + +<|ref|>text<|/ref|><|det|>[[118, 505, 874, 589]]<|/det|> +4. To judge the fidelity of the tomograms, it is also important to know how the applied focus of \(300\mu m\) determines the lateral resolution of the L-TEM images described by the spatial envelope. Also the regularization (not regularity as written in the paper) parameter q0 (line 272) determines on a certain way the fidelity of the 3D data. In best case, the authors should check by a simulated tilt series using same parameters (tilt range, defocus, q0), whether the tomogram reveals the original magnetic structure? + +<|ref|>text<|/ref|><|det|>[[118, 589, 872, 630]]<|/det|> +5. With respect to the resolution limitations mentioned in points 3 and 4, the observation of a very localized Bloch line in Figs. 3c,d is really questionable. The authors should check the reliability of this feature. + +<|ref|>text<|/ref|><|det|>[[118, 630, 870, 671]]<|/det|> +6. Why the authors do not provide the reconstructed 3D B-fields in Tesla. E.g., in Fig.4 the values range from \(+ - 10^{\circ}6\) (A/m?). They must not be denoted Mx and My, because these are B-fields. Minor comments + +<|ref|>text<|/ref|><|det|>[[118, 671, 870, 699]]<|/det|> +1. Can the authors give more information/data about the experiment and data treatment (at least in the Suppl. Mat.), such as + +<|ref|>text<|/ref|><|det|>[[118, 700, 544, 800]]<|/det|> +- TEM lamella preparation (by FIB?) +- Field cooling procedure +- Lorentz TEM tilt series (to be shown in supplement?) +- TIE reconstruction (influence of regularization) +- phase tilt series (to be shown in supplement?) +- Image alignment (line 275) +- W-SIRT parameters (influence of regularization) + +<|ref|>text<|/ref|><|det|>[[118, 800, 244, 812]]<|/det|> +2. Mathematics: + +<|ref|>text<|/ref|><|det|>[[118, 813, 867, 910]]<|/det|> +Could the authors more clearly describe the mathematics of TIE? - As shown by Lubk et al. (PRL 111, 173902 (2013)) Eq. 1 is only valid, if a) the object is a pure phase object, or b) the current density is conservative. What is valid here? - What is the meaning of symbol \(\nabla < \mathrm{sup} > - 2< /\mathrm{sup} > ?\) Isn't it the inversion of Laplacian, \(1 / \mathrm{q} < \mathrm{sup} > 2< /\mathrm{sup} >\) in Fourier space to be inserted in line 271 on the LHS instead \(\nabla \mathrm{xy}\) ? - Inconsistencies of notation, in Eq. (1) reciprocal vector is q, whereas in Eq. (2) reciprocal vector is k + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 355, 98]]<|/det|> +3. English writing and wording. + +<|ref|>text<|/ref|><|det|>[[117, 99, 876, 194]]<|/det|> +- there are numerous typos and sometimes inadequate choice of words, e.g. line 20: "magnetic moment" is misleading here, line 40 "need", line 48 "turns into" not appropriate in this context, line 64 "charity", line 116 "configuraton", line 232, 238 "configure", line 263 "3D structure reconstruction" not the right term The text needs very much polishing in general. 4. Fig.1b: Why there is a threshold in the simulated induction maps (black mask)? 5. Line 273: Please provide the value of q0 in "1/nm" not pixels. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 88, 425, 103]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 129, 852, 316]]<|/det|> +This manuscript reports on dynamic chirality flips of skyrmion bubbles found in a thin plate cut from a bulk sample of \((\mathrm{Mn}(1 - x)\mathrm{Nix})65\mathrm{Ga}35\) \(\mathrm{(x = 0.45)}\) . Magnetic skyrmions have been found in chiral non- centrosymmetric crystals such as MnSi, FeGe, \(\mathrm{Cu2OSeO3}\) , \(\mathrm{CoZnMn}\) , GaV4S8 etc. MnNiGa is centrosymmetric and hence cannot host conventional magnetic skyrmions. The authors have undertaken Lorentz transmission electron microscopy studies to investigate the structure of the magnetic objects found in MnNiGa. Using vector field tomography they have demonstrated that the objects are in fact skyrmion bubbles. They also demonstrate that these skyrmion bubbles can be observed to flip their chirality and transform their vorticity whilst retaining their positive polarity. + +<|ref|>text<|/ref|><|det|>[[147, 342, 852, 592]]<|/det|> +Unfortunately, nearly all of the conclusions they report in this paper have been reported, and published, before, and in papers not referenced by the authors. Loudon et al (Advanced Materials 31 (16) 1806598 2019) have previously reported a very similar study using Lorentz TEM on the same material and found both type I and type II bubbles and that the previously reported biskyrmions were in fact type II bubbles. They also demonstrated the internal structure of these objects using both x- ray holography and Lorentz TEM. Micromagnetic simulations and quantitative transport of intensity equation were used to determine the magnetisation of the objects. Figure 4 of their paper also shows the transformation, chirality flips, of individual bubbles in MnNiGa. I note that Loudon et al include a reference in their paper to an arXiv paper published by Y. Yao et al and including four of the manuscript authors. I am surprised that the authors of this manuscript have not found it worthwhile referencing the paper by Loudon et al. + +<|ref|>text<|/ref|><|det|>[[147, 618, 852, 826]]<|/det|> +This manuscript would be greatly improved by the authors referencing previous relevant studies and restricting their manuscript to the novel aspects which have not been published. The use of vector field tomography via LTEM is a wonderful demonstration and does have advantages over the earlier study by Loudon. However, the authors are not able to explain these advantages without referencing the earlier studies. I also note a later paper published by Turnbull et al (ACS NANO 15 (1) 387 2021) reporting on tilting x- ray holography of magnetic bubbles in the same material, which is a technique making progress towards vector tomography. The authors should also consider the arXiv paper published by Nakajima "Two types of magnetic bubbles in MnNiGa observed via Lorentz microscopy" arXiv:2110.15507 (2021) and also S.L. Zuo et al., Nanoscale 10, 2260 (2018). + +<|ref|>text<|/ref|><|det|>[[147, 853, 850, 890]]<|/det|> +I believe this manuscript is not worthy of publication in Nature Communications and should be rejected. The authors should in future take more care to adequately reference papers published by + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 849, 125]]<|/det|> +others in the field and to give suitable credit to them. The current manuscript certainly does contain novel and interesting results but is not worthy of publication in its present form. + +<|ref|>text<|/ref|><|det|>[[147, 150, 852, 316]]<|/det|> +R: We totally refuse the comments from the referee. We are familiar with Loudon's paper in Advanced Materials (31 (16) 1806598 2019) which also cited the arXiv version of our previous paper (the published version is Applied Physics Letters, 114, 102404, 2019). Both his AM paper and our previous APL paper claimed that the biskyrmions should be interpreted as the Type II bubbles. We appreciate the experimental design of combining the X- ray holography and LTEM imaging techniques to illuminate the magnetic detail of Type I and Type II bubbles. They also found that the structure changes from Type I to Type II bubbles under applying external magnetic field. + +<|ref|>text<|/ref|><|det|>[[148, 320, 852, 767]]<|/det|> +1. However, Loudon's work used X-ray to characterize the out-plane component (Bz) of the Type I bubbles but LTEM to observe the in-plane component (Bx-By) of the bubbles. Obviously, the combination of these two sets of data cannot confirm the chirality of individual bubble, whatever the Type I or Type II because the in-plane components of the moments are lost in X-ray experiments and the polarity of each bubble disappears in LTEM images. Although the polarity (Bz) may be confirmed in X-ray investigation, the actual chirality of bubbles in LTEM could not be directly determined from their swirling style of in-plane components unless they pre-specified the Bz direction of each bubble in LTEM (of cause they cannot), which is indicated clearly in fig. 1 of our submitted manuscript. Indeed based on Loudon's data, it is difficult to build the real 3D magnetic structure of bubbles and hard to claim that "demonstrated the internal structure of these objects" as referee said. Loudon et al employed micromagnetic simulation, a conventional method, to illustrate the 3D structure of the bubbles in their paper but it does not mean that they really observed the entire configurations in the 3D space. Compared with them, we did reconstruct the entire structure of bubbles in MnNiGa including the internal and surface moment orientation and this is exactly the novelty of our manuscript. We also indicated that based on the reconstructed 3D feature of the Bx or By component, the chirality of bubbles can be clarified qualitatively, which is another important contribution of our work. It seems like a natural anticipation from the simulation but cannot be revealed by Loudon's work or other literature listed by the referee. The referee's conclusion that Loudon et al have reconstructed the magnetic structure of the bubbles in MnNiGa is a misleading statement. + +<|ref|>text<|/ref|><|det|>[[148, 769, 852, 892]]<|/det|> +2. The referee said that the fig. 4 in Loudon's AM paper displayed the helical reversal of the bubbles and he concluded Loudon et al also confirmed the chirality changes as our reported. But referee forgets that there was an external out-plane field of 233 mT applied on the sample! (First sentence in second-to-last paragraph, page 4 of Loudon's paper.) Based on this condition, one can suppose that the Bz of bubbles were fixed and the reversal of the in-plane components implied the change of the chirality. However, without this assumption + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 86, 852, 338]]<|/det|> +or in a field free situation as described in our experiments, Bx- By changes could not infer whether the polarity varies simultaneously. If both vorticity (what can be seen in Loudon's work) and polarity (what cannot be seen in Loudon's work) change, the chirality maintains unchanged! Clearly, distinguishing what happens cannot be achieved by the traditional LTEM images in Loudon's paper or other's. The referee may skip the fig1 in our manuscript which demonstrates the importance of the real 3D exploration for spiral magnetic structures. We denoted this point and realized this discrimination in MnNiGa system for the more general case, which was impossible to be accomplished in Loudon's AM paper or other literature mentioned by the referee since the features in several tilted LTEM images cannot supply enough information to determine the detail of the magnetic structures. Actually, those papers did not show the conclusion that they really detected the chirality of studied bubbles at a field free condition. + +<|ref|>text<|/ref|><|det|>[[148, 342, 852, 657]]<|/det|> +3. Turnbull's paper (ACS NANO 15 (1) 387 2021, from the same research group with Loudon) described the progress in detecting the Type I and Type II bubbles by X-ray holography and an approach using two projection images at different angles to judge the type of bubbles. However, the vorticity of the in-plane components cannot be explored because X-ray is only sensitive to the components parallel the propagating direction. Tilting the sample also impossibly supplies the rotation manner of the in-plane features. This method cannot even demonstrate the swirling style of the bubble, let along the chirality! The highlights of our work are to draw the 3D configuration of the magnetic bubbles and clarify their topological characteristics, but are not to prove the existence of type-I or type-II bubbles in MnNiGa alloy. The arXiv paper of Nakajima 2110.15507 (2021) found there may be two kinds of Type II bubbles in MnNiGa, characterized by LTEM images. Zuo's paper studied the so-called "biskyrminons" in MnNiGaY. Both of two literatures did not mention the 3D structure or the chirality of the magnetic bubbles. We cannot understand why the referee mentioned these literatures as the evidence to debase the novelty of our work. + +<|ref|>text<|/ref|><|det|>[[148, 662, 851, 765]]<|/det|> +We respect Loudon's beautiful works and other related outstanding researches. Since we focused on the 3D structure recovery of the magnetic structure, their papers were not referenced in our manuscript. We can give more comparison with their reports in our work but cannot accept referee's misleading and biased comments. Some literature have been appended in the revised manuscript. Thus, we strongly appeal to editor to reconsider our modified manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 812, 425, 828]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 853, 850, 892]]<|/det|> +Review of manuscript NCOMMS- 21- 41870 entitled „The dynamic chirality flips of Skyrmion bubbles“ by Yuan Yao, Bei Ding, Jinjing Liang, Hang Li, Xi Shen, Richeng Yu, Wenhong Wang + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 107, 851, 253]]<|/det|> +Yuan Yao, Bei Ding and coworkers report on the tomographic 3D reconstruction of skyrmion bubbles in Mn- Ni- Ga from tilt series of Lorentz transmission electron micrographs. The goal of these investigations is to determine the 3D magnetic spin structure of different types of bubbles in terms of chirality, polarity and topology that is not possible from single L- TEM images. As a result, they found that bubbles switched their chirality (between reconstructions of two different Cartesian B- field components) but still keep the polarity to remain the singularity of the bubbles within the material. + +<|ref|>text<|/ref|><|det|>[[147, 278, 850, 359]]<|/det|> +I find the approach very appealing and suited to be published in Nature Communications. However, the paper in its current stage lacks from numerous experimental uncertainties, logical and theoretical inconsistencies, and physical flaws and hence I can only recommend it for publication after a careful and major revision considering the points below. + +<|ref|>text<|/ref|><|det|>[[148, 385, 684, 402]]<|/det|> +The major points of criticism which have to be addressed are the following: + +<|ref|>text<|/ref|><|det|>[[147, 469, 852, 700]]<|/det|> +1. The magnetic states of the Skyrmion bubbles seem to be very unstable (metastable) at RT and therefore susceptible to be modified by small magnetic fields (compare e.g. in Fig.2a left and right column). The authors observe this problem by comparing the 3D induction maps of Bx and By (e.g. Fig.4 and Table 1). Since Bx and By belong only to the same magnetic state in bubble #2 only, they could only be combined in this case to obtain the full 3D vector-field by solving \(\mathrm{divB = 0}\) . Could it be that the residual magnetic field of the Lorentz lens (how large?) has changed the magnetic states of the bubbles when the sample was retracted and inserted in the TEM for in-plane rotation? Even worse, did the authors has detected some changes within tilt series acquisition, i.e. when going to higher tilt angles due to the changed orientation of the residual field with respect to the specimen? To avoid this unintended flipping of the magnetic states, it would have been more favorable to cool the sample during acquisition or to use an in-plane rotation holder. + +<|ref|>text<|/ref|><|det|>[[147, 725, 852, 891]]<|/det|> +R: The residual magnetic field in LTEM JEOL 2100F- LM is below 10 Oe since it is a special designed instrument for the magnetic object characterization. So the residual field should not be a reasonable influence to the observed feature changes of the bubbles. The appearance of the bubbles varied little during the sample tilting, which has been testified by the images before and after tilting (fig. s14 in supplemental information or fig. r1 here). Indeed, the reconstruction of each Bx or By may include the tolerance of these possible distortion and strictly speaking the results were semi- quantitative to illuminate the moments behavior within the bubbles. We also avoid the quantificational description for the magnetic moment because of the regularization + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 852, 295]]<|/det|> +parameter, the missing- wedge effect and the uncertain in Bz calculation. Fortunately, these semi- quantitative features containing some details can supply enough information to investigate the type or the chirality of the bubbles. Unfortunately, the features of some bubbles changed obviously when sample rotated 90 degrees for acquisition in another tilting axis. The environment changes during operation MAY be considered but we have to say that the exact reason is not clear right now. One confirmation is that the configuration of the bubbles in MnNiGa is not stable. Cooling down the sample is a good suggestion to avoid some unknown effects but the tomography experiment needs a high- tilting holder, which excludes the possibility of the cooling holders in present study. In- plane 90 degrees rotation holder is not a general available apparatus for the tomography exploration now, but it is a valuable direction to be developed. + +<|ref|>image<|/ref|><|det|>[[207, 306, 796, 587]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[230, 600, 764, 616]]<|/det|> +
Fig. rf The features of bubbles did not change during the x-tilt operation.
+ +<|ref|>text<|/ref|><|det|>[[147, 666, 851, 789]]<|/det|> +2. The four magnetic states of the type I bubbles were computed by micromagnetic simulations as shown in Fig. 1. The Neel twisting at their surfaces leads to magnetic charges, i.e. a high contribution of H, but a low one of B. Since, L-TEM is only sensitive to B not M, it is worthwhile to know how the simulated B-field looks like especially at the surface. In this context, it is also interesting to know how extended in z-direction these Neel twists are and whether they can be resolved by VFET. + +<|ref|>text<|/ref|><|det|>[[147, 816, 850, 896]]<|/det|> +R: Yes, the LTEM only detect the magnetic induction B, not the magnetization M or magnetic field strength H. Following the suggestion, we computed the induction B in 3D space from the type I magnetic bubble with R+ configuration and verify the similar Neel features existing in both surfaces of the bubble, as the surface features in M cylinder. Of cause the size of B cylinder is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 850, 146]]<|/det|> +slightly larger than the M configuration and there are some differences resulted from the demagnetization in the simulation. These contents are added in the modified manuscript (fig. 3 and related discussion in manuscript, and fig. r2 here). + +<|ref|>image<|/ref|><|det|>[[180, 157, 816, 518]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 520, 850, 648]]<|/det|> +
Fig. r2 The magnetic \(\mathbf{R}+\) configuration of \(2\#\) bubble. a Distribution of in-plane magnetizations in 3D feature of the \(\mathbf{R}+\) model. b In-plane induction components computed from \(\mathbf{R}+\) model. c In-plane induction components reconstructed from the tilted LTEM images simulated based on \(\mathbf{R}+\) model. d In-plane induction components recovered from the experimental data of \(2\#\) bubble. The box frames in a)-c) indicate the physical size of \(\mathbf{R}+\) model. Only the pixels with values larger than \(20\%\) of the maximum intensity are rendered in b)-d) to depress the artifacts from regularization parameter and missing-wedge effect.
+ +<|ref|>text<|/ref|><|det|>[[147, 651, 851, 880]]<|/det|> +"Fig. 3a interprets the rendered orientation of in- plane magnetization components within simulated \(\mathbf{R}+\) model in three dimensions, demonstrating the surface convergent or divergent features, while Fig. 3b shows the calculated in- plane inductions. The induction field involving stray strength in Fig. 3b replicates the moment style of the \(\mathbf{R}+\) bubble. In order to testify the fidelity of the reconstruction, serial tilting LTEM images were simulated from \(\mathbf{R}+\) model with same experimental conditions to rebuild the induction shape with those processing parameters for experimental task. The product in Fig. 3c demonstrates the reliable recovery of the \(\mathbf{R}+\) bubble but bears some artifacts from the TIE parameters and missing- wedge effect (the weak extension along z direction owing to the limited tilting range in data acquisition). Fig. 3d outlines the in- plane induction retrieved for \(2\#\) bubble, which appears similar contour in Fig. 3c and confirms the \(\mathbf{R}+\) type." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 851, 232]]<|/det|> +3. The experimental tilt range is quite low: ca. \(+55^{\circ}\) instead of \(+90^{\circ}\) . Therefore the tomograms suffer from a large missing wedge, not discussed in the manuscript at all. I suppose, one problem is the slab geometry of the (FIB?) lamella, which is disadvantageous at high tilts, when new object information appears in the field-of-view and the projected thickness becomes thicker and thicker. How the authors tackled this issue especially when using a SIRT algorithm for reconstruction, where the reconstructed volume must be limited? Why the authors have not tried to prepare a needle-shaped sample much more suitable for tomography? + +<|ref|>text<|/ref|><|det|>[[147, 255, 852, 700]]<|/det|> +R: Yes, the limited tilting range is the intrinsic shortage of present tomography in TEM. Frankly speaking, the missing- wedge is the problem difficult to be solved in TEM tomography because of the narrow space between the pole pieces. FIB prepared needle is more suitable for scalar field tomography since it can be tilted along the long axis of the cylinder to increase the tilt range. But for vector field reconstruction, the sample should be tilted along the short axis for second component reconstruction and eventually the tilt angle is also limited by its cylinder shape. At last the available common range for two tilting axes is not as large as expected. A wider region can be investigated in \(\mathrm{Ar + }\) ion milling sample (not FIB prepared sample) used in our experiment, which favors the discovery of the bubbles. The prolonged features along z- axis are observed in our reconstructed 3D features of Bx or By component. It deteriorates the resolution in z direction and carried out worse spatial resolution for Bz component. We depressed the data below \(20\%\) of maximum value of the corresponding components in our work to remove the missing- wedge effect. Although it is not a good choice for accuracy, it is an effective approach to remove the attenuate extension part and to recognize the contour of magnetic microstructure. Both simulations and practices verified the validation of this method. Conquering this difficulty needs more technical improvement in data acquisition or data processing but it is out the scope of present work. We add some discussions about this issue in the modified manuscript and emphasize that the retrieved moment figuration is a semi- quantitative result in order to avoid misleading the readers. It should be denoted that the relative strength of B vector, although less spatial resolution and data accuracy, could believably depict the chirality of the bubbles. They are contained in the modified version. + +<|ref|>text<|/ref|><|det|>[[147, 747, 851, 870]]<|/det|> +4. To judge the fidelity of the tomograms, it is also important to know how the applied focus of \(300 \mu \mathrm{m}\) determines the lateral resolution of the L-TEM images described by the spatial envelope. Also the regularization (not regularity as written in the paper) parameter \(q0\) (line 272) determines on a certain way the fidelity of the 3D data. In best case, the authors should check by a simulated tilt series using same parameters (tilt range, defocus, \(q0\) ), whether the tomogram reveals the original magnetic structure? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 318]]<|/det|> +R: The lateral spatial resolution of the LTEM under large defocus (such as \(300 \mu \mathrm{m}\) ) is about \(5 \mathrm{~nm}\) , a coarse estimation. We try to use the simulated images with different tilting to reconstruct the entire virtue bubble to testify the validation of the method and parameters. We also tilted the simulated B configuration (R+) from \(- 50^{\circ}\) to \(50^{\circ}\) with \(2^{\circ}\) internal along tow orthogonal axes, generated the Fresnel images at each angle, retrieve each phase image with regularization parameter \(\mathrm{q}_{0} = 5 \times 10^{- 3} \mathrm{~nm}^{- 1}\) and reconstructed the entire induction matrix, as same as the experimental pipeline. Fig. s5 in supplemental information or fig. r3 here displays some simulated Fresnel images for different angles. The virtual operation demonstrated the parameters in experiment can ensure the recovery of the magnetic induction, while \(\mathrm{q}_{0} = 5 \times 10^{- 3} \mathrm{~nm}^{- 1}\) may enhance the extra artificial structure in the simulated structure than in the experimental data because of the low noise in the simulated images. This information has been appended in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[275, 323, 719, 610]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[164, 648, 832, 693]]<|/det|> +
Fig. r3 The simulated LTEM images for a \(\mathrm{R}+\) skyrmion. a) and b) under-focus and over-focus without tilting; c) and d) under-focus and over-focus with tilting \(-30^{\circ}\) around x axis.
+ +<|ref|>text<|/ref|><|det|>[[147, 722, 850, 780]]<|/det|> +5. With respect to the resolution limitations mentioned in points 3 and 4, the observation of a very localized Bloch line in Figs. 3c,d is really questionable. The authors should check the reliability of this feature. + +<|ref|>text<|/ref|><|det|>[[147, 808, 850, 866]]<|/det|> +R: We understand the concern from the reviewer. The approximate location of the Bloch line could be estimated by the orientation change of the inductions although the resolution is not perfect for present results. We removed that statement in the manuscript to avoid the confusing presentation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 108, 850, 145]]<|/det|> +6. Why the authors do not provide the reconstructed 3D B-fields in Tesla. E.g., in Fig.4 the values range from \(+ - 10^{6}\) (A/m?). They must not be denoted Mx and My, because these are B-fields. + +<|ref|>text<|/ref|><|det|>[[147, 171, 853, 338]]<|/det|> +R: Actually, the initial motivation of this study is to obtain the qualitative field of the bubble. But we found that the TIE method employed here can unavoidably distort the absolute value of the retrieved field because of the regularization parameter \(q_{0}\) though the relative value may be credible. Therefore, we abandoned to evaluate the real value of B or M. The used calculated value at each pixel from the reconstruction algorithm is to illustrate the relative changes of B components. It is correct true that the LTEM investigates the B-field, not M. We have modified the figures and added more pictures about the computed B field and recovered B field retrieved from the simulated tilting images. Please see Fig. 3 and related discussion in manuscript, or fig. r2 here. + +<|ref|>sub_title<|/ref|><|det|>[[148, 364, 272, 379]]<|/det|> +## Minor comments + +<|ref|>text<|/ref|><|det|>[[147, 385, 850, 423]]<|/det|> +1. Can the authors give more information/data about the experiment and data treatment (at least in the Suppl. Mat.), such as + +<|ref|>text<|/ref|><|det|>[[149, 428, 414, 444]]<|/det|> +- TEM lamella preparation (by FIB?) + +<|ref|>text<|/ref|><|det|>[[147, 470, 612, 486]]<|/det|> +R: The Ar+ ion milling process was added in the Method section. + +<|ref|>text<|/ref|><|det|>[[148, 514, 330, 529]]<|/det|> +- Field cooling procedure + +<|ref|>text<|/ref|><|det|>[[147, 555, 851, 656]]<|/det|> +R: The specific FC manipulation was performed in the Physical Property Measurement System (PPMS). The sample was fixed in the puck and put into the cavity. It was heated to \(380\mathrm{K}\) , which is higher than the Curie temperature ( \(\mathrm{T_{C} \sim 345K}\) ). Then a small magnetic field of \(500\mathrm{Oe}\) was applied and the sample was cooled gradually to \(300\mathrm{K}\) at which the field turned off. It was added in Method section. + +<|ref|>text<|/ref|><|det|>[[148, 684, 540, 700]]<|/det|> +- Lorentz TEM tilt series (to be shown in supplement?) + +<|ref|>text<|/ref|><|det|>[[147, 726, 778, 743]]<|/det|> +R: The some images in the experimental tilting series were shown in the supplement file. + +<|ref|>text<|/ref|><|det|>[[148, 769, 498, 785]]<|/det|> +- TIE reconstruction (influence of regularization) + +<|ref|>text<|/ref|><|det|>[[147, 811, 850, 848]]<|/det|> +R: The affect from the regularization \(q_{0}\) on retrieved phase images are shown in supplement for the experiment data. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[241, 88, 757, 262]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 275, 850, 320]]<|/det|> +
Fig. r4 The in-plane components of induction retrieved with a) \(\mathrm{q_0 = 5\times 10^{-3}nm^{-1}}\) and b) \(\mathrm{q_0 = 7.5\times 10^{-3}}\) \(\mathrm{nm^{-1}}\) , respectively.
+ +<|ref|>text<|/ref|><|det|>[[148, 370, 483, 386]]<|/det|> +- phase tilt series (to be shown in supplement?) + +<|ref|>text<|/ref|><|det|>[[147, 412, 848, 450]]<|/det|> +R: Due to limitations on space, some phase images from the tilting phase series are shown in Fig. s9 and s10 in supplement. We add the movie files of the phase stacks. + +<|ref|>text<|/ref|><|det|>[[149, 499, 353, 514]]<|/det|> +- Image alignment (line 275) + +<|ref|>text<|/ref|><|det|>[[147, 540, 852, 728]]<|/det|> +R: The phase images, such as for x-tilting, were formed to one stack file and aligned with the "Image Alignment" function in Gatan Microscopy Suite (GMS). A "bandpass filter" with default mode was employed to "automatic" register the images, followed by forward and backward corrections. After alignment, all phase images were merged into one image and that image were transformed to Fourier space. The prolonging diffuse background of the auto-correlation region (center part) in diffractogram indicated the tilt axis orientation, as shown in fig. r5. After the ailment, all phase images were rotated to make the tilting axis vertical or horizontal to the image boundary, facilitating the followed calculation of Bx or By components. It is denoted in the manuscript and some details are demonstrated in supplement. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[366, 86, 629, 265]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 275, 850, 319]]<|/det|> +
Fig. r5 Diffractogram of the merged phase image, where the dash denotes the orientation of tilt axis.
+ +<|ref|>text<|/ref|><|det|>[[148, 370, 508, 386]]<|/det|> +- W-SIRT parameters (influence of regularization) + +<|ref|>text<|/ref|><|det|>[[147, 412, 851, 494]]<|/det|> +R: The parameter in GUI of reconstruction plugin is added in the supplements. We think the referee wants to check whether different \(\mathrm{q}_0\) can make a significant change in the reconstructed 3D features. We added the investigation for reconstruction of the \(\mathrm{R + }\) model skyrmion in supplement to show this influence. + +<|ref|>sub_title<|/ref|><|det|>[[148, 520, 264, 535]]<|/det|> +## 2. Mathematics: + +<|ref|>text<|/ref|><|det|>[[148, 541, 612, 557]]<|/det|> +Could the authors more clearly describe the mathematics of TIE? + +<|ref|>text<|/ref|><|det|>[[147, 583, 851, 622]]<|/det|> +- As shown by Lubk et al. (PRL 111, 173902 (2013)) Eq. 1 is only valid, if a) the object is a pure phase object, or b) the current density is conservative. What is valid here? + +<|ref|>text<|/ref|><|det|>[[147, 632, 850, 691]]<|/det|> +- What is the meaning of symbol \(\overline{V_{x,y}^2}\) ? Isn't it the inversion of Laplacian, \(1 / \mathrm{q}^2\) in Fourier space to be inserted in line 271 on the LHS instead \(\overline{V_{x,y}^2}\) ? + +<|ref|>text<|/ref|><|det|>[[147, 700, 850, 738]]<|/det|> +- Inconsistencies of notation, in Eq. (1) reciprocal vector is \(\mathrm{q}\) , whereas in Eq. (2) reciprocal vector is \(\mathrm{k}\) + +<|ref|>text<|/ref|><|det|>[[147, 763, 851, 888]]<|/det|> +R: The principle of TIE is added in Supplement file. TIE is used to recover the phase of a wave, exactly the wave exiting the object in TEM experiments. Interpreting the physical meaning of the phase is not the responsibility of TIE, so actually it needn't any assumption for the wave characteristics. Eq. 1 only requires a conservation of Poynting current, described by the original Paganin's paper (D. Paganin and K. A. Nugent, Noninterferometric Phase Imaging with Partially Coherent Light, Phys. Rev. Lett., 80, 2586, 1998). Because the scattering ability of the specimen + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 86, 852, 316]]<|/det|> +is very weak so most features in images satisfy the conservation except the image boundaries which is out the interesting range in our studies. Eq. 1 is valid for most parts of the processed images. Lubk's paper proposed a method to deal with the vortex beam containing the phase singularity. The phase of the electron beam exiting the skyrmions does not have such singular portion - although the in-plane magnetic inductions show the singular point in bubble center the phase of exit wave is continue. Pure phase object assumption that was cited by Lubk is another literature (T. E. Gureyev and S.W. Wilkins, J. Opt. Soc. Am. A, 15, 579, 1998). Gureyev et al just used the phase contrast concept to introduce the image mode but not as the premise of deduction. In principle, the differential operation and the normalization by \(\mathrm{I}(z = z0)\) in Eq. 1 remove the influence from the amplitude of the wave since the intensity of in- focus image presents the amplitude of the wave. Therefore Eq. 1 can give the proper phase solution. + +<|ref|>text<|/ref|><|det|>[[148, 325, 848, 416]]<|/det|> +\(\overline{V_{x,y}^{2,2}}\) is the inverse Laplacian operator, and it can be substituted by \(- 1 / \mathrm{q}^2\) in Fourier transform. Allen's paper gave a deduction about this point. (Eq. 8- 10 in "L. J. Allen, M. P. Oxley, Phase retrieval from series of images obtained by defocus variation. Opt. Commu., 199, 65- 75, 2001 ") The errors and inconsistence about \(\mathrm{q}\) and \(\mathrm{k}\) have been corrected. + +<|ref|>text<|/ref|><|det|>[[149, 443, 375, 459]]<|/det|> +3. English writing and wording. + +<|ref|>text<|/ref|><|det|>[[148, 465, 850, 567]]<|/det|> +- there are numerous typos and sometimes inadequate choice of words, e.g. line 20: "magnetic moment" is misleading here, line 40 "need", line 48 "turns into" not appropriate in this context, line 64 "charity", line 116 "configuraiton", line 232, 238 "configure", line 263 "3D structure reconstruction" not the right term The text needs very much polishing in general. + +<|ref|>text<|/ref|><|det|>[[147, 593, 849, 630]]<|/det|> +R: We carefully modified the manuscript and tried our best to correct the typo and grammar errors. + +<|ref|>text<|/ref|><|det|>[[147, 656, 730, 673]]<|/det|> +4. Fig.1b: Why there is a threshold in the simulated induction maps (black mask)? + +<|ref|>text<|/ref|><|det|>[[147, 699, 850, 757]]<|/det|> +R: The color maps in Fig. 1b is the TIE retrieved induction maps which are influenced by the regularization parameter \(\mathrm{q}_0\) . Thus a threshold, \(5\%\) of the maximum induction, is used to get rid of that effect. + +<|ref|>text<|/ref|><|det|>[[147, 784, 606, 800]]<|/det|> +5. Line 273: Please provide the value of \(\mathrm{q0}\) in "1/nm" not pixels. + +<|ref|>text<|/ref|><|det|>[[147, 826, 388, 843]]<|/det|> +R: It was changed to \(5 \times 10^{- 3} \mathrm{~nm}^{- 1}\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 223, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 139]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 140, 876, 266]]<|/det|> +This is a much improved manuscript that now makes clear what has been done by the authors and by others in the past, and what is new. The major novelty of the paper is the three dimensional reconstruction of the magnetic induction. The authors have utilised the method of Wolf (reference 30) which first demonstrated how to accomplish the 3D magnetic texture of a Bloch skyrmion in FeGe using holographic vector tomography. That means that the authors can measure not just the vorticity of the skyrmion bubble but also its polarity and hence the chirality. This means that when a magnetic bubble switches its circular direction, they can say whether its chirality also changes. This is a degree of freedom which is not available to a skyrmion and its chirality is fixed by the Dzyaloshinskii- Moriya interaction and the orientation of the applied magnetic field. + +<|ref|>text<|/ref|><|det|>[[119, 280, 857, 322]]<|/det|> +The editor should decide whether this observed chirality switch in a skyrmion bubble in centrosymmetric MnNiGa is of sufficiently wide interest to a journal such as Nature Communications, or is more suited to a more specialist condensed matter or magnetism journal. + +<|ref|>text<|/ref|><|det|>[[118, 336, 610, 350]]<|/det|> +The few remaining comments about the revised manuscript are: + +<|ref|>text<|/ref|><|det|>[[118, 350, 825, 419]]<|/det|> +Fig 1a Why does the magnetization go to zero at a given radius? Are they magnetic disks? What model was used to generate the skyrmions? Fig 1b Why was the contrast below \(5\%\) of maximum magnitude masked in the magnetization mapping to filter the artifacts induced by the regularisation parameter in TIE? Fig 4 There is a confusion of B and M between the figures and the caption. + +<|ref|>text<|/ref|><|det|>[[118, 461, 223, 474]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 476, 300, 489]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 490, 871, 589]]<|/det|> +First of all, I appreciate that the authors have addressed all of my concerns and in general I am satisfied with their detailed reply and corresponding modifications of the main text. I do not doubt that the major findings namely the identification of the chirality and polarity of the type I bubble as well as the discrimination to the type II bubble is possible by inspecting the upper and lower surface of one component of the magnetic induction reconstructed by tomography. I also do not doubt the 3D reconstruction of the in- plane vector- field of one bubble (#2), one of the few which seemed to be stable for both tilt series. + +<|ref|>text<|/ref|><|det|>[[118, 602, 870, 630]]<|/det|> +However, by reading the revised text I identified remaining problems (in particular with respect to the papers' impact for the community): + +<|ref|>text<|/ref|><|det|>[[118, 630, 870, 715]]<|/det|> +1. The reason for the dynamic chirality flips (content of title!) is not resolved, because they were unintended. Maybe one reason could be a small in-plane field. This must be investigated further. For example, the authors mention in the last sentence of the abstract: "Our results offer valuable insights into the fundamental dynamics to understand the chirality behavior of skyrmion bubbles". But I miss exactly this understanding although it is extensive observation. Maybe also a micromagnetic simulation and corresponding energies could give more insight. + +<|ref|>text<|/ref|><|det|>[[118, 729, 860, 770]]<|/det|> +2. A way how to use the chirality (switching) information (e.g., as read-out for memory devices) and make it useful for technological applications is not discussed. As the authors mentioned the polarity (which could be easily read out) was not changed. + +<|ref|>text<|/ref|><|det|>[[118, 770, 864, 840]]<|/det|> +3. The central theme through the entire manuscript is not consistent. The title promises to study the reason for the chirality flips but it is not done. The abstract promises the 3D vector-field reconstruction of magnetic induction, i.e., all three components of all bubbles but in fact only two components of one bubble or one component of the other bubbles with two different states are presented. + +<|ref|>text<|/ref|><|det|>[[115, 854, 866, 880]]<|/det|> +4. Still the writing (wording) and presentation has serious flaws. In the following I mention only a few examples, but there are much more: + +<|ref|>text<|/ref|><|det|>[[118, 881, 870, 910]]<|/det|> +- the term Skyrmion bubble in general is questionable- sentence line 20: "The induction configuration of the bubbles was determined from investigating + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 852, 450]]<|/det|> +the magnetic vectors in entire space." contains strange combinations: "induction configuration" should be either "magnetic configuration" or "magnetic induction" One suggestion: "The magnetic configuration of the bubbles was determined from the reconstructed magnetic induction (B- field) at their surfaces and their center." - in Fig. 2 tilt axes should be indicated - line 134 Bx matrix wrong term better Bx array, By array - in Fig. 3 sub panel label must be in the upper corner - line 153 "serial tilting" wrong term, just say tilt series - line 157 "extension" must read: elongation (see for example Midgley and Weyland, Ultramicroscopy 96 (2003) 413, https://doi.org/10.1016/S0304- 3991(03)00105- 0 - line 165 "out- plane" must be out- of plane - line 168 "thickness measurement error" minor comment regarding content: thickness measurement should not influence the tomographic reconstruction - in Fig. 4: What is shown in a and b upper left panel labeled with Mx, My - line 219: "That is to say, they cannot reveal the dynamic behavior of the bubbles in a field free condition." Bad English - line 221 "be against" should be "anti- parallel" - line 236 "always fabricated by focus ion beam (FIB)" not always, self- grown NWs are also possible - line 240: "is tilted around its short axis." One way out is to orient the needle- axis \(+ - 45^{\circ}\) to the tilt axis. (e.g. see Wolf et al., Commun. Phys. 2 (2019) 87 https://doi.org/10.1038/s42005- 019- 0187- 8 ) - line 242 "prolongs" better "elongates" - lines 311,313, 314 "mappings" must read in these contexts "maps" - actually the whole sentence from lines 311- 315 is very badly written. There are much more issues like these, also in the supplement. + +<|ref|>text<|/ref|><|det|>[[118, 462, 867, 491]]<|/det|> +In its current form I still cannot recommend the paper to be published in Nature Communications. In my opinion, it needs a second major revision. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 87, 463, 103]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[177, 128, 821, 360]]<|/det|> +This is a much improved manuscript that now makes clear what has been done by the authors and by others in the past, and what is new. The major novelty of the paper is the three dimensional reconstruction of the magnetic induction. The authors have utilised the method of Wolf (reference 30) which first demonstrated how to accomplish the 3D magnetic texture of a Bloch skyrmion in FeGe using holographic vector tomography. That means that the authors can measure not just the vorticity of the skyrmion bubble but also its polarity and hence the chirality. This means that when a magnetic bubble switches its circular direction, they can say whether its chirality also changes. This is a degree of freedom which is not available to a skyrmion and its chirality is fixed by the Dzyaloshinskii- Moriya interaction and the orientation of the applied magnetic field. + +<|ref|>text<|/ref|><|det|>[[177, 383, 820, 466]]<|/det|> +The editor should decide whether this observed chirality switch in a skyrmion bubble in centrosymmetric MnNiGa is of sufficiently wide interest to a journal such as Nature Communications, or is more suited to a more specialist condensed matter or magnetism journal. + +<|ref|>text<|/ref|><|det|>[[177, 488, 821, 653]]<|/det|> +R: We sincerely thank the referee for carefully reading our manuscript and noting that the major novelty of our paper is the three- dimensional reconstruction of the magnetic induction. Following the referee's comments and suggestions, we carried out additional experiments and analyses. Moreover, we carefully and thoroughly revised the language in the manuscript. Below, we address the referee's comments and questions on a point- by- point basis. We hope the referee is satisfied with the revised manuscript and our response. + +<|ref|>text<|/ref|><|det|>[[177, 684, 819, 722]]<|/det|> +Fig 1a Why does the magnetization go to zero at a given radius? Are they magnetic disks? + +<|ref|>text<|/ref|><|det|>[[177, 747, 820, 829]]<|/det|> +R: Yes, we use a disk model to simulate the magnetic features of the bubbles. In general, DDI skyrmions can be stabilized by a sixfold symmetric array. To simplify the simulation, a single bubble was generated by the OOMMF code with a disk- shaped boundary. + +<|ref|>text<|/ref|><|det|>[[177, 854, 820, 893]]<|/det|> +Fig 1b Why was the contrast below \(5\%\) of maximum magnitude masked in the magnetization mapping to filter the artifacts induced by the regularisation parameter in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 87, 218, 101]]<|/det|> +TIE? + +<|ref|>text<|/ref|><|det|>[[177, 110, 821, 412]]<|/det|> +R: In the TIE method, the regularization parameter \(q_{0}\) is used to replace \(\frac{- 1}{|q|^{2}}\) with \(\frac{- |q|^{2}}{(|q|^{2} + q_{0}^{2})^{2}}\) to prevent the divergence of \(\mathcal{F}^{- 1}\left\{\frac{-\mathcal{F}[.]}{|q|^{2}}\right\}\) ; however, this parameter suppresses the low- frequency part of the original data. For example, if \(q_{0} = 2\) , the strength of information for \(q = 2\) may be 4 times smaller than the original value (1/4 vs. 1/16). However, for high- frequency information, such as \(q = 10\) , the influence is minimal (1/100 vs. 1/108.08). Thus, \(q_{0}\) exaggerates high- frequency information. As described in our previous papers [Cui, J. et al. Artifacts in magnetic spirals retrieved by transport of intensity equation (TIE). J. Magn. Magn. Mater. 454, 304- 313, (2018); Yao, Y et al. Magnetic hard nanobubble: A possible magnetization structure behind the bi- skyrmion. Appl. Phys. Lett. 114, 102404, (2019)], this distortion can lead to some artifacts in the results. Considering the noise in the experimental data, this distortion may also cause high- frequency noise. Therefore, a contrast threshold of \(5\%\) was employed to address this disturbance with a proper \(q_{0}\) . + +<|ref|>text<|/ref|><|det|>[[177, 436, 732, 475]]<|/det|> +Fig 4 There is a confusion of B and M between the figures and the caption. R: Thank you. This error has been corrected. + +<|ref|>text<|/ref|><|det|>[[178, 521, 463, 539]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[177, 563, 821, 732]]<|/det|> +First of all, I appreciate that the authors have addressed all of my concerns and in general I am satisfied with their detailed reply and corresponding modifications of the main text. I do not doubt that the major findings namely the identification of the chirality and polarity of the type I bubble as well as the discrimination to the type II bubble is possible by inspecting the upper and lower surface of one component of the magnetic induction reconstructed by tomography. I also do not doubt the 3D reconstruction of the in- plane vector- field of one bubble (#2), one of the few which seemed to be stable for both tilt series. + +<|ref|>text<|/ref|><|det|>[[178, 735, 820, 775]]<|/det|> +R: We thank the reviewer for his previous comments, which helped us to improve the presentation of the manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 799, 820, 839]]<|/det|> +However, by reading the revised text I identified remaining problems (in particular with respect to the papers' impact for the community): + +<|ref|>text<|/ref|><|det|>[[178, 842, 820, 903]]<|/det|> +1. The reason for the dynamic chirality flips (content of title!) is not resolved, because they were unintended. Maybe one reason could be a small in-plane field. This must be investigated further. For example, the authors mention in the last sentence of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 169]]<|/det|> +abstract: "Our results offer valuable insights into the fundamental dynamics to understand the chirality behavior of skyrmion bubbles". But I miss exactly this understanding although it is extensive observation. Maybe also a micromagnetic simulation and corresponding energies could give more insight. + +<|ref|>text<|/ref|><|det|>[[177, 172, 822, 553]]<|/det|> +R: Thank you for your helpful comments. As we mentioned in the manuscript, the field- free bubbles, which were obtained via the field cooling method, are in metastable states and can thus be manipulated by external stimulation. In practice, the electron beam can flip the bubbles during the initial observation; however, the bubbles were gradually stabilized after a shower period. We selected a region containing stable bubbles to acquire our data. During the data acquisition process, the investigated bubbles maintained their features, as shown in the SI. However, when the sample was removed from the LTEM for the 90- degree rotation for the next acquisition, the new beam illumination may change the configuration of some bubbles in the observation area. We assessed the influence of the electron beam the in SI to elucidate this effect. We believe that the electron beam may induce a local temperature increase that may be responsible for this dynamic flipping; this result was also verified in the temperature control experiment. The sample was initially balanced during the first characterization; however, when the sample was removed from the TEM and rotated for the next observation, a new balance must be established during the second beam irradiation, as some bubbles may have different configurations. Unfortunately, because we lack additional evidence to explain the detailed process, we modified the title of the manuscript to "Chirality flips of skyrmion bubbles" to prevent confusion. + +<|ref|>text<|/ref|><|det|>[[178, 576, 821, 636]]<|/det|> +2. A way how to use the chirality (switching) information (e.g., as read-out for memory devices) and make it useful for technological applications is not discussed. As the authors mentioned the polarity (which could be easily read out) was not changed. + +<|ref|>text<|/ref|><|det|>[[177, 639, 822, 872]]<|/det|> +R: We thank the referee for raising this interesting question. To date, the key operation of skyrmion racetrack memory is to assist the DMI skyrmion in reading/writing with electrical currents. Inspired by this method, we propose a new mechanism that uses the spin transfer torque technique to select different chiral DDI bubbles. A constant current carries bubbles with uniform chirality and polarity passing through an electron beam, and the beam can only determine whether the chirality of individual bubbles is flipped and does not change the orientation of the polarity. Then, the bubbles enter different branches due to the Magnus effect. The sensors in each branch detect only the existence of the bubbles (whatever their polarity) when recording the information state. The electron beam can easily be shrunk to tens of nanometers to manipulate individual DDI bubbles rather than changing the entire spin configuration of DMI skyrmions. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[232, 95, 808, 273]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[177, 290, 821, 393]]<|/det|> +3. The central theme through the entire manuscript is not consistent. The title promises to study the reason for the chirality flips but it is not done. The abstract promises the 3D vector-field reconstruction of magnetic induction, i.e., all three components of all bubbles but in fact only two components of one bubble or one component of the other bubbles with two different states are presented. + +<|ref|>text<|/ref|><|det|>[[177, 396, 821, 564]]<|/det|> +R: We apologize for the confusion. We understand the concerns of the reviewer. We evaluated chirality flipping by analyzing the 3D magnetic feature of the bubbles. After careful analyses, we recognized that it was not necessary to know all information about the bubble components to distinguish the type of bubble. Therefore, we focused on evaluating the 3D spin configurations of the bubbles after their chirality flipped. To clarify this point, the title has been changed to "Chirality flips of skyrmion bubbles". In addition, we added new experimental data to provide a possible explanation for the flip; however, this topic should be studied further in future work. + +<|ref|>text<|/ref|><|det|>[[177, 588, 820, 627]]<|/det|> +4. Still the writing (wording) and presentation has serious flaws. In the following I mention only a few examples, but there are much more: + +<|ref|>text<|/ref|><|det|>[[177, 630, 820, 732]]<|/det|> +- the term Skyrmion bubble in general is questionable- sentence line 20: "The induction configuration of the bubbles was determined from investigating the magnetic vectors in entire space." contains strange combinations: "induction configuration" should be either "magnetic configuration" or "magnetic induction" + +<|ref|>text<|/ref|><|det|>[[177, 737, 820, 777]]<|/det|> +One suggestion: "The magnetic configuration of the bubbles was determined from the reconstructed magnetic induction (B-field) at their surfaces and their center." + +<|ref|>text<|/ref|><|det|>[[177, 781, 820, 905]]<|/det|> +- in Fig. 2 tilt axes should be indicated- line 134 Bx matrix wrong term better Bx array, By array- in Fig. 3 sub panel label must be in the upper corner- line 153 "serial tilting" wrong term, just say tilt series- line 157 "extension" must read: elongation (see for example Midgley and Weyland, Ultramicroscopy 96 (2003) 413, https://doi.org/10.1016/S0304- 3991(03)00105- 0 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 85, 840, 425]]<|/det|> +- line 165 "out-plane" must be out-of plane- line 168 "thickness measurement error" minor comment regarding content: thickness measurement should not influence the tomographic reconstruction- in Fig. 4: What is shown in a and b upper left panel labeled with Mx, My- line 219: "That is to say, they cannot reveal the dynamic behavior of the bubbles in a field free condition." Bad English- line 221 "be against" should be "anti-parallel"- line 236 "always fabricated by focus ion beam (FIB)" not always, self-grown NWs are also possible- line 240: "is tilted around its short axis." One way out is to orient the needle-axis \(+\) \(45^{\circ}\) to the tilt axis. (e.g. see Wolf et al., Commun. Phys. 2 (2019) 87 https://doi.org/10.1038/s42005-019-0187-8)- line 242 "prolongs" better "elongates"- lines 311,313, 314 "mappings" must read in these contexts "maps"- actually the whole sentence from lines 311-315 is very badly written. There are much more issues like these, also in the supplement. + +<|ref|>text<|/ref|><|det|>[[177, 448, 822, 531]]<|/det|> +R: To address the language issues, the manuscript and the supporting information have been revised by one or more highly qualified native English-speaking editors at AJE. If the referee has additional sentences that they believe require revision, we would be happy to incorporate any suggestions. + +<|ref|>text<|/ref|><|det|>[[177, 575, 820, 616]]<|/det|> +In its current form I still cannot recommend the paper to be published in Nature Communications. In my opinion, it needs a second major revision. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 293, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 113, 300, 140]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 141, 864, 183]]<|/det|> +I am now content with the paper to be published. The paper reports noteworthy results and hopefully will be a significant paper in the field. The authors have acted upon the comments from the referees and as a result the manuscript is much improved. + +<|ref|>text<|/ref|><|det|>[[119, 225, 223, 237]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 240, 300, 252]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 253, 815, 281]]<|/det|> +The authors have severely revised and improved the manuscript further. I have only a few remarks left: + +<|ref|>text<|/ref|><|det|>[[119, 281, 868, 323]]<|/det|> +1. ) I find the proposed concept of race track memory using DDI skyrmions interesting (new Fig. 5 and corresponding text), but I cannot judge the validity of it, because this topic exceeds my expertise. + +<|ref|>text<|/ref|><|det|>[[119, 323, 405, 336]]<|/det|> +2. ) There are still some minor issues: + +<|ref|>text<|/ref|><|det|>[[119, 337, 870, 364]]<|/det|> +What are the units of the colorbar in Fig. 4? If the values are in A/m, then they are with \(\sim 4*10^{-6}\) too high, because they correspond to \(\sim 5\) Tesla! + +<|ref|>text<|/ref|><|det|>[[119, 365, 608, 378]]<|/det|> +Line 287: "spin transfer torch" must read "spin- transfer torque" + +<|ref|>text<|/ref|><|det|>[[119, 379, 810, 406]]<|/det|> +Line 358: I suggest to write: "Bx map was computed from the derivative of the phase in y direction." + +<|ref|>text<|/ref|><|det|>[[119, 406, 814, 421]]<|/det|> +Line 363: q is the coordinate or variable or spatial frequency in Fourier space, not the grid. + +<|ref|>text<|/ref|><|det|>[[119, 434, 772, 449]]<|/det|> +After especially my point 2) is addressed, I can recommend the paper for publication. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[178, 90, 399, 108]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[178, 145, 463, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 200, 821, 273]]<|/det|> +I am now content with the paper to be published. The paper reports noteworthy results and hopefully will be a significant paper in the field. The authors have acted upon the comments from the referees and as a result the manuscript is much improved. + +<|ref|>text<|/ref|><|det|>[[178, 283, 820, 329]]<|/det|> +R: Thank you for recommending our manuscript to be published in Nature Communications + +<|ref|>text<|/ref|><|det|>[[178, 367, 463, 385]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 421, 821, 467]]<|/det|> +The authors have severely revised and improved the manuscript further. I have only a few remarks left: + +<|ref|>text<|/ref|><|det|>[[178, 477, 821, 552]]<|/det|> +1. ) I find the proposed concept of race track memory using DDI skyrmions interesting (new Fig. 5 and corresponding text), but I cannot judge the validity of it, because this topic exceeds my expertise. + +<|ref|>text<|/ref|><|det|>[[177, 560, 822, 830]]<|/det|> +R: We sincerely thank the referee for careful reading of our manuscript, and for pointing out that race track memory using DDI skyrmions are intriguing. In fact, the race track memory using DMI skyrmions are extendedly studied by the theoretical and experimental group [Zhou Y, Ezawa M. A reversible conversion between a skyrmion and a domain-wall pair in a junction geometry. Nature communications, 2014, 5(1): 1- 8; Zhang X, Ezawa M, Zhou Y. Magnetic skyrmion logic gates: conversion, duplication and merging of skyrmions. Scientific reports, 2015, 5(1): 1- 8. ], but it's rare for the DDI skyrmions. We hope our work might evoke more theoretical studies on the race track memory using DDI skyrmions and may also lead to the realization of skyrmion- based spintronic devices. + +<|ref|>text<|/ref|><|det|>[[178, 867, 820, 912]]<|/det|> +2. ) There are still some minor issues: What are the units of the colorbar in Fig. 4? If the values are in A/m, then they are with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 90, 593, 108]]<|/det|> +\(\sim 4*10^{6}\) too high, because they correspond to \(\sim 5\) Tesla! + +<|ref|>text<|/ref|><|det|>[[176, 116, 823, 331]]<|/det|> +R: The resolution of Fig. 4 in the PDF file is not good. The order of the value is \(10^{\wedge}(- 6)\) , not \(10^{\wedge}6\) which represents the relative strength of magnetic induction deduced from the phase differential, but not the absolute value of the induction. However, in the revised manuscript, it has been changed to the absolute induction now. And the corresponding calculated magnetization is about \(7\times 10^{5}\mathrm{A / m}\) , which agrees well with the measured value of \(8\times 10^{5}\mathrm{A / m}\) [Bei Ding et al, Manipulating Spin Chirality of Magnetic Skyrmion Bubbles by In- Plane Reversed Magnetic Fields in (Mn1- xNix)65Ga35 (x =0.45) Magnet, Physical Review Applied, vol. 12, 054060 (2019)]. + +<|ref|>image<|/ref|><|det|>[[183, 368, 777, 655]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 664, 822, 850]]<|/det|> +
Fig. 4 The magnetic spin transition of bubble #5. The \(\mathrm{B}_{\mathrm{x}}\) (a) and \(\mathrm{B}_{\mathrm{y}}\) (b) features in the top, middle and bottom x-y sections. The solid arrows indicate the direction of the corresponding component, while the dashed arrows indicate the speculative direction of the orthogonal component based on prior knowledge of Bloch skyrmion bubbles. The color legend indicates the magnitude of induction components in x or y direction, which corresponds the magnetization between \(-6.5\times 10^{5}\sim 7\times 10^{5}\mathrm{A / m}\) and well agrees with the measured value of \(8\times 10^{5}\mathrm{A / m}\) .42
+ +<|ref|>text<|/ref|><|det|>[[177, 886, 647, 904]]<|/det|> +Line 287: "spin transfer torch" must read "spin- transfer torque" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 88, 820, 135]]<|/det|> +Line 358: I suggest to write: "Bx map was computed from the derivative of the phase in y direction." + +<|ref|>text<|/ref|><|det|>[[177, 144, 820, 191]]<|/det|> +Line 363: q is the coordinate or variable or spatial frequency in Fourier space, not the grid. + +<|ref|>text<|/ref|><|det|>[[177, 200, 812, 220]]<|/det|> +After especially my point 2) is addressed, I can recommend the paper for publication. + +<|ref|>text<|/ref|><|det|>[[177, 255, 820, 302]]<|/det|> +R: We sincerely thank the referee for recommending our manuscript to be published in Nature Communications. In the revised version, we have modified above issues. + +<--- Page Split ---> diff --git a/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/images_list.json b/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..380141ff9de7b9101b893868b329e6ea988aa50c --- /dev/null +++ b/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,521 @@ + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors of this manuscript report on the observation of pressure induced changes in the superconductivity of a newly discovered kagome metal, CsV3Sb5. The central claim is that pressure initially enhances the superconducting transition temperature while simultaneously suppressing the charge density wave order in this compound; however beyond this initial enhancement, they observe an unconventional suppression of Tc followed by a second enhancement, prior to being suppressed entirely at higher pressures. The result is a double superconducting "dome" in the pressure- driven superconducting phase diagram of this material. + +The key observation of the double- dome- type behavior suggests an unconventional superconducting ground state and the authors claim supporting evidence for a Lifshitz transition underpinning this behavior. The observation of weak, filamentary superconductivity at intermediate pressures is used to further support this conjecture. Overall, the topic and central claims of the paper are of sufficient novelty and broad community interest to merit consideration in Nature Communications. + +There are, however, a few central claims and issues with the manuscript that preclude recommendation for publication in Nature Communications in its current form. I list these below. + +(1) There have been several recent reports depicting a qualitatively different picture of the pressure-driven phase diagram in this class of kagome metals. For instance arXiv:2103.13759 which shows an extended high-pressure dome in CsV3Sb5 and arXiv:2102.10959 for a single dome in KV3Sb5. A similar double dome is noted in this paper as also being observed in CsV3Sb5 in arXiv:2102.09328. Can the authors provide analysis which can preclude extrinsic or disorder-driven effects in their present observation of a two-peak superconducting dome? I think this will be important for the paper and the field. + +(2) The conjecture of a Lifshitz transition is not immediately obvious from the quantum oscillation data in the supplementary material. The oscillations are seemingly rapidly damped, which is potentially due to pressure-induced disorder/damping effects. The frequency shifts observed prior to their disappearance are not immediately indicative of a Lifshitz transition to this referee. This claim should either be modified or better justified within the text. + +Minor comments: + +(3) The paper use some editorial review correcting minor typos/grammar issues throughout. + +(4) In Fig. 1, correlating colors between plots in the extended and zoomed-in T ranges would be helpful for the reader. It is a little confusing to trace the CDW and SC transitions in the current presentation at fixed pressure values. + +In summary, I believe the manuscript has the potential of presenting a finding of sufficient interest and novelty for Nature Communications, but these points/deficiencies must be satisfactorily addressed first. In particular if points (1) and (2) can be addressed, then the paper would be a valuable addition to a seemingly quickly growing field. + +Reviewer #2 (Remarks to the Author): + +<--- Page Split ---> + +This is a very interesting paper reporting the pressure phase diagram in the CsV3Sb5 superconductor with kagome lattice. The authors find a double- peak structure in the superconducting transition temperature \(T_{- }c\) as a function of pressure. The second peak at P2 corresponds to the end point of charge density wave (CDW) order, which can be similarly found in other superconductors with CDW. What is novel here is the observation of the first peak at P1, which is deep inside the CDW phase. To discuss the origin of this unusual peak inside the CDW phase, the authors performed magnetotransport measurements from which they find rapid changes in the Shubnikov- de Haas oscillations and the magnitude of magnetoresistance near P1. I find that these observations are intriguing and the discussion on the possible change in the CDW pattern that affects the superconductivity merits a timely publication in Nature Communications. I recommend that the authors consider the following minor comments before publication. + +1) The resistivity anomalies at the CDW transition temperature look different between low and high pressure regions. The temperature derivative shown in Fig.1b shows a peak structure below P1, but it shows a dip above 1.3 GPa. Can the author discuss the origin of such a change? + +2) The authors mention on the filamentary-like superconductivity in the pressure region between P1 and P2 from the width of superconducting transition. However, it would be more informative if the authors show the transition in fields. + +3) The relationship between superconductivity and the quasiparticle mass is also an important point. Can the authors comment on how the effective mass changes with pressure from the temperature dependence of quantum oscillations? + +Reviewer #3 (Remarks to the Author): + +The manuscript by Yu et al consolidates existing evidence of the evolution of the CDW and SC transitions in CsV3Sb5 with pressure and magnetic field. The present study compares electrical transport measurements on two different pressure experiments, PCC and DAC, and finds qualitatively similar albeit some quantitative differences in the critical parameters for the two. + +I have to state upfront that I find little new physics that the current study adds, to warrant publication in Nature Communications: CDW and SC in this and related compounds have already been reported (refs 15 and 21 particularly refer to the Cs compound, while refs 14- 21 all are reports on AV3Sb5 compounds and their transport properties). I will refer to some more specific points below, but I cannot recommend this study (or even a revised version of it) for publication in Nature Communications. + +I have a problem with the existing literature and the evidence of bulk SC in CsV3Sb5: in both refs 15 and 21, attempts are made to use thermodynamic measurements to demonstrate that the \(\sim 2K\) transition is bulk SC. However, the jump in specific heat deltaC/gamma T (fig. 2f in ref 15) is only \(\sim 5 / 40\) , far from a convincing 1.4 value for BCS. If not BCS, there is little to now discussion for the reason for the minute specific heat jump to prove bulk SC. One should be aware of possible secondary phases that can result in the small SC signal: V can show SC in a wide T range (1.8 - 6 K at ambient and applied pressure), CsV (+1.5 K), Sb (2.6 - 3.4 K), Sb0.01_0.03V0.99_0.97 (2.6- 3.7 K) can all show SC. (Roberts, J. Phys. Chem. Ref. Data, 5, 581 (1976)) + +While previous reports may demonstrate the CDW transition around 90 K, the present study makes little reference to that evidence. In this paper, the authors show only resistivity data, and the + +<--- Page Split ---> + +respective derivatives. The small feature only visible in dr/dT (and not r(T) itself) can be due to small structural distortions, not necessarily accompanied by charge order (CDW). Therefore any discussion of transport data must refer to any existing proof that this is indeed a CDW transition. + +To the point of unusual competition between SC and CDW in this compound, I can maybe see a qualitative change in the sharpness of the low T transition in S1 (Fig. 1a). But what the authors call P1 = 0.7 GPa and P2 - 2 GPa as the critical pressure values where the transition changes from sharp to broad and back, these values are not rigurously justified. How broad is broad, and what is a "sharp" transition? (delta T = ?) If I looked only at Fig. 1a, I would say the transition is broader for P = 1.06 - 1.3 GPa, but sharper otherwise. + +if there is indeed a double transition at P1 and P2 that should be discerned in the phase diagram, the authors must show a more detailed analysis and discuss the physical origin once the two are proven intrinsic to their sample, and not a result of twinning, or secondary phase. + +<--- Page Split ---> + +In the present manuscript, the authors report an unconventional two- dome like dependence of superconducting \(T_{c}\) in \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) on pressure, concomitant with the suppression of the CDW temperture \(T^{*}\) , with a significant broadening of the superconductive transition in between the domes. The authors attribute this behavior to the presence of a Lifschitz transition caused by the formation of domains close to a near commensurate- commensurate CDW transition. + +While these observations certainly add an interesting chapter to the rapidly unfolding \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) story, I find the analysis presented in the paper to be insufficient to reach the presented conclusions. In particular, the Lifschitz transition is inferred from the change of frequencies in SdH oscillations with pressure; however, the amplitude of the oscillations is strongly suppressed at the relevant pressure and some of the oscillations could be simply not resolved. Moreover, (see below), no characteristic change in SdH frequencies is demonstrated close to the supposed Lifshitz transition. The broadening of the resistive transition is attributed to the filamentary superconductivity, however, the broadening may also be present due to pressure inhomogeneity and, moreover, no comparison with the Meissner effect is given, which is important for reaching this conclusion unambiguously. Finally, the possibility of NCCCDW- CCDW transition is based on a weak anomaly that \(T^{*}\) shows around pressure P1. If present, this transition should exist over a range of temperatures, which is not demonstrated. Thus, all of the main points of the Authors' interpretation require further analysis and argumentation. Additionally, no quantitative fitting/analysis of the SdH oscillations or the magnetoresistance data is given, and the linear extrapolation used (without explanation) for \(H_{c2}(T)\) is in clear contrast to the actual data that is noticeably nonlinear. + +Therefore, I believe a strongly improved data analysis (see suggestions below) is necessary before the manuscript can be considered for publication in Nature Communications. Below I provide the particular points that the Authors, in my opinion, should address: + +(1) The shape of the anomaly of \(d\rho /dT\) at \(T^{*}\) (Fig. 1) clearly changes as a function of pressure - from a broad peak to sharp peak to a dip. This behavior should be studied systematically (e.g. by fitting the anomaly shape) and explained in connection to the other results. + +(2) The reduction of RRR between P1 and P2 is interpreted as being due to an enhanced scattering rate. However, (1) \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) has several bands [PRL 125, 247002 (2020)]; as the respective Fermi energies may depend on pressure without changing the total charge, this may also lead to the observed enhancement of RRR, if the scattering rates for different bands are different. (1a) This is further exacerbated by the author's claim of a Lifshitz transition which implies a strong reduction in + +<--- Page Split ---> + +carrier density of one of the bands. Moreover, (2) a mass enhancement near a CDW end point is in principle possible if it is a quantum critical point [see, e.g., J. Phys.: Condens. Matter 13 R723 (2001)] - this will also affect RRR. These scenarios should all be addressed - see a suggestion based on SdH oscillations below. Another option is to measure the Hall resistance and fit \(\rho (T)\) and Hall data together with a multiband model. + +(3) Apart from RRR and \(\rho_{0}\) an analysis of the pressure evolution of \(\rho (T)\) is needed: does the system show a Fermi liquid-like behavior (at least for low T) \(\rho (T) \sim \rho_{0} + AT^{2}\) everywhere in the phase diagram? How does the functional form of \(\rho (T)\) change with pressure? + +(4) Analysis of the MR data should be performed. The linear MR at low pressures may arise due to linear band crossings [Phys. Rev. B 58, 2788 (1998)], indeed present in CsV3Sb5 (Dirac points, see PRL 125, 247002 (2020)) although other explanations [PRL 117,256601 (2016) and refs therein], possibly related to CDW [PNAS June 4, 2019 116 (23) 11201-11206] are also possible. Additionally, the shape change between 1.93 and 2.06 GPa is quite dramatic, while not seen at 9T (Fig. 3c). One possible reason is that the onset of CDW below P2 leads to a reconstruction of the Fermi Surface - evidence for this scenario must come from SdH or Hall effect measurements. + +As for the kink around P1 Fig. 3c, to claim a relation between it and CDW a temperature-dependent MR should be presented - there may be something else occuring between 300 K and low-temperature regime. + +(5) The claim of a Lifshitz transition is based on the disappearance of some of the peaks in the Fourier spectra of SdH oscillations, Figure S3c. However, no further analysis of SdH oscillations is performed. First, the dependence of the oscillation frequencies on pressure is not reported. In the vicinity of a Lifshitz transition, the corresponding frequencies should be strongly pressure-dependent [for an unrelated example see e.g., Phys. Rev. Lett. 115, 186403 (2015) or npj Quant Mater 4, 2 (2019)]; in contrast to that, no change in frequencies (especially the ones that disappear at 0.75 GPa) is observed between 0 GPa and 0.36 GPa. + +Second, the amplitude of the oscillations contains important information about the scattering rates (via the Dingle factor \(\delta R \sim e^{-\pi /(\omega_{c}\tau)})\) and effective masses of the bands (via the Lifshitz-Kosevich temperature dependence). The latter may potentially reveal the mass enhancement near the CDW end point. + +In particular, an enhanced scattering rate may simply suppress the oscillations making them barely visible at 0.75 GPa without a Lifshitz transition. Indeed, a strong overall peak height suppression is seen at 0.75 GPa. On the other hand, between 0 GPa and 0.36 GPa, the peak at 30 T seems strongly enhanced, while \(\rho_{0}\) (Fig. 4b) monotonically grows. These trends should be analyzed (suggestion above) + +<--- Page Split ---> + +and discussed. + +(6) The broadening of the resistive transition between P1 and P2 is attributed to filamentary-like superconductivity. However, there are other possible explanations of this behavior. First, given the strong \(T_{c}(P)\) dependence any inhomogeneity of pressure in the sample would lead to a broadening of the transition. The authors should provide estimates of such inhomogeneity in their experiment to rule this effect out. Indeed, transition broadening under strain has been reported in Sr2RuO4 and attributed to extrinsic effects (Science 13 Jan 2017 Vol. 355, Issue 6321, eaaf9398). Additionally, the enhanced \(\rho_{0}\) may suggest an enhanced role of disorder that can affect the transition of an unconventional superconductor. + +A direct evidence of filamentary nature would have been a separation between the resistive \(T_{c}^{zero}\) and the onset of Meissner effect (see Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25- 44, for example) - the authors should provide that to prove their claim. + +(7) The determination of \(H_{c2}(0)\) by a linear extrapolation is clearly in conflict with the data: for all pressures in Fig. 2c,d one observes a noticeably nonlinear \(H_{c2}(T)\) behavior, especially pronounced near 0.72 and 0.84 GPa - the linear fit misses there all but two points. A better motivated description of the data should be used; one can start for example with WHH formula [Phys. Rev. 147, 295 (1966)] or its multiband extensions [A. Gurevich, Phys. Rev. B 82, 184504 (2010), Physica C 456 (2007) 160-169]. The convex shape of \(H_{c2}(T)\) suggests that a single-band model would not be enough. + +(8) The existence of some kind of (possibly CCDW-NCCDW) transition with pressure is proposed in the paper on the basis of \(T^{*}\) showing a weak anomaly around P1. However, this anomaly is not clearly visible in Fig. 3 - the authors should provide additional analysis close to that point to prove the existence of such anomaly. + +Furthermore, the proposed CCDW-NCCDW transition as a function of pressure should be a whole line in the phase diagram of Fig. 3a; the consequence of this would be additional anomalies in \(\rho (T)\) dependence (unless the critical pressure is completely independent of temperature) - see e.g., Phys. Rev. Lett. 81, 453 (1998), Scientific Reports volume 6, Article number: 24068 (2016). Are such anomalies observed? + +(9) Two more related preprints on superconductivity in \(\mathrm{CsV_3Sb_5}\) under pressure have recently appeared: arXiv:2103.12507 and arXiv:2103.13759. The latter may be of particular interest for comparison, as pressure-dependent DFT calculations (and the resulting Fermi surfaces) are reported there. + +Minor points: + +- Fig. 2 c and d: Is \(T_{c}\) on the horizontal axis a typo -should it be simply \(T\) ? I suggest to show \(H_{c2}(T)\) vs. \(T\) plots if this is not the case. + +<--- Page Split ---> + +- An enhanced competition between CDW and superconductivity is suggested to exist between P1 and P2. However, \(T^{*}\) monotonically decreases with P in this region, while \(T_{c}\) is nonmonotonic - for two competing states one would expect \(T_{c}\) to monotonically grow instead. Thus this statement seems to contradict the data. + +- The data obtained for 1.5 GPa with DAC Fig. 3b yields a noticeably larger \(T_{C}^{onset}\) than the one measured with PCC. The authors should comment on this discrepancy - this may suggest that the broadening is sample-dependent and hence extrinsic. + +- Comparison with \(\mathrm{La}_{2 - x}\mathrm{Ba}_{x}\mathrm{CuO4}\) is not very accurate, since the stripe order is the strongest in region of suppressed \(T_{c}\), unlike \(T^{*}\) in the current study. + +- What are the error bars for points in Figs 2c,d; 3 and 4? + +Wording/Typos: + +p.4 "...that two peaks locate at P1 and P2..." \(\rightarrow\) "...that two peaks are located at P1 and P2..." + +"...transition width of \(\Delta \mathrm{Tc}...\) " \(\rightarrow\) "...transition width \(\Delta \mathrm{Tc}...\) " + +(multiple places) "...sudden drops..." \(\rightarrow\) "...suddenly drops..." + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors of this manuscript report on the observation of pressure induced changes in the superconductivity of a newly discovered kagome metal, CsV3Sb5. The central claim is that pressure initially enhances the superconducting transition temperature while simultaneously suppressing the charge density wave order in this compound; however beyond this initial enhancement, they observe an unconventional suppression of Tc followed by a second enhancement, prior to being suppressed entirely at higher pressures. The result is a double superconducting "dome" in the pressure- driven superconducting phase diagram of this material. + +The key observation of the double- dome- type behavior suggests an unconventional superconducting ground state and the authors claim supporting evidence for a Lifshitz transition underpinning this behavior. The observation of weak, filamentary superconductivity at intermediate pressures is used to further support this conjecture. Overall, the topic and central claims of the paper are of sufficient novelty and broad community interest to merit consideration in Nature Communications. + +There are, however, a few central claims and issues with the manuscript that preclude recommendation for publication in Nature Communications in its current form. I list these below. + +(1) There have been several recent reports depicting a qualitatively different picture of the pressure-driven phase diagram in this class of kagome metals. For instance arXiv:2103.13759 which shows an extended high-pressure dome in CsV3Sb5 and arXiv:2102.10959 for a single dome in KV3Sb5. A similar double dome is noted in this paper as also being observed in CsV3Sb5 in arXiv:2102.09328. Can the authors provide analysis which can preclude extrinsic or disorder-driven effects in their present observation of a two-peak superconducting dome? I think this will be important for the paper and the field. + +Reply: We thank the reviewer for pointing out this issue. In arXiv: 2103.13759, they only used the DAC to generate the pressure. The pressure inhomogeneity is relatively large and pressure cannot be precisely controlled with DAC. For this reason, they do not observe the double dome behavior. While for KV3Sb5, it is exhibits both lower T\* and Tc comparing with CsV3Sb5 at ambient pressure. Therefore, the high-pressure phase diagram may be different due to the sample difference. + +Pressure inhomogeneity or pressure induced disorder in the sample may make the superconducting transition broad. However, the two- peak superconducting dome reported in our paper cannot origin from these extrinsic effects for the following reasons. These extrinsic effects become more prominent with increasing the pressure. Actually, the pressure inhomogeneity in PCC is rather small. In our case, with the pressure at P2 with PCC, the superconducting transition is very sharp ( \(\sim 0.2\mathrm{K}\) ). Therefore, such extrinsic effect is negligible in our experiments and the broadening of the superconducting transition between P1 and P2 could not origin from these extrinsic origins. We added the related discussion in the revised manuscript. + +(2) The conjecture of a Lifshitz transition is not immediately obvious from the quantum oscillation data in the supplementary material. The oscillations are seemingly rapidly damped, which is potentially due to pressure-induced disorder/damping effects. The frequency shifts observed prior to + +<--- Page Split ---> + +their disappearance are not immediately indicative of a Lifshitz transition to this referee. This claim should either be modified or better justified within the text. + +Reply: We thank the reviewer for pointing out this problem. We agree with the reviewer that the rapidly damping above P1 cannot support the conclusion of Lifshitz transition. Instead, it can be related to the enhanced scattering rate above P1, consistent with the sudden increment of the residual resistivity. we modified this claim in the revised manuscript. However, the sudden change of residual resistivity, MR behavior and quantum oscillation support the conclusion of a new CDW state above P1. + +Minor comments: + +(3) The paper use some editorial review correcting minor typos/grammar issues throughout. + +Reply: We corrected typos/grammar issues in the revised manuscript. + +(4) In Fig. 1, correlating colors between plots in the extended and zoomed-in T ranges would be helpful for the reader. It is a little confusing to trace the CDW and SC transitions in the current presentation at fixed pressure values. + +Reply: We use the same colors between plots in the extended and zoomed-in T ranges in Fig.1 as the reviewer suggested. + +In summary, I believe the manuscript has the potential of presenting a finding of sufficient interest and novelty for Nature Communications, but these points/deficiencies must be satisfactorily addressed first. In particular if points (1) and (2) can be addressed, then the paper would be a valuable addition to a seemingly quickly growing field. + +Reviewer #2 (Remarks to the Author): + +This is a very interesting paper reporting the pressure phase diagram in the CsV3Sb5 superconductor with kagome lattice. The authors find a double- peak structure in the superconducting transition temperature \(T_{- }c\) as a function of pressure. The second peak at P2 corresponds to the end point of charge density wave (CDW) order, which can be similarly found in other superconductors with CDW. What is novel here is the observation of the first peak at P1, which is deep inside the CDW phase. To discuss the origin of this unusual peak inside the CDW phase, the authors performed magnetotransport measurements from which they find rapid changes in the Shubnikov- de Haas oscillations and the magnitude of magnetoresistance near P1. I find that these observations are intriguing and the discussion on the possible change in the CDW pattern that affects the superconductivity merits a timely publication in Nature Communications. I recommend that the authors consider the following minor comments before publication. + +1) The resistivity anomalies at the CDW transition temperature look different between low and high + +<--- Page Split ---> + +pressure regions. The temperature derivative shown in Fig.1b shows a peak structure below P1, but it shows a dip above 1.3 GPa. Can the author discuss the origin of such a change? Reply: We thank the referee for pointing out this issue. The derivative curve shows a peak- dip behavior (for example, see 0.95GPa) above P1. Further increasing the pressure, the peak becomes much weaker (but still exist) and the dip becomes more pronounced. The resistivity anomaly is associated to the change for the band structure and electron scattering rate in the CDW state. The change of the shape of \(d\rho_{\mathrm{xv}} / dT\) anomaly indicates the possibly change of the CDW state Such behavior is consistent with sudden change of MR and residual resistivity above P1. We added the related discussion in the revised manuscript. + +2) The authors mention on the filamentary-like superconductivity in the pressure region between P1 and P2 from the width of superconducting transition. However, it would be more informative if the authors show the transition in fields. + +Reply: We have added a figure (Supplementary Fig.3, we also show below for convenience) in the supplementary information to show the superconducting transition in different fields with pressure between P1 and P2. We also performed the high-pressure magnetic susceptibility measurements (Supplementary Fig.2) to support our conclusions. With the pressure around P1, the superconducting volume fraction suddenly decreases. Further increasing the pressure, the bulk superconductivity \(T_{c}^{M2}\) emerges below 4 K around 1.1 GPa, but the magnetic susceptibility shows a weak reduction at \(T_{c}^{M1}\) with higher temperature, indicating a filamentary superconductivity at higher temperature, consistent with our resistivity measurements. + +![PLACEHOLDER_9_0] + + +3) The relationship between superconductivity and the quasiparticle mass is also an important point. Can the authors comment on how the effective mass changes with pressure from the temperature dependence of quantum oscillations? + +<--- Page Split ---> + +Reply: We extract the effective mass with pressure at 0.36 GPa as shown in Supplementary Fig.7. The extracted effective mass for F1 and F2 orbitals does not change much with pressure. We added related descriptions in the revised manuscript. However, we should point out that it is a multiband system. The evolution of the effective mass for the other Fermi pockets, especially the large Fermi pockets around Γ and K points cannot be determined in our experiments. + +Reviewer #3 (Remarks to the Author): + +The manuscript by Yu et al consolidates existing evidence of the evolution of the CDW and SC transitions in CsV3Sb5 with pressure and magnetic field. The present study compares electrical transport measurements on two different pressure experiments, PCC and DAC, and finds qualitatively similar albeit some quantitative differences in the critical parameters for the two. + +I have to state upfront that I find little new physics that the current study adds, to warrant publication in Nature Communications: CDW and SC in this and related compounds have already been reported (refs 15 and 21 particularly refer to the Cs compound, while refs 14- 21 all are reports on AV3Sb5 compounds and their transport properties). I will refer to some more specific points below, but I cannot recommend this study (or even a revised version of it) for publication in Nature Communications. + +Reply: We thank the reviewer's careful review. However, we cannot agree with the reviewer's comments that our paper adds little new physics to the current study. Although SC and CDW is already reported in CsV3Sb5, the interplay of SC and CDW is still unknown before our work. Usually, the suppression of CDW order by doping or pressure always enhances superconductivity and leads to a dome- like behavior for superconductivity in most of CDW materials with superconductivity. To our surprise, we find an unusual competition of CDW and SC under pressure. The Tc shows intriguing two- peak behavior which is never observed in the other CDW materials. Such behavior is possibly due to the formation of a new CDW order at high pressure, which have stronger competition with SC. Our discoveries indicate the unconventional interplay of CDW and SC in CsV3Sb5, which would stimulate broad interests on the study of the correlation between CDW and SC in many unconventional superconductors, such as cuprate superconductors. + +I have a problem with the existing literature and the evidence of bulk SC in CsV3Sb5: in both refs 15 and 21, attempts are made to use thermodynamic measurements to demonstrate that the \(\sim 2K\) transition is bulk SC. However, the jump in specific heat deltaC/gamma T (fig. 2f in ref 15) is only \(\sim 5 / 40\) , far from a convincing 1.4 value for BCS. If not BCS, there is little to now discussion for the reason for the minute specific heat jump to prove bulk SC. One should be aware of possible secondary phases that can result in the small SC signal: V can show SC in a wide T range (1.8 - 6 K at ambient and applied pressure), CsV (+1.5 K), Sb (2.6 - 3.4 K), Sb0.01_0.03V0.99_0.97 (2.6- 3.7 K) can all show SC. (Roberts, J. Phys. Chem. Ref. Data, 5, 581 (1976)) + +Reply: Although the mechanism of superconductivity in this material is still not well understood, a bulk superconducting state in CsV3Sb5 is already confirmed by different techniques, including magnetic susceptibility, heat capacity, thermal conductivity, STM and so on. Actually, we used the + +<--- Page Split ---> + +same batch of samples with arxiv: 2102.10987, arxiv:2103.04760 and arxiv: 2103.11796. In arxiv: 2103.11796, the heat capacity can be well fitted by using the two s- wave model and the bulk superconductivity is confirmed. In arxiv:2103.04760, superconducting gap is observed by STM, directly proves that the SC is from \(\mathsf{CsV}_3\mathsf{Sb}_5\) rather than the secondary phases. In addition, no impurity phases can be detected from the x- ray diffraction measurements (arxiv: 2102.10987). Our high- pressure susceptibility measurements also confirm the bulk superconductivity in our sample and exclude the possibility of the secondary phases. + +While previous reports may demonstrate the CDW transition around \(90~\mathsf{K}\) , the present study makes little reference to that evidence. In this paper, the authors show only resistivity data, and the respective derivatives. The small feature only visible in \(\mathrm{dr / dT}\) (and not \(\mathrm{r(T)}\) itself) can be due to small structural distortions, not necessarily accompanied by charge order (CDW). Therefore any discussion of transport data must refer to any existing proof that this is indeed a CDW transition. Reply: The anomaly of the resistivity is already confirmed to be associated with the CDW temperature at ambient pressure. We added the related references in the revised manuscript. The CDW transition is already confirmed by the STM and x- ray scattering measurements (arxiv: 2103.04760 and arxiv: 2103.09769). By increasing the pressure, \(\mathsf{T}^*\) determined by the anomaly of \(d\rho_{\mathrm{xx}} / dT\) smoothly changes with the pressure. Thus, it is a natural inference that such an anomaly should related to the CDW transition rather than the other small structural distortions. In addition, our cooperators also confirm the CDW transition at 1.8 GPa from the high- pressure NMR measurements which will be published elsewhere. For the above reasons, \(\mathsf{T}^*\) can be associated to the anomaly of \(d\rho_{\mathrm{xx}} / dT\) curves. + +To the point of unusual competition between SC and CDW in this compound, I can maybe see a qualitative change in the sharpness of the low T transition in S1 (Fig. 1a). But what the authors call P1 \(= 0.7\) GPa and P2 - 2 GPa as the critical pressure values where the transition changes from sharp to broad and back, these values are not rigurously justified. How broad is broad, and what is a "sharp" transition? (delta \(\mathsf{T} = ?\) ) If I looked only at Fig. 1a, I would say the transition is broader for \(\mathsf{P} = 1.06\) - 1.3 GPa, but sharper otherwise. + +Reply: The superconducting transition width \(\Delta \mathsf{Tc}\) is shown in Fig.4a. We can clearly see a larger \(\Delta \mathsf{Tc}\) between P1 and P2. Our high- pressure susceptibility measurements indicate filamentary superconductivity in this pressure range. Besides large \(\Delta \mathsf{Tc}\) in this region, MR and the residual resistivity also show sudden changes at P1 and P2. In addition, the SdH QOs damp rapidly above P1. For all the above reasons, P1 and P2 are the critical pressure values. + +if there is indeed a double transition at P1 and P2 that should be discerned in the phase diagram, the authors must show a more detailed analysis and discuss the physical origin once the two are proven intrinsic to their sample, and not a result of twinning, or secondary phase. + +Reply: Our single crystals are pure and the superconductivity could not be related to the secondary phase as already testified by the other experimental methods in the other papers (arxiv: 2102.10987, arxiv:2103.04760 and arxiv: 2103.11796. ). The pressure inhomogeneity become more pronounced with increasing the pressure. In our experiment, the pressure inhomogeneity of the PCC cell is small as evidenced by the sharp SC transition at \(\mathsf{P2}(\sim 0.2\mathsf{K})\) . Thus, the broadening of the superconducting + +<--- Page Split ---> + +transition and the double transition at P1 and P2 could not due the extrinsic effects. The origin of the Tc peak at P1 can be attributed to the emergence of a new CDW state which has much stronger competition with SC. We propose the possible CCDW to NCCDW transition at P1. We added the related discussion in the revised manuscript. + +Reviewer #4 (Remarks to the Authors): + +In the present manuscript, the authors report an unconventional two- dome like dependence of superconducting \(T_{C}\) in CsV3Sb5 on pressure, concomitant with the suppression of the CDW temperture \(T*\) , with a significant broadening of the superconductive transition in between the domes. The authors attribute this behavior to the presence of a Lifschitz transition caused by the formation of domains close to a near commensurate- commensurate CDW transition. + +While these observations certainly add an interesting chapter to the rapidly unfolding CsV3Sb5 story, I find the analysis presented in the paper to be insufficient to reach the presented conclusions. In particular, the Lifschitz transition is inferred from the change of frequencies in SdH oscillations with pressure; however, the amplitude of the oscillations is strongly suppressed at the relevant pressure and some of the oscillations could be simply not resolved. Moreover, (see below), no characteristic change in SdH frequencies is demonstrated close to the supposed Lifshitz transition. The broadening of the resistive transition is attributed to the filamentary superconductivity, however, the broadening may also be present due to pressure inhomogeneity and, moreover, no comparison with the Meissner effect is given, which is important for reaching this conclusion unambiguously. Finally, the possibility of NCCCDW- CCDW transition is based on a weak anomaly that \(T*\) shows around pressure P1. If present, this transition should exist over a range of temperatures, which is not demonstrated. Thus, all of the main points of the Authors' interpretation require further analysis and argumentation. Additionally, no quantitative fitting/analysis of the SdH oscillations or the magnetoresistance data is given, and the linear extrapolation used (without explanation) for \(Hc2(T)\) is in clear contrast to the actual data that is noticeably nonlinear. + +Therefore, I believe a strongly improved data analysis (see suggestions below) is necessary before the manuscript can be considered for publication in Nature Communications. Below I provide the particular points that the Authors, in my opinion, should address: + +(1) The shape of the anomaly of \(dp/dT\) at \(T*\) (Fig. 1) clearly changes as a function of pressure - from a broad peak to sharp peak to a dip. This behavior should be studied systematically (e.g. by fitting the anomaly shape) and explained in connection to the other results. + +Reply: We thank the reviewer's great suggestion. We added the related discussion in the revised manuscript. The shape of the anomaly of \(dp_{\infty} / dT\) at \(T*\) gradually evolves from the broad peak to peak- dip behavior around P1. Further increasing the pressure, the peak becomes much weaker and the dip becomes much pronounced. The resistivity is strongly connected with band structure and electron scattering. The sudden enhancement of residual resistivity and rapidly damping of QOs indicate the enhancement of the scattering rate (possible for some bands), which would naturally lead to the change of the \(dp_{\infty} / dT\) behavior. The change of the shape of \(dp_{\infty} / dT\) anomaly at \(T*\) can be also related to the evolution to a new CDW state, possibly from CCDW to NCCDW. + +<--- Page Split ---> + +(2) The reduction of RRR between P1 and P2 is interpreted as being due to an enhanced scattering rate. However, (1) CsV3Sb5 has several bands [PRL 125, 247002 (2020)]; as the respective Fermi energies may depend on pressure without changing the total charge, this may also lead to the observed enhancement of RRR, if the scattering rates for different bands are different. (1a) This is further exacerbated by the author's claim of a Lifshitz transition which implies a strong reduction in carrier density of one of the bands. Moreover, (2) a mass enhancement near a CDW end point is in principle possible if it is a quantum critical point [see, e.g., J. Phys.: Condens. Matter 13 R723 (2001)] - this will also affect RRR. These scenarios should all be addressed - see a suggestion based on SdH oscillations below. Another option is to measure the Hall resistance and fit \(\rho (T)\) and Hall data together with a multiband model. + +Reply: We agree with the referee that the RRR may change depends on the respective Fermi energies of different bands. Actually, the band structure of \(\mathrm{CsV_3Sb_5}\) is rather complicated, there are many bands at the Fermi energy. The dependence of each band under pressure is very important but out of the scope of our current work. Actually, the four frequencies resolved from the SdH oscillations only contribute less than \(1\%\) of the whole area of Brillouin zone. The large electron Fermi pockets around \(\Gamma\) and K points cannot be resolved in the SdH oscillations. For these reasons, we can not specify the explicit origins of RRR change under pressure. From the QO measurements, the rapidly damping of the QOs above P1 indicates the enhanced scattering rate for the four resolved frequencies. But we cannot figure out the change of the other bands above P1 from the current measurements. + +The quantum critical point near the CDW end point is an interesting topic, we checked our data and analyses the \(\rho (T)\) at low temperature to check the possibility of quantum critical point in the revised manuscript. Since \(\rho (T)\) follows \(T^2\) behavior and \(\rho_0\) is small at P2 as shown in Supplementary Fig.8. Thus, our data does not support the quantum criticality at the CDW end point. Since we cannot detect any QOs around P2, thus the effect mass could not be obtained from the QOs. The square of effective mass is proportional to the parameter A (which can be obtained from the \(\rho (T) \sim \rho_0 + AT^2\) fitting). We can clearly see the slope of the \(\rho_{xx}\) vs. \(T^2\) curves nearly does not change around P2 shown in Supplementary Fig.8. Therefore, our data does not support for the mass enhancement around P2. However, we should also point out that ultralow- temperature measurements are still needed to check the existence of quantum criticality in the lower temperature region. We added the related discussion in the revised manuscript. + +(3) Apart from RRR and \(\rho 0\) an analysis of the pressure evolution of \(\rho (T)\) is needed: does the system show a Fermi liquid-like behavior (at least for low T) \(\rho (T) \sim \rho_0 + AT^2\) everywhere in the phase diagram? How does the functional form of \(\rho (T)\) change with pressure? + +Reply: We thank referee's great suggestion. We analyses the \(\rho (T)\) at low temperature as shown in Supplementary Fig.8 (We also show the figure below for convenience). Below P1, \(\rho (T)\) does not follow the \(T^2\) well, however, with pressure at P2, \(\rho (T)\) follows \(T^2\) behavior indicating the Fermi liquid nature. In addition, the residual resistivity is small at P2, therefore, our data does not support the quantum criticality at the CDW end point. However, we should also point out that ultralow- temperature measurements are still needed to check the existence of quantum criticality at lower temperature in the future studies. The related description is added in the revised manuscript. + +<--- Page Split ---> +![PLACEHOLDER_14_0] + + +(4) Analysis of the MR data should be performed. The linear MR at low pressures may arise due to linear band crossings [Phys. Rev. B 58, 2788 (1998)], indeed present in CsV3Sb5 (Dirac points, see PRL 125, 247002 (2020)) although other explanations [PRL 117,256601 (2016) and refs therein], possibly related to CDW [PNAS June 4, 2019 116 (23) 11201-11206] are also possible. Additionally, the shape change between 1:93 and 2:06 GPa is quite dramatic, while not seen at 9T (Fig. 3c). One possible reason is that the onset of CDW below P2 leads to a reconstruction of the Fermi Surface - evidence for this scenario must come from SdH or Hall effect measurements. As for the kink around P1 Fig. 3c, to claim a relation between it and CDW a temperature-dependent MR should be presented - there may be something else occurring between 300 K and low-temperature regime. + +Reply: We thank the reviewer's great suggestions. The electronic structure and electron scattering may be quite different in the different pressure regions, which lead to the different MR behavior and RRR. We add the related discussion of the MR data in the revised manuscript. The linear MR at the low field region below P2 can possibly arise from the linear band crossings or/and CDW state. We also added a figure (Supplementary Fig.5, also shown below for convenience) to show the temperature- dependent MR at 1.02 GPa for sample 4 with PCC. The \(\mathrm{T}^*\) is suppressed to 49K. We can clearly see that the shape of MR sudden changes around \(\mathrm{T}^*\) , similar with shape change between 1.93 and 2.06 GPa shown in Supplementary Fig.4. These results confirm the low- field linear MR is related to the CDW state. It is possible that a reconstruction of the Fermi Surface may occur in the CDW state. In principle, SdH or Hall effect measurements may give some indication. However, in our case, SdH can be only observed at low temperature and pressure, we cannot extract any QOs across the CDW transition. While for Hall measurements, we can see the carrier density slightly changes around \(\mathrm{T}^*\) (arxiv: 2102.10987), but cannot prove the Fermi surface reconstruction even at ambient pressure. The Hall resistivity at low temperature becomes very complicated since it is a multiband system and anomalous Hall effect becomes more pronounced. It is still a challenge to understand its Hall effect right now. For these reasons, we cannot give any conclusion of Fermi surface reconstruction at \(\mathrm{T}^*\) from the current measurements. + +<--- Page Split ---> +![PLACEHOLDER_15_0] + + +(5) The claim of a Lifshitz transition is based on the disappearance of some of the peaks in the Fourier spectra of SdH oscillations, Figure S3c. However, no further analysis of SdH oscillations is performed. First, the dependence of the oscillation frequencies on pressure is not reported. In the vicinity of a Lifshitz transition, the corresponding frequencies should be strongly pressure-dependent [for an unrelated example see e.g., Phys. Rev. Lett. 115, 186403 (2015) or npj Quant Mater 4, 2 (2019)]; in contrast to that, no change in frequencies (especially the ones that disappear at 0.75 GPa) is observed between 0 GPa and 0.36 GPa. Second, the amplitude of the oscillations contains important information about the scattering rates (via the Dingle factor \(\delta R \sim e^{-\pi /(\omega \tau)}\) ) and effective masses of the bands (via the Lifshitz-Kosevich temperature dependence). The latter may potentially reveal the mass enhancement near the CDW end point. In particular, an enhanced scattering rate may simply suppress the oscillations making them barely visible at 0.75 GPa without a Lifshitz transition. Indeed, a strong overall peak height suppression is seen at 0.75 GPa. On the other hand, between 0 GPa and 0.36 GPa, the peak at 30 T seems strongly enhanced, while \(\rho 0\) (Fig. 4b) monotonically grows. These trends should be analyzed (suggestion above) and discussed. + +Reply: We thank reviewer's great suggestions. We agree with the reviewer that the current data cannot support the Lifshitz transition. Therefore, we modified our description of the Lifshitz transition in the revised manuscript. As the reviewer point out that the enhanced scattering rate can also suppress the oscillations without a Lifshitz transition, the rapid damping of the QOs can be attributed to the enhanced scattering rate for the 4 orbitals observed in our QOs which is consistent with the sudden enhancement of residual resistivity above P1. The QOs damping rapidly above P1. Therefore, we cannot extract the information from QOs near the CDW end point. + +We added more discussions about the SdH oscillations in the revised manuscript. We analyzed the SdH oscillations at 0.36GPa at different temperatures to extract the effect mass as shown in Supplementary Fig.7. We found the effect mass does not change much comparing with that at ambient pressure. We also analyzed the enhancement of amplitude for the 26 and 72T orbitals at 0.36 GPa in the revised manuscript. The amplitude of the QOs depends on thermal damping factor \(\mathsf{R}_{\mathsf{T}}\) and Dingle damping factor \(\mathsf{R}_{\mathsf{D}}\) . Since the effect mass does not change much at 0.36 GPa, the enhancement of amplitude can be attributed to the reduction of the scattering rate for the two bands. + +(6) The broadening of the resistive transition between P1 and P2 is attributed to filamentary-like superconductivity. However, there are other possible explanations of this behavior. First, given the strong \(T_{C}(P)\) dependence any inhomogeneity of pressure in the sample would lead to a broadening of + +<--- Page Split ---> + +the transition. The authors should provide estimates of such inhomogeneity in their experiment to rule this effect out. Indeed, transition broadening under strain has been reported in Sr2RuO4 and attributed to extrinsic effects (Science 13 Jan 2017 Vol. 355, Issue 6321, eaaf9398). Additionally, the enhanced \(\rho 0\) may suggest an enhanced role of disorder that can affect the transition of an unconventional superconductor. A direct evidence of filamentary nature would have been a separation between the resistive Tzero and the onset of Meissner effect (see Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25[44, for example) - the authors should provide that to prove their claim. + +Reply: The pressure inhomogeneity is a common problem in the high- pressure experiment. It is usually negligible in the PCC by using the liquid pressure medium. The pressure inhomogeneity increases with increasing the pressure, especially when the liquid pressure medium become solidified under pressure. In our case, the superconducting transition is very sharp ( \(\sim 0.2 \text{K}\) ) at P2 with PCC, which indicates the pressure inhomogeneity is negligible in our experiments. If we assume that the superconducting transition width totally comes from the pressure inhomogeneity (actually it is impossible in reality, but we can use this to give an estimation of upper limit of pressure inhomogeneity in PCC), the upper limit of pressure inhomogeneity can be estimated to be \(\sim 0.1 \text{GPa}\) around 2 GPa. Thus, the broadening of the superconducting transition between P1 and P2 cannot origin from the small pressure inhomogeneity. We added the related description in the revised manuscript. + +We performed the high- pressure magnetic susceptibility measurements as shown in Supplementary Fig.2 (We also show the figure below for convenience). The superconducting volume fraction suddenly decreases above P1. With pressure around 1.1GPa, two transitions can be observed. The bulk superconducting temperature \(T_{c1}^{M2}\) appears below 4 K, however, the magnetic susceptibility also shows a weak reduction at \(T_{c1}^{M2}\) which is much higher than \(T_{c1}^{M2}\) , representing the filamentary superconductivity, consistent with the resistivity measurements. The related description is added in the revised manuscript. + +![PLACEHOLDER_16_0] + + +(7) The determination of \(Hc2(0)\) by a linear extrapolation is clearly in conflict with the data: for all pressures in Fig. 2c,d one observes a noticeably nonlinear \(Hc2(T)\) behavior, especially pronounced near 0.72 and 0.84 GPa - the linear fit misses there all but two points. A better motivated description of the data should be used; one can start for example with WHH formula [Phys. Rev. 147, 295 (1966)] + +<--- Page Split ---> + +or its multiband extensions [A. Gurevich, Phys. Rev. B 82, 184504 (2010), Physica C 456 (2007) 160- 169]. The convex shape of \(Hc2(T)\) suggests that a single- band model would not be enough. + +Reply: We thank the reviewer for pointing out this problem. We totally agree with the reviewer that the convex shape of \(Hc2(T)\) suggests that a single- band model cannot describe the \(Hc2(T)\) behavior. Therefore, we used two- band model to fit the \(Hc2(T)\) in the revised manuscript. The nonlinear \(Hc2(T)\) behavior can be well fitted by using the two- band model. We can obtain \(Hc2(0)\) from the fitting of two- band model in the revised manuscript. + +(8) The existence of some kind of (possibly CCDW-NCCDW) transition with pressure is proposed in the paper on the basis of \(T*\) showing a weak anomaly around P1. However, this anomaly is not clearly visible in Fig. 3 - the authors should provide additional analysis close to that point to prove the existence of such anomaly. Furthermore, the proposed CCDW-NCCDW transition as a function of pressure should be a whole line in the phase diagram of Fig. 3a; the consequence of this would be additional anomalies in \(\rho (T)\) dependence (unless the critical pressure is completely independent of temperature) - see e.g., Phys. Rev. Lett. 81, 453 (1998), Scientific Reports volume 6, Article number: 24068 (2016). Are such anomalies observed? + +Reply: We added more discussion of the anomalies around P1. The RRR and MR shows a sudden change at P1. In addition, the SdH oscillations damping rapidly above \(\sim \mathsf{P1}\) . All these information indicate a transition around P1. From the current measurement we can hardly determine any anomalies from \(\rho (T)\) except the one around \(\mathsf{T}^*\) as shown in Fig.1. The domain walls may gradually emerge above P1, but it is not sensitive to the temperature in our case. Another possibility is that such transition may be rather broad, we cannot detect it in the resistivity measurement. In order to solve this problem, detailed high- pressure low- temperature x- ray diffraction measurements are highly required in the future experiment but not in our current work. For example, in compressed \(\mathsf{T}i\mathsf{Se}_2\) , x- ray diffraction measurements give a complex phase diagram (Nature Physics 10, 421- 425 (2014)) including the ICCDW and CCDW in the phase diagram. However, for the resistivity measurements, only one anomaly can be detected from the resistivity curves (Physical Review Letters 103, 236401 (2009).) + +(9) Two more related preprints on superconductivity in CsV3Sb5 under pressure have recently appeared: arXiv:2103.12507 and arXiv:2103.13759. The latter may be of particular interest for comparison, as pressure-dependent DFT calculations (and the resulting Fermi surfaces) are reported there. + +Reply: We thank the reviewer for providing these papers. In these papers, they focused on a new superconducting phase which emerges at much higher pressure(above\~15GPa). In our case, the most intriguing discovery was found with pressure below 2GPa. In addition, we are focusing on the unconventional competition of CDW and superconductivity in our paper. In the second superconducting phase reported in arXiv:2103.12507 and arXiv:2103.13759, the CDW order is absent and not taken into consideration in their DFT calculations. + +Minor points: + +<--- Page Split ---> + +- Fig. 2 c and d: Is \(T_c\) on the horizontal axis a typo - should it be simply \(T\) ? I suggest to show \(Hc2(T)\) vs. \(T\) plots if this is not the case. + +Reply: We thank the referee for pointing out this problem. We modified it in the revised manuscript. + +- An enhanced competition between CDW and superconductivity is suggested to exist between P1 and P2. However, \(T^*\) monotonically decreases with P in this region, while \(T_c\) is nonmonotonic - for two competing states one would expect \(T_c\) to monotonically grow instead. Thus this statement seems to contradict the data. + +Reply: The enhanced competition between CDW and superconductivity is referred to the region above P1 comparing with that below P1. The new CDW state appears above P1 which has stronger competition with superconductivity. We modified the description in the revised manuscript. + +- The data obtained for 1.5 GPa with DAC Fig. 3b yields a noticeably larger \(T_c^{\text{onset}}\) than the one measured with PCC. The authors should comment on this discrepancy - this may suggest that the broadening is sample-dependent and hence extrinsic. + +Reply: The pressure in DAC is determined at room temperature. The pressure in our DAC cell has \(\sim 5\%\) variation at low temperature. In addition, the pressure inhomogeneity in DAC is larger than that in PCC since we used solid pressure medium, which makes the superconducting transition slightly more broad comparing with that in PCC. However, the broadening of \(T_c\) within the P1 and P2 region is also obvious with DAC. Since the superconducting curve above P2 become sharp again which cannot be attributed to the pressure inhomogeneity effect. For these reasons, the observed broadening is intrinsic. + +- Comparison with La2-xBaxCuO4 is not very accurate, since the stripe order is the strongest in region of suppressed \(T_c\) , unlike \(T^*\) in the current study. + +Reply: We thank the reviewer for pointing out this issue. However, we should point out that the system may evolve to a new CDW state above P1, in which the new CDW state has strong competition with superconductivity, similar to the case in \(\mathrm{La}_{2 - x}\mathrm{Ba}_x\mathrm{CuO}_4\) . + +- What are the error bars for points in Figs 2c,d; 3 and 4? + +Reply: We added error bars in the revised manuscript. + +Wording/Typos: + +p.4 "...that two peaks locate at P1 and P2..." \(\rightarrow\) "...that two peaks are located at P1 and P2..." "...transition width of \(\Delta T_c\) ..." "...transition width \(\Delta T_c\) ..." (multiple places) "...sudden drops..." \(\rightarrow\) "...suddenly drops..." + +Reply: We thank the reviewer for pointing out these typos. We corrected the typos in the revised manuscript. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors addressed the initial concerns I had about the manuscript. The revised discussion and presentation are now more in line with the data presented. I now support publication in Nature Communications. + +Reviewer #2 (Remarks to the Author): + +In the revised manuscript the authors address my previous comments in a reasonable manner. I can support the publication of this paper in Nature Communications. + +<--- Page Split ---> + +In the revised version of the manuscript the Authors report additional experimental results (magnetic susceptibility and temperature dependence of resistivity and magnetoresistance), as well as provide additional discussion and new analysis of some results (critical field dependence on temperature). The sum of all results convincingly demonstrates an unconventional pressure- dependence of superconductivity in \(\mathrm{CsV_3Sb_5}\) concomitant with the suppression of the CDW and the intrinsic nature of the broadening of the superconducting transition between P1 and P2. I believe that these results can be of broad importance: on the one hand, they yield important information for the future identification of the possibly exotic SC and CDW orders in \(\mathrm{CsV_3Sb_5}\) ; on the other hand, they may help clarifying the origin of similar behaviors observed in other systems with competing orders (see below). + +However, the scenario put forward by the authors (a new, nearly commensurate CDW with domain walls, where filamentary superconductivity occurs, appearing above P1) still appears to be not supported by the data. In particular: + +(i) No features consistent with a second transition within the CDW phase (i.e. kinks, jumps) are observed between the CDW transition at \(T^{*}\) and \(T_{c}\) . + +(ii) The magnetic susceptibility data (provided in the revision) clearly shows a strong broadening of the SC transition already between 0.49 and 0.66 GPa, i.e. before P1. + +(iii) The onset of the diamagnetism coincides with the onset of resistivity suppression, while for quasi-1D filaments one would expect no diamagnetic signal (see also below). + +(iv) As the SdH oscillations are suppressed by P1, non-CDW related changes in the Fermi surface can not be excluded, especially since the oscillations corresponding to the large pockets, presumably most relevant for SC, are not observed. + +(v) Finally, the role of fluctuations and dimensionality is not assessed. \(\mathrm{CsV_3Sb_5}\) shows strong quasi-2D anisotropy and the coherence of superconductivity between the layers may play an important role. In particular, suppression of SC between P1 and P2 may indicate a disruption of the interlayer coupling which would lead to enhanced quasi-2D fluctuations broadening the transition. The Authors themselves draw a possible analogy with LBCO [PRL 99,067001 (2007)], where the suppression of SC occurs due to a decoupling of the layers by a commensurate density-wave order without requiring domain walls. + +As the Authors point out themselves in their Reply, only other types of experiments (e.g. high- resolution x- ray scattering under pressure) may give conclusive evidence for their scenario. Therefore, I think that claims of a pressure- induced transition to a NCCDW with domain walls should be only mentioned in the discussion part and removed from figures and the rest of the text. In addition to that I list + +<--- Page Split ---> + +below several suggestions to improve the manuscript: + +(1) Regarding filamentary superconductivity: for SC confined to quasi-1D filaments one would not expect diamagnetic signal to develop at all (see [J. Phys. Chem. Solids Vol. 52, No. 6. pp. 761-767. 1991] or [PRB 103, 024502 (2021)] and [Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25-44] for examples). Strong anisotropy of the SC transition [PRB 85, 184513 (2012)] or dependence on the applied current value [Solid State Communications, 44, 12, 1539 (1982)] could also be expected. However, the Author's data shows instead a consistent onset of diamagnetism at the same temperature as the resistivity suppression and no anomalies mentioned above. This behavior rather suggests inhomogeneous superconductivity, where SC onsets gradually within the volume, rather than measure-zero filaments. + +Consequently, the discussion of "filamentary" or inhomogenous SC should be modified: in the current version the use of this notion is not explained in text and no references are given. + +(2) Relation to works on other SC/density wave systems should be discussed more. In particular, a two-dome behavior has been observed previously in superconductors with competing density waves: JPSJ 82 033705 (2013), Nat. Comm. vol. 3, 943 (2012). Also, a nonmonotonic diamagnetic screening was reported Sci. Rep. 6:24068 (2016). While the control parameters in those studies are different (chemical substitution), the behavior is quite similar: close to the end point of the CDW phase SC is first enhanced on CDW suppression and then strongly suppressed, recovering only when moving further away from CDW phase. This suggests that the behavior reported by the Authors may be a general feature of SC/density wave competition. + +(3) The details of the two-model fit of \(H_{c2}(T)\) (formulas used and the resulting parameters) should be shown in the Supplementary; in particular, the dependence of the coherence lengths on pressure is a useful quantity and may be used to extract information about the scattering rates of individual bands. + +(4) Can the superconducting volume fraction be extracted from the magnetization measurements? Does it reach 100% or a close value for any pressure? This is an important point, since another Referee has pointed out a possibility of superconducting impurity phases. + +(5) I think that the temperature dependence of magnetoresistance is an important result that should be emphasized (e.g. by discussing Sup. Fig. 5 somewhere around lines 126-133). It demonstrates that the linear MR is an intrinsic property of the CDW phase, as MR becomes quadratic when CDW is suppressed both by heating and pressure. A T-dependent MR curve outside of the CDW phase, showing that it is quadratic at all T, would make this statement even more convincing. + +Note that in the previous version only low- T MR was shown, so it could have + +<--- Page Split ---> + +been possible that linear MR is the property of the band structure not related to the CDW phase (the absence of changes in \(\rho_{300K}\) vs. P does not immediately imply the absence of change in MR). + +(6) Related to the above, Fig. 4c misses an important feature of the data. Namely, the MR curves are clearly grouped in Supplementary Fig. 4 in three sets, roughly corresponding to regions \(0< \mathrm{P}< \mathrm{P}1\) , \(\mathrm{P}1< \mathrm{P}< \mathrm{P}2\) and \(\mathrm{P}2< \mathrm{P}\) . Thus, if MR of a lower field, e.g. 3T, is plotted, one will be able to see that MR experiences two noticeable changes: around \(\mathrm{P}1\) and \(\mathrm{P}2\) . + +(7) Regarding QCP signatures in resistivity: the range of temperatures presented in Supp. Fig. 8 appears much smaller than the actual temperature range measured - I suggest to provide the \(\rho\) in full temperature range vs. \(T^{2}\) in addition. Moreover, \(\rho \sim T^{2}\) in a certain temperature range can be consistent with quantum criticality of a finite-Q order (such as CDW) in the presence of disorder - see e.g., PRB 51, 9253 (1995), PRL 82, 4280 (1999) - thus a larger temperature range can be of relevance. + +Also, what appears more peculiar is the non- \(T^{2}\) behavior at low pressures and temperatures - could the authors comment on that? In particular, for pressures where \(T_{c}\) is low, \(\rho (T^{2})\) dependence can be shown down to lowest temperatures, e.g. \(2.5^{2} \mathrm{K}^{2}\) for \(\mathrm{P} = 0\) GPa. Indeed, data on a very similar compound \(\mathrm{KV}_{3} \mathrm{Sb}_{5}\) [PHYSICAL REVIEW MATERIALS 3, 094407 (2019)] is fully consistent with \(T^{2}\) behavior at low \(T\) , hence non- \(T^{2}\) behavior for \(\mathrm{P} = 0\) GPa appears anomalous. + +Suggestions for Fig. 3: + +(8) The coloring inside the CDW phase appears unrelated to data - perhaps MR% (see (6) above) or \(\rho\) can be used to provide a consistent and meaningful color scheme? Also, as is mentioned in the beginning of this Report, I suggest removing the NCCDW/domain cartoon as its presence is not supported by the data. + +(9) The SC transition points (blue triangles/squares) in Fig. 3a appear not aligned with the brown-colored region, unlike Fig. 3b. Is this a plotting issue? + +(10) The low-pressure region in Fig. 3b is rather crowded with points - I suggest to show an expanded view of the low-pressure region such that the correspondence between different measurement results could be better appreciated. + +Wording/Typos: + +Lines 19- 24: it should be mentioned that SC increases dramatically after 1.1 GPa. Perhaps, this can be simply summarized by the "two- dome shape" + +Line 25: "is linked" - - "is concomitant with" (a causal relation isn't demonstrated) + +Line 41: "attentions" - - "attention" + +Line 59: The results do not provide evidence of unconventional mechanisms of CDW and SC formation, but rather an unexpected (from the point of view of, e.g., + +<--- Page Split ---> + +Landau theory) competition between them. + +Line 77: "much broad" - > "much broader" + +Line 115,136,137,180: "emergence of a new CDW" state seems to imply a transition, but the data is also consistent with a crossover, so perhaps a "transformation (weak transition or crossover) of the CDW" is a better wording. + +Line 129: "shows suddenly drops" - > "suddenly drops" + +Line 147: "dramatically" - > "dramatic" + +Line 173: "does" - > "do" + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors addressed the initial concerns I had about the manuscript. The revised discussion and presentation are now more in line with the data presented. I now support publication in Nature Communications. + +Reply: We thank the reviewer for supporting publication in Nature Communications. + +Reviewer #2 (Remarks to the Author): + +In the revised manuscript the authors address my previous comments in a reasonable manner. I can support the publication of this paper in Nature Communications. + +Reply: We thank the reviewer for supporting publication in Nature Communications. + +Reviewer #4 (Remarks to the Author): + +In the revised version of the manuscript the Authors report additional experimental results (magnetic susceptibility and temperature dependence of resistivity and magnetoresistance), as well as provide additional discussion and new analysis of some results (critical field dependence on temperature). The sum of all results convincingly demonstrates an unconventional pressure- dependence of superconductivity in CsV3Sb5 concomitant with the suppression of the CDW and the intrinsic nature of the broadening of the superconducting transition between P1 and P2. I believe that these results can be of broad importance: on the one hand, they yield important information for the future identification of the possibly exotic SC and CDW orders in CsV3Sb5; on the other hand, they may help clarifying the origin of similar behaviors observed in other systems with competing orders (see below). + +However, the scenario put forward by the authors (a new, nearly commensurate CDW with domain walls, where filamentary superconductivity occurs, appearing above P1) still appears to be not supported by the data. In particular: + +(i) No features consistent with a second transition within the CDW phase (i.e. kinks, jumps) are observed between the CDW transition at \(T^*\) and \(T_c\). (ii) The magnetic susceptibility data (provided in the revision) clearly shows a strong broadening of the SC transition already between 0.49 and 0.66 GPa, i.e. before P1. (iii) The onset of the diamagnetism coincides with the onset of resistivity suppression, while for quasi-1D filaments one would expect no diamagnetic signal (see also below). (iv) As the SdH oscillations are suppressed by P1, non- CDW related changes in the Fermi surface can not be excluded, especially since the oscillations corresponding to the large pockets, presumably most relevant for SC, are not observed. (v) Finally, the role of fluctuations and dimensionality is not assessed. CsV3Sb5 shows strong quasi-2D anisotropy and the coherence of superconductivity between the layers may play an important role. In particular, suppression of SC between + +<--- Page Split ---> + +P1 and P2 may indicate a disruption of the interlayer coupling which would lead to enhanced quasi- 2D fluctuations broadening the transition. The Authors themselves draw a possible analogy with LBCO [PRL 99,067001 (2007)], where the suppression of SC occurs due to a decoupling of the layers by a commensurate density- wave order without requiring domain walls. + +As the Authors point out themselves in their Reply, only other types of experiments (e.g. high- resolution x- ray scattering under pressure) may give conclusive evidence for their scenario. Therefore, I think that claims of a pressure- induced transition to a NCCDW with domain walls should be only mentioned in the discussion part and removed from figures and the rest of the text. In addition to that I list below several suggestions to improve the manuscript: + +Reply: We thank the reviewer's careful review and appreciate reviewer's constructive suggestions which will definitely improve the manuscript. We agree with the reviewer that the NCCDW with domain walls scenario is not fully confirmed yet. Thus, we take the referee's point and only mentioned it in the discussion part. Correspondingly, we have changed the related figures and discussions of the main text, and the modified text is marked in blue color in the revised manuscript. + +(1) Regarding filamentary superconductivity: for SC confined to quasi-1D filaments one would not expect diamagnetic signal to develop at all (see [J. Phys. Chem. Solids Vol. 52, No. 6. pp. 761-767. 1991] or [PRB 103, 024502 (2021)] and [Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25-44] for examples). Strong anisotropy of the SC transition [PRB 85, 184513 (2012)] or dependence on the applied current value [Solid State Communications, 44, 12, 1539 (1982)] could also be expected. However, the Author's data shows instead a consistent onset of diamagnetism at the same temperature as the resistivity suppression and no anomalies mentioned above. This behavior rather suggests inhomogeneous superconductivity, where SC onsets gradually within the volume, rather than measure-zero filaments. + +Consequently, the discussion of "filamentary" or inhomogenous SC should be modified: in the current version the use of this notion is not explained in text and no references are given. + +Reply: We sincerely appreciate the reviewer's great suggestions. We agree with the referee that our resistivity and magnetic measurements are not significant to pin down a quasi- 1D filamentary superconductivity. We modified our description as 'inhomogeneous superconductivity' as the referee suggested. However, such change will not alter our conclusions. We also added the discussion of the notion of inhomogeneous superconductivity (multi superconducting phases coexists) in the revised manuscript. + +(2) Relation to works on other SC/density wave systems should be discussed more. In particular, a two-dome behavior has been observed previously in superconductors with competing density waves: JPSJ 82 033705 (2013), Nat. Comm. vol. 3, 943 (2012). Also, a nonmonotonic diamagnetic screening was reported Sci. Rep. 6:24068 (2016). While the control parameters in those studies are different (chemical substitution), the behavior is quite similar: close to the end point of the CDW phase SC is first enhanced on CDW suppression and then strongly + +<--- Page Split ---> + +suppressed, recovering only when moving further away from CDW phase. This suggests that the behavior reported by the Authors may be a general feature of SC/density wave competition. + +Reply: We thank the reviewer's suggestions. We added more discussion about the two- dome Tc behavior in the other superconductors with competing density waves. However, we would like to point out that our observation of two- dome behavior in \(\mathrm{CsV_3Sb_5}\) occurs WITHIN the CDW phase, which is different with the other superconductors (provided by the reviewer) where a second SC dome appears when the density wave order is completely suppressed. In the revised version, we have added 'Our discoveries may help to clarify the origin of similar behaviors observed in other systems with competing orders. In fact, two- dome Tc behavior were also observed in some superconductors \(^{32 - 34}\) , which might be a general feature for superconductors with competing density waves. However, we would like to note that two- dome SC behavior in \(\mathrm{CsV_3Sb_5}\) occurs within the CDW phase, which is different with the other systems where a second SC dome appears when the density wave order is completely suppressed'. + +(3) The details of the two-model fit of \(Hc2(T)\) (formulas used and the resulting parameters) should be shown in the Supplementary; in particular, the dependence of the coherence lengths on pressure is a useful quantity and may be used to extract information about the scattering rates of individual bands. + +Reply: We have added the details of the two- model fit of \(H_{c2}(T)\) in the supplementary information. We also include the coherence lengths on different pressures in Supplemental Fig.9 (We also show the figure below for convenience) as the referee suggested. However, the scattering rates of individual bands are still difficult to be calculated due to the lacking information of electron mean- free path and Fermi velocity for each band at high pressure. + +![PLACEHOLDER_26_0] + + +(4) Can the superconducting volume fraction be extracted from the magnetization + +<--- Page Split ---> + +measurements? Does it reach \(100\%\) or a close value for any pressure? This is an important point, since another Referee has pointed out a possibility of superconducting impurity phases. + +Reply: Actually, the superconducting volume in our sample reaches \(100\%\) at ambient pressure, as evidenced both by magnetic susceptibility and heat capacity measurements (arxiv: 2102.10987 and arxiv: 2103.11796). In the high- pressure magnetic measurements, the superconducting volume fraction is calculated to be even larger than \(100\%\) (except for \(\mathsf{P} = 0.72\) and 0.89) from our high- pressure magnetic measurements. In our high- pressure magnetic susceptibility experiment, magnetic field cannot be strictly along the ab plane because the sample is surrounded by liquid pressure medium. Therefore, the calculated superconducting volume fraction can be larger than \(100\%\) since the demagnetizing factor is not taken into consideration, especially for flake- like sample. On the other hand, demagnetizing factor do not need to be taken into account for the impurity phases because they are distributed uniformly in the sample (if exist), and the superconducting volume fraction cannot exceed \(100\%\) . Thus, the large diamagnetic signal could not relate to the impurity phases. + +(5) I think that the temperature dependence of magnetoresistance is an important result that should be emphasized (e.g. by discussing Sup. Fig. 5 somewhere around lines 126-133). It demonstrates that the linear MR is an intrinsic property of the CDW phase, as MR becomes quadratic when CDW is suppressed both by heating and pressure. A T-dependent MR curve outside of the CDW phase, showing that it is quadratic at all T, would make this statement even more convincing. Note that in the previous version only low-T MR was shown, so it could have been possible that linear MR is the property of the band structure not related to the CDW phase (the absence of changes in \(\rho 300K\) vs. P does not immediately imply the absence of change in MR). + +Reply: We appreciate the referee for pointing out this issue. We agree with the referee that temperature dependence of MR is an important result. We added 'Temperature dependence of MR at high pressure also evolves from "V" shape to "U" shape as shown in Supplementary Fig.5. These results indicate that the low-field linear MR is an intrinsic property of the CDW phase, since the MR exhibits quadratic temperature-dependence when the CDW is suppressed by both of heating and pressure.' in the revised manuscript as the referee suggested. + +(6) Related to the above, Fig. 4c misses an important feature of the data. Namely, the MR curves are clearly grouped in Supplementary Fig. 4 in three sets, roughly corresponding to regions \(0< P< P1\) , \(P1< P< P2\) and \(P2< P\) . Thus, if MR of a lower field, e.g. 3T, is plotted, one will be able to see that MR experiences two noticeable changes: around P1 and P2. + +Reply: We thank the reviewer's great suggestions. We added the MR data at 3T in Fig.4 in the revised manuscript. The related description was also added in the revised manuscript. + +(7) Regarding QCP signatures in resistivity: the range of temperatures presented in Supp. Fig. 8 appears much smaller than the actual temperature range measured - I suggest to provide the \(\rho\) in full temperature range vs. \(T^2\) in addition. Moreover, \(\rho \sim T^2\) in a certain temperature range can be consistent with quantum criticality of a finite-Q order (such as CDW) in the presence of disorder - see e.g., PRB 51, 9253 + +<--- Page Split ---> + +(1995), PRL 82, 4280 (1999) - thus a larger temperature range can be of relevance. Also, what appears more peculiar is the non- \(T^2\) behavior at low pressures and temperatures - could the authors comment on that? In particular, for pressures where \(T_c\) is low, \(\rho (T^2)\) dependence can be shown down to lowest temperatures, e.g. \(2.5^2 K^2\) for \(\mathsf{P} = 0\) GPa. Indeed, data on a very similar compound KV3Sb5 [PHYSICAL REVIEW MATERIALS 3, 094407 (2019)] is fully consistent with \(T^2\) behavior at low \(T,\) hence non- \(T^2\) behavior for \(\mathsf{P} = 0\) GPa appears anomalous. + +Reply: We thank the referee's great suggestion. We have shown \(\rho\) in a much larger temperature range in Supp. Fig.8 (We also show the figure below for convenience) as the referee suggested. Actually, the low- temperature resistivity follows \(T^2\) behavior below \(35K\) above P2. It severely deviates from \(T^2\) at higher temperature. The anomaly of resistivity with pressure between 1.64 and 1.84 GPa is related to the CDW transition. We should mention that the \(T^2\) behavior can only observed at low temperature even for a Fermi liquid system. At higher temperature, the electron- phonon scattering will make the resistivity deviate from the \(T^2\) behavior. The low- field MR shows linear behavior in the CDW state, which possibly arise from the linear band crossings, can possibly make the resistivity deviate from the \(T^2\) behavior. One of the remarkable differences between \(\mathsf{CsV}_3\mathsf{Sb}_5\) and \(\mathsf{KV}_3\mathsf{Sb}_5\) is that the former has very little (even no) vacancy. The vacancy in \(\mathsf{KV}_3\mathsf{Sb}_5\) is much more significant which could lead to slightly different resistivity behavior. However, it is still an open question need to be clarified in the future study. + +![PLACEHOLDER_28_0] + + +Suggestions for Fig. 3: + +(8) The coloring inside the CDW phase appears unrelated to data - perhaps MR% (see (6) above) or \(\rho\) can be used to provide a consistent and meaningful color scheme? Also, as is mentioned in the beginning of this Report, I suggest removing the NCCDW/domain cartoon as its presence is not supported by the data. + +Reply: We have used the magnitude of MR (measured at 9T,10K) as the color scheme in Fig.3 as the referee suggested. We have also removed the NCCDW/domain cartoon. + +<--- Page Split ---> + +(9) The SC transition points (blue triangles/squares) in Fig. 3a appear not aligned with the brown-colored region, unlike Fig. 3b. Is this a plotting issue? + +Reply: We thank the reviewer for point out this problem. We modified it in the revised manuscript. + +(10) The low-pressure region in Fig. 3b is rather crowded with points - I suggest to show an expanded view of the low-pressure region such that the correspondence between different measurement results could be better appreciated. + +Reply: We thank the reviewer's great suggestions. We expanded the view of the low-pressure region in Supplemental Fig.10 (We also show the figure below for convenience) in the revised manuscript. + +![PLACEHOLDER_29_0] + + +Wording/Typos: + +Lines 19- 24: it should be mentioned that SC increases dramatically after 1.1 GPa. Perhaps, this can be simply summarized by the "two- dome shape" + +Line 25: "is linked" - > "is concomitant with" (a causal relation isn't demonstrated) + +Line 41: "attentions" - > "attention" + +Line 59: The results do not provide evidence of unconventional mechanisms of CDW and SC formation, but rather an unexpected (from the point of view of, e.g., Landau theory) competition between them. + +Line 77: "much broad" - > "much broader" + +<--- Page Split ---> + +Line 115,136,137,180: "emergence of a new CDW" state seems to imply a transition, but the data is also consistent with a crossover, so perhaps a "transformation (weak transition or crossover) of the CDW" is a better wording. + +Line 129: "shows suddenly drops" - > "suddenly drops" + +Line 147: "dramatically" - > "dramatic" + +Line 173: "does" - > "do" + +Reply: We thank the referee for pointing out these typos. We made the related corrections in the revised manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a6b0a129bdcecfa1958591990a3c76a6fa33e0b7 --- /dev/null +++ b/peer_reviews/558a46d985df03adcba6811cfa37b76c3b1b73fe7f00a4c3e24b0f968c97172d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,705 @@ +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 287, 104]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 121, 404, 136]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 153, 871, 264]]<|/det|> +The authors of this manuscript report on the observation of pressure induced changes in the superconductivity of a newly discovered kagome metal, CsV3Sb5. The central claim is that pressure initially enhances the superconducting transition temperature while simultaneously suppressing the charge density wave order in this compound; however beyond this initial enhancement, they observe an unconventional suppression of Tc followed by a second enhancement, prior to being suppressed entirely at higher pressures. The result is a double superconducting "dome" in the pressure- driven superconducting phase diagram of this material. + +<|ref|>text<|/ref|><|det|>[[115, 280, 876, 358]]<|/det|> +The key observation of the double- dome- type behavior suggests an unconventional superconducting ground state and the authors claim supporting evidence for a Lifshitz transition underpinning this behavior. The observation of weak, filamentary superconductivity at intermediate pressures is used to further support this conjecture. Overall, the topic and central claims of the paper are of sufficient novelty and broad community interest to merit consideration in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 375, 836, 406]]<|/det|> +There are, however, a few central claims and issues with the manuscript that preclude recommendation for publication in Nature Communications in its current form. I list these below. + +<|ref|>text<|/ref|><|det|>[[115, 421, 872, 533]]<|/det|> +(1) There have been several recent reports depicting a qualitatively different picture of the pressure-driven phase diagram in this class of kagome metals. For instance arXiv:2103.13759 which shows an extended high-pressure dome in CsV3Sb5 and arXiv:2102.10959 for a single dome in KV3Sb5. A similar double dome is noted in this paper as also being observed in CsV3Sb5 in arXiv:2102.09328. Can the authors provide analysis which can preclude extrinsic or disorder-driven effects in their present observation of a two-peak superconducting dome? I think this will be important for the paper and the field. + +<|ref|>text<|/ref|><|det|>[[115, 549, 880, 627]]<|/det|> +(2) The conjecture of a Lifshitz transition is not immediately obvious from the quantum oscillation data in the supplementary material. The oscillations are seemingly rapidly damped, which is potentially due to pressure-induced disorder/damping effects. The frequency shifts observed prior to their disappearance are not immediately indicative of a Lifshitz transition to this referee. This claim should either be modified or better justified within the text. + +<|ref|>text<|/ref|><|det|>[[116, 645, 245, 659]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 676, 803, 692]]<|/det|> +(3) The paper use some editorial review correcting minor typos/grammar issues throughout. + +<|ref|>text<|/ref|><|det|>[[115, 708, 835, 755]]<|/det|> +(4) In Fig. 1, correlating colors between plots in the extended and zoomed-in T ranges would be helpful for the reader. It is a little confusing to trace the CDW and SC transitions in the current presentation at fixed pressure values. + +<|ref|>text<|/ref|><|det|>[[115, 772, 879, 835]]<|/det|> +In summary, I believe the manuscript has the potential of presenting a finding of sufficient interest and novelty for Nature Communications, but these points/deficiencies must be satisfactorily addressed first. In particular if points (1) and (2) can be addressed, then the paper would be a valuable addition to a seemingly quickly growing field. + +<|ref|>text<|/ref|><|det|>[[116, 883, 404, 898]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 103, 881, 279]]<|/det|> +This is a very interesting paper reporting the pressure phase diagram in the CsV3Sb5 superconductor with kagome lattice. The authors find a double- peak structure in the superconducting transition temperature \(T_{- }c\) as a function of pressure. The second peak at P2 corresponds to the end point of charge density wave (CDW) order, which can be similarly found in other superconductors with CDW. What is novel here is the observation of the first peak at P1, which is deep inside the CDW phase. To discuss the origin of this unusual peak inside the CDW phase, the authors performed magnetotransport measurements from which they find rapid changes in the Shubnikov- de Haas oscillations and the magnitude of magnetoresistance near P1. I find that these observations are intriguing and the discussion on the possible change in the CDW pattern that affects the superconductivity merits a timely publication in Nature Communications. I recommend that the authors consider the following minor comments before publication. + +<|ref|>text<|/ref|><|det|>[[115, 294, 876, 342]]<|/det|> +1) The resistivity anomalies at the CDW transition temperature look different between low and high pressure regions. The temperature derivative shown in Fig.1b shows a peak structure below P1, but it shows a dip above 1.3 GPa. Can the author discuss the origin of such a change? + +<|ref|>text<|/ref|><|det|>[[115, 358, 863, 405]]<|/det|> +2) The authors mention on the filamentary-like superconductivity in the pressure region between P1 and P2 from the width of superconducting transition. However, it would be more informative if the authors show the transition in fields. + +<|ref|>text<|/ref|><|det|>[[115, 421, 864, 469]]<|/det|> +3) The relationship between superconductivity and the quasiparticle mass is also an important point. Can the authors comment on how the effective mass changes with pressure from the temperature dependence of quantum oscillations? + +<|ref|>text<|/ref|><|det|>[[116, 500, 403, 515]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 532, 874, 596]]<|/det|> +The manuscript by Yu et al consolidates existing evidence of the evolution of the CDW and SC transitions in CsV3Sb5 with pressure and magnetic field. The present study compares electrical transport measurements on two different pressure experiments, PCC and DAC, and finds qualitatively similar albeit some quantitative differences in the critical parameters for the two. + +<|ref|>text<|/ref|><|det|>[[115, 611, 878, 707]]<|/det|> +I have to state upfront that I find little new physics that the current study adds, to warrant publication in Nature Communications: CDW and SC in this and related compounds have already been reported (refs 15 and 21 particularly refer to the Cs compound, while refs 14- 21 all are reports on AV3Sb5 compounds and their transport properties). I will refer to some more specific points below, but I cannot recommend this study (or even a revised version of it) for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 722, 877, 850]]<|/det|> +I have a problem with the existing literature and the evidence of bulk SC in CsV3Sb5: in both refs 15 and 21, attempts are made to use thermodynamic measurements to demonstrate that the \(\sim 2K\) transition is bulk SC. However, the jump in specific heat deltaC/gamma T (fig. 2f in ref 15) is only \(\sim 5 / 40\) , far from a convincing 1.4 value for BCS. If not BCS, there is little to now discussion for the reason for the minute specific heat jump to prove bulk SC. One should be aware of possible secondary phases that can result in the small SC signal: V can show SC in a wide T range (1.8 - 6 K at ambient and applied pressure), CsV (+1.5 K), Sb (2.6 - 3.4 K), Sb0.01_0.03V0.99_0.97 (2.6- 3.7 K) can all show SC. (Roberts, J. Phys. Chem. Ref. Data, 5, 581 (1976)) + +<|ref|>text<|/ref|><|det|>[[115, 866, 857, 898]]<|/det|> +While previous reports may demonstrate the CDW transition around 90 K, the present study makes little reference to that evidence. In this paper, the authors show only resistivity data, and the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 872, 136]]<|/det|> +respective derivatives. The small feature only visible in dr/dT (and not r(T) itself) can be due to small structural distortions, not necessarily accompanied by charge order (CDW). Therefore any discussion of transport data must refer to any existing proof that this is indeed a CDW transition. + +<|ref|>text<|/ref|><|det|>[[115, 153, 879, 246]]<|/det|> +To the point of unusual competition between SC and CDW in this compound, I can maybe see a qualitative change in the sharpness of the low T transition in S1 (Fig. 1a). But what the authors call P1 = 0.7 GPa and P2 - 2 GPa as the critical pressure values where the transition changes from sharp to broad and back, these values are not rigurously justified. How broad is broad, and what is a "sharp" transition? (delta T = ?) If I looked only at Fig. 1a, I would say the transition is broader for P = 1.06 - 1.3 GPa, but sharper otherwise. + +<|ref|>text<|/ref|><|det|>[[115, 263, 870, 310]]<|/det|> +if there is indeed a double transition at P1 and P2 that should be discerned in the phase diagram, the authors must show a more detailed analysis and discuss the physical origin once the two are proven intrinsic to their sample, and not a result of twinning, or secondary phase. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 120, 850, 228]]<|/det|> +In the present manuscript, the authors report an unconventional two- dome like dependence of superconducting \(T_{c}\) in \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) on pressure, concomitant with the suppression of the CDW temperture \(T^{*}\) , with a significant broadening of the superconductive transition in between the domes. The authors attribute this behavior to the presence of a Lifschitz transition caused by the formation of domains close to a near commensurate- commensurate CDW transition. + +<|ref|>text<|/ref|><|det|>[[147, 228, 850, 558]]<|/det|> +While these observations certainly add an interesting chapter to the rapidly unfolding \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) story, I find the analysis presented in the paper to be insufficient to reach the presented conclusions. In particular, the Lifschitz transition is inferred from the change of frequencies in SdH oscillations with pressure; however, the amplitude of the oscillations is strongly suppressed at the relevant pressure and some of the oscillations could be simply not resolved. Moreover, (see below), no characteristic change in SdH frequencies is demonstrated close to the supposed Lifshitz transition. The broadening of the resistive transition is attributed to the filamentary superconductivity, however, the broadening may also be present due to pressure inhomogeneity and, moreover, no comparison with the Meissner effect is given, which is important for reaching this conclusion unambiguously. Finally, the possibility of NCCCDW- CCDW transition is based on a weak anomaly that \(T^{*}\) shows around pressure P1. If present, this transition should exist over a range of temperatures, which is not demonstrated. Thus, all of the main points of the Authors' interpretation require further analysis and argumentation. Additionally, no quantitative fitting/analysis of the SdH oscillations or the magnetoresistance data is given, and the linear extrapolation used (without explanation) for \(H_{c2}(T)\) is in clear contrast to the actual data that is noticeably nonlinear. + +<|ref|>text<|/ref|><|det|>[[147, 558, 850, 630]]<|/det|> +Therefore, I believe a strongly improved data analysis (see suggestions below) is necessary before the manuscript can be considered for publication in Nature Communications. Below I provide the particular points that the Authors, in my opinion, should address: + +<|ref|>text<|/ref|><|det|>[[147, 630, 850, 703]]<|/det|> +(1) The shape of the anomaly of \(d\rho /dT\) at \(T^{*}\) (Fig. 1) clearly changes as a function of pressure - from a broad peak to sharp peak to a dip. This behavior should be studied systematically (e.g. by fitting the anomaly shape) and explained in connection to the other results. + +<|ref|>text<|/ref|><|det|>[[147, 704, 850, 813]]<|/det|> +(2) The reduction of RRR between P1 and P2 is interpreted as being due to an enhanced scattering rate. However, (1) \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) has several bands [PRL 125, 247002 (2020)]; as the respective Fermi energies may depend on pressure without changing the total charge, this may also lead to the observed enhancement of RRR, if the scattering rates for different bands are different. (1a) This is further exacerbated by the author's claim of a Lifshitz transition which implies a strong reduction in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 119, 850, 228]]<|/det|> +carrier density of one of the bands. Moreover, (2) a mass enhancement near a CDW end point is in principle possible if it is a quantum critical point [see, e.g., J. Phys.: Condens. Matter 13 R723 (2001)] - this will also affect RRR. These scenarios should all be addressed - see a suggestion based on SdH oscillations below. Another option is to measure the Hall resistance and fit \(\rho (T)\) and Hall data together with a multiband model. + +<|ref|>text<|/ref|><|det|>[[146, 228, 850, 301]]<|/det|> +(3) Apart from RRR and \(\rho_{0}\) an analysis of the pressure evolution of \(\rho (T)\) is needed: does the system show a Fermi liquid-like behavior (at least for low T) \(\rho (T) \sim \rho_{0} + AT^{2}\) everywhere in the phase diagram? How does the functional form of \(\rho (T)\) change with pressure? + +<|ref|>text<|/ref|><|det|>[[146, 301, 850, 446]]<|/det|> +(4) Analysis of the MR data should be performed. The linear MR at low pressures may arise due to linear band crossings [Phys. Rev. B 58, 2788 (1998)], indeed present in CsV3Sb5 (Dirac points, see PRL 125, 247002 (2020)) although other explanations [PRL 117,256601 (2016) and refs therein], possibly related to CDW [PNAS June 4, 2019 116 (23) 11201-11206] are also possible. Additionally, the shape change between 1.93 and 2.06 GPa is quite dramatic, while not seen at 9T (Fig. 3c). One possible reason is that the onset of CDW below P2 leads to a reconstruction of the Fermi Surface - evidence for this scenario must come from SdH or Hall effect measurements. + +<|ref|>text<|/ref|><|det|>[[146, 446, 850, 502]]<|/det|> +As for the kink around P1 Fig. 3c, to claim a relation between it and CDW a temperature-dependent MR should be presented - there may be something else occuring between 300 K and low-temperature regime. + +<|ref|>text<|/ref|><|det|>[[146, 503, 850, 648]]<|/det|> +(5) The claim of a Lifshitz transition is based on the disappearance of some of the peaks in the Fourier spectra of SdH oscillations, Figure S3c. However, no further analysis of SdH oscillations is performed. First, the dependence of the oscillation frequencies on pressure is not reported. In the vicinity of a Lifshitz transition, the corresponding frequencies should be strongly pressure-dependent [for an unrelated example see e.g., Phys. Rev. Lett. 115, 186403 (2015) or npj Quant Mater 4, 2 (2019)]; in contrast to that, no change in frequencies (especially the ones that disappear at 0.75 GPa) is observed between 0 GPa and 0.36 GPa. + +<|ref|>text<|/ref|><|det|>[[146, 648, 850, 720]]<|/det|> +Second, the amplitude of the oscillations contains important information about the scattering rates (via the Dingle factor \(\delta R \sim e^{-\pi /(\omega_{c}\tau)})\) and effective masses of the bands (via the Lifshitz-Kosevich temperature dependence). The latter may potentially reveal the mass enhancement near the CDW end point. + +<|ref|>text<|/ref|><|det|>[[146, 721, 850, 812]]<|/det|> +In particular, an enhanced scattering rate may simply suppress the oscillations making them barely visible at 0.75 GPa without a Lifshitz transition. Indeed, a strong overall peak height suppression is seen at 0.75 GPa. On the other hand, between 0 GPa and 0.36 GPa, the peak at 30 T seems strongly enhanced, while \(\rho_{0}\) (Fig. 4b) monotonically grows. These trends should be analyzed (suggestion above) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 120, 267, 137]]<|/det|> +and discussed. + +<|ref|>text<|/ref|><|det|>[[147, 138, 851, 301]]<|/det|> +(6) The broadening of the resistive transition between P1 and P2 is attributed to filamentary-like superconductivity. However, there are other possible explanations of this behavior. First, given the strong \(T_{c}(P)\) dependence any inhomogeneity of pressure in the sample would lead to a broadening of the transition. The authors should provide estimates of such inhomogeneity in their experiment to rule this effect out. Indeed, transition broadening under strain has been reported in Sr2RuO4 and attributed to extrinsic effects (Science 13 Jan 2017 Vol. 355, Issue 6321, eaaf9398). Additionally, the enhanced \(\rho_{0}\) may suggest an enhanced role of disorder that can affect the transition of an unconventional superconductor. + +<|ref|>text<|/ref|><|det|>[[147, 302, 851, 374]]<|/det|> +A direct evidence of filamentary nature would have been a separation between the resistive \(T_{c}^{zero}\) and the onset of Meissner effect (see Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25- 44, for example) - the authors should provide that to prove their claim. + +<|ref|>text<|/ref|><|det|>[[147, 375, 851, 520]]<|/det|> +(7) The determination of \(H_{c2}(0)\) by a linear extrapolation is clearly in conflict with the data: for all pressures in Fig. 2c,d one observes a noticeably nonlinear \(H_{c2}(T)\) behavior, especially pronounced near 0.72 and 0.84 GPa - the linear fit misses there all but two points. A better motivated description of the data should be used; one can start for example with WHH formula [Phys. Rev. 147, 295 (1966)] or its multiband extensions [A. Gurevich, Phys. Rev. B 82, 184504 (2010), Physica C 456 (2007) 160-169]. The convex shape of \(H_{c2}(T)\) suggests that a single-band model would not be enough. + +<|ref|>text<|/ref|><|det|>[[147, 521, 851, 593]]<|/det|> +(8) The existence of some kind of (possibly CCDW-NCCDW) transition with pressure is proposed in the paper on the basis of \(T^{*}\) showing a weak anomaly around P1. However, this anomaly is not clearly visible in Fig. 3 - the authors should provide additional analysis close to that point to prove the existence of such anomaly. + +<|ref|>text<|/ref|><|det|>[[147, 594, 851, 685]]<|/det|> +Furthermore, the proposed CCDW-NCCDW transition as a function of pressure should be a whole line in the phase diagram of Fig. 3a; the consequence of this would be additional anomalies in \(\rho (T)\) dependence (unless the critical pressure is completely independent of temperature) - see e.g., Phys. Rev. Lett. 81, 453 (1998), Scientific Reports volume 6, Article number: 24068 (2016). Are such anomalies observed? + +<|ref|>text<|/ref|><|det|>[[147, 686, 851, 757]]<|/det|> +(9) Two more related preprints on superconductivity in \(\mathrm{CsV_3Sb_5}\) under pressure have recently appeared: arXiv:2103.12507 and arXiv:2103.13759. The latter may be of particular interest for comparison, as pressure-dependent DFT calculations (and the resulting Fermi surfaces) are reported there. + +<|ref|>text<|/ref|><|det|>[[177, 758, 291, 775]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[147, 776, 851, 812]]<|/det|> +- Fig. 2 c and d: Is \(T_{c}\) on the horizontal axis a typo -should it be simply \(T\) ? I suggest to show \(H_{c2}(T)\) vs. \(T\) plots if this is not the case. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 118, 850, 192]]<|/det|> +- An enhanced competition between CDW and superconductivity is suggested to exist between P1 and P2. However, \(T^{*}\) monotonically decreases with P in this region, while \(T_{c}\) is nonmonotonic - for two competing states one would expect \(T_{c}\) to monotonically grow instead. Thus this statement seems to contradict the data. + +<|ref|>text<|/ref|><|det|>[[146, 192, 850, 264]]<|/det|> +- The data obtained for 1.5 GPa with DAC Fig. 3b yields a noticeably larger \(T_{C}^{onset}\) than the one measured with PCC. The authors should comment on this discrepancy - this may suggest that the broadening is sample-dependent and hence extrinsic. + +<|ref|>text<|/ref|><|det|>[[146, 264, 850, 302]]<|/det|> +- Comparison with \(\mathrm{La}_{2 - x}\mathrm{Ba}_{x}\mathrm{CuO4}\) is not very accurate, since the stripe order is the strongest in region of suppressed \(T_{c}\), unlike \(T^{*}\) in the current study. + +<|ref|>text<|/ref|><|det|>[[174, 302, 670, 320]]<|/det|> +- What are the error bars for points in Figs 2c,d; 3 and 4? + +<|ref|>text<|/ref|><|det|>[[175, 321, 315, 339]]<|/det|> +Wording/Typos: + +<|ref|>text<|/ref|><|det|>[[146, 339, 850, 375]]<|/det|> +p.4 "...that two peaks locate at P1 and P2..." \(\rightarrow\) "...that two peaks are located at P1 and P2..." + +<|ref|>text<|/ref|><|det|>[[175, 375, 693, 394]]<|/det|> +"...transition width of \(\Delta \mathrm{Tc}...\) " \(\rightarrow\) "...transition width \(\Delta \mathrm{Tc}...\) " + +<|ref|>text<|/ref|><|det|>[[175, 394, 693, 413]]<|/det|> +(multiple places) "...sudden drops..." \(\rightarrow\) "...suddenly drops..." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 91, 410, 106]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 133, 854, 256]]<|/det|> +The authors of this manuscript report on the observation of pressure induced changes in the superconductivity of a newly discovered kagome metal, CsV3Sb5. The central claim is that pressure initially enhances the superconducting transition temperature while simultaneously suppressing the charge density wave order in this compound; however beyond this initial enhancement, they observe an unconventional suppression of Tc followed by a second enhancement, prior to being suppressed entirely at higher pressures. The result is a double superconducting "dome" in the pressure- driven superconducting phase diagram of this material. + +<|ref|>text<|/ref|><|det|>[[144, 284, 854, 370]]<|/det|> +The key observation of the double- dome- type behavior suggests an unconventional superconducting ground state and the authors claim supporting evidence for a Lifshitz transition underpinning this behavior. The observation of weak, filamentary superconductivity at intermediate pressures is used to further support this conjecture. Overall, the topic and central claims of the paper are of sufficient novelty and broad community interest to merit consideration in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[144, 399, 853, 432]]<|/det|> +There are, however, a few central claims and issues with the manuscript that preclude recommendation for publication in Nature Communications in its current form. I list these below. + +<|ref|>text<|/ref|><|det|>[[144, 450, 854, 572]]<|/det|> +(1) There have been several recent reports depicting a qualitatively different picture of the pressure-driven phase diagram in this class of kagome metals. For instance arXiv:2103.13759 which shows an extended high-pressure dome in CsV3Sb5 and arXiv:2102.10959 for a single dome in KV3Sb5. A similar double dome is noted in this paper as also being observed in CsV3Sb5 in arXiv:2102.09328. Can the authors provide analysis which can preclude extrinsic or disorder-driven effects in their present observation of a two-peak superconducting dome? I think this will be important for the paper and the field. + +<|ref|>text<|/ref|><|det|>[[144, 583, 855, 671]]<|/det|> +Reply: We thank the reviewer for pointing out this issue. In arXiv: 2103.13759, they only used the DAC to generate the pressure. The pressure inhomogeneity is relatively large and pressure cannot be precisely controlled with DAC. For this reason, they do not observe the double dome behavior. While for KV3Sb5, it is exhibits both lower T\* and Tc comparing with CsV3Sb5 at ambient pressure. Therefore, the high-pressure phase diagram may be different due to the sample difference. + +<|ref|>text<|/ref|><|det|>[[144, 681, 854, 819]]<|/det|> +Pressure inhomogeneity or pressure induced disorder in the sample may make the superconducting transition broad. However, the two- peak superconducting dome reported in our paper cannot origin from these extrinsic effects for the following reasons. These extrinsic effects become more prominent with increasing the pressure. Actually, the pressure inhomogeneity in PCC is rather small. In our case, with the pressure at P2 with PCC, the superconducting transition is very sharp ( \(\sim 0.2\mathrm{K}\) ). Therefore, such extrinsic effect is negligible in our experiments and the broadening of the superconducting transition between P1 and P2 could not origin from these extrinsic origins. We added the related discussion in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 848, 853, 900]]<|/det|> +(2) The conjecture of a Lifshitz transition is not immediately obvious from the quantum oscillation data in the supplementary material. The oscillations are seemingly rapidly damped, which is potentially due to pressure-induced disorder/damping effects. The frequency shifts observed prior to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 853, 123]]<|/det|> +their disappearance are not immediately indicative of a Lifshitz transition to this referee. This claim should either be modified or better justified within the text. + +<|ref|>text<|/ref|><|det|>[[144, 152, 854, 256]]<|/det|> +Reply: We thank the reviewer for pointing out this problem. We agree with the reviewer that the rapidly damping above P1 cannot support the conclusion of Lifshitz transition. Instead, it can be related to the enhanced scattering rate above P1, consistent with the sudden increment of the residual resistivity. we modified this claim in the revised manuscript. However, the sudden change of residual resistivity, MR behavior and quantum oscillation support the conclusion of a new CDW state above P1. + +<|ref|>text<|/ref|><|det|>[[145, 286, 270, 301]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[144, 330, 789, 346]]<|/det|> +(3) The paper use some editorial review correcting minor typos/grammar issues throughout. + +<|ref|>text<|/ref|><|det|>[[145, 358, 631, 373]]<|/det|> +Reply: We corrected typos/grammar issues in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 401, 854, 452]]<|/det|> +(4) In Fig. 1, correlating colors between plots in the extended and zoomed-in T ranges would be helpful for the reader. It is a little confusing to trace the CDW and SC transitions in the current presentation at fixed pressure values. + +<|ref|>text<|/ref|><|det|>[[144, 465, 853, 498]]<|/det|> +Reply: We use the same colors between plots in the extended and zoomed-in T ranges in Fig.1 as the reviewer suggested. + +<|ref|>text<|/ref|><|det|>[[144, 526, 854, 595]]<|/det|> +In summary, I believe the manuscript has the potential of presenting a finding of sufficient interest and novelty for Nature Communications, but these points/deficiencies must be satisfactorily addressed first. In particular if points (1) and (2) can be addressed, then the paper would be a valuable addition to a seemingly quickly growing field. + +<|ref|>text<|/ref|><|det|>[[146, 624, 410, 639]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 669, 854, 860]]<|/det|> +This is a very interesting paper reporting the pressure phase diagram in the CsV3Sb5 superconductor with kagome lattice. The authors find a double- peak structure in the superconducting transition temperature \(T_{- }c\) as a function of pressure. The second peak at P2 corresponds to the end point of charge density wave (CDW) order, which can be similarly found in other superconductors with CDW. What is novel here is the observation of the first peak at P1, which is deep inside the CDW phase. To discuss the origin of this unusual peak inside the CDW phase, the authors performed magnetotransport measurements from which they find rapid changes in the Shubnikov- de Haas oscillations and the magnitude of magnetoresistance near P1. I find that these observations are intriguing and the discussion on the possible change in the CDW pattern that affects the superconductivity merits a timely publication in Nature Communications. I recommend that the authors consider the following minor comments before publication. + +<|ref|>text<|/ref|><|det|>[[142, 889, 853, 905]]<|/det|> +1) The resistivity anomalies at the CDW transition temperature look different between low and high + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 89, 854, 247]]<|/det|> +pressure regions. The temperature derivative shown in Fig.1b shows a peak structure below P1, but it shows a dip above 1.3 GPa. Can the author discuss the origin of such a change? Reply: We thank the referee for pointing out this issue. The derivative curve shows a peak- dip behavior (for example, see 0.95GPa) above P1. Further increasing the pressure, the peak becomes much weaker (but still exist) and the dip becomes more pronounced. The resistivity anomaly is associated to the change for the band structure and electron scattering rate in the CDW state. The change of the shape of \(d\rho_{\mathrm{xv}} / dT\) anomaly indicates the possibly change of the CDW state Such behavior is consistent with sudden change of MR and residual resistivity above P1. We added the related discussion in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 275, 853, 326]]<|/det|> +2) The authors mention on the filamentary-like superconductivity in the pressure region between P1 and P2 from the width of superconducting transition. However, it would be more informative if the authors show the transition in fields. + +<|ref|>text<|/ref|><|det|>[[144, 336, 854, 476]]<|/det|> +Reply: We have added a figure (Supplementary Fig.3, we also show below for convenience) in the supplementary information to show the superconducting transition in different fields with pressure between P1 and P2. We also performed the high-pressure magnetic susceptibility measurements (Supplementary Fig.2) to support our conclusions. With the pressure around P1, the superconducting volume fraction suddenly decreases. Further increasing the pressure, the bulk superconductivity \(T_{c}^{M2}\) emerges below 4 K around 1.1 GPa, but the magnetic susceptibility shows a weak reduction at \(T_{c}^{M1}\) with higher temperature, indicating a filamentary superconductivity at higher temperature, consistent with our resistivity measurements. + +<|ref|>image<|/ref|><|det|>[[265, 518, 737, 790]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 823, 853, 874]]<|/det|> +3) The relationship between superconductivity and the quasiparticle mass is also an important point. Can the authors comment on how the effective mass changes with pressure from the temperature dependence of quantum oscillations? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 854, 176]]<|/det|> +Reply: We extract the effective mass with pressure at 0.36 GPa as shown in Supplementary Fig.7. The extracted effective mass for F1 and F2 orbitals does not change much with pressure. We added related descriptions in the revised manuscript. However, we should point out that it is a multiband system. The evolution of the effective mass for the other Fermi pockets, especially the large Fermi pockets around Γ and K points cannot be determined in our experiments. + +<|ref|>text<|/ref|><|det|>[[146, 240, 410, 255]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 284, 854, 353]]<|/det|> +The manuscript by Yu et al consolidates existing evidence of the evolution of the CDW and SC transitions in CsV3Sb5 with pressure and magnetic field. The present study compares electrical transport measurements on two different pressure experiments, PCC and DAC, and finds qualitatively similar albeit some quantitative differences in the critical parameters for the two. + +<|ref|>text<|/ref|><|det|>[[144, 371, 854, 474]]<|/det|> +I have to state upfront that I find little new physics that the current study adds, to warrant publication in Nature Communications: CDW and SC in this and related compounds have already been reported (refs 15 and 21 particularly refer to the Cs compound, while refs 14- 21 all are reports on AV3Sb5 compounds and their transport properties). I will refer to some more specific points below, but I cannot recommend this study (or even a revised version of it) for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[144, 486, 855, 678]]<|/det|> +Reply: We thank the reviewer's careful review. However, we cannot agree with the reviewer's comments that our paper adds little new physics to the current study. Although SC and CDW is already reported in CsV3Sb5, the interplay of SC and CDW is still unknown before our work. Usually, the suppression of CDW order by doping or pressure always enhances superconductivity and leads to a dome- like behavior for superconductivity in most of CDW materials with superconductivity. To our surprise, we find an unusual competition of CDW and SC under pressure. The Tc shows intriguing two- peak behavior which is never observed in the other CDW materials. Such behavior is possibly due to the formation of a new CDW order at high pressure, which have stronger competition with SC. Our discoveries indicate the unconventional interplay of CDW and SC in CsV3Sb5, which would stimulate broad interests on the study of the correlation between CDW and SC in many unconventional superconductors, such as cuprate superconductors. + +<|ref|>text<|/ref|><|det|>[[144, 706, 854, 844]]<|/det|> +I have a problem with the existing literature and the evidence of bulk SC in CsV3Sb5: in both refs 15 and 21, attempts are made to use thermodynamic measurements to demonstrate that the \(\sim 2K\) transition is bulk SC. However, the jump in specific heat deltaC/gamma T (fig. 2f in ref 15) is only \(\sim 5 / 40\) , far from a convincing 1.4 value for BCS. If not BCS, there is little to now discussion for the reason for the minute specific heat jump to prove bulk SC. One should be aware of possible secondary phases that can result in the small SC signal: V can show SC in a wide T range (1.8 - 6 K at ambient and applied pressure), CsV (+1.5 K), Sb (2.6 - 3.4 K), Sb0.01_0.03V0.99_0.97 (2.6- 3.7 K) can all show SC. (Roberts, J. Phys. Chem. Ref. Data, 5, 581 (1976)) + +<|ref|>text<|/ref|><|det|>[[145, 856, 854, 906]]<|/det|> +Reply: Although the mechanism of superconductivity in this material is still not well understood, a bulk superconducting state in CsV3Sb5 is already confirmed by different techniques, including magnetic susceptibility, heat capacity, thermal conductivity, STM and so on. Actually, we used the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 89, 854, 211]]<|/det|> +same batch of samples with arxiv: 2102.10987, arxiv:2103.04760 and arxiv: 2103.11796. In arxiv: 2103.11796, the heat capacity can be well fitted by using the two s- wave model and the bulk superconductivity is confirmed. In arxiv:2103.04760, superconducting gap is observed by STM, directly proves that the SC is from \(\mathsf{CsV}_3\mathsf{Sb}_5\) rather than the secondary phases. In addition, no impurity phases can be detected from the x- ray diffraction measurements (arxiv: 2102.10987). Our high- pressure susceptibility measurements also confirm the bulk superconductivity in our sample and exclude the possibility of the secondary phases. + +<|ref|>text<|/ref|><|det|>[[143, 239, 854, 485]]<|/det|> +While previous reports may demonstrate the CDW transition around \(90~\mathsf{K}\) , the present study makes little reference to that evidence. In this paper, the authors show only resistivity data, and the respective derivatives. The small feature only visible in \(\mathrm{dr / dT}\) (and not \(\mathrm{r(T)}\) itself) can be due to small structural distortions, not necessarily accompanied by charge order (CDW). Therefore any discussion of transport data must refer to any existing proof that this is indeed a CDW transition. Reply: The anomaly of the resistivity is already confirmed to be associated with the CDW temperature at ambient pressure. We added the related references in the revised manuscript. The CDW transition is already confirmed by the STM and x- ray scattering measurements (arxiv: 2103.04760 and arxiv: 2103.09769). By increasing the pressure, \(\mathsf{T}^*\) determined by the anomaly of \(d\rho_{\mathrm{xx}} / dT\) smoothly changes with the pressure. Thus, it is a natural inference that such an anomaly should related to the CDW transition rather than the other small structural distortions. In addition, our cooperators also confirm the CDW transition at 1.8 GPa from the high- pressure NMR measurements which will be published elsewhere. For the above reasons, \(\mathsf{T}^*\) can be associated to the anomaly of \(d\rho_{\mathrm{xx}} / dT\) curves. + +<|ref|>text<|/ref|><|det|>[[144, 521, 854, 626]]<|/det|> +To the point of unusual competition between SC and CDW in this compound, I can maybe see a qualitative change in the sharpness of the low T transition in S1 (Fig. 1a). But what the authors call P1 \(= 0.7\) GPa and P2 - 2 GPa as the critical pressure values where the transition changes from sharp to broad and back, these values are not rigurously justified. How broad is broad, and what is a "sharp" transition? (delta \(\mathsf{T} = ?\) ) If I looked only at Fig. 1a, I would say the transition is broader for \(\mathsf{P} = 1.06\) - 1.3 GPa, but sharper otherwise. + +<|ref|>text<|/ref|><|det|>[[144, 637, 854, 723]]<|/det|> +Reply: The superconducting transition width \(\Delta \mathsf{Tc}\) is shown in Fig.4a. We can clearly see a larger \(\Delta \mathsf{Tc}\) between P1 and P2. Our high- pressure susceptibility measurements indicate filamentary superconductivity in this pressure range. Besides large \(\Delta \mathsf{Tc}\) in this region, MR and the residual resistivity also show sudden changes at P1 and P2. In addition, the SdH QOs damp rapidly above P1. For all the above reasons, P1 and P2 are the critical pressure values. + +<|ref|>text<|/ref|><|det|>[[144, 751, 854, 804]]<|/det|> +if there is indeed a double transition at P1 and P2 that should be discerned in the phase diagram, the authors must show a more detailed analysis and discuss the physical origin once the two are proven intrinsic to their sample, and not a result of twinning, or secondary phase. + +<|ref|>text<|/ref|><|det|>[[144, 815, 854, 902]]<|/det|> +Reply: Our single crystals are pure and the superconductivity could not be related to the secondary phase as already testified by the other experimental methods in the other papers (arxiv: 2102.10987, arxiv:2103.04760 and arxiv: 2103.11796. ). The pressure inhomogeneity become more pronounced with increasing the pressure. In our experiment, the pressure inhomogeneity of the PCC cell is small as evidenced by the sharp SC transition at \(\mathsf{P2}(\sim 0.2\mathsf{K})\) . Thus, the broadening of the superconducting + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 853, 158]]<|/det|> +transition and the double transition at P1 and P2 could not due the extrinsic effects. The origin of the Tc peak at P1 can be attributed to the emergence of a new CDW state which has much stronger competition with SC. We propose the possible CCDW to NCCDW transition at P1. We added the related discussion in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[145, 204, 416, 220]]<|/det|> +Reviewer #4 (Remarks to the Authors): + +<|ref|>text<|/ref|><|det|>[[144, 232, 853, 336]]<|/det|> +In the present manuscript, the authors report an unconventional two- dome like dependence of superconducting \(T_{C}\) in CsV3Sb5 on pressure, concomitant with the suppression of the CDW temperture \(T*\) , with a significant broadening of the superconductive transition in between the domes. The authors attribute this behavior to the presence of a Lifschitz transition caused by the formation of domains close to a near commensurate- commensurate CDW transition. + +<|ref|>text<|/ref|><|det|>[[143, 338, 853, 617]]<|/det|> +While these observations certainly add an interesting chapter to the rapidly unfolding CsV3Sb5 story, I find the analysis presented in the paper to be insufficient to reach the presented conclusions. In particular, the Lifschitz transition is inferred from the change of frequencies in SdH oscillations with pressure; however, the amplitude of the oscillations is strongly suppressed at the relevant pressure and some of the oscillations could be simply not resolved. Moreover, (see below), no characteristic change in SdH frequencies is demonstrated close to the supposed Lifshitz transition. The broadening of the resistive transition is attributed to the filamentary superconductivity, however, the broadening may also be present due to pressure inhomogeneity and, moreover, no comparison with the Meissner effect is given, which is important for reaching this conclusion unambiguously. Finally, the possibility of NCCCDW- CCDW transition is based on a weak anomaly that \(T*\) shows around pressure P1. If present, this transition should exist over a range of temperatures, which is not demonstrated. Thus, all of the main points of the Authors' interpretation require further analysis and argumentation. Additionally, no quantitative fitting/analysis of the SdH oscillations or the magnetoresistance data is given, and the linear extrapolation used (without explanation) for \(Hc2(T)\) is in clear contrast to the actual data that is noticeably nonlinear. + +<|ref|>text<|/ref|><|det|>[[144, 618, 852, 669]]<|/det|> +Therefore, I believe a strongly improved data analysis (see suggestions below) is necessary before the manuscript can be considered for publication in Nature Communications. Below I provide the particular points that the Authors, in my opinion, should address: + +<|ref|>text<|/ref|><|det|>[[144, 697, 852, 750]]<|/det|> +(1) The shape of the anomaly of \(dp/dT\) at \(T*\) (Fig. 1) clearly changes as a function of pressure - from a broad peak to sharp peak to a dip. This behavior should be studied systematically (e.g. by fitting the anomaly shape) and explained in connection to the other results. + +<|ref|>text<|/ref|><|det|>[[144, 760, 853, 900]]<|/det|> +Reply: We thank the reviewer's great suggestion. We added the related discussion in the revised manuscript. The shape of the anomaly of \(dp_{\infty} / dT\) at \(T*\) gradually evolves from the broad peak to peak- dip behavior around P1. Further increasing the pressure, the peak becomes much weaker and the dip becomes much pronounced. The resistivity is strongly connected with band structure and electron scattering. The sudden enhancement of residual resistivity and rapidly damping of QOs indicate the enhancement of the scattering rate (possible for some bands), which would naturally lead to the change of the \(dp_{\infty} / dT\) behavior. The change of the shape of \(dp_{\infty} / dT\) anomaly at \(T*\) can be also related to the evolution to a new CDW state, possibly from CCDW to NCCDW. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 106, 854, 280]]<|/det|> +(2) The reduction of RRR between P1 and P2 is interpreted as being due to an enhanced scattering rate. However, (1) CsV3Sb5 has several bands [PRL 125, 247002 (2020)]; as the respective Fermi energies may depend on pressure without changing the total charge, this may also lead to the observed enhancement of RRR, if the scattering rates for different bands are different. (1a) This is further exacerbated by the author's claim of a Lifshitz transition which implies a strong reduction in carrier density of one of the bands. Moreover, (2) a mass enhancement near a CDW end point is in principle possible if it is a quantum critical point [see, e.g., J. Phys.: Condens. Matter 13 R723 (2001)] - this will also affect RRR. These scenarios should all be addressed - see a suggestion based on SdH oscillations below. Another option is to measure the Hall resistance and fit \(\rho (T)\) and Hall data together with a multiband model. + +<|ref|>text<|/ref|><|det|>[[144, 290, 854, 466]]<|/det|> +Reply: We agree with the referee that the RRR may change depends on the respective Fermi energies of different bands. Actually, the band structure of \(\mathrm{CsV_3Sb_5}\) is rather complicated, there are many bands at the Fermi energy. The dependence of each band under pressure is very important but out of the scope of our current work. Actually, the four frequencies resolved from the SdH oscillations only contribute less than \(1\%\) of the whole area of Brillouin zone. The large electron Fermi pockets around \(\Gamma\) and K points cannot be resolved in the SdH oscillations. For these reasons, we can not specify the explicit origins of RRR change under pressure. From the QO measurements, the rapidly damping of the QOs above P1 indicates the enhanced scattering rate for the four resolved frequencies. But we cannot figure out the change of the other bands above P1 from the current measurements. + +<|ref|>text<|/ref|><|det|>[[144, 476, 854, 668]]<|/det|> +The quantum critical point near the CDW end point is an interesting topic, we checked our data and analyses the \(\rho (T)\) at low temperature to check the possibility of quantum critical point in the revised manuscript. Since \(\rho (T)\) follows \(T^2\) behavior and \(\rho_0\) is small at P2 as shown in Supplementary Fig.8. Thus, our data does not support the quantum criticality at the CDW end point. Since we cannot detect any QOs around P2, thus the effect mass could not be obtained from the QOs. The square of effective mass is proportional to the parameter A (which can be obtained from the \(\rho (T) \sim \rho_0 + AT^2\) fitting). We can clearly see the slope of the \(\rho_{xx}\) vs. \(T^2\) curves nearly does not change around P2 shown in Supplementary Fig.8. Therefore, our data does not support for the mass enhancement around P2. However, we should also point out that ultralow- temperature measurements are still needed to check the existence of quantum criticality in the lower temperature region. We added the related discussion in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 696, 853, 749]]<|/det|> +(3) Apart from RRR and \(\rho 0\) an analysis of the pressure evolution of \(\rho (T)\) is needed: does the system show a Fermi liquid-like behavior (at least for low T) \(\rho (T) \sim \rho_0 + AT^2\) everywhere in the phase diagram? How does the functional form of \(\rho (T)\) change with pressure? + +<|ref|>text<|/ref|><|det|>[[144, 758, 854, 879]]<|/det|> +Reply: We thank referee's great suggestion. We analyses the \(\rho (T)\) at low temperature as shown in Supplementary Fig.8 (We also show the figure below for convenience). Below P1, \(\rho (T)\) does not follow the \(T^2\) well, however, with pressure at P2, \(\rho (T)\) follows \(T^2\) behavior indicating the Fermi liquid nature. In addition, the residual resistivity is small at P2, therefore, our data does not support the quantum criticality at the CDW end point. However, we should also point out that ultralow- temperature measurements are still needed to check the existence of quantum criticality at lower temperature in the future studies. The related description is added in the revised manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[144, 102, 850, 348]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 405, 854, 580]]<|/det|> +(4) Analysis of the MR data should be performed. The linear MR at low pressures may arise due to linear band crossings [Phys. Rev. B 58, 2788 (1998)], indeed present in CsV3Sb5 (Dirac points, see PRL 125, 247002 (2020)) although other explanations [PRL 117,256601 (2016) and refs therein], possibly related to CDW [PNAS June 4, 2019 116 (23) 11201-11206] are also possible. Additionally, the shape change between 1:93 and 2:06 GPa is quite dramatic, while not seen at 9T (Fig. 3c). One possible reason is that the onset of CDW below P2 leads to a reconstruction of the Fermi Surface - evidence for this scenario must come from SdH or Hall effect measurements. As for the kink around P1 Fig. 3c, to claim a relation between it and CDW a temperature-dependent MR should be presented - there may be something else occurring between 300 K and low-temperature regime. + +<|ref|>text<|/ref|><|det|>[[144, 590, 854, 886]]<|/det|> +Reply: We thank the reviewer's great suggestions. The electronic structure and electron scattering may be quite different in the different pressure regions, which lead to the different MR behavior and RRR. We add the related discussion of the MR data in the revised manuscript. The linear MR at the low field region below P2 can possibly arise from the linear band crossings or/and CDW state. We also added a figure (Supplementary Fig.5, also shown below for convenience) to show the temperature- dependent MR at 1.02 GPa for sample 4 with PCC. The \(\mathrm{T}^*\) is suppressed to 49K. We can clearly see that the shape of MR sudden changes around \(\mathrm{T}^*\) , similar with shape change between 1.93 and 2.06 GPa shown in Supplementary Fig.4. These results confirm the low- field linear MR is related to the CDW state. It is possible that a reconstruction of the Fermi Surface may occur in the CDW state. In principle, SdH or Hall effect measurements may give some indication. However, in our case, SdH can be only observed at low temperature and pressure, we cannot extract any QOs across the CDW transition. While for Hall measurements, we can see the carrier density slightly changes around \(\mathrm{T}^*\) (arxiv: 2102.10987), but cannot prove the Fermi surface reconstruction even at ambient pressure. The Hall resistivity at low temperature becomes very complicated since it is a multiband system and anomalous Hall effect becomes more pronounced. It is still a challenge to understand its Hall effect right now. For these reasons, we cannot give any conclusion of Fermi surface reconstruction at \(\mathrm{T}^*\) from the current measurements. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[153, 88, 844, 228]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[143, 255, 854, 536]]<|/det|> +(5) The claim of a Lifshitz transition is based on the disappearance of some of the peaks in the Fourier spectra of SdH oscillations, Figure S3c. However, no further analysis of SdH oscillations is performed. First, the dependence of the oscillation frequencies on pressure is not reported. In the vicinity of a Lifshitz transition, the corresponding frequencies should be strongly pressure-dependent [for an unrelated example see e.g., Phys. Rev. Lett. 115, 186403 (2015) or npj Quant Mater 4, 2 (2019)]; in contrast to that, no change in frequencies (especially the ones that disappear at 0.75 GPa) is observed between 0 GPa and 0.36 GPa. Second, the amplitude of the oscillations contains important information about the scattering rates (via the Dingle factor \(\delta R \sim e^{-\pi /(\omega \tau)}\) ) and effective masses of the bands (via the Lifshitz-Kosevich temperature dependence). The latter may potentially reveal the mass enhancement near the CDW end point. In particular, an enhanced scattering rate may simply suppress the oscillations making them barely visible at 0.75 GPa without a Lifshitz transition. Indeed, a strong overall peak height suppression is seen at 0.75 GPa. On the other hand, between 0 GPa and 0.36 GPa, the peak at 30 T seems strongly enhanced, while \(\rho 0\) (Fig. 4b) monotonically grows. These trends should be analyzed (suggestion above) and discussed. + +<|ref|>text<|/ref|><|det|>[[144, 544, 854, 666]]<|/det|> +Reply: We thank reviewer's great suggestions. We agree with the reviewer that the current data cannot support the Lifshitz transition. Therefore, we modified our description of the Lifshitz transition in the revised manuscript. As the reviewer point out that the enhanced scattering rate can also suppress the oscillations without a Lifshitz transition, the rapid damping of the QOs can be attributed to the enhanced scattering rate for the 4 orbitals observed in our QOs which is consistent with the sudden enhancement of residual resistivity above P1. The QOs damping rapidly above P1. Therefore, we cannot extract the information from QOs near the CDW end point. + +<|ref|>text<|/ref|><|det|>[[144, 676, 854, 814]]<|/det|> +We added more discussions about the SdH oscillations in the revised manuscript. We analyzed the SdH oscillations at 0.36GPa at different temperatures to extract the effect mass as shown in Supplementary Fig.7. We found the effect mass does not change much comparing with that at ambient pressure. We also analyzed the enhancement of amplitude for the 26 and 72T orbitals at 0.36 GPa in the revised manuscript. The amplitude of the QOs depends on thermal damping factor \(\mathsf{R}_{\mathsf{T}}\) and Dingle damping factor \(\mathsf{R}_{\mathsf{D}}\) . Since the effect mass does not change much at 0.36 GPa, the enhancement of amplitude can be attributed to the reduction of the scattering rate for the two bands. + +<|ref|>text<|/ref|><|det|>[[144, 844, 854, 896]]<|/det|> +(6) The broadening of the resistive transition between P1 and P2 is attributed to filamentary-like superconductivity. However, there are other possible explanations of this behavior. First, given the strong \(T_{C}(P)\) dependence any inhomogeneity of pressure in the sample would lead to a broadening of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 89, 854, 229]]<|/det|> +the transition. The authors should provide estimates of such inhomogeneity in their experiment to rule this effect out. Indeed, transition broadening under strain has been reported in Sr2RuO4 and attributed to extrinsic effects (Science 13 Jan 2017 Vol. 355, Issue 6321, eaaf9398). Additionally, the enhanced \(\rho 0\) may suggest an enhanced role of disorder that can affect the transition of an unconventional superconductor. A direct evidence of filamentary nature would have been a separation between the resistive Tzero and the onset of Meissner effect (see Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25[44, for example) - the authors should provide that to prove their claim. + +<|ref|>text<|/ref|><|det|>[[144, 239, 854, 430]]<|/det|> +Reply: The pressure inhomogeneity is a common problem in the high- pressure experiment. It is usually negligible in the PCC by using the liquid pressure medium. The pressure inhomogeneity increases with increasing the pressure, especially when the liquid pressure medium become solidified under pressure. In our case, the superconducting transition is very sharp ( \(\sim 0.2 \text{K}\) ) at P2 with PCC, which indicates the pressure inhomogeneity is negligible in our experiments. If we assume that the superconducting transition width totally comes from the pressure inhomogeneity (actually it is impossible in reality, but we can use this to give an estimation of upper limit of pressure inhomogeneity in PCC), the upper limit of pressure inhomogeneity can be estimated to be \(\sim 0.1 \text{GPa}\) around 2 GPa. Thus, the broadening of the superconducting transition between P1 and P2 cannot origin from the small pressure inhomogeneity. We added the related description in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 441, 854, 566]]<|/det|> +We performed the high- pressure magnetic susceptibility measurements as shown in Supplementary Fig.2 (We also show the figure below for convenience). The superconducting volume fraction suddenly decreases above P1. With pressure around 1.1GPa, two transitions can be observed. The bulk superconducting temperature \(T_{c1}^{M2}\) appears below 4 K, however, the magnetic susceptibility also shows a weak reduction at \(T_{c1}^{M2}\) which is much higher than \(T_{c1}^{M2}\) , representing the filamentary superconductivity, consistent with the resistivity measurements. The related description is added in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[160, 580, 828, 808]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 834, 854, 902]]<|/det|> +(7) The determination of \(Hc2(0)\) by a linear extrapolation is clearly in conflict with the data: for all pressures in Fig. 2c,d one observes a noticeably nonlinear \(Hc2(T)\) behavior, especially pronounced near 0.72 and 0.84 GPa - the linear fit misses there all but two points. A better motivated description of the data should be used; one can start for example with WHH formula [Phys. Rev. 147, 295 (1966)] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 853, 124]]<|/det|> +or its multiband extensions [A. Gurevich, Phys. Rev. B 82, 184504 (2010), Physica C 456 (2007) 160- 169]. The convex shape of \(Hc2(T)\) suggests that a single- band model would not be enough. + +<|ref|>text<|/ref|><|det|>[[144, 134, 854, 221]]<|/det|> +Reply: We thank the reviewer for pointing out this problem. We totally agree with the reviewer that the convex shape of \(Hc2(T)\) suggests that a single- band model cannot describe the \(Hc2(T)\) behavior. Therefore, we used two- band model to fit the \(Hc2(T)\) in the revised manuscript. The nonlinear \(Hc2(T)\) behavior can be well fitted by using the two- band model. We can obtain \(Hc2(0)\) from the fitting of two- band model in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 248, 854, 390]]<|/det|> +(8) The existence of some kind of (possibly CCDW-NCCDW) transition with pressure is proposed in the paper on the basis of \(T*\) showing a weak anomaly around P1. However, this anomaly is not clearly visible in Fig. 3 - the authors should provide additional analysis close to that point to prove the existence of such anomaly. Furthermore, the proposed CCDW-NCCDW transition as a function of pressure should be a whole line in the phase diagram of Fig. 3a; the consequence of this would be additional anomalies in \(\rho (T)\) dependence (unless the critical pressure is completely independent of temperature) - see e.g., Phys. Rev. Lett. 81, 453 (1998), Scientific Reports volume 6, Article number: 24068 (2016). Are such anomalies observed? + +<|ref|>text<|/ref|><|det|>[[144, 400, 854, 610]]<|/det|> +Reply: We added more discussion of the anomalies around P1. The RRR and MR shows a sudden change at P1. In addition, the SdH oscillations damping rapidly above \(\sim \mathsf{P1}\) . All these information indicate a transition around P1. From the current measurement we can hardly determine any anomalies from \(\rho (T)\) except the one around \(\mathsf{T}^*\) as shown in Fig.1. The domain walls may gradually emerge above P1, but it is not sensitive to the temperature in our case. Another possibility is that such transition may be rather broad, we cannot detect it in the resistivity measurement. In order to solve this problem, detailed high- pressure low- temperature x- ray diffraction measurements are highly required in the future experiment but not in our current work. For example, in compressed \(\mathsf{T}i\mathsf{Se}_2\) , x- ray diffraction measurements give a complex phase diagram (Nature Physics 10, 421- 425 (2014)) including the ICCDW and CCDW in the phase diagram. However, for the resistivity measurements, only one anomaly can be detected from the resistivity curves (Physical Review Letters 103, 236401 (2009).) + +<|ref|>text<|/ref|><|det|>[[144, 638, 854, 707]]<|/det|> +(9) Two more related preprints on superconductivity in CsV3Sb5 under pressure have recently appeared: arXiv:2103.12507 and arXiv:2103.13759. The latter may be of particular interest for comparison, as pressure-dependent DFT calculations (and the resulting Fermi surfaces) are reported there. + +<|ref|>text<|/ref|><|det|>[[144, 719, 854, 821]]<|/det|> +Reply: We thank the reviewer for providing these papers. In these papers, they focused on a new superconducting phase which emerges at much higher pressure(above\~15GPa). In our case, the most intriguing discovery was found with pressure below 2GPa. In addition, we are focusing on the unconventional competition of CDW and superconductivity in our paper. In the second superconducting phase reported in arXiv:2103.12507 and arXiv:2103.13759, the CDW order is absent and not taken into consideration in their DFT calculations. + +<|ref|>text<|/ref|><|det|>[[144, 852, 240, 867]]<|/det|> +Minor points: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 107, 852, 140]]<|/det|> +- Fig. 2 c and d: Is \(T_c\) on the horizontal axis a typo - should it be simply \(T\) ? I suggest to show \(Hc2(T)\) vs. \(T\) plots if this is not the case. + +<|ref|>text<|/ref|><|det|>[[144, 152, 847, 169]]<|/det|> +Reply: We thank the referee for pointing out this problem. We modified it in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 196, 853, 266]]<|/det|> +- An enhanced competition between CDW and superconductivity is suggested to exist between P1 and P2. However, \(T^*\) monotonically decreases with P in this region, while \(T_c\) is nonmonotonic - for two competing states one would expect \(T_c\) to monotonically grow instead. Thus this statement seems to contradict the data. + +<|ref|>text<|/ref|><|det|>[[144, 278, 853, 329]]<|/det|> +Reply: The enhanced competition between CDW and superconductivity is referred to the region above P1 comparing with that below P1. The new CDW state appears above P1 which has stronger competition with superconductivity. We modified the description in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 356, 853, 409]]<|/det|> +- The data obtained for 1.5 GPa with DAC Fig. 3b yields a noticeably larger \(T_c^{\text{onset}}\) than the one measured with PCC. The authors should comment on this discrepancy - this may suggest that the broadening is sample-dependent and hence extrinsic. + +<|ref|>text<|/ref|><|det|>[[144, 420, 864, 541]]<|/det|> +Reply: The pressure in DAC is determined at room temperature. The pressure in our DAC cell has \(\sim 5\%\) variation at low temperature. In addition, the pressure inhomogeneity in DAC is larger than that in PCC since we used solid pressure medium, which makes the superconducting transition slightly more broad comparing with that in PCC. However, the broadening of \(T_c\) within the P1 and P2 region is also obvious with DAC. Since the superconducting curve above P2 become sharp again which cannot be attributed to the pressure inhomogeneity effect. For these reasons, the observed broadening is intrinsic. + +<|ref|>text<|/ref|><|det|>[[144, 569, 853, 604]]<|/det|> +- Comparison with La2-xBaxCuO4 is not very accurate, since the stripe order is the strongest in region of suppressed \(T_c\) , unlike \(T^*\) in the current study. + +<|ref|>text<|/ref|><|det|>[[144, 616, 853, 667]]<|/det|> +Reply: We thank the reviewer for pointing out this issue. However, we should point out that the system may evolve to a new CDW state above P1, in which the new CDW state has strong competition with superconductivity, similar to the case in \(\mathrm{La}_{2 - x}\mathrm{Ba}_x\mathrm{CuO}_4\) . + +<|ref|>text<|/ref|><|det|>[[144, 679, 545, 695]]<|/det|> +- What are the error bars for points in Figs 2c,d; 3 and 4? + +<|ref|>text<|/ref|><|det|>[[144, 707, 523, 722]]<|/det|> +Reply: We added error bars in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 752, 259, 767]]<|/det|> +Wording/Typos: + +<|ref|>text<|/ref|><|det|>[[144, 769, 853, 820]]<|/det|> +p.4 "...that two peaks locate at P1 and P2..." \(\rightarrow\) "...that two peaks are located at P1 and P2..." "...transition width of \(\Delta T_c\) ..." "...transition width \(\Delta T_c\) ..." (multiple places) "...sudden drops..." \(\rightarrow\) "...suddenly drops..." + +<|ref|>text<|/ref|><|det|>[[144, 832, 853, 865]]<|/det|> +Reply: We thank the reviewer for pointing out these typos. We corrected the typos in the revised manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 89, 288, 104]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 120, 404, 136]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 152, 850, 200]]<|/det|> +The authors addressed the initial concerns I had about the manuscript. The revised discussion and presentation are now more in line with the data presented. I now support publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[116, 231, 404, 247]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[112, 263, 867, 296]]<|/det|> +In the revised manuscript the authors address my previous comments in a reasonable manner. I can support the publication of this paper in Nature Communications. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 118, 850, 320]]<|/det|> +In the revised version of the manuscript the Authors report additional experimental results (magnetic susceptibility and temperature dependence of resistivity and magnetoresistance), as well as provide additional discussion and new analysis of some results (critical field dependence on temperature). The sum of all results convincingly demonstrates an unconventional pressure- dependence of superconductivity in \(\mathrm{CsV_3Sb_5}\) concomitant with the suppression of the CDW and the intrinsic nature of the broadening of the superconducting transition between P1 and P2. I believe that these results can be of broad importance: on the one hand, they yield important information for the future identification of the possibly exotic SC and CDW orders in \(\mathrm{CsV_3Sb_5}\) ; on the other hand, they may help clarifying the origin of similar behaviors observed in other systems with competing orders (see below). + +<|ref|>text<|/ref|><|det|>[[146, 320, 850, 375]]<|/det|> +However, the scenario put forward by the authors (a new, nearly commensurate CDW with domain walls, where filamentary superconductivity occurs, appearing above P1) still appears to be not supported by the data. In particular: + +<|ref|>text<|/ref|><|det|>[[145, 375, 850, 411]]<|/det|> +(i) No features consistent with a second transition within the CDW phase (i.e. kinks, jumps) are observed between the CDW transition at \(T^{*}\) and \(T_{c}\) . + +<|ref|>text<|/ref|><|det|>[[146, 411, 850, 465]]<|/det|> +(ii) The magnetic susceptibility data (provided in the revision) clearly shows a strong broadening of the SC transition already between 0.49 and 0.66 GPa, i.e. before P1. + +<|ref|>text<|/ref|><|det|>[[146, 466, 850, 520]]<|/det|> +(iii) The onset of the diamagnetism coincides with the onset of resistivity suppression, while for quasi-1D filaments one would expect no diamagnetic signal (see also below). + +<|ref|>text<|/ref|><|det|>[[146, 521, 850, 575]]<|/det|> +(iv) As the SdH oscillations are suppressed by P1, non-CDW related changes in the Fermi surface can not be excluded, especially since the oscillations corresponding to the large pockets, presumably most relevant for SC, are not observed. + +<|ref|>text<|/ref|><|det|>[[146, 575, 850, 721]]<|/det|> +(v) Finally, the role of fluctuations and dimensionality is not assessed. \(\mathrm{CsV_3Sb_5}\) shows strong quasi-2D anisotropy and the coherence of superconductivity between the layers may play an important role. In particular, suppression of SC between P1 and P2 may indicate a disruption of the interlayer coupling which would lead to enhanced quasi-2D fluctuations broadening the transition. The Authors themselves draw a possible analogy with LBCO [PRL 99,067001 (2007)], where the suppression of SC occurs due to a decoupling of the layers by a commensurate density-wave order without requiring domain walls. + +<|ref|>text<|/ref|><|det|>[[146, 721, 850, 812]]<|/det|> +As the Authors point out themselves in their Reply, only other types of experiments (e.g. high- resolution x- ray scattering under pressure) may give conclusive evidence for their scenario. Therefore, I think that claims of a pressure- induced transition to a NCCDW with domain walls should be only mentioned in the discussion part and removed from figures and the rest of the text. In addition to that I list + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 119, 594, 137]]<|/det|> +below several suggestions to improve the manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 137, 850, 320]]<|/det|> +(1) Regarding filamentary superconductivity: for SC confined to quasi-1D filaments one would not expect diamagnetic signal to develop at all (see [J. Phys. Chem. Solids Vol. 52, No. 6. pp. 761-767. 1991] or [PRB 103, 024502 (2021)] and [Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25-44] for examples). Strong anisotropy of the SC transition [PRB 85, 184513 (2012)] or dependence on the applied current value [Solid State Communications, 44, 12, 1539 (1982)] could also be expected. However, the Author's data shows instead a consistent onset of diamagnetism at the same temperature as the resistivity suppression and no anomalies mentioned above. This behavior rather suggests inhomogeneous superconductivity, where SC onsets gradually within the volume, rather than measure-zero filaments. + +<|ref|>text<|/ref|><|det|>[[147, 320, 850, 375]]<|/det|> +Consequently, the discussion of "filamentary" or inhomogenous SC should be modified: in the current version the use of this notion is not explained in text and no references are given. + +<|ref|>text<|/ref|><|det|>[[147, 375, 850, 539]]<|/det|> +(2) Relation to works on other SC/density wave systems should be discussed more. In particular, a two-dome behavior has been observed previously in superconductors with competing density waves: JPSJ 82 033705 (2013), Nat. Comm. vol. 3, 943 (2012). Also, a nonmonotonic diamagnetic screening was reported Sci. Rep. 6:24068 (2016). While the control parameters in those studies are different (chemical substitution), the behavior is quite similar: close to the end point of the CDW phase SC is first enhanced on CDW suppression and then strongly suppressed, recovering only when moving further away from CDW phase. This suggests that the behavior reported by the Authors may be a general feature of SC/density wave competition. + +<|ref|>text<|/ref|><|det|>[[147, 539, 850, 611]]<|/det|> +(3) The details of the two-model fit of \(H_{c2}(T)\) (formulas used and the resulting parameters) should be shown in the Supplementary; in particular, the dependence of the coherence lengths on pressure is a useful quantity and may be used to extract information about the scattering rates of individual bands. + +<|ref|>text<|/ref|><|det|>[[147, 612, 850, 685]]<|/det|> +(4) Can the superconducting volume fraction be extracted from the magnetization measurements? Does it reach 100% or a close value for any pressure? This is an important point, since another Referee has pointed out a possibility of superconducting impurity phases. + +<|ref|>text<|/ref|><|det|>[[147, 686, 850, 794]]<|/det|> +(5) I think that the temperature dependence of magnetoresistance is an important result that should be emphasized (e.g. by discussing Sup. Fig. 5 somewhere around lines 126-133). It demonstrates that the linear MR is an intrinsic property of the CDW phase, as MR becomes quadratic when CDW is suppressed both by heating and pressure. A T-dependent MR curve outside of the CDW phase, showing that it is quadratic at all T, would make this statement even more convincing. + +<|ref|>text<|/ref|><|det|>[[171, 795, 850, 813]]<|/det|> +Note that in the previous version only low- T MR was shown, so it could have + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 119, 850, 175]]<|/det|> +been possible that linear MR is the property of the band structure not related to the CDW phase (the absence of changes in \(\rho_{300K}\) vs. P does not immediately imply the absence of change in MR). + +<|ref|>text<|/ref|><|det|>[[147, 175, 850, 266]]<|/det|> +(6) Related to the above, Fig. 4c misses an important feature of the data. Namely, the MR curves are clearly grouped in Supplementary Fig. 4 in three sets, roughly corresponding to regions \(0< \mathrm{P}< \mathrm{P}1\) , \(\mathrm{P}1< \mathrm{P}< \mathrm{P}2\) and \(\mathrm{P}2< \mathrm{P}\) . Thus, if MR of a lower field, e.g. 3T, is plotted, one will be able to see that MR experiences two noticeable changes: around \(\mathrm{P}1\) and \(\mathrm{P}2\) . + +<|ref|>text<|/ref|><|det|>[[146, 266, 851, 375]]<|/det|> +(7) Regarding QCP signatures in resistivity: the range of temperatures presented in Supp. Fig. 8 appears much smaller than the actual temperature range measured - I suggest to provide the \(\rho\) in full temperature range vs. \(T^{2}\) in addition. Moreover, \(\rho \sim T^{2}\) in a certain temperature range can be consistent with quantum criticality of a finite-Q order (such as CDW) in the presence of disorder - see e.g., PRB 51, 9253 (1995), PRL 82, 4280 (1999) - thus a larger temperature range can be of relevance. + +<|ref|>text<|/ref|><|det|>[[146, 375, 850, 485]]<|/det|> +Also, what appears more peculiar is the non- \(T^{2}\) behavior at low pressures and temperatures - could the authors comment on that? In particular, for pressures where \(T_{c}\) is low, \(\rho (T^{2})\) dependence can be shown down to lowest temperatures, e.g. \(2.5^{2} \mathrm{K}^{2}\) for \(\mathrm{P} = 0\) GPa. Indeed, data on a very similar compound \(\mathrm{KV}_{3} \mathrm{Sb}_{5}\) [PHYSICAL REVIEW MATERIALS 3, 094407 (2019)] is fully consistent with \(T^{2}\) behavior at low \(T\) , hence non- \(T^{2}\) behavior for \(\mathrm{P} = 0\) GPa appears anomalous. + +<|ref|>text<|/ref|><|det|>[[176, 485, 368, 503]]<|/det|> +Suggestions for Fig. 3: + +<|ref|>text<|/ref|><|det|>[[146, 504, 850, 576]]<|/det|> +(8) The coloring inside the CDW phase appears unrelated to data - perhaps MR% (see (6) above) or \(\rho\) can be used to provide a consistent and meaningful color scheme? Also, as is mentioned in the beginning of this Report, I suggest removing the NCCDW/domain cartoon as its presence is not supported by the data. + +<|ref|>text<|/ref|><|det|>[[146, 576, 850, 612]]<|/det|> +(9) The SC transition points (blue triangles/squares) in Fig. 3a appear not aligned with the brown-colored region, unlike Fig. 3b. Is this a plotting issue? + +<|ref|>text<|/ref|><|det|>[[146, 613, 850, 667]]<|/det|> +(10) The low-pressure region in Fig. 3b is rather crowded with points - I suggest to show an expanded view of the low-pressure region such that the correspondence between different measurement results could be better appreciated. + +<|ref|>text<|/ref|><|det|>[[176, 668, 315, 686]]<|/det|> +Wording/Typos: + +<|ref|>text<|/ref|><|det|>[[146, 686, 849, 722]]<|/det|> +Lines 19- 24: it should be mentioned that SC increases dramatically after 1.1 GPa. Perhaps, this can be simply summarized by the "two- dome shape" + +<|ref|>text<|/ref|><|det|>[[146, 722, 849, 758]]<|/det|> +Line 25: "is linked" - - "is concomitant with" (a causal relation isn't demonstrated) + +<|ref|>text<|/ref|><|det|>[[175, 758, 499, 776]]<|/det|> +Line 41: "attentions" - - "attention" + +<|ref|>text<|/ref|><|det|>[[146, 777, 850, 813]]<|/det|> +Line 59: The results do not provide evidence of unconventional mechanisms of CDW and SC formation, but rather an unexpected (from the point of view of, e.g., + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 120, 512, 138]]<|/det|> +Landau theory) competition between them. + +<|ref|>text<|/ref|><|det|>[[174, 139, 551, 156]]<|/det|> +Line 77: "much broad" - > "much broader" + +<|ref|>text<|/ref|><|det|>[[146, 157, 850, 211]]<|/det|> +Line 115,136,137,180: "emergence of a new CDW" state seems to imply a transition, but the data is also consistent with a crossover, so perhaps a "transformation (weak transition or crossover) of the CDW" is a better wording. + +<|ref|>text<|/ref|><|det|>[[174, 212, 653, 229]]<|/det|> +Line 129: "shows suddenly drops" - > "suddenly drops" + +<|ref|>text<|/ref|><|det|>[[174, 230, 527, 247]]<|/det|> +Line 147: "dramatically" - > "dramatic" + +<|ref|>text<|/ref|><|det|>[[174, 248, 404, 265]]<|/det|> +Line 173: "does" - > "do" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 91, 410, 106]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[145, 124, 831, 176]]<|/det|> +The authors addressed the initial concerns I had about the manuscript. The revised discussion and presentation are now more in line with the data presented. I now support publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[144, 187, 733, 203]]<|/det|> +Reply: We thank the reviewer for supporting publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[145, 240, 410, 255]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 274, 844, 308]]<|/det|> +In the revised manuscript the authors address my previous comments in a reasonable manner. I can support the publication of this paper in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[144, 337, 733, 353]]<|/det|> +Reply: We thank the reviewer for supporting publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[145, 405, 410, 421]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 432, 854, 610]]<|/det|> +In the revised version of the manuscript the Authors report additional experimental results (magnetic susceptibility and temperature dependence of resistivity and magnetoresistance), as well as provide additional discussion and new analysis of some results (critical field dependence on temperature). The sum of all results convincingly demonstrates an unconventional pressure- dependence of superconductivity in CsV3Sb5 concomitant with the suppression of the CDW and the intrinsic nature of the broadening of the superconducting transition between P1 and P2. I believe that these results can be of broad importance: on the one hand, they yield important information for the future identification of the possibly exotic SC and CDW orders in CsV3Sb5; on the other hand, they may help clarifying the origin of similar behaviors observed in other systems with competing orders (see below). + +<|ref|>text<|/ref|><|det|>[[145, 610, 853, 661]]<|/det|> +However, the scenario put forward by the authors (a new, nearly commensurate CDW with domain walls, where filamentary superconductivity occurs, appearing above P1) still appears to be not supported by the data. In particular: + +<|ref|>text<|/ref|><|det|>[[170, 671, 854, 899]]<|/det|> +(i) No features consistent with a second transition within the CDW phase (i.e. kinks, jumps) are observed between the CDW transition at \(T^*\) and \(T_c\). (ii) The magnetic susceptibility data (provided in the revision) clearly shows a strong broadening of the SC transition already between 0.49 and 0.66 GPa, i.e. before P1. (iii) The onset of the diamagnetism coincides with the onset of resistivity suppression, while for quasi-1D filaments one would expect no diamagnetic signal (see also below). (iv) As the SdH oscillations are suppressed by P1, non- CDW related changes in the Fermi surface can not be excluded, especially since the oscillations corresponding to the large pockets, presumably most relevant for SC, are not observed. (v) Finally, the role of fluctuations and dimensionality is not assessed. CsV3Sb5 shows strong quasi-2D anisotropy and the coherence of superconductivity between the layers may play an important role. In particular, suppression of SC between + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[232, 90, 853, 175]]<|/det|> +P1 and P2 may indicate a disruption of the interlayer coupling which would lead to enhanced quasi- 2D fluctuations broadening the transition. The Authors themselves draw a possible analogy with LBCO [PRL 99,067001 (2007)], where the suppression of SC occurs due to a decoupling of the layers by a commensurate density- wave order without requiring domain walls. + +<|ref|>text<|/ref|><|det|>[[144, 187, 853, 291]]<|/det|> +As the Authors point out themselves in their Reply, only other types of experiments (e.g. high- resolution x- ray scattering under pressure) may give conclusive evidence for their scenario. Therefore, I think that claims of a pressure- induced transition to a NCCDW with domain walls should be only mentioned in the discussion part and removed from figures and the rest of the text. In addition to that I list below several suggestions to improve the manuscript: + +<|ref|>text<|/ref|><|det|>[[144, 302, 853, 393]]<|/det|> +Reply: We thank the reviewer's careful review and appreciate reviewer's constructive suggestions which will definitely improve the manuscript. We agree with the reviewer that the NCCDW with domain walls scenario is not fully confirmed yet. Thus, we take the referee's point and only mentioned it in the discussion part. Correspondingly, we have changed the related figures and discussions of the main text, and the modified text is marked in blue color in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 421, 853, 594]]<|/det|> +(1) Regarding filamentary superconductivity: for SC confined to quasi-1D filaments one would not expect diamagnetic signal to develop at all (see [J. Phys. Chem. Solids Vol. 52, No. 6. pp. 761-767. 1991] or [PRB 103, 024502 (2021)] and [Fig. 3 in Annu. Rev. Condens. Matter Phys. 2019. 10:25-44] for examples). Strong anisotropy of the SC transition [PRB 85, 184513 (2012)] or dependence on the applied current value [Solid State Communications, 44, 12, 1539 (1982)] could also be expected. However, the Author's data shows instead a consistent onset of diamagnetism at the same temperature as the resistivity suppression and no anomalies mentioned above. This behavior rather suggests inhomogeneous superconductivity, where SC onsets gradually within the volume, rather than measure-zero filaments. + +<|ref|>text<|/ref|><|det|>[[145, 607, 853, 657]]<|/det|> +Consequently, the discussion of "filamentary" or inhomogenous SC should be modified: in the current version the use of this notion is not explained in text and no references are given. + +<|ref|>text<|/ref|><|det|>[[144, 670, 853, 772]]<|/det|> +Reply: We sincerely appreciate the reviewer's great suggestions. We agree with the referee that our resistivity and magnetic measurements are not significant to pin down a quasi- 1D filamentary superconductivity. We modified our description as 'inhomogeneous superconductivity' as the referee suggested. However, such change will not alter our conclusions. We also added the discussion of the notion of inhomogeneous superconductivity (multi superconducting phases coexists) in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 785, 853, 887]]<|/det|> +(2) Relation to works on other SC/density wave systems should be discussed more. In particular, a two-dome behavior has been observed previously in superconductors with competing density waves: JPSJ 82 033705 (2013), Nat. Comm. vol. 3, 943 (2012). Also, a nonmonotonic diamagnetic screening was reported Sci. Rep. 6:24068 (2016). While the control parameters in those studies are different (chemical substitution), the behavior is quite similar: close to the end point of the CDW phase SC is first enhanced on CDW suppression and then strongly + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 853, 125]]<|/det|> +suppressed, recovering only when moving further away from CDW phase. This suggests that the behavior reported by the Authors may be a general feature of SC/density wave competition. + +<|ref|>text<|/ref|><|det|>[[144, 134, 854, 326]]<|/det|> +Reply: We thank the reviewer's suggestions. We added more discussion about the two- dome Tc behavior in the other superconductors with competing density waves. However, we would like to point out that our observation of two- dome behavior in \(\mathrm{CsV_3Sb_5}\) occurs WITHIN the CDW phase, which is different with the other superconductors (provided by the reviewer) where a second SC dome appears when the density wave order is completely suppressed. In the revised version, we have added 'Our discoveries may help to clarify the origin of similar behaviors observed in other systems with competing orders. In fact, two- dome Tc behavior were also observed in some superconductors \(^{32 - 34}\) , which might be a general feature for superconductors with competing density waves. However, we would like to note that two- dome SC behavior in \(\mathrm{CsV_3Sb_5}\) occurs within the CDW phase, which is different with the other systems where a second SC dome appears when the density wave order is completely suppressed'. + +<|ref|>text<|/ref|><|det|>[[144, 336, 854, 406]]<|/det|> +(3) The details of the two-model fit of \(Hc2(T)\) (formulas used and the resulting parameters) should be shown in the Supplementary; in particular, the dependence of the coherence lengths on pressure is a useful quantity and may be used to extract information about the scattering rates of individual bands. + +<|ref|>text<|/ref|><|det|>[[144, 416, 854, 504]]<|/det|> +Reply: We have added the details of the two- model fit of \(H_{c2}(T)\) in the supplementary information. We also include the coherence lengths on different pressures in Supplemental Fig.9 (We also show the figure below for convenience) as the referee suggested. However, the scattering rates of individual bands are still difficult to be calculated due to the lacking information of electron mean- free path and Fermi velocity for each band at high pressure. + +<|ref|>image<|/ref|><|det|>[[272, 544, 710, 825]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[140, 872, 853, 890]]<|/det|> +(4) Can the superconducting volume fraction be extracted from the magnetization + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 853, 124]]<|/det|> +measurements? Does it reach \(100\%\) or a close value for any pressure? This is an important point, since another Referee has pointed out a possibility of superconducting impurity phases. + +<|ref|>text<|/ref|><|det|>[[144, 134, 863, 344]]<|/det|> +Reply: Actually, the superconducting volume in our sample reaches \(100\%\) at ambient pressure, as evidenced both by magnetic susceptibility and heat capacity measurements (arxiv: 2102.10987 and arxiv: 2103.11796). In the high- pressure magnetic measurements, the superconducting volume fraction is calculated to be even larger than \(100\%\) (except for \(\mathsf{P} = 0.72\) and 0.89) from our high- pressure magnetic measurements. In our high- pressure magnetic susceptibility experiment, magnetic field cannot be strictly along the ab plane because the sample is surrounded by liquid pressure medium. Therefore, the calculated superconducting volume fraction can be larger than \(100\%\) since the demagnetizing factor is not taken into consideration, especially for flake- like sample. On the other hand, demagnetizing factor do not need to be taken into account for the impurity phases because they are distributed uniformly in the sample (if exist), and the superconducting volume fraction cannot exceed \(100\%\) . Thus, the large diamagnetic signal could not relate to the impurity phases. + +<|ref|>text<|/ref|><|det|>[[144, 371, 854, 510]]<|/det|> +(5) I think that the temperature dependence of magnetoresistance is an important result that should be emphasized (e.g. by discussing Sup. Fig. 5 somewhere around lines 126-133). It demonstrates that the linear MR is an intrinsic property of the CDW phase, as MR becomes quadratic when CDW is suppressed both by heating and pressure. A T-dependent MR curve outside of the CDW phase, showing that it is quadratic at all T, would make this statement even more convincing. Note that in the previous version only low-T MR was shown, so it could have been possible that linear MR is the property of the band structure not related to the CDW phase (the absence of changes in \(\rho 300K\) vs. P does not immediately imply the absence of change in MR). + +<|ref|>text<|/ref|><|det|>[[144, 520, 854, 625]]<|/det|> +Reply: We appreciate the referee for pointing out this issue. We agree with the referee that temperature dependence of MR is an important result. We added 'Temperature dependence of MR at high pressure also evolves from "V" shape to "U" shape as shown in Supplementary Fig.5. These results indicate that the low-field linear MR is an intrinsic property of the CDW phase, since the MR exhibits quadratic temperature-dependence when the CDW is suppressed by both of heating and pressure.' in the revised manuscript as the referee suggested. + +<|ref|>text<|/ref|><|det|>[[144, 654, 854, 740]]<|/det|> +(6) Related to the above, Fig. 4c misses an important feature of the data. Namely, the MR curves are clearly grouped in Supplementary Fig. 4 in three sets, roughly corresponding to regions \(0< P< P1\) , \(P1< P< P2\) and \(P2< P\) . Thus, if MR of a lower field, e.g. 3T, is plotted, one will be able to see that MR experiences two noticeable changes: around P1 and P2. + +<|ref|>text<|/ref|><|det|>[[144, 751, 853, 785]]<|/det|> +Reply: We thank the reviewer's great suggestions. We added the MR data at 3T in Fig.4 in the revised manuscript. The related description was also added in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 813, 854, 901]]<|/det|> +(7) Regarding QCP signatures in resistivity: the range of temperatures presented in Supp. Fig. 8 appears much smaller than the actual temperature range measured - I suggest to provide the \(\rho\) in full temperature range vs. \(T^2\) in addition. Moreover, \(\rho \sim T^2\) in a certain temperature range can be consistent with quantum criticality of a finite-Q order (such as CDW) in the presence of disorder - see e.g., PRB 51, 9253 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 89, 854, 211]]<|/det|> +(1995), PRL 82, 4280 (1999) - thus a larger temperature range can be of relevance. Also, what appears more peculiar is the non- \(T^2\) behavior at low pressures and temperatures - could the authors comment on that? In particular, for pressures where \(T_c\) is low, \(\rho (T^2)\) dependence can be shown down to lowest temperatures, e.g. \(2.5^2 K^2\) for \(\mathsf{P} = 0\) GPa. Indeed, data on a very similar compound KV3Sb5 [PHYSICAL REVIEW MATERIALS 3, 094407 (2019)] is fully consistent with \(T^2\) behavior at low \(T,\) hence non- \(T^2\) behavior for \(\mathsf{P} = 0\) GPa appears anomalous. + +<|ref|>text<|/ref|><|det|>[[144, 223, 854, 430]]<|/det|> +Reply: We thank the referee's great suggestion. We have shown \(\rho\) in a much larger temperature range in Supp. Fig.8 (We also show the figure below for convenience) as the referee suggested. Actually, the low- temperature resistivity follows \(T^2\) behavior below \(35K\) above P2. It severely deviates from \(T^2\) at higher temperature. The anomaly of resistivity with pressure between 1.64 and 1.84 GPa is related to the CDW transition. We should mention that the \(T^2\) behavior can only observed at low temperature even for a Fermi liquid system. At higher temperature, the electron- phonon scattering will make the resistivity deviate from the \(T^2\) behavior. The low- field MR shows linear behavior in the CDW state, which possibly arise from the linear band crossings, can possibly make the resistivity deviate from the \(T^2\) behavior. One of the remarkable differences between \(\mathsf{CsV}_3\mathsf{Sb}_5\) and \(\mathsf{KV}_3\mathsf{Sb}_5\) is that the former has very little (even no) vacancy. The vacancy in \(\mathsf{KV}_3\mathsf{Sb}_5\) is much more significant which could lead to slightly different resistivity behavior. However, it is still an open question need to be clarified in the future study. + +<|ref|>image<|/ref|><|det|>[[144, 454, 848, 701]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 760, 299, 775]]<|/det|> +Suggestions for Fig. 3: + +<|ref|>text<|/ref|><|det|>[[144, 787, 854, 855]]<|/det|> +(8) The coloring inside the CDW phase appears unrelated to data - perhaps MR% (see (6) above) or \(\rho\) can be used to provide a consistent and meaningful color scheme? Also, as is mentioned in the beginning of this Report, I suggest removing the NCCDW/domain cartoon as its presence is not supported by the data. + +<|ref|>text<|/ref|><|det|>[[144, 866, 853, 900]]<|/det|> +Reply: We have used the magnitude of MR (measured at 9T,10K) as the color scheme in Fig.3 as the referee suggested. We have also removed the NCCDW/domain cartoon. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[142, 90, 855, 125]]<|/det|> +(9) The SC transition points (blue triangles/squares) in Fig. 3a appear not aligned with the brown-colored region, unlike Fig. 3b. Is this a plotting issue? + +<|ref|>text<|/ref|><|det|>[[144, 134, 836, 152]]<|/det|> +Reply: We thank the reviewer for point out this problem. We modified it in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[144, 162, 853, 213]]<|/det|> +(10) The low-pressure region in Fig. 3b is rather crowded with points - I suggest to show an expanded view of the low-pressure region such that the correspondence between different measurement results could be better appreciated. + +<|ref|>text<|/ref|><|det|>[[144, 225, 853, 259]]<|/det|> +Reply: We thank the reviewer's great suggestions. We expanded the view of the low-pressure region in Supplemental Fig.10 (We also show the figure below for convenience) in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[192, 306, 808, 667]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 700, 259, 715]]<|/det|> +Wording/Typos: + +<|ref|>text<|/ref|><|det|>[[144, 717, 853, 750]]<|/det|> +Lines 19- 24: it should be mentioned that SC increases dramatically after 1.1 GPa. Perhaps, this can be simply summarized by the "two- dome shape" + +<|ref|>text<|/ref|><|det|>[[144, 761, 717, 778]]<|/det|> +Line 25: "is linked" - > "is concomitant with" (a causal relation isn't demonstrated) + +<|ref|>text<|/ref|><|det|>[[145, 789, 395, 804]]<|/det|> +Line 41: "attentions" - > "attention" + +<|ref|>text<|/ref|><|det|>[[144, 816, 854, 867]]<|/det|> +Line 59: The results do not provide evidence of unconventional mechanisms of CDW and SC formation, but rather an unexpected (from the point of view of, e.g., Landau theory) competition between them. + +<|ref|>text<|/ref|><|det|>[[144, 879, 440, 894]]<|/det|> +Line 77: "much broad" - > "much broader" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 854, 141]]<|/det|> +Line 115,136,137,180: "emergence of a new CDW" state seems to imply a transition, but the data is also consistent with a crossover, so perhaps a "transformation (weak transition or crossover) of the CDW" is a better wording. + +<|ref|>text<|/ref|><|det|>[[144, 152, 528, 168]]<|/det|> +Line 129: "shows suddenly drops" - > "suddenly drops" + +<|ref|>text<|/ref|><|det|>[[145, 180, 415, 195]]<|/det|> +Line 147: "dramatically" - > "dramatic" + +<|ref|>text<|/ref|><|det|>[[145, 207, 317, 222]]<|/det|> +Line 173: "does" - > "do" + +<|ref|>text<|/ref|><|det|>[[144, 235, 854, 268]]<|/det|> +Reply: We thank the referee for pointing out these typos. We made the related corrections in the revised manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/images_list.json b/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1b1fc7e2f5421050308c061d6353762100a813a9 --- /dev/null +++ b/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,31 @@ + +# nature portfolio + +Peer Review File + +# Bat-borne H9N2 influenza virus evades MxA restriction and exhibits efficient replication and transmission in ferrets + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The revised manuscript has been modified to address the reviewer comments and questions and has been improved. I have no further comments. + +Reviewer #2 (Remarks to the Author): + +The authors have addressed the majority of comments raised during peer review, and have improved the quality of the manuscript as a result, specifically by including infectious titer data to support in vivo work, clarifying the relative novelty of the transmission findings in general, and providing more specificity regarding the transmission setup employed. No further comments. + +Reviewer #3 (Remarks to the Author): + +I raised some minor revisions previously, and this, together with the other reviewer's responses, has been adequately addressed. I have no more additional comments + +<--- Page Split ---> diff --git a/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..4632880ac027fbcc5e212d8fb358d88cb45e0a13 --- /dev/null +++ b/peer_reviews/55ba63630650d33e87b0779992c6633d98b1f06dca3f8ce45d4083103b2d2c0a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,40 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 505, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[67, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[95, 154, 896, 257]]<|/det|> +# Bat-borne H9N2 influenza virus evades MxA restriction and exhibits efficient replication and transmission in ferrets + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 867, 138]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[118, 212, 308, 227]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 272, 404, 288]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 332, 875, 367]]<|/det|> +The revised manuscript has been modified to address the reviewer comments and questions and has been improved. I have no further comments. + +<|ref|>text<|/ref|><|det|>[[118, 440, 404, 456]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 500, 877, 573]]<|/det|> +The authors have addressed the majority of comments raised during peer review, and have improved the quality of the manuscript as a result, specifically by including infectious titer data to support in vivo work, clarifying the relative novelty of the transmission findings in general, and providing more specificity regarding the transmission setup employed. No further comments. + +<|ref|>text<|/ref|><|det|>[[118, 648, 404, 664]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 708, 870, 743]]<|/det|> +I raised some minor revisions previously, and this, together with the other reviewer's responses, has been adequately addressed. I have no more additional comments + +<--- Page Split ---> diff --git a/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..87fa4e4549a06b8f4e69b16623fcb56db4eba6c0 --- /dev/null +++ b/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,254 @@ + +# Automatic Speech Recognition Predicts Contemporaneous Earthquake Fault Displacement + +Corresponding Author: Dr Christopher Johnson + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Dear Editor, + +The manuscript presents a study on fault displacement prediction using advanced speech detection neural networks, which is described as a pioneering effort in the application of machine learning to seismology. This work builds on a prior study by Johnson and Johnson (2024). While the results do not demonstrate a significant improvement in prediction accuracy, they highlight the potential of speech detection networks to analyze continuous seismic signals, opening up promising avenues for future research in this field. As such, I strongly support its publication. My minor comments are as follows: + +- Figure 3: It is evident that in all displacement cycles, the predictions tend to be overestimated during the first half of the cycle and underestimated during the second half. This pattern is also observed in the results produced by GBT. How do the authors account for this behavior? Is not it the effect of the activation function in the last layer? If yes, other functions such as 'sigmoid' or 'tanh' may enhance it. + +- Lines 372-377: The authors state that "the Wav2Vec 2.0 model results rival the best laboratory shear model predictions...". It may cause misunderstanding, as Rouet-Leduc et al. (2017) and several subsequent studies have improved laboratory results by up to 90%. I suggest removing this statement. + +- Figure 5: A. If we consider the start of the 'vertical dark gray bar' as the onset of failure, panels 'f, g, l, m, q, and r' are not in agreement with others (this also applies to Figure 6). B. Following my earlier comment, the underestimation near failure leads to the prediction of relatively small displacements compared to the larger GNSS displacements. In a real-world application of this network, such low displacements might not be recognized as indicating the onset of failure, as seen in panels 'a, d, o, and s'. + +- Figures S1-S3: How do the authors explain the higher \(\mathsf{R}^2\) values for future predictions (67-77%) compared to contemporaneous predictions (49-63%), which contradicts the description in the text (lines 593-603)? Furthermore, the highest \(\mathsf{R}^2\) in Figure S2 is 77%, while in Figure S3, it is 62%. Clarification on this is needed. + +- Normalization: In line 780, it is mentioned how the waveform (input) is standardized. How about the outputs (displacements)? If min-max normalization is used, discuss about the problems in real applications, where the range of displacements may exceed the range of training data. + +Best Sadegh Karimpouli GFZ Potsdam + +Reviewer #2 + +(Remarks to the Author) Dear Authors and Editor, + +Please find below my review of the paper "Automatic Speech Recognition Predicts Contemporaneous Earthquake Fault Displacement," submitted to Nature Communications by Dr. Johnson and colleagues. Overall, I find the manuscript to be of high quality and believe it deserves publication. I have included only minor comments that I hope will help further strengthen the manuscript and foster continued discussion. + +The authors present an application of machine learning for seismic- to- displacement signal prediction in the case of the 2018 + +<--- Page Split ---> + +Kilauea crater collapse. Building on prior applications across diverse seismic cycles—experimental fault systems, slow- slip events in Cascadia—the authors extend their methods to this new context, demonstrating the robustness of their approach. Notably, they highlight that models trained in related domains can effectively capture seismic signal features necessary for predicting contemporaneous fault displacement, with the Wave2Vec 2.0 model proving particularly effective. An ambitious extension explored here is near- future displacement prediction, which, although not fully successful in this study, holds strong potential for future refinement. This suggests that continued advances in AI- based speech processing could significantly impact the field by enabling models with enhanced predictive capabilities. The introduction effectively presents the challenges posed by limited observational cycles in field data and the motivation for this work. + +My first point of discussion is the issue of non- stationarity in seismic cycles. In Figure 1, for instance, the absolute northward displacement at the CRIM station appears to saturate slightly, while eastward displacement does not. More importantly, this effect only affects the testing dataset. The long- period displacement amplitudes exceed the dynamic stick- slip motion, prompting the authors to remove this long- term trend to achieve stationarity. This decision raises several follow- up questions: (1) Could the displacement rate serve as an alternative dataset that balances stationarity with prediction accuracy? While calculating the derivative would increase noise, it might also retain critical non- stationary components to be predicted. (2) Given that training on a small, evolving segment of data may limit predictive accuracy, could this trend discrepancy between training and testing data affect generalization? (3) Are comparable non- stationary signals observed in lab simulations? If so, this might clarify whether these non- stationary elements hinder model predictions in real- world applications. + +Figure 3 reveals a notable pattern: predicted displacement saturates, forming a plateau as the model approaches the time- to- failure (visible in Figures 3A and C). This persistent issue, observed across several of the authors' prior studies, suggests a gap in model performance that resists improvement even with advanced features delivered by Wave2Vec. Do you have insights on this plateau in the context of Kilauea? I understand that answering this question may require an in- depth feature analysis, which the authors note as an objective for future research. + +Another interesting aspect of the study is the use of multiple seismic stations, which incorporates both spatial and temporal features. Although the methods section is comprehensive, it remains unclear whether the authors aggregated the traces in time (e.g., creating combined 4x300- second channel traces) or "vertically" (i.e., 4x3 channels of 300 seconds each). I am unsure if such a distinction would affect the model's performance, but this clarification could help readers better understand the model's approach to data structuring. A follow- up question arises: could model performance improve with advanced waveform combination techniques, such as cross- correlation functions or beamforming? + +Finally, I wonder if narrowing the frequency band of analysis could improve the model's performance. Currently, the study uses the broadband signal (from 0.1 to \(50 \text{Hz}\) ), which includes a substantial amount of information that may not be related to the crater collapse (e.g., oceanic microseismic noise). + +I remain available for further discussions and would be glad to read a revised version of the manuscript if needed. + +Sincerely, Leonard Seydoux + +Reviewer #3 + +(Remarks to the Author) + +The manuscript describes an approach in which a machine learning tool developed by FAIR (Facebook AI Research) called Wav2Vec 2.0 for speech recognition is here repurposed to predict earthquake fault displacement from continuous seismic data. The study uses data from the 2018 caldera collapses at the Kilauea volcano in Hawai'i, based on about 40 collapses within about 30 days, intervallled by slow reload. Continuous seismic record was done from a network of broadband stations which recorded moderate magnitude seismic events up to about Mw 5. The authors train Wav2Vec 2.0 to predict "Contemporaneous Displacement" as well as "Future Displacement" from seismic waveforms, fitting it with observed GNSS data. The method is a small improvement compared to recently published work on GRL, 2024, where the same data were predicted using a gradient boosted tree approach. Here they achieve an \(R^2\) of 0.63 in predictions, while in the study published on GRL they had obtained \(R^2 = 0.59\) . + +The authors highlight that their results show matching patterns between the observed real- world seismic record and the laboratory recording of controlled experiments, which suggest that the successes of machine learning in predicting laboratory events should be mirrored in real world correct predictions. However unfortunately, while they show a robust ability to detect "contemporaneous displacement" (I don't like their use of the world predict, which I would only reserve for "future" predictions) in seismic data, they are very honest at highlighting how Wav2Vec performs poorly when trying to predict future events. + +Overall, I find that although their results are interesting and their study stimulating future research, I do not believe that their progress is substantial compared to previous works. Here below I list more in detail the issues that I find in the manuscript: + +Comments: + +1) The data challenge is not described in quantitative detail. They only emphasize the challenges of applying machine learning to geophysical data with limited historical and comprehensive event coverage. Better knowledge of the computational training and testing time of the use of Wav2Vec vs other algorithms (e.g. gradient boosted tree) might + +<--- Page Split ---> + +reinforce the argument whether these should be or not adopted in the future, for example for instantaneous detection of the caldera movements, as the authors show their approach is successful in that. + +2) The discussion on data leakage could be expanded for clarity. The authors highlight that future displacement predictions are less reliable due to data leakage and model limitations. But in fact, what seems to me, "data leakage" is a term used to cover the fact that the algorithm "predicts" the slip after it has "detected" it. Maybe the authors intended something more sophisticated than that, and in this case how it could be mitigated, but for what results from this work, there is no real "prediction", even short term one, happening from this approach. + +3) Lack of clarity on how the 3D data of a broadband station is turned into a 1D Wav2Vec latent space vector as described. The authors describe in the technical part that they combine 8 sensors times 3 channels, i.e. a 24 dimensional vector times 30k data points (100Hz for 300s), which are initially expanded to 93x768 (71424) sized latent vector and then reduced to 93x256 (23808). I find the 93 timesteps hard to comprehend. What is the origin of this number? Symmetrically, I do not understand how optimal is 768. I understand that these numbers might not be relevant overall and that results would have likely be similar with other choices of the shape of the latent spaces, but still the rationale behind this specific choice should be given. + +4) The work compares (paragraph starting in 348) the results of a recently published GRL paper (Seismic Features Predict Ground Motions During Repeating Caldera Collapse Sequence) where the same data were used to train and predict displacement using the gradient boosted tree approach. However, they do not show clearly what the improvement was. From the text one reads that R2 increased from 0.59 to 0.63 by changing the method, but that does not seem such a drastic improvement. Overall, the authors explain at length the superiority of Wav2Vec in terms of being able to combine in a unique prediction all the 3x8 channels of data, however from this point of view, I would say that the improvement has been insufficient and one is confronted with the question whether actually these 24 channels offer more information than a single one. More in general, the authors do not offer an answer to the question that given the greater dataset used, why isn't the performance of Wav2Vec much better than gradient boosted tree? + +5) The text uses both the terms "future displacement" and "failure prediction," without an explicit definition. While as a reader I have an intuitive understanding of the fact that the first is the quantitative observed displacement in the following 30 seconds, while the second attempts at identifying the caldera collapses, I believe that the authors should have given clear definitions. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) Dear Editor, + +Following the responses provided in the response file and the revisions made to the manuscript, I support the publication of the manuscript. + +Best regards, Sadegh Karimpouli + +Reviewer #2 + +(Remarks to the Author) Dear Authors and Editor, + +I have carefully reviewed the insightful responses provided by the authors regarding the remarks I made on the manuscript. I appreciate the thorough answers and the related corrections, and I agree with all points addressed. Therefore, I fully support the publication of the paper in its current form. + +Best regards, Leonard Seydoux + +Reviewer #3 + +(Remarks to the Author) I believed that the authors have addressed all the points that I made and I recommend their work for publication + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Dear Editor, + +The manuscript presents a study on fault displacement prediction using advanced speech detection neural networks, which is described as a pioneering effort in the application of machine learning to seismology. This work builds on a prior study by Johnson and Johnson (2024). While the results do not demonstrate a significant improvement in prediction accuracy, they highlight the potential of speech detection networks to analyze continuous seismic signals, opening up promising avenues for future research in this field. As such, I strongly support its publication. We thank you for the time spent reviewing our manuscript and the constructive feedback. During the revisions we have taken the opportunity to further explain why these results are a significant advancement, primarily considering this is a self- supervised model and insensitive to the nonstationarity that required additional processing in the previous work. We now state, with additional added text "The limited ability of gradient boosted tree models to properly generalize due to the non- stationarity is problematic if trying to extract salient features directly from the data for downstream tasks as is done with a foundation model." + +Provided are response to each comment and our best effort to address the point or concern cited. + +My minor comments are as follows: + +- Figure 3: It is evident that in all displacement cycles, the predictions tend to be overestimated during the first half of the cycle and underestimated during the second half. This pattern is also observed in the results produced by GBT. How do the authors account for this behavior? Is not it the effect of the activation function in the last layer? If yes, other functions such as 'sigmoid' or 'tanh' may enhance it. + +This observation was a topic of much discussion while preparing the manuscript. This is not a function of an activation function in the final layer. In Johnson and Johnson (2024) this same feature is observed in the displacement predictions. In that study a boosted tree model was used, and models were developed using a data set that was reduced by excluding time windows containing an earthquake phase arrival (EQtransformer detection algorithm was applied to label time windows with P/S arrival). Since the seismicity rates increase throughout the loading cycle there was less temporal sampling at the time nearest failure. However, the results were largely unchanged and the displacement prediction still contain a similar plateau (see Fig. 4). We provide the reader with more context in the results we now state "Both the gradient boosted tree and Wav2Vec 2.0 model show an upper prediction threshold for the final 10- 20% of the loading cycles that does not match the GNSS (Fig. \ref{fig:Wav2Vec2.0}) A). This output is not well understood and various attempts to further improve the predictions in the near failure time intervals were unsuccessful. At this time we speculate the plateau results from increased 'noise' in the system since this is a volcano caldera collapse, not a more traditional earthquake fault. The additional signals introduced to the model would contain tremors and potentially other fluid related processed creating specific conditions in the loading rate that the model is unable to fully capture." + +- Lines 372-377: The authors state that "the Wav2Vec 2.0 model results rival the best laboratory shear model predictions...". It may cause misunderstanding, as Rouet-Leduc et al. (2017) and several subsequent studies have improved laboratory results by up to 90%. I suggest removing this statement. + +<--- Page Split ---> + +We have revised the statement to clearly convey the performance improvements when comparing to previous laboratory based analysis. We now state “Moreover, when considering the data availability and overall performance, the Wav2Vec 2.0 model results rival the best laboratory shear model predictions for both decision tree and deep learning models, where the data generally contains many more slip events and less variance due to the controlled laboratory conditions” + +- Figure 5: A. If we consider the start of the ‘vertical dark gray bar’ as the onset of failure, panels ‘f, g, l, m, q, and r’ are not in agreement with others (this also applies to Figure 6). B. Following my earlier comment, the underestimation near failure leads to the prediction of relatively small displacements compared to the larger GNSS displacements. In a real-world application of this network, such low displacements might not be recognized as indicating the onset of failure, as seen in panels ‘a, d, o, and s’. + +The vertical line is the selection window we prescribe using the timing estimate we obtain from the data. Using an observational perspective, we are not assigning a pass/fail criteria based on the amplitude of change. We note that in this real world application having a small displacement might not warrant a failure alert, however we are testing if the information is obtainable from the data in the model framework presented. For a more concise describing of the properly detected events we now state “The selection criteria is observational; we are looking for a decrease in displacement at the prescribed time step or a decrease that matches the GNSS measurements. The inclusion of events that match the GNSS (e.g., “g”, “l”, “q”, and “r”) arises from the potential timing discrepancy introduced by the 30 second windowing of the displacement data.” + +- Figures S1-S3: How do the authors explain the higher \(\mathrm{R}^2\) values for future predictions (67-77%) compared to contemporaneous predictions (49-63%), which contradicts the description in the text (lines 593-603)? Furthermore, the highest \(\mathrm{R}^2\) in Figure S2 is 77%, while in Figure S3, it is 62%. Clarification on this is needed. + +This is a good observation that we did not fully explore because the main test with the prediction of a large slip event. We note that this is specific to the training data because the testing data has very similar R2 values. We now state “Interestingly, the \(\mathrm{SR}^2 \times 2\mathrm{S}\) values for the input-output window pair selection (Fig. S2) are on-average higher the contemporaneous predictions (Fig. S1) with the training data set but quite similar with the testing data. The displacement predictions appear good throughout the earthquake cycle (Fig. S3), however, the \(\mathrm{SR}^2 \times 2\mathrm{S}\) value may be misleading as shown in expanded view for the earthquake failures.” + +- Normalization: In line 780, it is mentioned how the waveform (input) is standardized. How about the outputs (displacements)? If min-max normalization is used, discuss about the problems in real applications, where the range of displacements may exceed the range of training data. The model output is standardized for stability but reported with the variance and mean corrected back to the original scale. In this application the prediction is a continuous variable that can scale beyond the data, however we did not further explore those limitations. + +Best Sadegh Karimpouli GFZ Potsdam Sadegh, we again thank you for your time reviewing the manuscript. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +Dear Authors and Editor, + +Please find below my review of the paper "Automatic Speech Recognition Predicts Contemporaneous Earthquake Fault Displacement," submitted to Nature Communications by Dr. Johnson and colleagues. Overall, I find the manuscript to be of high quality and believe it deserves publication. I have included only minor comments that I hope will help further strengthen the manuscript and foster continued discussion. + +The authors present an application of machine learning for seismic- to- displacement signal prediction in the case of the 2018 Kilauea crater collapse. Building on prior applications across diverse seismic cycles—experimental fault systems, slow- slip events in Cascadia—the authors extend their methods to this new context, demonstrating the robustness of their approach. Notably, they highlight that models trained in related domains can effectively capture seismic signal features necessary for predicting contemporaneous fault displacement, with the Wave2Vec 2.0 model proving particularly effective. An ambitious extension explored here is near- future displacement prediction, which, although not fully successful in this study, holds strong potential for future refinement. This suggests that continued advances in AI- based speech processing could significantly impact the field by enabling models with enhanced predictive capabilities. The introduction effectively presents the challenges posed by limited observational cycles in field data and the motivation for this work. + +We thank you for the time spent reviewing our manuscript. We found the constructive feedback very helpful and have provided a response to each comment with our best effort to address the point or concern cited. + +My first point of discussion is the issue of non- stationarity in seismic cycles. In Figure 1, for instance, the absolute northward displacement at the CRIM station appears to saturate slightly, while eastward displacement does not. More importantly, this effect only affects the testing dataset. The long- period displacement amplitudes exceed the dynamic stick- slip motion, prompting the authors to remove this long- term trend to achieve stationarity. This decision raises several follow- up questions: (1) Could the displacement rate serve as an alternative dataset that balances stationarity with prediction accuracy? While calculating the derivative would increase noise, it might also retain critical non- stationary components to be predicted. (2) Given that training on a small, evolving segment of data may limit predictive accuracy, could this trend discrepancy between training and testing data affect generalization? (3) Are comparable nonstationary signals observed in lab simulations? If so, this might clarify whether these nonstationary elements hinder model predictions in real- world applications. + +The decision to remove the nonstationary component arose from our focus on the individual repeating slip events within the longer term deformation signal. This is an excellent question because, as noted by the reviewer, we are not prescribing the model to learn the full dynamics of the system. It is possible that the displacement rate could be incorporated into the dataset as an additional target label, however, that was not within the scope of the goals in this study. In our previous work we needed to perform a different scheme for the train/validate/test dataset due directly to this nonstationarity. Here, the Wav2Vec model can perform remarkably better without special consideration for this known quantity in the data. When comparing to laboratory data + +<--- Page Split ---> + +sets, there are some experiments with long term trends in the data, but typically the need for additional preprocessing is not required. + +Figure 3 reveals a notable pattern: predicted displacement saturates, forming a plateau as the model approaches the time- to- failure (visible in Figures 3A and C). This persistent issue, observed across several of the authors' prior studies, suggests a gap in model performance that resists improvement even with advanced features delivered by Wave2Vec. Do you have insights on this plateau in the context of Kilauea? I understand that answering this question may require an in- depth feature analysis, which the authors note as an objective for future research. Reviewer #1 also noticed the same pattern, and we repeat our reply here. This observation was a topic of much discussion while preparing the manuscript. This is not a function of an activation function in the final layer. In Johnson and Johnson (2024) this same feature is observed in the displacement predictions. In that study a boosted tree model was used, and models were developed using a data set that was reduced by excluding time windows containing an earthquake phase arrival (EQtransformer detection algorithm was applied to label time windows with P/S arrival). Since the seismicity rates increase throughout the loading cycle there was less temporal sampling at the time nearest failure. However, the results were largely unchanged and the displacement prediction still contain a similar plateau (see Fig. 4). We provide the reader with more context in the results we now state "Both the gradient boosted tree and Wav2Vec 2.0 model show an upper prediction threshold for the final \(10 - 20\%\) of the loading cycles that does not match the GNSS (Fig. \ref{fig:4A}). This output is not well understood and various attempts to further improve the predictions in the near failure time intervals were unsuccessful. At this time we speculate the plateau results from increased 'noise' in the system since this is a volcano caldera collapse, not a more traditional earthquake fault. The additional signals introduced to the model would contain tremors and potentially other fluid related processed creating specific conditions in the loading rate that the model is unable to fully capture." + +Another interesting aspect of the study is the use of multiple seismic stations, which incorporates both spatial and temporal features. Although the methods section is comprehensive, it remains unclear whether the authors aggregated the traces in time (e.g., creating combined 4x300- second channel traces) or "vertically" (i.e., 4x3 channels of 300 seconds each). I am unsure if such a distinction would affect the model's performance, but this clarification could help readers better understand the model's approach to data structuring. A follow- up question arises: could model performance improve with advanced waveform combination techniques, such as cross- correlation functions or beamforming? + +The model input is the 3- component 30 second waveform segments from all stations for model training. The data is structured such that a batch contains N, where the batch size is 8, waveform examples of 3- comp waveforms are for a tensor of shape [N, 3, 30,000]. For pretraining the input is reshaped to [24, 30,000] so each waveform channel is input independently in the self- supervised pretraining. We now state more clearly "Assuming a batch size of 8, the shape of the input batch tensor is [8 (batch size), 30,000 (data points), 3 (channels)]. We pass the waveform of each channel independently to the Wav2Vec 2.0 model by reshaping the input batch to [24 (waveform samples) = 8 (batch size) \* 3 (channels), 30,000 (data points)]." + +Beamforming has not been applied here, but we did use that approach in a previous study (see Umlauft et al., 2024 on glacier motions) using the beamformed catalog as a unique model input. + +<--- Page Split ---> + +That work focused on glacial sliding processes and the beamforming results were found to be a high ranking feature in the importance. Inputting station cross correlations is the topic of ongoing work in group now and results are showing success. Both great questions. + +Finally, I wonder if narrowing the frequency band of analysis could improve the model's performance. Currently, the study uses the broadband signal (from 0.1 to \(50\mathrm{Hz}\) ), which includes a substantial amount of information that may not be related to the crater collapse (e.g., oceanic microseismic noise). + +This is a good observation. Our thoughts is the time period considered (about 2 months) should not be largely affected by the known lower frequency signals which change periodically throughout the year and during large weather events. Our reasoning for including these lower frequency bands was to not constrain the model to a priori assumptions about important frequency content. Our justification is the model applied learned CNN filters that will account for a large range of frequencies when inputting the data to the transformer block. We now state "The hierarchical feature extraction captures information at different levels of abstraction, enabling the model to learn both low- level and high- level representations across a broad frequency spectrum of the input signal." + +I remain available for further discussions and would be glad to read a revised version of the manuscript if needed. + +Sincerely, Leonard Seydoux Leonard, we again thank you for your time reviewing the manuscript. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The manuscript describes an approach in which a machine learning tool developed by FAIR (Facebook AI Research) called Wav2Vec 2.0 for speech recognition is here repurposed to predict earthquake fault displacement from continuous seismic data. The study uses data from the 2018 caldera collapses at the Kilauea volcano in Hawai'i, based on about 40 collapses within about 30 days, intervallled by slow reload. Continuous seismic record was done from a network of broadband stations which recorded moderate magnitude seismic events up to about Mw 5. The authors train Wav2Vec 2.0 to predict "Contemporaneous Displacement" as well as "Future Displacement" from seismic waveforms, fitting it with observed GNSS data. The method is a small improvement compared to recently published work on GRL, 2024, where the same data were predicted using a gradient boosted tree approach. Here they achieve an \(\mathrm{R}^2\) of 0.63 in predictions, while in the study published on GRL they had obtained \(\mathrm{R}^2 = 0.59\) . + +The authors highlight that their results show matching patterns between the observed real- world seismic record and the laboratory recording of controlled experiments, which suggest that the successes of machine learning in predicting laboratory events should be mirrored in real world correct predictions. However unfortunately, while they show a robust ability to detect "contemporaneous displacement" (I don't like their use of the world predict, which I would only reserve for "future" predictions) in seismic data, they are very honest at highlighting how Wav2Vec performs poorly when trying to predict future events. + +Overall, I find that although their results are interesting and their study stimulating future research, I do not believe that their progress is substantial compared to previous works. Here below I list more in detail the issues that I find in the manuscript: + +We thank you for the time spent reviewing our manuscript and the constructive feedback. In particular we have addressed the concern raised about the progress compared to previous works. We now include more detailed description of using self- supervised learning models instead of the previous efforts applying supervised learning techniques. In the last paragraph of the introduction we now state "The widespread adoption of unsupervised, or self- supervised, learning techniques for signal classification has not seen the same rise in popularity for seismic waveform analysis as compared to other deep learning fields; despite intriguing results demonstrating the ability of ML models to separate signals with no a priori knowledge [e.g., 26- 28]. The lack of generalization in supervised learning models does not facilitate fine- tuning an existing model for out- of- distribution data, and instead requires large amounts of labeled training data to develop a new model for a specific application [29]. The supervised learning is now eclipsed by the development of self- supervised foundation models using unlabeled data to produce generative pre- trained transformer networks [30]." + +We then further describe the limitation in the previous work and include more details throughout for this advancement. + +Below we provide a response to each comment. + +Comments: + +1) The data challenge is not described in quantitative detail. They only emphasize the challenges of applying machine learning to geophysical data with limited historical and comprehensive + +<--- Page Split ---> + +event coverage. Better knowledge of the computational training and testing time of the use of Wav2Vec vs other algorithms (e.g. gradient boosted tree) might reinforce the argument whether these should be or not adopted in the future, for example for instantaneous detection of the caldera movements, as the authors show their approach is successful in that. + +The lack of data for a full earthquake cycle is comprehensively described in Wang, Johnson, Bennet, and Johnson (2024) Nature Communications. In that we present a transfer learning approach that could be implemented for decadal to century time scales that are common for recurrence times of earthquake faults. We now more clearly state "The primary challenge for applying machine learning to frictional failure on most faults hosting large magnitude earthquakes is the long repeat times, ranging from decades to thousands of years, and therefore, the lack of geophysical instrumental data that capture a complete loading cycle, often only a small fraction of a loading cycle." + +As for the computation expense and training time, yes, these modeling efforts require HPC GPU clusters to facilitate model development, training, validation, and test. Specifically, this compute cost scales with the size of the data. In this work the expense compounds when testing the optimal input and output time windows which are an important result. This is a necessary resource and a requirement to further test what types of model architectures are most applicable. + +We fully acknowledge these resources are not available at every research institute, but external options exist, e.g., AWS. This is not meant as a criticism but instead we use the analogy of a geochemist in a research institute with a \(\) 1\mathrm{M}\$ mass spectrometer to do her radiological dating studies. It's the correct resource for the work performed. As for adopting these types of models for future use, that is exactly what we aim to present. The goal of our research group is to determine the performance metrics with the ambition of developing a foundation model as has been successful in computer vision and natural language processing. We now state to clearly articulate this point "The limited ability of the gradient boosted tree model to properly generalize due to the non- stationarity is problematic if trying to extract salient features directly from the data for downstream tasks as is done with a foundation model. In the present work we develop a self- supervised learning approach to determine if contemporaneous and future predictions can be made directly from the continuous seismic data." + +2) The discussion on data leakage could be expanded for clarity. The authors highlight that future displacement predictions are less reliable due to data leakage and model limitations. But in fact, what seems to me, "data leakage" is a term used to cover the fact that the algorithm "predicts" the slip after it has "detected" it. Maybe the authors intended something more sophisticated than that, and in this case how it could be mitigated, but for what results from this work, there is no real "prediction", even short term one, happening from this approach. + +Point well taken and we have expanded our comments on the ability to make short term predictions. We now state "The delayed timing of predictions indicate this model is far less reliable and only predicts the slip after the failure event is observed in the data. As a test if data leakage associated with the model predicting timing, we conducted model tests using future predictions for two successively later time intervals. Those results clearly indicate slip is only predicted after the model input contains the slip event of interest. For this data the model fails to extract information that describes the short term future behavior and directly contrasts the performance of the contemporaneous results. Additional work is required to further address this + +<--- Page Split ---> + +issue but is beyond the scope of the results presented." + +3) Lack of clarity on how the 3D data of a broadband station is turned into a 1D Wav2Vec latent space vector as described. The authors describe in the technical part that they combine 8 sensors times 3 channels, i.e. a 24 dimensional vector times 30k data points (100Hz for 300s), which are initially expanded to 93x768 (71424) sized latent vector and then reduced to 93x256 (23808). I find the 93 timesteps hard to comprehend. What is the origin of this number? Symmetrically, I do not understand how optimal is 768. I understand that these numbers might not be relevant overall and that results would have likely be similar with other choices of the shape of the latent spaces, but still the rationale behind this specific choice should be given. + +The model input is the 3- component 30 second waveform segments from all stations for model training. The data is structured such that a batch contains N, where the batch size is 8, waveform examples of 3- comp waveforms are for a tensor of shape [N, 3, 30,000]. For pretraining the input is reshaped to [24, 30,000] so each waveform channel is input independently in the self- supervised pretraining. We now state more clearly "Assuming a batch size of 8, the shape of the input batch tensor is [8 (batch size), 30,000 (data points), 3 (channels)]. We pass the waveform of each channel independently to the Wav2Vec 2.0 model by reshaping the input batch to [24 (waveform samples) = 8 (batch size) \* 3 (channels), 30,000 (data points)]." + +The other dimensions arise from the wav2vec2 architecture as described in the original paper. The original model has the feature encoder that contains seven temporal convolutions blocks. The paper states "The feature encoder contains seven blocks and the temporal convolutions in each block have 512 channels with strides (5,2,2,2,2,2,2) and kernel widths (10,3,3,3,3,2,2)." 93 is the number that the 30k timesteps waveform is reduced to 93 timesteps after this series of CNN layers. This is the shape of the intermediate tensor. The 768 is from the BASE version of the transformer model in the original paper which states "BASE contains 12 transformer blocks, model dimension 768, inner dimension (FFN) 3,072 and 8 attention heads." These are hyperparameters that can be tuned for the AE waves, but beyond the scope of this project, hence we just adopted the original model hyperparameters. + +4) The work compares (paragraph starting in 348) the results of a recently published GRL paper (Seismic Features Predict Ground Motions During Repeating Caldera Collapse Sequence) where the same data were used to train and predict displacement using the gradient boosted tree approach. However, they do not show clearly what the improvement was. From the text one reads that R2 increased from 0.59 to 0.63 by changing the method, but that does not seem such a drastic improvement. Overall, the authors explain at length the superiority of Wav2Vec in terms of being able to combine in a unique prediction all the 3x8 channels of data, however from this point of view, I would say that the improvement has been insufficient and one is confronted with the question whether actually these 24 channels offer more information than a single one. More in general, the authors do not offer an answer to the question that given the greater dataset used, why isn't the performance of Wav2Vec much better than gradient boosted tree? + +We have revised the Section "Contemporaneous Displacement Prediction" to more clearly state the improvements, notably the ability of the model to generalize. The added text now includes these points: + +(1) "Quantitatively the increase in \(\mathrm{SR} \wedge 2 \mathrm{S}\) could be considered quite modest, qualitatively we show a large improvement in the range of values at the lower displacement prediction which + +<--- Page Split ---> + +occur following a slip event (Fig. \ref{F4}B). One would not expect the \(\$ \mathrm{R} \sim 2\$ value to solely capture the performance change considering the overall variance in the training data (Fig. \ref{F1}) and the inherent point- to- point fluctuations in GNSS high rate measurements." + +(2) "The self-supervised Wav2Vec 2.0 model was provided all data without excluding specific signals or tailoring the training data for the known non-stationarity by temporally sampling for a specific distribution. The data for the gradient boosted tree approach required special treatment to carefully account for non-stationarity in the timeseries and excluded 30 second time windows containing local earthquakes." + +(3) "In contrast, attempts to build a unified gradient boosted tree model using all data from all stations was largely unsuccessful. The gradient boosted tree model was trained for each station separately and was unable to converge or provide a general prediction when trained using all the available data" + +(4) "Provided the self-supervised Wav2Vec 2.0 model generalizes the input waveforms for multiple downstream tasks we shown a unique result for the prediction for the onset of slip during each collapse event" + +5) The text uses both the terms "future displacement" and "failure prediction," without an explicit definition. While as a reader I have an intuitive understanding of the fact that the first is the quantitative observed displacement in the following 30 seconds, while the second attempts at identifying the caldera collapses, I believe that the authors should have given clear definitions. Throughout the revision process we have made an effort to streamline and define the terms used, specifically with respect to failure, slip, predictions, etc. + +<--- Page Split ---> diff --git a/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..51f5d99197357a0f38792c33c5d6fc6e908f235c --- /dev/null +++ b/peer_reviews/55bb50661f85cad20a33e183bbf6373ddd12c2e99f749bafc1f51a628b8f15e9/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,355 @@ +<|ref|>title<|/ref|><|det|>[[72, 161, 890, 210]]<|/det|> +# Automatic Speech Recognition Predicts Contemporaneous Earthquake Fault Displacement + +<|ref|>text<|/ref|><|det|>[[73, 224, 480, 240]]<|/det|> +Corresponding Author: Dr Christopher Johnson + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 327, 145, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 354, 219, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 159, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 420, 156, 431]]<|/det|> +Dear Editor, + +<|ref|>text<|/ref|><|det|>[[72, 432, 916, 499]]<|/det|> +The manuscript presents a study on fault displacement prediction using advanced speech detection neural networks, which is described as a pioneering effort in the application of machine learning to seismology. This work builds on a prior study by Johnson and Johnson (2024). While the results do not demonstrate a significant improvement in prediction accuracy, they highlight the potential of speech detection networks to analyze continuous seismic signals, opening up promising avenues for future research in this field. As such, I strongly support its publication. My minor comments are as follows: + +<|ref|>text<|/ref|><|det|>[[72, 499, 916, 550]]<|/det|> +- Figure 3: It is evident that in all displacement cycles, the predictions tend to be overestimated during the first half of the cycle and underestimated during the second half. This pattern is also observed in the results produced by GBT. How do the authors account for this behavior? Is not it the effect of the activation function in the last layer? If yes, other functions such as 'sigmoid' or 'tanh' may enhance it. + +<|ref|>text<|/ref|><|det|>[[72, 550, 916, 589]]<|/det|> +- Lines 372-377: The authors state that "the Wav2Vec 2.0 model results rival the best laboratory shear model predictions...". It may cause misunderstanding, as Rouet-Leduc et al. (2017) and several subsequent studies have improved laboratory results by up to 90%. I suggest removing this statement. + +<|ref|>text<|/ref|><|det|>[[72, 589, 911, 653]]<|/det|> +- Figure 5: A. If we consider the start of the 'vertical dark gray bar' as the onset of failure, panels 'f, g, l, m, q, and r' are not in agreement with others (this also applies to Figure 6). B. Following my earlier comment, the underestimation near failure leads to the prediction of relatively small displacements compared to the larger GNSS displacements. In a real-world application of this network, such low displacements might not be recognized as indicating the onset of failure, as seen in panels 'a, d, o, and s'. + +<|ref|>text<|/ref|><|det|>[[72, 653, 889, 692]]<|/det|> +- Figures S1-S3: How do the authors explain the higher \(\mathsf{R}^2\) values for future predictions (67-77%) compared to contemporaneous predictions (49-63%), which contradicts the description in the text (lines 593-603)? Furthermore, the highest \(\mathsf{R}^2\) in Figure S2 is 77%, while in Figure S3, it is 62%. Clarification on this is needed. + +<|ref|>text<|/ref|><|det|>[[72, 692, 885, 732]]<|/det|> +- Normalization: In line 780, it is mentioned how the waveform (input) is standardized. How about the outputs (displacements)? If min-max normalization is used, discuss about the problems in real applications, where the range of displacements may exceed the range of training data. + +<|ref|>text<|/ref|><|det|>[[72, 745, 207, 783]]<|/det|> +Best Sadegh Karimpouli GFZ Potsdam + +<|ref|>text<|/ref|><|det|>[[73, 797, 161, 809]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 822, 244, 848]]<|/det|> +(Remarks to the Author) Dear Authors and Editor, + +<|ref|>text<|/ref|><|det|>[[72, 860, 920, 913]]<|/det|> +Please find below my review of the paper "Automatic Speech Recognition Predicts Contemporaneous Earthquake Fault Displacement," submitted to Nature Communications by Dr. Johnson and colleagues. Overall, I find the manuscript to be of high quality and believe it deserves publication. I have included only minor comments that I hope will help further strengthen the manuscript and foster continued discussion. + +<|ref|>text<|/ref|><|det|>[[72, 925, 920, 940]]<|/det|> +The authors present an application of machine learning for seismic- to- displacement signal prediction in the case of the 2018 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 916, 154]]<|/det|> +Kilauea crater collapse. Building on prior applications across diverse seismic cycles—experimental fault systems, slow- slip events in Cascadia—the authors extend their methods to this new context, demonstrating the robustness of their approach. Notably, they highlight that models trained in related domains can effectively capture seismic signal features necessary for predicting contemporaneous fault displacement, with the Wave2Vec 2.0 model proving particularly effective. An ambitious extension explored here is near- future displacement prediction, which, although not fully successful in this study, holds strong potential for future refinement. This suggests that continued advances in AI- based speech processing could significantly impact the field by enabling models with enhanced predictive capabilities. The introduction effectively presents the challenges posed by limited observational cycles in field data and the motivation for this work. + +<|ref|>text<|/ref|><|det|>[[72, 164, 923, 296]]<|/det|> +My first point of discussion is the issue of non- stationarity in seismic cycles. In Figure 1, for instance, the absolute northward displacement at the CRIM station appears to saturate slightly, while eastward displacement does not. More importantly, this effect only affects the testing dataset. The long- period displacement amplitudes exceed the dynamic stick- slip motion, prompting the authors to remove this long- term trend to achieve stationarity. This decision raises several follow- up questions: (1) Could the displacement rate serve as an alternative dataset that balances stationarity with prediction accuracy? While calculating the derivative would increase noise, it might also retain critical non- stationary components to be predicted. (2) Given that training on a small, evolving segment of data may limit predictive accuracy, could this trend discrepancy between training and testing data affect generalization? (3) Are comparable non- stationary signals observed in lab simulations? If so, this might clarify whether these non- stationary elements hinder model predictions in real- world applications. + +<|ref|>text<|/ref|><|det|>[[72, 307, 916, 374]]<|/det|> +Figure 3 reveals a notable pattern: predicted displacement saturates, forming a plateau as the model approaches the time- to- failure (visible in Figures 3A and C). This persistent issue, observed across several of the authors' prior studies, suggests a gap in model performance that resists improvement even with advanced features delivered by Wave2Vec. Do you have insights on this plateau in the context of Kilauea? I understand that answering this question may require an in- depth feature analysis, which the authors note as an objective for future research. + +<|ref|>text<|/ref|><|det|>[[72, 384, 914, 465]]<|/det|> +Another interesting aspect of the study is the use of multiple seismic stations, which incorporates both spatial and temporal features. Although the methods section is comprehensive, it remains unclear whether the authors aggregated the traces in time (e.g., creating combined 4x300- second channel traces) or "vertically" (i.e., 4x3 channels of 300 seconds each). I am unsure if such a distinction would affect the model's performance, but this clarification could help readers better understand the model's approach to data structuring. A follow- up question arises: could model performance improve with advanced waveform combination techniques, such as cross- correlation functions or beamforming? + +<|ref|>text<|/ref|><|det|>[[72, 476, 916, 518]]<|/det|> +Finally, I wonder if narrowing the frequency band of analysis could improve the model's performance. Currently, the study uses the broadband signal (from 0.1 to \(50 \text{Hz}\) ), which includes a substantial amount of information that may not be related to the crater collapse (e.g., oceanic microseismic noise). + +<|ref|>text<|/ref|><|det|>[[72, 528, 845, 544]]<|/det|> +I remain available for further discussions and would be glad to read a revised version of the manuscript if needed. + +<|ref|>text<|/ref|><|det|>[[72, 555, 197, 581]]<|/det|> +Sincerely, Leonard Seydoux + +<|ref|>text<|/ref|><|det|>[[72, 592, 161, 606]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 619, 238, 632]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 632, 920, 752]]<|/det|> +The manuscript describes an approach in which a machine learning tool developed by FAIR (Facebook AI Research) called Wav2Vec 2.0 for speech recognition is here repurposed to predict earthquake fault displacement from continuous seismic data. The study uses data from the 2018 caldera collapses at the Kilauea volcano in Hawai'i, based on about 40 collapses within about 30 days, intervallled by slow reload. Continuous seismic record was done from a network of broadband stations which recorded moderate magnitude seismic events up to about Mw 5. The authors train Wav2Vec 2.0 to predict "Contemporaneous Displacement" as well as "Future Displacement" from seismic waveforms, fitting it with observed GNSS data. The method is a small improvement compared to recently published work on GRL, 2024, where the same data were predicted using a gradient boosted tree approach. Here they achieve an \(R^2\) of 0.63 in predictions, while in the study published on GRL they had obtained \(R^2 = 0.59\) . + +<|ref|>text<|/ref|><|det|>[[72, 762, 888, 843]]<|/det|> +The authors highlight that their results show matching patterns between the observed real- world seismic record and the laboratory recording of controlled experiments, which suggest that the successes of machine learning in predicting laboratory events should be mirrored in real world correct predictions. However unfortunately, while they show a robust ability to detect "contemporaneous displacement" (I don't like their use of the world predict, which I would only reserve for "future" predictions) in seismic data, they are very honest at highlighting how Wav2Vec performs poorly when trying to predict future events. + +<|ref|>text<|/ref|><|det|>[[72, 854, 905, 882]]<|/det|> +Overall, I find that although their results are interesting and their study stimulating future research, I do not believe that their progress is substantial compared to previous works. Here below I list more in detail the issues that I find in the manuscript: + +<|ref|>text<|/ref|><|det|>[[72, 894, 152, 906]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[72, 907, 881, 948]]<|/det|> +1) The data challenge is not described in quantitative detail. They only emphasize the challenges of applying machine learning to geophysical data with limited historical and comprehensive event coverage. Better knowledge of the computational training and testing time of the use of Wav2Vec vs other algorithms (e.g. gradient boosted tree) might + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 909, 74]]<|/det|> +reinforce the argument whether these should be or not adopted in the future, for example for instantaneous detection of the caldera movements, as the authors show their approach is successful in that. + +<|ref|>text<|/ref|><|det|>[[72, 85, 912, 153]]<|/det|> +2) The discussion on data leakage could be expanded for clarity. The authors highlight that future displacement predictions are less reliable due to data leakage and model limitations. But in fact, what seems to me, "data leakage" is a term used to cover the fact that the algorithm "predicts" the slip after it has "detected" it. Maybe the authors intended something more sophisticated than that, and in this case how it could be mitigated, but for what results from this work, there is no real "prediction", even short term one, happening from this approach. + +<|ref|>text<|/ref|><|det|>[[72, 164, 914, 256]]<|/det|> +3) Lack of clarity on how the 3D data of a broadband station is turned into a 1D Wav2Vec latent space vector as described. The authors describe in the technical part that they combine 8 sensors times 3 channels, i.e. a 24 dimensional vector times 30k data points (100Hz for 300s), which are initially expanded to 93x768 (71424) sized latent vector and then reduced to 93x256 (23808). I find the 93 timesteps hard to comprehend. What is the origin of this number? Symmetrically, I do not understand how optimal is 768. I understand that these numbers might not be relevant overall and that results would have likely be similar with other choices of the shape of the latent spaces, but still the rationale behind this specific choice should be given. + +<|ref|>text<|/ref|><|det|>[[72, 268, 920, 386]]<|/det|> +4) The work compares (paragraph starting in 348) the results of a recently published GRL paper (Seismic Features Predict Ground Motions During Repeating Caldera Collapse Sequence) where the same data were used to train and predict displacement using the gradient boosted tree approach. However, they do not show clearly what the improvement was. From the text one reads that R2 increased from 0.59 to 0.63 by changing the method, but that does not seem such a drastic improvement. Overall, the authors explain at length the superiority of Wav2Vec in terms of being able to combine in a unique prediction all the 3x8 channels of data, however from this point of view, I would say that the improvement has been insufficient and one is confronted with the question whether actually these 24 channels offer more information than a single one. More in general, the authors do not offer an answer to the question that given the greater dataset used, why isn't the performance of Wav2Vec much better than gradient boosted tree? + +<|ref|>text<|/ref|><|det|>[[72, 397, 920, 450]]<|/det|> +5) The text uses both the terms "future displacement" and "failure prediction," without an explicit definition. While as a reader I have an intuitive understanding of the fact that the first is the quantitative observed displacement in the following 30 seconds, while the second attempts at identifying the caldera collapses, I believe that the authors should have given clear definitions. + +<|ref|>text<|/ref|><|det|>[[72, 501, 144, 515]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 528, 220, 542]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 554, 160, 567]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 580, 238, 606]]<|/det|> +(Remarks to the Author) Dear Editor, + +<|ref|>text<|/ref|><|det|>[[70, 618, 914, 647]]<|/det|> +Following the responses provided in the response file and the revisions made to the manuscript, I support the publication of the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 659, 207, 685]]<|/det|> +Best regards, Sadegh Karimpouli + +<|ref|>text<|/ref|><|det|>[[72, 697, 160, 710]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 723, 244, 749]]<|/det|> +(Remarks to the Author) Dear Authors and Editor, + +<|ref|>text<|/ref|><|det|>[[72, 762, 920, 802]]<|/det|> +I have carefully reviewed the insightful responses provided by the authors regarding the remarks I made on the manuscript. I appreciate the thorough answers and the related corrections, and I agree with all points addressed. Therefore, I fully support the publication of the paper in its current form. + +<|ref|>text<|/ref|><|det|>[[72, 815, 197, 840]]<|/det|> +Best regards, Leonard Seydoux + +<|ref|>text<|/ref|><|det|>[[72, 853, 160, 866]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 879, 830, 907]]<|/det|> +(Remarks to the Author) I believed that the authors have addressed all the points that I made and I recommend their work for publication + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 350, 107]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 108, 420, 125]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 126, 214, 142]]<|/det|> +Dear Editor, + +<|ref|>text<|/ref|><|det|>[[113, 143, 882, 373]]<|/det|> +The manuscript presents a study on fault displacement prediction using advanced speech detection neural networks, which is described as a pioneering effort in the application of machine learning to seismology. This work builds on a prior study by Johnson and Johnson (2024). While the results do not demonstrate a significant improvement in prediction accuracy, they highlight the potential of speech detection networks to analyze continuous seismic signals, opening up promising avenues for future research in this field. As such, I strongly support its publication. We thank you for the time spent reviewing our manuscript and the constructive feedback. During the revisions we have taken the opportunity to further explain why these results are a significant advancement, primarily considering this is a self- supervised model and insensitive to the nonstationarity that required additional processing in the previous work. We now state, with additional added text "The limited ability of gradient boosted tree models to properly generalize due to the non- stationarity is problematic if trying to extract salient features directly from the data for downstream tasks as is done with a foundation model." + +<|ref|>text<|/ref|><|det|>[[116, 370, 870, 388]]<|/det|> +Provided are response to each comment and our best effort to address the point or concern cited. + +<|ref|>text<|/ref|><|det|>[[116, 404, 400, 421]]<|/det|> +My minor comments are as follows: + +<|ref|>text<|/ref|><|det|>[[115, 421, 878, 508]]<|/det|> +- Figure 3: It is evident that in all displacement cycles, the predictions tend to be overestimated during the first half of the cycle and underestimated during the second half. This pattern is also observed in the results produced by GBT. How do the authors account for this behavior? Is not it the effect of the activation function in the last layer? If yes, other functions such as 'sigmoid' or 'tanh' may enhance it. + +<|ref|>text<|/ref|><|det|>[[113, 508, 876, 803]]<|/det|> +This observation was a topic of much discussion while preparing the manuscript. This is not a function of an activation function in the final layer. In Johnson and Johnson (2024) this same feature is observed in the displacement predictions. In that study a boosted tree model was used, and models were developed using a data set that was reduced by excluding time windows containing an earthquake phase arrival (EQtransformer detection algorithm was applied to label time windows with P/S arrival). Since the seismicity rates increase throughout the loading cycle there was less temporal sampling at the time nearest failure. However, the results were largely unchanged and the displacement prediction still contain a similar plateau (see Fig. 4). We provide the reader with more context in the results we now state "Both the gradient boosted tree and Wav2Vec 2.0 model show an upper prediction threshold for the final 10- 20% of the loading cycles that does not match the GNSS (Fig. \ref{fig:Wav2Vec2.0}) A). This output is not well understood and various attempts to further improve the predictions in the near failure time intervals were unsuccessful. At this time we speculate the plateau results from increased 'noise' in the system since this is a volcano caldera collapse, not a more traditional earthquake fault. The additional signals introduced to the model would contain tremors and potentially other fluid related processed creating specific conditions in the loading rate that the model is unable to fully capture." + +<|ref|>text<|/ref|><|det|>[[115, 820, 872, 891]]<|/det|> +- Lines 372-377: The authors state that "the Wav2Vec 2.0 model results rival the best laboratory shear model predictions...". It may cause misunderstanding, as Rouet-Leduc et al. (2017) and several subsequent studies have improved laboratory results by up to 90%. I suggest removing this statement. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 882, 195]]<|/det|> +We have revised the statement to clearly convey the performance improvements when comparing to previous laboratory based analysis. We now state “Moreover, when considering the data availability and overall performance, the Wav2Vec 2.0 model results rival the best laboratory shear model predictions for both decision tree and deep learning models, where the data generally contains many more slip events and less variance due to the controlled laboratory conditions” + +<|ref|>text<|/ref|><|det|>[[114, 211, 880, 317]]<|/det|> +- Figure 5: A. If we consider the start of the ‘vertical dark gray bar’ as the onset of failure, panels ‘f, g, l, m, q, and r’ are not in agreement with others (this also applies to Figure 6). B. Following my earlier comment, the underestimation near failure leads to the prediction of relatively small displacements compared to the larger GNSS displacements. In a real-world application of this network, such low displacements might not be recognized as indicating the onset of failure, as seen in panels ‘a, d, o, and s’. + +<|ref|>text<|/ref|><|det|>[[114, 316, 881, 473]]<|/det|> +The vertical line is the selection window we prescribe using the timing estimate we obtain from the data. Using an observational perspective, we are not assigning a pass/fail criteria based on the amplitude of change. We note that in this real world application having a small displacement might not warrant a failure alert, however we are testing if the information is obtainable from the data in the model framework presented. For a more concise describing of the properly detected events we now state “The selection criteria is observational; we are looking for a decrease in displacement at the prescribed time step or a decrease that matches the GNSS measurements. The inclusion of events that match the GNSS (e.g., “g”, “l”, “q”, and “r”) arises from the potential timing discrepancy introduced by the 30 second windowing of the displacement data.” + +<|ref|>text<|/ref|><|det|>[[114, 490, 881, 560]]<|/det|> +- Figures S1-S3: How do the authors explain the higher \(\mathrm{R}^2\) values for future predictions (67-77%) compared to contemporaneous predictions (49-63%), which contradicts the description in the text (lines 593-603)? Furthermore, the highest \(\mathrm{R}^2\) in Figure S2 is 77%, while in Figure S3, it is 62%. Clarification on this is needed. + +<|ref|>text<|/ref|><|det|>[[114, 560, 880, 682]]<|/det|> +This is a good observation that we did not fully explore because the main test with the prediction of a large slip event. We note that this is specific to the training data because the testing data has very similar R2 values. We now state “Interestingly, the \(\mathrm{SR}^2 \times 2\mathrm{S}\) values for the input-output window pair selection (Fig. S2) are on-average higher the contemporaneous predictions (Fig. S1) with the training data set but quite similar with the testing data. The displacement predictions appear good throughout the earthquake cycle (Fig. S3), however, the \(\mathrm{SR}^2 \times 2\mathrm{S}\) value may be misleading as shown in expanded view for the earthquake failures.” + +<|ref|>text<|/ref|><|det|>[[114, 699, 880, 803]]<|/det|> +- Normalization: In line 780, it is mentioned how the waveform (input) is standardized. How about the outputs (displacements)? If min-max normalization is used, discuss about the problems in real applications, where the range of displacements may exceed the range of training data. The model output is standardized for stability but reported with the variance and mean corrected back to the original scale. In this application the prediction is a continuous variable that can scale beyond the data, however we did not further explore those limitations. + +<|ref|>text<|/ref|><|det|>[[114, 821, 655, 891]]<|/det|> +Best Sadegh Karimpouli GFZ Potsdam Sadegh, we again thank you for your time reviewing the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 419, 108]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 125, 315, 142]]<|/det|> +Dear Authors and Editor, + +<|ref|>text<|/ref|><|det|>[[115, 159, 879, 247]]<|/det|> +Please find below my review of the paper "Automatic Speech Recognition Predicts Contemporaneous Earthquake Fault Displacement," submitted to Nature Communications by Dr. Johnson and colleagues. Overall, I find the manuscript to be of high quality and believe it deserves publication. I have included only minor comments that I hope will help further strengthen the manuscript and foster continued discussion. + +<|ref|>text<|/ref|><|det|>[[114, 263, 874, 473]]<|/det|> +The authors present an application of machine learning for seismic- to- displacement signal prediction in the case of the 2018 Kilauea crater collapse. Building on prior applications across diverse seismic cycles—experimental fault systems, slow- slip events in Cascadia—the authors extend their methods to this new context, demonstrating the robustness of their approach. Notably, they highlight that models trained in related domains can effectively capture seismic signal features necessary for predicting contemporaneous fault displacement, with the Wave2Vec 2.0 model proving particularly effective. An ambitious extension explored here is near- future displacement prediction, which, although not fully successful in this study, holds strong potential for future refinement. This suggests that continued advances in AI- based speech processing could significantly impact the field by enabling models with enhanced predictive capabilities. The introduction effectively presents the challenges posed by limited observational cycles in field data and the motivation for this work. + +<|ref|>text<|/ref|><|det|>[[115, 473, 870, 525]]<|/det|> +We thank you for the time spent reviewing our manuscript. We found the constructive feedback very helpful and have provided a response to each comment with our best effort to address the point or concern cited. + +<|ref|>text<|/ref|><|det|>[[114, 542, 878, 750]]<|/det|> +My first point of discussion is the issue of non- stationarity in seismic cycles. In Figure 1, for instance, the absolute northward displacement at the CRIM station appears to saturate slightly, while eastward displacement does not. More importantly, this effect only affects the testing dataset. The long- period displacement amplitudes exceed the dynamic stick- slip motion, prompting the authors to remove this long- term trend to achieve stationarity. This decision raises several follow- up questions: (1) Could the displacement rate serve as an alternative dataset that balances stationarity with prediction accuracy? While calculating the derivative would increase noise, it might also retain critical non- stationary components to be predicted. (2) Given that training on a small, evolving segment of data may limit predictive accuracy, could this trend discrepancy between training and testing data affect generalization? (3) Are comparable nonstationary signals observed in lab simulations? If so, this might clarify whether these nonstationary elements hinder model predictions in real- world applications. + +<|ref|>text<|/ref|><|det|>[[114, 751, 881, 891]]<|/det|> +The decision to remove the nonstationary component arose from our focus on the individual repeating slip events within the longer term deformation signal. This is an excellent question because, as noted by the reviewer, we are not prescribing the model to learn the full dynamics of the system. It is possible that the displacement rate could be incorporated into the dataset as an additional target label, however, that was not within the scope of the goals in this study. In our previous work we needed to perform a different scheme for the train/validate/test dataset due directly to this nonstationarity. Here, the Wav2Vec model can perform remarkably better without special consideration for this known quantity in the data. When comparing to laboratory data + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 840, 125]]<|/det|> +sets, there are some experiments with long term trends in the data, but typically the need for additional preprocessing is not required. + +<|ref|>text<|/ref|><|det|>[[113, 142, 879, 544]]<|/det|> +Figure 3 reveals a notable pattern: predicted displacement saturates, forming a plateau as the model approaches the time- to- failure (visible in Figures 3A and C). This persistent issue, observed across several of the authors' prior studies, suggests a gap in model performance that resists improvement even with advanced features delivered by Wave2Vec. Do you have insights on this plateau in the context of Kilauea? I understand that answering this question may require an in- depth feature analysis, which the authors note as an objective for future research. Reviewer #1 also noticed the same pattern, and we repeat our reply here. This observation was a topic of much discussion while preparing the manuscript. This is not a function of an activation function in the final layer. In Johnson and Johnson (2024) this same feature is observed in the displacement predictions. In that study a boosted tree model was used, and models were developed using a data set that was reduced by excluding time windows containing an earthquake phase arrival (EQtransformer detection algorithm was applied to label time windows with P/S arrival). Since the seismicity rates increase throughout the loading cycle there was less temporal sampling at the time nearest failure. However, the results were largely unchanged and the displacement prediction still contain a similar plateau (see Fig. 4). We provide the reader with more context in the results we now state "Both the gradient boosted tree and Wav2Vec 2.0 model show an upper prediction threshold for the final \(10 - 20\%\) of the loading cycles that does not match the GNSS (Fig. \ref{fig:4A}). This output is not well understood and various attempts to further improve the predictions in the near failure time intervals were unsuccessful. At this time we speculate the plateau results from increased 'noise' in the system since this is a volcano caldera collapse, not a more traditional earthquake fault. The additional signals introduced to the model would contain tremors and potentially other fluid related processed creating specific conditions in the loading rate that the model is unable to fully capture." + +<|ref|>text<|/ref|><|det|>[[114, 560, 880, 700]]<|/det|> +Another interesting aspect of the study is the use of multiple seismic stations, which incorporates both spatial and temporal features. Although the methods section is comprehensive, it remains unclear whether the authors aggregated the traces in time (e.g., creating combined 4x300- second channel traces) or "vertically" (i.e., 4x3 channels of 300 seconds each). I am unsure if such a distinction would affect the model's performance, but this clarification could help readers better understand the model's approach to data structuring. A follow- up question arises: could model performance improve with advanced waveform combination techniques, such as cross- correlation functions or beamforming? + +<|ref|>text<|/ref|><|det|>[[114, 700, 880, 840]]<|/det|> +The model input is the 3- component 30 second waveform segments from all stations for model training. The data is structured such that a batch contains N, where the batch size is 8, waveform examples of 3- comp waveforms are for a tensor of shape [N, 3, 30,000]. For pretraining the input is reshaped to [24, 30,000] so each waveform channel is input independently in the self- supervised pretraining. We now state more clearly "Assuming a batch size of 8, the shape of the input batch tensor is [8 (batch size), 30,000 (data points), 3 (channels)]. We pass the waveform of each channel independently to the Wav2Vec 2.0 model by reshaping the input batch to [24 (waveform samples) = 8 (batch size) \* 3 (channels), 30,000 (data points)]." + +<|ref|>text<|/ref|><|det|>[[115, 856, 870, 892]]<|/det|> +Beamforming has not been applied here, but we did use that approach in a previous study (see Umlauft et al., 2024 on glacier motions) using the beamformed catalog as a unique model input. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 142]]<|/det|> +That work focused on glacial sliding processes and the beamforming results were found to be a high ranking feature in the importance. Inputting station cross correlations is the topic of ongoing work in group now and results are showing success. Both great questions. + +<|ref|>text<|/ref|><|det|>[[115, 176, 875, 246]]<|/det|> +Finally, I wonder if narrowing the frequency band of analysis could improve the model's performance. Currently, the study uses the broadband signal (from 0.1 to \(50\mathrm{Hz}\) ), which includes a substantial amount of information that may not be related to the crater collapse (e.g., oceanic microseismic noise). + +<|ref|>text<|/ref|><|det|>[[115, 247, 866, 403]]<|/det|> +This is a good observation. Our thoughts is the time period considered (about 2 months) should not be largely affected by the known lower frequency signals which change periodically throughout the year and during large weather events. Our reasoning for including these lower frequency bands was to not constrain the model to a priori assumptions about important frequency content. Our justification is the model applied learned CNN filters that will account for a large range of frequencies when inputting the data to the transformer block. We now state "The hierarchical feature extraction captures information at different levels of abstraction, enabling the model to learn both low- level and high- level representations across a broad frequency spectrum of the input signal." + +<|ref|>text<|/ref|><|det|>[[115, 420, 836, 455]]<|/det|> +I remain available for further discussions and would be glad to read a revised version of the manuscript if needed. + +<|ref|>text<|/ref|><|det|>[[115, 473, 662, 524]]<|/det|> +Sincerely, Leonard Seydoux Leonard, we again thank you for your time reviewing the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 419, 107]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 124, 881, 317]]<|/det|> +The manuscript describes an approach in which a machine learning tool developed by FAIR (Facebook AI Research) called Wav2Vec 2.0 for speech recognition is here repurposed to predict earthquake fault displacement from continuous seismic data. The study uses data from the 2018 caldera collapses at the Kilauea volcano in Hawai'i, based on about 40 collapses within about 30 days, intervallled by slow reload. Continuous seismic record was done from a network of broadband stations which recorded moderate magnitude seismic events up to about Mw 5. The authors train Wav2Vec 2.0 to predict "Contemporaneous Displacement" as well as "Future Displacement" from seismic waveforms, fitting it with observed GNSS data. The method is a small improvement compared to recently published work on GRL, 2024, where the same data were predicted using a gradient boosted tree approach. Here they achieve an \(\mathrm{R}^2\) of 0.63 in predictions, while in the study published on GRL they had obtained \(\mathrm{R}^2 = 0.59\) . + +<|ref|>text<|/ref|><|det|>[[114, 333, 870, 456]]<|/det|> +The authors highlight that their results show matching patterns between the observed real- world seismic record and the laboratory recording of controlled experiments, which suggest that the successes of machine learning in predicting laboratory events should be mirrored in real world correct predictions. However unfortunately, while they show a robust ability to detect "contemporaneous displacement" (I don't like their use of the world predict, which I would only reserve for "future" predictions) in seismic data, they are very honest at highlighting how Wav2Vec performs poorly when trying to predict future events. + +<|ref|>text<|/ref|><|det|>[[114, 472, 850, 525]]<|/det|> +Overall, I find that although their results are interesting and their study stimulating future research, I do not believe that their progress is substantial compared to previous works. Here below I list more in detail the issues that I find in the manuscript: + +<|ref|>text<|/ref|><|det|>[[113, 525, 876, 752]]<|/det|> +We thank you for the time spent reviewing our manuscript and the constructive feedback. In particular we have addressed the concern raised about the progress compared to previous works. We now include more detailed description of using self- supervised learning models instead of the previous efforts applying supervised learning techniques. In the last paragraph of the introduction we now state "The widespread adoption of unsupervised, or self- supervised, learning techniques for signal classification has not seen the same rise in popularity for seismic waveform analysis as compared to other deep learning fields; despite intriguing results demonstrating the ability of ML models to separate signals with no a priori knowledge [e.g., 26- 28]. The lack of generalization in supervised learning models does not facilitate fine- tuning an existing model for out- of- distribution data, and instead requires large amounts of labeled training data to develop a new model for a specific application [29]. The supervised learning is now eclipsed by the development of self- supervised foundation models using unlabeled data to produce generative pre- trained transformer networks [30]." + +<|ref|>text<|/ref|><|det|>[[115, 752, 876, 786]]<|/det|> +We then further describe the limitation in the previous work and include more details throughout for this advancement. + +<|ref|>text<|/ref|><|det|>[[115, 804, 490, 821]]<|/det|> +Below we provide a response to each comment. + +<|ref|>text<|/ref|><|det|>[[115, 840, 207, 856]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[115, 857, 875, 892]]<|/det|> +1) The data challenge is not described in quantitative detail. They only emphasize the challenges of applying machine learning to geophysical data with limited historical and comprehensive + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 872, 160]]<|/det|> +event coverage. Better knowledge of the computational training and testing time of the use of Wav2Vec vs other algorithms (e.g. gradient boosted tree) might reinforce the argument whether these should be or not adopted in the future, for example for instantaneous detection of the caldera movements, as the authors show their approach is successful in that. + +<|ref|>text<|/ref|><|det|>[[114, 160, 870, 300]]<|/det|> +The lack of data for a full earthquake cycle is comprehensively described in Wang, Johnson, Bennet, and Johnson (2024) Nature Communications. In that we present a transfer learning approach that could be implemented for decadal to century time scales that are common for recurrence times of earthquake faults. We now more clearly state "The primary challenge for applying machine learning to frictional failure on most faults hosting large magnitude earthquakes is the long repeat times, ranging from decades to thousands of years, and therefore, the lack of geophysical instrumental data that capture a complete loading cycle, often only a small fraction of a loading cycle." + +<|ref|>text<|/ref|><|det|>[[114, 316, 875, 404]]<|/det|> +As for the computation expense and training time, yes, these modeling efforts require HPC GPU clusters to facilitate model development, training, validation, and test. Specifically, this compute cost scales with the size of the data. In this work the expense compounds when testing the optimal input and output time windows which are an important result. This is a necessary resource and a requirement to further test what types of model architectures are most applicable. + +<|ref|>text<|/ref|><|det|>[[114, 420, 879, 630]]<|/det|> +We fully acknowledge these resources are not available at every research institute, but external options exist, e.g., AWS. This is not meant as a criticism but instead we use the analogy of a geochemist in a research institute with a \(\) 1\mathrm{M}\$ mass spectrometer to do her radiological dating studies. It's the correct resource for the work performed. As for adopting these types of models for future use, that is exactly what we aim to present. The goal of our research group is to determine the performance metrics with the ambition of developing a foundation model as has been successful in computer vision and natural language processing. We now state to clearly articulate this point "The limited ability of the gradient boosted tree model to properly generalize due to the non- stationarity is problematic if trying to extract salient features directly from the data for downstream tasks as is done with a foundation model. In the present work we develop a self- supervised learning approach to determine if contemporaneous and future predictions can be made directly from the continuous seismic data." + +<|ref|>text<|/ref|><|det|>[[114, 647, 879, 751]]<|/det|> +2) The discussion on data leakage could be expanded for clarity. The authors highlight that future displacement predictions are less reliable due to data leakage and model limitations. But in fact, what seems to me, "data leakage" is a term used to cover the fact that the algorithm "predicts" the slip after it has "detected" it. Maybe the authors intended something more sophisticated than that, and in this case how it could be mitigated, but for what results from this work, there is no real "prediction", even short term one, happening from this approach. + +<|ref|>text<|/ref|><|det|>[[114, 752, 872, 891]]<|/det|> +Point well taken and we have expanded our comments on the ability to make short term predictions. We now state "The delayed timing of predictions indicate this model is far less reliable and only predicts the slip after the failure event is observed in the data. As a test if data leakage associated with the model predicting timing, we conducted model tests using future predictions for two successively later time intervals. Those results clearly indicate slip is only predicted after the model input contains the slip event of interest. For this data the model fails to extract information that describes the short term future behavior and directly contrasts the performance of the contemporaneous results. Additional work is required to further address this + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 545, 107]]<|/det|> +issue but is beyond the scope of the results presented." + +<|ref|>text<|/ref|><|det|>[[115, 124, 877, 265]]<|/det|> +3) Lack of clarity on how the 3D data of a broadband station is turned into a 1D Wav2Vec latent space vector as described. The authors describe in the technical part that they combine 8 sensors times 3 channels, i.e. a 24 dimensional vector times 30k data points (100Hz for 300s), which are initially expanded to 93x768 (71424) sized latent vector and then reduced to 93x256 (23808). I find the 93 timesteps hard to comprehend. What is the origin of this number? Symmetrically, I do not understand how optimal is 768. I understand that these numbers might not be relevant overall and that results would have likely be similar with other choices of the shape of the latent spaces, but still the rationale behind this specific choice should be given. + +<|ref|>text<|/ref|><|det|>[[115, 265, 880, 404]]<|/det|> +The model input is the 3- component 30 second waveform segments from all stations for model training. The data is structured such that a batch contains N, where the batch size is 8, waveform examples of 3- comp waveforms are for a tensor of shape [N, 3, 30,000]. For pretraining the input is reshaped to [24, 30,000] so each waveform channel is input independently in the self- supervised pretraining. We now state more clearly "Assuming a batch size of 8, the shape of the input batch tensor is [8 (batch size), 30,000 (data points), 3 (channels)]. We pass the waveform of each channel independently to the Wav2Vec 2.0 model by reshaping the input batch to [24 (waveform samples) = 8 (batch size) \* 3 (channels), 30,000 (data points)]." + +<|ref|>text<|/ref|><|det|>[[115, 420, 875, 595]]<|/det|> +The other dimensions arise from the wav2vec2 architecture as described in the original paper. The original model has the feature encoder that contains seven temporal convolutions blocks. The paper states "The feature encoder contains seven blocks and the temporal convolutions in each block have 512 channels with strides (5,2,2,2,2,2,2) and kernel widths (10,3,3,3,3,2,2)." 93 is the number that the 30k timesteps waveform is reduced to 93 timesteps after this series of CNN layers. This is the shape of the intermediate tensor. The 768 is from the BASE version of the transformer model in the original paper which states "BASE contains 12 transformer blocks, model dimension 768, inner dimension (FFN) 3,072 and 8 attention heads." These are hyperparameters that can be tuned for the AE waves, but beyond the scope of this project, hence we just adopted the original model hyperparameters. + +<|ref|>text<|/ref|><|det|>[[115, 611, 878, 803]]<|/det|> +4) The work compares (paragraph starting in 348) the results of a recently published GRL paper (Seismic Features Predict Ground Motions During Repeating Caldera Collapse Sequence) where the same data were used to train and predict displacement using the gradient boosted tree approach. However, they do not show clearly what the improvement was. From the text one reads that R2 increased from 0.59 to 0.63 by changing the method, but that does not seem such a drastic improvement. Overall, the authors explain at length the superiority of Wav2Vec in terms of being able to combine in a unique prediction all the 3x8 channels of data, however from this point of view, I would say that the improvement has been insufficient and one is confronted with the question whether actually these 24 channels offer more information than a single one. More in general, the authors do not offer an answer to the question that given the greater dataset used, why isn't the performance of Wav2Vec much better than gradient boosted tree? + +<|ref|>text<|/ref|><|det|>[[115, 804, 870, 856]]<|/det|> +We have revised the Section "Contemporaneous Displacement Prediction" to more clearly state the improvements, notably the ability of the model to generalize. The added text now includes these points: + +<|ref|>text<|/ref|><|det|>[[115, 857, 846, 891]]<|/det|> +(1) "Quantitatively the increase in \(\mathrm{SR} \wedge 2 \mathrm{S}\) could be considered quite modest, qualitatively we show a large improvement in the range of values at the lower displacement prediction which + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 860, 142]]<|/det|> +occur following a slip event (Fig. \ref{F4}B). One would not expect the \(\$ \mathrm{R} \sim 2\$ value to solely capture the performance change considering the overall variance in the training data (Fig. \ref{F1}) and the inherent point- to- point fluctuations in GNSS high rate measurements." + +<|ref|>text<|/ref|><|det|>[[113, 143, 875, 230]]<|/det|> +(2) "The self-supervised Wav2Vec 2.0 model was provided all data without excluding specific signals or tailoring the training data for the known non-stationarity by temporally sampling for a specific distribution. The data for the gradient boosted tree approach required special treatment to carefully account for non-stationarity in the timeseries and excluded 30 second time windows containing local earthquakes." + +<|ref|>text<|/ref|><|det|>[[113, 230, 875, 298]]<|/det|> +(3) "In contrast, attempts to build a unified gradient boosted tree model using all data from all stations was largely unsuccessful. The gradient boosted tree model was trained for each station separately and was unable to converge or provide a general prediction when trained using all the available data" + +<|ref|>text<|/ref|><|det|>[[114, 299, 835, 351]]<|/det|> +(4) "Provided the self-supervised Wav2Vec 2.0 model generalizes the input waveforms for multiple downstream tasks we shown a unique result for the prediction for the onset of slip during each collapse event" + +<|ref|>text<|/ref|><|det|>[[114, 368, 881, 473]]<|/det|> +5) The text uses both the terms "future displacement" and "failure prediction," without an explicit definition. While as a reader I have an intuitive understanding of the fact that the first is the quantitative observed displacement in the following 30 seconds, while the second attempts at identifying the caldera collapses, I believe that the authors should have given clear definitions. Throughout the revision process we have made an effort to streamline and define the terms used, specifically with respect to failure, slip, predictions, etc. + +<--- Page Split ---> diff --git a/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/images_list.json b/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9ba9b1b93a615e7885ead5e7f4ead6f9e2a5bc27 --- /dev/null +++ b/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,25 @@ + +# nature portfolio + +Peer Review File + +TFEB activation hallmarks antigenic experience of B lymphocytes and directs germinal center fate decisions + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #1 (Remarks to the Author): + +authors have made appropriate changes to manuscript in response to reviewer recommendations. + +<--- Page Split ---> diff --git a/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..5dcb2c2ec9fe05a20ee6c22c3c3a196583f88242 --- /dev/null +++ b/peer_reviews/55c9a9b7bdb090d10c06964a210d2756fb9fb8ad7aa216f1e29c181ecba31ab6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,29 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 828, 212]]<|/det|> +TFEB activation hallmarks antigenic experience of B lymphocytes and directs germinal center fate decisions + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 159, 877, 213]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 97, 339, 115]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 163, 417, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 201, 872, 218]]<|/det|> +authors have made appropriate changes to manuscript in response to reviewer recommendations. + +<--- Page Split ---> diff --git a/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/images_list.json b/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d7b608c6c755f5bf82923faf406feaa475df04d3 --- /dev/null +++ b/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,202 @@ + +# nature portfolio + +Peer Review File + +Pro- phagocytic function and structural basis of GPR84 signaling + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The manuscript "Pro- phagocytic function and structural basis of GPR84 signaling" by Zhang et al, reports a cryo- EM structure of 6- OAU- bound human GPR84- Gi complex. Together with mutation data and MD simulation, the authors discussed the binding pocket of 6- OAU and receptor activation. GPR84 is a promising target for immune disease and cancer, this work provides molecular basis for the ligand discovery for GPR84. However, the manuscript organization and contents should be largely improved. There are several concerns which need to be addressed: + +Major issues: + +1. The phagocytosis assay presented in Figure 1 is not convincing to claim the pro-phagocytic effects is induced by GPR84-Gi signaling. More additional assays or controls are needed. GLPG1205 was reported as a NAM of GPR84, does it bind to the similar orthosteric binding pocket with 6-OAU in GPR84? +2. "The structure was determined to a global resolution of 3.0-A by cryo-EM", according to the local resolution estimation in Fig. S2f, the resolution for the extracellular region is quite low. The electron density for the ligand and surrounding residues, as well as ECL2, should be shown. +3. In left panel of Figure 2, the author did not show the electron density for 6-OAU in the overall structure, while a strong piece of density is shown in the cytoplasmic parts of TM2-4. How does this density fit with cholesterol? +4. The expression data for mutants in Fig. 3d is missing, should be provided. +5. Does the disulfide bond between N-terminus and ECL2 affect the 6-OAU binding or the activation of the receptor? +6. MD simulations should be performed to support the docking poses of embelin, capric acid, and 2-hydroxy capric acid. +7. There are no mutagenesis data to verify the key residues that may related to GPR84 activation, such as Y3326.48, N1043.36, G1173.49. +8. How does K126 mutation affect the Gi coupling with GPR84? + +Reviewer #2: + +Remarks to the Author: + +GPR84 is a proinflammatory receptor whose roles in lipid metabolism and immune regulation are emerging. In this manuscript, Zhang et al. demonstrated that the increase of macrophage phagocytosis depends on GPR84 and Gi. They solved a high- resolution cryoEM structure of GPR84 with the agonist 6- OAU. The structural model explains the ligand specificity and shows the unique ligand- binding features and structural motifs of GPR84. The authors further used computational tools for docking the native ligands and running MD simulations to identify the possible path as the entry or exit for the agonist. Overall, the paper is well- written and clear on the data and interpretation. The density map and the structural models are sound. The work would lead to further studies on the molecular mechanism of GPR84, which was poorly understood and may help therapy development. However, I still have some issues that need to be addressed by the authors before publishing the manuscript. + +Major + +1. Fig.1b, the error bars seem missing. + +2. Fig. 3d, the mutation H352A has huge efficacy and potency change, but the authors did not explain the rationale for mutating this position or show the location of this residue. Why is this residue so crucial for the activation of GPR84? + +3. The authors did not describe the docking process in the method section. Please indicate the parameters that the authors used in Glide/Schrodinger package. + +<--- Page Split ---> + +4. The authors pointed out the unique features of GPR84-Gi interaction but did not show the comparison with the other GPCR-Gi pairs. The authors should support the claims like "in most of other Gi-coupled GPCR structures, the position 34.51 in the ICL2 is usually a hydrophobic residue." by providing some examples for the readers to compare. The authors compare the ligand binding pockets with the other lipid GPCRs in Figure 4. Receptors BLT1, S1PR1, and LPAR1 were solved with Gi-associated. Please provide a comparison of the Gi-binding mode of these related GPCRs either in the figures or in the supplementary data to support the claims. + +Minor: + +1. Fig. 1 legend the last sentence: "Each data point represents SD of data...". "Representing SD" cannot be accurate. Please correct the figure legend. +2. Fig. 4. For general readers, please describe how the receptor figures are generated. For example: "In each column, the cartoon model and surface representation are used for the same receptor." +3. The method section of cryoEM data processing indicates three subsets were used for 62,824 particles. Supplementary Fig. 2 suggested only one class after 3D classification was used. Please double-check and make them consistent. +4. The MD simulation should indicate the ligands' entry and exit routes. Do the authors only consider those paths as exit routes? Is there a reason for that? +5. GRY is a unique motif distinguishing the GPR84 from the other Class A GPCRs. Is it possible to introduce mutation on the Glycine or amino acids interacting with Glycine (like F55) and test the mutant in the function assay (like GTPyS incorporation assay) to show that the GRY motif also plays the same critical role as the DRY motif? + +<--- Page Split ---> + +We thank all reviewers for their constructive comments. Please see our detailed responses to the comments below. The reviewers' comments are in blue font and our responses are in black font. + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The manuscript "Pro- phagocytic function and structural basis of GPR84 signaling" by Zhang et al, reports a cryo- EM structure of 6- OAU- bound human GPR84- Gi complex. Together with mutation data and MD simulation, the authors discussed the binding pocket of 6- OAU and receptor activation. GPR84 is a promising target for immune disease and cancer, this work provides molecular basis for the ligand discovery for GPR84. However, the manuscript organization and contents should be largely improved. There are several concerns which need to be addressed: + +Major issues: + +1. The phagocytosis assay presented in Figure 1 is not convincing to claim the pro-phagocytic effects is induced by GPR84-Gi signaling. More additional assays or controls are needed. GLPG1205 was reported as a NAM of GPR84, does it bind to the similar orthosteric binding pocket with 6-OAU in GPR84? + +GLPG1205 may not bind to the same orthosteric binding pocket as that of 6- OAU in GPR84. Nonetheless, it functions as a specific antagonist of GPR84 and effectively inhibits GPR84 signaling induced by 6- OAU, even in the presence of 6- OAU binding (doi:10.1021/acs.jmedchem.0c00272). The fact that GLPG1205 abolishes 6- OAU- induced phagocytosis strongly suggests that this effect is mediated by GPR84. To further support this claim, we conducted CRISPR-Cas9- mediated knockout of GPR84 expression in primary macrophages and showed that the pro-phagocytic effect of 6- OAU was lost. These new findings are now presented in Fig. 1c. + +2. "The structure was determined to a global resolution of 3.0-Å by cryo-EM", according to the local resolution estimation in Fig. S2f, the resolution for the extracellular region is quite low. The electron density for the ligand and surrounding residues, as well as ECL2, should be shown. We have included the suggested electron density map in the revised Supplementary Figure 2g. The density of the ligand and surrounding residues is clear for modeling. + +3. In left panel of Figure 2, the author did not show the electron density for 6-OAU in the overall structure, while a strong piece of density is shown in the cytoplasmic parts of TM2-4. How does this density fit with cholesterol? The binding pocket of 6-OAU is completely embedded within the 7TM domain of GPR84. Therefore, it is difficult to see the density of 6-OAU in the overall structure showing the cryo-EM density of the receptor. Nevertheless, we show the density of 6-OAU alone in Figure 2. The + +<--- Page Split ---> + +density near the cytoplasmic region of TM2- 4 fits cholesterol well. We have included such density in the revised Supplementary Figure 2g. + +4. The expression data for mutants in Fig. 3d is missing, should be provided. + +We thank the reviewer for the suggestion. We have now provided expression data for the mutants as measured by the specific binding of both a radiolabelled orthosteric 1,2,4 triazine antagonist ([3H]140) and a similarly radiolabelled allosteric antagonist ([3H]38) that is closely related to the clinically trialled GPR84 blocker GLPG1205. The data is shown in + +## Supplementary Data Figure 3a. + +In some cases, the mutants were unable to bind either of these ligands with high affinity as predicted for [3H]140 from previous mutagenesis and homology modelling studies (Mahindra et al J. Med. Chem. 2022, doi.org/10.1021/acs.jmedchem.2c00804). However, for the Phe335Ala mutant for example, although it is unable to bind the orthosteric antagonist, which was also previously shown by Mahindra et al, its expression as a structurally intact protein was confirmed because this mutant does bind [3H]38 effectively. For a further set of mutants, for example the Gly117 to either Ala or Asp, both radiologands bound with high affinity. + +5. Does the disulfide bond between N-terminus and ECL2 affect the 6-OAU binding or the activation of the receptor? + +It appears that it does. Alteration of Cys11 to Ala (which will prevent the formation of such a disulfide bond) completely eliminated G protein activation by 6-OAU. However, a caveat to this conclusion is that we did not observe binding of either the allosteric antagonist [3H]38 or the orthosteric antagonist [3H]140 in membranes of cells transfected to express GPR84 Cys11Ala and therefore disruption of this disulfide bridge likely limits correct folding of the receptor. We have included the G protein activation data in revised Figure 3b and the radioligand binding data in Supplementary Data Figure 3a. This frequently is the outcome when the conserved ECL2- TM3 disulfide bond in class A GPCRs is disrupted in various receptors. + +It's worth noted that Liu et al (Nature Communications. 2023 Jun 6;14(1):3271) showed that they recorded reduced but still detectable cell surface expression of a C11A mutant, although they didn't probe its folding. Like us, they noted no agonist- induced signalling for this mutant. + +6. MD simulations should be performed to support the docking poses of embelin, capric acid, and 2-hydroxy capric acid. + +We thank the reviewer for the suggestion. We now include new MD simulations studies on embelin, capric acid, and 2- hydroxy capric acid starting from the docking poses in our revised manuscript. The data is presented in Extended Data Figure 7 and 8. Five copies (1us each) were run for each ligand, which totaled around \(5\mu \mathrm{s}\) dynamics for each of embelin, capric acid and 2- hydroxy capric acid. We found that the four ligands primarily occupy the native binding pocket, consistent with the docking poses, with occasional forays to metastable sites such as S1, S2 and S3. + +7. There are no mutagenesis data to verify the key residues that may related to GPR84 activation, such as Y3326.48, N1043.36, G1173.49. + +<--- Page Split ---> + +We thank the reviewer for the suggestion. We have now included such mutagenesis data in our revised manuscript. The data is shown in Figure 3b. As noted in our manuscript, alteration of G117 to D eliminated function of 6- OAU whereas alteration of G117 to A didn't significantly affect 6- OAU signaling (Fig. 3b). For both G117A and G117D specific binding of both the allosteric antagonist \([^{3}\mathrm{H}]38\) and the orthosteric antagonist \([^{3}\mathrm{H}]140\) confirmed successful expression of these mutants (Fig. S3a). + +Although residue 6.48 is most frequently W in class A GPCRs, in GPR84 this is replaced by Y322. Alteration of Y322 to W again resulted in reduced potency of 6- OAU whilst alteration to Ala all but eliminated responsiveness (Fig. 3b). + +We also explored the contribution of N104 by converting this residue to Ala. The N104A mutant did not respond to any concentration of 6- OAU that we were able to test and, as such, this Asn indeed is likely to play a key role (Fig. 3b). Once more, however, the caveat to this conclusion is that we were unable to detect specific binding of \([^{3}\mathrm{H}]38\) or \([^{3}\mathrm{H}]140\) in membranes from cells transiently transfected with this mutant (Fig. S3a). + +8. How does K126 mutation affect the Gi coupling with GPR84? + +We state in our manuscript that '34.51 in the ICL2 is usually a hydrophobic residue', but 'In GPR84, this position is K126. As a result, there is no direct interactions between ICL2 of GPR84 and \(\mathrm{G_{ai}}\) '. When we mutated K126 to Ala, this did not alter the potency of 6- OAU for G protein activation (Fig. 3b) or affect receptor expression (Fig S3a). + +Liu et al (Nature Communications. 2023 Jun 6;14(1):3271) also reported that mutations at this position had no effect on G protein activation. + +## Reviewer #2 (Remarks to the Author): + +GPR84 is a proinflammatory receptor whose roles in lipid metabolism and immune regulation are emerging. In this manuscript, Zhang et al. demonstrated that the increase of macrophage phagocytosis depends on GPR84 and Gi. They solved a high- resolution cryoEM structure of GPR84 with the agonist 6- OAU. The structural model explains the ligand specificity and shows the unique ligand- binding features and structural motifs of GPR84. The authors further used computational tools for docking the native ligands and running MD simulations to identify the possible path as the entry or exit for the agonist. Overall, the paper is well- written and clear on the data and interpretation. The density map and the structural models are sound. The work would lead to further studies on the molecular mechanism of GPR84, which was poorly understood and may help therapy development. However, I still have some issues that need to be addressed by the authors before publishing the manuscript. + +Major + +1. Fig.1b, the error bars seem missing. + +We have revised our figure accordingly to include the error bars. + +2. Fig. 3d, the mutation H352A has huge efficacy and potency change, but the authors did not explain the rationale for mutating this position or show the location of this residue. Why is this residue so crucial for the activation of GPR84? + +<--- Page Split ---> + +Indeed, the relative efficacy of 6- OAU at H352A was low compared to wild type and potency was also substantial reduced. We initially expected that mutations of this residue wouldn't disrupt 6- OAU function since it doesn't interact with the ligand (Fig. S3b). However, it turned out not to be the case. This is probably explained by the poor expression of the mutant, as defined by low specific binding of \([^{3}\mathrm{H}]38\) and \([^{3}\mathrm{H}]140\) to H352A GPR84 (Fig. S3a). It is likely that the H352A mutant fails to fold correctly. We added a few sentences at the end of the second paragraph of section "Structure of the 6- OAU- GPR84- G; complex and an occluded ligand binding pocket " to describe such findings. The position of this residue is shown in Supplemental Data Figure S3b. + +Supplemental Data Figure S3b. + +3. The authors did not describe the docking process in the method section. Please indicate the parameters that the authors used in Glide/Schrodinger package. + +We thank the reviewer for the suggestion. We now include details of docking in the Methods section. + +4. The authors pointed out the unique features of GPR84-Gi interaction but did not show the comparison with the other GPCR-Gi pairs. The authors should support the claims like "in most of other Gi-coupled GPCR structures, the position 34.51 in the ICL2 is usually a hydrophobic residue." by providing some examples for the readers to compare. The authors compare the ligand binding pockets with the other lipid GPCRs in Figure 4. Receptors BLT1, S1PR1, and LPAR1 were solved with Gi-associated. Please provide a comparison of the Gi-binding mode of these related GPCRs either in the figures or in the supplementary data to support the claims. + +We thank the reviewer for the suggestion. We now include a figure panel showing the comparison of the Gi-coupling to GPR84, BLT1, S1PR1, and LPAR1 at ICL2 in Supplemental Data Figure 10. + +Minor: + +1. Fig. 1 legend the last sentence: "Each data point represents SD of data...". "Representing SD" cannot be accurate. Please correct the figure legend. + +The figure legend has been revised. + +2. Fig. 4. For general readers, please describe how the receptor figures are generated. For example: "In each column, the cartoon model and surface representation are used for the same receptor." + +We thank the reviewer for the suggestion. We have included such information in the figure legend stating that "In each column, the cartoon model and surface representation are used for the same receptor. The structures of the five receptors are placed side by side in each column after structural alignment, providing a consistent viewpoint from the same angle.". + +3. The method section of cryoEM data processing indicates three subsets were used for 62,824 particles. Supplementary Fig. 2 suggested only one class after 3D classification was used. Please double-check and make them consistent. + +<--- Page Split ---> + +We confirm that only one class after 3D classification was used for obtaining the final map. We have corrected this error in the Method section. + +4. The MD simulation should indicate the ligands' entry and exit routes. Do the authors only consider those paths as exit routes? Is there a reason for that? + +The ligand dynamics from the large-scale MD simulations were analyzed to identify states where ligands deviated from the bound-sites observed in the cryo- EM structure or the docking structures. Our analysis suggests the existence of three potential exit routes, which were determined based on the proximity of ligands to membrane lipids or the extracellular matrix. However, due to the slow dynamics involved in the opening- up of the occluded pocket, it was challenging to observe a clear unbinding event within the timeframe of several microseconds of MD simulations. To capture a genuine binding event, simulations with several orders of magnitude longer periods would be required, demanding significant time and resources. Furthermore, extensive functional studies would be necessary for validation. Consequently, we believe that conducting such studies exceeds the scope of the present paper. + +5. GRY is a unique motif distinguishing the GPR84 from the other Class A GPCRs. Is it possible to introduce mutation on the Glycine or amino acids interacting with Glycine (like F55) and test the mutant in the function assay (like GTPyS incorporation assay) to show that the GRY motif also plays the same critical role as the DRY motif? + +We thank the reviewer for the suggestion. As in our response to Reviewer 1, we have now included data on the G117D and G117A GPR84 mutants in our revised manuscript. The data is shown in Figure 3b. As noted in our manuscript, alteration of G117 to D, which would clash with F55, eliminated function of 6-OAU, whereas alteration of G117 to A didn't significantly affect 6-OAU signaling (Fig. 3b). For both G117A and G117D specific binding of both the allosteric antagonist \([^{3}\mathrm{H}]38\) and the orthosteric antagonist \([^{3}\mathrm{H}]140\) confirmed successful expression of these mutants (Fig. S3a). + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: The authors have addressed all my questions and concerns. + +Reviewer #2: Remarks to the Author: + +The authors have done a great job responding to my initial comments. Especially additional mutagenesis assays confirming the contribution of the GRY motif. + +However, I have one issue with the revised manuscript: + +In the new Fig.1 panel c, the legends say "GPR84KD". Does that mean "GPR84 knockdown"? In the manuscript, the author indicates GPR84 was knockout. Please provide evidence of the GPR84 knockout or knockdown. + +<--- Page Split ---> + +We thank all reviewers for their constructive comments. Please see our detailed responses to the comments below. The reviewers' comments are in blue font and our responses are in black font. + +Reviewer #1 (Remarks to the Author): + +The authors have addressed all my questions and concerns. + +Thanks. + +Reviewer #2 (Remarks to the Author): + +The authors have done a great job responding to my initial comments. Especially additional mutagenesis assays confirming the contribution of the GRY motif. + +However, I have one issue with the revised manuscript: + +In the new Fig.1 panel c, the legends say "GPR84KD". Does that mean "GPR84 knockdown"? In the manuscript, the author indicates GPR84 was knockout. Please provide evidence of the GPR84 knockout or knockdown. + +It is GPR84 knockdown. We have provided evidence for GPR84 knockdown in Supplementary Figure 1c. + +<--- Page Split ---> diff --git a/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b6bfcda6d47e45d0bc5dbd1694144d018167150a --- /dev/null +++ b/peer_reviews/55d0086bfa91ce42864685a51247f20c6fc7f54919e583b9713cbfc7fe89fc22/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,275 @@ +<|ref|>title<|/ref|><|det|>[[99, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[108, 155, 784, 211]]<|/det|> +Pro- phagocytic function and structural basis of GPR84 signaling + +<|ref|>image<|/ref|><|det|>[[94, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 286, 103]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[116, 120, 217, 133]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[116, 135, 291, 148]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 149, 879, 239]]<|/det|> +The manuscript "Pro- phagocytic function and structural basis of GPR84 signaling" by Zhang et al, reports a cryo- EM structure of 6- OAU- bound human GPR84- Gi complex. Together with mutation data and MD simulation, the authors discussed the binding pocket of 6- OAU and receptor activation. GPR84 is a promising target for immune disease and cancer, this work provides molecular basis for the ligand discovery for GPR84. However, the manuscript organization and contents should be largely improved. There are several concerns which need to be addressed: + +<|ref|>text<|/ref|><|det|>[[115, 255, 214, 268]]<|/det|> +Major issues: + +<|ref|>text<|/ref|><|det|>[[112, 268, 880, 540]]<|/det|> +1. The phagocytosis assay presented in Figure 1 is not convincing to claim the pro-phagocytic effects is induced by GPR84-Gi signaling. More additional assays or controls are needed. GLPG1205 was reported as a NAM of GPR84, does it bind to the similar orthosteric binding pocket with 6-OAU in GPR84? +2. "The structure was determined to a global resolution of 3.0-A by cryo-EM", according to the local resolution estimation in Fig. S2f, the resolution for the extracellular region is quite low. The electron density for the ligand and surrounding residues, as well as ECL2, should be shown. +3. In left panel of Figure 2, the author did not show the electron density for 6-OAU in the overall structure, while a strong piece of density is shown in the cytoplasmic parts of TM2-4. How does this density fit with cholesterol? +4. The expression data for mutants in Fig. 3d is missing, should be provided. +5. Does the disulfide bond between N-terminus and ECL2 affect the 6-OAU binding or the activation of the receptor? +6. MD simulations should be performed to support the docking poses of embelin, capric acid, and 2-hydroxy capric acid. +7. There are no mutagenesis data to verify the key residues that may related to GPR84 activation, such as Y3326.48, N1043.36, G1173.49. +8. How does K126 mutation affect the Gi coupling with GPR84? + +<|ref|>text<|/ref|><|det|>[[115, 581, 216, 594]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 597, 293, 610]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 610, 881, 775]]<|/det|> +GPR84 is a proinflammatory receptor whose roles in lipid metabolism and immune regulation are emerging. In this manuscript, Zhang et al. demonstrated that the increase of macrophage phagocytosis depends on GPR84 and Gi. They solved a high- resolution cryoEM structure of GPR84 with the agonist 6- OAU. The structural model explains the ligand specificity and shows the unique ligand- binding features and structural motifs of GPR84. The authors further used computational tools for docking the native ligands and running MD simulations to identify the possible path as the entry or exit for the agonist. Overall, the paper is well- written and clear on the data and interpretation. The density map and the structural models are sound. The work would lead to further studies on the molecular mechanism of GPR84, which was poorly understood and may help therapy development. However, I still have some issues that need to be addressed by the authors before publishing the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 791, 160, 804]]<|/det|> +Major + +<|ref|>text<|/ref|><|det|>[[115, 805, 405, 819]]<|/det|> +1. Fig.1b, the error bars seem missing. + +<|ref|>text<|/ref|><|det|>[[115, 820, 875, 864]]<|/det|> +2. Fig. 3d, the mutation H352A has huge efficacy and potency change, but the authors did not explain the rationale for mutating this position or show the location of this residue. Why is this residue so crucial for the activation of GPR84? + +<|ref|>text<|/ref|><|det|>[[115, 864, 819, 894]]<|/det|> +3. The authors did not describe the docking process in the method section. Please indicate the parameters that the authors used in Glide/Schrodinger package. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 879, 195]]<|/det|> +4. The authors pointed out the unique features of GPR84-Gi interaction but did not show the comparison with the other GPCR-Gi pairs. The authors should support the claims like "in most of other Gi-coupled GPCR structures, the position 34.51 in the ICL2 is usually a hydrophobic residue." by providing some examples for the readers to compare. The authors compare the ligand binding pockets with the other lipid GPCRs in Figure 4. Receptors BLT1, S1PR1, and LPAR1 were solved with Gi-associated. Please provide a comparison of the Gi-binding mode of these related GPCRs either in the figures or in the supplementary data to support the claims. + +<|ref|>text<|/ref|><|det|>[[115, 209, 164, 222]]<|/det|> +Minor: + +<|ref|>text<|/ref|><|det|>[[112, 223, 866, 415]]<|/det|> +1. Fig. 1 legend the last sentence: "Each data point represents SD of data...". "Representing SD" cannot be accurate. Please correct the figure legend. +2. Fig. 4. For general readers, please describe how the receptor figures are generated. For example: "In each column, the cartoon model and surface representation are used for the same receptor." +3. The method section of cryoEM data processing indicates three subsets were used for 62,824 particles. Supplementary Fig. 2 suggested only one class after 3D classification was used. Please double-check and make them consistent. +4. The MD simulation should indicate the ligands' entry and exit routes. Do the authors only consider those paths as exit routes? Is there a reason for that? +5. GRY is a unique motif distinguishing the GPR84 from the other Class A GPCRs. Is it possible to introduce mutation on the Glycine or amino acids interacting with Glycine (like F55) and test the mutant in the function assay (like GTPyS incorporation assay) to show that the GRY motif also plays the same critical role as the DRY motif? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 122, 876, 158]]<|/det|> +We thank all reviewers for their constructive comments. Please see our detailed responses to the comments below. The reviewers' comments are in blue font and our responses are in black font. + +<|ref|>sub_title<|/ref|><|det|>[[116, 185, 350, 202]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 220, 439, 238]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 272, 874, 394]]<|/det|> +The manuscript "Pro- phagocytic function and structural basis of GPR84 signaling" by Zhang et al, reports a cryo- EM structure of 6- OAU- bound human GPR84- Gi complex. Together with mutation data and MD simulation, the authors discussed the binding pocket of 6- OAU and receptor activation. GPR84 is a promising target for immune disease and cancer, this work provides molecular basis for the ligand discovery for GPR84. However, the manuscript organization and contents should be largely improved. There are several concerns which need to be addressed: + +<|ref|>text<|/ref|><|det|>[[115, 412, 222, 428]]<|/det|> +Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 429, 857, 499]]<|/det|> +1. The phagocytosis assay presented in Figure 1 is not convincing to claim the pro-phagocytic effects is induced by GPR84-Gi signaling. More additional assays or controls are needed. GLPG1205 was reported as a NAM of GPR84, does it bind to the similar orthosteric binding pocket with 6-OAU in GPR84? + +<|ref|>text<|/ref|><|det|>[[115, 503, 872, 644]]<|/det|> +GLPG1205 may not bind to the same orthosteric binding pocket as that of 6- OAU in GPR84. Nonetheless, it functions as a specific antagonist of GPR84 and effectively inhibits GPR84 signaling induced by 6- OAU, even in the presence of 6- OAU binding (doi:10.1021/acs.jmedchem.0c00272). The fact that GLPG1205 abolishes 6- OAU- induced phagocytosis strongly suggests that this effect is mediated by GPR84. To further support this claim, we conducted CRISPR-Cas9- mediated knockout of GPR84 expression in primary macrophages and showed that the pro-phagocytic effect of 6- OAU was lost. These new findings are now presented in Fig. 1c. + +<|ref|>text<|/ref|><|det|>[[115, 664, 883, 737]]<|/det|> +2. "The structure was determined to a global resolution of 3.0-Å by cryo-EM", according to the local resolution estimation in Fig. S2f, the resolution for the extracellular region is quite low. The electron density for the ligand and surrounding residues, as well as ECL2, should be shown. We have included the suggested electron density map in the revised Supplementary Figure 2g. The density of the ligand and surrounding residues is clear for modeling. + +<|ref|>text<|/ref|><|det|>[[115, 737, 872, 912]]<|/det|> +3. In left panel of Figure 2, the author did not show the electron density for 6-OAU in the overall structure, while a strong piece of density is shown in the cytoplasmic parts of TM2-4. How does this density fit with cholesterol? The binding pocket of 6-OAU is completely embedded within the 7TM domain of GPR84. Therefore, it is difficult to see the density of 6-OAU in the overall structure showing the cryo-EM density of the receptor. Nevertheless, we show the density of 6-OAU alone in Figure 2. The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 831, 126]]<|/det|> +density near the cytoplasmic region of TM2- 4 fits cholesterol well. We have included such density in the revised Supplementary Figure 2g. + +<|ref|>text<|/ref|><|det|>[[115, 147, 717, 166]]<|/det|> +4. The expression data for mutants in Fig. 3d is missing, should be provided. + +<|ref|>text<|/ref|><|det|>[[115, 170, 857, 240]]<|/det|> +We thank the reviewer for the suggestion. We have now provided expression data for the mutants as measured by the specific binding of both a radiolabelled orthosteric 1,2,4 triazine antagonist ([3H]140) and a similarly radiolabelled allosteric antagonist ([3H]38) that is closely related to the clinically trialled GPR84 blocker GLPG1205. The data is shown in + +<|ref|>sub_title<|/ref|><|det|>[[116, 241, 380, 258]]<|/det|> +## Supplementary Data Figure 3a. + +<|ref|>text<|/ref|><|det|>[[115, 262, 877, 385]]<|/det|> +In some cases, the mutants were unable to bind either of these ligands with high affinity as predicted for [3H]140 from previous mutagenesis and homology modelling studies (Mahindra et al J. Med. Chem. 2022, doi.org/10.1021/acs.jmedchem.2c00804). However, for the Phe335Ala mutant for example, although it is unable to bind the orthosteric antagonist, which was also previously shown by Mahindra et al, its expression as a structurally intact protein was confirmed because this mutant does bind [3H]38 effectively. For a further set of mutants, for example the Gly117 to either Ala or Asp, both radiologands bound with high affinity. + +<|ref|>text<|/ref|><|det|>[[115, 406, 833, 441]]<|/det|> +5. Does the disulfide bond between N-terminus and ECL2 affect the 6-OAU binding or the activation of the receptor? + +<|ref|>text<|/ref|><|det|>[[115, 445, 881, 586]]<|/det|> +It appears that it does. Alteration of Cys11 to Ala (which will prevent the formation of such a disulfide bond) completely eliminated G protein activation by 6-OAU. However, a caveat to this conclusion is that we did not observe binding of either the allosteric antagonist [3H]38 or the orthosteric antagonist [3H]140 in membranes of cells transfected to express GPR84 Cys11Ala and therefore disruption of this disulfide bridge likely limits correct folding of the receptor. We have included the G protein activation data in revised Figure 3b and the radioligand binding data in Supplementary Data Figure 3a. This frequently is the outcome when the conserved ECL2- TM3 disulfide bond in class A GPCRs is disrupted in various receptors. + +<|ref|>text<|/ref|><|det|>[[115, 590, 860, 644]]<|/det|> +It's worth noted that Liu et al (Nature Communications. 2023 Jun 6;14(1):3271) showed that they recorded reduced but still detectable cell surface expression of a C11A mutant, although they didn't probe its folding. Like us, they noted no agonist- induced signalling for this mutant. + +<|ref|>text<|/ref|><|det|>[[115, 665, 852, 700]]<|/det|> +6. MD simulations should be performed to support the docking poses of embelin, capric acid, and 2-hydroxy capric acid. + +<|ref|>text<|/ref|><|det|>[[115, 705, 883, 826]]<|/det|> +We thank the reviewer for the suggestion. We now include new MD simulations studies on embelin, capric acid, and 2- hydroxy capric acid starting from the docking poses in our revised manuscript. The data is presented in Extended Data Figure 7 and 8. Five copies (1us each) were run for each ligand, which totaled around \(5\mu \mathrm{s}\) dynamics for each of embelin, capric acid and 2- hydroxy capric acid. We found that the four ligands primarily occupy the native binding pocket, consistent with the docking poses, with occasional forays to metastable sites such as S1, S2 and S3. + +<|ref|>text<|/ref|><|det|>[[115, 849, 879, 884]]<|/det|> +7. There are no mutagenesis data to verify the key residues that may related to GPR84 activation, such as Y3326.48, N1043.36, G1173.49. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 865, 195]]<|/det|> +We thank the reviewer for the suggestion. We have now included such mutagenesis data in our revised manuscript. The data is shown in Figure 3b. As noted in our manuscript, alteration of G117 to D eliminated function of 6- OAU whereas alteration of G117 to A didn't significantly affect 6- OAU signaling (Fig. 3b). For both G117A and G117D specific binding of both the allosteric antagonist \([^{3}\mathrm{H}]38\) and the orthosteric antagonist \([^{3}\mathrm{H}]140\) confirmed successful expression of these mutants (Fig. S3a). + +<|ref|>text<|/ref|><|det|>[[115, 199, 872, 253]]<|/det|> +Although residue 6.48 is most frequently W in class A GPCRs, in GPR84 this is replaced by Y322. Alteration of Y322 to W again resulted in reduced potency of 6- OAU whilst alteration to Ala all but eliminated responsiveness (Fig. 3b). + +<|ref|>text<|/ref|><|det|>[[115, 256, 879, 345]]<|/det|> +We also explored the contribution of N104 by converting this residue to Ala. The N104A mutant did not respond to any concentration of 6- OAU that we were able to test and, as such, this Asn indeed is likely to play a key role (Fig. 3b). Once more, however, the caveat to this conclusion is that we were unable to detect specific binding of \([^{3}\mathrm{H}]38\) or \([^{3}\mathrm{H}]140\) in membranes from cells transiently transfected with this mutant (Fig. S3a). + +<|ref|>text<|/ref|><|det|>[[115, 365, 627, 383]]<|/det|> +8. How does K126 mutation affect the Gi coupling with GPR84? + +<|ref|>text<|/ref|><|det|>[[115, 383, 880, 454]]<|/det|> +We state in our manuscript that '34.51 in the ICL2 is usually a hydrophobic residue', but 'In GPR84, this position is K126. As a result, there is no direct interactions between ICL2 of GPR84 and \(\mathrm{G_{ai}}\) '. When we mutated K126 to Ala, this did not alter the potency of 6- OAU for G protein activation (Fig. 3b) or affect receptor expression (Fig S3a). + +<|ref|>text<|/ref|><|det|>[[115, 458, 860, 494]]<|/det|> +Liu et al (Nature Communications. 2023 Jun 6;14(1):3271) also reported that mutations at this position had no effect on G protein activation. + +<|ref|>sub_title<|/ref|><|det|>[[115, 515, 439, 533]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 550, 875, 743]]<|/det|> +GPR84 is a proinflammatory receptor whose roles in lipid metabolism and immune regulation are emerging. In this manuscript, Zhang et al. demonstrated that the increase of macrophage phagocytosis depends on GPR84 and Gi. They solved a high- resolution cryoEM structure of GPR84 with the agonist 6- OAU. The structural model explains the ligand specificity and shows the unique ligand- binding features and structural motifs of GPR84. The authors further used computational tools for docking the native ligands and running MD simulations to identify the possible path as the entry or exit for the agonist. Overall, the paper is well- written and clear on the data and interpretation. The density map and the structural models are sound. The work would lead to further studies on the molecular mechanism of GPR84, which was poorly understood and may help therapy development. However, I still have some issues that need to be addressed by the authors before publishing the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 761, 169, 777]]<|/det|> +Major + +<|ref|>text<|/ref|><|det|>[[115, 778, 419, 795]]<|/det|> +1. Fig.1b, the error bars seem missing. + +<|ref|>text<|/ref|><|det|>[[115, 799, 625, 817]]<|/det|> +We have revised our figure accordingly to include the error bars. + +<|ref|>text<|/ref|><|det|>[[115, 839, 863, 891]]<|/det|> +2. Fig. 3d, the mutation H352A has huge efficacy and potency change, but the authors did not explain the rationale for mutating this position or show the location of this residue. Why is this residue so crucial for the activation of GPR84? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 875, 230]]<|/det|> +Indeed, the relative efficacy of 6- OAU at H352A was low compared to wild type and potency was also substantial reduced. We initially expected that mutations of this residue wouldn't disrupt 6- OAU function since it doesn't interact with the ligand (Fig. S3b). However, it turned out not to be the case. This is probably explained by the poor expression of the mutant, as defined by low specific binding of \([^{3}\mathrm{H}]38\) and \([^{3}\mathrm{H}]140\) to H352A GPR84 (Fig. S3a). It is likely that the H352A mutant fails to fold correctly. We added a few sentences at the end of the second paragraph of section "Structure of the 6- OAU- GPR84- G; complex and an occluded ligand binding pocket " to describe such findings. The position of this residue is shown in Supplemental Data Figure S3b. + +<|ref|>text<|/ref|><|det|>[[116, 230, 379, 247]]<|/det|> +Supplemental Data Figure S3b. + +<|ref|>text<|/ref|><|det|>[[114, 269, 852, 306]]<|/det|> +3. The authors did not describe the docking process in the method section. Please indicate the parameters that the authors used in Glide/Schrodinger package. + +<|ref|>text<|/ref|><|det|>[[116, 309, 850, 345]]<|/det|> +We thank the reviewer for the suggestion. We now include details of docking in the Methods section. + +<|ref|>text<|/ref|><|det|>[[114, 365, 876, 490]]<|/det|> +4. The authors pointed out the unique features of GPR84-Gi interaction but did not show the comparison with the other GPCR-Gi pairs. The authors should support the claims like "in most of other Gi-coupled GPCR structures, the position 34.51 in the ICL2 is usually a hydrophobic residue." by providing some examples for the readers to compare. The authors compare the ligand binding pockets with the other lipid GPCRs in Figure 4. Receptors BLT1, S1PR1, and LPAR1 were solved with Gi-associated. Please provide a comparison of the Gi-binding mode of these related GPCRs either in the figures or in the supplementary data to support the claims. + +<|ref|>text<|/ref|><|det|>[[116, 492, 872, 546]]<|/det|> +We thank the reviewer for the suggestion. We now include a figure panel showing the comparison of the Gi-coupling to GPR84, BLT1, S1PR1, and LPAR1 at ICL2 in Supplemental Data Figure 10. + +<|ref|>text<|/ref|><|det|>[[116, 568, 172, 584]]<|/det|> +Minor: + +<|ref|>text<|/ref|><|det|>[[116, 586, 872, 622]]<|/det|> +1. Fig. 1 legend the last sentence: "Each data point represents SD of data...". "Representing SD" cannot be accurate. Please correct the figure legend. + +<|ref|>text<|/ref|><|det|>[[116, 625, 395, 643]]<|/det|> +The figure legend has been revised. + +<|ref|>text<|/ref|><|det|>[[116, 664, 860, 717]]<|/det|> +2. Fig. 4. For general readers, please describe how the receptor figures are generated. For example: "In each column, the cartoon model and surface representation are used for the same receptor." + +<|ref|>text<|/ref|><|det|>[[116, 721, 858, 793]]<|/det|> +We thank the reviewer for the suggestion. We have included such information in the figure legend stating that "In each column, the cartoon model and surface representation are used for the same receptor. The structures of the five receptors are placed side by side in each column after structural alignment, providing a consistent viewpoint from the same angle.". + +<|ref|>text<|/ref|><|det|>[[116, 819, 875, 872]]<|/det|> +3. The method section of cryoEM data processing indicates three subsets were used for 62,824 particles. Supplementary Fig. 2 suggested only one class after 3D classification was used. Please double-check and make them consistent. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 870, 125]]<|/det|> +We confirm that only one class after 3D classification was used for obtaining the final map. We have corrected this error in the Method section. + +<|ref|>text<|/ref|><|det|>[[115, 152, 843, 188]]<|/det|> +4. The MD simulation should indicate the ligands' entry and exit routes. Do the authors only consider those paths as exit routes? Is there a reason for that? + +<|ref|>text<|/ref|><|det|>[[115, 192, 877, 368]]<|/det|> +The ligand dynamics from the large-scale MD simulations were analyzed to identify states where ligands deviated from the bound-sites observed in the cryo- EM structure or the docking structures. Our analysis suggests the existence of three potential exit routes, which were determined based on the proximity of ligands to membrane lipids or the extracellular matrix. However, due to the slow dynamics involved in the opening- up of the occluded pocket, it was challenging to observe a clear unbinding event within the timeframe of several microseconds of MD simulations. To capture a genuine binding event, simulations with several orders of magnitude longer periods would be required, demanding significant time and resources. Furthermore, extensive functional studies would be necessary for validation. Consequently, we believe that conducting such studies exceeds the scope of the present paper. + +<|ref|>text<|/ref|><|det|>[[115, 388, 879, 458]]<|/det|> +5. GRY is a unique motif distinguishing the GPR84 from the other Class A GPCRs. Is it possible to introduce mutation on the Glycine or amino acids interacting with Glycine (like F55) and test the mutant in the function assay (like GTPyS incorporation assay) to show that the GRY motif also plays the same critical role as the DRY motif? + +<|ref|>text<|/ref|><|det|>[[115, 459, 866, 581]]<|/det|> +We thank the reviewer for the suggestion. As in our response to Reviewer 1, we have now included data on the G117D and G117A GPR84 mutants in our revised manuscript. The data is shown in Figure 3b. As noted in our manuscript, alteration of G117 to D, which would clash with F55, eliminated function of 6-OAU, whereas alteration of G117 to A didn't significantly affect 6-OAU signaling (Fig. 3b). For both G117A and G117D specific binding of both the allosteric antagonist \([^{3}\mathrm{H}]38\) and the orthosteric antagonist \([^{3}\mathrm{H}]140\) confirmed successful expression of these mutants (Fig. S3a). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 286, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 120, 560, 164]]<|/det|> +Reviewer #1: Remarks to the Author: The authors have addressed all my questions and concerns. + +<|ref|>text<|/ref|><|det|>[[115, 209, 294, 238]]<|/det|> +Reviewer #2: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 240, 797, 269]]<|/det|> +The authors have done a great job responding to my initial comments. Especially additional mutagenesis assays confirming the contribution of the GRY motif. + +<|ref|>text<|/ref|><|det|>[[115, 284, 530, 299]]<|/det|> +However, I have one issue with the revised manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 299, 883, 343]]<|/det|> +In the new Fig.1 panel c, the legends say "GPR84KD". Does that mean "GPR84 knockdown"? In the manuscript, the author indicates GPR84 was knockout. Please provide evidence of the GPR84 knockout or knockdown. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 122, 883, 158]]<|/det|> +We thank all reviewers for their constructive comments. Please see our detailed responses to the comments below. The reviewers' comments are in blue font and our responses are in black font. + +<|ref|>text<|/ref|><|det|>[[115, 180, 420, 198]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 215, 580, 233]]<|/det|> +The authors have addressed all my questions and concerns. + +<|ref|>text<|/ref|><|det|>[[115, 255, 178, 272]]<|/det|> +Thanks. + +<|ref|>text<|/ref|><|det|>[[115, 289, 420, 307]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 324, 839, 360]]<|/det|> +The authors have done a great job responding to my initial comments. Especially additional mutagenesis assays confirming the contribution of the GRY motif. + +<|ref|>text<|/ref|><|det|>[[115, 376, 552, 394]]<|/det|> +However, I have one issue with the revised manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 394, 880, 445]]<|/det|> +In the new Fig.1 panel c, the legends say "GPR84KD". Does that mean "GPR84 knockdown"? In the manuscript, the author indicates GPR84 was knockout. Please provide evidence of the GPR84 knockout or knockdown. + +<|ref|>text<|/ref|><|det|>[[115, 472, 866, 508]]<|/det|> +It is GPR84 knockdown. We have provided evidence for GPR84 knockdown in Supplementary Figure 1c. + +<--- Page Split ---> diff --git a/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/images_list.json b/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..20165585813534dcef2776d842a06610564b35c7 --- /dev/null +++ b/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1. Performance comparison between the gene-expression-only method \"NJ-exp\" and other methods that use barcode information.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure R2. Colour palettes visualization for cell types and lineage barcode mutation annotations in Fig. 1", + "footnote": [], + "bbox": [ + [ + 128, + 680, + 870, + 727 + ] + ], + "page_idx": 7 + } +] \ No newline at end of file diff --git a/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..02acbfb7ca558c9850d3f033c60611441a55dd83 --- /dev/null +++ b/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,361 @@ + +# nature portfolio + +Peer Review File + +LinRace: cell division history reconstruction of single cells using paired lineage barcode and gene expression data + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +Pan et al. presented as a new computational tool (LinRace) to reconstruct the developmental lineages based upon paired single cell RNA- seq and CRISPR / Cas9 based lineage recorders. LinRace first reconstructed a lineage tree from the unique barcodes (CRISPR / Cas9 scares) from the recorders, and used the scRNA- seq data from of cells with the identical barcode to derive the subtrees. They have evaluated the LinRace on synthetic data simulated by TedSim (also from the same group), and two real datasets on C. elegans development and the scGESTAULT dataset. LinRace demonstrated better performance than state- of- the- art methods such as Cassiopeia and DCLEAR that reconstruct lineages solely from the CRISPR / Cas9 based lineage recorders, as well as LinTIMat that took both scRNA- seq and lineage recorders as the inputs. Overall, the manuscript is well written, and the analysis / benchmark is comprehensive. Here are a few issues the authors would consider to address: + +1. The authors need to include more recently tools such as Startle (https://www.biorxiv.org/content/10.1101/2022.12.18.520935v1.abstract) into the benchmark. +2. Performance of tree reconstructions from Slingshot along should also be included. It is curious to see if the lineage tree reconstructed from scRNA-seq (by Slingshot) has comparable performance with Cassiopeia or DCLEAR. For example, a corresponding tree can be constructed from the cell-cell distance matrix using the latent representation. +3. Other tools that such as TreeVAE that also used both CRISPR / Cas9 recorders and scRNA-seq data also should be be included in the benchmark. +4. The authors only examined the recorders with relatively small targets (16 and 9 targets in the synthetic data and C. elegans datasets, respectively). It is interesting to see the performance over more target sites. For example, 100 and 1,000 target sites were used in the DREAM challenge. +5. Section 4.7: Cassiopeia is written in Python. + +## Reviewer #2 (Remarks to the Author): + +This articles addresses an interesting question of how to infer the lineage phylogeny with higher resolution. To do so, they developed a sophisticated framework to integrate the lineage and cell state information. In particularly, they considered the cell division history, the differentiation dynamics on the cell state manifold, and the consistency between these two processes. In doing so, the reconstructed lineage tree are shown to achieve higher accuracy than existing methods. Their idea is cool, and the paper is overall well- written. I have the following comments. + +1, In order to correctly reconstruct the lineage phylogeny, it is important to consider barcode homoplasy, where two independent cells may spontaneously acquire the same mutations for lineage recording. In fact, target array editing with CARISPR- Cas9 generates outcomes (barcodes) with different frequencies, + +<--- Page Split ---> + +with some being highly frequent, labeling many unrelated (non- clonal) cells, and others being rare and more specific to a particular clone. The issue of barcode homoplasy becomes more severe when there is large scale dropouts of the target arrays, which is common to CARISPR- Cas9 based lineage recording. Indeed, in Supplementary Fig 1a, the largest clone (\~1500 cells) has large deletions and only a single detected mutation. Assuming that all the cells sharing this barcode come from the same founder cell is likely wrong, because the only mutation in this barcode may be generated independently from many cells among these 'pseudo' clone. Besides, it is also unlikely that a single founder cell could expand to \~1500 cells, while most other clones only have a single cell. The authors should clearly discuss how to address this issue of barcode homoplasy, due to having mutations with very different frequencies. Potentially, they can use their simulations to test this situation, and see how well their method performs in this context. + +2, In order to simulate the cell division history and the differentiation dynamics together, the authors assume that the sampled leaf nodes can form a state manifold, and the ancestor cell states (from the internal nodes in the reconstructed lineage tree) can be found from the sampled cell states. In systems with asynchronous differentiation, like in blood, such an assumption could indeed hold. But for developmental systems with more synchronous differentiation, all cell states change rapidly over time, and the early ancestor cell states are no longer there at the later stage of development. This is an unstated limitation of this study. The authors should address this limitation. At least, they should explicitly state this limitation. In doing so, they may also need to temper their claim that they can infer the ancestor state, by adding the restrictive conditions. + +3, There are two articles worth referencing in this paper. + +3. There are two articles worth referencing in this paper.3. 1 Li et.al., bioRxiv 2023, titled "A mouse model with high clonal barcode diversity for joint lineage, transcriptomic, and epigenomic profiling in single cells". They explicitly addressed the issue of low barcode diversity due to large inter-site deletions in CARISPR-Cas9 editing by adding TdT to increase mutation diversity. This could help to reduce the issue of barcode homoplasy in future applications.3.2 Wang et.al., Nat. Biotech. 2023, titled "CoSpar identifies early cell fate biases from single-cell transcriptomic and lineage information". They similarly integrated lineage and state information. Instead of learning the lineage tree, they inferred the cell fate choice. In their study, they explicitly addressed how to cope with barcode homoplasy in their algorithm. + +Minor issues for Main text + +Line 52, "Is it shown ..." \(\rightarrow\) "It is shown." + +Line 113- 116, the description of the clone size is very confusing here. + +Line 369- 374, how do you support your conjecture here about differentiation speed? I do not see any data. + +Line 457, does "bifurcating tree" means that it will learn a topology of just two branches? Please clarify + +<--- Page Split ---> + +Line 482 (Eq. 3), I believe the equation has typos. Also, I(.) function is not defined. Please clarify what this function is, and why it takes this form. + +Line 495, what is \(x_{- }\) ? Gene expression vector of a single cell? + +Line 561- 569, I did not follow this part. Could you make it more clear? + +Line 625, the definition of the I() function should go earlier when it first appears. + +Minor issues for Supplementary file + +Supplementary Fig 2, clarify the figure legend: LinRace_0.1_1. + +Could you provide a figure with varying cell number, and compare the performance of different methods at the same mutation rate, similar to Supplementary Figure 5? + +## Reviewer #3 (Remarks to the Author): + +In "LinRace: cell division history reconstruction of single cells using paired lineage barcode and gene expression data", the authors describe a new method to build cell lineage trees using CRISPR- Cas9 induced lineage barcode data supplemented with the simultaneously collected single cell RNA- seq data. The authors accurately describe the challenge in such data sets, specifically that the lineage barcodes alone often do not encode sufficient information to reconstruct the full lineage tree. To overcome this limitation, the authors leverage gene expression information to resolve the edges of the tree. + +I believe this manuscript is well written and clearly presented. The new strategy LinRace serves a useful role in the field providing a route to include gene expression data with lineage barcode data only when lineage data is limited. In this way, the lineage data itself is prioritized in determining the cell lineage tree when it is available, which seems reasonable. The authors make the appropriate comparisons of their method to field standards (DCLEAR, Cassiopeia, and in some ways, the most directly comparable LinTIMat) using de novo simulated data sets and simulated data based on the known C. elegans lineage. Overall, their strategy performs the best using appropriate criteria. Moreover, the authors offer good insights into why methods generally perform better or worse over different mutation rates and why they believe their method outperforms LinTIMat. The data and methodology are sound. + +Next, the authors apply their method to two real data sets where ground truth is not known, the zebrafish brain from scGESTALT and mouse embryos from the molecular recorder. In the former, they showcase an example where their strategy resolves lineages that undergo symmetric vs asymmetric cell division while in the latter, they describe the phenomenon of "partial consistency between transcriptome similarity and barcode similarity". In both cases, the biological findings are limited but I do + +<--- Page Split ---> + +not believe it detracts from this manuscript. Rather, it highlights how LinRace is useful in creating more detailed subtrees that may aid in future biological interpretation. For example, better tree topologies may lead to more accurate estimates of symmetric and asymmetric cell division likelihoods – a parameter that would affect the LinRace method itself. + +Overall, I think this manuscript presents a reasonable method for utilizing gene expression data to complement lineage tracing data in a manner that is very useful for the field. I believe the description of methods and analysis performed in the manuscript is sufficient for replication. + +## Suggestions: + +- Section 2.5 presents the lack of DE for the same cell state that exist in different lineages. Overall, this is not a surprising result and is in line with biological expectations. Nonetheless, their ability to detect DEs may simply be underpowered. I wonder if the intra-lineage gene expression distance for cells of the same state is lower than the inter-lineage distance across cells of the same state across the population of cells. I realize this suggestion can be a bit circular depending on the depth of tree examined since "neighbor distance likelihood" is used to establish the lineage. It might be interesting to look at regardless. + +- I am curious if the authors can comment on how these following suggestions might change/improve performance (which could perhaps be added to discussion): + +- I am curious if the authors can comment on how these following suggestions might change/improve performance (which could perhaps be added to discussion):o Alternate tree building method to make the tree backbone – perhaps DCLEAR or Cassiopeia.o Using time course scRNA-seq data instead of the scRNA-seq data collected with the lineage barcodes. Trajectories may be more accurately inferred when past cell states are more directly measured than relying on variability that exists within a time point. To calculate the GES, they use 3 terms, the first two of which utilizes only cell state information. They could use the cell state tree from scRNA-seq time course data sets, and still maintain the third term from the lineage traced data set. + +Minor points: + +Fig 1. It may be worthwhile to change the colors for cell states so that it is easier to distinguish between the black and navy, and red and pink + +Line 176- 8: I would recommend adding a half a sentence or a sentence about how to choose a root cell state outside of simulation environments. + +Line 309: GESTAULT should be GESTALT (and also Fig 4 legend, line 591) + +Fig 4a: Inner ring is barely visible + +Line 334: This may be a lack of understanding on my part, but to my knowledge, terminal cells do not undergo mitosis. Is there a different word that can be used here to express cells that can only undergo symmetric divisions? + +<--- Page Split ---> + +## Responses to Reviewers' Comments + +We thank the reviewers for their time to review our manuscript and their valuable comments. + +Please find below the reviewers' comments (in black) and our pointwise responses (in blue). The changes in the manuscript are marked in red. + +## Reviewer #1 + +Pan et al. presented as a new computational tool (LinRace) to reconstruct the developmental lineages based upon paired single cell RNA- seq and CRISPR / Cas9 based lineage recorders. LinRace first reconstructed a lineage tree from the unique barcodes (CRISPR / Cas9 scares) from the recorders, and used the scRNA- seq data from of cells with the identical barcode to derive the subtrees. They have evaluated the LinRace on synthetic data simulated by TedSim (also from the same group), and two real datasets on C.elegans development and the scGESTAULT dataset. LinRace demonstrated better performance than state- of- the- art methods such as Cassiopeia and DCLEAR that reconstruct lineages solely from the CRISPR / Cas9 based lineage recorders, as well as LinTIMat that took both scRNA- seq and lineage recorders as the inputs. Overall, the manuscript is well- written, and the analysis/benchmark is comprehensive. Here are a few issues the authors would consider to address: + +1. The authors need to include more recently tools such as Startle (https://www.biorxiv.org/content/10.1101/2022.12.18.520935v1.abstract) into the benchmark. + +We thank the reviewer for suggesting that we include the recent method, Startle, in our comparison. Startle infers cell division trees from lineage barcode data by enforcing the "non-modifiability" property of CRISPR-Cas9 mutations. + +Startle provides two modes, Startle- ILP and Startle- NNI. We encountered a running time issue with Startle- ILP (their preferred mode) on the scale of datasets we used: the solver could not find a valid solution with the default parameters. Based on communication with the authors of Startle, we used the Startle- NNI mode, which is much faster than Startle- ILP, although still slower than the other methods. As a result, we tested Startle- NNI on all simulated datasets except for those with 4096 cells. + +We included the results of Startle- NNI in the comparisons of LinRace and baseline methods, using accuracy measurements RF distance, Nye similarity, and CID, in Figs. 2- 3, and Supplementary Fig. 10 in the manuscript. The results show that LinRace outperforms Startle- NNI consistently. + +<--- Page Split ---> + +In the manuscript, we have also added modifications and corresponding discussions to reflect that we included Startle as an additional baseline method. These changes are in Lines 68- 69, 160, 221- 225, 332, 364- 366, 711- 717, 765. + +2. Performance of tree reconstructions from Slingshot along should also be included. It is curious to see if the lineage tree reconstructed from scRNA-seq (by Slingshot) has comparable performance with Cassiopedia or DCLEAR. For example, a corresponding tree can be constructed from the cell-cell distance matrix using the latent representation. + +We thank the reviewer for providing two suggestions on using only gene expression data to reconstruct the cell lineage tree. + +(1) Although Slingshot is widely used for the task "trajectory inference" which is to infer trajectory between cell states (and thus is used in LinRace to infer the cell state tree), it is not suited to infer cell division trees, which is the final goal of LinRace. We clarified the relationships between the cell state tree used in LinRace and the cell division tree in the manuscript (e.g. Lines 96-100). + +We understand that this can be confusing as the term "lineage tree" is sometimes used to refer to the trajectory between cell states, while in the context of cell division events, a lineage means the tree representing the cell division history. To avoid this confusion, we clarified the definition of "cell lineage tree" and trajectory inference in the paper (Lines 39- 42, 117- 121). + +The main reason that Slingshot can not be used to infer a cell division tree is the following: A common application of Slingshot is that given \(k\) clusters of cells, Slingshot infers a tree with \(k\) nodes. Similarly, if one cell is treated as a cluster, given the input of \(n\) cells, Slingshot infers a tree with \(n\) nodes, where some are internal nodes and some are leaf nodes of the tree. When inferring a cell division tree, all \(n\) cells need to be leaf nodes. In other words, Slingshot estimates pseudotime while the task of inferring cell division trees considers the time from the root to leaves as real- time. + +(2) Based on the suggestion of using the cell-cell distance matrix obtained from cell latent representations to reconstruct the cell division tree, we implemented and tested this approach (called NJ-exp) on the TedSim simulated datasets (1024 cells and 16 target sites). Specifically, we first performed PCA on the scRNA-seq count matrix, then used the first 50 PCs to calculate pairwise Euclidean distance between single cells, and reconstructed a NJ tree from the pairwise distance matrix. + +The results in terms of all three metrics, RF distance, Nye similarity, and Clustering Info Distance are shown below (orange boxes represent the expression-only approach NJ-exp). We can observe that the accuracy of NJ-exp is clearly worse than other methods that use lineage barcode information. In particular, the RF distance is close to 1 + +<--- Page Split ---> + +(with a very small standard deviation). This confirms that gene expression data alone is not sufficient to reconstruct cell division histories. We reckon that the reasons for this are both technical and biological: technically the scRNA-seq data measurements are highly noisy, and biologically the transcriptomes of cells do not necessarily reflect the whole cell division lineages. + +![](images/Figure_1.jpg) + +
Figure R1. Performance comparison between the gene-expression-only method "NJ-exp" and other methods that use barcode information.
+ +3. Other tools such as TreeVAE that also used both CRISPR / Cas9 recorders and scRNA-seq data should also be included in the benchmark. + +We thank the reviewer for this comment. Although TreeVAE (https://www.biorxiv.org/content/10.1101/2021.05.28.446021v1.abstract) also takes the lineage barcode and gene expression data of single cells as input, which is the same as the input the LinRace, the goal and output of TreeVAE is different from LinRace and other baseline methods included in our current comparison. TreeVAE employs existing methods (e.g. Cassiopeia) to reconstruct the cell division tree and then focuses on the inference of the gene + +<--- Page Split ---> + +expression profile of ancestral cells. Cassiopeia, the tree reconstruction method used in TreeVAE, has been included in our benchmark. Although TreeVAE can not be compared with LinRace and other baseline methods included in our benchmark, we have cited TreeVAE as a method that takes both lineage barcode and gene expression data of single cells as input (Lines 83- 84 in the manuscript). + +4. The authors only examined the recorders with relatively small targets (16 and 9 targets in the synthetic data and C. elegans datasets, respectively). It is interesting to see the performance over more target sites. For example, 100 and 1,000 target sites were used in the DREAM challenge. + +We thank the reviewer for this comment. First, the reason that we used a relatively small number of targets (16 for 1024 cells, 64 for 4096 cells) to test the methods is that in real datasets, the number of targets is small. Therefore, the results on simulated data can better resemble the case on real data. For example, scGESTALT (Raj et al. 2018) has 9 target sites, the mouse embryo dataset in (Chan et al. 2019) has 18 target sites, and the data in (Quinn et al. 2021) has 10 to 30 target sites. + +That being said, we agree that it is useful to demonstrate the performances of the methods on datasets with a larger number of target sites. We performed comparisons of LinRace and baseline methods (LinRace- IST, Cassiopeia- hybrid, DCLEAR- kmer, LinTIMaT) using 128 targets and 1024 cells, and included the results in Supplementary Fig. 4. Startle was not able to complete certain runs (after 12 hours), so results for Startle in these runs were not included. On barcode data with 128 target sites, LinRace still outperforms other methods, and overall, the tree accuracy obtained with 128 target sites is slightly higher than that obtained with 16 target sites. + +We have added discussions in the manuscript to reflect the new results on barcode data with 128 target sites (Lines 212, 225- 228). + +5. Section 4.7: Cassiopeia is written in Python. + +Thanks for the correction, and we have corrected this in the manuscript (Line 678). + +## Reviewer #2 + +This article addresses an interesting question of how to infer the lineage phylogeny with higher resolution. To do so, they developed a sophisticated framework to integrate the lineage and cell state information. In particularly, they considered the cell division history, the differentiation dynamics on the cell state manifold, and the consistency between these two processes. In doing so, the reconstructed lineage tree are shown to achieve higher accuracy than existing methods. Their idea is cool, and the paper is overall well- written. I have the following comments. + +<--- Page Split ---> + +1, In order to correctly reconstruct the lineage phylogeny, it is important to consider barcode homoplasy, where two independent cells may spontaneously acquire the same mutations for lineage recording. In fact, target array editing with CARISPR- Cas9 generates outcomes (barcodes) with different frequencies, with some being highly frequent, labeling many unrelated (non- clonal) cells, and others being rare and more specific to a particular clone. The issue of barcode homoplasy becomes more severe when there is large scale dropouts of the target arrays, which is common to CARISPR- Cas9 based lineage recording. Indeed, in Supplementary Fig 1a, the largest clone ( \(\sim 1500\) cells) has large deletions and only a single detected mutation. Assuming that all the cells sharing this barcode come from the same founder cell is likely wrong, because the only mutation in this barcode may be generated independently from many cells among these 'pseudo' clone. Besides, it is also unlikely that a single founder cell could expand to \(\sim 1500\) cells, while most other clones only have a single cell. The authors should clearly discuss how to address this issue of barcode homoplasy, due to having mutations with very different frequencies. Potentially, they can use their simulations to test this situation, and see how well their method performs in this context. + +This is a great point. To analyze barcode homoplasy in the data we used in our tests and show how LinRace contributes to alleviating the homoplasy issue, we added Supplementary Fig. 8 to the manuscript. Our response to this comment includes the following points: + +1. Although we did not explicitly discuss barcode homoplasy in our original submission, the simulated data we used in the tests models the exact two factors mentioned in the reviewer's comments that lead to barcode homoplasy: (1) the biased frequency of mutations in the barcode, and (2) the dropout events. (Details described in Methods "Simulating synthetic datasets with TedSim", Lines 610-613, 618-631.) By using simulated data modeling these factors, the accuracy of tree reconstruction methods reflects the performance of these methods on real data with large pseudo clones. + +2. In other words, the results we reported in the manuscript are indeed on datasets with the popular existence of barcode homoplasy, and we showed that LinRace performs better than other methods on such datasets. Supplementary Fig. 1b shows the large pseudo-clones in our simulated data. Next, we use a different measurement, "homoplasy edge ratio", to show the high frequency of the same mutation occurring on multiple lineages during the cell division process. Since with simulation we can obtain the true cell division tree and the barcode mutation on each edge of the tree, we can calculate the "homoplasy edge ratio" in the data as follows: for each edge connecting a parent cell and a daughter cell, we call it a "homoplasy edge" if there is no unique mutation on this edge (a "unique mutation" means the same mutation at the same target site does not happen at any other edge on the tree). The homoplasy edge ratio is calculated as the number of homoplasy edges divided by the total number of edges in the tree (Supplementary Fig. 8a). + +From Supplementary Fig. 8a, we can see that the homoplasy ratio in data with dropouts + +<--- Page Split ---> + +is much larger than in data without dropouts. Also, when there are dropouts, the trend of homoplasy edge ratio changes over the mutation rate is consistent with that of the accuracy of lineage reconstruction methods shown in Fig. 2a- d. This indicates that the homoplasy ratio we calculate can correlate with barcode data quality. With the existence of dropouts, the homoplasy ratio can be as high as 0.75. + +3. The results we included in the manuscript (Fig. 2a-d, Fig. 3, Supplementary Fig. 4) confirm that LinRace has superior performance compared to baseline methods on datasets with high amounts of barcode homoplasy. Here we show examples of subtrees where LinRace helps to correct homoplasy to a certain extent, thanks to the use of gene expression data. From one of our simulated datasets used in Fig. 2, we take a pseudo-clone with 13 cells. These cells have the same barcode but originate from different clones in the true tree (Supplementary Fig. 8b). When considering only these 13 cells, we can obtain the true tree among them (Supplementary Fig. 8c). Since they have the same barcode, lineage-barcode-based methods such as NJ, DCLEAR, and Cassiopeia can only randomly guess the tree of these cells (an example of the random tree is in Supplementary Fig. 8e). The LinRace reconstructed tree of these cells is shown in Supplementary Fig. 8d. Visually, we see that the LinRace reconstructed tree is able to recover correct branches such as cell 3 and cell 4, cell 13 and cell 14. We also show that the LinRace reconstructed tree of these cells is more accurate than the true tree (Supplementary Fig. 8f) in terms of the CID metric. When using RF distance, the random trees mostly have a RF distance of 1 while the LinRace reconstructed tree has a RF distance of 0.8. We also use heatmaps to provide cell-cell distance on the tree for the true tree, LinRace inferred tree, and a random tree (Supplementary Fig. 8f) to show that the LinRace inferred tree is closer to the true tree compared to a random tree. + +Overall, barcode homoplasy presents a significant challenge for methods of reconstructing cell division trees. The use of gene expression data in LinRace helps to partially recover the relative positions of cells with the same barcode in the tree. However, since the gene expression of cells is dominated by cell types rather than lineages, there is a limit to how much gene expression data can help. Moreover, for computational efficiency, LinRace runs tree refinement on local subtrees. To fully recover the positions of cells in the global tree, optimization on the global tree structure is needed, but methods that perform whole-tree structure optimization did not prove successful (e.g. LinTlMaT and Startle) due to the vast search space of the whole tree. + +In the manuscript, we have added this discussion in Lines 278- 313. We added the details of calculating the homoplasy edge ratio to the Methods section (Lines 745- 754). + +2, In order to simulate the cell division history and the differentiation dynamics together, the authors assume that the sampled leaf nodes can form a state manifold, and the ancestor cell states (from the internal nodes in the reconstructed lineage tree) can be found from the sampled cell states. In systems with asynchronous differentiation, like in blood, such an assumption could indeed hold. But for developmental systems with more synchronous differentiation, all cell states change rapidly over time, and the early ancestor cell states are no + +<--- Page Split ---> + +longer there at the later stage of development. This is an unstated limitation of this study. The authors should address this limitation. At least, they should explicitly state this limitation. In doing so, they may also need to temper their claim that they can infer the ancestor state, by adding the restrictive conditions. + +This is a great point. Indeed, for developmental systems where all cell states change rapidly over time, the early ancestor cell states are unlikely to exist in the scRNA- seq data, therefore, these states can not be observed in the data, nor can they be reconstructed by trajectory inference methods. + +If the scRNA- seq dataset does not cover such cell states, then LinRace can not incorporate these cell states, as LinRace uses the cell state tree inferred from data. However, if a prior cell state tree that includes these cell states is given, LinRace can assign cell states for ancestral cells as the cell states missing from scRNA- seq data. + +We have added a discussion about the limitation of utilizing the LinRace method for different systems of biology (main manuscript Line 471- 480). Also, we acknowledge the restrictive conditions when stating that LinRace infers cell states for ancestral cells (Lines 145, 380- 381). + +3, There are two articles worth referencing in this paper. + +3.1 Li et.al., bioRxiv 2023, titled "A mouse model with high clonal barcode diversity for joint lineage, transcriptomic, and epigenomic profiling in single cells". They explicitly addressed the issue of low barcode diversity due to large inter-site deletions in CARISRP-Cas9 editing by adding TdT to increase mutation diversity. This could help to reduce the issue of barcode homoplasy in future applications. + +3.2 Wang et.al., Nat. Biotech. 2023, titled "CoSpar identifies early cell fate biases from single-cell transcriptomic and lineage information". They similarly integrated lineage and state information. Instead of learning the lineage tree, they inferred the cell fate choice. In their study, they explicitly addressed how to cope with barcode homoplasy in their algorithm. + +We thank the reviewer for suggesting these relevant papers. We have cited these two papers in our revised manuscript (Lines 34, 482 for Li et al., and Line 83- 84 for Wang et al.). + +We did not discuss Wang et al. specifically in terms of their ability to cope with barcode homoplasy, as the method CoSpar does not aim to output the cell division tree, thus barcode homoplasy affects their task differently from how barcode homoplasy affects cell division tree reconstruction methods. Although in their results they showed the robustness of their method to homoplasy, their method did not appear to directly target the homoplasy issue. + +Minor issues for Main text + +Line 52, "Is it shown ..." \(\rightarrow\) "It is shown." This has been fixed (now Line 55). + +<--- Page Split ---> + +Line 113- 116, the description of the clone size is very confusing here. + +We thank the reviewer for pointing this out. This description aims to emphasize that there are a large number of cells that share the same barcode. Therefore, the barcode information alone can not distinguish these cells in the cell division tree. We rewrote this part (Lines 126- 132) and also added new figures to help demonstrate the large clone size in real data (Supplementary Figure 1a). + +Line 369- 374, how do you support your conjecture here about differentiation speed? I do not see any data. + +We thank the reviewer for raising this question. This paragraph on differentiation speed was intended to be an extended discussion in addition to all other results shown in the manuscript. It is related to the Reviewer's Comment 2, that certain biological systems go through asynchronous differentiation, and cells at different states exist in the scRNA- seq data. In the manuscript, we conjectured that cells at a later stage of development originate from lineages with fast differentiation speed. We realized that it is more appropriate to rephrase the conjecture as "cells at a later stage of development originate from lineages with more cell state transitions", as "differentiation speed" can be cell- specific and requires additional data to reach a conclusion, and the Reviewer is right that we did not show any data on differentiation speed. + +In the revised manuscript, we removed this paragraph of extended discussion, as it is not part of our major results and is not rigorously supported with results. + +Line 457, does "bifurcating tree" means that it will learn a topology of just two branches? Please clarify + +Yes. To make this more clear, we have (1) changed all "bifurcating tree" into "binary tree" as the latter may be familiar to a larger audience; (2) added an explanation of this term "(which means every non- leaf node has exactly two children nodes)" when it first appears in the "Methods" section (Line 540). Also, we have the same explanation of this term in Section 2.1 (Line 150). + +Line 482 (Eq. 3), I believe the equation has typos. Also, I(.) function is not defined. Please clarify what this function is, and why it takes this form. + +We thank the reviewer for pointing this out. We have corrected Eq. 3 and also added other equations and descriptions to improve the clarity of this part of the calculation (Lines 551- 585). The I(x) function is the characteristic function that returns 0 if x is TRUE; 0 otherwise. The main idea of the calculation of state transition likelihood is as follows: intuitively, the likelihood of transition from State \(S_{i}\) to State \(S_{j}\) is high if the distance from \(S_{i}\) to \(S_{j}\) on the cell state tree is small, and low if the distance from \(S_{i}\) to \(S_{j}\) on the cell state trees large. Since our procedure of ancestral state inference (described in Lines 527- 537) implicitly ensures that in the candidate cell division tree, the edges with state transition between states with shorter distances in the cell state tree are more frequent than edges with state transition between states with shorter + +<--- Page Split ---> + +distance in the cell state tree, we use the frequency of edges in the candidate cell division tree with the same state distance as that from \(S_{i}\) to \(S_{j}\) as the likelihood of state transition from \(S_{i}\) to \(S_{j}\) . + +Line 495, what is \(x_{- }i?\) Gene expression vector of a single cell? + +Yes, \(x_{i}\) is the gene expression vector of cell \(i\) . We clarified the notations in the manuscript (Lines 557- 558). + +Line 561- 569, I did not follow this part. Could you make it more clear? + +We realized that this part of the description of the Nye similarity lacks clarity. We have rewritten the derivations of Nye similarity and added context and description on notations to improve the readability (Lines 581- 582). + +Line 625, the definition of the I() function should go earlier when it first appears. + +This is a great point. We have added the definition of the characteristic function when it first appears (Line 565). + +Minor issues for Supplementary file + +Supplementary Fig 2, clarify the figure legend: LinRace_0.1_1. + +We now have updated the Figure Description under Supplementary Fig 2 to clarify this point: the first number in the legend is the weight for asymmetric division likelihood, and the second number is the weight for neighbor distance likelihood. + +Could you provide a figure with varying cell number, and compare the performance of different methods at the same mutation rate, similar to Supplementary Figure 5? + +This is a good point. We now have included a figure benchmarking performances of selected methods with varying numbers of cells in Supplementary Figure 6. We use the mutation rate = 0.1. As expected, the performance of all methods decreases with the increase in the number of cells, while LinRace outperforms all other methods. In the manuscript, we added discussions on this additional result in Lines 236- 239. + +## Reviewer #3 + +In "LinRace: cell division history reconstruction of single cells using paired lineage barcode and gene expression data", the authors describe a new method to build cell lineage trees using CRISPR- Cas9 induced lineage barcode data supplemented with the simultaneously collected single cell RNA- seq data. The authors accurately describe the challenge in such data sets, + +<--- Page Split ---> + +specifically that the lineage barcodes alone often do not encode sufficient information to reconstruct the full lineage tree. To overcome this limitation, the authors leverage gene expression information to resolve the edges of the tree. + +I believe this manuscript is well written and clearly presented. The new strategy LinRace serves a useful role in the field providing a route to include gene expression data with lineage barcode data only when lineage data is limited. In this way, the lineage data itself is prioritized in determining the cell lineage tree when it is available, which seems reasonable. The authors make the appropriate comparisons of their method to field standards (DCLEAR, Cassiopeia, and in some ways, the most directly comparable LinTIMat) using de novo simulated data sets and simulated data based on the known C. elegans lineage. Overall, their strategy performs the best using appropriate criteria. Moreover, the authors offer good insights into why methods generally perform better or worse over different mutation rates and why they believe their method outperforms LinTIMat. The data and methodology are sound. + +Next, the authors apply their method to two real data sets where ground truth is not known, the zebrafish brain from scGESTALT and mouse embryos from the molecular recorder. In the former, they showcase an example where their strategy resolves lineages that undergo symmetric vs asymmetric cell division while in the latter, they describe the phenomenon of "partial consistency between transcriptome similarity and barcode similarity". In both cases, the biological findings are limited but I do not believe it detracts from this manuscript. Rather, it highlights how LinRace is useful in creating more detailed subtrees that may aid in future biological interpretation. For example, better tree topologies may lead to more accurate estimates of symmetric and asymmetric cell division likelihoods – a parameter that would affect the LinRace method itself. + +Overall, I think this manuscript presents a reasonable method for utilizing gene expression data to complement lineage tracing data in a manner that is very useful for the field. I believe the description of methods and analysis performed in the manuscript is sufficient for replication. + +## Suggestions: + +- Section 2.5 presents the lack of DE for the same cell state that exist in different lineages. Overall, this is not a surprising result and is in line with biological expectations. Nonetheless, their ability to detect DEs may simply be underpowered. I wonder if the intra-lineage gene expression distance for cells of the same state is lower than the inter-lineage distance across cells of the same state across the population of cells. I realize this suggestion can be a bit circular depending on the depth of tree examined since "neighbor distance likelihood" is used to establish the lineage. It might be interesting to look at regardless. + +This is a great suggestion to complement the DE results. As suggested, we focused on cells in the Fore/MidBrain cell type, and compared intra- clone gene expression distances with inter- lineage distances. To do this, we took 3 clones from the Fore/MidBrain cell cells (clones 9, + +<--- Page Split ---> + +10, and 12 in Fig. 5d), and calculated for the following pairs of inter- clone or intra- clone distances: Clone 9 vs Clone 9 ("9_9" in the figure), Clone 9 vs Clone 10 (9_10), Clone 9 vs Clone 12 (9_12), Clone 10 vs Clone 10 (10_10), Clone 10 vs Clone 12 (10_12), Clone 12 vs Clone 12 (12_12). Each pair of comparisons corresponds to a box in the boxplot, which is included in the manuscript as Fig. 5e. + +First, we performed PCA on the gene expression data and kept the top 50 PCs for dimensionality reduction. Then to compare Clone \(i\) with Clone \(j\) , we calculated all pairwise Euclidean distances between any cell in Clone \(i\) and any cell in Clone \(j\) , and used these distances to generate the corresponding boxplot. + +As shown in Figure 5e, there are no observable differences between the intra- clone distances and the inter- clone distances. The use of the "neighbor distance likelihood" mentioned in the reviewer's comment can only contribute to the differences between intra- clone distances and the inter- clone distances. The fact that no clear differences are observed indicates that other factors, like the barcode similarity and state transition likelihood, are more dominant factors than the "neighbor distance likelihood" in forming the reconstructed tree. This additional result on gene expression distances is in line with the hypothesis in our manuscript and other publications (Packer et al. 2019) that cells' gene expression signatures are dominated by the cell types instead of lineages. + +We have added corresponding discussions on this result in the manuscript (Lines 440- 443). + +- I am curious if the authors can comment on how these following suggestions might change/improve performance (which could perhaps be added to discussion): o Alternate tree building method to make the tree backbone – perhaps DCLEAR or Cassiopeia. o Using time course scRNA-seq data instead of the scRNA-seq data collected with the lineage barcodes. Trajectories may be more accurately inferred when past cell states are more directly measured than relying on variability that exists within a time point. To calculate the GES, they use 3 terms, the first two of which utilizes only cell state information. They could use the cell state tree from scRNA-seq time course data sets, and still maintain the third term from the lineage traced data set. + +We thank the reviewer for these suggestions. Please see the following responses to the two suggestions separately: + +1. To find out how the methods used to build the backbone tree affect the final performance of LinRace, we conducted tests to use DCLEAR (using mode DCLEAR-kmer) and Cassiopeia (using mode Cassiopeia-greedy) to build the backbone tree (Fig. 2e, Supplementary Fig. 5). The results show that LinRace can improve upon the backbone tree inferred by DCLEAR-kmer and Cassiopeia-greedy. While using different backbone methods among these three choices (DCLEAR-kmer, Cassiopeia-greedy, and NJ) yields comparable results, the default combination we use (NJ and LinRace) + +<--- Page Split ---> + +performs slightly better than other choices. We have added discussions on these results in the manuscript (Lines 230- 236). + +2. We agree that time-course scRNA-seq data helps to reveal past cell states that may not be captured in one scRNA-seq sample at one time point. Furthermore, we have added discussions in the manuscript to acknowledge such scenarios and the limitations of applying LinRace to datasets where the scRNA-seq data does not capture all or most of the cell states in the developmental process (Lines 471-475, 145, 380-381). + +Time course scRNA-seq data will allow us to obtain a more complete set of cell states, with partial information on the temporal order of these cell states, which allows for the reconstruction of a more precise and comprehensive cell state tree. In this case, as suggested by the reviewer, only the cell state tree needs to be replaced by the one learned from the time course data, and other parts of LinRace can remain the same. We have added this discussion in the manuscript (Lines 477-479). + +Minor points: + +Fig 1. It may be worthwhile to change the colors for cell states so that it is easier to distinguish between the black and navy, and red and pink + +Thanks for this comment. For Fig. 1, we used colors from the default rainbow color palette from base R. We have tried different options and the seven colors we used from the rainbow palette are the most distinguishable (See Figure R2). The candidate color options are as follows, and the leftmost one is the panel we use in Fig. 1. + +We did modify Fig. 1 to make it easier to distinguish the colors, which is that we changed the border colors of the squares (and circles) to be the same as their respective fill colors. After removing the black border colors, we think it is now easier to distinguish black from navy, and red from pink. + +![PLACEHOLDER_16_0] + +
Figure R2. Colour palettes visualization for cell types and lineage barcode mutation annotations in Fig. 1
+ +Line 176- 8: I would recommend adding a half a sentence or a sentence about how to choose a root cell state outside of simulation environments. + +We have added one sentence on the common practice of trajectory inference on real data (Lines 195- 196). In the case of Slingshot, a root cell state needs to be provided to the algorithm based on domain knowledge. + +<--- Page Split ---> + +Line 309: GESTAULT should be GESTALT (and also Fig 4 legend, line 591) + +Thanks for the correction. We have modified the text in our manuscript accordingly (now Lines 386, 678, Fig. 4 description). + +Fig 4a: Inner ring is barely visible + +Since the inner ring provides similar information as the color of the outer ring, and the only difference is that the inner ring shows sub- cell types, we have removed the inner ring for clearer visualization in both Fig 4a and Supplementary Fig. 12, and updated the figure descriptions. + +Line 334: This may be a lack of understanding on my part, but to my knowledge, terminal cells do not undergo mitosis. Is there a different word that can be used here to express cells that can only undergo symmetric divisions? + +We thank the reviewer for pointing this out. We have changed the use of "terminal cell type" to the specific cell type we observed in the figures (the Forebrain or Midbrain cell type) to avoid making general statements that are not well- supported (Lines 405, 411,412 in the manuscript). + +## References + +Chan, Michelle M., Zachary D. Smith, Stefanie Grosswendt, Helene Kretzmer, Thomas M. Norman, Britt Adamson, Marco Jost, Jeffrey J. Quinn, Dian Yang, Matthew G. Jones, Alex Khodaverdian, Nir Yosef, Alexander Meissner, and Jonathan S. Weissman. 2019. "Molecular Recording of Mammalian Embryogenesis." Nature, May. doi:10.1038/s41586- 019- 1184- 5. Packer, Jonathan S., Qin Zhu, Chau Huynh, Priya Sivaramakrishnan, Elicia Preston, Hannah Dueck, Derek Stefanik, Kai Tan, Cole Trapnell, Junhyong Kim, Robert H. Waterston, and John I. Murray. 2019. "A Lineage- Resolved Molecular Atlas of C. Elegans Embryogenesis at Single- Cell Resolution." Science 365 (6459). science.sciencemag.org. doi:10.1126/science.aax1971. Quinn, Jeffrey J., Matthew G. Jones, Ross A. Okimoto, Shigeki Nanjo, Michelle M. Chan, Nir Yosef, Trever G. Bivona, and Jonathan S. Weissman. 2021. "Single- Cell Lineages Reveal the Rates, Routes, and Drivers of Metastasis in Cancer Xenografts." Science 371 (6532). doi:10.1126/science.abc1944. Raj, Bushra, Daniel E. Wagner, Aaron McKenna, Shristi Pandey, Allon M. Klein, Jay Shendure, James A. Gagnon, and Alexander F. Schier. 2018. "Simultaneous Single- Cell Profiling of Lineages and Cell Types in the Vertebrate Brain." Nature Biotechnology 36 (5): 442–50. doi:10.1038/nbt.4103. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The authors have thoroughly responded to all my concerns, incorporating additional tools and datasets in their benchmark. I believe the manuscript is now ready for publication. + +## Reviewer #2 (Remarks to the Author): + +The authors have addressed my concerns! + +## Reviewer #3 (Remarks to the Author): + +The authors have addressed my concerns and have updated their manuscript accordingly. I am satisfied with their revision. + +<--- Page Split ---> diff --git a/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..47a49474f976d96569b32ef1199b6923266b5f94 --- /dev/null +++ b/peer_reviews/55e986dcf5188c4d42b5c8daed790c3b21f4852a3cd7599f2b550e28cfce8b70/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,495 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[71, 154, 855, 211]]<|/det|> +LinRace: cell division history reconstruction of single cells using paired lineage barcode and gene expression data + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 98, 306, 115]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 164, 399, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 200, 876, 381]]<|/det|> +Pan et al. presented as a new computational tool (LinRace) to reconstruct the developmental lineages based upon paired single cell RNA- seq and CRISPR / Cas9 based lineage recorders. LinRace first reconstructed a lineage tree from the unique barcodes (CRISPR / Cas9 scares) from the recorders, and used the scRNA- seq data from of cells with the identical barcode to derive the subtrees. They have evaluated the LinRace on synthetic data simulated by TedSim (also from the same group), and two real datasets on C. elegans development and the scGESTAULT dataset. LinRace demonstrated better performance than state- of- the- art methods such as Cassiopeia and DCLEAR that reconstruct lineages solely from the CRISPR / Cas9 based lineage recorders, as well as LinTIMat that took both scRNA- seq and lineage recorders as the inputs. Overall, the manuscript is well written, and the analysis / benchmark is comprehensive. Here are a few issues the authors would consider to address: + +<|ref|>text<|/ref|><|det|>[[113, 400, 880, 620]]<|/det|> +1. The authors need to include more recently tools such as Startle (https://www.biorxiv.org/content/10.1101/2022.12.18.520935v1.abstract) into the benchmark. +2. Performance of tree reconstructions from Slingshot along should also be included. It is curious to see if the lineage tree reconstructed from scRNA-seq (by Slingshot) has comparable performance with Cassiopeia or DCLEAR. For example, a corresponding tree can be constructed from the cell-cell distance matrix using the latent representation. +3. Other tools that such as TreeVAE that also used both CRISPR / Cas9 recorders and scRNA-seq data also should be be included in the benchmark. +4. The authors only examined the recorders with relatively small targets (16 and 9 targets in the synthetic data and C. elegans datasets, respectively). It is interesting to see the performance over more target sites. For example, 100 and 1,000 target sites were used in the DREAM challenge. +5. Section 4.7: Cassiopeia is written in Python. + +<|ref|>sub_title<|/ref|><|det|>[[115, 687, 399, 703]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 722, 875, 831]]<|/det|> +This articles addresses an interesting question of how to infer the lineage phylogeny with higher resolution. To do so, they developed a sophisticated framework to integrate the lineage and cell state information. In particularly, they considered the cell division history, the differentiation dynamics on the cell state manifold, and the consistency between these two processes. In doing so, the reconstructed lineage tree are shown to achieve higher accuracy than existing methods. Their idea is cool, and the paper is overall well- written. I have the following comments. + +<|ref|>text<|/ref|><|det|>[[115, 850, 878, 904]]<|/det|> +1, In order to correctly reconstruct the lineage phylogeny, it is important to consider barcode homoplasy, where two independent cells may spontaneously acquire the same mutations for lineage recording. In fact, target array editing with CARISPR- Cas9 generates outcomes (barcodes) with different frequencies, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 95, 877, 298]]<|/det|> +with some being highly frequent, labeling many unrelated (non- clonal) cells, and others being rare and more specific to a particular clone. The issue of barcode homoplasy becomes more severe when there is large scale dropouts of the target arrays, which is common to CARISPR- Cas9 based lineage recording. Indeed, in Supplementary Fig 1a, the largest clone (\~1500 cells) has large deletions and only a single detected mutation. Assuming that all the cells sharing this barcode come from the same founder cell is likely wrong, because the only mutation in this barcode may be generated independently from many cells among these 'pseudo' clone. Besides, it is also unlikely that a single founder cell could expand to \~1500 cells, while most other clones only have a single cell. The authors should clearly discuss how to address this issue of barcode homoplasy, due to having mutations with very different frequencies. Potentially, they can use their simulations to test this situation, and see how well their method performs in this context. + +<|ref|>text<|/ref|><|det|>[[114, 316, 866, 480]]<|/det|> +2, In order to simulate the cell division history and the differentiation dynamics together, the authors assume that the sampled leaf nodes can form a state manifold, and the ancestor cell states (from the internal nodes in the reconstructed lineage tree) can be found from the sampled cell states. In systems with asynchronous differentiation, like in blood, such an assumption could indeed hold. But for developmental systems with more synchronous differentiation, all cell states change rapidly over time, and the early ancestor cell states are no longer there at the later stage of development. This is an unstated limitation of this study. The authors should address this limitation. At least, they should explicitly state this limitation. In doing so, they may also need to temper their claim that they can infer the ancestor state, by adding the restrictive conditions. + +<|ref|>text<|/ref|><|det|>[[115, 499, 527, 516]]<|/det|> +3, There are two articles worth referencing in this paper. + +<|ref|>text<|/ref|><|det|>[[114, 517, 877, 662]]<|/det|> +3. There are two articles worth referencing in this paper.3. 1 Li et.al., bioRxiv 2023, titled "A mouse model with high clonal barcode diversity for joint lineage, transcriptomic, and epigenomic profiling in single cells". They explicitly addressed the issue of low barcode diversity due to large inter-site deletions in CARISPR-Cas9 editing by adding TdT to increase mutation diversity. This could help to reduce the issue of barcode homoplasy in future applications.3.2 Wang et.al., Nat. Biotech. 2023, titled "CoSpar identifies early cell fate biases from single-cell transcriptomic and lineage information". They similarly integrated lineage and state information. Instead of learning the lineage tree, they inferred the cell fate choice. In their study, they explicitly addressed how to cope with barcode homoplasy in their algorithm. + +<|ref|>text<|/ref|><|det|>[[116, 700, 310, 716]]<|/det|> +Minor issues for Main text + +<|ref|>text<|/ref|><|det|>[[116, 736, 425, 753]]<|/det|> +Line 52, "Is it shown ..." \(\rightarrow\) "It is shown." + +<|ref|>text<|/ref|><|det|>[[115, 773, 618, 790]]<|/det|> +Line 113- 116, the description of the clone size is very confusing here. + +<|ref|>text<|/ref|><|det|>[[115, 810, 857, 845]]<|/det|> +Line 369- 374, how do you support your conjecture here about differentiation speed? I do not see any data. + +<|ref|>text<|/ref|><|det|>[[112, 882, 867, 900]]<|/det|> +Line 457, does "bifurcating tree" means that it will learn a topology of just two branches? Please clarify + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 97, 855, 133]]<|/det|> +Line 482 (Eq. 3), I believe the equation has typos. Also, I(.) function is not defined. Please clarify what this function is, and why it takes this form. + +<|ref|>text<|/ref|><|det|>[[114, 152, 562, 169]]<|/det|> +Line 495, what is \(x_{- }\) ? Gene expression vector of a single cell? + +<|ref|>text<|/ref|><|det|>[[114, 188, 626, 205]]<|/det|> +Line 561- 569, I did not follow this part. Could you make it more clear? + +<|ref|>text<|/ref|><|det|>[[114, 225, 702, 242]]<|/det|> +Line 625, the definition of the I() function should go earlier when it first appears. + +<|ref|>text<|/ref|><|det|>[[115, 280, 377, 297]]<|/det|> +Minor issues for Supplementary file + +<|ref|>text<|/ref|><|det|>[[114, 317, 566, 334]]<|/det|> +Supplementary Fig 2, clarify the figure legend: LinRace_0.1_1. + +<|ref|>text<|/ref|><|det|>[[114, 353, 877, 389]]<|/det|> +Could you provide a figure with varying cell number, and compare the performance of different methods at the same mutation rate, similar to Supplementary Figure 5? + +<|ref|>sub_title<|/ref|><|det|>[[115, 455, 399, 472]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 490, 874, 600]]<|/det|> +In "LinRace: cell division history reconstruction of single cells using paired lineage barcode and gene expression data", the authors describe a new method to build cell lineage trees using CRISPR- Cas9 induced lineage barcode data supplemented with the simultaneously collected single cell RNA- seq data. The authors accurately describe the challenge in such data sets, specifically that the lineage barcodes alone often do not encode sufficient information to reconstruct the full lineage tree. To overcome this limitation, the authors leverage gene expression information to resolve the edges of the tree. + +<|ref|>text<|/ref|><|det|>[[114, 618, 881, 783]]<|/det|> +I believe this manuscript is well written and clearly presented. The new strategy LinRace serves a useful role in the field providing a route to include gene expression data with lineage barcode data only when lineage data is limited. In this way, the lineage data itself is prioritized in determining the cell lineage tree when it is available, which seems reasonable. The authors make the appropriate comparisons of their method to field standards (DCLEAR, Cassiopeia, and in some ways, the most directly comparable LinTIMat) using de novo simulated data sets and simulated data based on the known C. elegans lineage. Overall, their strategy performs the best using appropriate criteria. Moreover, the authors offer good insights into why methods generally perform better or worse over different mutation rates and why they believe their method outperforms LinTIMat. The data and methodology are sound. + +<|ref|>text<|/ref|><|det|>[[114, 802, 880, 893]]<|/det|> +Next, the authors apply their method to two real data sets where ground truth is not known, the zebrafish brain from scGESTALT and mouse embryos from the molecular recorder. In the former, they showcase an example where their strategy resolves lineages that undergo symmetric vs asymmetric cell division while in the latter, they describe the phenomenon of "partial consistency between transcriptome similarity and barcode similarity". In both cases, the biological findings are limited but I do + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 97, 867, 169]]<|/det|> +not believe it detracts from this manuscript. Rather, it highlights how LinRace is useful in creating more detailed subtrees that may aid in future biological interpretation. For example, better tree topologies may lead to more accurate estimates of symmetric and asymmetric cell division likelihoods – a parameter that would affect the LinRace method itself. + +<|ref|>text<|/ref|><|det|>[[115, 189, 876, 243]]<|/det|> +Overall, I think this manuscript presents a reasonable method for utilizing gene expression data to complement lineage tracing data in a manner that is very useful for the field. I believe the description of methods and analysis performed in the manuscript is sufficient for replication. + +<|ref|>sub_title<|/ref|><|det|>[[115, 263, 208, 279]]<|/det|> +## Suggestions: + +<|ref|>text<|/ref|><|det|>[[114, 298, 882, 425]]<|/det|> +- Section 2.5 presents the lack of DE for the same cell state that exist in different lineages. Overall, this is not a surprising result and is in line with biological expectations. Nonetheless, their ability to detect DEs may simply be underpowered. I wonder if the intra-lineage gene expression distance for cells of the same state is lower than the inter-lineage distance across cells of the same state across the population of cells. I realize this suggestion can be a bit circular depending on the depth of tree examined since "neighbor distance likelihood" is used to establish the lineage. It might be interesting to look at regardless. + +<|ref|>text<|/ref|><|det|>[[114, 444, 864, 480]]<|/det|> +- I am curious if the authors can comment on how these following suggestions might change/improve performance (which could perhaps be added to discussion): + +<|ref|>text<|/ref|><|det|>[[114, 481, 870, 590]]<|/det|> +- I am curious if the authors can comment on how these following suggestions might change/improve performance (which could perhaps be added to discussion):o Alternate tree building method to make the tree backbone – perhaps DCLEAR or Cassiopeia.o Using time course scRNA-seq data instead of the scRNA-seq data collected with the lineage barcodes. Trajectories may be more accurately inferred when past cell states are more directly measured than relying on variability that exists within a time point. To calculate the GES, they use 3 terms, the first two of which utilizes only cell state information. They could use the cell state tree from scRNA-seq time course data sets, and still maintain the third term from the lineage traced data set. + +<|ref|>text<|/ref|><|det|>[[115, 610, 215, 625]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 646, 870, 681]]<|/det|> +Fig 1. It may be worthwhile to change the colors for cell states so that it is easier to distinguish between the black and navy, and red and pink + +<|ref|>text<|/ref|><|det|>[[115, 701, 869, 736]]<|/det|> +Line 176- 8: I would recommend adding a half a sentence or a sentence about how to choose a root cell state outside of simulation environments. + +<|ref|>text<|/ref|><|det|>[[115, 756, 634, 773]]<|/det|> +Line 309: GESTAULT should be GESTALT (and also Fig 4 legend, line 591) + +<|ref|>text<|/ref|><|det|>[[115, 793, 354, 809]]<|/det|> +Fig 4a: Inner ring is barely visible + +<|ref|>text<|/ref|><|det|>[[115, 829, 861, 882]]<|/det|> +Line 334: This may be a lack of understanding on my part, but to my knowledge, terminal cells do not undergo mitosis. Is there a different word that can be used here to express cells that can only undergo symmetric divisions? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[295, 90, 700, 112]]<|/det|> +## Responses to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[115, 131, 850, 150]]<|/det|> +We thank the reviewers for their time to review our manuscript and their valuable comments. + +<|ref|>text<|/ref|><|det|>[[115, 168, 880, 206]]<|/det|> +Please find below the reviewers' comments (in black) and our pointwise responses (in blue). The changes in the manuscript are marked in red. + +<|ref|>sub_title<|/ref|><|det|>[[116, 249, 256, 272]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[114, 282, 883, 492]]<|/det|> +Pan et al. presented as a new computational tool (LinRace) to reconstruct the developmental lineages based upon paired single cell RNA- seq and CRISPR / Cas9 based lineage recorders. LinRace first reconstructed a lineage tree from the unique barcodes (CRISPR / Cas9 scares) from the recorders, and used the scRNA- seq data from of cells with the identical barcode to derive the subtrees. They have evaluated the LinRace on synthetic data simulated by TedSim (also from the same group), and two real datasets on C.elegans development and the scGESTAULT dataset. LinRace demonstrated better performance than state- of- the- art methods such as Cassiopeia and DCLEAR that reconstruct lineages solely from the CRISPR / Cas9 based lineage recorders, as well as LinTIMat that took both scRNA- seq and lineage recorders as the inputs. Overall, the manuscript is well- written, and the analysis/benchmark is comprehensive. Here are a few issues the authors would consider to address: + +<|ref|>text<|/ref|><|det|>[[115, 510, 883, 549]]<|/det|> +1. The authors need to include more recently tools such as Startle (https://www.biorxiv.org/content/10.1101/2022.12.18.520935v1.abstract) into the benchmark. + +<|ref|>text<|/ref|><|det|>[[115, 567, 882, 626]]<|/det|> +We thank the reviewer for suggesting that we include the recent method, Startle, in our comparison. Startle infers cell division trees from lineage barcode data by enforcing the "non-modifiability" property of CRISPR-Cas9 mutations. + +<|ref|>text<|/ref|><|det|>[[114, 639, 883, 753]]<|/det|> +Startle provides two modes, Startle- ILP and Startle- NNI. We encountered a running time issue with Startle- ILP (their preferred mode) on the scale of datasets we used: the solver could not find a valid solution with the default parameters. Based on communication with the authors of Startle, we used the Startle- NNI mode, which is much faster than Startle- ILP, although still slower than the other methods. As a result, we tested Startle- NNI on all simulated datasets except for those with 4096 cells. + +<|ref|>text<|/ref|><|det|>[[115, 766, 882, 843]]<|/det|> +We included the results of Startle- NNI in the comparisons of LinRace and baseline methods, using accuracy measurements RF distance, Nye similarity, and CID, in Figs. 2- 3, and Supplementary Fig. 10 in the manuscript. The results show that LinRace outperforms Startle- NNI consistently. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 145]]<|/det|> +In the manuscript, we have also added modifications and corresponding discussions to reflect that we included Startle as an additional baseline method. These changes are in Lines 68- 69, 160, 221- 225, 332, 364- 366, 711- 717, 765. + +<|ref|>text<|/ref|><|det|>[[115, 158, 882, 234]]<|/det|> +2. Performance of tree reconstructions from Slingshot along should also be included. It is curious to see if the lineage tree reconstructed from scRNA-seq (by Slingshot) has comparable performance with Cassiopedia or DCLEAR. For example, a corresponding tree can be constructed from the cell-cell distance matrix using the latent representation. + +<|ref|>text<|/ref|><|det|>[[115, 255, 882, 291]]<|/det|> +We thank the reviewer for providing two suggestions on using only gene expression data to reconstruct the cell lineage tree. + +<|ref|>text<|/ref|><|det|>[[144, 305, 882, 400]]<|/det|> +(1) Although Slingshot is widely used for the task "trajectory inference" which is to infer trajectory between cell states (and thus is used in LinRace to infer the cell state tree), it is not suited to infer cell division trees, which is the final goal of LinRace. We clarified the relationships between the cell state tree used in LinRace and the cell division tree in the manuscript (e.g. Lines 96-100). + +<|ref|>text<|/ref|><|det|>[[173, 420, 882, 514]]<|/det|> +We understand that this can be confusing as the term "lineage tree" is sometimes used to refer to the trajectory between cell states, while in the context of cell division events, a lineage means the tree representing the cell division history. To avoid this confusion, we clarified the definition of "cell lineage tree" and trajectory inference in the paper (Lines 39- 42, 117- 121). + +<|ref|>text<|/ref|><|det|>[[173, 535, 882, 667]]<|/det|> +The main reason that Slingshot can not be used to infer a cell division tree is the following: A common application of Slingshot is that given \(k\) clusters of cells, Slingshot infers a tree with \(k\) nodes. Similarly, if one cell is treated as a cluster, given the input of \(n\) cells, Slingshot infers a tree with \(n\) nodes, where some are internal nodes and some are leaf nodes of the tree. When inferring a cell division tree, all \(n\) cells need to be leaf nodes. In other words, Slingshot estimates pseudotime while the task of inferring cell division trees considers the time from the root to leaves as real- time. + +<|ref|>text<|/ref|><|det|>[[145, 689, 882, 802]]<|/det|> +(2) Based on the suggestion of using the cell-cell distance matrix obtained from cell latent representations to reconstruct the cell division tree, we implemented and tested this approach (called NJ-exp) on the TedSim simulated datasets (1024 cells and 16 target sites). Specifically, we first performed PCA on the scRNA-seq count matrix, then used the first 50 PCs to calculate pairwise Euclidean distance between single cells, and reconstructed a NJ tree from the pairwise distance matrix. + +<|ref|>text<|/ref|><|det|>[[174, 823, 882, 898]]<|/det|> +The results in terms of all three metrics, RF distance, Nye similarity, and Clustering Info Distance are shown below (orange boxes represent the expression-only approach NJ-exp). We can observe that the accuracy of NJ-exp is clearly worse than other methods that use lineage barcode information. In particular, the RF distance is close to 1 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 88, 884, 184]]<|/det|> +(with a very small standard deviation). This confirms that gene expression data alone is not sufficient to reconstruct cell division histories. We reckon that the reasons for this are both technical and biological: technically the scRNA-seq data measurements are highly noisy, and biologically the transcriptomes of cells do not necessarily reflect the whole cell division lineages. + +<|ref|>image<|/ref|><|det|>[[141, 207, 856, 650]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[140, 656, 857, 690]]<|/det|> +
Figure R1. Performance comparison between the gene-expression-only method "NJ-exp" and other methods that use barcode information.
+ +<|ref|>text<|/ref|><|det|>[[115, 729, 853, 767]]<|/det|> +3. Other tools such as TreeVAE that also used both CRISPR / Cas9 recorders and scRNA-seq data should also be included in the benchmark. + +<|ref|>text<|/ref|><|det|>[[115, 787, 864, 901]]<|/det|> +We thank the reviewer for this comment. Although TreeVAE (https://www.biorxiv.org/content/10.1101/2021.05.28.446021v1.abstract) also takes the lineage barcode and gene expression data of single cells as input, which is the same as the input the LinRace, the goal and output of TreeVAE is different from LinRace and other baseline methods included in our current comparison. TreeVAE employs existing methods (e.g. Cassiopeia) to reconstruct the cell division tree and then focuses on the inference of the gene + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 881, 185]]<|/det|> +expression profile of ancestral cells. Cassiopeia, the tree reconstruction method used in TreeVAE, has been included in our benchmark. Although TreeVAE can not be compared with LinRace and other baseline methods included in our benchmark, we have cited TreeVAE as a method that takes both lineage barcode and gene expression data of single cells as input (Lines 83- 84 in the manuscript). + +<|ref|>text<|/ref|><|det|>[[114, 203, 882, 280]]<|/det|> +4. The authors only examined the recorders with relatively small targets (16 and 9 targets in the synthetic data and C. elegans datasets, respectively). It is interesting to see the performance over more target sites. For example, 100 and 1,000 target sites were used in the DREAM challenge. + +<|ref|>text<|/ref|><|det|>[[114, 299, 883, 414]]<|/det|> +We thank the reviewer for this comment. First, the reason that we used a relatively small number of targets (16 for 1024 cells, 64 for 4096 cells) to test the methods is that in real datasets, the number of targets is small. Therefore, the results on simulated data can better resemble the case on real data. For example, scGESTALT (Raj et al. 2018) has 9 target sites, the mouse embryo dataset in (Chan et al. 2019) has 18 target sites, and the data in (Quinn et al. 2021) has 10 to 30 target sites. + +<|ref|>text<|/ref|><|det|>[[114, 426, 883, 561]]<|/det|> +That being said, we agree that it is useful to demonstrate the performances of the methods on datasets with a larger number of target sites. We performed comparisons of LinRace and baseline methods (LinRace- IST, Cassiopeia- hybrid, DCLEAR- kmer, LinTIMaT) using 128 targets and 1024 cells, and included the results in Supplementary Fig. 4. Startle was not able to complete certain runs (after 12 hours), so results for Startle in these runs were not included. On barcode data with 128 target sites, LinRace still outperforms other methods, and overall, the tree accuracy obtained with 128 target sites is slightly higher than that obtained with 16 target sites. + +<|ref|>text<|/ref|><|det|>[[114, 574, 883, 611]]<|/det|> +We have added discussions in the manuscript to reflect the new results on barcode data with 128 target sites (Lines 212, 225- 228). + +<|ref|>text<|/ref|><|det|>[[115, 624, 494, 642]]<|/det|> +5. Section 4.7: Cassiopeia is written in Python. + +<|ref|>text<|/ref|><|det|>[[115, 656, 772, 675]]<|/det|> +Thanks for the correction, and we have corrected this in the manuscript (Line 678). + +<|ref|>sub_title<|/ref|><|det|>[[115, 737, 258, 760]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[115, 770, 883, 885]]<|/det|> +This article addresses an interesting question of how to infer the lineage phylogeny with higher resolution. To do so, they developed a sophisticated framework to integrate the lineage and cell state information. In particularly, they considered the cell division history, the differentiation dynamics on the cell state manifold, and the consistency between these two processes. In doing so, the reconstructed lineage tree are shown to achieve higher accuracy than existing methods. Their idea is cool, and the paper is overall well- written. I have the following comments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 376]]<|/det|> +1, In order to correctly reconstruct the lineage phylogeny, it is important to consider barcode homoplasy, where two independent cells may spontaneously acquire the same mutations for lineage recording. In fact, target array editing with CARISPR- Cas9 generates outcomes (barcodes) with different frequencies, with some being highly frequent, labeling many unrelated (non- clonal) cells, and others being rare and more specific to a particular clone. The issue of barcode homoplasy becomes more severe when there is large scale dropouts of the target arrays, which is common to CARISPR- Cas9 based lineage recording. Indeed, in Supplementary Fig 1a, the largest clone ( \(\sim 1500\) cells) has large deletions and only a single detected mutation. Assuming that all the cells sharing this barcode come from the same founder cell is likely wrong, because the only mutation in this barcode may be generated independently from many cells among these 'pseudo' clone. Besides, it is also unlikely that a single founder cell could expand to \(\sim 1500\) cells, while most other clones only have a single cell. The authors should clearly discuss how to address this issue of barcode homoplasy, due to having mutations with very different frequencies. Potentially, they can use their simulations to test this situation, and see how well their method performs in this context. + +<|ref|>text<|/ref|><|det|>[[115, 395, 882, 451]]<|/det|> +This is a great point. To analyze barcode homoplasy in the data we used in our tests and show how LinRace contributes to alleviating the homoplasy issue, we added Supplementary Fig. 8 to the manuscript. Our response to this comment includes the following points: + +<|ref|>text<|/ref|><|det|>[[144, 465, 883, 599]]<|/det|> +1. Although we did not explicitly discuss barcode homoplasy in our original submission, the simulated data we used in the tests models the exact two factors mentioned in the reviewer's comments that lead to barcode homoplasy: (1) the biased frequency of mutations in the barcode, and (2) the dropout events. (Details described in Methods "Simulating synthetic datasets with TedSim", Lines 610-613, 618-631.) By using simulated data modeling these factors, the accuracy of tree reconstruction methods reflects the performance of these methods on real data with large pseudo clones. + +<|ref|>text<|/ref|><|det|>[[144, 611, 883, 861]]<|/det|> +2. In other words, the results we reported in the manuscript are indeed on datasets with the popular existence of barcode homoplasy, and we showed that LinRace performs better than other methods on such datasets. Supplementary Fig. 1b shows the large pseudo-clones in our simulated data. Next, we use a different measurement, "homoplasy edge ratio", to show the high frequency of the same mutation occurring on multiple lineages during the cell division process. Since with simulation we can obtain the true cell division tree and the barcode mutation on each edge of the tree, we can calculate the "homoplasy edge ratio" in the data as follows: for each edge connecting a parent cell and a daughter cell, we call it a "homoplasy edge" if there is no unique mutation on this edge (a "unique mutation" means the same mutation at the same target site does not happen at any other edge on the tree). The homoplasy edge ratio is calculated as the number of homoplasy edges divided by the total number of edges in the tree (Supplementary Fig. 8a). + +<|ref|>text<|/ref|><|det|>[[170, 880, 880, 899]]<|/det|> +From Supplementary Fig. 8a, we can see that the homoplasy ratio in data with dropouts + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 89, 883, 183]]<|/det|> +is much larger than in data without dropouts. Also, when there are dropouts, the trend of homoplasy edge ratio changes over the mutation rate is consistent with that of the accuracy of lineage reconstruction methods shown in Fig. 2a- d. This indicates that the homoplasy ratio we calculate can correlate with barcode data quality. With the existence of dropouts, the homoplasy ratio can be as high as 0.75. + +<|ref|>text<|/ref|><|det|>[[145, 198, 883, 560]]<|/det|> +3. The results we included in the manuscript (Fig. 2a-d, Fig. 3, Supplementary Fig. 4) confirm that LinRace has superior performance compared to baseline methods on datasets with high amounts of barcode homoplasy. Here we show examples of subtrees where LinRace helps to correct homoplasy to a certain extent, thanks to the use of gene expression data. From one of our simulated datasets used in Fig. 2, we take a pseudo-clone with 13 cells. These cells have the same barcode but originate from different clones in the true tree (Supplementary Fig. 8b). When considering only these 13 cells, we can obtain the true tree among them (Supplementary Fig. 8c). Since they have the same barcode, lineage-barcode-based methods such as NJ, DCLEAR, and Cassiopeia can only randomly guess the tree of these cells (an example of the random tree is in Supplementary Fig. 8e). The LinRace reconstructed tree of these cells is shown in Supplementary Fig. 8d. Visually, we see that the LinRace reconstructed tree is able to recover correct branches such as cell 3 and cell 4, cell 13 and cell 14. We also show that the LinRace reconstructed tree of these cells is more accurate than the true tree (Supplementary Fig. 8f) in terms of the CID metric. When using RF distance, the random trees mostly have a RF distance of 1 while the LinRace reconstructed tree has a RF distance of 0.8. We also use heatmaps to provide cell-cell distance on the tree for the true tree, LinRace inferred tree, and a random tree (Supplementary Fig. 8f) to show that the LinRace inferred tree is closer to the true tree compared to a random tree. + +<|ref|>text<|/ref|><|det|>[[114, 574, 883, 727]]<|/det|> +Overall, barcode homoplasy presents a significant challenge for methods of reconstructing cell division trees. The use of gene expression data in LinRace helps to partially recover the relative positions of cells with the same barcode in the tree. However, since the gene expression of cells is dominated by cell types rather than lineages, there is a limit to how much gene expression data can help. Moreover, for computational efficiency, LinRace runs tree refinement on local subtrees. To fully recover the positions of cells in the global tree, optimization on the global tree structure is needed, but methods that perform whole-tree structure optimization did not prove successful (e.g. LinTlMaT and Startle) due to the vast search space of the whole tree. + +<|ref|>text<|/ref|><|det|>[[115, 740, 883, 778]]<|/det|> +In the manuscript, we have added this discussion in Lines 278- 313. We added the details of calculating the homoplasy edge ratio to the Methods section (Lines 745- 754). + +<|ref|>text<|/ref|><|det|>[[115, 791, 883, 904]]<|/det|> +2, In order to simulate the cell division history and the differentiation dynamics together, the authors assume that the sampled leaf nodes can form a state manifold, and the ancestor cell states (from the internal nodes in the reconstructed lineage tree) can be found from the sampled cell states. In systems with asynchronous differentiation, like in blood, such an assumption could indeed hold. But for developmental systems with more synchronous differentiation, all cell states change rapidly over time, and the early ancestor cell states are no + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 164]]<|/det|> +longer there at the later stage of development. This is an unstated limitation of this study. The authors should address this limitation. At least, they should explicitly state this limitation. In doing so, they may also need to temper their claim that they can infer the ancestor state, by adding the restrictive conditions. + +<|ref|>text<|/ref|><|det|>[[115, 185, 882, 260]]<|/det|> +This is a great point. Indeed, for developmental systems where all cell states change rapidly over time, the early ancestor cell states are unlikely to exist in the scRNA- seq data, therefore, these states can not be observed in the data, nor can they be reconstructed by trajectory inference methods. + +<|ref|>text<|/ref|><|det|>[[115, 274, 882, 349]]<|/det|> +If the scRNA- seq dataset does not cover such cell states, then LinRace can not incorporate these cell states, as LinRace uses the cell state tree inferred from data. However, if a prior cell state tree that includes these cell states is given, LinRace can assign cell states for ancestral cells as the cell states missing from scRNA- seq data. + +<|ref|>text<|/ref|><|det|>[[115, 363, 882, 420]]<|/det|> +We have added a discussion about the limitation of utilizing the LinRace method for different systems of biology (main manuscript Line 471- 480). Also, we acknowledge the restrictive conditions when stating that LinRace infers cell states for ancestral cells (Lines 145, 380- 381). + +<|ref|>text<|/ref|><|det|>[[115, 439, 559, 457]]<|/det|> +3, There are two articles worth referencing in this paper. + +<|ref|>text<|/ref|><|det|>[[115, 458, 882, 553]]<|/det|> +3.1 Li et.al., bioRxiv 2023, titled "A mouse model with high clonal barcode diversity for joint lineage, transcriptomic, and epigenomic profiling in single cells". They explicitly addressed the issue of low barcode diversity due to large inter-site deletions in CARISRP-Cas9 editing by adding TdT to increase mutation diversity. This could help to reduce the issue of barcode homoplasy in future applications. + +<|ref|>text<|/ref|><|det|>[[115, 555, 882, 630]]<|/det|> +3.2 Wang et.al., Nat. Biotech. 2023, titled "CoSpar identifies early cell fate biases from single-cell transcriptomic and lineage information". They similarly integrated lineage and state information. Instead of learning the lineage tree, they inferred the cell fate choice. In their study, they explicitly addressed how to cope with barcode homoplasy in their algorithm. + +<|ref|>text<|/ref|><|det|>[[115, 643, 882, 680]]<|/det|> +We thank the reviewer for suggesting these relevant papers. We have cited these two papers in our revised manuscript (Lines 34, 482 for Li et al., and Line 83- 84 for Wang et al.). + +<|ref|>text<|/ref|><|det|>[[115, 694, 882, 789]]<|/det|> +We did not discuss Wang et al. specifically in terms of their ability to cope with barcode homoplasy, as the method CoSpar does not aim to output the cell division tree, thus barcode homoplasy affects their task differently from how barcode homoplasy affects cell division tree reconstruction methods. Although in their results they showed the robustness of their method to homoplasy, their method did not appear to directly target the homoplasy issue. + +<|ref|>text<|/ref|><|det|>[[115, 809, 326, 825]]<|/det|> +Minor issues for Main text + +<|ref|>text<|/ref|><|det|>[[115, 846, 437, 882]]<|/det|> +Line 52, "Is it shown ..." \(\rightarrow\) "It is shown." This has been fixed (now Line 55). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 664, 107]]<|/det|> +Line 113- 116, the description of the clone size is very confusing here. + +<|ref|>text<|/ref|><|det|>[[115, 120, 883, 216]]<|/det|> +We thank the reviewer for pointing this out. This description aims to emphasize that there are a large number of cells that share the same barcode. Therefore, the barcode information alone can not distinguish these cells in the cell division tree. We rewrote this part (Lines 126- 132) and also added new figures to help demonstrate the large clone size in real data (Supplementary Figure 1a). + +<|ref|>text<|/ref|><|det|>[[115, 234, 880, 272]]<|/det|> +Line 369- 374, how do you support your conjecture here about differentiation speed? I do not see any data. + +<|ref|>text<|/ref|><|det|>[[114, 285, 883, 457]]<|/det|> +We thank the reviewer for raising this question. This paragraph on differentiation speed was intended to be an extended discussion in addition to all other results shown in the manuscript. It is related to the Reviewer's Comment 2, that certain biological systems go through asynchronous differentiation, and cells at different states exist in the scRNA- seq data. In the manuscript, we conjectured that cells at a later stage of development originate from lineages with fast differentiation speed. We realized that it is more appropriate to rephrase the conjecture as "cells at a later stage of development originate from lineages with more cell state transitions", as "differentiation speed" can be cell- specific and requires additional data to reach a conclusion, and the Reviewer is right that we did not show any data on differentiation speed. + +<|ref|>text<|/ref|><|det|>[[115, 470, 881, 508]]<|/det|> +In the revised manuscript, we removed this paragraph of extended discussion, as it is not part of our major results and is not rigorously supported with results. + +<|ref|>text<|/ref|><|det|>[[115, 526, 880, 564]]<|/det|> +Line 457, does "bifurcating tree" means that it will learn a topology of just two branches? Please clarify + +<|ref|>text<|/ref|><|det|>[[115, 577, 882, 653]]<|/det|> +Yes. To make this more clear, we have (1) changed all "bifurcating tree" into "binary tree" as the latter may be familiar to a larger audience; (2) added an explanation of this term "(which means every non- leaf node has exactly two children nodes)" when it first appears in the "Methods" section (Line 540). Also, we have the same explanation of this term in Section 2.1 (Line 150). + +<|ref|>text<|/ref|><|det|>[[115, 672, 877, 710]]<|/det|> +Line 482 (Eq. 3), I believe the equation has typos. Also, I(.) function is not defined. Please clarify what this function is, and why it takes this form. + +<|ref|>text<|/ref|><|det|>[[114, 723, 883, 896]]<|/det|> +We thank the reviewer for pointing this out. We have corrected Eq. 3 and also added other equations and descriptions to improve the clarity of this part of the calculation (Lines 551- 585). The I(x) function is the characteristic function that returns 0 if x is TRUE; 0 otherwise. The main idea of the calculation of state transition likelihood is as follows: intuitively, the likelihood of transition from State \(S_{i}\) to State \(S_{j}\) is high if the distance from \(S_{i}\) to \(S_{j}\) on the cell state tree is small, and low if the distance from \(S_{i}\) to \(S_{j}\) on the cell state trees large. Since our procedure of ancestral state inference (described in Lines 527- 537) implicitly ensures that in the candidate cell division tree, the edges with state transition between states with shorter distances in the cell state tree are more frequent than edges with state transition between states with shorter + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 146]]<|/det|> +distance in the cell state tree, we use the frequency of edges in the candidate cell division tree with the same state distance as that from \(S_{i}\) to \(S_{j}\) as the likelihood of state transition from \(S_{i}\) to \(S_{j}\) . + +<|ref|>text<|/ref|><|det|>[[114, 164, 604, 183]]<|/det|> +Line 495, what is \(x_{- }i?\) Gene expression vector of a single cell? + +<|ref|>text<|/ref|><|det|>[[114, 197, 875, 234]]<|/det|> +Yes, \(x_{i}\) is the gene expression vector of cell \(i\) . We clarified the notations in the manuscript (Lines 557- 558). + +<|ref|>text<|/ref|><|det|>[[114, 247, 667, 265]]<|/det|> +Line 561- 569, I did not follow this part. Could you make it more clear? + +<|ref|>text<|/ref|><|det|>[[114, 279, 875, 336]]<|/det|> +We realized that this part of the description of the Nye similarity lacks clarity. We have rewritten the derivations of Nye similarity and added context and description on notations to improve the readability (Lines 581- 582). + +<|ref|>text<|/ref|><|det|>[[114, 350, 748, 368]]<|/det|> +Line 625, the definition of the I() function should go earlier when it first appears. + +<|ref|>text<|/ref|><|det|>[[114, 381, 883, 419]]<|/det|> +This is a great point. We have added the definition of the characteristic function when it first appears (Line 565). + +<|ref|>text<|/ref|><|det|>[[115, 433, 400, 451]]<|/det|> +Minor issues for Supplementary file + +<|ref|>text<|/ref|><|det|>[[115, 470, 602, 488]]<|/det|> +Supplementary Fig 2, clarify the figure legend: LinRace_0.1_1. + +<|ref|>text<|/ref|><|det|>[[114, 502, 883, 558]]<|/det|> +We now have updated the Figure Description under Supplementary Fig 2 to clarify this point: the first number in the legend is the weight for asymmetric division likelihood, and the second number is the weight for neighbor distance likelihood. + +<|ref|>text<|/ref|><|det|>[[115, 578, 866, 616]]<|/det|> +Could you provide a figure with varying cell number, and compare the performance of different methods at the same mutation rate, similar to Supplementary Figure 5? + +<|ref|>text<|/ref|><|det|>[[114, 629, 883, 724]]<|/det|> +This is a good point. We now have included a figure benchmarking performances of selected methods with varying numbers of cells in Supplementary Figure 6. We use the mutation rate = 0.1. As expected, the performance of all methods decreases with the increase in the number of cells, while LinRace outperforms all other methods. In the manuscript, we added discussions on this additional result in Lines 236- 239. + +<|ref|>sub_title<|/ref|><|det|>[[115, 770, 257, 792]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[114, 821, 883, 897]]<|/det|> +In "LinRace: cell division history reconstruction of single cells using paired lineage barcode and gene expression data", the authors describe a new method to build cell lineage trees using CRISPR- Cas9 induced lineage barcode data supplemented with the simultaneously collected single cell RNA- seq data. The authors accurately describe the challenge in such data sets, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 145]]<|/det|> +specifically that the lineage barcodes alone often do not encode sufficient information to reconstruct the full lineage tree. To overcome this limitation, the authors leverage gene expression information to resolve the edges of the tree. + +<|ref|>text<|/ref|><|det|>[[114, 164, 882, 355]]<|/det|> +I believe this manuscript is well written and clearly presented. The new strategy LinRace serves a useful role in the field providing a route to include gene expression data with lineage barcode data only when lineage data is limited. In this way, the lineage data itself is prioritized in determining the cell lineage tree when it is available, which seems reasonable. The authors make the appropriate comparisons of their method to field standards (DCLEAR, Cassiopeia, and in some ways, the most directly comparable LinTIMat) using de novo simulated data sets and simulated data based on the known C. elegans lineage. Overall, their strategy performs the best using appropriate criteria. Moreover, the authors offer good insights into why methods generally perform better or worse over different mutation rates and why they believe their method outperforms LinTIMat. The data and methodology are sound. + +<|ref|>text<|/ref|><|det|>[[114, 374, 882, 564]]<|/det|> +Next, the authors apply their method to two real data sets where ground truth is not known, the zebrafish brain from scGESTALT and mouse embryos from the molecular recorder. In the former, they showcase an example where their strategy resolves lineages that undergo symmetric vs asymmetric cell division while in the latter, they describe the phenomenon of "partial consistency between transcriptome similarity and barcode similarity". In both cases, the biological findings are limited but I do not believe it detracts from this manuscript. Rather, it highlights how LinRace is useful in creating more detailed subtrees that may aid in future biological interpretation. For example, better tree topologies may lead to more accurate estimates of symmetric and asymmetric cell division likelihoods – a parameter that would affect the LinRace method itself. + +<|ref|>text<|/ref|><|det|>[[115, 584, 881, 640]]<|/det|> +Overall, I think this manuscript presents a reasonable method for utilizing gene expression data to complement lineage tracing data in a manner that is very useful for the field. I believe the description of methods and analysis performed in the manuscript is sufficient for replication. + +<|ref|>sub_title<|/ref|><|det|>[[115, 660, 220, 677]]<|/det|> +## Suggestions: + +<|ref|>text<|/ref|><|det|>[[114, 696, 882, 830]]<|/det|> +- Section 2.5 presents the lack of DE for the same cell state that exist in different lineages. Overall, this is not a surprising result and is in line with biological expectations. Nonetheless, their ability to detect DEs may simply be underpowered. I wonder if the intra-lineage gene expression distance for cells of the same state is lower than the inter-lineage distance across cells of the same state across the population of cells. I realize this suggestion can be a bit circular depending on the depth of tree examined since "neighbor distance likelihood" is used to establish the lineage. It might be interesting to look at regardless. + +<|ref|>text<|/ref|><|det|>[[115, 850, 881, 906]]<|/det|> +This is a great suggestion to complement the DE results. As suggested, we focused on cells in the Fore/MidBrain cell type, and compared intra- clone gene expression distances with inter- lineage distances. To do this, we took 3 clones from the Fore/MidBrain cell cells (clones 9, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 87, 883, 184]]<|/det|> +10, and 12 in Fig. 5d), and calculated for the following pairs of inter- clone or intra- clone distances: Clone 9 vs Clone 9 ("9_9" in the figure), Clone 9 vs Clone 10 (9_10), Clone 9 vs Clone 12 (9_12), Clone 10 vs Clone 10 (10_10), Clone 10 vs Clone 12 (10_12), Clone 12 vs Clone 12 (12_12). Each pair of comparisons corresponds to a box in the boxplot, which is included in the manuscript as Fig. 5e. + +<|ref|>text<|/ref|><|det|>[[115, 197, 882, 273]]<|/det|> +First, we performed PCA on the gene expression data and kept the top 50 PCs for dimensionality reduction. Then to compare Clone \(i\) with Clone \(j\) , we calculated all pairwise Euclidean distances between any cell in Clone \(i\) and any cell in Clone \(j\) , and used these distances to generate the corresponding boxplot. + +<|ref|>text<|/ref|><|det|>[[114, 285, 883, 459]]<|/det|> +As shown in Figure 5e, there are no observable differences between the intra- clone distances and the inter- clone distances. The use of the "neighbor distance likelihood" mentioned in the reviewer's comment can only contribute to the differences between intra- clone distances and the inter- clone distances. The fact that no clear differences are observed indicates that other factors, like the barcode similarity and state transition likelihood, are more dominant factors than the "neighbor distance likelihood" in forming the reconstructed tree. This additional result on gene expression distances is in line with the hypothesis in our manuscript and other publications (Packer et al. 2019) that cells' gene expression signatures are dominated by the cell types instead of lineages. + +<|ref|>text<|/ref|><|det|>[[115, 471, 841, 490]]<|/det|> +We have added corresponding discussions on this result in the manuscript (Lines 440- 443). + +<|ref|>text<|/ref|><|det|>[[113, 509, 870, 681]]<|/det|> +- I am curious if the authors can comment on how these following suggestions might change/improve performance (which could perhaps be added to discussion): o Alternate tree building method to make the tree backbone – perhaps DCLEAR or Cassiopeia. o Using time course scRNA-seq data instead of the scRNA-seq data collected with the lineage barcodes. Trajectories may be more accurately inferred when past cell states are more directly measured than relying on variability that exists within a time point. To calculate the GES, they use 3 terms, the first two of which utilizes only cell state information. They could use the cell state tree from scRNA-seq time course data sets, and still maintain the third term from the lineage traced data set. + +<|ref|>text<|/ref|><|det|>[[115, 701, 846, 740]]<|/det|> +We thank the reviewer for these suggestions. Please see the following responses to the two suggestions separately: + +<|ref|>text<|/ref|><|det|>[[144, 752, 883, 886]]<|/det|> +1. To find out how the methods used to build the backbone tree affect the final performance of LinRace, we conducted tests to use DCLEAR (using mode DCLEAR-kmer) and Cassiopeia (using mode Cassiopeia-greedy) to build the backbone tree (Fig. 2e, Supplementary Fig. 5). The results show that LinRace can improve upon the backbone tree inferred by DCLEAR-kmer and Cassiopeia-greedy. While using different backbone methods among these three choices (DCLEAR-kmer, Cassiopeia-greedy, and NJ) yields comparable results, the default combination we use (NJ and LinRace) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 89, 881, 126]]<|/det|> +performs slightly better than other choices. We have added discussions on these results in the manuscript (Lines 230- 236). + +<|ref|>text<|/ref|><|det|>[[144, 140, 875, 234]]<|/det|> +2. We agree that time-course scRNA-seq data helps to reveal past cell states that may not be captured in one scRNA-seq sample at one time point. Furthermore, we have added discussions in the manuscript to acknowledge such scenarios and the limitations of applying LinRace to datasets where the scRNA-seq data does not capture all or most of the cell states in the developmental process (Lines 471-475, 145, 380-381). + +<|ref|>text<|/ref|><|det|>[[172, 247, 883, 362]]<|/det|> +Time course scRNA-seq data will allow us to obtain a more complete set of cell states, with partial information on the temporal order of these cell states, which allows for the reconstruction of a more precise and comprehensive cell state tree. In this case, as suggested by the reviewer, only the cell state tree needs to be replaced by the one learned from the time course data, and other parts of LinRace can remain the same. We have added this discussion in the manuscript (Lines 477-479). + +<|ref|>text<|/ref|><|det|>[[115, 396, 222, 412]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 431, 870, 470]]<|/det|> +Fig 1. It may be worthwhile to change the colors for cell states so that it is easier to distinguish between the black and navy, and red and pink + +<|ref|>text<|/ref|><|det|>[[115, 482, 882, 558]]<|/det|> +Thanks for this comment. For Fig. 1, we used colors from the default rainbow color palette from base R. We have tried different options and the seven colors we used from the rainbow palette are the most distinguishable (See Figure R2). The candidate color options are as follows, and the leftmost one is the panel we use in Fig. 1. + +<|ref|>text<|/ref|><|det|>[[115, 572, 882, 648]]<|/det|> +We did modify Fig. 1 to make it easier to distinguish the colors, which is that we changed the border colors of the squares (and circles) to be the same as their respective fill colors. After removing the black border colors, we think it is now easier to distinguish black from navy, and red from pink. + +<|ref|>image<|/ref|><|det|>[[128, 680, 870, 727]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 748, 875, 766]]<|/det|> +
Figure R2. Colour palettes visualization for cell types and lineage barcode mutation annotations in Fig. 1
+ +<|ref|>text<|/ref|><|det|>[[115, 783, 870, 820]]<|/det|> +Line 176- 8: I would recommend adding a half a sentence or a sentence about how to choose a root cell state outside of simulation environments. + +<|ref|>text<|/ref|><|det|>[[115, 834, 881, 890]]<|/det|> +We have added one sentence on the common practice of trajectory inference on real data (Lines 195- 196). In the case of Slingshot, a root cell state needs to be provided to the algorithm based on domain knowledge. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 695, 125]]<|/det|> +Line 309: GESTAULT should be GESTALT (and also Fig 4 legend, line 591) + +<|ref|>text<|/ref|><|det|>[[115, 138, 867, 177]]<|/det|> +Thanks for the correction. We have modified the text in our manuscript accordingly (now Lines 386, 678, Fig. 4 description). + +<|ref|>text<|/ref|><|det|>[[115, 190, 377, 208]]<|/det|> +Fig 4a: Inner ring is barely visible + +<|ref|>text<|/ref|><|det|>[[115, 221, 882, 278]]<|/det|> +Since the inner ring provides similar information as the color of the outer ring, and the only difference is that the inner ring shows sub- cell types, we have removed the inner ring for clearer visualization in both Fig 4a and Supplementary Fig. 12, and updated the figure descriptions. + +<|ref|>text<|/ref|><|det|>[[115, 292, 882, 347]]<|/det|> +Line 334: This may be a lack of understanding on my part, but to my knowledge, terminal cells do not undergo mitosis. Is there a different word that can be used here to express cells that can only undergo symmetric divisions? + +<|ref|>text<|/ref|><|det|>[[115, 361, 882, 417]]<|/det|> +We thank the reviewer for pointing this out. We have changed the use of "terminal cell type" to the specific cell type we observed in the figures (the Forebrain or Midbrain cell type) to avoid making general statements that are not well- supported (Lines 405, 411,412 in the manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[115, 589, 240, 610]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[112, 661, 880, 887]]<|/det|> +Chan, Michelle M., Zachary D. Smith, Stefanie Grosswendt, Helene Kretzmer, Thomas M. Norman, Britt Adamson, Marco Jost, Jeffrey J. Quinn, Dian Yang, Matthew G. Jones, Alex Khodaverdian, Nir Yosef, Alexander Meissner, and Jonathan S. Weissman. 2019. "Molecular Recording of Mammalian Embryogenesis." Nature, May. doi:10.1038/s41586- 019- 1184- 5. Packer, Jonathan S., Qin Zhu, Chau Huynh, Priya Sivaramakrishnan, Elicia Preston, Hannah Dueck, Derek Stefanik, Kai Tan, Cole Trapnell, Junhyong Kim, Robert H. Waterston, and John I. Murray. 2019. "A Lineage- Resolved Molecular Atlas of C. Elegans Embryogenesis at Single- Cell Resolution." Science 365 (6459). science.sciencemag.org. doi:10.1126/science.aax1971. Quinn, Jeffrey J., Matthew G. Jones, Ross A. Okimoto, Shigeki Nanjo, Michelle M. Chan, Nir Yosef, Trever G. Bivona, and Jonathan S. Weissman. 2021. "Single- Cell Lineages Reveal the Rates, Routes, and Drivers of Metastasis in Cancer Xenografts." Science 371 (6532). doi:10.1126/science.abc1944. Raj, Bushra, Daniel E. Wagner, Aaron McKenna, Shristi Pandey, Allon M. Klein, Jay Shendure, James A. Gagnon, and Alexander F. Schier. 2018. "Simultaneous Single- Cell Profiling of Lineages and Cell Types in the Vertebrate Brain." Nature Biotechnology 36 (5): 442–50. doi:10.1038/nbt.4103. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 97, 303, 113]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 162, 399, 179]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 199, 867, 234]]<|/det|> +The authors have thoroughly responded to all my concerns, incorporating additional tools and datasets in their benchmark. I believe the manuscript is now ready for publication. + +<|ref|>sub_title<|/ref|><|det|>[[115, 300, 399, 317]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 337, 425, 354]]<|/det|> +The authors have addressed my concerns! + +<|ref|>sub_title<|/ref|><|det|>[[115, 420, 399, 437]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 456, 870, 491]]<|/det|> +The authors have addressed my concerns and have updated their manuscript accordingly. I am satisfied with their revision. + +<--- Page Split ---> diff --git a/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..566b28c349d9ba9c359a098962a1b594acd6b0dc --- /dev/null +++ b/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,273 @@ + +# nature portfolio + +Peer Review File + +# Metastability and Ostwald Step Rule in the Crystallisation of Diamond and Graphite from Molten Carbon + +Corresponding Author: Professor Davide Donadio + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The article discusses the nucleation of diamond and graphite in supercooled liquid carbon under various pressure- temperature conditions using molecular dynamics with a machine- learning potential. One of the key highlights of the paper is the nucleation of metastable graphite at pressures where diamond is expected to form—an effect explained in terms of two- step nucleation. This result is, to say the least, quite fascinating. + +However, from my perspective: + +1) The authors do not provide sufficient evidence. +2) The result could easily be an artifact of the MD model rather than a genuine physical process. I hope to be wrong in my second statement and invite the authors to address the following questions: + +1) One of the main claims of the paper is that graphite nucleates beyond its region of thermodynamic stability. However, the authors do not calculate or define the boundaries of this region according to their ML potential. Instead, they limit their discussion to the rather enigmatic phrase in the caption of Fig. 1: + +"The purple dashed line is our theoretical estimate of the graphite/diamond phase boundary." + +No explanation is provided regarding the basis of this "theoretical estimate". If the actual graphite stability region for the given ML potential extends up to 14- 15 GPa at the discussed temperatures, then the result is quite trivial, and there is no need to invoke two- step nucleation. + +2) The authors trained their model on the dataset from the original GAP-2017, obtained via LDA-DFT [reference 43 in the bibliography]. However, LDA is known to poorly describe liquid and amorphous carbon. Gábor Csányi and his team have since transitioned to more advanced exchange functionals in their later models for a reason. For example, consider the difference between LDA and PBE predictions for the density of liquid carbon—see Fig. 2 in [https://pubs.aip.org/aip/jap/article/116/1/013510/139206]—which reaches several dozen percent at certain pressures. Properly describing the liquid phase is crucial for the phase transition under discussion. Underestimating the density of liquid carbon could easily shift the graphite nucleation region to higher pressures. + +3) The integration timestep—0.5 fs—is quite large for the temperatures discussed. Typical values in similar studies range from 0.1 to 0.2 fs: + +0.1 fs in "Comparative study of melting of graphite and graphene" + +0.2 fs in "Non-equilibrium melting and sublimation of graphene simulated with two interatomic potentials" + +0.24 fs in "Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory" A large timestep can lead to poor energy conservation, which in turn could cause density fluctuations in liquid. Unfortunately, the authors do not provide any information on energy conservation at this timestep. + +4) Many technical details are missing. The authors do not provide links to their model or dataset, neither in the manuscript nor on arXiv. Their description of the two-phase modeling is limited to a single paragraph, whereas such calculations typically warrant entire papers. Additionally, the aforementioned "theoretical estimate of the graphite/diamond phase + +<--- Page Split ---> + +boundary" lacks elaboration. Since SI is unrestricted in length, I encourage the authors to provide all necessary data to reproduce their results. In its current state, the study is simply non- reproducible due to a lack of essential information. + +5) The statement regarding the validation of the potential with experimental data: + +"Our simulations successfully reproduce the experimental phase diagram and validate the accuracy of the machine learning potential utilized in this study." + +is nearly nonsensical, given the significant discrepancies among experimental results on the carbon phase diagram. E.g. you can find experimental studies predicting graphite melting temperatures in the range of 6300- 6700 K [https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.175702] as well as in the range of 4000- 4500 K (see the review in Carbon [https://doi.org/10.1016/j.carbon.2004.12.027]). In this context, nearly any potential—including REBO and Stillinger- Weber—could be considered in excellent agreement with the experimental phase diagram. + +If the authors could reproduce the effect using a better- benchmarked ML potential (e.g., GAP- 20) or perform a more in- depth analysis of their own potential, focusing on the carbon phase diagram parameters it predicts, I would be happy to withdraw my concerns. At present, however, the entire result could easily be an artifact of the MD potential, and the reader has no means to verify it. The history knows a number of cases when poorly validated carbon MD potentials tricked the researchers [https://journals.aps.org/prb/abstract/10.1103/PhysRevB.48.3591]. + +## Reviewer #2 + +(Remarks to the Author) + +The article "Metastability and Ostwald Step Rule in the Crystallisation of Diamond and Graphite from Molten Carbon" by Davide Donadio et al applies molecular dynamics simulations based on first- principles machine learning potentials to reveal the microscopic mechanisms of diamond and graphite nucleation from liquid carbon. The most important finding of this article is that at high pressures (10.5 \~ 15 GPa) in the thermodynamically stable region of diamond, liquid carbon preferrively forms metastable graphite rather than diamond through non- classical nucleation paths, following Ostwald's step rule. The article may be of interest to a wide range of specialists working in the field of earth and planetary science, and materials manufacturing, and deserves publication in nature communications. But I have two concerns. + +1. Liquid carbon contains different local atomic structures around the GDL triple point, it is necessary to verify that whether the NEP3 potential is suitable to model the structure of liquid carbon. In the supplementary materials, the structural and elastic properties of graphite and diamond are listed, the structural properties of liquid carbon should also be listed. +2. The authors claim that spontaneous crystallisation of diamond and graphite was observed in direct MD simulations of liquid carbon at constant pressure, in which the temperature was ramped from 5,000 K to 3,500 K in 25 ns, corresponding to a cooling rate of 60 K/ns. In Figure 1a, there are eight spontaneous crystallization points, and the authors should clearly show how the initial liquid was obtained and whether the liquid reached equilibrium in the eight isobaric simulations, especially the three points between 10.0 and 15.0 GPa. This could clarify whether the findings were related to the initial liquid structure. + +3. In Page 8, Figure 2(a-c) should be Figure 2(d-f). + +4. Reference 23 is incomplete. + +## Reviewer #3 + +(Remarks to the Author) + +The authors performed a range of simulations to study the crystallisation of carbon, particularly around the graphite- diamond- liquid triple point, where experimental measurements are inconclusive. To enable accurate behaviour of the model, they trained a machine learning based potential, and studied the phase behaviour and transitions, as well as the formation of critical nuclei under different pressure conditions. The manuscript is clearly written, the calculations appear to be carefully conducted with appropriate conditions drawn. I thus recommend the manuscript to be published, with a few minor details to be potentially considered by the authors: + +The authors use the spherical harmonic expansion of the atomic environment as order parameter to identify crystalline environments in the simulation - are these the same as the Steinhardt bond order parameters widely used by the community? (https://doi.org/10.1103/PhysRevB.28.784) + +The authors mention that reproducing the negative gradient of the graphite melting line is a challenge and most empirical models, or even ML potentials struggle to reproduce that. While I agree, there is some evidence that the highly accurate EDIP potential [https://doi.org/10.1103/PhysRevB.63.035401] might be able to capture this challenging feature (as shown in Ref 24 of the manuscript). Would the authors be able to comment on that? + +In case when graphite structures were formed during the nucleation or quenching process, have the authors considered checking or evaluating the different relative orientation or stacking of the graphite sheets (i.e. how the hexagonal rings are positioned relative to each other on different layers)? While the ground state structure is relatively well described, at higher temperatures a range of various orientations or stackings should appear, each with slightly different free energy - would it be possible to determine if certain arrangements are more likely to be formed or more likely to facilitate the graphite- diamond transition? + +<--- Page Split ---> + +The authors tested different radii for the various descriptors of their ML model, but I couldn't find the actual values they used. For graphite, where van de Waals interactions are important, and the atomic distance between layers is larger than within layers - this could be an important factor (as the authors also partially point out in their description). Could do authors present more details on this aspect of their model (maybe in the SI)? + +In case of two- phase coexistence simulations, what was the orientation of the graphite structure compared to the liquid interface? One would expect that especially the growth pf the solid phase is rather different if the graphite sheets are parallel to the interface than perpendicular. Have the authors considered this? + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The authors have conducted substantial additional computational work to address the questionable aspects of the original draft and have published a comprehensive SI. In my opinion, the article is now suitable for publication in its current form. + +P.S. + +Please do not encourage the carbon community to blindly train ML models on low- accuracy DFT functionals such as LDA. While you have performed a thorough comparison with OptB88, many others may not be as cautious. As you can see from the phase diagram, the pressures along the graphite- diamond coexistence line have shifted by a factor of \(x2 - x3\) . Thank you for your understanding :) + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +The data supplemented by the authors dispelled my doubts. It can be seen from the supplementary data that during the spontaneous crystallization simulation, the atomic coordination numbers in all the initial liquids are mainly in triple coordination, and the structure of the liquid changes continuously with the pressure. I think it can be published. However, for the integrity of the data, I think that in Figs. S3- S5 the author should supplement another data that is very close to 15 GPa in Fig. 1 and Fig. S2. Although their initial states were very close, after isobaric cooling, one spontaneously crystallized into a diamond structure and the other spontaneously crystallized into a graphite structure. I think this is very important. + +(Remarks on code availability) + +Reviewer #3 + +(Remarks to the Author) + +The Authors have considered the range of comments and feedback from reviewers. They performed more benchmarking calculations, provided more details on their analysis, and have also done some further free energy calculations to further validate their conclusions. + +I recommend the paper to be accepted for publication. + +(Remarks on code availability) + +I have looked at the github page. I haven't tried to install the packages and run the example input files, but there seem to be comprehensive step- by- step instructions and input files for the LAMMPS simulations, all arranged in an easy to navigate structure. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The article discusses the nucleation of diamond and graphite in supercooled liquid carbon under various pressure- temperature conditions using molecular dynamics with a machine- learning potential. One of the key highlights of the paper is the nucleation of metastable graphite at pressures where diamond is expected to form—an effect explained in terms of two- step nucleation. This result is, to say the least, quite fascinating. + +However, from my perspective: + +1) The authors do not provide sufficient evidence. +2) The result could easily be an artifact of the MD model rather than a genuine physical process. I hope to be wrong in my second statement and invite the authors to address the following questions: + +1) One of the main claims of the paper is that graphite nucleates beyond its region of thermodynamic stability. However, the authors do not calculate or define the boundaries of this region according to their ML potential. Instead, they limit their discussion to the rather enigmatic phrase in the caption of Fig. 1: + +"The purple dashed line is our theoretical estimate of the graphite/diamond phase boundary." + +No explanation is provided regarding the basis of this "theoretical estimate". If the actual graphite stability region for the given ML potential extends up to 14–15 GPa at the discussed temperatures, then the result is quite trivial, and there is no need to invoke two- step nucleation. + +<--- Page Split ---> + +We have calculated the graphite/diamond coexistence line using Gibbs- Duhem integration (Kofke 1993, Ref. 30) starting from the triple point estimated as the crossing between the graphite/liquid and the diamond/liquid melting lines (pressure = 10.3 GPa, temperature = 4640 K). + +This procedure is explained in the revised manuscript. Figure 1 has been updated, including the calculated points (maroon triangles) along the graphite/diamond coexistence line. + +2) The authors trained their model on the dataset from the original GAP-2017, obtained via LDA-DFT [reference 43 in the bibliography]. However, LDA is known to poorly describe liquid and amorphous carbon. Gábor Csányi and his team have since transitioned to more advanced exchange functionals in their later models for a reason. For example, consider the difference between LDA and PBE predictions for the density of liquid carbon—see Fig. 2 in [https://pubs.aip.org/aip/jap/article/116/1/013510/139206]—which reaches several dozen percent at certain pressures. Properly describing the liquid phase is crucial for the phase transition under discussion. Underestimating the density of liquid carbon could easily shift the graphite nucleation region to higher pressures. + +We have performed simulations using neuroevolution potential fitted to the optB88- vdW dataset in Rowe et al. (Ref. 28) (NEP@OptB88- vdW). We were reluctant to use this potential in the first place because in the phase diagram published in Marchant et al. npj Computational Materials (2023)9:131 the slope of the graphite/liquid coexistence line near the triple point is positive, whereas there is convincing experimental evidence that it should be negative [see, for example, Ref. 5]. + +In the revised manuscript, we have characterized the liquid state with both the NEP@LDA and NEP@OptB88- vdW potentials and repeated the calculation of the phase diagram of carbon in the pressure range from 5 to 30 GPa with this model. The two models give very similar results except for a pressure offset of about \(\sim 6\) GPa, as it can be seen in this figure where the solid lines represent the NEP@LDA phase diagram shifted to \(\sim 6\) GPa higher pressure. + +<--- Page Split ---> +![PLACEHOLDER_6_0] + + +We have also repeated the crystallization studies (quenching from 5000 K to 3500 K) with NEP@OptB88- vdW, reproducing the metastable crystallization of graphite above the graphitediiamond coexistence line. + +These results are now commented in the manuscript, and the comparison between the two phase diagrams, including the temperatures of spontaneous crystallization, is reported in Figure S2. + +3) The integration timestep—0.5 fs—is quite large for the temperatures discussed. Typical values in similar studies range from 0.1 to 0.2 fs: + +0.1 fs in "Comparative study of melting of graphite and graphene" 0.2 fs in "Non-equilibrium melting and sublimation of graphene simulated with two interatomic potentials" 0.24 fs in "Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory" A large timestep can lead to poor energy conservation, which in turn could cause density fluctuations in liquid. Unfortunately, the authors do not provide any information on energy conservation at this timestep. + +This is a very valid point. We checked energy conservation in microcanonical (NVE) MD simulations of a 4096- atom model of liquid carbon. For example, at T=4500 K and P=7 GPa, + +<--- Page Split ---> +![PLACEHOLDER_7_0] + + +and the total energy fluctuation is of the order of 1 meV/atom without any significant energy drift over 100 ps. This leads to no significant drift in temperature. The total energy per atom of liquid carbon is shown below for a 100- ps NVT equilibration run followed by a 100- ps NVE run. The insert zooms in on the total energy of the microcanonical run. + +To further address the reviewer's concern, we have repeated 4 quenching simulations (12, 14.5, 15.5, and 20 GPa) at the same quenching rates as the previous simulations with a timestep of 0.25 fs. The crystallization outcomes are the same, and the temperatures of spontaneous nucleation are within the statistical uncertainty range. Energy conservation is discussed in the methods section of the revised manuscript. + +4) Many technical details are missing. The authors do not provide links to their model or dataset, neither in the manuscript nor on arXiv. Their description of the two-phase modeling is limited to a single paragraph, whereas such calculations typically warrant entire papers. Additionally, the aforementioned "theoretical estimate of the graphite/diamond phase boundary" lacks elaboration. Since SI is unrestricted in length, I encourage the authors to provide all necessary data to reproduce their results. In its current state, the study is simply non-reproducible due to a lack of essential information. + +We have created an archive with the simulation setups, the parameters of the NEP potentials, the version of the GPUMD program used for these simulations, and the Python script to run Gibbs- Duhem integration, and forward flux sampling code together with FFS input and example runs. The data are publicly available at https://github.com/ddonadio/CarbonNucleation and https://github.com/WanyuZhao/FFS- LAMMPS, and will be deposited in MaterialsCloud if the paper is accepted. + +5) The statement regarding the validation of the potential with experimental data: + +<--- Page Split ---> + +"Our simulations successfully reproduce the experimental phase diagram and validate the accuracy of the machine learning potential utilized in this study." is nearly nonsensical, given the significant discrepancies among experimental results on the carbon phase diagram. E.g. you can find experimental studies predicting graphite melting temperatures in the range of 6300- 6700 K [https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.175702] as well as in the range of 4000- 4500 K (see the review in Carbon [https://doi.org/10.1016/j.carbon.2004.12.027]). In this context, nearly any potential—including REBO and Stillinger- Weber—could be considered in excellent agreement with the experimental phase diagram. + +We thank the reviewer for bringing to our attention more experimental material on the phase diagram of carbon. While we agree that there are large experimental uncertainties in the determination of the phase diagram of carbon, we may still argue that our model is more general and physically grounded than REBO and Stillinger- Weber that do not even predict graphite stability or suggest exotic liquid- liquid phase transitions in liquid carbon. + +The results by Kondratyev&Rakhel PRL 2019 push the melting point of graphite at much higher temperatures than all the previous experiments. Similarly, Liang et al. [Phys. Rev. Research 1, 033090, (2019)] suggest that the melting temperature of diamond at 15 GPa should be higher ( \(\sim 6000 \text{K}\) ) than previous estimates. These works are now cited to put our results in a better context (Refs. 7 and 8). + +If the authors could reproduce the effect using a better- benchmarked ML potential (e.g., GAP- 20) or perform a more in- depth analysis of their own potential, focusing on the carbon phase diagram parameters it predicts, I would be happy to withdraw my concerns. At present, however, the entire result could easily be an artifact of the MD potential, and the reader has no means to verify it. History knows a number of cases when poorly validated carbon MD potentials tricked the researchers [https://journals.aps.org/prb/abstract/10.1103/PhysRevB.48.3591]. + +The paper mentioned by the reviewer dates back to 1993 and uses a macroscopic model. It is not surprising that its conclusions about a liquid- liquid phase transition, although plausible, turned out to be incorrect. The same conclusions were reached by Glosli and Ree using the Brenner potential (REBO) (Ref. 22) + +Following the reviewer's suggestion, we have recalculated the phase diagram and repeated the spontaneous crystallization runs with a NEP potential fitted on the same dataset as the GAP- 20 (based on OptB88- vdW data). Although we notice a shift of the graphite/diamond coexistence line to higher pressure, these new calculations reproduce the same features as the original study, including the metastable crystallization of graphite in the region of stability of diamond. The phase diagram thus obtained, including the temperatures at which we observe spontaneous crystallization of graphite and diamond, is shown in Figure S2 of the SI. The results are discussed in the main text, in the section on the phase diagram and spontaneous crystallization. + +<--- Page Split ---> + +In passing, we need to point out that our results differ from the phase diagram published by Marchant et al. [npj Comput. Mater. Sci. 2023], which were obtained with simulations of very small cells, a method subject to much larger statistical uncertainties. + +## Reviewer #2 (Remarks to the Author): + +The article "Metastability and Ostwald Step Rule in the Crystallisation of Diamond and Graphite from Molten Carbon" by Davide Donadio et al applies molecular dynamics simulations based on first- principles machine learning potentials to reveal the microscopic mechanisms of diamond and graphite nucleation from liquid carbon. The most important finding of this article is that at high pressures (10.5 \~ 15 GPa) in the thermodynamically stable region of diamond, liquid carbon preferentially forms metastable graphite rather than diamond through non- classical nucleation paths, following Ostwald's step rule. The article may be of interest to a wide range of specialists working in the field of earth and planetary science and materials manufacturing, and deserves publication in Nature Communications. But I have two concerns. + +1. Liquid carbon contains different local atomic structures around the GDL triple point, it is necessary to verify that whether the NEP3 potential is suitable to model the structure of liquid carbon. In the supplementary materials, the structural and elastic properties of graphite and diamond are listed, the structural properties of liquid carbon should also be listed. + +A detailed analysis of the structure of liquid carbon has been added to the paper (Figures S3, S4, and S5 in the Supporting Information). These properties are consistent with previous studies. In particular, the NEP models reflect the differences previously observed in the structure and density of liquid carbon between LDA and GGA functionals (see references 32, 33 and 36). + +These differences, which lead to quantitative differences in the phase diagram, may be reconciled by shifting either the pressure or the density. Except for this pressure offset, the physical behavior of the liquid is qualitatively the same in the two models. A direct comparison with experiments suggests that the correct equation of state of the liquid is between those calculated (see Figure S3). + +2. The authors claim that spontaneous crystallisation of diamond and graphite was observed in direct MD simulations of liquid carbon at constant pressure, in which the temperature was ramped from 5,000 K to 3,500 K in 25 ns, corresponding to a cooling rate of 60 K/ns. In Figure 1a, there are eight spontaneous crystallization points, and the authors should clearly show how the initial liquid was obtained and whether the liquid reached equilibrium in the eight isobaric simulations, especially the three points between 10.0 and 15.0 GPa. This could clarify whether the findings were related to the initial liquid structure. + +The quenching simulations are initiated from liquid models equilibrated for at least 2 ns at 5000 K at each pressure. These are the same models that have been used to characterize the structure of liquid carbon. + +<--- Page Split ---> + +3. In Page 8, Figure 2(a-c) should be Figure 2(d-f). + +We have corrected the reference to the figure. + +4. Reference 23 is incomplete. + +We checked all the references. + +## Reviewer #3 (Remarks to the Author): + +The authors performed a range of simulations to study the crystallisation of carbon, particularly around the graphite- diamond- liquid triple point, where experimental measurements are inconclusive. To enable accurate behaviour of the model, they trained a machine learning based potential, and studied the phase behaviour and transitions, as well as the formation of critical nuclei under different pressure conditions. The manuscript is clearly written, the calculations appear to be carefully conducted with appropriate conditions drawn. I thus recommend the manuscript to be published, with a few minor details to be potentially considered by the authors: + +The authors use the spherical harmonic expansion of the atomic environment as order parameter to identify crystalline environments in the simulation - are these the same as the Steinhardt bond order parameters widely used by the community? (https://doi.org/10.1103/PhysRevB.28.784) + +These order parameters are derived from the original formulation in the Steinhardt paper; however, the version used here is "local," i.e., it provides a per- atom order parameter, whereas in the original Physical Review B article, Q6 was defined as a global quantity. The necessity for local order parameters in nucleation studies was recognized in several works around the early 2000s. The exact formulation of the order parameter in this paper is given in Li et al. JCP 2009. To help the readers, we have added a brief description in the Methods section. + +The authors mention that reproducing the negative gradient of the graphite melting line is a challenge and most empirical models, or even ML potentials struggle to reproduce that. While I agree, there is some evidence that the highly accurate EDIP potential [https://doi.org/10.1103/PhysRevB.63.035401] might be able to capture this challenging feature (as shown in Ref 24 of the manuscript). Would the authors be able to comment on that? + +On page 4, we have added a note on the phase diagram computed with EDIP. We also noticed that, while the original LCBOP polarizable model gives a positive slope, the revised version LCBOPII gives a more reasonable melting curve of graphite. We have added a comment and a reference about this, too. + +In case when graphite structures were formed during the nucleation or quenching process, have the authors considered checking or evaluating the different relative orientation or stacking of the graphite sheets (i.e. how the hexagonal rings are positioned relative to each other on different + +<--- Page Split ---> + +layers)? While the ground state structure is relatively well described, at higher temperatures a range of various orientations or stackings should appear, each with slightly different free energy - would it be possible to determine if certain arrangements are more likely to be formed or more likely to facilitate the graphite- diamond transition? + +The nuclei form in a highly dynamic state at high temperature. Under these conditions, the free energy differences among different stacking arrangements are below the thermal energy. We have examined the structure of graphite near critical size obtained in our FFS sampling, from which we found graphite nuclei appear to adopt random stacking. This is not surprising as the stacking fault energy of graphite was determined to be \(0.85 \text{mJ / m}^2\) (Rob H. Telling & Malcolm I. Heggie (2003), Philosophical Magazine Letters, 83:7, 411- 421), which is about 2 orders of magnitude smaller than thermal energy (3800K) for one \(1 \text{nm}^2\) area. + +The authors tested different radii for the various descriptors of their ML model, but I couldn't find the actual values they used. For graphite, where van de Waals interactions are important, and the atomic distance between layers is larger than within layers - this could be an important factor (as the authors also partially point out in their description). Could do authors present more details on this aspect of their model (maybe in the SI)? + +The NEP models used in this work are now provided in the data archive. We have tested potentials with 2- body radii from 4.2 to 8 A. We did not observe any significant differences either in the phase diagram or in the crystallization behavior. + +In case of two- phase coexistence simulations, what was the orientation of the graphite structure compared to the liquid interface? One would expect that especially the growth of the solid phase is rather different if the graphite sheets are parallel to the interface than perpendicular. Have the authors considered this? + +We tested configurations with the liquid in contact with the basal plane (0001) and the prismatic armchair plane (11- 20) of graphite. We have chosen to use the prismatic plane because it has a much faster growth and melting kinetics, thus reducing the cost of the simulations. We added a comment about this in the methods section and a figure (Fig. S7) showing both graphite- liquid and graphite- diamond two- phase configurations. + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS' COMMENTS + +Reviewer #2 (Remarks to the Author): + +The data supplemented by the authors dispelled my doubts. It can be seen from the supplementary data that during the spontaneous crystallization simulation, the atomic coordination numbers in all the initial liquids are mainly in triple coordination, and the structure of the liquid changes continuously with the pressure. I think it can be published. However, for the integrity of the data, I think that in Figs. S3- S5 the author should supplement another data that is very close to 15 GPa in Fig. 1 and Fig. S2. Although their initial states were very close, after isobaric cooling, one spontaneously crystallized into a diamond structure and the other spontaneously crystallized into a graphite structure. I think this is very important. + +We agree with the reviewer that showing there is no discontinuity in the structural properties of the liquid at the tipping pressure of diamond nucleation is important. We have added data to Figures S3 and S5 at \(\mathsf{P} = 15.5\mathsf{GPa}\) for the NEP@LDA model and \(\mathsf{P} = 19\mathsf{GPa}\) for the NEP@OptB88- vdW model, which show that there is indeed no discontinuity either in the density or in the coordination of the liquid. We are reluctant to add the 15.5 GPa and the 19 GPa lines to the RDF figures (S4) because they are nearly indistinguishable from the 15 and 20 GPa lines, respectively. + +Figures S3 and S5 and their captions have been updated with this information. + +<--- Page Split ---> diff --git a/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..dacf638d196c408691bdb71f14417405986bb5dc --- /dev/null +++ b/peer_reviews/55f2b7624e812eb9a974c4f7b37057b10c65085f9004ec01875788ba83807969/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,380 @@ +<|ref|>title<|/ref|><|det|>[[73, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[74, 161, 900, 210]]<|/det|> +# Metastability and Ostwald Step Rule in the Crystallisation of Diamond and Graphite from Molten Carbon + +<|ref|>text<|/ref|><|det|>[[73, 224, 500, 240]]<|/det|> +Corresponding Author: Professor Davide Donadio + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 219, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 404, 238, 417]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 418, 910, 470]]<|/det|> +The article discusses the nucleation of diamond and graphite in supercooled liquid carbon under various pressure- temperature conditions using molecular dynamics with a machine- learning potential. One of the key highlights of the paper is the nucleation of metastable graphite at pressures where diamond is expected to form—an effect explained in terms of two- step nucleation. This result is, to say the least, quite fascinating. + +<|ref|>text<|/ref|><|det|>[[73, 484, 286, 497]]<|/det|> +However, from my perspective: + +<|ref|>text<|/ref|><|det|>[[73, 498, 760, 536]]<|/det|> +1) The authors do not provide sufficient evidence. +2) The result could easily be an artifact of the MD model rather than a genuine physical process. I hope to be wrong in my second statement and invite the authors to address the following questions: + +<|ref|>text<|/ref|><|det|>[[72, 548, 911, 589]]<|/det|> +1) One of the main claims of the paper is that graphite nucleates beyond its region of thermodynamic stability. However, the authors do not calculate or define the boundaries of this region according to their ML potential. Instead, they limit their discussion to the rather enigmatic phrase in the caption of Fig. 1: + +<|ref|>text<|/ref|><|det|>[[73, 600, 707, 614]]<|/det|> +"The purple dashed line is our theoretical estimate of the graphite/diamond phase boundary." + +<|ref|>text<|/ref|><|det|>[[72, 626, 899, 666]]<|/det|> +No explanation is provided regarding the basis of this "theoretical estimate". If the actual graphite stability region for the given ML potential extends up to 14- 15 GPa at the discussed temperatures, then the result is quite trivial, and there is no need to invoke two- step nucleation. + +<|ref|>text<|/ref|><|det|>[[72, 678, 900, 770]]<|/det|> +2) The authors trained their model on the dataset from the original GAP-2017, obtained via LDA-DFT [reference 43 in the bibliography]. However, LDA is known to poorly describe liquid and amorphous carbon. Gábor Csányi and his team have since transitioned to more advanced exchange functionals in their later models for a reason. For example, consider the difference between LDA and PBE predictions for the density of liquid carbon—see Fig. 2 in [https://pubs.aip.org/aip/jap/article/116/1/013510/139206]—which reaches several dozen percent at certain pressures. Properly describing the liquid phase is crucial for the phase transition under discussion. Underestimating the density of liquid carbon could easily shift the graphite nucleation region to higher pressures. + +<|ref|>text<|/ref|><|det|>[[70, 781, 900, 808]]<|/det|> +3) The integration timestep—0.5 fs—is quite large for the temperatures discussed. Typical values in similar studies range from 0.1 to 0.2 fs: + +<|ref|>text<|/ref|><|det|>[[72, 821, 520, 835]]<|/det|> +0.1 fs in "Comparative study of melting of graphite and graphene" + +<|ref|>text<|/ref|><|det|>[[72, 835, 788, 849]]<|/det|> +0.2 fs in "Non-equilibrium melting and sublimation of graphene simulated with two interatomic potentials" + +<|ref|>text<|/ref|><|det|>[[72, 849, 920, 888]]<|/det|> +0.24 fs in "Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory" A large timestep can lead to poor energy conservation, which in turn could cause density fluctuations in liquid. Unfortunately, the authors do not provide any information on energy conservation at this timestep. + +<|ref|>text<|/ref|><|det|>[[72, 899, 904, 940]]<|/det|> +4) Many technical details are missing. The authors do not provide links to their model or dataset, neither in the manuscript nor on arXiv. Their description of the two-phase modeling is limited to a single paragraph, whereas such calculations typically warrant entire papers. Additionally, the aforementioned "theoretical estimate of the graphite/diamond phase + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 884, 75]]<|/det|> +boundary" lacks elaboration. Since SI is unrestricted in length, I encourage the authors to provide all necessary data to reproduce their results. In its current state, the study is simply non- reproducible due to a lack of essential information. + +<|ref|>text<|/ref|><|det|>[[72, 86, 625, 100]]<|/det|> +5) The statement regarding the validation of the potential with experimental data: + +<|ref|>text<|/ref|><|det|>[[72, 100, 918, 127]]<|/det|> +"Our simulations successfully reproduce the experimental phase diagram and validate the accuracy of the machine learning potential utilized in this study." + +<|ref|>text<|/ref|><|det|>[[72, 127, 914, 193]]<|/det|> +is nearly nonsensical, given the significant discrepancies among experimental results on the carbon phase diagram. E.g. you can find experimental studies predicting graphite melting temperatures in the range of 6300- 6700 K [https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.175702] as well as in the range of 4000- 4500 K (see the review in Carbon [https://doi.org/10.1016/j.carbon.2004.12.027]). In this context, nearly any potential—including REBO and Stillinger- Weber—could be considered in excellent agreement with the experimental phase diagram. + +<|ref|>text<|/ref|><|det|>[[72, 216, 919, 285]]<|/det|> +If the authors could reproduce the effect using a better- benchmarked ML potential (e.g., GAP- 20) or perform a more in- depth analysis of their own potential, focusing on the carbon phase diagram parameters it predicts, I would be happy to withdraw my concerns. At present, however, the entire result could easily be an artifact of the MD potential, and the reader has no means to verify it. The history knows a number of cases when poorly validated carbon MD potentials tricked the researchers [https://journals.aps.org/prb/abstract/10.1103/PhysRevB.48.3591]. + +<|ref|>sub_title<|/ref|><|det|>[[73, 308, 162, 321]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 335, 238, 348]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 348, 924, 435]]<|/det|> +The article "Metastability and Ostwald Step Rule in the Crystallisation of Diamond and Graphite from Molten Carbon" by Davide Donadio et al applies molecular dynamics simulations based on first- principles machine learning potentials to reveal the microscopic mechanisms of diamond and graphite nucleation from liquid carbon. The most important finding of this article is that at high pressures (10.5 \~ 15 GPa) in the thermodynamically stable region of diamond, liquid carbon preferrively forms metastable graphite rather than diamond through non- classical nucleation paths, following Ostwald's step rule. The article may be of interest to a wide range of specialists working in the field of earth and planetary science, and materials manufacturing, and deserves publication in nature communications. But I have two concerns. + +<|ref|>text<|/ref|><|det|>[[72, 435, 916, 560]]<|/det|> +1. Liquid carbon contains different local atomic structures around the GDL triple point, it is necessary to verify that whether the NEP3 potential is suitable to model the structure of liquid carbon. In the supplementary materials, the structural and elastic properties of graphite and diamond are listed, the structural properties of liquid carbon should also be listed. +2. The authors claim that spontaneous crystallisation of diamond and graphite was observed in direct MD simulations of liquid carbon at constant pressure, in which the temperature was ramped from 5,000 K to 3,500 K in 25 ns, corresponding to a cooling rate of 60 K/ns. In Figure 1a, there are eight spontaneous crystallization points, and the authors should clearly show how the initial liquid was obtained and whether the liquid reached equilibrium in the eight isobaric simulations, especially the three points between 10.0 and 15.0 GPa. This could clarify whether the findings were related to the initial liquid structure. + +<|ref|>text<|/ref|><|det|>[[72, 559, 412, 572]]<|/det|> +3. In Page 8, Figure 2(a-c) should be Figure 2(d-f). + +<|ref|>text<|/ref|><|det|>[[72, 572, 278, 584]]<|/det|> +4. Reference 23 is incomplete. + +<|ref|>sub_title<|/ref|><|det|>[[72, 608, 162, 621]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 635, 238, 648]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 648, 926, 725]]<|/det|> +The authors performed a range of simulations to study the crystallisation of carbon, particularly around the graphite- diamond- liquid triple point, where experimental measurements are inconclusive. To enable accurate behaviour of the model, they trained a machine learning based potential, and studied the phase behaviour and transitions, as well as the formation of critical nuclei under different pressure conditions. The manuscript is clearly written, the calculations appear to be carefully conducted with appropriate conditions drawn. I thus recommend the manuscript to be published, with a few minor details to be potentially considered by the authors: + +<|ref|>text<|/ref|><|det|>[[72, 737, 880, 778]]<|/det|> +The authors use the spherical harmonic expansion of the atomic environment as order parameter to identify crystalline environments in the simulation - are these the same as the Steinhardt bond order parameters widely used by the community? (https://doi.org/10.1103/PhysRevB.28.784) + +<|ref|>text<|/ref|><|det|>[[72, 789, 918, 842]]<|/det|> +The authors mention that reproducing the negative gradient of the graphite melting line is a challenge and most empirical models, or even ML potentials struggle to reproduce that. While I agree, there is some evidence that the highly accurate EDIP potential [https://doi.org/10.1103/PhysRevB.63.035401] might be able to capture this challenging feature (as shown in Ref 24 of the manuscript). Would the authors be able to comment on that? + +<|ref|>text<|/ref|><|det|>[[72, 854, 918, 934]]<|/det|> +In case when graphite structures were formed during the nucleation or quenching process, have the authors considered checking or evaluating the different relative orientation or stacking of the graphite sheets (i.e. how the hexagonal rings are positioned relative to each other on different layers)? While the ground state structure is relatively well described, at higher temperatures a range of various orientations or stackings should appear, each with slightly different free energy - would it be possible to determine if certain arrangements are more likely to be formed or more likely to facilitate the graphite- diamond transition? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 923, 101]]<|/det|> +The authors tested different radii for the various descriptors of their ML model, but I couldn't find the actual values they used. For graphite, where van de Waals interactions are important, and the atomic distance between layers is larger than within layers - this could be an important factor (as the authors also partially point out in their description). Could do authors present more details on this aspect of their model (maybe in the SI)? + +<|ref|>text<|/ref|><|det|>[[73, 112, 920, 153]]<|/det|> +In case of two- phase coexistence simulations, what was the orientation of the graphite structure compared to the liquid interface? One would expect that especially the growth pf the solid phase is rather different if the graphite sheets are parallel to the interface than perpendicular. Have the authors considered this? + +<|ref|>text<|/ref|><|det|>[[73, 177, 144, 190]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 203, 219, 216]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 229, 160, 243]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 256, 922, 297]]<|/det|> +(Remarks to the Author) The authors have conducted substantial additional computational work to address the questionable aspects of the original draft and have published a comprehensive SI. In my opinion, the article is now suitable for publication in its current form. + +<|ref|>text<|/ref|><|det|>[[73, 308, 102, 319]]<|/det|> +P.S. + +<|ref|>text<|/ref|><|det|>[[73, 320, 916, 374]]<|/det|> +Please do not encourage the carbon community to blindly train ML models on low- accuracy DFT functionals such as LDA. While you have performed a thorough comparison with OptB88, many others may not be as cautious. As you can see from the phase diagram, the pressures along the graphite- diamond coexistence line have shifted by a factor of \(x2 - x3\) . Thank you for your understanding :) + +<|ref|>text<|/ref|><|det|>[[73, 385, 282, 399]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 424, 161, 438]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 450, 238, 464]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 464, 919, 544]]<|/det|> +The data supplemented by the authors dispelled my doubts. It can be seen from the supplementary data that during the spontaneous crystallization simulation, the atomic coordination numbers in all the initial liquids are mainly in triple coordination, and the structure of the liquid changes continuously with the pressure. I think it can be published. However, for the integrity of the data, I think that in Figs. S3- S5 the author should supplement another data that is very close to 15 GPa in Fig. 1 and Fig. S2. Although their initial states were very close, after isobaric cooling, one spontaneously crystallized into a diamond structure and the other spontaneously crystallized into a graphite structure. I think this is very important. + +<|ref|>text<|/ref|><|det|>[[73, 555, 282, 568]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 593, 161, 606]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 619, 238, 632]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 632, 896, 672]]<|/det|> +The Authors have considered the range of comments and feedback from reviewers. They performed more benchmarking calculations, provided more details on their analysis, and have also done some further free energy calculations to further validate their conclusions. + +<|ref|>text<|/ref|><|det|>[[73, 672, 441, 686]]<|/det|> +I recommend the paper to be accepted for publication. + +<|ref|>text<|/ref|><|det|>[[73, 699, 282, 712]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 712, 911, 752]]<|/det|> +I have looked at the github page. I haven't tried to install the packages and run the example input files, but there seem to be comprehensive step- by- step instructions and input files for the LAMMPS simulations, all arranged in an easy to navigate structure. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 404, 475, 421]]<|/det|> +## RESPONSE TO REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 441, 419, 458]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 477, 882, 568]]<|/det|> +The article discusses the nucleation of diamond and graphite in supercooled liquid carbon under various pressure- temperature conditions using molecular dynamics with a machine- learning potential. One of the key highlights of the paper is the nucleation of metastable graphite at pressures where diamond is expected to form—an effect explained in terms of two- step nucleation. This result is, to say the least, quite fascinating. + +<|ref|>text<|/ref|><|det|>[[115, 588, 365, 605]]<|/det|> +However, from my perspective: + +<|ref|>text<|/ref|><|det|>[[115, 606, 881, 678]]<|/det|> +1) The authors do not provide sufficient evidence. +2) The result could easily be an artifact of the MD model rather than a genuine physical process. I hope to be wrong in my second statement and invite the authors to address the following questions: + +<|ref|>text<|/ref|><|det|>[[115, 697, 877, 771]]<|/det|> +1) One of the main claims of the paper is that graphite nucleates beyond its region of thermodynamic stability. However, the authors do not calculate or define the boundaries of this region according to their ML potential. Instead, they limit their discussion to the rather enigmatic phrase in the caption of Fig. 1: + +<|ref|>text<|/ref|><|det|>[[115, 789, 855, 808]]<|/det|> +"The purple dashed line is our theoretical estimate of the graphite/diamond phase boundary." + +<|ref|>text<|/ref|><|det|>[[115, 826, 872, 880]]<|/det|> +No explanation is provided regarding the basis of this "theoretical estimate". If the actual graphite stability region for the given ML potential extends up to 14–15 GPa at the discussed temperatures, then the result is quite trivial, and there is no need to invoke two- step nucleation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 870, 161]]<|/det|> +We have calculated the graphite/diamond coexistence line using Gibbs- Duhem integration (Kofke 1993, Ref. 30) starting from the triple point estimated as the crossing between the graphite/liquid and the diamond/liquid melting lines (pressure = 10.3 GPa, temperature = 4640 K). + +<|ref|>text<|/ref|><|det|>[[114, 162, 876, 199]]<|/det|> +This procedure is explained in the revised manuscript. Figure 1 has been updated, including the calculated points (maroon triangles) along the graphite/diamond coexistence line. + +<|ref|>text<|/ref|><|det|>[[114, 216, 872, 382]]<|/det|> +2) The authors trained their model on the dataset from the original GAP-2017, obtained via LDA-DFT [reference 43 in the bibliography]. However, LDA is known to poorly describe liquid and amorphous carbon. Gábor Csányi and his team have since transitioned to more advanced exchange functionals in their later models for a reason. For example, consider the difference between LDA and PBE predictions for the density of liquid carbon—see Fig. 2 in [https://pubs.aip.org/aip/jap/article/116/1/013510/139206]—which reaches several dozen percent at certain pressures. Properly describing the liquid phase is crucial for the phase transition under discussion. Underestimating the density of liquid carbon could easily shift the graphite nucleation region to higher pressures. + +<|ref|>text<|/ref|><|det|>[[114, 400, 878, 510]]<|/det|> +We have performed simulations using neuroevolution potential fitted to the optB88- vdW dataset in Rowe et al. (Ref. 28) (NEP@OptB88- vdW). We were reluctant to use this potential in the first place because in the phase diagram published in Marchant et al. npj Computational Materials (2023)9:131 the slope of the graphite/liquid coexistence line near the triple point is positive, whereas there is convincing experimental evidence that it should be negative [see, for example, Ref. 5]. + +<|ref|>text<|/ref|><|det|>[[114, 510, 870, 602]]<|/det|> +In the revised manuscript, we have characterized the liquid state with both the NEP@LDA and NEP@OptB88- vdW potentials and repeated the calculation of the phase diagram of carbon in the pressure range from 5 to 30 GPa with this model. The two models give very similar results except for a pressure offset of about \(\sim 6\) GPa, as it can be seen in this figure where the solid lines represent the NEP@LDA phase diagram shifted to \(\sim 6\) GPa higher pressure. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[131, 120, 748, 494]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 511, 870, 565]]<|/det|> +We have also repeated the crystallization studies (quenching from 5000 K to 3500 K) with NEP@OptB88- vdW, reproducing the metastable crystallization of graphite above the graphitediiamond coexistence line. + +<|ref|>text<|/ref|><|det|>[[114, 567, 878, 621]]<|/det|> +These results are now commented in the manuscript, and the comparison between the two phase diagrams, including the temperatures of spontaneous crystallization, is reported in Figure S2. + +<|ref|>text<|/ref|><|det|>[[114, 640, 835, 677]]<|/det|> +3) The integration timestep—0.5 fs—is quite large for the temperatures discussed. Typical values in similar studies range from 0.1 to 0.2 fs: + +<|ref|>text<|/ref|><|det|>[[113, 695, 865, 844]]<|/det|> +0.1 fs in "Comparative study of melting of graphite and graphene" 0.2 fs in "Non-equilibrium melting and sublimation of graphene simulated with two interatomic potentials" 0.24 fs in "Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory" A large timestep can lead to poor energy conservation, which in turn could cause density fluctuations in liquid. Unfortunately, the authors do not provide any information on energy conservation at this timestep. + +<|ref|>text<|/ref|><|det|>[[114, 861, 852, 897]]<|/det|> +This is a very valid point. We checked energy conservation in microcanonical (NVE) MD simulations of a 4096- atom model of liquid carbon. For example, at T=4500 K and P=7 GPa, + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[125, 105, 723, 400]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 408, 878, 483]]<|/det|> +and the total energy fluctuation is of the order of 1 meV/atom without any significant energy drift over 100 ps. This leads to no significant drift in temperature. The total energy per atom of liquid carbon is shown below for a 100- ps NVT equilibration run followed by a 100- ps NVE run. The insert zooms in on the total energy of the microcanonical run. + +<|ref|>text<|/ref|><|det|>[[114, 500, 881, 592]]<|/det|> +To further address the reviewer's concern, we have repeated 4 quenching simulations (12, 14.5, 15.5, and 20 GPa) at the same quenching rates as the previous simulations with a timestep of 0.25 fs. The crystallization outcomes are the same, and the temperatures of spontaneous nucleation are within the statistical uncertainty range. Energy conservation is discussed in the methods section of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 609, 881, 739]]<|/det|> +4) Many technical details are missing. The authors do not provide links to their model or dataset, neither in the manuscript nor on arXiv. Their description of the two-phase modeling is limited to a single paragraph, whereas such calculations typically warrant entire papers. Additionally, the aforementioned "theoretical estimate of the graphite/diamond phase boundary" lacks elaboration. Since SI is unrestricted in length, I encourage the authors to provide all necessary data to reproduce their results. In its current state, the study is simply non-reproducible due to a lack of essential information. + +<|ref|>text<|/ref|><|det|>[[114, 756, 877, 867]]<|/det|> +We have created an archive with the simulation setups, the parameters of the NEP potentials, the version of the GPUMD program used for these simulations, and the Python script to run Gibbs- Duhem integration, and forward flux sampling code together with FFS input and example runs. The data are publicly available at https://github.com/ddonadio/CarbonNucleation and https://github.com/WanyuZhao/FFS- LAMMPS, and will be deposited in MaterialsCloud if the paper is accepted. + +<|ref|>text<|/ref|><|det|>[[112, 886, 757, 904]]<|/det|> +5) The statement regarding the validation of the potential with experimental data: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 870, 253]]<|/det|> +"Our simulations successfully reproduce the experimental phase diagram and validate the accuracy of the machine learning potential utilized in this study." is nearly nonsensical, given the significant discrepancies among experimental results on the carbon phase diagram. E.g. you can find experimental studies predicting graphite melting temperatures in the range of 6300- 6700 K [https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.175702] as well as in the range of 4000- 4500 K (see the review in Carbon [https://doi.org/10.1016/j.carbon.2004.12.027]). In this context, nearly any potential—including REBO and Stillinger- Weber—could be considered in excellent agreement with the experimental phase diagram. + +<|ref|>text<|/ref|><|det|>[[114, 272, 850, 364]]<|/det|> +We thank the reviewer for bringing to our attention more experimental material on the phase diagram of carbon. While we agree that there are large experimental uncertainties in the determination of the phase diagram of carbon, we may still argue that our model is more general and physically grounded than REBO and Stillinger- Weber that do not even predict graphite stability or suggest exotic liquid- liquid phase transitions in liquid carbon. + +<|ref|>text<|/ref|><|det|>[[114, 381, 876, 474]]<|/det|> +The results by Kondratyev&Rakhel PRL 2019 push the melting point of graphite at much higher temperatures than all the previous experiments. Similarly, Liang et al. [Phys. Rev. Research 1, 033090, (2019)] suggest that the melting temperature of diamond at 15 GPa should be higher ( \(\sim 6000 \text{K}\) ) than previous estimates. These works are now cited to put our results in a better context (Refs. 7 and 8). + +<|ref|>text<|/ref|><|det|>[[114, 511, 882, 620]]<|/det|> +If the authors could reproduce the effect using a better- benchmarked ML potential (e.g., GAP- 20) or perform a more in- depth analysis of their own potential, focusing on the carbon phase diagram parameters it predicts, I would be happy to withdraw my concerns. At present, however, the entire result could easily be an artifact of the MD potential, and the reader has no means to verify it. History knows a number of cases when poorly validated carbon MD potentials tricked the researchers [https://journals.aps.org/prb/abstract/10.1103/PhysRevB.48.3591]. + +<|ref|>text<|/ref|><|det|>[[114, 638, 870, 711]]<|/det|> +The paper mentioned by the reviewer dates back to 1993 and uses a macroscopic model. It is not surprising that its conclusions about a liquid- liquid phase transition, although plausible, turned out to be incorrect. The same conclusions were reached by Glosli and Ree using the Brenner potential (REBO) (Ref. 22) + +<|ref|>text<|/ref|><|det|>[[114, 712, 876, 877]]<|/det|> +Following the reviewer's suggestion, we have recalculated the phase diagram and repeated the spontaneous crystallization runs with a NEP potential fitted on the same dataset as the GAP- 20 (based on OptB88- vdW data). Although we notice a shift of the graphite/diamond coexistence line to higher pressure, these new calculations reproduce the same features as the original study, including the metastable crystallization of graphite in the region of stability of diamond. The phase diagram thus obtained, including the temperatures at which we observe spontaneous crystallization of graphite and diamond, is shown in Figure S2 of the SI. The results are discussed in the main text, in the section on the phase diagram and spontaneous crystallization. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 850, 143]]<|/det|> +In passing, we need to point out that our results differ from the phase diagram published by Marchant et al. [npj Comput. Mater. Sci. 2023], which were obtained with simulations of very small cells, a method subject to much larger statistical uncertainties. + +<|ref|>sub_title<|/ref|><|det|>[[115, 162, 437, 180]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 198, 879, 364]]<|/det|> +The article "Metastability and Ostwald Step Rule in the Crystallisation of Diamond and Graphite from Molten Carbon" by Davide Donadio et al applies molecular dynamics simulations based on first- principles machine learning potentials to reveal the microscopic mechanisms of diamond and graphite nucleation from liquid carbon. The most important finding of this article is that at high pressures (10.5 \~ 15 GPa) in the thermodynamically stable region of diamond, liquid carbon preferentially forms metastable graphite rather than diamond through non- classical nucleation paths, following Ostwald's step rule. The article may be of interest to a wide range of specialists working in the field of earth and planetary science and materials manufacturing, and deserves publication in Nature Communications. But I have two concerns. + +<|ref|>text<|/ref|><|det|>[[115, 382, 860, 456]]<|/det|> +1. Liquid carbon contains different local atomic structures around the GDL triple point, it is necessary to verify that whether the NEP3 potential is suitable to model the structure of liquid carbon. In the supplementary materials, the structural and elastic properties of graphite and diamond are listed, the structural properties of liquid carbon should also be listed. + +<|ref|>text<|/ref|><|det|>[[114, 474, 880, 565]]<|/det|> +A detailed analysis of the structure of liquid carbon has been added to the paper (Figures S3, S4, and S5 in the Supporting Information). These properties are consistent with previous studies. In particular, the NEP models reflect the differences previously observed in the structure and density of liquid carbon between LDA and GGA functionals (see references 32, 33 and 36). + +<|ref|>text<|/ref|><|det|>[[115, 566, 866, 657]]<|/det|> +These differences, which lead to quantitative differences in the phase diagram, may be reconciled by shifting either the pressure or the density. Except for this pressure offset, the physical behavior of the liquid is qualitatively the same in the two models. A direct comparison with experiments suggests that the correct equation of state of the liquid is between those calculated (see Figure S3). + +<|ref|>text<|/ref|><|det|>[[114, 676, 872, 804]]<|/det|> +2. The authors claim that spontaneous crystallisation of diamond and graphite was observed in direct MD simulations of liquid carbon at constant pressure, in which the temperature was ramped from 5,000 K to 3,500 K in 25 ns, corresponding to a cooling rate of 60 K/ns. In Figure 1a, there are eight spontaneous crystallization points, and the authors should clearly show how the initial liquid was obtained and whether the liquid reached equilibrium in the eight isobaric simulations, especially the three points between 10.0 and 15.0 GPa. This could clarify whether the findings were related to the initial liquid structure. + +<|ref|>text<|/ref|><|det|>[[115, 822, 871, 877]]<|/det|> +The quenching simulations are initiated from liquid models equilibrated for at least 2 ns at 5000 K at each pressure. These are the same models that have been used to characterize the structure of liquid carbon. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 513, 107]]<|/det|> +3. In Page 8, Figure 2(a-c) should be Figure 2(d-f). + +<|ref|>text<|/ref|><|det|>[[115, 126, 483, 143]]<|/det|> +We have corrected the reference to the figure. + +<|ref|>text<|/ref|><|det|>[[115, 162, 354, 179]]<|/det|> +4. Reference 23 is incomplete. + +<|ref|>text<|/ref|><|det|>[[115, 199, 362, 215]]<|/det|> +We checked all the references. + +<|ref|>sub_title<|/ref|><|det|>[[115, 235, 437, 253]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 272, 881, 400]]<|/det|> +The authors performed a range of simulations to study the crystallisation of carbon, particularly around the graphite- diamond- liquid triple point, where experimental measurements are inconclusive. To enable accurate behaviour of the model, they trained a machine learning based potential, and studied the phase behaviour and transitions, as well as the formation of critical nuclei under different pressure conditions. The manuscript is clearly written, the calculations appear to be carefully conducted with appropriate conditions drawn. I thus recommend the manuscript to be published, with a few minor details to be potentially considered by the authors: + +<|ref|>text<|/ref|><|det|>[[115, 418, 840, 492]]<|/det|> +The authors use the spherical harmonic expansion of the atomic environment as order parameter to identify crystalline environments in the simulation - are these the same as the Steinhardt bond order parameters widely used by the community? (https://doi.org/10.1103/PhysRevB.28.784) + +<|ref|>text<|/ref|><|det|>[[115, 510, 872, 620]]<|/det|> +These order parameters are derived from the original formulation in the Steinhardt paper; however, the version used here is "local," i.e., it provides a per- atom order parameter, whereas in the original Physical Review B article, Q6 was defined as a global quantity. The necessity for local order parameters in nucleation studies was recognized in several works around the early 2000s. The exact formulation of the order parameter in this paper is given in Li et al. JCP 2009. To help the readers, we have added a brief description in the Methods section. + +<|ref|>text<|/ref|><|det|>[[115, 639, 872, 729]]<|/det|> +The authors mention that reproducing the negative gradient of the graphite melting line is a challenge and most empirical models, or even ML potentials struggle to reproduce that. While I agree, there is some evidence that the highly accurate EDIP potential [https://doi.org/10.1103/PhysRevB.63.035401] might be able to capture this challenging feature (as shown in Ref 24 of the manuscript). Would the authors be able to comment on that? + +<|ref|>text<|/ref|><|det|>[[115, 748, 872, 820]]<|/det|> +On page 4, we have added a note on the phase diagram computed with EDIP. We also noticed that, while the original LCBOP polarizable model gives a positive slope, the revised version LCBOPII gives a more reasonable melting curve of graphite. We have added a comment and a reference about this, too. + +<|ref|>text<|/ref|><|det|>[[115, 840, 879, 895]]<|/det|> +In case when graphite structures were formed during the nucleation or quenching process, have the authors considered checking or evaluating the different relative orientation or stacking of the graphite sheets (i.e. how the hexagonal rings are positioned relative to each other on different + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 877, 161]]<|/det|> +layers)? While the ground state structure is relatively well described, at higher temperatures a range of various orientations or stackings should appear, each with slightly different free energy - would it be possible to determine if certain arrangements are more likely to be formed or more likely to facilitate the graphite- diamond transition? + +<|ref|>text<|/ref|><|det|>[[114, 198, 872, 327]]<|/det|> +The nuclei form in a highly dynamic state at high temperature. Under these conditions, the free energy differences among different stacking arrangements are below the thermal energy. We have examined the structure of graphite near critical size obtained in our FFS sampling, from which we found graphite nuclei appear to adopt random stacking. This is not surprising as the stacking fault energy of graphite was determined to be \(0.85 \text{mJ / m}^2\) (Rob H. Telling & Malcolm I. Heggie (2003), Philosophical Magazine Letters, 83:7, 411- 421), which is about 2 orders of magnitude smaller than thermal energy (3800K) for one \(1 \text{nm}^2\) area. + +<|ref|>text<|/ref|><|det|>[[114, 345, 880, 436]]<|/det|> +The authors tested different radii for the various descriptors of their ML model, but I couldn't find the actual values they used. For graphite, where van de Waals interactions are important, and the atomic distance between layers is larger than within layers - this could be an important factor (as the authors also partially point out in their description). Could do authors present more details on this aspect of their model (maybe in the SI)? + +<|ref|>text<|/ref|><|det|>[[114, 454, 880, 510]]<|/det|> +The NEP models used in this work are now provided in the data archive. We have tested potentials with 2- body radii from 4.2 to 8 A. We did not observe any significant differences either in the phase diagram or in the crystallization behavior. + +<|ref|>text<|/ref|><|det|>[[114, 529, 880, 602]]<|/det|> +In case of two- phase coexistence simulations, what was the orientation of the graphite structure compared to the liquid interface? One would expect that especially the growth of the solid phase is rather different if the graphite sheets are parallel to the interface than perpendicular. Have the authors considered this? + +<|ref|>text<|/ref|><|det|>[[114, 620, 878, 713]]<|/det|> +We tested configurations with the liquid in contact with the basal plane (0001) and the prismatic armchair plane (11- 20) of graphite. We have chosen to use the prismatic plane because it has a much faster growth and melting kinetics, thus reducing the cost of the simulations. We added a comment about this in the methods section and a figure (Fig. S7) showing both graphite- liquid and graphite- diamond two- phase configurations. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 470, 108]]<|/det|> +## RESPONSE TO REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 127, 402, 143]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 144, 883, 280]]<|/det|> +The data supplemented by the authors dispelled my doubts. It can be seen from the supplementary data that during the spontaneous crystallization simulation, the atomic coordination numbers in all the initial liquids are mainly in triple coordination, and the structure of the liquid changes continuously with the pressure. I think it can be published. However, for the integrity of the data, I think that in Figs. S3- S5 the author should supplement another data that is very close to 15 GPa in Fig. 1 and Fig. S2. Although their initial states were very close, after isobaric cooling, one spontaneously crystallized into a diamond structure and the other spontaneously crystallized into a graphite structure. I think this is very important. + +<|ref|>text<|/ref|><|det|>[[114, 313, 880, 414]]<|/det|> +We agree with the reviewer that showing there is no discontinuity in the structural properties of the liquid at the tipping pressure of diamond nucleation is important. We have added data to Figures S3 and S5 at \(\mathsf{P} = 15.5\mathsf{GPa}\) for the NEP@LDA model and \(\mathsf{P} = 19\mathsf{GPa}\) for the NEP@OptB88- vdW model, which show that there is indeed no discontinuity either in the density or in the coordination of the liquid. We are reluctant to add the 15.5 GPa and the 19 GPa lines to the RDF figures (S4) because they are nearly indistinguishable from the 15 and 20 GPa lines, respectively. + +<|ref|>text<|/ref|><|det|>[[114, 431, 715, 448]]<|/det|> +Figures S3 and S5 and their captions have been updated with this information. + +<--- Page Split ---> diff --git a/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..89c4e62694729fef9acb0e86e67e9e4103d2b0ba --- /dev/null +++ b/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,197 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1. Band structure design of the Schottky Junction APD devices. a. Schematic diagram of the band structure of N-type Schottky junction with symmetric Schottky barrier, where \\(E_{\\mathrm{b1}}\\) and \\(E_{\\mathrm{b2}}\\) represent the built-in electric field direction. b. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing high carrier injection barrier and wide multiplication region at the forward bias case. c. Diagram band structure of a 2D asymmetric N-type Schottky Junction, showing low carrier injection and short multiplication region at the reverse bias case. d. Schematic diagram of the band structure of p-type Schottky junction with symmetric Schottky barrier, where \\(E_{\\mathrm{b3}}\\) and \\(E_{\\mathrm{b4}}\\) represent the built-in electric field direction. e. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing low carrier injection barrier and wide multiplication region at the forward bias case. f. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing high carrier injection barrier and short multiplication region at the reverse bias case. The shaded areas represent the multiplication regions.", + "footnote": [], + "bbox": [ + [ + 180, + 90, + 820, + 430 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R2. a. Typical \\(I - V\\) curve of the Graphene/InSe/Cr device at \\(100\\mathrm{K}\\) , showing completely different breakdown voltages and multiplication factor under positive and negative voltage. \\(V_{\\mathrm{bd - P}}\\) and \\(M_{\\mathrm{P}}\\) represent the positive-biased breakdown voltage and the multiplication factor under the forward-biased voltage, while \\(V_{\\mathrm{bd - N}}\\) and \\(M_{\\mathrm{N}}\\) represent the negative-biased breakdown voltage and the multiplication factor under the negative-biased breakdown voltage. b. Room temperature operation of the Graphene/InSe/Cr device under negative bias.", + "footnote": [], + "bbox": [ + [ + 230, + 225, + 763, + 570 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure R3. Room temperature performance of the GISC-SJ APD. a. I-V characteristics curves of the GISC-SJ APD under the reverse and forward biases in darkness at 300 K. b. The I-V curves at darkness and laser powers from 70.7 fW to 418.7 fW with a laser wavelength of 520 nm at 300 K.", + "footnote": [], + "bbox": [ + [ + 212, + 95, + 785, + 275 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure R4. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).", + "footnote": [], + "bbox": [ + [ + 295, + 88, + 701, + 321 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure R5. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).", + "footnote": [], + "bbox": [ + [ + 293, + 559, + 702, + 792 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Figure R6. a. \\(I - V\\) curves at darkness and laser powers from 70.7 fW to 418.7 fW with a laser wavelength of \\(520 \\mathrm{nm}\\) at room temperature. b. Gain as a function of the operation voltage at the power of 70.7 fW. c. Noise power spectral density of the GISC-SJ APD with different biases as a function of frequency at \\(300 \\mathrm{K}\\) .", + "footnote": [], + "bbox": [ + [ + 180, + 562, + 808, + 698 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Figure R7. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).", + "footnote": [], + "bbox": [ + [ + 293, + 308, + 705, + 544 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Figure R8. Normalized frequency response at different reverse biases when the incident light wavelength is \\(520 \\mathrm{nm}\\) .", + "footnote": [], + "bbox": [ + [ + 313, + 394, + 680, + 622 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Figure R9. a. Calculated fall time does not reach a stable value which is inaccurate, where \\(\\tau_{1}^{\\prime}\\) is inaccurate calculated fall time, \\(\\tau_{i}\\) is accurate calculated fall time. (The bule line represents the square signal curve, the yellow line represents the typical response curve of 2D photodetectors.) b. Response time measurement of photodetector may not reach a stable value under pulse signal, which will lead to an inaccurate result. The inset shows pulse signal. The \\(\\tau_{c}\\) is inaccurate calculated rise time. c. Rise and fall response time of photodetector should be calculated from a complete periodic signal.", + "footnote": [], + "bbox": [ + [ + 186, + 396, + 808, + 530 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Figure R10. a. The \\(I - V\\) curves of the Graphene/InSe/Cr Schottky junction APD in dark and under the light with various power at room temperature. b. The breakdown voltage of the Graphene/InSe/Cr Schottky junction APD as a function of light power.", + "footnote": [], + "bbox": [ + [ + 197, + 118, + 794, + 309 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Figure R1. Band diagrams and transport characteristics of the PN junction and 2D SJ APDs. a, Diagram device structure of a PN junction. b, Band diagram of a PN junction, showing the one-carrier multiplication process and dark current mechanisms. The shaded area represents the multiplication region. TAT and BBT denote trap-assisted tunneling and band-to-band tunneling, respectively. c, I-V curve for the PN APD. \\(I_{\\mathrm{Geiger}}\\) , \\(I_{\\mathrm{Linear}}\\) , and \\(I_{\\mathrm{R}}\\) are the current of the Geiger mode, linear mode, and reversed saturation, respectively. d, e, Diagram device structure and electron band structure of a 2D SJ, showing the carrier multiplication process at the reverse and forward cases. The shaded areas represent the multiplication regions. f, I-V curve of a 2D SJ APD with bilateral avalanche breakdown. \\(I_{\\mathrm{DIR}}\\) denotes the drift current.", + "footnote": [], + "bbox": [ + [ + 197, + 90, + 790, + 563 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Figure R2. Comparison of the breakdown voltage of Cr/InSe/Cr and Cr/InSe/Graphene APD devices with similar thickness. a. Optical image of the Cr/InSe/Graphene device. b. I-V curves of the Cr/InSe/Graphene device showing \\(V_{\\mathrm{bd - P}} = 13.1 \\mathrm{~V}\\) and \\(V_{\\mathrm{bd - N}} = 5.8 \\mathrm{~V}\\) . c. Optical image of the Cr/InSe/Cr device. d. I-V curves of the Cr/InSe/Graphene device showing \\(V_{\\mathrm{bd - N}} = 10.6 \\mathrm{~V}\\) .", + "footnote": [], + "bbox": [ + [ + 204, + 118, + 790, + 494 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Figure R3. The impact of the reduced dimensionality of e-ph coupling on the carrier acceleration and multiplication process.", + "footnote": [], + "bbox": [ + [ + 260, + 559, + 727, + 662 + ] + ], + "page_idx": 24 + } +] \ No newline at end of file diff --git a/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e67ed6380c0f7924a550e2a3ef0dd81c7ad41a2d --- /dev/null +++ b/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,366 @@ + +# nature portfolio + +Peer Review File + +# Bilateral Geiger mode avalanche in InSe Schottky photodiodes + +Corresponding Author: Dr Yan Chen + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The manuscript presented an avalanche photodiode (APD) whose performance might be superior to other 2D material based APDs due to the material choice (InSe & Graphene). However, a lot of essential data is missing, and also measured data is inconsistent overall or at least not organized well. A clear articulation of the specific disruptive application of their APDs is desirable. Some of the key issues are summarized below. + +1. Lack of novelty: + +In reference 6, Schottky barrier engineering using InSe/Graphite is already explored and their APD's performance is comparable to that in this manuscript. Authors also didn't clarify the necessity of their work over the previous work (ref.6). Nature Communications is a high- impact, multidisciplinary journal that seeks to publish significant advances. Must clearly articulate what significant advances/discoveries were made. + +2. Lack of APD's application focus: + +To specify the detection range (wavelength) is crucial when designing optical devices like photodiode since each wavelength range has its own application. For example, O- band and S- band is preferred in telecommunication and Visible range is preferred in medical sensors. Each application requires different detection performance; thus, wavelength selection is crucial. However, in this manuscript the wavelength 520nm is selected without context. Clarification of the reason behind the choice of specific wavelength (520nm) and the target application are desirable. + +3. Missing noise measurements and information: + +This manuscript is about a photodiode which is part of a signal receiver. It is essential to include noise measurement but there is none. In Supplementary Fig. S13, no noise is found despite the seemingly high sampling rate, which seems unrealistic. This can be only possible when excessively high optical power is used to shade the noise. In the figure description, authors argue claim that their APDs can detect 2900 photons based on their measured waveform, which is hard to justify. In order to assess the lowest number of photons one photodiode can detect, optical power must be reduced. Then the noise becomes gradually dominant and the SNR becomes zero. That is when the number of photons can be counted. Also, the noise power density depends on the signal frequency. Moreover, 520 nm range is preferred in health monitoring field, which requires extremely high noise performance. All such essential information is missing. + +4. Missing spectrum response (wavelength & light power) and bandwidth measurement: Please refer to: https://doi.org/10.3390/s22103873 and https://doi.org/10.3389/fmats.2021.736180. Responsivity changes depending on the wavelength. Also, refer to: https://doi.org/10.1002/aem.202300297. Transit time and threshold voltage changes depending on the input light power. See https://doi.org/10.1038/s41566-023-01208-x and https://doi.org/10.1038/s41467-021-22046-x. Bandwidth changes depending on the gain and bias voltage. With all these data, APDs can be assessed. + +5. Missing information on method of M estimation: + +Note that M is highly dependent on the bias voltage which varies with materials. It is therefore unfair to compare different APDs with M. Figure 2f is inappropriate. It is also unclear how M is defined and calculated. Supplementary note only shows + +<--- Page Split ---> + +the relation between M and the impact ionization rate \((\alpha)\) . Did the authors consider the ionization probability? + +6. Missing or inconsistent optical power, wavelength, and temperature conditions: Every measurement should be based on the same condition unless the change is necessary. What is the context to measure the APD at 100 K. Is this APD intended for cryogenic applications? + +## Reviewer #2 + +(Remarks to the Author) + +The authors reported bilateral Geiger mode avalanche in two- dimensional Graphene/InSe/Cr asymmetrical Schottky junction APDs featuring an extremely low breakdown voltage and ultrahigh gain over 107. APD is a practical component for detection of weak light signals and widely used in the fields optical communication, quantum cryptography, and LiDAR and so on. However, conventional semiconductor APDs suffer multiple detrimental shortcomings, such as ultra- high threshold voltage of tens of voltages and an ultra- large dark current, which increases their cost of design, fabrication and energy consumption, and impedes their practicality aspects. To resolve these issues, the authors give an interesting alternative route to reduce the breakdown voltage while maintain an ultra- high multiplication gain where an asymmetrical Schottky junction structures built from Graphene/InSe and Cr/InSe are proposed and designed. These devices show some interesting results, such as avalanche breakdown at room temperature, an extremely low level of dark current of 100 fA, positive temperature coefficient of the ionization rate, and an ultralow critical electric field of \(11.5\mathrm{kV / cm}\) , an extremely low breakdown voltage of \(1.4\mathrm{V}\) close to the limit of the energy band, and ultrahigh gain of \(6.3\times 107\) . A few photons down to 2900 can be detected in these APDs. The findings in this study appear to shed insights that can potentially motivate subsequent investigation. In my opinion, therefore, this is an interesting work with some important results, and could be published in Nature Communications after appropriate minor revisions. + +1. The authors are suggested to carefully examine the figures and correct several mistakes in the revised manuscript. For example, in Fig. 1d and 1e, the polarity is mistakenly reserved. +2. In Fig. 3d, the symmetrical Cr/InSe/Cr devices can well perform a steady avalanche breakdown with a low breakdown voltage. Why choosing the asymmetrical Cr/InSe/Graphene device structure rather than the symmetrical structure? The authors should elaborate this point in the revised manuscript. +3. A positive temperature coefficient of the ionization rate and a critical electric field of \(11.5\mathrm{kV / cm}\) are found in the Cr/InSe/Graphene APD. The working mechanism should be discussed in details. +4. I found some typos and grammatic errors, which should be corrected in the revised version. +5. In the discussion part of the current manuscript, some more relevant references should be added as well. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The authors have adequately addressed my technical questions. + +Reviewer #2 + +(Remarks to the Author) Since all my comments have been addressed by the authors, I have no further questions. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +We have studied the reviewer's reports carefully and made responses to those comments point by point in response letter to the reviewer. According to the reviewers' comments, we have added a lot of experiments, including but not limited to weak light detection, response spectrum, noise tests and bandwidth test. We are very grateful to the reviewers for their valuable comments, which helped us improve the quality of the article. + +The modifications in the manuscript and supplementary information are highlighted with yellow for reviewer #1 and blue for reviewer #2 in the file "Revised Manuscript- Marked Up" and "Revised Supplementary Information- Marked Up". The newly supplemented experiments and explanations of the experimental methods have been marked in green. + +We appreciate the editor and Reviewers' warm work earnestly and hope that the correction will meet with approval. + +## Response letter to the reviewers + +## Reviewer #1: + +The manuscript presented an avalanche photodiode (APD) whose performance might be superior to other 2D material based APDs due to the material choice (InSe & Graphene). However, a lot of essential data is missing, and also measured data is inconsistent overall or at least not organized well. A clear articulation of the specific disruptive application of their APDs is desirable. Some of the key issues are summarized below. + +Response: We appreciate the reviewer for professional constructive comments to help us revise the manuscript. We noticed that your main concerns related to the application scenarios and key data characterizing the performance of APD devices. We agree that some essential data should be supplemented to conduct a comprehensive assessment of the performance of APD devices. According to your suggestions, we have supplemented the experiments, such as weak light (few photons) detection, response spectrum, bandwidth and noise, and added corresponding descriptions in the revised + +<--- Page Split ---> + +manuscript and supplementary versions. We sincerely hope that our reply and the revised manuscript can solve your concerns. + +## 1. Lack of novelty: + +In reference 6, Schottky barrier engineering using InSe/Graphite is already explored and their APD's performance is comparable to that in this manuscript. Authors also didn't clarify the necessity of their work over the previous work (ref.6). Nature Communications is a high- impact, multidisciplinary journal that seeks to publish significant advances. Must clearly articulate what significant advances/discoveries were made. + +Response: Thank you for your comment. According to your suggestion, we have addressed novelties on device structures and operation principles, significant advances in detection performance such as extremely low breakdown voltage \(V_{\mathrm{bd}}\) and ultrahigh multiplication factor M, and significant discoveries with expanded response range to short- wavelength near infrared, ultralow noise equivalent power (NEP), high bandwidth and few photons detection. Moreover, we have added the corresponding descriptions in the introduction section of the main text about the necessity of carrying out our work (page 4, line 67- 80). The novelties of this work are also given as follows: + +(1) Unique device structure and work principle: Graphene/InSe/Cr asymmetric Schottky junction APD devices are designed, where p-type InSe conducting behavior from intrinsic bipolar InSe is achieved along with the different work functions of the Graphene, InSe and Cr, and thus the work principle is different from that of the n-type Graphite/InSe devices in Ref. Based on the unique device structure and work principle, therefore, the bilateral asymmetric Geiger mode avalanche phenomenon is observed. We detail these as follows, and corresponding descriptions are also given in the revised manuscript and supplementary version. + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Figure R1. Band structure design of the Schottky Junction APD devices. a. Schematic diagram of the band structure of N-type Schottky junction with symmetric Schottky barrier, where \(E_{\mathrm{b1}}\) and \(E_{\mathrm{b2}}\) represent the built-in electric field direction. b. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing high carrier injection barrier and wide multiplication region at the forward bias case. c. Diagram band structure of a 2D asymmetric N-type Schottky Junction, showing low carrier injection and short multiplication region at the reverse bias case. d. Schematic diagram of the band structure of p-type Schottky junction with symmetric Schottky barrier, where \(E_{\mathrm{b3}}\) and \(E_{\mathrm{b4}}\) represent the built-in electric field direction. e. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing low carrier injection barrier and wide multiplication region at the forward bias case. f. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing high carrier injection barrier and short multiplication region at the reverse bias case. The shaded areas represent the multiplication regions.
+ +As shown in Figure R1a and R1c, the N- type Schottky junction and the P- type Schottky junction show different working mechanisms due to the different directions of the built- in electric field and the types of carriers. For N- type Schottky junction devices, electrons are majority carriers. As shown in Figure R1a, when applying negative voltage to the device, electrons pass through the Schottky barrier. Because the + +<--- Page Split ---> + +direction of the applied electric field is opposite to the built- in electric field of the device \((E_{\mathrm{b1}})\) , electrons pass through the Schottky barrier \((\Phi_{1})\) and trigger carrier avalanche multiplication here. For P- type Schottky junction devices, holes are majority carriers. As shown in figure R1c, when applying negative voltage to the device, holes pass through the Schottky barrier. Since the direction of the applied electric field is the same as that of the built- in electric field on the hole injection side \((E_{\mathrm{b4}})\) . Holes do not trigger avalanches on the injection Schottky junction side but at another Schottky junction side. Compared with the N- type Schottky junction APD, the carrier injection region and avalanche region of the P- type Schottky junction APD are separate. To realize a higher gain at a lower \(V_{\mathrm{bd}}\) , the forward- biased Schottky junction is designed with a lower barrier height \((\Phi_{\mathrm{L}})\) for carriers to be injected easily, while the reverse- biased Schottky junction owns a higher barrier \((\Phi_{\mathrm{H}})\) to provide a strong built- in electrical field and a longer multiplication region for carriers to proceed multiple times impact ionization. It can be seen that this design is expected to be achieved in the P- type asymmetric Schottky junction (Figure R1e). + +Herein, the p- type InSe is selected and asymmetric low work function metal chromium (Cr) and medium work function graphene were adopted. The Schottky barrier height of Cr/InSe and Graphene/InSe are \(540\mathrm{mV}\) and \(180\mathrm{mV}\) respectively. In this work, the barrier difference between the two Schottky junctions is much larger than that in Ref. 6. The higher reverse barrier could also restrain the reverse leakage current, which may support room temperature operation. It can be seen in Figure R2 that the asymmetrical Schottky junction APD (Figure R2a) and the symmetric Schottky junction APD ((Figure R2b)) exhibit significantly different breakdown characteristics under forward and reverse bias, which confirms above statement in Figure R1. Figure R2b show the typical \(I - V\) curves of the Graphene/InSe/Cr Schottky junction APD, which show completely different breakdown voltages and multiplication factor under positive and negative voltage. The device can achieve an ultra- high multiplication factor \((6.3\times 10^{7})\) at a low breakdown voltage (5.0 V). Such performance is much better than that of the Graphite/InSe APD, other 2D APDs and traditional APDs. (Refer to the device performance comparison table presented in later response to Comment 5). + +<--- Page Split ---> + +Besides, our device can work well at room temperature, as shown in Figure R2b. In contrast, the InSe/Graphite APD reported in Ref. 6 is N- type Schottky junction APD, with the heights of the two Schottky barriers being \(150\mathrm{mV}\) and \(200\mathrm{mV}\) respectively. It realized a gain of \(3\times 10^{5}\) at \(5.5\mathrm{V}\) with the light wavelength of \(532\mathrm{nm}\) , while it needs to operate at a low temperature of \(160\mathrm{K}\) . + +![](images/Figure_unknown_1.jpg) + +
Figure R2. a. Typical \(I - V\) curve of the Graphene/InSe/Cr device at \(100\mathrm{K}\) , showing completely different breakdown voltages and multiplication factor under positive and negative voltage. \(V_{\mathrm{bd - P}}\) and \(M_{\mathrm{P}}\) represent the positive-biased breakdown voltage and the multiplication factor under the forward-biased voltage, while \(V_{\mathrm{bd - N}}\) and \(M_{\mathrm{N}}\) represent the negative-biased breakdown voltage and the multiplication factor under the negative-biased breakdown voltage. b. Room temperature operation of the Graphene/InSe/Cr device under negative bias.
+ +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Figure R3. Room temperature performance of the GISC-SJ APD. a. I-V characteristics curves of the GISC-SJ APD under the reverse and forward biases in darkness at 300 K. b. The I-V curves at darkness and laser powers from 70.7 fW to 418.7 fW with a laser wavelength of 520 nm at 300 K.
+ +(2) Multi-mode operation mechanisms are demonstrated: A combination of internal photoemission (IPE) effect and avalanche multiplication effect are found in the Graphene/InSe/Cr APD devices. + +Generally, the detection range of a photodetectors is restricted by the band gap of semiconductor materials, thereby limiting the application scenarios of the devices. The band gap of multi-layer InSe is \(1.25 \mathrm{eV}\) , and the corresponding cutoff wavelength is \(992 \mathrm{nm}\) . It is very difficult to apply InSe materials to the detection of short-wave infrared band light, such as \(1550 \mathrm{nm}\) . In this work, we demonstrated that the internal photoemission effect can be combined with the avalanche multiplication effect in Graphene/InSe/Cr devices to greatly enhance the response of the device's ultra-bandgap part, thereby enabling the device to achieve ultra-sensitive detection over a wide spectral range of \(520 - 1550 \mathrm{nm}\) (Figure R4). + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Figure R4. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).
+ +## 2. Lack of APD's application focus: + +To specify the detection range (wavelength) is crucial when designing optical devices like photodiode since each wavelength range has its own application. For example, O- band and S- band is preferred in telecommunication and Visible range is preferred in medical sensors. Each application requires different detection performance; thus, wavelength selection is crucial. However, in this manuscript the wavelength \(520 \mathrm{nm}\) is selected without context. Clarification of the reason behind the choice of specific wavelength ( \(520 \mathrm{nm}\) ) and the target application are desirable. + +Response: Thank you for your valuable suggestions. According to your suggestion, we have added the descriptions of the device detection wavelength selectivity in the revised tex. (page 13, line 316- 323) + +For photodetectors, improving the responsivity, detectivity, and response speed, reducing the operating voltage, and expanding the response spectral range are all of great significance. The band gap of InSe material is \(1.25 \mathrm{eV}\) , and the response range is mainly in the visible light and near- infrared light part (cut off wavelength \(\sim 992 \mathrm{nm}\) ). As shown in Figure R5, Graphene/InSe/Cr devices show the strongest photoresponse at \(520 \mathrm{nm}\) . Therefore, in order to study the weak light detection ability of the InSe APD + +<--- Page Split ---> + +device, the \(520~\mathrm{nm}\) was selected. Besides, photodetectors responding to \(520~\mathrm{nm}\) band light have significant applications in multiple fields, including biomedicine and health monitoring, environmental and agricultural sensing, industrial and consumer electronics, optical communication and optical sensing, laser measurement, security and anti- counterfeiting, etc. + +A wider spectral response for a photodetector is important and meaningful since expanding the response spectrum of the device can enhance its application potential. Wavelength of \(1550~\mathrm{nm}\) has the characteristics of low transmission loss, human eye safety and strong atmospheric penetration ability. Therefore, photodetectors responding to light in the \(1550~\mathrm{nm}\) band have key applications in multiple fields, such as optical fiber communication systems, lidar, quantum communication and sensing, defense and space applications, medical and biological imaging, etc. By combining IPE effect and avalanche multiplication effect in the Graphene/InSe/Cr device, we studied the response performance of the device in the wide spectral range of \(520 - 1550~\mathrm{nm}\) . As can be seen in Figure R5, the avalanche mode can increase the responsivity of the device by 5 to 7 orders of magnitude compared with the photovoltaic mode. Thereby enabling the device realized highly sensitive detection over a wide spectral range at APD mode. + +![](images/Figure_unknown_4.jpg) + +
Figure R5. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).
+ +In this work, we focus on the common problems existing in current APD devices, + +<--- Page Split ---> + +such as high breakdown voltage, low gain, high dark current, and the need of cooling operation, to conduct new devices rather than the specific applications of the APD devices. In the future research work, we will combine the actual application requirements and the current research foundation of InSe SJ APD to carry out research work on the application of specific wavelengths. + +## 3. Missing noise measurements and information: + +This manuscript is about a photodiode which is part of a signal receiver. It is essential to include noise measurement but there is none. In Supplementary Fig. S13, no noise is found despite the seemingly high sampling rate, which seems unrealistic. This can be only possible when excessively high optical power is used to shade the noise. In the figure description, authors argue claim that their APDs can detect 2900 photons based on their measured waveform, which is hard to justify. In order to assess the lowest number of photons one photodiode can detect, optical power must be reduced. Then the noise becomes gradually dominant and the SNR becomes zero. That is when the number of photons can be counted. Also, the noise power density depends on the signal frequency. Moreover, 520 nm range is preferred in health monitoring field, which requires extremely high noise performance. All such essential information is missing. + +Response: Thank you for your valuable suggestions. + +In the previous test, due to the limitations of the laser power meter, it could only calibrate the power at the pW level. Therefore, we only measured up to \(5.9\mathrm{pW}\) in the previous variable power test. According to your suggestion, we tested the photoresponse of the APD device at tens of fW of light power by trying a new power calibration method. It can be seen in figure R6a the GISC- SJ APD can respond to an optical power as low as \(70.7\mathrm{fw}\) at \(520\mathrm{nm}\) . Laser illumination precipitates earlier photocurrent avalanche onset and the avalanche breakdown voltage decreases from 2.6 to \(1.8\mathrm{V}\) with the increase of the light power from \(70.7\) to \(418.7\mathrm{fW}\) . The GISC- SJ APD also achieved an ultrahigh level of \(3.5\times 10^{6}\) of the GISC- SJ APDs (Figure R6c), which is larger than those of other 2D materials APDs. The Gain of the stepwise WSe \(_2\) homojunctions is only 470, which can detect \(7.7\times 10^{4}\) photons signals (Nat. Commun., + +<--- Page Split ---> + +2024, 15(1): 3639. ). In InSe/BP heterojunctions, 6000 photons signals are distinguished with the Gain of \(3 \times 10^{4}\) (Nat. nanotechnol., 2019, 14(3): 217. ). The ultrahigh Gain of \(3 \times 10^{5}\) avails the detection of 360 photons (equivalent to \(6.9 \mathrm{pW}\) ) in Graphite/InSe detectors (Adv. Mat., 2022, 34(47): 2206196. ). Herein, the GISC- SJ APDs with Gain of \(3.5 \times 10^{6}\) well support the few photons ( \(\sim 35\) photons) detection. + +Besides, we characterized the noise of the device according to your suggestions. The noise power spectrum of the GISC- SJ APD at varying operating voltages was assessed, as shown in Figure R4. It can be seen that the noise shapes of the device before and after avalanche are significantly different. The noise after the avalanche is mainly 1/f noise, which is similar to the noise currents of previously reported InSe/BP and Ni/WSe2/Pt APDs. (Nat. nanotechnol., 2019, 14(3): 217. Nano Lett., 2024, 24(42): 13255) The measured noise current ( \(I_{\mathrm{noise}}\) ) at \(1 \mathrm{Hz}\) is \(1.9 \times 10^{- 7} \mathrm{A} \mathrm{Hz}^{- 1 / 2}\) under the bias voltage of - 3 V. The noise equivalent power (NEP) is calculated using: \(NEP = I_{\mathrm{noise}} / R\) , where \(R\) is the responsivity of the photodetector. The Graphene/InSe/Cr Schottky Junction APD achieves a low NEP of \(39.6 \mathrm{fW} \mathrm{Hz}^{- 1 / 2}\) at \(300 \mathrm{K}\) . This value is comparable to the those of single- photon detectors demonstrating the excellent few photons detection capability of our APD devices (Nature, 2024, 627(8003): 295). + +![](images/Figure_unknown_5.jpg) + +
Figure R6. a. \(I - V\) curves at darkness and laser powers from 70.7 fW to 418.7 fW with a laser wavelength of \(520 \mathrm{nm}\) at room temperature. b. Gain as a function of the operation voltage at the power of 70.7 fW. c. Noise power spectral density of the GISC-SJ APD with different biases as a function of frequency at \(300 \mathrm{K}\) .
+ +4. Missing spectrum response (wavelength & light power) and bandwidth measurement: Please refer to: https://doi.org/10.3390/s22103873 and https://doi.org/10.3389/fmats.2021.736180. + +<--- Page Split ---> + +Responsivity changes depending on the wavelength. Also, refer to: https://doi.org/10.1002/aelm.202300297. Transit time and threshold voltage changes depending on the input light power. See https://doi.org/10.1038/s41566- 023- 01208- x and https://doi.org/10.1038/s41467- 021- 22046- x. Bandwidth changes depending on the gain and bias voltage. With all these data, APDs can be assessed. + +Response: Thank you for your valuable comments. + +![](images/Figure_unknown_6.jpg) + +
Figure R7. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).
+ +Spectrum response: According to your suggestions, we presented the responsivity spectra of the device (Figure R7) and the bandwidths under different bias voltage conditions (Figure R8). It can be seen that the device can achieve a wide spectral range response from \(520 \mathrm{nm}\) to \(1550 \mathrm{nm}\) . This phenomenon should be attributed to the internal photoelectron emission (IPE) effect. (ACS Photonics, 2022, 9(1): 282; InfoMat, 2022, 4(6): e12309; Adv. Sci., 2022, 9(21): 2200642.) For light beyond the cut- off wavelength of InSe, if the energy of hot electrons emitted from Cr (Graphene) is higher than the Schottky barrier at the interface of the Cr/InSe and Graphene/InSe junction ( \(0.5 \mathrm{hv} > \phi_{\mathrm{SBH}}\) ), photoexcited hot electrons directly transport over the barrier and form photocurrent. However, the responsivity of the near- infrared part is very weak due to + +<--- Page Split ---> + +the typically quite low quantum efficiencies of IPE effect (Opt. Express, 2023, 31(15): 25220). The responsivity of the device at PV mode for \(1550 \mathrm{nm}\) is \(3.7 \mathrm{nA / W}\) . However, by increasing the bias voltage to make the device work in the avalanche mode, the responsivity of the device can be greatly enhanced. The responsivity of the device at APD mode for \(1550 \mathrm{nm}\) is \(66.9 \mathrm{mA / W}\) , which is enhanced about 7 orders of magnitude compared with that of PV mode. + +Bandwidth: According to your suggestions, we tested the bandwidth of the device under different bias voltages as shown in the Figure R8. It can be seen that the 3 dB bandwidth increase abruptly after breakdown, which is due to rf enhancement effect. (Sensors, 2022, 22(10): 3873. Appl. Phys. Lett., 2003, 83(6): 1249. ) The 3 dB bandwidth obtained is \(121 \mathrm{kHz}\) when biased at - 3 V. + +![](images/Figure_unknown_7.jpg) + +
Figure R8. Normalized frequency response at different reverse biases when the incident light wavelength is \(520 \mathrm{nm}\) .
+ +Transit time (Response time): For the time parameter of 2D photodetectors, the time required for the output current of the photodetector to rise to a stable response value or to fall to the response value before irradiation is the response time \((\tau)\) . The rising/falling time is defined as the total time needed for the photocurrent to rise (fall) from \(10\%\) (90%) to \(90\%\) (10%) of the peak. The rising time and falling time of the photodetectors usually depends on the carrier generation time, transport time, recombination time, and the external circuit time constant. When measuring the response time of the photodetector, the rise time and fall time are not calculated from a complete response + +<--- Page Split ---> + +cycle signal, or the output response signal does not rise or fall to a stable value. The response signal of the photodetector may be not the stable response value, which is not a standardized measurement and can lead to an underestimation of the result (Figure R a and b). (Nat. Commun., 2023, 14(1): 2224. ) For the article mentioned by the reviewer (Adv. Electron. Mater., 2023, 9(11): 2300297. ), there is trapping and de-trapping effects due to high structure defect density and high oxygen vacancy density. Obviously, under low light power, the response of the device has not reached a stable state. The response time of our device at 0 V was measured when the device response was in a stable state, which is consistent with that in Figure. The result can reflect the true response speed of the device and such testing method is commonly adopted in 2D devices. (Nat. Commun., 2024, 15(1): 3639. Nat. Electron., 2021, 4(5): 357). + +![](images/Figure_unknown_8.jpg) + +
Figure R9. a. Calculated fall time does not reach a stable value which is inaccurate, where \(\tau_{1}^{\prime}\) is inaccurate calculated fall time, \(\tau_{i}\) is accurate calculated fall time. (The bule line represents the square signal curve, the yellow line represents the typical response curve of 2D photodetectors.) b. Response time measurement of photodetector may not reach a stable value under pulse signal, which will lead to an inaccurate result. The inset shows pulse signal. The \(\tau_{c}\) is inaccurate calculated rise time. c. Rise and fall response time of photodetector should be calculated from a complete periodic signal.
+ +Threshold voltage (breakdown voltage): The breakdown voltage of an APD device usually refers to the voltage value at the point where the current changes sharply in the dark state. When the device is exposed to light, photogenerated carriers will trigger an avalanche in advance, resulting in a decrease in the breakdown voltage of the device. As the light power increases, more photo- induced carriers are generated, activating the avalanche at a lower voltage. As can be seen in Figure R10, the breakdown voltage of + +<--- Page Split ---> + +the device decreased from \(2.9 \mathrm{V}\) to \(1.8 \mathrm{V}\) with the increase of light power. + +![](images/Figure_unknown_9.jpg) + +
Figure R10. a. The \(I - V\) curves of the Graphene/InSe/Cr Schottky junction APD in dark and under the light with various power at room temperature. b. The breakdown voltage of the Graphene/InSe/Cr Schottky junction APD as a function of light power.
+ +5. Missing information on method of M estimation: + +Note that M is highly dependent on the bias voltage which varies with materials. It is therefore unfair to compare different APDs with M. Figure 2f is inappropriate. It is also unclear how M is defined and calculated. Supplementary note only shows the relation between M and the impact ionization rate (a). Did the authors consider the ionization probability? + +Response: Thank you for your comment. The multiplication factor is also known as the avalanche gain, which is often used to evaluate the avalanche gain of devices in darkness. The multiplication factor (M) is obtained by the equation: \(\mathrm{M} = I / I_{\mathrm{sat}}\) , where \(I_{\mathrm{sat}}\) is the current at \(V_{\mathrm{bd}}\) and \(I\) is the current above \(V_{\mathrm{bd}}\) . (Nano lett., 2015, 15(5): 3048; Small, 2019, 15(38): 1805352). The avalanche gain (G) is calculated by the formula, \(\mathrm{G} = (I_{\mathrm{ph}} - I_{\mathrm{dark}}) / (I_{\mathrm{ph0}} - I_{\mathrm{dark0}})\) , which is often used to evaluate the avalanche gain of device under light illumination (Nat. nanotechnol., 2019, 14(5): 473; Sensors, 2022, 22(10): 3873). Here \(I_{\mathrm{ph}}\) and \(I_{\mathrm{dark}}\) denote the photocurrent and dark current, and \(I_{\mathrm{ph0}}\) and \(I_{\mathrm{dark0}}\) are the photocurrent and dark currents with \(G = 1\) . In order to conduct a relatively fair comparison of the \(M\) (G) values of different avalanche diodes, we have provided detailed information in a table regarding the operating temperature, breakdown voltage + +<--- Page Split ---> + +\((V_{\mathrm{bd}})\) , dark current \((I_{\mathrm{dark}})\) , \(M(G)\) , and the voltage value \((V_{\mathrm{d}})\) used for calculating \(M(G)\) of each device in table R1. + +Impact ionization rate \((\alpha)\) is an important parameter describing the avalanche multiplication phenomenon in a semiconductor material, which is defined as the number of generated electron- hole pairs by an initial charge carrier per unit distance traveled (ACS nano, 2022, 16(4): 5376- 5383). The impact ionization probability and impact ionization cross- section are two physical quantities that describe the process of impact ionization. The impact ionization probability is defined as the reciprocal of the average distance required for the generation of new electron- hole pairs due to collision ionization (Solid- State Electron., 1990, 33(6): 705; Solid- State Electron., 1976, 19(1): 57; WDM Technologies. Academic Press, 2002: 379). It is the average number of electron- hole pairs generated per unit distance along the direction of the electric field due to collision ionization. In order to generate impact ionization, the energy of the carriers must be equal to or greater than the collision ionization threshold energy \(E_{\mathrm{th,n}}\) . If the energy of the carrier is exactly equal to \(E_{\mathrm{th,n}}\) , then the ionization cross- section of this carrier is defined as zero. When it is higher than \(E_{\mathrm{th,n}}\) , considering the density of states, and since there are three final state particles after ionization, its ionization cross- section is a function that increases rapidly with the electron energy. Obviously, the probability of electron impact ionization per unit time along the direction of the electric field is proportional to its ionization cross- section. Therefore, the impact ionization rates of electrons \((\alpha_{\mathrm{n}})\) and holes \((\alpha_{\mathrm{p}})\) can be expressed as: + +\[\begin{array}{l}{{\alpha_{n}=\frac{q|E|}{E_{l h,n}}\left[\exp\left(\frac{-E_{l h,n}}{q|E|I_{l n}}\right)\right]}}\\ {{\alpha_{p}=\frac{q|E|}{E_{l h,p}}\left[\exp\left(\frac{-E_{l h,p}}{q|E|I_{l p}}\right)\right]}}\end{array} \quad (R1)\] + +where \(l_{n}\) and \(l_{p}\) represent the mean free path of electrons and holes, \(qE / E_{l h,n}\) is the reciprocal of \(l_{n}\) , so it is the impact ionization probability. The exponential term is the probability that the energy of the electron reaches the collision ionization threshold energy. However, solving this equation analytically is difficult. + +When avalanche multiplication occurs in a junction denoted as \(0 \leq x \leq L\) , then the relationship between the multiplication factor \(M\) and the impact ionization rate \(\alpha\) is + +<--- Page Split ---> + +given as the following equation (ACS nano, 2022, 16(4): 5376): + +\[1 - \frac{1}{M} = \int_{0}^{L}\alpha_{n}(E)\exp \left\{-\int_{0}^{x}\alpha_{n}(E) - \alpha_{p}(E)\mathrm{d}x\right\}\mathrm{d}x \quad (R3)\] + +It is assumed that the impact ionization rates of electrons and holes are comparable. And this assumption does not influence the final result critically. With this assumption, the relationship between the multiplication factor M and the impact ionization rate \(\alpha\) is given by the equation + +\[1 - \frac{1}{M} = \int_{0}^{L}\alpha (E)\mathrm{d}x \quad (R4)\] + +Note that \(E\) can be a function of \(x\) . In addition, it is assumed that the electric field in the channel does not depend on the position \(x\) . Then, the \(x\) - dependence of \(\alpha\) disappears, and we obtain the equation + +\[1 - \frac{1}{M} = L\alpha \quad (R5)\] + +which is the relation we used to calculate \(\alpha\) from M. + +Table R1. Summary of the \(M\) and breakdown voltage reported in this work and previous literatures with different types of material. + +
MaterialTemp. (K)Vbd (V)Idark (A)M @ VdRef.
Si30040-6×106 @ 40 V1
Si/Ge30010.31×10-101.2×102 @ 10.3 V2
InGaAs/InP22561.01×10-111.0×105 @ 61.0 V3
InAlAsSb30019.61×10-77.0×103 @ 19.6 V4
InAlAsSb/GaSb30045.01×10-61.5×102 @ 45.0 V5
WSe2/MoS23006.55×10-101.0×103 @ 30 V6
WSe23001.61×10-114.7×102 @ 3 V7
WSe2300241×10-145.0×105 @ 24 V8
MoS21004.51×10-121.2×103 @ 10 V9
Graphite/InSe/Ti1605.11×10-123×105 @ 5.1 V10
Graphene/InSe/Cr1003.91×10-132.3×107 @ 3.9 VThis work
Graphene/InSe/Cr3002.91×10-113.6×106 @ 3 VThis work
+ +[1] Hamamatsu S16835 series. https://www.hamamatsu.com.cn/cn/zhcn/product/optical-sensors/mppc/spad/S16835-050DG.html + +<--- Page Split ---> + +[2] Na, NL, et al. Room temperature operation of germanium- silicon single- photon avalanche diode. Nature. 627, 295- 300(2024). + +[3] Signorelli, F, et al. Low- Noise InGaAs/InP Single- Photon Avalanche Diodes for Fiber- Based and Free- Space Applications. IEEE J. Sel. Top. Quantum. Electron. 28, 1- 10(2022). + +[4] Chen, D, et al. Photon- trapping- enhanced avalanche photodiodes for mid- infrared applications. Nat. Photonics 7, 594- 600(2023). + +[5] Jones, AH, et al. Low- noise high- temperature AlInAsSb/GaSb avalanche photodiodes for 2- μm applications. Nat. Photonics 14, 559- 563(2020). + +[6] Son, B, et al. Efficient Avalanche Photodiodes with a WSe₂/MoS₂ Heterostructure via Two- Photon Absorption. Nano Lett. 22, 9616- 9522(2022). + +[7] Wang, H, et al. Room- temperature low- threshold avalanche effect in stepwise vander- Waals homojunction photodiodes. Nat. Commun. 15, 3639(2024). + +[8] Li, X, et al. Achieving a Noise Limit with a Few- layer WSe₂ Avalanche Photodetector at Room Temperature. Nano Lett. 24, 13255- 13262(2024). + +[9] Xia, H, et al. Pristine PN junction toward atomic layer devices. Light. Sci. Appl. 11, 170(2022). + +[10] Zhang, Z, et al. Approaching intrinsic threshold breakdown voltage and ultra- high gain in graphite/InSe Schottky photodetector. Adv Mater, e2206196(2022). + +6. Missing or inconsistent optical power, wavelength, and temperature conditions: + +Every measurement should be based on the same condition unless the change is necessary. What is the context to measure the APD at 100 K. Is this APD intended for cryogenic applications? + +Response: Thank you for your valuable questions. + +Wavelength and Optical power: Since the quantum efficiency of IPE effect is very low, in order to achieve a significant optical response, the optical power used in the response tests at 1270, 1450, and 1550 nm is relatively strong, but the power magnitudes remain consistent. Correspondingly, the power used in the response tests of 520, 638, 830, 940, and 1064nm is relatively small, and the power magnitudes remain the same. Besides, due to the obvious difference in the photoresponse performance of the devices before and after the avalanche. The optical power used in photovoltaic mode testing and avalanche mode testing is also different. To characterize the detection performance of the device in detail, two representative wavelengths, 520nm and 1550nm, were selected and the variable power response characteristics of the device were tested. + +Temperature: The final application of the Graphene/InSe/Cr Schottky junction APD + +<--- Page Split ---> + +is intended for room temperature operation. However, there are inevitably some defects in the InSe, which will produce non- ideal factors such as trap- assisted tunneling current under strong electric fields and high operating temperatures. At low temperatures, the thermionic exaction and thermal field emission induced carrier injection is greatly suppressed. At this time, the \(I - V\) curve can better reflect the influence of the asymmetric Schottky barrier height on the breakdown voltage. Therefore, the \(I - V\) curves were measured at \(100\mathrm{K}\) to illustrate the asymmetric electrical characteristics of the Graphene/InSe/Cr Schottky junction APD. According to your suggestions, we have added instructions for conducting tests using different temperatures in the text (page 8, line 171- 173). Regarding the photoresponse data at \(100\mathrm{K}\) , we replaced it with the supplementary data measured at room temperature to ensure the consistency of the photoresponse data and the test conditions. (revised supplementary version: Fig. S12 and S13). + +## Reviewer #2: + +The authors reported bilateral Geiger mode avalanche in two- dimensional Graphene/InSe/Cr asymmetrical Schottky junction APDs featuring an extremely low breakdown voltage and ultrahigh gain over \(10^{7}\) . APD is a practical component for detection of weak light signals and widely used in the fields optical communication, quantum cryptography, and LiDAR and so on. However, conventional semiconductor APDs suffer multiple detrimental shortcomings, such as ultra- high threshold voltage of tens of voltages and an ultra- large dark current, which increases their cost of design, fabrication and energy consumption, and impedes their practicality aspects. To resolve these issues, the authors give an interesting alternative route to reduce the breakdown voltage while maintain an ultra- high multiplication gain where an asymmetrical Schottky junction structures built from Graphene/InSe and Cr/InSe are proposed and designed. These devices show some interesting results, such as avalanche breakdown at room temperature, an extremely low level of dark current of \(100\mathrm{fA}\) , positive temperature coefficient of the ionization rate, and an ultralow critical electric field of \(11.5\mathrm{kV / cm}\) , an extremely low breakdown voltage of \(1.4\mathrm{V}\) close to the limit of the energy band, and ultrahigh gain of \(6.3\times 10^{7}\) . A few photons down to \(2900\mathrm{can}\) be + +<--- Page Split ---> + +detected in these APDs. The findings in this study appear to shed insights that can potentially motivate subsequent investigation. In my opinion, therefore, this is an interesting work with some important results, and could be published in Nature Communications after appropriate minor revisions. + +Thank you for your summary. We really appreciate your efforts in reviewing our manuscript, which is important for us to improve the quality of the work. Regarding the flaws in the article you pointed out, we have revised the manuscript accordingly. Our point- by- point responses are detailed below: + +1. The authors are suggested to carefully examine the figures and correct several mistakes in the revised manuscript. For example, in Fig. 1d and 1e, the polarity is mistakenly reserved. + +Response: Thanks for your comment. According to your reminder, we have modified the band structure of the device at different bias voltages as shown in the Figure R1d and R1e. + +<--- Page Split ---> +![](images/Figure_unknown_10.jpg) + +
Figure R1. Band diagrams and transport characteristics of the PN junction and 2D SJ APDs. a, Diagram device structure of a PN junction. b, Band diagram of a PN junction, showing the one-carrier multiplication process and dark current mechanisms. The shaded area represents the multiplication region. TAT and BBT denote trap-assisted tunneling and band-to-band tunneling, respectively. c, I-V curve for the PN APD. \(I_{\mathrm{Geiger}}\) , \(I_{\mathrm{Linear}}\) , and \(I_{\mathrm{R}}\) are the current of the Geiger mode, linear mode, and reversed saturation, respectively. d, e, Diagram device structure and electron band structure of a 2D SJ, showing the carrier multiplication process at the reverse and forward cases. The shaded areas represent the multiplication regions. f, I-V curve of a 2D SJ APD with bilateral avalanche breakdown. \(I_{\mathrm{DIR}}\) denotes the drift current.
+ +2. In Fig. 3d, the symmetrical Cr/InSe/Cr devices can well perform a steady avalanche breakdown with a low breakdown voltage. Why choosing the asymmetrical Cr/InSe/Graphene device structure rather than the symmetrical structure? The authors + +<--- Page Split ---> + +should elaborate this point in the revised manuscript. + +![](images/Figure_unknown_11.jpg) + +
Figure R2. Comparison of the breakdown voltage of Cr/InSe/Cr and Cr/InSe/Graphene APD devices with similar thickness. a. Optical image of the Cr/InSe/Graphene device. b. I-V curves of the Cr/InSe/Graphene device showing \(V_{\mathrm{bd - P}} = 13.1 \mathrm{~V}\) and \(V_{\mathrm{bd - N}} = 5.8 \mathrm{~V}\) . c. Optical image of the Cr/InSe/Cr device. d. I-V curves of the Cr/InSe/Graphene device showing \(V_{\mathrm{bd - N}} = 10.6 \mathrm{~V}\) .
+ +Response: Thanks for your question. It should be pointed out that the carrier multiplication in our asymmetrical Schottky junction APDs is triggered by the majority carriers. Therefore, the Schottky barrier height also affects the breakdown voltage of the device since the high Schottky barrier is difficult for carriers to be injected and trigger impact ionization. Compared with symmetrical structure, it is an efficient route to optimize the \(V_{\mathrm{bd}}\) by construction of an asymmetrical Schottky junction. As shown in Figure R2, for the Cr/InSe/Cr and Cr/InSe/Graphene devices with a similar InSe thickness, the breakdown voltage of the former is \(10.6 \mathrm{~V}\) and the latter are \(13.1 \mathrm{~V}\) at negative bias and \(5.8 \mathrm{~V}\) at positive bias. This result demonstrate that the performance of asymmetric Schottky barrier structures is better compared with the symmetrical structure under the same conditions. (page 10, line 246) + +<--- Page Split ---> + +Furthermore, the substrate also has a great influence on the performance of 2D material. In order to evaluate the intrinsic critical breakdown field of InSe material as accurately as possible, we fabricated Cr/InSe/Cr devices on hBN substrate to reduce the influence of Si/SiO₂ substrate on performance. Therefore, the symmetrical Cr/InSe/Cr devices can also perform a steady avalanche breakdown with a low breakdown voltage. However, under the same conditions, we believe that the performance of asymmetric Schottky barrier structure devices will be better. + +3. A positive temperature coefficient of the ionization rate and a critical electric field of \(11.5\mathrm{kV / cm}\) are found in the Cr/InSe/Graphene APD. The working mechanism should be discussed in details. + +Response: Thank you for your valuable suggestion. In layered 2D materials, there is a large vdW gap \((E_{\mathrm{vdWg}})\) presented between the interlayers and the \(E_{\mathrm{vdWg}}\) of InSe is 1.85 eV (Figure R3). It can well undertake a large potential barrier, and thus avail the in- plane carrier movement and suppresses the out- of- plane charge transport. Compared to the multiplication processes of traditional materials APDs, hence, 2D materials lose less energy related to the quantum confinement effect with the aid of the \(E_{\mathrm{vdWg}}\) , and the \(V_{\mathrm{bd}}\) dramatically drops in 2D APDs. + +![](images/Figure_unknown_12.jpg) + +
Figure R3. The impact of the reduced dimensionality of e-ph coupling on the carrier acceleration and multiplication process.
+ +For 2D layered APD devices, low temperature reduces lattice vibrations and phonon scattering in the material, and also lowers the saturation velocity of carriers and induces longer mean free path. However, during the 2D APD impact ionization process, phonon scattering has been suppressed by the interlayer potential barrier. Therefore, the influence of temperature variation on the thermal saturation velocity and mean free path of carriers is greater. This implies that the higher thermal carriers \(V_{\mathrm{sat}}\) and shorter mean free path defeat overwhelmingly the phonon scattering, and thus enhance impact + +<--- Page Split ---> + +possibility and dominate the avalanche processes at a higher temperature. The higher the temperature, the more likely the carriers are to collide and ionize. Therefore, a positive temperature coefficient of the ionization rate is found in the Cr/InSe/Graphene APD. + +4. I found some typos and grammatic errors, which should be corrected in the revised version. + +Response: Thank you for your careful review. We are very sorry for the mistakes in this manuscript and inconvenience they caused in your reading. We have thoroughly checked the format and grammar of the article and made corrections to the following mistakes. + +"The reverse leakage current could also be further restrained by constructing a higher and broader Schottky barrier." (page 5, line 110- 112) + +"In the APDs built from two SJs sitting back- to- back architecture, carriers need to conquer the first forward- biased barrier and arrive at the reverse- biased SJ." (page 5, line 113- 114) + +"To realize a higher gain at a lower \(V_{\mathrm{bd}}\) , the forward- biased SJ is designed with a lower barrier height for carriers to be easily injected. While the reverse- biased SJ has a higher barrier to provide a strong built- in electrical field and a longer multiplication region for carriers to proceed multiple times impact ionization." (page 5 and 6, line 114- 118) + +5. In the discussion part of the current manuscript, some more relevant references should be added as well. + +Response: We sincerely appreciate the valuable comments. We have checked the literature carefully and added more references in the discussion part of the revised manuscript. (page 5, line 97; page 13, line 321\335\339\354) + +<--- Page Split ---> diff --git a/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..aa9c6db4eda72dd66ab3bffd7de6f0c18778cc97 --- /dev/null +++ b/peer_reviews/5624700480c717ffac5d89aef1fa0dbf27713d41971584385dc636002591d8ef/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,475 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 757, 210]]<|/det|> +# Bilateral Geiger mode avalanche in InSe Schottky photodiodes + +<|ref|>text<|/ref|><|det|>[[73, 224, 387, 240]]<|/det|> +Corresponding Author: Dr Yan Chen + +<|ref|>text<|/ref|><|det|>[[72, 275, 864, 290]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 327, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 354, 220, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 418, 911, 470]]<|/det|> +The manuscript presented an avalanche photodiode (APD) whose performance might be superior to other 2D material based APDs due to the material choice (InSe & Graphene). However, a lot of essential data is missing, and also measured data is inconsistent overall or at least not organized well. A clear articulation of the specific disruptive application of their APDs is desirable. Some of the key issues are summarized below. + +<|ref|>text<|/ref|><|det|>[[73, 483, 198, 496]]<|/det|> +1. Lack of novelty: + +<|ref|>text<|/ref|><|det|>[[73, 496, 905, 549]]<|/det|> +In reference 6, Schottky barrier engineering using InSe/Graphite is already explored and their APD's performance is comparable to that in this manuscript. Authors also didn't clarify the necessity of their work over the previous work (ref.6). Nature Communications is a high- impact, multidisciplinary journal that seeks to publish significant advances. Must clearly articulate what significant advances/discoveries were made. + +<|ref|>text<|/ref|><|det|>[[73, 562, 312, 575]]<|/det|> +2. Lack of APD's application focus: + +<|ref|>text<|/ref|><|det|>[[72, 575, 918, 640]]<|/det|> +To specify the detection range (wavelength) is crucial when designing optical devices like photodiode since each wavelength range has its own application. For example, O- band and S- band is preferred in telecommunication and Visible range is preferred in medical sensors. Each application requires different detection performance; thus, wavelength selection is crucial. However, in this manuscript the wavelength 520nm is selected without context. Clarification of the reason behind the choice of specific wavelength (520nm) and the target application are desirable. + +<|ref|>text<|/ref|><|det|>[[73, 653, 406, 666]]<|/det|> +3. Missing noise measurements and information: + +<|ref|>text<|/ref|><|det|>[[72, 666, 920, 771]]<|/det|> +This manuscript is about a photodiode which is part of a signal receiver. It is essential to include noise measurement but there is none. In Supplementary Fig. S13, no noise is found despite the seemingly high sampling rate, which seems unrealistic. This can be only possible when excessively high optical power is used to shade the noise. In the figure description, authors argue claim that their APDs can detect 2900 photons based on their measured waveform, which is hard to justify. In order to assess the lowest number of photons one photodiode can detect, optical power must be reduced. Then the noise becomes gradually dominant and the SNR becomes zero. That is when the number of photons can be counted. Also, the noise power density depends on the signal frequency. Moreover, 520 nm range is preferred in health monitoring field, which requires extremely high noise performance. All such essential information is missing. + +<|ref|>text<|/ref|><|det|>[[72, 783, 740, 885]]<|/det|> +4. Missing spectrum response (wavelength & light power) and bandwidth measurement: Please refer to: https://doi.org/10.3390/s22103873 and https://doi.org/10.3389/fmats.2021.736180. Responsivity changes depending on the wavelength. Also, refer to: https://doi.org/10.1002/aem.202300297. Transit time and threshold voltage changes depending on the input light power. See https://doi.org/10.1038/s41566-023-01208-x and https://doi.org/10.1038/s41467-021-22046-x. Bandwidth changes depending on the gain and bias voltage. With all these data, APDs can be assessed. + +<|ref|>text<|/ref|><|det|>[[72, 899, 411, 911]]<|/det|> +5. Missing information on method of M estimation: + +<|ref|>text<|/ref|><|det|>[[70, 912, 915, 939]]<|/det|> +Note that M is highly dependent on the bias voltage which varies with materials. It is therefore unfair to compare different APDs with M. Figure 2f is inappropriate. It is also unclear how M is defined and calculated. Supplementary note only shows + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 814, 62]]<|/det|> +the relation between M and the impact ionization rate \((\alpha)\) . Did the authors consider the ionization probability? + +<|ref|>text<|/ref|><|det|>[[72, 73, 930, 115]]<|/det|> +6. Missing or inconsistent optical power, wavelength, and temperature conditions: Every measurement should be based on the same condition unless the change is necessary. What is the context to measure the APD at 100 K. Is this APD intended for cryogenic applications? + +<|ref|>sub_title<|/ref|><|det|>[[73, 139, 162, 152]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 164, 238, 178]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[71, 178, 924, 360]]<|/det|> +The authors reported bilateral Geiger mode avalanche in two- dimensional Graphene/InSe/Cr asymmetrical Schottky junction APDs featuring an extremely low breakdown voltage and ultrahigh gain over 107. APD is a practical component for detection of weak light signals and widely used in the fields optical communication, quantum cryptography, and LiDAR and so on. However, conventional semiconductor APDs suffer multiple detrimental shortcomings, such as ultra- high threshold voltage of tens of voltages and an ultra- large dark current, which increases their cost of design, fabrication and energy consumption, and impedes their practicality aspects. To resolve these issues, the authors give an interesting alternative route to reduce the breakdown voltage while maintain an ultra- high multiplication gain where an asymmetrical Schottky junction structures built from Graphene/InSe and Cr/InSe are proposed and designed. These devices show some interesting results, such as avalanche breakdown at room temperature, an extremely low level of dark current of 100 fA, positive temperature coefficient of the ionization rate, and an ultralow critical electric field of \(11.5\mathrm{kV / cm}\) , an extremely low breakdown voltage of \(1.4\mathrm{V}\) close to the limit of the energy band, and ultrahigh gain of \(6.3\times 107\) . A few photons down to 2900 can be detected in these APDs. The findings in this study appear to shed insights that can potentially motivate subsequent investigation. In my opinion, therefore, this is an interesting work with some important results, and could be published in Nature Communications after appropriate minor revisions. + +<|ref|>text<|/ref|><|det|>[[70, 371, 900, 490]]<|/det|> +1. The authors are suggested to carefully examine the figures and correct several mistakes in the revised manuscript. For example, in Fig. 1d and 1e, the polarity is mistakenly reserved. +2. In Fig. 3d, the symmetrical Cr/InSe/Cr devices can well perform a steady avalanche breakdown with a low breakdown voltage. Why choosing the asymmetrical Cr/InSe/Graphene device structure rather than the symmetrical structure? The authors should elaborate this point in the revised manuscript. +3. A positive temperature coefficient of the ionization rate and a critical electric field of \(11.5\mathrm{kV / cm}\) are found in the Cr/InSe/Graphene APD. The working mechanism should be discussed in details. +4. I found some typos and grammatic errors, which should be corrected in the revised version. +5. In the discussion part of the current manuscript, some more relevant references should be added as well. + +<|ref|>text<|/ref|><|det|>[[72, 501, 145, 514]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 528, 219, 542]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 554, 160, 568]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 580, 516, 608]]<|/det|> +(Remarks to the Author) The authors have adequately addressed my technical questions. + +<|ref|>text<|/ref|><|det|>[[72, 620, 161, 633]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 646, 672, 674]]<|/det|> +(Remarks to the Author) Since all my comments have been addressed by the authors, I have no further questions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 89, 821, 246]]<|/det|> +We have studied the reviewer's reports carefully and made responses to those comments point by point in response letter to the reviewer. According to the reviewers' comments, we have added a lot of experiments, including but not limited to weak light detection, response spectrum, noise tests and bandwidth test. We are very grateful to the reviewers for their valuable comments, which helped us improve the quality of the article. + +<|ref|>text<|/ref|><|det|>[[177, 256, 821, 386]]<|/det|> +The modifications in the manuscript and supplementary information are highlighted with yellow for reviewer #1 and blue for reviewer #2 in the file "Revised Manuscript- Marked Up" and "Revised Supplementary Information- Marked Up". The newly supplemented experiments and explanations of the experimental methods have been marked in green. + +<|ref|>text<|/ref|><|det|>[[178, 394, 820, 440]]<|/det|> +We appreciate the editor and Reviewers' warm work earnestly and hope that the correction will meet with approval. + +<|ref|>sub_title<|/ref|><|det|>[[372, 506, 624, 523]]<|/det|> +## Response letter to the reviewers + +<|ref|>sub_title<|/ref|><|det|>[[178, 533, 286, 550]]<|/det|> +## Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[177, 560, 821, 719]]<|/det|> +The manuscript presented an avalanche photodiode (APD) whose performance might be superior to other 2D material based APDs due to the material choice (InSe & Graphene). However, a lot of essential data is missing, and also measured data is inconsistent overall or at least not organized well. A clear articulation of the specific disruptive application of their APDs is desirable. Some of the key issues are summarized below. + +<|ref|>text<|/ref|><|det|>[[177, 727, 821, 913]]<|/det|> +Response: We appreciate the reviewer for professional constructive comments to help us revise the manuscript. We noticed that your main concerns related to the application scenarios and key data characterizing the performance of APD devices. We agree that some essential data should be supplemented to conduct a comprehensive assessment of the performance of APD devices. According to your suggestions, we have supplemented the experiments, such as weak light (few photons) detection, response spectrum, bandwidth and noise, and added corresponding descriptions in the revised + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 90, 819, 135]]<|/det|> +manuscript and supplementary versions. We sincerely hope that our reply and the revised manuscript can solve your concerns. + +<|ref|>sub_title<|/ref|><|det|>[[179, 173, 316, 190]]<|/det|> +## 1. Lack of novelty: + +<|ref|>text<|/ref|><|det|>[[177, 199, 821, 357]]<|/det|> +In reference 6, Schottky barrier engineering using InSe/Graphite is already explored and their APD's performance is comparable to that in this manuscript. Authors also didn't clarify the necessity of their work over the previous work (ref.6). Nature Communications is a high- impact, multidisciplinary journal that seeks to publish significant advances. Must clearly articulate what significant advances/discoveries were made. + +<|ref|>text<|/ref|><|det|>[[177, 366, 822, 580]]<|/det|> +Response: Thank you for your comment. According to your suggestion, we have addressed novelties on device structures and operation principles, significant advances in detection performance such as extremely low breakdown voltage \(V_{\mathrm{bd}}\) and ultrahigh multiplication factor M, and significant discoveries with expanded response range to short- wavelength near infrared, ultralow noise equivalent power (NEP), high bandwidth and few photons detection. Moreover, we have added the corresponding descriptions in the introduction section of the main text about the necessity of carrying out our work (page 4, line 67- 80). The novelties of this work are also given as follows: + +<|ref|>text<|/ref|><|det|>[[178, 588, 822, 830]]<|/det|> +(1) Unique device structure and work principle: Graphene/InSe/Cr asymmetric Schottky junction APD devices are designed, where p-type InSe conducting behavior from intrinsic bipolar InSe is achieved along with the different work functions of the Graphene, InSe and Cr, and thus the work principle is different from that of the n-type Graphite/InSe devices in Ref. Based on the unique device structure and work principle, therefore, the bilateral asymmetric Geiger mode avalanche phenomenon is observed. We detail these as follows, and corresponding descriptions are also given in the revised manuscript and supplementary version. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[180, 90, 820, 430]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 441, 822, 764]]<|/det|> +
Figure R1. Band structure design of the Schottky Junction APD devices. a. Schematic diagram of the band structure of N-type Schottky junction with symmetric Schottky barrier, where \(E_{\mathrm{b1}}\) and \(E_{\mathrm{b2}}\) represent the built-in electric field direction. b. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing high carrier injection barrier and wide multiplication region at the forward bias case. c. Diagram band structure of a 2D asymmetric N-type Schottky Junction, showing low carrier injection and short multiplication region at the reverse bias case. d. Schematic diagram of the band structure of p-type Schottky junction with symmetric Schottky barrier, where \(E_{\mathrm{b3}}\) and \(E_{\mathrm{b4}}\) represent the built-in electric field direction. e. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing low carrier injection barrier and wide multiplication region at the forward bias case. f. Diagram band structure of a 2D asymmetric PN-type Schottky Junction, showing high carrier injection barrier and short multiplication region at the reverse bias case. The shaded areas represent the multiplication regions.
+ +<|ref|>text<|/ref|><|det|>[[177, 774, 821, 905]]<|/det|> +As shown in Figure R1a and R1c, the N- type Schottky junction and the P- type Schottky junction show different working mechanisms due to the different directions of the built- in electric field and the types of carriers. For N- type Schottky junction devices, electrons are majority carriers. As shown in Figure R1a, when applying negative voltage to the device, electrons pass through the Schottky barrier. Because the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 87, 822, 498]]<|/det|> +direction of the applied electric field is opposite to the built- in electric field of the device \((E_{\mathrm{b1}})\) , electrons pass through the Schottky barrier \((\Phi_{1})\) and trigger carrier avalanche multiplication here. For P- type Schottky junction devices, holes are majority carriers. As shown in figure R1c, when applying negative voltage to the device, holes pass through the Schottky barrier. Since the direction of the applied electric field is the same as that of the built- in electric field on the hole injection side \((E_{\mathrm{b4}})\) . Holes do not trigger avalanches on the injection Schottky junction side but at another Schottky junction side. Compared with the N- type Schottky junction APD, the carrier injection region and avalanche region of the P- type Schottky junction APD are separate. To realize a higher gain at a lower \(V_{\mathrm{bd}}\) , the forward- biased Schottky junction is designed with a lower barrier height \((\Phi_{\mathrm{L}})\) for carriers to be injected easily, while the reverse- biased Schottky junction owns a higher barrier \((\Phi_{\mathrm{H}})\) to provide a strong built- in electrical field and a longer multiplication region for carriers to proceed multiple times impact ionization. It can be seen that this design is expected to be achieved in the P- type asymmetric Schottky junction (Figure R1e). + +<|ref|>text<|/ref|><|det|>[[175, 506, 822, 914]]<|/det|> +Herein, the p- type InSe is selected and asymmetric low work function metal chromium (Cr) and medium work function graphene were adopted. The Schottky barrier height of Cr/InSe and Graphene/InSe are \(540\mathrm{mV}\) and \(180\mathrm{mV}\) respectively. In this work, the barrier difference between the two Schottky junctions is much larger than that in Ref. 6. The higher reverse barrier could also restrain the reverse leakage current, which may support room temperature operation. It can be seen in Figure R2 that the asymmetrical Schottky junction APD (Figure R2a) and the symmetric Schottky junction APD ((Figure R2b)) exhibit significantly different breakdown characteristics under forward and reverse bias, which confirms above statement in Figure R1. Figure R2b show the typical \(I - V\) curves of the Graphene/InSe/Cr Schottky junction APD, which show completely different breakdown voltages and multiplication factor under positive and negative voltage. The device can achieve an ultra- high multiplication factor \((6.3\times 10^{7})\) at a low breakdown voltage (5.0 V). Such performance is much better than that of the Graphite/InSe APD, other 2D APDs and traditional APDs. (Refer to the device performance comparison table presented in later response to Comment 5). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 88, 821, 220]]<|/det|> +Besides, our device can work well at room temperature, as shown in Figure R2b. In contrast, the InSe/Graphite APD reported in Ref. 6 is N- type Schottky junction APD, with the heights of the two Schottky barriers being \(150\mathrm{mV}\) and \(200\mathrm{mV}\) respectively. It realized a gain of \(3\times 10^{5}\) at \(5.5\mathrm{V}\) with the light wavelength of \(532\mathrm{nm}\) , while it needs to operate at a low temperature of \(160\mathrm{K}\) . + +<|ref|>image<|/ref|><|det|>[[230, 225, 763, 570]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 580, 821, 736]]<|/det|> +
Figure R2. a. Typical \(I - V\) curve of the Graphene/InSe/Cr device at \(100\mathrm{K}\) , showing completely different breakdown voltages and multiplication factor under positive and negative voltage. \(V_{\mathrm{bd - P}}\) and \(M_{\mathrm{P}}\) represent the positive-biased breakdown voltage and the multiplication factor under the forward-biased voltage, while \(V_{\mathrm{bd - N}}\) and \(M_{\mathrm{N}}\) represent the negative-biased breakdown voltage and the multiplication factor under the negative-biased breakdown voltage. b. Room temperature operation of the Graphene/InSe/Cr device under negative bias.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[212, 95, 785, 275]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 293, 821, 366]]<|/det|> +
Figure R3. Room temperature performance of the GISC-SJ APD. a. I-V characteristics curves of the GISC-SJ APD under the reverse and forward biases in darkness at 300 K. b. The I-V curves at darkness and laser powers from 70.7 fW to 418.7 fW with a laser wavelength of 520 nm at 300 K.
+ +<|ref|>text<|/ref|><|det|>[[177, 375, 821, 450]]<|/det|> +(2) Multi-mode operation mechanisms are demonstrated: A combination of internal photoemission (IPE) effect and avalanche multiplication effect are found in the Graphene/InSe/Cr APD devices. + +<|ref|>text<|/ref|><|det|>[[176, 459, 822, 700]]<|/det|> +Generally, the detection range of a photodetectors is restricted by the band gap of semiconductor materials, thereby limiting the application scenarios of the devices. The band gap of multi-layer InSe is \(1.25 \mathrm{eV}\) , and the corresponding cutoff wavelength is \(992 \mathrm{nm}\) . It is very difficult to apply InSe materials to the detection of short-wave infrared band light, such as \(1550 \mathrm{nm}\) . In this work, we demonstrated that the internal photoemission effect can be combined with the avalanche multiplication effect in Graphene/InSe/Cr devices to greatly enhance the response of the device's ultra-bandgap part, thereby enabling the device to achieve ultra-sensitive detection over a wide spectral range of \(520 - 1550 \mathrm{nm}\) (Figure R4). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[295, 88, 701, 321]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 330, 820, 403]]<|/det|> +
Figure R4. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).
+ +<|ref|>sub_title<|/ref|><|det|>[[179, 440, 443, 459]]<|/det|> +## 2. Lack of APD's application focus: + +<|ref|>text<|/ref|><|det|>[[177, 467, 821, 655]]<|/det|> +To specify the detection range (wavelength) is crucial when designing optical devices like photodiode since each wavelength range has its own application. For example, O- band and S- band is preferred in telecommunication and Visible range is preferred in medical sensors. Each application requires different detection performance; thus, wavelength selection is crucial. However, in this manuscript the wavelength \(520 \mathrm{nm}\) is selected without context. Clarification of the reason behind the choice of specific wavelength ( \(520 \mathrm{nm}\) ) and the target application are desirable. + +<|ref|>text<|/ref|><|det|>[[177, 663, 820, 737]]<|/det|> +Response: Thank you for your valuable suggestions. According to your suggestion, we have added the descriptions of the device detection wavelength selectivity in the revised tex. (page 13, line 316- 323) + +<|ref|>text<|/ref|><|det|>[[177, 745, 821, 905]]<|/det|> +For photodetectors, improving the responsivity, detectivity, and response speed, reducing the operating voltage, and expanding the response spectral range are all of great significance. The band gap of InSe material is \(1.25 \mathrm{eV}\) , and the response range is mainly in the visible light and near- infrared light part (cut off wavelength \(\sim 992 \mathrm{nm}\) ). As shown in Figure R5, Graphene/InSe/Cr devices show the strongest photoresponse at \(520 \mathrm{nm}\) . Therefore, in order to study the weak light detection ability of the InSe APD + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 821, 220]]<|/det|> +device, the \(520~\mathrm{nm}\) was selected. Besides, photodetectors responding to \(520~\mathrm{nm}\) band light have significant applications in multiple fields, including biomedicine and health monitoring, environmental and agricultural sensing, industrial and consumer electronics, optical communication and optical sensing, laser measurement, security and anti- counterfeiting, etc. + +<|ref|>text<|/ref|><|det|>[[176, 228, 822, 555]]<|/det|> +A wider spectral response for a photodetector is important and meaningful since expanding the response spectrum of the device can enhance its application potential. Wavelength of \(1550~\mathrm{nm}\) has the characteristics of low transmission loss, human eye safety and strong atmospheric penetration ability. Therefore, photodetectors responding to light in the \(1550~\mathrm{nm}\) band have key applications in multiple fields, such as optical fiber communication systems, lidar, quantum communication and sensing, defense and space applications, medical and biological imaging, etc. By combining IPE effect and avalanche multiplication effect in the Graphene/InSe/Cr device, we studied the response performance of the device in the wide spectral range of \(520 - 1550~\mathrm{nm}\) . As can be seen in Figure R5, the avalanche mode can increase the responsivity of the device by 5 to 7 orders of magnitude compared with the photovoltaic mode. Thereby enabling the device realized highly sensitive detection over a wide spectral range at APD mode. + +<|ref|>image<|/ref|><|det|>[[293, 559, 702, 792]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 803, 821, 876]]<|/det|> +
Figure R5. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).
+ +<|ref|>text<|/ref|><|det|>[[211, 886, 818, 905]]<|/det|> +In this work, we focus on the common problems existing in current APD devices, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 821, 219]]<|/det|> +such as high breakdown voltage, low gain, high dark current, and the need of cooling operation, to conduct new devices rather than the specific applications of the APD devices. In the future research work, we will combine the actual application requirements and the current research foundation of InSe SJ APD to carry out research work on the application of specific wavelengths. + +<|ref|>sub_title<|/ref|><|det|>[[178, 255, 539, 273]]<|/det|> +## 3. Missing noise measurements and information: + +<|ref|>text<|/ref|><|det|>[[175, 281, 822, 580]]<|/det|> +This manuscript is about a photodiode which is part of a signal receiver. It is essential to include noise measurement but there is none. In Supplementary Fig. S13, no noise is found despite the seemingly high sampling rate, which seems unrealistic. This can be only possible when excessively high optical power is used to shade the noise. In the figure description, authors argue claim that their APDs can detect 2900 photons based on their measured waveform, which is hard to justify. In order to assess the lowest number of photons one photodiode can detect, optical power must be reduced. Then the noise becomes gradually dominant and the SNR becomes zero. That is when the number of photons can be counted. Also, the noise power density depends on the signal frequency. Moreover, 520 nm range is preferred in health monitoring field, which requires extremely high noise performance. All such essential information is missing. + +<|ref|>text<|/ref|><|det|>[[177, 588, 570, 606]]<|/det|> +Response: Thank you for your valuable suggestions. + +<|ref|>text<|/ref|><|det|>[[176, 615, 821, 913]]<|/det|> +In the previous test, due to the limitations of the laser power meter, it could only calibrate the power at the pW level. Therefore, we only measured up to \(5.9\mathrm{pW}\) in the previous variable power test. According to your suggestion, we tested the photoresponse of the APD device at tens of fW of light power by trying a new power calibration method. It can be seen in figure R6a the GISC- SJ APD can respond to an optical power as low as \(70.7\mathrm{fw}\) at \(520\mathrm{nm}\) . Laser illumination precipitates earlier photocurrent avalanche onset and the avalanche breakdown voltage decreases from 2.6 to \(1.8\mathrm{V}\) with the increase of the light power from \(70.7\) to \(418.7\mathrm{fW}\) . The GISC- SJ APD also achieved an ultrahigh level of \(3.5\times 10^{6}\) of the GISC- SJ APDs (Figure R6c), which is larger than those of other 2D materials APDs. The Gain of the stepwise WSe \(_2\) homojunctions is only 470, which can detect \(7.7\times 10^{4}\) photons signals (Nat. Commun., + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 822, 220]]<|/det|> +2024, 15(1): 3639. ). In InSe/BP heterojunctions, 6000 photons signals are distinguished with the Gain of \(3 \times 10^{4}\) (Nat. nanotechnol., 2019, 14(3): 217. ). The ultrahigh Gain of \(3 \times 10^{5}\) avails the detection of 360 photons (equivalent to \(6.9 \mathrm{pW}\) ) in Graphite/InSe detectors (Adv. Mat., 2022, 34(47): 2206196. ). Herein, the GISC- SJ APDs with Gain of \(3.5 \times 10^{6}\) well support the few photons ( \(\sim 35\) photons) detection. + +<|ref|>text<|/ref|><|det|>[[176, 228, 822, 553]]<|/det|> +Besides, we characterized the noise of the device according to your suggestions. The noise power spectrum of the GISC- SJ APD at varying operating voltages was assessed, as shown in Figure R4. It can be seen that the noise shapes of the device before and after avalanche are significantly different. The noise after the avalanche is mainly 1/f noise, which is similar to the noise currents of previously reported InSe/BP and Ni/WSe2/Pt APDs. (Nat. nanotechnol., 2019, 14(3): 217. Nano Lett., 2024, 24(42): 13255) The measured noise current ( \(I_{\mathrm{noise}}\) ) at \(1 \mathrm{Hz}\) is \(1.9 \times 10^{- 7} \mathrm{A} \mathrm{Hz}^{- 1 / 2}\) under the bias voltage of - 3 V. The noise equivalent power (NEP) is calculated using: \(NEP = I_{\mathrm{noise}} / R\) , where \(R\) is the responsivity of the photodetector. The Graphene/InSe/Cr Schottky Junction APD achieves a low NEP of \(39.6 \mathrm{fW} \mathrm{Hz}^{- 1 / 2}\) at \(300 \mathrm{K}\) . This value is comparable to the those of single- photon detectors demonstrating the excellent few photons detection capability of our APD devices (Nature, 2024, 627(8003): 295). + +<|ref|>image<|/ref|><|det|>[[180, 562, 808, 698]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 710, 821, 810]]<|/det|> +
Figure R6. a. \(I - V\) curves at darkness and laser powers from 70.7 fW to 418.7 fW with a laser wavelength of \(520 \mathrm{nm}\) at room temperature. b. Gain as a function of the operation voltage at the power of 70.7 fW. c. Noise power spectral density of the GISC-SJ APD with different biases as a function of frequency at \(300 \mathrm{K}\) .
+ +<|ref|>text<|/ref|><|det|>[[177, 820, 824, 895]]<|/det|> +4. Missing spectrum response (wavelength & light power) and bandwidth measurement: Please refer to: https://doi.org/10.3390/s22103873 and https://doi.org/10.3389/fmats.2021.736180. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 90, 814, 265]]<|/det|> +Responsivity changes depending on the wavelength. Also, refer to: https://doi.org/10.1002/aelm.202300297. Transit time and threshold voltage changes depending on the input light power. See https://doi.org/10.1038/s41566- 023- 01208- x and https://doi.org/10.1038/s41467- 021- 22046- x. Bandwidth changes depending on the gain and bias voltage. With all these data, APDs can be assessed. + +<|ref|>text<|/ref|><|det|>[[177, 284, 560, 301]]<|/det|> +Response: Thank you for your valuable comments. + +<|ref|>image<|/ref|><|det|>[[293, 308, 705, 544]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 553, 821, 625]]<|/det|> +
Figure R7. Normalized photoresponsivity as a function of the wavelength obtained in the Graphene/InSe/Cr Schottky junction device (red dot line) and the increased ratio of device responsivity in APD mode compared with in photovoltaic (PV) mode (blue dot).
+ +<|ref|>text<|/ref|><|det|>[[176, 636, 822, 906]]<|/det|> +Spectrum response: According to your suggestions, we presented the responsivity spectra of the device (Figure R7) and the bandwidths under different bias voltage conditions (Figure R8). It can be seen that the device can achieve a wide spectral range response from \(520 \mathrm{nm}\) to \(1550 \mathrm{nm}\) . This phenomenon should be attributed to the internal photoelectron emission (IPE) effect. (ACS Photonics, 2022, 9(1): 282; InfoMat, 2022, 4(6): e12309; Adv. Sci., 2022, 9(21): 2200642.) For light beyond the cut- off wavelength of InSe, if the energy of hot electrons emitted from Cr (Graphene) is higher than the Schottky barrier at the interface of the Cr/InSe and Graphene/InSe junction ( \(0.5 \mathrm{hv} > \phi_{\mathrm{SBH}}\) ), photoexcited hot electrons directly transport over the barrier and form photocurrent. However, the responsivity of the near- infrared part is very weak due to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 821, 247]]<|/det|> +the typically quite low quantum efficiencies of IPE effect (Opt. Express, 2023, 31(15): 25220). The responsivity of the device at PV mode for \(1550 \mathrm{nm}\) is \(3.7 \mathrm{nA / W}\) . However, by increasing the bias voltage to make the device work in the avalanche mode, the responsivity of the device can be greatly enhanced. The responsivity of the device at APD mode for \(1550 \mathrm{nm}\) is \(66.9 \mathrm{mA / W}\) , which is enhanced about 7 orders of magnitude compared with that of PV mode. + +<|ref|>text<|/ref|><|det|>[[177, 256, 821, 387]]<|/det|> +Bandwidth: According to your suggestions, we tested the bandwidth of the device under different bias voltages as shown in the Figure R8. It can be seen that the 3 dB bandwidth increase abruptly after breakdown, which is due to rf enhancement effect. (Sensors, 2022, 22(10): 3873. Appl. Phys. Lett., 2003, 83(6): 1249. ) The 3 dB bandwidth obtained is \(121 \mathrm{kHz}\) when biased at - 3 V. + +<|ref|>image<|/ref|><|det|>[[313, 394, 680, 622]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 636, 820, 680]]<|/det|> +
Figure R8. Normalized frequency response at different reverse biases when the incident light wavelength is \(520 \mathrm{nm}\) .
+ +<|ref|>text<|/ref|><|det|>[[177, 690, 821, 905]]<|/det|> +Transit time (Response time): For the time parameter of 2D photodetectors, the time required for the output current of the photodetector to rise to a stable response value or to fall to the response value before irradiation is the response time \((\tau)\) . The rising/falling time is defined as the total time needed for the photocurrent to rise (fall) from \(10\%\) (90%) to \(90\%\) (10%) of the peak. The rising time and falling time of the photodetectors usually depends on the carrier generation time, transport time, recombination time, and the external circuit time constant. When measuring the response time of the photodetector, the rise time and fall time are not calculated from a complete response + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 88, 824, 388]]<|/det|> +cycle signal, or the output response signal does not rise or fall to a stable value. The response signal of the photodetector may be not the stable response value, which is not a standardized measurement and can lead to an underestimation of the result (Figure R a and b). (Nat. Commun., 2023, 14(1): 2224. ) For the article mentioned by the reviewer (Adv. Electron. Mater., 2023, 9(11): 2300297. ), there is trapping and de-trapping effects due to high structure defect density and high oxygen vacancy density. Obviously, under low light power, the response of the device has not reached a stable state. The response time of our device at 0 V was measured when the device response was in a stable state, which is consistent with that in Figure. The result can reflect the true response speed of the device and such testing method is commonly adopted in 2D devices. (Nat. Commun., 2024, 15(1): 3639. Nat. Electron., 2021, 4(5): 357). + +<|ref|>image<|/ref|><|det|>[[186, 396, 808, 530]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 544, 822, 727]]<|/det|> +
Figure R9. a. Calculated fall time does not reach a stable value which is inaccurate, where \(\tau_{1}^{\prime}\) is inaccurate calculated fall time, \(\tau_{i}\) is accurate calculated fall time. (The bule line represents the square signal curve, the yellow line represents the typical response curve of 2D photodetectors.) b. Response time measurement of photodetector may not reach a stable value under pulse signal, which will lead to an inaccurate result. The inset shows pulse signal. The \(\tau_{c}\) is inaccurate calculated rise time. c. Rise and fall response time of photodetector should be calculated from a complete periodic signal.
+ +<|ref|>text<|/ref|><|det|>[[176, 736, 822, 895]]<|/det|> +Threshold voltage (breakdown voltage): The breakdown voltage of an APD device usually refers to the voltage value at the point where the current changes sharply in the dark state. When the device is exposed to light, photogenerated carriers will trigger an avalanche in advance, resulting in a decrease in the breakdown voltage of the device. As the light power increases, more photo- induced carriers are generated, activating the avalanche at a lower voltage. As can be seen in Figure R10, the breakdown voltage of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 90, 723, 108]]<|/det|> +the device decreased from \(2.9 \mathrm{V}\) to \(1.8 \mathrm{V}\) with the increase of light power. + +<|ref|>image<|/ref|><|det|>[[197, 118, 794, 309]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 321, 821, 394]]<|/det|> +
Figure R10. a. The \(I - V\) curves of the Graphene/InSe/Cr Schottky junction APD in dark and under the light with various power at room temperature. b. The breakdown voltage of the Graphene/InSe/Cr Schottky junction APD as a function of light power.
+ +<|ref|>text<|/ref|><|det|>[[177, 431, 557, 450]]<|/det|> +5. Missing information on method of M estimation: + +<|ref|>text<|/ref|><|det|>[[176, 458, 821, 590]]<|/det|> +Note that M is highly dependent on the bias voltage which varies with materials. It is therefore unfair to compare different APDs with M. Figure 2f is inappropriate. It is also unclear how M is defined and calculated. Supplementary note only shows the relation between M and the impact ionization rate (a). Did the authors consider the ionization probability? + +<|ref|>text<|/ref|><|det|>[[175, 597, 821, 896]]<|/det|> +Response: Thank you for your comment. The multiplication factor is also known as the avalanche gain, which is often used to evaluate the avalanche gain of devices in darkness. The multiplication factor (M) is obtained by the equation: \(\mathrm{M} = I / I_{\mathrm{sat}}\) , where \(I_{\mathrm{sat}}\) is the current at \(V_{\mathrm{bd}}\) and \(I\) is the current above \(V_{\mathrm{bd}}\) . (Nano lett., 2015, 15(5): 3048; Small, 2019, 15(38): 1805352). The avalanche gain (G) is calculated by the formula, \(\mathrm{G} = (I_{\mathrm{ph}} - I_{\mathrm{dark}}) / (I_{\mathrm{ph0}} - I_{\mathrm{dark0}})\) , which is often used to evaluate the avalanche gain of device under light illumination (Nat. nanotechnol., 2019, 14(5): 473; Sensors, 2022, 22(10): 3873). Here \(I_{\mathrm{ph}}\) and \(I_{\mathrm{dark}}\) denote the photocurrent and dark current, and \(I_{\mathrm{ph0}}\) and \(I_{\mathrm{dark0}}\) are the photocurrent and dark currents with \(G = 1\) . In order to conduct a relatively fair comparison of the \(M\) (G) values of different avalanche diodes, we have provided detailed information in a table regarding the operating temperature, breakdown voltage + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 89, 819, 135]]<|/det|> +\((V_{\mathrm{bd}})\) , dark current \((I_{\mathrm{dark}})\) , \(M(G)\) , and the voltage value \((V_{\mathrm{d}})\) used for calculating \(M(G)\) of each device in table R1. + +<|ref|>text<|/ref|><|det|>[[175, 144, 823, 664]]<|/det|> +Impact ionization rate \((\alpha)\) is an important parameter describing the avalanche multiplication phenomenon in a semiconductor material, which is defined as the number of generated electron- hole pairs by an initial charge carrier per unit distance traveled (ACS nano, 2022, 16(4): 5376- 5383). The impact ionization probability and impact ionization cross- section are two physical quantities that describe the process of impact ionization. The impact ionization probability is defined as the reciprocal of the average distance required for the generation of new electron- hole pairs due to collision ionization (Solid- State Electron., 1990, 33(6): 705; Solid- State Electron., 1976, 19(1): 57; WDM Technologies. Academic Press, 2002: 379). It is the average number of electron- hole pairs generated per unit distance along the direction of the electric field due to collision ionization. In order to generate impact ionization, the energy of the carriers must be equal to or greater than the collision ionization threshold energy \(E_{\mathrm{th,n}}\) . If the energy of the carrier is exactly equal to \(E_{\mathrm{th,n}}\) , then the ionization cross- section of this carrier is defined as zero. When it is higher than \(E_{\mathrm{th,n}}\) , considering the density of states, and since there are three final state particles after ionization, its ionization cross- section is a function that increases rapidly with the electron energy. Obviously, the probability of electron impact ionization per unit time along the direction of the electric field is proportional to its ionization cross- section. Therefore, the impact ionization rates of electrons \((\alpha_{\mathrm{n}})\) and holes \((\alpha_{\mathrm{p}})\) can be expressed as: + +<|ref|>equation<|/ref|><|det|>[[415, 668, 808, 742]]<|/det|> +\[\begin{array}{l}{{\alpha_{n}=\frac{q|E|}{E_{l h,n}}\left[\exp\left(\frac{-E_{l h,n}}{q|E|I_{l n}}\right)\right]}}\\ {{\alpha_{p}=\frac{q|E|}{E_{l h,p}}\left[\exp\left(\frac{-E_{l h,p}}{q|E|I_{l p}}\right)\right]}}\end{array} \quad (R1)\] + +<|ref|>text<|/ref|><|det|>[[175, 745, 821, 848]]<|/det|> +where \(l_{n}\) and \(l_{p}\) represent the mean free path of electrons and holes, \(qE / E_{l h,n}\) is the reciprocal of \(l_{n}\) , so it is the impact ionization probability. The exponential term is the probability that the energy of the electron reaches the collision ionization threshold energy. However, solving this equation analytically is difficult. + +<|ref|>text<|/ref|><|det|>[[177, 856, 820, 904]]<|/det|> +When avalanche multiplication occurs in a junction denoted as \(0 \leq x \leq L\) , then the relationship between the multiplication factor \(M\) and the impact ionization rate \(\alpha\) is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 90, 650, 107]]<|/det|> +given as the following equation (ACS nano, 2022, 16(4): 5376): + +<|ref|>equation<|/ref|><|det|>[[343, 115, 808, 145]]<|/det|> +\[1 - \frac{1}{M} = \int_{0}^{L}\alpha_{n}(E)\exp \left\{-\int_{0}^{x}\alpha_{n}(E) - \alpha_{p}(E)\mathrm{d}x\right\}\mathrm{d}x \quad (R3)\] + +<|ref|>text<|/ref|><|det|>[[177, 154, 821, 256]]<|/det|> +It is assumed that the impact ionization rates of electrons and holes are comparable. And this assumption does not influence the final result critically. With this assumption, the relationship between the multiplication factor M and the impact ionization rate \(\alpha\) is given by the equation + +<|ref|>equation<|/ref|><|det|>[[425, 264, 812, 293]]<|/det|> +\[1 - \frac{1}{M} = \int_{0}^{L}\alpha (E)\mathrm{d}x \quad (R4)\] + +<|ref|>text<|/ref|><|det|>[[177, 303, 821, 377]]<|/det|> +Note that \(E\) can be a function of \(x\) . In addition, it is assumed that the electric field in the channel does not depend on the position \(x\) . Then, the \(x\) - dependence of \(\alpha\) disappears, and we obtain the equation + +<|ref|>equation<|/ref|><|det|>[[444, 384, 817, 414]]<|/det|> +\[1 - \frac{1}{M} = L\alpha \quad (R5)\] + +<|ref|>text<|/ref|><|det|>[[177, 422, 564, 440]]<|/det|> +which is the relation we used to calculate \(\alpha\) from M. + +<|ref|>table<|/ref|><|det|>[[177, 499, 824, 870]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[177, 450, 820, 496]]<|/det|> +Table R1. Summary of the \(M\) and breakdown voltage reported in this work and previous literatures with different types of material. + +
MaterialTemp. (K)Vbd (V)Idark (A)M @ VdRef.
Si30040-6×106 @ 40 V1
Si/Ge30010.31×10-101.2×102 @ 10.3 V2
InGaAs/InP22561.01×10-111.0×105 @ 61.0 V3
InAlAsSb30019.61×10-77.0×103 @ 19.6 V4
InAlAsSb/GaSb30045.01×10-61.5×102 @ 45.0 V5
WSe2/MoS23006.55×10-101.0×103 @ 30 V6
WSe23001.61×10-114.7×102 @ 3 V7
WSe2300241×10-145.0×105 @ 24 V8
MoS21004.51×10-121.2×103 @ 10 V9
Graphite/InSe/Ti1605.11×10-123×105 @ 5.1 V10
Graphene/InSe/Cr1003.91×10-132.3×107 @ 3.9 VThis work
Graphene/InSe/Cr3002.91×10-113.6×106 @ 3 VThis work
+ +<|ref|>table_footnote<|/ref|><|det|>[[177, 870, 820, 907]]<|/det|> +[1] Hamamatsu S16835 series. https://www.hamamatsu.com.cn/cn/zhcn/product/optical-sensors/mppc/spad/S16835-050DG.html + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 84, 820, 120]]<|/det|> +[2] Na, NL, et al. Room temperature operation of germanium- silicon single- photon avalanche diode. Nature. 627, 295- 300(2024). + +<|ref|>text<|/ref|><|det|>[[176, 121, 820, 177]]<|/det|> +[3] Signorelli, F, et al. Low- Noise InGaAs/InP Single- Photon Avalanche Diodes for Fiber- Based and Free- Space Applications. IEEE J. Sel. Top. Quantum. Electron. 28, 1- 10(2022). + +<|ref|>text<|/ref|><|det|>[[176, 178, 820, 214]]<|/det|> +[4] Chen, D, et al. Photon- trapping- enhanced avalanche photodiodes for mid- infrared applications. Nat. Photonics 7, 594- 600(2023). + +<|ref|>text<|/ref|><|det|>[[176, 215, 820, 252]]<|/det|> +[5] Jones, AH, et al. Low- noise high- temperature AlInAsSb/GaSb avalanche photodiodes for 2- μm applications. Nat. Photonics 14, 559- 563(2020). + +<|ref|>text<|/ref|><|det|>[[176, 252, 820, 288]]<|/det|> +[6] Son, B, et al. Efficient Avalanche Photodiodes with a WSe₂/MoS₂ Heterostructure via Two- Photon Absorption. Nano Lett. 22, 9616- 9522(2022). + +<|ref|>text<|/ref|><|det|>[[176, 289, 820, 325]]<|/det|> +[7] Wang, H, et al. Room- temperature low- threshold avalanche effect in stepwise vander- Waals homojunction photodiodes. Nat. Commun. 15, 3639(2024). + +<|ref|>text<|/ref|><|det|>[[176, 326, 820, 362]]<|/det|> +[8] Li, X, et al. Achieving a Noise Limit with a Few- layer WSe₂ Avalanche Photodetector at Room Temperature. Nano Lett. 24, 13255- 13262(2024). + +<|ref|>text<|/ref|><|det|>[[176, 363, 820, 398]]<|/det|> +[9] Xia, H, et al. Pristine PN junction toward atomic layer devices. Light. Sci. Appl. 11, 170(2022). + +<|ref|>text<|/ref|><|det|>[[176, 400, 820, 437]]<|/det|> +[10] Zhang, Z, et al. Approaching intrinsic threshold breakdown voltage and ultra- high gain in graphite/InSe Schottky photodetector. Adv Mater, e2206196(2022). + +<|ref|>text<|/ref|><|det|>[[176, 441, 785, 459]]<|/det|> +6. Missing or inconsistent optical power, wavelength, and temperature conditions: + +<|ref|>text<|/ref|><|det|>[[176, 468, 820, 541]]<|/det|> +Every measurement should be based on the same condition unless the change is necessary. What is the context to measure the APD at 100 K. Is this APD intended for cryogenic applications? + +<|ref|>text<|/ref|><|det|>[[177, 551, 553, 569]]<|/det|> +Response: Thank you for your valuable questions. + +<|ref|>text<|/ref|><|det|>[[176, 578, 821, 875]]<|/det|> +Wavelength and Optical power: Since the quantum efficiency of IPE effect is very low, in order to achieve a significant optical response, the optical power used in the response tests at 1270, 1450, and 1550 nm is relatively strong, but the power magnitudes remain consistent. Correspondingly, the power used in the response tests of 520, 638, 830, 940, and 1064nm is relatively small, and the power magnitudes remain the same. Besides, due to the obvious difference in the photoresponse performance of the devices before and after the avalanche. The optical power used in photovoltaic mode testing and avalanche mode testing is also different. To characterize the detection performance of the device in detail, two representative wavelengths, 520nm and 1550nm, were selected and the variable power response characteristics of the device were tested. + +<|ref|>text<|/ref|><|det|>[[177, 885, 818, 904]]<|/det|> +Temperature: The final application of the Graphene/InSe/Cr Schottky junction APD + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 88, 821, 441]]<|/det|> +is intended for room temperature operation. However, there are inevitably some defects in the InSe, which will produce non- ideal factors such as trap- assisted tunneling current under strong electric fields and high operating temperatures. At low temperatures, the thermionic exaction and thermal field emission induced carrier injection is greatly suppressed. At this time, the \(I - V\) curve can better reflect the influence of the asymmetric Schottky barrier height on the breakdown voltage. Therefore, the \(I - V\) curves were measured at \(100\mathrm{K}\) to illustrate the asymmetric electrical characteristics of the Graphene/InSe/Cr Schottky junction APD. According to your suggestions, we have added instructions for conducting tests using different temperatures in the text (page 8, line 171- 173). Regarding the photoresponse data at \(100\mathrm{K}\) , we replaced it with the supplementary data measured at room temperature to ensure the consistency of the photoresponse data and the test conditions. (revised supplementary version: Fig. S12 and S13). + +<|ref|>sub_title<|/ref|><|det|>[[215, 451, 323, 468]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[176, 478, 821, 914]]<|/det|> +The authors reported bilateral Geiger mode avalanche in two- dimensional Graphene/InSe/Cr asymmetrical Schottky junction APDs featuring an extremely low breakdown voltage and ultrahigh gain over \(10^{7}\) . APD is a practical component for detection of weak light signals and widely used in the fields optical communication, quantum cryptography, and LiDAR and so on. However, conventional semiconductor APDs suffer multiple detrimental shortcomings, such as ultra- high threshold voltage of tens of voltages and an ultra- large dark current, which increases their cost of design, fabrication and energy consumption, and impedes their practicality aspects. To resolve these issues, the authors give an interesting alternative route to reduce the breakdown voltage while maintain an ultra- high multiplication gain where an asymmetrical Schottky junction structures built from Graphene/InSe and Cr/InSe are proposed and designed. These devices show some interesting results, such as avalanche breakdown at room temperature, an extremely low level of dark current of \(100\mathrm{fA}\) , positive temperature coefficient of the ionization rate, and an ultralow critical electric field of \(11.5\mathrm{kV / cm}\) , an extremely low breakdown voltage of \(1.4\mathrm{V}\) close to the limit of the energy band, and ultrahigh gain of \(6.3\times 10^{7}\) . A few photons down to \(2900\mathrm{can}\) be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 820, 191]]<|/det|> +detected in these APDs. The findings in this study appear to shed insights that can potentially motivate subsequent investigation. In my opinion, therefore, this is an interesting work with some important results, and could be published in Nature Communications after appropriate minor revisions. + +<|ref|>text<|/ref|><|det|>[[177, 199, 820, 303]]<|/det|> +Thank you for your summary. We really appreciate your efforts in reviewing our manuscript, which is important for us to improve the quality of the work. Regarding the flaws in the article you pointed out, we have revised the manuscript accordingly. Our point- by- point responses are detailed below: + +<|ref|>text<|/ref|><|det|>[[177, 311, 820, 385]]<|/det|> +1. The authors are suggested to carefully examine the figures and correct several mistakes in the revised manuscript. For example, in Fig. 1d and 1e, the polarity is mistakenly reserved. + +<|ref|>text<|/ref|><|det|>[[177, 394, 820, 468]]<|/det|> +Response: Thanks for your comment. According to your reminder, we have modified the band structure of the device at different bias voltages as shown in the Figure R1d and R1e. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[197, 90, 790, 563]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 572, 821, 811]]<|/det|> +
Figure R1. Band diagrams and transport characteristics of the PN junction and 2D SJ APDs. a, Diagram device structure of a PN junction. b, Band diagram of a PN junction, showing the one-carrier multiplication process and dark current mechanisms. The shaded area represents the multiplication region. TAT and BBT denote trap-assisted tunneling and band-to-band tunneling, respectively. c, I-V curve for the PN APD. \(I_{\mathrm{Geiger}}\) , \(I_{\mathrm{Linear}}\) , and \(I_{\mathrm{R}}\) are the current of the Geiger mode, linear mode, and reversed saturation, respectively. d, e, Diagram device structure and electron band structure of a 2D SJ, showing the carrier multiplication process at the reverse and forward cases. The shaded areas represent the multiplication regions. f, I-V curve of a 2D SJ APD with bilateral avalanche breakdown. \(I_{\mathrm{DIR}}\) denotes the drift current.
+ +<|ref|>text<|/ref|><|det|>[[177, 821, 820, 895]]<|/det|> +2. In Fig. 3d, the symmetrical Cr/InSe/Cr devices can well perform a steady avalanche breakdown with a low breakdown voltage. Why choosing the asymmetrical Cr/InSe/Graphene device structure rather than the symmetrical structure? The authors + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 91, 570, 108]]<|/det|> +should elaborate this point in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[204, 118, 790, 494]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 506, 822, 607]]<|/det|> +
Figure R2. Comparison of the breakdown voltage of Cr/InSe/Cr and Cr/InSe/Graphene APD devices with similar thickness. a. Optical image of the Cr/InSe/Graphene device. b. I-V curves of the Cr/InSe/Graphene device showing \(V_{\mathrm{bd - P}} = 13.1 \mathrm{~V}\) and \(V_{\mathrm{bd - N}} = 5.8 \mathrm{~V}\) . c. Optical image of the Cr/InSe/Cr device. d. I-V curves of the Cr/InSe/Graphene device showing \(V_{\mathrm{bd - N}} = 10.6 \mathrm{~V}\) .
+ +<|ref|>text<|/ref|><|det|>[[176, 617, 822, 914]]<|/det|> +Response: Thanks for your question. It should be pointed out that the carrier multiplication in our asymmetrical Schottky junction APDs is triggered by the majority carriers. Therefore, the Schottky barrier height also affects the breakdown voltage of the device since the high Schottky barrier is difficult for carriers to be injected and trigger impact ionization. Compared with symmetrical structure, it is an efficient route to optimize the \(V_{\mathrm{bd}}\) by construction of an asymmetrical Schottky junction. As shown in Figure R2, for the Cr/InSe/Cr and Cr/InSe/Graphene devices with a similar InSe thickness, the breakdown voltage of the former is \(10.6 \mathrm{~V}\) and the latter are \(13.1 \mathrm{~V}\) at negative bias and \(5.8 \mathrm{~V}\) at positive bias. This result demonstrate that the performance of asymmetric Schottky barrier structures is better compared with the symmetrical structure under the same conditions. (page 10, line 246) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 90, 821, 274]]<|/det|> +Furthermore, the substrate also has a great influence on the performance of 2D material. In order to evaluate the intrinsic critical breakdown field of InSe material as accurately as possible, we fabricated Cr/InSe/Cr devices on hBN substrate to reduce the influence of Si/SiO₂ substrate on performance. Therefore, the symmetrical Cr/InSe/Cr devices can also perform a steady avalanche breakdown with a low breakdown voltage. However, under the same conditions, we believe that the performance of asymmetric Schottky barrier structure devices will be better. + +<|ref|>text<|/ref|><|det|>[[177, 284, 820, 357]]<|/det|> +3. A positive temperature coefficient of the ionization rate and a critical electric field of \(11.5\mathrm{kV / cm}\) are found in the Cr/InSe/Graphene APD. The working mechanism should be discussed in details. + +<|ref|>text<|/ref|><|det|>[[176, 366, 821, 552]]<|/det|> +Response: Thank you for your valuable suggestion. In layered 2D materials, there is a large vdW gap \((E_{\mathrm{vdWg}})\) presented between the interlayers and the \(E_{\mathrm{vdWg}}\) of InSe is 1.85 eV (Figure R3). It can well undertake a large potential barrier, and thus avail the in- plane carrier movement and suppresses the out- of- plane charge transport. Compared to the multiplication processes of traditional materials APDs, hence, 2D materials lose less energy related to the quantum confinement effect with the aid of the \(E_{\mathrm{vdWg}}\) , and the \(V_{\mathrm{bd}}\) dramatically drops in 2D APDs. + +<|ref|>image<|/ref|><|det|>[[260, 559, 727, 662]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 674, 819, 718]]<|/det|> +
Figure R3. The impact of the reduced dimensionality of e-ph coupling on the carrier acceleration and multiplication process.
+ +<|ref|>text<|/ref|><|det|>[[177, 728, 821, 913]]<|/det|> +For 2D layered APD devices, low temperature reduces lattice vibrations and phonon scattering in the material, and also lowers the saturation velocity of carriers and induces longer mean free path. However, during the 2D APD impact ionization process, phonon scattering has been suppressed by the interlayer potential barrier. Therefore, the influence of temperature variation on the thermal saturation velocity and mean free path of carriers is greater. This implies that the higher thermal carriers \(V_{\mathrm{sat}}\) and shorter mean free path defeat overwhelmingly the phonon scattering, and thus enhance impact + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 820, 190]]<|/det|> +possibility and dominate the avalanche processes at a higher temperature. The higher the temperature, the more likely the carriers are to collide and ionize. Therefore, a positive temperature coefficient of the ionization rate is found in the Cr/InSe/Graphene APD. + +<|ref|>text<|/ref|><|det|>[[177, 200, 819, 245]]<|/det|> +4. I found some typos and grammatic errors, which should be corrected in the revised version. + +<|ref|>text<|/ref|><|det|>[[177, 255, 820, 356]]<|/det|> +Response: Thank you for your careful review. We are very sorry for the mistakes in this manuscript and inconvenience they caused in your reading. We have thoroughly checked the format and grammar of the article and made corrections to the following mistakes. + +<|ref|>text<|/ref|><|det|>[[177, 394, 819, 440]]<|/det|> +"The reverse leakage current could also be further restrained by constructing a higher and broader Schottky barrier." (page 5, line 110- 112) + +<|ref|>text<|/ref|><|det|>[[177, 477, 820, 551]]<|/det|> +"In the APDs built from two SJs sitting back- to- back architecture, carriers need to conquer the first forward- biased barrier and arrive at the reverse- biased SJ." (page 5, line 113- 114) + +<|ref|>text<|/ref|><|det|>[[177, 560, 820, 662]]<|/det|> +"To realize a higher gain at a lower \(V_{\mathrm{bd}}\) , the forward- biased SJ is designed with a lower barrier height for carriers to be easily injected. While the reverse- biased SJ has a higher barrier to provide a strong built- in electrical field and a longer multiplication region for carriers to proceed multiple times impact ionization." (page 5 and 6, line 114- 118) + +<|ref|>text<|/ref|><|det|>[[177, 700, 819, 745]]<|/det|> +5. In the discussion part of the current manuscript, some more relevant references should be added as well. + +<|ref|>text<|/ref|><|det|>[[177, 755, 820, 828]]<|/det|> +Response: We sincerely appreciate the valuable comments. We have checked the literature carefully and added more references in the discussion part of the revised manuscript. (page 5, line 97; page 13, line 321\335\339\354) + +<--- Page Split ---> diff --git a/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..00f3808a9f564cd81e445975131d6c5e21056c71 --- /dev/null +++ b/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,332 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig 1. Temporal dynamics in winter and summer land surface temperature effects of European forests ( \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) and \\(\\Delta \\mathrm{LST}_{\\mathrm{s}}\\) ) in recent two decades.", + "footnote": [], + "bbox": [ + [ + 180, + 536, + 812, + 840 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R1. Comparison of annual temperature, precipitation and radiation means from spatial paired site observations", + "footnote": [], + "bbox": [ + [ + 178, + 652, + 812, + 796 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. R2. Comparison of monthly temperature, precipitation and radiation ranges from spatial paired site observations.", + "footnote": [], + "bbox": [ + [ + 180, + 98, + 816, + 243 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. R3. Correlation of daily temperature precipitation and radiation between spatial paired site observations", + "footnote": [], + "bbox": [ + [ + 170, + 306, + 820, + 454 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_2c.jpg", + "caption": "Fig. R4. Comparison of the results binned by \\(\\mathrm{SC_w}\\) and \\(\\alpha_{\\mathrm{w}}\\) . (a) Spatial relationships between \\(\\mathrm{SC_w}\\) trends and \\(\\alpha_{\\mathrm{w}}\\) trends binned by \\(\\mathrm{SC_w}\\) trends (same as Fig. 2c in the manuscript). (b) Binned by \\(\\alpha_{\\mathrm{w}}\\) trends. (c) Temporal relationships between \\(\\mathrm{SC_w}\\) and \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) (same as Fig. 2e in the manuscript). (b) Temporal relationships between \\(\\Delta \\alpha_{\\mathrm{w}}\\) and \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) .", + "footnote": [], + "bbox": [ + [ + 234, + 480, + 748, + 809 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig 3. Dominant role of soil moisture in the temporal dynamics in the summer daytime cooling effect ( \\(\\Delta \\mathrm{LST}_s\\) ) of forests. (a) Regional mean correlation and partial correlation coefficients between five climate variables (vapor pressure deficit, downward solar radiation, precipitation, air temperature", + "footnote": [], + "bbox": [ + [ + 198, + 553, + 800, + 840 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. S10. Temporal correlation coefficient (r) between summer vapor pressure deficit \\((VPD_s)\\) and surface soil moisture \\((SM_s)\\) . (a) Spatial pattern of r between \\(VPD_s\\) and \\(SM_s\\) . (b) Density of the r values.", + "footnote": [], + "bbox": [ + [ + 201, + 188, + 785, + 333 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. S11. Impact of SM, on the temporal dynamics in \\(\\Delta \\mathrm{LST}_s\\) based on the random forest model. (a) The importance of climate variables is indicated by the absolute SHAP values and Gini coefficients. (b) Variation of SHAP values with changing SM, or VPD, anomaly. (c) Observed and modelled \\(\\Delta \\mathrm{LST}_s\\) trends, and the isolated contributions from climate variables.", + "footnote": [], + "bbox": [ + [ + 273, + 498, + 777, + 820 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig 4. Mechanisms underlying the effects of climate variables on the daytime LST effects of European forests (ALSTs) in summer. (a) Structure equation models describing the biophysical relationships between climate variables and ALSTs. The numbers denote the path value (mean \\(\\pm\\) standard error). The arrow color indicates the sign of the path (red for positive and blue for negative), and the thickness indicates the magnitude of the corresponding path value. (b) Bar plot of the pathway effects of climate variables affecting ALSTs. The error bars indicate the uncertainty based on error propagation.", + "footnote": [], + "bbox": [ + [ + 183, + 100, + 816, + 365 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig 3. Dominant role of soil moisture in the temporal dynamics in the summer daytime cooling effect ( \\(\\Delta LST_{s}\\) ) of forests. (a) Regional mean correlation and partial correlation coefficients between five climate variables (vapor pressure deficit, downward solar radiation, precipitation, air temperature and wind speed) and the daytime \\(\\Delta LST_{s}\\) . The error bars indicate the standard deviations. (b) Similar with (a), but replace vapor pressure deficit by the soil moisture. (c) Correlation coefficients between summer vapor pressure deficit ( \\(VPD_{s}\\) ) trends and summer soil moisture ( \\(SM_{s}\\) ) trends within either \\(SM_{s}\\) or \\(VPD_{s}\\) trends bins. (d) Correlation coefficients between \\(VPD_{s}\\) (or \\(SM_{s}\\) ) trends and \\(\\Delta LST_{s}\\) trends within \\(SM_{s}\\) (or \\(VPD_{s}\\) ) trends bins.", + "footnote": [], + "bbox": [ + [ + 200, + 217, + 800, + 502 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. S10. Temporal correlation coefficient (r) between summer vapor pressure deficit ( \\(VPD_{s}\\) ) and surface soil moisture ( \\(SM_{s}\\) ). (a) Spatial pattern of \\(r\\) between \\(VPD_{s}\\) and \\(SM_{s}\\) . (b) Density of the \\(r\\) values.", + "footnote": [], + "bbox": [ + [ + 201, + 668, + 785, + 814 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. S11. Impact of \\(SM_{s}\\) on the temporal dynamics in \\(\\Delta LST_{s}\\) based on the random forest model. (a) The importance of climate variables is indicated by the absolute SHAP values and Gini coefficients. (b) Variation of SHAP values with changing \\(SM_{s}\\) or VPDs, anomaly. (c) Observed and modelled \\(\\Delta LST_{s}\\) trends, and the isolated contributions from climate variables.", + "footnote": [], + "bbox": [ + [ + 257, + 163, + 760, + 485 + ] + ], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig 4. Mechanisms underlying the effects of climate variables on the daytime LST effects of European forests (ALSTs) in summer. (a) Structure equation models describing the biophysical relationships between climate variables and \\(\\Delta LST_{s}\\) . The numbers denote the path value (mean \\(\\pm\\) standard error). The arrow color indicates the sign of the path (red for positive and blue for negative), and the thickness indicates the magnitude of the corresponding path value. (b) Bar plot of the pathway effects of climate variables affecting \\(\\Delta LST_{s}\\) . The error bars indicate the uncertainty based on error propagation.", + "footnote": [], + "bbox": [ + [ + 184, + 100, + 816, + 365 + ] + ], + "page_idx": 28 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. S7. Temporal correlation coefficient (r) between \\(\\mathrm{LE}_{\\mathrm{w}}\\) and \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) . (a to c) Spatial pattern of r between \\(\\mathrm{LE}_{\\mathrm{w}}\\) and daily mean, daytime and nighttime \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) . (d) Density of the r values.", + "footnote": [], + "bbox": [ + [ + 221, + 213, + 775, + 488 + ] + ], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_2a.jpg", + "caption": "Fig 2a. Interannual variations of winter albedo effect of European forests ( \\(\\Delta \\alpha_{\\mathrm{w}}\\) ) and the individual winter albedo ( \\(\\alpha_{\\mathrm{w}}\\) ) for forests and openlands.", + "footnote": [], + "bbox": [ + [ + 262, + 97, + 729, + 284 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_3a.jpg", + "caption": "Fig 3a and 3b. Regional mean correlation and partial correlation coefficients between climate variables and the daytime \\(\\Delta \\mathrm{LST}_s\\) .", + "footnote": [], + "bbox": [ + [ + 156, + 629, + 840, + 790 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. R5. Temporal relationship between \\(\\Delta \\mathrm{LST}_w\\) and \\(\\Delta \\mathrm{LE}_w\\) or \\(\\Delta \\alpha_w\\) .", + "footnote": [], + "bbox": [ + [ + 241, + 362, + 752, + 508 + ] + ], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. R6. Winter latent heat flux (LE) at European forest and openland sites based on FLUXNET observations. Each data point represents the site mean. Red asterisk indicates the muti-site mean.", + "footnote": [], + "bbox": [ + [ + 343, + 691, + 653, + 853 + ] + ], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_3.jpg", + "caption": "Supplementary Fig. 3. Temporal variations of winter net solar radiation difference (ANSRw) and latent heat difference (ΔLEw) between forests and openlands in Europe. (a) All forest samples are used. (b) Only evergreen needleleaf forest samples are used.", + "footnote": [], + "bbox": [ + [ + 245, + 88, + 748, + 390 + ] + ], + "page_idx": 46 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_4.jpg", + "caption": "Supplementary Fig. 4. Temporal correlation coefficient (r) between \\(\\Delta \\mathrm{NSR}_{\\mathrm{w}}\\) and \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) . (a to c) Spatial pattern of \\(r\\) between \\(\\Delta \\mathrm{NSR}_{\\mathrm{w}}\\) and daily mean, daytime and nighttime \\(\\Delta \\mathrm{LST}_{\\mathrm{w}}\\) . (d) Density of the \\(r\\) values.", + "footnote": [], + "bbox": [ + [ + 211, + 487, + 785, + 776 + ] + ], + "page_idx": 46 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_5.jpg", + "caption": "Supplementary Fig. 5. Temporal correlation coefficient (r) between \\(\\Delta LE_{w}\\) and \\(\\Delta LST_{w}\\) . (a to c) Spatial pattern of \\(r\\) between \\(\\Delta LE_{w}\\) and daily mean, daytime and nighttime \\(\\Delta LST_{w}\\) . (d) Density of the \\(r\\) values.", + "footnote": [], + "bbox": [ + [ + 210, + 90, + 787, + 377 + ] + ], + "page_idx": 47 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_6.jpg", + "caption": "Supplementary Fig. 6. Temporal correlation coefficient (r) between \\(\\mathrm{DSR}_{w}\\) and \\(\\Delta LST_{w}\\) . (a to c) Spatial pattern of \\(r\\) between \\(\\mathrm{DSR}_{w}\\) and daily mean, daytime and nighttime \\(\\Delta LST_{w}\\) . (d) Density of the \\(r\\) values.", + "footnote": [], + "bbox": [ + [ + 210, + 469, + 787, + 757 + ] + ], + "page_idx": 47 + } +] \ No newline at end of file diff --git a/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a107a97c1ec33e91ab2348627f1bc252161b4044 --- /dev/null +++ b/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,1211 @@ + +# nature portfolio + +Peer Review File + +# Amplified Local Cooling Effect of Forestation in Warming Europe + +Corresponding Author: Professor Zhao- Liang Li + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +This manuscript is well- structured and well- written. The authors define \(\Delta \mathsf{LST}\) as the difference between forest LST and nearby open land LST. Their analysis reveals that \(\Delta \mathsf{LST}\) has intensified in recent decades, which they attribute to increasing VPD, favoring enhanced evaporative cooling in forests. I feel this manuscript is publishable if the authors can address the following questions: + +Line 14: VPD increase will trigger stomatal closure, thus reducing ET cooling. How to reconcile this? + +Lines 101- 110: The observed forest cooling - could this be influenced by elevation effects? In the Methods section (Line 577), is the assumption that the background climate remains uniform within a \(0.25^{\circ}\times 0.25^{\circ}\) area valid? I noticed that the authors set a threshold of a mean elevation of \(500m\) to mitigate this bias. However, given that the typical lapse rate is approximately \(6.5^{\circ}C\) per 1,000 meters, this effect may be substantial enough to alter the direction of the temperature difference (compare to the numbers you provided in Lines 101 to 110). In low- elevation hilly regions, forests may often be found at higher elevations, while open land, if resulting from deforestation, tends to be at lower elevations due to easier accessibility. This elevation difference may contribute to the observed forest cooling effect. + +Line 161: In Fig 2c, the relationship is binned by the trend of snow cover. Can the authors reproduce the result if binned by the trend of albedo? + +Line 165 - 168: not sure if the snow mass between forest and open land also can be affected by the elevation difference? + +Line 201 - 203: It is interesting to see a negative correlation between VPD and \(\Delta \mathsf{LST}\) . This suggests that when VPD is high, forests exhibit greater energy dissipation advantages compared to open lands. As the authors mentioned, VPD is highly positively correlated to air temperature. So, this reminds me of an earlier heatwave study "Teuling, A., Seneviratne, S., Stöckli, R. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nature Geosci 3, 722- 727 (2010). https://doi.org/10.1038/ngoe950". Teuling et al find "initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. ... We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long- lasting events." My question is whether the analysis in this Nature Communications manuscript represents short- term effects or longer- term effects? + +Line 272 - 275: The logic in this section feels somewhat unclear. The authors claim that higher VPD enhances \(\Delta \mathsf{LAI}\) and suggest multiple similar cause- and- effect relationships with other variables. How can the causal inferences be reliably established? It seems that the reverse statement is also valid. + +In the flowchart of Fig. 4, I notice a missing of surface resistance in the VPD- LE relationship. In the Penman- Monteith scheme, increasing VPD can have competing effects on ET: on one hand, increasing VPD enhances ET, while on the other, it also raises surface resistance, which suppresses ET. The results suggest that the VPD- driven enhancement of ET is more + +<--- Page Split ---> + +dominant. Could the authors clarify why this occurs when comparing ET between forests and open lands? I feel VPD is not the driver of such findings, but the biome type - forests/open lands and their associated biophysical and physiological responses - are the real drivers. Need to clarify this. + +See Novick, K., Ficklin, D., Stoy, P. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nature Clim Change 6, 1023- 1027 (2016). https://doi.org/10.1038/nclimate3114 + +(Remarks on code availability) + +I feel that this might be holding the authors to an excessively high standard. If Nature is asking whether I can strictly replicate results using their code, I believe it would take a significant amount of time, and I don't have the capacity to verify it. However, I feel is that it's unrealistic to expect the authors to cover every detail perfectly and provide a fully automated, one- click runnable code. + +Additionally, I believe that the provided code does not fully include all the components/scripts necessary to reproduce all the results of this paper (e.g., the ESM analysis, MODIS data processing). Again, I feel this is holding the authors to an excessively high standard. They are not software engineers. + +## Reviewer #2 + +(Remarks to the Author) I find this manuscript has a lot of interesting data and discussion. Moreover, for me personally, it was highly motivating to read this discussion. I did find, especially at the beginning of the manuscript, that the work was not very well situated in the principal literature. All four of the first references to appear in the manuscript do not seem well suited to set up this general discussion. I have provided a number of suggestions in the attached submission pdf and am hopeful that some of these suggestions will prove useful... + +I also found that the introduction was occasionally vague and would have benefitted from a somewhat more nuanced discussion... I have tried to point out places where I think this would be helpful. + +Finally, the discussion of radiative and non- radiative effects, as well as the discussion of winter and summertime effects, to my mind, were not adequately introduced and motivated in the introductory parts of the paper. When these concepts are suddenly announced, (the discussion about winter and summer time effects first comes up in the results section of the paper?), they are unexpected and seemingly unmotivated in the general context of the paper... This can be improved upon... + +I also find that the Authors do not adequately distinguish between global and local cooling... Both terms come up. But most of the time it sounds like the Authors are talking about local cooling... And the balance in terms of global cooling is never clearly estimated...? It is important not to conflate these terms, since local cooling is not necessarily equivalent to global cooling...? + +Further, I would have like to see more discussion of the role of the availability of water and surface moisture. The cooling potential of forests strongly depends on the availability of water. As soon as this surface moisture disappears, the loss of latent heat means the warming will suddenly take over... But there is little attention to this throughout the paper... + +Finally, I wonder why LEW never appears anywhere, but the effects of LEs are estimated... Clearly LEW will be significantly lower. But conifers can evapotranspire almost year round... So, to some degree, LEW should also be available and should have an impact on surface temperatures... ??? + +More to the main point, however, the general finding that wintertime effects exhibit increased cooling due to the loss of snow cover, more or less independently of tree cover (the effect is stronger over open fields than over forested land), is an interesting and valuable finding. However, it remains unclear why this phenomenon would be true in more forested areas... In other words, why would the land surface become lighter under more forested areas, thus leading to wintertime cooling...??? I do not think this is adequately explained...? + +All- in- all however, I did find the manuscript to be very interesting and compelling... I have included a number of comments in the attached submissions pdf. + +(Remarks on code availability) + +<--- Page Split ---> + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have made significant improvements, conducted substantial additional analyses, and even revised their conclusions regarding the role of VPD. I am satisfied with most of these efforts and have only one remaining comment. + +"In the summertime, the vegetation physiological response to decreased soil moisture boosts the cooling effect of forests." + +This statement may still be confusing or even misleading. It implies that forests have a stronger cooling effect than grasslands solely due to their physiological response to dry soils. + +In reality, while physiological processes such as stomatal regulation do influence surface energy balance, the observed cooling effect in forests may also stem from hydrological advantages, including deeper soil water storage and more consistent precipitation recharge in forested areas. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +I find that a lot of interesting points come up in this analysis. I am, however, a bit concerned that the paper could still benefit from some significant editing and rewriting. I raise a number of questions in the attached submission pdf. I guess that, primarily, I am unconvinced by the forest albedo logic used herein and would be tempted to argue in a different direction on many points. Please see the related comments in the text. Further, I do think that the paper seems inclined to somehow lay the blame for these changes on forests, when actually, most of the important changes seem to be occurring elsewhere (in open fields that have reduced amounts of forest cover, and not in heavily forested areas) and are primarily driven by climate warming (and not any change in forests themselves).... + +I do think that with another round of editing, this paper can be significantly improved... I am uncertain, however, how one should resolve the problem of over- emphasising forest albedo effects. This would ultimately require some different measures. Perhaps the Authors can respond to this point...? What do they think is the best procedure here...? Personally, I would be inclined to take this in a somewhat different direction. Moreover, while the forest albedo literature considers albedo effects, it entirely neglects cloud related effects... Since these are presumably also tied to forests, in part, what does this say about the methodology employed in the analysis...??? + +(Remarks on code availability) + +Version 2: + +Reviewer comments: + +Reviewer #2 + +(Remarks to the Author) + +I am impressed by the lengths to which the Authors have gone to address the many comments raised. Though ideally, I would like to continue this discussion, I do not wish to burden the Authors unnecessarily. I do think that this manuscript already provides a lot of interesting and highly relevant analysis. I did still make a number of comments in the attached submission pdf and would encourage the Authors to consider these. Most of the comments are relatively minor in character and can easily be addressed (or ignored where appropriate). Thus, I leave it up to the Authors whether they adopt these suggestions or not. + +I do think the manuscript could probably benefit from one last round of editing and perhaps some minor shortening. I do hope the provided comments can prove useful here. + +(Remarks on code availability) + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Response to Reviewers' Comments + +We greatly appreciate the opportunity to revise our manuscript and thank all anonymous reviewers for their constructive comments. The manuscript has been revised and improved accordingly. We hope that the revision will make it more acceptable for publication. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in red and Italic). The changes are also marked in red in the manuscript file. + +## Reviewer #1 (Remarks to the Author): + +This manuscript is well- structured and well- written. The authors define \(\Delta \mathrm{LST}\) as the difference between forest LST and nearby open land LST. Their analysis reveals that \(\Delta \mathrm{LST}\) has intensified in recent decades, which they attribute to increasing VPD, favoring enhanced evaporative cooling in forests. I feel this manuscript is publishable if the authors can address the following questions: + +Response: We appreciate the positive comments by the reviewer. We have carefully considered all the comments and suggestions and made corresponding point- by- point responses. To address your comment regarding the potential influence of elevation bias between forests and openlands, we have refined our results by setting additional elevation restrictions when selecting pixels for comparison. Also inspired by your comment regarding the short- term and long- term effects, we added new experiments to explored the potential impact of soil moisture in summer (SM). Accordingly, we updated the results and refined the research findings. These refinements have significantly strengthened the robustness of our findings, as detailed in our point- by- point responses below. + +Line 14: VPD increase will trigger stomatal closure, thus reducing ET cooling. How to reconcile this? + +Response: We appreciate your valuable comment about the impact of VPD. Based on your comment below, we have performed additional analyses to elucidate the mechanisms of enhanced forests cooling effects in summer ( \(\Delta \mathrm{LST}_5\) ). Our results demonstrates that while summer VPD (VPDs) exhibits a strong correlation with \(\Delta \mathrm{LST}_5\) , increased atmospheric dryness does not appear to be the actual factor driving the observed \(\Delta \mathrm{LST}_5\) patterns. Instead, the concurrent summer SM (SM) depletion (tight coupling with VPDs), should be the primary driver of the trends in \(\Delta \mathrm{LST}_5\) . Detailed analyses supporting this conclusion are presented in our responses to your subsequent comments. + +Therefore, we have revised the relevant text in the abstract to more accurately reflect this mechanism (Line 12): + +In the summertime, the vegetation physiological response to decreased soil moisture boosts the cooling effect of forests. + +Lines 101- 110: The observed forest cooling - could this be influenced by elevation effects? In the Methods section (Line 577), is the assumption that the background climate remains uniform within a \(0.25^{\circ} \times 0.25^{\circ}\) area valid? I noticed that the authors set a threshold of a mean elevation of \(500 \mathrm{~m}\) to mitigate this bias. However, given that the typical lapse rate is approximately \(6.5^{\circ} \mathrm{C}\) per 1,000 meters, this effect may be substantial enough to alter the + +<--- Page Split ---> + +direction of the temperature difference (compare to the numbers you provided in Lines 101 to 110). In low- elevation hilly regions, forests may often be found at higher elevations, while open land, if resulting from deforestation, tends to be at lower elevations due to easier accessibility. This elevation difference may contribute to the observed forest cooling effect. + +Response: Thanks for your insightful comments regarding the impact of elevation. We fully agree that elevation differences could have a potential impact on the evaluated LST effect of forests. We checked our results and found a mean elevation difference of \(\sim 150 \mathrm{~m}\) between forest and grassland samples under our original \(500 \mathrm{~m}\) mean elevation constrain. This may lead to an overestimation of the forest cooling effects, as you noted. + +To mitigate this, we implemented additional screening criteria. First, we identified the less dominant land cover type (either forest or openland) within each \(0.25^{\circ} \times 0.25^{\circ}\) grid, then applied a \(\pm 100 \mathrm{~m}\) elevation threshold around its mean elevation to select comparable samples from the other land cover type. Only when both forest and openland samples are larger than 5, the calculation of \(\Delta \mathrm{LST}\) was performed. In the revised manuscript, we revised corresponding methodological descriptions (Line 618): + +For each \(0.25^{\circ}\) grid, we first determine the less dominant land cover type (forest or openland) based on the count of valid samples, then apply a \(\pm 100 \mathrm{~m}\) elevation threshold around its mean elevation to select comparable samples from the other type. + +This refined approach reduced mean elevation differences to just \(\sim 20 \mathrm{~m}\) (vs. original \(\sim 150 \mathrm{~m}\) ). Based on the refined method, we have updated the all the related numbers and figures. Given the extensive revisions made, we do not list all modifications in the response letter. Please refer to the revised manuscript for detailed changes. However, we confirm that the original key finding, negative trends in \(\Delta \mathrm{LST}_{\mathrm{s}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) , persisted (Fig. 1). + +![](images/Figure_1.jpg) + +
Fig 1. Temporal dynamics in winter and summer land surface temperature effects of European forests ( \(\Delta \mathrm{LST}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{s}}\) ) in recent two decades.
+ +<--- Page Split ---> + +We also appreciate your comment about the background climate assumption. While perfect climate uniformity cannot be assumed at any spatial scale, our \(0.25^{\circ}\) grid setting was based on several considerations. + +First, previous research has shown that the decorrelation length of surface climate, the spatial scale at which these variables (e.g., temperature, precipitation) become relatively independent, typically exceeds \(30\mathrm{km}\) (Kim and Kosro, 2013; Larsen et al., 2013). This conclusion supports our assumption that sampled locations within each \(0.25^{\circ}\) ( \(\sim 30\mathrm{km}\) ) grid cell share similar climatic conditions. + +Second, the \(0.25^{\circ}\) window size is comparable with that in previous studies exploring the biophysical effect of vegetation changes (Table R1). We have added these references in Line 604. Several studies also confirmed that the estimated LST effect is robust to the window size selection (Li et al., 2015; Zhang et al., 2024; Zhao et al., 2024). + +Table R1. Window size setting for the same background climate assumption in previous studies + +
ReferenceWindow sizeData
(Lee et al., 2011)28 km (mean)Site observation
(Li et al., 2015)50 × 28 kmRemote sensing observation
(Alkama and Cescatti, 2016)50 kmRemote sensing observation
(Duveiller et al., 2018)25 kmRemote sensing observation
(Chen et al., 2018)21.6 km (mean)Site observation
(Barnes et al., 2024)30 km (maximum)Site observation
+ +Third, we also explored the background climate similarity using 43 paired and synchronous FLUXNET sites observations. The spatial distances of the paired sites range from 0 to \(150\mathrm{km}\) , and the elevation differences are less than \(200\mathrm{m}\) . Here, we compared the air temperature (AT), precipitation (P) and downward shortwave radiation (DSR) at different scales. For each variable, we compared the annual means (Fig. R1) and the monthly ranges (the difference between the monthly maximum and minimum values (Fig. R2). We also calculated the correlation coefficient between observations at the daily scale (Fig. R3). + +![](images/Figure_unknown_0.jpg) + +
Fig. R1. Comparison of annual temperature, precipitation and radiation means from spatial paired site observations
+ +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Fig. R2. Comparison of monthly temperature, precipitation and radiation ranges from spatial paired site observations.
+ +![](images/Figure_unknown_2.jpg) + +
Fig. R3. Correlation of daily temperature precipitation and radiation between spatial paired site observations
+ +Fig. R1 shows that the paired sites within \(30\mathrm{km}\) share similar annual mean AT, P and DSR, and the scatters are close to the 1:1 line. The average root mean square error (RMSE) for paired sites with distances less than \(30\mathrm{km}\) is significantly smaller than for samples at distances greater than \(30\mathrm{km}\) , especially for precipitation ( \(105\mathrm{mm / y}\) vs. \(229\mathrm{mm / y}\) ). Similar results are also found in monthly ranges, which describe the seasonal variations of the climate variables (Fig. R2). For the daily variation, the correlations between the paired site observations decrease with increasing distance. Especially for precipitation, the mean correlation for paired sites with distance less than \(30\mathrm{km}\) can reach 0.81, while for those paired sites with distance larger than \(30\mathrm{km}\) , the mean correlation is only 0.57. Overall, these evidences support the validity of the similar background climate at the \(0.25^{\circ}\) scale. + +## Reference: + +Alkama, R. & Cescatti, A. Biophysical climate impacts of recent changes in global forest cover. Science (80- ). 351, 600- 604 (2016). Barnes, M. L. et al. A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States. Earth's Futur. 12, (2024). Chen, L., Dirmeyer, P. A., Guo, Z. & Schultz, N. M. Pairing FLUXNET sites to validate model representations of land- use/land- cover change. Hydrol. Earth Syst. Sci. 22, 111- 125 (2018). Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64- 75 (2018). Kim, S. Y. & Kosro, P. M. Observations of near- inertial surface currents off Oregon: Decorrelation time and length scales. J. Geophys. Res. Ocean. 118, 3723- 3736 (2013). + +<--- Page Split ---> + +Larsen, M. A. D., Thejll, P., Christensen, J. H., Refsgaard, J. C. & Jensen, K. H. On the role of domain size and resolution in the simulations with the HIRHAM region climate model. Clim. Dyn. 40, 2903- 2918 (2013).Lee, X. et al. Observed increase in local cooling effect of deforestation at higher latitudes. Nature 479, 384- 387 (2011).Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1- 10 (2015).Zhang, Y. et al. Asymmetric impacts of forest gain and loss on tropical land surface temperature. Nat. Geosci. 13, 823- 831 (2024).Zhao, J. et al. Forest fire size amplifies postfire land surface warming. Nature 633, 828- 834 (2024). + +Line 161: In Fig 2c, the relationship is binned by the trend of snow cover. Can the authors reproduce the result if binned by the trend of albedo? + +Response: Thank you for raising this concern. Fig. 2c (also Fig. R4a) reveals that surface darkening \(\alpha_{\mathrm{w}}\) trends) is more sensitive to snow cover decline ( \(\mathrm{SC_w}\) trends) in openlands than in forests, as reflected by the steeper spatial regression slope for openlands. + +To further validate these findings, we conducted additional analyses using \(\alpha_{\mathrm{w}}\) trend- based data binning as you suggested. The results presented in Fig. R4b confirm the robustness of the initial correlation under this alternative binning approach. We further verified that substituting \(\mathrm{SC_w}\) with \(\Delta \alpha_{\mathrm{w}}\) also yields a robust temporal correlation with \(\Delta \mathrm{LST}_{\mathrm{w}}\) (Fig. R4c and R4d). + +![](images/Figure_2c.jpg) + +
Fig. R4. Comparison of the results binned by \(\mathrm{SC_w}\) and \(\alpha_{\mathrm{w}}\) . (a) Spatial relationships between \(\mathrm{SC_w}\) trends and \(\alpha_{\mathrm{w}}\) trends binned by \(\mathrm{SC_w}\) trends (same as Fig. 2c in the manuscript). (b) Binned by \(\alpha_{\mathrm{w}}\) trends. (c) Temporal relationships between \(\mathrm{SC_w}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) (same as Fig. 2e in the manuscript). (b) Temporal relationships between \(\Delta \alpha_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) .
+ +<--- Page Split ---> + +Line 165 – 168: not sure if the snow mass between forest and open land also can be affected by the elevation difference? + +Response: Thank you for raising the concern about snow mass. We agree that forests typically occur at higher elevations where lower temperatures may enhance snow retention compared to openlands. To mitigate this impact, we have added additional constraint of elevation differences between samples (please see the response to your comments about Lines 101- 110). Based on the refined method, we have updated the all the related numbers and figures. + +We found that the multi- year mean daytime \(\Delta \mathrm{LST_w}\) shifted from - 0.20 K to 0.01 K after accounting for elevation differences, while the negative temporal trend in \(\Delta \mathrm{LST_w}\) persists. These results suggest elevation induced snow differences may influence absolute value of \(\Delta \mathrm{LST_w}\) , but do not affect the key findings of the observed temporal trends. + +Line 201 – 203: It is interesting to see a negative correlation between VPD and \(\Delta \mathrm{LST_s}\) . This suggests that when VPD is high, forests exhibit greater energy dissipation advantages compared to open lands. As the authors mentioned, VPD is highly positively correlated to air temperature. So, this reminds me of an earlier heatwave study "Teuling, A., Seneviratne, S., Stöckli, R. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nature Geosci 3, 722–727 (2010). https://doi.org/10.1038/ngeo950”. Teuling et al find "initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. ... We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long- lasting events." My question is whether the analysis in this Nature Communications manuscript represents short- term effects or longer- term effects? + +Response: Thank you for raising this concern. We have carefully read the reference (Teuling et al., 2010), and find the revealed mechanism very insightful. Teuling et al. used in- situ observations to demonstrate that during a heatwave event, rising temperature (also rising VPD) and SM depletion dominate the turbulent fluxes of forests and grasslands at distinct stages: temperature (VPD) dominates initially, with grassland ET showing a stronger positive response; while SM becomes dominant later as water supply limits grassland ET cooling, and forests' conservative water- use strategy leads to lower temperature. Here, the temporal scale in Teuling et al.'s study focuses on heatwave events, while our manuscript evaluates interannual variations and trends. Therefore, we consider our analysis to represent the long- term effect. + +In the original version of our manuscript, we supposed that different ET responses to rising temperature (also rising VPD) dominate the observed enhanced forest cooling. Specifically, increased VPD may enhance forest ET more than grassland ET, thereby strengthening forest cooling. This hypothesis appears contradictory to the findings of Teuling et al. at the first stage, which may be due to the differences in the temporal scale. + +However, through reviewing Teuling et al.'s study, we recognized that SM can also influence the cooling effect of forests, and this aspect was not sufficiently addressed in our original manuscript. We also note that VPD and SM are strongly coupled at the annual scale. Thus, we conducted + +<--- Page Split ---> + +additional analyses to identify the actual driver of the observed trends in \(\Delta \mathrm{LST}_s\) . We used binning regression method (Liu et al., 2020) to disentangle the impacts of \(\mathrm{VPD}_s\) and \(\mathrm{SM}_s\) . The results demonstrated that \(\mathrm{SM}_s\) shows stronger correlation with daytime \(\Delta \mathrm{LST}_s\) than \(\mathrm{VPD}_s\) (Line 218): + +Temporal correlation analyses using \(\mathrm{VPD}_s\) , \(AT_s\) , \(\mathrm{DSR}_s\) , \(P_s\) and \(\mathrm{WS}_s\) as the potential drivers reveal strong relationships between daytime \(\Delta \mathrm{LST}_s\) and climatic variables except \(\mathrm{WS}_s\) (Fig. 3a). However, after accounting for covariates, the partial correlations between the daytime \(\Delta \mathrm{LST}_s\) and \(\mathrm{DSR}_s\) , \(P_s\) , and \(AT_s\) are greatly reduced and even reverse in sign. In contrast, \(\mathrm{VPD}_s\) maintain a predominant negative correlation with daytime \(\Delta \mathrm{LST}_s\) , with the mean partial correlation coefficient of - 0.42 (Fig. 3a). Notably, we can also find strong positive partial correlations between \(\mathrm{SM}_s\) and \(\Delta \mathrm{LST}_s\) (Fig. 3b) when replacing \(\mathrm{VPD}_s\) by the \(\mathrm{SM}_s\) , the other factor describing the dryness stress. This is due to the strong coupling between \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) at the annual scale ( \(r = 0.92\) , Supplementary Fig. 10). These findings raise the following question: whether variations in atmosphere or soil dryness are the primary factor governing changes in \(\Delta \mathrm{LST}_s\) over the past two decades? + +To answer this question, we then use the binning regression method to further disentangle the respective contributions of \(\mathrm{VPD}_s\) and \(\mathrm{SM}_s\) (Liu et al., 2020). We conduct this analysis using the spatial samples of \(\mathrm{VPD}_s\) trend and \(\mathrm{SM}_s\) trends with sufficient data for decoupling the two factors. We confirm the strong spatial correlation between \(\mathrm{SM}_s\) trend and \(\mathrm{VPD}_s\) trends ( \(r = - 0.65\) ) when all spatial samples are used. However, after stratifying either \(\mathrm{SM}_s\) or \(\mathrm{VPD}_s\) trends into 10 bins according to percentiles, correlations between the two variables show substantial attenuation (Fig. 3c), suggesting the two variables are decoupled. Then, we calculate the correlation between \(\mathrm{SM}_s\) (or \(\mathrm{VPD}_s\) ) trends and \(\Delta \mathrm{LST}_s\) trends in each \(\mathrm{VPD}_s\) (or \(\mathrm{SM}_s\) ) trend bin. We find the mean \(r\) between \(\mathrm{VPD}_s\) trends and \(\Delta \mathrm{LST}_s\) trends is only - 0.11, whereas the mean \(r\) between \(\mathrm{SM}_s\) trends and \(\Delta \mathrm{LST}_s\) trends reach 0.40 (Fig. 3d). This binning regression analysis suggests that change \(\mathrm{SM}_s\) is more likely to be the driver of \(\Delta \mathrm{LST}_s\) dynamic. + +![](images/Figure_3.jpg) + +
Fig 3. Dominant role of soil moisture in the temporal dynamics in the summer daytime cooling effect ( \(\Delta \mathrm{LST}_s\) ) of forests. (a) Regional mean correlation and partial correlation coefficients between five climate variables (vapor pressure deficit, downward solar radiation, precipitation, air temperature
+ +<--- Page Split ---> + +and wind speed) and the daytime \(\Delta LST_s\) . The error bars indicate the standard deviations. (b) Similar with (a), but replace vapor pressure deficit by the soil moisture. (c) Correlation coefficients between summer vapor pressure deficit \((VPD_s)\) trends and summer soil moisture \((SM_s)\) trends within either \(SM_s\) or \(VPD_s\) trends bins. (d) Correlation coefficients between \(VPD_s\) (or \(SM_s\) ) trends and \(\Delta LST_s\) trends within \(SM_s\) (or \(VPD_s\) ) trends bins. + +![](images/Figure_unknown_3.jpg) + +
Fig. S10. Temporal correlation coefficient (r) between summer vapor pressure deficit \((VPD_s)\) and surface soil moisture \((SM_s)\) . (a) Spatial pattern of r between \(VPD_s\) and \(SM_s\) . (b) Density of the r values.
+ +We also build a non- linear random forest model using both \(SM_s\) and \(VPD_s\) as the input. The results also support that \(SM_s\) plays the more important role in predicting temporal dynamics of \(\Delta LST_s\) (Line 255): + +The critical role of \(SM_s\) is corroborated by non- linear statistical analysis using a Random Forest (RF) model (Supplementary Text 1). Variable importance analysis demonstrates that \(SM_s\) exerts a stronger influence than \(VPD_s\) in predicting \(\Delta LST_s\) dynamics. Contribution analysis also reveals that \(SM_s\) changes account for the largest portion (0.152 K/decade, \(p < 0.05\) ) of the simulated negative \(\Delta LST_s\) trend (0.181 K/decade, \(p < 0.05\) ), highlighting its dominant role in driving the observed enhanced forest cooling effect (Supplementary Fig. 11). + +## Supplementary Text 1 Modelling \(\Delta LST_s\) based on random forest + +We apply a non- linear machine learning method, Random Forest (RF), to evaluate the importance and contribution of multiple potential climate drivers for predicting \(\Delta LST_s\) (sklearn package in Python). Specifically, we use all spatial samples over 20 years to build the dataset. It is worth mentioning that we normalize the input climate variables and \(\Delta LST_s\) by subtracting the 20- year means at the grid scale, since the model focus on the temporal dynamic of \(\Delta LST_s\) rather than the spatial variation. We excluded air temperature from the model inputs due to its high correlation with other climate variables. + +The dataset is divided into training (80% of the samples) and test sets (20% of the samples), with model parameters confirmed based on validation results from the test set (number of trees = 100; maximum depth of the tree = 6). All the samples are then used to fit the best model. The relative importance of each variable is indicated by the Gini coefficient. Moreover, we use the Shapley Additive Explanations (SHAP) method to quantify the individual contribution of each variable in each sample (shap package in Python). SHAP is an approach to explain machine learning models based on cooperative game theory, where SHAP values quantify the marginal contributions of predictors. We calculate the mean absolute SHAP values for each input variable as importance metrics and explore the non- linear impact of climate variables on \(\Delta LST_s\) by plotting their SHAP + +<--- Page Split ---> + +values against input values. + +Based on the RF model, we set several scenarios to separate the relative contributions of climate variables to the \(\Delta \mathrm{LST}_s\) trend. Specifically, we perform four experimental simulations: (S1) varying SM, only; (S2) varying SM, and VPD, while fixing \(\mathrm{DSR}_s\) \(P_s\) and \(WS_{s}\) ; (S3) varying SM, VPD, and \(\mathrm{DSR}_s\) , while fixing \(P_{s}\) and \(WS_{s}\) ; (S4) varying SM, VPD, \(\mathrm{DSR}_s\) and \(P_{s}\) , while fixing \(WS_{s}\) ; and (S5) varying SM, VPD, \(\mathrm{DSR}_s\) , \(P_{s}\) , and \(WS_{s}\) . The Theil- Sen slope and Mann- Kendall \(P\) - value of simulations S1, S2- S1, S3- S2, S4- S3, S5- S4 are used to evaluate the individual contributions of the changing climate to the \(\Delta \mathrm{LST}_s\) trend. + +The model shows good accuracy on the test dataset ( \(R^2 = 0.56\) , RMSE \(= 0.32\) K), supporting our further analysis. The Gini importance and mean absolute SHAP values both suggest that SM, is the most important driver, followed by VPD, \(P_s\) , \(\mathrm{DSR}_s\) and \(WS_{s}\) (Supplementary Fig 11a). The marginal contributions quantified by the SHAP value further reveal different impacts of SM, and VPD, (Supplementary Fig. 11b). SM exhibits the pronounce positive effect, with stronger impact when SM, anomaly is negative. While VPD, only show slight negative impact under certain condition. + +On the basis of the RF model, we estimate the contributions of climate variables to the long- term trend of daytime \(\Delta \mathrm{LST}_s\) (Supplementary Fig. 11c). We first compared the reconstructed trends with all forcings and the observed trends, showing good consistency (observed: 0.188 K/decade, \(p< 0.05\) ; simulated: 0.181 K/decade, \(p< 0.05\) ). By setting different scenarios, results suggest that decreasing SM, contributes the most to the negative trend in daytime \(\Delta \mathrm{LST}_s\) (- 0.152 K/decade, \(p< 0.05\) ), and increasing VPD, shows lower contribution (- 0.049 K/decade, \(p< 0.05\) ). The isolated contribution of \(\mathrm{DSR}_s\) is also statistically significant, but the value is relatively small (0.012 K/decade, \(p< 0.05\) ). The contribution of \(WS_{s}\) and \(P_{s}\) are not significant. + +![](images/Figure_unknown_4.jpg) + +
Fig. S11. Impact of SM, on the temporal dynamics in \(\Delta \mathrm{LST}_s\) based on the random forest model. (a) The importance of climate variables is indicated by the absolute SHAP values and Gini coefficients. (b) Variation of SHAP values with changing SM, or VPD, anomaly. (c) Observed and modelled \(\Delta \mathrm{LST}_s\) trends, and the isolated contributions from climate variables.
+ +<--- Page Split ---> + +In summary, we conclude that the SM depletion (similar with the second stage identified by Teuling et al.) is more likely to explain the observed intensification of summer forest cooling over Europe in recent decades. + +## Reference: + +Liu, L. et al. Soil moisture dominates dryness stress on ecosystem production globally. Nat. Commun. 11, 1- 9 (2020). + +Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). + +Line 272 - 275: The logic in this section feels somewhat unclear. The authors claim that higher VPD enhances \(\Delta \mathrm{LAI}_s\) and suggest multiple similar cause- and- effect relationships with other variables. How can the causal inferences be reliably established? It seems that the reverse statement is also valid. + +Response: Thank you raising this concern about the causal relationship. We fully acknowledge that establishing robust causal inferences is critical and fundamental in structural equation modeling (SEM) analysis. Our model design is based on established understanding of the biophysical processes of forests that influence local temperature and supported by previous research findings. + +First, we design the model by assuming that climate variables (temperature, precipitation...) exert different impacts on the vegetation growth and evapotranspiration (i.e. \(\Delta \mathrm{LAI}_s\) and \(\Delta \mathrm{LE}_s\) ) (Zheng et al., 2022). Such differences in LAI or LE between forests and openlands are unlikely to alter background climate patterns. Additionally, the adopted space- for- time approach assumes that the background climate remains constant within the window. This implies that changes in LAI and LE are solely driven by climatic factors and do not exert feedback effects on the atmosphere. Second, we assume that \(\Delta \mathrm{LAI}_s\) and \(\Delta \mathrm{LE}_s\) can impact \(\Delta \mathrm{LST}_s\) , which has been proved by the previous research (Prevedello et al., 2019). + +We have clarified the logic of SEM in the revised manuscript (Lines 715) and included additional references to support these assumptions: + +We use SEM to reveal the biophysical mechanism underlying the \(\Delta \mathrm{LST}_s\) dynamics (semopy package in Python). The SEM is designed based on previous studies (Prevedello et al., 2019; Zheng et al., 2022). Specifically, we assume that climate variables influence the temporal dynamics of \(\Delta \mathrm{LST}_s\) through three pathways: (P1) climate change affects \(\Delta \mathrm{LST}_s\) via \(\Delta \mathrm{LAI}_s\) ; (P2) climate change affects \(\Delta \mathrm{LST}_s\) via \(\Delta \mathrm{LE}_s\) ; and (P3) climate change affects \(\Delta \mathrm{LAI}_s\) , which further alters \(\Delta \mathrm{LE}_s\) and then \(\Delta \mathrm{LST}_s\) . For P1 and P3, the impact of climate variables on \(\Delta \mathrm{LAI}_s\) arises from the diverse sensitivities of different vegetation types to climate changes. Specifically, climate changes can differently promote or inhibit forest and non- forest vegetation growth, which further affects \(\Delta \mathrm{LST}_s\) through convective heat dissipation (P1) and the evaporative cooling effect (P3). Climate variables also directly modulate \(\Delta \mathrm{LE}_s\) even the vegetation greenness remain constant. This is due to inherent differences between different vegetation types (Teuling et al., 2010), resulting in diverse evaporative responses to climate change and, consequently, affecting \(\Delta \mathrm{LST}_s\) (P2). + +## Reference: + +Prevedello, J. A., Winck, G. R., Weber, M. M., Nichols, E. & Sinervo, B. Impacts of forestation and deforestation on local temperature across the globe. PLoS One 14, 1- 18 (2019). + +<--- Page Split ---> + +Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722–727 (2010). Zheng, H. et al. Effects of Vegetation Changes and Multiple Environmental Factors on Evapotranspiration Across China Over the Past 34 Years. Earth's Futur. 10, 1–16 (2022). + +In the flowchart of Fig. 4, I notice a missing of surface resistance in the VPD- LE relationship. In the Penman- Monteith scheme, increasing VPD can have competing effects on ET: on one hand, increasing VPD enhances ET, while on the other, it also raises surface resistance, which suppresses ET. The results suggest that the VPD- driven enhancement of ET is more dominant. Could the authors clarify why this occurs when comparing ET between forests and open lands? I feel VPD is not the driver of such findings, but the biome type – forests/open lands and their associated biophysical and physiological responses – are the real drivers. Need to clarify this. See Novick, K., Ficklin, D., Stoy, P. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nature Clim Change 6, 1023 – 1027 (2016). https://doi.org/10.1038/nclimate3114 + +Response: We sincerely appreciate the valuable comments. We have carefully read the referred paper and we fully agree with your perspective of the opposing effects of VPD on LE (or ET). However, it is difficult for our data- based analysis to explicitly incorporate the impact of surface resistance \((\mathbf{r}_{\mathrm{s}})\) , due to the lack of reliable \(\mathbf{r}_{\mathrm{s}}\) data. + +To address this issue, we performed additional analyses using in- situ observation and the Penman- Monteith framework, which can account for the impact of VPD on \(\mathbf{r}_{\mathrm{s}}\) . The results reveal that when neglecting the \(\mathbf{r}_{\mathrm{s}}\) effect, VPD demonstrates a more pronounced positive effect on LE in forests. However, when considering \(\mathbf{r}_{\mathrm{s}}\) responses to VPD, the sensitivity differences between forests and openlands become statistically insignificant. This result implies that the negative effect resulting from the \(\mathbf{r}_{\mathrm{s}}\) response to rising VPD offsets the direct positive effect of VPD on forest evapotranspiration. + +These findings challenge our initial hypothesis that VPD exerts stronger stimulation on evaporative cooling in forests, highlighting the critical role of surface resistance dynamics in mediating these relationships. We have incorporated this supplementary analysis in the revised manuscript (Line 262): + +We also evaluate the sensitivity of summer latent heat \((LE_{s})\) to VPD, in both forests and openlands using eddy covariance observations from European sites (Supplementary Text 2). The sensitivity analysis is based on the Penman- Monteith framework, which accounts for the influence of \(VPD_{s}\) on surface resistance (Novick et al., 2016). If \(VPD_{s}\) is the main driver of enhanced forest cooling effect, we expect to observe greater positive \(LE_{s}\) sensitivity in forests compared to openlands, in which case forests can produce stronger evaporative cooling effects in the context of rising \(VPD_{s}\) . However, we find openlands show slightly higher positive sensitivity than forests, although the difference is not significant. The direct regression analysis also supports the stronger \(LE_{s}\) responses to \(VPD_{s}\) increases in openlands (Supplementary Table. 1). This in- situ observational evidence, combined with our statistical results (binning regression and random forest regression), suggests that \(VPD_{s}\) may not explain the enhanced cooling effect of European forests, while the decline in \(SM_{s}\) appears to be the real dominant driver. + +<--- Page Split ---> + +## Supplementary Text 2. Sensitivity of summer latent heat to increasing vapor pressure deficit + +Elevated vapor pressure deficit (VPD) exerts dual opposing effects on latent heat (LE) flux: while it directly enhances LE through increased evaporative demand, it simultaneously elevates surface resistance (rs), thereby suppressing LE (Novick et al., 2016). To investigate how VPD differentially influences LE in forests and openlands and consequently affects the cooling effect of forests, we analyze European eddy covariance observations from the FLUXNET2015 dataset and conduct sensitivity analyses. + +The sensitivity of LE to VPD is assessed based on the Penman- Monteith framework, accounting for both the aforementioned opposing effects (Lin et al., 2018): + +\[LE = \frac{\Delta(Rn - G) + \rho C_p(VPD / r_a)}{\Delta + \gamma(1 + r_s / r_a)} \quad (1)\] + +\[G_{s} = G_{0} + G_{1}\frac{G P P}{\nu P D^{m}} \quad (2)\] + +Here, \(R n\) \((W / m^{2})\) is the net radiation; \(G\) \((W / m^{2})\) is the soil heat flux; \(\Delta\) \((kPa / K)\) is the slope of the saturated vapor pressure curve; \(\rho\) is the air density \((kg / m^{3})\) . \(C_{p}\) \((J / kg / K)\) is the specific heat of air; \(\gamma\) is the psychrometric constant \((kPa / K)\) ; \(r_{a}\) (s/m) is the aerodynamic resistance, estimated using vegetation height; \(G_{s}\) (surface conductance) is the inverse of \(r_{s}\) ; GPP is the gross primary productivity. The model parameters \((G_{0}, G_{1},\) and \(m\) ) is estimated via optimization (SciPy package in Python) using daily- scale observations. + +We analysis those observation in summer and we select sites with reliable LE accuracy (Nash- Sutcliffe Efficiency \(>0.5\) ), resulting in 19 forested and 12 openland (grassland and cropland) sites. We then introduce VPDs perturbations into the observation data to estimate summer LE \((LE_{s})\) sensitivity to VPDs \(\left(\frac{dLE_{s}}{dVPD_{s}}\right)\) \(LE_{s}\) response to a 1 hPa VPDs increase). For comparison, we also compute \(\frac{dLE_{s}}{dVPD_{s}}\) (i) without the impact of VPDs on \(r_{s}\) and (ii) via direct linear regression between VPDs and \(LE_{s}\) (Supplementary Table 1). + +If VPDs is the primary driver of enhanced forest cooling effect, forests should exhibit a higher \(\frac{dLE_{s}}{dVPD_{s}}\) than openlands, implying stronger evaporative cooling under rising VPDs. However, results indicate that this expectation holds only when neglecting the inhibitory effect of VPDs on \(LE_{s}\) (via \(r_{s}\) ). When considering both opposing effects of VPDs on \(LE_{s}\) , openlands show slightly higher mean sensitivity compared to forests. In addition, the direct regression analysis supports the stronger \(LE_{s}\) responses to VPDs increases in openlands. These findings suggest that VPDs may not explain the enhanced cooling effect observed in European forests. + +Table S1. Sensitivity of summer latent heat \((LE_{s})\) flux to rising vapor pressure deficit (VPDs) based on FLUXNET observations in Europe. + +
dLEs
dVPDs (w·m-2/hPa)
dLEs
dVPDs (w·m-2/hPa)
ignoring the impact of VPD on rs
Regression slope
between VPDs and LEs
(w·m-2/hPa)
Forest (n=19)2.08 ± 1.855.92 ± 2.953.87 ± 2.87
Openland (n=19)2.48 ± 1.714.87 ± 1.326.44 ± 2.67
+ +The values indicate the mean \(\pm\) standard deviation across sites. + +<--- Page Split ---> + +Combining this sensitivity analysis result and the statistical evidence (please see the response to your comment above), we recognized that the decreasing \(\mathrm{SM}_s\) appears to be the primary driver of the observed daytime \(\Delta \mathrm{LST}_s\) trends. Thus, we updated the Fig. 4 and the related descriptions (Line 276). The biophysical and physiological mechanisms corresponding to each path are also annotated to enhance conceptual clarity (Fig. 4a). + +We further conduct structural equation modeling (SEM) to elucidate the biophysical mechanisms underlying the impact of varying SM, on daytime \(\Delta \mathrm{LST}_s\) dynamics (Fig. 4a). Our SEM incorporates two key biophysical mediators: the leaf area index difference ( \(\Delta \mathrm{LAI}_s\) ) and latent heat flux difference ( \(\Delta \mathrm{LE}_s\) ) between nearby forests and openlands. The path effect (mean \(\pm\) standard error) is used to describe strength and direction of the relationship. Following previous studies, we build SEMs at the local scale and calculate the mean path effects of all models (Shen et al., 2024; Zhong et al., 2023). The analysis reveals three distinct pathways of SM, affecting \(\Delta \mathrm{LST}_s\) . + +(1) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) exerts a significant negative effect on \(\Delta \mathrm{LAI}_s\) (-0.41 \(\pm\) 0.15). Then, \(\Delta \mathrm{LAI}_s\) demonstrate a negative effect on \(\Delta \mathrm{LST}_s\) (-0.19 \(\pm\) 0.09). This pathway suggests that reduced \(\mathrm{SM}_s\) can amplify the greenness difference in forests and openlands, thereby enhancing forests' cooling advantage through improved convective heat dissipation. + +(2) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) have a negative effect on \(\Delta \mathrm{LE}_s\) (-0.25 \(\pm\) 0.11), followed by a strong negative influence of \(\Delta \mathrm{LE}_s\) on \(\Delta \mathrm{LST}_s\) (-0.54 \(\pm\) 0.09). This pathway indicates that declining \(\mathrm{SM}_s\) imposes less water limitation to forests compared to openlands, enabling forests to maintain stronger relative evaporative cooling through differential stomatal regulation (with greenness remaining constant). + +(3) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) -induced changes in \(\Delta \mathrm{LAI}_s\) subsequently enhance \(\Delta \mathrm{LE}_s\) (0.62 \(\pm\) 0.06), ultimately influencing \(\Delta \mathrm{LST}_s\) . This demonstrates that \(\mathrm{SM}_s\) reduction amplifies evaporative cooling effects of forests by increasing the vegetation greenness contrast with openlands. + +The pathway effects, representing the strength and direction of the mechanism, are quantified as the product of all constituent path coefficients (Fig. 4b). Results reveal that the second and third pathways (both mediated by \(\Delta \mathrm{LE}_s\) ) contribute equally to \(\Delta \mathrm{LST}_s\) variation (about 0.14 \(\pm\) 0.06), while the impact first pathway is weaker (0.08 \(\pm\) 0.05). These findings suggest \(\mathrm{SM}_s\) can modulate \(\Delta \mathrm{LST}_s\) dynamics through multiple mechanisms, with forest evaporative cooling regulation emerging as the dominant process. Previous studies have demonstrated that reduced soil moisture in Europe can amplify warming during heatwaves through land-atmosphere interactions (Dirmeyer et al., 2021; Fischer et al., 2007). Our findings confirm forests exhibit greater stability and resistance to increasing soil dryness compared to grasslands or croplands, which may mitigate land-atmosphere coupling feedback and consequently enhance the relative cooling effect of forests (Teuling et al., 2010). This stability of forests is reflected in both more moderate evaporative limitation and sustained vegetation greenness under increasing soil dryness. Our results provide observational evidence suggesting that the capacity of forest ecosystems to mitigate water deficit-induced warming persists not only during heatwave events but also across interannual timescales. + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Fig 4. Mechanisms underlying the effects of climate variables on the daytime LST effects of European forests (ALSTs) in summer. (a) Structure equation models describing the biophysical relationships between climate variables and ALSTs. The numbers denote the path value (mean \(\pm\) standard error). The arrow color indicates the sign of the path (red for positive and blue for negative), and the thickness indicates the magnitude of the corresponding path value. (b) Bar plot of the pathway effects of climate variables affecting ALSTs. The error bars indicate the uncertainty based on error propagation.
+ +Accordingly, we also revised the discussion about the summer mechanism (Line 434). + +Using a range of statistical methods, we find that declining SM, is the predominant factor contributing to both the interannual variation and the negative trend in ALSTs. Path analysis shows that SM, affects ALST, dynamics through two mechanisms. First, we show \(\Delta L A I_{s}\) is modulated by SM, implying that as the soil becomes drier, the vegetation structure difference between forests and openlands becomes more evident. The higher \(\Delta L A I_{s}\) could boost the cooling efficiency of forests through stronger direct heat dissipation and evaporative cooling. The impact of SM, on vegetation has been well-documented: increasing dryness pressure could trigger stomatal closure, inhibit photosynthesis, and increase vegetation mortality (Li et al., 2022; Stocker et al., 2018). Our results confirm a stronger negative effect of SM, on non- forest vegetation than on forests (Hoek van Dijke et al., 2023). The potential reason is that forest ecosystems with high species richness and deep roots are more stable and resilient to dryness (Isbell et al., 2015; Tumber- Dávila et al., 2022). Second, even under constant vegetation conditions, less soil water supply directly amplifies \(\Delta L E_{s}\) and enhances the cooling effect of forests. These findings are consistent with prior researches (Fu et al., 2022a, 2022b), indicating that soil moisture imposes stronger limitations on ET in grasslands and croplands relative to forest ecosystems. This differential response is evidenced by both the greater sensitivity of and the higher critical soil moisture thresholds in non- forest ecosystems. This phenomenon may be attributed to the capacity of forests to maintain ET through deep soil water extraction, thereby exhibiting greater resilience to warming- induced surface soil moisture deficits + +<--- Page Split ---> + +compared to openlands. Overall, the revealed impact of \(SM_{s}\) on \(\Delta LST_{s}\) essentially reflects the diverse vegetation physiological responses to climate changes. + +## Reference: + +Dirmeyer, P. A., Balsamo, G., Blyth, E. M., Morrison, R. & Cooper, H. M. Land- Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018. AGU Adv. 2, 1- 16 (2021). Fischer, E. M., Seneviratne, S. I., Lüthi, D. & Schär, C. Contribution of land- atmosphere coupling to recent European summer heat waves. Geophys. Res. Lett. 34, 1- 6 (2007). + +Fu, Z. et al. Critical soil moisture thresholds of plant water stress in terrestrial ecosystems. Sci. Adv. 8, 1- 12 (2022). Fu, Z. et al. Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems. Glob. Chang. Biol. 28, 2111- 2123 (2022). Hoek van Dijke, A. J. et al. Comparing forest and grassland drought responses inferred from eddy covariance and Earth observation. Agric. For. Meteorol. 341, (2023). Isbell, F. et al. Biodiversity increases the resistance of ecosystem productivity to climate extremes. Nature 526, 574- 577 (2015). Li, W. et al. Widespread increasing vegetation sensitivity to soil moisture. Nat. Commun. 13, 3959 (2022). Lin, C. et al. Diel ecosystem conductance response to vapor pressure deficit is suboptimal and independent of soil moisture. Agric. For. Meteorol. 250- 251, 24- 34 (2018). Novick, K. A. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nat. Clim. Chang. 6, 1023- 1027 (2016). Shen, P. et al. Biodiversity buffers the response of spring leaf unfolding to climate warming. Nat. Clim. Chang. 14, 863- 868 (2024). Stocker, B. D. et al. Quantifying soil moisture impacts on light use efficiency across biomes. New Phytol. 218, 1430- 1449 (2018). Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). Tumber- Dávila, S. J., Schenk, H. J., Du, E. & Jackson, R. B. Plant sizes and shapes above and belowground and their interactions with climate. New Phytol. 235, 1032- 1056 (2022). Zhong, Z. et al. Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity. Sci. Adv. 9, (2023). + +## Reviewer #1 (Remarks on code availability): + +I feel that this might be holding the authors to an excessively high standard. If Nature is asking whether I can strictly replicate results using their code, I believe it would take a significant amount of time, and I don't have the capacity to verify it. However, I feel is that it's unrealistic to expect the authors to cover every detail perfectly and provide a fully automated, one- click runnable code. + +Additionally, I believe that the provided code does not fully include all the components/scripts + +<--- Page Split ---> + +necessary to reproduce all the results of this paper (e.g., the ESM analysis, MODIS data processing). Again, I feel this is holding the authors to an excessively high standard. They are not software engineers. + +Response: Thank you for the feedback concerning code availability. We fully recognize the importance of transparent research practices. In response, we have repudiated the code, including all processed datasets necessary to execute the analysis scripts (https://zenodo.org/records/15625044). These materials enable researchers to fully reproduce all statistical analyses and figures presented in our manuscript. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +I find this manuscript has a lot of interesting data and discussion. Moreover, for me personally, it was highly motivating to read this discussion. I did find, especially at the beginning of the manuscript, that the work was not very well situated in the principal literature. All four of the first references to appear in the manuscript do not seem well suited to set up this general discussion. I have provided a number of suggestions in the attached submission pdf and am hopeful that some of these suggestions will prove useful... + +Response: We appreciate your positive comments. We have revised our manuscript carefully and the detailed corrections are listed below. Specifically, we have thoroughly reorganized the introduction section by incorporating more appropriate foundational literature as suggested in your comments. According to your concern regarding the water availability, we conducted additional experiments to explore the impact of soil moisture, and added related discussions. We hope the revised paper will be more suitable for publication. + +I also found that the introduction was occasionally vague and would have benefitted from a somewhat more nuanced discussion... I have tried to point out places where I think this would be helpful. + +Response: Thanks for the careful reading and pointing out the confusing statements. Your detailed suggestions have helped us significantly improve the manuscript. We provide point- by- point responses to each of your specific comments about the introduction in the PDF file, along with the corresponding revisions we have implemented (please see the response below). + +Finally, the discussion of radiative and non- radiative effects, as well as the discussion of winter and summertime effects, to my mind, were not adequately introduced and motivated in the introductory parts of the paper. When these concepts are suddenly announced, (the discussion about winter and summer time effects first comes up in the results section of the paper?), they are unexpected and seemingly unmotivated in the general context of the paper... This can be improved upon... + +Response: We appreciate this constructive suggestion. We have incorporated background on radiative/non- radiative mechanisms and seasonal (winter/summer) effects in the introduction, ensuring these concepts are properly motivated before appearing in later sections (Line 39). + +During the daytime, forests exhibit two competing effects compared to non- forest vegetation: (a) the non- radiative cooling effect driven by higher evapotranspiration (ET) rates (Mildrexler et al., 2011), and (b) the radiative warming effect resulting from lower albedo (R.A.Betts, 2000). The net temperature response depends on the balance between the opposing radiative and non- radiative effects (Bright et al., 2017), and their relative dominance is largely governed by background climatic conditions (Pitman et al., 2011). For instance, forests in mid- latitude regions (e.g., North America, Europe and China) demonstrate seasonally contrasting LST effects (Li et al., 2015; Tang et al., 2018). During cold winters, bright snow covers short vegetation but is masked by dense forest canopies. As a result, forests absorb more solar radiation and show a local warming effect compared to surrounding openlands. Conversely, during the peak growing season (warm summer), forests + +<--- Page Split ---> + +exert cooling effects under sufficient soil moisture conditions, owing to their higher ET rates compared to other vegetation types. However, in arid regions, limited soil moisture can constrain forest evaporative cooling despite abundant radiation and optimal temperature, causing radiative warming to dominate (Rohatyn et al., 2023). + +## Reference: + +Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1- 10 (2015). Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1- 15 (2011). Pitman, A. J. et al. Importance of background climate in determining impact of land- cover change on regional climate. Nat. Clim. Chang. 1, 472- 475 (2011). Rohatyn, S., Rotenberg, E., Tatarinov, F., Carmel, Y. & Yakir, D. Large variations in afforestation- related climate cooling and warming effects across short distances. Commun. Earth Environ. 4, 1- 10 (2023). R.A. Betts. Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. Nature 408, 187- 190 (2000). Tang, B., Zhao, X. & Zhao, W. Local effects of forests on temperatures across Europe. Remote Sens. 10, 1- 24 (2018). + +I also find that the Authors do not adequately distinguish between global and local cooling... Both terms come up. But most of the time it sounds like the Authors are talking about local cooling... And the balance in terms of global cooling is never clearly estimated...? It is important not to conflate these terms, since local cooling is not necessarily equivalent to global cooling...? + +Response: We appreciate this important criticism. We fully agree with that global and local effects are inherently different. As you mentioned, our manuscript focusses on the local effect. We have added explicit discussion distinguishing between local and global cooling effects of forests in the revised manuscript, with particular attention to their differing mechanisms (Line 477): + +There are several potential caveats or issues when interpreting our results. First, the adopted "space- for- time" method provides priori estimates of local temperature effects of forests (Wang et al., 2023), which is different from the global effects. At the planetary scale, forests can exert more complicated effects on climate through multiple processes such as changes in cloud formation and large- scale atmospheric circulations (Ellison et al., 2024; Xu et al., 2022). Thus, our results should be treated as the reference for local climate adaptation rather than global climate mitigation. + +We also distinguished between the global and local impacts in the background statement (Line 25): + +Through conservation, proper management, and restoration practices, forest ecosystems could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud formation (Cerasoli et al., 2021; Ellison et al., 2024; Luo et al., 2024). In addition to the global impact, forests exhibit significant local cooling or warming effects through altering + +<--- Page Split ---> + +surface energy and water fluxes (Ellison et al., 2024; Lawrence et al., 2022). + +## Reference: + +Cerasoli, S., Yin, J. & Porporato, A. Cloud cooling effects of afforestation and reforestation at midlatitudes. Proc. Natl. Acad. Sci. U. S. A. 118, 1- 7 (2021).Ellison, D., Pokorny, J. & Wild, M. Even cooler insights: On the power of forests to (water the Earth and) cool the planet. Glob. Chang. Biol. 30, 1- 20 (2024).Lawrence, D., Coe, M., Walker, W., Verchot, L. & Vandecar, K. The Unseen Effects of Deforestation: Biophysical Effects on Climate. Front. For. Glob. Chang. 5, 1- 13 (2022).Luo, H., Quaas, J. & Han, Y. Decreased cloud cover partially offsets the cooling effects of surface albedo change due to deforestation. Nat. Commun. 15, 7345 (2024).Wang, H., Yue, C. & Luyssaert, S. Reconciling different approaches to quantifying land surface temperature impacts of afforestation using satellite observations. Biogeosciences 20, 75- 92 (2023).Xu, R. et al. Contrasting impacts of forests on cloud cover based on satellite observations. Nat. Commun. 13, 670 (2022). + +Further, I would have like to see more discussion of the role of the availability of water and surface moisture. The cooling potential of forests strongly depends on the availability of water. As soon as this surface moisture disappears, the loss of latent heat means the warming will suddenly take over... But there is little attention to this throughout the paper... + +Response: Thank you for raising this essential issue. We full acknowledge that both atmospheric water demand (VPD) and soil water supply (soil moisture, SM) can have important effects on the evaporative cooling of vegetation. Given the strong annual- scale correlation between VPD and SM, their respective roles may have been conflated in the original manuscript. Thus, we conducted additional analyses to identify the actual driver of the observed trends in \(\Delta \mathrm{LST}_s\) . Specifically, we used binning regression method (Liu et al., 2020) to decouple summer VPD (VPDs) and summer SM (SMs). The results demonstrated that it is \(\mathrm{SM}_s\) , rather than VPD, dominates with the long- term trend of daytime \(\Delta \mathrm{LST}_s\) , which largely addresses this comment (Line 218): + +Temporal correlation analyses using VPDs, \(AT_s\) , DSRs, \(P_s\) and \(WS_s\) as the potential drivers reveal strong relationships between daytime \(\Delta \mathrm{LST}_s\) and climatic variables except \(WS_s\) (Fig. 3a). However, after accounting for covariates, the partial correlations between the daytime \(\Delta \mathrm{LST}_s\) and DSRs, \(P_s\) and \(AT_s\) are greatly reduced and even reverse in sign. In contrast, VPDs maintain a predominant negative correlation with daytime \(\Delta \mathrm{LST}_s\) , with the mean partial correlation coefficient of - 0.42 (Fig. 3a). Notably, we can also find strong positive partial correlations between SM and \(\Delta \mathrm{LST}_s\) (Fig. 3b) when replacing VPDs by the SMs, the other factor describing the dryness stress. This is due to the strong coupling between SM, \(VPD_s\) at the annual scale ( \(r = 0.92\) , Supplementary Fig. 10). These findings raise the following question: whether variations in atmosphere or soil dryness are the primary factor governing changes in \(\Delta \mathrm{LST}_s\) over the past two decades? + +To answer this question, we then use the binning regression method to further disentangle the respective contributions of VPDs and SMs (Liu et al., 2020). We conduct this analysis using the spatial samples of VPDs, trend and SM, trends with sufficient data for decoupling the two factors. We confirm the strong spatial correlation between SM, trend and VPDs, trends ( \(r = - 0.65\) ) when all + +<--- Page Split ---> + +spatial samples are used. However, after stratifying either \(SM_{s}\) or \(VPD_{s}\) trends into 10 bins according to percentiles, correlations between the two variables show substantial attenuation (Fig. 3c), suggesting the two variables are decoupled. Then, we calculate the correlation between \(SM_{s}\) (or \(VPD_{s}\) ) trends and \(\Delta LST_{s}\) trends in each \(VPD_{s}\) (or \(SM_{s}\) ) trend bin. We find the mean \(r\) between \(VPD_{s}\) trends and \(\Delta LST_{s}\) trends is only - 0.11, whereas the mean \(r\) between \(SM_{s}\) trends and \(\Delta LST_{s}\) trends reach 0.40 (Fig. 3d). This binning regression analysis suggests that change \(SM_{s}\) is more likely to be the driver of \(\Delta LST_{s}\) dynamic. + +![](images/Figure_3.jpg) + +
Fig 3. Dominant role of soil moisture in the temporal dynamics in the summer daytime cooling effect ( \(\Delta LST_{s}\) ) of forests. (a) Regional mean correlation and partial correlation coefficients between five climate variables (vapor pressure deficit, downward solar radiation, precipitation, air temperature and wind speed) and the daytime \(\Delta LST_{s}\) . The error bars indicate the standard deviations. (b) Similar with (a), but replace vapor pressure deficit by the soil moisture. (c) Correlation coefficients between summer vapor pressure deficit ( \(VPD_{s}\) ) trends and summer soil moisture ( \(SM_{s}\) ) trends within either \(SM_{s}\) or \(VPD_{s}\) trends bins. (d) Correlation coefficients between \(VPD_{s}\) (or \(SM_{s}\) ) trends and \(\Delta LST_{s}\) trends within \(SM_{s}\) (or \(VPD_{s}\) ) trends bins.
+ +![](images/Figure_unknown_5.jpg) + +
Fig. S10. Temporal correlation coefficient (r) between summer vapor pressure deficit ( \(VPD_{s}\) ) and surface soil moisture ( \(SM_{s}\) ). (a) Spatial pattern of \(r\) between \(VPD_{s}\) and \(SM_{s}\) . (b) Density of the \(r\) values.
+ +<--- Page Split ---> + +We then build a non- linear random forest model using both \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) as the input. The results also support that \(\mathrm{SM}_s\) plays the more important role in predicting temporal dynamics of \(\Delta \mathrm{LST}_s\) (Line 255): + +The critical role of \(\mathrm{SM}_s\) is corroborated by non- linear statistical analysis using a Random Forest (RF) model (Supplementary Text 1). Variable importance analysis demonstrates that \(\mathrm{SM}_s\) exerts a stronger influence than \(\mathrm{VPD}_s\) in predicting \(\Delta \mathrm{LST}_s\) dynamics. Contribution analysis also reveals that \(\mathrm{SM}_s\) changes account for the largest portion (0.152 K/decade, \(p < 0.05\) ) of the simulated negative \(\Delta \mathrm{LST}_s\) trend (0.181 K/decade, \(p < 0.05\) ), highlighting its dominant role in driving the observed enhanced forest cooling effect (Supplementary Fig. 11). + +## Supplementary Text 1 Modelling \(\Delta \mathrm{LST}_s\) based on random forest + +We apply a non- linear machine learning method, Random Forest (RF), to evaluate the importance and contribution of multiple potential climate drivers for predicting \(\Delta \mathrm{LST}_s\) (sklearn package in Python). Specifically, we use all spatial samples over 20 years to build the dataset. It is worth mentioning that we normalize the input climate variables and \(\Delta \mathrm{LST}_s\) by subtracting the 20- year means at the grid scale, since the model focus on the temporal dynamic of \(\Delta \mathrm{LST}_s\) rather than the spatial variation. We excluded air temperature from the model inputs due to its high correlation with other climate variables. + +The dataset is divided into training (80% of the samples) and test sets (20% of the samples), with model parameters confirmed based on validation results from the test set (number of trees = 100; maximum depth of the tree = 6). All the samples are then used to fit the best model. The relative importance of each variable is indicated by the Gini coefficient. Moreover, we use the Shapley Additive Explanations (SHAP) method to quantify the individual contribution of each variable in each sample (shap package in Python). SHAP is an approach to explain machine learning models based on cooperative game theory, where SHAP values quantify the marginal contributions of predictors. We calculate the mean absolute SHAP values for each input variable as importance metrics and explore the non- linear impact of climate variables on \(\Delta \mathrm{LST}_s\) by plotting their SHAP values against input values. + +Based on the RF model, we set several scenarios to separate the relative contributions of climate variables to the \(\Delta \mathrm{LST}_s\) trend. Specifically, we perform four experimental simulations: (S1) varying \(\mathrm{SM}_s\) only; (S2) varying \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) while fixing \(\mathrm{DSR}_s\) \(P_s\) and \(\mathrm{WS}_s\) ; (S3) varying \(\mathrm{SM}_s\) \(\mathrm{VPD}_s\) and \(\mathrm{DSR}_s\) , while fixing \(P_s\) and \(\mathrm{WS}_s\) ; (S4) varying \(\mathrm{SM}_s\) \(\mathrm{VPD}_s\) \(\mathrm{DSR}_s\) and \(P_s\) , while fixing \(\mathrm{WS}_s\) and (S5) varying \(\mathrm{SM}_s\) \(\mathrm{VPD}_s\) \(\mathrm{DSR}_s\) \(P_s\) and \(\mathrm{WS}_s\) . The Theil- Sen slope and Mann- Kendall \(P\) - value of simulations S1, S2- S1, S3- S2, S4- S3, S5- S4 are used to evaluate the individual contributions of the changing climate to the \(\Delta \mathrm{LST}_s\) trend. + +The model shows good accuracy on the test dataset ( \(R^2 = 0.56\) , \(\mathrm{RMSE} = 0.32 \mathrm{K}\) ), supporting our further analysis. The Gini importance and mean absolute SHAP values both suggest that \(\mathrm{SM}_s\) is the most important driver, followed by \(\mathrm{VPD}_s\) , \(P_s\) , \(\mathrm{DSR}_s\) and \(\mathrm{WS}_s\) (Supplementary Fig 11a). The marginal contributions quantified by the SHAP value further reveal different impacts of \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) (Supplementary Fig. 11b). \(\mathrm{SM}_s\) exhibits the pronounce positive effect, with stronger impact when \(\mathrm{SM}_s\) anomaly is negative. While \(\mathrm{VPD}_s\) only show slight negative impact under certain condition. + +On the basis of the RF model, we estimate the contributions of climate variables to the long- term trend of daytime \(\Delta \mathrm{LST}_s\) (Supplementary Fig. 11c). We first compared the reconstructed trends with all forcings and the observed trends, showing good consistency (observed: 0.188 K/decade, \(p < 0.05\) ; simulated: 0.181 K/decade, \(p < 0.05\) ). By setting different scenarios, results suggest that + +<--- Page Split ---> + +decreasing \(SM_{s}\) contributes the most to the negative trend in daytime \(\Delta LST_{s}\) (- 0.152 K/decade, \(p< 0.05\) ), and increasing VPDs shows lower contribution (- 0.049 K/decade, \(p< 0.05\) ). The isolated contribution of \(\Delta DSR_{s}\) is also statistically significant, but the value is relatively small (0.012 K/decade, \(p< 0.05\) ). The contribution of \(WS_{s}\) and \(P_{s}\) are not significant. + +![](images/Figure_unknown_6.jpg) + +
Fig. S11. Impact of \(SM_{s}\) on the temporal dynamics in \(\Delta LST_{s}\) based on the random forest model. (a) The importance of climate variables is indicated by the absolute SHAP values and Gini coefficients. (b) Variation of SHAP values with changing \(SM_{s}\) or VPDs, anomaly. (c) Observed and modelled \(\Delta LST_{s}\) trends, and the isolated contributions from climate variables.
+ +We also performed additional analyses using in- situ observation and the Penman- Monteith framework to evaluate the sensitivity of \(LE_{s}\) to VPDs. If VPDs is the main driver of enhanced forest cooling effect, we expect to observe greater positive \(LE_{s}\) sensitivity in forests compared to openlands. However, the results do not support this hypothesis (Line 262). + +We also evaluate the sensitivity of summer latent heat \((LE_{s})\) to VPDs in both forests and openlands using eddy covariance observations from European sites (Supplementary Text 2). The sensitivity analysis is based on the Penman- Monteith framework, which accounts for the influence of VPDs on surface resistance (Novick et al., 2016). If VPDs is the main driver of enhanced forest cooling effect, we expect to observe greater positive \(LE_{s}\) sensitivity in forests compared to openlands, in which case forests can produce stronger evaporative cooling effects in the context of rising VPDs. However, we find openlands show slightly higher positive sensitivity than forests, although the difference is not significant. The direct regression analysis also supports the stronger \(LE_{s}\) responses to VPDs increases in openlands (Supplementary Table. 1). This in- situ observational evidence, combined with our statistical results (binning regression and random forest regression), suggests that VPDs may not explain the enhanced cooling effect of European forests, while the decline in \(SM_{s}\) appears to be the real dominant driver. + +<--- Page Split ---> + +## Supplementary Text 2. Sensitivity of summer latent heat to increasing vapor pressure deficit + +Elevated vapor pressure deficit (VPD) exerts dual opposing effects on latent heat (LE) flux: while it directly enhances LE through increased evaporative demand, it simultaneously elevates surface resistance (rs), thereby suppressing LE (Novick et al., 2016). To investigate how VPD differentially influences LE in forests and openlands and consequently affects the cooling effect of forests, we analyze European eddy covariance observations from the FLUXNET2015 dataset and conduct sensitivity analyses. + +The sensitivity of LE to VPD is assessed based on the Penman- Monteith framework, accounting for both the aforementioned opposing effects (Lin et al., 2018): + +\[LE = \frac{\Delta(Rn - G) + \rho C_p(VPD / r_a)}{\Delta + \gamma(1 + r_s / r_a)} \quad (1)\] + +\[G_{s} = G_{0} + G_{1}\frac{G P P}{\nu P D^{m}} \quad (2)\] + +Here, \(R n\) \((W / m^{2})\) is the net radiation; \(G\) \((W / m^{2})\) is the soil heat flux; \(\Delta\) \((kPa / K)\) is the slope of the saturated vapor pressure curve; \(\rho\) is the air density \((kg / m^{3})\) . \(C_{p}\) \((J / kg / K)\) is the specific heat of air; \(\gamma\) is the psychrometric constant \((kPa / K)\) ; \(r_{a}\) (s/m) is the aerodynamic resistance, estimated using vegetation height; \(G_{s}\) (surface conductance) is the inverse of \(r_{s}\) ; GPP is the gross primary productivity. The model parameters \((G_{0}, G_{1},\) and \(m\) ) is estimated via optimization (SciPy package in Python) using daily- scale observations. + +We analysis those observation in summer and we select sites with reliable LE accuracy (Nash- Sutcliffe Efficiency \(>0.5\) ), resulting in 19 forested and 12 openland (grassland and cropland) sites. We then introduce VPDs perturbations into the observation data to estimate summer LE (LEs) sensitivity to VPDs \(\left(\frac{\mathrm{d}LE_{s}}{\mathrm{d}V P D_{s}}\right)\) \(LE_{s}\) response to a 1 hPa VPDs increase). For comparison, we also compute \(\frac{\mathrm{d}LE_{s}}{\mathrm{d}V P D_{s}}\) (i) without the impact of VPDs on \(r_{s}\) and (ii) via direct linear regression between VPDs and \(LE_{s}\) (Supplementary Table 1). + +If VPDs is the primary driver of enhanced forest cooling effect, forests should exhibit a higher \(\frac{\mathrm{d}LE_{s}}{\mathrm{d}V P D_{s}}\) than openlands, implying stronger evaporative cooling under rising VPDs. However, results indicate that this expectation holds only when neglecting the inhibitory effect of VPDs on \(LE_{s}\) (via \(r_{s}\) ). When considering both opposing effects of VPDs on \(LE_{s}\) , openlands show slightly higher mean sensitivity compared to forests. In addition, the direct regression analysis supports the stronger \(LE_{s}\) responses to VPDs increases in openlands. These findings suggest that VPDs may not explain the enhanced cooling effect observed in European forests. + +Table S1. Sensitivity of summer latent heat (LEs) flux to rising vapor pressure deficit (VPDs) based on FLUXNET observations in Europe. + +
dLEs
dVPDs (w·m-2/hPa)
dLEs
dVPDs (w·m-2/hPa)
ignoring the impact of VPD on rs
Regression slope
between VPDs and LEs
(w·m-2/hPa)
Forest (n=19)2.08 ± 1.855.92 ± 2.953.87 ± 2.87
Openland (n=19)2.48 ± 1.714.87 ± 1.326.44 ± 2.67
+ +The values indicate the mean \(\pm\) standard deviation across sites. + +<--- Page Split ---> + +Combined the sensitivity analysis result and the statistical evidence, we recognized that the decreasing \(\mathrm{SM}_s\) appears to be the primary driver of the observed daytime \(\Delta \mathrm{LST}_s\) trends. Thus, we updated the Fig. 4 and the related mechanism descriptions accordingly (Line 276). + +We further conduct structural equation modeling (SEM) to elucidate the biophysical mechanisms underlying the impact of varying \(\mathrm{SM}_s\) on daytime \(\Delta \mathrm{LST}_s\) dynamics (Fig. 4a). Our SEM incorporates two key biophysical mediators: the leaf area index difference ( \(\Delta \mathrm{LAI}_s\) ) and latent heat flux difference ( \(\Delta \mathrm{LE}_s\) ) between nearby forests and openlands. The path effect (mean \(\pm\) standard error) is used to describe strength and direction of the relationship. Following previous studies, we build SEMs at the local scale and calculate the mean path effects of all models (Shen et al., 2024; Zhong et al., 2023). The analysis reveals three distinct pathways of \(\mathrm{SM}_s\) affecting \(\Delta \mathrm{LST}_s\) . + +(1) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) exerts a significant negative effect on \(\Delta \mathrm{LAI}_s\) (-0.41 \(\pm\) 0.15). Then, \(\Delta \mathrm{LAI}_s\) demonstrate a negative effect on \(\Delta \mathrm{LST}_s\) (-0.19 \(\pm\) 0.09). This pathway suggests that reduced \(\mathrm{SM}_s\) can amplify the greenness difference in forests and openlands, thereby enhancing forests' cooling advantage through improved convective heat dissipation. + +(2) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) have a negative effect on \(\Delta \mathrm{LE}_s\) (-0.25 \(\pm\) 0.11), followed by a strong negative influence of \(\Delta \mathrm{LE}_s\) on \(\Delta \mathrm{LST}_s\) (-0.54 \(\pm\) 0.09). This pathway indicates that declining \(\mathrm{SM}_s\) imposes less water limitation to forests compared to openlands, enabling forests to maintain stronger relative evaporative cooling through differential stomatal regulation (with greenness remaining constant). + +(3) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) -induced changes in \(\Delta \mathrm{LAI}_s\) subsequently enhance \(\Delta \mathrm{LE}_s\) (0.62 \(\pm\) 0.06), ultimately influencing \(\Delta \mathrm{LST}_s\) . This demonstrates that \(\mathrm{SM}_s\) reduction amplifies evaporative cooling effects of forests by increasing the vegetation greenness contrast with openlands. + +The pathway effects, representing the strength and direction of the mechanism, are quantified as the product of all constituent path coefficients (Fig. 4b). Results reveal that the second and third pathways (both mediated by \(\Delta \mathrm{LE}_s\) ) contribute equally to \(\Delta \mathrm{LST}_s\) variation (about 0.14 \(\pm\) 0.06), while the impact first pathway is weaker (0.08 \(\pm\) 0.05). These findings suggest \(\mathrm{SM}_s\) can modulate \(\Delta \mathrm{LST}_s\) dynamics through multiple mechanisms, with forest evaporative cooling regulation emerging as the dominant process. Previous studies have demonstrated that reduced soil moisture in Europe can amplify warming during heatwaves through land-atmosphere interactions (Dirmeyer et al., 2021; Fischer et al., 2007). Our findings confirm forests exhibit greater stability and resistance to increasing soil dryness compared to grasslands or croplands, which may mitigate land-atmosphere coupling feedback and consequently enhance the relative cooling effect of forests (Teuling et al., 2010). This stability of forests is reflected in both more moderate evaporative limitation and sustained vegetation greenness under increasing soil dryness. Our results provide observational evidence suggesting that the capacity of forest ecosystems to mitigate water deficit-induced warming persists not only during heatwave events but also across interannual timescales. + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Fig 4. Mechanisms underlying the effects of climate variables on the daytime LST effects of European forests (ALSTs) in summer. (a) Structure equation models describing the biophysical relationships between climate variables and \(\Delta LST_{s}\) . The numbers denote the path value (mean \(\pm\) standard error). The arrow color indicates the sign of the path (red for positive and blue for negative), and the thickness indicates the magnitude of the corresponding path value. (b) Bar plot of the pathway effects of climate variables affecting \(\Delta LST_{s}\) . The error bars indicate the uncertainty based on error propagation.
+ +We also revised the discussion about the summer mechanism (Line 434). + +Using a range of statistical methods, we find that declining \(SM_{s}\) is the predominant factor contributing to both the interannual variation and the negative trend in \(\Delta LST_{s}\) . Path analysis shows that \(SM_{s}\) affects \(\Delta LST_{s}\) dynamics through two mechanisms. First, we show \(\Delta LAI_{s}\) is modulated by \(SM_{s}\) , implying that as the soil becomes drier, the vegetation structure difference between forests and openlands becomes more evident. The higher \(\Delta LAI_{s}\) could boost the cooling efficiency of forests through stronger direct heat dissipation and evaporative cooling. The impact of \(SM_{s}\) on vegetation has been well-documented: increasing dryness pressure could trigger stomatal closure, inhibit photosynthesis, and increase vegetation mortality (Li et al., 2022; Stocker et al., 2018). Our results confirm a stronger negative effect of \(SM_{s}\) on non- forest vegetation than on forests (Hoek van Dijke et al., 2023). The potential reason is that forest ecosystems with high species richness and deep roots are more stable and resilient to dryness (Isbell et al., 2015; Tumber- Dávila et al., 2022). Second, even under constant vegetation conditions, less soil water supply directly amplifies \(\Delta LE_{s}\) and enhances the relative cooling effect of forests. These findings are consistent with prior researches (Fu et al., 2022a, 2022b), indicating that soil moisture imposes stronger limitations on ET in grasslands and croplands relative to forest ecosystems. This differential response is evidenced by both the greater sensitivity of and the higher critical soil moisture thresholds in non- forest ecosystems. This phenomenon may be attributed to the capacity of forests to maintain ET through deep soil water extraction, thereby exhibiting greater resilience to warming- induced surface soil + +<--- Page Split ---> + +moisture deficits compared to openlands. Overall, the revealed impact of \(SM_{s}\) on \(\Delta LST_{s}\) essentially reflects the diverse vegetation physiological responses to climate changes. + +## Reference: + +Dirmeyer, P. A., Balsamo, G., Blyth, E. M., Morrison, R. & Cooper, H. M. Land- Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018. AGU Adv. 2, 1- 16 (2021). + +Fisher, E. M., Seneviratne, S. I., Lüthi, D. & Schär, C. Contribution of land- atmosphere coupling to recent European summer heat waves. Geophys. Res. Lett. 34, 1- 6 (2007). + +Fu, Z. et al. Critical soil moisture thresholds of plant water stress in terrestrial ecosystems. Sci. Adv. 8, 1- 12 (2022). + +Fu, Z. et al. Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems. Glob. Chang. Biol. 28, 2111- 2123 (2022). + +Hook van Dijke, A. J. et al. Comparing forest and grassland drought responses inferred from eddy covariance and Earth observation. Agric. For. Meteorol. 341, (2023). + +Isbell, F. et al. Biodiversity increases the resistance of ecosystem productivity to climate extremes. Nature 526, 574- 577 (2015). + +Li, W. et al. Widespread increasing vegetation sensitivity to soil moisture. Nat. Commun. 13, 3959 (2022). + +Lin, C. et al. Diel ecosystem conductance response to vapor pressure deficit is suboptimal and independent of soil moisture. Agric. For. Meteorol. 250- 251, 24- 34 (2018). + +Liu, L. et al. Soil moisture dominates dryness stress on ecosystem production globally. Nat. Commun. 11, 1- 9 (2020). + +Novick, K. A. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nat. Clim. Chang. 6, 1023- 1027 (2016). + +Shen, P. et al. Biodiversity buffers the response of spring leaf unfolding to climate warming. Nat. Clim. Chang. 14, 863- 868 (2024). + +Shen, P. et al. Biodiversity buffers the response of spring leaf unfolding to climate warming. Nat. Clim. Chang. 14, 863- 868 (2024). + +Stocker, B. D. et al. Quantifying soil moisture impacts on light use efficiency across biomes. New Phytol. 218, 1430- 1449 (2018). + +Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). + +Tumber- Dávila, S. J., Schenk, H. J., Du, E. & Jackson, R. B. Plant sizes and shapes above and belowground and their interactions with climate. New Phytol. 235, 1032- 1056 (2022). + +Zhong, Z. et al. Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity. Sci. Adv. 9, (2023). + +Finally, I wonder why LEW never appears anywhere, but the effects of LEs are estimated... Clearly LEW will be significantly lower. But conifers can evapotranspire almost year round... So, to some degree, LEW should also be available and should have an impact on surface temperatures... ??? + +Response: Thank you for your insightful comment. We fully agree that evergreen forests can sustain transpiration throughout the year. To investigate this potential effect, we calculated the winter latent heat flux (LE) difference between forests and openlands ( \(\Delta \mathrm{LE}_{\mathrm{w}}\) ), and then examined the relationship + +<--- Page Split ---> + +between the winter land surface temperature effect of forests ( \(\Delta \mathrm{LST}_{\mathrm{w}}\) ) and \(\Delta \mathrm{LE}_{\mathrm{w}}\) . Results indicate that the correlation between \(\Delta \mathrm{LE}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) is statistically insignificant (Line 200). This finding supports previous studies reporting that the albedo effect dominates the local temperature effect of boreal forests in the cold season (Alkama and Cescatti, 2016; Lawrence et al., 2022). + +Similarly, we find negligible correlation between \(\Delta \mathrm{LST}_{\mathrm{w}}\) and non- radiative processes represented by winter latent heat flux differences ( \(\Delta \mathrm{LE}_{\mathrm{w}}\) ) (Supplementary Fig. 7). + +![](images/Figure_unknown_7.jpg) + +
Fig. S7. Temporal correlation coefficient (r) between \(\mathrm{LE}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (a to c) Spatial pattern of r between \(\mathrm{LE}_{\mathrm{w}}\) and daily mean, daytime and nighttime \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (d) Density of the r values.
+ +## Reference: + +Alkama, R. & Cescatti, A. Biophysical climate impacts of recent changes in global forest cover. Science (80- .). 351, 600- 604 (2016). Lawrence, D., Coe, M., Walker, W., Verchot, L. & Vandecar, K. The Unseen Effects of Deforestation: Biophysical Effects on Climate. Front. For. Glob. Chang. 5, 1- 13 (2022). + +More to the main point, however, the general finding that wintertime effects exhibit increased cooling due to the loss of snow cover, more or less independently of tree cover (the effect is stronger over open fields than over forested land), is an interesting and valuable finding. However, it remains unclear why this phenomenon would be true in more forested areas... In other words, why would the land surface become lighter under more forested areas, thus leading to wintertime cooling...??? I do not think this is adequately explained...? + +Response: We sincerely appreciate the opportunity to clarify this important point. It is important to note that forests have become "relatively" brighter compared to openlands during the past two decades of snow decline. This relatively brighter trend is evidenced by the increasing \(\Delta \alpha_{\mathrm{w}}\) trend (brown line in Fig. 2a), despite both ecosystems exhibiting absolute darkening trends. The relative brightening stems from forests (green line) darkening at a slower rate than openlands (yellow line). The mechanism is that snow tends to be masked by tree canopies in forest ecosystems, resulting in the greater sensitivity of openland \(\alpha_{\mathrm{w}}\) to snow changes compared to forest \(\alpha_{\mathrm{w}}\) . + +<--- Page Split ---> +![](images/Figure_2a.jpg) + +
Fig 2a. Interannual variations of winter albedo effect of European forests ( \(\Delta \alpha_{\mathrm{w}}\) ) and the individual winter albedo ( \(\alpha_{\mathrm{w}}\) ) for forests and openlands.
+ +To prevent misinterpretation, we have modified the result description (Line 166): + +These results indicate that although forest albedo tends to decline due to snow cover loss, the relative darkening effect of forests, and the additional solar radiation absorbed by forests (compared to adjacent openlands) have diminished in the recent two decades. + +All- in- all however, I did find the manuscript to be very interesting and compelling... I have included a number of comments in the attached submissions pdf. + +Response: Thank you for your positive feedback. Below are the detailed responses to the comments as provided in the PDF document. + +Reviewer #2's comments in the PDF documents: + +Line 17: incomplete sentence... + +Response: Thanks for pointing this out. We have revised the sentence and now it reads (Line 14): + +The negative trends in LST effects of European forests are broadly supported by four state- of- the- art earth system models, though substantial inter- model variability persists in the multi- year means. + +Line 24: There are many much better references for supporting this point... For example, neither reference noted here talks about advantages of forests for water availability in downwind areas...??? + +A few options to consider: + +Cool Insights https://bit.ly/40zILv2 + +On the Forest Cover- Water Yield Debate https://bit.ly/40t3fUM + +From Myth to Concept and Beyond https://bit.ly/4hAenGp + +Response: Thank you for pointing this out. We have replaced the original reference with those you recommended (Line 23). + +Forests provide numerous benefits to humans and the planet, such as producing food and + +<--- Page Split ---> + +energy, reducing soil erosion, and increasing water availability in downwind areas (Bonan, 2008; Borrelli et al., 2017; Ellison et al., 2017, 2012). + +## Reference: + +Ellison, D., Futter, M. N. & Bishop, K. On the forest cover- water yield debate: From demand- to supply- side thinking. Global Change Biology vol. 18 806- 820 (2012). + +Borrelli, P. et al. An assessment of the global impact of 21st century land use change on soil erosion. Nat. Commun. 8, (2017). + +Ellison, D. et al. Trees, forests and water: Cool insights for a hot world. Glob. Environ. Chang. 43, 51- 61 (2017). + +Bonan, G. B. Forests and climate change: Forcings, feedbacks, and the climate benefits of forests. Science (80- .). 320, 1444- 1449 (2008). + +Line 26: Again, the cited references here do not really discuss and defend impacts global climate cooling... But there are several appropriate references that do... + +Even Cooler Insights https://bit.ly/46PTpzi + +https://doi.org/10.1073/pnas.2026241118 + +https://www.nature.com/articles/s41467- 024- 51783- y + +Response: Thank you for your valuable suggestion. We have replaced the original reference with those you recommended (Line 25). + +Through conservation, proper management, and restoration practices, forest ecosystems could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud formation (Cerasoli et al., 2021; Ellison et al., 2024; Luo et al., 2024). + +## Reference: + +Cerasoli, S., Yin, J. & Porporato, A. Cloud cooling effects of afforestation and reforestation at midlatitudes. Proc. Natl. Acad. Sci. U. S. A. 118, 1- 7 (2021). + +Luo, H., Quaas, J. & Han, Y. Decreased cloud cover partially offsets the cooling effects of surface albedo change due to deforestation. Nat. Commun. 15, 7345 (2024). + +Ellison, D., Pokorny, J. & Wild, M. Even cooler insights: On the power of forests to (water the Earth and) cool the planet. Glob. Chang. Biol. 30, 1- 20 (2024). + +Line 27: While certainly the role of carbon is "overemphasized" in this literature, there is in fact a far more extensive literature... Much of it, for example, is referenced and detailed in this paper: + +Even Cooler Insights https://bit.ly/46PTpzi + +I see that a small part of this literature does appear in the following sentences, which suggests that the sentence itself here is primarily misleading... + +Response: Thank you for point this out. For clarity, we have removed the detailed statements about the carbon sink effects of forests. Now the background part reads (Line 23): + +Forests provide numerous benefits to humans and the planet, such as producing food and energy, reducing soil erosion, and increasing water availability in downwind areas. Through conservation, proper management, and restoration practices, forest ecosystems could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud + +<--- Page Split ---> + +formation. In addition to the global impacts, forests exhibit local cooling or warming effects due to their unique biophysical characteristics that regulate surface energy and water fluxes. The biophysical effects of forests on local climate have garnered particular attention in recent years, as it can significantly intensify or offset the climate mitigation effects of carbon sequestration. + +Line 45: Vague..., in what ways...? I would have put the emphasis on the availability of water and how that might change with some climate driven processes and temperature change...??? + +Again, see: Even Cooler Insights https://bit.ly/46PTpzi + +Response: Thanks for the comment. We have revised the discussions about the background climate and added sentence about the impact of water availability (Line 42): + +The net temperature response depends on the balance between the opposing radiative and non- radiative effects (Bright et al., 2017), and their relative dominance is largely governed by background climatic conditions (Pitman et al., 2011). For instance, forests in mid- latitude regions (e.g., North America, Europe and China) demonstrate seasonally contrasting LST effects (Li et al., 2015; Tang et al., 2018). During cold winters, bright snow covers short vegetation but is masked by dense forest canopies. As a result, forests absorb more solar radiation and show a local warming effect compared to surrounding openlands. Conversely, during the peak growing season (warm summer), forests exert cooling effects under sufficient soil moisture conditions, owing to their higher ET rates compared to other vegetation types. However, in arid regions, limited soil moisture can constrain forest evaporative cooling despite abundant radiation and optimal temperature, causing radiative warming to dominate (Rohatyn et al., 2023). + +## Reference: + +Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Pitman, A. J. et al. Importance of background climate in determining impact of land- cover change on regional climate. Nat. Clim. Chang. 1, 472- 475 (2011). Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1- 10 (2015). Tang, B., Zhao, X. & Zhao, W. Local effects of forests on temperatures across Europe. Remote Sens. 10, 1- 24 (2018). Rohatyn, S., Rotenberg, E., Tatarinov, F., Carmel, Y. & Yakir, D. Large variations in afforestation- related climate cooling and warming effects across short distances. Commun. Earth Environ. 4, 1- 10 (2023). + +Line 56: This statement is quite broad...??? Platitude...??? Can you be more precise, more nuanced...? + +Response: Thank for the comment. We have revised the sentence and now it reads (Line 55): + +Given the profound influence of background climate on forest biophysical processes, it is reasonable to infer that the regulation of forests on local temperature will shift in response to rising \(CO_2\) concentration, global warming, or varying water availability. + +<--- Page Split ---> + +Line 76: can you be more explicit...??? This could be more clearly motivated with stronger discussions of radiative and non- radiative impacts more clearly delineated and categorized from the beginning... + +Response: Thanks for the suggestion. We have clarified the radiative and non- radiative impacts in the introduction section (Line 39): + +During the daytime, forests exhibit two competing effects compared to non- forest vegetation: (a) the non- radiative cooling effect driven by higher evapotranspiration (ET) rates (Mildrexler et al., 2011), and (b) the radiative warming effect resulting from lower albedo (R.A.Betts, 2000). + +## Reference: + +Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1- 15 (2011). + +R.A.Betts. Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. Nature 408, 187- 190 (2000). + +Line 104: Up to now, nighttime effects have NOT been previously mentioned... However, you note that such effects have been found previously, and that there is a literature... Can you motivate these effects...? And shouldn't they also be discussed in to introductory sections above...? The drivers of these effects need to be carefully founded and described...??? + +Response: Thanks for pointing this out. We have added description about the nighttime LST effect of forests in the introduction section (Line 36): + +At night, forests warm the land surface through two mechanisms: (1) the release of daytime heat storage during nighttime, and (2) reduced aerodynamic resistance that enhances turbulent mixing, facilitating downward heat transfer from warmer air aloft (Lee et al., 2011; Schultz et al., 2017). + +## Reference: + +Lee, X. et al. Observed increase in local cooling effect of deforestation at higher latitudes. Nature 479, 384- 387 (2011). + +Schultz, N. M., Lawrence, P. J. & Lee, X. Global satellite data highlights the diurnal asymmetry of the surface temperature response to deforestation. J. Geophys. Res. Biogeosciences 122, 903- 917 (2017). + +Line 150: Could this relationship also be confirmed via other methods, such as NDVI...? And more generally, why would forested areas become lighter in color over time, if snow cover is declining...? This seems counter- intuitive and contradictory...??? + +Response: Sorry for the misleading. Our results demonstrate that while both forested and open areas experience surface darkening due to snow cover decline, the darkening effect is more pronounced in openlands. This differential response means forests have become "relatively brighter" compared to adjacent openlands over time. We have clarified this point in the revised manuscript (Line 166): + +These results indicate that although forest albedo tends to decline due to snow cover loss, the relative darkening effect of forests, and the additional solar radiation absorbed by forests (compared + +<--- Page Split ---> + +Line 205: VPD is of course also tied to the availability of water on the land surface... If less water can evaporate, VPD will rise... + +Response: Thanks for the professional comment. Since VPD and availability of water (soil moisture) are strongly coupled at the annual scale, we have added new experiments disentangle the contributions of increasing VPD and decreasing soil moisture in the revised manuscript. Please see the response to your major comment about soil moisture above. + +Line 226: Clearly some of these variables, in particular VPD and T, exhibit significant colinearity... How is this handled... And how do you know which of these two variables is the dominant factor...??? + +Response: Thank you for raising this methodological consideration. We fully acknowledge the collinearity between climate variables, particularly VPD and T. To address this inherent covariation among meteorological drivers, we employed partial correlation analysis, which is a robust approach that isolates the unique relationship between the driver and the target variable (e.g., VPD and \(\Delta \mathrm{LST}_s\) ) while statistically controlling for confounding effects of covariates (e.g., T, precipitation, radiation...). By removing the influence of covariance, the residual VPD- \(\Delta \mathrm{LST}_s\) correlation reflects moisture- driven effects independent of thermal or radiation contributions, as well as any non- linear or interactive relationships not captured by simple linear covariation with temperature. + +Using partial correlation, we reveal a critical distinction (Fig. 3a- b): while direct correlations (light bars) showed significant relationships between \(\Delta \mathrm{LST}_s\) and all climate variables (except wind speed), partial correlations (dark bars) demonstrated that VPD or soil moisture (SM) maintain the strongest independent associations with \(\Delta \mathrm{LST}_s\) even after accounting for other drivers. It is important to note that partial correlation cannot fully disentangle the effects of SM and VPD when both two variables are included in one model simultaneously, as they exhibit near- perfect collinearity at the annual scale ( \(r = 0.92\) ). That's why we add other experiments to disentangle their contributions. + +![](images/Figure_3a.jpg) + +
Fig 3a and 3b. Regional mean correlation and partial correlation coefficients between climate variables and the daytime \(\Delta \mathrm{LST}_s\) .
+ +We have enhanced the methods section to provide a detailed explanation of our partial temporal correlation analysis approach (Line 696): + +<--- Page Split ---> + +In addition, partial temporal correlation analysis is used to explore the relative impacts of multiple climate drivers on \(\Delta \mathrm{LST}_s\) at the pixel scale (pinguin package in Python). The partial correlation can determine whether a climate variable can exert an independent effect on target variable beyond its covariation with other climate drivers. For instance, the partial correlation can isolate the association between \(\Delta \mathrm{LST}_s\) and \(\mathrm{SM}_s\) while accounting for the influence of other covariates (e.g., temperature and precipitation) on \(\mathrm{SM}_s\) . + +Line 266: Are there any estimates of LEw...? Evergreen forests will evapotranspire almost year round...??? So what does this relationship look like...? + +Response: Thank you for your insightful comment. We examined the relationship between \(\Delta \mathrm{LST}_w\) and \(\Delta \mathrm{LE}_w\) (Fig. R5). Results indicate that the correlation between \(\Delta \mathrm{LE}_w\) and \(\Delta \mathrm{LST}_w\) is statistically insignificant (Fig. R5a). In contrast, \(\Delta \alpha_w\) exhibits a significant correlation with \(\Delta \mathrm{LST}_w\) (Fig. R5b). These findings suggest that temporal variations in radiative processes, rather than evapotranspiration- related mechanisms, are more likely to drive the observed changes in \(\Delta \mathrm{LST}_w\) . + +![](images/Figure_unknown_8.jpg) + +
Fig. R5. Temporal relationship between \(\Delta \mathrm{LST}_w\) and \(\Delta \mathrm{LE}_w\) or \(\Delta \alpha_w\) .
+ +In addition, we observed an unexpected negative \(\Delta \mathrm{LE}_w\) , indicating that forest latent heat flux was slightly lower than that of openlands (multi- year mean: \(- 1.3 \mathrm{w} / \mathrm{m}^2\) ). This finding is aligned with previous study based on land surface model simulation and remote sensing data (Breil et al., 2021; Zan et al., 2024). To further assess this result, we compared winter LE observations from European forest and openland (grassland and cropland) sites using FLUXNET2015 dataset (Fig. R6). The results revealed that, on average, openland LE exceeded forest LE, though the difference was not statistically significant. This result ensures the reliability of our remote sensing- based results. + +![](images/Figure_unknown_9.jpg) + +
Fig. R6. Winter latent heat flux (LE) at European forest and openland sites based on FLUXNET observations. Each data point represents the site mean. Red asterisk indicates the muti-site mean.
+ +<--- Page Split ---> + +In summary, our results indicate that while wintertime evapotranspiration persists in forests, its magnitude does not differ significantly from openlands. The temporal variation in \(\Delta \mathrm{LST}_{\mathrm{w}}\) appears to be driven primarily by radiative processes rather than LE- related mechanisms. + +## Reference: + +Breil, M., Davin, E. L. & Rechid, D. What determines the sign of the evapotranspiration response to afforestation in European summer? Biogeosciences 18, 1499- 1510 (2021). + +Zan, B. et al. Spatiotemporal inequality in land water availability amplified by global tree restoration. Nat. Water (2024) doi:10.1038/s44221- 024- 00296- 5. + +Line 278: The availability of water, however, is also key here... If the water disappears, then these effects will flip... So, how does one integrate the effects of water availability into these measures...??? + +Response: Thanks for pointing this issue. Please see our response to your comment above, in which the role of water availability (soil moisture) is explored and discussed in detail. + +Line 391: This could be better expressed... One could just as easily substitute southwards here, since you do not clearly specify distinctions between cooling and warming effects...??? + +Response: Thanks for your suggestion about the expression. We have modified the sentence and now it reads (Line 413): + +This result implies that forests in mid- to high- latitude regions could exhibit similar reduced warming effects or even reversed net cooling in a warming world. Such changes may push the latitudinal boundary between forest warming and cooling effects poleward, primarily due to diminished snow- related albedo feedback. + +<--- Page Split ---> + +## Response to Reviewers' Comments + +We greatly appreciate the anonymous reviewers for the constructive comments. The manuscript has been revised and improved accordingly. We hope that the revision will make it more acceptable for publication. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in red and Italic). The changes are also marked in red in the manuscript file. + +## Reviewer #1 (Remarks to the Author): + +The authors have made significant improvements, conducted substantial additional analyses, and even revised their conclusions regarding the role of VPD. I am satisfied with most of these efforts and have only one remaining comment. + +Response: We appreciate the constructive and valuable comments by the reviewer during the review process. + +"In the summertime, the vegetation physiological response to decreased soil moisture boosts the cooling effect of forests." + +This statement may still be confusing or even misleading. It implies that forests have a stronger cooling effect than grasslands solely due to their physiological response to dry soils. In reality, while physiological processes such as stomatal regulation do influence surface energy balance, the observed cooling effect in forests may also stem from hydrological advantages, including deeper soil water storage and more consistent precipitation recharge in forested areas. + +Response: Thanks for pointing this out. We have revised the sentence to accurately describe this mechanism (Line 13): + +During summer, the daytime cooling effect intensifies (- 0.188 K/decade) because forests remain more physiologically and hydrologically resilient to increasing soil dryness. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +I find that a lot of interesting points come up in this analysis. I am, however, a bit concerned that the paper could still benefit from some significant editing and rewriting. I raise a number of questions in the attached submission pdf. I guess that, primarily, I am unconvinced by the forest albedo logic used herein and would be tempted to argue in a different direction on many points. Please see the related comments in the text. + +Response: We sincerely appreciate your positive and constructive feedback. We understand your concerns regarding our interpretation of the winter land surface temperature effect of conversion from openlands to forests (ALSTw). In response to your feedback, we have conducted additional experiments to quantitatively compare the contributions of albedo- and ET- related processes to the ALSTw trend. We identify the albedo- related process, rather than the ET- related process, as the main driver of ALSTw change. Please see the response to your later comments on line 115. + +Further, I do think that the paper seems inclined to somehow lay the blame for these changes on forests, when actually, most of the important changes seem to be occurring elsewhere (in open fields that have reduced amounts of forest cover, and not in heavily forested areas) and are primarily driven by climate warming (and not any change in forests themselves).... + +Response: Thank you for pointing this out. Our study analyzes differences between forests and adjacent openlands (Δx) to derive a priori estimates of potential forestation effects (openland- to- forest conversion). We fully agree with your view that the change in Δx should not be exclusively attributed to forests. The Δx variations may stem from either forest modifications or alterations in the reference openlands. To ensure clarity, we employ the term "forestation" to emphasize that our analysis specifically examines forest- openland comparisons. We have carefully reviewed the manuscript and modified ambiguous descriptions accordingly. + +For instance, we have revised the title (Line 1): + +Amplified Local Cooling Effect of Forestation in Warming Europe + +We also revised the sentence in the abstract (Line 7): + +By comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify the temporal trends in local land surface temperature (LST) effects of potential forestation in Europe. + +We added a sentence to highlight that the change is more significant in openlands in winter results (Line 189): + +Notably, the observed ALSTw trend should not be attributed to structural or physiological changes in forests, but rather to the more pronounced albedo reduction in openlands in a warming world. + +Furthermore, we added a discussion to clarify that the change in ALST may originate from both forests or openlands (Line 505): + +First, the observed negative trends in ALSTw and ALSTs reflect variations in LST difference when comparing forests and openlands, rather than the inherent capacity of existing forests to reverse warming trends. These patterns may originate from either modifications in forest characteristics or changes in the adjacent openland used as reference. Fundamentally, the negative trends emerge because forests exhibit a weaker temperature response than openlands in a warming + +<--- Page Split ---> + +climate, and this divergence stems from distinct biophysical and physiological properties between forest and openland vegetation. + +We hope these revisions will enhance the readability. + +I do think that with another round of editing, this paper can be significantly improved... I am uncertain, however, how one should resolve the problem of over- emphasising forest albedo effects. This would ultimately require some different measures. Perhaps the Authors can respond to this point...? What do they think is the best procedure here...? Personally, I would be inclined to take this in a somewhat different direction. + +Response: We sincerely appreciate your insightful suggestion regarding the potential mechanism of the \(\Delta \mathrm{LST}_{\mathrm{w}}\) variations. In response to your valuable feedback, we have added experiments to compare the albedo- and ET- related effect based on the energy balance equation. This analysis is to quantitatively assess the relative importance of these two processes in \(\Delta \mathrm{LST}\) changes. We also added a discussion about the ET- related mechanism. Please see the detailed response to your later comments on line 115. + +Moreover, while the forest albedo literature considers albedo effects, it entirely neglects cloud related effects... Since these are presumably also tied to forests, in part, what does this say about the methodology employed in the analysis...??? + +Response: We appreciate your insightful critique regarding cloud- related effects. We fully agree that cloud feedback is an important pathway of forest affecting the climate system. As you rightly pointed out, the space- for- time substitution method employed in our study primarily captures forests' direct modulation of surface albedo rather than planetary albedo. We would like to note that several studies have qualitatively assessed forests' impact on cloud formation using similar methodologies combined with satellite observations (Duveiller et al., 2021; Xu et al., 2022). However, quantitatively evaluating the equivalent radiative forcing of forest- cloud feedback remains challenging. + +If the remote sensing- based results are properly interpreted, we believe that our methodological approach and findings are scientifically valid and useful. First, while the method focuses on the local effects, it provides accurate assessments that can serve as valuable benchmarks for improving climate models and reanalysis datasets regarding the land- atmosphere interaction, which is a fundamental prerequisite for understanding forests' influence on cloud formation. Previous modeling studies examining forest cover impacts on cloud- radiative effects have shown considerable uncertainty in their results (Cerasoli et al., 2021; Luo et al., 2024). Second, the used method captures the direct impacts of forest on local LST, which are effective across spatial scales. In contrast, forest- cloud feedback operates at the regional scale and depends on the intensity of forest change. For instance, even forestation/deforestation in a small area can immediately affect LST, while cloud impacts may be masked by the atmospheric advection. Thus, our assessments provide insights for climate adaptation strategies at the local scale. These findings complement rather than contradict other regional or larger- scale modeling studies. We have added a discussion about this issue (Line 504): + +Second, the adopted "space- for- time" method provides a priori estimates of the local temperature effect. The influence of forests on regional cloud formation and subsequent downward + +<--- Page Split ---> + +radiation represents a significant yet overlooked mechanism in current assessments. This omission may lead to a systematic underestimation of forests' net cooling effect. Meanwhile, forests can exert more complicated effects on climate through multiple processes such as changes in large- scale atmospheric circulations. Coupled models can effectively estimate these effects, notwithstanding the considerable uncertainties. Thus, our results should be treated as the reference for local climate adaptation rather than global climate mitigation. + +## Reference: + +Cerasoli, S., Yin, J. & Porporato, A. Cloud cooling effects of afforestation and reforestation at midlatitudes. Proc. Natl. Acad. Sci. U. S. A. 118, 1- 7 (2021). + +Duveiller, G. et al. Revealing the widespread potential of forests to increase low level cloud cover. Nat. Commun. 12, 1- 15 (2021). + +Luo, H., Quaas, J. & Han, Y. Decreased cloud cover partially offsets the cooling effects of surface albedo change due to deforestation. Nat. Commun. 15, 7345 (2024). + +Xu, R. et al. Contrasting impacts of forests on cloud cover based on satellite observations. Nat. Commun. 13, 670 (2022). + +Line 11: Since this observation runs in the face of quite a large amount of literature which suggests the opposite relationship, perhaps this is worth highlighting, or perhaps this should be stated in a more nuanced fashion...? See for example some of the literature highlighted in Ellison et al., 2024, perhaps, in particular, Davin et al., http://journals.ametsoc.org/doi/10.1175/2009JCLI3102.1 or, Lawrence et al., 2022 + +Response: Thank you for pointing this out. Our findings reveal a winter daytime warming effect in forests compared to openlands initially. However, this daytime warming gradually diminishes and eventually reverses, while the nighttime warming effect persists. For clarity, we have revised the relevant sentence (Line 7): + +By comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify the temporal trends in local land surface temperature (LST) effects of potential forestation in Europe. During winter, the daytime warming effect of forestation diminishes and reverses to cooling (- 0.142 K/decade) due to weaker surface darkening trends in forests than openlands, induced by decreasing snow cover. + +Line 26: Could perhaps highlight relative importance of enhancing/increasing forest cover..., since only change in forest cover is likely to help redress global warming... + +Response: Thank you for the suggestion. We have revised the sentence and now it reads (Line 26): + +Increasing forest cover through restoration practices could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud formation. + +Line 39: ???... + +Response: Thank you for the comment. We have expanded the description of this mechanism (Line 37): + +At night, forests warm the land surface compared to open lands through two mechanisms. First, + +<--- Page Split ---> + +forest canopies absorb solar radiation and store heat during the daytime and subsequently release this energy at night. Second, the nighttime land surface is typically cooler than the near- surface air, forming a stable boundary layer where downward atmospheric heat fluxes warm the land surface. Forests, with their greater surface roughness, can intensify turbulent mixing, enhance this heat exchange process, leading to higher nighttime LST observed in forested areas. + +Line 41: I think this is not entirely correct... I agree this is the way we commonly think about this relationship. But, consider the following: (b) only or primarily occurs in the absence of (a). The net temperature effect is a function of the availability of soil moisture, not of the net radiative balance. ...? + +Warming occurs when soil moisture is depleted and is no longer able to mitigate albedo effects, otherwise the surface is kept from warming through ET production (energy absorption, latent heat) and the transfer of heat energy into the lower atmosphere. + +So warming/cooling is not measured by the net radiative effects, but rather of the relative duration of time during which soil moisture is available and not...??? (I am sure this can be better expressed...). + +This is especially true at the micro/local LST scale at which you measure climate impacts here, but ignores larger scale global climate impacts.... + +Response: Thanks for your insightful comment. We fully recognize the fundamental role of soil moisture (SM) in governing vegetation water availability and its consequent influence on evapotranspiration- mediated cooling effects. However, we hold the view that this SM- related mechanism remains consistent with the established paradigm that "the net temperature response is determined by the balance between competing radiative and non- radiative processes", which is based on the surface energy balance (SEB) framework (Bright et al., 2017; Duveiller et al., 2018; Rigden and Li, 2017). In the SEB equation, LST governs upward longwave radiation (LW↑), which can be expressed as: + +\[LW\uparrow = \epsilon \sigma LST^{4} = SW\downarrow (1 - \alpha) + LW\downarrow -LE - H - G \quad (R1)\] + +where \(\epsilon\) represents emissivity, \(\sigma\) denotes the Stefan- Boltzmann constant, SW↓ indicates downward shortwave radiation, \(\alpha\) is albedo, LW↓ represents downward longwave radiation, and LE, H, and G correspond to latent heat, sensible heat, and ground heat flux, respectively. + +Assuming limited impact of forest cover on background downward radiation and neglecting the emissivity differences between forests and open lands, the LST effect (ΔLST, forest minus open lands) can be expressed in differential form (with \(\Delta\) prefix representing forest minus open land differences): + +\[\Delta LST = \frac{1}{4\sigma ELST^3} (-\Delta \alpha \cdot SW\downarrow -\Delta LE - \Delta (H + G)) \quad (R2)\] + +Equation R2 decomposes \(\Delta LST\) into three components on the right side. The radiative effect is captured by the first, while non- radiative effects are represented by the remaining two terms, with \(\Delta LE\) being the dominant component. + +The control of SM can be well integrated into this framework. Specifically, SM is a critical environmental factor modulating transpiration rates of vegetation, and thus serves as a key driver of \(\Delta LE\) (i.e. \(\Delta LE = f(SM)\) ). Through affecting \(\Delta LE\) , SM can further influence both the sign and magnitude of \(\Delta LST\) . Specifically, forests maintain higher transpiration rates than non- forest + +<--- Page Split ---> + +vegetation (positive \(\Delta \mathrm{LE}\) ) across a broad spectrum of soil moisture, resulting in a significant cooling effect of forests (negative \(\Delta \mathrm{LST}\) ). However, if soil moisture falls below the wilting point of trees, the forests' evaporative advantage should be constrained, allowing albedo- driven radiative effects to dominate \(\Delta \mathrm{LST}\) . + +Therefore, we believe that the impact of SM does not conflict with the mechanism of the balance between radiative and non- radiative effects. We emphasize that SM's control operates through its influence on the radiative/non- radiative balance by regulating \(\Delta \mathrm{LE}\) . This creates a unified framework where background climatic or environmental conditions determine the feasibility of evaporative cooling, and the energy balance further quantifies the \(\Delta \mathrm{LST}\) expression. + +Based on your comment, we have revised the paragraph to highlight the role of background climate and environmental conditions, including SM (Line 44): + +During the daytime, forests commonly exhibit two competing effects compared to non- forest vegetation: (a) the non- radiative cooling effect driven by higher evapotranspiration (ET) rates (when water supply is sufficient), and (b) the radiative warming effect resulting from lower albedo. The net temperature response depends on the balance between these opposing effects, which is predominantly governed by the background climatic or environmental conditions (e.g., temperature, snow cover, and water availability). For instance, during boreal winter when ET is rendered inactive by low temperatures, the dense forest canopies obscure bright snow, which remains exposed in openlands. This snow masking effect creates a strong albedo contrast between forests and openlands and causes forests to absorb more solar radiation compared to surrounding openlands, resulting in the local warming effect. In warm and wet tropics, forests demonstrate pronounced local cooling effects due to their enhanced ET rates relative to other vegetation types. Limited soil moisture in arid regions or during drought events can constrain forests' evaporative advantage, enabling radiative warming to dominate. Consequently, the magnitude of forests' cooling effect at seasonal or annual scale may depends on the duration of sufficient water availability. + +Regarding the scale- dependency of climate effects, we acknowledge that our remote sensing- based approach has limitations in capturing forest- climate effect at larger scales. We have explicitly addressed this constraint in our discussion and emphasized the importance of proper interpretation of our findings (Line 517): + +Meanwhile, forests can exert more complicated effects on climate through multiple processes such as changes in large- scale atmospheric circulations. Coupled models can effectively estimate these effects, notwithstanding the considerable uncertainties. Thus, our results should be treated as the reference for local climate adaptation rather than global climate mitigation. + +## Reference: + +Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64- 75 (2018). Rigden, A. J. & Li, D. Attribution of surface temperature anomalies induced by land use and land cover changes. Geophys. Res. Lett. 44, 6814- 6822 (2017). + +<--- Page Split ---> + +Line 49: At least as long as ET is rendered inactive by lower temperatures.... This could be made more explicit... Note that coniferous trees evapotranspire for much longer periods of time on the annual scale... ??? + +Response: Thanks for the professional comment. We have revised the sentence and now it reads (Line 51): + +For instance, during boreal winter when ET is rendered inactive by low temperatures, the dense forest canopies obscure bright snow, which remains exposed in openlands. This snow masking effect creates a strong albedo contrast between forests and openlands and causes forests to absorb more solar radiation compared to surrounding openlands, resulting in the local warming effect. + +Line 115: I tend to think that these estimates should be paired with indications of the changes in wintertime ET behavior. One might expect, with coniferous species at least, that warming will increase the potential for wintertime ET production, and therefore wintertime cooling effects from forests...? + +Response: Thanks for the insightful comment. We agree with your opinion that in the warmer winter, the evaporative cooling effect of forests (compared to openlands) may be intensified and lead to the observed \(\Delta \mathrm{LST}_{\mathrm{w}}\) trends. In response to your suggestion, we have conducted additional experiments examining this process (Supplementary text 1). Our results confirm that albedo- driven variations, rather than evapotranspiration- related processes, are primarily responsible for the observed trend in \(\Delta \mathrm{LST}_{\mathrm{w}}\) (Line 147). + +During winter, the sign and absolute value of \(\Delta \mathrm{LST}_{\mathrm{w}}\) are generally dominated by the magnitude of the radiative process. However, the negative trend in \(\Delta \mathrm{LST}_{\mathrm{w}}\) could potentially arise from two mechanisms: (a) climate- driven alterations in net shortwave radiation absorption differences between forests and openlands ( \(\Delta \mathrm{NSR}_{\mathrm{w}}\) ), or (b) winter warming- induced enhancement in forests' evaporative cooling advantage, represented by latent heat differences between the two land cover types ( \(\Delta \mathrm{LE}_{\mathrm{w}}\) ). To identify the dominant mechanism, we estimate the equivalent perturbations of the two processes on the surface energy balance (Supplementary Text 1). Our analysis reveals that only \(\Delta \mathrm{NSR}_{\mathrm{w}}\) exhibits a statistically significant trend (- 0.86 w·m- 2/decade, \(p = 0.05\) ), whereas the \(\Delta \mathrm{LE}_{\mathrm{w}}\) trend remains non- significant (- 0.02 w·m- 2/decade, \(p = 0.97\) ) (Supplementary Fig. 3). Correlation analyses of interannual variability further support the greater importance of radiative processes, and confirm that this effect is mediated through modifications in the albedo difference ( \(\Delta \alpha_{\mathrm{w}}\) ) between forests and openlands (Supplementary Figs. 4 to 6). + +## Supplementary Text 1. Identifying the dominant process of \(\Delta \mathrm{LST}_{\mathrm{w}}\) change + +We employ the surface energy balance (SEB) framework to identify the primary processes driving variations in \(\Delta \mathrm{LST}_{\mathrm{w}}\) . This framework has been widely adopted for decomposing the effects of vegetation changes on local LST (Bright et al., 2017; Duveiller et al., 2018; Rigden and Li, 2017). In the SEB equation, LST governs upward longwave radiation (LW↑), which can be expressed as: + +\[LW\uparrow = \epsilon \sigma LST^4 = SW\downarrow (1 - \alpha) + LW\downarrow -LE - H - G \quad (1)\] + +where \(\epsilon\) represents emissivity, \(\sigma\) denotes the Stefan- Boltzmann constant, \(SW\downarrow\) indicates downward shortwave radiation, \(\alpha\) is albedo, \(LW\downarrow\) represents downward longwave radiation, and \(LE\) , \(H\) , and \(G\) + +<--- Page Split ---> + +correspond to latent heat, sensible heat, and ground heat flux, respectively. + +Assuming minimal forest cover influence on background downward radiation and negligible emissivity differences between forests and openlands, the LST effect (ALST, forest minus openlands) can be expressed in differential form (with \(\Delta\) prefix representing forest minus open land differences): + +\[\Delta LST = \frac{1}{4\sigma ELST^3} (-\Delta \alpha \cdot SW \downarrow -\Delta LE - \Delta (H + G)) \quad (2)\] + +Equation 2 decomposes \(\Delta LST\) into three components on the right side. The radiative effect is captured by the first, while non- radiative effects are represented by the remaining two terms, with \(\Delta LE\) being the dominant component. + +We calculate winter differences in net solar radiation (ANSRw = - \(\Delta \alpha_{w}SW\downarrow\) ) and latent heat (ALEw) between spatially adjacent forests and openlands for each year; analogous to \(\Delta LST_{w}\) . As shown in Supplementary Fig. 3a, positive \(\Delta NSR_{w}\) values indicate a warming effect from potential forestation. Surprisingly, we consistently observe negative \(\Delta LE\) values (positive - \(\Delta LE\) across all years, suggesting slightly lower latent heat flux in forests compared to openlands during winter. This finding aligns with previous modeling and remote sensing studies (Breil et al., 2021; Zan et al., 2024), indicating that forests exhibit no evaporative cooling advantage over openlands in winter. + +Temporal analysis reveals a statistically insignificant trend in \(\Delta LE_{w}\) \((p = 0.97)\) , while \(\Delta NSR_{w}\) showed a significant negative trend \((p = 0.05)\) (Supplementary Fig. 3a). Similar results are obtained when comparing evergreen needleleaf forests (which maintain winter evapotranspiration) with openlands (Supplementary Fig. 3b). These findings strongly suggest that the observed trend in \(\Delta LST_{w}\) is driven primarily by decreasing shortwave radiation absorption differences between forests and openlands, rather than by changes in \(\Delta LE_{w}\) . + +Furthermore, we compute annual correlation coefficients between \(\Delta LST_{w}\) (daily, daytime, and nighttime) and both \(\Delta NSR_{w}\) and \(\Delta LE_{w}\) . A positive correlation emerged between daytime \(\Delta LST_{w}\) and \(\Delta NSR_{w}\) \((r = 0.42\) ; Supplementary Fig. 4), while correlations between \(\Delta LST_{w}\) and \(\Delta LE_{w}\) are statistically insignificant (Supplementary Fig. 5). These interannual correlation patterns corroborate our trend- based conclusions. + +Notably, \(\Delta NSR_{w}\) represents the product of both background downward solar radiation (DSRw) and albedo differences ( \(\Delta \alpha_{w}\) ) between forests and openlands. Additional analysis reveals weak correlation between \(\Delta DSR_{w}\) and \(\Delta LST_{w}\) (Supplementary Fig. 6). These results suggest that \(\Delta \alpha_{w}\) , rather than \(\Delta DSR_{w}\) , should serve as the principal driver of \(\Delta LST_{w}\) variation. + +<--- Page Split ---> +![](images/Supplementary_Figure_3.jpg) + +
Supplementary Fig. 3. Temporal variations of winter net solar radiation difference (ANSRw) and latent heat difference (ΔLEw) between forests and openlands in Europe. (a) All forest samples are used. (b) Only evergreen needleleaf forest samples are used.
+ +![](images/Supplementary_Figure_4.jpg) + +
Supplementary Fig. 4. Temporal correlation coefficient (r) between \(\Delta \mathrm{NSR}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (a to c) Spatial pattern of \(r\) between \(\Delta \mathrm{NSR}_{\mathrm{w}}\) and daily mean, daytime and nighttime \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (d) Density of the \(r\) values.
+ +<--- Page Split ---> +![](images/Supplementary_Figure_5.jpg) + +
Supplementary Fig. 5. Temporal correlation coefficient (r) between \(\Delta LE_{w}\) and \(\Delta LST_{w}\) . (a to c) Spatial pattern of \(r\) between \(\Delta LE_{w}\) and daily mean, daytime and nighttime \(\Delta LST_{w}\) . (d) Density of the \(r\) values.
+ +![](images/Supplementary_Figure_6.jpg) + +
Supplementary Fig. 6. Temporal correlation coefficient (r) between \(\mathrm{DSR}_{w}\) and \(\Delta LST_{w}\) . (a to c) Spatial pattern of \(r\) between \(\mathrm{DSR}_{w}\) and daily mean, daytime and nighttime \(\Delta LST_{w}\) . (d) Density of the \(r\) values.
+ +Moreover, we concur with your perspective that warmer winters could theoretically enhance the evaporative cooling effect of forests relative to openlands, potentially contributing to \(\Delta LST_{w}\) variations. Our results did not detect such signals in the current climate regime. This absence may + +<--- Page Split ---> + +be attributed to the nonlinear response of LE to temperature increases. Specifically, current winter warming trends in Europe remain insufficient to significantly stimulate transpiration in forests. In the future, continued warming may eventually cross a critical threshold where temperature increases become sufficient to activate wintertime evapotranspiration processes. Under such a scenario, ET- related mechanisms could potentially emerge as a more dominant factor in governing winter land surface temperature differences. We have added a discussion about this mechanism in the discussion (Line 199): + +Furthermore, though not yet observed, rising temperatures may exceed a critical threshold that enhances cold- season ET in the future. This may strengthen the evaporative cooling effect of forests under future warming conditions, especially in coniferous forests with year- round transpiration activity. + +## Reference: + +Breil, M., Davin, E. L. & Rechid, D. What determines the sign of the evapotranspiration response to afforestation in European summer? Biogeosciences 18, 1499- 1510 (2021). Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64- 75 (2018). Rigden, A. J. & Li, D. Attribution of surface temperature anomalies induced by land use and land cover changes. Geophys. Res. Lett. 44, 6814- 6822 (2017). Zan, B. et al. Spatiotemporal inequality in land water availability amplified by global tree restoration. Nat. Water (2024) doi:10.1038/s44221- 024- 00296- 5. + +Moreover, since these effects are small overall, one wonders how much they really matter in the larger picture... Should we worry more about summertime warming (and the related tree cooling potential), or should we be more concerned about wintertime changes overall...??? Which of these two phenomena has the larger, more important impact on climate change phenomena...? + +Response: We appreciate your insightful comments. We acknowledge that the observed \(\Delta \mathrm{LST}\) trend is limited compared to the magnitude of climate change, as we discussed in the manuscript (Line 513): + +Third, the enhanced forest local cooling effect implies that planting trees in proper areas remains a promising local solution against the risk of warming, especially in highly populated regions. Nonetheless, tree restoration is not a panacea for climate change. Although our results highlight the negative biophysical feedback to the warming trend in forests, this feedback is unable to offset the warming trend driven by rising atmospheric \(\mathrm{CO_2}\) . + +About the comparison between summer and winter signals, our analysis reveals that the magnitude of \(\Delta \mathrm{LST_w}\) and \(\Delta \mathrm{LST_s}\) changes are equivalent to about 2- 6% and 6- 9% climate warming trend in winter and summer, respectively (Supplementary Text 4). We recognize that summer effects may remain more directly relevant for human comfort and safety in a warming world. However, the winter effects operate through distinct mechanisms requiring separate consideration, and carry + +<--- Page Split ---> + +important ecological implications that should not be overlooked. + +First, the revealed relationship between snow and \(\Delta \mathrm{LST}_{\mathrm{w}}\) could provide constraints for climate models predicting vegetation- snow interactions. Second, there is an ongoing debate regarding the suitability of afforestation for mid- to high latitudes due to the undesired warming effect of afforestation in the cold season. Our result suggests the potential for expanded forestation feasibility in such regions. Specifically, the weakening winter warming signal suggests we may need to re- evaluate traditional limitations on forestation in mid- or high- latitudes, as projected snow cover reductions under climate change could further diminish albedo- related positive forcing and potentially expand suitable areas for climate mitigation through forestation (as we discussed in Line 449). The observed changes in \(\Delta \mathrm{LST}_{\mathrm{w}}\) provide valuable insights into how forestation strategies might need to adapt to changing snow regimes under global warming. Overall, the understanding of seasonal forest- climate interactions contributes to more geographically targeted and feasible forestation approaches. + +Line 145: From my perspective, as noted also above, it is not obvious that this should be true. Response: Thanks for the comment. We have added additional results to identify the mechanism. Please see the detailed response to your comments on line 115. + +Line 149: Empirically, these findings correspond well with what I would expect... + +Response: We appreciate the reviewers' recognition of our findings. We refined this sentence to identify the direction of change in \(\Delta \alpha_{\mathrm{w}}\) (Line 162): + +Specifically, we show that forests are darker than openlands, as evidenced by the negative \(\Delta \alpha_{\mathrm{w}}\) value (- 0.077, Supplementary Fig. 7). However, \(\Delta \alpha_{\mathrm{w}}\) shows a positive trend (0.018 unitless/decade, \(p = 0.04\) ) (Fig. 2a), indicating that the albedo contrast between forests and openlands has been diminishing. + +Line 155: I think one still has to demonstrate that these differences are not true in the longer term...? Has the direction of change actually changed, or only become more pronounced...? + +Response: We appreciate your comments regarding the long- term dynamics of snow- albedo effects. Our satellite- based analysis demonstrates a consistent pattern over the past two decades (2004- 2023): both forests and openlands have exhibited significant albedo declines, with a less pronounced reduction in forests (- 0.017 unitless/decade, \(p< 0.05\) ) compared to openlands (- 0.036 unitless/decade, \(p< 0.05\) ). This divergence results in a significant positive trend in \(\Delta \alpha_{\mathrm{w}}\) (forest minus openland), reducing the albedo contrast between these land cover types. + +We understand your potential concerns about the long- term persistence of these snow- albedo effects. While our MODIS- based analysis is constrained by the temporal limitations of the satellite record, our findings align well with established literature. Previous studies have shown stronger snow- albedo feedback mechanisms in openlands compared to vegetated surfaces (Alessandri et al., 2020; Yu et al., 2022), supporting our observed patterns. This difference arises primarily from the greater snow- masking effect of forest canopies, which diminishes snow's contribution to surface albedo relative to openlands. We have incorporated these supporting references and refined our description accordingly (Line 168): + +<--- Page Split ---> + +The revealed positive \(\Delta \alpha_{w}\) trend can be traced back to the stronger albedo decrease in openlands (multi- year mean: 0.236; trend: - 0.036 unitless/decade, \(p = 0.04\) ) than in forests (multi- year mean: 0.159; trend: - 0.017 unitless/decade, \(p = 0.03\) ) from 2004 to 2023 (Fig. 2a). This observed divergence in surface darkening trends may be associated with snow cover ( \(SC_{w}\) ) reductions (Supplementary Fig. 8), and differences in the snow- albedo feedback intensity in different land covers (Alessandri et al., 2020; Atlaskina et al., 2015; Li et al., 2017; Manninen et al., 2019; Yu et al., 2022). + +## Reference: + +Alessandri, A., Catalano, F., De Felice, M., van den Hurk, B. & Balsamo, G. Varying snow and vegetation signatures of surface albedo feedback on the Northern Hemisphere land warming. Environ. Res. Lett. 16, (2020). Atlaskina, K., Berninger, F. & de Leeuw, G. Satellite observations of changes in snow- covered land surface albedo during spring in the Northern Hemisphere. Cryosph. 9, 1879- 1893 (2015). Li, Q., Ma, M., Wu, X. & Yang, H. Snow Cover and Vegetation- Induced Decrease in Global Albedo From 2002 to 2016. J. Geophys. Res. Atmos. 124- 138 (2017) doi:10.1002/2017JD027010. Manninen, T. et al. Monitoring changes in forestry and seasonal snow using surface albedo during 1982- 2016 as an indicator. Biogeosciences 16, 223- 240 (2019). Yu, L., Leng, G. & Python, A. Attribution of the spatial heterogeneity of Arctic surface albedo feedback to the dynamics of vegetation, snow and soil properties and their interactions. Environ. Res. Lett. 17, (2022). + +Line 201: this is interesting and could be highlighted more... But it is important to weigh the warming effect against this negligible correlation...??? + +Response: Thank you for raising this important point. We suppose that our correlation analysis may be insufficient to prove the conclusion of the limited role of \(\Delta \mathrm{LE}_{w}\) in the observed \(\Delta \mathrm{LST}_{w}\) trends. To address this, we conducted additional experiments that clearly show albedo- driven processes, rather than LE- related mechanisms, dominate the winter \(\Delta \mathrm{LST}\) variations. Please see the detailed response to your comments on line 115. + +Line 212: And this lack of moisture should also correlate strongly with the increasing importance and impact of albedo effects, since there is no, or there is a reduced, latent heat effect to minimize them...??? + +Response: We appreciate your insightful view. As you correctly pointed out, decreased water availability can constrain vegetation's evaporative cooling capacity and amplify the relative importance of albedo effects. However, we would like to clarify that our study examines the trend and impacts of surface SM (0- 7 cm, based on the definition of ERA5 data), which has been widely used in previous observation- and model- based climate change studies (Hsu and Dirmeyer, 2023; Liu et al., 2023; Yao et al., 2025). We have revised the abbreviation to \(\mathrm{SSM}_{s}\) (summer surface soil moisture) in the manuscript for clarity. + +In forest ecosystems, \(\mathrm{SSM}_{s}\) represents only a fraction of the total available water, as trees can access deeper water reserves through their root systems. In contrast, herbaceous plants in openlands + +<--- Page Split ---> + +primarily rely on SM in the upper layers. Therefore, we suppose that the reductions in \(\mathrm{SSM}_\mathrm{s}\) would more severely limit evaporative cooling in openland vegetation than in forests. + +Our subsequent findings support this hypothesis, demonstrating that \(\mathrm{SSM}_\mathrm{s}\) negatively affects the latent heat and leaf area index differences ( \(\Delta \mathrm{LE}_\mathrm{s}\) and \(\Delta \mathrm{LAI}_\mathrm{s}\) ) between forests and openlands (Fig. 4), which means decreasing \(\mathrm{SSM}_\mathrm{s}\) can have a stronger limitation on short vegetation, resulting in the amplification of the difference between forests and openlands. It should be noted that we did not include deep layer SM in the analysis, mainly due to its high uncertainty. + +This differential response has been documented in a previous study (Teuling et al., 2010), which investigated heatwave- induced temperature variations across vegetation types, indicating the more significant warming in grassland than forests due to the rapid SM loss. Our work extends these findings by validating this mechanism over the annual scale. + +Furthermore, we acknowledge the potential nonlinearity of the SM's impacts, as you mentioned in the comment. Specifically, under extreme water scarcity (perhaps beyond a critical threshold), even forests may lose their evaporative cooling advantage, and the albedo warming effect may become dominant. However, currently available observational data have not yet captured these nonlinear effects. We have added a discussion about this mechanism (Line 349): + +However, it should be noted that our observational results represent the impact of soil moisture within a limited range under current climate regimes. If persistent warming or reduced precipitation drives soil moisture below a critical threshold, forests may lose their stability and the evaporative cooling capacity, thus failing to compensate for the warming effect induced by the dark canopy. + +## Reference: + +Hsu, H. & Dirmeyer, P. A. Soil moisture- evaporation coupling shifts into new gears under increasing CO2. Nat. Commun. 14, (2023). Liu, Y., Yang, Y. & Song, J. Variations in Global Soil Moisture During the Past Decades: Climate or Human Causes? Water Resour. Res. 59, (2023). Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). Yao, L. et al. Emergent constraints on global soil moisture projections under climate change. Commun. Earth Environ. 6, 1- 8 (2023). + +Line 237: we would of course expect this decoupling as SM tends to zero...? + +Response: Thank you for the comment. We agree with your view regarding the decoupling between summer vapor pressure deficit (VPDs) and surface soil moisture ( \(\mathrm{SSM}_\mathrm{s}\) ) as soil moisture approaches zero. However, our decoupling methodology is not specifically designed to address this particular condition. + +We should first highlight the need for a decoupling process because VPDs and \(\mathrm{SSM}_\mathrm{s}\) exhibit a strong correlation, and both are significantly correlated with \(\Delta \mathrm{LST}_\mathrm{s}\) . This high collinearity makes it challenging to determine which factor primarily drives \(\Delta \mathrm{LST}_\mathrm{s}\) variability based on temporal correlation analysis (as suggested by Fig. 3a and 3b, not shown here). + +<--- Page Split ---> + +To address this, we drew upon a previous study (Liu et al., 2020), and adopted a binning regression method. Here, our analysis is based on spatial samples of \(\mathrm{VPD}_5\) trends and \(\mathrm{SSM}_5\) trends with sufficient data to decouple the two factors. For clarity, we have added a schematic illustration of this method in the supplementary materials (Supplementary Fig. 13a). + +In this framework, we first stratified \(\mathrm{VPD}_5\) trends into 10 quantile- based groups to constrain their variation. Within each subset, we then examined the relationship between \(\mathrm{SSM}_5\) trends and \(\Delta \mathrm{LST}_5\) trends using identical samples (Supplementary Fig. 13c), thereby isolating the independent effect of \(\mathrm{SSM}_5\) by controlling for \(\mathrm{VPD}_5\) variability. We subsequently reversed this process, grouping data by \(\mathrm{SSM}_5\) trends quantiles to evaluate the \(\mathrm{VPD}_5\) - \(\Delta \mathrm{LST}_5\) relationship (Supplementary Fig. 13b and 3d). + +The results reveal a clear pattern: \(\mathrm{SSM}_5\) maintain robust correlations with \(\Delta \mathrm{LST}_5\) when accounting for \(\mathrm{VPD}_5\) variation, and the \(\mathrm{VPD}_5\) - \(\Delta \mathrm{LST}_5\) relationships became statistically insignificant when controlling for \(\mathrm{SSM}_5\) (Fig. 3d, not shown here). This analysis provides evidence that \(\mathrm{SSM}_5\) variation is the primary driver of \(\Delta \mathrm{LST}_5\) trends, resolving the initial ambiguity caused by the collinearity between \(\mathrm{VPD}_5\) and \(\mathrm{SSM}_5\) . + +![PLACEHOLDER_52_0] + + +Supplementary Fig. 13. Schematic illustration of the binning regression method for isolating the effects of summer vapor pressure deficit (VPD5) and surface soil moisture (SSM5) on the land surface temperature effect of potential forestation (LST5). (a) Stratification of VPD5 trends into 10 quantile- based groups. (b) Stratification of SSM5 trends into 10 quantile- based groups. (c) SSM5- \(\Delta \mathrm{LST}_5\) relationship within the given constrained VPD5 trend group. (d) VPD5- \(\Delta \mathrm{LST}_5\) relationship within the given constrained SSM5 trend group. + +## Reference: + +Liu, L. et al. Soil moisture dominates dryness stress on ecosystem production globally. Nat. Commun. 11, 1- 9 (2020). + +<--- Page Split ---> + +Line 310: What is missing for me, here, is the pathway effect of LAI on SM...? Of the two variables, forest effects in my view are primary, while SM effects are dependent upon the presence/absence of forest...??? How do you address this...? + +Response: Thank you for raising this concern about the causal relationship. We agree with your view that there may be a bidirectional relationship between SM and LAI. We should first emphasize the definition of the variables used to build the model. The summer surface SM (SSMs) is the grid- level average that includes all land cover types (forest, openland, etc.). Thus, SSMs primarily reflects background environmental conditions driven by climate change, rather than vegetation- specific characteristics. On the other hand, \(\Delta \mathrm{LAI}_s\) specifically captures the difference in LAI between forest and openland samples within the grid. + +Our modeling approach is based on the logic that climate- driven increase or decline in SSMs may affect forest and openland vegetation differently. For instance, in dry years, forests with their deeper root systems may maintain higher LAI compared to more sensitive openland vegetation. This would increase \(\Delta \mathrm{LAI}_s\) . + +We recognize your point about potential feedback mechanisms. However, we believe that in our framework, the influence of \(\Delta \mathrm{LAI}_s\) on grid- scale SSMs is likely minimal. This is because \(\Delta \mathrm{LAI}_s\) represents relative differences in vegetation within stable pixels (where land cover type has not changed). This internal difference may not affect the overall SM of the grid. We have added a description to clarify this causality issue (Line 764): + +It should be noted that all drivers used in SEM (SSMs, ATs, DSRs, WSs and Ps) represent grid- level mean values, which primarily reflect background climatic and environmental conditions. These variables are unlikely to be influenced by internal variations within the grids ( \(\Delta \mathrm{LE}_s\) and \(\Delta \mathrm{LST}_s\) ). + +Line 319: I did not see this tested in any way in the modeled pathways...? See related comment above...??? + +Response: Thank you for identifying this logical issue. Our structural equation modeling (SEM) results demonstrate that SSMs negatively affect both the LE and LAI differences ( \(\Delta \mathrm{LE}_s\) and \(\Delta \mathrm{LAI}_s\) ) between forests and openlands. This negative relationship indicates that declining SSMs can amplify the ET and greenness difference between these land cover types. Building upon our findings and existing literature about soil moisture deficit impacts on warming, we conclude that the observed negative effect likely stems from forests' greater stability and resilience to soil dryness. We have revised this section to improve clarity and better illustrate this mechanism (Line 332): + +During summer, the vegetation greenness and ET rates are generally higher in forests than in adjacent openlands (Tang et al., 2018). The negative effects of SSMs on \(\Delta \mathrm{LAI}_s\) and \(\Delta \mathrm{LE}_s\) revealed by the SEM analysis demonstrate that the decreased SSMs can amplify these greenness and ET differences between forests and openlands. Given the well- established constraint of soil moisture on vegetation growth (Kamenberg et al., 2024), we tend to attribute the negative effects of SSMs to forests' stability and resilience to increasing soil dryness (i.e., lower sensitivity of forest greenness and ET to SSMs), enabling forests to better maintain their cooling capacity under climate change compared to openland vegetation. + +<--- Page Split ---> + +Previous studies indicate that soil moisture depletion in Europe can exacerbate warming through land- atmosphere feedback mechanisms during heatwave events (Dirmeyer et al., 2021; Fischer et al., 2007). A comparative analysis of temperature responses across land cover types shows that openlands experience pronounced warming during long- lasting heatwaves, whereas forests exhibit moderate warming due to their conservative water- use strategies and sustained evaporative cooling (Teuling et al., 2010). Our results provide observational evidence that forests' capacity to mitigate water deficit- induced warming persists not only during heatwave events but also across the interannual scales. + +## Reference: + +Dirmeyer, P. A., Balsamo, G., Blyth, E. M., Morrison, R. & Cooper, H. M. Land- Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018. AGU Adv. 2, 1- 16 (2021). Fischer, E. M., Seneviratne, S. I., Luthi, D. & Schär, C. Contribution of land- atmosphere coupling to recent European summer heat waves. Geophys. Res. Lett. 34, 1- 6 (2007). Kannenberg, S. A., Anderegg, W. R. L., Barnes, M. L., Dannenberg, M. P. & Knapp, A. K. Dominant role of soil moisture in mediating carbon and water fluxes in dryland ecosystems. Nat. Geosci. (2024) doi:10.1038/s41561- 023- 01351- 8. Tang, B., Zhao, X. & Zhao, W. Local effects of forests on temperatures across Europe. Remote Sens. 10, 1- 24 (2018). Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). + +Line 321: Of course, at some point, one might expect this "stability" to slip as warming surpasses the ability of a forest to store adequate soil moisture and as ET begins to exceed the supply of water (due to long- term rising temperatures and declining rainfall)...??? + +Response: Thanks for raising this important issue. We have added a discussion about this mechanism (Line 349): + +However, it should be noted that our observational results represent the impact of soil moisture within a limited range under current climate regimes. If persistent warming or reduced precipitation drives soil moisture below a critical threshold, forests may lose their stability and the evaporative cooling capacity, thus failing to compensate for the warming effect induced by the dark canopy. + +Line 334: ??? + +Response: Thanks for the careful reading. We have corrected the typo. + +Line 401: ??? Why not say that the radiative forcing of European forests is virtually unchanged...??? The changes you highlight occur elsewhere, not in the forested areas...??? I do not think it makes sense to confuse forests with this phenomenon...??? And it certainly doesn't make sense to blame forests (or suggest they are in any way responsible) for this outcome...??? + +<--- Page Split ---> + +Response: Thank you for the constructive criticism. We apologize for the confusion caused by the wording. We have revised the relevant sentence to improve clarity (Line 435): + +Thus, the diminished \(SC_w\) could result in a more pronounced reduction in openland albedo but have a limited impact on forest albedo, thereby weakening the relative radiative warming effect of forests compared to openlands. + +Line 416: Same comment as above... And this statement should include a stronger sense of the directionality implied in the effects...? + +Response: Thank you for your feedback. After consideration, we have removed this statement from the revised version for two reasons: (1) large uncertainties remain concerning both the local climatic effects of mid- latitude forestation and the precise transitional latitude between warming and cooling effects; and (2) the original wording's potential for misinterpretation. We note that this particular point was not central to our overall argument, and its removal does not affect the conclusions. + +<--- Page Split ---> + +## Response to Reviewer #2's Comments + +We greatly appreciate the anonymous reviewer #2 for the constructive comments. The manuscript has been revised and improved accordingly. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in red and Italic). The changes are also marked in red in the manuscript file. + +## Reviewer #2 (Remarks to the Author): + +I am impressed by the lengths to which the Authors have gone to address the many comments raised. Though ideally, I would like to continue this discussion, I do not wish to burden the Authors unnecessarily. I do think that this manuscript already provides a lot of interesting and highly relevant analysis. I did still make a number of comments in the attached submission pdf and would encourage the Authors to consider these. Most of the comments are relatively minor in character and can easily be addressed (or ignored where appropriate). Thus, I leave it up to the Authors whether they adopt these suggestions or not. + +I do think the manuscript could probably benefit from one last round of editing and perhaps some minor shortening. I do hope the provided comments can prove useful here. + +Response: We sincerely appreciate your positive feedback. We have considered your comments raised in the PDF file and made corresponding revisions. Please see the following responses for details. + +Line 9: And/or the consequences of more extensive forest loss... I think the phrasing matters here, in particular because the conventional view is that more forest cover means more warming, due to the albedo effects... But you are saying the opposite here... So I would try to emphasize this more prominently... You are not really criticizing forestation, but rather its opposite... + +Response: Thanks for the advice. We have revised the wording to avoid ambiguity (Line 43): + +By comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify temporal trends in local land surface temperature (LST) effects of forest change in Europe. + +Line 12: Some minor editing here and there would still be helpful. Here, I would move this phrase to just after "the daytime warming effect of forestation induced by... + +Response: Thanks for the comment. We have revised the sentence as you suggested (Line 45): + +During winter, the daytime warming effect of potential forestation weakens and reverses to cooling (- 0.142 K/decade) with decreasing snow cover, as forests show less pronounced surface darkening trends than openlands. + +<--- Page Split ---> + +Line 144: Rephrase slightly...? In contrast, forests exhibit strong land surface cooling in summer (), at the strong daytime cooling effect () is minimally offset by a much smaller nighttime warming effect (). + +Response: Thanks for the advice. We have revised the sentence as you suggested (Line 148): + +In contrast, forests exhibit strong land surface cooling in summer (- 0.75 ± 0.41 K), as the daytime cooling (- 2.11 ± 0.98 K) is minimally offset by a much smaller nighttime warming (0.25 ± 0.23 K). + +Line 120: Our/The results... + +Response: Revised as you suggested. + +Line 125: with only...? + +Response: Revised as you suggested. + +Line 156: new paragraph...? + +Response: Revised as you suggested. + +Line 171: It may also be worth noting that snow cover under forests disappears more slowly/is more easily retained for longer periods of time than snow cover in open areas... + +Response: Thanks for the suggestion. We have added related descriptions (Line 205): + +The possible mechanism is that snow tends to be masked by tree canopies and retained for longer durations in forest ecosystems, resulting in a lower sensitivity of forest albedo to snowpack. + +Line 175: suggested, evidenced by, supported by... + +Response: Revised as you suggested. + +Line 177: Or mention the point raised above here... Or further condense... + +Response: We have added related descriptions in Line 205. Please see the above response for the revision. + +Line 255: I tend to think this analysis should also still consider the differences across openlands and forested lands...? I would expect to see significant differences here...? + +Response: Thank you for raising this concern. We admit that soil moisture may have difference in forested area and openland. We have highlight this point in Line 336: + +Specifically, forests possess deeper root systems and enhanced soil moisture storage capacity, enabling them to sustain their cooling efficiency under climate change compared to openland vegetation. + +<--- Page Split ---> + +Line 307: good... I see this point is covered here... Perhaps above one could mention that it will be discussed further below... Above, it just feels like this point is missing... + +Response: Thanks for the advice. We have mentioned this point above as you suggested (Line 245): + +Notably, the climate variables may themselves be influenced by the presence of forests (e.g., soil moisture retention and evaporative cooling of trees). However, it should be emphasized that the climate drivers used in our analysis are the grid means at the coarse resolution, reflecting large- scale patterns rather than microclimates. Our analysis tends to capture the distinct responses of forests and openlands to background climate change. + +Line 336: There are presumably two things going on here: 1) forests have deeper root systems and can dig deeper for water... and 2) forested areas presumably store more soil moisture and thus are not as quickly or easily affected by soil moisture decline... + +Does one see higher soil moisture measurements, in general, across the forested areas...? + +You also mention below that forests may be better at conserving water (e.g., shutting down stomata)... So this would be a third mechanism... + +Response: We fully agree with the point you mentioned. We have highlighted the two mechanisms you mentioned here (Line 336): + +Specifically, forests possess deeper root systems and enhanced soil moisture storage capacity, enabling them to sustain their cooling efficiency under climate change compared to openland vegetation. + +Line 504: This paragraph needs to be broken up into smaller pieces... Way too long... + +Response: The paragraph has been separated into 3 parts as you suggested. + +Line 520: I appreciate this point... It might be wise to find ways to introduce this restriction earlier on in the discussion, and perhaps even the abstract... Just to say that the analysis is focused strictly on local level effects... + +Response: Thanks for the advice. We have highlighted the restriction at the beginning of the manuscript (Line 114): + +It should be noted that the evaluated LST effects are local effects and should be treated as the reference for local climate adaptation rather than global climate mitigation. + +Line 548: Is it forestation that exhibits negative trends, or effects on open lands...??? + +Response: Thanks for pointing this out. We have revised the sentence for clarity (Line 534): + +<--- Page Split ---> + +Overall, our findings provide solid satellite evidence that the cooling effects of forest conversion from openlands in Europe have been amplified in the last two decades. + +<--- Page Split ---> diff --git a/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b5f44f82e3fad6280545f9e447c4dea37dd37eae --- /dev/null +++ b/peer_reviews/562c159203555cb1206f6d8b32efc85051e5967295ef550e27639a4105f00657/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1659 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 97, 295, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 860, 210]]<|/det|> +# Amplified Local Cooling Effect of Forestation in Warming Europe + +<|ref|>text<|/ref|><|det|>[[73, 225, 483, 241]]<|/det|> +Corresponding Author: Professor Zhao- Liang Li + +<|ref|>text<|/ref|><|det|>[[70, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 327, 144, 341]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 354, 219, 368]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 160, 394]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 406, 238, 420]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 420, 921, 472]]<|/det|> +This manuscript is well- structured and well- written. The authors define \(\Delta \mathsf{LST}\) as the difference between forest LST and nearby open land LST. Their analysis reveals that \(\Delta \mathsf{LST}\) has intensified in recent decades, which they attribute to increasing VPD, favoring enhanced evaporative cooling in forests. I feel this manuscript is publishable if the authors can address the following questions: + +<|ref|>text<|/ref|><|det|>[[70, 496, 759, 511]]<|/det|> +Line 14: VPD increase will trigger stomatal closure, thus reducing ET cooling. How to reconcile this? + +<|ref|>text<|/ref|><|det|>[[72, 521, 900, 614]]<|/det|> +Lines 101- 110: The observed forest cooling - could this be influenced by elevation effects? In the Methods section (Line 577), is the assumption that the background climate remains uniform within a \(0.25^{\circ}\times 0.25^{\circ}\) area valid? I noticed that the authors set a threshold of a mean elevation of \(500m\) to mitigate this bias. However, given that the typical lapse rate is approximately \(6.5^{\circ}C\) per 1,000 meters, this effect may be substantial enough to alter the direction of the temperature difference (compare to the numbers you provided in Lines 101 to 110). In low- elevation hilly regions, forests may often be found at higher elevations, while open land, if resulting from deforestation, tends to be at lower elevations due to easier accessibility. This elevation difference may contribute to the observed forest cooling effect. + +<|ref|>text<|/ref|><|det|>[[70, 626, 904, 654]]<|/det|> +Line 161: In Fig 2c, the relationship is binned by the trend of snow cover. Can the authors reproduce the result if binned by the trend of albedo? + +<|ref|>text<|/ref|><|det|>[[70, 665, 900, 680]]<|/det|> +Line 165 - 168: not sure if the snow mass between forest and open land also can be affected by the elevation difference? + +<|ref|>text<|/ref|><|det|>[[72, 691, 921, 833]]<|/det|> +Line 201 - 203: It is interesting to see a negative correlation between VPD and \(\Delta \mathsf{LST}\) . This suggests that when VPD is high, forests exhibit greater energy dissipation advantages compared to open lands. As the authors mentioned, VPD is highly positively correlated to air temperature. So, this reminds me of an earlier heatwave study "Teuling, A., Seneviratne, S., Stöckli, R. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nature Geosci 3, 722- 727 (2010). https://doi.org/10.1038/ngoe950". Teuling et al find "initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. ... We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long- lasting events." My question is whether the analysis in this Nature Communications manuscript represents short- term effects or longer- term effects? + +<|ref|>text<|/ref|><|det|>[[72, 846, 911, 886]]<|/det|> +Line 272 - 275: The logic in this section feels somewhat unclear. The authors claim that higher VPD enhances \(\Delta \mathsf{LAI}\) and suggest multiple similar cause- and- effect relationships with other variables. How can the causal inferences be reliably established? It seems that the reverse statement is also valid. + +<|ref|>text<|/ref|><|det|>[[72, 898, 920, 939]]<|/det|> +In the flowchart of Fig. 4, I notice a missing of surface resistance in the VPD- LE relationship. In the Penman- Monteith scheme, increasing VPD can have competing effects on ET: on one hand, increasing VPD enhances ET, while on the other, it also raises surface resistance, which suppresses ET. The results suggest that the VPD- driven enhancement of ET is more + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 914, 88]]<|/det|> +dominant. Could the authors clarify why this occurs when comparing ET between forests and open lands? I feel VPD is not the driver of such findings, but the biome type - forests/open lands and their associated biophysical and physiological responses - are the real drivers. Need to clarify this. + +<|ref|>text<|/ref|><|det|>[[70, 99, 875, 127]]<|/det|> +See Novick, K., Ficklin, D., Stoy, P. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nature Clim Change 6, 1023- 1027 (2016). https://doi.org/10.1038/nclimate3114 + +<|ref|>text<|/ref|><|det|>[[73, 165, 283, 179]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 179, 920, 231]]<|/det|> +I feel that this might be holding the authors to an excessively high standard. If Nature is asking whether I can strictly replicate results using their code, I believe it would take a significant amount of time, and I don't have the capacity to verify it. However, I feel is that it's unrealistic to expect the authors to cover every detail perfectly and provide a fully automated, one- click runnable code. + +<|ref|>text<|/ref|><|det|>[[72, 242, 920, 284]]<|/det|> +Additionally, I believe that the provided code does not fully include all the components/scripts necessary to reproduce all the results of this paper (e.g., the ESM analysis, MODIS data processing). Again, I feel this is holding the authors to an excessively high standard. They are not software engineers. + +<|ref|>sub_title<|/ref|><|det|>[[72, 398, 161, 411]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 424, 922, 503]]<|/det|> +(Remarks to the Author) I find this manuscript has a lot of interesting data and discussion. Moreover, for me personally, it was highly motivating to read this discussion. I did find, especially at the beginning of the manuscript, that the work was not very well situated in the principal literature. All four of the first references to appear in the manuscript do not seem well suited to set up this general discussion. I have provided a number of suggestions in the attached submission pdf and am hopeful that some of these suggestions will prove useful... + +<|ref|>text<|/ref|><|det|>[[72, 514, 870, 542]]<|/det|> +I also found that the introduction was occasionally vague and would have benefitted from a somewhat more nuanced discussion... I have tried to point out places where I think this would be helpful. + +<|ref|>text<|/ref|><|det|>[[72, 553, 916, 607]]<|/det|> +Finally, the discussion of radiative and non- radiative effects, as well as the discussion of winter and summertime effects, to my mind, were not adequately introduced and motivated in the introductory parts of the paper. When these concepts are suddenly announced, (the discussion about winter and summer time effects first comes up in the results section of the paper?), they are unexpected and seemingly unmotivated in the general context of the paper... This can be improved upon... + +<|ref|>text<|/ref|><|det|>[[72, 618, 912, 672]]<|/det|> +I also find that the Authors do not adequately distinguish between global and local cooling... Both terms come up. But most of the time it sounds like the Authors are talking about local cooling... And the balance in terms of global cooling is never clearly estimated...? It is important not to conflate these terms, since local cooling is not necessarily equivalent to global cooling...? + +<|ref|>text<|/ref|><|det|>[[72, 683, 899, 725]]<|/det|> +Further, I would have like to see more discussion of the role of the availability of water and surface moisture. The cooling potential of forests strongly depends on the availability of water. As soon as this surface moisture disappears, the loss of latent heat means the warming will suddenly take over... But there is little attention to this throughout the paper... + +<|ref|>text<|/ref|><|det|>[[72, 735, 911, 777]]<|/det|> +Finally, I wonder why LEW never appears anywhere, but the effects of LEs are estimated... Clearly LEW will be significantly lower. But conifers can evapotranspire almost year round... So, to some degree, LEW should also be available and should have an impact on surface temperatures... ??? + +<|ref|>text<|/ref|><|det|>[[72, 788, 917, 855]]<|/det|> +More to the main point, however, the general finding that wintertime effects exhibit increased cooling due to the loss of snow cover, more or less independently of tree cover (the effect is stronger over open fields than over forested land), is an interesting and valuable finding. However, it remains unclear why this phenomenon would be true in more forested areas... In other words, why would the land surface become lighter under more forested areas, thus leading to wintertime cooling...??? I do not think this is adequately explained...? + +<|ref|>text<|/ref|><|det|>[[70, 866, 920, 894]]<|/det|> +All- in- all however, I did find the manuscript to be very interesting and compelling... I have included a number of comments in the attached submissions pdf. + +<|ref|>text<|/ref|><|det|>[[72, 906, 282, 920]]<|/det|> +(Remarks on code availability) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 145, 60]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 73, 220, 87]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 100, 160, 113]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 126, 238, 139]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 140, 884, 166]]<|/det|> +The authors have made significant improvements, conducted substantial additional analyses, and even revised their conclusions regarding the role of VPD. I am satisfied with most of these efforts and have only one remaining comment. + +<|ref|>text<|/ref|><|det|>[[73, 178, 901, 192]]<|/det|> +"In the summertime, the vegetation physiological response to decreased soil moisture boosts the cooling effect of forests." + +<|ref|>text<|/ref|><|det|>[[73, 204, 852, 231]]<|/det|> +This statement may still be confusing or even misleading. It implies that forests have a stronger cooling effect than grasslands solely due to their physiological response to dry soils. + +<|ref|>text<|/ref|><|det|>[[73, 243, 890, 283]]<|/det|> +In reality, while physiological processes such as stomatal regulation do influence surface energy balance, the observed cooling effect in forests may also stem from hydrological advantages, including deeper soil water storage and more consistent precipitation recharge in forested areas. + +<|ref|>text<|/ref|><|det|>[[73, 334, 283, 347]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 372, 161, 385]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 399, 238, 412]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 412, 914, 504]]<|/det|> +I find that a lot of interesting points come up in this analysis. I am, however, a bit concerned that the paper could still benefit from some significant editing and rewriting. I raise a number of questions in the attached submission pdf. I guess that, primarily, I am unconvinced by the forest albedo logic used herein and would be tempted to argue in a different direction on many points. Please see the related comments in the text. Further, I do think that the paper seems inclined to somehow lay the blame for these changes on forests, when actually, most of the important changes seem to be occurring elsewhere (in open fields that have reduced amounts of forest cover, and not in heavily forested areas) and are primarily driven by climate warming (and not any change in forests themselves).... + +<|ref|>text<|/ref|><|det|>[[72, 515, 920, 594]]<|/det|> +I do think that with another round of editing, this paper can be significantly improved... I am uncertain, however, how one should resolve the problem of over- emphasising forest albedo effects. This would ultimately require some different measures. Perhaps the Authors can respond to this point...? What do they think is the best procedure here...? Personally, I would be inclined to take this in a somewhat different direction. Moreover, while the forest albedo literature considers albedo effects, it entirely neglects cloud related effects... Since these are presumably also tied to forests, in part, what does this say about the methodology employed in the analysis...??? + +<|ref|>text<|/ref|><|det|>[[73, 607, 283, 620]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 646, 144, 658]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 672, 220, 685]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 698, 161, 711]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 725, 238, 737]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 738, 914, 817]]<|/det|> +I am impressed by the lengths to which the Authors have gone to address the many comments raised. Though ideally, I would like to continue this discussion, I do not wish to burden the Authors unnecessarily. I do think that this manuscript already provides a lot of interesting and highly relevant analysis. I did still make a number of comments in the attached submission pdf and would encourage the Authors to consider these. Most of the comments are relatively minor in character and can easily be addressed (or ignored where appropriate). Thus, I leave it up to the Authors whether they adopt these suggestions or not. + +<|ref|>text<|/ref|><|det|>[[70, 828, 920, 855]]<|/det|> +I do think the manuscript could probably benefit from one last round of editing and perhaps some minor shortening. I do hope the provided comments can prove useful here. + +<|ref|>text<|/ref|><|det|>[[73, 868, 283, 881]]<|/det|> +(Remarks on code availability) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[348, 85, 649, 102]]<|/det|> +## Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[148, 113, 851, 204]]<|/det|> +We greatly appreciate the opportunity to revise our manuscript and thank all anonymous reviewers for their constructive comments. The manuscript has been revised and improved accordingly. We hope that the revision will make it more acceptable for publication. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in red and Italic). The changes are also marked in red in the manuscript file. + +<|ref|>sub_title<|/ref|><|det|>[[150, 239, 450, 255]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 273, 851, 364]]<|/det|> +This manuscript is well- structured and well- written. The authors define \(\Delta \mathrm{LST}\) as the difference between forest LST and nearby open land LST. Their analysis reveals that \(\Delta \mathrm{LST}\) has intensified in recent decades, which they attribute to increasing VPD, favoring enhanced evaporative cooling in forests. I feel this manuscript is publishable if the authors can address the following questions: + +<|ref|>text<|/ref|><|det|>[[148, 368, 851, 516]]<|/det|> +Response: We appreciate the positive comments by the reviewer. We have carefully considered all the comments and suggestions and made corresponding point- by- point responses. To address your comment regarding the potential influence of elevation bias between forests and openlands, we have refined our results by setting additional elevation restrictions when selecting pixels for comparison. Also inspired by your comment regarding the short- term and long- term effects, we added new experiments to explored the potential impact of soil moisture in summer (SM). Accordingly, we updated the results and refined the research findings. These refinements have significantly strengthened the robustness of our findings, as detailed in our point- by- point responses below. + +<|ref|>text<|/ref|><|det|>[[148, 540, 850, 575]]<|/det|> +Line 14: VPD increase will trigger stomatal closure, thus reducing ET cooling. How to reconcile this? + +<|ref|>text<|/ref|><|det|>[[148, 580, 851, 711]]<|/det|> +Response: We appreciate your valuable comment about the impact of VPD. Based on your comment below, we have performed additional analyses to elucidate the mechanisms of enhanced forests cooling effects in summer ( \(\Delta \mathrm{LST}_5\) ). Our results demonstrates that while summer VPD (VPDs) exhibits a strong correlation with \(\Delta \mathrm{LST}_5\) , increased atmospheric dryness does not appear to be the actual factor driving the observed \(\Delta \mathrm{LST}_5\) patterns. Instead, the concurrent summer SM (SM) depletion (tight coupling with VPDs), should be the primary driver of the trends in \(\Delta \mathrm{LST}_5\) . Detailed analyses supporting this conclusion are presented in our responses to your subsequent comments. + +<|ref|>text<|/ref|><|det|>[[148, 715, 850, 749]]<|/det|> +Therefore, we have revised the relevant text in the abstract to more accurately reflect this mechanism (Line 12): + +<|ref|>text<|/ref|><|det|>[[148, 754, 850, 789]]<|/det|> +In the summertime, the vegetation physiological response to decreased soil moisture boosts the cooling effect of forests. + +<|ref|>text<|/ref|><|det|>[[148, 814, 851, 906]]<|/det|> +Lines 101- 110: The observed forest cooling - could this be influenced by elevation effects? In the Methods section (Line 577), is the assumption that the background climate remains uniform within a \(0.25^{\circ} \times 0.25^{\circ}\) area valid? I noticed that the authors set a threshold of a mean elevation of \(500 \mathrm{~m}\) to mitigate this bias. However, given that the typical lapse rate is approximately \(6.5^{\circ} \mathrm{C}\) per 1,000 meters, this effect may be substantial enough to alter the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 157]]<|/det|> +direction of the temperature difference (compare to the numbers you provided in Lines 101 to 110). In low- elevation hilly regions, forests may often be found at higher elevations, while open land, if resulting from deforestation, tends to be at lower elevations due to easier accessibility. This elevation difference may contribute to the observed forest cooling effect. + +<|ref|>text<|/ref|><|det|>[[148, 163, 851, 253]]<|/det|> +Response: Thanks for your insightful comments regarding the impact of elevation. We fully agree that elevation differences could have a potential impact on the evaluated LST effect of forests. We checked our results and found a mean elevation difference of \(\sim 150 \mathrm{~m}\) between forest and grassland samples under our original \(500 \mathrm{~m}\) mean elevation constrain. This may lead to an overestimation of the forest cooling effects, as you noted. + +<|ref|>text<|/ref|><|det|>[[147, 259, 850, 367]]<|/det|> +To mitigate this, we implemented additional screening criteria. First, we identified the less dominant land cover type (either forest or openland) within each \(0.25^{\circ} \times 0.25^{\circ}\) grid, then applied a \(\pm 100 \mathrm{~m}\) elevation threshold around its mean elevation to select comparable samples from the other land cover type. Only when both forest and openland samples are larger than 5, the calculation of \(\Delta \mathrm{LST}\) was performed. In the revised manuscript, we revised corresponding methodological descriptions (Line 618): + +<|ref|>text<|/ref|><|det|>[[148, 372, 850, 426]]<|/det|> +For each \(0.25^{\circ}\) grid, we first determine the less dominant land cover type (forest or openland) based on the count of valid samples, then apply a \(\pm 100 \mathrm{~m}\) elevation threshold around its mean elevation to select comparable samples from the other type. + +<|ref|>text<|/ref|><|det|>[[147, 434, 850, 525]]<|/det|> +This refined approach reduced mean elevation differences to just \(\sim 20 \mathrm{~m}\) (vs. original \(\sim 150 \mathrm{~m}\) ). Based on the refined method, we have updated the all the related numbers and figures. Given the extensive revisions made, we do not list all modifications in the response letter. Please refer to the revised manuscript for detailed changes. However, we confirm that the original key finding, negative trends in \(\Delta \mathrm{LST}_{\mathrm{s}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) , persisted (Fig. 1). + +<|ref|>image<|/ref|><|det|>[[180, 536, 812, 840]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[163, 849, 832, 882]]<|/det|> +
Fig 1. Temporal dynamics in winter and summer land surface temperature effects of European forests ( \(\Delta \mathrm{LST}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{s}}\) ) in recent two decades.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 850, 138]]<|/det|> +We also appreciate your comment about the background climate assumption. While perfect climate uniformity cannot be assumed at any spatial scale, our \(0.25^{\circ}\) grid setting was based on several considerations. + +<|ref|>text<|/ref|><|det|>[[148, 145, 850, 234]]<|/det|> +First, previous research has shown that the decorrelation length of surface climate, the spatial scale at which these variables (e.g., temperature, precipitation) become relatively independent, typically exceeds \(30\mathrm{km}\) (Kim and Kosro, 2013; Larsen et al., 2013). This conclusion supports our assumption that sampled locations within each \(0.25^{\circ}\) ( \(\sim 30\mathrm{km}\) ) grid cell share similar climatic conditions. + +<|ref|>text<|/ref|><|det|>[[148, 241, 850, 311]]<|/det|> +Second, the \(0.25^{\circ}\) window size is comparable with that in previous studies exploring the biophysical effect of vegetation changes (Table R1). We have added these references in Line 604. Several studies also confirmed that the estimated LST effect is robust to the window size selection (Li et al., 2015; Zhang et al., 2024; Zhao et al., 2024). + +<|ref|>table<|/ref|><|det|>[[148, 340, 841, 493]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[152, 322, 835, 338]]<|/det|> +Table R1. Window size setting for the same background climate assumption in previous studies + +
ReferenceWindow sizeData
(Lee et al., 2011)28 km (mean)Site observation
(Li et al., 2015)50 × 28 kmRemote sensing observation
(Alkama and Cescatti, 2016)50 kmRemote sensing observation
(Duveiller et al., 2018)25 kmRemote sensing observation
(Chen et al., 2018)21.6 km (mean)Site observation
(Barnes et al., 2024)30 km (maximum)Site observation
+ +<|ref|>text<|/ref|><|det|>[[147, 501, 851, 629]]<|/det|> +Third, we also explored the background climate similarity using 43 paired and synchronous FLUXNET sites observations. The spatial distances of the paired sites range from 0 to \(150\mathrm{km}\) , and the elevation differences are less than \(200\mathrm{m}\) . Here, we compared the air temperature (AT), precipitation (P) and downward shortwave radiation (DSR) at different scales. For each variable, we compared the annual means (Fig. R1) and the monthly ranges (the difference between the monthly maximum and minimum values (Fig. R2). We also calculated the correlation coefficient between observations at the daily scale (Fig. R3). + +<|ref|>image<|/ref|><|det|>[[178, 652, 812, 796]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 810, 844, 844]]<|/det|> +
Fig. R1. Comparison of annual temperature, precipitation and radiation means from spatial paired site observations
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[180, 98, 816, 243]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[170, 256, 828, 290]]<|/det|> +
Fig. R2. Comparison of monthly temperature, precipitation and radiation ranges from spatial paired site observations.
+ +<|ref|>image<|/ref|><|det|>[[170, 306, 820, 454]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[160, 466, 835, 500]]<|/det|> +
Fig. R3. Correlation of daily temperature precipitation and radiation between spatial paired site observations
+ +<|ref|>text<|/ref|><|det|>[[147, 506, 852, 688]]<|/det|> +Fig. R1 shows that the paired sites within \(30\mathrm{km}\) share similar annual mean AT, P and DSR, and the scatters are close to the 1:1 line. The average root mean square error (RMSE) for paired sites with distances less than \(30\mathrm{km}\) is significantly smaller than for samples at distances greater than \(30\mathrm{km}\) , especially for precipitation ( \(105\mathrm{mm / y}\) vs. \(229\mathrm{mm / y}\) ). Similar results are also found in monthly ranges, which describe the seasonal variations of the climate variables (Fig. R2). For the daily variation, the correlations between the paired site observations decrease with increasing distance. Especially for precipitation, the mean correlation for paired sites with distance less than \(30\mathrm{km}\) can reach 0.81, while for those paired sites with distance larger than \(30\mathrm{km}\) , the mean correlation is only 0.57. Overall, these evidences support the validity of the similar background climate at the \(0.25^{\circ}\) scale. + +<|ref|>sub_title<|/ref|><|det|>[[148, 699, 231, 712]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 719, 850, 902]]<|/det|> +Alkama, R. & Cescatti, A. Biophysical climate impacts of recent changes in global forest cover. Science (80- ). 351, 600- 604 (2016). Barnes, M. L. et al. A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States. Earth's Futur. 12, (2024). Chen, L., Dirmeyer, P. A., Guo, Z. & Schultz, N. M. Pairing FLUXNET sites to validate model representations of land- use/land- cover change. Hydrol. Earth Syst. Sci. 22, 111- 125 (2018). Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64- 75 (2018). Kim, S. Y. & Kosro, P. M. Observations of near- inertial surface currents off Oregon: Decorrelation time and length scales. J. Geophys. Res. Ocean. 118, 3723- 3736 (2013). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 270]]<|/det|> +Larsen, M. A. D., Thejll, P., Christensen, J. H., Refsgaard, J. C. & Jensen, K. H. On the role of domain size and resolution in the simulations with the HIRHAM region climate model. Clim. Dyn. 40, 2903- 2918 (2013).Lee, X. et al. Observed increase in local cooling effect of deforestation at higher latitudes. Nature 479, 384- 387 (2011).Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1- 10 (2015).Zhang, Y. et al. Asymmetric impacts of forest gain and loss on tropical land surface temperature. Nat. Geosci. 13, 823- 831 (2024).Zhao, J. et al. Forest fire size amplifies postfire land surface warming. Nature 633, 828- 834 (2024). + +<|ref|>text<|/ref|><|det|>[[148, 293, 850, 329]]<|/det|> +Line 161: In Fig 2c, the relationship is binned by the trend of snow cover. Can the authors reproduce the result if binned by the trend of albedo? + +<|ref|>text<|/ref|><|det|>[[148, 334, 850, 389]]<|/det|> +Response: Thank you for raising this concern. Fig. 2c (also Fig. R4a) reveals that surface darkening \(\alpha_{\mathrm{w}}\) trends) is more sensitive to snow cover decline ( \(\mathrm{SC_w}\) trends) in openlands than in forests, as reflected by the steeper spatial regression slope for openlands. + +<|ref|>text<|/ref|><|det|>[[148, 392, 850, 466]]<|/det|> +To further validate these findings, we conducted additional analyses using \(\alpha_{\mathrm{w}}\) trend- based data binning as you suggested. The results presented in Fig. R4b confirm the robustness of the initial correlation under this alternative binning approach. We further verified that substituting \(\mathrm{SC_w}\) with \(\Delta \alpha_{\mathrm{w}}\) also yields a robust temporal correlation with \(\Delta \mathrm{LST}_{\mathrm{w}}\) (Fig. R4c and R4d). + +<|ref|>image<|/ref|><|det|>[[234, 480, 748, 809]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[156, 825, 840, 899]]<|/det|> +
Fig. R4. Comparison of the results binned by \(\mathrm{SC_w}\) and \(\alpha_{\mathrm{w}}\) . (a) Spatial relationships between \(\mathrm{SC_w}\) trends and \(\alpha_{\mathrm{w}}\) trends binned by \(\mathrm{SC_w}\) trends (same as Fig. 2c in the manuscript). (b) Binned by \(\alpha_{\mathrm{w}}\) trends. (c) Temporal relationships between \(\mathrm{SC_w}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) (same as Fig. 2e in the manuscript). (b) Temporal relationships between \(\Delta \alpha_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) .
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 849, 120]]<|/det|> +Line 165 – 168: not sure if the snow mass between forest and open land also can be affected by the elevation difference? + +<|ref|>text<|/ref|><|det|>[[148, 125, 850, 217]]<|/det|> +Response: Thank you for raising the concern about snow mass. We agree that forests typically occur at higher elevations where lower temperatures may enhance snow retention compared to openlands. To mitigate this impact, we have added additional constraint of elevation differences between samples (please see the response to your comments about Lines 101- 110). Based on the refined method, we have updated the all the related numbers and figures. + +<|ref|>text<|/ref|><|det|>[[148, 222, 850, 293]]<|/det|> +We found that the multi- year mean daytime \(\Delta \mathrm{LST_w}\) shifted from - 0.20 K to 0.01 K after accounting for elevation differences, while the negative temporal trend in \(\Delta \mathrm{LST_w}\) persists. These results suggest elevation induced snow differences may influence absolute value of \(\Delta \mathrm{LST_w}\) , but do not affect the key findings of the observed temporal trends. + +<|ref|>text<|/ref|><|det|>[[147, 318, 851, 577]]<|/det|> +Line 201 – 203: It is interesting to see a negative correlation between VPD and \(\Delta \mathrm{LST_s}\) . This suggests that when VPD is high, forests exhibit greater energy dissipation advantages compared to open lands. As the authors mentioned, VPD is highly positively correlated to air temperature. So, this reminds me of an earlier heatwave study "Teuling, A., Seneviratne, S., Stöckli, R. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nature Geosci 3, 722–727 (2010). https://doi.org/10.1038/ngeo950”. Teuling et al find "initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. ... We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long- lasting events." My question is whether the analysis in this Nature Communications manuscript represents short- term effects or longer- term effects? + +<|ref|>text<|/ref|><|det|>[[148, 581, 851, 747]]<|/det|> +Response: Thank you for raising this concern. We have carefully read the reference (Teuling et al., 2010), and find the revealed mechanism very insightful. Teuling et al. used in- situ observations to demonstrate that during a heatwave event, rising temperature (also rising VPD) and SM depletion dominate the turbulent fluxes of forests and grasslands at distinct stages: temperature (VPD) dominates initially, with grassland ET showing a stronger positive response; while SM becomes dominant later as water supply limits grassland ET cooling, and forests' conservative water- use strategy leads to lower temperature. Here, the temporal scale in Teuling et al.'s study focuses on heatwave events, while our manuscript evaluates interannual variations and trends. Therefore, we consider our analysis to represent the long- term effect. + +<|ref|>text<|/ref|><|det|>[[148, 751, 851, 842]]<|/det|> +In the original version of our manuscript, we supposed that different ET responses to rising temperature (also rising VPD) dominate the observed enhanced forest cooling. Specifically, increased VPD may enhance forest ET more than grassland ET, thereby strengthening forest cooling. This hypothesis appears contradictory to the findings of Teuling et al. at the first stage, which may be due to the differences in the temporal scale. + +<|ref|>text<|/ref|><|det|>[[149, 847, 851, 902]]<|/det|> +However, through reviewing Teuling et al.'s study, we recognized that SM can also influence the cooling effect of forests, and this aspect was not sufficiently addressed in our original manuscript. We also note that VPD and SM are strongly coupled at the annual scale. Thus, we conducted + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 140]]<|/det|> +additional analyses to identify the actual driver of the observed trends in \(\Delta \mathrm{LST}_s\) . We used binning regression method (Liu et al., 2020) to disentangle the impacts of \(\mathrm{VPD}_s\) and \(\mathrm{SM}_s\) . The results demonstrated that \(\mathrm{SM}_s\) shows stronger correlation with daytime \(\Delta \mathrm{LST}_s\) than \(\mathrm{VPD}_s\) (Line 218): + +<|ref|>text<|/ref|><|det|>[[147, 145, 851, 346]]<|/det|> +Temporal correlation analyses using \(\mathrm{VPD}_s\) , \(AT_s\) , \(\mathrm{DSR}_s\) , \(P_s\) and \(\mathrm{WS}_s\) as the potential drivers reveal strong relationships between daytime \(\Delta \mathrm{LST}_s\) and climatic variables except \(\mathrm{WS}_s\) (Fig. 3a). However, after accounting for covariates, the partial correlations between the daytime \(\Delta \mathrm{LST}_s\) and \(\mathrm{DSR}_s\) , \(P_s\) , and \(AT_s\) are greatly reduced and even reverse in sign. In contrast, \(\mathrm{VPD}_s\) maintain a predominant negative correlation with daytime \(\Delta \mathrm{LST}_s\) , with the mean partial correlation coefficient of - 0.42 (Fig. 3a). Notably, we can also find strong positive partial correlations between \(\mathrm{SM}_s\) and \(\Delta \mathrm{LST}_s\) (Fig. 3b) when replacing \(\mathrm{VPD}_s\) by the \(\mathrm{SM}_s\) , the other factor describing the dryness stress. This is due to the strong coupling between \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) at the annual scale ( \(r = 0.92\) , Supplementary Fig. 10). These findings raise the following question: whether variations in atmosphere or soil dryness are the primary factor governing changes in \(\Delta \mathrm{LST}_s\) over the past two decades? + +<|ref|>text<|/ref|><|det|>[[147, 349, 851, 550]]<|/det|> +To answer this question, we then use the binning regression method to further disentangle the respective contributions of \(\mathrm{VPD}_s\) and \(\mathrm{SM}_s\) (Liu et al., 2020). We conduct this analysis using the spatial samples of \(\mathrm{VPD}_s\) trend and \(\mathrm{SM}_s\) trends with sufficient data for decoupling the two factors. We confirm the strong spatial correlation between \(\mathrm{SM}_s\) trend and \(\mathrm{VPD}_s\) trends ( \(r = - 0.65\) ) when all spatial samples are used. However, after stratifying either \(\mathrm{SM}_s\) or \(\mathrm{VPD}_s\) trends into 10 bins according to percentiles, correlations between the two variables show substantial attenuation (Fig. 3c), suggesting the two variables are decoupled. Then, we calculate the correlation between \(\mathrm{SM}_s\) (or \(\mathrm{VPD}_s\) ) trends and \(\Delta \mathrm{LST}_s\) trends in each \(\mathrm{VPD}_s\) (or \(\mathrm{SM}_s\) ) trend bin. We find the mean \(r\) between \(\mathrm{VPD}_s\) trends and \(\Delta \mathrm{LST}_s\) trends is only - 0.11, whereas the mean \(r\) between \(\mathrm{SM}_s\) trends and \(\Delta \mathrm{LST}_s\) trends reach 0.40 (Fig. 3d). This binning regression analysis suggests that change \(\mathrm{SM}_s\) is more likely to be the driver of \(\Delta \mathrm{LST}_s\) dynamic. + +<|ref|>image<|/ref|><|det|>[[198, 553, 800, 840]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 849, 851, 903]]<|/det|> +
Fig 3. Dominant role of soil moisture in the temporal dynamics in the summer daytime cooling effect ( \(\Delta \mathrm{LST}_s\) ) of forests. (a) Regional mean correlation and partial correlation coefficients between five climate variables (vapor pressure deficit, downward solar radiation, precipitation, air temperature
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 177]]<|/det|> +and wind speed) and the daytime \(\Delta LST_s\) . The error bars indicate the standard deviations. (b) Similar with (a), but replace vapor pressure deficit by the soil moisture. (c) Correlation coefficients between summer vapor pressure deficit \((VPD_s)\) trends and summer soil moisture \((SM_s)\) trends within either \(SM_s\) or \(VPD_s\) trends bins. (d) Correlation coefficients between \(VPD_s\) (or \(SM_s\) ) trends and \(\Delta LST_s\) trends within \(SM_s\) (or \(VPD_s\) ) trends bins. + +<|ref|>image<|/ref|><|det|>[[201, 188, 785, 333]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 345, 851, 398]]<|/det|> +
Fig. S10. Temporal correlation coefficient (r) between summer vapor pressure deficit \((VPD_s)\) and surface soil moisture \((SM_s)\) . (a) Spatial pattern of r between \(VPD_s\) and \(SM_s\) . (b) Density of the r values.
+ +<|ref|>text<|/ref|><|det|>[[147, 419, 851, 472]]<|/det|> +We also build a non- linear random forest model using both \(SM_s\) and \(VPD_s\) as the input. The results also support that \(SM_s\) plays the more important role in predicting temporal dynamics of \(\Delta LST_s\) (Line 255): + +<|ref|>text<|/ref|><|det|>[[147, 477, 851, 587]]<|/det|> +The critical role of \(SM_s\) is corroborated by non- linear statistical analysis using a Random Forest (RF) model (Supplementary Text 1). Variable importance analysis demonstrates that \(SM_s\) exerts a stronger influence than \(VPD_s\) in predicting \(\Delta LST_s\) dynamics. Contribution analysis also reveals that \(SM_s\) changes account for the largest portion (0.152 K/decade, \(p < 0.05\) ) of the simulated negative \(\Delta LST_s\) trend (0.181 K/decade, \(p < 0.05\) ), highlighting its dominant role in driving the observed enhanced forest cooling effect (Supplementary Fig. 11). + +<|ref|>sub_title<|/ref|><|det|>[[148, 598, 616, 614]]<|/det|> +## Supplementary Text 1 Modelling \(\Delta LST_s\) based on random forest + +<|ref|>text<|/ref|><|det|>[[147, 616, 851, 742]]<|/det|> +We apply a non- linear machine learning method, Random Forest (RF), to evaluate the importance and contribution of multiple potential climate drivers for predicting \(\Delta LST_s\) (sklearn package in Python). Specifically, we use all spatial samples over 20 years to build the dataset. It is worth mentioning that we normalize the input climate variables and \(\Delta LST_s\) by subtracting the 20- year means at the grid scale, since the model focus on the temporal dynamic of \(\Delta LST_s\) rather than the spatial variation. We excluded air temperature from the model inputs due to its high correlation with other climate variables. + +<|ref|>text<|/ref|><|det|>[[147, 745, 852, 910]]<|/det|> +The dataset is divided into training (80% of the samples) and test sets (20% of the samples), with model parameters confirmed based on validation results from the test set (number of trees = 100; maximum depth of the tree = 6). All the samples are then used to fit the best model. The relative importance of each variable is indicated by the Gini coefficient. Moreover, we use the Shapley Additive Explanations (SHAP) method to quantify the individual contribution of each variable in each sample (shap package in Python). SHAP is an approach to explain machine learning models based on cooperative game theory, where SHAP values quantify the marginal contributions of predictors. We calculate the mean absolute SHAP values for each input variable as importance metrics and explore the non- linear impact of climate variables on \(\Delta LST_s\) by plotting their SHAP + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 87, 346, 101]]<|/det|> +values against input values. + +<|ref|>text<|/ref|><|det|>[[147, 105, 853, 233]]<|/det|> +Based on the RF model, we set several scenarios to separate the relative contributions of climate variables to the \(\Delta \mathrm{LST}_s\) trend. Specifically, we perform four experimental simulations: (S1) varying SM, only; (S2) varying SM, and VPD, while fixing \(\mathrm{DSR}_s\) \(P_s\) and \(WS_{s}\) ; (S3) varying SM, VPD, and \(\mathrm{DSR}_s\) , while fixing \(P_{s}\) and \(WS_{s}\) ; (S4) varying SM, VPD, \(\mathrm{DSR}_s\) and \(P_{s}\) , while fixing \(WS_{s}\) ; and (S5) varying SM, VPD, \(\mathrm{DSR}_s\) , \(P_{s}\) , and \(WS_{s}\) . The Theil- Sen slope and Mann- Kendall \(P\) - value of simulations S1, S2- S1, S3- S2, S4- S3, S5- S4 are used to evaluate the individual contributions of the changing climate to the \(\Delta \mathrm{LST}_s\) trend. + +<|ref|>text<|/ref|><|det|>[[147, 235, 851, 344]]<|/det|> +The model shows good accuracy on the test dataset ( \(R^2 = 0.56\) , RMSE \(= 0.32\) K), supporting our further analysis. The Gini importance and mean absolute SHAP values both suggest that SM, is the most important driver, followed by VPD, \(P_s\) , \(\mathrm{DSR}_s\) and \(WS_{s}\) (Supplementary Fig 11a). The marginal contributions quantified by the SHAP value further reveal different impacts of SM, and VPD, (Supplementary Fig. 11b). SM exhibits the pronounce positive effect, with stronger impact when SM, anomaly is negative. While VPD, only show slight negative impact under certain condition. + +<|ref|>text<|/ref|><|det|>[[146, 346, 853, 492]]<|/det|> +On the basis of the RF model, we estimate the contributions of climate variables to the long- term trend of daytime \(\Delta \mathrm{LST}_s\) (Supplementary Fig. 11c). We first compared the reconstructed trends with all forcings and the observed trends, showing good consistency (observed: 0.188 K/decade, \(p< 0.05\) ; simulated: 0.181 K/decade, \(p< 0.05\) ). By setting different scenarios, results suggest that decreasing SM, contributes the most to the negative trend in daytime \(\Delta \mathrm{LST}_s\) (- 0.152 K/decade, \(p< 0.05\) ), and increasing VPD, shows lower contribution (- 0.049 K/decade, \(p< 0.05\) ). The isolated contribution of \(\mathrm{DSR}_s\) is also statistically significant, but the value is relatively small (0.012 K/decade, \(p< 0.05\) ). The contribution of \(WS_{s}\) and \(P_{s}\) are not significant. + +<|ref|>image<|/ref|><|det|>[[273, 498, 777, 820]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 827, 850, 899]]<|/det|> +
Fig. S11. Impact of SM, on the temporal dynamics in \(\Delta \mathrm{LST}_s\) based on the random forest model. (a) The importance of climate variables is indicated by the absolute SHAP values and Gini coefficients. (b) Variation of SHAP values with changing SM, or VPD, anomaly. (c) Observed and modelled \(\Delta \mathrm{LST}_s\) trends, and the isolated contributions from climate variables.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 138]]<|/det|> +In summary, we conclude that the SM depletion (similar with the second stage identified by Teuling et al.) is more likely to explain the observed intensification of summer forest cooling over Europe in recent decades. + +<|ref|>sub_title<|/ref|><|det|>[[148, 149, 232, 163]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 170, 850, 203]]<|/det|> +Liu, L. et al. Soil moisture dominates dryness stress on ecosystem production globally. Nat. Commun. 11, 1- 9 (2020). + +<|ref|>text<|/ref|><|det|>[[148, 207, 850, 240]]<|/det|> +Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). + +<|ref|>text<|/ref|><|det|>[[148, 265, 850, 336]]<|/det|> +Line 272 - 275: The logic in this section feels somewhat unclear. The authors claim that higher VPD enhances \(\Delta \mathrm{LAI}_s\) and suggest multiple similar cause- and- effect relationships with other variables. How can the causal inferences be reliably established? It seems that the reverse statement is also valid. + +<|ref|>text<|/ref|><|det|>[[148, 342, 850, 414]]<|/det|> +Response: Thank you raising this concern about the causal relationship. We fully acknowledge that establishing robust causal inferences is critical and fundamental in structural equation modeling (SEM) analysis. Our model design is based on established understanding of the biophysical processes of forests that influence local temperature and supported by previous research findings. + +<|ref|>text<|/ref|><|det|>[[148, 419, 852, 565]]<|/det|> +First, we design the model by assuming that climate variables (temperature, precipitation...) exert different impacts on the vegetation growth and evapotranspiration (i.e. \(\Delta \mathrm{LAI}_s\) and \(\Delta \mathrm{LE}_s\) ) (Zheng et al., 2022). Such differences in LAI or LE between forests and openlands are unlikely to alter background climate patterns. Additionally, the adopted space- for- time approach assumes that the background climate remains constant within the window. This implies that changes in LAI and LE are solely driven by climatic factors and do not exert feedback effects on the atmosphere. Second, we assume that \(\Delta \mathrm{LAI}_s\) and \(\Delta \mathrm{LE}_s\) can impact \(\Delta \mathrm{LST}_s\) , which has been proved by the previous research (Prevedello et al., 2019). + +<|ref|>text<|/ref|><|det|>[[148, 571, 850, 605]]<|/det|> +We have clarified the logic of SEM in the revised manuscript (Lines 715) and included additional references to support these assumptions: + +<|ref|>text<|/ref|><|det|>[[147, 610, 852, 832]]<|/det|> +We use SEM to reveal the biophysical mechanism underlying the \(\Delta \mathrm{LST}_s\) dynamics (semopy package in Python). The SEM is designed based on previous studies (Prevedello et al., 2019; Zheng et al., 2022). Specifically, we assume that climate variables influence the temporal dynamics of \(\Delta \mathrm{LST}_s\) through three pathways: (P1) climate change affects \(\Delta \mathrm{LST}_s\) via \(\Delta \mathrm{LAI}_s\) ; (P2) climate change affects \(\Delta \mathrm{LST}_s\) via \(\Delta \mathrm{LE}_s\) ; and (P3) climate change affects \(\Delta \mathrm{LAI}_s\) , which further alters \(\Delta \mathrm{LE}_s\) and then \(\Delta \mathrm{LST}_s\) . For P1 and P3, the impact of climate variables on \(\Delta \mathrm{LAI}_s\) arises from the diverse sensitivities of different vegetation types to climate changes. Specifically, climate changes can differently promote or inhibit forest and non- forest vegetation growth, which further affects \(\Delta \mathrm{LST}_s\) through convective heat dissipation (P1) and the evaporative cooling effect (P3). Climate variables also directly modulate \(\Delta \mathrm{LE}_s\) even the vegetation greenness remain constant. This is due to inherent differences between different vegetation types (Teuling et al., 2010), resulting in diverse evaporative responses to climate change and, consequently, affecting \(\Delta \mathrm{LST}_s\) (P2). + +<|ref|>sub_title<|/ref|><|det|>[[148, 841, 232, 855]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 862, 850, 895]]<|/det|> +Prevedello, J. A., Winck, G. R., Weber, M. M., Nichols, E. & Sinervo, B. Impacts of forestation and deforestation on local temperature across the globe. PLoS One 14, 1- 18 (2019). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 157]]<|/det|> +Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722–727 (2010). Zheng, H. et al. Effects of Vegetation Changes and Multiple Environmental Factors on Evapotranspiration Across China Over the Past 34 Years. Earth's Futur. 10, 1–16 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 177, 857, 361]]<|/det|> +In the flowchart of Fig. 4, I notice a missing of surface resistance in the VPD- LE relationship. In the Penman- Monteith scheme, increasing VPD can have competing effects on ET: on one hand, increasing VPD enhances ET, while on the other, it also raises surface resistance, which suppresses ET. The results suggest that the VPD- driven enhancement of ET is more dominant. Could the authors clarify why this occurs when comparing ET between forests and open lands? I feel VPD is not the driver of such findings, but the biome type – forests/open lands and their associated biophysical and physiological responses – are the real drivers. Need to clarify this. See Novick, K., Ficklin, D., Stoy, P. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nature Clim Change 6, 1023 – 1027 (2016). https://doi.org/10.1038/nclimate3114 + +<|ref|>text<|/ref|><|det|>[[148, 366, 850, 438]]<|/det|> +Response: We sincerely appreciate the valuable comments. We have carefully read the referred paper and we fully agree with your perspective of the opposing effects of VPD on LE (or ET). However, it is difficult for our data- based analysis to explicitly incorporate the impact of surface resistance \((\mathbf{r}_{\mathrm{s}})\) , due to the lack of reliable \(\mathbf{r}_{\mathrm{s}}\) data. + +<|ref|>text<|/ref|><|det|>[[148, 443, 851, 571]]<|/det|> +To address this issue, we performed additional analyses using in- situ observation and the Penman- Monteith framework, which can account for the impact of VPD on \(\mathbf{r}_{\mathrm{s}}\) . The results reveal that when neglecting the \(\mathbf{r}_{\mathrm{s}}\) effect, VPD demonstrates a more pronounced positive effect on LE in forests. However, when considering \(\mathbf{r}_{\mathrm{s}}\) responses to VPD, the sensitivity differences between forests and openlands become statistically insignificant. This result implies that the negative effect resulting from the \(\mathbf{r}_{\mathrm{s}}\) response to rising VPD offsets the direct positive effect of VPD on forest evapotranspiration. + +<|ref|>text<|/ref|><|det|>[[148, 575, 850, 648]]<|/det|> +These findings challenge our initial hypothesis that VPD exerts stronger stimulation on evaporative cooling in forests, highlighting the critical role of surface resistance dynamics in mediating these relationships. We have incorporated this supplementary analysis in the revised manuscript (Line 262): + +<|ref|>text<|/ref|><|det|>[[147, 653, 851, 872]]<|/det|> +We also evaluate the sensitivity of summer latent heat \((LE_{s})\) to VPD, in both forests and openlands using eddy covariance observations from European sites (Supplementary Text 2). The sensitivity analysis is based on the Penman- Monteith framework, which accounts for the influence of \(VPD_{s}\) on surface resistance (Novick et al., 2016). If \(VPD_{s}\) is the main driver of enhanced forest cooling effect, we expect to observe greater positive \(LE_{s}\) sensitivity in forests compared to openlands, in which case forests can produce stronger evaporative cooling effects in the context of rising \(VPD_{s}\) . However, we find openlands show slightly higher positive sensitivity than forests, although the difference is not significant. The direct regression analysis also supports the stronger \(LE_{s}\) responses to \(VPD_{s}\) increases in openlands (Supplementary Table. 1). This in- situ observational evidence, combined with our statistical results (binning regression and random forest regression), suggests that \(VPD_{s}\) may not explain the enhanced cooling effect of European forests, while the decline in \(SM_{s}\) appears to be the real dominant driver. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 85, 817, 102]]<|/det|> +## Supplementary Text 2. Sensitivity of summer latent heat to increasing vapor pressure deficit + +<|ref|>text<|/ref|><|det|>[[147, 104, 852, 213]]<|/det|> +Elevated vapor pressure deficit (VPD) exerts dual opposing effects on latent heat (LE) flux: while it directly enhances LE through increased evaporative demand, it simultaneously elevates surface resistance (rs), thereby suppressing LE (Novick et al., 2016). To investigate how VPD differentially influences LE in forests and openlands and consequently affects the cooling effect of forests, we analyze European eddy covariance observations from the FLUXNET2015 dataset and conduct sensitivity analyses. + +<|ref|>text<|/ref|><|det|>[[147, 216, 850, 251]]<|/det|> +The sensitivity of LE to VPD is assessed based on the Penman- Monteith framework, accounting for both the aforementioned opposing effects (Lin et al., 2018): + +<|ref|>equation<|/ref|><|det|>[[400, 254, 848, 285]]<|/det|> +\[LE = \frac{\Delta(Rn - G) + \rho C_p(VPD / r_a)}{\Delta + \gamma(1 + r_s / r_a)} \quad (1)\] + +<|ref|>equation<|/ref|><|det|>[[413, 293, 848, 320]]<|/det|> +\[G_{s} = G_{0} + G_{1}\frac{G P P}{\nu P D^{m}} \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[147, 325, 850, 436]]<|/det|> +Here, \(R n\) \((W / m^{2})\) is the net radiation; \(G\) \((W / m^{2})\) is the soil heat flux; \(\Delta\) \((kPa / K)\) is the slope of the saturated vapor pressure curve; \(\rho\) is the air density \((kg / m^{3})\) . \(C_{p}\) \((J / kg / K)\) is the specific heat of air; \(\gamma\) is the psychrometric constant \((kPa / K)\) ; \(r_{a}\) (s/m) is the aerodynamic resistance, estimated using vegetation height; \(G_{s}\) (surface conductance) is the inverse of \(r_{s}\) ; GPP is the gross primary productivity. The model parameters \((G_{0}, G_{1},\) and \(m\) ) is estimated via optimization (SciPy package in Python) using daily- scale observations. + +<|ref|>text<|/ref|><|det|>[[147, 438, 850, 584]]<|/det|> +We analysis those observation in summer and we select sites with reliable LE accuracy (Nash- Sutcliffe Efficiency \(>0.5\) ), resulting in 19 forested and 12 openland (grassland and cropland) sites. We then introduce VPDs perturbations into the observation data to estimate summer LE \((LE_{s})\) sensitivity to VPDs \(\left(\frac{dLE_{s}}{dVPD_{s}}\right)\) \(LE_{s}\) response to a 1 hPa VPDs increase). For comparison, we also compute \(\frac{dLE_{s}}{dVPD_{s}}\) (i) without the impact of VPDs on \(r_{s}\) and (ii) via direct linear regression between VPDs and \(LE_{s}\) (Supplementary Table 1). + +<|ref|>text<|/ref|><|det|>[[147, 586, 850, 732]]<|/det|> +If VPDs is the primary driver of enhanced forest cooling effect, forests should exhibit a higher \(\frac{dLE_{s}}{dVPD_{s}}\) than openlands, implying stronger evaporative cooling under rising VPDs. However, results indicate that this expectation holds only when neglecting the inhibitory effect of VPDs on \(LE_{s}\) (via \(r_{s}\) ). When considering both opposing effects of VPDs on \(LE_{s}\) , openlands show slightly higher mean sensitivity compared to forests. In addition, the direct regression analysis supports the stronger \(LE_{s}\) responses to VPDs increases in openlands. These findings suggest that VPDs may not explain the enhanced cooling effect observed in European forests. + +<|ref|>table<|/ref|><|det|>[[147, 780, 848, 884]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[152, 752, 844, 784]]<|/det|> +Table S1. Sensitivity of summer latent heat \((LE_{s})\) flux to rising vapor pressure deficit (VPDs) based on FLUXNET observations in Europe. + +
dLEs
dVPDs (w·m-2/hPa)
dLEs
dVPDs (w·m-2/hPa)
ignoring the impact of VPD on rs
Regression slope
between VPDs and LEs
(w·m-2/hPa)
Forest (n=19)2.08 ± 1.855.92 ± 2.953.87 ± 2.87
Openland (n=19)2.48 ± 1.714.87 ± 1.326.44 ± 2.67
+ +<|ref|>table_footnote<|/ref|><|det|>[[149, 886, 532, 899]]<|/det|> +The values indicate the mean \(\pm\) standard deviation across sites. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 106, 851, 198]]<|/det|> +Combining this sensitivity analysis result and the statistical evidence (please see the response to your comment above), we recognized that the decreasing \(\mathrm{SM}_s\) appears to be the primary driver of the observed daytime \(\Delta \mathrm{LST}_s\) trends. Thus, we updated the Fig. 4 and the related descriptions (Line 276). The biophysical and physiological mechanisms corresponding to each path are also annotated to enhance conceptual clarity (Fig. 4a). + +<|ref|>text<|/ref|><|det|>[[147, 202, 854, 331]]<|/det|> +We further conduct structural equation modeling (SEM) to elucidate the biophysical mechanisms underlying the impact of varying SM, on daytime \(\Delta \mathrm{LST}_s\) dynamics (Fig. 4a). Our SEM incorporates two key biophysical mediators: the leaf area index difference ( \(\Delta \mathrm{LAI}_s\) ) and latent heat flux difference ( \(\Delta \mathrm{LE}_s\) ) between nearby forests and openlands. The path effect (mean \(\pm\) standard error) is used to describe strength and direction of the relationship. Following previous studies, we build SEMs at the local scale and calculate the mean path effects of all models (Shen et al., 2024; Zhong et al., 2023). The analysis reveals three distinct pathways of SM, affecting \(\Delta \mathrm{LST}_s\) . + +<|ref|>text<|/ref|><|det|>[[147, 333, 852, 404]]<|/det|> +(1) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) exerts a significant negative effect on \(\Delta \mathrm{LAI}_s\) (-0.41 \(\pm\) 0.15). Then, \(\Delta \mathrm{LAI}_s\) demonstrate a negative effect on \(\Delta \mathrm{LST}_s\) (-0.19 \(\pm\) 0.09). This pathway suggests that reduced \(\mathrm{SM}_s\) can amplify the greenness difference in forests and openlands, thereby enhancing forests' cooling advantage through improved convective heat dissipation. + +<|ref|>text<|/ref|><|det|>[[147, 406, 851, 496]]<|/det|> +(2) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) have a negative effect on \(\Delta \mathrm{LE}_s\) (-0.25 \(\pm\) 0.11), followed by a strong negative influence of \(\Delta \mathrm{LE}_s\) on \(\Delta \mathrm{LST}_s\) (-0.54 \(\pm\) 0.09). This pathway indicates that declining \(\mathrm{SM}_s\) imposes less water limitation to forests compared to openlands, enabling forests to maintain stronger relative evaporative cooling through differential stomatal regulation (with greenness remaining constant). + +<|ref|>text<|/ref|><|det|>[[147, 498, 852, 553]]<|/det|> +(3) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) -induced changes in \(\Delta \mathrm{LAI}_s\) subsequently enhance \(\Delta \mathrm{LE}_s\) (0.62 \(\pm\) 0.06), ultimately influencing \(\Delta \mathrm{LST}_s\) . This demonstrates that \(\mathrm{SM}_s\) reduction amplifies evaporative cooling effects of forests by increasing the vegetation greenness contrast with openlands. + +<|ref|>text<|/ref|><|det|>[[147, 555, 852, 812]]<|/det|> +The pathway effects, representing the strength and direction of the mechanism, are quantified as the product of all constituent path coefficients (Fig. 4b). Results reveal that the second and third pathways (both mediated by \(\Delta \mathrm{LE}_s\) ) contribute equally to \(\Delta \mathrm{LST}_s\) variation (about 0.14 \(\pm\) 0.06), while the impact first pathway is weaker (0.08 \(\pm\) 0.05). These findings suggest \(\mathrm{SM}_s\) can modulate \(\Delta \mathrm{LST}_s\) dynamics through multiple mechanisms, with forest evaporative cooling regulation emerging as the dominant process. Previous studies have demonstrated that reduced soil moisture in Europe can amplify warming during heatwaves through land-atmosphere interactions (Dirmeyer et al., 2021; Fischer et al., 2007). Our findings confirm forests exhibit greater stability and resistance to increasing soil dryness compared to grasslands or croplands, which may mitigate land-atmosphere coupling feedback and consequently enhance the relative cooling effect of forests (Teuling et al., 2010). This stability of forests is reflected in both more moderate evaporative limitation and sustained vegetation greenness under increasing soil dryness. Our results provide observational evidence suggesting that the capacity of forest ecosystems to mitigate water deficit-induced warming persists not only during heatwave events but also across interannual timescales. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[183, 100, 816, 365]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 382, 852, 511]]<|/det|> +
Fig 4. Mechanisms underlying the effects of climate variables on the daytime LST effects of European forests (ALSTs) in summer. (a) Structure equation models describing the biophysical relationships between climate variables and ALSTs. The numbers denote the path value (mean \(\pm\) standard error). The arrow color indicates the sign of the path (red for positive and blue for negative), and the thickness indicates the magnitude of the corresponding path value. (b) Bar plot of the pathway effects of climate variables affecting ALSTs. The error bars indicate the uncertainty based on error propagation.
+ +<|ref|>text<|/ref|><|det|>[[183, 533, 794, 550]]<|/det|> +Accordingly, we also revised the discussion about the summer mechanism (Line 434). + +<|ref|>text<|/ref|><|det|>[[147, 555, 852, 887]]<|/det|> +Using a range of statistical methods, we find that declining SM, is the predominant factor contributing to both the interannual variation and the negative trend in ALSTs. Path analysis shows that SM, affects ALST, dynamics through two mechanisms. First, we show \(\Delta L A I_{s}\) is modulated by SM, implying that as the soil becomes drier, the vegetation structure difference between forests and openlands becomes more evident. The higher \(\Delta L A I_{s}\) could boost the cooling efficiency of forests through stronger direct heat dissipation and evaporative cooling. The impact of SM, on vegetation has been well-documented: increasing dryness pressure could trigger stomatal closure, inhibit photosynthesis, and increase vegetation mortality (Li et al., 2022; Stocker et al., 2018). Our results confirm a stronger negative effect of SM, on non- forest vegetation than on forests (Hoek van Dijke et al., 2023). The potential reason is that forest ecosystems with high species richness and deep roots are more stable and resilient to dryness (Isbell et al., 2015; Tumber- Dávila et al., 2022). Second, even under constant vegetation conditions, less soil water supply directly amplifies \(\Delta L E_{s}\) and enhances the cooling effect of forests. These findings are consistent with prior researches (Fu et al., 2022a, 2022b), indicating that soil moisture imposes stronger limitations on ET in grasslands and croplands relative to forest ecosystems. This differential response is evidenced by both the greater sensitivity of and the higher critical soil moisture thresholds in non- forest ecosystems. This phenomenon may be attributed to the capacity of forests to maintain ET through deep soil water extraction, thereby exhibiting greater resilience to warming- induced surface soil moisture deficits + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 121]]<|/det|> +compared to openlands. Overall, the revealed impact of \(SM_{s}\) on \(\Delta LST_{s}\) essentially reflects the diverse vegetation physiological responses to climate changes. + +<|ref|>sub_title<|/ref|><|det|>[[148, 149, 232, 164]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 170, 852, 280]]<|/det|> +Dirmeyer, P. A., Balsamo, G., Blyth, E. M., Morrison, R. & Cooper, H. M. Land- Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018. AGU Adv. 2, 1- 16 (2021). Fischer, E. M., Seneviratne, S. I., Lüthi, D. & Schär, C. Contribution of land- atmosphere coupling to recent European summer heat waves. Geophys. Res. Lett. 34, 1- 6 (2007). + +<|ref|>text<|/ref|><|det|>[[147, 260, 850, 703]]<|/det|> +Fu, Z. et al. Critical soil moisture thresholds of plant water stress in terrestrial ecosystems. Sci. Adv. 8, 1- 12 (2022). Fu, Z. et al. Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems. Glob. Chang. Biol. 28, 2111- 2123 (2022). Hoek van Dijke, A. J. et al. Comparing forest and grassland drought responses inferred from eddy covariance and Earth observation. Agric. For. Meteorol. 341, (2023). Isbell, F. et al. Biodiversity increases the resistance of ecosystem productivity to climate extremes. Nature 526, 574- 577 (2015). Li, W. et al. Widespread increasing vegetation sensitivity to soil moisture. Nat. Commun. 13, 3959 (2022). Lin, C. et al. Diel ecosystem conductance response to vapor pressure deficit is suboptimal and independent of soil moisture. Agric. For. Meteorol. 250- 251, 24- 34 (2018). Novick, K. A. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nat. Clim. Chang. 6, 1023- 1027 (2016). Shen, P. et al. Biodiversity buffers the response of spring leaf unfolding to climate warming. Nat. Clim. Chang. 14, 863- 868 (2024). Stocker, B. D. et al. Quantifying soil moisture impacts on light use efficiency across biomes. New Phytol. 218, 1430- 1449 (2018). Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). Tumber- Dávila, S. J., Schenk, H. J., Du, E. & Jackson, R. B. Plant sizes and shapes above and belowground and their interactions with climate. New Phytol. 235, 1032- 1056 (2022). Zhong, Z. et al. Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity. Sci. Adv. 9, (2023). + +<|ref|>sub_title<|/ref|><|det|>[[149, 757, 498, 774]]<|/det|> +## Reviewer #1 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[148, 792, 850, 881]]<|/det|> +I feel that this might be holding the authors to an excessively high standard. If Nature is asking whether I can strictly replicate results using their code, I believe it would take a significant amount of time, and I don't have the capacity to verify it. However, I feel is that it's unrealistic to expect the authors to cover every detail perfectly and provide a fully automated, one- click runnable code. + +<|ref|>text<|/ref|><|det|>[[147, 885, 848, 902]]<|/det|> +Additionally, I believe that the provided code does not fully include all the components/scripts + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 138]]<|/det|> +necessary to reproduce all the results of this paper (e.g., the ESM analysis, MODIS data processing). Again, I feel this is holding the authors to an excessively high standard. They are not software engineers. + +<|ref|>text<|/ref|><|det|>[[147, 144, 850, 234]]<|/det|> +Response: Thank you for the feedback concerning code availability. We fully recognize the importance of transparent research practices. In response, we have repudiated the code, including all processed datasets necessary to execute the analysis scripts (https://zenodo.org/records/15625044). These materials enable researchers to fully reproduce all statistical analyses and figures presented in our manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 98, 450, 114]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 132, 851, 243]]<|/det|> +I find this manuscript has a lot of interesting data and discussion. Moreover, for me personally, it was highly motivating to read this discussion. I did find, especially at the beginning of the manuscript, that the work was not very well situated in the principal literature. All four of the first references to appear in the manuscript do not seem well suited to set up this general discussion. I have provided a number of suggestions in the attached submission pdf and am hopeful that some of these suggestions will prove useful... + +<|ref|>text<|/ref|><|det|>[[148, 247, 851, 356]]<|/det|> +Response: We appreciate your positive comments. We have revised our manuscript carefully and the detailed corrections are listed below. Specifically, we have thoroughly reorganized the introduction section by incorporating more appropriate foundational literature as suggested in your comments. According to your concern regarding the water availability, we conducted additional experiments to explore the impact of soil moisture, and added related discussions. We hope the revised paper will be more suitable for publication. + +<|ref|>text<|/ref|><|det|>[[148, 382, 850, 435]]<|/det|> +I also found that the introduction was occasionally vague and would have benefitted from a somewhat more nuanced discussion... I have tried to point out places where I think this would be helpful. + +<|ref|>text<|/ref|><|det|>[[148, 440, 850, 514]]<|/det|> +Response: Thanks for the careful reading and pointing out the confusing statements. Your detailed suggestions have helped us significantly improve the manuscript. We provide point- by- point responses to each of your specific comments about the introduction in the PDF file, along with the corresponding revisions we have implemented (please see the response below). + +<|ref|>text<|/ref|><|det|>[[148, 539, 851, 648]]<|/det|> +Finally, the discussion of radiative and non- radiative effects, as well as the discussion of winter and summertime effects, to my mind, were not adequately introduced and motivated in the introductory parts of the paper. When these concepts are suddenly announced, (the discussion about winter and summer time effects first comes up in the results section of the paper?), they are unexpected and seemingly unmotivated in the general context of the paper... This can be improved upon... + +<|ref|>text<|/ref|><|det|>[[148, 654, 850, 708]]<|/det|> +Response: We appreciate this constructive suggestion. We have incorporated background on radiative/non- radiative mechanisms and seasonal (winter/summer) effects in the introduction, ensuring these concepts are properly motivated before appearing in later sections (Line 39). + +<|ref|>text<|/ref|><|det|>[[147, 713, 851, 896]]<|/det|> +During the daytime, forests exhibit two competing effects compared to non- forest vegetation: (a) the non- radiative cooling effect driven by higher evapotranspiration (ET) rates (Mildrexler et al., 2011), and (b) the radiative warming effect resulting from lower albedo (R.A.Betts, 2000). The net temperature response depends on the balance between the opposing radiative and non- radiative effects (Bright et al., 2017), and their relative dominance is largely governed by background climatic conditions (Pitman et al., 2011). For instance, forests in mid- latitude regions (e.g., North America, Europe and China) demonstrate seasonally contrasting LST effects (Li et al., 2015; Tang et al., 2018). During cold winters, bright snow covers short vegetation but is masked by dense forest canopies. As a result, forests absorb more solar radiation and show a local warming effect compared to surrounding openlands. Conversely, during the peak growing season (warm summer), forests + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 157]]<|/det|> +exert cooling effects under sufficient soil moisture conditions, owing to their higher ET rates compared to other vegetation types. However, in arid regions, limited soil moisture can constrain forest evaporative cooling despite abundant radiation and optimal temperature, causing radiative warming to dominate (Rohatyn et al., 2023). + +<|ref|>sub_title<|/ref|><|det|>[[148, 170, 231, 185]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 191, 850, 485]]<|/det|> +Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1- 10 (2015). Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1- 15 (2011). Pitman, A. J. et al. Importance of background climate in determining impact of land- cover change on regional climate. Nat. Clim. Chang. 1, 472- 475 (2011). Rohatyn, S., Rotenberg, E., Tatarinov, F., Carmel, Y. & Yakir, D. Large variations in afforestation- related climate cooling and warming effects across short distances. Commun. Earth Environ. 4, 1- 10 (2023). R.A. Betts. Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. Nature 408, 187- 190 (2000). Tang, B., Zhao, X. & Zhao, W. Local effects of forests on temperatures across Europe. Remote Sens. 10, 1- 24 (2018). + +<|ref|>text<|/ref|><|det|>[[148, 507, 850, 598]]<|/det|> +I also find that the Authors do not adequately distinguish between global and local cooling... Both terms come up. But most of the time it sounds like the Authors are talking about local cooling... And the balance in terms of global cooling is never clearly estimated...? It is important not to conflate these terms, since local cooling is not necessarily equivalent to global cooling...? + +<|ref|>text<|/ref|><|det|>[[148, 603, 850, 675]]<|/det|> +Response: We appreciate this important criticism. We fully agree with that global and local effects are inherently different. As you mentioned, our manuscript focusses on the local effect. We have added explicit discussion distinguishing between local and global cooling effects of forests in the revised manuscript, with particular attention to their differing mechanisms (Line 477): + +<|ref|>text<|/ref|><|det|>[[148, 681, 850, 790]]<|/det|> +There are several potential caveats or issues when interpreting our results. First, the adopted "space- for- time" method provides priori estimates of local temperature effects of forests (Wang et al., 2023), which is different from the global effects. At the planetary scale, forests can exert more complicated effects on climate through multiple processes such as changes in cloud formation and large- scale atmospheric circulations (Ellison et al., 2024; Xu et al., 2022). Thus, our results should be treated as the reference for local climate adaptation rather than global climate mitigation. + +<|ref|>text<|/ref|><|det|>[[148, 795, 850, 829]]<|/det|> +We also distinguished between the global and local impacts in the background statement (Line 25): + +<|ref|>text<|/ref|><|det|>[[148, 835, 850, 907]]<|/det|> +Through conservation, proper management, and restoration practices, forest ecosystems could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud formation (Cerasoli et al., 2021; Ellison et al., 2024; Luo et al., 2024). In addition to the global impact, forests exhibit significant local cooling or warming effects through altering + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 691, 101]]<|/det|> +surface energy and water fluxes (Ellison et al., 2024; Lawrence et al., 2022). + +<|ref|>sub_title<|/ref|><|det|>[[149, 114, 232, 128]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 135, 852, 374]]<|/det|> +Cerasoli, S., Yin, J. & Porporato, A. Cloud cooling effects of afforestation and reforestation at midlatitudes. Proc. Natl. Acad. Sci. U. S. A. 118, 1- 7 (2021).Ellison, D., Pokorny, J. & Wild, M. Even cooler insights: On the power of forests to (water the Earth and) cool the planet. Glob. Chang. Biol. 30, 1- 20 (2024).Lawrence, D., Coe, M., Walker, W., Verchot, L. & Vandecar, K. The Unseen Effects of Deforestation: Biophysical Effects on Climate. Front. For. Glob. Chang. 5, 1- 13 (2022).Luo, H., Quaas, J. & Han, Y. Decreased cloud cover partially offsets the cooling effects of surface albedo change due to deforestation. Nat. Commun. 15, 7345 (2024).Wang, H., Yue, C. & Luyssaert, S. Reconciling different approaches to quantifying land surface temperature impacts of afforestation using satellite observations. Biogeosciences 20, 75- 92 (2023).Xu, R. et al. Contrasting impacts of forests on cloud cover based on satellite observations. Nat. Commun. 13, 670 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 396, 850, 468]]<|/det|> +Further, I would have like to see more discussion of the role of the availability of water and surface moisture. The cooling potential of forests strongly depends on the availability of water. As soon as this surface moisture disappears, the loss of latent heat means the warming will suddenly take over... But there is little attention to this throughout the paper... + +<|ref|>text<|/ref|><|det|>[[148, 474, 851, 620]]<|/det|> +Response: Thank you for raising this essential issue. We full acknowledge that both atmospheric water demand (VPD) and soil water supply (soil moisture, SM) can have important effects on the evaporative cooling of vegetation. Given the strong annual- scale correlation between VPD and SM, their respective roles may have been conflated in the original manuscript. Thus, we conducted additional analyses to identify the actual driver of the observed trends in \(\Delta \mathrm{LST}_s\) . Specifically, we used binning regression method (Liu et al., 2020) to decouple summer VPD (VPDs) and summer SM (SMs). The results demonstrated that it is \(\mathrm{SM}_s\) , rather than VPD, dominates with the long- term trend of daytime \(\Delta \mathrm{LST}_s\) , which largely addresses this comment (Line 218): + +<|ref|>text<|/ref|><|det|>[[148, 625, 851, 826]]<|/det|> +Temporal correlation analyses using VPDs, \(AT_s\) , DSRs, \(P_s\) and \(WS_s\) as the potential drivers reveal strong relationships between daytime \(\Delta \mathrm{LST}_s\) and climatic variables except \(WS_s\) (Fig. 3a). However, after accounting for covariates, the partial correlations between the daytime \(\Delta \mathrm{LST}_s\) and DSRs, \(P_s\) and \(AT_s\) are greatly reduced and even reverse in sign. In contrast, VPDs maintain a predominant negative correlation with daytime \(\Delta \mathrm{LST}_s\) , with the mean partial correlation coefficient of - 0.42 (Fig. 3a). Notably, we can also find strong positive partial correlations between SM and \(\Delta \mathrm{LST}_s\) (Fig. 3b) when replacing VPDs by the SMs, the other factor describing the dryness stress. This is due to the strong coupling between SM, \(VPD_s\) at the annual scale ( \(r = 0.92\) , Supplementary Fig. 10). These findings raise the following question: whether variations in atmosphere or soil dryness are the primary factor governing changes in \(\Delta \mathrm{LST}_s\) over the past two decades? + +<|ref|>text<|/ref|><|det|>[[148, 830, 850, 901]]<|/det|> +To answer this question, we then use the binning regression method to further disentangle the respective contributions of VPDs and SMs (Liu et al., 2020). We conduct this analysis using the spatial samples of VPDs, trend and SM, trends with sufficient data for decoupling the two factors. We confirm the strong spatial correlation between SM, trend and VPDs, trends ( \(r = - 0.65\) ) when all + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 213]]<|/det|> +spatial samples are used. However, after stratifying either \(SM_{s}\) or \(VPD_{s}\) trends into 10 bins according to percentiles, correlations between the two variables show substantial attenuation (Fig. 3c), suggesting the two variables are decoupled. Then, we calculate the correlation between \(SM_{s}\) (or \(VPD_{s}\) ) trends and \(\Delta LST_{s}\) trends in each \(VPD_{s}\) (or \(SM_{s}\) ) trend bin. We find the mean \(r\) between \(VPD_{s}\) trends and \(\Delta LST_{s}\) trends is only - 0.11, whereas the mean \(r\) between \(SM_{s}\) trends and \(\Delta LST_{s}\) trends reach 0.40 (Fig. 3d). This binning regression analysis suggests that change \(SM_{s}\) is more likely to be the driver of \(\Delta LST_{s}\) dynamic. + +<|ref|>image<|/ref|><|det|>[[200, 217, 800, 502]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 512, 852, 658]]<|/det|> +
Fig 3. Dominant role of soil moisture in the temporal dynamics in the summer daytime cooling effect ( \(\Delta LST_{s}\) ) of forests. (a) Regional mean correlation and partial correlation coefficients between five climate variables (vapor pressure deficit, downward solar radiation, precipitation, air temperature and wind speed) and the daytime \(\Delta LST_{s}\) . The error bars indicate the standard deviations. (b) Similar with (a), but replace vapor pressure deficit by the soil moisture. (c) Correlation coefficients between summer vapor pressure deficit ( \(VPD_{s}\) ) trends and summer soil moisture ( \(SM_{s}\) ) trends within either \(SM_{s}\) or \(VPD_{s}\) trends bins. (d) Correlation coefficients between \(VPD_{s}\) (or \(SM_{s}\) ) trends and \(\Delta LST_{s}\) trends within \(SM_{s}\) (or \(VPD_{s}\) ) trends bins.
+ +<|ref|>image<|/ref|><|det|>[[201, 668, 785, 814]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 826, 852, 879]]<|/det|> +
Fig. S10. Temporal correlation coefficient (r) between summer vapor pressure deficit ( \(VPD_{s}\) ) and surface soil moisture ( \(SM_{s}\) ). (a) Spatial pattern of \(r\) between \(VPD_{s}\) and \(SM_{s}\) . (b) Density of the \(r\) values.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +We then build a non- linear random forest model using both \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) as the input. The results also support that \(\mathrm{SM}_s\) plays the more important role in predicting temporal dynamics of \(\Delta \mathrm{LST}_s\) (Line 255): + +<|ref|>text<|/ref|><|det|>[[148, 144, 850, 254]]<|/det|> +The critical role of \(\mathrm{SM}_s\) is corroborated by non- linear statistical analysis using a Random Forest (RF) model (Supplementary Text 1). Variable importance analysis demonstrates that \(\mathrm{SM}_s\) exerts a stronger influence than \(\mathrm{VPD}_s\) in predicting \(\Delta \mathrm{LST}_s\) dynamics. Contribution analysis also reveals that \(\mathrm{SM}_s\) changes account for the largest portion (0.152 K/decade, \(p < 0.05\) ) of the simulated negative \(\Delta \mathrm{LST}_s\) trend (0.181 K/decade, \(p < 0.05\) ), highlighting its dominant role in driving the observed enhanced forest cooling effect (Supplementary Fig. 11). + +<|ref|>sub_title<|/ref|><|det|>[[148, 265, 616, 281]]<|/det|> +## Supplementary Text 1 Modelling \(\Delta \mathrm{LST}_s\) based on random forest + +<|ref|>text<|/ref|><|det|>[[147, 283, 850, 410]]<|/det|> +We apply a non- linear machine learning method, Random Forest (RF), to evaluate the importance and contribution of multiple potential climate drivers for predicting \(\Delta \mathrm{LST}_s\) (sklearn package in Python). Specifically, we use all spatial samples over 20 years to build the dataset. It is worth mentioning that we normalize the input climate variables and \(\Delta \mathrm{LST}_s\) by subtracting the 20- year means at the grid scale, since the model focus on the temporal dynamic of \(\Delta \mathrm{LST}_s\) rather than the spatial variation. We excluded air temperature from the model inputs due to its high correlation with other climate variables. + +<|ref|>text<|/ref|><|det|>[[147, 412, 851, 595]]<|/det|> +The dataset is divided into training (80% of the samples) and test sets (20% of the samples), with model parameters confirmed based on validation results from the test set (number of trees = 100; maximum depth of the tree = 6). All the samples are then used to fit the best model. The relative importance of each variable is indicated by the Gini coefficient. Moreover, we use the Shapley Additive Explanations (SHAP) method to quantify the individual contribution of each variable in each sample (shap package in Python). SHAP is an approach to explain machine learning models based on cooperative game theory, where SHAP values quantify the marginal contributions of predictors. We calculate the mean absolute SHAP values for each input variable as importance metrics and explore the non- linear impact of climate variables on \(\Delta \mathrm{LST}_s\) by plotting their SHAP values against input values. + +<|ref|>text<|/ref|><|det|>[[147, 597, 851, 725]]<|/det|> +Based on the RF model, we set several scenarios to separate the relative contributions of climate variables to the \(\Delta \mathrm{LST}_s\) trend. Specifically, we perform four experimental simulations: (S1) varying \(\mathrm{SM}_s\) only; (S2) varying \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) while fixing \(\mathrm{DSR}_s\) \(P_s\) and \(\mathrm{WS}_s\) ; (S3) varying \(\mathrm{SM}_s\) \(\mathrm{VPD}_s\) and \(\mathrm{DSR}_s\) , while fixing \(P_s\) and \(\mathrm{WS}_s\) ; (S4) varying \(\mathrm{SM}_s\) \(\mathrm{VPD}_s\) \(\mathrm{DSR}_s\) and \(P_s\) , while fixing \(\mathrm{WS}_s\) and (S5) varying \(\mathrm{SM}_s\) \(\mathrm{VPD}_s\) \(\mathrm{DSR}_s\) \(P_s\) and \(\mathrm{WS}_s\) . The Theil- Sen slope and Mann- Kendall \(P\) - value of simulations S1, S2- S1, S3- S2, S4- S3, S5- S4 are used to evaluate the individual contributions of the changing climate to the \(\Delta \mathrm{LST}_s\) trend. + +<|ref|>text<|/ref|><|det|>[[147, 728, 850, 836]]<|/det|> +The model shows good accuracy on the test dataset ( \(R^2 = 0.56\) , \(\mathrm{RMSE} = 0.32 \mathrm{K}\) ), supporting our further analysis. The Gini importance and mean absolute SHAP values both suggest that \(\mathrm{SM}_s\) is the most important driver, followed by \(\mathrm{VPD}_s\) , \(P_s\) , \(\mathrm{DSR}_s\) and \(\mathrm{WS}_s\) (Supplementary Fig 11a). The marginal contributions quantified by the SHAP value further reveal different impacts of \(\mathrm{SM}_s\) and \(\mathrm{VPD}_s\) (Supplementary Fig. 11b). \(\mathrm{SM}_s\) exhibits the pronounce positive effect, with stronger impact when \(\mathrm{SM}_s\) anomaly is negative. While \(\mathrm{VPD}_s\) only show slight negative impact under certain condition. + +<|ref|>text<|/ref|><|det|>[[147, 839, 850, 911]]<|/det|> +On the basis of the RF model, we estimate the contributions of climate variables to the long- term trend of daytime \(\Delta \mathrm{LST}_s\) (Supplementary Fig. 11c). We first compared the reconstructed trends with all forcings and the observed trends, showing good consistency (observed: 0.188 K/decade, \(p < 0.05\) ; simulated: 0.181 K/decade, \(p < 0.05\) ). By setting different scenarios, results suggest that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 853, 158]]<|/det|> +decreasing \(SM_{s}\) contributes the most to the negative trend in daytime \(\Delta LST_{s}\) (- 0.152 K/decade, \(p< 0.05\) ), and increasing VPDs shows lower contribution (- 0.049 K/decade, \(p< 0.05\) ). The isolated contribution of \(\Delta DSR_{s}\) is also statistically significant, but the value is relatively small (0.012 K/decade, \(p< 0.05\) ). The contribution of \(WS_{s}\) and \(P_{s}\) are not significant. + +<|ref|>image<|/ref|><|det|>[[257, 163, 760, 485]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 494, 850, 566]]<|/det|> +
Fig. S11. Impact of \(SM_{s}\) on the temporal dynamics in \(\Delta LST_{s}\) based on the random forest model. (a) The importance of climate variables is indicated by the absolute SHAP values and Gini coefficients. (b) Variation of SHAP values with changing \(SM_{s}\) or VPDs, anomaly. (c) Observed and modelled \(\Delta LST_{s}\) trends, and the isolated contributions from climate variables.
+ +<|ref|>text<|/ref|><|det|>[[147, 589, 852, 662]]<|/det|> +We also performed additional analyses using in- situ observation and the Penman- Monteith framework to evaluate the sensitivity of \(LE_{s}\) to VPDs. If VPDs is the main driver of enhanced forest cooling effect, we expect to observe greater positive \(LE_{s}\) sensitivity in forests compared to openlands. However, the results do not support this hypothesis (Line 262). + +<|ref|>text<|/ref|><|det|>[[147, 666, 852, 888]]<|/det|> +We also evaluate the sensitivity of summer latent heat \((LE_{s})\) to VPDs in both forests and openlands using eddy covariance observations from European sites (Supplementary Text 2). The sensitivity analysis is based on the Penman- Monteith framework, which accounts for the influence of VPDs on surface resistance (Novick et al., 2016). If VPDs is the main driver of enhanced forest cooling effect, we expect to observe greater positive \(LE_{s}\) sensitivity in forests compared to openlands, in which case forests can produce stronger evaporative cooling effects in the context of rising VPDs. However, we find openlands show slightly higher positive sensitivity than forests, although the difference is not significant. The direct regression analysis also supports the stronger \(LE_{s}\) responses to VPDs increases in openlands (Supplementary Table. 1). This in- situ observational evidence, combined with our statistical results (binning regression and random forest regression), suggests that VPDs may not explain the enhanced cooling effect of European forests, while the decline in \(SM_{s}\) appears to be the real dominant driver. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 85, 817, 102]]<|/det|> +## Supplementary Text 2. Sensitivity of summer latent heat to increasing vapor pressure deficit + +<|ref|>text<|/ref|><|det|>[[147, 104, 852, 213]]<|/det|> +Elevated vapor pressure deficit (VPD) exerts dual opposing effects on latent heat (LE) flux: while it directly enhances LE through increased evaporative demand, it simultaneously elevates surface resistance (rs), thereby suppressing LE (Novick et al., 2016). To investigate how VPD differentially influences LE in forests and openlands and consequently affects the cooling effect of forests, we analyze European eddy covariance observations from the FLUXNET2015 dataset and conduct sensitivity analyses. + +<|ref|>text<|/ref|><|det|>[[147, 216, 850, 251]]<|/det|> +The sensitivity of LE to VPD is assessed based on the Penman- Monteith framework, accounting for both the aforementioned opposing effects (Lin et al., 2018): + +<|ref|>equation<|/ref|><|det|>[[400, 254, 848, 285]]<|/det|> +\[LE = \frac{\Delta(Rn - G) + \rho C_p(VPD / r_a)}{\Delta + \gamma(1 + r_s / r_a)} \quad (1)\] + +<|ref|>equation<|/ref|><|det|>[[413, 293, 848, 320]]<|/det|> +\[G_{s} = G_{0} + G_{1}\frac{G P P}{\nu P D^{m}} \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[147, 325, 850, 436]]<|/det|> +Here, \(R n\) \((W / m^{2})\) is the net radiation; \(G\) \((W / m^{2})\) is the soil heat flux; \(\Delta\) \((kPa / K)\) is the slope of the saturated vapor pressure curve; \(\rho\) is the air density \((kg / m^{3})\) . \(C_{p}\) \((J / kg / K)\) is the specific heat of air; \(\gamma\) is the psychrometric constant \((kPa / K)\) ; \(r_{a}\) (s/m) is the aerodynamic resistance, estimated using vegetation height; \(G_{s}\) (surface conductance) is the inverse of \(r_{s}\) ; GPP is the gross primary productivity. The model parameters \((G_{0}, G_{1},\) and \(m\) ) is estimated via optimization (SciPy package in Python) using daily- scale observations. + +<|ref|>text<|/ref|><|det|>[[147, 438, 850, 584]]<|/det|> +We analysis those observation in summer and we select sites with reliable LE accuracy (Nash- Sutcliffe Efficiency \(>0.5\) ), resulting in 19 forested and 12 openland (grassland and cropland) sites. We then introduce VPDs perturbations into the observation data to estimate summer LE (LEs) sensitivity to VPDs \(\left(\frac{\mathrm{d}LE_{s}}{\mathrm{d}V P D_{s}}\right)\) \(LE_{s}\) response to a 1 hPa VPDs increase). For comparison, we also compute \(\frac{\mathrm{d}LE_{s}}{\mathrm{d}V P D_{s}}\) (i) without the impact of VPDs on \(r_{s}\) and (ii) via direct linear regression between VPDs and \(LE_{s}\) (Supplementary Table 1). + +<|ref|>text<|/ref|><|det|>[[147, 586, 850, 732]]<|/det|> +If VPDs is the primary driver of enhanced forest cooling effect, forests should exhibit a higher \(\frac{\mathrm{d}LE_{s}}{\mathrm{d}V P D_{s}}\) than openlands, implying stronger evaporative cooling under rising VPDs. However, results indicate that this expectation holds only when neglecting the inhibitory effect of VPDs on \(LE_{s}\) (via \(r_{s}\) ). When considering both opposing effects of VPDs on \(LE_{s}\) , openlands show slightly higher mean sensitivity compared to forests. In addition, the direct regression analysis supports the stronger \(LE_{s}\) responses to VPDs increases in openlands. These findings suggest that VPDs may not explain the enhanced cooling effect observed in European forests. + +<|ref|>table<|/ref|><|det|>[[147, 780, 848, 884]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[152, 752, 844, 784]]<|/det|> +Table S1. Sensitivity of summer latent heat (LEs) flux to rising vapor pressure deficit (VPDs) based on FLUXNET observations in Europe. + +
dLEs
dVPDs (w·m-2/hPa)
dLEs
dVPDs (w·m-2/hPa)
ignoring the impact of VPD on rs
Regression slope
between VPDs and LEs
(w·m-2/hPa)
Forest (n=19)2.08 ± 1.855.92 ± 2.953.87 ± 2.87
Openland (n=19)2.48 ± 1.714.87 ± 1.326.44 ± 2.67
+ +<|ref|>table_footnote<|/ref|><|det|>[[149, 886, 532, 899]]<|/det|> +The values indicate the mean \(\pm\) standard deviation across sites. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 140]]<|/det|> +Combined the sensitivity analysis result and the statistical evidence, we recognized that the decreasing \(\mathrm{SM}_s\) appears to be the primary driver of the observed daytime \(\Delta \mathrm{LST}_s\) trends. Thus, we updated the Fig. 4 and the related mechanism descriptions accordingly (Line 276). + +<|ref|>text<|/ref|><|det|>[[147, 144, 855, 272]]<|/det|> +We further conduct structural equation modeling (SEM) to elucidate the biophysical mechanisms underlying the impact of varying \(\mathrm{SM}_s\) on daytime \(\Delta \mathrm{LST}_s\) dynamics (Fig. 4a). Our SEM incorporates two key biophysical mediators: the leaf area index difference ( \(\Delta \mathrm{LAI}_s\) ) and latent heat flux difference ( \(\Delta \mathrm{LE}_s\) ) between nearby forests and openlands. The path effect (mean \(\pm\) standard error) is used to describe strength and direction of the relationship. Following previous studies, we build SEMs at the local scale and calculate the mean path effects of all models (Shen et al., 2024; Zhong et al., 2023). The analysis reveals three distinct pathways of \(\mathrm{SM}_s\) affecting \(\Delta \mathrm{LST}_s\) . + +<|ref|>text<|/ref|><|det|>[[147, 273, 852, 346]]<|/det|> +(1) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) exerts a significant negative effect on \(\Delta \mathrm{LAI}_s\) (-0.41 \(\pm\) 0.15). Then, \(\Delta \mathrm{LAI}_s\) demonstrate a negative effect on \(\Delta \mathrm{LST}_s\) (-0.19 \(\pm\) 0.09). This pathway suggests that reduced \(\mathrm{SM}_s\) can amplify the greenness difference in forests and openlands, thereby enhancing forests' cooling advantage through improved convective heat dissipation. + +<|ref|>text<|/ref|><|det|>[[147, 347, 851, 439]]<|/det|> +(2) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) have a negative effect on \(\Delta \mathrm{LE}_s\) (-0.25 \(\pm\) 0.11), followed by a strong negative influence of \(\Delta \mathrm{LE}_s\) on \(\Delta \mathrm{LST}_s\) (-0.54 \(\pm\) 0.09). This pathway indicates that declining \(\mathrm{SM}_s\) imposes less water limitation to forests compared to openlands, enabling forests to maintain stronger relative evaporative cooling through differential stomatal regulation (with greenness remaining constant). + +<|ref|>text<|/ref|><|det|>[[147, 440, 852, 495]]<|/det|> +(3) \(\mathrm{SM}_s \rightarrow \Delta \mathrm{LAI}_s \rightarrow \Delta \mathrm{LE}_s \rightarrow \Delta \mathrm{LST}_s\) . \(\mathrm{SM}_s\) -induced changes in \(\Delta \mathrm{LAI}_s\) subsequently enhance \(\Delta \mathrm{LE}_s\) (0.62 \(\pm\) 0.06), ultimately influencing \(\Delta \mathrm{LST}_s\) . This demonstrates that \(\mathrm{SM}_s\) reduction amplifies evaporative cooling effects of forests by increasing the vegetation greenness contrast with openlands. + +<|ref|>text<|/ref|><|det|>[[147, 496, 852, 753]]<|/det|> +The pathway effects, representing the strength and direction of the mechanism, are quantified as the product of all constituent path coefficients (Fig. 4b). Results reveal that the second and third pathways (both mediated by \(\Delta \mathrm{LE}_s\) ) contribute equally to \(\Delta \mathrm{LST}_s\) variation (about 0.14 \(\pm\) 0.06), while the impact first pathway is weaker (0.08 \(\pm\) 0.05). These findings suggest \(\mathrm{SM}_s\) can modulate \(\Delta \mathrm{LST}_s\) dynamics through multiple mechanisms, with forest evaporative cooling regulation emerging as the dominant process. Previous studies have demonstrated that reduced soil moisture in Europe can amplify warming during heatwaves through land-atmosphere interactions (Dirmeyer et al., 2021; Fischer et al., 2007). Our findings confirm forests exhibit greater stability and resistance to increasing soil dryness compared to grasslands or croplands, which may mitigate land-atmosphere coupling feedback and consequently enhance the relative cooling effect of forests (Teuling et al., 2010). This stability of forests is reflected in both more moderate evaporative limitation and sustained vegetation greenness under increasing soil dryness. Our results provide observational evidence suggesting that the capacity of forest ecosystems to mitigate water deficit-induced warming persists not only during heatwave events but also across interannual timescales. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[184, 100, 816, 365]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 382, 852, 511]]<|/det|> +
Fig 4. Mechanisms underlying the effects of climate variables on the daytime LST effects of European forests (ALSTs) in summer. (a) Structure equation models describing the biophysical relationships between climate variables and \(\Delta LST_{s}\) . The numbers denote the path value (mean \(\pm\) standard error). The arrow color indicates the sign of the path (red for positive and blue for negative), and the thickness indicates the magnitude of the corresponding path value. (b) Bar plot of the pathway effects of climate variables affecting \(\Delta LST_{s}\) . The error bars indicate the uncertainty based on error propagation.
+ +<|ref|>text<|/ref|><|det|>[[183, 533, 702, 550]]<|/det|> +We also revised the discussion about the summer mechanism (Line 434). + +<|ref|>text<|/ref|><|det|>[[147, 555, 852, 887]]<|/det|> +Using a range of statistical methods, we find that declining \(SM_{s}\) is the predominant factor contributing to both the interannual variation and the negative trend in \(\Delta LST_{s}\) . Path analysis shows that \(SM_{s}\) affects \(\Delta LST_{s}\) dynamics through two mechanisms. First, we show \(\Delta LAI_{s}\) is modulated by \(SM_{s}\) , implying that as the soil becomes drier, the vegetation structure difference between forests and openlands becomes more evident. The higher \(\Delta LAI_{s}\) could boost the cooling efficiency of forests through stronger direct heat dissipation and evaporative cooling. The impact of \(SM_{s}\) on vegetation has been well-documented: increasing dryness pressure could trigger stomatal closure, inhibit photosynthesis, and increase vegetation mortality (Li et al., 2022; Stocker et al., 2018). Our results confirm a stronger negative effect of \(SM_{s}\) on non- forest vegetation than on forests (Hoek van Dijke et al., 2023). The potential reason is that forest ecosystems with high species richness and deep roots are more stable and resilient to dryness (Isbell et al., 2015; Tumber- Dávila et al., 2022). Second, even under constant vegetation conditions, less soil water supply directly amplifies \(\Delta LE_{s}\) and enhances the relative cooling effect of forests. These findings are consistent with prior researches (Fu et al., 2022a, 2022b), indicating that soil moisture imposes stronger limitations on ET in grasslands and croplands relative to forest ecosystems. This differential response is evidenced by both the greater sensitivity of and the higher critical soil moisture thresholds in non- forest ecosystems. This phenomenon may be attributed to the capacity of forests to maintain ET through deep soil water extraction, thereby exhibiting greater resilience to warming- induced surface soil + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 120]]<|/det|> +moisture deficits compared to openlands. Overall, the revealed impact of \(SM_{s}\) on \(\Delta LST_{s}\) essentially reflects the diverse vegetation physiological responses to climate changes. + +<|ref|>sub_title<|/ref|><|det|>[[148, 149, 231, 163]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 170, 852, 202]]<|/det|> +Dirmeyer, P. A., Balsamo, G., Blyth, E. M., Morrison, R. & Cooper, H. M. Land- Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018. AGU Adv. 2, 1- 16 (2021). + +<|ref|>text<|/ref|><|det|>[[148, 203, 850, 238]]<|/det|> +Fisher, E. M., Seneviratne, S. I., Lüthi, D. & Schär, C. Contribution of land- atmosphere coupling to recent European summer heat waves. Geophys. Res. Lett. 34, 1- 6 (2007). + +<|ref|>text<|/ref|><|det|>[[148, 240, 850, 273]]<|/det|> +Fu, Z. et al. Critical soil moisture thresholds of plant water stress in terrestrial ecosystems. Sci. Adv. 8, 1- 12 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 275, 850, 309]]<|/det|> +Fu, Z. et al. Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems. Glob. Chang. Biol. 28, 2111- 2123 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 310, 850, 345]]<|/det|> +Hook van Dijke, A. J. et al. Comparing forest and grassland drought responses inferred from eddy covariance and Earth observation. Agric. For. Meteorol. 341, (2023). + +<|ref|>text<|/ref|><|det|>[[148, 346, 850, 380]]<|/det|> +Isbell, F. et al. Biodiversity increases the resistance of ecosystem productivity to climate extremes. Nature 526, 574- 577 (2015). + +<|ref|>text<|/ref|><|det|>[[148, 382, 850, 415]]<|/det|> +Li, W. et al. Widespread increasing vegetation sensitivity to soil moisture. Nat. Commun. 13, 3959 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 418, 850, 451]]<|/det|> +Lin, C. et al. Diel ecosystem conductance response to vapor pressure deficit is suboptimal and independent of soil moisture. Agric. For. Meteorol. 250- 251, 24- 34 (2018). + +<|ref|>text<|/ref|><|det|>[[148, 453, 850, 488]]<|/det|> +Liu, L. et al. Soil moisture dominates dryness stress on ecosystem production globally. Nat. Commun. 11, 1- 9 (2020). + +<|ref|>text<|/ref|><|det|>[[148, 489, 850, 523]]<|/det|> +Novick, K. A. et al. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nat. Clim. Chang. 6, 1023- 1027 (2016). + +<|ref|>text<|/ref|><|det|>[[148, 525, 850, 559]]<|/det|> +Shen, P. et al. Biodiversity buffers the response of spring leaf unfolding to climate warming. Nat. Clim. Chang. 14, 863- 868 (2024). + +<|ref|>text<|/ref|><|det|>[[148, 560, 850, 595]]<|/det|> +Shen, P. et al. Biodiversity buffers the response of spring leaf unfolding to climate warming. Nat. Clim. Chang. 14, 863- 868 (2024). + +<|ref|>text<|/ref|><|det|>[[148, 596, 850, 630]]<|/det|> +Stocker, B. D. et al. Quantifying soil moisture impacts on light use efficiency across biomes. New Phytol. 218, 1430- 1449 (2018). + +<|ref|>text<|/ref|><|det|>[[148, 632, 850, 666]]<|/det|> +Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). + +<|ref|>text<|/ref|><|det|>[[148, 668, 850, 703]]<|/det|> +Tumber- Dávila, S. J., Schenk, H. J., Du, E. & Jackson, R. B. Plant sizes and shapes above and belowground and their interactions with climate. New Phytol. 235, 1032- 1056 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 705, 850, 740]]<|/det|> +Zhong, Z. et al. Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity. Sci. Adv. 9, (2023). + +<|ref|>text<|/ref|><|det|>[[148, 763, 850, 836]]<|/det|> +Finally, I wonder why LEW never appears anywhere, but the effects of LEs are estimated... Clearly LEW will be significantly lower. But conifers can evapotranspire almost year round... So, to some degree, LEW should also be available and should have an impact on surface temperatures... ??? + +<|ref|>text<|/ref|><|det|>[[148, 842, 850, 897]]<|/det|> +Response: Thank you for your insightful comment. We fully agree that evergreen forests can sustain transpiration throughout the year. To investigate this potential effect, we calculated the winter latent heat flux (LE) difference between forests and openlands ( \(\Delta \mathrm{LE}_{\mathrm{w}}\) ), and then examined the relationship + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 852, 159]]<|/det|> +between the winter land surface temperature effect of forests ( \(\Delta \mathrm{LST}_{\mathrm{w}}\) ) and \(\Delta \mathrm{LE}_{\mathrm{w}}\) . Results indicate that the correlation between \(\Delta \mathrm{LE}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) is statistically insignificant (Line 200). This finding supports previous studies reporting that the albedo effect dominates the local temperature effect of boreal forests in the cold season (Alkama and Cescatti, 2016; Lawrence et al., 2022). + +<|ref|>text<|/ref|><|det|>[[148, 163, 850, 199]]<|/det|> +Similarly, we find negligible correlation between \(\Delta \mathrm{LST}_{\mathrm{w}}\) and non- radiative processes represented by winter latent heat flux differences ( \(\Delta \mathrm{LE}_{\mathrm{w}}\) ) (Supplementary Fig. 7). + +<|ref|>image<|/ref|><|det|>[[221, 213, 775, 488]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[152, 502, 846, 538]]<|/det|> +
Fig. S7. Temporal correlation coefficient (r) between \(\mathrm{LE}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (a to c) Spatial pattern of r between \(\mathrm{LE}_{\mathrm{w}}\) and daily mean, daytime and nighttime \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (d) Density of the r values.
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 547, 232, 561]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 641]]<|/det|> +Alkama, R. & Cescatti, A. Biophysical climate impacts of recent changes in global forest cover. Science (80- .). 351, 600- 604 (2016). Lawrence, D., Coe, M., Walker, W., Verchot, L. & Vandecar, K. The Unseen Effects of Deforestation: Biophysical Effects on Climate. Front. For. Glob. Chang. 5, 1- 13 (2022). + +<|ref|>text<|/ref|><|det|>[[148, 660, 851, 770]]<|/det|> +More to the main point, however, the general finding that wintertime effects exhibit increased cooling due to the loss of snow cover, more or less independently of tree cover (the effect is stronger over open fields than over forested land), is an interesting and valuable finding. However, it remains unclear why this phenomenon would be true in more forested areas... In other words, why would the land surface become lighter under more forested areas, thus leading to wintertime cooling...??? I do not think this is adequately explained...? + +<|ref|>text<|/ref|><|det|>[[148, 774, 851, 903]]<|/det|> +Response: We sincerely appreciate the opportunity to clarify this important point. It is important to note that forests have become "relatively" brighter compared to openlands during the past two decades of snow decline. This relatively brighter trend is evidenced by the increasing \(\Delta \alpha_{\mathrm{w}}\) trend (brown line in Fig. 2a), despite both ecosystems exhibiting absolute darkening trends. The relative brightening stems from forests (green line) darkening at a slower rate than openlands (yellow line). The mechanism is that snow tends to be masked by tree canopies in forest ecosystems, resulting in the greater sensitivity of openland \(\alpha_{\mathrm{w}}\) to snow changes compared to forest \(\alpha_{\mathrm{w}}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[262, 97, 729, 284]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 292, 847, 328]]<|/det|> +
Fig 2a. Interannual variations of winter albedo effect of European forests ( \(\Delta \alpha_{\mathrm{w}}\) ) and the individual winter albedo ( \(\alpha_{\mathrm{w}}\) ) for forests and openlands.
+ +<|ref|>text<|/ref|><|det|>[[183, 353, 761, 370]]<|/det|> +To prevent misinterpretation, we have modified the result description (Line 166): + +<|ref|>text<|/ref|><|det|>[[148, 375, 851, 429]]<|/det|> +These results indicate that although forest albedo tends to decline due to snow cover loss, the relative darkening effect of forests, and the additional solar radiation absorbed by forests (compared to adjacent openlands) have diminished in the recent two decades. + +<|ref|>text<|/ref|><|det|>[[148, 454, 850, 490]]<|/det|> +All- in- all however, I did find the manuscript to be very interesting and compelling... I have included a number of comments in the attached submissions pdf. + +<|ref|>text<|/ref|><|det|>[[148, 495, 850, 531]]<|/det|> +Response: Thank you for your positive feedback. Below are the detailed responses to the comments as provided in the PDF document. + +<|ref|>text<|/ref|><|det|>[[148, 556, 515, 572]]<|/det|> +Reviewer #2's comments in the PDF documents: + +<|ref|>text<|/ref|><|det|>[[149, 578, 382, 593]]<|/det|> +Line 17: incomplete sentence... + +<|ref|>text<|/ref|><|det|>[[148, 599, 844, 616]]<|/det|> +Response: Thanks for pointing this out. We have revised the sentence and now it reads (Line 14): + +<|ref|>text<|/ref|><|det|>[[148, 621, 850, 675]]<|/det|> +The negative trends in LST effects of European forests are broadly supported by four state- of- the- art earth system models, though substantial inter- model variability persists in the multi- year means. + +<|ref|>text<|/ref|><|det|>[[148, 700, 850, 754]]<|/det|> +Line 24: There are many much better references for supporting this point... For example, neither reference noted here talks about advantages of forests for water availability in downwind areas...??? + +<|ref|>text<|/ref|><|det|>[[148, 760, 350, 776]]<|/det|> +A few options to consider: + +<|ref|>text<|/ref|><|det|>[[148, 781, 410, 797]]<|/det|> +Cool Insights https://bit.ly/40zILv2 + +<|ref|>text<|/ref|><|det|>[[148, 802, 633, 819]]<|/det|> +On the Forest Cover- Water Yield Debate https://bit.ly/40t3fUM + +<|ref|>text<|/ref|><|det|>[[148, 824, 593, 840]]<|/det|> +From Myth to Concept and Beyond https://bit.ly/4hAenGp + +<|ref|>text<|/ref|><|det|>[[148, 846, 850, 881]]<|/det|> +Response: Thank you for pointing this out. We have replaced the original reference with those you recommended (Line 23). + +<|ref|>text<|/ref|><|det|>[[179, 886, 850, 903]]<|/det|> +Forests provide numerous benefits to humans and the planet, such as producing food and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 849, 120]]<|/det|> +energy, reducing soil erosion, and increasing water availability in downwind areas (Bonan, 2008; Borrelli et al., 2017; Ellison et al., 2017, 2012). + +<|ref|>sub_title<|/ref|><|det|>[[148, 127, 230, 141]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 147, 850, 193]]<|/det|> +Ellison, D., Futter, M. N. & Bishop, K. On the forest cover- water yield debate: From demand- to supply- side thinking. Global Change Biology vol. 18 806- 820 (2012). + +<|ref|>text<|/ref|><|det|>[[147, 186, 850, 220]]<|/det|> +Borrelli, P. et al. An assessment of the global impact of 21st century land use change on soil erosion. Nat. Commun. 8, (2017). + +<|ref|>text<|/ref|><|det|>[[147, 222, 849, 255]]<|/det|> +Ellison, D. et al. Trees, forests and water: Cool insights for a hot world. Glob. Environ. Chang. 43, 51- 61 (2017). + +<|ref|>text<|/ref|><|det|>[[147, 258, 848, 293]]<|/det|> +Bonan, G. B. Forests and climate change: Forcings, feedbacks, and the climate benefits of forests. Science (80- .). 320, 1444- 1449 (2008). + +<|ref|>text<|/ref|><|det|>[[147, 313, 821, 348]]<|/det|> +Line 26: Again, the cited references here do not really discuss and defend impacts global climate cooling... But there are several appropriate references that do... + +<|ref|>text<|/ref|><|det|>[[147, 353, 468, 370]]<|/det|> +Even Cooler Insights https://bit.ly/46PTpzi + +<|ref|>text<|/ref|><|det|>[[147, 375, 468, 390]]<|/det|> +https://doi.org/10.1073/pnas.2026241118 + +<|ref|>text<|/ref|><|det|>[[147, 396, 562, 412]]<|/det|> +https://www.nature.com/articles/s41467- 024- 51783- y + +<|ref|>text<|/ref|><|det|>[[147, 418, 850, 453]]<|/det|> +Response: Thank you for your valuable suggestion. We have replaced the original reference with those you recommended (Line 25). + +<|ref|>text<|/ref|><|det|>[[147, 458, 851, 512]]<|/det|> +Through conservation, proper management, and restoration practices, forest ecosystems could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud formation (Cerasoli et al., 2021; Ellison et al., 2024; Luo et al., 2024). + +<|ref|>sub_title<|/ref|><|det|>[[148, 518, 230, 532]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 538, 850, 573]]<|/det|> +Cerasoli, S., Yin, J. & Porporato, A. Cloud cooling effects of afforestation and reforestation at midlatitudes. Proc. Natl. Acad. Sci. U. S. A. 118, 1- 7 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 576, 850, 611]]<|/det|> +Luo, H., Quaas, J. & Han, Y. Decreased cloud cover partially offsets the cooling effects of surface albedo change due to deforestation. Nat. Commun. 15, 7345 (2024). + +<|ref|>text<|/ref|><|det|>[[147, 614, 850, 648]]<|/det|> +Ellison, D., Pokorny, J. & Wild, M. Even cooler insights: On the power of forests to (water the Earth and) cool the planet. Glob. Chang. Biol. 30, 1- 20 (2024). + +<|ref|>text<|/ref|><|det|>[[147, 671, 830, 724]]<|/det|> +Line 27: While certainly the role of carbon is "overemphasized" in this literature, there is in fact a far more extensive literature... Much of it, for example, is referenced and detailed in this paper: + +<|ref|>text<|/ref|><|det|>[[148, 729, 468, 745]]<|/det|> +Even Cooler Insights https://bit.ly/46PTpzi + +<|ref|>text<|/ref|><|det|>[[147, 750, 790, 785]]<|/det|> +I see that a small part of this literature does appear in the following sentences, which suggests that the sentence itself here is primarily misleading... + +<|ref|>text<|/ref|><|det|>[[147, 790, 850, 825]]<|/det|> +Response: Thank you for point this out. For clarity, we have removed the detailed statements about the carbon sink effects of forests. Now the background part reads (Line 23): + +<|ref|>text<|/ref|><|det|>[[147, 831, 851, 903]]<|/det|> +Forests provide numerous benefits to humans and the planet, such as producing food and energy, reducing soil erosion, and increasing water availability in downwind areas. Through conservation, proper management, and restoration practices, forest ecosystems could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 159]]<|/det|> +formation. In addition to the global impacts, forests exhibit local cooling or warming effects due to their unique biophysical characteristics that regulate surface energy and water fluxes. The biophysical effects of forests on local climate have garnered particular attention in recent years, as it can significantly intensify or offset the climate mitigation effects of carbon sequestration. + +<|ref|>text<|/ref|><|det|>[[148, 184, 840, 238]]<|/det|> +Line 45: Vague..., in what ways...? I would have put the emphasis on the availability of water and how that might change with some climate driven processes and temperature change...??? + +<|ref|>text<|/ref|><|det|>[[148, 242, 554, 259]]<|/det|> +Again, see: Even Cooler Insights https://bit.ly/46PTpzi + +<|ref|>text<|/ref|><|det|>[[148, 264, 850, 300]]<|/det|> +Response: Thanks for the comment. We have revised the discussions about the background climate and added sentence about the impact of water availability (Line 42): + +<|ref|>text<|/ref|><|det|>[[147, 304, 850, 507]]<|/det|> +The net temperature response depends on the balance between the opposing radiative and non- radiative effects (Bright et al., 2017), and their relative dominance is largely governed by background climatic conditions (Pitman et al., 2011). For instance, forests in mid- latitude regions (e.g., North America, Europe and China) demonstrate seasonally contrasting LST effects (Li et al., 2015; Tang et al., 2018). During cold winters, bright snow covers short vegetation but is masked by dense forest canopies. As a result, forests absorb more solar radiation and show a local warming effect compared to surrounding openlands. Conversely, during the peak growing season (warm summer), forests exert cooling effects under sufficient soil moisture conditions, owing to their higher ET rates compared to other vegetation types. However, in arid regions, limited soil moisture can constrain forest evaporative cooling despite abundant radiation and optimal temperature, causing radiative warming to dominate (Rohatyn et al., 2023). + +<|ref|>sub_title<|/ref|><|det|>[[148, 516, 232, 530]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 537, 850, 740]]<|/det|> +Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Pitman, A. J. et al. Importance of background climate in determining impact of land- cover change on regional climate. Nat. Clim. Chang. 1, 472- 475 (2011). Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1- 10 (2015). Tang, B., Zhao, X. & Zhao, W. Local effects of forests on temperatures across Europe. Remote Sens. 10, 1- 24 (2018). Rohatyn, S., Rotenberg, E., Tatarinov, F., Carmel, Y. & Yakir, D. Large variations in afforestation- related climate cooling and warming effects across short distances. Commun. Earth Environ. 4, 1- 10 (2023). + +<|ref|>text<|/ref|><|det|>[[148, 761, 820, 795]]<|/det|> +Line 56: This statement is quite broad...??? Platitude...??? Can you be more precise, more nuanced...? + +<|ref|>text<|/ref|><|det|>[[147, 802, 810, 818]]<|/det|> +Response: Thank for the comment. We have revised the sentence and now it reads (Line 55): + +<|ref|>text<|/ref|><|det|>[[148, 823, 850, 877]]<|/det|> +Given the profound influence of background climate on forest biophysical processes, it is reasonable to infer that the regulation of forests on local temperature will shift in response to rising \(CO_2\) concentration, global warming, or varying water availability. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 841, 139]]<|/det|> +Line 76: can you be more explicit...??? This could be more clearly motivated with stronger discussions of radiative and non- radiative impacts more clearly delineated and categorized from the beginning... + +<|ref|>text<|/ref|><|det|>[[148, 144, 850, 179]]<|/det|> +Response: Thanks for the suggestion. We have clarified the radiative and non- radiative impacts in the introduction section (Line 39): + +<|ref|>text<|/ref|><|det|>[[148, 185, 839, 238]]<|/det|> +During the daytime, forests exhibit two competing effects compared to non- forest vegetation: (a) the non- radiative cooling effect driven by higher evapotranspiration (ET) rates (Mildrexler et al., 2011), and (b) the radiative warming effect resulting from lower albedo (R.A.Betts, 2000). + +<|ref|>sub_title<|/ref|><|det|>[[148, 249, 232, 263]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 269, 850, 320]]<|/det|> +Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1- 15 (2011). + +<|ref|>text<|/ref|><|det|>[[148, 324, 848, 358]]<|/det|> +R.A.Betts. Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. Nature 408, 187- 190 (2000). + +<|ref|>text<|/ref|><|det|>[[147, 381, 828, 472]]<|/det|> +Line 104: Up to now, nighttime effects have NOT been previously mentioned... However, you note that such effects have been found previously, and that there is a literature... Can you motivate these effects...? And shouldn't they also be discussed in to introductory sections above...? The drivers of these effects need to be carefully founded and described...??? + +<|ref|>text<|/ref|><|det|>[[148, 478, 850, 512]]<|/det|> +Response: Thanks for pointing this out. We have added description about the nighttime LST effect of forests in the introduction section (Line 36): + +<|ref|>text<|/ref|><|det|>[[148, 518, 841, 589]]<|/det|> +At night, forests warm the land surface through two mechanisms: (1) the release of daytime heat storage during nighttime, and (2) reduced aerodynamic resistance that enhances turbulent mixing, facilitating downward heat transfer from warmer air aloft (Lee et al., 2011; Schultz et al., 2017). + +<|ref|>sub_title<|/ref|><|det|>[[148, 602, 232, 616]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 622, 844, 655]]<|/det|> +Lee, X. et al. Observed increase in local cooling effect of deforestation at higher latitudes. Nature 479, 384- 387 (2011). + +<|ref|>text<|/ref|><|det|>[[148, 660, 850, 712]]<|/det|> +Schultz, N. M., Lawrence, P. J. & Lee, X. Global satellite data highlights the diurnal asymmetry of the surface temperature response to deforestation. J. Geophys. Res. Biogeosciences 122, 903- 917 (2017). + +<|ref|>text<|/ref|><|det|>[[148, 735, 850, 789]]<|/det|> +Line 150: Could this relationship also be confirmed via other methods, such as NDVI...? And more generally, why would forested areas become lighter in color over time, if snow cover is declining...? This seems counter- intuitive and contradictory...??? + +<|ref|>text<|/ref|><|det|>[[148, 795, 850, 867]]<|/det|> +Response: Sorry for the misleading. Our results demonstrate that while both forested and open areas experience surface darkening due to snow cover decline, the darkening effect is more pronounced in openlands. This differential response means forests have become "relatively brighter" compared to adjacent openlands over time. We have clarified this point in the revised manuscript (Line 166): + +<|ref|>text<|/ref|><|det|>[[148, 873, 850, 907]]<|/det|> +These results indicate that although forest albedo tends to decline due to snow cover loss, the relative darkening effect of forests, and the additional solar radiation absorbed by forests (compared + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 130, 825, 164]]<|/det|> +Line 205: VPD is of course also tied to the availability of water on the land surface... If less water can evaporate, VPD will rise... + +<|ref|>text<|/ref|><|det|>[[148, 169, 855, 241]]<|/det|> +Response: Thanks for the professional comment. Since VPD and availability of water (soil moisture) are strongly coupled at the annual scale, we have added new experiments disentangle the contributions of increasing VPD and decreasing soil moisture in the revised manuscript. Please see the response to your major comment about soil moisture above. + +<|ref|>text<|/ref|><|det|>[[148, 266, 847, 320]]<|/det|> +Line 226: Clearly some of these variables, in particular VPD and T, exhibit significant colinearity... How is this handled... And how do you know which of these two variables is the dominant factor...??? + +<|ref|>text<|/ref|><|det|>[[147, 325, 852, 472]]<|/det|> +Response: Thank you for raising this methodological consideration. We fully acknowledge the collinearity between climate variables, particularly VPD and T. To address this inherent covariation among meteorological drivers, we employed partial correlation analysis, which is a robust approach that isolates the unique relationship between the driver and the target variable (e.g., VPD and \(\Delta \mathrm{LST}_s\) ) while statistically controlling for confounding effects of covariates (e.g., T, precipitation, radiation...). By removing the influence of covariance, the residual VPD- \(\Delta \mathrm{LST}_s\) correlation reflects moisture- driven effects independent of thermal or radiation contributions, as well as any non- linear or interactive relationships not captured by simple linear covariation with temperature. + +<|ref|>text<|/ref|><|det|>[[147, 476, 852, 622]]<|/det|> +Using partial correlation, we reveal a critical distinction (Fig. 3a- b): while direct correlations (light bars) showed significant relationships between \(\Delta \mathrm{LST}_s\) and all climate variables (except wind speed), partial correlations (dark bars) demonstrated that VPD or soil moisture (SM) maintain the strongest independent associations with \(\Delta \mathrm{LST}_s\) even after accounting for other drivers. It is important to note that partial correlation cannot fully disentangle the effects of SM and VPD when both two variables are included in one model simultaneously, as they exhibit near- perfect collinearity at the annual scale ( \(r = 0.92\) ). That's why we add other experiments to disentangle their contributions. + +<|ref|>image<|/ref|><|det|>[[156, 629, 840, 790]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[163, 797, 831, 831]]<|/det|> +
Fig 3a and 3b. Regional mean correlation and partial correlation coefficients between climate variables and the daytime \(\Delta \mathrm{LST}_s\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 858, 850, 894]]<|/det|> +We have enhanced the methods section to provide a detailed explanation of our partial temporal correlation analysis approach (Line 696): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 195]]<|/det|> +In addition, partial temporal correlation analysis is used to explore the relative impacts of multiple climate drivers on \(\Delta \mathrm{LST}_s\) at the pixel scale (pinguin package in Python). The partial correlation can determine whether a climate variable can exert an independent effect on target variable beyond its covariation with other climate drivers. For instance, the partial correlation can isolate the association between \(\Delta \mathrm{LST}_s\) and \(\mathrm{SM}_s\) while accounting for the influence of other covariates (e.g., temperature and precipitation) on \(\mathrm{SM}_s\) . + +<|ref|>text<|/ref|><|det|>[[148, 220, 815, 255]]<|/det|> +Line 266: Are there any estimates of LEw...? Evergreen forests will evapotranspire almost year round...??? So what does this relationship look like...? + +<|ref|>text<|/ref|><|det|>[[147, 260, 851, 352]]<|/det|> +Response: Thank you for your insightful comment. We examined the relationship between \(\Delta \mathrm{LST}_w\) and \(\Delta \mathrm{LE}_w\) (Fig. R5). Results indicate that the correlation between \(\Delta \mathrm{LE}_w\) and \(\Delta \mathrm{LST}_w\) is statistically insignificant (Fig. R5a). In contrast, \(\Delta \alpha_w\) exhibits a significant correlation with \(\Delta \mathrm{LST}_w\) (Fig. R5b). These findings suggest that temporal variations in radiative processes, rather than evapotranspiration- related mechanisms, are more likely to drive the observed changes in \(\Delta \mathrm{LST}_w\) . + +<|ref|>image<|/ref|><|det|>[[241, 362, 752, 508]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[262, 524, 733, 540]]<|/det|> +
Fig. R5. Temporal relationship between \(\Delta \mathrm{LST}_w\) and \(\Delta \mathrm{LE}_w\) or \(\Delta \alpha_w\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 549, 852, 678]]<|/det|> +In addition, we observed an unexpected negative \(\Delta \mathrm{LE}_w\) , indicating that forest latent heat flux was slightly lower than that of openlands (multi- year mean: \(- 1.3 \mathrm{w} / \mathrm{m}^2\) ). This finding is aligned with previous study based on land surface model simulation and remote sensing data (Breil et al., 2021; Zan et al., 2024). To further assess this result, we compared winter LE observations from European forest and openland (grassland and cropland) sites using FLUXNET2015 dataset (Fig. R6). The results revealed that, on average, openland LE exceeded forest LE, though the difference was not statistically significant. This result ensures the reliability of our remote sensing- based results. + +<|ref|>image<|/ref|><|det|>[[343, 691, 653, 853]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[155, 870, 842, 905]]<|/det|> +
Fig. R6. Winter latent heat flux (LE) at European forest and openland sites based on FLUXNET observations. Each data point represents the site mean. Red asterisk indicates the muti-site mean.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 140]]<|/det|> +In summary, our results indicate that while wintertime evapotranspiration persists in forests, its magnitude does not differ significantly from openlands. The temporal variation in \(\Delta \mathrm{LST}_{\mathrm{w}}\) appears to be driven primarily by radiative processes rather than LE- related mechanisms. + +<|ref|>sub_title<|/ref|><|det|>[[148, 151, 232, 165]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 172, 842, 205]]<|/det|> +Breil, M., Davin, E. L. & Rechid, D. What determines the sign of the evapotranspiration response to afforestation in European summer? Biogeosciences 18, 1499- 1510 (2021). + +<|ref|>text<|/ref|><|det|>[[148, 208, 785, 243]]<|/det|> +Zan, B. et al. Spatiotemporal inequality in land water availability amplified by global tree restoration. Nat. Water (2024) doi:10.1038/s44221- 024- 00296- 5. + +<|ref|>text<|/ref|><|det|>[[148, 266, 844, 320]]<|/det|> +Line 278: The availability of water, however, is also key here... If the water disappears, then these effects will flip... So, how does one integrate the effects of water availability into these measures...??? + +<|ref|>text<|/ref|><|det|>[[148, 325, 850, 361]]<|/det|> +Response: Thanks for pointing this issue. Please see our response to your comment above, in which the role of water availability (soil moisture) is explored and discussed in detail. + +<|ref|>text<|/ref|><|det|>[[148, 386, 848, 421]]<|/det|> +Line 391: This could be better expressed... One could just as easily substitute southwards here, since you do not clearly specify distinctions between cooling and warming effects...??? + +<|ref|>text<|/ref|><|det|>[[148, 426, 850, 461]]<|/det|> +Response: Thanks for your suggestion about the expression. We have modified the sentence and now it reads (Line 413): + +<|ref|>text<|/ref|><|det|>[[148, 467, 851, 539]]<|/det|> +This result implies that forests in mid- to high- latitude regions could exhibit similar reduced warming effects or even reversed net cooling in a warming world. Such changes may push the latitudinal boundary between forest warming and cooling effects poleward, primarily due to diminished snow- related albedo feedback. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[348, 86, 650, 103]]<|/det|> +## Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[148, 108, 851, 181]]<|/det|> +We greatly appreciate the anonymous reviewers for the constructive comments. The manuscript has been revised and improved accordingly. We hope that the revision will make it more acceptable for publication. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in red and Italic). The changes are also marked in red in the manuscript file. + +<|ref|>sub_title<|/ref|><|det|>[[150, 215, 451, 231]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 249, 850, 303]]<|/det|> +The authors have made significant improvements, conducted substantial additional analyses, and even revised their conclusions regarding the role of VPD. I am satisfied with most of these efforts and have only one remaining comment. + +<|ref|>text<|/ref|><|det|>[[149, 310, 849, 344]]<|/det|> +Response: We appreciate the constructive and valuable comments by the reviewer during the review process. + +<|ref|>text<|/ref|><|det|>[[149, 372, 850, 406]]<|/det|> +"In the summertime, the vegetation physiological response to decreased soil moisture boosts the cooling effect of forests." + +<|ref|>text<|/ref|><|det|>[[148, 409, 851, 518]]<|/det|> +This statement may still be confusing or even misleading. It implies that forests have a stronger cooling effect than grasslands solely due to their physiological response to dry soils. In reality, while physiological processes such as stomatal regulation do influence surface energy balance, the observed cooling effect in forests may also stem from hydrological advantages, including deeper soil water storage and more consistent precipitation recharge in forested areas. + +<|ref|>text<|/ref|><|det|>[[148, 521, 850, 555]]<|/det|> +Response: Thanks for pointing this out. We have revised the sentence to accurately describe this mechanism (Line 13): + +<|ref|>text<|/ref|><|det|>[[148, 561, 850, 597]]<|/det|> +During summer, the daytime cooling effect intensifies (- 0.188 K/decade) because forests remain more physiologically and hydrologically resilient to increasing soil dryness. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 85, 450, 101]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 107, 851, 198]]<|/det|> +I find that a lot of interesting points come up in this analysis. I am, however, a bit concerned that the paper could still benefit from some significant editing and rewriting. I raise a number of questions in the attached submission pdf. I guess that, primarily, I am unconvinced by the forest albedo logic used herein and would be tempted to argue in a different direction on many points. Please see the related comments in the text. + +<|ref|>text<|/ref|><|det|>[[148, 203, 851, 313]]<|/det|> +Response: We sincerely appreciate your positive and constructive feedback. We understand your concerns regarding our interpretation of the winter land surface temperature effect of conversion from openlands to forests (ALSTw). In response to your feedback, we have conducted additional experiments to quantitatively compare the contributions of albedo- and ET- related processes to the ALSTw trend. We identify the albedo- related process, rather than the ET- related process, as the main driver of ALSTw change. Please see the response to your later comments on line 115. + +<|ref|>text<|/ref|><|det|>[[148, 340, 851, 412]]<|/det|> +Further, I do think that the paper seems inclined to somehow lay the blame for these changes on forests, when actually, most of the important changes seem to be occurring elsewhere (in open fields that have reduced amounts of forest cover, and not in heavily forested areas) and are primarily driven by climate warming (and not any change in forests themselves).... + +<|ref|>text<|/ref|><|det|>[[148, 417, 851, 547]]<|/det|> +Response: Thank you for pointing this out. Our study analyzes differences between forests and adjacent openlands (Δx) to derive a priori estimates of potential forestation effects (openland- to- forest conversion). We fully agree with your view that the change in Δx should not be exclusively attributed to forests. The Δx variations may stem from either forest modifications or alterations in the reference openlands. To ensure clarity, we employ the term "forestation" to emphasize that our analysis specifically examines forest- openland comparisons. We have carefully reviewed the manuscript and modified ambiguous descriptions accordingly. + +<|ref|>text<|/ref|><|det|>[[183, 552, 522, 567]]<|/det|> +For instance, we have revised the title (Line 1): + +<|ref|>text<|/ref|><|det|>[[280, 574, 751, 590]]<|/det|> +Amplified Local Cooling Effect of Forestation in Warming Europe + +<|ref|>text<|/ref|><|det|>[[183, 596, 560, 611]]<|/det|> +We also revised the sentence in the abstract (Line 7): + +<|ref|>text<|/ref|><|det|>[[148, 618, 851, 672]]<|/det|> +By comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify the temporal trends in local land surface temperature (LST) effects of potential forestation in Europe. + +<|ref|>text<|/ref|><|det|>[[148, 677, 850, 711]]<|/det|> +We added a sentence to highlight that the change is more significant in openlands in winter results (Line 189): + +<|ref|>text<|/ref|><|det|>[[148, 717, 850, 770]]<|/det|> +Notably, the observed ALSTw trend should not be attributed to structural or physiological changes in forests, but rather to the more pronounced albedo reduction in openlands in a warming world. + +<|ref|>text<|/ref|><|det|>[[148, 776, 850, 811]]<|/det|> +Furthermore, we added a discussion to clarify that the change in ALST may originate from both forests or openlands (Line 505): + +<|ref|>text<|/ref|><|det|>[[148, 817, 851, 908]]<|/det|> +First, the observed negative trends in ALSTw and ALSTs reflect variations in LST difference when comparing forests and openlands, rather than the inherent capacity of existing forests to reverse warming trends. These patterns may originate from either modifications in forest characteristics or changes in the adjacent openland used as reference. Fundamentally, the negative trends emerge because forests exhibit a weaker temperature response than openlands in a warming + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +climate, and this divergence stems from distinct biophysical and physiological properties between forest and openland vegetation. + +<|ref|>text<|/ref|><|det|>[[183, 127, 559, 143]]<|/det|> +We hope these revisions will enhance the readability. + +<|ref|>text<|/ref|><|det|>[[148, 170, 850, 261]]<|/det|> +I do think that with another round of editing, this paper can be significantly improved... I am uncertain, however, how one should resolve the problem of over- emphasising forest albedo effects. This would ultimately require some different measures. Perhaps the Authors can respond to this point...? What do they think is the best procedure here...? Personally, I would be inclined to take this in a somewhat different direction. + +<|ref|>text<|/ref|><|det|>[[148, 267, 851, 375]]<|/det|> +Response: We sincerely appreciate your insightful suggestion regarding the potential mechanism of the \(\Delta \mathrm{LST}_{\mathrm{w}}\) variations. In response to your valuable feedback, we have added experiments to compare the albedo- and ET- related effect based on the energy balance equation. This analysis is to quantitatively assess the relative importance of these two processes in \(\Delta \mathrm{LST}\) changes. We also added a discussion about the ET- related mechanism. Please see the detailed response to your later comments on line 115. + +<|ref|>text<|/ref|><|det|>[[148, 402, 850, 456]]<|/det|> +Moreover, while the forest albedo literature considers albedo effects, it entirely neglects cloud related effects... Since these are presumably also tied to forests, in part, what does this say about the methodology employed in the analysis...??? + +<|ref|>text<|/ref|><|det|>[[148, 462, 853, 608]]<|/det|> +Response: We appreciate your insightful critique regarding cloud- related effects. We fully agree that cloud feedback is an important pathway of forest affecting the climate system. As you rightly pointed out, the space- for- time substitution method employed in our study primarily captures forests' direct modulation of surface albedo rather than planetary albedo. We would like to note that several studies have qualitatively assessed forests' impact on cloud formation using similar methodologies combined with satellite observations (Duveiller et al., 2021; Xu et al., 2022). However, quantitatively evaluating the equivalent radiative forcing of forest- cloud feedback remains challenging. + +<|ref|>text<|/ref|><|det|>[[148, 614, 851, 870]]<|/det|> +If the remote sensing- based results are properly interpreted, we believe that our methodological approach and findings are scientifically valid and useful. First, while the method focuses on the local effects, it provides accurate assessments that can serve as valuable benchmarks for improving climate models and reanalysis datasets regarding the land- atmosphere interaction, which is a fundamental prerequisite for understanding forests' influence on cloud formation. Previous modeling studies examining forest cover impacts on cloud- radiative effects have shown considerable uncertainty in their results (Cerasoli et al., 2021; Luo et al., 2024). Second, the used method captures the direct impacts of forest on local LST, which are effective across spatial scales. In contrast, forest- cloud feedback operates at the regional scale and depends on the intensity of forest change. For instance, even forestation/deforestation in a small area can immediately affect LST, while cloud impacts may be masked by the atmospheric advection. Thus, our assessments provide insights for climate adaptation strategies at the local scale. These findings complement rather than contradict other regional or larger- scale modeling studies. We have added a discussion about this issue (Line 504): + +<|ref|>text<|/ref|><|det|>[[149, 877, 850, 912]]<|/det|> +Second, the adopted "space- for- time" method provides a priori estimates of the local temperature effect. The influence of forests on regional cloud formation and subsequent downward + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 195]]<|/det|> +radiation represents a significant yet overlooked mechanism in current assessments. This omission may lead to a systematic underestimation of forests' net cooling effect. Meanwhile, forests can exert more complicated effects on climate through multiple processes such as changes in large- scale atmospheric circulations. Coupled models can effectively estimate these effects, notwithstanding the considerable uncertainties. Thus, our results should be treated as the reference for local climate adaptation rather than global climate mitigation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 201, 232, 215]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 222, 850, 261]]<|/det|> +Cerasoli, S., Yin, J. & Porporato, A. Cloud cooling effects of afforestation and reforestation at midlatitudes. Proc. Natl. Acad. Sci. U. S. A. 118, 1- 7 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 264, 848, 300]]<|/det|> +Duveiller, G. et al. Revealing the widespread potential of forests to increase low level cloud cover. Nat. Commun. 12, 1- 15 (2021). + +<|ref|>text<|/ref|><|det|>[[147, 304, 848, 340]]<|/det|> +Luo, H., Quaas, J. & Han, Y. Decreased cloud cover partially offsets the cooling effects of surface albedo change due to deforestation. Nat. Commun. 15, 7345 (2024). + +<|ref|>text<|/ref|><|det|>[[147, 344, 848, 380]]<|/det|> +Xu, R. et al. Contrasting impacts of forests on cloud cover based on satellite observations. Nat. Commun. 13, 670 (2022). + +<|ref|>text<|/ref|><|det|>[[147, 406, 851, 498]]<|/det|> +Line 11: Since this observation runs in the face of quite a large amount of literature which suggests the opposite relationship, perhaps this is worth highlighting, or perhaps this should be stated in a more nuanced fashion...? See for example some of the literature highlighted in Ellison et al., 2024, perhaps, in particular, Davin et al., http://journals.ametsoc.org/doi/10.1175/2009JCLI3102.1 or, Lawrence et al., 2022 + +<|ref|>text<|/ref|><|det|>[[147, 503, 851, 576]]<|/det|> +Response: Thank you for pointing this out. Our findings reveal a winter daytime warming effect in forests compared to openlands initially. However, this daytime warming gradually diminishes and eventually reverses, while the nighttime warming effect persists. For clarity, we have revised the relevant sentence (Line 7): + +<|ref|>text<|/ref|><|det|>[[147, 581, 851, 672]]<|/det|> +By comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify the temporal trends in local land surface temperature (LST) effects of potential forestation in Europe. During winter, the daytime warming effect of forestation diminishes and reverses to cooling (- 0.142 K/decade) due to weaker surface darkening trends in forests than openlands, induced by decreasing snow cover. + +<|ref|>text<|/ref|><|det|>[[147, 699, 848, 735]]<|/det|> +Line 26: Could perhaps highlight relative importance of enhancing/increasing forest cover..., since only change in forest cover is likely to help redress global warming... + +<|ref|>text<|/ref|><|det|>[[147, 740, 848, 757]]<|/det|> +Response: Thank you for the suggestion. We have revised the sentence and now it reads (Line 26): + +<|ref|>text<|/ref|><|det|>[[147, 762, 848, 798]]<|/det|> +Increasing forest cover through restoration practices could play a crucial role in addressing global warming by regulating the hydrological cycle and enhancing cloud formation. + +<|ref|>text<|/ref|><|det|>[[147, 824, 248, 840]]<|/det|> +Line 39: ???... + +<|ref|>text<|/ref|><|det|>[[147, 847, 848, 881]]<|/det|> +Response: Thank you for the comment. We have expanded the description of this mechanism (Line 37): + +<|ref|>text<|/ref|><|det|>[[179, 888, 848, 905]]<|/det|> +At night, forests warm the land surface compared to open lands through two mechanisms. First, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 85, 851, 177]]<|/det|> +forest canopies absorb solar radiation and store heat during the daytime and subsequently release this energy at night. Second, the nighttime land surface is typically cooler than the near- surface air, forming a stable boundary layer where downward atmospheric heat fluxes warm the land surface. Forests, with their greater surface roughness, can intensify turbulent mixing, enhance this heat exchange process, leading to higher nighttime LST observed in forested areas. + +<|ref|>text<|/ref|><|det|>[[147, 203, 851, 275]]<|/det|> +Line 41: I think this is not entirely correct... I agree this is the way we commonly think about this relationship. But, consider the following: (b) only or primarily occurs in the absence of (a). The net temperature effect is a function of the availability of soil moisture, not of the net radiative balance. ...? + +<|ref|>text<|/ref|><|det|>[[147, 278, 852, 332]]<|/det|> +Warming occurs when soil moisture is depleted and is no longer able to mitigate albedo effects, otherwise the surface is kept from warming through ET production (energy absorption, latent heat) and the transfer of heat energy into the lower atmosphere. + +<|ref|>text<|/ref|><|det|>[[147, 334, 851, 387]]<|/det|> +So warming/cooling is not measured by the net radiative effects, but rather of the relative duration of time during which soil moisture is available and not...??? (I am sure this can be better expressed...). + +<|ref|>text<|/ref|><|det|>[[147, 389, 850, 424]]<|/det|> +This is especially true at the micro/local LST scale at which you measure climate impacts here, but ignores larger scale global climate impacts.... + +<|ref|>text<|/ref|><|det|>[[147, 429, 851, 576]]<|/det|> +Response: Thanks for your insightful comment. We fully recognize the fundamental role of soil moisture (SM) in governing vegetation water availability and its consequent influence on evapotranspiration- mediated cooling effects. However, we hold the view that this SM- related mechanism remains consistent with the established paradigm that "the net temperature response is determined by the balance between competing radiative and non- radiative processes", which is based on the surface energy balance (SEB) framework (Bright et al., 2017; Duveiller et al., 2018; Rigden and Li, 2017). In the SEB equation, LST governs upward longwave radiation (LW↑), which can be expressed as: + +<|ref|>equation<|/ref|><|det|>[[308, 580, 848, 599]]<|/det|> +\[LW\uparrow = \epsilon \sigma LST^{4} = SW\downarrow (1 - \alpha) + LW\downarrow -LE - H - G \quad (R1)\] + +<|ref|>text<|/ref|><|det|>[[147, 603, 850, 657]]<|/det|> +where \(\epsilon\) represents emissivity, \(\sigma\) denotes the Stefan- Boltzmann constant, SW↓ indicates downward shortwave radiation, \(\alpha\) is albedo, LW↓ represents downward longwave radiation, and LE, H, and G correspond to latent heat, sensible heat, and ground heat flux, respectively. + +<|ref|>text<|/ref|><|det|>[[147, 662, 850, 734]]<|/det|> +Assuming limited impact of forest cover on background downward radiation and neglecting the emissivity differences between forests and open lands, the LST effect (ΔLST, forest minus open lands) can be expressed in differential form (with \(\Delta\) prefix representing forest minus open land differences): + +<|ref|>equation<|/ref|><|det|>[[325, 742, 848, 770]]<|/det|> +\[\Delta LST = \frac{1}{4\sigma ELST^3} (-\Delta \alpha \cdot SW\downarrow -\Delta LE - \Delta (H + G)) \quad (R2)\] + +<|ref|>text<|/ref|><|det|>[[147, 780, 850, 833]]<|/det|> +Equation R2 decomposes \(\Delta LST\) into three components on the right side. The radiative effect is captured by the first, while non- radiative effects are represented by the remaining two terms, with \(\Delta LE\) being the dominant component. + +<|ref|>text<|/ref|><|det|>[[147, 839, 851, 912]]<|/det|> +The control of SM can be well integrated into this framework. Specifically, SM is a critical environmental factor modulating transpiration rates of vegetation, and thus serves as a key driver of \(\Delta LE\) (i.e. \(\Delta LE = f(SM)\) ). Through affecting \(\Delta LE\) , SM can further influence both the sign and magnitude of \(\Delta LST\) . Specifically, forests maintain higher transpiration rates than non- forest + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 158]]<|/det|> +vegetation (positive \(\Delta \mathrm{LE}\) ) across a broad spectrum of soil moisture, resulting in a significant cooling effect of forests (negative \(\Delta \mathrm{LST}\) ). However, if soil moisture falls below the wilting point of trees, the forests' evaporative advantage should be constrained, allowing albedo- driven radiative effects to dominate \(\Delta \mathrm{LST}\) . + +<|ref|>text<|/ref|><|det|>[[148, 163, 850, 255]]<|/det|> +Therefore, we believe that the impact of SM does not conflict with the mechanism of the balance between radiative and non- radiative effects. We emphasize that SM's control operates through its influence on the radiative/non- radiative balance by regulating \(\Delta \mathrm{LE}\) . This creates a unified framework where background climatic or environmental conditions determine the feasibility of evaporative cooling, and the energy balance further quantifies the \(\Delta \mathrm{LST}\) expression. + +<|ref|>text<|/ref|><|det|>[[148, 260, 849, 294]]<|/det|> +Based on your comment, we have revised the paragraph to highlight the role of background climate and environmental conditions, including SM (Line 44): + +<|ref|>text<|/ref|><|det|>[[147, 300, 851, 558]]<|/det|> +During the daytime, forests commonly exhibit two competing effects compared to non- forest vegetation: (a) the non- radiative cooling effect driven by higher evapotranspiration (ET) rates (when water supply is sufficient), and (b) the radiative warming effect resulting from lower albedo. The net temperature response depends on the balance between these opposing effects, which is predominantly governed by the background climatic or environmental conditions (e.g., temperature, snow cover, and water availability). For instance, during boreal winter when ET is rendered inactive by low temperatures, the dense forest canopies obscure bright snow, which remains exposed in openlands. This snow masking effect creates a strong albedo contrast between forests and openlands and causes forests to absorb more solar radiation compared to surrounding openlands, resulting in the local warming effect. In warm and wet tropics, forests demonstrate pronounced local cooling effects due to their enhanced ET rates relative to other vegetation types. Limited soil moisture in arid regions or during drought events can constrain forests' evaporative advantage, enabling radiative warming to dominate. Consequently, the magnitude of forests' cooling effect at seasonal or annual scale may depends on the duration of sufficient water availability. + +<|ref|>text<|/ref|><|det|>[[148, 585, 850, 656]]<|/det|> +Regarding the scale- dependency of climate effects, we acknowledge that our remote sensing- based approach has limitations in capturing forest- climate effect at larger scales. We have explicitly addressed this constraint in our discussion and emphasized the importance of proper interpretation of our findings (Line 517): + +<|ref|>text<|/ref|><|det|>[[148, 662, 850, 735]]<|/det|> +Meanwhile, forests can exert more complicated effects on climate through multiple processes such as changes in large- scale atmospheric circulations. Coupled models can effectively estimate these effects, notwithstanding the considerable uncertainties. Thus, our results should be treated as the reference for local climate adaptation rather than global climate mitigation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 764, 231, 777]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 784, 850, 900]]<|/det|> +Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64- 75 (2018). Rigden, A. J. & Li, D. Attribution of surface temperature anomalies induced by land use and land cover changes. Geophys. Res. Lett. 44, 6814- 6822 (2017). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 106, 850, 161]]<|/det|> +Line 49: At least as long as ET is rendered inactive by lower temperatures.... This could be made more explicit... Note that coniferous trees evapotranspire for much longer periods of time on the annual scale... ??? + +<|ref|>text<|/ref|><|det|>[[148, 166, 850, 201]]<|/det|> +Response: Thanks for the professional comment. We have revised the sentence and now it reads (Line 51): + +<|ref|>text<|/ref|><|det|>[[147, 207, 850, 280]]<|/det|> +For instance, during boreal winter when ET is rendered inactive by low temperatures, the dense forest canopies obscure bright snow, which remains exposed in openlands. This snow masking effect creates a strong albedo contrast between forests and openlands and causes forests to absorb more solar radiation compared to surrounding openlands, resulting in the local warming effect. + +<|ref|>text<|/ref|><|det|>[[148, 305, 850, 379]]<|/det|> +Line 115: I tend to think that these estimates should be paired with indications of the changes in wintertime ET behavior. One might expect, with coniferous species at least, that warming will increase the potential for wintertime ET production, and therefore wintertime cooling effects from forests...? + +<|ref|>text<|/ref|><|det|>[[147, 384, 852, 494]]<|/det|> +Response: Thanks for the insightful comment. We agree with your opinion that in the warmer winter, the evaporative cooling effect of forests (compared to openlands) may be intensified and lead to the observed \(\Delta \mathrm{LST}_{\mathrm{w}}\) trends. In response to your suggestion, we have conducted additional experiments examining this process (Supplementary text 1). Our results confirm that albedo- driven variations, rather than evapotranspiration- related processes, are primarily responsible for the observed trend in \(\Delta \mathrm{LST}_{\mathrm{w}}\) (Line 147). + +<|ref|>text<|/ref|><|det|>[[147, 499, 852, 721]]<|/det|> +During winter, the sign and absolute value of \(\Delta \mathrm{LST}_{\mathrm{w}}\) are generally dominated by the magnitude of the radiative process. However, the negative trend in \(\Delta \mathrm{LST}_{\mathrm{w}}\) could potentially arise from two mechanisms: (a) climate- driven alterations in net shortwave radiation absorption differences between forests and openlands ( \(\Delta \mathrm{NSR}_{\mathrm{w}}\) ), or (b) winter warming- induced enhancement in forests' evaporative cooling advantage, represented by latent heat differences between the two land cover types ( \(\Delta \mathrm{LE}_{\mathrm{w}}\) ). To identify the dominant mechanism, we estimate the equivalent perturbations of the two processes on the surface energy balance (Supplementary Text 1). Our analysis reveals that only \(\Delta \mathrm{NSR}_{\mathrm{w}}\) exhibits a statistically significant trend (- 0.86 w·m- 2/decade, \(p = 0.05\) ), whereas the \(\Delta \mathrm{LE}_{\mathrm{w}}\) trend remains non- significant (- 0.02 w·m- 2/decade, \(p = 0.97\) ) (Supplementary Fig. 3). Correlation analyses of interannual variability further support the greater importance of radiative processes, and confirm that this effect is mediated through modifications in the albedo difference ( \(\Delta \alpha_{\mathrm{w}}\) ) between forests and openlands (Supplementary Figs. 4 to 6). + +<|ref|>sub_title<|/ref|><|det|>[[148, 746, 690, 764]]<|/det|> +## Supplementary Text 1. Identifying the dominant process of \(\Delta \mathrm{LST}_{\mathrm{w}}\) change + +<|ref|>text<|/ref|><|det|>[[148, 768, 850, 842]]<|/det|> +We employ the surface energy balance (SEB) framework to identify the primary processes driving variations in \(\Delta \mathrm{LST}_{\mathrm{w}}\) . This framework has been widely adopted for decomposing the effects of vegetation changes on local LST (Bright et al., 2017; Duveiller et al., 2018; Rigden and Li, 2017). In the SEB equation, LST governs upward longwave radiation (LW↑), which can be expressed as: + +<|ref|>equation<|/ref|><|det|>[[293, 845, 848, 864]]<|/det|> +\[LW\uparrow = \epsilon \sigma LST^4 = SW\downarrow (1 - \alpha) + LW\downarrow -LE - H - G \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[147, 868, 850, 904]]<|/det|> +where \(\epsilon\) represents emissivity, \(\sigma\) denotes the Stefan- Boltzmann constant, \(SW\downarrow\) indicates downward shortwave radiation, \(\alpha\) is albedo, \(LW\downarrow\) represents downward longwave radiation, and \(LE\) , \(H\) , and \(G\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 679, 102]]<|/det|> +correspond to latent heat, sensible heat, and ground heat flux, respectively. + +<|ref|>text<|/ref|><|det|>[[149, 107, 850, 163]]<|/det|> +Assuming minimal forest cover influence on background downward radiation and negligible emissivity differences between forests and openlands, the LST effect (ALST, forest minus openlands) can be expressed in differential form (with \(\Delta\) prefix representing forest minus open land differences): + +<|ref|>equation<|/ref|><|det|>[[310, 171, 848, 198]]<|/det|> +\[\Delta LST = \frac{1}{4\sigma ELST^3} (-\Delta \alpha \cdot SW \downarrow -\Delta LE - \Delta (H + G)) \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[149, 207, 850, 262]]<|/det|> +Equation 2 decomposes \(\Delta LST\) into three components on the right side. The radiative effect is captured by the first, while non- radiative effects are represented by the remaining two terms, with \(\Delta LE\) being the dominant component. + +<|ref|>text<|/ref|><|det|>[[148, 267, 851, 394]]<|/det|> +We calculate winter differences in net solar radiation (ANSRw = - \(\Delta \alpha_{w}SW\downarrow\) ) and latent heat (ALEw) between spatially adjacent forests and openlands for each year; analogous to \(\Delta LST_{w}\) . As shown in Supplementary Fig. 3a, positive \(\Delta NSR_{w}\) values indicate a warming effect from potential forestation. Surprisingly, we consistently observe negative \(\Delta LE\) values (positive - \(\Delta LE\) across all years, suggesting slightly lower latent heat flux in forests compared to openlands during winter. This finding aligns with previous modeling and remote sensing studies (Breil et al., 2021; Zan et al., 2024), indicating that forests exhibit no evaporative cooling advantage over openlands in winter. + +<|ref|>text<|/ref|><|det|>[[148, 399, 851, 510]]<|/det|> +Temporal analysis reveals a statistically insignificant trend in \(\Delta LE_{w}\) \((p = 0.97)\) , while \(\Delta NSR_{w}\) showed a significant negative trend \((p = 0.05)\) (Supplementary Fig. 3a). Similar results are obtained when comparing evergreen needleleaf forests (which maintain winter evapotranspiration) with openlands (Supplementary Fig. 3b). These findings strongly suggest that the observed trend in \(\Delta LST_{w}\) is driven primarily by decreasing shortwave radiation absorption differences between forests and openlands, rather than by changes in \(\Delta LE_{w}\) . + +<|ref|>text<|/ref|><|det|>[[148, 515, 851, 606]]<|/det|> +Furthermore, we compute annual correlation coefficients between \(\Delta LST_{w}\) (daily, daytime, and nighttime) and both \(\Delta NSR_{w}\) and \(\Delta LE_{w}\) . A positive correlation emerged between daytime \(\Delta LST_{w}\) and \(\Delta NSR_{w}\) \((r = 0.42\) ; Supplementary Fig. 4), while correlations between \(\Delta LST_{w}\) and \(\Delta LE_{w}\) are statistically insignificant (Supplementary Fig. 5). These interannual correlation patterns corroborate our trend- based conclusions. + +<|ref|>text<|/ref|><|det|>[[148, 611, 850, 685]]<|/det|> +Notably, \(\Delta NSR_{w}\) represents the product of both background downward solar radiation (DSRw) and albedo differences ( \(\Delta \alpha_{w}\) ) between forests and openlands. Additional analysis reveals weak correlation between \(\Delta DSR_{w}\) and \(\Delta LST_{w}\) (Supplementary Fig. 6). These results suggest that \(\Delta \alpha_{w}\) , rather than \(\Delta DSR_{w}\) , should serve as the principal driver of \(\Delta LST_{w}\) variation. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[245, 88, 748, 390]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 404, 850, 458]]<|/det|> +
Supplementary Fig. 3. Temporal variations of winter net solar radiation difference (ANSRw) and latent heat difference (ΔLEw) between forests and openlands in Europe. (a) All forest samples are used. (b) Only evergreen needleleaf forest samples are used.
+ +<|ref|>image<|/ref|><|det|>[[211, 487, 785, 776]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 785, 850, 838]]<|/det|> +
Supplementary Fig. 4. Temporal correlation coefficient (r) between \(\Delta \mathrm{NSR}_{\mathrm{w}}\) and \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (a to c) Spatial pattern of \(r\) between \(\Delta \mathrm{NSR}_{\mathrm{w}}\) and daily mean, daytime and nighttime \(\Delta \mathrm{LST}_{\mathrm{w}}\) . (d) Density of the \(r\) values.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[210, 90, 787, 377]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 386, 850, 440]]<|/det|> +
Supplementary Fig. 5. Temporal correlation coefficient (r) between \(\Delta LE_{w}\) and \(\Delta LST_{w}\) . (a to c) Spatial pattern of \(r\) between \(\Delta LE_{w}\) and daily mean, daytime and nighttime \(\Delta LST_{w}\) . (d) Density of the \(r\) values.
+ +<|ref|>image<|/ref|><|det|>[[210, 469, 787, 757]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 767, 850, 820]]<|/det|> +
Supplementary Fig. 6. Temporal correlation coefficient (r) between \(\mathrm{DSR}_{w}\) and \(\Delta LST_{w}\) . (a to c) Spatial pattern of \(r\) between \(\mathrm{DSR}_{w}\) and daily mean, daytime and nighttime \(\Delta LST_{w}\) . (d) Density of the \(r\) values.
+ +<|ref|>text<|/ref|><|det|>[[148, 848, 850, 902]]<|/det|> +Moreover, we concur with your perspective that warmer winters could theoretically enhance the evaporative cooling effect of forests relative to openlands, potentially contributing to \(\Delta LST_{w}\) variations. Our results did not detect such signals in the current climate regime. This absence may + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 212]]<|/det|> +be attributed to the nonlinear response of LE to temperature increases. Specifically, current winter warming trends in Europe remain insufficient to significantly stimulate transpiration in forests. In the future, continued warming may eventually cross a critical threshold where temperature increases become sufficient to activate wintertime evapotranspiration processes. Under such a scenario, ET- related mechanisms could potentially emerge as a more dominant factor in governing winter land surface temperature differences. We have added a discussion about this mechanism in the discussion (Line 199): + +<|ref|>text<|/ref|><|det|>[[148, 219, 851, 290]]<|/det|> +Furthermore, though not yet observed, rising temperatures may exceed a critical threshold that enhances cold- season ET in the future. This may strengthen the evaporative cooling effect of forests under future warming conditions, especially in coniferous forests with year- round transpiration activity. + +<|ref|>sub_title<|/ref|><|det|>[[148, 319, 231, 333]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 340, 850, 536]]<|/det|> +Breil, M., Davin, E. L. & Rechid, D. What determines the sign of the evapotranspiration response to afforestation in European summer? Biogeosciences 18, 1499- 1510 (2021). Bright, R. M. et al. Local temperature response to land cover and management change driven by non- radiative processes. Nat. Clim. Chang. 7, 296- 302 (2017). Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64- 75 (2018). Rigden, A. J. & Li, D. Attribution of surface temperature anomalies induced by land use and land cover changes. Geophys. Res. Lett. 44, 6814- 6822 (2017). Zan, B. et al. Spatiotemporal inequality in land water availability amplified by global tree restoration. Nat. Water (2024) doi:10.1038/s44221- 024- 00296- 5. + +<|ref|>text<|/ref|><|det|>[[148, 565, 851, 654]]<|/det|> +Moreover, since these effects are small overall, one wonders how much they really matter in the larger picture... Should we worry more about summertime warming (and the related tree cooling potential), or should we be more concerned about wintertime changes overall...??? Which of these two phenomena has the larger, more important impact on climate change phenomena...? + +<|ref|>text<|/ref|><|det|>[[148, 662, 850, 715]]<|/det|> +Response: We appreciate your insightful comments. We acknowledge that the observed \(\Delta \mathrm{LST}\) trend is limited compared to the magnitude of climate change, as we discussed in the manuscript (Line 513): + +<|ref|>text<|/ref|><|det|>[[148, 722, 851, 812]]<|/det|> +Third, the enhanced forest local cooling effect implies that planting trees in proper areas remains a promising local solution against the risk of warming, especially in highly populated regions. Nonetheless, tree restoration is not a panacea for climate change. Although our results highlight the negative biophysical feedback to the warming trend in forests, this feedback is unable to offset the warming trend driven by rising atmospheric \(\mathrm{CO_2}\) . + +<|ref|>text<|/ref|><|det|>[[148, 818, 851, 907]]<|/det|> +About the comparison between summer and winter signals, our analysis reveals that the magnitude of \(\Delta \mathrm{LST_w}\) and \(\Delta \mathrm{LST_s}\) changes are equivalent to about 2- 6% and 6- 9% climate warming trend in winter and summer, respectively (Supplementary Text 4). We recognize that summer effects may remain more directly relevant for human comfort and safety in a warming world. However, the winter effects operate through distinct mechanisms requiring separate consideration, and carry + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 606, 101]]<|/det|> +important ecological implications that should not be overlooked. + +<|ref|>text<|/ref|><|det|>[[148, 106, 852, 328]]<|/det|> +First, the revealed relationship between snow and \(\Delta \mathrm{LST}_{\mathrm{w}}\) could provide constraints for climate models predicting vegetation- snow interactions. Second, there is an ongoing debate regarding the suitability of afforestation for mid- to high latitudes due to the undesired warming effect of afforestation in the cold season. Our result suggests the potential for expanded forestation feasibility in such regions. Specifically, the weakening winter warming signal suggests we may need to re- evaluate traditional limitations on forestation in mid- or high- latitudes, as projected snow cover reductions under climate change could further diminish albedo- related positive forcing and potentially expand suitable areas for climate mitigation through forestation (as we discussed in Line 449). The observed changes in \(\Delta \mathrm{LST}_{\mathrm{w}}\) provide valuable insights into how forestation strategies might need to adapt to changing snow regimes under global warming. Overall, the understanding of seasonal forest- climate interactions contributes to more geographically targeted and feasible forestation approaches. + +<|ref|>text<|/ref|><|det|>[[148, 354, 848, 412]]<|/det|> +Line 145: From my perspective, as noted also above, it is not obvious that this should be true. Response: Thanks for the comment. We have added additional results to identify the mechanism. Please see the detailed response to your comments on line 115. + +<|ref|>text<|/ref|><|det|>[[148, 439, 747, 456]]<|/det|> +Line 149: Empirically, these findings correspond well with what I would expect... + +<|ref|>text<|/ref|><|det|>[[148, 461, 850, 497]]<|/det|> +Response: We appreciate the reviewers' recognition of our findings. We refined this sentence to identify the direction of change in \(\Delta \alpha_{\mathrm{w}}\) (Line 162): + +<|ref|>text<|/ref|><|det|>[[148, 502, 850, 576]]<|/det|> +Specifically, we show that forests are darker than openlands, as evidenced by the negative \(\Delta \alpha_{\mathrm{w}}\) value (- 0.077, Supplementary Fig. 7). However, \(\Delta \alpha_{\mathrm{w}}\) shows a positive trend (0.018 unitless/decade, \(p = 0.04\) ) (Fig. 2a), indicating that the albedo contrast between forests and openlands has been diminishing. + +<|ref|>text<|/ref|><|det|>[[148, 601, 850, 637]]<|/det|> +Line 155: I think one still has to demonstrate that these differences are not true in the longer term...? Has the direction of change actually changed, or only become more pronounced...? + +<|ref|>text<|/ref|><|det|>[[148, 642, 853, 753]]<|/det|> +Response: We appreciate your comments regarding the long- term dynamics of snow- albedo effects. Our satellite- based analysis demonstrates a consistent pattern over the past two decades (2004- 2023): both forests and openlands have exhibited significant albedo declines, with a less pronounced reduction in forests (- 0.017 unitless/decade, \(p< 0.05\) ) compared to openlands (- 0.036 unitless/decade, \(p< 0.05\) ). This divergence results in a significant positive trend in \(\Delta \alpha_{\mathrm{w}}\) (forest minus openland), reducing the albedo contrast between these land cover types. + +<|ref|>text<|/ref|><|det|>[[148, 758, 852, 905]]<|/det|> +We understand your potential concerns about the long- term persistence of these snow- albedo effects. While our MODIS- based analysis is constrained by the temporal limitations of the satellite record, our findings align well with established literature. Previous studies have shown stronger snow- albedo feedback mechanisms in openlands compared to vegetated surfaces (Alessandri et al., 2020; Yu et al., 2022), supporting our observed patterns. This difference arises primarily from the greater snow- masking effect of forest canopies, which diminishes snow's contribution to surface albedo relative to openlands. We have incorporated these supporting references and refined our description accordingly (Line 168): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 213]]<|/det|> +The revealed positive \(\Delta \alpha_{w}\) trend can be traced back to the stronger albedo decrease in openlands (multi- year mean: 0.236; trend: - 0.036 unitless/decade, \(p = 0.04\) ) than in forests (multi- year mean: 0.159; trend: - 0.017 unitless/decade, \(p = 0.03\) ) from 2004 to 2023 (Fig. 2a). This observed divergence in surface darkening trends may be associated with snow cover ( \(SC_{w}\) ) reductions (Supplementary Fig. 8), and differences in the snow- albedo feedback intensity in different land covers (Alessandri et al., 2020; Atlaskina et al., 2015; Li et al., 2017; Manninen et al., 2019; Yu et al., 2022). + +<|ref|>sub_title<|/ref|><|det|>[[148, 242, 232, 256]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 263, 852, 499]]<|/det|> +Alessandri, A., Catalano, F., De Felice, M., van den Hurk, B. & Balsamo, G. Varying snow and vegetation signatures of surface albedo feedback on the Northern Hemisphere land warming. Environ. Res. Lett. 16, (2020). Atlaskina, K., Berninger, F. & de Leeuw, G. Satellite observations of changes in snow- covered land surface albedo during spring in the Northern Hemisphere. Cryosph. 9, 1879- 1893 (2015). Li, Q., Ma, M., Wu, X. & Yang, H. Snow Cover and Vegetation- Induced Decrease in Global Albedo From 2002 to 2016. J. Geophys. Res. Atmos. 124- 138 (2017) doi:10.1002/2017JD027010. Manninen, T. et al. Monitoring changes in forestry and seasonal snow using surface albedo during 1982- 2016 as an indicator. Biogeosciences 16, 223- 240 (2019). Yu, L., Leng, G. & Python, A. Attribution of the spatial heterogeneity of Arctic surface albedo feedback to the dynamics of vegetation, snow and soil properties and their interactions. Environ. Res. Lett. 17, (2022). + +<|ref|>text<|/ref|><|det|>[[148, 524, 850, 560]]<|/det|> +Line 201: this is interesting and could be highlighted more... But it is important to weigh the warming effect against this negligible correlation...??? + +<|ref|>text<|/ref|><|det|>[[148, 565, 850, 656]]<|/det|> +Response: Thank you for raising this important point. We suppose that our correlation analysis may be insufficient to prove the conclusion of the limited role of \(\Delta \mathrm{LE}_{w}\) in the observed \(\Delta \mathrm{LST}_{w}\) trends. To address this, we conducted additional experiments that clearly show albedo- driven processes, rather than LE- related mechanisms, dominate the winter \(\Delta \mathrm{LST}\) variations. Please see the detailed response to your comments on line 115. + +<|ref|>text<|/ref|><|det|>[[148, 684, 850, 737]]<|/det|> +Line 212: And this lack of moisture should also correlate strongly with the increasing importance and impact of albedo effects, since there is no, or there is a reduced, latent heat effect to minimize them...??? + +<|ref|>text<|/ref|><|det|>[[148, 744, 850, 871]]<|/det|> +Response: We appreciate your insightful view. As you correctly pointed out, decreased water availability can constrain vegetation's evaporative cooling capacity and amplify the relative importance of albedo effects. However, we would like to clarify that our study examines the trend and impacts of surface SM (0- 7 cm, based on the definition of ERA5 data), which has been widely used in previous observation- and model- based climate change studies (Hsu and Dirmeyer, 2023; Liu et al., 2023; Yao et al., 2025). We have revised the abbreviation to \(\mathrm{SSM}_{s}\) (summer surface soil moisture) in the manuscript for clarity. + +<|ref|>text<|/ref|><|det|>[[148, 876, 850, 911]]<|/det|> +In forest ecosystems, \(\mathrm{SSM}_{s}\) represents only a fraction of the total available water, as trees can access deeper water reserves through their root systems. In contrast, herbaceous plants in openlands + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 849, 120]]<|/det|> +primarily rely on SM in the upper layers. Therefore, we suppose that the reductions in \(\mathrm{SSM}_\mathrm{s}\) would more severely limit evaporative cooling in openland vegetation than in forests. + +<|ref|>text<|/ref|><|det|>[[148, 125, 850, 217]]<|/det|> +Our subsequent findings support this hypothesis, demonstrating that \(\mathrm{SSM}_\mathrm{s}\) negatively affects the latent heat and leaf area index differences ( \(\Delta \mathrm{LE}_\mathrm{s}\) and \(\Delta \mathrm{LAI}_\mathrm{s}\) ) between forests and openlands (Fig. 4), which means decreasing \(\mathrm{SSM}_\mathrm{s}\) can have a stronger limitation on short vegetation, resulting in the amplification of the difference between forests and openlands. It should be noted that we did not include deep layer SM in the analysis, mainly due to its high uncertainty. + +<|ref|>text<|/ref|><|det|>[[148, 222, 850, 294]]<|/det|> +This differential response has been documented in a previous study (Teuling et al., 2010), which investigated heatwave- induced temperature variations across vegetation types, indicating the more significant warming in grassland than forests due to the rapid SM loss. Our work extends these findings by validating this mechanism over the annual scale. + +<|ref|>text<|/ref|><|det|>[[148, 299, 850, 390]]<|/det|> +Furthermore, we acknowledge the potential nonlinearity of the SM's impacts, as you mentioned in the comment. Specifically, under extreme water scarcity (perhaps beyond a critical threshold), even forests may lose their evaporative cooling advantage, and the albedo warming effect may become dominant. However, currently available observational data have not yet captured these nonlinear effects. We have added a discussion about this mechanism (Line 349): + +<|ref|>text<|/ref|><|det|>[[148, 395, 850, 468]]<|/det|> +However, it should be noted that our observational results represent the impact of soil moisture within a limited range under current climate regimes. If persistent warming or reduced precipitation drives soil moisture below a critical threshold, forests may lose their stability and the evaporative cooling capacity, thus failing to compensate for the warming effect induced by the dark canopy. + +<|ref|>sub_title<|/ref|><|det|>[[148, 496, 231, 511]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 518, 850, 672]]<|/det|> +Hsu, H. & Dirmeyer, P. A. Soil moisture- evaporation coupling shifts into new gears under increasing CO2. Nat. Commun. 14, (2023). Liu, Y., Yang, Y. & Song, J. Variations in Global Soil Moisture During the Past Decades: Climate or Human Causes? Water Resour. Res. 59, (2023). Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). Yao, L. et al. Emergent constraints on global soil moisture projections under climate change. Commun. Earth Environ. 6, 1- 8 (2023). + +<|ref|>text<|/ref|><|det|>[[148, 700, 721, 717]]<|/det|> +Line 237: we would of course expect this decoupling as SM tends to zero...? + +<|ref|>text<|/ref|><|det|>[[148, 723, 850, 795]]<|/det|> +Response: Thank you for the comment. We agree with your view regarding the decoupling between summer vapor pressure deficit (VPDs) and surface soil moisture ( \(\mathrm{SSM}_\mathrm{s}\) ) as soil moisture approaches zero. However, our decoupling methodology is not specifically designed to address this particular condition. + +<|ref|>text<|/ref|><|det|>[[148, 801, 850, 874]]<|/det|> +We should first highlight the need for a decoupling process because VPDs and \(\mathrm{SSM}_\mathrm{s}\) exhibit a strong correlation, and both are significantly correlated with \(\Delta \mathrm{LST}_\mathrm{s}\) . This high collinearity makes it challenging to determine which factor primarily drives \(\Delta \mathrm{LST}_\mathrm{s}\) variability based on temporal correlation analysis (as suggested by Fig. 3a and 3b, not shown here). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 159]]<|/det|> +To address this, we drew upon a previous study (Liu et al., 2020), and adopted a binning regression method. Here, our analysis is based on spatial samples of \(\mathrm{VPD}_5\) trends and \(\mathrm{SSM}_5\) trends with sufficient data to decouple the two factors. For clarity, we have added a schematic illustration of this method in the supplementary materials (Supplementary Fig. 13a). + +<|ref|>text<|/ref|><|det|>[[148, 163, 851, 273]]<|/det|> +In this framework, we first stratified \(\mathrm{VPD}_5\) trends into 10 quantile- based groups to constrain their variation. Within each subset, we then examined the relationship between \(\mathrm{SSM}_5\) trends and \(\Delta \mathrm{LST}_5\) trends using identical samples (Supplementary Fig. 13c), thereby isolating the independent effect of \(\mathrm{SSM}_5\) by controlling for \(\mathrm{VPD}_5\) variability. We subsequently reversed this process, grouping data by \(\mathrm{SSM}_5\) trends quantiles to evaluate the \(\mathrm{VPD}_5\) - \(\Delta \mathrm{LST}_5\) relationship (Supplementary Fig. 13b and 3d). + +<|ref|>text<|/ref|><|det|>[[148, 278, 851, 368]]<|/det|> +The results reveal a clear pattern: \(\mathrm{SSM}_5\) maintain robust correlations with \(\Delta \mathrm{LST}_5\) when accounting for \(\mathrm{VPD}_5\) variation, and the \(\mathrm{VPD}_5\) - \(\Delta \mathrm{LST}_5\) relationships became statistically insignificant when controlling for \(\mathrm{SSM}_5\) (Fig. 3d, not shown here). This analysis provides evidence that \(\mathrm{SSM}_5\) variation is the primary driver of \(\Delta \mathrm{LST}_5\) trends, resolving the initial ambiguity caused by the collinearity between \(\mathrm{VPD}_5\) and \(\mathrm{SSM}_5\) . + +<|ref|>image<|/ref|><|det|>[[200, 377, 800, 707]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 712, 851, 820]]<|/det|> +Supplementary Fig. 13. Schematic illustration of the binning regression method for isolating the effects of summer vapor pressure deficit (VPD5) and surface soil moisture (SSM5) on the land surface temperature effect of potential forestation (LST5). (a) Stratification of VPD5 trends into 10 quantile- based groups. (b) Stratification of SSM5 trends into 10 quantile- based groups. (c) SSM5- \(\Delta \mathrm{LST}_5\) relationship within the given constrained VPD5 trend group. (d) VPD5- \(\Delta \mathrm{LST}_5\) relationship within the given constrained SSM5 trend group. + +<|ref|>sub_title<|/ref|><|det|>[[148, 848, 231, 862]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 870, 848, 903]]<|/det|> +Liu, L. et al. Soil moisture dominates dryness stress on ecosystem production globally. Nat. Commun. 11, 1- 9 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 106, 850, 161]]<|/det|> +Line 310: What is missing for me, here, is the pathway effect of LAI on SM...? Of the two variables, forest effects in my view are primary, while SM effects are dependent upon the presence/absence of forest...??? How do you address this...? + +<|ref|>text<|/ref|><|det|>[[148, 167, 851, 295]]<|/det|> +Response: Thank you for raising this concern about the causal relationship. We agree with your view that there may be a bidirectional relationship between SM and LAI. We should first emphasize the definition of the variables used to build the model. The summer surface SM (SSMs) is the grid- level average that includes all land cover types (forest, openland, etc.). Thus, SSMs primarily reflects background environmental conditions driven by climate change, rather than vegetation- specific characteristics. On the other hand, \(\Delta \mathrm{LAI}_s\) specifically captures the difference in LAI between forest and openland samples within the grid. + +<|ref|>text<|/ref|><|det|>[[148, 300, 850, 372]]<|/det|> +Our modeling approach is based on the logic that climate- driven increase or decline in SSMs may affect forest and openland vegetation differently. For instance, in dry years, forests with their deeper root systems may maintain higher LAI compared to more sensitive openland vegetation. This would increase \(\Delta \mathrm{LAI}_s\) . + +<|ref|>text<|/ref|><|det|>[[148, 377, 850, 469]]<|/det|> +We recognize your point about potential feedback mechanisms. However, we believe that in our framework, the influence of \(\Delta \mathrm{LAI}_s\) on grid- scale SSMs is likely minimal. This is because \(\Delta \mathrm{LAI}_s\) represents relative differences in vegetation within stable pixels (where land cover type has not changed). This internal difference may not affect the overall SM of the grid. We have added a description to clarify this causality issue (Line 764): + +<|ref|>text<|/ref|><|det|>[[148, 474, 850, 546]]<|/det|> +It should be noted that all drivers used in SEM (SSMs, ATs, DSRs, WSs and Ps) represent grid- level mean values, which primarily reflect background climatic and environmental conditions. These variables are unlikely to be influenced by internal variations within the grids ( \(\Delta \mathrm{LE}_s\) and \(\Delta \mathrm{LST}_s\) ). + +<|ref|>text<|/ref|><|det|>[[148, 573, 850, 607]]<|/det|> +Line 319: I did not see this tested in any way in the modeled pathways...? See related comment above...??? + +<|ref|>text<|/ref|><|det|>[[148, 613, 851, 742]]<|/det|> +Response: Thank you for identifying this logical issue. Our structural equation modeling (SEM) results demonstrate that SSMs negatively affect both the LE and LAI differences ( \(\Delta \mathrm{LE}_s\) and \(\Delta \mathrm{LAI}_s\) ) between forests and openlands. This negative relationship indicates that declining SSMs can amplify the ET and greenness difference between these land cover types. Building upon our findings and existing literature about soil moisture deficit impacts on warming, we conclude that the observed negative effect likely stems from forests' greater stability and resilience to soil dryness. We have revised this section to improve clarity and better illustrate this mechanism (Line 332): + +<|ref|>text<|/ref|><|det|>[[148, 747, 851, 893]]<|/det|> +During summer, the vegetation greenness and ET rates are generally higher in forests than in adjacent openlands (Tang et al., 2018). The negative effects of SSMs on \(\Delta \mathrm{LAI}_s\) and \(\Delta \mathrm{LE}_s\) revealed by the SEM analysis demonstrate that the decreased SSMs can amplify these greenness and ET differences between forests and openlands. Given the well- established constraint of soil moisture on vegetation growth (Kamenberg et al., 2024), we tend to attribute the negative effects of SSMs to forests' stability and resilience to increasing soil dryness (i.e., lower sensitivity of forest greenness and ET to SSMs), enabling forests to better maintain their cooling capacity under climate change compared to openland vegetation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 852, 232]]<|/det|> +Previous studies indicate that soil moisture depletion in Europe can exacerbate warming through land- atmosphere feedback mechanisms during heatwave events (Dirmeyer et al., 2021; Fischer et al., 2007). A comparative analysis of temperature responses across land cover types shows that openlands experience pronounced warming during long- lasting heatwaves, whereas forests exhibit moderate warming due to their conservative water- use strategies and sustained evaporative cooling (Teuling et al., 2010). Our results provide observational evidence that forests' capacity to mitigate water deficit- induced warming persists not only during heatwave events but also across the interannual scales. + +<|ref|>sub_title<|/ref|><|det|>[[148, 260, 232, 275]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 280, 852, 515]]<|/det|> +Dirmeyer, P. A., Balsamo, G., Blyth, E. M., Morrison, R. & Cooper, H. M. Land- Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018. AGU Adv. 2, 1- 16 (2021). Fischer, E. M., Seneviratne, S. I., Luthi, D. & Schär, C. Contribution of land- atmosphere coupling to recent European summer heat waves. Geophys. Res. Lett. 34, 1- 6 (2007). Kannenberg, S. A., Anderegg, W. R. L., Barnes, M. L., Dannenberg, M. P. & Knapp, A. K. Dominant role of soil moisture in mediating carbon and water fluxes in dryland ecosystems. Nat. Geosci. (2024) doi:10.1038/s41561- 023- 01351- 8. Tang, B., Zhao, X. & Zhao, W. Local effects of forests on temperatures across Europe. Remote Sens. 10, 1- 24 (2018). Teuling, A. J. et al. Contrasting response of European forest and grassland energy exchange to heatwaves. Nat. Geosci. 3, 722- 727 (2010). + +<|ref|>text<|/ref|><|det|>[[148, 542, 850, 597]]<|/det|> +Line 321: Of course, at some point, one might expect this "stability" to slip as warming surpasses the ability of a forest to store adequate soil moisture and as ET begins to exceed the supply of water (due to long- term rising temperatures and declining rainfall)...??? + +<|ref|>text<|/ref|><|det|>[[148, 602, 850, 638]]<|/det|> +Response: Thanks for raising this important issue. We have added a discussion about this mechanism (Line 349): + +<|ref|>text<|/ref|><|det|>[[148, 644, 850, 717]]<|/det|> +However, it should be noted that our observational results represent the impact of soil moisture within a limited range under current climate regimes. If persistent warming or reduced precipitation drives soil moisture below a critical threshold, forests may lose their stability and the evaporative cooling capacity, thus failing to compensate for the warming effect induced by the dark canopy. + +<|ref|>text<|/ref|><|det|>[[148, 743, 247, 758]]<|/det|> +Line 334: ??? + +<|ref|>text<|/ref|><|det|>[[148, 765, 650, 781]]<|/det|> +Response: Thanks for the careful reading. We have corrected the typo. + +<|ref|>text<|/ref|><|det|>[[147, 809, 850, 903]]<|/det|> +Line 401: ??? Why not say that the radiative forcing of European forests is virtually unchanged...??? The changes you highlight occur elsewhere, not in the forested areas...??? I do not think it makes sense to confuse forests with this phenomenon...??? And it certainly doesn't make sense to blame forests (or suggest they are in any way responsible) for this outcome...??? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 121]]<|/det|> +Response: Thank you for the constructive criticism. We apologize for the confusion caused by the wording. We have revised the relevant sentence to improve clarity (Line 435): + +<|ref|>text<|/ref|><|det|>[[148, 126, 852, 181]]<|/det|> +Thus, the diminished \(SC_w\) could result in a more pronounced reduction in openland albedo but have a limited impact on forest albedo, thereby weakening the relative radiative warming effect of forests compared to openlands. + +<|ref|>text<|/ref|><|det|>[[148, 207, 850, 242]]<|/det|> +Line 416: Same comment as above... And this statement should include a stronger sense of the directionality implied in the effects...? + +<|ref|>text<|/ref|><|det|>[[148, 248, 852, 339]]<|/det|> +Response: Thank you for your feedback. After consideration, we have removed this statement from the revised version for two reasons: (1) large uncertainties remain concerning both the local climatic effects of mid- latitude forestation and the precise transitional latitude between warming and cooling effects; and (2) the original wording's potential for misinterpretation. We note that this particular point was not central to our overall argument, and its removal does not affect the conclusions. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[334, 86, 663, 103]]<|/det|> +## Response to Reviewer #2's Comments + +<|ref|>text<|/ref|><|det|>[[148, 107, 850, 180]]<|/det|> +We greatly appreciate the anonymous reviewer #2 for the constructive comments. The manuscript has been revised and improved accordingly. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in red and Italic). The changes are also marked in red in the manuscript file. + +<|ref|>sub_title<|/ref|><|det|>[[148, 207, 468, 222]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 229, 850, 376]]<|/det|> +I am impressed by the lengths to which the Authors have gone to address the many comments raised. Though ideally, I would like to continue this discussion, I do not wish to burden the Authors unnecessarily. I do think that this manuscript already provides a lot of interesting and highly relevant analysis. I did still make a number of comments in the attached submission pdf and would encourage the Authors to consider these. Most of the comments are relatively minor in character and can easily be addressed (or ignored where appropriate). Thus, I leave it up to the Authors whether they adopt these suggestions or not. + +<|ref|>text<|/ref|><|det|>[[148, 380, 849, 433]]<|/det|> +I do think the manuscript could probably benefit from one last round of editing and perhaps some minor shortening. I do hope the provided comments can prove useful here. + +<|ref|>text<|/ref|><|det|>[[148, 440, 849, 492]]<|/det|> +Response: We sincerely appreciate your positive feedback. We have considered your comments raised in the PDF file and made corresponding revisions. Please see the following responses for details. + +<|ref|>text<|/ref|><|det|>[[148, 520, 850, 610]]<|/det|> +Line 9: And/or the consequences of more extensive forest loss... I think the phrasing matters here, in particular because the conventional view is that more forest cover means more warming, due to the albedo effects... But you are saying the opposite here... So I would try to emphasize this more prominently... You are not really criticizing forestation, but rather its opposite... + +<|ref|>text<|/ref|><|det|>[[147, 617, 814, 633]]<|/det|> +Response: Thanks for the advice. We have revised the wording to avoid ambiguity (Line 43): + +<|ref|>text<|/ref|><|det|>[[148, 639, 850, 693]]<|/det|> +By comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify temporal trends in local land surface temperature (LST) effects of forest change in Europe. + +<|ref|>text<|/ref|><|det|>[[148, 721, 850, 773]]<|/det|> +Line 12: Some minor editing here and there would still be helpful. Here, I would move this phrase to just after "the daytime warming effect of forestation induced by... + +<|ref|>text<|/ref|><|det|>[[147, 780, 822, 796]]<|/det|> +Response: Thanks for the comment. We have revised the sentence as you suggested (Line 45): + +<|ref|>text<|/ref|><|det|>[[148, 802, 850, 855]]<|/det|> +During winter, the daytime warming effect of potential forestation weakens and reverses to cooling (- 0.142 K/decade) with decreasing snow cover, as forests show less pronounced surface darkening trends than openlands. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 139]]<|/det|> +Line 144: Rephrase slightly...? In contrast, forests exhibit strong land surface cooling in summer (), at the strong daytime cooling effect () is minimally offset by a much smaller nighttime warming effect (). + +<|ref|>text<|/ref|><|det|>[[148, 145, 812, 162]]<|/det|> +Response: Thanks for the advice. We have revised the sentence as you suggested (Line 148): + +<|ref|>text<|/ref|><|det|>[[148, 168, 850, 221]]<|/det|> +In contrast, forests exhibit strong land surface cooling in summer (- 0.75 ± 0.41 K), as the daytime cooling (- 2.11 ± 0.98 K) is minimally offset by a much smaller nighttime warming (0.25 ± 0.23 K). + +<|ref|>text<|/ref|><|det|>[[148, 248, 390, 264]]<|/det|> +Line 120: Our/The results... + +<|ref|>text<|/ref|><|det|>[[148, 271, 416, 287]]<|/det|> +Response: Revised as you suggested. + +<|ref|>text<|/ref|><|det|>[[148, 314, 355, 329]]<|/det|> +Line 125: with only...? + +<|ref|>text<|/ref|><|det|>[[148, 337, 416, 352]]<|/det|> +Response: Revised as you suggested. + +<|ref|>text<|/ref|><|det|>[[148, 380, 390, 396]]<|/det|> +Line 156: new paragraph...? + +<|ref|>text<|/ref|><|det|>[[148, 403, 416, 418]]<|/det|> +Response: Revised as you suggested. + +<|ref|>text<|/ref|><|det|>[[148, 446, 850, 499]]<|/det|> +Line 171: It may also be worth noting that snow cover under forests disappears more slowly/is more easily retained for longer periods of time than snow cover in open areas... + +<|ref|>text<|/ref|><|det|>[[148, 506, 758, 522]]<|/det|> +Response: Thanks for the suggestion. We have added related descriptions (Line 205): + +<|ref|>text<|/ref|><|det|>[[148, 528, 850, 563]]<|/det|> +The possible mechanism is that snow tends to be masked by tree canopies and retained for longer durations in forest ecosystems, resulting in a lower sensitivity of forest albedo to snowpack. + +<|ref|>text<|/ref|><|det|>[[148, 591, 587, 606]]<|/det|> +Line 175: suggested, evidenced by, supported by... + +<|ref|>text<|/ref|><|det|>[[148, 613, 416, 628]]<|/det|> +Response: Revised as you suggested. + +<|ref|>text<|/ref|><|det|>[[148, 656, 798, 672]]<|/det|> +Line 177: Or mention the point raised above here... Or further condense... + +<|ref|>text<|/ref|><|det|>[[148, 678, 850, 712]]<|/det|> +Response: We have added related descriptions in Line 205. Please see the above response for the revision. + +<|ref|>text<|/ref|><|det|>[[148, 741, 850, 794]]<|/det|> +Line 255: I tend to think this analysis should also still consider the differences across openlands and forested lands...? I would expect to see significant differences here...? + +<|ref|>text<|/ref|><|det|>[[148, 801, 850, 835]]<|/det|> +Response: Thank you for raising this concern. We admit that soil moisture may have difference in forested area and openland. We have highlight this point in Line 336: + +<|ref|>text<|/ref|><|det|>[[148, 842, 850, 894]]<|/det|> +Specifically, forests possess deeper root systems and enhanced soil moisture storage capacity, enabling them to sustain their cooling efficiency under climate change compared to openland vegetation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 106, 850, 161]]<|/det|> +Line 307: good... I see this point is covered here... Perhaps above one could mention that it will be discussed further below... Above, it just feels like this point is missing... + +<|ref|>text<|/ref|><|det|>[[147, 167, 848, 184]]<|/det|> +Response: Thanks for the advice. We have mentioned this point above as you suggested (Line 245): + +<|ref|>text<|/ref|><|det|>[[147, 189, 851, 280]]<|/det|> +Notably, the climate variables may themselves be influenced by the presence of forests (e.g., soil moisture retention and evaporative cooling of trees). However, it should be emphasized that the climate drivers used in our analysis are the grid means at the coarse resolution, reflecting large- scale patterns rather than microclimates. Our analysis tends to capture the distinct responses of forests and openlands to background climate change. + +<|ref|>text<|/ref|><|det|>[[147, 306, 850, 379]]<|/det|> +Line 336: There are presumably two things going on here: 1) forests have deeper root systems and can dig deeper for water... and 2) forested areas presumably store more soil moisture and thus are not as quickly or easily affected by soil moisture decline... + +<|ref|>text<|/ref|><|det|>[[147, 385, 850, 420]]<|/det|> +Does one see higher soil moisture measurements, in general, across the forested areas...? + +<|ref|>text<|/ref|><|det|>[[147, 426, 848, 461]]<|/det|> +You also mention below that forests may be better at conserving water (e.g., shutting down stomata)... So this would be a third mechanism... + +<|ref|>text<|/ref|><|det|>[[147, 467, 850, 501]]<|/det|> +Response: We fully agree with the point you mentioned. We have highlighted the two mechanisms you mentioned here (Line 336): + +<|ref|>text<|/ref|><|det|>[[147, 507, 850, 561]]<|/det|> +Specifically, forests possess deeper root systems and enhanced soil moisture storage capacity, enabling them to sustain their cooling efficiency under climate change compared to openland vegetation. + +<|ref|>text<|/ref|><|det|>[[147, 588, 850, 622]]<|/det|> +Line 504: This paragraph needs to be broken up into smaller pieces... Way too long... + +<|ref|>text<|/ref|><|det|>[[147, 629, 674, 645]]<|/det|> +Response: The paragraph has been separated into 3 parts as you suggested. + +<|ref|>text<|/ref|><|det|>[[147, 672, 850, 726]]<|/det|> +Line 520: I appreciate this point... It might be wise to find ways to introduce this restriction earlier on in the discussion, and perhaps even the abstract... Just to say that the analysis is focused strictly on local level effects... + +<|ref|>text<|/ref|><|det|>[[147, 732, 850, 767]]<|/det|> +Response: Thanks for the advice. We have highlighted the restriction at the beginning of the manuscript (Line 114): + +<|ref|>text<|/ref|><|det|>[[147, 773, 850, 807]]<|/det|> +It should be noted that the evaluated LST effects are local effects and should be treated as the reference for local climate adaptation rather than global climate mitigation. + +<|ref|>text<|/ref|><|det|>[[147, 835, 850, 869]]<|/det|> +Line 548: Is it forestation that exhibits negative trends, or effects on open lands...??? + +<|ref|>text<|/ref|><|det|>[[147, 875, 805, 892]]<|/det|> +Response: Thanks for pointing this out. We have revised the sentence for clarity (Line 534): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 121]]<|/det|> +Overall, our findings provide solid satellite evidence that the cooling effects of forest conversion from openlands in Europe have been amplified in the last two decades. + +<--- Page Split ---> diff --git a/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/images_list.json b/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..ffa7a605b5bef98860d2e8ac6c4dfc464dcddfa7 --- /dev/null +++ b/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1,77 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1: Taken from Heenan et al. (2017) Scientific Data: During training dives, observer accuracy is assessed by divers estimating the size of wooden fish models of known lengths (a), which are haphazardly distributed throughout a mock SPC cylinder. Example mean difference ( \\(\\leftarrow\\) -standard error) between actual and estimated length of model fishes by trained staff (b—open circles) and by trainee survey divers (c—closed circles) during size estimation training trials between 2014–2016. The closer the difference between size estimates and actual model sizes is to zero, the more accurate the sizing. Trainee fish survey divers, which includes novices in the middle of the training program, people who have done fish surveys but not the SPC method, as well as people who are taking an SPC refresher tend to towards more variable size estimates compared to core staff. Typically new fish surveyors are required to have conducted a minimum of 30 survey dives prior to joining a RAMP cruise.", + "footnote": [], + "bbox": [ + [ + 131, + 130, + 855, + 545 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R2: Example 400-m radial buffers used to estimate site-level mean bathymetric steepness where the buffers overlapped islets or peninsula landmass. a, b: Examples of cases where buffers encompassed landmass and would require drawing a line from land to the buffer circumference to differentiate areas to include/exclude. c: an example of where the landmass divided the buffer into two areas (A1 and A3).", + "footnote": [], + "bbox": [ + [ + 118, + 110, + 875, + 459 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure S4 Biomass model prior distributions and unpopulated posterior intercept estimations for each trophic group of reef fish. Specified prior distributions for each biomass group are shown with the blue line. Posterior intercept distributions are shown in orange.", + "footnote": [], + "bbox": [ + [ + 122, + 111, + 875, + 430 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure S3 Island-level depth effects on reef fish biomass among distinct study ecoregions (Samoa Islands; Phoenix/Tokelau/Northern Cook islands (P/T/NC); Mariana Islands; Line Islands; Hawaii Islands). Point estimates and associated \\(95\\%\\) credible interval (CI) lines indicate the effect of increasing depth on fish biomass (proportional change) at each island (increase if \\(>1\\) , decrease with depth if \\(<1\\) ). The population status of islands is indicated by CI line thickness (thick CI, populated; thin CI, unpopulated). Pale shaded boxes underlying point estimates and CIs represent the average proportionate global effect of depth on biomass given the human population status and average bathymetric steepness, and are provided to aid visual assessment of spatial consistency in depth effects across the study. For example, at islands where depth effects on fish biomass follow the over-all global depth trend for a given trophic group, point estimates are positioned on top of the pale shaded boxes. Conversely, at islands where the effect of depth differs from the global effect, point estimates are positioned outside the shaded box (e.g., in Kauai, there is a greater observed decrease in the biomass density of primary consumers with increasing depth than the over-all effect of depth for that group at populated islands; in Tutuila there is a greater proportionate increase in planktivore biomass with increasing depth relative to the global depth effect for that group at populated islands).", + "footnote": [], + "bbox": [ + [ + 118, + 103, + 870, + 644 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure S4 Piscivore fish biomass, excluding and including the biomass of Carcharhinidae, Carangidae, and Sphyrnidae (see Table S12), across gradients of depth (a) and bathymetric steepness (b) at unpopulated (colour) and populated (grey) islands. Estimates represent conditional posterior medians (lines), 75% percentiles (shaded areas), and partial residuals (points) at the study mean values of bathymetric steepness (panel a) and depth (panel b). The y axis is limited to \\(1.05x\\) the maximum value of the \\(75\\%\\) CI so partial residuals exceeding axis limits are not displayed. \\(N = 5,525\\) stationary point count (SPC) surveys (across 2,253 foreverest sites, 35 islands, five ecoregions).", + "footnote": [], + "bbox": [ + [ + 139, + 125, + 864, + 472 + ] + ], + "page_idx": 47 + } +] \ No newline at end of file diff --git a/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1169831f674665428fd7097b9215355c61bb14cb --- /dev/null +++ b/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,1173 @@ + +# nature portfolio + +# Peer Review Information + +Journal: Nature Ecology & Evolution Manuscript Title: Local human impacts disrupt depth- dependent zonation of tropical reef fish communities Corresponding author name(s): Laura E. Richardson + +Editorial Notes: + +<--- Page Split ---> + +# natureportfolio + +Reviewer Comments & Decisions: + +<--- Page Split ---> + +# nature portfolio + +## Decision Letter, initial version: + +9th January 2023 + +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +Dear Dr Richardson, + +I am writing to you in the temporary absence of my colleague, [REDACTED]. Your Article, "Revisiting the paradigm of coral reef depth zonation on contemporary reefs" has now been seen by 3 reviewers. You will see from their comments copied below that while they find your work of considerable potential interest, they have raised quite substantial concerns that must be addressed. In light of these comments, we cannot accept the manuscript for publication, but would be very interested in considering a revised version that addresses these serious concerns. + +We hope you will find the reviewers' comments useful as you decide how to proceed. If you wish to submit a substantially revised manuscript, please bear in mind that we will be reluctant to approach the reviewers again in the absence of major revisions. + +If you choose to revise your manuscript taking into account all reviewer and editor comments, please highlight all changes in the manuscript text file. + +We are committed to providing a fair and constructive peer- review process. Please do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +If revising your manuscript: + +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the referees along with the revised manuscript. + +\* If you have not done so already we suggest that you begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +Please use the link below to submit a revised paper: + +## [REDACTED] + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +If you wish to submit a suitably revised manuscript we would hope to receive it within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our + +<--- Page Split ---> + +# nature portfolio + +efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +Thank you for the opportunity to review your work. + +## [REDACTED] + +Reviewers' comments: + +Reviewer #1 (Remarks to the Author): + +This is a well- structured and well- written study that provides basin- scale patterns of reef fish trophic group and biomass zonation across different spatial scales. + +It is interesting to know how these differ across different groups and how these have been linked to ecological mechanisms such as upwelling. + +It was also interesting to find out about thresholds of bathymetrics steepness below which fish biomass is enhanced. + +Overall, this a good study that would benefit from some edits / clarifications. + +Below some overall comments, and more specific comments per section with line numbers. + +Overall comments to address + +- More methodological information, especially in relation to the survey method and how consistency in fish identification and fish length measurements was achieved. +- Bayesian modelling is not something that I have myself used before (all lines between 444-510), therefore, I cannot comment on if it has been applied correctly or not. I would advise having someone familiar with this method to review the statistical methodology used. +- Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups. + +Introduction + +Line 67. Define deep- water (e.g. \(>200m\) ) or change to "particulate foods and nutrients derived from deeper water..." + +Line 69. Increase instead of increases + +Line 70. Define shallow- water + +Line 82. span vast spaces of the ocean. This is because it has been argued to refer to one ocean (https://doi.org/10.1002/aqc.3512) + +Results + +Line 116: I would remove "predictably" as it's the results section + +Table 1: I would change underlining negative associations to adding a - in front of numbers. e.g. - 0.75. That is more intuitive to me. + +Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +Lines 203- 214. This would fit better in the materials and methods or introduction section. If something needs to be kept in the Results section I would only do that if absolutely necessary. + +<--- Page Split ---> + +Line 224: "exceeding island- scale variance (9%; P(sdsSITE > sdsISLAND) = 0.95)". Is that not already captured in lines 261- 218? Line 225: Why does the site- scale variance here (38- 64%) differ from that at line 25- 52%? The same applies for ecoregion scale. I think it has to do with the way they have been estimated - looking at Table S11 you talk about probabilities, so I would mention that in the main text as well. + +## Discussion + +Line 239: Some of those studies, e.g. Goreau, 1959 talk about zonation focusing on species composition rather than changes in biomass. + +Line 245: I would rephrase to "To our knowledge, this is the first time..." + +Lines 245- 246: However, + +Line 255: Only unpopulated? + +Lines 304- 306: Can you expand a little bit more here? Do you mean that below 30m steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +Line 307: For most part the depth- related changes in biomass remained the for trophic groups, it's just the absolute values that were reduced, no? + +Line 333- 334: True, but you have not focused on species in this study. Would mentioning specific trophic groups that perform distinct functions be more accurate? + +Line 377: Again refs 6 and 25 concern zonation because of changes in species and not trophic group biomass. + +Lines 381- 383: The direction of change was the same though. I know you mention it, but the way it's presented both here and in the discussion, is like it is very different. + +The difference lies mostly in the absolute numbers. Maybe it's not that important, and I am getting too caught up in it. + +Lines 386- 388. Can you add examples of ecological paradigms that are included in the refs you cite, here? + +General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? + +If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +## Methods + +Line 413 onwards (Reef fish survey data section). + +Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +SPC curves: Then there is the question of the survey method itself. Can the authors cite other studies that have used this method? + +Lengths: From what I understand actual fish lengths have been estimated (to the nearest cm) rather than fish size classes. I am struggling to understand how this could be achieved underwater without a significant amount of bias given that some fish could be as far away as 15m. + +Can you explain a bit more on how consistency of length measurements was assured between divers across all the different surveys? Even if that information exists in another reference, it is worth mentioning it in this manuscript, given the large dataset that is being used. + +Lines 440- 442: Does this mean that 400m was cross- checked against all surveyed sites to make sure it does not include opposite sides of the island? What about encompassing the reef flat and reef crest zones? + +Lines 444- 451: I am not familiar with this method to be able to evaluate if it has been applied correctly. Can you cite 1- 2 refs for the type of model you ended up using? + +Line 480: What criterion was used to determine if the proportion of zeros was low enough? + +<--- Page Split ---> + +The study by Richardson and coauthors entitled: "Re- visiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECoLEVEL- 221117855) sets out to explore depth zonation patterns of coral reef fishes across gradients of biophysical processes and human disturbance. This study builds upon a broad body of work focused on contributing to our understanding of how habitat, depth, and other important biophysical drivers influence the structure and distribution of fishes. To date, most contributions to the literature have focused on describing these patterns at single locations or groups of sites across a limited spatial scale. This study complements these efforts by assembling a large and comprehensive dataset including over 5,000 in situ reef fish surveys spanning across 35 islands to explore these ecological patterns. Overall, I found the study to be well designed, scientifically interesting, and well written. I think the results provide valuable insights into how coral reef fish communities are structured in a changing world. However, I feel that there are a couple areas that should be considered before the manuscript is published. I have outlined these broad recommendations along with a couple more detailed comments below. Once these items are addressed, I feel that this manuscript will make a valuable contribution to the field of Ecology. + +First, I would like the authors to consider how they filtered and selected the reef fishes for this study. While I appreciate the complexity and variability of coral reef fish data, I am concerned about the exclusion of ecologically important species (Sharks and Jacks). I am familiar with the literature identifying potential biases associated with large- bodied and mobile species as well as the behavioral effects associated with diver presence. Many of these biases or behavioral effects could be observed for other large- bodied mobile species within important groups such as parrotfishes (Scaridae), wrasses (Labridae) and snappers (Lutjanidae). I would like the authors to consider the potential biases associated with choosing to remove ecologically important species. For example, in most coral reef communities Jacks (Carangidae) are voracious predators exerting strong top- down effects on prey species. This is particularly evident with species such as Caranx ignobilis, C. melampygus, and C. lugubris that can be observed actively hunting across coral reef habitats preying on fishes and other invertebrates. This predatory behavior has been well documented in ecoregions included in this study (Hawaiian Islands and Line Islands). This is also the case with reef sharks (Carcharhinidae) excluded from this study (e.g., Carcharhinus melanopterus, C. amblyrhynchos, and Triaenodon obesus). I ask that the authors reconsider removing the entire group of sharks and jacks and be more selective in their filtering to factor in the ecological relevance of their choices. + +Second, the authors take advantage of a previously published dataset (MacNeil et al. 2015) that provides an estimate of the total unfished global fish biomass to serve as the mean for analysis in this study. The intercept value was used for all trophic groups included in this study with the exception of the secondary consumers. While I do not disagree with this approach, I have concerns over the comparability of datasets. Specifically, the previous study uses a filtering process to exclude certain species. It does not seem like the authors in this study used the same filtering process to exclude the same species. Therefore, this would introduce potential biases in the analysis and statistical modeling outputs. Again, I recommend that the authors consider the ecological implications of the species filtering process and provide a justification for how they selected species or groups to exclude. I think the MacNeil work is great but maybe the authors from this study should consider using the approach they used for the secondary consumers when data were not comparable between studies. + +Lastly, I found the dataset included in this study to be impressive and I appreciate the efforts involved with synthesizing data from across 5 ecoregions. As the authors point out, each of the 5 ecoregions included in this study are exposed to different biophysical forces and levels of human disturbance. I understand the major aim of this study was to compare patterns of reef fish biomass across depth gradients for 5 ecoregions. However, I think it would be interesting to see if these patterns hold up within each ecoregion. I found the results from figure 5 to be interesting and wanted explore these results more. I am not suggesting that the authors create additional figures etc. However, I would recommend that the authors provide some additional discussion to expand on their findings. Are the patterns consistent within each ecoregion? + +<--- Page Split ---> + +# nature portfolio + +Line 445 - (biomass density; g- m2) do you mean g m- 2 + +Figures - In general I found the figures to be great. However, I am not sure if it was the download process but the figures appear to be low resolution and slightly blurry. I know a lot of work went into creating the figures and it would be good to confirm the quality for publication. + +Table S1 - Agujian categorized as "Populated"? I assume this is due to its proximity to Tinian and Saipan rather than its small resident population? + +Reviewer #3 (Remarks to the Author): + +This well- written paper uses a uniquely large data set to examine the effects of depth on reef fish assemblages, and how population pressure influences this pattern. The paper uses modern analytical techniques to provide a convincing story of depth- related gradients for both major trophic groups and total biomass. The paper also includes an interesting finding of the role of reef bathymetry on reef fishes - the influence of reef steepness on fish assemblages intuitively might be expected, but has rarely been demonstrated at this scale and with such good bathymetry data. + +My issue with the paper is whether the story is sufficiently interesting for such a high- profile journal for two reasons: 1) the interest in revisiting basic depth gradients and examining homogenization by human impacts and 2) the lack of detailed covariates. The depth- related gradient of zones on reefs is indeed a well- described and accepted paradigm, although I would argue we now have enough descriptions of changes with depth that the ability to generalize is stronger than indicated here (first line of abstract, L77- 80). The homogenization of assemblages because of human impacts is also well known in a range of ecosystems (including on reefs). Therefore, it isn't particularly surprising that the zonation is less clear near highly populated islands. I agree this hasn't been demonstrated as clearly as in this study and it needs to be quantified, but I question whether this elevates the paper to one that should be published in Nature Ecology & Evolution. More fundamentally, I'm not sure how this would change our approach to studying or conserving reefs - the underlying ecological paradigm is clearly still true given the significance of the variables that change with increasing depth, and management is rarely zone specific. For example, any meaningful study of patterns of fish assemblages already controls for variable fishing pressure. Therefore, does this study really suggest that revisiting existing paradigms would change our approach to studying or managing ecosystems? + +More significantly this study feels like it misses opportunities to consider depth in the context of other variables, which potentially either excludes the chance of examining some interesting nuances in the data or possibly confounds the analyses. Firstly, human population pressure simply places reefs into one of two categories (populated or unpopulated) which seems overly simplified - why not consider population pressure as a continuous variable and look at more general trends and thresholds? Secondly, the analyses pool all sites from 'reef slopes', which standardizes the geomorphological zone but ignores any differences in benthic assemblages. Thus the reader is left wondering, for example, whether populated islands have more homogenous benthic assemblages across depth gradients that limits fish zonation. I'm sure the divers collected some benthic data, so why not include a basic metric like coral cover (or even habitat type) in the analyses to better isolate the depth signal? I appreciate that the aim was to examine a basic biophysical gradient (depth), but I feel the paper would have been more interesting to consider depth in the context of all the other variables that we know affect reef fishes. To me, one of the most interesting parts of this paper was examining the role of steepness on zonation and I kept wanting to know which other factors were critical in explaining the deviance in the data set. One of the benefits of modern ecology is the access to large- scale, reliable data layers of a range of covariates. However, this study doesn't use these rich sources of information to fill out the models of fish abundance. This is particularly problematic when considering spatial scales of variation (regions / islands / sites) - because the analyses only uses spatial scale in the model the Discussion has to be quite + +<--- Page Split ---> + +speculative about the actual drivers of these patterns. But had the models included covariates of e.g. net primary productivity, temperature, or wave exposure (all of which are relatively straightforward to obtain) – or island type (see Taylor et al, 2018, Ecography 38:520- 530 for why this variable might be critical) - then we could have seen actual correlations in the data rather than have to guess at what might be varying from island to island ("potential indicators", L210). + +In summary, had I been reviewing this for a general marine journal I would have suggested revisiting the analyses with some key additional covariates and perhaps human pressure as a continuous variable, but recommended the paper eventually be published as examining depth- related patterns with a data set of this size and examining the homogenizing role of human populations is worth quantifying. Plus the importance of steepness and the variation among trophic groups are interesting. However, the threshold for this journal is higher and I am not convinced that the underlying question is sufficiently interesting, especially given the relatively cursory treatment of other important covariates that limits understanding of which variables are critical at large scales. + +## Author Rebuttal to Initial comments + +## Reviewer #1 (Remarks to the Author): + +R1.1: This is a well- structured and well- written study that provides basin- scale patterns of reef fish trophic group and biomass zonation across different spatial scales. It is interesting to know how these differ across different groups and how these have been linked to ecological mechanisms such as upwelling. It was also interesting to find out about thresholds of bathymetrics steepness below which fish biomass is enhanced. Overall, this a good study that would benefit from some edits / clarifications. Below some overall comments, and more specific comments per section with line numbers. + +We thank Reviewer #1 for their careful and considered evaluation of our manuscript. We are glad they found the results interesting, and the article well- structured and well- written. We have addressed the areas in the text that required clarification, revision, or expansion as suggested, taking into account the points they have raised. + +Overall comments to address + +R1.2: More methodological information, especially in relation to the survey method and how consistency in fish identification and fish length measurements was achieved. - Bayesian modelling is not something that I have myself used before (all lines between 444- 510), therefore, I cannot comment on if it has been applied correctly or not. I would advise having someone familiar with this method to review the statistical methodology used. + +Thank- you. See our detailed responses to R1.25- R1.27, and R1.29. + +R1.3: Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups + +Thanks for this. For now, and to favour brevity in the title for the journal, we have not incorporated this suggestion into the title, but we have revised it to make it more concise: 'Re- visiting the paradigm + +<--- Page Split ---> + +of depth zonation on contemporary coral reefs'. We agree with the Reviewer that further clarification of the term zonation is needed early in the introduction. In addition to the existing definition of ecological zonation as "the distribution of organisms across space" (L58), we have added a more detailed definition of 'depth zonation' at first mention as follows: + +L67: "Here we revisit this basic principle in the context of depth zonation of tropical coral reef communities- the distribution of reef fish biomass among distinct trophic groups." + +## Introduction + +R1.4: Line 67. Define deep- water (e.g. \(>200m\) ) or change to "particulate foods and nutrients derived from deeper water..." + +Thanks. We have changed this to "particulate foods and nutrients derived from deeper water" as suggested (L73). + +R1.5: Line 69. Increase instead of increases. Changed. + +R1.6: Line 70. Define shallow- water. + +Changed to "shallow- water (<30 m depth37)" (L76). + +- Stefanoudis et al. (2019). Depth-dependent structuring of reef fish assemblages from the shallows to the rariphotic zone. Front Mar Sci 6, 307. + +R1.7: Line 82. span vast spaces of the ocean. This is because it has been argued to refer to one ocean (https://doi.org/10.1002/aqc.3512) + +Thanks for this suggestion. To avoid the plural term "oceans", the text is changed to: "Modern- day island reefs span vast ocean expanses..." (L88). + +## Results + +R1.8: Line 116: I would remove "predictably" as it's the results section. + +Thanks, removed. + +R1.9: Table 1: I would change underlining negative associations to adding a - in front of numbers. e.g. - 0.75. That is more intuitive to me. + +Thanks for this suggestion. We would agree that adding a "- " in front of the numbers to indicate decrease would be intuitive if the table presented depth and population status effect sizes on fish biomass. Unfortunately, adding "- " might indicate negative probability estimates. Classical probabilities range from 0- 1, such that a negative probability would indicate that an event or observation is less likely than 'impossible'. Indeed, negative probability is discussed in relation to quantum mechanics, and is centred on the concept of event 'cancelation' (e.g. Feynman 1987). If the Reviewer agreed, an alternative option for presenting probabilities associated with a negative relationship between biomass and depth in this Table could be to change underlining negative associations to colouring the text in red (or an alternative colour), which we will gladly do on request. + +<--- Page Split ---> + +# nature portfolio + +- Feynman. (1987). Negative probability. Quantum implications: essays in honour of David Bohm, 235-248. + +R1.10: Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +To aid clearer visualisation of the scaled effects of depth, bathymetric steepness, and human population status on the positive reef fish biomass data, the effect estimates of hurdle components (presence- absence) from the piscivore and planktivore models were not included in Fig. 1. Including them, as presented in Fig. S1, clusters the effect estimates and their percentiles such that the reader may be less able to effectively interpret relative effect size. However, we will gladly exchange Fig. 1 for Fig. S1 on request. + +R1.11: Lines 203- 214. This would fit better in the materials and methods or introduction section. If something needs to be kept in the Results section I would only do that if absolutely necessary. + +Thanks. We have moved these lines as suggested to the methods (L522- 534), and revised the new opening statement as follows: + +L230: "The proportion of variation in fish biomass explained by each spatial scale, quantified by extracting the posterior standard deviations of these modelled random effects, varied among trophic fish groups (Fig. 5; Table S10 and S11; see Fig. S3 for variation in island- level depth effects among ecoregions)." + +R1.12: Line 224: "exceeding island- scale variance (9%; \(P(\text{sdsSITE} > \text{sdsISLAND}) = 0.95\) ). Is that not already captured in lines 261- 218? + +Deleted this detail to streamline results, thank you. + +R1.13: Line 225: Why does the site- scale variance here (38- 64%) differ from that at line 25- 52%? The same applies for ecoregion scale. I think it has to do with the way they have been estimated - looking at Table S11 you talk about probabilities, so I would mention that in the main text as well. + +Thanks for highlighting this area of potential confusion. Line 217 presented the range in variance explained for all fish groups except secondary consumers (i.e. planktivores, piscivores, primary consumers and total fish biomass). L225 described the range in variance explained for all groups except planktivores (i.e. piscivores, primary consumers, secondary consumers, and total fish biomass). To avoid this potential confusion, we have removed the percentage ranges previously provided in L225 and retained reference to Fig. 5 and the complete summary in Table S10. + +## Discussion + +R1.14: Line 239: Some of those studies, e.g. Goreau, 1959 talk about zonation focusing on species composition rather than changes in biomass. + +This is correct. To make this explicit, we have revised this sentence as follows: + +L256: "However, while the structuring force of depth on reef ecology featured among the earliest descriptions of tropical coral reefs (for example, zonation in species composition) \(^{7,27,28}\) , these observations were restricted to single- point locations and the generality of a depth zonation paradigm remains untested across broad geographies." + +R1.15: Line 245: I would rephrase to "To our knowledge, this is the first time..." + +<--- Page Split ---> + +Changed as recommended, thanks (L265). + +R1.16: Lines 245- 246: However, + +Apologies, we are unclear what the Reviewer is suggesting here. We will be glad to address this point if we can request some additional direction. + +R1.17: Line 255: Only unpopulated? + +This paragraph focusses on depth patterns at just unpopulated islands. However, we see that the original wording might have suggested that depth zonation was only observed at unpopulated reefs. We have revised as follows: + +L275: "At geographically distinct unpopulated islands, we show that reef fish biomass of all broad trophic groups correlated predictably and relatively consistently across depth despite underlying variation in biophysical drivers known to affect standing reef fish biomass33,41,50." + +R1.18: Lines 304- 306: Can you expand a little bit more here? Do you mean that below 30m steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +We see that this sentence was potentially unclear. Studies looking at depth zonation beyond the 0- 30 m limit in our study report contrasting peaks in abundance of piscivores and planktivores. For example, at Linden Bank, a submerged shoal on the outer shelf of the Great Barrier Reef, reported dominance of piscivores (and mobile invertivores) between 50- 70 m depth (Scott et al. 2022). In contrast, the proportion of planktivores on forereefs at Enewetak Atoll in the Marshall Islands increased from 50% at 30 m to >90% from 90- 200 m, which the authors suggest may relate to upwelling processes increasing plankton and shallow reef productivity (Thresher and Colin 1986). In L304- 306, we suggest that these variable peaks in trophic group biomass at mesophotic depths are potentially indicative of spatial variation in upwelling, which could be linked- among other oceanographic factors- to variable local bathymetric steepness among those study locations. To make this clearer, we have revised the manuscript as follows: + +L325: "Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the 30 m limit of this study54,67, which may be indicative of spatial variation in upwelling, potentially linked to- among other oceanographic factors- variable local bathymetric steepness among those study locations." + +- Thresher and Colin. (1986). Trophic structure, diversity and abundance of fishes of the deep reef (30-300m) at Enewetak, Marshall Islands. Bull Mar Sci 38, 253-272. Scott et al. (2022). Variation in abundance, diversity and composition of coral reef fishes with increasing depth at a submerged shoal in the northern Great Barrier Reef. Rev Fish Biol Fish 32, 941-962. + +R1.19: Line 307: For most part the depth- related changes in biomass remained the for trophic groups, it's just the absolute values that were reduced, no? + +This is a useful point, highlighting that better clarity in the text might avoid potential confusion. We have amended the sentence as follows: + +L332: "Despite marked bathymetric gradients in fish biomass at unpopulated islands, we show that depth related changes in biomass were altered by depleted biomass baselines at islands inhabited by people. There was overall lower fish biomass across the depth gradient + +<--- Page Split ---> + +# nature portfolio + +for all trophic groups at populated locations. Further, the change in absolute biomass of planktivores, piscivores, and secondary consumers across depth was substantially reduced at populated islands, and depth zonation in primary consumers was lost." + +R1.20: Line 333- 334: True, but you have not focused on species in this study. Would mentioning specific trophic groups that perform distinct functions be more accurate? + +Thanks. We have changed this statement from discussing functionally important species to the need for protection of "...depth- constrained trophic groups that perform distinct and important functions" (L359). + +R1.21: Line 377: Again refs 6 and 25 concern zonation because of changes in species and not trophic group biomass. + +This is correct. As defined in the introduction, the term zonation refers to "the distribution of organisms across space" (L58), and we have clarified our use of the term 'depth zonation' at first mention, to include (though not be limited to) "the distribution of reef fish biomass among distinct trophic groups" with depth (L68; see R1.3). To remove any potential confusion, we have revised L377 in the original manuscript as follows: + +L409: "We revisited ecological depth zonation- recognised as a fundamental structuring force of tropical coral reef communities over six decades ago \(^{7,26 - 28}\) - with two purposes: first, to test the generality of depth zonation of reef fish biomass for the first time across an ocean- basin scale; and second, to assess whether a zonation paradigm holds on reefs exposed to direct local human impacts." + +R1.22: Lines 381- 383: The direction of change was the same though. I know you mention it, but the way it's presented both here and in the discussion, is like it is very different. The difference lies mostly in the absolute numbers. Maybe it's not that important, and I am getting too caught up in it. + +Thanks for highlighting this. We have revised the statement as follows to clarify the exact result: + +L415: "However, we found that while the principle of resource- driven depth zonation held at populated islands for some trophic groups (e.g. direction of change for planktivores, piscivores, secondary consumers), their magnitude of change with depth (i.e. absolute biomass) was substantially reduced by human depletion." + +R1.23: Lines 386- 388. Can you add examples of ecological paradigms that are included in the refs you cite, here? + +Thanks for highlighting potential confusion here. We had provided references to recent papers that discuss the need to revisit classic ecological paradigms for understanding contemporary coral reef ecology, including Hughes et al. 2017 Nature, and Williams et al. 2019 Functional Ecology. These articles emphasise how human impacts are increasingly transforming reefs into new configurations unlike anything observed previously by humans, requiring radical changes in how we study and manage them. The articles do not assess specific paradigms. However, the reference to Helmus et al. 2014 Nature offers an example of island biogeography theory no longer being an effective predictor of species richness in the Anthropocene. To bring in this example earlier we have added it to the introduction, reiterated the example in the opening discussion paragraph, and revised the final conclusion sentence for clarity, as follows: + +<--- Page Split ---> + +L58: "Human impacts confound natural drivers of ecological organisation in most contemporary ecosystems20- 22, and historical paradigms are now failing to capture ecological patterns where there is anthropogenic forcing (e.g. island biogeography theory18)." L272: "These findings support calls for revisiting and potentially updating twentieth century ecological paradigms (e.g. island biogeography theory18) that may no longer capture ecological patterns and processes in a human- dominated world23." L420: "However, where the influence of a physical feature as fundamental as depth on coral reef ecological organisation is being disrupted, we reiterate recent calls to revisit classic and influential ecological paradigms to determine their relevance in this era of rapid change18,23,24." + +- Helmus et al. (2014). Island biogeography of the Anthropocene. Nature 513(7519), 543-546. +- Hughes et al. (2017). Coral reefs in the Anthropocene. Nature 546(7656), 82-90. +- Williams et al. (2019). Coral reef ecology in the Anthropocene. Funct Ecol 33(6), 1014-1022. + +R1.24: General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +Thanks to the Reviewer for highlighting where further discussion on cross- scale spatial variation in fish biomass patterns would improve the manuscript. Coral reefs are considered to be highly hierarchical in structure, determined by processes occurring at multiple spatial and temporal scales (Hughes et al. 1999, MacNeil et al. 2009). As the Reviewer rightly highlights, within this hierarchical context, management and governance efforts are considered most effective when carried out at scales aligning with scales of ecological heterogeneity (Cumming and Dobbs 2020). We describe this in detail in the paragraph L335- 345, and we link our results to scaled management and conservation efforts in L361- 368 in the original manuscript. However, we now provide additional discussion exploring the relative differences in variation observed across scales, notably discussing the relatively lower variation observed at the island- scale as follows: + +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale. In this context, our findings suggest that management of primary consumers, piscivores, total standing biomass, and especially secondary consumers might achieve satisfactory outcomes at local within- island scales with no- take areas80, habitat restoration, or better regulated destructive human activities79. Local management of planktivores is no doubt also important34. But, given the potential influence of regional- scale drivers on planktivore biomass production and the importance of this group as the prey base for higher trophic levels32, more nuanced, region- specific targets for recovery81 or take of planktivores may be advisable in areas of naturally lower primary production." + +- Cumming and Dobbs. (2020). Quantifying social-ecological scale mismatches suggests people should be managed at broader scales than ecosystems. One Earth 3(2), 251-259. +- Hughes et al. (1999). Patterns of recruitment and abundance of corals along the Great Barrier Reef. Nature 397:59-63 +- MacNeil et al. (2009). Hierarchical drivers of reef-fish metacommunity structure. Ecology 90:252-264. + +<--- Page Split ---> + +In response to a similar question of spatial scale by Reviewer #2 (R2.4), we have also now created an additional figure (Fig. S3 below) for the reader to visualise the observed within- and among- island scale variation in depth zonation (island- level depth effects, overlying global depth for comparison, across each trophic group; within- island variation is indicated by \(95\%\) credible intervals associated with island point estimates). + +## Methods + +Line 413 onwards (Reef fish survey data section). + +R1.25: Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +Thanks for this important consideration. The National Oceanic and Atmospheric Administration (NOAA) has multiple trained fish survey divers who conduct in situ observations across sampling cruises, across distinct ecoregions and years. Divers must have a minimum of 30 underwater visual fish survey census dives conducted prior to joining a monitoring cruise. In addition, to ensure consistency in observer species identification and size estimation, NOAA employs extensive training, testing, and technical validation protocols both outside of the cruise period and during (detailed in Heenan et al. 2017). These protocols address the potential for intra- and inter- diver variability in two ways: + +1. New and experienced divers receive full training in fish identification and survey protocol, in classroom and in-water sessions; prior to each survey cruise, all divers must accurately identify \(>90\%\) of regional-specific fish species in a test that is specifically weighted towards rare species and those that have conspecifics with similar appearance. +2. For the timeframe of the data used here, between cruises divers conducted in-water training exercises to practice survey protocol, fish identification and fish size estimation (see response to comment R1.27 for detail on size estimation protocol and technical validation). + +During the cruises, there are typically 4- 10 fish survey divers who routinely discuss and compare species identification and sizes immediately after a survey, and during data entry. Diver pairs are continually rotated, and diver performance is estimated as the difference between the estimates of each diver and those of their dive partner at each site, calculated for total fish biomass, species richness, and body- size distributions of commonly observed species. As divers survey adjacent cylinders on the reef (i.e. not identical areas of the reef), real differences between diver observations are expected. But the diver performance estimate is measured to detect potential consistent bias made by each diver (i.e. if there is no consistent bias, the median difference with their buddy partner should be close to zero). Diver performance is measured every few days during survey cruises to allow for early detection of observer error (Heenan et al. 2017). + +In addition to these technical validation protocols, we included a group- level random intercept for 'diver identity' in all of our statistical models of fish biomass to account for any remaining effect of observer bias. By assuming inherent correlations among divers and their observations that affect the estimated means and associated errors, we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) (sensu Macneil et al. 2015 Nature). + +- Heenan et al. (2017). Long-term monitoring of coral reef fish assemblages in the Western central pacific. Sci Data 4(1), 1-12. +- MacNeil et al. (2015). Recovery potential of the world's coral reef fishes. Nature 520(7547), 341-344. + +We have revised the manuscript as follows to provide the required additional information: + +<--- Page Split ---> + +L457: "Surveys were conducted by multiple observers across the study ecoregions and years. NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation49. Full details on SPC survey methods and technical validation steps are available in [49]. To further mitigate any confounding effect of observer bias among fish surveys, we included 'diver identity' as a random intercept in all statistical models (described below) (sensu53)." + +L514: "A random intercept for 'diver identity' was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations (sensu53)." + +L514: "A random intercept for 'diver identity' was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations (sensu53)." + +R1.26: SPC surveys: Then there is the question of the survey method itself. Can the authors cite other studies that have used this method? + +Yes - the stationary point count is one of the three main methods used to survey coral reef fish assemblages globally (Caldwell et al. 2016). This survey method has been used since 2010 by the United States government agency, the National Oceanic and Atmospheric Administration (NOAA) in their Pacific monitoring program (Towle et al. 2022). The full details of which are available in the data descriptor paper (Heenan et al. 2017). The dataset has been used in numerous peer- reviewed scientific publications, some of which are cited in the manuscript (now referenced in L453 of the revised manuscript): + +- Caldwell et al. (2016). Reef fish survey techniques: Assessing the potential for standardizing methodologies. PLoS One 11(4): e0153066. +- Heenan et al. (2019). Natural variation in coral reef trophic structure across environmental gradients. Front Ecol Environ 18(2), 69-75. +- Towle et al. (2022). A National Status Report on United States Coral Reefs Based on 2012–2018 Data From National Oceanic and Atmospheric Administration’s National Coral Reef Monitoring Program. Front Mar Sci, 8. +- Williams et al. (2015). Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS One 10(4), e0120516. +- Yeager et al. (2017). Scale dependence of environmental controls on the functional diversity of coral reef fish communities. Glob Ecol Biogeogr 26(10), 1177-1189. + +L453: "The abundance and body- size of all diurnal, non- cryptic reef fishes were estimated using stationary point count (SPC) surveys (sensu8,9,15,49,82,83)." + +R1.27: Lengths: From what I understand actual fish lengths have been estimated (to the nearest cm) rather than fish size classes. I am struggling to understand how this could be achieved underwater without a significant amount of bias given that some fish could be as far away as 15m. Can you explain a bit more on how consistency of length measurements was assured between divers across all the different surveys? Even if that information exists in another reference, it is worth mentioning it in this manuscript, given the large dataset that is being used. + +This is another important question. As in response to R1.25, NOAA employs extensive training and technical validation protocols to ensure consistency in sampling. This includes practice size calibration dives during the out of cruise season. These calibration surveys involve divers visually estimating the size of anchored wooden cut- outs of fish with known body lengths, placed throughout the full extent of the survey cylinder (Fig. R1a). While it is true that there is a degree of variability in novice divers, or those new to the training program (Fig. R1c), the experienced trained staff are reasonably consistent (Fig. R1b) with no systematic tendency to over or underestimate size. It is also important to note that as divers remain at the centre of their cylinder, except towards then end of the survey when the size of smaller benthic site- attached species are estimated, typically the furthest distance the diver will be from any fish that is being estimated in length is 7.5 m, not 15 m. + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Figure R1: Taken from Heenan et al. (2017) Scientific Data: During training dives, observer accuracy is assessed by divers estimating the size of wooden fish models of known lengths (a), which are haphazardly distributed throughout a mock SPC cylinder. Example mean difference ( \(\leftarrow\) -standard error) between actual and estimated length of model fishes by trained staff (b—open circles) and by trainee survey divers (c—closed circles) during size estimation training trials between 2014–2016. The closer the difference between size estimates and actual model sizes is to zero, the more accurate the sizing. Trainee fish survey divers, which includes novices in the middle of the training program, people who have done fish surveys but not the SPC method, as well as people who are taking an SPC refresher tend to towards more variable size estimates compared to core staff. Typically new fish surveyors are required to have conducted a minimum of 30 survey dives prior to joining a RAMP cruise.
+ +L458 has been revised to highlight the technical validation protocols designed to ensure consistency in length measurements, with reference to the data descriptor paper (Heenan et al. 2017): "NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation49. Full details on SPC survey methods and technical validation steps are available in 49." + +R1.28: Lines 440- 442: Does this mean that 400m was cross- checked against all surveyed sites to make sure it does not include opposite sides of the island? What about encompassing the reef flat and reef crest zones? + +We selected an automated process to estimate mean bathymetric steepness within a 400- m radial buffer around each site to remove potential subjectivity in the method. We confirm that we visually cross- checked all 2,262 survey sites to see whether these buffers overlapped landmass (N.B. landmass areas were excluded as standard). While there was no observed overlap of the buffers across opposite + +<--- Page Split ---> + +# nature portfolio + +sides of the primary 35 study islands, we found a total of 15 sites where some degree of overlap of an adjoining islet or peninsula was observed ( \(< 1\%\) of sites). Ten of these cases occurred where the buffer encompassed the end of an islet or a protruding peninsula, which would require drawing an arbitrary line in the buffer from the islet out to the buffer circumference in order to differentiate one area of ocean from the other (e.g. Fig. R2a,b). Given that the hydrodynamics at each site are predominantly unknown (i.e. the likely direction of currents and upwelling), we selected not to introduce this bias and accepted a level of uncertainty introduced by our a priori determination of radial buffer extent (L436- 439 original manuscript: "A radial buffer- size of 400 m was selected to encompass depths that would capture the propensity for pulsed delivery of nutrient- rich sub- thermocline water by upwelling \(^{86,87}\) and for this upwelling to propagate onto shallow reef habitats at depths \(\leq 30 m^{35}\) ."). The five remaining cases (representing \(0.2\%\) of the total sites) included landmass where the buffer was split into two areas of sea (e.g. A1 and A3 in Fig. R2c). We calculated the percentage of forereef area included from opposite sides of the landmass that contributed to the estimate of mean bathymetric steepness for these sites as: \(1.0\%\) , \(2.1\%\) , \(5.0\%\) , \(24.1\%\) , and \(43.1\%\) (Table R1). + +We selected this automated method of estimating coarse- scale bathymetric steepness to mitigate potential subjectivity in a site- by- site assessment. However, prompted by the Reviewer's question and to ensure the highest levels of confidence in our data, we have subsequently decided to remove two sites where the percentage of the buffer area that was located on an opposite side of a landmass contributed \(>5\%\) to the bathymetry estimates (i.e. sites TUT- 00376 and TUT- 00516; Table R1; Fig. R2c). We have also removed an additional 7 sites that are officially classified as 'forereef' in NOAA's National Coral Reef Monitoring Program (Heenan et al. 2017) but could also be classified as reef crest or reef flat. We have re- run all models and adjusted the minor details of results (e.g. precise probability estimates) throughout, though we note that the broad study results remain unchanged from the original submission. + +To clarify our cross- checking process and site filtering approach, we have revised the methods section as follows: + +L490: "All sites were visually cross- checked for island overlap, and those including \(>5\%\) radial- buffer bathymetry on the opposite site of a landmass were excluded from all analyses." + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Figure R2: Example 400-m radial buffers used to estimate site-level mean bathymetric steepness where the buffers overlapped islets or peninsula landmass. a, b: Examples of cases where buffers encompassed landmass and would require drawing a line from land to the buffer circumference to differentiate areas to include/exclude. c: an example of where the landmass divided the buffer into two areas (A1 and A3).
+ +Table R1: Proportion of 400-m radial buffer area on the opposite side of a landmass area contributing to site-level average bathymetric steepness estimates. Site names include the three-letter island reference codes detailed in Table S1. + +
Site nameA1: Site side (m²)A3: Opposite side (m²)Percentage of area on opposite side contributing to site average estimate (%)
PAG-00379340,1577,2682.1
TUT-00376257,666195,13143.1
TUT-00516343,405109,20924.1
OFU-00437176,2591,8651.0
OAH-00300356,73018,6725.0
+ +R1.29: Lines 444- 451: I am not familiar with this method to be able to evaluate if it has been applied correctly. Can you cite 1- 2 refs for the type of model you ended up using? + +We have added a reference to the peer- reviewed paper by Bürkner (2017) which provides a detailed description of the Bayesian multi- level statistical model approach using the R software package brms as used in our study. The paper includes description of the multi- level regression models we have applied, the use of priors and selection of population- or group- level specific family parameters, and a worked example: + +- Bürkner (2017). brms: An R Package for Bayesian Multilevel Models Using Stan. J Stat Softw 80, 1-28. + +<--- Page Split ---> + +R1.30: Line 480: What criterion was used to determine if the proportion of zeros was low enough? + +We tested initial biomass models with a hurdle structure and found that the hurdle component only affected model results when the number of zeros were sufficient (i.e. \(>5\%\) ). To accommodate zerocount observations by fitting a hurdle model, a sufficient contrast (i.e. a sufficient number of zeros and ones) is required to be able to estimate effects in the presence- absence component of the model. If nearly all values are \(>0\) , then there are only a few datapoints to inform the model about factors that lead to a zero outcome. In those cases, the probability of positives will be close to one (particularly with a dataset as large as in this study since are 1000s of positive data observations), and the hurdle component will only add noise. In the case of primary and secondary consumer biomass where the percentage of zeros was \(1.09\%\) and \(0.05\%\) respectively, in our dataset, the low contrast for the hurdle components affected model convergence and only added noise, so those were deemed not useful. To clarify this, we have provided additional description in the methods as follows: + +L542: "Where the proportion of zeros was too low to effectively estimate effect sizes in the presence- absence component (i.e. an insufficient contrast between the number of zeros and ones), the use of a hurdle structure affected model convergence and only added noise. This occurred for primary consumers ( \(1.09\%\) zeros) and secondary consumers ( \(0.05\%\) zeros), so for these groups the zero biomass replicates were removed from the analysis and the Gamma model detailed above was fitted." + +## Reviewer #2 (Remarks to the Author): + +R2.1: The study by Richardson and coauthors entitled: "Re- visiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECOLEVOL- 221117855) sets out to explore depth zonation patterns of coral reef fishes across gradients of biophysical processes and human disturbance. This study builds upon a broad body of work focused on contributing to our understanding of how habitat, depth, and other important biophysical drivers influence the structure and distribution of fishes. To date, most contributions to the literature have focused on describing these patterns at single locations or groups of sites across a limited spatial scale. This study complements these efforts by assembling a large and comprehensive dataset including over 5,000 in situ reef fish surveys spanning across 35 islands to explore these ecological patterns. Overall, I found the study to be well designed, scientifically interesting, and well written. I think the results provide valuable insights into how coral reef fish communities are structured in a changing world. However, I feel that there are a couple areas that should be considered before the manuscript is published. I have outlined these broad recommendations along with a couple more detailed comments below. Once these items are addressed, I feel that this manuscript will make a valuable contribution to the field of Ecology. + +Thanks to Reviewer #2 for their positive comments and thoughtful evaluation of our manuscript. We are pleased they found the article to be interesting, valuable to the field of Ecology, well- designed, and well- written. We have addressed the broad and detailed recommendations made, editing, or adding the required detail in the revised submission. + +R2.2: First, I would like the authors to consider how they filtered and selected the reef fishes for this study. While I appreciate the complexity and variability of coral reef fish data, I am concerned about the exclusion of ecologically important species (Sharks and Jacks). I am familiar with the literature identifying potential biases associated with large- bodied and mobile species as well as the behavioral effects associated with diver presence. Many of these biases or behavioral effects could be observed for other large- bodied mobile species within important groups such as parrotfishes (Scaridae), wrasses (Labridae) and snappers (Lutjanidae). I would like the authors to consider the potential biases associated with choosing to remove ecologically important species. For example, in most coral reef communities Jacks (Carangidae) are voracious predators exerting strong top- down effects on + +<--- Page Split ---> + +prey species. This is particularly evident with species such as Caranx ignobilis, C. melampygus, and C. lugubris that can be observed actively hunting across coral reef habitats preying on fishes and other invertebrates. This predatory behavior has been well documented in ecoregions included in this study (Hawaiian Islands and Line Islands). This is also the case with reef sharks (Carcharhinidae) excluded from this study (e.g., Carcharhinus melanopterus, C. amblyrhynchos, and Triaenodon obesus). I ask that the authors reconsider removing the entire group of sharks and jacks and be more selective in their filtering to factor in the ecological relevance of their choices. + +We thank the Reviewer for raising this. We agree that it would be interesting to explore piscivore biomass trends including sharks and jacks (despite their known daily vertical migrations up and down the reef slope; Meyer et al. 2007, Afonso et al. 2009, Vianna et al. 2013) if we had robust, unbiased estimates of these larger predators. As the Reviewer notes, piscivorous species of jacks and sharks are critically important to trophic dynamics and ecological organisation on coral reefs via top- down predation processes. However, as the Reviewer also highlights, published evidence shows that the body- size, mobility, curiosity, and trophic position of sharks and jacks influences their detectability and can introduce substantial sampling bias (Kulbicki 1998), particularly in surveys involving stationary divers (as in our study; Heenan et al. 2019). Common 'mobbing' behaviour of survey divers by sharks and jacks can lead to systematic overestimates in density (Parrish and Boland 2004), particularly in remote unpopulated areas where mobile roving piscivores can remain curious and unafraid of humans such as in the northwestern Hawaiian Islands (Williams et al. 2015). To mitigate this method bias, and in particular likely spatial variation in sampling bias among populated vs unpopulated locations, sharks and jacks are routinely excluded from reef fish survey analyses (sensu MacNeil et al. 2015; Table R2). + +Table R2 Examples of studies globally that exclude sharks and other large semi-pelagic (associated with both shallow reef and pelagic environments) piscivorous fish such as jacks. + +
Geographic study regionExcludes sharksExcludes sharks and semi-pelagics
GlobalD'Agata et al. 2016 Roy Soc Proc BMacNeil et al. 2015 Nature
Cinner et al. 2016 Nature
CaribbeanHawkins and Roberts 2004 Cons Biol
PacificD'Agata et al. 2016 Nat Comms
Gray et al. 2016 PLoS ONE
Williams et al. 2015 PLoS ONE
Yeager et al. 2017 Glob Ecol Biogeog
Indian OceanMcClanahan et al. 2009 MEPSMcClanahan et al. 2020 Aqu Conserv
Samoyils et al. 2018 PLoS ONE
Cowburn et al. 2018 Mar Pol Bull
+ +Unlike jacks and sharks, 'mobbing' behaviour towards divers by other large- bodied mobile species of reef fish such as parrotfishes, wrasses, and snappers is less routinely observed, as they may be less strongly affected by diver- presence (Longo and Floeter 2012). Our study authors have observed some hair- raising instances of diver- mobbing by the snapper, Lutjanus bohar, in the southern Line Islands (a geography not included in our study) where they are dominant in abundance over sharks (G. J. Williams, pers. comms.). However, such occurrences appear specific to that geography and are less commonly reported than the diver- positive behaviour documented for sharks and jacks, specifically in our study region. Indeed, efforts to quantify the effect of diver- presence on detectability of reef fishes across distinct families have described these other large- bodied groups as either diver- neutral (no detected effect on observed abundance, e.g. Lutjanidae), or diver- negative (where diver- disturbance reduces rather than increases detectability, e.g. Scaridae, Labridae, Serranidae) (Emslie et al. 2018). + +<--- Page Split ---> + +- Afonso et al. (2009). Multi-scale patterns of habitat use in a highly mobile reef fish, the white trevally Pseudocaranx dentex, and their implications for marine reserve design. Mar Ecol Prog Ser 381, 273-286. +- Emslie et al. (2018). Reef fish communities are spooked by scuba surveys and may take hours to recover. PeerJ 6, e4886. +- Heenan et al. (2019). Natural variation in coral reef trophic structure across environmental gradients. Front Ecol Env 18(2), 69-75. +- Kulbicki. (1998). How the acquired behaviour of commercial reef fishes may influence the results obtained from visual censuses. J Exp Mar Biol Ecol 222(1-2), 11-30. +- Longo and Floeter. (2012). Comparison of remote video and diver's direct observations to quantify reef fishes feeding on benthos in coral and rocky reefs. J Fish Biol 81(5), 1773-1780. +- Meyer et al. (2007). Seasonal and diel movements of giant trevally Caranx ignobilis at remote Hawaiian atolls: implications for the design of marine protected areas. Mar Ecol Prog Ser 333, 13-25. +- Parrish and Boland. (2004). Habitat and reef-fish assemblages of banks in the northwestern Hawaiian Islands. Mar Biol 144: 1065-73. +- Vianna et al. (2013). Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks (Carcharhinus amblyrhynchos) at aggregation sites. PloS ONE 8(4), e60331. +- Williams et al. (2015). Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS ONE 10: e0120516. + +Therefore, while we appreciate the Reviewer's point and reiterate that we would consider exploring trends with sharks and jacks if we had unbiased estimates, we believe that including them from this data source where there is known systematic method bias would be misleading. Further, we are keen to ensure comparability between our study and existing publications in the literature that quantify unfished biomass baselines and drivers of reef fish assemblage structure (e.g. Table R2). However, we recognise that more detailed explanation for our filtering method would better equip the reader, which we have now added to the revised manuscript as follows: + +L469: "Sharks and jacks (families Carcharhinidae, Carangidae, Sphyrnidae) were also excluded as these highly mobile, large-bodied, roving piscivores are known to be affected by the presence of stationary divers, typically resulting in systematic over- inflation of visual survey density estimates \(^{85}\) (sensu \(^{8,53}\) ). The presence of divers was also a potential source of differential bias of biomass estimates of these fishes among study locations, with 'mobbing' behaviour by jacks and sharks known to occur particularly in remote, unpopulated areas such as the northwestern Hawaiian Islands \(^{8,50}\) ." + +R2.3: Second, the authors take advantage of a previously published dataset (MacNeil et al. 2015) that provides an estimate of the total unfished global fish biomass to serve as the mean for analysis in this study. The intercept value was used for all trophic groups included in this study with the exception of the secondary consumers. While I do not disagree with this approach, I have concerns over the comparability of datasets. Specifically, the previous study uses a filtering process to exclude certain species. It does not seem like the authors in this study used the same filtering process to exclude the same species. Therefore, this would introduce potential biases in the analysis and statistical modeling outputs. Again, I recommend that the authors consider the ecological implications of the species filtering process and provide a justification for how they selected species or groups to exclude. I think the MacNeil work is great but maybe the authors from this study should consider using the approach they used for the secondary consumers when data were not comparable between studies. + +We are glad the Reviewer broadly agrees with our approach for setting priors ("the mean for analysis in this study") for our models of fish biomass, albeit with reservations about the potential incomparability of datasets between our study and that by MacNeil et al. (2015). By using 'prior' + +<--- Page Split ---> + +information on global unfished biomass estimates from MacNeil et al., we provide the models with a ‘real world’ starting point to begin exploring the basis of the given conjectures (e.g. whether or not there is a depth effect). Incorporating prior information is the defining characteristic of Bayesian philosophy, allowing us to directly integrate information about the scientific context and remove the implicit equal weighting of possibilities that is more akin to frequentist analyses (Lemione 2019, McElreath 2020). It is worth noting that, in general, “the prior data and new data can be of different types” (McElreath 2020). + +Nevertheless, while not identical, our approach to filtering jacks and reef- sharks is very close to that of MacNeil et al., who “retained counts of diurnally active, non- cryptic reef fish that are resident on the reef slope, excluding sharks and semi- pelagics”. We explicitly inflated the prior standard deviation in the intercepts for our models, which is based on the MacNeil et al. study, to account for factors that may limit comparability. These factors include species filtering approaches, but also geographical representativeness, and census method. In other words, we selected the MacNeil et al. study as the most relevant information to base a prior mean on (i.e., to determine the order of magnitude we might expect in unfished biomass on a reef), we do not think that the precision in their estimates would be useful for our prior. We therefore inflated our prior standard deviation considerably (by an order of magnitude, given the prior is on the log- scale). Given the large amounts of data that inform our models (previously \(n = 5,549\) , now \(n = 5,525\) stationary point count fish surveys), the prior had a negligible impact, and estimated mean densities were often significantly shifted from the prior. We have added clarification about our prior specification to the methods (detailed below), and have added an additional figure to the Supplemental Information showing the prior and posterior intercept for unpopulated islands to illustrate how the data moves our posterior estimates from the prior (Fig. S4 below). + +- Lemoine (2019). Moving beyond noninformative priors: why and how to choose weakly informative priors in Bayesian analyses. Oikos, 128(7), 912-928. +- McElreath (2020). Statistical rethinking: A Bayesian course with examples in R and Stan. 2nd Edition, Chapman and Hall/CRC, New York, pp 612. + +L549: “This study builds on existing knowledge established in previous research that estimated a global baseline of total resident reef fish biomass in the absence of fishing \(^{53}\) . We integrate this prior information by using their published posterior biomass estimate (1,013 kg ha \(^{- 1}\) ) as the mean of the prior for log of total biomass ( \(\alpha\) ; converted to g m \(^{- 2}\) ) (with standard deviation set at 1).” + +L560: “MacNeil et al. \(^{53}\) and our study employ comparable data (i.e. in situ counts of diurnally active, non- cryptic reef fish on forereef slopes, excluding sharks and semi- pelagics such as jacks). However, to account for potential differentiating factors between the studies, such as species filtering approaches, census method, or geographical representativeness, we inflated the prior standard deviation in the intercepts for our models by an order of magnitude. Model priors are detailed in Table S3 and plotted with unpopulated posterior intercept estimations in Fig. S4.” + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Figure S4 Biomass model prior distributions and unpopulated posterior intercept estimations for each trophic group of reef fish. Specified prior distributions for each biomass group are shown with the blue line. Posterior intercept distributions are shown in orange.
+ +R2.4: Lastly, I found the dataset included in this study to be impressive and I appreciate the efforts involved with synthesizing data from across 5 ecoregions. As the authors point out, each of the 5 ecoregions included in this study are exposed to different biophysical forces and levels of human disturbance. I understand the major aim of this study was to compare patterns of reef fish biomass across depth gradients for 5 ecoregions. However, I think it would be interesting to see if these patterns hold up within each ecoregion. I found the results from figure 5 to be interesting and wanted explore these results more. I am not suggesting that the authors create additional figures etc. However, I would recommend that the authors provide some additional discussion to expand on their findings. Are the patterns consistent within each ecoregion? + +We thank Reviewer #2 for this helpful suggestion - we agree that the consistency of the patterns among sites, islands, and ecoregions is interesting and warrants further discussion (also per R1.24). While our study primarily strives to quantify generality in depth effects across the dataset (L98 original manuscript; response to R3.3 and revised text L106- 113), we also emphasise the role of scale- dependent biophysical gradients that likely influence the spatial variation in fish biomass trends we observed across the Pacific (manuscript Fig.5, Tables S10 and S11). We have added discussion on the spatial heterogeneity observed across scales (detailed below) and the consistency of fish biomass depth zonation patterns across scales, including ecoregion (detailed below). The Reviewer's comment also inspired us to create an additional figure for the Supplemental Information (Fig. S3 below) to help the reader visualise spatial consistency, by showing depth effects at each of the study islands (within each ecoregion) and where depth zonation patterns deviated from the global depth effects. Broadly, few islands across the study ecoregions deviated from the global depth effect, indicating spatial consistency in the observed patterns. Though we note high levels of within- island variation in these estimates (indicated by the 95% credible intervals for each island), consistent with the high levels of observed site- level variation in the study (Fig.5, Table S10). + +Results: + +<--- Page Split ---> + +# nature portfolio + +L230: "The proportion of variation in fish biomass explained by each spatial scale, quantified by extracting the posterior standard deviations of these modelled random effects, varied among trophic fish groups (Fig. 5; Table S10 and S11; see Fig. S3 for variation in island- level depth effects among ecoregions)." + +## Discussion: + +L262: "These patterns hold true across the study area which spans distinct biogeographic regions, with high spatial consistency across islands and ecoregions (Fig. S3) despite varying spatial heterogeneity in fish biomass observed among trophic groups suggesting the role of distinct scale- dependent drivers." + +L275: "At geographically distinct unpopulated islands, we show that reef fish biomass of all broad trophic groups correlated predictably and relatively consistently across depth despite underlying variation in biophysical drivers known to affect standing reef fish biomass33,41,50." + +L372: "While there was minimal observed deviation from the global depth effect across the study islands and ecoregions, our results show that spatial variation in fish biomass—across site, island, and ecoregion scales—was differentially and unevenly distributed among trophic groups, underscoring the importance of scale of observation in ecological enquiry10,77." + +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale." + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Figure S3 Island-level depth effects on reef fish biomass among distinct study ecoregions (Samoa Islands; Phoenix/Tokelau/Northern Cook islands (P/T/NC); Mariana Islands; Line Islands; Hawaii Islands). Point estimates and associated \(95\%\) credible interval (CI) lines indicate the effect of increasing depth on fish biomass (proportional change) at each island (increase if \(>1\) , decrease with depth if \(<1\) ). The population status of islands is indicated by CI line thickness (thick CI, populated; thin CI, unpopulated). Pale shaded boxes underlying point estimates and CIs represent the average proportionate global effect of depth on biomass given the human population status and average bathymetric steepness, and are provided to aid visual assessment of spatial consistency in depth effects across the study. For example, at islands where depth effects on fish biomass follow the over-all global depth trend for a given trophic group, point estimates are positioned on top of the pale shaded boxes. Conversely, at islands where the effect of depth differs from the global effect, point estimates are positioned outside the shaded box (e.g., in Kauai, there is a greater observed decrease in the biomass density of primary consumers with increasing depth than the over-all effect of depth for that group at populated islands; in Tutuila there is a greater proportionate increase in planktivore biomass with increasing depth relative to the global depth effect for that group at populated islands).
+ +R2.5: Line 445 – (biomass density; g-m2) do you mean g m-2? + +<--- Page Split ---> + +Corrected, thanks. + +R2.6: Figures – In general I found the figures to be great. However, I am not sure if it was the download process but the figures appear to be low resolution and slightly blurry. I know a lot of work went into creating the figures and it would be good to confirm the quality for publication. + +We confirm that that all the figures have a minimum resolution of 300 dpi and saved at a maximum width of \(180\mathrm{mm}\) per the journal requirements. The figures presented in the original submission were lower resolution to reduce the manuscript file size (apologies). + +R2.7: Table S1 – Agujian categorized as “Populated”? I assume this is due to its proximity to Tinian and Saipan rather than its small resident population? + +This is correct. We classified islands as ‘populated’ based on having \(>50\) residents or located \(< 100\mathrm{km}\) from the nearest larger human settlement (sensu Williams et al. 2011; Williams et al. 2015), per L400- 403 (in original submission). + +- Williams et al. (2011). Differences in reef fish assemblages between populated and remote reefs spanning multiple archipelagos across the Central and Western Pacific. J Mar Biol 2011:826234. +- Williams et al. (2015). Local human impacts decouple natural biophysical relationships on Pacific coral reefs. Ecography 38(8), 751-761. + +## Reviewer #3 (Remarks to the Author): + +## R3.1: + +This well- written paper uses a uniquely large data set to examine the effects of depth on reef fish assemblages, and how population pressure influences this pattern. The paper uses modern analytical techniques to provide a convincing story of depth- related gradients for both major trophic groups and total biomass. + +The paper also includes an interesting finding of the role of reef bathymetry on reef fishes – the influence of reef steepness on fish assemblages intuitively might be expected, but has rarely been demonstrated at this scale and with such good bathymetry data. + +We thank Reviewer #3 for their positive comments and specific consideration of the overall position of our study in the context of the scope of Nature Ecology & Evolution. We are pleased they consider the manuscript to be well- written, employing a “uniquely large” and high- resolution dataset and “modern analyses” to provide a convincing story, with interesting results that have “rarely been demonstrated at this scale”. We have addressed the concerns raised, providing detailed explanation where possible and added clarification in this response document and in the revised manuscript, accordingly. + +R3.2: My issue with the paper is whether the story is sufficiently interesting for such a high- profile journal for two reasons: 1) the interest in revisiting basic depth gradients and examining homogenization by human impacts and 2) the lack of detailed covariates. The depth- related gradient of zones on reefs is indeed a well- described and accepted paradigm, although I would argue we now have enough descriptions of changes with depth that the ability to generalize is stronger than indicated here (first line of abstract, L77- 80). The homogenization of assemblages because of human impacts is also well known in a range of ecosystems (including on reefs). Therefore, it isn’t particularly surprising that the zonation is less clear near highly populated islands. I agree this hasn’t been demonstrated as clearly as in this study and it needs to be quantified, but I question + +<--- Page Split ---> + +whether this elevates the paper to one that should be published in Nature Ecology & Evolution. More fundamentally, I'm not sure how this would change our approach to studying or conserving reefs – the underlying ecological paradigm is clearly still true given the significance of the variables that change with increasing depth, and management is rarely zone specific. For example, any meaningful study of patterns of fish assemblages already controls for variable fishing pressure. Therefore, does this study really suggest that revisiting existing paradigms would change our approach to studying or managing ecosystems? + +We are disappointed (and sorry) that Reviewer #3 did not find the study as interesting as Reviewers #1 and #2. We are encouraged though that they found the demonstrated role of reef steepness on reef fishes interesting and novel in the scale at which it is demonstrated and that they recognise the uniquely large dataset and modern analytical techniques used. We are also pleased that the Reviewer recognises that while depth zonation is an accepted paradigm, as is the increasing propensity for ecological homogenisation under mounting human impacts, that these things need to be quantified and that we offer the clearest empirical demonstration of these to date. + +Nonetheless, the Reviewer's comment has highlighted that the broader context and importance of our enquiry could be made clearer for the reader. As described by Underwood et al. (2000), we cannot make progress on understanding processes in ecology until we have understood the patterns of taxa distribution across scales relevant to (and as large as) biophysical gradients that structure communities. This requires that for testing principle ecological theories, widely accepted or otherwise, observations must be made across large- scales (in time, or space, or both) (Underwood et al. 2000, Marquet 2009). Until recently, testing ecological theory at (and across) large enough scales simply has not been possible due to a lack of spatially comprehensive, standardised ecological data, and accessible statistical tools (Marquet 2009, Farley et al. 2018). The result is a potential bias in ecology, and coastal marine ecology in particular, against the development of understanding ecological generality (Underwood et al. 2000). In our study, we have tested the theory of ecological depth zonation for the first time across an ocean- basin scale, via access to standardised, high- resolution ecological and environmental data and a Bayesian hierarchical modelling approach. The results do not indicate that the management of reefs requires an overhaul in respect to identified patterns of depth zonation (nor does the discussion). Instead, we emphasise that many existing widely accepted ecological paradigms that have informed the management of natural systems, to date remain largely untested at sufficient scale. + +We thank the Reviewer for prompting us to revisit how we have described this fundamental premise for the paper. To better set- up this context for the reader, we have added to the introduction and discussion sections as follows: + +## Introduction: + +L43: "However, two fundamental issues limit the application of these paradigms. First, scale and predictability". We cannot understand ecological generality without observations of patterns spanning scales that are large enough to encompass relevant environmental gradients". Biophysical processes governing ecological organisation often occur across broad geographies (e.g. regional or continental10- 13), mediating local community structure', and introducing inherent scale- dependent spatial heterogeneity in observed ecological patterns14- 16. To assess generality of ecological theories, a large enough lens is required to capture processes occurring across a land- or seascape of local environmental variation12. Without it, perceptual bias is introduced where observed ecological patterns have a unique set of scale- specific causes and consequences10,13, and an understanding of ecological generality is left without empirical grounding2. + +L102: "Using a standardised Pacific- wide set of reef fish surveys49, composite data on bathymetric steepness, and hierarchical statistical models, we test for the first time whether + +<--- Page Split ---> + +depth zonation patterns are generalisable on tropical coral reefs across broad geographies, and compare patterns in locations with and without local human populations." + +## Discussion: + +L409: "We revisited ecological depth zonation—recognised as a fundamental structuring force of tropical coral reef communities over six decades ago but remains untested at scale7,26- 28 with two purposes: first, to test the generality of depth zonation of reef fish biomass for the first time across an ocean- basin scale; and second, to assess whether a zonation paradigm holds on reefs exposed to direct local human impacts." + +- Farley et al. (2018). Situating ecology as a big-data science: Current advances, challenges, and solutions. Bioscience 68, 563-576. +- Marquet. (2009). Macroecological perspectives on communities and ecosystems. in The Princeton guide to ecology (ed. Levin et al.), pp 386. +- Underwood et al. (2000). Observations in ecology: you can't make progress on processes without understanding the patterns. J Exp Mar Biol Ecol 250(1-2), 97-115. + +R3.3: More significantly this study feels like it misses opportunities to consider depth in the context of other variables, which potentially either excludes the chance of examining some interesting nuances in the data or possibly confounds the analyses. Firstly, human population pressure simply places reefs into one of two categories (populated or unpopulated) which seems overly simplified – why not consider population pressure as a continuous variable and look at more general trends and thresholds? Secondly, the analyses pool all sites from 'reef slopes', which standardizes the geomorphological zone but ignores any differences in benthic assemblages. Thus the reader is left wondering, for example, whether populated islands have more homogenous benthic assemblages across depth gradients that limits fish zonation. I'm sure the divers collected some benthic data, so why not include a basic metric like coral cover (or even habitat type) in the analyses to better isolate the depth signal? I appreciate that the aim was to examine a basic biophysical gradient (depth), but I feel the paper would have been more interesting to consider depth in the context of all the other variables that we know affect reef fishes. To me, one of the most interesting parts of this paper was examining the role of steepness on zonation and I kept wanting to know which other factors were critical in explaining the deviance in the data set. One of the benefits of modern ecology is the access to large-scale, reliable data layers of a range of covariates. However, this study doesn't use these rich sources of information to fill out the models of fish abundance. This is particularly problematic when considering spatial scales of variation (regions / islands / sites) – because the analyses only uses spatial scale in the model the Discussion has to be quite speculative about the actual drivers of these patterns. But had the models included covariates of e.g. net primary productivity, temperature, or wave exposure (all of which are relatively straightforward to obtain) – or island type (see Taylor et al, 2018, Ecography 38:520- 530 for why this variable might be critical) - then we could have seen actual correlations in the data rather than have to guess at what might be varying from island to island ("potential indicators", L210). In summary, had I been reviewing this for a general marine journal I would have suggested revisiting the analyses with some key additional covariates and perhaps human pressure as a continuous variable, but recommended the paper eventually be published as examining depth- related patterns with a data set of this size and examining the homogenizing role of human populations is worth quantifying. Plus the importance of steepness and the variation among trophic groups are interesting. However, the threshold for this journal is higher and I am not convinced that the underlying question is sufficiently interesting, especially given the relatively cursory treatment of other important covariates that limits understanding of which variables are critical at large scales. + +We agree - coral reefs are highly complex socio- ecological systems, structured by numerous socioeconomic and biogeophysical factors and processes (Cinner et al. 2016; Hughes et al. 2017; Williams et al. 2019). Well- described interacting natural biophysical processes and human impacts + +<--- Page Split ---> + +occur across a range of temporal and spatial scales to determine contemporary ecological organisation of organisms on reefs (Hughes et al. 1999; MacNeil et al. 2009; Cinner et al. 2013; Williams et al. 2015b; Richardson et al. 2018). For example, the Reviewer correctly highlights the critical role of live coral cover in habitat provisioning at small scales (from the coral colony scale to site scale; Richardson et al. 2017) for determining the distribution of reef fishes (Graham and Nash 2013; Williams et al. 2015b; Heenan et al. 2016). Similarly, numerous indices can be used as proxies to estimate the impacts of humans on reefs, including human population density, distance to market, 'gravity' (combining human population size and accessibility to reefs), fishing intensity, or a simple binary human population status index (Nadon et al. 2012; Williams et al. 2015b; Williams et al. 2015a; Cinner et al. 2016, 2018; Heenan et al. 2016). Biophysical factors such as temperature, wave energy, primary productivity, and island morphology are also known correlates with reef fish community structure (Williams et al. 2015b; Yeager et al. 2017; Heenan et al. 2019). Indeed, many of these covariates have been identified as critical structuring forces of reef fish assemblages across the Pacific study region (e.g. Williams et al. 2011; Williams et al. 2015b; Yeager et al. 2017; Heenan et al. 2019). + +Nonetheless, we a- priori designed our study to test a principle ecological theory which until now has been widely assumed but never tested at scale: The generality and predictive capacity of depth on reef fish biomass across an ocean- basin scale, in the presence vs absence of local human populations. We intentionally strove for simplicity by testing our hypotheses (with covariates: depth, steepness, binary 'humans/no humans') across a spatial extent characterised by known environmental and anthropogenic variation (Gove et al. 2013; Williams et al. 2015b). In doing so, we were able to quantify and attribute variation (sensu MacNeil et al. 2009) in our models to hierarchical spatial scales corresponding to known differential drivers of central and western Pacific reef fish assemblages (Williams et al. 2015b; Heenan et al. 2019). We agree with the Reviewer that it would be an interesting exercise to make use of the rich sources of detailed environmental and anthropogenic information available to explain as much variance in the fish biomass as possible. However, while unquestionably interesting, especially to us coral reef ecologists, this approach would achieve something quite different to an intentionally parsimonious test of ecological theory, with coral reefs as just a model system. Adding a range of known influential covariates would not help to reveal the generality of a depth effect. Rather, it would instead move the study towards using statistics to describe the 'whole system', mopping up unexplained noise in the data through the creation a complex 'causal salad' (McElreath 2020). Instead, we used a logically constructed framework of a- priori defined hypotheses with theoretical basis, with the primary goal of advancing conceptual understanding of an established ecological theory (sensu Underwood et al. 2000). + +Perhaps our overall intentions in terms of study design and goal were not clear enough, and so we have rephrased the introduction as follows to make our overarching goal and study objectives clearer (thanks for the prompt): + +L106: "To explicitly assess generality, we isolate the study focus to test a framework of a- priori defined hypotheses of the effects of depth, bathymetric steepness, and human population status on the biomass of reef fishes across a broad spatial extent characterised by known environmental and anthropogenic variation8,41. In doing so, we intentionally exclude other known influential biophysical and anthropogenic covariates on reef fish biomass (e.g. 8,50) to test the predictive capacity of depth at an ocean- basin scale on the biomass of fishes grouped by their major dietary sources51 – primary consumers, planktivores, secondary consumers, and piscivores." + +<--- Page Split ---> + +- Cinner et al. (2013). Global effects of local human population density and distance to markets on the condition of coral reef fisheries. Conserv Biol 27:453-458. +- Cinner et al. (2016). Bright spots among the world's coral reefs. Nature 535(7612), 416-419. +- Cinner et al. (2018). Gravity of human impacts mediates coral reef conservation gains. Proc Natl Acad Sci 115:E6116-E6125. +- Fox et al. (2018). Gradients in primary production predict trophic strategies of mixotrophic corals across spatial scales. Curr Biol 28:3355-3363.e4. +- Gove et al. (2013). Quantifying climatological ranges and anomalies for Pacific coral reef ecosystems. PLoS One 8:e61974. +- Graham and Nash (2013). The importance of structural complexity in coral reef ecosystems. Coral Reefs 32:315-326. +- Heenan et al. (2016). Natural bounds on herbivorous coral reef fishes. Proc R Soc B Biol Sci 283:20161716. +- Heenan et al. (2019). Natural variation in coral reef trophic structure across environmental gradients. Front Ecol Environ 18:69-75. +- Hughes et al. (1999). Patterns of recruitment and abundance of corals along the Great Barrier Reef. Nature 397:59-63. +- Hughes et al. (2017). Coral reefs in the Anthropocene. Nature 546(7656), 82-90. +- MacNeil et al. (2009). Hierarchical drivers of reef-fish metacommunity structure. Ecology 90:252-264. +- McElreath. (2020). Statistical rethinking: A Bayesian course with examples in R and Stan. Chapman and Hall/CRC. +- Nadon et al. (2012). Re-creating missing population baselines for Pacific reef sharks. Conserv Biol 26:493-503. +- Richardson et al. (2017). Cross-scale habitat structure driven by coral species composition on tropical reefs. Sci Rep 7(1), 7557. +- Richardson et al. (2018) Mass coral bleaching causes biotic homogenization of reef fish assemblages. Glob Chang Biol 24:3117-3129. +- Underwood et al. (2000). Observations in ecology: you can't make progress on processes without understanding the patterns. J Exp Mar Biol Ecol 250(1-2), 97-115. +- Williams et al. (2011). Differences in reef fish assemblages between populated and remote reefs spanning multiple archipelagos across the Central and Western Pacific. J Mar Biol 2011:826234. +- Williams et al. (2015a). Local human impacts decouple natural biophysical relationships on Pacific coral reefs. Ecography 38:751-761. +- Williams et al. (2015b) Human, oceanographic and habitat drivers of Central and Western Pacific coral reef fish assemblages. PLoS One 10:e0120516. +- Williams et al. (2019). Coral reef ecology in the Anthropocene. Funct Ecol 33(6), 1014-1022. +- Yeager et al. (2017). Scale dependence of environmental controls on the functional diversity of coral reef fish communities. Glob Ecol Biogeogr 26:1177-1189. + +## Decision Letter, first revision: + +14th April 2023 + +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +Dear Dr Richardson, + +Your manuscript entitled "Re- visiting the paradigm of depth zonation on contemporary coral reefs" + +<--- Page Split ---> + +has now been seen again by the same by 3 reviewers, whose comments are attached. As you can see from the reports, although the reviewers acknowledge the effort to revise the manuscript in response to their previous concerns, they continue to highlight a number of issues which will need to be addressed before we can offer publication in Nature Ecology & Evolution. We will therefore need to once again see your responses to the latest comment and to some editorial concerns, along with a revised manuscript, before we can reach a final decision regarding publication. + +In particular, we expect to only need to send your revised version back to Reviewer 2, and we hope that some additional explanation in the revised paper of your data choices and filtering, and exploration of potential covariance, will be satisfactory to that reviewer. + +We therefore invite you to revise your manuscript taking into account all reviewer and editor comments. Please highlight all changes in the manuscript text file in Microsoft Word format. + +We are committed to providing a fair and constructive peer- review process. 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As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. + +We look forward to seeing the revised manuscript and thank you for the opportunity to review + +<--- Page Split ---> + +# nature portfolio + +your work. + +## [REDACTED] + +Reviewers' comments: + +Reviewer #1 (Remarks to the Author): + +Dear Authors, + +I would like to thank you for the thorough revision you undertook to address mine and the other reviewers' comments. + +I have only small follow- up questions / suggestions to make based on your revisions. + +To better track of those, I am copying below my original comment, your responses, followed by my new response (it will be indicated by saying "Follow- up comment" in front of it. + +Alternatively, I have also attached a word doc where I am using a different colour font (dark blue) instead to mark my new comments. + +R1.3: Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups + +Thanks for this. For now, and to favour brevity in the title for the journal, we have not incorporated this suggestion into the title, but we have revised it to make it more concise: 'Revisiting the paradigm of depth zonation on contemporary coral reefs'. We agree with the Reviewer that further clarification of the term zonation is needed early in the introduction. In addition to the existing definition of ecological zonation as "the distribution of organisms across space" (L58), we have added a more detailed definition of 'depth zonation' at first mention as follows: + +L67: "Here we revisit this basic principle in the context of depth zonation of tropical coral reef communities- the distribution of reef fish biomass among distinct trophic groups." + +Follow- up comment: I still think that it would be better if the zonation refers to trophic groups, and specifically that of reef fish, so the title could be changed to: "Re- visiting the paradigm of trophic group depth zonation on coral reef fish". + +However, no strong feelings there, as I know that papers in high- impact journals tend to favour generic all- encompassing titles. + +## Results + +R1.10: Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +To aid clearer visualisation of the scaled effects of depth, bathymetric steepness, and human population status on the positive reef fish biomass data, the effect estimates of hurdle components (presence- absence) from the piscivore and planktivore models were not included in Fig. 1. Including them, as presented in Fig. S1, clusters the effect estimates and their percentiles such that the reader may be less able to effectively interpret relative effect size. However, we will gladly exchange Fig. 1 for Fig. S1 on request. + +Follow- up comment: I think it's fine to keep Fig. 1 and Fig. S1 separate, but you should only report the effect estimates of hurdle components in Fig. S1, since the top half is a repetition of Fig. 1. Unless it's required for interpreting the figure. + +<--- Page Split ---> + +# nature portfolio + +## Discussion + +R1.18: Lines 304- 306: Can you expand a little bit more here? Do you mean that below \(30m\) steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +We see that this sentence was potentially unclear. Studies looking at depth zonation beyond the \(0 - 30m\) limit in our study report contrasting peaks in abundance of piscivores and planktivores. For example, at Linden Bank, a submerged shoal on the outer shelf of the Great Barrier Reef, reported dominance of piscivores (and mobile invertivores) between \(50 - 70m\) depth (Scott et al. 2022). In contrast, the proportion of planktivores on forereefs at Enewetak Atoll in the Marshall Islands increased from \(50\%\) at \(30m\) to \(>90\%\) from \(90 - 200m\) , which the authors suggest may relate to upwelling processes increasing plankton and shallow reef productivity (Thresher and Colin 1986). In L304- 306, we suggest that these variable peaks in trophic group biomass at mesophotic depths are potentially indicative of spatial variation in upwelling, which could be linked- among other oceanographic factors- to variable local bathymetric steepness among those study locations. To make this clearer, we have revised the manuscript as follows: + +L325: "Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the \(30m\) limit of this study54,67, which may be indicative of spatial variation in upwelling, potentially linked to- among other oceanographic factors- variable local bathymetric steepness among those study locations." + +- Thresher and Colin. (1986). Trophic structure, diversity and abundance of fishes of the deep reef (30-300m) at Enewetak, Marshall Islands. Bull Mar Sci 38, 253-272. +- Scott et al. (2022). Variation in abundance, diversity and composition of coral reef fishes with increasing depth at a submerged shoal in the northern Great Barrier Reef. Rev Fish Biol Fish 32, 941-962. + +Follow- up comment: I would perhaps also touch on the effect of changes in benthic community composition in reef fish trophic structure, similar to some of the comments of Reviewer 3 who asked for the role of benthos in explaining reef- fish patterns. For example, see loss of concurrent loss of herbivorous fish and hard corals in Bermuda (Stefanoudis et al. 2019 - paper you already cite); or the one from Russ et al. 2021 showing how coral cover affects fish trophic structuring in the shallows + +Russ, G.R., Rizzari, J.R., Abesamis, R.A. and Alcala, A.C., 2021. Coral cover a stronger driver of reef fish trophic biomass than fishing. Ecological Applications, 31(1), p.e02224. + +R1.24: General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +Thanks to the Reviewer for highlighting where further discussion on cross- scale spatial variation in fish biomass patterns would improve the manuscript. Coral reefs are considered to be highly hierarchical in structure, determined by processes occurring at multiple spatial and temporal scales (Hughes et al. 1999, MacNeil et al. 2009). As the Reviewer rightly highlights, within this hierarchical context, management and governance efforts are considered most effective when carried out at scales aligning with scales of ecological heterogeneity (Cumming and Dobbs 2020). We describe this in detail in the paragraph L335- 345, and we link our results to scaled management and conservation efforts in L361- 368 in the original manuscript. However, we now provide additional discussion exploring the relative differences in variation observed across scales, notably discussing the relatively lower variation observed at the island- scale as follows: + +<--- Page Split ---> + +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale. In this context, our findings suggest that management of primary consumers, piscivores, total standing biomass, and especially secondary consumers might achieve satisfactory outcomes at local within- island scales with no- take areas80, habitat restoration, or better regulated destructive human activities79. Local management of planktivores is no doubt also important34. But, given the potential influence of regional- scale drivers on planktivore biomass production and the importance of this group as the prey base for higher trophic levels32, more nuanced, region- specific targets for recovery81 or take of planktivores may be advisable in areas of naturally lower primary production." + +Follow- up comment: In the last sentence after ref. 81, do you mean "or no- take zones of..." I would also ask the authors to consider the recent findings of Pinheiro et al. 2023. Pinheiro, H.T., MacDonald, C., Quimbayo, J.P., Shepherd, B., Phelps, T.A., Loss, A.C., Teixeira, J.B. and Rocha, L.A., 2023. Assembly rules of coral reef fish communities along the depth gradient. Current Biology. + +Based on this, the statement in lines 265- 267 could perhaps be modified. + +## Methods + +R1.25: Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +Thanks for this important consideration. The National Oceanic and Atmospheric Administration (NOAA) has multiple trained fish survey divers who conduct in situ observations across sampling cruises, across distinct ecoregions and years. Divers must have a minimum of 30 underwater visual fish survey census dives conducted prior to joining a monitoring cruise. In addition, to ensure consistency in observer species identification and size estimation, NOAA employs extensive training, testing, and technical validation protocols both outside of the cruise period and during (detailed in Heenan et al. 2017). These protocols address the potential for intra- and inter- diver variability in two ways: + +1. New and experienced divers receive full training in fish identification and survey protocol, in classroom and in-water sessions; prior to each survey cruise, all divers must accurately identify \(>90\%\) of regional-specific fish species in a test that is specifically weighted towards rare species and those that have conspecifics with similar appearance. +2. For the timeframe of the data used here, between cruises divers conducted in-water training exercises to practice survey protocol, fish identification and fish size estimation (see response to comment R1.27 for detail on size estimation protocol and technical validation). + +During the cruises, there are typically 4- 10 fish survey divers who routinely discuss and compare species identification and sizes immediately after a survey, and during data entry. Diver pairs are continually rotated, and diver performance is estimated as the difference between the estimates of each diver and those of their dive partner at each site, calculated for total fish biomass, species richness, and body- size distributions of commonly observed species. As divers survey adjacent cylinders on the reef (i.e. not identical areas of the reef), real differences between diver observations are expected. But the diver performance estimate is measured to detect potential consistent bias made by each diver (i.e. if there is no consistent bias, the median difference with their buddy partner should be close to zero). Diver performance is measured every few days during survey cruises to allow for early detection of observer error (Heenan et al. 2017). + +In addition to these technical validation protocols, we included a group- level random intercept for 'diver identity' in all of our statistical models of fish biomass to account for any remaining effect of + +<--- Page Split ---> + +# nature portfolio + +observer bias. By assuming inherent correlations among divers and their observations that affect the estimated means and associated errors, we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) (sensu Macneil et al. 2015 Nature). + +- Heenan et al. (2017). Long-term monitoring of coral reef fish assemblages in the Western central pacific. Sci Data 4(1), 1-12. + +- MacNeil et al. (2015). Recovery potential of the world's coral reef fishes. Nature 520(7547), 341-344. + +We have revised the manuscript as follows to provide the required additional information: + +L457: "Surveys were conducted by multiple observers across the study ecoregions and years. NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation49. Full details on SPC survey methods and technical validation steps are available in [49]. To further mitigate any confounding effect of observer bias among fish surveys, we included 'diver identity' as a random intercept in all statistical models (described below) (sensu53)." L514: "A random intercept for 'diver identity' was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations (sensu53)." + +Follow- up comment: Great, thanks for the explanation and additional information. Based on the revised text above, presumably the multiple observer effect came up as no significant? If so, then perhaps worth mentioning here, and explain that because of this it won't be discussed further in the paper. + +Reviewer #2 (Remarks to the Author): + +This is my second review of the manuscript submitted by Richardson and coauthors entitled: "Revisiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECoLEVOL- 221117855). During my initial review, I felt that the manuscript was well written and provided interesting results. I provided several recommendations for the authors to consider during the revision process. Overall, I appreciate the time and effort that the authors put in to address my recommendations. I know how much time it takes to incorporate suggestions and provide thoughtful responses. In general, I feel that authors made an effort to address my recommendations and made adequate revisions to the manuscript. The theme and structure of the manuscript remains consistent with the initial submission and continues to reinforce what has been shown in other geographies regarding depth zonation patterns in coral reef fishes. The revised version contributes to this body of work by examining these patterns across ecoregions. However, after revisiting this manuscript and evaluating the authors' responses I have a couple additional concerns and recommendations that I would like the authors to consider before the manuscript is considered for publication. + +First, one of my recommendations during the initial review focused on the process by which reef fish taxa were filtered and selected in this study. The authors provided a detailed response to my initial comment citing a number of publications to justifying why certain piscivores or apex predator groups were omitted from this study. I am familiar with these studies to describe movement patterns or behavioral observations of particular taxa; as well as the studies to describe patterns of reef fish assemblage structure at local, regional, or global scales. In the cited studies describing fish assemblage structure, authors chose to exclude or filter certain taxa based on a priori or a posteriori knowledge of coral reef fishes. In the case of a priori filtering or selection, fish taxa are excluded during the initial study design and in- situ surveys due to methodological limitations of observing certain species or to account for observer inexperience. For example, some monitoring efforts include a subset of large- bodied species or certain ecologically important taxa in + +<--- Page Split ---> + +the survey design to reduce the number of species facilitate observers from across a range of experience levels. In studies using a posteriori filtering, species or groups of taxa are excluded during the analysis phase due to limitations in the dataset or to facilitate data comparability across multiple studies using different sampling methodologies. + +However, in this study submitted by Richardson and coauthors, the authors chose to filter taxa a posteriori to remove non- reef associated taxa and species that are known to exhibit 'mobbing' behavior in certain locations. While I understand the authors motivation for filtering groups of fishes, it is unclear why entire groups of fishes were omitted when this behavior is documented for only a handful of species. For example, the authors provide a few site- specific or regional examples from the literature where certain taxa (i.e., Caranx ignobilis and Carcharhinus amblyrhynchos) are known to be abundant and exhibit 'mobbing' behavior in the absence of human fishing pressure. Further, the authors provide an example of personal observations of another common predator (i.e., Lutjanus bohar) exhibiting 'mobbing behavior. However, the authors chose not to omit this species or group (snappers) because the behavior was observed in a region not included in this study. However, L. bohar, it is one of the most common and formattable predators on found across coral reefs of the Pacific and it is likely that the observed behavior is limited only to the Line Islands. Regardless, these examples are either species- specific or region- specific. I am therefore finding the authors filtering or selection process to the arbitrary and flawed. I am curious to know why the authors chose to exclude entire groups of ecologically important fishes rather than be more selective in their filtering especially when the groups included in the filtering include upwards of 100 species within each group and 'mobbing' behavior is generally only observed in a handful of species and only in a few locations. I don't want to be difficult but want to encourage the authors as they move forward in their research endeavors to be thoughtful of their selection process when characterizing fish assemblages and describing patterns of reef fishes across coral reef communities. + +Second and related to the first, is based on the quality of the dataset included in this study. The authors point out that the reef survey data used in this study were collected by highly skilled divers from NOAA. They point out that divers responsible for collecting quantitative in situ data are trained to estimate the size and abundance of all diurnal and non- cryptic fishes observed in the survey area and make efforts to ensure data are collected with consistency and without biases. I am curious to know why the authors chose to filter or select certain taxa when NOAA invests significant resources into training divers on the survey methods to record all taxa. This includes training divers to avoid double counting individuals entering the survey area or 'mobbing divers. Further, the standardization of survey protocols across regions and time periods represents one of the most comprehensive datasets for coral reef fishes. e classes. Did the authors attempt perform an initial analysis using all taxa before enlisting filtering? Again, simply picking and choosing to omit ecologically important species or groups likely has important implications to the results. Third, after reading through the results and examining the figures in more detail, I am curious to know if the authors have considered the non- independence of the predictors (Steepness and Depth). Based on the figures it seems as though depth and steepness covary? Is this a result of methodological limitations where it is not possible to have to have a survey instance where data are collected a t site that both steep and shallow? It seems as though this could lead to a biased interpretation of the data? Please consider this potential non- independence of the predictors. Lastly, the authors provide some interpretation of the results in the discussion (lines 360- 375) where they posit that the spatial variance of the observations was greatest at the site- scale.. indicating that intra- island heterogeneity in habitat availability. However, I encourage the authors to reconsider this statement. Coral reef fish data are inherently noisy and variable at the site and temporal scale. For example, if the authors were to conduct surveys at a single site multiple times the estimates would be highly variable among samples. Therefore the observed results are likely due to variability of the observed data and not directly linked to the local dynamics as they suggest. + +Reviewer #3 (Remarks to the Author): + +The authors make a vigorous defense of their paper, and to reiterate this is a comprehensive study + +<--- Page Split ---> + +# nature portfolio + +of the impacts of depth on fish assemblages - and the impacts of humans on that pattern - and I will cite it when I need to make that point. The problem of stripping away many of the complexities (how does the role of depth compare to other covariates? What is the relationship between growing population size and the depth pattern (not just unpopulated / populated)?) is that the paper lives or dies based on interest in the core question being tested - and I'm not convinced that the relationship between fish and depth is as interesting a component of ecological theory as the authors do. Everything we know about fish assemblages (including many zonation papers) suggests that depth is critical and I don't think anyone would argue that depth isn't important. So while this is a comprehensive treatment of the question, and does provide new insights into human impacts and the role of bathymetric steepness, I still struggle to see this as a Nature Ecology & Evolution paper. The paper still makes me wonder about the mechanism (what are fish actually responding to since depth is a proxy for a range of drivers?), what is the relative importance of human direct effects (fishing) versus indirect effects (e.g. affecting coral cover or removing nursery habitats), are there any systematic differences between populated and unpopulated islands, and what is driving the patterns seen at the different spatial scales. But I can see that this concern isn't shared by the other reviewers and I appreciate that novelty is in the eye of the beholder. So given that there aren't any critical flaws in the analyses I think at this point I will defer to the Editor to judge the value of the new insights provided by this paper. + +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*END\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\* + +## Author Rebuttal, first revision: + +## Reviewer #1 (Remarks to the Author): + +I would like to thank you for the thorough revision you undertook to address mine and the other reviewers' comments. I have only small follow- up questions / suggestions to make based on your revisions. To better track of those, I am copying below my original comment, your responses, followed by my new response (it will be indicated by saying "Follow- up comment" in front of it. + +Thanks to Reviewer #1 again for their time and thoughtful consideration on our article. The feedback and suggestions have made valuable improvements to the manuscript. + +R1.3: Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups + +Thanks for this. For now, and to favour brevity in the title for the journal, we have not incorporated this suggestion into the title, but we have revised it to make it more concise: 'Re- visiting the paradigm of depth zonation on contemporary coral reefs'. We agree with the Reviewer that further clarification of the term zonation is needed early in the introduction. In addition to the existing definition of ecological zonation as "the distribution of organisms across space" (L58), we have added a more detailed definition of 'depth zonation' at first mention as follows: + +L67: "Here we revisit this basic principle in the context of depth zonation of tropical coral reef communities—the distribution of reef fish biomass among distinct trophic groups." + +<--- Page Split ---> + +# nature portfolio + +Follow- up comment: I still think that it would be better if the zonation refers to trophic groups, and specifically that of reef fish, so the title could be changed to: "Re- visiting the paradigm of trophic group depth zonation on coral reef fish". However, no strong feelings there, as I know that papers in high- impact journals tend to favour generic all- encompassing titles. + +Thanks for this alternative suggestion. Our preferred title is the more concise version 'Re- visiting the paradigm of depth zonation on contemporary coral reefs' and we think that because we clarify this point early on in the text, readers will understand early that it is trophic group biomass zonation we refer too. If preferred by the reviewer and editor(s), we will revisit the title to suggest an alternative. + +## Results + +R1.10: Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +To aid clearer visualisation of the scaled effects of depth, bathymetric steepness, and human population status on the positive reef fish biomass data, the effect estimates of hurdle components (presence- absence) from the piscivore and planktivore models were not included in Fig. 1. Including them, as presented in Fig. S1, clusters the effect estimates and their percentiles such that the reader may be less able to effectively interpret relative effect size. However, we will gladly exchange Fig. 1 for Fig. S1 on request. + +Follow- up comment: I think it's fine to keep Fig. 1 and Fig. S1 separate, but you should only report the effect estimates of hurdle components in Fig. S1, since the top half is a repetition of Fig. 1. Unless it's required for interpreting the figure. + +Thanks. We have revised Fig. S1 to present only the effect estimates of the hurdle components as suggested. + +## Discussion + +R1.18: Lines 304- 306: Can you expand a little bit more here? Do you mean that below 30m steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +We see that this sentence was potentially unclear. Studies looking at depth zonation beyond the 0- 30 m limit in our study report contrasting peaks in abundance of piscivores and planktivores. For example, at Linden Bank, a submerged shoal on the outer shelf of the Great Barrier Reef, reported dominance of piscivores (and mobile invertivores) between 50- 70 m depth (Scott et al. 2022). In contrast, the proportion of planktivores on forereefs at Enewetak Atoll in the Marshall Islands increased from 50% at 30 m to >90% from 90- 200 m, which the authors suggest may relate to upwelling processes increasing plankton and shallow reef productivity (Thresher and Colin 1986). In L304- 306, we suggest that these variable peaks in trophic group biomass at mesophotic depths are potentially indicative of spatial variation in upwelling, which could be linked- among other oceanographic factors- to variable local bathymetric steepness among those study locations. To make this clearer, we have revised the manuscript as follows: + +<--- Page Split ---> + +L325: “Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the \(30\mathrm{m}\) limit of this study \(^{54,67}\) , which may be indicative of spatial variation in upwelling, potentially linked to–among other oceanographic factors–variable local bathymetric steepness among those study locations.” + +- Thresher and Colin. (1986). Trophic structure, diversity and abundance of fishes of the deep reef (30–300m) at Enewetak, Marshall Islands. Bull Mar Sci 38, 253–272. + +- Scott et al. (2022). Variation in abundance, diversity and composition of coral reef fishes with increasing depth at a submerged shoal in the northern Great Barrier Reef. Rev Fish Biol Fish 32, 941–962. + +Follow- up comment: I would perhaps also touch on the effect of changes in benthic community composition in reef fish trophic structure, similar to some of the comments of Reviewer 3 who asked for the role of benthos in explaining reef- fish patterns. For example, see loss of concurrent loss of herbivorous fish and hard corals in Bermuda (Stefanoudis et al. 2019 – paper you already cite); or the one from Russ et al. 2021 showing how coral cover affects fish trophic structuring in the shallows + +Russ, G.R., Rizzari, J.R., Abesamis, R.A. and Alcala, A.C., 2021. Coral cover a stronger driver of reef fish trophic biomass than fishing. Ecological Applications, 31(1), p.e02224. + +Thanks for this suggestion. We have revised the manuscript as follows: + +L315: “Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the \(30\mathrm{m}\) limit of this study \(^{55,68}\) . These variable peaks may be indicative of spatial variation in upwelling, potentially linked to–among other oceanographic factors and associated changes in benthic composition \(^{38}\) – differences in local bathymetric steepness among those study locations.” + +The journal limit is 100 references. As we now cite 101 references and the Stefanoudis et al. (2019) study supports the statement, we have elected not to include the additional reference of Russ et al. (2021) for now. But we are grateful for the recommendation, and will be happy to include it if required. + +R1.24: General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +Thanks to the Reviewer for highlighting where further discussion on cross- scale spatial variation in fish biomass patterns would improve the manuscript. Coral reefs are considered to be highly hierarchical in structure, determined by processes occurring at multiple spatial and temporal scales (Hughes et al. 1999, MacNeil et al. 2009). As the Reviewer rightly highlights, within this hierarchical context, management and governance efforts are considered most effective when carried out at scales aligning with scales of ecological heterogeneity (Cumming and Dobbs 2020). We describe this in detail in the paragraph L335- 345, and we link our results to scaled management and conservation efforts in L361- 368 in the original manuscript. However, we now provide additional discussion exploring the relative differences in variation observed across scales, notably discussing the relatively lower variation observed at the island- scale as follows: + +<--- Page Split ---> + +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale. In this context, our findings suggest that management of primary consumers, piscivores, total standing biomass, and especially secondary consumers might achieve satisfactory outcomes at local within- island scales with no- take areas80, habitat restoration, or better regulated destructive human activities79. Local management of planktivores is no doubt also important34. But, given the potential influence of regional- scale drivers on planktivore biomass production and the importance of this group as the prey base for higher trophic levels32, more nuanced, region- specific targets for recovery81 or take of planktivores may be advisable in areas of naturally lower primary production." + +Follow- up comment: In the last sentence after ref. 81, do you mean "or no- take zones of...". + +Thanks for asking for clarification here. In the sentence after ref. 81, in fact we mean 'take' to refer to catch- limits. We have revised the manuscript accordingly: + +L393: "...more nuanced, region- specific targets for recovery82 or catch of planktivores may be advisable in areas of naturally lower primary production." + +I would also ask the authors to consider the recent findings of Pinheiro et al. 2023. + +Pinheiro, H.T., MacDonald, C., Quimbayo, J.P., Shepherd, B., Phelps, T.A., Loss, A.C., Teixeira, J.B. and Rocha, L.A., 2023. Assembly rules of coral reef fish communities along the depth gradient. Current Biology. + +Based on this, the statement in lines 265- 267 could perhaps be modified. + +Thanks too for highlighting the recent paper by Pinheiro et al. (2023) which has come out since our previous revision and response. Their findings are relevant and complimentary to ours of course, and as such we now refer to the study in the context of our findings as follows: + +L69: "Depth was recognised as a fundamental structuring force over six decades ago7,26- 28, and recently shown to be an important predictor of fish diversity as fewer species are found on deeper reefs29." + +L252: "Recent work details declining patterns of reef fish diversity with increasing depth from the shallows to the mesophotic zone (max 150 m depth)29. We build on these findings by, to our knowledge, revealing for the first time a common degree of ecological organisation in relation to both depth and bathymetric steepness across geographically distinct reefs." + +<--- Page Split ---> + +R1.25: Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +Thanks for this important consideration. The National Oceanic and Atmospheric Administration (NOAA) has multiple trained fish survey divers who conduct in situ observations across sampling cruises, across distinct ecoregions and years. Divers must have a minimum of 30 underwater visual fish survey census dives conducted prior to joining a monitoring cruise. In addition, to ensure consistency in observer species identification and size estimation, NOAA employs extensive training, testing, and technical validation protocols both outside of the cruise period and during (detailed in Heenan et al. 2017). These protocols address the potential for intra- and inter- diver variability in two ways: + +1. New and experienced divers receive full training in fish identification and survey protocol, in classroom and in-water sessions; prior to each survey cruise, all divers must accurately identify \(>90\%\) of regional-specific fish species in a test that is specifically weighted towards rare species and those that have conspecifics with similar appearance. + +2. For the timeframe of the data used here, between cruises divers conducted in-water training exercises to practice survey protocol, fish identification and fish size estimation (see response to comment R1.27 for detail on size estimation protocol and technical validation). + +During the cruises, there are typically 4- 10 fish survey divers who routinely discuss and compare species identification and sizes immediately after a survey, and during data entry. Diver pairs are continually rotated, and diver performance is estimated as the difference between the estimates of each diver and those of their dive partner at each site, calculated for total fish biomass, species richness, and body- size distributions of commonly observed species. As divers survey adjacent cylinders on the reef (i.e. not identical areas of the reef), real differences between diver observations are expected. But the diver performance estimate is measured to detect potential consistent bias made by each diver (i.e. if there is no consistent bias, the median difference with their buddy partner should be close to zero). Diver performance is measured every few days during survey cruises to allow for early detection of observer error (Heenan et al. 2017). + +In addition to these technical validation protocols, we included a group- level random intercept for 'diver identity' in all of our statistical models of fish biomass to account for any remaining effect of observer bias. By assuming inherent correlations among divers and their observations that affect the estimated means and associated errors, we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) (sensu Macneil et al. 2015 Nature). + +- Heenan et al. (2017). Long-term monitoring of coral reef fish assemblages in the Western central pacific. Sci Data 4(1), 1-12. + +- MacNeil et al. (2015). Recovery potential of the world's coral reef fishes. Nature 520(7547), 341-344. + +We have revised the manuscript as follows to provide the required additional information: + +L457: "Surveys were conducted by multiple observers across the study ecoregions and years. NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation". Full details on SPC survey methods and technical validation steps are available in [49]. To further mitigate any confounding effect + +<--- Page Split ---> + +of observer bias among fish surveys, we included ‘diver identity’ as a random intercept in all statistical models (described below) \((sensu^{53})\) .” + +L514: “A random intercept for ‘diver identity’ was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations \((sensu^{53})\) .” + +Follow- up comment: Great, thanks for the explanation and additional information. Based on the revised text above, presumably the multiple observer effect came up as no significant? If so, then perhaps worth mentioning here, and explain that because of this it won’t be discussed further in the paper. + +Thanks to the Reviewer for highlighting where additional clarification would be useful in our description of how any potential residual observer effect was handled. The structure of these models allows us to conservatively assume (and control for) an observer effect, rather than testing for one. By assuming an inherent non- independence of observed fish counts by individual divers, we then control for (centre) any effects of observers to then isolate the estimated population level effects on fish biomass. Apologies for not including this important detail in the previous revisions. We have added it to the newly revised manuscript as follows: + +L516: “A group- level random intercept for ‘diver identity’ was included to account for the potential effect of individual observer bias. By assuming an inherent non- independence within divers and their observations that might affect the estimated means and associated errors of fish biomass \((sensu^{54})\) , we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) \((sensu^{54})\) . More broadly, by controlling these potential sources of variability, we can more accurately test a- priori hypotheses about ecological zonation occurring across spatial scales and with greater inferential strength \(^{45}\) .” + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +This is my second review of the manuscript submitted by Richardson and coauthors entitled: "Revisiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECOLEVOL- 221117855). During my initial review, I felt that the manuscript was well written and provided interesting results. I provided several recommendations for the authors to consider during the revision process. Overall, I appreciate the time and effort that the authors put in to address my recommendations. I know how much time it takes to incorporate suggestions and provide thoughtful responses. In general, I feel that authors made an effort to address my recommendations and made adequate revisions to the manuscript. The theme and structure of the manuscript remains consistent with the initial submission and continues to reinforce what has been shown in other geographies regarding depth zonation patterns in coral reef fishes. The revised version contributes to this body of work by examining these patterns across ecoregions. However, after revisiting this manuscript and evaluating the authors' responses I have a couple additional concerns and recommendations that I would like the authors to consider before the manuscript is considered for publication. + +We thank the Reviewer again for generously providing their time and continued careful consideration of our article. We have addressed the additional concerns and recommendations as follows. + +R.2ii.1: First, one of my recommendations during the initial review focused on the process by which reef fish taxa were filtered and selected in this study. The authors provided a detailed response to my initial comment citing a number of publications to justifying why certain piscivores or apex predator groups were omitted from this study. I am familiar with these studies to describe movement patterns or behavioral observations of particular taxa; as well as the studies to describe patterns of reef fish assemblage structure at local, regional, or global scales. In the cited studies describing fish assemblage structure, authors chose to exclude or filter certain taxa based on a priori or a posteriori knowledge of coral reef fishes. In the case of a priori filtering or selection, fish taxa are excluded during the initial study design and in-situ surveys due to methodological limitations of observing certain species or to account for observer inexperience. For example, some monitoring efforts include a subset of large-bodied species or certain ecologically important taxa in the survey design to reduce the number of species facilitate observers from across a range of experience levels. In studies using a posteriori filtering, species or groups of taxa are excluded during the analysis phase due to limitations in the dataset or to facilitate data comparability across multiple studies using different sampling methodologies. + +However, in this study submitted by Richardson and coauthors, the authors chose to filter taxa a posteriori to remove non- reef associated taxa and species that are known to exhibit 'mobbing' behavior in certain locations. While I understand the authors motivation for filtering groups of fishes, it is unclear why entire groups of fishes were omitted when this behavior is documented for only a handful of species. For example, the authors provide a few site- specific or regional examples from the literature where certain taxa (i.e., Caranx ignobilis and Carcharhinus amblyrhynchos) are known to be abundant and exhibit 'mobbing' behavior in the absence of human fishing pressure. Further, the authors provide an example of personal observations of another common predator (i.e., Lutjanus bohar) exhibiting 'mobbing behavior. However, the authors chose not to omit this species or group (snappers) because the behavior was observed in a region not included in this study. However, L. bohar, it is one of the most common and formattable predators on found across coral reefs of the + +<--- Page Split ---> + +Pacific and it is likely that the observed behavior is limited only to the Line Islands. Regardless, these examples are either species- specific or region- specific. I am therefore finding the authors filtering or selection process to the arbitrary and flawed. I am curious to know why the authors chose to exclude entire groups of ecologically important fishes rather than be more selective in their filtering especially when the groups included in the filtering include upwards of 100 species within each group and 'mobbing' behavior is generally only observed in a handful of species and only in a few locations. I don't want to be difficult but want to encourage the authors as they move forward in their research endeavors to be thoughtful of their selection process when characterizing fish assemblages and describing patterns of reef fishes across coral reef communities. + +We thank Reviewer #2 for these additional contributions. First, apologies for not clarifying sooner that the filtering approach omitted 16 species from the families Carcharhinidae, Carangidae, and Sphyrnidae, as opposed to hundreds as feared. It was an oversight to not make that explicit in the original submission. This has been corrected as detailed below, in the methods text and by including a table in the supplementary information (Table S12). + +Nonetheless, to address the reviewer's other concerns: we agree that piscivorous fishes such as sharks and large roving jacks are ecologically important to reef trophodynamics (Boaden and Kingsford 2015; Roff et al. 2016), as are other excluded groups such as cryptobenthic reef fishes (Depczynski and Bellwood 2003). We also acknowledge that while the filtering of sharks and large- bodied semi- pelagic piscivores is commonly applied (Table R2 in Response #1) due to well evidenced systematic bias (e.g. Parrish and Boland 2004; Williams et al. 2015), this approach is not used universally (e.g. DeMartini et al. 2008; Friedlander et al. 2010; Pinheiro et al. 2023; though we note that these cited examples are based on typically more mobile diver transect surveys rather than stationary point count surveys in our study). Nevertheless, the resulting dichotomy in how in situ fish assemblage survey data are handled within our field represents an interesting, relevant (and/or potentially frustrating - apologies!) area of discussion about when conservative exclusion of groups mitigates known systematic bias and/or introduces further bias as an artifact of the filtering process. + +In consideration of this, we have thought through some options as follows: Option 1) species- specific filtering (opposed to group filtering based on shared traits such as body- size, mobility, curiosity, and trophic position; Kulbicki 1998). This approach would require a priori evidence of species- specific mobbing behaviour, and/or an observed statistical threshold that we (arguably arbitrarily) deem to represent a mobbing event. Unfortunately, both these data handling choices would more likely produce an artifact than does filtering by group to remove any potential mobbers. The most probable issue we foresee from this individual species approach is false negative error, i.e. leaving in a true mobbing species and having that inclusion artificially inflate the piscivore biomass for unpopulated islands compared to populated. In other words, individual species may display unknown and idiosyncratic patterns of spatial variability in mobbing behaviour that do not reach our radar with this approach and therefore we do not see any defensible way to filter some, but not all species within the group. Option 2) compare candidate piscivore biomass models, both with and without the filtered group of sharks, jacks, barracuda to assess whether and how observed patterns change as result of filtering. + +Due to false negative error issues related to Option 1, we elected to pursue Option 2. We ran the analyses for the piscivore biomass group, both with and without the filtered group. The result was comparable observed zonation patterns in piscivore biomass, suggesting that the reported patterns described in our study are not an artifact of filtering (Fig. S4). However, the model outputs of population level effects of depth and bathymetric steepness between populated and unpopulated + +<--- Page Split ---> + +# nature portfolio + +locations showed much greater biomass estimates at unpopulated than at populated islands where biomass remained comparable despite differences in filtering. We derived from this that while there may indeed be simply more of these large, roving piscivores on uninhabited reefs (Asher et al. 2017), we are unable to reliably distinguish inflated observation rates due to sheer greater abundance from systematic detectability bias associated with the specific survey method across unpopulated versus populated locations in the study (Parrish and Boland 2004; Williams et al. 2015). Therefore, we determine that the broad observed zonation patterns do not substantially vary as an artifact of filtering (and would unlikely show completely new patterns by including a subset of species). As a result, we can mitigate potential issues of survey bias by conservatively excluding this group to produce more cautious estimates of piscivore biomass patterns (Fig. S4). + +We recognise that additional explanation and justification of our data filtering to make this clearer is needed, and have added model output figures with both filtered and unfiltered piscivore biomass data to the supplementary information document (Fig. S4), presenting posterior estimates for population- level effects (depth, steepness) between populated and unpopulated locations: + +L463: "Taxa that are not typically reef- associated were excluded from the analyses, including tuna, bonito, and milkfish (families Chandiae, Myliobatidae, Scombridae; Table S12). Sixteen species of shark, jack, and barracuda (families Carcharhinidae, Carangidae, Sphyrnidae) were also excluded from the analyses as these highly mobile, large- bodied, roving piscivores are known to be affected by the presence of stationary divers, typically resulting in systematic over- inflation of visual survey density estimates86 (sensu8,54; Table S12)." + +L472: "Zonation patterns in piscivore biomass were comparable with and without this filtering approach. This suggests that the reported patterns in piscivore biomass were not an artifact of the data handling choice to exclude some species known to be affected and systematically overestimated by divers (Fig. S4). However, model outputs of population level effects of depth and bathymetric steepness between populated and unpopulated locations showed much greater biomass estimates at uninhabited than habited islands, indicating that conservative exclusion of these species mitigated potential systematic bias associated with the survey method among locations on reported patterns (Fig. S4)." + +<--- Page Split ---> + +# nature portfolio + +Table S12 Surveyed fish taxa omitted from the study analyses. Reasons for omission include known systematic detectability bias²-⁴ (Carcharhinidae, Carangidae, Sphyrnidae), species not typically reef-associated (Scombridae, Chanidae, Myliobatidae), and cryptobenthic eels whose body-size cannot be estimated (Congridae, Muraenidae). + +
FamilySpeciesCommon nameTrophic groupReason for omission
CarangidaeCarangoides ferduaBlue trevallyPiscivorePotential overinflation in estimates
Carangoides orthogrammusIsland trevallyPiscivorePotential overinflation in estimates
Caranx ignobilisGiant trevallyPiscivorePotential overinflation in estimates
Caranx lugubrisBlack jackPiscivorePotential overinflation in estimates
Caranx melampygusBluefin trevallyPiscivorePotential overinflation in estimates
CaranpapuensisBrassy trevallyPiscivorePotential overinflation in estimates
Caranx sexfasciatusBigeye trevallyPiscivorePotential overinflation in estimates
Decapterus macarellusMackerel scadPlanktivorePotential overinflation in estimates
Elagatis bipinnulataRainbow runnerPiscivorePotential overinflation in estimates
Scomberoides lysanDoublespotted queenfishPiscivorePotential overinflation in estimates
Selar crumenophthalmusBigeye scadPlanktivorePotential overinflation in estimates
Seriola dumeriliGreater amberjackPiscivorePotential overinflation in estimates
Trachinotus bailloniSmallspotted dartPiscivorePotential overinflation in estimates
Caranx spp.n/aPiscivorePotential overinflation in estimates
CarcharhinidaeCarcharhinus amblyrhynchosGrey reef sharkPiscivorePotential overinflation in estimates
Carcharhinus galapagensisGalapagos sharkPiscivorePotential overinflation in estimates
Carcharinus melanopterusBlacktip reef sharkPiscivorePotential overinflation in estimates
Triaenodon obesusWhitetip reef sharkPiscivorePotential overinflation in estimates
ChanidaeChanos chanosMilkfishPrimary consumerNon-reef-associated
CongridaeCongridae spp.Conger eel or Garden eelPiscivoreCryptobenthic
MuraenidaeEchidna nebulosaSnowflake moray eelSecondary consumerCryptobenthic
Enchelycore pardalisLeopard moray eelPiscivoreCryptobenthic
Gymnomuraena zebraZebra moray eelSecondary consumerCryptobenthic
Gymnothorax breedeniBlackcheek moray eelPiscivoreCryptobenthic
Gymnothorax eurostusAbbott's moray eelSecondaryCryptobenthic
+ +<--- Page Split ---> + +nature portfolio + +
consumer
Gymnothorax flavimarginatusYellow-edged moray eelPiscivoreCryptobenthic
Gymnothorax javanicusGiant moray eelPiscivoreCryptobenthic
Dwarf moray eelSecondary consumerCryptobenthic
Gymnothorax meleagrisTurkey moray eelPiscivoreCryptobenthic
Gymnothorax steindachneriSteindachner's moray eelPiscivoreCryptobenthic
Gymnothorax undulatusUndulated moray eelPiscivoreCryptobenthic
Moray eelPiscivoreCryptobenthic
MyliobatidaeManta birostrisGiant mantaPlanktivore
ScombridaeEuthynnus affinisKawakawaPiscivore
Gymnosarda unicolorDogtooth tunaPiscivore
Thunnus albacaresYellowfin tunaPiscivore
Scombridae spp.Striped bonitoPiscivore
SphyraenidaeSphyraena qenieBlackfin barracudaPiscivore
+ +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
Figure S4 Piscivore fish biomass, excluding and including the biomass of Carcharhinidae, Carangidae, and Sphyrnidae (see Table S12), across gradients of depth (a) and bathymetric steepness (b) at unpopulated (colour) and populated (grey) islands. Estimates represent conditional posterior medians (lines), 75% percentiles (shaded areas), and partial residuals (points) at the study mean values of bathymetric steepness (panel a) and depth (panel b). The y axis is limited to \(1.05x\) the maximum value of the \(75\%\) CI so partial residuals exceeding axis limits are not displayed. \(N = 5,525\) stationary point count (SPC) surveys (across 2,253 foreverest sites, 35 islands, five ecoregions).
+ +- Asher J, Williams ID, Harvey ES (2017). An assessment of mobile predator populations along shallow and mesophotic depth gradients in the Hawaiian Archipelago. Sci Rep 7:1-18. + +- Boaden AE & Kingsford MJ (2015). Predators drive community structure in coral reef fish assemblages. Ecosphere 6:1-33. + +- DeMartini EE, Friedlander AM, Sandin SA, Sala E (2008) Differences in fish-assemblage structure between fished and unfished atolls in the northern Line Islands, central Pacific. Mar Ecol Prog Ser 365:199-215. + +- Depczynski M, & Bellwood DR (2003). The role of cryptobenthic reef fishes in coral reef trophodynamics. Mar Ecol Prog Ser 256:183-191. + +- Friedlander AM, Sandin SA, DeMartini EE, Sala E (2010) Spatial patterns of the structure of reef fish assemblages at a pristine atoll in the central Pacific. Mar Ecol Prog Ser 410:219-231. + +- Kulbicki. (1998). How the acquired behaviour of commercial reef fishes may influence the results obtained from visual censuses. J Exp Mar Biol Ecol 222: 11-30. + +<--- Page Split ---> + +# nature portfolio + +- Pinheiro HT, MacDonald C, Quimbayo JP, Shepherd B, Phelps TA, Loss AC, ... & Rocha LA (2023). Assembly rules of coral reef fish communities along the depth gradient. Curr Biol 33:1421-1430. +- Roff G, Doropoulos C, Rogers A, Bozec YM, Krueck NC, Aurellado E, ... & Mumby PJ (2016). The ecological role of sharks on coral reefs. TREE, 31:395-407. +- Williams ID, Baum JK, Heenan A, Hanson KM, Nadon MO, Brainard RE (2015). Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS ONE 10: e0120516. + +R.2ii.2: Second and related to the first, is based on the quality of the dataset included in this study. The authors point out that the reef survey data used in this study were collected by highly skilled divers from NOAA. They point out that divers responsible for collecting quantitative in situ data are trained to estimate the size and abundance of all diurnal and non-cryptic fishes observed in the survey area and make efforts to ensure data are collected with consistency and without biases. I am curious to know why the authors chose to filter or select certain taxa when NOAA invests significant resources into training divers on the survey methods to record all taxa. This includes training divers to avoid double counting individuals entering the survey area or 'mobbing divers. Further, the standardization of survey protocols across regions and time periods represents one of the most comprehensive datasets for coral reef fishes. e classes. Did the authors attempt perform an initial analysis using all taxa before enlisting filtering? Again, simply picking and choosing to omit ecologically important species or groups likely has important implications to the results. + +We are glad that the Reviewer recognises the extensive technical data validation protocols that NOAA employs to minimise measurement error as much as possible (e.g. doing instantaneous counts and training divers to minimise double counting in a single survey). While these protocols ensure that NOAA divers are highly skilled at avoiding double counting, they do not eliminate the problem of spatially variable mobbing behaviour of mobile species because the protocol cannot control for it. For example, these divers could achieve a perfect count of mobbing jacks within an SPC survey cylinder on one island, but still have a systematic bias if the same species avoids those divers at other islands. The NOAA National Coral Reef Monitoring Programme does indeed invest significant resources in collecting this high- quality dataset and this is because the fish data are used for a wide variety of purposes, many of which would not involve or require filtering of species in the way we have for the current paper. For example, managers that have specific questions about Lutjanus bohar, sharks, or reef fish assemblage diversity or biomass at their specific islands or regions. We did not take the decision to filter these species out lightly and we agree they are ecologically important. However, because our priority focus was to make Pacific- wide assessment, we exclude known biases among islands driven by strong spatial variance in behaviour among these highly mobile roving piscivore species (per R.2ii.1). + +R.2ii.3: Third, after reading through the results and examining the figures in more detail, I am curious to know if the authors have considered the non-independence of the predictors (Steepness and Depth). Based on the figures it seems as though depth and steepness covary? Is this a result of methodological limitations where it is not possible to have to have a survey instance where data are collected at a site that + +<--- Page Split ---> + +# nature portfolio + +both steep and shallow? It seems as though this could lead to a biased interpretation of the data? Please consider this potential non- independence of the predictors. + +Thanks for this question. We checked for non- independence of our predictors (including depth and steepness) for each fish biomass model by plotting bivariate correlations between the posterior samples (MCMC draws) of predictor coefficients and quantifying the Pearson correlation coefficients between paired samples, as follows: + +("b_predictor" relates to the model slope coefficient for that population- level effect; "c" indicates that the predictor is centred and scaled; SITE_SLOPE_400m_c is the data name for the bathymetric steepness effect) + +![PLACEHOLDER_49_0] + + +<--- Page Split ---> +![PLACEHOLDER_50_0] + + +<--- Page Split ---> + +# nature portfolio + +![PLACEHOLDER_51_0] + + +Correlation coefficients were all \(< 5\%\) , bar one: a single pairwise correlation coefficient for hurdle components depth and steepness in the planktivore model which was still relatively low at \(28\%\) . Therefore, we derived that the predictors were sufficiently independent so as to not bias the posterior estimates. All study data and code, including code for these and all other model validation plots are available in this open repository: https://github.com/LauraERichardson/Depth- Fish. + +We have added these plots to the supplementary information (Fig. S6) and revised the methods to make this clearer as follows: + +L579: "Non- independence of population- level predictors was assessed by plotting bivariate correlations between the posterior samples (MCMC draws) of predictor coefficients and quantifying Pearson correlation coefficients between paired samples (Fig. S6) \(^{94}\) . Correlation coefficients were all \(< 5\%\) , bar one: a single pairwise correlation coefficient for hurdle components depth and steepness in the planktivore model which was still relatively low at \(28\%\) ." + +L588: "...independence of model predictors assessed with gqpairs in GGally 2.1.2 \(^{101}\) ." + +R.2ii.4: Lastly, the authors provide some interpretation of the results in the discussion (lines 360- 375) where they posit that the spatial variance of the observations was greatest at the site- scale... indicating + +<--- Page Split ---> + +# nature portfolio + +that intra- island heterogeneity in habitat availability. However, I encourage the authors to reconsider this statement. Coral reef fish data are inherently noisy and variable at the site and temporal scale. For example, if the authors were to conduct surveys at a single site multiple times the estimates would be highly variable among samples. Therefore the observed results are likely due to variability of the observed data and not directly linked to the local dynamics as they suggest. + +Thanks for this point. We have revised the manuscript to position our results in the discussion more cautiously as advised: + +L368: "We found that the greatest spatial variance was at the site- scale for primary and secondary consumers, piscivores, and total biomass. We note that unmeasured temporal stochasticity at the site- level due to factors like fish recruitment, mobility, or behaviour can influence small- scale single time point observations and their associated variability at that scale45. Nonetheless, the importance of site- scale characteristics, indicated by this intra- island heterogeneity, supports numerous studies that identify habitat availability79, local hydrodynamics15, and local disturbances23,69,80 as predominant mediators of the biomass of those groups45." + +L384: "That we observed lower variation at the island- scale than site and ecoregion scales may be due, in part, to a dominant influence of local variation in habitat, hydrodynamics, or disturbances and variable background levels of productivity across ecoregions, over processes occurring at the island- scale." + +<--- Page Split ---> + +# nature portfolio + +## Reviewer #3 (Remarks to the Author): + +The authors make a vigorous defense of their paper, and to reiterate this is a comprehensive study of the impacts of depth on fish assemblages - and the impacts of humans on that pattern - and I will cite it when I need to make that point. The problem of stripping away many of the complexities (how does the role of depth compare to other covariates? What is the relationship between growing population size and the depth pattern (not just unpopulated / populated)?) is that the paper lives or dies based on interest in the core question being tested - and I'm not convinced that the relationship between fish and depth is as interesting a component of ecological theory as the authors do. Everything we know about fish assemblages (including many zonation papers) suggests that depth is critical and I don't think anyone would argue that depth isn't important. So while this is a comprehensive treatment of the question, and does provide new insights into human impacts and the role of bathymetric steepness, I still struggle to see this as a Nature Ecology & Evolution paper. The paper still makes me wonder about the mechanism (what are fish actually responding to since depth is a proxy for a range of drivers?), what is the relative importance of human direct effects (fishing) versus indirect effects (e.g. affecting coral cover or removing nursery habitats), are there any systematic differences between populated and unpopulated islands, and what is driving the patterns seen at the different spatial scales. But I can see that this concern isn't shared by the other reviewers and I appreciate that novelty is in the eye of the beholder. So given that there aren't any critical flaws in the analyses I think at this point I will defer to the Editor to judge the value of the new insights provided by this paper. + +We thank the reviewer again for thoughtfully engaging with the fit of our overarching study aim and context. We are very pleased that they recognise the study to be comprehensive and robust with no critical flaws, offering novel insight into human impacts on classic depth zonation and the role of bathymetric steepness in mediating reef fish biomass baselines. We are glad that the reviewer highlights that no- one would argue that depth isn't important to the zonation of coral reef fish as this widespread assumption is at the heart our study. For the first time, we provide unequivocal empirical grounding for, until now, the broadly assumed but untested (at sufficient scale) paradigm of depth zonation. With this now well documented through a rigorous test at scale, we are in a better position to embark on tackling the next phase of more complex questions. We fully agree that research into the mechanisms of zonation and how their effects are damped or disrupted by human impacts would be interesting and is indeed the next logical direction for future studies. + +# Decision Letter, second revision: + +<--- Page Split ---> + +# nature portfolio + +Dear Laura, + +Thank you for submitting your revised manuscript "Re- visiting the paradigm of depth zonation on contemporary coral reefs" (NATECoLEVOL- 221117855B). I'm sorry it has taken us longer than desirable to get this decision to you. We had been hoping to get comments from Reviewer 2 on this revision, but we have not heard back from that reviewer. We have discussed your responses to all reviewers' previous comments and feel confident that we can now offer, in principle, to publish it in Nature Ecology & Evolution, pending minor revisions to comply with our editorial and formatting guidelines. + +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex) - - we can not proceed with PDFs at this stage. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +## [REDACTED] + +Our ref: NATECoLEVEL- 221117855B + +17th July 2023 + +Dear Dr. Richardson, + +Thank you for your patience as we've prepared the guidelines for final submission of your Nature Ecology & Evolution manuscript, "Re- visiting the paradigm of depth zonation on contemporary coral reefs" (NATECoLEVEL- 221117855B). Please carefully follow the step- by- step instructions provided in the attached file, and add a response in each row of the table to indicate the changes that you have made. Please also check and comment on any additional marked- up edits we have proposed within the text. Ensuring that each point is addressed will help to ensure that your revised manuscript can be swiftly handed over to our production team. + +\*\*We would like to start working on your revised paper, with all of the requested files and forms, as soon as possible (preferably within two weeks). 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If you have any questions please click here.** + +<--- Page Split ---> diff --git a/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..40e115e62e17339f1357d60c5d1fde21cd046a7a --- /dev/null +++ b/peer_reviews/5689aa8ea14e3cfac1a18e6860e8ec406b904d5cf50dee6effac8ad2d27bb8ac/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,1609 @@ +<|ref|>title<|/ref|><|det|>[[595, 44, 970, 90]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[115, 161, 571, 194]]<|/det|> +# Peer Review Information + +<|ref|>text<|/ref|><|det|>[[114, 220, 835, 290]]<|/det|> +Journal: Nature Ecology & Evolution Manuscript Title: Local human impacts disrupt depth- dependent zonation of tropical reef fish communities Corresponding author name(s): Laura E. Richardson + +<|ref|>text<|/ref|><|det|>[[115, 327, 327, 351]]<|/det|> +Editorial Notes: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[595, 45, 970, 88]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[115, 148, 569, 173]]<|/det|> +Reviewer Comments & Decisions: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 84]]<|/det|> +# nature portfolio + +<|ref|>sub_title<|/ref|><|det|>[[119, 128, 353, 143]]<|/det|> +## Decision Letter, initial version: + +<|ref|>text<|/ref|><|det|>[[119, 160, 255, 175]]<|/det|> +9th January 2023 + +<|ref|>text<|/ref|><|det|>[[118, 189, 875, 218]]<|/det|> +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +<|ref|>text<|/ref|><|det|>[[119, 231, 273, 245]]<|/det|> +Dear Dr Richardson, + +<|ref|>text<|/ref|><|det|>[[118, 259, 877, 344]]<|/det|> +I am writing to you in the temporary absence of my colleague, [REDACTED]. Your Article, "Revisiting the paradigm of coral reef depth zonation on contemporary reefs" has now been seen by 3 reviewers. You will see from their comments copied below that while they find your work of considerable potential interest, they have raised quite substantial concerns that must be addressed. In light of these comments, we cannot accept the manuscript for publication, but would be very interested in considering a revised version that addresses these serious concerns. + +<|ref|>text<|/ref|><|det|>[[118, 357, 878, 400]]<|/det|> +We hope you will find the reviewers' comments useful as you decide how to proceed. If you wish to submit a substantially revised manuscript, please bear in mind that we will be reluctant to approach the reviewers again in the absence of major revisions. + +<|ref|>text<|/ref|><|det|>[[118, 413, 840, 442]]<|/det|> +If you choose to revise your manuscript taking into account all reviewer and editor comments, please highlight all changes in the manuscript text file. + +<|ref|>text<|/ref|><|det|>[[118, 455, 872, 499]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Please do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[119, 512, 332, 526]]<|/det|> +If revising your manuscript: + +<|ref|>text<|/ref|><|det|>[[118, 539, 867, 582]]<|/det|> +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the referees along with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 596, 864, 638]]<|/det|> +\* If you have not done so already we suggest that you begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +<|ref|>text<|/ref|><|det|>[[118, 651, 875, 694]]<|/det|> +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +<|ref|>text<|/ref|><|det|>[[118, 708, 518, 722]]<|/det|> +Please use the link below to submit a revised paper: + +<|ref|>sub_title<|/ref|><|det|>[[118, 735, 228, 750]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[118, 763, 860, 806]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[118, 820, 877, 876]]<|/det|> +If you wish to submit a suitably revised manuscript we would hope to receive it within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[115, 889, 860, 905]]<|/det|> +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 42, 999, 83]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[118, 110, 875, 209]]<|/det|> +efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[118, 222, 812, 250]]<|/det|> +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +<|ref|>text<|/ref|><|det|>[[119, 264, 511, 278]]<|/det|> +Thank you for the opportunity to review your work. + +<|ref|>sub_title<|/ref|><|det|>[[119, 292, 228, 306]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[119, 335, 290, 348]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[119, 363, 415, 377]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 390, 864, 430]]<|/det|> +This is a well- structured and well- written study that provides basin- scale patterns of reef fish trophic group and biomass zonation across different spatial scales. + +<|ref|>text<|/ref|><|det|>[[118, 430, 864, 457]]<|/det|> +It is interesting to know how these differ across different groups and how these have been linked to ecological mechanisms such as upwelling. + +<|ref|>text<|/ref|><|det|>[[118, 456, 844, 483]]<|/det|> +It was also interesting to find out about thresholds of bathymetrics steepness below which fish biomass is enhanced. + +<|ref|>text<|/ref|><|det|>[[120, 475, 707, 489]]<|/det|> +Overall, this a good study that would benefit from some edits / clarifications. + +<|ref|>text<|/ref|><|det|>[[120, 489, 810, 503]]<|/det|> +Below some overall comments, and more specific comments per section with line numbers. + +<|ref|>text<|/ref|><|det|>[[119, 518, 344, 530]]<|/det|> +Overall comments to address + +<|ref|>text<|/ref|><|det|>[[118, 531, 875, 660]]<|/det|> +- More methodological information, especially in relation to the survey method and how consistency in fish identification and fish length measurements was achieved. +- Bayesian modelling is not something that I have myself used before (all lines between 444-510), therefore, I cannot comment on if it has been applied correctly or not. I would advise having someone familiar with this method to review the statistical methodology used. +- Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups. + +<|ref|>text<|/ref|><|det|>[[119, 690, 213, 701]]<|/det|> +Introduction + +<|ref|>text<|/ref|><|det|>[[118, 701, 848, 728]]<|/det|> +Line 67. Define deep- water (e.g. \(>200m\) ) or change to "particulate foods and nutrients derived from deeper water..." + +<|ref|>text<|/ref|><|det|>[[119, 728, 410, 741]]<|/det|> +Line 69. Increase instead of increases + +<|ref|>text<|/ref|><|det|>[[119, 742, 352, 754]]<|/det|> +Line 70. Define shallow- water + +<|ref|>text<|/ref|><|det|>[[118, 755, 857, 782]]<|/det|> +Line 82. span vast spaces of the ocean. This is because it has been argued to refer to one ocean (https://doi.org/10.1002/aqc.3512) + +<|ref|>text<|/ref|><|det|>[[119, 797, 177, 809]]<|/det|> +Results + +<|ref|>text<|/ref|><|det|>[[119, 810, 616, 824]]<|/det|> +Line 116: I would remove "predictably" as it's the results section + +<|ref|>text<|/ref|><|det|>[[118, 825, 870, 852]]<|/det|> +Table 1: I would change underlining negative associations to adding a - in front of numbers. e.g. - 0.75. That is more intuitive to me. + +<|ref|>text<|/ref|><|det|>[[118, 852, 870, 879]]<|/det|> +Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 880, 844, 908]]<|/det|> +Lines 203- 214. This would fit better in the materials and methods or introduction section. If something needs to be kept in the Results section I would only do that if absolutely necessary. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 856, 198]]<|/det|> +Line 224: "exceeding island- scale variance (9%; P(sdsSITE > sdsISLAND) = 0.95)". Is that not already captured in lines 261- 218? Line 225: Why does the site- scale variance here (38- 64%) differ from that at line 25- 52%? The same applies for ecoregion scale. I think it has to do with the way they have been estimated - looking at Table S11 you talk about probabilities, so I would mention that in the main text as well. + +<|ref|>sub_title<|/ref|><|det|>[[118, 210, 201, 222]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[118, 222, 825, 250]]<|/det|> +Line 239: Some of those studies, e.g. Goreau, 1959 talk about zonation focusing on species composition rather than changes in biomass. + +<|ref|>text<|/ref|><|det|>[[118, 250, 678, 265]]<|/det|> +Line 245: I would rephrase to "To our knowledge, this is the first time..." + +<|ref|>text<|/ref|><|det|>[[118, 265, 312, 278]]<|/det|> +Lines 245- 246: However, + +<|ref|>text<|/ref|><|det|>[[118, 279, 340, 293]]<|/det|> +Line 255: Only unpopulated? + +<|ref|>text<|/ref|><|det|>[[118, 293, 850, 335]]<|/det|> +Lines 304- 306: Can you expand a little bit more here? Do you mean that below 30m steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +<|ref|>text<|/ref|><|det|>[[118, 335, 875, 363]]<|/det|> +Line 307: For most part the depth- related changes in biomass remained the for trophic groups, it's just the absolute values that were reduced, no? + +<|ref|>text<|/ref|><|det|>[[118, 363, 870, 391]]<|/det|> +Line 333- 334: True, but you have not focused on species in this study. Would mentioning specific trophic groups that perform distinct functions be more accurate? + +<|ref|>text<|/ref|><|det|>[[118, 391, 840, 419]]<|/det|> +Line 377: Again refs 6 and 25 concern zonation because of changes in species and not trophic group biomass. + +<|ref|>text<|/ref|><|det|>[[118, 419, 875, 447]]<|/det|> +Lines 381- 383: The direction of change was the same though. I know you mention it, but the way it's presented both here and in the discussion, is like it is very different. + +<|ref|>text<|/ref|><|det|>[[118, 447, 875, 475]]<|/det|> +The difference lies mostly in the absolute numbers. Maybe it's not that important, and I am getting too caught up in it. + +<|ref|>text<|/ref|><|det|>[[118, 475, 875, 503]]<|/det|> +Lines 386- 388. Can you add examples of ecological paradigms that are included in the refs you cite, here? + +<|ref|>text<|/ref|><|det|>[[118, 516, 833, 545]]<|/det|> +General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? + +<|ref|>text<|/ref|><|det|>[[118, 545, 836, 587]]<|/det|> +If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +<|ref|>sub_title<|/ref|><|det|>[[118, 615, 185, 627]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[118, 629, 497, 642]]<|/det|> +Line 413 onwards (Reef fish survey data section). + +<|ref|>text<|/ref|><|det|>[[118, 643, 850, 670]]<|/det|> +Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +<|ref|>text<|/ref|><|det|>[[118, 670, 848, 698]]<|/det|> +SPC curves: Then there is the question of the survey method itself. Can the authors cite other studies that have used this method? + +<|ref|>text<|/ref|><|det|>[[118, 699, 875, 741]]<|/det|> +Lengths: From what I understand actual fish lengths have been estimated (to the nearest cm) rather than fish size classes. I am struggling to understand how this could be achieved underwater without a significant amount of bias given that some fish could be as far away as 15m. + +<|ref|>text<|/ref|><|det|>[[118, 741, 850, 784]]<|/det|> +Can you explain a bit more on how consistency of length measurements was assured between divers across all the different surveys? Even if that information exists in another reference, it is worth mentioning it in this manuscript, given the large dataset that is being used. + +<|ref|>text<|/ref|><|det|>[[118, 784, 860, 825]]<|/det|> +Lines 440- 442: Does this mean that 400m was cross- checked against all surveyed sites to make sure it does not include opposite sides of the island? What about encompassing the reef flat and reef crest zones? + +<|ref|>text<|/ref|><|det|>[[118, 825, 840, 853]]<|/det|> +Lines 444- 451: I am not familiar with this method to be able to evaluate if it has been applied correctly. Can you cite 1- 2 refs for the type of model you ended up using? + +<|ref|>text<|/ref|><|det|>[[118, 853, 808, 867]]<|/det|> +Line 480: What criterion was used to determine if the proportion of zeros was low enough? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 123, 876, 335]]<|/det|> +The study by Richardson and coauthors entitled: "Re- visiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECoLEVEL- 221117855) sets out to explore depth zonation patterns of coral reef fishes across gradients of biophysical processes and human disturbance. This study builds upon a broad body of work focused on contributing to our understanding of how habitat, depth, and other important biophysical drivers influence the structure and distribution of fishes. To date, most contributions to the literature have focused on describing these patterns at single locations or groups of sites across a limited spatial scale. This study complements these efforts by assembling a large and comprehensive dataset including over 5,000 in situ reef fish surveys spanning across 35 islands to explore these ecological patterns. Overall, I found the study to be well designed, scientifically interesting, and well written. I think the results provide valuable insights into how coral reef fish communities are structured in a changing world. However, I feel that there are a couple areas that should be considered before the manuscript is published. I have outlined these broad recommendations along with a couple more detailed comments below. Once these items are addressed, I feel that this manuscript will make a valuable contribution to the field of Ecology. + +<|ref|>text<|/ref|><|det|>[[118, 347, 870, 586]]<|/det|> +First, I would like the authors to consider how they filtered and selected the reef fishes for this study. While I appreciate the complexity and variability of coral reef fish data, I am concerned about the exclusion of ecologically important species (Sharks and Jacks). I am familiar with the literature identifying potential biases associated with large- bodied and mobile species as well as the behavioral effects associated with diver presence. Many of these biases or behavioral effects could be observed for other large- bodied mobile species within important groups such as parrotfishes (Scaridae), wrasses (Labridae) and snappers (Lutjanidae). I would like the authors to consider the potential biases associated with choosing to remove ecologically important species. For example, in most coral reef communities Jacks (Carangidae) are voracious predators exerting strong top- down effects on prey species. This is particularly evident with species such as Caranx ignobilis, C. melampygus, and C. lugubris that can be observed actively hunting across coral reef habitats preying on fishes and other invertebrates. This predatory behavior has been well documented in ecoregions included in this study (Hawaiian Islands and Line Islands). This is also the case with reef sharks (Carcharhinidae) excluded from this study (e.g., Carcharhinus melanopterus, C. amblyrhynchos, and Triaenodon obesus). I ask that the authors reconsider removing the entire group of sharks and jacks and be more selective in their filtering to factor in the ecological relevance of their choices. + +<|ref|>text<|/ref|><|det|>[[118, 599, 867, 768]]<|/det|> +Second, the authors take advantage of a previously published dataset (MacNeil et al. 2015) that provides an estimate of the total unfished global fish biomass to serve as the mean for analysis in this study. The intercept value was used for all trophic groups included in this study with the exception of the secondary consumers. While I do not disagree with this approach, I have concerns over the comparability of datasets. Specifically, the previous study uses a filtering process to exclude certain species. It does not seem like the authors in this study used the same filtering process to exclude the same species. Therefore, this would introduce potential biases in the analysis and statistical modeling outputs. Again, I recommend that the authors consider the ecological implications of the species filtering process and provide a justification for how they selected species or groups to exclude. I think the MacNeil work is great but maybe the authors from this study should consider using the approach they used for the secondary consumers when data were not comparable between studies. + +<|ref|>text<|/ref|><|det|>[[118, 781, 870, 908]]<|/det|> +Lastly, I found the dataset included in this study to be impressive and I appreciate the efforts involved with synthesizing data from across 5 ecoregions. As the authors point out, each of the 5 ecoregions included in this study are exposed to different biophysical forces and levels of human disturbance. I understand the major aim of this study was to compare patterns of reef fish biomass across depth gradients for 5 ecoregions. However, I think it would be interesting to see if these patterns hold up within each ecoregion. I found the results from figure 5 to be interesting and wanted explore these results more. I am not suggesting that the authors create additional figures etc. However, I would recommend that the authors provide some additional discussion to expand on their findings. Are the patterns consistent within each ecoregion? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 85]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[118, 123, 550, 138]]<|/det|> +Line 445 - (biomass density; g- m2) do you mean g m- 2 + +<|ref|>text<|/ref|><|det|>[[118, 151, 875, 194]]<|/det|> +Figures - In general I found the figures to be great. However, I am not sure if it was the download process but the figures appear to be low resolution and slightly blurry. I know a lot of work went into creating the figures and it would be good to confirm the quality for publication. + +<|ref|>text<|/ref|><|det|>[[118, 207, 867, 236]]<|/det|> +Table S1 - Agujian categorized as "Populated"? I assume this is due to its proximity to Tinian and Saipan rather than its small resident population? + +<|ref|>text<|/ref|><|det|>[[120, 277, 415, 291]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 305, 870, 390]]<|/det|> +This well- written paper uses a uniquely large data set to examine the effects of depth on reef fish assemblages, and how population pressure influences this pattern. The paper uses modern analytical techniques to provide a convincing story of depth- related gradients for both major trophic groups and total biomass. The paper also includes an interesting finding of the role of reef bathymetry on reef fishes - the influence of reef steepness on fish assemblages intuitively might be expected, but has rarely been demonstrated at this scale and with such good bathymetry data. + +<|ref|>text<|/ref|><|det|>[[117, 404, 877, 629]]<|/det|> +My issue with the paper is whether the story is sufficiently interesting for such a high- profile journal for two reasons: 1) the interest in revisiting basic depth gradients and examining homogenization by human impacts and 2) the lack of detailed covariates. The depth- related gradient of zones on reefs is indeed a well- described and accepted paradigm, although I would argue we now have enough descriptions of changes with depth that the ability to generalize is stronger than indicated here (first line of abstract, L77- 80). The homogenization of assemblages because of human impacts is also well known in a range of ecosystems (including on reefs). Therefore, it isn't particularly surprising that the zonation is less clear near highly populated islands. I agree this hasn't been demonstrated as clearly as in this study and it needs to be quantified, but I question whether this elevates the paper to one that should be published in Nature Ecology & Evolution. More fundamentally, I'm not sure how this would change our approach to studying or conserving reefs - the underlying ecological paradigm is clearly still true given the significance of the variables that change with increasing depth, and management is rarely zone specific. For example, any meaningful study of patterns of fish assemblages already controls for variable fishing pressure. Therefore, does this study really suggest that revisiting existing paradigms would change our approach to studying or managing ecosystems? + +<|ref|>text<|/ref|><|det|>[[117, 642, 876, 908]]<|/det|> +More significantly this study feels like it misses opportunities to consider depth in the context of other variables, which potentially either excludes the chance of examining some interesting nuances in the data or possibly confounds the analyses. Firstly, human population pressure simply places reefs into one of two categories (populated or unpopulated) which seems overly simplified - why not consider population pressure as a continuous variable and look at more general trends and thresholds? Secondly, the analyses pool all sites from 'reef slopes', which standardizes the geomorphological zone but ignores any differences in benthic assemblages. Thus the reader is left wondering, for example, whether populated islands have more homogenous benthic assemblages across depth gradients that limits fish zonation. I'm sure the divers collected some benthic data, so why not include a basic metric like coral cover (or even habitat type) in the analyses to better isolate the depth signal? I appreciate that the aim was to examine a basic biophysical gradient (depth), but I feel the paper would have been more interesting to consider depth in the context of all the other variables that we know affect reef fishes. To me, one of the most interesting parts of this paper was examining the role of steepness on zonation and I kept wanting to know which other factors were critical in explaining the deviance in the data set. One of the benefits of modern ecology is the access to large- scale, reliable data layers of a range of covariates. However, this study doesn't use these rich sources of information to fill out the models of fish abundance. This is particularly problematic when considering spatial scales of variation (regions / islands / sites) - because the analyses only uses spatial scale in the model the Discussion has to be quite + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 109, 870, 181]]<|/det|> +speculative about the actual drivers of these patterns. But had the models included covariates of e.g. net primary productivity, temperature, or wave exposure (all of which are relatively straightforward to obtain) – or island type (see Taylor et al, 2018, Ecography 38:520- 530 for why this variable might be critical) - then we could have seen actual correlations in the data rather than have to guess at what might be varying from island to island ("potential indicators", L210). + +<|ref|>text<|/ref|><|det|>[[118, 194, 879, 320]]<|/det|> +In summary, had I been reviewing this for a general marine journal I would have suggested revisiting the analyses with some key additional covariates and perhaps human pressure as a continuous variable, but recommended the paper eventually be published as examining depth- related patterns with a data set of this size and examining the homogenizing role of human populations is worth quantifying. Plus the importance of steepness and the variation among trophic groups are interesting. However, the threshold for this journal is higher and I am not convinced that the underlying question is sufficiently interesting, especially given the relatively cursory treatment of other important covariates that limits understanding of which variables are critical at large scales. + +<|ref|>sub_title<|/ref|><|det|>[[118, 339, 397, 353]]<|/det|> +## Author Rebuttal to Initial comments + +<|ref|>sub_title<|/ref|><|det|>[[119, 372, 422, 388]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 402, 875, 507]]<|/det|> +R1.1: This is a well- structured and well- written study that provides basin- scale patterns of reef fish trophic group and biomass zonation across different spatial scales. It is interesting to know how these differ across different groups and how these have been linked to ecological mechanisms such as upwelling. It was also interesting to find out about thresholds of bathymetrics steepness below which fish biomass is enhanced. Overall, this a good study that would benefit from some edits / clarifications. Below some overall comments, and more specific comments per section with line numbers. + +<|ref|>text<|/ref|><|det|>[[118, 521, 878, 582]]<|/det|> +We thank Reviewer #1 for their careful and considered evaluation of our manuscript. We are glad they found the results interesting, and the article well- structured and well- written. We have addressed the areas in the text that required clarification, revision, or expansion as suggested, taking into account the points they have raised. + +<|ref|>text<|/ref|><|det|>[[119, 598, 336, 612]]<|/det|> +Overall comments to address + +<|ref|>text<|/ref|><|det|>[[117, 628, 875, 708]]<|/det|> +R1.2: More methodological information, especially in relation to the survey method and how consistency in fish identification and fish length measurements was achieved. - Bayesian modelling is not something that I have myself used before (all lines between 444- 510), therefore, I cannot comment on if it has been applied correctly or not. I would advise having someone familiar with this method to review the statistical methodology used. + +<|ref|>text<|/ref|><|det|>[[118, 744, 619, 760]]<|/det|> +Thank- you. See our detailed responses to R1.25- R1.27, and R1.29. + +<|ref|>text<|/ref|><|det|>[[118, 786, 875, 834]]<|/det|> +R1.3: Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups + +<|ref|>text<|/ref|><|det|>[[118, 871, 877, 902]]<|/det|> +Thanks for this. For now, and to favour brevity in the title for the journal, we have not incorporated this suggestion into the title, but we have revised it to make it more concise: 'Re- visiting the paradigm + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 109, 872, 174]]<|/det|> +of depth zonation on contemporary coral reefs'. We agree with the Reviewer that further clarification of the term zonation is needed early in the introduction. In addition to the existing definition of ecological zonation as "the distribution of organisms across space" (L58), we have added a more detailed definition of 'depth zonation' at first mention as follows: + +<|ref|>text<|/ref|><|det|>[[177, 210, 848, 243]]<|/det|> +L67: "Here we revisit this basic principle in the context of depth zonation of tropical coral reef communities- the distribution of reef fish biomass among distinct trophic groups." + +<|ref|>sub_title<|/ref|><|det|>[[118, 269, 212, 284]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[118, 309, 872, 341]]<|/det|> +R1.4: Line 67. Define deep- water (e.g. \(>200m\) ) or change to "particulate foods and nutrients derived from deeper water..." + +<|ref|>text<|/ref|><|det|>[[118, 354, 833, 386]]<|/det|> +Thanks. We have changed this to "particulate foods and nutrients derived from deeper water" as suggested (L73). + +<|ref|>text<|/ref|><|det|>[[118, 399, 527, 415]]<|/det|> +R1.5: Line 69. Increase instead of increases. Changed. + +<|ref|>text<|/ref|><|det|>[[118, 429, 396, 445]]<|/det|> +R1.6: Line 70. Define shallow- water. + +<|ref|>text<|/ref|><|det|>[[118, 459, 504, 475]]<|/det|> +Changed to "shallow- water (<30 m depth37)" (L76). + +<|ref|>text<|/ref|><|det|>[[147, 489, 835, 520]]<|/det|> +- Stefanoudis et al. (2019). Depth-dependent structuring of reef fish assemblages from the shallows to the rariphotic zone. Front Mar Sci 6, 307. + +<|ref|>text<|/ref|><|det|>[[118, 534, 872, 565]]<|/det|> +R1.7: Line 82. span vast spaces of the ocean. This is because it has been argued to refer to one ocean (https://doi.org/10.1002/aqc.3512) + +<|ref|>text<|/ref|><|det|>[[118, 579, 853, 611]]<|/det|> +Thanks for this suggestion. To avoid the plural term "oceans", the text is changed to: "Modern- day island reefs span vast ocean expanses..." (L88). + +<|ref|>sub_title<|/ref|><|det|>[[118, 625, 175, 639]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[118, 654, 650, 670]]<|/det|> +R1.8: Line 116: I would remove "predictably" as it's the results section. + +<|ref|>text<|/ref|><|det|>[[118, 685, 251, 700]]<|/det|> +Thanks, removed. + +<|ref|>text<|/ref|><|det|>[[118, 715, 852, 746]]<|/det|> +R1.9: Table 1: I would change underlining negative associations to adding a - in front of numbers. e.g. - 0.75. That is more intuitive to me. + +<|ref|>text<|/ref|><|det|>[[118, 760, 870, 896]]<|/det|> +Thanks for this suggestion. We would agree that adding a "- " in front of the numbers to indicate decrease would be intuitive if the table presented depth and population status effect sizes on fish biomass. Unfortunately, adding "- " might indicate negative probability estimates. Classical probabilities range from 0- 1, such that a negative probability would indicate that an event or observation is less likely than 'impossible'. Indeed, negative probability is discussed in relation to quantum mechanics, and is centred on the concept of event 'cancelation' (e.g. Feynman 1987). If the Reviewer agreed, an alternative option for presenting probabilities associated with a negative relationship between biomass and depth in this Table could be to change underlining negative associations to colouring the text in red (or an alternative colour), which we will gladly do on request. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[147, 110, 850, 140]]<|/det|> +- Feynman. (1987). Negative probability. Quantum implications: essays in honour of David Bohm, 235-248. + +<|ref|>text<|/ref|><|det|>[[118, 155, 870, 187]]<|/det|> +R1.10: Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 200, 866, 291]]<|/det|> +To aid clearer visualisation of the scaled effects of depth, bathymetric steepness, and human population status on the positive reef fish biomass data, the effect estimates of hurdle components (presence- absence) from the piscivore and planktivore models were not included in Fig. 1. Including them, as presented in Fig. S1, clusters the effect estimates and their percentiles such that the reader may be less able to effectively interpret relative effect size. However, we will gladly exchange Fig. 1 for Fig. S1 on request. + +<|ref|>text<|/ref|><|det|>[[118, 305, 860, 336]]<|/det|> +R1.11: Lines 203- 214. This would fit better in the materials and methods or introduction section. If something needs to be kept in the Results section I would only do that if absolutely necessary. + +<|ref|>text<|/ref|><|det|>[[118, 350, 844, 381]]<|/det|> +Thanks. We have moved these lines as suggested to the methods (L522- 534), and revised the new opening statement as follows: + +<|ref|>text<|/ref|><|det|>[[178, 395, 875, 456]]<|/det|> +L230: "The proportion of variation in fish biomass explained by each spatial scale, quantified by extracting the posterior standard deviations of these modelled random effects, varied among trophic fish groups (Fig. 5; Table S10 and S11; see Fig. S3 for variation in island- level depth effects among ecoregions)." + +<|ref|>text<|/ref|><|det|>[[118, 470, 861, 501]]<|/det|> +R1.12: Line 224: "exceeding island- scale variance (9%; \(P(\text{sdsSITE} > \text{sdsISLAND}) = 0.95\) ). Is that not already captured in lines 261- 218? + +<|ref|>text<|/ref|><|det|>[[118, 516, 496, 531]]<|/det|> +Deleted this detail to streamline results, thank you. + +<|ref|>text<|/ref|><|det|>[[118, 545, 850, 591]]<|/det|> +R1.13: Line 225: Why does the site- scale variance here (38- 64%) differ from that at line 25- 52%? The same applies for ecoregion scale. I think it has to do with the way they have been estimated - looking at Table S11 you talk about probabilities, so I would mention that in the main text as well. + +<|ref|>text<|/ref|><|det|>[[118, 605, 876, 696]]<|/det|> +Thanks for highlighting this area of potential confusion. Line 217 presented the range in variance explained for all fish groups except secondary consumers (i.e. planktivores, piscivores, primary consumers and total fish biomass). L225 described the range in variance explained for all groups except planktivores (i.e. piscivores, primary consumers, secondary consumers, and total fish biomass). To avoid this potential confusion, we have removed the percentage ranges previously provided in L225 and retained reference to Fig. 5 and the complete summary in Table S10. + +<|ref|>sub_title<|/ref|><|det|>[[118, 711, 202, 725]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[118, 741, 850, 771]]<|/det|> +R1.14: Line 239: Some of those studies, e.g. Goreau, 1959 talk about zonation focusing on species composition rather than changes in biomass. + +<|ref|>text<|/ref|><|det|>[[118, 786, 704, 801]]<|/det|> +This is correct. To make this explicit, we have revised this sentence as follows: + +<|ref|>text<|/ref|><|det|>[[178, 816, 844, 877]]<|/det|> +L256: "However, while the structuring force of depth on reef ecology featured among the earliest descriptions of tropical coral reefs (for example, zonation in species composition) \(^{7,27,28}\) , these observations were restricted to single- point locations and the generality of a depth zonation paradigm remains untested across broad geographies." + +<|ref|>text<|/ref|><|det|>[[118, 891, 717, 907]]<|/det|> +R1.15: Line 245: I would rephrase to "To our knowledge, this is the first time..." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 125, 433, 140]]<|/det|> +Changed as recommended, thanks (L265). + +<|ref|>text<|/ref|><|det|>[[119, 155, 364, 170]]<|/det|> +R1.16: Lines 245- 246: However, + +<|ref|>text<|/ref|><|det|>[[118, 185, 872, 216]]<|/det|> +Apologies, we are unclear what the Reviewer is suggesting here. We will be glad to address this point if we can request some additional direction. + +<|ref|>text<|/ref|><|det|>[[119, 230, 395, 246]]<|/det|> +R1.17: Line 255: Only unpopulated? + +<|ref|>text<|/ref|><|det|>[[119, 260, 857, 306]]<|/det|> +This paragraph focusses on depth patterns at just unpopulated islands. However, we see that the original wording might have suggested that depth zonation was only observed at unpopulated reefs. We have revised as follows: + +<|ref|>text<|/ref|><|det|>[[178, 320, 870, 366]]<|/det|> +L275: "At geographically distinct unpopulated islands, we show that reef fish biomass of all broad trophic groups correlated predictably and relatively consistently across depth despite underlying variation in biophysical drivers known to affect standing reef fish biomass33,41,50." + +<|ref|>text<|/ref|><|det|>[[118, 380, 875, 411]]<|/det|> +R1.18: Lines 304- 306: Can you expand a little bit more here? Do you mean that below 30m steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +<|ref|>text<|/ref|><|det|>[[117, 424, 870, 590]]<|/det|> +We see that this sentence was potentially unclear. Studies looking at depth zonation beyond the 0- 30 m limit in our study report contrasting peaks in abundance of piscivores and planktivores. For example, at Linden Bank, a submerged shoal on the outer shelf of the Great Barrier Reef, reported dominance of piscivores (and mobile invertivores) between 50- 70 m depth (Scott et al. 2022). In contrast, the proportion of planktivores on forereefs at Enewetak Atoll in the Marshall Islands increased from 50% at 30 m to >90% from 90- 200 m, which the authors suggest may relate to upwelling processes increasing plankton and shallow reef productivity (Thresher and Colin 1986). In L304- 306, we suggest that these variable peaks in trophic group biomass at mesophotic depths are potentially indicative of spatial variation in upwelling, which could be linked- among other oceanographic factors- to variable local bathymetric steepness among those study locations. To make this clearer, we have revised the manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[177, 605, 872, 666]]<|/det|> +L325: "Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the 30 m limit of this study54,67, which may be indicative of spatial variation in upwelling, potentially linked to- among other oceanographic factors- variable local bathymetric steepness among those study locations." + +<|ref|>text<|/ref|><|det|>[[147, 680, 875, 755]]<|/det|> +- Thresher and Colin. (1986). Trophic structure, diversity and abundance of fishes of the deep reef (30-300m) at Enewetak, Marshall Islands. Bull Mar Sci 38, 253-272. Scott et al. (2022). Variation in abundance, diversity and composition of coral reef fishes with increasing depth at a submerged shoal in the northern Great Barrier Reef. Rev Fish Biol Fish 32, 941-962. + +<|ref|>text<|/ref|><|det|>[[118, 770, 822, 801]]<|/det|> +R1.19: Line 307: For most part the depth- related changes in biomass remained the for trophic groups, it's just the absolute values that were reduced, no? + +<|ref|>text<|/ref|><|det|>[[118, 815, 860, 846]]<|/det|> +This is a useful point, highlighting that better clarity in the text might avoid potential confusion. We have amended the sentence as follows: + +<|ref|>text<|/ref|><|det|>[[178, 860, 857, 907]]<|/det|> +L332: "Despite marked bathymetric gradients in fish biomass at unpopulated islands, we show that depth related changes in biomass were altered by depleted biomass baselines at islands inhabited by people. There was overall lower fish biomass across the depth gradient + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 85]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[179, 110, 866, 155]]<|/det|> +for all trophic groups at populated locations. Further, the change in absolute biomass of planktivores, piscivores, and secondary consumers across depth was substantially reduced at populated islands, and depth zonation in primary consumers was lost." + +<|ref|>text<|/ref|><|det|>[[118, 169, 835, 201]]<|/det|> +R1.20: Line 333- 334: True, but you have not focused on species in this study. Would mentioning specific trophic groups that perform distinct functions be more accurate? + +<|ref|>text<|/ref|><|det|>[[118, 214, 864, 261]]<|/det|> +Thanks. We have changed this statement from discussing functionally important species to the need for protection of "...depth- constrained trophic groups that perform distinct and important functions" (L359). + +<|ref|>text<|/ref|><|det|>[[118, 274, 872, 306]]<|/det|> +R1.21: Line 377: Again refs 6 and 25 concern zonation because of changes in species and not trophic group biomass. + +<|ref|>text<|/ref|><|det|>[[118, 320, 850, 395]]<|/det|> +This is correct. As defined in the introduction, the term zonation refers to "the distribution of organisms across space" (L58), and we have clarified our use of the term 'depth zonation' at first mention, to include (though not be limited to) "the distribution of reef fish biomass among distinct trophic groups" with depth (L68; see R1.3). To remove any potential confusion, we have revised L377 in the original manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[178, 409, 877, 485]]<|/det|> +L409: "We revisited ecological depth zonation- recognised as a fundamental structuring force of tropical coral reef communities over six decades ago \(^{7,26 - 28}\) - with two purposes: first, to test the generality of depth zonation of reef fish biomass for the first time across an ocean- basin scale; and second, to assess whether a zonation paradigm holds on reefs exposed to direct local human impacts." + +<|ref|>text<|/ref|><|det|>[[118, 500, 875, 546]]<|/det|> +R1.22: Lines 381- 383: The direction of change was the same though. I know you mention it, but the way it's presented both here and in the discussion, is like it is very different. The difference lies mostly in the absolute numbers. Maybe it's not that important, and I am getting too caught up in it. + +<|ref|>text<|/ref|><|det|>[[118, 560, 835, 576]]<|/det|> +Thanks for highlighting this. We have revised the statement as follows to clarify the exact result: + +<|ref|>text<|/ref|><|det|>[[178, 590, 870, 652]]<|/det|> +L415: "However, we found that while the principle of resource- driven depth zonation held at populated islands for some trophic groups (e.g. direction of change for planktivores, piscivores, secondary consumers), their magnitude of change with depth (i.e. absolute biomass) was substantially reduced by human depletion." + +<|ref|>text<|/ref|><|det|>[[118, 666, 875, 696]]<|/det|> +R1.23: Lines 386- 388. Can you add examples of ecological paradigms that are included in the refs you cite, here? + +<|ref|>text<|/ref|><|det|>[[118, 710, 864, 862]]<|/det|> +Thanks for highlighting potential confusion here. We had provided references to recent papers that discuss the need to revisit classic ecological paradigms for understanding contemporary coral reef ecology, including Hughes et al. 2017 Nature, and Williams et al. 2019 Functional Ecology. These articles emphasise how human impacts are increasingly transforming reefs into new configurations unlike anything observed previously by humans, requiring radical changes in how we study and manage them. The articles do not assess specific paradigms. However, the reference to Helmus et al. 2014 Nature offers an example of island biogeography theory no longer being an effective predictor of species richness in the Anthropocene. To bring in this example earlier we have added it to the introduction, reiterated the example in the opening discussion paragraph, and revised the final conclusion sentence for clarity, as follows: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 109, 868, 262]]<|/det|> +L58: "Human impacts confound natural drivers of ecological organisation in most contemporary ecosystems20- 22, and historical paradigms are now failing to capture ecological patterns where there is anthropogenic forcing (e.g. island biogeography theory18)." L272: "These findings support calls for revisiting and potentially updating twentieth century ecological paradigms (e.g. island biogeography theory18) that may no longer capture ecological patterns and processes in a human- dominated world23." L420: "However, where the influence of a physical feature as fundamental as depth on coral reef ecological organisation is being disrupted, we reiterate recent calls to revisit classic and influential ecological paradigms to determine their relevance in this era of rapid change18,23,24." + +<|ref|>text<|/ref|><|det|>[[148, 274, 870, 321]]<|/det|> +- Helmus et al. (2014). Island biogeography of the Anthropocene. Nature 513(7519), 543-546. +- Hughes et al. (2017). Coral reefs in the Anthropocene. Nature 546(7656), 82-90. +- Williams et al. (2019). Coral reef ecology in the Anthropocene. Funct Ecol 33(6), 1014-1022. + +<|ref|>text<|/ref|><|det|>[[118, 335, 872, 396]]<|/det|> +R1.24: General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +<|ref|>text<|/ref|><|det|>[[118, 409, 875, 560]]<|/det|> +Thanks to the Reviewer for highlighting where further discussion on cross- scale spatial variation in fish biomass patterns would improve the manuscript. Coral reefs are considered to be highly hierarchical in structure, determined by processes occurring at multiple spatial and temporal scales (Hughes et al. 1999, MacNeil et al. 2009). As the Reviewer rightly highlights, within this hierarchical context, management and governance efforts are considered most effective when carried out at scales aligning with scales of ecological heterogeneity (Cumming and Dobbs 2020). We describe this in detail in the paragraph L335- 345, and we link our results to scaled management and conservation efforts in L361- 368 in the original manuscript. However, we now provide additional discussion exploring the relative differences in variation observed across scales, notably discussing the relatively lower variation observed at the island- scale as follows: + +<|ref|>text<|/ref|><|det|>[[177, 574, 880, 787]]<|/det|> +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale. In this context, our findings suggest that management of primary consumers, piscivores, total standing biomass, and especially secondary consumers might achieve satisfactory outcomes at local within- island scales with no- take areas80, habitat restoration, or better regulated destructive human activities79. Local management of planktivores is no doubt also important34. But, given the potential influence of regional- scale drivers on planktivore biomass production and the importance of this group as the prey base for higher trophic levels32, more nuanced, region- specific targets for recovery81 or take of planktivores may be advisable in areas of naturally lower primary production." + +<|ref|>text<|/ref|><|det|>[[147, 801, 870, 892]]<|/det|> +- Cumming and Dobbs. (2020). Quantifying social-ecological scale mismatches suggests people should be managed at broader scales than ecosystems. One Earth 3(2), 251-259. +- Hughes et al. (1999). Patterns of recruitment and abundance of corals along the Great Barrier Reef. Nature 397:59-63 +- MacNeil et al. (2009). Hierarchical drivers of reef-fish metacommunity structure. Ecology 90:252-264. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 872, 186]]<|/det|> +In response to a similar question of spatial scale by Reviewer #2 (R2.4), we have also now created an additional figure (Fig. S3 below) for the reader to visualise the observed within- and among- island scale variation in depth zonation (island- level depth effects, overlying global depth for comparison, across each trophic group; within- island variation is indicated by \(95\%\) credible intervals associated with island point estimates). + +<|ref|>sub_title<|/ref|><|det|>[[118, 201, 185, 215]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[118, 231, 485, 246]]<|/det|> +Line 413 onwards (Reef fish survey data section). + +<|ref|>text<|/ref|><|det|>[[118, 260, 872, 291]]<|/det|> +R1.25: Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +<|ref|>text<|/ref|><|det|>[[118, 305, 872, 426]]<|/det|> +Thanks for this important consideration. The National Oceanic and Atmospheric Administration (NOAA) has multiple trained fish survey divers who conduct in situ observations across sampling cruises, across distinct ecoregions and years. Divers must have a minimum of 30 underwater visual fish survey census dives conducted prior to joining a monitoring cruise. In addition, to ensure consistency in observer species identification and size estimation, NOAA employs extensive training, testing, and technical validation protocols both outside of the cruise period and during (detailed in Heenan et al. 2017). These protocols address the potential for intra- and inter- diver variability in two ways: + +<|ref|>text<|/ref|><|det|>[[147, 426, 872, 530]]<|/det|> +1. New and experienced divers receive full training in fish identification and survey protocol, in classroom and in-water sessions; prior to each survey cruise, all divers must accurately identify \(>90\%\) of regional-specific fish species in a test that is specifically weighted towards rare species and those that have conspecifics with similar appearance. +2. For the timeframe of the data used here, between cruises divers conducted in-water training exercises to practice survey protocol, fish identification and fish size estimation (see response to comment R1.27 for detail on size estimation protocol and technical validation). + +<|ref|>text<|/ref|><|det|>[[118, 545, 873, 696]]<|/det|> +During the cruises, there are typically 4- 10 fish survey divers who routinely discuss and compare species identification and sizes immediately after a survey, and during data entry. Diver pairs are continually rotated, and diver performance is estimated as the difference between the estimates of each diver and those of their dive partner at each site, calculated for total fish biomass, species richness, and body- size distributions of commonly observed species. As divers survey adjacent cylinders on the reef (i.e. not identical areas of the reef), real differences between diver observations are expected. But the diver performance estimate is measured to detect potential consistent bias made by each diver (i.e. if there is no consistent bias, the median difference with their buddy partner should be close to zero). Diver performance is measured every few days during survey cruises to allow for early detection of observer error (Heenan et al. 2017). + +<|ref|>text<|/ref|><|det|>[[118, 711, 872, 787]]<|/det|> +In addition to these technical validation protocols, we included a group- level random intercept for 'diver identity' in all of our statistical models of fish biomass to account for any remaining effect of observer bias. By assuming inherent correlations among divers and their observations that affect the estimated means and associated errors, we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) (sensu Macneil et al. 2015 Nature). + +<|ref|>text<|/ref|><|det|>[[147, 802, 860, 862]]<|/det|> +- Heenan et al. (2017). Long-term monitoring of coral reef fish assemblages in the Western central pacific. Sci Data 4(1), 1-12. +- MacNeil et al. (2015). Recovery potential of the world's coral reef fishes. Nature 520(7547), 341-344. + +<|ref|>text<|/ref|><|det|>[[118, 876, 785, 892]]<|/det|> +We have revised the manuscript as follows to provide the required additional information: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 110, 873, 175]]<|/det|> +L457: "Surveys were conducted by multiple observers across the study ecoregions and years. NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation49. Full details on SPC survey methods and technical validation steps are available in [49]. To further mitigate any confounding effect of observer bias among fish surveys, we included 'diver identity' as a random intercept in all statistical models (described below) (sensu53)." + +<|ref|>text<|/ref|><|det|>[[178, 175, 875, 202]]<|/det|> +L514: "A random intercept for 'diver identity' was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations (sensu53)." + +<|ref|>text<|/ref|><|det|>[[178, 202, 875, 247]]<|/det|> +L514: "A random intercept for 'diver identity' was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations (sensu53)." + +<|ref|>text<|/ref|><|det|>[[118, 260, 875, 291]]<|/det|> +R1.26: SPC surveys: Then there is the question of the survey method itself. Can the authors cite other studies that have used this method? + +<|ref|>text<|/ref|><|det|>[[118, 305, 874, 411]]<|/det|> +Yes - the stationary point count is one of the three main methods used to survey coral reef fish assemblages globally (Caldwell et al. 2016). This survey method has been used since 2010 by the United States government agency, the National Oceanic and Atmospheric Administration (NOAA) in their Pacific monitoring program (Towle et al. 2022). The full details of which are available in the data descriptor paper (Heenan et al. 2017). The dataset has been used in numerous peer- reviewed scientific publications, some of which are cited in the manuscript (now referenced in L453 of the revised manuscript): + +<|ref|>text<|/ref|><|det|>[[147, 425, 866, 592]]<|/det|> +- Caldwell et al. (2016). Reef fish survey techniques: Assessing the potential for standardizing methodologies. PLoS One 11(4): e0153066. +- Heenan et al. (2019). Natural variation in coral reef trophic structure across environmental gradients. Front Ecol Environ 18(2), 69-75. +- Towle et al. (2022). A National Status Report on United States Coral Reefs Based on 2012–2018 Data From National Oceanic and Atmospheric Administration’s National Coral Reef Monitoring Program. Front Mar Sci, 8. +- Williams et al. (2015). Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS One 10(4), e0120516. +- Yeager et al. (2017). Scale dependence of environmental controls on the functional diversity of coral reef fish communities. Glob Ecol Biogeogr 26(10), 1177-1189. + +<|ref|>text<|/ref|><|det|>[[177, 606, 850, 637]]<|/det|> +L453: "The abundance and body- size of all diurnal, non- cryptic reef fishes were estimated using stationary point count (SPC) surveys (sensu8,9,15,49,82,83)." + +<|ref|>text<|/ref|><|det|>[[118, 652, 864, 743]]<|/det|> +R1.27: Lengths: From what I understand actual fish lengths have been estimated (to the nearest cm) rather than fish size classes. I am struggling to understand how this could be achieved underwater without a significant amount of bias given that some fish could be as far away as 15m. Can you explain a bit more on how consistency of length measurements was assured between divers across all the different surveys? Even if that information exists in another reference, it is worth mentioning it in this manuscript, given the large dataset that is being used. + +<|ref|>text<|/ref|><|det|>[[118, 756, 870, 908]]<|/det|> +This is another important question. As in response to R1.25, NOAA employs extensive training and technical validation protocols to ensure consistency in sampling. This includes practice size calibration dives during the out of cruise season. These calibration surveys involve divers visually estimating the size of anchored wooden cut- outs of fish with known body lengths, placed throughout the full extent of the survey cylinder (Fig. R1a). While it is true that there is a degree of variability in novice divers, or those new to the training program (Fig. R1c), the experienced trained staff are reasonably consistent (Fig. R1b) with no systematic tendency to over or underestimate size. It is also important to note that as divers remain at the centre of their cylinder, except towards then end of the survey when the size of smaller benthic site- attached species are estimated, typically the furthest distance the diver will be from any fish that is being estimated in length is 7.5 m, not 15 m. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[131, 130, 855, 545]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 550, 880, 662]]<|/det|> +
Figure R1: Taken from Heenan et al. (2017) Scientific Data: During training dives, observer accuracy is assessed by divers estimating the size of wooden fish models of known lengths (a), which are haphazardly distributed throughout a mock SPC cylinder. Example mean difference ( \(\leftarrow\) -standard error) between actual and estimated length of model fishes by trained staff (b—open circles) and by trainee survey divers (c—closed circles) during size estimation training trials between 2014–2016. The closer the difference between size estimates and actual model sizes is to zero, the more accurate the sizing. Trainee fish survey divers, which includes novices in the middle of the training program, people who have done fish surveys but not the SPC method, as well as people who are taking an SPC refresher tend to towards more variable size estimates compared to core staff. Typically new fish surveyors are required to have conducted a minimum of 30 survey dives prior to joining a RAMP cruise.
+ +<|ref|>text<|/ref|><|det|>[[177, 676, 875, 767]]<|/det|> +L458 has been revised to highlight the technical validation protocols designed to ensure consistency in length measurements, with reference to the data descriptor paper (Heenan et al. 2017): "NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation49. Full details on SPC survey methods and technical validation steps are available in 49." + +<|ref|>text<|/ref|><|det|>[[118, 781, 874, 826]]<|/det|> +R1.28: Lines 440- 442: Does this mean that 400m was cross- checked against all surveyed sites to make sure it does not include opposite sides of the island? What about encompassing the reef flat and reef crest zones? + +<|ref|>text<|/ref|><|det|>[[118, 841, 875, 902]]<|/det|> +We selected an automated process to estimate mean bathymetric steepness within a 400- m radial buffer around each site to remove potential subjectivity in the method. We confirm that we visually cross- checked all 2,262 survey sites to see whether these buffers overlapped landmass (N.B. landmass areas were excluded as standard). While there was no observed overlap of the buffers across opposite + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 999, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[117, 109, 875, 320]]<|/det|> +sides of the primary 35 study islands, we found a total of 15 sites where some degree of overlap of an adjoining islet or peninsula was observed ( \(< 1\%\) of sites). Ten of these cases occurred where the buffer encompassed the end of an islet or a protruding peninsula, which would require drawing an arbitrary line in the buffer from the islet out to the buffer circumference in order to differentiate one area of ocean from the other (e.g. Fig. R2a,b). Given that the hydrodynamics at each site are predominantly unknown (i.e. the likely direction of currents and upwelling), we selected not to introduce this bias and accepted a level of uncertainty introduced by our a priori determination of radial buffer extent (L436- 439 original manuscript: "A radial buffer- size of 400 m was selected to encompass depths that would capture the propensity for pulsed delivery of nutrient- rich sub- thermocline water by upwelling \(^{86,87}\) and for this upwelling to propagate onto shallow reef habitats at depths \(\leq 30 m^{35}\) ."). The five remaining cases (representing \(0.2\%\) of the total sites) included landmass where the buffer was split into two areas of sea (e.g. A1 and A3 in Fig. R2c). We calculated the percentage of forereef area included from opposite sides of the landmass that contributed to the estimate of mean bathymetric steepness for these sites as: \(1.0\%\) , \(2.1\%\) , \(5.0\%\) , \(24.1\%\) , and \(43.1\%\) (Table R1). + +<|ref|>text<|/ref|><|det|>[[117, 334, 878, 487]]<|/det|> +We selected this automated method of estimating coarse- scale bathymetric steepness to mitigate potential subjectivity in a site- by- site assessment. However, prompted by the Reviewer's question and to ensure the highest levels of confidence in our data, we have subsequently decided to remove two sites where the percentage of the buffer area that was located on an opposite side of a landmass contributed \(>5\%\) to the bathymetry estimates (i.e. sites TUT- 00376 and TUT- 00516; Table R1; Fig. R2c). We have also removed an additional 7 sites that are officially classified as 'forereef' in NOAA's National Coral Reef Monitoring Program (Heenan et al. 2017) but could also be classified as reef crest or reef flat. We have re- run all models and adjusted the minor details of results (e.g. precise probability estimates) throughout, though we note that the broad study results remain unchanged from the original submission. + +<|ref|>text<|/ref|><|det|>[[118, 500, 875, 531]]<|/det|> +To clarify our cross- checking process and site filtering approach, we have revised the methods section as follows: + +<|ref|>text<|/ref|><|det|>[[176, 545, 872, 576]]<|/det|> +L490: "All sites were visually cross- checked for island overlap, and those including \(>5\%\) radial- buffer bathymetry on the opposite site of a landmass were excluded from all analyses." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 110, 875, 459]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[118, 459, 878, 511]]<|/det|> +
Figure R2: Example 400-m radial buffers used to estimate site-level mean bathymetric steepness where the buffers overlapped islets or peninsula landmass. a, b: Examples of cases where buffers encompassed landmass and would require drawing a line from land to the buffer circumference to differentiate areas to include/exclude. c: an example of where the landmass divided the buffer into two areas (A1 and A3).
+ +<|ref|>table<|/ref|><|det|>[[108, 548, 874, 714]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[115, 523, 877, 549]]<|/det|> +Table R1: Proportion of 400-m radial buffer area on the opposite side of a landmass area contributing to site-level average bathymetric steepness estimates. Site names include the three-letter island reference codes detailed in Table S1. + +
Site nameA1: Site side (m²)A3: Opposite side (m²)Percentage of area on opposite side contributing to site average estimate (%)
PAG-00379340,1577,2682.1
TUT-00376257,666195,13143.1
TUT-00516343,405109,20924.1
OFU-00437176,2591,8651.0
OAH-00300356,73018,6725.0
+ +<|ref|>text<|/ref|><|det|>[[118, 728, 870, 760]]<|/det|> +R1.29: Lines 444- 451: I am not familiar with this method to be able to evaluate if it has been applied correctly. Can you cite 1- 2 refs for the type of model you ended up using? + +<|ref|>text<|/ref|><|det|>[[118, 773, 875, 850]]<|/det|> +We have added a reference to the peer- reviewed paper by Bürkner (2017) which provides a detailed description of the Bayesian multi- level statistical model approach using the R software package brms as used in our study. The paper includes description of the multi- level regression models we have applied, the use of priors and selection of population- or group- level specific family parameters, and a worked example: + +<|ref|>text<|/ref|><|det|>[[147, 863, 835, 894]]<|/det|> +- Bürkner (2017). brms: An R Package for Bayesian Multilevel Models Using Stan. J Stat Softw 80, 1-28. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 844, 126]]<|/det|> +R1.30: Line 480: What criterion was used to determine if the proportion of zeros was low enough? + +<|ref|>text<|/ref|><|det|>[[118, 140, 876, 307]]<|/det|> +We tested initial biomass models with a hurdle structure and found that the hurdle component only affected model results when the number of zeros were sufficient (i.e. \(>5\%\) ). To accommodate zerocount observations by fitting a hurdle model, a sufficient contrast (i.e. a sufficient number of zeros and ones) is required to be able to estimate effects in the presence- absence component of the model. If nearly all values are \(>0\) , then there are only a few datapoints to inform the model about factors that lead to a zero outcome. In those cases, the probability of positives will be close to one (particularly with a dataset as large as in this study since are 1000s of positive data observations), and the hurdle component will only add noise. In the case of primary and secondary consumer biomass where the percentage of zeros was \(1.09\%\) and \(0.05\%\) respectively, in our dataset, the low contrast for the hurdle components affected model convergence and only added noise, so those were deemed not useful. To clarify this, we have provided additional description in the methods as follows: + +<|ref|>text<|/ref|><|det|>[[178, 320, 869, 411]]<|/det|> +L542: "Where the proportion of zeros was too low to effectively estimate effect sizes in the presence- absence component (i.e. an insufficient contrast between the number of zeros and ones), the use of a hurdle structure affected model convergence and only added noise. This occurred for primary consumers ( \(1.09\%\) zeros) and secondary consumers ( \(0.05\%\) zeros), so for these groups the zero biomass replicates were removed from the analysis and the Gamma model detailed above was fitted." + +<|ref|>sub_title<|/ref|><|det|>[[120, 440, 422, 456]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 470, 875, 681]]<|/det|> +R2.1: The study by Richardson and coauthors entitled: "Re- visiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECOLEVOL- 221117855) sets out to explore depth zonation patterns of coral reef fishes across gradients of biophysical processes and human disturbance. This study builds upon a broad body of work focused on contributing to our understanding of how habitat, depth, and other important biophysical drivers influence the structure and distribution of fishes. To date, most contributions to the literature have focused on describing these patterns at single locations or groups of sites across a limited spatial scale. This study complements these efforts by assembling a large and comprehensive dataset including over 5,000 in situ reef fish surveys spanning across 35 islands to explore these ecological patterns. Overall, I found the study to be well designed, scientifically interesting, and well written. I think the results provide valuable insights into how coral reef fish communities are structured in a changing world. However, I feel that there are a couple areas that should be considered before the manuscript is published. I have outlined these broad recommendations along with a couple more detailed comments below. Once these items are addressed, I feel that this manuscript will make a valuable contribution to the field of Ecology. + +<|ref|>text<|/ref|><|det|>[[118, 695, 868, 757]]<|/det|> +Thanks to Reviewer #2 for their positive comments and thoughtful evaluation of our manuscript. We are pleased they found the article to be interesting, valuable to the field of Ecology, well- designed, and well- written. We have addressed the broad and detailed recommendations made, editing, or adding the required detail in the revised submission. + +<|ref|>text<|/ref|><|det|>[[117, 771, 876, 907]]<|/det|> +R2.2: First, I would like the authors to consider how they filtered and selected the reef fishes for this study. While I appreciate the complexity and variability of coral reef fish data, I am concerned about the exclusion of ecologically important species (Sharks and Jacks). I am familiar with the literature identifying potential biases associated with large- bodied and mobile species as well as the behavioral effects associated with diver presence. Many of these biases or behavioral effects could be observed for other large- bodied mobile species within important groups such as parrotfishes (Scaridae), wrasses (Labridae) and snappers (Lutjanidae). I would like the authors to consider the potential biases associated with choosing to remove ecologically important species. For example, in most coral reef communities Jacks (Carangidae) are voracious predators exerting strong top- down effects on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 110, 875, 217]]<|/det|> +prey species. This is particularly evident with species such as Caranx ignobilis, C. melampygus, and C. lugubris that can be observed actively hunting across coral reef habitats preying on fishes and other invertebrates. This predatory behavior has been well documented in ecoregions included in this study (Hawaiian Islands and Line Islands). This is also the case with reef sharks (Carcharhinidae) excluded from this study (e.g., Carcharhinus melanopterus, C. amblyrhynchos, and Triaenodon obesus). I ask that the authors reconsider removing the entire group of sharks and jacks and be more selective in their filtering to factor in the ecological relevance of their choices. + +<|ref|>text<|/ref|><|det|>[[117, 230, 875, 473]]<|/det|> +We thank the Reviewer for raising this. We agree that it would be interesting to explore piscivore biomass trends including sharks and jacks (despite their known daily vertical migrations up and down the reef slope; Meyer et al. 2007, Afonso et al. 2009, Vianna et al. 2013) if we had robust, unbiased estimates of these larger predators. As the Reviewer notes, piscivorous species of jacks and sharks are critically important to trophic dynamics and ecological organisation on coral reefs via top- down predation processes. However, as the Reviewer also highlights, published evidence shows that the body- size, mobility, curiosity, and trophic position of sharks and jacks influences their detectability and can introduce substantial sampling bias (Kulbicki 1998), particularly in surveys involving stationary divers (as in our study; Heenan et al. 2019). Common 'mobbing' behaviour of survey divers by sharks and jacks can lead to systematic overestimates in density (Parrish and Boland 2004), particularly in remote unpopulated areas where mobile roving piscivores can remain curious and unafraid of humans such as in the northwestern Hawaiian Islands (Williams et al. 2015). To mitigate this method bias, and in particular likely spatial variation in sampling bias among populated vs unpopulated locations, sharks and jacks are routinely excluded from reef fish survey analyses (sensu MacNeil et al. 2015; Table R2). + +<|ref|>table<|/ref|><|det|>[[108, 518, 875, 666]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[115, 487, 880, 518]]<|/det|> +Table R2 Examples of studies globally that exclude sharks and other large semi-pelagic (associated with both shallow reef and pelagic environments) piscivorous fish such as jacks. + +
Geographic study regionExcludes sharksExcludes sharks and semi-pelagics
GlobalD'Agata et al. 2016 Roy Soc Proc BMacNeil et al. 2015 Nature
Cinner et al. 2016 Nature
CaribbeanHawkins and Roberts 2004 Cons Biol
PacificD'Agata et al. 2016 Nat Comms
Gray et al. 2016 PLoS ONE
Williams et al. 2015 PLoS ONE
Yeager et al. 2017 Glob Ecol Biogeog
Indian OceanMcClanahan et al. 2009 MEPSMcClanahan et al. 2020 Aqu Conserv
Samoyils et al. 2018 PLoS ONE
Cowburn et al. 2018 Mar Pol Bull
+ +<|ref|>text<|/ref|><|det|>[[117, 679, 876, 858]]<|/det|> +Unlike jacks and sharks, 'mobbing' behaviour towards divers by other large- bodied mobile species of reef fish such as parrotfishes, wrasses, and snappers is less routinely observed, as they may be less strongly affected by diver- presence (Longo and Floeter 2012). Our study authors have observed some hair- raising instances of diver- mobbing by the snapper, Lutjanus bohar, in the southern Line Islands (a geography not included in our study) where they are dominant in abundance over sharks (G. J. Williams, pers. comms.). However, such occurrences appear specific to that geography and are less commonly reported than the diver- positive behaviour documented for sharks and jacks, specifically in our study region. Indeed, efforts to quantify the effect of diver- presence on detectability of reef fishes across distinct families have described these other large- bodied groups as either diver- neutral (no detected effect on observed abundance, e.g. Lutjanidae), or diver- negative (where diver- disturbance reduces rather than increases detectability, e.g. Scaridae, Labridae, Serranidae) (Emslie et al. 2018). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 110, 877, 430]]<|/det|> +- Afonso et al. (2009). Multi-scale patterns of habitat use in a highly mobile reef fish, the white trevally Pseudocaranx dentex, and their implications for marine reserve design. Mar Ecol Prog Ser 381, 273-286. +- Emslie et al. (2018). Reef fish communities are spooked by scuba surveys and may take hours to recover. PeerJ 6, e4886. +- Heenan et al. (2019). Natural variation in coral reef trophic structure across environmental gradients. Front Ecol Env 18(2), 69-75. +- Kulbicki. (1998). How the acquired behaviour of commercial reef fishes may influence the results obtained from visual censuses. J Exp Mar Biol Ecol 222(1-2), 11-30. +- Longo and Floeter. (2012). Comparison of remote video and diver's direct observations to quantify reef fishes feeding on benthos in coral and rocky reefs. J Fish Biol 81(5), 1773-1780. +- Meyer et al. (2007). Seasonal and diel movements of giant trevally Caranx ignobilis at remote Hawaiian atolls: implications for the design of marine protected areas. Mar Ecol Prog Ser 333, 13-25. +- Parrish and Boland. (2004). Habitat and reef-fish assemblages of banks in the northwestern Hawaiian Islands. Mar Biol 144: 1065-73. +- Vianna et al. (2013). Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks (Carcharhinus amblyrhynchos) at aggregation sites. PloS ONE 8(4), e60331. +- Williams et al. (2015). Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS ONE 10: e0120516. + +<|ref|>text<|/ref|><|det|>[[118, 441, 866, 548]]<|/det|> +Therefore, while we appreciate the Reviewer's point and reiterate that we would consider exploring trends with sharks and jacks if we had unbiased estimates, we believe that including them from this data source where there is known systematic method bias would be misleading. Further, we are keen to ensure comparability between our study and existing publications in the literature that quantify unfished biomass baselines and drivers of reef fish assemblage structure (e.g. Table R2). However, we recognise that more detailed explanation for our filtering method would better equip the reader, which we have now added to the revised manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[177, 562, 870, 668]]<|/det|> +L469: "Sharks and jacks (families Carcharhinidae, Carangidae, Sphyrnidae) were also excluded as these highly mobile, large-bodied, roving piscivores are known to be affected by the presence of stationary divers, typically resulting in systematic over- inflation of visual survey density estimates \(^{85}\) (sensu \(^{8,53}\) ). The presence of divers was also a potential source of differential bias of biomass estimates of these fishes among study locations, with 'mobbing' behaviour by jacks and sharks known to occur particularly in remote, unpopulated areas such as the northwestern Hawaiian Islands \(^{8,50}\) ." + +<|ref|>text<|/ref|><|det|>[[117, 682, 876, 848]]<|/det|> +R2.3: Second, the authors take advantage of a previously published dataset (MacNeil et al. 2015) that provides an estimate of the total unfished global fish biomass to serve as the mean for analysis in this study. The intercept value was used for all trophic groups included in this study with the exception of the secondary consumers. While I do not disagree with this approach, I have concerns over the comparability of datasets. Specifically, the previous study uses a filtering process to exclude certain species. It does not seem like the authors in this study used the same filtering process to exclude the same species. Therefore, this would introduce potential biases in the analysis and statistical modeling outputs. Again, I recommend that the authors consider the ecological implications of the species filtering process and provide a justification for how they selected species or groups to exclude. I think the MacNeil work is great but maybe the authors from this study should consider using the approach they used for the secondary consumers when data were not comparable between studies. + +<|ref|>text<|/ref|><|det|>[[118, 863, 870, 911]]<|/det|> +We are glad the Reviewer broadly agrees with our approach for setting priors ("the mean for analysis in this study") for our models of fish biomass, albeit with reservations about the potential incomparability of datasets between our study and that by MacNeil et al. (2015). By using 'prior' + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 108, 868, 224]]<|/det|> +information on global unfished biomass estimates from MacNeil et al., we provide the models with a ‘real world’ starting point to begin exploring the basis of the given conjectures (e.g. whether or not there is a depth effect). Incorporating prior information is the defining characteristic of Bayesian philosophy, allowing us to directly integrate information about the scientific context and remove the implicit equal weighting of possibilities that is more akin to frequentist analyses (Lemione 2019, McElreath 2020). It is worth noting that, in general, “the prior data and new data can be of different types” (McElreath 2020). + +<|ref|>text<|/ref|><|det|>[[117, 236, 876, 497]]<|/det|> +Nevertheless, while not identical, our approach to filtering jacks and reef- sharks is very close to that of MacNeil et al., who “retained counts of diurnally active, non- cryptic reef fish that are resident on the reef slope, excluding sharks and semi- pelagics”. We explicitly inflated the prior standard deviation in the intercepts for our models, which is based on the MacNeil et al. study, to account for factors that may limit comparability. These factors include species filtering approaches, but also geographical representativeness, and census method. In other words, we selected the MacNeil et al. study as the most relevant information to base a prior mean on (i.e., to determine the order of magnitude we might expect in unfished biomass on a reef), we do not think that the precision in their estimates would be useful for our prior. We therefore inflated our prior standard deviation considerably (by an order of magnitude, given the prior is on the log- scale). Given the large amounts of data that inform our models (previously \(n = 5,549\) , now \(n = 5,525\) stationary point count fish surveys), the prior had a negligible impact, and estimated mean densities were often significantly shifted from the prior. We have added clarification about our prior specification to the methods (detailed below), and have added an additional figure to the Supplemental Information showing the prior and posterior intercept for unpopulated islands to illustrate how the data moves our posterior estimates from the prior (Fig. S4 below). + +<|ref|>text<|/ref|><|det|>[[147, 510, 877, 574]]<|/det|> +- Lemoine (2019). Moving beyond noninformative priors: why and how to choose weakly informative priors in Bayesian analyses. Oikos, 128(7), 912-928. +- McElreath (2020). Statistical rethinking: A Bayesian course with examples in R and Stan. 2nd Edition, Chapman and Hall/CRC, New York, pp 612. + +<|ref|>text<|/ref|><|det|>[[178, 586, 872, 668]]<|/det|> +L549: “This study builds on existing knowledge established in previous research that estimated a global baseline of total resident reef fish biomass in the absence of fishing \(^{53}\) . We integrate this prior information by using their published posterior biomass estimate (1,013 kg ha \(^{- 1}\) ) as the mean of the prior for log of total biomass ( \(\alpha\) ; converted to g m \(^{- 2}\) ) (with standard deviation set at 1).” + +<|ref|>text<|/ref|><|det|>[[178, 701, 875, 817]]<|/det|> +L560: “MacNeil et al. \(^{53}\) and our study employ comparable data (i.e. in situ counts of diurnally active, non- cryptic reef fish on forereef slopes, excluding sharks and semi- pelagics such as jacks). However, to account for potential differentiating factors between the studies, such as species filtering approaches, census method, or geographical representativeness, we inflated the prior standard deviation in the intercepts for our models by an order of magnitude. Model priors are detailed in Table S3 and plotted with unpopulated posterior intercept estimations in Fig. S4.” + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[122, 111, 875, 430]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 442, 880, 483]]<|/det|> +
Figure S4 Biomass model prior distributions and unpopulated posterior intercept estimations for each trophic group of reef fish. Specified prior distributions for each biomass group are shown with the blue line. Posterior intercept distributions are shown in orange.
+ +<|ref|>text<|/ref|><|det|>[[115, 505, 875, 641]]<|/det|> +R2.4: Lastly, I found the dataset included in this study to be impressive and I appreciate the efforts involved with synthesizing data from across 5 ecoregions. As the authors point out, each of the 5 ecoregions included in this study are exposed to different biophysical forces and levels of human disturbance. I understand the major aim of this study was to compare patterns of reef fish biomass across depth gradients for 5 ecoregions. However, I think it would be interesting to see if these patterns hold up within each ecoregion. I found the results from figure 5 to be interesting and wanted explore these results more. I am not suggesting that the authors create additional figures etc. However, I would recommend that the authors provide some additional discussion to expand on their findings. Are the patterns consistent within each ecoregion? + +<|ref|>text<|/ref|><|det|>[[116, 655, 876, 883]]<|/det|> +We thank Reviewer #2 for this helpful suggestion - we agree that the consistency of the patterns among sites, islands, and ecoregions is interesting and warrants further discussion (also per R1.24). While our study primarily strives to quantify generality in depth effects across the dataset (L98 original manuscript; response to R3.3 and revised text L106- 113), we also emphasise the role of scale- dependent biophysical gradients that likely influence the spatial variation in fish biomass trends we observed across the Pacific (manuscript Fig.5, Tables S10 and S11). We have added discussion on the spatial heterogeneity observed across scales (detailed below) and the consistency of fish biomass depth zonation patterns across scales, including ecoregion (detailed below). The Reviewer's comment also inspired us to create an additional figure for the Supplemental Information (Fig. S3 below) to help the reader visualise spatial consistency, by showing depth effects at each of the study islands (within each ecoregion) and where depth zonation patterns deviated from the global depth effects. Broadly, few islands across the study ecoregions deviated from the global depth effect, indicating spatial consistency in the observed patterns. Though we note high levels of within- island variation in these estimates (indicated by the 95% credible intervals for each island), consistent with the high levels of observed site- level variation in the study (Fig.5, Table S10). + +<|ref|>text<|/ref|><|det|>[[118, 898, 180, 912]]<|/det|> +Results: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[178, 110, 876, 176]]<|/det|> +L230: "The proportion of variation in fish biomass explained by each spatial scale, quantified by extracting the posterior standard deviations of these modelled random effects, varied among trophic fish groups (Fig. 5; Table S10 and S11; see Fig. S3 for variation in island- level depth effects among ecoregions)." + +<|ref|>sub_title<|/ref|><|det|>[[118, 191, 207, 205]]<|/det|> +## Discussion: + +<|ref|>text<|/ref|><|det|>[[178, 206, 870, 269]]<|/det|> +L262: "These patterns hold true across the study area which spans distinct biogeographic regions, with high spatial consistency across islands and ecoregions (Fig. S3) despite varying spatial heterogeneity in fish biomass observed among trophic groups suggesting the role of distinct scale- dependent drivers." + +<|ref|>text<|/ref|><|det|>[[178, 283, 870, 331]]<|/det|> +L275: "At geographically distinct unpopulated islands, we show that reef fish biomass of all broad trophic groups correlated predictably and relatively consistently across depth despite underlying variation in biophysical drivers known to affect standing reef fish biomass33,41,50." + +<|ref|>text<|/ref|><|det|>[[178, 346, 871, 410]]<|/det|> +L372: "While there was minimal observed deviation from the global depth effect across the study islands and ecoregions, our results show that spatial variation in fish biomass—across site, island, and ecoregion scales—was differentially and unevenly distributed among trophic groups, underscoring the importance of scale of observation in ecological enquiry10,77." + +<|ref|>text<|/ref|><|det|>[[178, 424, 877, 538]]<|/det|> +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 103, 870, 644]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 657, 880, 831]]<|/det|> +
Figure S3 Island-level depth effects on reef fish biomass among distinct study ecoregions (Samoa Islands; Phoenix/Tokelau/Northern Cook islands (P/T/NC); Mariana Islands; Line Islands; Hawaii Islands). Point estimates and associated \(95\%\) credible interval (CI) lines indicate the effect of increasing depth on fish biomass (proportional change) at each island (increase if \(>1\) , decrease with depth if \(<1\) ). The population status of islands is indicated by CI line thickness (thick CI, populated; thin CI, unpopulated). Pale shaded boxes underlying point estimates and CIs represent the average proportionate global effect of depth on biomass given the human population status and average bathymetric steepness, and are provided to aid visual assessment of spatial consistency in depth effects across the study. For example, at islands where depth effects on fish biomass follow the over-all global depth trend for a given trophic group, point estimates are positioned on top of the pale shaded boxes. Conversely, at islands where the effect of depth differs from the global effect, point estimates are positioned outside the shaded box (e.g., in Kauai, there is a greater observed decrease in the biomass density of primary consumers with increasing depth than the over-all effect of depth for that group at populated islands; in Tutuila there is a greater proportionate increase in planktivore biomass with increasing depth relative to the global depth effect for that group at populated islands).
+ +<|ref|>text<|/ref|><|det|>[[118, 854, 585, 870]]<|/det|> +R2.5: Line 445 – (biomass density; g-m2) do you mean g m-2? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 253, 125]]<|/det|> +Corrected, thanks. + +<|ref|>text<|/ref|><|det|>[[118, 140, 875, 187]]<|/det|> +R2.6: Figures – In general I found the figures to be great. However, I am not sure if it was the download process but the figures appear to be low resolution and slightly blurry. I know a lot of work went into creating the figures and it would be good to confirm the quality for publication. + +<|ref|>text<|/ref|><|det|>[[118, 200, 870, 247]]<|/det|> +We confirm that that all the figures have a minimum resolution of 300 dpi and saved at a maximum width of \(180\mathrm{mm}\) per the journal requirements. The figures presented in the original submission were lower resolution to reduce the manuscript file size (apologies). + +<|ref|>text<|/ref|><|det|>[[116, 260, 870, 292]]<|/det|> +R2.7: Table S1 – Agujian categorized as “Populated”? I assume this is due to its proximity to Tinian and Saipan rather than its small resident population? + +<|ref|>text<|/ref|><|det|>[[118, 305, 860, 352]]<|/det|> +This is correct. We classified islands as ‘populated’ based on having \(>50\) residents or located \(< 100\mathrm{km}\) from the nearest larger human settlement (sensu Williams et al. 2011; Williams et al. 2015), per L400- 403 (in original submission). + +<|ref|>text<|/ref|><|det|>[[146, 365, 852, 442]]<|/det|> +- Williams et al. (2011). Differences in reef fish assemblages between populated and remote reefs spanning multiple archipelagos across the Central and Western Pacific. J Mar Biol 2011:826234. +- Williams et al. (2015). Local human impacts decouple natural biophysical relationships on Pacific coral reefs. Ecography 38(8), 751-761. + +<|ref|>sub_title<|/ref|><|det|>[[118, 470, 422, 486]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[118, 500, 163, 514]]<|/det|> +## R3.1: + +<|ref|>text<|/ref|><|det|>[[118, 516, 878, 577]]<|/det|> +This well- written paper uses a uniquely large data set to examine the effects of depth on reef fish assemblages, and how population pressure influences this pattern. The paper uses modern analytical techniques to provide a convincing story of depth- related gradients for both major trophic groups and total biomass. + +<|ref|>text<|/ref|><|det|>[[118, 590, 839, 637]]<|/det|> +The paper also includes an interesting finding of the role of reef bathymetry on reef fishes – the influence of reef steepness on fish assemblages intuitively might be expected, but has rarely been demonstrated at this scale and with such good bathymetry data. + +<|ref|>text<|/ref|><|det|>[[118, 650, 870, 757]]<|/det|> +We thank Reviewer #3 for their positive comments and specific consideration of the overall position of our study in the context of the scope of Nature Ecology & Evolution. We are pleased they consider the manuscript to be well- written, employing a “uniquely large” and high- resolution dataset and “modern analyses” to provide a convincing story, with interesting results that have “rarely been demonstrated at this scale”. We have addressed the concerns raised, providing detailed explanation where possible and added clarification in this response document and in the revised manuscript, accordingly. + +<|ref|>text<|/ref|><|det|>[[117, 770, 868, 907]]<|/det|> +R3.2: My issue with the paper is whether the story is sufficiently interesting for such a high- profile journal for two reasons: 1) the interest in revisiting basic depth gradients and examining homogenization by human impacts and 2) the lack of detailed covariates. The depth- related gradient of zones on reefs is indeed a well- described and accepted paradigm, although I would argue we now have enough descriptions of changes with depth that the ability to generalize is stronger than indicated here (first line of abstract, L77- 80). The homogenization of assemblages because of human impacts is also well known in a range of ecosystems (including on reefs). Therefore, it isn’t particularly surprising that the zonation is less clear near highly populated islands. I agree this hasn’t been demonstrated as clearly as in this study and it needs to be quantified, but I question + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 874, 217]]<|/det|> +whether this elevates the paper to one that should be published in Nature Ecology & Evolution. More fundamentally, I'm not sure how this would change our approach to studying or conserving reefs – the underlying ecological paradigm is clearly still true given the significance of the variables that change with increasing depth, and management is rarely zone specific. For example, any meaningful study of patterns of fish assemblages already controls for variable fishing pressure. Therefore, does this study really suggest that revisiting existing paradigms would change our approach to studying or managing ecosystems? + +<|ref|>text<|/ref|><|det|>[[118, 230, 869, 336]]<|/det|> +We are disappointed (and sorry) that Reviewer #3 did not find the study as interesting as Reviewers #1 and #2. We are encouraged though that they found the demonstrated role of reef steepness on reef fishes interesting and novel in the scale at which it is demonstrated and that they recognise the uniquely large dataset and modern analytical techniques used. We are also pleased that the Reviewer recognises that while depth zonation is an accepted paradigm, as is the increasing propensity for ecological homogenisation under mounting human impacts, that these things need to be quantified and that we offer the clearest empirical demonstration of these to date. + +<|ref|>text<|/ref|><|det|>[[117, 350, 878, 625]]<|/det|> +Nonetheless, the Reviewer's comment has highlighted that the broader context and importance of our enquiry could be made clearer for the reader. As described by Underwood et al. (2000), we cannot make progress on understanding processes in ecology until we have understood the patterns of taxa distribution across scales relevant to (and as large as) biophysical gradients that structure communities. This requires that for testing principle ecological theories, widely accepted or otherwise, observations must be made across large- scales (in time, or space, or both) (Underwood et al. 2000, Marquet 2009). Until recently, testing ecological theory at (and across) large enough scales simply has not been possible due to a lack of spatially comprehensive, standardised ecological data, and accessible statistical tools (Marquet 2009, Farley et al. 2018). The result is a potential bias in ecology, and coastal marine ecology in particular, against the development of understanding ecological generality (Underwood et al. 2000). In our study, we have tested the theory of ecological depth zonation for the first time across an ocean- basin scale, via access to standardised, high- resolution ecological and environmental data and a Bayesian hierarchical modelling approach. The results do not indicate that the management of reefs requires an overhaul in respect to identified patterns of depth zonation (nor does the discussion). Instead, we emphasise that many existing widely accepted ecological paradigms that have informed the management of natural systems, to date remain largely untested at sufficient scale. + +<|ref|>text<|/ref|><|det|>[[119, 640, 863, 686]]<|/det|> +We thank the Reviewer for prompting us to revisit how we have described this fundamental premise for the paper. To better set- up this context for the reader, we have added to the introduction and discussion sections as follows: + +<|ref|>sub_title<|/ref|><|det|>[[118, 702, 216, 715]]<|/det|> +## Introduction: + +<|ref|>text<|/ref|><|det|>[[178, 716, 870, 881]]<|/det|> +L43: "However, two fundamental issues limit the application of these paradigms. First, scale and predictability". We cannot understand ecological generality without observations of patterns spanning scales that are large enough to encompass relevant environmental gradients". Biophysical processes governing ecological organisation often occur across broad geographies (e.g. regional or continental10- 13), mediating local community structure', and introducing inherent scale- dependent spatial heterogeneity in observed ecological patterns14- 16. To assess generality of ecological theories, a large enough lens is required to capture processes occurring across a land- or seascape of local environmental variation12. Without it, perceptual bias is introduced where observed ecological patterns have a unique set of scale- specific causes and consequences10,13, and an understanding of ecological generality is left without empirical grounding2. + +<|ref|>text<|/ref|><|det|>[[178, 881, 855, 911]]<|/det|> +L102: "Using a standardised Pacific- wide set of reef fish surveys49, composite data on bathymetric steepness, and hierarchical statistical models, we test for the first time whether + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 110, 877, 142]]<|/det|> +depth zonation patterns are generalisable on tropical coral reefs across broad geographies, and compare patterns in locations with and without local human populations." + +<|ref|>sub_title<|/ref|><|det|>[[118, 142, 206, 156]]<|/det|> +## Discussion: + +<|ref|>text<|/ref|><|det|>[[178, 156, 878, 231]]<|/det|> +L409: "We revisited ecological depth zonation—recognised as a fundamental structuring force of tropical coral reef communities over six decades ago but remains untested at scale7,26- 28 with two purposes: first, to test the generality of depth zonation of reef fish biomass for the first time across an ocean- basin scale; and second, to assess whether a zonation paradigm holds on reefs exposed to direct local human impacts." + +<|ref|>text<|/ref|><|det|>[[147, 244, 850, 336]]<|/det|> +- Farley et al. (2018). Situating ecology as a big-data science: Current advances, challenges, and solutions. Bioscience 68, 563-576. +- Marquet. (2009). Macroecological perspectives on communities and ecosystems. in The Princeton guide to ecology (ed. Levin et al.), pp 386. +- Underwood et al. (2000). Observations in ecology: you can't make progress on processes without understanding the patterns. J Exp Mar Biol Ecol 250(1-2), 97-115. + +<|ref|>text<|/ref|><|det|>[[115, 363, 880, 846]]<|/det|> +R3.3: More significantly this study feels like it misses opportunities to consider depth in the context of other variables, which potentially either excludes the chance of examining some interesting nuances in the data or possibly confounds the analyses. Firstly, human population pressure simply places reefs into one of two categories (populated or unpopulated) which seems overly simplified – why not consider population pressure as a continuous variable and look at more general trends and thresholds? Secondly, the analyses pool all sites from 'reef slopes', which standardizes the geomorphological zone but ignores any differences in benthic assemblages. Thus the reader is left wondering, for example, whether populated islands have more homogenous benthic assemblages across depth gradients that limits fish zonation. I'm sure the divers collected some benthic data, so why not include a basic metric like coral cover (or even habitat type) in the analyses to better isolate the depth signal? I appreciate that the aim was to examine a basic biophysical gradient (depth), but I feel the paper would have been more interesting to consider depth in the context of all the other variables that we know affect reef fishes. To me, one of the most interesting parts of this paper was examining the role of steepness on zonation and I kept wanting to know which other factors were critical in explaining the deviance in the data set. One of the benefits of modern ecology is the access to large-scale, reliable data layers of a range of covariates. However, this study doesn't use these rich sources of information to fill out the models of fish abundance. This is particularly problematic when considering spatial scales of variation (regions / islands / sites) – because the analyses only uses spatial scale in the model the Discussion has to be quite speculative about the actual drivers of these patterns. But had the models included covariates of e.g. net primary productivity, temperature, or wave exposure (all of which are relatively straightforward to obtain) – or island type (see Taylor et al, 2018, Ecography 38:520- 530 for why this variable might be critical) - then we could have seen actual correlations in the data rather than have to guess at what might be varying from island to island ("potential indicators", L210). In summary, had I been reviewing this for a general marine journal I would have suggested revisiting the analyses with some key additional covariates and perhaps human pressure as a continuous variable, but recommended the paper eventually be published as examining depth- related patterns with a data set of this size and examining the homogenizing role of human populations is worth quantifying. Plus the importance of steepness and the variation among trophic groups are interesting. However, the threshold for this journal is higher and I am not convinced that the underlying question is sufficiently interesting, especially given the relatively cursory treatment of other important covariates that limits understanding of which variables are critical at large scales. + +<|ref|>text<|/ref|><|det|>[[119, 860, 852, 909]]<|/det|> +We agree - coral reefs are highly complex socio- ecological systems, structured by numerous socioeconomic and biogeophysical factors and processes (Cinner et al. 2016; Hughes et al. 2017; Williams et al. 2019). Well- described interacting natural biophysical processes and human impacts + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 108, 878, 352]]<|/det|> +occur across a range of temporal and spatial scales to determine contemporary ecological organisation of organisms on reefs (Hughes et al. 1999; MacNeil et al. 2009; Cinner et al. 2013; Williams et al. 2015b; Richardson et al. 2018). For example, the Reviewer correctly highlights the critical role of live coral cover in habitat provisioning at small scales (from the coral colony scale to site scale; Richardson et al. 2017) for determining the distribution of reef fishes (Graham and Nash 2013; Williams et al. 2015b; Heenan et al. 2016). Similarly, numerous indices can be used as proxies to estimate the impacts of humans on reefs, including human population density, distance to market, 'gravity' (combining human population size and accessibility to reefs), fishing intensity, or a simple binary human population status index (Nadon et al. 2012; Williams et al. 2015b; Williams et al. 2015a; Cinner et al. 2016, 2018; Heenan et al. 2016). Biophysical factors such as temperature, wave energy, primary productivity, and island morphology are also known correlates with reef fish community structure (Williams et al. 2015b; Yeager et al. 2017; Heenan et al. 2019). Indeed, many of these covariates have been identified as critical structuring forces of reef fish assemblages across the Pacific study region (e.g. Williams et al. 2011; Williams et al. 2015b; Yeager et al. 2017; Heenan et al. 2019). + +<|ref|>text<|/ref|><|det|>[[117, 366, 880, 675]]<|/det|> +Nonetheless, we a- priori designed our study to test a principle ecological theory which until now has been widely assumed but never tested at scale: The generality and predictive capacity of depth on reef fish biomass across an ocean- basin scale, in the presence vs absence of local human populations. We intentionally strove for simplicity by testing our hypotheses (with covariates: depth, steepness, binary 'humans/no humans') across a spatial extent characterised by known environmental and anthropogenic variation (Gove et al. 2013; Williams et al. 2015b). In doing so, we were able to quantify and attribute variation (sensu MacNeil et al. 2009) in our models to hierarchical spatial scales corresponding to known differential drivers of central and western Pacific reef fish assemblages (Williams et al. 2015b; Heenan et al. 2019). We agree with the Reviewer that it would be an interesting exercise to make use of the rich sources of detailed environmental and anthropogenic information available to explain as much variance in the fish biomass as possible. However, while unquestionably interesting, especially to us coral reef ecologists, this approach would achieve something quite different to an intentionally parsimonious test of ecological theory, with coral reefs as just a model system. Adding a range of known influential covariates would not help to reveal the generality of a depth effect. Rather, it would instead move the study towards using statistics to describe the 'whole system', mopping up unexplained noise in the data through the creation a complex 'causal salad' (McElreath 2020). Instead, we used a logically constructed framework of a- priori defined hypotheses with theoretical basis, with the primary goal of advancing conceptual understanding of an established ecological theory (sensu Underwood et al. 2000). + +<|ref|>text<|/ref|><|det|>[[119, 688, 868, 737]]<|/det|> +Perhaps our overall intentions in terms of study design and goal were not clear enough, and so we have rephrased the introduction as follows to make our overarching goal and study objectives clearer (thanks for the prompt): + +<|ref|>text<|/ref|><|det|>[[178, 751, 863, 881]]<|/det|> +L106: "To explicitly assess generality, we isolate the study focus to test a framework of a- priori defined hypotheses of the effects of depth, bathymetric steepness, and human population status on the biomass of reef fishes across a broad spatial extent characterised by known environmental and anthropogenic variation8,41. In doing so, we intentionally exclude other known influential biophysical and anthropogenic covariates on reef fish biomass (e.g. 8,50) to test the predictive capacity of depth at an ocean- basin scale on the biomass of fishes grouped by their major dietary sources51 – primary consumers, planktivores, secondary consumers, and piscivores." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 108, 875, 720]]<|/det|> +- Cinner et al. (2013). Global effects of local human population density and distance to markets on the condition of coral reef fisheries. Conserv Biol 27:453-458. +- Cinner et al. (2016). Bright spots among the world's coral reefs. Nature 535(7612), 416-419. +- Cinner et al. (2018). Gravity of human impacts mediates coral reef conservation gains. Proc Natl Acad Sci 115:E6116-E6125. +- Fox et al. (2018). Gradients in primary production predict trophic strategies of mixotrophic corals across spatial scales. Curr Biol 28:3355-3363.e4. +- Gove et al. (2013). Quantifying climatological ranges and anomalies for Pacific coral reef ecosystems. PLoS One 8:e61974. +- Graham and Nash (2013). The importance of structural complexity in coral reef ecosystems. Coral Reefs 32:315-326. +- Heenan et al. (2016). Natural bounds on herbivorous coral reef fishes. Proc R Soc B Biol Sci 283:20161716. +- Heenan et al. (2019). Natural variation in coral reef trophic structure across environmental gradients. Front Ecol Environ 18:69-75. +- Hughes et al. (1999). Patterns of recruitment and abundance of corals along the Great Barrier Reef. Nature 397:59-63. +- Hughes et al. (2017). Coral reefs in the Anthropocene. Nature 546(7656), 82-90. +- MacNeil et al. (2009). Hierarchical drivers of reef-fish metacommunity structure. Ecology 90:252-264. +- McElreath. (2020). Statistical rethinking: A Bayesian course with examples in R and Stan. Chapman and Hall/CRC. +- Nadon et al. (2012). Re-creating missing population baselines for Pacific reef sharks. Conserv Biol 26:493-503. +- Richardson et al. (2017). Cross-scale habitat structure driven by coral species composition on tropical reefs. Sci Rep 7(1), 7557. +- Richardson et al. (2018) Mass coral bleaching causes biotic homogenization of reef fish assemblages. Glob Chang Biol 24:3117-3129. +- Underwood et al. (2000). Observations in ecology: you can't make progress on processes without understanding the patterns. J Exp Mar Biol Ecol 250(1-2), 97-115. +- Williams et al. (2011). Differences in reef fish assemblages between populated and remote reefs spanning multiple archipelagos across the Central and Western Pacific. J Mar Biol 2011:826234. +- Williams et al. (2015a). Local human impacts decouple natural biophysical relationships on Pacific coral reefs. Ecography 38:751-761. +- Williams et al. (2015b) Human, oceanographic and habitat drivers of Central and Western Pacific coral reef fish assemblages. PLoS One 10:e0120516. +- Williams et al. (2019). Coral reef ecology in the Anthropocene. Funct Ecol 33(6), 1014-1022. +- Yeager et al. (2017). Scale dependence of environmental controls on the functional diversity of coral reef fish communities. Glob Ecol Biogeogr 26:1177-1189. + +<|ref|>sub_title<|/ref|><|det|>[[118, 766, 345, 781]]<|/det|> +## Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[119, 799, 240, 813]]<|/det|> +14th April 2023 + +<|ref|>text<|/ref|><|det|>[[115, 825, 875, 855]]<|/det|> +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +<|ref|>text<|/ref|><|det|>[[118, 869, 275, 883]]<|/det|> +Dear Dr Richardson, + +<|ref|>text<|/ref|><|det|>[[118, 897, 872, 912]]<|/det|> +Your manuscript entitled "Re- visiting the paradigm of depth zonation on contemporary coral reefs" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 870, 194]]<|/det|> +has now been seen again by the same by 3 reviewers, whose comments are attached. As you can see from the reports, although the reviewers acknowledge the effort to revise the manuscript in response to their previous concerns, they continue to highlight a number of issues which will need to be addressed before we can offer publication in Nature Ecology & Evolution. We will therefore need to once again see your responses to the latest comment and to some editorial concerns, along with a revised manuscript, before we can reach a final decision regarding publication. + +<|ref|>text<|/ref|><|det|>[[118, 208, 866, 250]]<|/det|> +In particular, we expect to only need to send your revised version back to Reviewer 2, and we hope that some additional explanation in the revised paper of your data choices and filtering, and exploration of potential covariance, will be satisfactory to that reviewer. + +<|ref|>text<|/ref|><|det|>[[118, 264, 830, 292]]<|/det|> +We therefore invite you to revise your manuscript taking into account all reviewer and editor comments. Please highlight all changes in the manuscript text file in Microsoft Word format. + +<|ref|>text<|/ref|><|det|>[[118, 305, 841, 348]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[119, 362, 363, 376]]<|/det|> +When revising your manuscript: + +<|ref|>text<|/ref|><|det|>[[118, 390, 866, 432]]<|/det|> +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each reviewer comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the reviewers along with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 446, 866, 488]]<|/det|> +\* If you have not done so already please begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +<|ref|>text<|/ref|><|det|>[[118, 502, 875, 544]]<|/det|> +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +<|ref|>text<|/ref|><|det|>[[118, 558, 712, 572]]<|/det|> +Please use the link below to submit your revised manuscript and related files: + +<|ref|>sub_title<|/ref|><|det|>[[118, 586, 228, 600]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[118, 614, 859, 656]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[118, 670, 870, 712]]<|/det|> +We hope to receive your revised manuscript within four to eight weeks. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[118, 726, 875, 833]]<|/det|> +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[118, 853, 831, 880]]<|/det|> +Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. + +<|ref|>text<|/ref|><|det|>[[115, 894, 840, 908]]<|/det|> +We look forward to seeing the revised manuscript and thank you for the opportunity to review + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 85]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[118, 110, 201, 123]]<|/det|> +your work. + +<|ref|>sub_title<|/ref|><|det|>[[118, 137, 228, 152]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[118, 207, 290, 220]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[118, 234, 415, 248]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 263, 225, 277]]<|/det|> +Dear Authors, + +<|ref|>text<|/ref|><|det|>[[115, 291, 860, 320]]<|/det|> +I would like to thank you for the thorough revision you undertook to address mine and the other reviewers' comments. + +<|ref|>text<|/ref|><|det|>[[118, 320, 770, 334]]<|/det|> +I have only small follow- up questions / suggestions to make based on your revisions. + +<|ref|>text<|/ref|><|det|>[[118, 335, 860, 360]]<|/det|> +To better track of those, I am copying below my original comment, your responses, followed by my new response (it will be indicated by saying "Follow- up comment" in front of it. + +<|ref|>text<|/ref|><|det|>[[118, 360, 870, 389]]<|/det|> +Alternatively, I have also attached a word doc where I am using a different colour font (dark blue) instead to mark my new comments. + +<|ref|>text<|/ref|><|det|>[[118, 404, 852, 446]]<|/det|> +R1.3: Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups + +<|ref|>text<|/ref|><|det|>[[118, 460, 870, 544]]<|/det|> +Thanks for this. For now, and to favour brevity in the title for the journal, we have not incorporated this suggestion into the title, but we have revised it to make it more concise: 'Revisiting the paradigm of depth zonation on contemporary coral reefs'. We agree with the Reviewer that further clarification of the term zonation is needed early in the introduction. In addition to the existing definition of ecological zonation as "the distribution of organisms across space" (L58), we have added a more detailed definition of 'depth zonation' at first mention as follows: + +<|ref|>text<|/ref|><|det|>[[118, 558, 839, 586]]<|/det|> +L67: "Here we revisit this basic principle in the context of depth zonation of tropical coral reef communities- the distribution of reef fish biomass among distinct trophic groups." + +<|ref|>text<|/ref|><|det|>[[118, 600, 848, 641]]<|/det|> +Follow- up comment: I still think that it would be better if the zonation refers to trophic groups, and specifically that of reef fish, so the title could be changed to: "Re- visiting the paradigm of trophic group depth zonation on coral reef fish". + +<|ref|>text<|/ref|><|det|>[[118, 642, 852, 670]]<|/det|> +However, no strong feelings there, as I know that papers in high- impact journals tend to favour generic all- encompassing titles. + +<|ref|>sub_title<|/ref|><|det|>[[118, 699, 176, 711]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[118, 726, 866, 754]]<|/det|> +R1.10: Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 769, 878, 852]]<|/det|> +To aid clearer visualisation of the scaled effects of depth, bathymetric steepness, and human population status on the positive reef fish biomass data, the effect estimates of hurdle components (presence- absence) from the piscivore and planktivore models were not included in Fig. 1. Including them, as presented in Fig. S1, clusters the effect estimates and their percentiles such that the reader may be less able to effectively interpret relative effect size. However, we will gladly exchange Fig. 1 for Fig. S1 on request. + +<|ref|>text<|/ref|><|det|>[[118, 866, 875, 908]]<|/det|> +Follow- up comment: I think it's fine to keep Fig. 1 and Fig. S1 separate, but you should only report the effect estimates of hurdle components in Fig. S1, since the top half is a repetition of Fig. 1. Unless it's required for interpreting the figure. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 996, 84]]<|/det|> +# nature portfolio + +<|ref|>sub_title<|/ref|><|det|>[[119, 137, 200, 150]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[119, 165, 855, 208]]<|/det|> +R1.18: Lines 304- 306: Can you expand a little bit more here? Do you mean that below \(30m\) steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +<|ref|>text<|/ref|><|det|>[[118, 221, 876, 375]]<|/det|> +We see that this sentence was potentially unclear. Studies looking at depth zonation beyond the \(0 - 30m\) limit in our study report contrasting peaks in abundance of piscivores and planktivores. For example, at Linden Bank, a submerged shoal on the outer shelf of the Great Barrier Reef, reported dominance of piscivores (and mobile invertivores) between \(50 - 70m\) depth (Scott et al. 2022). In contrast, the proportion of planktivores on forereefs at Enewetak Atoll in the Marshall Islands increased from \(50\%\) at \(30m\) to \(>90\%\) from \(90 - 200m\) , which the authors suggest may relate to upwelling processes increasing plankton and shallow reef productivity (Thresher and Colin 1986). In L304- 306, we suggest that these variable peaks in trophic group biomass at mesophotic depths are potentially indicative of spatial variation in upwelling, which could be linked- among other oceanographic factors- to variable local bathymetric steepness among those study locations. To make this clearer, we have revised the manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[119, 388, 853, 445]]<|/det|> +L325: "Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the \(30m\) limit of this study54,67, which may be indicative of spatial variation in upwelling, potentially linked to- among other oceanographic factors- variable local bathymetric steepness among those study locations." + +<|ref|>text<|/ref|><|det|>[[118, 458, 873, 530]]<|/det|> +- Thresher and Colin. (1986). Trophic structure, diversity and abundance of fishes of the deep reef (30-300m) at Enewetak, Marshall Islands. Bull Mar Sci 38, 253-272. +- Scott et al. (2022). Variation in abundance, diversity and composition of coral reef fishes with increasing depth at a submerged shoal in the northern Great Barrier Reef. Rev Fish Biol Fish 32, 941-962. + +<|ref|>text<|/ref|><|det|>[[118, 543, 864, 628]]<|/det|> +Follow- up comment: I would perhaps also touch on the effect of changes in benthic community composition in reef fish trophic structure, similar to some of the comments of Reviewer 3 who asked for the role of benthos in explaining reef- fish patterns. For example, see loss of concurrent loss of herbivorous fish and hard corals in Bermuda (Stefanoudis et al. 2019 - paper you already cite); or the one from Russ et al. 2021 showing how coral cover affects fish trophic structuring in the shallows + +<|ref|>text<|/ref|><|det|>[[118, 628, 855, 656]]<|/det|> +Russ, G.R., Rizzari, J.R., Abesamis, R.A. and Alcala, A.C., 2021. Coral cover a stronger driver of reef fish trophic biomass than fishing. Ecological Applications, 31(1), p.e02224. + +<|ref|>text<|/ref|><|det|>[[118, 685, 857, 741]]<|/det|> +R1.24: General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +<|ref|>text<|/ref|><|det|>[[118, 754, 876, 894]]<|/det|> +Thanks to the Reviewer for highlighting where further discussion on cross- scale spatial variation in fish biomass patterns would improve the manuscript. Coral reefs are considered to be highly hierarchical in structure, determined by processes occurring at multiple spatial and temporal scales (Hughes et al. 1999, MacNeil et al. 2009). As the Reviewer rightly highlights, within this hierarchical context, management and governance efforts are considered most effective when carried out at scales aligning with scales of ecological heterogeneity (Cumming and Dobbs 2020). We describe this in detail in the paragraph L335- 345, and we link our results to scaled management and conservation efforts in L361- 368 in the original manuscript. However, we now provide additional discussion exploring the relative differences in variation observed across scales, notably discussing the relatively lower variation observed at the island- scale as follows: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 109, 879, 292]]<|/det|> +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale. In this context, our findings suggest that management of primary consumers, piscivores, total standing biomass, and especially secondary consumers might achieve satisfactory outcomes at local within- island scales with no- take areas80, habitat restoration, or better regulated destructive human activities79. Local management of planktivores is no doubt also important34. But, given the potential influence of regional- scale drivers on planktivore biomass production and the importance of this group as the prey base for higher trophic levels32, more nuanced, region- specific targets for recovery81 or take of planktivores may be advisable in areas of naturally lower primary production." + +<|ref|>text<|/ref|><|det|>[[118, 305, 848, 377]]<|/det|> +Follow- up comment: In the last sentence after ref. 81, do you mean "or no- take zones of..." I would also ask the authors to consider the recent findings of Pinheiro et al. 2023. Pinheiro, H.T., MacDonald, C., Quimbayo, J.P., Shepherd, B., Phelps, T.A., Loss, A.C., Teixeira, J.B. and Rocha, L.A., 2023. Assembly rules of coral reef fish communities along the depth gradient. Current Biology. + +<|ref|>text<|/ref|><|det|>[[118, 390, 680, 404]]<|/det|> +Based on this, the statement in lines 265- 267 could perhaps be modified. + +<|ref|>sub_title<|/ref|><|det|>[[119, 432, 185, 445]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[118, 460, 866, 488]]<|/det|> +R1.25: Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +<|ref|>text<|/ref|><|det|>[[118, 501, 873, 612]]<|/det|> +Thanks for this important consideration. The National Oceanic and Atmospheric Administration (NOAA) has multiple trained fish survey divers who conduct in situ observations across sampling cruises, across distinct ecoregions and years. Divers must have a minimum of 30 underwater visual fish survey census dives conducted prior to joining a monitoring cruise. In addition, to ensure consistency in observer species identification and size estimation, NOAA employs extensive training, testing, and technical validation protocols both outside of the cruise period and during (detailed in Heenan et al. 2017). These protocols address the potential for intra- and inter- diver variability in two ways: + +<|ref|>text<|/ref|><|det|>[[118, 613, 860, 712]]<|/det|> +1. New and experienced divers receive full training in fish identification and survey protocol, in classroom and in-water sessions; prior to each survey cruise, all divers must accurately identify \(>90\%\) of regional-specific fish species in a test that is specifically weighted towards rare species and those that have conspecifics with similar appearance. +2. For the timeframe of the data used here, between cruises divers conducted in-water training exercises to practice survey protocol, fish identification and fish size estimation (see response to comment R1.27 for detail on size estimation protocol and technical validation). + +<|ref|>text<|/ref|><|det|>[[118, 725, 875, 866]]<|/det|> +During the cruises, there are typically 4- 10 fish survey divers who routinely discuss and compare species identification and sizes immediately after a survey, and during data entry. Diver pairs are continually rotated, and diver performance is estimated as the difference between the estimates of each diver and those of their dive partner at each site, calculated for total fish biomass, species richness, and body- size distributions of commonly observed species. As divers survey adjacent cylinders on the reef (i.e. not identical areas of the reef), real differences between diver observations are expected. But the diver performance estimate is measured to detect potential consistent bias made by each diver (i.e. if there is no consistent bias, the median difference with their buddy partner should be close to zero). Diver performance is measured every few days during survey cruises to allow for early detection of observer error (Heenan et al. 2017). + +<|ref|>text<|/ref|><|det|>[[118, 879, 871, 908]]<|/det|> +In addition to these technical validation protocols, we included a group- level random intercept for 'diver identity' in all of our statistical models of fish biomass to account for any remaining effect of + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 999, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[118, 110, 864, 167]]<|/det|> +observer bias. By assuming inherent correlations among divers and their observations that affect the estimated means and associated errors, we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) (sensu Macneil et al. 2015 Nature). + +<|ref|>text<|/ref|><|det|>[[118, 180, 875, 208]]<|/det|> +- Heenan et al. (2017). Long-term monitoring of coral reef fish assemblages in the Western central pacific. Sci Data 4(1), 1-12. + +<|ref|>text<|/ref|><|det|>[[118, 208, 875, 235]]<|/det|> +- MacNeil et al. (2015). Recovery potential of the world's coral reef fishes. Nature 520(7547), 341-344. + +<|ref|>text<|/ref|><|det|>[[118, 250, 803, 264]]<|/det|> +We have revised the manuscript as follows to provide the required additional information: + +<|ref|>text<|/ref|><|det|>[[118, 278, 863, 400]]<|/det|> +L457: "Surveys were conducted by multiple observers across the study ecoregions and years. NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation49. Full details on SPC survey methods and technical validation steps are available in [49]. To further mitigate any confounding effect of observer bias among fish surveys, we included 'diver identity' as a random intercept in all statistical models (described below) (sensu53)." L514: "A random intercept for 'diver identity' was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations (sensu53)." + +<|ref|>text<|/ref|><|det|>[[118, 431, 869, 488]]<|/det|> +Follow- up comment: Great, thanks for the explanation and additional information. Based on the revised text above, presumably the multiple observer effect came up as no significant? If so, then perhaps worth mentioning here, and explain that because of this it won't be discussed further in the paper. + +<|ref|>text<|/ref|><|det|>[[120, 530, 415, 544]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 558, 877, 750]]<|/det|> +This is my second review of the manuscript submitted by Richardson and coauthors entitled: "Revisiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECoLEVOL- 221117855). During my initial review, I felt that the manuscript was well written and provided interesting results. I provided several recommendations for the authors to consider during the revision process. Overall, I appreciate the time and effort that the authors put in to address my recommendations. I know how much time it takes to incorporate suggestions and provide thoughtful responses. In general, I feel that authors made an effort to address my recommendations and made adequate revisions to the manuscript. The theme and structure of the manuscript remains consistent with the initial submission and continues to reinforce what has been shown in other geographies regarding depth zonation patterns in coral reef fishes. The revised version contributes to this body of work by examining these patterns across ecoregions. However, after revisiting this manuscript and evaluating the authors' responses I have a couple additional concerns and recommendations that I would like the authors to consider before the manuscript is considered for publication. + +<|ref|>text<|/ref|><|det|>[[118, 753, 879, 908]]<|/det|> +First, one of my recommendations during the initial review focused on the process by which reef fish taxa were filtered and selected in this study. The authors provided a detailed response to my initial comment citing a number of publications to justifying why certain piscivores or apex predator groups were omitted from this study. I am familiar with these studies to describe movement patterns or behavioral observations of particular taxa; as well as the studies to describe patterns of reef fish assemblage structure at local, regional, or global scales. In the cited studies describing fish assemblage structure, authors chose to exclude or filter certain taxa based on a priori or a posteriori knowledge of coral reef fishes. In the case of a priori filtering or selection, fish taxa are excluded during the initial study design and in- situ surveys due to methodological limitations of observing certain species or to account for observer inexperience. For example, some monitoring efforts include a subset of large- bodied species or certain ecologically important taxa in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 876, 166]]<|/det|> +the survey design to reduce the number of species facilitate observers from across a range of experience levels. In studies using a posteriori filtering, species or groups of taxa are excluded during the analysis phase due to limitations in the dataset or to facilitate data comparability across multiple studies using different sampling methodologies. + +<|ref|>text<|/ref|><|det|>[[117, 166, 876, 459]]<|/det|> +However, in this study submitted by Richardson and coauthors, the authors chose to filter taxa a posteriori to remove non- reef associated taxa and species that are known to exhibit 'mobbing' behavior in certain locations. While I understand the authors motivation for filtering groups of fishes, it is unclear why entire groups of fishes were omitted when this behavior is documented for only a handful of species. For example, the authors provide a few site- specific or regional examples from the literature where certain taxa (i.e., Caranx ignobilis and Carcharhinus amblyrhynchos) are known to be abundant and exhibit 'mobbing' behavior in the absence of human fishing pressure. Further, the authors provide an example of personal observations of another common predator (i.e., Lutjanus bohar) exhibiting 'mobbing behavior. However, the authors chose not to omit this species or group (snappers) because the behavior was observed in a region not included in this study. However, L. bohar, it is one of the most common and formattable predators on found across coral reefs of the Pacific and it is likely that the observed behavior is limited only to the Line Islands. Regardless, these examples are either species- specific or region- specific. I am therefore finding the authors filtering or selection process to the arbitrary and flawed. I am curious to know why the authors chose to exclude entire groups of ecologically important fishes rather than be more selective in their filtering especially when the groups included in the filtering include upwards of 100 species within each group and 'mobbing' behavior is generally only observed in a handful of species and only in a few locations. I don't want to be difficult but want to encourage the authors as they move forward in their research endeavors to be thoughtful of their selection process when characterizing fish assemblages and describing patterns of reef fishes across coral reef communities. + +<|ref|>text<|/ref|><|det|>[[117, 460, 876, 824]]<|/det|> +Second and related to the first, is based on the quality of the dataset included in this study. The authors point out that the reef survey data used in this study were collected by highly skilled divers from NOAA. They point out that divers responsible for collecting quantitative in situ data are trained to estimate the size and abundance of all diurnal and non- cryptic fishes observed in the survey area and make efforts to ensure data are collected with consistency and without biases. I am curious to know why the authors chose to filter or select certain taxa when NOAA invests significant resources into training divers on the survey methods to record all taxa. This includes training divers to avoid double counting individuals entering the survey area or 'mobbing divers. Further, the standardization of survey protocols across regions and time periods represents one of the most comprehensive datasets for coral reef fishes. e classes. Did the authors attempt perform an initial analysis using all taxa before enlisting filtering? Again, simply picking and choosing to omit ecologically important species or groups likely has important implications to the results. Third, after reading through the results and examining the figures in more detail, I am curious to know if the authors have considered the non- independence of the predictors (Steepness and Depth). Based on the figures it seems as though depth and steepness covary? Is this a result of methodological limitations where it is not possible to have to have a survey instance where data are collected a t site that both steep and shallow? It seems as though this could lead to a biased interpretation of the data? Please consider this potential non- independence of the predictors. Lastly, the authors provide some interpretation of the results in the discussion (lines 360- 375) where they posit that the spatial variance of the observations was greatest at the site- scale.. indicating that intra- island heterogeneity in habitat availability. However, I encourage the authors to reconsider this statement. Coral reef fish data are inherently noisy and variable at the site and temporal scale. For example, if the authors were to conduct surveys at a single site multiple times the estimates would be highly variable among samples. Therefore the observed results are likely due to variability of the observed data and not directly linked to the local dynamics as they suggest. + +<|ref|>text<|/ref|><|det|>[[120, 867, 415, 881]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[120, 895, 877, 910]]<|/det|> +The authors make a vigorous defense of their paper, and to reiterate this is a comprehensive study + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 999, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[117, 108, 875, 364]]<|/det|> +of the impacts of depth on fish assemblages - and the impacts of humans on that pattern - and I will cite it when I need to make that point. The problem of stripping away many of the complexities (how does the role of depth compare to other covariates? What is the relationship between growing population size and the depth pattern (not just unpopulated / populated)?) is that the paper lives or dies based on interest in the core question being tested - and I'm not convinced that the relationship between fish and depth is as interesting a component of ecological theory as the authors do. Everything we know about fish assemblages (including many zonation papers) suggests that depth is critical and I don't think anyone would argue that depth isn't important. So while this is a comprehensive treatment of the question, and does provide new insights into human impacts and the role of bathymetric steepness, I still struggle to see this as a Nature Ecology & Evolution paper. The paper still makes me wonder about the mechanism (what are fish actually responding to since depth is a proxy for a range of drivers?), what is the relative importance of human direct effects (fishing) versus indirect effects (e.g. affecting coral cover or removing nursery habitats), are there any systematic differences between populated and unpopulated islands, and what is driving the patterns seen at the different spatial scales. But I can see that this concern isn't shared by the other reviewers and I appreciate that novelty is in the eye of the beholder. So given that there aren't any critical flaws in the analyses I think at this point I will defer to the Editor to judge the value of the new insights provided by this paper. + +<|ref|>text<|/ref|><|det|>[[120, 417, 536, 429]]<|/det|> +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*END\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*/\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\* + +<|ref|>sub_title<|/ref|><|det|>[[119, 451, 354, 466]]<|/det|> +## Author Rebuttal, first revision: + +<|ref|>sub_title<|/ref|><|det|>[[119, 484, 424, 500]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 509, 880, 574]]<|/det|> +I would like to thank you for the thorough revision you undertook to address mine and the other reviewers' comments. I have only small follow- up questions / suggestions to make based on your revisions. To better track of those, I am copying below my original comment, your responses, followed by my new response (it will be indicated by saying "Follow- up comment" in front of it. + +<|ref|>text<|/ref|><|det|>[[118, 608, 870, 641]]<|/det|> +Thanks to Reviewer #1 again for their time and thoughtful consideration on our article. The feedback and suggestions have made valuable improvements to the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 692, 860, 741]]<|/det|> +R1.3: Depth zonation patters: I think most people seeing this term would instinctively think of zonation because of changes in community composition. I think it is important to clarify even in the title that this concerns zonation in biomass and/or trophic groups + +<|ref|>text<|/ref|><|det|>[[118, 750, 877, 848]]<|/det|> +Thanks for this. For now, and to favour brevity in the title for the journal, we have not incorporated this suggestion into the title, but we have revised it to make it more concise: 'Re- visiting the paradigm of depth zonation on contemporary coral reefs'. We agree with the Reviewer that further clarification of the term zonation is needed early in the introduction. In addition to the existing definition of ecological zonation as "the distribution of organisms across space" (L58), we have added a more detailed definition of 'depth zonation' at first mention as follows: + +<|ref|>text<|/ref|><|det|>[[118, 857, 822, 890]]<|/det|> +L67: "Here we revisit this basic principle in the context of depth zonation of tropical coral reef communities—the distribution of reef fish biomass among distinct trophic groups." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 999, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[118, 110, 870, 172]]<|/det|> +Follow- up comment: I still think that it would be better if the zonation refers to trophic groups, and specifically that of reef fish, so the title could be changed to: "Re- visiting the paradigm of trophic group depth zonation on coral reef fish". However, no strong feelings there, as I know that papers in high- impact journals tend to favour generic all- encompassing titles. + +<|ref|>text<|/ref|><|det|>[[118, 202, 868, 268]]<|/det|> +Thanks for this alternative suggestion. Our preferred title is the more concise version 'Re- visiting the paradigm of depth zonation on contemporary coral reefs' and we think that because we clarify this point early on in the text, readers will understand early that it is trophic group biomass zonation we refer too. If preferred by the reviewer and editor(s), we will revisit the title to suggest an alternative. + +<|ref|>sub_title<|/ref|><|det|>[[118, 303, 174, 317]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[118, 328, 872, 361]]<|/det|> +R1.10: Fig. S1: I would merge it with Fig. 1 as they both show important information. However, I am not wedded to the suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 370, 870, 467]]<|/det|> +To aid clearer visualisation of the scaled effects of depth, bathymetric steepness, and human population status on the positive reef fish biomass data, the effect estimates of hurdle components (presence- absence) from the piscivore and planktivore models were not included in Fig. 1. Including them, as presented in Fig. S1, clusters the effect estimates and their percentiles such that the reader may be less able to effectively interpret relative effect size. However, we will gladly exchange Fig. 1 for Fig. S1 on request. + +<|ref|>text<|/ref|><|det|>[[118, 476, 872, 524]]<|/det|> +Follow- up comment: I think it's fine to keep Fig. 1 and Fig. S1 separate, but you should only report the effect estimates of hurdle components in Fig. S1, since the top half is a repetition of Fig. 1. Unless it's required for interpreting the figure. + +<|ref|>text<|/ref|><|det|>[[118, 553, 840, 586]]<|/det|> +Thanks. We have revised Fig. S1 to present only the effect estimates of the hurdle components as suggested. + +<|ref|>sub_title<|/ref|><|det|>[[118, 622, 201, 636]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[118, 672, 875, 706]]<|/det|> +R1.18: Lines 304- 306: Can you expand a little bit more here? Do you mean that below 30m steepness has been found to have contrasting effects because the steepness in the studies sites was different? + +<|ref|>text<|/ref|><|det|>[[117, 714, 872, 892]]<|/det|> +We see that this sentence was potentially unclear. Studies looking at depth zonation beyond the 0- 30 m limit in our study report contrasting peaks in abundance of piscivores and planktivores. For example, at Linden Bank, a submerged shoal on the outer shelf of the Great Barrier Reef, reported dominance of piscivores (and mobile invertivores) between 50- 70 m depth (Scott et al. 2022). In contrast, the proportion of planktivores on forereefs at Enewetak Atoll in the Marshall Islands increased from 50% at 30 m to >90% from 90- 200 m, which the authors suggest may relate to upwelling processes increasing plankton and shallow reef productivity (Thresher and Colin 1986). In L304- 306, we suggest that these variable peaks in trophic group biomass at mesophotic depths are potentially indicative of spatial variation in upwelling, which could be linked- among other oceanographic factors- to variable local bathymetric steepness among those study locations. To make this clearer, we have revised the manuscript as follows: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 110, 822, 175]]<|/det|> +L325: “Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the \(30\mathrm{m}\) limit of this study \(^{54,67}\) , which may be indicative of spatial variation in upwelling, potentially linked to–among other oceanographic factors–variable local bathymetric steepness among those study locations.” + +<|ref|>text<|/ref|><|det|>[[118, 183, 848, 216]]<|/det|> +- Thresher and Colin. (1986). Trophic structure, diversity and abundance of fishes of the deep reef (30–300m) at Enewetak, Marshall Islands. Bull Mar Sci 38, 253–272. + +<|ref|>text<|/ref|><|det|>[[118, 225, 875, 273]]<|/det|> +- Scott et al. (2022). Variation in abundance, diversity and composition of coral reef fishes with increasing depth at a submerged shoal in the northern Great Barrier Reef. Rev Fish Biol Fish 32, 941–962. + +<|ref|>text<|/ref|><|det|>[[118, 284, 872, 364]]<|/det|> +Follow- up comment: I would perhaps also touch on the effect of changes in benthic community composition in reef fish trophic structure, similar to some of the comments of Reviewer 3 who asked for the role of benthos in explaining reef- fish patterns. For example, see loss of concurrent loss of herbivorous fish and hard corals in Bermuda (Stefanoudis et al. 2019 – paper you already cite); or the one from Russ et al. 2021 showing how coral cover affects fish trophic structuring in the shallows + +<|ref|>text<|/ref|><|det|>[[118, 373, 875, 406]]<|/det|> +Russ, G.R., Rizzari, J.R., Abesamis, R.A. and Alcala, A.C., 2021. Coral cover a stronger driver of reef fish trophic biomass than fishing. Ecological Applications, 31(1), p.e02224. + +<|ref|>text<|/ref|><|det|>[[118, 436, 646, 453]]<|/det|> +Thanks for this suggestion. We have revised the manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[177, 462, 868, 543]]<|/det|> +L315: “Previous studies document variable peaks in planktivorous and piscivorous fishes at mesophotic depths beyond the \(30\mathrm{m}\) limit of this study \(^{55,68}\) . These variable peaks may be indicative of spatial variation in upwelling, potentially linked to–among other oceanographic factors and associated changes in benthic composition \(^{38}\) – differences in local bathymetric steepness among those study locations.” + +<|ref|>text<|/ref|><|det|>[[118, 552, 860, 617]]<|/det|> +The journal limit is 100 references. As we now cite 101 references and the Stefanoudis et al. (2019) study supports the statement, we have elected not to include the additional reference of Russ et al. (2021) for now. But we are grateful for the recommendation, and will be happy to include it if required. + +<|ref|>text<|/ref|><|det|>[[118, 652, 870, 717]]<|/det|> +R1.24: General Discussion Comment: Something that was not explored. Why was variation between islands less than between sites or between ecoregions? If site- scale variance is greater than island or ecoregion scale for most groups, then does this mean that conservation efforts should focus on site- level information more compared to information at higher spatial scales? + +<|ref|>text<|/ref|><|det|>[[118, 726, 875, 889]]<|/det|> +Thanks to the Reviewer for highlighting where further discussion on cross- scale spatial variation in fish biomass patterns would improve the manuscript. Coral reefs are considered to be highly hierarchical in structure, determined by processes occurring at multiple spatial and temporal scales (Hughes et al. 1999, MacNeil et al. 2009). As the Reviewer rightly highlights, within this hierarchical context, management and governance efforts are considered most effective when carried out at scales aligning with scales of ecological heterogeneity (Cumming and Dobbs 2020). We describe this in detail in the paragraph L335- 345, and we link our results to scaled management and conservation efforts in L361- 368 in the original manuscript. However, we now provide additional discussion exploring the relative differences in variation observed across scales, notably discussing the relatively lower variation observed at the island- scale as follows: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 108, 875, 321]]<|/det|> +L389: "These findings align with previous studies that describe habitat composition at the site- level to be the likely dominant driver of reef fish metacommunity structure, including diversity and the biomass of most trophic groups, while attributing greater prevalence of planktivores to larger- scale gradients in overall ocean productivity44. That we observed lower variation at the island- scale than site and ecoregion scales may be due to a dominant influence of habitat and background levels of productivity, over processes occurring at the island- scale. In this context, our findings suggest that management of primary consumers, piscivores, total standing biomass, and especially secondary consumers might achieve satisfactory outcomes at local within- island scales with no- take areas80, habitat restoration, or better regulated destructive human activities79. Local management of planktivores is no doubt also important34. But, given the potential influence of regional- scale drivers on planktivore biomass production and the importance of this group as the prey base for higher trophic levels32, more nuanced, region- specific targets for recovery81 or take of planktivores may be advisable in areas of naturally lower primary production." + +<|ref|>text<|/ref|><|det|>[[120, 330, 803, 346]]<|/det|> +Follow- up comment: In the last sentence after ref. 81, do you mean "or no- take zones of...". + +<|ref|>text<|/ref|><|det|>[[118, 376, 872, 410]]<|/det|> +Thanks for asking for clarification here. In the sentence after ref. 81, in fact we mean 'take' to refer to catch- limits. We have revised the manuscript accordingly: + +<|ref|>text<|/ref|><|det|>[[175, 418, 860, 451]]<|/det|> +L393: "...more nuanced, region- specific targets for recovery82 or catch of planktivores may be advisable in areas of naturally lower primary production." + +<|ref|>text<|/ref|><|det|>[[118, 486, 738, 503]]<|/det|> +I would also ask the authors to consider the recent findings of Pinheiro et al. 2023. + +<|ref|>text<|/ref|><|det|>[[118, 511, 872, 561]]<|/det|> +Pinheiro, H.T., MacDonald, C., Quimbayo, J.P., Shepherd, B., Phelps, T.A., Loss, A.C., Teixeira, J.B. and Rocha, L.A., 2023. Assembly rules of coral reef fish communities along the depth gradient. Current Biology. + +<|ref|>text<|/ref|><|det|>[[118, 570, 657, 586]]<|/det|> +Based on this, the statement in lines 265- 267 could perhaps be modified. + +<|ref|>text<|/ref|><|det|>[[118, 620, 869, 670]]<|/det|> +Thanks too for highlighting the recent paper by Pinheiro et al. (2023) which has come out since our previous revision and response. Their findings are relevant and complimentary to ours of course, and as such we now refer to the study in the context of our findings as follows: + +<|ref|>text<|/ref|><|det|>[[177, 679, 860, 729]]<|/det|> +L69: "Depth was recognised as a fundamental structuring force over six decades ago7,26- 28, and recently shown to be an important predictor of fish diversity as fewer species are found on deeper reefs29." + +<|ref|>text<|/ref|><|det|>[[177, 738, 875, 804]]<|/det|> +L252: "Recent work details declining patterns of reef fish diversity with increasing depth from the shallows to the mesophotic zone (max 150 m depth)29. We build on these findings by, to our knowledge, revealing for the first time a common degree of ecological organisation in relation to both depth and bathymetric steepness across geographically distinct reefs." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 109, 874, 142]]<|/det|> +R1.25: Divers: Where all the surveys conducted by the same team of divers? If not, then authors must acknowledge the variability in species identifications. + +<|ref|>text<|/ref|><|det|>[[117, 151, 874, 281]]<|/det|> +Thanks for this important consideration. The National Oceanic and Atmospheric Administration (NOAA) has multiple trained fish survey divers who conduct in situ observations across sampling cruises, across distinct ecoregions and years. Divers must have a minimum of 30 underwater visual fish survey census dives conducted prior to joining a monitoring cruise. In addition, to ensure consistency in observer species identification and size estimation, NOAA employs extensive training, testing, and technical validation protocols both outside of the cruise period and during (detailed in Heenan et al. 2017). These protocols address the potential for intra- and inter- diver variability in two ways: + +<|ref|>text<|/ref|><|det|>[[117, 290, 874, 355]]<|/det|> +1. New and experienced divers receive full training in fish identification and survey protocol, in classroom and in-water sessions; prior to each survey cruise, all divers must accurately identify \(>90\%\) of regional-specific fish species in a test that is specifically weighted towards rare species and those that have conspecifics with similar appearance. + +<|ref|>text<|/ref|><|det|>[[117, 364, 835, 413]]<|/det|> +2. For the timeframe of the data used here, between cruises divers conducted in-water training exercises to practice survey protocol, fish identification and fish size estimation (see response to comment R1.27 for detail on size estimation protocol and technical validation). + +<|ref|>text<|/ref|><|det|>[[117, 448, 874, 610]]<|/det|> +During the cruises, there are typically 4- 10 fish survey divers who routinely discuss and compare species identification and sizes immediately after a survey, and during data entry. Diver pairs are continually rotated, and diver performance is estimated as the difference between the estimates of each diver and those of their dive partner at each site, calculated for total fish biomass, species richness, and body- size distributions of commonly observed species. As divers survey adjacent cylinders on the reef (i.e. not identical areas of the reef), real differences between diver observations are expected. But the diver performance estimate is measured to detect potential consistent bias made by each diver (i.e. if there is no consistent bias, the median difference with their buddy partner should be close to zero). Diver performance is measured every few days during survey cruises to allow for early detection of observer error (Heenan et al. 2017). + +<|ref|>text<|/ref|><|det|>[[117, 620, 874, 702]]<|/det|> +In addition to these technical validation protocols, we included a group- level random intercept for 'diver identity' in all of our statistical models of fish biomass to account for any remaining effect of observer bias. By assuming inherent correlations among divers and their observations that affect the estimated means and associated errors, we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) (sensu Macneil et al. 2015 Nature). + +<|ref|>text<|/ref|><|det|>[[117, 710, 850, 743]]<|/det|> +- Heenan et al. (2017). Long-term monitoring of coral reef fish assemblages in the Western central pacific. Sci Data 4(1), 1-12. + +<|ref|>text<|/ref|><|det|>[[117, 752, 854, 784]]<|/det|> +- MacNeil et al. (2015). Recovery potential of the world's coral reef fishes. Nature 520(7547), 341-344. + +<|ref|>text<|/ref|><|det|>[[117, 821, 785, 837]]<|/det|> +We have revised the manuscript as follows to provide the required additional information: + +<|ref|>text<|/ref|><|det|>[[117, 846, 877, 911]]<|/det|> +L457: "Surveys were conducted by multiple observers across the study ecoregions and years. NOAA employs extensive training and technical validation protocols to ensure consistency and avoid bias in survey technique, fish species identification, and size estimation". Full details on SPC survey methods and technical validation steps are available in [49]. To further mitigate any confounding effect + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 108, 808, 142]]<|/det|> +of observer bias among fish surveys, we included ‘diver identity’ as a random intercept in all statistical models (described below) \((sensu^{53})\) .” + +<|ref|>text<|/ref|><|det|>[[117, 151, 835, 200]]<|/det|> +L514: “A random intercept for ‘diver identity’ was included to account for any specific effect of observer bias by assuming an inherent correlation structure among divers and their observations \((sensu^{53})\) .” + +<|ref|>text<|/ref|><|det|>[[117, 209, 860, 275]]<|/det|> +Follow- up comment: Great, thanks for the explanation and additional information. Based on the revised text above, presumably the multiple observer effect came up as no significant? If so, then perhaps worth mentioning here, and explain that because of this it won’t be discussed further in the paper. + +<|ref|>text<|/ref|><|det|>[[117, 315, 876, 428]]<|/det|> +Thanks to the Reviewer for highlighting where additional clarification would be useful in our description of how any potential residual observer effect was handled. The structure of these models allows us to conservatively assume (and control for) an observer effect, rather than testing for one. By assuming an inherent non- independence of observed fish counts by individual divers, we then control for (centre) any effects of observers to then isolate the estimated population level effects on fish biomass. Apologies for not including this important detail in the previous revisions. We have added it to the newly revised manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[177, 464, 864, 594]]<|/det|> +L516: “A group- level random intercept for ‘diver identity’ was included to account for the potential effect of individual observer bias. By assuming an inherent non- independence within divers and their observations that might affect the estimated means and associated errors of fish biomass \((sensu^{54})\) , we were then able to estimate isolated population level effects (i.e. depth, human population status, bathymetric steepness) \((sensu^{54})\) . More broadly, by controlling these potential sources of variability, we can more accurately test a- priori hypotheses about ecological zonation occurring across spatial scales and with greater inferential strength \(^{45}\) .” + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 135, 422, 151]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 161, 870, 371]]<|/det|> +This is my second review of the manuscript submitted by Richardson and coauthors entitled: "Revisiting the paradigm of coral reef depth zonation on contemporary reefs" (NATECOLEVOL- 221117855). During my initial review, I felt that the manuscript was well written and provided interesting results. I provided several recommendations for the authors to consider during the revision process. Overall, I appreciate the time and effort that the authors put in to address my recommendations. I know how much time it takes to incorporate suggestions and provide thoughtful responses. In general, I feel that authors made an effort to address my recommendations and made adequate revisions to the manuscript. The theme and structure of the manuscript remains consistent with the initial submission and continues to reinforce what has been shown in other geographies regarding depth zonation patterns in coral reef fishes. The revised version contributes to this body of work by examining these patterns across ecoregions. However, after revisiting this manuscript and evaluating the authors' responses I have a couple additional concerns and recommendations that I would like the authors to consider before the manuscript is considered for publication. + +<|ref|>text<|/ref|><|det|>[[118, 406, 870, 439]]<|/det|> +We thank the Reviewer again for generously providing their time and continued careful consideration of our article. We have addressed the additional concerns and recommendations as follows. + +<|ref|>text<|/ref|><|det|>[[117, 474, 876, 718]]<|/det|> +R.2ii.1: First, one of my recommendations during the initial review focused on the process by which reef fish taxa were filtered and selected in this study. The authors provided a detailed response to my initial comment citing a number of publications to justifying why certain piscivores or apex predator groups were omitted from this study. I am familiar with these studies to describe movement patterns or behavioral observations of particular taxa; as well as the studies to describe patterns of reef fish assemblage structure at local, regional, or global scales. In the cited studies describing fish assemblage structure, authors chose to exclude or filter certain taxa based on a priori or a posteriori knowledge of coral reef fishes. In the case of a priori filtering or selection, fish taxa are excluded during the initial study design and in-situ surveys due to methodological limitations of observing certain species or to account for observer inexperience. For example, some monitoring efforts include a subset of large-bodied species or certain ecologically important taxa in the survey design to reduce the number of species facilitate observers from across a range of experience levels. In studies using a posteriori filtering, species or groups of taxa are excluded during the analysis phase due to limitations in the dataset or to facilitate data comparability across multiple studies using different sampling methodologies. + +<|ref|>text<|/ref|><|det|>[[117, 727, 877, 906]]<|/det|> +However, in this study submitted by Richardson and coauthors, the authors chose to filter taxa a posteriori to remove non- reef associated taxa and species that are known to exhibit 'mobbing' behavior in certain locations. While I understand the authors motivation for filtering groups of fishes, it is unclear why entire groups of fishes were omitted when this behavior is documented for only a handful of species. For example, the authors provide a few site- specific or regional examples from the literature where certain taxa (i.e., Caranx ignobilis and Carcharhinus amblyrhynchos) are known to be abundant and exhibit 'mobbing' behavior in the absence of human fishing pressure. Further, the authors provide an example of personal observations of another common predator (i.e., Lutjanus bohar) exhibiting 'mobbing behavior. However, the authors chose not to omit this species or group (snappers) because the behavior was observed in a region not included in this study. However, L. bohar, it is one of the most common and formattable predators on found across coral reefs of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 108, 876, 257]]<|/det|> +Pacific and it is likely that the observed behavior is limited only to the Line Islands. Regardless, these examples are either species- specific or region- specific. I am therefore finding the authors filtering or selection process to the arbitrary and flawed. I am curious to know why the authors chose to exclude entire groups of ecologically important fishes rather than be more selective in their filtering especially when the groups included in the filtering include upwards of 100 species within each group and 'mobbing' behavior is generally only observed in a handful of species and only in a few locations. I don't want to be difficult but want to encourage the authors as they move forward in their research endeavors to be thoughtful of their selection process when characterizing fish assemblages and describing patterns of reef fishes across coral reef communities. + +<|ref|>text<|/ref|><|det|>[[118, 290, 875, 372]]<|/det|> +We thank Reviewer #2 for these additional contributions. First, apologies for not clarifying sooner that the filtering approach omitted 16 species from the families Carcharhinidae, Carangidae, and Sphyrnidae, as opposed to hundreds as feared. It was an oversight to not make that explicit in the original submission. This has been corrected as detailed below, in the methods text and by including a table in the supplementary information (Table S12). + +<|ref|>text<|/ref|><|det|>[[117, 380, 875, 577]]<|/det|> +Nonetheless, to address the reviewer's other concerns: we agree that piscivorous fishes such as sharks and large roving jacks are ecologically important to reef trophodynamics (Boaden and Kingsford 2015; Roff et al. 2016), as are other excluded groups such as cryptobenthic reef fishes (Depczynski and Bellwood 2003). We also acknowledge that while the filtering of sharks and large- bodied semi- pelagic piscivores is commonly applied (Table R2 in Response #1) due to well evidenced systematic bias (e.g. Parrish and Boland 2004; Williams et al. 2015), this approach is not used universally (e.g. DeMartini et al. 2008; Friedlander et al. 2010; Pinheiro et al. 2023; though we note that these cited examples are based on typically more mobile diver transect surveys rather than stationary point count surveys in our study). Nevertheless, the resulting dichotomy in how in situ fish assemblage survey data are handled within our field represents an interesting, relevant (and/or potentially frustrating - apologies!) area of discussion about when conservative exclusion of groups mitigates known systematic bias and/or introduces further bias as an artifact of the filtering process. + +<|ref|>text<|/ref|><|det|>[[117, 585, 875, 813]]<|/det|> +In consideration of this, we have thought through some options as follows: Option 1) species- specific filtering (opposed to group filtering based on shared traits such as body- size, mobility, curiosity, and trophic position; Kulbicki 1998). This approach would require a priori evidence of species- specific mobbing behaviour, and/or an observed statistical threshold that we (arguably arbitrarily) deem to represent a mobbing event. Unfortunately, both these data handling choices would more likely produce an artifact than does filtering by group to remove any potential mobbers. The most probable issue we foresee from this individual species approach is false negative error, i.e. leaving in a true mobbing species and having that inclusion artificially inflate the piscivore biomass for unpopulated islands compared to populated. In other words, individual species may display unknown and idiosyncratic patterns of spatial variability in mobbing behaviour that do not reach our radar with this approach and therefore we do not see any defensible way to filter some, but not all species within the group. Option 2) compare candidate piscivore biomass models, both with and without the filtered group of sharks, jacks, barracuda to assess whether and how observed patterns change as result of filtering. + +<|ref|>text<|/ref|><|det|>[[118, 821, 844, 904]]<|/det|> +Due to false negative error issues related to Option 1, we elected to pursue Option 2. We ran the analyses for the piscivore biomass group, both with and without the filtered group. The result was comparable observed zonation patterns in piscivore biomass, suggesting that the reported patterns described in our study are not an artifact of filtering (Fig. S4). However, the model outputs of population level effects of depth and bathymetric steepness between populated and unpopulated + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[612, 40, 999, 84]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[118, 109, 875, 273]]<|/det|> +locations showed much greater biomass estimates at unpopulated than at populated islands where biomass remained comparable despite differences in filtering. We derived from this that while there may indeed be simply more of these large, roving piscivores on uninhabited reefs (Asher et al. 2017), we are unable to reliably distinguish inflated observation rates due to sheer greater abundance from systematic detectability bias associated with the specific survey method across unpopulated versus populated locations in the study (Parrish and Boland 2004; Williams et al. 2015). Therefore, we determine that the broad observed zonation patterns do not substantially vary as an artifact of filtering (and would unlikely show completely new patterns by including a subset of species). As a result, we can mitigate potential issues of survey bias by conservatively excluding this group to produce more cautious estimates of piscivore biomass patterns (Fig. S4). + +<|ref|>text<|/ref|><|det|>[[118, 281, 872, 346]]<|/det|> +We recognise that additional explanation and justification of our data filtering to make this clearer is needed, and have added model output figures with both filtered and unfiltered piscivore biomass data to the supplementary information document (Fig. S4), presenting posterior estimates for population- level effects (depth, steepness) between populated and unpopulated locations: + +<|ref|>text<|/ref|><|det|>[[177, 355, 874, 470]]<|/det|> +L463: "Taxa that are not typically reef- associated were excluded from the analyses, including tuna, bonito, and milkfish (families Chandiae, Myliobatidae, Scombridae; Table S12). Sixteen species of shark, jack, and barracuda (families Carcharhinidae, Carangidae, Sphyrnidae) were also excluded from the analyses as these highly mobile, large- bodied, roving piscivores are known to be affected by the presence of stationary divers, typically resulting in systematic over- inflation of visual survey density estimates86 (sensu8,54; Table S12)." + +<|ref|>text<|/ref|><|det|>[[177, 479, 878, 608]]<|/det|> +L472: "Zonation patterns in piscivore biomass were comparable with and without this filtering approach. This suggests that the reported patterns in piscivore biomass were not an artifact of the data handling choice to exclude some species known to be affected and systematically overestimated by divers (Fig. S4). However, model outputs of population level effects of depth and bathymetric steepness between populated and unpopulated locations showed much greater biomass estimates at uninhabited than habited islands, indicating that conservative exclusion of these species mitigated potential systematic bias associated with the survey method among locations on reported patterns (Fig. S4)." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[550, 40, 936, 85]]<|/det|> +# nature portfolio + +<|ref|>table_caption<|/ref|><|det|>[[56, 111, 940, 155]]<|/det|> +Table S12 Surveyed fish taxa omitted from the study analyses. Reasons for omission include known systematic detectability bias²-⁴ (Carcharhinidae, Carangidae, Sphyrnidae), species not typically reef-associated (Scombridae, Chanidae, Myliobatidae), and cryptobenthic eels whose body-size cannot be estimated (Congridae, Muraenidae). + +<|ref|>table<|/ref|><|det|>[[47, 175, 933, 916]]<|/det|> +
FamilySpeciesCommon nameTrophic groupReason for omission
CarangidaeCarangoides ferduaBlue trevallyPiscivorePotential overinflation in estimates
Carangoides orthogrammusIsland trevallyPiscivorePotential overinflation in estimates
Caranx ignobilisGiant trevallyPiscivorePotential overinflation in estimates
Caranx lugubrisBlack jackPiscivorePotential overinflation in estimates
Caranx melampygusBluefin trevallyPiscivorePotential overinflation in estimates
CaranpapuensisBrassy trevallyPiscivorePotential overinflation in estimates
Caranx sexfasciatusBigeye trevallyPiscivorePotential overinflation in estimates
Decapterus macarellusMackerel scadPlanktivorePotential overinflation in estimates
Elagatis bipinnulataRainbow runnerPiscivorePotential overinflation in estimates
Scomberoides lysanDoublespotted queenfishPiscivorePotential overinflation in estimates
Selar crumenophthalmusBigeye scadPlanktivorePotential overinflation in estimates
Seriola dumeriliGreater amberjackPiscivorePotential overinflation in estimates
Trachinotus bailloniSmallspotted dartPiscivorePotential overinflation in estimates
Caranx spp.n/aPiscivorePotential overinflation in estimates
CarcharhinidaeCarcharhinus amblyrhynchosGrey reef sharkPiscivorePotential overinflation in estimates
Carcharhinus galapagensisGalapagos sharkPiscivorePotential overinflation in estimates
Carcharinus melanopterusBlacktip reef sharkPiscivorePotential overinflation in estimates
Triaenodon obesusWhitetip reef sharkPiscivorePotential overinflation in estimates
ChanidaeChanos chanosMilkfishPrimary consumerNon-reef-associated
CongridaeCongridae spp.Conger eel or Garden eelPiscivoreCryptobenthic
MuraenidaeEchidna nebulosaSnowflake moray eelSecondary consumerCryptobenthic
Enchelycore pardalisLeopard moray eelPiscivoreCryptobenthic
Gymnomuraena zebraZebra moray eelSecondary consumerCryptobenthic
Gymnothorax breedeniBlackcheek moray eelPiscivoreCryptobenthic
Gymnothorax eurostusAbbott's moray eelSecondaryCryptobenthic
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[545, 37, 936, 82]]<|/det|> +nature portfolio + +<|ref|>table<|/ref|><|det|>[[46, 106, 930, 519]]<|/det|> +
consumer
Gymnothorax flavimarginatusYellow-edged moray eelPiscivoreCryptobenthic
Gymnothorax javanicusGiant moray eelPiscivoreCryptobenthic
Dwarf moray eelSecondary consumerCryptobenthic
Gymnothorax meleagrisTurkey moray eelPiscivoreCryptobenthic
Gymnothorax steindachneriSteindachner's moray eelPiscivoreCryptobenthic
Gymnothorax undulatusUndulated moray eelPiscivoreCryptobenthic
Moray eelPiscivoreCryptobenthic
MyliobatidaeManta birostrisGiant mantaPlanktivore
ScombridaeEuthynnus affinisKawakawaPiscivore
Gymnosarda unicolorDogtooth tunaPiscivore
Thunnus albacaresYellowfin tunaPiscivore
Scombridae spp.Striped bonitoPiscivore
SphyraenidaeSphyraena qenieBlackfin barracudaPiscivore
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[139, 125, 864, 472]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 488, 883, 580]]<|/det|> +
Figure S4 Piscivore fish biomass, excluding and including the biomass of Carcharhinidae, Carangidae, and Sphyrnidae (see Table S12), across gradients of depth (a) and bathymetric steepness (b) at unpopulated (colour) and populated (grey) islands. Estimates represent conditional posterior medians (lines), 75% percentiles (shaded areas), and partial residuals (points) at the study mean values of bathymetric steepness (panel a) and depth (panel b). The y axis is limited to \(1.05x\) the maximum value of the \(75\%\) CI so partial residuals exceeding axis limits are not displayed. \(N = 5,525\) stationary point count (SPC) surveys (across 2,253 foreverest sites, 35 islands, five ecoregions).
+ +<|ref|>text<|/ref|><|det|>[[142, 648, 857, 675]]<|/det|> +- Asher J, Williams ID, Harvey ES (2017). An assessment of mobile predator populations along shallow and mesophotic depth gradients in the Hawaiian Archipelago. Sci Rep 7:1-18. + +<|ref|>text<|/ref|><|det|>[[142, 677, 833, 711]]<|/det|> +- Boaden AE & Kingsford MJ (2015). Predators drive community structure in coral reef fish assemblages. Ecosphere 6:1-33. + +<|ref|>text<|/ref|><|det|>[[142, 713, 850, 765]]<|/det|> +- DeMartini EE, Friedlander AM, Sandin SA, Sala E (2008) Differences in fish-assemblage structure between fished and unfished atolls in the northern Line Islands, central Pacific. Mar Ecol Prog Ser 365:199-215. + +<|ref|>text<|/ref|><|det|>[[142, 767, 825, 801]]<|/det|> +- Depczynski M, & Bellwood DR (2003). The role of cryptobenthic reef fishes in coral reef trophodynamics. Mar Ecol Prog Ser 256:183-191. + +<|ref|>text<|/ref|><|det|>[[142, 803, 880, 836]]<|/det|> +- Friedlander AM, Sandin SA, DeMartini EE, Sala E (2010) Spatial patterns of the structure of reef fish assemblages at a pristine atoll in the central Pacific. Mar Ecol Prog Ser 410:219-231. + +<|ref|>text<|/ref|><|det|>[[142, 837, 880, 871]]<|/det|> +- Kulbicki. (1998). How the acquired behaviour of commercial reef fishes may influence the results obtained from visual censuses. J Exp Mar Biol Ecol 222: 11-30. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[595, 44, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[142, 116, 870, 253]]<|/det|> +- Pinheiro HT, MacDonald C, Quimbayo JP, Shepherd B, Phelps TA, Loss AC, ... & Rocha LA (2023). Assembly rules of coral reef fish communities along the depth gradient. Curr Biol 33:1421-1430. +- Roff G, Doropoulos C, Rogers A, Bozec YM, Krueck NC, Aurellado E, ... & Mumby PJ (2016). The ecological role of sharks on coral reefs. TREE, 31:395-407. +- Williams ID, Baum JK, Heenan A, Hanson KM, Nadon MO, Brainard RE (2015). Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS ONE 10: e0120516. + +<|ref|>text<|/ref|><|det|>[[113, 283, 881, 490]]<|/det|> +R.2ii.2: Second and related to the first, is based on the quality of the dataset included in this study. The authors point out that the reef survey data used in this study were collected by highly skilled divers from NOAA. They point out that divers responsible for collecting quantitative in situ data are trained to estimate the size and abundance of all diurnal and non-cryptic fishes observed in the survey area and make efforts to ensure data are collected with consistency and without biases. I am curious to know why the authors chose to filter or select certain taxa when NOAA invests significant resources into training divers on the survey methods to record all taxa. This includes training divers to avoid double counting individuals entering the survey area or 'mobbing divers. Further, the standardization of survey protocols across regions and time periods represents one of the most comprehensive datasets for coral reef fishes. e classes. Did the authors attempt perform an initial analysis using all taxa before enlisting filtering? Again, simply picking and choosing to omit ecologically important species or groups likely has important implications to the results. + +<|ref|>text<|/ref|><|det|>[[114, 526, 882, 787]]<|/det|> +We are glad that the Reviewer recognises the extensive technical data validation protocols that NOAA employs to minimise measurement error as much as possible (e.g. doing instantaneous counts and training divers to minimise double counting in a single survey). While these protocols ensure that NOAA divers are highly skilled at avoiding double counting, they do not eliminate the problem of spatially variable mobbing behaviour of mobile species because the protocol cannot control for it. For example, these divers could achieve a perfect count of mobbing jacks within an SPC survey cylinder on one island, but still have a systematic bias if the same species avoids those divers at other islands. The NOAA National Coral Reef Monitoring Programme does indeed invest significant resources in collecting this high- quality dataset and this is because the fish data are used for a wide variety of purposes, many of which would not involve or require filtering of species in the way we have for the current paper. For example, managers that have specific questions about Lutjanus bohar, sharks, or reef fish assemblage diversity or biomass at their specific islands or regions. We did not take the decision to filter these species out lightly and we agree they are ecologically important. However, because our priority focus was to make Pacific- wide assessment, we exclude known biases among islands driven by strong spatial variance in behaviour among these highly mobile roving piscivore species (per R.2ii.1). + +<|ref|>text<|/ref|><|det|>[[115, 822, 878, 892]]<|/det|> +R.2ii.3: Third, after reading through the results and examining the figures in more detail, I am curious to know if the authors have considered the non-independence of the predictors (Steepness and Depth). Based on the figures it seems as though depth and steepness covary? Is this a result of methodological limitations where it is not possible to have to have a survey instance where data are collected at a site that + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[596, 45, 970, 87]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[113, 117, 870, 153]]<|/det|> +both steep and shallow? It seems as though this could lead to a biased interpretation of the data? Please consider this potential non- independence of the predictors. + +<|ref|>text<|/ref|><|det|>[[114, 189, 864, 259]]<|/det|> +Thanks for this question. We checked for non- independence of our predictors (including depth and steepness) for each fish biomass model by plotting bivariate correlations between the posterior samples (MCMC draws) of predictor coefficients and quantifying the Pearson correlation coefficients between paired samples, as follows: + +<|ref|>text<|/ref|><|det|>[[172, 268, 872, 320]]<|/det|> +("b_predictor" relates to the model slope coefficient for that population- level effect; "c" indicates that the predictor is centred and scaled; SITE_SLOPE_400m_c is the data name for the bathymetric steepness effect) + +<|ref|>image<|/ref|><|det|>[[105, 330, 925, 884]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[105, 115, 770, 550]]<|/det|> + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[595, 42, 970, 87]]<|/det|> +# nature portfolio + +<|ref|>image<|/ref|><|det|>[[105, 115, 770, 550]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 574, 845, 661]]<|/det|> +Correlation coefficients were all \(< 5\%\) , bar one: a single pairwise correlation coefficient for hurdle components depth and steepness in the planktivore model which was still relatively low at \(28\%\) . Therefore, we derived that the predictors were sufficiently independent so as to not bias the posterior estimates. All study data and code, including code for these and all other model validation plots are available in this open repository: https://github.com/LauraERichardson/Depth- Fish. + +<|ref|>text<|/ref|><|det|>[[115, 670, 864, 705]]<|/det|> +We have added these plots to the supplementary information (Fig. S6) and revised the methods to make this clearer as follows: + +<|ref|>text<|/ref|><|det|>[[172, 714, 875, 802]]<|/det|> +L579: "Non- independence of population- level predictors was assessed by plotting bivariate correlations between the posterior samples (MCMC draws) of predictor coefficients and quantifying Pearson correlation coefficients between paired samples (Fig. S6) \(^{94}\) . Correlation coefficients were all \(< 5\%\) , bar one: a single pairwise correlation coefficient for hurdle components depth and steepness in the planktivore model which was still relatively low at \(28\%\) ." + +<|ref|>text<|/ref|><|det|>[[172, 810, 800, 829]]<|/det|> +L588: "...independence of model predictors assessed with gqpairs in GGally 2.1.2 \(^{101}\) ." + +<|ref|>text<|/ref|><|det|>[[115, 865, 864, 901]]<|/det|> +R.2ii.4: Lastly, the authors provide some interpretation of the results in the discussion (lines 360- 375) where they posit that the spatial variance of the observations was greatest at the site- scale... indicating + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[596, 44, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[115, 116, 866, 204]]<|/det|> +that intra- island heterogeneity in habitat availability. However, I encourage the authors to reconsider this statement. Coral reef fish data are inherently noisy and variable at the site and temporal scale. For example, if the authors were to conduct surveys at a single site multiple times the estimates would be highly variable among samples. Therefore the observed results are likely due to variability of the observed data and not directly linked to the local dynamics as they suggest. + +<|ref|>text<|/ref|><|det|>[[115, 241, 835, 276]]<|/det|> +Thanks for this point. We have revised the manuscript to position our results in the discussion more cautiously as advised: + +<|ref|>text<|/ref|><|det|>[[173, 285, 880, 407]]<|/det|> +L368: "We found that the greatest spatial variance was at the site- scale for primary and secondary consumers, piscivores, and total biomass. We note that unmeasured temporal stochasticity at the site- level due to factors like fish recruitment, mobility, or behaviour can influence small- scale single time point observations and their associated variability at that scale45. Nonetheless, the importance of site- scale characteristics, indicated by this intra- island heterogeneity, supports numerous studies that identify habitat availability79, local hydrodynamics15, and local disturbances23,69,80 as predominant mediators of the biomass of those groups45." + +<|ref|>text<|/ref|><|det|>[[174, 415, 881, 485]]<|/det|> +L384: "That we observed lower variation at the island- scale than site and ecoregion scales may be due, in part, to a dominant influence of local variation in habitat, hydrodynamics, or disturbances and variable background levels of productivity across ecoregions, over processes occurring at the island- scale." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[595, 44, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>sub_title<|/ref|><|det|>[[115, 145, 412, 162]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 172, 881, 484]]<|/det|> +The authors make a vigorous defense of their paper, and to reiterate this is a comprehensive study of the impacts of depth on fish assemblages - and the impacts of humans on that pattern - and I will cite it when I need to make that point. The problem of stripping away many of the complexities (how does the role of depth compare to other covariates? What is the relationship between growing population size and the depth pattern (not just unpopulated / populated)?) is that the paper lives or dies based on interest in the core question being tested - and I'm not convinced that the relationship between fish and depth is as interesting a component of ecological theory as the authors do. Everything we know about fish assemblages (including many zonation papers) suggests that depth is critical and I don't think anyone would argue that depth isn't important. So while this is a comprehensive treatment of the question, and does provide new insights into human impacts and the role of bathymetric steepness, I still struggle to see this as a Nature Ecology & Evolution paper. The paper still makes me wonder about the mechanism (what are fish actually responding to since depth is a proxy for a range of drivers?), what is the relative importance of human direct effects (fishing) versus indirect effects (e.g. affecting coral cover or removing nursery habitats), are there any systematic differences between populated and unpopulated islands, and what is driving the patterns seen at the different spatial scales. But I can see that this concern isn't shared by the other reviewers and I appreciate that novelty is in the eye of the beholder. So given that there aren't any critical flaws in the analyses I think at this point I will defer to the Editor to judge the value of the new insights provided by this paper. + +<|ref|>text<|/ref|><|det|>[[114, 545, 881, 737]]<|/det|> +We thank the reviewer again for thoughtfully engaging with the fit of our overarching study aim and context. We are very pleased that they recognise the study to be comprehensive and robust with no critical flaws, offering novel insight into human impacts on classic depth zonation and the role of bathymetric steepness in mediating reef fish biomass baselines. We are glad that the reviewer highlights that no- one would argue that depth isn't important to the zonation of coral reef fish as this widespread assumption is at the heart our study. For the first time, we provide unequivocal empirical grounding for, until now, the broadly assumed but untested (at sufficient scale) paradigm of depth zonation. With this now well documented through a rigorous test at scale, we are in a better position to embark on tackling the next phase of more complex questions. We fully agree that research into the mechanisms of zonation and how their effects are damped or disrupted by human impacts would be interesting and is indeed the next logical direction for future studies. + +<|ref|>title<|/ref|><|det|>[[113, 832, 358, 847]]<|/det|> +# Decision Letter, second revision: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[596, 44, 970, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[116, 118, 203, 132]]<|/det|> +Dear Laura, + +<|ref|>text<|/ref|><|det|>[[115, 147, 858, 253]]<|/det|> +Thank you for submitting your revised manuscript "Re- visiting the paradigm of depth zonation on contemporary coral reefs" (NATECoLEVOL- 221117855B). I'm sorry it has taken us longer than desirable to get this decision to you. We had been hoping to get comments from Reviewer 2 on this revision, but we have not heard back from that reviewer. We have discussed your responses to all reviewers' previous comments and feel confident that we can now offer, in principle, to publish it in Nature Ecology & Evolution, pending minor revisions to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[115, 267, 857, 297]]<|/det|> +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex) - - we can not proceed with PDFs at this stage. + +<|ref|>text<|/ref|><|det|>[[115, 311, 858, 355]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[115, 370, 870, 400]]<|/det|> +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +<|ref|>sub_title<|/ref|><|det|>[[115, 414, 221, 430]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[115, 595, 391, 609]]<|/det|> +Our ref: NATECoLEVEL- 221117855B + +<|ref|>text<|/ref|><|det|>[[116, 640, 228, 655]]<|/det|> +17th July 2023 + +<|ref|>text<|/ref|><|det|>[[116, 686, 271, 700]]<|/det|> +Dear Dr. Richardson, + +<|ref|>text<|/ref|><|det|>[[115, 715, 878, 820]]<|/det|> +Thank you for your patience as we've prepared the guidelines for final submission of your Nature Ecology & Evolution manuscript, "Re- visiting the paradigm of depth zonation on contemporary coral reefs" (NATECoLEVEL- 221117855B). Please carefully follow the step- by- step instructions provided in the attached file, and add a response in each row of the table to indicate the changes that you have made. Please also check and comment on any additional marked- up edits we have proposed within the text. 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Please get in contact with us immediately if you anticipate it taking more than two weeks to submit these revised files.\*\* + +<|ref|>text<|/ref|><|det|>[[115, 892, 839, 908]]<|/det|> +When you upload your final materials, please include a point- by- point response to any remaining + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[596, 45, 969, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[116, 118, 266, 132]]<|/det|> +reviewer comments. + +<|ref|>text<|/ref|><|det|>[[116, 147, 869, 207]]<|/det|> +If you have not done so already, please alert us to any related manuscripts from your group that are under consideration or in press at other journals, or are being written up for submission to other journals (see: https://www.nature.com/nature- research/editorial- policies/plagiarism#policy- on- duplicate- publication for details). + +<|ref|>text<|/ref|><|det|>[[116, 221, 881, 296]]<|/det|> +In recognition of the time and expertise our reviewers provide to Nature Ecology & Evolution's editorial process, we would like to formally acknowledge their contribution to the external peer review of your manuscript entitled "Re- visiting the paradigm of depth zonation on contemporary coral reefs". 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Please note that failure to state your preference will result in delays in accepting your manuscript for publication. + +<|ref|>sub_title<|/ref|><|det|>[[116, 430, 268, 446]]<|/det|> +## Cover suggestions + +<|ref|>text<|/ref|><|det|>[[116, 460, 816, 490]]<|/det|> +As you prepare your final files we encourage you to consider whether you have any images or illustrations that may be appropriate for use on the cover of Nature Ecology & Evolution. + +<|ref|>text<|/ref|><|det|>[[116, 504, 880, 549]]<|/det|> +Covers should be both aesthetically appealing and scientifically relevant, and should be supplied at the best quality available. 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This email is just to let you know that it has now been accepted for publication in Nature Ecology & Evolution. Thanks also for your patience in the earlier stages - I'm sorry some were slower than we'd usually aim for. + +<|ref|>text<|/ref|><|det|>[[115, 753, 874, 814]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Ecology and Evolution style. Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required + +<|ref|>text<|/ref|><|det|>[[115, 828, 865, 872]]<|/det|> +After the grant of rights is completed, you will receive a link to your electronic proof via email with a request to make any corrections within 48 hours. 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Once your paper has been scheduled for online publication, the Nature press office will be in touch to confirm the details. + +<|ref|>text<|/ref|><|det|>[[115, 192, 858, 253]]<|/det|> +Acceptance of your manuscript is conditional on all authors' agreement with our publication policies (see www.nature.com/authors/policies/index.html). In particular your manuscript must not be published elsewhere and there must be no announcement of the work to any media outlet until the publication date (the day on which it is uploaded onto our web site). + +<|ref|>text<|/ref|><|det|>[[115, 266, 868, 357]]<|/det|> +Please note that Nature Ecology & Evolution is a Transformative Journal (TJ). Authors may publish their research with us through the traditional subscription access route or make their paper immediately open access through payment of an article- processing charge (APC). Authors will not be required to make a final decision about access to their article until it has been accepted. Find out more about Transformative Journals + +<|ref|>sub_title<|/ref|><|det|>[[115, 370, 580, 386]]<|/det|> +## Authors may need to take specific actions to achieve text<|/ref|><|det|>[[115, 386, 880, 520]]<|/det|> +href="https://www.springernature.com/gp/open- research/funding/policy- compliance- faqs"> compliance with funder and institutional open access mandates. If your research is supported by a funder that requires immediate open access (e.g. according to Plan S principles) then you should select the gold OA route, and we will direct you to the compliant route where possible. For authors selecting the subscription publication route, the journal's standard licensing terms will need to be accepted, including https://www.nature.com/reprints/author- reprints.html. All co- authors, authors' institutions and authors' funding agencies can order reprints using the form appropriate to their geographical region. + +<|ref|>text<|/ref|><|det|>[[115, 728, 881, 848]]<|/det|> +We welcome the submission of potential cover material (including a short caption of around 40 words) related to your manuscript; suggestions should be sent to Nature Ecology & Evolution as electronic files (the image should be 300 dpi at \(210 \times 297 \text{mm}\) in either TIFF or JPEG format). Please note that such pictures should be selected more for their aesthetic appeal than for their scientific content, and that colour images work better than black and white or grayscale images. Please do not try to design a cover with the Nature Ecology & Evolution logo etc., and please do not submit composites of images related to your work. 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If you have any questions please click here.** + +<--- Page Split ---> diff --git a/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/images_list.json b/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/supplementary_0_Peer review file.mmd b/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/supplementary_0_Peer review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..abd4b7f381c46dc6a11842515590021d7ffdd2cc --- /dev/null +++ b/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/supplementary_0_Peer review file.mmd @@ -0,0 +1,397 @@ + +# nature portfolio + +Peer Review File + +Early Treatment Regimens Achieve Sustained Virologic Remission in Infant Macaques Infected with SIV at Birth + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +Overall, the manuscript by Wang et al., presents very interesting data demonstrating the efficacy of early ART in neonates to effectively suppress virus (SIV/HIV), even after the removal of ART. The animal studies demonstrate that the initiation of ART 3 days after IV inoculation of SIV, with continuation of ART for 9 months, prevented viral rebound after ART discontinuation in \(80\%\) of animals. These observations are significant and are important contributions to the field. However, the conclusion raised and the interpretation of the data, as related to the establishment of reservoirs, are not well- justified. + +The study examines the dynamics of early ART on the establishment of SIV reservoirs by quantifying cell- associated RNA and DNA, as well as integrated DNA using an Alu- PCR method. They found that integrated viral DNA did not appear until day 3, although total SIV DNA was found on day 1 in lymph node, colon and PBMC. The study equates efficacy of early ART with the presumption that integrated reservoirs are not established until at least day 3 (lines 90- 96, 160, and much of the discussion). There are several problems with this interpretation. While it is possible that unintegrated virus can contribute to the production of plasma virus, the early and rapid kinetics of viral expression in the plasma between days 1 and 3 are very likely to result from integrated provirus. It has not been shown that unintegrated virus would significantly contribute to the early (and rapid) kinetics of viral expression observed following IV inoculation. It is highly plausible that the inability to detect integrated provirus at day 1 or day 3 is due to the sensitivity of the Alu- PCR assay. It is critical to demonstrate the sensitivity of this assay and show that it has the same level of sensitivity as the total DNA to support this claim. The method section does not adequately detail the differences in the integrated and total SIV DNA assays. The authors indicate a sensitivity of the nested, qPCR alu- SIV qPCR assay as 1 copy in 240,000 cells, but they do not compare that with the sensitivity of the total SIV DNA assay nor detail how this was determined/confirmed. The standard used for quantification of integrated DNA is not clear and sufficient details (or a reference) for the sensitivity of the integrated DNA assay are not provided, including the total amount of cell DNA (cell equivalents analyzed). + +Despite the limitations regarding their interpretation of integrated provirus, the paper does detail novel and important data regarding the efficacy of early ART in a pediatric population. + +Below are a few specific comments that would enhance the manuscript. + +Revise all discussion regarding the evidence for lack of reservoir establishment, with the inclusion of assay sensitivity and interpretation of results reported with these limitations. + +<--- Page Split ---> + +Figure 1: + +The plasma viral load data in Figure 1B is not complete (only shows 6 of 14 animals), and interpretation is limited. It would be helpful to know the plasma viral load of the animals that were sacrificed, and that is not easily discerned from data shown on days 1 and 3. + +Plasma VL at day 1 is shown for 6 animals, 3 positive and 3 negative. Which of these are from the animals euthanized and correspond to the data shown from PBMC? What subsequent data is available for the 3 negative? Do the viral loads at day 3 represent the 8 remaining animals? It is difficult to count the number of symbols shown for Day 3; are 8 remaining animals represented in 1B? How do specificplasma VL compare to those in tissues? Is there a threshold of plasma virus levels that correlate with detection of total DNA and/or integrated DNA (suggesting sensitivity of detection methods?) Why do the y axis for the integrated DNA in panels I- M start at 10- 2? + +Figure 2: + +The legend/text state that 9 control animals were used for comparison, yet only 3 are represented in panels E, F, G. How many are represented in the various time points of panel D, as error bars are only shown for the day 9 time point? + +Reviewer #2 (Remarks to the Author): + +In this manuscript Wang et al. assessed the impact of very early antiretroviral initiation on the viral reservoir in perinatally SIV- infected rhesus macaque infants. Specifically, the study investigated SIV DNA and RNA levels in RM infants infected i.v. with SIVmac251 within 6 hours after birth and treated or not with ART initiated between day 3 and day 5. The impact of early ART on the viral reservoir was estimated by measuring total or integrated SIV DNA in cells isolated from blood, lymph nodes and gut and/or by analytical treatment interruption. The main result of this study is the long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. This absence of viral rebound was observed for up to 18 months even following experimental \(\mathrm{CD8 + }\) T cell depletion. + +The manuscript needs serious English editing. It also suffers from the choice of graphical representation- at best the graphs are difficult to read but they also can be misleading. The assays used to evaluate reservoir seeding are not optimal and the methods are insufficiently described. The data are not appropriately described and interpreted. The significance of the results is questionable notably because they are not very novel. It is well documented that early ART restricts the latent reservoir + +<--- Page Split ---> + +establishment in adults and infants. Delayed viral rebound or sustained virologic control following ART interruption has been reported in children treated early post infection. The Mississippi baby treated 31 hours after birth maintained undetectable viremia for 27 months in absence of ART. Preliminary results from the IMPAACT P1115 study showed that two years after starting ART within 48 hours of birth, two thirds of infants had nondetectable cell- associated HIV DNA and almost \(90\%\) tested negative for HIV antibody. ATI will be performed in eligible study participants. + +Please see specific comments and detailed review below: + +1- To interrogate SIV dynamics or the viral reservoir seeding, the accuracy and sensitivity of the assays used is critical. In this manuscript, some key information regarding the methods is missing such as the limit of detection of each assay and the number of cells assessed (known limiting factor in pediatric studies). The type of cells assessed is also unclear to this reviewer (PBMC and lymphocytes/CD3+ isolated from tissues or tissue mononuclear cells?). If I understand correctly, dilutions of a plasmid in DNA from uninfected cells was used as a standard for the integrated SIV DNA quantification which bypasses the Alu- gag PCR and is thus not appropriate. The manuscript reports unintegrated SIV DNA which has not been measured but extrapolated from the measurement of total and integrated SIV DNA (total SIV DNA in that case is not shown). + +2- Untreated SIV infection (Figure 1). The number of animals euthanized or initiated on ART for each time point is not indicated on the study design schematic nor in its legend. The LOD of the assays is missing for total SIV RNA and integrated DNA. It is also unclear if PVL was assessed for all living animals at each time point. Using individual symbols for each animal would greatly improve the figure. I count 9 symbols of the PVL at day 3 but according to the study design, only 8 animals were still alive by then. + +3- Early short- term ART (Figure 2): It is unclear what comparisons are the p values representing although the legend states that comparison were made with d3 p.i. Surprisingly, SIV RNA levels appear to be higher in the group of animals receiving ART at day 5 p.i. than in the untreated control group. Were those all assessed at the same time point (day 28 p.i.)? The results indicate that in untreated infection, viremia plateaued at 7 day p.i. but the graph shows a peak at day 9 p.i. + +4- Early "long- term" ART and ATI (Figure 3): A control group initiated on ART later and going through ATI is missing. In panel A, it is difficult to distinguish the PVL of each animal at day 3 p.i. One RM out of 5 experienced a viral rebound following ATI. The rebound was detected 2 months post ATI. Was the PVL assessed during these 2 months? The absence of symbol in panel A does not allow the reader to get that information. The antibody used to assess CD8 expression following experimental depletion is not indicated. + +<--- Page Split ---> + +One restatement of the conclusions of this work that could be drawn from this observation is that the authors have not induced HIV remissions, but simply observed successful post- exposure prophylaxis, and that in the setting of new infection of the infant immune system, that potent ART that includes an INSTI within 3 days, but not later, of viral exposure is sufficient to block all persistent infection in \(80\%\) of exposed infant animals. There may have been viral integration events that led to productive infection before day 3, but few enough so that no latent, persistent infections were established that could lead to viral rebound upon later ATI. + +I view this work as suggestive, but preliminary. A larger cohort should be studied. Longer ATI and more tissue sampling should be pursued. Cell infection transfer experiments, to test if infection can be passed by cells from one animal to another should be done. These points should be discussed by the authors. + +However, the findings of this work are potentially important and should be disseminated to stimulate the field. + +Current US guidelines (Dec. 2021) state that: + +A newborn's ARV regimen should be determined based on maternal and infant factors that influence the risk of perinatal transmission of HIV (All). The uses of ARV regimens in newborns include the following: + +- ARV Prophylaxis: The administration of one or more ARV drugs to a newborn without documented HIV infection to reduce the risk of perinatal acquisition of HIV. + +- Presumptive HIV Therapy: The administration of a three-drug ARV regimen to newborns who are at highest risk of perinatal acquisition of HIV. Presumptive HIV therapy is intended to be preliminary treatment for a newborn who is later documented to have HIV, but it also serves as prophylaxis against HIV acquisition for those newborns who are exposed to HIV in utero, during the birthing process, or during breastfeeding and who do not acquire HIV. + +- HIV Therapy: The administration of a three-drug ARV regimen at treatment doses (called antiretroviral therapy [ART]) to newborns with documented HIV infection (see Diagnosis of HIV Infection in Infants and Children). + +These findings suggest that such presumptive HIV therapy or therapy given for HIV infection documented at birth should include an INSTI if possible. Further support for the findings in this manuscript could lead to the study of ATIs in newborns treated with INSTIs. + +Such studies are underway but it is unclear if they are sufficiently enrolled or powered to answer the question anytime soon. Therefore, even these preliminary findings are of interest. + +<--- Page Split ---> + +Minor points: + +Line 59: Protease inhibitors for "proteinase inhibitors" + +Line 59- 60: "prevent cells from viral genome integration" is awkward. Change to "prevent viral genome integration in cells"? + +Line 201: typographical error: Integrated + +<--- Page Split ---> + +## Nature Communications + +RE: NCOMMS- 22- 04053, point to point responses to reviewer comments + +## Reviewer #1 + +1. Overall, the manuscript by Wang et al., presents very interesting data demonstrating the efficacy of early ART in neonates to effectively suppress virus (SIV/HIV), even after the removal of ART. The animal studies demonstrate that the initiation of ART 3 days after IV inoculation of SIV, with continuation of ART for 9 months, prevented viral rebound after ART discontinuation in 80% of animals. These observations are significant and are important contributions to the field. However, the conclusion raised and the interpretation of the data, as related to the establishment of reservoirs, are not well-justified. + +Response: We appreciate the insightful comments that the reviewer provided and thank you for the interest showed in our work. We have accommodated the requests and thoroughly revised the manuscript as suggested. + +2. The study examines the dynamics of early ART on the establishment of SIV reservoirs by quantifying cell-associated RNA and DNA, as well as integrated DNA using an Alu-PCR method. They found that integrated viral DNA did not appear until day 3, although total SIV DNA was found on day 1 in lymph node, colon and PBMC. The study equates efficacy of early ART with the presumption that integrated reservoirs are not established until at least day 3 (lines 90-96, 160, and much of the discussion). There are several problems with this interpretation. While it is possible that unintegrated virus can contribute to the production of plasma virus, the early and rapid kinetics of viral expression in the plasma between days 1 and 3 are very likely to result from integrated provirus. It has not been shown that unintegrated virus would significantly contribute to the early (and rapid) kinetics of viral expression observed following IV inoculation. It is highly plausible that the inability to detect integrated provirus at day 1 or day 3 is due to the sensitivity of the Alu-PCR assay. It is critical to demonstrate the sensitivity of this assay and show that it has the same level of sensitivity as the total DNA to support this claim. The method section does not adequately detail the differences in the integrated and total SIV DNA assays. The authors indicate a sensitivity of the nested, qPCR Alu-SIV qPCR assay as 1 copy in 240,000 cells, but they do not compare that with the sensitivity of the total SIV DNA assay nor detail how this was determined or confirmed. The standard used for quantification of integrated DNA is not clear and sufficient details (or a reference) for the sensitivity of the integrated DNA assay are not provided, including the total amount of cell DNA (cell equivalents analyzed). + +Response: We appreciate the reviewer's concerns. To address the concerns regarding the early virion production from unintegrated viral DNA and the sensitivity of the qPCR assay, we performed additional in vitro experiments, in combination with viral parameters measured by nested (Alu) qPCR. Briefly, PBMCs isolated from one- month- old infant macaques (due to limited blood collected from newborns or neonates even at animal necropsy) were first activated for 3 days by CD4+ T + +<--- Page Split ---> + +cell activation kit (Miltenyi) in the presence of human IL- 2 (10%, Hemagen), and then infected with SIVmac251 (3x10^7 cell/mL with 100 TCID50 SIV) for 2 hours in CO2 incubator, followed by 3 washes and seeding in 24-well plate at 1x10^6 cell/well/mL, without or with raltegravir (RTG) at final 1μM concentration. Cells and cell supernatants were harvested to measure CA SIV RNA/DNA and supernatant viral load. Please see the revised Method section in the revised manuscript. + +As shown in Suppl Fig.1, cell- associated (CA) integrated SIV DNA was indeed not detected in PBMCs in presence of RTG, yet total CA SIV RNA/DNA were still detectable as early as 6 hours after SIV infection, suggesting that viral genome integration was fully blocked by RTG treatment while total SIV DNA predominantly represented unintegrated form at such scenario. Please note that supernatant VLs have not shown significant differences at early SIV infection (3 and 7dpi) between RTG treated and untreated samples. This suggests early virus particles in cell supernatants are not likely produced from integrated SIV DNA when PBMCs were treated by RTG. Although integrated proviral DNA is believed a template for stable HIV/SIV replication, however, unintegrated viral DNA per se may contribute to the early viral replication and virus production, even when cells are treated by RTG (Kelly, 2008; Chan CN, 2016; Trinite B, 2013), explaining viremia emergence in very early SIV infection in vivo prior to viral genome integration. Again, these results suggested that, i) Alu qPCR assay here could essentially reflect the status of SIV genome integration; ii) integrase inhibitor treatment could efficiently suppress viral genome integration; iii) viral load in cell supernatants was detectable at early infection in presence of integrase inhibitor (lack of integrated viral DNA), indicating early unintegrated viral DNA is able to rapidly yield infectious virions. + +We would prefer to add even more detail in Methods but have space limitations. However, these assays are based on prior studies of integrated SIV DNA measurement which target one conserved region of human and rhesus common Alu DNA sequence by outward primer Alu- 1 and - 2 (Nishimura Y, 2009; Mavigner M, 2016; Whitney JB, 2014 and 2018). Combined unique rhesus Alu repetitive sequences (Hamdi H, 1999), we further optimized and improved the Alu qPCR to target multiple Alu islands, combined Alu- 1, - 2 with additional rhesus specific Alu - 3 and - 4 primers, potentially increasing the sensitivity and detection rate of integrated SIV DNA. Human CEMx174 Cell line (#ARP- 13239, NIH AIDS Reagent Program), carrying 1 copy of integrated SIV DNA, is used to extract cellular genomic DNA, which is serially diluted to determine copies of proviral DNA in terms of cell numbers, and then quantified by our nested Alu qPCR. Unfortunately, there is no rhesus- derived cell line that contains single copy of SIV proviral DNA and specific rhesus Alu, thus we cannot test human CEMx174 Cell lines by our new Alu primers (Alu 3- and - 4). However, our nested qPCR with Alu 1- 4 primers generates consistently higher levels of proviral DNA in macaque- derived cell samples, compared with of those using human/rhesus Alu 1- 2 only. Limit of detection (LOD) of proviral SIV DNA is 5.3 per million cells, determined by GenEx software based on standard curve and deviation, please see %CV for individual standard in Table 1 in this letter. In our assay, lymphocytes (1x10^7 cells per sample in general) are isolated to extract cellular DNA (final volume to 100μL) and 2.5μL cellular DNA sample (2.5x10^5 cell equivalents) is added to the Master Mix (final 25μL). The data showed that 1 copy SIV genomic DNA contained cellular DNA equivalent to cell numbers, + +Table 1. Nested qPCR reproducibility ( \(\% \mathrm{CV}\) ; \(n = 6\) + +
STD CopiesCCR5LTR U5
10^40.2%2.9%
10^30.3%2.5%
10^20.4%2.1%
10^10.5%2.4%
10^01.2%3.5%
+ +on standard curve and deviation, please see %CV for individual standard in Table 1 in this letter. In our assay, lymphocytes (1x10^7 cells per sample in general) are isolated to extract cellular DNA (final volume to 100μL) and 2.5μL cellular DNA sample (2.5x10^5 cell equivalents) is added to the Master Mix (final 25μL). The data showed that 1 copy SIV genomic DNA contained cellular DNA equivalent to cell numbers, + +<--- Page Split ---> +![PLACEHOLDER_8_0] + + +ranging from \(1 \times 10^{5}\) to \(2.4 \times 10^{5}\) cell equivalents, could be consistently detected (stated probability) as detection quantification (LOQ, 1 copy in \(2.4 \times 10^{5}\) cell equivalents, \(\% \mathrm{CV} = 4.2\%\) ). In brief, first- step routine PCR (pre- amplification) is performed to amplify SIV LTR U5 (for total SIV DNA and standard) or SIV U5/Alu 1- 4 fragments (for proviral DNA) for 20 cycles, followed by second- step qPCR using same U5 primer/probe set for 40 cycles with 1/10 volume of \(1^{\mathrm{st}}\) amplicon. Internal standard curve was used to calculate the initial copies of both total SIV DNA and proviral DNA (an example of STD cure attached here, very stable from batch to batch). + +of \(1^{\mathrm{st}}\) amplicon. Internal standard curve was used to calculate the initial copies of both total SIV DNA and proviral DNA (an example of STD cure attached here, very stable from batch to batch). + +Using this assay, we have measured hundreds of samples from SIV- infected animal cohorts (Ziani W, 2021a,b,c; Wang X, 2021). We performed nested qPCR in parallel to quantify both total viral DNA and proviral DNA in each sample (yielding comparable data), along with standard. Thus, nested qPCR assay can generate sensitive and comparable data of both total SIV DNA and proviral DNA. Also, the results shown in Supple Fig. 1 suggest that Alu qPCR is able to essentially reflect the sensitivity and status of SIV genome integration in RTG- or untreated- PBMCs, thus inferring lymphocyte samples isolated from tissues. Basically, nested qPCR (two- rounds PCR amplification) can increase sensitivity and specificity of target gene, however, we admit that the possibility that proviral DNA may not be fully detected due to viral reservoir distribution in various tissues in the body and likely lack of chromosomal Alu islands situated near the integrated SIV genome, we discussed this in the revised DISCUSSION. Alu islands are widely dispersed within the chromosomal DNA (accounting for 6- 13% of genomic DNA), which are likely lacked or far from SIV LTR region, albeit very few such case existed. qPCR targeting SIV gag is used to determine plasma viral load with a limit of detection of 83 copies per mL (core service). Together, early treatment, building on viral genome integration assessed by our assay, achieved sustained virologic remission in the neonates infected with SIV, which were largely consistent with the onset of proviral reservoirs in typical systemic and lymphoid tissues of very early SIV infection. We realize that more animal cohorts/sampling are needed, in combination with intrauterine/postnatal infection, one or more ARV regimens as well as optimal period of treatment and so on. We have carefully considered the interpretations of our results and added more information and detail in Method section, please see in our revised manuscript. + +3. Despite the limitations regarding their interpretation of integrated provirus, the paper does detail novel and important data regarding the efficacy of early ART in a pediatric population. + +Response: We thank reviewer's positive comments, we have carefully read through the text and made appropriate interpretations and caveats to our results. + +4. Revise all discussion regarding the evidence for lack of reservoir establishment, with the inclusion of assay sensitivity and interpretation of results reported with these limitations. + +<--- Page Split ---> + +Response: We thank reviewer's suggestion, we discussed proviral reservoir establishment in neonates, especially assay sensitivity and interpretation of proviral reservoir measurement in vitro and in vivo studies, please see DISCUSSION in our revised manuscript. + +5. Figure 1: The plasma viral load data in Figure 1B is not complete (only shows 6 of 14 animals), and interpretation is limited. It would be helpful to know the plasma viral load of the animals that were sacrificed, and that is not easily discerned from data shown on days 1 and 3. + +Response: We apologize for not making it clearer. Whole blood request and neonatal anesthesia is strictly controlled in terms of IACUC (12mL/Kg/Month in total) and limited volume of experimental blood available because of newborns weight ( \(\sim 400\mathrm{g}\) , only 1.2cc EDTA blood available in general), physiologic weight loss after birth as well as mandatory bleeding for CBC. It is not feasible to consistently collect 1.2cc whole blood from newborn infants and neonates in the first few days of birth and larger volumes are limited to collection at necropsy. Therefore, whole blood is collected by staggered request from individual newborn/neonates. We added the grouped animals, the day(s) post SIV inoculation, plasma viral load from blood sampling as well as text in revised manuscript as Suppl. Table 1. Hope it will be clearer. + +6. Plasma VL at day 1 is shown for 6 animals, 3 positive and 3 negative. Which of these are from the animals euthanized and correspond to the data shown from PBMC? What subsequent data is available for the 3 negative? Do the viral loads at day 3 represent the 8 remaining animals? It is difficult to count the number of symbols shown for Day 3; are 8 remaining animals represented in 1B? How do specific plasma VL compare to those in tissues? Is there a threshold of plasma virus levels that correlate with detection of total DNA and/or integrated DNA (suggesting sensitivity of detection methods?) Why do the y axis for the integrated DNA in panels 1-M start at 10-2? + +Response: We apologize for the confusion. Here we improved the figures to specifically track cell- associated (CA) SIV RNA/DNA in PBMC, LN and colon, and corresponding plasma viral load (PVL) in individual animals at early SIV infection by colored symbols. As we mentioned in Question #5 and shown in Suppl. Table 1, plasma viral load measured at 1dpi (n=6) also include staggered blood samples collected from 3 animals that were euthanized at 28dpi (n=3; PVL, 1 negative and 2 positive at 1dpi), the remaining three animals euthanized at 1dpi are highlighted by colored symbols now to accommodate plasma viral load (2 negative and 1 positive), CA SIV RNA/DNA in PBMC, LN and colon in individual animals. Likewise, viral parameters from neonates euthanized at 2dpi (n=3), 3dpi (5 euthanized neonatal animals plus additional 3 staggered blood samples from other 28- day infected animals for PVL measurement, see Suppl. Table 1), 5dpi (n=2) and 7dpi (n=1) are highlighted by colored symbols for individual animals post SIV infection in revised manuscript (Figs. 1B- 1H). As for sensitivity and LOD of qPCR detection, please see Answer #2. Given y- axis represents power of 10, value below the LOD is considered to be undetectable, we now revised the figures. We added necessary description in Results, and hope it is more understandable now. + +7. Figure 2: The legend/text state that 9 control animals were used for comparison, yet only 3 are represented in panels E, + +<--- Page Split ---> + +F, G. How many are represented in the various time points of panel D, as error bars are only shown for the day 9 time point? + +Response: We are sorry for our careless. We longitudinally tracked plasma viral load in plasma including staggered blood samples (Figs. 2A- 2C), CA SIV RNA and paralleled CA SIV DNA/proviral DNA in fresh tissues of 3 groups on cART initiated at 3-, 4- or 5dpi, and one group without treatment control (n=3), all these animals are euthanized at 28dpi. Additional data (not samples) from our previous study with age- matched SIV- infected infant macaques (n=9) are used to compare routine plasma viral load and the percentages of peripheral CD4+ T cells (Fig. 2D and Figs. 3A- 3B). We went through the data and revised our text and Figure Legend. As for Fig.2D, which is summarized from Figs. 2A- 2C with statistical analysis for each group, the error bars cannot be displayed because of low S.E.M in Y- axis at timepoints. + +## Reviewer #2 + +In this manuscript Wang et al. assessed the impact of very early antiretroviral initiation on the viral reservoir in perinatally SIV- infected rhesus macaque infants. Specifically, the study investigated SIV DNA and RNA levels in RM infants infected i.v. with SIVmac251 within 6 hours after birth and treated or not with ART initiated between day 3 and day 5. The impact of early ART on the viral reservoir was estimated by measuring total or integrated SIV DNA in cells isolated from blood, lymph nodes and gut and/or by analytical treatment interruption. The main result of this study is the long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. This absence of viral rebound was observed for up to 18 months even following experimental CD8+ T cell depletion. + +8. The manuscript needs serious English editing. It also suffers from the choice of graphical representation—at best the graphs are difficult to read but they also can be misleading. The assays used to evaluate reservoir seeding are not optimal and the methods are insufficiently described. The data are not appropriately described and interpreted. The significance of the results is questionable notably because they are not very novel. It is well documented that early ART restricts the latent reservoir establishment in adults and infants. Delayed viral rebound or sustained virologic control following ART interruption has been reported in children treated early post infection. The Mississippi baby treated 31 hours after birth maintained undetectable viremia for 27 months in absence of ART. Preliminary results from the IMPAACT P1115 study showed that two years after starting ART within 48 hours of birth, two thirds of infants had nondetectable cell-associated HIV DNA and almost 90% tested negative for HIV antibody. ATI will be performed in eligible study participants. + +Response: We appreciate the reviewer's comments. We have carefully looked over the manuscript and improved the typos, grammar issues and interpretation. We apologize for not making the graphs clearer, especially Fig.1, and have thoroughly revised the figures for plasma viral load and counterpart CA SIV RNA/DNA in individual animals at very early SIV infection as described above. Now neonates used are summarized in Suppl. Table 1. We also added more detailed description regarding our qPCR assays in Methods, including how we quantified the viral parameters using our optimized nested (Alu) PCR based on other published reports (Nishimura Y, 2009; Mavigner M, 2016; Whitney JB, 2014 and 2018), and also please see Answer #2 in this letter. Specifically, we added the supplementary data (Suppl Fig. 1) to directly address specificity + +<--- Page Split ---> + +and sensitivity of the assay especially for integrated viral DNA measurement, with or without raltegravir (RTG) treatment. As shown in Suppl Fig.1, CA integrated viral DNA was consistently not detected in PBMCs in presence of RTG (viral genome integration blockade), while CA SIV RNA/DNA (unintegrated, due to undetectable integrated vDNA) as well as supernatant viral load were still detectable in the early SIV infection. These data strongly suggest that our assay can essentially reflect the status of SIV genome integration, by comparing the results in the presence or absence of RTG treatment, and thus inferring this application to measure the lymphocyte samples isolated from tissues ex vivo. + +In this study, we utilized the neonatal NHP model intravenously infected with SIV, facilitating to precisely time the very early days of infection (compared with uncertain dip by repeated SIV/SHIV challenges to the infant macaques by oral route or HIV+ children in the clinic) and collected complete tissue sets at necropsy for examination of viral reservoirs. As shown in Fig.2 in this letter, early cART initiation at 3dpi in adult animals showed \(100\%\) viral rebound within three weeks once treatment is discontinued (Whitney, 2018). In comparison, early treatment regimen initiated at same timepoint achieved sustained virologic remission in \(80\%\) infant macaques, suggesting the features and outcomes in neonates/infants to the early SIV/HIV infection and early treatment are indeed distinct from those of adult subjects, which is of great significance to understand early events and providing a critical treatment window for pediatric functional cure or even absolute cure. + +It is true that early ART in children, treatment ranging from immediate (Butler, 2015), within hours after delivery (Giacomet, 2014), or months/years- old (Martinez- Bonet, 2015; Frange, 2016; Violari, 2019), is documented well, including reduction of the reservoir size and skewing of viral rebound in the clinic setting. However, viral rebound or rapid increase of HIV RNA/DNA in these early treated pediatric cases are detected once treatment is stopped in these clinical trials. The Mississippi baby case treated 30 hours after birth ultimately showed viral rebound even after 27- months ATI, in utero HIV infection during pregnancy likely occurred in this case (Faye A, 2020), and conceivably, viral integration occurred in perinatal period. We do not know either status of intrauterine infection even starting ART within 48 hours of birth, and based on what happened if treatment is allowed to withdraw in IMPAACT P1115 study, the outcomes presumably depend on status of viral genome integration. + +In this study, we evaluated the dynamics and tissue distribution of viral reservoirs and plasma viral load in several newborn macaques at very early timed- stages of SIV infection, which provided critical clues for early treatment interventions, as indicated by outcomes of viral remission achieved by early treatment for 9 months and further confirmed by subsequent CD8+ cell depletion in vivo. We consider this a de facto success to achieve viral remission in 4/5 infant macaques by early treatment (all 5 infants infected with identical SIV inoculum at birth and treated at 3dpi for 9 months). These 4 cured infants are still alive with ART- free viral remission, and currently resisting repeated SIV challenges by the rectal route. Here we + +<--- Page Split ---> + +precisely explored the neonatal distinct patterns, early viral reservoir seeding and optimal early treatment (timing and regimen) utilizing the neonatal macaque model of HIV, which permits thorough examinations of blood and tissue reservoirs that cannot be achieved studying human infants. Even if this data shows only a few unique findings we believe this data is directly translational to the clinic and may provide knowledge that may save a few infants from lifelong HIV infection. + +9. To interrogate SIV dynamics or the viral reservoir seeding, the accuracy and sensitivity of the assays used is critical. In this manuscript, some key information regarding the methods is missing such as the limit of detection of each assay and the number of cells assessed (known limiting factor in pediatric studies). The type of cells assessed is also unclear to this reviewer (PBMC and lymphocytes/CD3+ isolated from tissues or tissue mononuclear cells?). If I understand correctly, dilutions of a plasmid in DNA from uninfected cells was used as a standard for the integrated SIV DNA quantification which bypasses the Alu-gag PCR and is thus not appropriate. The manuscript reports unintegrated SIV DNA which has not been measured but extrapolated from the measurement of total and integrated SIV DNA (total SIV DNA in that case is not shown). + +Response: We appreciate the reviewer's concerns. We absolutely agree with the opinion that the viral reservoir assays are highly challenging for the current studies and researchers in general, as indicated by continuous efforts and attempts made for development of scalable assays, including RT qPCR, Alu qPCR, QVOA, TILDA, IPDA and FLIPS, etc. As mentioned in DISCUSSION, we acknowledge that there is no de facto gold standard thus far to reflect absolute size of viral reservoirs especially viral DNA (e.g., unintegrated, or integrated vDNA, circular vDNA, defective or intact viral genome, functional or dysfunctional, Indel/polymorphism at different levels, inserted regions with gene dessert, etc), with obvious both advantages and weaknesses with each approach. To our knowledge, it is a challenge to measure integrated HIV/SIV DNA efficiently, comprehensively, and accurately in the cells, tissues, and organs throughout the body, while most have only assessed peripheral blood mononuclear cells, and/or even sorted CD4+ T cells thus far, which obviously misses important residual reservoirs in tissues. + +Considering sensitivity, rapidity, and feasibility of qPCR, we spent several years to develop and optimize nested Alu qPCR for quantification of the CA integrated SIV DNA, based on previous published reports using conserved human/rhesus Alu- 1 and - 2 (please see refs by Nishimura Y, 2009; Mavigner M, 2016; Whitney JB, 2014 and 2018, etc). To strengthen proviral SIV DNA assay, rhesus specific repetitive Alu DNA, which are widely dispersed within the chromosomal DNA in rhesus macaques, is targeted by additional Alu- 3 and - 4 primers. Our optimized Alu qPCR thus includes Alu 1- 4 outward primers to target multiple Alu islands in rhesus species. As for the accuracy and sensitivity of the assays concerned, please see Answer#2. + +It is true that we use plasmids as standard containing SIV gene as standard with known copies, which is indispensable to perform nested qPCR (unlike the RNA quantification by Droplet digital PCR, STD not required). Human CEMx174 Cell line (#ARP- 13239, NIH AIDS Reagent Program), carrying 1 copy of integrated SIV DNA, is generally used to quantify proviral DNA by nested Alu qPCR with conserved human/rhesus Alu- 1 and - 2 outward primers. Additional Alu primers (Alu- 3 and - 4), targeting rhesus specific Alu sequences, are not applicable for human CEMx174 Cell line- associated + +<--- Page Split ---> + +standard. Outward Alu 1- 4 primers used in qPCR indeed increase the sensitivity and detection rate of proviral SIV DNA in rhesus samples. To yield comparable data in the quantification of total SIV DNA and proviral DNA, nested qPCR is performed in parallel to quantify both total SIV DNA and proviral DNA for each sample. Type of cells are lymphocytes that are freshly isolated from systemic and lymphoid tissues at biopsies or necropsies, \(10^{7}\) lymphocytes per sample are generally collected for nested qPCR assay. Briefly, we performed nested qPCR to quantify total viral DNA, proviral DNA, along with standard. First- step routine PCR is used to pre- amplify total SIV DNA and standard (by LTR U5 primer pair) or integrated SIV DNA (by U5/Alu 1- 4 primer pairs) for 20 cycles (optimized cycle for the \(1^{\mathrm{st}}\) PCR in our assay). Second qPCR is further performed with 1/10 volume of \(1^{\mathrm{st}}\) amplicon targeting SIV LTR U5 with same primer/probe set for 40 cycles. Internal standard curve is used to calculate the initial copies of both total and integrated SIV DNA. Please note that it is essentially difficult to quantify gene fragments of SIV/Alu by qPCR in the first round PCR due to unpredictable size of gene fragments generated (tens of bp to several kb) and thereby amplification efficiency is variable from sample to sample. Thus, it is feasible and reasonable to use plasmid standard in the quantification of both CA total SIV DNA and proviral DNA at 2nd qPCR using same primer/probe set, irrelevant to Alu repetitive sequences. We agree with reviewer's comments about unintegrated SIV DNA, now we changed wording to indicate total SIV DNA in the revised figures. + +Although our assay is far more sensitive to measure proviral DNA, nested qPCR increases sensitivity and specificity of gene targets, as also indicated by Ct (e.g., cycle threshold of 10copies, from \(\sim 36\) at \(1^{\mathrm{st}}\) to \(\sim 16\) at \(2^{\mathrm{nd}}\) PCR). However, status of viral genome integration by our assay essentially matches the actual scenario: undetectable proviral DNA in PBMCs infected with SIV in presence of RTG, and achievable ART- free viral remission in infants when early cART is initiated prior to proviral reservoir seeding. We have thoroughly modified our text as suggested in the revised manuscript. + +10. Untreated SIV infection (Figure 1). The number of animals euthanized or initiated on ART for each time point is not indicated on the study design schematic nor in its legend. The LOD of the assays is missing for total SIV RNA and integrated DNA. It is also unclear if PVL was assessed for all living animals at each time point. Using individual symbols for each animal would greatly improve the figure. I count 9 symbols of the PVL at day 3 but according to the study design, only 8 animals were still alive by then. + +Response: We appreciate the reviewer's suggestion and have improved the figure as suggested to track individual animals. PVL is measured in plasma from euthanized animals or staggered blood samples. The LOD of assay is added in the revised manuscript. Also please see the Answer #5 and #6 above in this letter including animals used and corresponding PVL at different timepoints (Suppl. Table 1). + +11. Early short-term ART (Figure 2): It is unclear what comparisons are the p values representing although the legend states that comparison were made with d3 p.i. Surprisingly, SIV RNA levels appear to be higher in the group of animals receiving ART at day 5 p.i. than in the untreated control group. Were those all assessed at the same time point (day 28 p.i.)? The results indicate that in untreated infection, viremia plateaued at 7 day p.i. but the graph shows a peak at day 9 p.i. + +<--- Page Split ---> + +Response: We thank the reviewer for these comments and for not making comparisons clearer among the groups. We revised figures and legend in the manuscript. We did see levels of CA SIV RNA are higher at 28dpi by late treatment. Conceivably, cART (FTC/TFV/DTG) suppresses reverse transcription of viral RNA and viral integration, late treatment may result in accumulation of intracellular SIV RNA which are transcribed from both unintegrated and proviral DNA (e.g., before treatment at 5dpi), while CA SIV RNA in untreated control may be relatively exhausted by virus packaging/release, contributing to viral peak and thereafter. All samples examined are freshly collected from euthanized animal cohorts at 28dpi (Figs. 2E- 2F). PVL data in age- matched SIV- infected infant controls come from our previous studies. PVL in SIV- infected neonatal macaques is generally monitored at 7, 14 and 21dpi, viremia actually reaches the peak at 7- 9 dpi, we have corrected the description. + +12. Early "long-term" ART and ATI (Figure 3): A control group initiated on ART later and going through ATI is missing. In panel A, it is difficult to distinguish the PVL of each animal at day 3 p.i. One RM out of 5 experienced a viral rebound following ATI. The rebound was detected 2 months post ATI. Was the PVL assessed during these 2 months? The absence of symbol in panel A does not allow the reader to get that information. The antibody used to assess CD8 expression following experimental depletion is not indicated. + +Response: We thank the reviewer for these comments and suggestions. Neonates and infants infected with HIV/SIV show higher viremia and rapid disease progression compared to adults, most of infant macaques intravenously infected with SIV develop to the final stage of AIDS after 4- 5 months of infection (Wang X, 2010). These infants are sacrificed because of AIDS- like symptoms, so the PVL data are shown only in this period. In panel A, PVL levels are very closed in neonatal macaques at 3dpi (Please see PVL of other neonates at this timepoint in Suppl Table 1), one RM (NG24, red line) with viral rebound after ATI does not show significantly different levels of plasma viral load compared to remaining 4 animals at this timepoint. Now we showed NG24 PVL line in bold and individual symbols for 5 animals at designated timepoints. All 5 infant animals are weekly monitored by PVL to see if there is viral rebound after ATI. Anti- CD8 Ab clone used to assess CD8+ cells is also added in the revised manuscript. + +## Reviewer #3 + +13. One restatement of the conclusions of this work that could be drawn from this observation is that the authors have not induced HIV remissions, but simply observed successful post-exposure prophylaxis, and that in the setting of new infection of the infant immune system, that potent ART that includes an INSTI within 3 days, but not later, of viral exposure is sufficient to block all persistent infection in 80% of exposed infant animals. There may have been viral integration events that led to productive infection before day 3, but few enough so that no latent, persistent infections were established that could lead to viral rebound upon later ATI. + +I view this work as suggestive, but preliminary. A larger cohort should be studied. Longer ATI and more tissue sampling should be pursued. Cell infection transfer experiments, to test if infection can be passed by cells from one animal to another should be done. These points should be discussed by the authors. + +Response: We thank the reviewer for these thoughtful comments and suggestions. We have since performed experiments + +<--- Page Split ---> + +with one- month- old infant PBMC infected with SIV in vitro, in presence or absence of integrase inhibitor (raltegravir/RTG), followed by CA SIV RNA/DNA and viral load measurement, which are expected to address the efficiency of RTG on the blockade of viral genome integration, ability of early unintegrated SIV DNA in the virion production as well as sensitivity of qPCR assay, please see the Suppl. Fig.1 in the revised manuscript. Besides typical systemic and mucosal lymphoid tissues presented, other tissues, including spleen, thymus, jejunum, colon and liver, were actually examined in our study, proviral DNA was not detected in these tissues of very early SIV- infected neonates. We agree with reviewer's constructive advice that more studies are needed, including animal numbers, comprehensive tissue sampling, optimal period of early treatment, prolonged ATI, cell transfer in vivo to repeated challenge, etc, please see our discussion in the revised manuscript. After CD8+ cell depletion in vivo, the 4 infant animals with ART- free viral remission are still alive and healthy, further study with repeated SIV challenge by rectal route is underway. Finally, even if this is only "post exposure prophylaxis" it is clearly different from adults and remains translationally relevant to clinical pediatric HIV care, thus we consider these findings highly significant. + +14. However, the findings of this work are potentially important and should be disseminated to stimulate the field. + +Current US guidelines (Dec. 2021) state that: + +A newborn's ARV regimen should be determined based on maternal and infant factors that influence the risk of perinatal transmission of HIV (AII). The uses of ARV regimens in newborns include the following: + +- ARV Prophylaxis: The administration of one or more ARV drugs to a newborn without documented HIV infection to reduce the risk of perinatal acquisition of HIV. + +- Presumptive HIV Therapy: The administration of a three-drug ARV regimen to newborns who are at highest risk of perinatal acquisition of HIV. Presumptive HIV therapy is intended to be preliminary treatment for a newborn who is later documented to have HIV, but it also serves as prophylaxis against HIV acquisition for those newborns who are exposed to HIV in utero, during the birthing process, or during breastfeeding and who do not acquire HIV. + +- HIV Therapy: The administration of a three-drug ARV regimen at treatment doses (called antiretroviral therapy [ART]) to newborns with documented HIV infection (see Diagnosis of HIV Infection in Infants and Children). + +These findings suggest that such presumptive HIV therapy or therapy given for HIV infection documented at birth should include an INSTI if possible. Further support for the findings in this manuscript could lead to the study of ATIs in newborns treated with INSTIs. Such studies are underway but it is unclear if they are sufficiently enrolled or powered to answer the question anytime soon. Therefore, even these preliminary findings are of interest. + +Response: We really appreciate the reviewer's encouraging comments for our attempts. Current US guidelines are informative for the preclinical studies utilizing NHP model of HIV. Given our finding that status of viral genome integration at or near the ART initiation may determine the clinical outcomes, we are thus requesting more seasonal newborns, infant macaques of one- month- old and pregnant animals. All these animals will be utilized to investigate the ARV regimens (one or more drugs), fetal and maternal factors, intrauterine infection, INSTI- based prior or after viral integration, optimal timepoint and period of early treatment and outcomes (immune development and viral rebound) etc. + +<--- Page Split ---> + +Minor points: + +15. Line 59: Protease inhibitors for "proteinase inhibitors" + +Response: Corrected. + +16. Line 59-60: "prevent cells from viral genome integration" is awkward. Change to "prevent viral genome integration in cells"? + +Response: Thank you for this helpful suggestion. It has been corrected. + +17. Line 201: typographical error: Integrated + +Response: Corrected. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The additions and edits regarding the sensitivity of the SIV DNA and RNA quantification assays have addressed several of the concerns raised in the first review. + +There have been some qualifications added to the discussion stating the limitations of the Alu qPCR, however the authors have not demonstrated the sensitivity of the Alu qPCR in "real" samples. Admittedly, this is very difficult to demonstrate, but the assay sensitivity observed with spiked samples does not demonstrate sensitivity in samples with provirus randomly integrated into different cells. The authors also provided in vitro experiments (S1) to demonstrate production of virions, despite absence of integrated virus (with INT administration). These results do not take into account the initial input virus that would still be present in the media. + +Collectively, the data does suggest that there are few proviral copies in the early days of infection, but this is to be expected. Without a clear limit of detection for the Alu PCR, it is not possible to make the claim that virions are a result unintegrated viral DNA. Indeed, the early dynamics will be difficult to determine in vivo, as only small samples of PBMC can be analyzed. + +Other concerns raised in the initial review have been satisfactorily addressed with the edits. + +Reviewer #2 (Remarks to the Author): + +The authors have addressed most reviewer's comments and edited manuscript and figures. + +ART initiated 3dpi in infant RMs infected with SIV at birth prevented viral rebound following ATI in 4/5 animals. This result is of interest, but interpretations and conclusions must be more cautious. It seems premature to claim an absence of viral integration for 3dpi that would be specific to infants as opposed to adults, notably because the sensitivity of the integrated assay used is not clear, or specific to the ART regimen used as there is no group treated without DTG. And finally, as noted by Reviewer #3, as ART + +<--- Page Split ---> + +was initiated within 72h of infection the outcome might be closer to a successful PEP than a cure or remission and this should be discussed. + +Please see additional comments below: + +Regarding the novel ex vivo experiment presented in supplementing Fig 1, not detecting integration before 5dpi in pre- stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. The response to Reviewer 1 does not provide the sensitivity of the integrated assay nor a comparison of the LOD of this assay with that of the total DNA assay. Similarly, in the in vivo study, it cannot be excluded that integration is not detected before 3dpi in tissues and 5 dpi in PBMC because of a lack of sensitivity of the Alu gag PCR assay. Because the absence of detection of integrated DNA does not necessarily means that there is no integration, the authors should dampen their interpretations and conclusions. This won't take away from the main finding of this study that shows long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. + +I believe there is an error in supplemental table 1 as according to Fig1A no animals were sacrificed 4dpi (I think the animals sampled at 4dpi were sacrificed at 28dpi). This should be corrected. Further, the sentence "The results showed that plasma viral load was detectable in \(\sim 50\%\) neonates at 1dpi and subsequent time points thereafter" should be reformulated. After 1dpi all tested samples were positive (not \(50\%\) ). In the results section, only the first group of animals is introduced "Newborn macaques were intravenously inoculated with identical doses of SIVmac251 within 6 hours after birth, and then euthanized at day 1, 2, 3, 5 and 7 post SIV inoculation for complete tissue collections (Fig. 1A)" before presenting the PVL results of figure 1B that includes animals from the other group of animals (necropsy at 28 dpi after ART). This is confusing. The authors should make clear that PVL were obtained from both groups in absence of ART. The new color coding of the symbols in Figure 1 is not explained in the legend or on the figure. I assume that all animals sacrificed at day 28 have a black symbol and the other ones got a color. I am not sure why the same color was used on different shapes for different animals. This could be made much easier for the readers. At least a key animal ID (as presented in supplemental Fig1)/symbol should be added to this figure. + +Comment 8- It has to be noted that while all adult macaques experienced viral rebound following ATI in the Whitney paper, some adult macaques maintained undetectable PVL in the Okoye paper (Nat Med, 2019). While it is clear that the reservoir is seeded early, some differences are seen between models and while the pediatric model might be different, it seems premature to draw definitive conclusions. + +Comment 9- Cell type (how they have been isolated), cell number per PCR ("generally 10M") and integration assay sensitivity are still obscure. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +I appreciate the authors efforts to revise their work in response to the comments of my review, and those of other reviewers + +<--- Page Split ---> + +## Nature Communications + +RE: NCOMMS- 22- 04053A, point to point responses to reviewer comments + +## Reviewer #1 + +The additions and edits regarding the sensitivity of the SIV DNA and RNA quantification assays have addressed several of the concerns raised in the first review. There have been some qualifications added to the discussion stating the limitations of the Alu qPCR, however the authors have not demonstrated the sensitivity of the Alu qPCR in "real" samples. Admittedly, this is very difficult to demonstrate, but the assay sensitivity observed with spiked samples does not demonstrate sensitivity in samples with provirus randomly integrated into different cells. The authors also provided in vitro experiments (S1) to demonstrate production of virions, despite absence of integrated virus (with INT administration). These results do not take into account the initial input virus that would still be present in the media. + +Response: We appreciate reviewer's comments and admit that the Alu qPCR assay may not accurately reflect the bona fide seeding and size of viral reservoirs, and that the data based on this assay are not adequate to fully assess levels of potential provirus, so we cautiously interpreted the results. We also realize that protective mechanisms cannot be explained based on these assays, and more animal studies may provide more insight into the relationship of early provirus seeding and cure strategies. To this end, we recently requested newborn macaques for the comparison in the outcomes of treatment regimens with one or more antiretroviral drugs. Although these studies are underway, our primary study showed that plasma viral load was maintained high levels in infants on single DTG initiated at 2dpi (2dpi: \(1.8 \times 10^{4} \pm 8128\) ; 7dpi: \(7.4 \times 10^{4} \pm 25172\) ; 14dpi: \(5.8 \times 10^{6} \pm 3748497\) , n=3), at least partly demonstrating the contribution of linear viral DNA in virus production under integrase inhibitor treatment. We expect that our further studies and findings could answer these key questions. + +Collectively, the data does suggest that there are few proviral copies in the early days of infection, but this is to be expected. Without a clear limit of detection for the Alu PCR, it is not possible to make the claim that virions are a result unintegrated viral DNA. Indeed, the early dynamics will be difficult to determine in vivo, as only small samples of PBMC can be analyzed. + +Response: We agree with the reviewer's comments, we sincerely revised description in the manuscript. + +Other concerns raised in the initial review have been satisfactorily addressed with the edits. + +<--- Page Split ---> + +Response: We appreciate reviewer for the time and comments, and the opportunity to improve our manuscript. + +## Reviewer #2 + +The authors have addressed most reviewer's comments and edited manuscript and figures. ART initiated 3dpi in infant RMs infected with SIV at birth prevented viral rebound following ATI in 4/5 animals. This result is of interest, but interpretations and conclusions must be more cautious. It seems premature to claim an absence of viral integration for 3dpi that would be specific to infants as opposed to adults, notably because the sensitivity of the integrated assay used is not clear, or specific to the ART regimen used as there is no group treated without DTG. And finally, as noted by Reviewer #3, as ART was initiated within 72h of infection the outcome might be closer to a successful PEP than a cure or remission and this should be discussed. + +Response: We appreciate reviewer's comments. As mentioned above, we cautiously interpretate the Results and counterpart conclusion, and discuss the aspects of PEP, remission, or cure, please see in our revisions. We also absolutely agree with the suggestions, further in vivo studies are needed to fully address the proviruses seeding, early treatment regimens and outcomes in a cure or remission for pediatric HIV infection. Therefore, we recently requested newborn macaques for the different animal groups, treated by one or more antiretroviral drugs administered at the specific early timepoint. We expect that the findings could answer these questions in near future. + +Regarding the novel ex vivo experiment presented in supplementing Fig 1, not detecting integration before 5dpi in pre- stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. The response to Reviewer 1 does not provide the sensitivity of the integrated assay nor a comparison of the LOD of this assay with that of the total DNA assay. Similarly, in the in vivo study, it cannot be excluded that integration is not detected before 3dpi in tissues and 5 dpi in PBMC because of a lack of sensitivity of the Alu gag PCR assay. Because the absence of detection of integrated DNA does not necessarily means that there is no integration, the authors should dampen their interpretations and conclusions. This won't take away from the main finding of this study that shows long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. + +<--- Page Split ---> + +**Response**: We thank the reviewer's comments. Again, we admit that assay per se, due to many limitations, is difficult to exclude the possibility of potential proviral DNA existence in samples, so we carefully interpret the results and corresponding conclusion, and focus more on the main findings that 4/5 infant macaques, by early ART at 3dpi up to 9 months, do not show viral rebound after removal of treatment. + +I believe there is an error in supplemental table 1 as according to Fig1A no animals were sacrificed 4dpi (I think the animals sampled at 4dpi were sacrificed at 28dpi). This should be corrected. Further, the sentence “The results showed that plasma viral load was detectable in \(\sim 50\%\) neonates at 1dpi and subsequent time points thereafter” should be reformulated. After 1dpi all tested samples were positive (not \(50\%\) ). In the results section, only the first group of animals is introduced “Newborn macaques were intravenously inoculated with identical doses of SIVmac251 within 6 hours after birth, and then euthanized at day 1, 2, 3, 5 and 7 post SIV inoculation for complete tissue collections (Fig. 1A)” before presenting the PVL results of figure 1B that includes animals from the other group of animals (necropsy at 28 dpi after ART). This is confusing. The authors should make clear that PVL were obtained from both groups in absence of ART. The new color coding of the symbols in Figure 1 is not explained in the legend or on the figure. I assume that all animals sacrificed at day 28 have a black symbol and the other ones got a color. I am not sure why the same color was used on different shapes for different animals. This could be made much easier for the readers. At least a key animal ID (as presented in supplemental Fig1)/symbol should be added to this figure. + +**Response**: We thank reviewer to point out and feel sorry to make confused. We corrected the typo in the supplemental table 1 and other descriptions as suggested. To track the viral parameters in individual animal, colored symbols with different shapes are coded. In Figure 1A, different symbol shapes represented plasma viral load of individual animals which were euthanized at day 1, 2, 3, 5 or 7 post SIV infection (colored solid symbols), or from staggered blood samples in infant animals that were sacrificed at 28dpi without treatment (opened black symbols). We added necessary notes and information in the figure legend. + +Comment 8- It has to be noted that while all adult macaques experienced viral rebound following ATI in the Whitney paper, some adult macaques maintained undetectable PVL in the Okoye paper (Nat Med, 2019). While it is clear that the reservoir is seeded early, some differences are seen between models and while the pediatric model might be different, it seems premature to draw definitive conclusions. + +<--- Page Split ---> + +Response: We thank reviewer's concerns. We also noticed the obviously discrepant findings regarding early treatment and viral rebound off- ART in adult animals, as shown that viral rebound is not observed in 4/16 (ART initiation at 4- 5dpi) or 3/17 animals (ART initiation at 6dpi) (Okoye, 2019), essentially contradictory to the reports (100% viral rebound in animals on ART initiation at 3dpi, Whitney, 2018) and clinical setting. It is interesting that total viral DNA is nearly undetectable in both PBMC and lymph node- derived lymphocytes in all SIV- infected adult on early ART throughout the studies (Okoye, 2019), yet only small animal populations ultimately do not show viral rebound after ATI. It is also curious to know the status of proviral DNA in the animal cohorts, unfortunately, proviruses have not been examined. The possible reason may lie in vaccination relevance and sensitivity of assays, despite the reason is still intrigued. We discussed these concerns in revised manuscript. + +Comment 9- Cell type (how they have been isolated), cell number per PCR ("generally 10M") and integration assay sensitivity are still obscure. + +Response: We added more detail in Methods in revised manuscript. + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The revised manuscript has satisfactorily addressed the concerns noted in the second review. + +Reviewer #2 (Remarks to the Author): + +Most comments from the previous review have been addressed. Please see remaining comments below + +1- The first sentence of the abstract sounds like early ART leads to rapid viral rebound. ATI is followed by viral rebound despite years of treatment + +2- Introduction. It is largely admitted that current ART regimens block new cycle of virus replication (with or without integrase inhibitor). Why would the pediatric treatment regimens "permit new or continual proviral seeding"? + +3- Results. The new paragraph describing assay validation is poorly written. Supplementary Fig 1A is not referenced in the text and a slope of - 2.3 is not good for a standard curve (- 3.2?). As mentioned in the previous review, not detecting integration + +before 5dpi in pre- stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. + +4- As the sensitivity of the integration quantification assay is still unclear, I would suggest removing or rephrasing the following sentences: + +- "Our studies showed that in contrast to adults, skewing of viral integration was observed in neonatal macaques..." (Abstract page 2) + +- "the onset of integrated reservoir seeding did not appear until day 3 of infection" (Results page 5) + +<--- Page Split ---> + +Nature Communications RE: NCOMMS- 22- 04053 Final, point to point responses to reviewer comments + +Reviewer #1: + +The revised manuscript has satisfactorily addressed the concerns noted in the second review. + +Response: We appreciate reviewer's positive feedback and valuable comments to improve our manuscript, we also would like to thank the reviewer for taking the time to review the manuscript. + +Reviewer #2 + +Most comments from the previous review have been addressed. Please see remaining comments below: + +1. The first sentence of the abstract sounds like early ART leads to rapid viral rebound. ATI is followed by viral rebound despite years of treatment. + +Answer: This sentence has been revised. + +2. Introduction. It is largely admitted that current ART regimens block new cycle of virus replication (with or without integrase inhibitor). Why would the pediatric treatment regimens "permit new or continual proviral seeding"? + +Answer: Sorry to make confused. Although incorporation of nucleoside reverse transcriptase inhibitors (NRTIs) into the nascent viral DNA terminates its synthesis in the viral life cycle, current early ART regimen with a combination of dual- NRTI (AZT+3TC) plus protease inhibitors (LPV/r) may not fully prevent initial viral RNA/DNA production since total viral RNA/DNA are detected as early as 6h after SIV infection, any residue viral DNA could potentially increase the risk of proviral reservoir seeding. This concept is also supported by off- ART viral rebound observed in infant macaques receiving late ART regimen containing integrase inhibitor. Overall, all these points suggest that proviral reservoirs, once established, are likely difficult to eradicate by conventional cure strategies, and prevention of initial viral integration may be critical to overcome this major obstacle. We have clarified it in the revised version. + +3. Results. The new paragraph describing assay validation is poorly written. Supplementary Fig 1A is not referenced in the text and a slope of -2.3 is not good for a standard curve (-3.2?). As mentioned in the previous review, not detecting integration before 5dpi in pre-stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. + +Answer: We thoroughly edited the paragraph and referenced Supplementary Fig. 1a in the text. We also corrected the typo and made the graph of standard cure clear in revised Supplementary Fig. 1a. For a geometric efficiency of \(100\%\) in qPCR, the slope is -3.32. The slope value here is shallower, implying acceptable amplification efficiency. As for undetectable proviral DNA before 5dpi (not examined at 4dpi) in pre-stimulated infant PBMCs infected in vitro in absence of RTG treatment, these results were de facto consistent with in vivo data that viral genome integration was not observed in PBMCs in neonates within 1- 3dpi after SIV infection. Note that there are still tremendous gaps in our understanding of pediatric HIV infection and treatment outcomes thus far. For example, plasma viral load could be detected (or higher) in some neonates as early as one day post SIV infection but undetectable (or lower) in others; all neonatal + +<--- Page Split ---> + +animals infected with identical SIV inoculum after birth, including three animals born at same day, only one animal on early treatment at 3dpi shows viral rebound off- ART; some infants infected with HIV/SIV show rapid AIDS development but not others, and so on, which remain elusive. In the qPCR assay, the total and integrated assays were parallelly performed within same batch for each sample, generating comparable data with similar sensitivity. Overall, this result mentioned should make sense, at least not completely question the assay per se. We added in the Discussion. Actually, we also primarily tested viral integration using fresh PBMCs from SIV naïve adult animals. Proviar DNA in adult PBMCs without treatment was detected as early as 1dpi while shown individual sample difference: undetectable in one of three cell samples yet detected in another two cell samples (11 and 5.5 copies of proviral DNA per million cells) at 1dpi; detected in all cell samples at 3dpi (74, 38 and 67 copies of proviral DNA per million cells), essentially consistent with the adult animal study that viral rebound off- ART is observed in \(20\%\) adult macaques when early treatment is initiated at day 1 post SIV infection, \(100\%\) viral rebound off- ART with ART initiation at 3dpi (Whitney, Nat Commun 2018). + +4. As the sensitivity of the integration quantification assay is still unclear, I would suggest removing or rephrasing the following sentences: "Our studies showed that in contrast to adults, skewing of viral integration was observed in neonatal macaques..." (Abstract page 2); "the onset of integrated reservoir seeding did not appear until day 3 of infection" (Results page 5). + +Answer: As we mentioned and discussed in the text and previous rebuttal letter, viral reservoir assay and its sensitivity, especially for proviral reservoirs, are highly challenging for all current scalable assays, absolute quantification is essentially not reachable, and sensitivity of assay is also highly associated with many aspects. With the improved assay here, the treatment outcomes with viral remission basically correlate with status of viral integration (but not other parameters examined), thus trying to interpret the possible mechanisms. As suggested, we rephrased the sentences in the revised text. + +<--- Page Split ---> diff --git a/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/supplementary_0_Peer review file_det.mmd b/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/supplementary_0_Peer review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9f2fe88e357fd0e5e8ca42efcb70d06e9d5c9969 --- /dev/null +++ b/peer_reviews/5709a3790d0cbb86ad0cbf7075e7f7d1496b61a67ba687e494bb10aa7a1e956e/supplementary_0_Peer review file/supplementary_0_Peer review file_det.mmd @@ -0,0 +1,538 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 833, 211]]<|/det|> +Early Treatment Regimens Achieve Sustained Virologic Remission in Infant Macaques Infected with SIV at Birth + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 147, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 203, 880, 312]]<|/det|> +Overall, the manuscript by Wang et al., presents very interesting data demonstrating the efficacy of early ART in neonates to effectively suppress virus (SIV/HIV), even after the removal of ART. The animal studies demonstrate that the initiation of ART 3 days after IV inoculation of SIV, with continuation of ART for 9 months, prevented viral rebound after ART discontinuation in \(80\%\) of animals. These observations are significant and are important contributions to the field. However, the conclusion raised and the interpretation of the data, as related to the establishment of reservoirs, are not well- justified. + +<|ref|>text<|/ref|><|det|>[[113, 351, 878, 680]]<|/det|> +The study examines the dynamics of early ART on the establishment of SIV reservoirs by quantifying cell- associated RNA and DNA, as well as integrated DNA using an Alu- PCR method. They found that integrated viral DNA did not appear until day 3, although total SIV DNA was found on day 1 in lymph node, colon and PBMC. The study equates efficacy of early ART with the presumption that integrated reservoirs are not established until at least day 3 (lines 90- 96, 160, and much of the discussion). There are several problems with this interpretation. While it is possible that unintegrated virus can contribute to the production of plasma virus, the early and rapid kinetics of viral expression in the plasma between days 1 and 3 are very likely to result from integrated provirus. It has not been shown that unintegrated virus would significantly contribute to the early (and rapid) kinetics of viral expression observed following IV inoculation. It is highly plausible that the inability to detect integrated provirus at day 1 or day 3 is due to the sensitivity of the Alu- PCR assay. It is critical to demonstrate the sensitivity of this assay and show that it has the same level of sensitivity as the total DNA to support this claim. The method section does not adequately detail the differences in the integrated and total SIV DNA assays. The authors indicate a sensitivity of the nested, qPCR alu- SIV qPCR assay as 1 copy in 240,000 cells, but they do not compare that with the sensitivity of the total SIV DNA assay nor detail how this was determined/confirmed. The standard used for quantification of integrated DNA is not clear and sufficient details (or a reference) for the sensitivity of the integrated DNA assay are not provided, including the total amount of cell DNA (cell equivalents analyzed). + +<|ref|>text<|/ref|><|det|>[[115, 719, 875, 755]]<|/det|> +Despite the limitations regarding their interpretation of integrated provirus, the paper does detail novel and important data regarding the efficacy of early ART in a pediatric population. + +<|ref|>text<|/ref|><|det|>[[115, 794, 642, 811]]<|/det|> +Below are a few specific comments that would enhance the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 850, 850, 886]]<|/det|> +Revise all discussion regarding the evidence for lack of reservoir establishment, with the inclusion of assay sensitivity and interpretation of results reported with these limitations. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 120, 181, 135]]<|/det|> +Figure 1: + +<|ref|>text<|/ref|><|det|>[[115, 146, 876, 199]]<|/det|> +The plasma viral load data in Figure 1B is not complete (only shows 6 of 14 animals), and interpretation is limited. It would be helpful to know the plasma viral load of the animals that were sacrificed, and that is not easily discerned from data shown on days 1 and 3. + +<|ref|>text<|/ref|><|det|>[[115, 211, 872, 338]]<|/det|> +Plasma VL at day 1 is shown for 6 animals, 3 positive and 3 negative. Which of these are from the animals euthanized and correspond to the data shown from PBMC? What subsequent data is available for the 3 negative? Do the viral loads at day 3 represent the 8 remaining animals? It is difficult to count the number of symbols shown for Day 3; are 8 remaining animals represented in 1B? How do specificplasma VL compare to those in tissues? Is there a threshold of plasma virus levels that correlate with detection of total DNA and/or integrated DNA (suggesting sensitivity of detection methods?) Why do the y axis for the integrated DNA in panels I- M start at 10- 2? + +<|ref|>text<|/ref|><|det|>[[115, 378, 181, 393]]<|/det|> +Figure 2: + +<|ref|>text<|/ref|><|det|>[[115, 405, 859, 458]]<|/det|> +The legend/text state that 9 control animals were used for comparison, yet only 3 are represented in panels E, F, G. How many are represented in the various time points of panel D, as error bars are only shown for the day 9 time point? + +<|ref|>text<|/ref|><|det|>[[115, 556, 393, 572]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 612, 880, 777]]<|/det|> +In this manuscript Wang et al. assessed the impact of very early antiretroviral initiation on the viral reservoir in perinatally SIV- infected rhesus macaque infants. Specifically, the study investigated SIV DNA and RNA levels in RM infants infected i.v. with SIVmac251 within 6 hours after birth and treated or not with ART initiated between day 3 and day 5. The impact of early ART on the viral reservoir was estimated by measuring total or integrated SIV DNA in cells isolated from blood, lymph nodes and gut and/or by analytical treatment interruption. The main result of this study is the long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. This absence of viral rebound was observed for up to 18 months even following experimental \(\mathrm{CD8 + }\) T cell depletion. + +<|ref|>text<|/ref|><|det|>[[115, 816, 879, 906]]<|/det|> +The manuscript needs serious English editing. It also suffers from the choice of graphical representation- at best the graphs are difficult to read but they also can be misleading. The assays used to evaluate reservoir seeding are not optimal and the methods are insufficiently described. The data are not appropriately described and interpreted. The significance of the results is questionable notably because they are not very novel. It is well documented that early ART restricts the latent reservoir + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 872, 199]]<|/det|> +establishment in adults and infants. Delayed viral rebound or sustained virologic control following ART interruption has been reported in children treated early post infection. The Mississippi baby treated 31 hours after birth maintained undetectable viremia for 27 months in absence of ART. Preliminary results from the IMPAACT P1115 study showed that two years after starting ART within 48 hours of birth, two thirds of infants had nondetectable cell- associated HIV DNA and almost \(90\%\) tested negative for HIV antibody. ATI will be performed in eligible study participants. + +<|ref|>text<|/ref|><|det|>[[114, 238, 535, 254]]<|/det|> +Please see specific comments and detailed review below: + +<|ref|>text<|/ref|><|det|>[[114, 294, 872, 457]]<|/det|> +1- To interrogate SIV dynamics or the viral reservoir seeding, the accuracy and sensitivity of the assays used is critical. In this manuscript, some key information regarding the methods is missing such as the limit of detection of each assay and the number of cells assessed (known limiting factor in pediatric studies). The type of cells assessed is also unclear to this reviewer (PBMC and lymphocytes/CD3+ isolated from tissues or tissue mononuclear cells?). If I understand correctly, dilutions of a plasmid in DNA from uninfected cells was used as a standard for the integrated SIV DNA quantification which bypasses the Alu- gag PCR and is thus not appropriate. The manuscript reports unintegrated SIV DNA which has not been measured but extrapolated from the measurement of total and integrated SIV DNA (total SIV DNA in that case is not shown). + +<|ref|>text<|/ref|><|det|>[[114, 469, 875, 560]]<|/det|> +2- Untreated SIV infection (Figure 1). The number of animals euthanized or initiated on ART for each time point is not indicated on the study design schematic nor in its legend. The LOD of the assays is missing for total SIV RNA and integrated DNA. It is also unclear if PVL was assessed for all living animals at each time point. Using individual symbols for each animal would greatly improve the figure. I count 9 symbols of the PVL at day 3 but according to the study design, only 8 animals were still alive by then. + +<|ref|>text<|/ref|><|det|>[[114, 570, 880, 661]]<|/det|> +3- Early short- term ART (Figure 2): It is unclear what comparisons are the p values representing although the legend states that comparison were made with d3 p.i. Surprisingly, SIV RNA levels appear to be higher in the group of animals receiving ART at day 5 p.i. than in the untreated control group. Were those all assessed at the same time point (day 28 p.i.)? The results indicate that in untreated infection, viremia plateaued at 7 day p.i. but the graph shows a peak at day 9 p.i. + +<|ref|>text<|/ref|><|det|>[[114, 672, 881, 780]]<|/det|> +4- Early "long- term" ART and ATI (Figure 3): A control group initiated on ART later and going through ATI is missing. In panel A, it is difficult to distinguish the PVL of each animal at day 3 p.i. One RM out of 5 experienced a viral rebound following ATI. The rebound was detected 2 months post ATI. Was the PVL assessed during these 2 months? The absence of symbol in panel A does not allow the reader to get that information. The antibody used to assess CD8 expression following experimental depletion is not indicated. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 116, 879, 246]]<|/det|> +One restatement of the conclusions of this work that could be drawn from this observation is that the authors have not induced HIV remissions, but simply observed successful post- exposure prophylaxis, and that in the setting of new infection of the infant immune system, that potent ART that includes an INSTI within 3 days, but not later, of viral exposure is sufficient to block all persistent infection in \(80\%\) of exposed infant animals. There may have been viral integration events that led to productive infection before day 3, but few enough so that no latent, persistent infections were established that could lead to viral rebound upon later ATI. + +<|ref|>text<|/ref|><|det|>[[114, 284, 877, 338]]<|/det|> +I view this work as suggestive, but preliminary. A larger cohort should be studied. Longer ATI and more tissue sampling should be pursued. Cell infection transfer experiments, to test if infection can be passed by cells from one animal to another should be done. These points should be discussed by the authors. + +<|ref|>text<|/ref|><|det|>[[114, 377, 860, 412]]<|/det|> +However, the findings of this work are potentially important and should be disseminated to stimulate the field. + +<|ref|>text<|/ref|><|det|>[[115, 423, 444, 440]]<|/det|> +Current US guidelines (Dec. 2021) state that: + +<|ref|>text<|/ref|><|det|>[[114, 452, 857, 505]]<|/det|> +A newborn's ARV regimen should be determined based on maternal and infant factors that influence the risk of perinatal transmission of HIV (All). The uses of ARV regimens in newborns include the following: + +<|ref|>text<|/ref|><|det|>[[113, 517, 877, 552]]<|/det|> +- ARV Prophylaxis: The administration of one or more ARV drugs to a newborn without documented HIV infection to reduce the risk of perinatal acquisition of HIV. + +<|ref|>text<|/ref|><|det|>[[114, 564, 874, 654]]<|/det|> +- Presumptive HIV Therapy: The administration of a three-drug ARV regimen to newborns who are at highest risk of perinatal acquisition of HIV. Presumptive HIV therapy is intended to be preliminary treatment for a newborn who is later documented to have HIV, but it also serves as prophylaxis against HIV acquisition for those newborns who are exposed to HIV in utero, during the birthing process, or during breastfeeding and who do not acquire HIV. + +<|ref|>text<|/ref|><|det|>[[114, 665, 877, 719]]<|/det|> +- HIV Therapy: The administration of a three-drug ARV regimen at treatment doses (called antiretroviral therapy [ART]) to newborns with documented HIV infection (see Diagnosis of HIV Infection in Infants and Children). + +<|ref|>text<|/ref|><|det|>[[115, 758, 810, 812]]<|/det|> +These findings suggest that such presumptive HIV therapy or therapy given for HIV infection documented at birth should include an INSTI if possible. Further support for the findings in this manuscript could lead to the study of ATIs in newborns treated with INSTIs. + +<|ref|>text<|/ref|><|det|>[[113, 823, 853, 859]]<|/det|> +Such studies are underway but it is unclear if they are sufficiently enrolled or powered to answer the question anytime soon. Therefore, even these preliminary findings are of interest. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 216, 106]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 118, 514, 135]]<|/det|> +Line 59: Protease inhibitors for "proteinase inhibitors" + +<|ref|>text<|/ref|><|det|>[[115, 146, 872, 181]]<|/det|> +Line 59- 60: "prevent cells from viral genome integration" is awkward. Change to "prevent viral genome integration in cells"? + +<|ref|>text<|/ref|><|det|>[[115, 194, 416, 210]]<|/det|> +Line 201: typographical error: Integrated + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[56, 155, 243, 170]]<|/det|> +## Nature Communications + +<|ref|>text<|/ref|><|det|>[[56, 170, 595, 188]]<|/det|> +RE: NCOMMS- 22- 04053, point to point responses to reviewer comments + +<|ref|>sub_title<|/ref|><|det|>[[56, 210, 149, 226]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[55, 233, 945, 350]]<|/det|> +1. Overall, the manuscript by Wang et al., presents very interesting data demonstrating the efficacy of early ART in neonates to effectively suppress virus (SIV/HIV), even after the removal of ART. The animal studies demonstrate that the initiation of ART 3 days after IV inoculation of SIV, with continuation of ART for 9 months, prevented viral rebound after ART discontinuation in 80% of animals. These observations are significant and are important contributions to the field. However, the conclusion raised and the interpretation of the data, as related to the establishment of reservoirs, are not well-justified. + +<|ref|>text<|/ref|><|det|>[[56, 377, 943, 421]]<|/det|> +Response: We appreciate the insightful comments that the reviewer provided and thank you for the interest showed in our work. We have accommodated the requests and thoroughly revised the manuscript as suggested. + +<|ref|>text<|/ref|><|det|>[[53, 446, 941, 828]]<|/det|> +2. The study examines the dynamics of early ART on the establishment of SIV reservoirs by quantifying cell-associated RNA and DNA, as well as integrated DNA using an Alu-PCR method. They found that integrated viral DNA did not appear until day 3, although total SIV DNA was found on day 1 in lymph node, colon and PBMC. The study equates efficacy of early ART with the presumption that integrated reservoirs are not established until at least day 3 (lines 90-96, 160, and much of the discussion). There are several problems with this interpretation. While it is possible that unintegrated virus can contribute to the production of plasma virus, the early and rapid kinetics of viral expression in the plasma between days 1 and 3 are very likely to result from integrated provirus. It has not been shown that unintegrated virus would significantly contribute to the early (and rapid) kinetics of viral expression observed following IV inoculation. It is highly plausible that the inability to detect integrated provirus at day 1 or day 3 is due to the sensitivity of the Alu-PCR assay. It is critical to demonstrate the sensitivity of this assay and show that it has the same level of sensitivity as the total DNA to support this claim. The method section does not adequately detail the differences in the integrated and total SIV DNA assays. The authors indicate a sensitivity of the nested, qPCR Alu-SIV qPCR assay as 1 copy in 240,000 cells, but they do not compare that with the sensitivity of the total SIV DNA assay nor detail how this was determined or confirmed. The standard used for quantification of integrated DNA is not clear and sufficient details (or a reference) for the sensitivity of the integrated DNA assay are not provided, including the total amount of cell DNA (cell equivalents analyzed). + +<|ref|>text<|/ref|><|det|>[[55, 854, 944, 944]]<|/det|> +Response: We appreciate the reviewer's concerns. To address the concerns regarding the early virion production from unintegrated viral DNA and the sensitivity of the qPCR assay, we performed additional in vitro experiments, in combination with viral parameters measured by nested (Alu) qPCR. Briefly, PBMCs isolated from one- month- old infant macaques (due to limited blood collected from newborns or neonates even at animal necropsy) were first activated for 3 days by CD4+ T + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[55, 42, 944, 135]]<|/det|> +cell activation kit (Miltenyi) in the presence of human IL- 2 (10%, Hemagen), and then infected with SIVmac251 (3x10^7 cell/mL with 100 TCID50 SIV) for 2 hours in CO2 incubator, followed by 3 washes and seeding in 24-well plate at 1x10^6 cell/well/mL, without or with raltegravir (RTG) at final 1μM concentration. Cells and cell supernatants were harvested to measure CA SIV RNA/DNA and supernatant viral load. Please see the revised Method section in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[54, 161, 945, 470]]<|/det|> +As shown in Suppl Fig.1, cell- associated (CA) integrated SIV DNA was indeed not detected in PBMCs in presence of RTG, yet total CA SIV RNA/DNA were still detectable as early as 6 hours after SIV infection, suggesting that viral genome integration was fully blocked by RTG treatment while total SIV DNA predominantly represented unintegrated form at such scenario. Please note that supernatant VLs have not shown significant differences at early SIV infection (3 and 7dpi) between RTG treated and untreated samples. This suggests early virus particles in cell supernatants are not likely produced from integrated SIV DNA when PBMCs were treated by RTG. Although integrated proviral DNA is believed a template for stable HIV/SIV replication, however, unintegrated viral DNA per se may contribute to the early viral replication and virus production, even when cells are treated by RTG (Kelly, 2008; Chan CN, 2016; Trinite B, 2013), explaining viremia emergence in very early SIV infection in vivo prior to viral genome integration. Again, these results suggested that, i) Alu qPCR assay here could essentially reflect the status of SIV genome integration; ii) integrase inhibitor treatment could efficiently suppress viral genome integration; iii) viral load in cell supernatants was detectable at early infection in presence of integrase inhibitor (lack of integrated viral DNA), indicating early unintegrated viral DNA is able to rapidly yield infectious virions. + +<|ref|>text<|/ref|><|det|>[[54, 497, 945, 781]]<|/det|> +We would prefer to add even more detail in Methods but have space limitations. However, these assays are based on prior studies of integrated SIV DNA measurement which target one conserved region of human and rhesus common Alu DNA sequence by outward primer Alu- 1 and - 2 (Nishimura Y, 2009; Mavigner M, 2016; Whitney JB, 2014 and 2018). Combined unique rhesus Alu repetitive sequences (Hamdi H, 1999), we further optimized and improved the Alu qPCR to target multiple Alu islands, combined Alu- 1, - 2 with additional rhesus specific Alu - 3 and - 4 primers, potentially increasing the sensitivity and detection rate of integrated SIV DNA. Human CEMx174 Cell line (#ARP- 13239, NIH AIDS Reagent Program), carrying 1 copy of integrated SIV DNA, is used to extract cellular genomic DNA, which is serially diluted to determine copies of proviral DNA in terms of cell numbers, and then quantified by our nested Alu qPCR. Unfortunately, there is no rhesus- derived cell line that contains single copy of SIV proviral DNA and specific rhesus Alu, thus we cannot test human CEMx174 Cell lines by our new Alu primers (Alu 3- and - 4). However, our nested qPCR with Alu 1- 4 primers generates consistently higher levels of proviral DNA in macaque- derived cell samples, compared with of those using human/rhesus Alu 1- 2 only. Limit of detection (LOD) of proviral SIV DNA is 5.3 per million cells, determined by GenEx software based on standard curve and deviation, please see %CV for individual standard in Table 1 in this letter. In our assay, lymphocytes (1x10^7 cells per sample in general) are isolated to extract cellular DNA (final volume to 100μL) and 2.5μL cellular DNA sample (2.5x10^5 cell equivalents) is added to the Master Mix (final 25μL). The data showed that 1 copy SIV genomic DNA contained cellular DNA equivalent to cell numbers, + +<|ref|>table<|/ref|><|det|>[[60, 805, 405, 920]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[65, 787, 404, 803]]<|/det|> +Table 1. Nested qPCR reproducibility ( \(\% \mathrm{CV}\) ; \(n = 6\) + +
STD CopiesCCR5LTR U5
10^40.2%2.9%
10^30.3%2.5%
10^20.4%2.1%
10^10.5%2.4%
10^01.2%3.5%
+ +<|ref|>text<|/ref|><|det|>[[416, 787, 944, 925]]<|/det|> +on standard curve and deviation, please see %CV for individual standard in Table 1 in this letter. In our assay, lymphocytes (1x10^7 cells per sample in general) are isolated to extract cellular DNA (final volume to 100μL) and 2.5μL cellular DNA sample (2.5x10^5 cell equivalents) is added to the Master Mix (final 25μL). The data showed that 1 copy SIV genomic DNA contained cellular DNA equivalent to cell numbers, + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[52, 48, 475, 225]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[488, 43, 944, 230]]<|/det|> +ranging from \(1 \times 10^{5}\) to \(2.4 \times 10^{5}\) cell equivalents, could be consistently detected (stated probability) as detection quantification (LOQ, 1 copy in \(2.4 \times 10^{5}\) cell equivalents, \(\% \mathrm{CV} = 4.2\%\) ). In brief, first- step routine PCR (pre- amplification) is performed to amplify SIV LTR U5 (for total SIV DNA and standard) or SIV U5/Alu 1- 4 fragments (for proviral DNA) for 20 cycles, followed by second- step qPCR using same U5 primer/probe set for 40 cycles with 1/10 volume of \(1^{\mathrm{st}}\) amplicon. Internal standard curve was used to calculate the initial copies of both total SIV DNA and proviral DNA (an example of STD cure attached here, very stable from batch to batch). + +<|ref|>text<|/ref|><|det|>[[55, 235, 944, 278]]<|/det|> +of \(1^{\mathrm{st}}\) amplicon. Internal standard curve was used to calculate the initial copies of both total SIV DNA and proviral DNA (an example of STD cure attached here, very stable from batch to batch). + +<|ref|>text<|/ref|><|det|>[[54, 281, 945, 685]]<|/det|> +Using this assay, we have measured hundreds of samples from SIV- infected animal cohorts (Ziani W, 2021a,b,c; Wang X, 2021). We performed nested qPCR in parallel to quantify both total viral DNA and proviral DNA in each sample (yielding comparable data), along with standard. Thus, nested qPCR assay can generate sensitive and comparable data of both total SIV DNA and proviral DNA. Also, the results shown in Supple Fig. 1 suggest that Alu qPCR is able to essentially reflect the sensitivity and status of SIV genome integration in RTG- or untreated- PBMCs, thus inferring lymphocyte samples isolated from tissues. Basically, nested qPCR (two- rounds PCR amplification) can increase sensitivity and specificity of target gene, however, we admit that the possibility that proviral DNA may not be fully detected due to viral reservoir distribution in various tissues in the body and likely lack of chromosomal Alu islands situated near the integrated SIV genome, we discussed this in the revised DISCUSSION. Alu islands are widely dispersed within the chromosomal DNA (accounting for 6- 13% of genomic DNA), which are likely lacked or far from SIV LTR region, albeit very few such case existed. qPCR targeting SIV gag is used to determine plasma viral load with a limit of detection of 83 copies per mL (core service). Together, early treatment, building on viral genome integration assessed by our assay, achieved sustained virologic remission in the neonates infected with SIV, which were largely consistent with the onset of proviral reservoirs in typical systemic and lymphoid tissues of very early SIV infection. We realize that more animal cohorts/sampling are needed, in combination with intrauterine/postnatal infection, one or more ARV regimens as well as optimal period of treatment and so on. We have carefully considered the interpretations of our results and added more information and detail in Method section, please see in our revised manuscript. + +<|ref|>text<|/ref|><|det|>[[55, 716, 933, 759]]<|/det|> +3. Despite the limitations regarding their interpretation of integrated provirus, the paper does detail novel and important data regarding the efficacy of early ART in a pediatric population. + +<|ref|>text<|/ref|><|det|>[[55, 788, 881, 830]]<|/det|> +Response: We thank reviewer's positive comments, we have carefully read through the text and made appropriate interpretations and caveats to our results. + +<|ref|>text<|/ref|><|det|>[[55, 860, 927, 903]]<|/det|> +4. Revise all discussion regarding the evidence for lack of reservoir establishment, with the inclusion of assay sensitivity and interpretation of results reported with these limitations. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[55, 43, 921, 110]]<|/det|> +Response: We thank reviewer's suggestion, we discussed proviral reservoir establishment in neonates, especially assay sensitivity and interpretation of proviral reservoir measurement in vitro and in vivo studies, please see DISCUSSION in our revised manuscript. + +<|ref|>text<|/ref|><|det|>[[55, 139, 925, 205]]<|/det|> +5. Figure 1: The plasma viral load data in Figure 1B is not complete (only shows 6 of 14 animals), and interpretation is limited. It would be helpful to know the plasma viral load of the animals that were sacrificed, and that is not easily discerned from data shown on days 1 and 3. + +<|ref|>text<|/ref|><|det|>[[54, 234, 945, 397]]<|/det|> +Response: We apologize for not making it clearer. Whole blood request and neonatal anesthesia is strictly controlled in terms of IACUC (12mL/Kg/Month in total) and limited volume of experimental blood available because of newborns weight ( \(\sim 400\mathrm{g}\) , only 1.2cc EDTA blood available in general), physiologic weight loss after birth as well as mandatory bleeding for CBC. It is not feasible to consistently collect 1.2cc whole blood from newborn infants and neonates in the first few days of birth and larger volumes are limited to collection at necropsy. Therefore, whole blood is collected by staggered request from individual newborn/neonates. We added the grouped animals, the day(s) post SIV inoculation, plasma viral load from blood sampling as well as text in revised manuscript as Suppl. Table 1. Hope it will be clearer. + +<|ref|>text<|/ref|><|det|>[[54, 425, 930, 565]]<|/det|> +6. Plasma VL at day 1 is shown for 6 animals, 3 positive and 3 negative. Which of these are from the animals euthanized and correspond to the data shown from PBMC? What subsequent data is available for the 3 negative? Do the viral loads at day 3 represent the 8 remaining animals? It is difficult to count the number of symbols shown for Day 3; are 8 remaining animals represented in 1B? How do specific plasma VL compare to those in tissues? Is there a threshold of plasma virus levels that correlate with detection of total DNA and/or integrated DNA (suggesting sensitivity of detection methods?) Why do the y axis for the integrated DNA in panels 1-M start at 10-2? + +<|ref|>text<|/ref|><|det|>[[53, 593, 945, 876]]<|/det|> +Response: We apologize for the confusion. Here we improved the figures to specifically track cell- associated (CA) SIV RNA/DNA in PBMC, LN and colon, and corresponding plasma viral load (PVL) in individual animals at early SIV infection by colored symbols. As we mentioned in Question #5 and shown in Suppl. Table 1, plasma viral load measured at 1dpi (n=6) also include staggered blood samples collected from 3 animals that were euthanized at 28dpi (n=3; PVL, 1 negative and 2 positive at 1dpi), the remaining three animals euthanized at 1dpi are highlighted by colored symbols now to accommodate plasma viral load (2 negative and 1 positive), CA SIV RNA/DNA in PBMC, LN and colon in individual animals. Likewise, viral parameters from neonates euthanized at 2dpi (n=3), 3dpi (5 euthanized neonatal animals plus additional 3 staggered blood samples from other 28- day infected animals for PVL measurement, see Suppl. Table 1), 5dpi (n=2) and 7dpi (n=1) are highlighted by colored symbols for individual animals post SIV infection in revised manuscript (Figs. 1B- 1H). As for sensitivity and LOD of qPCR detection, please see Answer #2. Given y- axis represents power of 10, value below the LOD is considered to be undetectable, we now revised the figures. We added necessary description in Results, and hope it is more understandable now. + +<|ref|>text<|/ref|><|det|>[[57, 905, 937, 924]]<|/det|> +7. Figure 2: The legend/text state that 9 control animals were used for comparison, yet only 3 are represented in panels E, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[55, 44, 914, 86]]<|/det|> +F, G. How many are represented in the various time points of panel D, as error bars are only shown for the day 9 time point? + +<|ref|>text<|/ref|><|det|>[[54, 107, 945, 271]]<|/det|> +Response: We are sorry for our careless. We longitudinally tracked plasma viral load in plasma including staggered blood samples (Figs. 2A- 2C), CA SIV RNA and paralleled CA SIV DNA/proviral DNA in fresh tissues of 3 groups on cART initiated at 3-, 4- or 5dpi, and one group without treatment control (n=3), all these animals are euthanized at 28dpi. Additional data (not samples) from our previous study with age- matched SIV- infected infant macaques (n=9) are used to compare routine plasma viral load and the percentages of peripheral CD4+ T cells (Fig. 2D and Figs. 3A- 3B). We went through the data and revised our text and Figure Legend. As for Fig.2D, which is summarized from Figs. 2A- 2C with statistical analysis for each group, the error bars cannot be displayed because of low S.E.M in Y- axis at timepoints. + +<|ref|>sub_title<|/ref|><|det|>[[56, 292, 150, 308]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[54, 315, 933, 503]]<|/det|> +In this manuscript Wang et al. assessed the impact of very early antiretroviral initiation on the viral reservoir in perinatally SIV- infected rhesus macaque infants. Specifically, the study investigated SIV DNA and RNA levels in RM infants infected i.v. with SIVmac251 within 6 hours after birth and treated or not with ART initiated between day 3 and day 5. The impact of early ART on the viral reservoir was estimated by measuring total or integrated SIV DNA in cells isolated from blood, lymph nodes and gut and/or by analytical treatment interruption. The main result of this study is the long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. This absence of viral rebound was observed for up to 18 months even following experimental CD8+ T cell depletion. + +<|ref|>text<|/ref|><|det|>[[54, 529, 940, 742]]<|/det|> +8. The manuscript needs serious English editing. It also suffers from the choice of graphical representation—at best the graphs are difficult to read but they also can be misleading. The assays used to evaluate reservoir seeding are not optimal and the methods are insufficiently described. The data are not appropriately described and interpreted. The significance of the results is questionable notably because they are not very novel. It is well documented that early ART restricts the latent reservoir establishment in adults and infants. Delayed viral rebound or sustained virologic control following ART interruption has been reported in children treated early post infection. The Mississippi baby treated 31 hours after birth maintained undetectable viremia for 27 months in absence of ART. Preliminary results from the IMPAACT P1115 study showed that two years after starting ART within 48 hours of birth, two thirds of infants had nondetectable cell-associated HIV DNA and almost 90% tested negative for HIV antibody. ATI will be performed in eligible study participants. + +<|ref|>text<|/ref|><|det|>[[54, 768, 945, 934]]<|/det|> +Response: We appreciate the reviewer's comments. We have carefully looked over the manuscript and improved the typos, grammar issues and interpretation. We apologize for not making the graphs clearer, especially Fig.1, and have thoroughly revised the figures for plasma viral load and counterpart CA SIV RNA/DNA in individual animals at very early SIV infection as described above. Now neonates used are summarized in Suppl. Table 1. We also added more detailed description regarding our qPCR assays in Methods, including how we quantified the viral parameters using our optimized nested (Alu) PCR based on other published reports (Nishimura Y, 2009; Mavigner M, 2016; Whitney JB, 2014 and 2018), and also please see Answer #2 in this letter. Specifically, we added the supplementary data (Suppl Fig. 1) to directly address specificity + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[55, 42, 944, 182]]<|/det|> +and sensitivity of the assay especially for integrated viral DNA measurement, with or without raltegravir (RTG) treatment. As shown in Suppl Fig.1, CA integrated viral DNA was consistently not detected in PBMCs in presence of RTG (viral genome integration blockade), while CA SIV RNA/DNA (unintegrated, due to undetectable integrated vDNA) as well as supernatant viral load were still detectable in the early SIV infection. These data strongly suggest that our assay can essentially reflect the status of SIV genome integration, by comparing the results in the presence or absence of RTG treatment, and thus inferring this application to measure the lymphocyte samples isolated from tissues ex vivo. + +<|ref|>text<|/ref|><|det|>[[54, 210, 945, 397]]<|/det|> +In this study, we utilized the neonatal NHP model intravenously infected with SIV, facilitating to precisely time the very early days of infection (compared with uncertain dip by repeated SIV/SHIV challenges to the infant macaques by oral route or HIV+ children in the clinic) and collected complete tissue sets at necropsy for examination of viral reservoirs. As shown in Fig.2 in this letter, early cART initiation at 3dpi in adult animals showed \(100\%\) viral rebound within three weeks once treatment is discontinued (Whitney, 2018). In comparison, early treatment regimen initiated at same timepoint achieved sustained virologic remission in \(80\%\) infant macaques, suggesting the features and outcomes in neonates/infants to the early SIV/HIV infection and early treatment are indeed distinct from those of adult subjects, which is of great significance to understand early events and providing a critical treatment window for pediatric functional cure or even absolute cure. + +<|ref|>text<|/ref|><|det|>[[54, 558, 945, 770]]<|/det|> +It is true that early ART in children, treatment ranging from immediate (Butler, 2015), within hours after delivery (Giacomet, 2014), or months/years- old (Martinez- Bonet, 2015; Frange, 2016; Violari, 2019), is documented well, including reduction of the reservoir size and skewing of viral rebound in the clinic setting. However, viral rebound or rapid increase of HIV RNA/DNA in these early treated pediatric cases are detected once treatment is stopped in these clinical trials. The Mississippi baby case treated 30 hours after birth ultimately showed viral rebound even after 27- months ATI, in utero HIV infection during pregnancy likely occurred in this case (Faye A, 2020), and conceivably, viral integration occurred in perinatal period. We do not know either status of intrauterine infection even starting ART within 48 hours of birth, and based on what happened if treatment is allowed to withdraw in IMPAACT P1115 study, the outcomes presumably depend on status of viral genome integration. + +<|ref|>text<|/ref|><|det|>[[54, 798, 945, 939]]<|/det|> +In this study, we evaluated the dynamics and tissue distribution of viral reservoirs and plasma viral load in several newborn macaques at very early timed- stages of SIV infection, which provided critical clues for early treatment interventions, as indicated by outcomes of viral remission achieved by early treatment for 9 months and further confirmed by subsequent CD8+ cell depletion in vivo. We consider this a de facto success to achieve viral remission in 4/5 infant macaques by early treatment (all 5 infants infected with identical SIV inoculum at birth and treated at 3dpi for 9 months). These 4 cured infants are still alive with ART- free viral remission, and currently resisting repeated SIV challenges by the rectal route. Here we + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[55, 42, 944, 135]]<|/det|> +precisely explored the neonatal distinct patterns, early viral reservoir seeding and optimal early treatment (timing and regimen) utilizing the neonatal macaque model of HIV, which permits thorough examinations of blood and tissue reservoirs that cannot be achieved studying human infants. Even if this data shows only a few unique findings we believe this data is directly translational to the clinic and may provide knowledge that may save a few infants from lifelong HIV infection. + +<|ref|>text<|/ref|><|det|>[[54, 161, 941, 350]]<|/det|> +9. To interrogate SIV dynamics or the viral reservoir seeding, the accuracy and sensitivity of the assays used is critical. In this manuscript, some key information regarding the methods is missing such as the limit of detection of each assay and the number of cells assessed (known limiting factor in pediatric studies). The type of cells assessed is also unclear to this reviewer (PBMC and lymphocytes/CD3+ isolated from tissues or tissue mononuclear cells?). If I understand correctly, dilutions of a plasmid in DNA from uninfected cells was used as a standard for the integrated SIV DNA quantification which bypasses the Alu-gag PCR and is thus not appropriate. The manuscript reports unintegrated SIV DNA which has not been measured but extrapolated from the measurement of total and integrated SIV DNA (total SIV DNA in that case is not shown). + +<|ref|>text<|/ref|><|det|>[[54, 377, 945, 613]]<|/det|> +Response: We appreciate the reviewer's concerns. We absolutely agree with the opinion that the viral reservoir assays are highly challenging for the current studies and researchers in general, as indicated by continuous efforts and attempts made for development of scalable assays, including RT qPCR, Alu qPCR, QVOA, TILDA, IPDA and FLIPS, etc. As mentioned in DISCUSSION, we acknowledge that there is no de facto gold standard thus far to reflect absolute size of viral reservoirs especially viral DNA (e.g., unintegrated, or integrated vDNA, circular vDNA, defective or intact viral genome, functional or dysfunctional, Indel/polymorphism at different levels, inserted regions with gene dessert, etc), with obvious both advantages and weaknesses with each approach. To our knowledge, it is a challenge to measure integrated HIV/SIV DNA efficiently, comprehensively, and accurately in the cells, tissues, and organs throughout the body, while most have only assessed peripheral blood mononuclear cells, and/or even sorted CD4+ T cells thus far, which obviously misses important residual reservoirs in tissues. + +<|ref|>text<|/ref|><|det|>[[54, 639, 945, 805]]<|/det|> +Considering sensitivity, rapidity, and feasibility of qPCR, we spent several years to develop and optimize nested Alu qPCR for quantification of the CA integrated SIV DNA, based on previous published reports using conserved human/rhesus Alu- 1 and - 2 (please see refs by Nishimura Y, 2009; Mavigner M, 2016; Whitney JB, 2014 and 2018, etc). To strengthen proviral SIV DNA assay, rhesus specific repetitive Alu DNA, which are widely dispersed within the chromosomal DNA in rhesus macaques, is targeted by additional Alu- 3 and - 4 primers. Our optimized Alu qPCR thus includes Alu 1- 4 outward primers to target multiple Alu islands in rhesus species. As for the accuracy and sensitivity of the assays concerned, please see Answer#2. + +<|ref|>text<|/ref|><|det|>[[54, 832, 945, 949]]<|/det|> +It is true that we use plasmids as standard containing SIV gene as standard with known copies, which is indispensable to perform nested qPCR (unlike the RNA quantification by Droplet digital PCR, STD not required). Human CEMx174 Cell line (#ARP- 13239, NIH AIDS Reagent Program), carrying 1 copy of integrated SIV DNA, is generally used to quantify proviral DNA by nested Alu qPCR with conserved human/rhesus Alu- 1 and - 2 outward primers. Additional Alu primers (Alu- 3 and - 4), targeting rhesus specific Alu sequences, are not applicable for human CEMx174 Cell line- associated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[53, 42, 945, 375]]<|/det|> +standard. Outward Alu 1- 4 primers used in qPCR indeed increase the sensitivity and detection rate of proviral SIV DNA in rhesus samples. To yield comparable data in the quantification of total SIV DNA and proviral DNA, nested qPCR is performed in parallel to quantify both total SIV DNA and proviral DNA for each sample. Type of cells are lymphocytes that are freshly isolated from systemic and lymphoid tissues at biopsies or necropsies, \(10^{7}\) lymphocytes per sample are generally collected for nested qPCR assay. Briefly, we performed nested qPCR to quantify total viral DNA, proviral DNA, along with standard. First- step routine PCR is used to pre- amplify total SIV DNA and standard (by LTR U5 primer pair) or integrated SIV DNA (by U5/Alu 1- 4 primer pairs) for 20 cycles (optimized cycle for the \(1^{\mathrm{st}}\) PCR in our assay). Second qPCR is further performed with 1/10 volume of \(1^{\mathrm{st}}\) amplicon targeting SIV LTR U5 with same primer/probe set for 40 cycles. Internal standard curve is used to calculate the initial copies of both total and integrated SIV DNA. Please note that it is essentially difficult to quantify gene fragments of SIV/Alu by qPCR in the first round PCR due to unpredictable size of gene fragments generated (tens of bp to several kb) and thereby amplification efficiency is variable from sample to sample. Thus, it is feasible and reasonable to use plasmid standard in the quantification of both CA total SIV DNA and proviral DNA at 2nd qPCR using same primer/probe set, irrelevant to Alu repetitive sequences. We agree with reviewer's comments about unintegrated SIV DNA, now we changed wording to indicate total SIV DNA in the revised figures. + +<|ref|>text<|/ref|><|det|>[[55, 397, 944, 512]]<|/det|> +Although our assay is far more sensitive to measure proviral DNA, nested qPCR increases sensitivity and specificity of gene targets, as also indicated by Ct (e.g., cycle threshold of 10copies, from \(\sim 36\) at \(1^{\mathrm{st}}\) to \(\sim 16\) at \(2^{\mathrm{nd}}\) PCR). However, status of viral genome integration by our assay essentially matches the actual scenario: undetectable proviral DNA in PBMCs infected with SIV in presence of RTG, and achievable ART- free viral remission in infants when early cART is initiated prior to proviral reservoir seeding. We have thoroughly modified our text as suggested in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[55, 540, 940, 655]]<|/det|> +10. Untreated SIV infection (Figure 1). The number of animals euthanized or initiated on ART for each time point is not indicated on the study design schematic nor in its legend. The LOD of the assays is missing for total SIV RNA and integrated DNA. It is also unclear if PVL was assessed for all living animals at each time point. Using individual symbols for each animal would greatly improve the figure. I count 9 symbols of the PVL at day 3 but according to the study design, only 8 animals were still alive by then. + +<|ref|>text<|/ref|><|det|>[[55, 684, 943, 777]]<|/det|> +Response: We appreciate the reviewer's suggestion and have improved the figure as suggested to track individual animals. PVL is measured in plasma from euthanized animals or staggered blood samples. The LOD of assay is added in the revised manuscript. Also please see the Answer #5 and #6 above in this letter including animals used and corresponding PVL at different timepoints (Suppl. Table 1). + +<|ref|>text<|/ref|><|det|>[[55, 805, 925, 920]]<|/det|> +11. Early short-term ART (Figure 2): It is unclear what comparisons are the p values representing although the legend states that comparison were made with d3 p.i. Surprisingly, SIV RNA levels appear to be higher in the group of animals receiving ART at day 5 p.i. than in the untreated control group. Were those all assessed at the same time point (day 28 p.i.)? The results indicate that in untreated infection, viremia plateaued at 7 day p.i. but the graph shows a peak at day 9 p.i. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[54, 43, 945, 255]]<|/det|> +Response: We thank the reviewer for these comments and for not making comparisons clearer among the groups. We revised figures and legend in the manuscript. We did see levels of CA SIV RNA are higher at 28dpi by late treatment. Conceivably, cART (FTC/TFV/DTG) suppresses reverse transcription of viral RNA and viral integration, late treatment may result in accumulation of intracellular SIV RNA which are transcribed from both unintegrated and proviral DNA (e.g., before treatment at 5dpi), while CA SIV RNA in untreated control may be relatively exhausted by virus packaging/release, contributing to viral peak and thereafter. All samples examined are freshly collected from euthanized animal cohorts at 28dpi (Figs. 2E- 2F). PVL data in age- matched SIV- infected infant controls come from our previous studies. PVL in SIV- infected neonatal macaques is generally monitored at 7, 14 and 21dpi, viremia actually reaches the peak at 7- 9 dpi, we have corrected the description. + +<|ref|>text<|/ref|><|det|>[[54, 281, 936, 399]]<|/det|> +12. Early "long-term" ART and ATI (Figure 3): A control group initiated on ART later and going through ATI is missing. In panel A, it is difficult to distinguish the PVL of each animal at day 3 p.i. One RM out of 5 experienced a viral rebound following ATI. The rebound was detected 2 months post ATI. Was the PVL assessed during these 2 months? The absence of symbol in panel A does not allow the reader to get that information. The antibody used to assess CD8 expression following experimental depletion is not indicated. + +<|ref|>text<|/ref|><|det|>[[54, 425, 945, 637]]<|/det|> +Response: We thank the reviewer for these comments and suggestions. Neonates and infants infected with HIV/SIV show higher viremia and rapid disease progression compared to adults, most of infant macaques intravenously infected with SIV develop to the final stage of AIDS after 4- 5 months of infection (Wang X, 2010). These infants are sacrificed because of AIDS- like symptoms, so the PVL data are shown only in this period. In panel A, PVL levels are very closed in neonatal macaques at 3dpi (Please see PVL of other neonates at this timepoint in Suppl Table 1), one RM (NG24, red line) with viral rebound after ATI does not show significantly different levels of plasma viral load compared to remaining 4 animals at this timepoint. Now we showed NG24 PVL line in bold and individual symbols for 5 animals at designated timepoints. All 5 infant animals are weekly monitored by PVL to see if there is viral rebound after ATI. Anti- CD8 Ab clone used to assess CD8+ cells is also added in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[56, 667, 149, 683]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[54, 690, 943, 830]]<|/det|> +13. One restatement of the conclusions of this work that could be drawn from this observation is that the authors have not induced HIV remissions, but simply observed successful post-exposure prophylaxis, and that in the setting of new infection of the infant immune system, that potent ART that includes an INSTI within 3 days, but not later, of viral exposure is sufficient to block all persistent infection in 80% of exposed infant animals. There may have been viral integration events that led to productive infection before day 3, but few enough so that no latent, persistent infections were established that could lead to viral rebound upon later ATI. + +<|ref|>text<|/ref|><|det|>[[55, 833, 930, 902]]<|/det|> +I view this work as suggestive, but preliminary. A larger cohort should be studied. Longer ATI and more tissue sampling should be pursued. Cell infection transfer experiments, to test if infection can be passed by cells from one animal to another should be done. These points should be discussed by the authors. + +<|ref|>text<|/ref|><|det|>[[60, 929, 940, 949]]<|/det|> +Response: We thank the reviewer for these thoughtful comments and suggestions. We have since performed experiments + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[54, 42, 945, 327]]<|/det|> +with one- month- old infant PBMC infected with SIV in vitro, in presence or absence of integrase inhibitor (raltegravir/RTG), followed by CA SIV RNA/DNA and viral load measurement, which are expected to address the efficiency of RTG on the blockade of viral genome integration, ability of early unintegrated SIV DNA in the virion production as well as sensitivity of qPCR assay, please see the Suppl. Fig.1 in the revised manuscript. Besides typical systemic and mucosal lymphoid tissues presented, other tissues, including spleen, thymus, jejunum, colon and liver, were actually examined in our study, proviral DNA was not detected in these tissues of very early SIV- infected neonates. We agree with reviewer's constructive advice that more studies are needed, including animal numbers, comprehensive tissue sampling, optimal period of early treatment, prolonged ATI, cell transfer in vivo to repeated challenge, etc, please see our discussion in the revised manuscript. After CD8+ cell depletion in vivo, the 4 infant animals with ART- free viral remission are still alive and healthy, further study with repeated SIV challenge by rectal route is underway. Finally, even if this is only "post exposure prophylaxis" it is clearly different from adults and remains translationally relevant to clinical pediatric HIV care, thus we consider these findings highly significant. + +<|ref|>text<|/ref|><|det|>[[57, 355, 880, 374]]<|/det|> +14. However, the findings of this work are potentially important and should be disseminated to stimulate the field. + +<|ref|>text<|/ref|><|det|>[[57, 382, 389, 400]]<|/det|> +Current US guidelines (Dec. 2021) state that: + +<|ref|>text<|/ref|><|det|>[[55, 408, 935, 451]]<|/det|> +A newborn's ARV regimen should be determined based on maternal and infant factors that influence the risk of perinatal transmission of HIV (AII). The uses of ARV regimens in newborns include the following: + +<|ref|>text<|/ref|><|det|>[[55, 455, 911, 500]]<|/det|> +- ARV Prophylaxis: The administration of one or more ARV drugs to a newborn without documented HIV infection to reduce the risk of perinatal acquisition of HIV. + +<|ref|>text<|/ref|><|det|>[[55, 504, 940, 596]]<|/det|> +- Presumptive HIV Therapy: The administration of a three-drug ARV regimen to newborns who are at highest risk of perinatal acquisition of HIV. Presumptive HIV therapy is intended to be preliminary treatment for a newborn who is later documented to have HIV, but it also serves as prophylaxis against HIV acquisition for those newborns who are exposed to HIV in utero, during the birthing process, or during breastfeeding and who do not acquire HIV. + +<|ref|>text<|/ref|><|det|>[[55, 600, 937, 644]]<|/det|> +- HIV Therapy: The administration of a three-drug ARV regimen at treatment doses (called antiretroviral therapy [ART]) to newborns with documented HIV infection (see Diagnosis of HIV Infection in Infants and Children). + +<|ref|>text<|/ref|><|det|>[[55, 648, 933, 740]]<|/det|> +These findings suggest that such presumptive HIV therapy or therapy given for HIV infection documented at birth should include an INSTI if possible. Further support for the findings in this manuscript could lead to the study of ATIs in newborns treated with INSTIs. Such studies are underway but it is unclear if they are sufficiently enrolled or powered to answer the question anytime soon. Therefore, even these preliminary findings are of interest. + +<|ref|>text<|/ref|><|det|>[[55, 767, 945, 907]]<|/det|> +Response: We really appreciate the reviewer's encouraging comments for our attempts. Current US guidelines are informative for the preclinical studies utilizing NHP model of HIV. Given our finding that status of viral genome integration at or near the ART initiation may determine the clinical outcomes, we are thus requesting more seasonal newborns, infant macaques of one- month- old and pregnant animals. All these animals will be utilized to investigate the ARV regimens (one or more drugs), fetal and maternal factors, intrauterine infection, INSTI- based prior or after viral integration, optimal timepoint and period of early treatment and outcomes (immune development and viral rebound) etc. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[56, 70, 156, 85]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[56, 92, 490, 110]]<|/det|> +15. Line 59: Protease inhibitors for "proteinase inhibitors" + +<|ref|>text<|/ref|><|det|>[[56, 117, 214, 133]]<|/det|> +Response: Corrected. + +<|ref|>text<|/ref|><|det|>[[55, 164, 930, 205]]<|/det|> +16. Line 59-60: "prevent cells from viral genome integration" is awkward. Change to "prevent viral genome integration in cells"? + +<|ref|>text<|/ref|><|det|>[[56, 211, 572, 229]]<|/det|> +Response: Thank you for this helpful suggestion. It has been corrected. + +<|ref|>text<|/ref|><|det|>[[56, 260, 391, 278]]<|/det|> +17. Line 201: typographical error: Integrated + +<|ref|>text<|/ref|><|det|>[[56, 285, 214, 301]]<|/det|> +Response: Corrected. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 393, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 844, 238]]<|/det|> +The additions and edits regarding the sensitivity of the SIV DNA and RNA quantification assays have addressed several of the concerns raised in the first review. + +<|ref|>text<|/ref|><|det|>[[114, 277, 881, 404]]<|/det|> +There have been some qualifications added to the discussion stating the limitations of the Alu qPCR, however the authors have not demonstrated the sensitivity of the Alu qPCR in "real" samples. Admittedly, this is very difficult to demonstrate, but the assay sensitivity observed with spiked samples does not demonstrate sensitivity in samples with provirus randomly integrated into different cells. The authors also provided in vitro experiments (S1) to demonstrate production of virions, despite absence of integrated virus (with INT administration). These results do not take into account the initial input virus that would still be present in the media. + +<|ref|>text<|/ref|><|det|>[[115, 444, 864, 516]]<|/det|> +Collectively, the data does suggest that there are few proviral copies in the early days of infection, but this is to be expected. Without a clear limit of detection for the Alu PCR, it is not possible to make the claim that virions are a result unintegrated viral DNA. Indeed, the early dynamics will be difficult to determine in vivo, as only small samples of PBMC can be analyzed. + +<|ref|>text<|/ref|><|det|>[[115, 555, 786, 573]]<|/det|> +Other concerns raised in the initial review have been satisfactorily addressed with the edits. + +<|ref|>text<|/ref|><|det|>[[115, 699, 393, 715]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 755, 783, 772]]<|/det|> +The authors have addressed most reviewer's comments and edited manuscript and figures. + +<|ref|>text<|/ref|><|det|>[[115, 783, 874, 874]]<|/det|> +ART initiated 3dpi in infant RMs infected with SIV at birth prevented viral rebound following ATI in 4/5 animals. This result is of interest, but interpretations and conclusions must be more cautious. It seems premature to claim an absence of viral integration for 3dpi that would be specific to infants as opposed to adults, notably because the sensitivity of the integrated assay used is not clear, or specific to the ART regimen used as there is no group treated without DTG. And finally, as noted by Reviewer #3, as ART + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 844, 125]]<|/det|> +was initiated within 72h of infection the outcome might be closer to a successful PEP than a cure or remission and this should be discussed. + +<|ref|>text<|/ref|><|det|>[[116, 165, 405, 181]]<|/det|> +Please see additional comments below: + +<|ref|>text<|/ref|><|det|>[[114, 220, 882, 421]]<|/det|> +Regarding the novel ex vivo experiment presented in supplementing Fig 1, not detecting integration before 5dpi in pre- stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. The response to Reviewer 1 does not provide the sensitivity of the integrated assay nor a comparison of the LOD of this assay with that of the total DNA assay. Similarly, in the in vivo study, it cannot be excluded that integration is not detected before 3dpi in tissues and 5 dpi in PBMC because of a lack of sensitivity of the Alu gag PCR assay. Because the absence of detection of integrated DNA does not necessarily means that there is no integration, the authors should dampen their interpretations and conclusions. This won't take away from the main finding of this study that shows long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. + +<|ref|>text<|/ref|><|det|>[[114, 460, 878, 717]]<|/det|> +I believe there is an error in supplemental table 1 as according to Fig1A no animals were sacrificed 4dpi (I think the animals sampled at 4dpi were sacrificed at 28dpi). This should be corrected. Further, the sentence "The results showed that plasma viral load was detectable in \(\sim 50\%\) neonates at 1dpi and subsequent time points thereafter" should be reformulated. After 1dpi all tested samples were positive (not \(50\%\) ). In the results section, only the first group of animals is introduced "Newborn macaques were intravenously inoculated with identical doses of SIVmac251 within 6 hours after birth, and then euthanized at day 1, 2, 3, 5 and 7 post SIV inoculation for complete tissue collections (Fig. 1A)" before presenting the PVL results of figure 1B that includes animals from the other group of animals (necropsy at 28 dpi after ART). This is confusing. The authors should make clear that PVL were obtained from both groups in absence of ART. The new color coding of the symbols in Figure 1 is not explained in the legend or on the figure. I assume that all animals sacrificed at day 28 have a black symbol and the other ones got a color. I am not sure why the same color was used on different shapes for different animals. This could be made much easier for the readers. At least a key animal ID (as presented in supplemental Fig1)/symbol should be added to this figure. + +<|ref|>text<|/ref|><|det|>[[115, 755, 883, 828]]<|/det|> +Comment 8- It has to be noted that while all adult macaques experienced viral rebound following ATI in the Whitney paper, some adult macaques maintained undetectable PVL in the Okoye paper (Nat Med, 2019). While it is clear that the reservoir is seeded early, some differences are seen between models and while the pediatric model might be different, it seems premature to draw definitive conclusions. + +<|ref|>text<|/ref|><|det|>[[115, 867, 825, 903]]<|/det|> +Comment 9- Cell type (how they have been isolated), cell number per PCR ("generally 10M") and integration assay sensitivity are still obscure. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 175, 394, 191]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 232, 846, 267]]<|/det|> +I appreciate the authors efforts to revise their work in response to the comments of my review, and those of other reviewers + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 301, 106]]<|/det|> +## Nature Communications + +<|ref|>text<|/ref|><|det|>[[115, 108, 661, 125]]<|/det|> +RE: NCOMMS- 22- 04053A, point to point responses to reviewer comments + +<|ref|>sub_title<|/ref|><|det|>[[115, 143, 207, 159]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[113, 166, 880, 354]]<|/det|> +The additions and edits regarding the sensitivity of the SIV DNA and RNA quantification assays have addressed several of the concerns raised in the first review. There have been some qualifications added to the discussion stating the limitations of the Alu qPCR, however the authors have not demonstrated the sensitivity of the Alu qPCR in "real" samples. Admittedly, this is very difficult to demonstrate, but the assay sensitivity observed with spiked samples does not demonstrate sensitivity in samples with provirus randomly integrated into different cells. The authors also provided in vitro experiments (S1) to demonstrate production of virions, despite absence of integrated virus (with INT administration). These results do not take into account the initial input virus that would still be present in the media. + +<|ref|>text<|/ref|><|det|>[[113, 383, 886, 642]]<|/det|> +Response: We appreciate reviewer's comments and admit that the Alu qPCR assay may not accurately reflect the bona fide seeding and size of viral reservoirs, and that the data based on this assay are not adequate to fully assess levels of potential provirus, so we cautiously interpreted the results. We also realize that protective mechanisms cannot be explained based on these assays, and more animal studies may provide more insight into the relationship of early provirus seeding and cure strategies. To this end, we recently requested newborn macaques for the comparison in the outcomes of treatment regimens with one or more antiretroviral drugs. Although these studies are underway, our primary study showed that plasma viral load was maintained high levels in infants on single DTG initiated at 2dpi (2dpi: \(1.8 \times 10^{4} \pm 8128\) ; 7dpi: \(7.4 \times 10^{4} \pm 25172\) ; 14dpi: \(5.8 \times 10^{6} \pm 3748497\) , n=3), at least partly demonstrating the contribution of linear viral DNA in virus production under integrase inhibitor treatment. We expect that our further studies and findings could answer these key questions. + +<|ref|>text<|/ref|><|det|>[[115, 670, 857, 761]]<|/det|> +Collectively, the data does suggest that there are few proviral copies in the early days of infection, but this is to be expected. Without a clear limit of detection for the Alu PCR, it is not possible to make the claim that virions are a result unintegrated viral DNA. Indeed, the early dynamics will be difficult to determine in vivo, as only small samples of PBMC can be analyzed. + +<|ref|>text<|/ref|><|det|>[[115, 791, 860, 810]]<|/det|> +Response: We agree with the reviewer's comments, we sincerely revised description in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 842, 780, 860]]<|/det|> +Other concerns raised in the initial review have been satisfactorily addressed with the edits. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 828, 131]]<|/det|> +Response: We appreciate reviewer for the time and comments, and the opportunity to improve our manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 175, 208, 191]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[113, 198, 883, 384]]<|/det|> +The authors have addressed most reviewer's comments and edited manuscript and figures. ART initiated 3dpi in infant RMs infected with SIV at birth prevented viral rebound following ATI in 4/5 animals. This result is of interest, but interpretations and conclusions must be more cautious. It seems premature to claim an absence of viral integration for 3dpi that would be specific to infants as opposed to adults, notably because the sensitivity of the integrated assay used is not clear, or specific to the ART regimen used as there is no group treated without DTG. And finally, as noted by Reviewer #3, as ART was initiated within 72h of infection the outcome might be closer to a successful PEP than a cure or remission and this should be discussed. + +<|ref|>text<|/ref|><|det|>[[113, 412, 886, 576]]<|/det|> +Response: We appreciate reviewer's comments. As mentioned above, we cautiously interpretate the Results and counterpart conclusion, and discuss the aspects of PEP, remission, or cure, please see in our revisions. We also absolutely agree with the suggestions, further in vivo studies are needed to fully address the proviruses seeding, early treatment regimens and outcomes in a cure or remission for pediatric HIV infection. Therefore, we recently requested newborn macaques for the different animal groups, treated by one or more antiretroviral drugs administered at the specific early timepoint. We expect that the findings could answer these questions in near future. + +<|ref|>text<|/ref|><|det|>[[113, 604, 880, 863]]<|/det|> +Regarding the novel ex vivo experiment presented in supplementing Fig 1, not detecting integration before 5dpi in pre- stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. The response to Reviewer 1 does not provide the sensitivity of the integrated assay nor a comparison of the LOD of this assay with that of the total DNA assay. Similarly, in the in vivo study, it cannot be excluded that integration is not detected before 3dpi in tissues and 5 dpi in PBMC because of a lack of sensitivity of the Alu gag PCR assay. Because the absence of detection of integrated DNA does not necessarily means that there is no integration, the authors should dampen their interpretations and conclusions. This won't take away from the main finding of this study that shows long- term control of SIV replication following treatment interruption in 4 out of 5 rhesus macaque infants initiated on ART 3 days post infection and maintained on ART for 9 months. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 884, 181]]<|/det|> +**Response**: We thank the reviewer's comments. Again, we admit that assay per se, due to many limitations, is difficult to exclude the possibility of potential proviral DNA existence in samples, so we carefully interpret the results and corresponding conclusion, and focus more on the main findings that 4/5 infant macaques, by early ART at 3dpi up to 9 months, do not show viral rebound after removal of treatment. + +<|ref|>text<|/ref|><|det|>[[112, 208, 880, 540]]<|/det|> +I believe there is an error in supplemental table 1 as according to Fig1A no animals were sacrificed 4dpi (I think the animals sampled at 4dpi were sacrificed at 28dpi). This should be corrected. Further, the sentence “The results showed that plasma viral load was detectable in \(\sim 50\%\) neonates at 1dpi and subsequent time points thereafter” should be reformulated. After 1dpi all tested samples were positive (not \(50\%\) ). In the results section, only the first group of animals is introduced “Newborn macaques were intravenously inoculated with identical doses of SIVmac251 within 6 hours after birth, and then euthanized at day 1, 2, 3, 5 and 7 post SIV inoculation for complete tissue collections (Fig. 1A)” before presenting the PVL results of figure 1B that includes animals from the other group of animals (necropsy at 28 dpi after ART). This is confusing. The authors should make clear that PVL were obtained from both groups in absence of ART. The new color coding of the symbols in Figure 1 is not explained in the legend or on the figure. I assume that all animals sacrificed at day 28 have a black symbol and the other ones got a color. I am not sure why the same color was used on different shapes for different animals. This could be made much easier for the readers. At least a key animal ID (as presented in supplemental Fig1)/symbol should be added to this figure. + +<|ref|>text<|/ref|><|det|>[[113, 567, 886, 707]]<|/det|> +**Response**: We thank reviewer to point out and feel sorry to make confused. We corrected the typo in the supplemental table 1 and other descriptions as suggested. To track the viral parameters in individual animal, colored symbols with different shapes are coded. In Figure 1A, different symbol shapes represented plasma viral load of individual animals which were euthanized at day 1, 2, 3, 5 or 7 post SIV infection (colored solid symbols), or from staggered blood samples in infant animals that were sacrificed at 28dpi without treatment (opened black symbols). We added necessary notes and information in the figure legend. + +<|ref|>text<|/ref|><|det|>[[114, 751, 872, 844]]<|/det|> +Comment 8- It has to be noted that while all adult macaques experienced viral rebound following ATI in the Whitney paper, some adult macaques maintained undetectable PVL in the Okoye paper (Nat Med, 2019). While it is clear that the reservoir is seeded early, some differences are seen between models and while the pediatric model might be different, it seems premature to draw definitive conclusions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 885, 323]]<|/det|> +Response: We thank reviewer's concerns. We also noticed the obviously discrepant findings regarding early treatment and viral rebound off- ART in adult animals, as shown that viral rebound is not observed in 4/16 (ART initiation at 4- 5dpi) or 3/17 animals (ART initiation at 6dpi) (Okoye, 2019), essentially contradictory to the reports (100% viral rebound in animals on ART initiation at 3dpi, Whitney, 2018) and clinical setting. It is interesting that total viral DNA is nearly undetectable in both PBMC and lymph node- derived lymphocytes in all SIV- infected adult on early ART throughout the studies (Okoye, 2019), yet only small animal populations ultimately do not show viral rebound after ATI. It is also curious to know the status of proviral DNA in the animal cohorts, unfortunately, proviruses have not been examined. The possible reason may lie in vaccination relevance and sensitivity of assays, despite the reason is still intrigued. We discussed these concerns in revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 351, 832, 395]]<|/det|> +Comment 9- Cell type (how they have been isolated), cell number per PCR ("generally 10M") and integration assay sensitivity are still obscure. + +<|ref|>text<|/ref|><|det|>[[115, 424, 609, 442]]<|/det|> +Response: We added more detail in Methods in revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 300, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 146, 394, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 203, 799, 220]]<|/det|> +The revised manuscript has satisfactorily addressed the concerns noted in the second review. + +<|ref|>text<|/ref|><|det|>[[115, 289, 394, 305]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 345, 877, 363]]<|/det|> +Most comments from the previous review have been addressed. Please see remaining comments below + +<|ref|>text<|/ref|><|det|>[[115, 401, 878, 437]]<|/det|> +1- The first sentence of the abstract sounds like early ART leads to rapid viral rebound. ATI is followed by viral rebound despite years of treatment + +<|ref|>text<|/ref|><|det|>[[115, 449, 843, 502]]<|/det|> +2- Introduction. It is largely admitted that current ART regimens block new cycle of virus replication (with or without integrase inhibitor). Why would the pediatric treatment regimens "permit new or continual proviral seeding"? + +<|ref|>text<|/ref|><|det|>[[115, 513, 875, 567]]<|/det|> +3- Results. The new paragraph describing assay validation is poorly written. Supplementary Fig 1A is not referenced in the text and a slope of - 2.3 is not good for a standard curve (- 3.2?). As mentioned in the previous review, not detecting integration + +<|ref|>text<|/ref|><|det|>[[115, 578, 840, 614]]<|/det|> +before 5dpi in pre- stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. + +<|ref|>text<|/ref|><|det|>[[115, 625, 861, 661]]<|/det|> +4- As the sensitivity of the integration quantification assay is still unclear, I would suggest removing or rephrasing the following sentences: + +<|ref|>text<|/ref|><|det|>[[115, 671, 864, 707]]<|/det|> +- "Our studies showed that in contrast to adults, skewing of viral integration was observed in neonatal macaques..." (Abstract page 2) + +<|ref|>text<|/ref|><|det|>[[115, 718, 841, 736]]<|/det|> +- "the onset of integrated reservoir seeding did not appear until day 3 of infection" (Results page 5) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 700, 123]]<|/det|> +Nature Communications RE: NCOMMS- 22- 04053 Final, point to point responses to reviewer comments + +<|ref|>text<|/ref|><|det|>[[115, 146, 211, 161]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 180, 785, 196]]<|/det|> +The revised manuscript has satisfactorily addressed the concerns noted in the second review. + +<|ref|>text<|/ref|><|det|>[[115, 220, 821, 251]]<|/det|> +Response: We appreciate reviewer's positive feedback and valuable comments to improve our manuscript, we also would like to thank the reviewer for taking the time to review the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 286, 208, 301]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[115, 303, 860, 318]]<|/det|> +Most comments from the previous review have been addressed. Please see remaining comments below: + +<|ref|>text<|/ref|><|det|>[[115, 335, 880, 367]]<|/det|> +1. The first sentence of the abstract sounds like early ART leads to rapid viral rebound. ATI is followed by viral rebound despite years of treatment. + +<|ref|>text<|/ref|><|det|>[[115, 384, 409, 400]]<|/det|> +Answer: This sentence has been revised. + +<|ref|>text<|/ref|><|det|>[[115, 417, 843, 466]]<|/det|> +2. Introduction. It is largely admitted that current ART regimens block new cycle of virus replication (with or without integrase inhibitor). Why would the pediatric treatment regimens "permit new or continual proviral seeding"? + +<|ref|>text<|/ref|><|det|>[[115, 483, 882, 626]]<|/det|> +Answer: Sorry to make confused. Although incorporation of nucleoside reverse transcriptase inhibitors (NRTIs) into the nascent viral DNA terminates its synthesis in the viral life cycle, current early ART regimen with a combination of dual- NRTI (AZT+3TC) plus protease inhibitors (LPV/r) may not fully prevent initial viral RNA/DNA production since total viral RNA/DNA are detected as early as 6h after SIV infection, any residue viral DNA could potentially increase the risk of proviral reservoir seeding. This concept is also supported by off- ART viral rebound observed in infant macaques receiving late ART regimen containing integrase inhibitor. Overall, all these points suggest that proviral reservoirs, once established, are likely difficult to eradicate by conventional cure strategies, and prevention of initial viral integration may be critical to overcome this major obstacle. We have clarified it in the revised version. + +<|ref|>text<|/ref|><|det|>[[115, 650, 878, 730]]<|/det|> +3. Results. The new paragraph describing assay validation is poorly written. Supplementary Fig 1A is not referenced in the text and a slope of -2.3 is not good for a standard curve (-3.2?). As mentioned in the previous review, not detecting integration before 5dpi in pre-stimulated PBMC infected in vitro in absence of RTG treatment is surprising and suggest that the integrated assay might be less sensitive than the total DNA one. + +<|ref|>text<|/ref|><|det|>[[115, 747, 882, 891]]<|/det|> +Answer: We thoroughly edited the paragraph and referenced Supplementary Fig. 1a in the text. We also corrected the typo and made the graph of standard cure clear in revised Supplementary Fig. 1a. For a geometric efficiency of \(100\%\) in qPCR, the slope is -3.32. The slope value here is shallower, implying acceptable amplification efficiency. As for undetectable proviral DNA before 5dpi (not examined at 4dpi) in pre-stimulated infant PBMCs infected in vitro in absence of RTG treatment, these results were de facto consistent with in vivo data that viral genome integration was not observed in PBMCs in neonates within 1- 3dpi after SIV infection. Note that there are still tremendous gaps in our understanding of pediatric HIV infection and treatment outcomes thus far. For example, plasma viral load could be detected (or higher) in some neonates as early as one day post SIV infection but undetectable (or lower) in others; all neonatal + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 882, 298]]<|/det|> +animals infected with identical SIV inoculum after birth, including three animals born at same day, only one animal on early treatment at 3dpi shows viral rebound off- ART; some infants infected with HIV/SIV show rapid AIDS development but not others, and so on, which remain elusive. In the qPCR assay, the total and integrated assays were parallelly performed within same batch for each sample, generating comparable data with similar sensitivity. Overall, this result mentioned should make sense, at least not completely question the assay per se. We added in the Discussion. Actually, we also primarily tested viral integration using fresh PBMCs from SIV naïve adult animals. Proviar DNA in adult PBMCs without treatment was detected as early as 1dpi while shown individual sample difference: undetectable in one of three cell samples yet detected in another two cell samples (11 and 5.5 copies of proviral DNA per million cells) at 1dpi; detected in all cell samples at 3dpi (74, 38 and 67 copies of proviral DNA per million cells), essentially consistent with the adult animal study that viral rebound off- ART is observed in \(20\%\) adult macaques when early treatment is initiated at day 1 post SIV infection, \(100\%\) viral rebound off- ART with ART initiation at 3dpi (Whitney, Nat Commun 2018). + +<|ref|>text<|/ref|><|det|>[[115, 321, 870, 386]]<|/det|> +4. As the sensitivity of the integration quantification assay is still unclear, I would suggest removing or rephrasing the following sentences: "Our studies showed that in contrast to adults, skewing of viral integration was observed in neonatal macaques..." (Abstract page 2); "the onset of integrated reservoir seeding did not appear until day 3 of infection" (Results page 5). + +<|ref|>text<|/ref|><|det|>[[115, 400, 872, 497]]<|/det|> +Answer: As we mentioned and discussed in the text and previous rebuttal letter, viral reservoir assay and its sensitivity, especially for proviral reservoirs, are highly challenging for all current scalable assays, absolute quantification is essentially not reachable, and sensitivity of assay is also highly associated with many aspects. With the improved assay here, the treatment outcomes with viral remission basically correlate with status of viral integration (but not other parameters examined), thus trying to interpret the possible mechanisms. As suggested, we rephrased the sentences in the revised text. + +<--- Page Split ---> diff --git a/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/images_list.json b/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7d55bb37f0b0343654b3a438ba9aa1569c71af41 --- /dev/null +++ b/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,594 @@ + +# nature portfolio + +Peer Review File + +# Global hotspots of butterfly diversity are threatened in a warming world + +Corresponding Author: Dr Stefan Pinkert + +Version 0: + +Decision Letter: + +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +Dear Dr Pinkert, + +Thank you for your patience while your manuscript entitled "Global hotspots of butterfly diversity in a warming world" was under review. As you will see from the reports below, the reviewers find your work of considerable potential interest but have raised quite substantial points that must be addressed. We would like to see a revised manuscript that addresses these concerns. + +We hope you will find the reviewers' comments useful as you decide how to proceed. We expect the revision to include additional work to strengthen the niche erosion projection component (see Reviewer 1's comments). Please also consider whether Reviewer 1's point on the interpretation of the elevational patterns warrants supplementary analyses using local altitude instead of elevation above sea level. + +We are committed to providing a fair and constructive peer- review process. Please do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +If revising your manuscript: + +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the referees along with the revised manuscript. + +\* Provide the manuscript file in Microsoft Word format and highlight all changes. + +\* If you have not done so already we suggest that you begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +Please use the link below to submit a revised paper: + +Link Redacted + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We hope to receive the revised manuscript within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous + +<--- Page Split ---> + +attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +Thank you for the opportunity to review your work. + +[redacted] + +Reviewers' comments: + +Reviewer #1 (Remarks to the Author): + +There are many strengths to the manuscript related to global hotspots of butterfly diversity. Understanding the biogeography of different taxonomic groups is important for providing an assessment of where biodiversity is located and how best to protect it. The work is novel in attempting to provide a global assessment of species diversity and rarity of butterflies. A strength is the focus on different measures to assess hotspots of diversity as well as the comparison of how these butterfly hotspots align with other taxa. The compilation of data and the distribution maps for over 12,000 species are impressive, and such databases are valuable tools for the scientific community. + +There were several places where the manuscript could be improved, which are outlined below. + +In general, the writing was hard to follow and/or interpret, which made the manuscript challenging to understand and greatly detracted from the main points. An example of a sentence that was hard to understand was (L98): "Given a much lesser dominance of a minority of wide- ranging species in driving range rarity and a stronger signature of idiosyncratic biogeographic histories, we expect overall weaker associations for this measure than for species richness patterns". Parts of the results were particularly hard to follow. For example, (L65) "Notably in most realms, both metrics show limited congruence, particularly for peaks in narrow- ranged species, which are usually of greatest conservation concern". After reading this several times, it's still hard to know what it means. Even some basic sentences did not flow easily. For instance, the sentence "For terrestrial vertebrates, the thus far dominant model system for global ecology and conservation, prior work has documented..." is too complex and could be simplified. Similarly, (L175) "Butterfly hotspot temperature niche loss ranges from..." is also too complex. + +The assessment of niche erosion was not well integrated into the manuscript and was rather simplistic. It doesn't account for movement of butterflies. The temperatures are rather course and do not include microclimates that insects often use to modify body temperatures. These issues call into question the conclusion that mountains would be (L186) "traps for butterfly biodiversity". + +Some of the novelty is overstated. The finding that mountains are butterfly hotspots is not particularly novel; butterfly diversity is known to be especially high in montane areas, which is likely due to the change in temperature and vegetation across elevation. Similarly, it's not surprising that species richness of butterflies is positively associated with other taxa as we tend to see general trends in diversity across different groups. + +The interpretation of the overlap in diversity centers of butterflies with those of ants doesn't quite fit with the values presented in the manuscript. (L11): with regards to "Only a small portion (14%- 54%...", those percentages are not really a "small portion". + +L61- 62: Higher elevation is relative, and 2500 m is a mid- elevation in many places. The manuscript is suggesting richness increases with elevation based on how it is written, but this sounds more like a mid- elevation peak, which is common in many taxa. More broadly, it seems there could be issues identifying peaks in abundance across elevation given the course resolution of the distribution data. A 10 km- resolution could contain a broad range of elevations. Could this skew ranges to higher elevations in topographically complex landscapes? + +L113: Under "range rarity", the text shifts to discussing diversity (i.e. "Even stronger cross- taxon mismatches emerge when comparing the top 5% diversity centers per realm and taxon."), which is confusing. Is this referring to phylogenetic diversity? + +L120: The manuscript notes that "These results indicate that priority areas identified based on vertebrates miss critical places needed to safeguard the diversity of insects", however, isn't this statement based on range rarity (a measure of endemism) rather than species diversity per se? It seems that a better measure of safeguarding diversity of insects should be focused on species richness, not simply endemism. + +L144: The manuscript notes that "We find that the concentration of butterfly diversity in mountains substantially exceeds that of almost all globally studied taxa". However, isn't this simply because other insects haven't been assessed? In other words, it's not surprising this is the case given that most other globally studied animal taxa are vertebrates. + +<--- Page Split ---> + +L 627. Do the authors mean "across latitude" rather than "in space" in the figure caption? Fig.1 | Global variation in butterfly diversity in space and along elevation + +Reviewer #2 (Remarks to the Author): + +This nice study investigates the spatial structure of butterfly diversity across the globe using an impressive variety of sources and methods. To keep myself accountable, and to make it easier for the authors to confirm that I understood their methodology, I below attempt to summarize this (quite major) study. + +With descending order of priority, the authors use species distribution models (based on occurrence records), expert range maps, and ecoregional range maps (grouping areas by their similarity in ecologically relevant variables) to infer biodiversity at a \(110\mathrm{km}\times 110\mathrm{km}\) spatial resolution. The authors also use three biodiversity metrics: species richness (number of species in a cell), average range rarity (the average of the inverse global ranges for the species in a cell), and phylogenetic diversity (calculated as deviations from a null model—is there more spatial phylogenetic structure than expected by chance?). + +The authors identify discrepancies between the different diversity metrics, indicating that one cannot be substituted for another without loss of information. However, the general conclusion is—perhaps unsurprisingly to most—that tropical and subtropical regions are most diverse, but more importantly also that mountainous regions have disproportionately diverse and rare butterfly communities (even in contrast with other taxa). This pattern, while ecologically interesting in its own right, carries with it dire implications for global butterfly diversity in a warmer future, due to the local nature of elevational temperature gradients. To make an analogy for butterflies limited to high elevations in the tropics: the mountains are cool islands in a dangerously warm ocean, and water levels are rising. With no other land in sight, the butterflies have nowhere to go. + +It's unclear from the paper whether loss of high- altitude butterfly diversity in the tropics generally comes with any socioeconomic costs related to, for instance, ecosystem services, but from a global biodiversity- perspective the findings of this (very comprehensive) study in the present study are potentially alarming. Additionally, butterflies are quite charismatic and well- liked animals. Therefore, I believe this paper is broadly interesting to biologists, and the theme suitable for Nature Ecology & Evolution. + +However, I still have some reservations regarding the manuscript's suitability for publication in its current state. These mostly relate to the writing and the storytelling. First, the writing could be clearer (see some examples in the line- by- line comments below). Second, when reading the manuscript, it is not immediately clear what the take- home messages are regarding the actual biology. In its present form, the manuscript is largely descriptive (butterflies are here and there), and the brief sentences about the biology of butterflies seem quite ad hoc. The authors appear not particularly interested in butterflies, but rather the nice resources available for quantifying their distributions. That is of course completely fine, but in this case, the biological reasons for why the patterns described in this study are exaggerated in butterflies might carry crucial information for future conservation efforts, or at least projections. Indeed, after identifying global patterns of biodiversity in butterflies, it would be very nice if the authors could dive into some potential biological explanations for why butterfly diversity/rarity stand out as particularly concentrated at high elevations. Then, the findings in the study, and the massive amount of work put into quantifying butterfly diversity globally, could give broader insights into what other organism groups might be threatened. Personally, I think the story would be more coherent if it was structured, at least to some extent, like this: + +Biology (what traits make butterflies special) \(\rightharpoonup\) Biodiversity patterns (what spatial distributions do these traits correlate with) \(\rightharpoonup\) Threat levels (what does a warm future hold in store for species with these spatial distributions) \(\rightharpoonup\) Biology (what other organisms fall into the same category). + +I don't want to micromanage how the paper is written, and I am sure there are many ways to shape the findings in this paper into a nice story. But I do think that the manuscript's quality would improve drastically if the writing was just a bit more coherent. This is particularly important given the complex analyses in the study. + +## Specific comments: + +Title: I think the title could be a bit more precise, to highlight the implications of the study (e.g. "Global hotspots of butterfly biodiversity are threatened in a warming world"). + +Abstract: At line 6- 7, "their [the butterflies'] diversity and threat" sounds wrong (particularly the threat part). I suggest really describing why lines 13- 15 are true. That is, explain in some way that living on a mountain makes it hard to shift the geographical range to track a changing climate in the long run. This is perhaps somewhat obvious, but it could help make the message clearer. + +Lines 24- 28: The last section of the paragraph is a bit unclear. What does "heterogeneous representation" mean in this context? "Cause and consequence" of what exactly? I think I get the idea but wording could be more precise. + +Line 29: Extends from what to what? + +<--- Page Split ---> + +Lines 38- 40: Which recognized differences? + +Line 44: "their own isolation" seems to me like a somewhat awkward phrase here. + +Line 53- 54: Is it really the butterflies' information? + +Line 149- 151: Perhaps diapause would be good to mention here? + +Figure 2: Legends are not entirely clear (e.g., the color of the bars in the bar plots are not described explicitly). + +Figure 6: Legends/figures need to be clearer. As it stands, the meaning is quite difficult to extract from the figure. + +Version 1: + +Decision Letter: + +14th January 2025 + +Dear Stefan, + +Thank you for submitting your revised manuscript "Global hotspots of butterfly diversity are threatened in a warming world" (NATECOLEVOL- 24061491A). Based on the reviewers' comments (copied below), we'll be happy in principle to publish it in Nature Ecology & Evolution, pending minor revisions to satisfy the reviewers' final requests and to comply with our editorial and formatting guidelines. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +[redacted] + +Reviewer #1 (Remarks to the Author): + +The work is of broad interest and is novel in providing a global assessment of butterfly species rarity and diversity. The authors have thoughtfully responded to all concerns and added additional analyses that strengthen the manuscript. + +Reviewer #2 (Remarks to the Author): + +The writing is much improved, which makes the manuscript easier to read, and thus more impactful. I still have some suggestions that I think will improve the manuscript, which I hope that the authors will consider and appreciate. I probably missed some parts, so I recommend the authors to carefully read through their manuscript and fix language/sentence structure errors before resubmitting—perhaps with help of a native English speaker. Still, I am generally pleased with the revisions. + +Line- by- line: + +4: Remove "in decline and". + +7: "their" -> "butterfly". + +21: "the prerequisite" -> "a prerequisite". + +27: "documented and safeguarded" -> "prioritized"? + +41: Unclear what "takes on an additional weight" really means. + +43: Consider using semi- colon (;) after "mountains" to make "their" in the follow sentence more clear. + +44: Remove "their". + +49- 51: What about the ant work in Science Advances? This sentence is not needed, we see the importance of this work without it. + +57: "Highly adapted" does not sit right with me. I would not say that their traits are "more" adapted than other species'. Perhaps "Owing to distinct...". + +57- 59: I think https://doi.org/10.1038/s41467- 023- 39359- 8 would be a good additional reference here (regarding thermal niches). + +59: What does separately mean here? + +61- 65: I think these two sentences could be written more clearly. + +76: Remove "and" and "are". + +92: "... the previously argued" sounds a bit strange to me. What about "previous findings on hotspots of deep ..."? Or something else. + +<--- Page Split ---> + +101- 102: "Within ectotherm taxa" makes it seem like ectotherms are a monophyletic group somehow. Perhaps just remove, works without it. + +104- 105: What "known co- evolutionary association"? Change sentence structure. + +138- 140: Possesses -> possess. Also, I think the point here is: why would insects be especially diverse in mountainous regions? I could see the point that insects have general adaptations (e.g., diapause - more so than other groups, where such adaptations appear more specialized) that allows them to endure prolonged periods of inhospitable cold conditions. If I'm right with what you are implying, perhaps the sentence could be changed to more clearly reflect this? E.g.: + +"In addition, many insects possess general physiological adaptations for enduring inhospitable cold conditions, potentially acting as pre- adaptations for colonizing mountainous regions in the first place." + +Here are three more generally relevant references for this: + +https://doi.org/10.1016/j.jinsphys.2005.09.008 + +https://isbnsearch.org/isbn/9780195036350 + +https://doi.org/10.1073/pnas.2407057121 + +145: "odd" -> "odds". + +156: Remove average? Or write, "On average, toward higher ...". + +161: See previous refs. + +198: Replace "for instance" with "either" for better structure? + +206: "As a next step". + +208- 212: Revise sentence structure. + +215- 216: Revise sentence. Avoid "their" before mentioning what you are talking about. Also, this should probably be referenced: + +https://doi.org/10.1002/ecm.1553 + +218: "unusually strongly exposed" -> "exceptionally susceptible". + +219: "that" -> "which". + +220- 221: "this species group yet" -> "butterflies". + +221- 222: "due to their geographically rare and isolated environmental conditions are now bound to become ecological dead ends" -> "but might become ecological dead ends in a warmer future". + +223- 224: "mountain areas where identified rarity and threat most strongly coincide" -> "threatened mountain areas". + +224: Consider replacing "sound a clarion call". Might be a darling that is better off killed. "Strongly emphasize the need" or something else typically boring might be more suitable". + +Middle of figure legend 2: Change to "mountains" to "mountains (full bars)", and "odd" to "odds". + +Beginning of figure legend 5: Change "mountains" to "mountains (full bars)". Also, shouldn't the y- label be "mountain/non- mountain"? + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons + +<--- Page Split ---> + +license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## General comment: + +Reviewer #1 (Remarks to the Author): + +There are many strengths to the manuscript related to global hotspots of butterfly diversity. Understanding the biogeography of different taxonomic groups is important for providing an assessment of where biodiversity is located and how best to protect it. The work is novel in attempting to provide a global assessment of species diversity and rarity of butterflies. A strength is the focus on different measures to assess hotspots of diversity as well as the comparison of how these butterfly hotspots align with other taxa. The compilation of data and the distribution maps for over 12,000 species are impressive, and such databases are valuable tools for the scientific community. + +There were several places where the manuscript could be improved, which are outlined below. + +General response: Thank you very much for the helpful and detailed suggestions that strengthened our article both in terms of clarity and robustness of the results. + +In general, the writing was hard to follow and/or interpret, which made the manuscript challenging to understand and greatly detracted from the main points. An example of a sentence that was hard to understand was (L98): "Given a much lesser dominance of a minority of wide- ranging species in driving range rarity and a stronger signature of idiosyncratic biogeographic histories, we expect overall weaker associations for this measure than for species richness patterns". + +Response: We apologize for the complex writing style and carefully revised this sentence (L106- 108) and many other parts of the text to improve clarity. + +Comment: Parts of the results were particularly hard to follow. For example, (L65) "Notably in most realms, both metrics show limited congruence, particularly for peaks in narrow- ranged species, which are usually of greatest conservation concern". After reading this several times, it's still hard to know what it means. + +Response: We agree that several sentences including this one were hard to follow. Accordingly, we revised this sentence and the following sentence to improve clarity (L69- 81). + +Comment: Even some basic sentences did not flow easily. For instance, the sentence "For terrestrial vertebrates, the thus far dominant model system for global ecology and conservation, prior work has documented..." is too complex and could be simplified. + +Response: Many thanks. We simplified this sentence and revised parts of the paragraph (L28- 40). + +<--- Page Split ---> + +Comment: Similarly, (L175) "Butterfly hotspot temperature niche loss ranges from..." is also too complex. + +Response: We simplified this sentence. It now reads: "Temperature niche loss ranged from \(6\%\) to \(64\%\) across realms and diversity aspects, with generally greater losses for hotspots of butterfly PD and species richness than for rare rarity hotspots (global mean: \(33\% > 31\% > 11\%\) ; Fig. 6a, Extended Data Fig. 4)." + +Comment: The assessment of niche erosion was not well integrated into the manuscript and was rather simplistic. It doesn't account for movement of butterflies. The temperatures are rather course and do not include microclimates that insects often use to modify body temperatures. These issues call into question the conclusion that mountains would be (L186) "traps for butterfly biodiversity". + +Response: Thank you for these additional considerations. We have now extended discussion of the importance of animal dispersal for interpreting climate change projections and added analyses to assess the issues of spatial analysis grain size. + +## 1) Extended discussion of the effects of dispersal on niche loss estimates + +Our original text included discussion of the potential impact of dispersal and the challenges of incorporating in L198- 212. Current modelling approaches of future trends generally suffer from assuming either full or no dispersal. We believe our approach is more nuanced in this regard, using realm- level projections of the available temperature niche as well as contrasting losses of hotspot niches with those of random and non- hotspot cells as counterfactual. We have revised the respective paragraph, which now reads: + +"Assessments of climate change impacts often neglect niche availability, for instance because they are based on absolute climate changes in focal areas \(^{51 - 63}\) , or rely on simple, binary scenarios of dispersal (i.e. full or no niche tracking) \(^{64,65}\) . We aimed to address some of these limitations by using realm- level projections of the available temperature niche and by contrasting hotspot locations with random and non- hotspot cells as counterfactual. Our results suggest that quantifying geographic niche availability is crucial for understanding threats to mountain biodiversity, due to the nuanced and gradual decline of specific temperature regimes at upslope locations following warming. These trends are mirrored by local population declines at highest elevations despite concurrent up- slope range shifts in the last decades \(^{30,66}\) . As next step, additional work is needed to gauge species- level responses. For example, more detailed data tuned to specific requirements could refine estimated availability and accessibility of habitats in the future. Insights on species- specific dispersal constraints will be particularly helpful and in the case of island endemics (e.g. range rarity hotspots in Australasia and Indomalaya) and in regions where the latitudinal orientation of mountain ranges hinders northward shifts might reveal yet greater niche losses than estimated here (Fig. 6 and Extended Data Fig. 4)." + +We are uncertain if "movement" was referring to species dispersal at the macroscale or to individual movement facilitating shifts to colder microclimates within the 110 km- resolution hotspot grid cells. Latter behavior cannot be reliably incorporated into projections, as temperature may greatly vary even between open/shaded areas but in the following provide insights into the microclimatic variation and importantly its changes under projected warming between hotspots and non- hotspots. All else being equal we expect similar changes in + +<--- Page Split ---> + +microclimates at 1 km- resolution, rendering 110 km averages representative. If cold and warm cells withing a 110 km cells warm to a similar degree (no variation in changes) opportunities for the use of microclimates erode alike. + +2) Additional section and analysis on grain size and niche metrics: + +The reviewer indicates that especially for relatively small organisms such as butterflies coarse grains might miss climatic refugia that support survival under a changing climate. We much appreciate this point and are astutely aware of the scale- dependence of climate change assessments (e.g. Lu and Jetz, 2023 Scale- sensitivity in the measurement and interpretation of environmental niches. Trends Ecol Evol. 38:554- 67). First, we note that for the great majority of species we trained and predicted species distribution models at 1 km resolution (the finest resolution for global climate data) in way that does carry forward temperature variation at that very fine grain. It was for harmonization with expert data and for maximizing overall map accuracy that we resampled to the relatively coarse 110 km grid. We note that any "micro"- climate conditions at 1 km- resolution that support a species presence would cause a presence for that species in a 110 km cell (different to had we done the original predictions at 110 km resolution where averaging could have missed important fine- grain pockets of suitable condition). Similarly, all climate projections we used also have an original resolution of 1 km and were only subsequently aggregated to 110 km. In our original submission, this result is based on niche overlaps calculated with 110 km cell values. To as much as reasonably feasible address the reviewer's concern we have now conducted two assessments: + +To recap, the reviewer is interested in whether our projection of butterfly hotspots (of which many are in mountains) experiencing particularly high niche temperature loss might be different if the fine- grain variation of temperature was considered. We have now added a new section "Grain size and niche metrics" to our methods and address the issue with two dedicated analyses. + +First, we understand that the reviewer's concern is related to a potential buffering against the projected niche erosion in areas with high topographical diversity (hotspots) and hence great fine- grain climatic variation (that would include climatic refugia with limited temperature change). To assess whether this issue could affect our overall conclusion (of greater niche loss in hotspots), we evaluate whether the fine- grain variation in projected temperature change differs strongly between hotspots vs non- hotspots. + +Specifically, we evaluated the variance in the warming (temperature under rcp8.5 - current) among the 1 km pixels of hotspot cells versus those of non- hotspot cells. We find no consistent differences. Species richness and PD hotspots show slightly smaller variation than their respective non- hotspots, and the opposite is the case for range rarity hotspots. However, the differences are very small indeed (< 0.002 absolute difference in median coefficient of variation). Hence, under projected temperature changes hotspots even tend to show less buffering (less variability in 1 km- resolution temperatures) than non- hotspots. This finding supports the robustness of our overall results. We provide these results in the new Supplementary Table 3 and added a section describing the motivation and details for this analysis to the methods (L435- 447). + +<--- Page Split ---> + +Second, to directly gage the sensitivity of our niche loss results to grain size, we repeated our analysis at 10 km resolution. That is, for every single one grid cell the 110 km analysis, we now use 121 cells. We find the difference between the 10 km and 110 km resolution analysis to be small. Specifically, the projected temperature niche loss across realm- level non- /hotspots was on average 5% (SR: 8%, RR: 2%, PD: 6%) lower for the 10 km- resolution than for the original 110 km- resolution results (Supplementary Table 4). Note that the niche loss in non- hotspots also decreases, although to a lesser extent than for hotspots (1% on average). The average temperature niche loss for hotspots versus non- hotspots across realms based on 10 km results was 20% and 10% for species richness, 9% and 10% for range rarity, and 22% and 10% for PD. For all realms, the higher resolution and the original 110 km- resolution results underscore greater niche loss for species richness and PD hotspots than for non- hotspots. Only for range rarity hotspots of tropical realms losses in non- hotspots became slightly greater than for their respective hotspots at the 10 km- resolution. + +We did not repeat the same analyses at yet finer resolution because of the computationally prohibitive cost and the additional biases circumventing them would introduce. Conducting the same analysis at 1 km- resolution would involve 150million records. And pairwise calculations would necessarily need to be done on a very small subset, that would be insufficient to describe a complex realm- level temperature distribution (multiple modals with long tails; see Extended Data Fig. 2). Appropriate are at least 15 million records for sampling densities and the same number of overlap calculations for this input (for both non- /hotspots and each combination of diversity aspects, and realms), which was computationally not feasible. Random samples of fewer cells are driven by the central tendency, hence for instance not reflecting the cold extremes and do the opposite of accounting for variations. At the 110 km- resolution, we see that the closer one gets to number of samples and calculations recommended in the documentation of the R- package 'NicheROVER', the closer they were to our original estimates. Although notably the simpler non- hotspot distributions seemed to be described well with fewer records. + +While we fully acknowledge that microclimates at even finer grain (e.g. 10 m, see ref. \(^{90}\) ) could modulate climate change outcomes for specific species and regions, the empirically possible sensitivity analysis gives no indication that this would affect the overall direction of our findings at broadest taxonomic and spatial scope. The respective analysis and results are now described in detail with additional text in the section "Grain size and niche metrics" (L448- 468). + +Comment: Some of the novelty is overstated. The finding that mountains are butterfly hotspots is not particularly novel; butterfly diversity is known to be especially high in montane areas, which is likely due to the change in temperature and vegetation across elevation. Similarly, it's not surprising that species richness of butterflies is positively associated with other taxa as we tend to see general trends in diversity across different groups. + +Response: With these novelty statements we refer to the exceptionally high concentration of hotspots of the global butterfly diversity, including previously unknown patterns of rare rarity and PD. We are not aware of a global study of any of these aspects, even for species richness, and more so a comparison with other taxa (plants, ants or vertebrates) that allow such a conclusion. As butterfly experts we are aware of local elevational diversity gradients, of which we cite many (e.g. 38, 39, 42- 44, 53, 55, 58, 66) and which were our motivation to conduct this rigorous test. We now mention these studies earlier, include three additional butterfly- specific references and more specifically address the expected role of mountains in the hypothesis section. We did not + +<--- Page Split ---> + +find a statement stressing that the positive relationship between butterfly species richness and that of other taxa is novel, but our tests are clearly the by far most rigorous evaluations of this pattern. The general positive association of species richness patterns itself is intuitive. Does this maybe refer to the "coincide of their diversity and threat" statement in the abstract? Here we meant that the temperatures underpinning locations of hotspots of butterfly diversity will are eroding faster than non- hotspot temperature regimes. We rephrased this sentence to improve clarity. + +Comment: The interpretation of the overlap in diversity centers of butterflies with those of ants doesn't quite fit with the values presented in the manuscript. (L11): with regards to "Only a small portion \((14\% - 54\%)\) ...", those percentages are not really a "small portion". + +Responses: Thank you for the comment. This is a summary statement addressing overlaps of all taxa (quote: "ants, terrestrial vertebrates and vascular plants"). Rare rarity hotspots of ants overlap to only \(16\%\) and ant species richness hotspots to \(30\%\) with those of butterflies. The statement, however, contains an error. The maximum of overlap of butterfly hotspots is \(36\%\) (species richness hotspots of mammals) not \(54\%\) as previously stated. Thank you for highlighting this mistake! + +Comment: L61- 62: Higher elevation is relative, and 2500 m is a mid- elevation in many places. The manuscript is suggesting richness increases with elevation based on how it is written, but this sounds more like a mid- elevation peak, which is common in many taxa. More broadly, it seems there could be issues identifying peaks in abundance across elevation given the course resolution of the distribution data. A 10 km- resolution could contain a broad range of elevations. Could this skew ranges to higher elevations in topographically complex landscapes? + +Response: We appreciate this comment and from our above response the reviewer can hopefully see that scale and grain issues are very much on our mind. We hence tried to be very cognizant about them make in our choice of analytical approach and interpretation. First, we repeat the for the great majority of our species we modelled distributions at 1 km- resolution and then only later coarsened to 110 km. That means that 110 km cells with great topographic heterogeneity could (correctly) emerges as harbouring a high number of species. And thus, richness might be as much or more related to a cell's elevation range than its mean elevation (such is the limitation of a single elevational gradient perspective). However, we are uncertain how this would cause a skew toward higher or lower elevations. + +The first part of the sentence addresses the trend (increases with elevation), while the second highlights the peak of this non- linear relationship. In the text, we avoid the term mid elevation because this is indeed rather difficult to define. Instead we refer to elevation "higher"/"above" or "lower than 2500 m". Hence, we agree with the interpretation that 2500 m is rather a mid- elevation. In the context of our global scale analysis, we note that this peak in butterfly diversity is at higher elevation than in most other taxa (Fig. 5b). For a more nuanced understanding we provided an analysis of realm- and taxon- specific elevational diversity gradients in the Supplementary Information (Fig. 10). This demonstrates that species richness and range rarity are highest between 2500 m and the realm- level maximum elevations. In the Palearctic, species richness slightly declines above 4000 m, and the only true mid- elevation peak occurs in the Neotropics. While we can confirm that mid- elevation peaks are common for other taxa in most realms, idiosyncratic trends, such as those for plants and ants, suggest no skew due to + +<--- Page Split ---> + +topographical complexity. Although we expect lower elevations to be better sampled due to accessibility and human population density, data limitations prevent us from assessing abundance patterns. Our study prioritized an optimal strategy for describing species ranges, including spatial thinning to improve modeling accuracy. + +We now strengthen links to the Supplementary Information and the stronger relative preference of butterflies for higher elevations in the context of all considered taxa. + +Comment: L113: Under "range rarity", the text shifts to discussing diversity (i.e. "Even stronger cross- taxon mismatches emerge when comparing the top \(5\%\) diversity centers per realm and taxon."), which is confusing. Is this referring to phylogenetic diversity? + +Response: In the mentioned sentence the discussion shifts from a comparison of the cross- taxon congruence in species richness with that of rare rarity patterns to overlap in their hotspots. We used the term "diversity" for describing multiple aspects of diversity but rephrased that sentence to clarify that the statement refers to "hotspots of species richness and rarity" (L122). + +Comment: L120: The manuscript notes that "These results indicate that priority areas identified based on vertebrates miss critical places needed to safeguard the diversity of insects", however, isn't this statement based on range rarity (a measure of endemism) rather than species diversity per se? It seems that a better measure of safeguarding diversity of insects should be focused on species richness, not simply endemism. + +Response: In our statement "safeguard the diversity of insects" we meant "global diversity" and have now added that word to clarify (L129). In other words, we are focused here on minimizing the number of species extinctions (not on maximizing the average cell species richness). For this, range rarity is the appropriate metric, as we explain at the beginning of the paragraph that "Range rarity hotspots harbor many species not occurring anywhere else...". + +Comment: L144: The manuscript notes that "We find that the concentration of butterfly diversity in mountains substantially exceeds that of almost all globally studied taxa". However, isn't this simply because other insects haven't been assessed? In other words, it's not surprising this is the case given that most other globally studied animal taxa are vertebrates. + +Response: The phrase "studied taxa" specifies our claim to addressing globally assessed taxa and avoiding speculation about all taxa. To clarify this, we have now rephrased the sentence to "taxa that have been globally studied to date". Please note that we included ants in the respective analysis. + +Comment: L627. Do the authors mean "across latitude" rather than "in space" in the figure caption? Fig.1 | Global variation in butterfly diversity in space and along elevation + +Response: The intention was to collectively title the map (spanning longitude and latitude) and surface- plots (spanning elevation and latitude). We now specify "across latitude". + +<--- Page Split ---> + +## General comment: + +Reviewer #2 (Remarks to the Author): + +This nice study investigates the spatial structure of butterfly diversity across the globe using an impressive variety of sources and methods. To keep myself accountable, and to make it easier for the authors to confirm that I understood their methodology, I below attempt to summarize this (quite major) study. + +With descending order of priority, the authors use species distribution models (based on occurrence records), expert range maps, and ecoregional range maps (grouping areas by their similarity in ecologically relevant variables) to infer biodiversity at a \(110\mathrm{km}\times 110\mathrm{km}\) spatial resolution. The authors also use three biodiversity metrics: species richness (number of species in a cell), average range rarity (the average of the inverse global ranges for the species in a cell), and phylogenetic diversity (calculated as deviations from a null model — is there more spatial phylogenetic structure than expected by chance?). + +The authors identify discrepancies between the different diversity metrics, indicating that one cannot be substituted for another without loss of information. However, the general conclusion is — perhaps unsurprisingly to most — that tropical and subtropical regions are most diverse, but more importantly also that mountainous regions have disproportionately diverse and rare butterfly communities (even in contrast with other taxa). This pattern, while ecologically interesting in its own right, carries with it dire implications for global butterfly diversity in a warmer future, due to the local nature of elevational temperature gradients. To make an analogy for butterflies limited to high elevations in the tropics: the mountains are cool islands in a dangerously warm ocean, and water levels are rising. With no other land in sight, the butterflies have nowhere to go. + +It's unclear from the paper whether loss of high- altitude butterfly diversity in the tropics generally comes with any socio- economic costs related to, for instance, ecosystem services, but from a global biodiversity- perspective the findings of this (very comprehensive) study in the present study are potentially alarming. Additionally, butterflies are quite charismatic and well- liked animals. Therefore, I believe this paper is broadly interesting to biologists, and the theme suitable for Nature Ecology & Evolution. + +General response: Thank you for the constructive feedback. + +Comment: However, I still have some reservations regarding the manuscript's suitability for publication in its current state. These mostly relate to the writing and the storytelling. First, the writing could be clearer (see some examples in the line- by- line comments below). Second, when reading the manuscript, it is not immediately clear what the take- home messages are regarding the actual biology. In its present form, the manuscript is largely descriptive (butterflies are here and there), and the brief sentences about the biology of butterflies seem quite ad hoc. The authors appear not particularly interested in butterflies, but rather the nice resources + +<--- Page Split ---> + +available for quantifying their distributions. That is of course completely fine, but in this case, the biological reasons for why the patterns described in this study are exaggerated in butterflies might carry crucial information for future conservation efforts, or at least projections. Indeed, after identifying global patterns of biodiversity in butterflies, it would be very nice if the authors could dive into some potential biological explanations for why butterfly diversity/rarity stand out as particularly concentrated at high elevations. Then, the findings in the study, and the massive amount of work put into quantifying butterfly diversity globally, could give broader insights into what other organism groups might be threatened. Personally, I think the story would be more coherent if it was structured, at least to some extent, like this: + +Biology (what traits make butterflies special) - > Biodiversity patterns (what spatial distributions do these traits correlate with) - > Threat levels (what does a warm future hold in store for species with these spatial distributions) - > Biology (what other organisms fall into the same category). + +I don't want to micromanage how the paper is written, and I am sure there are many ways to shape the findings in this paper into a nice story. But I do think that the manuscript's quality would improve drastically if the writing was just a bit more coherent. This is particularly important given the complex analyses in the study. + +Response: Thank you for these helpful suggestions. Our revised article now mostly follows the structure you proposed, except that "what other organisms fall into the same category" appears earlier to highlight the importance of mountains, even among ecotherms. We've revised the hypothesis presentation, which was initially detailed throughout the results and discussion. Despite some redundancy, this addition strengthens the study's foundation and clarifies the aims now already in the introduction (L53- 65). The aims of the study are now followed by a description of butterfly traits that explain: 1) the critical role of mountains in their diversity, 2) the relatively high overlap with other ectotherms and plants compared to endotherms, and 3) the temperature- driven erosion of hotspots for butterfly diversity. Given the mixed evidence for point (2), we address the implications for other organisms later in the discussion. Specifically, for insect taxa closely tied to plants, we anticipate severe losses of species richness and phylogenetic diversity in mountain areas due to global warming. + +## Comment: Specific comments: + +Title: I think the title could be a bit more precise, to highlight the implications of the study (e.g. "Global hotspots of butterfly biodiversity are threatened in a warming world"). + +Response: Thank you. We changed the title as per your suggestion. + +Comment: Abstract: At line 6- 7, "their [the butterflies'] diversity and threat" sounds wrong (particularly the threat part). I suggest really describing why lines 13- 15 are true. That is, explain in some way that living on a mountain makes it hard to shift the geographical range to track a changing climate in the long run. This is perhaps somewhat obvious, but it could help make the message clearer. + +Response: Thank you for this detailed suggestion. The sentence now reads: "Here we use butterflies as a global model insect system" and uncover a remarkable concentration of their diversity in rare and rapidly shrinking high- elevation climates." + +<--- Page Split ---> + +Comment: Lines 24- 28: The last section of the paragraph is a bit unclear. What does "heterogeneous representation" mean in this context? "Cause and consequence" of what exactly? I think I get the idea but wording could be more precise. + +Response: We simplified and clarified this statement. The sentence now reads: "Recent work has highlighted the range of implications arising from an uneven geographic distribution of biodiversity, such as vast differences in countries' conservation responsibilities" and the biodiversity coverage of their protected areas \(^{15,16}\) ." + +Comment: Line 29: Extends from what to what? + +Response: We removed this sentence. + +Comment: Lines 38- 40: Which recognized differences? + +Response: We clarified our statement. It now reads: "These recognized limitations in our understanding of insect diversity patterns exemplify the precarious foundation of the current knowledgebase for global biodiversity conservation at large scales and leave insect biodiversity poorly represented." + +Comment: Line 44: "their own isolation" seems to me like a somewhat awkward phrase here. + +Response: Adapted removing the word "own". + +Comment: Line 53- 54: Is it really the butterflies' information? + +Response: We substantially revised the respective paragraph and avoided this phrasing. + +Comment: Line 149- 151: Perhaps diapause would be good to mention here? + +Response: Thank you for this helpful suggestion! We extended the statement to include the commonness of pre- reproductive cold- diapause in butterflies as an additional adaptation to high- elevation climate, supporting their exceptionally high diversity in mountains. We added new references to support this argument. + +Comment: Figure 2: Legends are not entirely clear (e.g., the color of the bars in the bar plots are not described explicitly). + +Response: The meaning of color of the bars is now both given visually in the legend in the lower left corner (colors of the labels PD, SR, RR and Any) and described in the legend. + +Comment: Figure 6: Legends/figures need to be clearer. As it stands, the meaning is quite difficult to extract from the figure. + +<--- Page Split ---> + +Response: We now include the temperature differences as (a) in this plot to clarify the connection between temperature differences and temperature niche loss estimates for hotspots in (d). We also revised the caption to support the legend and extended the conclusion statement for this figure to clarify the meaning of these results. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## General comment: + +Reviewer #1: + +Remarks to the Author: + +The work is of broad interest and is novel in providing a global assessment of butterfly species rarity and diversity. The authors have thoughtfully responded to all concerns and added additional analyses that strengthen the manuscript. + +General response: Thank you very much for all the time you have invested to improve the manuscript. We are happy that we could address your concerns. + +## General comment: + +Reviewer #2: + +Remarks to the Author: + +The writing is much improved, which makes the manuscript easier to read, and thus more impactful. I still have some suggestions that I think will improve the manuscript, which I hope that the authors will consider and appreciate. I probably missed some parts, so I recommend the authors to carefully read through their manuscript and fix language/sentence structure errors before resubmitting—perhaps with help of a native English speaker. Still, I am generally pleased with the revisions. + +General response: We are deeply grateful for the time you have invested. Your explicit comments and the additional context were very helpful! + +## Comment: + +Line- by- line: + +4: Remove "in decline and". + +Response: Done. + +Comment: 7: "their" -> "butterfly". + +Response: Done. + +Comment: 21: "the prerequisite" -> "a prerequisite". + +Response: Done. + +Comment: 27: "documented and safeguarded" -> "prioritized"? + +<--- Page Split ---> + +Response: Done. + +Comment: 41: Unclear what "takes on an additional weight" really means. + +Response: Adapted to "...becomes an even greater challenge..." + +Comment: 43: Consider using semi- colon (;) after "mountains" to make "their" in the follow sentence more clear. + +Response: Done. + +Comment: 44: Remove "their". + +Response: Done. + +Comment: 49- 51: What about the ant work in Science Advances? This sentence is not needed, we see the importance of this work without it. + +Response: The Science Advances article on ants does not address climate change. Note that we highlight it later in terms of existing work on global diversity patterns. + +Comment: 57: "Highly adapted" does not sit right with me. I would not say that their traits are "more" adapted than other species". Perhaps "Owing to distinct...". + +Response: Done as suggested. + +Comment: 57- 59: I think https://doi.org/10.1038/s41467- 023- 39359- 8 would be a good additional reference here (regarding thermal niches). + +Response: This is an interesting read and good fit. However, with five references we feel this statement is already sufficiently supported. Note that we added one of your other suggestions to make efficient use of the included references. + +Comment: 59: What does separately mean here? + +Response: The sentence now starts with "In addition..." + +Comment: 61- 65: I think these two sentences could be written more clearly. + +Response: We now write: "These characteristics suggest that patterns in butterfly diversity differ strongly from those of terrestrial vertebrates, challenging the effectiveness of existing conservation priorities, which have been largely based on vertebrate taxa. Adaptations to cold climates and host plant diversity likely also support high concentrations of butterfly diversity in mountain systems41- 43, implying dire consequences under global warming." + +<--- Page Split ---> + +Comment: 76: Remove "and" and "are". + +Response: Done. + +Comment: 92: "...the previously argued" sounds a bit strange to me. What about "previous findings on hotspots of deep ..."? Or something else. + +Response: Done as suggested. + +Comment: 101- 102: "Within ectotherm taxa" makes it seem like ectotherms are a monophyletic group somehow. Perhaps just remove, works without it. + +Response: Adapted to "Among ectothermic taxa..." + +Comment: 104- 105: What "known co- evolutionary association"? Change sentence structure. + +Response: Done. + +Comment: 138- 140: Possesses -> possess. Also, I think the point here is: why would insects be especially diverse in mountainous regions? I could see the point that insects have general adaptations (e.g., diapause — more so than other groups, where such adaptations appear more specialized) that allows them to endure prolonged periods of inhospitable cold conditions. If I'm right with what you are implying, perhaps the sentence could be changed to more clearly reflect this? E.g.: + +"In addition, many insects possess general physiological adaptations for enduring inhospitable cold conditions, potentially acting as pre- adaptations for colonizing mountainous regions in the first place." + +Here are three more generally relevant references for this: + +https://doi.org/10.1016/j.jinsphys.2005.09.008 + +https://isbnsearch.org/isbn/9780195036350 + +https://doi.org/10.1073/pnas.2407057121 + +Response: Rephrased to "In addition, many insects possess general physiological adaptations for enduring inhospitable cold conditions, potentially acting as pre- adaptations for colonizing mountainous regions." + +Note that we want to cover a range of adaptations with these references (now six). Two of them are on diapause. This now included the first reference you suggested. + +Comment: 145: "odd" -> "odds". + +Response: Adapted to "odds ratio". Here and throughout the text. + +<--- Page Split ---> + +Comment: 156: Remove average? Or write, "On average, toward higher ...". + +Response: Removed. + +Comment: 161: See previous refs. + +Response: With two references we feel this statement is sufficiently supported. + +Comment: 198: Replace "for instance" with "either" for better structure? + +Response: Done. + +Comment: 206: "As a next step". + +Response: Done as suggested. + +Comment: 208- 212: Revise sentence structure. + +Response: We have split this long sentence and rephrased the second part. We now write: "Insights on species- specific dispersal constraints will be particularly helpful in the case of island endemics (e.g. range rarity hotspots in Australasia and Indomalaya) and in regions where the latitudinal orientation of mountain ranges hinders northward shifts (Fig. 6 and Extended Data Fig. 4). Such additional constraints would imply yet greater niche losses than estimated here." + +Comment: 215- 216: Revise sentence. Avoid "their" before mentioning what you are talking about. Also, this should probably be referenced: + +https://doi.org/10.1002/ecm.1553 + +Response: Done. Thank you for highlighting this. We appreciate the additional reference and include it. + +Comment: 218: "unusually strongly exposed" -> "exceptionally susceptible". + +Response: Done. + +Comment: 219: "that" -> ", which". + +Response: Done. + +Comment: 220- 221: "this species group yet" -> "butterflies". + +Response: Done. + +<--- Page Split ---> + +Comment: 221- 222: "due to their geographically rare and isolated environmental conditions are now bound to become ecological dead ends" -> "but might become ecological dead ends in a warmer future". + +Response: Done as suggested. + +Comment: 223- 224: "mountain areas where identified rarity and threat most strongly coincide" -> "threatened mountain areas". + +Response: Rephrased to: "...in mountain regions where climate change poses a significant threat to biodiversity." + +Comment: 224: Consider replacing "sound a clarion call". Might be a darling that is better off killed. "Strongly emphasize the need" or something else typically boring might be more suitable" + +Response: Rephrased to "...highlight the need...". + +Comment: Middle of figure legend 2: Change to "mountains" to "mountains (full bars)", and "odd" to "odds". + +Response: Done. + +Comment: Beginning of figure legend 5: Change "mountains" to "mountains (full bars)". Also, shouldn't the y- label be "mountain/non- mountain"? the meaning of these results. + +Response: Adapted. + +<--- Page Split ---> diff --git a/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6b4d66f487783039a5ff36d2865810f4d039ac41 --- /dev/null +++ b/peer_reviews/5807ae0bbde3619b85fd2720c5a4461e6479b4c81f02f8bd580a7c0500d43dd7/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,849 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 297, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 161, 848, 210]]<|/det|> +# Global hotspots of butterfly diversity are threatened in a warming world + +<|ref|>text<|/ref|><|det|>[[73, 224, 424, 240]]<|/det|> +Corresponding Author: Dr Stefan Pinkert + +<|ref|>text<|/ref|><|det|>[[73, 275, 145, 288]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 301, 182, 315]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 327, 866, 341]]<|/det|> +\*Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. + +<|ref|>text<|/ref|><|det|>[[73, 354, 185, 367]]<|/det|> +Dear Dr Pinkert, + +<|ref|>text<|/ref|><|det|>[[72, 379, 920, 432]]<|/det|> +Thank you for your patience while your manuscript entitled "Global hotspots of butterfly diversity in a warming world" was under review. As you will see from the reports below, the reviewers find your work of considerable potential interest but have raised quite substantial points that must be addressed. We would like to see a revised manuscript that addresses these concerns. + +<|ref|>text<|/ref|><|det|>[[72, 444, 908, 498]]<|/det|> +We hope you will find the reviewers' comments useful as you decide how to proceed. We expect the revision to include additional work to strengthen the niche erosion projection component (see Reviewer 1's comments). Please also consider whether Reviewer 1's point on the interpretation of the elevational patterns warrants supplementary analyses using local altitude instead of elevation above sea level. + +<|ref|>text<|/ref|><|det|>[[70, 509, 907, 538]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Please do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[73, 549, 257, 563]]<|/det|> +If revising your manuscript: + +<|ref|>text<|/ref|><|det|>[[72, 575, 895, 615]]<|/det|> +\* Include a "Response to reviewers" document detailing, point- by- point, how you addressed each referee comment. If no action was taken to address a point, you must provide a compelling argument. This response will be sent back to the referees along with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 626, 615, 641]]<|/det|> +\* Provide the manuscript file in Microsoft Word format and highlight all changes. + +<|ref|>text<|/ref|><|det|>[[70, 652, 920, 680]]<|/det|> +\* If you have not done so already we suggest that you begin to revise your manuscript so that it conforms to our Article format instructions at http://www.nature.com/natecolevol/info/final- submission. Refer also to any guidelines provided in this letter. + +<|ref|>text<|/ref|><|det|>[[70, 692, 920, 720]]<|/det|> +\* Include a revised version of any required reporting checklist. It will be available to referees (and, potentially, statisticians) to aid in their evaluation if the manuscript goes back for peer review. A revised checklist is essential for re- review of the paper. + +<|ref|>text<|/ref|><|det|>[[73, 731, 431, 745]]<|/det|> +Please use the link below to submit a revised paper: + +<|ref|>text<|/ref|><|det|>[[73, 757, 175, 770]]<|/det|> +Link Redacted + +<|ref|>text<|/ref|><|det|>[[72, 782, 883, 824]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[72, 835, 920, 875]]<|/det|> +We hope to receive the revised manuscript within 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Ecology & Evolution or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[72, 886, 910, 940]]<|/det|> +Nature Ecology & Evolution is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 913, 88]]<|/det|> +attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[70, 99, 868, 114]]<|/det|> +Please do not hesitate to contact me if you have any questions or would like to discuss the required revisions further. + +<|ref|>text<|/ref|><|det|>[[73, 125, 415, 140]]<|/det|> +Thank you for the opportunity to review your work. + +<|ref|>text<|/ref|><|det|>[[73, 152, 143, 166]]<|/det|> +[redacted] + +<|ref|>text<|/ref|><|det|>[[73, 203, 230, 216]]<|/det|> +Reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[73, 229, 333, 243]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 255, 921, 333]]<|/det|> +There are many strengths to the manuscript related to global hotspots of butterfly diversity. Understanding the biogeography of different taxonomic groups is important for providing an assessment of where biodiversity is located and how best to protect it. The work is novel in attempting to provide a global assessment of species diversity and rarity of butterflies. A strength is the focus on different measures to assess hotspots of diversity as well as the comparison of how these butterfly hotspots align with other taxa. The compilation of data and the distribution maps for over 12,000 species are impressive, and such databases are valuable tools for the scientific community. + +<|ref|>text<|/ref|><|det|>[[73, 345, 720, 359]]<|/det|> +There were several places where the manuscript could be improved, which are outlined below. + +<|ref|>text<|/ref|><|det|>[[72, 371, 921, 503]]<|/det|> +In general, the writing was hard to follow and/or interpret, which made the manuscript challenging to understand and greatly detracted from the main points. An example of a sentence that was hard to understand was (L98): "Given a much lesser dominance of a minority of wide- ranging species in driving range rarity and a stronger signature of idiosyncratic biogeographic histories, we expect overall weaker associations for this measure than for species richness patterns". Parts of the results were particularly hard to follow. For example, (L65) "Notably in most realms, both metrics show limited congruence, particularly for peaks in narrow- ranged species, which are usually of greatest conservation concern". After reading this several times, it's still hard to know what it means. Even some basic sentences did not flow easily. For instance, the sentence "For terrestrial vertebrates, the thus far dominant model system for global ecology and conservation, prior work has documented..." is too complex and could be simplified. Similarly, (L175) "Butterfly hotspot temperature niche loss ranges from..." is also too complex. + +<|ref|>text<|/ref|><|det|>[[72, 515, 920, 569]]<|/det|> +The assessment of niche erosion was not well integrated into the manuscript and was rather simplistic. It doesn't account for movement of butterflies. The temperatures are rather course and do not include microclimates that insects often use to modify body temperatures. These issues call into question the conclusion that mountains would be (L186) "traps for butterfly biodiversity". + +<|ref|>text<|/ref|><|det|>[[72, 580, 920, 635]]<|/det|> +Some of the novelty is overstated. The finding that mountains are butterfly hotspots is not particularly novel; butterfly diversity is known to be especially high in montane areas, which is likely due to the change in temperature and vegetation across elevation. Similarly, it's not surprising that species richness of butterflies is positively associated with other taxa as we tend to see general trends in diversity across different groups. + +<|ref|>text<|/ref|><|det|>[[72, 646, 920, 687]]<|/det|> +The interpretation of the overlap in diversity centers of butterflies with those of ants doesn't quite fit with the values presented in the manuscript. (L11): with regards to "Only a small portion (14%- 54%...", those percentages are not really a "small portion". + +<|ref|>text<|/ref|><|det|>[[72, 698, 911, 765]]<|/det|> +L61- 62: Higher elevation is relative, and 2500 m is a mid- elevation in many places. The manuscript is suggesting richness increases with elevation based on how it is written, but this sounds more like a mid- elevation peak, which is common in many taxa. More broadly, it seems there could be issues identifying peaks in abundance across elevation given the course resolution of the distribution data. A 10 km- resolution could contain a broad range of elevations. Could this skew ranges to higher elevations in topographically complex landscapes? + +<|ref|>text<|/ref|><|det|>[[70, 789, 915, 816]]<|/det|> +L113: Under "range rarity", the text shifts to discussing diversity (i.e. "Even stronger cross- taxon mismatches emerge when comparing the top 5% diversity centers per realm and taxon."), which is confusing. Is this referring to phylogenetic diversity? + +<|ref|>text<|/ref|><|det|>[[72, 827, 921, 880]]<|/det|> +L120: The manuscript notes that "These results indicate that priority areas identified based on vertebrates miss critical places needed to safeguard the diversity of insects", however, isn't this statement based on range rarity (a measure of endemism) rather than species diversity per se? It seems that a better measure of safeguarding diversity of insects should be focused on species richness, not simply endemism. + +<|ref|>text<|/ref|><|det|>[[72, 892, 920, 933]]<|/det|> +L144: The manuscript notes that "We find that the concentration of butterfly diversity in mountains substantially exceeds that of almost all globally studied taxa". However, isn't this simply because other insects haven't been assessed? In other words, it's not surprising this is the case given that most other globally studied animal taxa are vertebrates. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 910, 75]]<|/det|> +L 627. Do the authors mean "across latitude" rather than "in space" in the figure caption? Fig.1 | Global variation in butterfly diversity in space and along elevation + +<|ref|>text<|/ref|><|det|>[[74, 98, 333, 113]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[73, 124, 920, 167]]<|/det|> +This nice study investigates the spatial structure of butterfly diversity across the globe using an impressive variety of sources and methods. To keep myself accountable, and to make it easier for the authors to confirm that I understood their methodology, I below attempt to summarize this (quite major) study. + +<|ref|>text<|/ref|><|det|>[[73, 177, 915, 257]]<|/det|> +With descending order of priority, the authors use species distribution models (based on occurrence records), expert range maps, and ecoregional range maps (grouping areas by their similarity in ecologically relevant variables) to infer biodiversity at a \(110\mathrm{km}\times 110\mathrm{km}\) spatial resolution. The authors also use three biodiversity metrics: species richness (number of species in a cell), average range rarity (the average of the inverse global ranges for the species in a cell), and phylogenetic diversity (calculated as deviations from a null model—is there more spatial phylogenetic structure than expected by chance?). + +<|ref|>text<|/ref|><|det|>[[72, 267, 920, 374]]<|/det|> +The authors identify discrepancies between the different diversity metrics, indicating that one cannot be substituted for another without loss of information. However, the general conclusion is—perhaps unsurprisingly to most—that tropical and subtropical regions are most diverse, but more importantly also that mountainous regions have disproportionately diverse and rare butterfly communities (even in contrast with other taxa). This pattern, while ecologically interesting in its own right, carries with it dire implications for global butterfly diversity in a warmer future, due to the local nature of elevational temperature gradients. To make an analogy for butterflies limited to high elevations in the tropics: the mountains are cool islands in a dangerously warm ocean, and water levels are rising. With no other land in sight, the butterflies have nowhere to go. + +<|ref|>text<|/ref|><|det|>[[72, 384, 910, 452]]<|/det|> +It's unclear from the paper whether loss of high- altitude butterfly diversity in the tropics generally comes with any socioeconomic costs related to, for instance, ecosystem services, but from a global biodiversity- perspective the findings of this (very comprehensive) study in the present study are potentially alarming. Additionally, butterflies are quite charismatic and well- liked animals. Therefore, I believe this paper is broadly interesting to biologists, and the theme suitable for Nature Ecology & Evolution. + +<|ref|>text<|/ref|><|det|>[[71, 462, 923, 620]]<|/det|> +However, I still have some reservations regarding the manuscript's suitability for publication in its current state. These mostly relate to the writing and the storytelling. First, the writing could be clearer (see some examples in the line- by- line comments below). Second, when reading the manuscript, it is not immediately clear what the take- home messages are regarding the actual biology. In its present form, the manuscript is largely descriptive (butterflies are here and there), and the brief sentences about the biology of butterflies seem quite ad hoc. The authors appear not particularly interested in butterflies, but rather the nice resources available for quantifying their distributions. That is of course completely fine, but in this case, the biological reasons for why the patterns described in this study are exaggerated in butterflies might carry crucial information for future conservation efforts, or at least projections. Indeed, after identifying global patterns of biodiversity in butterflies, it would be very nice if the authors could dive into some potential biological explanations for why butterfly diversity/rarity stand out as particularly concentrated at high elevations. Then, the findings in the study, and the massive amount of work put into quantifying butterfly diversity globally, could give broader insights into what other organism groups might be threatened. Personally, I think the story would be more coherent if it was structured, at least to some extent, like this: + +<|ref|>text<|/ref|><|det|>[[72, 630, 916, 673]]<|/det|> +Biology (what traits make butterflies special) \(\rightharpoonup\) Biodiversity patterns (what spatial distributions do these traits correlate with) \(\rightharpoonup\) Threat levels (what does a warm future hold in store for species with these spatial distributions) \(\rightharpoonup\) Biology (what other organisms fall into the same category). + +<|ref|>text<|/ref|><|det|>[[72, 683, 917, 725]]<|/det|> +I don't want to micromanage how the paper is written, and I am sure there are many ways to shape the findings in this paper into a nice story. But I do think that the manuscript's quality would improve drastically if the writing was just a bit more coherent. This is particularly important given the complex analyses in the study. + +<|ref|>sub_title<|/ref|><|det|>[[72, 749, 208, 763]]<|/det|> +## Specific comments: + +<|ref|>text<|/ref|><|det|>[[72, 774, 900, 804]]<|/det|> +Title: I think the title could be a bit more precise, to highlight the implications of the study (e.g. "Global hotspots of butterfly biodiversity are threatened in a warming world"). + +<|ref|>text<|/ref|><|det|>[[72, 814, 900, 868]]<|/det|> +Abstract: At line 6- 7, "their [the butterflies'] diversity and threat" sounds wrong (particularly the threat part). I suggest really describing why lines 13- 15 are true. That is, explain in some way that living on a mountain makes it hard to shift the geographical range to track a changing climate in the long run. This is perhaps somewhat obvious, but it could help make the message clearer. + +<|ref|>text<|/ref|><|det|>[[70, 878, 885, 908]]<|/det|> +Lines 24- 28: The last section of the paragraph is a bit unclear. What does "heterogeneous representation" mean in this context? "Cause and consequence" of what exactly? I think I get the idea but wording could be more precise. + +<|ref|>text<|/ref|><|det|>[[72, 918, 323, 933]]<|/det|> +Line 29: Extends from what to what? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 377, 60]]<|/det|> +Lines 38- 40: Which recognized differences? + +<|ref|>text<|/ref|><|det|>[[73, 72, 633, 87]]<|/det|> +Line 44: "their own isolation" seems to me like a somewhat awkward phrase here. + +<|ref|>text<|/ref|><|det|>[[73, 99, 411, 113]]<|/det|> +Line 53- 54: Is it really the butterflies' information? + +<|ref|>text<|/ref|><|det|>[[73, 125, 525, 140]]<|/det|> +Line 149- 151: Perhaps diapause would be good to mention here? + +<|ref|>text<|/ref|><|det|>[[73, 151, 820, 166]]<|/det|> +Figure 2: Legends are not entirely clear (e.g., the color of the bars in the bar plots are not described explicitly). + +<|ref|>text<|/ref|><|det|>[[73, 177, 835, 192]]<|/det|> +Figure 6: Legends/figures need to be clearer. As it stands, the meaning is quite difficult to extract from the figure. + +<|ref|>text<|/ref|><|det|>[[73, 204, 144, 217]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 230, 183, 243]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[73, 255, 203, 269]]<|/det|> +14th January 2025 + +<|ref|>text<|/ref|><|det|>[[73, 282, 161, 296]]<|/det|> +Dear Stefan, + +<|ref|>text<|/ref|><|det|>[[72, 307, 920, 360]]<|/det|> +Thank you for submitting your revised manuscript "Global hotspots of butterfly diversity are threatened in a warming world" (NATECOLEVOL- 24061491A). Based on the reviewers' comments (copied below), we'll be happy in principle to publish it in Nature Ecology & Evolution, pending minor revisions to satisfy the reviewers' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[72, 371, 900, 411]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[72, 422, 875, 450]]<|/det|> +Thank you again for your interest in Nature Ecology & Evolution. Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[72, 462, 143, 476]]<|/det|> +[redacted] + +<|ref|>text<|/ref|><|det|>[[73, 501, 333, 515]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 527, 881, 555]]<|/det|> +The work is of broad interest and is novel in providing a global assessment of butterfly species rarity and diversity. The authors have thoughtfully responded to all concerns and added additional analyses that strengthen the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 579, 333, 593]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 605, 900, 672]]<|/det|> +The writing is much improved, which makes the manuscript easier to read, and thus more impactful. I still have some suggestions that I think will improve the manuscript, which I hope that the authors will consider and appreciate. I probably missed some parts, so I recommend the authors to carefully read through their manuscript and fix language/sentence structure errors before resubmitting—perhaps with help of a native English speaker. Still, I am generally pleased with the revisions. + +<|ref|>text<|/ref|><|det|>[[72, 685, 160, 698]]<|/det|> +Line- by- line: + +<|ref|>text<|/ref|><|det|>[[72, 710, 211, 723]]<|/det|> +4: Remove "in decline and". + +<|ref|>text<|/ref|><|det|>[[72, 724, 220, 736]]<|/det|> +7: "their" -> "butterfly". + +<|ref|>text<|/ref|><|det|>[[72, 737, 350, 750]]<|/det|> +21: "the prerequisite" -> "a prerequisite". + +<|ref|>text<|/ref|><|det|>[[72, 750, 422, 763]]<|/det|> +27: "documented and safeguarded" -> "prioritized"? + +<|ref|>text<|/ref|><|det|>[[72, 763, 504, 776]]<|/det|> +41: Unclear what "takes on an additional weight" really means. + +<|ref|>text<|/ref|><|det|>[[72, 777, 756, 790]]<|/det|> +43: Consider using semi- colon (;) after "mountains" to make "their" in the follow sentence more clear. + +<|ref|>text<|/ref|><|det|>[[72, 791, 202, 802]]<|/det|> +44: Remove "their". + +<|ref|>text<|/ref|><|det|>[[72, 803, 890, 828]]<|/det|> +49- 51: What about the ant work in Science Advances? This sentence is not needed, we see the importance of this work without it. + +<|ref|>text<|/ref|><|det|>[[72, 828, 870, 855]]<|/det|> +57: "Highly adapted" does not sit right with me. I would not say that their traits are "more" adapted than other species'. Perhaps "Owing to distinct...". + +<|ref|>text<|/ref|><|det|>[[72, 855, 890, 881]]<|/det|> +57- 59: I think https://doi.org/10.1038/s41467- 023- 39359- 8 would be a good additional reference here (regarding thermal niches). + +<|ref|>text<|/ref|><|det|>[[72, 881, 336, 893]]<|/det|> +59: What does separately mean here? + +<|ref|>text<|/ref|><|det|>[[72, 894, 512, 907]]<|/det|> +61- 65: I think these two sentences could be written more clearly. + +<|ref|>text<|/ref|><|det|>[[72, 908, 264, 920]]<|/det|> +76: Remove "and" and "are". + +<|ref|>text<|/ref|><|det|>[[70, 920, 866, 946]]<|/det|> +92: "... the previously argued" sounds a bit strange to me. What about "previous findings on hotspots of deep ..."? Or something else. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 911, 75]]<|/det|> +101- 102: "Within ectotherm taxa" makes it seem like ectotherms are a monophyletic group somehow. Perhaps just remove, works without it. + +<|ref|>text<|/ref|><|det|>[[72, 73, 627, 88]]<|/det|> +104- 105: What "known co- evolutionary association"? Change sentence structure. + +<|ref|>text<|/ref|><|det|>[[72, 87, 912, 140]]<|/det|> +138- 140: Possesses -> possess. Also, I think the point here is: why would insects be especially diverse in mountainous regions? I could see the point that insects have general adaptations (e.g., diapause - more so than other groups, where such adaptations appear more specialized) that allows them to endure prolonged periods of inhospitable cold conditions. If I'm right with what you are implying, perhaps the sentence could be changed to more clearly reflect this? E.g.: + +<|ref|>text<|/ref|><|det|>[[72, 139, 910, 167]]<|/det|> +"In addition, many insects possess general physiological adaptations for enduring inhospitable cold conditions, potentially acting as pre- adaptations for colonizing mountainous regions in the first place." + +<|ref|>text<|/ref|><|det|>[[72, 167, 470, 180]]<|/det|> +Here are three more generally relevant references for this: + +<|ref|>text<|/ref|><|det|>[[72, 180, 384, 193]]<|/det|> +https://doi.org/10.1016/j.jinsphys.2005.09.008 + +<|ref|>text<|/ref|><|det|>[[72, 193, 370, 206]]<|/det|> +https://isbnsearch.org/isbn/9780195036350 + +<|ref|>text<|/ref|><|det|>[[72, 206, 355, 219]]<|/det|> +https://doi.org/10.1073/pnas.2407057121 + +<|ref|>text<|/ref|><|det|>[[72, 220, 214, 232]]<|/det|> +145: "odd" -> "odds". + +<|ref|>text<|/ref|><|det|>[[72, 232, 515, 245]]<|/det|> +156: Remove average? Or write, "On average, toward higher ...". + +<|ref|>text<|/ref|><|det|>[[72, 245, 230, 257]]<|/det|> +161: See previous refs. + +<|ref|>text<|/ref|><|det|>[[72, 258, 481, 271]]<|/det|> +198: Replace "for instance" with "either" for better structure? + +<|ref|>text<|/ref|><|det|>[[72, 272, 216, 284]]<|/det|> +206: "As a next step". + +<|ref|>text<|/ref|><|det|>[[72, 285, 325, 297]]<|/det|> +208- 212: Revise sentence structure. + +<|ref|>text<|/ref|><|det|>[[72, 297, 866, 323]]<|/det|> +215- 216: Revise sentence. Avoid "their" before mentioning what you are talking about. Also, this should probably be referenced: + +<|ref|>text<|/ref|><|det|>[[72, 323, 300, 336]]<|/det|> +https://doi.org/10.1002/ecm.1553 + +<|ref|>text<|/ref|><|det|>[[72, 336, 515, 349]]<|/det|> +218: "unusually strongly exposed" -> "exceptionally susceptible". + +<|ref|>text<|/ref|><|det|>[[72, 349, 225, 362]]<|/det|> +219: "that" -> "which". + +<|ref|>text<|/ref|><|det|>[[72, 362, 400, 375]]<|/det|> +220- 221: "this species group yet" -> "butterflies". + +<|ref|>text<|/ref|><|det|>[[72, 375, 916, 401]]<|/det|> +221- 222: "due to their geographically rare and isolated environmental conditions are now bound to become ecological dead ends" -> "but might become ecological dead ends in a warmer future". + +<|ref|>text<|/ref|><|det|>[[72, 400, 860, 414]]<|/det|> +223- 224: "mountain areas where identified rarity and threat most strongly coincide" -> "threatened mountain areas". + +<|ref|>text<|/ref|><|det|>[[72, 414, 901, 440]]<|/det|> +224: Consider replacing "sound a clarion call". Might be a darling that is better off killed. "Strongly emphasize the need" or something else typically boring might be more suitable". + +<|ref|>text<|/ref|><|det|>[[72, 451, 720, 465]]<|/det|> +Middle of figure legend 2: Change to "mountains" to "mountains (full bars)", and "odd" to "odds". + +<|ref|>text<|/ref|><|det|>[[72, 476, 901, 504]]<|/det|> +Beginning of figure legend 5: Change "mountains" to "mountains (full bars)". Also, shouldn't the y- label be "mountain/non- mountain"? + +<|ref|>text<|/ref|><|det|>[[72, 844, 916, 897]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 897, 796, 911]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 911, 896, 937]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 910, 88]]<|/det|> +license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[88, 185, 233, 196]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[88, 204, 207, 215]]<|/det|> +## General comment: + +<|ref|>text<|/ref|><|det|>[[88, 224, 310, 235]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[88, 265, 655, 368]]<|/det|> +There are many strengths to the manuscript related to global hotspots of butterfly diversity. Understanding the biogeography of different taxonomic groups is important for providing an assessment of where biodiversity is located and how best to protect it. The work is novel in attempting to provide a global assessment of species diversity and rarity of butterflies. A strength is the focus on different measures to assess hotspots of diversity as well as the comparison of how these butterfly hotspots align with other taxa. The compilation of data and the distribution maps for over 12,000 species are impressive, and such databases are valuable tools for the scientific community. + +<|ref|>text<|/ref|><|det|>[[88, 395, 653, 407]]<|/det|> +There were several places where the manuscript could be improved, which are outlined below. + +<|ref|>text<|/ref|><|det|>[[88, 415, 600, 440]]<|/det|> +General response: Thank you very much for the helpful and detailed suggestions that strengthened our article both in terms of clarity and robustness of the results. + +<|ref|>text<|/ref|><|det|>[[88, 468, 660, 544]]<|/det|> +In general, the writing was hard to follow and/or interpret, which made the manuscript challenging to understand and greatly detracted from the main points. An example of a sentence that was hard to understand was (L98): "Given a much lesser dominance of a minority of wide- ranging species in driving range rarity and a stronger signature of idiosyncratic biogeographic histories, we expect overall weaker associations for this measure than for species richness patterns". + +<|ref|>text<|/ref|><|det|>[[87, 553, 660, 579]]<|/det|> +Response: We apologize for the complex writing style and carefully revised this sentence (L106- 108) and many other parts of the text to improve clarity. + +<|ref|>text<|/ref|><|det|>[[88, 606, 650, 657]]<|/det|> +Comment: Parts of the results were particularly hard to follow. For example, (L65) "Notably in most realms, both metrics show limited congruence, particularly for peaks in narrow- ranged species, which are usually of greatest conservation concern". After reading this several times, it's still hard to know what it means. + +<|ref|>text<|/ref|><|det|>[[87, 666, 660, 691]]<|/det|> +Response: We agree that several sentences including this one were hard to follow. Accordingly, we revised this sentence and the following sentence to improve clarity (L69- 81). + +<|ref|>text<|/ref|><|det|>[[87, 719, 661, 757]]<|/det|> +Comment: Even some basic sentences did not flow easily. For instance, the sentence "For terrestrial vertebrates, the thus far dominant model system for global ecology and conservation, prior work has documented..." is too complex and could be simplified. + +<|ref|>text<|/ref|><|det|>[[87, 765, 648, 789]]<|/det|> +Response: Many thanks. We simplified this sentence and revised parts of the paragraph (L28- 40). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 185, 641, 211]]<|/det|> +Comment: Similarly, (L175) "Butterfly hotspot temperature niche loss ranges from..." is also too complex. + +<|ref|>text<|/ref|><|det|>[[87, 219, 664, 272]]<|/det|> +Response: We simplified this sentence. It now reads: "Temperature niche loss ranged from \(6\%\) to \(64\%\) across realms and diversity aspects, with generally greater losses for hotspots of butterfly PD and species richness than for rare rarity hotspots (global mean: \(33\% > 31\% > 11\%\) ; Fig. 6a, Extended Data Fig. 4)." + +<|ref|>text<|/ref|><|det|>[[87, 298, 652, 362]]<|/det|> +Comment: The assessment of niche erosion was not well integrated into the manuscript and was rather simplistic. It doesn't account for movement of butterflies. The temperatures are rather course and do not include microclimates that insects often use to modify body temperatures. These issues call into question the conclusion that mountains would be (L186) "traps for butterfly biodiversity". + +<|ref|>text<|/ref|><|det|>[[87, 370, 661, 409]]<|/det|> +Response: Thank you for these additional considerations. We have now extended discussion of the importance of animal dispersal for interpreting climate change projections and added analyses to assess the issues of spatial analysis grain size. + +<|ref|>sub_title<|/ref|><|det|>[[88, 436, 525, 448]]<|/det|> +## 1) Extended discussion of the effects of dispersal on niche loss estimates + +<|ref|>text<|/ref|><|det|>[[87, 456, 661, 534]]<|/det|> +Our original text included discussion of the potential impact of dispersal and the challenges of incorporating in L198- 212. Current modelling approaches of future trends generally suffer from assuming either full or no dispersal. We believe our approach is more nuanced in this regard, using realm- level projections of the available temperature niche as well as contrasting losses of hotspot niches with those of random and non- hotspot cells as counterfactual. We have revised the respective paragraph, which now reads: + +<|ref|>text<|/ref|><|det|>[[87, 541, 664, 733]]<|/det|> +"Assessments of climate change impacts often neglect niche availability, for instance because they are based on absolute climate changes in focal areas \(^{51 - 63}\) , or rely on simple, binary scenarios of dispersal (i.e. full or no niche tracking) \(^{64,65}\) . We aimed to address some of these limitations by using realm- level projections of the available temperature niche and by contrasting hotspot locations with random and non- hotspot cells as counterfactual. Our results suggest that quantifying geographic niche availability is crucial for understanding threats to mountain biodiversity, due to the nuanced and gradual decline of specific temperature regimes at upslope locations following warming. These trends are mirrored by local population declines at highest elevations despite concurrent up- slope range shifts in the last decades \(^{30,66}\) . As next step, additional work is needed to gauge species- level responses. For example, more detailed data tuned to specific requirements could refine estimated availability and accessibility of habitats in the future. Insights on species- specific dispersal constraints will be particularly helpful and in the case of island endemics (e.g. range rarity hotspots in Australasia and Indomalaya) and in regions where the latitudinal orientation of mountain ranges hinders northward shifts might reveal yet greater niche losses than estimated here (Fig. 6 and Extended Data Fig. 4)." + +<|ref|>text<|/ref|><|det|>[[87, 741, 647, 820]]<|/det|> +We are uncertain if "movement" was referring to species dispersal at the macroscale or to individual movement facilitating shifts to colder microclimates within the 110 km- resolution hotspot grid cells. Latter behavior cannot be reliably incorporated into projections, as temperature may greatly vary even between open/shaded areas but in the following provide insights into the microclimatic variation and importantly its changes under projected warming between hotspots and non- hotspots. All else being equal we expect similar changes in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 185, 652, 223]]<|/det|> +microclimates at 1 km- resolution, rendering 110 km averages representative. If cold and warm cells withing a 110 km cells warm to a similar degree (no variation in changes) opportunities for the use of microclimates erode alike. + +<|ref|>text<|/ref|><|det|>[[88, 247, 480, 259]]<|/det|> +2) Additional section and analysis on grain size and niche metrics: + +<|ref|>text<|/ref|><|det|>[[87, 267, 664, 475]]<|/det|> +The reviewer indicates that especially for relatively small organisms such as butterflies coarse grains might miss climatic refugia that support survival under a changing climate. We much appreciate this point and are astutely aware of the scale- dependence of climate change assessments (e.g. Lu and Jetz, 2023 Scale- sensitivity in the measurement and interpretation of environmental niches. Trends Ecol Evol. 38:554- 67). First, we note that for the great majority of species we trained and predicted species distribution models at 1 km resolution (the finest resolution for global climate data) in way that does carry forward temperature variation at that very fine grain. It was for harmonization with expert data and for maximizing overall map accuracy that we resampled to the relatively coarse 110 km grid. We note that any "micro"- climate conditions at 1 km- resolution that support a species presence would cause a presence for that species in a 110 km cell (different to had we done the original predictions at 110 km resolution where averaging could have missed important fine- grain pockets of suitable condition). Similarly, all climate projections we used also have an original resolution of 1 km and were only subsequently aggregated to 110 km. In our original submission, this result is based on niche overlaps calculated with 110 km cell values. To as much as reasonably feasible address the reviewer's concern we have now conducted two assessments: + +<|ref|>text<|/ref|><|det|>[[87, 482, 660, 547]]<|/det|> +To recap, the reviewer is interested in whether our projection of butterfly hotspots (of which many are in mountains) experiencing particularly high niche temperature loss might be different if the fine- grain variation of temperature was considered. We have now added a new section "Grain size and niche metrics" to our methods and address the issue with two dedicated analyses. + +<|ref|>text<|/ref|><|det|>[[87, 574, 655, 653]]<|/det|> +First, we understand that the reviewer's concern is related to a potential buffering against the projected niche erosion in areas with high topographical diversity (hotspots) and hence great fine- grain climatic variation (that would include climatic refugia with limited temperature change). To assess whether this issue could affect our overall conclusion (of greater niche loss in hotspots), we evaluate whether the fine- grain variation in projected temperature change differs strongly between hotspots vs non- hotspots. + +<|ref|>text<|/ref|><|det|>[[87, 660, 661, 787]]<|/det|> +Specifically, we evaluated the variance in the warming (temperature under rcp8.5 - current) among the 1 km pixels of hotspot cells versus those of non- hotspot cells. We find no consistent differences. Species richness and PD hotspots show slightly smaller variation than their respective non- hotspots, and the opposite is the case for range rarity hotspots. However, the differences are very small indeed (< 0.002 absolute difference in median coefficient of variation). Hence, under projected temperature changes hotspots even tend to show less buffering (less variability in 1 km- resolution temperatures) than non- hotspots. This finding supports the robustness of our overall results. We provide these results in the new Supplementary Table 3 and added a section describing the motivation and details for this analysis to the methods (L435- 447). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[86, 184, 660, 352]]<|/det|> +Second, to directly gage the sensitivity of our niche loss results to grain size, we repeated our analysis at 10 km resolution. That is, for every single one grid cell the 110 km analysis, we now use 121 cells. We find the difference between the 10 km and 110 km resolution analysis to be small. Specifically, the projected temperature niche loss across realm- level non- /hotspots was on average 5% (SR: 8%, RR: 2%, PD: 6%) lower for the 10 km- resolution than for the original 110 km- resolution results (Supplementary Table 4). Note that the niche loss in non- hotspots also decreases, although to a lesser extent than for hotspots (1% on average). The average temperature niche loss for hotspots versus non- hotspots across realms based on 10 km results was 20% and 10% for species richness, 9% and 10% for range rarity, and 22% and 10% for PD. For all realms, the higher resolution and the original 110 km- resolution results underscore greater niche loss for species richness and PD hotspots than for non- hotspots. Only for range rarity hotspots of tropical realms losses in non- hotspots became slightly greater than for their respective hotspots at the 10 km- resolution. + +<|ref|>text<|/ref|><|det|>[[86, 360, 663, 529]]<|/det|> +We did not repeat the same analyses at yet finer resolution because of the computationally prohibitive cost and the additional biases circumventing them would introduce. Conducting the same analysis at 1 km- resolution would involve 150million records. And pairwise calculations would necessarily need to be done on a very small subset, that would be insufficient to describe a complex realm- level temperature distribution (multiple modals with long tails; see Extended Data Fig. 2). Appropriate are at least 15 million records for sampling densities and the same number of overlap calculations for this input (for both non- /hotspots and each combination of diversity aspects, and realms), which was computationally not feasible. Random samples of fewer cells are driven by the central tendency, hence for instance not reflecting the cold extremes and do the opposite of accounting for variations. At the 110 km- resolution, we see that the closer one gets to number of samples and calculations recommended in the documentation of the R- package 'NicheROVER', the closer they were to our original estimates. Although notably the simpler non- hotspot distributions seemed to be described well with fewer records. + +<|ref|>text<|/ref|><|det|>[[87, 555, 664, 620]]<|/det|> +While we fully acknowledge that microclimates at even finer grain (e.g. 10 m, see ref. \(^{90}\) ) could modulate climate change outcomes for specific species and regions, the empirically possible sensitivity analysis gives no indication that this would affect the overall direction of our findings at broadest taxonomic and spatial scope. The respective analysis and results are now described in detail with additional text in the section "Grain size and niche metrics" (L448- 468). + +<|ref|>text<|/ref|><|det|>[[87, 648, 655, 713]]<|/det|> +Comment: Some of the novelty is overstated. The finding that mountains are butterfly hotspots is not particularly novel; butterfly diversity is known to be especially high in montane areas, which is likely due to the change in temperature and vegetation across elevation. Similarly, it's not surprising that species richness of butterflies is positively associated with other taxa as we tend to see general trends in diversity across different groups. + +<|ref|>text<|/ref|><|det|>[[87, 720, 660, 823]]<|/det|> +Response: With these novelty statements we refer to the exceptionally high concentration of hotspots of the global butterfly diversity, including previously unknown patterns of rare rarity and PD. We are not aware of a global study of any of these aspects, even for species richness, and more so a comparison with other taxa (plants, ants or vertebrates) that allow such a conclusion. As butterfly experts we are aware of local elevational diversity gradients, of which we cite many (e.g. 38, 39, 42- 44, 53, 55, 58, 66) and which were our motivation to conduct this rigorous test. We now mention these studies earlier, include three additional butterfly- specific references and more specifically address the expected role of mountains in the hypothesis section. We did not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 186, 660, 275]]<|/det|> +find a statement stressing that the positive relationship between butterfly species richness and that of other taxa is novel, but our tests are clearly the by far most rigorous evaluations of this pattern. The general positive association of species richness patterns itself is intuitive. Does this maybe refer to the "coincide of their diversity and threat" statement in the abstract? Here we meant that the temperatures underpinning locations of hotspots of butterfly diversity will are eroding faster than non- hotspot temperature regimes. We rephrased this sentence to improve clarity. + +<|ref|>text<|/ref|><|det|>[[87, 303, 655, 342]]<|/det|> +Comment: The interpretation of the overlap in diversity centers of butterflies with those of ants doesn't quite fit with the values presented in the manuscript. (L11): with regards to "Only a small portion \((14\% - 54\%)\) ...", those percentages are not really a "small portion". + +<|ref|>text<|/ref|><|det|>[[87, 349, 664, 427]]<|/det|> +Responses: Thank you for the comment. This is a summary statement addressing overlaps of all taxa (quote: "ants, terrestrial vertebrates and vascular plants"). Rare rarity hotspots of ants overlap to only \(16\%\) and ant species richness hotspots to \(30\%\) with those of butterflies. The statement, however, contains an error. The maximum of overlap of butterfly hotspots is \(36\%\) (species richness hotspots of mammals) not \(54\%\) as previously stated. Thank you for highlighting this mistake! + +<|ref|>text<|/ref|><|det|>[[87, 454, 664, 531]]<|/det|> +Comment: L61- 62: Higher elevation is relative, and 2500 m is a mid- elevation in many places. The manuscript is suggesting richness increases with elevation based on how it is written, but this sounds more like a mid- elevation peak, which is common in many taxa. More broadly, it seems there could be issues identifying peaks in abundance across elevation given the course resolution of the distribution data. A 10 km- resolution could contain a broad range of elevations. Could this skew ranges to higher elevations in topographically complex landscapes? + +<|ref|>text<|/ref|><|det|>[[87, 539, 661, 654]]<|/det|> +Response: We appreciate this comment and from our above response the reviewer can hopefully see that scale and grain issues are very much on our mind. We hence tried to be very cognizant about them make in our choice of analytical approach and interpretation. First, we repeat the for the great majority of our species we modelled distributions at 1 km- resolution and then only later coarsened to 110 km. That means that 110 km cells with great topographic heterogeneity could (correctly) emerges as harbouring a high number of species. And thus, richness might be as much or more related to a cell's elevation range than its mean elevation (such is the limitation of a single elevational gradient perspective). However, we are uncertain how this would cause a skew toward higher or lower elevations. + +<|ref|>text<|/ref|><|det|>[[87, 662, 664, 817]]<|/det|> +The first part of the sentence addresses the trend (increases with elevation), while the second highlights the peak of this non- linear relationship. In the text, we avoid the term mid elevation because this is indeed rather difficult to define. Instead we refer to elevation "higher"/"above" or "lower than 2500 m". Hence, we agree with the interpretation that 2500 m is rather a mid- elevation. In the context of our global scale analysis, we note that this peak in butterfly diversity is at higher elevation than in most other taxa (Fig. 5b). For a more nuanced understanding we provided an analysis of realm- and taxon- specific elevational diversity gradients in the Supplementary Information (Fig. 10). This demonstrates that species richness and range rarity are highest between 2500 m and the realm- level maximum elevations. In the Palearctic, species richness slightly declines above 4000 m, and the only true mid- elevation peak occurs in the Neotropics. While we can confirm that mid- elevation peaks are common for other taxa in most realms, idiosyncratic trends, such as those for plants and ants, suggest no skew due to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 186, 636, 237]]<|/det|> +topographical complexity. Although we expect lower elevations to be better sampled due to accessibility and human population density, data limitations prevent us from assessing abundance patterns. Our study prioritized an optimal strategy for describing species ranges, including spatial thinning to improve modeling accuracy. + +<|ref|>text<|/ref|><|det|>[[87, 244, 655, 270]]<|/det|> +We now strengthen links to the Supplementary Information and the stronger relative preference of butterflies for higher elevations in the context of all considered taxa. + +<|ref|>text<|/ref|><|det|>[[87, 297, 655, 336]]<|/det|> +Comment: L113: Under "range rarity", the text shifts to discussing diversity (i.e. "Even stronger cross- taxon mismatches emerge when comparing the top \(5\%\) diversity centers per realm and taxon."), which is confusing. Is this referring to phylogenetic diversity? + +<|ref|>text<|/ref|><|det|>[[87, 344, 662, 408]]<|/det|> +Response: In the mentioned sentence the discussion shifts from a comparison of the cross- taxon congruence in species richness with that of rare rarity patterns to overlap in their hotspots. We used the term "diversity" for describing multiple aspects of diversity but rephrased that sentence to clarify that the statement refers to "hotspots of species richness and rarity" (L122). + +<|ref|>text<|/ref|><|det|>[[87, 435, 660, 499]]<|/det|> +Comment: L120: The manuscript notes that "These results indicate that priority areas identified based on vertebrates miss critical places needed to safeguard the diversity of insects", however, isn't this statement based on range rarity (a measure of endemism) rather than species diversity per se? It seems that a better measure of safeguarding diversity of insects should be focused on species richness, not simply endemism. + +<|ref|>text<|/ref|><|det|>[[87, 506, 660, 571]]<|/det|> +Response: In our statement "safeguard the diversity of insects" we meant "global diversity" and have now added that word to clarify (L129). In other words, we are focused here on minimizing the number of species extinctions (not on maximizing the average cell species richness). For this, range rarity is the appropriate metric, as we explain at the beginning of the paragraph that "Range rarity hotspots harbor many species not occurring anywhere else...". + +<|ref|>text<|/ref|><|det|>[[87, 598, 655, 650]]<|/det|> +Comment: L144: The manuscript notes that "We find that the concentration of butterfly diversity in mountains substantially exceeds that of almost all globally studied taxa". However, isn't this simply because other insects haven't been assessed? In other words, it's not surprising this is the case given that most other globally studied animal taxa are vertebrates. + +<|ref|>text<|/ref|><|det|>[[87, 658, 654, 709]]<|/det|> +Response: The phrase "studied taxa" specifies our claim to addressing globally assessed taxa and avoiding speculation about all taxa. To clarify this, we have now rephrased the sentence to "taxa that have been globally studied to date". Please note that we included ants in the respective analysis. + +<|ref|>text<|/ref|><|det|>[[87, 737, 639, 763]]<|/det|> +Comment: L627. Do the authors mean "across latitude" rather than "in space" in the figure caption? Fig.1 | Global variation in butterfly diversity in space and along elevation + +<|ref|>text<|/ref|><|det|>[[87, 771, 654, 796]]<|/det|> +Response: The intention was to collectively title the map (spanning longitude and latitude) and surface- plots (spanning elevation and latitude). We now specify "across latitude". + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[88, 185, 207, 196]]<|/det|> +## General comment: + +<|ref|>text<|/ref|><|det|>[[88, 205, 310, 216]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[87, 245, 655, 297]]<|/det|> +This nice study investigates the spatial structure of butterfly diversity across the globe using an impressive variety of sources and methods. To keep myself accountable, and to make it easier for the authors to confirm that I understood their methodology, I below attempt to summarize this (quite major) study. + +<|ref|>text<|/ref|><|det|>[[87, 325, 661, 414]]<|/det|> +With descending order of priority, the authors use species distribution models (based on occurrence records), expert range maps, and ecoregional range maps (grouping areas by their similarity in ecologically relevant variables) to infer biodiversity at a \(110\mathrm{km}\times 110\mathrm{km}\) spatial resolution. The authors also use three biodiversity metrics: species richness (number of species in a cell), average range rarity (the average of the inverse global ranges for the species in a cell), and phylogenetic diversity (calculated as deviations from a null model — is there more spatial phylogenetic structure than expected by chance?). + +<|ref|>text<|/ref|><|det|>[[86, 442, 662, 572]]<|/det|> +The authors identify discrepancies between the different diversity metrics, indicating that one cannot be substituted for another without loss of information. However, the general conclusion is — perhaps unsurprisingly to most — that tropical and subtropical regions are most diverse, but more importantly also that mountainous regions have disproportionately diverse and rare butterfly communities (even in contrast with other taxa). This pattern, while ecologically interesting in its own right, carries with it dire implications for global butterfly diversity in a warmer future, due to the local nature of elevational temperature gradients. To make an analogy for butterflies limited to high elevations in the tropics: the mountains are cool islands in a dangerously warm ocean, and water levels are rising. With no other land in sight, the butterflies have nowhere to go. + +<|ref|>text<|/ref|><|det|>[[87, 599, 653, 675]]<|/det|> +It's unclear from the paper whether loss of high- altitude butterfly diversity in the tropics generally comes with any socio- economic costs related to, for instance, ecosystem services, but from a global biodiversity- perspective the findings of this (very comprehensive) study in the present study are potentially alarming. Additionally, butterflies are quite charismatic and well- liked animals. Therefore, I believe this paper is broadly interesting to biologists, and the theme suitable for Nature Ecology & Evolution. + +<|ref|>text<|/ref|><|det|>[[88, 683, 450, 695]]<|/det|> +General response: Thank you for the constructive feedback. + +<|ref|>text<|/ref|><|det|>[[87, 724, 661, 814]]<|/det|> +Comment: However, I still have some reservations regarding the manuscript's suitability for publication in its current state. These mostly relate to the writing and the storytelling. First, the writing could be clearer (see some examples in the line- by- line comments below). Second, when reading the manuscript, it is not immediately clear what the take- home messages are regarding the actual biology. In its present form, the manuscript is largely descriptive (butterflies are here and there), and the brief sentences about the biology of butterflies seem quite ad hoc. The authors appear not particularly interested in butterflies, but rather the nice resources + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 185, 660, 303]]<|/det|> +available for quantifying their distributions. That is of course completely fine, but in this case, the biological reasons for why the patterns described in this study are exaggerated in butterflies might carry crucial information for future conservation efforts, or at least projections. Indeed, after identifying global patterns of biodiversity in butterflies, it would be very nice if the authors could dive into some potential biological explanations for why butterfly diversity/rarity stand out as particularly concentrated at high elevations. Then, the findings in the study, and the massive amount of work put into quantifying butterfly diversity globally, could give broader insights into what other organism groups might be threatened. Personally, I think the story would be more coherent if it was structured, at least to some extent, like this: + +<|ref|>text<|/ref|><|det|>[[87, 310, 659, 349]]<|/det|> +Biology (what traits make butterflies special) - > Biodiversity patterns (what spatial distributions do these traits correlate with) - > Threat levels (what does a warm future hold in store for species with these spatial distributions) - > Biology (what other organisms fall into the same category). + +<|ref|>text<|/ref|><|det|>[[87, 355, 636, 408]]<|/det|> +I don't want to micromanage how the paper is written, and I am sure there are many ways to shape the findings in this paper into a nice story. But I do think that the manuscript's quality would improve drastically if the writing was just a bit more coherent. This is particularly important given the complex analyses in the study. + +<|ref|>text<|/ref|><|det|>[[87, 414, 661, 570]]<|/det|> +Response: Thank you for these helpful suggestions. Our revised article now mostly follows the structure you proposed, except that "what other organisms fall into the same category" appears earlier to highlight the importance of mountains, even among ecotherms. We've revised the hypothesis presentation, which was initially detailed throughout the results and discussion. Despite some redundancy, this addition strengthens the study's foundation and clarifies the aims now already in the introduction (L53- 65). The aims of the study are now followed by a description of butterfly traits that explain: 1) the critical role of mountains in their diversity, 2) the relatively high overlap with other ectotherms and plants compared to endotherms, and 3) the temperature- driven erosion of hotspots for butterfly diversity. Given the mixed evidence for point (2), we address the implications for other organisms later in the discussion. Specifically, for insect taxa closely tied to plants, we anticipate severe losses of species richness and phylogenetic diversity in mountain areas due to global warming. + +<|ref|>sub_title<|/ref|><|det|>[[88, 598, 279, 610]]<|/det|> +## Comment: Specific comments: + +<|ref|>text<|/ref|><|det|>[[87, 618, 645, 644]]<|/det|> +Title: I think the title could be a bit more precise, to highlight the implications of the study (e.g. "Global hotspots of butterfly biodiversity are threatened in a warming world"). + +<|ref|>text<|/ref|><|det|>[[87, 652, 490, 664]]<|/det|> +Response: Thank you. We changed the title as per your suggestion. + +<|ref|>text<|/ref|><|det|>[[87, 691, 656, 755]]<|/det|> +Comment: Abstract: At line 6- 7, "their [the butterflies'] diversity and threat" sounds wrong (particularly the threat part). I suggest really describing why lines 13- 15 are true. That is, explain in some way that living on a mountain makes it hard to shift the geographical range to track a changing climate in the long run. This is perhaps somewhat obvious, but it could help make the message clearer. + +<|ref|>text<|/ref|><|det|>[[87, 763, 650, 802]]<|/det|> +Response: Thank you for this detailed suggestion. The sentence now reads: "Here we use butterflies as a global model insect system" and uncover a remarkable concentration of their diversity in rare and rapidly shrinking high- elevation climates." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[87, 185, 624, 225]]<|/det|> +Comment: Lines 24- 28: The last section of the paragraph is a bit unclear. What does "heterogeneous representation" mean in this context? "Cause and consequence" of what exactly? I think I get the idea but wording could be more precise. + +<|ref|>text<|/ref|><|det|>[[87, 232, 649, 284]]<|/det|> +Response: We simplified and clarified this statement. The sentence now reads: "Recent work has highlighted the range of implications arising from an uneven geographic distribution of biodiversity, such as vast differences in countries' conservation responsibilities" and the biodiversity coverage of their protected areas \(^{15,16}\) ." + +<|ref|>text<|/ref|><|det|>[[88, 311, 375, 323]]<|/det|> +Comment: Line 29: Extends from what to what? + +<|ref|>text<|/ref|><|det|>[[88, 332, 321, 343]]<|/det|> +Response: We removed this sentence. + +<|ref|>text<|/ref|><|det|>[[88, 371, 421, 383]]<|/det|> +Comment: Lines 38- 40: Which recognized differences? + +<|ref|>text<|/ref|><|det|>[[87, 392, 657, 443]]<|/det|> +Response: We clarified our statement. It now reads: "These recognized limitations in our understanding of insect diversity patterns exemplify the precarious foundation of the current knowledgebase for global biodiversity conservation at large scales and leave insect biodiversity poorly represented." + +<|ref|>text<|/ref|><|det|>[[87, 470, 645, 483]]<|/det|> +Comment: Line 44: "their own isolation" seems to me like a somewhat awkward phrase here. + +<|ref|>text<|/ref|><|det|>[[88, 491, 368, 503]]<|/det|> +Response: Adapted removing the word "own". + +<|ref|>text<|/ref|><|det|>[[87, 531, 457, 544]]<|/det|> +Comment: Line 53- 54: Is it really the butterflies' information? + +<|ref|>text<|/ref|><|det|>[[87, 551, 616, 564]]<|/det|> +Response: We substantially revised the respective paragraph and avoided this phrasing. + +<|ref|>text<|/ref|><|det|>[[87, 592, 549, 603]]<|/det|> +Comment: Line 149- 151: Perhaps diapause would be good to mention here? + +<|ref|>text<|/ref|><|det|>[[87, 611, 640, 663]]<|/det|> +Response: Thank you for this helpful suggestion! We extended the statement to include the commonness of pre- reproductive cold- diapause in butterflies as an additional adaptation to high- elevation climate, supporting their exceptionally high diversity in mountains. We added new references to support this argument. + +<|ref|>text<|/ref|><|det|>[[87, 691, 660, 716]]<|/det|> +Comment: Figure 2: Legends are not entirely clear (e.g., the color of the bars in the bar plots are not described explicitly). + +<|ref|>text<|/ref|><|det|>[[87, 723, 656, 748]]<|/det|> +Response: The meaning of color of the bars is now both given visually in the legend in the lower left corner (colors of the labels PD, SR, RR and Any) and described in the legend. + +<|ref|>text<|/ref|><|det|>[[87, 777, 625, 802]]<|/det|> +Comment: Figure 6: Legends/figures need to be clearer. As it stands, the meaning is quite difficult to extract from the figure. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[86, 185, 655, 237]]<|/det|> +Response: We now include the temperature differences as (a) in this plot to clarify the connection between temperature differences and temperature niche loss estimates for hotspots in (d). We also revised the caption to support the legend and extended the conclusion statement for this figure to clarify the meaning of these results. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[117, 82, 310, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[117, 108, 275, 123]]<|/det|> +## General comment: + +<|ref|>text<|/ref|><|det|>[[117, 135, 220, 149]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[117, 161, 301, 176]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[117, 188, 860, 238]]<|/det|> +The work is of broad interest and is novel in providing a global assessment of butterfly species rarity and diversity. The authors have thoughtfully responded to all concerns and added additional analyses that strengthen the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 275, 827, 308]]<|/det|> +General response: Thank you very much for all the time you have invested to improve the manuscript. We are happy that we could address your concerns. + +<|ref|>sub_title<|/ref|><|det|>[[117, 346, 275, 361]]<|/det|> +## General comment: + +<|ref|>text<|/ref|><|det|>[[117, 373, 220, 388]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[117, 400, 301, 415]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 426, 860, 529]]<|/det|> +The writing is much improved, which makes the manuscript easier to read, and thus more impactful. I still have some suggestions that I think will improve the manuscript, which I hope that the authors will consider and appreciate. I probably missed some parts, so I recommend the authors to carefully read through their manuscript and fix language/sentence structure errors before resubmitting—perhaps with help of a native English speaker. Still, I am generally pleased with the revisions. + +<|ref|>text<|/ref|><|det|>[[116, 539, 803, 572]]<|/det|> +General response: We are deeply grateful for the time you have invested. Your explicit comments and the additional context were very helpful! + +<|ref|>sub_title<|/ref|><|det|>[[117, 610, 207, 625]]<|/det|> +## Comment: + +<|ref|>text<|/ref|><|det|>[[117, 637, 217, 652]]<|/det|> +Line- by- line: + +<|ref|>text<|/ref|><|det|>[[117, 664, 340, 679]]<|/det|> +4: Remove "in decline and". + +<|ref|>text<|/ref|><|det|>[[117, 691, 258, 706]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[117, 744, 393, 759]]<|/det|> +Comment: 7: "their" -> "butterfly". + +<|ref|>text<|/ref|><|det|>[[117, 771, 258, 785]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 823, 540, 839]]<|/det|> +Comment: 21: "the prerequisite" -> "a prerequisite". + +<|ref|>text<|/ref|><|det|>[[117, 850, 258, 865]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 902, 628, 918]]<|/det|> +Comment: 27: "documented and safeguarded" -> "prioritized"? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 84, 258, 99]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[115, 135, 710, 152]]<|/det|> +Comment: 41: Unclear what "takes on an additional weight" really means. + +<|ref|>text<|/ref|><|det|>[[116, 163, 625, 179]]<|/det|> +Response: Adapted to "...becomes an even greater challenge..." + +<|ref|>text<|/ref|><|det|>[[116, 216, 850, 249]]<|/det|> +Comment: 43: Consider using semi- colon (;) after "mountains" to make "their" in the follow sentence more clear. + +<|ref|>text<|/ref|><|det|>[[116, 260, 258, 275]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 313, 367, 328]]<|/det|> +Comment: 44: Remove "their". + +<|ref|>text<|/ref|><|det|>[[116, 340, 258, 355]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[115, 393, 868, 426]]<|/det|> +Comment: 49- 51: What about the ant work in Science Advances? This sentence is not needed, we see the importance of this work without it. + +<|ref|>text<|/ref|><|det|>[[115, 437, 860, 471]]<|/det|> +Response: The Science Advances article on ants does not address climate change. Note that we highlight it later in terms of existing work on global diversity patterns. + +<|ref|>text<|/ref|><|det|>[[115, 508, 860, 541]]<|/det|> +Comment: 57: "Highly adapted" does not sit right with me. I would not say that their traits are "more" adapted than other species". Perhaps "Owing to distinct...". + +<|ref|>text<|/ref|><|det|>[[116, 552, 366, 567]]<|/det|> +Response: Done as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 605, 812, 639]]<|/det|> +Comment: 57- 59: I think https://doi.org/10.1038/s41467- 023- 39359- 8 would be a good additional reference here (regarding thermal niches). + +<|ref|>text<|/ref|><|det|>[[116, 650, 880, 700]]<|/det|> +Response: This is an interesting read and good fit. However, with five references we feel this statement is already sufficiently supported. Note that we added one of your other suggestions to make efficient use of the included references. + +<|ref|>text<|/ref|><|det|>[[115, 737, 512, 752]]<|/det|> +Comment: 59: What does separately mean here? + +<|ref|>text<|/ref|><|det|>[[116, 764, 564, 779]]<|/det|> +Response: The sentence now starts with "In addition..." + +<|ref|>text<|/ref|><|det|>[[115, 817, 723, 833]]<|/det|> +Comment: 61- 65: I think these two sentences could be written more clearly. + +<|ref|>text<|/ref|><|det|>[[116, 844, 865, 930]]<|/det|> +Response: We now write: "These characteristics suggest that patterns in butterfly diversity differ strongly from those of terrestrial vertebrates, challenging the effectiveness of existing conservation priorities, which have been largely based on vertebrate taxa. Adaptations to cold climates and host plant diversity likely also support high concentrations of butterfly diversity in mountain systems41- 43, implying dire consequences under global warming." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 108, 442, 125]]<|/det|> +Comment: 76: Remove "and" and "are". + +<|ref|>text<|/ref|><|det|>[[117, 136, 258, 151]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[117, 189, 840, 223]]<|/det|> +Comment: 92: "...the previously argued" sounds a bit strange to me. What about "previous findings on hotspots of deep ..."? Or something else. + +<|ref|>text<|/ref|><|det|>[[117, 233, 366, 249]]<|/det|> +Response: Done as suggested. + +<|ref|>text<|/ref|><|det|>[[117, 286, 771, 320]]<|/det|> +Comment: 101- 102: "Within ectotherm taxa" makes it seem like ectotherms are a monophyletic group somehow. Perhaps just remove, works without it. + +<|ref|>text<|/ref|><|det|>[[117, 330, 530, 347]]<|/det|> +Response: Adapted to "Among ectothermic taxa..." + +<|ref|>text<|/ref|><|det|>[[117, 383, 861, 400]]<|/det|> +Comment: 104- 105: What "known co- evolutionary association"? Change sentence structure. + +<|ref|>text<|/ref|><|det|>[[117, 411, 258, 426]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 463, 880, 568]]<|/det|> +Comment: 138- 140: Possesses -> possess. Also, I think the point here is: why would insects be especially diverse in mountainous regions? I could see the point that insects have general adaptations (e.g., diapause — more so than other groups, where such adaptations appear more specialized) that allows them to endure prolonged periods of inhospitable cold conditions. If I'm right with what you are implying, perhaps the sentence could be changed to more clearly reflect this? E.g.: + +<|ref|>text<|/ref|><|det|>[[117, 577, 878, 628]]<|/det|> +"In addition, many insects possess general physiological adaptations for enduring inhospitable cold conditions, potentially acting as pre- adaptations for colonizing mountainous regions in the first place." + +<|ref|>text<|/ref|><|det|>[[116, 639, 577, 656]]<|/det|> +Here are three more generally relevant references for this: + +<|ref|>text<|/ref|><|det|>[[116, 666, 491, 682]]<|/det|> +https://doi.org/10.1016/j.jinsphys.2005.09.008 + +<|ref|>text<|/ref|><|det|>[[116, 693, 473, 708]]<|/det|> +https://isbnsearch.org/isbn/9780195036350 + +<|ref|>text<|/ref|><|det|>[[116, 719, 455, 735]]<|/det|> +https://doi.org/10.1073/pnas.2407057121 + +<|ref|>text<|/ref|><|det|>[[116, 745, 871, 796]]<|/det|> +Response: Rephrased to "In addition, many insects possess general physiological adaptations for enduring inhospitable cold conditions, potentially acting as pre- adaptations for colonizing mountainous regions." + +<|ref|>text<|/ref|><|det|>[[116, 807, 866, 840]]<|/det|> +Note that we want to cover a range of adaptations with these references (now six). Two of them are on diapause. This now included the first reference you suggested. + +<|ref|>text<|/ref|><|det|>[[117, 877, 383, 893]]<|/det|> +Comment: 145: "odd" -> "odds". + +<|ref|>text<|/ref|><|det|>[[116, 904, 640, 920]]<|/det|> +Response: Adapted to "odds ratio". Here and throughout the text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 716, 125]]<|/det|> +Comment: 156: Remove average? Or write, "On average, toward higher ...". + +<|ref|>text<|/ref|><|det|>[[116, 136, 291, 152]]<|/det|> +Response: Removed. + +<|ref|>text<|/ref|><|det|>[[116, 189, 392, 205]]<|/det|> +Comment: 161: See previous refs. + +<|ref|>text<|/ref|><|det|>[[115, 216, 748, 233]]<|/det|> +Response: With two references we feel this statement is sufficiently supported. + +<|ref|>text<|/ref|><|det|>[[115, 269, 700, 286]]<|/det|> +Comment: 198: Replace "for instance" with "either" for better structure? + +<|ref|>text<|/ref|><|det|>[[116, 297, 258, 312]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 350, 383, 366]]<|/det|> +Comment: 206: "As a next step". + +<|ref|>text<|/ref|><|det|>[[116, 377, 367, 393]]<|/det|> +Response: Done as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 430, 500, 446]]<|/det|> +Comment: 208- 212: Revise sentence structure. + +<|ref|>text<|/ref|><|det|>[[115, 456, 880, 543]]<|/det|> +Response: We have split this long sentence and rephrased the second part. We now write: "Insights on species- specific dispersal constraints will be particularly helpful in the case of island endemics (e.g. range rarity hotspots in Australasia and Indomalaya) and in regions where the latitudinal orientation of mountain ranges hinders northward shifts (Fig. 6 and Extended Data Fig. 4). Such additional constraints would imply yet greater niche losses than estimated here." + +<|ref|>text<|/ref|><|det|>[[115, 578, 840, 612]]<|/det|> +Comment: 215- 216: Revise sentence. Avoid "their" before mentioning what you are talking about. Also, this should probably be referenced: + +<|ref|>text<|/ref|><|det|>[[117, 622, 392, 638]]<|/det|> +https://doi.org/10.1002/ecm.1553 + +<|ref|>text<|/ref|><|det|>[[115, 649, 852, 683]]<|/det|> +Response: Done. Thank you for highlighting this. We appreciate the additional reference and include it. + +<|ref|>text<|/ref|><|det|>[[115, 719, 733, 737]]<|/det|> +Comment: 218: "unusually strongly exposed" -> "exceptionally susceptible". + +<|ref|>text<|/ref|><|det|>[[116, 747, 258, 763]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 800, 402, 816]]<|/det|> +Comment: 219: "that" -> ", which". + +<|ref|>text<|/ref|><|det|>[[116, 828, 258, 843]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[115, 880, 603, 897]]<|/det|> +Comment: 220- 221: "this species group yet" -> "butterflies". + +<|ref|>text<|/ref|><|det|>[[116, 908, 258, 923]]<|/det|> +Response: Done. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 108, 881, 160]]<|/det|> +Comment: 221- 222: "due to their geographically rare and isolated environmental conditions are now bound to become ecological dead ends" -> "but might become ecological dead ends in a warmer future". + +<|ref|>text<|/ref|><|det|>[[117, 170, 366, 187]]<|/det|> +Response: Done as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 223, 875, 257]]<|/det|> +Comment: 223- 224: "mountain areas where identified rarity and threat most strongly coincide" -> "threatened mountain areas". + +<|ref|>text<|/ref|><|det|>[[116, 267, 842, 302]]<|/det|> +Response: Rephrased to: "...in mountain regions where climate change poses a significant threat to biodiversity." + +<|ref|>text<|/ref|><|det|>[[116, 337, 860, 389]]<|/det|> +Comment: 224: Consider replacing "sound a clarion call". Might be a darling that is better off killed. "Strongly emphasize the need" or something else typically boring might be more suitable" + +<|ref|>text<|/ref|><|det|>[[116, 399, 515, 416]]<|/det|> +Response: Rephrased to "...highlight the need...". + +<|ref|>text<|/ref|><|det|>[[116, 452, 850, 486]]<|/det|> +Comment: Middle of figure legend 2: Change to "mountains" to "mountains (full bars)", and "odd" to "odds". + +<|ref|>text<|/ref|><|det|>[[116, 497, 258, 513]]<|/det|> +Response: Done. + +<|ref|>text<|/ref|><|det|>[[116, 549, 863, 584]]<|/det|> +Comment: Beginning of figure legend 5: Change "mountains" to "mountains (full bars)". Also, shouldn't the y- label be "mountain/non- mountain"? the meaning of these results. + +<|ref|>text<|/ref|><|det|>[[116, 594, 283, 610]]<|/det|> +Response: Adapted. + +<--- Page Split ---> diff --git a/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/images_list.json b/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..3e141911a3e2f652e65f7ced25dd2b1133cb9ae0 --- /dev/null +++ b/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/images_list.json @@ -0,0 +1,17 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Rebuttal Figure 1. Duplicate removal leads to an improved correlation of exRNA abundance estimates between RNA purification method replicates. Comparison of RNA purification replicates of the Norgen method (gene counts) without (left) and with (right) duplicate removal. R2 is the coefficient of determination (linear model that fits log10 values). Higher R2-values indicate better reproducibility. Green dots represent data points that are filtered out using the count threshold. This is a threshold that reduces the fraction of single positives in technical replicates by at least 95 % (see Methods).", + "footnote": [], + "bbox": [ + [ + 120, + 178, + 870, + 410 + ] + ], + "page_idx": 6 + } +] \ No newline at end of file diff --git a/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file.mmd b/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..eb6f483125d98cedc4c0a5f9681359a583141fb0 --- /dev/null +++ b/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file.mmd @@ -0,0 +1,208 @@ + +# nature portfolio + +Peer Review File + +# Blood collection tube and RNA purification method recommendations for extracellular RNA transcriptome profiling + +Corresponding Author: Professor Jo Vandesompel + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors present a comprehensive study about the quality of different RNA purification methods. With a well- thought- out study design, they compared the performance of classic and manufacturer- designated preservation tubes by sequencing either mRNA or miRNA and evaluate the results with purposely designed performance metrics. In general, the study is well designed and clearly written, despite some complex metrics. With minor adjustments, the study could help to provide a validated and clinically applicable gold- standard for RNA- and miRNA- sequencing from blood samples. + +Minor comments. + +- Preservation tubes were only tested for after longer time intervals. It would be interesting to see how the classic tubes perform after 7 or 14 days. + +- Fig 2a-b could be presented as a boxplot. Thereby the variance would still be visible, but the figure would be easier to understand, while showing additional statistics, including the variance between replicates. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +Very interesting work that provides useful information for the design of exRNAseq studies. + +Major: + +1) I verified the access to the raw data (FASTQ), and now it is necessary to request permission to access it. + +To be done: The FASTQ data must be made openly accessible without any restrictions once the article is published. 2) Although the GitHub repository is well-documented (https://github.com/OncoRNALab/exRNAQC/), there are several issues related to data reproducibility. The repository lacks a section outlining the overall structure of the analysis steps. In its current format, the GitHub relies on a Slurm workflow tailored to the UGent HPC system, which makes it virtually impossible to reproduce the data analysis on an independent system, unless rewriting all code. + +3) The GitHub repository lacks a clear description of the files required for each analysis. For instance, in the RNASeq_preprocessing.py file, the data to be processed is located in the folder NSQ_run453-84636552_Run458-86026942, but the contents of this folder are not clearly explained. This issue also extends to the preprocessing of miRNAs. + +To be done: The input of the pipelines must be the folder containing the downloadable fastqs. + +4) I reviewed the steps provided in https://github.com/OncoRNALab/exRNAQC/, and I noticed that some files, such as genome annotation including spikes, cannot be directly downloaded from a specific repository. + +To be done: The authors must provide the procedure and input files necessary to generate the STAR index files and the BED files specified in RNASeq_preprocessing.py. To ensure reproducibility, the software used for the analysis should be supplied as a Docker or Singularity container. Additionally, all supplementary files required for the analyses should be made available in a Zenodo or fileshare repository, with the data structure pre-configured for access by the analysis software within the provided Docker/Singularity container. + +<--- Page Split ---> + +5) I also noticed that deduplication of reads was applied during the RNAseq preprocessing. However, several publications suggest that removing duplicates in bulk RNAseq does not necessarily improve data quality (https://pubmed.ncbi.nlm.nih.gov/28321364/, https://pubmed.ncbi.nlm.nih.gov/30001700/). To be done: The authors should provide a justification for their decision to include the deduplication procedure in their analysis. + +6) In the miRNAseq preprocessing, it appears that Bowtie was used to map miRNAs to the hg38 genome. The annotation procedure is described in mat and met, but I could not identify the part of code associated to the miRNA annotation. To be done: Adding in the README, a summary of the steps performed in each analysis workflow would enhance its readability and usage of the scripts. + +7) The link http://r2platform.com/exRNAQC/ provides 404 Not Found + +Minor: + +1) In fig. 2A/B the x axis refers to number of detected mRNAs/miRNAs. I was unable to find in the text which criteria were used to define a detectable mRNA/miRNA. + +(Remarks on code availability) + +Reviewer #3 + +(Remarks to the Author) + +The manuscript provides a very well designed, comprehensive evaluation of pre- analytical factors that may affect miRNA and mRNA results in biomarker studies. The authors evaluated 10 different types of blood collection tubes, 3 different time intervals, and 8 different purification methods. One of the more surprising results is that the "basic" EDTA blood tubes performed better than the preservation tubes. Other findings are less surprising (such as that increasing input volume provides better results), but provide important considerations for users collecting biofluid samples. The work is well supported by the data and the methodology is sound. Additionally, the authors have made the data publicly available so future researchers can further analyze the results. + +(Remarks on code availability) + +I have verified that the link works but have not tried to run the code or assess it. + +Version 2: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors addressed all my comments and reasonably explained their choices of data illustrations. + +Additionally they updated their github repository to make the data easier to be reproduced. + +I have no further objections that stand in the way of publication. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +All points raised were clearly addressed. No extra work is required for what concern my review. + +(Remarks on code availability) + +All points associated to the code were sufficiently addressed. No extra work is required from my point of view. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Revision of manuscript NCOMMS-23-01885A-Z Blood collection tube and RNA purification method recommendations for extracellular RNA transcriptome profiling: A large-scale pre-analytical variable performance evaluation + +## Point-by-point response + +Below, you can find our answers to the reviewers' comments. Corresponding revisions of the manuscript are highlighted in the manuscript; page numbers below refer to the revised manuscript version. + +## Reviewer #1 + +The authors present a comprehensive study about the quality of different RNA purification methods. With a well- thought- out study design, they compared the performance of classic and manufacturer- designated preservation tubes by sequencing either mRNA or miRNA and evaluate the results with purposely designed performance metrices. In general, the study is well designed and clearly written, despite some complex metrices. With minor adjustments, the study could help to provide a validated and clinically applicable gold- standard for RNA- and miRNA- sequencing from blood samples. + +Minor comments. + +- Preservation tubes were only tested for after longer time intervals. It would be interesting to see how the classic tubes perform after 7 or 14 days. + +For each tube type (both preservation and classic tubes), a baseline value was established by processing the blood tube immediately after collection. To mimic same- day and next- day processing in routine lab situations, additional processing time intervals were set to 4 and 16 hours for classic tube types. For preservation tubes, which are specifically marketed to stabilize extracellular nucleic acids for 7 (and up to 14) days, additional processing time intervals of 24 and 72 hours were selected. Preservation tubes have thus indeed been tested for longer processing time intervals compared to the classic tubes, but not for the extremes claimed by the manufacturer. Additionally, we opted to only use longer processing time intervals for preservation tubes, as these tubes were purposely developed to conveniently allow more time between the blood draw and further processing steps, while classic tubes are not specifically designed to stabilize cell- free nucleic acids. Of note, based on the differential abundance analyses, GSEA and deconvolution analyses (results described in lines 233- 241, lines 244- 250 and lines 273- 280), we conclude that even the high- performing classic tubes processed within 4 and 16 hours demonstrate mRNA composition changes over time, and that these changes become more pronounced over time. As such, testing longer time intervals for these classic tubes will not change the recommendations put forward in our manuscript, i.e. blood processing should be completed within 4 hours after collection. These findings are supported by other publications demonstrating changes over time for specific extracellular m(i)RNAs derived from classic tubes (Fernando et al., Clin Biochem., 2012; Page et al., PLoS One, 2013; Glinge et al., PLoS One, 2017; Gahlawat et al., Int J Mol Sci., 2019; Murray et al., Cancer Epidemiol Biomarkers Prev., 2018). + +- Fig 2a-b could be presented as a boxplot. Thereby the variance would still be visible, but the figure would be easier to understand, while showing additional statistics, including the variance between replicates. + +Figure 2a and b represent the absolute number of detected mRNAs (a) and miRNAs (b) that reached the count threshold (see Methods) for each of the tested RNA purification and plasma input volume combinations. Each combination was tested in triplicate, resulting in 3 dots for each of them. As such, we demonstrate all individual data points, which is preferred for samples size less than 5. Box plot construction requires at least 5 data points (preferably + +<--- Page Split ---> + +larger; Krzywinski M et al., Nat Methods, 2014). Therefore, we decided not to transform this figure into a boxplot. + +## Reviewer #2 + +Very interesting work that provides useful information for the design of exRNAseq studies. Major: 1) I verified the access to the raw data (FASTQ), and now it is necessary to request permission to access it. To be done: The FASTQ data must be made openly accessible without any restrictions once the article is published. + +Samples from healthy donors have been collected under the General Data Protection Regulation (or GDPR) (EU) 2016/679 of April 27, 2016 and the Belgian law of July 30, 2018, on the protection of individuals related to the processing of personal data and on the free movement of such data. In this context, the ICF of our study (approved by the ethics committee of Ghent University Hospital; approval number B670201733701) states that pseudonymised data may be shared with other researchers for future research projects. Though, such future studies first need to be ethically approved. For that reason, the fastq data cannot be made openly accessible without any restrictions and were therefore shared through EGA, providing secure access to data for authorised researchers and clinicians. The data of our study have already been released by EGA, and sharing requests can be submitted. We want to contribute to the practice of open science and are open for collaborations, but need to adhere to Belgian and European legislations on data sharing. Note that the derived count data are openly accessible (without any restrictions) through ArrayExpress, and browsable access is provided through the R2 Genomics Analysis and Visualization Platform. We recognize that part of this information was lacking in the Data Availability statement, and have updated this in the revised manuscript (line 742- 762). + +In context of the manuscript review process, we have contacted the EGA helpdesk to provide anonymous data access to the reviewers. Unfortunately, there is no easy solution to share data in EGA with reviewers. Data access is possible, but requires several steps to be taken to secure the reviewers anonymity: + +(1) We inform EGA that we agree to have our data downloaded by an anonymous person and include a contact person at Nature Communications in this e-mail communication. +(2) EGA will contact Nature Communications to confirm the download details. A download account for the reviewer will be set up (using the email address of the reviewer; needed for security reasons). Nature Communications needs to contact the reviewer to make them aware that: (i) The reviewer must inform EGA as soon as the data are downloaded. (ii) That the data will be deleted once the review is completed. +(3) EGA will share the data with the reviewer. Please, reach out to the editor to get access to the data. + +2) Although the GitHub repository is well-documented (https://github.com/OncoRNALab/exRNAQC/), there are several issues related to data reproducibility. The repository lacks a section outlining the overall structure of the analysis steps. In its current format, the GitHub relies on a Slurm workflow tailored to the UGent HPC system, which makes it virtually impossible to reproduce the data analysis on an independent system, unless rewriting all code. + +We agree with the reviewer that, in its current form, the code would be difficult to reproduce. The following steps have been taken to address this concern: + +Singularity Containerization: a Singularity definition file was developed that packages the complete software environment, including all dependencies. This enables the preprocessing pipelines to be executed on any Linux- based system with Singularity installed, increasing the portability of the analysis. + +<--- Page Split ---> + +- Rewritten Preprocessing Pipelines: The preprocessing pipelines have been adapted to work within the Singularity container, ensuring that the entire workflow can now be reproduced across various computational environments without modification to the core code. + +- Repository Updates: The pipeline scripts, along with the Singularity definition file, have been added to the GitHub repository. Furthermore, we have included a section that outlines the overall structure of the analysis steps and provides detailed instructions on running the pipeline using Singularity. This section aims to guide users through setting up and executing the analysis on their own systems, independent of the UGent HPC environment. Finally, a small dataset have been added to the repository for testing purposes. + +3) The GitHub repository lacks a clear description of the files required for each analysis. For instance, in the RNASeq_preprocessing.py file, the data to be processed is located in the folder NSQ_run453-84636552_Run458-86026942, but the contents of this folder are not clearly explained. This issue also extends to the preprocessing of miRNAs. + +To be done: The input of the pipelines must be the folder containing the downloadable fastqs. + +The pipeline now uses a sample sheet as the input, which contains information about the sample name or sample ID, along with the paths to the respective fastq files. This makes the structure of the input directory flexible, as the pipeline will reference the paths provided in the sample sheet rather than relying on specific folder structures. To assist users, we have included a script in the repository that can automatically generate a sample sheet from a given directory of files. This simplifies the process for users and ensures the sample sheet is formatted correctly for the pipeline. Finally, we have also provided an example sample sheet in the repository. + +4) I reviewed the steps provided in https://github.com/OncoRNALab/exRNAQC/, and I noticed that some files, such as genome annotation including spikes, cannot be directly downloaded from a specific repository. + +To be done: The authors must provide the procedure and input files necessary to generate the STAR index files and the BED files specified in RNASeq_preprocessing.py. To ensure reproducibility, the software used for the analysis should be supplied as a Docker or Singularity container. Additionally, all supplementary files required for the analyses should be made available in a Zenodo or fileshare repository, with the data structure pre-configured for access by the analysis software within the provided Docker/Singularity container. + +Detailed instructions, along with the necessary files, have been added to the repository to guide users in generating the required indexes (STAR, Kallisto, Bowtie) as well as the GTF and BED files. This includes clear steps for building the indexes used in the preprocessing pipelines, ensuring that users can replicate the setup on their own systems. As mentioned in our response to the second comment of Reviewer 2, we have provided a Singularity container that packages all the software and dependencies required for the analysis. + +5) I also noticed that deduplication of reads was applied during the RNASeq preprocessing. However, several publications suggest that removing duplicates in bulk RNASeq does not necessarily improve data quality (https://pubmed.ncbi.nlm.nih.gov/28321364/, https://pubmed.ncbi.nlm.nih.gov/30001700/). + +To be done: The authors should provide a justification for their decision to include the deduplication procedure in their analysis. + +Several papers indeed suggest that removing PCR duplicates does not improve data quality. However, these studies were performed on RNA- sequencing data from tissue samples, which typically contains a relatively limited number of PCR duplicates (below \(50\%\) ). RNA- sequencing data from exRNA samples is characterized by high PCR duplication rates (driven by the low amount of RNA input in the library preparation). We therefore decided to assess the impact of + +<--- Page Split ---> + +duplicate removal on data reproducibility and observed that the correlation of exRNA abundance estimates between replicate samples improved upon duplicate removal (see Rebuttal Figure 1). Based on these observations, we decided to implement duplicate removal for all samples. We have added this info to the manuscript and included the figure in the supplements as Supplementary Fig. S17. + +![](images/Figure_1.jpg) + +
Rebuttal Figure 1. Duplicate removal leads to an improved correlation of exRNA abundance estimates between RNA purification method replicates. Comparison of RNA purification replicates of the Norgen method (gene counts) without (left) and with (right) duplicate removal. R2 is the coefficient of determination (linear model that fits log10 values). Higher R2-values indicate better reproducibility. Green dots represent data points that are filtered out using the count threshold. This is a threshold that reduces the fraction of single positives in technical replicates by at least 95 % (see Methods).
+ +6) In the miRNAseq preprocessing, it appears that Bowtie was used to map miRNAs to the hg38 genome. The annotation procedure is described in mat and met, but I could not identify the part of code associated to the miRNA annotation. + +To be done: Adding in the README, a summary of the steps performed in each analysis workflow would enhance its readability and usage of the scripts. + +A high- level description of the workflow for each preprocessing pipeline has been added to the README file of the repository, which further clarifies how the scripts operate. Additionally, the scripts themselves are thoroughly commented. All of this, together with the descriptions in the methods section of the manuscript, should be sufficient for users to follow and execute the scripts with ease. + +7) The link http://r2platform.com/exRNAQC/ provides 404 Not Found + +The forward link included in the initial manuscript version was case sensitive (exrnaqc versus exRNAQC). This is now solved; both links (http://r2platform.com/exRNAQC/ and http://r2platform.com/exrnaqc/) can be used to access the data in R2. + +Minor: 1) In fig. 2A/B the x axis refers to number of detected mRNAs/miRNAs. I was unable to find in the text which criteria were used to define a detectable mRNA/miRNA. + +As stated in the caption of Fig. 2, this number refers to the number of detected mRNAs (a) or miRNAs (b) that reached the count threshold. Details on how this threshold was set are described in the Methods (lines 635- 646). In the revised manuscript, we included a cross- reference to the Methods section in the caption of Fig. 2 to make this more clear. + +<--- Page Split ---> + +## Reviewer #3 + +The manuscript provides a very well designed, comprehensive evaluation of pre- analytical factors that may affect miRNA and mRNA results in biomarker studies. The authors evaluated 10 different types of blood collection tubes, 3 different time intervals, and 8 different purification methods. One of the more surprising results is that the "basic" EDTA blood tubes performed better than the preservation tubes. Other findings are less surprising (such as that increasing input volume provides better results), but provide important considerations for users collecting biofluid samples. The work is well supported by the data and the methodology is sound. Additionally, the authors have made the data publicly available so future researchers can further analyze the results. + +I have verified that the link works but have not tried to run the code or assess it. + +<--- Page Split ---> diff --git a/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file_det.mmd b/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..24d29f049841fee2e4b6b281f558823263ebc35f --- /dev/null +++ b/peer_reviews/596c2134155e3922c72a3c459db5cee8f2d8e11ca0995d47c8f2c2807e017c4f/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file_det.mmd @@ -0,0 +1,293 @@ +<|ref|>title<|/ref|><|det|>[[73, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 97, 296, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 828, 237]]<|/det|> +# Blood collection tube and RNA purification method recommendations for extracellular RNA transcriptome profiling + +<|ref|>text<|/ref|><|det|>[[73, 249, 518, 266]]<|/det|> +Corresponding Author: Professor Jo Vandesompel + +<|ref|>text<|/ref|><|det|>[[72, 299, 864, 313]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 351, 144, 365]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 377, 219, 391]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 403, 160, 416]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 430, 238, 443]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 443, 920, 508]]<|/det|> +The authors present a comprehensive study about the quality of different RNA purification methods. With a well- thought- out study design, they compared the performance of classic and manufacturer- designated preservation tubes by sequencing either mRNA or miRNA and evaluate the results with purposely designed performance metrics. In general, the study is well designed and clearly written, despite some complex metrics. With minor adjustments, the study could help to provide a validated and clinically applicable gold- standard for RNA- and miRNA- sequencing from blood samples. + +<|ref|>text<|/ref|><|det|>[[73, 521, 191, 533]]<|/det|> +Minor comments. + +<|ref|>text<|/ref|><|det|>[[73, 533, 884, 560]]<|/det|> +- Preservation tubes were only tested for after longer time intervals. It would be interesting to see how the classic tubes perform after 7 or 14 days. + +<|ref|>text<|/ref|><|det|>[[73, 560, 888, 587]]<|/det|> +- Fig 2a-b could be presented as a boxplot. Thereby the variance would still be visible, but the figure would be easier to understand, while showing additional statistics, including the variance between replicates. + +<|ref|>text<|/ref|><|det|>[[73, 611, 282, 625]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 650, 160, 663]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 677, 238, 690]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 690, 686, 704]]<|/det|> +Very interesting work that provides useful information for the design of exRNAseq studies. + +<|ref|>text<|/ref|><|det|>[[73, 705, 118, 716]]<|/det|> +Major: + +<|ref|>text<|/ref|><|det|>[[73, 717, 802, 730]]<|/det|> +1) I verified the access to the raw data (FASTQ), and now it is necessary to request permission to access it. + +<|ref|>text<|/ref|><|det|>[[73, 730, 920, 789]]<|/det|> +To be done: The FASTQ data must be made openly accessible without any restrictions once the article is published. 2) Although the GitHub repository is well-documented (https://github.com/OncoRNALab/exRNAQC/), there are several issues related to data reproducibility. The repository lacks a section outlining the overall structure of the analysis steps. In its current format, the GitHub relies on a Slurm workflow tailored to the UGent HPC system, which makes it virtually impossible to reproduce the data analysis on an independent system, unless rewriting all code. + +<|ref|>text<|/ref|><|det|>[[73, 790, 920, 830]]<|/det|> +3) The GitHub repository lacks a clear description of the files required for each analysis. For instance, in the RNASeq_preprocessing.py file, the data to be processed is located in the folder NSQ_run453-84636552_Run458-86026942, but the contents of this folder are not clearly explained. This issue also extends to the preprocessing of miRNAs. + +<|ref|>text<|/ref|><|det|>[[73, 830, 910, 856]]<|/det|> +To be done: The input of the pipelines must be the folder containing the downloadable fastqs. + +<|ref|>text<|/ref|><|det|>[[73, 855, 920, 881]]<|/det|> +4) I reviewed the steps provided in https://github.com/OncoRNALab/exRNAQC/, and I noticed that some files, such as genome annotation including spikes, cannot be directly downloaded from a specific repository. + +<|ref|>text<|/ref|><|det|>[[73, 880, 920, 936]]<|/det|> +To be done: The authors must provide the procedure and input files necessary to generate the STAR index files and the BED files specified in RNASeq_preprocessing.py. To ensure reproducibility, the software used for the analysis should be supplied as a Docker or Singularity container. Additionally, all supplementary files required for the analyses should be made available in a Zenodo or fileshare repository, with the data structure pre-configured for access by the analysis software within the provided Docker/Singularity container. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 45, 908, 97]]<|/det|> +5) I also noticed that deduplication of reads was applied during the RNAseq preprocessing. However, several publications suggest that removing duplicates in bulk RNAseq does not necessarily improve data quality (https://pubmed.ncbi.nlm.nih.gov/28321364/, https://pubmed.ncbi.nlm.nih.gov/30001700/). To be done: The authors should provide a justification for their decision to include the deduplication procedure in their analysis. + +<|ref|>text<|/ref|><|det|>[[70, 97, 904, 150]]<|/det|> +6) In the miRNAseq preprocessing, it appears that Bowtie was used to map miRNAs to the hg38 genome. The annotation procedure is described in mat and met, but I could not identify the part of code associated to the miRNA annotation. To be done: Adding in the README, a summary of the steps performed in each analysis workflow would enhance its readability and usage of the scripts. + +<|ref|>text<|/ref|><|det|>[[72, 150, 541, 164]]<|/det|> +7) The link http://r2platform.com/exRNAQC/ provides 404 Not Found + +<|ref|>text<|/ref|><|det|>[[72, 177, 118, 189]]<|/det|> +Minor: + +<|ref|>text<|/ref|><|det|>[[70, 189, 895, 216]]<|/det|> +1) In fig. 2A/B the x axis refers to number of detected mRNAs/miRNAs. I was unable to find in the text which criteria were used to define a detectable mRNA/miRNA. + +<|ref|>text<|/ref|><|det|>[[73, 243, 283, 256]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 281, 161, 295]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 308, 238, 320]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 321, 904, 411]]<|/det|> +The manuscript provides a very well designed, comprehensive evaluation of pre- analytical factors that may affect miRNA and mRNA results in biomarker studies. The authors evaluated 10 different types of blood collection tubes, 3 different time intervals, and 8 different purification methods. One of the more surprising results is that the "basic" EDTA blood tubes performed better than the preservation tubes. Other findings are less surprising (such as that increasing input volume provides better results), but provide important considerations for users collecting biofluid samples. The work is well supported by the data and the methodology is sound. Additionally, the authors have made the data publicly available so future researchers can further analyze the results. + +<|ref|>text<|/ref|><|det|>[[73, 424, 283, 437]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 437, 610, 450]]<|/det|> +I have verified that the link works but have not tried to run the code or assess it. + +<|ref|>text<|/ref|><|det|>[[73, 464, 144, 477]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 490, 219, 503]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 515, 160, 528]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 542, 238, 554]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 555, 761, 568]]<|/det|> +The authors addressed all my comments and reasonably explained their choices of data illustrations. + +<|ref|>text<|/ref|><|det|>[[73, 568, 690, 581]]<|/det|> +Additionally they updated their github repository to make the data easier to be reproduced. + +<|ref|>text<|/ref|><|det|>[[73, 581, 504, 594]]<|/det|> +I have no further objections that stand in the way of publication. + +<|ref|>text<|/ref|><|det|>[[73, 607, 283, 620]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 646, 160, 659]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 672, 238, 685]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 685, 722, 699]]<|/det|> +All points raised were clearly addressed. No extra work is required for what concern my review. + +<|ref|>text<|/ref|><|det|>[[73, 711, 283, 724]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[70, 724, 817, 738]]<|/det|> +All points associated to the code were sufficiently addressed. No extra work is required from my point of view. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 84, 881, 145]]<|/det|> +## Revision of manuscript NCOMMS-23-01885A-Z Blood collection tube and RNA purification method recommendations for extracellular RNA transcriptome profiling: A large-scale pre-analytical variable performance evaluation + +<|ref|>sub_title<|/ref|><|det|>[[119, 159, 333, 174]]<|/det|> +## Point-by-point response + +<|ref|>text<|/ref|><|det|>[[119, 175, 878, 220]]<|/det|> +Below, you can find our answers to the reviewers' comments. Corresponding revisions of the manuscript are highlighted in the manuscript; page numbers below refer to the revised manuscript version. + +<|ref|>sub_title<|/ref|><|det|>[[119, 235, 226, 250]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[119, 263, 879, 370]]<|/det|> +The authors present a comprehensive study about the quality of different RNA purification methods. With a well- thought- out study design, they compared the performance of classic and manufacturer- designated preservation tubes by sequencing either mRNA or miRNA and evaluate the results with purposely designed performance metrices. In general, the study is well designed and clearly written, despite some complex metrices. With minor adjustments, the study could help to provide a validated and clinically applicable gold- standard for RNA- and miRNA- sequencing from blood samples. + +<|ref|>text<|/ref|><|det|>[[119, 385, 260, 399]]<|/det|> +Minor comments. + +<|ref|>text<|/ref|><|det|>[[119, 400, 878, 430]]<|/det|> +- Preservation tubes were only tested for after longer time intervals. It would be interesting to see how the classic tubes perform after 7 or 14 days. + +<|ref|>text<|/ref|><|det|>[[118, 444, 879, 760]]<|/det|> +For each tube type (both preservation and classic tubes), a baseline value was established by processing the blood tube immediately after collection. To mimic same- day and next- day processing in routine lab situations, additional processing time intervals were set to 4 and 16 hours for classic tube types. For preservation tubes, which are specifically marketed to stabilize extracellular nucleic acids for 7 (and up to 14) days, additional processing time intervals of 24 and 72 hours were selected. Preservation tubes have thus indeed been tested for longer processing time intervals compared to the classic tubes, but not for the extremes claimed by the manufacturer. Additionally, we opted to only use longer processing time intervals for preservation tubes, as these tubes were purposely developed to conveniently allow more time between the blood draw and further processing steps, while classic tubes are not specifically designed to stabilize cell- free nucleic acids. Of note, based on the differential abundance analyses, GSEA and deconvolution analyses (results described in lines 233- 241, lines 244- 250 and lines 273- 280), we conclude that even the high- performing classic tubes processed within 4 and 16 hours demonstrate mRNA composition changes over time, and that these changes become more pronounced over time. As such, testing longer time intervals for these classic tubes will not change the recommendations put forward in our manuscript, i.e. blood processing should be completed within 4 hours after collection. These findings are supported by other publications demonstrating changes over time for specific extracellular m(i)RNAs derived from classic tubes (Fernando et al., Clin Biochem., 2012; Page et al., PLoS One, 2013; Glinge et al., PLoS One, 2017; Gahlawat et al., Int J Mol Sci., 2019; Murray et al., Cancer Epidemiol Biomarkers Prev., 2018). + +<|ref|>text<|/ref|><|det|>[[119, 775, 878, 819]]<|/det|> +- Fig 2a-b could be presented as a boxplot. Thereby the variance would still be visible, but the figure would be easier to understand, while showing additional statistics, including the variance between replicates. + +<|ref|>text<|/ref|><|det|>[[118, 834, 879, 910]]<|/det|> +Figure 2a and b represent the absolute number of detected mRNAs (a) and miRNAs (b) that reached the count threshold (see Methods) for each of the tested RNA purification and plasma input volume combinations. Each combination was tested in triplicate, resulting in 3 dots for each of them. As such, we demonstrate all individual data points, which is preferred for samples size less than 5. Box plot construction requires at least 5 data points (preferably + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 878, 115]]<|/det|> +larger; Krzywinski M et al., Nat Methods, 2014). Therefore, we decided not to transform this figure into a boxplot. + +<|ref|>sub_title<|/ref|><|det|>[[119, 130, 228, 144]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[118, 159, 880, 250]]<|/det|> +Very interesting work that provides useful information for the design of exRNAseq studies. Major: 1) I verified the access to the raw data (FASTQ), and now it is necessary to request permission to access it. To be done: The FASTQ data must be made openly accessible without any restrictions once the article is published. + +<|ref|>text<|/ref|><|det|>[[118, 264, 880, 504]]<|/det|> +Samples from healthy donors have been collected under the General Data Protection Regulation (or GDPR) (EU) 2016/679 of April 27, 2016 and the Belgian law of July 30, 2018, on the protection of individuals related to the processing of personal data and on the free movement of such data. In this context, the ICF of our study (approved by the ethics committee of Ghent University Hospital; approval number B670201733701) states that pseudonymised data may be shared with other researchers for future research projects. Though, such future studies first need to be ethically approved. For that reason, the fastq data cannot be made openly accessible without any restrictions and were therefore shared through EGA, providing secure access to data for authorised researchers and clinicians. The data of our study have already been released by EGA, and sharing requests can be submitted. We want to contribute to the practice of open science and are open for collaborations, but need to adhere to Belgian and European legislations on data sharing. Note that the derived count data are openly accessible (without any restrictions) through ArrayExpress, and browsable access is provided through the R2 Genomics Analysis and Visualization Platform. We recognize that part of this information was lacking in the Data Availability statement, and have updated this in the revised manuscript (line 742- 762). + +<|ref|>text<|/ref|><|det|>[[118, 504, 880, 563]]<|/det|> +In context of the manuscript review process, we have contacted the EGA helpdesk to provide anonymous data access to the reviewers. Unfortunately, there is no easy solution to share data in EGA with reviewers. Data access is possible, but requires several steps to be taken to secure the reviewers anonymity: + +<|ref|>text<|/ref|><|det|>[[118, 564, 880, 699]]<|/det|> +(1) We inform EGA that we agree to have our data downloaded by an anonymous person and include a contact person at Nature Communications in this e-mail communication. +(2) EGA will contact Nature Communications to confirm the download details. A download account for the reviewer will be set up (using the email address of the reviewer; needed for security reasons). Nature Communications needs to contact the reviewer to make them aware that: (i) The reviewer must inform EGA as soon as the data are downloaded. (ii) That the data will be deleted once the review is completed. +(3) EGA will share the data with the reviewer. Please, reach out to the editor to get access to the data. + +<|ref|>text<|/ref|><|det|>[[118, 714, 880, 805]]<|/det|> +2) Although the GitHub repository is well-documented (https://github.com/OncoRNALab/exRNAQC/), there are several issues related to data reproducibility. The repository lacks a section outlining the overall structure of the analysis steps. In its current format, the GitHub relies on a Slurm workflow tailored to the UGent HPC system, which makes it virtually impossible to reproduce the data analysis on an independent system, unless rewriting all code. + +<|ref|>text<|/ref|><|det|>[[118, 805, 876, 835]]<|/det|> +We agree with the reviewer that, in its current form, the code would be difficult to reproduce. The following steps have been taken to address this concern: + +<|ref|>text<|/ref|><|det|>[[146, 836, 878, 896]]<|/det|> +Singularity Containerization: a Singularity definition file was developed that packages the complete software environment, including all dependencies. This enables the preprocessing pipelines to be executed on any Linux- based system with Singularity installed, increasing the portability of the analysis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 880, 150]]<|/det|> +- Rewritten Preprocessing Pipelines: The preprocessing pipelines have been adapted to work within the Singularity container, ensuring that the entire workflow can now be reproduced across various computational environments without modification to the core code. + +<|ref|>text<|/ref|><|det|>[[147, 145, 880, 251]]<|/det|> +- Repository Updates: The pipeline scripts, along with the Singularity definition file, have been added to the GitHub repository. Furthermore, we have included a section that outlines the overall structure of the analysis steps and provides detailed instructions on running the pipeline using Singularity. This section aims to guide users through setting up and executing the analysis on their own systems, independent of the UGent HPC environment. Finally, a small dataset have been added to the repository for testing purposes. + +<|ref|>text<|/ref|><|det|>[[118, 250, 880, 310]]<|/det|> +3) The GitHub repository lacks a clear description of the files required for each analysis. For instance, in the RNASeq_preprocessing.py file, the data to be processed is located in the folder NSQ_run453-84636552_Run458-86026942, but the contents of this folder are not clearly explained. This issue also extends to the preprocessing of miRNAs. + +<|ref|>text<|/ref|><|det|>[[120, 309, 875, 325]]<|/det|> +To be done: The input of the pipelines must be the folder containing the downloadable fastqs. + +<|ref|>text<|/ref|><|det|>[[118, 339, 880, 461]]<|/det|> +The pipeline now uses a sample sheet as the input, which contains information about the sample name or sample ID, along with the paths to the respective fastq files. This makes the structure of the input directory flexible, as the pipeline will reference the paths provided in the sample sheet rather than relying on specific folder structures. To assist users, we have included a script in the repository that can automatically generate a sample sheet from a given directory of files. This simplifies the process for users and ensures the sample sheet is formatted correctly for the pipeline. Finally, we have also provided an example sample sheet in the repository. + +<|ref|>text<|/ref|><|det|>[[118, 474, 880, 520]]<|/det|> +4) I reviewed the steps provided in https://github.com/OncoRNALab/exRNAQC/, and I noticed that some files, such as genome annotation including spikes, cannot be directly downloaded from a specific repository. + +<|ref|>text<|/ref|><|det|>[[118, 519, 880, 609]]<|/det|> +To be done: The authors must provide the procedure and input files necessary to generate the STAR index files and the BED files specified in RNASeq_preprocessing.py. To ensure reproducibility, the software used for the analysis should be supplied as a Docker or Singularity container. Additionally, all supplementary files required for the analyses should be made available in a Zenodo or fileshare repository, with the data structure pre-configured for access by the analysis software within the provided Docker/Singularity container. + +<|ref|>text<|/ref|><|det|>[[118, 623, 880, 715]]<|/det|> +Detailed instructions, along with the necessary files, have been added to the repository to guide users in generating the required indexes (STAR, Kallisto, Bowtie) as well as the GTF and BED files. This includes clear steps for building the indexes used in the preprocessing pipelines, ensuring that users can replicate the setup on their own systems. As mentioned in our response to the second comment of Reviewer 2, we have provided a Singularity container that packages all the software and dependencies required for the analysis. + +<|ref|>text<|/ref|><|det|>[[118, 729, 880, 789]]<|/det|> +5) I also noticed that deduplication of reads was applied during the RNASeq preprocessing. However, several publications suggest that removing duplicates in bulk RNASeq does not necessarily improve data quality (https://pubmed.ncbi.nlm.nih.gov/28321364/, https://pubmed.ncbi.nlm.nih.gov/30001700/). + +<|ref|>text<|/ref|><|det|>[[118, 789, 880, 820]]<|/det|> +To be done: The authors should provide a justification for their decision to include the deduplication procedure in their analysis. + +<|ref|>text<|/ref|><|det|>[[118, 834, 880, 911]]<|/det|> +Several papers indeed suggest that removing PCR duplicates does not improve data quality. However, these studies were performed on RNA- sequencing data from tissue samples, which typically contains a relatively limited number of PCR duplicates (below \(50\%\) ). RNA- sequencing data from exRNA samples is characterized by high PCR duplication rates (driven by the low amount of RNA input in the library preparation). We therefore decided to assess the impact of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 160]]<|/det|> +duplicate removal on data reproducibility and observed that the correlation of exRNA abundance estimates between replicate samples improved upon duplicate removal (see Rebuttal Figure 1). Based on these observations, we decided to implement duplicate removal for all samples. We have added this info to the manuscript and included the figure in the supplements as Supplementary Fig. S17. + +<|ref|>image<|/ref|><|det|>[[120, 178, 870, 410]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[118, 413, 880, 490]]<|/det|> +
Rebuttal Figure 1. Duplicate removal leads to an improved correlation of exRNA abundance estimates between RNA purification method replicates. Comparison of RNA purification replicates of the Norgen method (gene counts) without (left) and with (right) duplicate removal. R2 is the coefficient of determination (linear model that fits log10 values). Higher R2-values indicate better reproducibility. Green dots represent data points that are filtered out using the count threshold. This is a threshold that reduces the fraction of single positives in technical replicates by at least 95 % (see Methods).
+ +<|ref|>text<|/ref|><|det|>[[118, 518, 880, 564]]<|/det|> +6) In the miRNAseq preprocessing, it appears that Bowtie was used to map miRNAs to the hg38 genome. The annotation procedure is described in mat and met, but I could not identify the part of code associated to the miRNA annotation. + +<|ref|>text<|/ref|><|det|>[[120, 564, 880, 595]]<|/det|> +To be done: Adding in the README, a summary of the steps performed in each analysis workflow would enhance its readability and usage of the scripts. + +<|ref|>text<|/ref|><|det|>[[118, 608, 880, 685]]<|/det|> +A high- level description of the workflow for each preprocessing pipeline has been added to the README file of the repository, which further clarifies how the scripts operate. Additionally, the scripts themselves are thoroughly commented. All of this, together with the descriptions in the methods section of the manuscript, should be sufficient for users to follow and execute the scripts with ease. + +<|ref|>text<|/ref|><|det|>[[120, 698, 682, 714]]<|/det|> +7) The link http://r2platform.com/exRNAQC/ provides 404 Not Found + +<|ref|>text<|/ref|><|det|>[[118, 728, 880, 775]]<|/det|> +The forward link included in the initial manuscript version was case sensitive (exrnaqc versus exRNAQC). This is now solved; both links (http://r2platform.com/exRNAQC/ and http://r2platform.com/exrnaqc/) can be used to access the data in R2. + +<|ref|>text<|/ref|><|det|>[[118, 790, 874, 835]]<|/det|> +Minor: 1) In fig. 2A/B the x axis refers to number of detected mRNAs/miRNAs. I was unable to find in the text which criteria were used to define a detectable mRNA/miRNA. + +<|ref|>text<|/ref|><|det|>[[118, 849, 880, 910]]<|/det|> +As stated in the caption of Fig. 2, this number refers to the number of detected mRNAs (a) or miRNAs (b) that reached the count threshold. Details on how this threshold was set are described in the Methods (lines 635- 646). In the revised manuscript, we included a cross- reference to the Methods section in the caption of Fig. 2 to make this more clear. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 99, 228, 115]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[118, 130, 881, 266]]<|/det|> +The manuscript provides a very well designed, comprehensive evaluation of pre- analytical factors that may affect miRNA and mRNA results in biomarker studies. The authors evaluated 10 different types of blood collection tubes, 3 different time intervals, and 8 different purification methods. One of the more surprising results is that the "basic" EDTA blood tubes performed better than the preservation tubes. Other findings are less surprising (such as that increasing input volume provides better results), but provide important considerations for users collecting biofluid samples. The work is well supported by the data and the methodology is sound. Additionally, the authors have made the data publicly available so future researchers can further analyze the results. + +<|ref|>text<|/ref|><|det|>[[118, 279, 766, 295]]<|/det|> +I have verified that the link works but have not tried to run the code or assess it. + +<--- Page Split ---> diff --git a/peer_reviews/5990cefd5d727b2ec991fe98ed069cbd1a125f801e574cfe8b44205a3aa75716/supplementary_1_Peer Review File/images_list.json b/peer_reviews/5990cefd5d727b2ec991fe98ed069cbd1a125f801e574cfe8b44205a3aa75716/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..4f75aff67e3222eca0a84b73795852ad65556c89 --- /dev/null +++ b/peer_reviews/5990cefd5d727b2ec991fe98ed069cbd1a125f801e574cfe8b44205a3aa75716/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1,40 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 400 px.", + "footnote": [], + "bbox": [ + [ + 95, + 533, + 700, + 778 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 560 px (original box size).", + "footnote": [], + "bbox": [ + [ + 95, + 88, + 700, + 330 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Response Letter Figure 2. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 560 px (original box size).", + "footnote": [], + "bbox": [], + "page_idx": 35 + } +] \ No newline at end of file diff --git a/peer_reviews/5990cefd5d727b2ec991fe98ed069cbd1a125f801e574cfe8b44205a3aa75716/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/5990cefd5d727b2ec991fe98ed069cbd1a125f801e574cfe8b44205a3aa75716/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a3d04f31ac0be41029a37215b46a06fb5f45959a --- /dev/null +++ b/peer_reviews/5990cefd5d727b2ec991fe98ed069cbd1a125f801e574cfe8b44205a3aa75716/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,830 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Structural & Molecular Biology Manuscript Title: Structure and Interactions of the Endogenous Human Commander Complex Corresponding author name(s): Markku Varjosalo, Juha Huiskonen + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +Message: 11th Aug 2023 + +Dear Dr. Varjosalo, + +Thank you again for submitting your manuscript "Structure and Interactions of the Endogenous Human Commander Complex". We now have comments (below) from the 2 reviewers who evaluated your paper. In light of those reports, we remain interested in your study and would like to see your response to the comments of the referees, in the form of a revised manuscript. + +You will see that while reviewers appreciate the results, they raise several concerns which will need to be addressed in a revision. Specifically, we would ask you to restructure the manuscript, including comparative analysis, to highlight the novelty and significance of the presented data, as suggested by the reviewers. You will notice that while reviewer #1 noted the value of the structure of the native complex, as clearly different from the model presented by Healy et al, reviewer #2 points out lack of novelty in the structure itself. We ourselves had to look at the cryo- EM data and models to understand the advance, which is why we would recommend this to be rectified in the manuscript itself, clearly stating the difference of the native complex obtained in this study, and how it stands compared to published literature. While we agree with reviewer #1 that further functional analysis would strengthen the manuscript, in the interest of timeliness we do not consider it essential in the context of the current work, especially considering the added value of the interactome. + +Please be sure to address/respond to all concerns of the referees in full in a point- by- point response and highlight all changes in the revised manuscript text file. If you have comments that are intended for editors only, please include those in a separate cover letter. + +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are + +<--- Page Split ---> + +# natureresearch + +technically impossible or unlikely to yield a meaningful outcome. We are always happy to discuss revision plans over the phone if the requests are not clear. Please reach out to me if you would like to schedule a call. + +We expect to see your revised manuscript within 6 weeks. If you cannot send it within this time, please contact us to discuss an extension; we would still consider your revision, provided that no similar work has been accepted for publication at NSMB or published elsewhere. + +As you already know, we put great emphasis on ensuring that the methods and statistics reported in our papers are correct and accurate. 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Deposition of deep sequencing and microarray data is mandatory, and the datasets must be released prior to or upon publication. To avoid delays in publication, dataset accession numbers must be supplied with the final accepted manuscript and appropriate release dates must be indicated at the galley proof stage. + +While we encourage the use of color in preparing figures, please note that this will incur a charge to partially defray the cost of printing. Information about color charges can be found at http://www.nature.com/nsmb/authors/submit/index.html#costs + +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please use the link below to submit your revised manuscript and related files: + +## [Redacted] + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +<--- Page Split ---> + +# natureresearch + +Sincerely, + +Katarzyna Ciazynska (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +Referee expertise: + +Referee #1: cryo- EM, endosomal trafficking + +Referee #2: cryo- EM, endosomal trafficking + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +Recently discovered Commander complex exerts its function in multiple processes; however, structural information is lacking to deconvolute the underlying mechanisms. The proposed manuscript elegantly combines mass- spectrometric analysis with cryo- electron microscopy to visualize the whole commander complex and systematically analyze its interactome. This approach is granted for a 16- subunit commander complex and, in the broader context, sets up a promising way to parallelize molecular and structural discoveries of challenging biological assemblies. + +The authors first created cell lines with one of the commander subunits with MAC tag (BIRA\* biotinylation enzyme plus affinity purification peptides). They systematically explored subunits interactomes, cross- referencing Bio- ID and affinity purification mass spectroscopy (AP- MS) to get an insight into the stability and composition of commander assembled from endogenously expressed properties (except the bait under control of inducible promotor). The verified reported and discovered a plethora of new binders. The binders list highlights multiple roles of the commander. It includes proteins working in the Cilium Assembly pathway, membrane trafficking (exocyst, PI3P phosphatase), inflammation, and cytoskeleton organization, to name a few functional clusters. Finally, the MS analysis pinpointed posttranslational modification sites. + +Following the MS, the cell line with COMMD9 bait was used to isolate the natively assembled commander for cryo- EM structure determination. SPA analysis converged on the map resolving primarily the COMMD ring. Cross- linking was used to restrict the conformational heterogeneity of the complex and succeeded in resolving the whole commander complex. As expected, the COMMD ring map still led in resolution and resolved side chains; nevertheless, the CCDCs and Retriever modules of the commander could now be resolved to the secondary structure using focused alignment. Commander architecture from cryo- EM map drastically differs from the predicted models (Healy et al. 2023; Boesch et al. 2023), featuring \(\sim 90\) degrees of the COMMD ring rotation and other major differences. This finding is also valuable as a benchmark for predicting complex + +<--- Page Split ---> + +# natureresearch + +tertiary structures. Furthermore, the structural studies were complemented by molecular dynamic simulations pinpointing conformation variability in COMMD that may bridge retriever and DENND10. + +Finally, the manuscript looks closely at the loosely associated interactors discovered by proximity biotinylation (BioID- MS). BioID- MS proteome is dominated by inter- complex binding reiterating on commander multiple roles. Distance dependence of biotinylation by BirA\* allowed the identification of two interaction clusters in the commander surface. + +Overall the manuscript brings important novel insights and is written compellingly with sufficient experiential evidence. Authors deserve special credit for clear visual language and concise text. + +Here I propose text and figure changes to improve manuscript clarity further. + +## Figure1 + +Fig1A is a good entry illustration but can be made more explicit. I suggest adding a legend for the elements of MAC tag and affinity resins that allow understanding of which tag element is used, similar to the figures in your Liu et al 2018 paper. + +The arrows from AP- MS and XL- MS branches point to a mass spectrometer (?), but the BioID- MS - to the PPI analysis icon. I suggest leaving only PPI analysis in and converging on it all three paths. + +Outline conditions for harsh and soft lysis conditions in the figure, i.e. "harsh, 0.1% SDS", "soft, 0.5% IGEPAL". + +Replace the SEC panel in panel A with panel E. Use text instead of pictograms of molecules for SEC peaks designation. + +On the right from the Cryo- EM block, you could name and show all four maps from grey circles in FigS2. + +Also, please include Coomassie stained PAGE of native and cross- linked Commander used for cryo- EM. + +Fig 1D. Define table axes. If feasible, introduce a better graphical explanation of the colour/circle size code. Panel A can be used to reference specific branches of the MS. + +Consider moving panel B to supplementary if more space is needed. + +AvgSpec/Relative AvgSpec abundance needs a better explanation for readers outside the MS field. Consider extending the Quantification and statistical analysis chapter and explaining the interpretation of two marginal data points (i.e. for good and bad binders). + +Line 142. Comment why COMMD9 was chosen as bait. + +Line 480. Cloning of Commander complex components. Describe cell genotype in plain language. If I understand correctly, cell lines contained an additional copy (over the WT genome) of genome- integrated MAC- tagged tagged bait under a tetracycline- inducible promotor. Upon induction, the binders will preferentially bind to the tagged due to its higher titer than WT copies. What is the estimated bait expression level compared to the endogenously expressed protein? + +Line 91. Highlight these newly discovered interactors in Fig S1. + +Line 567. Give protein concentration in the BS3 cross- linking reaction + +FigS2. Add title "cross- linked" above panels D- G. Show FSC curves for the final maps. + +<--- Page Split ---> + +Line 596. Should "tandem" be replaced with "in parallel"? Tandem implies sequential order. + +Fig3J. Indicate the NN- CH domain in the figure. Should CCDC93 NTD be changed to CCDC93 NN- CH? + +FigS4. Fix panel assignment (F panel is skipped). The comparison to Healy at al 2023 AF2 model is interesting and will be clearer using pipes and plunks depiction or "ragdoll model" with complex parts presented as geometrical shapes to highlight dramatic differences in COMMDS ring rotation and CCDCs coils. Aligning the models on Vps35L may be more informative. + +Line 134. DENND10 binds the commander via CCDCs, making the statement in line 134 counterintuitive. Please clarify this point. + +Boesch DJ et al. (2023) Structural Organization of the Retriever- CCC Endosomal Recycling Complex. bioRxiv. doi:10.1101/2023.06.06.543888 Healy MD et al. (2023) Structure of the endosomal Commander complex linked to Ritscher- Schinzel syndrome. Cell 186:2219- 2237 e2229. doi:10.1016/j.cell.2023.04.003 + +## Reviewer #2: + +Remarks to the Author: + +Laulumaa et al. here report the use of AP- MS and BioID- MS to make a comprehensive characterization of stable and transient interactions of the human Commander complex. The authors propose a set of biological processes where Commander could have essential roles such as endosomal transport, actin nucleation, immune response, transcription regulation, centriole replication, centrosomal targeting and cilium assembly. In addition, the authors purified and solved the structure of the whole Commander complex by single particle cryo- EM. The structure consist of a 16- protein assembly arranged in two sub- complexes; an heterodecameric ring of the COMMD proteins (COMMD 1- 10) connected to the retriever sub- complex (VPS35L, VPS26C and VPS29) by the CCDC22- CCDC93 heterodimer which interacts with DENND10 through a V- shaped coil (R- coil). The atomic model built into the cryo- EM density is supported by several XL- MS crosslinks. Overall, this is a well- executed study that provides the molecular architecture of the full Commander complex and spans its interactome. Unfortunately, the recent publication of the structure of the Commander complex (Healy et al. 2023) diminishes the originality of the present work. Nevertheless, while the structure of the Commander complex from Healy et al. was determined by combining data form cryo- EM, X- ray crystallography and AF modelling of distinct sub- structures, the present work by Laulumaa et al. provides a complete picture of the full sixteen subunits. Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al. On the other hand, the interactome analysis reads as a dry catalog of interactions with assigned GO terms and biological processes. The manuscript lacks a logical flow where functional/biological mechanisms are addressed throughout the structure. Similarly, the lack of functional assays 'in cellulo' diminishes general interest. For example, assessing the integrity of the Commander complex throughout site directed mutagenesis and evaluating the significance on novel roles such + +<--- Page Split ---> + +# natureresearch + +as cilia modulation could add novelty and interest to a wider audience. In summary, the lack of novelty in the structure and the absence of functional implications connected to Commander assembly have dumped the excitement for this manuscript. Other more specific issues include: + +- This reviewer has not been able to see the PDB validation report to assess the PDB model. +- Supplementary Table (REAGENT or RESOURCE) lacks several EMDB and PDB codes. They are denoted as 'EMD-XXX' or 'PDB: XXXX'. Same in 'Data availability' (lines 710-718) +- There is a very early fall of in the FCS(unmasked). Could it be because of the very large box size used in relation to the size of the complex?. Was it intended to capture flexible regions?. +- In section 4.2 of the validation report, there is a big difference in the reported resolution and the unmasked-calculated resolution. Could this be related to the large box size used? +- It might be something odd from the validation report but the mask looks larger in 2.6.1 than the projection in 2.1 (although the map in 2.5.1 looks large like the mask, it looks different to the 2.5.2). + +<--- Page Split ---> + +Dear reviewers, + +Dear reviewers,We thank you for your detailed and positive comments on our manuscript "Structure and Interactions of the Endogenous Human Commander Complex". See below our point- by- point response to your comments (in gray italics). Further, we have listed additional modifications and reported additional experiments at the end of this response. + +Reviewer 1: + +Remarks to the Author: + +Remarks to the Author:Recently discovered Commander complex exerts its function in multiple processes; however, structural information is lacking to deconvolute the underlying mechanisms. The proposed manuscript elegantly combines mass- spectrometric analysis with cryo- electron microscopy to visualize the whole commander complex and systematically analyze its interactome. This approach is granted for a 16- subunit commander complex and, in the broader context, sets up a promising way to parallelize molecular and structural discoveries of challenging biological assemblies. + +The authors first created cell lines with one of the commander subunits with MAC tag (BlrA\\* biotinylation enzyme plus affinity purification peptides). They systematically explored subunits interactomes, cross- referencing Bio- ID and affinity purification mass spectroscopy (AP- MS) to get an insight into the stability and composition of commander assembled from endogenously expressed properties (except the bait under control of inducible promotor). The verified reported and discovered a plethora of new binders. The binders list highlights multiple roles of the commander. It includes proteins working in the Cilium Assembly pathway, membrane trafficking (exocyst, PI3P phosphatase), inflammation, and cytoskeleton organization, to name a few functional clusters. Finally, the MS analysis pinpointed posttranslational modification sites. + +Following the MS, the cell line with COMMD9 bait was used to isolate the natively assembled commander for cryo- EM structure determination. SPA analysis converged on the map resolving primarily the COMMD ring. Cross- linking was used to restrict the conformational heterogeneity of the complex and succeeded in resolving the whole commander complex. As expected, the COMMD ring map still led in resolution and resolved side chains; nevertheless, the CCDCs and Retriever modules of the commander could now be resolved to the secondary structure using focused alignment. Commander architecture from cryo- EM map drastically differs from the predicted models (Healy et al. 2023; Boesch et al. 2023), featuring \(\sim 90\) degrees of the COMMD ring rotation and other major differences. This finding is also valuable as a benchmark for predicting complex tertiary structures. Furthermore, the structural studies were complemented by molecular dynamic simulations pinpointing conformation variability in COMMD that may bridge retriever and DENND10. Finally, the manuscript looks closely at the loosely associated interactors discovered by proximity biotinylation (BioID- MS). BioID- MS proteome is dominated by inter- complex binding reiterating on commander multiple roles. Distance dependence of biotinylation by + +<--- Page Split ---> + +BirA\* allowed the identification of two interaction clusters in the commander surface. + +Overall the manuscript brings important novel insights and is written compellingly with sufficient experiential evidence. Authors deserve special credit for clear visual language and concise text. + +Here I propose text and figure changes to improve manuscript clarity further. + +Figure 1 + +Fig 1A is a good entry illustration but can be made more explicit. I suggest adding a legend for the elements of MAC tag and affinity resins that allow understanding of which tag element is used, similar to the figures in your Liu et el 2018 paper. The arrows from AP- MS and XL- MS branches point to a mass spectrometer (?), but the BioID- MS - to the PPI analysis icon. I suggest leaving only PPI analysis in and converging on it all three paths. Outline conditions for harsh and soft lysis conditions in the figure, i.e. "harsh, 0.1% SDS", "soft, 0.5% IGEPAL". + +Thank you for your feedback on Figure 1. + +In response to your suggestions, we have revised Fig 1A to enhance its clarity and understandability. We added labels for both the SH- tag and the biotin ligase BirA, aiming to provide clearer visualization of the involved elements. + +We would like to clarify the representation of the Mass spectrometer and PPI analysis in Fig 1A. They are intended to represent the same analytical endpoint. To address the inconsistency you pointed out, we've adjusted the figure such that the arrow from BioID- MS now correctly points to the combined MS- analysis and PPI analysis icon. This should now provide a consistent representation of the analytical endpoints for the different techniques. + +Regarding the 'lysis conditions', we appreciate your suggestion on detailing the lysis conditions directly in the figure. However, the distinction between soft and harsh lysis is nuanced, involving more than just the choice of detergent. Specifically, the harsh lysis procedure also incorporates sonication in the presence of benzonase. We believe that these intricacies are best detailed in the experimental section, where they can be elaborated upon more extensively. Hence, we've opted to maintain a streamlined representation in Fig 1A, without the specific detergent details, to ensure its simplicity and accessibility. + +Replace the SEC panel in panel A with panel E. Use text instead of pictograms of molecules for SEC peaks designation. + +To clarify, the SEC depiction in panel A is intended as a schematic representation, designed to provide an overview of the workflow employed in our study. It is not a direct representation of experimental results. + +<--- Page Split ---> + +On the right from the Cryo- EM block, you could name and show all four maps from grey circles in FigS2. + +Thank you for your feedback regarding the representation of the Cryo- EM block in our figure. + +We understand the value in showcasing detailed results, as you've suggested with the four maps from grey circles in FigS2. However, the primary intent behind Figure 1 panel A was to provide a schematic overview of the entire workflow. Introducing specific results into this schematic might divert from its original purpose of giving a broad- strokes view of the methodology. + +Also, please include Coomassie stained PAGE of native and cross- linked Commander used for cryo- EM. + +Thank you for your suggestion to include a Coomassie stained PAGE of the native and cross- linked Commander used for cryo- EM. + +While in general we appreciate the value of such data, here we've decided against this inclusion for the following critical reasons: + +1. The procedure for purifying the cross-linked Commander complex results in a very limited yield ( \(\sim 25 \mu l\) at \(\sim 0.1 \mathrm{mg / ml}\) ). We, therefore, prioritized cryo-EM grid preparation over PAGE analysis. We were confident in this approach, as we had extensive AP-MS evidence of the constituents of the complex before cross-linking and identified all components of the complex in the MS data we collected. +2. Furthermore, given the mild nature of our cross-linking procedure, we anticipate a set of heterogeneously cross-linked complex isoforms in a PAGE analysis. Such an analysis would primarily indicate that cross-linking has occurred, without providing intricate details. We can obtain more precise information about the cross-linking pattern from the MS data we collected from the cross-linked, gel-filtered complex. + +Fig 1D. Define table axes. + +Table axes (bait / prey) have now been added to Figure 1 panel D. + +If feasible, introduce a better graphical explanation of the colour/circle size code. + +Thank you for the feedback on our graphical representation. + +To enhance clarity, we've renamed the colour/circle size codes to "Bait normalized AvgSpec" and "Relative AvgSpec." We've expanded on this in the figure legend with the + +<--- Page Split ---> + +following explanation on Page 25, line 8: "The color of each circle represents the abundance of each prey normalized to the mean abundance of the bait protein, and the circle radius indicates the relative abundance across all samples calculated by ProHits- Viz." + +We hope this adjustment provides a clearer understanding of the graphical elements used. + +Panel A can be used to reference specific branches of the MS. Consider moving panel B to supplementary if more space is needed. + +We have incorporated a reference to panel A in the text. + +AvgSpec/Relative AvgSpec abundance needs a better explanation for readers outside the MS field. Consider extending the Quantification and statistical analysis chapter and explaining the interpretation of two marginal data points (i.e. for good and bad binders). + +The average spectral count corresponds to the abundance of each prey protein in the sample and is represented by the node color. To evaluate the relative weight of each interaction among the presented samples, we calculated the relative abundance using the ProHits- Viz tool. + +We have updated the Figure 1 legend on Page 25, line 8 to read: "The color of each circle represents the abundance of each prey, normalized to the mean abundance of the bait protein. The circle radius indicates the relative abundance across all samples, as calculated by ProHits- Viz." + +Line 142. Comment why COMMD9 was chosen as bait. + +As there was initially very little information about the Commander complex assembly, we selected a few bait proteins for purification optimization. Out of the tested bait proteins, COMMD9 gave the highest yield, and was thus chosen for further optimization. + +Line 480. Cloning of Commander complex components. Describe cell genotype in plain language. If I understand correctly, cell lines contained an additional copy (over the WT genome) of genome- integrated MAC- tagged tagged bait under a tetracycline- inducible promotor. Upon induction, the binders will preferentially bind to the tagged due to its higher titer than WT copies. What is the estimated bait expression level compared to the endogenously expressed protein? + +The cell line used employs the Flp- In™ system, which allows the insertion of a single copy of the gene of interest at the FRT site in HEK cells. Expression of the protein of interest is + +<--- Page Split ---> + +induced using tetracycline, resulting in an expression level parallel to and on the same scale as the endogenous protein [PMID:19156129; PMID:23455922; PMID:28330616]. In BioID- MS experiments, proximity labeling biotinylation is induced using biotin. Intact protein complexes (AP- MS) or biotinylated proteins (after disruption of native protein complexes in BioID- MS) are extracted from the cell lysate using Strep- tactin resin, which binds both biotin and the SH- tag. The method is described in more detail in the articles by Liu et al [PMID:29568061], which we reference in the text on Page 12, line 30, and on Page 13, line 6. + +Line 91. Highlight these newly discovered interactors in Fig S1. + +Figure S1 was updated according to the reviewer's suggestion. Novel interactions are now presented on a grey square background. The legend for Figure S1A on Page 26, line 5, has been updated to: "(A) Dot- plot visualization of the Commander complex proteins' interactors detected by AP- MS. Each node color corresponds to the abundance of the average spectral count for each prey, and the node size indicates the relative abundance of the prey. BFDR values are denoted by circles around the nodes, and novel interactions are highlighted with a grey background." + +Line 567. Give protein concentration in the BS3 cross- linking reaction. + +As the cross- linking was conducted during ultrafiltration, the protein concentration increased during the crosslinking process. Therefore, we cannot specify the exact protein concentration. The 2 mM BS3 concentration we used was recommended in a protocol provided by the manufacturer. + +FigS2. Add title "cross- linked" above panels D- G. Show FSC curves for the final maps. + +The requested titles were added and FSC curves plotted for the final reconstructions as requested. + +Line 596. Should "tandem" be replaced with "in parallel"? Tandem implies sequential order. + +The text was modified according to reviewer's suggestion. + +<--- Page Split ---> + +Fig3J. Indicate the NN- CH domain in the figure. Should CCDC93 NTD be changed to CCDC93 NN- CH? + +We have changed the labeling to improve the distinction between NTDs of COMMD proteins and the NN- CH domains of CCDC proteins. These changes have also been implemented in the text by replacing CCDC NTDs with NN- CH. + +FigS4. Fix panel assignment (F panel is skipped). The comparison to Healy at al 2023 AF2 model is interesting and will be clearer using pipes and plunks depiction or "ragdoll model" with complex parts presented as geometrical shapes to highlight dramatic differences in COMMDS ring rotation and CCDCs coils. Aligning the models on Vps35L may be more informative. + +We thank the reviewer for pointing out the error in panel assignment and have rectified the issue. We settled on pipes representation for the comparison as it clarified the visualization significantly. While we did align the coils via VPS35L to test the representation, we felt that the current alignment center at DENND10 provides a clearer distinction on the relative differences in overall conformation of Retriever vs. the COMMD ring. + +Line 134. DENND10 binds the commander via CCDCs, making the statement in line 134 counterintuitive. Please clarify this point. + +We previously wrote: "Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker," which is indeed confusing. The clustering to find relative similarities takes into account the relative amount of each prey in each sample, and compares that to the other samples. As CCDCs have interactions that are different from the rest of the Commander complex proteins, their association to the other proteins is weaker despite their physical proximity to the COMMD proteins in the Commander complex. The text on Page 4, line 12 was modified to "Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker due to their interactions different from the rest of the complex (Fig. 1C)." + +<--- Page Split ---> + +Complex. bioRxiv. doi:10.1101/2023.06.06.543888 Healy MD et al. (2023) Structure of the endosomal Commander complex linked to Ritscher- Schinzel syndrome. Cell 186:2219-2237 e2229. doi:10.1016/j.cell.2023.04.003 + +<--- Page Split ---> + +Reviewer #2: + +Remarks to the Author: + +Laulumaa et al. here report the use of AP- MS and BioID- MS to make a comprehensive characterization of stable and transient interactions of the human Commander complex. The authors propose a set of biological processes where Commander could have essential roles such as endosomal transport, actin nucleation, immune response, transcription regulation, centriole replication, centrosomal targeting and cilium assembly. In addition, the authors purified and solved the structure of the whole Commander complex by single particle cryo- EM. The structure consist of a 16- protein assembly arranged in two sub- complexes; an heterodecameric ring of the COMMD proteins (COMMD 1- 10) connected to the retriever subcomplex (VPS35L, VPS26C and VPS29) by the CCDC22- CCDC93 heterodimer which interacts with DENND10 through a V- shaped coil (R- coil). The atomic model built into the cryo- EM density is supported by several XL- MS crosslinks. Overall, this is a well- executed study that provides the molecular architecture of the full Commander complex and spans its interactome. Unfortunately, the recent publication of the structure of the Commander complex (Healy et al. 2023) diminishes the originality of the present work. Nevertheless, while the structure of the Commander complex from Healy et al. was determined by combining data form cryo- EM, X- ray crystallography and AF modelling of distinct substructures, the present work by Laulumaa et al. provides a complete picture of the full sixteen subunits. Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al. On the other hand, the interactome analysis reads as a dry catalog of interactions with assigned GO terms and biological processes. The manuscript lacks a logical flow where functional/biological mechanisms are addressed throughout the structure. Similarly, the lack of functional assays 'in cellulo' diminishes general interest. For example, assessing the integrity of the Commander complex throughout site directed mutagenesis and evaluating the significance on novel roles such as cilia modulation could add novelty and interest to a wider audience. In summary, the lack of novelty in the structure and the absence of functional implications connected to Commander assembly have dumped the excitement for this manuscript. + +Regarding the reviewer's comment "Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al.", we would like to justify the lack of explicit comparisons to the Healy et al. structure. Their model's quaternary structure is based on predictions by alphafold2, while ours is based on experimental evidence combined with predictions. For the substructures that both models have experimental evidence on, our models agree. Therefore, we feel that extensive comparisons between the models is not relevant in the context of the present manuscript. + +<--- Page Split ---> + +Other more specific issues include: +- This reviewer has not been able to see the PDB validation report to assess the PDB model. + +We apologize and acknowledge that the reports were only provided during the review process for the editor and reviewers. + +- Supplementary Table (REAGENT or RESOURCE) lacks several EMDB and PDB codes. They are denoted as 'EMD-XXX' or 'PDB: XXXX'. Same in 'Data availability' (lines 710-718) + +We have rectified this error in the manuscript on Page 17, lines 35- 40, and thank the reviewer for pointing out the missing codes. + +- There is a very early fall of in the FCS(unmasked). Could it be because of the very large box size used in relation to the size of the complex?. Was it intended to capture flexible regions?. + +We acknowledge this feature in the FSC curves and as the Reviewer suspects it is due to the relatively large box size used here (required for not cropping out flexible parts of the complex). To demonstrate the effect of box size on FSC(unmasked), we have prepared cropped half- maps and recalculated the unmasked FSC, presented below (Figures 1 and 2). Please note that the "corrected" curves give highly similar results as expected and these values are the reported ones as they take this issue with box size into account. + +![](images/Figure_1.jpg) + +
Figure 1. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 400 px.
+ +<--- Page Split ---> +![](images/Figure_2.jpg) + +
Figure 2. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 560 px (original box size).
+ +- In section 4.2 of the validation report, there is a big difference in the reported resolution and the unmasked-calculated resolution. Could this be related to the large box size used? + +Yes. See above. + +- It might be something odd from the validation report but the mask looks larger in 2.6.1 than the projection in 2.1 (although the map in 2.5.1 looks large like the mask, it looks different to the 2.5.2). + +We have carefully checked the map and mask visualizations in the validation report, section 6 (map visualization). We note that the maps are shown at different scale in 6.5.1 (primary map) and 6.5.2 (raw map). This is a feature of the PDB validation server and beyond our control. The mask visualized in 6.6.1 is visualized in the same scale as the primary map. We confirm that these are how maps are displayed in the validation reports and do not affect our results or the maps we have deposited. + +<--- Page Split ---> + +The following additional modifications were made to the manuscript: + +1) + +We added additional experiments to the manuscript to further strengthen the interactome data. We generated HEK cell lines with pathogenic point mutations associated with Ritscher- Schinzel syndrome in VPS35L and CCDC22, and conducted BioID- MS for those samples. The following text was added to the manuscript on Page 10, line 3: "Ritscher- Schinzel syndrome point mutations alter PPIs of CCDC22 and VPS35L. + +The Commander complex has been associated with Ritscher- Schinzel syndrome (RSS) or X- linked intellectual disability (XLID) via point mutations in VPS35L and CCDC22 [PMID:31712251; PMID:21826058; PMID:23563313; PMID: 24916641]. Disease variants CCDC22(T17A), CCDC22(Y557C), and VPS35L(A830T) (Fig. 6A) are listed as "pathogenic" for RSS in GnomAD database [PMID:32461654]. Cell lines expressing these disease variants were generated for BioID- MS analysis to investigate their effect at the PPI level (Data S1). + +VPS35L(A830T) was shown to abolish its interaction with VPS29 [PMID:31712251]. Our data shows that the A830T mutation does not inhibit interaction with VPS26C, but separates VPS35L from the rest of the Commander complex and disrupts its interaction with the WASH complex (Fig. 6A- B). The RSS disease variants of CCDC22 have weaker interactions to COMMD proteins compared to the wild- type, but interact more with the WASH complex (Fig. S6B). The Reactome pathway analysis of disease mutant specific PPIs shows the strongest enrichment of R- HSA- 5617833.4- Cilium assembly pathway for CCDC22(T17A), and R- HSA- 6811440.2- Retrograde transport at the Trans- Golgi- Network for both variants (Fig. S6E)." + +2) + +In the discussion section on Page 11 line 7, we added "Interestingly, our finding that besides disrupting the Commander complex assembly, the RSS variant VPS35L(A830T) also loses its affinity to the WASH complex. This is consistent with the presented prediction for potential WASH binding interface, where VPS29 is located at the centre." + +3) + +The following paragraph was added to the discussion on Page 12, line 9: "We used point mutants CCDC22(T17A), CCDC22(Y557C), and VPS35L(A830T) to investigate the disease mechanism of RSS at the PPI level. The VPS35L(A830T) mutation disrupted the Commander complex assembly, and completely blocked interaction to WASH complex, whereas RSS mutations shifted the HCIs of CCDC22 from the Commander complex towards retrograde transport and Golgi trafficking. This implies a complex molecular etiology of RSS." + +<--- Page Split ---> + +4) + +The following paragraph was added to Materials and methods on Page 12, line 31: "Generation of RSS disease variants. RSS disease point mutations were introduced to CCDC22 and VPS35L genes by site- directed mutagenesis using Q5® High- Fidelity DNA Polymerase (NEB #M0491) and the following primers: 5'- GGCGCGGCAGTTCC and 3'- AACTGCCGCGCCGGCC (CCDC22(T17A)), 5'- AAGGCCTGTAAGTATCTAGCTGC and 3'- GATACTTACAGGCCTTCCGAACA (CCDC22(Y557C)), and 5'- TCCACCATGAGCCAGGAG and 3'- CTCATGGTGGAGAGGAGATGC (VPS35L_A830). The disease variants and wild- type genes were cloned into C- terminal ultralD containing MAC3- tagged vectors [PMID:35384245]." + +5) + +Following update was made to Affinity purification protocol on Page 13, line 9: "An additional \(50 \mu M\) of biotin was added for proximity labelling (BioID) for 24 h (MAC- tagged constructs) or 5 hours (MAC3- tagged constructs)." + +6) + +Figure S6 legend on Page 28, line 14 was updated to: "Fig. S6. Molecular interactors, context, and cellular pathways connected with individual Commander complex components, related to Figure 5. (A) Dot- plot visualization (BFDR \(\leq 0.05\) ) of interactors of the Commander complex detected by the BioID- MS. Node color corresponds to the abundance of the average spectral count for each prey, and node radius to its relative abundance. (B) Dot- plot visualization of RSS syndrome related point mutants of CCDC22 analyzed by BioID- MS. All PPIs passing HCl criteria to any of the CCDC22 variants are plotted, with HCIs are indicated with black outline and non- HCIs with light blue. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz. (C) Reactome pathways enriched for the Commander complex proteins. (D) Molecular level localization of the Commander complex proteins obtained by MS- microscopy. (E) Reactome pathways enriched \((p< 0.005\) , values marked in bars) for the RSS disease variant HCIs distinct from the wild- type CCDC22." + +7) + +Figure 6 legend on Page 26, line 35was updated to: "Fig. 6. RSS and XLID related mutations and putative interaction interfaces of the Commander complex. (A) Three mutations associated with RSS or XLID are highlighted within the context of the Commander complex structure. (B) Effect of A830T mutation on VPS35L in BioID- MS. All PPIs passing HCl criteria to either wild- type VPS35L or VPS35L(A830T) are plotted for both constructs, with HCIs indicated using black outline and non- HCIs with light blue outline. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz (C) Composite model of the Commander complex, + +<--- Page Split ---> + +indicating putative interaction interfaces with tubulin polyglutamylase complex (TPGC). (D) Rotated view of the model in (C), with putative interaction interface of the WASH complex indicated." + +8) + +Sentence on Page 11, line 44 "We did not detect any Rab proteins as PPIs of any of the Commander complex proteins, supported by the decoupling of Rab7 function from Retriever" was changed to "We did not detect any Rab proteins as HCIs of the Commander complex proteins except for Rab9a in the RSS variants of CCDC22. This observation aligns with the known decoupling of Rab7 function from the Retriever." + +<--- Page Split ---> + +# natureresearch + +Decision Letter, first revision: + +Message: 28th Sep 2023 + +Dear Professor Varjosalo, + +Thank you for submitting your revised manuscript, "Structure and Interactions of the Endogenous Human Commander Complex". After careful consideration and discussion with my colleagues, I am sorry to have to tell you that we do not feel that the referees' comments have been sufficiently addressed to justify sending this revision back for peer review. + +This unusual course of action is taken occasionally to avoid unproductive rounds of review that result in reviewer fatigue and damage the chances of the manuscript obtaining a fair and objective evaluation. Such situations are not in an author's best interest so we try to avoid them when it seems prudent to do so. + +In order to consider this manuscript further we would request that you please do your best to fully address all of the comments of the reviewers, as well as our editorial guidance. In particular, please do make an effort to visually compare the models (experimental or predicted) of the complex, as well as add further discussion to the text. Both reviewers pointed out this to be an issue with the previous version of the manuscript, and editorially, we agree with their comments. This will be important for the readers to fully understand how this study compares with the literature, and will increase impact and accessibility of your work. + +We would kindly ask that in the revised manuscript, you clearly state the differences in the native complex obtained in this study, and how it stands compared to published literature. Please revise both the manuscript and the point- by- point response to address these points. + +Should you be able to adequately respond to these and the reviewers' other concerns, we would be happy to look at a revised manuscript again. + +We shall hope to receive your revised version as soon as possible. If you anticipate a delay of more than four weeks, however, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Structural & Molecular Biology or published elsewhere. Should your manuscript be substantially delayed without notifying us in advance and your article is eventually published, the received date may be that of the revised, not the original, version. + +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly + +<--- Page Split ---> + +# natureresearch + +contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +If you are not interested in submitting a suitably revised manuscript in the future please let me know immediately so we can close your file. If you have any questions, please contact me. + +Please use the link below to submit a suitably revised manuscript and updated response to referees when they are ready. + +[Redacted] + +Sincerely, + +Katarzyna Ciazynska (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +## Author Rebuttal, first revision: + +We thank the reviewers for detailed and positive comments on our manuscript "Structure and Interactions of the Endogenous Human Commander Complex". See below our point- by- point response to the comments (in gray italics). We have expanded our comparison to the existing model of Healy et al. by including two new main figures and adding new material to the supplementary figures. We have also included two pages worth of text on the comparisons, to highlight where the two models differ. Furthermore, we have included additional experiments on the disease mutations, not requested by the reviewers. We feel that these experiments complement well the other comparison we have added on the differences between these two models. These and other additional modifications are reported at the end of this rebuttal. + +Reviewer 1: + +Remarks to the Author: + +<--- Page Split ---> + +# natureresearch + +Recently discovered Commander complex exerts its function in multiple processes; however, structural information is lacking to deconvolute the underlying mechanisms. The proposed manuscript elegantly combines mass- spectrometric analysis with cryo- electron microscopy to visualize the whole commander complex and systematically analyze its interactome. This approach is granted for a 16- subunit commander complex and, in the broader context, sets up a promising way to parallelize molecular and structural discoveries of challenging biological assemblies. + +The authors first created cell lines with one of the commander subunits with MAC tag (BlrA\\* biotinylation enzyme plus affinity purification peptides). They systematically explored subunits interactomes, cross- referencing Bio- ID and affinity purification mass spectroscopy (AP- MS) to get an insight into the stability and composition of commander assembled from endogenously expressed properties (except the bait under control of inducible promotor). The verified reported and discovered a plethora of new binders. The binders list highlights multiple roles of the commander. It includes proteins working in the Cilium Assembly pathway, membrane trafficking (exocyst, PI3P phosphatase), inflammation, and cytoskeleton organization, to name a few functional clusters. Finally, the MS analysis pinpointed posttranslational modification sites. + +Following the MS, the cell line with COMMD9 bait was used to isolate the natively assembled commander for cryo- EM structure determination. SPA analysis converged on the map resolving primarily the COMMD ring. Cross- linking was used to restrict the conformational heterogeneity of the complex and succeeded in resolving the whole commander complex. As expected, the COMMD ring map still led in resolution and resolved side chains; nevertheless, the CCDCs and Retriever modules of the commander could now be resolved to the secondary structure using focused alignment. Commander architecture from cryo- EM map drastically differs from the predicted models (Healy et al. 2023; Boesch et al. 2023), featuring \(\sim 90\) degrees of the COMMD ring rotation and other major differences. This finding is also valuable as a benchmark for predicting complex tertiary structures. Furthermore, the structural studies were complemented by molecular dynamic simulations pinpointing conformation variability in COMMD that may bridge retriever and DENND10. Finally, the manuscript looks closely at the loosely associated interactors discovered by proximity biotinylation (BioID- MS). BioID- MS proteome is dominated by inter- complex binding reiterating on commander multiple roles. Distance dependence of biotinylation by + +<--- Page Split ---> + +# natureresearch + +BirA\\* allowed the identification of two interaction clusters in the commander surface. + +Overall the manuscript brings important novel insights and is written compellingly with sufficient experiential evidence. Authors deserve special credit for clear visual language and concise text. + +Here I propose text and figure changes to improve manuscript clarity further. + +Figure1 + +Figure1Fig1A is a good entry illustration but can be made more explicit. I suggest adding a legend for the elements of MAC tag and affinity resins that allow understanding of which tag element is used, similar to the figures in your Liu et el 2018 paper. The arrows from AP- MS and XL- MS branches point to a mass spectrometer (?), but the BioID- MS - to the PPI analysis icon. I suggest leaving only PPI analysis in and converging on it all three paths. Outline conditions for harsh and soft lysis conditions in the figure, i.e. "harsh, 0.1% SDS", "soft, 0.5% IGEPAL". + +Thank you for your feedback on Figure 1. + +In response to your suggestions, we have revised Fig 1A to enhance its clarity and understandability. We added labels for both the SH- tag and the biotin ligase BirA, aiming to provide clearer visualization of the involved elements. + +We would like to clarify the representation of the Mass spectrometer and PPI analysis in Fig 1A. They are intended to represent the same analytical endpoint. To address the inconsistency you pointed out, we've adjusted the figure such that the arrow from BioID- MS now correctly points to the combined MS- analysis and PPI analysis icon. This should now provide a consistent representation of the analytical endpoints for the different techniques. + +Regarding the 'lysis conditions', we appreciate your suggestion on detailing the lysis conditions directly in the figure. However, the distinction between soft and harsh lysis is nuanced, involving more than just the choice of detergent. Specifically, the harsh lysis procedure also incorporates sonication in the presence of benzonase. We believe that these intricacies are best detailed in the experimental section, where they can be elaborated upon more extensively. Hence, we've opted to maintain a streamlined + +<--- Page Split ---> + +# natureresearch + +representation in Fig 1A, without the specific detergent details, to ensure its simplicity and accessibility. + +<--- Page Split ---> + +# natureresearch + +Replace the SEC panel in panel A with panel E. Use text instead of pictograms of molecules for SEC peaks designation. + +To clarify, the SEC depiction in panel A is intended as a schematic representation, designed to provide an overview of the workflow employed in our study. It is not a direct representation of experimental results. + +On the right from the Cryo- EM block, you could name and show all four maps from grey circles in FigS2. + +Thank you for your feedback regarding the representation of the Cryo- EM block in our figure. + +We understand the value in showcasing detailed results, as you've suggested with the four maps from grey circles in FigS2. However, the primary intent behind Figure 1 panel A was to provide a schematic overview of the entire workflow. Introducing specific results into this schematic might divert from its original purpose of giving a broad- strokes view of the methodology. + +Also, please include Coomassie stained PAGE of native and cross- linked Commander used for cryo- EM. + +Thank you for your suggestion to include a Coomassie stained PAGE of the native and crosslinked Commander used for cryo- EM. + +While in general we appreciate the value of such data, here we've decided against this inclusion for the following critical reasons: + +1. The procedure for purifying the crosslinked Commander complex results in a very limited yield ( \(\sim 25 \mu l\) at \(\sim 0.1 \mathrm{mg / ml}\) ). We, therefore, prioritized cryo-EM grid preparation over PAGE analysis. We were confident in this approach, as we had extensive AP-MS evidence of the constituents of the complex before crosslinking and identified all components of the complex in the MS data we collected. + +<--- Page Split ---> + +# natureresearch + +2. Furthermore, given the mild nature of our crosslinking procedure, we anticipate a set of heterogeneously crosslinked complex isoforms in a PAGE analysis. Such an analysis would primarily indicate that crosslinking has occurred, without providing intricate details. We can obtain more precise information about the crosslinking pattern from the MS data we collected from the crosslinked, gel-filtered complex. + +Fig 1D. Define table axes. + +Table axes (bait / prey) have now been added to Figure 1 panel D. If feasible, introduce a better graphical explanation of the colour/circle size code. + +Thank you for the feedback on our graphical representation. + +To enhance clarity, we've renamed the colour/circle size codes to "Bait normalized AvgSpec" and "Relative AvgSpec." We've expanded on this in the figure legend with the following explanation on Page 26, line 9: "The color of each circle represents the abundance of each prey normalized to the mean abundance of the bait protein, and the circle radius indicates the relative abundance across all samples calculated by ProHits- Viz." + +We hope this adjustment provides a clearer understanding of the graphical elements used. + +Panel A can be used to reference specific branches of the MS. Consider moving panel B to supplementary if more space is needed. + +We have incorporated a reference to panel A in the text. + +AvgSpec/Relative AvgSpec abundance needs a better explanation for readers outside the MS field. Consider extending the Quantification and statistical analysis chapter and explaining the interpretation of two marginal data points (i.e. for good and bad binders). + +<--- Page Split ---> + +# natureresearch + +The average spectral count corresponds to the abundance of each prey protein in the sample and is represented by the node color. To evaluate the relative weight of each interaction among the presented samples, we calculated the relative abundance using the ProHits- Viz tool. + +We have updated the Figure 1 legend on Page 26, line 9 to read: "The color of each circle represents the abundance of each prey, normalized to the mean abundance of the bait protein, and the circle radius indicates the relative abundance across all samples calculated by ProHits- Viz." + +Line 142. Comment why COMMD9 was chosen as bait. + +As there was initially very little information about the Commander complex assembly, we selected a few bait proteins for purification optimization. Out of the tested bait proteins, COMMD9 gave the highest yield, and was thus chosen for further optimization. + +<--- Page Split ---> + +# natureresearch + +Line 480. Cloning of Commander complex components. Describe cell genotype in plain language. If I understand correctly, cell lines contained an additional copy (over the WT genome) of genome- integrated MAC- tagged tagged bait under a tetracycline- inducible promotor. Upon induction, the binders will preferentially bind to the tagged due to its higher titer than WT copies. What is the estimated bait expression level compared to the endogenously expressed protein? + +The cell line used employs the Flp- In™ system, which allows the insertion of a single copy of the gene of interest at the FRT site in HEK cells. Expression of the protein of interest is induced using tetracycline, resulting in an expression level parallel to and on the same scale as the endogenous protein [PMID:19156129; PMID:23455922; PMID:28330616]. In BioID- MS experiments, proximity labeling biotinylation is induced using biotin. Intact protein complexes (AP- MS) or biotinylated proteins (after disruption of native protein complexes in BioID- MS) are extracted from the cell lysate using Strep- tactin resin, which binds both biotin and the SH- tag. The method is described in more detail in the articles by Liu et al [PMID:29568061], which we reference in the text on Page 3, line 5, and on Page 13, line 27. + +Line 91. Highlight these newly discovered interactors in Fig S1. + +Figure S1 was updated according to the reviewer's suggestion. Novel interactions are now presented on a grey square background. The legend for Figure S1A on Page 28, line 20, has been updated to: "(A) Dot- plot visualization of the Commander complex proteins' interactors detected by AP- MS. Each node color corresponds to the abundance of the average spectral count for each prey, and the node size indicates the relative abundance of the prey. BFDR values are denoted by circles around the nodes, and novel interactions are highlighted with a grey background." + +Line 567. Give protein concentration in the BS3 cross- linking reaction. + +As the crosslinking was conducted during ultrafiltration, the protein concentration increased during the crosslinking process. Therefore, we cannot specify the exact protein + +<--- Page Split ---> + +# natureresearch + +concentration. The 2 mM BS3 concentration we used was recommended in a protocol provided by the manufacturer. + +FigS2. Add title "cross- linked" above panels D- G. Show FSC curves for the final maps. + +The requested titles were added and FSC curves plotted for the final reconstructions as requested. + +Line 596. Should "tandem" be replaced with "in parallel"? Tandem implies sequential order. + +The text was modified according to reviewer's suggestion. + +Fig3J. Indicate the NN- CH domain in the figure. Should CCDC93 NTD be changed to CCDC93 NN- CH? + +We have changed the labeling to improve the distinction between NTDs of COMMD proteins and the NN- CH domains of CCDC proteins. These changes have also been implemented in the text by replacing CCDC NTDs with NN- CH. + +FigS4. Fix panel assignment (F panel is skipped). The comparison to Healy at al 2023 AF2 model is interesting and will be clearer using pipes and plunks depiction or "ragdoll model" with complex parts presented as geometrical shapes to highlight dramatic differences in COMMDS ring rotation and CCDCs coils. Aligning the models on Vps35L may be more informative. + +We thank the reviewer for pointing out the error in panel assignment and have rectified the issue. A "ragdoll model" using geometric shapes as suggested has now been included + +<--- Page Split ---> + +# natureresearch + +as new Figure 5. We have carried out the alignment of Healy et al. model on our model in two different ways to highlight the differences from multiple angles in Figure 5: + +"A simplified "ragdoll" representation of major components of the Commander complex (A) from this study and (B- D) the overall structural model from Healy et al. highlight the major differences between these models with alignment centers of the models located at the (B) COMMD- ring, (C) V- coil, and (D) DENND10. The COMMD- ring is represented by a disc aligned to the COMMD domains, the coiled- coil domains are represented by cylinders (I and R- coils), or a trapezoidal prism (V- coil + CCDC22 NN- CH), DENND10 as a cylinder and Retriever subcomplex as spheres (VPS29, VPS26C + N- terminal half of VPS35L \(\alpha\) - solenoid) or a cylinder (VPS35L C- terminal half of VPS35L \(\alpha\) - solenoid). Component relative rotation angles are calculated based on the underlying atomic coordinates of backbone \(\mathrm{Ca}\) atoms." + +<--- Page Split ---> + +# natureresearch + +Line 134. DENND10 binds the commander via CCDCs, making the statement in line 134 counterintuitive. Please clarify this point. + +We previously wrote:"Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker," which is indeed confusing. The clustering to find relative similarities takes into account the relative amount of each prey in each sample, and compares that to the other samples. As CCDCs have interactions that are different from the rest of the Commander complex proteins, their association to the other proteins is weaker despite their physical proximity to the COMMD proteins in the Commander complex. The text on Page 4, line 11 was modified to "Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker due to their interactions different from the rest of the complex (Fig. 1C)." + +Boesch DJ et al. (2023) Structural Organization of the Retriever- CCC Endosomal Recycling Complex. bioRxiv. doi:10.1101/2023.06.06.543888 + +Healy MD et al. (2023) Structure of the endosomal Commander complex linked to Ritscher- Schinzel syndrome. Cell 186:2219- 2237 e2229. doi:10.1016/j.cell.2023.04.003 + +<--- Page Split ---> + +# natureresearch + +Reviewer #2: + +Remarks to the Author: + +Laulumaa et al. here report the use of AP- MS and BioID- MS to make a comprehensive characterization of stable and transient interactions of the human Commander complex. The authors propose a set of biological processes where Commander could have essential roles such as endosomal transport, actin nucleation, immune response, transcription regulation, centriole replication, centrosomal targeting and cilium assembly. In addition, the authors purified and solved the structure of the whole Commander complex by single particle cryo- EM. The structure consist of a 16- protein assembly arranged in two sub- complexes; an heterodecameric ring of the COMMD proteins (COMMD 1- 10) connected to the retriever sub- complex (VPS35L, VPS26C and VPS29) by the CCDC22- CCDC93 heterodimer which interacts with DENND10 through a V- shaped coil (R- coil). The atomic model built into the cryo- EM density is supported by several XL- MS crosslinks. Overall, this is a well- executed study that provides the molecular architecture of the full Commander complex and spans its interactome. Unfortunately, the recent publication of the structure of the Commander complex (Healy et al. 2023) diminishes the originality of the present work. Nevertheless, while the structure of the Commander complex from Healy et al. was determined by combining data form cryo- EM, X- ray crystallography and AF modelling of distinct sub- structures, the present work by Laulumaa et al. provides a complete picture of the full sixteen subunits. Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al. On the other hand, the interactome analysis reads as a dry catalog of interactions with assigned GO terms and biological processes. The manuscript lacks a logical flow where functional/biological mechanisms are addressed throughout the structure. Similarly, the lack of functional assays 'in cellulo' diminishes general interest. For example, assessing the integrity of the Commander complex throughout site directed mutagenesis and evaluating the significance on novel roles such as cilia modulation could add novelty and interest to a wider audience. In summary, the lack of novelty in the structure and the absence of functional implications connected to Commander assembly have dumped the excitement for this manuscript. + +Regarding the reviewer's comment "Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not + +<--- Page Split ---> + +# natureresearch + +presented/discussed by Healy et al.", we have now expanded our comparative analysis by including two new main figures detailing the differences at the major structural region level (Fig. 5) as well as within these structural regions (Fig. 6). + +The following text was added to the results starting from Page 8, line 13: + +"Recently, Healy et al. published an integrated structural model for the Commander complex [PMID:37172566]. As the model differs significantly in overall arrangement from the structure presented in this study (Fig. S4G), we compared the structures first by superposing the Healy et al. model using different alignment centers to our model (Fig. 5). The CCDC scaffolding is similar in both complexes, and the COMMD- ring, DENND10, and the Retriever subcomplex are located in similar positions along it (Fig. S4G). Three major differences between the models were found (Fig 5): (i) the overall structure is more compactly packed in our model than in the Healy et al. model. (ii) The orientation of the COMMD- ring relative to the CCDC scaffolding is different so that in Healy et al. model the COMMD- ring lacks contact to I- coil which is evident both in our cryo- EM and XL- MS data (Fig. 2A- B, Fig. S4D). Notably, the Healy et al. model is incompatible with the crosslink between CCDC93 and COMMD7 detected in this study. Furthermore, the relative orientation between COMMD- ring and DENND10 or V- coil differ by \(76^{\circ}\) and \(117^{\circ}\) , respectively. (iii) The twistedness of the scaffolding is dissimilar such that the relative orientation of DENND10 and Retriever differs by \(65^{\circ}\) . + +Healy et al. compiled the overall model of the Commander complex using AF2 combined with X- ray crystallography and cryo- EM data from certain regions of the complex. When compared to our structure, models of the COMMD- ring align well as both studies base the structural models on high- resolution cryo- EM data (Fig. 6B). CCDC22 helices \(\alpha 15\) and \(\alpha 16\) , and the HLH- motif of CCDC93 are placed differently in the two models. They are absent in the cryo- EM structure by Healy et al. (EMD- 28827, PDB ID 8F2U) whereas their placement in our model is supported by cryo- EM density (Fig. S4H). The conformation of DENND10, I- coil, and R- coil is based heavily on AF2 prediction in both models, as our cryo- EM reconstruction has limited resolution in this region (Fig. S5D), and the Healy et al. model is entirely based on AF2 prediction for this part (Fig. 6C). The overall folds are similar, except that an interaction between the N- lobe of DENND10 and I- coil presented in Healy et al. model (indicated with an asterisk, Fig. 6C) is not featured in our model. This may be explained by conformational heterogeneity, as evidenced by our 3DVA analysis of this region (Fig. 4F). + +<--- Page Split ---> + +# natureresearch + +In our model, the Retriever subcomplex extends out of the main body of the complex (Fig. 2E- F). The tip extension of VPS35L binds VPS26C, while in the Healy et al. model it forms an interaction surface with the CCDC22 part of V- coil (Fig. 6D). This interaction seen in the Healy et al. model was predicted by AF2 and may reflect conformational heterogeneity in this region. Finally, Healy et al. solved the crystal structure of VPS29 with VPS35L (24- 38) peptide (PDB ID 8ESE), which is consistent with our cryo- EM structure (Fig. 6E)." + +Other more specific issues include: - This reviewer has not been able to see the PDB validation report to assess the PDB model. + +We apologize and acknowledge that the reports were only provided during the review process for the editor and reviewers. + +<--- Page Split ---> + +# natureresearch + +- Supplementary Table (REAGENT or RESOURCE) lacks several EMDB and PDB codes. They are denoted as 'EMD-XXX' or 'PDB: XXXX'. Same in 'Data availability' (lines 710-718) + +We have rectified this error in the manuscript on Page 19, lines 7- 12, and thank the reviewer for pointing out the missing codes. + +- There is a very early fall of in the FCS(unmasked). Could it be because of the very large box size used in relation to the size of the complex?. Was it intended to capture flexible regions?. + +We acknowledge this feature in the FSC curves and as the Reviewer suspects it is due to the relatively large box size used here (required for not cropping out flexible parts of the complex). To demonstrate the effect of box size on FSC(unmasked), we have prepared cropped half- maps and recalculated the unmasked FSC, presented below (Response Letter Figures 1 and 2). Please note that the "corrected" curves give highly similar results as expected and these values are the reported ones as they take this issue with box size into account. + +![](images/Figure_2.jpg) + + +<--- Page Split ---> + +# natureresearch + +Response Letter Figure 1. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 400 px. + +![PLACEHOLDER_36_0] + +
Response Letter Figure 2. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 560 px (original box size).
+ +- In section 4.2 of the validation report, there is a big difference in the reported resolution and the unmasked-calculated resolution. Could this be related to the large box size used? + +Yes. See above. + +- It might be something odd from the validation report but the mask looks larger in 2.6.1 than the projection in 2.1 (although the map in 2.5.1 looks large like the mask, it looks different to the 2.5.2). + +We have carefully checked the map and mask visualizations in the validation report, section 6 (map visualization). We note that the maps are shown at different scale in 6.5.1 (primary map) and 6.5.2 (raw map). This is a feature of the PDB validation server and beyond our control. The mask visualized in 6.6.1 is visualized in the same scale as the + +<--- Page Split ---> + +# natureresearch + +primary map. We confirm that these are how maps are displayed in the validation reports and do not affect our results or the maps we have deposited. + +<--- Page Split ---> + +# natureresearch + +The following additional modifications were made to the manuscript: + +1) + +We added additional experiments to the manuscript to further strengthen the interactome data. We generated HEK cell lines with pathogenic point mutations associated with Ritscher- Schinzel syndrome in VPS35L and CCDC22, and conducted BioID- MS for those samples. The following text was added to the manuscript on Page 10, line 41: "The Commander complex has been associated with Ritscher- Schinzel syndrome (RSS) or X- linked intellectual disability (XLID) via point mutations in VPS35L and CCDC22 13,31,70,71. Disease variants CCDC22(T17A), CCDC22(Y557C), and VPS35L(A830T) (Fig. 2D, Fig. 8A) are listed as "pathogenic" for RSS in GnomAD database 72. Cell lines expressing these disease variants were generated for BioID- MS analysis to investigate their effect at the PPI level (Data S1). + +The VPS35L(A830T) has been suggested to abolish its interaction with VPS29 70. Our data shows that the A830T mutation does not inhibit interaction with VPS26C, but separates VPS35L from the rest of the Commander complex and disrupts its interaction with the WASH complex (Fig. 8A- B). + +With the CCDC22 RSS disease variants, we discovered less interactions to COMMD proteins (especially to COMMDs 3, 6, and 7), whereas interactions with the WASH complex become pronounced (Fig. S6B). Using the Reactome pathway analysis on the CCDC22 disease mutant interactors, we could detect enrichment of 'Cilium assembly pathway' for CCDC22(T17A), and 'Retrograde transport at the Trans- Golgi- Network' for both variants (Fig. S6E). The CCDC22(Y557C) mutation is situated at the tip of the CCDC22 part of V- coil, a region predicted to interact with VPS35L by Healy et al. Surprisingly, our BioID data shows no major changes in the interactome that could be expected if this interaction was significant. On the other hand, the distal location of VPS26C, and thus the tip of VPS35L, from the V- coil is supported by our BioID data where VPS26C and CCDCs are not in close proximity (Fig. 7B). However, possible effects on the VPS35L- V- coil interaction caused by this mutation need to be experimentally interrogated." + +2) + +The disease mutations were further discussed on Page 12 line 2, "Intriguingly, aside from its effect on Commander complex assembly, the RSS variant VPS35L(A830T) also displays reduced affinity for the WASH complex. The mutation site is located at the + +<--- Page Split ---> + +# natureresearch + +interface between VPS35L and VPS29, and therefore this observation fits well with our proposed WASH binding interface model where VPS29 is located at the center. In contrast, while CCDC22 variants (T17A and Y557C) are also in close proximity to the putative WASH binding site, they have the opposite effect on WASH complex interactions, implying a complex molecular etiology of RSS." + +<--- Page Split ---> + +# natureresearch + +3) + +The following paragraph was added to Materials and methods on Page 13, line 30: "RSS disease point mutations were introduced to CCDC22 and VPS35L genes by site- directed mutagenesis using Q5® High- Fidelity DNA Polymerase (NEB #M0491) and the following primers: 5'- GGCGCGGCAGTTCCT and 3'- AACTGCCGCGCCGGC (CCDC22(T17A)), 5'- AAGGCCTGTAAGTATCTAGCTGC and 3'- GATACTTACAGGCCTTCCGAACA (CCDC22(Y557C)), and 5'- TCCACCATGAGCCAGGAG and 3'- CTCATGGTGGAGAGGAGATGC (VPS35L_A830). The disease variants and wild- type genes were cloned into C- terminal ultralD containing MAC3- tag vector [PMID:35384245]." + +4) + +Following update was made to Affinity purification protocol on Page 14, line 3: "An additional \(50\mu \mathrm{M}\) of biotin was added for proximity labelling (BiolD) for \(24\mathrm{h}\) (MAC- tagged constructs) or 5 hours (MAC3- tagged constructs)." + +5) + +The following paragraph was updated on Page 12, line 24: "The top half of the Commander complex contains flexible components (NTDs of COMMDs 1, 7, 9, and 10; HLH- motif of CCDC93), and the bottom half exhibits compositional and conformational heterogeneity, particularly within the Retriever subcomplex. This may reflect physiological assembly and/or the function of the complex. Indeed, COMMD proteins and the CCDCs have been proposed to form a complex without Retriever, termed the CCC- complex 75. Interestingly, assuming a similar head- to- head dimerization mode as Retromer, the structure of Commander permits binding of the CCC- complex on a Retriever dimer without obvious steric clashes (Fig. S5F- H). Such analysis relies on having access to complete native structure featuring external surfaces and exposed domains facilitating biological functions in the cellular context. This highlights the need for experimental data in addition to in silico predictions for quaternary structure analysis of large macromolecular complexes (Fig. 5, Fig. 6)." + +6) + +Sentence on Page 13, line 2 "We did not detect any Rab proteins as PPLs of any of the Commander complex proteins, supported by the decoupling of Rab7 function from Retriever" was changed to "We did not detect any Rab proteins as HCLs of the + +<--- Page Split ---> + +# natureresearch + +Commander complex proteins except for Rab9a in the RSS variants of CCDC22. This observation aligns with the known decoupling of Rab7 function from the Retriever." + +7) + +Figure S6 legend on Page 29, line 30 was updated to: "Fig. S6. Molecular interactors, context, and cellular pathways connected with individual Commander complex components, related to Figure 5. (A) Dot-plot visualization (BFDR \(\leq 0.05\) ) of interactors of the Commander complex detected by the BioID- MS. Node color corresponds to the abundance of the average spectral count for each prey, and node radius to its relative abundance. (B) Dot-plot visualization of RSS syndrome related point mutants of CCDC22 analyzed by BioID- MS. All PPIs passing HCl criteria to any of the CCDC22 variants are plotted, with HCLs are indicated with black outline and non- HCLs with light blue. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz. (C) Reactome pathways enriched for the Commander complex proteins. (D) Molecular level localization of the Commander complex proteins obtained by MS- microscopy. (E) Reactome pathways enriched \((p< 0.005\) , values marked in bars) for the RSS disease variant HCLs distinct from the wild- type CCDC22." + +8) + +Figure 8 legend on Page 28, line 7 was updated to: "Fig. 6. RSS and XLID related mutations and putative interaction interfaces of the Commander complex. (A) Three mutations associated with RSS or XLID are highlighted within the context of the Commander complex structure. (B) Effect of A830T mutation on VPS35L in BioID- MS. All PPIs passing HCl criteria to either wild- type VPS35L or VPS35L(A830T) are plotted for both constructs, with HCLs indicated using black outline and non- HCLs with light blue outline. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz (C) Composite model of the Commander complex, indicating putative interaction interfaces with tubulin polyglutamylase complex (TPGC). (D) Rotated view of the model in (C), with putative interaction interface of the WASH complex indicated." + +<--- Page Split ---> + +# natureresearch + +9) + +Figures 5 and 6 from the previous iteration of the manuscript were renumbered to figures 7 and 8. Figure legends for new figures 5 and 6 were added on Page 27, line 21: Fig. 5. Analysis of overall tertiary fold of the endogenous Commander complex compared to existing literature. A simplified "ragdoll" representation of major components of the Commander complex (A) from this study and (B-D) the overall structural model from Healy et al. highlight the major differences between these models with alignment centers of the models located at the (B) COMMD- ring, (C) V-coil, and (D) DENND10. The COMMD-ring is represented by a disc aligned to the COMMD domains, the coiled-coil domains are represented by cylinders (I and R-coils), or a trapezoidal prism (V-coil + CCDC22 NN-CH), DENND10 as a cylinder and Retriever subcomplex as spheres (VPS29, VPS26C + N-terminal half of VPS35L \(\alpha\) - solenoid) or a cylinder (VPS35L C-terminal half of VPS35L \(\alpha\) - solenoid). Component relative rotation angles are calculated based on the underlying atomic coordinates of backbone Cα atoms. + +Fig. 6. Comparative analysis of conformational variation in the Commander complex structure compared to existing literature. (A) Overview of the Commander complex structure with location of following panels indicated. Comparison of (B) the COMMD-ring, (C) DENND10, I-coil, and R-coil region, (D) Retriever subcomplex from the structure presented in this study and the overall model presented by Healy et al. (E) Comparison of VPS29 with VPS35L (13-37) presented in this study (left) and crystal structure of VPS29 with VPS35L (16-38) peptide (right). Major structural differences are highlighted with yellow, and sources of structural data are indicated for each structure. The three disease mutations analyzed in AP- MS and BioID (Fig. 8) are indicated in (D). + +10) + +Figure S4H legend on Page 29, line 17 was changed to: " (H) Density supporting the placement of CCDC22 \(\alpha 15\) and \(\alpha 16\) . Map (EMD- 17340) was low- pass filtered to 7 Å using Bsoft." + +<--- Page Split ---> + +# natureresearch + +Message: Our ref: NSMB- A47767B + +15th Nov 2023 + +Dear Dr. Varjosalo, + +Thank you for submitting your revised manuscript "Structure and Interactions of the Endogenous Human Commander Complex" (NSMB- A47767B). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Structural & Molecular Biology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +In particular, please note that we consulted reviewer #2 again regarding the PDB validation reports. While they did not indicate major issues, they pointed out that there appears to be a noticeable lack of fitting between the COMM domain- containing protein 1 (Chain A; Molecule 1) and the COMM domain- containing protein 7 (Chain G; Molecule 7) with the map. Please ensure to address this discrepancy and discuss it in the manuscript. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about 2 weeks. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +Thank you again for your interest in Nature Structural & Molecular Biology Please do not hesitate to contact me if you have any questions. + +Sincerely, + +Katarzyna Ciazynska, PhD (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +# Author Rebuttal, second revision: + +## Response to Reviewer 1: + +We thank the reviewer for the positive comments on our manuscript "Structure and Interactions of the Endogenous Human Commander Complex". + +Reviewer 1: + +My apologies for the delayed reply. I thank the authors for thoroughly addressing my + +<--- Page Split ---> + +# natureresearch + +suggestions. A new Figure 5 elaborating on the global conformation of commander is a welcome addition. I have no further questions to the manuscript. + +## Final Decision Letter: + +Message: 19th Jan 2024 + +Dear Dr. Varjosalo, + +We are now happy to accept your revised paper "Structure and Interactions of the Endogenous Human Commander Complex" for publication as an Article in Nature Structural & Molecular Biology. + +Acceptance is conditional on the manuscript's not being published elsewhere and on there being no announcement of this work to the newspapers, magazines, radio or television until the publication date in Nature Structural & Molecular Biology. + +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Structural & Molecular Biology style. 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We now have comments (below) from the 2 reviewers who evaluated your paper. In light of those reports, we remain interested in your study and would like to see your response to the comments of the referees, in the form of a revised manuscript. + +<|ref|>text<|/ref|><|det|>[[200, 564, 877, 744]]<|/det|> +You will see that while reviewers appreciate the results, they raise several concerns which will need to be addressed in a revision. Specifically, we would ask you to restructure the manuscript, including comparative analysis, to highlight the novelty and significance of the presented data, as suggested by the reviewers. You will notice that while reviewer #1 noted the value of the structure of the native complex, as clearly different from the model presented by Healy et al, reviewer #2 points out lack of novelty in the structure itself. We ourselves had to look at the cryo- EM data and models to understand the advance, which is why we would recommend this to be rectified in the manuscript itself, clearly stating the difference of the native complex obtained in this study, and how it stands compared to published literature. While we agree with reviewer #1 that further functional analysis would strengthen the manuscript, in the interest of timeliness we do not consider it essential in the context of the current work, especially considering the added value of the interactome. + +<|ref|>text<|/ref|><|det|>[[201, 757, 875, 813]]<|/det|> +Please be sure to address/respond to all concerns of the referees in full in a point- by- point response and highlight all changes in the revised manuscript text file. If you have comments that are intended for editors only, please include those in a separate cover letter. + +<|ref|>text<|/ref|><|det|>[[200, 826, 877, 855]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[201, 145, 872, 188]]<|/det|> +technically impossible or unlikely to yield a meaningful outcome. We are always happy to discuss revision plans over the phone if the requests are not clear. Please reach out to me if you would like to schedule a call. + +<|ref|>text<|/ref|><|det|>[[201, 201, 875, 257]]<|/det|> +We expect to see your revised manuscript within 6 weeks. If you cannot send it within this time, please contact us to discuss an extension; we would still consider your revision, provided that no similar work has been accepted for publication at NSMB or published elsewhere. + +<|ref|>text<|/ref|><|det|>[[201, 270, 866, 326]]<|/det|> +As you already know, we put great emphasis on ensuring that the methods and statistics reported in our papers are correct and accurate. As such, if there are any changes that should be reported, please submit an updated version of the Reporting Summary along with your revision. + +<|ref|>text<|/ref|><|det|>[[201, 338, 595, 353]]<|/det|> +Please follow the links below to download these files: + +<|ref|>text<|/ref|><|det|>[[201, 367, 678, 396]]<|/det|> +Reporting Summary: https://www.nature.com/documents/nr- reporting- summary.pdf + +<|ref|>text<|/ref|><|det|>[[201, 407, 872, 437]]<|/det|> +Please note that the form is a dynamic 'smart pdf' and must therefore be downloaded and completed in Adobe Reader. + +<|ref|>text<|/ref|><|det|>[[201, 463, 872, 506]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +<|ref|>text<|/ref|><|det|>[[200, 518, 870, 601]]<|/det|> +- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. +- that control panels for gels and western blots are appropriately described as loading on sample processing controls +- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +<|ref|>text<|/ref|><|det|>[[201, 614, 844, 657]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[200, 684, 872, 713]]<|/det|> +If there are additional or modified structures presented in the final revision, please submit the corresponding PDB validation reports. + +<|ref|>text<|/ref|><|det|>[[201, 726, 867, 782]]<|/det|> +Please note that all key data shown in the main figures as cropped gels or blots MUST be presented in uncropped form, with molecular weight markers. These data can be aggregated into a single supplementary figure item. While these data can be displayed in a relatively informal style, they must refer back to the relevant figures. + +<|ref|>text<|/ref|><|det|>[[201, 794, 867, 850]]<|/det|> +SOURCE DATA: we request that the authors provide, in tabular form, the data underlying the graphical representations used in figures. This is to further increase transparency in data reporting, as detailed in this editorial (http://www.nature.com/nsmb/journal/v22/n10/full/nsmb.3110. html). Spreadsheets can + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 871, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[202, 144, 867, 216]]<|/det|> +be submitted in excel format. Only one (1) file per figure is permitted; thus, for multipaneled figures, the source data for each panel should be clearly labeled in the Excel file; alternately the data can be provided as multiple, clearly labeled sheets in an Excel file. 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Please note that for some data types, deposition in a public repository is mandatory - more information on our data deposition policies and available repositories can be found below: https://www.nature.com/nature- research/editorial- policies/reporting- standards#availability- of- data + +<|ref|>text<|/ref|><|det|>[[201, 353, 875, 479]]<|/det|> +We require deposition of coordinates (and, in the case of crystal structures, structure factors) into the Protein Data Bank with the designation of immediate release upon publication (HPUB). Electron microscopy- derived density maps and coordinate data must be deposited in EMDB and released upon publication. Deposition and immediate release of NMR chemical shift assignments are highly encouraged. Deposition of deep sequencing and microarray data is mandatory, and the datasets must be released prior to or upon publication. To avoid delays in publication, dataset accession numbers must be supplied with the final accepted manuscript and appropriate release dates must be indicated at the galley proof stage. + +<|ref|>text<|/ref|><|det|>[[201, 491, 870, 533]]<|/det|> +While we encourage the use of color in preparing figures, please note that this will incur a charge to partially defray the cost of printing. Information about color charges can be found at http://www.nature.com/nsmb/authors/submit/index.html#costs + +<|ref|>text<|/ref|><|det|>[[200, 546, 872, 685]]<|/det|> +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[201, 698, 778, 713]]<|/det|> +Please use the link below to submit your revised manuscript and related files: + +<|ref|>sub_title<|/ref|><|det|>[[201, 726, 284, 741]]<|/det|> +## [Redacted] + +<|ref|>text<|/ref|><|det|>[[201, 753, 870, 795]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[200, 808, 850, 837]]<|/det|> +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[201, 146, 275, 161]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[201, 174, 504, 244]]<|/det|> +Katarzyna Ciazynska (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +<|ref|>text<|/ref|><|det|>[[201, 270, 338, 285]]<|/det|> +Referee expertise: + +<|ref|>text<|/ref|><|det|>[[201, 297, 528, 312]]<|/det|> +Referee #1: cryo- EM, endosomal trafficking + +<|ref|>text<|/ref|><|det|>[[201, 325, 528, 340]]<|/det|> +Referee #2: cryo- EM, endosomal trafficking + +<|ref|>text<|/ref|><|det|>[[201, 393, 371, 408]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[201, 421, 302, 435]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[201, 436, 377, 449]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[201, 450, 872, 547]]<|/det|> +Recently discovered Commander complex exerts its function in multiple processes; however, structural information is lacking to deconvolute the underlying mechanisms. The proposed manuscript elegantly combines mass- spectrometric analysis with cryo- electron microscopy to visualize the whole commander complex and systematically analyze its interactome. This approach is granted for a 16- subunit commander complex and, in the broader context, sets up a promising way to parallelize molecular and structural discoveries of challenging biological assemblies. + +<|ref|>text<|/ref|><|det|>[[201, 560, 872, 699]]<|/det|> +The authors first created cell lines with one of the commander subunits with MAC tag (BIRA\* biotinylation enzyme plus affinity purification peptides). They systematically explored subunits interactomes, cross- referencing Bio- ID and affinity purification mass spectroscopy (AP- MS) to get an insight into the stability and composition of commander assembled from endogenously expressed properties (except the bait under control of inducible promotor). The verified reported and discovered a plethora of new binders. The binders list highlights multiple roles of the commander. It includes proteins working in the Cilium Assembly pathway, membrane trafficking (exocyst, PI3P phosphatase), inflammation, and cytoskeleton organization, to name a few functional clusters. Finally, the MS analysis pinpointed posttranslational modification sites. + +<|ref|>text<|/ref|><|det|>[[201, 712, 861, 850]]<|/det|> +Following the MS, the cell line with COMMD9 bait was used to isolate the natively assembled commander for cryo- EM structure determination. SPA analysis converged on the map resolving primarily the COMMD ring. Cross- linking was used to restrict the conformational heterogeneity of the complex and succeeded in resolving the whole commander complex. As expected, the COMMD ring map still led in resolution and resolved side chains; nevertheless, the CCDCs and Retriever modules of the commander could now be resolved to the secondary structure using focused alignment. Commander architecture from cryo- EM map drastically differs from the predicted models (Healy et al. 2023; Boesch et al. 2023), featuring \(\sim 90\) degrees of the COMMD ring rotation and other major differences. This finding is also valuable as a benchmark for predicting complex + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[201, 145, 866, 187]]<|/det|> +tertiary structures. Furthermore, the structural studies were complemented by molecular dynamic simulations pinpointing conformation variability in COMMD that may bridge retriever and DENND10. + +<|ref|>text<|/ref|><|det|>[[202, 187, 867, 244]]<|/det|> +Finally, the manuscript looks closely at the loosely associated interactors discovered by proximity biotinylation (BioID- MS). BioID- MS proteome is dominated by inter- complex binding reiterating on commander multiple roles. Distance dependence of biotinylation by BirA\* allowed the identification of two interaction clusters in the commander surface. + +<|ref|>text<|/ref|><|det|>[[202, 256, 852, 299]]<|/det|> +Overall the manuscript brings important novel insights and is written compellingly with sufficient experiential evidence. Authors deserve special credit for clear visual language and concise text. + +<|ref|>text<|/ref|><|det|>[[201, 311, 776, 327]]<|/det|> +Here I propose text and figure changes to improve manuscript clarity further. + +<|ref|>sub_title<|/ref|><|det|>[[201, 340, 257, 353]]<|/det|> +## Figure1 + +<|ref|>text<|/ref|><|det|>[[201, 354, 875, 396]]<|/det|> +Fig1A is a good entry illustration but can be made more explicit. I suggest adding a legend for the elements of MAC tag and affinity resins that allow understanding of which tag element is used, similar to the figures in your Liu et al 2018 paper. + +<|ref|>text<|/ref|><|det|>[[201, 396, 870, 437]]<|/det|> +The arrows from AP- MS and XL- MS branches point to a mass spectrometer (?), but the BioID- MS - to the PPI analysis icon. I suggest leaving only PPI analysis in and converging on it all three paths. + +<|ref|>text<|/ref|><|det|>[[201, 436, 870, 464]]<|/det|> +Outline conditions for harsh and soft lysis conditions in the figure, i.e. "harsh, 0.1% SDS", "soft, 0.5% IGEPAL". + +<|ref|>text<|/ref|><|det|>[[201, 464, 802, 492]]<|/det|> +Replace the SEC panel in panel A with panel E. Use text instead of pictograms of molecules for SEC peaks designation. + +<|ref|>text<|/ref|><|det|>[[201, 492, 860, 519]]<|/det|> +On the right from the Cryo- EM block, you could name and show all four maps from grey circles in FigS2. + +<|ref|>text<|/ref|><|det|>[[200, 519, 867, 547]]<|/det|> +Also, please include Coomassie stained PAGE of native and cross- linked Commander used for cryo- EM. + +<|ref|>text<|/ref|><|det|>[[201, 547, 833, 575]]<|/det|> +Fig 1D. Define table axes. If feasible, introduce a better graphical explanation of the colour/circle size code. Panel A can be used to reference specific branches of the MS. + +<|ref|>text<|/ref|><|det|>[[201, 575, 700, 589]]<|/det|> +Consider moving panel B to supplementary if more space is needed. + +<|ref|>text<|/ref|><|det|>[[201, 589, 864, 630]]<|/det|> +AvgSpec/Relative AvgSpec abundance needs a better explanation for readers outside the MS field. Consider extending the Quantification and statistical analysis chapter and explaining the interpretation of two marginal data points (i.e. for good and bad binders). + +<|ref|>text<|/ref|><|det|>[[201, 642, 605, 657]]<|/det|> +Line 142. Comment why COMMD9 was chosen as bait. + +<|ref|>text<|/ref|><|det|>[[201, 670, 861, 755]]<|/det|> +Line 480. Cloning of Commander complex components. Describe cell genotype in plain language. If I understand correctly, cell lines contained an additional copy (over the WT genome) of genome- integrated MAC- tagged tagged bait under a tetracycline- inducible promotor. Upon induction, the binders will preferentially bind to the tagged due to its higher titer than WT copies. What is the estimated bait expression level compared to the endogenously expressed protein? + +<|ref|>text<|/ref|><|det|>[[201, 767, 670, 782]]<|/det|> +Line 91. Highlight these newly discovered interactors in Fig S1. + +<|ref|>text<|/ref|><|det|>[[201, 795, 718, 809]]<|/det|> +Line 567. Give protein concentration in the BS3 cross- linking reaction + +<|ref|>text<|/ref|><|det|>[[200, 822, 840, 838]]<|/det|> +FigS2. Add title "cross- linked" above panels D- G. Show FSC curves for the final maps. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[201, 145, 830, 174]]<|/det|> +Line 596. Should "tandem" be replaced with "in parallel"? Tandem implies sequential order. + +<|ref|>text<|/ref|><|det|>[[201, 186, 825, 215]]<|/det|> +Fig3J. Indicate the NN- CH domain in the figure. Should CCDC93 NTD be changed to CCDC93 NN- CH? + +<|ref|>text<|/ref|><|det|>[[202, 228, 876, 298]]<|/det|> +FigS4. Fix panel assignment (F panel is skipped). The comparison to Healy at al 2023 AF2 model is interesting and will be clearer using pipes and plunks depiction or "ragdoll model" with complex parts presented as geometrical shapes to highlight dramatic differences in COMMDS ring rotation and CCDCs coils. Aligning the models on Vps35L may be more informative. + +<|ref|>text<|/ref|><|det|>[[201, 311, 857, 340]]<|/det|> +Line 134. DENND10 binds the commander via CCDCs, making the statement in line 134 counterintuitive. Please clarify this point. + +<|ref|>text<|/ref|><|det|>[[201, 379, 874, 437]]<|/det|> +Boesch DJ et al. (2023) Structural Organization of the Retriever- CCC Endosomal Recycling Complex. bioRxiv. doi:10.1101/2023.06.06.543888 Healy MD et al. (2023) Structure of the endosomal Commander complex linked to Ritscher- Schinzel syndrome. Cell 186:2219- 2237 e2229. doi:10.1016/j.cell.2023.04.003 + +<|ref|>sub_title<|/ref|><|det|>[[202, 477, 302, 490]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[202, 491, 377, 504]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[200, 504, 874, 850]]<|/det|> +Laulumaa et al. here report the use of AP- MS and BioID- MS to make a comprehensive characterization of stable and transient interactions of the human Commander complex. The authors propose a set of biological processes where Commander could have essential roles such as endosomal transport, actin nucleation, immune response, transcription regulation, centriole replication, centrosomal targeting and cilium assembly. In addition, the authors purified and solved the structure of the whole Commander complex by single particle cryo- EM. The structure consist of a 16- protein assembly arranged in two sub- complexes; an heterodecameric ring of the COMMD proteins (COMMD 1- 10) connected to the retriever sub- complex (VPS35L, VPS26C and VPS29) by the CCDC22- CCDC93 heterodimer which interacts with DENND10 through a V- shaped coil (R- coil). The atomic model built into the cryo- EM density is supported by several XL- MS crosslinks. Overall, this is a well- executed study that provides the molecular architecture of the full Commander complex and spans its interactome. Unfortunately, the recent publication of the structure of the Commander complex (Healy et al. 2023) diminishes the originality of the present work. Nevertheless, while the structure of the Commander complex from Healy et al. was determined by combining data form cryo- EM, X- ray crystallography and AF modelling of distinct sub- structures, the present work by Laulumaa et al. provides a complete picture of the full sixteen subunits. Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al. On the other hand, the interactome analysis reads as a dry catalog of interactions with assigned GO terms and biological processes. The manuscript lacks a logical flow where functional/biological mechanisms are addressed throughout the structure. Similarly, the lack of functional assays 'in cellulo' diminishes general interest. For example, assessing the integrity of the Commander complex throughout site directed mutagenesis and evaluating the significance on novel roles such + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[200, 145, 860, 201]]<|/det|> +as cilia modulation could add novelty and interest to a wider audience. In summary, the lack of novelty in the structure and the absence of functional implications connected to Commander assembly have dumped the excitement for this manuscript. Other more specific issues include: + +<|ref|>text<|/ref|><|det|>[[200, 201, 876, 333]]<|/det|> +- This reviewer has not been able to see the PDB validation report to assess the PDB model. +- Supplementary Table (REAGENT or RESOURCE) lacks several EMDB and PDB codes. They are denoted as 'EMD-XXX' or 'PDB: XXXX'. Same in 'Data availability' (lines 710-718) +- There is a very early fall of in the FCS(unmasked). Could it be because of the very large box size used in relation to the size of the complex?. Was it intended to capture flexible regions?. +- In section 4.2 of the validation report, there is a big difference in the reported resolution and the unmasked-calculated resolution. Could this be related to the large box size used? +- It might be something odd from the validation report but the mask looks larger in 2.6.1 than the projection in 2.1 (although the map in 2.5.1 looks large like the mask, it looks different to the 2.5.2). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 86, 230, 101]]<|/det|> +Dear reviewers, + +<|ref|>text<|/ref|><|det|>[[93, 122, 888, 198]]<|/det|> +Dear reviewers,We thank you for your detailed and positive comments on our manuscript "Structure and Interactions of the Endogenous Human Commander Complex". See below our point- by- point response to your comments (in gray italics). Further, we have listed additional modifications and reported additional experiments at the end of this response. + +<|ref|>text<|/ref|><|det|>[[93, 217, 194, 234]]<|/det|> +Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[93, 255, 297, 271]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[92, 272, 904, 404]]<|/det|> +Remarks to the Author:Recently discovered Commander complex exerts its function in multiple processes; however, structural information is lacking to deconvolute the underlying mechanisms. The proposed manuscript elegantly combines mass- spectrometric analysis with cryo- electron microscopy to visualize the whole commander complex and systematically analyze its interactome. This approach is granted for a 16- subunit commander complex and, in the broader context, sets up a promising way to parallelize molecular and structural discoveries of challenging biological assemblies. + +<|ref|>text<|/ref|><|det|>[[91, 421, 900, 612]]<|/det|> +The authors first created cell lines with one of the commander subunits with MAC tag (BlrA\\* biotinylation enzyme plus affinity purification peptides). They systematically explored subunits interactomes, cross- referencing Bio- ID and affinity purification mass spectroscopy (AP- MS) to get an insight into the stability and composition of commander assembled from endogenously expressed properties (except the bait under control of inducible promotor). The verified reported and discovered a plethora of new binders. The binders list highlights multiple roles of the commander. It includes proteins working in the Cilium Assembly pathway, membrane trafficking (exocyst, PI3P phosphatase), inflammation, and cytoskeleton organization, to name a few functional clusters. Finally, the MS analysis pinpointed posttranslational modification sites. + +<|ref|>text<|/ref|><|det|>[[90, 629, 904, 914]]<|/det|> +Following the MS, the cell line with COMMD9 bait was used to isolate the natively assembled commander for cryo- EM structure determination. SPA analysis converged on the map resolving primarily the COMMD ring. Cross- linking was used to restrict the conformational heterogeneity of the complex and succeeded in resolving the whole commander complex. As expected, the COMMD ring map still led in resolution and resolved side chains; nevertheless, the CCDCs and Retriever modules of the commander could now be resolved to the secondary structure using focused alignment. Commander architecture from cryo- EM map drastically differs from the predicted models (Healy et al. 2023; Boesch et al. 2023), featuring \(\sim 90\) degrees of the COMMD ring rotation and other major differences. This finding is also valuable as a benchmark for predicting complex tertiary structures. Furthermore, the structural studies were complemented by molecular dynamic simulations pinpointing conformation variability in COMMD that may bridge retriever and DENND10. Finally, the manuscript looks closely at the loosely associated interactors discovered by proximity biotinylation (BioID- MS). BioID- MS proteome is dominated by inter- complex binding reiterating on commander multiple roles. Distance dependence of biotinylation by + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 85, 830, 102]]<|/det|> +BirA\* allowed the identification of two interaction clusters in the commander surface. + +<|ref|>text<|/ref|><|det|>[[93, 120, 888, 177]]<|/det|> +Overall the manuscript brings important novel insights and is written compellingly with sufficient experiential evidence. Authors deserve special credit for clear visual language and concise text. + +<|ref|>text<|/ref|><|det|>[[93, 195, 758, 214]]<|/det|> +Here I propose text and figure changes to improve manuscript clarity further. + +<|ref|>text<|/ref|><|det|>[[93, 234, 161, 250]]<|/det|> +Figure 1 + +<|ref|>text<|/ref|><|det|>[[92, 251, 895, 383]]<|/det|> +Fig 1A is a good entry illustration but can be made more explicit. I suggest adding a legend for the elements of MAC tag and affinity resins that allow understanding of which tag element is used, similar to the figures in your Liu et el 2018 paper. The arrows from AP- MS and XL- MS branches point to a mass spectrometer (?), but the BioID- MS - to the PPI analysis icon. I suggest leaving only PPI analysis in and converging on it all three paths. Outline conditions for harsh and soft lysis conditions in the figure, i.e. "harsh, 0.1% SDS", "soft, 0.5% IGEPAL". + +<|ref|>text<|/ref|><|det|>[[93, 403, 459, 421]]<|/det|> +Thank you for your feedback on Figure 1. + +<|ref|>text<|/ref|><|det|>[[92, 440, 888, 497]]<|/det|> +In response to your suggestions, we have revised Fig 1A to enhance its clarity and understandability. We added labels for both the SH- tag and the biotin ligase BirA, aiming to provide clearer visualization of the involved elements. + +<|ref|>text<|/ref|><|det|>[[92, 498, 884, 612]]<|/det|> +We would like to clarify the representation of the Mass spectrometer and PPI analysis in Fig 1A. They are intended to represent the same analytical endpoint. To address the inconsistency you pointed out, we've adjusted the figure such that the arrow from BioID- MS now correctly points to the combined MS- analysis and PPI analysis icon. This should now provide a consistent representation of the analytical endpoints for the different techniques. + +<|ref|>text<|/ref|><|det|>[[92, 612, 895, 764]]<|/det|> +Regarding the 'lysis conditions', we appreciate your suggestion on detailing the lysis conditions directly in the figure. However, the distinction between soft and harsh lysis is nuanced, involving more than just the choice of detergent. Specifically, the harsh lysis procedure also incorporates sonication in the presence of benzonase. We believe that these intricacies are best detailed in the experimental section, where they can be elaborated upon more extensively. Hence, we've opted to maintain a streamlined representation in Fig 1A, without the specific detergent details, to ensure its simplicity and accessibility. + +<|ref|>text<|/ref|><|det|>[[92, 782, 880, 819]]<|/det|> +Replace the SEC panel in panel A with panel E. Use text instead of pictograms of molecules for SEC peaks designation. + +<|ref|>text<|/ref|><|det|>[[92, 838, 900, 895]]<|/det|> +To clarify, the SEC depiction in panel A is intended as a schematic representation, designed to provide an overview of the workflow employed in our study. It is not a direct representation of experimental results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 864, 121]]<|/det|> +On the right from the Cryo- EM block, you could name and show all four maps from grey circles in FigS2. + +<|ref|>text<|/ref|><|det|>[[92, 141, 866, 179]]<|/det|> +Thank you for your feedback regarding the representation of the Cryo- EM block in our figure. + +<|ref|>text<|/ref|><|det|>[[92, 198, 898, 293]]<|/det|> +We understand the value in showcasing detailed results, as you've suggested with the four maps from grey circles in FigS2. However, the primary intent behind Figure 1 panel A was to provide a schematic overview of the entire workflow. Introducing specific results into this schematic might divert from its original purpose of giving a broad- strokes view of the methodology. + +<|ref|>text<|/ref|><|det|>[[92, 330, 904, 367]]<|/det|> +Also, please include Coomassie stained PAGE of native and cross- linked Commander used for cryo- EM. + +<|ref|>text<|/ref|><|det|>[[92, 387, 861, 424]]<|/det|> +Thank you for your suggestion to include a Coomassie stained PAGE of the native and cross- linked Commander used for cryo- EM. + +<|ref|>text<|/ref|><|det|>[[92, 425, 861, 462]]<|/det|> +While in general we appreciate the value of such data, here we've decided against this inclusion for the following critical reasons: + +<|ref|>text<|/ref|><|det|>[[121, 482, 890, 670]]<|/det|> +1. The procedure for purifying the cross-linked Commander complex results in a very limited yield ( \(\sim 25 \mu l\) at \(\sim 0.1 \mathrm{mg / ml}\) ). We, therefore, prioritized cryo-EM grid preparation over PAGE analysis. We were confident in this approach, as we had extensive AP-MS evidence of the constituents of the complex before cross-linking and identified all components of the complex in the MS data we collected. +2. Furthermore, given the mild nature of our cross-linking procedure, we anticipate a set of heterogeneously cross-linked complex isoforms in a PAGE analysis. Such an analysis would primarily indicate that cross-linking has occurred, without providing intricate details. We can obtain more precise information about the cross-linking pattern from the MS data we collected from the cross-linked, gel-filtered complex. + +<|ref|>text<|/ref|><|det|>[[94, 707, 313, 724]]<|/det|> +Fig 1D. Define table axes. + +<|ref|>text<|/ref|><|det|>[[92, 744, 679, 763]]<|/det|> +Table axes (bait / prey) have now been added to Figure 1 panel D. + +<|ref|>text<|/ref|><|det|>[[92, 802, 790, 820]]<|/det|> +If feasible, introduce a better graphical explanation of the colour/circle size code. + +<|ref|>text<|/ref|><|det|>[[92, 839, 630, 857]]<|/det|> +Thank you for the feedback on our graphical representation. + +<|ref|>text<|/ref|><|det|>[[92, 877, 875, 914]]<|/det|> +To enhance clarity, we've renamed the colour/circle size codes to "Bait normalized AvgSpec" and "Relative AvgSpec." We've expanded on this in the figure legend with the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 899, 140]]<|/det|> +following explanation on Page 25, line 8: "The color of each circle represents the abundance of each prey normalized to the mean abundance of the bait protein, and the circle radius indicates the relative abundance across all samples calculated by ProHits- Viz." + +<|ref|>text<|/ref|><|det|>[[92, 159, 899, 178]]<|/det|> +We hope this adjustment provides a clearer understanding of the graphical elements used. + +<|ref|>text<|/ref|><|det|>[[92, 217, 871, 254]]<|/det|> +Panel A can be used to reference specific branches of the MS. Consider moving panel B to supplementary if more space is needed. + +<|ref|>text<|/ref|><|det|>[[92, 274, 592, 292]]<|/det|> +We have incorporated a reference to panel A in the text. + +<|ref|>text<|/ref|><|det|>[[92, 330, 894, 386]]<|/det|> +AvgSpec/Relative AvgSpec abundance needs a better explanation for readers outside the MS field. Consider extending the Quantification and statistical analysis chapter and explaining the interpretation of two marginal data points (i.e. for good and bad binders). + +<|ref|>text<|/ref|><|det|>[[92, 405, 893, 480]]<|/det|> +The average spectral count corresponds to the abundance of each prey protein in the sample and is represented by the node color. To evaluate the relative weight of each interaction among the presented samples, we calculated the relative abundance using the ProHits- Viz tool. + +<|ref|>text<|/ref|><|det|>[[92, 499, 894, 575]]<|/det|> +We have updated the Figure 1 legend on Page 25, line 8 to read: "The color of each circle represents the abundance of each prey, normalized to the mean abundance of the bait protein. The circle radius indicates the relative abundance across all samples, as calculated by ProHits- Viz." + +<|ref|>text<|/ref|><|det|>[[92, 612, 568, 630]]<|/det|> +Line 142. Comment why COMMD9 was chosen as bait. + +<|ref|>text<|/ref|><|det|>[[92, 650, 883, 706]]<|/det|> +As there was initially very little information about the Commander complex assembly, we selected a few bait proteins for purification optimization. Out of the tested bait proteins, COMMD9 gave the highest yield, and was thus chosen for further optimization. + +<|ref|>text<|/ref|><|det|>[[92, 744, 896, 856]]<|/det|> +Line 480. Cloning of Commander complex components. Describe cell genotype in plain language. If I understand correctly, cell lines contained an additional copy (over the WT genome) of genome- integrated MAC- tagged tagged bait under a tetracycline- inducible promotor. Upon induction, the binders will preferentially bind to the tagged due to its higher titer than WT copies. What is the estimated bait expression level compared to the endogenously expressed protein? + +<|ref|>text<|/ref|><|det|>[[92, 875, 888, 912]]<|/det|> +The cell line used employs the Flp- In™ system, which allows the insertion of a single copy of the gene of interest at the FRT site in HEK cells. Expression of the protein of interest is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 900, 235]]<|/det|> +induced using tetracycline, resulting in an expression level parallel to and on the same scale as the endogenous protein [PMID:19156129; PMID:23455922; PMID:28330616]. In BioID- MS experiments, proximity labeling biotinylation is induced using biotin. Intact protein complexes (AP- MS) or biotinylated proteins (after disruption of native protein complexes in BioID- MS) are extracted from the cell lysate using Strep- tactin resin, which binds both biotin and the SH- tag. The method is described in more detail in the articles by Liu et al [PMID:29568061], which we reference in the text on Page 12, line 30, and on Page 13, line 6. + +<|ref|>text<|/ref|><|det|>[[93, 274, 632, 292]]<|/det|> +Line 91. Highlight these newly discovered interactors in Fig S1. + +<|ref|>text<|/ref|><|det|>[[92, 310, 904, 444]]<|/det|> +Figure S1 was updated according to the reviewer's suggestion. Novel interactions are now presented on a grey square background. The legend for Figure S1A on Page 26, line 5, has been updated to: "(A) Dot- plot visualization of the Commander complex proteins' interactors detected by AP- MS. Each node color corresponds to the abundance of the average spectral count for each prey, and the node size indicates the relative abundance of the prey. BFDR values are denoted by circles around the nodes, and novel interactions are highlighted with a grey background." + +<|ref|>text<|/ref|><|det|>[[93, 480, 697, 499]]<|/det|> +Line 567. Give protein concentration in the BS3 cross- linking reaction. + +<|ref|>text<|/ref|><|det|>[[92, 519, 883, 595]]<|/det|> +As the cross- linking was conducted during ultrafiltration, the protein concentration increased during the crosslinking process. Therefore, we cannot specify the exact protein concentration. The 2 mM BS3 concentration we used was recommended in a protocol provided by the manufacturer. + +<|ref|>text<|/ref|><|det|>[[92, 631, 828, 650]]<|/det|> +FigS2. Add title "cross- linked" above panels D- G. Show FSC curves for the final maps. + +<|ref|>text<|/ref|><|det|>[[92, 670, 867, 707]]<|/det|> +The requested titles were added and FSC curves plotted for the final reconstructions as requested. + +<|ref|>text<|/ref|><|det|>[[92, 741, 884, 760]]<|/det|> +Line 596. Should "tandem" be replaced with "in parallel"? Tandem implies sequential order. + +<|ref|>text<|/ref|><|det|>[[92, 778, 570, 796]]<|/det|> +The text was modified according to reviewer's suggestion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 831, 121]]<|/det|> +Fig3J. Indicate the NN- CH domain in the figure. Should CCDC93 NTD be changed to CCDC93 NN- CH? + +<|ref|>text<|/ref|><|det|>[[92, 142, 844, 202]]<|/det|> +We have changed the labeling to improve the distinction between NTDs of COMMD proteins and the NN- CH domains of CCDC proteins. These changes have also been implemented in the text by replacing CCDC NTDs with NN- CH. + +<|ref|>text<|/ref|><|det|>[[92, 245, 886, 355]]<|/det|> +FigS4. Fix panel assignment (F panel is skipped). The comparison to Healy at al 2023 AF2 model is interesting and will be clearer using pipes and plunks depiction or "ragdoll model" with complex parts presented as geometrical shapes to highlight dramatic differences in COMMDS ring rotation and CCDCs coils. Aligning the models on Vps35L may be more informative. + +<|ref|>text<|/ref|><|det|>[[91, 381, 890, 515]]<|/det|> +We thank the reviewer for pointing out the error in panel assignment and have rectified the issue. We settled on pipes representation for the comparison as it clarified the visualization significantly. While we did align the coils via VPS35L to test the representation, we felt that the current alignment center at DENND10 provides a clearer distinction on the relative differences in overall conformation of Retriever vs. the COMMD ring. + +<|ref|>text<|/ref|><|det|>[[92, 561, 864, 602]]<|/det|> +Line 134. DENND10 binds the commander via CCDCs, making the statement in line 134 counterintuitive. Please clarify this point. + +<|ref|>text<|/ref|><|det|>[[91, 628, 901, 855]]<|/det|> +We previously wrote: "Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker," which is indeed confusing. The clustering to find relative similarities takes into account the relative amount of each prey in each sample, and compares that to the other samples. As CCDCs have interactions that are different from the rest of the Commander complex proteins, their association to the other proteins is weaker despite their physical proximity to the COMMD proteins in the Commander complex. The text on Page 4, line 12 was modified to "Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker due to their interactions different from the rest of the complex (Fig. 1C)." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 85, 888, 140]]<|/det|> +Complex. bioRxiv. doi:10.1101/2023.06.06.543888 Healy MD et al. (2023) Structure of the endosomal Commander complex linked to Ritscher- Schinzel syndrome. Cell 186:2219-2237 e2229. doi:10.1016/j.cell.2023.04.003 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 85, 205, 101]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[93, 104, 297, 120]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[91, 120, 903, 654]]<|/det|> +Laulumaa et al. here report the use of AP- MS and BioID- MS to make a comprehensive characterization of stable and transient interactions of the human Commander complex. The authors propose a set of biological processes where Commander could have essential roles such as endosomal transport, actin nucleation, immune response, transcription regulation, centriole replication, centrosomal targeting and cilium assembly. In addition, the authors purified and solved the structure of the whole Commander complex by single particle cryo- EM. The structure consist of a 16- protein assembly arranged in two sub- complexes; an heterodecameric ring of the COMMD proteins (COMMD 1- 10) connected to the retriever subcomplex (VPS35L, VPS26C and VPS29) by the CCDC22- CCDC93 heterodimer which interacts with DENND10 through a V- shaped coil (R- coil). The atomic model built into the cryo- EM density is supported by several XL- MS crosslinks. Overall, this is a well- executed study that provides the molecular architecture of the full Commander complex and spans its interactome. Unfortunately, the recent publication of the structure of the Commander complex (Healy et al. 2023) diminishes the originality of the present work. Nevertheless, while the structure of the Commander complex from Healy et al. was determined by combining data form cryo- EM, X- ray crystallography and AF modelling of distinct substructures, the present work by Laulumaa et al. provides a complete picture of the full sixteen subunits. Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al. On the other hand, the interactome analysis reads as a dry catalog of interactions with assigned GO terms and biological processes. The manuscript lacks a logical flow where functional/biological mechanisms are addressed throughout the structure. Similarly, the lack of functional assays 'in cellulo' diminishes general interest. For example, assessing the integrity of the Commander complex throughout site directed mutagenesis and evaluating the significance on novel roles such as cilia modulation could add novelty and interest to a wider audience. In summary, the lack of novelty in the structure and the absence of functional implications connected to Commander assembly have dumped the excitement for this manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 670, 905, 824]]<|/det|> +Regarding the reviewer's comment "Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al.", we would like to justify the lack of explicit comparisons to the Healy et al. structure. Their model's quaternary structure is based on predictions by alphafold2, while ours is based on experimental evidence combined with predictions. For the substructures that both models have experimental evidence on, our models agree. Therefore, we feel that extensive comparisons between the models is not relevant in the context of the present manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 85, 876, 122]]<|/det|> +Other more specific issues include: +- This reviewer has not been able to see the PDB validation report to assess the PDB model. + +<|ref|>text<|/ref|><|det|>[[92, 143, 864, 181]]<|/det|> +We apologize and acknowledge that the reports were only provided during the review process for the editor and reviewers. + +<|ref|>text<|/ref|><|det|>[[92, 199, 880, 236]]<|/det|> +- Supplementary Table (REAGENT or RESOURCE) lacks several EMDB and PDB codes. They are denoted as 'EMD-XXX' or 'PDB: XXXX'. Same in 'Data availability' (lines 710-718) + +<|ref|>text<|/ref|><|det|>[[92, 255, 844, 293]]<|/det|> +We have rectified this error in the manuscript on Page 17, lines 35- 40, and thank the reviewer for pointing out the missing codes. + +<|ref|>text<|/ref|><|det|>[[92, 313, 899, 351]]<|/det|> +- There is a very early fall of in the FCS(unmasked). Could it be because of the very large box size used in relation to the size of the complex?. Was it intended to capture flexible regions?. + +<|ref|>text<|/ref|><|det|>[[92, 370, 902, 492]]<|/det|> +We acknowledge this feature in the FSC curves and as the Reviewer suspects it is due to the relatively large box size used here (required for not cropping out flexible parts of the complex). To demonstrate the effect of box size on FSC(unmasked), we have prepared cropped half- maps and recalculated the unmasked FSC, presented below (Figures 1 and 2). Please note that the "corrected" curves give highly similar results as expected and these values are the reported ones as they take this issue with box size into account. + +<|ref|>image<|/ref|><|det|>[[95, 533, 700, 778]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[92, 800, 796, 837]]<|/det|> +
Figure 1. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 400 px.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[95, 88, 700, 330]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 349, 894, 388]]<|/det|> +
Figure 2. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 560 px (original box size).
+ +<|ref|>text<|/ref|><|det|>[[92, 406, 872, 444]]<|/det|> +- In section 4.2 of the validation report, there is a big difference in the reported resolution and the unmasked-calculated resolution. Could this be related to the large box size used? + +<|ref|>text<|/ref|><|det|>[[92, 465, 230, 483]]<|/det|> +Yes. See above. + +<|ref|>text<|/ref|><|det|>[[92, 527, 866, 586]]<|/det|> +- It might be something odd from the validation report but the mask looks larger in 2.6.1 than the projection in 2.1 (although the map in 2.5.1 looks large like the mask, it looks different to the 2.5.2). + +<|ref|>text<|/ref|><|det|>[[91, 606, 888, 741]]<|/det|> +We have carefully checked the map and mask visualizations in the validation report, section 6 (map visualization). We note that the maps are shown at different scale in 6.5.1 (primary map) and 6.5.2 (raw map). This is a feature of the PDB validation server and beyond our control. The mask visualized in 6.6.1 is visualized in the same scale as the primary map. We confirm that these are how maps are displayed in the validation reports and do not affect our results or the maps we have deposited. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 85, 707, 102]]<|/det|> +The following additional modifications were made to the manuscript: + +<|ref|>text<|/ref|><|det|>[[95, 123, 113, 138]]<|/det|> +1) + +<|ref|>text<|/ref|><|det|>[[128, 141, 892, 252]]<|/det|> +We added additional experiments to the manuscript to further strengthen the interactome data. We generated HEK cell lines with pathogenic point mutations associated with Ritscher- Schinzel syndrome in VPS35L and CCDC22, and conducted BioID- MS for those samples. The following text was added to the manuscript on Page 10, line 3: "Ritscher- Schinzel syndrome point mutations alter PPIs of CCDC22 and VPS35L. + +<|ref|>text<|/ref|><|det|>[[128, 254, 895, 386]]<|/det|> +The Commander complex has been associated with Ritscher- Schinzel syndrome (RSS) or X- linked intellectual disability (XLID) via point mutations in VPS35L and CCDC22 [PMID:31712251; PMID:21826058; PMID:23563313; PMID: 24916641]. Disease variants CCDC22(T17A), CCDC22(Y557C), and VPS35L(A830T) (Fig. 6A) are listed as "pathogenic" for RSS in GnomAD database [PMID:32461654]. Cell lines expressing these disease variants were generated for BioID- MS analysis to investigate their effect at the PPI level (Data S1). + +<|ref|>text<|/ref|><|det|>[[128, 386, 904, 558]]<|/det|> +VPS35L(A830T) was shown to abolish its interaction with VPS29 [PMID:31712251]. Our data shows that the A830T mutation does not inhibit interaction with VPS26C, but separates VPS35L from the rest of the Commander complex and disrupts its interaction with the WASH complex (Fig. 6A- B). The RSS disease variants of CCDC22 have weaker interactions to COMMD proteins compared to the wild- type, but interact more with the WASH complex (Fig. S6B). The Reactome pathway analysis of disease mutant specific PPIs shows the strongest enrichment of R- HSA- 5617833.4- Cilium assembly pathway for CCDC22(T17A), and R- HSA- 6811440.2- Retrograde transport at the Trans- Golgi- Network for both variants (Fig. S6E)." + +<|ref|>text<|/ref|><|det|>[[92, 579, 113, 594]]<|/det|> +2) + +<|ref|>text<|/ref|><|det|>[[128, 596, 901, 671]]<|/det|> +In the discussion section on Page 11 line 7, we added "Interestingly, our finding that besides disrupting the Commander complex assembly, the RSS variant VPS35L(A830T) also loses its affinity to the WASH complex. This is consistent with the presented prediction for potential WASH binding interface, where VPS29 is located at the centre." + +<|ref|>text<|/ref|><|det|>[[92, 692, 113, 707]]<|/det|> +3) + +<|ref|>text<|/ref|><|det|>[[128, 710, 904, 841]]<|/det|> +The following paragraph was added to the discussion on Page 12, line 9: "We used point mutants CCDC22(T17A), CCDC22(Y557C), and VPS35L(A830T) to investigate the disease mechanism of RSS at the PPI level. The VPS35L(A830T) mutation disrupted the Commander complex assembly, and completely blocked interaction to WASH complex, whereas RSS mutations shifted the HCIs of CCDC22 from the Commander complex towards retrograde transport and Golgi trafficking. This implies a complex molecular etiology of RSS." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 85, 113, 100]]<|/det|> +4) + +<|ref|>text<|/ref|><|det|>[[125, 102, 899, 275]]<|/det|> +The following paragraph was added to Materials and methods on Page 12, line 31: "Generation of RSS disease variants. RSS disease point mutations were introduced to CCDC22 and VPS35L genes by site- directed mutagenesis using Q5® High- Fidelity DNA Polymerase (NEB #M0491) and the following primers: 5'- GGCGCGGCAGTTCC and 3'- AACTGCCGCGCCGGCC (CCDC22(T17A)), 5'- AAGGCCTGTAAGTATCTAGCTGC and 3'- GATACTTACAGGCCTTCCGAACA (CCDC22(Y557C)), and 5'- TCCACCATGAGCCAGGAG and 3'- CTCATGGTGGAGAGGAGATGC (VPS35L_A830). The disease variants and wild- type genes were cloned into C- terminal ultralD containing MAC3- tagged vectors [PMID:35384245]." + +<|ref|>text<|/ref|><|det|>[[92, 294, 113, 310]]<|/det|> +5) + +<|ref|>text<|/ref|><|det|>[[127, 312, 870, 369]]<|/det|> +Following update was made to Affinity purification protocol on Page 13, line 9: "An additional \(50 \mu M\) of biotin was added for proximity labelling (BioID) for 24 h (MAC- tagged constructs) or 5 hours (MAC3- tagged constructs)." + +<|ref|>text<|/ref|><|det|>[[92, 388, 113, 404]]<|/det|> +6) + +<|ref|>text<|/ref|><|det|>[[126, 406, 900, 690]]<|/det|> +Figure S6 legend on Page 28, line 14 was updated to: "Fig. S6. Molecular interactors, context, and cellular pathways connected with individual Commander complex components, related to Figure 5. (A) Dot- plot visualization (BFDR \(\leq 0.05\) ) of interactors of the Commander complex detected by the BioID- MS. Node color corresponds to the abundance of the average spectral count for each prey, and node radius to its relative abundance. (B) Dot- plot visualization of RSS syndrome related point mutants of CCDC22 analyzed by BioID- MS. All PPIs passing HCl criteria to any of the CCDC22 variants are plotted, with HCIs are indicated with black outline and non- HCIs with light blue. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz. (C) Reactome pathways enriched for the Commander complex proteins. (D) Molecular level localization of the Commander complex proteins obtained by MS- microscopy. (E) Reactome pathways enriched \((p< 0.005\) , values marked in bars) for the RSS disease variant HCIs distinct from the wild- type CCDC22." + +<|ref|>text<|/ref|><|det|>[[92, 710, 113, 725]]<|/det|> +7) + +<|ref|>text<|/ref|><|det|>[[127, 728, 904, 899]]<|/det|> +Figure 6 legend on Page 26, line 35was updated to: "Fig. 6. RSS and XLID related mutations and putative interaction interfaces of the Commander complex. (A) Three mutations associated with RSS or XLID are highlighted within the context of the Commander complex structure. (B) Effect of A830T mutation on VPS35L in BioID- MS. All PPIs passing HCl criteria to either wild- type VPS35L or VPS35L(A830T) are plotted for both constructs, with HCIs indicated using black outline and non- HCIs with light blue outline. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz (C) Composite model of the Commander complex, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 84, 901, 140]]<|/det|> +indicating putative interaction interfaces with tubulin polyglutamylase complex (TPGC). (D) Rotated view of the model in (C), with putative interaction interface of the WASH complex indicated." + +<|ref|>text<|/ref|><|det|>[[92, 160, 113, 177]]<|/det|> +8) + +<|ref|>text<|/ref|><|det|>[[128, 179, 901, 273]]<|/det|> +Sentence on Page 11, line 44 "We did not detect any Rab proteins as PPIs of any of the Commander complex proteins, supported by the decoupling of Rab7 function from Retriever" was changed to "We did not detect any Rab proteins as HCIs of the Commander complex proteins except for Rab9a in the RSS variants of CCDC22. This observation aligns with the known decoupling of Rab7 function from the Retriever." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[120, 145, 345, 160]]<|/det|> +Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[120, 201, 312, 215]]<|/det|> +Message: 28th Sep 2023 + +<|ref|>text<|/ref|><|det|>[[202, 242, 390, 256]]<|/det|> +Dear Professor Varjosalo, + +<|ref|>text<|/ref|><|det|>[[202, 269, 877, 339]]<|/det|> +Thank you for submitting your revised manuscript, "Structure and Interactions of the Endogenous Human Commander Complex". After careful consideration and discussion with my colleagues, I am sorry to have to tell you that we do not feel that the referees' comments have been sufficiently addressed to justify sending this revision back for peer review. + +<|ref|>text<|/ref|><|det|>[[202, 352, 872, 409]]<|/det|> +This unusual course of action is taken occasionally to avoid unproductive rounds of review that result in reviewer fatigue and damage the chances of the manuscript obtaining a fair and objective evaluation. Such situations are not in an author's best interest so we try to avoid them when it seems prudent to do so. + +<|ref|>text<|/ref|><|det|>[[201, 422, 877, 533]]<|/det|> +In order to consider this manuscript further we would request that you please do your best to fully address all of the comments of the reviewers, as well as our editorial guidance. In particular, please do make an effort to visually compare the models (experimental or predicted) of the complex, as well as add further discussion to the text. Both reviewers pointed out this to be an issue with the previous version of the manuscript, and editorially, we agree with their comments. This will be important for the readers to fully understand how this study compares with the literature, and will increase impact and accessibility of your work. + +<|ref|>text<|/ref|><|det|>[[202, 545, 878, 602]]<|/det|> +We would kindly ask that in the revised manuscript, you clearly state the differences in the native complex obtained in this study, and how it stands compared to published literature. Please revise both the manuscript and the point- by- point response to address these points. + +<|ref|>text<|/ref|><|det|>[[201, 628, 870, 657]]<|/det|> +Should you be able to adequately respond to these and the reviewers' other concerns, we would be happy to look at a revised manuscript again. + +<|ref|>text<|/ref|><|det|>[[201, 669, 878, 755]]<|/det|> +We shall hope to receive your revised version as soon as possible. If you anticipate a delay of more than four weeks, however, please let us know. We will be happy to consider your revision so long as nothing similar has been accepted for publication at Nature Structural & Molecular Biology or published elsewhere. Should your manuscript be substantially delayed without notifying us in advance and your article is eventually published, the received date may be that of the revised, not the original, version. + +<|ref|>text<|/ref|><|det|>[[201, 768, 872, 850]]<|/det|> +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[201, 145, 866, 202]]<|/det|> +contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[201, 214, 865, 259]]<|/det|> +If you are not interested in submitting a suitably revised manuscript in the future please let me know immediately so we can close your file. If you have any questions, please contact me. + +<|ref|>text<|/ref|><|det|>[[200, 270, 875, 300]]<|/det|> +Please use the link below to submit a suitably revised manuscript and updated response to referees when they are ready. + +<|ref|>text<|/ref|><|det|>[[201, 311, 284, 327]]<|/det|> +[Redacted] + +<|ref|>text<|/ref|><|det|>[[201, 339, 275, 354]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[200, 367, 504, 437]]<|/det|> +Katarzyna Ciazynska (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +<|ref|>sub_title<|/ref|><|det|>[[120, 476, 354, 492]]<|/det|> +## Author Rebuttal, first revision: + +<|ref|>text<|/ref|><|det|>[[114, 512, 884, 728]]<|/det|> +We thank the reviewers for detailed and positive comments on our manuscript "Structure and Interactions of the Endogenous Human Commander Complex". See below our point- by- point response to the comments (in gray italics). We have expanded our comparison to the existing model of Healy et al. by including two new main figures and adding new material to the supplementary figures. We have also included two pages worth of text on the comparisons, to highlight where the two models differ. Furthermore, we have included additional experiments on the disease mutations, not requested by the reviewers. We feel that these experiments complement well the other comparison we have added on the differences between these two models. These and other additional modifications are reported at the end of this rebuttal. + +<|ref|>text<|/ref|><|det|>[[115, 781, 213, 798]]<|/det|> +Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[115, 819, 312, 836]]<|/det|> +Remarks to the Author: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 163, 884, 303]]<|/det|> +Recently discovered Commander complex exerts its function in multiple processes; however, structural information is lacking to deconvolute the underlying mechanisms. The proposed manuscript elegantly combines mass- spectrometric analysis with cryo- electron microscopy to visualize the whole commander complex and systematically analyze its interactome. This approach is granted for a 16- subunit commander complex and, in the broader context, sets up a promising way to parallelize molecular and structural discoveries of challenging biological assemblies. + +<|ref|>text<|/ref|><|det|>[[114, 322, 884, 525]]<|/det|> +The authors first created cell lines with one of the commander subunits with MAC tag (BlrA\\* biotinylation enzyme plus affinity purification peptides). They systematically explored subunits interactomes, cross- referencing Bio- ID and affinity purification mass spectroscopy (AP- MS) to get an insight into the stability and composition of commander assembled from endogenously expressed properties (except the bait under control of inducible promotor). The verified reported and discovered a plethora of new binders. The binders list highlights multiple roles of the commander. It includes proteins working in the Cilium Assembly pathway, membrane trafficking (exocyst, PI3P phosphatase), inflammation, and cytoskeleton organization, to name a few functional clusters. Finally, the MS analysis pinpointed posttranslational modification sites. + +<|ref|>text<|/ref|><|det|>[[114, 543, 884, 844]]<|/det|> +Following the MS, the cell line with COMMD9 bait was used to isolate the natively assembled commander for cryo- EM structure determination. SPA analysis converged on the map resolving primarily the COMMD ring. Cross- linking was used to restrict the conformational heterogeneity of the complex and succeeded in resolving the whole commander complex. As expected, the COMMD ring map still led in resolution and resolved side chains; nevertheless, the CCDCs and Retriever modules of the commander could now be resolved to the secondary structure using focused alignment. Commander architecture from cryo- EM map drastically differs from the predicted models (Healy et al. 2023; Boesch et al. 2023), featuring \(\sim 90\) degrees of the COMMD ring rotation and other major differences. This finding is also valuable as a benchmark for predicting complex tertiary structures. Furthermore, the structural studies were complemented by molecular dynamic simulations pinpointing conformation variability in COMMD that may bridge retriever and DENND10. Finally, the manuscript looks closely at the loosely associated interactors discovered by proximity biotinylation (BioID- MS). BioID- MS proteome is dominated by inter- complex binding reiterating on commander multiple roles. Distance dependence of biotinylation by + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 880, 165]]<|/det|> +BirA\\* allowed the identification of two interaction clusters in the commander surface. + +<|ref|>text<|/ref|><|det|>[[115, 182, 882, 243]]<|/det|> +Overall the manuscript brings important novel insights and is written compellingly with sufficient experiential evidence. Authors deserve special credit for clear visual language and concise text. + +<|ref|>text<|/ref|><|det|>[[115, 262, 880, 283]]<|/det|> +Here I propose text and figure changes to improve manuscript clarity further. + +<|ref|>text<|/ref|><|det|>[[115, 303, 181, 320]]<|/det|> +Figure1 + +<|ref|>text<|/ref|><|det|>[[115, 322, 883, 462]]<|/det|> +Figure1Fig1A is a good entry illustration but can be made more explicit. I suggest adding a legend for the elements of MAC tag and affinity resins that allow understanding of which tag element is used, similar to the figures in your Liu et el 2018 paper. The arrows from AP- MS and XL- MS branches point to a mass spectrometer (?), but the BioID- MS - to the PPI analysis icon. I suggest leaving only PPI analysis in and converging on it all three paths. Outline conditions for harsh and soft lysis conditions in the figure, i.e. "harsh, 0.1% SDS", "soft, 0.5% IGEPAL". + +<|ref|>text<|/ref|><|det|>[[115, 483, 472, 502]]<|/det|> +Thank you for your feedback on Figure 1. + +<|ref|>text<|/ref|><|det|>[[115, 522, 882, 583]]<|/det|> +In response to your suggestions, we have revised Fig 1A to enhance its clarity and understandability. We added labels for both the SH- tag and the biotin ligase BirA, aiming to provide clearer visualization of the involved elements. + +<|ref|>text<|/ref|><|det|>[[115, 584, 882, 705]]<|/det|> +We would like to clarify the representation of the Mass spectrometer and PPI analysis in Fig 1A. They are intended to represent the same analytical endpoint. To address the inconsistency you pointed out, we've adjusted the figure such that the arrow from BioID- MS now correctly points to the combined MS- analysis and PPI analysis icon. This should now provide a consistent representation of the analytical endpoints for the different techniques. + +<|ref|>text<|/ref|><|det|>[[115, 706, 882, 825]]<|/det|> +Regarding the 'lysis conditions', we appreciate your suggestion on detailing the lysis conditions directly in the figure. However, the distinction between soft and harsh lysis is nuanced, involving more than just the choice of detergent. Specifically, the harsh lysis procedure also incorporates sonication in the presence of benzonase. We believe that these intricacies are best detailed in the experimental section, where they can be elaborated upon more extensively. Hence, we've opted to maintain a streamlined + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 144, 883, 186]]<|/det|> +representation in Fig 1A, without the specific detergent details, to ensure its simplicity and accessibility. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 882, 185]]<|/det|> +Replace the SEC panel in panel A with panel E. Use text instead of pictograms of molecules for SEC peaks designation. + +<|ref|>text<|/ref|><|det|>[[115, 205, 882, 265]]<|/det|> +To clarify, the SEC depiction in panel A is intended as a schematic representation, designed to provide an overview of the workflow employed in our study. It is not a direct representation of experimental results. + +<|ref|>text<|/ref|><|det|>[[115, 305, 882, 345]]<|/det|> +On the right from the Cryo- EM block, you could name and show all four maps from grey circles in FigS2. + +<|ref|>text<|/ref|><|det|>[[115, 366, 882, 406]]<|/det|> +Thank you for your feedback regarding the representation of the Cryo- EM block in our figure. + +<|ref|>text<|/ref|><|det|>[[115, 426, 882, 527]]<|/det|> +We understand the value in showcasing detailed results, as you've suggested with the four maps from grey circles in FigS2. However, the primary intent behind Figure 1 panel A was to provide a schematic overview of the entire workflow. Introducing specific results into this schematic might divert from its original purpose of giving a broad- strokes view of the methodology. + +<|ref|>text<|/ref|><|det|>[[115, 566, 882, 606]]<|/det|> +Also, please include Coomassie stained PAGE of native and cross- linked Commander used for cryo- EM. + +<|ref|>text<|/ref|><|det|>[[115, 626, 882, 666]]<|/det|> +Thank you for your suggestion to include a Coomassie stained PAGE of the native and crosslinked Commander used for cryo- EM. + +<|ref|>text<|/ref|><|det|>[[115, 667, 882, 707]]<|/det|> +While in general we appreciate the value of such data, here we've decided against this inclusion for the following critical reasons: + +<|ref|>text<|/ref|><|det|>[[145, 727, 883, 827]]<|/det|> +1. The procedure for purifying the crosslinked Commander complex results in a very limited yield ( \(\sim 25 \mu l\) at \(\sim 0.1 \mathrm{mg / ml}\) ). We, therefore, prioritized cryo-EM grid preparation over PAGE analysis. We were confident in this approach, as we had extensive AP-MS evidence of the constituents of the complex before crosslinking and identified all components of the complex in the MS data we collected. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[144, 144, 883, 247]]<|/det|> +2. Furthermore, given the mild nature of our crosslinking procedure, we anticipate a set of heterogeneously crosslinked complex isoforms in a PAGE analysis. Such an analysis would primarily indicate that crosslinking has occurred, without providing intricate details. We can obtain more precise information about the crosslinking pattern from the MS data we collected from the crosslinked, gel-filtered complex. + +<|ref|>text<|/ref|><|det|>[[116, 283, 330, 303]]<|/det|> +Fig 1D. Define table axes. + +<|ref|>text<|/ref|><|det|>[[115, 323, 796, 363]]<|/det|> +Table axes (bait / prey) have now been added to Figure 1 panel D. If feasible, introduce a better graphical explanation of the colour/circle size code. + +<|ref|>text<|/ref|><|det|>[[115, 383, 636, 403]]<|/det|> +Thank you for the feedback on our graphical representation. + +<|ref|>text<|/ref|><|det|>[[115, 423, 883, 543]]<|/det|> +To enhance clarity, we've renamed the colour/circle size codes to "Bait normalized AvgSpec" and "Relative AvgSpec." We've expanded on this in the figure legend with the following explanation on Page 26, line 9: "The color of each circle represents the abundance of each prey normalized to the mean abundance of the bait protein, and the circle radius indicates the relative abundance across all samples calculated by ProHits- Viz." + +<|ref|>text<|/ref|><|det|>[[115, 564, 882, 604]]<|/det|> +We hope this adjustment provides a clearer understanding of the graphical elements used. + +<|ref|>text<|/ref|><|det|>[[115, 645, 883, 686]]<|/det|> +Panel A can be used to reference specific branches of the MS. Consider moving panel B to supplementary if more space is needed. + +<|ref|>text<|/ref|><|det|>[[115, 706, 601, 726]]<|/det|> +We have incorporated a reference to panel A in the text. + +<|ref|>text<|/ref|><|det|>[[115, 765, 883, 825]]<|/det|> +AvgSpec/Relative AvgSpec abundance needs a better explanation for readers outside the MS field. Consider extending the Quantification and statistical analysis chapter and explaining the interpretation of two marginal data points (i.e. for good and bad binders). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 883, 224]]<|/det|> +The average spectral count corresponds to the abundance of each prey protein in the sample and is represented by the node color. To evaluate the relative weight of each interaction among the presented samples, we calculated the relative abundance using the ProHits- Viz tool. + +<|ref|>text<|/ref|><|det|>[[115, 244, 883, 325]]<|/det|> +We have updated the Figure 1 legend on Page 26, line 9 to read: "The color of each circle represents the abundance of each prey, normalized to the mean abundance of the bait protein, and the circle radius indicates the relative abundance across all samples calculated by ProHits- Viz." + +<|ref|>text<|/ref|><|det|>[[115, 364, 577, 384]]<|/det|> +Line 142. Comment why COMMD9 was chosen as bait. + +<|ref|>text<|/ref|><|det|>[[115, 404, 883, 465]]<|/det|> +As there was initially very little information about the Commander complex assembly, we selected a few bait proteins for purification optimization. Out of the tested bait proteins, COMMD9 gave the highest yield, and was thus chosen for further optimization. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 144, 883, 266]]<|/det|> +Line 480. Cloning of Commander complex components. Describe cell genotype in plain language. If I understand correctly, cell lines contained an additional copy (over the WT genome) of genome- integrated MAC- tagged tagged bait under a tetracycline- inducible promotor. Upon induction, the binders will preferentially bind to the tagged due to its higher titer than WT copies. What is the estimated bait expression level compared to the endogenously expressed protein? + +<|ref|>text<|/ref|><|det|>[[114, 286, 883, 488]]<|/det|> +The cell line used employs the Flp- In™ system, which allows the insertion of a single copy of the gene of interest at the FRT site in HEK cells. Expression of the protein of interest is induced using tetracycline, resulting in an expression level parallel to and on the same scale as the endogenous protein [PMID:19156129; PMID:23455922; PMID:28330616]. In BioID- MS experiments, proximity labeling biotinylation is induced using biotin. Intact protein complexes (AP- MS) or biotinylated proteins (after disruption of native protein complexes in BioID- MS) are extracted from the cell lysate using Strep- tactin resin, which binds both biotin and the SH- tag. The method is described in more detail in the articles by Liu et al [PMID:29568061], which we reference in the text on Page 3, line 5, and on Page 13, line 27. + +<|ref|>text<|/ref|><|det|>[[116, 526, 640, 546]]<|/det|> +Line 91. Highlight these newly discovered interactors in Fig S1. + +<|ref|>text<|/ref|><|det|>[[114, 566, 883, 708]]<|/det|> +Figure S1 was updated according to the reviewer's suggestion. Novel interactions are now presented on a grey square background. The legend for Figure S1A on Page 28, line 20, has been updated to: "(A) Dot- plot visualization of the Commander complex proteins' interactors detected by AP- MS. Each node color corresponds to the abundance of the average spectral count for each prey, and the node size indicates the relative abundance of the prey. BFDR values are denoted by circles around the nodes, and novel interactions are highlighted with a grey background." + +<|ref|>text<|/ref|><|det|>[[116, 747, 702, 767]]<|/det|> +Line 567. Give protein concentration in the BS3 cross- linking reaction. + +<|ref|>text<|/ref|><|det|>[[116, 788, 883, 828]]<|/det|> +As the crosslinking was conducted during ultrafiltration, the protein concentration increased during the crosslinking process. Therefore, we cannot specify the exact protein + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 883, 185]]<|/det|> +concentration. The 2 mM BS3 concentration we used was recommended in a protocol provided by the manufacturer. + +<|ref|>text<|/ref|><|det|>[[115, 223, 830, 243]]<|/det|> +FigS2. Add title "cross- linked" above panels D- G. Show FSC curves for the final maps. + +<|ref|>text<|/ref|><|det|>[[115, 263, 883, 304]]<|/det|> +The requested titles were added and FSC curves plotted for the final reconstructions as requested. + +<|ref|>text<|/ref|><|det|>[[115, 360, 875, 380]]<|/det|> +Line 596. Should "tandem" be replaced with "in parallel"? Tandem implies sequential order. + +<|ref|>text<|/ref|><|det|>[[115, 398, 579, 417]]<|/det|> +The text was modified according to reviewer's suggestion. + +<|ref|>text<|/ref|><|det|>[[115, 455, 883, 495]]<|/det|> +Fig3J. Indicate the NN- CH domain in the figure. Should CCDC93 NTD be changed to CCDC93 NN- CH? + +<|ref|>text<|/ref|><|det|>[[115, 517, 883, 581]]<|/det|> +We have changed the labeling to improve the distinction between NTDs of COMMD proteins and the NN- CH domains of CCDC proteins. These changes have also been implemented in the text by replacing CCDC NTDs with NN- CH. + +<|ref|>text<|/ref|><|det|>[[115, 626, 884, 744]]<|/det|> +FigS4. Fix panel assignment (F panel is skipped). The comparison to Healy at al 2023 AF2 model is interesting and will be clearer using pipes and plunks depiction or "ragdoll model" with complex parts presented as geometrical shapes to highlight dramatic differences in COMMDS ring rotation and CCDCs coils. Aligning the models on Vps35L may be more informative. + +<|ref|>text<|/ref|><|det|>[[115, 773, 883, 817]]<|/det|> +We thank the reviewer for pointing out the error in panel assignment and have rectified the issue. A "ragdoll model" using geometric shapes as suggested has now been included + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 883, 189]]<|/det|> +as new Figure 5. We have carried out the alignment of Healy et al. model on our model in two different ways to highlight the differences from multiple angles in Figure 5: + +<|ref|>text<|/ref|><|det|>[[113, 215, 885, 455]]<|/det|> +"A simplified "ragdoll" representation of major components of the Commander complex (A) from this study and (B- D) the overall structural model from Healy et al. highlight the major differences between these models with alignment centers of the models located at the (B) COMMD- ring, (C) V- coil, and (D) DENND10. The COMMD- ring is represented by a disc aligned to the COMMD domains, the coiled- coil domains are represented by cylinders (I and R- coils), or a trapezoidal prism (V- coil + CCDC22 NN- CH), DENND10 as a cylinder and Retriever subcomplex as spheres (VPS29, VPS26C + N- terminal half of VPS35L \(\alpha\) - solenoid) or a cylinder (VPS35L C- terminal half of VPS35L \(\alpha\) - solenoid). Component relative rotation angles are calculated based on the underlying atomic coordinates of backbone \(\mathrm{Ca}\) atoms." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 883, 189]]<|/det|> +Line 134. DENND10 binds the commander via CCDCs, making the statement in line 134 counterintuitive. Please clarify this point. + +<|ref|>text<|/ref|><|det|>[[113, 216, 884, 456]]<|/det|> +We previously wrote:"Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker," which is indeed confusing. The clustering to find relative similarities takes into account the relative amount of each prey in each sample, and compares that to the other samples. As CCDCs have interactions that are different from the rest of the Commander complex proteins, their association to the other proteins is weaker despite their physical proximity to the COMMD proteins in the Commander complex. The text on Page 4, line 11 was modified to "Furthermore, VPS35L and DENND10 are predominantly associated with the complex, while the association of the CCDCs appears weaker due to their interactions different from the rest of the complex (Fig. 1C)." + +<|ref|>text<|/ref|><|det|>[[115, 497, 883, 538]]<|/det|> +Boesch DJ et al. (2023) Structural Organization of the Retriever- CCC Endosomal Recycling Complex. bioRxiv. doi:10.1101/2023.06.06.543888 + +<|ref|>text<|/ref|><|det|>[[115, 557, 882, 599]]<|/det|> +Healy MD et al. (2023) Structure of the endosomal Commander complex linked to Ritscher- Schinzel syndrome. Cell 186:2219- 2237 e2229. doi:10.1016/j.cell.2023.04.003 + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 146, 225, 163]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[116, 185, 312, 202]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[113, 220, 884, 789]]<|/det|> +Laulumaa et al. here report the use of AP- MS and BioID- MS to make a comprehensive characterization of stable and transient interactions of the human Commander complex. The authors propose a set of biological processes where Commander could have essential roles such as endosomal transport, actin nucleation, immune response, transcription regulation, centriole replication, centrosomal targeting and cilium assembly. In addition, the authors purified and solved the structure of the whole Commander complex by single particle cryo- EM. The structure consist of a 16- protein assembly arranged in two sub- complexes; an heterodecameric ring of the COMMD proteins (COMMD 1- 10) connected to the retriever sub- complex (VPS35L, VPS26C and VPS29) by the CCDC22- CCDC93 heterodimer which interacts with DENND10 through a V- shaped coil (R- coil). The atomic model built into the cryo- EM density is supported by several XL- MS crosslinks. Overall, this is a well- executed study that provides the molecular architecture of the full Commander complex and spans its interactome. Unfortunately, the recent publication of the structure of the Commander complex (Healy et al. 2023) diminishes the originality of the present work. Nevertheless, while the structure of the Commander complex from Healy et al. was determined by combining data form cryo- EM, X- ray crystallography and AF modelling of distinct sub- structures, the present work by Laulumaa et al. provides a complete picture of the full sixteen subunits. Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not presented/discussed by Healy et al. On the other hand, the interactome analysis reads as a dry catalog of interactions with assigned GO terms and biological processes. The manuscript lacks a logical flow where functional/biological mechanisms are addressed throughout the structure. Similarly, the lack of functional assays 'in cellulo' diminishes general interest. For example, assessing the integrity of the Commander complex throughout site directed mutagenesis and evaluating the significance on novel roles such as cilia modulation could add novelty and interest to a wider audience. In summary, the lack of novelty in the structure and the absence of functional implications connected to Commander assembly have dumped the excitement for this manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 808, 883, 849]]<|/det|> +Regarding the reviewer's comment "Sadly, the authors have not done a clear comparative analysis between both structures putting an emphasis on aspects that were not + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 47, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 883, 204]]<|/det|> +presented/discussed by Healy et al.", we have now expanded our comparative analysis by including two new main figures detailing the differences at the major structural region level (Fig. 5) as well as within these structural regions (Fig. 6). + +<|ref|>text<|/ref|><|det|>[[115, 224, 743, 243]]<|/det|> +The following text was added to the results starting from Page 8, line 13: + +<|ref|>text<|/ref|><|det|>[[114, 244, 883, 545]]<|/det|> +"Recently, Healy et al. published an integrated structural model for the Commander complex [PMID:37172566]. As the model differs significantly in overall arrangement from the structure presented in this study (Fig. S4G), we compared the structures first by superposing the Healy et al. model using different alignment centers to our model (Fig. 5). The CCDC scaffolding is similar in both complexes, and the COMMD- ring, DENND10, and the Retriever subcomplex are located in similar positions along it (Fig. S4G). Three major differences between the models were found (Fig 5): (i) the overall structure is more compactly packed in our model than in the Healy et al. model. (ii) The orientation of the COMMD- ring relative to the CCDC scaffolding is different so that in Healy et al. model the COMMD- ring lacks contact to I- coil which is evident both in our cryo- EM and XL- MS data (Fig. 2A- B, Fig. S4D). Notably, the Healy et al. model is incompatible with the crosslink between CCDC93 and COMMD7 detected in this study. Furthermore, the relative orientation between COMMD- ring and DENND10 or V- coil differ by \(76^{\circ}\) and \(117^{\circ}\) , respectively. (iii) The twistedness of the scaffolding is dissimilar such that the relative orientation of DENND10 and Retriever differs by \(65^{\circ}\) . + +<|ref|>text<|/ref|><|det|>[[114, 565, 883, 847]]<|/det|> +Healy et al. compiled the overall model of the Commander complex using AF2 combined with X- ray crystallography and cryo- EM data from certain regions of the complex. When compared to our structure, models of the COMMD- ring align well as both studies base the structural models on high- resolution cryo- EM data (Fig. 6B). CCDC22 helices \(\alpha 15\) and \(\alpha 16\) , and the HLH- motif of CCDC93 are placed differently in the two models. They are absent in the cryo- EM structure by Healy et al. (EMD- 28827, PDB ID 8F2U) whereas their placement in our model is supported by cryo- EM density (Fig. S4H). The conformation of DENND10, I- coil, and R- coil is based heavily on AF2 prediction in both models, as our cryo- EM reconstruction has limited resolution in this region (Fig. S5D), and the Healy et al. model is entirely based on AF2 prediction for this part (Fig. 6C). The overall folds are similar, except that an interaction between the N- lobe of DENND10 and I- coil presented in Healy et al. model (indicated with an asterisk, Fig. 6C) is not featured in our model. This may be explained by conformational heterogeneity, as evidenced by our 3DVA analysis of this region (Fig. 4F). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 163, 884, 305]]<|/det|> +In our model, the Retriever subcomplex extends out of the main body of the complex (Fig. 2E- F). The tip extension of VPS35L binds VPS26C, while in the Healy et al. model it forms an interaction surface with the CCDC22 part of V- coil (Fig. 6D). This interaction seen in the Healy et al. model was predicted by AF2 and may reflect conformational heterogeneity in this region. Finally, Healy et al. solved the crystal structure of VPS29 with VPS35L (24- 38) peptide (PDB ID 8ESE), which is consistent with our cryo- EM structure (Fig. 6E)." + +<|ref|>text<|/ref|><|det|>[[115, 345, 876, 384]]<|/det|> +Other more specific issues include: - This reviewer has not been able to see the PDB validation report to assess the PDB model. + +<|ref|>text<|/ref|><|det|>[[115, 406, 884, 446]]<|/det|> +We apologize and acknowledge that the reports were only provided during the review process for the editor and reviewers. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 883, 185]]<|/det|> +- Supplementary Table (REAGENT or RESOURCE) lacks several EMDB and PDB codes. They are denoted as 'EMD-XXX' or 'PDB: XXXX'. Same in 'Data availability' (lines 710-718) + +<|ref|>text<|/ref|><|det|>[[115, 204, 883, 245]]<|/det|> +We have rectified this error in the manuscript on Page 19, lines 7- 12, and thank the reviewer for pointing out the missing codes. + +<|ref|>text<|/ref|><|det|>[[115, 287, 883, 351]]<|/det|> +- There is a very early fall of in the FCS(unmasked). Could it be because of the very large box size used in relation to the size of the complex?. Was it intended to capture flexible regions?. + +<|ref|>text<|/ref|><|det|>[[114, 374, 884, 525]]<|/det|> +We acknowledge this feature in the FSC curves and as the Reviewer suspects it is due to the relatively large box size used here (required for not cropping out flexible parts of the complex). To demonstrate the effect of box size on FSC(unmasked), we have prepared cropped half- maps and recalculated the unmasked FSC, presented below (Response Letter Figures 1 and 2). Please note that the "corrected" curves give highly similar results as expected and these values are the reported ones as they take this issue with box size into account. + +<|ref|>image<|/ref|><|det|>[[118, 570, 705, 831]]<|/det|> + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 47, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 144, 883, 185]]<|/det|> +Response Letter Figure 1. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 400 px. + +<|ref|>image<|/ref|><|det|>[[117, 189, 704, 445]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 465, 883, 506]]<|/det|> +
Response Letter Figure 2. Gold standard Fourier shell correlation plot for the consensus map of Commander complex at box size of 560 px (original box size).
+ +<|ref|>text<|/ref|><|det|>[[115, 526, 883, 567]]<|/det|> +- In section 4.2 of the validation report, there is a big difference in the reported resolution and the unmasked-calculated resolution. Could this be related to the large box size used? + +<|ref|>text<|/ref|><|det|>[[115, 590, 249, 608]]<|/det|> +Yes. See above. + +<|ref|>text<|/ref|><|det|>[[115, 650, 883, 711]]<|/det|> +- It might be something odd from the validation report but the mask looks larger in 2.6.1 than the projection in 2.1 (although the map in 2.5.1 looks large like the mask, it looks different to the 2.5.2). + +<|ref|>text<|/ref|><|det|>[[115, 735, 883, 828]]<|/det|> +We have carefully checked the map and mask visualizations in the validation report, section 6 (map visualization). We note that the maps are shown at different scale in 6.5.1 (primary map) and 6.5.2 (raw map). This is a feature of the PDB validation server and beyond our control. The mask visualized in 6.6.1 is visualized in the same scale as the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 884, 189]]<|/det|> +primary map. We confirm that these are how maps are displayed in the validation reports and do not affect our results or the maps we have deposited. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 712, 164]]<|/det|> +The following additional modifications were made to the manuscript: + +<|ref|>text<|/ref|><|det|>[[116, 187, 133, 203]]<|/det|> +1) + +<|ref|>text<|/ref|><|det|>[[148, 207, 883, 404]]<|/det|> +We added additional experiments to the manuscript to further strengthen the interactome data. We generated HEK cell lines with pathogenic point mutations associated with Ritscher- Schinzel syndrome in VPS35L and CCDC22, and conducted BioID- MS for those samples. The following text was added to the manuscript on Page 10, line 41: "The Commander complex has been associated with Ritscher- Schinzel syndrome (RSS) or X- linked intellectual disability (XLID) via point mutations in VPS35L and CCDC22 13,31,70,71. Disease variants CCDC22(T17A), CCDC22(Y557C), and VPS35L(A830T) (Fig. 2D, Fig. 8A) are listed as "pathogenic" for RSS in GnomAD database 72. Cell lines expressing these disease variants were generated for BioID- MS analysis to investigate their effect at the PPI level (Data S1). + +<|ref|>text<|/ref|><|det|>[[149, 405, 883, 485]]<|/det|> +The VPS35L(A830T) has been suggested to abolish its interaction with VPS29 70. Our data shows that the A830T mutation does not inhibit interaction with VPS26C, but separates VPS35L from the rest of the Commander complex and disrupts its interaction with the WASH complex (Fig. 8A- B). + +<|ref|>text<|/ref|><|det|>[[149, 487, 883, 748]]<|/det|> +With the CCDC22 RSS disease variants, we discovered less interactions to COMMD proteins (especially to COMMDs 3, 6, and 7), whereas interactions with the WASH complex become pronounced (Fig. S6B). Using the Reactome pathway analysis on the CCDC22 disease mutant interactors, we could detect enrichment of 'Cilium assembly pathway' for CCDC22(T17A), and 'Retrograde transport at the Trans- Golgi- Network' for both variants (Fig. S6E). The CCDC22(Y557C) mutation is situated at the tip of the CCDC22 part of V- coil, a region predicted to interact with VPS35L by Healy et al. Surprisingly, our BioID data shows no major changes in the interactome that could be expected if this interaction was significant. On the other hand, the distal location of VPS26C, and thus the tip of VPS35L, from the V- coil is supported by our BioID data where VPS26C and CCDCs are not in close proximity (Fig. 7B). However, possible effects on the VPS35L- V- coil interaction caused by this mutation need to be experimentally interrogated." + +<|ref|>text<|/ref|><|det|>[[115, 771, 133, 787]]<|/det|> +2) + +<|ref|>text<|/ref|><|det|>[[150, 791, 883, 849]]<|/det|> +The disease mutations were further discussed on Page 12 line 2, "Intriguingly, aside from its effect on Commander complex assembly, the RSS variant VPS35L(A830T) also displays reduced affinity for the WASH complex. The mutation site is located at the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[149, 143, 883, 247]]<|/det|> +interface between VPS35L and VPS29, and therefore this observation fits well with our proposed WASH binding interface model where VPS29 is located at the center. In contrast, while CCDC22 variants (T17A and Y557C) are also in close proximity to the putative WASH binding site, they have the opposite effect on WASH complex interactions, implying a complex molecular etiology of RSS." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 133, 161]]<|/det|> +3) + +<|ref|>text<|/ref|><|det|>[[149, 164, 883, 345]]<|/det|> +The following paragraph was added to Materials and methods on Page 13, line 30: "RSS disease point mutations were introduced to CCDC22 and VPS35L genes by site- directed mutagenesis using Q5® High- Fidelity DNA Polymerase (NEB #M0491) and the following primers: 5'- GGCGCGGCAGTTCCT and 3'- AACTGCCGCGCCGGC (CCDC22(T17A)), 5'- AAGGCCTGTAAGTATCTAGCTGC and 3'- GATACTTACAGGCCTTCCGAACA (CCDC22(Y557C)), and 5'- TCCACCATGAGCCAGGAG and 3'- CTCATGGTGGAGAGGAGATGC (VPS35L_A830). The disease variants and wild- type genes were cloned into C- terminal ultralD containing MAC3- tag vector [PMID:35384245]." + +<|ref|>text<|/ref|><|det|>[[115, 366, 133, 382]]<|/det|> +4) + +<|ref|>text<|/ref|><|det|>[[150, 386, 882, 446]]<|/det|> +Following update was made to Affinity purification protocol on Page 14, line 3: "An additional \(50\mu \mathrm{M}\) of biotin was added for proximity labelling (BiolD) for \(24\mathrm{h}\) (MAC- tagged constructs) or 5 hours (MAC3- tagged constructs)." + +<|ref|>text<|/ref|><|det|>[[115, 468, 133, 484]]<|/det|> +5) + +<|ref|>text<|/ref|><|det|>[[149, 487, 883, 748]]<|/det|> +The following paragraph was updated on Page 12, line 24: "The top half of the Commander complex contains flexible components (NTDs of COMMDs 1, 7, 9, and 10; HLH- motif of CCDC93), and the bottom half exhibits compositional and conformational heterogeneity, particularly within the Retriever subcomplex. This may reflect physiological assembly and/or the function of the complex. Indeed, COMMD proteins and the CCDCs have been proposed to form a complex without Retriever, termed the CCC- complex 75. Interestingly, assuming a similar head- to- head dimerization mode as Retromer, the structure of Commander permits binding of the CCC- complex on a Retriever dimer without obvious steric clashes (Fig. S5F- H). Such analysis relies on having access to complete native structure featuring external surfaces and exposed domains facilitating biological functions in the cellular context. This highlights the need for experimental data in addition to in silico predictions for quaternary structure analysis of large macromolecular complexes (Fig. 5, Fig. 6)." + +<|ref|>text<|/ref|><|det|>[[115, 770, 133, 786]]<|/det|> +6) + +<|ref|>text<|/ref|><|det|>[[150, 790, 882, 849]]<|/det|> +Sentence on Page 13, line 2 "We did not detect any Rab proteins as PPLs of any of the Commander complex proteins, supported by the decoupling of Rab7 function from Retriever" was changed to "We did not detect any Rab proteins as HCLs of the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[150, 144, 883, 185]]<|/det|> +Commander complex proteins except for Rab9a in the RSS variants of CCDC22. This observation aligns with the known decoupling of Rab7 function from the Retriever." + +<|ref|>text<|/ref|><|det|>[[115, 207, 133, 222]]<|/det|> +7) + +<|ref|>text<|/ref|><|det|>[[148, 225, 884, 528]]<|/det|> +Figure S6 legend on Page 29, line 30 was updated to: "Fig. S6. Molecular interactors, context, and cellular pathways connected with individual Commander complex components, related to Figure 5. (A) Dot-plot visualization (BFDR \(\leq 0.05\) ) of interactors of the Commander complex detected by the BioID- MS. Node color corresponds to the abundance of the average spectral count for each prey, and node radius to its relative abundance. (B) Dot-plot visualization of RSS syndrome related point mutants of CCDC22 analyzed by BioID- MS. All PPIs passing HCl criteria to any of the CCDC22 variants are plotted, with HCLs are indicated with black outline and non- HCLs with light blue. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz. (C) Reactome pathways enriched for the Commander complex proteins. (D) Molecular level localization of the Commander complex proteins obtained by MS- microscopy. (E) Reactome pathways enriched \((p< 0.005\) , values marked in bars) for the RSS disease variant HCLs distinct from the wild- type CCDC22." + +<|ref|>text<|/ref|><|det|>[[115, 550, 133, 565]]<|/det|> +8) + +<|ref|>text<|/ref|><|det|>[[148, 568, 884, 809]]<|/det|> +Figure 8 legend on Page 28, line 7 was updated to: "Fig. 6. RSS and XLID related mutations and putative interaction interfaces of the Commander complex. (A) Three mutations associated with RSS or XLID are highlighted within the context of the Commander complex structure. (B) Effect of A830T mutation on VPS35L in BioID- MS. All PPIs passing HCl criteria to either wild- type VPS35L or VPS35L(A830T) are plotted for both constructs, with HCLs indicated using black outline and non- HCLs with light blue outline. Node color corresponds to the bait normalized abundance of the average spectral count for each prey, and node radius to its relative abundance across all baits determined by ProHits- Viz (C) Composite model of the Commander complex, indicating putative interaction interfaces with tubulin polyglutamylase complex (TPGC). (D) Rotated view of the model in (C), with putative interaction interface of the WASH complex indicated." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 135, 161]]<|/det|> +9) + +<|ref|>text<|/ref|><|det|>[[149, 164, 884, 446]]<|/det|> +Figures 5 and 6 from the previous iteration of the manuscript were renumbered to figures 7 and 8. Figure legends for new figures 5 and 6 were added on Page 27, line 21: Fig. 5. Analysis of overall tertiary fold of the endogenous Commander complex compared to existing literature. A simplified "ragdoll" representation of major components of the Commander complex (A) from this study and (B-D) the overall structural model from Healy et al. highlight the major differences between these models with alignment centers of the models located at the (B) COMMD- ring, (C) V-coil, and (D) DENND10. The COMMD-ring is represented by a disc aligned to the COMMD domains, the coiled-coil domains are represented by cylinders (I and R-coils), or a trapezoidal prism (V-coil + CCDC22 NN-CH), DENND10 as a cylinder and Retriever subcomplex as spheres (VPS29, VPS26C + N-terminal half of VPS35L \(\alpha\) - solenoid) or a cylinder (VPS35L C-terminal half of VPS35L \(\alpha\) - solenoid). Component relative rotation angles are calculated based on the underlying atomic coordinates of backbone Cα atoms. + +<|ref|>text<|/ref|><|det|>[[149, 465, 884, 666]]<|/det|> +Fig. 6. Comparative analysis of conformational variation in the Commander complex structure compared to existing literature. (A) Overview of the Commander complex structure with location of following panels indicated. Comparison of (B) the COMMD-ring, (C) DENND10, I-coil, and R-coil region, (D) Retriever subcomplex from the structure presented in this study and the overall model presented by Healy et al. (E) Comparison of VPS29 with VPS35L (13-37) presented in this study (left) and crystal structure of VPS29 with VPS35L (16-38) peptide (right). Major structural differences are highlighted with yellow, and sources of structural data are indicated for each structure. The three disease mutations analyzed in AP- MS and BioID (Fig. 8) are indicated in (D). + +<|ref|>text<|/ref|><|det|>[[117, 688, 144, 704]]<|/det|> +10) + +<|ref|>text<|/ref|><|det|>[[150, 707, 883, 766]]<|/det|> +Figure S4H legend on Page 29, line 17 was changed to: " (H) Density supporting the placement of CCDC22 \(\alpha 15\) and \(\alpha 16\) . Map (EMD- 17340) was low- pass filtered to 7 Å using Bsoft." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[120, 146, 384, 161]]<|/det|> +Message: Our ref: NSMB- A47767B + +<|ref|>text<|/ref|><|det|>[[202, 174, 313, 188]]<|/det|> +15th Nov 2023 + +<|ref|>text<|/ref|><|det|>[[201, 201, 344, 215]]<|/det|> +Dear Dr. Varjosalo, + +<|ref|>text<|/ref|><|det|>[[201, 228, 873, 313]]<|/det|> +Thank you for submitting your revised manuscript "Structure and Interactions of the Endogenous Human Commander Complex" (NSMB- A47767B). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Structural & Molecular Biology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[201, 325, 866, 397]]<|/det|> +In particular, please note that we consulted reviewer #2 again regarding the PDB validation reports. While they did not indicate major issues, they pointed out that there appears to be a noticeable lack of fitting between the COMM domain- containing protein 1 (Chain A; Molecule 1) and the COMM domain- containing protein 7 (Chain G; Molecule 7) with the map. Please ensure to address this discrepancy and discuss it in the manuscript. + +<|ref|>text<|/ref|><|det|>[[201, 408, 875, 465]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about 2 weeks. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[200, 477, 860, 508]]<|/det|> +Thank you again for your interest in Nature Structural & Molecular Biology Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[201, 520, 274, 535]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[200, 547, 503, 617]]<|/det|> +Katarzyna Ciazynska, PhD (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +<|ref|>title<|/ref|><|det|>[[122, 639, 376, 654]]<|/det|> +# Author Rebuttal, second revision: + +<|ref|>sub_title<|/ref|><|det|>[[116, 676, 342, 694]]<|/det|> +## Response to Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[115, 715, 883, 754]]<|/det|> +We thank the reviewer for the positive comments on our manuscript "Structure and Interactions of the Endogenous Human Commander Complex". + +<|ref|>text<|/ref|><|det|>[[115, 777, 213, 793]]<|/det|> +Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[113, 815, 884, 835]]<|/det|> +My apologies for the delayed reply. I thank the authors for thoroughly addressing my + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 145, 882, 185]]<|/det|> +suggestions. A new Figure 5 elaborating on the global conformation of commander is a welcome addition. I have no further questions to the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[120, 222, 283, 237]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[120, 259, 310, 274]]<|/det|> +Message: 19th Jan 2024 + +<|ref|>text<|/ref|><|det|>[[201, 287, 345, 302]]<|/det|> +Dear Dr. Varjosalo, + +<|ref|>text<|/ref|><|det|>[[201, 315, 815, 357]]<|/det|> +We are now happy to accept your revised paper "Structure and Interactions of the Endogenous Human Commander Complex" for publication as an Article in Nature Structural & Molecular Biology. + +<|ref|>text<|/ref|><|det|>[[201, 369, 870, 412]]<|/det|> +Acceptance is conditional on the manuscript's not being published elsewhere and on there being no announcement of this work to the newspapers, magazines, radio or television until the publication date in Nature Structural & Molecular Biology. + +<|ref|>text<|/ref|><|det|>[[201, 424, 860, 495]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Structural & Molecular Biology style. 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Those licensing terms will supersede any other terms that the author or any third party may assert apply to any version of the manuscript. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[201, 159, 839, 202]]<|/det|> +In approximately 10 business days you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. + +<|ref|>text<|/ref|><|det|>[[200, 215, 870, 244]]<|/det|> +You will not receive your proofs until the publishing agreement has been received through our system. + +<|ref|>text<|/ref|><|det|>[[200, 256, 870, 286]]<|/det|> +If you have any questions about our publishing options, costs, Open Access requirements, or our legal forms, please contact ASJournals@springernature.com + +<|ref|>text<|/ref|><|det|>[[201, 298, 275, 313]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[200, 339, 504, 409]]<|/det|> +Katarzyna Ciazynska, PhD (she/her) Associate Editor Nature Structural & Molecular Biology https://orcid.org/0000- 0002- 9899- 2428 + +<--- Page Split ---> diff --git a/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/images_list.json b/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..58ee88e215773699ab44d319da43c1ceeb11bbb8 --- /dev/null +++ b/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/images_list.json @@ -0,0 +1,332 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R1 a, b Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized. c, d show the possible coupling of the magnon with ferron and phonon in the strong coupling case.", + "footnote": [], + "bbox": [ + [ + 258, + 567, + 728, + 808 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. R2 Comparison of the measured non-local voltage \\(V_{\\mathrm{nl}}^{\\mathrm{DC}}\\) amplitude (red line) and the charge (blue line) as the functions of the gate voltage pulse \\(V_{\\mathrm{g}}\\) for device 1.", + "footnote": [], + "bbox": [ + [ + 346, + 290, + 682, + 462 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. R3 a Schematic loop of a non-local voltage signal generated by the usual SSE. b, c Magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d, g present the corresponding voltage peaks occurring after and before", + "footnote": [], + "bbox": [ + [ + 243, + 546, + 755, + 822 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. R4 a Measured non-local voltages with different values of \\(I_{\\mathrm{DC}}\\) . b Dependence of the jump signal voltage with the square of \\(I_{\\mathrm{DC}}\\) .", + "footnote": [], + "bbox": [ + [ + 240, + 293, + 748, + 461 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. R5 a X-ray diffraction of a 400-nm (001)-oriented PZT film grown on an Nb-doped \\(\\mathrm{SrTiO_3(001)}\\) substrate. b Electrical polarization loop of the PZT film shown in a. c Magnetic hysteresis loop of a 65-nm YIG film on top of the PZT film with a MgO buffer layer. d Non-local voltage \\(V_{\\mathrm{nl}}^{\\mathrm{DC}}\\) amplitude as a function of the gate voltage pulse \\(V_{\\mathrm{g}}\\) for the device prepared on the PZT film.", + "footnote": [], + "bbox": [ + [ + 240, + 409, + 755, + 732 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. R6 a HAADF-TEM image of the PMN-PT/YIG/Pt sample. b, c, d and e Zoom-in features of a for regions I, II, III, IV, respectively. The inset of c and e (bottom panel) show the corresponding diffraction patterns of YIG and PMN-PT, respectively. The inset of e (top panel) shows the magnified view of YIG layer. f The corresponding EDS elemental mapping as marked in each panel.", + "footnote": [], + "bbox": [ + [ + 190, + 446, + 802, + 763 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. R7 a X-ray diffraction of a 400-nm (001)-oriented PZT film grown on an Nb-doped SrTiO₃(001) substrate. b Electrical polarization loop of the PZT film shown in a. c Magnetic hysteresis loop of a 65-nm YIG film on top of the PZT film with a MgO buffer layer. d Non-local voltage \\(V_{\\mathrm{nl}}^{\\mathrm{DC}}\\) amplitude as a function of the gate voltage pulse \\(V_{\\mathrm{g}}\\) for the device prepared on the PZT film.", + "footnote": [], + "bbox": [ + [ + 240, + 365, + 755, + 686 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. R8 a Frequency-dependent linewidth \\(\\Delta H\\) under \\(\\pm 200 \\mathrm{V}\\) -gate voltages, respectively. The dots are the experimental data and the lines are the linear fittings. b Field-dependent resonance frequency \\(f\\) under \\(\\pm 200 \\mathrm{V}\\) -gate voltages, respectively. The dots are experimental data and the lines are the fittings with the Kittel equation.", + "footnote": [], + "bbox": [ + [ + 247, + 433, + 755, + 602 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. R10 a. Schematic loop of a non-local voltage signal generated by the usual SSE. b, c. Magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d, g present the corresponding voltage peaks occurring after and before the coercive field, respectively. e, h present the corresponding total voltage signals, respectively. f, i present the results observed in our experimental measurements. They show apparent similarities with e, h, respectively.", + "footnote": [], + "bbox": [ + [ + 243, + 272, + 755, + 549 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. R11 Gate width dependent on/off ratio for two series samples prepared on two PMN-PT substrates, respectively.", + "footnote": [], + "bbox": [ + [ + 354, + 496, + 644, + 679 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Fig. R12 a Dependence of the resistivity of Pt stripe, \\(\\rho_{\\mathrm{pt}}\\) on the square of DC current \\(I\\) . The symbols are the experimental data and the line is a linear fitting. b Dependence of \\(\\rho_{\\mathrm{pt}}\\) on the measurement time.", + "footnote": [], + "bbox": [ + [ + 252, + 284, + 757, + 450 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Fig. R13 a, b Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized. c, d show the possible coupling of the magnon with ferron and phonon in the strong coupling case.", + "footnote": [], + "bbox": [ + [ + 256, + 138, + 732, + 375 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Fig. R14 Non-local voltage \\(V_{\\mathrm{nl}}^{\\mathrm{DC}}\\) amplitude(red line) and the charge(blue line) as the functions of the gate voltage pulse \\(V_{\\mathrm{g}}\\) for device 1, respectively.", + "footnote": [], + "bbox": [ + [ + 330, + 658, + 667, + 830 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Fig. R15 The non-local voltages measurement with different gate voltages. The curves are shifted for clarity.", + "footnote": [], + "bbox": [ + [ + 340, + 250, + 654, + 450 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_14.jpg", + "caption": "Fig. R16 Gate width dependent on/off ratio for two series samples prepared on two PMN-PT substrates, respectively.", + "footnote": [], + "bbox": [ + [ + 370, + 116, + 660, + 301 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_15.jpg", + "caption": "Fig. R17 Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized.", + "footnote": [], + "bbox": [ + [ + 258, + 450, + 730, + 690 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_16.jpg", + "caption": "Fig. R18 a. Schematic loop of a non-local voltage signal generated by the usual SSE. b and c. The magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d and g show the corresponding voltage peaks occurring after and before the coercive field, respectively. e and h show the corresponding total voltage signals, respectively. f and i show the results observed in our experimental measurements. They show apparent similarities with e, h, respectively.", + "footnote": [], + "bbox": [ + [ + 243, + 93, + 755, + 370 + ] + ], + "page_idx": 26 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_17.jpg", + "caption": "Fig. R19 a, b The non-local measurements in two samples under as-grown (0 V) and \\(\\pm 200\\) V-gate voltages, respectively.", + "footnote": [], + "bbox": [ + [ + 243, + 610, + 756, + 783 + ] + ], + "page_idx": 26 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_18.jpg", + "caption": "Fig. R1 a Magnon chemical potential as a function of distance for \\(P< 0\\) (red line) and", + "footnote": [], + "bbox": [ + [ + 195, + 90, + 806, + 286 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_19.jpg", + "caption": "Fig. R2 a The HAADF image of PMN-PT/YIG/Pt sample. b EDS integrated signal profiles of Fe, Y, Mg, Pb, Ti and Nb obtained through area scans crossing layers shown in the orange dashed rectangle of a.", + "footnote": [], + "bbox": [ + [ + 216, + 490, + 731, + 682 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_20.jpg", + "caption": "Fig. R3 a The integrated charge as the function of the gate voltage pulse \\(V_{\\mathrm{g}}\\) for PMN-PT/YIG/Pt sample. b The non-local voltages measurement with gate voltages holding \\((+300 \\mathrm{~V})\\) and removal \\((+0 \\mathrm{~V})\\) , respectively.", + "footnote": [], + "bbox": [ + [ + 240, + 260, + 752, + 430 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_21.jpg", + "caption": "Fig. R4 Summary of the on/off ratio of 16 PMN-PT/YIG/Pt samples for 60-nm, 80-nm, and 100-nm YIG thicknesses, respectively.", + "footnote": [], + "bbox": [ + [ + 352, + 208, + 645, + 390 + ] + ], + "page_idx": 38 + } +] \ No newline at end of file diff --git a/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file.mmd b/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..253df3a5f6fe290036cf293a837246fcfb481788 --- /dev/null +++ b/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file.mmd @@ -0,0 +1,717 @@ + +# nature portfolio + +Peer Review File + +# A nonvolatile magnon field effect transistor at room temperature + +Corresponding Author: Professor Haifeng Ding + +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In this manuscript, the authors report a three- terminal lateral magnon field effect transistor which can work at room temperature. The ferromagnetic insulator material Y3Fe5O12 (YIG) and heavy metal Pt is used here. The large on/off ratio can be achieved by applied a voltage pulse in G- stripes of devices up to \(400\%\) . There is no doubt that devices related to magneton control are very important for information transmission. However, the data in this manuscript are not well discussed. There are also problems with the function of the device. The manuscript cannot be recommended to be published on Nature Communications based on the following questions. + +Main comments + +1. So far, there have been many reports on the YIG/PNM-PT ferroelectric-ferromagnetic heterostructures. Such as magnetoelectric coupling and non-volatility (DOI: 10.1002/aem.201800663), and achieve changes in amplitude and phase (DOI:10.1088/1361-6463/abce7c). It seems that the work is not innovative enough to justify its publication on Nature Communications. + +2. The mechanism of operation of the device is not clearly discussed. The authors ruled out temperature change, piezoelectricity, spin Seebeck effect, spin reflection, etc., and attributed the cause to the change of the local electric polarization direction under the G-strip. For the main conclusions of the work, it would be helpful to present more evidence. +3. The author mentions that the main function of the device is to realize the control of signal amplitude. However, the device only mentions an on/off ratio of \(400\%\) , and the minimum value is not 0, which may cause difficulties for the real applications. Besides, the on/off can be considered as a switcher. The transistor should own an amplifying transport magnon current function. + +4. What is the contribution of non-volatility to the device, which seems to create additional difficulties for the control of the functionality of the device. + +5. (p. 9, figure 3(c)) Most hysteresis loops exhibit strange behavior. An additional jump signal occurs when the magnetic moment reaches a stable value. A more detailed explanation would be helpful. + +6. The manuscript realized the modulation of signal amplitude with a high electric voltage (hundreds of volts). However, the integration of the PNM-PT crystal layer is quite difficult. The interfacial characteristics of the YIG/PNM-PT heterostructure should be discussed. + +## Reviewer #2 + +(Remarks to the Author) + +The presented work is well-founded and holds a significantly innovative character. The success in inducing a ferrimagnetic (non-ferromagnetic) phase in the YIG film on a PMN-PT substrate is surprising. + +Undoubtedly, the suggested sample geometry may have a potential technological impact in the future. However, in its current form, the article presents some significant weaknesses. + +The most fragile point is the necessity of a high polarization voltage in the PMN- PT for the effect to become attractive for + +<--- Page Split ---> + +technological applications. Reaching 200 V is unfeasible in real systems. Although the authors address this fragility in the article, they suggest that the deposition of PMN- PT films could reduce this polarization voltage. However, the induction of a ferrimagnetic phase in YIG on buffer layers is very difficult to achieve. + +Therefore, studies regarding the induction of the ferrimagnetic phase of YIG on thin films of PMN- PT become crucial for this work. Moreover, a rigorous study of FMR to verify the linewidth, which can provide information on the damping parameter in the system, should be conducted. + +To assist the authors to improving the quality of the article, I highlight some points to be clarified: + +Line 66: YIG presents a ferrimagnetic phase, not a ferromagnetic one, as highlighted in the article. + +Line 159: The mechanism observed in the results of this article may be connected with "recoil magnetization curves" presented in the reference PHYSICAL REVIEW B 104, 054436 (2021). + +Line 204: It is not clear in the article the difference between the named Device 1 and Device 2 referenced by the authors. This point needs correction. + +Line 210: The measurement of local temperature from the change in Pt resistance should be reviewed by the authors. No study of thermal stability in the platinum film was presented. + +Line 245: The authors indicate that there might be a change in the magnetic anisotropy of YIG due to magnetoelastic coupling between the PMN- PT layer and YIG. However, studies demonstrate that the magnetostriction of YIG is small. This statement needs further discussion. + +In summary, although the article has been written quite carefully and the results are promising for technological applications, complementary studies need to be carried out. Especially concerning the production of devices in which the polarization voltage is accessible to integrate this structure into real systems. + +## Reviewer #3 + +(Remarks to the Author) + +In this manuscript, the authors have demonstrated a nonvolatile three- terminal lateral magnon FET based on YIG/PMN- PT heterostructures. They attribute the observed nonvolatile modulations to changes in magnon relaxation within the YIG sublayers. The possible mechanism behind these modulations, including temperature variation, anisotropic exchange stiffness and the emergent electric dipoles from noncollinear spin configuration in YIG, are discussed. While the research topic is interesting, I find that both the experimental setup and related discussion presented by the authors lack sufficient evidence to convince me of its suitability for publication in NC. Therefore, I kindly request that the authors consider the following suggestions and concerns: + +Nonvolatile modulation has been extensively investigated in various systems through transport measurement, such as VO2/PMN- PT(ACS Appl. Mater. Interfaces 2014, 6, 4603- 4608), FePt/PMN- PT(Appl. Phys. Lett. 112, 033506 (2018)), MnPt/PMN- PT (Nat. Nanotech. 14, 131- 136 (2019)), SrRuO3/PMN- PT(Appl. Phys. Lett. 110, 182403 (2017)), and others. Considering device's aspects, similar magnon transistors have also been mentioned in Ref. [22], [31] and [32]. What is the main advantage of the structure in the present study? + +The authors propose that electric polarization is responsible for the large nonvolatile modulation of V_nl^DC. However, it should be noted that in Supplementary Figure 2c, the ferroelectric hysteresis loop (P- E loop) saturates at least \(\pm 8 \text{kV / cm}\) , whereas in Fig. 3b, the maximum voltage is only \(\pm 200 \text{V}\) (equivalent to \(\pm 4 \text{kV / cm}\) with a 0.5 mm thickness of FE substrate), which corresponds to the coercive electric field value. Consequently, under this conditions, the modulation remains unsaturated and unstable due to its dominance by strain, as mentioned in previous literatures refereed to Q1. Did the author conduct experiments using an electric field around or beyond \(\pm 8 \text{kV / cm}\) and then cycle Vg? Additionally, we also notice that there are different on/off ration between device 1 (400%) and device 2 (115%), despite both devices having identical dimensions. How can sample fabrication result in such a significant difference? Is it disparity attributable to an unstable modulation caused by strain? If not, what mechanism accounts for this large variation? + +The authors assume that this non- volatile modulation is due to electric polarization of FE substrate. Given that YIG is oxide insulator, how does electrical polarization transmit? Did the author perform measurements by changing the thickness of YIG? + +In Fig. 3c, the magnetic- field- dependent V_nl^DC exhibits an enhancement near the coercivity at some electric filed (such as \(+200 \text{V}\) ), while disappears at other electric filed (- 160 V). What is the underlying reason for this significant dependence on electric field? Additionally, there is a noticeable difference in coercivity. The authors refer to Ref. 36; however, it seems that this magnetic- field dependence has not been directly measured in their report rather treated to some extent. Therefore it is necessary for the authors to provide an explanation and present the magnetic- field- dependent V_nl^DC before applying any electric field (OV). + +<--- Page Split ---> + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In this work, the authors deposited ferrimagnet YIG on top of PMN- PT substrate, a nonvolatile magnon transport behavior was experimentally observed. They try to explain the underlying mechanism as an electrical field modulation of the Fe3+ or O2- ions accumulation at the YIG/PMN- PT interface, which could result in magnetoelectric coupling between magnons and the collective excitations of PMN- PT. However, this discussion lack strong evidence for both the collective excitations of PMN- PT and Fe3+ or O2- ions accumulation at interface. How to excite the collective excitations (ferron or phonon) of PMN- PT for a non- local electric measurements? What is the theoretical model of these excitations? + +For the TEM image of the PMN- PT/YIG/Pt heterostructure, not only Mg2+ but also Nb2+ and Ti4+ ions migrated into YIG layer after the deposition. The YIG layer could not a pure YIG in this case. So, the origin of the electric modulation magnon transportation still need to be studied. In this manuscript form, there is not innovative enough to justify its publication on Nature Communications. + +Reviewer #2 + +(Remarks to the Author) Dear, + +All the weaknesses presented in the original version of the article have been addressed in this new version. The crucial points were resolved by producing new samples and conducting new measurements. For these reasons, I suggest that the present article can be published in Nature Communications. + +Reviewer #3 + +(Remarks to the Author) + +I have carefully read the revised version of the manuscript. I appreciate the efforts by the authors to address my raised questions. However, I have to follow up on certain points within the response of the authors and hope the authors can address these points. In more detail, see the below: In response to Q2: I notice that the authors demonstrate "all curves were obtained after the electric field had been removed" in the main text, if I understand this correctly, the authors obtain all V_ nl^DC at residual polarization state despite removing from large electric field. If so, I suggest that the authors perform the measurements under +400 V(do not remove electric field, or measuring under the maximum voltage before the device burning except 200 V) and +0 V(residual polarization). In response to Q3: I am confused that the authors demonstrate "For the thickness of YIG increased to 80 nm and 100 nm, the experimental results do not show apparent thickness dependence, all can achieve 20% \(\sim 100\%\) on/off ratio". However, in the main text, for 60 nm YIG, the on/off ratio of device 1 and device 2 are 400 % and 150 %, respectively. How to understand "do not show apparent thickness dependence"? + +Version 3: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The article have been revised according to all my concerns. A resonable theoretical model about the coupling between ferron and magnon and its influence on the magnon transport was provided. Therefore, I would like to suggest its publication in Nature Communications in the current form. + +Reviewer #3 + +(Remarks to the Author) + +I have carefully read the revised version of the manuscript (NCOMMS- 23- 58821C). The authors gave a detailed response to the raised concerns of the reviewers and also carried out necessary changes in their revised manuscript. So, I think the current version can be published in Nature Communications. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Reviewer #1 (Remarks to the Author):In this manuscript, the authors report a three- terminal lateral magnon field effect transistor which can work at room temperature. The ferromagnetic insulator material \(\mathrm{Y}_3\mathrm{Fe}_5\mathrm{O}_{12}\) (YIG) and heavy metal Pt is used here. The large on/off ratio can be achieved by applied a voltage pulse in G- stripes of devices up to \(400\%\) . There is no doubt that devices related to magneton control are very important for information transmission. However, the data in this manuscript are not well discussed. There are also problems with the function of the device. The manuscript cannot be recommended to be published on Nature Communications based on the following questions. + +## General response Reviewer #1: + +General response Reviewer #1:We sincerely thank Reviewer #1 for the time and efforts spent in evaluating our manuscript. We are grateful to Reviewer #1 for commenting that devices related to magneton control are very important for information transmission. In the following, we provide point- by- point answers to all the questions/comments raised. + +## Main comments + +Main comments1. So far, there have been many reports on the YIG/PNM- PT ferroelectric- ferromagnetic heterostructures. Such as magnetoelectric coupling and non- volatility (DOI: 10.1002/aelm.201800663), and achieve changes in amplitude and phase (DOI:10.1088/1361- 6463/abce7c). It seems that the work is not innovative enough to justify its publication on Nature Communications. + +## Response Reviewer #1-1: + +We thank Reviewer #1 for pointing out these references to us. We are aware of these, and the first one is from our previous work. The first reference (DOI: 10.1002/aelm.201800663) reported the nonvolatile control of the in- plane magnetic anisotropy of YIG films deposited on PMN- PT as well as the spin pumping induced inverse spin Hall effect in Pt on top of the YIG films. And the second reference (DOI:10.1088/1361- 6463/abce7c) discussed the volatile manipulation of the damping constant of the YIG films on PMN- PT via the piezo effect. + +It is quite clear none of these works deal with the non- local magnon transport, not to mention the nonvolatile magnon field effect transistor. To our best knowledge, this manuscript is the first report on the nonvolatile magnon field effect transistor. As the reviewer points out, there is no doubt that the devices related to magneton control are very important for information transmission. We hope the reviewer will find our revised manuscript suitable for publication on Nature Communications. + +2. The mechanism of operation of the device is not clearly discussed. The authors ruled + +<--- Page Split ---> + +out temperature change, piezoelectricity, spin Seebeck effect, spin reflection, etc., and attributed the cause to the change of the local electric polarization direction under the G- strip. For the main conclusions of the work, it would be helpful to present more evidence. + +## Response Reviewer #1-2: + +We thank Reviewer #1 for raising this question. We are sorry for not providing a mechanism in the previous version. In the following, we propose a possible mechanism to explain our main findings. + +As reported by D. Chiba et al. [Sci. Rep. 6, 38005 (2016)], when a ferroelectric layer is electrically polarized oppositely, the strong electrical field induces opposite charge accumulation in its adjacent layer. In our case, when the PMN- PT layer is negatively polarized (Fig. R1a), it could induce \(\mathrm{Fe}^{3 + }\) ions accumulation at the interface. On the contrary, it induces \(\mathrm{O}^{2 - }\) ions accumulation at the interface when the PMN- PT layer is positively polarized (Fig. R1b). Since the \(\mathrm{Fe}^{3 + }\) ions contain magnetic moment and \(\mathrm{O}^{2 - }\) ions have none, this could result in a stronger coupling between the magnon and the collective excitations of PMN- PT in the \(1^{\mathrm{st}}\) case as compared with the \(2^{\mathrm{nd}}\) one. The collective excitation can be either the ferron (Fig. R1c) or phonon (Fig. R1d) [Phys. Rev. Lett. 128, 047601 (2022); Phys. Rev. B 106, L081105 (2022); Rev. Mod. Phys. 70, 523- 536 (1998); Appl. Phys. Lett. 107, 062901 (2015)], especially when they have similar energy and wavevector as the magnon. The magnon thus has different dissipation and diffusion lengths when PMN- PT is polarized oppositely, resulting in an electrical field modulation of the magnon propagation, i.e., the magnon FET. + +![](images/Figure_unknown_0.jpg) + +
Fig. R1 a, b Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized. c, d show the possible coupling of the magnon with ferron and phonon in the strong coupling case.
+ +<--- Page Split ---> + +To support the electrical polarization induced modulation of the magnon transport, we provide the comparison of the measured non- local voltage (Fig. 3b in the main text) with the electric modulation of the charge from the same sample. The modulation of the charge, obtained from the sweeping voltage- dependent leakage current shown in Supplementary Fig. 4a [we use the method reported in Ferroelectrics 411, 86 (2010)], can be viewed as an alternative measurement of the electrical polarization. As presented in Fig. R2, they show apparent similarity. This strongly indicates that our voltage control results are closely related to the electrical polarization of PMN- PT. + +![](images/Figure_unknown_1.jpg) + +
Fig. R2 Comparison of the measured non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude (red line) and the charge (blue line) as the functions of the gate voltage pulse \(V_{\mathrm{g}}\) for device 1.
+ +Updated manuscript (lines 176- 179; lines 288- 291): + +We also calculated the charge loop (blue curve in Fig. 3b) with the \(V_{\mathrm{g}}\) - dependent leakage current \(^{42}\) and found that they exhibited close similarity, indicating a strong correlation between the observed magnon current modulation and the change of the electric polarization of the FE layer. + +We propose that the modulation is due to polarization- dependent ions ( \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ) accumulation in the YIG layer adjacent to the interface, resulting in different coupling since \(\mathrm{Fe}^{3 + }\) is magnetic while \(\mathrm{O}^{2 - }\) is not. Dynamically, the magnon in YIG could couple with the collective excitation, such as the ferron or phonon in PMN- PT (Supplementary Note 11). + +3. The author mentions that the main function of the device is to realize the control of signal amplitude. However, the device only mentions an on/off ratio of \(400\%\) , and the minimum value is not 0, which may cause difficulties for the real applications. Besides, the on/off can be considered as a switcher. The transistor should own an amplifying transport magnon current function. + +<--- Page Split ---> + +## Response Reviewer #1-3: + +We thank Reviewer #1 for raising these questions. As shown in Fig. 3d in the main text, we can have well- defined high/low states. This is similar to the high resistance/low resistance states in giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR) where the low resistance values are also not zero. It, however, does not impede their applications, such as magnetic storage and magnetic sensors. Moreover, this is only the first report on the magnon FET. Namely, this kind of study is just in its beginning. We believe its qualities will be significantly improved with further pursuit in near future, leading to real applications. + +We agree that the transistor can either serve as an amplifier or a switch. The amplifying of magnon has also been extensively studied [Phys. Rep. 699, 1 (2017)]. Therefore, it is not the focus of this study. Owning to the high demand for logic devices with low power consumption in post- Moore's era, the modulation of magnon transport with a high on/off ratio and high energy efficiency is main stream of current magnonics studies and hotly pursued. However, it still remains challenging [Phys. Rev. Lett. 120, 097702 (2018); Phys. Rev. B 101, 054436 (2020); Phys. Rev. Lett. 129, 087601 (2022); Sci. Adv. 7, eabg1669 (2021); Phys. Rev. Lett. 132, 076701 (2024)]. In our work, we use a nonvolatile electric field to control the magnon transport, which is the most energy- efficient method reported so far. Given the large on/off ratio we reported, we hope the reviewer will find our results are of critical importance and can recommend the publication of our manuscript. + +Updated manuscript (lines 210- 213): + +Though the minimum value of \(V_{\mathrm{nl}}^{\mathrm{DC}}\) is not 0, it does not impede their applications as long as the high/low states can be well- defined. This is similar to the high resistance/low resistance states in giant magnetoresistance or tunneling magnetoresistance devices, where the low resistance values are also not zero. + +4. What is the contribution of non-volatility to the device, which seems to create additional difficulties for the control of the functionality of the device. + +## Response Reviewer #1-4: + +We thank Reviewer #1 for raising this question. As mentioned in Response Reviewer #1- 3, the modulation of magnon transport with a high on/off ratio and high energy efficiency is main stream in current magnonics studies. Non- volatility only requires applying a voltage pulse instead of a constant voltage to change the functionality of the device when necessary. It does not need to maintain any voltage on the device to keep the functionality, thus significantly reducing power consumption. To + +<--- Page Split ---> + +our understanding, it is not much more difficult to apply a voltage pulse than to apply a constant voltage where the sign needs to be switched instantly. + +5. (p. 9, figure 3(c)) Most hysteresis loops exhibit strange behavior. An additional jump signal occurs when the magnetic moment reaches a stable value. A more detailed explanation would be helpful. + +## Response Reviewer #1-5: + +We thank Reviewer #1 for this excellent suggestion. We propose a possible explanation for the additional jump signal. A carton figure shown in Fig. R3 illustrates this process and can qualitatively explain our experimental finding. As mentioned by the reviewer, this additional jump signal occurs near the magnetization switching. During the switching, the system encounters a substantial increase in magnetic susceptibility (Fig. R3b). In this process, the system may generate a burst of magnon upon the thermal excitation (Fig. R3c). The burst of magnon subsequently generates a voltage signal. The sign of the voltage signal is positive or negative depending on whether the excitation of the magnon occurs after or before the coercive field (Figs. R3d and R3g) since it is controlled by the magnetization direction. The measured signal is the sum of both the magnetization- dependent magnon signal (Fig. R3a) and the susceptibility peak induced magnon signal (Figs. R3d or R3g), resulting in the interesting and unusual shapes of loops (Figs. R3e or R3h), respectively. Both loops are observed in our experiments (Figs. R3f and R3i). + +![](images/Figure_unknown_2.jpg) + +
Fig. R3 a Schematic loop of a non-local voltage signal generated by the usual SSE. b, c Magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d, g present the corresponding voltage peaks occurring after and before
+ +<--- Page Split ---> + +the coercive field, respectively. \(\mathbf{e}\) , \(\mathbf{h}\) present the corresponding total voltage signals, respectively. \(\mathbf{f}\) , \(\mathbf{i}\) show the typical results observed in our experiments. They show similarities with \(\mathbf{e}\) , \(\mathbf{h}\) , respectively. + +According to the above analysis, these additional jump signals are also generated thermally. It is expected to depend linearly on the heating power, namely, the square of the current. To confirm this, we perform measurements with different values of \(I_{\mathrm{DC}}\) (Fig. R4a). We find that the jump signal ( \(V_{\mathrm{peak}}\) ) indeed scales with the square of \(I_{\mathrm{DC}}\) with the slope of \(644.38 \mathrm{nV / mA^2}\) (Fig. R4b), indicating its thermal origin. + +![](images/Figure_unknown_3.jpg) + +
Fig. R4 a Measured non-local voltages with different values of \(I_{\mathrm{DC}}\) . b Dependence of the jump signal voltage with the square of \(I_{\mathrm{DC}}\) .
+ +Updated manuscript (lines 166- 168): + +A similar phenomenon was observed previously, though its origin was not mentioned41. We proposed a possible explanation for this phenomenon (see Supplementary Note 4). + +6. The manuscript realized the modulation of signal amplitude with a high electric voltage (hundreds of volts). However, the integration of the PMN-PT crystal layer is quite difficult. The interfacial characteristics of the YIG/PMN-PT heterostructure should be discussed. + +## Response Reviewer #1-6: + +We thank Reviewer #1 for raising these questions. We understand your concern about the required \(\sim 200\) volts for the device operation. In our previous version, we anticipate that a low voltage operation of the device can be achieved by replacing the PMN-PT crystal with PMN-PT thin film since it can be grown with sputtering on Si or SrTiO3 substrates with considerable polarization at relatively low voltage [Science 334, 958 (2011); Nature 578, 75 (2020)]. The growth temperature of high-quality PMN-PT film, however, is beyond the maximum temperature that we can reach in our sputtering system. Alternatively, we prepared a 400- nm PZT (PbZr0.52Ti0.48O3) film on an Nb- + +<--- Page Split ---> + +doped \(\mathrm{SrTiO_3(001)}\) substrate. Figure R5a presents the X- ray diffraction data, where the peaks of the PZT film have a similar order of intensities with those from the substrate (denoted with \*) indicating the high quality of the 001- oriented PZT film. The electrical polarization curve exhibits a clear hysteresis loop with remnant polarization of \(\sim 37 \mu \mathrm{C / cm}^2\) , and it can be switched less than \(10 \mathrm{~V}\) (Fig. R5b). On top of it, we grow 65- nm thick YIG film, which shows a saturation magnetization around \(9.66 \times 10^4 \mathrm{~A / m}\) (Fig. R5c), slightly smaller than the value of the YIG film grown on PMN- PT substrate. We further used it and prepared the magnon FET device similar to the one shown in Fig. 3 in the main text. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{~V}\) gate voltages (Fig. R5d). This demonstrates the feasibility of our anticipation, i.e., the device can be operated in the \(\sim 10 \mathrm{~V}\) range when a thin ferroelectric film is used. It also indicates the generality of our magnon FET device since it works with either PMN- PT or PZT material. + +![](images/Figure_unknown_4.jpg) + +
Fig. R5 a X-ray diffraction of a 400-nm (001)-oriented PZT film grown on an Nb-doped \(\mathrm{SrTiO_3(001)}\) substrate. b Electrical polarization loop of the PZT film shown in a. c Magnetic hysteresis loop of a 65-nm YIG film on top of the PZT film with a MgO buffer layer. d Non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude as a function of the gate voltage pulse \(V_{\mathrm{g}}\) for the device prepared on the PZT film.
+ +<--- Page Split ---> + +We also followed the reviewer's suggestion and performed the cross- sectional TEM measurements to characterize the interfacial characteristics of the PMN- PT/YIG/Pt heterostructure. Figure R6 presents the high- angle angular dark field (HAADF) images with energy dispersive X- ray spectroscopy (EDS) of PMN- PT/YIG/Pt sample, performed via a JEM- ARM200F microscope at \(200\mathrm{kV}\) . Figure R6a presents the HAADF image of the cross- sectional view of PMN- PT/YIG/Pt with four regions (I, II, III, IV) zoom- in view shown in Figs. R6b- R6e, respectively. Figures R6b and R6e show sharp interfaces between Pt and YIG layer, and between YIG layer and PMN- PT substrate, respectively. We notice that the YIG layer (for example, region III) looks a bit of a color gradient. However, zoom- in features on all four regions show that the YIG has good crystallinity with almost the same lattice distribution. To that end, we further performed elemental mapping along the layers stack (Fig. R6f). The different colored maps of Pt, Fe, Y, Mg, Pb, Ti and Nb elements indicate they are well separated in their corresponding regions. Even though there is a slight migration of Mg into the YIG layer, the YIG layer near the YIG/PMN- PT interface maintains its structure well (top panel of Fig. R6e). + +![](images/Figure_unknown_5.jpg) + +
Fig. R6 a HAADF-TEM image of the PMN-PT/YIG/Pt sample. b, c, d and e Zoom-in features of a for regions I, II, III, IV, respectively. The inset of c and e (bottom panel) show the corresponding diffraction patterns of YIG and PMN-PT, respectively. The inset of e (top panel) shows the magnified view of YIG layer. f The corresponding EDS elemental mapping as marked in each panel.
+ +<--- Page Split ---> + +Updated manuscript (line 93; lines 318- 323): + +The structure and magnetic properties are presented in Supplementary Note 1. + +The growth temperature of high- quality PMN- PT film, however, is beyond the maximum temperature that we can reach in our sputtering system. Instead, we deposited a 400- nm PZT (PbZr \(_{0.52}\) Ti \(_{0.48}\) O \(_{3}\) ) film on an Nb- doped SrTiO \(_{3}\) (001) substrate and further prepared a magnon field effect transistor. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{~V}\) gate voltages (Supplementary Note 12). + +Reviewer #2 (Remarks to the Author): + +The presented work is well- founded and holds a significantly innovative character. The success in inducing a ferrimagnetic (non- ferromagnetic) phase in the YIG film on a PMN- PT substrate is surprising. Undoubtedly, the suggested sample geometry may have a potential technological impact in the future. However, in its current form, the article presents some significant weaknesses. The most fragile point is the necessity of a high polarization voltage in the PMN- PT for the effect to become attractive for technological applications. Reaching 200 V is unfeasible in real systems. Although the authors address this fragility in the article, they suggest that the deposition of PMN- PT films could reduce this polarization voltage. However, the induction of a ferrimagnetic phase in YIG on buffer layers is very difficult to achieve. Therefore, studies regarding the induction of the ferrimagnetic phase of YIG on thin films of PMN- PT become crucial for this work. Moreover, a rigorous study of FMR to verify the linewidth, which can provide information on the damping parameter in the system, should be conducted. + +## General response Reviewer #2: + +We sincerely thank Reviewer #2 for the time and effort spent in evaluating our manuscript. We are grateful to Reviewer #2 for commenting that our work is "well- founded and holds a significantly innovative character" and that "the suggested sample geometry may have a potential technological impact in the future undoubtedly". In the following, we provide detailed answers to all the questions/comments raised point- by- point. + +## Response Reviewer #2-1: + +We understand Reviewer #2's concern about the required \(\sim 200\) volts for the device operation. In our previous version, we anticipate that a low voltage operation of the device can be achieved by replacing the PMN- PT bulk crystal with PMN- PT thin film since it can be grown with sputtering on Si or SrTiO \(_{3}\) substrates with considerable polarization at relatively low voltage [Science 334, 958 (2011); Nature 578, 75 (2020)]. The growth temperature of high- quality PMN- PT film, however, is beyond the maximum temperature that we can reach in our sputtering system. Alternatively, we prepared a 400- nm PZT (PbZr \(_{0.52}\) Ti \(_{0.48}\) O \(_{3}\) ) film on an Nb- doped SrTiO \(_{3}\) (001) substrate. Figure R7a presents the X- ray diffraction data, where the peaks of the PZT film have a + +<--- Page Split ---> + +similar order of intensities with those from the substrate (denoted with \*) indicating the high quality of the 001- oriented PZT film. The electrical polarization curve exhibits a clear hysteresis loop with remnant polarization of \(\sim 37 \mu \mathrm{C} / \mathrm{cm}^2\) and it can be switched using a voltage of less than \(10 \mathrm{~V}\) (Fig. R7b). On top of it, we grow 65- nm thick YIG film, which shows a saturation magnetization around \(9.66 \times 10^4 \mathrm{~A} / \mathrm{m}\) (Fig. R7c), slightly smaller than the value of the YIG film grown on PMN- PT substrate. We further used it and prepared the magnon FET device similar to the one shown in Fig. 3 in the main text. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{~V}\) gate voltages (Fig. R7d). This demonstrates the feasibility of our anticipation, i.e., the device can be operated in the \(\sim 10 \mathrm{~V}\) range when a thin ferroelectric film is used. It also indicates the generality of our magnon FET device since it works with either PMN- PT or PZT material. + +![](images/Figure_unknown_6.jpg) + +
Fig. R7 a X-ray diffraction of a 400-nm (001)-oriented PZT film grown on an Nb-doped SrTiO₃(001) substrate. b Electrical polarization loop of the PZT film shown in a. c Magnetic hysteresis loop of a 65-nm YIG film on top of the PZT film with a MgO buffer layer. d Non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude as a function of the gate voltage pulse \(V_{\mathrm{g}}\) for the device prepared on the PZT film.
+ +Updated manuscript (lines 318- 323): + +The growth temperature of high- quality PMN- PT film, however, is beyond the + +<--- Page Split ---> + +maximum temperature that we can reach in our sputtering system. Instead, we deposited a 400- nm PZT (PbZr \(_{0.52}\) Ti \(_{0.48}\) O \(_{3}\) ) film on an Nb- doped SrTiO \(_{3}\) (001) substrate and further prepared a magnon field effect transistor. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{V}\) gate voltages (Supplementary Note 12). + +## Response Reviewer #2-2: + +We followed the suggestions and investigated the damping parameter and magnetization information of our sample on the PMN- PT substrate. Figure R8a presents the relationship between linewidth and microwave frequency under \(\pm 200 \mathrm{V}\) - gate voltages, the damping factor by linear fitting at \(- 200 \mathrm{V}\) ( \(1.95 \times 10^{- 3}\) ) is \(\sim 11\%\) lower than that of \(+200 \mathrm{V}\) ( \(2.16 \times 10^{- 3}\) ). In addition, we measured the relationship between the microwave frequency and the resonant magnetic field of the system under \(\pm 200 \mathrm{V}\) - gate voltages (Fig. R8b), and the Kittel equation fitting results show that the effective magnetization change is less than \(1.8\%\) . + +![](images/Figure_unknown_7.jpg) + +
Fig. R8 a Frequency-dependent linewidth \(\Delta H\) under \(\pm 200 \mathrm{V}\) -gate voltages, respectively. The dots are the experimental data and the lines are the linear fittings. b Field-dependent resonance frequency \(f\) under \(\pm 200 \mathrm{V}\) -gate voltages, respectively. The dots are experimental data and the lines are the fittings with the Kittel equation.
+ +It is generally believed that the smaller the damping factor, the further magnons can travel. The measured change of the damping constant seems to contradict to our non- local voltage results where \(+200 \mathrm{V}\) has a larger amplitude. This seeming discrepancy could be understood as follows. The measurement performed at GHz range (Fig. R8a) only characterizes the damping constant of the Kittel model. Recent theoretical calculation by Joseph Barker and Gerrit E.W. Bauer [Phys. Rev. Lett. 117, 217201 (2016)] about the thermal spin dynamics of Yttrium Iron Garnet, however, shows that the antiferromagnetic or optical mode is found to suppress the spin Seebeck + +<--- Page Split ---> + +effect at room temperature and beyond. For the convenience of the reviewer, we copy Fig. 1 in this reference as Fig. R9 herein. It shows that the spin Seebeck effect is dominated by the high- frequency mode at \(\sim 6\) THz at \(300\mathrm{K}\) . At this frequency, the strong coupling of the magnon with the ferron/phonon may open up new additional dissipation channel and significantly influence the non- local magnon transport, resulting in a magnon FET according to the mechanism proposed in Fig. R1. + +Fig. R9 [copied from Phys. Rev. Lett. 117, 217201 (2016) and for Reviewers only] YIG spin wave spectrum as calculated for different temperatures. + +Updated manuscript (line 93): + +The structure and magnetic properties are presented in Supplementary Note 1. + +To assist the authors to improving the quality of the article, I highlight some points to be clarified: + +1. Line 66: YIG presents a ferrimagnetic phase, not a ferromagnetic one, as highlighted in the article. + +## Response Reviewer #2-2: + +We thank Reviewer #2 for raising this important comment. We corrected this in the updated manuscript. + +2. Line 159: The mechanism observed in the results of this article may be connected with "recoil magnetization curves" presented in the reference PHYSICAL REVIEW B 104, 054436 (2021). + +## Response Reviewer #2-3: + +We sincerely thank Reviewer #2 for providing the relevant reference to us. In the data of this reference, the peak occurs near the hard axis in the film plane, which is different from ours. + +We propose a possible mechanism and further conduct relevant experimental measurements. This additional jump signal occurs near the magnetization switching. During the switching, the system encounters a substantial increase in magnetic susceptibility. In this process, the system may generate a burst of magnon upon the thermal excitation. The burst of magnon subsequently generates a voltage signal. The sign of the voltage signal is positive or negative depending on whether the excitation of the magnon occurs after or before the coercive field (Figs. R10d and R10g). The + +<--- Page Split ---> + +measured signal is the sum of both the magnetization- dependent magnon signal (Fig. R10a) and the susceptibility peak induced magnon signal (Figs. R10d and R10g), resulting in the interesting and unusual shape of loops (Figs. R10e and R10h), respectively. Both loops are observed in our experiments (Figs. R10f and R10i). According to our experimental measurements (Fig. R4), the peak voltages are scaled with the square of the \(I_{\mathrm{DC}}\) , indicating its thermal origin. The detailed results are presented in Response Reviewer #1- 5. For the convenience of Reviewer #2, we also present the main schematic diagram here (Fig. R10). + +![](images/Figure_unknown_8.jpg) + +
Fig. R10 a. Schematic loop of a non-local voltage signal generated by the usual SSE. b, c. Magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d, g present the corresponding voltage peaks occurring after and before the coercive field, respectively. e, h present the corresponding total voltage signals, respectively. f, i present the results observed in our experimental measurements. They show apparent similarities with e, h, respectively.
+ +Updated manuscript (lines 166- 168): + +A similar phenomenon was observed previously, though its origin was not mentioned41. We proposed a possible explanation for this phenomenon (see Supplementary Note 4). + +3. Line 204: It is not clear in the article the difference between the named Device 1 and Device 2 referenced by the authors. This point needs correction. + +## Response Reviewer #2-4: + +We thank Reviewer #1 for raising this question. Device 1 and device 2 are prepared + +<--- Page Split ---> + +on different PMN- PT substrates. The different on/off ratio between device 1 (400%) and device 2 (115%) may be caused by various reasons, such as different substrates induced variation and the variation caused by complicated fabrication process. The ferroelectric substrate we used is \(\mathrm{[Pb(Mg_{1 / 3}Nb_{2 / 3})O_{3}]_{(1 - x)}[PbTiO_{3}]_{x}}\) (PMN- PT), whose property depends sensitively on the composition. The substrate from the different positions of a wafer may have different properties resulting in different device performance. And the YIG films may also exhibit non- uniform properties after polarizing the PMN- PT substrates. In addition, the fabrication processes may also introduce performance fluctuations among different samples. We took these two samples and performed the scanning electron microscopy measurements and found that the gap widths of these two devices are slightly different (585 nm for device 1 vs. 526 nm for device 2) even though we intended to have 550- nm width originally. To further reveal the role of the gap width, we prepared two series of samples with different gate widths on two substrates, respectively. The measured results (Fig. R11) show a tendency of a higher on/off ratio with larger gate- stipe widths in both series, suggesting the dissipation of the magnon transport in the gate is of critical importance for the magnon FET. The quantitative difference in the performance of these two series also indicates the important role of the substrate. + +![](images/Figure_unknown_9.jpg) + +
Fig. R11 Gate width dependent on/off ratio for two series samples prepared on two PMN-PT substrates, respectively.
+ +Updated manuscript (lines 221- 222; lines 232- 234): + +Fig. 4a, devices 2 and device 1 have similar dimensions but were prepared on different PMN- PT substrates. + +To further reveal the role of the gap width and substrate, we performed the gate width dependent on/off ratio measurements with two series of samples fabricated on two different pieces of PMN- PT substrates (Supplementary Note 7). + +<--- Page Split ---> + +4. Line 210: The measurement of local temperature from the change in Pt resistance should be reviewed by the authors. No study of thermal stability in the platinum film was presented. + +## Response Reviewer #2-5: + +We thank Reviewer #2 for this excellent suggestion. We follow the reviewer's suggestions and measure the change of Pt resistivity by varying the injection DC current \(I\) and the measurement time \(t\) , the results show that the Pt resistivity is linear with the square of \(I\) (Fig. R12a), and the change of Pt resistivity is lower than \(0.2\%\) with \(I = 0.30\) mA for almost 60 minutes (Fig. R12b). + +![](images/Figure_unknown_10.jpg) + +
Fig. R12 a Dependence of the resistivity of Pt stripe, \(\rho_{\mathrm{pt}}\) on the square of DC current \(I\) . The symbols are the experimental data and the line is a linear fitting. b Dependence of \(\rho_{\mathrm{pt}}\) on the measurement time.
+ +Updated manuscript (lines 238- 239): + +And the resistance remains almost constant under a certain DC current (Supplementary Note 8). + +5. Line 245: The authors indicate that there might be a change in the magnetic anisotropy of YIG due to magnetoelastic coupling between the PMN-PT layer and YIG. However, studies demonstrate that the magnetostriction of YIG is small. This statement needs further discussion. + +## Response Reviewer #2-6: + +We thank Reviewer #2 for raising this question. In line 245 of our previous manuscript, we mentioned that "magnetoelectric coupling between YIG and PMN- PT can result in a change of magnetic anisotropy in YIG". In addition to the magnetoelastic coupling, the charge accumulation at the interface due to the different polarization may also influence the properties of YIG (as depicted in Figs. R1a and R1b). For the convenience, we copy Fig. R1 as Fig. R13 herein. And the control of anisotropy in YIG/PMN- PT bilayer has been reported in the literatures [such as Phys. Rev. Applied + +<--- Page Split ---> + +10, 014004 (2018), Adv. Electron. Mater. 5, 1800663 (2019)]. We added a short discussion in the revised manuscript. + +![](images/Figure_unknown_11.jpg) + +
Fig. R13 a, b Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized. c, d show the possible coupling of the magnon with ferron and phonon in the strong coupling case.
+ +Updated manuscript (lines 288- 291): + +We propose that the modulation is due to polarization- dependent ions \(\mathrm{(Fe^{3 + }}\) or \(\mathrm{O^{2 - }}\) accumulation in the YIG layer adjacent to the interface, resulting in different coupling since \(\mathrm{Fe^{3 + }}\) is magnetic while \(\mathrm{O^{2 - }}\) is not. Dynamically, the magnon in YIG could couple with the collective excitation, such as the ferron or phonon in PMN- PT (Supplementary Note 11). + +In summary, although the article has been written quite carefully and the results are promising for technological applications, complementary studies need to be carried out. Especially concerning the production of devices in which the polarization voltage is accessible to integrate this structure into real systems. + +## Summarized response Reviewer #2: + +We are very grateful to Reviewer #2 for giving us the above positive comments. We also thank Reviewer #2 for raising several critical questions/comments which are very helpful in improving the quality of our manuscript. As listed above, we addressed all these questions/comments with our best efforts, especially including the significantly lowered voltage, which is accessible when integrating this structure into real systems. We hope the reviewer will find our responses satisfying and can recommend the publication of our revised manuscript on Nature Communications. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +Reviewer #3 (Remarks to the Author):In this manuscript, the authors have demonstrated a nonvolatile three- terminal lateral magnon FET based on YIG/PMN- PT heterostructures. They attribute the observed nonvolatile modulations to changes in magnon relaxation within the YIG sublayers. The possible mechanism behind these modulations, including temperature variation, anisotropic exchange stiffness and the emergent electric dipoles from noncollinear spin configuration in YIG, are discussed. While the research topic is interesting, I find that both the experimental setup and related discussion presented by the authors lack sufficient evidence to convince me of its suitability for publication in NC. + +## General response Reviewer #3: + +We sincerely thank Reviewer #3 for the time and effort spent in evaluating our manuscript. We are delighted to learn that Reviewer #3 thinks the research topic of nonvolatile three- terminal lateral magnon FET is interesting. In the following, we provide detailed answers to all the questions/comments raised point- by- point. + +Therefore, I kindly request that the authors consider the following suggestions and concerns: + +1. Nonvolatile modulation has been extensively investigated in various systems through transport measurement, such as \(\mathrm{VO_2 / PMN - PT(ACS}\) Appl. Mater. Interfaces 2014, 6, 4603-4608), FePt/PMN-PT(Appl. Phys. Lett. 112, 033506 (2018)), MnPt/PMN-PT (Nat. Nanotech. 14, 131-136 (2019)), SrRuO3/PMN-PT(Appl. Phys. Lett. 110, 182403 (2017)), and others. Considering device's aspects, similar magnon transistors have also been mentioned in Ref. [22], [31] and [32]. What is the main advantage of the structure in the present study? + +## Response Reviewer #3-1: + +Response Reviewer #3- 1:We sincerely thank Reviewer #3 for raising these questions. For researchers seeking magnonic transistors, the most important consideration is how to reduce the power consumption of the device, compared to the electronic transistor. A magnetic insulator (such as YIG) are better than a conductor as the Joule heating is absent in the insulator. In addition, one needs to find a way to control of the magnon transmission process without introducing additional power consumption. In this sense, electric- field- controlled with non- volatility (this work) is naturally the best choice. The pioneer works such as microwave current- controlled [A. V. Chumak et al. Nat. Commun. 5, 4700 (2014)], magnetic field- controlled [K. S. Das et al. Phys. Rev. B 101, 054436 (2020); Santos, O. A. et al. Phys. Rev. Applied 15, 014038 (2021)] or DC current- controlled [L. J. Cornelissen et al. Phys. Rev. Lett. 120, 097702 (2018)] present different possibilities in controlling the magnon current, but not the most energy efficient. In our manuscript, we cited these pioneer works and compared them with our devices. We also included the references recommended by Reviewer #3. + +<--- Page Split ---> + +Updated manuscript (lines 93- 96): + +YIG is chosen because it has low damping, which is suitable for magnon transport, and is an insulator where the joule heating is absent. Besides, PMN- PT has been demonstrated to exhibit nonvolatile modulation on various transport properties34- 37. + +2. The authors propose that electric polarization is responsible for the large nonvolatile modulation of \(\mathrm{V\_nl^{\wedge}DC}\) . However, it should be noted that in Supplementary Figure 2c, the ferroelectric hysteresis loop (P-E loop) saturates at least \(\pm 8\mathrm{kV / cm}\) , whereas in Fig. 3b, the maximum voltage is only \(\pm 200\mathrm{V}\) (equivalent to \(\pm 4\mathrm{kV / cm}\) with a \(0.5\mathrm{mm}\) thickness of FE substrate), which corresponds to the coercive electric field value. Consequently, under these conditions, the modulation remains unsaturated and unstable due to its dominance by strain, as mentioned in previous literatures refereed to Q1. Did the author conduct experiments using an electric field around or beyond \(\pm 8\mathrm{kV / cm}\) and then cycle \(\mathrm{V_g?}\) Additionally, we also notice that there are different on/off ration between device 1 \((400\%)\) and device 2 \((115\%)\) , despite both devices having identical dimensions. How can sample fabrication result in such a significant difference? Is it disparity attributable to an unstable modulation caused by strain? If not, what mechanism accounts for this large variation? + +## Response Reviewer #3-2: + +We thank Reviewer #3 for raising these questions. + +We first provide the comparison of the measured gate voltage- dependent non- local voltage (Fig. 3b in the main text) with the charge from the same sample. The modulation of the charge, which represents the polarization change, is obtained through integration over the sweeping time from the sweeping voltage- dependent leakage curve shown in Supplementary Fig. 4a [Ferroelectrics 411, 86 (2010)]. The result is presented in Fig. R14 and they show close similarity. This strongly indicates that our voltage control results are related to the electrical polarization of PMN- PT. + +![](images/Figure_unknown_12.jpg) + +
Fig. R14 Non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude(red line) and the charge(blue line) as the functions of the gate voltage pulse \(V_{\mathrm{g}}\) for device 1, respectively.
+ +We also noticed that the electric field required for the saturation of \(P - E\) curve is + +<--- Page Split ---> + +larger than that we used in the magnon transport modulation. We followed the suggestion and performed measurements with higher gate voltage. The experimental results show that the larger (lower) non- local voltage with higher positive (negative) gate voltages (Fig. R15), indicating its dependence on the residual polarization values and directions of FE substrate. We found that the devices are easily burned when the applied voltage is larger than 200 V. Thus, we limited our discussion with the applying voltage smaller than 200 V. + +![](images/Figure_unknown_13.jpg) + +
Fig. R15 The non-local voltages measurement with different gate voltages. The curves are shifted for clarity.
+ +As for the different on/off ratio between device 1 (400%) and device 2 (115%), it may be caused by various reasons, such as different substrates induced variation and the variation caused by complicated fabrication processes. The ferroelectric substrate we used is \([\mathrm{Pb(Mg_{1 / 3}Nb_{2 / 3})O_{3}}]_{(1 - x)} - [\mathrm{PbTiO_{3}}]_{x}\) (PMN- PT), whose property depends sensitively on the composition. The substrate from the different positions of a wafer may have different properties, resulting in different device performance. And the YIG films may also exhibit non- uniform properties after polarizing the PMN- PT substrates. In addition, the fabrication processes may also introduce performance fluctuations among different samples. We took these two samples and performed the scanning electron microscopy measurements and found that the gap widths of these two devices are slightly different (585 nm for device 1 vs. 526 nm for device 2) even though we intended to have 550- nm width originally. To further reveal the role of the gap width, we prepared two series of samples with different gate widths on two substrates, respectively. The measured results (Fig. R16) show a tendency of a higher on/off ratio with larger gate- stripe widths in both series, suggesting the dissipation of the magnon transport in the gate is of critical importance for the magnon FET. The quantitative difference on the performance of these two series devices also indicates the important + +<--- Page Split ---> + +role of the substrate. + +![](images/Figure_unknown_14.jpg) + +
Fig. R16 Gate width dependent on/off ratio for two series samples prepared on two PMN-PT substrates, respectively.
+ +Updated manuscript (lines 176- 179; lines 214- 216; lines 224- 234): + +We also calculated the charge loop (blue curve in Fig. 3b) with the \(V_{\mathrm{g}}\) - dependent leakage current \(^{42}\) and found that they exhibited close similarity, indicating a strong correlation between the observed magnon current modulation and the electric polarization of the FE layer. + +And the magnetic field- dependent \(V_{\mathrm{n}}^{\mathrm{DC}}\) curves under higher gate voltage for a new sample are presented in Supplementary Note 6. + +The different on/off ratio between device 1 ( \(400\%\) ) and device 2 ( \(115\%\) ) may be caused by various reasons, such as different substrates- induced variation and those caused by complicated fabrication processes. The ferroelectric substrate we used is \(\mathrm{[Pb(Mg_{1 / 3}Nb_{2 / 3})O_{3}]_{(1 - x)}[PbTiO_{3}]_{x}}\) (PMN- PT), whose property depends sensitively on the composition. The substrate from the different positions of a wafer may have different properties, resulting in different device performance. And the YIG films may exhibit non- uniform properties after polarizing the PMN- PT substrates. In addition, the fabrication processes may also introduce discrepancies in quantity between different samples. To further reveal the role of the gap width and substrate, we performed the gate width dependent on/off ratio measurements with two series of samples fabricated on two different pieces of PMN- PT substrates (Supplementary Note 7). + +3. The authors assume that this non-volatile modulation is due to electric polarization of FE substrate. Given that YIG is oxide insulator, how does electrical polarization transmit? Did the author perform measurements by changing the thickness of YIG? + +Response Reviewer #3- 3: + +<--- Page Split ---> + +We thank Reviewer #3 for raising these questions. We believe that the electric field caused by the electric polarization of the FE substrate plays a role, although the electric field cannot act on the inside of a metal due to the screening effect, it could induce charge accumulation in an insulator. As reported by D. Chiba et al. [Sci. Rep. 6, 38005 (2016)], when the ferroelectric layer is electrically polarized oppositely, the strong electrical field induces opposite charge accumulation in its adjacent layer. In our case, when the PMN- PT layer is negatively polarized (Fig. R17a), it induces \(\mathrm{Fe}^{3 + }\) ions accumulation at the interface. On the contrary, it induces \(\mathrm{O}^{2 - }\) ions accumulation at the interface when the PMN- PT layer is positively polarized (Fig. R17b). Since the \(\mathrm{Fe}^{3 + }\) ions contain magnetic moment and \(\mathrm{O}^{2 - }\) ions have none, this results in a stronger coupling between the magnon and the collective excitations of PMN- PT in the \(1^{\mathrm{st}}\) case as compared to the \(2^{\mathrm{nd}}\) one. The collective excitation can be either the ferron (Fig. R17c) or phonon (Fig. R17d), especially when they have a similar energy and wavevector as the magnon. The magnon thus has different dissipation and diffusion lengths when PMN- PT is polarized oppositely, resulting in an electrical field modulation of the magnon propagation, i.e., the magnon FET. + +![](images/Figure_unknown_15.jpg) + +
Fig. R17 Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized.
+ +We further followed the suggestion of Reviewer #3 and conducted experimental measurements by changing the thickness of YIG. For the thickness of YIG increased to \(80 \mathrm{nm}\) and \(100 \mathrm{nm}\) , the experimental results do not show apparent thickness dependence, all can achieve \(20\% \sim 100\%\) on/off ratio under \(\pm 200 \mathrm{V}\) gate voltages. + +Updated manuscript (lines 288- 291): + +<--- Page Split ---> + +We propose that the modulation is due to polarization- dependent ions \(\mathrm{(Fe^{3 + }}\) or \(\mathrm{O^{2 - }}\) accumulation in the YIG layer adjacent to the interface, resulting in different coupling since \(\mathrm{Fe^{3 + }}\) is magnetic while \(\mathrm{O^{2 - }}\) is not. Dynamically, the magnon in YIG could couple with the collective excitation, such as the ferron or phonon in PMN- PT (Supplementary Note 11). + +4. In Fig. 3c, the magnetic-field-dependent \(\mathrm{V} \cdot \mathrm{nl}^{\wedge} \mathrm{DC}\) exhibits an enhancement near the coercivity at some electric filed (such as \(+200 \mathrm{~V}\) ), while disappears at other electric filed \((-160 \mathrm{~V})\) . What is the underlying reason for this significant dependence on electric field? Additionally, there is a noticeable difference in coercivity. The authors refer to Ref. 36; however, it seems that this magnetic-field dependence has not been directly measured in their report rather treated to some extent. Therefore, it is necessary for the authors to provide an explanation and present the magnetic-field-dependent \(\mathrm{V} \cdot \mathrm{nl}^{\wedge} \mathrm{DC}\) before applying any electric field (0V). + +## Response Reviewer #3-4: + +We thank Reviewer #3 for raising these questions. We propose a possible mechanism for the enhancement near the coercivity. During the switching, the system encounters a substantial increase in magnetic susceptibility. In this process, the system may generate a burst of magnon upon the thermal excitation. The burst of magnon subsequently generates a voltage signal. The sign of the voltage signal is positive or negative depending on whether the excitation of the magnon occurs after or before the coercive field (Figs. R18d and R18g). The measured signal is the sum of both the magnetization- dependent magnon signal (Fig. R18a) and the susceptibility peak induced magnon signal (Figs. R18d and R18g), resulting in the interesting and unusual shape of loops (Figs. R18e and R18h), respectively. Both loops are observed in our experiments (Figs. R18f and R18i). According to our measurements (Fig. R4 in Response Reviewer #1- 5), the peak voltages are scaled with the square of the \(I_{\mathrm{DC}}\) , indicating its thermal origin. For the convenience of Reviewer #3, we also present the main schematic diagram here (Fig. R18). + +The possible reason for the difference in peak value under different electric fields is that the magnetic anisotropy variation of YIG leads to the different intensity and magnetic field location of magnon excitation. + +<--- Page Split ---> +![](images/Figure_unknown_16.jpg) + +
Fig. R18 a. Schematic loop of a non-local voltage signal generated by the usual SSE. b and c. The magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d and g show the corresponding voltage peaks occurring after and before the coercive field, respectively. e and h show the corresponding total voltage signals, respectively. f and i show the results observed in our experimental measurements. They show apparent similarities with e, h, respectively.
+ +Figure R19 shows the non- local measurements of different samples under as- grown (0 V) and \(\pm 200\) V- gate voltages, and the as- grown (0V) measurement results do not show obvious regularity. + +![](images/Figure_unknown_17.jpg) + +
Fig. R19 a, b The non-local measurements in two samples under as-grown (0 V) and \(\pm 200\) V-gate voltages, respectively.
+ +Updated manuscript (lines 166- 168): + +A similar phenomenon was observed previously, though its origin was not + +<--- Page Split ---> + +mentioned41. We proposed a possible explanation for this phenomenon (see Supplementary Note 4). + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this work, the authors deposited ferrimagnet YIG on top of PMN- PT substrate, a nonvolatile magnon transport behavior was experimentally observed. They try to explain the underlying mechanism as an electrical field modulation of the \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ions accumulation at the YIG/PMN- PT interface, which could result in magnetoelectric coupling between magnons and the collective excitations of PMN- PT. However, this discussion lack strong evidence for both the collective excitations of PMN- PT and \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ions accumulation at interface. How to excite the collective excitations (ferron or phonon) of PMN- PT for a non- local electric measurements? What is the theoretical model of these excitations? + +For the TEM image of the PMN- PT/YIG/Pt heterostructure, not only \(\mathrm{Mg}^{2 + }\) but also \(\mathrm{Nb}^{2 + }\) and \(\mathrm{Ti}^{4 + }\) ions migrated into YIG layer after the deposition. The YIG layer could not a pure YIG in this case. So, the origin of the electric modulation magnon transportation still need to be studied. In this manuscript form, there is not innovative enough to justify its publication on Nature Communications. + +## General response Reviewer #1: + +We sincerely thank Reviewer #1 for the time and efforts spent in evaluating our manuscript. Following his/her suggestions, we provided a theoretical model about the coupling between the magnons and the collective excitations (ferron or phonon) of ferrielectric materials as well as its influence on the magnon transport, and further discussions about our TEM results of the PMN- PT/YIG/Pt sample. In the following, we provide point- by- point answers to all the raised questions/ comments. + +## Response Reviewer #1-1: + +We thank Reviewer #1 for raising these questions. To explain the different magnetoelectric coupling of the PMN- PT/YIG bilayer with opposite electric polarization, we proposed the electric field modulation of the \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ions accumulation at the YIG/PMN- PT interface in our last response. We also wish to observe this effect experimentally. Our TEM, however, could not apply voltage across the sample in situ. It could be an interesting project in the near future. On the other hand, in a similar system, D. Chiba et al. reported that the opposite electric field indeed induced accumulation of ions with opposite charges in the Co/ZnO interface [Sci. Rep. 6, 38005 (2016)]. Therefore, we believe this assumption is reasonable. + +The collective excitations (ferron or phonon) of PMN- PT can be caused by thermal fluctuation, similar to the magnon excitation in YIG. As discussed below, the magnon + +<--- Page Split ---> + +could also create/annihilate these excitations due to magnetoelectric (ME) coupling between PMN- PT and YIG. The magnon- phonon coupling was observed experimentally in similar systems like \(\mathrm{CoFe_2O_4 / PMN - PT}\) , \(\mathrm{NiFe_2O_4 / SrRuO_3 / PMN - PT}\) and \(\mathrm{SmFeO_3 / PMN - PT}\) systems [J. Mater. Sci.- Mater. Electron. 33, 19766 (2022); Appl. Phys. Lett. 119, 112902 (2021); Appl. Phys. Lett. 109, 082902 (2016)]. Though the authors termed it as the spin- phonon coupling, due to the high- frequency nature and the spin character, it has to be the coupling between magnon and phonon. The ferron excitation in ferroelectric materials was theoretically predicted by Ping Tang and Gerrit E.W. Bauer et al. very recently [Phys. Rev. Lett. 128, 047601 (2022); Phys. Rev. B 106, L081105 (2022)], the direct experimental observations are still yet to be demonstrated. + +In the following, we present a theory to study the influence of ferron excitation in the ferroelectric layer on the magnon transport in the ferromagnetic layer. The idea is that magnon excitation can couple with ferrons through magnetoelectric interaction at the interface of ferroelectric (FE) and ferromagnetic(ferrimagnetic) insulator (FI). This coupling can enhance the dissipation and thus reduce the thermal diffusion length of magnons, then the non- local electric voltage proportional to the magnon density at the detector terminal will be reduced. On the other hand, the ME coupling changes when the stationary ferroelectric polarization is reversed due to the different spatial distribution of ferromagnetic ions (Supplementary Fig. 17), then the magnon diffusion length and subsequent non- local electric voltage will also differ. This explains the experimental observation. + +Model and Hamiltonian.- We consider a hybrid FI and FE system coupled through ME coupling at the interface. The total Hamiltonian of the hybrid system can be written as \(\mathrm{H} = \mathrm{H}_{\mathrm{im}} + \mathrm{H}_{\mathrm{fe}} + \mathrm{H}_{\mathrm{int}}\) , where \(\mathrm{H}_{\mathrm{im}}, \mathrm{H}_{\mathrm{fe}}, \mathrm{H}_{\mathrm{int}}\) are the magnetic Hamiltonian, ferroelectric Hamiltonian and their interaction, respectively. The magnetic component reads + +\[\mathrm{H}_{\mathrm{im}} = -JS^2\sum_{\langle i,j\rangle}\mathbf{m}_i\cdot \mathbf{m}_j - \mu_0M_s\mathbf{H}\cdot \sum_i\mathbf{m}_i, \quad (1)\] + +where the first and second terms represent the Heisenberg exchange and Zeeman energy, respectively, with \(\mathbf{m}_i\) being the unit spin orientation at \(i\) - th site, the first sum being taken on the nearest sites, \(J\) being the exchange coefficient, \(S\) being the length of spin, \(M_s\) being saturation magnetization, \(\mu_0\) being the vacuum permeability and \(\mathbf{H}\) being the external magnetic field. + +Within the Landau- Ginzburg- Devonshire theory, the ferroelectric Hamiltonian reads [Nano. Lett. 16, 7290 (2016); Phys. Rev. B 106, L081105 (2022)] + +<--- Page Split ---> + +\[\mathrm{H}_{\mathrm{fe}} = \frac{A}{2}\sum_{i}(\nabla \mathbf{P}_{i})^{2} - \frac{\alpha}{2} (\mathbf{P}_{i})^{2} + \frac{\beta}{4} (\mathbf{P}_{i})^{4} - \mathbf{P}_{i}\cdot \mathbf{E}_{e}, \quad (2)\] + +where \(\mathbf{P}_{i}\) stands for the discretized ferroelectric polarization at \(i-\) th site. The first term resembles the ferromagnetic exchange energy, with \(A\) being the exchange coefficient, the second and third terms are the potential terms that account for the stationary ferroelectric polarization with \(\alpha >0\) and \(\beta >0\) being the potential coefficients. The last term resembles the magnetic Zeeman energy with \(E_{e}\) being the external electric field. + +The leading term of the ME interaction is the linear coupling between magnetic order and electric polarization that in the form [Phys. Rev. B 90, 054423 (2014)] + +\[\mathrm{H}_{\mathrm{int}} = -g_{\mathrm{ME}}M_{s}\sum_{i}\mathbf{m}_{i}\cdot \mathbf{P}_{i}, \quad (3)\] + +where \(g_{\mathrm{ME}}\) is the ME coupling strength. + +Quantization. Next, we shall quantize the total Hamiltonian \(\mathrm{H}\) to show how the ferroelectric excitations i.e., ferrons can influence the behavior of magnetic excitations i.e., magnons. To mimic the experimental condition, we apply an in- plane external magnetic field \(\mathbf{H} = H_{e}e_{x}\) , which is sufficiently strong to polarize all the spins along this direction. Then we can perform the Holstein- Breakoff transformation [Phys. Rev. 58, 1098 (1940)] above the classical ground state \(\mathbf{m}_{i} = e_{x}\) , i.e. + +\[m_{i}^{+} = \sqrt{2 / S}\hat{a}_{i},m_{i}^{-} = \sqrt{2 / S}\hat{a}_{i}^{+},m_{i}^{+} = 1 - \hat{a}_{i}^{+}\hat{a}_{i} / S, \quad (4)\] + +where \(\hat{a}_{i}\left(\hat{a}_{i}^{+}\right)\) are magnon annihilation (creation) operators at \(i-\) th site, \(m_{i}^{\pm}\) are spin raising (lowering) operators defined as \(m_{i}^{\pm}\equiv m_{i}^{z}\mp i m_{i}^{y}\) . After rearranging Eq. (4) in the form of \(m_{i}^{z(y)}\) , we derive \(m_{i}^{z} = \sqrt{1 / 2S}\left(\hat{a}_{i} + \hat{a}_{i}^{+}\right),m_{i}^{y} = i\sqrt{1 / 2S}\left(\hat{a}_{i} - \hat{a}_{i}^{+}\right)\) . By substituting the quantized forms of \(\mathbf{m}_{i}\) into the Hamiltonian \(\mathrm{H}_{\mathrm{im}}\) and transferring to Fourier space, we derive the quantized form of magnetic Hamiltonian as \(\mathrm{H}_{\mathrm{im}} = \sum_{k}\omega_{k}\hat{a}_{k}^{+}\hat{a}_{k}\) , where \(\omega_{k}\) is the dispersion relation of magnons, \(\hat{a}_{k}\) ( \(\hat{a}_{k}^{+}\) ) are the magnon annihilation (creation) operators with momentum \(\mathbf{k}\) . + +Similarly, the ferron excitation \(\delta P_{iz} = \mathbf{P}_{i} - \mathbf{P}_{0}\) around the stationary polarization + +<--- Page Split ---> + +\(\mathbf{P}_{0} = P_{0}e_{z}\) at \(z - \mathrm{axis}\) can be quantized as [Phys. Rev. B 106, L081105 (2022)] + +\[\delta P_{i z} = \sqrt{\frac{\hbar}{2m_{p}V_{\mathrm{FE}}}}\sum_{\mathbf{q}}\left(\frac{\hat{b}_{\mathbf{q}}}{\sqrt{\Omega_{q}}} e^{i\mathbf{q}\cdot \mathbf{r}_{i}} + \frac{\hat{b}_{\mathbf{q}}^{\dagger}}{\sqrt{\Omega_{q}}} e^{-i\mathbf{q}\cdot \mathbf{r}_{i}}\right), \quad (5)\] + +where \(\Omega_{q} = \sqrt{\Delta^{2} + A^{\prime}q^{2}}\) is the dispersion relation of ferrons with energy gap \(\Delta = \sqrt{\left(\alpha + 3\beta P_{0}^{2}\right) / m_{p}}\) and \(A^{\prime} = A / m_{p}\) , \(m_{p}\) is the polarization inertia, \(V_{\mathrm{FE}}\) is the volume of ferroelectric, \(\hat{b}_{q}\) \((\hat{b}_{q}^{\dagger})\) is the annihilation (creation) operator of ferrons. By substituting the quantized form of \(\mathbf{P}\) and \(\mathbf{M}\) into the interaction Hamiltonian \(\mathrm{H}_{\mathrm{int}}\) , we derive the quantized interaction component as + +\[\mathrm{H}_{\mathrm{int}} = \sum_{\mathbf{k},\mathbf{q}}\left(V(\mathbf{k},\mathbf{q})\hat{a}_{\mathbf{k}}\hat{b}_{\mathbf{q}}^{\dagger} + V^{*}(\mathbf{k},\mathbf{q})\hat{a}_{\mathbf{k}}^{\dagger}\hat{b}_{\mathbf{q}}\right), \quad (6)\] + +where the coupling strength + +\[V(\mathbf{k},\mathbf{q}) = -g_{\mathrm{ME}}M_{s}\sqrt{\frac{\hbar}{2m_{p}V_{\mathrm{FE}}N_{s}}}\sum_{i}\frac{e^{i(\mathbf{k} - \mathbf{q})\cdot\mathbf{r}_{i}}}{\sqrt{\omega_{q}}}. \quad (7)\] + +In the experiments, the magnon transport is measured at room temperature. This implies that the magnon modes with energy \(\hbar \omega_{k_{0}} \approx k_{B}T\) (around THz scale) dominate the contribution to transport behavior while the magnon gap induced by anisotropy and external field (around GHz scale) do not play a significant role here. Then it seems reasonable to only consider a proper THz magnon mode with the effective Hamiltonian + +\[\mathrm{H}_{\mathrm{int}} = \sum_{\mathbf{q}}\left(V(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}\hat{b}_{\mathbf{q}}^{\dagger} + V^{*}(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}^{\dagger}\hat{b}_{\mathbf{q}}\right). \quad (8)\] + +Above all, we come to the total quantized Hamiltonian of the hybrid system + +\[\mathrm{H} = \omega_{k_{0}}\hat{a}_{k_{0}}^{\dagger}\hat{a}_{k_{0}} + \sum_{q}\Omega_{q}\hat{b}_{q}^{\dagger}\hat{b}_{q} + \sum_{\mathbf{q}}\left(V(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}\hat{b}_{q}^{\dagger} + V^{*}(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}^{\dagger}\hat{b}_{q}\right). \quad (9)\] + +Next, we will use this Hamiltonian to study the influence of ferron excitation on the dissipation of magnons. + +Ferron- induced magnon dissipation. Here we denote the state of magnons by a density matrix \(\hat{\rho}\) and treat the influence of ferron excitation as a bath that contributes to the dissipation of magnons. Following the standard Lindbald formalism [Phys. Rev. B 106, 224422 (2022)], we can trace out the bath degrees of freedom in Eq. (9) and derive a master equation governing the magnon dynamics as + +<--- Page Split ---> + +\[\frac{\partial\hat{\rho}}{\partial t} = \frac{i}{\hbar}\big[\hat{\rho},\mathrm{H}_{\mathrm{im}}\big] + \kappa_{\mathrm{me}}\big(n_{\mathrm{th}} + 1\big)\mathrm{L}_{a}\big(\hat{\rho}\big) + \kappa_{\mathrm{me}}n_{\mathrm{th}}\mathrm{L}_{a}\big(\hat{\rho}\big), \quad (10)\] + +where \(n_{\mathrm{th}}\) is the thermal occupation of magnons, \(\mathrm{L}_{A}(\hat{\rho}) = 2\hat{A}\hat{\rho}\hat{A}^{\dagger} - \hat{A}^{\dagger}\hat{A}\hat{\rho} - \hat{\rho}\hat{A}^{\dagger}\hat{A}\) is the Lindblad operator. The relaxation rate of magnons coming from magnon- ferron coupling is + +\[\kappa_{\mathrm{me}} = \frac{\pi g_{\mathrm{ME}}^{2}M_{s}^{2}D\big(\Omega_{k_{0}}\big)}{2\hbar m_{p}V_{\mathrm{FE}}\Omega_{k_{0}}}, \quad (11)\] + +where \(D\big(\Omega_{k_{0}}\big)\) is the density states of ferrons that can be readily evaluated from the ferron dispersion as \(D\big(\Omega_{k_{0}}\big) = A^{- 3 / 2}V_{\mathrm{FE}} / \big(2\pi^{2}\big)\Omega_{k_{0}}\sqrt{\Omega_{k_{0}}^{2} - \Delta^{2}}\) . Note that, besides the magnon- ferron coupling, there are additional channels of magnon dissipation which may come from magnon- phonon scattering, magnon- magnon interaction, defects, and disorders in a magnet. The total dissipation rate is the sum of all these contributions as \(\kappa = \kappa_{\mathrm{me}} + \kappa_{\mathrm{im}}\) . Then we can evaluate the thermal diffusion length of magnons as + +\[I_{m} = \nu_{\mathrm{th}}\tau = \frac{\nu_{\mathrm{th}}}{\kappa_{\mathrm{me}} + \kappa_{\mathrm{im}}}, \quad (12)\] + +where \(\tau = 1 / \big(\kappa_{\mathrm{me}} + \kappa_{\mathrm{im}}\big)\) is the total diffusion time of magnons, \(\nu_{\mathrm{th}} = 2\sqrt{J_{s}k_{B}T} /\hbar\) is the thermal velocity of magnons [Phys. Rev. B 94, 014412 (2016)], and \(\kappa_{\mathrm{im}}\) includes all the other contributions of magnon dissipations except ME coupling. + +Comparison with experiments. To compare with the experimental results, we recall that magnon transport in a magnetic insulator may be described by the diffusion equation [Phys. Rev. B 94, 014412 (2016)] + +\[\frac{\partial^{2}\mu_{m}}{\partial^{2}x} = \frac{\mu_{m}}{I_{m}^{2}}, \quad (13)\] + +where \(\mu_{m}\) is the chemical potential of magnons. By solving the diffusion equation (13), we obtain \(\mu_{m}\left(x\right) = \mu_{0}\mathrm{exp}\left(- x / I_{m}\right)\) . Note that the non- local electric voltage measured in experiments is proportional to the magnon chemical potential at the position of the electrode \((x = L)\) , i.e., \(V_{\mathrm{nl}}\propto \mu_{m}\left(x = d\right)\) . + +<--- Page Split ---> +![](images/Figure_unknown_18.jpg) + +
Fig. R1 a Magnon chemical potential as a function of distance for \(P< 0\) (red line) and
+ +\(P > 0\) (black line), respectively. \(g_{\mathrm{ME}} = 0.5 \mathrm{s / F}\) for \(P< 0\) and \(0.25 \mathrm{s / F}\) for \(P > 0\) , respectively, \(A = 0.2 A_{0}\) , \(d = 2 \mu \mathrm{m}\) is the distance between the source and detector. The blue dashed line indicates the position at which the electric voltage is measured. b Non- local voltage ratio: \(V_{\mathrm{nl}}^{- } / V_{\mathrm{nl}}^{+}\) as a function of magnetoelectric coupling strength for \(P< 0\) and the value for \(P > 0\) is assumed to be \(50\%\) of that for \(P< 0\) . Where \(V_{\mathrm{nl}}^{\pm}\) represent the nonlocal voltage at different gate voltages \(V_{\mathrm{nl}}^{\mathrm{DC}}\left(V_{g} = \pm 200 \mathrm{V}\right)\) , respectively. The purple, red and blue dashed lines refer to the experimental values on the sample YIG/PZT, device 2 of YIG/PMN-PT and device 1 of YIG/PMN-PT, respectively. Magnetic parameters of YIG are used with \(M_{s} = 1.36 \times 10^{5} \mathrm{A / m}\) (the experimental value of our YIG sample), \(J_{s} = 8.46 \times 10^{- 40} \mathrm{J} \cdot \mathrm{m}^{2}\) , \(a = 1.24 \mathrm{nm}\) [Phys. Rev. B 94, 014412 (2016)]. Since the ferron excitation parameters of PMN-PT and PZT are still not complete in literature, parameters of typical ferroelectric are used with \(\Delta = 20 \mathrm{THz}\) , \(m_{p} = 9 \times 10^{- 18} \mathrm{J} \cdot \mathrm{m} \cdot \mathrm{s}^{2} / \mathrm{C}^{2}\) , \(A_{0} = 10^{- 10} \mathrm{J} \cdot \mathrm{m}^{3} / \mathrm{C}^{2}\) [Phys. Rev. B 106, L081105 (2022)]. The temperature is \(T = 300 \mathrm{K}\) . + +Figure R1a shows the non- local voltage as a function of the propagation distance of magnons. Clearly, for \(P< 0\) ( \(P > 0\) ) with stronger (weaker) ME coupling, the magnon chemical potential as well as the non- local voltage decay faster (slower) with distance, as shown by the red line (black line) in Fig. R1a. When one measures the electric voltage at \(x = d\) , this leads to a voltage difference between positively and negatively polarized ferroelectric polarization. Figure R1b shows the theoretical values + +<--- Page Split ---> + +of \(V_{\mathrm{nl}}^{- } / V_{\mathrm{nl}}^{+}\) as a function of magnetoelectric coupling strength in the range of typical values of ferroelectric and ferromagnetic(ferrimagnetic) interface [Phys. Rev. B 100, 104410 (2019)]. Typical values of \(g_{\mathrm{ME}}\) around \(0.5 \mathrm{s / F}\) for \(P< 0\) can reproduce the experimental observations. Note that this result is sensitive to the exchange stiffness of ferrons i.e., \(A\) in Eq. (2). When \(A\) is smaller, the ferron band is flatter and more ferrons excitations around THz can contribute to the magnon dissipation. Hence the magnon diffusion length will be reduced on a larger scale, implying a larger on/off ratio. + +Lastly, we would like to discuss the role of magnon- phonon coupling at the interface of an FI/FE hybrid. In general, there exist phonon modes excited at THz regime and can thus enhance the dissipation of magnons. The theoretical formalism to quantify this influence is quite similar to the case of magnon- ferron coupling presented above within the linear coupling regime [https://doi.org/10.48550/arXiv.2310.05621]. The strength of this coupling is yet to be known. Currently, it is still difficult to estimate its contribution. On the other hand, at the interface of FI and FE, the spin excitations will strongly influence the elastic properties in the FE layer [Phys. Status. Solidi B 257, 1900750 (2020)], i.e., the phonons, while the elastic excitation is further coupled to the ferroelectric polarization [J. Alloys Compounds 928, 167181 (2022)]. This suggests that the interplay of magnons, phonons and ferrons may mix at the interface. In principle, magnon- phonon coupling could also contribute to the strength of magnon- ferron coupling ( \(g_{\mathrm{ME}}\) ). A detailed study of the underlying physics and the effective coupling strength is our future work. + +Updated manuscript (lines 299- 301): + +A theoretical model about the influence of these couplings on the magnon transport is presented in Supplementary Note 14. + +## Response Reviewer #1-2: + +We thank Reviewer #1 for raising the concern about YIG quality. We plot the area - dependent element distributions in Fig. R2 below. According to it, PMN- PT/YIG heterostructure can be divided into three regions: the PMN- PT layer, buffer layer, and YIG layer. In the buffer layer region ( \(\sim 30 \mathrm{nm}\) thickness), four elements (Mg, Pb, Ti, and Nb) of PMN- PT penetrate the YIG due to the high- temperature post- annealing treatment. However, for the YIG far from the interface, there is only a distribution of Y and Fe, and it maintains an excellent YIG crystallinity (HAADF- TEM images of the + +<--- Page Split ---> + +YIG layer in Supplementary Figs. 2b, c, and d). In addition, the lattice constant of YIG film is 12.486 Å obtained from the diffraction pattern in Supplementary Fig.2c inset, which is less than \(0.89\%\) different from the bulk value (12.376 Å) [J. Phys. D Appl. Phys. 51, 253001 (2018)], indicating the formation of a pure YIG. Despite the significant difference in lattice constant between YIG (12.376 Å) and PMN- PT (4.024 Å), the formation of a buffer layer helps the crystallization of YIG. Although we expect that the thickness of the buffer layer can be reduced by optimizing annealing conditions and/or inserting a suitable interlayer, we believe that it does not influence the merit of our manuscript. Given the fact that the Coulomb interaction is a long- range interaction, the formation of a thin buffer layer may reduce the magnetoelectric coupling but will not erase it completely. Moreover, the magnon field- effect- transistor only requires a ferromagnetic or ferrimagnetic layer with a relatively long magnon diffusion length, which has been demonstrated in Fig. 2f in the main text, coupled with a layer with good ferroelectricity which is also evidenced by the ferroelectric hysteresis loop shown in Fig. 3b in the main text. As you may find, the effect remains even after replacing the PMN- PT crystal with a PZT film. We believe it will also work if we replace YIG with other ferromagnetic or ferrimagnetic insulators, providing it has a long magnon diffusion length. + +![](images/Figure_unknown_19.jpg) + +
Fig. R2 a The HAADF image of PMN-PT/YIG/Pt sample. b EDS integrated signal profiles of Fe, Y, Mg, Pb, Ti and Nb obtained through area scans crossing layers shown in the orange dashed rectangle of a.
+ +With the first demonstration of the magnon field- effect- transistor and the updated information, we hope that you will now recommend the publication of our manuscript in Nature Communications. + +Updated manuscript (Supplementary Information): In Supplementary Note 1. The structure and magnetic properties of the samples, + +<--- Page Split ---> + +we added the discussion about the quality of YIG film. + +Reviewer #2 (Remarks to the Author): + +Dear, + +All the weaknesses presented in the original version of the article have been addressed in this new version. The crucial points were resolved by producing new samples and conducting new measurements. For these reasons, I suggest that the present article can be published in Nature Communications. + +## General response Reviewer #2: + +We sincerely thank Reviewer #2 for recommending the publication of the present manuscript in Nature Communications. We are grateful to Reviewer #2 for commenting that "all the weaknesses presented in the original version of the article have been addressed in this new version" and that "the crucial points were resolved by producing new samples and conducting new measurements". + +Reviewer #3 (Remarks to the Author): + +I have carefully read the revised version of the manuscript. I appreciate the efforts by the authors to address my raised questions. However, I have to follow up on certain points within the response of the authors and hope the authors can address these points. In more detail, see the below: + +## General response Reviewer #3: + +We sincerely thank Reviewer #3 for the time and effort spent in evaluating our revised manuscript. We are happy to answer further questions in a point- by- point manner below. + +In response to Q2: I notice that the authors demonstrate "all curves were obtained after the electric field had been removed" in the main text, if I understand this correctly, the authors obtain all \(\mathrm{V\_nl^{\wedge}DC}\) at residual polarization state despite removing from large electric field. If so, I suggest that the authors perform the measurements under \(+400\) V(do not remove electric field, or measuring under the maximum voltage before the device burning except \(200\mathrm{V}\) ) and \(+0\mathrm{V}\) (residual polarization). + +## Response Reviewer #3-1: + +We thank Reviewer #3 for raising this question. The reviewer is correct, we measured all \(V_{\mathrm{nl}}^{\mathrm{DC}}\) at the residual polarization state. We followed the suggestion and conducted the measurements with \(V_{\mathrm{g}}\) holding and removal, respectively. We prepared a PMN- PT/YIG/Pt sample with an on/off ratio of \(\sim 102\%\) , and measured the relationship between integrated charge with gate voltage \(V_{\mathrm{g}}\) in \(\pm 300\mathrm{V}\) range in situ (Fig. R3a). The + +<--- Page Split ---> + +residual polarization value \((+0 \mathrm{~V})\) is almost the same as the polarization value at \(+300 \mathrm{~V}\) . Figure R3b presents the non- local voltage measurements with gate voltages holding \((+300 \mathrm{~V})\) and removal \((+0 \mathrm{~V})\) , respectively. The measurement curves show that the signal- to- noise ratio with gate voltage removed is obviously better than that with gate voltage maintained. However, the curves in the two cases show similar results, with a slightly smaller \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude value at \(+0 \mathrm{~V}\) . This is consistent with the polarization value under two situations measured by the ferroelectric loop (Fig. R3a). + +![](images/Figure_unknown_20.jpg) + +
Fig. R3 a The integrated charge as the function of the gate voltage pulse \(V_{\mathrm{g}}\) for PMN-PT/YIG/Pt sample. b The non-local voltages measurement with gate voltages holding \((+300 \mathrm{~V})\) and removal \((+0 \mathrm{~V})\) , respectively.
+ +Updated manuscript (lines 220- 221): + +In addition, the comparison of non- local voltage with \(V_{\mathrm{g}}\) holding and removal is presented in Supplementary Note 7. + +In response to Q3: I am confused that the authors demonstrate “For the thickness of YIG increased to \(80 \mathrm{~nm}\) and \(100 \mathrm{~nm}\) , the experimental results do not show apparent thickness dependence, all can achieve \(20\% \sim 100\%\) on/off ratio”. However, in the main text, for \(60 \mathrm{~nm}\) YIG, the on/off ratio of device 1 and device 2 are \(400 \%\) and \(150 \%\) , respectively. How to understand “do not show apparent thickness dependence”? + +## Response Reviewer #3-2: + +We thank Reviewer #3 for raising this question. To better explain that the on/off ratio did not show apparent YIG thickness dependence, we summarize the on/off ratio of 16 PMN- PT/YIG/Pt samples in Fig. R4. The on/off ratios with YIG thickness \(60 \mathrm{~nm}\) , \(80 \mathrm{~nm}\) and \(100 \mathrm{~nm}\) vary between \(18.2\% \sim 404\%\) , \(12.7\% \sim 21\%\) and \(17.1\% \sim 102.8\%\) , respectively. The on/off ratio fluctuates even for the same YIG thickness, which may be caused by various reasons, such as different substrates induced variation, the non + +<--- Page Split ---> + +uniform properties of PMN- PT substrate and YIG films, different interface properties, and the variation caused by complicated fabrication processes (see our previous responses). Therefore, we cannot obtain a clear YIG thickness dependence of the on/off ratio at present stage. We mentioned this in the revised manuscript and replaced “all” with “most”. + +![](images/Figure_unknown_21.jpg) + +
Fig. R4 Summary of the on/off ratio of 16 PMN-PT/YIG/Pt samples for 60-nm, 80-nm, and 100-nm YIG thicknesses, respectively.
+ +Updated manuscript (lines 240- 242): + +Furthermore, we present a summary of the on/off ratio of 16 PMN- PT/YIG/Pt samples with different YIG thicknesses, where most of the samples can achieve \(20\% \sim 100\%\) on/off ratio (Supplementary Note 9). + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Reviewer #1 (Remarks to the Author):The article has been revised according to all my concerns. A reasonable theoretical model about the coupling between ferron and magnon and its influence on the magnon transport was provided. Therefore, I would like to suggest its publication in Nature Communications in the current form. + +Reviewer #3 (Remarks to the Author): + +Reviewer #3 (Remarks to the Author):I have carefully read the revised version of the manuscript (NCOMMS- 23- 58821C). The authors gave a detailed response to the raised concerns of the reviewers and also carried out necessary changes in their revised manuscript. So, I think the current version can be published in Nature Communications. + +## Our response: + +Our response:We sincerely thank both reviewers for the helpful comments and excellent recommendation. + +<--- Page Split ---> diff --git a/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file_det.mmd b/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0613c04ae3f677474c5c845ee13c847df7ebbf7a --- /dev/null +++ b/peer_reviews/5a01d09a39bf3367d68ef013906d008999f598f85b90499e2f7becebfab6cdf9/supplementary_1_Transparent Peer Review file/supplementary_1_Transparent Peer Review file_det.mmd @@ -0,0 +1,954 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 785, 209]]<|/det|> +# A nonvolatile magnon field effect transistor at room temperature + +<|ref|>text<|/ref|><|det|>[[73, 224, 475, 240]]<|/det|> +Corresponding Author: Professor Haifeng Ding + +<|ref|>text<|/ref|><|det|>[[73, 274, 712, 288]]<|/det|> +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +<|ref|>text<|/ref|><|det|>[[72, 300, 864, 315]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 353, 144, 366]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 379, 219, 392]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 404, 160, 417]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 431, 238, 444]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 444, 905, 524]]<|/det|> +In this manuscript, the authors report a three- terminal lateral magnon field effect transistor which can work at room temperature. The ferromagnetic insulator material Y3Fe5O12 (YIG) and heavy metal Pt is used here. The large on/off ratio can be achieved by applied a voltage pulse in G- stripes of devices up to \(400\%\) . There is no doubt that devices related to magneton control are very important for information transmission. However, the data in this manuscript are not well discussed. There are also problems with the function of the device. The manuscript cannot be recommended to be published on Nature Communications based on the following questions. + +<|ref|>text<|/ref|><|det|>[[72, 536, 183, 548]]<|/det|> +Main comments + +<|ref|>text<|/ref|><|det|>[[72, 549, 914, 600]]<|/det|> +1. So far, there have been many reports on the YIG/PNM-PT ferroelectric-ferromagnetic heterostructures. Such as magnetoelectric coupling and non-volatility (DOI: 10.1002/aem.201800663), and achieve changes in amplitude and phase (DOI:10.1088/1361-6463/abce7c). It seems that the work is not innovative enough to justify its publication on Nature Communications. + +<|ref|>text<|/ref|><|det|>[[72, 600, 914, 689]]<|/det|> +2. The mechanism of operation of the device is not clearly discussed. The authors ruled out temperature change, piezoelectricity, spin Seebeck effect, spin reflection, etc., and attributed the cause to the change of the local electric polarization direction under the G-strip. For the main conclusions of the work, it would be helpful to present more evidence. +3. The author mentions that the main function of the device is to realize the control of signal amplitude. However, the device only mentions an on/off ratio of \(400\%\) , and the minimum value is not 0, which may cause difficulties for the real applications. Besides, the on/off can be considered as a switcher. The transistor should own an amplifying transport magnon current function. + +<|ref|>text<|/ref|><|det|>[[70, 690, 897, 717]]<|/det|> +4. What is the contribution of non-volatility to the device, which seems to create additional difficulties for the control of the functionality of the device. + +<|ref|>text<|/ref|><|det|>[[70, 717, 897, 744]]<|/det|> +5. (p. 9, figure 3(c)) Most hysteresis loops exhibit strange behavior. An additional jump signal occurs when the magnetic moment reaches a stable value. A more detailed explanation would be helpful. + +<|ref|>text<|/ref|><|det|>[[70, 744, 912, 783]]<|/det|> +6. The manuscript realized the modulation of signal amplitude with a high electric voltage (hundreds of volts). However, the integration of the PNM-PT crystal layer is quite difficult. The interfacial characteristics of the YIG/PNM-PT heterostructure should be discussed. + +<|ref|>sub_title<|/ref|><|det|>[[73, 808, 162, 821]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 835, 237, 848]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 848, 911, 875]]<|/det|> +The presented work is well-founded and holds a significantly innovative character. The success in inducing a ferrimagnetic (non-ferromagnetic) phase in the YIG film on a PMN-PT substrate is surprising. + +<|ref|>text<|/ref|><|det|>[[70, 887, 875, 913]]<|/det|> +Undoubtedly, the suggested sample geometry may have a potential technological impact in the future. However, in its current form, the article presents some significant weaknesses. + +<|ref|>text<|/ref|><|det|>[[70, 925, 890, 940]]<|/det|> +The most fragile point is the necessity of a high polarization voltage in the PMN- PT for the effect to become attractive for + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 912, 87]]<|/det|> +technological applications. Reaching 200 V is unfeasible in real systems. Although the authors address this fragility in the article, they suggest that the deposition of PMN- PT films could reduce this polarization voltage. However, the induction of a ferrimagnetic phase in YIG on buffer layers is very difficult to achieve. + +<|ref|>text<|/ref|><|det|>[[73, 98, 913, 140]]<|/det|> +Therefore, studies regarding the induction of the ferrimagnetic phase of YIG on thin films of PMN- PT become crucial for this work. Moreover, a rigorous study of FMR to verify the linewidth, which can provide information on the damping parameter in the system, should be conducted. + +<|ref|>text<|/ref|><|det|>[[73, 164, 728, 179]]<|/det|> +To assist the authors to improving the quality of the article, I highlight some points to be clarified: + +<|ref|>text<|/ref|><|det|>[[72, 202, 740, 217]]<|/det|> +Line 66: YIG presents a ferrimagnetic phase, not a ferromagnetic one, as highlighted in the article. + +<|ref|>text<|/ref|><|det|>[[72, 229, 870, 257]]<|/det|> +Line 159: The mechanism observed in the results of this article may be connected with "recoil magnetization curves" presented in the reference PHYSICAL REVIEW B 104, 054436 (2021). + +<|ref|>text<|/ref|><|det|>[[72, 268, 896, 295]]<|/det|> +Line 204: It is not clear in the article the difference between the named Device 1 and Device 2 referenced by the authors. This point needs correction. + +<|ref|>text<|/ref|><|det|>[[72, 307, 900, 334]]<|/det|> +Line 210: The measurement of local temperature from the change in Pt resistance should be reviewed by the authors. No study of thermal stability in the platinum film was presented. + +<|ref|>text<|/ref|><|det|>[[72, 346, 912, 386]]<|/det|> +Line 245: The authors indicate that there might be a change in the magnetic anisotropy of YIG due to magnetoelastic coupling between the PMN- PT layer and YIG. However, studies demonstrate that the magnetostriction of YIG is small. This statement needs further discussion. + +<|ref|>text<|/ref|><|det|>[[72, 398, 918, 439]]<|/det|> +In summary, although the article has been written quite carefully and the results are promising for technological applications, complementary studies need to be carried out. Especially concerning the production of devices in which the polarization voltage is accessible to integrate this structure into real systems. + +<|ref|>sub_title<|/ref|><|det|>[[73, 463, 162, 476]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 490, 238, 503]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 503, 907, 594]]<|/det|> +In this manuscript, the authors have demonstrated a nonvolatile three- terminal lateral magnon FET based on YIG/PMN- PT heterostructures. They attribute the observed nonvolatile modulations to changes in magnon relaxation within the YIG sublayers. The possible mechanism behind these modulations, including temperature variation, anisotropic exchange stiffness and the emergent electric dipoles from noncollinear spin configuration in YIG, are discussed. While the research topic is interesting, I find that both the experimental setup and related discussion presented by the authors lack sufficient evidence to convince me of its suitability for publication in NC. Therefore, I kindly request that the authors consider the following suggestions and concerns: + +<|ref|>text<|/ref|><|det|>[[72, 606, 909, 672]]<|/det|> +Nonvolatile modulation has been extensively investigated in various systems through transport measurement, such as VO2/PMN- PT(ACS Appl. Mater. Interfaces 2014, 6, 4603- 4608), FePt/PMN- PT(Appl. Phys. Lett. 112, 033506 (2018)), MnPt/PMN- PT (Nat. Nanotech. 14, 131- 136 (2019)), SrRuO3/PMN- PT(Appl. Phys. Lett. 110, 182403 (2017)), and others. Considering device's aspects, similar magnon transistors have also been mentioned in Ref. [22], [31] and [32]. What is the main advantage of the structure in the present study? + +<|ref|>text<|/ref|><|det|>[[72, 672, 916, 790]]<|/det|> +The authors propose that electric polarization is responsible for the large nonvolatile modulation of V_nl^DC. However, it should be noted that in Supplementary Figure 2c, the ferroelectric hysteresis loop (P- E loop) saturates at least \(\pm 8 \text{kV / cm}\) , whereas in Fig. 3b, the maximum voltage is only \(\pm 200 \text{V}\) (equivalent to \(\pm 4 \text{kV / cm}\) with a 0.5 mm thickness of FE substrate), which corresponds to the coercive electric field value. Consequently, under this conditions, the modulation remains unsaturated and unstable due to its dominance by strain, as mentioned in previous literatures refereed to Q1. Did the author conduct experiments using an electric field around or beyond \(\pm 8 \text{kV / cm}\) and then cycle Vg? Additionally, we also notice that there are different on/off ration between device 1 (400%) and device 2 (115%), despite both devices having identical dimensions. How can sample fabrication result in such a significant difference? Is it disparity attributable to an unstable modulation caused by strain? If not, what mechanism accounts for this large variation? + +<|ref|>text<|/ref|><|det|>[[72, 790, 911, 829]]<|/det|> +The authors assume that this non- volatile modulation is due to electric polarization of FE substrate. Given that YIG is oxide insulator, how does electrical polarization transmit? Did the author perform measurements by changing the thickness of YIG? + +<|ref|>text<|/ref|><|det|>[[72, 829, 920, 908]]<|/det|> +In Fig. 3c, the magnetic- field- dependent V_nl^DC exhibits an enhancement near the coercivity at some electric filed (such as \(+200 \text{V}\) ), while disappears at other electric filed (- 160 V). What is the underlying reason for this significant dependence on electric field? Additionally, there is a noticeable difference in coercivity. The authors refer to Ref. 36; however, it seems that this magnetic- field dependence has not been directly measured in their report rather treated to some extent. Therefore it is necessary for the authors to provide an explanation and present the magnetic- field- dependent V_nl^DC before applying any electric field (OV). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 61, 219, 73]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 86, 160, 99]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 111, 238, 125]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 125, 915, 211]]<|/det|> +In this work, the authors deposited ferrimagnet YIG on top of PMN- PT substrate, a nonvolatile magnon transport behavior was experimentally observed. They try to explain the underlying mechanism as an electrical field modulation of the Fe3+ or O2- ions accumulation at the YIG/PMN- PT interface, which could result in magnetoelectric coupling between magnons and the collective excitations of PMN- PT. However, this discussion lack strong evidence for both the collective excitations of PMN- PT and Fe3+ or O2- ions accumulation at interface. How to excite the collective excitations (ferron or phonon) of PMN- PT for a non- local electric measurements? What is the theoretical model of these excitations? + +<|ref|>text<|/ref|><|det|>[[73, 210, 910, 260]]<|/det|> +For the TEM image of the PMN- PT/YIG/Pt heterostructure, not only Mg2+ but also Nb2+ and Ti4+ ions migrated into YIG layer after the deposition. The YIG layer could not a pure YIG in this case. So, the origin of the electric modulation magnon transportation still need to be studied. In this manuscript form, there is not innovative enough to justify its publication on Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 283, 162, 296]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 308, 238, 335]]<|/det|> +(Remarks to the Author) Dear, + +<|ref|>text<|/ref|><|det|>[[73, 347, 911, 387]]<|/det|> +All the weaknesses presented in the original version of the article have been addressed in this new version. The crucial points were resolved by producing new samples and conducting new measurements. For these reasons, I suggest that the present article can be published in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 398, 162, 411]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 424, 238, 437]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 437, 916, 578]]<|/det|> +I have carefully read the revised version of the manuscript. I appreciate the efforts by the authors to address my raised questions. However, I have to follow up on certain points within the response of the authors and hope the authors can address these points. In more detail, see the below: In response to Q2: I notice that the authors demonstrate "all curves were obtained after the electric field had been removed" in the main text, if I understand this correctly, the authors obtain all V_ nl^DC at residual polarization state despite removing from large electric field. If so, I suggest that the authors perform the measurements under +400 V(do not remove electric field, or measuring under the maximum voltage before the device burning except 200 V) and +0 V(residual polarization). In response to Q3: I am confused that the authors demonstrate "For the thickness of YIG increased to 80 nm and 100 nm, the experimental results do not show apparent thickness dependence, all can achieve 20% \(\sim 100\%\) on/off ratio". However, in the main text, for 60 nm YIG, the on/off ratio of device 1 and device 2 are 400 % and 150 %, respectively. How to understand "do not show apparent thickness dependence"? + +<|ref|>text<|/ref|><|det|>[[73, 605, 144, 618]]<|/det|> +Version 3: + +<|ref|>text<|/ref|><|det|>[[73, 632, 219, 645]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 658, 160, 671]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 684, 238, 697]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 697, 920, 737]]<|/det|> +The article have been revised according to all my concerns. A resonable theoretical model about the coupling between ferron and magnon and its influence on the magnon transport was provided. Therefore, I would like to suggest its publication in Nature Communications in the current form. + +<|ref|>text<|/ref|><|det|>[[73, 750, 162, 763]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 776, 238, 790]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 790, 920, 829]]<|/det|> +I have carefully read the revised version of the manuscript (NCOMMS- 23- 58821C). The authors gave a detailed response to the raised concerns of the reviewers and also carried out necessary changes in their revised manuscript. So, I think the current version can be published in Nature Communications. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[179, 123, 385, 139]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[179, 142, 463, 158]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 160, 819, 306]]<|/det|> +Reviewer #1 (Remarks to the Author):In this manuscript, the authors report a three- terminal lateral magnon field effect transistor which can work at room temperature. The ferromagnetic insulator material \(\mathrm{Y}_3\mathrm{Fe}_5\mathrm{O}_{12}\) (YIG) and heavy metal Pt is used here. The large on/off ratio can be achieved by applied a voltage pulse in G- stripes of devices up to \(400\%\) . There is no doubt that devices related to magneton control are very important for information transmission. However, the data in this manuscript are not well discussed. There are also problems with the function of the device. The manuscript cannot be recommended to be published on Nature Communications based on the following questions. + +<|ref|>sub_title<|/ref|><|det|>[[179, 310, 422, 326]]<|/det|> +## General response Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[178, 331, 819, 415]]<|/det|> +General response Reviewer #1:We sincerely thank Reviewer #1 for the time and efforts spent in evaluating our manuscript. We are grateful to Reviewer #1 for commenting that devices related to magneton control are very important for information transmission. In the following, we provide point- by- point answers to all the questions/comments raised. + +<|ref|>sub_title<|/ref|><|det|>[[178, 437, 300, 453]]<|/det|> +## Main comments + +<|ref|>text<|/ref|><|det|>[[178, 456, 819, 547]]<|/det|> +Main comments1. So far, there have been many reports on the YIG/PNM- PT ferroelectric- ferromagnetic heterostructures. Such as magnetoelectric coupling and non- volatility (DOI: 10.1002/aelm.201800663), and achieve changes in amplitude and phase (DOI:10.1088/1361- 6463/abce7c). It seems that the work is not innovative enough to justify its publication on Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[179, 550, 375, 566]]<|/det|> +## Response Reviewer #1-1: + +<|ref|>text<|/ref|><|det|>[[178, 572, 819, 723]]<|/det|> +We thank Reviewer #1 for pointing out these references to us. We are aware of these, and the first one is from our previous work. The first reference (DOI: 10.1002/aelm.201800663) reported the nonvolatile control of the in- plane magnetic anisotropy of YIG films deposited on PMN- PT as well as the spin pumping induced inverse spin Hall effect in Pt on top of the YIG films. And the second reference (DOI:10.1088/1361- 6463/abce7c) discussed the volatile manipulation of the damping constant of the YIG films on PMN- PT via the piezo effect. + +<|ref|>text<|/ref|><|det|>[[178, 728, 819, 855]]<|/det|> +It is quite clear none of these works deal with the non- local magnon transport, not to mention the nonvolatile magnon field effect transistor. To our best knowledge, this manuscript is the first report on the nonvolatile magnon field effect transistor. As the reviewer points out, there is no doubt that the devices related to magneton control are very important for information transmission. We hope the reviewer will find our revised manuscript suitable for publication on Nature Communications. + +<|ref|>text<|/ref|><|det|>[[177, 876, 817, 894]]<|/det|> +2. The mechanism of operation of the device is not clearly discussed. The authors ruled + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 819, 158]]<|/det|> +out temperature change, piezoelectricity, spin Seebeck effect, spin reflection, etc., and attributed the cause to the change of the local electric polarization direction under the G- strip. For the main conclusions of the work, it would be helpful to present more evidence. + +<|ref|>sub_title<|/ref|><|det|>[[178, 161, 376, 179]]<|/det|> +## Response Reviewer #1-2: + +<|ref|>text<|/ref|><|det|>[[178, 183, 819, 246]]<|/det|> +We thank Reviewer #1 for raising this question. We are sorry for not providing a mechanism in the previous version. In the following, we propose a possible mechanism to explain our main findings. + +<|ref|>text<|/ref|><|det|>[[177, 249, 821, 558]]<|/det|> +As reported by D. Chiba et al. [Sci. Rep. 6, 38005 (2016)], when a ferroelectric layer is electrically polarized oppositely, the strong electrical field induces opposite charge accumulation in its adjacent layer. In our case, when the PMN- PT layer is negatively polarized (Fig. R1a), it could induce \(\mathrm{Fe}^{3 + }\) ions accumulation at the interface. On the contrary, it induces \(\mathrm{O}^{2 - }\) ions accumulation at the interface when the PMN- PT layer is positively polarized (Fig. R1b). Since the \(\mathrm{Fe}^{3 + }\) ions contain magnetic moment and \(\mathrm{O}^{2 - }\) ions have none, this could result in a stronger coupling between the magnon and the collective excitations of PMN- PT in the \(1^{\mathrm{st}}\) case as compared with the \(2^{\mathrm{nd}}\) one. The collective excitation can be either the ferron (Fig. R1c) or phonon (Fig. R1d) [Phys. Rev. Lett. 128, 047601 (2022); Phys. Rev. B 106, L081105 (2022); Rev. Mod. Phys. 70, 523- 536 (1998); Appl. Phys. Lett. 107, 062901 (2015)], especially when they have similar energy and wavevector as the magnon. The magnon thus has different dissipation and diffusion lengths when PMN- PT is polarized oppositely, resulting in an electrical field modulation of the magnon propagation, i.e., the magnon FET. + +<|ref|>image<|/ref|><|det|>[[258, 567, 728, 808]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 818, 820, 905]]<|/det|> +
Fig. R1 a, b Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized. c, d show the possible coupling of the magnon with ferron and phonon in the strong coupling case.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 108, 821, 282]]<|/det|> +To support the electrical polarization induced modulation of the magnon transport, we provide the comparison of the measured non- local voltage (Fig. 3b in the main text) with the electric modulation of the charge from the same sample. The modulation of the charge, obtained from the sweeping voltage- dependent leakage current shown in Supplementary Fig. 4a [we use the method reported in Ferroelectrics 411, 86 (2010)], can be viewed as an alternative measurement of the electrical polarization. As presented in Fig. R2, they show apparent similarity. This strongly indicates that our voltage control results are closely related to the electrical polarization of PMN- PT. + +<|ref|>image<|/ref|><|det|>[[346, 290, 682, 462]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 469, 820, 515]]<|/det|> +
Fig. R2 Comparison of the measured non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude (red line) and the charge (blue line) as the functions of the gate voltage pulse \(V_{\mathrm{g}}\) for device 1.
+ +<|ref|>text<|/ref|><|det|>[[178, 558, 562, 576]]<|/det|> +Updated manuscript (lines 176- 179; lines 288- 291): + +<|ref|>text<|/ref|><|det|>[[177, 586, 820, 680]]<|/det|> +We also calculated the charge loop (blue curve in Fig. 3b) with the \(V_{\mathrm{g}}\) - dependent leakage current \(^{42}\) and found that they exhibited close similarity, indicating a strong correlation between the observed magnon current modulation and the change of the electric polarization of the FE layer. + +<|ref|>text<|/ref|><|det|>[[177, 685, 820, 790]]<|/det|> +We propose that the modulation is due to polarization- dependent ions ( \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ) accumulation in the YIG layer adjacent to the interface, resulting in different coupling since \(\mathrm{Fe}^{3 + }\) is magnetic while \(\mathrm{O}^{2 - }\) is not. Dynamically, the magnon in YIG could couple with the collective excitation, such as the ferron or phonon in PMN- PT (Supplementary Note 11). + +<|ref|>text<|/ref|><|det|>[[177, 816, 820, 908]]<|/det|> +3. The author mentions that the main function of the device is to realize the control of signal amplitude. However, the device only mentions an on/off ratio of \(400\%\) , and the minimum value is not 0, which may cause difficulties for the real applications. Besides, the on/off can be considered as a switcher. The transistor should own an amplifying transport magnon current function. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[178, 87, 375, 104]]<|/det|> +## Response Reviewer #1-3: + +<|ref|>text<|/ref|><|det|>[[177, 108, 820, 283]]<|/det|> +We thank Reviewer #1 for raising these questions. As shown in Fig. 3d in the main text, we can have well- defined high/low states. This is similar to the high resistance/low resistance states in giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR) where the low resistance values are also not zero. It, however, does not impede their applications, such as magnetic storage and magnetic sensors. Moreover, this is only the first report on the magnon FET. Namely, this kind of study is just in its beginning. We believe its qualities will be significantly improved with further pursuit in near future, leading to real applications. + +<|ref|>text<|/ref|><|det|>[[177, 287, 821, 550]]<|/det|> +We agree that the transistor can either serve as an amplifier or a switch. The amplifying of magnon has also been extensively studied [Phys. Rep. 699, 1 (2017)]. Therefore, it is not the focus of this study. Owning to the high demand for logic devices with low power consumption in post- Moore's era, the modulation of magnon transport with a high on/off ratio and high energy efficiency is main stream of current magnonics studies and hotly pursued. However, it still remains challenging [Phys. Rev. Lett. 120, 097702 (2018); Phys. Rev. B 101, 054436 (2020); Phys. Rev. Lett. 129, 087601 (2022); Sci. Adv. 7, eabg1669 (2021); Phys. Rev. Lett. 132, 076701 (2024)]. In our work, we use a nonvolatile electric field to control the magnon transport, which is the most energy- efficient method reported so far. Given the large on/off ratio we reported, we hope the reviewer will find our results are of critical importance and can recommend the publication of our manuscript. + +<|ref|>text<|/ref|><|det|>[[179, 570, 451, 588]]<|/det|> +Updated manuscript (lines 210- 213): + +<|ref|>text<|/ref|><|det|>[[178, 597, 820, 693]]<|/det|> +Though the minimum value of \(V_{\mathrm{nl}}^{\mathrm{DC}}\) is not 0, it does not impede their applications as long as the high/low states can be well- defined. This is similar to the high resistance/low resistance states in giant magnetoresistance or tunneling magnetoresistance devices, where the low resistance values are also not zero. + +<|ref|>text<|/ref|><|det|>[[178, 716, 819, 754]]<|/det|> +4. What is the contribution of non-volatility to the device, which seems to create additional difficulties for the control of the functionality of the device. + +<|ref|>sub_title<|/ref|><|det|>[[179, 756, 375, 772]]<|/det|> +## Response Reviewer #1-4: + +<|ref|>text<|/ref|><|det|>[[178, 777, 820, 907]]<|/det|> +We thank Reviewer #1 for raising this question. As mentioned in Response Reviewer #1- 3, the modulation of magnon transport with a high on/off ratio and high energy efficiency is main stream in current magnonics studies. Non- volatility only requires applying a voltage pulse instead of a constant voltage to change the functionality of the device when necessary. It does not need to maintain any voltage on the device to keep the functionality, thus significantly reducing power consumption. To + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 87, 818, 127]]<|/det|> +our understanding, it is not much more difficult to apply a voltage pulse than to apply a constant voltage where the sign needs to be switched instantly. + +<|ref|>text<|/ref|><|det|>[[178, 148, 819, 204]]<|/det|> +5. (p. 9, figure 3(c)) Most hysteresis loops exhibit strange behavior. An additional jump signal occurs when the magnetic moment reaches a stable value. A more detailed explanation would be helpful. + +<|ref|>sub_title<|/ref|><|det|>[[178, 207, 375, 223]]<|/det|> +## Response Reviewer #1-5: + +<|ref|>text<|/ref|><|det|>[[177, 228, 821, 534]]<|/det|> +We thank Reviewer #1 for this excellent suggestion. We propose a possible explanation for the additional jump signal. A carton figure shown in Fig. R3 illustrates this process and can qualitatively explain our experimental finding. As mentioned by the reviewer, this additional jump signal occurs near the magnetization switching. During the switching, the system encounters a substantial increase in magnetic susceptibility (Fig. R3b). In this process, the system may generate a burst of magnon upon the thermal excitation (Fig. R3c). The burst of magnon subsequently generates a voltage signal. The sign of the voltage signal is positive or negative depending on whether the excitation of the magnon occurs after or before the coercive field (Figs. R3d and R3g) since it is controlled by the magnetization direction. The measured signal is the sum of both the magnetization- dependent magnon signal (Fig. R3a) and the susceptibility peak induced magnon signal (Figs. R3d or R3g), resulting in the interesting and unusual shapes of loops (Figs. R3e or R3h), respectively. Both loops are observed in our experiments (Figs. R3f and R3i). + +<|ref|>image<|/ref|><|det|>[[243, 546, 755, 822]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 834, 820, 898]]<|/det|> +
Fig. R3 a Schematic loop of a non-local voltage signal generated by the usual SSE. b, c Magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d, g present the corresponding voltage peaks occurring after and before
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 819, 149]]<|/det|> +the coercive field, respectively. \(\mathbf{e}\) , \(\mathbf{h}\) present the corresponding total voltage signals, respectively. \(\mathbf{f}\) , \(\mathbf{i}\) show the typical results observed in our experiments. They show similarities with \(\mathbf{e}\) , \(\mathbf{h}\) , respectively. + +<|ref|>text<|/ref|><|det|>[[177, 174, 821, 283]]<|/det|> +According to the above analysis, these additional jump signals are also generated thermally. It is expected to depend linearly on the heating power, namely, the square of the current. To confirm this, we perform measurements with different values of \(I_{\mathrm{DC}}\) (Fig. R4a). We find that the jump signal ( \(V_{\mathrm{peak}}\) ) indeed scales with the square of \(I_{\mathrm{DC}}\) with the slope of \(644.38 \mathrm{nV / mA^2}\) (Fig. R4b), indicating its thermal origin. + +<|ref|>image<|/ref|><|det|>[[240, 293, 748, 461]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 471, 810, 512]]<|/det|> +
Fig. R4 a Measured non-local voltages with different values of \(I_{\mathrm{DC}}\) . b Dependence of the jump signal voltage with the square of \(I_{\mathrm{DC}}\) .
+ +<|ref|>text<|/ref|><|det|>[[178, 535, 452, 552]]<|/det|> +Updated manuscript (lines 166- 168): + +<|ref|>text<|/ref|><|det|>[[178, 557, 820, 619]]<|/det|> +A similar phenomenon was observed previously, though its origin was not mentioned41. We proposed a possible explanation for this phenomenon (see Supplementary Note 4). + +<|ref|>text<|/ref|><|det|>[[178, 640, 820, 714]]<|/det|> +6. The manuscript realized the modulation of signal amplitude with a high electric voltage (hundreds of volts). However, the integration of the PMN-PT crystal layer is quite difficult. The interfacial characteristics of the YIG/PMN-PT heterostructure should be discussed. + +<|ref|>sub_title<|/ref|><|det|>[[179, 717, 376, 733]]<|/det|> +## Response Reviewer #1-6: + +<|ref|>text<|/ref|><|det|>[[177, 737, 821, 912]]<|/det|> +We thank Reviewer #1 for raising these questions. We understand your concern about the required \(\sim 200\) volts for the device operation. In our previous version, we anticipate that a low voltage operation of the device can be achieved by replacing the PMN-PT crystal with PMN-PT thin film since it can be grown with sputtering on Si or SrTiO3 substrates with considerable polarization at relatively low voltage [Science 334, 958 (2011); Nature 578, 75 (2020)]. The growth temperature of high-quality PMN-PT film, however, is beyond the maximum temperature that we can reach in our sputtering system. Alternatively, we prepared a 400- nm PZT (PbZr0.52Ti0.48O3) film on an Nb- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 85, 822, 401]]<|/det|> +doped \(\mathrm{SrTiO_3(001)}\) substrate. Figure R5a presents the X- ray diffraction data, where the peaks of the PZT film have a similar order of intensities with those from the substrate (denoted with \*) indicating the high quality of the 001- oriented PZT film. The electrical polarization curve exhibits a clear hysteresis loop with remnant polarization of \(\sim 37 \mu \mathrm{C / cm}^2\) , and it can be switched less than \(10 \mathrm{~V}\) (Fig. R5b). On top of it, we grow 65- nm thick YIG film, which shows a saturation magnetization around \(9.66 \times 10^4 \mathrm{~A / m}\) (Fig. R5c), slightly smaller than the value of the YIG film grown on PMN- PT substrate. We further used it and prepared the magnon FET device similar to the one shown in Fig. 3 in the main text. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{~V}\) gate voltages (Fig. R5d). This demonstrates the feasibility of our anticipation, i.e., the device can be operated in the \(\sim 10 \mathrm{~V}\) range when a thin ferroelectric film is used. It also indicates the generality of our magnon FET device since it works with either PMN- PT or PZT material. + +<|ref|>image<|/ref|><|det|>[[240, 409, 755, 732]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[175, 738, 821, 867]]<|/det|> +
Fig. R5 a X-ray diffraction of a 400-nm (001)-oriented PZT film grown on an Nb-doped \(\mathrm{SrTiO_3(001)}\) substrate. b Electrical polarization loop of the PZT film shown in a. c Magnetic hysteresis loop of a 65-nm YIG film on top of the PZT film with a MgO buffer layer. d Non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude as a function of the gate voltage pulse \(V_{\mathrm{g}}\) for the device prepared on the PZT film.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 85, 821, 438]]<|/det|> +We also followed the reviewer's suggestion and performed the cross- sectional TEM measurements to characterize the interfacial characteristics of the PMN- PT/YIG/Pt heterostructure. Figure R6 presents the high- angle angular dark field (HAADF) images with energy dispersive X- ray spectroscopy (EDS) of PMN- PT/YIG/Pt sample, performed via a JEM- ARM200F microscope at \(200\mathrm{kV}\) . Figure R6a presents the HAADF image of the cross- sectional view of PMN- PT/YIG/Pt with four regions (I, II, III, IV) zoom- in view shown in Figs. R6b- R6e, respectively. Figures R6b and R6e show sharp interfaces between Pt and YIG layer, and between YIG layer and PMN- PT substrate, respectively. We notice that the YIG layer (for example, region III) looks a bit of a color gradient. However, zoom- in features on all four regions show that the YIG has good crystallinity with almost the same lattice distribution. To that end, we further performed elemental mapping along the layers stack (Fig. R6f). The different colored maps of Pt, Fe, Y, Mg, Pb, Ti and Nb elements indicate they are well separated in their corresponding regions. Even though there is a slight migration of Mg into the YIG layer, the YIG layer near the YIG/PMN- PT interface maintains its structure well (top panel of Fig. R6e). + +<|ref|>image<|/ref|><|det|>[[190, 446, 802, 763]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 774, 821, 882]]<|/det|> +
Fig. R6 a HAADF-TEM image of the PMN-PT/YIG/Pt sample. b, c, d and e Zoom-in features of a for regions I, II, III, IV, respectively. The inset of c and e (bottom panel) show the corresponding diffraction patterns of YIG and PMN-PT, respectively. The inset of e (top panel) shows the magnified view of YIG layer. f The corresponding EDS elemental mapping as marked in each panel.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 83, 512, 100]]<|/det|> +Updated manuscript (line 93; lines 318- 323): + +<|ref|>text<|/ref|><|det|>[[214, 105, 792, 125]]<|/det|> +The structure and magnetic properties are presented in Supplementary Note 1. + +<|ref|>text<|/ref|><|det|>[[177, 128, 820, 236]]<|/det|> +The growth temperature of high- quality PMN- PT film, however, is beyond the maximum temperature that we can reach in our sputtering system. Instead, we deposited a 400- nm PZT (PbZr \(_{0.52}\) Ti \(_{0.48}\) O \(_{3}\) ) film on an Nb- doped SrTiO \(_{3}\) (001) substrate and further prepared a magnon field effect transistor. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{~V}\) gate voltages (Supplementary Note 12). + +<|ref|>text<|/ref|><|det|>[[178, 256, 462, 274]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[177, 275, 820, 515]]<|/det|> +The presented work is well- founded and holds a significantly innovative character. The success in inducing a ferrimagnetic (non- ferromagnetic) phase in the YIG film on a PMN- PT substrate is surprising. Undoubtedly, the suggested sample geometry may have a potential technological impact in the future. However, in its current form, the article presents some significant weaknesses. The most fragile point is the necessity of a high polarization voltage in the PMN- PT for the effect to become attractive for technological applications. Reaching 200 V is unfeasible in real systems. Although the authors address this fragility in the article, they suggest that the deposition of PMN- PT films could reduce this polarization voltage. However, the induction of a ferrimagnetic phase in YIG on buffer layers is very difficult to achieve. Therefore, studies regarding the induction of the ferrimagnetic phase of YIG on thin films of PMN- PT become crucial for this work. Moreover, a rigorous study of FMR to verify the linewidth, which can provide information on the damping parameter in the system, should be conducted. + +<|ref|>sub_title<|/ref|><|det|>[[178, 517, 424, 534]]<|/det|> +## General response Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[177, 538, 820, 669]]<|/det|> +We sincerely thank Reviewer #2 for the time and effort spent in evaluating our manuscript. We are grateful to Reviewer #2 for commenting that our work is "well- founded and holds a significantly innovative character" and that "the suggested sample geometry may have a potential technological impact in the future undoubtedly". In the following, we provide detailed answers to all the questions/comments raised point- by- point. + +<|ref|>sub_title<|/ref|><|det|>[[178, 695, 375, 712]]<|/det|> +## Response Reviewer #2-1: + +<|ref|>text<|/ref|><|det|>[[177, 716, 820, 914]]<|/det|> +We understand Reviewer #2's concern about the required \(\sim 200\) volts for the device operation. In our previous version, we anticipate that a low voltage operation of the device can be achieved by replacing the PMN- PT bulk crystal with PMN- PT thin film since it can be grown with sputtering on Si or SrTiO \(_{3}\) substrates with considerable polarization at relatively low voltage [Science 334, 958 (2011); Nature 578, 75 (2020)]. The growth temperature of high- quality PMN- PT film, however, is beyond the maximum temperature that we can reach in our sputtering system. Alternatively, we prepared a 400- nm PZT (PbZr \(_{0.52}\) Ti \(_{0.48}\) O \(_{3}\) ) film on an Nb- doped SrTiO \(_{3}\) (001) substrate. Figure R7a presents the X- ray diffraction data, where the peaks of the PZT film have a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 85, 822, 357]]<|/det|> +similar order of intensities with those from the substrate (denoted with \*) indicating the high quality of the 001- oriented PZT film. The electrical polarization curve exhibits a clear hysteresis loop with remnant polarization of \(\sim 37 \mu \mathrm{C} / \mathrm{cm}^2\) and it can be switched using a voltage of less than \(10 \mathrm{~V}\) (Fig. R7b). On top of it, we grow 65- nm thick YIG film, which shows a saturation magnetization around \(9.66 \times 10^4 \mathrm{~A} / \mathrm{m}\) (Fig. R7c), slightly smaller than the value of the YIG film grown on PMN- PT substrate. We further used it and prepared the magnon FET device similar to the one shown in Fig. 3 in the main text. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{~V}\) gate voltages (Fig. R7d). This demonstrates the feasibility of our anticipation, i.e., the device can be operated in the \(\sim 10 \mathrm{~V}\) range when a thin ferroelectric film is used. It also indicates the generality of our magnon FET device since it works with either PMN- PT or PZT material. + +<|ref|>image<|/ref|><|det|>[[240, 365, 755, 686]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[175, 693, 822, 823]]<|/det|> +
Fig. R7 a X-ray diffraction of a 400-nm (001)-oriented PZT film grown on an Nb-doped SrTiO₃(001) substrate. b Electrical polarization loop of the PZT film shown in a. c Magnetic hysteresis loop of a 65-nm YIG film on top of the PZT film with a MgO buffer layer. d Non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude as a function of the gate voltage pulse \(V_{\mathrm{g}}\) for the device prepared on the PZT film.
+ +<|ref|>text<|/ref|><|det|>[[177, 853, 452, 871]]<|/det|> +Updated manuscript (lines 318- 323): + +<|ref|>text<|/ref|><|det|>[[212, 875, 819, 894]]<|/det|> +The growth temperature of high- quality PMN- PT film, however, is beyond the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 820, 172]]<|/det|> +maximum temperature that we can reach in our sputtering system. Instead, we deposited a 400- nm PZT (PbZr \(_{0.52}\) Ti \(_{0.48}\) O \(_{3}\) ) film on an Nb- doped SrTiO \(_{3}\) (001) substrate and further prepared a magnon field effect transistor. This device exhibits \(\sim 28\%\) on/off ratio under \(\pm 10 \mathrm{V}\) gate voltages (Supplementary Note 12). + +<|ref|>sub_title<|/ref|><|det|>[[178, 198, 375, 215]]<|/det|> +## Response Reviewer #2-2: + +<|ref|>text<|/ref|><|det|>[[177, 219, 821, 424]]<|/det|> +We followed the suggestions and investigated the damping parameter and magnetization information of our sample on the PMN- PT substrate. Figure R8a presents the relationship between linewidth and microwave frequency under \(\pm 200 \mathrm{V}\) - gate voltages, the damping factor by linear fitting at \(- 200 \mathrm{V}\) ( \(1.95 \times 10^{- 3}\) ) is \(\sim 11\%\) lower than that of \(+200 \mathrm{V}\) ( \(2.16 \times 10^{- 3}\) ). In addition, we measured the relationship between the microwave frequency and the resonant magnetic field of the system under \(\pm 200 \mathrm{V}\) - gate voltages (Fig. R8b), and the Kittel equation fitting results show that the effective magnetization change is less than \(1.8\%\) . + +<|ref|>image<|/ref|><|det|>[[247, 433, 755, 602]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 612, 820, 697]]<|/det|> +
Fig. R8 a Frequency-dependent linewidth \(\Delta H\) under \(\pm 200 \mathrm{V}\) -gate voltages, respectively. The dots are the experimental data and the lines are the linear fittings. b Field-dependent resonance frequency \(f\) under \(\pm 200 \mathrm{V}\) -gate voltages, respectively. The dots are experimental data and the lines are the fittings with the Kittel equation.
+ +<|ref|>text<|/ref|><|det|>[[177, 722, 821, 898]]<|/det|> +It is generally believed that the smaller the damping factor, the further magnons can travel. The measured change of the damping constant seems to contradict to our non- local voltage results where \(+200 \mathrm{V}\) has a larger amplitude. This seeming discrepancy could be understood as follows. The measurement performed at GHz range (Fig. R8a) only characterizes the damping constant of the Kittel model. Recent theoretical calculation by Joseph Barker and Gerrit E.W. Bauer [Phys. Rev. Lett. 117, 217201 (2016)] about the thermal spin dynamics of Yttrium Iron Garnet, however, shows that the antiferromagnetic or optical mode is found to suppress the spin Seebeck + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 820, 216]]<|/det|> +effect at room temperature and beyond. For the convenience of the reviewer, we copy Fig. 1 in this reference as Fig. R9 herein. It shows that the spin Seebeck effect is dominated by the high- frequency mode at \(\sim 6\) THz at \(300\mathrm{K}\) . At this frequency, the strong coupling of the magnon with the ferron/phonon may open up new additional dissipation channel and significantly influence the non- local magnon transport, resulting in a magnon FET according to the mechanism proposed in Fig. R1. + +<|ref|>text<|/ref|><|det|>[[177, 330, 818, 370]]<|/det|> +Fig. R9 [copied from Phys. Rev. Lett. 117, 217201 (2016) and for Reviewers only] YIG spin wave spectrum as calculated for different temperatures. + +<|ref|>text<|/ref|><|det|>[[178, 394, 401, 411]]<|/det|> +Updated manuscript (line 93): + +<|ref|>text<|/ref|><|det|>[[178, 417, 755, 435]]<|/det|> +The structure and magnetic properties are presented in Supplementary Note 1. + +<|ref|>text<|/ref|><|det|>[[178, 455, 818, 491]]<|/det|> +To assist the authors to improving the quality of the article, I highlight some points to be clarified: + +<|ref|>text<|/ref|><|det|>[[178, 493, 818, 528]]<|/det|> +1. Line 66: YIG presents a ferrimagnetic phase, not a ferromagnetic one, as highlighted in the article. + +<|ref|>sub_title<|/ref|><|det|>[[178, 532, 375, 549]]<|/det|> +## Response Reviewer #2-2: + +<|ref|>text<|/ref|><|det|>[[178, 554, 818, 592]]<|/det|> +We thank Reviewer #2 for raising this important comment. We corrected this in the updated manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 614, 818, 669]]<|/det|> +2. Line 159: The mechanism observed in the results of this article may be connected with "recoil magnetization curves" presented in the reference PHYSICAL REVIEW B 104, 054436 (2021). + +<|ref|>sub_title<|/ref|><|det|>[[178, 673, 375, 690]]<|/det|> +## Response Reviewer #2-3: + +<|ref|>text<|/ref|><|det|>[[178, 695, 818, 757]]<|/det|> +We sincerely thank Reviewer #2 for providing the relevant reference to us. In the data of this reference, the peak occurs near the hard axis in the film plane, which is different from ours. + +<|ref|>text<|/ref|><|det|>[[178, 761, 820, 912]]<|/det|> +We propose a possible mechanism and further conduct relevant experimental measurements. This additional jump signal occurs near the magnetization switching. During the switching, the system encounters a substantial increase in magnetic susceptibility. In this process, the system may generate a burst of magnon upon the thermal excitation. The burst of magnon subsequently generates a voltage signal. The sign of the voltage signal is positive or negative depending on whether the excitation of the magnon occurs after or before the coercive field (Figs. R10d and R10g). The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 85, 821, 261]]<|/det|> +measured signal is the sum of both the magnetization- dependent magnon signal (Fig. R10a) and the susceptibility peak induced magnon signal (Figs. R10d and R10g), resulting in the interesting and unusual shape of loops (Figs. R10e and R10h), respectively. Both loops are observed in our experiments (Figs. R10f and R10i). According to our experimental measurements (Fig. R4), the peak voltages are scaled with the square of the \(I_{\mathrm{DC}}\) , indicating its thermal origin. The detailed results are presented in Response Reviewer #1- 5. For the convenience of Reviewer #2, we also present the main schematic diagram here (Fig. R10). + +<|ref|>image<|/ref|><|det|>[[243, 272, 755, 549]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 560, 821, 690]]<|/det|> +
Fig. R10 a. Schematic loop of a non-local voltage signal generated by the usual SSE. b, c. Magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d, g present the corresponding voltage peaks occurring after and before the coercive field, respectively. e, h present the corresponding total voltage signals, respectively. f, i present the results observed in our experimental measurements. They show apparent similarities with e, h, respectively.
+ +<|ref|>text<|/ref|><|det|>[[178, 712, 452, 730]]<|/det|> +Updated manuscript (lines 166- 168): + +<|ref|>text<|/ref|><|det|>[[178, 735, 820, 798]]<|/det|> +A similar phenomenon was observed previously, though its origin was not mentioned41. We proposed a possible explanation for this phenomenon (see Supplementary Note 4). + +<|ref|>text<|/ref|><|det|>[[178, 818, 820, 855]]<|/det|> +3. Line 204: It is not clear in the article the difference between the named Device 1 and Device 2 referenced by the authors. This point needs correction. + +<|ref|>sub_title<|/ref|><|det|>[[178, 858, 376, 874]]<|/det|> +## Response Reviewer #2-4: + +<|ref|>text<|/ref|><|det|>[[210, 879, 818, 897]]<|/det|> +We thank Reviewer #1 for raising this question. Device 1 and device 2 are prepared + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[176, 85, 821, 483]]<|/det|> +on different PMN- PT substrates. The different on/off ratio between device 1 (400%) and device 2 (115%) may be caused by various reasons, such as different substrates induced variation and the variation caused by complicated fabrication process. The ferroelectric substrate we used is \(\mathrm{[Pb(Mg_{1 / 3}Nb_{2 / 3})O_{3}]_{(1 - x)}[PbTiO_{3}]_{x}}\) (PMN- PT), whose property depends sensitively on the composition. The substrate from the different positions of a wafer may have different properties resulting in different device performance. And the YIG films may also exhibit non- uniform properties after polarizing the PMN- PT substrates. In addition, the fabrication processes may also introduce performance fluctuations among different samples. We took these two samples and performed the scanning electron microscopy measurements and found that the gap widths of these two devices are slightly different (585 nm for device 1 vs. 526 nm for device 2) even though we intended to have 550- nm width originally. To further reveal the role of the gap width, we prepared two series of samples with different gate widths on two substrates, respectively. The measured results (Fig. R11) show a tendency of a higher on/off ratio with larger gate- stipe widths in both series, suggesting the dissipation of the magnon transport in the gate is of critical importance for the magnon FET. The quantitative difference in the performance of these two series also indicates the important role of the substrate. + +<|ref|>image<|/ref|><|det|>[[354, 496, 644, 679]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 690, 819, 730]]<|/det|> +
Fig. R11 Gate width dependent on/off ratio for two series samples prepared on two PMN-PT substrates, respectively.
+ +<|ref|>text<|/ref|><|det|>[[178, 754, 562, 771]]<|/det|> +Updated manuscript (lines 221- 222; lines 232- 234): + +<|ref|>text<|/ref|><|det|>[[178, 777, 818, 815]]<|/det|> +Fig. 4a, devices 2 and device 1 have similar dimensions but were prepared on different PMN- PT substrates. + +<|ref|>text<|/ref|><|det|>[[178, 820, 819, 882]]<|/det|> +To further reveal the role of the gap width and substrate, we performed the gate width dependent on/off ratio measurements with two series of samples fabricated on two different pieces of PMN- PT substrates (Supplementary Note 7). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 819, 140]]<|/det|> +4. Line 210: The measurement of local temperature from the change in Pt resistance should be reviewed by the authors. No study of thermal stability in the platinum film was presented. + +<|ref|>sub_title<|/ref|><|det|>[[178, 143, 376, 160]]<|/det|> +## Response Reviewer #2-5: + +<|ref|>text<|/ref|><|det|>[[177, 164, 821, 272]]<|/det|> +We thank Reviewer #2 for this excellent suggestion. We follow the reviewer's suggestions and measure the change of Pt resistivity by varying the injection DC current \(I\) and the measurement time \(t\) , the results show that the Pt resistivity is linear with the square of \(I\) (Fig. R12a), and the change of Pt resistivity is lower than \(0.2\%\) with \(I = 0.30\) mA for almost 60 minutes (Fig. R12b). + +<|ref|>image<|/ref|><|det|>[[252, 284, 757, 450]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 466, 820, 545]]<|/det|> +
Fig. R12 a Dependence of the resistivity of Pt stripe, \(\rho_{\mathrm{pt}}\) on the square of DC current \(I\) . The symbols are the experimental data and the line is a linear fitting. b Dependence of \(\rho_{\mathrm{pt}}\) on the measurement time.
+ +<|ref|>text<|/ref|><|det|>[[178, 575, 451, 593]]<|/det|> +Updated manuscript (lines 238- 239): + +<|ref|>text<|/ref|><|det|>[[178, 598, 819, 638]]<|/det|> +And the resistance remains almost constant under a certain DC current (Supplementary Note 8). + +<|ref|>text<|/ref|><|det|>[[178, 658, 819, 732]]<|/det|> +5. Line 245: The authors indicate that there might be a change in the magnetic anisotropy of YIG due to magnetoelastic coupling between the PMN-PT layer and YIG. However, studies demonstrate that the magnetostriction of YIG is small. This statement needs further discussion. + +<|ref|>sub_title<|/ref|><|det|>[[178, 735, 376, 752]]<|/det|> +## Response Reviewer #2-6: + +<|ref|>text<|/ref|><|det|>[[178, 756, 821, 908]]<|/det|> +We thank Reviewer #2 for raising this question. In line 245 of our previous manuscript, we mentioned that "magnetoelectric coupling between YIG and PMN- PT can result in a change of magnetic anisotropy in YIG". In addition to the magnetoelastic coupling, the charge accumulation at the interface due to the different polarization may also influence the properties of YIG (as depicted in Figs. R1a and R1b). For the convenience, we copy Fig. R1 as Fig. R13 herein. And the control of anisotropy in YIG/PMN- PT bilayer has been reported in the literatures [such as Phys. Rev. Applied + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 127]]<|/det|> +10, 014004 (2018), Adv. Electron. Mater. 5, 1800663 (2019)]. We added a short discussion in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[256, 138, 732, 375]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 388, 820, 475]]<|/det|> +
Fig. R13 a, b Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized. c, d show the possible coupling of the magnon with ferron and phonon in the strong coupling case.
+ +<|ref|>text<|/ref|><|det|>[[178, 498, 452, 515]]<|/det|> +Updated manuscript (lines 288- 291): + +<|ref|>text<|/ref|><|det|>[[177, 520, 820, 627]]<|/det|> +We propose that the modulation is due to polarization- dependent ions \(\mathrm{(Fe^{3 + }}\) or \(\mathrm{O^{2 - }}\) accumulation in the YIG layer adjacent to the interface, resulting in different coupling since \(\mathrm{Fe^{3 + }}\) is magnetic while \(\mathrm{O^{2 - }}\) is not. Dynamically, the magnon in YIG could couple with the collective excitation, such as the ferron or phonon in PMN- PT (Supplementary Note 11). + +<|ref|>text<|/ref|><|det|>[[178, 648, 820, 722]]<|/det|> +In summary, although the article has been written quite carefully and the results are promising for technological applications, complementary studies need to be carried out. Especially concerning the production of devices in which the polarization voltage is accessible to integrate this structure into real systems. + +<|ref|>sub_title<|/ref|><|det|>[[178, 725, 460, 742]]<|/det|> +## Summarized response Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[177, 746, 820, 898]]<|/det|> +We are very grateful to Reviewer #2 for giving us the above positive comments. We also thank Reviewer #2 for raising several critical questions/comments which are very helpful in improving the quality of our manuscript. As listed above, we addressed all these questions/comments with our best efforts, especially including the significantly lowered voltage, which is accessible when integrating this structure into real systems. We hope the reviewer will find our responses satisfying and can recommend the publication of our revised manuscript on Nature Communications. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 103, 463, 120]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 122, 820, 270]]<|/det|> +Reviewer #3 (Remarks to the Author):In this manuscript, the authors have demonstrated a nonvolatile three- terminal lateral magnon FET based on YIG/PMN- PT heterostructures. They attribute the observed nonvolatile modulations to changes in magnon relaxation within the YIG sublayers. The possible mechanism behind these modulations, including temperature variation, anisotropic exchange stiffness and the emergent electric dipoles from noncollinear spin configuration in YIG, are discussed. While the research topic is interesting, I find that both the experimental setup and related discussion presented by the authors lack sufficient evidence to convince me of its suitability for publication in NC. + +<|ref|>sub_title<|/ref|><|det|>[[179, 273, 424, 290]]<|/det|> +## General response Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[178, 294, 821, 378]]<|/det|> +We sincerely thank Reviewer #3 for the time and effort spent in evaluating our manuscript. We are delighted to learn that Reviewer #3 thinks the research topic of nonvolatile three- terminal lateral magnon FET is interesting. In the following, we provide detailed answers to all the questions/comments raised point- by- point. + +<|ref|>text<|/ref|><|det|>[[178, 399, 820, 436]]<|/det|> +Therefore, I kindly request that the authors consider the following suggestions and concerns: + +<|ref|>text<|/ref|><|det|>[[178, 437, 820, 567]]<|/det|> +1. Nonvolatile modulation has been extensively investigated in various systems through transport measurement, such as \(\mathrm{VO_2 / PMN - PT(ACS}\) Appl. Mater. Interfaces 2014, 6, 4603-4608), FePt/PMN-PT(Appl. Phys. Lett. 112, 033506 (2018)), MnPt/PMN-PT (Nat. Nanotech. 14, 131-136 (2019)), SrRuO3/PMN-PT(Appl. Phys. Lett. 110, 182403 (2017)), and others. Considering device's aspects, similar magnon transistors have also been mentioned in Ref. [22], [31] and [32]. What is the main advantage of the structure in the present study? + +<|ref|>sub_title<|/ref|><|det|>[[179, 570, 375, 586]]<|/det|> +## Response Reviewer #3-1: + +<|ref|>text<|/ref|><|det|>[[177, 590, 820, 898]]<|/det|> +Response Reviewer #3- 1:We sincerely thank Reviewer #3 for raising these questions. For researchers seeking magnonic transistors, the most important consideration is how to reduce the power consumption of the device, compared to the electronic transistor. A magnetic insulator (such as YIG) are better than a conductor as the Joule heating is absent in the insulator. In addition, one needs to find a way to control of the magnon transmission process without introducing additional power consumption. In this sense, electric- field- controlled with non- volatility (this work) is naturally the best choice. The pioneer works such as microwave current- controlled [A. V. Chumak et al. Nat. Commun. 5, 4700 (2014)], magnetic field- controlled [K. S. Das et al. Phys. Rev. B 101, 054436 (2020); Santos, O. A. et al. Phys. Rev. Applied 15, 014038 (2021)] or DC current- controlled [L. J. Cornelissen et al. Phys. Rev. Lett. 120, 097702 (2018)] present different possibilities in controlling the magnon current, but not the most energy efficient. In our manuscript, we cited these pioneer works and compared them with our devices. We also included the references recommended by Reviewer #3. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 106, 433, 123]]<|/det|> +Updated manuscript (lines 93- 96): + +<|ref|>text<|/ref|><|det|>[[178, 129, 819, 191]]<|/det|> +YIG is chosen because it has low damping, which is suitable for magnon transport, and is an insulator where the joule heating is absent. Besides, PMN- PT has been demonstrated to exhibit nonvolatile modulation on various transport properties34- 37. + +<|ref|>text<|/ref|><|det|>[[177, 211, 820, 452]]<|/det|> +2. The authors propose that electric polarization is responsible for the large nonvolatile modulation of \(\mathrm{V\_nl^{\wedge}DC}\) . However, it should be noted that in Supplementary Figure 2c, the ferroelectric hysteresis loop (P-E loop) saturates at least \(\pm 8\mathrm{kV / cm}\) , whereas in Fig. 3b, the maximum voltage is only \(\pm 200\mathrm{V}\) (equivalent to \(\pm 4\mathrm{kV / cm}\) with a \(0.5\mathrm{mm}\) thickness of FE substrate), which corresponds to the coercive electric field value. Consequently, under these conditions, the modulation remains unsaturated and unstable due to its dominance by strain, as mentioned in previous literatures refereed to Q1. Did the author conduct experiments using an electric field around or beyond \(\pm 8\mathrm{kV / cm}\) and then cycle \(\mathrm{V_g?}\) Additionally, we also notice that there are different on/off ration between device 1 \((400\%)\) and device 2 \((115\%)\) , despite both devices having identical dimensions. How can sample fabrication result in such a significant difference? Is it disparity attributable to an unstable modulation caused by strain? If not, what mechanism accounts for this large variation? + +<|ref|>sub_title<|/ref|><|det|>[[178, 456, 375, 472]]<|/det|> +## Response Reviewer #3-2: + +<|ref|>text<|/ref|><|det|>[[214, 477, 586, 495]]<|/det|> +We thank Reviewer #3 for raising these questions. + +<|ref|>text<|/ref|><|det|>[[177, 499, 820, 650]]<|/det|> +We first provide the comparison of the measured gate voltage- dependent non- local voltage (Fig. 3b in the main text) with the charge from the same sample. The modulation of the charge, which represents the polarization change, is obtained through integration over the sweeping time from the sweeping voltage- dependent leakage curve shown in Supplementary Fig. 4a [Ferroelectrics 411, 86 (2010)]. The result is presented in Fig. R14 and they show close similarity. This strongly indicates that our voltage control results are related to the electrical polarization of PMN- PT. + +<|ref|>image<|/ref|><|det|>[[330, 658, 667, 830]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 836, 820, 882]]<|/det|> +
Fig. R14 Non-local voltage \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude(red line) and the charge(blue line) as the functions of the gate voltage pulse \(V_{\mathrm{g}}\) for device 1, respectively.
+ +<|ref|>text<|/ref|><|det|>[[213, 891, 820, 909]]<|/det|> +We also noticed that the electric field required for the saturation of \(P - E\) curve is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 237]]<|/det|> +larger than that we used in the magnon transport modulation. We followed the suggestion and performed measurements with higher gate voltage. The experimental results show that the larger (lower) non- local voltage with higher positive (negative) gate voltages (Fig. R15), indicating its dependence on the residual polarization values and directions of FE substrate. We found that the devices are easily burned when the applied voltage is larger than 200 V. Thus, we limited our discussion with the applying voltage smaller than 200 V. + +<|ref|>image<|/ref|><|det|>[[340, 250, 654, 450]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 463, 818, 504]]<|/det|> +
Fig. R15 The non-local voltages measurement with different gate voltages. The curves are shifted for clarity.
+ +<|ref|>text<|/ref|><|det|>[[177, 529, 821, 905]]<|/det|> +As for the different on/off ratio between device 1 (400%) and device 2 (115%), it may be caused by various reasons, such as different substrates induced variation and the variation caused by complicated fabrication processes. The ferroelectric substrate we used is \([\mathrm{Pb(Mg_{1 / 3}Nb_{2 / 3})O_{3}}]_{(1 - x)} - [\mathrm{PbTiO_{3}}]_{x}\) (PMN- PT), whose property depends sensitively on the composition. The substrate from the different positions of a wafer may have different properties, resulting in different device performance. And the YIG films may also exhibit non- uniform properties after polarizing the PMN- PT substrates. In addition, the fabrication processes may also introduce performance fluctuations among different samples. We took these two samples and performed the scanning electron microscopy measurements and found that the gap widths of these two devices are slightly different (585 nm for device 1 vs. 526 nm for device 2) even though we intended to have 550- nm width originally. To further reveal the role of the gap width, we prepared two series of samples with different gate widths on two substrates, respectively. The measured results (Fig. R16) show a tendency of a higher on/off ratio with larger gate- stripe widths in both series, suggesting the dissipation of the magnon transport in the gate is of critical importance for the magnon FET. The quantitative difference on the performance of these two series devices also indicates the important + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 88, 330, 103]]<|/det|> +role of the substrate. + +<|ref|>image<|/ref|><|det|>[[370, 116, 660, 301]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[177, 312, 819, 352]]<|/det|> +
Fig. R16 Gate width dependent on/off ratio for two series samples prepared on two PMN-PT substrates, respectively.
+ +<|ref|>text<|/ref|><|det|>[[178, 375, 673, 394]]<|/det|> +Updated manuscript (lines 176- 179; lines 214- 216; lines 224- 234): + +<|ref|>text<|/ref|><|det|>[[177, 403, 820, 499]]<|/det|> +We also calculated the charge loop (blue curve in Fig. 3b) with the \(V_{\mathrm{g}}\) - dependent leakage current \(^{42}\) and found that they exhibited close similarity, indicating a strong correlation between the observed magnon current modulation and the electric polarization of the FE layer. + +<|ref|>text<|/ref|><|det|>[[178, 507, 819, 557]]<|/det|> +And the magnetic field- dependent \(V_{\mathrm{n}}^{\mathrm{DC}}\) curves under higher gate voltage for a new sample are presented in Supplementary Note 6. + +<|ref|>text<|/ref|><|det|>[[177, 561, 821, 802]]<|/det|> +The different on/off ratio between device 1 ( \(400\%\) ) and device 2 ( \(115\%\) ) may be caused by various reasons, such as different substrates- induced variation and those caused by complicated fabrication processes. The ferroelectric substrate we used is \(\mathrm{[Pb(Mg_{1 / 3}Nb_{2 / 3})O_{3}]_{(1 - x)}[PbTiO_{3}]_{x}}\) (PMN- PT), whose property depends sensitively on the composition. The substrate from the different positions of a wafer may have different properties, resulting in different device performance. And the YIG films may exhibit non- uniform properties after polarizing the PMN- PT substrates. In addition, the fabrication processes may also introduce discrepancies in quantity between different samples. To further reveal the role of the gap width and substrate, we performed the gate width dependent on/off ratio measurements with two series of samples fabricated on two different pieces of PMN- PT substrates (Supplementary Note 7). + +<|ref|>text<|/ref|><|det|>[[178, 822, 819, 880]]<|/det|> +3. The authors assume that this non-volatile modulation is due to electric polarization of FE substrate. Given that YIG is oxide insulator, how does electrical polarization transmit? Did the author perform measurements by changing the thickness of YIG? + +<|ref|>text<|/ref|><|det|>[[178, 882, 376, 898]]<|/det|> +Response Reviewer #3- 3: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 85, 821, 440]]<|/det|> +We thank Reviewer #3 for raising these questions. We believe that the electric field caused by the electric polarization of the FE substrate plays a role, although the electric field cannot act on the inside of a metal due to the screening effect, it could induce charge accumulation in an insulator. As reported by D. Chiba et al. [Sci. Rep. 6, 38005 (2016)], when the ferroelectric layer is electrically polarized oppositely, the strong electrical field induces opposite charge accumulation in its adjacent layer. In our case, when the PMN- PT layer is negatively polarized (Fig. R17a), it induces \(\mathrm{Fe}^{3 + }\) ions accumulation at the interface. On the contrary, it induces \(\mathrm{O}^{2 - }\) ions accumulation at the interface when the PMN- PT layer is positively polarized (Fig. R17b). Since the \(\mathrm{Fe}^{3 + }\) ions contain magnetic moment and \(\mathrm{O}^{2 - }\) ions have none, this results in a stronger coupling between the magnon and the collective excitations of PMN- PT in the \(1^{\mathrm{st}}\) case as compared to the \(2^{\mathrm{nd}}\) one. The collective excitation can be either the ferron (Fig. R17c) or phonon (Fig. R17d), especially when they have a similar energy and wavevector as the magnon. The magnon thus has different dissipation and diffusion lengths when PMN- PT is polarized oppositely, resulting in an electrical field modulation of the magnon propagation, i.e., the magnon FET. + +<|ref|>image<|/ref|><|det|>[[258, 450, 730, 690]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[175, 700, 821, 742]]<|/det|> +
Fig. R17 Sketch of different coupling between a ferromagnetic insulator (FI: YIG) with a ferroelectric layer (FE: PMN-PT) when the FE layer is negatively/positively polarized.
+ +<|ref|>text<|/ref|><|det|>[[176, 767, 822, 853]]<|/det|> +We further followed the suggestion of Reviewer #3 and conducted experimental measurements by changing the thickness of YIG. For the thickness of YIG increased to \(80 \mathrm{nm}\) and \(100 \mathrm{nm}\) , the experimental results do not show apparent thickness dependence, all can achieve \(20\% \sim 100\%\) on/off ratio under \(\pm 200 \mathrm{V}\) gate voltages. + +<|ref|>text<|/ref|><|det|>[[178, 876, 451, 894]]<|/det|> +Updated manuscript (lines 288- 291): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 820, 194]]<|/det|> +We propose that the modulation is due to polarization- dependent ions \(\mathrm{(Fe^{3 + }}\) or \(\mathrm{O^{2 - }}\) accumulation in the YIG layer adjacent to the interface, resulting in different coupling since \(\mathrm{Fe^{3 + }}\) is magnetic while \(\mathrm{O^{2 - }}\) is not. Dynamically, the magnon in YIG could couple with the collective excitation, such as the ferron or phonon in PMN- PT (Supplementary Note 11). + +<|ref|>text<|/ref|><|det|>[[177, 214, 820, 363]]<|/det|> +4. In Fig. 3c, the magnetic-field-dependent \(\mathrm{V} \cdot \mathrm{nl}^{\wedge} \mathrm{DC}\) exhibits an enhancement near the coercivity at some electric filed (such as \(+200 \mathrm{~V}\) ), while disappears at other electric filed \((-160 \mathrm{~V})\) . What is the underlying reason for this significant dependence on electric field? Additionally, there is a noticeable difference in coercivity. The authors refer to Ref. 36; however, it seems that this magnetic-field dependence has not been directly measured in their report rather treated to some extent. Therefore, it is necessary for the authors to provide an explanation and present the magnetic-field-dependent \(\mathrm{V} \cdot \mathrm{nl}^{\wedge} \mathrm{DC}\) before applying any electric field (0V). + +<|ref|>sub_title<|/ref|><|det|>[[178, 365, 375, 382]]<|/det|> +## Response Reviewer #3-4: + +<|ref|>text<|/ref|><|det|>[[177, 386, 821, 693]]<|/det|> +We thank Reviewer #3 for raising these questions. We propose a possible mechanism for the enhancement near the coercivity. During the switching, the system encounters a substantial increase in magnetic susceptibility. In this process, the system may generate a burst of magnon upon the thermal excitation. The burst of magnon subsequently generates a voltage signal. The sign of the voltage signal is positive or negative depending on whether the excitation of the magnon occurs after or before the coercive field (Figs. R18d and R18g). The measured signal is the sum of both the magnetization- dependent magnon signal (Fig. R18a) and the susceptibility peak induced magnon signal (Figs. R18d and R18g), resulting in the interesting and unusual shape of loops (Figs. R18e and R18h), respectively. Both loops are observed in our experiments (Figs. R18f and R18i). According to our measurements (Fig. R4 in Response Reviewer #1- 5), the peak voltages are scaled with the square of the \(I_{\mathrm{DC}}\) , indicating its thermal origin. For the convenience of Reviewer #3, we also present the main schematic diagram here (Fig. R18). + +<|ref|>text<|/ref|><|det|>[[178, 697, 819, 759]]<|/det|> +The possible reason for the difference in peak value under different electric fields is that the magnetic anisotropy variation of YIG leads to the different intensity and magnetic field location of magnon excitation. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[243, 93, 755, 370]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 381, 821, 513]]<|/det|> +
Fig. R18 a. Schematic loop of a non-local voltage signal generated by the usual SSE. b and c. The magnetic susceptibility peaks and magnon excitation peaks near the coercive field, respectively. d and g show the corresponding voltage peaks occurring after and before the coercive field, respectively. e and h show the corresponding total voltage signals, respectively. f and i show the results observed in our experimental measurements. They show apparent similarities with e, h, respectively.
+ +<|ref|>text<|/ref|><|det|>[[177, 537, 820, 601]]<|/det|> +Figure R19 shows the non- local measurements of different samples under as- grown (0 V) and \(\pm 200\) V- gate voltages, and the as- grown (0V) measurement results do not show obvious regularity. + +<|ref|>image<|/ref|><|det|>[[243, 610, 756, 783]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 790, 820, 832]]<|/det|> +
Fig. R19 a, b The non-local measurements in two samples under as-grown (0 V) and \(\pm 200\) V-gate voltages, respectively.
+ +<|ref|>text<|/ref|><|det|>[[178, 850, 451, 868]]<|/det|> +Updated manuscript (lines 166- 168): + +<|ref|>text<|/ref|><|det|>[[212, 872, 820, 892]]<|/det|> +A similar phenomenon was observed previously, though its origin was not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 819, 127]]<|/det|> +mentioned41. We proposed a possible explanation for this phenomenon (see Supplementary Note 4). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[179, 123, 398, 139]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[179, 141, 462, 158]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 159, 820, 325]]<|/det|> +In this work, the authors deposited ferrimagnet YIG on top of PMN- PT substrate, a nonvolatile magnon transport behavior was experimentally observed. They try to explain the underlying mechanism as an electrical field modulation of the \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ions accumulation at the YIG/PMN- PT interface, which could result in magnetoelectric coupling between magnons and the collective excitations of PMN- PT. However, this discussion lack strong evidence for both the collective excitations of PMN- PT and \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ions accumulation at interface. How to excite the collective excitations (ferron or phonon) of PMN- PT for a non- local electric measurements? What is the theoretical model of these excitations? + +<|ref|>text<|/ref|><|det|>[[178, 344, 819, 437]]<|/det|> +For the TEM image of the PMN- PT/YIG/Pt heterostructure, not only \(\mathrm{Mg}^{2 + }\) but also \(\mathrm{Nb}^{2 + }\) and \(\mathrm{Ti}^{4 + }\) ions migrated into YIG layer after the deposition. The YIG layer could not a pure YIG in this case. So, the origin of the electric modulation magnon transportation still need to be studied. In this manuscript form, there is not innovative enough to justify its publication on Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[179, 458, 423, 475]]<|/det|> +## General response Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[178, 479, 820, 608]]<|/det|> +We sincerely thank Reviewer #1 for the time and efforts spent in evaluating our manuscript. Following his/her suggestions, we provided a theoretical model about the coupling between the magnons and the collective excitations (ferron or phonon) of ferrielectric materials as well as its influence on the magnon transport, and further discussions about our TEM results of the PMN- PT/YIG/Pt sample. In the following, we provide point- by- point answers to all the raised questions/ comments. + +<|ref|>sub_title<|/ref|><|det|>[[179, 634, 375, 651]]<|/det|> +## Response Reviewer #1-1: + +<|ref|>text<|/ref|><|det|>[[178, 655, 820, 852]]<|/det|> +We thank Reviewer #1 for raising these questions. To explain the different magnetoelectric coupling of the PMN- PT/YIG bilayer with opposite electric polarization, we proposed the electric field modulation of the \(\mathrm{Fe}^{3 + }\) or \(\mathrm{O}^{2 - }\) ions accumulation at the YIG/PMN- PT interface in our last response. We also wish to observe this effect experimentally. Our TEM, however, could not apply voltage across the sample in situ. It could be an interesting project in the near future. On the other hand, in a similar system, D. Chiba et al. reported that the opposite electric field indeed induced accumulation of ions with opposite charges in the Co/ZnO interface [Sci. Rep. 6, 38005 (2016)]. Therefore, we believe this assumption is reasonable. + +<|ref|>text<|/ref|><|det|>[[179, 856, 819, 896]]<|/det|> +The collective excitations (ferron or phonon) of PMN- PT can be caused by thermal fluctuation, similar to the magnon excitation in YIG. As discussed below, the magnon + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 305]]<|/det|> +could also create/annihilate these excitations due to magnetoelectric (ME) coupling between PMN- PT and YIG. The magnon- phonon coupling was observed experimentally in similar systems like \(\mathrm{CoFe_2O_4 / PMN - PT}\) , \(\mathrm{NiFe_2O_4 / SrRuO_3 / PMN - PT}\) and \(\mathrm{SmFeO_3 / PMN - PT}\) systems [J. Mater. Sci.- Mater. Electron. 33, 19766 (2022); Appl. Phys. Lett. 119, 112902 (2021); Appl. Phys. Lett. 109, 082902 (2016)]. Though the authors termed it as the spin- phonon coupling, due to the high- frequency nature and the spin character, it has to be the coupling between magnon and phonon. The ferron excitation in ferroelectric materials was theoretically predicted by Ping Tang and Gerrit E.W. Bauer et al. very recently [Phys. Rev. Lett. 128, 047601 (2022); Phys. Rev. B 106, L081105 (2022)], the direct experimental observations are still yet to be demonstrated. + +<|ref|>text<|/ref|><|det|>[[177, 308, 821, 548]]<|/det|> +In the following, we present a theory to study the influence of ferron excitation in the ferroelectric layer on the magnon transport in the ferromagnetic layer. The idea is that magnon excitation can couple with ferrons through magnetoelectric interaction at the interface of ferroelectric (FE) and ferromagnetic(ferrimagnetic) insulator (FI). This coupling can enhance the dissipation and thus reduce the thermal diffusion length of magnons, then the non- local electric voltage proportional to the magnon density at the detector terminal will be reduced. On the other hand, the ME coupling changes when the stationary ferroelectric polarization is reversed due to the different spatial distribution of ferromagnetic ions (Supplementary Fig. 17), then the magnon diffusion length and subsequent non- local electric voltage will also differ. This explains the experimental observation. + +<|ref|>text<|/ref|><|det|>[[177, 552, 820, 673]]<|/det|> +Model and Hamiltonian.- We consider a hybrid FI and FE system coupled through ME coupling at the interface. The total Hamiltonian of the hybrid system can be written as \(\mathrm{H} = \mathrm{H}_{\mathrm{im}} + \mathrm{H}_{\mathrm{fe}} + \mathrm{H}_{\mathrm{int}}\) , where \(\mathrm{H}_{\mathrm{im}}, \mathrm{H}_{\mathrm{fe}}, \mathrm{H}_{\mathrm{int}}\) are the magnetic Hamiltonian, ferroelectric Hamiltonian and their interaction, respectively. The magnetic component reads + +<|ref|>equation<|/ref|><|det|>[[353, 675, 817, 711]]<|/det|> +\[\mathrm{H}_{\mathrm{im}} = -JS^2\sum_{\langle i,j\rangle}\mathbf{m}_i\cdot \mathbf{m}_j - \mu_0M_s\mathbf{H}\cdot \sum_i\mathbf{m}_i, \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[177, 715, 820, 852]]<|/det|> +where the first and second terms represent the Heisenberg exchange and Zeeman energy, respectively, with \(\mathbf{m}_i\) being the unit spin orientation at \(i\) - th site, the first sum being taken on the nearest sites, \(J\) being the exchange coefficient, \(S\) being the length of spin, \(M_s\) being saturation magnetization, \(\mu_0\) being the vacuum permeability and \(\mathbf{H}\) being the external magnetic field. + +<|ref|>text<|/ref|><|det|>[[177, 856, 819, 897]]<|/det|> +Within the Landau- Ginzburg- Devonshire theory, the ferroelectric Hamiltonian reads [Nano. Lett. 16, 7290 (2016); Phys. Rev. B 106, L081105 (2022)] + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[327, 90, 818, 131]]<|/det|> +\[\mathrm{H}_{\mathrm{fe}} = \frac{A}{2}\sum_{i}(\nabla \mathbf{P}_{i})^{2} - \frac{\alpha}{2} (\mathbf{P}_{i})^{2} + \frac{\beta}{4} (\mathbf{P}_{i})^{4} - \mathbf{P}_{i}\cdot \mathbf{E}_{e}, \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[176, 146, 821, 316]]<|/det|> +where \(\mathbf{P}_{i}\) stands for the discretized ferroelectric polarization at \(i-\) th site. The first term resembles the ferromagnetic exchange energy, with \(A\) being the exchange coefficient, the second and third terms are the potential terms that account for the stationary ferroelectric polarization with \(\alpha >0\) and \(\beta >0\) being the potential coefficients. The last term resembles the magnetic Zeeman energy with \(E_{e}\) being the external electric field. + +<|ref|>text<|/ref|><|det|>[[177, 319, 820, 362]]<|/det|> +The leading term of the ME interaction is the linear coupling between magnetic order and electric polarization that in the form [Phys. Rev. B 90, 054423 (2014)] + +<|ref|>equation<|/ref|><|det|>[[404, 363, 818, 396]]<|/det|> +\[\mathrm{H}_{\mathrm{int}} = -g_{\mathrm{ME}}M_{s}\sum_{i}\mathbf{m}_{i}\cdot \mathbf{P}_{i}, \quad (3)\] + +<|ref|>text<|/ref|><|det|>[[177, 406, 486, 427]]<|/det|> +where \(g_{\mathrm{ME}}\) is the ME coupling strength. + +<|ref|>text<|/ref|><|det|>[[176, 436, 821, 590]]<|/det|> +Quantization. Next, we shall quantize the total Hamiltonian \(\mathrm{H}\) to show how the ferroelectric excitations i.e., ferrons can influence the behavior of magnetic excitations i.e., magnons. To mimic the experimental condition, we apply an in- plane external magnetic field \(\mathbf{H} = H_{e}e_{x}\) , which is sufficiently strong to polarize all the spins along this direction. Then we can perform the Holstein- Breakoff transformation [Phys. Rev. 58, 1098 (1940)] above the classical ground state \(\mathbf{m}_{i} = e_{x}\) , i.e. + +<|ref|>equation<|/ref|><|det|>[[327, 602, 818, 628]]<|/det|> +\[m_{i}^{+} = \sqrt{2 / S}\hat{a}_{i},m_{i}^{-} = \sqrt{2 / S}\hat{a}_{i}^{+},m_{i}^{+} = 1 - \hat{a}_{i}^{+}\hat{a}_{i} / S, \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[176, 639, 821, 864]]<|/det|> +where \(\hat{a}_{i}\left(\hat{a}_{i}^{+}\right)\) are magnon annihilation (creation) operators at \(i-\) th site, \(m_{i}^{\pm}\) are spin raising (lowering) operators defined as \(m_{i}^{\pm}\equiv m_{i}^{z}\mp i m_{i}^{y}\) . After rearranging Eq. (4) in the form of \(m_{i}^{z(y)}\) , we derive \(m_{i}^{z} = \sqrt{1 / 2S}\left(\hat{a}_{i} + \hat{a}_{i}^{+}\right),m_{i}^{y} = i\sqrt{1 / 2S}\left(\hat{a}_{i} - \hat{a}_{i}^{+}\right)\) . By substituting the quantized forms of \(\mathbf{m}_{i}\) into the Hamiltonian \(\mathrm{H}_{\mathrm{im}}\) and transferring to Fourier space, we derive the quantized form of magnetic Hamiltonian as \(\mathrm{H}_{\mathrm{im}} = \sum_{k}\omega_{k}\hat{a}_{k}^{+}\hat{a}_{k}\) , where \(\omega_{k}\) is the dispersion relation of magnons, \(\hat{a}_{k}\) ( \(\hat{a}_{k}^{+}\) ) are the magnon annihilation (creation) operators with momentum \(\mathbf{k}\) . + +<|ref|>text<|/ref|><|det|>[[210, 872, 819, 893]]<|/det|> +Similarly, the ferron excitation \(\delta P_{iz} = \mathbf{P}_{i} - \mathbf{P}_{0}\) around the stationary polarization + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 91, 760, 112]]<|/det|> +\(\mathbf{P}_{0} = P_{0}e_{z}\) at \(z - \mathrm{axis}\) can be quantized as [Phys. Rev. B 106, L081105 (2022)] + +<|ref|>equation<|/ref|><|det|>[[330, 120, 818, 176]]<|/det|> +\[\delta P_{i z} = \sqrt{\frac{\hbar}{2m_{p}V_{\mathrm{FE}}}}\sum_{\mathbf{q}}\left(\frac{\hat{b}_{\mathbf{q}}}{\sqrt{\Omega_{q}}} e^{i\mathbf{q}\cdot \mathbf{r}_{i}} + \frac{\hat{b}_{\mathbf{q}}^{\dagger}}{\sqrt{\Omega_{q}}} e^{-i\mathbf{q}\cdot \mathbf{r}_{i}}\right), \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[177, 183, 821, 348]]<|/det|> +where \(\Omega_{q} = \sqrt{\Delta^{2} + A^{\prime}q^{2}}\) is the dispersion relation of ferrons with energy gap \(\Delta = \sqrt{\left(\alpha + 3\beta P_{0}^{2}\right) / m_{p}}\) and \(A^{\prime} = A / m_{p}\) , \(m_{p}\) is the polarization inertia, \(V_{\mathrm{FE}}\) is the volume of ferroelectric, \(\hat{b}_{q}\) \((\hat{b}_{q}^{\dagger})\) is the annihilation (creation) operator of ferrons. By substituting the quantized form of \(\mathbf{P}\) and \(\mathbf{M}\) into the interaction Hamiltonian \(\mathrm{H}_{\mathrm{int}}\) , we derive the quantized interaction component as + +<|ref|>equation<|/ref|><|det|>[[350, 353, 818, 394]]<|/det|> +\[\mathrm{H}_{\mathrm{int}} = \sum_{\mathbf{k},\mathbf{q}}\left(V(\mathbf{k},\mathbf{q})\hat{a}_{\mathbf{k}}\hat{b}_{\mathbf{q}}^{\dagger} + V^{*}(\mathbf{k},\mathbf{q})\hat{a}_{\mathbf{k}}^{\dagger}\hat{b}_{\mathbf{q}}\right), \quad (6)\] + +<|ref|>text<|/ref|><|det|>[[178, 405, 387, 423]]<|/det|> +where the coupling strength + +<|ref|>equation<|/ref|><|det|>[[339, 422, 818, 476]]<|/det|> +\[V(\mathbf{k},\mathbf{q}) = -g_{\mathrm{ME}}M_{s}\sqrt{\frac{\hbar}{2m_{p}V_{\mathrm{FE}}N_{s}}}\sum_{i}\frac{e^{i(\mathbf{k} - \mathbf{q})\cdot\mathbf{r}_{i}}}{\sqrt{\omega_{q}}}. \quad (7)\] + +<|ref|>text<|/ref|><|det|>[[177, 483, 821, 605]]<|/det|> +In the experiments, the magnon transport is measured at room temperature. This implies that the magnon modes with energy \(\hbar \omega_{k_{0}} \approx k_{B}T\) (around THz scale) dominate the contribution to transport behavior while the magnon gap induced by anisotropy and external field (around GHz scale) do not play a significant role here. Then it seems reasonable to only consider a proper THz magnon mode with the effective Hamiltonian + +<|ref|>equation<|/ref|><|det|>[[338, 610, 818, 653]]<|/det|> +\[\mathrm{H}_{\mathrm{int}} = \sum_{\mathbf{q}}\left(V(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}\hat{b}_{\mathbf{q}}^{\dagger} + V^{*}(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}^{\dagger}\hat{b}_{\mathbf{q}}\right). \quad (8)\] + +<|ref|>text<|/ref|><|det|>[[177, 663, 741, 683]]<|/det|> +Above all, we come to the total quantized Hamiltonian of the hybrid system + +<|ref|>equation<|/ref|><|det|>[[258, 690, 817, 733]]<|/det|> +\[\mathrm{H} = \omega_{k_{0}}\hat{a}_{k_{0}}^{\dagger}\hat{a}_{k_{0}} + \sum_{q}\Omega_{q}\hat{b}_{q}^{\dagger}\hat{b}_{q} + \sum_{\mathbf{q}}\left(V(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}\hat{b}_{q}^{\dagger} + V^{*}(\mathbf{k}_{0},\mathbf{q})\hat{a}_{k_{0}}^{\dagger}\hat{b}_{q}\right). \quad (9)\] + +<|ref|>text<|/ref|><|det|>[[177, 741, 820, 783]]<|/det|> +Next, we will use this Hamiltonian to study the influence of ferron excitation on the dissipation of magnons. + +<|ref|>text<|/ref|><|det|>[[177, 786, 820, 910]]<|/det|> +Ferron- induced magnon dissipation. Here we denote the state of magnons by a density matrix \(\hat{\rho}\) and treat the influence of ferron excitation as a bath that contributes to the dissipation of magnons. Following the standard Lindbald formalism [Phys. Rev. B 106, 224422 (2022)], we can trace out the bath degrees of freedom in Eq. (9) and derive a master equation governing the magnon dynamics as + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[304, 92, 817, 130]]<|/det|> +\[\frac{\partial\hat{\rho}}{\partial t} = \frac{i}{\hbar}\big[\hat{\rho},\mathrm{H}_{\mathrm{im}}\big] + \kappa_{\mathrm{me}}\big(n_{\mathrm{th}} + 1\big)\mathrm{L}_{a}\big(\hat{\rho}\big) + \kappa_{\mathrm{me}}n_{\mathrm{th}}\mathrm{L}_{a}\big(\hat{\rho}\big), \quad (10)\] + +<|ref|>text<|/ref|><|det|>[[176, 145, 819, 220]]<|/det|> +where \(n_{\mathrm{th}}\) is the thermal occupation of magnons, \(\mathrm{L}_{A}(\hat{\rho}) = 2\hat{A}\hat{\rho}\hat{A}^{\dagger} - \hat{A}^{\dagger}\hat{A}\hat{\rho} - \hat{\rho}\hat{A}^{\dagger}\hat{A}\) is the Lindblad operator. The relaxation rate of magnons coming from magnon- ferron coupling is + +<|ref|>equation<|/ref|><|det|>[[407, 224, 817, 272]]<|/det|> +\[\kappa_{\mathrm{me}} = \frac{\pi g_{\mathrm{ME}}^{2}M_{s}^{2}D\big(\Omega_{k_{0}}\big)}{2\hbar m_{p}V_{\mathrm{FE}}\Omega_{k_{0}}}, \quad (11)\] + +<|ref|>text<|/ref|><|det|>[[176, 283, 821, 446]]<|/det|> +where \(D\big(\Omega_{k_{0}}\big)\) is the density states of ferrons that can be readily evaluated from the ferron dispersion as \(D\big(\Omega_{k_{0}}\big) = A^{- 3 / 2}V_{\mathrm{FE}} / \big(2\pi^{2}\big)\Omega_{k_{0}}\sqrt{\Omega_{k_{0}}^{2} - \Delta^{2}}\) . Note that, besides the magnon- ferron coupling, there are additional channels of magnon dissipation which may come from magnon- phonon scattering, magnon- magnon interaction, defects, and disorders in a magnet. The total dissipation rate is the sum of all these contributions as \(\kappa = \kappa_{\mathrm{me}} + \kappa_{\mathrm{im}}\) . Then we can evaluate the thermal diffusion length of magnons as + +<|ref|>equation<|/ref|><|det|>[[416, 463, 817, 501]]<|/det|> +\[I_{m} = \nu_{\mathrm{th}}\tau = \frac{\nu_{\mathrm{th}}}{\kappa_{\mathrm{me}} + \kappa_{\mathrm{im}}}, \quad (12)\] + +<|ref|>text<|/ref|><|det|>[[177, 515, 820, 605]]<|/det|> +where \(\tau = 1 / \big(\kappa_{\mathrm{me}} + \kappa_{\mathrm{im}}\big)\) is the total diffusion time of magnons, \(\nu_{\mathrm{th}} = 2\sqrt{J_{s}k_{B}T} /\hbar\) is the thermal velocity of magnons [Phys. Rev. B 94, 014412 (2016)], and \(\kappa_{\mathrm{im}}\) includes all the other contributions of magnon dissipations except ME coupling. + +<|ref|>text<|/ref|><|det|>[[177, 607, 820, 672]]<|/det|> +Comparison with experiments. To compare with the experimental results, we recall that magnon transport in a magnetic insulator may be described by the diffusion equation [Phys. Rev. B 94, 014412 (2016)] + +<|ref|>equation<|/ref|><|det|>[[450, 679, 817, 722]]<|/det|> +\[\frac{\partial^{2}\mu_{m}}{\partial^{2}x} = \frac{\mu_{m}}{I_{m}^{2}}, \quad (13)\] + +<|ref|>text<|/ref|><|det|>[[177, 735, 820, 855]]<|/det|> +where \(\mu_{m}\) is the chemical potential of magnons. By solving the diffusion equation (13), we obtain \(\mu_{m}\left(x\right) = \mu_{0}\mathrm{exp}\left(- x / I_{m}\right)\) . Note that the non- local electric voltage measured in experiments is proportional to the magnon chemical potential at the position of the electrode \((x = L)\) , i.e., \(V_{\mathrm{nl}}\propto \mu_{m}\left(x = d\right)\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[195, 90, 806, 286]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 289, 821, 309]]<|/det|> +
Fig. R1 a Magnon chemical potential as a function of distance for \(P< 0\) (red line) and
+ +<|ref|>text<|/ref|><|det|>[[175, 316, 821, 737]]<|/det|> +\(P > 0\) (black line), respectively. \(g_{\mathrm{ME}} = 0.5 \mathrm{s / F}\) for \(P< 0\) and \(0.25 \mathrm{s / F}\) for \(P > 0\) , respectively, \(A = 0.2 A_{0}\) , \(d = 2 \mu \mathrm{m}\) is the distance between the source and detector. The blue dashed line indicates the position at which the electric voltage is measured. b Non- local voltage ratio: \(V_{\mathrm{nl}}^{- } / V_{\mathrm{nl}}^{+}\) as a function of magnetoelectric coupling strength for \(P< 0\) and the value for \(P > 0\) is assumed to be \(50\%\) of that for \(P< 0\) . Where \(V_{\mathrm{nl}}^{\pm}\) represent the nonlocal voltage at different gate voltages \(V_{\mathrm{nl}}^{\mathrm{DC}}\left(V_{g} = \pm 200 \mathrm{V}\right)\) , respectively. The purple, red and blue dashed lines refer to the experimental values on the sample YIG/PZT, device 2 of YIG/PMN-PT and device 1 of YIG/PMN-PT, respectively. Magnetic parameters of YIG are used with \(M_{s} = 1.36 \times 10^{5} \mathrm{A / m}\) (the experimental value of our YIG sample), \(J_{s} = 8.46 \times 10^{- 40} \mathrm{J} \cdot \mathrm{m}^{2}\) , \(a = 1.24 \mathrm{nm}\) [Phys. Rev. B 94, 014412 (2016)]. Since the ferron excitation parameters of PMN-PT and PZT are still not complete in literature, parameters of typical ferroelectric are used with \(\Delta = 20 \mathrm{THz}\) , \(m_{p} = 9 \times 10^{- 18} \mathrm{J} \cdot \mathrm{m} \cdot \mathrm{s}^{2} / \mathrm{C}^{2}\) , \(A_{0} = 10^{- 10} \mathrm{J} \cdot \mathrm{m}^{3} / \mathrm{C}^{2}\) [Phys. Rev. B 106, L081105 (2022)]. The temperature is \(T = 300 \mathrm{K}\) . + +<|ref|>text<|/ref|><|det|>[[176, 763, 821, 893]]<|/det|> +Figure R1a shows the non- local voltage as a function of the propagation distance of magnons. Clearly, for \(P< 0\) ( \(P > 0\) ) with stronger (weaker) ME coupling, the magnon chemical potential as well as the non- local voltage decay faster (slower) with distance, as shown by the red line (black line) in Fig. R1a. When one measures the electric voltage at \(x = d\) , this leads to a voltage difference between positively and negatively polarized ferroelectric polarization. Figure R1b shows the theoretical values + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 91, 821, 290]]<|/det|> +of \(V_{\mathrm{nl}}^{- } / V_{\mathrm{nl}}^{+}\) as a function of magnetoelectric coupling strength in the range of typical values of ferroelectric and ferromagnetic(ferrimagnetic) interface [Phys. Rev. B 100, 104410 (2019)]. Typical values of \(g_{\mathrm{ME}}\) around \(0.5 \mathrm{s / F}\) for \(P< 0\) can reproduce the experimental observations. Note that this result is sensitive to the exchange stiffness of ferrons i.e., \(A\) in Eq. (2). When \(A\) is smaller, the ferron band is flatter and more ferrons excitations around THz can contribute to the magnon dissipation. Hence the magnon diffusion length will be reduced on a larger scale, implying a larger on/off ratio. + +<|ref|>text<|/ref|><|det|>[[177, 294, 821, 615]]<|/det|> +Lastly, we would like to discuss the role of magnon- phonon coupling at the interface of an FI/FE hybrid. In general, there exist phonon modes excited at THz regime and can thus enhance the dissipation of magnons. The theoretical formalism to quantify this influence is quite similar to the case of magnon- ferron coupling presented above within the linear coupling regime [https://doi.org/10.48550/arXiv.2310.05621]. The strength of this coupling is yet to be known. Currently, it is still difficult to estimate its contribution. On the other hand, at the interface of FI and FE, the spin excitations will strongly influence the elastic properties in the FE layer [Phys. Status. Solidi B 257, 1900750 (2020)], i.e., the phonons, while the elastic excitation is further coupled to the ferroelectric polarization [J. Alloys Compounds 928, 167181 (2022)]. This suggests that the interplay of magnons, phonons and ferrons may mix at the interface. In principle, magnon- phonon coupling could also contribute to the strength of magnon- ferron coupling ( \(g_{\mathrm{ME}}\) ). A detailed study of the underlying physics and the effective coupling strength is our future work. + +<|ref|>text<|/ref|><|det|>[[179, 636, 451, 653]]<|/det|> +Updated manuscript (lines 299- 301): + +<|ref|>text<|/ref|><|det|>[[179, 656, 819, 694]]<|/det|> +A theoretical model about the influence of these couplings on the magnon transport is presented in Supplementary Note 14. + +<|ref|>sub_title<|/ref|><|det|>[[179, 718, 375, 735]]<|/det|> +## Response Reviewer #1-2: + +<|ref|>text<|/ref|><|det|>[[178, 740, 820, 891]]<|/det|> +We thank Reviewer #1 for raising the concern about YIG quality. We plot the area - dependent element distributions in Fig. R2 below. According to it, PMN- PT/YIG heterostructure can be divided into three regions: the PMN- PT layer, buffer layer, and YIG layer. In the buffer layer region ( \(\sim 30 \mathrm{nm}\) thickness), four elements (Mg, Pb, Ti, and Nb) of PMN- PT penetrate the YIG due to the high- temperature post- annealing treatment. However, for the YIG far from the interface, there is only a distribution of Y and Fe, and it maintains an excellent YIG crystallinity (HAADF- TEM images of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 85, 822, 483]]<|/det|> +YIG layer in Supplementary Figs. 2b, c, and d). In addition, the lattice constant of YIG film is 12.486 Å obtained from the diffraction pattern in Supplementary Fig.2c inset, which is less than \(0.89\%\) different from the bulk value (12.376 Å) [J. Phys. D Appl. Phys. 51, 253001 (2018)], indicating the formation of a pure YIG. Despite the significant difference in lattice constant between YIG (12.376 Å) and PMN- PT (4.024 Å), the formation of a buffer layer helps the crystallization of YIG. Although we expect that the thickness of the buffer layer can be reduced by optimizing annealing conditions and/or inserting a suitable interlayer, we believe that it does not influence the merit of our manuscript. Given the fact that the Coulomb interaction is a long- range interaction, the formation of a thin buffer layer may reduce the magnetoelectric coupling but will not erase it completely. Moreover, the magnon field- effect- transistor only requires a ferromagnetic or ferrimagnetic layer with a relatively long magnon diffusion length, which has been demonstrated in Fig. 2f in the main text, coupled with a layer with good ferroelectricity which is also evidenced by the ferroelectric hysteresis loop shown in Fig. 3b in the main text. As you may find, the effect remains even after replacing the PMN- PT crystal with a PZT film. We believe it will also work if we replace YIG with other ferromagnetic or ferrimagnetic insulators, providing it has a long magnon diffusion length. + +<|ref|>image<|/ref|><|det|>[[216, 490, 731, 682]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 688, 820, 744]]<|/det|> +
Fig. R2 a The HAADF image of PMN-PT/YIG/Pt sample. b EDS integrated signal profiles of Fe, Y, Mg, Pb, Ti and Nb obtained through area scans crossing layers shown in the orange dashed rectangle of a.
+ +<|ref|>text<|/ref|><|det|>[[177, 769, 820, 829]]<|/det|> +With the first demonstration of the magnon field- effect- transistor and the updated information, we hope that you will now recommend the publication of our manuscript in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[177, 852, 805, 892]]<|/det|> +Updated manuscript (Supplementary Information): In Supplementary Note 1. The structure and magnetic properties of the samples, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 87, 581, 104]]<|/det|> +we added the discussion about the quality of YIG film. + +<|ref|>text<|/ref|><|det|>[[178, 129, 462, 146]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 150, 220, 164]]<|/det|> +Dear, + +<|ref|>text<|/ref|><|det|>[[178, 167, 819, 240]]<|/det|> +All the weaknesses presented in the original version of the article have been addressed in this new version. The crucial points were resolved by producing new samples and conducting new measurements. For these reasons, I suggest that the present article can be published in Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[178, 261, 423, 278]]<|/det|> +## General response Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[178, 283, 820, 389]]<|/det|> +We sincerely thank Reviewer #2 for recommending the publication of the present manuscript in Nature Communications. We are grateful to Reviewer #2 for commenting that "all the weaknesses presented in the original version of the article have been addressed in this new version" and that "the crucial points were resolved by producing new samples and conducting new measurements". + +<|ref|>text<|/ref|><|det|>[[178, 411, 462, 427]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 430, 819, 502]]<|/det|> +I have carefully read the revised version of the manuscript. I appreciate the efforts by the authors to address my raised questions. However, I have to follow up on certain points within the response of the authors and hope the authors can address these points. In more detail, see the below: + +<|ref|>sub_title<|/ref|><|det|>[[178, 523, 423, 540]]<|/det|> +## General response Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[178, 545, 819, 606]]<|/det|> +We sincerely thank Reviewer #3 for the time and effort spent in evaluating our revised manuscript. We are happy to answer further questions in a point- by- point manner below. + +<|ref|>text<|/ref|><|det|>[[178, 628, 819, 739]]<|/det|> +In response to Q2: I notice that the authors demonstrate "all curves were obtained after the electric field had been removed" in the main text, if I understand this correctly, the authors obtain all \(\mathrm{V\_nl^{\wedge}DC}\) at residual polarization state despite removing from large electric field. If so, I suggest that the authors perform the measurements under \(+400\) V(do not remove electric field, or measuring under the maximum voltage before the device burning except \(200\mathrm{V}\) ) and \(+0\mathrm{V}\) (residual polarization). + +<|ref|>sub_title<|/ref|><|det|>[[178, 761, 375, 777]]<|/det|> +## Response Reviewer #3-1: + +<|ref|>text<|/ref|><|det|>[[178, 782, 820, 905]]<|/det|> +We thank Reviewer #3 for raising this question. The reviewer is correct, we measured all \(V_{\mathrm{nl}}^{\mathrm{DC}}\) at the residual polarization state. We followed the suggestion and conducted the measurements with \(V_{\mathrm{g}}\) holding and removal, respectively. We prepared a PMN- PT/YIG/Pt sample with an on/off ratio of \(\sim 102\%\) , and measured the relationship between integrated charge with gate voltage \(V_{\mathrm{g}}\) in \(\pm 300\mathrm{V}\) range in situ (Fig. R3a). The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 85, 821, 253]]<|/det|> +residual polarization value \((+0 \mathrm{~V})\) is almost the same as the polarization value at \(+300 \mathrm{~V}\) . Figure R3b presents the non- local voltage measurements with gate voltages holding \((+300 \mathrm{~V})\) and removal \((+0 \mathrm{~V})\) , respectively. The measurement curves show that the signal- to- noise ratio with gate voltage removed is obviously better than that with gate voltage maintained. However, the curves in the two cases show similar results, with a slightly smaller \(V_{\mathrm{nl}}^{\mathrm{DC}}\) amplitude value at \(+0 \mathrm{~V}\) . This is consistent with the polarization value under two situations measured by the ferroelectric loop (Fig. R3a). + +<|ref|>image<|/ref|><|det|>[[240, 260, 752, 430]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 439, 820, 503]]<|/det|> +
Fig. R3 a The integrated charge as the function of the gate voltage pulse \(V_{\mathrm{g}}\) for PMN-PT/YIG/Pt sample. b The non-local voltages measurement with gate voltages holding \((+300 \mathrm{~V})\) and removal \((+0 \mathrm{~V})\) , respectively.
+ +<|ref|>text<|/ref|><|det|>[[178, 525, 452, 544]]<|/det|> +Updated manuscript (lines 220- 221): + +<|ref|>text<|/ref|><|det|>[[177, 553, 820, 603]]<|/det|> +In addition, the comparison of non- local voltage with \(V_{\mathrm{g}}\) holding and removal is presented in Supplementary Note 7. + +<|ref|>text<|/ref|><|det|>[[177, 627, 821, 720]]<|/det|> +In response to Q3: I am confused that the authors demonstrate “For the thickness of YIG increased to \(80 \mathrm{~nm}\) and \(100 \mathrm{~nm}\) , the experimental results do not show apparent thickness dependence, all can achieve \(20\% \sim 100\%\) on/off ratio”. However, in the main text, for \(60 \mathrm{~nm}\) YIG, the on/off ratio of device 1 and device 2 are \(400 \%\) and \(150 \%\) , respectively. How to understand “do not show apparent thickness dependence”? + +<|ref|>sub_title<|/ref|><|det|>[[178, 744, 375, 761]]<|/det|> +## Response Reviewer #3-2: + +<|ref|>text<|/ref|><|det|>[[177, 765, 821, 896]]<|/det|> +We thank Reviewer #3 for raising this question. To better explain that the on/off ratio did not show apparent YIG thickness dependence, we summarize the on/off ratio of 16 PMN- PT/YIG/Pt samples in Fig. R4. The on/off ratios with YIG thickness \(60 \mathrm{~nm}\) , \(80 \mathrm{~nm}\) and \(100 \mathrm{~nm}\) vary between \(18.2\% \sim 404\%\) , \(12.7\% \sim 21\%\) and \(17.1\% \sim 102.8\%\) , respectively. The on/off ratio fluctuates even for the same YIG thickness, which may be caused by various reasons, such as different substrates induced variation, the non + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 194]]<|/det|> +uniform properties of PMN- PT substrate and YIG films, different interface properties, and the variation caused by complicated fabrication processes (see our previous responses). Therefore, we cannot obtain a clear YIG thickness dependence of the on/off ratio at present stage. We mentioned this in the revised manuscript and replaced “all” with “most”. + +<|ref|>image<|/ref|><|det|>[[352, 208, 645, 390]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[176, 398, 818, 437]]<|/det|> +
Fig. R4 Summary of the on/off ratio of 16 PMN-PT/YIG/Pt samples for 60-nm, 80-nm, and 100-nm YIG thicknesses, respectively.
+ +<|ref|>text<|/ref|><|det|>[[178, 460, 452, 478]]<|/det|> +Updated manuscript (lines 240- 242): + +<|ref|>text<|/ref|><|det|>[[177, 483, 820, 545]]<|/det|> +Furthermore, we present a summary of the on/off ratio of 16 PMN- PT/YIG/Pt samples with different YIG thicknesses, where most of the samples can achieve \(20\% \sim 100\%\) on/off ratio (Supplementary Note 9). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 122, 390, 140]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 160, 460, 176]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 179, 850, 250]]<|/det|> +Reviewer #1 (Remarks to the Author):The article has been revised according to all my concerns. A reasonable theoretical model about the coupling between ferron and magnon and its influence on the magnon transport was provided. Therefore, I would like to suggest its publication in Nature Communications in the current form. + +<|ref|>text<|/ref|><|det|>[[149, 271, 460, 287]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 290, 850, 362]]<|/det|> +Reviewer #3 (Remarks to the Author):I have carefully read the revised version of the manuscript (NCOMMS- 23- 58821C). The authors gave a detailed response to the raised concerns of the reviewers and also carried out necessary changes in their revised manuscript. So, I think the current version can be published in Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[149, 384, 272, 400]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[149, 405, 850, 444]]<|/det|> +Our response:We sincerely thank both reviewers for the helpful comments and excellent recommendation. + +<--- Page Split ---> diff --git a/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/images_list.json b/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..8c69f7f040e36386bfd34cdb3060be87f4537330 --- /dev/null +++ b/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R1. Differences in (a) GPI and (b) precipitation between MIS5e and MIS5d during the TC peak seasons across different ocean basins (i.e., JAS in North Pacific and North Atlantic basins; JFM in Southern Hemisphere basins; OND in North Indian Ocean).", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1225cefebc9db417b1f5bbc57ae89f4a5259f92c --- /dev/null +++ b/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,327 @@ + +# nature portfolio + +Peer Review File + +Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors tried to give an idea of future tropical cyclone activity by comparing past and future climate simulations. They used the MIS5e, MIS5d scenarios for the past climate and the PD, CO2 doubling scenarios for the future climate. By comparing the responses of tropical cyclone activity to past and future climate, they found that moisture plays a critical role in tropical cyclone activity. In general, the manuscript is well organised. However, I have several concerns about its publication. + +1) I found that the authors have a deep knowledge of paleo-climate studies. Since the NCC is a letter, I understand that the authors have tried to shorten the length of the manuscript. However, this makes it difficult for readers who are not experts in palaeo-climate to follow the significance of their findings. Since the NCC is a letter to the non-expert in the field, I suggest that the authors add more explanation and information about palaeoclimate studies. + +For example, in lines 53- 59, I don't know what is the limitation of the previous studies of warm climate episodes. Please provide more information. + +Also, what is the difference between the MIS5e and MIS5d simulations compared to the last interglacial, the Eocene and the Pliocene simulations? Please explain and highlight the difference. + +2) According to the introduction, it seems to me that the authors have found striking evidence in the projection of future tropical cyclone activity. However, their main finding is that only moisture is the most important. In fact, this result can only be found with the result of PD, CO2 doubling experiments. I don't know why the MIS5e and MIS5d experiments are essential to the authors' argument. Although the authors insist that the different experiments can reduce the uncertainty, I think the authors still cannot avoid the uncertainty problem by using the single model, CESM. I think the importance of this study is not to reduce the uncertainty, but rather a possible importance of tropospheric humidity. + +3) Lines 155-174: I can acknowledge that RH related variables are most similar to GPI. If the quantitative contribution of each factor is given in the table, it will be much easier to understand the results. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +The following is a review of the manuscript submitted by Raavi et al entitled Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. The results are interesting and provides new insights on the paleoclimatology of tropical cyclones, which are timely and relevant particularly in the advent of discussions surrounding global environmental changes. I have few comments, clarifications, and suggestions to the author. I believe the manuscript has potential for publication after the following comments have been adequately answered: + +L65- 66 - the use of NH summer vis- a- vis boreal summer here is confusing + +L75 - What is MIS5d. It is not yet explained. why are they called extreme orbital conditions? + +L98 - consider putting this explanation in earlier parts to provided clarity in the discussion + +L148 - is it possible to put a timeseries of GPI in Fig. 1 to show such reduction in response to MIS5ed, PDO, and 2xCO2? This is for ease of reading for readers that are universally adept to paleoclimate. + +L158 - "TC genesis" + +L161 - WNP typically covers until 100E while NI covers until 95E + +L167- 168 - vertical wind shear in the WNP; how to determine the contribution of one term in GPI? is there a way to determine significance? + +L171- 173 - same with comments above. Looking at Fig. 3A and Fig S3C, there is a meridional component of dGPI extending from south to north in the WNP, which is not captured in Fig 3D but is captured in Fig. 3E. Same can be be said in the Caribbean and Eastern Pacific where VWS seems to affect the dGPI. + +Similarly, the filament of negative 850 hPa abs. vorticity in Fig 3B, resembles that in the eastern Pacific indicating that atmospheric component (VWS and Abs. Vort) also affect dGPI. how to determine the contribution of one term in GPI? is there a way to determine significance? + +L176- 181 - There is a need to characterize the term "most" here because it can be seen that VWS also has considerable changes. This leads to my next question - does the blue mean decrease in VWS? If yes, does it mean more favorable TC genesis environment? Both sides remain to ask how to determine their significant contribution. + +<--- Page Split ---> + +L197- 198: this is confusing because I though that the GPI in Fig. 3 denotes decrease in TC genesis. A northward ITCZ means favorable TC genesis environment because the moisture associated with the ITCZ is found in the WNP. + +L215 - this is related to my previous comment. The mention of Fig S9 without relating to Fig. 4A first is confusing to the reader. + +L264 - where in the figure does it show the correlation? is it through eyeball only? + +L271 - what does it mean by global ocean changes in relation to VWS and TC frequency? + +L272 - the mismatch in the anomaly patterns vis- a- vis GPI in two simulations show that thermodynamic is more important that dynamic variable? In a paper by Sharmila and Walsh (2017; https://doi.org/10.1175/JCLI- D- 16- 0900.1), they mentioned that dynamic parameters are more important in the WNP and South Pacific. + +L295 - did you combine the peak season for each basin then plot the NH? Each basin has different peak season which has to be considered. + +I think there is a need to provide more explanation/analysis on the influence and contribution of each GPI terms to justify that thermodynamics is more important. This is particularly true for WNP since it has the most TCs worldwide. + +L555 - explain these acronyms, are MIS5e and 5d the gray columns only? kindly explain in the figures. + +L585 - what does the line plot mean? kindly explain it in the caption. there is no x- axis label in Fig. 4A- B. + +<--- Page Split ---> + +## Reply to Reviewer's comments: + +"Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate" by Pavan Harika Raavi, Jung- Eun Chu, Axel Timmermann, Sun- Seon Lee, and Kevin J. E. Walsh + +<--- Page Split ---> + +## Response to Reviewer 1: + +Thank you very much for your valuable and helpful comments. We have answered your comments carefully and have made corrections according to your comments. The main response to your comments is as follows: + +## General comments + +The authors tried to give an idea of future tropical cyclone activity by comparing past and future climate simulations. They used the MIS5e, MIS5d scenarios for the past climate and the PD, CO2 doubling scenarios for the future climate. By comparing the responses of tropical cyclone activity to past and future climate, they found that moisture plays a critical role in tropical cyclone activity. In general, the manuscript is well organised. However, I have several concerns about its publication. + +## Major comments + +1. I found that the authors have a deep knowledge of paleo-climate studies. Since the NCC is a letter, I understand that the authors have tried to shorten the length of the manuscript. However, this makes it difficult for readers who are not experts in palaeo-climate to follow the significance of their findings. Since the NCC is a letter to the non-expert in the field, I suggest that the authors add more explanation and information about palaeoclimate studies. For example, in lines 53-59, I don't know what is the limitation of the previous studies of warm climate episodes. Please provide more information. + +## Response: + +Thank you for your suggestion. We agree with the reviewer's comment that the limitations of the paleoclimate studies were not adequately addressed. We have expanded into more details about those paleoclimate studies in the introduction of the revised manuscript (Lines: 55- 86). + +To highlight the several sentences, most of the studies are based on low- resolution models and/or the idea that large- scale environments such as an empirical TC genesis potential index (GPI) can represent changes in TC activity. To obtain a detailed perspective on the relationship between large- scale climatic drivers and TC statistics, it is important to explicitly resolve TCs and their key mesoscale features in a climate model. To the best of our knowledge, there are no systematic paleotimeslice studies that explicitly resolve TCs using a fully coupled high- resolution Earth system model. Especially, simulation for MIS5e (LIG) has not been conducted. In other words, TC statistics such as frequency and intensity under different background conditions have not been fully tested. + +This study is the first systematic approach to understand controlling factor of TC characteristics for both orbital forcing (MIS5e vs MIS5d) and greenhouse gas forcing (2xCO2 vs PD) using fully coupled high- resolution CESM simulations. In addition, to improve the robustness of our results, + +<--- Page Split ---> + +we also included two tracking schemes, two GPI indices, and a relatively long TC tracking period (60 years) for each simulation. + +Also, what is the difference between the MIS5e and MIS5d simulations compared to the last interglacial, the Eocene and the Pliocene simulations? Please explain and highlight the difference. + +## Response: + +The last interglacial (LIG) was the most recent warm period that that took place at around 125ka and is also referred to as Marine Isotope Stage (MIS) 5e. Contrary to the present- day (PD) orbital configuration, the MIS5e was characterized by Northern Hemisphere (NH) summer perihelion conditions and warmer (colder) NH (SH) summers. The MIS5d is the glacial sub- stage characterized by Southern Hemisphere (SH) summer perihelion conditions and warmer (colder) SH (NH) summers. Stronger seasonal anomalies are caused by variations in the orbital forcing, which varies in the incoming solar radiation. A comparison of MIS5e and MIS5d helps us to understand the role of the orbital forcing on TC characteristics. + +During the early- Eocene the global mean annual surface temperatures were \(13 + 2.6\) degrees warmer than the late \(20^{\mathrm{th}}\) century temperatures and atmospheric \(\mathrm{CO_2}\) was 1400 ppmv. The Mid- . pliocene is the most recent period with the atmospheric \(\mathrm{CO_2}\) concentration comparable to the present (400 ppmv), global mean annual surface temperatures are 1.8 to 3.6 degrees higher than the pre- industrial temperatures. + +In the LIG (MIS5e- MIS5d), global mean annual surface temperatures are 0.8- 1.3 degrees warmer than the pre- industrial average with \(\mathrm{CO_2}\) levels of around 280 ppmv. The LIG period has lower \(\mathrm{CO_2}\) levels than other warmer epochs like the Eocene and Pliocene; the elevated temperatures are caused by significant seasonal variations in the incoming solar radiation and climate rectifications. The LIG period is the most recent time frame with higher global mean surface temperatures that can serve as an analogue to the current interglacial period. + +These details are included in the revised manuscript at lines 55- 65 and 89- 98. + +2. According to the introduction, it seems to me that the authors have found striking evidence in the projection of future tropical cyclone activity. However, their main finding is that only moisture is the most important. In fact, this result can only be found with the result of PD, CO2 doubling experiments. I don't know why the MIS5e and MIS5d experiments are essential to the authors' argument. Although the authors insist that the different experiments can reduce the uncertainty, I think the authors still cannot avoid the uncertainty problem by using the single model, CESM. I think the importance of this study is not to reduce the uncertainty, but rather a possible importance of tropospheric humidity. + +Response: + +<--- Page Split ---> + +We totally understand the reviewer's concern on uncertainty problem, and we appreciate this comment. In the revised manuscript, we tried to emphasize our efforts to improve robustness of our results. + +Currently, there is no consensus on changes in future TC frequency. This brought us an idea to determine whether there is a common link between the large- scale environments and changes in TC characteristics from the past to the future climates. As the reviewer stated, our result is simple that moisture related variable or thermodynamical conditions are the dominating factors influencing the TC frequency both in the past and future warmer climates and we were happy to find this key factor. + +It is noted that moisture related variable or thermodynamical conditions are the dominating factors influencing the TC frequency both in the past and future warmer climates. We may infer from the current study that one of the key contributing factors for TC frequency fluctuations related to various model climates (Past, present, and future) is moist entropy deficit. + +The selection of MIS5e and MIS5d was made because these two periods represent the most recent extreme orbital conditions with low and high precession indexes respectively and large eccentricity. A low (high) precession index corresponds to NH summer perihelion (aphelion) condition and associated intensified (weakened) NH summer solar radiation. This effect is visible only for high values of Earth's orbit eccentricity and the intervals from 125- 115 ka represent one of these periods. Therefore, MIS5e and MIS5d serve as excellent test grounds. + +One of the limitations of this study is that we rely on a single model and a single ensemble. However, this model is among the highest TC- resolving scale fully coupled model and shows an excellent performance in representing TC characteristics and their air- sea interaction (Chu et al. 2020). To compensate for this limitation, we used a relatively long TC tracking period (60 years) for each simulation compared to previous work which used the last 20 years only. In addition, to improve the robustness of our results, we also included two fundamentally different tracking schemes and two different GPI indices. We hope you'll find this response to be acceptable. + +3. Lines 155-174: I can acknowledge that RH related variables are most similar to GPI. If the quantitative contribution of each factor is given in the table, it will be much easier to understand the results. + +## Response: + +Thank you for your good suggestion. In the revised manuscript, we included Table 2 that describes percentage contribution of the different GPI terms to total GPI change (MIS5e – MIS5d; 2xCO2 – PD). The table clearly shows that moist related variable is the largest contributor among others. + +<--- Page Split ---> + +## Response to Reviewer 2: + +Response to Reviewer 2:We wish to thank the reviewer for insightful comments and suggestions on our manuscript, which were very useful to revise the first version. The followings are point- by- point responses to the comments: + +## General comments + +General commentsThe following is a review of the manuscript submitted by Raavi et al entitled Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. The results are interesting and provides new insights on the paleoclimatology of tropical cyclones, which are timely and relevant particularly in the advent of discussions surrounding global environmental changes. I have few comments, clarifications, and suggestions to the author. I believe the manuscript has potential for publication after the following comments have been adequately answered: + +L65- 66 - the use of NH summer vis- a- vis boreal summer here is confusing + +## Response: + +Thank you for your suggestion. The boreal summer is replaced with NH summer and the austral summer is replaced with SH summer. + +L75 - What is MIS5d. It is not yet explained. why are they called extreme orbital conditions? + +## Response: + +Thank you for raising this point. Based on this question raised by two reviewers, we learn that the explanation about the selection of MIS5e and MIS5d are not well addressed. + +The MIS5d is a glacial sub- stage characterized by SH summer perihelion conditions and warmer (colder) SH (NH) summers. The selection of MIS5e and MIS5d was made because these two periods represent the most recent extreme orbital conditions with low and high precession indexes respectively and large eccentricity. The precession index is \(e \sin (\omega_{s})\) , where \(e\) is the eccentricity and \(\omega_{s}\) measures how close the sun is to the earth at midsummer. A low (high) precession index corresponds to NH summer perihelion (aphelion) condition and associated intensified (weakened) boreal summer solar radiation. This effect is visible only for high values of Earth's orbit eccentricity and the intervals from 125- 115 ka represent one of these periods. Therefore, MIS5e and MIS5d serve as excellent test grounds. + +L98 - consider putting this explanation in earlier parts to provided clarity in the discussion Response: + +<--- Page Split ---> + +Thank you for your suggestion. The detailed explanation of MIS5e and MIS5d are now added in the introduction part of the revised draft at lines 89- 98. + +L148 - is it possible to put a timeseries of GPI in Fig. 1 to show such reduction in response to MIS5e- d, PDO, and \(2\mathrm{xCO2}\) ? This is for ease of reading for readers that are universally adept to paleoclimate. + +## Response: + +Thank you for your comment. We do agree that adding the GPI time series will ease the readers. However, our experiments (MIS5e, MIS5d, PD, and \(2\mathrm{xCO2}\) ) are paleo and future timeslice simulations using a high- resolution CESM model with \(0.25^{\circ}\) in the atmosphere and \(0.1^{\circ}\) in the ocean, whereas the time series in Fig. 1 are from the long- term transient climate simulation using a low- resolution CESM with the horizontal resolution of \(3.75^{\circ}\times 3.75^{\circ}\) (Timmermann et al. 2022). Therefore, the experiments are fundamentally different. To avoid confusion from two different simulations, we would like to keep Fig. 1 in its current form. We hope the reviewer understands our intention. + +## L158 - "TC genesis" + +## Response: + +Thank you for your comment. It is corrected in the revised manuscript. + +## L161 - WNP typically covers until 100E while NI covers until 95E + +## Response: + +Thank you for your comment. This is corrected in the revised manuscript for the respective figures. + +L167- 168 - vertical wind shear in the WNP; how to determine the contribution of one term in GPI? is there a way to determine significance? + +## Response: + +Thank you for your comment. In the revised manuscript, we included Table 2 that describes percentage contribution of the different GPI terms to total GPI change (MIS5e - MIS5d; \(2\mathrm{xCO2}\) - PD) with significant test. The table clearly shows that moisture related variable is the largest contributor among others. + +L171- 173 - same with comments above. Looking at Fig. 3A and Fig S3C, there is a meridional component of dGPI extending from south to north in the WNP, which is not captured in Fig 3D but is captured in Fig. 3E. Same can be said in the Caribbean and Eastern Pacific where VWS seems to affect the dGPI. + +<--- Page Split ---> + +## Response: + +Thank you for pointing this out. As the reviewer stated, VWS plays an important role in determining dGPI over the western North Pacific, eastern Pacific, and Atlantic Ocean, especially in response to the orbital forcing (i.e., MIS5e- MIS5d). Therefore, their role is not negligible on the regional scale. However, the contribution of VWS is limited to the off- equatorial zone at around \(10^{\circ}\mathrm{N}\) , making its overall contribution over the entire NA and WNP less important than MED (Table 2). In addition, the contribution of VWS in response to greenhouse gas forcing is not statistically significant (Table 2). + +Similarly, the filament of negative 850 hPa abs. vorticity in Fig 3B, resembles that in the eastern Pacific indicating that atmospheric component (VWS and Abs. Vort) also affect dGPI. how to determine the contribution of one term in GPI? is there a way to determine significance? + +## Response: + +Our response to this question will be similar to the above answer. Likewise in vertical wind shear, the \(850\mathrm{hPa}\) absolute vorticity seems to play an important role in the off- equatorial zone. But its contribution over the entire basin is less important and is not statistically significant in both forcings. As this study aims to determine whether there is a common link between the large- scale environments and changes in TC characteristics that works both in the past to the future conditions, we emphasized more on the moist- entropy deficit (MED). But as we mentioned, VWS and AVOR are also important in some areas. + +The percent contribution in Table 2 is calculated by dividing the relative role of each GPI term (each term on the right- hand side of the GPI component analysis) by total changes in GPI (dGPI). Because the GPI has no units, we expressed the percentage contribution rather than the actual dGPI value. The statistical significance of each term at individual grid points was tested by calculating GPIs by replacing only one term from each simulation. For example, the significance of the MED contribution between MIS5e and MIS5d was calculated by comparing two GPIs: one with all terms in the MIS5e simulation and the other with all terms in the MIS5e simulation except for MED in the MIS5d simulation. + +L176- 181 - There is a need to characterize the term "most" here because it can be seen that VWS also has considerable changes. This leads to my next question - does the blue mean decrease in VWS? If yes, does it mean more favorable TC genesis environment? Both sides remain to ask how to determine their significant contribution. + +## Response: + +We apologize for any confusion caused due to insufficient explanation. Colors in Fig. 3 from individual terms indicate their contribution to dGPI. For example, dGPI in Fig. 3A is the sum of Fig. 3B to Fig. 3E. Red colors in each term indicate favorable TC genesis environment and blue colors indicates unfavorable condition. For example, blue colors in vertical wind shear term (e.g., + +<--- Page Split ---> + +Fig. 3E) means decreases in Term4 (i.e., \((25 + V_{shear})^{- 4})\) which is driven by increased vertical wind shear. Regarding the significant contribution, we believe the newly added Table 2 will help in understanding better. + +L197- 198: this is confusing because I though that the GPI in Fig. 3 denotes decrease in TC genesis. A northward ITCZ means favorable TC genesis environment because the moisture associated with the ITCZ is found in the WNP. + +## Response: + +You are right. In general, unfavorable conditions (decreases in TC generation) are produced in the NH summer due to changes in the thermodynamic environment in response to orbital forcing. However, a northward- shifted ITCZ partly offsets this effect, and we found that this influence is limited to the NI and ENP regions, not in the WNP basin (Fig. R1). + +![PLACEHOLDER_11_0] + +
Fig. R1. Differences in (a) GPI and (b) precipitation between MIS5e and MIS5d during the TC peak seasons across different ocean basins (i.e., JAS in North Pacific and North Atlantic basins; JFM in Southern Hemisphere basins; OND in North Indian Ocean).
+ +L215 - this is related to my previous comment. The mention of Fig S9 without relating to Fig. 4A first is confusing to the reader. + +Response: + +<--- Page Split ---> + +Thank you for your valuable comment. We tried to increase the readability in the figure transition between Fig. 4 and Fig. S9 in lines 245- 257. + +## L264 - where in the figure does it show the correlation? is it through eyeball only? + +## Response: + +Thank you for pointing out this inadequate word "correlate". The sentence is modified in lines 300- 302 as below. + +"Seasonal variations in the mid- level vertical velocity (Fig. S6F) correspond with changes in relative humidity;" + +L271 - what does it mean by global ocean changes in relation to VWS and TC frequency? + +## Response: + +The "global ocean changes" is now corrected to "global changes" in line 308. Thank you. + +L272 - the mismatch in the anomaly patterns vis- a- vis GPI in two simulations show that thermodynamic is more important that dynamic variable? In a paper by Sharmila and Walsh (2017; https://doi.org/10.1175/JCLI- D- 16- 0900.1), they mentioned that dynamic parameters are more important in the WNP and South Pacific. + +## Response: + +Thank you for your comment. The dynamical factors play a role in the orbital forcing simulations. However, we looked for a consistent or common limiting factor that applies to the majority of the global basins both in past and future warmer climates, and we emphasize that thermodynamic factor is the major controlling factor. + +L295 - did you combine the peak season for each basin then plot the NH? Each basin has different peak season which has to be considered. I think there is a need to provide more explanation/analysis on the influence and contribution of each GPI terms to justify that thermodynamics is more important. This is particularly true for WNP since it has the most TCs worldwide. + +## Response: + +Thank you for your comments. We have considered different peak seasons for different ocean basins, including JAS for the NA, ENP, and WNP; OND for the NI; and JFM for the SI and SP basins. As we have many components from two forcings, we wanted to exhibit them on one map instead of showing all seasons in separate figures. In the revised manuscript, we have included Table 2 to quantitatively identify the governing factors associated with the TC frequency changes + +<--- Page Split ---> + +in both orbital and greenhouse warming experiments. We also tested that changing one month before and after the peak season in the WNP does not change our conclusions. + +L555 - explain these acronyms, are MIS5e and 5d the gray columns only? kindly explain in the figures. + +## Response: + +Thank you for your comments. The gray bars indicate the timing for four timeslice simulations. We included this information in the Fig. 1 caption of the revised manuscript. + +L585 - what does the line plot mean? kindly explain it in the caption. there is no x- axis label in Fig. 4A- B. + +## Response: + +Thank you for pointing out this missing information. The blue line plot shows the zonal mean latitudinal distribution of TC frequency changes. We added this information to the figure caption and plotted the x- axis label in the updated revised manuscript. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +I appreciate the authors' efforts to respond to my comments. All my comments are well addressed, but there is just one point where I feel a bit uncomfortable. + +I think the importance of this study is to show that moisture is the most controlling factor for tropical cyclone frequency under global climate change, regardless of whether the origin of climate change is greenhouse gases or other external forcings. I think this is a very interesting finding and may provide clues to understanding future tropical cyclone activity. However, this is only true for the single model used in this study, which is the limitation of this study as the authors replied. In this respect, I don't agree that this study contributes to reducing uncertainty about future changes in tropical cyclone activity. In the revised version of the manuscript, the related argument is weakened, so I don't have a strong disagreement against the revised manuscript. Nevertheless, I would recommend that the authors avoid the statement about "uncertainty" in the introduction if they can. This is because the statement may mislead readers into expecting that their study reduces uncertainty problems. Another alternative is for the authors to make the limitations of their study clearer in the conclusion. + +Reviewer #2 (Remarks to the Author): + +This is a review of the manuscript submitted by Raavi et al entitled Moisture + +control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. + +I believe that the results are interesting and provides new insights on the paleoclimatology of tropical + +cyclones. I believe that the authors have adequately replied to my comments in the previous revision. I have minor editorial comments to which I defer to the editors for their discretion on such comments. I would like to see bigger font/typeface size in ALL FIGURES (both main and supplementary) as it is quite challenging to squint through the manuscript. Where it is possible, use bigger font sizes as some readers prefer printed copy rather than electronic copy. Make sure that the color palette are also color blind- safe. The green in Fig. 5 is almost difficult to see. The contour in Fig. S1 is too thick compared to the rest of the image. After all of these minor editorial comments have been answered, I believe the manuscript can be considered for publication. + +<--- Page Split ---> + +## Response to Reviewers + +"Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate" by Pavan Harika Raavi, Jung- Eun Chu, Axel Timmermann, Sun- Seon Lee, and Kevin J. E. Walsh + +Dear Editor: + +We appreciate the opportunity to address the reviewers' constructive suggestions and revise our manuscript "Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate" once again. We appreciate the editor and the reviewers for their thorough reviews and useful comments that have been of great help in improving the manuscript. A response to the individual comments is provided below, with the reviewer's comments in bold- faced text and our answers in the light- faced text. Finally, we thoroughly checked the editorial requests and revised our figures and texts carefully. + +Yours sincerely, + +Pavan Harika Raavi and Jung- Eun Chu + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +I appreciate the authors' efforts to respond to my comments. All my comments are well addressed, but there is just one point where I feel a bit uncomfortable. I think the importance of this study is to show that moisture is the most controlling factor for tropical cyclone frequency under global climate change, regardless of whether the origin of climate change is greenhouse gases or other external forcings. I think this is a very interesting finding and may provide clues to understanding future tropical cyclone activity. However, this is only true for the single model used in this study, which is the limitation of this study as the authors replied. In this respect, I don't agree that this study contributes to reducing uncertainty about future changes in tropical cyclone activity. In the revised version of the manuscript, the related argument is weakened, so I don't have a strong disagreement against the revised manuscript. Nevertheless, I would recommend that the authors avoid the statement about "uncertainty" in the introduction if they can. This is because the statement may mislead readers into expecting that their study reduces uncertainty problems. Another alternative is for the authors to make the limitations of their study clearer in the conclusion. + +Thank you very much for your valuable comments. In the revised manuscript, we included a statement regarding the limitation of the study which is based on single model usage (Line 416- 418). In addition, to avoid overstating the uncertainty issue, we removed the statement about uncertainty reduction in the introduction of the revised manuscript. Thank you. + +## Reviewer #2 (Remarks to the Author): + +This is a review of the manuscript submitted by Raavi et al entitled Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. I believe that the results are interesting and provides new insights on the paleoclimatology of tropical cyclones. I believe that the authors have adequately replied to my comments in the previous revision. I have minor editorial comments to which I defer to the editors for their discretion on such comments. I would like to see bigger font/typeface size in ALL FIGURES (both main and supplementary) as it is quite challenging to squint through the manuscript. Where it is possible, use bigger font sizes as some readers prefer printed copy rather than electronic copy. Make sure that the color palette are also color blind- safe. The green in Fig. 5 is almost difficult to see. The contour in Fig. S1 is too thick compared to the rest of the image. After all of these minor editorial comments have been answered, I believe the manuscript can be considered for publication. + +Thank you for your considerate comments. To enhance the readability, we carefully checked the font sizes, information, and blind- safe colors for all figures in the revised manuscript, including Fig. 5 and Fig. S1 as you suggested. Thank you. + +<--- Page Split ---> diff --git a/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0660a4990fac47a58e4ed3abae671324fd913d61 --- /dev/null +++ b/peer_reviews/77e03ed245d6dd4528141df3b1abe4a1430b026fad4a1cd4a5f7261531d06321/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,452 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[66, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[96, 153, 913, 255]]<|/det|> +Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 145, 404, 160]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 203, 870, 295]]<|/det|> +The authors tried to give an idea of future tropical cyclone activity by comparing past and future climate simulations. They used the MIS5e, MIS5d scenarios for the past climate and the PD, CO2 doubling scenarios for the future climate. By comparing the responses of tropical cyclone activity to past and future climate, they found that moisture plays a critical role in tropical cyclone activity. In general, the manuscript is well organised. However, I have several concerns about its publication. + +<|ref|>text<|/ref|><|det|>[[118, 338, 878, 427]]<|/det|> +1) I found that the authors have a deep knowledge of paleo-climate studies. Since the NCC is a letter, I understand that the authors have tried to shorten the length of the manuscript. However, this makes it difficult for readers who are not experts in palaeo-climate to follow the significance of their findings. Since the NCC is a letter to the non-expert in the field, I suggest that the authors add more explanation and information about palaeoclimate studies. + +<|ref|>text<|/ref|><|det|>[[118, 471, 831, 506]]<|/det|> +For example, in lines 53- 59, I don't know what is the limitation of the previous studies of warm climate episodes. Please provide more information. + +<|ref|>text<|/ref|><|det|>[[118, 550, 855, 586]]<|/det|> +Also, what is the difference between the MIS5e and MIS5d simulations compared to the last interglacial, the Eocene and the Pliocene simulations? Please explain and highlight the difference. + +<|ref|>text<|/ref|><|det|>[[117, 628, 876, 775]]<|/det|> +2) According to the introduction, it seems to me that the authors have found striking evidence in the projection of future tropical cyclone activity. However, their main finding is that only moisture is the most important. In fact, this result can only be found with the result of PD, CO2 doubling experiments. I don't know why the MIS5e and MIS5d experiments are essential to the authors' argument. Although the authors insist that the different experiments can reduce the uncertainty, I think the authors still cannot avoid the uncertainty problem by using the single model, CESM. I think the importance of this study is not to reduce the uncertainty, but rather a possible importance of tropospheric humidity. + +<|ref|>text<|/ref|><|det|>[[118, 818, 876, 870]]<|/det|> +3) Lines 155-174: I can acknowledge that RH related variables are most similar to GPI. If the quantitative contribution of each factor is given in the table, it will be much easier to understand the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 115, 404, 130]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 174, 872, 284]]<|/det|> +The following is a review of the manuscript submitted by Raavi et al entitled Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. The results are interesting and provides new insights on the paleoclimatology of tropical cyclones, which are timely and relevant particularly in the advent of discussions surrounding global environmental changes. I have few comments, clarifications, and suggestions to the author. I believe the manuscript has potential for publication after the following comments have been adequately answered: + +<|ref|>text<|/ref|><|det|>[[118, 326, 669, 343]]<|/det|> +L65- 66 - the use of NH summer vis- a- vis boreal summer here is confusing + +<|ref|>text<|/ref|><|det|>[[118, 356, 807, 373]]<|/det|> +L75 - What is MIS5d. It is not yet explained. why are they called extreme orbital conditions? + +<|ref|>text<|/ref|><|det|>[[118, 387, 793, 404]]<|/det|> +L98 - consider putting this explanation in earlier parts to provided clarity in the discussion + +<|ref|>text<|/ref|><|det|>[[118, 417, 875, 452]]<|/det|> +L148 - is it possible to put a timeseries of GPI in Fig. 1 to show such reduction in response to MIS5ed, PDO, and 2xCO2? This is for ease of reading for readers that are universally adept to paleoclimate. + +<|ref|>text<|/ref|><|det|>[[118, 466, 263, 482]]<|/det|> +L158 - "TC genesis" + +<|ref|>text<|/ref|><|det|>[[118, 496, 596, 512]]<|/det|> +L161 - WNP typically covers until 100E while NI covers until 95E + +<|ref|>text<|/ref|><|det|>[[118, 526, 874, 561]]<|/det|> +L167- 168 - vertical wind shear in the WNP; how to determine the contribution of one term in GPI? is there a way to determine significance? + +<|ref|>text<|/ref|><|det|>[[118, 574, 875, 646]]<|/det|> +L171- 173 - same with comments above. Looking at Fig. 3A and Fig S3C, there is a meridional component of dGPI extending from south to north in the WNP, which is not captured in Fig 3D but is captured in Fig. 3E. Same can be be said in the Caribbean and Eastern Pacific where VWS seems to affect the dGPI. + +<|ref|>text<|/ref|><|det|>[[118, 689, 838, 744]]<|/det|> +Similarly, the filament of negative 850 hPa abs. vorticity in Fig 3B, resembles that in the eastern Pacific indicating that atmospheric component (VWS and Abs. Vort) also affect dGPI. how to determine the contribution of one term in GPI? is there a way to determine significance? + +<|ref|>text<|/ref|><|det|>[[118, 787, 872, 859]]<|/det|> +L176- 181 - There is a need to characterize the term "most" here because it can be seen that VWS also has considerable changes. This leads to my next question - does the blue mean decrease in VWS? If yes, does it mean more favorable TC genesis environment? Both sides remain to ask how to determine their significant contribution. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 870, 138]]<|/det|> +L197- 198: this is confusing because I though that the GPI in Fig. 3 denotes decrease in TC genesis. A northward ITCZ means favorable TC genesis environment because the moisture associated with the ITCZ is found in the WNP. + +<|ref|>text<|/ref|><|det|>[[118, 151, 870, 186]]<|/det|> +L215 - this is related to my previous comment. The mention of Fig S9 without relating to Fig. 4A first is confusing to the reader. + +<|ref|>text<|/ref|><|det|>[[118, 199, 736, 216]]<|/det|> +L264 - where in the figure does it show the correlation? is it through eyeball only? + +<|ref|>text<|/ref|><|det|>[[118, 230, 781, 247]]<|/det|> +L271 - what does it mean by global ocean changes in relation to VWS and TC frequency? + +<|ref|>text<|/ref|><|det|>[[118, 260, 866, 332]]<|/det|> +L272 - the mismatch in the anomaly patterns vis- a- vis GPI in two simulations show that thermodynamic is more important that dynamic variable? In a paper by Sharmila and Walsh (2017; https://doi.org/10.1175/JCLI- D- 16- 0900.1), they mentioned that dynamic parameters are more important in the WNP and South Pacific. + +<|ref|>text<|/ref|><|det|>[[118, 345, 857, 380]]<|/det|> +L295 - did you combine the peak season for each basin then plot the NH? Each basin has different peak season which has to be considered. + +<|ref|>text<|/ref|><|det|>[[118, 393, 860, 447]]<|/det|> +I think there is a need to provide more explanation/analysis on the influence and contribution of each GPI terms to justify that thermodynamics is more important. This is particularly true for WNP since it has the most TCs worldwide. + +<|ref|>text<|/ref|><|det|>[[118, 460, 825, 496]]<|/det|> +L555 - explain these acronyms, are MIS5e and 5d the gray columns only? kindly explain in the figures. + +<|ref|>text<|/ref|><|det|>[[118, 509, 855, 544]]<|/det|> +L585 - what does the line plot mean? kindly explain it in the caption. there is no x- axis label in Fig. 4A- B. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[114, 92, 514, 117]]<|/det|> +## Reply to Reviewer's comments: + +<|ref|>text<|/ref|><|det|>[[114, 127, 872, 186]]<|/det|> +"Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate" by Pavan Harika Raavi, Jung- Eun Chu, Axel Timmermann, Sun- Seon Lee, and Kevin J. E. Walsh + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 388, 114]]<|/det|> +## Response to Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[115, 124, 882, 181]]<|/det|> +Thank you very much for your valuable and helpful comments. We have answered your comments carefully and have made corrections according to your comments. The main response to your comments is as follows: + +<|ref|>sub_title<|/ref|><|det|>[[115, 219, 275, 237]]<|/det|> +## General comments + +<|ref|>text<|/ref|><|det|>[[114, 246, 882, 360]]<|/det|> +The authors tried to give an idea of future tropical cyclone activity by comparing past and future climate simulations. They used the MIS5e, MIS5d scenarios for the past climate and the PD, CO2 doubling scenarios for the future climate. By comparing the responses of tropical cyclone activity to past and future climate, they found that moisture plays a critical role in tropical cyclone activity. In general, the manuscript is well organised. However, I have several concerns about its publication. + +<|ref|>sub_title<|/ref|><|det|>[[115, 400, 260, 417]]<|/det|> +## Major comments + +<|ref|>text<|/ref|><|det|>[[114, 427, 883, 560]]<|/det|> +1. I found that the authors have a deep knowledge of paleo-climate studies. Since the NCC is a letter, I understand that the authors have tried to shorten the length of the manuscript. However, this makes it difficult for readers who are not experts in palaeo-climate to follow the significance of their findings. Since the NCC is a letter to the non-expert in the field, I suggest that the authors add more explanation and information about palaeoclimate studies. For example, in lines 53-59, I don't know what is the limitation of the previous studies of warm climate episodes. Please provide more information. + +<|ref|>sub_title<|/ref|><|det|>[[115, 571, 201, 588]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 599, 882, 655]]<|/det|> +Thank you for your suggestion. We agree with the reviewer's comment that the limitations of the paleoclimate studies were not adequately addressed. We have expanded into more details about those paleoclimate studies in the introduction of the revised manuscript (Lines: 55- 86). + +<|ref|>text<|/ref|><|det|>[[114, 665, 882, 833]]<|/det|> +To highlight the several sentences, most of the studies are based on low- resolution models and/or the idea that large- scale environments such as an empirical TC genesis potential index (GPI) can represent changes in TC activity. To obtain a detailed perspective on the relationship between large- scale climatic drivers and TC statistics, it is important to explicitly resolve TCs and their key mesoscale features in a climate model. To the best of our knowledge, there are no systematic paleotimeslice studies that explicitly resolve TCs using a fully coupled high- resolution Earth system model. Especially, simulation for MIS5e (LIG) has not been conducted. In other words, TC statistics such as frequency and intensity under different background conditions have not been fully tested. + +<|ref|>text<|/ref|><|det|>[[115, 844, 882, 900]]<|/det|> +This study is the first systematic approach to understand controlling factor of TC characteristics for both orbital forcing (MIS5e vs MIS5d) and greenhouse gas forcing (2xCO2 vs PD) using fully coupled high- resolution CESM simulations. In addition, to improve the robustness of our results, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 127]]<|/det|> +we also included two tracking schemes, two GPI indices, and a relatively long TC tracking period (60 years) for each simulation. + +<|ref|>text<|/ref|><|det|>[[115, 156, 881, 211]]<|/det|> +Also, what is the difference between the MIS5e and MIS5d simulations compared to the last interglacial, the Eocene and the Pliocene simulations? Please explain and highlight the difference. + +<|ref|>sub_title<|/ref|><|det|>[[115, 224, 201, 240]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 251, 882, 400]]<|/det|> +The last interglacial (LIG) was the most recent warm period that that took place at around 125ka and is also referred to as Marine Isotope Stage (MIS) 5e. Contrary to the present- day (PD) orbital configuration, the MIS5e was characterized by Northern Hemisphere (NH) summer perihelion conditions and warmer (colder) NH (SH) summers. The MIS5d is the glacial sub- stage characterized by Southern Hemisphere (SH) summer perihelion conditions and warmer (colder) SH (NH) summers. Stronger seasonal anomalies are caused by variations in the orbital forcing, which varies in the incoming solar radiation. A comparison of MIS5e and MIS5d helps us to understand the role of the orbital forcing on TC characteristics. + +<|ref|>text<|/ref|><|det|>[[115, 411, 882, 504]]<|/det|> +During the early- Eocene the global mean annual surface temperatures were \(13 + 2.6\) degrees warmer than the late \(20^{\mathrm{th}}\) century temperatures and atmospheric \(\mathrm{CO_2}\) was 1400 ppmv. The Mid- . pliocene is the most recent period with the atmospheric \(\mathrm{CO_2}\) concentration comparable to the present (400 ppmv), global mean annual surface temperatures are 1.8 to 3.6 degrees higher than the pre- industrial temperatures. + +<|ref|>text<|/ref|><|det|>[[115, 515, 882, 626]]<|/det|> +In the LIG (MIS5e- MIS5d), global mean annual surface temperatures are 0.8- 1.3 degrees warmer than the pre- industrial average with \(\mathrm{CO_2}\) levels of around 280 ppmv. The LIG period has lower \(\mathrm{CO_2}\) levels than other warmer epochs like the Eocene and Pliocene; the elevated temperatures are caused by significant seasonal variations in the incoming solar radiation and climate rectifications. The LIG period is the most recent time frame with higher global mean surface temperatures that can serve as an analogue to the current interglacial period. + +<|ref|>text<|/ref|><|det|>[[115, 638, 725, 656]]<|/det|> +These details are included in the revised manuscript at lines 55- 65 and 89- 98. + +<|ref|>text<|/ref|><|det|>[[115, 695, 882, 844]]<|/det|> +2. According to the introduction, it seems to me that the authors have found striking evidence in the projection of future tropical cyclone activity. However, their main finding is that only moisture is the most important. In fact, this result can only be found with the result of PD, CO2 doubling experiments. I don't know why the MIS5e and MIS5d experiments are essential to the authors' argument. Although the authors insist that the different experiments can reduce the uncertainty, I think the authors still cannot avoid the uncertainty problem by using the single model, CESM. I think the importance of this study is not to reduce the uncertainty, but rather a possible importance of tropospheric humidity. + +<|ref|>text<|/ref|><|det|>[[115, 857, 201, 873]]<|/det|> +Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 145]]<|/det|> +We totally understand the reviewer's concern on uncertainty problem, and we appreciate this comment. In the revised manuscript, we tried to emphasize our efforts to improve robustness of our results. + +<|ref|>text<|/ref|><|det|>[[114, 157, 883, 268]]<|/det|> +Currently, there is no consensus on changes in future TC frequency. This brought us an idea to determine whether there is a common link between the large- scale environments and changes in TC characteristics from the past to the future climates. As the reviewer stated, our result is simple that moisture related variable or thermodynamical conditions are the dominating factors influencing the TC frequency both in the past and future warmer climates and we were happy to find this key factor. + +<|ref|>text<|/ref|><|det|>[[114, 279, 882, 354]]<|/det|> +It is noted that moisture related variable or thermodynamical conditions are the dominating factors influencing the TC frequency both in the past and future warmer climates. We may infer from the current study that one of the key contributing factors for TC frequency fluctuations related to various model climates (Past, present, and future) is moist entropy deficit. + +<|ref|>text<|/ref|><|det|>[[114, 364, 882, 476]]<|/det|> +The selection of MIS5e and MIS5d was made because these two periods represent the most recent extreme orbital conditions with low and high precession indexes respectively and large eccentricity. A low (high) precession index corresponds to NH summer perihelion (aphelion) condition and associated intensified (weakened) NH summer solar radiation. This effect is visible only for high values of Earth's orbit eccentricity and the intervals from 125- 115 ka represent one of these periods. Therefore, MIS5e and MIS5d serve as excellent test grounds. + +<|ref|>text<|/ref|><|det|>[[114, 486, 883, 617]]<|/det|> +One of the limitations of this study is that we rely on a single model and a single ensemble. However, this model is among the highest TC- resolving scale fully coupled model and shows an excellent performance in representing TC characteristics and their air- sea interaction (Chu et al. 2020). To compensate for this limitation, we used a relatively long TC tracking period (60 years) for each simulation compared to previous work which used the last 20 years only. In addition, to improve the robustness of our results, we also included two fundamentally different tracking schemes and two different GPI indices. We hope you'll find this response to be acceptable. + +<|ref|>text<|/ref|><|det|>[[114, 657, 882, 712]]<|/det|> +3. Lines 155-174: I can acknowledge that RH related variables are most similar to GPI. If the quantitative contribution of each factor is given in the table, it will be much easier to understand the results. + +<|ref|>sub_title<|/ref|><|det|>[[115, 725, 201, 741]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 753, 882, 807]]<|/det|> +Thank you for your good suggestion. In the revised manuscript, we included Table 2 that describes percentage contribution of the different GPI terms to total GPI change (MIS5e – MIS5d; 2xCO2 – PD). The table clearly shows that moist related variable is the largest contributor among others. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 388, 113]]<|/det|> +## Response to Reviewer 2: + +<|ref|>text<|/ref|><|det|>[[115, 124, 882, 181]]<|/det|> +Response to Reviewer 2:We wish to thank the reviewer for insightful comments and suggestions on our manuscript, which were very useful to revise the first version. The followings are point- by- point responses to the comments: + +<|ref|>sub_title<|/ref|><|det|>[[115, 220, 275, 238]]<|/det|> +## General comments + +<|ref|>text<|/ref|><|det|>[[114, 248, 883, 380]]<|/det|> +General commentsThe following is a review of the manuscript submitted by Raavi et al entitled Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. The results are interesting and provides new insights on the paleoclimatology of tropical cyclones, which are timely and relevant particularly in the advent of discussions surrounding global environmental changes. I have few comments, clarifications, and suggestions to the author. I believe the manuscript has potential for publication after the following comments have been adequately answered: + +<|ref|>text<|/ref|><|det|>[[115, 418, 731, 437]]<|/det|> +L65- 66 - the use of NH summer vis- a- vis boreal summer here is confusing + +<|ref|>sub_title<|/ref|><|det|>[[115, 449, 201, 466]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 477, 882, 514]]<|/det|> +Thank you for your suggestion. The boreal summer is replaced with NH summer and the austral summer is replaced with SH summer. + +<|ref|>text<|/ref|><|det|>[[115, 542, 880, 561]]<|/det|> +L75 - What is MIS5d. It is not yet explained. why are they called extreme orbital conditions? + +<|ref|>sub_title<|/ref|><|det|>[[115, 573, 201, 590]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 601, 882, 638]]<|/det|> +Thank you for raising this point. Based on this question raised by two reviewers, we learn that the explanation about the selection of MIS5e and MIS5d are not well addressed. + +<|ref|>text<|/ref|><|det|>[[114, 649, 882, 817]]<|/det|> +The MIS5d is a glacial sub- stage characterized by SH summer perihelion conditions and warmer (colder) SH (NH) summers. The selection of MIS5e and MIS5d was made because these two periods represent the most recent extreme orbital conditions with low and high precession indexes respectively and large eccentricity. The precession index is \(e \sin (\omega_{s})\) , where \(e\) is the eccentricity and \(\omega_{s}\) measures how close the sun is to the earth at midsummer. A low (high) precession index corresponds to NH summer perihelion (aphelion) condition and associated intensified (weakened) boreal summer solar radiation. This effect is visible only for high values of Earth's orbit eccentricity and the intervals from 125- 115 ka represent one of these periods. Therefore, MIS5e and MIS5d serve as excellent test grounds. + +<|ref|>text<|/ref|><|det|>[[115, 846, 875, 894]]<|/det|> +L98 - consider putting this explanation in earlier parts to provided clarity in the discussion Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 127]]<|/det|> +Thank you for your suggestion. The detailed explanation of MIS5e and MIS5d are now added in the introduction part of the revised draft at lines 89- 98. + +<|ref|>text<|/ref|><|det|>[[115, 156, 882, 211]]<|/det|> +L148 - is it possible to put a timeseries of GPI in Fig. 1 to show such reduction in response to MIS5e- d, PDO, and \(2\mathrm{xCO2}\) ? This is for ease of reading for readers that are universally adept to paleoclimate. + +<|ref|>sub_title<|/ref|><|det|>[[115, 223, 201, 240]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 251, 882, 400]]<|/det|> +Thank you for your comment. We do agree that adding the GPI time series will ease the readers. However, our experiments (MIS5e, MIS5d, PD, and \(2\mathrm{xCO2}\) ) are paleo and future timeslice simulations using a high- resolution CESM model with \(0.25^{\circ}\) in the atmosphere and \(0.1^{\circ}\) in the ocean, whereas the time series in Fig. 1 are from the long- term transient climate simulation using a low- resolution CESM with the horizontal resolution of \(3.75^{\circ}\times 3.75^{\circ}\) (Timmermann et al. 2022). Therefore, the experiments are fundamentally different. To avoid confusion from two different simulations, we would like to keep Fig. 1 in its current form. We hope the reviewer understands our intention. + +<|ref|>sub_title<|/ref|><|det|>[[115, 430, 286, 448]]<|/det|> +## L158 - "TC genesis" + +<|ref|>sub_title<|/ref|><|det|>[[115, 460, 201, 477]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 488, 671, 507]]<|/det|> +Thank you for your comment. It is corrected in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 535, 664, 554]]<|/det|> +## L161 - WNP typically covers until 100E while NI covers until 95E + +<|ref|>sub_title<|/ref|><|det|>[[115, 566, 201, 583]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 594, 881, 612]]<|/det|> +Thank you for your comment. This is corrected in the revised manuscript for the respective figures. + +<|ref|>text<|/ref|><|det|>[[115, 640, 882, 678]]<|/det|> +L167- 168 - vertical wind shear in the WNP; how to determine the contribution of one term in GPI? is there a way to determine significance? + +<|ref|>sub_title<|/ref|><|det|>[[115, 690, 201, 707]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 718, 882, 791]]<|/det|> +Thank you for your comment. In the revised manuscript, we included Table 2 that describes percentage contribution of the different GPI terms to total GPI change (MIS5e - MIS5d; \(2\mathrm{xCO2}\) - PD) with significant test. The table clearly shows that moisture related variable is the largest contributor among others. + +<|ref|>text<|/ref|><|det|>[[115, 821, 882, 895]]<|/det|> +L171- 173 - same with comments above. Looking at Fig. 3A and Fig S3C, there is a meridional component of dGPI extending from south to north in the WNP, which is not captured in Fig 3D but is captured in Fig. 3E. Same can be said in the Caribbean and Eastern Pacific where VWS seems to affect the dGPI. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 91, 201, 108]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[114, 118, 883, 250]]<|/det|> +Thank you for pointing this out. As the reviewer stated, VWS plays an important role in determining dGPI over the western North Pacific, eastern Pacific, and Atlantic Ocean, especially in response to the orbital forcing (i.e., MIS5e- MIS5d). Therefore, their role is not negligible on the regional scale. However, the contribution of VWS is limited to the off- equatorial zone at around \(10^{\circ}\mathrm{N}\) , making its overall contribution over the entire NA and WNP less important than MED (Table 2). In addition, the contribution of VWS in response to greenhouse gas forcing is not statistically significant (Table 2). + +<|ref|>text<|/ref|><|det|>[[114, 278, 882, 353]]<|/det|> +Similarly, the filament of negative 850 hPa abs. vorticity in Fig 3B, resembles that in the eastern Pacific indicating that atmospheric component (VWS and Abs. Vort) also affect dGPI. how to determine the contribution of one term in GPI? is there a way to determine significance? + +<|ref|>sub_title<|/ref|><|det|>[[115, 365, 201, 382]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[114, 392, 882, 523]]<|/det|> +Our response to this question will be similar to the above answer. Likewise in vertical wind shear, the \(850\mathrm{hPa}\) absolute vorticity seems to play an important role in the off- equatorial zone. But its contribution over the entire basin is less important and is not statistically significant in both forcings. As this study aims to determine whether there is a common link between the large- scale environments and changes in TC characteristics that works both in the past to the future conditions, we emphasized more on the moist- entropy deficit (MED). But as we mentioned, VWS and AVOR are also important in some areas. + +<|ref|>text<|/ref|><|det|>[[114, 534, 882, 683]]<|/det|> +The percent contribution in Table 2 is calculated by dividing the relative role of each GPI term (each term on the right- hand side of the GPI component analysis) by total changes in GPI (dGPI). Because the GPI has no units, we expressed the percentage contribution rather than the actual dGPI value. The statistical significance of each term at individual grid points was tested by calculating GPIs by replacing only one term from each simulation. For example, the significance of the MED contribution between MIS5e and MIS5d was calculated by comparing two GPIs: one with all terms in the MIS5e simulation and the other with all terms in the MIS5e simulation except for MED in the MIS5d simulation. + +<|ref|>text<|/ref|><|det|>[[114, 713, 882, 788]]<|/det|> +L176- 181 - There is a need to characterize the term "most" here because it can be seen that VWS also has considerable changes. This leads to my next question - does the blue mean decrease in VWS? If yes, does it mean more favorable TC genesis environment? Both sides remain to ask how to determine their significant contribution. + +<|ref|>sub_title<|/ref|><|det|>[[115, 800, 201, 817]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 828, 882, 901]]<|/det|> +We apologize for any confusion caused due to insufficient explanation. Colors in Fig. 3 from individual terms indicate their contribution to dGPI. For example, dGPI in Fig. 3A is the sum of Fig. 3B to Fig. 3E. Red colors in each term indicate favorable TC genesis environment and blue colors indicates unfavorable condition. For example, blue colors in vertical wind shear term (e.g., + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 882, 146]]<|/det|> +Fig. 3E) means decreases in Term4 (i.e., \((25 + V_{shear})^{- 4})\) which is driven by increased vertical wind shear. Regarding the significant contribution, we believe the newly added Table 2 will help in understanding better. + +<|ref|>text<|/ref|><|det|>[[114, 174, 882, 231]]<|/det|> +L197- 198: this is confusing because I though that the GPI in Fig. 3 denotes decrease in TC genesis. A northward ITCZ means favorable TC genesis environment because the moisture associated with the ITCZ is found in the WNP. + +<|ref|>sub_title<|/ref|><|det|>[[115, 243, 202, 260]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[114, 270, 882, 346]]<|/det|> +You are right. In general, unfavorable conditions (decreases in TC generation) are produced in the NH summer due to changes in the thermodynamic environment in response to orbital forcing. However, a northward- shifted ITCZ partly offsets this effect, and we found that this influence is limited to the NI and ENP regions, not in the WNP basin (Fig. R1). + +<|ref|>image<|/ref|><|det|>[[180, 356, 805, 700]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 711, 876, 768]]<|/det|> +
Fig. R1. Differences in (a) GPI and (b) precipitation between MIS5e and MIS5d during the TC peak seasons across different ocean basins (i.e., JAS in North Pacific and North Atlantic basins; JFM in Southern Hemisphere basins; OND in North Indian Ocean).
+ +<|ref|>text<|/ref|><|det|>[[114, 797, 882, 835]]<|/det|> +L215 - this is related to my previous comment. The mention of Fig S9 without relating to Fig. 4A first is confusing to the reader. + +<|ref|>text<|/ref|><|det|>[[115, 847, 202, 864]]<|/det|> +Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 882, 127]]<|/det|> +Thank you for your valuable comment. We tried to increase the readability in the figure transition between Fig. 4 and Fig. S9 in lines 245- 257. + +<|ref|>sub_title<|/ref|><|det|>[[114, 185, 800, 204]]<|/det|> +## L264 - where in the figure does it show the correlation? is it through eyeball only? + +<|ref|>sub_title<|/ref|><|det|>[[115, 215, 202, 232]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 243, 882, 279]]<|/det|> +Thank you for pointing out this inadequate word "correlate". The sentence is modified in lines 300- 302 as below. + +<|ref|>text<|/ref|><|det|>[[115, 290, 882, 327]]<|/det|> +"Seasonal variations in the mid- level vertical velocity (Fig. S6F) correspond with changes in relative humidity;" + +<|ref|>text<|/ref|><|det|>[[115, 355, 861, 375]]<|/det|> +L271 - what does it mean by global ocean changes in relation to VWS and TC frequency? + +<|ref|>sub_title<|/ref|><|det|>[[115, 386, 202, 404]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 415, 819, 433]]<|/det|> +The "global ocean changes" is now corrected to "global changes" in line 308. Thank you. + +<|ref|>text<|/ref|><|det|>[[115, 461, 882, 537]]<|/det|> +L272 - the mismatch in the anomaly patterns vis- a- vis GPI in two simulations show that thermodynamic is more important that dynamic variable? In a paper by Sharmila and Walsh (2017; https://doi.org/10.1175/JCLI- D- 16- 0900.1), they mentioned that dynamic parameters are more important in the WNP and South Pacific. + +<|ref|>sub_title<|/ref|><|det|>[[115, 548, 202, 565]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 576, 882, 650]]<|/det|> +Thank you for your comment. The dynamical factors play a role in the orbital forcing simulations. However, we looked for a consistent or common limiting factor that applies to the majority of the global basins both in past and future warmer climates, and we emphasize that thermodynamic factor is the major controlling factor. + +<|ref|>text<|/ref|><|det|>[[115, 679, 882, 773]]<|/det|> +L295 - did you combine the peak season for each basin then plot the NH? Each basin has different peak season which has to be considered. I think there is a need to provide more explanation/analysis on the influence and contribution of each GPI terms to justify that thermodynamics is more important. This is particularly true for WNP since it has the most TCs worldwide. + +<|ref|>sub_title<|/ref|><|det|>[[115, 786, 202, 802]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 814, 882, 906]]<|/det|> +Thank you for your comments. We have considered different peak seasons for different ocean basins, including JAS for the NA, ENP, and WNP; OND for the NI; and JFM for the SI and SP basins. As we have many components from two forcings, we wanted to exhibit them on one map instead of showing all seasons in separate figures. In the revised manuscript, we have included Table 2 to quantitatively identify the governing factors associated with the TC frequency changes + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 882, 127]]<|/det|> +in both orbital and greenhouse warming experiments. We also tested that changing one month before and after the peak season in the WNP does not change our conclusions. + +<|ref|>text<|/ref|><|det|>[[114, 155, 882, 194]]<|/det|> +L555 - explain these acronyms, are MIS5e and 5d the gray columns only? kindly explain in the figures. + +<|ref|>sub_title<|/ref|><|det|>[[115, 204, 202, 222]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 232, 882, 270]]<|/det|> +Thank you for your comments. The gray bars indicate the timing for four timeslice simulations. We included this information in the Fig. 1 caption of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 299, 882, 336]]<|/det|> +L585 - what does the line plot mean? kindly explain it in the caption. there is no x- axis label in Fig. 4A- B. + +<|ref|>sub_title<|/ref|><|det|>[[115, 348, 202, 365]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 376, 882, 432]]<|/det|> +Thank you for pointing out this missing information. The blue line plot shows the zonal mean latitudinal distribution of TC frequency changes. We added this information to the figure caption and plotted the x- axis label in the updated revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 144, 404, 159]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 204, 866, 239]]<|/det|> +I appreciate the authors' efforts to respond to my comments. All my comments are well addressed, but there is just one point where I feel a bit uncomfortable. + +<|ref|>text<|/ref|><|det|>[[117, 253, 880, 473]]<|/det|> +I think the importance of this study is to show that moisture is the most controlling factor for tropical cyclone frequency under global climate change, regardless of whether the origin of climate change is greenhouse gases or other external forcings. I think this is a very interesting finding and may provide clues to understanding future tropical cyclone activity. However, this is only true for the single model used in this study, which is the limitation of this study as the authors replied. In this respect, I don't agree that this study contributes to reducing uncertainty about future changes in tropical cyclone activity. In the revised version of the manuscript, the related argument is weakened, so I don't have a strong disagreement against the revised manuscript. Nevertheless, I would recommend that the authors avoid the statement about "uncertainty" in the introduction if they can. This is because the statement may mislead readers into expecting that their study reduces uncertainty problems. Another alternative is for the authors to make the limitations of their study clearer in the conclusion. + +<|ref|>text<|/ref|><|det|>[[119, 548, 404, 562]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 606, 692, 622]]<|/det|> +This is a review of the manuscript submitted by Raavi et al entitled Moisture + +<|ref|>text<|/ref|><|det|>[[118, 636, 819, 652]]<|/det|> +control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. + +<|ref|>text<|/ref|><|det|>[[118, 667, 822, 701]]<|/det|> +I believe that the results are interesting and provides new insights on the paleoclimatology of tropical + +<|ref|>text<|/ref|><|det|>[[117, 715, 877, 860]]<|/det|> +cyclones. I believe that the authors have adequately replied to my comments in the previous revision. I have minor editorial comments to which I defer to the editors for their discretion on such comments. I would like to see bigger font/typeface size in ALL FIGURES (both main and supplementary) as it is quite challenging to squint through the manuscript. Where it is possible, use bigger font sizes as some readers prefer printed copy rather than electronic copy. Make sure that the color palette are also color blind- safe. The green in Fig. 5 is almost difficult to see. The contour in Fig. S1 is too thick compared to the rest of the image. After all of these minor editorial comments have been answered, I believe the manuscript can be considered for publication. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 92, 372, 114]]<|/det|> +## Response to Reviewers + +<|ref|>text<|/ref|><|det|>[[115, 145, 882, 205]]<|/det|> +"Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate" by Pavan Harika Raavi, Jung- Eun Chu, Axel Timmermann, Sun- Seon Lee, and Kevin J. E. Walsh + +<|ref|>text<|/ref|><|det|>[[115, 245, 213, 262]]<|/det|> +Dear Editor: + +<|ref|>text<|/ref|><|det|>[[115, 304, 883, 444]]<|/det|> +We appreciate the opportunity to address the reviewers' constructive suggestions and revise our manuscript "Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate" once again. We appreciate the editor and the reviewers for their thorough reviews and useful comments that have been of great help in improving the manuscript. A response to the individual comments is provided below, with the reviewer's comments in bold- faced text and our answers in the light- faced text. Finally, we thoroughly checked the editorial requests and revised our figures and texts carefully. + +<|ref|>text<|/ref|><|det|>[[115, 485, 230, 503]]<|/det|> +Yours sincerely, + +<|ref|>text<|/ref|><|det|>[[115, 514, 425, 532]]<|/det|> +Pavan Harika Raavi and Jung- Eun Chu + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 437, 108]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 118, 883, 381]]<|/det|> +I appreciate the authors' efforts to respond to my comments. All my comments are well addressed, but there is just one point where I feel a bit uncomfortable. I think the importance of this study is to show that moisture is the most controlling factor for tropical cyclone frequency under global climate change, regardless of whether the origin of climate change is greenhouse gases or other external forcings. I think this is a very interesting finding and may provide clues to understanding future tropical cyclone activity. However, this is only true for the single model used in this study, which is the limitation of this study as the authors replied. In this respect, I don't agree that this study contributes to reducing uncertainty about future changes in tropical cyclone activity. In the revised version of the manuscript, the related argument is weakened, so I don't have a strong disagreement against the revised manuscript. Nevertheless, I would recommend that the authors avoid the statement about "uncertainty" in the introduction if they can. This is because the statement may mislead readers into expecting that their study reduces uncertainty problems. Another alternative is for the authors to make the limitations of their study clearer in the conclusion. + +<|ref|>text<|/ref|><|det|>[[115, 391, 883, 466]]<|/det|> +Thank you very much for your valuable comments. In the revised manuscript, we included a statement regarding the limitation of the study which is based on single model usage (Line 416- 418). In addition, to avoid overstating the uncertainty issue, we removed the statement about uncertainty reduction in the introduction of the revised manuscript. Thank you. + +<|ref|>sub_title<|/ref|><|det|>[[115, 506, 437, 524]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 534, 883, 760]]<|/det|> +This is a review of the manuscript submitted by Raavi et al entitled Moisture control of tropical cyclones in high- resolution simulations of paleoclimate and future climate. I believe that the results are interesting and provides new insights on the paleoclimatology of tropical cyclones. I believe that the authors have adequately replied to my comments in the previous revision. I have minor editorial comments to which I defer to the editors for their discretion on such comments. I would like to see bigger font/typeface size in ALL FIGURES (both main and supplementary) as it is quite challenging to squint through the manuscript. Where it is possible, use bigger font sizes as some readers prefer printed copy rather than electronic copy. Make sure that the color palette are also color blind- safe. The green in Fig. 5 is almost difficult to see. The contour in Fig. S1 is too thick compared to the rest of the image. After all of these minor editorial comments have been answered, I believe the manuscript can be considered for publication. + +<|ref|>text<|/ref|><|det|>[[115, 770, 882, 826]]<|/det|> +Thank you for your considerate comments. To enhance the readability, we carefully checked the font sizes, information, and blind- safe colors for all figures in the revised manuscript, including Fig. 5 and Fig. S1 as you suggested. Thank you. + +<--- Page Split ---> diff --git a/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/images_list.json b/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b0bed340b8205fa0d282a06577aad81fa310e6ac --- /dev/null +++ b/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,630 @@ + +# nature portfolio + +Peer Review File + +Ustilago maydis PR- 1- like protein has evolved two distinct domains for dual virulence activities + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +PR- 1- like proteins belong to a large protein family, and they have been implicated in many different biological processes including immune defense and cancer progression. These proteins share a conserved CAP domain and are mostly secreted glycoproteins. Their mode of action, however, remains poorly characterized. Thus, progress in understanding the function of these proteins at a molecular level would be a welcome advancement. + +Lin et al. now report that the corn smut Ustilago maydis pathogenesis- related 1- like protein (UmPR- 1La) acts in detoxification of phenolic compounds, and that its Ser/Thr- rich N- terminal domain mediates cell surface association. In addition, the authors report that UmPR- 1La has gained a specialized activity in eliciting hyphal formation and they suggest that the protein senses phenolic compounds to direct hyphal growth in plants. The third reported finding is that UmPR- 1La is cleaved by a plant cathepsin B- like protease to release a functional signaling peptide (CAPE- like) that suppresses plant immunity and promotes fungal virulence. + +The main limitation of this study is that it presents an assembly of three more or less independent observations but fails to convey a compelling and significant overall progress in our understanding of the mode of action of PR- 1- like proteins. Moreover, each of the three findings is not sufficiently supported by data. + +Specific comments: + +Fig1a, the consensus sequence for the CAPE1 cleavage is CNYx. It is not clear why the authors change this consensus to CxYx. The same applies for the 11- amino acid CAPE- like peptide sequence. The plant PR- 1 derived CAPE1 peptides all end in R/KPY but this is not conserved in UmPR- 1L. It is not clear what criteria these authors apply to define the CAPE- like peptide derived from UmPR- 1La as being similar/like to that of the plant CAPE1 peptides. + +Fig1b, the normalized read counts for pr- 1la appear to be very low, especially when compared to those for pr- 1lb, which are 100- fold higher (FigS1b), or CatB3, which are about 500- fold higher (Fig5a). The gene thus appears to be expressed only at very low levels. + +<--- Page Split ---> + +Fig1d, are the disease symptoms between the single mutant (Δa) and the double mutant (ΔΔab) statistically significant? The authors describe these differences as "more pronounced" (L137). + +Fig2a,b, the authors say that UmPR1- La and ScPry1- mCherry are cell surface associated proteins, and that UmPR1- La localizes to bud necks and growing tips in sporidal cells. However, they do not show any colocalization experiments with established cell wall markers. At the same time, they show that these proteins are secreted, but they do not include a cell wall- associated protein in the Western blots as control. Are these proteins now secreted or are they cell wall associated? + +Fig2e, shows that recombinant full length and the Ser/Thr- rich domain of UmPR1- La bind chitin and chitosan. The authors do not show whether these proteins are soluble under these conditions in the absence of chitin or chitosan. If the Ser/Thr- rich domain would promote protein self- association, it would appear as binding to chitin/chitosan. These proteins were expressed and purified from bacteria, nevertheless, the authors suggest that they associate with the fungal cell wall by binding to chitin/chitosan via glycosidic linkages (L169- 172). Does the CAP domain bind lignin and is this abrogated in a CBM (FY\*) mutant version? This seems to be important given that the authors subsequently show that the CAP domain binds phenolic compounds that are the precursors and building blocks of lignin. + +Fig3, the apparent role of UmPR1- La in conferring eugenol resistance and the putative function of UmPR1- La in sensing phenolic compounds to signal pseudohyphal growth is based on cells that overexpress this protein, i.e., a SG200 wild- type strain expressing an additional copy of UmPR1- La from a constitutive promoter. Thus, this is a gain- of- function phenotype that may have little in common with the native function of this gene/protein. These crucial experiments need to be supported by showing that mutant cells lacking one (Δa) or both (ΔΔab) UmPR1- L are hypersensitive to eugenol, and that this sensitivity and hyphal growth can be complemented in the deletion strain by expression of one or both UmPR1- L from their respective native promoters. The putative function of the CBM should then be tested in this sensitized background and not in an overexpressing strain. Are the WT and FY\* mutant proteins used in Fig3c and Fig4b expressed at comparable levels, please provide Western data. + +Fig4, as in Fig3, the authors should make sure that they are not scoring an overexpression phenotype. Is an SG200 strain not expressing WT or FY\* mutant version of UmPR1- La sensitive to ferulic acid, what is its morphology? The binding assay shown in Fig4c does not indicate whether binding is specific, concentration- dependent, and saturable. Could it be that the protein gets denatured in the presence of ferulic acid and that this is scored as "binding"? This also applies to FigS4b. + +Fig5, the authors fail to detect the UmCAPE- La peptide in the apoplastic fluid of U. maydis infected leaves (L239). Hence there is no evidence that this peptide is actually produced in planta. Did they try infection with an overexpression strain? Fig5b, CatB3, which shows cleavage activity towards recombinant UmPR1- La, was purified from the apoplastic fluid of tobacco leaves and this protein + +<--- Page Split ---> + +preparation is not pure (FigS5b). Purification and cleavage assay with a catalytically dead mutant version of CatB3 would be needed to claim that the observed cleavage is indeed due to CatB3 and not a contaminating protease. This seems to be particularly important given that the cleavage of the native secreted version of UmPR1- L by CatB3 appears to be very slow and inefficient. + +Fig6, if CAPE- L indeed has immune suppressive activity one would expect that U. maydis strains overexpressing UmPR1- La show enhanced virulence. What is the induction of PR gene expression when non- infected plants are treated with ZmCAPE, CAPE- L, or both peptides together, compared to plants treated with scrambled peptide sequences? + +Reviewer #2 (Remarks to the Author): + +The authors provide a functional characterization of 1 (2) effector(s) of the fungal maize pathogen Ustilago maydis, which have homology with plant PR1 proteins, including the C- terminal CAPE peptide which is known to play an important role in PR- 1 mediated induction of plant defenses. The findings shown in the paper are new and exciting. Also, the experiments are all over sound. However, the presentation and documentation of data is partially incomplete. Also, this reviewer is not completely convinced how the two proposed functions of eugenol detoxification (which is actually rather resistance/tolerance than detox) and CAPE- release to block plant immunity are linked. Also, it appears unclear why/how the Um- PR1 released CAPE interferes with the generation of Zm- derived CAPE peptide. + +General questions and comments: + +- Are orthologs of related smuts able to complement the PR-1La disease phenotype, or is this specific to the Ustilago maydis protein? + +- Does the PR-1La deletion mutant have any (growth/developmental) defects besides in-planta development? Given its function at cell-surface localization this seems to be relevant for the interpretation of the results and the actual biological function of the PR-1La. + +- It appears (particular at level of this journal) somehow inappropriate to show gene expression data in the main figures (Fig 1; Fig 5) that is actually just extracted from a publication by others. Authors may provide own qPCR data to confirm the proposed expression patterns in their own experimental conditions (and refer to the published data in the supplements) + +<--- Page Split ---> + +- The figure labels are missing some relevant information to make them accessible. In Fig 2 it took me a while to understand that I am looking on an "otef" OE which explains the signals in sporidia. In Figure 3C I needed to search for "FY\*\* and found it in the legend for 3D. However, as the figure 3C is shown, one would understand that there is a "WT" and a "FY\*\* both being somehow with "SG200_PR-1LaHA". What I guess it is, is strain SG200 (which actually should not be called a "wild type", because it is an artificial lab strain) vs the pr-1la deletion strain. Right? + +Allover, it took me lots of time to look up this kind information up, as descriptions in the figures are sparse/sometimes misleading and also the legends lack information (e.g. legend Fig 3 "same strains used in 2a" – this is not sufficient. Please name the strains which are shown!) Thus, the authors should carefully revise their figures (including supplements, where also info is missing), provide more precise labels and information on strains wherever it is needed, otherwise it is very difficult to follow and interpret results. + +- Does the CAPE-peptide have a virulence function for U. maydis? Figure 6 implies that it has a role in virulence. So, is a mutant with a C-terminally truncated PR-1La reduced in virulence? If so, can other (e.g. Zm) CAPE sequences not complement this? + +- If Ustilago CAPE competes for Zm-CAPE with the receptor – how is it then not activating it (if it has a stronger binding affinity?) + +Specific questions: + +- In L136 it is stated that "double deletion phenotype is more pronounced" – Is this really significant compared to the single deletion? + +- Figure 3 and corresponding text: what is the evidence for a "detoxification" – what is shown is resistance to a toxic compound, but not its detox. + +- Figure 4C – what is actually detected here by the spectrophotometer? At which wavelength? Why are no biological reps shown but only technical reps? + +- Figure 5 – also here, biological reps are not shown (MS data). Also, it is not possible for me to understand the figure completely. What are the sequences below 5b? What is shown in 5C (what is "y7" "y6" etc?) What is scale of "intensity"? How does this show a specific cleavage of PR-1La by CatB3? + +- Fig S5A indicates degradation of PR-1La by apoplastic fluid of maize. However, none of the inhibitors used could fully block this degradation completely. This actually suggests that multiple proteases are involved in degradation of the protein beyond Cat3B. How do the authors interpret this? + +<--- Page Split ---> + +The submission, "Ustilago maydis PR- 1- like protein has evolved two distinct domains for dual virulence activities" by Lin et al describes a fungal protein, PR- 1- like, that has homology to the well described yeast, PRY1 and plant PR1. The authors show that the U. maydis PR- 1- like proteins contains two domains, Ser/Thr- rich region and the CAP domain with a predicted C- terminal peptide similar to PRY1, while plant PR- 1's only contain the CAP domain with a C- terminal peptide. The authors show that the Ser/Thr- rich region is responsible for the binding of PR- 1- like to Chitin and therefore its localisation to the fungal cell wall. While the CAP domain is responsible for sterol/phenolic binding which induces a switch in U. maydis from sporidia to pseudohyphal structures which allows survival of the fungi. Additionally, the authors show that the C- terminal peptide of PR- 1- like is cleaved by CatB3 a member of the cystine protease family and that PR- 1- like can modulate known plant immune genes which is likely to occur via the C- terminal peptide. Overall, this paper is quite well written and logically structured making it relatively easy to follow the narrative, however some work on Figure layout and labelling will help greatly. I have below some major and minor points to address which should improve the article prior to publication. + +Major point to address + +- Figure 2 – These microscope images (a and d) are not good enough quality to be the only evidence of cell surface localisation. I would like to see better quality and higher resolution images as well as colocalisation with a known cell surface protein so show co-localisation. Arrows would also help to direct reader. + +- Please review all figures as many are lacking good labelling e.g. Fig2, no labels on western blot for expected size of protein especially important for PR-1Lb as there are multiple bands and the band sizes don't seem to match my calculations based on the amino acids described in fig 1. Also Fig2a - PRY1HA I believe should be labelled Umsp:PRY1-HA this was very unclear as the labelling did not match the description in the text of the results. These are just two examples. + +- Add in the O-glycosylation data into a sup figure + +- Figure 3b – Given that the authors base this experiment off the PRY1 literature of PR1 binding Eugenol this seems an unexpected result that the cells do not survive, please expand on/discuss this. Could it be linked to the data in Fig2a where PRY1 does not localise to cell surface in U. maydis? Make clear your reasons for reader. + +- Add loading controls to immunoblot panels. + +<--- Page Split ---> + +- I find it surprising not to have seen an enhancement of defence by the application of the maise CAPE peptide. I would suggest you repeat this experiment, but this time pre-treat the maise with ZmCAPE 1 day prior to infection. This experimental set up is how previous publication have conducted the experiment e.g. Chen et al, 2014 Plant cell and Sung et al, 2021 New Phyt (refs 8 & 9 on your list). Have you also tried it with WT SG200? + +Minor point to address + +- Line 79-81 "However, it is unclear whether a protease involves in the cleavage of the CNYx motif and a receptor to perceive CAPE peptide to activate" suggest editing to read "However, it is unclear whether a protease is involved in the cleavage of the CNYx motif and if there is a receptor to perceive CAPE peptides that activate" + +- Line 95 – “sexual life cycle, it requires U. maydis fine sensing and integrating environmental” suggest editing it to “sexual life cycle, U. maydis requires fine sensing of environmental” + +- Line 97 – “U. maydis secrete a” edit to “U. maydis secretes a” + +- Line 108 – “elicit hyphal-like structures. A CAPE-like peptide” suggest edit to “elicit hyphal-like structures, while a CAPE-like peptide” + +- Line 172-173 – I think this statement has not been 100% proven therefore I would say “the results indicates that this PR-1La may incorporate into the cell-wall chitin/chitosan-glucan matrix possibly via glycosidic linkages” + +- Remind reader that PR-1-likes are not expressed in culture therefore the native PR-1-like’s are not affecting the phenolic binding assays. + +- Figure S3a – there is wrong labelling between the graph and the images or there is a wrong image added – graph shows PR-1La showing cell survival and growth however image is showing PR-1Lb data. Need consistency between graph and images, suggest adding PR-1La and PR-1Lb to both. + +- Line 193 – Wrong Figure, should read Fig 2a. + +<--- Page Split ---> + +- Fig3d – suggesting adding in WT complementation line. Also inconsistent labelling between Fig 1d and 3d + +- Line 218 – CA-treated PR-1La (FY\*) cells show a swollen morphology, based on the image shown for PR-1La WT treated with CA these pseudohyphae also look swollen + +- Inconsistent labelling of sterol graphs between Fig3 and 4. FigS3 and FigS4 + +- Lines 241-244 – re-word sentence, it is difficult to follow. You need to get the phrase culture filtrate or culture supernatant in there as well as saying U. maydis SG200 +PR-1La-HA line. + +- Figure S5a legend is missing information – treatments and concentrations used. Labelling of figure and description in materials and methods don’t match i.e. is control on figure the PIC as in materials you mention DMSO is the control? + +- Line 249 – “Cathepsin B-like 3 (CatB3) has a similar expression profile as umpr-1la” I disagree PR-1La expression is all over the place. I would just say CatB3 is induced during infection or CatB3 is strongly induced from 4dpi compared to mock treatment. + +- Fig5b add arrow to indicate PR-1La band also labels for Coomassie and immunoblot. + +- Fig5b make the second blot on U. maydis secreted PR-1LaHA blot Fig 5c as currently the legend is hard to follow what is being described. Quantify band intensity against total protein stain as there is no size shift (due to small cleavage size) as observed in the previous gel and no loading controls shown. + +- Line 265 – “In maize, homolog Xcp2 is highly expressed in the 266 early infection process and then slowly declines during biotrophy (Fig. S5d).” – I disagree with this statement, there is no difference in expression of Xcp2 between mock and infected tissue. Remove or reword. + +- Line 268 – suggested edit “truncated fragments were detected by Coomassie-blue-staining-PAGE and immunoblot for PRB1-3 and PR-1b” + +<--- Page Split ---> + +- Line 313-317 – “U. maydis probably acquired pr-1-like genes via horizontal gene transfer from the host plants during the coevolutionary arms race.” – I know speculation is acceptable in the discussion but I am not sure this is supported by the literature since most organisms contain a CAP-domain containing protein (or CMB motif) including human glioma PR-1 protein and a snake-venom cysteine-rich secretory protein, yeast as you described. This is also unlikely since the plant PR-1’s don’t contain the Ser/Thr rich region whereas PRY1 does. I think it would be better to rephrase this section. + +- Line 326-328 – “PR-1La lacks a transmembrane domain, it is not clear how the signals perceived at the cell surface is transduced to activate the downstream signaling pathway.” Suggest edit it to “PR-1La lacks a transmembrane domain, therefore it is not clear how the cell surface signals would be perceived and transduced to activate downstream signaling.” + +- Line 387 – “performed as described” – incomplete sentence! + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +PR- 1- like proteins belong to a large protein family, and they have been implicated in many different biological processes including immune defense and cancer progression. These proteins share a conserved CAP domain and are mostly secreted glycoproteins. Their mode of action, however, remains poorly characterized. Thus, progress in understanding the function of these proteins at a molecular level would be a welcome advancement. + +Lin et al. now report that the corn smut Ustilago maydis pathogenesis- related 1- like protein (UmPR- 1La) acts in detoxification of phenolic compounds, and that its Ser/Thr- rich N- terminal domain mediates cell surface association. In addition, the authors report that UmPR- 1La has gained a specialized activity in eliciting hyphal formation and they suggest that the protein senses phenolic compounds to direct hyphal growth in plants. The third reported finding is that UmPR- 1La is cleaved by a plant cathepsin B- like protease to release a functional signaling peptide (CAPE- like) that suppresses plant immunity and promotes fungal virulence. + +The main limitation of this study is that it presents an assembly of three more or less independent observations but fails to convey a compelling and significant overall progress in our understanding of the mode of action of PR- 1- like proteins. Moreover, each of the three findings is not sufficiently supported by data. + +We thank the reviewer for the valuable comments and apologize for the incomplete conveyance of the findings in the previous version of the manuscript. To rectify this, we have made necessary modifications to the respective sections of the results and discussion, and have introduced a new model to effectively communicate the findings of this study. Apart from this, in response to the concerns raised by the reviewer, we have carried out additional experiments to specifically address those issues. + +Specific comments: + +1). Fig1a, the consensus sequence for the CAPE1 cleavage is CNYx. It is not clear why the authors change this consensus to CxYx. The same applies for the 11-amino acid CAPE- like peptide sequence. The plant PR- 1 derived CAPE1 peptides all end in R/KPY but this is not conserved in UmPR- 1L. It is not clear what criteria these authors apply to define the CAPE- like peptide derived from UmPR- 1La as being similar/like to that of the plant CAPE1 peptides. + +We thank the reviewer for bringing these mistakes to our attention. We have made the necessary corrections in the figure legend of Fig.1a. Regarding your second question about the definition of the CAPE- like peptide (CAPE- L) from UmPR- ILa, we compared the peptide sequences between smut fungal PR- 1Ls and plant PR- 1s (Fig. 1b), and revealed a high conservation of the first seven amino acids after CNYx motifs of PR- 1 and PR- 1L proteins. Consequently, we have designated peptides containing the MEME- derived consensus sequence P[P/V]GN[Φ/V][I/V]G as CAPE- like peptides (CAPE- L). The peptide sequence comparison has been incorporated into Fig. 1b in the revised manuscript. Our current hypothesis is that UmCAPE- La may compete for binding to the plant CAPE receptor, thereby blocking the CAPE- dependent signaling pathway. This hypothesis could be tested in the future once the receptor is identified. + +<--- Page Split ---> +![PLACEHOLDER_10_0] + + +The green line denotes the consensus sequence conserved in fungal PR- 1Ls and plant PR- 1s. + +2). Fig1b, the normalized read counts for pr- 1la appear to be very low, especially when compared to those for pr- 1lb, which are 100- fold higher (FigS1b), or CatB3, which are about 500- fold higher (Fig5a). The gene thus appears to be expressed only at very low levels. + +We have observed this discrepancy, and one possible explanation is that PR- 1La may have longer mRNA and protein half- lives or exhibit higher translation activity. However, it is important to note that this hypothesis remains speculative. In our recent study, we investigated the expression of the Sccda2 gene, which was found to be 200 times more abundant than the Sccda1 gene. Surprisingly, despite this significant difference, only ScCda1 proteins were detectable (https://doi.org/10.1128/mbio.00093- 23). This finding suggests that there may not always be a positive correlation between gene expression and protein levels. Moreover, a high expression level of effector genes might not necessarily correlate with their contribution to the virulence of U. maydis. + +3). Fig1d, are the disease symptoms between the single mutant (Δa) and the double mutant (ΔΔab) statistically significant? The authors describe these differences as "more pronounced" (L137). After re- analyzing the data obtained from the four biological replicates, there is no statistical significance in disease symptoms caused by these two mutants. As a result, we have revised our statement to read as 'a similar decrease in virulence was also observed in the double mutant ΔΔpr- 1lab'. + +![PLACEHOLDER_10_1] + + +4). Fig2a,b, the authors say that UmPR1- La and ScPry1- mCherry are cell surface associated proteins, and that UmPR1- La localizes to bud necks and growing tips in sporidal cells. However, they do not show any colocalization experiments with established cell wall markers. At the same time, they show that these + +<--- Page Split ---> + +proteins are secreted, but they do not include a cell wall- associated protein in the Western blots as control. Are these proteins now secreted or are they cell wall associated? + +To confirm the localization of UmPR- 1La on the cell surface, we conducted an experiment involving the overexpression of HA- tagged UmPR- 1La in the AB33 strain. The AB33 strain was chosen for its efficient filament induction, controlled by the nitrate- inducible nar1 promoter, when cultured in a nitrate- containing liquid medium, enabling us to perform plasmolysis to separate the cell wall and plasma membrane. Immunostaining was performed, along with labeling of chitin using WGA- AF488. Subsequently, plasmolysis was carried out. The results demonstrated the colocalization of UmPR- 1La with the chitin on the cell surface, while the fluorescence of UmPR- 1La was not detected inside the expanded space resulting from plasmolysis (\*). This provides conclusive evidence for the cell- wall localization of UmPR- 1La. The corresponding data has been incorporated into Fig. 2c. + +![PLACEHOLDER_11_0] + + +Arrows and (\*) indicate spaces enlarged by plasmolysis. - HA- tagged UmPR- La was labeled by anti- HA and anti- IgG- AF595. - Chitin was stained by WGA- AF488. + +Regarding the concern about protein secretion, it is important to note that, due to the overexpression conditions and the absence of a GPI- anchor, certain cell- wall localized proteins may not bind tightly to the cell walls, as GPI- anchored proteins do. Consequently, these proteins can be detected both on the cell walls and in the culture supernatant if overexpressed. Our finding is also in line with other cell- wall protein studies (Tanaka et al., 2020, https://doi.org/10.1111/nph.16508; Cottier et al., 2020, https://doi.org/10.1242/bio.053470). + +5). Fig2e, shows that recombinant full length and the Ser/Thr- rich domain of UmPR1- La bind chitin and chitosan. The authors do not show whether these proteins are soluble under these conditions in the absence of chitin or chitosan. If the Ser/Thr- rich domain would promote protein self- association, it would appear as binding to chitin/chitosan. These proteins were expressed and purified from bacteria, nevertheless, the authors suggest that they associate with the fungal cell wall by binding to chitin/chitosan via glycosidic linkages (L169- 172). + +We appreciate the concern raised by reviewer #1 regarding protein solubility, which we initially overlooked. As suggested, we conducted protein solubility tests in the assay buffer (50 mM Tris- Cl and 150 mM NaCl, pH 8) without ligands. However, the results were inconsistent in the three replicates (shown below). Full- length (FL) and S/T recombinant proteins showed a tendency to be insoluble, while CAP- domain proteins appeared to be more soluble. Due to these inconsistent findings, we have decided to remove the results of the polysaccharide binding assay from the revised manuscript. + +<--- Page Split ---> +![PLACEHOLDER_12_0] + + +Does the CAP domain bind lignin and is this abrogated in a CBM (FY\\*) mutant version? This seems to be important given that the authors subsequently show that the CAP domain binds phenolic compounds that are the precursors and building blocks of lignin. + +To perform the lignin binding assay, we tested the solubility of lignin in the buffer (50 mM Tris- Cl and \(150~\mathrm{mM~NaCl}\) , pH 8), and observed that the buffer turned brown, indicating that lignin might dissolve in the buffer. Under this condition, all the recombinant proteins were detected in the supernatant fractions in the presence of lignin. However, this result does not indicate that the FL or CAP domain proteins do not bind phenolics. They could bind to the phenolics released from the lignin in the supernatants. + +![PLACEHOLDER_12_1] + + +We next attempted the binding assay in \(\mathrm{H}_2\mathrm{O}\) , where lignin is insoluble. However, the solubility of FL recombinant proteins in \(\mathrm{H}_2\mathrm{O}\) without lignin was inconsistent, even though they appeared in the supernatant fractions with lignin. Similarly, the solubility of S/T or CAP- domain proteins was inconsistent, with CAP proteins tending to be found more in the pellet fraction with lignin. Given that lignin is a complex, three- dimensional highly branched polymer and whether CAP- domains are able to access phenolics in such a complex or only bind to free phenolics is unclear, and the inconsistent solubility test results prevent us from reaching a definitive conclusion, we therefore report our findings here for the reviewers. + +![PLACEHOLDER_12_2] + + +<--- Page Split ---> + +6). Fig3, the apparent role of UmPR1- La in conferring eugenol resistance and the putative function of UmPR1- La in sensing phenolic compounds to signal pseudohypal growth is based on cells that overexpress this protein, i.e., a SG200 wild- type strain expressing an additional copy of UmPR1- La from a constitutive promoter. Thus, this is a gain- of- function phenotype that may have little in common with the native function of this gene/protein. These crucial experiments need to be supported by showing that mutant cells lacking one (Δa) or both (ΔΔab) UmPR1- L are hypersensitive to eugenol, and that this sensitivity and hyphal growth can be complemented in the deletion strain by expression of one or both UmPR1- L from their respective native promoters. The putative function of the CBM should then be tested in this sensitized background and not in an overexpressing strain. Are the WT and FY\* mutant proteins used in Fig3c and Fig4b expressed at comparable levels, please provide Western data. + +We express our gratitude to the reviewer for this comment, which indicates that our description in the text was insufficient. The gene expression data shown in Fig.1d indicates that U. maydis cells grown in liquid medium do not express PR- 1La and PR- 1Lb genes, and induces their expression during the biotrophic development. As a result, the wild- type strain SG200 is hypersensitive to eugenol due to the absence of native PR- 1La gene expression. Therefore, the protection of cells against eugenol requires the overexpression of PR- 1La proteins in SG200. To ensure readers are reminded of this fact, we have added the sentence " PR- 1La and PR- 1Lb genes were not expressed in axenic culture, but they were induced during biotrophic development of U. maydis SG200." + +With regards to protein levels of PR- 1La and PR- 1La(FY\*) expressed in SG200, we have now included the protein expression and secretion data in the revised manuscript to show that the comparable levels of the proteins expressed in the cells (Fig. 3c). + +![PLACEHOLDER_13_0] + + +7). Fig4, as in Fig3, the authors should make sure that they are not scoring an overexpression phenotype. Is an SG200 strain not expressing WT or FY\* mutant version of UmPR1- La sensitive to ferulic acid, what is its morphology? The binding assay shown in Fig4c does not indicate whether binding is specific, concentration- dependent, and saturable. Could it be that the protein gets denatured in the presence of ferulic acid and that this is scored as "binding"? This also applies to FigS4b. + +In Fig. 4b, we have included microscopy data depicting the cell morphologies of SG200, as well as the overexpression strains SG200_PR- 1La and SG200_PR- 1La (FY\*), with and without ferulic acid (FA) treatment. After exposed to FA, both the SG200 and SG200_PR- 1La (FY\*) strains displayed similar morphology and appeared slightly less healthy in the presence of FA. However, the presence of a hyphal- like structure was exclusively observed in the FA- treated SG200_PR- 1La strain. + +<--- Page Split ---> +![PLACEHOLDER_14_0] + + +Regarding the FA binding assay, our titration results demonstrated the dose- dependent binding of PR- 1La protein to FA. We observed that the saturation of FA binding occurred before reaching a concentration of \(10 \mu \mathrm{M}\) FA, as evidenced by the presence of a peak in the absorption spectrum of free FA at approximately \(420 \mathrm{nm}\) . In contrast, the mutant protein PR- 1La(FY\*) exhibited no response to different FA concentrations. The fluorescence of FA at \(330 \mathrm{nm}\) was detected but remained constant regardless of the FA concentration. These findings are now presented in Supplementary Figure S4b. + +![PLACEHOLDER_14_1] + + +We thank the reviewer for raising the concern regarding protein stability in the presence of phenolics, an aspect we had overlooked. To address this concern, we investigated the stability of the protein after exposure to phenolics for 15 minutes prior to fluorescence measurement. Our observations revealed no substantial protein degradation following the incubation period, suggesting that the observed fluorescence change is indeed attributed to the binding of phenolics to PR- 1La. We have included one of the replicate experiments in the revised manuscript as Supplementary Figure S4d. + +![PLACEHOLDER_14_2] + + +<--- Page Split ---> + +8). Fig5, the authors fail to detect the UmCAPE-La peptide in the apoplastic fluid of U. maydis infected leaves (L239). Hence there is no evidence that this peptide is actually produced in planta. Did they try infection with an overexpression strain? Fig5b, CatB3, which shows cleavage activity towards recombinant UmPR1-La, was purified from the apoplastic fluid of tobacco leaves and this protein preparation is not pure (FigS5b). Purification and cleavage assay with a catalytically dead mutant version of CatB3 would be needed to claim that the observed cleavage is indeed due to CatB3 and not a contaminating protease. This seems to be particularly important given that the cleavage of the native secreted version of UmPR1-L by CatB3 appears to be very slow and inefficient. + +- We attempted infections using various overexpression strains, including those with the otef promoter or multiple copy integration under the control of the native promoter. Additionally, we collected the apoplastic fluids at 1 dpi and 8 dpi, but we were unable to successfully identify the UmCAPE-La peptide. We lack a satisfactory explanation for this outcome but hypothesize that the UmCAPE-La peptide's concentration might be low, or it could potentially bind to an unidentified receptor upon being released.- We acknowledge that there is a low efficiency of cleavage by CatB3 in our assay under the current conditions. We do not have a definitive explanation for this observation. However, we speculate that either an unknown factor is required for the activity of CatB3, or CatB3 may not be able to efficiently access the CNYD motif for cleavage.- In response to the concern raised by reviewer #1 about the purity of CatB3 proteins, we fully agree on the importance of having an inactive form of CatB3. To address this, we introduced mutations in the catalytic site of CatB3 (Cys121 and His276). Both the wild-type and mutant versions of CatB3 were purified in parallel, and the protein purity is illustrated in Fig. S5e. We found that both the catalytic inactive mutants (C121A or C121A H276A) blocked the cleavage of UmPR-1La, while the wild-type CatB3 consistently cleaved UmPR-1La. These results provide support for our claim regarding the cleavage by CatB3 (Fig. 5c). + +![PLACEHOLDER_15_0] + + +9). Fig6, if CAPE-L indeed has immune suppressive activity one would expect that U. maydis strains overexpressing UmPR1-La show enhanced virulence. What is the induction of PR gene expression when non- infected plants are treated with ZmCAPE, CAPE-L, or both peptides together, compared to plants treated with scrambled peptide sequences? + +<--- Page Split ---> + +Overexpression of UmPR- 1La might result in an increase in \(U\) . maydis virulence. However, this is not always happened, particularly in \(U\) . maydis. We had overexpressed it using the promoter of UmPR- 1Lb, and it did not complement the virulence of the pr- 1la deletion mutant. Nevertheless, we followed the suggestions by infiltrating peptides into maize leaves, followed a protocol as described in a previous study (https://doi.org/10.1038/s41477- 018- 0116- y). Briefly, the synthetic peptides were dissolved in water, and the peptides was infiltrated using a blunt needless syringe at the base of fourth leaves of 10- day old plants. The leaf samples were harvest 24hr later. We attempted using both \(0.6 \mu \mathrm{M}\) and \(2 \mu \mathrm{M}\) peptides for infiltration and did not observe any significant differences among the treatments. Due to the structure of maize leaves, it was challenging to avoid causing wounds during peptide inoculations. The variations in \(PR\) gene expression may be attributed to these wounds. Consequently, we present these findings to the reviewers. Presented below are the results obtained from three (2 \(\mu \mathrm{M}\) ) and five (0.6 \(\mu \mathrm{M}\) ) independent biological replicates. + +![PLACEHOLDER_16_0] + + +Mixed peptides: Mixed with an equal concentration of CAPE- La and ZmCAPE. Scrambled peptides: contains an identical amino acid composition to CAPE- La. Maize GAPDH gene was used for normalization. The \(PR\) gene expression level in \(\mathrm{H}_2\mathrm{O}\) was set to 1.0. Average values of three or five biological replicates are shown. Error bars indicate \(\pm \mathrm{SD}\) + +Despite our inability to demonstrate the role of ZmCAPE in plant defense through peptide infiltration, we successfully exhibited a notable reduction in the virulence of \(U\) . maydis. This outcome was achieved by substituting UmCAPE- La peptide of UmPR- 1La with ZmCAPE, and delivered them via \(U\) . maydis. (Figure 6e- f). (Please refer to the response to question #13). + +<--- Page Split ---> + +The authors provide a functional characterization of 1 (2) effector(s) of the fungal maize pathogen Ustilago mayidis, which have homology with plant PR1 proteins, including the C-terminal CAPE peptide which is known to play an important role in PR- 1 mediated induction of plant defenses. The findings shown in the paper are new and exciting. Also, the experiments are all over sound. However, the presentation and documentation of data is partially incomplete. Also, this reviewer is not completely convinced how the two proposed functions of eugenol detoxification (which is actually rather resistance/tolerance than detox) and CAPE- release to block plant immunity are linked. Also, it appears unclear why/how the Um- PR1 released CAPE interferes with the generation of Zm- derived CAPE peptide. + +General questions and comments: + +9). Are orthologs of related smuts able to complement the PR- 1La disease phenotype, or is this specific to the Ustilago maydis protein? + +We appreciate the review for raising this question, as it has provided us with an opportunity to uncover additional interesting findings for further exploration in the future. In response to this question, we generated a complementation strain using the ortholog Sr10279 from Sporisorium reilianum, a maize- infecting fungus. Despite Sr10279 being able to localize to the U. maydis cell wall and possessing the conserved CNYD and CBM motifs, it was unable to rescue the virulence of U. maydis \(\Delta \mathrm{pr} - 1\mathrm{la}\) strain, and it did not form pseudohyphae upon exposure to ferulic acids. This discrepancy may be attributed to potential divergence in downstream signal reception partners between Sr10279 and UmPR- 1La. Consequently, Sr10279 is incapable of substituting the role of UmPR- 1La in eliciting hyphal- like structures in U. maydis. The corresponding data has been incorporated into Fig 4c- e. + +![PLACEHOLDER_17_0] + + +10). Does the PR- 1La deletion mutant have any (growth/developmental) defects besides in- planta development? Given its function at cell- surface localization this seems to be relevant for the interpretation of the results and the actual biological function of the PR- 1La. + +<--- Page Split ---> + +The deletion mutants, complementation strain ( \(\Delta \mathrm{pr - 1la}\) PR- 1La; controlled by the native promoter), and the overexpression strains (SG200 PR- 1La and SG200 PR- 1La(FY\*) driven by the otet promoter) displayed no visible abnormalities during their growth in a liquid medium or in their ability to form filaments on charcoal plates. Their morphologies were comparable to SG200. As a result, we can conclude that PR- 1La is associated with the in- planta development of U. maydis. These results have been included in supplementary figure S1d. + +![PLACEHOLDER_18_0] + + +11). Based on the expression profiles, both pr- 1l genes are not expressed when cell growth in liquid culture. + +- It appears (particular at level of this journal) somehow inappropriate to show gene expression data in the main figures (Fig 1; Fig 5) that is actually just extracted from a publication by others. Authors may provide own qPCR data to confirm the proposed expression patterns in their own experimental conditions (and refer to the published data in the supplements). + +We completely agree with the reviewer. We have removed the expression data and conducted a qRT- PCR assay to analyze the expressions of UmPR- 1La and UmPR- 1Lb using samples from SG200- infected leaves. These figures have been added to the revised manuscript (Fig. 1d and S1b). + +![PLACEHOLDER_18_1] + + +12). The figure labels are missing some relevant information to make them accessible. In Fig 2 it took me a while to understand that I am looking on an "otet" OE which explains the signals in sporidia. In Figure 3C I needed to search for "FY\*" and found it in the legend for 3D. However, as the figure 3C is shown, one would understand that there is a "WT" and a "FY\*" both being somehow with "SG200_PR- 1LaHA". What I guess it is, is strain SG200 (which actually should not be called a "wild type", because it is an artificial lab strain) vs the pr- 1la deletion strain. Right? + +<--- Page Split ---> + +Allover, it took me lots of time to look up this kind information up, as descriptions in the figures are sparse/sometimes misleading and also the legends lack information (e.g. legend Fig 3 "same strains used in 2a" – this is not sufficient. Please name the strains which are shown!) Thus, the authors should carefully revise their figures (including supplements, where also info is missing), provide more precise labels and information on strains wherever it is needed, otherwise it is very difficult to follow and interpret results. + +We offer our sincerest apologies for the inadequate and inattentive explanation provided, as well as the incorrect labeling of the experimental data depicted in the figures. To avoid any possible confusion, we have made the necessary revisions, substituting 'WT and FY\*' with 'PR- 1La and PR- 1La(FY\*)' in both the text and figures. Additionally, we have made every effort to provide comprehensive information in the figure legends within the given word limits. + +13). Does the CAPE-peptide have a virulence function for U. maydis? Figure 6 implies that it has a role in virulence. So, is a mutant with a C-terminally truncated PR-1La reduced in virulence? If so, can other (e.g. Zm) CAPE sequences not complement this? + +We appreciate the reviewer for suggesting this experiment, which allowed us to confirm the role of ZmCAPE in priming maize defense. Following the suggestions of the reviewer, we generated the complementation strains in which the UmPR- 1La's CAPE- La sequence was replaced with either ZmCAPE or UmCAPE- Lb after the CNYD motif. The complemented strain expressing PR- 1La (CAPELb) proteins under the PR- 1La promoter partially restored the virulence of \(\Delta pr - 1la\) , resulting in an intermediate phenotype that showed no significant difference from SG200 or \(\Delta pr - 1la\) . Surprisingly, the virulence of the complementation strain \(\Delta pr - 1la\) PR- 1La(ZmCAPE) was severely affected, leading to the development of tiny tumors with a size of less than 1 mm. The significant decrease in disease symptoms caused by ZmCAPE suggests a role of plant defense, and the spatial and temporal delivery of ZmCAPE peptides by U. maydis could effectively boost plant immunity to suppress fungal virulence. This negative impact could be partially reversed by the application of UmCAPE- La peptides, further supporting the contradictory role of UmCAPE- La and ZmCAPE in regulating plant immunity during the maize- U. maydis interactions. We have now included the data in Figure 6d- e. + +![PLACEHOLDER_19_0] + + +14). If Ustilago CAPE competes for Zm- CAPE with the receptor – how is it then not activating it (if it has a stronger binding affinity?) + +Based on our findings in Fig 6e, it appears that the use of UmCAPE- La could mitigate the negative impact of ZmCAPE on U. maydis virulence. Our current hypothesis is that UmCAPE- La may compete for the unidentified receptor binding, leading to the inhibition of the receptor's role in activating PR gene + +<--- Page Split ---> + +expression (as depicted in Fig. 6f). In maize B73, among the seventeen PR- 1 genes examined, four contain peptides longer than 11 amino acids that do not end with [R/K]PY, while the remaining peptides end with [R/K/S]P[Y/F] (Am J Transl Res. 2022; 14(11): 8315–8331). We speculate that the first seven conserved amino acids found in UmCAPE- La and maize CAPE peptides could be sufficient for receptor binding, while the last few amino acids of the peptides might influence the degree of receptor activation. The precise mechanism by which plant CAPE triggers the SA- signaling pathway remains unclear. However, once the receptor is identified, further investigation can be conducted to assess the role of these amino acids in modulating plant CAPE- dependent signaling pathway. + +## Specific questions: + +15). In L136 it is stated that "double deletion phenotype is more pronounced" – Is this really significant compared to the single deletion? + +The same argument is also raised by Reviewer#1. We have re- analyzed the data and there is no significant difference between single and double deletion mutants, and we have reworded it to 'a similar decrease in virulence was also observed in the double mutant \(\Delta \Delta \mathrm{pr} - \mathrm{llab}\) '. + +16). Figure 3 and corresponding text: what is the evidence for a "detoxification" – what is shown is resistance to a toxic compound, but not its detox. + +We fully concur with the reviewer's assessment, as we did not have evidence to substantiate its detoxification properties. In the revised manuscript, we have now replaced it with the term 'resistance'. + +17). Figure 4C – what is actually detected here by the spectrophotometer? At which wavelength? Why are no biological reps shown but only technical reps? + +Fluorescence spectrophotometry could be used to study the ligand binding- induced conformational change of a protein. The natural fluorescence of tryptophan is used as a reporter of the conformational changes induced by the ligand binding. Tryptophan were excited at \(290 \mathrm{nm}\) , and emission spectra were recorded in the range of \(310 - 450 \mathrm{nm}\) . The experimental detail has been provided in 'Methods' section. In our previous manuscript, we chose to present only one biological replicate because the figure with three biological replicates appeared crowded and untidy. The excessive number of data points resulted in extensive error bars, leading to visual clutter. Due to the concern regarding the absence of biological replicates, we have now replaced it with a new one that displays the mean and standard deviation of all three biological replicates (Fig. 4f). + +![PLACEHOLDER_20_0] + + +<--- Page Split ---> + +18). - Figure 5 – also here, biological reps are not shown (MS data). Also, it is not possible for me to understand the figure completely. What are the sequences below 5b? What is shown in 5C (what is “γ7” “γ6” etc?) What is scale of “intensity”? How does this show a specific cleavage of PR-1La by CatB3? + +We apologize for not providing sufficient information to access Figure 5e. We have revised the figure legend for clarity. The peak area of fragment ions was used to quantify the quantity of tryptic UmCAPE- La peptide in both the - CatB3 and +CatB3 samples. Fragment ions γ6 and γ7 extend from the C- terminus, and γ7++ is a doubly charged ion. The b5 ions extend from the N- terminus. To illustrate the fragment ions of the peptide, we have included a cartoon in Figure 5d. The term “intensity” refers to the amplitude of the free induction decay signal. Because the intensity is not a precise measurement to represent the absolute peptide abundance, therefore it is usually not labeled. + +Regarding the issue of biological replicates, the His- and HA- tagged UmPR- 1La served as two separate replicates for CatB3 cleavage and consistently produced similar results. This observation indicates that only the +CatB3 sample displayed fragment ions derived from the UmCAPE- La peptide. + +19). - Fig S5A indicates degradation of PR- 1La by apoplastic fluid of maize. However, none of the inhibitors used could fully block this degradation completely. This actually suggests that multiple proteases are involved in degradation of the protein beyond Cat3B. How do the authors interpret this? + +Thanks for the question. We believe that the insufficient amount of protease inhibitors added is the reason for this. To address this issue, we conducted a titration assay by adding varying amounts of DMSO- dissolved E- 64 to apoplastic fluid proteins (AF). In this assay, we also reduced the amount of AF by half, using \(15 \mu \mathrm{g}\) AF instead of the amount used previously in Fig. S5A. Our findings indicate that the cleavage of PR- 1La in the apoplast was blocked in the presence of E- 64. Additionally, E64 also inhibited the activity of CatB3. These results suggest that the cleavage of UmPR- 1La in the apoplast is caused by cysteine proteases, and CatB3 is one of them. These figures have been incorporated into Fig. 5a and 5b of the revised manuscript. + +![PLACEHOLDER_21_0] + + +<--- Page Split ---> + +The submission, "Ustilago maydis PR- 1- like protein has evolved two distinct domains for dual virulence activities" by Lin et al describes a fungal protein, PR- 1- like, that has homology to the well described yeast, PRY1 and plant PR1. The authors show that the U. maydis PR- 1- like proteins contains two domains, Ser/Thr- rich region and the CAP domain with a predicted C- terminal peptide similar to PRY1, while plant PR- 1's only contain the CAP domain with a C- terminal peptide. The authors show that the Ser/Thr- rich region is responsible for the binding of PR- 1- like to Chitin and therefore its localisation to the fungal cell wall. While the CAP domain is responsible for sterol/phenolic binding which induces a switch in U. maydis from sporidia to pseudohyphal structures which allows survival of the fungi. Additionally, the authors show that the C- terminal peptide of PR- 1- like is cleaved by CatB3 a member of the cystine protease family and that PR- 1- like can modulate known plant immune genes which is likely to occur via the C- terminal peptide. Overall, this paper is quite well written and logically structured making it relatively easy to follow the narrative, however some work on Figure layout and labelling will help greatly. I have below some major and minor points to address which should improve the article prior to publication. + +Major point to address + +20). Figure 2 - These microscope images (a and d) are not good enough quality to be the only evidence of cell surface localisation. I would like to see better quality and higher resolution images as well as co- localisation with a known cell surface protein so show co- localisation. Arrows would also help to direct reader. + +Same question (#4) regarding the cell- wall localization is also raised by reviewer #1. To address this issue, we performed co- localization experiments of UmPR- 1La with chitins in the AB33 PR- 1La strain treated with plasmolysis, and found that UmPR- 1La co- localized with chitin on the filamentous cell surface and not located inside the space enlarged by plasmolysis. Please refer to our response to question #4 raised by reviewer #1. + +To improve the image resolution in Fig. 2, we have replaced them with high- resolution enlarged images. This clearly shows the localization of PR- 1- like proteins on the cell surface. + +21). Please review all figures as many are lacking good labelling e.g. Fig2, no labels on western blot for expected size of protein especially important for PR- 1Lb as there are multiple bands and the band sizes don't seem to match my calculations based on the amino acids described in fig 1. Also Fig2a - PRY1HA I believe should be labelled Umsp:PRY1- HA this was very unclear as the labelling did not match the description in the text of the results. These are just two examples. + +We apologize for any confusion caused by our previous lack of clarity in the figure legends. We have now taken the necessary steps to revise all figures and their corresponding legends to ensure that they are clear and unambiguous to readers. Thank you for bringing this to our attention, and we hope that our revised figures and legends will be more helpful to readers. + +We have noticed that the molecular weights of PR- 1- like proteins are higher than anticipated. Specifically, PRY1 expressed in SG200 cells exhibited slower migration than expected in SDS- PAGE, despite an expected weight of 33kDa, it was detected at 72kDa. This finding is consistent with the result from Roger Schneiter's team, who discovered that yeast PRY1 is a high molecular weight glycoprotein that migrates at \(>70\mathrm{kDa}\) in SDS- PAGE (https://doi.org/10.1242/bio.053470). Based on this information, we suspect that PR- 1L proteins are also glycosylated to some extent. + +<--- Page Split ---> + +22). Add in the O- glycosylation data into a sup figure + +Due to the inconsistency in protein solubility, we have excluded the polysaccharide binding result from Figure 2e (Please refer to our response to question #5). + +23). Figure 3b – Given that the authors base this experiment off the PRY1 literature of PR1 binding Eugenol this seems an unexpected result that the cells do not survive, please expand on/discuss this. Could it be linked to the data in Fig2a where PRY1 does not localise to cell surface in U. maydis? Make clear your reasons for reader. + +Based on this question, we have realized the problem of providing insufficient explanation in our previous manuscript. We have made efforts to address this issue. According to our findings, PRY1's inability to protect U. maydis cells is not solely due to localization and eugenol- binding issues. This is evident from the fact that the chimera protein, despite being localized to the cell wall, failed to provide protection. Additionally, it has been reported that the CAP domain of PRY1 can bind eugenols. The absence of hyphal- like structures is the key reason why PRY1 fails to protect U. maydis cells but not S. cerevisiae cells (Fig. S3 and Fig 3b). These hyphal- like structures are essential for protection in U. maydis, whereas complete shielding of S. cerevisiae cells by PRY1 is sufficient to prevent eugenol toxicity. + +To induce UmPR- 1La- shielded hyphae, UmPR- 1La needs to transmit signals to its specific receptor, which likely does not interact with either PRY1 or Sr10279, leading to the failure in inducing hyphal- like structures in U. maydis. However, we speculate that Sr10279, based on conserved motifs and its grouping with UmPR- 1La in the same clade (Fig 1b- c), can induce such structures in S. reilianum. We have discussed this aspect in the line 251- 256 in the results section. + +- Add loading controls to immunoblot panels. We have now provided necessary loading controls to immunoblots. + +24). I find it surprising not to have seen an enhancement of defence by the application of the maize CAPE peptide. I would suggest you repeat this experiment, but this time pre- treat the maize with ZmCAPE 1 day prior to infection. This experimental set up is how previous publication have conducted the experiment e.g. Chen et al, 2014 Plant cell and Sung et al, 2021 New Phyt (refs 8 & 9 on your list). Have you also tried it with WT SG200? + +We had conducted this experiment previously, where we pre- treated maize seedlings with ZmCAPE a day before U. maydis infections. However, we did not observe any reduction in the virulence of SG200 or \(\Delta pr - 1lab\) , which was puzzling to us as we lacked a satisfactory explanation. In this revision, we followed the suggestion of reviewer#2 (please refer to our response to Question #13) by replacing the UmPR- 1La's UmCAPE- La sequence with ZmCAPE and delivering it via U. maydis. Using this delivery method, we observed a significant decrease in the disease symptoms of this complementation strain. This finding supports the conserved role of ZmCAPE in priming plant immunity and also suggests that the lack of enhanced maize resistance by the application of ZmCAPE could be due to the timing and method of peptide delivery in maize. Furthermore, the negative impact of ZmCAPE on U. maydis virulence delivered by this strain was mitigated by the application of UmCAPE- La peptides. These figures have been included in the revised manuscript (Fig. 6d- e). + +Minor point to address + +- Line 79-81 "However, it is unclear whether a protease involves in the cleavage of the CNYx motif and a receptor to perceive CAPE peptide to activate" suggest editing to read "However, it is unclear whether a protease is involved in the cleavage of the CNYx motif and if there is a receptor to perceive CAPE + +<--- Page Split ---> + +peptides that activate" We have replaced the sentence as suggested. + +- Line 95 - "sexual life cycle, it requires U. maydis fine sensing and integrating environmental" suggest editing it to "sexual life cycle, U. maydis requires fine sensing of environmental" The sentence has been modified. + +- Line 97 - "U. maydis secrete a" edit to "U. maydis secretes a" It has been edited. + +- Line 108 - "elicit hyphal-like structures. A CAPE-like peptide" suggest edit to "elicit hyphal-like structures, while a CAPE-like peptide" This sentence has been modified. + +- Line 172-173 - I think this statement has not been 100% proven therefore I would say "the results indicates that this PR-1La may incorporate into the cell-wall chitin/chitosan-glucan matrix possibly via glycosidic linkages" + +The insolubility issue of recombinant proteins in the absence of a ligand prevented the confirmation of the finding that PR- 1La protein binds to chitin/chitosan in the polysaccharide precipitation assay. This statement has been deleted (Please refer to our response to question #5). + +- Remind reader that PR-1-likes are not expressed in culture therefore the native PR-1-like's are not affecting the phenolic binding assays. + +Thanks for your suggestion. A sentence has been included at the start of the text as a reminder for readers that PR1-L proteins are not expressed when cells are grown in liquid culture. + +- Figure S3a - there is wrong labelling between the graph and the images or there is a wrong image added - graph shows PR-1La showing cell survival and growth however image is showing PR-1Lb data. + +Need consistency between graph and images, suggest adding PR- 1La and PR- 1Lb to both. + +To prevent unnecessary duplication and ambiguity, we have followed your suggestion and rearranged the images and placed in fig. 3b. + +- Line 193 - Wrong Figure, should read Fig 2a. + +We have made the corrections. + +- Fig3d - suggesting adding in WT complementation line. Also inconsistent labelling between Fig 1d and 3d + +To have consistency in labeling and prevent any confusion, we have relabeled the strains that express wild-type and mutant PR- 1La proteins as SG200_PR- 1La and SG200_PR- 1La(FY\*), respectively. + +- Line 218 - CA-treated PR-1La (FY\*) cells show a swollen morphology, based on the image shown for PR-1La WT treated with CA these pseudohyphae also look swollen. + +U. maydis exhibited greater sensitivity to coniferyl-alcohol (CA) than to ferulic acids and coumaric acids. Since we did not titrate the dosage of CA to determine the minimal effective concentration for inducing pseudohyphae, the use of 5 mM CA in our treatment assay is likely excessive, resulting in damage to the wild-type PR-1La protein-expressing cells. + +<--- Page Split ---> + +- Inconsistent labelling of sterol graphs between Fig3 and 4. FigS3 and FigS4 We have now consistently re-labeled all graphs in the revised manuscript. + +- Lines 241-244 – re-word sentence, it is difficult to follow. You need to get the phrase culture filtrate or culture supernatant in there as well as saying U. maydis SG200 +PR-1La-HA line. + +We have rephrased the sentences to "we explored UmPR- 1La cleavage by incubating the culture supernatant of SG200_PR- 1La strain with the apoplastic fluid of SA-inoculated maize leaves, along with different protease inhibitors". + +- Figure S5a legend is missing information – treatments and concentrations used. Labelling of figure and description in materials and methods don't match i.e. is control on figure the PIC as in materials you mention DMSO is the control? + +We have added the detailed information in figure legend of fig. S5a. + +- Line 249 – "Cathepsin B-like 3 (CatB3) has a similar expression profile as umpr-1la" I disagree PR-1La expression is all over the place. I would just say CatB3 is induced during infection or CatB3 is strongly induced from 4dpi compared to mock treatment. + +We have modified the sentence to "Cathepsin B-like 3 (CatB3) is expressed in the early stage and strongly induced from 4dpi and onwards". + +- Fig5b add arrow to indicate PR-1La band also labels for Coomassie and immunoblot. + +The previous fig. 5b is now moved to fig. 5d. Black and red open arrows indicate full-length and truncated PR-1La proteins respectively, have been added in both Coomassie-blue-staining PAGE and immunoblot. + +- Fig5b make the second blot on U. maydis secreted PR-1LaHA blot Fig 5c as currently the legend is hard to follow what is being described. Quantify band intensity against total protein stain as there is no size shift (due to small cleavage size) as observed in the previous gel and no loading controls shown. The immunoblot for UmPR-1LaHA in the previous Figure 5b has been replaced with a new figure, which includes the catalytically inactive mutants of CatB3 to support the cleavage of UmPR-1La by CatB3 (Figure 5c). In this new figure, we have also included a silver-stained gel to serve as a loading control. + +- Line 265 – "In maize, homolog Xcp2 is highly expressed in the early infection process and then slowly declines during biotrophy (Fig. S5d)." – I disagree with this statement, there is no difference in expression of Xcp2 between mock and infected tissue. Remove or reword. + +The sentence has been rewritten as 'Xcp2 is expressed at all infection/wounding stages.' + +- Line 268 – suggested edit "truncated fragments were detected by Coomassie-blue-staining-PAGE and immunoblot for PRB1-3 and PR-1b" + +The sentence has been edited accordingly. + +- Line 313-317 – "U. maydis probably acquired pr-1-like genes via horizontal gene transfer from the host plants during the coevolutionary arms race." – I know speculation is acceptable in the discussion but I am not sure this is supported by the literature since most organisms contain a CAP-domain containing protein (or CMB motif) including human glioma PR-1 protein and a snake-venom cysteine-rich secretory + +<--- Page Split ---> + +protein, yeast as you described. This is also unlikely since the plant PR- 1's don't contain the Ser/Thr rich region whereas PRY1 does. I think it would be better to rephrase this section. + +Thanks for pointing it out. In a study on the genome- wide analysis of maize PR- 1s, it reported that three out of the 17 maize PR- 1s contain an extension region at their N- termini. This extension region is notably enriched in Ser, Thr, and Gly (Am J Transl Res 2022;14(11):8315- 8331). However, it is unknown how fungal pathogens acquire PR- 1L genes during co- evolution. We agree that the previous speculation has no support by literature, we have rephrased the sentences to' While the exact origins of PR- 1L genes in fungal pathogens remain unclear, their capacity to act as substrates for plant proteases and conservation at CAP domain residues underscore a related role in plant- pathogen interactions during the process of co- evolution'. + +In addition, we also added the sentence 'the extension region is also present in three out of the 17 maize PR- 1 proteins' at the beginning of the Result section. + +- Line 326-328 - "PR-1La lacks a transmembrane domain, it is not clear how the signals perceived at the cell surface is transduced to activate the downstream signaling pathway." Suggest edit it to "PR-1La lacks a transmembrane domain, therefore it is not clear how the cell surface signals would be perceived and transduced to activate downstream signaling." + +The sentence has been edited as suggested. + +- Line 387 - "performed as described" - incomplete sentence! The sentence has now been completed and written as 'The transformation of U. maydis and genomic DNA isolation procedures were performed as described in a previous study'. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +We appreciate the author's efforts to address our concerns and think that the revised version of this manuscript has been greatly improved. Our main concern, however, that the results do not provide a strong coherent picture of the function of UmPR- 1La in pathogen virulence, was not fully resolved. While we applaud the inclusion of the model shown in Fig 6F, the interdependence of these different stages of UmPR- 1La action is not well supported by experimental data. In particular, we do not know whether cell wall association of UmPR- 1La is important for virulence. While we know that that a mutation (FY\*) in the CBM affect virulence (Fig 3E), we do not know whether cleavage of CAPE- La would repress host immunity, independently of the function of the CBM. The virulence of the FY\* appears to be as repressed as that of a deletion, even though the FY\* mutant version should still be able to release the CAPE- La peptide and thereby promote virulence. Thus, a more complete set of data defining the function of these different elements through which UmPR- 1La appears to promote fungal virulence is needed to support the interdependence of the individual stages shown in Fig 6F, including abrogation of its cell wall association, mutation of the protease cleavage site (CNYx), and a truncation of the CAPE- La peptide. + +In addition, the data supporting binding of the phenolic compound to UmPR- 1La are still weak and subject to interpretation. Ligand binding is dose dependent and saturable. The authors do not provide strong support for either of these two criteria. They observe quenching of Trp fluorescence upon addition of phenolic compounds and interpret this as binding. These phenolic compounds could by themselves quench Trp fluorescence or induce partial denaturation of the protein rather than exhibiting a stoichiometric ligand- type of binding to the protein. In their revision, the authors have addressed the stability of the protein in the presence of the phenolic compounds but did not address the possibility that these phenolics induce partial denaturation or quench fluorescence. In addition, the authors do not show evidence that UmPR- 1La binds Eugenol itself or whether this binding is dependent on the CBM. Overexpression of UmPR- 1La confers resistance to Eugenol, and this resistance is affected by a mutation (FY\*) in the CBM (Fig 3D). However, the FY\* mutant grows better than WT in the presence of Ferulic acid (FA, Fig 4B), even though the FY\* mutant does not "bind" FA in vitro (Fig 4F). Clearly, this is not consistent with the model proposed by the authors that UmPR- 1La binds FA through its CBM to induce pseudohyphal growth and FA resistance. The same applies for the improved growth of the FY\* mutant observed in presence of Coumaric acid (Fig S4A). + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +My questions and concerns have been addressed sufficiently. The revised manuscript is significantly improved and major issues have been fixed / new experiments add clarifying and interesting information. + +Reviewer #3 (Remarks to the Author): + +The authors have addressed all of my concerns with the original manuscript. + +Below are some minor edits to further improve the manuscript, some are just typos and some are to improve the figure legends further, as although greatly improved, they are not quite right in a couple of cases. + +Minor corrections + +Line 164: AF594- immunostained PR- 1La – the figure legend also calls this AF594 however in the figure it is labelled AF595. + +Figure 2a legend still needs improved. Authors only describe some of the constructs (Overexpression of WT constructs not listed) additionally, the list is in reverse order compared to the figure i.e. the last construct SG200_PRY1 is listed first in legend, please re- order. Please make the names in figure and legend the same SG200_PRY1 not PRY1 + +Figure 2d legend: Please indicate size of proteins, in the legend, to direct reader to correct bands especially important for Pr- 1Lb and PRY1. + +<--- Page Split ---> + +Figure S4d: Coomassie stain for loading control is missing. + +Line 303: "Cathepsin B- like 302 3 (CatB3; GRMZM2G108849), which is expressed in the early stage and strongly induced from 4dpi and onwards (Fig. S5b)." please rephrase to include "of infection" + +<--- Page Split ---> + +## REVIEWER COMMENTS + +We extend our gratitude to all the reviewers for their valuable constructive suggestions and comments, as well as their dedicated efforts to enhance the quality of our work. + +Reviewer #1 (Remarks to the Author): + +We appreciate the author's efforts to address our concerns and think that the revised version of this manuscript has been greatly improved. Our main concern, however, that the results do not provide a strong coherent picture of the function of UmPR- 1la in pathogen virulence, was not fully resolved. While we applaud the inclusion of the model shown in Fig 6F, the interdependence of these different stages of UmPR- 1la action is not well supported by experimental data. + +In particular, we do not know whether cell wall association of UmPR- 1la is important for virulence. Thank you for drawing our attention to this matter. We acknowledge that the current evidence falls short of directly demonstrating the essentiality of UmPR- 1la's cell wall association for virulence. To establish this link definitively, we must first investigate how UmPR- 1la localizes to the cell wall by identifying the specific cell wall component(s) it interacts with and the corresponding interacting motif. This endeavour would require a considerable amount of effort and resources. + +Given the scope of this study, we find it more appropriate to reserve these experiments for our future research- Investigating how UmPR- 1la induces hyphal- like structures and the cleavage mechanism. In the meantime, we think the evidence we have gathered so far (as elaborated below) substantiates our proposed working model, which emphasizes the critical role of UmPR- 1la's cell wall association in its virulence. + +Given that PRY1 expression in SG200 cells cannot localize to the cell walls and protect cells, even though both the full- length proteins and the CAP domain alone can bind eugenols (Choudhary and Schneiter, 2012 PNAS; https://doi.org/10.1073/pnas.1209086109), we might anticipate that expressing a cell- wall localization- defective UmPR- 1la protein with an intact CBM will similarly fail to protect cells. In contrast to ScPRY1, which localizes to the cell periphery of S. cerevisiae and shields them from eugenols (Fig. 2b), UmPR- 1la primarily accumulates at the cell division sites of U. maydis sporidal cells (Fig. 2a). This localization pattern is insufficient to prevent eugenols from disrupting the cell membrane of U. maydis, unless they can lead to the formation of UmPR- 1La- shielded hyphae for protection. This underscores the significance of localized UmPR- 1La on the cell wall in inducing protective hyphal- like structures. + +The cell- wall localization of UmPR- 1La doesn't ensure protection for sporidal cells. Despite their cell- wall localization, both the chimera and Sr10279 failed to induce hyphal- like structures and provide cell protection. This likely results from their inability to transmit crucial intracellular signals needed for shielded hyphae formation. The chimera's PRY1 CAP domain might not induce a conformational change in UmPR- 1la's N- terminus, which may have an additional role in downstream partner interaction. Similarly, Sr10279 may struggle to interact with the necessary UmPR- 1La partner for structure initiation. Our findings underscore a sequential process for initiating protective hyphae: proteins must first localize to U. maydis sporidal cell walls to detect signals and then transmit them intracellularly for hyphal- like structure induction. Failure in these steps won't restore \(\Delta pr - 1la\) virulence. + +By comparing the virulence phenotypes of complementation strains \(\Delta pr - 1la\_ PR - 1la(FY^*)\) and \(\Delta pr - 1la\_ PR - 1la(CAPE - Lb)\) (Fig 3e and 6d), we noted that the truncated PR- 1La(CAPE- Lb) protein with the CAPE- Lb peptide partially restored \(\Delta pr - 1la\) virulence phenotype. This happened because the truncated protein, carrying a defective peptide, retained the intact N- terminus and CBM, allowing it to localize to the cell wall and induce hyphal structures for protection, resulting in an intermediate virulence phenotype. Conversely, \(\mathrm{FY^*}\) proteins, unable to induce protective + +<--- Page Split ---> + +hyphal- like structures, failed to complement \(\Delta pr - 1a\) 's virulence. These findings underscore the crucial role of inducing hyphal structures for PR- 1La's virulence function. + +To provide clarity for readers, we have incorporated this information into both the discussion and results sections. Presently, the mechanism through which UmPR- 1La triggers the formation of hyphal structures for cell protection remains unclear. Further research is necessary to comprehend how the N- terminus and CAP domains contribute to signal transduction and, at a minimum, to pinpoint the involved receptor. This aspect is the primary focus of our ongoing investigation. + +While we know that that a mutation (FY\\*) in the CBM affect virulence (Fig 3E), we do not know whether cleavage of CAPE- La would repress host immunity, independently of the function of the CBM. The virulence of the FY\\* appears to be as repressed as that of a deletion, even though the FY\\* mutant version should still be able to release the CAPE- La peptide and thereby promote virulence. Thanks for raising this point. Please allow us to explain it. + +As mentioned above, hyphal formation plays a crucial role in the protective function of PR- 1La, regardless of having an intact CNYx motif and CAPE- La peptides. Without hyphal formation, UmPR- 1La mainly localizes at the site of cell division and cannot fully shield cells from plant toxic phenolics. Consequently, the \(\Delta pr - 1la\_ PR - 1La(FY^*)\) complementation strain that unable to trigger hyphal formation compromised the \(\Delta pr - 1la\) virulence (fig.3E). This underscores the importance of inducing hyphal formation for survival within the plant, as this subsequently facilitates the release of the CAPE- La peptide, further suppressing plant immunity. + +As expected, the in- vitro cleavage assay showed that FY\\* mutant proteins could be cleaved by CatB3 (see western blot below). Based on our genetic data and biochemical assay, it is clear that the inability of FY\\* mutant proteins to restore virulence is due to their inability to sense phenolics and thereby fail to trigger the protective hyphae. As CatB3 selectively cleaves PR- 1La proteins but not plant PR- 1 and this cleavage mechanism is the focus of our next investigation, we have decided not to include this data in the revised manuscript. But, we provide it here for the reviewers. + +![PLACEHOLDER_31_0] + + +Thus, a more complete set of data defining the function of these different elements through which UmPR- 1La appears to promote fungal virulence is needed to support the interdependence of the individual stages shown in Fig 6F, including abrogation of its cell wall association, mutation of the protease cleavage site (CNYx), and a truncation of the CAPE- La peptide. + +We wholeheartedly agree with the reviewer's comments. However, this requires further efforts for dissection, which is the focus of our next investigation. We believe that the findings in the discovery of the dual virulence functions and the underlying mechanism of UmPR- 1La in sensing and adapting to the plant environment for survival, as well as countering plant defense to enhance the virulence of Ustilago maydis, not only provide important knowledge but also open a new research direction for the fields of effector biology and fungal- plant interactions. + +Regarding the truncation of CAPE- La, we have used a scrambled peptide of CAPE- La as a negative control to support the suppressive function of CAPE- La (Fig. 6e). Furthermore, we replaced UmPR + +<--- Page Split ---> + +1La's CAPE-La with CAPE-Lb to demonstrate the decrease in virulence (Fig. 6d). The results from these experiments had provided sufficient evidence to support our conclusion on the role of CAPE-La in suppressing plant immunity. + +- As for the mutation on the CNYx motif, it has been shown that the tyrosine mutation in the plant PR-1's CNYD motif prevents the release of the AtCAPE9 peptide by AtXcp1 protease (https://doi.org/10.21203/rs.3.rs-155784/v1). However, in Ustilago maydis, a mutation on the Y residue (CNAD) abolishes the secretion of UmPR-1La. This finding is consistent with the work done by Tamara et al (https://doi.org/10.1111/mpp.13187) showing the PR1 trafficking dependent on the intact CNYD motif. Therefore, performing the in-vitro cleavage assay on this CNAD mutant protein is not biologically relevant, as it is not secreted. + +![PLACEHOLDER_32_0] + + +In addition, the data supporting binding of the phenolic compound to UmPR- 1La are still weak and subject to interpretation. Ligand binding is dose dependent and saturable. The authors do not provide strong support for either of these two criteria. + +- We respectfully hold a different view from the reviewer concerning the binding strength of FA to PR-1La. It's also important to consider that the Y-axis scale is larger, potentially causing visual misinterpretation. The observed difference of approximately 250 a.u. (ranging from 1100 a.u. at \(0 \mu M\) FA to 850 a.u. at \(10 \mu M\) FA) does not necessarily imply weak binding. Notably, the similar fluorescence pattern shift was also reported in several protein-ligand binding assays using fluorescence spectrometry (https://doi.org/10.1002/jsfa.11733; https://doi.org/10.1074/jbc.M111.301630). + +- The titration assay depicted in fig. S4b illustrated the dose-dependent response of PR-1La proteins to ferulic acids (FA), reaching saturation at approximately \(10 \mu M\) and exhibiting detectable free FA absorption at 410-430 nm. Conversely, the control PR-1La(FY\*) proteins displayed no responsiveness to FA, showing no shifts in fluorescent intensity regardless of the added FA quantity. When considered alongside the information presented in fig. 4f, these findings indicate that the interaction between PR-1La and ferulic acids relies on the intact CBM in a manner that varies with the dose. + +They observe quenching of Trp fluorescence upon addition of phenolic compounds and interpret this as binding. These phenolic compounds could by themselves quench Trp fluorescence or induce partial denaturation of the protein rather than exhibiting a stoichiometric ligand- type of binding to the protein. In their revision, the authors have addressed the stability of the protein in the presence of the phenolic compounds but did not address the possibility that these phenolics induce partial denaturation or quench fluorescence. + +Thanks for asking these questions. Please allow us to explain our thought. + +- If Trp fluorescence is quenched by phenolic compounds, we should also expect a similar fluorescent shift in the FY\* proteins, but this was not observed in the FY\* titration assay (fig. S4b). + +<--- Page Split ---> + +- If the observed shift in the PR-1La protein was caused by partial denaturation, we would anticipate a decrease in the intensity of both PR-1La and the FY\* mutant proteins, regardless of the type of phenolics. However, the intensity of FY\* proteins did not decrease during incubation with ferulic acids. It is worth noting that the FY\* proteins seemed less stable than the wild-type PR-1La proteins, as indicated by the detection of the truncated form (Fig. S4d). Furthermore, we also noticed an increase in the intrinsic fluorescence intensity of PR-1La when incubated with coniferyl alcohol (Fig. S4c). Based on these results and the induced hyphal-like structure phenotype in Fig 3d, this allows us to suggest that the PR-1La is able to bind phenolics. + +In addition, the authors do not show evidence that UmPR- 1La binds Eugenol itself or whether this binding is dependent on the CBM. + +Due to the lipophilic property of eugenols, it exhibits strong fluorescence, making it unsuitable for demonstrating the binding of PR- 1La to phenolics using fluorescence spectrometry or isothermal titration calorimetry (ITC). Since cells expressing UmPR- 1La responded to both eugenols and ferulic acids by forming similar hyphal- like structures, we used ferulic acids to demonstrate the phenolic binding of PR- 1La. + +Overexpression of UmPR- 1La confers resistance to Eugenol, and this resistance is affected by a mutation (FY\*) in the CBM (Fig 3D). However, the FY\* mutant grows better than WT in the presence of Ferulic acid (FA, Fig 4B), even though the FY\* mutant does not "bind" FA in vitro (Fig 4F). Clearly, this is not consistent with the model proposed by the authors that UmPR- 1La binds FA through its CBM to induce pseudohyphal growth and FA resistance. The same applies for the improved growth of the FY\* mutant observed in presence of Coumaric acid (Fig S4A). + +The survival of FY\*- expressing cells in the presence of phenolics depends on the toxicity level of the tested compounds. Cells cannot survive in the presence of eugenols due to the disruption of the cell membrane caused by eugenols, as documented in the reference (DOI: 10.3109/13693786.2012.742966). Therefore, the cell membrane needs to be protected thru triggering UmPR- 1La- shielded hyphae to block eugenols. The survival of cells in the presence of ferulic acids/coumaric acids, on the other hand, is observed to be higher, indicating their lower toxicity to U. maydis cells under the tested conditions. Despite the inability of FY\* proteins to induce hyphae structures, FY\*- expressing cells still manage to survive and multiply in the presence of FA- containing medium. This observation supports our proposal that UmPR- 1La can sense various plant phenolics, regardless of their toxicity level, and trigger UmPR- 1La- shielded hyphal branching to confer protection within the plant. + +Reviewer #2 (Remarks to the Author): + +My questions and concerns have been addressed sufficiently. The revised manuscript is significantly improved and major issues have been fixed / new experiments add clarifying and interesting information. + +Thank you. + +Reviewer #3 (Remarks to the Author): + +The authors have addressed all of my concerns with the original manuscript. + +Below are some minor edits to further improve the manuscript, some are just typos and some are to improve the figure legends further, as although greatly improved, they are not quite right in a couple of + +<--- Page Split ---> + +cases. + +Minor corrections + +Line 164: AF594- immunostained PR- 1La - the figure legend also calls this AF594 however in the figure it is labelled AF595. + +Thanks for pointing it out. It has been corrected. + +Figure 2a legend still needs improved. Authors only describe some of the constructs (Overexpression of WT constructs not listed) additionally, the list is in reverse order compared to the figure i.e. the last construct SG200_PRY1 is listed first in legend, please re- order. Please make the names in figure and legend the same SG200_PRY1 not PRY1. + +We have made the changes accordingly. + +Figure 2d legend: Please indicate size of proteins, in the legend, to direct reader to correct bands especially important for Pr- 1Lb and PRY1. + +Thank you. We have added the expected size of full- length proteins in the legend of fig 2d. + +Figure S4d: Coomassie stain for loading control is missing. We have now included the loading controls in fig. S4d. + +Line 303: "Cathepsin B- like 302 3 (CatB3; GRMZM2G108849), which is expressed in the early stage and strongly induced from 4dpi and onwards (Fig. S5b)." please rephrase to include "of infection" The sentence has been rephrased as suggested. + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +Thank you for having addressed our remaining concerns. + +<--- Page Split ---> diff --git a/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c4c3557949a1aa59c86044e535b891e0be35baa2 --- /dev/null +++ b/peer_reviews/77ea046c853721e568cc5ec58b8a2a5e842842b35558b6cfa1b14162b4ef9caa/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,825 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[71, 162, 866, 218]]<|/det|> +Ustilago maydis PR- 1- like protein has evolved two distinct domains for dual virulence activities + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 393, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 201, 880, 293]]<|/det|> +PR- 1- like proteins belong to a large protein family, and they have been implicated in many different biological processes including immune defense and cancer progression. These proteins share a conserved CAP domain and are mostly secreted glycoproteins. Their mode of action, however, remains poorly characterized. Thus, progress in understanding the function of these proteins at a molecular level would be a welcome advancement. + +<|ref|>text<|/ref|><|det|>[[115, 333, 883, 461]]<|/det|> +Lin et al. now report that the corn smut Ustilago maydis pathogenesis- related 1- like protein (UmPR- 1La) acts in detoxification of phenolic compounds, and that its Ser/Thr- rich N- terminal domain mediates cell surface association. In addition, the authors report that UmPR- 1La has gained a specialized activity in eliciting hyphal formation and they suggest that the protein senses phenolic compounds to direct hyphal growth in plants. The third reported finding is that UmPR- 1La is cleaved by a plant cathepsin B- like protease to release a functional signaling peptide (CAPE- like) that suppresses plant immunity and promotes fungal virulence. + +<|ref|>text<|/ref|><|det|>[[115, 500, 882, 572]]<|/det|> +The main limitation of this study is that it presents an assembly of three more or less independent observations but fails to convey a compelling and significant overall progress in our understanding of the mode of action of PR- 1- like proteins. Moreover, each of the three findings is not sufficiently supported by data. + +<|ref|>text<|/ref|><|det|>[[115, 612, 258, 628]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[115, 668, 879, 759]]<|/det|> +Fig1a, the consensus sequence for the CAPE1 cleavage is CNYx. It is not clear why the authors change this consensus to CxYx. The same applies for the 11- amino acid CAPE- like peptide sequence. The plant PR- 1 derived CAPE1 peptides all end in R/KPY but this is not conserved in UmPR- 1L. It is not clear what criteria these authors apply to define the CAPE- like peptide derived from UmPR- 1La as being similar/like to that of the plant CAPE1 peptides. + +<|ref|>text<|/ref|><|det|>[[115, 798, 870, 852]]<|/det|> +Fig1b, the normalized read counts for pr- 1la appear to be very low, especially when compared to those for pr- 1lb, which are 100- fold higher (FigS1b), or CatB3, which are about 500- fold higher (Fig5a). The gene thus appears to be expressed only at very low levels. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 819, 125]]<|/det|> +Fig1d, are the disease symptoms between the single mutant (Δa) and the double mutant (ΔΔab) statistically significant? The authors describe these differences as "more pronounced" (L137). + +<|ref|>text<|/ref|><|det|>[[115, 164, 879, 256]]<|/det|> +Fig2a,b, the authors say that UmPR1- La and ScPry1- mCherry are cell surface associated proteins, and that UmPR1- La localizes to bud necks and growing tips in sporidal cells. However, they do not show any colocalization experiments with established cell wall markers. At the same time, they show that these proteins are secreted, but they do not include a cell wall- associated protein in the Western blots as control. Are these proteins now secreted or are they cell wall associated? + +<|ref|>text<|/ref|><|det|>[[114, 294, 877, 441]]<|/det|> +Fig2e, shows that recombinant full length and the Ser/Thr- rich domain of UmPR1- La bind chitin and chitosan. The authors do not show whether these proteins are soluble under these conditions in the absence of chitin or chitosan. If the Ser/Thr- rich domain would promote protein self- association, it would appear as binding to chitin/chitosan. These proteins were expressed and purified from bacteria, nevertheless, the authors suggest that they associate with the fungal cell wall by binding to chitin/chitosan via glycosidic linkages (L169- 172). Does the CAP domain bind lignin and is this abrogated in a CBM (FY\*) mutant version? This seems to be important given that the authors subsequently show that the CAP domain binds phenolic compounds that are the precursors and building blocks of lignin. + +<|ref|>text<|/ref|><|det|>[[114, 479, 874, 660]]<|/det|> +Fig3, the apparent role of UmPR1- La in conferring eugenol resistance and the putative function of UmPR1- La in sensing phenolic compounds to signal pseudohyphal growth is based on cells that overexpress this protein, i.e., a SG200 wild- type strain expressing an additional copy of UmPR1- La from a constitutive promoter. Thus, this is a gain- of- function phenotype that may have little in common with the native function of this gene/protein. These crucial experiments need to be supported by showing that mutant cells lacking one (Δa) or both (ΔΔab) UmPR1- L are hypersensitive to eugenol, and that this sensitivity and hyphal growth can be complemented in the deletion strain by expression of one or both UmPR1- L from their respective native promoters. The putative function of the CBM should then be tested in this sensitized background and not in an overexpressing strain. Are the WT and FY\* mutant proteins used in Fig3c and Fig4b expressed at comparable levels, please provide Western data. + +<|ref|>text<|/ref|><|det|>[[114, 699, 876, 790]]<|/det|> +Fig4, as in Fig3, the authors should make sure that they are not scoring an overexpression phenotype. Is an SG200 strain not expressing WT or FY\* mutant version of UmPR1- La sensitive to ferulic acid, what is its morphology? The binding assay shown in Fig4c does not indicate whether binding is specific, concentration- dependent, and saturable. Could it be that the protein gets denatured in the presence of ferulic acid and that this is scored as "binding"? This also applies to FigS4b. + +<|ref|>text<|/ref|><|det|>[[114, 829, 860, 902]]<|/det|> +Fig5, the authors fail to detect the UmCAPE- La peptide in the apoplastic fluid of U. maydis infected leaves (L239). Hence there is no evidence that this peptide is actually produced in planta. Did they try infection with an overexpression strain? Fig5b, CatB3, which shows cleavage activity towards recombinant UmPR1- La, was purified from the apoplastic fluid of tobacco leaves and this protein + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 879, 163]]<|/det|> +preparation is not pure (FigS5b). Purification and cleavage assay with a catalytically dead mutant version of CatB3 would be needed to claim that the observed cleavage is indeed due to CatB3 and not a contaminating protease. This seems to be particularly important given that the cleavage of the native secreted version of UmPR1- L by CatB3 appears to be very slow and inefficient. + +<|ref|>text<|/ref|><|det|>[[115, 201, 875, 275]]<|/det|> +Fig6, if CAPE- L indeed has immune suppressive activity one would expect that U. maydis strains overexpressing UmPR1- La show enhanced virulence. What is the induction of PR gene expression when non- infected plants are treated with ZmCAPE, CAPE- L, or both peptides together, compared to plants treated with scrambled peptide sequences? + +<|ref|>text<|/ref|><|det|>[[115, 398, 393, 414]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 454, 870, 619]]<|/det|> +The authors provide a functional characterization of 1 (2) effector(s) of the fungal maize pathogen Ustilago maydis, which have homology with plant PR1 proteins, including the C- terminal CAPE peptide which is known to play an important role in PR- 1 mediated induction of plant defenses. The findings shown in the paper are new and exciting. Also, the experiments are all over sound. However, the presentation and documentation of data is partially incomplete. Also, this reviewer is not completely convinced how the two proposed functions of eugenol detoxification (which is actually rather resistance/tolerance than detox) and CAPE- release to block plant immunity are linked. Also, it appears unclear why/how the Um- PR1 released CAPE interferes with the generation of Zm- derived CAPE peptide. + +<|ref|>text<|/ref|><|det|>[[116, 658, 368, 674]]<|/det|> +General questions and comments: + +<|ref|>text<|/ref|><|det|>[[112, 686, 874, 722]]<|/det|> +- Are orthologs of related smuts able to complement the PR-1La disease phenotype, or is this specific to the Ustilago maydis protein? + +<|ref|>text<|/ref|><|det|>[[115, 733, 810, 787]]<|/det|> +- Does the PR-1La deletion mutant have any (growth/developmental) defects besides in-planta development? Given its function at cell-surface localization this seems to be relevant for the interpretation of the results and the actual biological function of the PR-1La. + +<|ref|>text<|/ref|><|det|>[[115, 798, 868, 870]]<|/det|> +- It appears (particular at level of this journal) somehow inappropriate to show gene expression data in the main figures (Fig 1; Fig 5) that is actually just extracted from a publication by others. Authors may provide own qPCR data to confirm the proposed expression patterns in their own experimental conditions (and refer to the published data in the supplements) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 881, 199]]<|/det|> +- The figure labels are missing some relevant information to make them accessible. In Fig 2 it took me a while to understand that I am looking on an "otef" OE which explains the signals in sporidia. In Figure 3C I needed to search for "FY\*\* and found it in the legend for 3D. However, as the figure 3C is shown, one would understand that there is a "WT" and a "FY\*\* both being somehow with "SG200_PR-1LaHA". What I guess it is, is strain SG200 (which actually should not be called a "wild type", because it is an artificial lab strain) vs the pr-1la deletion strain. Right? + +<|ref|>text<|/ref|><|det|>[[114, 209, 882, 318]]<|/det|> +Allover, it took me lots of time to look up this kind information up, as descriptions in the figures are sparse/sometimes misleading and also the legends lack information (e.g. legend Fig 3 "same strains used in 2a" – this is not sufficient. Please name the strains which are shown!) Thus, the authors should carefully revise their figures (including supplements, where also info is missing), provide more precise labels and information on strains wherever it is needed, otherwise it is very difficult to follow and interpret results. + +<|ref|>text<|/ref|><|det|>[[115, 357, 856, 411]]<|/det|> +- Does the CAPE-peptide have a virulence function for U. maydis? Figure 6 implies that it has a role in virulence. So, is a mutant with a C-terminally truncated PR-1La reduced in virulence? If so, can other (e.g. Zm) CAPE sequences not complement this? + +<|ref|>text<|/ref|><|det|>[[115, 421, 857, 458]]<|/det|> +- If Ustilago CAPE competes for Zm-CAPE with the receptor – how is it then not activating it (if it has a stronger binding affinity?) + +<|ref|>text<|/ref|><|det|>[[115, 499, 252, 515]]<|/det|> +Specific questions: + +<|ref|>text<|/ref|><|det|>[[115, 526, 848, 562]]<|/det|> +- In L136 it is stated that "double deletion phenotype is more pronounced" – Is this really significant compared to the single deletion? + +<|ref|>text<|/ref|><|det|>[[115, 573, 816, 608]]<|/det|> +- Figure 3 and corresponding text: what is the evidence for a "detoxification" – what is shown is resistance to a toxic compound, but not its detox. + +<|ref|>text<|/ref|><|det|>[[115, 619, 864, 655]]<|/det|> +- Figure 4C – what is actually detected here by the spectrophotometer? At which wavelength? Why are no biological reps shown but only technical reps? + +<|ref|>text<|/ref|><|det|>[[115, 665, 875, 720]]<|/det|> +- Figure 5 – also here, biological reps are not shown (MS data). Also, it is not possible for me to understand the figure completely. What are the sequences below 5b? What is shown in 5C (what is "y7" "y6" etc?) What is scale of "intensity"? How does this show a specific cleavage of PR-1La by CatB3? + +<|ref|>text<|/ref|><|det|>[[115, 730, 861, 785]]<|/det|> +- Fig S5A indicates degradation of PR-1La by apoplastic fluid of maize. However, none of the inhibitors used could fully block this degradation completely. This actually suggests that multiple proteases are involved in degradation of the protein beyond Cat3B. How do the authors interpret this? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 116, 875, 373]]<|/det|> +The submission, "Ustilago maydis PR- 1- like protein has evolved two distinct domains for dual virulence activities" by Lin et al describes a fungal protein, PR- 1- like, that has homology to the well described yeast, PRY1 and plant PR1. The authors show that the U. maydis PR- 1- like proteins contains two domains, Ser/Thr- rich region and the CAP domain with a predicted C- terminal peptide similar to PRY1, while plant PR- 1's only contain the CAP domain with a C- terminal peptide. The authors show that the Ser/Thr- rich region is responsible for the binding of PR- 1- like to Chitin and therefore its localisation to the fungal cell wall. While the CAP domain is responsible for sterol/phenolic binding which induces a switch in U. maydis from sporidia to pseudohyphal structures which allows survival of the fungi. Additionally, the authors show that the C- terminal peptide of PR- 1- like is cleaved by CatB3 a member of the cystine protease family and that PR- 1- like can modulate known plant immune genes which is likely to occur via the C- terminal peptide. Overall, this paper is quite well written and logically structured making it relatively easy to follow the narrative, however some work on Figure layout and labelling will help greatly. I have below some major and minor points to address which should improve the article prior to publication. + +<|ref|>text<|/ref|><|det|>[[115, 412, 285, 429]]<|/det|> +Major point to address + +<|ref|>text<|/ref|><|det|>[[115, 440, 870, 513]]<|/det|> +- Figure 2 – These microscope images (a and d) are not good enough quality to be the only evidence of cell surface localisation. I would like to see better quality and higher resolution images as well as colocalisation with a known cell surface protein so show co-localisation. Arrows would also help to direct reader. + +<|ref|>text<|/ref|><|det|>[[115, 551, 871, 644]]<|/det|> +- Please review all figures as many are lacking good labelling e.g. Fig2, no labels on western blot for expected size of protein especially important for PR-1Lb as there are multiple bands and the band sizes don't seem to match my calculations based on the amino acids described in fig 1. Also Fig2a - PRY1HA I believe should be labelled Umsp:PRY1-HA this was very unclear as the labelling did not match the description in the text of the results. These are just two examples. + +<|ref|>text<|/ref|><|det|>[[115, 682, 482, 700]]<|/det|> +- Add in the O-glycosylation data into a sup figure + +<|ref|>text<|/ref|><|det|>[[115, 737, 878, 811]]<|/det|> +- Figure 3b – Given that the authors base this experiment off the PRY1 literature of PR1 binding Eugenol this seems an unexpected result that the cells do not survive, please expand on/discuss this. Could it be linked to the data in Fig2a where PRY1 does not localise to cell surface in U. maydis? Make clear your reasons for reader. + +<|ref|>text<|/ref|><|det|>[[115, 850, 450, 867]]<|/det|> +- Add loading controls to immunoblot panels. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 870, 181]]<|/det|> +- I find it surprising not to have seen an enhancement of defence by the application of the maise CAPE peptide. I would suggest you repeat this experiment, but this time pre-treat the maise with ZmCAPE 1 day prior to infection. This experimental set up is how previous publication have conducted the experiment e.g. Chen et al, 2014 Plant cell and Sung et al, 2021 New Phyt (refs 8 & 9 on your list). Have you also tried it with WT SG200? + +<|ref|>text<|/ref|><|det|>[[115, 277, 285, 293]]<|/det|> +Minor point to address + +<|ref|>text<|/ref|><|det|>[[115, 304, 880, 377]]<|/det|> +- Line 79-81 "However, it is unclear whether a protease involves in the cleavage of the CNYx motif and a receptor to perceive CAPE peptide to activate" suggest editing to read "However, it is unclear whether a protease is involved in the cleavage of the CNYx motif and if there is a receptor to perceive CAPE peptides that activate" + +<|ref|>text<|/ref|><|det|>[[115, 415, 867, 452]]<|/det|> +- Line 95 – “sexual life cycle, it requires U. maydis fine sensing and integrating environmental” suggest editing it to “sexual life cycle, U. maydis requires fine sensing of environmental” + +<|ref|>text<|/ref|><|det|>[[115, 491, 578, 508]]<|/det|> +- Line 97 – “U. maydis secrete a” edit to “U. maydis secretes a” + +<|ref|>text<|/ref|><|det|>[[115, 547, 818, 583]]<|/det|> +- Line 108 – “elicit hyphal-like structures. A CAPE-like peptide” suggest edit to “elicit hyphal-like structures, while a CAPE-like peptide” + +<|ref|>text<|/ref|><|det|>[[115, 622, 860, 677]]<|/det|> +- Line 172-173 – I think this statement has not been 100% proven therefore I would say “the results indicates that this PR-1La may incorporate into the cell-wall chitin/chitosan-glucan matrix possibly via glycosidic linkages” + +<|ref|>text<|/ref|><|det|>[[115, 716, 848, 752]]<|/det|> +- Remind reader that PR-1-likes are not expressed in culture therefore the native PR-1-like’s are not affecting the phenolic binding assays. + +<|ref|>text<|/ref|><|det|>[[115, 791, 861, 846]]<|/det|> +- Figure S3a – there is wrong labelling between the graph and the images or there is a wrong image added – graph shows PR-1La showing cell survival and growth however image is showing PR-1Lb data. Need consistency between graph and images, suggest adding PR-1La and PR-1Lb to both. + +<|ref|>text<|/ref|><|det|>[[115, 885, 454, 901]]<|/det|> +- Line 193 – Wrong Figure, should read Fig 2a. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 117, 875, 153]]<|/det|> +- Fig3d – suggesting adding in WT complementation line. Also inconsistent labelling between Fig 1d and 3d + +<|ref|>text<|/ref|><|det|>[[115, 193, 860, 228]]<|/det|> +- Line 218 – CA-treated PR-1La (FY\*) cells show a swollen morphology, based on the image shown for PR-1La WT treated with CA these pseudohyphae also look swollen + +<|ref|>text<|/ref|><|det|>[[115, 268, 671, 286]]<|/det|> +- Inconsistent labelling of sterol graphs between Fig3 and 4. FigS3 and FigS4 + +<|ref|>text<|/ref|><|det|>[[115, 324, 877, 361]]<|/det|> +- Lines 241-244 – re-word sentence, it is difficult to follow. You need to get the phrase culture filtrate or culture supernatant in there as well as saying U. maydis SG200 +PR-1La-HA line. + +<|ref|>text<|/ref|><|det|>[[115, 400, 878, 454]]<|/det|> +- Figure S5a legend is missing information – treatments and concentrations used. Labelling of figure and description in materials and methods don’t match i.e. is control on figure the PIC as in materials you mention DMSO is the control? + +<|ref|>text<|/ref|><|det|>[[115, 492, 863, 547]]<|/det|> +- Line 249 – “Cathepsin B-like 3 (CatB3) has a similar expression profile as umpr-1la” I disagree PR-1La expression is all over the place. I would just say CatB3 is induced during infection or CatB3 is strongly induced from 4dpi compared to mock treatment. + +<|ref|>text<|/ref|><|det|>[[115, 586, 742, 604]]<|/det|> +- Fig5b add arrow to indicate PR-1La band also labels for Coomassie and immunoblot. + +<|ref|>text<|/ref|><|det|>[[115, 642, 877, 697]]<|/det|> +- Fig5b make the second blot on U. maydis secreted PR-1LaHA blot Fig 5c as currently the legend is hard to follow what is being described. Quantify band intensity against total protein stain as there is no size shift (due to small cleavage size) as observed in the previous gel and no loading controls shown. + +<|ref|>text<|/ref|><|det|>[[115, 736, 857, 790]]<|/det|> +- Line 265 – “In maize, homolog Xcp2 is highly expressed in the 266 early infection process and then slowly declines during biotrophy (Fig. S5d).” – I disagree with this statement, there is no difference in expression of Xcp2 between mock and infected tissue. Remove or reword. + +<|ref|>text<|/ref|><|det|>[[115, 829, 870, 864]]<|/det|> +- Line 268 – suggested edit “truncated fragments were detected by Coomassie-blue-staining-PAGE and immunoblot for PRB1-3 and PR-1b” + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 200]]<|/det|> +- Line 313-317 – “U. maydis probably acquired pr-1-like genes via horizontal gene transfer from the host plants during the coevolutionary arms race.” – I know speculation is acceptable in the discussion but I am not sure this is supported by the literature since most organisms contain a CAP-domain containing protein (or CMB motif) including human glioma PR-1 protein and a snake-venom cysteine-rich secretory protein, yeast as you described. This is also unlikely since the plant PR-1’s don’t contain the Ser/Thr rich region whereas PRY1 does. I think it would be better to rephrase this section. + +<|ref|>text<|/ref|><|det|>[[115, 237, 877, 310]]<|/det|> +- Line 326-328 – “PR-1La lacks a transmembrane domain, it is not clear how the signals perceived at the cell surface is transduced to activate the downstream signaling pathway.” Suggest edit it to “PR-1La lacks a transmembrane domain, therefore it is not clear how the cell surface signals would be perceived and transduced to activate downstream signaling.” + +<|ref|>text<|/ref|><|det|>[[115, 348, 574, 365]]<|/det|> +- Line 387 – “performed as described” – incomplete sentence! + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 290, 107]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 393, 144]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 163, 879, 253]]<|/det|> +PR- 1- like proteins belong to a large protein family, and they have been implicated in many different biological processes including immune defense and cancer progression. These proteins share a conserved CAP domain and are mostly secreted glycoproteins. Their mode of action, however, remains poorly characterized. Thus, progress in understanding the function of these proteins at a molecular level would be a welcome advancement. + +<|ref|>text<|/ref|><|det|>[[115, 272, 881, 399]]<|/det|> +Lin et al. now report that the corn smut Ustilago maydis pathogenesis- related 1- like protein (UmPR- 1La) acts in detoxification of phenolic compounds, and that its Ser/Thr- rich N- terminal domain mediates cell surface association. In addition, the authors report that UmPR- 1La has gained a specialized activity in eliciting hyphal formation and they suggest that the protein senses phenolic compounds to direct hyphal growth in plants. The third reported finding is that UmPR- 1La is cleaved by a plant cathepsin B- like protease to release a functional signaling peptide (CAPE- like) that suppresses plant immunity and promotes fungal virulence. + +<|ref|>text<|/ref|><|det|>[[115, 418, 881, 490]]<|/det|> +The main limitation of this study is that it presents an assembly of three more or less independent observations but fails to convey a compelling and significant overall progress in our understanding of the mode of action of PR- 1- like proteins. Moreover, each of the three findings is not sufficiently supported by data. + +<|ref|>text<|/ref|><|det|>[[115, 491, 877, 577]]<|/det|> +We thank the reviewer for the valuable comments and apologize for the incomplete conveyance of the findings in the previous version of the manuscript. To rectify this, we have made necessary modifications to the respective sections of the results and discussion, and have introduced a new model to effectively communicate the findings of this study. Apart from this, in response to the concerns raised by the reviewer, we have carried out additional experiments to specifically address those issues. + +<|ref|>text<|/ref|><|det|>[[116, 595, 258, 611]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[115, 629, 880, 712]]<|/det|> +1). Fig1a, the consensus sequence for the CAPE1 cleavage is CNYx. It is not clear why the authors change this consensus to CxYx. The same applies for the 11-amino acid CAPE- like peptide sequence. The plant PR- 1 derived CAPE1 peptides all end in R/KPY but this is not conserved in UmPR- 1L. It is not clear what criteria these authors apply to define the CAPE- like peptide derived from UmPR- 1La as being similar/like to that of the plant CAPE1 peptides. + +<|ref|>text<|/ref|><|det|>[[115, 714, 883, 868]]<|/det|> +We thank the reviewer for bringing these mistakes to our attention. We have made the necessary corrections in the figure legend of Fig.1a. Regarding your second question about the definition of the CAPE- like peptide (CAPE- L) from UmPR- ILa, we compared the peptide sequences between smut fungal PR- 1Ls and plant PR- 1s (Fig. 1b), and revealed a high conservation of the first seven amino acids after CNYx motifs of PR- 1 and PR- 1L proteins. Consequently, we have designated peptides containing the MEME- derived consensus sequence P[P/V]GN[Φ/V][I/V]G as CAPE- like peptides (CAPE- L). The peptide sequence comparison has been incorporated into Fig. 1b in the revised manuscript. Our current hypothesis is that UmCAPE- La may compete for binding to the plant CAPE receptor, thereby blocking the CAPE- dependent signaling pathway. This hypothesis could be tested in the future once the receptor is identified. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[148, 100, 473, 295]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[506, 175, 860, 210]]<|/det|> +The green line denotes the consensus sequence conserved in fungal PR- 1Ls and plant PR- 1s. + +<|ref|>text<|/ref|><|det|>[[113, 313, 865, 368]]<|/det|> +2). Fig1b, the normalized read counts for pr- 1la appear to be very low, especially when compared to those for pr- 1lb, which are 100- fold higher (FigS1b), or CatB3, which are about 500- fold higher (Fig5a). The gene thus appears to be expressed only at very low levels. + +<|ref|>text<|/ref|><|det|>[[113, 368, 876, 505]]<|/det|> +We have observed this discrepancy, and one possible explanation is that PR- 1La may have longer mRNA and protein half- lives or exhibit higher translation activity. However, it is important to note that this hypothesis remains speculative. In our recent study, we investigated the expression of the Sccda2 gene, which was found to be 200 times more abundant than the Sccda1 gene. Surprisingly, despite this significant difference, only ScCda1 proteins were detectable (https://doi.org/10.1128/mbio.00093- 23). This finding suggests that there may not always be a positive correlation between gene expression and protein levels. Moreover, a high expression level of effector genes might not necessarily correlate with their contribution to the virulence of U. maydis. + +<|ref|>text<|/ref|><|det|>[[113, 522, 880, 612]]<|/det|> +3). Fig1d, are the disease symptoms between the single mutant (Δa) and the double mutant (ΔΔab) statistically significant? The authors describe these differences as "more pronounced" (L137). After re- analyzing the data obtained from the four biological replicates, there is no statistical significance in disease symptoms caused by these two mutants. As a result, we have revised our statement to read as 'a similar decrease in virulence was also observed in the double mutant ΔΔpr- 1lab'. + +<|ref|>image<|/ref|><|det|>[[358, 617, 603, 803]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 832, 879, 884]]<|/det|> +4). Fig2a,b, the authors say that UmPR1- La and ScPry1- mCherry are cell surface associated proteins, and that UmPR1- La localizes to bud necks and growing tips in sporidal cells. However, they do not show any colocalization experiments with established cell wall markers. At the same time, they show that these + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 844, 123]]<|/det|> +proteins are secreted, but they do not include a cell wall- associated protein in the Western blots as control. Are these proteins now secreted or are they cell wall associated? + +<|ref|>text<|/ref|><|det|>[[113, 123, 881, 268]]<|/det|> +To confirm the localization of UmPR- 1La on the cell surface, we conducted an experiment involving the overexpression of HA- tagged UmPR- 1La in the AB33 strain. The AB33 strain was chosen for its efficient filament induction, controlled by the nitrate- inducible nar1 promoter, when cultured in a nitrate- containing liquid medium, enabling us to perform plasmolysis to separate the cell wall and plasma membrane. Immunostaining was performed, along with labeling of chitin using WGA- AF488. Subsequently, plasmolysis was carried out. The results demonstrated the colocalization of UmPR- 1La with the chitin on the cell surface, while the fluorescence of UmPR- 1La was not detected inside the expanded space resulting from plasmolysis (\*). This provides conclusive evidence for the cell- wall localization of UmPR- 1La. The corresponding data has been incorporated into Fig. 2c. + +<|ref|>image<|/ref|><|det|>[[130, 277, 444, 421]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[460, 283, 853, 320]]<|/det|> +Arrows and (\*) indicate spaces enlarged by plasmolysis. - HA- tagged UmPR- La was labeled by anti- HA and anti- IgG- AF595. - Chitin was stained by WGA- AF488. + +<|ref|>text<|/ref|><|det|>[[114, 437, 875, 534]]<|/det|> +Regarding the concern about protein secretion, it is important to note that, due to the overexpression conditions and the absence of a GPI- anchor, certain cell- wall localized proteins may not bind tightly to the cell walls, as GPI- anchored proteins do. Consequently, these proteins can be detected both on the cell walls and in the culture supernatant if overexpressed. Our finding is also in line with other cell- wall protein studies (Tanaka et al., 2020, https://doi.org/10.1111/nph.16508; Cottier et al., 2020, https://doi.org/10.1242/bio.053470). + +<|ref|>text<|/ref|><|det|>[[114, 550, 870, 651]]<|/det|> +5). Fig2e, shows that recombinant full length and the Ser/Thr- rich domain of UmPR1- La bind chitin and chitosan. The authors do not show whether these proteins are soluble under these conditions in the absence of chitin or chitosan. If the Ser/Thr- rich domain would promote protein self- association, it would appear as binding to chitin/chitosan. These proteins were expressed and purified from bacteria, nevertheless, the authors suggest that they associate with the fungal cell wall by binding to chitin/chitosan via glycosidic linkages (L169- 172). + +<|ref|>text<|/ref|><|det|>[[114, 668, 882, 766]]<|/det|> +We appreciate the concern raised by reviewer #1 regarding protein solubility, which we initially overlooked. As suggested, we conducted protein solubility tests in the assay buffer (50 mM Tris- Cl and 150 mM NaCl, pH 8) without ligands. However, the results were inconsistent in the three replicates (shown below). Full- length (FL) and S/T recombinant proteins showed a tendency to be insoluble, while CAP- domain proteins appeared to be more soluble. Due to these inconsistent findings, we have decided to remove the results of the polysaccharide binding assay from the revised manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[181, 105, 747, 243]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 275, 873, 327]]<|/det|> +Does the CAP domain bind lignin and is this abrogated in a CBM (FY\\*) mutant version? This seems to be important given that the authors subsequently show that the CAP domain binds phenolic compounds that are the precursors and building blocks of lignin. + +<|ref|>text<|/ref|><|det|>[[114, 342, 877, 424]]<|/det|> +To perform the lignin binding assay, we tested the solubility of lignin in the buffer (50 mM Tris- Cl and \(150~\mathrm{mM~NaCl}\) , pH 8), and observed that the buffer turned brown, indicating that lignin might dissolve in the buffer. Under this condition, all the recombinant proteins were detected in the supernatant fractions in the presence of lignin. However, this result does not indicate that the FL or CAP domain proteins do not bind phenolics. They could bind to the phenolics released from the lignin in the supernatants. + +<|ref|>image<|/ref|><|det|>[[360, 432, 504, 560]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 579, 860, 710]]<|/det|> +We next attempted the binding assay in \(\mathrm{H}_2\mathrm{O}\) , where lignin is insoluble. However, the solubility of FL recombinant proteins in \(\mathrm{H}_2\mathrm{O}\) without lignin was inconsistent, even though they appeared in the supernatant fractions with lignin. Similarly, the solubility of S/T or CAP- domain proteins was inconsistent, with CAP proteins tending to be found more in the pellet fraction with lignin. Given that lignin is a complex, three- dimensional highly branched polymer and whether CAP- domains are able to access phenolics in such a complex or only bind to free phenolics is unclear, and the inconsistent solubility test results prevent us from reaching a definitive conclusion, we therefore report our findings here for the reviewers. + +<|ref|>image<|/ref|><|det|>[[116, 781, 535, 900]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 123, 876, 293]]<|/det|> +6). Fig3, the apparent role of UmPR1- La in conferring eugenol resistance and the putative function of UmPR1- La in sensing phenolic compounds to signal pseudohypal growth is based on cells that overexpress this protein, i.e., a SG200 wild- type strain expressing an additional copy of UmPR1- La from a constitutive promoter. Thus, this is a gain- of- function phenotype that may have little in common with the native function of this gene/protein. These crucial experiments need to be supported by showing that mutant cells lacking one (Δa) or both (ΔΔab) UmPR1- L are hypersensitive to eugenol, and that this sensitivity and hyphal growth can be complemented in the deletion strain by expression of one or both UmPR1- L from their respective native promoters. The putative function of the CBM should then be tested in this sensitized background and not in an overexpressing strain. Are the WT and FY\* mutant proteins used in Fig3c and Fig4b expressed at comparable levels, please provide Western data. + +<|ref|>text<|/ref|><|det|>[[114, 292, 880, 422]]<|/det|> +We express our gratitude to the reviewer for this comment, which indicates that our description in the text was insufficient. The gene expression data shown in Fig.1d indicates that U. maydis cells grown in liquid medium do not express PR- 1La and PR- 1Lb genes, and induces their expression during the biotrophic development. As a result, the wild- type strain SG200 is hypersensitive to eugenol due to the absence of native PR- 1La gene expression. Therefore, the protection of cells against eugenol requires the overexpression of PR- 1La proteins in SG200. To ensure readers are reminded of this fact, we have added the sentence " PR- 1La and PR- 1Lb genes were not expressed in axenic culture, but they were induced during biotrophic development of U. maydis SG200." + +<|ref|>text<|/ref|><|det|>[[115, 435, 884, 486]]<|/det|> +With regards to protein levels of PR- 1La and PR- 1La(FY\*) expressed in SG200, we have now included the protein expression and secretion data in the revised manuscript to show that the comparable levels of the proteins expressed in the cells (Fig. 3c). + +<|ref|>image<|/ref|><|det|>[[395, 490, 620, 650]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 680, 881, 770]]<|/det|> +7). Fig4, as in Fig3, the authors should make sure that they are not scoring an overexpression phenotype. Is an SG200 strain not expressing WT or FY\* mutant version of UmPR1- La sensitive to ferulic acid, what is its morphology? The binding assay shown in Fig4c does not indicate whether binding is specific, concentration- dependent, and saturable. Could it be that the protein gets denatured in the presence of ferulic acid and that this is scored as "binding"? This also applies to FigS4b. + +<|ref|>text<|/ref|><|det|>[[115, 771, 877, 857]]<|/det|> +In Fig. 4b, we have included microscopy data depicting the cell morphologies of SG200, as well as the overexpression strains SG200_PR- 1La and SG200_PR- 1La (FY\*), with and without ferulic acid (FA) treatment. After exposed to FA, both the SG200 and SG200_PR- 1La (FY\*) strains displayed similar morphology and appeared slightly less healthy in the presence of FA. However, the presence of a hyphal- like structure was exclusively observed in the FA- treated SG200_PR- 1La strain. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[270, 108, 595, 291]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 316, 880, 420]]<|/det|> +Regarding the FA binding assay, our titration results demonstrated the dose- dependent binding of PR- 1La protein to FA. We observed that the saturation of FA binding occurred before reaching a concentration of \(10 \mu \mathrm{M}\) FA, as evidenced by the presence of a peak in the absorption spectrum of free FA at approximately \(420 \mathrm{nm}\) . In contrast, the mutant protein PR- 1La(FY\*) exhibited no response to different FA concentrations. The fluorescence of FA at \(330 \mathrm{nm}\) was detected but remained constant regardless of the FA concentration. These findings are now presented in Supplementary Figure S4b. + +<|ref|>image<|/ref|><|det|>[[123, 450, 820, 595]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 614, 879, 718]]<|/det|> +We thank the reviewer for raising the concern regarding protein stability in the presence of phenolics, an aspect we had overlooked. To address this concern, we investigated the stability of the protein after exposure to phenolics for 15 minutes prior to fluorescence measurement. Our observations revealed no substantial protein degradation following the incubation period, suggesting that the observed fluorescence change is indeed attributed to the binding of phenolics to PR- 1La. We have included one of the replicate experiments in the revised manuscript as Supplementary Figure S4d. + +<|ref|>image<|/ref|><|det|>[[283, 737, 641, 860]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 880, 236]]<|/det|> +8). Fig5, the authors fail to detect the UmCAPE-La peptide in the apoplastic fluid of U. maydis infected leaves (L239). Hence there is no evidence that this peptide is actually produced in planta. Did they try infection with an overexpression strain? Fig5b, CatB3, which shows cleavage activity towards recombinant UmPR1-La, was purified from the apoplastic fluid of tobacco leaves and this protein preparation is not pure (FigS5b). Purification and cleavage assay with a catalytically dead mutant version of CatB3 would be needed to claim that the observed cleavage is indeed due to CatB3 and not a contaminating protease. This seems to be particularly important given that the cleavage of the native secreted version of UmPR1-L by CatB3 appears to be very slow and inefficient. + +<|ref|>text<|/ref|><|det|>[[144, 246, 880, 545]]<|/det|> +- We attempted infections using various overexpression strains, including those with the otef promoter or multiple copy integration under the control of the native promoter. Additionally, we collected the apoplastic fluids at 1 dpi and 8 dpi, but we were unable to successfully identify the UmCAPE-La peptide. We lack a satisfactory explanation for this outcome but hypothesize that the UmCAPE-La peptide's concentration might be low, or it could potentially bind to an unidentified receptor upon being released.- We acknowledge that there is a low efficiency of cleavage by CatB3 in our assay under the current conditions. We do not have a definitive explanation for this observation. However, we speculate that either an unknown factor is required for the activity of CatB3, or CatB3 may not be able to efficiently access the CNYD motif for cleavage.- In response to the concern raised by reviewer #1 about the purity of CatB3 proteins, we fully agree on the importance of having an inactive form of CatB3. To address this, we introduced mutations in the catalytic site of CatB3 (Cys121 and His276). Both the wild-type and mutant versions of CatB3 were purified in parallel, and the protein purity is illustrated in Fig. S5e. We found that both the catalytic inactive mutants (C121A or C121A H276A) blocked the cleavage of UmPR-1La, while the wild-type CatB3 consistently cleaved UmPR-1La. These results provide support for our claim regarding the cleavage by CatB3 (Fig. 5c). + +<|ref|>image<|/ref|><|det|>[[317, 571, 560, 729]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 745, 861, 824]]<|/det|> +9). Fig6, if CAPE-L indeed has immune suppressive activity one would expect that U. maydis strains overexpressing UmPR1-La show enhanced virulence. What is the induction of PR gene expression when non- infected plants are treated with ZmCAPE, CAPE-L, or both peptides together, compared to plants treated with scrambled peptide sequences? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 870, 296]]<|/det|> +Overexpression of UmPR- 1La might result in an increase in \(U\) . maydis virulence. However, this is not always happened, particularly in \(U\) . maydis. We had overexpressed it using the promoter of UmPR- 1Lb, and it did not complement the virulence of the pr- 1la deletion mutant. Nevertheless, we followed the suggestions by infiltrating peptides into maize leaves, followed a protocol as described in a previous study (https://doi.org/10.1038/s41477- 018- 0116- y). Briefly, the synthetic peptides were dissolved in water, and the peptides was infiltrated using a blunt needless syringe at the base of fourth leaves of 10- day old plants. The leaf samples were harvest 24hr later. We attempted using both \(0.6 \mu \mathrm{M}\) and \(2 \mu \mathrm{M}\) peptides for infiltration and did not observe any significant differences among the treatments. Due to the structure of maize leaves, it was challenging to avoid causing wounds during peptide inoculations. The variations in \(PR\) gene expression may be attributed to these wounds. Consequently, we present these findings to the reviewers. Presented below are the results obtained from three (2 \(\mu \mathrm{M}\) ) and five (0.6 \(\mu \mathrm{M}\) ) independent biological replicates. + +<|ref|>image<|/ref|><|det|>[[111, 312, 901, 586]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 608, 884, 673]]<|/det|> +Mixed peptides: Mixed with an equal concentration of CAPE- La and ZmCAPE. Scrambled peptides: contains an identical amino acid composition to CAPE- La. Maize GAPDH gene was used for normalization. The \(PR\) gene expression level in \(\mathrm{H}_2\mathrm{O}\) was set to 1.0. Average values of three or five biological replicates are shown. Error bars indicate \(\pm \mathrm{SD}\) + +<|ref|>text<|/ref|><|det|>[[114, 690, 868, 766]]<|/det|> +Despite our inability to demonstrate the role of ZmCAPE in plant defense through peptide infiltration, we successfully exhibited a notable reduction in the virulence of \(U\) . maydis. This outcome was achieved by substituting UmCAPE- La peptide of UmPR- 1La with ZmCAPE, and delivered them via \(U\) . maydis. (Figure 6e- f). (Please refer to the response to question #13). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 868, 290]]<|/det|> +The authors provide a functional characterization of 1 (2) effector(s) of the fungal maize pathogen Ustilago mayidis, which have homology with plant PR1 proteins, including the C-terminal CAPE peptide which is known to play an important role in PR- 1 mediated induction of plant defenses. The findings shown in the paper are new and exciting. Also, the experiments are all over sound. However, the presentation and documentation of data is partially incomplete. Also, this reviewer is not completely convinced how the two proposed functions of eugenol detoxification (which is actually rather resistance/tolerance than detox) and CAPE- release to block plant immunity are linked. Also, it appears unclear why/how the Um- PR1 released CAPE interferes with the generation of Zm- derived CAPE peptide. + +<|ref|>text<|/ref|><|det|>[[115, 310, 368, 325]]<|/det|> +General questions and comments: + +<|ref|>text<|/ref|><|det|>[[115, 328, 870, 362]]<|/det|> +9). Are orthologs of related smuts able to complement the PR- 1La disease phenotype, or is this specific to the Ustilago maydis protein? + +<|ref|>text<|/ref|><|det|>[[114, 364, 880, 519]]<|/det|> +We appreciate the review for raising this question, as it has provided us with an opportunity to uncover additional interesting findings for further exploration in the future. In response to this question, we generated a complementation strain using the ortholog Sr10279 from Sporisorium reilianum, a maize- infecting fungus. Despite Sr10279 being able to localize to the U. maydis cell wall and possessing the conserved CNYD and CBM motifs, it was unable to rescue the virulence of U. maydis \(\Delta \mathrm{pr} - 1\mathrm{la}\) strain, and it did not form pseudohyphae upon exposure to ferulic acids. This discrepancy may be attributed to potential divergence in downstream signal reception partners between Sr10279 and UmPR- 1La. Consequently, Sr10279 is incapable of substituting the role of UmPR- 1La in eliciting hyphal- like structures in U. maydis. The corresponding data has been incorporated into Fig 4c- e. + +<|ref|>image<|/ref|><|det|>[[137, 540, 770, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 809, 832, 862]]<|/det|> +10). Does the PR- 1La deletion mutant have any (growth/developmental) defects besides in- planta development? Given its function at cell- surface localization this seems to be relevant for the interpretation of the results and the actual biological function of the PR- 1La. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 877, 187]]<|/det|> +The deletion mutants, complementation strain ( \(\Delta \mathrm{pr - 1la}\) PR- 1La; controlled by the native promoter), and the overexpression strains (SG200 PR- 1La and SG200 PR- 1La(FY\*) driven by the otet promoter) displayed no visible abnormalities during their growth in a liquid medium or in their ability to form filaments on charcoal plates. Their morphologies were comparable to SG200. As a result, we can conclude that PR- 1La is associated with the in- planta development of U. maydis. These results have been included in supplementary figure S1d. + +<|ref|>image<|/ref|><|det|>[[120, 216, 670, 438]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 477, 844, 512]]<|/det|> +11). Based on the expression profiles, both pr- 1l genes are not expressed when cell growth in liquid culture. + +<|ref|>text<|/ref|><|det|>[[114, 514, 870, 586]]<|/det|> +- It appears (particular at level of this journal) somehow inappropriate to show gene expression data in the main figures (Fig 1; Fig 5) that is actually just extracted from a publication by others. Authors may provide own qPCR data to confirm the proposed expression patterns in their own experimental conditions (and refer to the published data in the supplements). + +<|ref|>text<|/ref|><|det|>[[115, 588, 879, 639]]<|/det|> +We completely agree with the reviewer. We have removed the expression data and conducted a qRT- PCR assay to analyze the expressions of UmPR- 1La and UmPR- 1Lb using samples from SG200- infected leaves. These figures have been added to the revised manuscript (Fig. 1d and S1b). + +<|ref|>image<|/ref|><|det|>[[213, 658, 596, 760]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 786, 880, 895]]<|/det|> +12). The figure labels are missing some relevant information to make them accessible. In Fig 2 it took me a while to understand that I am looking on an "otet" OE which explains the signals in sporidia. In Figure 3C I needed to search for "FY\*" and found it in the legend for 3D. However, as the figure 3C is shown, one would understand that there is a "WT" and a "FY\*" both being somehow with "SG200_PR- 1LaHA". What I guess it is, is strain SG200 (which actually should not be called a "wild type", because it is an artificial lab strain) vs the pr- 1la deletion strain. Right? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 198]]<|/det|> +Allover, it took me lots of time to look up this kind information up, as descriptions in the figures are sparse/sometimes misleading and also the legends lack information (e.g. legend Fig 3 "same strains used in 2a" – this is not sufficient. Please name the strains which are shown!) Thus, the authors should carefully revise their figures (including supplements, where also info is missing), provide more precise labels and information on strains wherever it is needed, otherwise it is very difficult to follow and interpret results. + +<|ref|>text<|/ref|><|det|>[[114, 199, 883, 286]]<|/det|> +We offer our sincerest apologies for the inadequate and inattentive explanation provided, as well as the incorrect labeling of the experimental data depicted in the figures. To avoid any possible confusion, we have made the necessary revisions, substituting 'WT and FY\*' with 'PR- 1La and PR- 1La(FY\*)' in both the text and figures. Additionally, we have made every effort to provide comprehensive information in the figure legends within the given word limits. + +<|ref|>text<|/ref|><|det|>[[114, 303, 880, 356]]<|/det|> +13). Does the CAPE-peptide have a virulence function for U. maydis? Figure 6 implies that it has a role in virulence. So, is a mutant with a C-terminally truncated PR-1La reduced in virulence? If so, can other (e.g. Zm) CAPE sequences not complement this? + +<|ref|>text<|/ref|><|det|>[[114, 368, 877, 576]]<|/det|> +We appreciate the reviewer for suggesting this experiment, which allowed us to confirm the role of ZmCAPE in priming maize defense. Following the suggestions of the reviewer, we generated the complementation strains in which the UmPR- 1La's CAPE- La sequence was replaced with either ZmCAPE or UmCAPE- Lb after the CNYD motif. The complemented strain expressing PR- 1La (CAPELb) proteins under the PR- 1La promoter partially restored the virulence of \(\Delta pr - 1la\) , resulting in an intermediate phenotype that showed no significant difference from SG200 or \(\Delta pr - 1la\) . Surprisingly, the virulence of the complementation strain \(\Delta pr - 1la\) PR- 1La(ZmCAPE) was severely affected, leading to the development of tiny tumors with a size of less than 1 mm. The significant decrease in disease symptoms caused by ZmCAPE suggests a role of plant defense, and the spatial and temporal delivery of ZmCAPE peptides by U. maydis could effectively boost plant immunity to suppress fungal virulence. This negative impact could be partially reversed by the application of UmCAPE- La peptides, further supporting the contradictory role of UmCAPE- La and ZmCAPE in regulating plant immunity during the maize- U. maydis interactions. We have now included the data in Figure 6d- e. + +<|ref|>image<|/ref|><|det|>[[189, 588, 732, 792]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[112, 814, 872, 847]]<|/det|> +14). If Ustilago CAPE competes for Zm- CAPE with the receptor – how is it then not activating it (if it has a stronger binding affinity?) + +<|ref|>text<|/ref|><|det|>[[114, 848, 872, 897]]<|/det|> +Based on our findings in Fig 6e, it appears that the use of UmCAPE- La could mitigate the negative impact of ZmCAPE on U. maydis virulence. Our current hypothesis is that UmCAPE- La may compete for the unidentified receptor binding, leading to the inhibition of the receptor's role in activating PR gene + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 877, 220]]<|/det|> +expression (as depicted in Fig. 6f). In maize B73, among the seventeen PR- 1 genes examined, four contain peptides longer than 11 amino acids that do not end with [R/K]PY, while the remaining peptides end with [R/K/S]P[Y/F] (Am J Transl Res. 2022; 14(11): 8315–8331). We speculate that the first seven conserved amino acids found in UmCAPE- La and maize CAPE peptides could be sufficient for receptor binding, while the last few amino acids of the peptides might influence the degree of receptor activation. The precise mechanism by which plant CAPE triggers the SA- signaling pathway remains unclear. However, once the receptor is identified, further investigation can be conducted to assess the role of these amino acids in modulating plant CAPE- dependent signaling pathway. + +<|ref|>sub_title<|/ref|><|det|>[[115, 237, 252, 252]]<|/det|> +## Specific questions: + +<|ref|>text<|/ref|><|det|>[[115, 253, 870, 287]]<|/det|> +15). In L136 it is stated that "double deletion phenotype is more pronounced" – Is this really significant compared to the single deletion? + +<|ref|>text<|/ref|><|det|>[[115, 303, 881, 355]]<|/det|> +The same argument is also raised by Reviewer#1. We have re- analyzed the data and there is no significant difference between single and double deletion mutants, and we have reworded it to 'a similar decrease in virulence was also observed in the double mutant \(\Delta \Delta \mathrm{pr} - \mathrm{llab}\) '. + +<|ref|>text<|/ref|><|det|>[[115, 374, 840, 408]]<|/det|> +16). Figure 3 and corresponding text: what is the evidence for a "detoxification" – what is shown is resistance to a toxic compound, but not its detox. + +<|ref|>text<|/ref|><|det|>[[115, 410, 857, 444]]<|/det|> +We fully concur with the reviewer's assessment, as we did not have evidence to substantiate its detoxification properties. In the revised manuscript, we have now replaced it with the term 'resistance'. + +<|ref|>text<|/ref|><|det|>[[115, 462, 864, 497]]<|/det|> +17). Figure 4C – what is actually detected here by the spectrophotometer? At which wavelength? Why are no biological reps shown but only technical reps? + +<|ref|>text<|/ref|><|det|>[[114, 499, 872, 655]]<|/det|> +Fluorescence spectrophotometry could be used to study the ligand binding- induced conformational change of a protein. The natural fluorescence of tryptophan is used as a reporter of the conformational changes induced by the ligand binding. Tryptophan were excited at \(290 \mathrm{nm}\) , and emission spectra were recorded in the range of \(310 - 450 \mathrm{nm}\) . The experimental detail has been provided in 'Methods' section. In our previous manuscript, we chose to present only one biological replicate because the figure with three biological replicates appeared crowded and untidy. The excessive number of data points resulted in extensive error bars, leading to visual clutter. Due to the concern regarding the absence of biological replicates, we have now replaced it with a new one that displays the mean and standard deviation of all three biological replicates (Fig. 4f). + +<|ref|>image<|/ref|><|det|>[[128, 664, 388, 840]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 878, 144]]<|/det|> +18). - Figure 5 – also here, biological reps are not shown (MS data). Also, it is not possible for me to understand the figure completely. What are the sequences below 5b? What is shown in 5C (what is “γ7” “γ6” etc?) What is scale of “intensity”? How does this show a specific cleavage of PR-1La by CatB3? + +<|ref|>text<|/ref|><|det|>[[115, 154, 880, 275]]<|/det|> +We apologize for not providing sufficient information to access Figure 5e. We have revised the figure legend for clarity. The peak area of fragment ions was used to quantify the quantity of tryptic UmCAPE- La peptide in both the - CatB3 and +CatB3 samples. Fragment ions γ6 and γ7 extend from the C- terminus, and γ7++ is a doubly charged ion. The b5 ions extend from the N- terminus. To illustrate the fragment ions of the peptide, we have included a cartoon in Figure 5d. The term “intensity” refers to the amplitude of the free induction decay signal. Because the intensity is not a precise measurement to represent the absolute peptide abundance, therefore it is usually not labeled. + +<|ref|>text<|/ref|><|det|>[[115, 285, 866, 337]]<|/det|> +Regarding the issue of biological replicates, the His- and HA- tagged UmPR- 1La served as two separate replicates for CatB3 cleavage and consistently produced similar results. This observation indicates that only the +CatB3 sample displayed fragment ions derived from the UmCAPE- La peptide. + +<|ref|>text<|/ref|><|det|>[[115, 365, 870, 418]]<|/det|> +19). - Fig S5A indicates degradation of PR- 1La by apoplastic fluid of maize. However, none of the inhibitors used could fully block this degradation completely. This actually suggests that multiple proteases are involved in degradation of the protein beyond Cat3B. How do the authors interpret this? + +<|ref|>text<|/ref|><|det|>[[115, 436, 880, 567]]<|/det|> +Thanks for the question. We believe that the insufficient amount of protease inhibitors added is the reason for this. To address this issue, we conducted a titration assay by adding varying amounts of DMSO- dissolved E- 64 to apoplastic fluid proteins (AF). In this assay, we also reduced the amount of AF by half, using \(15 \mu \mathrm{g}\) AF instead of the amount used previously in Fig. S5A. Our findings indicate that the cleavage of PR- 1La in the apoplast was blocked in the presence of E- 64. Additionally, E64 also inhibited the activity of CatB3. These results suggest that the cleavage of UmPR- 1La in the apoplast is caused by cysteine proteases, and CatB3 is one of them. These figures have been incorporated into Fig. 5a and 5b of the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[120, 588, 707, 730]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 872, 380]]<|/det|> +The submission, "Ustilago maydis PR- 1- like protein has evolved two distinct domains for dual virulence activities" by Lin et al describes a fungal protein, PR- 1- like, that has homology to the well described yeast, PRY1 and plant PR1. The authors show that the U. maydis PR- 1- like proteins contains two domains, Ser/Thr- rich region and the CAP domain with a predicted C- terminal peptide similar to PRY1, while plant PR- 1's only contain the CAP domain with a C- terminal peptide. The authors show that the Ser/Thr- rich region is responsible for the binding of PR- 1- like to Chitin and therefore its localisation to the fungal cell wall. While the CAP domain is responsible for sterol/phenolic binding which induces a switch in U. maydis from sporidia to pseudohyphal structures which allows survival of the fungi. Additionally, the authors show that the C- terminal peptide of PR- 1- like is cleaved by CatB3 a member of the cystine protease family and that PR- 1- like can modulate known plant immune genes which is likely to occur via the C- terminal peptide. Overall, this paper is quite well written and logically structured making it relatively easy to follow the narrative, however some work on Figure layout and labelling will help greatly. I have below some major and minor points to address which should improve the article prior to publication. + +<|ref|>text<|/ref|><|det|>[[115, 401, 285, 417]]<|/det|> +Major point to address + +<|ref|>text<|/ref|><|det|>[[115, 419, 870, 490]]<|/det|> +20). Figure 2 - These microscope images (a and d) are not good enough quality to be the only evidence of cell surface localisation. I would like to see better quality and higher resolution images as well as co- localisation with a known cell surface protein so show co- localisation. Arrows would also help to direct reader. + +<|ref|>text<|/ref|><|det|>[[115, 491, 870, 573]]<|/det|> +Same question (#4) regarding the cell- wall localization is also raised by reviewer #1. To address this issue, we performed co- localization experiments of UmPR- 1La with chitins in the AB33 PR- 1La strain treated with plasmolysis, and found that UmPR- 1La co- localized with chitin on the filamentous cell surface and not located inside the space enlarged by plasmolysis. Please refer to our response to question #4 raised by reviewer #1. + +<|ref|>text<|/ref|><|det|>[[115, 572, 870, 605]]<|/det|> +To improve the image resolution in Fig. 2, we have replaced them with high- resolution enlarged images. This clearly shows the localization of PR- 1- like proteins on the cell surface. + +<|ref|>text<|/ref|><|det|>[[115, 622, 870, 712]]<|/det|> +21). Please review all figures as many are lacking good labelling e.g. Fig2, no labels on western blot for expected size of protein especially important for PR- 1Lb as there are multiple bands and the band sizes don't seem to match my calculations based on the amino acids described in fig 1. Also Fig2a - PRY1HA I believe should be labelled Umsp:PRY1- HA this was very unclear as the labelling did not match the description in the text of the results. These are just two examples. + +<|ref|>text<|/ref|><|det|>[[115, 713, 874, 782]]<|/det|> +We apologize for any confusion caused by our previous lack of clarity in the figure legends. We have now taken the necessary steps to revise all figures and their corresponding legends to ensure that they are clear and unambiguous to readers. Thank you for bringing this to our attention, and we hope that our revised figures and legends will be more helpful to readers. + +<|ref|>text<|/ref|><|det|>[[115, 799, 870, 897]]<|/det|> +We have noticed that the molecular weights of PR- 1- like proteins are higher than anticipated. Specifically, PRY1 expressed in SG200 cells exhibited slower migration than expected in SDS- PAGE, despite an expected weight of 33kDa, it was detected at 72kDa. This finding is consistent with the result from Roger Schneiter's team, who discovered that yeast PRY1 is a high molecular weight glycoprotein that migrates at \(>70\mathrm{kDa}\) in SDS- PAGE (https://doi.org/10.1242/bio.053470). Based on this information, we suspect that PR- 1L proteins are also glycosylated to some extent. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 501, 107]]<|/det|> +22). Add in the O- glycosylation data into a sup figure + +<|ref|>text<|/ref|><|det|>[[115, 108, 863, 140]]<|/det|> +Due to the inconsistency in protein solubility, we have excluded the polysaccharide binding result from Figure 2e (Please refer to our response to question #5). + +<|ref|>text<|/ref|><|det|>[[115, 155, 864, 222]]<|/det|> +23). Figure 3b – Given that the authors base this experiment off the PRY1 literature of PR1 binding Eugenol this seems an unexpected result that the cells do not survive, please expand on/discuss this. Could it be linked to the data in Fig2a where PRY1 does not localise to cell surface in U. maydis? Make clear your reasons for reader. + +<|ref|>text<|/ref|><|det|>[[115, 223, 881, 351]]<|/det|> +Based on this question, we have realized the problem of providing insufficient explanation in our previous manuscript. We have made efforts to address this issue. According to our findings, PRY1's inability to protect U. maydis cells is not solely due to localization and eugenol- binding issues. This is evident from the fact that the chimera protein, despite being localized to the cell wall, failed to provide protection. Additionally, it has been reported that the CAP domain of PRY1 can bind eugenols. The absence of hyphal- like structures is the key reason why PRY1 fails to protect U. maydis cells but not S. cerevisiae cells (Fig. S3 and Fig 3b). These hyphal- like structures are essential for protection in U. maydis, whereas complete shielding of S. cerevisiae cells by PRY1 is sufficient to prevent eugenol toxicity. + +<|ref|>text<|/ref|><|det|>[[115, 352, 879, 431]]<|/det|> +To induce UmPR- 1La- shielded hyphae, UmPR- 1La needs to transmit signals to its specific receptor, which likely does not interact with either PRY1 or Sr10279, leading to the failure in inducing hyphal- like structures in U. maydis. However, we speculate that Sr10279, based on conserved motifs and its grouping with UmPR- 1La in the same clade (Fig 1b- c), can induce such structures in S. reilianum. We have discussed this aspect in the line 251- 256 in the results section. + +<|ref|>text<|/ref|><|det|>[[115, 450, 602, 484]]<|/det|> +- Add loading controls to immunoblot panels. We have now provided necessary loading controls to immunoblots. + +<|ref|>text<|/ref|><|det|>[[115, 503, 865, 591]]<|/det|> +24). I find it surprising not to have seen an enhancement of defence by the application of the maize CAPE peptide. I would suggest you repeat this experiment, but this time pre- treat the maize with ZmCAPE 1 day prior to infection. This experimental set up is how previous publication have conducted the experiment e.g. Chen et al, 2014 Plant cell and Sung et al, 2021 New Phyt (refs 8 & 9 on your list). Have you also tried it with WT SG200? + +<|ref|>text<|/ref|><|det|>[[115, 593, 882, 783]]<|/det|> +We had conducted this experiment previously, where we pre- treated maize seedlings with ZmCAPE a day before U. maydis infections. However, we did not observe any reduction in the virulence of SG200 or \(\Delta pr - 1lab\) , which was puzzling to us as we lacked a satisfactory explanation. In this revision, we followed the suggestion of reviewer#2 (please refer to our response to Question #13) by replacing the UmPR- 1La's UmCAPE- La sequence with ZmCAPE and delivering it via U. maydis. Using this delivery method, we observed a significant decrease in the disease symptoms of this complementation strain. This finding supports the conserved role of ZmCAPE in priming plant immunity and also suggests that the lack of enhanced maize resistance by the application of ZmCAPE could be due to the timing and method of peptide delivery in maize. Furthermore, the negative impact of ZmCAPE on U. maydis virulence delivered by this strain was mitigated by the application of UmCAPE- La peptides. These figures have been included in the revised manuscript (Fig. 6d- e). + +<|ref|>text<|/ref|><|det|>[[116, 812, 285, 827]]<|/det|> +Minor point to address + +<|ref|>text<|/ref|><|det|>[[116, 848, 879, 901]]<|/det|> +- Line 79-81 "However, it is unclear whether a protease involves in the cleavage of the CNYx motif and a receptor to perceive CAPE peptide to activate" suggest editing to read "However, it is unclear whether a protease is involved in the cleavage of the CNYx motif and if there is a receptor to perceive CAPE + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 439, 125]]<|/det|> +peptides that activate" We have replaced the sentence as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 143, 866, 196]]<|/det|> +- Line 95 - "sexual life cycle, it requires U. maydis fine sensing and integrating environmental" suggest editing it to "sexual life cycle, U. maydis requires fine sensing of environmental" The sentence has been modified. + +<|ref|>text<|/ref|><|det|>[[115, 216, 578, 250]]<|/det|> +- Line 97 - "U. maydis secrete a" edit to "U. maydis secretes a" It has been edited. + +<|ref|>text<|/ref|><|det|>[[115, 269, 818, 322]]<|/det|> +- Line 108 - "elicit hyphal-like structures. A CAPE-like peptide" suggest edit to "elicit hyphal-like structures, while a CAPE-like peptide" This sentence has been modified. + +<|ref|>text<|/ref|><|det|>[[115, 341, 860, 394]]<|/det|> +- Line 172-173 - I think this statement has not been 100% proven therefore I would say "the results indicates that this PR-1La may incorporate into the cell-wall chitin/chitosan-glucan matrix possibly via glycosidic linkages" + +<|ref|>text<|/ref|><|det|>[[115, 396, 880, 446]]<|/det|> +The insolubility issue of recombinant proteins in the absence of a ligand prevented the confirmation of the finding that PR- 1La protein binds to chitin/chitosan in the polysaccharide precipitation assay. This statement has been deleted (Please refer to our response to question #5). + +<|ref|>text<|/ref|><|det|>[[115, 464, 850, 499]]<|/det|> +- Remind reader that PR-1-likes are not expressed in culture therefore the native PR-1-like's are not affecting the phenolic binding assays. + +<|ref|>text<|/ref|><|det|>[[115, 500, 875, 534]]<|/det|> +Thanks for your suggestion. A sentence has been included at the start of the text as a reminder for readers that PR1-L proteins are not expressed when cells are grown in liquid culture. + +<|ref|>text<|/ref|><|det|>[[115, 553, 866, 585]]<|/det|> +- Figure S3a - there is wrong labelling between the graph and the images or there is a wrong image added - graph shows PR-1La showing cell survival and growth however image is showing PR-1Lb data. + +<|ref|>text<|/ref|><|det|>[[115, 587, 770, 604]]<|/det|> +Need consistency between graph and images, suggest adding PR- 1La and PR- 1Lb to both. + +<|ref|>text<|/ref|><|det|>[[115, 606, 875, 640]]<|/det|> +To prevent unnecessary duplication and ambiguity, we have followed your suggestion and rearranged the images and placed in fig. 3b. + +<|ref|>text<|/ref|><|det|>[[115, 659, 454, 675]]<|/det|> +- Line 193 - Wrong Figure, should read Fig 2a. + +<|ref|>text<|/ref|><|det|>[[115, 678, 339, 693]]<|/det|> +We have made the corrections. + +<|ref|>text<|/ref|><|det|>[[115, 711, 875, 744]]<|/det|> +- Fig3d - suggesting adding in WT complementation line. Also inconsistent labelling between Fig 1d and 3d + +<|ref|>text<|/ref|><|det|>[[115, 745, 848, 779]]<|/det|> +To have consistency in labeling and prevent any confusion, we have relabeled the strains that express wild-type and mutant PR- 1La proteins as SG200_PR- 1La and SG200_PR- 1La(FY\*), respectively. + +<|ref|>text<|/ref|><|det|>[[115, 797, 860, 832]]<|/det|> +- Line 218 - CA-treated PR-1La (FY\*) cells show a swollen morphology, based on the image shown for PR-1La WT treated with CA these pseudohyphae also look swollen. + +<|ref|>text<|/ref|><|det|>[[115, 834, 875, 900]]<|/det|> +U. maydis exhibited greater sensitivity to coniferyl-alcohol (CA) than to ferulic acids and coumaric acids. Since we did not titrate the dosage of CA to determine the minimal effective concentration for inducing pseudohyphae, the use of 5 mM CA in our treatment assay is likely excessive, resulting in damage to the wild-type PR-1La protein-expressing cells. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 672, 140]]<|/det|> +- Inconsistent labelling of sterol graphs between Fig3 and 4. FigS3 and FigS4 We have now consistently re-labeled all graphs in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 160, 877, 195]]<|/det|> +- Lines 241-244 – re-word sentence, it is difficult to follow. You need to get the phrase culture filtrate or culture supernatant in there as well as saying U. maydis SG200 +PR-1La-HA line. + +<|ref|>text<|/ref|><|det|>[[115, 196, 875, 247]]<|/det|> +We have rephrased the sentences to "we explored UmPR- 1La cleavage by incubating the culture supernatant of SG200_PR- 1La strain with the apoplastic fluid of SA-inoculated maize leaves, along with different protease inhibitors". + +<|ref|>text<|/ref|><|det|>[[115, 266, 878, 317]]<|/det|> +- Figure S5a legend is missing information – treatments and concentrations used. Labelling of figure and description in materials and methods don't match i.e. is control on figure the PIC as in materials you mention DMSO is the control? + +<|ref|>text<|/ref|><|det|>[[115, 319, 606, 336]]<|/det|> +We have added the detailed information in figure legend of fig. S5a. + +<|ref|>text<|/ref|><|det|>[[115, 355, 861, 408]]<|/det|> +- Line 249 – "Cathepsin B-like 3 (CatB3) has a similar expression profile as umpr-1la" I disagree PR-1La expression is all over the place. I would just say CatB3 is induced during infection or CatB3 is strongly induced from 4dpi compared to mock treatment. + +<|ref|>text<|/ref|><|det|>[[115, 410, 820, 443]]<|/det|> +We have modified the sentence to "Cathepsin B-like 3 (CatB3) is expressed in the early stage and strongly induced from 4dpi and onwards". + +<|ref|>text<|/ref|><|det|>[[115, 460, 744, 476]]<|/det|> +- Fig5b add arrow to indicate PR-1La band also labels for Coomassie and immunoblot. + +<|ref|>text<|/ref|><|det|>[[115, 477, 850, 525]]<|/det|> +The previous fig. 5b is now moved to fig. 5d. Black and red open arrows indicate full-length and truncated PR-1La proteins respectively, have been added in both Coomassie-blue-staining PAGE and immunoblot. + +<|ref|>text<|/ref|><|det|>[[115, 542, 877, 640]]<|/det|> +- Fig5b make the second blot on U. maydis secreted PR-1LaHA blot Fig 5c as currently the legend is hard to follow what is being described. Quantify band intensity against total protein stain as there is no size shift (due to small cleavage size) as observed in the previous gel and no loading controls shown. The immunoblot for UmPR-1LaHA in the previous Figure 5b has been replaced with a new figure, which includes the catalytically inactive mutants of CatB3 to support the cleavage of UmPR-1La by CatB3 (Figure 5c). In this new figure, we have also included a silver-stained gel to serve as a loading control. + +<|ref|>text<|/ref|><|det|>[[115, 657, 866, 707]]<|/det|> +- Line 265 – "In maize, homolog Xcp2 is highly expressed in the early infection process and then slowly declines during biotrophy (Fig. S5d)." – I disagree with this statement, there is no difference in expression of Xcp2 between mock and infected tissue. Remove or reword. + +<|ref|>text<|/ref|><|det|>[[115, 708, 748, 724]]<|/det|> +The sentence has been rewritten as 'Xcp2 is expressed at all infection/wounding stages.' + +<|ref|>text<|/ref|><|det|>[[115, 741, 870, 775]]<|/det|> +- Line 268 – suggested edit "truncated fragments were detected by Coomassie-blue-staining-PAGE and immunoblot for PRB1-3 and PR-1b" + +<|ref|>text<|/ref|><|det|>[[115, 776, 420, 792]]<|/det|> +The sentence has been edited accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 809, 880, 876]]<|/det|> +- Line 313-317 – "U. maydis probably acquired pr-1-like genes via horizontal gene transfer from the host plants during the coevolutionary arms race." – I know speculation is acceptable in the discussion but I am not sure this is supported by the literature since most organisms contain a CAP-domain containing protein (or CMB motif) including human glioma PR-1 protein and a snake-venom cysteine-rich secretory + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 866, 123]]<|/det|> +protein, yeast as you described. This is also unlikely since the plant PR- 1's don't contain the Ser/Thr rich region whereas PRY1 does. I think it would be better to rephrase this section. + +<|ref|>text<|/ref|><|det|>[[115, 123, 880, 252]]<|/det|> +Thanks for pointing it out. In a study on the genome- wide analysis of maize PR- 1s, it reported that three out of the 17 maize PR- 1s contain an extension region at their N- termini. This extension region is notably enriched in Ser, Thr, and Gly (Am J Transl Res 2022;14(11):8315- 8331). However, it is unknown how fungal pathogens acquire PR- 1L genes during co- evolution. We agree that the previous speculation has no support by literature, we have rephrased the sentences to' While the exact origins of PR- 1L genes in fungal pathogens remain unclear, their capacity to act as substrates for plant proteases and conservation at CAP domain residues underscore a related role in plant- pathogen interactions during the process of co- evolution'. + +<|ref|>text<|/ref|><|det|>[[115, 252, 866, 284]]<|/det|> +In addition, we also added the sentence 'the extension region is also present in three out of the 17 maize PR- 1 proteins' at the beginning of the Result section. + +<|ref|>text<|/ref|><|det|>[[115, 300, 877, 368]]<|/det|> +- Line 326-328 - "PR-1La lacks a transmembrane domain, it is not clear how the signals perceived at the cell surface is transduced to activate the downstream signaling pathway." Suggest edit it to "PR-1La lacks a transmembrane domain, therefore it is not clear how the cell surface signals would be perceived and transduced to activate downstream signaling." + +<|ref|>text<|/ref|><|det|>[[117, 369, 426, 384]]<|/det|> +The sentence has been edited as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 401, 842, 450]]<|/det|> +- Line 387 - "performed as described" - incomplete sentence! The sentence has now been completed and written as 'The transformation of U. maydis and genomic DNA isolation procedures were performed as described in a previous study'. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 150, 393, 165]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 203, 881, 458]]<|/det|> +We appreciate the author's efforts to address our concerns and think that the revised version of this manuscript has been greatly improved. Our main concern, however, that the results do not provide a strong coherent picture of the function of UmPR- 1La in pathogen virulence, was not fully resolved. While we applaud the inclusion of the model shown in Fig 6F, the interdependence of these different stages of UmPR- 1La action is not well supported by experimental data. In particular, we do not know whether cell wall association of UmPR- 1La is important for virulence. While we know that that a mutation (FY\*) in the CBM affect virulence (Fig 3E), we do not know whether cleavage of CAPE- La would repress host immunity, independently of the function of the CBM. The virulence of the FY\* appears to be as repressed as that of a deletion, even though the FY\* mutant version should still be able to release the CAPE- La peptide and thereby promote virulence. Thus, a more complete set of data defining the function of these different elements through which UmPR- 1La appears to promote fungal virulence is needed to support the interdependence of the individual stages shown in Fig 6F, including abrogation of its cell wall association, mutation of the protease cleavage site (CNYx), and a truncation of the CAPE- La peptide. + +<|ref|>text<|/ref|><|det|>[[113, 497, 882, 771]]<|/det|> +In addition, the data supporting binding of the phenolic compound to UmPR- 1La are still weak and subject to interpretation. Ligand binding is dose dependent and saturable. The authors do not provide strong support for either of these two criteria. They observe quenching of Trp fluorescence upon addition of phenolic compounds and interpret this as binding. These phenolic compounds could by themselves quench Trp fluorescence or induce partial denaturation of the protein rather than exhibiting a stoichiometric ligand- type of binding to the protein. In their revision, the authors have addressed the stability of the protein in the presence of the phenolic compounds but did not address the possibility that these phenolics induce partial denaturation or quench fluorescence. In addition, the authors do not show evidence that UmPR- 1La binds Eugenol itself or whether this binding is dependent on the CBM. Overexpression of UmPR- 1La confers resistance to Eugenol, and this resistance is affected by a mutation (FY\*) in the CBM (Fig 3D). However, the FY\* mutant grows better than WT in the presence of Ferulic acid (FA, Fig 4B), even though the FY\* mutant does not "bind" FA in vitro (Fig 4F). Clearly, this is not consistent with the model proposed by the authors that UmPR- 1La binds FA through its CBM to induce pseudohyphal growth and FA resistance. The same applies for the improved growth of the FY\* mutant observed in presence of Coumaric acid (Fig S4A). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 393, 135]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 175, 848, 229]]<|/det|> +My questions and concerns have been addressed sufficiently. The revised manuscript is significantly improved and major issues have been fixed / new experiments add clarifying and interesting information. + +<|ref|>text<|/ref|><|det|>[[115, 382, 393, 399]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 438, 673, 456]]<|/det|> +The authors have addressed all of my concerns with the original manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 495, 875, 550]]<|/det|> +Below are some minor edits to further improve the manuscript, some are just typos and some are to improve the figure legends further, as although greatly improved, they are not quite right in a couple of cases. + +<|ref|>text<|/ref|><|det|>[[115, 589, 249, 605]]<|/det|> +Minor corrections + +<|ref|>text<|/ref|><|det|>[[115, 644, 875, 680]]<|/det|> +Line 164: AF594- immunostained PR- 1La – the figure legend also calls this AF594 however in the figure it is labelled AF595. + +<|ref|>text<|/ref|><|det|>[[115, 719, 874, 792]]<|/det|> +Figure 2a legend still needs improved. Authors only describe some of the constructs (Overexpression of WT constructs not listed) additionally, the list is in reverse order compared to the figure i.e. the last construct SG200_PRY1 is listed first in legend, please re- order. Please make the names in figure and legend the same SG200_PRY1 not PRY1 + +<|ref|>text<|/ref|><|det|>[[115, 831, 825, 867]]<|/det|> +Figure 2d legend: Please indicate size of proteins, in the legend, to direct reader to correct bands especially important for Pr- 1Lb and PRY1. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 537, 107]]<|/det|> +Figure S4d: Coomassie stain for loading control is missing. + +<|ref|>text<|/ref|><|det|>[[114, 146, 867, 183]]<|/det|> +Line 303: "Cathepsin B- like 302 3 (CatB3; GRMZM2G108849), which is expressed in the early stage and strongly induced from 4dpi and onwards (Fig. S5b)." please rephrase to include "of infection" + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 291, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 108, 872, 141]]<|/det|> +We extend our gratitude to all the reviewers for their valuable constructive suggestions and comments, as well as their dedicated efforts to enhance the quality of our work. + +<|ref|>text<|/ref|><|det|>[[116, 158, 393, 174]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 191, 864, 276]]<|/det|> +We appreciate the author's efforts to address our concerns and think that the revised version of this manuscript has been greatly improved. Our main concern, however, that the results do not provide a strong coherent picture of the function of UmPR- 1la in pathogen virulence, was not fully resolved. While we applaud the inclusion of the model shown in Fig 6F, the interdependence of these different stages of UmPR- 1la action is not well supported by experimental data. + +<|ref|>text<|/ref|><|det|>[[115, 277, 870, 377]]<|/det|> +In particular, we do not know whether cell wall association of UmPR- 1la is important for virulence. Thank you for drawing our attention to this matter. We acknowledge that the current evidence falls short of directly demonstrating the essentiality of UmPR- 1la's cell wall association for virulence. To establish this link definitively, we must first investigate how UmPR- 1la localizes to the cell wall by identifying the specific cell wall component(s) it interacts with and the corresponding interacting motif. This endeavour would require a considerable amount of effort and resources. + +<|ref|>text<|/ref|><|det|>[[115, 378, 870, 461]]<|/det|> +Given the scope of this study, we find it more appropriate to reserve these experiments for our future research- Investigating how UmPR- 1la induces hyphal- like structures and the cleavage mechanism. In the meantime, we think the evidence we have gathered so far (as elaborated below) substantiates our proposed working model, which emphasizes the critical role of UmPR- 1la's cell wall association in its virulence. + +<|ref|>text<|/ref|><|det|>[[142, 463, 882, 632]]<|/det|> +Given that PRY1 expression in SG200 cells cannot localize to the cell walls and protect cells, even though both the full- length proteins and the CAP domain alone can bind eugenols (Choudhary and Schneiter, 2012 PNAS; https://doi.org/10.1073/pnas.1209086109), we might anticipate that expressing a cell- wall localization- defective UmPR- 1la protein with an intact CBM will similarly fail to protect cells. In contrast to ScPRY1, which localizes to the cell periphery of S. cerevisiae and shields them from eugenols (Fig. 2b), UmPR- 1la primarily accumulates at the cell division sites of U. maydis sporidal cells (Fig. 2a). This localization pattern is insufficient to prevent eugenols from disrupting the cell membrane of U. maydis, unless they can lead to the formation of UmPR- 1La- shielded hyphae for protection. This underscores the significance of localized UmPR- 1La on the cell wall in inducing protective hyphal- like structures. + +<|ref|>text<|/ref|><|det|>[[142, 634, 878, 802]]<|/det|> +The cell- wall localization of UmPR- 1La doesn't ensure protection for sporidal cells. Despite their cell- wall localization, both the chimera and Sr10279 failed to induce hyphal- like structures and provide cell protection. This likely results from their inability to transmit crucial intracellular signals needed for shielded hyphae formation. The chimera's PRY1 CAP domain might not induce a conformational change in UmPR- 1la's N- terminus, which may have an additional role in downstream partner interaction. Similarly, Sr10279 may struggle to interact with the necessary UmPR- 1La partner for structure initiation. Our findings underscore a sequential process for initiating protective hyphae: proteins must first localize to U. maydis sporidal cell walls to detect signals and then transmit them intracellularly for hyphal- like structure induction. Failure in these steps won't restore \(\Delta pr - 1la\) virulence. + +<|ref|>text<|/ref|><|det|>[[143, 804, 878, 905]]<|/det|> +By comparing the virulence phenotypes of complementation strains \(\Delta pr - 1la\_ PR - 1la(FY^*)\) and \(\Delta pr - 1la\_ PR - 1la(CAPE - Lb)\) (Fig 3e and 6d), we noted that the truncated PR- 1La(CAPE- Lb) protein with the CAPE- Lb peptide partially restored \(\Delta pr - 1la\) virulence phenotype. This happened because the truncated protein, carrying a defective peptide, retained the intact N- terminus and CBM, allowing it to localize to the cell wall and induce hyphal structures for protection, resulting in an intermediate virulence phenotype. Conversely, \(\mathrm{FY^*}\) proteins, unable to induce protective + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[170, 90, 872, 125]]<|/det|> +hyphal- like structures, failed to complement \(\Delta pr - 1a\) 's virulence. These findings underscore the crucial role of inducing hyphal structures for PR- 1La's virulence function. + +<|ref|>text<|/ref|><|det|>[[144, 126, 875, 227]]<|/det|> +To provide clarity for readers, we have incorporated this information into both the discussion and results sections. Presently, the mechanism through which UmPR- 1La triggers the formation of hyphal structures for cell protection remains unclear. Further research is necessary to comprehend how the N- terminus and CAP domains contribute to signal transduction and, at a minimum, to pinpoint the involved receptor. This aspect is the primary focus of our ongoing investigation. + +<|ref|>text<|/ref|><|det|>[[115, 243, 877, 330]]<|/det|> +While we know that that a mutation (FY\\*) in the CBM affect virulence (Fig 3E), we do not know whether cleavage of CAPE- La would repress host immunity, independently of the function of the CBM. The virulence of the FY\\* appears to be as repressed as that of a deletion, even though the FY\\* mutant version should still be able to release the CAPE- La peptide and thereby promote virulence. Thanks for raising this point. Please allow us to explain it. + +<|ref|>text<|/ref|><|det|>[[115, 330, 879, 466]]<|/det|> +As mentioned above, hyphal formation plays a crucial role in the protective function of PR- 1La, regardless of having an intact CNYx motif and CAPE- La peptides. Without hyphal formation, UmPR- 1La mainly localizes at the site of cell division and cannot fully shield cells from plant toxic phenolics. Consequently, the \(\Delta pr - 1la\_ PR - 1La(FY^*)\) complementation strain that unable to trigger hyphal formation compromised the \(\Delta pr - 1la\) virulence (fig.3E). This underscores the importance of inducing hyphal formation for survival within the plant, as this subsequently facilitates the release of the CAPE- La peptide, further suppressing plant immunity. + +<|ref|>text<|/ref|><|det|>[[115, 448, 880, 550]]<|/det|> +As expected, the in- vitro cleavage assay showed that FY\\* mutant proteins could be cleaved by CatB3 (see western blot below). Based on our genetic data and biochemical assay, it is clear that the inability of FY\\* mutant proteins to restore virulence is due to their inability to sense phenolics and thereby fail to trigger the protective hyphae. As CatB3 selectively cleaves PR- 1La proteins but not plant PR- 1 and this cleavage mechanism is the focus of our next investigation, we have decided not to include this data in the revised manuscript. But, we provide it here for the reviewers. + +<|ref|>image<|/ref|><|det|>[[397, 560, 533, 671]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 702, 840, 771]]<|/det|> +Thus, a more complete set of data defining the function of these different elements through which UmPR- 1La appears to promote fungal virulence is needed to support the interdependence of the individual stages shown in Fig 6F, including abrogation of its cell wall association, mutation of the protease cleavage site (CNYx), and a truncation of the CAPE- La peptide. + +<|ref|>text<|/ref|><|det|>[[115, 772, 875, 872]]<|/det|> +We wholeheartedly agree with the reviewer's comments. However, this requires further efforts for dissection, which is the focus of our next investigation. We believe that the findings in the discovery of the dual virulence functions and the underlying mechanism of UmPR- 1La in sensing and adapting to the plant environment for survival, as well as countering plant defense to enhance the virulence of Ustilago maydis, not only provide important knowledge but also open a new research direction for the fields of effector biology and fungal- plant interactions. + +<|ref|>text<|/ref|><|det|>[[115, 873, 864, 907]]<|/det|> +Regarding the truncation of CAPE- La, we have used a scrambled peptide of CAPE- La as a negative control to support the suppressive function of CAPE- La (Fig. 6e). Furthermore, we replaced UmPR + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 870, 141]]<|/det|> +1La's CAPE-La with CAPE-Lb to demonstrate the decrease in virulence (Fig. 6d). The results from these experiments had provided sufficient evidence to support our conclusion on the role of CAPE-La in suppressing plant immunity. + +<|ref|>text<|/ref|><|det|>[[115, 143, 881, 260]]<|/det|> +- As for the mutation on the CNYx motif, it has been shown that the tyrosine mutation in the plant PR-1's CNYD motif prevents the release of the AtCAPE9 peptide by AtXcp1 protease (https://doi.org/10.21203/rs.3.rs-155784/v1). However, in Ustilago maydis, a mutation on the Y residue (CNAD) abolishes the secretion of UmPR-1La. This finding is consistent with the work done by Tamara et al (https://doi.org/10.1111/mpp.13187) showing the PR1 trafficking dependent on the intact CNYD motif. Therefore, performing the in-vitro cleavage assay on this CNAD mutant protein is not biologically relevant, as it is not secreted. + +<|ref|>image<|/ref|><|det|>[[360, 270, 557, 415]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 445, 864, 496]]<|/det|> +In addition, the data supporting binding of the phenolic compound to UmPR- 1La are still weak and subject to interpretation. Ligand binding is dose dependent and saturable. The authors do not provide strong support for either of these two criteria. + +<|ref|>text<|/ref|><|det|>[[144, 498, 881, 612]]<|/det|> +- We respectfully hold a different view from the reviewer concerning the binding strength of FA to PR-1La. It's also important to consider that the Y-axis scale is larger, potentially causing visual misinterpretation. The observed difference of approximately 250 a.u. (ranging from 1100 a.u. at \(0 \mu M\) FA to 850 a.u. at \(10 \mu M\) FA) does not necessarily imply weak binding. Notably, the similar fluorescence pattern shift was also reported in several protein-ligand binding assays using fluorescence spectrometry (https://doi.org/10.1002/jsfa.11733; https://doi.org/10.1074/jbc.M111.301630). + +<|ref|>text<|/ref|><|det|>[[144, 616, 870, 735]]<|/det|> +- The titration assay depicted in fig. S4b illustrated the dose-dependent response of PR-1La proteins to ferulic acids (FA), reaching saturation at approximately \(10 \mu M\) and exhibiting detectable free FA absorption at 410-430 nm. Conversely, the control PR-1La(FY\*) proteins displayed no responsiveness to FA, showing no shifts in fluorescent intensity regardless of the added FA quantity. When considered alongside the information presented in fig. 4f, these findings indicate that the interaction between PR-1La and ferulic acids relies on the intact CBM in a manner that varies with the dose. + +<|ref|>text<|/ref|><|det|>[[115, 752, 876, 853]]<|/det|> +They observe quenching of Trp fluorescence upon addition of phenolic compounds and interpret this as binding. These phenolic compounds could by themselves quench Trp fluorescence or induce partial denaturation of the protein rather than exhibiting a stoichiometric ligand- type of binding to the protein. In their revision, the authors have addressed the stability of the protein in the presence of the phenolic compounds but did not address the possibility that these phenolics induce partial denaturation or quench fluorescence. + +<|ref|>text<|/ref|><|det|>[[115, 855, 655, 870]]<|/det|> +Thanks for asking these questions. Please allow us to explain our thought. + +<|ref|>text<|/ref|><|det|>[[115, 873, 875, 906]]<|/det|> +- If Trp fluorescence is quenched by phenolic compounds, we should also expect a similar fluorescent shift in the FY\* proteins, but this was not observed in the FY\* titration assay (fig. S4b). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 226]]<|/det|> +- If the observed shift in the PR-1La protein was caused by partial denaturation, we would anticipate a decrease in the intensity of both PR-1La and the FY\* mutant proteins, regardless of the type of phenolics. However, the intensity of FY\* proteins did not decrease during incubation with ferulic acids. It is worth noting that the FY\* proteins seemed less stable than the wild-type PR-1La proteins, as indicated by the detection of the truncated form (Fig. S4d). Furthermore, we also noticed an increase in the intrinsic fluorescence intensity of PR-1La when incubated with coniferyl alcohol (Fig. S4c). Based on these results and the induced hyphal-like structure phenotype in Fig 3d, this allows us to suggest that the PR-1La is able to bind phenolics. + +<|ref|>text<|/ref|><|det|>[[115, 243, 835, 277]]<|/det|> +In addition, the authors do not show evidence that UmPR- 1La binds Eugenol itself or whether this binding is dependent on the CBM. + +<|ref|>text<|/ref|><|det|>[[115, 277, 881, 362]]<|/det|> +Due to the lipophilic property of eugenols, it exhibits strong fluorescence, making it unsuitable for demonstrating the binding of PR- 1La to phenolics using fluorescence spectrometry or isothermal titration calorimetry (ITC). Since cells expressing UmPR- 1La responded to both eugenols and ferulic acids by forming similar hyphal- like structures, we used ferulic acids to demonstrate the phenolic binding of PR- 1La. + +<|ref|>text<|/ref|><|det|>[[115, 362, 881, 464]]<|/det|> +Overexpression of UmPR- 1La confers resistance to Eugenol, and this resistance is affected by a mutation (FY\*) in the CBM (Fig 3D). However, the FY\* mutant grows better than WT in the presence of Ferulic acid (FA, Fig 4B), even though the FY\* mutant does not "bind" FA in vitro (Fig 4F). Clearly, this is not consistent with the model proposed by the authors that UmPR- 1La binds FA through its CBM to induce pseudohyphal growth and FA resistance. The same applies for the improved growth of the FY\* mutant observed in presence of Coumaric acid (Fig S4A). + +<|ref|>text<|/ref|><|det|>[[115, 464, 881, 635]]<|/det|> +The survival of FY\*- expressing cells in the presence of phenolics depends on the toxicity level of the tested compounds. Cells cannot survive in the presence of eugenols due to the disruption of the cell membrane caused by eugenols, as documented in the reference (DOI: 10.3109/13693786.2012.742966). Therefore, the cell membrane needs to be protected thru triggering UmPR- 1La- shielded hyphae to block eugenols. The survival of cells in the presence of ferulic acids/coumaric acids, on the other hand, is observed to be higher, indicating their lower toxicity to U. maydis cells under the tested conditions. Despite the inability of FY\* proteins to induce hyphae structures, FY\*- expressing cells still manage to survive and multiply in the presence of FA- containing medium. This observation supports our proposal that UmPR- 1La can sense various plant phenolics, regardless of their toxicity level, and trigger UmPR- 1La- shielded hyphal branching to confer protection within the plant. + +<|ref|>text<|/ref|><|det|>[[116, 667, 392, 683]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 701, 848, 752]]<|/det|> +My questions and concerns have been addressed sufficiently. The revised manuscript is significantly improved and major issues have been fixed / new experiments add clarifying and interesting information. + +<|ref|>text<|/ref|><|det|>[[116, 770, 196, 785]]<|/det|> +Thank you. + +<|ref|>text<|/ref|><|det|>[[116, 803, 393, 819]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 836, 673, 853]]<|/det|> +The authors have addressed all of my concerns with the original manuscript. + +<|ref|>text<|/ref|><|det|>[[112, 870, 875, 905]]<|/det|> +Below are some minor edits to further improve the manuscript, some are just typos and some are to improve the figure legends further, as although greatly improved, they are not quite right in a couple of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 92, 160, 106]]<|/det|> +cases. + +<|ref|>text<|/ref|><|det|>[[115, 125, 249, 141]]<|/det|> +Minor corrections + +<|ref|>text<|/ref|><|det|>[[115, 157, 875, 191]]<|/det|> +Line 164: AF594- immunostained PR- 1La - the figure legend also calls this AF594 however in the figure it is labelled AF595. + +<|ref|>text<|/ref|><|det|>[[115, 193, 469, 209]]<|/det|> +Thanks for pointing it out. It has been corrected. + +<|ref|>text<|/ref|><|det|>[[115, 225, 872, 293]]<|/det|> +Figure 2a legend still needs improved. Authors only describe some of the constructs (Overexpression of WT constructs not listed) additionally, the list is in reverse order compared to the figure i.e. the last construct SG200_PRY1 is listed first in legend, please re- order. Please make the names in figure and legend the same SG200_PRY1 not PRY1. + +<|ref|>text<|/ref|><|det|>[[115, 293, 410, 310]]<|/det|> +We have made the changes accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 326, 825, 360]]<|/det|> +Figure 2d legend: Please indicate size of proteins, in the legend, to direct reader to correct bands especially important for Pr- 1Lb and PRY1. + +<|ref|>text<|/ref|><|det|>[[115, 361, 777, 378]]<|/det|> +Thank you. We have added the expected size of full- length proteins in the legend of fig 2d. + +<|ref|>text<|/ref|><|det|>[[115, 394, 875, 428]]<|/det|> +Figure S4d: Coomassie stain for loading control is missing. We have now included the loading controls in fig. S4d. + +<|ref|>text<|/ref|><|det|>[[115, 445, 867, 497]]<|/det|> +Line 303: "Cathepsin B- like 302 3 (CatB3; GRMZM2G108849), which is expressed in the early stage and strongly induced from 4dpi and onwards (Fig. S5b)." please rephrase to include "of infection" The sentence has been rephrased as suggested. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 300, 134]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 175, 393, 191]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 232, 531, 249]]<|/det|> +Thank you for having addressed our remaining concerns. + +<--- Page Split ---> diff --git a/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..99c09cfeed540aa91b59790fcfe637be87ce9773 --- /dev/null +++ b/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Time from A onset (ms)", + "footnote": [], + "bbox": [ + [ + 112, + 245, + 475, + 432 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure S7. Main results of Experiment 2 for operant trials only. Panel (a) shows the anticipation of perceived movement timing for voluntary vs involuntary movements ( \\(p = 0.011\\) , Wilcoxon). Panel (b) shows the phase", + "footnote": [], + "bbox": [], + "page_idx": 16 + } +] \ No newline at end of file diff --git a/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a35c319482fe155a076ad4630beff0ec0d23410c --- /dev/null +++ b/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,866 @@ + +# nature portfolio + +Peer Review File + +# Pre-movement sensorimotor oscillations shape the sense of agency by gating cortical connectivity + +Corresponding Author: Dr Tommaso Bertoni + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Bertoni and colleagues investigated the relationship between "alpha oscillations" at the level of M1 and the sense of agency perceived by a tetraplegic individual over specific movements mediated by a brain- machine interface (BMI). In particular, the authors manipulated the congruence between intended and executed actions. The results suggest that "low- alpha" oscillations recorded in M1 during the pre- movement phase were associated with the level of (explicit and implicit) sense of agency (SOA) in the patient during the execution of the experimental tasks. + +This link between pre- movement alpha oscillations and the sense of agency was further supported by an EEG study on healthy controls using a (sham) EEG- BMI setting: this highlighted the role of SMA in the agency experience rather than area M1. + +There are interesting elements of novelty in the Ms. Yet, there are a few problems as well. + +My general impression, also considering recently published work from this group, is that the Authors might be working on a large data- base from multiple experiments, not always preplanned in a concerted manner: some data were probably described also in reference #30. For example, Experiment 1 has already been described in a previous paper, where the authors described the role of area M1 in the agency experience. The authors should therefore better specify the novelty of the present data with respect to the previous ones and how these results might be integrated with the previous paper. + +Coherence. In the present Ms, the reader is forced to learn from multiple different - unvalidated- paradigms tapping the SOA rather than, for example, an orderly attempt to measure the same behavioural variables in a very interesting patient and in a group of normal controls. This is inevitable when moving from implicit to explicit SOA; yet the implicit SOA paradigm could have been the same for the patient and the controls. The implications are that the importance of the non- negligible differences in the results cannot be assessed well. + +The presentation of the data also suffers from a myriad of control analyses on the data, apparently not planned in the methods, that one finds unexpectedly: this makes reading the MS quite cumbersome and a detailed commentary on each and every aspect impossible in a single run of review. I will therefore concentrate on the main points that require clarification before any further consideration. + +I found stylistic, theoretical and methodological issues that should be considered. I'll start with the methods. + +Methodological issues. + +As said, overall, I have the impression that the present drawing from a larger data set might have created some confusion while drafting the MS and surely in the reader as the methods are described sometimes in an incomplete manner: for example, some experimental manipulations or abbreviations are never explained, and so forth. The authors should double- check that all details are provided for a clear comprehension of what was done and for the reproducibility of the procedures and replicability of the results. + +<--- Page Split ---> + +Experiment 2. The authors adopted a Libet- like paradigm to measure the implicit component of the sense of agency. The patient performed a movement through BMI, which was followed by a sound. + +According to the intentional binding phenomenon (Haggard et al., 2002), voluntary movements are perceived as shifting in time towards the generated sound, while the sound is perceived as occurring earlier, closer to the action. Based on this phenomenon, the higher this "time compression" that "binds" the voluntary action to its outcome, the stronger an implicit sense of agency for the action and the produced physical outcome. + +Here, the authors only measured the perceived time of the movement onset while ignoring the timing of sound perception. More importantly, they observed the opposite result with respect to the intentional binding phenomenon since voluntary movements were perceived EARLIER in time. This would imply a lower implicit sense of agency, according to the intentional binding phenomenology. The authors discussed this result as a temporal binding between intentions and actions, but they cannot provide any evidence for this explanation; moreover, they do not explain how this binding can be considered a marker of increased implicit sense of agency (the cited reference #30 is a preprint on the very same data). + +Incomplete methods description. There is some missing information in the MS. Figure 3a mentions an "operant movement" condition, which is not described in the text. I assume that there might be a baseline "non- operant movement" condition, in line with the intentional binding paradigm, but I cannot find any information about this. These conditions are mentioned but not described also in Figure S15. + +Experiment 3. According to the main text, participants were instructed to imagine a specific (unknown) right- hand movement, followed by (congruent?) visual feedback. At the end of each trial, they were asked to rate their perceived explicit agency. First, I was wondering how there could be an agency modulation if the movement to imagine and the displayed feedback were always the same. Maybe I missed some details here. + +However, the main issue here is related to the behavioural dependent variable that (i) should validate the use of sham EEG- BMI trials and (ii) should guide the EEG analyses: the agency ratings. These agency judgments were inevitably biased by the experimenters' who warned participants "to keep the mean rating around 5" in the two conditions; for this reason, they cannot represent a valid measure of agency. + +## Data interpretation + +Puzzling interpretation of the LFP data. Exploration of the LFP data, in Figure 3c, suggests that the two curves clearly dissociate AFTER movement execution. I was wondering why the authors concentrate only on minute differences before Time 0 and do not discuss this result. + +The "alfa band" is really the same in all experiments? + +For some reason, the Authors have decided that signals coming from different frequency ranges are the same thing. In the patient, the frequency of the electrical signal measured from area M1 peaks at 6.2 Hz (below the canonical alfa); in the normal controls the peak of the electrical signal measured this time from area SMA peaks at 9- 12 Hz. I am not convinced by this analogy. As said, and unfortunately, because the paradigms used in the patients and in normal controls are not the same these differences are not interpretable. + +## Coherence of the results + +Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small - EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls. + +## Theoretical issues. + +A paper of this magnitude cannot be neutral towards the previous theories on the sense of agency. There are at least three theoretical models proposed to address the arising of the agency experience. The authors seem to consider only one of these nor they do make an effort to discuss whether and why their findings are in support of this specific theory. The "Comparator Model", the only model mentioned in the paper, postulates that the sense of agency arises from a series of comparator processes within the motor control system. However, in an alternative perspective, the "Apparent Mental Causation Theory" proposes that the emergence of the sense of agency is a post hoc and retrospective phenomenon. Accordingly, the sense of agency arises through an inferential sense- making process that occurs after the completion of a movement. Finally, in the "Cue Integration Theory", the sense of agency should arise from integrating low- level cues (sensorimotor proprioceptive and exteroceptive cues) and high- level cues (cognitive cues). The weight assigned to these different cues varies for the implicit and explicit components of agency. Hence, I feel that the authors should try to frame their data considering the previous theoretical and experimental efforts on the very same topic over the last 20 years. + +Style. + +For sure, there is already a broad body of literature investigating the neural correlates of the sense of agency that makes an opening statement in the abstract (".... the underlying neural mechanisms of the sense of agency are still unknown") too + +<--- Page Split ---> + +strong for two reasons: (1) the previous evidence connecting brain physiology and the SOA (2) the correlational nature of the evidence provided; this lacks the identification of a clear "mechanism" that causally connects brain physiology and the complex phenomenology of the SOA. + +## Reviewer #2 + +(Remarks to the Author) + +The manuscript by Bertoni et al reports very interesting data and experimental designs. The authors recorded single neurons and LFP from M1 of a tetraplegic patient who, with the help of a prosthetic devise, is able to guide fake- hand reaching movements. The authors correlated the LFP with the reported simulated action of the subject and specifically with his sense of agency, demonstrating a phase dependence of alpha band endogenous oscillation with the sense of agency. To complete the study the authors measured the effect in typical subjects, and used high density EEG coupled with simulation of the moving hand to demonstrate again a phase dependence. Unfortunately and not surprising this data are less compelling with a small and just significant effect. + +While I like the paper and the material presented, I have several unclear and not- discussed technical problems that make me uneasy to give a strong recommendation at this stage. The main one being the synchronization with the prosthetic devise. For this reason I would like to postpone my acceptance/rejection recommendation after a major revision giving the possibility to the authors to explain better their technique and rationale and write a more clear and critical manuscript. + +## Main problem + +Phase depends on the time origin of the synchronisation trigger. Here the authors trust the prosthetic algorithm and set the synchronisation with the onset threshold for the fake- hand movement. However, this relies on a very strong assumption: the algorithm should operate with the same delay for the high and low agency perception. This may be wrong and would be mainly CONTRARY to their data. They show that the agency state signal can be derived from the phase of the LFP and supposedly also the decoding algorithm is using this signal, possibly by introducing a delay (50 ms would be sufficient) to give an apparent phase change. In other words, the argument to me is circular! + +However, the authors have access to single cell firing. A simple threshold to the ensemble recording firing could be used for synchronize the LFP and analyse the change in phase. It is true that they found a strong correlation between pre- movement of fake- hand LFP and neuronal firing. However, the amount of firing may be independent of onset phase. Maybe I misunderstood something, and the tetraplegic patient does not modulate at all M1 firing during Motor Imagery. But if so, this needs to be explained in detail, at least in the methods. In addition the variability of the decoding delay to generate the phantom hand movement needs to be reported! + +Again, I am surprised that the Readiness Potentials, usually associated with SMA activity, are never present in recordings, either in the patient or in the typical subjects. Probably they have been filtered out given the high- pass with 0.2Hz. If so I advise to analyse and show them. These potentials are so strong and rich of information about the internal motor state and motor intention of the participants that it may contain already important information about agency. + +Figure 5. Could you split the M1- LFP correlation between high and low agency trials? Did you obtain a difference in the correlation? Low agency may reduce correlation and this would be a stronger and physiological more important effect that the phase difference of LFP. + +Results of Fig 6 are somewhat disappointing. If anything, the phase opposition seems from Fig 6e stronger around 500 ms post movement. The scale of Fig 6d is not really readable to judge the robustness of the effect. Why has figure 7f directionally phase effects only on temporal cortex? Blue means that that ROI was not analysed? Please explain. + +Please make clear if 8Hz is theta or alpha for you.... To me looks like a typical subject alpha band LFP. + +## Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +I thank the authors for their response and the clarifications they gave about their experiment. Despite these clarifications, I maintain reservations regarding the experimental paradigm used and the conclusions that can be drawn from it. + +Experiment 2. The authors compared action timing judgments that were given after voluntary and involuntary actions, pooling together operant (Hand closing movement followed by sound) and non- operant (Hand opening movement alone) conditions (page 7 of the rebuttal letter). + +1st issue: pooling together different actions and different conditions. The sense of agency is defined as "the feeling of + +<--- Page Split ---> + +making something happen" (Haggard, 2017). Here, the authors are mixing together conditions in which (different) actions caused a sound (i.e., the action makes happen a tone) with conditions in which the action did not produce any kind of external feedback (i.e., the action does not make happen a tone). In other words, they considered two very different conditions as equivalent, according to the literature on the sense of agency (see also the next comment. + +2nd issue: Comparing voluntary vs involuntary actions. The authors compared action timing judgments after voluntary and involuntary (unpredictable) actions. The two conditions clearly differ based on the fact that the passive movement cannot be predicted: "In the involuntary session, the movement was randomly generated via the NMES system". This may explain the delay in action timing judgment observed with respect to voluntary movements. + +The authors correctly cited Haggard et al., 2002 mentioning that this paper compared active and passive movements: indeed, Haggard et al. compared action timing judgments in voluntary vs involuntary actions yet this was done AFTER subtracting for the same measures collected in control conditions: timing judgment for voluntary actions recorded in the action+sound trials compared with timing judgment for voluntary actions recorded in the action- alone trials OR timing judgments for TMS- induced actions recorded in the action + sound trials compared with timing judgments for TMS- induced actions recorded in the action- alone trials, see Table 1 of Haggard et al., 2002). + +In the present Ms, the authors adopted a different approach that cannot control for possible intervening factors not directly related to the agency dimension (e.g., surprise effect by unexpected externally generated muscle twitches). + +Figure 2, shown in Haggard et al., 2017 may help in clarifying my comment (below called "The Figure"). https://www.nature.com/articles/nrn.2017.14 + +Regarding the 1st issue, the authors here are pooling together conditions represented by the fourth (operant condition) and second (non- operant condition) rows of the upper part of the Figure (voluntary- action condition). + +For what concerns the 2nd issue, the authors are comparing the conditions illustrated in the second/fourth row of the upper part of The Figure with the second/third row of the lower part of The figure. + +To sum up, the authors of the present Ms are mixing together conditions that, in the intentional binding literature, refer to experimental and control conditions. Accordingly, there is no isolation of the crucial judgements of intentional acts and ensuing consequences. + +Experiment 3. In the first version of the paper, the authors acknowledged that participants were invited to "keep the mean (agency) rating around 5". I criticised this approach since it seems that they were actively inviting their subjects to give specific rating values and thus manipulating the dependent variable of the experiment. + +In the revised version of the paper, they now write that participants: "were also asked to focus on the differences between trials rather than on the absolute levels of agency, to provide variable ratings using all the available range, and consider 5 as an intermediate point to distinguish between higher and lower agency levels." + +This is something very different, and I am not sure that such changes from the original to the revised version are acceptable. On a related note, they confirmed that no agency manipulation was applied in this experiment. This was aimed at measuring a sort of "intrinsic noise" in agency ratings. I am not sure that such noise can be considered related to the agency dimension since it does not vary according to a specific agency manipulation. + +Finally, in my previous comment, I mentioned: "Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. + +Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small - EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls." + +The authors replied: "Based on the previous literature about the neural bases of the sense of agency (see e.g., Haggard, Nature Neuroscience Reviews, 2017) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12), applying FDR correction for multiple comparisons within this network. This analysis revealed the strongest phase opposition in SMA, and that the second strongest phase opposition in M1 (p = 0.023). If focusing purely on the left M1, with the purpose of replicating the effect observed in the implanted participant, and thus dropping multiple comparisons correction, the uncorrected M1 effect is highly significant with p = 0.003. The uncorrected p- value is not reported for in the text, for being maximally conservative. In sum, phase position was significant in both SMA and M1. For completeness, we also reported the results of a whole- cortex search for phase opposition across all 114 ROIs of the cortex. This whole- cortex search confirmed significant phase opposition in the SMA after adjusting for 114 comparisons; in contrast, M1 did not survive multiple correction. We refrain from making interpretations of the null result for M1 in this whole- cortex search as this analysis is underpowered." + +I have the following comments: + +1. Haggard 2017 did not mention M1, but temporo-parietal and premotor regions. +2. The whole brain analysis cannot survive a formal multiple comparison correction, and the authors commented on this result as a consequence of low power: I am not sure that this kind of comment is acceptable; given the simplicity of running an EEG experiment in normal controls, there is no excuse for low-powered experiments. Given that expanding the same sample of subjects at this stage is not acceptable, a replication of this experiment with a fresh sample of subjects could make the whole story more tenable. + +On a final note, the authors mentioned Wegner as a support to their approach: "Finally, concerning the validation of our Sham BMI approach. As correctly pointed out by Wegner in his mental causation theory, it is entirely possible for healthy individuals to experience a genuine sense of agency even when not truly in control of an external event, as we believe was + +<--- Page Split ---> + +the case in our sham BMI setup." + +However, please note that this model was based on a "reconstructive" vision of the sense of agency, whereby the agency experience is formed AFTER the execution of the action. This is something different from what the authors are supporting in this paper. + +## Reviewer #2 + +(Remarks to the Author) + +The authors addressed my main concerns about the technical issue very thoroughly and clearly. I now appreciate well the design of the experiment and I found that the additional analysis that they performed dismissed all the possible criticisms that I raised in the previous version, and I believe that the data strongly support the fact that the phase of pre- movement low- alpha rhythms in M1 and SMA encodes the sense of agency. Given the importance and the novelty of the message, the originality of the technical design and the fact that the intracortical recording in M1 human are rare and precious, I strongly support publication of the manuscript in Nature Communication. + +However, in the present form the manuscript still needs an additional revision to meet the standard of the journal. Clarity of the writing: + +1) The introduction is very general and not informative about the state of art of mechanisms and circuits of sense of agency; the same criticism applies to the literature on phase of endogenous oscillations encoding motor information. Also about half of the introduction is about the presentation of the logic and result of the experiments, that is not useful for the reader given the complexity of the experiments. In addition, the same data from the same patients have already been published. It is important that the readers know about this in the introduction. The authors should clearly state and describe the results already obtained and published and, if possible, these should be used to motivate this new research. This means a fresh rewrite of most of the introduction. + +2) The language used in the paper to explain analysis procedures is not appropriate, using many technical terms that are used currently in the EEG laboratories, but often mathematical incomplete. One author is an excellent mathematician, and he should check accurately the language. For example equation 1, line 891, they not report what is Wi and in any case as it not mathematically correct. If Wi is the complex number associated with the frequency it should be added the term Arctangent of the imagery/real part...if it is already phase, it cannot be divided by the norm of the phase! Similarly, no indication of the other term in the equation, like the number of trials. Another example in lines 944 and 1335. The Hilbert transform is not needed to calculate the phase at the various frequency. What exactly has been done to calculate it? Another example appearing many times, time-frequency point is a colloquial term: there are maxima energy points or other point that can be marked on other specifications in the time-frequency domain. Please correct. Another example in line 1325. Normalization is associated mathematically to a division, while inspecting the figure there is clearly also a subtraction. Line 243 very mathematically unclear: do you mean that phase is expressed with respect to a different origin? In other words, that the phase has been rotated to take into account the difference in delay respect to experiment 1? In most cases I understood what the authors have done, because it is what normally it is done in EEG or LPF analysis: but please express the procedure in mathematically correct language in these examples and in many other instances. + +## Data analysis: + +The authors assess differences in phases between the two conditions using inter- trial phase coherence and apply an equation that maximize anti- phase difference. However, in principle the system could work in quadrature phase that offers other advantages. It is essential to show that a difference in phase of the 8Hz component of the average LFP between the two conditions is statistically significant and report the value. This can be obtained simply by applying circular statistics across the vector (amplitude and phase) cluster for the two conditions. I think that it is important to consider simultaneously amplitude and phase of the 8 Hz oscillation. + +Figure 3h reports LFP amplitude, but it is never defined what exactly it is measured. Is it the amplitude at 8 Hz, so it becomes negative due to the phase? Or it is the value in voltage of the LFP at the time point chosen? Please explain also in the text. + +Concetta Morrone + +Version 2: + +Reviewer comments: + +Reviewer #2 + +(Remarks to the Author) The authors have dealt adequately to all my criticisms, and I strongly support publication in the present form + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Bertoni and colleagues investigated the relationship between "alpha oscillations" at the level of M1 and the sense of agency perceived by a tetraplegic individual over specific movements mediated by a brain- machine interface (BMI). In particular, the authors manipulated the congruence between intended and executed actions. The results suggest that "low- alpha" oscillations recorded in M1 during the pre- movement phase were associated with the level of (explicit and implicit) sense of agency (SOA) in the patient during the execution of the experimental tasks. + +This link between pre- movement alpha oscillations and the sense of agency was further supported by an EEG study on healthy controls using a (sham) EEG- BMI setting: this highlighted the role of SMA in the agency experience rather than area M1. + +There are interesting elements of novelty in the Ms. Yet, there are a few problems as well. + +We thank the reviewer for their careful revision of our work. Please find our point- by- point response below. We highlighted our responses in bold, and indicated with quotation marks and italics passages reported from the revised text, highlighting changes in red. To allow referring to specific points, we have numbered reviewer comments and our responses (e.g., comment 1: C1; response 1: R1). The numbering continues across comments from the two reviewers. + +## C1) + +My general impression, also considering recently published work from this group, is that the Authors might be working on a large data- base from multiple experiments, not always preplanned in a concerted manner: some data were probably described also in reference #30. For example, Experiment 1 has already been described in a previous paper, where the authors described the role of area M1 in the agency experience. The authors should therefore better specify the novelty of the present data with respect to the previous ones and how these results might be integrated with the previous paper. + +## R1) + +Experiment 1 and 2 represent separate analyses of a comprehensive set of experiments performed in a BMI participant with an M1 implant, and the present work also includes a large separate study in healthy participants, Experiment 3. Some data from Experiment 1 and 2 have been described in two previous studies. The first focused on the role of sensory feedback in explicitly assessed sense of agency and its encoding in post- movement LFPs and multiunit activity (Serino et al., Nat Hum Beh, 2022). The second focused on temporal perception of BMI- mediated actions used as an implicit measure of agency and how this is reflected in M1 activity (Noel et al., Biorxiv, 2023). + +While the two previous works studied the effect of exogenous manipulations on the sense of agency and its neural encoding, the present manuscript focuses on the role of endogenous signals, i.e., the state of the brain before movement onset, which is determined by internal fluctuations rather than external sensory inputs. While exogenous contributions have been extensively studied, reports on the endogenous factors determining the sense of agency are much scarcer in the literature. Specifically, here we investigated the role of pre- movement theta- alpha oscillations in the sense of agency, and their link with M1 spiking activity and whole brain connectivity. To this aim, we applied to Experiment 1 and Experiment 2 completely new analyses on the power and phase of pre- movement oscillations, while previous works focused on LFP amplitude and multiunit activity. The scientific questions and analyses in Experiment 1 and Experiment 2 are thus entirely novel with respect to previously published data. + +Additionally, we designed and performed Experiment 3 specifically to corroborate our findings from the implanted patient in a cohort of healthy participants, to extend our investigation to whole brain signals and to study our hypothesis on brain connectivity, which could not be investigated in the patient data where we recorded only from M1. + +<--- Page Split ---> + +We have revised our manuscript to clearly acknowledge the use of previously collected data and better explain the novelty of our hypothesis and analysis approach with respect to both previous studies, as visible on pages 3 and 5: + +"Nevertheless, we still lack specific knowledge of the mechanisms leading to the integration of endogenous pre- movement signals with post- movement reafferent information." (p. 3) + +"Data analysed in Experiment 1 were collected as part of a comprehensive set of experiments performed in a BMI participant with an M1 implant. In a previous work, we investigated how post- movement LFP amplitude and multiunit activity in M1 encode exogenous sensory feedback congruency, and how these signals covary with agency judgements for BMI actions 13. Here we conducted novel analyses on these previously collected data focusing on endogenous signals, to test the hypothesis that pre- movement theta- alpha oscillations in M1 predict agency judgements." (p. 5) + +We also now discuss the relation between present results and the previously published findings on page 19: + +"In our previous work 13 (including data from Experiment 1), we showed how post- movement LFPs and multiunit activity in M1 encode congruency between motor commands and sensory feedback, a key aspect in the sensorimotor comparisons underlying the sense of agency. Our findings in Experiment 1 extend these previous results, suggesting that M1 and SMA also play pivotal roles in the sense of agency at an earlier stage, when sensorimotor predictions are computed during motor preparation and before execution." + +This way, we hope to have clarified that the approach, analyses, and results of the present study are entirely novel. + +C2) + +Coherence. In the present Ms, the reader is forced to learn from multiple different - unvalidated- paradigms tapping the SOA rather than, for example, an orderly attempt to measure the same behavioural variables in a very interesting patient and in a group of normal controls. This is inevitable when moving from implicit to explicit SOA; yet the implicit SOA paradigm could have been the same for the patient and the controls. The implications are that the importance of the non- negligible differences in the results cannot be assessed well. + +R2) + +Thank you for giving us the opportunity to better clarify these important aspects. In the present study, we aimed at investigating the role of pre- movement oscillations in modulating the subsequent sense of agency. Although the paradigms used present some differences, mainly due to the necessity of adapting our investigation from an implanted patient to healthy controls, the principle underlying our key phase opposition analysis is applied coherently across these experiments. Across three experiments, we divided trials based on explicit or implicit measures of agency (and not on experimental manipulations, whose impact we tried to minimise or regress out), and studied how the pre- movement oscillatory phases were clustered in the high and low agency groups of trials. + +Both Experiment 1 (whose paradigm is presented in our previously published study, Serino et al., Nat Hum Beh, 2022) and Experiment 3 use classic agency judgements/ratings as measures of agency. Thus, we believe that they measure the same behavioural variable. The main difference between Experiment 1 and Experiment 3 is that the sensory feedback presented to the tetraplegic participant (visual and somatosensory) and able- bodied participants (visual only) are different, due to the difficulty of reliably implementing somatosensory feedback in able- bodied individuals. Any externally implemented movement of the upper limb of a healthy participant, via, for instance, a robotic exoskeleton or functional electrical stimulation, would result in completely different sensory feedback than that produced by the NMES system in our tetraplegic participant (see also below). Said that, importantly our key analysis, phase opposition, was based on a contrast between trials with different subjective reports, and not between experimental conditions. Furthermore, our main result was found in the pre- movement period, so it should be + +<--- Page Split ---> + +independent from the specific type of sensory feedback used to elicit a sense of agency. Thus, within the scope of the present results, we believe that Experiment 3 represents the closest conceptual replication of Experiment 1 which could be performed in able- bodied individuals. + +Concerning another point made by Reviewer: - "the implicit SOA paradigm could have been the same for the patient and the controls": + +The possibility of reproducing our BMI- based temporal judgement task (Experiment 2) in healthy participants was indeed the object of in- depth discussion in our group, but was finally discarded as it was deemed technically impossible in healthy participants. The crucial point is that, while visual feedback alone can be used to elicit a sense of agency and is thus suitable for explicit judgements (used in Experiment 1 and 3), a combination of visual and somatosensory feedback would be needed for a paradigm based on action timing perception, like in Experiment 2. Indeed, simply judging the timing of BMI- generated virtual hand movements, while observing a clock on the same screen, would result in a purely temporal visual task between the two visual cues (the virtual hand and the clock), independently from judging the time of an action. On the other hand, implementing actual hand movements in healthy participants based on the decoding of motor imagery would instead be technically challenging, requiring either FES stimulation, or using an external exoskeleton. More importantly, these solutions provide sensory feedback that is not comparable to that of a natural arm movement, thus potentially biasing the sense of agency associated to temporal judgement. Finally, these methods are uncomfortable and potentially painful, and may interfere with motor imagery and BMI decoding. Based on these considerations, we now explain our choice to extend Experiment 1 to Experiment 3, rather than Experiment 2, in more detail, on page 14 and 27: + +"To investigate the potential contribution of areas beyond M1, in Experiment 3, we devised an EEG- based version of Experiment 1, which we believe to be the closest conceptual extension of that paradigm achievable in healthy participants." (p. 14) + +"When extending our investigation to healthy participants, we chose to focus on the paradigm of Experiment 1 rather than the one of Experiment 2, as we believe that producing genuine temporal binding effects in a BMI setup would require externally inducing a real upper limb movement following BMI decoding, which is hardly feasible in healthy participants and produces sensory feedback that is not comparable to natural movements. On the other hand, simply using virtual movements on a screen would result in a purely visual temporal judgement task between two visual events (the virtual arm and the clock), without necessarily implying any temporal estimation about actions, thus providing no information about the sense of agency." (p. 27) + +For the validation of the implicit task described in Experiment 2, and of the sham BMI paradigm of Experiment 3, please refer to our detailed responses in subsequent points of the present response letter (R5 and R9). + +We further conducted new analyses and rephrased passages in the results and discussions to better support the coherence of our results between the implanted patient and healthy controls, namely the frequency and anatomical localisation of the phase opposition effect. Please refer to the detailed responses to the relative comments (R11 and R12). + +To conclude, we agree with the reviewer that differences in our setups, mainly required by the uniqueness of our implanted participant, may have made the comparison of our results more difficult, and we thank the reviewer for giving us the opportunity to better address this point as presented in R11 and R12. On the other hand, we believe that these differences allowed us to show that pre- movement oscillations consistently predicted the subsequent sense of agency in different cohorts of subjects, using different recording techniques and behavioural paradigms, speaking in favour of the generality of our results. + +<--- Page Split ---> + +C3) + +C3)The presentation of the data also suffers from a myriad of control analyses on the data, apparently not planned in the methods, that one finds unexpectedly: this makes reading the MS quite cumbersome and a detailed commentary on each and every aspect impossible in a single run of review. I will therefore concentrate on the main points that require clarification before any further consideration. + +## R3) + +R3)To avoid that control analyses impact the readability of the main text of the manuscript, we have streamlined their presentation, describing control analyses and their rationale in the methods (pp. 31, 32, 33, 34, 35) and removing unnecessary references to supplementary figures from the results section. Since we believe that these control analyses still represent an added value, demonstrating the solidity of our results, we have chosen to keep the original control analyses in the supplementary figures. + +I found stylistic, theoretical and methodological issues that should be considered. I'll start with the methods. + +Methodological issues. + +C4) + +C4)As said, overall, I have the impression that the present drawing from a larger data set might have created some confusion while drafting the MS and surely in the reader as the methods are described sometimes in an incomplete manner: for example, some experimental manipulations or abbreviations are never explained, and so forth. The authors should double- check that all details are provided for a clear comprehension of what was done and for the reproducibility of the procedures and replicability of the results. + +## R4) + +R4)Indeed, we have realized that some details of experimental procedures and methods were not sufficiently clear and improved their presentation. We have improved the revised methods, figures and figure captions to better explain these details (pp. 7, 10, 24, 25, 26, 27, 28, 29, 30). + +C5) + +C5)Experiment 2. The authors adopted a Libet- like paradigm to measure the implicit component of the sense of agency. The patient performed a movement through BMI, which was followed by a sound. According to the intentional binding phenomenon (Haggard et al., 2002), voluntary movements are perceived as shifting in time towards the generated sound, while the sound is perceived as occurring earlier, closer to the action. Based on this phenomenon, the higher this "time compression" that "binds" the voluntary action to its outcome, the stronger an implicit sense of agency for the action and the produced physical outcome. + +Here, the authors only measured the perceived time of the movement onset while ignoring the timing of sound perception. More importantly, they observed the opposite result with respect to the intentional binding phenomenon since voluntary movements were perceived EARLIER in time. This would imply a lower implicit sense of agency, according to the intentional binding phenomenology. The authors discussed this result as a temporal binding between intentions and actions, but they cannot provide any evidence for this explanation; moreover, they do not explain how this binding can be considered a marker of increased implicit sense of agency (the cited reference #30 is a preprint on the very same data). + +## R5) + +R5)Here the Reviewer is raising a few related points, and we are grateful as it would allow us to clarify our approach. + +<--- Page Split ---> + +First, and main point: while our paradigm is inspired by the intentional binding task, as well as to the Libet experiment, the uniqueness of our BMI setup and design resulted in a new paradigm, allowing us to investigate a new form of binding between intention and action that differs from the classical intentional binding between action and effect. A full analysis and discussion of the intentional binding effect in this setup are the focus of the previous work by our group cited in the present manuscript (Noel et al., Biorxiv, 2023, currently under review at Current Biology), and goes beyond the aim of the present study. To better reflect the uniqueness of our setup, we have rephrased the introduction of Experiment 2, and now describe our paradigm as an implicit agency paradigm based on time perception. In particular, the difference between the perceived time of actions preceded by subject's intention to move and those passively implemented is taken as on index of the sense of agency. See page 8: + +"The previous analyses establish a relationship between pre- movement low- alpha oscillations and explicit agency judgements. We next tested whether the same phase opposition can distinguish between high vs. low agency actions as defined from an implicit marker of agency based on the subjective perception of the timing of self- initiated movement 32. Leveraging our BMI setup, in a previous study, we have shown that temporal judgements of voluntary actions triggered by the participant's intention to move are anticipated compared with involuntary actions triggered by NMES, resulting in a temporal compression between the intention to move and the action 32. + +The experimental paradigm and temporal compression results are extensively reported in our previous work 32. Below we provide a brief summary of the methods and findings in the subset of conditions relevant to this study. A rotating clock was displayed on a screen, and the participant was asked to report the position of the clock at the onset of a hand movement triggered by the NMES system (Fig. 3a). In the voluntary session, the action was triggered by the participant's intention to move as decoded by the BMI system. In the involuntary session, the movement was randomly generated via the NMES system without motor intention. The participant perceived voluntary BMI- generated movements as occurring earlier relative to their actual timing than involuntary movements (median voluntary \(= - 497.8 \pm 299\) ms interquartile range, median involuntary \(= - 384 \pm 185\) ms, Wilcoxon \(p = 0.033\) , Fig. 3b). We thus leveraged this finding to classify trials associated with putatively higher agency, as those showing stronger intention- action temporal compression, and trials with putatively low- agency as those showing weaker temporal compression. To this aim, we performed a median split of trials within the voluntary session based on the amount of anticipation and computed the phase opposition product between trials in which the movement was perceived earlier (high agency) and trials in which the movement was perceived later (low agency)." + +A second point by the Reviewer is that we focus our analysis on movement timing, not analysing effect timing, i.e., the tone. Please note that the perceived time of the tone and intention was also collected in this participant as reported in Noel et al.'s paper. However, to be consistent with Experiment 1, the analysis on pre- movement phase has to be time- locked to action onset. Therefore, also in Experiment 2 we focused on trials where action timing was reported. Indeed, time- locking the phase opposition analysis to the effect would include post- movement signals. On the other hand, it would be arbitrary to time- lock the analysis to the intention, as there is no objective timing for it. In sum, reports about intention and event go beyond the scope of the present manuscript, but they are the focus of Noel et al.'s paper. Thus, we prefer to cite these results in our manuscript rather than reporting them again in full. We now motivate our choice to focus on action timing in the methods, on page 26: + +"Experiment 2 is part of a comprehensive set of experiments in which the intentional chain was manipulated, and reports about the perceived timing of intention, action and effect were collected 32. For consistency with Experiment 1, where the analysis was time- locked to action onset, we focused on conditions where action timing was reported." + +A third point concerns the different effects between the classic intentional binding and our new intention- action compression. The paper by Noel et al focuses on a full analysis and discussion on the full "intentional chain", i.e., the relationship between intention- action- effect as highlighted by temporal judgement. For convenience, we summarize their findings and interpretation in the following lines. + +<--- Page Split ---> + +As highlighted above, with our tetraplegic participant, we observed that voluntary actions are perceived as happening earlier in time than involuntary ones. This was true regardless of whether these actions were or were not followed by a tone (Row I and IV vs II in Fig. 1 from Noel's paper, reported below). Importantly, the perceived time of intention was instead postponed when motor commands led to a bodily action compared to no action (Rows I and IV vs III). Thus, perceived timing of will and action seemed to be pulled towards each other when they happened in the same timeline, similarly to what observed for action and effect in classical intentional binding effects. + +We report here Fig. 1 from Noel et al.'s paper, showing the perceived time of intention (red), action (green) and effect (blue) in six different types of intentional chain: + +![](images/Figure_unknown_0.jpg) + +
Time from A onset (ms)
+ +As reported in Noel's paper, this result was interpreted in the perspective of a recent computational accounts of intentional binding (Legaspi et al., Nature Communications, 2019), suggesting that perceived timing compression should occur not only between actions and their consequences, but between any pair of events that the brain determines to be causally related, such as intentions/motor commands and actions. Due to the inherent noise of neural recordings and decoding, BMI movements show a significant and variable delay \((\sim 1.2 \pm 0.48 \text{SD}, \text{see p. 24 of revised text})\) between motor commands and actions, so that the exact timing of the movement is subjectively hard to predict. When our patient executed voluntary movements, such delay got possibly "compressed" by perceived causality, as compared to involuntary movements. That this action- intention compression was not reported in classical intentional binding studies is unsurprising. First, no previous study systematically assessed the perceived time of intention and action in able bodied individuals. Second, the action anticipation effect might not be evident in healthy participants because the delay between motor commands and movements is arguably much shorter and subjectively more predictable than in our BMI setup. This possibly results in a smaller binding compared to the one occurring between action and effect, leading to perceive the action as occurring later. In our patient instead, due to the longer and unpredictable delays, intention- action compression may dominate over action- effect binding, leading to overall action anticipation. + +In sum, we believe Noel's paper to be the most appropriate source of validation for our implicit index, and we have rephrased the presentation of Experiment 2 to better introduce such previous validation on page 8: + +"Leveraging our BMI setup, in a previous study, we have shown that temporal judgements of voluntary actions triggered by the participant's intention to move are anticipated compared with involuntary actions triggered by NMES, resulting in a temporal compression between the intention to move and the action \(^{32}\) ." + +Finally, the Reviewer expresses concern for the lack of an external validation as a marker of agency. In this regard, we wish to highlight that our approach is aligned with that adopted in the original intentional binding paper by Haggard et al., Nature Neuroscience, 2002. In that study, the conclusion that the temporal shift is an implicit marker of agency was drawn based on the observation that such a shift occurred in voluntary vs. involuntary movements. Here, we applied the same logic, taking the temporal shift occurring + +<--- Page Split ---> + +in voluntary movements compared to involuntary ones (action anticipation) as an implicit marker of the sense of agency. Importantly, not only did we observe the same effect of \(8 \text{Hz}\) pre- movement phase as in Experiment 1, but the phase relation was the same. In other words, restricting ourselves to facts without any interpretation, anticipated action perception was associated with precisely the same \(8 \text{Hz}\) phase preceding explicit judgements of high agency in Experiment 1, and with voluntary movements compared to involuntary ones in Experiment 2. Although internal to our participant (due to the uniqueness of the setup), we believe the coherence of these results supports the interpretation that, in our setup, action anticipation is an implicit marker of higher agency. Still, we agree that the lack of external validation, due to the uniqueness of our setup, constitutes a limitation, as now acknowledged in a new limitations paragraph on page 22: + +"Our unique BMI set up enabled us to relate pre- movement phase opposition to the temporal compression between intention and action observed for voluntary actions. More studies are needed to validate this intention- action compression as an implicit marker of agency." + +We have further toned- down the following passages in the introduction and results to reflect the putative state of such marker of agency, as visible on pages 4 and 8: + +"In Experiment 2, we showed that these oscillations also predicted the temporal binding between intentions and actions, a putative implicit measure of the sense of agency \(^{32}\) " (p. 4) + +"We thus leveraged this finding to classify trials associated with putatively higher agency, as those showing stronger intention- action temporal compression, and trials with putatively low- agency as those showing weaker temporal compression." (p. 8) + +C6) + +Incomplete methods description. There is some missing information in the MS. Figure 3a mentions an "operant movement" condition, which is not described in the text. I assume that there might be a baseline "non- operant movement" condition, in line with the intentional binding paradigm, but I cannot find any information about this. These conditions are mentioned but not described also in Figure S15. + +R6) + +We apologize for the lack of clarity. Indeed, to study the full intentional chain (as done in Noel et al., Biorxiv, 2023) two types of movements were used. One (hand closing, operant movement) led to a tone being produced 300 ms later, and the other (hand opening, non- operant movement) was not followed by a tone. Since the focus of the present manuscript is pre- movement signals, occurring before the timeline of operant and non- operant movements bifurcate, we pooled operant and non- operant movements in our analyses. The differential effects of operant and non- operant movements in temporal judgements are presented Noel et al. (Biorxiv, 2023). We now have better explained these aspects in the methods on page 26: + +"Movements were triggered by the activation of the neural decoder, but the NMES was always activated congruently with decoded motor commands. Additionally, 300 ms after HC was executed, a 1000 Hz "beep" was produced, lasting 100 ms (operant condition). No additional consequence followed HO execution (non- operant condition). Here, we focused on pre- movement signals, occurring before the differentiation between operant and non- operant trials, and our key contrast is between the voluntary and involuntary session. Thus, we pooled trials from the operant and non- operant conditions in the present analyses." + +To increase the readability of the results section, we removed references to operant and non- operant conditions from Fig. 3, as the two conditions were pooled in the analyses and the purpose of the figure is to present the behavioural contrast between voluntary and involuntary movements. + +<--- Page Split ---> + +C7) + +Experiment 3. According to the main text, participants were instructed to imagine a specific (unknown) righthand movement, followed by (congruent?) visual feedback. At the end of each trial, they were asked to rate their perceived explicit agency. + +## R7) + +As described in the methods, participants had to imagine a continuous squeezing effort of their right hand. Visual feedback showed the virtual hand closing in all trials, so the feedback was always "spatially" congruent with the imagined movement. The text has now been revised to improve clarity (page 27): + +"For motor imagery, they were asked to imagine the physical sensation of squeezing their right hand. They had to imagine a continuous and strong squeezing effort, as if they were on the verge of making a movement, but without contracting the arm, shoulder, or face muscles." + +C8) + +First, I was wondering how there could be an agency modulation if the movement to imagine and the displayed feedback were always the same. Maybe I missed some details here. + +## R8) + +Experiment 3 was designed based on our hypothesis on pre- movement oscillations and findings from Experiment 1 and 2, suggesting that even in the absence of external manipulation, variability in agency ratings for BMI actions is to be expected, and such variability should be (at least in part) explained by the pre- movement endogenous phase, which is independent from sensory feedback. In this sense, note that the phase effect in Experiment 1 held even at fixed sensory feedback congruency (Fig. 2g) and is thus purely endogenous. Thus, the goal of Experiment 3 was not to measure the effect of exogenous manipulations on the sense of agency induced by sensory feedback, already broadly studied (e.g., Serino et al., Nature Human Behaviour, 2022, Marchesotti et al., Human Brain Mapping, 2017; Evans at al., PLoS One, 2015), but to study the link between "residual" variability in agency ratings which does not depend on external manipulations but on endogenous pre- movement oscillations. To effectively do this, we aimed creating a setup in which, at a given sensory feedback, the sense of agency is uncertain and variable, and thus more likely to depend on endogenous factors such as the pre- movement phase. If we simply asked participants to perform actual movements and rate their sense of agency, agency ratings would be constantly very high and no meaningful variability would be observed, therefore we used a BMI setup. We expanded the description of the task in the methods to better explain its rationale on page 28: + +"The aim of the experiment was to induce a trial- by- trial varying sense of agency with minimal exogenous manipulations, and independently from sensory feedback, to highlight the role of endogenous neural oscillations in modulating agency ratings." + +For these reasons, participants were asked to imagine squeezing their right hand to generate virtual movements of a hand closing. Visual feedback was always the same and "spatially" congruent with the imagined movement. To keep agency uncertain and not have a stereotyped task, we randomly manipulated the temporal delay between go cue and sensory feedback. Importantly, our key analysis was based on contrasting high and low agency trials based on participant's reports, and not on the exogenous delay manipulation, to maximize the effect of endogenous factors such as the pre- movement phase. Indeed, since the pre- movement phase is endogenous and cannot depend on externally determined post- movement conditions, external manipulations may actually confound the phase effect, and were thus kept at a minimum and regressed out from the agency ratings before the phase opposition analysis, as stated in the methods on page 33: + +"To remove the effect of such exogenous factor, we regressed out the effect of delay on agency ratings within each participant before splitting trials and computing POP values." + +<--- Page Split ---> + +C9) + +However, the main issue here is related to the behavioural dependent variable that (i) should validate the use of sham EEG- BMI trials and (ii) should guide the EEG analyses: the agency ratings. These agency judgments were inevitably biased by the experimenters' who warned participants "to keep the mean rating around 5" in the two conditions; for this reason, they cannot represent a valid measure of agency. + +## R9) + +We are sorry that the too original description of our instructions, which was too concise, has generated a misunderstanding. Our instructions clearly explained to the participants to use 5 as an "anchor" between the highest and the lowest agency trials, and to focus on the differences between trials to provide variable ratings spanning the whole scale. This was to avoid having participants constantly reporting the extreme value of the scale, which was noted in few pilot subjects who always reported very high agency, hindering meaningful splitting of trials for phase opposition analyses. We have now rephrased the passage to better reflect the detailed instructions provided to participants on page 29: + +"Before the experiment, subjects were instructed to focus on pre- reflexive aspects of the control experience, and not to use cognitive reasoning to provide the ratings. They were also asked to focus on the differences between trials rather than on the absolute levels of agency, to provide variable ratings using all the available range, and considering 5 as an intermediate point to distinguish between higher and lower agency levels." + +Importantly, even if the instructions had affected the average agency rating (anchoring it for instance around 5), this would be irrelevant for our analysis, as it would not affect the subset of trials being assigned to the "high" or "low" agency condition based on participant's rating. Thus, we believe that the agency ratings collected during our experiment are appropriate for our EEG analyses. We included these considerations to the methods on page 29: + +"Note that a potential bias in average ratings due to using 5 as a reference value cannot affect the results of our analyses, which are always based on relative agency ratings, compared within participants." + +Finally, concerning the validation of our Sham BMI approach. As correctly pointed out by Wegner in his mental causation theory, it is entirely possible for healthy individuals to experience a genuine sense of agency even when not truly in control of an external event, as we believe was the case in our sham BMI setup. To validate this, we compared agency ratings between sham and actual BMI trials, and found no significant difference (Fig. S7). The reasonings reported above concerning the instructions given to the participants apply also in this case. Indeed, even if the instructions biased average ratings towards 5, there would be no reason to expect that such bias would be different between sham and BMI trials. Since the comparison of ratings to validate the sham setup is done within participants, we believe it cannot be affected by such potential bias. + +We expanded and clarified passages about the rationale and validation of our sham setups in the methods on pages 28 and 33: + +"We chose to use sham BMI as the main experimental condition, as it allowed us to reliably produce the illusion that the participant is controlling the virtual hand, while being less subject to fatigue and decoder variability than real BMI. This allowed us to collect a large and constant number of trials, regardless of each participant's proficiency with BMI. The illusion was made possible by the fact that in EEG- BMI delays are long, and require a prolonged and continuous effort lasting several seconds to reach the decoding threshold. Therefore, even when truly controlling the BMI, the participant could not predict the exact timing of the movement, and thus habituated to experience control for delayed and temporally unpredictable movements. If the movement is provided at a randomized delay comparable to the intrinsic delay of the BMI system (hence the careful adjustment of decoding thresholds after BMI training), a sham BMI trial is hardly distinguishable from a real BMI trial." (p. 28) + +"We assessed the validity of the sham- BMI setup, by testing whether sham and real BMI trials could be distinguished by participants and led to different agency levels. We found that sham BMI and real BMI + +<--- Page Split ---> + +trials elicited comparable agency levels (mean sham BMI \(5.75 \pm 0.13\) SEM, mean real BMI \(5.57 \pm 0.21\) SEM, \(p = 0.33\) , Fig. S7). In addition, when told that they were truly in control of the virtual hand only in self- paced trials, at the end of the experiment, all subjects reported that they were not aware of it. Thus, participants were not aware of the sham BMI setup, and believed to be causing the hand movement." (p. 33) + +Data interpretation. + +C10) + +Puzzling interpretation of the LFP data. Exploration of the LFP data, in Figure 3c, suggests that the two curves clearly dissociate AFTER movement execution. I was wondering why the authors concentrate only on minute differences before Time 0 and do not discuss this result. + +## R10) + +We thank the reviewer for giving us the opportunity to discuss these important aspects. The pre- movement phase opposition appears small to visual inspection in the plots reporting trial- averaged traces (in Figs. 2c and 3c) because the trial- averaged LFP trace is not suited to visually highlight phase opposition effects, as it conflates in a non- separable way the effects of phase and amplitude of the LFP. To provide a better visualization of the contribution of phase and amplitude in discriminating between movement perceived early and perceived late, we now complement the trial- averaged LFP plot of Fig. 3c (and 2c) with plots of single- trial phase and amplitudes. To visually appreciate the phase effect, in Fig. 3d (reported below, also see the analogous Fig. 2d for Experiment 1), we plot the instantaneous phase for individual trials throughout the entire trial, highlighting (black dashed lines) the pre- movement phase opposition window of the alpha band for early vs. late movement perception. To illustrate the effects of amplitude, we also plot in Fig 3h individual- trial LFP amplitude, showing that early vs late differences are larger and more reliable in the post- movement than in the pre- movement period. However, these differences is less strong and reliable than differences in the pre- movement phase. In Fig. 3i we plot the histograms of post- movement LFP amplitude values across all trials for the early and late condition, at the timepoint of maximal difference between early and late trials. Further, there is considerably more overlap between the distributions of post- movement LFP amplitude (Fig. 3i) at the post- movement time with the strongest early- late discriminability than between the distributions of 8 Hz phase at the pre- movement time with highest early- late discriminability (Fig. 3f). Thus, pre- movement phase discriminates between trials with early and late perception better than post- movement amplitude does. + +The visual inspection is confirmed by rigorous statistical analysis of the discriminability between high and low agency movements from the instantaneous phase and amplitude across the movement time, showing that pre- movement phase opposition is statistically stronger than post- movement amplitude differences. In Experiment 1, when movements started in the optimal phase, \(74.8\%\) of trials had high agency, while only \(44.9\%\) had high agency when movements started in the non- optimal phase. In Experiment 2, \(75.8\%\) of trials in the optimal phase vs. only \(21.2\%\) of trials in the non- optimal phase were associated with an early perception of the movement. This results in a p- value of 0.0001 for the phase opposition at peak time, with p being below 0.001 between - 0.6 and - 0.2 s pre- movement. For comparison, the minimum p- value in the amplitude comparison of the two LFPs was 0.00035, reached for a very short post- movement interval (we use p- values to compare effect sizes because there is no standard method to determine effect size for phase opposition). Thus, unlike the phase opposition effect, the LFP amplitude difference did not survive cluster correction for multiple comparisons, as shown in Fig. 3g. + +We thank the reviewer for giving us the opportunity to clarify these aspects, which are now detailed in the results on page 10: + +"Importantly, the early vs late differences in pre- movement LFP phase were far stronger and more significant in pre- movement LFP phase than in either pre- or post- movement LFP amplitude. LFP amplitude discriminated maximally between the two conditions at 544 ms post- movement (minimal p- value, t- test, Fig. 3g). Such difference was not significant after cluster correction for multiple comparisons across timepoints ( \(p > 0.08\) ). Accordingly, phase distributions within the pre- movement phase opposition cluster + +<--- Page Split ---> + +(- 256 ms, Fig. 3f) had much less overlap than LFP amplitude distributions at the post- movement timepoint of maximal amplitude- based discriminability across early and late movement perception (Fig. 3i)." + +We report below the changes in Fig. 3 and the relative caption, visible on page 11: + +![](images/Figure_unknown_1.jpg) + + +"(c) Trial-averaged LFP for trials with early (blue) and late (red) perception of movement (median split). Shades denote standard errors. (d) Instantaneous pre-movement phase (as in Fig. 2d) for individual early (top) and late (bottom) movement perception trials, showing clustering of the two subsets around opposite phases. Black dashed lines indicate the time limits of the cluster shown in panel (e), the white dashed line indicates the timepoint shown in panel (f). (e) P-values for the phase opposition product between trials with early and late movement perception. The red contour delimits the significant cluster after a cluster-based permutation test. The black bracket above the plot indicates the time window of interest for cluster-based correction (-0.5/0 s). (f) Histograms of phase angles for individual trials at the time-frequency point of maximal phase opposition in Experiment 1 (-256 ms, 8 Hz, red cross in panel d) to allow comparison with Figure 2e. Blue/red lines indicate the preferred angles for high/low implicit agency respectively, and their length is proportional to the ITC. (g) Comparison of the statistical significance of phase differences (red, 10000 permutations) and LFP amplitude differences (black, t-test). Solid horizontal lines indicate time windows surviving cluster correction for multiple comparisons across timepoints. No significant cluster was found for LFP amplitude differences. (h) Instantaneous post-movement amplitude for individual early (top) and late (bottom) movement perception trials. (i) Histogram of LFP amplitudes at the timepoint of maximal dissociation between early (blue) and late (red) trials." + +In sum, besides the theoretical interest of this study on pre- movement neural oscillations, there is also a quantitative justification in focusing on the pre- movement phase. We hope the new plots and analyses following this important comment help illustrate the reasons for this choice. + +<--- Page Split ---> + +That being said, an effect of pre- movement oscillations does not exclude that post- movement signals may be also contributing to the final reported sense of agency or movement timing, as now mentioned in the discussion on page 20: + +"Our results do not rule out the contribution of post- movement signals to the sense of agency. These may be relevant for postdictive inference of causality (apparent mental causation theory \(^7\) ), or for sensorimotor comparisons, whereby sensorimotor oscillations may be integrated with higher level cognitive cues to determine the final experience of agency (cue integration theory \(^6\) ). This contribution may be reflected in a dissociation of post- movement LFP between high and low agency trials, which was here observed in Experiment 2 and extensively investigated in \(^{13}\) . Pre- movement sensorimotor oscillations may also serve as a trigger for apparent mental causation, and gauge the integration between low- and high- level cues in determining the sense of agency." + +## C11) + +The "alfa band" is really the same in all experiments? + +For some reason, the Authors have decided that signals coming from different frequency ranges are the same thing. In the patient, the frequency of the electrical signal measured from area M1 peaks at \(6.2 \text{Hz}\) (below the canonical alfa); in the normal controls the peak of the electrical signal measured this time from area SMA peaks at \(9 - 12 \text{Hz}\) . I am not convinced by this analogy. As said, and unfortunately, because the paradigms used in the patients and in normal controls are not the same these differences are not interpretable. + +## R11) + +Thank you for pointing out this aspect which deserves more in- depth discussion. There is a considerable variability across studies in the definition of frequency bands, and the neural origin of EEG or LFP activity at each frequency is often unclear. Reviewer 2 commented that the 8 Hz oscillations in the implanted patient "looks like a typical subject alpha band LFP" (see C21). However, we acknowledge that in the previous versions of the manuscript we have not been sufficiently clear in noting that we cannot and do not wish to assume or conclude that neural phenomena observed with different techniques in different paradigms, different subjects, and different frequencies are analogous or are generated by the same neural processes. We can only unbiasedly document where frequency information about agency is encoded in each experimental paradigm. We have revised discussion (page 22) to emphasize this: + +"Furthermore, differences in techniques and experimental paradigms applied in one implanted participant and healthy controls make it difficult to infer whether comparable phase opposition effects observed at different frequencies across different experiments are related to the same or different neural mechanisms. Because of this, and of the general difficulties in imputing neural phenomena to frequency bands \(^{41}\) , here we refrained from making such inference, and unbiasedly reported the precise frequency of the observed effects in each subject and experimental paradigm." + +Said that, we run further analyses to characterize and understand the subject- to- subject variability within the same experimental paradigm in the frequency of maximal agency encoding in the phase. In particular, we analysed individual spectral peak of low frequency oscillations (for brevity: individual alpha peak). Since many behavioural effects seem to be tied to the individual alpha peak frequency (Haegens et al., Neuroimage 2014), or even to its fluctuations across trials within the same participant (Drewes et al., Cerebral Cortex, 2022), we hypothesized that also variations across individuals in the frequency of the strongest phase opposition could be reflect variations across individuals of their idiosyncratic alpha peak. The new analyses indeed showed that the individual frequency of maximal phase opposition correlates with the individual alpha peak in SMA. We now present and discuss this novel finding in the results section (page 14) and in Fig. 6f: + +"The SMA effect peaked at 9 Hz, close to what was observed in our implanted participant, but was relatively spread across the whole alpha band (Fig. 6d). Since alpha- band peak frequencies vary across individuals \(^{45}\) and correlations of alpha- band activity with behaviour are stronger at frequencies closer to the individual + +<--- Page Split ---> + +alpha peak 46, we predicted that individual variations in agency- related phase opposition might reflect individual variations in alpha peak frequency. Confirming this prediction, the frequency at which maximal SMA phase opposition was found for each subject correlated with their individual SMA alpha band frequency of maximal power \((R = 0.46, p = 0.011, \text{Fig. 6f})\) . This suggests that individual variations in the frequency at which the phase better predicts agency depends on individuals' idiosyncratic alpha band peak." (p. 14) + +We report below Fig. 6f and the relative caption: + +![PLACEHOLDER_18_0] + + +"(f) Correlation between the individual alpha peak and the frequency of strongest phase opposition in the left SMA. Data of the tetraplegic participant from Experiments 1-2 (not included in the regression) is shown for comparison (red dot)." + +Crucially, a spectral peak below the conventional alpha band has been previously and commonly observed in tetra or paraplegic participants (Foldes et al., J Neurophysiol, 2017), including our implanted patient (6.2 Hz). Thus, although lower in absolute frequency with respect to healthy controls, the phase opposition observed in the implanted participant also peaked close to his individual alpha peak (see red dot in Fig. 6f above). As visible in the figure, most participants with a low individual alpha peak (around 8 Hz) presented a phase opposition effect peaking close to the one observed in the implanted participant. + +To address the difference between M1 and SMA, we now also report the spectral peak in M1 for healthy participants, which is very close to the SMA spectral peak (Fig. S3). Therefore, we believe it is unlikely that the difference in frequency can be explained by the different anatomical location, but rather by the different frequency of the peak of power of oscillatory activity. + +In sum, our new analyses suggest that the apparent discrepancy in frequency can be resolved by considering that: (i) the phase effect is tied to the individual low- frequency spectral peak and that (ii) the spectral peak in the implanted participant is lower than in healthy participants, likely due to the patient's chronic paralysis. This is now mentioned in the discussion on page 22: + +"We could, however, gain some intuition about the individual variability of effects within Experiment 3. Namely, individual differences in the peak phase opposition frequency could be accounted for by individual variations in the individual alpha peak (Fig. 6f). Compatibily with other reports in chronic paralysis 39, the individual alpha peak in the implanted participant was lower than in healthy participants, possibly explaining the lower frequency of the phase opposition effect observed in Experiment 1 and 2." + +<--- Page Split ---> + +C12) Coherence of the results. + +Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. + +Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small- EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls. + +## R12) + +The different source of the effect from the patient and healthy individuals indeed deserved more clarification. We did observe an effect in M1 in healthy participants. We apologize if this was not reported and analysed with sufficient clarity in the original manuscript. We have rephrased this part to clarify our hypotheses and results. + +Based on the previous literature about the neural bases of the sense of agency (see e.g., Haggard, Nature Neuroscience Reviews, 2017) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12), applying FDR correction for multiple comparisons within this network. This analysis revealed the strongest phase opposition in SMA, and that the second strongest phase opposition in M1 (p = 0.023). If focusing purely on the left M1, with the purpose of replicating the effect observed in the implanted participant, and thus dropping multiple comparisons correction, the uncorrected M1 effect is highly significant with p = 0.003. The uncorrected p- value is not reported for in the text, for being maximally conservative. In sum, phase position was significant in both SMA and M1. For completeness, we also reported the results of a whole- cortex search for phase opposition across all 114 ROIs of the cortex. This whole- cortex search confirmed significant phase opposition in the SMA after adjusting for 114 comparisons; in contrast, M1 did not survive multiple correction. We refrain from making interpretations of the null result for M1 in this whole- cortex search as this analysis is underpowered. Taking this into account, have rephrased the presentation of the results as follows (page 14): + +"Based on the previous literature about the neural bases of the sense of agency (see e.g. 44) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12, shown in Fig. S8). Two regions survived FDR correction for multiple comparisons across regions within this network. The stronger phase opposition was observed in the posterior part of the left supplementary motor area (SMA, p = 0.0024, Fig. 6c- e). Phase opposition in the dorsal part of the left primary motor cortex contralateral to the BMI movement was also significant (p = 0.023), consistent with our result in the implanted participant. No other ROI yielded significant phase opposition. For completeness, we repeated the analysis searching for significant phase opposition across all 114 ROIs of the source reconstruction. This whole- cortex search confirmed a significant phase opposition in SMA (p = 0.03), whereas phase opposition in M1 did not survive correction for multiple comparisons, likely due to the analysis being relatively underpowered. As shown in Fig. S9a- B, SMA effects were robust to the specific choice of the frequency range (Fig. S9a- b)." + +It is also important to note that, while for further analyses in the main text we focused on SMA, the region showing the strongest effects, the key results on connectivity are also observed when using M1 as a seed (Fig. S10). Also note that we may have observed an effect only in M1 in the implanted participant simply because the only available recording site was in M1. We cannot exclude that, as in healthy participants, an effect, possibly even stronger, could have been observed in SMA if an electrode was also implanted there. An alternative explanation of the anatomical difference may be that, while the implanted participant was using genuine motor attempts to control the BMI, healthy participants had to use motor imagery, which is known to activate SMA more than M1. These considerations were added to the discussion on page 21: + +<--- Page Split ---> + +"Interestingly, in healthy participants, the phase opposition effect was stronger in SMA than in M1. Since the invasive implant was limited to M1, we cannot exclude that a stronger phase opposition in SMA was also present in our tetraplegic participant but not directly observed." + +"Experiment 3 employed motor imagery rather than genuine motor attempts, as in Experiment 1. Given that motor imagery is known to induce comparably higher activations in SMA than in M1 \(^{56}\) , a possibility, to be addressed in future work, is that the relative contributions of SMA and M1 vary depending on the modality of BMI control (e.g., imagery versus execution)." + +We would also like to add that, in our opinion, the key common result cross- validating findings across Experiment 3 and Experiment 1- 2 is not just that the phase opposition effect was found in the pre- movement period. Indeed, these results pertain the oscillatory phase, a very specific and peculiar feature of neural potentials, they were observed at similar frequencies (tied to the alpha peak), and effects in the contralateral M1 were significant in the implanted participant and in healthy controls. Further effects in SMA, a region that was simply not recorded in the implanted participant, were clearly observed only in healthy controls. + +## C13) + +Theoretical issues. + +A paper of this magnitude cannot be neutral towards the previous theories on the sense of agency. There are at least three theoretical models proposed to address the arising of the agency experience. The authors seem to consider only one of these nor they do make an effort to discuss whether and why their findings are in support of this specific theory. The "Comparator Model", the only model mentioned in the paper, postulates that the sense of agency arises from a series of comparator processes within the motor control system. However, in an alternative perspective, the "Apparent Mental Causation Theory" proposes that the emergence of the sense of agency is a post hoc and retrospective phenomenon. Accordingly, the sense of agency arises through an inferential sense- making process that occurs after the completion of a movement. Finally, in the "Cue Integration Theory", the sense of agency should arise from integrating low- level cues (sensorimotor proprioceptive and exteroceptive cues) and high- level cues (cognitive cues). The weight assigned to these different cues varies for the implicit and explicit components of agency. Hence, I feel that the authors should try to frame their data considering the previous theoretical and experimental efforts on the very same topic over the last 20 years. + +## R13) + +Thank you for this suggestion. We are glad to discuss our results on pre- movement signals affecting the sense of agency in line with the current most relevant theories on this topic. The presence of a pre- movement signal correlating with the subsequent sense of agency (and neural connectivity) resonates with key elements of the "predictive" comparator model. Alpha band oscillations, gating cortical connectivity, are in our view a promising candidate to be the neural substrate carrying sensorimotor predictions from motor to sensory areas, and performing the subsequent comparisons. This mechanism is also compatible with the low- level components in the cue integration theory, while higher level neural processes on a slower temporal scale may contribute to postictive inference. At the same time, our findings do not exclude that post- movement, retrospective inference of mental causation may also play a role in the phenomenology of agency. We have now integrated these aspects in the discussion on page 20: + +"In our previous work \(^{13}\) (including data from Experiment 1), we showed how post- movement LFPs and multiunit activity in M1 encode congruency between motor commands and sensory feedback, a key aspect in the sensorimotor comparisons underlying the sense of agency. Our findings in Experiment 1 extend these previous results, suggesting that M1 and SMA also play pivotal roles in the sense of agency at an earlier stage, when sensorimotor predictions are computed during motor preparation and before execution. Our results do not rule out the contribution of post- movement signals to the sense of agency. These may be relevant for postictive inference of causality (apparent mental causation theory \(^{7}\) ), or for sensorimotor comparisons, whereby sensorimotor oscillations may be integrated with higher level cognitive cues to + +<--- Page Split ---> + +determine the final experience of agency (cue integration theory 6). This contribution may be reflected in a dissociation of post- movement LFP between high and low agency trials, which was here observed in Experiment 2 and extensively investigated in 13. Pre- movement sensorimotor oscillations may also serve as a trigger for apparent mental causation, and gauge the integration between low- and high- level cues in determining the sense of agency." + +In addition to the comparator model, we now also mention the alternative theories of the sense of agency in the introduction on page 3: + +"Different explanations have been offered for the sense of agency 6- 8. Among those, one influential view states that the sense of agency arises from the comparison between predicted and observed sensory outcomes of intended actions 8,9. " + +C14) Style. + +For sure, there is already a broad body of literature investigating the neural correlates of the sense of agency that makes an opening statement in the abstract (".... the underlying neural mechanisms of the sense of agency are still unknown") too strong for two reasons: (1) the previous evidence connecting brain physiology and the SOA (2) the correlational nature of the evidence provided; this lacks the identification of a clear "mechanism" that causally connects brain physiology and the complex phenomenology of the SOA. + +## R14) + +We are sorry if we gave the impression of stating that no previous knowledge of the neural mechanisms of the sense of agency was available, which is not the case. We more specifically meant that the dynamical interaction between functional areas is still poorly understood, as most previous studies are either "static" fMRI activation maps, single- site lesion or perturbative studies. We have rephrased the abstract and introduction accordingly. Furthermore, we have thoroughly revised the text to clarify that we do not provide causal evidence about the role of pre- movement oscillations (pp. 4, 12, 19, 21). We also now acknowledge the correlational nature of our evidence in a new limitations paragraph which was added to the discussion on page 22: + +"Nonetheless, without direct experimental intervention, the current evidence remains correlational. Further studies are needed to causally assess the contribution of pre- movement phase to sense of agency, both when measured explicitly and implicitly." + +<--- Page Split ---> + +The manuscript by Bertoni et al reports very interesting data and experimental designs. The authors recorded single neurons and LFP from M1 of a tetraplegic patient who, with the help of a prosthetic devise, is able to guide fake- hand reaching movements. The authors correlated the LFP with the reported simulated action of the subject and specifically with his sense of agency, demonstrating a phase dependence of alpha band endogenous oscillation with the sense of agency. To complete the study the authors measured the effect in typical subjects, and used high density EEG coupled with simulation of the moving hand to demonstrate again a phase dependence. Unfortunately and not surprising this data are less compelling with a small and just significant effect. + +While I like the paper and the material presented, I have several unclear and not- discussed technical problems that make me uneasy to give a strong recommendation at this stage. The main one being the synchronization with the prosthetic devise. For this reason I would like to postpone my acceptance/rejection recommendation after a major revision giving the possibility to the authors to explain better their technique and rationale and write a more clear and critical manuscript. + +We thank the reviewer for their appreciation of our work, the many insightful comments, and the possibility of clarifying technical problems. A detailed response to the reviewer's main concerns, as well as other major points are provided in the following paragraphs. We highlighted our responses in bold, and indicated with quotation marks and italics passages reported from the revised text, highlighting changes in red. To allow referring to specific points, we have numbered reviewer comments and our responses (e.g., comment 1: C1; response 1: R1). The numbering continues across comments from the two reviewers. + +C15) Main problem + +Phase depends on the time origin of the synchronisation trigger. Here the authors trust the prosthetic algorithm and set the synchronisation with the onset threshold for the fake- hand movement. However, this relies on a very strong assumption: the algorithm should operate with the same delay for the high and low agency perception. This may be wrong and would be mainly CONTRARY to their data. They show that the agency state signal can be derived from the phase of the LFP and supposedly also the decoding algorithm is using this signal, possibly by introducing a delay (50 ms would be sufficient) to give an apparent phase change. In other words, the argument to me is circular! + +## R15) + +We understand the reviewer's concern, and apologize for an insufficiently clear presentation of technical aspects of the neuroprosthesis setup which may have led to a few critical misunderstandings. + +First, the feature used by the BMI decoder in the implanted participant is the high frequency (>235 Hz) power (not phase) of the LFP signal, reflecting multiunit firing rate at each electrode. Due to the extreme gap in frequencies, and the fact that the power and not the phase of oscillations are considered, the BMI features are essentially independent of the 8 Hz phase. BMI input features are further smoothed over a 500 ms window, spanning and averaging several alpha cycles, and processed in externally determined 100 ms bins; thus, there is no reason to expect a dependency between BMI decoder threshold crossing and 8 Hz phase. + +We report the passage detailing the input features of the decoder from page 24: + +"The SVM used 96 input features consisting of the mean wavelet power (MWP) for each channel and 100 ms bin. To obtain the MWPs, neural activity was decomposed into 11 wavelet scales (Daubechies wavelet, MATLAB), and the coefficients of wavelets 3- 6, corresponding to the multi- unit frequency band spanning from 235 to 3.75kHz, were averaged for each channel. Thus, the decoder's input features were closely + +<--- Page Split ---> + +related to high frequency power at each channel, a robust and computationally not intensive proxy of multi- unit activity." + +We also have added further details in the methods to provide all the necessary information regarding this point, on page 25: + +"At the end of each 100 ms acquisition bin, the decoder analysed neural signals and provided four numbers in the - 1/1 range, indicating the decoded relative probability for each of the four movement. Again every 100 ms, the output of the decoder was further smoothed on a 500 ms time window to determine whether and which movement to implement." + +To support empirically that there is no dependence between decoding delay and 8 Hz phase/agency, we compared the decoding delay between high and low agency trials, and between trials starting in the optimal vs. non- optimal phase. No significant difference was found. These analyses are mentioned in the methods (page 32) and are shown in the Supplementary Materials (Fig. S13): + +"To rule out that the relation between pre- movement phase and sense of agency could be due to differences in BMI decoding delays for high and low agency trials, we compared the delay between go cue and NMES movement onset between high and low agency trials, and between trials with optimal vs. non- optimal phase. We found no difference (t(29) = 0.15, \(p = 0.84\) and t(29) = 0.71, \(p = 0.48\) respectively, Fig. S13)." (p. 32) + +We report Fig. S13 and its caption below: + +![PLACEHOLDER_23_0] + + +"Figure S13: Control analyses on the decoder delays. The left panel shows the delay between go cue and NMES movement onset compared for high and low agency trials ( \(p = 0.84\) ). The right panel compares the same delay between trials starting in the optimal vs. non- optimal phase ( \(p = 0.48\) ). The grey bars represent standard errors." + +In addition to this, even if present, a "constant" delay of 50 ms (or any duration) may potentially affect agency judgements, but cannot lead to a systematic phase shift. This is because the "initial" phase (at the timepoint relative to which the delay is defined, e.g., the go cue) is randomly determined by the timeline of the experiment, which is independent from the phase of endogenous neural oscillations. Even if the phase at "time 0" was always the same, which is not the case, a constant delay would not introduce a phase shift, since the BMI decoder takes more than one second to trigger a movement (more than 3 with EEG), and temporal correlation between initial and current phase is lost after only a few oscillatory cycles, due to the different duration of each oscillatory cycle in noisy physiological processes. The average delay and its variability are now mentioned in the methods on page 25: + +<--- Page Split ---> + +"Due to decoder output smoothing, plus neural and acquisition noise, the delay from the go cue to decoder threshold crossing was variable and significantly larger \((1.2 s \pm 0.48 SD)\) than in natural movements. Being an expert user of the BMI system, the participant is accustomed to these long delays, allowing him to experience a strong sense of agency for BMI movements." + +Thus, the circularity mentioned by the reviewer could be present only if the decoder selectively time- locked its threshold crossing to a specific \(8 \text{Hz}\) phase based on the agency judgement reported by the participant at the end of the trial. In other words, the decoder would need to be able to predict the participant's agency judgement before the movement starts, and trigger the movement in the optimal phase when a positive judgement is predicted, and vice versa. This is clearly not possible. Finally, it is important to add that the phase effect is pre- movement and visible even at fixed sensory feedback (Fig. 2g), so it is independent of exogenous factors, such as sensory feedback, which may potentially interact with decoder output. + +All the above reasonings also apply to the EEG experiment in healthy participants. In addition, in the EEG experiment the go- movement delay is regressed out from agency ratings to enhance the contribution of endogenous factors (i.e., pre- movement phase), and cannot thus contribute to our analysis. + +For all these reasons, we believe there is no circularity between our phase- dependent effect on the sense of agency and how the BMI system decodes the participant's motor intention. + +## C16) + +However, the authors have access to single cell firing. A simple threshold to the ensemble recording firing could be used for synchronize the LFP and analyse the change in phase. It is true that they found a strong correlation between pre- movement of fake- hand LFP and neuronal firing. However, the amount of firing may be independent of onset phase. Maybe I misunderstood something, and the tetraplegic patient does not modulate at all M1 firing during Motor Imagery. But if so, this needs to be explained in detail, at least in the methods. In addition the variability of the decoding delay to generate the phantom hand movement needs to be reported! + +## R16) + +We thank the reviewer for giving us the opportunity to discuss these important aspects of our analysis. First, let us clarify that differently from healthy participants, the tetraplegic participant did not perform motor imagery, but controlled his own hand by attempting actual hand movements, which was decoded by the BMI and triggered neuromuscular electrical stimulation of his forearm muscles (see Fig. 1 and caption). Thus, he did modulate M1 firing rates to generate hand movements, as shown by previous studies (Bouton et al., Nature, 2015; Serino et al., Nature Human Behaviour, 2022; Noel et al., Biorxyv, 2023) and the current data (see for example Fig. 5d, showing the buildup of M1 firing rate leading to the decoder crossing threshold). Movement- specific patterns of M1 firing were detected by the BMI system to recognize the intended movement. We have better clarified these aspects in the methods on page 24: + +"The BMI system consisted in a 96 channels Utah array (Blackrock microsystems) acquiring M1 signals, a standard desktop computer decoding the intended movement from M1 activity, and an electrode patch stimulating right forearm muscles to translate decoded movements into functional hand movements. To account for natural changes in the signal from the Utah array, the decoder was re- trained before each experimental session. Training data was generated by asking the participant to attempt performing one of four hand movements (hand open, HO, hand close, HC, thumb extension, TE, thumb flexion, TF). Clearly, due to chronic paralysis, these motor attempts did not lead to actual hand movements as long as electrical stimulation was off, but modulated M1 firing rates in movement- specific patterns, which could be detected by the BMI algorithm. In each training session, the subject performed 7 blocks consisting of 3 repetitions per movement type each." + +Following the interesting suggestion of the reviewer, we now also analysed phase opposition after time- locking to a simple threshold on M1 firing rates. We found no significant phase opposition, as now stated in the methods (p. 32) and shown in the Supplementary Materials (Fig. S14): + +<--- Page Split ---> + +"We also tested whether phase opposition results could be replicated by time- locking the LFPs to the crossing of a simple threshold on average M1 firing rates, rather than to the onset of the actual hand movement, and found no significant result (Fig. S14). We believe this was the case because the BMI decoder does not produce a movement by threshold crossing of population activity, but rather by decoding specific activity patterns across neurons \(^{33}\) . Thus, population rate threshold crossing is an internal event which, unlike BMI decoder crossing threshold, does not produce a movements or salient subjective percepts." (p. 32) + +Expanding the reasoning above, we believe the analysis did not yield significant results for one technical and one conceptual reason. + +Technically, in each trial, the participant performed one of four (or two) randomized movements, each corresponding to a different pattern of M1 activation across the 96 channels of the Utah array. In addition, signals from the Utah array changed across experimental sessions due to natural movements of the electrode array in the cortical tissue (hence the necessity to re- train the decoder at each experimental session). Thus, the modulation of M1 firing rates varied across trials and experimental sessions, making a simple threshold on M1 firing not suitable to capture the onset of the participant's motor commands. Furthermore, being used to the response delays of the BMI system and unable to generate natural movements, the participant does not generate strong bursts of M1 activity with a clear onset which could be used for time- locking, but slowly builds up M1 activity, gradually increasing his effort until a movement is generated (see for example firing rates in Fig. 5d). In other words, the best available proxy of the onset of the participant's motor attempt is likely the neural decoder itself, which was optimized to detect complex patterns of activity corresponding to specific movements in each experimental session. + +Besides these technical aspects, there is a more important and interesting conceptual aspect that in our view explains this null result. The analysis presented in the paper was not simply time- locked to the BMI decoder's output, but to an actual sensory event with a clearly perceivable onset, i.e., the onset of the NMES stimulation inducing a hand movement, and the simultaneous onset of a virtual hand movement displayed on the screen. As now more clearly stated in the methods, NMES and visual stimulation invariably followed BMI threshold crossing by a fixed hardware delay. Due to the small variability of such delay (10 ms) compared to the duration of one 8 Hz oscillatory cycle, BMI threshold crossing and movement onset cannot be dissociated in our analyses (the average delay between go cue and BMI threshold crossing is already reported in the previous response). Our analyses thus reveal that it is the 8 Hz phase relative not only to BMI crossing threshold, but also (in our opinion, more importantly) to the onset of the hand movement and reafferent sensory feedback, that correlates with the sense of agency. In other words, the state of the brain in the precise moments preceding the onset of a movement determines the subsequent sense of agency. We have rephrased several paragraphs in the methods to better highlight the technical aspects underlying this reasoning (page 25 and 30): + +"The participant was instructed to start attempting the cued movement when the go cue appeared, without anticipating. During the 4 seconds following the go cue, the BMI algorithm decoded changes in M1 multiunit activity generated by the participant as he attempted the cued movement, and translated them into visual and somatosensory feedback, according to the decoded movement and the feedback congruency assigned for that trial and sensory modality. Somatosensory feedback was delivered by eliciting the target movement through the NMES sleeve, and thus consisted in a functional hand movement. Visual feedback was constituted by an animation of a virtual hand performing the target movement, displayed on a screen placed horizontally to cover the participant's right hand. Note that the participant has sufficient residual proprioception to recognize the hand movement performed even with his real hand being hidden by the screen (see \(^{13,33}\) )." (p. 25) + +"Due to hardware delays, the onset of NMES stimulation followed the end of the 100 ms acquisition bin in which the neural decoder crossed threshold by a stereotyped \(70 \pm 10\) ms (SD) delay." (p. 25) + +"For both LFP and multiunit activity, the data was epoched by time- locking to the onset of hand movements (sensory feedback). The exact timing of the onset of hand movements ( \(70 \pm 10\) ms after the neural decoder + +<--- Page Split ---> + +crossing threshold) was determined by detecting the 50 Hz stimulation artifact induced by the NMES system." (p. 30) + +In sum, we believe that, to observe phase- agency correlations, it is conceptually not appropriate to time- lock our analysis to the crossing of a firing rate threshold. This is because, unlike the crossing of the BMI threshold, the crossing of a firing threshold would be a purely "internal" event, as it would not necessarily be time- locked to an actual salient sensorimotor event, i.e. the onset of a hand movement. Indeed, due to the reasons stated above, there is a significant variability in the delay between M1 firing rate threshold crossing and hand movement/BMI threshold crossing. Put differently, we believe that our analysis worked when synchronized to the decoder crossing threshold not because this moment corresponds to a "special" internal state, but because this moment also corresponds to the onset of an actual movement (excluding an almost fixed hardware delay which was corrected as described above). If a random delay with larger variability (of e.g. 100 ms) had been added between decoder crossing threshold and movement onset, we believe the phase opposition would have been observed only when time- locking to the movement onset, and not to decoder crossing threshold. + +## C17) + +Again, I am surprised that the Readiness Potentials, usually associated with SMA activity, are never present in recordings, either in the patient or in the typical subjects. Probably they have been filtered out given the high- pass with \(0.2\mathrm{Hz}\) . If so I advise to analyse and show them. These potentials are so strong and rich of information about the internal motor state and motor intention of the participants that it may contain already important information about agency. + +## R17) + +Thank you for this interesting suggestion. We cannot exclude that, in our BMI setups, readiness potentials may be weaker than in natural able- bodied movements. Nevertheless, readiness potentials are visible in our data, and should not be affected by the high- pass filtering, since the cutoff frequency is lower than that of typical readiness potentials (notice that in the implanted participant the high- pass filter cannot be removed as it was performed at the hardware level). Readiness potentials were simply not evident in the main text figures due to the scale and aspect ratio of the plots presented in the manuscript. + +We have now analysed readiness potentials hypothesizing that, in addition to the phase effect, a stronger (i.e., more negative) pre- movement deflection would lead to a higher sense of agency. In Experiment 1 the negative deflection constituting the readiness potential started at about - 1.5 s, and the high and low agency signals overlapped until about - 0.5s. After - 0.5s, the two curves slightly dissociate, with a stronger negative deflection for high agency trials. However, this effect was statistically weaker than the phase effect. The minimum p- value for a T- test on the readiness potential between high and low agency trials was 0.002, and did not survive cluster- based correction, compared to 0.0001 for phase opposition (we use p- values to compare effect sizes, since there is no standard way to measure effect size for phase opposition). Also, this effect was not replicated in Experiment 2 or Experiment 3. We have now mentioned this analysis in the results (page 6), and show it in detail in the Supplementary Materials (Fig. S4): + +"As a complementary analysis, we also investigated the relationship between agency and readiness potentials, the negative deflection of the LFP thought to be a correlate of pre- movement neural activity." We observed a trend of higher agency trials associated with a stronger negative deflection of the readiness potential. However, this effect did not survive correction for multiple comparisons (see Fig. S4)." (p. 6) + +<--- Page Split ---> + +We report Fig. S4 and its caption below: + +![PLACEHOLDER_27_0] + + +"Figure S4: analysis of readiness potentials. To decouple slow readiness potentials from phase opposition effects, the data was low pass filtered at 5 Hz, and LFPs/ERPs were compared between high and low agency trials. The panels show LFPs/ERPs for Experiment 1, Experiment 2, Experiment 3 – M1, and Experiment 3 – SMA (left to right). Shades indicate standard errors, the horizontal dashed line at 0 is shown to highlight the negative deflection corresponding to the readiness potential, the vertical dashed line indicates the time of the movement. No difference survived multiple comparison correction across timepoints." + +We are grateful for this suggestion, as these additional results help clarify the differences between the present work and other classic EEG literature on the sense of agency. + +C18) + +Figure 5. Could you split the M1- LFP correlation between high and low agency trials? Did you obtain a difference in the correlation? Low agency may reduce correlation and this would be a stronger and physiological more important effect that the phase difference of LFP. + +## R18) + +Thank you for this insightful suggestion. We have compared the spike- LFP coupling between high and low agency trials in Experiment 1 (the small number of trials in Experiment 2 does not allow to perform the same analysis). We performed the analysis both in the pre- and post- movement 1 second time windows, as smaller time windows would not contain enough spikes to estimate PLV values. We did not observe any striking differences, but there was a slight increase of PLV values for low agency trials at 11 and 12 Hz. This result is contrary to the hypothesis proposed by the reviewer (and our own expectations), it occurs at significantly higher frequencies than 8 Hz, and did not survive multiple comparison correction across frequencies. We now mention the analysis in the results (page 12), and show it in detail in the Supplementary Materials (Fig. S6). + +"Moreover, LFP- spike PLV values did not differ trials between trials of high vs high agency (Fig. S6), suggesting that only the oscillatory 8 Hz phase, but not the amount of coupling between such phase and spiking activity, covaries with agency ratings." (p. 12) + +C19) + +Results of Fig 6 are somewhat disappointing. If anything, the phase opposition seems from Fig 6f stronger around 500 ms post movement. The scale of Fig 6d is not really readable to judge the robustness of the effect. + +R19) + +Please note that Fig. 6e showed results from an example participant, since averaging potentials from all + +<--- Page Split ---> + +participants would not best show the phase opposition effect due to the differences in individual frequency of the effect (see new analyses in Fig. 6f). We have thus changed the visualization of our result, directly showing the output of the permutations used for our statistical analysis. Fig. 6e now shows how the observed phase opposition value lies far from the distribution of phase opposition values obtained by shuffling agency ratings within participants 10000 times. + +C20) + +Why has figure 7f directionally phase effects only on temporal cortex? Blue means that that ROI was not analysed? Please explain. + +R20) + +Thank you for pointing out the potential lack of clarity. Indeed, Fig. 7f (now 7g) shows results on our 114 ROI parcellation only within the temporal cortex, because only the temporal cortex showed significant results for the directionality analysis at the coarser parcellation level of 8 cerebral lobes. We have better clarified this in the main text (p. 18) and in the figure caption (p. 19): + +"To better localise this effect, we performed the same directionality analysis at a finer spatial resolution only within the temporal lobe (the only region showing a significant effect at the coarser spatial resolution), at the scale of the original 114 ROIs used for source reconstruction." (p. 18) + +"(h) P-values for the directionality analysis, as in panel (g), performed only within the temporal lobe at the finer spatial scale of the original source reconstruction (114 ROIs). Dark blue areas indicate ROIs outside the temporal lobe, which were not analysed at this parcellation level." (p. 19) + +Also, to better characterize the spatial features of the connectivity changes, we now also present the results of the previous connectivity analysis at the level of the 114 ROIs in addition to the level of cerebral lobes (Fig. 7d), as reported on page 17: + +"When performing the analysis at a finer spatial scale with 114 ROIs, six regions survived FDR correction: three regions in the middle prefrontal cortex and anterior cingulate, two in the superior part of the posterior parietal cortex, and one region in the anterior temporal cortex (Fig. 7d)." + +We have rephrased passages in the discussion to incorporate these new results, as visible on page 21: + +"Specifically, changes in functional connectivity occurred between SMA and part of the posterior parietal cortex, a region which is has been classically associated with visual guidance of movements \(^{57,58}\) (Fig. 7d). Further connectivity changes were observed between SMA and the medial prefrontal cortex and anterior cingulate, two regions implicated in action selection and initiation \(^{44}\) . These results point at SMA as a key hub in a network of regions classically associated with the sense of agency and are in line with the hypothesis \(^{44}\) that sense of agency may emerge from neural connectivity within such network." + +C21) + +Please make clear if 8Hz is theta or alpha for you.... To me looks like a typical subject alpha band LFP. + +R21) + +We have been careful in phrasing because of considerable debate in the community about the exact definition and limits of frequency bands. In this respect, note that Reviewer 1 instead raised doubts on whether the effect in the implanted participant actually is in the alpha band, and on the coherence of the results between implanted participant and healthy controls based on small frequency discrepancies (see C11). To address this comment, in the revised manuscript we show that the phase effect in healthy participants is tied to the individual alpha peak, following interindividual differences (see R11 and Fig. 6f). We report here the reviewed passage in the results, on page 14: + +<--- Page Split ---> + +"The SMA effect peaked at 9 Hz, close to what was observed in our implanted participant, but was relatively spread across the whole alpha band (Fig. 6d). Since alpha- band peak frequencies vary across individuals \(^{45}\) and correlations of alpha- band activity with behaviour are stronger at frequencies closer to the individual alpha peak \(^{46}\) , we predicted that individual variations in agency- related phase opposition might reflect individual variations in alpha peak frequency. Confirming this prediction, the frequency at which maximal SMA phase opposition was found for each subject correlated with their individual SMA alpha band frequency of maximal power ( \(R = 0.46\) , \(p = 0.011\) , Fig. 6f). This suggests that individual variations in the frequency at which the phase better predicts agency depends on individuals' idiosyncratic alpha band peak." (p. 14) + +Thus, the effect is consistent between the implanted participant and healthy controls when put in relation to the individual spectral peak. Indeed, we believe the position relative to the spectral peak to be a better indicator that these effects may be linked to the same neural phenomenon, rather than the specific frequency in Hertz. + +<--- Page Split ---> + +I thank the authors for their response and the clarifications they gave about their experiment. Despite these clarifications, I maintain reservations regarding the experimental paradigm used and the conclusions that can be drawn from it. + +We thank the Reviewer for the deep review of our paper. We reply point by point below. Our responses are highlighted in bold and changes the revised version of the manuscript reported here are highlighted in red. + +Experiment 2. The authors compared action timing judgments that were given after voluntary and involuntary actions, pooling together operant (Hand closing movement followed by sound) and non- operant (Hand opening movement alone) conditions (page 7 of the rebuttal letter). + +1st issue: pooling together different actions and different conditions. The sense of agency is defined as "the feeling of making something happen" (Haggard, 2017). Here, the authors are mixing together conditions in which (different) actions caused a sound (i.e., the action makes happen a tone) with conditions in which the action did not produce any kind of external feedback (i.e., the action does not make happen a tone). In other words, they considered two very different conditions as equivalent, according to the literature on the sense of agency (see also the next comment. + +We thank the Reviewer for raising these additional points. To demonstrate that our effect is not simply confounded by pooling operant and non- operant trials, we now show in Fig. S7 (reported below) that both the phase and the behavioural effect hold even when only considering the key condition of classical intentional binding studies, operant trials (see pages 11 and 48): + +![PLACEHOLDER_30_0] + +
Figure S7. Main results of Experiment 2 for operant trials only. Panel (a) shows the anticipation of perceived movement timing for voluntary vs involuntary movements ( \(p = 0.011\) , Wilcoxon). Panel (b) shows the phase
+ +<--- Page Split ---> + +opposition product for early vs. late perception of the movement within voluntary operant trials. The red contour denotes the significant cluster of phase opposition \((p = 0.039)\) ." + +In addition, the Reviewer's comment refers to the conditions used in the standard intentional binding paradigm. We would like to restate that our paradigm was inspired by the intentional binding paradigm in that it uses temporal judgements, but differs from it for several reasons, which makes comparison with previous results (and external validation) difficult, as we clearly acknowledged in the discussion (page 22). As far as sense of agency for the hand movement is concerned, as the topic here, we believe that both operant and non- operant conditions can provide meaningful information, and should be included. Importantly, the crucial signal we are studying precedes movement onset, and should not be related to further consequences of the action, which may or may not occur much later, but to the action itself. + +2nd issue: Comparing voluntary vs involuntary actions. The authors compared action timing judgments after voluntary and involuntary (unpredictable) actions. The two conditions clearly differ based on the fact that the passive movement cannot be predicted: "In the involuntary session, the movement was randomly generated via the NMES system". This may explain the delay in action timing judgment observed with respect to voluntary movements. + +The authors correctly cited Haggard et al., 2002 mentioning that this paper compared active and passive movements: indeed, Haggard et al. compared action timing judgements in voluntary vs involuntary actions yet this was done AFTER subtracting for the same measures collected in control conditions: timing judgment for voluntary actions recorded in the action+sound trials compared with timing judgment for voluntary actions recorded in the action- alone trials OR timing judgments for TMS- induced actions recorded in the action + sound trials compared with timing judgments for TMS- induced actions recorded in the action- alone trials, see Table 1 of Haggard et al., 2002). + +In the present Ms, the authors adopted a different approach that cannot control for possible intervening factors not directly related to the agency dimension (e.g., surprise effect by unexpected externally generated muscle twitches). + +Figure 2, shown in Haggard et al., 2017 may help in clarifying my comment (below called "The Figure"). https://www.nature.com/articles/nrn.2017.14 + +The potential confounding effect of surprise was indeed not properly controlled in our first revision. To search for a potential effect of surprise, we have compared tone perception following voluntary and involuntary movements. If the anticipation of the perceived stimulus timing was driven by its predictability in the voluntary condition, as compared to the surprise generated by involuntary movements, we would also observe the same effect also for the tone. We could not detect such an effect \((p = 0.25)\) , as now mentioned in the main text (page 8) and shown in Fig. S5 (reported below). + +<--- Page Split ---> +![PLACEHOLDER_32_0] + + +Control analysis on the perceived time of the sound in the operant condition. The p- value reported is from a Wilcoxon rank sum test, as for all other behavioural analyses in Experiment 2. + +We would also like to point out that, as visible in Noel et al.'s complete report about this experiment, not only does action perception get anticipated in voluntary movements, but intention perception gets postponed when it is followed by an action. This further supports the intention- action binding interpretation, in a condition where surprise cannot play a role, since intention is internally generated and precedes the action. + +Regarding the 1st issue, the authors here are pooling together conditions represented by the fourth (operant condition) and second (non- operant condition) rows of the upper part of the Figure (voluntary- action condition). + +For what concerns the 2nd issue, the authors are comparing the conditions illustrated in the second/fourth row of the upper part of TheFigure with the second/third row of the lower part of The figure. To sum up, the authors of the present Ms are mixing together conditions that, in the intentional binding literature, refer to experimental and control conditions. Accordingly, there is no isolation of the crucial judgements of intentional acts and ensuing consequences. + +We believe that our further analyses directly address these potential issues. Nevertheless, in the revised text we have acknowledged these potentially confounding factors. We have further toned down our interpretation of these findings, focusing strictly on objective facts: in this particular setup, action anticipation was associated with voluntary vs. involuntary movements with the very same 8 Hz phase associated with high agency movements (see pages 8, 9, 11). For example (page 11): + +"Therefore, the same pre- movement 8 Hz oscillatory phase was associated with a higher explicit judgement of agency, and with anticipated action timing perception, which was also observed in voluntary vs. involuntary movements." + +<--- Page Split ---> + +Finally, we restate that, although partially inspired by the intentional binding paradigm, this experiment does not aim at fully reproducing its conditions and effects. + +Experiment 3. In the first version of the paper, the authors acknowledged that participants were invited to "keep the mean (agency) rating around 5". I criticised this approach since it seems that they were actively inviting their subjects to give specific rating values and thus manipulating the dependent variable of the experiment. + +In the revised version of the paper, they now write that participants: "were also asked to focus on the differences between trials rather than on the absolute levels of agency, to provide variable ratings using all the available range, and consider 5 as an intermediate point to distinguish between higher and lower agency levels." + +This is something very different, and I am not sure that such changes from the original to the revised version are acceptable. + +On a related note, they confirmed that no agency manipulation was applied in this experiment. This was aimed at measuring a sort of "intrinsic noise" in agency ratings. I am not sure that such noise can be considered related to the agency dimension since it does not vary according to a specific agency manipulation. + +It is crucial to notice that our instructions, even in their original formulation could potentially only bias average ratings. As clearly stated in our previous response, a bias in participants' average rating would have strictly no effect on our analyses, which are based on a median split between individual trials. The Reviewer then states that our paradigm measures "intrinsic noise" in agency ratings and that "I am not sure that such noise can be considered related to the agency dimension since it does not vary according to a specific agency manipulation". The Reviewer seems to imply that only variations in subjective reports which are linked to external manipulations can be genuinely linked to agency. However, literature about perceptual awareness and pre- stimulus oscillations, which inspired our analyses, is grounded on studies in which variations in subjective reports at fixed experimental conditions are used as the key dependent variable, indicating that variability in subjective reports is not mere "intrinsic noise" but can be meaningfully studied (e.g., Busch et al., J Neurosci, 2009; Hanslmayr et al., Curr Bio, 2013; Ai et al., J Neurophysiol, 2014). This endogenous variability in the ratings can provide important insights into perceptual and cognitive phenomena, directly related to spontaneous fluctuations in the underlying neural activity, without potential confounds due to external manipulations. For example, previous studies used this approach to highlight the role of occipital alpha phase in visual awareness (Mathewson 2009). Here, it allowed us to uncover the role of M1- SMA oscillations for the sense of agency. Importantly, studying endogenous variability in subjective ratings at equal sensory stimulation is arguably the only appropriate approach to study pre- movement signals. Indeed, since a hypothetical agency manipulation on sensory feedback could only affect signals after movement onset, it would be impossible to observe our pre + +<--- Page Split ---> + +movement phase effect by contrasting experimental conditions. Indeed, exogenous manipulations act as a confounding factor for pre- movement signals, so all the effects we report were observed despite the effect of these manipulations, rather than thanks to them. This is another reason for which previous studies try to minimise stimulus variability (see papers cited above). These considerations have been integrated in our manuscript, to better explain and support our paradigm and its rationale on page 28: + +"A similar approach, keeping experimental stimuli constant and contrasting trials based on fluctuations in subjective reports, is the one routinely applied in similar previous studies, investigating the link between perception and pre- stimulus oscillations (e.g., 29- 31)." + +Finally, in my previous comment, I mentioned: "Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small- EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls." + +The authors replied: "Based on the previous literature about the neural bases of the sense of agency (see e.g., Haggard, Nature Neuroscience Reviews, 2017) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12), applying FDR correction for multiple comparisons within this network. This analysis revealed the strongest phase opposition in SMA, and that the second strongest phase opposition in M1 (p = 0.023). If focusing purely on the left M1, with the purpose of replicating the effect observed in the implanted participant, and thus dropping multiple comparisons correction, the uncorrected M1 effect is highly significant with p = 0.003. The uncorrected p- value is not reported for in the text, for being maximally conservative. In sum, phase position was significant in both SMA and M1. For completeness, we also reported the results of a whole- cortex search for phase opposition across all 114 ROIs of the cortex. This whole- cortex search confirmed significant phase opposition in the SMA after adjusting for 114 comparisons; in contrast, M1 did not survive multiple correction. We refrain from making interpretations of the null result for M1 in this whole- cortex search as this analysis is underpowered." I have the following comments: + +1. Haggard 2017 did not mention M1, but temporo-parietal and premotor regions. +2. The whole brain analysis cannot survive a formal multiple comparison correction, and the authors commented on this result as a consequence of low power: I am not sure that this kind of comment is acceptable; given the simplicity of running an EEG experiment in normal controls, there is no excuse for low + +<--- Page Split ---> + +powered experiments. Given that expanding the same sample of subjects at this stage is not acceptable, a replication of this experiment with a fresh sample of subjects could make the whole story more tenable. + +We apologise if our previous submission was confusing about the whole brain analyses, which were presented just as examples and were not performed with the highest statistical power. Indeed, FDR correction was mainly used to support the SMA result, as in our view prior evidence from Experiment 1 and 2 was sufficient to lift the requirement for multiple comparison correction for M1. However, we believe that it is important not to draw conclusions from non- significant results obtained with analyses not offering the highest possible statistical power, and we thus removed FDR- corrected analyses from the text. We would like to clarify that we do indeed have the statistical power and cohort sizes to perform a whole brain analysis. We have now performed the most appropriate analysis for whole brain data, which is cluster- based correction (Maris & Oostenveld 2007). This analysis is the most established one for whole brain effects in EEG or MEG data, as it provides the highest statistical power exploiting regularities in the temporal, frequency or spatial domain. In the revised version of the manuscript, we thus applied cluster- based statistics to all whole brain comparisons (Figs 6 and 7), in order to support our results with "formal whole- brain analysis". Specifically, M1 showed significant whole- brain corrected results, as the cluster formed by the two contiguous regions M1 and SMA was significant as reported on page 14: + +"A cluster of two regions survived multiple comparison correction across all 114 ROIs \((p = 0.04)\) . These regions correspond to the posterior part of the left supplementary motor area (SMA), showing the strongest effect with uncorrected \(p = 0.0002\) , and the left M1 (uncorrected \(p = 0.003\) ), consistent with our results in the implanted participant." + +On these grounds, we hope we have fully addressed the statistical doubts raised by the reviewer, and that the reviewer will agree that replicating the experiment in a fresh sample of participants is no longer necessary. + +On the conceptual level, we do not see major discrepancies between Experiment 3 and previous results. Our key results in Experiment 3 are found in M1 and SMA, a key region for intention and sense of agency, immediately upstream of M1 in the intentional chain, and adjacent and strongly connected to it. As stated in the discussion, SMA was simply not observable in the implanted participant, where we could not decide where to implant the electrodes, but may have presented an even stronger result, if recorded. Actually, it is entirely possible that SMA may be the key origin of the observed effect, driving the effect in M1. + +In any case, since the Reviewer was clearly not convinced by the design and results of Experiment 3, instead of merely replicating it, we decided to re- analyse previous unpublished data based on a classic agency + +<--- Page Split ---> + +manipulation to demonstrate the same agency- related pre- movement phase effect from M1 and SMA. In the experiment, we used a classical (Yes/No) agency rating and a temporal manipulation of visuo- motor delays, whereby movements of a virtual hand could randomly occur before or after the participant's real hand movements to generate variable agency judgements. These data again show significant phase opposition for Yes vs. No agency judgements, localized in the left SMA and M1, further addressing statistical concern about our M1 result in Experiment 3. Due to length constrains in Nature Communications, the replication of our results is briefly mentioned in the main text (page 14, see below) and detailed in the methods (pages 29- 32 and 38) and Supplementary Materials. + +"To further confirm that pre- movement alpha oscillations discriminate high- agency and low- agency actions, we analysed data from an independent cohort of 10 participants, who performed a classic agency judgment paradigm. Briefly, participants were asked to freely lift their index finger, while receiving congruent visual feedback from a virtual hand, superimposed on their own. Visual feedback was delivered at various temporal delays from their actual movement. At the end of each trial, participants were asked to report whether they felt agency or not for the virtual hand. Comparing trials with "yes" vs. "no" agency reports we identified the same phase opposition in alpha in M1 and SMA, thus confirming and further generalizing our results to a different experimental paradigm (Experiment 4, see methods and Fig. S11)." + +We provide a snapshot of the replication of our results (From Fig. S11) in M1 and SMA below: + +![PLACEHOLDER_36_0] + + +Replication of our key results in M1 (top, \(p = 0.027\) ) and SMA (bottom, \(p = 0.0055\) ) in an independent cohort of 10 subjects using a different paradigm. + +We believe these new results, replicating for the fourth time the same phase- opposition effect from M1 and/or SMA, strongly support our main conclusion. + +On a final note, the authors mentioned Wegner as a support to their approach: "Finally, concerning the validation of our Sham BMI approach. As correctly pointed out by Wegner in his mental causation theory, it is entirely possible for healthy individuals to experience a genuine sense of agency even when not truly in + +<--- Page Split ---> + +control of an external event, as we believe was the case in our sham BMI setup." However, please note that this model was based on a "reconstructive" vision of the sense of agency, whereby the agency experience is formed AFTER the execution of the action. This is something different from what the authors are supporting in this paper. + +This is an interesting point. First, we would like to state that we do not wish to take a strong stance in the prediction vs. postdiction debate, since our data does not necessarily support either of these views, and there is increasing support towards the idea that both predictive and postdictive aspects contribute to the sense of agency (e.g., Synofzik 2013). Here, we mainly report that pre- movement signals contribute to the (subsequent) sense of agency, but do not investigate when the subjective feeling of agency arises. We cited Wegner's work as a prominent example that a sense of agency can be experienced regardless of the true causal relationship between motor commands and sensory feedback. However, this is also compatible with a "predictive" view of the sense of agency: if sensory feedback is congruent with expectations, a sense of agency is experienced, regardless of whether that sensory feedback was truly caused by motor commands. This stems from the simple fact that the brain has no direct access to causal relationships, but only to sensorimotor contingencies upon which it infers causalities, as pointed out in the paper aiming to reconcile predictive and postdictive theories (Synofzik 2013). + +Reviewer #2 (Remarks to the Author): + +The authors addressed my main concerns about the technical issue very thoroughly and clearly. I now appreciate well the design of the experiment and I found that the additional analysis that they performed dismissed all the possible criticisms that I raised in the previous version, and I believe that the data strongly support the fact that the phase of pre- movement low- alpha rhythms in M1 and SMA encodes the sense of agency. Given the importance and the novelty of the message, the originality of the technical design and the fact that the intracortical recording in M1 human are rare and precious, I strongly support publication of the manuscript in Nature Communication. + +We thank the Prof. Morrone for her appreciation of our work and the constructive additional feedback. We provide our point- by- point response below, highlighting our responses in bold. + +However, in the present form the manuscript still needs an additional revision to meet the standard of the journal. + +Clarity of the writing: + +1) The introduction is very general and not informative about the state of art of mechanisms and circuits of sense of agency; the same criticism applies to the literature on phase of endogenous oscillations encoding + +<--- Page Split ---> + +motor information. Also about half of the introduction is about the presentation of the logic and result of the experiments, that is not useful for the reader given the complexity of the experiments. In addition, the same data from the same patients have already been published. It is important that the readers know about this in the introduction. The authors should clearly state and describe the results already obtained and published and, if possible, these should be used to motivate this new research. This means a fresh rewrite of most of the introduction. + +Thank you for the suggestion which we hope will make the introduction more useful to readers. We have extensively modified the introduction removing the anticipation of our results, and expanding the presentation of the current state of research for sense of agency and neural oscillations. We have also addressed the link with our previous work in the introduction, rather than in the results as in the previous version of the manuscript. + +2) The language used in the paper to explain analysis procedures is not appropriate, using many technical terms that are used currently in the EEG laboratories, but often mathematical incomplete. One author is an excellent mathematician, and he should check accurately the language. For example equation 1, line 891, they not report what is Wi and in any case as it not mathematically correct. If Wi is the complex number associated with the frequency it should be added the term Arctangent of the imagery/real part...if it is already phase, it cannot be divided by the norm of the phase! Similarly, no indication of the other term in the equation, like the number of trials. Another example in lines 944 and 1335. The Hilbert transform is not needed to calculate the phase at the various frequency. What exactly has been done to calculate it? Another example appearing many times, time-frequency point is a colloquial term: there are maxima energy points or other point that can be marked on other specifications in the time-frequency domain. Please correct. Another example in line 1325. Normalization is associated mathematically to a division, while inspecting the figure there is clearly also a subtraction. Line 243 very mathematically unclear: do you mean that phase is expressed with respect to a different origin? In other words, that the phase has been rotated to take into account the difference in delay respect to experiment 1? In most cases I understood what the authors have done, because it is what normally it is done in EEG or LPF analysis: but please express the procedure in mathematically correct language in these examples and in many other instances. + +Thank you for pointing out these inaccuracies. We provide below a point- by- point summary of our edits to improve the mathematical rigour of methods presentation. + +- Line 891. The formula we used for inter-trial-coherence is the one used in the cited paper (VanRullen 2016): \(\mathrm{ITC}_{\mathrm{ALL}} = |\Sigma_{\mathrm{i} = 1:\mathrm{n}}\omega_{\mathrm{i}} / |\omega_{\mathrm{i}}|| / \mathrm{n}\) (1) + +<--- Page Split ---> + +where \(\omega_{i}\) represents the analytic signal, the complex number whose absolute value is the instantaneous amplitude at a given frequency, and whose argument is the instantaneous phase at that frequency. We apologize that this crucial information was missing from the original manuscript. It has now been added, as well as the indication about the number of trials (see page 33). In words, complex vectors representing amplitude- phase are first normalized to have unit length (division by the norm) and then summed, and the length of the resulting vector is divided by the number of trials. This way, if all phase angles are perfectly aligned, ITC will be equal to 1. If phase angles are random, ITC will be equal to the length of the sum of random vectors, approaching 0 as the number of trials increases, with ITC \(\sim 1 / \text{sqrt}(n)\) , similarly to what observed for Brownian diffusion. + +- Line 944-1335. As done in (Kayser 2009, ref. 41 in the main text), the Hilbert transform, coupled with a causal filter, was used as an alternative way to Morelet wavelets to compute analytic signals \(\omega_{i}\) (then used to compute phase opposition) to demonstrate that the observed effect originates before sensory feedback onset. The signal was first band-passed in the frequency range of interest, then the analytic signal \(\omega_{i}\) was computed from the signal as the complex number whose real part is the original signal, and the imaginary part is the Hilbert transform. We have provided these details in the methods (see page 35). + +- Line 1325. As now stated in the revised figure legend, firing rates were divided by their average on the first 100 ms time bin. Please note that the normalized firing rate values are not visible in the figure, as they were only used to time-lock LFP values (displayed in the figure). + +- Line 243. Sorry for the lack of clarity. We actually meant that we chose to directly plot phase angles at -256 ms (maximal phase opposition for Experiment 1) also for Experiment 2, rather than at the time of maximal phase opposition for Experiment 2 (-342 ms). This aimed at allowing comparison between the two experiments without rotating the phases, which could introduce distortions, and is justified by the fact that phase opposition at -256 ms is strongly significant also in Experiment 2 (see e.g., Fig. 3g., indicating p < 0.0001 for -256 ms). We have clarified this in the text. + +Data analysis: + +The authors assess differences in phases between the two conditions using inter- trial phase coherence and apply an equation that maximize anti- phase difference. However, in principle the system could work in quadrature phase that offers other advantages. It is essential to show that a difference in phase of the 8Hz component of the average LFP between the two conditions is statistically significant and report the value. This can be obtained simply by applying circular statistics across the vector (amplitude and phase) cluster for the two conditions. I think that it is important to consider simultaneously amplitude and phase of the 8 Hz + +<--- Page Split ---> + +oscillation. + +Thank you for raising this interesting point. To simultaneously study amplitude and phase of 8 Hz LFP oscillations, we compared the analytic signals \((\omega_{i})\) for high and low agency trials at 8 Hz, - 256 ms, the time and frequency of strongest phase opposition, without normalizing them to unit length to include amplitude information (figure below). To the best of our knowledge, circular statistics is used for unit length vectors not including amplitude information. We instead used a Hotelling \(T^{2}\) to simultaneously compare phase and amplitude of the LFP. The test was significant \((T^{2}(208) = 21.4, p < 0.0001)\) , indicating that phase differences were significant also when taking into account 8 Hz LFP amplitude. A further T- test on the sole amplitude was not significant \((T(208) = 1.03, p = 0.31)\) , confirming that the observed differences emerge from phase rather than amplitude differences. These results are summarised below and reported on page 34. + +![PLACEHOLDER_40_0] + + +Real (x axis) and imaginary (y axis) part of analytic signals at - 256 ms, 8 Hz for individual trials in Experiment 1, extracted through Morelet wavelets. + +<--- Page Split ---> + +Figure 3h reports LFP amplitude, but it is never defined what exactly it is measured. Is it the amplitude at 8 Hz, so it becomes negative due to the phase? Or it is the value in voltage of the LFP at the time point chosen? Please explain also in the text. + +The figure shows the raw, unfiltered LFP value, as now clarified in the text and figure legend. The analysis aimed demonstrating that pre- movement 8 Hz phase differences are stronger than post- movement raw LFP value differences, to address a concern raised by the other Reviewer. + +Concetta Morrone + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +The authors have dealt adequately to all my criticisms, and I strongly support publication in the present formWe thank again Prof. Morrone for her support of our work and the constructive review process. + +<--- Page Split ---> diff --git a/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..11b8d5d1cf3ff92a0b83ae1f157ad00f881fcf0d --- /dev/null +++ b/peer_reviews/7816c0a37395a208a75a10d26a7144a270efcc7036f929ef918ef8d333711f76/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1192 @@ +<|ref|>title<|/ref|><|det|>[[72, 50, 295, 78]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 910, 211]]<|/det|> +# Pre-movement sensorimotor oscillations shape the sense of agency by gating cortical connectivity + +<|ref|>text<|/ref|><|det|>[[73, 224, 456, 240]]<|/det|> +Corresponding Author: Dr Tommaso Bertoni + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 219, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 404, 238, 417]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 417, 919, 483]]<|/det|> +Bertoni and colleagues investigated the relationship between "alpha oscillations" at the level of M1 and the sense of agency perceived by a tetraplegic individual over specific movements mediated by a brain- machine interface (BMI). In particular, the authors manipulated the congruence between intended and executed actions. The results suggest that "low- alpha" oscillations recorded in M1 during the pre- movement phase were associated with the level of (explicit and implicit) sense of agency (SOA) in the patient during the execution of the experimental tasks. + +<|ref|>text<|/ref|><|det|>[[72, 483, 919, 523]]<|/det|> +This link between pre- movement alpha oscillations and the sense of agency was further supported by an EEG study on healthy controls using a (sham) EEG- BMI setting: this highlighted the role of SMA in the agency experience rather than area M1. + +<|ref|>text<|/ref|><|det|>[[72, 523, 683, 536]]<|/det|> +There are interesting elements of novelty in the Ms. Yet, there are a few problems as well. + +<|ref|>text<|/ref|><|det|>[[72, 548, 912, 614]]<|/det|> +My general impression, also considering recently published work from this group, is that the Authors might be working on a large data- base from multiple experiments, not always preplanned in a concerted manner: some data were probably described also in reference #30. For example, Experiment 1 has already been described in a previous paper, where the authors described the role of area M1 in the agency experience. The authors should therefore better specify the novelty of the present data with respect to the previous ones and how these results might be integrated with the previous paper. + +<|ref|>text<|/ref|><|det|>[[72, 626, 914, 692]]<|/det|> +Coherence. In the present Ms, the reader is forced to learn from multiple different - unvalidated- paradigms tapping the SOA rather than, for example, an orderly attempt to measure the same behavioural variables in a very interesting patient and in a group of normal controls. This is inevitable when moving from implicit to explicit SOA; yet the implicit SOA paradigm could have been the same for the patient and the controls. The implications are that the importance of the non- negligible differences in the results cannot be assessed well. + +<|ref|>text<|/ref|><|det|>[[72, 692, 919, 745]]<|/det|> +The presentation of the data also suffers from a myriad of control analyses on the data, apparently not planned in the methods, that one finds unexpectedly: this makes reading the MS quite cumbersome and a detailed commentary on each and every aspect impossible in a single run of review. I will therefore concentrate on the main points that require clarification before any further consideration. + +<|ref|>text<|/ref|><|det|>[[70, 781, 802, 795]]<|/det|> +I found stylistic, theoretical and methodological issues that should be considered. I'll start with the methods. + +<|ref|>text<|/ref|><|det|>[[73, 821, 231, 835]]<|/det|> +Methodological issues. + +<|ref|>text<|/ref|><|det|>[[72, 847, 912, 912]]<|/det|> +As said, overall, I have the impression that the present drawing from a larger data set might have created some confusion while drafting the MS and surely in the reader as the methods are described sometimes in an incomplete manner: for example, some experimental manipulations or abbreviations are never explained, and so forth. The authors should double- check that all details are provided for a clear comprehension of what was done and for the reproducibility of the procedures and replicability of the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 904, 75]]<|/det|> +Experiment 2. The authors adopted a Libet- like paradigm to measure the implicit component of the sense of agency. The patient performed a movement through BMI, which was followed by a sound. + +<|ref|>text<|/ref|><|det|>[[72, 75, 911, 128]]<|/det|> +According to the intentional binding phenomenon (Haggard et al., 2002), voluntary movements are perceived as shifting in time towards the generated sound, while the sound is perceived as occurring earlier, closer to the action. Based on this phenomenon, the higher this "time compression" that "binds" the voluntary action to its outcome, the stronger an implicit sense of agency for the action and the produced physical outcome. + +<|ref|>text<|/ref|><|det|>[[72, 127, 920, 205]]<|/det|> +Here, the authors only measured the perceived time of the movement onset while ignoring the timing of sound perception. More importantly, they observed the opposite result with respect to the intentional binding phenomenon since voluntary movements were perceived EARLIER in time. This would imply a lower implicit sense of agency, according to the intentional binding phenomenology. The authors discussed this result as a temporal binding between intentions and actions, but they cannot provide any evidence for this explanation; moreover, they do not explain how this binding can be considered a marker of increased implicit sense of agency (the cited reference #30 is a preprint on the very same data). + +<|ref|>text<|/ref|><|det|>[[72, 216, 914, 270]]<|/det|> +Incomplete methods description. There is some missing information in the MS. Figure 3a mentions an "operant movement" condition, which is not described in the text. I assume that there might be a baseline "non- operant movement" condition, in line with the intentional binding paradigm, but I cannot find any information about this. These conditions are mentioned but not described also in Figure S15. + +<|ref|>text<|/ref|><|det|>[[72, 294, 920, 348]]<|/det|> +Experiment 3. According to the main text, participants were instructed to imagine a specific (unknown) right- hand movement, followed by (congruent?) visual feedback. At the end of each trial, they were asked to rate their perceived explicit agency. First, I was wondering how there could be an agency modulation if the movement to imagine and the displayed feedback were always the same. Maybe I missed some details here. + +<|ref|>text<|/ref|><|det|>[[72, 347, 918, 401]]<|/det|> +However, the main issue here is related to the behavioural dependent variable that (i) should validate the use of sham EEG- BMI trials and (ii) should guide the EEG analyses: the agency ratings. These agency judgments were inevitably biased by the experimenters' who warned participants "to keep the mean rating around 5" in the two conditions; for this reason, they cannot represent a valid measure of agency. + +<|ref|>sub_title<|/ref|><|det|>[[72, 425, 202, 438]]<|/det|> +## Data interpretation + +<|ref|>text<|/ref|><|det|>[[72, 438, 897, 477]]<|/det|> +Puzzling interpretation of the LFP data. Exploration of the LFP data, in Figure 3c, suggests that the two curves clearly dissociate AFTER movement execution. I was wondering why the authors concentrate only on minute differences before Time 0 and do not discuss this result. + +<|ref|>text<|/ref|><|det|>[[72, 515, 435, 528]]<|/det|> +The "alfa band" is really the same in all experiments? + +<|ref|>text<|/ref|><|det|>[[72, 528, 914, 593]]<|/det|> +For some reason, the Authors have decided that signals coming from different frequency ranges are the same thing. In the patient, the frequency of the electrical signal measured from area M1 peaks at 6.2 Hz (below the canonical alfa); in the normal controls the peak of the electrical signal measured this time from area SMA peaks at 9- 12 Hz. I am not convinced by this analogy. As said, and unfortunately, because the paradigms used in the patients and in normal controls are not the same these differences are not interpretable. + +<|ref|>sub_title<|/ref|><|det|>[[72, 607, 243, 620]]<|/det|> +## Coherence of the results + +<|ref|>text<|/ref|><|det|>[[72, 620, 917, 686]]<|/det|> +Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small - EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls. + +<|ref|>sub_title<|/ref|><|det|>[[72, 710, 203, 722]]<|/det|> +## Theoretical issues. + +<|ref|>text<|/ref|><|det|>[[72, 722, 920, 880]]<|/det|> +A paper of this magnitude cannot be neutral towards the previous theories on the sense of agency. There are at least three theoretical models proposed to address the arising of the agency experience. The authors seem to consider only one of these nor they do make an effort to discuss whether and why their findings are in support of this specific theory. The "Comparator Model", the only model mentioned in the paper, postulates that the sense of agency arises from a series of comparator processes within the motor control system. However, in an alternative perspective, the "Apparent Mental Causation Theory" proposes that the emergence of the sense of agency is a post hoc and retrospective phenomenon. Accordingly, the sense of agency arises through an inferential sense- making process that occurs after the completion of a movement. Finally, in the "Cue Integration Theory", the sense of agency should arise from integrating low- level cues (sensorimotor proprioceptive and exteroceptive cues) and high- level cues (cognitive cues). The weight assigned to these different cues varies for the implicit and explicit components of agency. Hence, I feel that the authors should try to frame their data considering the previous theoretical and experimental efforts on the very same topic over the last 20 years. + +<|ref|>text<|/ref|><|det|>[[72, 892, 113, 905]]<|/det|> +Style. + +<|ref|>text<|/ref|><|det|>[[72, 918, 911, 945]]<|/det|> +For sure, there is already a broad body of literature investigating the neural correlates of the sense of agency that makes an opening statement in the abstract (".... the underlying neural mechanisms of the sense of agency are still unknown") too + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 923, 88]]<|/det|> +strong for two reasons: (1) the previous evidence connecting brain physiology and the SOA (2) the correlational nature of the evidence provided; this lacks the identification of a clear "mechanism" that causally connects brain physiology and the complex phenomenology of the SOA. + +<|ref|>sub_title<|/ref|><|det|>[[73, 150, 161, 163]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 176, 237, 190]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 202, 920, 296]]<|/det|> +The manuscript by Bertoni et al reports very interesting data and experimental designs. The authors recorded single neurons and LFP from M1 of a tetraplegic patient who, with the help of a prosthetic devise, is able to guide fake- hand reaching movements. The authors correlated the LFP with the reported simulated action of the subject and specifically with his sense of agency, demonstrating a phase dependence of alpha band endogenous oscillation with the sense of agency. To complete the study the authors measured the effect in typical subjects, and used high density EEG coupled with simulation of the moving hand to demonstrate again a phase dependence. Unfortunately and not surprising this data are less compelling with a small and just significant effect. + +<|ref|>text<|/ref|><|det|>[[72, 295, 910, 349]]<|/det|> +While I like the paper and the material presented, I have several unclear and not- discussed technical problems that make me uneasy to give a strong recommendation at this stage. The main one being the synchronization with the prosthetic devise. For this reason I would like to postpone my acceptance/rejection recommendation after a major revision giving the possibility to the authors to explain better their technique and rationale and write a more clear and critical manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[73, 360, 168, 373]]<|/det|> +## Main problem + +<|ref|>text<|/ref|><|det|>[[72, 384, 916, 465]]<|/det|> +Phase depends on the time origin of the synchronisation trigger. Here the authors trust the prosthetic algorithm and set the synchronisation with the onset threshold for the fake- hand movement. However, this relies on a very strong assumption: the algorithm should operate with the same delay for the high and low agency perception. This may be wrong and would be mainly CONTRARY to their data. They show that the agency state signal can be derived from the phase of the LFP and supposedly also the decoding algorithm is using this signal, possibly by introducing a delay (50 ms would be sufficient) to give an apparent phase change. In other words, the argument to me is circular! + +<|ref|>text<|/ref|><|det|>[[72, 464, 918, 542]]<|/det|> +However, the authors have access to single cell firing. A simple threshold to the ensemble recording firing could be used for synchronize the LFP and analyse the change in phase. It is true that they found a strong correlation between pre- movement of fake- hand LFP and neuronal firing. However, the amount of firing may be independent of onset phase. Maybe I misunderstood something, and the tetraplegic patient does not modulate at all M1 firing during Motor Imagery. But if so, this needs to be explained in detail, at least in the methods. In addition the variability of the decoding delay to generate the phantom hand movement needs to be reported! + +<|ref|>text<|/ref|><|det|>[[72, 541, 911, 595]]<|/det|> +Again, I am surprised that the Readiness Potentials, usually associated with SMA activity, are never present in recordings, either in the patient or in the typical subjects. Probably they have been filtered out given the high- pass with 0.2Hz. If so I advise to analyse and show them. These potentials are so strong and rich of information about the internal motor state and motor intention of the participants that it may contain already important information about agency. + +<|ref|>text<|/ref|><|det|>[[72, 605, 910, 646]]<|/det|> +Figure 5. Could you split the M1- LFP correlation between high and low agency trials? Did you obtain a difference in the correlation? Low agency may reduce correlation and this would be a stronger and physiological more important effect that the phase difference of LFP. + +<|ref|>text<|/ref|><|det|>[[72, 645, 911, 688]]<|/det|> +Results of Fig 6 are somewhat disappointing. If anything, the phase opposition seems from Fig 6e stronger around 500 ms post movement. The scale of Fig 6d is not really readable to judge the robustness of the effect. Why has figure 7f directionally phase effects only on temporal cortex? Blue means that that ROI was not analysed? Please explain. + +<|ref|>text<|/ref|><|det|>[[72, 696, 777, 710]]<|/det|> +Please make clear if 8Hz is theta or alpha for you.... To me looks like a typical subject alpha band LFP. + +<|ref|>sub_title<|/ref|><|det|>[[73, 750, 144, 763]]<|/det|> +## Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 775, 218, 789]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 802, 159, 815]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 828, 238, 841]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 841, 904, 868]]<|/det|> +I thank the authors for their response and the clarifications they gave about their experiment. Despite these clarifications, I maintain reservations regarding the experimental paradigm used and the conclusions that can be drawn from it. + +<|ref|>text<|/ref|><|det|>[[72, 879, 900, 920]]<|/det|> +Experiment 2. The authors compared action timing judgments that were given after voluntary and involuntary actions, pooling together operant (Hand closing movement followed by sound) and non- operant (Hand opening movement alone) conditions (page 7 of the rebuttal letter). + +<|ref|>text<|/ref|><|det|>[[70, 931, 870, 946]]<|/det|> +1st issue: pooling together different actions and different conditions. The sense of agency is defined as "the feeling of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 46, 900, 100]]<|/det|> +making something happen" (Haggard, 2017). Here, the authors are mixing together conditions in which (different) actions caused a sound (i.e., the action makes happen a tone) with conditions in which the action did not produce any kind of external feedback (i.e., the action does not make happen a tone). In other words, they considered two very different conditions as equivalent, according to the literature on the sense of agency (see also the next comment. + +<|ref|>text<|/ref|><|det|>[[72, 111, 916, 165]]<|/det|> +2nd issue: Comparing voluntary vs involuntary actions. The authors compared action timing judgments after voluntary and involuntary (unpredictable) actions. The two conditions clearly differ based on the fact that the passive movement cannot be predicted: "In the involuntary session, the movement was randomly generated via the NMES system". This may explain the delay in action timing judgment observed with respect to voluntary movements. + +<|ref|>text<|/ref|><|det|>[[72, 164, 911, 245]]<|/det|> +The authors correctly cited Haggard et al., 2002 mentioning that this paper compared active and passive movements: indeed, Haggard et al. compared action timing judgments in voluntary vs involuntary actions yet this was done AFTER subtracting for the same measures collected in control conditions: timing judgment for voluntary actions recorded in the action+sound trials compared with timing judgment for voluntary actions recorded in the action- alone trials OR timing judgments for TMS- induced actions recorded in the action + sound trials compared with timing judgments for TMS- induced actions recorded in the action- alone trials, see Table 1 of Haggard et al., 2002). + +<|ref|>text<|/ref|><|det|>[[72, 243, 901, 271]]<|/det|> +In the present Ms, the authors adopted a different approach that cannot control for possible intervening factors not directly related to the agency dimension (e.g., surprise effect by unexpected externally generated muscle twitches). + +<|ref|>text<|/ref|><|det|>[[72, 295, 778, 323]]<|/det|> +Figure 2, shown in Haggard et al., 2017 may help in clarifying my comment (below called "The Figure"). https://www.nature.com/articles/nrn.2017.14 + +<|ref|>text<|/ref|><|det|>[[72, 333, 911, 361]]<|/det|> +Regarding the 1st issue, the authors here are pooling together conditions represented by the fourth (operant condition) and second (non- operant condition) rows of the upper part of the Figure (voluntary- action condition). + +<|ref|>text<|/ref|><|det|>[[72, 360, 911, 388]]<|/det|> +For what concerns the 2nd issue, the authors are comparing the conditions illustrated in the second/fourth row of the upper part of The Figure with the second/third row of the lower part of The figure. + +<|ref|>text<|/ref|><|det|>[[72, 387, 891, 427]]<|/det|> +To sum up, the authors of the present Ms are mixing together conditions that, in the intentional binding literature, refer to experimental and control conditions. Accordingly, there is no isolation of the crucial judgements of intentional acts and ensuing consequences. + +<|ref|>text<|/ref|><|det|>[[72, 426, 900, 465]]<|/det|> +Experiment 3. In the first version of the paper, the authors acknowledged that participants were invited to "keep the mean (agency) rating around 5". I criticised this approach since it seems that they were actively inviting their subjects to give specific rating values and thus manipulating the dependent variable of the experiment. + +<|ref|>text<|/ref|><|det|>[[72, 464, 920, 505]]<|/det|> +In the revised version of the paper, they now write that participants: "were also asked to focus on the differences between trials rather than on the absolute levels of agency, to provide variable ratings using all the available range, and consider 5 as an intermediate point to distinguish between higher and lower agency levels." + +<|ref|>text<|/ref|><|det|>[[72, 504, 920, 557]]<|/det|> +This is something very different, and I am not sure that such changes from the original to the revised version are acceptable. On a related note, they confirmed that no agency manipulation was applied in this experiment. This was aimed at measuring a sort of "intrinsic noise" in agency ratings. I am not sure that such noise can be considered related to the agency dimension since it does not vary according to a specific agency manipulation. + +<|ref|>text<|/ref|><|det|>[[72, 567, 920, 607]]<|/det|> +Finally, in my previous comment, I mentioned: "Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. + +<|ref|>text<|/ref|><|det|>[[72, 606, 920, 647]]<|/det|> +Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small - EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls." + +<|ref|>text<|/ref|><|det|>[[72, 646, 920, 808]]<|/det|> +The authors replied: "Based on the previous literature about the neural bases of the sense of agency (see e.g., Haggard, Nature Neuroscience Reviews, 2017) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12), applying FDR correction for multiple comparisons within this network. This analysis revealed the strongest phase opposition in SMA, and that the second strongest phase opposition in M1 (p = 0.023). If focusing purely on the left M1, with the purpose of replicating the effect observed in the implanted participant, and thus dropping multiple comparisons correction, the uncorrected M1 effect is highly significant with p = 0.003. The uncorrected p- value is not reported for in the text, for being maximally conservative. In sum, phase position was significant in both SMA and M1. For completeness, we also reported the results of a whole- cortex search for phase opposition across all 114 ROIs of the cortex. This whole- cortex search confirmed significant phase opposition in the SMA after adjusting for 114 comparisons; in contrast, M1 did not survive multiple correction. We refrain from making interpretations of the null result for M1 in this whole- cortex search as this analysis is underpowered." + +<|ref|>text<|/ref|><|det|>[[73, 807, 286, 820]]<|/det|> +I have the following comments: + +<|ref|>text<|/ref|><|det|>[[72, 819, 920, 894]]<|/det|> +1. Haggard 2017 did not mention M1, but temporo-parietal and premotor regions. +2. The whole brain analysis cannot survive a formal multiple comparison correction, and the authors commented on this result as a consequence of low power: I am not sure that this kind of comment is acceptable; given the simplicity of running an EEG experiment in normal controls, there is no excuse for low-powered experiments. Given that expanding the same sample of subjects at this stage is not acceptable, a replication of this experiment with a fresh sample of subjects could make the whole story more tenable. + +<|ref|>text<|/ref|><|det|>[[72, 905, 914, 947]]<|/det|> +On a final note, the authors mentioned Wegner as a support to their approach: "Finally, concerning the validation of our Sham BMI approach. As correctly pointed out by Wegner in his mental causation theory, it is entirely possible for healthy individuals to experience a genuine sense of agency even when not truly in control of an external event, as we believe was + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 48, 300, 60]]<|/det|> +the case in our sham BMI setup." + +<|ref|>text<|/ref|><|det|>[[73, 61, 916, 101]]<|/det|> +However, please note that this model was based on a "reconstructive" vision of the sense of agency, whereby the agency experience is formed AFTER the execution of the action. This is something different from what the authors are supporting in this paper. + +<|ref|>sub_title<|/ref|><|det|>[[73, 125, 161, 138]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 152, 237, 165]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 165, 918, 245]]<|/det|> +The authors addressed my main concerns about the technical issue very thoroughly and clearly. I now appreciate well the design of the experiment and I found that the additional analysis that they performed dismissed all the possible criticisms that I raised in the previous version, and I believe that the data strongly support the fact that the phase of pre- movement low- alpha rhythms in M1 and SMA encodes the sense of agency. Given the importance and the novelty of the message, the originality of the technical design and the fact that the intracortical recording in M1 human are rare and precious, I strongly support publication of the manuscript in Nature Communication. + +<|ref|>text<|/ref|><|det|>[[73, 245, 840, 272]]<|/det|> +However, in the present form the manuscript still needs an additional revision to meet the standard of the journal. Clarity of the writing: + +<|ref|>text<|/ref|><|det|>[[72, 272, 916, 358]]<|/det|> +1) The introduction is very general and not informative about the state of art of mechanisms and circuits of sense of agency; the same criticism applies to the literature on phase of endogenous oscillations encoding motor information. Also about half of the introduction is about the presentation of the logic and result of the experiments, that is not useful for the reader given the complexity of the experiments. In addition, the same data from the same patients have already been published. It is important that the readers know about this in the introduction. The authors should clearly state and describe the results already obtained and published and, if possible, these should be used to motivate this new research. This means a fresh rewrite of most of the introduction. + +<|ref|>text<|/ref|><|det|>[[71, 359, 920, 540]]<|/det|> +2) The language used in the paper to explain analysis procedures is not appropriate, using many technical terms that are used currently in the EEG laboratories, but often mathematical incomplete. One author is an excellent mathematician, and he should check accurately the language. For example equation 1, line 891, they not report what is Wi and in any case as it not mathematically correct. If Wi is the complex number associated with the frequency it should be added the term Arctangent of the imagery/real part...if it is already phase, it cannot be divided by the norm of the phase! Similarly, no indication of the other term in the equation, like the number of trials. Another example in lines 944 and 1335. The Hilbert transform is not needed to calculate the phase at the various frequency. What exactly has been done to calculate it? Another example appearing many times, time-frequency point is a colloquial term: there are maxima energy points or other point that can be marked on other specifications in the time-frequency domain. Please correct. Another example in line 1325. Normalization is associated mathematically to a division, while inspecting the figure there is clearly also a subtraction. Line 243 very mathematically unclear: do you mean that phase is expressed with respect to a different origin? In other words, that the phase has been rotated to take into account the difference in delay respect to experiment 1? In most cases I understood what the authors have done, because it is what normally it is done in EEG or LPF analysis: but please express the procedure in mathematically correct language in these examples and in many other instances. + +<|ref|>sub_title<|/ref|><|det|>[[73, 565, 172, 578]]<|/det|> +## Data analysis: + +<|ref|>text<|/ref|><|det|>[[72, 592, 907, 673]]<|/det|> +The authors assess differences in phases between the two conditions using inter- trial phase coherence and apply an equation that maximize anti- phase difference. However, in principle the system could work in quadrature phase that offers other advantages. It is essential to show that a difference in phase of the 8Hz component of the average LFP between the two conditions is statistically significant and report the value. This can be obtained simply by applying circular statistics across the vector (amplitude and phase) cluster for the two conditions. I think that it is important to consider simultaneously amplitude and phase of the 8 Hz oscillation. + +<|ref|>text<|/ref|><|det|>[[72, 685, 920, 712]]<|/det|> +Figure 3h reports LFP amplitude, but it is never defined what exactly it is measured. Is it the amplitude at 8 Hz, so it becomes negative due to the phase? Or it is the value in voltage of the LFP at the time point chosen? Please explain also in the text. + +<|ref|>text<|/ref|><|det|>[[73, 724, 197, 736]]<|/det|> +Concetta Morrone + +<|ref|>text<|/ref|><|det|>[[73, 763, 144, 776]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 789, 219, 802]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 815, 161, 828]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 841, 808, 868]]<|/det|> +(Remarks to the Author) The authors have dealt adequately to all my criticisms, and I strongly support publication in the present form + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 123, 905, 220]]<|/det|> +Bertoni and colleagues investigated the relationship between "alpha oscillations" at the level of M1 and the sense of agency perceived by a tetraplegic individual over specific movements mediated by a brain- machine interface (BMI). In particular, the authors manipulated the congruence between intended and executed actions. The results suggest that "low- alpha" oscillations recorded in M1 during the pre- movement phase were associated with the level of (explicit and implicit) sense of agency (SOA) in the patient during the execution of the experimental tasks. + +<|ref|>text<|/ref|><|det|>[[93, 230, 905, 277]]<|/det|> +This link between pre- movement alpha oscillations and the sense of agency was further supported by an EEG study on healthy controls using a (sham) EEG- BMI setting: this highlighted the role of SMA in the agency experience rather than area M1. + +<|ref|>text<|/ref|><|det|>[[93, 287, 766, 303]]<|/det|> +There are interesting elements of novelty in the Ms. Yet, there are a few problems as well. + +<|ref|>text<|/ref|><|det|>[[92, 312, 905, 392]]<|/det|> +We thank the reviewer for their careful revision of our work. Please find our point- by- point response below. We highlighted our responses in bold, and indicated with quotation marks and italics passages reported from the revised text, highlighting changes in red. To allow referring to specific points, we have numbered reviewer comments and our responses (e.g., comment 1: C1; response 1: R1). The numbering continues across comments from the two reviewers. + +<|ref|>sub_title<|/ref|><|det|>[[93, 428, 120, 442]]<|/det|> +## C1) + +<|ref|>text<|/ref|><|det|>[[92, 443, 905, 539]]<|/det|> +My general impression, also considering recently published work from this group, is that the Authors might be working on a large data- base from multiple experiments, not always preplanned in a concerted manner: some data were probably described also in reference #30. For example, Experiment 1 has already been described in a previous paper, where the authors described the role of area M1 in the agency experience. The authors should therefore better specify the novelty of the present data with respect to the previous ones and how these results might be integrated with the previous paper. + +<|ref|>sub_title<|/ref|><|det|>[[92, 550, 120, 563]]<|/det|> +## R1) + +<|ref|>text<|/ref|><|det|>[[92, 564, 905, 675]]<|/det|> +Experiment 1 and 2 represent separate analyses of a comprehensive set of experiments performed in a BMI participant with an M1 implant, and the present work also includes a large separate study in healthy participants, Experiment 3. Some data from Experiment 1 and 2 have been described in two previous studies. The first focused on the role of sensory feedback in explicitly assessed sense of agency and its encoding in post- movement LFPs and multiunit activity (Serino et al., Nat Hum Beh, 2022). The second focused on temporal perception of BMI- mediated actions used as an implicit measure of agency and how this is reflected in M1 activity (Noel et al., Biorxiv, 2023). + +<|ref|>text<|/ref|><|det|>[[92, 685, 905, 844]]<|/det|> +While the two previous works studied the effect of exogenous manipulations on the sense of agency and its neural encoding, the present manuscript focuses on the role of endogenous signals, i.e., the state of the brain before movement onset, which is determined by internal fluctuations rather than external sensory inputs. While exogenous contributions have been extensively studied, reports on the endogenous factors determining the sense of agency are much scarcer in the literature. Specifically, here we investigated the role of pre- movement theta- alpha oscillations in the sense of agency, and their link with M1 spiking activity and whole brain connectivity. To this aim, we applied to Experiment 1 and Experiment 2 completely new analyses on the power and phase of pre- movement oscillations, while previous works focused on LFP amplitude and multiunit activity. The scientific questions and analyses in Experiment 1 and Experiment 2 are thus entirely novel with respect to previously published data. + +<|ref|>text<|/ref|><|det|>[[92, 854, 904, 917]]<|/det|> +Additionally, we designed and performed Experiment 3 specifically to corroborate our findings from the implanted patient in a cohort of healthy participants, to extend our investigation to whole brain signals and to study our hypothesis on brain connectivity, which could not be investigated in the patient data where we recorded only from M1. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 131]]<|/det|> +We have revised our manuscript to clearly acknowledge the use of previously collected data and better explain the novelty of our hypothesis and analysis approach with respect to both previous studies, as visible on pages 3 and 5: + +<|ref|>text<|/ref|><|det|>[[92, 140, 904, 173]]<|/det|> +"Nevertheless, we still lack specific knowledge of the mechanisms leading to the integration of endogenous pre- movement signals with post- movement reafferent information." (p. 3) + +<|ref|>text<|/ref|><|det|>[[92, 181, 905, 279]]<|/det|> +"Data analysed in Experiment 1 were collected as part of a comprehensive set of experiments performed in a BMI participant with an M1 implant. In a previous work, we investigated how post- movement LFP amplitude and multiunit activity in M1 encode exogenous sensory feedback congruency, and how these signals covary with agency judgements for BMI actions 13. Here we conducted novel analyses on these previously collected data focusing on endogenous signals, to test the hypothesis that pre- movement theta- alpha oscillations in M1 predict agency judgements." (p. 5) + +<|ref|>text<|/ref|><|det|>[[92, 287, 904, 319]]<|/det|> +We also now discuss the relation between present results and the previously published findings on page 19: + +<|ref|>text<|/ref|><|det|>[[92, 327, 905, 407]]<|/det|> +"In our previous work 13 (including data from Experiment 1), we showed how post- movement LFPs and multiunit activity in M1 encode congruency between motor commands and sensory feedback, a key aspect in the sensorimotor comparisons underlying the sense of agency. Our findings in Experiment 1 extend these previous results, suggesting that M1 and SMA also play pivotal roles in the sense of agency at an earlier stage, when sensorimotor predictions are computed during motor preparation and before execution." + +<|ref|>text<|/ref|><|det|>[[92, 416, 904, 448]]<|/det|> +This way, we hope to have clarified that the approach, analyses, and results of the present study are entirely novel. + +<|ref|>text<|/ref|><|det|>[[92, 485, 120, 500]]<|/det|> +C2) + +<|ref|>text<|/ref|><|det|>[[92, 501, 905, 580]]<|/det|> +Coherence. In the present Ms, the reader is forced to learn from multiple different - unvalidated- paradigms tapping the SOA rather than, for example, an orderly attempt to measure the same behavioural variables in a very interesting patient and in a group of normal controls. This is inevitable when moving from implicit to explicit SOA; yet the implicit SOA paradigm could have been the same for the patient and the controls. The implications are that the importance of the non- negligible differences in the results cannot be assessed well. + +<|ref|>text<|/ref|><|det|>[[92, 590, 120, 603]]<|/det|> +R2) + +<|ref|>text<|/ref|><|det|>[[92, 605, 905, 734]]<|/det|> +Thank you for giving us the opportunity to better clarify these important aspects. In the present study, we aimed at investigating the role of pre- movement oscillations in modulating the subsequent sense of agency. Although the paradigms used present some differences, mainly due to the necessity of adapting our investigation from an implanted patient to healthy controls, the principle underlying our key phase opposition analysis is applied coherently across these experiments. Across three experiments, we divided trials based on explicit or implicit measures of agency (and not on experimental manipulations, whose impact we tried to minimise or regress out), and studied how the pre- movement oscillatory phases were clustered in the high and low agency groups of trials. + +<|ref|>text<|/ref|><|det|>[[92, 742, 905, 917]]<|/det|> +Both Experiment 1 (whose paradigm is presented in our previously published study, Serino et al., Nat Hum Beh, 2022) and Experiment 3 use classic agency judgements/ratings as measures of agency. Thus, we believe that they measure the same behavioural variable. The main difference between Experiment 1 and Experiment 3 is that the sensory feedback presented to the tetraplegic participant (visual and somatosensory) and able- bodied participants (visual only) are different, due to the difficulty of reliably implementing somatosensory feedback in able- bodied individuals. Any externally implemented movement of the upper limb of a healthy participant, via, for instance, a robotic exoskeleton or functional electrical stimulation, would result in completely different sensory feedback than that produced by the NMES system in our tetraplegic participant (see also below). Said that, importantly our key analysis, phase opposition, was based on a contrast between trials with different subjective reports, and not between experimental conditions. Furthermore, our main result was found in the pre- movement period, so it should be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 130]]<|/det|> +independent from the specific type of sensory feedback used to elicit a sense of agency. Thus, within the scope of the present results, we believe that Experiment 3 represents the closest conceptual replication of Experiment 1 which could be performed in able- bodied individuals. + +<|ref|>text<|/ref|><|det|>[[92, 140, 904, 172]]<|/det|> +Concerning another point made by Reviewer: - "the implicit SOA paradigm could have been the same for the patient and the controls": + +<|ref|>text<|/ref|><|det|>[[92, 182, 905, 421]]<|/det|> +The possibility of reproducing our BMI- based temporal judgement task (Experiment 2) in healthy participants was indeed the object of in- depth discussion in our group, but was finally discarded as it was deemed technically impossible in healthy participants. The crucial point is that, while visual feedback alone can be used to elicit a sense of agency and is thus suitable for explicit judgements (used in Experiment 1 and 3), a combination of visual and somatosensory feedback would be needed for a paradigm based on action timing perception, like in Experiment 2. Indeed, simply judging the timing of BMI- generated virtual hand movements, while observing a clock on the same screen, would result in a purely temporal visual task between the two visual cues (the virtual hand and the clock), independently from judging the time of an action. On the other hand, implementing actual hand movements in healthy participants based on the decoding of motor imagery would instead be technically challenging, requiring either FES stimulation, or using an external exoskeleton. More importantly, these solutions provide sensory feedback that is not comparable to that of a natural arm movement, thus potentially biasing the sense of agency associated to temporal judgement. Finally, these methods are uncomfortable and potentially painful, and may interfere with motor imagery and BMI decoding. Based on these considerations, we now explain our choice to extend Experiment 1 to Experiment 3, rather than Experiment 2, in more detail, on page 14 and 27: + +<|ref|>text<|/ref|><|det|>[[92, 430, 905, 479]]<|/det|> +"To investigate the potential contribution of areas beyond M1, in Experiment 3, we devised an EEG- based version of Experiment 1, which we believe to be the closest conceptual extension of that paradigm achievable in healthy participants." (p. 14) + +<|ref|>text<|/ref|><|det|>[[92, 488, 905, 616]]<|/det|> +"When extending our investigation to healthy participants, we chose to focus on the paradigm of Experiment 1 rather than the one of Experiment 2, as we believe that producing genuine temporal binding effects in a BMI setup would require externally inducing a real upper limb movement following BMI decoding, which is hardly feasible in healthy participants and produces sensory feedback that is not comparable to natural movements. On the other hand, simply using virtual movements on a screen would result in a purely visual temporal judgement task between two visual events (the virtual arm and the clock), without necessarily implying any temporal estimation about actions, thus providing no information about the sense of agency." (p. 27) + +<|ref|>text<|/ref|><|det|>[[92, 625, 905, 673]]<|/det|> +For the validation of the implicit task described in Experiment 2, and of the sham BMI paradigm of Experiment 3, please refer to our detailed responses in subsequent points of the present response letter (R5 and R9). + +<|ref|>text<|/ref|><|det|>[[92, 683, 905, 747]]<|/det|> +We further conducted new analyses and rephrased passages in the results and discussions to better support the coherence of our results between the implanted patient and healthy controls, namely the frequency and anatomical localisation of the phase opposition effect. Please refer to the detailed responses to the relative comments (R11 and R12). + +<|ref|>text<|/ref|><|det|>[[92, 756, 905, 852]]<|/det|> +To conclude, we agree with the reviewer that differences in our setups, mainly required by the uniqueness of our implanted participant, may have made the comparison of our results more difficult, and we thank the reviewer for giving us the opportunity to better address this point as presented in R11 and R12. On the other hand, we believe that these differences allowed us to show that pre- movement oscillations consistently predicted the subsequent sense of agency in different cohorts of subjects, using different recording techniques and behavioural paradigms, speaking in favour of the generality of our results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 120, 97]]<|/det|> +C3) + +<|ref|>text<|/ref|><|det|>[[92, 99, 905, 163]]<|/det|> +C3)The presentation of the data also suffers from a myriad of control analyses on the data, apparently not planned in the methods, that one finds unexpectedly: this makes reading the MS quite cumbersome and a detailed commentary on each and every aspect impossible in a single run of review. I will therefore concentrate on the main points that require clarification before any further consideration. + +<|ref|>sub_title<|/ref|><|det|>[[92, 174, 120, 188]]<|/det|> +## R3) + +<|ref|>text<|/ref|><|det|>[[92, 189, 905, 268]]<|/det|> +R3)To avoid that control analyses impact the readability of the main text of the manuscript, we have streamlined their presentation, describing control analyses and their rationale in the methods (pp. 31, 32, 33, 34, 35) and removing unnecessary references to supplementary figures from the results section. Since we believe that these control analyses still represent an added value, demonstrating the solidity of our results, we have chosen to keep the original control analyses in the supplementary figures. + +<|ref|>text<|/ref|><|det|>[[92, 302, 903, 318]]<|/det|> +I found stylistic, theoretical and methodological issues that should be considered. I'll start with the methods. + +<|ref|>text<|/ref|><|det|>[[93, 351, 264, 366]]<|/det|> +Methodological issues. + +<|ref|>text<|/ref|><|det|>[[92, 402, 120, 416]]<|/det|> +C4) + +<|ref|>text<|/ref|><|det|>[[92, 418, 905, 497]]<|/det|> +C4)As said, overall, I have the impression that the present drawing from a larger data set might have created some confusion while drafting the MS and surely in the reader as the methods are described sometimes in an incomplete manner: for example, some experimental manipulations or abbreviations are never explained, and so forth. The authors should double- check that all details are provided for a clear comprehension of what was done and for the reproducibility of the procedures and replicability of the results. + +<|ref|>sub_title<|/ref|><|det|>[[92, 507, 120, 520]]<|/det|> +## R4) + +<|ref|>text<|/ref|><|det|>[[92, 522, 905, 570]]<|/det|> +R4)Indeed, we have realized that some details of experimental procedures and methods were not sufficiently clear and improved their presentation. We have improved the revised methods, figures and figure captions to better explain these details (pp. 7, 10, 24, 25, 26, 27, 28, 29, 30). + +<|ref|>text<|/ref|><|det|>[[92, 606, 120, 620]]<|/det|> +C5) + +<|ref|>text<|/ref|><|det|>[[92, 622, 905, 717]]<|/det|> +C5)Experiment 2. The authors adopted a Libet- like paradigm to measure the implicit component of the sense of agency. The patient performed a movement through BMI, which was followed by a sound. According to the intentional binding phenomenon (Haggard et al., 2002), voluntary movements are perceived as shifting in time towards the generated sound, while the sound is perceived as occurring earlier, closer to the action. Based on this phenomenon, the higher this "time compression" that "binds" the voluntary action to its outcome, the stronger an implicit sense of agency for the action and the produced physical outcome. + +<|ref|>text<|/ref|><|det|>[[92, 726, 905, 838]]<|/det|> +Here, the authors only measured the perceived time of the movement onset while ignoring the timing of sound perception. More importantly, they observed the opposite result with respect to the intentional binding phenomenon since voluntary movements were perceived EARLIER in time. This would imply a lower implicit sense of agency, according to the intentional binding phenomenology. The authors discussed this result as a temporal binding between intentions and actions, but they cannot provide any evidence for this explanation; moreover, they do not explain how this binding can be considered a marker of increased implicit sense of agency (the cited reference #30 is a preprint on the very same data). + +<|ref|>sub_title<|/ref|><|det|>[[92, 849, 120, 862]]<|/det|> +## R5) + +<|ref|>text<|/ref|><|det|>[[92, 864, 905, 895]]<|/det|> +R5)Here the Reviewer is raising a few related points, and we are grateful as it would allow us to clarify our approach. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 243]]<|/det|> +First, and main point: while our paradigm is inspired by the intentional binding task, as well as to the Libet experiment, the uniqueness of our BMI setup and design resulted in a new paradigm, allowing us to investigate a new form of binding between intention and action that differs from the classical intentional binding between action and effect. A full analysis and discussion of the intentional binding effect in this setup are the focus of the previous work by our group cited in the present manuscript (Noel et al., Biorxiv, 2023, currently under review at Current Biology), and goes beyond the aim of the present study. To better reflect the uniqueness of our setup, we have rephrased the introduction of Experiment 2, and now describe our paradigm as an implicit agency paradigm based on time perception. In particular, the difference between the perceived time of actions preceded by subject's intention to move and those passively implemented is taken as on index of the sense of agency. See page 8: + +<|ref|>text<|/ref|><|det|>[[92, 251, 905, 364]]<|/det|> +"The previous analyses establish a relationship between pre- movement low- alpha oscillations and explicit agency judgements. We next tested whether the same phase opposition can distinguish between high vs. low agency actions as defined from an implicit marker of agency based on the subjective perception of the timing of self- initiated movement 32. Leveraging our BMI setup, in a previous study, we have shown that temporal judgements of voluntary actions triggered by the participant's intention to move are anticipated compared with involuntary actions triggered by NMES, resulting in a temporal compression between the intention to move and the action 32. + +<|ref|>text<|/ref|><|det|>[[91, 370, 905, 594]]<|/det|> +The experimental paradigm and temporal compression results are extensively reported in our previous work 32. Below we provide a brief summary of the methods and findings in the subset of conditions relevant to this study. A rotating clock was displayed on a screen, and the participant was asked to report the position of the clock at the onset of a hand movement triggered by the NMES system (Fig. 3a). In the voluntary session, the action was triggered by the participant's intention to move as decoded by the BMI system. In the involuntary session, the movement was randomly generated via the NMES system without motor intention. The participant perceived voluntary BMI- generated movements as occurring earlier relative to their actual timing than involuntary movements (median voluntary \(= - 497.8 \pm 299\) ms interquartile range, median involuntary \(= - 384 \pm 185\) ms, Wilcoxon \(p = 0.033\) , Fig. 3b). We thus leveraged this finding to classify trials associated with putatively higher agency, as those showing stronger intention- action temporal compression, and trials with putatively low- agency as those showing weaker temporal compression. To this aim, we performed a median split of trials within the voluntary session based on the amount of anticipation and computed the phase opposition product between trials in which the movement was perceived earlier (high agency) and trials in which the movement was perceived later (low agency)." + +<|ref|>text<|/ref|><|det|>[[91, 600, 905, 760]]<|/det|> +A second point by the Reviewer is that we focus our analysis on movement timing, not analysing effect timing, i.e., the tone. Please note that the perceived time of the tone and intention was also collected in this participant as reported in Noel et al.'s paper. However, to be consistent with Experiment 1, the analysis on pre- movement phase has to be time- locked to action onset. Therefore, also in Experiment 2 we focused on trials where action timing was reported. Indeed, time- locking the phase opposition analysis to the effect would include post- movement signals. On the other hand, it would be arbitrary to time- lock the analysis to the intention, as there is no objective timing for it. In sum, reports about intention and event go beyond the scope of the present manuscript, but they are the focus of Noel et al.'s paper. Thus, we prefer to cite these results in our manuscript rather than reporting them again in full. We now motivate our choice to focus on action timing in the methods, on page 26: + +<|ref|>text<|/ref|><|det|>[[92, 769, 905, 833]]<|/det|> +"Experiment 2 is part of a comprehensive set of experiments in which the intentional chain was manipulated, and reports about the perceived timing of intention, action and effect were collected 32. For consistency with Experiment 1, where the analysis was time- locked to action onset, we focused on conditions where action timing was reported." + +<|ref|>text<|/ref|><|det|>[[92, 842, 905, 907]]<|/det|> +A third point concerns the different effects between the classic intentional binding and our new intention- action compression. The paper by Noel et al focuses on a full analysis and discussion on the full "intentional chain", i.e., the relationship between intention- action- effect as highlighted by temporal judgement. For convenience, we summarize their findings and interpretation in the following lines. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 195]]<|/det|> +As highlighted above, with our tetraplegic participant, we observed that voluntary actions are perceived as happening earlier in time than involuntary ones. This was true regardless of whether these actions were or were not followed by a tone (Row I and IV vs II in Fig. 1 from Noel's paper, reported below). Importantly, the perceived time of intention was instead postponed when motor commands led to a bodily action compared to no action (Rows I and IV vs III). Thus, perceived timing of will and action seemed to be pulled towards each other when they happened in the same timeline, similarly to what observed for action and effect in classical intentional binding effects. + +<|ref|>text<|/ref|><|det|>[[92, 204, 904, 237]]<|/det|> +We report here Fig. 1 from Noel et al.'s paper, showing the perceived time of intention (red), action (green) and effect (blue) in six different types of intentional chain: + +<|ref|>image<|/ref|><|det|>[[112, 245, 475, 432]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[228, 435, 398, 448]]<|/det|> +
Time from A onset (ms)
+ +<|ref|>text<|/ref|><|det|>[[91, 460, 905, 715]]<|/det|> +As reported in Noel's paper, this result was interpreted in the perspective of a recent computational accounts of intentional binding (Legaspi et al., Nature Communications, 2019), suggesting that perceived timing compression should occur not only between actions and their consequences, but between any pair of events that the brain determines to be causally related, such as intentions/motor commands and actions. Due to the inherent noise of neural recordings and decoding, BMI movements show a significant and variable delay \((\sim 1.2 \pm 0.48 \text{SD}, \text{see p. 24 of revised text})\) between motor commands and actions, so that the exact timing of the movement is subjectively hard to predict. When our patient executed voluntary movements, such delay got possibly "compressed" by perceived causality, as compared to involuntary movements. That this action- intention compression was not reported in classical intentional binding studies is unsurprising. First, no previous study systematically assessed the perceived time of intention and action in able bodied individuals. Second, the action anticipation effect might not be evident in healthy participants because the delay between motor commands and movements is arguably much shorter and subjectively more predictable than in our BMI setup. This possibly results in a smaller binding compared to the one occurring between action and effect, leading to perceive the action as occurring later. In our patient instead, due to the longer and unpredictable delays, intention- action compression may dominate over action- effect binding, leading to overall action anticipation. + +<|ref|>text<|/ref|><|det|>[[92, 724, 905, 773]]<|/det|> +In sum, we believe Noel's paper to be the most appropriate source of validation for our implicit index, and we have rephrased the presentation of Experiment 2 to better introduce such previous validation on page 8: + +<|ref|>text<|/ref|><|det|>[[92, 782, 905, 830]]<|/det|> +"Leveraging our BMI setup, in a previous study, we have shown that temporal judgements of voluntary actions triggered by the participant's intention to move are anticipated compared with involuntary actions triggered by NMES, resulting in a temporal compression between the intention to move and the action \(^{32}\) ." + +<|ref|>text<|/ref|><|det|>[[92, 839, 905, 920]]<|/det|> +Finally, the Reviewer expresses concern for the lack of an external validation as a marker of agency. In this regard, we wish to highlight that our approach is aligned with that adopted in the original intentional binding paper by Haggard et al., Nature Neuroscience, 2002. In that study, the conclusion that the temporal shift is an implicit marker of agency was drawn based on the observation that such a shift occurred in voluntary vs. involuntary movements. Here, we applied the same logic, taking the temporal shift occurring + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 243]]<|/det|> +in voluntary movements compared to involuntary ones (action anticipation) as an implicit marker of the sense of agency. Importantly, not only did we observe the same effect of \(8 \text{Hz}\) pre- movement phase as in Experiment 1, but the phase relation was the same. In other words, restricting ourselves to facts without any interpretation, anticipated action perception was associated with precisely the same \(8 \text{Hz}\) phase preceding explicit judgements of high agency in Experiment 1, and with voluntary movements compared to involuntary ones in Experiment 2. Although internal to our participant (due to the uniqueness of the setup), we believe the coherence of these results supports the interpretation that, in our setup, action anticipation is an implicit marker of higher agency. Still, we agree that the lack of external validation, due to the uniqueness of our setup, constitutes a limitation, as now acknowledged in a new limitations paragraph on page 22: + +<|ref|>text<|/ref|><|det|>[[92, 252, 904, 300]]<|/det|> +"Our unique BMI set up enabled us to relate pre- movement phase opposition to the temporal compression between intention and action observed for voluntary actions. More studies are needed to validate this intention- action compression as an implicit marker of agency." + +<|ref|>text<|/ref|><|det|>[[92, 310, 904, 342]]<|/det|> +We have further toned- down the following passages in the introduction and results to reflect the putative state of such marker of agency, as visible on pages 4 and 8: + +<|ref|>text<|/ref|><|det|>[[92, 351, 904, 383]]<|/det|> +"In Experiment 2, we showed that these oscillations also predicted the temporal binding between intentions and actions, a putative implicit measure of the sense of agency \(^{32}\) " (p. 4) + +<|ref|>text<|/ref|><|det|>[[92, 392, 905, 440]]<|/det|> +"We thus leveraged this finding to classify trials associated with putatively higher agency, as those showing stronger intention- action temporal compression, and trials with putatively low- agency as those showing weaker temporal compression." (p. 8) + +<|ref|>text<|/ref|><|det|>[[92, 472, 120, 485]]<|/det|> +C6) + +<|ref|>text<|/ref|><|det|>[[92, 488, 905, 550]]<|/det|> +Incomplete methods description. There is some missing information in the MS. Figure 3a mentions an "operant movement" condition, which is not described in the text. I assume that there might be a baseline "non- operant movement" condition, in line with the intentional binding paradigm, but I cannot find any information about this. These conditions are mentioned but not described also in Figure S15. + +<|ref|>text<|/ref|><|det|>[[92, 559, 120, 572]]<|/det|> +R6) + +<|ref|>text<|/ref|><|det|>[[92, 574, 905, 700]]<|/det|> +We apologize for the lack of clarity. Indeed, to study the full intentional chain (as done in Noel et al., Biorxiv, 2023) two types of movements were used. One (hand closing, operant movement) led to a tone being produced 300 ms later, and the other (hand opening, non- operant movement) was not followed by a tone. Since the focus of the present manuscript is pre- movement signals, occurring before the timeline of operant and non- operant movements bifurcate, we pooled operant and non- operant movements in our analyses. The differential effects of operant and non- operant movements in temporal judgements are presented Noel et al. (Biorxiv, 2023). We now have better explained these aspects in the methods on page 26: + +<|ref|>text<|/ref|><|det|>[[92, 709, 905, 805]]<|/det|> +"Movements were triggered by the activation of the neural decoder, but the NMES was always activated congruently with decoded motor commands. Additionally, 300 ms after HC was executed, a 1000 Hz "beep" was produced, lasting 100 ms (operant condition). No additional consequence followed HO execution (non- operant condition). Here, we focused on pre- movement signals, occurring before the differentiation between operant and non- operant trials, and our key contrast is between the voluntary and involuntary session. Thus, we pooled trials from the operant and non- operant conditions in the present analyses." + +<|ref|>text<|/ref|><|det|>[[92, 814, 905, 861]]<|/det|> +To increase the readability of the results section, we removed references to operant and non- operant conditions from Fig. 3, as the two conditions were pooled in the analyses and the purpose of the figure is to present the behavioural contrast between voluntary and involuntary movements. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 120, 97]]<|/det|> +C7) + +<|ref|>text<|/ref|><|det|>[[92, 100, 904, 147]]<|/det|> +Experiment 3. According to the main text, participants were instructed to imagine a specific (unknown) righthand movement, followed by (congruent?) visual feedback. At the end of each trial, they were asked to rate their perceived explicit agency. + +<|ref|>sub_title<|/ref|><|det|>[[92, 158, 120, 171]]<|/det|> +## R7) + +<|ref|>text<|/ref|><|det|>[[92, 173, 904, 221]]<|/det|> +As described in the methods, participants had to imagine a continuous squeezing effort of their right hand. Visual feedback showed the virtual hand closing in all trials, so the feedback was always "spatially" congruent with the imagined movement. The text has now been revised to improve clarity (page 27): + +<|ref|>text<|/ref|><|det|>[[92, 230, 904, 277]]<|/det|> +"For motor imagery, they were asked to imagine the physical sensation of squeezing their right hand. They had to imagine a continuous and strong squeezing effort, as if they were on the verge of making a movement, but without contracting the arm, shoulder, or face muscles." + +<|ref|>text<|/ref|><|det|>[[92, 288, 120, 301]]<|/det|> +C8) + +<|ref|>text<|/ref|><|det|>[[92, 312, 904, 344]]<|/det|> +First, I was wondering how there could be an agency modulation if the movement to imagine and the displayed feedback were always the same. Maybe I missed some details here. + +<|ref|>sub_title<|/ref|><|det|>[[92, 355, 120, 368]]<|/det|> +## R8) + +<|ref|>text<|/ref|><|det|>[[91, 370, 905, 608]]<|/det|> +Experiment 3 was designed based on our hypothesis on pre- movement oscillations and findings from Experiment 1 and 2, suggesting that even in the absence of external manipulation, variability in agency ratings for BMI actions is to be expected, and such variability should be (at least in part) explained by the pre- movement endogenous phase, which is independent from sensory feedback. In this sense, note that the phase effect in Experiment 1 held even at fixed sensory feedback congruency (Fig. 2g) and is thus purely endogenous. Thus, the goal of Experiment 3 was not to measure the effect of exogenous manipulations on the sense of agency induced by sensory feedback, already broadly studied (e.g., Serino et al., Nature Human Behaviour, 2022, Marchesotti et al., Human Brain Mapping, 2017; Evans at al., PLoS One, 2015), but to study the link between "residual" variability in agency ratings which does not depend on external manipulations but on endogenous pre- movement oscillations. To effectively do this, we aimed creating a setup in which, at a given sensory feedback, the sense of agency is uncertain and variable, and thus more likely to depend on endogenous factors such as the pre- movement phase. If we simply asked participants to perform actual movements and rate their sense of agency, agency ratings would be constantly very high and no meaningful variability would be observed, therefore we used a BMI setup. We expanded the description of the task in the methods to better explain its rationale on page 28: + +<|ref|>text<|/ref|><|det|>[[92, 617, 904, 666]]<|/det|> +"The aim of the experiment was to induce a trial- by- trial varying sense of agency with minimal exogenous manipulations, and independently from sensory feedback, to highlight the role of endogenous neural oscillations in modulating agency ratings." + +<|ref|>text<|/ref|><|det|>[[92, 675, 905, 835]]<|/det|> +For these reasons, participants were asked to imagine squeezing their right hand to generate virtual movements of a hand closing. Visual feedback was always the same and "spatially" congruent with the imagined movement. To keep agency uncertain and not have a stereotyped task, we randomly manipulated the temporal delay between go cue and sensory feedback. Importantly, our key analysis was based on contrasting high and low agency trials based on participant's reports, and not on the exogenous delay manipulation, to maximize the effect of endogenous factors such as the pre- movement phase. Indeed, since the pre- movement phase is endogenous and cannot depend on externally determined post- movement conditions, external manipulations may actually confound the phase effect, and were thus kept at a minimum and regressed out from the agency ratings before the phase opposition analysis, as stated in the methods on page 33: + +<|ref|>text<|/ref|><|det|>[[92, 844, 904, 876]]<|/det|> +"To remove the effect of such exogenous factor, we regressed out the effect of delay on agency ratings within each participant before splitting trials and computing POP values." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 85, 120, 98]]<|/det|> +C9) + +<|ref|>text<|/ref|><|det|>[[93, 100, 905, 163]]<|/det|> +However, the main issue here is related to the behavioural dependent variable that (i) should validate the use of sham EEG- BMI trials and (ii) should guide the EEG analyses: the agency ratings. These agency judgments were inevitably biased by the experimenters' who warned participants "to keep the mean rating around 5" in the two conditions; for this reason, they cannot represent a valid measure of agency. + +<|ref|>sub_title<|/ref|><|det|>[[93, 174, 120, 188]]<|/det|> +## R9) + +<|ref|>text<|/ref|><|det|>[[92, 189, 905, 300]]<|/det|> +We are sorry that the too original description of our instructions, which was too concise, has generated a misunderstanding. Our instructions clearly explained to the participants to use 5 as an "anchor" between the highest and the lowest agency trials, and to focus on the differences between trials to provide variable ratings spanning the whole scale. This was to avoid having participants constantly reporting the extreme value of the scale, which was noted in few pilot subjects who always reported very high agency, hindering meaningful splitting of trials for phase opposition analyses. We have now rephrased the passage to better reflect the detailed instructions provided to participants on page 29: + +<|ref|>text<|/ref|><|det|>[[92, 309, 905, 389]]<|/det|> +"Before the experiment, subjects were instructed to focus on pre- reflexive aspects of the control experience, and not to use cognitive reasoning to provide the ratings. They were also asked to focus on the differences between trials rather than on the absolute levels of agency, to provide variable ratings using all the available range, and considering 5 as an intermediate point to distinguish between higher and lower agency levels." + +<|ref|>text<|/ref|><|det|>[[92, 398, 905, 479]]<|/det|> +Importantly, even if the instructions had affected the average agency rating (anchoring it for instance around 5), this would be irrelevant for our analysis, as it would not affect the subset of trials being assigned to the "high" or "low" agency condition based on participant's rating. Thus, we believe that the agency ratings collected during our experiment are appropriate for our EEG analyses. We included these considerations to the methods on page 29: + +<|ref|>text<|/ref|><|det|>[[92, 488, 904, 520]]<|/det|> +"Note that a potential bias in average ratings due to using 5 as a reference value cannot affect the results of our analyses, which are always based on relative agency ratings, compared within participants." + +<|ref|>text<|/ref|><|det|>[[92, 529, 905, 672]]<|/det|> +Finally, concerning the validation of our Sham BMI approach. As correctly pointed out by Wegner in his mental causation theory, it is entirely possible for healthy individuals to experience a genuine sense of agency even when not truly in control of an external event, as we believe was the case in our sham BMI setup. To validate this, we compared agency ratings between sham and actual BMI trials, and found no significant difference (Fig. S7). The reasonings reported above concerning the instructions given to the participants apply also in this case. Indeed, even if the instructions biased average ratings towards 5, there would be no reason to expect that such bias would be different between sham and BMI trials. Since the comparison of ratings to validate the sham setup is done within participants, we believe it cannot be affected by such potential bias. + +<|ref|>text<|/ref|><|det|>[[92, 682, 904, 714]]<|/det|> +We expanded and clarified passages about the rationale and validation of our sham setups in the methods on pages 28 and 33: + +<|ref|>text<|/ref|><|det|>[[92, 723, 905, 882]]<|/det|> +"We chose to use sham BMI as the main experimental condition, as it allowed us to reliably produce the illusion that the participant is controlling the virtual hand, while being less subject to fatigue and decoder variability than real BMI. This allowed us to collect a large and constant number of trials, regardless of each participant's proficiency with BMI. The illusion was made possible by the fact that in EEG- BMI delays are long, and require a prolonged and continuous effort lasting several seconds to reach the decoding threshold. Therefore, even when truly controlling the BMI, the participant could not predict the exact timing of the movement, and thus habituated to experience control for delayed and temporally unpredictable movements. If the movement is provided at a randomized delay comparable to the intrinsic delay of the BMI system (hence the careful adjustment of decoding thresholds after BMI training), a sham BMI trial is hardly distinguishable from a real BMI trial." (p. 28) + +<|ref|>text<|/ref|><|det|>[[92, 892, 904, 924]]<|/det|> +"We assessed the validity of the sham- BMI setup, by testing whether sham and real BMI trials could be distinguished by participants and led to different agency levels. We found that sham BMI and real BMI + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 147]]<|/det|> +trials elicited comparable agency levels (mean sham BMI \(5.75 \pm 0.13\) SEM, mean real BMI \(5.57 \pm 0.21\) SEM, \(p = 0.33\) , Fig. S7). In addition, when told that they were truly in control of the virtual hand only in self- paced trials, at the end of the experiment, all subjects reported that they were not aware of it. Thus, participants were not aware of the sham BMI setup, and believed to be causing the hand movement." (p. 33) + +<|ref|>text<|/ref|><|det|>[[93, 172, 242, 187]]<|/det|> +Data interpretation. + +<|ref|>text<|/ref|><|det|>[[93, 198, 130, 211]]<|/det|> +C10) + +<|ref|>text<|/ref|><|det|>[[93, 214, 905, 260]]<|/det|> +Puzzling interpretation of the LFP data. Exploration of the LFP data, in Figure 3c, suggests that the two curves clearly dissociate AFTER movement execution. I was wondering why the authors concentrate only on minute differences before Time 0 and do not discuss this result. + +<|ref|>sub_title<|/ref|><|det|>[[93, 272, 130, 285]]<|/det|> +## R10) + +<|ref|>text<|/ref|><|det|>[[92, 287, 906, 590]]<|/det|> +We thank the reviewer for giving us the opportunity to discuss these important aspects. The pre- movement phase opposition appears small to visual inspection in the plots reporting trial- averaged traces (in Figs. 2c and 3c) because the trial- averaged LFP trace is not suited to visually highlight phase opposition effects, as it conflates in a non- separable way the effects of phase and amplitude of the LFP. To provide a better visualization of the contribution of phase and amplitude in discriminating between movement perceived early and perceived late, we now complement the trial- averaged LFP plot of Fig. 3c (and 2c) with plots of single- trial phase and amplitudes. To visually appreciate the phase effect, in Fig. 3d (reported below, also see the analogous Fig. 2d for Experiment 1), we plot the instantaneous phase for individual trials throughout the entire trial, highlighting (black dashed lines) the pre- movement phase opposition window of the alpha band for early vs. late movement perception. To illustrate the effects of amplitude, we also plot in Fig 3h individual- trial LFP amplitude, showing that early vs late differences are larger and more reliable in the post- movement than in the pre- movement period. However, these differences is less strong and reliable than differences in the pre- movement phase. In Fig. 3i we plot the histograms of post- movement LFP amplitude values across all trials for the early and late condition, at the timepoint of maximal difference between early and late trials. Further, there is considerably more overlap between the distributions of post- movement LFP amplitude (Fig. 3i) at the post- movement time with the strongest early- late discriminability than between the distributions of 8 Hz phase at the pre- movement time with highest early- late discriminability (Fig. 3f). Thus, pre- movement phase discriminates between trials with early and late perception better than post- movement amplitude does. + +<|ref|>text<|/ref|><|det|>[[92, 598, 905, 792]]<|/det|> +The visual inspection is confirmed by rigorous statistical analysis of the discriminability between high and low agency movements from the instantaneous phase and amplitude across the movement time, showing that pre- movement phase opposition is statistically stronger than post- movement amplitude differences. In Experiment 1, when movements started in the optimal phase, \(74.8\%\) of trials had high agency, while only \(44.9\%\) had high agency when movements started in the non- optimal phase. In Experiment 2, \(75.8\%\) of trials in the optimal phase vs. only \(21.2\%\) of trials in the non- optimal phase were associated with an early perception of the movement. This results in a p- value of 0.0001 for the phase opposition at peak time, with p being below 0.001 between - 0.6 and - 0.2 s pre- movement. For comparison, the minimum p- value in the amplitude comparison of the two LFPs was 0.00035, reached for a very short post- movement interval (we use p- values to compare effect sizes because there is no standard method to determine effect size for phase opposition). Thus, unlike the phase opposition effect, the LFP amplitude difference did not survive cluster correction for multiple comparisons, as shown in Fig. 3g. + +<|ref|>text<|/ref|><|det|>[[92, 800, 904, 832]]<|/det|> +We thank the reviewer for giving us the opportunity to clarify these aspects, which are now detailed in the results on page 10: + +<|ref|>text<|/ref|><|det|>[[92, 841, 905, 920]]<|/det|> +"Importantly, the early vs late differences in pre- movement LFP phase were far stronger and more significant in pre- movement LFP phase than in either pre- or post- movement LFP amplitude. LFP amplitude discriminated maximally between the two conditions at 544 ms post- movement (minimal p- value, t- test, Fig. 3g). Such difference was not significant after cluster correction for multiple comparisons across timepoints ( \(p > 0.08\) ). Accordingly, phase distributions within the pre- movement phase opposition cluster + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 115]]<|/det|> +(- 256 ms, Fig. 3f) had much less overlap than LFP amplitude distributions at the post- movement timepoint of maximal amplitude- based discriminability across early and late movement perception (Fig. 3i)." + +<|ref|>text<|/ref|><|det|>[[92, 124, 722, 141]]<|/det|> +We report below the changes in Fig. 3 and the relative caption, visible on page 11: + +<|ref|>image<|/ref|><|det|>[[101, 160, 884, 590]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[91, 605, 907, 860]]<|/det|> +"(c) Trial-averaged LFP for trials with early (blue) and late (red) perception of movement (median split). Shades denote standard errors. (d) Instantaneous pre-movement phase (as in Fig. 2d) for individual early (top) and late (bottom) movement perception trials, showing clustering of the two subsets around opposite phases. Black dashed lines indicate the time limits of the cluster shown in panel (e), the white dashed line indicates the timepoint shown in panel (f). (e) P-values for the phase opposition product between trials with early and late movement perception. The red contour delimits the significant cluster after a cluster-based permutation test. The black bracket above the plot indicates the time window of interest for cluster-based correction (-0.5/0 s). (f) Histograms of phase angles for individual trials at the time-frequency point of maximal phase opposition in Experiment 1 (-256 ms, 8 Hz, red cross in panel d) to allow comparison with Figure 2e. Blue/red lines indicate the preferred angles for high/low implicit agency respectively, and their length is proportional to the ITC. (g) Comparison of the statistical significance of phase differences (red, 10000 permutations) and LFP amplitude differences (black, t-test). Solid horizontal lines indicate time windows surviving cluster correction for multiple comparisons across timepoints. No significant cluster was found for LFP amplitude differences. (h) Instantaneous post-movement amplitude for individual early (top) and late (bottom) movement perception trials. (i) Histogram of LFP amplitudes at the timepoint of maximal dissociation between early (blue) and late (red) trials." + +<|ref|>text<|/ref|><|det|>[[92, 870, 905, 918]]<|/det|> +In sum, besides the theoretical interest of this study on pre- movement neural oscillations, there is also a quantitative justification in focusing on the pre- movement phase. We hope the new plots and analyses following this important comment help illustrate the reasons for this choice. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 131]]<|/det|> +That being said, an effect of pre- movement oscillations does not exclude that post- movement signals may be also contributing to the final reported sense of agency or movement timing, as now mentioned in the discussion on page 20: + +<|ref|>text<|/ref|><|det|>[[92, 140, 905, 268]]<|/det|> +"Our results do not rule out the contribution of post- movement signals to the sense of agency. These may be relevant for postdictive inference of causality (apparent mental causation theory \(^7\) ), or for sensorimotor comparisons, whereby sensorimotor oscillations may be integrated with higher level cognitive cues to determine the final experience of agency (cue integration theory \(^6\) ). This contribution may be reflected in a dissociation of post- movement LFP between high and low agency trials, which was here observed in Experiment 2 and extensively investigated in \(^{13}\) . Pre- movement sensorimotor oscillations may also serve as a trigger for apparent mental causation, and gauge the integration between low- and high- level cues in determining the sense of agency." + +<|ref|>sub_title<|/ref|><|det|>[[93, 304, 130, 318]]<|/det|> +## C11) + +<|ref|>text<|/ref|><|det|>[[93, 319, 490, 334]]<|/det|> +The "alfa band" is really the same in all experiments? + +<|ref|>text<|/ref|><|det|>[[92, 344, 905, 423]]<|/det|> +For some reason, the Authors have decided that signals coming from different frequency ranges are the same thing. In the patient, the frequency of the electrical signal measured from area M1 peaks at \(6.2 \text{Hz}\) (below the canonical alfa); in the normal controls the peak of the electrical signal measured this time from area SMA peaks at \(9 - 12 \text{Hz}\) . I am not convinced by this analogy. As said, and unfortunately, because the paradigms used in the patients and in normal controls are not the same these differences are not interpretable. + +<|ref|>sub_title<|/ref|><|det|>[[92, 434, 130, 448]]<|/det|> +## R11) + +<|ref|>text<|/ref|><|det|>[[92, 450, 905, 592]]<|/det|> +Thank you for pointing out this aspect which deserves more in- depth discussion. There is a considerable variability across studies in the definition of frequency bands, and the neural origin of EEG or LFP activity at each frequency is often unclear. Reviewer 2 commented that the 8 Hz oscillations in the implanted patient "looks like a typical subject alpha band LFP" (see C21). However, we acknowledge that in the previous versions of the manuscript we have not been sufficiently clear in noting that we cannot and do not wish to assume or conclude that neural phenomena observed with different techniques in different paradigms, different subjects, and different frequencies are analogous or are generated by the same neural processes. We can only unbiasedly document where frequency information about agency is encoded in each experimental paradigm. We have revised discussion (page 22) to emphasize this: + +<|ref|>text<|/ref|><|det|>[[92, 600, 905, 698]]<|/det|> +"Furthermore, differences in techniques and experimental paradigms applied in one implanted participant and healthy controls make it difficult to infer whether comparable phase opposition effects observed at different frequencies across different experiments are related to the same or different neural mechanisms. Because of this, and of the general difficulties in imputing neural phenomena to frequency bands \(^{41}\) , here we refrained from making such inference, and unbiasedly reported the precise frequency of the observed effects in each subject and experimental paradigm." + +<|ref|>text<|/ref|><|det|>[[92, 707, 905, 866]]<|/det|> +Said that, we run further analyses to characterize and understand the subject- to- subject variability within the same experimental paradigm in the frequency of maximal agency encoding in the phase. In particular, we analysed individual spectral peak of low frequency oscillations (for brevity: individual alpha peak). Since many behavioural effects seem to be tied to the individual alpha peak frequency (Haegens et al., Neuroimage 2014), or even to its fluctuations across trials within the same participant (Drewes et al., Cerebral Cortex, 2022), we hypothesized that also variations across individuals in the frequency of the strongest phase opposition could be reflect variations across individuals of their idiosyncratic alpha peak. The new analyses indeed showed that the individual frequency of maximal phase opposition correlates with the individual alpha peak in SMA. We now present and discuss this novel finding in the results section (page 14) and in Fig. 6f: + +<|ref|>text<|/ref|><|det|>[[92, 875, 905, 923]]<|/det|> +"The SMA effect peaked at 9 Hz, close to what was observed in our implanted participant, but was relatively spread across the whole alpha band (Fig. 6d). Since alpha- band peak frequencies vary across individuals \(^{45}\) and correlations of alpha- band activity with behaviour are stronger at frequencies closer to the individual + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 181]]<|/det|> +alpha peak 46, we predicted that individual variations in agency- related phase opposition might reflect individual variations in alpha peak frequency. Confirming this prediction, the frequency at which maximal SMA phase opposition was found for each subject correlated with their individual SMA alpha band frequency of maximal power \((R = 0.46, p = 0.011, \text{Fig. 6f})\) . This suggests that individual variations in the frequency at which the phase better predicts agency depends on individuals' idiosyncratic alpha band peak." (p. 14) + +<|ref|>text<|/ref|><|det|>[[92, 189, 466, 205]]<|/det|> +We report below Fig. 6f and the relative caption: + +<|ref|>image<|/ref|><|det|>[[365, 245, 614, 418]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[92, 439, 905, 488]]<|/det|> +"(f) Correlation between the individual alpha peak and the frequency of strongest phase opposition in the left SMA. Data of the tetraplegic participant from Experiments 1-2 (not included in the regression) is shown for comparison (red dot)." + +<|ref|>text<|/ref|><|det|>[[92, 497, 905, 594]]<|/det|> +Crucially, a spectral peak below the conventional alpha band has been previously and commonly observed in tetra or paraplegic participants (Foldes et al., J Neurophysiol, 2017), including our implanted patient (6.2 Hz). Thus, although lower in absolute frequency with respect to healthy controls, the phase opposition observed in the implanted participant also peaked close to his individual alpha peak (see red dot in Fig. 6f above). As visible in the figure, most participants with a low individual alpha peak (around 8 Hz) presented a phase opposition effect peaking close to the one observed in the implanted participant. + +<|ref|>text<|/ref|><|det|>[[92, 602, 905, 667]]<|/det|> +To address the difference between M1 and SMA, we now also report the spectral peak in M1 for healthy participants, which is very close to the SMA spectral peak (Fig. S3). Therefore, we believe it is unlikely that the difference in frequency can be explained by the different anatomical location, but rather by the different frequency of the peak of power of oscillatory activity. + +<|ref|>text<|/ref|><|det|>[[92, 676, 905, 740]]<|/det|> +In sum, our new analyses suggest that the apparent discrepancy in frequency can be resolved by considering that: (i) the phase effect is tied to the individual low- frequency spectral peak and that (ii) the spectral peak in the implanted participant is lower than in healthy participants, likely due to the patient's chronic paralysis. This is now mentioned in the discussion on page 22: + +<|ref|>text<|/ref|><|det|>[[92, 749, 905, 829]]<|/det|> +"We could, however, gain some intuition about the individual variability of effects within Experiment 3. Namely, individual differences in the peak phase opposition frequency could be accounted for by individual variations in the individual alpha peak (Fig. 6f). Compatibily with other reports in chronic paralysis 39, the individual alpha peak in the implanted participant was lower than in healthy participants, possibly explaining the lower frequency of the phase opposition effect observed in Experiment 1 and 2." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 283, 113]]<|/det|> +C12) Coherence of the results. + +<|ref|>text<|/ref|><|det|>[[92, 124, 904, 171]]<|/det|> +Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. + +<|ref|>text<|/ref|><|det|>[[92, 173, 904, 236]]<|/det|> +Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small- EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls. + +<|ref|>sub_title<|/ref|><|det|>[[92, 248, 130, 261]]<|/det|> +## R12) + +<|ref|>text<|/ref|><|det|>[[92, 262, 904, 325]]<|/det|> +The different source of the effect from the patient and healthy individuals indeed deserved more clarification. We did observe an effect in M1 in healthy participants. We apologize if this was not reported and analysed with sufficient clarity in the original manuscript. We have rephrased this part to clarify our hypotheses and results. + +<|ref|>text<|/ref|><|det|>[[91, 334, 905, 575]]<|/det|> +Based on the previous literature about the neural bases of the sense of agency (see e.g., Haggard, Nature Neuroscience Reviews, 2017) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12), applying FDR correction for multiple comparisons within this network. This analysis revealed the strongest phase opposition in SMA, and that the second strongest phase opposition in M1 (p = 0.023). If focusing purely on the left M1, with the purpose of replicating the effect observed in the implanted participant, and thus dropping multiple comparisons correction, the uncorrected M1 effect is highly significant with p = 0.003. The uncorrected p- value is not reported for in the text, for being maximally conservative. In sum, phase position was significant in both SMA and M1. For completeness, we also reported the results of a whole- cortex search for phase opposition across all 114 ROIs of the cortex. This whole- cortex search confirmed significant phase opposition in the SMA after adjusting for 114 comparisons; in contrast, M1 did not survive multiple correction. We refrain from making interpretations of the null result for M1 in this whole- cortex search as this analysis is underpowered. Taking this into account, have rephrased the presentation of the results as follows (page 14): + +<|ref|>text<|/ref|><|det|>[[91, 583, 905, 791]]<|/det|> +"Based on the previous literature about the neural bases of the sense of agency (see e.g. 44) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12, shown in Fig. S8). Two regions survived FDR correction for multiple comparisons across regions within this network. The stronger phase opposition was observed in the posterior part of the left supplementary motor area (SMA, p = 0.0024, Fig. 6c- e). Phase opposition in the dorsal part of the left primary motor cortex contralateral to the BMI movement was also significant (p = 0.023), consistent with our result in the implanted participant. No other ROI yielded significant phase opposition. For completeness, we repeated the analysis searching for significant phase opposition across all 114 ROIs of the source reconstruction. This whole- cortex search confirmed a significant phase opposition in SMA (p = 0.03), whereas phase opposition in M1 did not survive correction for multiple comparisons, likely due to the analysis being relatively underpowered. As shown in Fig. S9a- B, SMA effects were robust to the specific choice of the frequency range (Fig. S9a- b)." + +<|ref|>text<|/ref|><|det|>[[91, 800, 905, 928]]<|/det|> +It is also important to note that, while for further analyses in the main text we focused on SMA, the region showing the strongest effects, the key results on connectivity are also observed when using M1 as a seed (Fig. S10). Also note that we may have observed an effect only in M1 in the implanted participant simply because the only available recording site was in M1. We cannot exclude that, as in healthy participants, an effect, possibly even stronger, could have been observed in SMA if an electrode was also implanted there. An alternative explanation of the anatomical difference may be that, while the implanted participant was using genuine motor attempts to control the BMI, healthy participants had to use motor imagery, which is known to activate SMA more than M1. These considerations were added to the discussion on page 21: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 904, 131]]<|/det|> +"Interestingly, in healthy participants, the phase opposition effect was stronger in SMA than in M1. Since the invasive implant was limited to M1, we cannot exclude that a stronger phase opposition in SMA was also present in our tetraplegic participant but not directly observed." + +<|ref|>text<|/ref|><|det|>[[92, 139, 897, 205]]<|/det|> +"Experiment 3 employed motor imagery rather than genuine motor attempts, as in Experiment 1. Given that motor imagery is known to induce comparably higher activations in SMA than in M1 \(^{56}\) , a possibility, to be addressed in future work, is that the relative contributions of SMA and M1 vary depending on the modality of BMI control (e.g., imagery versus execution)." + +<|ref|>text<|/ref|><|det|>[[92, 214, 905, 326]]<|/det|> +We would also like to add that, in our opinion, the key common result cross- validating findings across Experiment 3 and Experiment 1- 2 is not just that the phase opposition effect was found in the pre- movement period. Indeed, these results pertain the oscillatory phase, a very specific and peculiar feature of neural potentials, they were observed at similar frequencies (tied to the alpha peak), and effects in the contralateral M1 were significant in the implanted participant and in healthy controls. Further effects in SMA, a region that was simply not recorded in the implanted participant, were clearly observed only in healthy controls. + +<|ref|>sub_title<|/ref|><|det|>[[92, 360, 130, 374]]<|/det|> +## C13) + +<|ref|>text<|/ref|><|det|>[[93, 377, 231, 391]]<|/det|> +Theoretical issues. + +<|ref|>text<|/ref|><|det|>[[92, 401, 905, 609]]<|/det|> +A paper of this magnitude cannot be neutral towards the previous theories on the sense of agency. There are at least three theoretical models proposed to address the arising of the agency experience. The authors seem to consider only one of these nor they do make an effort to discuss whether and why their findings are in support of this specific theory. The "Comparator Model", the only model mentioned in the paper, postulates that the sense of agency arises from a series of comparator processes within the motor control system. However, in an alternative perspective, the "Apparent Mental Causation Theory" proposes that the emergence of the sense of agency is a post hoc and retrospective phenomenon. Accordingly, the sense of agency arises through an inferential sense- making process that occurs after the completion of a movement. Finally, in the "Cue Integration Theory", the sense of agency should arise from integrating low- level cues (sensorimotor proprioceptive and exteroceptive cues) and high- level cues (cognitive cues). The weight assigned to these different cues varies for the implicit and explicit components of agency. Hence, I feel that the authors should try to frame their data considering the previous theoretical and experimental efforts on the very same topic over the last 20 years. + +<|ref|>sub_title<|/ref|><|det|>[[92, 618, 130, 632]]<|/det|> +## R13) + +<|ref|>text<|/ref|><|det|>[[92, 633, 905, 794]]<|/det|> +Thank you for this suggestion. We are glad to discuss our results on pre- movement signals affecting the sense of agency in line with the current most relevant theories on this topic. The presence of a pre- movement signal correlating with the subsequent sense of agency (and neural connectivity) resonates with key elements of the "predictive" comparator model. Alpha band oscillations, gating cortical connectivity, are in our view a promising candidate to be the neural substrate carrying sensorimotor predictions from motor to sensory areas, and performing the subsequent comparisons. This mechanism is also compatible with the low- level components in the cue integration theory, while higher level neural processes on a slower temporal scale may contribute to postictive inference. At the same time, our findings do not exclude that post- movement, retrospective inference of mental causation may also play a role in the phenomenology of agency. We have now integrated these aspects in the discussion on page 20: + +<|ref|>text<|/ref|><|det|>[[92, 802, 905, 931]]<|/det|> +"In our previous work \(^{13}\) (including data from Experiment 1), we showed how post- movement LFPs and multiunit activity in M1 encode congruency between motor commands and sensory feedback, a key aspect in the sensorimotor comparisons underlying the sense of agency. Our findings in Experiment 1 extend these previous results, suggesting that M1 and SMA also play pivotal roles in the sense of agency at an earlier stage, when sensorimotor predictions are computed during motor preparation and before execution. Our results do not rule out the contribution of post- movement signals to the sense of agency. These may be relevant for postictive inference of causality (apparent mental causation theory \(^{7}\) ), or for sensorimotor comparisons, whereby sensorimotor oscillations may be integrated with higher level cognitive cues to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 163]]<|/det|> +determine the final experience of agency (cue integration theory 6). This contribution may be reflected in a dissociation of post- movement LFP between high and low agency trials, which was here observed in Experiment 2 and extensively investigated in 13. Pre- movement sensorimotor oscillations may also serve as a trigger for apparent mental causation, and gauge the integration between low- and high- level cues in determining the sense of agency." + +<|ref|>text<|/ref|><|det|>[[92, 172, 904, 205]]<|/det|> +In addition to the comparator model, we now also mention the alternative theories of the sense of agency in the introduction on page 3: + +<|ref|>text<|/ref|><|det|>[[92, 213, 905, 262]]<|/det|> +"Different explanations have been offered for the sense of agency 6- 8. Among those, one influential view states that the sense of agency arises from the comparison between predicted and observed sensory outcomes of intended actions 8,9. " + +<|ref|>text<|/ref|><|det|>[[92, 296, 133, 328]]<|/det|> +C14) Style. + +<|ref|>text<|/ref|><|det|>[[92, 338, 905, 419]]<|/det|> +For sure, there is already a broad body of literature investigating the neural correlates of the sense of agency that makes an opening statement in the abstract (".... the underlying neural mechanisms of the sense of agency are still unknown") too strong for two reasons: (1) the previous evidence connecting brain physiology and the SOA (2) the correlational nature of the evidence provided; this lacks the identification of a clear "mechanism" that causally connects brain physiology and the complex phenomenology of the SOA. + +<|ref|>sub_title<|/ref|><|det|>[[92, 428, 130, 442]]<|/det|> +## R14) + +<|ref|>text<|/ref|><|det|>[[92, 443, 905, 572]]<|/det|> +We are sorry if we gave the impression of stating that no previous knowledge of the neural mechanisms of the sense of agency was available, which is not the case. We more specifically meant that the dynamical interaction between functional areas is still poorly understood, as most previous studies are either "static" fMRI activation maps, single- site lesion or perturbative studies. We have rephrased the abstract and introduction accordingly. Furthermore, we have thoroughly revised the text to clarify that we do not provide causal evidence about the role of pre- movement oscillations (pp. 4, 12, 19, 21). We also now acknowledge the correlational nature of our evidence in a new limitations paragraph which was added to the discussion on page 22: + +<|ref|>text<|/ref|><|det|>[[92, 580, 904, 629]]<|/det|> +"Nonetheless, without direct experimental intervention, the current evidence remains correlational. Further studies are needed to causally assess the contribution of pre- movement phase to sense of agency, both when measured explicitly and implicitly." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[93, 124, 905, 252]]<|/det|> +The manuscript by Bertoni et al reports very interesting data and experimental designs. The authors recorded single neurons and LFP from M1 of a tetraplegic patient who, with the help of a prosthetic devise, is able to guide fake- hand reaching movements. The authors correlated the LFP with the reported simulated action of the subject and specifically with his sense of agency, demonstrating a phase dependence of alpha band endogenous oscillation with the sense of agency. To complete the study the authors measured the effect in typical subjects, and used high density EEG coupled with simulation of the moving hand to demonstrate again a phase dependence. Unfortunately and not surprising this data are less compelling with a small and just significant effect. + +<|ref|>text<|/ref|><|det|>[[92, 261, 905, 341]]<|/det|> +While I like the paper and the material presented, I have several unclear and not- discussed technical problems that make me uneasy to give a strong recommendation at this stage. The main one being the synchronization with the prosthetic devise. For this reason I would like to postpone my acceptance/rejection recommendation after a major revision giving the possibility to the authors to explain better their technique and rationale and write a more clear and critical manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 350, 905, 447]]<|/det|> +We thank the reviewer for their appreciation of our work, the many insightful comments, and the possibility of clarifying technical problems. A detailed response to the reviewer's main concerns, as well as other major points are provided in the following paragraphs. We highlighted our responses in bold, and indicated with quotation marks and italics passages reported from the revised text, highlighting changes in red. To allow referring to specific points, we have numbered reviewer comments and our responses (e.g., comment 1: C1; response 1: R1). The numbering continues across comments from the two reviewers. + +<|ref|>text<|/ref|><|det|>[[92, 480, 201, 511]]<|/det|> +C15) Main problem + +<|ref|>text<|/ref|><|det|>[[92, 537, 905, 650]]<|/det|> +Phase depends on the time origin of the synchronisation trigger. Here the authors trust the prosthetic algorithm and set the synchronisation with the onset threshold for the fake- hand movement. However, this relies on a very strong assumption: the algorithm should operate with the same delay for the high and low agency perception. This may be wrong and would be mainly CONTRARY to their data. They show that the agency state signal can be derived from the phase of the LFP and supposedly also the decoding algorithm is using this signal, possibly by introducing a delay (50 ms would be sufficient) to give an apparent phase change. In other words, the argument to me is circular! + +<|ref|>sub_title<|/ref|><|det|>[[92, 660, 130, 673]]<|/det|> +## R15) + +<|ref|>text<|/ref|><|det|>[[92, 675, 904, 707]]<|/det|> +We understand the reviewer's concern, and apologize for an insufficiently clear presentation of technical aspects of the neuroprosthesis setup which may have led to a few critical misunderstandings. + +<|ref|>text<|/ref|><|det|>[[92, 716, 905, 828]]<|/det|> +First, the feature used by the BMI decoder in the implanted participant is the high frequency (>235 Hz) power (not phase) of the LFP signal, reflecting multiunit firing rate at each electrode. Due to the extreme gap in frequencies, and the fact that the power and not the phase of oscillations are considered, the BMI features are essentially independent of the 8 Hz phase. BMI input features are further smoothed over a 500 ms window, spanning and averaging several alpha cycles, and processed in externally determined 100 ms bins; thus, there is no reason to expect a dependency between BMI decoder threshold crossing and 8 Hz phase. + +<|ref|>text<|/ref|><|det|>[[92, 837, 707, 853]]<|/det|> +We report the passage detailing the input features of the decoder from page 24: + +<|ref|>text<|/ref|><|det|>[[92, 862, 905, 927]]<|/det|> +"The SVM used 96 input features consisting of the mean wavelet power (MWP) for each channel and 100 ms bin. To obtain the MWPs, neural activity was decomposed into 11 wavelet scales (Daubechies wavelet, MATLAB), and the coefficients of wavelets 3- 6, corresponding to the multi- unit frequency band spanning from 235 to 3.75kHz, were averaged for each channel. Thus, the decoder's input features were closely + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 904, 113]]<|/det|> +related to high frequency power at each channel, a robust and computationally not intensive proxy of multi- unit activity." + +<|ref|>text<|/ref|><|det|>[[92, 123, 904, 157]]<|/det|> +We also have added further details in the methods to provide all the necessary information regarding this point, on page 25: + +<|ref|>text<|/ref|><|det|>[[92, 165, 905, 230]]<|/det|> +"At the end of each 100 ms acquisition bin, the decoder analysed neural signals and provided four numbers in the - 1/1 range, indicating the decoded relative probability for each of the four movement. Again every 100 ms, the output of the decoder was further smoothed on a 500 ms time window to determine whether and which movement to implement." + +<|ref|>text<|/ref|><|det|>[[92, 238, 905, 304]]<|/det|> +To support empirically that there is no dependence between decoding delay and 8 Hz phase/agency, we compared the decoding delay between high and low agency trials, and between trials starting in the optimal vs. non- optimal phase. No significant difference was found. These analyses are mentioned in the methods (page 32) and are shown in the Supplementary Materials (Fig. S13): + +<|ref|>text<|/ref|><|det|>[[92, 312, 905, 393]]<|/det|> +"To rule out that the relation between pre- movement phase and sense of agency could be due to differences in BMI decoding delays for high and low agency trials, we compared the delay between go cue and NMES movement onset between high and low agency trials, and between trials with optimal vs. non- optimal phase. We found no difference (t(29) = 0.15, \(p = 0.84\) and t(29) = 0.71, \(p = 0.48\) respectively, Fig. S13)." (p. 32) + +<|ref|>text<|/ref|><|det|>[[92, 401, 410, 418]]<|/det|> +We report Fig. S13 and its caption below: + +<|ref|>image<|/ref|><|det|>[[163, 439, 830, 658]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[92, 682, 905, 747]]<|/det|> +"Figure S13: Control analyses on the decoder delays. The left panel shows the delay between go cue and NMES movement onset compared for high and low agency trials ( \(p = 0.84\) ). The right panel compares the same delay between trials starting in the optimal vs. non- optimal phase ( \(p = 0.48\) ). The grey bars represent standard errors." + +<|ref|>text<|/ref|><|det|>[[92, 755, 905, 900]]<|/det|> +In addition to this, even if present, a "constant" delay of 50 ms (or any duration) may potentially affect agency judgements, but cannot lead to a systematic phase shift. This is because the "initial" phase (at the timepoint relative to which the delay is defined, e.g., the go cue) is randomly determined by the timeline of the experiment, which is independent from the phase of endogenous neural oscillations. Even if the phase at "time 0" was always the same, which is not the case, a constant delay would not introduce a phase shift, since the BMI decoder takes more than one second to trigger a movement (more than 3 with EEG), and temporal correlation between initial and current phase is lost after only a few oscillatory cycles, due to the different duration of each oscillatory cycle in noisy physiological processes. The average delay and its variability are now mentioned in the methods on page 25: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 147]]<|/det|> +"Due to decoder output smoothing, plus neural and acquisition noise, the delay from the go cue to decoder threshold crossing was variable and significantly larger \((1.2 s \pm 0.48 SD)\) than in natural movements. Being an expert user of the BMI system, the participant is accustomed to these long delays, allowing him to experience a strong sense of agency for BMI movements." + +<|ref|>text<|/ref|><|det|>[[92, 155, 905, 269]]<|/det|> +Thus, the circularity mentioned by the reviewer could be present only if the decoder selectively time- locked its threshold crossing to a specific \(8 \text{Hz}\) phase based on the agency judgement reported by the participant at the end of the trial. In other words, the decoder would need to be able to predict the participant's agency judgement before the movement starts, and trigger the movement in the optimal phase when a positive judgement is predicted, and vice versa. This is clearly not possible. Finally, it is important to add that the phase effect is pre- movement and visible even at fixed sensory feedback (Fig. 2g), so it is independent of exogenous factors, such as sensory feedback, which may potentially interact with decoder output. + +<|ref|>text<|/ref|><|det|>[[92, 277, 905, 326]]<|/det|> +All the above reasonings also apply to the EEG experiment in healthy participants. In addition, in the EEG experiment the go- movement delay is regressed out from agency ratings to enhance the contribution of endogenous factors (i.e., pre- movement phase), and cannot thus contribute to our analysis. + +<|ref|>text<|/ref|><|det|>[[92, 334, 904, 367]]<|/det|> +For all these reasons, we believe there is no circularity between our phase- dependent effect on the sense of agency and how the BMI system decodes the participant's motor intention. + +<|ref|>sub_title<|/ref|><|det|>[[92, 402, 130, 416]]<|/det|> +## C16) + +<|ref|>text<|/ref|><|det|>[[92, 418, 905, 529]]<|/det|> +However, the authors have access to single cell firing. A simple threshold to the ensemble recording firing could be used for synchronize the LFP and analyse the change in phase. It is true that they found a strong correlation between pre- movement of fake- hand LFP and neuronal firing. However, the amount of firing may be independent of onset phase. Maybe I misunderstood something, and the tetraplegic patient does not modulate at all M1 firing during Motor Imagery. But if so, this needs to be explained in detail, at least in the methods. In addition the variability of the decoding delay to generate the phantom hand movement needs to be reported! + +<|ref|>sub_title<|/ref|><|det|>[[92, 539, 130, 553]]<|/det|> +## R16) + +<|ref|>text<|/ref|><|det|>[[92, 554, 905, 699]]<|/det|> +We thank the reviewer for giving us the opportunity to discuss these important aspects of our analysis. First, let us clarify that differently from healthy participants, the tetraplegic participant did not perform motor imagery, but controlled his own hand by attempting actual hand movements, which was decoded by the BMI and triggered neuromuscular electrical stimulation of his forearm muscles (see Fig. 1 and caption). Thus, he did modulate M1 firing rates to generate hand movements, as shown by previous studies (Bouton et al., Nature, 2015; Serino et al., Nature Human Behaviour, 2022; Noel et al., Biorxyv, 2023) and the current data (see for example Fig. 5d, showing the buildup of M1 firing rate leading to the decoder crossing threshold). Movement- specific patterns of M1 firing were detected by the BMI system to recognize the intended movement. We have better clarified these aspects in the methods on page 24: + +<|ref|>text<|/ref|><|det|>[[92, 707, 905, 867]]<|/det|> +"The BMI system consisted in a 96 channels Utah array (Blackrock microsystems) acquiring M1 signals, a standard desktop computer decoding the intended movement from M1 activity, and an electrode patch stimulating right forearm muscles to translate decoded movements into functional hand movements. To account for natural changes in the signal from the Utah array, the decoder was re- trained before each experimental session. Training data was generated by asking the participant to attempt performing one of four hand movements (hand open, HO, hand close, HC, thumb extension, TE, thumb flexion, TF). Clearly, due to chronic paralysis, these motor attempts did not lead to actual hand movements as long as electrical stimulation was off, but modulated M1 firing rates in movement- specific patterns, which could be detected by the BMI algorithm. In each training session, the subject performed 7 blocks consisting of 3 repetitions per movement type each." + +<|ref|>text<|/ref|><|det|>[[92, 876, 905, 925]]<|/det|> +Following the interesting suggestion of the reviewer, we now also analysed phase opposition after time- locking to a simple threshold on M1 firing rates. We found no significant phase opposition, as now stated in the methods (p. 32) and shown in the Supplementary Materials (Fig. S14): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 195]]<|/det|> +"We also tested whether phase opposition results could be replicated by time- locking the LFPs to the crossing of a simple threshold on average M1 firing rates, rather than to the onset of the actual hand movement, and found no significant result (Fig. S14). We believe this was the case because the BMI decoder does not produce a movement by threshold crossing of population activity, but rather by decoding specific activity patterns across neurons \(^{33}\) . Thus, population rate threshold crossing is an internal event which, unlike BMI decoder crossing threshold, does not produce a movements or salient subjective percepts." (p. 32) + +<|ref|>text<|/ref|><|det|>[[92, 204, 904, 235]]<|/det|> +Expanding the reasoning above, we believe the analysis did not yield significant results for one technical and one conceptual reason. + +<|ref|>text<|/ref|><|det|>[[92, 245, 905, 438]]<|/det|> +Technically, in each trial, the participant performed one of four (or two) randomized movements, each corresponding to a different pattern of M1 activation across the 96 channels of the Utah array. In addition, signals from the Utah array changed across experimental sessions due to natural movements of the electrode array in the cortical tissue (hence the necessity to re- train the decoder at each experimental session). Thus, the modulation of M1 firing rates varied across trials and experimental sessions, making a simple threshold on M1 firing not suitable to capture the onset of the participant's motor commands. Furthermore, being used to the response delays of the BMI system and unable to generate natural movements, the participant does not generate strong bursts of M1 activity with a clear onset which could be used for time- locking, but slowly builds up M1 activity, gradually increasing his effort until a movement is generated (see for example firing rates in Fig. 5d). In other words, the best available proxy of the onset of the participant's motor attempt is likely the neural decoder itself, which was optimized to detect complex patterns of activity corresponding to specific movements in each experimental session. + +<|ref|>text<|/ref|><|det|>[[92, 446, 905, 670]]<|/det|> +Besides these technical aspects, there is a more important and interesting conceptual aspect that in our view explains this null result. The analysis presented in the paper was not simply time- locked to the BMI decoder's output, but to an actual sensory event with a clearly perceivable onset, i.e., the onset of the NMES stimulation inducing a hand movement, and the simultaneous onset of a virtual hand movement displayed on the screen. As now more clearly stated in the methods, NMES and visual stimulation invariably followed BMI threshold crossing by a fixed hardware delay. Due to the small variability of such delay (10 ms) compared to the duration of one 8 Hz oscillatory cycle, BMI threshold crossing and movement onset cannot be dissociated in our analyses (the average delay between go cue and BMI threshold crossing is already reported in the previous response). Our analyses thus reveal that it is the 8 Hz phase relative not only to BMI crossing threshold, but also (in our opinion, more importantly) to the onset of the hand movement and reafferent sensory feedback, that correlates with the sense of agency. In other words, the state of the brain in the precise moments preceding the onset of a movement determines the subsequent sense of agency. We have rephrased several paragraphs in the methods to better highlight the technical aspects underlying this reasoning (page 25 and 30): + +<|ref|>text<|/ref|><|det|>[[92, 679, 905, 840]]<|/det|> +"The participant was instructed to start attempting the cued movement when the go cue appeared, without anticipating. During the 4 seconds following the go cue, the BMI algorithm decoded changes in M1 multiunit activity generated by the participant as he attempted the cued movement, and translated them into visual and somatosensory feedback, according to the decoded movement and the feedback congruency assigned for that trial and sensory modality. Somatosensory feedback was delivered by eliciting the target movement through the NMES sleeve, and thus consisted in a functional hand movement. Visual feedback was constituted by an animation of a virtual hand performing the target movement, displayed on a screen placed horizontally to cover the participant's right hand. Note that the participant has sufficient residual proprioception to recognize the hand movement performed even with his real hand being hidden by the screen (see \(^{13,33}\) )." (p. 25) + +<|ref|>text<|/ref|><|det|>[[92, 848, 904, 880]]<|/det|> +"Due to hardware delays, the onset of NMES stimulation followed the end of the 100 ms acquisition bin in which the neural decoder crossed threshold by a stereotyped \(70 \pm 10\) ms (SD) delay." (p. 25) + +<|ref|>text<|/ref|><|det|>[[92, 889, 904, 921]]<|/det|> +"For both LFP and multiunit activity, the data was epoched by time- locking to the onset of hand movements (sensory feedback). The exact timing of the onset of hand movements ( \(70 \pm 10\) ms after the neural decoder + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 904, 115]]<|/det|> +crossing threshold) was determined by detecting the 50 Hz stimulation artifact induced by the NMES system." (p. 30) + +<|ref|>text<|/ref|><|det|>[[91, 123, 905, 316]]<|/det|> +In sum, we believe that, to observe phase- agency correlations, it is conceptually not appropriate to time- lock our analysis to the crossing of a firing rate threshold. This is because, unlike the crossing of the BMI threshold, the crossing of a firing threshold would be a purely "internal" event, as it would not necessarily be time- locked to an actual salient sensorimotor event, i.e. the onset of a hand movement. Indeed, due to the reasons stated above, there is a significant variability in the delay between M1 firing rate threshold crossing and hand movement/BMI threshold crossing. Put differently, we believe that our analysis worked when synchronized to the decoder crossing threshold not because this moment corresponds to a "special" internal state, but because this moment also corresponds to the onset of an actual movement (excluding an almost fixed hardware delay which was corrected as described above). If a random delay with larger variability (of e.g. 100 ms) had been added between decoder crossing threshold and movement onset, we believe the phase opposition would have been observed only when time- locking to the movement onset, and not to decoder crossing threshold. + +<|ref|>sub_title<|/ref|><|det|>[[92, 352, 130, 366]]<|/det|> +## C17) + +<|ref|>text<|/ref|><|det|>[[92, 367, 905, 447]]<|/det|> +Again, I am surprised that the Readiness Potentials, usually associated with SMA activity, are never present in recordings, either in the patient or in the typical subjects. Probably they have been filtered out given the high- pass with \(0.2\mathrm{Hz}\) . If so I advise to analyse and show them. These potentials are so strong and rich of information about the internal motor state and motor intention of the participants that it may contain already important information about agency. + +<|ref|>sub_title<|/ref|><|det|>[[92, 457, 130, 471]]<|/det|> +## R17) + +<|ref|>text<|/ref|><|det|>[[92, 472, 905, 569]]<|/det|> +Thank you for this interesting suggestion. We cannot exclude that, in our BMI setups, readiness potentials may be weaker than in natural able- bodied movements. Nevertheless, readiness potentials are visible in our data, and should not be affected by the high- pass filtering, since the cutoff frequency is lower than that of typical readiness potentials (notice that in the implanted participant the high- pass filter cannot be removed as it was performed at the hardware level). Readiness potentials were simply not evident in the main text figures due to the scale and aspect ratio of the plots presented in the manuscript. + +<|ref|>text<|/ref|><|det|>[[91, 577, 905, 737]]<|/det|> +We have now analysed readiness potentials hypothesizing that, in addition to the phase effect, a stronger (i.e., more negative) pre- movement deflection would lead to a higher sense of agency. In Experiment 1 the negative deflection constituting the readiness potential started at about - 1.5 s, and the high and low agency signals overlapped until about - 0.5s. After - 0.5s, the two curves slightly dissociate, with a stronger negative deflection for high agency trials. However, this effect was statistically weaker than the phase effect. The minimum p- value for a T- test on the readiness potential between high and low agency trials was 0.002, and did not survive cluster- based correction, compared to 0.0001 for phase opposition (we use p- values to compare effect sizes, since there is no standard way to measure effect size for phase opposition). Also, this effect was not replicated in Experiment 2 or Experiment 3. We have now mentioned this analysis in the results (page 6), and show it in detail in the Supplementary Materials (Fig. S4): + +<|ref|>text<|/ref|><|det|>[[92, 752, 905, 817]]<|/det|> +"As a complementary analysis, we also investigated the relationship between agency and readiness potentials, the negative deflection of the LFP thought to be a correlate of pre- movement neural activity." We observed a trend of higher agency trials associated with a stronger negative deflection of the readiness potential. However, this effect did not survive correction for multiple comparisons (see Fig. S4)." (p. 6) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 108, 400, 123]]<|/det|> +We report Fig. S4 and its caption below: + +<|ref|>image<|/ref|><|det|>[[117, 149, 876, 308]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[92, 334, 905, 430]]<|/det|> +"Figure S4: analysis of readiness potentials. To decouple slow readiness potentials from phase opposition effects, the data was low pass filtered at 5 Hz, and LFPs/ERPs were compared between high and low agency trials. The panels show LFPs/ERPs for Experiment 1, Experiment 2, Experiment 3 – M1, and Experiment 3 – SMA (left to right). Shades indicate standard errors, the horizontal dashed line at 0 is shown to highlight the negative deflection corresponding to the readiness potential, the vertical dashed line indicates the time of the movement. No difference survived multiple comparison correction across timepoints." + +<|ref|>text<|/ref|><|det|>[[92, 439, 904, 471]]<|/det|> +We are grateful for this suggestion, as these additional results help clarify the differences between the present work and other classic EEG literature on the sense of agency. + +<|ref|>text<|/ref|><|det|>[[92, 506, 130, 520]]<|/det|> +C18) + +<|ref|>text<|/ref|><|det|>[[92, 521, 904, 569]]<|/det|> +Figure 5. Could you split the M1- LFP correlation between high and low agency trials? Did you obtain a difference in the correlation? Low agency may reduce correlation and this would be a stronger and physiological more important effect that the phase difference of LFP. + +<|ref|>sub_title<|/ref|><|det|>[[92, 580, 130, 593]]<|/det|> +## R18) + +<|ref|>text<|/ref|><|det|>[[92, 595, 905, 739]]<|/det|> +Thank you for this insightful suggestion. We have compared the spike- LFP coupling between high and low agency trials in Experiment 1 (the small number of trials in Experiment 2 does not allow to perform the same analysis). We performed the analysis both in the pre- and post- movement 1 second time windows, as smaller time windows would not contain enough spikes to estimate PLV values. We did not observe any striking differences, but there was a slight increase of PLV values for low agency trials at 11 and 12 Hz. This result is contrary to the hypothesis proposed by the reviewer (and our own expectations), it occurs at significantly higher frequencies than 8 Hz, and did not survive multiple comparison correction across frequencies. We now mention the analysis in the results (page 12), and show it in detail in the Supplementary Materials (Fig. S6). + +<|ref|>text<|/ref|><|det|>[[92, 747, 904, 797]]<|/det|> +"Moreover, LFP- spike PLV values did not differ trials between trials of high vs high agency (Fig. S6), suggesting that only the oscillatory 8 Hz phase, but not the amount of coupling between such phase and spiking activity, covaries with agency ratings." (p. 12) + +<|ref|>text<|/ref|><|det|>[[92, 832, 130, 846]]<|/det|> +C19) + +<|ref|>text<|/ref|><|det|>[[92, 847, 904, 878]]<|/det|> +Results of Fig 6 are somewhat disappointing. If anything, the phase opposition seems from Fig 6f stronger around 500 ms post movement. The scale of Fig 6d is not really readable to judge the robustness of the effect. + +<|ref|>text<|/ref|><|det|>[[92, 889, 130, 902]]<|/det|> +R19) + +<|ref|>text<|/ref|><|det|>[[92, 904, 904, 920]]<|/det|> +Please note that Fig. 6e showed results from an example participant, since averaging potentials from all + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 163]]<|/det|> +participants would not best show the phase opposition effect due to the differences in individual frequency of the effect (see new analyses in Fig. 6f). We have thus changed the visualization of our result, directly showing the output of the permutations used for our statistical analysis. Fig. 6e now shows how the observed phase opposition value lies far from the distribution of phase opposition values obtained by shuffling agency ratings within participants 10000 times. + +<|ref|>text<|/ref|><|det|>[[92, 198, 129, 212]]<|/det|> +C20) + +<|ref|>text<|/ref|><|det|>[[92, 214, 904, 245]]<|/det|> +Why has figure 7f directionally phase effects only on temporal cortex? Blue means that that ROI was not analysed? Please explain. + +<|ref|>text<|/ref|><|det|>[[92, 255, 130, 270]]<|/det|> +R20) + +<|ref|>text<|/ref|><|det|>[[92, 271, 905, 336]]<|/det|> +Thank you for pointing out the potential lack of clarity. Indeed, Fig. 7f (now 7g) shows results on our 114 ROI parcellation only within the temporal cortex, because only the temporal cortex showed significant results for the directionality analysis at the coarser parcellation level of 8 cerebral lobes. We have better clarified this in the main text (p. 18) and in the figure caption (p. 19): + +<|ref|>text<|/ref|><|det|>[[92, 344, 905, 393]]<|/det|> +"To better localise this effect, we performed the same directionality analysis at a finer spatial resolution only within the temporal lobe (the only region showing a significant effect at the coarser spatial resolution), at the scale of the original 114 ROIs used for source reconstruction." (p. 18) + +<|ref|>text<|/ref|><|det|>[[92, 400, 905, 450]]<|/det|> +"(h) P-values for the directionality analysis, as in panel (g), performed only within the temporal lobe at the finer spatial scale of the original source reconstruction (114 ROIs). Dark blue areas indicate ROIs outside the temporal lobe, which were not analysed at this parcellation level." (p. 19) + +<|ref|>text<|/ref|><|det|>[[92, 458, 905, 507]]<|/det|> +Also, to better characterize the spatial features of the connectivity changes, we now also present the results of the previous connectivity analysis at the level of the 114 ROIs in addition to the level of cerebral lobes (Fig. 7d), as reported on page 17: + +<|ref|>text<|/ref|><|det|>[[92, 515, 905, 565]]<|/det|> +"When performing the analysis at a finer spatial scale with 114 ROIs, six regions survived FDR correction: three regions in the middle prefrontal cortex and anterior cingulate, two in the superior part of the posterior parietal cortex, and one region in the anterior temporal cortex (Fig. 7d)." + +<|ref|>text<|/ref|><|det|>[[92, 573, 870, 590]]<|/det|> +We have rephrased passages in the discussion to incorporate these new results, as visible on page 21: + +<|ref|>text<|/ref|><|det|>[[92, 598, 905, 696]]<|/det|> +"Specifically, changes in functional connectivity occurred between SMA and part of the posterior parietal cortex, a region which is has been classically associated with visual guidance of movements \(^{57,58}\) (Fig. 7d). Further connectivity changes were observed between SMA and the medial prefrontal cortex and anterior cingulate, two regions implicated in action selection and initiation \(^{44}\) . These results point at SMA as a key hub in a network of regions classically associated with the sense of agency and are in line with the hypothesis \(^{44}\) that sense of agency may emerge from neural connectivity within such network." + +<|ref|>text<|/ref|><|det|>[[92, 730, 130, 744]]<|/det|> +C21) + +<|ref|>text<|/ref|><|det|>[[92, 746, 840, 761]]<|/det|> +Please make clear if 8Hz is theta or alpha for you.... To me looks like a typical subject alpha band LFP. + +<|ref|>text<|/ref|><|det|>[[92, 771, 130, 785]]<|/det|> +R21) + +<|ref|>text<|/ref|><|det|>[[92, 787, 905, 900]]<|/det|> +We have been careful in phrasing because of considerable debate in the community about the exact definition and limits of frequency bands. In this respect, note that Reviewer 1 instead raised doubts on whether the effect in the implanted participant actually is in the alpha band, and on the coherence of the results between implanted participant and healthy controls based on small frequency discrepancies (see C11). To address this comment, in the revised manuscript we show that the phase effect in healthy participants is tied to the individual alpha peak, following interindividual differences (see R11 and Fig. 6f). We report here the reviewed passage in the results, on page 14: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[91, 81, 905, 227]]<|/det|> +"The SMA effect peaked at 9 Hz, close to what was observed in our implanted participant, but was relatively spread across the whole alpha band (Fig. 6d). Since alpha- band peak frequencies vary across individuals \(^{45}\) and correlations of alpha- band activity with behaviour are stronger at frequencies closer to the individual alpha peak \(^{46}\) , we predicted that individual variations in agency- related phase opposition might reflect individual variations in alpha peak frequency. Confirming this prediction, the frequency at which maximal SMA phase opposition was found for each subject correlated with their individual SMA alpha band frequency of maximal power ( \(R = 0.46\) , \(p = 0.011\) , Fig. 6f). This suggests that individual variations in the frequency at which the phase better predicts agency depends on individuals' idiosyncratic alpha band peak." (p. 14) + +<|ref|>text<|/ref|><|det|>[[92, 234, 904, 300]]<|/det|> +Thus, the effect is consistent between the implanted participant and healthy controls when put in relation to the individual spectral peak. Indeed, we believe the position relative to the spectral peak to be a better indicator that these effects may be linked to the same neural phenomenon, rather than the specific frequency in Hertz. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 140, 905, 205]]<|/det|> +I thank the authors for their response and the clarifications they gave about their experiment. Despite these clarifications, I maintain reservations regarding the experimental paradigm used and the conclusions that can be drawn from it. + +<|ref|>text<|/ref|><|det|>[[92, 221, 905, 286]]<|/det|> +We thank the Reviewer for the deep review of our paper. We reply point by point below. Our responses are highlighted in bold and changes the revised version of the manuscript reported here are highlighted in red. + +<|ref|>text<|/ref|><|det|>[[92, 325, 905, 392]]<|/det|> +Experiment 2. The authors compared action timing judgments that were given after voluntary and involuntary actions, pooling together operant (Hand closing movement followed by sound) and non- operant (Hand opening movement alone) conditions (page 7 of the rebuttal letter). + +<|ref|>text<|/ref|><|det|>[[91, 429, 907, 569]]<|/det|> +1st issue: pooling together different actions and different conditions. The sense of agency is defined as "the feeling of making something happen" (Haggard, 2017). Here, the authors are mixing together conditions in which (different) actions caused a sound (i.e., the action makes happen a tone) with conditions in which the action did not produce any kind of external feedback (i.e., the action does not make happen a tone). In other words, they considered two very different conditions as equivalent, according to the literature on the sense of agency (see also the next comment. + +<|ref|>text<|/ref|><|det|>[[91, 584, 907, 675]]<|/det|> +We thank the Reviewer for raising these additional points. To demonstrate that our effect is not simply confounded by pooling operant and non- operant trials, we now show in Fig. S7 (reported below) that both the phase and the behavioural effect hold even when only considering the key condition of classical intentional binding studies, operant trials (see pages 11 and 48): + +<|ref|>image<|/ref|><|det|>[[101, 720, 888, 864]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 881, 905, 923]]<|/det|> +
Figure S7. Main results of Experiment 2 for operant trials only. Panel (a) shows the anticipation of perceived movement timing for voluntary vs involuntary movements ( \(p = 0.011\) , Wilcoxon). Panel (b) shows the phase
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 125]]<|/det|> +opposition product for early vs. late perception of the movement within voluntary operant trials. The red contour denotes the significant cluster of phase opposition \((p = 0.039)\) ." + +<|ref|>text<|/ref|><|det|>[[91, 139, 908, 325]]<|/det|> +In addition, the Reviewer's comment refers to the conditions used in the standard intentional binding paradigm. We would like to restate that our paradigm was inspired by the intentional binding paradigm in that it uses temporal judgements, but differs from it for several reasons, which makes comparison with previous results (and external validation) difficult, as we clearly acknowledged in the discussion (page 22). As far as sense of agency for the hand movement is concerned, as the topic here, we believe that both operant and non- operant conditions can provide meaningful information, and should be included. Importantly, the crucial signal we are studying precedes movement onset, and should not be related to further consequences of the action, which may or may not occur much later, but to the action itself. + +<|ref|>text<|/ref|><|det|>[[91, 339, 907, 454]]<|/det|> +2nd issue: Comparing voluntary vs involuntary actions. The authors compared action timing judgments after voluntary and involuntary (unpredictable) actions. The two conditions clearly differ based on the fact that the passive movement cannot be predicted: "In the involuntary session, the movement was randomly generated via the NMES system". This may explain the delay in action timing judgment observed with respect to voluntary movements. + +<|ref|>text<|/ref|><|det|>[[91, 469, 908, 631]]<|/det|> +The authors correctly cited Haggard et al., 2002 mentioning that this paper compared active and passive movements: indeed, Haggard et al. compared action timing judgements in voluntary vs involuntary actions yet this was done AFTER subtracting for the same measures collected in control conditions: timing judgment for voluntary actions recorded in the action+sound trials compared with timing judgment for voluntary actions recorded in the action- alone trials OR timing judgments for TMS- induced actions recorded in the action + sound trials compared with timing judgments for TMS- induced actions recorded in the action- alone trials, see Table 1 of Haggard et al., 2002). + +<|ref|>text<|/ref|><|det|>[[92, 646, 907, 712]]<|/det|> +In the present Ms, the authors adopted a different approach that cannot control for possible intervening factors not directly related to the agency dimension (e.g., surprise effect by unexpected externally generated muscle twitches). + +<|ref|>text<|/ref|><|det|>[[92, 728, 905, 770]]<|/det|> +Figure 2, shown in Haggard et al., 2017 may help in clarifying my comment (below called "The Figure"). https://www.nature.com/articles/nrn.2017.14 + +<|ref|>text<|/ref|><|det|>[[91, 784, 908, 923]]<|/det|> +The potential confounding effect of surprise was indeed not properly controlled in our first revision. To search for a potential effect of surprise, we have compared tone perception following voluntary and involuntary movements. If the anticipation of the perceived stimulus timing was driven by its predictability in the voluntary condition, as compared to the surprise generated by involuntary movements, we would also observe the same effect also for the tone. We could not detect such an effect \((p = 0.25)\) , as now mentioned in the main text (page 8) and shown in Fig. S5 (reported below). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[347, 85, 625, 255]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[92, 270, 905, 312]]<|/det|> +Control analysis on the perceived time of the sound in the operant condition. The p- value reported is from a Wilcoxon rank sum test, as for all other behavioural analyses in Experiment 2. + +<|ref|>text<|/ref|><|det|>[[91, 327, 907, 441]]<|/det|> +We would also like to point out that, as visible in Noel et al.'s complete report about this experiment, not only does action perception get anticipated in voluntary movements, but intention perception gets postponed when it is followed by an action. This further supports the intention- action binding interpretation, in a condition where surprise cannot play a role, since intention is internally generated and precedes the action. + +<|ref|>text<|/ref|><|det|>[[92, 480, 907, 546]]<|/det|> +Regarding the 1st issue, the authors here are pooling together conditions represented by the fourth (operant condition) and second (non- operant condition) rows of the upper part of the Figure (voluntary- action condition). + +<|ref|>text<|/ref|><|det|>[[91, 553, 907, 666]]<|/det|> +For what concerns the 2nd issue, the authors are comparing the conditions illustrated in the second/fourth row of the upper part of TheFigure with the second/third row of the lower part of The figure. To sum up, the authors of the present Ms are mixing together conditions that, in the intentional binding literature, refer to experimental and control conditions. Accordingly, there is no isolation of the crucial judgements of intentional acts and ensuing consequences. + +<|ref|>text<|/ref|><|det|>[[91, 681, 907, 797]]<|/det|> +We believe that our further analyses directly address these potential issues. Nevertheless, in the revised text we have acknowledged these potentially confounding factors. We have further toned down our interpretation of these findings, focusing strictly on objective facts: in this particular setup, action anticipation was associated with voluntary vs. involuntary movements with the very same 8 Hz phase associated with high agency movements (see pages 8, 9, 11). For example (page 11): + +<|ref|>text<|/ref|><|det|>[[91, 811, 905, 876]]<|/det|> +"Therefore, the same pre- movement 8 Hz oscillatory phase was associated with a higher explicit judgement of agency, and with anticipated action timing perception, which was also observed in voluntary vs. involuntary movements." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 123]]<|/det|> +Finally, we restate that, although partially inspired by the intentional binding paradigm, this experiment does not aim at fully reproducing its conditions and effects. + +<|ref|>text<|/ref|><|det|>[[92, 139, 906, 227]]<|/det|> +Experiment 3. In the first version of the paper, the authors acknowledged that participants were invited to "keep the mean (agency) rating around 5". I criticised this approach since it seems that they were actively inviting their subjects to give specific rating values and thus manipulating the dependent variable of the experiment. + +<|ref|>text<|/ref|><|det|>[[92, 235, 906, 323]]<|/det|> +In the revised version of the paper, they now write that participants: "were also asked to focus on the differences between trials rather than on the absolute levels of agency, to provide variable ratings using all the available range, and consider 5 as an intermediate point to distinguish between higher and lower agency levels." + +<|ref|>text<|/ref|><|det|>[[92, 332, 905, 372]]<|/det|> +This is something very different, and I am not sure that such changes from the original to the revised version are acceptable. + +<|ref|>text<|/ref|><|det|>[[92, 388, 906, 454]]<|/det|> +On a related note, they confirmed that no agency manipulation was applied in this experiment. This was aimed at measuring a sort of "intrinsic noise" in agency ratings. I am not sure that such noise can be considered related to the agency dimension since it does not vary according to a specific agency manipulation. + +<|ref|>text<|/ref|><|det|>[[90, 468, 908, 918]]<|/det|> +It is crucial to notice that our instructions, even in their original formulation could potentially only bias average ratings. As clearly stated in our previous response, a bias in participants' average rating would have strictly no effect on our analyses, which are based on a median split between individual trials. The Reviewer then states that our paradigm measures "intrinsic noise" in agency ratings and that "I am not sure that such noise can be considered related to the agency dimension since it does not vary according to a specific agency manipulation". The Reviewer seems to imply that only variations in subjective reports which are linked to external manipulations can be genuinely linked to agency. However, literature about perceptual awareness and pre- stimulus oscillations, which inspired our analyses, is grounded on studies in which variations in subjective reports at fixed experimental conditions are used as the key dependent variable, indicating that variability in subjective reports is not mere "intrinsic noise" but can be meaningfully studied (e.g., Busch et al., J Neurosci, 2009; Hanslmayr et al., Curr Bio, 2013; Ai et al., J Neurophysiol, 2014). This endogenous variability in the ratings can provide important insights into perceptual and cognitive phenomena, directly related to spontaneous fluctuations in the underlying neural activity, without potential confounds due to external manipulations. For example, previous studies used this approach to highlight the role of occipital alpha phase in visual awareness (Mathewson 2009). Here, it allowed us to uncover the role of M1- SMA oscillations for the sense of agency. Importantly, studying endogenous variability in subjective ratings at equal sensory stimulation is arguably the only appropriate approach to study pre- movement signals. Indeed, since a hypothetical agency manipulation on sensory feedback could only affect signals after movement onset, it would be impossible to observe our pre + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 908, 196]]<|/det|> +movement phase effect by contrasting experimental conditions. Indeed, exogenous manipulations act as a confounding factor for pre- movement signals, so all the effects we report were observed despite the effect of these manipulations, rather than thanks to them. This is another reason for which previous studies try to minimise stimulus variability (see papers cited above). These considerations have been integrated in our manuscript, to better explain and support our paradigm and its rationale on page 28: + +<|ref|>text<|/ref|><|det|>[[92, 212, 907, 277]]<|/det|> +"A similar approach, keeping experimental stimuli constant and contrasting trials based on fluctuations in subjective reports, is the one routinely applied in similar previous studies, investigating the link between perception and pre- stimulus oscillations (e.g., 29- 31)." + +<|ref|>text<|/ref|><|det|>[[91, 306, 908, 468]]<|/det|> +Finally, in my previous comment, I mentioned: "Contrary to what was seen in the patient, the normal control EEG data do not reveal activity in area M1 but in the SMA. The authors do not seem to be bothered by this. Yet this discrepancy deserves more than a comment. Indeed, as the two signals come from different areas, measured with different techniques, some differences should be expected. The key common thing here is that the crucial - small- EEG signal that correlates with the agency measures comes before action. This is the more solid cross- validation from the patient to the normal controls." + +<|ref|>text<|/ref|><|det|>[[90, 475, 909, 803]]<|/det|> +The authors replied: "Based on the previous literature about the neural bases of the sense of agency (see e.g., Haggard, Nature Neuroscience Reviews, 2017) and our results in the implanted patient (Experiment 1 and 2), we expected to observe phase opposition in motor and premotor areas. Consequently, we targeted our search for phase opposition on motor and premotor regions (n = 12), applying FDR correction for multiple comparisons within this network. This analysis revealed the strongest phase opposition in SMA, and that the second strongest phase opposition in M1 (p = 0.023). If focusing purely on the left M1, with the purpose of replicating the effect observed in the implanted participant, and thus dropping multiple comparisons correction, the uncorrected M1 effect is highly significant with p = 0.003. The uncorrected p- value is not reported for in the text, for being maximally conservative. In sum, phase position was significant in both SMA and M1. For completeness, we also reported the results of a whole- cortex search for phase opposition across all 114 ROIs of the cortex. This whole- cortex search confirmed significant phase opposition in the SMA after adjusting for 114 comparisons; in contrast, M1 did not survive multiple correction. We refrain from making interpretations of the null result for M1 in this whole- cortex search as this analysis is underpowered." I have the following comments: + +<|ref|>text<|/ref|><|det|>[[91, 819, 907, 909]]<|/det|> +1. Haggard 2017 did not mention M1, but temporo-parietal and premotor regions. +2. The whole brain analysis cannot survive a formal multiple comparison correction, and the authors commented on this result as a consequence of low power: I am not sure that this kind of comment is acceptable; given the simplicity of running an EEG experiment in normal controls, there is no excuse for low + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 905, 123]]<|/det|> +powered experiments. Given that expanding the same sample of subjects at this stage is not acceptable, a replication of this experiment with a fresh sample of subjects could make the whole story more tenable. + +<|ref|>text<|/ref|><|det|>[[90, 138, 909, 469]]<|/det|> +We apologise if our previous submission was confusing about the whole brain analyses, which were presented just as examples and were not performed with the highest statistical power. Indeed, FDR correction was mainly used to support the SMA result, as in our view prior evidence from Experiment 1 and 2 was sufficient to lift the requirement for multiple comparison correction for M1. However, we believe that it is important not to draw conclusions from non- significant results obtained with analyses not offering the highest possible statistical power, and we thus removed FDR- corrected analyses from the text. We would like to clarify that we do indeed have the statistical power and cohort sizes to perform a whole brain analysis. We have now performed the most appropriate analysis for whole brain data, which is cluster- based correction (Maris & Oostenveld 2007). This analysis is the most established one for whole brain effects in EEG or MEG data, as it provides the highest statistical power exploiting regularities in the temporal, frequency or spatial domain. In the revised version of the manuscript, we thus applied cluster- based statistics to all whole brain comparisons (Figs 6 and 7), in order to support our results with "formal whole- brain analysis". Specifically, M1 showed significant whole- brain corrected results, as the cluster formed by the two contiguous regions M1 and SMA was significant as reported on page 14: + +<|ref|>text<|/ref|><|det|>[[92, 497, 907, 588]]<|/det|> +"A cluster of two regions survived multiple comparison correction across all 114 ROIs \((p = 0.04)\) . These regions correspond to the posterior part of the left supplementary motor area (SMA), showing the strongest effect with uncorrected \(p = 0.0002\) , and the left M1 (uncorrected \(p = 0.003\) ), consistent with our results in the implanted participant." + +<|ref|>text<|/ref|><|det|>[[92, 617, 907, 682]]<|/det|> +On these grounds, we hope we have fully addressed the statistical doubts raised by the reviewer, and that the reviewer will agree that replicating the experiment in a fresh sample of participants is no longer necessary. + +<|ref|>text<|/ref|><|det|>[[91, 712, 909, 850]]<|/det|> +On the conceptual level, we do not see major discrepancies between Experiment 3 and previous results. Our key results in Experiment 3 are found in M1 and SMA, a key region for intention and sense of agency, immediately upstream of M1 in the intentional chain, and adjacent and strongly connected to it. As stated in the discussion, SMA was simply not observable in the implanted participant, where we could not decide where to implant the electrodes, but may have presented an even stronger result, if recorded. Actually, it is entirely possible that SMA may be the key origin of the observed effect, driving the effect in M1. + +<|ref|>text<|/ref|><|det|>[[92, 880, 907, 921]]<|/det|> +In any case, since the Reviewer was clearly not convinced by the design and results of Experiment 3, instead of merely replicating it, we decided to re- analyse previous unpublished data based on a classic agency + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[91, 81, 908, 269]]<|/det|> +manipulation to demonstrate the same agency- related pre- movement phase effect from M1 and SMA. In the experiment, we used a classical (Yes/No) agency rating and a temporal manipulation of visuo- motor delays, whereby movements of a virtual hand could randomly occur before or after the participant's real hand movements to generate variable agency judgements. These data again show significant phase opposition for Yes vs. No agency judgements, localized in the left SMA and M1, further addressing statistical concern about our M1 result in Experiment 3. Due to length constrains in Nature Communications, the replication of our results is briefly mentioned in the main text (page 14, see below) and detailed in the methods (pages 29- 32 and 38) and Supplementary Materials. + +<|ref|>text<|/ref|><|det|>[[91, 297, 908, 485]]<|/det|> +"To further confirm that pre- movement alpha oscillations discriminate high- agency and low- agency actions, we analysed data from an independent cohort of 10 participants, who performed a classic agency judgment paradigm. Briefly, participants were asked to freely lift their index finger, while receiving congruent visual feedback from a virtual hand, superimposed on their own. Visual feedback was delivered at various temporal delays from their actual movement. At the end of each trial, participants were asked to report whether they felt agency or not for the virtual hand. Comparing trials with "yes" vs. "no" agency reports we identified the same phase opposition in alpha in M1 and SMA, thus confirming and further generalizing our results to a different experimental paradigm (Experiment 4, see methods and Fig. S11)." + +<|ref|>text<|/ref|><|det|>[[91, 498, 812, 516]]<|/det|> +We provide a snapshot of the replication of our results (From Fig. S11) in M1 and SMA below: + +<|ref|>image<|/ref|><|det|>[[355, 521, 636, 737]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[91, 740, 905, 774]]<|/det|> +Replication of our key results in M1 (top, \(p = 0.027\) ) and SMA (bottom, \(p = 0.0055\) ) in an independent cohort of 10 subjects using a different paradigm. + +<|ref|>text<|/ref|><|det|>[[91, 789, 904, 822]]<|/det|> +We believe these new results, replicating for the fourth time the same phase- opposition effect from M1 and/or SMA, strongly support our main conclusion. + +<|ref|>text<|/ref|><|det|>[[92, 844, 907, 909]]<|/det|> +On a final note, the authors mentioned Wegner as a support to their approach: "Finally, concerning the validation of our Sham BMI approach. As correctly pointed out by Wegner in his mental causation theory, it is entirely possible for healthy individuals to experience a genuine sense of agency even when not truly in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 907, 172]]<|/det|> +control of an external event, as we believe was the case in our sham BMI setup." However, please note that this model was based on a "reconstructive" vision of the sense of agency, whereby the agency experience is formed AFTER the execution of the action. This is something different from what the authors are supporting in this paper. + +<|ref|>text<|/ref|><|det|>[[90, 201, 908, 484]]<|/det|> +This is an interesting point. First, we would like to state that we do not wish to take a strong stance in the prediction vs. postdiction debate, since our data does not necessarily support either of these views, and there is increasing support towards the idea that both predictive and postdictive aspects contribute to the sense of agency (e.g., Synofzik 2013). Here, we mainly report that pre- movement signals contribute to the (subsequent) sense of agency, but do not investigate when the subjective feeling of agency arises. We cited Wegner's work as a prominent example that a sense of agency can be experienced regardless of the true causal relationship between motor commands and sensory feedback. However, this is also compatible with a "predictive" view of the sense of agency: if sensory feedback is congruent with expectations, a sense of agency is experienced, regardless of whether that sensory feedback was truly caused by motor commands. This stems from the simple fact that the brain has no direct access to causal relationships, but only to sensorimotor contingencies upon which it infers causalities, as pointed out in the paper aiming to reconcile predictive and postdictive theories (Synofzik 2013). + +<|ref|>text<|/ref|><|det|>[[93, 514, 377, 529]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[91, 570, 908, 731]]<|/det|> +The authors addressed my main concerns about the technical issue very thoroughly and clearly. I now appreciate well the design of the experiment and I found that the additional analysis that they performed dismissed all the possible criticisms that I raised in the previous version, and I believe that the data strongly support the fact that the phase of pre- movement low- alpha rhythms in M1 and SMA encodes the sense of agency. Given the importance and the novelty of the message, the originality of the technical design and the fact that the intracortical recording in M1 human are rare and precious, I strongly support publication of the manuscript in Nature Communication. + +<|ref|>text<|/ref|><|det|>[[92, 747, 905, 789]]<|/det|> +We thank the Prof. Morrone for her appreciation of our work and the constructive additional feedback. We provide our point- by- point response below, highlighting our responses in bold. + +<|ref|>text<|/ref|><|det|>[[92, 805, 905, 846]]<|/det|> +However, in the present form the manuscript still needs an additional revision to meet the standard of the journal. + +<|ref|>text<|/ref|><|det|>[[92, 854, 253, 870]]<|/det|> +Clarity of the writing: + +<|ref|>text<|/ref|><|det|>[[92, 886, 905, 927]]<|/det|> +1) The introduction is very general and not informative about the state of art of mechanisms and circuits of sense of agency; the same criticism applies to the literature on phase of endogenous oscillations encoding + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[91, 81, 908, 220]]<|/det|> +motor information. Also about half of the introduction is about the presentation of the logic and result of the experiments, that is not useful for the reader given the complexity of the experiments. In addition, the same data from the same patients have already been published. It is important that the readers know about this in the introduction. The authors should clearly state and describe the results already obtained and published and, if possible, these should be used to motivate this new research. This means a fresh rewrite of most of the introduction. + +<|ref|>text<|/ref|><|det|>[[91, 235, 907, 350]]<|/det|> +Thank you for the suggestion which we hope will make the introduction more useful to readers. We have extensively modified the introduction removing the anticipation of our results, and expanding the presentation of the current state of research for sense of agency and neural oscillations. We have also addressed the link with our previous work in the introduction, rather than in the results as in the previous version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[90, 388, 908, 767]]<|/det|> +2) The language used in the paper to explain analysis procedures is not appropriate, using many technical terms that are used currently in the EEG laboratories, but often mathematical incomplete. One author is an excellent mathematician, and he should check accurately the language. For example equation 1, line 891, they not report what is Wi and in any case as it not mathematically correct. If Wi is the complex number associated with the frequency it should be added the term Arctangent of the imagery/real part...if it is already phase, it cannot be divided by the norm of the phase! Similarly, no indication of the other term in the equation, like the number of trials. Another example in lines 944 and 1335. The Hilbert transform is not needed to calculate the phase at the various frequency. What exactly has been done to calculate it? Another example appearing many times, time-frequency point is a colloquial term: there are maxima energy points or other point that can be marked on other specifications in the time-frequency domain. Please correct. Another example in line 1325. Normalization is associated mathematically to a division, while inspecting the figure there is clearly also a subtraction. Line 243 very mathematically unclear: do you mean that phase is expressed with respect to a different origin? In other words, that the phase has been rotated to take into account the difference in delay respect to experiment 1? In most cases I understood what the authors have done, because it is what normally it is done in EEG or LPF analysis: but please express the procedure in mathematically correct language in these examples and in many other instances. + +<|ref|>text<|/ref|><|det|>[[91, 781, 905, 822]]<|/det|> +Thank you for pointing out these inaccuracies. We provide below a point- by- point summary of our edits to improve the mathematical rigour of methods presentation. + +<|ref|>text<|/ref|><|det|>[[90, 838, 905, 890]]<|/det|> +- Line 891. The formula we used for inter-trial-coherence is the one used in the cited paper (VanRullen 2016): \(\mathrm{ITC}_{\mathrm{ALL}} = |\Sigma_{\mathrm{i} = 1:\mathrm{n}}\omega_{\mathrm{i}} / |\omega_{\mathrm{i}}|| / \mathrm{n}\) (1) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 81, 909, 291]]<|/det|> +where \(\omega_{i}\) represents the analytic signal, the complex number whose absolute value is the instantaneous amplitude at a given frequency, and whose argument is the instantaneous phase at that frequency. We apologize that this crucial information was missing from the original manuscript. It has now been added, as well as the indication about the number of trials (see page 33). In words, complex vectors representing amplitude- phase are first normalized to have unit length (division by the norm) and then summed, and the length of the resulting vector is divided by the number of trials. This way, if all phase angles are perfectly aligned, ITC will be equal to 1. If phase angles are random, ITC will be equal to the length of the sum of random vectors, approaching 0 as the number of trials increases, with ITC \(\sim 1 / \text{sqrt}(n)\) , similarly to what observed for Brownian diffusion. + +<|ref|>text<|/ref|><|det|>[[90, 306, 908, 444]]<|/det|> +- Line 944-1335. As done in (Kayser 2009, ref. 41 in the main text), the Hilbert transform, coupled with a causal filter, was used as an alternative way to Morelet wavelets to compute analytic signals \(\omega_{i}\) (then used to compute phase opposition) to demonstrate that the observed effect originates before sensory feedback onset. The signal was first band-passed in the frequency range of interest, then the analytic signal \(\omega_{i}\) was computed from the signal as the complex number whose real part is the original signal, and the imaginary part is the Hilbert transform. We have provided these details in the methods (see page 35). + +<|ref|>text<|/ref|><|det|>[[91, 459, 907, 526]]<|/det|> +- Line 1325. As now stated in the revised figure legend, firing rates were divided by their average on the first 100 ms time bin. Please note that the normalized firing rate values are not visible in the figure, as they were only used to time-lock LFP values (displayed in the figure). + +<|ref|>text<|/ref|><|det|>[[90, 541, 908, 678]]<|/det|> +- Line 243. Sorry for the lack of clarity. We actually meant that we chose to directly plot phase angles at -256 ms (maximal phase opposition for Experiment 1) also for Experiment 2, rather than at the time of maximal phase opposition for Experiment 2 (-342 ms). This aimed at allowing comparison between the two experiments without rotating the phases, which could introduce distortions, and is justified by the fact that phase opposition at -256 ms is strongly significant also in Experiment 2 (see e.g., Fig. 3g., indicating p < 0.0001 for -256 ms). We have clarified this in the text. + +<|ref|>text<|/ref|><|det|>[[92, 719, 197, 734]]<|/det|> +Data analysis: + +<|ref|>text<|/ref|><|det|>[[91, 775, 908, 913]]<|/det|> +The authors assess differences in phases between the two conditions using inter- trial phase coherence and apply an equation that maximize anti- phase difference. However, in principle the system could work in quadrature phase that offers other advantages. It is essential to show that a difference in phase of the 8Hz component of the average LFP between the two conditions is statistically significant and report the value. This can be obtained simply by applying circular statistics across the vector (amplitude and phase) cluster for the two conditions. I think that it is important to consider simultaneously amplitude and phase of the 8 Hz + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 175, 98]]<|/det|> +oscillation. + +<|ref|>text<|/ref|><|det|>[[90, 138, 909, 350]]<|/det|> +Thank you for raising this interesting point. To simultaneously study amplitude and phase of 8 Hz LFP oscillations, we compared the analytic signals \((\omega_{i})\) for high and low agency trials at 8 Hz, - 256 ms, the time and frequency of strongest phase opposition, without normalizing them to unit length to include amplitude information (figure below). To the best of our knowledge, circular statistics is used for unit length vectors not including amplitude information. We instead used a Hotelling \(T^{2}\) to simultaneously compare phase and amplitude of the LFP. The test was significant \((T^{2}(208) = 21.4, p < 0.0001)\) , indicating that phase differences were significant also when taking into account 8 Hz LFP amplitude. A further T- test on the sole amplitude was not significant \((T(208) = 1.03, p = 0.31)\) , confirming that the observed differences emerge from phase rather than amplitude differences. These results are summarised below and reported on page 34. + +<|ref|>image<|/ref|><|det|>[[110, 388, 744, 795]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[90, 817, 905, 859]]<|/det|> +Real (x axis) and imaginary (y axis) part of analytic signals at - 256 ms, 8 Hz for individual trials in Experiment 1, extracted through Morelet wavelets. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 905, 146]]<|/det|> +Figure 3h reports LFP amplitude, but it is never defined what exactly it is measured. Is it the amplitude at 8 Hz, so it becomes negative due to the phase? Or it is the value in voltage of the LFP at the time point chosen? Please explain also in the text. + +<|ref|>text<|/ref|><|det|>[[92, 163, 905, 228]]<|/det|> +The figure shows the raw, unfiltered LFP value, as now clarified in the text and figure legend. The analysis aimed demonstrating that pre- movement 8 Hz phase differences are stronger than post- movement raw LFP value differences, to address a concern raised by the other Reviewer. + +<|ref|>text<|/ref|><|det|>[[92, 271, 232, 285]]<|/det|> +Concetta Morrone + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 84, 377, 99]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[92, 140, 905, 191]]<|/det|> +The authors have dealt adequately to all my criticisms, and I strongly support publication in the present formWe thank again Prof. Morrone for her support of our work and the constructive review process. + +<--- Page Split ---> diff --git a/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/images_list.json b/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..23174c492bf110b408562351cdc5f2ee76d43158 --- /dev/null +++ b/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1: Selection of districts: (a) All districts; (b) Selected districts.", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d94fc7a2f4b9b56057c0f6a31fa1753f0a124c08 --- /dev/null +++ b/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,371 @@ + +# nature portfolio + +Peer Review File + +The changing impact of rural electrification on Indian agriculture + +![](images/Figure_1.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: + +The central premise of this project is that rural electrification impacts household incomes and a key pathway through which it does so is via enabling households engaged in agriculture to pump groundwater for irrigation. The hypothesis which they proceed to test is that a 2000s turn in policy focus towards household electrification rather than electrification for agriculture, which therefore undermined the growth of electric pumps in agriculture. This "crowding out" of electric agricultural pumps by domestic electrification in turn affected income growth. They proceed to demonstrate this through a series of steps - first, by demonstrating that the relationship of electricity based pumping and domestic access to electricity is on average lower among "late electrifier" districts and the "early electrifier" districts and by showing that rural electrification was not income enhancing for the "late electrifiers" as it was for the "early electrifiers". + +This paper is on a very interesting topic and the authors make very original and creative use of the data. It is motivated very well and the authors produce very useful insights. However, I was left underwhelmed by their bewildering empirical approach and the confusing use of data. + +The backbone of this paper is the empirical specification in Lines 319- 322 that regresses electric pumps (and then acreage irrigated by them) on households with electricity and an interaction term that combines electrified households with and indicator variable denoting if this is greater than \(50\%\) of all households. The authors claim + +The coefficient on the interaction of elecrhit with LateEleci, \(\beta\) , is of main interest. It captures the difference O in the effect of household electrification on pump electrification between early and late electrifying districts. In other words, a captures the relationship between rural electrification and groundwater irrigation among early electrifying districts, while \(\alpha + \beta\) captures the estimate for late electrifying districts. + +I beg to differ. In essence, this is like a classic structural break model but defined in terms of a \(50\%\) threshold based on electrified households. Note that this is exactly the specification one would use to detect threshold effects that beyond a threshold of electricity diffusion in the village, the relationship between domestic and agricultural use of electricity changes. One could tell several alternate stories with this model: that there is a preference ordering of investment among rural households so that in the early stages of diffusion of electricity people invest in electricity pumps; or a story of village level development - in the early stages of electrification, one invests in agriculture (electric pumps) and eventually as surplus is generated in agriculture, one invests in off farm activities. I simply don't see the empirical specification delivering the story that the authors are trying to get at. Indeed, one could argue just based on the model, that it has little to do with any policy or crowding out, but a story of the evolution or dynamics of electricity use. + +The authors robustness checks "We also consider models where we include electrification quantiles instead of a single binary classifier and find similar results (see appendix tables A1 and A2), in fact illustrate the diminishing importance of agricultural pump electrification as domestic electrification expands. In short, the authors have an exciting story here (they should write that one), but it is not the one they are trying to tell! + +The fundamental problem is "construct" validity. Their bewildering approach to identifying those districts "exposed" to the policy and irrigation oriented versus a domestic oriented electrification policy, named "early" and "late" electrifiers derives not from the time when electrification was introduced but to the extent of electrification (in 2001?) i.e., as "majorly electrified" (lines 116). I struggled to see for myself nor access evidence to see why this is a good construct of early versus late + +<--- Page Split ---> + +and not more versus less! + +A better approach would be a structural break in terms of time (treat 1986 as a base period and use an indicator variable for post 2000s) to proxy the policy shift. The authors could add a piece- wise analysis based on what proportion of households are electrified. + +I would always want state- year interaction fixed effects to control for time- varying policy changes (including electricity pricing policies, irrigation technology subsidies, other infrastructure, etc.) + +I would like to see a greater discussion of diesel pumps (lines 66- 68) used not as a substitute for electricity but for poor quality of electricity and hours of power supply. There are several discussions of these in the literature on subsidies in India (notably by Ashok Gulati and co- authors). + +Line 23 "Perhaps it is time to reevaluate uniform prescriptive electricity loads and uses in formulating RE policies" This sentence can be clarified. It becomes clear later on but on line 23, it is too early for readers unfamiliar with the policy and the sector. + +The authors claim that they use "newly constructed panel- dataset spanning three decades" (in the abstract). Yet the figure 2 notes that the "Relationship between electrified households and electrified wells in 2013 was stronger among early electrifiers compared to late electrifying districts. The point estimates represent district- level data on electrified houses and wells with electrified pumps." This suggests misleadingly that the regression was run for just 1 year, i.e., 2013. + +The undertone at least in the initial parts of the paper is a celebration of electricity for pumping groundwater, barring some reflections in line 68. Perhaps you could start the paper early on by suggesting that despite the problem of overextraction etc. irrigation is known to have large benefits, and the culprit for that is more in the pricing than the extraction. + +Reviewer #2: Remarks to the Author: The authors tackle a very important question with both energy and human development implications. + +This is a good dataset and strong analytics - but the interpretations and framings need to be questioned. The study very nicely shows there is a disconnect for irrigation coverage vs. household electrification by time (early vs late), but it's not clear causality can be linked to policies favoring household electrification. + +Utilities likely did slow down connections to farmers, but that was independent of any focus on household electrification. Farmers underpay, as well known, and this non- remunerative supply is a strain on utilities. Note, free power to farmers only started in 1977 in Andhra Pradesh, and wasn't widespread for a few more years. + +While electricity access policy DOES favor households, it's not clear why that would be at the expense of agriculture. BOTH segments enjoy heavily cross- subsidized and subsidized electricity (cross- subsidies for homes being for lower slabs or tiers of consumption). + +One has to start with the reality that agricultural supply is very expensive for the utility - being both subsidized and cross- subsidized. Are there enough takers for a pumpset? Let's also start with SECC data - 55% of farmers are landless (laborers) so increasing pumpsets helps a subset. Here's a counterfactual Q: Now that households are \(\sim 100\%\) electrified, does this now "free up" policy for pumpsets? The pumpsets policy has been the way it is (limited by design, with largesse and political + +<--- Page Split ---> + +connections important) for a long while in the face of heterogeneity in connectivity. + +There is no limited incorporation of the physics, design, and practicality of rural connections. Recent policies (last \(\sim 10\) years) have been towards feeder segregation, but even before this, most states had "rosters" or schedules where agricultural supply was limited to, say, 6 or 8 hours per day. This was controlled through phase- separation, with single phase supply (for homes) meant to be as much as possible, ideally 24 hours in theory (but never in practice). + +The second reality that questions the model and framing is how we have "incremental electrification". Most challenges for household electrification have been with the "last mile connection". The earlier (and insufficient) definitions of electrification focused on a single lightbulb meant the village was electrified, updated to then be \(10\%\) of homes. This was progressively upgraded, which is a good thing, but there is no evidence of a \(^*\) policy reason\\* this was at the expense of pumpsets. Your analysis does bring out the point that household supply doesn't increase wealth much - so it is a separate question of how much one can/should increase pumpsets. If they were charged "full cost" there would be no problem but we know they are not. Money for loss- making utilities is scarce, and so there is a call to be made how much pumpset deployment is appropriate. + +Aside: There was also a period (early 2000s) where power supply quality impacted affordability of pumpsets. Even with "cheap power", frequent burnouts meant rewinding costs were more than the cost of electricity. This raises the general question of why don't people want a pumpset versus how many people want a pumpset but can't get one. + +Do you measure size of wells (borewells), measured by HP (horsepower)? 20 wells isn't comparable across regions. This also links to issues of water- sharing. Local politics and influence can be a factor. This also means larger farmers with pumpsets sell water to their neighbors. Anecdotally, it is prevalent in many eastern states of India. + +Is there any analysis of farm size and pumpsets? Many farms in the less irrigated sections of India (easter) are more subsistence, and also (as you rightly observe) have limitations in market access. These regions also have much lower water demands based on water tables. Crop choices also matter - Punjab went for cash crops much earlier on. + +An interesting analysis would be to examine districts within a state. One can assume a state has certain policy - but we note there is disparity in pumpsets within states. This suggests it's not a policy reason but fundamentals driven by farmer wealth, crop choices, water tables, rainfall patterns etc. See interior Maharashtra vs. coastal, and similar for some other states. + +A fundamental question: What if earlier electrifiers were simply richer regions or had more resources? Thus BOTH homes and pumpsets would be faster. The 8 times more pumpsets for earlier electrifiers then is explained by economic reasons, as opposed to the framing you have, which is a policy choice with a tradeoff. + +Figure 3 - we can note that even in 2013, it is the east that lags - both household electrification and irrigation. + +Figure 4 - There is a clear split between late vs. early electrifiers, but that split may also have many confounding factors instead of your theory of policies that favored one over the other. Note that there are very few districts with over 5 lakh (500,000) households electrified. + +Line 163: "transformer capacities could be constraining even households with the financial means to access electricity for groundwater irrigation." Your math is correct that household connections are small, but transformers are always based on multiple homes, and, more importantly, almost NEVER smaller than tens of kW. Esp. in those days, there were no plans for LVDS (low voltage distribution + +<--- Page Split ---> + +systems) which had smaller transformers. Typically, there was a fixed model used that covered a variety of uses. There was no separate transformer then for house vs. agriculture. So size limitations is unlikely to be a bottleneck until we have many pumpsets connected. + +In summary: Interest and strong analysis, but the claims made aren't proven, and the econometrics only partially answer some of the issues above (like wealth as a factor - it's not just RURAL HOUSEHOLD WEALTH that matters - state wealth matters for the utility, e.g., the presence of richer consumers to offset rural losses. + +<--- Page Split ---> + +# Beyond Lights: The Changing Impact of Rural Electrification on Indian + +Agriculture + +Review Responses + +## Reviewer 1 + +The central premise of this project is that rural electrification impacts household incomes and a key pathway through which it does so is via enabling households engaged in agriculture to pump groundwater for irrigation. The hypothesis which they proceed to test is that a 2000s turn in policy focus towards household electrification rather than electrification for agriculture, which therefore undermined the growth of electric pumps in agriculture. This "crowding out" of electric agricultural pumps by domestic electrification in turn affected income growth. They proceed to demonstrate this through a series of steps - first, by demonstrating that the relationship of electricity based pumping and domestic access to electricity is on average lower among "late electrifier" districts and the "early electrifier" districts and by showing that rural electrification was not income enhancing for the "late electrifiers" as it was for the "early electrifiers". + +This paper is on a very interesting topic and the authors make very original and creative use of the data. It is motivated very well and the authors produce very useful insights. However, I was left underwhelmed by their bewildering empirical approach and the confusing use of data. + +Thank you for your detailed and insightful comments. We have taken your suggestions and added three pieces of analyses to strengthen our claim that electrification timing which captures a change in electrification policy is associated with the slow expansion of agricultural electricity. We understand why in its current form our paper may lead readers to believe that the level of electrification rather than timing may be important in predicting the number of electrified wells. We believe the additional analyses which include - (1) using a different treatment indicator; (2) analysis on a subset of districts with comparable electrification rates and; (3) sub- district analysis within a state, strengthen our claim that it is indeed when electrification took place that impacts where electricity is used for groundwater irrigation. Additionally, to clarify our intent to capture electrification policy change, we have replaced Late Elec with \(PC\) to identify districts that were majorly electrified after the focus of rural electrification policy shifted towards domestic electrification from agriculture. The definition of \(PC\) is the same as what we previously used for Late Elec. We now refer to late electrifying districts as PC districts or districts that electrified post policy change, and early electrifiers as non- PC districts or districts that electrified pre policy change. We highlight changes in the manuscript by using blue- coloured text. Please see detailed responses to your points below. + +The backbone of this paper is the empirical specification in Lines 319- 322 that regresses electric pumps (and then acreage irrigated by them) on households with electricity and an interaction term that combines electrified households with and indicator variable denoting if this is greater than \(50\%\) of all households. The authors claim the coefficient on the interaction of \(elech_{it}\) with \(LateElec_{i}\) , \(\beta\) , is of main interest. It captures the difference 0 in the effect of household electrification on pump electrification between early and late electrifying districts. In other words, \(\alpha\) captures the relationship between rural electrification and groundwater irrigation among early electrifying districts, while \(\alpha + \beta\) captures the estimate for late electrifying districts. + +I beg to differ. In essence, this is like a classic structural break model but defined in terms of a \(50\%\) threshold based on electrified households. Note that this is exactly the specification one would use to detect threshold + +<--- Page Split ---> + +effects that beyond a threshold of electricity diffusion in the village, the relationship between domestic and agricultural use of electricity changes. One could tell several alternate stories with this model: that there is a preference ordering of investment among rural households so that in the early stages of diffusion of electricity people invest in electricity pumps; or a story of village level development - in the early stages of electrification, one invests in agriculture (electric pumps) and eventually as surplus is generated in agriculture, one invests in off farm activities. I simply don't see the empirical specification delivering the story that the authors are trying to get at. Indeed, one could argue just based on the model, that it has little to do with any policy or crowding out, but a story of the evolution or dynamics of electricity use. + +We use household electrification to measure rural electrification in our analysis. However, early attempts at rural electrification expansion in India were focused on providing electricity infrastructure to villages with a small number of domestic connections (about \(10\%\) ) (Banerjee et al., 2014a). It was only in the early 2000s that the focus shifted towards electrifying all households. The target of Rajeev Gandhi Vidhyatikaran Yojana (RGGVY) were villages with populations greater than a 100 and lacking electricity infrastructure. We find regions electrified under RGGVY to experience limited expansion in agricultural electricity. Therefore it is not how electricity diffuses which impacts its use in agriculture rather when, since villages which got electrified for the first time under RGGVY experienced almost no expansion in agriculture (Banerjee et al., 2014a; Planning Commission of India, 2014; Parikh et al., 2013). We include three specific analyses that strengthen our claim of the relationship between weak expansion of agricultural electricity supply and the timing of electrification - + +1. Replace \(PC_i\) with \(RGGVY_i\) - We replace \(50\%\) household electrification threshold captured by \(PC_i\) (previously LateElec_i with an indicator variable \(RGGVY_i\) , which is 1 for districts that were funded under the first wave of electricity expansion under RGGVY during India's \(X^{th}\) five year plan spanning 2002-2007. We find our main conclusions to hold with some changes in the precision of the estimates (results included in table 1, columns 5-7). Our reason for not using \(RGGVY_i\) in our primary specification is due to issues of data integrity. RGGVY was majorly carried out under the \(X^{th}\) (2002-2007), \(X^{th}\) (2007-2012) and \(XII^{th}\) (2012-2017) five year plans. However, data for the selection of districts in each wave is unavailable. Even with the limited data, our primary specification picks up the slow expansion of agricultural electricity supply for RGGVY phase I districts. A point to note - the results no longer remain statistically significant with the inclusion of state specific year fixed effects. + +2. Sub-district analysis within a state - We also run our primary specification at the block level in Madhya Pradesh. Blocks are administrative units in between villages and districts. Therefore there is variation in the electrification rates within each district, which is another way we test the threshold effect. We chose Madhya Pradesh as it has a high diversity of PC (previously late electrifier) (28) and non-PC (10) (previously early electrifying) districts and is a major agricultural state. + +We use the Defense Meteorological Program Operation Line Scan System (DMSP- OLS) night time luminosity data compiled by Asher et al. (2021) to measure electrification. We use this additional source as population census does not publish electrification data at the block level or any level lower than districts. We matched the second, third and fifth rounds Minor Irrigation Census with SHRUG nightlight and population census datasets (Asher et al., 2021). The first minor irrigation census does not report data at the block or village level. We use total light luminosity values which range from 0 to 63 and are calibrated by Elvidge et al. (2014) for consistent measure across the range of years between 1994- 2013. + +On average we find DMSP- OLS data to be a conservative estimate of electrification (see figure appendix figure A1). The block- level analysis with DMSP- OLS and Minor Irrigation Census for Madhya Pradesh are consistent with our results overall with some differences in the interpretation due to the use of nightlight luminosity. On average, a \(1\%\) increase in luminosity among blocks within non- PC districts (previously early electrifier) is associated with an increase in over 1,500 electrified wells. This value decreases by nearly 1,000 wells and a \(1\%\) increase in nighttime luminosity is associated with a cumulative increase of 500 electrified wells in blocks across PC districts (previously late electrifier) in Madhya Pradesh. We do not find a relationship between nighttime luminosity and wells with diesel pumps. + +<--- Page Split ---> + +3. District Selection - Finally, to isolate timing rather than proportion of electrification, we select districts from both PC and non-PC districts based on a common window of electrification rates. Figure 1 illustrates our selection process where we choose districts from both groups in the 25% to 50% electrification rates in 1986 for non-PC and in 2001 for PC districts. Using this subset of districts we run our primary specification. For the subset of districts among non-PC districts, we regress the change in electrified wells on change in household electrification between 1986 and 2001. We do the same for PC district subset between 2001 and 2013. Doing so helps us measure similar electrification thresholds between PC and non-PC districts but across different time periods. Results from this analysis have similar implications as our main results (table 1). Across non-PC districts, electrification of 100 households is on average associated with approximately 18 additional wells with electric pumps. Whereas, this number reduces to less than 4 among PC districts. + +![PLACEHOLDER_7_0] + +
Figure 1: Selection of districts: (a) All districts; (b) Selected districts.
+ +Table 1: Implications remain the same even for selected districts within common bandwidth of electrification rates + +
Groundwater wells
TotalWith electric pumpsWith diesel pumps
Electrified households0.089**
(0.044)
0.180***
(0.051)
0.002
(0.015)
Electrified households × PC-0.0832**
(0.039)
-0.1408***
(0.049)
0.020
(0.025)
Total households-0.050
(0.056)
-0.071
(0.053)
-0.015
(0.019)
Fixed-effects
DistrictYesYesYes
YearYesYesYes
Fit statistics
Observations236236236
0.960.930.93
Within R²0.050.170.03
+ +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Estimated using equation 1 and a subset of districts from the panel dataset constructed from district-level population and minor irrigation census data. + +The authors robustness checks "We also consider models where we include electrification quantiles instead of a single binary classifier and find similar results (see appendix tables A1 and A2), in fact illustrate the diminishing importance of agricultural pump electrification as domestic electrification expands. In short, the authors have an exciting story here (they should write that one), but it is not the one they are trying to tell! + +<--- Page Split ---> + +The fundamental problem is "construct" validity. Their bewildering approach to identifying those districts "exposed" to the policy and irrigation oriented versus a domestic oriented electrification policy, named "early" and "late" electrifiers derives not from the time when electrification was introduced but to the extent of electrification (in 2001?) i.e., as "majorly electrified" (lines 116). I struggled to see for myself nor access evidence to see why this is a good construct of early versus late and not more versus less! + +We hope that we have been able to convince you as to why we believe that limited expansion of agricultural electricity is related to the timing of electrification and not the extent of electrification with the three additional analyses described above. Additionally, we have also changed LateElec to \(PC_{i}\) to better reflect the treatment we measure. \(PC_{i}\) refers to policy change and is defined similarly as LateElec. + +A better approach would be a structural break in terms of time (treat 1986 as a base period and use an indicator variable for post 2000s) to proxy the policy shift. The authors could add a piece- wise analysis based on what proportion of households are electrified. + +The issue with using 1986 as a base year and treating all districts similarly is that we are unable to distinguish between districts that majorly electrified before 2001 and those that electrified post 2001 when the target of rural electrification changed from agriculture to domestic connections. Electrified wells have continued to increase in number across both categories of districts till the latest available round in 2013. However, the rate of increase is different and important to isolate, which we are unable to do in the proposed analysis. + +I would always want state- year interaction fixed effects to control for time- varying policy changes (including electricity pricing policies, irrigation technology subsidies, other infrastructure, etc.) + +We include state- year interaction fixed effects in our primary specification and find similar implications for electrified wells with some changes in the precision of our estimate (tables 2 and 3). Electrification of 100 households among non- PC districts is on average associated with approximately 10 electrified wells compared to nearly 16 in our original analysis. The penalty for electrifying post policy change remains statistically significant and reduces to nearly 3 electrified wells compared to our earlier estimate of 2 additional electrified wells. + +Interestingly, although electrification is still associated with a decrease in the use of diesel pumps, the penalty for electrification post policy change no longer remains statistically significant. This is likely due to low cross- state variation in the use of diesel pumps which may be stemming from a loss of statistical power, or perhaps reflective of the dominant use of diesel pumps in alluvial aquifers which are regionally concentrated across India (Shah, 2009). Results for irrigated area also have similar implications for all seasons. On average, electrification of a 100 households is on average associated with increase in nearly 12ha of irrigation during Kharif and 10ha during Rabi among non- PC districts. These numbers are a bit higher than our previous estimates of 11ha and 9ha respectively. We find post- policy change electrification penalty completely negates any increase in irrigation expansion during Rabi, similar to our previous estimates. + +<--- Page Split ---> + + +Table 2: Household electrification in PC districts is also associated with smaller expansion in irrigated area across all season with variations explained by electrified pumps + +
Groundwater wells
TotalWith electric pumpsWith diesel pumps
Electrified households0.058***
(0.020)
0.101***
(0.025)
-0.028***
(0.008)
Electrified households × PC-0.0543**
(0.027)
-0.0709**
(0.028)
0.0201
(0.013)
Total households0.0294**
(0.014)
0.0036
(0.009)
0.0101
(0.011)
Fixed-effects
DistrictYesYesYes
State × YearYesYesYes
Fit statistics
Observations969969969
0.740.930.87
Within R²0.120.640.42
+ +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Estimated using equation 1 and panel dataset constructed from district-level population and minor irrigation census data. + +Table 3: Household electrification in late-electrifiers is also associated with smaller expansion in irrigated area across all season with variations explained by electrified pumps + +
Irrigated area (ha)
Annual (ha)Kharif (ha)Rabi (ha)
(1)(2)(3)(4)(5)(6)
Electrified households0.199***
(0.0665)
0.050
(0.0527)
0.117***
(0.0337)
0.037
(0.0253)
0.096***
(0.0320)
0.034
(0.0275)
Electrified Households × PC-0.178***
(0.058)
-0.070
(0.043)
-0.063**
(0.030)
-0.005
(0.021)
-0.010***
(0.029)
-0.060**
(0.025)
Wells with electric pumps1.492***
(0.182)
0.801***
(0.111)
0.594***
(0.075)
Total households0.082
(0.060)
0.079
(0.051)
0.026
(0.025)
0.025
(0.021)
-0.005
(0.025)
-0.006
(0.021)
Cumulative Average Monthly Rain↑-11.43
(7.872)
-4.053
(7.458)
-11.91**
(4.659)
-6.641
(4.252)
23.00
(35.14)
0.174
(32.52)
Fixed-effects
DistrictYesYesYesYesYesYes
State × YearYesYesYesYesYesYes
Fit statistics
Observations969969969969969969
0.890.900.880.890.890.90
Within R²0.450.510.420.510.420.47
+ +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Annual, average rainfall during November to March and average rainfall during June to October were used for annual, Rabi and Kharif cultivation seasons respectively. Estimated using equation 1 and panel dataset constructed from district-level population and minor irrigation census data. + +I would like to see a greater discussion of diesel pumps (lines 66- 68) used not as a substitute for electricity but for poor quality of electricity and hours of power supply. There are several discussions of these in the literature on + +<--- Page Split ---> + +subsidies in India (notably by Ashok Gulati and co- authors). + +Included text in Lines 67- 75 - "Electricity is preferred even in shallower wells where the option of pumping using diesel exists and is reflected in the declining proportion of wells operated by diesel pumps from over \(30\%\) in 1986 to below \(28\%\) in 2013, despite greater than \(90\%\) growth in the total number of irrigation wells during the same period (Statistics Division, 2017). At greater than INR 40/1 since price deregulation in 2014, diesel is more expensive than agricultural electricity rates in most Indian states. (Verma and Patnaik, 2018; CCEA, 2014) Therefore, only in regions where electricity is unavailable or suffers from quality issues of intermittency and low voltage, diesel pumps are used to power irrigation either exclusively, or in conjunction with electric pumps to compensate for unreliable electricity supply (Gulati and Narayanan, 2003; Gulati et al., 2019). Where available, electricity is subsidized by way of flat or no tariffs effectively eroding the marginal cost of consuming electricity (Gulati and Narayanan, 2003)." + +Line 23 "Perhaps it is time to reevaluate uniform prescriptive electricity loads and uses in formulating RE policies" This sentence can be clarified. It becomes clear later on but on line 23, it is too early for readers unfamiliar with the policy and the sector. + +Changed text in Line 24- 27 - "Perhaps it is time to reevaluate domestic electrification as the primary target of RE policies, and instead consider income generation as a primary goal to unleash the true power of electrification in the rural developing world." + +The authors claim that they use "newly constructed panel- dataset spanning three decades" (in the abstract). Yet the figure 2 notes that the "Relationship between electrified households and electrified wells in 2013 was stronger among early electrifiers compared to late electrifying districts. The point estimates represent district- level data on electrified houses and wells with electrified pumps." This suggests misleadingly that the regression was run for just 1 year, i.e., 2013. + +Figure 4 serves as the descriptive evidence to motivate our analysis and is explained by the accompanying text in lines 130- 134 - "Before presenting our regression models, figure 4 presents cross- sectional, descriptive evidence to motivate our analysis. In 2013, our most recent round of data, we see a stark difference in the relationship between household electrification and electrified groundwater pumps in PC versus non- PC districts. PC districts had far fewer wells with electric pumps compared to non- PC districts with similar numbers of electrified households (Figure 4). This divergent cross- sectional relationship between the two sets of districts could be driven by unobserved factors." + +We have added the following line (lines 140- 141) to clarify that the regression estimates considers three time periods - "Our fixed effects regression estimates measures the association between the number of electrified households with the number of groundwater wells using electric and diesel pumps across 1986 to 2013. The estimates show that, on average, the electrification of ..." + +The undertone at least in the initial parts of the paper is a celebration of electricity for pumping groundwater, barring some reflections in line 68. Perhaps you could start the paper early on by suggesting that despite the problem of overextraction etc. irrigation is known to have large benefits, and the culprit for that is more in the pricing than the extraction. + +Included text in Lines 9- 11 - "This vast consumption of groundwater has not been without its adverse impacts. Every year India pumps twice as much groundwater as the US or China, and houses regions with the greatest rates of global groundwater depletion (Aeschbach- Hertig and Gleeson, 2012; Famiglietti, 2014; Lo et al., 2016)." + +<--- Page Split ---> + +## Reviewer 2 + +The authors tackle a very important question with both energy and human development implications. + +This is a good dataset and strong analytics - but the interpretations and framings need to be questioned. The study very nicely shows there is a disconnect for irrigation coverage vs. household electrification by time (early vs late), but it's not clear causality can be linked to policies favoring household electrification. + +We thank you for your insightful and helpful comments. We have made additions to the manuscript with a new block- level analysis for Madhya Pradesh and text in response to your points and in support of our original claims. Additionally, to clarify our intent to capture electrification policy change, we have replaced Late Elec with PC to identify districts that were majorly electrified after the focus of rural electrification policy shifted towards domestic electrification from agriculture. The definition of PC is the same as what we previously used for Late Elec. We now refer to late electrifying districts as PC districts or districts that electrified post policy change, and early electrifiers as non- PC districts or districts that electrified pre policy change. We highlight changes in the manuscript by using blue- coloured text. Our responses to the individual points are found below. + +Utilities likely did slow down connections to farmers, but that was independent of any focus on household electrification. Farmers underpay, as well known, and this non- remunerative supply is a strain on utilities. Note, free power to farmers only started in 1977 in Andhra Pradesh, and wasn't widespread for a few more years. + +While electricity access policy DOES favor households, it's not clear why that would be at the expense of agriculture. BOTH segments enjoy heavily cross- subsidized and subsidized electricity (cross- subsides for homes being for lower slabs or tiers of consumption). + +It is likely that rural electric supply on average is loss- making in India for the power utilities, whether it is subsidized domestic connections or agricultural supply. It is for precisely this reason, that we think there is some rationing occurring in who gets electricity and where. Together, our results imply that while power utilities or the government may not have deliberately neglected agricultural electricity supply, the singular focus on electricity expansion through domestic connections to fulfill stated targets may have resulted in the unintended neglect of electricity supply to agriculture. We do not have empirically robust methods of teasing out exactly how this may have occurred, but from a synthesis of literature and field visits to Odisha identify two main routes - + +1. Transformer sizing - Two independent evaluations of the Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY) by Parikh et al. (2013) and Planning Commission of India (2014) find frequent burnout of transformers in RGGVY electrified villages. Through surveys, they find overloading (rather than infrastructural defects) as a key reason for these burnouts. Further, Parikh et al. (2013) breakdown the calculation of the standard size of installed transformers of 457kW (16kVA with a power factor of 0.7) load result in average loads of 600W per household (implying average village size of \(\sim 760\) households). Therefore, the average household load is less than the capacity of a 1 HP pump-set ( \(\sim 746\) W). In such a scenario, nearly 50% of the total calculated load could come from only pumps if even 10% of the houses operated 4HP pump-sets. To place this in context, over 80% of all wells in MI Census 2013 used pumps larger than 4HP (Government of India, 2017)s. Additionally, Banerjee et al. (2014b) also state the limited capacity of transformers as one of the major contributors to low reliability of electricity among RGGVY electrified villages. + +2. Distance from transformer and lack of electric infrastructure that provide physical access (poles, wires etc.) for non-domestic uses of electricity - The two studies note voltage drops experienced by far flung houses in villages leading to equipment failure. Additionally, Parikh et al. (2013) find a complete absence of any commercial activities outside of homes in surveyed villages electrified by RGGVY. They find a small number of commercial activities including weaving and handicraft occurring inside homes. Planning Commission of India (2014) find the use of electric motor-pumps for agriculture in less than 1% of households surveyed in RGGVY villages. + +We identified similar constraints in field visits conducted during 2016 and 2018 in rural Odisha. Farmers in the + +<--- Page Split ---> + +state are expected to pay the additional cost of poles and wiring required to access electricity on their fields (Orissa Lift Irrigation Corporation, 2014; Department of Energy, 2016). Transformer burnouts were also frequently experienced and attributed by the energy department officials to the hooking up of a handful of electric pumps. + +One has to start with the reality that agricultural supply is very expensive for the utility - being both subsidized and cross- subsidized. Are there enough takers for a pumpset? Let's also start with SECC data - 55% of farmers are landless (laborers) so increasing pumpsets helps a subset. Here's a counterfactual Q: Now that households are 100% electrified, does this now "free up" policy for pumpsets? The pumpsets policy has been the way it is (limited by design, with largesse and political connections important) for a long while in the face of heterogeneity in connectivity. + +Data on landless and landed farmers are not available for all years of our analysis and therefore cannot be included in our primary specification. Instead, we conduct a balance test between PC and non- PC districts (previously late and early electrifiers respectively) and find that on average, PC districts are larger with greater numbers of both landed and landless households (table 4). Holding all else equal, greater number of landed households are expected to be associated with greater demand for electrified wells, which we do not find. This makes our results even more stark as we find larger PC districts with fewer electrified wells than the smaller non- PC districts. + +Table 4: PC districts on average were larger with more households across all categories. + +
Non-PC districtsPC districtsp-value
Average landless households (‘000)178.3621211.93990.04
Average land owning households (‘000)119.9451165.43550.00
Average total land in district (‘000 acre)1,414.80732,884.28860.02
+ +Data is based on district-level \((N = 425)\) Socioeconomic Caste Census carried out in 2011 (Department of Rural Development, 2011). + +There is no limited incorporation of the physics, design, and practicality of rural connections. Recent policies (last 10 years) have been towards feeder segregation, but even before this, most states had "rosters" or schedules where agricultural supply was limited to, say, 6 or 8 hours per day. This was controlled through phase- separation, with single phase supply (for homes) meant to be as much as possible, ideally 24 hours in theory (but never in practice). + +We are limited in our capacity to carry out an exhaustive analysis of how states operationalize electrification in their respective rural areas. However, in at least one state where rural electrification occurred majorly through RGGVY, farmers are expected to bear the cost of additional poles and wires to use electricity on agricultural fields (Orissa Lift Irrigation Corporation, 2014; Department of Energy, 2016). Further, limited capacities of transformers in RGGVY electrified villages are found to be a major contributor to poor electricity supply (Banerjee et al., 2014b; Planning Commission of India, 2014; Parikh et al., 2013). As noted, the period when feeder separation was largely carried out does not apply to our analysis as the former is being undertaken more recently. Whether separate feeders will be installed in areas where agricultural demand does not currently exist is a question that remains, and one that is important to address. + +The second reality that questions the model and framing is how we have "incremental electrification". Most challenges for household electrification have been with the "last mile connection". The earlier (and insufficient) definitions of electrification focused on a single lightbulb meant the village was electrified, updated to then be 10% of homes. This was progressively upgraded, which is a good thing, but there is no evidence of a "policy reason" this was at the expense of pumpsets. Your analysis does bring out the point that household supply doesn't increase wealth much - so it is a separate question of how much one can/should increase pumpsets. If they were charged "full cost" there would be no problem but we know they are not. Money for loss- making utilities is scarce, and so there is a call to be made how much pumpset deployment is appropriate. + +Aside: There was also a period (early 2000s) where power supply quality impacted affordability of pumpsets. Even with "cheap power", frequent burnouts meant rewinding costs were more than the cost of electricity. This raises the general question of why don't people want a pumpset versus how many people want a pumpset but + +<--- Page Split ---> + +can't get one. + +Not wanting agricultural pump- sets from the farmers' perspectives can stem from broadly two main reasons. We address the first reason of not needing one by incorporating seasonal rainfall in our analysis. It is also widely accepted that surface water irrigation is insufficient for cultivation during Rabi and is increasingly inadequate for cultivation during Kharif (Shah, 2009; Shah et al., 2012). The second reason of not wanting may stem from inadequate returns to pump- set investments. We do not address the latter sufficiently in our analysis beyond looking at irrigation access across households of similar wealth across PC and non- PC districts (previously late and early electrifying respectively). We agree that this may be a potential source of error and make a note of it in Lines 227- 234. However, if true, our results remain valid as poor electricity quality would then be experienced disproportionately higher by PC (previously late electrifying) districts and would merit further investigations. Not wanting pump- sets from the government's or the utilities' perspectives are important points that are beyond the scope of our study. + +Do you measure size of wells (borewells), measured by HP (horsepower)? 20 wells isn't comparable across regions. This also links to issues of water- sharing. Local politics and influence can be a factor. This also means larger farmers with pump- sets sell water to their neighbors. Anecdotally, it is prevalent in many eastern states of India. + +Unfortunately, the size of pumps is not provided in the first round of data. We use the classification of wells based on their depths and rerun our primary specification. There are three main types of wells recorded in the Minor Irrigation Census - dug wells which are constructed without the use of drilling machines and have average depths of 8- 15m, shallow and deep tube- wells are constructed with drilling machines and are classified as those shallower than and those deeper than 70m respectively. We include these details in the data section under Minor Irrigation Census. + +We run the main specification separately for each category of wells and find persistent negative and statistically significant effects among PC districts (table 5). Interestingly, the negative impact of electrifying post policy change is greatest on a relative scale for dug wells, where PC districts experience no gains from electrification in terms of electrified irrigation wells. We are unable to address the issue of water markets due to limitations of data and make a note of this in the discussion section in Lines 231- 234 - "We are also unable to account for water markets that are reported to exist in some eastern states in the country (Mukherji et al., 2009). Nevertheless, these factors are important to account for while designing policies that target irrigation expansion across PC districts." + +Is there any analysis of farm size and pumpsets? Many farms in the less irrigated sections of India (easter) are more subsistence, and also (as you rightly observe) have limitations in market access. These regions also have much lower water demands based on water tables. Crop choices also matter - Punjab went for cash crops much earlier on. + +As such we are unable to control for the size of farms in our main specification as data on farm size are not available for the years included in our analysis. We do however, control for it when measuring the differences in irrigation across households of similar wealth in PC and non- PC districts. Households with similar consumption in PC districts irrigate less than households in non- PC districts on average, even after controlling for the size of land owned and operated. Additionally, we run a balance test on the surveyed agrarian households included in the Situation Assessment Survey carried out by the NSSO (National Sample Survey Office, 2014). We find that on average, farmers in PC districts do have smaller plots - 1.4 ha compared to 2.2 ha on average in non- PC districts (table 6). On average, PC districts run about half a hectare smaller up until the \(75^{th}\) quartile. So it is possible that a systematic difference in parcel size may be contributing to lower returns on electric pump investment and thereby adding to the disincentives to invest in electric pumps. We have added text in the discussion and policy section to note this in Lines 227- 234 - "Our analysis does not exhaustively capture all possible disincentives to electric pump investments - poor supply of electricity, small or scattered parcels of landholdings and inadequate returns to irrigation are some potential biases to our results. For instance, households on average owned smaller parcels of land among PC districts compared to non- PC districts. While we control for land sizes in our analysis, + +<--- Page Split ---> + + +Table 5: Negative penalty holds for PC districts across all categories of wells + +
Groundwater wells with electric pumps
Deep tube-wellsShallow tube-wellsDug wells
Electrified households0.045***
(0.008)
0.074***
(0.013)
0.040**
(0.018)
Electrified households × PC-0.038***
(0.010)
-0.041***
(0.014)
-0.059***
(0.018)
Total households-0.007
(0.005)
-0.005
(0.004)
0.001
(0.007)
Fixed-effects
DistrictYesYesYes
YearYesYesYes
Fit statistics
Observations969969969
0.520.780.87
Within R²0.140.180.04
+ +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Estimated using equation 1 and panel dataset constructed from district-level population and minor irrigation census data. + +we are unable to consider poor quality of supply, scattered parcels or returns to irrigation due to data limitations. We are also unable to account for water markets that are reported to exist in some eastern states in the country (Mukherji et al., 2009). Nevertheless, these factors are important to account for while designing policies that target irrigation expansion among PC districts." + +Table 6: Farm sizes were smaller on average in PC districts in 2013 + +
Non-PC districtsPC districtsp-value
Land owned (ha)2.231.420.00
Land operated (owned and leased) (ha)2.611.550.00
Land cultivated during Rabi1.661.010.00
Land cultivated during Kharif2.091.170.00
+ +Data is based on a nationally representative survey data of agricultural households \((N =\) 11,182) in 2012-13 (National Sample Survey Office, 2014). + +An interesting analysis would be to examine districts within a state. One can assume a state has certain policy - but we note there is disparity in pumpsets within states. This suggests it's not a policy reason but fundamentals driven by farmer wealth, crop choices, water tables, rainfall patterns etc. See interior Maharashtra vs. coastal, and similar for some other states. + +We run our primary specification at the block level in Madhya Pradesh. We chose Madhya Pradesh as it has a high diversity of PC (28) and non- PC (10) districts and is a major agricultural state. We use the Defense Meteorological Program Operation Line Scan System (DMSP- OLS) night time luminosity data compiled by Asher et al. (2021) to measure electrification. We use this additional source as population census does not publish electrification data at the block level. We matched the second, third and fifth rounds Minor Irrigation Census with SHRUG nightlight and population census datasets (Asher et al., 2021). The first minor irrigation census does not report data at the block or village level. We use total light luminosity values which range from 0 to 63 and are calibrated by Elvidge et al. (2014) for consistent measure across the range of years 1994- 2013. + +On average we find DMSP- OLS data to be a conservative estimate of electrification (see appendix figure A1). The block- level analysis with DMSP- OLS and Minor Irrigation Census for Madhya Pradesh are consistent with our results overall with some differences in the interpretation due to the use of nightlight luminosity. On average, a \(1\%\) increase in luminosity among blocks within non- PC districts is associated with an increase in over 1,500 + +<--- Page Split ---> + +electrified wells. This value decreases by nearly 1,000 wells and a \(1\%\) increase in nighttime luminosity is associated with a cumulative increase of 500 electrified wells in blocks across PC districts. We do not find a relationship between nighttime luminosity and wells with diesel pumps. + +Additionally our analysis using the National Sample Survey Office's Situation Assessment Survey of Agricultural Households data in section titled "Income does not explain irrigation differences between PC and non- PC districts" considers the roles that farmer wealth and rainfall play and we find that rural electrification policy change is a stronger predictor of irrigation area than is farmer wealth. Compared to the poorest \(15^{th}\) percentile households, all other farming households among non- PC districts irrigated larger tracts of cultivated land during Rabi. We find no similar differences in irrigated area between the poorest \(15^{th}\) percentile households in non- PC districts and households among PC districts that were even in the top \(85^{th}\) consumption percentile. The NSSO analysis includes state- level fixed effects which translates to a comparison of agrarian households across PC and non- PC districts within each state. However, the state level fixed effects work only when states with more PC districts do not systematically differ from states with fewer PC districts. + +A fundamental question: What if earlier electrifiers were simply richer regions or had more resources? Thus BOTH homes and pumpsets would be faster. The 8 times more pumpsets for earlier electrifiers then is explained by economic reasons, as opposed to the framing you have, which is a policy choice with a tradeoff. + +We agree that systematic differences between PC and non- PC districts are potential sources of biases in our results. We conduct a household level analysis (results illustrated in figure 5) where we test for irrigation coverage among households of similar wealth but compare across PC and non- PC districts. We find that the differences persist even among households of similar wealth across PC and non- PC districts. Unfortunately we cannot test this across time since situation assessment of agricultural households has not been repeated since 2013. As you rightly point out in your previous comment, it could be that district- level wealth may be a stronger predictor of pump- set use than household wealth, which this analysis would not address. Our new block- level analysis in Madhya Pradesh compares blocks across PC and non- PC districts. While it does not fully address a possibility of systematic differences across the two categories of districts, it does remove state- level differences that may be present in our primary specification. + +If, in fact, non- PC districts are systematically different from PC districts in ways that influence both electrification of houses and wells, while the precision of our estimate may be questionable, our analysis is helpful in at least identifying that irrigation expansion remains unaffected despite rural electrification expansion in the latter. A point that is important to be addressed to tackle rural poverty and climate change. + +Figure 3 - we can note that even in 2013, it is the east that lags - both household electrification and irrigation. + +We agree it is the east where both rural electrification has been slow to spread and so has groundwater irrigation. Recent estimates suggest near universal electrification of this region ((see Saubhagya dashboard). It will be interesting to note the associated expansion in groundwater irrigation once the latest round of Minor Irrigation Census becomes publicly available. + +Figure 4 - There is a clear split between late vs. early electrifiers, but that split may also have many confounding factors instead of your theory of policies that favored one over the other. Note that there are very few districts with over 5 lakh (500,000) households electrified. + +We agree there could be a number of confounding factors which is why our estimates are based on a two- way fixed effects regression to control for the confounders and explain the details of the estimation strategy in methods section of the paper. Figure 4 simply serves as the descriptive evidence to motivate our analysis and is explained by the accompanying text in lines 130- 134 - "Before presenting our regression models, figure 4 presents cross- sectional, descriptive evidence to motivate our analysis. In 2013, our most recent round of data, we see a stark difference in the relationship between household electrification and electrified groundwater pumps in PC versus non- PC districts. PC districts had far fewer wells with electric pumps compared to non- PC districts with similar numbers of electrified households (Figure 4). This divergent cross- sectional relationship between the two sets of districts could be driven by unobserved factors..." + +We have added the following line (lines 140- 141) to clarify that the regression estimates considers three time + +<--- Page Split ---> + +periods - "Our fixed effects regression estimates measures the association between the number of electrified households with the number of groundwater wells using electric and diesel pumps across 1986 to 2013. The estimates show that, on average, the electrification of ..." + +Line 163: "transformer capacities could be constraining even households with the financial means to access electricity for groundwater irrigation." Your math is correct that household connections are small, but transformers are always based on multiple homes, and, more importantly, almost NEVER smaller than tens of kW. Esp. in those days, there were no plans for LVDS (low voltage distribution systems) which had smaller transformers. Typically, there was a fixed model used that covered a variety of uses. There was no separate transformer then for house vs. agriculture. So size limitations is unlikely to be a bottleneck until we have many pumpsets connected. + +Calculations by Parikh et al. (2013) suggest the standard size of installed transformers of 457kW (16kVA with a power factor of 0.7) load result in average loads of 600W per household (implying average village size of \(\sim 760\) households). Therefore, the average household load is less than the capacity of a 1 HP pump- set ( \(\sim 746W\) ). This would mean that even if \(10\%\) households were to own a 4HP pumpset, they would account for nearly \(50\%\) of the total village load. Over \(80\%\) of all wells in MI Census 2013 used pumps larger than 4HP (Government of India, 2017). Additionally Banerjee et al. (2014b) report on Indian electrification experience notes that many states installed transformers that fall short of full village load leading to issues of reliability. + +In summary: Interest and strong analysis, but the claims made aren't proven, and the econometrics only partially answer some of the issues above (like wealth as a factor - it's not just RURAL HOUSEHOLD WEALTH that matters - state wealth matters for the utility, e.g., the presence of richer consumers to offset rural losses. + +We added state specific time trends to account for time variant state- level differences in our primary specification. Our results are robust to the inclusion of these state specific time trends (tables 2 and 3). Additionally, the new block level analysis carried out for Madhya Pradesh implies similar differences in block level outcomes between PC and non- PC districts. + +We hope that we have convinced you with the new set of analyses which, in our view, add robustness to our claim that differences in the number of electrified wells is independent of household and state wealth, and the need for irrigation. + +<--- Page Split ---> + +## References + +Aeschbach- Hertig, W. and Gleeson, T. (2012). Regional strategies for the accelerating global problem of groundwater depletion. Nature Geoscience, 5(12):853- 861. + +Asher, S., Lunt, T., Matsuura, R., and Novosad, P. (2021). Development Research at High Geographic Resolution: An Analysis of Night Lights, Firms, and Poverty in India using the SHRUG Open Data Platform. The World Bank Economic Review. + +Banerjee, S. G., Barnes, D. F., Mayer, K., Samad, H. A., and Singh, B. N. (2014a). Chapter 2: Closing the Electricity Access Gap. In Power for all: electricity access challenge in India. World Bank Group, Washington, DC. + +Banerjee, S. G., Barnes, D. F., Mayer, K., Samad, H. A., and Singh, B. N. (2014b). Chapter 4: History of Rural Electrification and Institutional Organization. In Power for all: electricity access challenge in India. World Bank Group, Washington, DC. + +CCEA, C. C. o. E. A. (2014). Deregulation of Diesel Prices. Press Release, Press Information Bureau (PIB), Government of India, New Delhi. + +Department of Energy, G. o. O. (2016). Office Memorandum - Amendment of Biju Gram Jyoti- Rural Electrification programme of the State Government. + +Department of Rural Development, Ministry of Rural Development, G. o. I. (2011). Socio Economic and Caste Census 2011 (SECC). + +Elvidge, C. D., Feng- Chi, H., Baugh, K. E., and Ghosh, T. (2014). National trends on satellite- observed lighting. Global urban monitoring and assessment through earth observation, (23). + +Famiglietti, J. S. (2014). The global groundwater crisis. Nature Climate Change, 4(11):945- 948. + +Government of India, Ministry of Water Resources, R. D. a. G. R. (2017). 5th Census of Minor Irrigation Schemes Report. + +Gulati, A. and Narayanan, S. (2003). Power Subsidies. In The Subsidy Syndrome in Indian Agriculture. Oxford University Press, New Delhi. + +Gulati, A., Sharma, B., Banerjee, P., and Mohan, G. (2019). Getting More from Less: Story of India's Shrinking Water Resources. Technical report, Indian Council for Research on International Economic Relations (ICRIER), Delhi. + +Lo, M.- H., Famiglietti, J. S., Reager, J. T., Rodell, M., Swenson, S., and Wu, W.- Y. (2016). GRACE- Based Estimates of Global Groundwater Depletion. In Tang, Q. and Oki, T., editors, Terrestrial water cycle and climate change: natural and human- induced impacts, number 221 in Geophysical monograph series. AGU, American Geophysical Union, Washington, D.C. + +Mukherji, A., Das, B., Majumdar, N., Nayak, N., Sethi, R., and Sharma, B. (2009). Metering of agricultural power supply in West Bengal, India: Who gains and who loses? Energy Policy, 37(12):5530- 5539. + +National Sample Survey Office, M. o. S. a. P. I. (2014). Situation Assessment Survey of Agricultural Households - 2013. Technical report, Government of India, New Delhi. + +Orissa Lift Irrigation Corporation, G. o. O. (2014). Detail Information about Jalindhi- I. + +Parikh, J., Dutta Biswas, C., and Panda, R. R. (2013). Combined Report on Evaluation of Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY) of Rajasthan, Assam, Gujarat, Himachal Pradesh and Uttar Pradesh. Technical report, Integrated Research and Action for Development (IRADe), New Delhi. + +Planning Commission of India (2014). Evaluation Report on Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY). 224, Programme Evaluation Organisation, Planning Commission, Government of India, New Delhi. + +<--- Page Split ---> + +Shah, T. (2009). Climate change and groundwater: India's opportunities for mitigation and adaptation. Environmental Research Letters, 4(3):035005. + +Shah, T., Giordano, M., and Mukherji, A. (2012). Political economy of the energy- groundwater nexus in India: exploring issues and assessing policy options. Hydrology Journal, 20(5):995- 1006. + +Statistics Division, M. I. (2017). Manual For Data Collection in the Census of Minor Irrigation Schemes 2013- 14. Technical report, Ministry of Water Resources, Government of India, New Delhi. + +Verma, N. and Patnaik, S. (2018). Graphic: India's petrol, diesel prices surge to record. Reuters. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +Thank you for the efforts you have made in addressing each comment from the reviewers seriously and as comprehensively as your dataset would allow. + +<--- Page Split ---> diff --git a/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1fb97dc76022d4b67c74b3736c38b3bea316bb40 --- /dev/null +++ b/peer_reviews/781af362c0d9d20b2d2a9e018e05357926ffcdd64829d68e471c252ee90c2793/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,509 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 111, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 798, 210]]<|/det|> +The changing impact of rural electrification on Indian agriculture + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 285, 136]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 150, 291, 177]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 191, 866, 328]]<|/det|> +The central premise of this project is that rural electrification impacts household incomes and a key pathway through which it does so is via enabling households engaged in agriculture to pump groundwater for irrigation. The hypothesis which they proceed to test is that a 2000s turn in policy focus towards household electrification rather than electrification for agriculture, which therefore undermined the growth of electric pumps in agriculture. This "crowding out" of electric agricultural pumps by domestic electrification in turn affected income growth. They proceed to demonstrate this through a series of steps - first, by demonstrating that the relationship of electricity based pumping and domestic access to electricity is on average lower among "late electrifier" districts and the "early electrifier" districts and by showing that rural electrification was not income enhancing for the "late electrifiers" as it was for the "early electrifiers". + +<|ref|>text<|/ref|><|det|>[[115, 341, 857, 383]]<|/det|> +This paper is on a very interesting topic and the authors make very original and creative use of the data. It is motivated very well and the authors produce very useful insights. However, I was left underwhelmed by their bewildering empirical approach and the confusing use of data. + +<|ref|>text<|/ref|><|det|>[[115, 396, 880, 451]]<|/det|> +The backbone of this paper is the empirical specification in Lines 319- 322 that regresses electric pumps (and then acreage irrigated by them) on households with electricity and an interaction term that combines electrified households with and indicator variable denoting if this is greater than \(50\%\) of all households. The authors claim + +<|ref|>text<|/ref|><|det|>[[115, 464, 856, 534]]<|/det|> +The coefficient on the interaction of elecrhit with LateEleci, \(\beta\) , is of main interest. It captures the difference O in the effect of household electrification on pump electrification between early and late electrifying districts. In other words, a captures the relationship between rural electrification and groundwater irrigation among early electrifying districts, while \(\alpha + \beta\) captures the estimate for late electrifying districts. + +<|ref|>text<|/ref|><|det|>[[115, 546, 872, 696]]<|/det|> +I beg to differ. In essence, this is like a classic structural break model but defined in terms of a \(50\%\) threshold based on electrified households. Note that this is exactly the specification one would use to detect threshold effects that beyond a threshold of electricity diffusion in the village, the relationship between domestic and agricultural use of electricity changes. One could tell several alternate stories with this model: that there is a preference ordering of investment among rural households so that in the early stages of diffusion of electricity people invest in electricity pumps; or a story of village level development - in the early stages of electrification, one invests in agriculture (electric pumps) and eventually as surplus is generated in agriculture, one invests in off farm activities. I simply don't see the empirical specification delivering the story that the authors are trying to get at. Indeed, one could argue just based on the model, that it has little to do with any policy or crowding out, but a story of the evolution or dynamics of electricity use. + +<|ref|>text<|/ref|><|det|>[[115, 709, 863, 778]]<|/det|> +The authors robustness checks "We also consider models where we include electrification quantiles instead of a single binary classifier and find similar results (see appendix tables A1 and A2), in fact illustrate the diminishing importance of agricultural pump electrification as domestic electrification expands. In short, the authors have an exciting story here (they should write that one), but it is not the one they are trying to tell! + +<|ref|>text<|/ref|><|det|>[[115, 791, 880, 860]]<|/det|> +The fundamental problem is "construct" validity. Their bewildering approach to identifying those districts "exposed" to the policy and irrigation oriented versus a domestic oriented electrification policy, named "early" and "late" electrifiers derives not from the time when electrification was introduced but to the extent of electrification (in 2001?) i.e., as "majorly electrified" (lines 116). I struggled to see for myself nor access evidence to see why this is a good construct of early versus late + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 309, 136]]<|/det|> +and not more versus less! + +<|ref|>text<|/ref|><|det|>[[115, 163, 864, 206]]<|/det|> +A better approach would be a structural break in terms of time (treat 1986 as a base period and use an indicator variable for post 2000s) to proxy the policy shift. The authors could add a piece- wise analysis based on what proportion of households are electrified. + +<|ref|>text<|/ref|><|det|>[[115, 219, 844, 247]]<|/det|> +I would always want state- year interaction fixed effects to control for time- varying policy changes (including electricity pricing policies, irrigation technology subsidies, other infrastructure, etc.) + +<|ref|>text<|/ref|><|det|>[[115, 259, 881, 302]]<|/det|> +I would like to see a greater discussion of diesel pumps (lines 66- 68) used not as a substitute for electricity but for poor quality of electricity and hours of power supply. There are several discussions of these in the literature on subsidies in India (notably by Ashok Gulati and co- authors). + +<|ref|>text<|/ref|><|det|>[[115, 314, 870, 356]]<|/det|> +Line 23 "Perhaps it is time to reevaluate uniform prescriptive electricity loads and uses in formulating RE policies" This sentence can be clarified. It becomes clear later on but on line 23, it is too early for readers unfamiliar with the policy and the sector. + +<|ref|>text<|/ref|><|det|>[[115, 369, 865, 439]]<|/det|> +The authors claim that they use "newly constructed panel- dataset spanning three decades" (in the abstract). Yet the figure 2 notes that the "Relationship between electrified households and electrified wells in 2013 was stronger among early electrifiers compared to late electrifying districts. The point estimates represent district- level data on electrified houses and wells with electrified pumps." This suggests misleadingly that the regression was run for just 1 year, i.e., 2013. + +<|ref|>text<|/ref|><|det|>[[115, 451, 864, 507]]<|/det|> +The undertone at least in the initial parts of the paper is a celebration of electricity for pumping groundwater, barring some reflections in line 68. Perhaps you could start the paper early on by suggesting that despite the problem of overextraction etc. irrigation is known to have large benefits, and the culprit for that is more in the pricing than the extraction. + +<|ref|>text<|/ref|><|det|>[[115, 546, 868, 588]]<|/det|> +Reviewer #2: Remarks to the Author: The authors tackle a very important question with both energy and human development implications. + +<|ref|>text<|/ref|><|det|>[[115, 600, 857, 655]]<|/det|> +This is a good dataset and strong analytics - but the interpretations and framings need to be questioned. The study very nicely shows there is a disconnect for irrigation coverage vs. household electrification by time (early vs late), but it's not clear causality can be linked to policies favoring household electrification. + +<|ref|>text<|/ref|><|det|>[[115, 668, 850, 725]]<|/det|> +Utilities likely did slow down connections to farmers, but that was independent of any focus on household electrification. Farmers underpay, as well known, and this non- remunerative supply is a strain on utilities. Note, free power to farmers only started in 1977 in Andhra Pradesh, and wasn't widespread for a few more years. + +<|ref|>text<|/ref|><|det|>[[115, 737, 872, 780]]<|/det|> +While electricity access policy DOES favor households, it's not clear why that would be at the expense of agriculture. BOTH segments enjoy heavily cross- subsidized and subsidized electricity (cross- subsidies for homes being for lower slabs or tiers of consumption). + +<|ref|>text<|/ref|><|det|>[[115, 792, 866, 862]]<|/det|> +One has to start with the reality that agricultural supply is very expensive for the utility - being both subsidized and cross- subsidized. Are there enough takers for a pumpset? Let's also start with SECC data - 55% of farmers are landless (laborers) so increasing pumpsets helps a subset. Here's a counterfactual Q: Now that households are \(\sim 100\%\) electrified, does this now "free up" policy for pumpsets? The pumpsets policy has been the way it is (limited by design, with largesse and political + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 733, 137]]<|/det|> +connections important) for a long while in the face of heterogeneity in connectivity. + +<|ref|>text<|/ref|><|det|>[[115, 150, 878, 220]]<|/det|> +There is no limited incorporation of the physics, design, and practicality of rural connections. Recent policies (last \(\sim 10\) years) have been towards feeder segregation, but even before this, most states had "rosters" or schedules where agricultural supply was limited to, say, 6 or 8 hours per day. This was controlled through phase- separation, with single phase supply (for homes) meant to be as much as possible, ideally 24 hours in theory (but never in practice). + +<|ref|>text<|/ref|><|det|>[[115, 232, 880, 356]]<|/det|> +The second reality that questions the model and framing is how we have "incremental electrification". Most challenges for household electrification have been with the "last mile connection". The earlier (and insufficient) definitions of electrification focused on a single lightbulb meant the village was electrified, updated to then be \(10\%\) of homes. This was progressively upgraded, which is a good thing, but there is no evidence of a \(^*\) policy reason\\* this was at the expense of pumpsets. Your analysis does bring out the point that household supply doesn't increase wealth much - so it is a separate question of how much one can/should increase pumpsets. If they were charged "full cost" there would be no problem but we know they are not. Money for loss- making utilities is scarce, and so there is a call to be made how much pumpset deployment is appropriate. + +<|ref|>text<|/ref|><|det|>[[115, 368, 857, 425]]<|/det|> +Aside: There was also a period (early 2000s) where power supply quality impacted affordability of pumpsets. Even with "cheap power", frequent burnouts meant rewinding costs were more than the cost of electricity. This raises the general question of why don't people want a pumpset versus how many people want a pumpset but can't get one. + +<|ref|>text<|/ref|><|det|>[[115, 437, 881, 492]]<|/det|> +Do you measure size of wells (borewells), measured by HP (horsepower)? 20 wells isn't comparable across regions. This also links to issues of water- sharing. Local politics and influence can be a factor. This also means larger farmers with pumpsets sell water to their neighbors. Anecdotally, it is prevalent in many eastern states of India. + +<|ref|>text<|/ref|><|det|>[[115, 505, 870, 560]]<|/det|> +Is there any analysis of farm size and pumpsets? Many farms in the less irrigated sections of India (easter) are more subsistence, and also (as you rightly observe) have limitations in market access. These regions also have much lower water demands based on water tables. Crop choices also matter - Punjab went for cash crops much earlier on. + +<|ref|>text<|/ref|><|det|>[[115, 573, 881, 628]]<|/det|> +An interesting analysis would be to examine districts within a state. One can assume a state has certain policy - but we note there is disparity in pumpsets within states. This suggests it's not a policy reason but fundamentals driven by farmer wealth, crop choices, water tables, rainfall patterns etc. See interior Maharashtra vs. coastal, and similar for some other states. + +<|ref|>text<|/ref|><|det|>[[115, 641, 875, 696]]<|/det|> +A fundamental question: What if earlier electrifiers were simply richer regions or had more resources? Thus BOTH homes and pumpsets would be faster. The 8 times more pumpsets for earlier electrifiers then is explained by economic reasons, as opposed to the framing you have, which is a policy choice with a tradeoff. + +<|ref|>text<|/ref|><|det|>[[115, 709, 870, 737]]<|/det|> +Figure 3 - we can note that even in 2013, it is the east that lags - both household electrification and irrigation. + +<|ref|>text<|/ref|><|det|>[[115, 750, 872, 791]]<|/det|> +Figure 4 - There is a clear split between late vs. early electrifiers, but that split may also have many confounding factors instead of your theory of policies that favored one over the other. Note that there are very few districts with over 5 lakh (500,000) households electrified. + +<|ref|>text<|/ref|><|det|>[[115, 804, 864, 860]]<|/det|> +Line 163: "transformer capacities could be constraining even households with the financial means to access electricity for groundwater irrigation." Your math is correct that household connections are small, but transformers are always based on multiple homes, and, more importantly, almost NEVER smaller than tens of kW. Esp. in those days, there were no plans for LVDS (low voltage distribution + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 867, 165]]<|/det|> +systems) which had smaller transformers. Typically, there was a fixed model used that covered a variety of uses. There was no separate transformer then for house vs. agriculture. So size limitations is unlikely to be a bottleneck until we have many pumpsets connected. + +<|ref|>text<|/ref|><|det|>[[115, 178, 864, 234]]<|/det|> +In summary: Interest and strong analysis, but the claims made aren't proven, and the econometrics only partially answer some of the issues above (like wealth as a factor - it's not just RURAL HOUSEHOLD WEALTH that matters - state wealth matters for the utility, e.g., the presence of richer consumers to offset rural losses. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[90, 101, 907, 123]]<|/det|> +# Beyond Lights: The Changing Impact of Rural Electrification on Indian + +<|ref|>text<|/ref|><|det|>[[432, 135, 565, 154]]<|/det|> +Agriculture + +<|ref|>text<|/ref|><|det|>[[395, 167, 603, 186]]<|/det|> +Review Responses + +<|ref|>sub_title<|/ref|><|det|>[[90, 271, 219, 288]]<|/det|> +## Reviewer 1 + +<|ref|>text<|/ref|><|det|>[[89, 305, 907, 464]]<|/det|> +The central premise of this project is that rural electrification impacts household incomes and a key pathway through which it does so is via enabling households engaged in agriculture to pump groundwater for irrigation. The hypothesis which they proceed to test is that a 2000s turn in policy focus towards household electrification rather than electrification for agriculture, which therefore undermined the growth of electric pumps in agriculture. This "crowding out" of electric agricultural pumps by domestic electrification in turn affected income growth. They proceed to demonstrate this through a series of steps - first, by demonstrating that the relationship of electricity based pumping and domestic access to electricity is on average lower among "late electrifier" districts and the "early electrifier" districts and by showing that rural electrification was not income enhancing for the "late electrifiers" as it was for the "early electrifiers". + +<|ref|>text<|/ref|><|det|>[[90, 471, 905, 522]]<|/det|> +This paper is on a very interesting topic and the authors make very original and creative use of the data. It is motivated very well and the authors produce very useful insights. However, I was left underwhelmed by their bewildering empirical approach and the confusing use of data. + +<|ref|>text<|/ref|><|det|>[[88, 529, 910, 775]]<|/det|> +Thank you for your detailed and insightful comments. We have taken your suggestions and added three pieces of analyses to strengthen our claim that electrification timing which captures a change in electrification policy is associated with the slow expansion of agricultural electricity. We understand why in its current form our paper may lead readers to believe that the level of electrification rather than timing may be important in predicting the number of electrified wells. We believe the additional analyses which include - (1) using a different treatment indicator; (2) analysis on a subset of districts with comparable electrification rates and; (3) sub- district analysis within a state, strengthen our claim that it is indeed when electrification took place that impacts where electricity is used for groundwater irrigation. Additionally, to clarify our intent to capture electrification policy change, we have replaced Late Elec with \(PC\) to identify districts that were majorly electrified after the focus of rural electrification policy shifted towards domestic electrification from agriculture. The definition of \(PC\) is the same as what we previously used for Late Elec. We now refer to late electrifying districts as PC districts or districts that electrified post policy change, and early electrifiers as non- PC districts or districts that electrified pre policy change. We highlight changes in the manuscript by using blue- coloured text. Please see detailed responses to your points below. + +<|ref|>text<|/ref|><|det|>[[89, 782, 908, 905]]<|/det|> +The backbone of this paper is the empirical specification in Lines 319- 322 that regresses electric pumps (and then acreage irrigated by them) on households with electricity and an interaction term that combines electrified households with and indicator variable denoting if this is greater than \(50\%\) of all households. The authors claim the coefficient on the interaction of \(elech_{it}\) with \(LateElec_{i}\) , \(\beta\) , is of main interest. It captures the difference 0 in the effect of household electrification on pump electrification between early and late electrifying districts. In other words, \(\alpha\) captures the relationship between rural electrification and groundwater irrigation among early electrifying districts, while \(\alpha + \beta\) captures the estimate for late electrifying districts. + +<|ref|>text<|/ref|><|det|>[[90, 912, 904, 945]]<|/det|> +I beg to differ. In essence, this is like a classic structural break model but defined in terms of a \(50\%\) threshold based on electrified households. Note that this is exactly the specification one would use to detect threshold + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 53, 904, 194]]<|/det|> +effects that beyond a threshold of electricity diffusion in the village, the relationship between domestic and agricultural use of electricity changes. One could tell several alternate stories with this model: that there is a preference ordering of investment among rural households so that in the early stages of diffusion of electricity people invest in electricity pumps; or a story of village level development - in the early stages of electrification, one invests in agriculture (electric pumps) and eventually as surplus is generated in agriculture, one invests in off farm activities. I simply don't see the empirical specification delivering the story that the authors are trying to get at. Indeed, one could argue just based on the model, that it has little to do with any policy or crowding out, but a story of the evolution or dynamics of electricity use. + +<|ref|>text<|/ref|><|det|>[[89, 201, 908, 376]]<|/det|> +We use household electrification to measure rural electrification in our analysis. However, early attempts at rural electrification expansion in India were focused on providing electricity infrastructure to villages with a small number of domestic connections (about \(10\%\) ) (Banerjee et al., 2014a). It was only in the early 2000s that the focus shifted towards electrifying all households. The target of Rajeev Gandhi Vidhyatikaran Yojana (RGGVY) were villages with populations greater than a 100 and lacking electricity infrastructure. We find regions electrified under RGGVY to experience limited expansion in agricultural electricity. Therefore it is not how electricity diffuses which impacts its use in agriculture rather when, since villages which got electrified for the first time under RGGVY experienced almost no expansion in agriculture (Banerjee et al., 2014a; Planning Commission of India, 2014; Parikh et al., 2013). We include three specific analyses that strengthen our claim of the relationship between weak expansion of agricultural electricity supply and the timing of electrification - + +<|ref|>text<|/ref|><|det|>[[113, 391, 911, 567]]<|/det|> +1. Replace \(PC_i\) with \(RGGVY_i\) - We replace \(50\%\) household electrification threshold captured by \(PC_i\) (previously LateElec_i with an indicator variable \(RGGVY_i\) , which is 1 for districts that were funded under the first wave of electricity expansion under RGGVY during India's \(X^{th}\) five year plan spanning 2002-2007. We find our main conclusions to hold with some changes in the precision of the estimates (results included in table 1, columns 5-7). Our reason for not using \(RGGVY_i\) in our primary specification is due to issues of data integrity. RGGVY was majorly carried out under the \(X^{th}\) (2002-2007), \(X^{th}\) (2007-2012) and \(XII^{th}\) (2012-2017) five year plans. However, data for the selection of districts in each wave is unavailable. Even with the limited data, our primary specification picks up the slow expansion of agricultural electricity supply for RGGVY phase I districts. A point to note - the results no longer remain statistically significant with the inclusion of state specific year fixed effects. + +<|ref|>text<|/ref|><|det|>[[113, 576, 900, 662]]<|/det|> +2. Sub-district analysis within a state - We also run our primary specification at the block level in Madhya Pradesh. Blocks are administrative units in between villages and districts. Therefore there is variation in the electrification rates within each district, which is another way we test the threshold effect. We chose Madhya Pradesh as it has a high diversity of PC (previously late electrifier) (28) and non-PC (10) (previously early electrifying) districts and is a major agricultural state. + +<|ref|>text<|/ref|><|det|>[[125, 665, 910, 787]]<|/det|> +We use the Defense Meteorological Program Operation Line Scan System (DMSP- OLS) night time luminosity data compiled by Asher et al. (2021) to measure electrification. We use this additional source as population census does not publish electrification data at the block level or any level lower than districts. We matched the second, third and fifth rounds Minor Irrigation Census with SHRUG nightlight and population census datasets (Asher et al., 2021). The first minor irrigation census does not report data at the block or village level. We use total light luminosity values which range from 0 to 63 and are calibrated by Elvidge et al. (2014) for consistent measure across the range of years between 1994- 2013. + +<|ref|>text<|/ref|><|det|>[[127, 790, 907, 930]]<|/det|> +On average we find DMSP- OLS data to be a conservative estimate of electrification (see figure appendix figure A1). The block- level analysis with DMSP- OLS and Minor Irrigation Census for Madhya Pradesh are consistent with our results overall with some differences in the interpretation due to the use of nightlight luminosity. On average, a \(1\%\) increase in luminosity among blocks within non- PC districts (previously early electrifier) is associated with an increase in over 1,500 electrified wells. This value decreases by nearly 1,000 wells and a \(1\%\) increase in nighttime luminosity is associated with a cumulative increase of 500 electrified wells in blocks across PC districts (previously late electrifier) in Madhya Pradesh. We do not find a relationship between nighttime luminosity and wells with diesel pumps. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[110, 54, 910, 229]]<|/det|> +3. District Selection - Finally, to isolate timing rather than proportion of electrification, we select districts from both PC and non-PC districts based on a common window of electrification rates. Figure 1 illustrates our selection process where we choose districts from both groups in the 25% to 50% electrification rates in 1986 for non-PC and in 2001 for PC districts. Using this subset of districts we run our primary specification. For the subset of districts among non-PC districts, we regress the change in electrified wells on change in household electrification between 1986 and 2001. We do the same for PC district subset between 2001 and 2013. Doing so helps us measure similar electrification thresholds between PC and non-PC districts but across different time periods. Results from this analysis have similar implications as our main results (table 1). Across non-PC districts, electrification of 100 households is on average associated with approximately 18 additional wells with electric pumps. Whereas, this number reduces to less than 4 among PC districts. + +<|ref|>image<|/ref|><|det|>[[100, 245, 888, 434]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[245, 444, 750, 459]]<|/det|> +
Figure 1: Selection of districts: (a) All districts; (b) Selected districts.
+ +<|ref|>table<|/ref|><|det|>[[120, 525, 877, 797]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[90, 482, 907, 497]]<|/det|> +Table 1: Implications remain the same even for selected districts within common bandwidth of electrification rates + +
Groundwater wells
TotalWith electric pumpsWith diesel pumps
Electrified households0.089**
(0.044)
0.180***
(0.051)
0.002
(0.015)
Electrified households × PC-0.0832**
(0.039)
-0.1408***
(0.049)
0.020
(0.025)
Total households-0.050
(0.056)
-0.071
(0.053)
-0.015
(0.019)
Fixed-effects
DistrictYesYesYes
YearYesYesYes
Fit statistics
Observations236236236
0.960.930.93
Within R²0.050.170.03
+ +<|ref|>table_footnote<|/ref|><|det|>[[130, 800, 870, 857]]<|/det|> +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Estimated using equation 1 and a subset of districts from the panel dataset constructed from district-level population and minor irrigation census data. + +<|ref|>text<|/ref|><|det|>[[89, 879, 907, 947]]<|/det|> +The authors robustness checks "We also consider models where we include electrification quantiles instead of a single binary classifier and find similar results (see appendix tables A1 and A2), in fact illustrate the diminishing importance of agricultural pump electrification as domestic electrification expands. In short, the authors have an exciting story here (they should write that one), but it is not the one they are trying to tell! + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 53, 904, 140]]<|/det|> +The fundamental problem is "construct" validity. Their bewildering approach to identifying those districts "exposed" to the policy and irrigation oriented versus a domestic oriented electrification policy, named "early" and "late" electrifiers derives not from the time when electrification was introduced but to the extent of electrification (in 2001?) i.e., as "majorly electrified" (lines 116). I struggled to see for myself nor access evidence to see why this is a good construct of early versus late and not more versus less! + +<|ref|>text<|/ref|><|det|>[[90, 148, 907, 217]]<|/det|> +We hope that we have been able to convince you as to why we believe that limited expansion of agricultural electricity is related to the timing of electrification and not the extent of electrification with the three additional analyses described above. Additionally, we have also changed LateElec to \(PC_{i}\) to better reflect the treatment we measure. \(PC_{i}\) refers to policy change and is defined similarly as LateElec. + +<|ref|>text<|/ref|><|det|>[[90, 224, 904, 275]]<|/det|> +A better approach would be a structural break in terms of time (treat 1986 as a base period and use an indicator variable for post 2000s) to proxy the policy shift. The authors could add a piece- wise analysis based on what proportion of households are electrified. + +<|ref|>text<|/ref|><|det|>[[90, 282, 907, 368]]<|/det|> +The issue with using 1986 as a base year and treating all districts similarly is that we are unable to distinguish between districts that majorly electrified before 2001 and those that electrified post 2001 when the target of rural electrification changed from agriculture to domestic connections. Electrified wells have continued to increase in number across both categories of districts till the latest available round in 2013. However, the rate of increase is different and important to isolate, which we are unable to do in the proposed analysis. + +<|ref|>text<|/ref|><|det|>[[90, 375, 890, 409]]<|/det|> +I would always want state- year interaction fixed effects to control for time- varying policy changes (including electricity pricing policies, irrigation technology subsidies, other infrastructure, etc.) + +<|ref|>text<|/ref|><|det|>[[90, 416, 900, 503]]<|/det|> +We include state- year interaction fixed effects in our primary specification and find similar implications for electrified wells with some changes in the precision of our estimate (tables 2 and 3). Electrification of 100 households among non- PC districts is on average associated with approximately 10 electrified wells compared to nearly 16 in our original analysis. The penalty for electrifying post policy change remains statistically significant and reduces to nearly 3 electrified wells compared to our earlier estimate of 2 additional electrified wells. + +<|ref|>text<|/ref|><|det|>[[90, 506, 910, 663]]<|/det|> +Interestingly, although electrification is still associated with a decrease in the use of diesel pumps, the penalty for electrification post policy change no longer remains statistically significant. This is likely due to low cross- state variation in the use of diesel pumps which may be stemming from a loss of statistical power, or perhaps reflective of the dominant use of diesel pumps in alluvial aquifers which are regionally concentrated across India (Shah, 2009). Results for irrigated area also have similar implications for all seasons. On average, electrification of a 100 households is on average associated with increase in nearly 12ha of irrigation during Kharif and 10ha during Rabi among non- PC districts. These numbers are a bit higher than our previous estimates of 11ha and 9ha respectively. We find post- policy change electrification penalty completely negates any increase in irrigation expansion during Rabi, similar to our previous estimates. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[117, 106, 880, 375]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[88, 53, 909, 80]]<|/det|> +Table 2: Household electrification in PC districts is also associated with smaller expansion in irrigated area across all season with variations explained by electrified pumps + +
Groundwater wells
TotalWith electric pumpsWith diesel pumps
Electrified households0.058***
(0.020)
0.101***
(0.025)
-0.028***
(0.008)
Electrified households × PC-0.0543**
(0.027)
-0.0709**
(0.028)
0.0201
(0.013)
Total households0.0294**
(0.014)
0.0036
(0.009)
0.0101
(0.011)
Fixed-effects
DistrictYesYesYes
State × YearYesYesYes
Fit statistics
Observations969969969
0.740.930.87
Within R²0.120.640.42
+ +<|ref|>table_footnote<|/ref|><|det|>[[127, 384, 870, 428]]<|/det|> +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Estimated using equation 1 and panel dataset constructed from district-level population and minor irrigation census data. + +<|ref|>table<|/ref|><|det|>[[88, 488, 965, 816]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[88, 444, 965, 470]]<|/det|> +Table 3: Household electrification in late-electrifiers is also associated with smaller expansion in irrigated area across all season with variations explained by electrified pumps + +
Irrigated area (ha)
Annual (ha)Kharif (ha)Rabi (ha)
(1)(2)(3)(4)(5)(6)
Electrified households0.199***
(0.0665)
0.050
(0.0527)
0.117***
(0.0337)
0.037
(0.0253)
0.096***
(0.0320)
0.034
(0.0275)
Electrified Households × PC-0.178***
(0.058)
-0.070
(0.043)
-0.063**
(0.030)
-0.005
(0.021)
-0.010***
(0.029)
-0.060**
(0.025)
Wells with electric pumps1.492***
(0.182)
0.801***
(0.111)
0.594***
(0.075)
Total households0.082
(0.060)
0.079
(0.051)
0.026
(0.025)
0.025
(0.021)
-0.005
(0.025)
-0.006
(0.021)
Cumulative Average Monthly Rain↑-11.43
(7.872)
-4.053
(7.458)
-11.91**
(4.659)
-6.641
(4.252)
23.00
(35.14)
0.174
(32.52)
Fixed-effects
DistrictYesYesYesYesYesYes
State × YearYesYesYesYesYesYes
Fit statistics
Observations969969969969969969
0.890.900.880.890.890.90
Within R²0.450.510.420.510.420.47
+ +<|ref|>table_footnote<|/ref|><|det|>[[88, 824, 960, 890]]<|/det|> +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Annual, average rainfall during November to March and average rainfall during June to October were used for annual, Rabi and Kharif cultivation seasons respectively. Estimated using equation 1 and panel dataset constructed from district-level population and minor irrigation census data. + +<|ref|>text<|/ref|><|det|>[[88, 905, 909, 937]]<|/det|> +I would like to see a greater discussion of diesel pumps (lines 66- 68) used not as a substitute for electricity but for poor quality of electricity and hours of power supply. There are several discussions of these in the literature on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 54, 526, 68]]<|/det|> +subsidies in India (notably by Ashok Gulati and co- authors). + +<|ref|>text<|/ref|><|det|>[[89, 76, 902, 252]]<|/det|> +Included text in Lines 67- 75 - "Electricity is preferred even in shallower wells where the option of pumping using diesel exists and is reflected in the declining proportion of wells operated by diesel pumps from over \(30\%\) in 1986 to below \(28\%\) in 2013, despite greater than \(90\%\) growth in the total number of irrigation wells during the same period (Statistics Division, 2017). At greater than INR 40/1 since price deregulation in 2014, diesel is more expensive than agricultural electricity rates in most Indian states. (Verma and Patnaik, 2018; CCEA, 2014) Therefore, only in regions where electricity is unavailable or suffers from quality issues of intermittency and low voltage, diesel pumps are used to power irrigation either exclusively, or in conjunction with electric pumps to compensate for unreliable electricity supply (Gulati and Narayanan, 2003; Gulati et al., 2019). Where available, electricity is subsidized by way of flat or no tariffs effectively eroding the marginal cost of consuming electricity (Gulati and Narayanan, 2003)." + +<|ref|>text<|/ref|><|det|>[[90, 260, 877, 309]]<|/det|> +Line 23 "Perhaps it is time to reevaluate uniform prescriptive electricity loads and uses in formulating RE policies" This sentence can be clarified. It becomes clear later on but on line 23, it is too early for readers unfamiliar with the policy and the sector. + +<|ref|>text<|/ref|><|det|>[[90, 317, 907, 367]]<|/det|> +Changed text in Line 24- 27 - "Perhaps it is time to reevaluate domestic electrification as the primary target of RE policies, and instead consider income generation as a primary goal to unleash the true power of electrification in the rural developing world." + +<|ref|>text<|/ref|><|det|>[[90, 375, 899, 461]]<|/det|> +The authors claim that they use "newly constructed panel- dataset spanning three decades" (in the abstract). Yet the figure 2 notes that the "Relationship between electrified households and electrified wells in 2013 was stronger among early electrifiers compared to late electrifying districts. The point estimates represent district- level data on electrified houses and wells with electrified pumps." This suggests misleadingly that the regression was run for just 1 year, i.e., 2013. + +<|ref|>text<|/ref|><|det|>[[89, 469, 908, 590]]<|/det|> +Figure 4 serves as the descriptive evidence to motivate our analysis and is explained by the accompanying text in lines 130- 134 - "Before presenting our regression models, figure 4 presents cross- sectional, descriptive evidence to motivate our analysis. In 2013, our most recent round of data, we see a stark difference in the relationship between household electrification and electrified groundwater pumps in PC versus non- PC districts. PC districts had far fewer wells with electric pumps compared to non- PC districts with similar numbers of electrified households (Figure 4). This divergent cross- sectional relationship between the two sets of districts could be driven by unobserved factors." + +<|ref|>text<|/ref|><|det|>[[90, 594, 895, 662]]<|/det|> +We have added the following line (lines 140- 141) to clarify that the regression estimates considers three time periods - "Our fixed effects regression estimates measures the association between the number of electrified households with the number of groundwater wells using electric and diesel pumps across 1986 to 2013. The estimates show that, on average, the electrification of ..." + +<|ref|>text<|/ref|><|det|>[[90, 670, 907, 737]]<|/det|> +The undertone at least in the initial parts of the paper is a celebration of electricity for pumping groundwater, barring some reflections in line 68. Perhaps you could start the paper early on by suggesting that despite the problem of overextraction etc. irrigation is known to have large benefits, and the culprit for that is more in the pricing than the extraction. + +<|ref|>text<|/ref|><|det|>[[90, 746, 905, 796]]<|/det|> +Included text in Lines 9- 11 - "This vast consumption of groundwater has not been without its adverse impacts. Every year India pumps twice as much groundwater as the US or China, and houses regions with the greatest rates of global groundwater depletion (Aeschbach- Hertig and Gleeson, 2012; Famiglietti, 2014; Lo et al., 2016)." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[90, 52, 220, 68]]<|/det|> +## Reviewer 2 + +<|ref|>text<|/ref|><|det|>[[90, 87, 820, 101]]<|/det|> +The authors tackle a very important question with both energy and human development implications. + +<|ref|>text<|/ref|><|det|>[[90, 109, 907, 160]]<|/det|> +This is a good dataset and strong analytics - but the interpretations and framings need to be questioned. The study very nicely shows there is a disconnect for irrigation coverage vs. household electrification by time (early vs late), but it's not clear causality can be linked to policies favoring household electrification. + +<|ref|>text<|/ref|><|det|>[[90, 168, 907, 306]]<|/det|> +We thank you for your insightful and helpful comments. We have made additions to the manuscript with a new block- level analysis for Madhya Pradesh and text in response to your points and in support of our original claims. Additionally, to clarify our intent to capture electrification policy change, we have replaced Late Elec with PC to identify districts that were majorly electrified after the focus of rural electrification policy shifted towards domestic electrification from agriculture. The definition of PC is the same as what we previously used for Late Elec. We now refer to late electrifying districts as PC districts or districts that electrified post policy change, and early electrifiers as non- PC districts or districts that electrified pre policy change. We highlight changes in the manuscript by using blue- coloured text. Our responses to the individual points are found below. + +<|ref|>text<|/ref|><|det|>[[90, 314, 897, 364]]<|/det|> +Utilities likely did slow down connections to farmers, but that was independent of any focus on household electrification. Farmers underpay, as well known, and this non- remunerative supply is a strain on utilities. Note, free power to farmers only started in 1977 in Andhra Pradesh, and wasn't widespread for a few more years. + +<|ref|>text<|/ref|><|det|>[[90, 372, 888, 422]]<|/det|> +While electricity access policy DOES favor households, it's not clear why that would be at the expense of agriculture. BOTH segments enjoy heavily cross- subsidized and subsidized electricity (cross- subsides for homes being for lower slabs or tiers of consumption). + +<|ref|>text<|/ref|><|det|>[[89, 430, 907, 553]]<|/det|> +It is likely that rural electric supply on average is loss- making in India for the power utilities, whether it is subsidized domestic connections or agricultural supply. It is for precisely this reason, that we think there is some rationing occurring in who gets electricity and where. Together, our results imply that while power utilities or the government may not have deliberately neglected agricultural electricity supply, the singular focus on electricity expansion through domestic connections to fulfill stated targets may have resulted in the unintended neglect of electricity supply to agriculture. We do not have empirically robust methods of teasing out exactly how this may have occurred, but from a synthesis of literature and field visits to Odisha identify two main routes - + +<|ref|>text<|/ref|><|det|>[[110, 568, 900, 779]]<|/det|> +1. Transformer sizing - Two independent evaluations of the Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY) by Parikh et al. (2013) and Planning Commission of India (2014) find frequent burnout of transformers in RGGVY electrified villages. Through surveys, they find overloading (rather than infrastructural defects) as a key reason for these burnouts. Further, Parikh et al. (2013) breakdown the calculation of the standard size of installed transformers of 457kW (16kVA with a power factor of 0.7) load result in average loads of 600W per household (implying average village size of \(\sim 760\) households). Therefore, the average household load is less than the capacity of a 1 HP pump-set ( \(\sim 746\) W). In such a scenario, nearly 50% of the total calculated load could come from only pumps if even 10% of the houses operated 4HP pump-sets. To place this in context, over 80% of all wells in MI Census 2013 used pumps larger than 4HP (Government of India, 2017)s. Additionally, Banerjee et al. (2014b) also state the limited capacity of transformers as one of the major contributors to low reliability of electricity among RGGVY electrified villages. + +<|ref|>text<|/ref|><|det|>[[110, 789, 907, 911]]<|/det|> +2. Distance from transformer and lack of electric infrastructure that provide physical access (poles, wires etc.) for non-domestic uses of electricity - The two studies note voltage drops experienced by far flung houses in villages leading to equipment failure. Additionally, Parikh et al. (2013) find a complete absence of any commercial activities outside of homes in surveyed villages electrified by RGGVY. They find a small number of commercial activities including weaving and handicraft occurring inside homes. Planning Commission of India (2014) find the use of electric motor-pumps for agriculture in less than 1% of households surveyed in RGGVY villages. + +<|ref|>text<|/ref|><|det|>[[90, 927, 886, 942]]<|/det|> +We identified similar constraints in field visits conducted during 2016 and 2018 in rural Odisha. Farmers in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 54, 907, 105]]<|/det|> +state are expected to pay the additional cost of poles and wiring required to access electricity on their fields (Orissa Lift Irrigation Corporation, 2014; Department of Energy, 2016). Transformer burnouts were also frequently experienced and attributed by the energy department officials to the hooking up of a handful of electric pumps. + +<|ref|>text<|/ref|><|det|>[[90, 112, 904, 216]]<|/det|> +One has to start with the reality that agricultural supply is very expensive for the utility - being both subsidized and cross- subsidized. Are there enough takers for a pumpset? Let's also start with SECC data - 55% of farmers are landless (laborers) so increasing pumpsets helps a subset. Here's a counterfactual Q: Now that households are 100% electrified, does this now "free up" policy for pumpsets? The pumpsets policy has been the way it is (limited by design, with largesse and political connections important) for a long while in the face of heterogeneity in connectivity. + +<|ref|>text<|/ref|><|det|>[[90, 224, 891, 345]]<|/det|> +Data on landless and landed farmers are not available for all years of our analysis and therefore cannot be included in our primary specification. Instead, we conduct a balance test between PC and non- PC districts (previously late and early electrifiers respectively) and find that on average, PC districts are larger with greater numbers of both landed and landless households (table 4). Holding all else equal, greater number of landed households are expected to be associated with greater demand for electrified wells, which we do not find. This makes our results even more stark as we find larger PC districts with fewer electrified wells than the smaller non- PC districts. + +<|ref|>table<|/ref|><|det|>[[185, 372, 812, 440]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[185, 350, 810, 365]]<|/det|> +Table 4: PC districts on average were larger with more households across all categories. + +
Non-PC districtsPC districtsp-value
Average landless households (‘000)178.3621211.93990.04
Average land owning households (‘000)119.9451165.43550.00
Average total land in district (‘000 acre)1,414.80732,884.28860.02
+ +<|ref|>table_footnote<|/ref|><|det|>[[186, 437, 810, 460]]<|/det|> +Data is based on district-level \((N = 425)\) Socioeconomic Caste Census carried out in 2011 (Department of Rural Development, 2011). + +<|ref|>text<|/ref|><|det|>[[90, 490, 907, 576]]<|/det|> +There is no limited incorporation of the physics, design, and practicality of rural connections. Recent policies (last 10 years) have been towards feeder segregation, but even before this, most states had "rosters" or schedules where agricultural supply was limited to, say, 6 or 8 hours per day. This was controlled through phase- separation, with single phase supply (for homes) meant to be as much as possible, ideally 24 hours in theory (but never in practice). + +<|ref|>text<|/ref|><|det|>[[90, 584, 905, 740]]<|/det|> +We are limited in our capacity to carry out an exhaustive analysis of how states operationalize electrification in their respective rural areas. However, in at least one state where rural electrification occurred majorly through RGGVY, farmers are expected to bear the cost of additional poles and wires to use electricity on agricultural fields (Orissa Lift Irrigation Corporation, 2014; Department of Energy, 2016). Further, limited capacities of transformers in RGGVY electrified villages are found to be a major contributor to poor electricity supply (Banerjee et al., 2014b; Planning Commission of India, 2014; Parikh et al., 2013). As noted, the period when feeder separation was largely carried out does not apply to our analysis as the former is being undertaken more recently. Whether separate feeders will be installed in areas where agricultural demand does not currently exist is a question that remains, and one that is important to address. + +<|ref|>text<|/ref|><|det|>[[90, 748, 910, 888]]<|/det|> +The second reality that questions the model and framing is how we have "incremental electrification". Most challenges for household electrification have been with the "last mile connection". The earlier (and insufficient) definitions of electrification focused on a single lightbulb meant the village was electrified, updated to then be 10% of homes. This was progressively upgraded, which is a good thing, but there is no evidence of a "policy reason" this was at the expense of pumpsets. Your analysis does bring out the point that household supply doesn't increase wealth much - so it is a separate question of how much one can/should increase pumpsets. If they were charged "full cost" there would be no problem but we know they are not. Money for loss- making utilities is scarce, and so there is a call to be made how much pumpset deployment is appropriate. + +<|ref|>text<|/ref|><|det|>[[90, 896, 895, 946]]<|/det|> +Aside: There was also a period (early 2000s) where power supply quality impacted affordability of pumpsets. Even with "cheap power", frequent burnouts meant rewinding costs were more than the cost of electricity. This raises the general question of why don't people want a pumpset versus how many people want a pumpset but + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 56, 189, 68]]<|/det|> +can't get one. + +<|ref|>text<|/ref|><|det|>[[89, 77, 910, 270]]<|/det|> +Not wanting agricultural pump- sets from the farmers' perspectives can stem from broadly two main reasons. We address the first reason of not needing one by incorporating seasonal rainfall in our analysis. It is also widely accepted that surface water irrigation is insufficient for cultivation during Rabi and is increasingly inadequate for cultivation during Kharif (Shah, 2009; Shah et al., 2012). The second reason of not wanting may stem from inadequate returns to pump- set investments. We do not address the latter sufficiently in our analysis beyond looking at irrigation access across households of similar wealth across PC and non- PC districts (previously late and early electrifying respectively). We agree that this may be a potential source of error and make a note of it in Lines 227- 234. However, if true, our results remain valid as poor electricity quality would then be experienced disproportionately higher by PC (previously late electrifying) districts and would merit further investigations. Not wanting pump- sets from the government's or the utilities' perspectives are important points that are beyond the scope of our study. + +<|ref|>text<|/ref|><|det|>[[90, 277, 903, 345]]<|/det|> +Do you measure size of wells (borewells), measured by HP (horsepower)? 20 wells isn't comparable across regions. This also links to issues of water- sharing. Local politics and influence can be a factor. This also means larger farmers with pump- sets sell water to their neighbors. Anecdotally, it is prevalent in many eastern states of India. + +<|ref|>text<|/ref|><|det|>[[90, 353, 903, 457]]<|/det|> +Unfortunately, the size of pumps is not provided in the first round of data. We use the classification of wells based on their depths and rerun our primary specification. There are three main types of wells recorded in the Minor Irrigation Census - dug wells which are constructed without the use of drilling machines and have average depths of 8- 15m, shallow and deep tube- wells are constructed with drilling machines and are classified as those shallower than and those deeper than 70m respectively. We include these details in the data section under Minor Irrigation Census. + +<|ref|>text<|/ref|><|det|>[[90, 460, 904, 599]]<|/det|> +We run the main specification separately for each category of wells and find persistent negative and statistically significant effects among PC districts (table 5). Interestingly, the negative impact of electrifying post policy change is greatest on a relative scale for dug wells, where PC districts experience no gains from electrification in terms of electrified irrigation wells. We are unable to address the issue of water markets due to limitations of data and make a note of this in the discussion section in Lines 231- 234 - "We are also unable to account for water markets that are reported to exist in some eastern states in the country (Mukherji et al., 2009). Nevertheless, these factors are important to account for while designing policies that target irrigation expansion across PC districts." + +<|ref|>text<|/ref|><|det|>[[90, 607, 907, 674]]<|/det|> +Is there any analysis of farm size and pumpsets? Many farms in the less irrigated sections of India (easter) are more subsistence, and also (as you rightly observe) have limitations in market access. These regions also have much lower water demands based on water tables. Crop choices also matter - Punjab went for cash crops much earlier on. + +<|ref|>text<|/ref|><|det|>[[90, 683, 907, 928]]<|/det|> +As such we are unable to control for the size of farms in our main specification as data on farm size are not available for the years included in our analysis. We do however, control for it when measuring the differences in irrigation across households of similar wealth in PC and non- PC districts. Households with similar consumption in PC districts irrigate less than households in non- PC districts on average, even after controlling for the size of land owned and operated. Additionally, we run a balance test on the surveyed agrarian households included in the Situation Assessment Survey carried out by the NSSO (National Sample Survey Office, 2014). We find that on average, farmers in PC districts do have smaller plots - 1.4 ha compared to 2.2 ha on average in non- PC districts (table 6). On average, PC districts run about half a hectare smaller up until the \(75^{th}\) quartile. So it is possible that a systematic difference in parcel size may be contributing to lower returns on electric pump investment and thereby adding to the disincentives to invest in electric pumps. We have added text in the discussion and policy section to note this in Lines 227- 234 - "Our analysis does not exhaustively capture all possible disincentives to electric pump investments - poor supply of electricity, small or scattered parcels of landholdings and inadequate returns to irrigation are some potential biases to our results. For instance, households on average owned smaller parcels of land among PC districts compared to non- PC districts. While we control for land sizes in our analysis, + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[123, 95, 876, 360]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[222, 53, 775, 67]]<|/det|> +Table 5: Negative penalty holds for PC districts across all categories of wells + +
Groundwater wells with electric pumps
Deep tube-wellsShallow tube-wellsDug wells
Electrified households0.045***
(0.008)
0.074***
(0.013)
0.040**
(0.018)
Electrified households × PC-0.038***
(0.010)
-0.041***
(0.014)
-0.059***
(0.018)
Total households-0.007
(0.005)
-0.005
(0.004)
0.001
(0.007)
Fixed-effects
DistrictYesYesYes
YearYesYesYes
Fit statistics
Observations969969969
0.520.780.87
Within R²0.140.180.04
+ +<|ref|>table_footnote<|/ref|><|det|>[[130, 370, 869, 430]]<|/det|> +Note: \\*p<0.1; \\*\\*p<0.05; \\*\\*\\*p<0.01 Standard errors are clustered at the district level. Estimated using equation 1 and panel dataset constructed from district-level population and minor irrigation census data. + +<|ref|>text<|/ref|><|det|>[[90, 442, 905, 510]]<|/det|> +we are unable to consider poor quality of supply, scattered parcels or returns to irrigation due to data limitations. We are also unable to account for water markets that are reported to exist in some eastern states in the country (Mukherji et al., 2009). Nevertheless, these factors are important to account for while designing policies that target irrigation expansion among PC districts." + +<|ref|>table<|/ref|><|det|>[[189, 538, 808, 617]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[255, 517, 741, 531]]<|/det|> +Table 6: Farm sizes were smaller on average in PC districts in 2013 + +
Non-PC districtsPC districtsp-value
Land owned (ha)2.231.420.00
Land operated (owned and leased) (ha)2.611.550.00
Land cultivated during Rabi1.661.010.00
Land cultivated during Kharif2.091.170.00
+ +<|ref|>table_footnote<|/ref|><|det|>[[190, 617, 808, 641]]<|/det|> +Data is based on a nationally representative survey data of agricultural households \((N =\) 11,182) in 2012-13 (National Sample Survey Office, 2014). + +<|ref|>text<|/ref|><|det|>[[90, 656, 910, 725]]<|/det|> +An interesting analysis would be to examine districts within a state. One can assume a state has certain policy - but we note there is disparity in pumpsets within states. This suggests it's not a policy reason but fundamentals driven by farmer wealth, crop choices, water tables, rainfall patterns etc. See interior Maharashtra vs. coastal, and similar for some other states. + +<|ref|>text<|/ref|><|det|>[[90, 732, 910, 871]]<|/det|> +We run our primary specification at the block level in Madhya Pradesh. We chose Madhya Pradesh as it has a high diversity of PC (28) and non- PC (10) districts and is a major agricultural state. We use the Defense Meteorological Program Operation Line Scan System (DMSP- OLS) night time luminosity data compiled by Asher et al. (2021) to measure electrification. We use this additional source as population census does not publish electrification data at the block level. We matched the second, third and fifth rounds Minor Irrigation Census with SHRUG nightlight and population census datasets (Asher et al., 2021). The first minor irrigation census does not report data at the block or village level. We use total light luminosity values which range from 0 to 63 and are calibrated by Elvidge et al. (2014) for consistent measure across the range of years 1994- 2013. + +<|ref|>text<|/ref|><|det|>[[90, 874, 904, 942]]<|/det|> +On average we find DMSP- OLS data to be a conservative estimate of electrification (see appendix figure A1). The block- level analysis with DMSP- OLS and Minor Irrigation Census for Madhya Pradesh are consistent with our results overall with some differences in the interpretation due to the use of nightlight luminosity. On average, a \(1\%\) increase in luminosity among blocks within non- PC districts is associated with an increase in over 1,500 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 53, 907, 104]]<|/det|> +electrified wells. This value decreases by nearly 1,000 wells and a \(1\%\) increase in nighttime luminosity is associated with a cumulative increase of 500 electrified wells in blocks across PC districts. We do not find a relationship between nighttime luminosity and wells with diesel pumps. + +<|ref|>text<|/ref|><|det|>[[90, 107, 904, 283]]<|/det|> +Additionally our analysis using the National Sample Survey Office's Situation Assessment Survey of Agricultural Households data in section titled "Income does not explain irrigation differences between PC and non- PC districts" considers the roles that farmer wealth and rainfall play and we find that rural electrification policy change is a stronger predictor of irrigation area than is farmer wealth. Compared to the poorest \(15^{th}\) percentile households, all other farming households among non- PC districts irrigated larger tracts of cultivated land during Rabi. We find no similar differences in irrigated area between the poorest \(15^{th}\) percentile households in non- PC districts and households among PC districts that were even in the top \(85^{th}\) consumption percentile. The NSSO analysis includes state- level fixed effects which translates to a comparison of agrarian households across PC and non- PC districts within each state. However, the state level fixed effects work only when states with more PC districts do not systematically differ from states with fewer PC districts. + +<|ref|>text<|/ref|><|det|>[[90, 290, 900, 341]]<|/det|> +A fundamental question: What if earlier electrifiers were simply richer regions or had more resources? Thus BOTH homes and pumpsets would be faster. The 8 times more pumpsets for earlier electrifiers then is explained by economic reasons, as opposed to the framing you have, which is a policy choice with a tradeoff. + +<|ref|>text<|/ref|><|det|>[[89, 348, 909, 523]]<|/det|> +We agree that systematic differences between PC and non- PC districts are potential sources of biases in our results. We conduct a household level analysis (results illustrated in figure 5) where we test for irrigation coverage among households of similar wealth but compare across PC and non- PC districts. We find that the differences persist even among households of similar wealth across PC and non- PC districts. Unfortunately we cannot test this across time since situation assessment of agricultural households has not been repeated since 2013. As you rightly point out in your previous comment, it could be that district- level wealth may be a stronger predictor of pump- set use than household wealth, which this analysis would not address. Our new block- level analysis in Madhya Pradesh compares blocks across PC and non- PC districts. While it does not fully address a possibility of systematic differences across the two categories of districts, it does remove state- level differences that may be present in our primary specification. + +<|ref|>text<|/ref|><|det|>[[90, 526, 905, 595]]<|/det|> +If, in fact, non- PC districts are systematically different from PC districts in ways that influence both electrification of houses and wells, while the precision of our estimate may be questionable, our analysis is helpful in at least identifying that irrigation expansion remains unaffected despite rural electrification expansion in the latter. A point that is important to be addressed to tackle rural poverty and climate change. + +<|ref|>text<|/ref|><|det|>[[110, 602, 905, 618]]<|/det|> +Figure 3 - we can note that even in 2013, it is the east that lags - both household electrification and irrigation. + +<|ref|>text<|/ref|><|det|>[[90, 625, 890, 694]]<|/det|> +We agree it is the east where both rural electrification has been slow to spread and so has groundwater irrigation. Recent estimates suggest near universal electrification of this region ((see Saubhagya dashboard). It will be interesting to note the associated expansion in groundwater irrigation once the latest round of Minor Irrigation Census becomes publicly available. + +<|ref|>text<|/ref|><|det|>[[90, 700, 888, 752]]<|/det|> +Figure 4 - There is a clear split between late vs. early electrifiers, but that split may also have many confounding factors instead of your theory of policies that favored one over the other. Note that there are very few districts with over 5 lakh (500,000) households electrified. + +<|ref|>text<|/ref|><|det|>[[89, 759, 905, 916]]<|/det|> +We agree there could be a number of confounding factors which is why our estimates are based on a two- way fixed effects regression to control for the confounders and explain the details of the estimation strategy in methods section of the paper. Figure 4 simply serves as the descriptive evidence to motivate our analysis and is explained by the accompanying text in lines 130- 134 - "Before presenting our regression models, figure 4 presents cross- sectional, descriptive evidence to motivate our analysis. In 2013, our most recent round of data, we see a stark difference in the relationship between household electrification and electrified groundwater pumps in PC versus non- PC districts. PC districts had far fewer wells with electric pumps compared to non- PC districts with similar numbers of electrified households (Figure 4). This divergent cross- sectional relationship between the two sets of districts could be driven by unobserved factors..." + +<|ref|>text<|/ref|><|det|>[[110, 919, 890, 935]]<|/det|> +We have added the following line (lines 140- 141) to clarify that the regression estimates considers three time + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 53, 860, 104]]<|/det|> +periods - "Our fixed effects regression estimates measures the association between the number of electrified households with the number of groundwater wells using electric and diesel pumps across 1986 to 2013. The estimates show that, on average, the electrification of ..." + +<|ref|>text<|/ref|><|det|>[[90, 112, 890, 234]]<|/det|> +Line 163: "transformer capacities could be constraining even households with the financial means to access electricity for groundwater irrigation." Your math is correct that household connections are small, but transformers are always based on multiple homes, and, more importantly, almost NEVER smaller than tens of kW. Esp. in those days, there were no plans for LVDS (low voltage distribution systems) which had smaller transformers. Typically, there was a fixed model used that covered a variety of uses. There was no separate transformer then for house vs. agriculture. So size limitations is unlikely to be a bottleneck until we have many pumpsets connected. + +<|ref|>text<|/ref|><|det|>[[90, 241, 904, 365]]<|/det|> +Calculations by Parikh et al. (2013) suggest the standard size of installed transformers of 457kW (16kVA with a power factor of 0.7) load result in average loads of 600W per household (implying average village size of \(\sim 760\) households). Therefore, the average household load is less than the capacity of a 1 HP pump- set ( \(\sim 746W\) ). This would mean that even if \(10\%\) households were to own a 4HP pumpset, they would account for nearly \(50\%\) of the total village load. Over \(80\%\) of all wells in MI Census 2013 used pumps larger than 4HP (Government of India, 2017). Additionally Banerjee et al. (2014b) report on Indian electrification experience notes that many states installed transformers that fall short of full village load leading to issues of reliability. + +<|ref|>text<|/ref|><|det|>[[90, 371, 907, 422]]<|/det|> +In summary: Interest and strong analysis, but the claims made aren't proven, and the econometrics only partially answer some of the issues above (like wealth as a factor - it's not just RURAL HOUSEHOLD WEALTH that matters - state wealth matters for the utility, e.g., the presence of richer consumers to offset rural losses. + +<|ref|>text<|/ref|><|det|>[[90, 429, 910, 497]]<|/det|> +We added state specific time trends to account for time variant state- level differences in our primary specification. Our results are robust to the inclusion of these state specific time trends (tables 2 and 3). Additionally, the new block level analysis carried out for Madhya Pradesh implies similar differences in block level outcomes between PC and non- PC districts. + +<|ref|>text<|/ref|><|det|>[[90, 500, 910, 551]]<|/det|> +We hope that we have convinced you with the new set of analyses which, in our view, add robustness to our claim that differences in the number of electrified wells is independent of household and state wealth, and the need for irrigation. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[90, 52, 216, 68]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[88, 80, 840, 115]]<|/det|> +Aeschbach- Hertig, W. and Gleeson, T. (2012). Regional strategies for the accelerating global problem of groundwater depletion. Nature Geoscience, 5(12):853- 861. + +<|ref|>text<|/ref|><|det|>[[90, 124, 900, 176]]<|/det|> +Asher, S., Lunt, T., Matsuura, R., and Novosad, P. (2021). Development Research at High Geographic Resolution: An Analysis of Night Lights, Firms, and Poverty in India using the SHRUG Open Data Platform. The World Bank Economic Review. + +<|ref|>text<|/ref|><|det|>[[90, 185, 905, 236]]<|/det|> +Banerjee, S. G., Barnes, D. F., Mayer, K., Samad, H. A., and Singh, B. N. (2014a). Chapter 2: Closing the Electricity Access Gap. In Power for all: electricity access challenge in India. World Bank Group, Washington, DC. + +<|ref|>text<|/ref|><|det|>[[90, 247, 900, 298]]<|/det|> +Banerjee, S. G., Barnes, D. F., Mayer, K., Samad, H. A., and Singh, B. N. (2014b). Chapter 4: History of Rural Electrification and Institutional Organization. In Power for all: electricity access challenge in India. World Bank Group, Washington, DC. + +<|ref|>text<|/ref|><|det|>[[90, 308, 870, 341]]<|/det|> +CCEA, C. C. o. E. A. (2014). Deregulation of Diesel Prices. Press Release, Press Information Bureau (PIB), Government of India, New Delhi. + +<|ref|>text<|/ref|><|det|>[[90, 352, 819, 385]]<|/det|> +Department of Energy, G. o. O. (2016). Office Memorandum - Amendment of Biju Gram Jyoti- Rural Electrification programme of the State Government. + +<|ref|>text<|/ref|><|det|>[[90, 395, 888, 428]]<|/det|> +Department of Rural Development, Ministry of Rural Development, G. o. I. (2011). Socio Economic and Caste Census 2011 (SECC). + +<|ref|>text<|/ref|><|det|>[[90, 438, 900, 472]]<|/det|> +Elvidge, C. D., Feng- Chi, H., Baugh, K. E., and Ghosh, T. (2014). National trends on satellite- observed lighting. Global urban monitoring and assessment through earth observation, (23). + +<|ref|>text<|/ref|><|det|>[[90, 482, 780, 498]]<|/det|> +Famiglietti, J. S. (2014). The global groundwater crisis. Nature Climate Change, 4(11):945- 948. + +<|ref|>text<|/ref|><|det|>[[90, 508, 908, 541]]<|/det|> +Government of India, Ministry of Water Resources, R. D. a. G. R. (2017). 5th Census of Minor Irrigation Schemes Report. + +<|ref|>text<|/ref|><|det|>[[90, 551, 896, 585]]<|/det|> +Gulati, A. and Narayanan, S. (2003). Power Subsidies. In The Subsidy Syndrome in Indian Agriculture. Oxford University Press, New Delhi. + +<|ref|>text<|/ref|><|det|>[[90, 595, 900, 646]]<|/det|> +Gulati, A., Sharma, B., Banerjee, P., and Mohan, G. (2019). Getting More from Less: Story of India's Shrinking Water Resources. Technical report, Indian Council for Research on International Economic Relations (ICRIER), Delhi. + +<|ref|>text<|/ref|><|det|>[[90, 656, 866, 725]]<|/det|> +Lo, M.- H., Famiglietti, J. S., Reager, J. T., Rodell, M., Swenson, S., and Wu, W.- Y. (2016). GRACE- Based Estimates of Global Groundwater Depletion. In Tang, Q. and Oki, T., editors, Terrestrial water cycle and climate change: natural and human- induced impacts, number 221 in Geophysical monograph series. AGU, American Geophysical Union, Washington, D.C. + +<|ref|>text<|/ref|><|det|>[[90, 735, 866, 769]]<|/det|> +Mukherji, A., Das, B., Majumdar, N., Nayak, N., Sethi, R., and Sharma, B. (2009). Metering of agricultural power supply in West Bengal, India: Who gains and who loses? Energy Policy, 37(12):5530- 5539. + +<|ref|>text<|/ref|><|det|>[[90, 779, 905, 812]]<|/det|> +National Sample Survey Office, M. o. S. a. P. I. (2014). Situation Assessment Survey of Agricultural Households - 2013. Technical report, Government of India, New Delhi. + +<|ref|>text<|/ref|><|det|>[[90, 822, 720, 837]]<|/det|> +Orissa Lift Irrigation Corporation, G. o. O. (2014). Detail Information about Jalindhi- I. + +<|ref|>text<|/ref|><|det|>[[90, 847, 907, 899]]<|/det|> +Parikh, J., Dutta Biswas, C., and Panda, R. R. (2013). Combined Report on Evaluation of Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY) of Rajasthan, Assam, Gujarat, Himachal Pradesh and Uttar Pradesh. Technical report, Integrated Research and Action for Development (IRADe), New Delhi. + +<|ref|>text<|/ref|><|det|>[[90, 909, 904, 942]]<|/det|> +Planning Commission of India (2014). Evaluation Report on Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY). 224, Programme Evaluation Organisation, Planning Commission, Government of India, New Delhi. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[88, 53, 833, 88]]<|/det|> +Shah, T. (2009). Climate change and groundwater: India's opportunities for mitigation and adaptation. Environmental Research Letters, 4(3):035005. + +<|ref|>text<|/ref|><|det|>[[88, 97, 888, 132]]<|/det|> +Shah, T., Giordano, M., and Mukherji, A. (2012). Political economy of the energy- groundwater nexus in India: exploring issues and assessing policy options. Hydrology Journal, 20(5):995- 1006. + +<|ref|>text<|/ref|><|det|>[[88, 140, 900, 175]]<|/det|> +Statistics Division, M. I. (2017). Manual For Data Collection in the Census of Minor Irrigation Schemes 2013- 14. Technical report, Ministry of Water Resources, Government of India, New Delhi. + +<|ref|>text<|/ref|><|det|>[[88, 184, 785, 200]]<|/det|> +Verma, N. and Patnaik, S. (2018). Graphic: India's petrol, diesel prices surge to record. Reuters. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 124, 285, 137]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 152, 216, 164]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 166, 291, 179]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 180, 857, 207]]<|/det|> +Thank you for the efforts you have made in addressing each comment from the reviewers seriously and as comprehensively as your dataset would allow. + +<--- Page Split ---> diff --git a/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/images_list.json b/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..064446f370a3403f5cc0f7ca197cbdd167767953 --- /dev/null +++ b/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_9.jpg", + "caption": "Supplementary Figure 9. The spatial localization of the His-Asp in the structures of SenB and other GT-B type GTs.", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..2eb6681fb77892a56a7f2c972f723811baaea822 --- /dev/null +++ b/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,378 @@ + +# nature portfolio + +Peer Review File + +Substrate binding and catalytic mechanism of the Se- glycosyltransferase SenB in the biosynthesis of selenoneine + +![](images/Supplementary_Figure_9.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +Reviewer #1 (Remarks to the Author): + +This is a revised submission of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in a three gene cluster that catalyzes the synthesis of a Scontaining metabolite in a broad collection of bacteria. The initial submission had numerous concerns regarding the writing, summary of prior work on selenium metabolism, and interpretation of the experimental data. The revised submission addressed some of these concerns, but numerous problems in the writing in the revision result in continuing overall problems with the manuscript. These major and minor concerns include numerous problems with English usage and interpretation of data. + +The editing and data interpretation concerns include: + +Abstract, line 20: 'tested' not 'testified' + +Abstract, lines 21- 22: "...structure- guided mutagenesis indicating that SenB forms C- Se glycosidic bonds via spontaneous deprotonation and nucleophilic attack with the critical residue K158 assisting in Se- P bond cleavage..." + +Abstract, line 23: "Furthermore, we functionally and structurally..." + +Introduction, line 34: 'majorly' is not appropriate word usage here. + +Introduction, line 38: I am not sure that 'catalyzation' is a word. + +Introduction, line 44: 'With the exception that SEN could protect against...' + +Introduction, lines 47- 49: The sentence starting with 'Recently...' is very awkwardly worded. Please revise. + +Introduction, line 59: '...glycosyltransferases (GTs), suggesting that SenB could also be considered as a Se- glycosyltransferase...' + +Results and discussion, line 81: 'Previous studies showed that SenB can utilize UDP- GlcNAc, UDP- GalNAc, and UDP- Glc as sugar donors...' + +Results and discussion, line 102: 'This result is consistent with...' + +Results and discussion, line 105: '...on the sugar contribute to the catalytic efficiency...' + +Results and discussion, line 150: This paragraph describes the structural basis for the specificity toward uridine versus adenine/guanine bases for the sugar nucleotide donor, but then attempts to use the K158A and E239A mutations as justification. K158 interacts with the beta phosphate and E239 interacts with the ribose. Neither interact with the nucleotide base to provide an explanation for base specificity. + +Results and discussion, line 153- 154: The sentence that starts with 'Limited...' makes no sense. + +Results and discussion, line 161: 'It was proposed earlier...' Where was it proposed earlier? Is there a reference? + +<--- Page Split ---> + +Results and discussion, line 174: '...hydroxymethyl group of the sugar moiety in each complex.' + +Results and discussion, line 181- 182: 'These results suggested that the core site composed of N20/T23/E231 determines the sugar donor promiscuity of SenB.' I'm not sure that I understand the logic here. These residues interact with all gluco- and galacto- configured sugars similarly because the C2 and C6 hydroxyls of these sugars are all bound in structurally equivalent positions. They confer binding affinity to all four of the sugars at C2OH and C6OH. The 'promiscuity' comes from the fact that there is not a steric barrier or profound binding affinity difference for the gluco- versus galacto- epimers at C4, so UDP derivatives of Glc(±NAC) and Gal(±NAC) are all 'allowed'. I am not sure that I agree that "N20/T23/E231 determines the sugar donor promiscuity of SenB". + +Results and discussion, line 209- 210: "...GT- B type GTs, a highly conserved catalytic dyad His- Asp mainly accounts for acceptor deprotonation18,36- 38" This is a considerable overstatement. The His- Asp dyad is only conserved for a minor subset of GT- B enzymes (mostly plant natural product UDP- glycosyltransferases). + +Results and discussion, line 216- 217: "catalytic dyad His- Asp is almost identical, both being closely sandwiched by the UDP- sugar and acceptor18,36- 38" Based on Fig. 5a, the His- Asp is not sandwiched by the UDP- sugar and acceptor. Besides, in the SenB structure in Fig. 5a D86 is not even facing H58. + +Results and discussion, line 240- 243: "However, the near complete loss of catalytic activity of the K158A mutant was observed, suggesting that the hydrogen bond's influence on K158's proton abstraction may be minimal, and it underscores the significance of K158 for the enzymatic activity of SenB." I am not sure that I understand the logic here. If the role of K158 is to stabilize the forming negative charge on the beta phosphate during sugar transfer (with no role as catalytic base in cleavage of Se- PO4) then you would expect the K158A mutation to inactivate the enzyme. + +Results and discussion, line 275: '...K158 exhibits..." + +Results and discussion, line 302: '...(Fig. 6h)..." + +Results and discussion, line 307: ...structure and catalytic mechanism were completely unknown." + +Results and discussion, line 314- 315: "...and mutagenesis revealed the critical amino acids N20, T23, and E231 that control sugar donor promiscuity of SenB." I still don't agree that they 'control' promiscuity. + +Overall, the manuscript is improved in some areas, but the writing and interpretation of some of the data is still problematic. Please consider revisions to the above sections. + +Reviewer #2 (Remarks to the Author): + +Huang and co- workers reported the cocrystal structures of SenB, a Se- glycosyltransferase and investigated the enzyme's recognition and catalytic mechanism. By performing biochemical studies using different sugars, the authors characterized SenB's substrate promiscuity toward these ligands. Through follow- up structural modeling, they identified the key residues for substrate binding and catalysis, and corroborated the results by enzymatic activity assays. The combined structural and biochemical studies provided insights into the reaction mechanism of SenB and contributed to our understanding on the selenium transfer mechanism as well. Overall, the authors did a good job on the biochemical and structural studies, and they carefully proposed a tentative mechanism for SenB catalysis. While the results of the manuscript and the high- quality structural work are interesting, the authors need to clarify several following issues before the manuscript is accepted. + +1. While proposing the mechanism (line 248 on page 10), the authors say "SenB involves the amino + +<--- Page Split ---> + +side chain of K158 capturing a proton from a water molecule, becoming a negatively charged nucleophile that attacks the positively charged phosphorus atom in the Se- P bond...". There are problems with this sentence and the related figure (Fig. 5f). First, it was the water molecule that becomes negatively charged, not SenB; second, the phosphorus atom here is only "partially positively charged" due to the unequal polarities between P and Se; third, there are several problems with in the "C- Se bond formation" and "Se- P cleavage" steps of the Fig. 5f cartoon, where the arrows were pointing to the wrong atoms or positions; 2. Site- Directed Mutagenesis in the Methods section: the quikchange method should be clearly stated; 3. The manuscript could've used some language editing; typos or grammatical errors are seen. For instance, a. line 222 on page 9 "...deploy different strategy": missing "a" b. line 379 on page 15 "...Tri- HCl"? c. line 381 on page 15 "...a 6 h incubation period": missing a hyphen; + +Reviewer #3 (Remarks to the Author): + +I already wrote in my previous review of this paper about the relevance and value of this work; I stand by it: it's a valuable addition for selenium research. Regarding the revision: + +The minor issues I raised were addressed. I still recommend improvements in English language throughout the whole document; perhaps authors can use a professional service? Or the journal can step in to help? + +<--- Page Split ---> + +## Point-by-point response + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +This is a revised submission of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in a three gene cluster that catalyzes the synthesis of a Se- containing metabolite in a broad collection of bacteria. The initial submission had numerous concerns regarding the writing, summary of prior work on selenium metabolism, and interpretation of the experimental data. The revised submission addressed some of these concerns, but numerous problems in the writing in the revision result in continuing overall problems with the manuscript. These major and minor concerns include numerous problems with English usage and interpretation of data. + +## Response: + +We greatly appreciate the reviewer for valuable comments and corrections. We have corrected the English usage and adjusted the interpretation of our data according to the comments. The language has been further improved from the Nature Research Editing Service. + +The editing and data interpretation concerns include: + +Abstract, line 20: 'tested' not 'testified' + +## Response: + +The "testified" has been corrected to "tested". + +Abstract, lines 21- 22: "...structure- guided mutagenesis indicating that SenB forms C- Se glycosidic bonds via spontaneous deprotonation and nucleophilic attack with the critical residue K158 assisting in Se- P bond cleavage..." + +## Response: + +We have made the corresponding revision. "A proposed catalytic mechanism was tested by structure- guided mutagenesis, revealing that SenB yields selenosugars by forming C- Se glycosidic bonds via spontaneous deprotonation and disrupting Se- P bonds by nucleophilic water attack, which is initiated by the critical residue K158." + +Abstract, line 23: "Furthermore, we functionally and structurally..." + +## Response: + +We have made the corresponding revision. "Furthermore, we functionally and structurally characterized two other Se- glycosyltransferases," + +Introduction, line 34: 'majorly' is not appropriate word usage here. + +## Response: + +We have made the corresponding revision. "In nature, Se can perform biological roles in inorganic forms, such as sodium selenite, or in organic forms, such as + +<--- Page Split ---> + +selenocysteine (Sec), which can be incorporated into physiologically active selenoproteins." + +Introduction, line 38: I am not sure that 'catalyzation' is a word. + +## Response: + +The "catalyzation" has been corrected to "catalysis". + +Introduction, line 44: 'With the exception that SEN could protect against...' + +## Response: + +We have made the corresponding revision. "With the exception that SEN could protect against mercury toxicity and act as an effective antioxidant," + +Introduction, lines 47- 49: The sentence starting with 'Recently...' is very awkwardly worded. Please revise. + +## Response: + +We have made the corresponding revision. "A specific SEN biosynthetic pathway was identified in Variovorax paradoxus DSM 30034, which is recognized as a novel way to incorporate Se into organic matter in bacteria \(^{15}\) ." + +Introduction, line 59: '...glycosyltransferases (GTs), suggesting that SenB could also be considered as a Se-glycosyltransferase...' + +## Response: + +We have made the corresponding correction. "...glycosyltransferases (GTs), suggesting that SenB could also be considered as a Se-glycosyltransferase (SeGT)." + +Results and discussion, line 81: 'Previous studies showed that SenB can utilize UDP- GlcNAc, UDP- GalNAc, and UDP- Glc as sugar donors...' + +## Response: + +We have made the corresponding correction. "Previous studies have shown that SenB can utilize UDP- GlcNAc, UDP- GalNAc, and UDP- Glc as sugar donors to generate corresponding selenosugars \(^{15}\) ." + +Results and discussion, line 102: 'This result is consistent with...' + +## Response: + +We have made the corresponding correction. "This finding is consistent with the results of previous substrate competition studies (UDP- GlcNAc > UDP- GalNAc > UDP- Glc) \(^{15}\) ." + +Results and discussion, line 105: '...on the sugar contribute to the catalytic efficiency...' + +## Response: + +We have made the corresponding revision. "...on the sugar contribute to the catalytic efficiency of SenB." + +Results and discussion, line 150: This paragraph describes the structural basis for the + +<--- Page Split ---> + +specificity toward uridine versus adenine/guanine bases for the sugar nucleotide donor, but then attempts to use the K158A and E239A mutations as justification. K158 interacts with the beta phosphate and E239 interacts with the ribose. Neither interact with the nucleotide base to provide an explanation for base specificity. + +# Response: + +We are sorry for our misleading interpretation. The catalytic activity assay for the representative mutants K158A, E239A, L209A, and T214 was designed to investigate the potential impact of the residues interacting with different parts of UDP on the catalytic activity of SenB. The above listed four residues interact with ribose, phosphate or uracil moieties of UDP. The corresponding mutants showed differently influenced catalytic activity. In our study, the uracil base preference was found mainly associated with the space limitation of the UDP binding pocket. To clarify our results and avoid potential confusion for the readers, we have reorganized the Supplementary Table 2 and rephrased the text on page 6-7, line 143-156. + +Supplementary Table 2. Detailed interactions between SenB and UDP. + +
ResidueResidue atomLigand moietyLigand atomDistance (Å)
Hydrogen bond
R155NH2\(\beta \)-phosphateO2B2.7
K158NZO2B3.2
G19NO1B3.2
H235ND1/N\(\alpha \)-phosphateO1A2.8/2.8
V236NO2A3.3
R22NH1/NERibose ringO3C3.0/4.0
V236OE2O3C2.6
E239OE1O2C2.9
N17ND2Uracil ringO22.8
L209O/NN3/O43.2/3.5
T214OG1N33.3
hydrophobic interaction
V151CG1Uracil ringC53.7
+ +Results and discussion, line 153-154: The sentence that starts with ‘Limited...’ makes no sense. + +# Response: + +The referred sentence has been deleted in the revised manuscript. + +Results and discussion, line 161: ‘It was proposed earlier...’ Where was it proposed earlier? Is there a reference? + +# Response: + +We are sorry for our misleading interpretation. We were meant to refer to our finding described on page 5, line 106-108, “the N-acetyl group of C-2' and the hydroxymethyl group of C-5' on the sugar moiety contribute to the catalytic efficiency of SenB.”. To improve the interpretation, the corresponding sentence has been rephrased as, “Since the chemical groups at the C-2' and C-5' positions of the sugar + +<--- Page Split ---> + +moiety are correlated with the catalytic efficiency of SenB, the residues that interact with these chemical groups likely influence the catalytic activity of SenB." + +Results and discussion, line 174: '...hydroxymethyl group of the sugar moiety in each complex.' + +## Response: + +We have made the corresponding revision. "Comparative analysis revealed that N20 and T23 were essential for stabilizing the C- 5' hydroxymethyl group of the sugar moiety in each complex." + +Results and discussion, line 181- 182: 'These results suggested that the core site composed of N20/T23/E231 determines the sugar donor promiscuity of SenB.' I'm not sure that I understand the logic here. These residues interact with all gluco- and galactoconfigured sugars similarly because the C2 and C6 hydroxyls of these sugars are all bound in structurally equivalent positions. They confer binding affinity to all four of the sugars at C2OH and C6OH. The 'promiscuity' comes from the fact that there is not a steric barrier or profound binding affinity difference for the gluco- versus galacto- epimers at C4, so UDP derivatives of Glc(±NAc) and Gal(±NAc) are all 'allowed'. I am not sure that I agree that "N20/T23/E231 determines the sugar donor promiscuity of SenB". + +## Response: + +Thank you for your valuable comments. We have carefully considered your concerns regarding the role of residues N20/T23/E231 in determining the sugar donor promiscuity of SenB, and reanalyzed our data accordingly. We agree that our previous statement that the core site composed of N20/T23/E231 determines the sugar donor promiscuity of SenB, was inaccurate. We apologize for this overstatement. However, we still believe that the N20/T23/E231 residues are crucial for both the sugar donor preference and catalytic activity of SenB. As you have pointed out there is no steric hindrance or profound binding environment around the C- 4 position, it might allow various sugars. In fact, our results showed the similar C- 4 hydroxyl configurations (such as UDP- GlcA and UDP- GalA, with variations at the C- 6 positions) could not assure acceptance by SenB as the sugar donor. Preference of sugar donors greatly depends on the interaction strength between UDP- sugar and SenB, which is determined by the interactive residues. Our amended mutation assays also confirmed the impact of N20/T23/E231 on the sugar donor preference of the homologs CbSenB and RsSenB. Therefore, the N20/T23/E231 residues are essentially involved in the sugar donor preference of SenB. The corrected description and new data (Figure S14) have been added in the revised manuscript on page 8. line 185- 186 and page 12, line 298- 300. + +<--- Page Split ---> +![PLACEHOLDER_8_0] + + +Supplementary Figure 14. HPLC- UV/DAD analysis of the mBBr derivatives of the reaction products catalyzed by CbSenB, RsSenB and their mutants using different sugar donors. a- d, Product detection of CbSenB and its triple mutant N21A/T24A/E233A using UDP- Glc (a), UDP- Gal (b), UDP- GlcNAc (c), or UDP- GalNAc (d) as the sugar donor. e- f, Product detection of RsSenB and its triple mutant N20A/T23A/E231A using UDP- Glc (e), UDP- Gal (f), UDP- GlcNAc (g), or UDP- GalNAc (h) as the sugar donor. + +Results and discussion, line 209- 210: "...GT- B type GTs, a highly conserved catalytic dyad His- Asp mainly accounts for acceptor deprotonation18,36- 38" This is a + +<--- Page Split ---> + +considerable overstatement. The His- Asp dyad is only conserved for a minor subset of GT- B enzymes (mostly plant natural product UDP- glycosyltransferases). + +## Response: + +Thank you for your valuable comments. We have corrected the sentence to "In GT- B- type GTs, many plant natural product UGTs, as well as a few microbial UGTs, contain a conserved catalytic dyad His- Asp that accounts for acceptor deprotonation18,33- 36." + +Results and discussion, line 216- 217: "catalytic dyad His- Asp is almost identical, both being closely sandwiched by the UDP- sugar and acceptor18,36- 38" Based on Fig. 5a, the His- Asp is not sandwiched by the UDP- sugar and acceptor. Besides, in the SenB structure in Fig. 5a D86 is not even facing H58. + +## Response: + +We are sorry for our misleading interpretation. Thank you for your valuable comments. For better metaphorical illustration, we changed "sandwiched" to "clamped". Indeed, the His- Asp in SenB is not clamped between UDP- sugars and the receptor. As mentioned in your comment, D86 is not facing H58. This structural feature actually distinguishes SenB from the other GT- B type glycosyltransferases that depend on a His- Asp catalytic dyad for catalytic function. As shown in Fig.S9, the His- Asp dyad is clamped between the sugar donor and acceptor in many GT- B GTs except SenB. Therefore, the catalytic mechanism of SenB might be unique. Our mutagenesis study indicates that the H58A mutation does not lead to complete inactivation of SenB, implying that SeP's deprotonation does not rely on H58. It could be deduced that the His58- Asp86 in SenB may not function as a catalytic dyad. We apologize for the confusion and have carefully revised the interpretation of our results to enhance the readability. The corresponding changes are shown in the revised manuscript on page 9, line 211- 228. + +"In GT- B- type GTs, many plant natural product UGTs, as well as a few microbial UGTs, contain a conserved catalytic dyad His- Asp that accounts for acceptor deprotonation18,33- 36 (Fig. S8). In the His- Asp- dependent GT- B- type GT structures, the spatial localization of the His- Asp catalytic dyad was almost identical, as both were closely clamped by the UDP- sugar and acceptor18,33- 36 (Fig. S9). Although the corresponding catalytic dyad (His58- Asp86) of SenB was found in the neighbourhood of the SeP- binding site (Fig. 5a), structural localization revealed that this pair of residues in SenB is located at the outer edge of the SeP acceptor and away from the UDP- sugar, which has not been observed in other structures of GT- B- type GTs. Moreover, our mutagenesis results showed only a reduction but not complete loss of enzymatic activity in the H58A, H58Q, and H58D mutants (Fig. 5c). The protein folding of these three purified mutants was demonstrated to be identical to that of the wild type by size- exclusion chromatography analysis, excluding the possibility that the reduced catalytic activity was caused by structural misfolding of SenB (Fig. S10). These results suggest that the deprotonation of SeP is not dependent on His58- Asp86, implying that the His- Asp in SenB is not a catalytic dyad and that SenB may utilize a different strategy to deprotonate the acceptor." + +<--- Page Split ---> +![PLACEHOLDER_10_0] + +
Supplementary Figure 9. The spatial localization of the His-Asp in the structures of SenB and other GT-B type GTs.
+ +Results and discussion, line 240- 243: "However, the near complete loss of catalytic activity of the K158A mutant was observed, suggesting that the hydrogen bond's influence on K158's proton abstraction may be minimal, and it underscores the significance of K158 for the enzymatic activity of SenB." I am not sure that I understand the logic here. If the role of K158 is to stabilize the forming negative charge on the beta phosphate during sugar transfer (with no role as catalytic base in cleavage of Se- PO4) then you would expect the K158A mutation to inactivate the enzyme. + +## Response: + +Thank you for your valuable suggestions. We have changed "minimal" to "subtle" on page 10, line 248. Structural analysis revealed that, in addition to K158 (3.2 Å), residues R155 (2.7 Å) and G19 (3.2 Å) also interact with the \(\beta\) - phosphate of UDP- Sugar in SenB. During glycosyl transfer, all these three residues could stabilize the negative charge on the \(\beta\) - phosphate. To this extent, R155A and K158A might have similar influence on the catalytic activity. However, compared to R155A ( \(\sim 60\%\) relative catalytic activity), the near- complete loss of catalytic activity was observed in the K158A mutant, suggesting that K158 might be involved in other important catalytic process beyond merely stabilizing the negative charge on the \(\beta\) - phosphate. In fact, we found out that K158 is very critical for the Se- P bond cleavage. The amino side chain of K158 captures a proton from a water molecule. The resulted negatively charged water molecule attacks the partially positively charged phosphorus atom in the Se- P bond, and leads to bond disruption and the formation of a selenosugar product. Accordingly, we have amended our interpretation on the SenB catalytic mechanism on page 10, line 249- 253. + +<--- Page Split ---> + +Results and discussion, line 275: ‘...K158 exhibits...’ + +## Response: + +We have made the corresponding correction. + +Results and discussion, line 302: ‘...(Fig. 6h)...’ + +## Response: + +We have made the corresponding correction. + +Results and discussion, line 307: ...structure and catalytic mechanism were completely unknown.” + +## Response: + +We have made the corresponding correction. “In conclusion, SenB is the only functionally identified SeGT in nature, but its structure and catalytic mechanism were unknown.” + +Results and discussion, line 314- 315: ‘...and mutagenesis revealed the critical amino acids N20, T23, and E231 that control sugar donor promiscuity of SenB.” I still don’t agree that they ‘control’ promiscuity. + +## Response: + +Thank you for your valuable comments and suggestions. We have changed “control sugar donor promiscuity” to “modulate sugar donor preference” in hopes of more accurately describing the functional impact of these amino acids of SenB. + +Overall, the manuscript is improved in some areas, but the writing and interpretation of some of the data is still problematic. Please consider revisions to the above sections. + +<--- Page Split ---> + +Huang and co- workers reported the cocrystal structures of SenB, a Se- glycosyltransferase and investigated the enzyme's recognition and catalytic mechanism. By performing biochemical studies using different sugars, the authors characterized SenB's substrate promiscuity toward these ligands. Through follow- up structural modeling, they identified the key residues for substrate binding and catalysis, and corroborated the results by enzymatic activity assays. The combined structural and biochemical studies provided insights into the reaction mechanism of SenB and contributed to our understanding on the selenium transfer mechanism as well. Overall, the authors did a good job on the biochemical and structural studies, and they carefully proposed a tentative mechanism for SenB catalysis. While the results of the manuscript and the high- quality structural work are interesting, the authors need to clarify several following issues before the manuscript is accepted. + +## Response: + +Thank you for your valuable comments and suggestions. + +1. While proposing the mechanism (line 248 on page 10), the authors say "SenB involves the amino side chain of K158 capturing a proton from a water molecule, becoming a negatively charged nucleophile that attacks the positively charged phosphorus atom in the Se-P bond...". There are problems with this sentence and the related figure (Fig. 5f). First, it was the water molecule that becomes negatively charged, not SenB; second, the phosphorus atom here is only "partially positively charged" due to the unequal polarities between P and Se; third, there are several problems with in the "C-Se bond formation" and "Se-P cleavage" steps of the Fig. 5f cartoon, where the arrows were pointing to the wrong atoms or positions; + +## Response: + +Thank you for your valuable comments. We have corrected the sentence to "Thus, the Se-P bond cleavage mediated by K158 in SenB may begin with the amino side chain of K158, which captures a proton from a water molecule. The resulting negatively charged water molecules attack the partially positively charged phosphorus atom in the Se-P bond, leading to bond disruption and the formation of a selenosugar product." In addition, the Fig. 5f has been corrected in the revised manuscript. + +![PLACEHOLDER_12_0] + + +2. Site-Directed Mutagenesis in the Methods section: the quickchange method should be clearly stated; + +Response: + +<--- Page Split ---> + +Thank you for your valuable comments. Description of the Site- Directed Mutagenesis method has been added in the revised manuscript on page 14 line 351- 363. + +3. The manuscript could've used some language editing; typos or grammatical errors are seen. For instance, + +a. line 222 on page 9 "...deploy different strategy": missing "a" + +b. line 379 on page 15 "...Tri-HCI"? + +c. line 381 on page 15 "...a 6 h incubation period": missing a hyphen; + +## Response: + +Thank you for your valuable comments. "...deploy different strategy" has been corrected to "...deploy a different strategy"; "...Tri- HCI" has been corrected to "...Tri- HCI"; "...a 6 h incubation period" has been corrected to "...a 6- h incubation period". We have corrected the English usage of the whole document through the Nature Research Editing Service. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +I already wrote in my previous review of this paper about the relevance and value of this work; I stand by it: it's a valuable addition for selenium research. Regarding the revision: + +## Response: + +Thank you for your valuable comments. + +The minor issues I raised were addressed. + +I still recommend improvements in English language throughout the whole document; perhaps authors can use a professional service? Or the journal can step in to help? + +## Response: + +We have corrected the English usage of the whole document through the Nature Research Editing Service. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +This is the second revision of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in the synthesis of a Se- containing metabolite in a broad collection of bacteria. The initial and revised submissions had numerous concerns regarding the writing and interpretation of the experimental data. This revised submission addressed all of these prior concerns and is exceptionally improved. It is presently acceptable for publication and will be a wonderful addition to the seleno- chemistry literature. + +One exceptionally minor point that the authors should consider is a revision to Fig. 3b. The linear diagram at the top of Fig. 3b shows the N- terminal domain in blue and C- term domain in green box format but the highlighting boxes in the bottom of the same panel have coloring that is the opposite. Revision of this figure to match the coloring between the top and bottom of the panel would eliminate potential confusion for the reader. + +Reviewer #2 (Remarks to the Author): + +The authors have succesfully addressed all the concerns from this reviewer. + +<--- Page Split ---> + +## Point-by-point response + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +This is the second revision of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in the synthesis of a Se- containing metabolite in a broad collection of bacteria. The initial and revised submissions had numerous concerns regarding the writing and interpretation of the experimental data. This revised submission addressed all of these prior concerns and is exceptionally improved. It is presently acceptable for publication and will be a wonderful addition to the seleno- chemistry literature. + +## Response: + +Thank you for your valuable comments. + +One exceptionally minor point that the authors should consider is a revision to Fig. 3b. The linear diagram at the top of Fig. 3b shows the N- terminal domain in blue and C- term domain in green box format but the highlighting boxes in the bottom of the same panel have coloring that is the opposite. Revision of this figure to match the coloring between the top and bottom of the panel would eliminate potential confusion for the reader. + +## Response: + +We greatly appreciate the reviewer for valuable comments and corrections. We have corrected the Fig. 3b in the revised manuscript. + +![PLACEHOLDER_16_0] + + +Reviewer #2 (Remarks to the Author): + +The authors have succesfully addressed all the concerns from this reviewer. + +## Response: + +Thank you for your valuable comments. + +<--- Page Split ---> diff --git a/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..edf5043c302332539fd3b869e87502a544bb6542 --- /dev/null +++ b/peer_reviews/781fbf2f2b23644ffbbeb3da89ddb31ed6a558e34d2d571aaa27a436ea5304af/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,525 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[106, 161, 890, 220]]<|/det|> +Substrate binding and catalytic mechanism of the Se- glycosyltransferase SenB in the biosynthesis of selenoneine + +<|ref|>image<|/ref|><|det|>[[95, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 844, 140]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[116, 151, 402, 167]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 181, 881, 286]]<|/det|> +This is a revised submission of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in a three gene cluster that catalyzes the synthesis of a Scontaining metabolite in a broad collection of bacteria. The initial submission had numerous concerns regarding the writing, summary of prior work on selenium metabolism, and interpretation of the experimental data. The revised submission addressed some of these concerns, but numerous problems in the writing in the revision result in continuing overall problems with the manuscript. These major and minor concerns include numerous problems with English usage and interpretation of data. + +<|ref|>text<|/ref|><|det|>[[115, 300, 510, 315]]<|/det|> +The editing and data interpretation concerns include: + +<|ref|>text<|/ref|><|det|>[[115, 330, 407, 345]]<|/det|> +Abstract, line 20: 'tested' not 'testified' + +<|ref|>text<|/ref|><|det|>[[115, 359, 880, 405]]<|/det|> +Abstract, lines 21- 22: "...structure- guided mutagenesis indicating that SenB forms C- Se glycosidic bonds via spontaneous deprotonation and nucleophilic attack with the critical residue K158 assisting in Se- P bond cleavage..." + +<|ref|>text<|/ref|><|det|>[[115, 419, 610, 435]]<|/det|> +Abstract, line 23: "Furthermore, we functionally and structurally..." + +<|ref|>text<|/ref|><|det|>[[115, 449, 614, 465]]<|/det|> +Introduction, line 34: 'majorly' is not appropriate word usage here. + +<|ref|>text<|/ref|><|det|>[[115, 479, 595, 494]]<|/det|> +Introduction, line 38: I am not sure that 'catalyzation' is a word. + +<|ref|>text<|/ref|><|det|>[[115, 508, 670, 524]]<|/det|> +Introduction, line 44: 'With the exception that SEN could protect against...' + +<|ref|>text<|/ref|><|det|>[[115, 539, 852, 569]]<|/det|> +Introduction, lines 47- 49: The sentence starting with 'Recently...' is very awkwardly worded. Please revise. + +<|ref|>text<|/ref|><|det|>[[115, 583, 869, 614]]<|/det|> +Introduction, line 59: '...glycosyltransferases (GTs), suggesting that SenB could also be considered as a Se- glycosyltransferase...' + +<|ref|>text<|/ref|><|det|>[[115, 628, 841, 659]]<|/det|> +Results and discussion, line 81: 'Previous studies showed that SenB can utilize UDP- GlcNAc, UDP- GalNAc, and UDP- Glc as sugar donors...' + +<|ref|>text<|/ref|><|det|>[[115, 672, 595, 688]]<|/det|> +Results and discussion, line 102: 'This result is consistent with...' + +<|ref|>text<|/ref|><|det|>[[115, 702, 758, 718]]<|/det|> +Results and discussion, line 105: '...on the sugar contribute to the catalytic efficiency...' + +<|ref|>text<|/ref|><|det|>[[115, 732, 877, 808]]<|/det|> +Results and discussion, line 150: This paragraph describes the structural basis for the specificity toward uridine versus adenine/guanine bases for the sugar nucleotide donor, but then attempts to use the K158A and E239A mutations as justification. K158 interacts with the beta phosphate and E239 interacts with the ribose. Neither interact with the nucleotide base to provide an explanation for base specificity. + +<|ref|>text<|/ref|><|det|>[[115, 821, 822, 837]]<|/det|> +Results and discussion, line 153- 154: The sentence that starts with 'Limited...' makes no sense. + +<|ref|>text<|/ref|><|det|>[[112, 851, 866, 881]]<|/det|> +Results and discussion, line 161: 'It was proposed earlier...' Where was it proposed earlier? Is there a reference? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 822, 105]]<|/det|> +Results and discussion, line 174: '...hydroxymethyl group of the sugar moiety in each complex.' + +<|ref|>text<|/ref|><|det|>[[115, 118, 880, 239]]<|/det|> +Results and discussion, line 181- 182: 'These results suggested that the core site composed of N20/T23/E231 determines the sugar donor promiscuity of SenB.' I'm not sure that I understand the logic here. These residues interact with all gluco- and galacto- configured sugars similarly because the C2 and C6 hydroxyls of these sugars are all bound in structurally equivalent positions. They confer binding affinity to all four of the sugars at C2OH and C6OH. The 'promiscuity' comes from the fact that there is not a steric barrier or profound binding affinity difference for the gluco- versus galacto- epimers at C4, so UDP derivatives of Glc(±NAC) and Gal(±NAC) are all 'allowed'. I am not sure that I agree that "N20/T23/E231 determines the sugar donor promiscuity of SenB". + +<|ref|>text<|/ref|><|det|>[[116, 252, 864, 313]]<|/det|> +Results and discussion, line 209- 210: "...GT- B type GTs, a highly conserved catalytic dyad His- Asp mainly accounts for acceptor deprotonation18,36- 38" This is a considerable overstatement. The His- Asp dyad is only conserved for a minor subset of GT- B enzymes (mostly plant natural product UDP- glycosyltransferases). + +<|ref|>text<|/ref|><|det|>[[116, 327, 875, 373]]<|/det|> +Results and discussion, line 216- 217: "catalytic dyad His- Asp is almost identical, both being closely sandwiched by the UDP- sugar and acceptor18,36- 38" Based on Fig. 5a, the His- Asp is not sandwiched by the UDP- sugar and acceptor. Besides, in the SenB structure in Fig. 5a D86 is not even facing H58. + +<|ref|>text<|/ref|><|det|>[[116, 386, 870, 476]]<|/det|> +Results and discussion, line 240- 243: "However, the near complete loss of catalytic activity of the K158A mutant was observed, suggesting that the hydrogen bond's influence on K158's proton abstraction may be minimal, and it underscores the significance of K158 for the enzymatic activity of SenB." I am not sure that I understand the logic here. If the role of K158 is to stabilize the forming negative charge on the beta phosphate during sugar transfer (with no role as catalytic base in cleavage of Se- PO4) then you would expect the K158A mutation to inactivate the enzyme. + +<|ref|>text<|/ref|><|det|>[[116, 490, 497, 505]]<|/det|> +Results and discussion, line 275: '...K158 exhibits..." + +<|ref|>text<|/ref|><|det|>[[116, 520, 463, 536]]<|/det|> +Results and discussion, line 302: '...(Fig. 6h)..." + +<|ref|>text<|/ref|><|det|>[[115, 550, 840, 566]]<|/det|> +Results and discussion, line 307: ...structure and catalytic mechanism were completely unknown." + +<|ref|>text<|/ref|><|det|>[[116, 580, 867, 626]]<|/det|> +Results and discussion, line 314- 315: "...and mutagenesis revealed the critical amino acids N20, T23, and E231 that control sugar donor promiscuity of SenB." I still don't agree that they 'control' promiscuity. + +<|ref|>text<|/ref|><|det|>[[115, 641, 863, 671]]<|/det|> +Overall, the manuscript is improved in some areas, but the writing and interpretation of some of the data is still problematic. Please consider revisions to the above sections. + +<|ref|>text<|/ref|><|det|>[[116, 700, 402, 715]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 729, 876, 880]]<|/det|> +Huang and co- workers reported the cocrystal structures of SenB, a Se- glycosyltransferase and investigated the enzyme's recognition and catalytic mechanism. By performing biochemical studies using different sugars, the authors characterized SenB's substrate promiscuity toward these ligands. Through follow- up structural modeling, they identified the key residues for substrate binding and catalysis, and corroborated the results by enzymatic activity assays. The combined structural and biochemical studies provided insights into the reaction mechanism of SenB and contributed to our understanding on the selenium transfer mechanism as well. Overall, the authors did a good job on the biochemical and structural studies, and they carefully proposed a tentative mechanism for SenB catalysis. While the results of the manuscript and the high- quality structural work are interesting, the authors need to clarify several following issues before the manuscript is accepted. + +<|ref|>text<|/ref|><|det|>[[115, 880, 861, 895]]<|/det|> +1. While proposing the mechanism (line 248 on page 10), the authors say "SenB involves the amino + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 881, 290]]<|/det|> +side chain of K158 capturing a proton from a water molecule, becoming a negatively charged nucleophile that attacks the positively charged phosphorus atom in the Se- P bond...". There are problems with this sentence and the related figure (Fig. 5f). First, it was the water molecule that becomes negatively charged, not SenB; second, the phosphorus atom here is only "partially positively charged" due to the unequal polarities between P and Se; third, there are several problems with in the "C- Se bond formation" and "Se- P cleavage" steps of the Fig. 5f cartoon, where the arrows were pointing to the wrong atoms or positions; 2. Site- Directed Mutagenesis in the Methods section: the quikchange method should be clearly stated; 3. The manuscript could've used some language editing; typos or grammatical errors are seen. For instance, a. line 222 on page 9 "...deploy different strategy": missing "a" b. line 379 on page 15 "...Tri- HCl"? c. line 381 on page 15 "...a 6 h incubation period": missing a hyphen; + +<|ref|>text<|/ref|><|det|>[[116, 314, 402, 329]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 343, 839, 374]]<|/det|> +I already wrote in my previous review of this paper about the relevance and value of this work; I stand by it: it's a valuable addition for selenium research. Regarding the revision: + +<|ref|>text<|/ref|><|det|>[[115, 387, 831, 432]]<|/det|> +The minor issues I raised were addressed. I still recommend improvements in English language throughout the whole document; perhaps authors can use a professional service? Or the journal can step in to help? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[396, 91, 602, 108]]<|/det|> +## Point-by-point response + +<|ref|>sub_title<|/ref|><|det|>[[149, 113, 390, 130]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 150, 460, 167]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 187, 851, 352]]<|/det|> +This is a revised submission of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in a three gene cluster that catalyzes the synthesis of a Se- containing metabolite in a broad collection of bacteria. The initial submission had numerous concerns regarding the writing, summary of prior work on selenium metabolism, and interpretation of the experimental data. The revised submission addressed some of these concerns, but numerous problems in the writing in the revision result in continuing overall problems with the manuscript. These major and minor concerns include numerous problems with English usage and interpretation of data. + +<|ref|>sub_title<|/ref|><|det|>[[149, 356, 238, 371]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 373, 850, 445]]<|/det|> +We greatly appreciate the reviewer for valuable comments and corrections. We have corrected the English usage and adjusted the interpretation of our data according to the comments. The language has been further improved from the Nature Research Editing Service. + +<|ref|>text<|/ref|><|det|>[[149, 466, 576, 483]]<|/det|> +The editing and data interpretation concerns include: + +<|ref|>text<|/ref|><|det|>[[149, 502, 467, 518]]<|/det|> +Abstract, line 20: 'tested' not 'testified' + +<|ref|>sub_title<|/ref|><|det|>[[149, 522, 238, 537]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[189, 539, 593, 556]]<|/det|> +The "testified" has been corrected to "tested". + +<|ref|>text<|/ref|><|det|>[[149, 575, 850, 630]]<|/det|> +Abstract, lines 21- 22: "...structure- guided mutagenesis indicating that SenB forms C- Se glycosidic bonds via spontaneous deprotonation and nucleophilic attack with the critical residue K158 assisting in Se- P bond cleavage..." + +<|ref|>sub_title<|/ref|><|det|>[[149, 633, 238, 648]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 651, 850, 723]]<|/det|> +We have made the corresponding revision. "A proposed catalytic mechanism was tested by structure- guided mutagenesis, revealing that SenB yields selenosugars by forming C- Se glycosidic bonds via spontaneous deprotonation and disrupting Se- P bonds by nucleophilic water attack, which is initiated by the critical residue K158." + +<|ref|>text<|/ref|><|det|>[[149, 743, 700, 760]]<|/det|> +Abstract, line 23: "Furthermore, we functionally and structurally..." + +<|ref|>sub_title<|/ref|><|det|>[[149, 763, 238, 778]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 780, 850, 815]]<|/det|> +We have made the corresponding revision. "Furthermore, we functionally and structurally characterized two other Se- glycosyltransferases," + +<|ref|>text<|/ref|><|det|>[[149, 836, 689, 853]]<|/det|> +Introduction, line 34: 'majorly' is not appropriate word usage here. + +<|ref|>sub_title<|/ref|><|det|>[[149, 856, 238, 870]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 873, 850, 907]]<|/det|> +We have made the corresponding revision. "In nature, Se can perform biological roles in inorganic forms, such as sodium selenite, or in organic forms, such as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 849, 120]]<|/det|> +selenocysteine (Sec), which can be incorporated into physiologically active selenoproteins." + +<|ref|>text<|/ref|><|det|>[[148, 140, 666, 158]]<|/det|> +Introduction, line 38: I am not sure that 'catalyzation' is a word. + +<|ref|>sub_title<|/ref|><|det|>[[148, 160, 238, 176]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 178, 616, 195]]<|/det|> +The "catalyzation" has been corrected to "catalysis". + +<|ref|>text<|/ref|><|det|>[[148, 214, 763, 232]]<|/det|> +Introduction, line 44: 'With the exception that SEN could protect against...' + +<|ref|>sub_title<|/ref|><|det|>[[148, 234, 238, 250]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 251, 849, 287]]<|/det|> +We have made the corresponding revision. "With the exception that SEN could protect against mercury toxicity and act as an effective antioxidant," + +<|ref|>text<|/ref|><|det|>[[148, 306, 849, 342]]<|/det|> +Introduction, lines 47- 49: The sentence starting with 'Recently...' is very awkwardly worded. Please revise. + +<|ref|>sub_title<|/ref|><|det|>[[148, 345, 238, 361]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 363, 849, 416]]<|/det|> +We have made the corresponding revision. "A specific SEN biosynthetic pathway was identified in Variovorax paradoxus DSM 30034, which is recognized as a novel way to incorporate Se into organic matter in bacteria \(^{15}\) ." + +<|ref|>text<|/ref|><|det|>[[148, 435, 849, 472]]<|/det|> +Introduction, line 59: '...glycosyltransferases (GTs), suggesting that SenB could also be considered as a Se-glycosyltransferase...' + +<|ref|>sub_title<|/ref|><|det|>[[148, 475, 238, 490]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 492, 849, 527]]<|/det|> +We have made the corresponding correction. "...glycosyltransferases (GTs), suggesting that SenB could also be considered as a Se-glycosyltransferase (SeGT)." + +<|ref|>text<|/ref|><|det|>[[148, 546, 849, 583]]<|/det|> +Results and discussion, line 81: 'Previous studies showed that SenB can utilize UDP- GlcNAc, UDP- GalNAc, and UDP- Glc as sugar donors...' + +<|ref|>sub_title<|/ref|><|det|>[[148, 586, 238, 602]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 603, 849, 657]]<|/det|> +We have made the corresponding correction. "Previous studies have shown that SenB can utilize UDP- GlcNAc, UDP- GalNAc, and UDP- Glc as sugar donors to generate corresponding selenosugars \(^{15}\) ." + +<|ref|>text<|/ref|><|det|>[[148, 676, 683, 695]]<|/det|> +Results and discussion, line 102: 'This result is consistent with...' + +<|ref|>sub_title<|/ref|><|det|>[[148, 697, 238, 712]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 714, 849, 767]]<|/det|> +We have made the corresponding correction. "This finding is consistent with the results of previous substrate competition studies (UDP- GlcNAc > UDP- GalNAc > UDP- Glc) \(^{15}\) ." + +<|ref|>text<|/ref|><|det|>[[148, 787, 853, 806]]<|/det|> +Results and discussion, line 105: '...on the sugar contribute to the catalytic efficiency...' + +<|ref|>sub_title<|/ref|><|det|>[[148, 808, 238, 823]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 825, 849, 860]]<|/det|> +We have made the corresponding revision. "...on the sugar contribute to the catalytic efficiency of SenB." + +<|ref|>text<|/ref|><|det|>[[147, 880, 849, 899]]<|/det|> +Results and discussion, line 150: This paragraph describes the structural basis for the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 159]]<|/det|> +specificity toward uridine versus adenine/guanine bases for the sugar nucleotide donor, but then attempts to use the K158A and E239A mutations as justification. K158 interacts with the beta phosphate and E239 interacts with the ribose. Neither interact with the nucleotide base to provide an explanation for base specificity. + +<|ref|>title<|/ref|><|det|>[[148, 163, 240, 175]]<|/det|> +# Response: + +<|ref|>text<|/ref|><|det|>[[148, 180, 850, 343]]<|/det|> +We are sorry for our misleading interpretation. The catalytic activity assay for the representative mutants K158A, E239A, L209A, and T214 was designed to investigate the potential impact of the residues interacting with different parts of UDP on the catalytic activity of SenB. The above listed four residues interact with ribose, phosphate or uracil moieties of UDP. The corresponding mutants showed differently influenced catalytic activity. In our study, the uracil base preference was found mainly associated with the space limitation of the UDP binding pocket. To clarify our results and avoid potential confusion for the readers, we have reorganized the Supplementary Table 2 and rephrased the text on page 6-7, line 143-156. + +<|ref|>table_caption<|/ref|><|det|>[[148, 347, 732, 362]]<|/det|> +Supplementary Table 2. Detailed interactions between SenB and UDP. + +<|ref|>table<|/ref|><|det|>[[150, 364, 848, 650]]<|/det|> + +
ResidueResidue atomLigand moietyLigand atomDistance (Å)
Hydrogen bond
R155NH2\(\beta \)-phosphateO2B2.7
K158NZO2B3.2
G19NO1B3.2
H235ND1/N\(\alpha \)-phosphateO1A2.8/2.8
V236NO2A3.3
R22NH1/NERibose ringO3C3.0/4.0
V236OE2O3C2.6
E239OE1O2C2.9
N17ND2Uracil ringO22.8
L209O/NN3/O43.2/3.5
T214OG1N33.3
hydrophobic interaction
V151CG1Uracil ringC53.7
+ +<|ref|>text<|/ref|><|det|>[[148, 670, 850, 702]]<|/det|> +Results and discussion, line 153-154: The sentence that starts with ‘Limited...’ makes no sense. + +<|ref|>title<|/ref|><|det|>[[148, 708, 240, 720]]<|/det|> +# Response: + +<|ref|>text<|/ref|><|det|>[[190, 725, 717, 738]]<|/det|> +The referred sentence has been deleted in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 761, 850, 794]]<|/det|> +Results and discussion, line 161: ‘It was proposed earlier...’ Where was it proposed earlier? Is there a reference? + +<|ref|>title<|/ref|><|det|>[[148, 800, 240, 812]]<|/det|> +# Response: + +<|ref|>text<|/ref|><|det|>[[148, 818, 850, 906]]<|/det|> +We are sorry for our misleading interpretation. We were meant to refer to our finding described on page 5, line 106-108, “the N-acetyl group of C-2' and the hydroxymethyl group of C-5' on the sugar moiety contribute to the catalytic efficiency of SenB.”. To improve the interpretation, the corresponding sentence has been rephrased as, “Since the chemical groups at the C-2' and C-5' positions of the sugar + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 849, 120]]<|/det|> +moiety are correlated with the catalytic efficiency of SenB, the residues that interact with these chemical groups likely influence the catalytic activity of SenB." + +<|ref|>text<|/ref|><|det|>[[149, 141, 849, 176]]<|/det|> +Results and discussion, line 174: '...hydroxymethyl group of the sugar moiety in each complex.' + +<|ref|>sub_title<|/ref|><|det|>[[149, 180, 238, 195]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 197, 850, 250]]<|/det|> +We have made the corresponding revision. "Comparative analysis revealed that N20 and T23 were essential for stabilizing the C- 5' hydroxymethyl group of the sugar moiety in each complex." + +<|ref|>text<|/ref|><|det|>[[148, 270, 851, 455]]<|/det|> +Results and discussion, line 181- 182: 'These results suggested that the core site composed of N20/T23/E231 determines the sugar donor promiscuity of SenB.' I'm not sure that I understand the logic here. These residues interact with all gluco- and galactoconfigured sugars similarly because the C2 and C6 hydroxyls of these sugars are all bound in structurally equivalent positions. They confer binding affinity to all four of the sugars at C2OH and C6OH. The 'promiscuity' comes from the fact that there is not a steric barrier or profound binding affinity difference for the gluco- versus galacto- epimers at C4, so UDP derivatives of Glc(±NAc) and Gal(±NAc) are all 'allowed'. I am not sure that I agree that "N20/T23/E231 determines the sugar donor promiscuity of SenB". + +<|ref|>sub_title<|/ref|><|det|>[[149, 459, 238, 474]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 476, 851, 789]]<|/det|> +Thank you for your valuable comments. We have carefully considered your concerns regarding the role of residues N20/T23/E231 in determining the sugar donor promiscuity of SenB, and reanalyzed our data accordingly. We agree that our previous statement that the core site composed of N20/T23/E231 determines the sugar donor promiscuity of SenB, was inaccurate. We apologize for this overstatement. However, we still believe that the N20/T23/E231 residues are crucial for both the sugar donor preference and catalytic activity of SenB. As you have pointed out there is no steric hindrance or profound binding environment around the C- 4 position, it might allow various sugars. In fact, our results showed the similar C- 4 hydroxyl configurations (such as UDP- GlcA and UDP- GalA, with variations at the C- 6 positions) could not assure acceptance by SenB as the sugar donor. Preference of sugar donors greatly depends on the interaction strength between UDP- sugar and SenB, which is determined by the interactive residues. Our amended mutation assays also confirmed the impact of N20/T23/E231 on the sugar donor preference of the homologs CbSenB and RsSenB. Therefore, the N20/T23/E231 residues are essentially involved in the sugar donor preference of SenB. The corrected description and new data (Figure S14) have been added in the revised manuscript on page 8. line 185- 186 and page 12, line 298- 300. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[170, 90, 825, 710]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 714, 850, 844]]<|/det|> +Supplementary Figure 14. HPLC- UV/DAD analysis of the mBBr derivatives of the reaction products catalyzed by CbSenB, RsSenB and their mutants using different sugar donors. a- d, Product detection of CbSenB and its triple mutant N21A/T24A/E233A using UDP- Glc (a), UDP- Gal (b), UDP- GlcNAc (c), or UDP- GalNAc (d) as the sugar donor. e- f, Product detection of RsSenB and its triple mutant N20A/T23A/E231A using UDP- Glc (e), UDP- Gal (f), UDP- GlcNAc (g), or UDP- GalNAc (h) as the sugar donor. + +<|ref|>text<|/ref|><|det|>[[148, 862, 850, 900]]<|/det|> +Results and discussion, line 209- 210: "...GT- B type GTs, a highly conserved catalytic dyad His- Asp mainly accounts for acceptor deprotonation18,36- 38" This is a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 121]]<|/det|> +considerable overstatement. The His- Asp dyad is only conserved for a minor subset of GT- B enzymes (mostly plant natural product UDP- glycosyltransferases). + +<|ref|>sub_title<|/ref|><|det|>[[149, 124, 238, 140]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 142, 850, 213]]<|/det|> +Thank you for your valuable comments. We have corrected the sentence to "In GT- B- type GTs, many plant natural product UGTs, as well as a few microbial UGTs, contain a conserved catalytic dyad His- Asp that accounts for acceptor deprotonation18,33- 36." + +<|ref|>text<|/ref|><|det|>[[149, 233, 850, 306]]<|/det|> +Results and discussion, line 216- 217: "catalytic dyad His- Asp is almost identical, both being closely sandwiched by the UDP- sugar and acceptor18,36- 38" Based on Fig. 5a, the His- Asp is not sandwiched by the UDP- sugar and acceptor. Besides, in the SenB structure in Fig. 5a D86 is not even facing H58. + +<|ref|>sub_title<|/ref|><|det|>[[149, 309, 238, 324]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 327, 850, 583]]<|/det|> +We are sorry for our misleading interpretation. Thank you for your valuable comments. For better metaphorical illustration, we changed "sandwiched" to "clamped". Indeed, the His- Asp in SenB is not clamped between UDP- sugars and the receptor. As mentioned in your comment, D86 is not facing H58. This structural feature actually distinguishes SenB from the other GT- B type glycosyltransferases that depend on a His- Asp catalytic dyad for catalytic function. As shown in Fig.S9, the His- Asp dyad is clamped between the sugar donor and acceptor in many GT- B GTs except SenB. Therefore, the catalytic mechanism of SenB might be unique. Our mutagenesis study indicates that the H58A mutation does not lead to complete inactivation of SenB, implying that SeP's deprotonation does not rely on H58. It could be deduced that the His58- Asp86 in SenB may not function as a catalytic dyad. We apologize for the confusion and have carefully revised the interpretation of our results to enhance the readability. The corresponding changes are shown in the revised manuscript on page 9, line 211- 228. + +<|ref|>text<|/ref|><|det|>[[148, 585, 850, 899]]<|/det|> +"In GT- B- type GTs, many plant natural product UGTs, as well as a few microbial UGTs, contain a conserved catalytic dyad His- Asp that accounts for acceptor deprotonation18,33- 36 (Fig. S8). In the His- Asp- dependent GT- B- type GT structures, the spatial localization of the His- Asp catalytic dyad was almost identical, as both were closely clamped by the UDP- sugar and acceptor18,33- 36 (Fig. S9). Although the corresponding catalytic dyad (His58- Asp86) of SenB was found in the neighbourhood of the SeP- binding site (Fig. 5a), structural localization revealed that this pair of residues in SenB is located at the outer edge of the SeP acceptor and away from the UDP- sugar, which has not been observed in other structures of GT- B- type GTs. Moreover, our mutagenesis results showed only a reduction but not complete loss of enzymatic activity in the H58A, H58Q, and H58D mutants (Fig. 5c). The protein folding of these three purified mutants was demonstrated to be identical to that of the wild type by size- exclusion chromatography analysis, excluding the possibility that the reduced catalytic activity was caused by structural misfolding of SenB (Fig. S10). These results suggest that the deprotonation of SeP is not dependent on His58- Asp86, implying that the His- Asp in SenB is not a catalytic dyad and that SenB may utilize a different strategy to deprotonate the acceptor." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 83, 849, 396]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 400, 850, 437]]<|/det|> +
Supplementary Figure 9. The spatial localization of the His-Asp in the structures of SenB and other GT-B type GTs.
+ +<|ref|>text<|/ref|><|det|>[[149, 454, 850, 584]]<|/det|> +Results and discussion, line 240- 243: "However, the near complete loss of catalytic activity of the K158A mutant was observed, suggesting that the hydrogen bond's influence on K158's proton abstraction may be minimal, and it underscores the significance of K158 for the enzymatic activity of SenB." I am not sure that I understand the logic here. If the role of K158 is to stabilize the forming negative charge on the beta phosphate during sugar transfer (with no role as catalytic base in cleavage of Se- PO4) then you would expect the K158A mutation to inactivate the enzyme. + +<|ref|>sub_title<|/ref|><|det|>[[149, 587, 238, 602]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 604, 850, 881]]<|/det|> +Thank you for your valuable suggestions. We have changed "minimal" to "subtle" on page 10, line 248. Structural analysis revealed that, in addition to K158 (3.2 Å), residues R155 (2.7 Å) and G19 (3.2 Å) also interact with the \(\beta\) - phosphate of UDP- Sugar in SenB. During glycosyl transfer, all these three residues could stabilize the negative charge on the \(\beta\) - phosphate. To this extent, R155A and K158A might have similar influence on the catalytic activity. However, compared to R155A ( \(\sim 60\%\) relative catalytic activity), the near- complete loss of catalytic activity was observed in the K158A mutant, suggesting that K158 might be involved in other important catalytic process beyond merely stabilizing the negative charge on the \(\beta\) - phosphate. In fact, we found out that K158 is very critical for the Se- P bond cleavage. The amino side chain of K158 captures a proton from a water molecule. The resulted negatively charged water molecule attacks the partially positively charged phosphorus atom in the Se- P bond, and leads to bond disruption and the formation of a selenosugar product. Accordingly, we have amended our interpretation on the SenB catalytic mechanism on page 10, line 249- 253. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 590, 103]]<|/det|> +Results and discussion, line 275: ‘...K158 exhibits...’ + +<|ref|>sub_title<|/ref|><|det|>[[148, 106, 238, 121]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 123, 550, 140]]<|/det|> +We have made the corresponding correction. + +<|ref|>text<|/ref|><|det|>[[148, 159, 548, 177]]<|/det|> +Results and discussion, line 302: ‘...(Fig. 6h)...’ + +<|ref|>sub_title<|/ref|><|det|>[[148, 180, 238, 195]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 197, 550, 214]]<|/det|> +We have made the corresponding correction. + +<|ref|>text<|/ref|><|det|>[[148, 233, 849, 268]]<|/det|> +Results and discussion, line 307: ...structure and catalytic mechanism were completely unknown.” + +<|ref|>sub_title<|/ref|><|det|>[[148, 272, 238, 287]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 289, 849, 343]]<|/det|> +We have made the corresponding correction. “In conclusion, SenB is the only functionally identified SeGT in nature, but its structure and catalytic mechanism were unknown.” + +<|ref|>text<|/ref|><|det|>[[148, 362, 850, 417]]<|/det|> +Results and discussion, line 314- 315: ‘...and mutagenesis revealed the critical amino acids N20, T23, and E231 that control sugar donor promiscuity of SenB.” I still don’t agree that they ‘control’ promiscuity. + +<|ref|>sub_title<|/ref|><|det|>[[148, 419, 238, 435]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 437, 850, 491]]<|/det|> +Thank you for your valuable comments and suggestions. We have changed “control sugar donor promiscuity” to “modulate sugar donor preference” in hopes of more accurately describing the functional impact of these amino acids of SenB. + +<|ref|>text<|/ref|><|det|>[[148, 510, 850, 547]]<|/det|> +Overall, the manuscript is improved in some areas, but the writing and interpretation of some of the data is still problematic. Please consider revisions to the above sections. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 123, 850, 344]]<|/det|> +Huang and co- workers reported the cocrystal structures of SenB, a Se- glycosyltransferase and investigated the enzyme's recognition and catalytic mechanism. By performing biochemical studies using different sugars, the authors characterized SenB's substrate promiscuity toward these ligands. Through follow- up structural modeling, they identified the key residues for substrate binding and catalysis, and corroborated the results by enzymatic activity assays. The combined structural and biochemical studies provided insights into the reaction mechanism of SenB and contributed to our understanding on the selenium transfer mechanism as well. Overall, the authors did a good job on the biochemical and structural studies, and they carefully proposed a tentative mechanism for SenB catalysis. While the results of the manuscript and the high- quality structural work are interesting, the authors need to clarify several following issues before the manuscript is accepted. + +<|ref|>sub_title<|/ref|><|det|>[[149, 346, 238, 361]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[189, 364, 647, 380]]<|/det|> +Thank you for your valuable comments and suggestions. + +<|ref|>text<|/ref|><|det|>[[148, 400, 852, 565]]<|/det|> +1. While proposing the mechanism (line 248 on page 10), the authors say "SenB involves the amino side chain of K158 capturing a proton from a water molecule, becoming a negatively charged nucleophile that attacks the positively charged phosphorus atom in the Se-P bond...". There are problems with this sentence and the related figure (Fig. 5f). First, it was the water molecule that becomes negatively charged, not SenB; second, the phosphorus atom here is only "partially positively charged" due to the unequal polarities between P and Se; third, there are several problems with in the "C-Se bond formation" and "Se-P cleavage" steps of the Fig. 5f cartoon, where the arrows were pointing to the wrong atoms or positions; + +<|ref|>sub_title<|/ref|><|det|>[[149, 568, 238, 583]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 586, 850, 694]]<|/det|> +Thank you for your valuable comments. We have corrected the sentence to "Thus, the Se-P bond cleavage mediated by K158 in SenB may begin with the amino side chain of K158, which captures a proton from a water molecule. The resulting negatively charged water molecules attack the partially positively charged phosphorus atom in the Se-P bond, leading to bond disruption and the formation of a selenosugar product." In addition, the Fig. 5f has been corrected in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[190, 700, 816, 821]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 844, 848, 881]]<|/det|> +2. Site-Directed Mutagenesis in the Methods section: the quickchange method should be clearly stated; + +<|ref|>text<|/ref|><|det|>[[148, 883, 238, 899]]<|/det|> +Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 849, 120]]<|/det|> +Thank you for your valuable comments. Description of the Site- Directed Mutagenesis method has been added in the revised manuscript on page 14 line 351- 363. + +<|ref|>text<|/ref|><|det|>[[147, 140, 849, 175]]<|/det|> +3. The manuscript could've used some language editing; typos or grammatical errors are seen. For instance, + +<|ref|>text<|/ref|><|det|>[[147, 177, 666, 195]]<|/det|> +a. line 222 on page 9 "...deploy different strategy": missing "a" + +<|ref|>text<|/ref|><|det|>[[148, 196, 446, 212]]<|/det|> +b. line 379 on page 15 "...Tri-HCI"? + +<|ref|>text<|/ref|><|det|>[[147, 215, 715, 232]]<|/det|> +c. line 381 on page 15 "...a 6 h incubation period": missing a hyphen; + +<|ref|>sub_title<|/ref|><|det|>[[148, 234, 238, 250]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 252, 850, 343]]<|/det|> +Thank you for your valuable comments. "...deploy different strategy" has been corrected to "...deploy a different strategy"; "...Tri- HCI" has been corrected to "...Tri- HCI"; "...a 6 h incubation period" has been corrected to "...a 6- h incubation period". We have corrected the English usage of the whole document through the Nature Research Editing Service. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 460, 102]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 122, 850, 177]]<|/det|> +I already wrote in my previous review of this paper about the relevance and value of this work; I stand by it: it's a valuable addition for selenium research. Regarding the revision: + +<|ref|>sub_title<|/ref|><|det|>[[148, 180, 238, 196]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[189, 198, 515, 214]]<|/det|> +Thank you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 234, 485, 251]]<|/det|> +The minor issues I raised were addressed. + +<|ref|>text<|/ref|><|det|>[[148, 253, 850, 289]]<|/det|> +I still recommend improvements in English language throughout the whole document; perhaps authors can use a professional service? Or the journal can step in to help? + +<|ref|>sub_title<|/ref|><|det|>[[148, 291, 238, 307]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 308, 850, 344]]<|/det|> +We have corrected the English usage of the whole document through the Nature Research Editing Service. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 402, 104]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 118, 875, 210]]<|/det|> +This is the second revision of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in the synthesis of a Se- containing metabolite in a broad collection of bacteria. The initial and revised submissions had numerous concerns regarding the writing and interpretation of the experimental data. This revised submission addressed all of these prior concerns and is exceptionally improved. It is presently acceptable for publication and will be a wonderful addition to the seleno- chemistry literature. + +<|ref|>text<|/ref|><|det|>[[115, 224, 874, 298]]<|/det|> +One exceptionally minor point that the authors should consider is a revision to Fig. 3b. The linear diagram at the top of Fig. 3b shows the N- terminal domain in blue and C- term domain in green box format but the highlighting boxes in the bottom of the same panel have coloring that is the opposite. Revision of this figure to match the coloring between the top and bottom of the panel would eliminate potential confusion for the reader. + +<|ref|>text<|/ref|><|det|>[[116, 342, 404, 357]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 372, 669, 387]]<|/det|> +The authors have succesfully addressed all the concerns from this reviewer. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[395, 91, 602, 107]]<|/det|> +## Point-by-point response + +<|ref|>sub_title<|/ref|><|det|>[[149, 113, 390, 130]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 151, 422, 166]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 187, 851, 296]]<|/det|> +This is the second revision of a paper that describes the biochemical and structural characterization of a novel glycosyltransferase involved in the synthesis of a Se- containing metabolite in a broad collection of bacteria. The initial and revised submissions had numerous concerns regarding the writing and interpretation of the experimental data. This revised submission addressed all of these prior concerns and is exceptionally improved. It is presently acceptable for publication and will be a wonderful addition to the seleno- chemistry literature. + +<|ref|>sub_title<|/ref|><|det|>[[148, 300, 238, 315]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 317, 515, 333]]<|/det|> +Thank you for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[148, 354, 851, 444]]<|/det|> +One exceptionally minor point that the authors should consider is a revision to Fig. 3b. The linear diagram at the top of Fig. 3b shows the N- terminal domain in blue and C- term domain in green box format but the highlighting boxes in the bottom of the same panel have coloring that is the opposite. Revision of this figure to match the coloring between the top and bottom of the panel would eliminate potential confusion for the reader. + +<|ref|>sub_title<|/ref|><|det|>[[148, 448, 238, 463]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 465, 850, 500]]<|/det|> +We greatly appreciate the reviewer for valuable comments and corrections. We have corrected the Fig. 3b in the revised manuscript. + +<|ref|>image<|/ref|><|det|>[[151, 512, 841, 805]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 818, 422, 833]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 855, 677, 870]]<|/det|> +The authors have succesfully addressed all the concerns from this reviewer. + +<|ref|>sub_title<|/ref|><|det|>[[148, 874, 238, 888]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 891, 515, 907]]<|/det|> +Thank you for your valuable comments. + +<--- Page Split ---> diff --git a/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/images_list.json b/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..336383c9db0a61182eac0510c72f1734c9b7afe1 --- /dev/null +++ b/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,157 @@ + +# nature portfolio + +Peer Review File + +Efficacy of ChAdOx1 nCoV- 19 (AZD1222) vaccine against SARS- CoV- 2 lineages circulating in Brazil + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +Despite being an important study, due to the number of outcomes per variant, it is difficult to compare the effectiveness for all variants. It is important to rewrite the manuscript with the correct VOC names (Alpha, Beta, Gamma, Zeta, etc.) + +The main finding concerns the efficacy of ChAdOx1 nCoV- 19 against the P2 variant which appears to be similar to the B.1.1.28 variant. + +Importantly, the authors determine the efficacy for different variants according to the number of doses (D1 and D2). Currently, Brazil uses a 12- week interval between doses and understanding the efficacy and/or effectiveness of ChAdOx1 nCoV- 19 for one dose and two doses in the context of the Gamma variant is very relevant. Several manuscripts and pre- prints have demonstrated the need for 2 doses of ChAdOx1 nCoV- 19 to preserve vaccine effectiveness for the new variants (especially the Gamma and Delta variants). Therefore, I suggest adding this comparative analysis as was done in the clinical trial to see if there are important differences regarding the effectiveness of the first dose of ChAdOx1 for the different variants. + +In the discussion it is not out of context to discuss CoronaVac. There are no published data, there is no data regarding the variants in the studies cited, and there is no direct relationship with the assessment of ChAdOx1 for new variants. + +It would be important that efficacy data even after blind removal were calculated and discussed in the manuscript. There is only one pre- print that evaluated the effectiveness of ChAdOx1 nCoV- 19 for the Gamma/Beta variant in Canada and for just one dose of ChAdOx1 nCoV- 19. The efficacy and/or effectiveness information of ChAdOx1 nCoV- 19 for the P1 variant is extraordinarily relevant despite the limitations. The authors should present not only the evaluation of 18 cases of Gamma variants identified before unblinding, but all 160 that occurred after unblinding. As all the analysis present is a post- hoc analysis, with some limitation regard to the power, I don't understand the reason for not include in the analysis this participants with the properly discuss the limitation of non- blinding in the estimation of efficacy. + +Reviewer #2: + +Remarks to the Author: + +This is a well- written paper (except for an odd incomplete sentence on line 312). It addresses an important scientific question, namely how the efficacy differs for the different variants. I have a few detailed comments: + +1. As shown in Table S2, only about one tenth of the P.2 cases are included in the efficacy analysis due to unblinding. For a secondary analysis of this efficacy trial, it seems that additional analyses of cases after unblinding with sensitivity studies are essential to answering the scientific question of interest. + +2. Since the primary paper for the immunogenicity data has also been published, studying variants-specific immunogenicity and relate that to the efficacy seems valuable. + +3. Will variants-specific efficacy results for other geographical regions be reported elsewhere? It would be worth briefly explaining what to expect in the paper. + +4. In statistical analyses, what covariates are adjusted in the Poisson models? + +5. How do the Poisson models address competing risk? + +<--- Page Split ---> + +Reviewer #3: + +Remarks to the Author: + +Overall, this is important work and the paper has been carefully prepared. The statistical analysis plan is robust and uses appropriate statistical methodology. There are a few minor clarifications that are to be considered. + +The inclusion of subjects and events that occurred after the approval of the vaccine is somewhat complex. Consider developing a figure that shows how the final inclusion / exclusion into the analysis set was implemented. Some text such as page 10, lines 202 - 204 would suggest that infections after the public availability / unblinding were not gathered. In a way, this is understandable from a pure study perspective, but from a public health perspective with emerging variants, one would hope all available data would be summarized. Said differently, if there were events that happened after unblinding, where they included in the active vaccine group? What about the crossed over patients? Were there any placebo vaccinated that were never crossed over—could this data be shown? + +The paper makes what could be a strong statistical claim of "similar" response across the variants. The study was not designed to assess equivalence across variants and typical methods for equivalence designs were not implemented (e.g., a priori limits of equivalence). Most likely, the best path forward is to not interpret the data in the context of similarity and instead, just report the effectiveness of the vaccine in each group. If "similar" is desired as a construct, estimate the difference in effectiveness and it's \(95\%\) CI. This can help the reader determine just how similar the effectiveness ratios are. It is expected that the confidence interval will be quite wide suggesting limited data on the equivalence across variants. + +While the variants may capture the temporal changes in vaccine effectiveness, it may also be important to show some of the data using a few different time scales - time from vaccination; and infections by calendar day. This could be purely exploratory and posted as a supplement. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Despite being an important study, due to the number of outcomes per variant, it is difficult to compare the effectiveness for all variants. It is important to rewrite the manuscript with the correct VOC names (Alpha, Beta, Gamma, Zeta, etc.) + +RESPONSE: WHO Greek names have been added as suggested and lineage retained in brackets as non- VOC/VUIs lineages are also included in manuscript. + +The main finding concerns the efficacy of ChAdOx1 nCoV- 19 against the P2 variant which appears to be similar to the B.1.1.28 variant. + +Importantly, the authors determine the efficacy for different variants according to the number of doses (D1 and D2). Currently, Brazil uses a 12- week interval between doses and understanding the efficacy and/or effectiveness of ChAdOx1 nCoV- 19 for one dose and two doses in the context of the Gamma variant is very relevant. Several manuscripts and preprints have demonstrated the need for 2 doses of ChAdOx1 nCoV- 19 to preserve vaccine effectiveness for the new variants (especially the Gamma and Delta variants). Therefore, I suggest adding this comparative analysis as was done in the clinical trial to see if there are important differences regarding the effectiveness of the first dose of ChAdOx1 for the different variants. + +RESPONSE: This has now been added as suggested as Supplementary Table 4. There are fewer cases occurring after a single dose than after two doses as there was only a short period of follow up before the second dose was received, and the cases occurred earlier in the trial. There is only 1 case of P.1. The P.2 variant is the only one with more than 10 cases. Efficacy analyses have not been performed due to the small numbers but the data are presented in tabular form by vaccine arm. + +In the discussion it is not out of context to discuss CoronaVac. There are no published data, there is no data regarding the variants in the studies cited, and there is no direct relationship with the assessment of ChAdOx1 for new variants. + +<--- Page Split ---> + +RESPONSE: We have interpreted this comment to mean the reviewer felt it was out of context to discuss CoronaVac and so this section has been removed from the discussion. + +It would be important that efficacy data even after blind removal were calculated and discussed in the manuscript. There is only one pre- print that evaluated the effectiveness of ChAdOx1 nCoV- 19 for the Gamma/Beta variant in Canada and for just one dose of ChAdOx1 nCoV- 19. The efficacy and/or effectiveness information of ChAdOx1 nCoV- 19 for the P1 variant is extraordinarily relevant despite the limitations. The authors should present not only the evaluation of 18 cases of Gamma variants identified before unblinding, but all 160 that occurred after unblinding. As all the analysis present is a post- hoc analysis, with some limitation regard to the power, I don't understand the reason for not include in the analysis this participants with the properly discuss the limitation of non- blinding in the estimation of efficacy. + +RESPONSE: We agree on the importance and relevance of understanding the efficacy against P.1. When participants in the trial were unblinded, the control group were vaccinated with ChAdOx1 nCoV- 19. Therefore there is now no longer a control group that can be used to calculate efficacy. Instead we have two groups that have both been vaccinated with the same vaccine. It is very unfortunate that this data is not useful to inform us on the efficacy of the vaccine against P.1 due to the timing of this variant arriving in our study sites. We have added the Canadian preprint to the discussion and thank the reviewer for this suggestion. + +Reviewer #2 (Remarks to the Author): + +This is a well- written paper (except for an odd incomplete sentence on line 312). It addresses an important scientific question, namely how the efficacy differs for the different variants. I have a few detailed comments: + +RESPONSE: Thank you for pointing out the typo in line 312 which has now been amended. + +1. As shown in Table S2, only about one tenth of the P.2 cases are included in the efficacy analysis due to unblinding. For a secondary analysis of this efficacy trial, it seems that additional analyses of cases after unblinding with sensitivity studies are essential to answering the scientific question of interest. + +<--- Page Split ---> + +RESPONSE: We agree that this is an important scientific question and would like to have included all the cases. When participants in the trial were unblinded, the control group were vaccinated with ChAdOx1 nCoV- 19. Therefore there is now no longer a control group that can be used to calculate efficacy. Instead we have two groups that have both been vaccinated with the same vaccine. It is very unfortunate that this data cannot be used to inform us on the efficacy of the vaccine after unblinding. + +2. Since the primary paper for the immunogenicity data has also been published, studying variants-specific immunogenicity and relate that to the efficacy seems valuable. RESPONSE: We agree that this would be a valuable analysis. We have published some data on immune responses against P1 (https://doi.org/10.1016/j.cell.2021.06.020), but data are not currently available to relate variant-specific immunity to efficacy in a formal correlates analysis. We have added a comment about immunogenicity in the discussion + +3. Will variants-specific efficacy results for other geographical regions be reported elsewhere? It would be worth briefly explaining what to expect in the paper. RESPONSE: Yes these are published already. The efficacy results for South Africa (Beta) and UK (Alpha) are published in the NEJM and Lancet journals as follows: + +https://www.nejm.org/doi/full/10.1056/nejmoa2102214 + +https://www.thelancet.com/journals/lancet/article/PIIS0140- 6736(21)00628- 0/fulltext + +Both these papers are referred to in the paper. Arrival of Delta variant occurred after study unblinding and so further efficacy analysis for this variant is not possible, but real- world effectiveness has been reported. + +4. In statistical analyses, what covariates are adjusted in the Poisson models? + +RESPONSE: The Poisson model was unadjusted. This has been added to the methods section for clarity. + +5. How do the Poisson models address competing risk? + +RESPONSE: The Poisson model is not a competing risk model. Whilst it is possible that a second infection or other event may occur which would introduce a competing risk bias, there were only an extremely small numbers of participants with a second infection, and very good retention an follow up, therefore competing risk models were not implemented. + +Reviewer #3 (Remarks to the Author): + +<--- Page Split ---> + +Overall, this is important work and the paper has been carefully prepared. The statistical analysis plan is robust and uses appropriate statistical methodology. There are a few minor clarifications that are to be considered. + +The inclusion of subjects and events that occurred after the approval of the vaccine is somewhat complex. Consider developing a figure that shows how the final inclusion / exclusion into the analysis set was implemented. Some text such as page 10, lines 202 – 204 would suggest that infections after the public availability / unblinding were not gathered. In a way, this is understandable from a pure study perspective, but from a public health perspective with emerging variants, one would hope all available data would be summarized. Said differently, if there were events that happened after unblinding, where they included in the active vaccine group? What about the crossed over patients? Were there any placebo vaccinated that were never crossed over—could this data be shown? + +RESPONSE: Thank you for the suggestion. We have amended the consort diagram in Figure 1 to show the cases that occurred after the unblinding/revaccination of the control group, and the number of control group participants who did not accept vaccination at the time of unblinding or shortly thereafter (<10%). We have also updated the text in the methods page 10 to be more clear about the continuing follow up of cases after unblinding. + +The paper makes what could be a strong statistical claim of "similar" response across the variants. The study was not designed to assess equivalence across variants and typical methods for equivalence designs were not implemented (e.g., a priori limits of equivalence). Most likely, the best path forward is to not interpret the data in the context of similarity and instead, just report the effectiveness of the vaccine in each group. If "similar" is desired as a construct, estimate the difference in effectiveness and it's 95% CI. This can help the reader determine just how similar the effectiveness ratios are. It is expected that the confidence interval will be quite wide suggesting limited data on the equivalence across variants. + +RESPONSE: We agree with the reviewer and have removed these references to similar efficacy across variants. + +While the variants may capture the temporal changes in vaccine effectiveness, it may also be important to show some of the data using a few different time scales – time from vaccination; + +<--- Page Split ---> + +and infections by calendar day. This could be purely exploratory and posted as a supplement. RESPONSE: We have shown infections by calendar week in Figure 2A. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The authors answered all que questions and modified the text according to the suggestions. The manuscript has improved a lot mainly by making clear the limitations of the results in relation to power due to the reduced number of samples. Thus, I approve the current version for publications without additional comments. + +Reviewer #2: + +None + +Reviewer #3: + +Remarks to the Author: + +The authors have amended the paper consistent with the prior review. No further concerns. + +<--- Page Split ---> diff --git a/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f583fc09b1f7e3f1542590f1cf5a9eccd9cb4de0 --- /dev/null +++ b/peer_reviews/782e2f50cd0f014bfe77b90272af8d07faf589fbb0c27e985a2713412c825079/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,215 @@ +<|ref|>title<|/ref|><|det|>[[99, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[105, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[107, 154, 890, 211]]<|/det|> +Efficacy of ChAdOx1 nCoV- 19 (AZD1222) vaccine against SARS- CoV- 2 lineages circulating in Brazil + +<|ref|>image<|/ref|><|det|>[[94, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 286, 103]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[116, 120, 216, 133]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[116, 135, 291, 148]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 150, 880, 194]]<|/det|> +Despite being an important study, due to the number of outcomes per variant, it is difficult to compare the effectiveness for all variants. It is important to rewrite the manuscript with the correct VOC names (Alpha, Beta, Gamma, Zeta, etc.) + +<|ref|>text<|/ref|><|det|>[[116, 195, 867, 224]]<|/det|> +The main finding concerns the efficacy of ChAdOx1 nCoV- 19 against the P2 variant which appears to be similar to the B.1.1.28 variant. + +<|ref|>text<|/ref|><|det|>[[115, 225, 876, 342]]<|/det|> +Importantly, the authors determine the efficacy for different variants according to the number of doses (D1 and D2). Currently, Brazil uses a 12- week interval between doses and understanding the efficacy and/or effectiveness of ChAdOx1 nCoV- 19 for one dose and two doses in the context of the Gamma variant is very relevant. Several manuscripts and pre- prints have demonstrated the need for 2 doses of ChAdOx1 nCoV- 19 to preserve vaccine effectiveness for the new variants (especially the Gamma and Delta variants). Therefore, I suggest adding this comparative analysis as was done in the clinical trial to see if there are important differences regarding the effectiveness of the first dose of ChAdOx1 for the different variants. + +<|ref|>text<|/ref|><|det|>[[115, 344, 864, 387]]<|/det|> +In the discussion it is not out of context to discuss CoronaVac. There are no published data, there is no data regarding the variants in the studies cited, and there is no direct relationship with the assessment of ChAdOx1 for new variants. + +<|ref|>text<|/ref|><|det|>[[115, 387, 875, 522]]<|/det|> +It would be important that efficacy data even after blind removal were calculated and discussed in the manuscript. There is only one pre- print that evaluated the effectiveness of ChAdOx1 nCoV- 19 for the Gamma/Beta variant in Canada and for just one dose of ChAdOx1 nCoV- 19. The efficacy and/or effectiveness information of ChAdOx1 nCoV- 19 for the P1 variant is extraordinarily relevant despite the limitations. The authors should present not only the evaluation of 18 cases of Gamma variants identified before unblinding, but all 160 that occurred after unblinding. As all the analysis present is a post- hoc analysis, with some limitation regard to the power, I don't understand the reason for not include in the analysis this participants with the properly discuss the limitation of non- blinding in the estimation of efficacy. + +<|ref|>text<|/ref|><|det|>[[116, 566, 216, 579]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[116, 581, 291, 594]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 596, 860, 640]]<|/det|> +This is a well- written paper (except for an odd incomplete sentence on line 312). It addresses an important scientific question, namely how the efficacy differs for the different variants. I have a few detailed comments: + +<|ref|>text<|/ref|><|det|>[[115, 656, 861, 714]]<|/det|> +1. As shown in Table S2, only about one tenth of the P.2 cases are included in the efficacy analysis due to unblinding. For a secondary analysis of this efficacy trial, it seems that additional analyses of cases after unblinding with sensitivity studies are essential to answering the scientific question of interest. + +<|ref|>text<|/ref|><|det|>[[115, 730, 860, 760]]<|/det|> +2. Since the primary paper for the immunogenicity data has also been published, studying variants-specific immunogenicity and relate that to the efficacy seems valuable. + +<|ref|>text<|/ref|><|det|>[[115, 774, 876, 805]]<|/det|> +3. Will variants-specific efficacy results for other geographical regions be reported elsewhere? It would be worth briefly explaining what to expect in the paper. + +<|ref|>text<|/ref|><|det|>[[115, 819, 696, 835]]<|/det|> +4. In statistical analyses, what covariates are adjusted in the Poisson models? + +<|ref|>text<|/ref|><|det|>[[115, 850, 525, 865]]<|/det|> +5. How do the Poisson models address competing risk? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 104, 216, 117]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 120, 291, 133]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 134, 876, 178]]<|/det|> +Overall, this is important work and the paper has been carefully prepared. The statistical analysis plan is robust and uses appropriate statistical methodology. There are a few minor clarifications that are to be considered. + +<|ref|>text<|/ref|><|det|>[[115, 193, 876, 313]]<|/det|> +The inclusion of subjects and events that occurred after the approval of the vaccine is somewhat complex. Consider developing a figure that shows how the final inclusion / exclusion into the analysis set was implemented. Some text such as page 10, lines 202 - 204 would suggest that infections after the public availability / unblinding were not gathered. In a way, this is understandable from a pure study perspective, but from a public health perspective with emerging variants, one would hope all available data would be summarized. Said differently, if there were events that happened after unblinding, where they included in the active vaccine group? What about the crossed over patients? Were there any placebo vaccinated that were never crossed over—could this data be shown? + +<|ref|>text<|/ref|><|det|>[[115, 327, 880, 447]]<|/det|> +The paper makes what could be a strong statistical claim of "similar" response across the variants. The study was not designed to assess equivalence across variants and typical methods for equivalence designs were not implemented (e.g., a priori limits of equivalence). Most likely, the best path forward is to not interpret the data in the context of similarity and instead, just report the effectiveness of the vaccine in each group. If "similar" is desired as a construct, estimate the difference in effectiveness and it's \(95\%\) CI. This can help the reader determine just how similar the effectiveness ratios are. It is expected that the confidence interval will be quite wide suggesting limited data on the equivalence across variants. + +<|ref|>text<|/ref|><|det|>[[115, 462, 850, 507]]<|/det|> +While the variants may capture the temporal changes in vaccine effectiveness, it may also be important to show some of the data using a few different time scales - time from vaccination; and infections by calendar day. This could be purely exploratory and posted as a supplement. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[151, 83, 371, 101]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[151, 133, 437, 150]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[150, 181, 841, 250]]<|/det|> +Despite being an important study, due to the number of outcomes per variant, it is difficult to compare the effectiveness for all variants. It is important to rewrite the manuscript with the correct VOC names (Alpha, Beta, Gamma, Zeta, etc.) + +<|ref|>text<|/ref|><|det|>[[150, 264, 800, 308]]<|/det|> +RESPONSE: WHO Greek names have been added as suggested and lineage retained in brackets as non- VOC/VUIs lineages are also included in manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 347, 835, 392]]<|/det|> +The main finding concerns the efficacy of ChAdOx1 nCoV- 19 against the P2 variant which appears to be similar to the B.1.1.28 variant. + +<|ref|>text<|/ref|><|det|>[[149, 397, 842, 612]]<|/det|> +Importantly, the authors determine the efficacy for different variants according to the number of doses (D1 and D2). Currently, Brazil uses a 12- week interval between doses and understanding the efficacy and/or effectiveness of ChAdOx1 nCoV- 19 for one dose and two doses in the context of the Gamma variant is very relevant. Several manuscripts and preprints have demonstrated the need for 2 doses of ChAdOx1 nCoV- 19 to preserve vaccine effectiveness for the new variants (especially the Gamma and Delta variants). Therefore, I suggest adding this comparative analysis as was done in the clinical trial to see if there are important differences regarding the effectiveness of the first dose of ChAdOx1 for the different variants. + +<|ref|>text<|/ref|><|det|>[[149, 626, 844, 770]]<|/det|> +RESPONSE: This has now been added as suggested as Supplementary Table 4. There are fewer cases occurring after a single dose than after two doses as there was only a short period of follow up before the second dose was received, and the cases occurred earlier in the trial. There is only 1 case of P.1. The P.2 variant is the only one with more than 10 cases. Efficacy analyses have not been performed due to the small numbers but the data are presented in tabular form by vaccine arm. + +<|ref|>text<|/ref|><|det|>[[150, 809, 831, 878]]<|/det|> +In the discussion it is not out of context to discuss CoronaVac. There are no published data, there is no data regarding the variants in the studies cited, and there is no direct relationship with the assessment of ChAdOx1 for new variants. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 82, 802, 126]]<|/det|> +RESPONSE: We have interpreted this comment to mean the reviewer felt it was out of context to discuss CoronaVac and so this section has been removed from the discussion. + +<|ref|>text<|/ref|><|det|>[[148, 141, 835, 383]]<|/det|> +It would be important that efficacy data even after blind removal were calculated and discussed in the manuscript. There is only one pre- print that evaluated the effectiveness of ChAdOx1 nCoV- 19 for the Gamma/Beta variant in Canada and for just one dose of ChAdOx1 nCoV- 19. The efficacy and/or effectiveness information of ChAdOx1 nCoV- 19 for the P1 variant is extraordinarily relevant despite the limitations. The authors should present not only the evaluation of 18 cases of Gamma variants identified before unblinding, but all 160 that occurred after unblinding. As all the analysis present is a post- hoc analysis, with some limitation regard to the power, I don't understand the reason for not include in the analysis this participants with the properly discuss the limitation of non- blinding in the estimation of efficacy. + +<|ref|>text<|/ref|><|det|>[[148, 397, 847, 565]]<|/det|> +RESPONSE: We agree on the importance and relevance of understanding the efficacy against P.1. When participants in the trial were unblinded, the control group were vaccinated with ChAdOx1 nCoV- 19. Therefore there is now no longer a control group that can be used to calculate efficacy. Instead we have two groups that have both been vaccinated with the same vaccine. It is very unfortunate that this data is not useful to inform us on the efficacy of the vaccine against P.1 due to the timing of this variant arriving in our study sites. We have added the Canadian preprint to the discussion and thank the reviewer for this suggestion. + +<|ref|>text<|/ref|><|det|>[[150, 594, 437, 612]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[150, 643, 839, 710]]<|/det|> +This is a well- written paper (except for an odd incomplete sentence on line 312). It addresses an important scientific question, namely how the efficacy differs for the different variants. I have a few detailed comments: + +<|ref|>text<|/ref|><|det|>[[150, 726, 832, 745]]<|/det|> +RESPONSE: Thank you for pointing out the typo in line 312 which has now been amended. + +<|ref|>text<|/ref|><|det|>[[150, 775, 821, 869]]<|/det|> +1. As shown in Table S2, only about one tenth of the P.2 cases are included in the efficacy analysis due to unblinding. For a secondary analysis of this efficacy trial, it seems that additional analyses of cases after unblinding with sensitivity studies are essential to answering the scientific question of interest. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 83, 842, 225]]<|/det|> +RESPONSE: We agree that this is an important scientific question and would like to have included all the cases. When participants in the trial were unblinded, the control group were vaccinated with ChAdOx1 nCoV- 19. Therefore there is now no longer a control group that can be used to calculate efficacy. Instead we have two groups that have both been vaccinated with the same vaccine. It is very unfortunate that this data cannot be used to inform us on the efficacy of the vaccine after unblinding. + +<|ref|>text<|/ref|><|det|>[[149, 255, 837, 399]]<|/det|> +2. Since the primary paper for the immunogenicity data has also been published, studying variants-specific immunogenicity and relate that to the efficacy seems valuable. RESPONSE: We agree that this would be a valuable analysis. We have published some data on immune responses against P1 (https://doi.org/10.1016/j.cell.2021.06.020), but data are not currently available to relate variant-specific immunity to efficacy in a formal correlates analysis. We have added a comment about immunogenicity in the discussion + +<|ref|>text<|/ref|><|det|>[[149, 413, 820, 508]]<|/det|> +3. Will variants-specific efficacy results for other geographical regions be reported elsewhere? It would be worth briefly explaining what to expect in the paper. RESPONSE: Yes these are published already. The efficacy results for South Africa (Beta) and UK (Alpha) are published in the NEJM and Lancet journals as follows: + +<|ref|>text<|/ref|><|det|>[[150, 521, 565, 540]]<|/det|> +https://www.nejm.org/doi/full/10.1056/nejmoa2102214 + +<|ref|>text<|/ref|><|det|>[[150, 555, 787, 574]]<|/det|> +https://www.thelancet.com/journals/lancet/article/PIIS0140- 6736(21)00628- 0/fulltext + +<|ref|>text<|/ref|><|det|>[[150, 589, 820, 656]]<|/det|> +Both these papers are referred to in the paper. Arrival of Delta variant occurred after study unblinding and so further efficacy analysis for this variant is not possible, but real- world effectiveness has been reported. + +<|ref|>text<|/ref|><|det|>[[150, 672, 722, 690]]<|/det|> +4. In statistical analyses, what covariates are adjusted in the Poisson models? + +<|ref|>text<|/ref|><|det|>[[150, 696, 844, 739]]<|/det|> +RESPONSE: The Poisson model was unadjusted. This has been added to the methods section for clarity. + +<|ref|>text<|/ref|><|det|>[[150, 746, 562, 764]]<|/det|> +5. How do the Poisson models address competing risk? + +<|ref|>text<|/ref|><|det|>[[150, 770, 842, 862]]<|/det|> +RESPONSE: The Poisson model is not a competing risk model. Whilst it is possible that a second infection or other event may occur which would introduce a competing risk bias, there were only an extremely small numbers of participants with a second infection, and very good retention an follow up, therefore competing risk models were not implemented. + +<|ref|>text<|/ref|><|det|>[[150, 894, 456, 911]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 107, 824, 175]]<|/det|> +Overall, this is important work and the paper has been carefully prepared. The statistical analysis plan is robust and uses appropriate statistical methodology. There are a few minor clarifications that are to be considered. + +<|ref|>text<|/ref|><|det|>[[149, 205, 844, 422]]<|/det|> +The inclusion of subjects and events that occurred after the approval of the vaccine is somewhat complex. Consider developing a figure that shows how the final inclusion / exclusion into the analysis set was implemented. Some text such as page 10, lines 202 – 204 would suggest that infections after the public availability / unblinding were not gathered. In a way, this is understandable from a pure study perspective, but from a public health perspective with emerging variants, one would hope all available data would be summarized. Said differently, if there were events that happened after unblinding, where they included in the active vaccine group? What about the crossed over patients? Were there any placebo vaccinated that were never crossed over—could this data be shown? + +<|ref|>text<|/ref|><|det|>[[150, 436, 842, 555]]<|/det|> +RESPONSE: Thank you for the suggestion. We have amended the consort diagram in Figure 1 to show the cases that occurred after the unblinding/revaccination of the control group, and the number of control group participants who did not accept vaccination at the time of unblinding or shortly thereafter (<10%). We have also updated the text in the methods page 10 to be more clear about the continuing follow up of cases after unblinding. + +<|ref|>text<|/ref|><|det|>[[149, 584, 838, 775]]<|/det|> +The paper makes what could be a strong statistical claim of "similar" response across the variants. The study was not designed to assess equivalence across variants and typical methods for equivalence designs were not implemented (e.g., a priori limits of equivalence). Most likely, the best path forward is to not interpret the data in the context of similarity and instead, just report the effectiveness of the vaccine in each group. If "similar" is desired as a construct, estimate the difference in effectiveness and it's 95% CI. This can help the reader determine just how similar the effectiveness ratios are. It is expected that the confidence interval will be quite wide suggesting limited data on the equivalence across variants. + +<|ref|>text<|/ref|><|det|>[[150, 790, 797, 833]]<|/det|> +RESPONSE: We agree with the reviewer and have removed these references to similar efficacy across variants. + +<|ref|>text<|/ref|><|det|>[[150, 864, 845, 908]]<|/det|> +While the variants may capture the temporal changes in vaccine effectiveness, it may also be important to show some of the data using a few different time scales – time from vaccination; + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 83, 840, 125]]<|/det|> +and infections by calendar day. This could be purely exploratory and posted as a supplement. RESPONSE: We have shown infections by calendar week in Figure 2A. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 286, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 120, 216, 133]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 136, 293, 149]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 150, 850, 211]]<|/det|> +The authors answered all que questions and modified the text according to the suggestions. The manuscript has improved a lot mainly by making clear the limitations of the results in relation to power due to the reduced number of samples. Thus, I approve the current version for publications without additional comments. + +<|ref|>text<|/ref|><|det|>[[115, 255, 216, 268]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 270, 155, 282]]<|/det|> +None + +<|ref|>text<|/ref|><|det|>[[115, 300, 216, 313]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 315, 293, 328]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 329, 797, 344]]<|/det|> +The authors have amended the paper consistent with the prior review. No further concerns. + +<--- Page Split ---> diff --git a/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/images_list.json b/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..54df9e7be9fc959ee6d0074bbe80533222054354 --- /dev/null +++ b/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,40 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_1.jpg", + "caption": "Supplementary Figure 1. Representative immunohistochemical staining image of the tumor tissue stained with anti-CD160 and anti-LGR6 for sample 341.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_2.jpg", + "caption": "Supplementary Figure 2. Comparison of differentially expressed genes and pathways between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype. A, Overlap of significantly differentially expressed genes (limma \\(p< 0.01\\) ) between EP300 mut vs. wt and NOTCH1 mut vs. wt. B, Up- and downregulated pathways (GSEA FDR \\(q< 0.05\\) ) and the comparisons between EP300 (mut vs. wt) and NOTCH1 (mut vs. wt). C, Scatter plot of log2 fold changes for all the profiled genes between EP300 (mut vs. wt) and NOTCH1 (mut vs. wt). D, Scatter plot of mRNA expression between EP300 and NOTCH1.", + "footnote": [], + "bbox": [ + [ + 160, + 85, + 736, + 350 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Supplementary Figure S3", + "footnote": [], + "bbox": [ + [ + 152, + 516, + 816, + 678 + ] + ], + "page_idx": 11 + } +] \ No newline at end of file diff --git a/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c3868df9f60dedd102593a47ea00cb1156f50493 --- /dev/null +++ b/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,740 @@ + +# nature portfolio + +Peer Review File + +The integrated molecular and histological analysis defines subtypes of esophageal squamous cell carcinoma + +![](images/Supplementary_Figure_1.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: Figure on page 39 of this Peer Review File have been redacted as indicated to remove third- party material where no permission to publish could be obtained. "Chen, D., et al. An Ensemble Deep Neural Network for Footprint Image Retrieval Based on Transfer Learning. Journal of Sensors 2021, 6631029 (2021)." + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): Expert in oesophageal cancer genomics + +Jiang et al. performed whole- exome sequencing and transcriptome analysis on Chinese 120 ESCC samples to characterize ESCC in detail. The authors classified four subtypes based on the expression and three based on the estimated immune cells in cancer tissues. They found that the stemness subtype showed poor prognosis and enriched in C3 immune subtype. In addition, they showed some relationships between transcripts and subtypes and analyzed them functionally. Moreover, they found NK cell- like expression signature in cancer cells. Genetic analysis also gave some insights. However, overall, their claims are not well supported by the results, and there are many overstatements as described below. + +Major points: + +Line 97- 98 The authors classified ESCC based on 1500 gene expressions with the highest MAD score and adopted four subtypes. The methods section describes that the cluster number with the highest cophenetic coefficient was adopted. As shown in Extended Data Figure 1a, the cophenetic coefficient for \(\mathsf{k} = 2\) is 0.9928 and \(\mathsf{k} = 4\) is 0.985, but they adopted \(\mathsf{k} = 4\) instead of \(\mathsf{k} = 2\) . Is there any other reason why the authors adopted \(\mathsf{k} = 4\) ? + +Line 110- 111 Fig. 1b does not show "interferon gamma pathway" or "chemokine signaling pathway". Were these pathways significantly downregulated in the stemness subgroup? + +Line 115- 120 The authors claimed histological characteristics of each subtype. However, there is little evidence to support their claim because they just showed the representative images and did not show any quantitative data extracted from histological images. + +Line 124- 127 The result is unreliable because functional analysis of SFPR1 overexpression was performed in just one cell line. Also, it is highly recommended to show the result of the knockdown experiment using more than one effective shRNA to exclude off- target effects. + +Line 154 The association between "stemness" and "NK cell estimates" is not strong because the correlation r- value of 0.32 – 0.4 is not high. + +Line 165- 166 The authors showed immunohistochemical images of Sample 401 in Fig.2g and Extended Data Fig. 5c. How is the difference of LGR6- staining in the same tumor explained? Also, the architecture of cancer cells is different. Are these derived from the same tumor sample? + +Line 198- 201 The result is uncredible because the authors performed overexpression of XCL1 in just one cell line. In addition, it is strongly recommended to show the result of the knockdown experiment of XCL1 to support their claim. + +Line 247- 250 Among EP300 mutations, 30 % were truncating mutations or deletion. The authors showed higher expression of the mutated allele. However, if the cancer had a truncating/deletion mutation, the + +<--- Page Split ---> + +mutated allele is expected to result in loss of function. Therefore, their claim of a gain- of- function mode of EP300 mutations is not supported. + +Line 254- 277 The authors showed a higher frequency of NOTCH1 mutation as well as EP300 mutation in the stemness subgroup. Therefore, these results may derive from the effect of NOTCH1 mutation. To investigate the effect of EP300 mutation, it is reasonable to compare EP300- wild and mutant cancers among the same subgroup because the genetic backgrounds of subgroups are different from each other. + +Line296- 299 In Fig. 9c left panel, three subtypes other than the stemness subtype showed a comparable frequency of truncating mutations in wnt pathway genes. Therefore, because the prediction of the effect of mutations is more reliable for truncating mutation than for missense mutation, it seems that deleterious Wnt pathway mutations are similar. + +Minor points: + +Line 99- 101 They designated four subgroups based on known functional gene expression rather than GSEA. + +Reviewer #2 (Remarks to the Author): Expert in tumour immunology, NK cells, and oesophageal cancer + +Comments for the manuscript entitled "Stemness and NK- like signatures define the poorest subtype of oesophageal squamous cell carcinoma" by Guozhong Jian et al. + +This referee aims to comment on the non- bioinformatical part if this manuscript, leaving the comments for the precise bioinformatics to experts on bioinformatics and statistics. + +The manuscript presents an impressive molecular investigation of oesophageal squamous cell carcinoma (ESCC) from 120 Chinese patients. The authors have performed transcriptomics with GSEA and immune profiling, and mutational enrichment analyses, with the aim to find subtypes of tumors, and link this information to novel immune evasion strategies or drug sensitivity. The focus of the study is using bioinformatics, and the results from the authors own patient cohort is compared to previous studies on related cohorts, especially regarding the immune profiling strategy. There is no doubt that the study is of large importance, with ESCCs being one of the deadliest cancers worldwide today, with no effective therapies at hand. A study if this size, at this detailed molecular level, is difficult to find in the literature and will make a difference. Whereas the bioinformatics part of this study seems strong, the immunology and pathology sections are less robust. The manuscript is written in a very condensed scientific English, which makes it difficult to actually understand what has been done in the various panels of experiments. This also makes the reader insecure of what the authors actually have accomplished (the materials and methods (and figure legends) does not help or guide). To be able to fully understand this study, the manuscript has to be rewritten in a more detailed manner. Some comments are given below. 1) Every panel of each figure needs to be explained better, both experimentally and statistically, to be able to understand what has been done. This goes for the material and methods part too. Controls should be added where appropriate, and in cases where a value is calculated compared to a control, the + +<--- Page Split ---> + +control needs to be described equally well. Full statistics should be explained also in Figure legends. + +2) Row 114. "The molecular subtypes present distinguished histological features". Is this based on these four photographs of four tumors? How representative are they? Where are the statistics behind this to be able to state this quite important finding? The authors should have access to all tumors, and thus be able to perform a tumor tissue array of paraffinized samples, to compare the histology of all 120 tumors on one single glass slide using a light microscope. This way statistics can be added. + +3) Row 116-120. The authors describe these histological features using nomenclature of keratin pearls, extensive immune infiltration etc, without showing it or even presenting how this was done or annotated. Again, to say this a tumor tissue array would be good and should be annotated and evaluated statistically. The material and methods section should be updated accordingly, presenting how keratin pearls or immune cell infiltration was assayed. + +4) Row 126. Xenograft models are presented in the text, but no ethical permit or precise description of how it was exactly performed in present in the text or materials and methods. Just very vague descriptions referring to Extended data Fig 3. What is Ext data Fig 3a? Explain each panel. Extended data Fig 3 is a typical representative for the concerns mentioned above of too limited explanations. + +5) Figure 2e, row 149, is this a Fisher's exact test? Where is the statistics shown in the figure? The figure legend is minimal. + +6) Fig 2g. IHC controls are absent. A normal tissue should be used as control, and a cell line lacking (negative) or expressing (positive) should be shown to trust the IHC antibody specificity. Again, a tissue tumor array would be good to be able to conclude the results, only four samples are not enough to conclude. + +7) Row 158-166. How is this IHC annotation performed and shown? The authors show statistics in the text that is not described in detail, and cannot be found in the figures or legends. Is it Pearson Chi-square tests or what fo authors mean with co-expression? Tables of annotations? This needs to be clearly shown. + +8) From row 177 and on "NK-like tumor cells" are used to described tumor cells expressing CD160. It would be preferrable to not name the tumor cells "NK-like tumor cells", since they are tumor cells and not lymphocytes. + +9) Fig 3f. How is the IC50 experiment performed exactly. The materials and methods do not describe what is being shown in panel 3f. How are the numbers calculated? At what concentration, time and compared to what? If a Mann-Whitney test is used, what exact control are the bars compared to? + +XCL1 as a promising biomarker for drug sensitivity, using cell lines, and EP300 for survival in the patient cohort. How can these be linked in patient material and survival? + +11) Figure 5, the authors present immune infiltration and association with clonal diversity, and is also important. It would be good to perform IHC panels on some basic immune populations of the tumors to be able to support the data from the Shannon diversity index. Immune exclusion of T cells compared to M2 macrophages, as well as NK cells would be interesting to see. If CD160 is expressed on tumor cells. 12) The manuscript needs to be rewritten, to add much more detail for each panel, to be able to understand what has been done. As it is now, it is difficult to interpret the results. + +<--- Page Split ---> + +In this study Jiang et al., aims at defining novel molecular subgroups in human Oesophageal Squamous Cell Carcinoma (ESCC) by analysing the transcriptome and genome of a big cohort of ESCC from Chinese patients. + +The authors, using bulk- RNA sequencing, identify four distinct ESCC transcriptomic subtypes. Among them one shows the worst survival rate and is characterized by the expression of WFDC2, SFRP1, LGR6 and VWA2 genes ("stemness" subtype). The data obtained from the RNA sequencing analysis is then analysed using deconvolution methods to determine the tumor immune composition of the ESCC samples. Using this approach, they divide the tumors in three categories according to the content/type of immune cells present within the sample and identify a group of tumors showing high expression of NK- like gene signature, the group associated with the poorest survival rate. Interestingly, they observe that tumors showing high expression of XCL1 (gene upregulated within the NK gene signature and C3 immune type) present higher resistance to several drugs. Thirdly, the authors characterize the genomic landscape of the same cohort of patients and describe genomic landscapes similar to those described in the numerous genomic analyses that have been reported on ESCC (The Cancer Genome Atlas Research, N. et al. Nature 541, 169- 175 (2017); Song, Y. et al. Nature 509,91- 95 (2014); Lin, D. C. et al. Nat. Genet. 46, 467- 473 (2014); Gao, Y. B. et al. Nat. Genet. 46,1097- 1102 (2014)). Finally, the authors determine if there is any correlation between the transcriptomic and immune signatures and the mutational landscape of the ESCC analysed. + +The main criticism is that this study lacks accuracy as many of the statements are not well sustained or only based on correlations. There is a lack of validation of the transcriptomic and immune signatures in biological samples and lack of experiments in biological samples aimed at supporting the numerous correlations present in the study. These validations and experiments would certainly help to strengthen and confirm the message of the paper. + +Remarkably, there are some points that need to be further developed or clarified: + +1- Using bulk RNA- sequencing the authors classify the ESCC analysed in 4 different subtypes characterized by the expression of different markers, subtypes that show different morphological characteristics and patient survival rates (Figure 1). The authors claim that they are interested to characterize both the tumor and tumor microenvironment. However, they do not analyse if the genes found to be upregulated in the different subgroups are expressed by the tumor cells or by the tumor microenvironment, which is extremely relevant to validate and strengthen this key point the authors want to make. This validation could be accomplished by performing immunostainings for the different markers in tumors from the 4 ESCC subtypes or alternatively using techniques that would allow a deeper characterization of the different cell populations present in the samples (single cell RNA sequencing). Using the latter approach, a recent paper (Zhang, X., Peng, L., Luo, Y. et al. Nat Commun 12, 5291, 2021) identified eight different common expression programs of epithelial cells in ESCC tumors and characterized the populations present in the tumor microenvironment of the same tumors. + +2- In Figure 2 the authors identify a cluster, cluster 3, characterized by the expression of NK markers, + +<--- Page Split ---> + +again it is not clear if these NK markers are expressed by the tumor cells (staining for XCL1 and Lgr6 Fig2 g superior panel is too weak to be able to conclude anything and morphologically the tumor shown does not seem a “stemness” tumor) or if there is infiltration of NK cells or presence of NK cells surrounding the tumors (staining for a NK marker would be extremely helpful). Therefore the description of the immune infiltration and immune microenvironment is superficial and needs to be improved. In addition, only \(50\%\) of the stemness- subtype tumors could be classified as belonging to the immune cluster 3 (Fig 2e), so the statement “given the strong association between stemness and NK cell estimates- line 154- 155” is overstated and should be corrected. + +3- One of the genes that characterize Cluster 3 (NK- like signature) is XCL1. The authors show using GSEA that XCL1- high cells exhibit upregulation of drug metabolism of cytochrome P450, retinol metabolism and biological oxidations (line 185) and in line 106 the authors state “the metabolic subtype is associated with the upregulation of genes involved in drug metabolism by cytochrome P450 and retinol metabolism”. Would this mean that tumors showing high XCL1 expression belong to the “metabolic subtype”? This is confusing and highlights that the link between XCL1 (NK- like) and “stemness subtype” or “metabolic subtype” should be better explained. + +4- In Figure 2g, Extended Data Figure 5c and line 164- 172, the authors state that XCL1 is exclusively expressed in cancer cells showing adenocarcinoma morphology. Should we consider all XCL1- expressing tumours adeno- squamous cell carcinomas? If so, the authors should repeat the analysis by studying the ESCC and adeno- squamous cell carcinomas separately as relevant differences may be found in terms of transcriptomics, genomics and response to chemotherapy. + +5- The authors suggest that XCL1- high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +<--- Page Split ---> + +## Point by point responses to the revisers' comments + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): Expert in oesophageal cancer genomics + +Jiang et al. performed whole- exome sequencing and transcriptome analysis on Chinese 120 ESCC samples to characterize ESCC in detail. The authors classified four subtypes based on the expression and three based on the estimated immune cells in cancer tissues. They found that the stemness subtype showed poor prognosis and enriched in C3 immune subtype. In addition, they showed some relationships between transcripts and subtypes and analyzed them functionally. Moreover, they found NK cell- like expression signature in cancer cells. Genetic analysis also gave some insights. However, overall, their claims are not well supported by the results, and there are many overstatements as described below. + +Major points: + +1. Line 97-98 The authors classified ESCC based on 1500 gene expressions with the highest MAD score and adopted four subtypes. The methods section describes that the cluster number with the highest cophenetic coefficient was adopted. As shown in Extended Data Figure 1a, the cophenetic coefficient for \(k = 2\) is 0.9928 and \(k = 4\) is 0.985, but they adopted \(k = 4\) instead of \(k = 2\) . Is there any other reason why the authors adopted \(k = 4\) ? + +Response: We thank the reviewer for such detailed observation. Our choice of \(k = 4\) used in NMF was based on the combination factors of NMF cophenetic coefficient and the heterogeneous molecular signatures sufficiently revealed by our data. When \(k = 2\) was used, based on the signature gene sets of the two groups and their functional annotation, only two molecular subtypes were revealed, differentiated and immunogenic. The signatures of metabolic and stemness subtypes could not be identified by \(k = 2\) . This is also supported by the Supplementary Table S1 of this rebuttal that the top signature genes of our differentiated and immunogenic subtypes were still significant genes for the two subgroups when \(k = 2\) , but top signature genes of the metabolic and stemness subtypes were not significant anymore when \(k = 2\) . Most importantly, our four transcriptomic subtypes and their signatures were successfully validated by three independent cohorts (Extended Data Figure 1b), and were strongly supported by the following clinical, histopathology, in vitro and in vivo (for stemness) experiments. + +<--- Page Split ---> + + +Supplementary Table S1. Comparison of signature genes of our four subtypes between \(\mathsf{k} = 4\) and \(\mathsf{k} = 2\) in NMF + +
Signature geneslog2FC (one group vs others)P.Valueadj.P.Valk=4 groupsk=2 groupslog2FC (group2 vs group1)P.Valueadj.P.Val
LCE3D4.2921.54E-122.95E-10DifferentiatedDifferentiated-2.4190.000162960.00252447
CDSN3.9667.01E-141.05E-10DifferentiatedDifferentiated-2.3004.28E-050.00084861
KLK53.8847.18E-131.79E-10DifferentiatedDifferentiated-2.3164.81E-050.0009412
SPRR2G3.6851.02E-094.77E-08DifferentiatedDifferentiated-1.7240.006289540.03822871
DSG13.5902.00E-112.00E-09DifferentiatedDifferentiated-1.5250.007171460.04182777
MS4A12.5911.56E-124.04E-11ImmunogenicImmunogenic2.5035.35E-141.09E-11
CD79A2.5581.16E-195.82E-17ImmunogenicImmunogenic2.3522.05E-207.17E-17
CXCL92.2638.70E-121.95E-10ImmunogenicImmunogenic2.1172.20E-122.82E-10
MZB12.2627.31E-221.10E-18ImmunogenicImmunogenic2.0811.01E-232.81E-19
IDO12.2061.48E-091.94E-08ImmunogenicImmunogenic2.4443.15E-146.79E-12
GSTA13.9563.37E-092.10E-07Metabolic-0.5050.416094760.59872715
ADH73.8626.39E-124.79E-09Metabolic-0.2760.60408430.75100198
UGT1A103.7973.52E-071.04E-05Metabolic-0.4850.476546160.65090706
UGT1A33.6921.17E-074.08E-06Metabolic-0.5770.366088990.55313354
ALDH3A13.5748.64E-111.62E-08Metabolic-0.0050.993017510.99646932
WFD22.4467.43E-071.71E-05Stemness-0.5790.206508540.38417833
PEG101.7910.000249810.00148696Stemness--0.4870.272895870.46017491
SFRP11.7810.000129490.00087493Stemness-0.0900.831019810.90348777
LGR61.7314.19E-050.00035815Stemness--0.0370.922517860.95710801
VWA21.6781.18E-074.44E-06Stemness-0.0010.997490750.99871802
+ +We added one sentence in Methods Line 723- 725 to clarify the reason why we adopted \(\mathsf{k} = 4\) , "Our choice of the optimal cluster count in NMF was based on the combination factors of NMF cophenetic coefficient and the heterogeneous molecular signatures sufficiently revealed by our data.". + +2. Line 110- 111 Fig. 1b does not show "interferon gamma pathway" or "chemokine signaling pathway". Were these pathways significantly downregulated in the stemness subgroup? + +Response: We appreciate the reviewer's comment here (in line 112- 114). We've included the two terms "interferon gamma pathway" or "chemokine signaling pathway" into the Figure 1b heatmap, In Figure 1b, the heatmap was based on the "- log10" transformed p- values from the hypergeometric test against the mSigDB database genesets (v.6.2) using signature genes from each transcriptomic group (Extended Data Table S2), while the enrichment plots of three immune pathways (downregulated in stemness, Figure 1b) were based on the GSEA analysis (https://www.gseasmigdb.org/gsea/index.jsp) developed by the Broad Institute, using all profiled genes and associated ranked t- statistics. Both methods independently highlighted that all immune pathways were significantly upregulated in the immunogenic subgroup, but downregulated in the stemness subgroups (revealed by GSEA), and genes from immune pathways were not over- represented in the stemness signature genes (by the hypergeometric test). + +3. Line 115-120 The authors claimed histological characteristics of each subtype. However, there is little evidence to support their claim because they just showed the representative images and did not show any quantitative data extracted from histological images. + +Response: We appreciate the reviewer's insightful comment. This was also pointed by reviewer #2 comment #2. To further quantify and compare the histopathological features of four subgroups of ESCC, we developed a deep- learning model using five state- of- the- art convolutional networks, namely Inception- V3, Inception- ResNet- V2, DenseNet- 121, VGG16 and ResNet- 50, and performed feature extraction on selected tiles from each whole slide image (WSI) from the scanned H&E sections. We then compared features among the four transcriptomic groups, and identified features + +<--- Page Split ---> + +strongly associated with each group (i.e., features that were significantly higher in one group compared to the rest). We then selected top five features for each group, and summed these features to create four stable, statistically significant histological markers of gene expression- based classifications, namely DIFF- Feature, MET- Feature, IMM- Feature and STEM- Feature. We performed this analysis using a \(65\%:35\%\) discovery and validation/test of our WSI samples, see Methods Line 834 - 867 for full detail, also Extended Data Figure 1c. Tiles with the highest scores of each feature were selected for reviewing by a pathologist (Figure 1c). + +Indeed, tiles with the highest subtype specific features all contained the distinct histopathological features corresponding to each molecular subgroup (Figure 1C). DIFF- Feature, characterised by that keratin pearls within tumours and differentiated squamous dysplastic cells were significantly higher in the differentiated subgroup samples than the non- differentiated samples (Figure 1c and Extended Data Figure 1c). The MET- Feature, marked by moderate differentiated squamous tumour cells, with some tumour cells showing eosinophilic cytoplasm with less immune cell infiltration. The immunogenic subgroup showed extensive immune cell infiltration within tumours compared to other groups; The stemness subgroup presented poorly differentiated tumour cells and had few immune cell infiltrating within the tumour (Figure 1c and Extended Data Figure 1c). We have included the AI digital pathology results into the revised manuscript Line 152- 169. We also include a paragraph discussing this in Line 489 - 500. + +4. Line 124-127 The result is unreliable because functional analysis of SFPR1 overexpression was performed in just one cell line. Also, it is highly recommended to show the result of the knockdown experiment using more than one effective shRNA to exclude off-target effects. + +Response: According to the reviewer's comment, SFRP1 overexpression experiment was performed in another cell line KYSE- 140, and more effective shRNAs were designed to confirm the knockdown results. All shRNA sequences were selected from Sigma which were validated by the provider. The new results are presented in Extended Data Figure 4, and shRNA sequence were provided in the methods section Line 930- 940. + +5. Line 154 The association between "stemness" and "NK cell estimates" is not strong because the correlation r-value of 0.32 - 0.4 is not high. + +Response: We agree with the reviewer's comment, and have changed our wording throughout the manuscript, and state "suggesting a degree of certain association between stemness and NK cell estimates." in Line 205-206. + +6. Line 165-166 The authors showed immunohistochemical images of Sample 401 in Fig.2g and Extended Data Fig. 5c. How is the difference of LGR6-staining in the same tumor explained? Also, the architecture of cancer cells is different. Are these derived from the same tumor sample? + +Response: Thanks for providing us with the valuable comment. We apologize for any inconvenience caused by the mix- up of samples depicted in Fig 2g. (now Fig. 2h) Upon further investigation, we have confirmed that the staining of CD160 and LGR6 shown in original Fig 2g are from sample 341, but due to our limited perspective, its sequential segmentation may not have been apparent. We have provided additional supporting evidence of this rebuttal (Supplementary Figure 1, shown below) indicating that both are indeed from the same source. To provide greater clarity, we have replaced the staining in Figure 2g for sample 341 with two new field of views that are more similar, as illustrated in the new Figure 2h. + +<--- Page Split ---> +![](images/Supplementary_Figure_2.jpg) + +
Supplementary Figure 1. Representative immunohistochemical staining image of the tumor tissue stained with anti-CD160 and anti-LGR6 for sample 341.
+ +We have also updated Extended Data Fig 6c accordingly, and showed the anti- CD160 and anti- LGR6 staining for Sample 369, and anti- XCL1 and anti- LGR6 staining for Sample 401 in sequential sections. All these confirmed the co- expression of LGR6 with XCL1 or CD160 in a subset of our samples. We have updated this section of results in Line 212 - 219. + +7. Line 198-201 The result is incredible because the authors performed overexpression of XCL1 in just one cell line. In addition, it is strongly recommended to show the result of the knockdown experiment of XCL1 to support their claim. + +Response: Following this reviewer's insightful comment, we have further performed the overexpression of XCL1 in two additional XCL1- low cell lines, KYSE- 180 and KYSE- 410, and the results were consistent to what was shown in XCL1- low KYSE- 150 cell line, overexpression of XCL1 significantly increased the IC50 values, making them more resistant to 5- FU, the new results have been added into (Figure 3g). Knockdown of XCL1 would be ideal to consolidate the conclusion, but we could not make XCL1 significantly knockdown subclone cell lines, possibly due to the low proportion of XCL1 overexpressing cells in ESCC cell lines (from our IHC data and sRNA deep sequencing data, XCL1 postive cells are less than \(1\%\) of total tumour cells). The alternative approach CRISPR Cas9 knockout strategy was also considered, but it is difficult to design XCL1- specific gRNA given the the high similarity to XCL2. However, we think the overexpression of XCL1 in two additional cell lines is strong enough to support our claim that the overexpressing of XCL1 in cancer cells is associated with the sensitivity to 5- FU. + +8. Line 247-250 Among EP300 mutations, \(30\%\) were truncating mutations or deletion. The authors showed higher expression of the mutated allele. However, if the cancer had a truncating/deletion mutation, the mutated allele is expected to result in loss of function. Therefore, their claim of a gain-of-function mode of EP300 mutations is not supported. + +Response: We thank the reviewer for this useful comment. We further looked into the allelic imbalance for the eight samples with mutations in EP300, including 4 missense, 1 splice site, 1 + +<--- Page Split ---> + +nonsense, 1 frame- shift deletion and 1 in- frame deletion, and compared variant allele frequency (VAF) between the WES DNA and RNA- seq data. Three single nucleotide mutations (2 missense mutations, c.4312T>C, c.4355C>G and one splice site mutation, c.4617+1G>A) showed significantly elevated levels of the alternative (mutated) allele in RNA- compared to the DNA- level, as shown in current Fig. 4f. Amongst the remaining five mutations, one nonsense (c.3244C>T) and one frame- shift deletion (c.1914_1915del) in fact showed significantly decreased levels of the alternative allele in RNA than in DNA, suggesting potentially loss- of- function for the mutated allele. We have included this data as Supplementary Table S9, and updated the wording accordingly (Line 314- 319), as "Three single nucleotide mutations (2 missense mutations, c.4312T>C, c.4355C>G and one splice site mutation, c.4617+1G>A) showed significantly elevated levels of the alternative (mutated) allele in RNA- compared to the DNA- level. While for two codon- affecting mutations, one nonsense (c.3244C>T) and one frame- shift deletion (c.1914_1915del), the opposite pattern was observed, with decreased levels of the alternative allele in RNA than in DNA". + +However, the result for higher EP300 expression levels in EP300- mutated patient samples than in EP300- wildtype samples (Fig. 4e) remains unchanged on the RNA expression level comparison. + +9. Line 254-277 The authors showed a higher frequency of NOTCH1 mutation as well as EP300 mutation in the stemness subgroup. Therefore, these results may derive from the effect of NOTCH1 mutation. To investigate the effect of EP300 mutation, it is reasonable to compare EP300-wild and mutant cancers among the same subgroup because the genetic backgrounds of subgroups are different from each other. + +Response: We thank the reviewer for this comment. However, as shown in Fig. 4a, the mutational landscape figure among the four transcriptomic groups, mutations in EP300 and NOTCH1 occurred almost exclusively. Only one patient sample that had a missense mutation in EP300, also had a missense mutation in NOTCH1 (fourth sample in the Stemness panel), with another sample having a missense mutation in EP300 and copy number deletion in NOTCH1 (second sample in the Stemness panel). Thus, it is less likely that what we observed between EP300 mutant versus wildtype samples was drived from the effect of NOTCH1 mutations. In fact, we selected NOTCH1 mutated samples (excluding samples with copy number changes in NOTCH1) and compared them with NOTCH1 wildtype samples by differential expression analysis and GSEA. The results demonstrated that the dysregulated genes and pathways were completely different between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype (Supplementary Figure 2a- b of this rebuttal below). The most significantly upregulated pathways (GSEA results) for EP300 mutant vs. wildtype included mitotic prometaphase, mRNA processing and splicing, ATM and Fanconi pathway, spliceosome, DNA replication and chromosome maintenance, while signalling by BMP was the only upregulated pathway for NOTCH1 mutant vs. wildtype. For the most significantly downregulated pathways, the EP300 mutant had core matrisome, integrin1 pathway, cytokine- cytokine receptor interaction, ECM glycoproteins and a large number of immune pathways downregulated compared to wildtype, while the NOTCH1 mutant had RNA POL1 promoter opening, packaging of telomere ends, amyloids, telomere maintenance, meiotic synapsis and recombination and meiosis as top downregulated pathways compared to wildtype. In addition, there was no correlation in the global transcriptomic changes between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype (Supplementary Figure 2c, see below). Furthermore, there was no correlation in mRNA expression between EP300 and NOTCH1 (Supplementary Figure 2d). Therefore, all the results here suggest that our results observed for EP300 mutations were not derived from the effect of NOTCH1 mutations. We have addressed this in the revised manuscript following this reasonable comment. + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Supplementary Figure 2. Comparison of differentially expressed genes and pathways between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype. A, Overlap of significantly differentially expressed genes (limma \(p< 0.01\) ) between EP300 mut vs. wt and NOTCH1 mut vs. wt. B, Up- and downregulated pathways (GSEA FDR \(q< 0.05\) ) and the comparisons between EP300 (mut vs. wt) and NOTCH1 (mut vs. wt). C, Scatter plot of log2 fold changes for all the profiled genes between EP300 (mut vs. wt) and NOTCH1 (mut vs. wt). D, Scatter plot of mRNA expression between EP300 and NOTCH1.
+ +Of note, it is not possible to perform meaningful DE analysis comparing EP300 mutant vs wildtype within the same subgroup, as the number of mutated samples was too low in each subgroup, \(n = 1\) in differentiated, \(n = 2\) in immunogenic, \(n = 0\) in metabolic and \(n = 5\) in stemness groups. + +10. Line296-299 In Fig. 9c left panel, three subtypes other than the stemness subtype showed a comparable frequency of truncating mutations in wnt pathway genes. Therefore, because the prediction of the effect of mutations is more reliable for truncating mutation than for missense mutation, it seems that deleterious Wnt pathway mutations are similar. + +Response: We appreciated the reviewer's comment here. Our investigation here focussed on comparing the effect of mutations in Wnt pathways genes between stemness and other subtypes. We added one sentence in Line 364- 365 to make it clearer, "The stemness subtype also seemed to have the highest proportion of nonsense mutations in Wnt pathway genes". For the SIFT and PolyPhen- 2 analysis, we further clarified this as it was for "missense" mutations in Line 373. + +Minor points: + +Line 99- 101 They designated four subgroups based on known functional gene expression rather than GSEA. + +Response: We updated the wording here to "Functional annotation of representative genes in each cluster against known gene sets annotated these subtypes as..." In Line 102 + +Reviewer #2 (Remarks to the Author): Expert in tumour immunology, NK cells, and oesophageal cancer + +Comments for the manuscript entitled "Stemness and NK- like signatures define the poorest subtype + +<--- Page Split ---> + +of oesophageal squamous cell carcinoma" by Guozhong Jian et al. + +This referee aims to comment on the non- bioinformaticall part if this manuscript, leaving the comments for the precise bioinformatics to experts on bioinformatics and statistics. + +The manuscript presents an impressive molecular investigation of oesophageal squamous cell carcinoma (ESCC) from 120 Chinese patients. The authors have performed transcriptomics with GSEA and immune profiling, and mutational enrichment analyses, with the aim to find subtypes of tumors, and link this information to novel immune evasion strategies or drug sensitivity. The focus of the study is using bioinformatics, and the results from the authors own patient cohort is compared to previous studies on related cohorts, especially regarding the immune profiling strategy. There is no doubt that the study is of large importance, with ESCCs being one of the deadliest cancers worldwide today, with no effective therapies at hand. A study if this size, at this detailed molecular level, is difficult to find in the literature and will make a difference. Whereas the bioinformatics part of this study seems strong, the immunology and pathology sections are less robust. The manuscript is written in a very condensed scientific English, which makes it difficult to actually understand what has been done in the various panels of experiments. This also makes the reader insecure of what the authors actually have accomplished (the materials and methods (and figure legends) does not help or guide). To be able to fully understand this study, the manuscript has to be rewritten in a more detailed manner. Some comments are given below. + +Response: We are glad that the reviewer found our study interesting and important for the field. We also thank the reviewer for such constructive comments for consolidating our conclusions to improve the quality of this manuscript. We have rewritten the manuscript in many places and added more detail in materials and methods, figure legends for various panels of experiments, which further clarified our results and improved the robustness. + +1) Every panel of each figure needs to be explained better, both experimentally and statistically, to be able to understand what has been done. This goes for the material and methods part too. Controls should be added where appropriate, and in cases where a value is calculated compared to a control, the control needs to be described equally well. Full statistics should be explained also in Figure legends. + +Response: Many thanks for these careful comments, we have extensively addressed and revised our manuscript in all aspects raised by this reviewer. We have expanded and explained our figure panels, figure legends and results. + +2) Row 114. "The molecular subtypes present distinguished histological features". Is this based on these four photographs of four tumors? How representative are they? Where are the statistics behind this to be able to state this quite important finding? The authors should have access to all tumors, and thus be able to perform a tumor tissue array of paraffinized samples, to compare the histology of all 120 tumors on one single glass slide using a light microscope. This way statistics can be added. + +Response: This is the same comment as comment #3 of reviewer #1. Our statement of the molecular subtypes present distinguished histological features was based on our observation of whole tumour tissue sections. In order to quantitatively and comprehensively identify the features of each subtype, we had generated the digitised whole slide images of H&E histology slides for all the tumour tissue, we instead developed a deep- learning/Al model, which used five pre- trained models, namely Inception- V3, Inception- ResNet- V2, DenseNet- 121, VGG16 and ResNet- 50, and performed feature extraction and correlated these features with the four transcriptomic subtypes to + +<--- Page Split ---> + +identify significantly enriched histopathological features for each subgroup (see detail in the response of comment #3 of reviewer #1). These AI results still support our previous statement, with more quantitative measures to distinct molecular subtypes of ESCC based on the simple histopathological features. We believe this AI approach assessing the whole slide images of the tissue offers the more comprehensive overview of the tumour tissue compared to tissue array suggested here. Our deep- learning model identified significant enriched histopathological features in each transcriptomic subtype, which showed great consistency to the subtype annotation derived from signature genes of each subtype. + +3) Row 116-120. The authors describe these histological features using nomenclature of keratin pearls, extensive immune infiltration etc, without showing it or even presenting how this was done or annotated. Again, to say this a tumor tissue array would be good and should be annotated and evaluated statistically. The material and methods section should be updated accordingly, presenting how keratin pearls or immune cell infiltration was assayed. + +Response: We thank the reviewer for this insightful comment. Please see above response the AI model. We have also added the AI model part in the material and methods, and results. Furthermore, regarding immune infiltration, we also performed IHC of various immune cell markers, including CD4, CD8, and CD56, quantified and compared the IHC measurements among the transcriptomic and immune subtypes, in Fig2.c and Extend Data Figure 8a-b. The results demonstrated that immunogenetic subtype and the C2 subtype indeed had the highest level of immune cell infiltration, which was also supported by our AI pathology results (Extend Data Figure 1c). Regarding the quantification of keratin pearls, our deep-learning resource identified the DIFF- Feature significantly higher in the differentiated group compared to other groups. Tiles with high DIFF-Feature scores were enriched for keratin pearls (Figure 1c). we have added this part of the results in Line 152-169. + +4) Row 126. Xenograft models are presented in the text, but no ethical permit or precise description of how it was exactly performed in present in the text or materials and methods. Just very vague descriptions referring to Extended data Fig 3. What is Ext data Fig 3a? Explain each panel. Extended data Fig 3 is a typical representative for the concerns mentioned above of too limited explanations. + +Response: Thanks for the reviewer's comment. The ethical permit and details about Xenografts model were added in the Methods line 938- 940 in the revised manuscript. Besides, more results, descriptions and figure legends for new Extended data Fig. 4 (previously Extended data Fig. 3) were also added in the revised manuscript. + +5) Figure 2e, row 149, is this a Fisher's exact test? Where is the statistics shown in the figure? The figure legend is minimal. + +Response: This is Fisher's exact test we used to test if there is any difference in the proportion of transcriptomic subtypes between different immune subtypes. We have added the statistics in the figure and explained in detail in the figure legend, Fig. 2f (line 605- 607). + +6) Fig 2g. IHC controls are absent. A normal tissue should be used as control, and a cell line lacking (negative) or expressing (positive) should be shown to trust the IHC antibody specificity. Again, a tissue tumor array would be good to be able to conclude the results, only four samples are not enough to conclude. + +Response: Thanks for the reviewer's helpful suggestion. All negative control had been performed before conducting IHC assay, and these results was now provided in Extended data Fig. 7 and Fig. 9. + +<--- Page Split ---> + +Besides, all our staining were performed in paired slides including adjacent normal and cancer tissues, these results have been added in Extended data Fig 9. In fact, we had stained some markers in ESCC tissues microarrays (Shanghai Xinchao Biotechnology Co., Ltd.), while due to the sample area was too small and mostly devoid of submucosal adjunction tissue, so we finally used 99 pairs of original pathological sections for staining analysis of XCL1 and detailed results were provided in the revised manuscript Line 212- 219, Supplementary Table S4 and S5 of the revised manuscript to summarise the IHC staining of LGR6, XCL1 and CD160 in consecutive sections. In addition, the antibodies specificity were also confirmed by protein atlas or other users, and our Western blot results. + +7) Row 158-166. How is this IHC annotation performed and shown? The authors show statistics in the text that is not described in detail, and cannot be found in the figures or legends. Is it Pearson Chi-square tests or what fo authors mean with co-expression? Tables of annotations? This needs to be clearly shown. + +Response: We thank the reviewer for this insightful comment. We did IHC staining for detection of XCL1, CD160 and LGR6 in serial sections of each specimen. The H-score was calculated for the expression of LGR6 and XCL1 by the following formula. H-score value is \(= [1 \times (\text{% cells} 1+) + 2 \times (\text{% cells} 2+) + 3 \times (\text{% cells} 3+)\) in QuPath program. The number of cases coexpressing LGR6 and XCL1 or LGR6 and CD160 were counted and the percentage was calculated. We have included the detailed annotation of LGR6 and XCL1 IHC staining for all 99 available samples and CD160 IHC staining for 91 samples in the new Supplementary Table S4. Based on this table, we further counted the cases with LGR6+/XCL1+, LGR6+/XCL1-, LGR6-/XCL1+, LGR6-/XCL1- in the format of 2x2 contingency table to test if these two markers were expressed co-occasionally or not, using the two- tailed Fisher's exact test (Supplementary Table S5). This procedure was also done for the LGR6 and CD160 staining (Supplementary Table S4-5). Our IHC results show that LGR6 and XCL1 staining were significantly associated (co- stained or co- expressed) in our samples (two- tailed Fisher's exact test, \(p < 0.0001\) ), but LGR6 and CD160 staining were not significantly associated ( \(p = 1\) ). + +We have updated this section of results in Line 212- 219. + +8) From row 177 and on "NK-like tumor cells" are used to described tumor cells expressing CD160. It would be preferrable to not name the tumor cells "NK-like tumor cells", since they are tumor cells and not lymphocytes. + +Response: We agree with the reviewer's suggestion, and have changed the wording to "tumour cells expressing NK marker genes", and removed "NK-like tumour cells" from our manuscript(From line 171). We also changed "NK-like signatures" to "NK marker XCL1 related signatures" to be more explicit in the manuscript. + +9) Fig 3f. How is the IC50 experiment performed exactly. The materials and methods do not describe what is being shown in panel 3f. How are the numbers calculated? At what concentration, time and compared to what? If a Mann-Whitney test is used, what exact control are the bars compared to? + +Response: Following the reviewer's comments, we had revised and drug sensitivity analysis in the Method part Line 881- 897 "Drug sensitivity analysis". In the new Figure 3g (previous Fig. 3f), The IC50 experiment was performed on KYSE- 150, KYSE- 180, KYSE- 410 as normal controls and the corresponding XCL1 overexpressed cells from the same three cell lines. Mann- Whitney test is used to compare the IC50 values between the control vectors and the corresponding XCL1 overexpressing cells. To make it clear we now modified the figure labels: "control" changed to "vector", "XCL+" changed to "XCL". + +<--- Page Split ---> + +10) Figure 4 present the genomic mutational landscape. This is important. The authors continue with XCL1 as a promising biomarker for drug sensitivity, using cell lines, and EP300 for survival in the patient cohort. How can these be linked in patient material and survival? + +Response: We thank the reviewer for this comment. We further investigated the expression of XCL1 in our patient cohort, and found that high XCL1 expression was significantly associated with worse overall survival (Extended Data Fig 10c). This is consistent with our results of NK cells and their clinical association (Figure 2e), since XCL1 is one of the major markers of our NK cell in silico estimates. Furthermore, we also found that both XCL1 and XCL2 had much more elevated expression in patient tumour samples compared to their matched normal (Extended Data Fig 10a- b). All these data suggest that XCL1 may have a tumour promoting role in ESCC. We have added these in the manuscript line 230- 234. + +Furthermore, as demonstrated in Fig. 4b ESCC cell line mutational landscape, XCL1 high vs. low, \(36\%\) of XCL1 high cell lines had mutations in EP300, while there is no EP300 alteration in XCL1 downregulated cell line. This observation supports the potential association between XCL1 overexpression and EP300 mutations in the ESCC cancer cells. + +11) Figure 5, the authors present immune infiltration and association with clonal diversity, and is also important. It would be good to perform IHC panels on some basic immune populations of the tumors to be able to support the data from the Shannon diversity index. Immune exclusion of T cells compared to M2 macrophages, as well as NK cells would be interesting to see. If CD160 is expressed on tumor cells. + +Response: We have performed IHC on immune cell markers of CD4, CD8, CD56 and compared IHC measurement among the subtypes, in Fig 2c and Extend Data Figure 8. Consistent with our RNA- seq results, the IHC results demonstrated that the levels of these immune cells were significantly higher in immunogenic and C2 subgroups compared to other groups (Extended Data Fig 8 and Fig 2c). We also correlated the IHC measurements of immune cells with the Shannon diversity index (SDI) measured from the genomic data, and found the significantly negative correlations between them for CD8+ (correlation coefficient, \(r = - 0.29\) , \(p = 0.017\) ) and CD56+ ( \(r = - 0.274\) , \(p = 0.017\) ) stained cells (Extended Data Fig 8c), supporting our results of the potential interplay between immune infiltration and tumour clonal evolution (i.e., higher immune infiltration is associated with lower level of ITH, measured by Shannon diversity) (Fig. 5f). We have added this result in Extended Data Figure 8, and in Line 378 - 380. + +Regarding the expression of CD160, the mRNA expression of CD160 was the highest in C3 immune subgroup, but not in C2 subgroup (Extended Data Fig 6a), and the IHC of CD56 and CD160 (Extend Data Figure 7 and 9) further demonstrated that CD160 was not expressed by CD56+ NK cells but by tumour and dysplastic cells. Indeed, we observed the evidence of CD160 expressed by LGR6+ tumour cells in 25 out of 91 cases (27%) (Supplementary Table S5). We included the co- staining data of CD56, CD160 and LGR6 in consecutive sections in Extended Data Figure 9. However, across the whole cohort of 91 available samples, LGR6 and CD160 IHC staining were not significantly associated ( \(p = 1\) , i.e., not significantly co- expressed by the tumour cells across the cohort). + +(12) The manuscript needs to be rewritten, to add much more detail for each panel, to be able to understand what has been done. As it is now, it is difficult to interpret the results. + +<--- Page Split ---> + +Response: We have followed the reviewer's advice and added much more detail in the results, figure legends and Methods and Materials for various panels of experiments throughout the manuscript. + +Reviewer #3 (Remarks to the Author): Expert in cancer stem cells + +In this study Jiang et al., aims at defining novel molecular subgroups in human Oesophageal Squamous Cell Carcinoma (ESCC) by analysing the transcriptome and genome of a big cohort of ESCC from Chinese patients. + +The authors, using bulk- RNA sequencing, identify four distinct ESCC transcriptomic subtypes. Among them one shows the worst survival rate and is characterized by the expression of WFDC2, SFRP1, LGR6 and VWA2 genes ("stemness" subtype). The data obtained from the RNA sequencing analysis is then analysed using deconvolution methods to determine the tumor immune composition of the ESCC samples. Using this approach, they divide the tumors in three categories according to the content/type of immune cells present within the sample and identify a group of tumors showing high expression of NK- like gene signature, the group associated with the poorest survival rate. Interestingly, they observe that tumors showing high expression of XCL1 (gene upregulated within the NK gene signature and C3 immune type) present higher resistance to several drugs. Thirdly, the authors characterize the genomic landscape of the same cohort of patients and describe genomic landscapes similar to those described in the numerous genomic analyses that have been reported on ESCC (The Cancer Genome Atlas Research, N. et al. Nature 541, 169- 175 (2017); Song, Y. et al. Nature 509, 91- 95 (2014); Lin, D. C. et al. Nat. Genet. 46, 467- 473 (2014); Gao, Y. B. et al. Nat. Genet. 46, 1097- 1102 (2014)). Finally, the authors determine if there is any correlation between the transcriptomic and immune signatures and the mutational landscape of the ESCC analysed. + +The main criticism is that this study lacks accuracy as many of the statements are not well sustained or only based on correlations. There is a lack of validation of the transcriptomic and immune signatures in biological samples and lack of experiments in biological samples aimed at supporting the numerous correlations present in the study. These validations and experiments would certainly help to strengthen and confirm the message of the paper. + +Remarkably, there are some points that need to be further developed or clarified: + +1- Using bulk RNA- sequencing the authors classify the ESCC analysed in 4 different subtypes characterized by the expression of different markers, subtypes that show different morphological characteristics and patient survival rates (Figure 1). The authors claim that they are interested to characterize both the tumor and tumor microenvironment. However, they do not analyse if the genes found to be upregulated in the different subgroups are expressed by the tumor cells or by the tumor microenvironment, which is extremely relevant to validate and strengthen this key point the authors want to make. This validation could be accomplished by performing immunostainings for the different markers in tumors from the 4 ESCC subtypes or alternatively using techniques that would allow a deeper characterization of the different cell populations present in the samples (single cell RNA sequencing). Using the latter approach, a recent paper (Zhang, X., Peng, L., Luo, Y. et al. Nat Commun 12, 5291, 2021) identified eight different common expression programs of epithelial cells in ESCC tumors and characterized the populations present in the tumor microenvironment of the same tumors. + +Response: We thank the reviewer for such constructive comments here. We utilised the single cell RNA- seq data of 208,659 single cells from 60 individuals of ESCC (Zhang et al. Nat Commun 12, 5291, + +<--- Page Split ---> + +2021) to validate our subtype specific gene signatures. Based on the annotated cell clusters, we were able to see in which cell types / subtypes our signature genes were expressed. Out of the 208,659 cells, 44,122 were epithelial cells that were dominantly cancer cells (Zhang et al. Nat Commun. 2021). As shown in our Fig. 1a and Extended Data Figure 3, signature genes from differentiated, metabolic and stemness subtypes were mainly expressed by epithelial cells. Moreover, signature genes from these three subtypes seemed to be expressed by different subpopulations of epithelial cells, i.e., occupying different epithelial subclusters in UMAP. In fact, our differentiated subtype corresponds to the epithelial differentiation (Epi1/2) program identified by Zhang et al., with the overlap of many signature genes, such as LGALS7, LGALS7B, KRT16, KRT6B/C, FABP5 and LY6D of the Epi1 programme, S100A7/8/9, SPRR1A/B and SPRR2D of the Epi2 programme. Our metabolic subtype corresponds to the oxidative stress or detoxification (Oxd) program, with shared genes as CES1, ALDH1A1, ALDH3A1, AKR1C1/2/3 and GPX2 of the Oxd program. Although our stemness subtype was not characterised by the eight epithelial gene signatures of Zhang et al., the feature plot of LGR6, WFDC2 and SFRP1 in single cells clearly showed that these genes were expressed by a distinct subpopulation of epithelial cells (Fig. 1a and Extend Data Figure 3). As expected, signature genes of our immunogenic subtype were all expressed by non- tumour cells. For example, MS4A1, CD79A and MZB1 were expressed by B cells, CXCL9 was expressed mainly by myeloid cells, with some in fibroblasts, endothelial and pericytes (Fig. 1a and Extend Data Figure 3). Therefore, the single cell results further validated our findings derived from bulk tissue RNA- seq, and supported our four distinct transcriptomic subtypes. We have included this set of results in Line 118- 137. In addition, we have also done IHC for several immune cells characterisation, it is indeed that our four molecular subtypes show different immune cells infiltration (see our response to Reviewer 2 comment 11). + +2- In Figure 2 the authors identify a cluster, cluster 3, characterized by the expression of NK markers, again it is not clear if these NK markers are expressed by the tumor cells (staining for XCL1 and Lgr6 Fig2 g superior panel is too weak to be able to conclude anything and morphologically the tumor shown does not seem a "stemness" tumor) or if there is infiltration of NK cells or presence of NK cells surrounding the tumors (staining for a NK marker would be extremely helpful). Therefore the description of the immune infiltration and immune microenvironment is superficial and needs to be improved. In addition, only \(50\%\) of the stemness- subtype tumors could be classified as belonging to the immune cluster 3 (Fig 2e), so the statement "given the strong association between stemness and NK cell estimates- line 154- 155" is overstated and should be corrected. + +Response: We thank the reviewers for the insightful comment here. Our RNA- seq data showed that NK markers XCL1, XCL2 and CD160 were the highest in the C3 cluster (Fig 2b and Extended Data Fig6a). Following the reviewer's advice, we further stained NK cell marker CD56 in our cohort, and the IHC results showed that the level of CD56 was the highest in C2 cluster, but significantly lower in both C1 and C3 clusters (Fig 2c). This was also supported by the mRNA expression of other NK markers, such as NKG7 and KLRC1, being the highest in C2 cluster, but low in C3 and C1 clusters (Extended Data Fig 6a). These results suggest that the level of CD56+ NK cell infiltration was low in the C3 cluster. Following further inspection of the XCL1 and LGR6 IHC staining in stemness and other groups, we concluded that XCL1 were not expressed by NK cells (CD56+) in our tissues, instead by tumour cells and other dysplastic epithelial cells of submucosa glands. These results suggest that XCL1 was expressed by tumour cells and dysplastic cells of submucosa gland across our cohort. We have included the IHC staining results in Figure 2h, Extended Data Fig 6- 9, Supplementary Table S4- 5, and added the results in Line 212- 219. + +<--- Page Split ---> + +We also agree with the reviewer's comment regarding "the strong association between stemness and NK cell estimates", and have changed our wording throughout the manuscript to "there is a degree of positive correlation between stemness and NK estimate high subgroups". + +3- One of the genes that characterize Cluster 3 (NK- like signature) is XCL1. The authors show using GSEA that XCL1- high cells exhibit upregulation of drug metabolism of cytochrome P450, retinol metabolism and biological oxidations (line 185) and in line 106 the authors state "the metabolic subtype is associated with the upregulation of genes involved in drug metabolism by cytochrome P450 and retinol metabolism". Would this mean that tumors showing high XCL1 expression belong to the "metabolic subtype"? This is confusing and highlights that the link between XCL1 (NK- like) and "stemness subtype" or "metabolic subtype" should be better explained. + +Response: We thank the reviewer for this detailed observation. To further test how similar the pathway activity is for drug metabolism by cytochrome P450 and retinol metabolism between XCL1- high vs. low and metabolic vs. others comparisons, we compared the t- statistics derived from limma differential expression analysis (a statistics combining both log2 fold change 'magnitude' and p- value 'significance') for genes involved in these two pathways. As shown in the figures below (Supplementary Figure S3 of this rebuttal), there was a weak correlation in t- statistics between XCL1- high and metabolic subtypes for genes involved in drug metabolism by cytochrome P450 and retinol metabolism. This analysis suggests that different subsets of genes contributed to the upregulation of these two pathways seen in XCL- high cells and the metabolic subtype. Furthermore, there was also very minimum number of signature genes shared between XCL1- high and metabolic subtype. Therefore, there is no evidence that suggests tumours showing high XCL1 expression belong to the metabolic subtype. + +![PLACEHOLDER_18_0] + +
Supplementary Figure S3
+ +The association between immune and transcriptomic subtypes was based on Fig. 2f. Out of 31 samples in C3 (NK high), 15 were from the stemness, 6 from metabolic, 8 from differentiated and 2 from immunogenic subtypes, suggesting there is a degree of enrichment of stemness samples in the C3 subgroup. We have followed the reviewer's advice, and rephrase the association between stemness and NK estimate high subgroups throughout the manuscript. We have also added a sentence in Line 248- 250, "it is worth noting that different subsets of genes contributed to the upregulation of drug metabolism by cytochrome P450 and retinol metabolism were seen in XCL- high cells and the metabolic subtype" to further clarify the point here. + +4- In Figure 2g, Extended Data Figure 5c and line 164- 172, the authors state that XCL1 is exclusively expressed in cancer cells showing adenocarcinoma morphology. Should we consider all XCL1- expressing tumours adeno- squamous cell carcinomas? If so, the authors should repeat the analysis + +<--- Page Split ---> + +by studying the ESCC and adeno- squamous cell carcinomas separately as relevant differences may be found in terms of transcriptomics, genomics and response to chemotherapy. + +Response: We appreciate the reviewer's insightful comment here. Following this reviewer's comments, we comprehensively reviewed the whole section of resected samples of IHC staining for XCL1 expression from 99 available samples, XCL1 espression was predominantly expressed in cancer cells showing adenocarcinoma morphology, but some squamous carcinoma cells also expressed XCL1. Therefore, we have updated our description and conclusion in our revised manuscript accordingly. Esophageal adeno- squamous cell carcinoma is a very rare disease clinically. It is an extremely difficult task to assemble an Esophageal adeno- squamous cell carcinoma sample cohort in a decent size that allows to investigate the transcriptomic / genomic landscape with enough statistic power. To study the transcriptomics, genomics and response to chemotherapy of adeno- squamous cell carcinomas is an extremely interesting and valuable topic scientifically and clinically. However, this is beyond the scope of our current study. + +5- The authors suggest that XCL1- high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +Response: We thank the reviewer for this comment. To further support our results based on RNA- seq, we utilised the single cell RNA- seq data from Zhang et al. (Nat Commun 12, 5291, 2021) to perform further studies. Focussing on the epithelial cells, we were able to identify 515 XCL1 positive cells (expression level CPM>0) and 32,944 XCL1 negative cells (expression level =0). We then calculated the expression level of each gene programme of cell cycle on single cell level (e.g., REACTOME_CELL_CYCLE_CHECKPOINTS, REACTOME_CELL_CYCLE_MITOTIC) using Seurat AddModuleScore function, and showed that XCL1 positive (XCL1+) cells had significantly lower cell cycle activities than XCL1 negative (XCL1-) cells (Wilcox test, \(p = 7.48e - 06\) for REACTOME_CELL_CYCLE_CHECKPOINTS; \(p = 0.001\) for REACTOME_CELL_CYCLE_MITOTIC), which is consistent to our data. We have added this results in Fig. 3e and Line 256- 259. Of note, overexpression of XCL1 does not significantly affect the cell proliferation (see extended data Fig 11d), the reviewer's suggestion to do Brdu/Edu incorporation might be helpful, which is to be performed in a separate project. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have substantially clarified the figures and manuscript, and addressed the majority of points raised, but still the first point remained. + +In the Results section (lines 97- ), they claimed that they first performed unsupervised clustering and then identified gene signatures based on the classification. However, in their rebuttal, they explained that they chose \(k = 4\) (the number of clusters) based on NMF cophenetic coefficient and heterogeneous molecular signatures. As these molecular signatures appear to be predefined, they intentionally opted for four clusters, which represent differentiation, immunogenicity, metabolic characteristics, and stemness. If this is indeed the case, they should have initially mentioned the prior knowledge of the four classifications. + +Reviewer #2 (Remarks to the Author): + +The authors have answered my comments and improved the clarity/statistics in the text. + +Reviewer #3 (Remarks to the Author): + +The data and figures have improved substantially. However, in this revision the authors have only partially addressed my previous questions and comments. The new version of manuscript is difficult to follow as it is written in a rather condensed manner and the supplementary figures do not follow the same order as the text (ie. Extended Data Fig 6b). + +There are some points that need to be addressed: + +1. In Figure 1a lower panel the authors analyse the scRNAseq data from another study (Zhang et al). However, it is not possible to interpret this figure 1a without going to Ext DataFig 3. The main figures of an article should be self-explanatory. For this reason, the description of the clusters should be in Figure 1a not in a supplementary figure. Or alternatively the authors should move all the scRNAseq to Ext Data Fig 3. + +2. In Figure 1c the authors should better describe and annotate within the images the features characteristic of each of the subtypes. And ideally, validate the results of the bulk RNA seq using in situ hybridization or immunofluorescence. + +<--- Page Split ---> + +3. The quality of many of the stainings presented are poor. + +Fig 2 and Ext Data Fig 9: stainings for XCL1, CD56 and CD160 not to work. In Ext Data Fig 9 XCL1 and the rest of the stainings are not "matched serial sections of tumour tissues" as described in the text line 208. The staining of serial sections for the markers described is essential to prove the authors' hypothesis and should be performed accurately. + +The images for LGR6 staining need to be improved. + +4. In line 136 the authors claim "Therefore, the single cell results further validated our findings derived from bulk tissue RNA-seq, and supported our four distinct transcriptomic subtypes". In the scRNAseq data from Zhang et al the stemness subtype is not described, so this statement should be corrected. + +5. In line 248 the authors claim "It is worth noting that different subsets of genes that contributed to the upregulation of drug metabolism of cytochrome P450 and retinol metabolism were seen in XCL-high cells and metabolic subtype". How did the authors reach that conclusion? What and where is the data that made them conclude that? This point should be better explained. + +6. The authors did not reply to my previous question number 5: + +The authors suggest that XCL1-high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +The answer that they provide is a correlation based on the data of the scRNA seq from Zang et al. and from that correlation it cannot be concluded that the cells are slow- cycling/ quiescent. Performing BrdU/EdU incorporation studies in cell lines or staining for quiescence markers in human samples is relatively quick to accomplish and needed in order to conclude such a statement. + +8. In the abstract line 50 the authors state "functional mutation enrichment in the Wnt signalling". What does this mean: mutations that lead to the in/activation of the Wnt signalling pathway? This should be clarified. + +Minor comment: + +The image scale in Ext Data Fig7 needs to be improved. + +<--- Page Split ---> + +Reviewer #4 (Remarks to the Author): Expert in oesophageal cancer subtypes, genomics, and bioinformatics + +Disclaimer: I did not participate in the first round of review of the initial submission, and I am providing my review on their revised work. + +In this manuscript, the authors performed whole- exome sequencing and bulk RNA- seq on 120 Chinese ESCC patients. They identified 4 RNA- defined subtypes: differentiated, metabolic, immunogenic and stemness. Using deep- learning model, they showed that these 4 subtypes were associated with different histological features, implying their biological basis. Moreover, they identified that NK cell markers including XCL1 and CD160, were surprisingly expressed by a subset of tumor cells. XCL1 were followed upon and its expression confers the sensitivity of ESCC cells to chemotherapeutic drugs. + +This is a comprehensive work of tour de force: there were large amount of sequencing data, bioinformatic analyses, massive imaging data processing, as well as fairly extensive biological investigations. Some of the findings are strong and may have significant implications, such as the identification of 4 subtypes and XCL1 investigation. However, I do find a number of weaknesses which need to be addressed. + +Major issues: + +1) What is the relationship between these newly designated subtypes with the TCGA subtypes? This can be done by looking at shared pathways enriched in different subtyping schema. For example, in TCGA, ESCC1 has frequent upregulation of oxidative pathways. Is ESCC1 similar as the Metabolic subtype here? + +2) The validation using external single-cell RNA-seq data is useful but somewhat superficial. What was shown was merely that the selected genes from different subtypes could be expressed by different clusters from scRNA-seq, which is largely expected. What really needs to be addressed is do these different clusters from scRNA-seq show similar biology or transcriptional programs to bulk RNA-seq defined subtypes? + +3) The investigation of SFRP1 needs further development. The authors described that IHC staining was done on its protein, but did not mention how many tumor and normal samples were stained. Is SFRP1 expressed higher in tumor vs normal samples? What is the percentage of SFRP1 expression in tumor samples? Since it was proposed as a stemness related genes, does it correlate with the differentiation status of the tumors? The knockdown efficiency (Fig. s1e,f) appears poor, and the WB needs to be quantified. + +4) Associating histological features to different transcriptomic subtypes is helpful and can support their biological underpinnings. However, at this scale (Fig.1C), the histological features are difficult to discern for most readers who are not trained pathologists. For example, it is hard to see immune cells or eosinophilic cytoplasm at this resolution. It would be very helpful to add certain IHC markers to make these histological features conspicuous. + +<--- Page Split ---> + +5) The investigation of XCL1 in cancer cells was a highlight in this work. However, I could not find any IHC image showing strong XCL1 staining. The ones included, such as Fig.2h, Fig.5c, were very weak. The authors need to show convincing strong IHC signals of XCL1 in cancer cells, since this is one of their key findings. + +6) Line 224-228. "Interestingly, we observed that XCL1-expressing dysplastic cells in the submucosal gland in most of the cases are completely separated from the squamous cell carcinoma, suggesting that this subgroup of patients might concurrently have both squamous cell carcinoma and adenocarcinoma or this adeno-squamous carcinoma might be derived from submucosa gland epithelial cells". These are indeed very interesting! However, no data was shown. Can the authors perform a statistical analysis to compare the histology of these tumors vs. XCL1 expression? + +7) Line 256-258, it is a bit concerning that XCL1 is only expressed in 515 out of 33459 (1.5%) total epithelial cells from the single-cell RNA-seq data. Can the authors explain why such low frequency? Is it because of the high cutoff used? This low positivity negatively affects the significance of the biological contribution of XCL1 in ESCC. + +## Minor points: + +1) The RNA-seq and WES data are still under controlled access and not publicly available. I think it is Nat Communication's policy that these data will need to be made publicly available upon acceptance. +2) "an independent cohort of 65 ESCC patients" in Fig.1e was not described in the methods or results. Where were these samples from? Were they all primary tumors? + +Reviewer #5 (Remarks to the Author): Expert in digital pathology and deep learning + +In this article, the authors propose a new subclassification of esophageal squamous cell carcinoma. This is clinically interesting because most previous efforts at subtyping this disease also included other histologies of esophageal cancer such as adenocarcinomas or gastroesophageal junction tumors. It is sensible to focus exclusively on squamous cell esophageal cancer and attempt to subtype it. + +My expertise is specifically in digital pathology, so I am reviewing the digital histopathology model which the authors utilized. + +Unfortunately, there are some concerns regarding the deep learning analysis. + +1. Some methodological details are not entirely clear. For instance, what does a downsampling factor of 64 fold mean? The authors should specify their final resolution in micrometers per pixel and then provide the absolute pixel size for their tiles. + +2. Additionally, they mention that they manually discarded some images. This is concerning, and it is crucial for them to clearly state why these images were discarded. What precisely constituted "poor quality"? Moreover, it would be beneficial to know how many images per class were discarded. The + +<--- Page Split ---> + +manuscript would benefit from a CONSORT- style diagram to elucidate these points. + +3. It is also vital that the study adheres to the STARD (or similar) guidelines, ensuring that all boxes in this guideline are ticked. + +4. Regarding the design of the algorithm, the authors mention that they extracted features with five pretrained neural networks. However, the rationale for this decision is unclear. This choice, which appears quite uncommon, needs further explanation. Typically, one would use just a single robust network, selected through a hyperparameter tuning experiment on a dedicated tuning set. Alternatively, one might opt for a network that has been validated in previous studies. Ideally, the contemporary standard involves not using a network pre-trained on ImageNet, but rather one that has been pretrained in a self-supervised manner on histopathology images, such as the RetCCL network or the CTransPath network. In summary, the image analysis algorithm presented seems non-standard. While the authors might have had valid reasons for these unconventional design choices, they need to elucidate their reasoning in the manuscript. It would be even more beneficial if the authors employed a state-of-the-art pipeline (such as CLAM or the one from Wagner et al., Cancer Cell, 2023), or if they presented benchmarking experimental results showing their methods' superiority compared to more conventional methods. + +5. Lastly, there are concerns regarding the statistical measures for the gene expression classification. The authors used a t-test, but they did not specify whether all the prerequisites for a t-test were met. This information needs to be explicitly stated. + +<--- Page Split ---> + +## Point by point responses to the Reviewers comments + +Reviewer #1 (Remarks to the Author): + +The authors have substantially clarified the figures and manuscript, and addressed the majority of points raised, but still the first point remained. + +In the Results section (lines 97- ), they claimed that they first performed unsupervised clustering and then identified gene signatures based on the classification. However, in their rebuttal, they explained that they chose \(k = 4\) (the number of clusters) based on NMF cophenetic coefficient and heterogeneous molecular signatures. As these molecular signatures appear to be predefined, they intentionally opted for four clusters, which represent differentiation, immunogenicity, metabolic characteristics, and stemness. If this is indeed the case, they should have initially mentioned the prior knowledge of the four classifications. + +Response: Thanks for this reviewer's appreciation on our substantial work done in the revised manuscript. We did not predefine any molecular signatures before the NMF clustering. NMF clustering is an unsupervised clustering algorithm that identifies patient clusters simply based on the expression values of input genes, i.e., in our case, top 1,500 variable genes with largest mean absolute deviation values across samples were used. Although \(k = 2\) gave the best cophenetic correlation \(r = 0.99\) , this was followed by almost equally great performances of \(k = 4\) and \(k = 3\) , with both having the cophenetic correlation \(r > 0.98\) (Extended Data Fig. 1a). As \(k = 4\) uncovered the level of heterogeneity and granularity of transcriptomic patterns in a finer resolution, and samples were evenly distributed among the four groups, \(k = 4\) was therefore selected. This has led to the discovery of our four transcriptomic clusters. + +We have updated the wording in Methods as "Although \(k = 2\) gave the best cophenetic correlation \(r = 0.99\) , \(k = 4\) also achieved great clustering performance with cophenetic correlation \(r = 0.985\) , and the latter ( \(k = 4\) ) uncovered the level of heterogeneity and granularity of transcriptomic patterns in a finer resolution, thus was selected for our investigation", highlighted in line 742- 745. + +Reviewer #2 (Remarks to the Author): + +The authors have answered my comments and improved the clarity/statistics in the text. + +Response: We really appreciate Reviewer #2's positive response. + +Reviewer #3 (Remarks to the Author): + +The data and figures have improved substantially. However, in this revision the authors have only partially addressed my previous questions and comments. The new version of manuscript is difficult to follow as it is written in a rather condensed manner and the supplementary figures do not follow the same order as the text (ie. Extended Data Fig 6b). + +There are some points that need to be addressed: + +1. In Figure 1a lower panel the authors analyse the scRNAseq data from another study (Zhang et al). + +<--- Page Split ---> + +However, it is not possible to interpret this figure 1a without going to Ext DataFig 3. The main figures of an article should be self- explanatory. For this reason, the description of the clusters should be in Figure 1a not in a supplementary figure. Or alternatively the authors should move all the scRNAseq to Ext Data Fig 3. + +Response: Following the reviewer's helpful comment, we have moved all single cell RNA- seq related data to the new Ext Data Fig 3 and 4, and also created a new Ext Data Fig 4 regarding the subtypes of ESCC epithelial single cells, as requested by the comment #2 of Reviewer #4. + +2. In Figure 1c the authors should better describe and annotate within the images the features characteristic of each of the subtypes. And ideally, validate the results of the bulk RNA seq using in situ hybridization or immunofluorescence. + +Response: Thanks for this helpful comment. We have redone the Fig 1c with the inserted high magnification pictures to address the specific features of each subtype, in addition to the further explanation in the figure legend. We completely agree with this reviewer's comment, in situ hybridization or immune- fluorescence staining is an ideal way to validate the bulk RNA sequencing data, regrettably we were not able to do this in an available time frame due to the difficulty to find specific probes and antibodies specifically recognising the specific markers in each subtype of ESCC. However, one of the major findings in this manuscript is that we developed AI pathology (see new Extended Data Fig. 6), which can correlate and predict the subtype of ESCC based on the H&E morphology. The features described in Fig 1C with further annotation may be sufficient to support the conclusion of this manuscript. Furthermore, we have also validated our transcriptomic subtypes using the single cell RNA-seq data of 60 ESCC samples (new Ext Data Fig 3 and 4). Therefore, we hope the reviewer would agree that the data and results supported from the deep- learning histopathology model and single- cell RNA-seq were strong and convincing to support the subtypes derived from our bulk RNA-seq. + +3. The quality of many of the stainings presented are poor. + +Fig 2 and Ext Data Fig 9: stainings for XCL1, CD56 and CD160 not to work. In Ext Data Fig 9 XCL1 and the rest of the stainings are not "matched serial sections of tumour tissues" as described in the text line 208. The staining of serial sections for the markers described is essential to prove the authors' hypothesis and should be performed accurately. + +The images for LGR6 staining need to be improved. + +Response: Apologies for this. We found that the pictures in the convert version of pdf file for the reviewer's review were indeed not clear due to the compressed file. We have now provided the high quality of all pictures in Fig 2h, Extended Data Fig 8- 9 and Extended Data Fig 11 in the new version. In particular, we have redone Ext Data Fig 11 (the previous Ext Data Fig 9) for XCL1 staining using the matched serial sections of tumour tissues and the corresponding normal tissues in our revised manuscript (Ext Data Fig 11 panel a and panel b). In particular, the data demonstrated the co- staining of LGR6 and CD160 and/or XCL1 in many ESCC tumour cells which were CD56 negative. + +We sincere hope that this reviewer will be satisfied with the new set of pictures. + +4. In line 136 the authors claim "Therefore, the single cell results further validated our findings + +<--- Page Split ---> + +derived from bulk tissue RNA- seq, and supported our four distinct transcriptomic subtypes". In the scRNAseq data from Zhang et al the stemness subtype is not described, so this statement should be corrected. + +Response: We thank the reviewer for this comment. This comment is highly related to the second comment from Reviewer #4. We have updated this section as follows: + +To further look into the heterogeneity and granularity of transcriptional programmes of ESCC epithelial cells, the NMF clustering with \(k = 10\) factors was performed on \(\sim 44,000\) epithelial cells of Zhang et al., Nat Comms 2021 (similar techniques also used in Gojo et al., Cancer Cell 2020, Lai et al., Int J Cancer 2021 and DeMartino et al., Nat Comms 2023, and many others), followed by the differential expression analysis using the Seurat "FindMarkers" function to identify top differentially expressed genes. Signature genes for each cluster were identified based on adjusted p- value \(< 0.0001\) and log2 fold change \(>1\) . Top 50 signature genes were then selected based on the log2 fold change for each cluster (new Extended Data Fig. 4). The NMF clusters were annotated based on their signature genes and up/down- regulated pathways. Their corresponding expression programmes of Zhang et al., 2021 and our related transcriptomic subtypes were identified based on shared signature genes (Extended Data Fig. 4). The NMF Cluster 5 and 10 appeared to correspond to the differentiated subtype, with Cluster 4 corresponding to the metabolic subtype, Cluster 6 corresponding to the immunogenic subtype, while Cluster 1 shared many stemness signature genes, such as SFRP1, WFDC2 and LGR6 (Extended Data Fig. 4). Cluster 1 also had significantly upregulated Wnt signalling and NCAM1 interactions, and the most downregulated keratinization / cornified envelope and metabolism pathways, which were all signature pathway activities for the stemness subtype. Reassuringly, all previous eight expression programmes of epithelial cells from Zhang et al., 2021 were identified in our single- cell NMF clusters. These single cell results further validated and support the robustness of our four transcriptomic subtypes derived from bulk tissue RNA- seq. + +We have updated this section in Results section highlighted in line 125- 147 and Methods section line 909 - 916. + +5. In line 248 the authors claim "It is worth noting that different subsets of genes that contributed to the upregulation of drug metabolism of cytochrome P450 and retinol metabolism were seen in XCL-high cells and metabolic subtype". How did the authors reach that conclusion? What and where is the data that made them conclude that? This point should be better explained. + +Response: We previously showed this result only in our responses to the reviewers' comments, but not included in the main text, please see below (in green font) from the rebuttal of last round. We have now included this figure in the new Extended Data Fig. 13 and the associated results in the figure legend to clarify and support this point here, in new Line 267- 270 (Extended Data Fig. 13). + +"Response: We thank the reviewer for this detailed observation. To further test how similar the pathway activity is for drug metabolism by cytochrome P450 and retinol metabolism between XCL1- high vs. low and metabolic vs. others comparisons, we compared the t- statistics derived from limma differential expression analysis (a statistics combining both log2 fold change 'magnitude' and p- value 'significance') for genes involved in these two pathways. As shown in the figures below (Supplementary Figure S3 of this rebuttal), there was a weak correlation in t- statistics between XCL1- high and metabolic subtypes for genes involved in drug metabolism by cytochrome P450 and retinol metabolism. This analysis suggests that different subsets of genes contributed to the upregulation of these two pathways seen in XCL- high cells and the metabolic subtype. Furthermore, there was also very minimum number of signature genes (i.e., significantly upregulated genes) + +<--- Page Split ---> + +shared between XCL1- high and metabolic subtype. Therefore, there is no evidence that suggests tumours showing high XCL1 expression belong to the metabolic subtype. + +## Supplementary Figure S3 + +![PLACEHOLDER_28_0] + + +We have also added a sentence in Line 256- 258, "it is worth noting that different subsets of genes contributed to the upregulation of drug metabolism by cytochrome P450 and retinol metabolism were seen in XCL- high cells and the metabolic subtype" to further clarify the point here." + +6. The authors did not reply to my previous question number 5: + +The authors suggest that XCL1- high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +The answer that they provide is a correlation based on the data of the scRNA seq from Zang et al. and from that correlation it cannot be concluded that the cells are slow- cycling/ quiescent. Performing BrdU/EdU incorporation studies in cell lines or staining for quiescence markers in human samples is relatively quick to accomplish and needed in order to conclude such a statement. + +Response: Following this insightful comment, we did Edu incorporation studies and cell cycle analysis of XCL1 overexpressed cell lines and the counterpart control cell line, the detailed results were shown in the new Extended Data Fig. 14, and also included the method section Line 965- 975. It seemed that there was no significant difference of Edu incorporation between the XCL1 overexpressed cell lines and the control cell lines. This suggests that XCL1 did not seem to affect the G1/S phase of cell cycle although mRNA expression levels of cell cycle related genes were significantly reduced in XCL1 high cells compared to low cells. This warrants further investigation. We have rephrased our results of this part as follows in Results Line 278- 282 in our revised version. + +"Although mRNA expression levels of cell cycle related genes were reduced in XCL1- high cells compared to XCL low cells, XCL1 overexpression in ESCC cells did not functionally affect cell cycle (Extended Data Fig. 14). More work is needed to further elucidate its role in cell cycle and other pathways associated with ESCC." + +In addition, we have rephrased the term of "cell cycle activities" with the term of "cell cycle gene set enrichment scores" to more accurately reflect the results derived from RNA- seq and single- cell RNA- seq gene set enrichment analysis, as shown in Results Line 273- 278. + +<--- Page Split ---> + +8. In the abstract line 50 the authors state "functional mutation enrichment in the Wnt signalling". What does this mean: mutations that lead to the in/activation of the Wnt signalling pathway? This should be clarified. + +Response: We thank the reviewer for raising this point. This point was previously made clear in our Results "Functional mutation enrichment in pathways among ESCC subtypes" section. + +Our results shown in Figure 5d/e and Extended Data Fig. 18 suggest that there were significantly more functionally relevant mutations in the Wnt/b-catenin signalling genes in the stemness subtype, compared to other subtypes (Results Line 373- 377). In Results Line 379- 385, "we then evaluated whether the pathway functional mutation enrichment affected the expression of pathway genes, and found that mutation enrichment in Wnt/β- catenin signalling, inflammatory response and hypoxia were positively correlated with pathway gene expression activities for the corresponding ESCC subtypes (Fig. 5e), suggesting that high level of Wnt signalling expression in the stemness group could be a consequence of functional mutations in regulators of the Wnt pathway, and these functional mutations were the most enriched in stemness samples". Thus, our results did support that these functionally relevant mutations may lead to the activation of the Wnt pathway. However, we were careful with our wording, as such observation was not validated by further biological function studies, which is beyond the scope of this study. + +Minor comment: + +The image scale in Ext Data Fig7 needs to be improved. + +Response: We have done this in our revised manuscript, now the new Ext Data Fig 9. + +Reviewer #4 (Remarks to the Author): Expert in oesophageal cancer subtypes, genomics, and bioinformatics + +Disclaimer: I did not participate in the first round of review of the initial submission, and I am providing my review on their revised work. + +In this manuscript, the authors performed whole- exome sequencing and bulk RNA- seq on 120 Chinese ESCC patients. They identified 4 RNA- defined subtypes: differentiated, metabolic, immunogenic and stemness. Using deep- learning model, they showed that these 4 subtypes were associated with different histological features, implying their biological basis. Moreover, they identified that NK cell markers including XCL1 and CD160, were surprisingly expressed by a subset of tumor cells. XCL1 were followed upon and its expression confers the sensitivity of ESCC cells to chemotherapeutic drugs. + +This is a comprehensive work of tour de force: there were large amount of sequencing data, bioinformatic analyses, massive imaging data processing, as well as fairly extensive biological investigations. Some of the findings are strong and may have significant implications, such as the identification of 4 subtypes and XCL1 investigation. However, I do find a number of weaknesses which need to be addressed. + +We thank the reviewer for the positive response of our study. + +<--- Page Split ---> + +Major issues: + +1) What is the relationship between these newly designated subtypes with the TCGA subtypes? This can be done by looking at shared pathways enriched in different subtyping schema. For example, in TCGA, ESCC1 has frequent upregulation of oxidative pathways. Is ESCC1 similar as the Metabolic subtype here? + +Response: We thank the reviewer for this comment. The TCGA ESCC molecular subtypes 1/2/3 were derived from the clustering using multi- omics data including mutations, mRNA/miRNA expression, DNA methylation and copy number aberrations, while our four subtypes were only based on transcriptomics. For the 90 TCGA ESCC samples, they came from patients with very diverse ethnic background, including Brazil \((n = 15)\) , Canada \((n = 4)\) , Russia \((n = 12)\) , Ukraine \((n = 4)\) , United States \((n = 14)\) and Vietnam \((n = 41)\) , while our 120 samples all came from a high ESCC incidence area (Henan Province) in China. Therefore, it is not feasible to compare the subtypes derived from different omics technologies and different ethnic background. However, we did some analysis of association between our subtypes and TCGA subtypes, as shown in Figure 4A (mutation oncoplot) and addressed in the Discussion, there was no association in mutations profiles between TCGA and our subtypes. + +Following the reviewer's advice, we also performed the differential expression analysis and gene set enrichment analysis between TCGA ESCC subtypes using TCGA mRNA expression data. Only ESCC1 \((n = 50,56\%)\) had three pathways upregulated at an FDR level \(< 0.25\) , including RESPONSE_TO_OXIDIZED_PHOSPHOLIPIDS (FDR \(= 0.15\) ), and ESCC2 \((n = 36,40\%)\) and ESCC3 \((n = 4,4\%)\) had no significantly up- or down- regulated pathways. For ESCC1, apart from oxidized phospholipids, no other metabolic and oxidative pathways were significantly upregulated compared to ESCC2/3. Therefore, based on all these data, there did not seem to be strong associations between TCGA and our subtypes, as they were derived from different omics signatures and different ethnic background. + +2) The validation using external single-cell RNA-seq data is useful but somewhat superficial. What was shown was merely that the selected genes from different subtypes could be expressed by different clusters from scRNA-seq, which is largely expected. What really needs to be addressed is do these different clusters from scRNA-seq show similar biology or transcriptional programs to bulk RNA-seq defined subtypes? + +Response: We really appreciate the reviewer for this insightful comment. To further investigate the heterogeneity and granularity of transcriptional programmes of ESCC epithelial cells, the NMF clustering with \(k = 10\) factors was performed on \(\sim 44,000\) epithelial cells of Zhang et al., Nat Comms 2021 (similar techniques also used in Gojo et al., Cancer Cell 2020, Lai et al., Int J Cancer 2021 and DeMartino et al., Nat Comms 2023), followed by the differential expression analysis using the Seurat "FindMarkers" function to identify top differentially expressed genes, as well as gene set enrichment analysis for each cluster. Signature genes for each cluster were identified based on adjusted p-value \(< 0.0001\) and log2 fold change \(>1\) . Top 50 signature genes were then selected based on the log2 fold change for each cluster (new Extended Data Fig. 4). The NMF clusters were annotated based on their signature genes and up/down-regulated pathways. Their corresponding expression programmes of Zhang et al., 2021 and our related transcriptomic subtypes were identified based on shared signature genes (Extended Data Fig. 4). The NMF Cluster 5 and 10 appeared to correspond to our differentiated subtype, with Cluster 4 corresponding to the metabolic subtype, Cluster 6 corresponding to the immunogenic subtype, while Cluster 1 shared many stemness signature genes, such as SFRP1, WFDC2 and LGR6 (Extended Data Fig. 4a). Cluster 1 also had significantly upregulated Wnt signalling and NCAM1 interactions, and the mostly downregulated keratinization / cornified envelope and + +<--- Page Split ---> + +metabolism pathways, which were all signature pathway activities for the stemness subtype. Reassuringly, all previous eight expression programmes of epithelial cells from Zhang et al., 2021 were identified in our single cell NMF clusters. These single cell results further validated and support the robustness of our four transcriptomic subtypes derived from bulk tissue RNA- seq. + +We have updated this section in Results section line 125- 147 and Methods section line 909- 916. + +3) The investigation of SFRP1 needs further development. The authors described that IHC staining was done on its protein, but did not mention how many tumor and normal samples were stained. Is SFRP1 expressed higher in tumor vs normal samples? What is the percentage of SFRP1 expression in tumor samples? Since it was proposed as a stemness related genes, does it correlate with the differentiation status of the tumors? The knockdown efficiency (Fig.s1e,f) appears poor, and the WB needs to be quantified. + +Response: SFRP1 was found as one of a set of genes showing the overexpression of mRNA in the Stemness group compared to other three groups based on the differential RNA expression in 120 tumour samples of ESCC. The frequency of SFRP1 protein expression was low in human ESCC, IHC assay revealed SFRP1 protein was positive in \(4.3\%\) (3/70) of ESCC tissue and no positive in the matched normal samples. We have provided this detailed data in our revised manuscript, Line 155- 158. + +Although SFRP1 is a stemness related genes, its expression does not significantly correlate with the differentiation status. The knockdown efficiency in WB is quantified, shown by Ext Data Fig 5 panel g and h, indicating significant \(20 - 40\%\) knockdown efficiency in KYSE- 520 cells and \(\sim 50\%\) knockdown efficiency in KYSE- 450. + +4) Associating histological features to different transcriptomic subtypes is helpful and can support their biological underpinnings. However, at this scale (Fig.1C), the histological features are difficult to discern for most readers who are not trained pathologists. For example, it is hard to see immune cells or eosinophilic cytoplasm at this resolution. It would be very helpful to add certain IHC markers to make these histological features conspicuous. + +Response: We fully understood this reviewer's comment, similar as the comment #2 from Reviewer 3. We have redone the Fig 1c with the inserted high magnification pictures to address the specific features of each subtype, with more explanation in the text and figure legend. Please see more our response to the comment 2 from the reviewer 3. We have done some IHC for immune cells, such as CD4, CD8 and CD56, which showed significantly higher expression in immunogenic group (see Figure 2c, Extended Data Fig 9 and Fig 10). Given the lack of specific IHC markers to differentiate the histopathological features presented in each subtype in an available time frame, we are not able to provide more IHC staining to make these histopathological features conspicuous as suggested by the reviewer although it would be indeed helpful. However, we have developed a deep- learning AI histology model that strongly correlated histological features with transcriptomic subtypes. This AI model identified subtype specific histological features and these distinct features corresponded nicely with their respective transcriptomic subtypes. Please see the section of "Distinct histological features among transcriptomic subtypes" Line 164- 188 for more detail. Furthermore, we have also validated our transcriptomic subtypes using the single cell RNA-seq data of 60 ESCC samples (new Ext Data Fig 3 and 4). Therefore, we hope the reviewer would agree that the data and results supported from the deep- learning histopathology model and single- cell RNA-seq were strong and convincing to support the subtypes derived from our bulk RNA-seq. + +<--- Page Split ---> + +5) The investigation of XCL1 in cancer cells was a highlight in this work. However, I could not find any IHC image showing strong XCL1 staining. The ones included, such as Fig.2h, Fig.5c6, were very weak. The authors need to show convincing strong IHC signals of XCL1 in cancer cells, since this is one of their key findings. + +Response: Apologies for this. We found that the pictures in the converted version of pdf file for the reviewers were indeed not clear somehow. We now have provided the high quality of all pictures with higher magnification, which demonstrate the real positive staining of XCL1 in cancer cells although the overall staining of XCL1 staining is weaker than other markers, in Fig 2h, new Ext Data Fig 8 and Ext Data Fig 11. + +6) Line 224-228. "Interestingly, we observed that XCL1-expressing dysplastic cells in the submucosal gland in most of the cases are completely separated from the squamous cell carcinoma, suggesting that this subgroup of patients might concurrently have both squamous cell carcinoma and adenocarcinoma or this adeno-squamous carcinoma might be derived from submucosa gland epithelial cells". These are indeed very interesting! However, no data was shown. Can the authors perform a statistical analysis to compare the histology of these tumors vs. XCL1 expression? + +Response: Really appreciate this reviewer's comment on this interesting finding. Adeno-squamous carcinoma (ASC) of the esophagus is an uncommon type of esophageal cancer that contains both adenocarcinoma and squamous cell carcinoma elements. Data on this biologically unique type of cancer are limited and mainly stem from case reports and small case series. Given that the incidence of adeno-squamous carcinoma of human oesophageal cancer is very low (between 0.37%-1%), the number of ASC in this study is too low to perform a meaningful statistical analysis. We are approaching more collaborators to get more samples for the further investigation on this very interesting finding. + +7) Line 256-258, it is a bit concerning that XCL1 is only expressed in 515 out of 33459 (1.5%) total epithelial cells from the single-cell RNA-seq data. Can the authors explain why such low frequency? Is it because of the high cutoff used? This low positivity negatively affects the significance of the biological contribution of XCL1 in ESCC. + +Response: We thank the reviewer for raising this comment. XCL1 positive and negative cells were identified based on the Seurat SCTransform based normalised gene-level counts: as positive when normalised gene-level counts \(>0\) ; and negative when normalised gene-level counts \(= 0\) . This led to the identification of \(\sim 1.5\%\) XCL-positive epithelial cells. We have updated this sentence in Methods Line 905-906 to make it clear. + +Low frequency of XCL1 positive cells was also seen in the IHC staining in human primary ESCC samples, the positive cells within whole cancer tissues were around 1- 2%. The biological function of XCL1 expression in cancer cells is not fully understood although our preliminary result has demonstrated that XCL1 overexpression decreases the sensitivity of cancer cells to chemotherapy drug. Although XCL1 expresses in a very low proportion of cancer cells, these cells may present the cancer stem cells or therapeutic resistant cells and play some important role in cancer recurrence or poor prognosis. This definitely warrants further investigation. + +<--- Page Split ---> + +Minor points: + +1) The RNA-seq and WES data are still under controlled access and not publicly available. I think it is Nat Communication's policy that these data will need to be made publicly available upon acceptance. + +Response: The data has been publicized at the National Genomics Data Centre of China with the Bioproject Access ID of PRJCA001577 (https://ngdc.cncb.ac.cn/bioproject/browse/PRJCA001577), and researchers can access the data after filling in a data request form following the guideline set by the Ministry of Science and Technology of China. If there is any difficulty for any researcher to access the data, we could provide help. + +2) "an independent cohort of 65 ESCC patients" in Fig.1e was not described in the methods or results. Where were these samples from? Were they all primary tumors? + +Response: We have now provided more information about this 65 ESCC patients in our revised manuscript, in Methods Lind 712- 714. + +They were all primary tumour, treatment naive, from Anyang Cancer Hospital, under the approve of ethics committee of Both Anyang Cancer Hospital and The First Affiliated Hospital of Zhengzhou University. + +Reviewer #5 (Remarks to the Author): Expert in digital pathology and deep learning + +In this article, the authors propose a new subclassification of esophageal squamous cell carcinoma. This is clinically interesting because most previous efforts at subtyping this disease also included other histologies of esophageal cancer such as adenocarcinomas or gastroesophageal junction tumors. It is sensible to focus exclusively on squamous cell esophageal cancer and attempt to subtype it. + +My expertise is specifically in digital pathology, so I am reviewing the digital histopathology model which the authors utilized. + +Unfortunately, there are some concerns regarding the deep learning analysis. + +1. Some methodological details are not entirely clear. For instance, what does a downsampling factor of 64 fold mean? The authors should specify their final resolution in micrometers per pixel and then provide the absolute pixel size for their tiles. + +Response: We used the Openslide API for handling our whole slide images (WSI). The API processes the multiresolution images as pyramid levels with each subsequent level representing a down- sampled version of the previous level. There is no image scaling by the library, instead levels are already available in the slide file (Goode et al., Journal of pathology informatics 2013). 64 is the down sample factor we used to determine the image level we extracted from the slide files and all the slides were scanned at 20x objective power at 0.44 \(\mu m\) per pixel resolution. The tiles used for feature extraction were extracted at \(300 \times 300\) pixels for all samples. We have updated the method text to make this clear in Methods Line 858- 860, and line 867. + +<--- Page Split ---> + +2. Additionally, they mention that they manually discarded some images. This is concerning, and it is crucial for them to clearly state why these images were discarded. What precisely constituted "poor quality"? Moreover, it would be beneficial to know how many images per class were discarded. The manuscript would benefit from a CONSORT-style diagram to elucidate these points. + +Response: Each WSI was manually reviewed by a qualified pathologist, and poor quality images were discarded under the direct pathologist's supervision, poor quality of imaging means that, the sections were folded without clear morphology or there were not enough tumour cells presented in the slides obtained from the Department of histopathology. A total of 91 WSIs were retained for the deep-learning analysis, i.e., differentiated group, \(n = 28\) ; immunogenic group, \(n = 27\) ; metabolic group, \(n = 18\) ; stemness group, \(n = 18\) . We have updated this section in Methods Line 862- 867. + +3. It is also vital that the study adheres to the STARD (or similar) guidelines, ensuring that all boxes in this guideline are ticked. + +Response: We have checked and followed the STARD guidelines, report as much detail as required. + +4. Regarding the design of the algorithm, the authors mention that they extracted features with five pretrained neural networks. However, the rationale for this decision is unclear. + +This choice, which appears quite uncommon, needs further explanation. Typically, one would use just a single robust network, selected through a hyperparameter tuning experiment on a dedicated tuning set. Alternatively, one might opt for a network that has been validated in previous studies. Ideally, the contemporary standard involves not using a network pre-trained on ImageNet, but rather one that has been pre-trained in a self- supervised manner on histopathology images, such as the RetCCL network or the CTransPath network. In summary, the image analysis algorithm presented seems non- standard. While the authors might have had valid reasons for these unconventional design choices, they need to elucidate their reasoning in the manuscript. It would be even more beneficial if the authors employed a state- of- the- art pipeline (such as CLAM or the one from Wagner et al., Cancer Cell, 2023), or if they presented benchmarking experimental results showing their methods' superiority compared to more conventional methods. + +Response: We acknowledge this reviewer's point regarding the number of pretrained models used for feature extraction. Utilising multiple pretrained networks allowed us to capture a broader range of features and patterns. Each of the pretrained models utilised different model architectures, which can result in diverse feature representations. For example, the Inception and ResNet architecture are known to have different feature representation due to the use of residual connection in the latter. This diversity can enhance performance by capturing different predictive elements and building more enriched feature representations into our system. As shown in the new Supplementary Table 4, features from different pretrained models contributed differently to the top features for each subtype. + +Previous studies, such as Fu et al., Nat Cancer 2020, and Courtiol et al., Nat Med 2019, have efficiently utilised Imagenet pretrained models for extraction of histology features. Although some of these studies opt for either training a new 2D convolutional layer to perform weighted sum between the extracted features (Courtiol et al., 2019) or model fine- tuning, this is not applicable in our study because of our sample size ( \(n = 91\) slides, distributed as \(\text{DIF} = 28\) , \(\text{IMM} = 27\) , \(\text{MET} = 18\) and \(\text{STEM} = 18\) ). These numbers are not suitable for robust model training but will work for classical statistics + +<--- Page Split ---> + +comparing the extracted features between defined groups. Our aim was to implement a simple robust system to consistently extract histological features that capture the gene expression subtypes in both Discovery and Test sets. Indeed, we were able to effectively classify the gene expression subtypes using the meta histological features (new Supplementary Table 4 and 5). + +Finally, we are aware of the alternative systems such as CLAM and currently use them in our ongoing projects when appropriate. However, these systems require additional model training and often have specific domain unlike the general- purpose image recognition capabilities of the Imagenet pretrained models (Courtiol et al., 2019). + +In the revised manuscript, we have elaborated on these points to provide a clearer rational for using multiple pretrained models for feature extraction. We also added one sentence in Results Line 171- 173, "This model diversity can enhance performance by capturing different predictive elements and building more enriched representations into the system." to elaborate the rationale more. We have also included a workflow diagram to clearly describe our steps (new Extend Data Fig 6a). We hope this will address your concern and improve the overall clarity of our process. + +Fu Y, Jung AW, Torne RV, Gonzalez S, Vöhringer H, Shmatko A, Yates LR, Jimenez- Linan M, Moore L, Gerstung M. Pan- cancer computational histopathology reveals mutations, tumor composition and prognosis. Nat Cancer. 2020 Aug;1(8):800- 810. doi: 10.1038/s43018- 020- 0085- 8. Epub 2020 Jul 27. PMID: 35122049. + +Courtiol P, Maussion C, Moarii M, Pronier E, Pilcer S, Sefta M, Manceron P, Toldo S, Zaslavskiy M, Le Stang N, Girard N, Elemento O, Nicholson AG, Blay JY, Galateau- Salle F, Wainrib G, Clozel T. Deep learning- based classification of mesothelioma improves prediction of patient outcome. Nat Med. 2019 Oct;25(10):1519- 1525. doi: 10.1038/s41591- 019- 0583- 3. Epub 2019 Oct 7. PMID: 31591589. + +5. Lastly, there are concerns regarding the statistical measures for the gene expression classification. The authors used a t-test, but they did not specify whether all the prerequisites for a t-test were met. This information needs to be explicitly stated. + +Response: Thank you for raising this point. Assumption checks across the extracted features revealed that normality was not met for several of the features and the combined features. Therefore, we have replaced the t-test with the Wilcoxon rank-sum test and repeated the relevant analysis (new Supplementary Table 5, also Methods Line 883). Importantly, our results revealed that these features remain predictive of the subtypes and our interpretation remains the same. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have addressed this reviewer's remaining point and revised their manuscript accordingly. + +Reviewer #3 (Remarks to the Author): + +The authors have substantially addressed the points raised and improved the quality of the text and figures. + +Reviewer #4 (Remarks to the Author): + +The authors have addressed all my concerns. I have no more critiques. + +Reviewer #5 (Remarks to the Author): + +The authors have responded to my comments - - thank you + +the authors provide some justification for their design choices for the neural network architecture, but they do not solve the issue that the model design is very uncommon and probably not optimal. The fundamental problem seems to be the rather low sample size (N=91). + +Having said that, the authors are transparent about their approach and although it is not state of the art and there is a risk for overfitting, the methods are transparently reported and the interpretation seems to be backed up by the data. + +Major issue: the github repos seem to be unusable (only partial codes stored in the repository, no documentation, poor structure, no example data). With the current github repos it is not possible to reproduce the results. + +I suggest to remove the "The" from the title. + +<--- Page Split ---> + +Reviewer #5 (Remarks on code availability): + +Major issue: the github repos seem to be unusable (only partial codes stored in the repository, no documentation, poor structure, no example data). With the current github repos it is not possible to reproduce the results. + +<--- Page Split ---> + +Point by point responses to the Reviewer #5 (Remarks to the Author): + +The authors have responded to my comments - - thank you + +the authors provide some justification for their design choices for the neural network architecture, but they do not solve the issue that the model design is very uncommon and probably not optimal. The fundamental problem seems to be the rather low sample size \((N = 91)\) . + +Having said that, the authors are transparent about their approach and although it is not state of the art and there is a risk for overfitting, the methods are transparently reported and the interpretation seems to be backed up by the data. + +Response: We appreciate that this reviewer agrees that our methods are transparently reported, and our interpretation is backed up by the data. + +The ensemble approach of using multiple CNN models for feature extraction is not uncommon and has been used previously although not much in the field of computational pathology, exemplified by + +- F. Shaheen and B. Verma, "An ensemble of deep learning architectures for automatic feature extraction," 2016 IEEE Symposium Series on Computational Intelligence (SSCI), Athens, Greece, 2016, pp. 1-5, doi: 10.1109/SSCI.2016.7850047.- Bhandi, V., Sumithra Devi, K.A. (2021). Feature Extraction from Ensemble of Deep CNN Model for Image Retrieval Application. In: Jeena Jacob, I., Kolandapalayam Shanmugam, S., Piramuthu, S., Falkowski-Gilski, P. (eds) Data Intelligence and Cognitive Informatics. Algorithms for Intelligent Systems. Springer, Singapore. https://doi.org/10.1007/978-981-15-8530-2_57.- Dechao Chen, Yang Chen, Jieming Ma, Cheng Cheng, Xuefeng Xi, Run Zhu, Zhiming Cui, "An Ensemble Deep Neural Network for Footprint Image Retrieval Based on Transfer Learning", Journal of Sensors, vol. 2021, Article ID 6631029, 9 pages, 2021. https://doi.org/10.1155/2021/6631029 + +[Figure Redacted] + +<--- Page Split ---> + +All these studies showed that the ensemble approach retains more features for the final retrieval and achieves better accuracy than a separate feature extraction (Shaheen and Verma 2016 IEEE Symposium Series on Computational Intelligence (SSCI); Chen et al., 2021 Journal of Sensors). + +Given our low sample size \((n = 91)\) of four subtypes, our feature extraction could benefit from this ensemble approach by increasing the numbers of useful features for the final retrieval. The feature representations of the images extracted by different models are different, but these different feature representations contain some essential information components (Chen et al., 2021 Journal of Sensors). Indeed, our results showed that more diverse representative features could be identified using the feature extraction from multiple CNN models (shown in Supplementary Table 4). This produced more robust features that were fused together to create subtype specific Meta Features (Supplementary Table 5). + +We have added one sentence in Results Line 173 to highlight the advantage of this ensemble approach, "This ensemble approach was reported to retain more informative features for the final retrieval and achieve better accuracy than a separate feature extraction", and cited the papers above. + +Larger independent cohorts are needed to further validate our ensemble model and top features, which are under planning but beyond the scope of this study. + +Major issue: the github repos seem to be unusable (only partial codes stored in the repository, no documentation, poor structure, no example data). With the current github repos it is not possible to reproduce the results. + +Response: Following on this comment, We have now added extensive detail about the functions and scripts used in our workflow at https://github.com/BiolnforCore- BCI/giExtract, forked from https://github.com/caanene1/giExtract. We also provide example dataset and run functions inside dedicated folder. In particular, we created a "manuscript" folder in the repos, containing "run.sh", "downstream.R" and "example data" folder, ensuring the reproducibility of our results. + +To make it easy for other researchers to use our code, we have now uploaded the python part of the workflow to the Pypi package database. This enables a user to install the tool like any other python package. The interface provides detailed documentation of the inputs and requirements (see below). Please also visit the Pypi website for our package at https://pypi.org/project/giExtract/1.0.1/ + +<--- Page Split ---> + +Last login: Wed Mar 6 18:10:10 on ttysooo chinedus- MacBook- Pro:- chineduanene\$ giExtract - h usage: giExtract [-h] - p PATH - c CONTEXT - k COLUMN [-b BATCH] [-s NATCOM] + +optional arguments: - h, - - help show this help message and exit - p PATH, - - path PATH Path to images - c CONTEXT, - - context CONTEXT Context file with at least a column for flowing the images - k COLUMN, - - column COLUMN The column name in context to use for flowing data - b BATCH, - - batch BATCH Batch size for flowing the data into the models - s NATCOM, - - natcom NATCOM Indicate if the NatCom et al features should be calculated chinedus- MacBook- Pro:- chineduanene\$ + +I suggest to remove the "The" from the title. + +Response: We have updated the title to "Integrated molecular and histological analysis defines subtypes of esophageal squamous cell carcinoma" + +We'd like to take this opportunity to thank all the reviewers for their invaluable comments and critique that has made our study much more thorough and robust! + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #5 (Remarks to the Author): + +Thank you for addressing all of my comments. + +<--- Page Split ---> diff --git a/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a8332a513a7ab5e8520b09f899c7c4ba57a1e826 --- /dev/null +++ b/peer_reviews/78300ad3e6e386e1046e7296f3f75ac6261c0e68da3c3f3ba99068db3bcfd549/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1016 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 864, 211]]<|/det|> +The integrated molecular and histological analysis defines subtypes of esophageal squamous cell carcinoma + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 66, 884, 135]]<|/det|> +Editorial Note: Figure on page 39 of this Peer Review File have been redacted as indicated to remove third- party material where no permission to publish could be obtained. "Chen, D., et al. An Ensemble Deep Neural Network for Footprint Image Retrieval Based on Transfer Learning. Journal of Sensors 2021, 6631029 (2021)." + +<|ref|>sub_title<|/ref|><|det|>[[116, 152, 291, 168]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 188, 683, 205]]<|/det|> +Reviewer #1 (Remarks to the Author): Expert in oesophageal cancer genomics + +<|ref|>text<|/ref|><|det|>[[114, 224, 877, 369]]<|/det|> +Jiang et al. performed whole- exome sequencing and transcriptome analysis on Chinese 120 ESCC samples to characterize ESCC in detail. The authors classified four subtypes based on the expression and three based on the estimated immune cells in cancer tissues. They found that the stemness subtype showed poor prognosis and enriched in C3 immune subtype. In addition, they showed some relationships between transcripts and subtypes and analyzed them functionally. Moreover, they found NK cell- like expression signature in cancer cells. Genetic analysis also gave some insights. However, overall, their claims are not well supported by the results, and there are many overstatements as described below. + +<|ref|>text<|/ref|><|det|>[[116, 390, 216, 405]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[115, 407, 877, 497]]<|/det|> +Line 97- 98 The authors classified ESCC based on 1500 gene expressions with the highest MAD score and adopted four subtypes. The methods section describes that the cluster number with the highest cophenetic coefficient was adopted. As shown in Extended Data Figure 1a, the cophenetic coefficient for \(\mathsf{k} = 2\) is 0.9928 and \(\mathsf{k} = 4\) is 0.985, but they adopted \(\mathsf{k} = 4\) instead of \(\mathsf{k} = 2\) . Is there any other reason why the authors adopted \(\mathsf{k} = 4\) ? + +<|ref|>text<|/ref|><|det|>[[115, 516, 850, 552]]<|/det|> +Line 110- 111 Fig. 1b does not show "interferon gamma pathway" or "chemokine signaling pathway". Were these pathways significantly downregulated in the stemness subgroup? + +<|ref|>text<|/ref|><|det|>[[115, 571, 864, 625]]<|/det|> +Line 115- 120 The authors claimed histological characteristics of each subtype. However, there is little evidence to support their claim because they just showed the representative images and did not show any quantitative data extracted from histological images. + +<|ref|>text<|/ref|><|det|>[[115, 644, 881, 698]]<|/det|> +Line 124- 127 The result is unreliable because functional analysis of SFPR1 overexpression was performed in just one cell line. Also, it is highly recommended to show the result of the knockdown experiment using more than one effective shRNA to exclude off- target effects. + +<|ref|>text<|/ref|><|det|>[[115, 717, 814, 752]]<|/det|> +Line 154 The association between "stemness" and "NK cell estimates" is not strong because the correlation r- value of 0.32 – 0.4 is not high. + +<|ref|>text<|/ref|><|det|>[[115, 772, 870, 826]]<|/det|> +Line 165- 166 The authors showed immunohistochemical images of Sample 401 in Fig.2g and Extended Data Fig. 5c. How is the difference of LGR6- staining in the same tumor explained? Also, the architecture of cancer cells is different. Are these derived from the same tumor sample? + +<|ref|>text<|/ref|><|det|>[[115, 845, 875, 899]]<|/det|> +Line 198- 201 The result is uncredible because the authors performed overexpression of XCL1 in just one cell line. In addition, it is strongly recommended to show the result of the knockdown experiment of XCL1 to support their claim. + +<|ref|>text<|/ref|><|det|>[[115, 919, 877, 954]]<|/det|> +Line 247- 250 Among EP300 mutations, 30 % were truncating mutations or deletion. The authors showed higher expression of the mutated allele. However, if the cancer had a truncating/deletion mutation, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 125]]<|/det|> +mutated allele is expected to result in loss of function. Therefore, their claim of a gain- of- function mode of EP300 mutations is not supported. + +<|ref|>text<|/ref|><|det|>[[115, 144, 876, 216]]<|/det|> +Line 254- 277 The authors showed a higher frequency of NOTCH1 mutation as well as EP300 mutation in the stemness subgroup. Therefore, these results may derive from the effect of NOTCH1 mutation. To investigate the effect of EP300 mutation, it is reasonable to compare EP300- wild and mutant cancers among the same subgroup because the genetic backgrounds of subgroups are different from each other. + +<|ref|>text<|/ref|><|det|>[[115, 235, 879, 308]]<|/det|> +Line296- 299 In Fig. 9c left panel, three subtypes other than the stemness subtype showed a comparable frequency of truncating mutations in wnt pathway genes. Therefore, because the prediction of the effect of mutations is more reliable for truncating mutation than for missense mutation, it seems that deleterious Wnt pathway mutations are similar. + +<|ref|>text<|/ref|><|det|>[[115, 328, 216, 344]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 346, 852, 380]]<|/det|> +Line 99- 101 They designated four subgroups based on known functional gene expression rather than GSEA. + +<|ref|>text<|/ref|><|det|>[[115, 437, 866, 454]]<|/det|> +Reviewer #2 (Remarks to the Author): Expert in tumour immunology, NK cells, and oesophageal cancer + +<|ref|>text<|/ref|><|det|>[[115, 473, 867, 509]]<|/det|> +Comments for the manuscript entitled "Stemness and NK- like signatures define the poorest subtype of oesophageal squamous cell carcinoma" by Guozhong Jian et al. + +<|ref|>text<|/ref|><|det|>[[115, 528, 870, 564]]<|/det|> +This referee aims to comment on the non- bioinformatical part if this manuscript, leaving the comments for the precise bioinformatics to experts on bioinformatics and statistics. + +<|ref|>text<|/ref|><|det|>[[113, 582, 881, 888]]<|/det|> +The manuscript presents an impressive molecular investigation of oesophageal squamous cell carcinoma (ESCC) from 120 Chinese patients. The authors have performed transcriptomics with GSEA and immune profiling, and mutational enrichment analyses, with the aim to find subtypes of tumors, and link this information to novel immune evasion strategies or drug sensitivity. The focus of the study is using bioinformatics, and the results from the authors own patient cohort is compared to previous studies on related cohorts, especially regarding the immune profiling strategy. There is no doubt that the study is of large importance, with ESCCs being one of the deadliest cancers worldwide today, with no effective therapies at hand. A study if this size, at this detailed molecular level, is difficult to find in the literature and will make a difference. Whereas the bioinformatics part of this study seems strong, the immunology and pathology sections are less robust. The manuscript is written in a very condensed scientific English, which makes it difficult to actually understand what has been done in the various panels of experiments. This also makes the reader insecure of what the authors actually have accomplished (the materials and methods (and figure legends) does not help or guide). To be able to fully understand this study, the manuscript has to be rewritten in a more detailed manner. Some comments are given below. 1) Every panel of each figure needs to be explained better, both experimentally and statistically, to be able to understand what has been done. This goes for the material and methods part too. Controls should be added where appropriate, and in cases where a value is calculated compared to a control, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 840, 107]]<|/det|> +control needs to be described equally well. Full statistics should be explained also in Figure legends. + +<|ref|>text<|/ref|><|det|>[[113, 108, 877, 199]]<|/det|> +2) Row 114. "The molecular subtypes present distinguished histological features". Is this based on these four photographs of four tumors? How representative are they? Where are the statistics behind this to be able to state this quite important finding? The authors should have access to all tumors, and thus be able to perform a tumor tissue array of paraffinized samples, to compare the histology of all 120 tumors on one single glass slide using a light microscope. This way statistics can be added. + +<|ref|>text<|/ref|><|det|>[[113, 200, 881, 290]]<|/det|> +3) Row 116-120. The authors describe these histological features using nomenclature of keratin pearls, extensive immune infiltration etc, without showing it or even presenting how this was done or annotated. Again, to say this a tumor tissue array would be good and should be annotated and evaluated statistically. The material and methods section should be updated accordingly, presenting how keratin pearls or immune cell infiltration was assayed. + +<|ref|>text<|/ref|><|det|>[[113, 291, 877, 364]]<|/det|> +4) Row 126. Xenograft models are presented in the text, but no ethical permit or precise description of how it was exactly performed in present in the text or materials and methods. Just very vague descriptions referring to Extended data Fig 3. What is Ext data Fig 3a? Explain each panel. Extended data Fig 3 is a typical representative for the concerns mentioned above of too limited explanations. + +<|ref|>text<|/ref|><|det|>[[113, 364, 872, 400]]<|/det|> +5) Figure 2e, row 149, is this a Fisher's exact test? Where is the statistics shown in the figure? The figure legend is minimal. + +<|ref|>text<|/ref|><|det|>[[113, 401, 870, 473]]<|/det|> +6) Fig 2g. IHC controls are absent. A normal tissue should be used as control, and a cell line lacking (negative) or expressing (positive) should be shown to trust the IHC antibody specificity. Again, a tissue tumor array would be good to be able to conclude the results, only four samples are not enough to conclude. + +<|ref|>text<|/ref|><|det|>[[113, 475, 881, 546]]<|/det|> +7) Row 158-166. How is this IHC annotation performed and shown? The authors show statistics in the text that is not described in detail, and cannot be found in the figures or legends. Is it Pearson Chi-square tests or what fo authors mean with co-expression? Tables of annotations? This needs to be clearly shown. + +<|ref|>text<|/ref|><|det|>[[113, 548, 864, 601]]<|/det|> +8) From row 177 and on "NK-like tumor cells" are used to described tumor cells expressing CD160. It would be preferrable to not name the tumor cells "NK-like tumor cells", since they are tumor cells and not lymphocytes. + +<|ref|>text<|/ref|><|det|>[[113, 603, 864, 675]]<|/det|> +9) Fig 3f. How is the IC50 experiment performed exactly. The materials and methods do not describe what is being shown in panel 3f. How are the numbers calculated? At what concentration, time and compared to what? If a Mann-Whitney test is used, what exact control are the bars compared to? + +<|ref|>text<|/ref|><|det|>[[113, 676, 870, 710]]<|/det|> +XCL1 as a promising biomarker for drug sensitivity, using cell lines, and EP300 for survival in the patient cohort. How can these be linked in patient material and survival? + +<|ref|>text<|/ref|><|det|>[[113, 712, 875, 821]]<|/det|> +11) Figure 5, the authors present immune infiltration and association with clonal diversity, and is also important. It would be good to perform IHC panels on some basic immune populations of the tumors to be able to support the data from the Shannon diversity index. Immune exclusion of T cells compared to M2 macrophages, as well as NK cells would be interesting to see. If CD160 is expressed on tumor cells. 12) The manuscript needs to be rewritten, to add much more detail for each panel, to be able to understand what has been done. As it is now, it is difficult to interpret the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 871, 162]]<|/det|> +In this study Jiang et al., aims at defining novel molecular subgroups in human Oesophageal Squamous Cell Carcinoma (ESCC) by analysing the transcriptome and genome of a big cohort of ESCC from Chinese patients. + +<|ref|>text<|/ref|><|det|>[[113, 181, 872, 450]]<|/det|> +The authors, using bulk- RNA sequencing, identify four distinct ESCC transcriptomic subtypes. Among them one shows the worst survival rate and is characterized by the expression of WFDC2, SFRP1, LGR6 and VWA2 genes ("stemness" subtype). The data obtained from the RNA sequencing analysis is then analysed using deconvolution methods to determine the tumor immune composition of the ESCC samples. Using this approach, they divide the tumors in three categories according to the content/type of immune cells present within the sample and identify a group of tumors showing high expression of NK- like gene signature, the group associated with the poorest survival rate. Interestingly, they observe that tumors showing high expression of XCL1 (gene upregulated within the NK gene signature and C3 immune type) present higher resistance to several drugs. Thirdly, the authors characterize the genomic landscape of the same cohort of patients and describe genomic landscapes similar to those described in the numerous genomic analyses that have been reported on ESCC (The Cancer Genome Atlas Research, N. et al. Nature 541, 169- 175 (2017); Song, Y. et al. Nature 509,91- 95 (2014); Lin, D. C. et al. Nat. Genet. 46, 467- 473 (2014); Gao, Y. B. et al. Nat. Genet. 46,1097- 1102 (2014)). Finally, the authors determine if there is any correlation between the transcriptomic and immune signatures and the mutational landscape of the ESCC analysed. + +<|ref|>text<|/ref|><|det|>[[115, 494, 870, 584]]<|/det|> +The main criticism is that this study lacks accuracy as many of the statements are not well sustained or only based on correlations. There is a lack of validation of the transcriptomic and immune signatures in biological samples and lack of experiments in biological samples aimed at supporting the numerous correlations present in the study. These validations and experiments would certainly help to strengthen and confirm the message of the paper. + +<|ref|>text<|/ref|><|det|>[[115, 601, 710, 618]]<|/det|> +Remarkably, there are some points that need to be further developed or clarified: + +<|ref|>text<|/ref|><|det|>[[114, 638, 878, 857]]<|/det|> +1- Using bulk RNA- sequencing the authors classify the ESCC analysed in 4 different subtypes characterized by the expression of different markers, subtypes that show different morphological characteristics and patient survival rates (Figure 1). The authors claim that they are interested to characterize both the tumor and tumor microenvironment. However, they do not analyse if the genes found to be upregulated in the different subgroups are expressed by the tumor cells or by the tumor microenvironment, which is extremely relevant to validate and strengthen this key point the authors want to make. This validation could be accomplished by performing immunostainings for the different markers in tumors from the 4 ESCC subtypes or alternatively using techniques that would allow a deeper characterization of the different cell populations present in the samples (single cell RNA sequencing). Using the latter approach, a recent paper (Zhang, X., Peng, L., Luo, Y. et al. Nat Commun 12, 5291, 2021) identified eight different common expression programs of epithelial cells in ESCC tumors and characterized the populations present in the tumor microenvironment of the same tumors. + +<|ref|>text<|/ref|><|det|>[[112, 876, 844, 894]]<|/det|> +2- In Figure 2 the authors identify a cluster, cluster 3, characterized by the expression of NK markers, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 879, 234]]<|/det|> +again it is not clear if these NK markers are expressed by the tumor cells (staining for XCL1 and Lgr6 Fig2 g superior panel is too weak to be able to conclude anything and morphologically the tumor shown does not seem a “stemness” tumor) or if there is infiltration of NK cells or presence of NK cells surrounding the tumors (staining for a NK marker would be extremely helpful). Therefore the description of the immune infiltration and immune microenvironment is superficial and needs to be improved. In addition, only \(50\%\) of the stemness- subtype tumors could be classified as belonging to the immune cluster 3 (Fig 2e), so the statement “given the strong association between stemness and NK cell estimates- line 154- 155” is overstated and should be corrected. + +<|ref|>text<|/ref|><|det|>[[114, 254, 874, 381]]<|/det|> +3- One of the genes that characterize Cluster 3 (NK- like signature) is XCL1. The authors show using GSEA that XCL1- high cells exhibit upregulation of drug metabolism of cytochrome P450, retinol metabolism and biological oxidations (line 185) and in line 106 the authors state “the metabolic subtype is associated with the upregulation of genes involved in drug metabolism by cytochrome P450 and retinol metabolism”. Would this mean that tumors showing high XCL1 expression belong to the “metabolic subtype”? This is confusing and highlights that the link between XCL1 (NK- like) and “stemness subtype” or “metabolic subtype” should be better explained. + +<|ref|>text<|/ref|><|det|>[[114, 400, 875, 491]]<|/det|> +4- In Figure 2g, Extended Data Figure 5c and line 164- 172, the authors state that XCL1 is exclusively expressed in cancer cells showing adenocarcinoma morphology. Should we consider all XCL1- expressing tumours adeno- squamous cell carcinomas? If so, the authors should repeat the analysis by studying the ESCC and adeno- squamous cell carcinomas separately as relevant differences may be found in terms of transcriptomics, genomics and response to chemotherapy. + +<|ref|>text<|/ref|><|det|>[[114, 510, 883, 584]]<|/det|> +5- The authors suggest that XCL1- high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[272, 85, 724, 103]]<|/det|> +## Point by point responses to the revisers' comments + +<|ref|>sub_title<|/ref|><|det|>[[152, 137, 316, 152]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[152, 168, 686, 184]]<|/det|> +Reviewer #1 (Remarks to the Author): Expert in oesophageal cancer genomics + +<|ref|>text<|/ref|><|det|>[[150, 200, 845, 328]]<|/det|> +Jiang et al. performed whole- exome sequencing and transcriptome analysis on Chinese 120 ESCC samples to characterize ESCC in detail. The authors classified four subtypes based on the expression and three based on the estimated immune cells in cancer tissues. They found that the stemness subtype showed poor prognosis and enriched in C3 immune subtype. In addition, they showed some relationships between transcripts and subtypes and analyzed them functionally. Moreover, they found NK cell- like expression signature in cancer cells. Genetic analysis also gave some insights. However, overall, their claims are not well supported by the results, and there are many overstatements as described below. + +<|ref|>text<|/ref|><|det|>[[150, 345, 245, 359]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[150, 361, 846, 440]]<|/det|> +1. Line 97-98 The authors classified ESCC based on 1500 gene expressions with the highest MAD score and adopted four subtypes. The methods section describes that the cluster number with the highest cophenetic coefficient was adopted. As shown in Extended Data Figure 1a, the cophenetic coefficient for \(k = 2\) is 0.9928 and \(k = 4\) is 0.985, but they adopted \(k = 4\) instead of \(k = 2\) . Is there any other reason why the authors adopted \(k = 4\) ? + +<|ref|>text<|/ref|><|det|>[[149, 455, 848, 648]]<|/det|> +Response: We thank the reviewer for such detailed observation. Our choice of \(k = 4\) used in NMF was based on the combination factors of NMF cophenetic coefficient and the heterogeneous molecular signatures sufficiently revealed by our data. When \(k = 2\) was used, based on the signature gene sets of the two groups and their functional annotation, only two molecular subtypes were revealed, differentiated and immunogenic. The signatures of metabolic and stemness subtypes could not be identified by \(k = 2\) . This is also supported by the Supplementary Table S1 of this rebuttal that the top signature genes of our differentiated and immunogenic subtypes were still significant genes for the two subgroups when \(k = 2\) , but top signature genes of the metabolic and stemness subtypes were not significant anymore when \(k = 2\) . Most importantly, our four transcriptomic subtypes and their signatures were successfully validated by three independent cohorts (Extended Data Figure 1b), and were strongly supported by the following clinical, histopathology, in vitro and in vivo (for stemness) experiments. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[155, 101, 824, 390]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[156, 85, 772, 98]]<|/det|> +Supplementary Table S1. Comparison of signature genes of our four subtypes between \(\mathsf{k} = 4\) and \(\mathsf{k} = 2\) in NMF + +
Signature geneslog2FC (one group vs others)P.Valueadj.P.Valk=4 groupsk=2 groupslog2FC (group2 vs group1)P.Valueadj.P.Val
LCE3D4.2921.54E-122.95E-10DifferentiatedDifferentiated-2.4190.000162960.00252447
CDSN3.9667.01E-141.05E-10DifferentiatedDifferentiated-2.3004.28E-050.00084861
KLK53.8847.18E-131.79E-10DifferentiatedDifferentiated-2.3164.81E-050.0009412
SPRR2G3.6851.02E-094.77E-08DifferentiatedDifferentiated-1.7240.006289540.03822871
DSG13.5902.00E-112.00E-09DifferentiatedDifferentiated-1.5250.007171460.04182777
MS4A12.5911.56E-124.04E-11ImmunogenicImmunogenic2.5035.35E-141.09E-11
CD79A2.5581.16E-195.82E-17ImmunogenicImmunogenic2.3522.05E-207.17E-17
CXCL92.2638.70E-121.95E-10ImmunogenicImmunogenic2.1172.20E-122.82E-10
MZB12.2627.31E-221.10E-18ImmunogenicImmunogenic2.0811.01E-232.81E-19
IDO12.2061.48E-091.94E-08ImmunogenicImmunogenic2.4443.15E-146.79E-12
GSTA13.9563.37E-092.10E-07Metabolic-0.5050.416094760.59872715
ADH73.8626.39E-124.79E-09Metabolic-0.2760.60408430.75100198
UGT1A103.7973.52E-071.04E-05Metabolic-0.4850.476546160.65090706
UGT1A33.6921.17E-074.08E-06Metabolic-0.5770.366088990.55313354
ALDH3A13.5748.64E-111.62E-08Metabolic-0.0050.993017510.99646932
WFD22.4467.43E-071.71E-05Stemness-0.5790.206508540.38417833
PEG101.7910.000249810.00148696Stemness--0.4870.272895870.46017491
SFRP11.7810.000129490.00087493Stemness-0.0900.831019810.90348777
LGR61.7314.19E-050.00035815Stemness--0.0370.922517860.95710801
VWA21.6781.18E-074.44E-06Stemness-0.0010.997490750.99871802
+ +<|ref|>text<|/ref|><|det|>[[150, 409, 825, 474]]<|/det|> +We added one sentence in Methods Line 723- 725 to clarify the reason why we adopted \(\mathsf{k} = 4\) , "Our choice of the optimal cluster count in NMF was based on the combination factors of NMF cophenetic coefficient and the heterogeneous molecular signatures sufficiently revealed by our data.". + +<|ref|>text<|/ref|><|det|>[[150, 506, 789, 539]]<|/det|> +2. Line 110- 111 Fig. 1b does not show "interferon gamma pathway" or "chemokine signaling pathway". Were these pathways significantly downregulated in the stemness subgroup? + +<|ref|>text<|/ref|><|det|>[[150, 554, 841, 732]]<|/det|> +Response: We appreciate the reviewer's comment here (in line 112- 114). We've included the two terms "interferon gamma pathway" or "chemokine signaling pathway" into the Figure 1b heatmap, In Figure 1b, the heatmap was based on the "- log10" transformed p- values from the hypergeometric test against the mSigDB database genesets (v.6.2) using signature genes from each transcriptomic group (Extended Data Table S2), while the enrichment plots of three immune pathways (downregulated in stemness, Figure 1b) were based on the GSEA analysis (https://www.gseasmigdb.org/gsea/index.jsp) developed by the Broad Institute, using all profiled genes and associated ranked t- statistics. Both methods independently highlighted that all immune pathways were significantly upregulated in the immunogenic subgroup, but downregulated in the stemness subgroups (revealed by GSEA), and genes from immune pathways were not over- represented in the stemness signature genes (by the hypergeometric test). + +<|ref|>text<|/ref|><|det|>[[150, 747, 833, 795]]<|/det|> +3. Line 115-120 The authors claimed histological characteristics of each subtype. However, there is little evidence to support their claim because they just showed the representative images and did not show any quantitative data extracted from histological images. + +<|ref|>text<|/ref|><|det|>[[150, 810, 844, 907]]<|/det|> +Response: We appreciate the reviewer's insightful comment. This was also pointed by reviewer #2 comment #2. To further quantify and compare the histopathological features of four subgroups of ESCC, we developed a deep- learning model using five state- of- the- art convolutional networks, namely Inception- V3, Inception- ResNet- V2, DenseNet- 121, VGG16 and ResNet- 50, and performed feature extraction on selected tiles from each whole slide image (WSI) from the scanned H&E sections. We then compared features among the four transcriptomic groups, and identified features + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 837, 197]]<|/det|> +strongly associated with each group (i.e., features that were significantly higher in one group compared to the rest). We then selected top five features for each group, and summed these features to create four stable, statistically significant histological markers of gene expression- based classifications, namely DIFF- Feature, MET- Feature, IMM- Feature and STEM- Feature. We performed this analysis using a \(65\%:35\%\) discovery and validation/test of our WSI samples, see Methods Line 834 - 867 for full detail, also Extended Data Figure 1c. Tiles with the highest scores of each feature were selected for reviewing by a pathologist (Figure 1c). + +<|ref|>text<|/ref|><|det|>[[150, 212, 845, 388]]<|/det|> +Indeed, tiles with the highest subtype specific features all contained the distinct histopathological features corresponding to each molecular subgroup (Figure 1C). DIFF- Feature, characterised by that keratin pearls within tumours and differentiated squamous dysplastic cells were significantly higher in the differentiated subgroup samples than the non- differentiated samples (Figure 1c and Extended Data Figure 1c). The MET- Feature, marked by moderate differentiated squamous tumour cells, with some tumour cells showing eosinophilic cytoplasm with less immune cell infiltration. The immunogenic subgroup showed extensive immune cell infiltration within tumours compared to other groups; The stemness subgroup presented poorly differentiated tumour cells and had few immune cell infiltrating within the tumour (Figure 1c and Extended Data Figure 1c). We have included the AI digital pathology results into the revised manuscript Line 152- 169. We also include a paragraph discussing this in Line 489 - 500. + +<|ref|>text<|/ref|><|det|>[[150, 420, 836, 468]]<|/det|> +4. Line 124-127 The result is unreliable because functional analysis of SFPR1 overexpression was performed in just one cell line. Also, it is highly recommended to show the result of the knockdown experiment using more than one effective shRNA to exclude off-target effects. + +<|ref|>text<|/ref|><|det|>[[150, 484, 848, 564]]<|/det|> +Response: According to the reviewer's comment, SFRP1 overexpression experiment was performed in another cell line KYSE- 140, and more effective shRNAs were designed to confirm the knockdown results. All shRNA sequences were selected from Sigma which were validated by the provider. The new results are presented in Extended Data Figure 4, and shRNA sequence were provided in the methods section Line 930- 940. + +<|ref|>text<|/ref|><|det|>[[150, 580, 828, 612]]<|/det|> +5. Line 154 The association between "stemness" and "NK cell estimates" is not strong because the correlation r-value of 0.32 - 0.4 is not high. + +<|ref|>text<|/ref|><|det|>[[150, 628, 832, 675]]<|/det|> +Response: We agree with the reviewer's comment, and have changed our wording throughout the manuscript, and state "suggesting a degree of certain association between stemness and NK cell estimates." in Line 205-206. + +<|ref|>text<|/ref|><|det|>[[150, 692, 845, 740]]<|/det|> +6. Line 165-166 The authors showed immunohistochemical images of Sample 401 in Fig.2g and Extended Data Fig. 5c. How is the difference of LGR6-staining in the same tumor explained? Also, the architecture of cancer cells is different. Are these derived from the same tumor sample? + +<|ref|>text<|/ref|><|det|>[[150, 756, 836, 883]]<|/det|> +Response: Thanks for providing us with the valuable comment. We apologize for any inconvenience caused by the mix- up of samples depicted in Fig 2g. (now Fig. 2h) Upon further investigation, we have confirmed that the staining of CD160 and LGR6 shown in original Fig 2g are from sample 341, but due to our limited perspective, its sequential segmentation may not have been apparent. We have provided additional supporting evidence of this rebuttal (Supplementary Figure 1, shown below) indicating that both are indeed from the same source. To provide greater clarity, we have replaced the staining in Figure 2g for sample 341 with two new field of views that are more similar, as illustrated in the new Figure 2h. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[158, 87, 545, 396]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 399, 820, 430]]<|/det|> +
Supplementary Figure 1. Representative immunohistochemical staining image of the tumor tissue stained with anti-CD160 and anti-LGR6 for sample 341.
+ +<|ref|>text<|/ref|><|det|>[[151, 445, 835, 510]]<|/det|> +We have also updated Extended Data Fig 6c accordingly, and showed the anti- CD160 and anti- LGR6 staining for Sample 369, and anti- XCL1 and anti- LGR6 staining for Sample 401 in sequential sections. All these confirmed the co- expression of LGR6 with XCL1 or CD160 in a subset of our samples. We have updated this section of results in Line 212 - 219. + +<|ref|>text<|/ref|><|det|>[[151, 525, 828, 573]]<|/det|> +7. Line 198-201 The result is incredible because the authors performed overexpression of XCL1 in just one cell line. In addition, it is strongly recommended to show the result of the knockdown experiment of XCL1 to support their claim. + +<|ref|>text<|/ref|><|det|>[[150, 588, 842, 781]]<|/det|> +Response: Following this reviewer's insightful comment, we have further performed the overexpression of XCL1 in two additional XCL1- low cell lines, KYSE- 180 and KYSE- 410, and the results were consistent to what was shown in XCL1- low KYSE- 150 cell line, overexpression of XCL1 significantly increased the IC50 values, making them more resistant to 5- FU, the new results have been added into (Figure 3g). Knockdown of XCL1 would be ideal to consolidate the conclusion, but we could not make XCL1 significantly knockdown subclone cell lines, possibly due to the low proportion of XCL1 overexpressing cells in ESCC cell lines (from our IHC data and sRNA deep sequencing data, XCL1 postive cells are less than \(1\%\) of total tumour cells). The alternative approach CRISPR Cas9 knockout strategy was also considered, but it is difficult to design XCL1- specific gRNA given the the high similarity to XCL2. However, we think the overexpression of XCL1 in two additional cell lines is strong enough to support our claim that the overexpressing of XCL1 in cancer cells is associated with the sensitivity to 5- FU. + +<|ref|>text<|/ref|><|det|>[[150, 797, 844, 861]]<|/det|> +8. Line 247-250 Among EP300 mutations, \(30\%\) were truncating mutations or deletion. The authors showed higher expression of the mutated allele. However, if the cancer had a truncating/deletion mutation, the mutated allele is expected to result in loss of function. Therefore, their claim of a gain-of-function mode of EP300 mutations is not supported. + +<|ref|>text<|/ref|><|det|>[[150, 877, 800, 909]]<|/det|> +Response: We thank the reviewer for this useful comment. We further looked into the allelic imbalance for the eight samples with mutations in EP300, including 4 missense, 1 splice site, 1 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 848, 291]]<|/det|> +nonsense, 1 frame- shift deletion and 1 in- frame deletion, and compared variant allele frequency (VAF) between the WES DNA and RNA- seq data. Three single nucleotide mutations (2 missense mutations, c.4312T>C, c.4355C>G and one splice site mutation, c.4617+1G>A) showed significantly elevated levels of the alternative (mutated) allele in RNA- compared to the DNA- level, as shown in current Fig. 4f. Amongst the remaining five mutations, one nonsense (c.3244C>T) and one frame- shift deletion (c.1914_1915del) in fact showed significantly decreased levels of the alternative allele in RNA than in DNA, suggesting potentially loss- of- function for the mutated allele. We have included this data as Supplementary Table S9, and updated the wording accordingly (Line 314- 319), as "Three single nucleotide mutations (2 missense mutations, c.4312T>C, c.4355C>G and one splice site mutation, c.4617+1G>A) showed significantly elevated levels of the alternative (mutated) allele in RNA- compared to the DNA- level. While for two codon- affecting mutations, one nonsense (c.3244C>T) and one frame- shift deletion (c.1914_1915del), the opposite pattern was observed, with decreased levels of the alternative allele in RNA than in DNA". + +<|ref|>text<|/ref|><|det|>[[152, 292, 825, 323]]<|/det|> +However, the result for higher EP300 expression levels in EP300- mutated patient samples than in EP300- wildtype samples (Fig. 4e) remains unchanged on the RNA expression level comparison. + +<|ref|>text<|/ref|><|det|>[[151, 338, 839, 418]]<|/det|> +9. Line 254-277 The authors showed a higher frequency of NOTCH1 mutation as well as EP300 mutation in the stemness subgroup. Therefore, these results may derive from the effect of NOTCH1 mutation. To investigate the effect of EP300 mutation, it is reasonable to compare EP300-wild and mutant cancers among the same subgroup because the genetic backgrounds of subgroups are different from each other. + +<|ref|>text<|/ref|><|det|>[[149, 433, 842, 833]]<|/det|> +Response: We thank the reviewer for this comment. However, as shown in Fig. 4a, the mutational landscape figure among the four transcriptomic groups, mutations in EP300 and NOTCH1 occurred almost exclusively. Only one patient sample that had a missense mutation in EP300, also had a missense mutation in NOTCH1 (fourth sample in the Stemness panel), with another sample having a missense mutation in EP300 and copy number deletion in NOTCH1 (second sample in the Stemness panel). Thus, it is less likely that what we observed between EP300 mutant versus wildtype samples was drived from the effect of NOTCH1 mutations. In fact, we selected NOTCH1 mutated samples (excluding samples with copy number changes in NOTCH1) and compared them with NOTCH1 wildtype samples by differential expression analysis and GSEA. The results demonstrated that the dysregulated genes and pathways were completely different between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype (Supplementary Figure 2a- b of this rebuttal below). The most significantly upregulated pathways (GSEA results) for EP300 mutant vs. wildtype included mitotic prometaphase, mRNA processing and splicing, ATM and Fanconi pathway, spliceosome, DNA replication and chromosome maintenance, while signalling by BMP was the only upregulated pathway for NOTCH1 mutant vs. wildtype. For the most significantly downregulated pathways, the EP300 mutant had core matrisome, integrin1 pathway, cytokine- cytokine receptor interaction, ECM glycoproteins and a large number of immune pathways downregulated compared to wildtype, while the NOTCH1 mutant had RNA POL1 promoter opening, packaging of telomere ends, amyloids, telomere maintenance, meiotic synapsis and recombination and meiosis as top downregulated pathways compared to wildtype. In addition, there was no correlation in the global transcriptomic changes between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype (Supplementary Figure 2c, see below). Furthermore, there was no correlation in mRNA expression between EP300 and NOTCH1 (Supplementary Figure 2d). Therefore, all the results here suggest that our results observed for EP300 mutations were not derived from the effect of NOTCH1 mutations. We have addressed this in the revised manuscript following this reasonable comment. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[160, 85, 736, 350]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[156, 355, 790, 434]]<|/det|> +
Supplementary Figure 2. Comparison of differentially expressed genes and pathways between EP300 mutant vs. wildtype and NOTCH1 mutant vs. wildtype. A, Overlap of significantly differentially expressed genes (limma \(p< 0.01\) ) between EP300 mut vs. wt and NOTCH1 mut vs. wt. B, Up- and downregulated pathways (GSEA FDR \(q< 0.05\) ) and the comparisons between EP300 (mut vs. wt) and NOTCH1 (mut vs. wt). C, Scatter plot of log2 fold changes for all the profiled genes between EP300 (mut vs. wt) and NOTCH1 (mut vs. wt). D, Scatter plot of mRNA expression between EP300 and NOTCH1.
+ +<|ref|>text<|/ref|><|det|>[[152, 449, 840, 497]]<|/det|> +Of note, it is not possible to perform meaningful DE analysis comparing EP300 mutant vs wildtype within the same subgroup, as the number of mutated samples was too low in each subgroup, \(n = 1\) in differentiated, \(n = 2\) in immunogenic, \(n = 0\) in metabolic and \(n = 5\) in stemness groups. + +<|ref|>text<|/ref|><|det|>[[152, 513, 810, 576]]<|/det|> +10. Line296-299 In Fig. 9c left panel, three subtypes other than the stemness subtype showed a comparable frequency of truncating mutations in wnt pathway genes. Therefore, because the prediction of the effect of mutations is more reliable for truncating mutation than for missense mutation, it seems that deleterious Wnt pathway mutations are similar. + +<|ref|>text<|/ref|><|det|>[[151, 593, 832, 673]]<|/det|> +Response: We appreciated the reviewer's comment here. Our investigation here focussed on comparing the effect of mutations in Wnt pathways genes between stemness and other subtypes. We added one sentence in Line 364- 365 to make it clearer, "The stemness subtype also seemed to have the highest proportion of nonsense mutations in Wnt pathway genes". For the SIFT and PolyPhen- 2 analysis, we further clarified this as it was for "missense" mutations in Line 373. + +<|ref|>text<|/ref|><|det|>[[151, 690, 245, 704]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[150, 705, 844, 736]]<|/det|> +Line 99- 101 They designated four subgroups based on known functional gene expression rather than GSEA. + +<|ref|>text<|/ref|><|det|>[[150, 753, 839, 785]]<|/det|> +Response: We updated the wording here to "Functional annotation of representative genes in each cluster against known gene sets annotated these subtypes as..." In Line 102 + +<|ref|>text<|/ref|><|det|>[[150, 833, 810, 865]]<|/det|> +Reviewer #2 (Remarks to the Author): Expert in tumour immunology, NK cells, and oesophageal cancer + +<|ref|>text<|/ref|><|det|>[[150, 881, 840, 897]]<|/det|> +Comments for the manuscript entitled "Stemness and NK- like signatures define the poorest subtype + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[152, 85, 602, 100]]<|/det|> +of oesophageal squamous cell carcinoma" by Guozhong Jian et al. + +<|ref|>text<|/ref|><|det|>[[152, 116, 788, 148]]<|/det|> +This referee aims to comment on the non- bioinformaticall part if this manuscript, leaving the comments for the precise bioinformatics to experts on bioinformatics and statistics. + +<|ref|>text<|/ref|><|det|>[[150, 164, 848, 404]]<|/det|> +The manuscript presents an impressive molecular investigation of oesophageal squamous cell carcinoma (ESCC) from 120 Chinese patients. The authors have performed transcriptomics with GSEA and immune profiling, and mutational enrichment analyses, with the aim to find subtypes of tumors, and link this information to novel immune evasion strategies or drug sensitivity. The focus of the study is using bioinformatics, and the results from the authors own patient cohort is compared to previous studies on related cohorts, especially regarding the immune profiling strategy. There is no doubt that the study is of large importance, with ESCCs being one of the deadliest cancers worldwide today, with no effective therapies at hand. A study if this size, at this detailed molecular level, is difficult to find in the literature and will make a difference. Whereas the bioinformatics part of this study seems strong, the immunology and pathology sections are less robust. The manuscript is written in a very condensed scientific English, which makes it difficult to actually understand what has been done in the various panels of experiments. This also makes the reader insecure of what the authors actually have accomplished (the materials and methods (and figure legends) does not help or guide). To be able to fully understand this study, the manuscript has to be rewritten in a more detailed manner. Some comments are given below. + +<|ref|>text<|/ref|><|det|>[[150, 419, 844, 499]]<|/det|> +Response: We are glad that the reviewer found our study interesting and important for the field. We also thank the reviewer for such constructive comments for consolidating our conclusions to improve the quality of this manuscript. We have rewritten the manuscript in many places and added more detail in materials and methods, figure legends for various panels of experiments, which further clarified our results and improved the robustness. + +<|ref|>text<|/ref|><|det|>[[150, 514, 847, 595]]<|/det|> +1) Every panel of each figure needs to be explained better, both experimentally and statistically, to be able to understand what has been done. This goes for the material and methods part too. Controls should be added where appropriate, and in cases where a value is calculated compared to a control, the control needs to be described equally well. Full statistics should be explained also in Figure legends. + +<|ref|>text<|/ref|><|det|>[[150, 610, 846, 658]]<|/det|> +Response: Many thanks for these careful comments, we have extensively addressed and revised our manuscript in all aspects raised by this reviewer. We have expanded and explained our figure panels, figure legends and results. + +<|ref|>text<|/ref|><|det|>[[150, 674, 835, 770]]<|/det|> +2) Row 114. "The molecular subtypes present distinguished histological features". Is this based on these four photographs of four tumors? How representative are they? Where are the statistics behind this to be able to state this quite important finding? The authors should have access to all tumors, and thus be able to perform a tumor tissue array of paraffinized samples, to compare the histology of all 120 tumors on one single glass slide using a light microscope. This way statistics can be added. + +<|ref|>text<|/ref|><|det|>[[150, 786, 845, 899]]<|/det|> +Response: This is the same comment as comment #3 of reviewer #1. Our statement of the molecular subtypes present distinguished histological features was based on our observation of whole tumour tissue sections. In order to quantitatively and comprehensively identify the features of each subtype, we had generated the digitised whole slide images of H&E histology slides for all the tumour tissue, we instead developed a deep- learning/Al model, which used five pre- trained models, namely Inception- V3, Inception- ResNet- V2, DenseNet- 121, VGG16 and ResNet- 50, and performed feature extraction and correlated these features with the four transcriptomic subtypes to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 847, 213]]<|/det|> +identify significantly enriched histopathological features for each subgroup (see detail in the response of comment #3 of reviewer #1). These AI results still support our previous statement, with more quantitative measures to distinct molecular subtypes of ESCC based on the simple histopathological features. We believe this AI approach assessing the whole slide images of the tissue offers the more comprehensive overview of the tumour tissue compared to tissue array suggested here. Our deep- learning model identified significant enriched histopathological features in each transcriptomic subtype, which showed great consistency to the subtype annotation derived from signature genes of each subtype. + +<|ref|>text<|/ref|><|det|>[[150, 229, 842, 308]]<|/det|> +3) Row 116-120. The authors describe these histological features using nomenclature of keratin pearls, extensive immune infiltration etc, without showing it or even presenting how this was done or annotated. Again, to say this a tumor tissue array would be good and should be annotated and evaluated statistically. The material and methods section should be updated accordingly, presenting how keratin pearls or immune cell infiltration was assayed. + +<|ref|>text<|/ref|><|det|>[[149, 323, 842, 499]]<|/det|> +Response: We thank the reviewer for this insightful comment. Please see above response the AI model. We have also added the AI model part in the material and methods, and results. Furthermore, regarding immune infiltration, we also performed IHC of various immune cell markers, including CD4, CD8, and CD56, quantified and compared the IHC measurements among the transcriptomic and immune subtypes, in Fig2.c and Extend Data Figure 8a-b. The results demonstrated that immunogenetic subtype and the C2 subtype indeed had the highest level of immune cell infiltration, which was also supported by our AI pathology results (Extend Data Figure 1c). Regarding the quantification of keratin pearls, our deep-learning resource identified the DIFF- Feature significantly higher in the differentiated group compared to other groups. Tiles with high DIFF-Feature scores were enriched for keratin pearls (Figure 1c). we have added this part of the results in Line 152-169. + +<|ref|>text<|/ref|><|det|>[[150, 514, 841, 579]]<|/det|> +4) Row 126. Xenograft models are presented in the text, but no ethical permit or precise description of how it was exactly performed in present in the text or materials and methods. Just very vague descriptions referring to Extended data Fig 3. What is Ext data Fig 3a? Explain each panel. Extended data Fig 3 is a typical representative for the concerns mentioned above of too limited explanations. + +<|ref|>text<|/ref|><|det|>[[150, 595, 836, 658]]<|/det|> +Response: Thanks for the reviewer's comment. The ethical permit and details about Xenografts model were added in the Methods line 938- 940 in the revised manuscript. Besides, more results, descriptions and figure legends for new Extended data Fig. 4 (previously Extended data Fig. 3) were also added in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 675, 825, 707]]<|/det|> +5) Figure 2e, row 149, is this a Fisher's exact test? Where is the statistics shown in the figure? The figure legend is minimal. + +<|ref|>text<|/ref|><|det|>[[150, 723, 847, 770]]<|/det|> +Response: This is Fisher's exact test we used to test if there is any difference in the proportion of transcriptomic subtypes between different immune subtypes. We have added the statistics in the figure and explained in detail in the figure legend, Fig. 2f (line 605- 607). + +<|ref|>text<|/ref|><|det|>[[150, 786, 828, 849]]<|/det|> +6) Fig 2g. IHC controls are absent. A normal tissue should be used as control, and a cell line lacking (negative) or expressing (positive) should be shown to trust the IHC antibody specificity. Again, a tissue tumor array would be good to be able to conclude the results, only four samples are not enough to conclude. + +<|ref|>text<|/ref|><|det|>[[150, 865, 845, 897]]<|/det|> +Response: Thanks for the reviewer's helpful suggestion. All negative control had been performed before conducting IHC assay, and these results was now provided in Extended data Fig. 7 and Fig. 9. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 849, 213]]<|/det|> +Besides, all our staining were performed in paired slides including adjacent normal and cancer tissues, these results have been added in Extended data Fig 9. In fact, we had stained some markers in ESCC tissues microarrays (Shanghai Xinchao Biotechnology Co., Ltd.), while due to the sample area was too small and mostly devoid of submucosal adjunction tissue, so we finally used 99 pairs of original pathological sections for staining analysis of XCL1 and detailed results were provided in the revised manuscript Line 212- 219, Supplementary Table S4 and S5 of the revised manuscript to summarise the IHC staining of LGR6, XCL1 and CD160 in consecutive sections. In addition, the antibodies specificity were also confirmed by protein atlas or other users, and our Western blot results. + +<|ref|>text<|/ref|><|det|>[[150, 228, 837, 291]]<|/det|> +7) Row 158-166. How is this IHC annotation performed and shown? The authors show statistics in the text that is not described in detail, and cannot be found in the figures or legends. Is it Pearson Chi-square tests or what fo authors mean with co-expression? Tables of annotations? This needs to be clearly shown. + +<|ref|>text<|/ref|><|det|>[[149, 307, 846, 516]]<|/det|> +Response: We thank the reviewer for this insightful comment. We did IHC staining for detection of XCL1, CD160 and LGR6 in serial sections of each specimen. The H-score was calculated for the expression of LGR6 and XCL1 by the following formula. H-score value is \(= [1 \times (\text{% cells} 1+) + 2 \times (\text{% cells} 2+) + 3 \times (\text{% cells} 3+)\) in QuPath program. The number of cases coexpressing LGR6 and XCL1 or LGR6 and CD160 were counted and the percentage was calculated. We have included the detailed annotation of LGR6 and XCL1 IHC staining for all 99 available samples and CD160 IHC staining for 91 samples in the new Supplementary Table S4. Based on this table, we further counted the cases with LGR6+/XCL1+, LGR6+/XCL1-, LGR6-/XCL1+, LGR6-/XCL1- in the format of 2x2 contingency table to test if these two markers were expressed co-occasionally or not, using the two- tailed Fisher's exact test (Supplementary Table S5). This procedure was also done for the LGR6 and CD160 staining (Supplementary Table S4-5). Our IHC results show that LGR6 and XCL1 staining were significantly associated (co- stained or co- expressed) in our samples (two- tailed Fisher's exact test, \(p < 0.0001\) ), but LGR6 and CD160 staining were not significantly associated ( \(p = 1\) ). + +<|ref|>text<|/ref|><|det|>[[150, 532, 537, 548]]<|/det|> +We have updated this section of results in Line 212- 219. + +<|ref|>text<|/ref|><|det|>[[150, 563, 843, 611]]<|/det|> +8) From row 177 and on "NK-like tumor cells" are used to described tumor cells expressing CD160. It would be preferrable to not name the tumor cells "NK-like tumor cells", since they are tumor cells and not lymphocytes. + +<|ref|>text<|/ref|><|det|>[[150, 627, 843, 691]]<|/det|> +Response: We agree with the reviewer's suggestion, and have changed the wording to "tumour cells expressing NK marker genes", and removed "NK-like tumour cells" from our manuscript(From line 171). We also changed "NK-like signatures" to "NK marker XCL1 related signatures" to be more explicit in the manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 708, 843, 755]]<|/det|> +9) Fig 3f. How is the IC50 experiment performed exactly. The materials and methods do not describe what is being shown in panel 3f. How are the numbers calculated? At what concentration, time and compared to what? If a Mann-Whitney test is used, what exact control are the bars compared to? + +<|ref|>text<|/ref|><|det|>[[150, 771, 845, 882]]<|/det|> +Response: Following the reviewer's comments, we had revised and drug sensitivity analysis in the Method part Line 881- 897 "Drug sensitivity analysis". In the new Figure 3g (previous Fig. 3f), The IC50 experiment was performed on KYSE- 150, KYSE- 180, KYSE- 410 as normal controls and the corresponding XCL1 overexpressed cells from the same three cell lines. Mann- Whitney test is used to compare the IC50 values between the control vectors and the corresponding XCL1 overexpressing cells. To make it clear we now modified the figure labels: "control" changed to "vector", "XCL+" changed to "XCL". + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[151, 100, 845, 148]]<|/det|> +10) Figure 4 present the genomic mutational landscape. This is important. The authors continue with XCL1 as a promising biomarker for drug sensitivity, using cell lines, and EP300 for survival in the patient cohort. How can these be linked in patient material and survival? + +<|ref|>text<|/ref|><|det|>[[150, 164, 845, 291]]<|/det|> +Response: We thank the reviewer for this comment. We further investigated the expression of XCL1 in our patient cohort, and found that high XCL1 expression was significantly associated with worse overall survival (Extended Data Fig 10c). This is consistent with our results of NK cells and their clinical association (Figure 2e), since XCL1 is one of the major markers of our NK cell in silico estimates. Furthermore, we also found that both XCL1 and XCL2 had much more elevated expression in patient tumour samples compared to their matched normal (Extended Data Fig 10a- b). All these data suggest that XCL1 may have a tumour promoting role in ESCC. We have added these in the manuscript line 230- 234. + +<|ref|>text<|/ref|><|det|>[[150, 307, 845, 370]]<|/det|> +Furthermore, as demonstrated in Fig. 4b ESCC cell line mutational landscape, XCL1 high vs. low, \(36\%\) of XCL1 high cell lines had mutations in EP300, while there is no EP300 alteration in XCL1 downregulated cell line. This observation supports the potential association between XCL1 overexpression and EP300 mutations in the ESCC cancer cells. + +<|ref|>text<|/ref|><|det|>[[150, 402, 844, 483]]<|/det|> +11) Figure 5, the authors present immune infiltration and association with clonal diversity, and is also important. It would be good to perform IHC panels on some basic immune populations of the tumors to be able to support the data from the Shannon diversity index. Immune exclusion of T cells compared to M2 macrophages, as well as NK cells would be interesting to see. If CD160 is expressed on tumor cells. + +<|ref|>text<|/ref|><|det|>[[149, 498, 845, 674]]<|/det|> +Response: We have performed IHC on immune cell markers of CD4, CD8, CD56 and compared IHC measurement among the subtypes, in Fig 2c and Extend Data Figure 8. Consistent with our RNA- seq results, the IHC results demonstrated that the levels of these immune cells were significantly higher in immunogenic and C2 subgroups compared to other groups (Extended Data Fig 8 and Fig 2c). We also correlated the IHC measurements of immune cells with the Shannon diversity index (SDI) measured from the genomic data, and found the significantly negative correlations between them for CD8+ (correlation coefficient, \(r = - 0.29\) , \(p = 0.017\) ) and CD56+ ( \(r = - 0.274\) , \(p = 0.017\) ) stained cells (Extended Data Fig 8c), supporting our results of the potential interplay between immune infiltration and tumour clonal evolution (i.e., higher immune infiltration is associated with lower level of ITH, measured by Shannon diversity) (Fig. 5f). We have added this result in Extended Data Figure 8, and in Line 378 - 380. + +<|ref|>text<|/ref|><|det|>[[150, 689, 843, 818]]<|/det|> +Regarding the expression of CD160, the mRNA expression of CD160 was the highest in C3 immune subgroup, but not in C2 subgroup (Extended Data Fig 6a), and the IHC of CD56 and CD160 (Extend Data Figure 7 and 9) further demonstrated that CD160 was not expressed by CD56+ NK cells but by tumour and dysplastic cells. Indeed, we observed the evidence of CD160 expressed by LGR6+ tumour cells in 25 out of 91 cases (27%) (Supplementary Table S5). We included the co- staining data of CD56, CD160 and LGR6 in consecutive sections in Extended Data Figure 9. However, across the whole cohort of 91 available samples, LGR6 and CD160 IHC staining were not significantly associated ( \(p = 1\) , i.e., not significantly co- expressed by the tumour cells across the cohort). + +<|ref|>text<|/ref|><|det|>[[150, 851, 825, 883]]<|/det|> +(12) The manuscript needs to be rewritten, to add much more detail for each panel, to be able to understand what has been done. As it is now, it is difficult to interpret the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 845, 115]]<|/det|> +Response: We have followed the reviewer's advice and added much more detail in the results, figure legends and Methods and Materials for various panels of experiments throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[152, 148, 598, 163]]<|/det|> +Reviewer #3 (Remarks to the Author): Expert in cancer stem cells + +<|ref|>text<|/ref|><|det|>[[152, 180, 845, 227]]<|/det|> +In this study Jiang et al., aims at defining novel molecular subgroups in human Oesophageal Squamous Cell Carcinoma (ESCC) by analysing the transcriptome and genome of a big cohort of ESCC from Chinese patients. + +<|ref|>text<|/ref|><|det|>[[150, 243, 848, 500]]<|/det|> +The authors, using bulk- RNA sequencing, identify four distinct ESCC transcriptomic subtypes. Among them one shows the worst survival rate and is characterized by the expression of WFDC2, SFRP1, LGR6 and VWA2 genes ("stemness" subtype). The data obtained from the RNA sequencing analysis is then analysed using deconvolution methods to determine the tumor immune composition of the ESCC samples. Using this approach, they divide the tumors in three categories according to the content/type of immune cells present within the sample and identify a group of tumors showing high expression of NK- like gene signature, the group associated with the poorest survival rate. Interestingly, they observe that tumors showing high expression of XCL1 (gene upregulated within the NK gene signature and C3 immune type) present higher resistance to several drugs. Thirdly, the authors characterize the genomic landscape of the same cohort of patients and describe genomic landscapes similar to those described in the numerous genomic analyses that have been reported on ESCC (The Cancer Genome Atlas Research, N. et al. Nature 541, 169- 175 (2017); Song, Y. et al. Nature 509, 91- 95 (2014); Lin, D. C. et al. Nat. Genet. 46, 467- 473 (2014); Gao, Y. B. et al. Nat. Genet. 46, 1097- 1102 (2014)). Finally, the authors determine if there is any correlation between the transcriptomic and immune signatures and the mutational landscape of the ESCC analysed. + +<|ref|>text<|/ref|><|det|>[[151, 514, 840, 593]]<|/det|> +The main criticism is that this study lacks accuracy as many of the statements are not well sustained or only based on correlations. There is a lack of validation of the transcriptomic and immune signatures in biological samples and lack of experiments in biological samples aimed at supporting the numerous correlations present in the study. These validations and experiments would certainly help to strengthen and confirm the message of the paper. + +<|ref|>text<|/ref|><|det|>[[152, 609, 714, 625]]<|/det|> +Remarkably, there are some points that need to be further developed or clarified: + +<|ref|>text<|/ref|><|det|>[[150, 641, 848, 850]]<|/det|> +1- Using bulk RNA- sequencing the authors classify the ESCC analysed in 4 different subtypes characterized by the expression of different markers, subtypes that show different morphological characteristics and patient survival rates (Figure 1). The authors claim that they are interested to characterize both the tumor and tumor microenvironment. However, they do not analyse if the genes found to be upregulated in the different subgroups are expressed by the tumor cells or by the tumor microenvironment, which is extremely relevant to validate and strengthen this key point the authors want to make. This validation could be accomplished by performing immunostainings for the different markers in tumors from the 4 ESCC subtypes or alternatively using techniques that would allow a deeper characterization of the different cell populations present in the samples (single cell RNA sequencing). Using the latter approach, a recent paper (Zhang, X., Peng, L., Luo, Y. et al. Nat Commun 12, 5291, 2021) identified eight different common expression programs of epithelial cells in ESCC tumors and characterized the populations present in the tumor microenvironment of the same tumors. + +<|ref|>text<|/ref|><|det|>[[150, 866, 844, 898]]<|/det|> +Response: We thank the reviewer for such constructive comments here. We utilised the single cell RNA- seq data of 208,659 single cells from 60 individuals of ESCC (Zhang et al. Nat Commun 12, 5291, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 84, 847, 455]]<|/det|> +2021) to validate our subtype specific gene signatures. Based on the annotated cell clusters, we were able to see in which cell types / subtypes our signature genes were expressed. Out of the 208,659 cells, 44,122 were epithelial cells that were dominantly cancer cells (Zhang et al. Nat Commun. 2021). As shown in our Fig. 1a and Extended Data Figure 3, signature genes from differentiated, metabolic and stemness subtypes were mainly expressed by epithelial cells. Moreover, signature genes from these three subtypes seemed to be expressed by different subpopulations of epithelial cells, i.e., occupying different epithelial subclusters in UMAP. In fact, our differentiated subtype corresponds to the epithelial differentiation (Epi1/2) program identified by Zhang et al., with the overlap of many signature genes, such as LGALS7, LGALS7B, KRT16, KRT6B/C, FABP5 and LY6D of the Epi1 programme, S100A7/8/9, SPRR1A/B and SPRR2D of the Epi2 programme. Our metabolic subtype corresponds to the oxidative stress or detoxification (Oxd) program, with shared genes as CES1, ALDH1A1, ALDH3A1, AKR1C1/2/3 and GPX2 of the Oxd program. Although our stemness subtype was not characterised by the eight epithelial gene signatures of Zhang et al., the feature plot of LGR6, WFDC2 and SFRP1 in single cells clearly showed that these genes were expressed by a distinct subpopulation of epithelial cells (Fig. 1a and Extend Data Figure 3). As expected, signature genes of our immunogenic subtype were all expressed by non- tumour cells. For example, MS4A1, CD79A and MZB1 were expressed by B cells, CXCL9 was expressed mainly by myeloid cells, with some in fibroblasts, endothelial and pericytes (Fig. 1a and Extend Data Figure 3). Therefore, the single cell results further validated our findings derived from bulk tissue RNA- seq, and supported our four distinct transcriptomic subtypes. We have included this set of results in Line 118- 137. In addition, we have also done IHC for several immune cells characterisation, it is indeed that our four molecular subtypes show different immune cells infiltration (see our response to Reviewer 2 comment 11). + +<|ref|>text<|/ref|><|det|>[[150, 485, 848, 628]]<|/det|> +2- In Figure 2 the authors identify a cluster, cluster 3, characterized by the expression of NK markers, again it is not clear if these NK markers are expressed by the tumor cells (staining for XCL1 and Lgr6 Fig2 g superior panel is too weak to be able to conclude anything and morphologically the tumor shown does not seem a "stemness" tumor) or if there is infiltration of NK cells or presence of NK cells surrounding the tumors (staining for a NK marker would be extremely helpful). Therefore the description of the immune infiltration and immune microenvironment is superficial and needs to be improved. In addition, only \(50\%\) of the stemness- subtype tumors could be classified as belonging to the immune cluster 3 (Fig 2e), so the statement "given the strong association between stemness and NK cell estimates- line 154- 155" is overstated and should be corrected. + +<|ref|>text<|/ref|><|det|>[[150, 645, 848, 857]]<|/det|> +Response: We thank the reviewers for the insightful comment here. Our RNA- seq data showed that NK markers XCL1, XCL2 and CD160 were the highest in the C3 cluster (Fig 2b and Extended Data Fig6a). Following the reviewer's advice, we further stained NK cell marker CD56 in our cohort, and the IHC results showed that the level of CD56 was the highest in C2 cluster, but significantly lower in both C1 and C3 clusters (Fig 2c). This was also supported by the mRNA expression of other NK markers, such as NKG7 and KLRC1, being the highest in C2 cluster, but low in C3 and C1 clusters (Extended Data Fig 6a). These results suggest that the level of CD56+ NK cell infiltration was low in the C3 cluster. Following further inspection of the XCL1 and LGR6 IHC staining in stemness and other groups, we concluded that XCL1 were not expressed by NK cells (CD56+) in our tissues, instead by tumour cells and other dysplastic epithelial cells of submucosa glands. These results suggest that XCL1 was expressed by tumour cells and dysplastic cells of submucosa gland across our cohort. We have included the IHC staining results in Figure 2h, Extended Data Fig 6- 9, Supplementary Table S4- 5, and added the results in Line 212- 219. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[151, 84, 823, 132]]<|/det|> +We also agree with the reviewer's comment regarding "the strong association between stemness and NK cell estimates", and have changed our wording throughout the manuscript to "there is a degree of positive correlation between stemness and NK estimate high subgroups". + +<|ref|>text<|/ref|><|det|>[[150, 165, 845, 276]]<|/det|> +3- One of the genes that characterize Cluster 3 (NK- like signature) is XCL1. The authors show using GSEA that XCL1- high cells exhibit upregulation of drug metabolism of cytochrome P450, retinol metabolism and biological oxidations (line 185) and in line 106 the authors state "the metabolic subtype is associated with the upregulation of genes involved in drug metabolism by cytochrome P450 and retinol metabolism". Would this mean that tumors showing high XCL1 expression belong to the "metabolic subtype"? This is confusing and highlights that the link between XCL1 (NK- like) and "stemness subtype" or "metabolic subtype" should be better explained. + +<|ref|>text<|/ref|><|det|>[[150, 293, 845, 484]]<|/det|> +Response: We thank the reviewer for this detailed observation. To further test how similar the pathway activity is for drug metabolism by cytochrome P450 and retinol metabolism between XCL1- high vs. low and metabolic vs. others comparisons, we compared the t- statistics derived from limma differential expression analysis (a statistics combining both log2 fold change 'magnitude' and p- value 'significance') for genes involved in these two pathways. As shown in the figures below (Supplementary Figure S3 of this rebuttal), there was a weak correlation in t- statistics between XCL1- high and metabolic subtypes for genes involved in drug metabolism by cytochrome P450 and retinol metabolism. This analysis suggests that different subsets of genes contributed to the upregulation of these two pathways seen in XCL- high cells and the metabolic subtype. Furthermore, there was also very minimum number of signature genes shared between XCL1- high and metabolic subtype. Therefore, there is no evidence that suggests tumours showing high XCL1 expression belong to the metabolic subtype. + +<|ref|>image<|/ref|><|det|>[[152, 516, 816, 678]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[152, 501, 328, 514]]<|/det|> +
Supplementary Figure S3
+ +<|ref|>text<|/ref|><|det|>[[150, 712, 844, 840]]<|/det|> +The association between immune and transcriptomic subtypes was based on Fig. 2f. Out of 31 samples in C3 (NK high), 15 were from the stemness, 6 from metabolic, 8 from differentiated and 2 from immunogenic subtypes, suggesting there is a degree of enrichment of stemness samples in the C3 subgroup. We have followed the reviewer's advice, and rephrase the association between stemness and NK estimate high subgroups throughout the manuscript. We have also added a sentence in Line 248- 250, "it is worth noting that different subsets of genes contributed to the upregulation of drug metabolism by cytochrome P450 and retinol metabolism were seen in XCL- high cells and the metabolic subtype" to further clarify the point here. + +<|ref|>text<|/ref|><|det|>[[150, 856, 833, 903]]<|/det|> +4- In Figure 2g, Extended Data Figure 5c and line 164- 172, the authors state that XCL1 is exclusively expressed in cancer cells showing adenocarcinoma morphology. Should we consider all XCL1- expressing tumours adeno- squamous cell carcinomas? If so, the authors should repeat the analysis + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 828, 116]]<|/det|> +by studying the ESCC and adeno- squamous cell carcinomas separately as relevant differences may be found in terms of transcriptomics, genomics and response to chemotherapy. + +<|ref|>text<|/ref|><|det|>[[150, 132, 840, 308]]<|/det|> +Response: We appreciate the reviewer's insightful comment here. Following this reviewer's comments, we comprehensively reviewed the whole section of resected samples of IHC staining for XCL1 expression from 99 available samples, XCL1 espression was predominantly expressed in cancer cells showing adenocarcinoma morphology, but some squamous carcinoma cells also expressed XCL1. Therefore, we have updated our description and conclusion in our revised manuscript accordingly. Esophageal adeno- squamous cell carcinoma is a very rare disease clinically. It is an extremely difficult task to assemble an Esophageal adeno- squamous cell carcinoma sample cohort in a decent size that allows to investigate the transcriptomic / genomic landscape with enough statistic power. To study the transcriptomics, genomics and response to chemotherapy of adeno- squamous cell carcinomas is an extremely interesting and valuable topic scientifically and clinically. However, this is beyond the scope of our current study. + +<|ref|>text<|/ref|><|det|>[[150, 323, 843, 387]]<|/det|> +5- The authors suggest that XCL1- high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +<|ref|>text<|/ref|><|det|>[[149, 402, 839, 610]]<|/det|> +Response: We thank the reviewer for this comment. To further support our results based on RNA- seq, we utilised the single cell RNA- seq data from Zhang et al. (Nat Commun 12, 5291, 2021) to perform further studies. Focussing on the epithelial cells, we were able to identify 515 XCL1 positive cells (expression level CPM>0) and 32,944 XCL1 negative cells (expression level =0). We then calculated the expression level of each gene programme of cell cycle on single cell level (e.g., REACTOME_CELL_CYCLE_CHECKPOINTS, REACTOME_CELL_CYCLE_MITOTIC) using Seurat AddModuleScore function, and showed that XCL1 positive (XCL1+) cells had significantly lower cell cycle activities than XCL1 negative (XCL1-) cells (Wilcox test, \(p = 7.48e - 06\) for REACTOME_CELL_CYCLE_CHECKPOINTS; \(p = 0.001\) for REACTOME_CELL_CYCLE_MITOTIC), which is consistent to our data. We have added this results in Fig. 3e and Line 256- 259. Of note, overexpression of XCL1 does not significantly affect the cell proliferation (see extended data Fig 11d), the reviewer's suggestion to do Brdu/Edu incorporation might be helpful, which is to be performed in a separate project. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 291, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 392, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 163, 879, 199]]<|/det|> +The authors have substantially clarified the figures and manuscript, and addressed the majority of points raised, but still the first point remained. + +<|ref|>text<|/ref|><|det|>[[114, 217, 878, 345]]<|/det|> +In the Results section (lines 97- ), they claimed that they first performed unsupervised clustering and then identified gene signatures based on the classification. However, in their rebuttal, they explained that they chose \(k = 4\) (the number of clusters) based on NMF cophenetic coefficient and heterogeneous molecular signatures. As these molecular signatures appear to be predefined, they intentionally opted for four clusters, which represent differentiation, immunogenicity, metabolic characteristics, and stemness. If this is indeed the case, they should have initially mentioned the prior knowledge of the four classifications. + +<|ref|>text<|/ref|><|det|>[[116, 411, 392, 427]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 448, 759, 465]]<|/det|> +The authors have answered my comments and improved the clarity/statistics in the text. + +<|ref|>text<|/ref|><|det|>[[116, 521, 392, 537]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 557, 865, 630]]<|/det|> +The data and figures have improved substantially. However, in this revision the authors have only partially addressed my previous questions and comments. The new version of manuscript is difficult to follow as it is written in a rather condensed manner and the supplementary figures do not follow the same order as the text (ie. Extended Data Fig 6b). + +<|ref|>text<|/ref|><|det|>[[115, 666, 480, 683]]<|/det|> +There are some points that need to be addressed: + +<|ref|>text<|/ref|><|det|>[[115, 703, 872, 794]]<|/det|> +1. In Figure 1a lower panel the authors analyse the scRNAseq data from another study (Zhang et al). However, it is not possible to interpret this figure 1a without going to Ext DataFig 3. The main figures of an article should be self-explanatory. For this reason, the description of the clusters should be in Figure 1a not in a supplementary figure. Or alternatively the authors should move all the scRNAseq to Ext Data Fig 3. + +<|ref|>text<|/ref|><|det|>[[115, 850, 865, 904]]<|/det|> +2. In Figure 1c the authors should better describe and annotate within the images the features characteristic of each of the subtypes. And ideally, validate the results of the bulk RNA seq using in situ hybridization or immunofluorescence. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 542, 125]]<|/det|> +3. The quality of many of the stainings presented are poor. + +<|ref|>text<|/ref|><|det|>[[115, 144, 880, 217]]<|/det|> +Fig 2 and Ext Data Fig 9: stainings for XCL1, CD56 and CD160 not to work. In Ext Data Fig 9 XCL1 and the rest of the stainings are not "matched serial sections of tumour tissues" as described in the text line 208. The staining of serial sections for the markers described is essential to prove the authors' hypothesis and should be performed accurately. + +<|ref|>text<|/ref|><|det|>[[115, 237, 487, 253]]<|/det|> +The images for LGR6 staining need to be improved. + +<|ref|>text<|/ref|><|det|>[[115, 272, 867, 326]]<|/det|> +4. In line 136 the authors claim "Therefore, the single cell results further validated our findings derived from bulk tissue RNA-seq, and supported our four distinct transcriptomic subtypes". In the scRNAseq data from Zhang et al the stemness subtype is not described, so this statement should be corrected. + +<|ref|>text<|/ref|><|det|>[[115, 345, 882, 418]]<|/det|> +5. In line 248 the authors claim "It is worth noting that different subsets of genes that contributed to the upregulation of drug metabolism of cytochrome P450 and retinol metabolism were seen in XCL-high cells and metabolic subtype". How did the authors reach that conclusion? What and where is the data that made them conclude that? This point should be better explained. + +<|ref|>text<|/ref|><|det|>[[115, 438, 579, 455]]<|/det|> +6. The authors did not reply to my previous question number 5: + +<|ref|>text<|/ref|><|det|>[[115, 474, 865, 546]]<|/det|> +The authors suggest that XCL1-high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +<|ref|>text<|/ref|><|det|>[[115, 565, 857, 637]]<|/det|> +The answer that they provide is a correlation based on the data of the scRNA seq from Zang et al. and from that correlation it cannot be concluded that the cells are slow- cycling/ quiescent. Performing BrdU/EdU incorporation studies in cell lines or staining for quiescence markers in human samples is relatively quick to accomplish and needed in order to conclude such a statement. + +<|ref|>text<|/ref|><|det|>[[115, 656, 875, 709]]<|/det|> +8. In the abstract line 50 the authors state "functional mutation enrichment in the Wnt signalling". What does this mean: mutations that lead to the in/activation of the Wnt signalling pathway? This should be clarified. + +<|ref|>text<|/ref|><|det|>[[115, 768, 240, 783]]<|/det|> +Minor comment: + +<|ref|>text<|/ref|><|det|>[[115, 804, 517, 820]]<|/det|> +The image scale in Ext Data Fig7 needs to be improved. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 794, 125]]<|/det|> +Reviewer #4 (Remarks to the Author): Expert in oesophageal cancer subtypes, genomics, and bioinformatics + +<|ref|>text<|/ref|><|det|>[[115, 144, 869, 180]]<|/det|> +Disclaimer: I did not participate in the first round of review of the initial submission, and I am providing my review on their revised work. + +<|ref|>text<|/ref|><|det|>[[115, 199, 880, 309]]<|/det|> +In this manuscript, the authors performed whole- exome sequencing and bulk RNA- seq on 120 Chinese ESCC patients. They identified 4 RNA- defined subtypes: differentiated, metabolic, immunogenic and stemness. Using deep- learning model, they showed that these 4 subtypes were associated with different histological features, implying their biological basis. Moreover, they identified that NK cell markers including XCL1 and CD160, were surprisingly expressed by a subset of tumor cells. XCL1 were followed upon and its expression confers the sensitivity of ESCC cells to chemotherapeutic drugs. + +<|ref|>text<|/ref|><|det|>[[115, 327, 860, 418]]<|/det|> +This is a comprehensive work of tour de force: there were large amount of sequencing data, bioinformatic analyses, massive imaging data processing, as well as fairly extensive biological investigations. Some of the findings are strong and may have significant implications, such as the identification of 4 subtypes and XCL1 investigation. However, I do find a number of weaknesses which need to be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 439, 213, 455]]<|/det|> +Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 474, 876, 528]]<|/det|> +1) What is the relationship between these newly designated subtypes with the TCGA subtypes? This can be done by looking at shared pathways enriched in different subtyping schema. For example, in TCGA, ESCC1 has frequent upregulation of oxidative pathways. Is ESCC1 similar as the Metabolic subtype here? + +<|ref|>text<|/ref|><|det|>[[115, 546, 861, 637]]<|/det|> +2) The validation using external single-cell RNA-seq data is useful but somewhat superficial. What was shown was merely that the selected genes from different subtypes could be expressed by different clusters from scRNA-seq, which is largely expected. What really needs to be addressed is do these different clusters from scRNA-seq show similar biology or transcriptional programs to bulk RNA-seq defined subtypes? + +<|ref|>text<|/ref|><|det|>[[115, 655, 863, 764]]<|/det|> +3) The investigation of SFRP1 needs further development. The authors described that IHC staining was done on its protein, but did not mention how many tumor and normal samples were stained. Is SFRP1 expressed higher in tumor vs normal samples? What is the percentage of SFRP1 expression in tumor samples? Since it was proposed as a stemness related genes, does it correlate with the differentiation status of the tumors? The knockdown efficiency (Fig. s1e,f) appears poor, and the WB needs to be quantified. + +<|ref|>text<|/ref|><|det|>[[115, 783, 869, 874]]<|/det|> +4) Associating histological features to different transcriptomic subtypes is helpful and can support their biological underpinnings. However, at this scale (Fig.1C), the histological features are difficult to discern for most readers who are not trained pathologists. For example, it is hard to see immune cells or eosinophilic cytoplasm at this resolution. It would be very helpful to add certain IHC markers to make these histological features conspicuous. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 875, 162]]<|/det|> +5) The investigation of XCL1 in cancer cells was a highlight in this work. However, I could not find any IHC image showing strong XCL1 staining. The ones included, such as Fig.2h, Fig.5c, were very weak. The authors need to show convincing strong IHC signals of XCL1 in cancer cells, since this is one of their key findings. + +<|ref|>text<|/ref|><|det|>[[114, 181, 872, 290]]<|/det|> +6) Line 224-228. "Interestingly, we observed that XCL1-expressing dysplastic cells in the submucosal gland in most of the cases are completely separated from the squamous cell carcinoma, suggesting that this subgroup of patients might concurrently have both squamous cell carcinoma and adenocarcinoma or this adeno-squamous carcinoma might be derived from submucosa gland epithelial cells". These are indeed very interesting! However, no data was shown. Can the authors perform a statistical analysis to compare the histology of these tumors vs. XCL1 expression? + +<|ref|>text<|/ref|><|det|>[[115, 309, 871, 381]]<|/det|> +7) Line 256-258, it is a bit concerning that XCL1 is only expressed in 515 out of 33459 (1.5%) total epithelial cells from the single-cell RNA-seq data. Can the authors explain why such low frequency? Is it because of the high cutoff used? This low positivity negatively affects the significance of the biological contribution of XCL1 in ESCC. + +<|ref|>sub_title<|/ref|><|det|>[[115, 402, 216, 417]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 419, 872, 491]]<|/det|> +1) The RNA-seq and WES data are still under controlled access and not publicly available. I think it is Nat Communication's policy that these data will need to be made publicly available upon acceptance. +2) "an independent cohort of 65 ESCC patients" in Fig.1e was not described in the methods or results. Where were these samples from? Were they all primary tumors? + +<|ref|>text<|/ref|><|det|>[[115, 558, 723, 575]]<|/det|> +Reviewer #5 (Remarks to the Author): Expert in digital pathology and deep learning + +<|ref|>text<|/ref|><|det|>[[115, 594, 872, 666]]<|/det|> +In this article, the authors propose a new subclassification of esophageal squamous cell carcinoma. This is clinically interesting because most previous efforts at subtyping this disease also included other histologies of esophageal cancer such as adenocarcinomas or gastroesophageal junction tumors. It is sensible to focus exclusively on squamous cell esophageal cancer and attempt to subtype it. + +<|ref|>text<|/ref|><|det|>[[115, 685, 875, 720]]<|/det|> +My expertise is specifically in digital pathology, so I am reviewing the digital histopathology model which the authors utilized. + +<|ref|>text<|/ref|><|det|>[[115, 740, 678, 757]]<|/det|> +Unfortunately, there are some concerns regarding the deep learning analysis. + +<|ref|>text<|/ref|><|det|>[[115, 777, 872, 830]]<|/det|> +1. Some methodological details are not entirely clear. For instance, what does a downsampling factor of 64 fold mean? The authors should specify their final resolution in micrometers per pixel and then provide the absolute pixel size for their tiles. + +<|ref|>text<|/ref|><|det|>[[115, 850, 847, 904]]<|/det|> +2. Additionally, they mention that they manually discarded some images. This is concerning, and it is crucial for them to clearly state why these images were discarded. What precisely constituted "poor quality"? Moreover, it would be beneficial to know how many images per class were discarded. The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 722, 107]]<|/det|> +manuscript would benefit from a CONSORT- style diagram to elucidate these points. + +<|ref|>text<|/ref|><|det|>[[115, 126, 879, 162]]<|/det|> +3. It is also vital that the study adheres to the STARD (or similar) guidelines, ensuring that all boxes in this guideline are ticked. + +<|ref|>text<|/ref|><|det|>[[114, 181, 879, 417]]<|/det|> +4. Regarding the design of the algorithm, the authors mention that they extracted features with five pretrained neural networks. However, the rationale for this decision is unclear. This choice, which appears quite uncommon, needs further explanation. Typically, one would use just a single robust network, selected through a hyperparameter tuning experiment on a dedicated tuning set. Alternatively, one might opt for a network that has been validated in previous studies. Ideally, the contemporary standard involves not using a network pre-trained on ImageNet, but rather one that has been pretrained in a self-supervised manner on histopathology images, such as the RetCCL network or the CTransPath network. In summary, the image analysis algorithm presented seems non-standard. While the authors might have had valid reasons for these unconventional design choices, they need to elucidate their reasoning in the manuscript. It would be even more beneficial if the authors employed a state-of-the-art pipeline (such as CLAM or the one from Wagner et al., Cancer Cell, 2023), or if they presented benchmarking experimental results showing their methods' superiority compared to more conventional methods. + +<|ref|>text<|/ref|><|det|>[[115, 437, 878, 491]]<|/det|> +5. Lastly, there are concerns regarding the statistical measures for the gene expression classification. The authors used a t-test, but they did not specify whether all the prerequisites for a t-test were met. This information needs to be explicitly stated. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[293, 85, 702, 100]]<|/det|> +## Point by point responses to the Reviewers comments + +<|ref|>text<|/ref|><|det|>[[120, 116, 402, 131]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 147, 856, 179]]<|/det|> +The authors have substantially clarified the figures and manuscript, and addressed the majority of points raised, but still the first point remained. + +<|ref|>text<|/ref|><|det|>[[118, 195, 875, 307]]<|/det|> +In the Results section (lines 97- ), they claimed that they first performed unsupervised clustering and then identified gene signatures based on the classification. However, in their rebuttal, they explained that they chose \(k = 4\) (the number of clusters) based on NMF cophenetic coefficient and heterogeneous molecular signatures. As these molecular signatures appear to be predefined, they intentionally opted for four clusters, which represent differentiation, immunogenicity, metabolic characteristics, and stemness. If this is indeed the case, they should have initially mentioned the prior knowledge of the four classifications. + +<|ref|>text<|/ref|><|det|>[[117, 323, 877, 483]]<|/det|> +Response: Thanks for this reviewer's appreciation on our substantial work done in the revised manuscript. We did not predefine any molecular signatures before the NMF clustering. NMF clustering is an unsupervised clustering algorithm that identifies patient clusters simply based on the expression values of input genes, i.e., in our case, top 1,500 variable genes with largest mean absolute deviation values across samples were used. Although \(k = 2\) gave the best cophenetic correlation \(r = 0.99\) , this was followed by almost equally great performances of \(k = 4\) and \(k = 3\) , with both having the cophenetic correlation \(r > 0.98\) (Extended Data Fig. 1a). As \(k = 4\) uncovered the level of heterogeneity and granularity of transcriptomic patterns in a finer resolution, and samples were evenly distributed among the four groups, \(k = 4\) was therefore selected. This has led to the discovery of our four transcriptomic clusters. + +<|ref|>text<|/ref|><|det|>[[118, 499, 873, 564]]<|/det|> +We have updated the wording in Methods as "Although \(k = 2\) gave the best cophenetic correlation \(r = 0.99\) , \(k = 4\) also achieved great clustering performance with cophenetic correlation \(r = 0.985\) , and the latter ( \(k = 4\) ) uncovered the level of heterogeneity and granularity of transcriptomic patterns in a finer resolution, thus was selected for our investigation", highlighted in line 742- 745. + +<|ref|>text<|/ref|><|det|>[[119, 610, 402, 625]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 642, 780, 658]]<|/det|> +The authors have answered my comments and improved the clarity/statistics in the text. + +<|ref|>text<|/ref|><|det|>[[118, 674, 603, 690]]<|/det|> +Response: We really appreciate Reviewer #2's positive response. + +<|ref|>text<|/ref|><|det|>[[119, 737, 402, 753]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 769, 868, 834]]<|/det|> +The data and figures have improved substantially. However, in this revision the authors have only partially addressed my previous questions and comments. The new version of manuscript is difficult to follow as it is written in a rather condensed manner and the supplementary figures do not follow the same order as the text (ie. Extended Data Fig 6b). + +<|ref|>text<|/ref|><|det|>[[119, 850, 493, 866]]<|/det|> +There are some points that need to be addressed: + +<|ref|>text<|/ref|><|det|>[[115, 882, 866, 898]]<|/det|> +1. In Figure 1a lower panel the authors analyse the scRNAseq data from another study (Zhang et al). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 872, 148]]<|/det|> +However, it is not possible to interpret this figure 1a without going to Ext DataFig 3. The main figures of an article should be self- explanatory. For this reason, the description of the clusters should be in Figure 1a not in a supplementary figure. Or alternatively the authors should move all the scRNAseq to Ext Data Fig 3. + +<|ref|>text<|/ref|><|det|>[[118, 164, 874, 212]]<|/det|> +Response: Following the reviewer's helpful comment, we have moved all single cell RNA- seq related data to the new Ext Data Fig 3 and 4, and also created a new Ext Data Fig 4 regarding the subtypes of ESCC epithelial single cells, as requested by the comment #2 of Reviewer #4. + +<|ref|>text<|/ref|><|det|>[[118, 243, 860, 290]]<|/det|> +2. In Figure 1c the authors should better describe and annotate within the images the features characteristic of each of the subtypes. And ideally, validate the results of the bulk RNA seq using in situ hybridization or immunofluorescence. + +<|ref|>text<|/ref|><|det|>[[117, 307, 876, 530]]<|/det|> +Response: Thanks for this helpful comment. We have redone the Fig 1c with the inserted high magnification pictures to address the specific features of each subtype, in addition to the further explanation in the figure legend. We completely agree with this reviewer's comment, in situ hybridization or immune- fluorescence staining is an ideal way to validate the bulk RNA sequencing data, regrettably we were not able to do this in an available time frame due to the difficulty to find specific probes and antibodies specifically recognising the specific markers in each subtype of ESCC. However, one of the major findings in this manuscript is that we developed AI pathology (see new Extended Data Fig. 6), which can correlate and predict the subtype of ESCC based on the H&E morphology. The features described in Fig 1C with further annotation may be sufficient to support the conclusion of this manuscript. Furthermore, we have also validated our transcriptomic subtypes using the single cell RNA-seq data of 60 ESCC samples (new Ext Data Fig 3 and 4). Therefore, we hope the reviewer would agree that the data and results supported from the deep- learning histopathology model and single- cell RNA-seq were strong and convincing to support the subtypes derived from our bulk RNA-seq. + +<|ref|>text<|/ref|><|det|>[[118, 562, 556, 577]]<|/det|> +3. The quality of many of the stainings presented are poor. + +<|ref|>text<|/ref|><|det|>[[118, 593, 866, 657]]<|/det|> +Fig 2 and Ext Data Fig 9: stainings for XCL1, CD56 and CD160 not to work. In Ext Data Fig 9 XCL1 and the rest of the stainings are not "matched serial sections of tumour tissues" as described in the text line 208. The staining of serial sections for the markers described is essential to prove the authors' hypothesis and should be performed accurately. + +<|ref|>text<|/ref|><|det|>[[118, 674, 500, 689]]<|/det|> +The images for LGR6 staining need to be improved. + +<|ref|>text<|/ref|><|det|>[[118, 705, 878, 817]]<|/det|> +Response: Apologies for this. We found that the pictures in the convert version of pdf file for the reviewer's review were indeed not clear due to the compressed file. We have now provided the high quality of all pictures in Fig 2h, Extended Data Fig 8- 9 and Extended Data Fig 11 in the new version. In particular, we have redone Ext Data Fig 11 (the previous Ext Data Fig 9) for XCL1 staining using the matched serial sections of tumour tissues and the corresponding normal tissues in our revised manuscript (Ext Data Fig 11 panel a and panel b). In particular, the data demonstrated the co- staining of LGR6 and CD160 and/or XCL1 in many ESCC tumour cells which were CD56 negative. + +<|ref|>text<|/ref|><|det|>[[118, 834, 718, 849]]<|/det|> +We sincere hope that this reviewer will be satisfied with the new set of pictures. + +<|ref|>text<|/ref|><|det|>[[115, 881, 826, 897]]<|/det|> +4. In line 136 the authors claim "Therefore, the single cell results further validated our findings + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 866, 132]]<|/det|> +derived from bulk tissue RNA- seq, and supported our four distinct transcriptomic subtypes". In the scRNAseq data from Zhang et al the stemness subtype is not described, so this statement should be corrected. + +<|ref|>text<|/ref|><|det|>[[118, 148, 852, 179]]<|/det|> +Response: We thank the reviewer for this comment. This comment is highly related to the second comment from Reviewer #4. We have updated this section as follows: + +<|ref|>text<|/ref|><|det|>[[116, 196, 879, 499]]<|/det|> +To further look into the heterogeneity and granularity of transcriptional programmes of ESCC epithelial cells, the NMF clustering with \(k = 10\) factors was performed on \(\sim 44,000\) epithelial cells of Zhang et al., Nat Comms 2021 (similar techniques also used in Gojo et al., Cancer Cell 2020, Lai et al., Int J Cancer 2021 and DeMartino et al., Nat Comms 2023, and many others), followed by the differential expression analysis using the Seurat "FindMarkers" function to identify top differentially expressed genes. Signature genes for each cluster were identified based on adjusted p- value \(< 0.0001\) and log2 fold change \(>1\) . Top 50 signature genes were then selected based on the log2 fold change for each cluster (new Extended Data Fig. 4). The NMF clusters were annotated based on their signature genes and up/down- regulated pathways. Their corresponding expression programmes of Zhang et al., 2021 and our related transcriptomic subtypes were identified based on shared signature genes (Extended Data Fig. 4). The NMF Cluster 5 and 10 appeared to correspond to the differentiated subtype, with Cluster 4 corresponding to the metabolic subtype, Cluster 6 corresponding to the immunogenic subtype, while Cluster 1 shared many stemness signature genes, such as SFRP1, WFDC2 and LGR6 (Extended Data Fig. 4). Cluster 1 also had significantly upregulated Wnt signalling and NCAM1 interactions, and the most downregulated keratinization / cornified envelope and metabolism pathways, which were all signature pathway activities for the stemness subtype. Reassuringly, all previous eight expression programmes of epithelial cells from Zhang et al., 2021 were identified in our single- cell NMF clusters. These single cell results further validated and support the robustness of our four transcriptomic subtypes derived from bulk tissue RNA- seq. + +<|ref|>text<|/ref|><|det|>[[118, 515, 872, 546]]<|/det|> +We have updated this section in Results section highlighted in line 125- 147 and Methods section line 909 - 916. + +<|ref|>text<|/ref|><|det|>[[118, 578, 875, 641]]<|/det|> +5. In line 248 the authors claim "It is worth noting that different subsets of genes that contributed to the upregulation of drug metabolism of cytochrome P450 and retinol metabolism were seen in XCL-high cells and metabolic subtype". How did the authors reach that conclusion? What and where is the data that made them conclude that? This point should be better explained. + +<|ref|>text<|/ref|><|det|>[[118, 658, 866, 721]]<|/det|> +Response: We previously showed this result only in our responses to the reviewers' comments, but not included in the main text, please see below (in green font) from the rebuttal of last round. We have now included this figure in the new Extended Data Fig. 13 and the associated results in the figure legend to clarify and support this point here, in new Line 267- 270 (Extended Data Fig. 13). + +<|ref|>text<|/ref|><|det|>[[117, 737, 876, 897]]<|/det|> +"Response: We thank the reviewer for this detailed observation. To further test how similar the pathway activity is for drug metabolism by cytochrome P450 and retinol metabolism between XCL1- high vs. low and metabolic vs. others comparisons, we compared the t- statistics derived from limma differential expression analysis (a statistics combining both log2 fold change 'magnitude' and p- value 'significance') for genes involved in these two pathways. As shown in the figures below (Supplementary Figure S3 of this rebuttal), there was a weak correlation in t- statistics between XCL1- high and metabolic subtypes for genes involved in drug metabolism by cytochrome P450 and retinol metabolism. This analysis suggests that different subsets of genes contributed to the upregulation of these two pathways seen in XCL- high cells and the metabolic subtype. Furthermore, there was also very minimum number of signature genes (i.e., significantly upregulated genes) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 844, 117]]<|/det|> +shared between XCL1- high and metabolic subtype. Therefore, there is no evidence that suggests tumours showing high XCL1 expression belong to the metabolic subtype. + +<|ref|>sub_title<|/ref|><|det|>[[119, 133, 312, 147]]<|/det|> +## Supplementary Figure S3 + +<|ref|>image<|/ref|><|det|>[[120, 150, 825, 305]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 337, 852, 386]]<|/det|> +We have also added a sentence in Line 256- 258, "it is worth noting that different subsets of genes contributed to the upregulation of drug metabolism by cytochrome P450 and retinol metabolism were seen in XCL- high cells and the metabolic subtype" to further clarify the point here." + +<|ref|>text<|/ref|><|det|>[[118, 417, 595, 433]]<|/det|> +6. The authors did not reply to my previous question number 5: + +<|ref|>text<|/ref|><|det|>[[118, 448, 866, 513]]<|/det|> +The authors suggest that XCL1- high cells are slow cycling (line 191- 193). This is an important point that could explain the higher chemotherapy resistance observed (Fig3). I would recommend the authors to study this point in more detail as it is quite relevant and could increase the impact of the study. BrdU/EdU incorporation studies can help to uncover this matter. + +<|ref|>text<|/ref|><|det|>[[118, 529, 870, 592]]<|/det|> +The answer that they provide is a correlation based on the data of the scRNA seq from Zang et al. and from that correlation it cannot be concluded that the cells are slow- cycling/ quiescent. Performing BrdU/EdU incorporation studies in cell lines or staining for quiescence markers in human samples is relatively quick to accomplish and needed in order to conclude such a statement. + +<|ref|>text<|/ref|><|det|>[[117, 608, 877, 737]]<|/det|> +Response: Following this insightful comment, we did Edu incorporation studies and cell cycle analysis of XCL1 overexpressed cell lines and the counterpart control cell line, the detailed results were shown in the new Extended Data Fig. 14, and also included the method section Line 965- 975. It seemed that there was no significant difference of Edu incorporation between the XCL1 overexpressed cell lines and the control cell lines. This suggests that XCL1 did not seem to affect the G1/S phase of cell cycle although mRNA expression levels of cell cycle related genes were significantly reduced in XCL1 high cells compared to low cells. This warrants further investigation. We have rephrased our results of this part as follows in Results Line 278- 282 in our revised version. + +<|ref|>text<|/ref|><|det|>[[118, 752, 844, 815]]<|/det|> +"Although mRNA expression levels of cell cycle related genes were reduced in XCL1- high cells compared to XCL low cells, XCL1 overexpression in ESCC cells did not functionally affect cell cycle (Extended Data Fig. 14). More work is needed to further elucidate its role in cell cycle and other pathways associated with ESCC." + +<|ref|>text<|/ref|><|det|>[[118, 832, 872, 879]]<|/det|> +In addition, we have rephrased the term of "cell cycle activities" with the term of "cell cycle gene set enrichment scores" to more accurately reflect the results derived from RNA- seq and single- cell RNA- seq gene set enrichment analysis, as shown in Results Line 273- 278. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 855, 147]]<|/det|> +8. In the abstract line 50 the authors state "functional mutation enrichment in the Wnt signalling". What does this mean: mutations that lead to the in/activation of the Wnt signalling pathway? This should be clarified. + +<|ref|>text<|/ref|><|det|>[[118, 164, 863, 196]]<|/det|> +Response: We thank the reviewer for raising this point. This point was previously made clear in our Results "Functional mutation enrichment in pathways among ESCC subtypes" section. + +<|ref|>text<|/ref|><|det|>[[117, 212, 876, 403]]<|/det|> +Our results shown in Figure 5d/e and Extended Data Fig. 18 suggest that there were significantly more functionally relevant mutations in the Wnt/b-catenin signalling genes in the stemness subtype, compared to other subtypes (Results Line 373- 377). In Results Line 379- 385, "we then evaluated whether the pathway functional mutation enrichment affected the expression of pathway genes, and found that mutation enrichment in Wnt/β- catenin signalling, inflammatory response and hypoxia were positively correlated with pathway gene expression activities for the corresponding ESCC subtypes (Fig. 5e), suggesting that high level of Wnt signalling expression in the stemness group could be a consequence of functional mutations in regulators of the Wnt pathway, and these functional mutations were the most enriched in stemness samples". Thus, our results did support that these functionally relevant mutations may lead to the activation of the Wnt pathway. However, we were careful with our wording, as such observation was not validated by further biological function studies, which is beyond the scope of this study. + +<|ref|>text<|/ref|><|det|>[[118, 435, 247, 450]]<|/det|> +Minor comment: + +<|ref|>text<|/ref|><|det|>[[118, 467, 530, 483]]<|/det|> +The image scale in Ext Data Fig7 needs to be improved. + +<|ref|>text<|/ref|><|det|>[[118, 499, 753, 514]]<|/det|> +Response: We have done this in our revised manuscript, now the new Ext Data Fig 9. + +<|ref|>text<|/ref|><|det|>[[118, 562, 816, 593]]<|/det|> +Reviewer #4 (Remarks to the Author): Expert in oesophageal cancer subtypes, genomics, and bioinformatics + +<|ref|>text<|/ref|><|det|>[[118, 609, 816, 641]]<|/det|> +Disclaimer: I did not participate in the first round of review of the initial submission, and I am providing my review on their revised work. + +<|ref|>text<|/ref|><|det|>[[118, 658, 870, 770]]<|/det|> +In this manuscript, the authors performed whole- exome sequencing and bulk RNA- seq on 120 Chinese ESCC patients. They identified 4 RNA- defined subtypes: differentiated, metabolic, immunogenic and stemness. Using deep- learning model, they showed that these 4 subtypes were associated with different histological features, implying their biological basis. Moreover, they identified that NK cell markers including XCL1 and CD160, were surprisingly expressed by a subset of tumor cells. XCL1 were followed upon and its expression confers the sensitivity of ESCC cells to chemotherapeutic drugs. + +<|ref|>text<|/ref|><|det|>[[118, 786, 844, 865]]<|/det|> +This is a comprehensive work of tour de force: there were large amount of sequencing data, bioinformatic analyses, massive imaging data processing, as well as fairly extensive biological investigations. Some of the findings are strong and may have significant implications, such as the identification of 4 subtypes and XCL1 investigation. However, I do find a number of weaknesses which need to be addressed. + +<|ref|>text<|/ref|><|det|>[[118, 882, 579, 897]]<|/det|> +We thank the reviewer for the positive response of our study. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 101, 219, 115]]<|/det|> +Major issues: + +<|ref|>text<|/ref|><|det|>[[119, 131, 869, 195]]<|/det|> +1) What is the relationship between these newly designated subtypes with the TCGA subtypes? This can be done by looking at shared pathways enriched in different subtyping schema. For example, in TCGA, ESCC1 has frequent upregulation of oxidative pathways. Is ESCC1 similar as the Metabolic subtype here? + +<|ref|>text<|/ref|><|det|>[[118, 210, 878, 372]]<|/det|> +Response: We thank the reviewer for this comment. The TCGA ESCC molecular subtypes 1/2/3 were derived from the clustering using multi- omics data including mutations, mRNA/miRNA expression, DNA methylation and copy number aberrations, while our four subtypes were only based on transcriptomics. For the 90 TCGA ESCC samples, they came from patients with very diverse ethnic background, including Brazil \((n = 15)\) , Canada \((n = 4)\) , Russia \((n = 12)\) , Ukraine \((n = 4)\) , United States \((n = 14)\) and Vietnam \((n = 41)\) , while our 120 samples all came from a high ESCC incidence area (Henan Province) in China. Therefore, it is not feasible to compare the subtypes derived from different omics technologies and different ethnic background. However, we did some analysis of association between our subtypes and TCGA subtypes, as shown in Figure 4A (mutation oncoplot) and addressed in the Discussion, there was no association in mutations profiles between TCGA and our subtypes. + +<|ref|>text<|/ref|><|det|>[[118, 386, 875, 516]]<|/det|> +Following the reviewer's advice, we also performed the differential expression analysis and gene set enrichment analysis between TCGA ESCC subtypes using TCGA mRNA expression data. Only ESCC1 \((n = 50,56\%)\) had three pathways upregulated at an FDR level \(< 0.25\) , including RESPONSE_TO_OXIDIZED_PHOSPHOLIPIDS (FDR \(= 0.15\) ), and ESCC2 \((n = 36,40\%)\) and ESCC3 \((n = 4,4\%)\) had no significantly up- or down- regulated pathways. For ESCC1, apart from oxidized phospholipids, no other metabolic and oxidative pathways were significantly upregulated compared to ESCC2/3. Therefore, based on all these data, there did not seem to be strong associations between TCGA and our subtypes, as they were derived from different omics signatures and different ethnic background. + +<|ref|>text<|/ref|><|det|>[[118, 545, 876, 626]]<|/det|> +2) The validation using external single-cell RNA-seq data is useful but somewhat superficial. What was shown was merely that the selected genes from different subtypes could be expressed by different clusters from scRNA-seq, which is largely expected. What really needs to be addressed is do these different clusters from scRNA-seq show similar biology or transcriptional programs to bulk RNA-seq defined subtypes? + +<|ref|>text<|/ref|><|det|>[[117, 641, 878, 899]]<|/det|> +Response: We really appreciate the reviewer for this insightful comment. To further investigate the heterogeneity and granularity of transcriptional programmes of ESCC epithelial cells, the NMF clustering with \(k = 10\) factors was performed on \(\sim 44,000\) epithelial cells of Zhang et al., Nat Comms 2021 (similar techniques also used in Gojo et al., Cancer Cell 2020, Lai et al., Int J Cancer 2021 and DeMartino et al., Nat Comms 2023), followed by the differential expression analysis using the Seurat "FindMarkers" function to identify top differentially expressed genes, as well as gene set enrichment analysis for each cluster. Signature genes for each cluster were identified based on adjusted p-value \(< 0.0001\) and log2 fold change \(>1\) . Top 50 signature genes were then selected based on the log2 fold change for each cluster (new Extended Data Fig. 4). The NMF clusters were annotated based on their signature genes and up/down-regulated pathways. Their corresponding expression programmes of Zhang et al., 2021 and our related transcriptomic subtypes were identified based on shared signature genes (Extended Data Fig. 4). The NMF Cluster 5 and 10 appeared to correspond to our differentiated subtype, with Cluster 4 corresponding to the metabolic subtype, Cluster 6 corresponding to the immunogenic subtype, while Cluster 1 shared many stemness signature genes, such as SFRP1, WFDC2 and LGR6 (Extended Data Fig. 4a). Cluster 1 also had significantly upregulated Wnt signalling and NCAM1 interactions, and the mostly downregulated keratinization / cornified envelope and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 873, 148]]<|/det|> +metabolism pathways, which were all signature pathway activities for the stemness subtype. Reassuringly, all previous eight expression programmes of epithelial cells from Zhang et al., 2021 were identified in our single cell NMF clusters. These single cell results further validated and support the robustness of our four transcriptomic subtypes derived from bulk tissue RNA- seq. + +<|ref|>text<|/ref|><|det|>[[118, 164, 836, 180]]<|/det|> +We have updated this section in Results section line 125- 147 and Methods section line 909- 916. + +<|ref|>text<|/ref|><|det|>[[118, 212, 870, 308]]<|/det|> +3) The investigation of SFRP1 needs further development. The authors described that IHC staining was done on its protein, but did not mention how many tumor and normal samples were stained. Is SFRP1 expressed higher in tumor vs normal samples? What is the percentage of SFRP1 expression in tumor samples? Since it was proposed as a stemness related genes, does it correlate with the differentiation status of the tumors? The knockdown efficiency (Fig.s1e,f) appears poor, and the WB needs to be quantified. + +<|ref|>text<|/ref|><|det|>[[118, 324, 861, 418]]<|/det|> +Response: SFRP1 was found as one of a set of genes showing the overexpression of mRNA in the Stemness group compared to other three groups based on the differential RNA expression in 120 tumour samples of ESCC. The frequency of SFRP1 protein expression was low in human ESCC, IHC assay revealed SFRP1 protein was positive in \(4.3\%\) (3/70) of ESCC tissue and no positive in the matched normal samples. We have provided this detailed data in our revised manuscript, Line 155- 158. + +<|ref|>text<|/ref|><|det|>[[118, 435, 870, 498]]<|/det|> +Although SFRP1 is a stemness related genes, its expression does not significantly correlate with the differentiation status. The knockdown efficiency in WB is quantified, shown by Ext Data Fig 5 panel g and h, indicating significant \(20 - 40\%\) knockdown efficiency in KYSE- 520 cells and \(\sim 50\%\) knockdown efficiency in KYSE- 450. + +<|ref|>text<|/ref|><|det|>[[118, 530, 874, 609]]<|/det|> +4) Associating histological features to different transcriptomic subtypes is helpful and can support their biological underpinnings. However, at this scale (Fig.1C), the histological features are difficult to discern for most readers who are not trained pathologists. For example, it is hard to see immune cells or eosinophilic cytoplasm at this resolution. It would be very helpful to add certain IHC markers to make these histological features conspicuous. + +<|ref|>text<|/ref|><|det|>[[117, 625, 876, 899]]<|/det|> +Response: We fully understood this reviewer's comment, similar as the comment #2 from Reviewer 3. We have redone the Fig 1c with the inserted high magnification pictures to address the specific features of each subtype, with more explanation in the text and figure legend. Please see more our response to the comment 2 from the reviewer 3. We have done some IHC for immune cells, such as CD4, CD8 and CD56, which showed significantly higher expression in immunogenic group (see Figure 2c, Extended Data Fig 9 and Fig 10). Given the lack of specific IHC markers to differentiate the histopathological features presented in each subtype in an available time frame, we are not able to provide more IHC staining to make these histopathological features conspicuous as suggested by the reviewer although it would be indeed helpful. However, we have developed a deep- learning AI histology model that strongly correlated histological features with transcriptomic subtypes. This AI model identified subtype specific histological features and these distinct features corresponded nicely with their respective transcriptomic subtypes. Please see the section of "Distinct histological features among transcriptomic subtypes" Line 164- 188 for more detail. Furthermore, we have also validated our transcriptomic subtypes using the single cell RNA-seq data of 60 ESCC samples (new Ext Data Fig 3 and 4). Therefore, we hope the reviewer would agree that the data and results supported from the deep- learning histopathology model and single- cell RNA-seq were strong and convincing to support the subtypes derived from our bulk RNA-seq. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 131, 870, 196]]<|/det|> +5) The investigation of XCL1 in cancer cells was a highlight in this work. However, I could not find any IHC image showing strong XCL1 staining. The ones included, such as Fig.2h, Fig.5c6, were very weak. The authors need to show convincing strong IHC signals of XCL1 in cancer cells, since this is one of their key findings. + +<|ref|>text<|/ref|><|det|>[[118, 211, 869, 292]]<|/det|> +Response: Apologies for this. We found that the pictures in the converted version of pdf file for the reviewers were indeed not clear somehow. We now have provided the high quality of all pictures with higher magnification, which demonstrate the real positive staining of XCL1 in cancer cells although the overall staining of XCL1 staining is weaker than other markers, in Fig 2h, new Ext Data Fig 8 and Ext Data Fig 11. + +<|ref|>text<|/ref|><|det|>[[118, 323, 866, 419]]<|/det|> +6) Line 224-228. "Interestingly, we observed that XCL1-expressing dysplastic cells in the submucosal gland in most of the cases are completely separated from the squamous cell carcinoma, suggesting that this subgroup of patients might concurrently have both squamous cell carcinoma and adenocarcinoma or this adeno-squamous carcinoma might be derived from submucosa gland epithelial cells". These are indeed very interesting! However, no data was shown. Can the authors perform a statistical analysis to compare the histology of these tumors vs. XCL1 expression? + +<|ref|>text<|/ref|><|det|>[[118, 434, 874, 564]]<|/det|> +Response: Really appreciate this reviewer's comment on this interesting finding. Adeno-squamous carcinoma (ASC) of the esophagus is an uncommon type of esophageal cancer that contains both adenocarcinoma and squamous cell carcinoma elements. Data on this biologically unique type of cancer are limited and mainly stem from case reports and small case series. Given that the incidence of adeno-squamous carcinoma of human oesophageal cancer is very low (between 0.37%-1%), the number of ASC in this study is too low to perform a meaningful statistical analysis. We are approaching more collaborators to get more samples for the further investigation on this very interesting finding. + +<|ref|>text<|/ref|><|det|>[[118, 594, 878, 658]]<|/det|> +7) Line 256-258, it is a bit concerning that XCL1 is only expressed in 515 out of 33459 (1.5%) total epithelial cells from the single-cell RNA-seq data. Can the authors explain why such low frequency? Is it because of the high cutoff used? This low positivity negatively affects the significance of the biological contribution of XCL1 in ESCC. + +<|ref|>text<|/ref|><|det|>[[118, 675, 877, 753]]<|/det|> +Response: We thank the reviewer for raising this comment. XCL1 positive and negative cells were identified based on the Seurat SCTransform based normalised gene-level counts: as positive when normalised gene-level counts \(>0\) ; and negative when normalised gene-level counts \(= 0\) . This led to the identification of \(\sim 1.5\%\) XCL-positive epithelial cells. We have updated this sentence in Methods Line 905-906 to make it clear. + +<|ref|>text<|/ref|><|det|>[[118, 770, 870, 881]]<|/det|> +Low frequency of XCL1 positive cells was also seen in the IHC staining in human primary ESCC samples, the positive cells within whole cancer tissues were around 1- 2%. The biological function of XCL1 expression in cancer cells is not fully understood although our preliminary result has demonstrated that XCL1 overexpression decreases the sensitivity of cancer cells to chemotherapy drug. Although XCL1 expresses in a very low proportion of cancer cells, these cells may present the cancer stem cells or therapeutic resistant cells and play some important role in cancer recurrence or poor prognosis. This definitely warrants further investigation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 101, 222, 115]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[119, 117, 866, 163]]<|/det|> +1) The RNA-seq and WES data are still under controlled access and not publicly available. I think it is Nat Communication's policy that these data will need to be made publicly available upon acceptance. + +<|ref|>text<|/ref|><|det|>[[118, 180, 872, 260]]<|/det|> +Response: The data has been publicized at the National Genomics Data Centre of China with the Bioproject Access ID of PRJCA001577 (https://ngdc.cncb.ac.cn/bioproject/browse/PRJCA001577), and researchers can access the data after filling in a data request form following the guideline set by the Ministry of Science and Technology of China. If there is any difficulty for any researcher to access the data, we could provide help. + +<|ref|>text<|/ref|><|det|>[[118, 276, 825, 307]]<|/det|> +2) "an independent cohort of 65 ESCC patients" in Fig.1e was not described in the methods or results. Where were these samples from? Were they all primary tumors? + +<|ref|>text<|/ref|><|det|>[[118, 323, 830, 354]]<|/det|> +Response: We have now provided more information about this 65 ESCC patients in our revised manuscript, in Methods Lind 712- 714. + +<|ref|>text<|/ref|><|det|>[[119, 370, 866, 418]]<|/det|> +They were all primary tumour, treatment naive, from Anyang Cancer Hospital, under the approve of ethics committee of Both Anyang Cancer Hospital and The First Affiliated Hospital of Zhengzhou University. + +<|ref|>text<|/ref|><|det|>[[119, 466, 744, 482]]<|/det|> +Reviewer #5 (Remarks to the Author): Expert in digital pathology and deep learning + +<|ref|>text<|/ref|><|det|>[[118, 498, 860, 578]]<|/det|> +In this article, the authors propose a new subclassification of esophageal squamous cell carcinoma. This is clinically interesting because most previous efforts at subtyping this disease also included other histologies of esophageal cancer such as adenocarcinomas or gastroesophageal junction tumors. It is sensible to focus exclusively on squamous cell esophageal cancer and attempt to subtype it. + +<|ref|>text<|/ref|><|det|>[[118, 594, 852, 625]]<|/det|> +My expertise is specifically in digital pathology, so I am reviewing the digital histopathology model which the authors utilized. + +<|ref|>text<|/ref|><|det|>[[119, 643, 696, 658]]<|/det|> +Unfortunately, there are some concerns regarding the deep learning analysis. + +<|ref|>text<|/ref|><|det|>[[118, 674, 875, 721]]<|/det|> +1. Some methodological details are not entirely clear. For instance, what does a downsampling factor of 64 fold mean? The authors should specify their final resolution in micrometers per pixel and then provide the absolute pixel size for their tiles. + +<|ref|>text<|/ref|><|det|>[[118, 737, 878, 864]]<|/det|> +Response: We used the Openslide API for handling our whole slide images (WSI). The API processes the multiresolution images as pyramid levels with each subsequent level representing a down- sampled version of the previous level. There is no image scaling by the library, instead levels are already available in the slide file (Goode et al., Journal of pathology informatics 2013). 64 is the down sample factor we used to determine the image level we extracted from the slide files and all the slides were scanned at 20x objective power at 0.44 \(\mu m\) per pixel resolution. The tiles used for feature extraction were extracted at \(300 \times 300\) pixels for all samples. We have updated the method text to make this clear in Methods Line 858- 860, and line 867. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 871, 163]]<|/det|> +2. Additionally, they mention that they manually discarded some images. This is concerning, and it is crucial for them to clearly state why these images were discarded. What precisely constituted "poor quality"? Moreover, it would be beneficial to know how many images per class were discarded. The manuscript would benefit from a CONSORT-style diagram to elucidate these points. + +<|ref|>text<|/ref|><|det|>[[118, 180, 875, 276]]<|/det|> +Response: Each WSI was manually reviewed by a qualified pathologist, and poor quality images were discarded under the direct pathologist's supervision, poor quality of imaging means that, the sections were folded without clear morphology or there were not enough tumour cells presented in the slides obtained from the Department of histopathology. A total of 91 WSIs were retained for the deep-learning analysis, i.e., differentiated group, \(n = 28\) ; immunogenic group, \(n = 27\) ; metabolic group, \(n = 18\) ; stemness group, \(n = 18\) . We have updated this section in Methods Line 862- 867. + +<|ref|>text<|/ref|><|det|>[[118, 308, 872, 339]]<|/det|> +3. It is also vital that the study adheres to the STARD (or similar) guidelines, ensuring that all boxes in this guideline are ticked. + +<|ref|>text<|/ref|><|det|>[[118, 355, 860, 371]]<|/det|> +Response: We have checked and followed the STARD guidelines, report as much detail as required. + +<|ref|>text<|/ref|><|det|>[[118, 403, 868, 435]]<|/det|> +4. Regarding the design of the algorithm, the authors mention that they extracted features with five pretrained neural networks. However, the rationale for this decision is unclear. + +<|ref|>text<|/ref|><|det|>[[117, 451, 876, 625]]<|/det|> +This choice, which appears quite uncommon, needs further explanation. Typically, one would use just a single robust network, selected through a hyperparameter tuning experiment on a dedicated tuning set. Alternatively, one might opt for a network that has been validated in previous studies. Ideally, the contemporary standard involves not using a network pre-trained on ImageNet, but rather one that has been pre-trained in a self- supervised manner on histopathology images, such as the RetCCL network or the CTransPath network. In summary, the image analysis algorithm presented seems non- standard. While the authors might have had valid reasons for these unconventional design choices, they need to elucidate their reasoning in the manuscript. It would be even more beneficial if the authors employed a state- of- the- art pipeline (such as CLAM or the one from Wagner et al., Cancer Cell, 2023), or if they presented benchmarking experimental results showing their methods' superiority compared to more conventional methods. + +<|ref|>text<|/ref|><|det|>[[117, 642, 879, 785]]<|/det|> +Response: We acknowledge this reviewer's point regarding the number of pretrained models used for feature extraction. Utilising multiple pretrained networks allowed us to capture a broader range of features and patterns. Each of the pretrained models utilised different model architectures, which can result in diverse feature representations. For example, the Inception and ResNet architecture are known to have different feature representation due to the use of residual connection in the latter. This diversity can enhance performance by capturing different predictive elements and building more enriched feature representations into our system. As shown in the new Supplementary Table 4, features from different pretrained models contributed differently to the top features for each subtype. + +<|ref|>text<|/ref|><|det|>[[118, 802, 877, 897]]<|/det|> +Previous studies, such as Fu et al., Nat Cancer 2020, and Courtiol et al., Nat Med 2019, have efficiently utilised Imagenet pretrained models for extraction of histology features. Although some of these studies opt for either training a new 2D convolutional layer to perform weighted sum between the extracted features (Courtiol et al., 2019) or model fine- tuning, this is not applicable in our study because of our sample size ( \(n = 91\) slides, distributed as \(\text{DIF} = 28\) , \(\text{IMM} = 27\) , \(\text{MET} = 18\) and \(\text{STEM} = 18\) ). These numbers are not suitable for robust model training but will work for classical statistics + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 874, 148]]<|/det|> +comparing the extracted features between defined groups. Our aim was to implement a simple robust system to consistently extract histological features that capture the gene expression subtypes in both Discovery and Test sets. Indeed, we were able to effectively classify the gene expression subtypes using the meta histological features (new Supplementary Table 4 and 5). + +<|ref|>text<|/ref|><|det|>[[118, 164, 877, 228]]<|/det|> +Finally, we are aware of the alternative systems such as CLAM and currently use them in our ongoing projects when appropriate. However, these systems require additional model training and often have specific domain unlike the general- purpose image recognition capabilities of the Imagenet pretrained models (Courtiol et al., 2019). + +<|ref|>text<|/ref|><|det|>[[118, 243, 870, 340]]<|/det|> +In the revised manuscript, we have elaborated on these points to provide a clearer rational for using multiple pretrained models for feature extraction. We also added one sentence in Results Line 171- 173, "This model diversity can enhance performance by capturing different predictive elements and building more enriched representations into the system." to elaborate the rationale more. We have also included a workflow diagram to clearly describe our steps (new Extend Data Fig 6a). We hope this will address your concern and improve the overall clarity of our process. + +<|ref|>text<|/ref|><|det|>[[178, 370, 853, 429]]<|/det|> +Fu Y, Jung AW, Torne RV, Gonzalez S, Vöhringer H, Shmatko A, Yates LR, Jimenez- Linan M, Moore L, Gerstung M. Pan- cancer computational histopathology reveals mutations, tumor composition and prognosis. Nat Cancer. 2020 Aug;1(8):800- 810. doi: 10.1038/s43018- 020- 0085- 8. Epub 2020 Jul 27. PMID: 35122049. + +<|ref|>text<|/ref|><|det|>[[178, 443, 877, 502]]<|/det|> +Courtiol P, Maussion C, Moarii M, Pronier E, Pilcer S, Sefta M, Manceron P, Toldo S, Zaslavskiy M, Le Stang N, Girard N, Elemento O, Nicholson AG, Blay JY, Galateau- Salle F, Wainrib G, Clozel T. Deep learning- based classification of mesothelioma improves prediction of patient outcome. Nat Med. 2019 Oct;25(10):1519- 1525. doi: 10.1038/s41591- 019- 0583- 3. Epub 2019 Oct 7. PMID: 31591589. + +<|ref|>text<|/ref|><|det|>[[118, 533, 875, 581]]<|/det|> +5. Lastly, there are concerns regarding the statistical measures for the gene expression classification. The authors used a t-test, but they did not specify whether all the prerequisites for a t-test were met. This information needs to be explicitly stated. + +<|ref|>text<|/ref|><|det|>[[118, 597, 877, 677]]<|/det|> +Response: Thank you for raising this point. Assumption checks across the extracted features revealed that normality was not met for several of the features and the combined features. Therefore, we have replaced the t-test with the Wilcoxon rank-sum test and repeated the relevant analysis (new Supplementary Table 5, also Methods Line 883). Importantly, our results revealed that these features remain predictive of the subtypes and our interpretation remains the same. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 291, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 127, 393, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[112, 163, 857, 181]]<|/det|> +The authors have addressed this reviewer's remaining point and revised their manuscript accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 236, 393, 253]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 272, 844, 308]]<|/det|> +The authors have substantially addressed the points raised and improved the quality of the text and figures. + +<|ref|>text<|/ref|><|det|>[[115, 364, 393, 381]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 401, 627, 418]]<|/det|> +The authors have addressed all my concerns. I have no more critiques. + +<|ref|>text<|/ref|><|det|>[[115, 493, 393, 509]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 530, 544, 547]]<|/det|> +The authors have responded to my comments - - thank you + +<|ref|>text<|/ref|><|det|>[[115, 566, 866, 619]]<|/det|> +the authors provide some justification for their design choices for the neural network architecture, but they do not solve the issue that the model design is very uncommon and probably not optimal. The fundamental problem seems to be the rather low sample size (N=91). + +<|ref|>text<|/ref|><|det|>[[115, 639, 874, 692]]<|/det|> +Having said that, the authors are transparent about their approach and although it is not state of the art and there is a risk for overfitting, the methods are transparently reported and the interpretation seems to be backed up by the data. + +<|ref|>text<|/ref|><|det|>[[115, 712, 848, 765]]<|/det|> +Major issue: the github repos seem to be unusable (only partial codes stored in the repository, no documentation, poor structure, no example data). With the current github repos it is not possible to reproduce the results. + +<|ref|>text<|/ref|><|det|>[[115, 785, 440, 802]]<|/det|> +I suggest to remove the "The" from the title. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 108, 433, 125]]<|/det|> +Reviewer #5 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[115, 162, 847, 216]]<|/det|> +Major issue: the github repos seem to be unusable (only partial codes stored in the repository, no documentation, poor structure, no example data). With the current github repos it is not possible to reproduce the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 688, 101]]<|/det|> +Point by point responses to the Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 119, 600, 136]]<|/det|> +The authors have responded to my comments - - thank you + +<|ref|>text<|/ref|><|det|>[[118, 154, 857, 224]]<|/det|> +the authors provide some justification for their design choices for the neural network architecture, but they do not solve the issue that the model design is very uncommon and probably not optimal. The fundamental problem seems to be the rather low sample size \((N = 91)\) . + +<|ref|>text<|/ref|><|det|>[[118, 241, 847, 293]]<|/det|> +Having said that, the authors are transparent about their approach and although it is not state of the art and there is a risk for overfitting, the methods are transparently reported and the interpretation seems to be backed up by the data. + +<|ref|>text<|/ref|><|det|>[[118, 311, 832, 345]]<|/det|> +Response: We appreciate that this reviewer agrees that our methods are transparently reported, and our interpretation is backed up by the data. + +<|ref|>text<|/ref|><|det|>[[118, 363, 861, 415]]<|/det|> +The ensemble approach of using multiple CNN models for feature extraction is not uncommon and has been used previously although not much in the field of computational pathology, exemplified by + +<|ref|>text<|/ref|><|det|>[[147, 416, 872, 626]]<|/det|> +- F. Shaheen and B. Verma, "An ensemble of deep learning architectures for automatic feature extraction," 2016 IEEE Symposium Series on Computational Intelligence (SSCI), Athens, Greece, 2016, pp. 1-5, doi: 10.1109/SSCI.2016.7850047.- Bhandi, V., Sumithra Devi, K.A. (2021). Feature Extraction from Ensemble of Deep CNN Model for Image Retrieval Application. In: Jeena Jacob, I., Kolandapalayam Shanmugam, S., Piramuthu, S., Falkowski-Gilski, P. (eds) Data Intelligence and Cognitive Informatics. Algorithms for Intelligent Systems. Springer, Singapore. https://doi.org/10.1007/978-981-15-8530-2_57.- Dechao Chen, Yang Chen, Jieming Ma, Cheng Cheng, Xuefeng Xi, Run Zhu, Zhiming Cui, "An Ensemble Deep Neural Network for Footprint Image Retrieval Based on Transfer Learning", Journal of Sensors, vol. 2021, Article ID 6631029, 9 pages, 2021. https://doi.org/10.1155/2021/6631029 + +<|ref|>text<|/ref|><|det|>[[179, 679, 325, 695]]<|/det|> +[Figure Redacted] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 861, 154]]<|/det|> +All these studies showed that the ensemble approach retains more features for the final retrieval and achieves better accuracy than a separate feature extraction (Shaheen and Verma 2016 IEEE Symposium Series on Computational Intelligence (SSCI); Chen et al., 2021 Journal of Sensors). + +<|ref|>text<|/ref|><|det|>[[117, 171, 875, 310]]<|/det|> +Given our low sample size \((n = 91)\) of four subtypes, our feature extraction could benefit from this ensemble approach by increasing the numbers of useful features for the final retrieval. The feature representations of the images extracted by different models are different, but these different feature representations contain some essential information components (Chen et al., 2021 Journal of Sensors). Indeed, our results showed that more diverse representative features could be identified using the feature extraction from multiple CNN models (shown in Supplementary Table 4). This produced more robust features that were fused together to create subtype specific Meta Features (Supplementary Table 5). + +<|ref|>text<|/ref|><|det|>[[118, 327, 877, 397]]<|/det|> +We have added one sentence in Results Line 173 to highlight the advantage of this ensemble approach, "This ensemble approach was reported to retain more informative features for the final retrieval and achieve better accuracy than a separate feature extraction", and cited the papers above. + +<|ref|>text<|/ref|><|det|>[[118, 415, 842, 450]]<|/det|> +Larger independent cohorts are needed to further validate our ensemble model and top features, which are under planning but beyond the scope of this study. + +<|ref|>text<|/ref|><|det|>[[118, 467, 850, 519]]<|/det|> +Major issue: the github repos seem to be unusable (only partial codes stored in the repository, no documentation, poor structure, no example data). With the current github repos it is not possible to reproduce the results. + +<|ref|>text<|/ref|><|det|>[[117, 537, 875, 641]]<|/det|> +Response: Following on this comment, We have now added extensive detail about the functions and scripts used in our workflow at https://github.com/BiolnforCore- BCI/giExtract, forked from https://github.com/caanene1/giExtract. We also provide example dataset and run functions inside dedicated folder. In particular, we created a "manuscript" folder in the repos, containing "run.sh", "downstream.R" and "example data" folder, ensuring the reproducibility of our results. + +<|ref|>text<|/ref|><|det|>[[117, 642, 875, 729]]<|/det|> +To make it easy for other researchers to use our code, we have now uploaded the python part of the workflow to the Pypi package database. This enables a user to install the tool like any other python package. The interface provides detailed documentation of the inputs and requirements (see below). Please also visit the Pypi website for our package at https://pypi.org/project/giExtract/1.0.1/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 707, 120]]<|/det|> +Last login: Wed Mar 6 18:10:10 on ttysooo chinedus- MacBook- Pro:- chineduanene\$ giExtract - h usage: giExtract [-h] - p PATH - c CONTEXT - k COLUMN [-b BATCH] [-s NATCOM] + +<|ref|>text<|/ref|><|det|>[[118, 130, 777, 270]]<|/det|> +optional arguments: - h, - - help show this help message and exit - p PATH, - - path PATH Path to images - c CONTEXT, - - context CONTEXT Context file with at least a column for flowing the images - k COLUMN, - - column COLUMN The column name in context to use for flowing data - b BATCH, - - batch BATCH Batch size for flowing the data into the models - s NATCOM, - - natcom NATCOM Indicate if the NatCom et al features should be calculated chinedus- MacBook- Pro:- chineduanene\$ + +<|ref|>text<|/ref|><|det|>[[118, 303, 481, 320]]<|/det|> +I suggest to remove the "The" from the title. + +<|ref|>text<|/ref|><|det|>[[118, 338, 832, 372]]<|/det|> +Response: We have updated the title to "Integrated molecular and histological analysis defines subtypes of esophageal squamous cell carcinoma" + +<|ref|>text<|/ref|><|det|>[[118, 405, 857, 441]]<|/det|> +We'd like to take this opportunity to thank all the reviewers for their invaluable comments and critique that has made our study much more thorough and robust! + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 303, 106]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 127, 393, 143]]<|/det|> +Reviewer #5 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 164, 451, 180]]<|/det|> +Thank you for addressing all of my comments. + +<--- Page Split ---> diff --git a/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/images_list.json b/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..356dc2439aefe134105202c9fcb64df57a6d3356 --- /dev/null +++ b/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,32 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Statistics of byte frequency of all the files used in the simulation. According to Li et al., 2005, green ones were considered as files with balanced byte frequency. (For review usage only)", + "footnote": [], + "bbox": [ + [ + 115, + 163, + 789, + 696 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R2. Distribution of degree of packets generated by DNA fountain with/without screening (For review usage only)", + "footnote": [], + "bbox": [ + [ + 116, + 145, + 790, + 556 + ] + ], + "page_idx": 39 + } +] \ No newline at end of file diff --git a/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..ba7cc34ae8eac2a3fdea391d7c6d10c4a8a11d1f --- /dev/null +++ b/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,841 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Computational Science Manuscript Title: Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System Corresponding author name(s): Yue Shen, George M. Church, Xun Xu + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +Date: 1st September 21 10:48:22 Last Sent: 1st September 21 10:48:22 Triggered By: Ananya Rastogi From: ananya.rastogi@nature.com To: shenyue@genomics.cn BCC: ananya.rastogi@nature.com + +Subject: Decision on Nature Computational Science manuscript NATCOMPUTSCI- 21- 0438 + +Message: \*\* Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. \*\* + +Dear Dr Shen, + +Your manuscript "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" has now been seen by 3 referees, whose comments are appended below. You will see that while they find your work of interest, they have raised points that need to be addressed before we can make a decision on publication. + +The referees' reports seem to be quite clear. Naturally, we will need you to address all of the points raised. + +While we ask you to address all of the points raised, the following points need to be substantially worked on: + +- Please provide a more appropriate experiment to assess YYC's performance against DNA fountain as requested by Reviewer #2. +- Please provide an argument as to how any unique feature of YYC is relevant for in vivo storage besides the higher coding density. + +<--- Page Split ---> + +# natureresearch + +- As pointed out by Reviewer #2, please discuss the impact of parameter choices made in the study. +- Please present the mathematical analysis in the study in a way which is accessible to a broad readership. + +Please use the following link to submit your revised manuscript and a point- by- point response to the referees' comments (which should be in a separate document to any cover letter): + +## [REDACTED] + +\*\* This url links to your confidential homepage and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this e- mail to co- authors, please delete this link to your homepage first. \*\* + +To aid in the review process, we would appreciate it if you could also provide a copy of your manuscript files that indicates your revisions by making of use of Track Changes or similar mark- up tools. Please also ensure that all correspondence is marked with your Nature Computational Science reference number in the subject line. + +In addition, please make sure to upload a Word Document or LaTeX version of your text, to assist us in the editorial stage. + +To improve transparency in authorship, we request that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +We hope to receive your revised paper within three weeks. If you cannot send it within this time, please let us know. + +We look forward to hearing from you soon. + +Best regards, + +Ananya Rastogi, PhD Associate Editor Nature Computational Science + +Reviewers comments: + +Reviewer #1 (Remarks to the Author): + +Motivated by the Goldman's rotating encoding strategy and the DNA fountain encoding strategy, this paper presents an interesting encoding scheme called as Yin- Yang Codec + +<--- Page Split ---> + +# natureresearch + +(YYC) for archival DNA data storage. The YYC scheme has three main steps. In the first step, the byte strings are partitioned into segments of equal length. In the second step of incorporation, two binary segments are selected randomly and are combined bit by bit using Yang rule first and then Yin rule, giving a final nucleotide as an output. In the final step, the generated DNA strings are screened for pre- set constraints for GC content (40%- 60%), maximum homopolymer length \(< 5\) , and the secondary structure free energy \((> = - 30\) kcal/mol). In a failed case, through an iteration process another randomly generated binary segment is used. It is observed that there are 1536 options for encoding the binary sequence. These different options give a maximum information density (theoretical) of 1.965 bits per base under specific constraints. + +This encoding has been simulated on a computer and compared with well- known encoding schemes using a developed tool called Chamaeleo. The fountain DNA code and the YYC are specifically compared. The robustness of the YYC scheme was tested by introducing random and systematic errors and it was found that the data recovery percentage can be maintained at 98% when the sequence loss rate is \(< 2\%\) . + +The experimental validation of the work was done using two file formats and these were stored in in vitro as 200 nts oligos and in vivo as an 54240- bp DNA fragment in yeast cell. This resulted in physical information density of \(\sim 198.8\) Exabytes per gram of DNA. This is much better than the previous work in the literature. + +I think the present work is an interesting approach. The introduced YYC scheme outperforms many previous schemes in terms of reliable data storage and physical information density. Some of my observations are listed below: + +1. I feel that the YYC encoding scheme can be better presented. There are a few problems in the current writing. For example, in Figure 1, the choice of alphabet for Xn and Yn should be given. Although a working example is given in Figure S1, the presentation is from bits and nucleotides to nucleotides whereas in the general scheme it is nucleotides and nucleotides to bits. Another working example may be given either in the supplementary files or in the paper itself that will make it very clear. +2. I could not find the supplementary video mentioned at page 4 and page 14. Perhaps, including that will also be helpful. +3. Also, in the YYC scheme, there are 1536 possible options, so maybe it would be interesting to include a summary of all the rules in a table. This table could also include the rule number such as rule no. 888 that is used in Figure S1 or other rules in supplementary information. It is not clear how these rule numbers are assigned? Do they have some significance? I mean why the specific rule 888 was used. +4. At page 5, it is mentioned that when most of the binary segment contains more than 80% repeated 0's and 1's, the corresponding encoding process may enter an infinite loop or generate a poor result. Can we give some algebraic explanation for this from the YYC scheme? +5. At page 12, statement "YYC offers the opportunity to incorporate multiple rules for one file transcoding and thus provide a novel strategy for secure data archiving." Can we give a specific example? This will motivate the reader. +6. At page 15, line 10, What is Fq in Definition 1, line 1? Normally, Fq is a finite field having q elements but here, Fq is a set of 4 nucleotides, so q has no role to play. Maybe, the notation can be modified or Fq can be defined in line 1 and later, we can choose it to be an alphabet of size 4. + +<--- Page Split ---> + +# natureresearch + +With these suggestions, I recommend for the publication of the manuscript. + +Manish K Gupta + +Reviewer #2 (Remarks to the Author): + +The authors have introduced an interesting DNA encoding scheme called YYC (or Ying- Yang coding) with complementary rule sets to increase the coding density of current encoding methods. It is a dynamic transcoding scheme that transforms binary data into DNA sequences that could get close to the theoretical maximum information sensitivity of 2 bits per base. While the encoding approach is novel, there are inconsistencies and lack of exploration of parameters in the manuscript that make it difficult (or impossible) for anyone to assess the claimed merits of the work. It requires massive revisions, proper parameter studies, and significant retooling of how this paper is compared or "advertised" against other works. + +Summarized below are the major concerns: + +1. Data recovery rate - in the manuscript, DNA oligos are present at roughly 1e8 copies per designed oligo sequence, which by my calculation is \(\sim 175\) nanograms of total synthesis mass for Pool 1. They then dilute this down 10,000x fold in order to show that YYC/DNA fountain can get good recovery, but it completely breaks down at further serial dilutions. This is somewhat of a contrived experiment because it means the first dilution \((10^{4}4\) molecules, which by my calculation of \(10103*(10^{4}4\) molecules) \(\ast (200\ast 330g / mol)\ast (1mol / (6.02\ast 10^{23}\) molecules)) is 10 picograms of DNA. That is already an incredibly tiny amount of DNA. Given the data presented, it's not clear whether YYC's benefits are marginal or substantial. A more appropriate experiment to assess YYC's performance against DNA fountain in this context would be to show its performance for higher input copies (eg. 1e7, 1e6, etc.), as well as performances of re-amplifying pools from smaller dilutions (eg. dilution down to 1e7, 1e6, 1e5, amplifying back to 1e8 and using that as input). + +2. In vivo storage - This part actually has very little to do with the YYC encoding and I don't understand its relevance to the manuscript's presentation of YYC encoding as a whole. You assemble DNA oligonucleotides or amplicons of any kind and clone into a plasmid for storage. The authors did not make any kind of argument about how any unique feature of YYC is relevant for in vivo storage besides the higher coding density, as you could theoretically just use any other high performance code. Interestingly, the authors did not touch on this point at all. + +Furthermore, one of the most eye- catching errors in the paper is the advertisement of the storage density of \(\sim 200\mathrm{EB / g}\) . Storage densities, as reflected in bits of information per mass, is limited by the synthesis of unique fragments and also by the coding density of the encoding procedure. Given these considerations, it is impossible that YYC achieves densities of \(\sim 1000x\) higher than DNA fountain (and other works in Table 1) despite similar orders of magnitude in coding density. Even looking at the authors' formula as to how to calculate their vivo storage metric, it appears that nothing in that formula is fundamentally unique to the YYC coding scheme or that by plugging in the stated coding density of DNA fountain would get you a \(\sim 1000x\) difference in performance. In fact, the differences are marginal or negligible when plugging in + +<--- Page Split ---> + +# natureresearch + +different coding densities (into the information/nucleotide section, adjusting for plasmid backbone size) from Table 1. + +Investigating the calculation further (by briefly reading the DNA fountain work which this manuscript cites often), it appears that there is a fundamental difference in how the calculations were determined. It appears that Erlich et al cited their 215PB metric as part of a serial dilution scheme for assessing successful/perfect retrieval of synthesized DNA. Taking the logic from the Erlich paper, the authors should have diluted down their yeast preps accordingly as well (to specific copies of plasmid loaded per sequencing library). Further, there seems to be a methods typo, where the authors stated that they picked three colonies but later in the methods it says they picked 12. + +3. Other concerns regarding YYC encoding - it's clear that there is some sort of performance dependence according to the 1536 transcoding rules (Fig. S3 shows this pretty well). Across the manuscript there are tables with selected parameters but little discussion of the exact impact of them. It's difficult to assess what exactly the impact this has on performance when these parameters were not exhaustively studied either in silico or through actual experiments. Given the fact that this is a new coding scheme, the authors should have at minimum done an in silico demonstration of every single rule and how it affects every single metric in the paper. Off the top of my head, because the selection of the rule parameter greatly affects the information density, sequencing errors will play a large role in the overall performance. + +Reviewer #3 (Remarks to the Author): + +The paper presents a new efficient coding scheme that improves the recovery rate in case of large sequence loss. The method maintains linear dependency between the percentage of oligos that were fully recovered, and the data recovery. Additionally, the paper demonstrates in vivo data storage with high information density. Roughly speaking, the paper is fairly written, however there are several parts which are not well explained, as will be elaborated below. + +## Comments: + +1. The code works well, I used it through the "chameleo" tool (that was also published by this group). +2. Like I sent you in another email - I could not access the data from their experiment, so either the link is broken, or they should add more explanations on the data and how to access it. +3. As far as I understand, the authors did not perform any reconstruction algorithm on the sequenced oligos. Can you please comment whether such an algorithm can improve the data recovery success and/or achieve faster data recovery? +4. There are several terms in the introduction that should be better explained before used for the average reader. Examples of these expressions are: secondary structure, free energy calculation. +5. The sentence between lines 80-82 is not clear to me. +6. Description of the YYC between lines 114-126 is not clear. What do \(X_n\) and \(Y_n\) refer to? +7. The caption of Fig. 1 is not clear either. +8. The description in page 11 of lines 282-310 is not clear to me. +9. I could not find the supplementary video of Fig. S1b. + +<--- Page Split ---> + +# natureresearch + +10. The statement in Lemma 3 is not properly stated. + +11. In general, all the mathematical analysis in page 15 is very sloppy. The equations are explained and their correctness is not justified. There should be a clear statement about the properties that the YCC scheme satisfies and a proof for the redundancy. As written this way, I cannot truly understand and evaluate the code construction. + +12. The authors compare mostly with fountain codes. What about comparison with the other coding schemes? + +<--- Page Split ---> + +# natureresearch + +Reviewers comments: + +Reviewer #1 (Remarks to the Author): + +Motivated by the Goldman's rotating encoding strategy and the DNA fountain encoding strategy, this paper presents an interesting encoding scheme called as Yin- Yang Codec (YYC) for archival DNA data storage. The YYC scheme has three main steps. In the first step, the byte strings are partitioned into segments of equal length. In the second step of incorporation, two binary segments are selected randomly and are combined bit by bit using Yang rule first and then Yin rule, giving a final nucleotide as an output. In the final step, the generated DNA strings are screened for pre- set constraints for GC content (40%- 60%), maximum homopolymer length \(< 5\) , and the secondary structure free energy ( \(\geq - 30\) kcal/mol). In a failed case, through an iteration process another randomly generated binary segment is used. It is observed that there are 1536 options for encoding the binary sequence. These different options give a maximum information density (theoretical) of 1.965 bits per base under specific constraints. + +This encoding has been simulated on a computer and compared with well- known encoding schemes using a developed tool called Chamaeleo. The fountain DNA code and the YYC are specifically compared. The robustness of the YYC scheme was tested by introducing random and systematic errors and it was found that the data recovery percentage can be maintained at 98% when the sequence loss rate is \(< 2\%\) . + +The experimental validation of the work was done using two file formats and these were stored in in vitro as 200 nts oligos and in vivo as an 54240- bp DNA fragment in yeast cell. This resulted in physical information density of \(\sim 198.8\) Exabytes per gram of DNA. This is much better than the previous work in the literature. + +I think the present work is an interesting approach. The introduced YYC scheme outperforms many previous schemes in terms of reliable data storage and physical information density. Some of my observations are listed below: + +<--- Page Split ---> + +# natureresearch + +1. I feel that the YYC encoding scheme can be better presented. There are a few problems in the current writing. For example, in Figure 1, the choice of alphabet for Xn and Yn should be given. Although a working example is given in Figure S1, the presentation is from bits and nucleotides to nucleotides whereas in the general scheme it is nucleotides and nucleotides to bits. Another working example may be given either in the supplementary files or in the paper itself that will make it very clear. + +Response 1: We thank the reviewer for the comment. We have revised the manuscript accordingly to include detailed description in the main text highlighted on the page 4 (line 121- 132) and figure S1 in supplementary. In addition, we have also re- uploaded a step- by- step demonstration video to show the encoding process for further elaboration. + +2. I could not find the supplementary video mentioned at page 4 and page 14. Perhaps, including that will also be helpful. + +Response 2: We apology to the reviewer on this. We have re- uploaded the video file as "supplementary video S1" in the supplementary for further description. + +3. Also, in the YYC scheme, there are 1536 possible options, so maybe it would be interesting to include a summary of all the rules in a table. This table could also include the rule number such as rule no. 888 that is used in Figure S1 or other rules in supplementary information. It is not clear how these rule numbers are assigned? Do they have some significance? I mean why the specific rule 888 was used. + +Response 3: We thank the reviewer for the comment. The rule number is assigned in numeric order from Rule no. 1 to Rule no. 1536. We followed the reviewer's suggestion to include a summary of all rules in the main text on page 6 (line 172 - 180) and Figure S2 to demonstrate the general performance regarding information density of all 1,536 coding schemes using 1 GB testing data including text, image, audio and video files. As screening criteria settings on sequence compatibility, the GC content, max homopolymer all fell into the criteria of constraints. The corresponding results are described in the main text highlighted on page 6 (line 183 - 198) and Table + +<--- Page Split ---> + +# natureresearch + +1. In this study, No. 888 was selected as a representing coding scheme with information density at medium level. + +4. At page 5, it is mentioned that when most of the binary segment contains more than \(80\%\) repeated \(0\) 's and \(1\) 's, the corresponding encoding process may enter an infinite loop or generate a poor result. Can we give some algebraic explanation for this from the YYC scheme? + +Response 4: We thank the reviewer for the comment. We followed the reviewer's suggestion to include an analysis to show the general performance of 1,536 combinatoric rules. The analysis is based on incorporation of two short binary segments (each binary segment contains 8 bits, which give 65,536 different combinations) based on its ratio of binary digit 0 and 1. When \(0 / 1\) ratio is less than \(20\%\) , it is shown that the number of coding schemes that can generate valid DNA sequence drops significantly from \(100\%\) to \(49.7\%\) and even lower when \(0 / 1\) ratio keeps decreasing. Therefore, \(0 / 1\) biased binary segments are firstly separated to improve the encoding efficiency. We set a "firewall" to limit the iteration run time at 100. For extreme cases, when most of the binary segments are \(0 / 1\) biased, "pseudo" binary segments with random \(0 / 1\) but in balanced ratio will be introduced to allow the generation of valid sequence. We have updated with description in the main text highlighted on page 5 (line 148 - 162) and Table S2 for further declaration. + +5. At page 12, statement "YYC offers the opportunity to incorporate multiple rules for one file transcoding and thus provide a novel strategy for secure data archiving." Can we give a specific example? This will motivate the reader. + +Response 5: We thank the reviewer for the comment. Generally, for other developed methods, the coding process follows a unitary transcoding rule. In contrast, YYC offers in total 1536 combinatorial transcoding rules, that each rule will generate distinct DNA sequencing. Thus, YYC offers the possibility to use multiple rules in one file transcoding and therefore could significantly increase the difficulty of deciphering the coding rule by brute-force attacks or other manners. We have revised this in the main text highlighted on page 14 (line 384 - 387). + +<--- Page Split ---> + +# natureresearch + +6. At page 15, line 10, What is Fq in Definition 1, line 1? Normally, Fq is a finite field having q elements but here, Fq is a set of 4 nucleotides, so q has no role to play. Maybe, the notation can be modified or Fq can be defined in line 1 and later, we can choose it to be an alphabet of size 4. + +Response 6: We thank the reviewer for the comment. We have revised this according to the reviewer's suggestion. The choice of two binary digits and four nucleotides is stated in "Quantitative analysis" section of the supplementary. We have rewritten this part to make it easier to understand. + +With these suggestions, I recommend for the publication of the manuscript. + +Manish K Gupta + +Response 7: We thank the reviewer for the recognition on YYC and significant help on improving our work. We hope our revised manuscript will reach to the level of publication on Nature Computational Science. + +Reviewer #2 (Remarks to the Author): + +The authors have introduced an interesting DNA encoding scheme called YYC (or Ying- Yang coding) with complementary rule sets to increase the coding density of current encoding methods. It is a dynamic transcoding scheme that transforms binary data into DNA sequences that could get close to the theoretical maximum information sensitivity of 2 bits per base. While the encoding approach is novel, there are inconsistencies and lack of exploration of parameters in the manuscript that make it difficult (or impossible) for anyone to assess the claimed merits of the work. It requires massive revisions, proper parameter studies, and significant retooling of how this paper is compared or "advertised" against other works. + +<--- Page Split ---> + +# natureresearch + +Summarized below are the major concerns: + +1. Data recovery rate - in the manuscript, DNA oligos are present at roughly 1e8 copies per designed oligo sequence, which by my calculation is \(\sim 175\) nanograms of total synthesis mass for Pool 1. They then dilute this down 10,000x fold in order to show that YYC/DNA fountain can get good recovery, but it completely breaks down at further serial dilutions. This is somewhat of a contrived experiment because it means the first dilution (10^4 molecules, which by my calculation of 10103 \* (10^4 molecules) \* (200 \* 330g/mol) \* (1 mol / (6.02 \* 10^23 molecules)) is 10 picograms of DNA. That is already an incredibly tiny amount of DNA. Given the data presented, it's not clear whether YYC's benefits are marginal or substantial. A more appropriate experiment to assess YYC's performance against DNA fountain in this context would be to show its performance for higher input copies (eg. 1e7, 1e6, etc.), as well as performances of re-amplifying pools from smaller dilutions (eg. dilution down to 1e7, 1e6, 1e5, amplifying back to 1e8 and using that as input). + +Response 8: We thank the reviewer for the comment. As for the reason to perform dilution assay at the starting level of 1e4 copies: The three master pools of 200nt DNA oligos we ordered from TWIST Bioscience are delivered in the form of lyophilized powder (190 ng, 182 ng and 172 ng respectively for P1, P2 and P3) with the yield of \(\sim 0.2 - 1\) fmol per oligo, which equals to the copy number at \(\sim 1\) e8 as indicated by the reviewer. The reason to perform dilution assay at the starting level of 1e4 copies is that in Erlich et. al, 2017 of DNA fountain, they validated the successful recovery of stored information at the level of 1e3 copies. Then in our study, we used the same setting as claimed in the paper and proven that both YYC and DNA fountain can perfectly recover stored data at the level of 1e4 copies, indicating that there will be no difference between the two methods on the recovery rate for higher input at 1e5, 1e6 and 1e7 copies. + +To perform data recovery rate assessment under low input copies, given that data retrieval from master pool is a consuming process for synthesized DNA molecules and synthesizing substantial DNA is still too costly at the moment, thus in our study, further serial dilutions from 1e3 down to the 1e1 is designed to evaluate the data recovery performance of YYC under low amount of synthesized DNA. + +<--- Page Split ---> + +# natureresearch + +However, we revised the experiment design according to the reviewer's suggestion by including the experimental evaluation from high input (at 1e7 copies in this study) all the way to low input (at 1e0 copies in this study). The DNA samples were re- ordered from the same vendor (TWIST Bioscience) we used in this study to repeat the whole experiment. In general, our updated results show that YYC exhibits relatively better performance regarding data recovery. With the input of 1e4 to 1e6 copies, the data recovery rate of YYC remains stable at comparable level with DNA fountain. And for the input of low copies (1e2 to 1e3 copies), YYC shows superior performance in data recovery. In addition, we found that at extreme low input level (1e0 to 1e1 copies), even the DNA molecules were re- amplified to 1e8 copies, the data recovery rate still cannot be guaranteed. + +We have updated all related results shown in main text highlighted on page 10- 12 (line 267 - 325), Figure 3, methods "Library preparation and sequencing" section on page 19 (line 543 - 558), supplementary excel file, Sheet 2 & 3 accordingly. + +2. In vivo storage - This part actually has very little to do with the YYC encoding and I don't understand its relevance to the manuscript's presentation of YYC encoding as a whole. You assemble DNA oligonucleotides or amplicons of any kind and clone into a plasmid for storage. The authors did not make any kind of argument about how any unique feature of YYC is relevant for in vivo storage besides the higher coding density, as you could theoretically just use any other high performance code. Interestingly, the authors did not touch on this point at all. + +Response 9: We thank the reviewer for the comment. The fast technical development of DNA synthesis and assembly promotes both in vitro and in vivo storage as well recognized approaches in recently years (Shipman et. al, Nature, 2017, Tabatabaei et. al, Nature Communications, 2020 and Chen et. al, National Science Review, 2021). Thus, we include both approaches in our study for experimental demonstrations. Previous study suggest that in vivo storage holds the advantage of retrieving data can be easily performed by cell subculturing and DNA extraction, and stored data can be well maintained. However, we noticed that introducing substantial heterogenous DNA into host strains could be problematic for data recovery. By sequencing of multiple single colonies isolated from the plate, we observed partial data coding DNA loss in + +<--- Page Split ---> + +# natureresearch + +varying degrees. Our result further suggests that data recovery performance of the coding scheme is essentially important. It is common to observe spontaneous mutations or unexpected variations accumulated during long term passing of living cells. Therefore, it would be very important to apply more robust coding algorithms to retain as much original information as possible. We thank the reviewer for pointing out the importance of providing adequate justification on the reason of doing in vivo storage. We have revised the main text highlighted on page 12 (line 328 - 355), Figure 4, methods "Synthesis and assembly" section on page 19 (line 537 - 540), methods "Data analysis" section on page 20 (line 575 - 601) and supplementary Table S7 to further clarify the importance of robustness of coding algorithm for in vivo storage. + +Furthermore, one of the most eye- catching errors in the paper is the advertisement of the storage density of \(\sim 200\mathrm{EB / g}\) . Storage densities, as reflected in bits of information per mass, is limited by the synthesis of unique fragments and also by the coding density of the encoding procedure. Given these considerations, it is impossible that YYC achieves densities of \(\sim 1000\mathrm{x}\) higher than DNA fountain (and other works in Table 1) despite similar orders of magnitude in coding density. Even looking at the authors' formula as to how to calculate their vivo storage metric, it appears that nothing in that formula is fundamentally unique to the YYC coding scheme or that by plugging in the stated coding density of DNA fountain would get you a \(\sim 1000\mathrm{x}\) difference in performance. In fact, the differences are marginal or negligible when plugging in different coding densities (into the information/nucleotide section, adjusting for plasmid backbone size) from Table 1. + +Investigating the calculation further (by briefly reading the DNA fountain work which this manuscript cites often), it appears that there is a fundamental difference in how the calculations were determined. It appears that Erlich et al cited their 215PB metric as part of a serial dilution scheme for assessing successful/perfect retrieval of synthesized DNA. Taking the logic from the Erlich paper, the authors should have diluted down their yeast preps accordingly as well (to specific copies of plasmid loaded per sequencing library). Further, there seems to be a methods typo, where the authors stated that they picked three colonies but later in the methods it says they picked 12. + +<--- Page Split ---> + +# natureresearch + +Response 10: We thank the reviewer for the comment. First, we would like to point out that information density is different concept from the physical density as we suggested in the manuscript on page 3 (line 83 - 87). Our argument is also supported previously by Organick et. al., 2020. Information density is determined by the algorithm itself, while the physical density indeed will vary by the selected approaches of storage (i.e. in vitro as DNA powder or in vivo as plasmid or integrated in the host genome). In the main text, we clarified that the physical density achieved in this study is based on in vivo storage on page 20 (line 584 - 601). And the calculation logic is consistent with previous study performed experimental demonstration using the approach of in vivo storage (Tabatabaei et. al, Nature Communications, 2020 and Chen et. al, National Science Review, 2021), which is not covered in Erlich et al.'s work. + +We accept the reviewer's suggestion and have revised Table 1 by: 1) providing corresponding physical density of both in vitro and in vivo storage performed in our study and 2) to include the physical density achieved in the recent published in vivo storage study (Chen et. al, National Science Review, 2021) to avoid misleading conclusion for readers. The calculation formula is also provided in the method "Data analysis" section highlighted on page 20 (line 584 - 601) for further clarification. For the method typo, we apology for the unintentional mistake, we have revised the description in the main text highlighted on page 12 (line 340 - 342), Figure 4 and method description "Synthesis and assembly" section on page 18 (line 533 - 540) to clarify the correct numbers. + +3. Other concerns regarding YYC encoding - it's clear that there is some sort of performance dependence according to the 1536 transcoding rules (Fig. S3 shows this pretty well). Across the manuscript there are tables with selected parameters but little discussion of the exact impact of them. It's difficult to assess what exactly the impact this has on performance when these parameters were not exhaustively studied either in silico or through actual experiments. Given the fact that this is a new coding scheme, the authors should have at minimum done an in silico demonstration of every single rule and how it affects every single metric in the paper. Off the top of my head, because the selection of the rule parameter greatly affects the information density, sequencing errors will play a large role in the overall performance. + +<--- Page Split ---> + +# natureresearch + +Response 11: We thank the reviewer for the comment. Parameters in Table 1 and the experimental design (Figure 3) is selected to be consistent with previous studies for the purpose of comparability. + +We accept the reviewer's suggestion and have revised accordingly in the main text highlighted on page 6 (line 172- 180) and page 8 (line 220 - 232) to provide the insilico demonstration to systematically evaluate their performance of all 1536 coding schemes using 1 GB data collection including different formats of files (text, image, audio, and video). To conclude in general, we have shown that: 1) although the information density of each coding schemes in the 1536 collections varies, but in the range from 1.75 bits/nt to 1.78 bits/nt under well- accepted constraints. 2) the overall performance including InDels and SNVs is not affected by sequencing/synthesis errors. + +Reviewer #3 (Remarks to the Author): + +The paper presents a new efficient coding scheme that improves the recovery rate in case of large sequence loss. The method maintains linear dependency between the percentage of oligos that were fully recovered, and the data recovery. Additionally, the paper demonstrates in vivo data storage with high information density. Roughly speaking, the paper is fairly written, however there are several parts which are not well explained, as will be elaborated below. + +## Comments: + +1. The code works well, I used it through the "chameleo" tool (that was also published by this group). + +Response 12: We thank the reviewer for the recognition of YYC code and careful testing efforts made to evaluate on YYC. + +2. Like I sent you in another email - I could not access the data from their experiment, so either the link is broken, or they should add more explanations on the data and how to access it. + +<--- Page Split ---> + +# natureresearch + +Response 13: We apology to the reviewer for that the access link was not working. We didn't notice that there were some technical problems on linking our raw data to the project site. We have solved the problem and now the reviewer should be able to access the raw data by: + +https://db.cngb.org/search/project/CNP0001650/ + +The raw sequencing data can also be accessed from: + +https://ftp.cngb.org/pub/CNSA/data3/CNP0001650 + +3. As far as I understand, the authors did not perform any reconstruction algorithm on the sequenced oligos. Can you please comment whether such an algorithm can improve the data recovery success and/or achieve faster data recovery? + +Response 14: We thank the reviewer for the comment. For both in vitro and in vivo experimental validations performed in our study, we used the standard de novo assembly algorithm SOAPdenovo (Luo et. al., 2012, Li et. al., 2010) applied in the next-generation sequencing analysis workflow. According to our result, we found that data recovery success/improvement is not achieved solely by the reconstruction algorithm itself but determined by the coding scheme and affected by errors introduced during synthesis/sequencing. However, we do think there could be a better algorithm or strategy designed specifically for this application in the future would improve the transcoding efficiency as well as the data recovery rate by better identifying and eliminating errors. We have revised this according to the reviewer's suggestion in the main text highlighted on page 12 (line 328 – 355) and included corresponding citations for algorithms used for sequence reconstruction in this study in the "Data analysis" section of method highlighted on page 20 (line 575 - 583). + +4. There are several terms in the introduction that should be better explained before used for the average reader. Examples of these expressions are: secondary structure, free energy calculation. + +Response 15: We thank the reviewer for the comment. We have revised this according to the reviewer's suggestion in the main text highlighted on page 2 (line 63 – 67). + +<--- Page Split ---> + +# natureresearch + +5. The sentence between lines 80-82 is not clear to me. + +Response 16: We thank the reviewer for the comment. In previous studies, two types of "redundancy" have been proposed and applied in DNA storage (one at transcoding level, while the other one refers to biochemical operation level). The logical redundancy of different transcoding methods varies, for example, it is mandatory for DNA fountain but not necessary for YYC. However, the physical redundancy (using extra molecule copies by synthesis) can be applied to all developed transcoding methods. They both can play a positive role in data recovery, but functioning in fundamentally different approaches. Thus we want to distinguish the difference between the two types of redundancy. We have revised this accordingly to make it clear in the main text highlighted on page 3 (line 83 – 87) and added relevant references (Ref No. 23,24). + +6. Description of the YYC between lines 114-126 is not clear. What do X_n and Y_n refer to? + +Response 17: We thank the reviewer for the comment. Here we use N1/N2/N3/N4 to represents one of the four nucleic acids A/T/C/G. In 'Yang' rule, 0 and 1 are mapped to two nucleotides: for example, if A or T represents 0, then the only choice for 1 is C or G. In 'Yin' rule, 0 and 1 are also mapped to two nucleotides, but in a different manner: Xj and Yj represent different binary digits 0 and 1. When j is an integer chosen from 1 to 8, Xj+Yj=1 and Xj×Yj=0 (i.e. eight independent sets of X and Y, with Xj /Yj being either 1/0 or 0/1). Since N1 and N2, or N3 and N4 represent identical binary digits in 'Yang' rule, but represent different digit in 'Yin' rule, it will only give one and only one consensus nucleotide during encoding. We have revised this accordingly to make it clearer in the main text highlighted on page 4 (line 121 - 132) and updated additional illustration in the supplementary video S1 for further clarification. + +7. The caption of Fig. 1 is not clear either. + +<--- Page Split ---> + +# natureresearch + +Response 18: We thank the reviewer for the comment. We have revised the figure caption accordingly to make it clearer in the main text highlighted on page 4 (line 121 - 132). + +8. The description in page 11 of lines 282-310 is not clear to me. + +Response 19: We thank the reviewer for the comment. The fast technical development of DNA synthesis and assembly promotes both in vitro and in vivo storage as well recognized approaches in recently years (Shipman et. al, Nature, 2017, Tabatabaei et. al, Nature Communications, 2020 and Chen et. al, National Science Review, 2021). Thus, we include both approaches in our study for experimental demonstrations. Previous study suggest that in vivo storage holds the advantage of retrieving data can be easily performed by cell subculturing and DNA extraction, and stored data can be well maintained. However, we noticed that introducing substantial heterogenous DNA into host strains could be problematic for data recovery. By sequencing of single colonies isolated from the construct, we observed partial data coding DNA loss in varying degrees. Our result further suggests that data recovery performance of the coding scheme is essentially important. We have revised the description accordingly to make it clearer in the main text highlighted on page 12 (line 328 - 355). + +9. I could not find the supplementary video of Fig. S1b. + +Response 20: We apology to the reviewer on this. We have re- uploaded the video file as "supplementary video S1" in the supplementary for further description. + +10. The statement in Lemma 3 is not properly stated. + +Response 21: We thank the reviewer for the comment. We have rewritten this part to make it clearer to understand. The new section is in the "Quantitative analysis" section of Supplementary. + +<--- Page Split ---> + +# natureresearch + +11. In general, all the mathematical analysis in page 15 is very sloppy. The equations are explained and their correctness is not justified. There should be a clear statement about the properties that the YCC scheme satisfies and a proof for the redundancy. As written this way, I cannot truly understand and evaluate the code construction. + +Response 22: We thank the reviewer for the comment. We have rewritten this part to make it clearer to understand. The new section is in the "Quantitative analysis" section of Supplementary. + +12. The authors compare mostly with fountain codes. What about comparison with the other coding schemes? + +Response 23: We thank the reviewer for the comment. As we explained in our introduction part on page 3, all early efforts have paved the way of facilitating the fast development of DNA storage, with focus on biochemical compatibility and/or chasing the extreme of information density. The comparison with all developed coding scheme is performed by encoding 1GB data collection in our study for in silico simulation analysis. Relative result is described in the "General principle and features of the Yin-Yang codec" part on page 6 (line 183 - 198) and supplementary Table S1. Since DNA fountain has performed comprehensive analysis to show its superior performance in comparison with other above mentioned coding schemes (Yaniv Erlich and Dina Zielinski, Science 2017), thus in our study, we choose to focus the comparison between DNA fountain and YYC for experimental validation comparison. + +<--- Page Split ---> + +# natureresearch + +Decision Letter, first revision: + +Date: 17th January 22 04:48:08 Last Sent: 17th January 22 04:48:08 Triggered By: Ananya Rastogi + +From: ananya.rastogi@nature.com + +To: shenyue@genomics.cn + +BCC: ananya.rastogi@nature.com + +Subject: Decision on Nature Computational Science manuscript NATCOMPUTSCI- 21- 0438A + +Message: \*\* Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. \*\* + +Dear Dr Shen, + +Your manuscript "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" has now been seen by the 3 referees that we had contacted earlier. In addition, we contacted 1 more reviewer for a more technical review. The reviewers' comments are appended below. You will see that while they find your work of interest, they have raised points that need to be addressed before we can make a decision on publication. + +While we ask you to address all of the points raised, the following points need to be substantially worked on: + +- Please provide more insight into the way indices are assigned to segments along with the effect this has on pool capacity. +- Please discuss the policy for what to do when a sequence fails to encode. +- Please provide a discussion on where the proposed codec fits in and how it could be used with other approaches. +- Please provide an insight into the observed poor performance of DNA Fountain. + +Please use the following link to submit your revised manuscript and a point- by- point response to the referees' comments (which should be in a separate document to any cover letter): + +## [REDACTED] + +\*\* This url links to your confidential homepage and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this e- mail to co- authors, please delete this link to your homepage first. \*\* + +To aid in the review process, we would appreciate it if you could also provide a copy of your manuscript files that indicates your revisions by making use of Track Changes or similar mark- up tools. Please also ensure that all correspondence is marked with your Nature Computational Science reference number in the subject line. + +In addition, please make sure to upload a Word Document or LaTeX version of your text, to assist us in the editorial stage. + +<--- Page Split ---> + +# natureresearch + +To improve transparency in authorship, we request that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +We hope to receive your revised paper within three weeks. If you cannot send it within this time, please let us know. + +We look forward to hearing from you soon. + +Best regards, + +Ananya Rastogi, PhD Associate Editor Nature Computational Science + +Reviewers comments: + +Reviewer #1 (Remarks to the Author): + +The points you raised in the previous round of review have been satisfactorily addressed. + +The paper can be accepted now. + +Reviewer #2 (Remarks to the Author): + +The authors have adequately addressed all of my concerns. + +Reviewer #3 (Remarks to the Author): + +The authors addressed most of my comments as well as the ones by the other two reviewers. I still have several concerns with the paper presentation and my previous comments (I was reviewer #3). + +- In my third comments, I asked about the use of some reconstruction algorithm. From your explanation it is implied that a voting strategy was applied to generate a consensus sequence. What exactly does it mean and why don't you use other algorithms for reconstruction. + +- In comment 12, I still don't see the rationale behind the comparison with only DNA fountain codes. In general, you should mathematically describe the problem that is solved in the paper and why Yin-Yang codes are better than other known schemes for this problem. + +<--- Page Split ---> + +# natureresearch + +Reviewer #4 (Remarks to the Author): + +Reviewer Summary + +This work describes a novel codec for DNA storage called the Yin- Yang Codec (YYC). It's based on the observation that it is difficult to achieve both theoretical information densities and sequences that meet critical biomolecular constraints, such as avoiding homopolymers, imbalanced GC content, or harmful structures. The YYC is effective at reaching high density because it supports a variety of encoding strategies. + +Here's a brief summary of how it works. A file is divided into segments of a fixed length as binary strings; an index is added to each segment to mark its location in the file. Then, two segments, say a and b, are selected at random and sent through a two- step encoding process (Yin and Yang). One bit is taken from each of the two segments and is encoded into a single nucleotide. Using 2 bits to encode each nucleotide is what give it a high information density. The Yin step uses a[i] to select a set of possible encoding bases, which narrows it down to 2 of the 4 bases based on a look- up table, call this set A. The Yang step uses the b[i] bit and the previous nucleotide that was encoded to looks up its encoding, which is also a set of possible nucleotides, lets call it set B. Then, the intersection of A and B is emitted as the output nucleotide. The Yin and Yang coding tables are designed to ensure a unique nucleotide is emitted. This process repeats for all bits in a and b until the sequence is generated. Because two bits are used to produce each base, it has the potential to reach the information theoretical limit of 2 bits / nt. However, after the sequence is created, it's sent through a filter to weed out bad sequences based on GC content, homopolymers, and thermodynamic analysis. If it fails this step, the sequence is thrown out. This process of selecting segments, encoding them, and checking them is repeated until enough good sequences are created to enable decoding of the file. No additional logical redundancy is included since this process is only meant as a way of encoding the data and is not meant to provide error correction. + +Experiments are conducted in silico, in vitro, and in vivo to understand its utility and verify its usefulness for DNA storage. The YYC approach is applied to a suite of files of various formats and shown to successfully encode and decode while achieving good information densities. Its effectiveness is compared primarily to DNA Fountain given their overall similarity in goals and approach. + +The most interesting part of the evaluation is in how well the codec works in silico. The in vitro studies are expected to work since they largely follow proven experimental methodologies. The in vivo studies add some new analysis to the field concerning storage and retrieval of data in yeast. + +## Significance + +This work aims to further the field by presenting a new codec that provides high information density while still avoiding problematic sequences. This codec bears significant similarity to the goals of DNA Fountain, and that's why they compare against DNA Fountain. However, this work is not a Fountain code, and that enables some simplifications while also creating potential weaknesses. + +<--- Page Split ---> + +# natureresearch + +## Advantages: + +\(+A\) potential advantage of this work is the straightforward encoding and decoding process with respect to segments and their indices. This work can embed the indices directly in the encoded segments and recover them through standard decoding, but fountain codes need to encode that information as separate meta- data or hard code a lookup table or enumerator function a priori in the encoder and decoder. + +\(+\) Another potential advantage of this work is the large variety of Yin and Yang coding tables, up to 1536, that allow a wide variety of ways to encode data. However, this may be a weakness, as described below. + +## Disadvantages: + +- A fountain code can pick an arbitrary number of segments to merge, but this can only pick 2. YYC makes up for this limitation to some degree by having non-unitary mapping rules, however, this is achieved using a trial and error process. The trial and error process is not described in the paper or in the supplementary material, as far as I could tell. While the YYC can allow up to 1536 different coding tables, it was not demonstrated in the work that all of these combinations are actually useful, and I suspect that many of the tables end up producing similar results and may not all be equally useful. + +- Fountain codes and rateless codes, in general, can add an arbitrary number of additional symbols to the encoded file, but this work can pick from at most \(n^2\) combinations of segments, where n is the number of segments in the file, giving it far fewer combinations to work with to find usable sequences than Fountain codes. + +- This work shares the disadvantage of DNA Fountain of needing to verify a sequence after its encoded, which means that either the pair of segments or the mapping tables could have been a poor choice. This can lead to large encode-time overheads and many failed attempts when encoding strands. The number of trials used to encode data and its compute time is not reported, but it should be for a fair assessment of the work. The work does report a limit of 100 attempts per strand, but the total number of attempts while encoding a file is not reported. + +- The policy for what to do when a sequence fails to encode is not described in much detail. I am concerned with the computational complexity of choosing a suitable table - how many attempts are needed? Also, I'm concerned about what happens if there is no suitable encoding for some part of the data. If 100 attempts are made and all fail, at this point, is a suitable synthetic sequence created just to ensure encodability? Is this synthetic sequence somehow always guaranteed to succeed or might multiple attempts be needed here as well? It would be good to quantify this as well. + +## Clarity and Context + +\* I think the work does not position itself as well as it could with respect to prior codecs or with respect to DNA Fountain. Many different codecs have been proposed to deal with various challenges of DNA storage. The presentation of where this one fits in and how it could be used with other approaches could be done with greater clarity. For example, this is really just part of the codec and doesn't include any new support for + +<--- Page Split ---> + +# natureresearch + +error correction. Also, this article takes a fairly limited view of what is relevant and does not discuss deeply how other codes were designed and what their advantages and disadvantages are. Organick et al. [Nature Biotech 2018] deal with these same issues but in different ways. Also, DNA Fountain, and fountain codes in general, could be configured and tuned to work potentially much better than the DNA Fountain work that is compared against, but this is not done or considered. The claimed advantages of YYC over DNA Fountain may be true for the specific implementation of DNA Fountain that was compared against, but those advantages likely do not extend to an optimized Fountain code for data storage. + +\* The example of the Yin- Yang Codec given in the paper is hard to understand. I think you should move a similar example as in the video into the paper. Make it concrete so that readers can understand how one of the configurations actually works. You can always add more explanation on how to generalize it elsewhere. Without a good example, the paper is not self- contained and reviewers will need the supplementary material to make sense of the work, which is not ideal in my opinion. + +- The way indices are assigned to segments is not explained in enough detail. Also, how segments are assigned to either the Yin or Yang rule is not explained. These are important details because they have a large bearing on the overall efficiency of the system. For example, suppose a file is partitioned into segments and each one is labeled with a unique binary index, of length k (2\*\*k total segments are possible). Now, suppose these segments are selected at random and passed arbitrarily into either the Yin or Yang rule. This means that k nucleotides are used to represent the index and 4\*\*k sequences are possible, but only 2\*\*k total indices are available in the file. This implies that indices have at most a coding density of 1 bit/base. Large files will need large indices, which substantially cuts into the claimed high density of the system since oligo synthesis has relatively hard limits on synthesized strand length. Other codecs which do not use a binary index will have a significant advantage in overall capacity and density. It's possible that I've misunderstood some aspect of how indices are assigned and used in this codec, so it would be good for this aspect of the paper to be improved. + +## Major Suggestions + +1. The paper makes a strong claim about density that needs to be clarified. As mentioned earlier, the work does not explain well how indices are handled (as mentioned previously in my review), but the indices appear to achieve no better than a binary encoding (1 bit/base) density. One implication of this is that a high-density encoding is somewhat reliant on having small indices, which implies small file sizes and small capacity overall. This is an undesirable result for what should be a dense medium. Another implication of this is that the total capacity of the system (total unique strands) appears to be lower than those systems that achieve ternary indices, for example. While the claimed figures of merit for density are high, they hide the fact that the total capacity of a pool of DNA may be severely negatively impacted by binary indices. I would like to see a better explanation of how indices are handled and the effect this has on pool capacity. + +2. The capabilities of the YYC codec with respect to the variety of mapping tables is not well justified. It's not clear that the ability to select one of the 1536 configurations + +<--- Page Split ---> + +# natureresearch + +actually helps or not. The work claims to leverage a combinatoric scheme, but that is not demonstrated through an experiment, except to some degree in the small one that analyzes strands with large fractions of 0 or 1 to see if any mapping tables can encode them satisfactorily. + +To really demonstrate the advantage of all these combinations, several things need to be shown. (1) That having a choice among mapping tables is helpful and leads to less overhead as compared to DNA Fountain. (2) That the choice of mapping table can be made efficiently. It would be interesting to report the number of failed attempts at selecting segments and encoding them. (3) That the overhead of holding the choice of mapping table in meta- data is a reasonable cost, even if done electronically. If a mapping table selection needs to be remembered per strand, then that implies approximately 11 bits of overhead per segment- pair, which for an exabyte scale system would add up to a very large cost. If it only needs to be remembered per file, it's a lower meta- data cost but higher compute cost to find a mapping. These trade- offs need some further explanations. + +If this analysis is prohibitive to conduct, then I would suggest softening the claims over how useful these tables are. + +3. It's surprising that DNA Fountain does so poorly in the in silico experiment (Figure 2). I agree with the general arguments that DNA Fountain will have high degree packets that include many segments. However, I'm not convinced this is the entire answer unless DNA Fountain mostly selects high degree packets. Also, some important information is missing in this analysis. It appears that no error correction is used. In that case, what is done with strands that have insertions, deletions, and substitutions? Without error correction support, such problems cannot even be detected much less corrected. So, are they treated as correct and allowed to pollute the file with errors? This raises questions about how the DNA Fountain approach is utilized. Is the DNA Fountain code base used for this analysis? If so, is it possible that something is going wrong in how it handles these errors? For example, since segments are more likely repeated in multiple high degree packets, it may be detecting errors and throwing them out, whereas YYC has no such detection capability. Instead, YYC may be making a best-effort attempt to keep the data. More details of how this analysis is conducted are needed to fully explain DNA Fountain's poorer behavior. + +## Minor Suggestions + +1. Perhaps add a brief explanation for a few things in the thermodynamic screening, such as at what temperature was the simulated free energy screening conducted? And, what other parameters were used, if any? Why did you pick -30 kcal/mol as the cutoff? + +2. In the text regarding in vitro experiments, please make it clear which encoding was used for each pool. I think P2 and P3 were done using DNA Fountain. + +3. On Page 9, line 242-244, it says that loss of one strand in YYC can lead to the loss of two segments. This is true. But, isn't it possible that a segment is repeatedly selected for pairing due to some good pattern in its data, decreasing the odds it is lost? Or, do you prevent selecting the same sequence many times? + +Thank you for an interesting paper. + +<--- Page Split ---> + +# natureresearch + +Reviewers' comments: + +## Reviewer #1 (Remarks to the Author): + +The points you raised in the previous round of review have been satisfactorily addressed. + +The paper can be accepted now. + +Response 1: We thank the reviewer for the significant help in improving our work. + +## Reviewer #2 (Remarks to the Author): + +The authors have adequately addressed all of my concerns. + +Response 2: We thank the reviewer for the significant help in improving our work. + +## Reviewer #3 (Remarks to the Author): + +The authors addressed most of my comments as well as the ones by the other two reviewers. I still have several concerns with the paper presentation and my previous comments (I was reviewer #3). + +- In my third comments, I asked about the use of some reconstruction algorithm. From your explanation it is implied that a voting strategy was applied to generate a consensus sequence. What exactly does it mean and why don't you use other algorithms for reconstruction. + +Response 3: We thank the reviewer for the comment. The voting strategy here is the single- winner plurality voting strategy where each candidate sequence has the same weight. As this strategy is straightforward and effective with the stored data fully recovered, we chose this strategy over other algorithms to minimize complexity and avoid algorithmic bias. We have revised the coordinating manuscript on page 13 (line 376 to 378) to avoid confusion. + +<--- Page Split ---> + +# natureresearch + +- In comment 12, I still don't see the rationale behind the comparison with only DNA fountain codes. In general, you should mathematically describe the problem that is solved in the paper and why Yin-Yang codes are better than other known schemes for this problem. + +Response 4: We thank the reviewer for the comment. Excepting DNA fountain, early established coding schemes apply a single fixed rule for bit- to- base transcoding, in which no screening process is used. On the contrary, DNA Fountain and YYC are the only two known coding schemes that combine transcoding rules and screening as a whole process to make sure the generated DNA sequences can meet the biochemical constraints, such as GC content and maximum homopolymer length. Thus, we reason that direct mathematical analysis should be focused on the comparison between DNA Fountain and YYC due to the similarity of coding strategy between YYC and DNA Fountain. Both algorithms employ the strategy of incorporation of two or more binary segments and generate a corresponding DNA sequence/ information packet. The information packets generated by DNA fountain are topologically connected with each other and form a grid- like structure. For current information communication using cables or radio, this procedure is feasible because even if some packets are lost or with error, new packets can be immediately re- sent for successful data recovery. However, receiving information in the process of DNA storage is not synchronous. Thus, the errors or packets loss will lead to a domino effect or error propagation for DNA Fountain. In contrast, the information packets generated by YYC are mutually independent. The effect on data recovery caused by the errors or packets loss is greatly minimized for YYC. + +In addition, as we explained in our previous response, we have included the performance comparison among all developed coding schemes by encoding 1GB data collection in our study for in silico simulation analysis (Table 1). And our result suggests that YYC shows superior performance in comparison with other existing coding schemes. + +## Reviewer #4 (Remarks to the Author): + +Reviewer Summary + +This work describes a novel codec for DNA storage called the Yin- Yang Codec (YYC). It's based on the observation that it is difficult to achieve both theoretical + +<--- Page Split ---> + +# natureresearch + +information densities and sequences that meet critical biomolecular constraints, such as avoiding homopolymers, imbalanced GC content, or harmful structures. The YYC is effective at reaching high density because it supports a variety of encoding strategies. + +Here's a brief summary of how it works. A file is divided into segments of a fixed length as binary strings; an index is added to each segment to mark its location in the file. Then, two segments, say a and b, are selected at random and sent through a two- step encoding process (Yin and Yang). One bit is taken from each of the two segments and is encoded into a single nucleotide. Using 2 bits to encode each nucleotide is what give it a high information density. The Yin step uses a[i] to select a set of possible encoding bases, which narrows it down to 2 of the 4 bases based on a look- up table, call this set A. The Yang step uses the b[i] bit and the previous nucleotide that was encoded to looks up its encoding, which is also a set of possible nucleotides, lets call it set B. Then, the intersection of A and B is emitted as the output nucleotide. The Yin and Yang coding tables are designed to ensure a unique nucleotide is emitted. This process repeats for all bits in a and b until the sequence is generated. Because two bits are used to produce each base, it has the potential to reach the information theoretical limit of 2 bits / nt. However, after the sequence is created, it's sent through a filter to weed out bad sequences based on GC content, homopolymers, and thermodynamic analysis. If it fails this step, the sequence is thrown out. This process of selecting segments, encoding them, and checking them is repeated until enough good sequences are created to enable decoding of the file. No additional logical redundancy is included since this process is only meant as a way of encoding the data and is not meant to provide error correction. + +Experiments are conducted in silico, in vitro, and in vivo to understand its utility and verify its usefulness for DNA storage. The YYC approach is applied to a suite of files of various formats and shown to successfully encode and decode while achieving good information densities. Its effectiveness is compared primarily to DNA Fountain given their overall similarity in goals and approach. + +The most interesting part of the evaluation is in how well the codec works in silico. The in vitro studies are expected to work since they largely follow proven experimental methodologies. The in vivo studies add some new analysis to the field concerning storage and retrieval of data in yeast. + +Significance + +<--- Page Split ---> + +# natureresearch + +This work aims to further the field by presenting a new codec that provides high information density while still avoiding problematic sequences. This codec bears significant similarity to the goals of DNA Fountain, and that's why they compare against DNA Fountain. However, this work is not a Fountain code, and that enables some simplifications while also creating potential weaknesses. + +Advantages + +\(+A\) potential advantage of this work is the straightforward encoding and decoding process with respect to segments and their indices. This work can embed the indices directly in the encoded segments and recover them through standard decoding, but fountain codes need to encode that information as separate meta- data or hard code a lookup table or enumerator function a priori in the encoder and decoder. + +\(+\) Another potential advantage of this work is the large variety of Yin and Yang coding tables, up to 1536, that allow a wide variety of ways to encode data. However, this may be a weakness, as described below. + +Disadvantages: + +- A fountain code can pick an arbitrary number of segments to merge, but this can only pick 2. YYC makes up for this limitation to some degree by having non-unitary mapping rules, however, this is achieved using a trial and error process. The trial and error process is not described in the paper or in the supplementary material, as far as I could tell. While the YYC can allow up to 1536 different coding tables, it was not demonstrated in the work that all of these combinations are actually useful, and I suspect that many of the tables end up producing similar results and may not all be equally useful. + +Response 5: We thank the reviewer for the comprehensive summary and recognition of our work. To briefly summarize the two major concerns/suggestions from the reviewer: 1) providing the detailed description of the trail- and- error process; 2) describing the differences of the proposed 1536 coding schemes in this study. To answer the questions: + +For the trial- and- error process, it is the iteration process as the reviewer understands in the above summary part: "This process of selecting segments, encoding them, and checking them is repeated until enough good sequences are created to enable decoding of the file". We further revised the description to make it clearer and highlighted it in the manuscript on page 5 (line 144 to 151). + +<--- Page Split ---> + +# natureresearch + +For the difference analysis of 1,536 combinatory coding schemes, we followed the reviewer's suggestion and performed further analysis on the difference of generated DNA sequences by using individual coding scheme to transcode various types of files. The DNA sequence difference are evaluated by the average hamming distance, which is the number of bit positions in which the two bits are different. Our result shows that for the same digital files, 1328 of the 1536 coding schemes can generate corresponding DNA sequences with identity less than \(40\%\) and only less than \(0.5\%\) of full coding scheme collections (7 coding schemes) generating DNA sequences with identity between \(80\%\) to \(91.85\%\) (Fig. S3). Our analysis suggests that the 1536 coding schemes can generate significantly different DNA sequences. We have revised the manuscript on page 7 (line 192 to 196) and supplementary information on Figure S3 to further clarify. + +- Fountain codes and rateless codes, in general, can add an arbitrary number of additional symbols to the encoded file, but this work can pick from at most \(n^2\) combinations of segments, where n is the number of segments in the file, giving it far fewer combinations to work with to find usable sequences than Fountain codes. + +Response 6: We thank the reviewer for the comment. We understand that the reviewer's concern is that \(n^2\) combinations of segments may not be sufficiently enough to generate valid DNA sequences. First, we would like to point out that in the general circumstance, rateless codes like LT codes, Raptor codes, etc., can generate an arbitrary number of packets from the information source and increase the redundancy correspondingly to find usable sequences. However, that doesn't apply if the digital information shows extreme data patterns. We have proved our point in our work by transcoding 5 different binary patterns in Table. S1 and the figures of 9 different national flags shown in Table. S6 of the supplementary information. For DNA Fountain, even with \(300\%\) redundancy being introduced, there is still no solution for successful transcoding. + +We would also like to clarify that the maximum combinations of YYC can be much higher than \(n^2\) because YYC allows the introduction of additional "pseudo" binary segments to avoid the situation that there is no desired combination for existing segments (as stated in the manuscript on page 6 from line 165 to 167). Thus, the actual maximum number of combinations of YYC is \(n^* 2^k\) (k refers to the number of additionally added segments). The approach by incorporating + +<--- Page Split ---> + +# natureresearch + +additional binary segments is essentially useful and important for digital file with extreme data patterns. For the same examples we mentioned above that DNA Fountain failed to provide solution, using YYC, we successfully transcoded the figure into DNA sequences with high biocompatibility to DNA synthesis and sequencing processes. + +Although archiving of the source digital file can balance the data pattern, however, as we described in the highlighted main text on page 14 (line 402- 407), it also brings significant challenges to data decoding because the errors introduced during DNA synthesis and sequencing will significantly affect the success rate of decoding. To summarize, our result suggests that YYC shows superior performance on the general coding/decoding processes by the proposed combination strategy with no preference on particular data patterns. + +- This work shares the disadvantage of DNA Fountain of needing to verify a sequence after its encoded, which means that either the pair of segments or the mapping tables could have been a poor choice. This can lead to large encode-time overheads and many failed attempts when encoding strands. The number of trials used to encode data and its compute time is not reported, but it should be for a fair assessment of the work. The work does report a limit of 100 attempts per strand, but the total number of attempts while encoding a file is not reported. + +Response 7: We thank the reviewer for the comment. We understand the reviewer concerns that whether the iteration cycle/attempts cost significant encoding- time overheads to generate valid DNA sequence. + +We performed the evaluation of average iteration run required by transcoding ten different formats of files and have shown that the average number from 1 to 7 trails (Table S3). We further took the reviewer's suggestion and conducted further analysis by estimating the total number of trails while encoding the 1 GB data collection used in our study for in silico simulation. As shown in Fig. S4a, in general, 65% of the segment can be successfully incorporated with another segment with a single run of trail, and for files with balanced byte frequency (Fig. R1 shown below), the percentage further increase to \(\sim 77\%\) (Fig. S4b). From our observation, less than 0.3% of segments requires more than 10 runs of trail. Our results imply that for an arbitrary file, YYC encoding would not cost a large encode- time overheads. We have revised the manuscript accordingly to include these analysis results in the main text highlighted on page 6 (line 164 – 172), as well as supplementary (Figure S4). + +<--- Page Split ---> + +# natureresearch + +![](images/Figure_unknown_0.jpg) + +
Statistics of byte frequency of all the files used in the simulation. According to Li et al., 2005, green ones were considered as files with balanced byte frequency. (For review usage only)
+ +- The policy for what to do when a sequence fails to encode is not described in much detail. I am concerned with the computational complexity of choosing a suitable table -- how many attempts are needed? Also, I'm concerned about what happens if there is no suitable encoding for some part of the data. If 100 attempts are made and all fail, at this point, is a suitable synthetic sequence created just to + +<--- Page Split ---> + +# natureresearch + +ensure encodability? Is this synthetic sequence somehow always guaranteed to succeed or might multiple attempts be needed here as well? It would be good to quantify this as well. + +Response 8: We thank the reviewer for the comment. We think there might be some misunderstanding on that poor choice is made when suitable encoding failed after 100 attempts. In the transcoding process of YYC, all the generated sequence must fulfill the constraints without any exception, and this is achieved by the incorporation of "pseudo" binary segment with random 0/1 but in balanced ratio as we mentioned in the response #6. This can make sure that a valid DNA sequence will be generated for each binary segment. The addition of "pseudo" segment will of course reduce the bit- to- base information density. But according to our simulation analysis using the 1GB data collection, less than \(0.002\%\) of overall segments need this "back- up" plan (Fig. S4). In the "worst" case we observed in Table S3, the additional information added to the source file for successful transcoding accounts for only \(19.25\%\) of the original file size, with the average number of trails at \(\sim 7\) and information density at \(\sim 1.45\) . We have updated the description in the manuscript accordingly on page 6 (line 164 to 172). + +## Clarity and Context + +\* I think the work does not position itself as well as it could with respect to prior codecs or with respect to DNA Fountain. Many different codecs have been proposed to deal with various challenges of DNA storage. The presentation of where this one fits in and how it could be used with other approaches could be done with greater clarity. For example, this is really just part of the codec and doesn't include any new support for error correction. Also, this article takes a fairly limited view of what is relevant and does not discuss deeply how other codes were designed and what their advantages and disadvantages are. Organick et al. [Nature Biotech 2018] deal with these same issues but in different ways. Also, DNA Fountain, and fountain codes in general, could be configured and tuned to work potentially much better than the DNA Fountain work that is compared against, but this is not done or considered. The claimed advantages of YYC over DNA Fountain may be true for the specific implementation of DNA Fountain that was compared against, but those advantages likely do not extend to an optimized Fountain code for data storage. + +<--- Page Split ---> + +# natureresearch + +Response 9: We thank the reviewer for the comment. To briefly summarize, we think there are two issues from the reviewer's view: 1) Comparison between YYC and other coding schemes apart from DNA fountain; relationship with other efforts (such as error correction) been made in the field of DNA storage; 2) Comparison towards DNA Fountain is limited at specific implementation. + +For the first concern, as we described in the Response #4, excepting DNA fountain, early established coding schemes apply a single fixed rule for bit- to- base transcoding, in which no screening process is used. On the contrary, DNA Fountain and YYC are the only two coding schemes that combine transcoding rules and screening as a whole process to make sure the generated DNA sequences can meet the biochemical constraints, such as GC content and maximum homopolymer length. Thus, we reason that direct mathematical analysis should be focused on the comparison between DNA Fountain and YYC due to the similarity of coding strategy between YYC and DNA Fountain. Both algorithms employ the strategy of incorporation of two or more binary segments and generate a corresponding DNA sequence/ information packets. However, we did include the functional comparison with all developed coding scheme by encoding 1GB data collection in our study for in silico simulation analysis. Relative result is described in the "General principle and features of the Yin- Yang codec" part. From our point of view, the whole DNA storage process includes several function modules: bit- to- base encoding, error- correction, indices assignment, redundancy handling, etc. YYC is developed as a bit- to- base encoding algorithm for improving the practicality and robustness of DNA data storage. It can be used separately or in corporation with other developed function modules. For example, in this study we used RS code to implement the function of error correction. Future efforts can be performed to incorporate more functionalities and we proposed some of the orientations in the discussion part in main text, page 15 (line 418- 424). + +For the second suggestion, the in silico simulation analysis and experimental validations were performed with recommended configuration and parameters of DNA Fountain claimed in their study. In addition, we agree with the reviewer that the configuration and parameter adjustment could improve the general performance of a coding scheme like DNA Fountain, but the improvement will be in a relatively limited range. As described in our manuscript, increasing logical redundancy could greatly improve the probability of successful decoding for all the coding schemes. However, we have proven that even with exceeding high redundancy at \(300\%\) (Table S6), for some digital files, DNA Fountain still failed to generate an encoding solution. And + +<--- Page Split ---> + +# natureresearch + +this is caused by the fundamental limitation of DNA Fountain rather than the selection of configuration and parameters. + +\* The example of the Yin- Yang Codec given in the paper is hard to understand. I think you should move a similar example as in the video into the paper. Make it concrete so that readers can understand how one of the configurations actually works. You can always add more explanation on how to generalize it elsewhere. Without a good example, the paper is not self- contained and reviewers will need the supplementary material to make sense of the work, which is not ideal in my opinion. + +Response 10: We thank the reviewer for the comment. We have revised the manuscript and provided a similar example as in the video to make the paper selfcontained (page 16 from line 469 to 481). + +- The way indices are assigned to segments is not explained in enough detail. Also, how segments are assigned to either the Yin or Yang rule is not explained. These are important details because they have a large bearing on the overall efficiency of the system. For example, suppose a file is partitioned into segments and each one is labeled with a unique binary index, of length k (2\*\*k total segments are possible). Now, suppose these segments are selected at random and passed arbitrarily into either the Yin or Yang rule. This means that k nucleotides are used to represent the index and 4\*\*k sequences are possible, but only 2\*\*k total indices are available in the file. This implies that indices have at most a coding density of 1 bit/base. Large files will need large indices, which substantially cuts into the claimed high density of the system since oligo synthesis has relatively hard limits on synthesized strand length. Other codecs which do not use a binary index will have a significant advantage in overall capacity and density. It's possible that I've misunderstood some aspect of how indices are assigned and used in this codec, so it would be good for this aspect of the paper to be improved. + +Response 11: We thank the reviewer for the comment. The reviewer suggested that: 1) Incorporation of index will decrease the coding density to 1 bit/base; 2) Indices for large file could be enormous and might further reduce the information density; 3) Other coding schemes avoiding the use of binary index have advantage in the overall capacity and density. + +<--- Page Split ---> + +# natureresearch + +For the first suggestion, we think there might be some misunderstanding about indices assignment. As the reviewer concluded, if a file is partitioned into \(2^{\wedge}k\) segments and each one is labeled with a unique binary index, the index length will be k. The index will be attached to the partitioned binary segment as a new segment (information + index) before encoding corporation. Therefore, for the k nucleotides representing index, they are the corporation product of two indices, which means each nucleotide will encode 2 bits of the indices' information at most rather than 1 bit/base. We understand that k nucleotide will give \(4^{\wedge}k\) possible sequences, but coding density refers to (total information / total base), rather than (total information / possible choices). + +For the second suggestion, we agree with the reviewer that large files indeed need more indices only if the configuration and parameters remain defined. However, there are many alternative choices other than index itself for the application of DNA storage. For example, flanking region usually has a length of 16- 20 nucleotides for PCR amplification. And according to Organick et al., 2018, random access of DNA storage using flanking region can be one of the examples to expand the indexing. In addition, as the DNA synthesis technology keeps advancing, the length of synthetic DNA can be further increased to maintain a relatively high level of information density. In addition, using artificial data coding chromosome for storage further demonstrate the feasibility of reducing the number of indices and leads to a significant increase of coding capacity. + +For the third suggestion, according to Shannon's information theory, there will be always overheads to record the addresses, or indices. For electrical devices, the address is the physical position of the spot, while for DNA storage the address is the index sequence. DNA fountain does not directly use a binary index. However, recording random seeds for segment trace- back can be also considered as indexing. Therefore, binary indices, or other forms for recording address, are indispensable elements especially for massive data storage by DNA. And in our study, we have demonstrated that YYC shows superior performance of information density in both in vitro and in vivo storage. + +## Major Suggestions + +1. The paper makes a strong claim about density that needs to be clarified. As mentioned earlier, the work does not explain well how indices are handled (as + +<--- Page Split ---> + +# natureresearch + +mentioned previously in my review), but the indices appear to achieve no better than a binary encoding (1 bit /base) density. One implication of this is that a high- density encoding is somewhat reliant on having small indices, which implies small file sizes and small capacity overall. This is an undesirable result for what should be a dense medium. Another implication of this is that the total capacity of the system (total unique strands) appears to be lower than those systems that achieve ternary indices, for example. While the claimed figures of merit for density are high, they hide the fact that the total capacity of a pool of DNA may be severely negatively impacted by binary indices. I would like to see a better explanation of how indices are handled and the effect this has on pool capacity. + +Response 12: We thank the reviewer for the comment. As described in response 11, the coding density refers to (total information / total base), rather than (total information / possible choices). Therefore, if one nucleotide encodes two binary digits of two different indices, the information density is 2 bits/base. In previous studies including Erlich et al., 2017, the density can be calculated in different ways. The coding potential (or information density) usually refers to (information stored/bases used to store information only). The coding density (or net information density) refers to (information stored/total bases used for information, indices, error- correction and flanking region). The physical density is related to experimental validation and refers to (information stored/total mass of DNA used). In this work, we used the consistent definition to calculate the information density. We believed that the 'pool capacity' the reviewer mentioned might refers to coding density (or net information density). Based on this, we have provided the statement of how indices would affect pool capacity and give some possible solution. + +we have revised the effect of indices on pool capacity accordingly in the main text highlighted on page 6 (line 179 - 182). + +2. The capabilities of the YYC codec with respect to the variety of mapping tables is not well justified. It's not clear that the ability to select one of the 1536 configurations actually helps or not. The work claims to leverage a combinatoric scheme, but that is not demonstrated through an experiment, except to some degree in the small one that analyzes strands with large fractions of 0 or 1 to see if any mapping tables can encode them satisfactorily. + +To really demonstrate the advantage of all these combinations, several things need to be shown. (1) That having a choice among mapping tables is helpful and leads + +<--- Page Split ---> + +# natureresearch + +to less overhead as compared to DNA Fountain. (2) That the choice of mapping table can be made efficiently. It would be interesting to report the number of failed attempts at selecting segments and encoding them. (3) That the overhead of holding the choice of mapping table in meta- data is a reasonable cost, even if done electronically. If a mapping table selection needs to be remembered per strand, then that implies approximately 11 bits of overhead per segment- pair, which for an exabyte scale system would add up to a very large cost. If it only needs to be remembered per file, it's a lower meta- data cost but higher compute cost to find a mapping. These trade- offs need some further explanations. + +If this analysis is prohibitive to conduct, then I would suggest softening the claims over how useful these tables are. + +Response 13: We thank the reviewer for the instructive comment. + +First of all, we would like to clarify that the 1536 coding schemes of YYC offer alternative choices for encoding process, meaning it is not mandatory requirement to use all coding schemes in one case, and therefore the 11 bits of overhead is not for each segment- pair. We have demonstrated in the Response #5 that the 1536 coding schemes can generate significantly different DNA sequences. Thus, it offers one of the advantages that for an individual arbitrary file, we can always find some scheme(s) that can generate higher information density than others (Table S4). We performed a benchmarking test by encoding different files using all the 1,536 coding schemes. As described in the Response #7, we counted the iteration runs of these coding schemes on encoding 1 GB of data by all the 1,536 coding schemes. The incorporation failure rate for segment pairing over 100 iteration runs is only at \(0.002\%\) . In our previous study, we also performed some benchmarking tests on encoding and decoding efficiency (https://doi.org/10.1101/2020.01.02.892588), showing that the transcoding overheads of YYC is less than that of DNA fountain, YYC is 2- 7 times faster. + +For the efficiency of trail- and- error iteration, as we described in the Response #5 and 7, we performed the evaluation of average iteration run required by transcoding ten different formats of files and have shown that the average number from 1 to 7 trails (Table S3). We further took the reviewer's suggestion and conducted further analysis by estimating the total number of trails while encoding the 1 GB data collection used in our study for in silico simulation. As shown in Fig. S4a, in general, \(65\%\) of the segment can be successfully incorporated with another segment with a single run of trail, and for files with balanced byte frequency, the percentage further increase to + +<--- Page Split ---> + +# natureresearch + +\(\sim 77\%\) (Fig. S4b). From our observation, less than \(0.3\%\) of segments requires more than 10 runs of trail. Our results imply that for an arbitrary file, YYC encoding would not cost a large encode- time overheads. + +3. It's surprising that DNA Fountain does so poorly in the in silico experiment (Figure 2). I agree with the general arguments that DNA Fountain will have high degree packets that include many segments. However, I'm not convinced this is the entire answer unless DNA Fountain mostly selects high degree packets. Also, some important information is missing in this analysis. It appears that no error correction is used. In that case, what is done with strands that have insertions, deletions, and substitutions? Without error correction support, such problems cannot even be detected much less corrected. So, are they treated as correct and allowed to pollute the file with errors? This raises questions about how the DNA Fountain approach is utilized. Is the DNA Fountain code base used for this analysis? If so, is it possible that something is going wrong in how it handles these errors? For example, since segments are more likely repeated in multiple high degree packets, it may be detecting errors and throwing them out, whereas YYC has no such detection capability. Instead, YYC may be making a best-effort attempt to keep the data. More details of how this analysis is conducted are needed to fully explain DNA Fountain's poorer behavior. + +Response 14: We thank the reviewer for the comment. The reviewer suggests that DNA fountain may have no bias on generating high degree packets. For fountain code itself and balanced byte frequency data pattern, high degree packets and low degree packets should share equal odds to be selected. However, our observation is that the screening step of DNA Fountain offers an increased chance to pass the screening for high degree packets. We performed a few tests to encode different files using DNA Fountain with and without screening to estimate the corresponding ratio of high degree packets (as the figure R2 shown below). We used a bmp image (united nation flag) and its zip-compressed package as test file. For zip file, of which the byte frequency is balanced (upper), there was no significant difference with screening (middle). However, for the original bmp image itself, it turned out that among the encoded files with screening, the degree of packets generated is significantly biased without screening. + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Figure R2. Distribution of degree of packets generated by DNA fountain with/without screening (For review usage only)
+ +The second suggestion from the reviewer is that error- correction code should be used in the in- silico test. As described in the Response #9, error correction codes, such as Reed- Solomon code used in our study, can be used as one of the function modules in the whole DNA storage process to improve the robustness for all coding schemes, but the improvement is within limited range. The reason is that current error- correction code is capable of correcting substitution errors but not insertion and deletion errors. For almost all known coding schemes including DNA Fountain and YYC, the sequence with indels cannot be corrected and is discarded before decoding. This is also the reason why error- correction code cannot improve the robustness of DNA fountain significantly. In our experimental validation, we encoded files using the original package provided by Erlich et al. with error correction code applied. The + +<--- Page Split ---> + +# natureresearch + +result is consistent with in- silico simulation and proved our point of view. We have revised accordingly in the manuscript on page 9 (line 250- 258). + +## Minor Suggestions + +1. Perhaps add a brief explanation for a few things in the thermodynamic screening, such as at what temperature was the simulated free energy screening conducted? And, what other parameters were used, if any? Why did you pick -30 kcal/mol as the cutoff? + +Response 15: We thank the reviewer for the comment. The thermodynamic screening cut- off is defined based on previous studies (Noguera et. al., 2014 and Yilmaz et. al., 2004). The free energy cutoff for probe design was set as - 13 kcal/mol for \(\sim 20\) nt DNA sequence, and considering the length of data coding DNA at 160nt, we adjusted the cutoff to - 30 kcal/mol. We have revised the manuscript accordingly to further clarify on page 18 (line 515 to 517). + +2. In the text regarding in vitro experiments, please make it clear which encoding was used for each pool. I think P2 and P3 were done using DNA Fountain. + +Response 16: We thank the reviewer for the comment. we have revised this accordingly in the main text highlighted on page 10 (line 296 - 302). + +3. On Page 9, line 242-244, it says that loss of one strand in YYC can lead to the loss of two segments. This is true. But, isn't it possible that a segment is repeatedly selected for pairing due to some good pattern in its data, decreasing the odds it is lost? Or, do you prevent selecting the same sequence many times? Thank you for an interesting paper. + +Response 17: We thank the reviewer for the instructive comment and recognition of our work. We agree with the reviewer that repeated priority selection of segment with "good" pattern will increase the success rate of pairing. However, it will decrease the overall bit- to- base information density. In our study, we select each segment once and only once for the segment pairing process. The key difference between YYC and DNA Fountain is the segment incorporation strategy applied. For YYC each incorporation only involves two segments, so the loss of one segment will only affect the corresponding paired segment. However, for DNA Fountain the loss of one + +<--- Page Split ---> + +# natureresearch + +segment will affect all related paired segment. We have proven that without repeated selection of "good" pattern segments, YYC can greatly decrease the decoding failure caused by segment loss comparing to DNA Fountain. + +Decision Letter, second revision: + +Date: 8th February 22 17:18:31 Last Sent: 8th February 22 17:18:31 Triggered By: Ananya Rastogi From: ananya.rastogi@nature.com To: shenyue@genomics.cn CC: computationalscience@nature.com Subject: AIP Decision on Manuscript NATCOMPUTSCI- 21- 0438B Message: Our ref: NATCOMPUTSCI- 21- 0438B + +8th February 2022 + +Dear Dr. Shen, + +Thank you for submitting your revised manuscript "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" (NATCOMPUTSCI- 21- 0438B). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Computational Science, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +## TRANSPARENT PEER REVIEW + +Nature Computational Science offers a transparent peer review option for new original research manuscripts submitted from 17th February 2021. We encourage increased transparency in peer review by publishing the reviewer comments, author rebuttal letters and editorial decision letters if the authors agree. Such peer review material is made available as a supplementary peer review file. 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For more information, please refer to our FAQ page. + +Thank you again for your interest in Nature Computational Science Please do not hesitate to contact me if you have any questions. + +Sincerely, + +Ananya Rastogi, PhD Associate Editor Nature Computational Science + +ORCID IMPORTANT: Non- corresponding authors do not have to link their ORCIDs but are encouraged to do so. Please note that it will not be possible to add/modify ORCIDs at proof. Thus, please let your co- authors know that if they wish to have their ORCID added to the paper they must follow the procedure described in the following link prior to acceptance: https://www.springernature.com/gp/researchers/orcid/orcid- for- nature- research + +Reviewer #3 (Remarks to the Author): + +The authors addressed all my comments and the paper can be accepted. + +Reviewer #4 (Remarks to the Author): + +Thank you very much for the revisions and responses. You included some very nice analysis. Overall, they satisfy my concerns. I recommend acceptance. + +I think there may be yet some misunderstanding between us about how indices are represented. I agree that you encode 2 bits per base for the indices. But, your approach appears to limit the total number of possible indices that fit into those k bases (k bases used for the index). This concerns me because it architecturally limits the pool capacity of the system. By pool capacity, I'm referring to the total amount of data in bytes that can be stored in the archive if this technique is employed. However, even if what I say is true, as you point out in your response, you can make up for it elsewhere with flanking primers, etc. So, I'm fine to accept the paper. + +<--- Page Split ---> + +# natureresearch + +Author Rebuttal, second revision: + +Reviewer's comments: + +## Reviewer #4 (Remarks to the Author): + +Thank you very much for the revisions and responses. You included some very nice analysis. Overall, they satisfy my concerns. I recommend acceptance. + +I think there may be yet some misunderstanding between us about how indices are represented. I agree that you encode 2 bits per base for the indices. But, your approach appears to limit the total number of possible indices that fit into those k bases (k bases used for the index). This concerns me because it architecturally limits the pool capacity of the system. By pool capacity, I'm referring to the total amount of data in bytes that can be stored in the archive if this technique is employed. However, even if what I say is true, as you point out in your response, you can make up for it elsewhere with flanking primers, etc. So, I'm fine to accept the paper. + +Response 1: We thank the reviewer for the significant help in improving our work. It is true that large files indeed need more indices, but there are many other approaches can be applied to expand the indexing. As we mentioned in our previous point- by- point reply, the application of flanking primer is just one of the choices. Also, as relative technologies keep advancing, increasing the length of DNA that encodes digital data can actually decrease the need of total indices number. Due to the word limit, we include a brief discussion in the Discussion section in the main text as highlighted at page 10, line 315- 318. + +<--- Page Split ---> + +# natureresearch + +Final Decision Letter: + +Date: 18th March 22 17:19:05 Last Sent: 18th March 22 17:19:05 Triggered By: Ananya Rastogi From: ananya.rastogi@nature.com To: shenyue@genomics.cn + +Subject: Decision on Nature Computational Science manuscript NATCOMPUTSCI- 21- 0438C Message: Dear Dr Shen, + +We are pleased to inform you that your Article "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" has now been accepted for publication in Nature Computational Science. + +In approximately 10 business days you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. + +Please note that Nature Computational Science is a Transformative Journal (TJ). 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If you have any questions please click here.\*\* + +<--- Page Split ---> diff --git a/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8bed03d952413117a244d56b47457182c454901f --- /dev/null +++ b/peer_reviews/7832447b3fe074fa4092b61e5b581cf3c6807df684fffd6d77860e65b215b1af/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1156 @@ +<|ref|>title<|/ref|><|det|>[[549, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>title<|/ref|><|det|>[[115, 188, 571, 219]]<|/det|> +# Peer Review Information + +<|ref|>text<|/ref|><|det|>[[114, 245, 875, 315]]<|/det|> +Journal: Nature Computational Science Manuscript Title: Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System Corresponding author name(s): Yue Shen, George M. Church, Xun Xu + +<|ref|>sub_title<|/ref|><|det|>[[115, 360, 568, 384]]<|/det|> +## Reviewer Comments & Decisions: + +<|ref|>title<|/ref|><|det|>[[115, 419, 344, 435]]<|/det|> +# Decision Letter, initial version: + +<|ref|>text<|/ref|><|det|>[[115, 456, 444, 570]]<|/det|> +Date: 1st September 21 10:48:22 Last Sent: 1st September 21 10:48:22 Triggered By: Ananya Rastogi From: ananya.rastogi@nature.com To: shenyue@genomics.cn BCC: ananya.rastogi@nature.com + +<|ref|>text<|/ref|><|det|>[[150, 565, 848, 580]]<|/det|> +Subject: Decision on Nature Computational Science manuscript NATCOMPUTSCI- 21- 0438 + +<|ref|>text<|/ref|><|det|>[[150, 583, 848, 613]]<|/det|> +Message: \*\* Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. \*\* + +<|ref|>text<|/ref|><|det|>[[232, 625, 339, 639]]<|/det|> +Dear Dr Shen, + +<|ref|>text<|/ref|><|det|>[[232, 652, 875, 710]]<|/det|> +Your manuscript "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" has now been seen by 3 referees, whose comments are appended below. You will see that while they find your work of interest, they have raised points that need to be addressed before we can make a decision on publication. + +<|ref|>text<|/ref|><|det|>[[231, 721, 875, 751]]<|/det|> +The referees' reports seem to be quite clear. Naturally, we will need you to address all of the points raised. + +<|ref|>text<|/ref|><|det|>[[231, 763, 860, 793]]<|/det|> +While we ask you to address all of the points raised, the following points need to be substantially worked on: + +<|ref|>text<|/ref|><|det|>[[231, 792, 866, 848]]<|/det|> +- Please provide a more appropriate experiment to assess YYC's performance against DNA fountain as requested by Reviewer #2. +- Please provide an argument as to how any unique feature of YYC is relevant for in vivo storage besides the higher coding density. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[231, 144, 879, 202]]<|/det|> +- As pointed out by Reviewer #2, please discuss the impact of parameter choices made in the study. +- Please present the mathematical analysis in the study in a way which is accessible to a broad readership. + +<|ref|>text<|/ref|><|det|>[[232, 214, 865, 257]]<|/det|> +Please use the following link to submit your revised manuscript and a point- by- point response to the referees' comments (which should be in a separate document to any cover letter): + +<|ref|>sub_title<|/ref|><|det|>[[232, 269, 327, 285]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[232, 297, 857, 339]]<|/det|> +\*\* This url links to your confidential homepage and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this e- mail to co- authors, please delete this link to your homepage first. \*\* + +<|ref|>text<|/ref|><|det|>[[232, 352, 879, 409]]<|/det|> +To aid in the review process, we would appreciate it if you could also provide a copy of your manuscript files that indicates your revisions by making of use of Track Changes or similar mark- up tools. Please also ensure that all correspondence is marked with your Nature Computational Science reference number in the subject line. + +<|ref|>text<|/ref|><|det|>[[232, 421, 856, 450]]<|/det|> +In addition, please make sure to upload a Word Document or LaTeX version of your text, to assist us in the editorial stage. + +<|ref|>text<|/ref|><|det|>[[231, 463, 875, 575]]<|/det|> +To improve transparency in authorship, we request that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[231, 586, 880, 615]]<|/det|> +We hope to receive your revised paper within three weeks. If you cannot send it within this time, please let us know. + +<|ref|>text<|/ref|><|det|>[[232, 628, 551, 642]]<|/det|> +We look forward to hearing from you soon. + +<|ref|>text<|/ref|><|det|>[[232, 656, 333, 670]]<|/det|> +Best regards, + +<|ref|>text<|/ref|><|det|>[[231, 684, 458, 726]]<|/det|> +Ananya Rastogi, PhD Associate Editor Nature Computational Science + +<|ref|>text<|/ref|><|det|>[[232, 767, 396, 780]]<|/det|> +Reviewers comments: + +<|ref|>text<|/ref|><|det|>[[232, 794, 520, 808]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[231, 821, 880, 850]]<|/det|> +Motivated by the Goldman's rotating encoding strategy and the DNA fountain encoding strategy, this paper presents an interesting encoding scheme called as Yin- Yang Codec + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[231, 143, 881, 284]]<|/det|> +(YYC) for archival DNA data storage. The YYC scheme has three main steps. In the first step, the byte strings are partitioned into segments of equal length. In the second step of incorporation, two binary segments are selected randomly and are combined bit by bit using Yang rule first and then Yin rule, giving a final nucleotide as an output. In the final step, the generated DNA strings are screened for pre- set constraints for GC content (40%- 60%), maximum homopolymer length \(< 5\) , and the secondary structure free energy \((> = - 30\) kcal/mol). In a failed case, through an iteration process another randomly generated binary segment is used. It is observed that there are 1536 options for encoding the binary sequence. These different options give a maximum information density (theoretical) of 1.965 bits per base under specific constraints. + +<|ref|>text<|/ref|><|det|>[[232, 296, 870, 368]]<|/det|> +This encoding has been simulated on a computer and compared with well- known encoding schemes using a developed tool called Chamaeleo. The fountain DNA code and the YYC are specifically compared. The robustness of the YYC scheme was tested by introducing random and systematic errors and it was found that the data recovery percentage can be maintained at 98% when the sequence loss rate is \(< 2\%\) . + +<|ref|>text<|/ref|><|det|>[[232, 379, 867, 436]]<|/det|> +The experimental validation of the work was done using two file formats and these were stored in in vitro as 200 nts oligos and in vivo as an 54240- bp DNA fragment in yeast cell. This resulted in physical information density of \(\sim 198.8\) Exabytes per gram of DNA. This is much better than the previous work in the literature. + +<|ref|>text<|/ref|><|det|>[[232, 448, 850, 491]]<|/det|> +I think the present work is an interesting approach. The introduced YYC scheme outperforms many previous schemes in terms of reliable data storage and physical information density. Some of my observations are listed below: + +<|ref|>text<|/ref|><|det|>[[230, 504, 881, 837]]<|/det|> +1. I feel that the YYC encoding scheme can be better presented. There are a few problems in the current writing. For example, in Figure 1, the choice of alphabet for Xn and Yn should be given. Although a working example is given in Figure S1, the presentation is from bits and nucleotides to nucleotides whereas in the general scheme it is nucleotides and nucleotides to bits. Another working example may be given either in the supplementary files or in the paper itself that will make it very clear. +2. I could not find the supplementary video mentioned at page 4 and page 14. Perhaps, including that will also be helpful. +3. Also, in the YYC scheme, there are 1536 possible options, so maybe it would be interesting to include a summary of all the rules in a table. This table could also include the rule number such as rule no. 888 that is used in Figure S1 or other rules in supplementary information. It is not clear how these rule numbers are assigned? Do they have some significance? I mean why the specific rule 888 was used. +4. At page 5, it is mentioned that when most of the binary segment contains more than 80% repeated 0's and 1's, the corresponding encoding process may enter an infinite loop or generate a poor result. Can we give some algebraic explanation for this from the YYC scheme? +5. At page 12, statement "YYC offers the opportunity to incorporate multiple rules for one file transcoding and thus provide a novel strategy for secure data archiving." Can we give a specific example? This will motivate the reader. +6. At page 15, line 10, What is Fq in Definition 1, line 1? Normally, Fq is a finite field having q elements but here, Fq is a set of 4 nucleotides, so q has no role to play. Maybe, the notation can be modified or Fq can be defined in line 1 and later, we can choose it to be an alphabet of size 4. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[232, 143, 795, 159]]<|/det|> +With these suggestions, I recommend for the publication of the manuscript. + +<|ref|>text<|/ref|><|det|>[[232, 172, 350, 187]]<|/det|> +Manish K Gupta + +<|ref|>text<|/ref|><|det|>[[232, 214, 520, 228]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[232, 240, 874, 368]]<|/det|> +The authors have introduced an interesting DNA encoding scheme called YYC (or Ying- Yang coding) with complementary rule sets to increase the coding density of current encoding methods. It is a dynamic transcoding scheme that transforms binary data into DNA sequences that could get close to the theoretical maximum information sensitivity of 2 bits per base. While the encoding approach is novel, there are inconsistencies and lack of exploration of parameters in the manuscript that make it difficult (or impossible) for anyone to assess the claimed merits of the work. It requires massive revisions, proper parameter studies, and significant retooling of how this paper is compared or "advertised" against other works. + +<|ref|>text<|/ref|><|det|>[[232, 380, 557, 394]]<|/det|> +Summarized below are the major concerns: + +<|ref|>text<|/ref|><|det|>[[232, 407, 879, 588]]<|/det|> +1. Data recovery rate - in the manuscript, DNA oligos are present at roughly 1e8 copies per designed oligo sequence, which by my calculation is \(\sim 175\) nanograms of total synthesis mass for Pool 1. They then dilute this down 10,000x fold in order to show that YYC/DNA fountain can get good recovery, but it completely breaks down at further serial dilutions. This is somewhat of a contrived experiment because it means the first dilution \((10^{4}4\) molecules, which by my calculation of \(10103*(10^{4}4\) molecules) \(\ast (200\ast 330g / mol)\ast (1mol / (6.02\ast 10^{23}\) molecules)) is 10 picograms of DNA. That is already an incredibly tiny amount of DNA. Given the data presented, it's not clear whether YYC's benefits are marginal or substantial. A more appropriate experiment to assess YYC's performance against DNA fountain in this context would be to show its performance for higher input copies (eg. 1e7, 1e6, etc.), as well as performances of re-amplifying pools from smaller dilutions (eg. dilution down to 1e7, 1e6, 1e5, amplifying back to 1e8 and using that as input). + +<|ref|>text<|/ref|><|det|>[[232, 600, 877, 698]]<|/det|> +2. In vivo storage - This part actually has very little to do with the YYC encoding and I don't understand its relevance to the manuscript's presentation of YYC encoding as a whole. You assemble DNA oligonucleotides or amplicons of any kind and clone into a plasmid for storage. The authors did not make any kind of argument about how any unique feature of YYC is relevant for in vivo storage besides the higher coding density, as you could theoretically just use any other high performance code. Interestingly, the authors did not touch on this point at all. + +<|ref|>text<|/ref|><|det|>[[232, 710, 879, 850]]<|/det|> +Furthermore, one of the most eye- catching errors in the paper is the advertisement of the storage density of \(\sim 200\mathrm{EB / g}\) . Storage densities, as reflected in bits of information per mass, is limited by the synthesis of unique fragments and also by the coding density of the encoding procedure. Given these considerations, it is impossible that YYC achieves densities of \(\sim 1000x\) higher than DNA fountain (and other works in Table 1) despite similar orders of magnitude in coding density. Even looking at the authors' formula as to how to calculate their vivo storage metric, it appears that nothing in that formula is fundamentally unique to the YYC coding scheme or that by plugging in the stated coding density of DNA fountain would get you a \(\sim 1000x\) difference in performance. In fact, the differences are marginal or negligible when plugging in + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[232, 143, 824, 172]]<|/det|> +different coding densities (into the information/nucleotide section, adjusting for plasmid backbone size) from Table 1. + +<|ref|>text<|/ref|><|det|>[[232, 185, 881, 298]]<|/det|> +Investigating the calculation further (by briefly reading the DNA fountain work which this manuscript cites often), it appears that there is a fundamental difference in how the calculations were determined. It appears that Erlich et al cited their 215PB metric as part of a serial dilution scheme for assessing successful/perfect retrieval of synthesized DNA. Taking the logic from the Erlich paper, the authors should have diluted down their yeast preps accordingly as well (to specific copies of plasmid loaded per sequencing library). Further, there seems to be a methods typo, where the authors stated that they picked three colonies but later in the methods it says they picked 12. + +<|ref|>text<|/ref|><|det|>[[232, 311, 879, 450]]<|/det|> +3. Other concerns regarding YYC encoding - it's clear that there is some sort of performance dependence according to the 1536 transcoding rules (Fig. S3 shows this pretty well). Across the manuscript there are tables with selected parameters but little discussion of the exact impact of them. It's difficult to assess what exactly the impact this has on performance when these parameters were not exhaustively studied either in silico or through actual experiments. Given the fact that this is a new coding scheme, the authors should have at minimum done an in silico demonstration of every single rule and how it affects every single metric in the paper. Off the top of my head, because the selection of the rule parameter greatly affects the information density, sequencing errors will play a large role in the overall performance. + +<|ref|>text<|/ref|><|det|>[[233, 476, 520, 491]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[232, 504, 880, 588]]<|/det|> +The paper presents a new efficient coding scheme that improves the recovery rate in case of large sequence loss. The method maintains linear dependency between the percentage of oligos that were fully recovered, and the data recovery. Additionally, the paper demonstrates in vivo data storage with high information density. Roughly speaking, the paper is fairly written, however there are several parts which are not well explained, as will be elaborated below. + +<|ref|>sub_title<|/ref|><|det|>[[232, 601, 318, 614]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[230, 614, 880, 852]]<|/det|> +1. The code works well, I used it through the "chameleo" tool (that was also published by this group). +2. Like I sent you in another email - I could not access the data from their experiment, so either the link is broken, or they should add more explanations on the data and how to access it. +3. As far as I understand, the authors did not perform any reconstruction algorithm on the sequenced oligos. Can you please comment whether such an algorithm can improve the data recovery success and/or achieve faster data recovery? +4. There are several terms in the introduction that should be better explained before used for the average reader. Examples of these expressions are: secondary structure, free energy calculation. +5. The sentence between lines 80-82 is not clear to me. +6. Description of the YYC between lines 114-126 is not clear. What do \(X_n\) and \(Y_n\) refer to? +7. The caption of Fig. 1 is not clear either. +8. The description in page 11 of lines 282-310 is not clear to me. +9. I could not find the supplementary video of Fig. S1b. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 871, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[231, 144, 631, 160]]<|/det|> +10. The statement in Lemma 3 is not properly stated. + +<|ref|>text<|/ref|><|det|>[[231, 160, 876, 216]]<|/det|> +11. In general, all the mathematical analysis in page 15 is very sloppy. The equations are explained and their correctness is not justified. There should be a clear statement about the properties that the YCC scheme satisfies and a proof for the redundancy. As written this way, I cannot truly understand and evaluate the code construction. + +<|ref|>text<|/ref|><|det|>[[230, 216, 875, 244]]<|/det|> +12. The authors compare mostly with fountain codes. What about comparison with the other coding schemes? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 195, 312, 214]]<|/det|> +Reviewers comments: + +<|ref|>text<|/ref|><|det|>[[115, 227, 457, 247]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 259, 881, 534]]<|/det|> +Motivated by the Goldman's rotating encoding strategy and the DNA fountain encoding strategy, this paper presents an interesting encoding scheme called as Yin- Yang Codec (YYC) for archival DNA data storage. The YYC scheme has three main steps. In the first step, the byte strings are partitioned into segments of equal length. In the second step of incorporation, two binary segments are selected randomly and are combined bit by bit using Yang rule first and then Yin rule, giving a final nucleotide as an output. In the final step, the generated DNA strings are screened for pre- set constraints for GC content (40%- 60%), maximum homopolymer length \(< 5\) , and the secondary structure free energy ( \(\geq - 30\) kcal/mol). In a failed case, through an iteration process another randomly generated binary segment is used. It is observed that there are 1536 options for encoding the binary sequence. These different options give a maximum information density (theoretical) of 1.965 bits per base under specific constraints. + +<|ref|>text<|/ref|><|det|>[[115, 545, 874, 651]]<|/det|> +This encoding has been simulated on a computer and compared with well- known encoding schemes using a developed tool called Chamaeleo. The fountain DNA code and the YYC are specifically compared. The robustness of the YYC scheme was tested by introducing random and systematic errors and it was found that the data recovery percentage can be maintained at 98% when the sequence loss rate is \(< 2\%\) . + +<|ref|>text<|/ref|><|det|>[[115, 662, 872, 744]]<|/det|> +The experimental validation of the work was done using two file formats and these were stored in in vitro as 200 nts oligos and in vivo as an 54240- bp DNA fragment in yeast cell. This resulted in physical information density of \(\sim 198.8\) Exabytes per gram of DNA. This is much better than the previous work in the literature. + +<|ref|>text<|/ref|><|det|>[[115, 756, 844, 819]]<|/det|> +I think the present work is an interesting approach. The introduced YYC scheme outperforms many previous schemes in terms of reliable data storage and physical information density. Some of my observations are listed below: + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[548, 49, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 142, 882, 270]]<|/det|> +1. I feel that the YYC encoding scheme can be better presented. There are a few problems in the current writing. For example, in Figure 1, the choice of alphabet for Xn and Yn should be given. Although a working example is given in Figure S1, the presentation is from bits and nucleotides to nucleotides whereas in the general scheme it is nucleotides and nucleotides to bits. Another working example may be given either in the supplementary files or in the paper itself that will make it very clear. + +<|ref|>text<|/ref|><|det|>[[114, 280, 877, 385]]<|/det|> +Response 1: We thank the reviewer for the comment. We have revised the manuscript accordingly to include detailed description in the main text highlighted on the page 4 (line 121- 132) and figure S1 in supplementary. In addition, we have also re- uploaded a step- by- step demonstration video to show the encoding process for further elaboration. + +<|ref|>text<|/ref|><|det|>[[114, 413, 880, 456]]<|/det|> +2. I could not find the supplementary video mentioned at page 4 and page 14. Perhaps, including that will also be helpful. + +<|ref|>text<|/ref|><|det|>[[114, 465, 864, 509]]<|/det|> +Response 2: We apology to the reviewer on this. We have re- uploaded the video file as "supplementary video S1" in the supplementary for further description. + +<|ref|>text<|/ref|><|det|>[[114, 549, 876, 656]]<|/det|> +3. Also, in the YYC scheme, there are 1536 possible options, so maybe it would be interesting to include a summary of all the rules in a table. This table could also include the rule number such as rule no. 888 that is used in Figure S1 or other rules in supplementary information. It is not clear how these rule numbers are assigned? Do they have some significance? I mean why the specific rule 888 was used. + +<|ref|>text<|/ref|><|det|>[[114, 665, 879, 833]]<|/det|> +Response 3: We thank the reviewer for the comment. The rule number is assigned in numeric order from Rule no. 1 to Rule no. 1536. We followed the reviewer's suggestion to include a summary of all rules in the main text on page 6 (line 172 - 180) and Figure S2 to demonstrate the general performance regarding information density of all 1,536 coding schemes using 1 GB testing data including text, image, audio and video files. As screening criteria settings on sequence compatibility, the GC content, max homopolymer all fell into the criteria of constraints. The corresponding results are described in the main text highlighted on page 6 (line 183 - 198) and Table + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 783, 185]]<|/det|> +1. In this study, No. 888 was selected as a representing coding scheme with information density at medium level. + +<|ref|>text<|/ref|><|det|>[[114, 226, 879, 310]]<|/det|> +4. At page 5, it is mentioned that when most of the binary segment contains more than \(80\%\) repeated \(0\) 's and \(1\) 's, the corresponding encoding process may enter an infinite loop or generate a poor result. Can we give some algebraic explanation for this from the YYC scheme? + +<|ref|>text<|/ref|><|det|>[[113, 321, 876, 597]]<|/det|> +Response 4: We thank the reviewer for the comment. We followed the reviewer's suggestion to include an analysis to show the general performance of 1,536 combinatoric rules. The analysis is based on incorporation of two short binary segments (each binary segment contains 8 bits, which give 65,536 different combinations) based on its ratio of binary digit 0 and 1. When \(0 / 1\) ratio is less than \(20\%\) , it is shown that the number of coding schemes that can generate valid DNA sequence drops significantly from \(100\%\) to \(49.7\%\) and even lower when \(0 / 1\) ratio keeps decreasing. Therefore, \(0 / 1\) biased binary segments are firstly separated to improve the encoding efficiency. We set a "firewall" to limit the iteration run time at 100. For extreme cases, when most of the binary segments are \(0 / 1\) biased, "pseudo" binary segments with random \(0 / 1\) but in balanced ratio will be introduced to allow the generation of valid sequence. We have updated with description in the main text highlighted on page 5 (line 148 - 162) and Table S2 for further declaration. + +<|ref|>text<|/ref|><|det|>[[114, 637, 879, 700]]<|/det|> +5. At page 12, statement "YYC offers the opportunity to incorporate multiple rules for one file transcoding and thus provide a novel strategy for secure data archiving." Can we give a specific example? This will motivate the reader. + +<|ref|>text<|/ref|><|det|>[[114, 710, 872, 858]]<|/det|> +Response 5: We thank the reviewer for the comment. Generally, for other developed methods, the coding process follows a unitary transcoding rule. In contrast, YYC offers in total 1536 combinatorial transcoding rules, that each rule will generate distinct DNA sequencing. Thus, YYC offers the possibility to use multiple rules in one file transcoding and therefore could significantly increase the difficulty of deciphering the coding rule by brute-force attacks or other manners. We have revised this in the main text highlighted on page 14 (line 384 - 387). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[113, 160, 879, 245]]<|/det|> +6. At page 15, line 10, What is Fq in Definition 1, line 1? Normally, Fq is a finite field having q elements but here, Fq is a set of 4 nucleotides, so q has no role to play. Maybe, the notation can be modified or Fq can be defined in line 1 and later, we can choose it to be an alphabet of size 4. + +<|ref|>text<|/ref|><|det|>[[114, 256, 875, 340]]<|/det|> +Response 6: We thank the reviewer for the comment. We have revised this according to the reviewer's suggestion. The choice of two binary digits and four nucleotides is stated in "Quantitative analysis" section of the supplementary. We have rewritten this part to make it easier to understand. + +<|ref|>text<|/ref|><|det|>[[115, 381, 780, 402]]<|/det|> +With these suggestions, I recommend for the publication of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 442, 264, 462]]<|/det|> +Manish K Gupta + +<|ref|>text<|/ref|><|det|>[[115, 502, 861, 565]]<|/det|> +Response 7: We thank the reviewer for the recognition on YYC and significant help on improving our work. We hope our revised manuscript will reach to the level of publication on Nature Computational Science. + +<|ref|>text<|/ref|><|det|>[[115, 594, 457, 614]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 633, 878, 824]]<|/det|> +The authors have introduced an interesting DNA encoding scheme called YYC (or Ying- Yang coding) with complementary rule sets to increase the coding density of current encoding methods. It is a dynamic transcoding scheme that transforms binary data into DNA sequences that could get close to the theoretical maximum information sensitivity of 2 bits per base. While the encoding approach is novel, there are inconsistencies and lack of exploration of parameters in the manuscript that make it difficult (or impossible) for anyone to assess the claimed merits of the work. It requires massive revisions, proper parameter studies, and significant retooling of how this paper is compared or "advertised" against other works. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 500, 163]]<|/det|> +Summarized below are the major concerns: + +<|ref|>text<|/ref|><|det|>[[114, 174, 876, 450]]<|/det|> +1. Data recovery rate - in the manuscript, DNA oligos are present at roughly 1e8 copies per designed oligo sequence, which by my calculation is \(\sim 175\) nanograms of total synthesis mass for Pool 1. They then dilute this down 10,000x fold in order to show that YYC/DNA fountain can get good recovery, but it completely breaks down at further serial dilutions. This is somewhat of a contrived experiment because it means the first dilution (10^4 molecules, which by my calculation of 10103 \* (10^4 molecules) \* (200 \* 330g/mol) \* (1 mol / (6.02 \* 10^23 molecules)) is 10 picograms of DNA. That is already an incredibly tiny amount of DNA. Given the data presented, it's not clear whether YYC's benefits are marginal or substantial. A more appropriate experiment to assess YYC's performance against DNA fountain in this context would be to show its performance for higher input copies (eg. 1e7, 1e6, etc.), as well as performances of re-amplifying pools from smaller dilutions (eg. dilution down to 1e7, 1e6, 1e5, amplifying back to 1e8 and using that as input). + +<|ref|>text<|/ref|><|det|>[[114, 459, 880, 712]]<|/det|> +Response 8: We thank the reviewer for the comment. As for the reason to perform dilution assay at the starting level of 1e4 copies: The three master pools of 200nt DNA oligos we ordered from TWIST Bioscience are delivered in the form of lyophilized powder (190 ng, 182 ng and 172 ng respectively for P1, P2 and P3) with the yield of \(\sim 0.2 - 1\) fmol per oligo, which equals to the copy number at \(\sim 1\) e8 as indicated by the reviewer. The reason to perform dilution assay at the starting level of 1e4 copies is that in Erlich et. al, 2017 of DNA fountain, they validated the successful recovery of stored information at the level of 1e3 copies. Then in our study, we used the same setting as claimed in the paper and proven that both YYC and DNA fountain can perfectly recover stored data at the level of 1e4 copies, indicating that there will be no difference between the two methods on the recovery rate for higher input at 1e5, 1e6 and 1e7 copies. + +<|ref|>text<|/ref|><|det|>[[115, 723, 867, 828]]<|/det|> +To perform data recovery rate assessment under low input copies, given that data retrieval from master pool is a consuming process for synthesized DNA molecules and synthesizing substantial DNA is still too costly at the moment, thus in our study, further serial dilutions from 1e3 down to the 1e1 is designed to evaluate the data recovery performance of YYC under low amount of synthesized DNA. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 879, 376]]<|/det|> +However, we revised the experiment design according to the reviewer's suggestion by including the experimental evaluation from high input (at 1e7 copies in this study) all the way to low input (at 1e0 copies in this study). The DNA samples were re- ordered from the same vendor (TWIST Bioscience) we used in this study to repeat the whole experiment. In general, our updated results show that YYC exhibits relatively better performance regarding data recovery. With the input of 1e4 to 1e6 copies, the data recovery rate of YYC remains stable at comparable level with DNA fountain. And for the input of low copies (1e2 to 1e3 copies), YYC shows superior performance in data recovery. In addition, we found that at extreme low input level (1e0 to 1e1 copies), even the DNA molecules were re- amplified to 1e8 copies, the data recovery rate still cannot be guaranteed. + +<|ref|>text<|/ref|><|det|>[[115, 385, 871, 450]]<|/det|> +We have updated all related results shown in main text highlighted on page 10- 12 (line 267 - 325), Figure 3, methods "Library preparation and sequencing" section on page 19 (line 543 - 558), supplementary excel file, Sheet 2 & 3 accordingly. + +<|ref|>text<|/ref|><|det|>[[114, 477, 879, 625]]<|/det|> +2. In vivo storage - This part actually has very little to do with the YYC encoding and I don't understand its relevance to the manuscript's presentation of YYC encoding as a whole. You assemble DNA oligonucleotides or amplicons of any kind and clone into a plasmid for storage. The authors did not make any kind of argument about how any unique feature of YYC is relevant for in vivo storage besides the higher coding density, as you could theoretically just use any other high performance code. Interestingly, the authors did not touch on this point at all. + +<|ref|>text<|/ref|><|det|>[[113, 635, 880, 848]]<|/det|> +Response 9: We thank the reviewer for the comment. The fast technical development of DNA synthesis and assembly promotes both in vitro and in vivo storage as well recognized approaches in recently years (Shipman et. al, Nature, 2017, Tabatabaei et. al, Nature Communications, 2020 and Chen et. al, National Science Review, 2021). Thus, we include both approaches in our study for experimental demonstrations. Previous study suggest that in vivo storage holds the advantage of retrieving data can be easily performed by cell subculturing and DNA extraction, and stored data can be well maintained. However, we noticed that introducing substantial heterogenous DNA into host strains could be problematic for data recovery. By sequencing of multiple single colonies isolated from the plate, we observed partial data coding DNA loss in + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 882, 355]]<|/det|> +varying degrees. Our result further suggests that data recovery performance of the coding scheme is essentially important. It is common to observe spontaneous mutations or unexpected variations accumulated during long term passing of living cells. Therefore, it would be very important to apply more robust coding algorithms to retain as much original information as possible. We thank the reviewer for pointing out the importance of providing adequate justification on the reason of doing in vivo storage. We have revised the main text highlighted on page 12 (line 328 - 355), Figure 4, methods "Synthesis and assembly" section on page 19 (line 537 - 540), methods "Data analysis" section on page 20 (line 575 - 601) and supplementary Table S7 to further clarify the importance of robustness of coding algorithm for in vivo storage. + +<|ref|>text<|/ref|><|det|>[[114, 382, 875, 635]]<|/det|> +Furthermore, one of the most eye- catching errors in the paper is the advertisement of the storage density of \(\sim 200\mathrm{EB / g}\) . Storage densities, as reflected in bits of information per mass, is limited by the synthesis of unique fragments and also by the coding density of the encoding procedure. Given these considerations, it is impossible that YYC achieves densities of \(\sim 1000\mathrm{x}\) higher than DNA fountain (and other works in Table 1) despite similar orders of magnitude in coding density. Even looking at the authors' formula as to how to calculate their vivo storage metric, it appears that nothing in that formula is fundamentally unique to the YYC coding scheme or that by plugging in the stated coding density of DNA fountain would get you a \(\sim 1000\mathrm{x}\) difference in performance. In fact, the differences are marginal or negligible when plugging in different coding densities (into the information/nucleotide section, adjusting for plasmid backbone size) from Table 1. + +<|ref|>text<|/ref|><|det|>[[114, 645, 875, 836]]<|/det|> +Investigating the calculation further (by briefly reading the DNA fountain work which this manuscript cites often), it appears that there is a fundamental difference in how the calculations were determined. It appears that Erlich et al cited their 215PB metric as part of a serial dilution scheme for assessing successful/perfect retrieval of synthesized DNA. Taking the logic from the Erlich paper, the authors should have diluted down their yeast preps accordingly as well (to specific copies of plasmid loaded per sequencing library). Further, there seems to be a methods typo, where the authors stated that they picked three colonies but later in the methods it says they picked 12. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 875, 396]]<|/det|> +Response 10: We thank the reviewer for the comment. First, we would like to point out that information density is different concept from the physical density as we suggested in the manuscript on page 3 (line 83 - 87). Our argument is also supported previously by Organick et. al., 2020. Information density is determined by the algorithm itself, while the physical density indeed will vary by the selected approaches of storage (i.e. in vitro as DNA powder or in vivo as plasmid or integrated in the host genome). In the main text, we clarified that the physical density achieved in this study is based on in vivo storage on page 20 (line 584 - 601). And the calculation logic is consistent with previous study performed experimental demonstration using the approach of in vivo storage (Tabatabaei et. al, Nature Communications, 2020 and Chen et. al, National Science Review, 2021), which is not covered in Erlich et al.'s work. + +<|ref|>text<|/ref|><|det|>[[114, 406, 872, 616]]<|/det|> +We accept the reviewer's suggestion and have revised Table 1 by: 1) providing corresponding physical density of both in vitro and in vivo storage performed in our study and 2) to include the physical density achieved in the recent published in vivo storage study (Chen et. al, National Science Review, 2021) to avoid misleading conclusion for readers. The calculation formula is also provided in the method "Data analysis" section highlighted on page 20 (line 584 - 601) for further clarification. For the method typo, we apology for the unintentional mistake, we have revised the description in the main text highlighted on page 12 (line 340 - 342), Figure 4 and method description "Synthesis and assembly" section on page 18 (line 533 - 540) to clarify the correct numbers. + +<|ref|>text<|/ref|><|det|>[[114, 627, 883, 839]]<|/det|> +3. Other concerns regarding YYC encoding - it's clear that there is some sort of performance dependence according to the 1536 transcoding rules (Fig. S3 shows this pretty well). Across the manuscript there are tables with selected parameters but little discussion of the exact impact of them. It's difficult to assess what exactly the impact this has on performance when these parameters were not exhaustively studied either in silico or through actual experiments. Given the fact that this is a new coding scheme, the authors should have at minimum done an in silico demonstration of every single rule and how it affects every single metric in the paper. Off the top of my head, because the selection of the rule parameter greatly affects the information density, sequencing errors will play a large role in the overall performance. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 867, 207]]<|/det|> +Response 11: We thank the reviewer for the comment. Parameters in Table 1 and the experimental design (Figure 3) is selected to be consistent with previous studies for the purpose of comparability. + +<|ref|>text<|/ref|><|det|>[[114, 216, 866, 405]]<|/det|> +We accept the reviewer's suggestion and have revised accordingly in the main text highlighted on page 6 (line 172- 180) and page 8 (line 220 - 232) to provide the insilico demonstration to systematically evaluate their performance of all 1536 coding schemes using 1 GB data collection including different formats of files (text, image, audio, and video). To conclude in general, we have shown that: 1) although the information density of each coding schemes in the 1536 collections varies, but in the range from 1.75 bits/nt to 1.78 bits/nt under well- accepted constraints. 2) the overall performance including InDels and SNVs is not affected by sequencing/synthesis errors. + +<|ref|>text<|/ref|><|det|>[[115, 435, 457, 455]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 475, 864, 601]]<|/det|> +The paper presents a new efficient coding scheme that improves the recovery rate in case of large sequence loss. The method maintains linear dependency between the percentage of oligos that were fully recovered, and the data recovery. Additionally, the paper demonstrates in vivo data storage with high information density. Roughly speaking, the paper is fairly written, however there are several parts which are not well explained, as will be elaborated below. + +<|ref|>sub_title<|/ref|><|det|>[[115, 631, 218, 650]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[115, 661, 879, 704]]<|/det|> +1. The code works well, I used it through the "chameleo" tool (that was also published by this group). + +<|ref|>text<|/ref|><|det|>[[115, 714, 840, 755]]<|/det|> +Response 12: We thank the reviewer for the recognition of YYC code and careful testing efforts made to evaluate on YYC. + +<|ref|>text<|/ref|><|det|>[[114, 784, 879, 847]]<|/det|> +2. Like I sent you in another email - I could not access the data from their experiment, so either the link is broken, or they should add more explanations on the data and how to access it. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 865, 227]]<|/det|> +Response 13: We apology to the reviewer for that the access link was not working. We didn't notice that there were some technical problems on linking our raw data to the project site. We have solved the problem and now the reviewer should be able to access the raw data by: + +<|ref|>text<|/ref|><|det|>[[118, 237, 555, 259]]<|/det|> +https://db.cngb.org/search/project/CNP0001650/ + +<|ref|>text<|/ref|><|det|>[[116, 269, 579, 290]]<|/det|> +The raw sequencing data can also be accessed from: + +<|ref|>text<|/ref|><|det|>[[118, 300, 579, 322]]<|/det|> +https://ftp.cngb.org/pub/CNSA/data3/CNP0001650 + +<|ref|>text<|/ref|><|det|>[[115, 350, 875, 414]]<|/det|> +3. As far as I understand, the authors did not perform any reconstruction algorithm on the sequenced oligos. Can you please comment whether such an algorithm can improve the data recovery success and/or achieve faster data recovery? + +<|ref|>text<|/ref|><|det|>[[113, 421, 879, 699]]<|/det|> +Response 14: We thank the reviewer for the comment. For both in vitro and in vivo experimental validations performed in our study, we used the standard de novo assembly algorithm SOAPdenovo (Luo et. al., 2012, Li et. al., 2010) applied in the next-generation sequencing analysis workflow. According to our result, we found that data recovery success/improvement is not achieved solely by the reconstruction algorithm itself but determined by the coding scheme and affected by errors introduced during synthesis/sequencing. However, we do think there could be a better algorithm or strategy designed specifically for this application in the future would improve the transcoding efficiency as well as the data recovery rate by better identifying and eliminating errors. We have revised this according to the reviewer's suggestion in the main text highlighted on page 12 (line 328 – 355) and included corresponding citations for algorithms used for sequence reconstruction in this study in the "Data analysis" section of method highlighted on page 20 (line 575 - 583). + +<|ref|>text<|/ref|><|det|>[[115, 725, 861, 790]]<|/det|> +4. There are several terms in the introduction that should be better explained before used for the average reader. Examples of these expressions are: secondary structure, free energy calculation. + +<|ref|>text<|/ref|><|det|>[[115, 800, 880, 843]]<|/det|> +Response 15: We thank the reviewer for the comment. We have revised this according to the reviewer's suggestion in the main text highlighted on page 2 (line 63 – 67). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 600, 163]]<|/det|> +5. The sentence between lines 80-82 is not clear to me. + +<|ref|>text<|/ref|><|det|>[[114, 174, 872, 406]]<|/det|> +Response 16: We thank the reviewer for the comment. In previous studies, two types of "redundancy" have been proposed and applied in DNA storage (one at transcoding level, while the other one refers to biochemical operation level). The logical redundancy of different transcoding methods varies, for example, it is mandatory for DNA fountain but not necessary for YYC. However, the physical redundancy (using extra molecule copies by synthesis) can be applied to all developed transcoding methods. They both can play a positive role in data recovery, but functioning in fundamentally different approaches. Thus we want to distinguish the difference between the two types of redundancy. We have revised this accordingly to make it clear in the main text highlighted on page 3 (line 83 – 87) and added relevant references (Ref No. 23,24). + +<|ref|>text<|/ref|><|det|>[[115, 435, 872, 476]]<|/det|> +6. Description of the YYC between lines 114-126 is not clear. What do X_n and Y_n refer to? + +<|ref|>text<|/ref|><|det|>[[114, 487, 876, 740]]<|/det|> +Response 17: We thank the reviewer for the comment. Here we use N1/N2/N3/N4 to represents one of the four nucleic acids A/T/C/G. In 'Yang' rule, 0 and 1 are mapped to two nucleotides: for example, if A or T represents 0, then the only choice for 1 is C or G. In 'Yin' rule, 0 and 1 are also mapped to two nucleotides, but in a different manner: Xj and Yj represent different binary digits 0 and 1. When j is an integer chosen from 1 to 8, Xj+Yj=1 and Xj×Yj=0 (i.e. eight independent sets of X and Y, with Xj /Yj being either 1/0 or 0/1). Since N1 and N2, or N3 and N4 represent identical binary digits in 'Yang' rule, but represent different digit in 'Yin' rule, it will only give one and only one consensus nucleotide during encoding. We have revised this accordingly to make it clearer in the main text highlighted on page 4 (line 121 - 132) and updated additional illustration in the supplementary video S1 for further clarification. + +<|ref|>text<|/ref|><|det|>[[115, 770, 488, 790]]<|/det|> +7. The caption of Fig. 1 is not clear either. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 875, 206]]<|/det|> +Response 18: We thank the reviewer for the comment. We have revised the figure caption accordingly to make it clearer in the main text highlighted on page 4 (line 121 - 132). + +<|ref|>text<|/ref|><|det|>[[115, 245, 686, 266]]<|/det|> +8. The description in page 11 of lines 282-310 is not clear to me. + +<|ref|>text<|/ref|><|det|>[[113, 276, 880, 553]]<|/det|> +Response 19: We thank the reviewer for the comment. The fast technical development of DNA synthesis and assembly promotes both in vitro and in vivo storage as well recognized approaches in recently years (Shipman et. al, Nature, 2017, Tabatabaei et. al, Nature Communications, 2020 and Chen et. al, National Science Review, 2021). Thus, we include both approaches in our study for experimental demonstrations. Previous study suggest that in vivo storage holds the advantage of retrieving data can be easily performed by cell subculturing and DNA extraction, and stored data can be well maintained. However, we noticed that introducing substantial heterogenous DNA into host strains could be problematic for data recovery. By sequencing of single colonies isolated from the construct, we observed partial data coding DNA loss in varying degrees. Our result further suggests that data recovery performance of the coding scheme is essentially important. We have revised the description accordingly to make it clearer in the main text highlighted on page 12 (line 328 - 355). + +<|ref|>text<|/ref|><|det|>[[115, 580, 607, 601]]<|/det|> +9. I could not find the supplementary video of Fig. S1b. + +<|ref|>text<|/ref|><|det|>[[115, 611, 874, 653]]<|/det|> +Response 20: We apology to the reviewer on this. We have re- uploaded the video file as "supplementary video S1" in the supplementary for further description. + +<|ref|>text<|/ref|><|det|>[[115, 682, 582, 703]]<|/det|> +10. The statement in Lemma 3 is not properly stated. + +<|ref|>text<|/ref|><|det|>[[115, 713, 867, 777]]<|/det|> +Response 21: We thank the reviewer for the comment. We have rewritten this part to make it clearer to understand. The new section is in the "Quantitative analysis" section of Supplementary. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 877, 227]]<|/det|> +11. In general, all the mathematical analysis in page 15 is very sloppy. The equations are explained and their correctness is not justified. There should be a clear statement about the properties that the YCC scheme satisfies and a proof for the redundancy. As written this way, I cannot truly understand and evaluate the code construction. + +<|ref|>text<|/ref|><|det|>[[115, 237, 870, 302]]<|/det|> +Response 22: We thank the reviewer for the comment. We have rewritten this part to make it clearer to understand. The new section is in the "Quantitative analysis" section of Supplementary. + +<|ref|>text<|/ref|><|det|>[[115, 339, 881, 382]]<|/det|> +12. The authors compare mostly with fountain codes. What about comparison with the other coding schemes? + +<|ref|>text<|/ref|><|det|>[[114, 391, 880, 625]]<|/det|> +Response 23: We thank the reviewer for the comment. As we explained in our introduction part on page 3, all early efforts have paved the way of facilitating the fast development of DNA storage, with focus on biochemical compatibility and/or chasing the extreme of information density. The comparison with all developed coding scheme is performed by encoding 1GB data collection in our study for in silico simulation analysis. Relative result is described in the "General principle and features of the Yin-Yang codec" part on page 6 (line 183 - 198) and supplementary Table S1. Since DNA fountain has performed comprehensive analysis to show its superior performance in comparison with other above mentioned coding schemes (Yaniv Erlich and Dina Zielinski, Science 2017), thus in our study, we choose to focus the comparison between DNA fountain and YYC for experimental validation comparison. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 163, 335, 178]]<|/det|> +Decision Letter, first revision: + +<|ref|>text<|/ref|><|det|>[[115, 201, 440, 270]]<|/det|> +Date: 17th January 22 04:48:08 Last Sent: 17th January 22 04:48:08 Triggered By: Ananya Rastogi + +<|ref|>text<|/ref|><|det|>[[194, 272, 403, 286]]<|/det|> +From: ananya.rastogi@nature.com + +<|ref|>text<|/ref|><|det|>[[200, 270, 402, 286]]<|/det|> +To: shenyue@genomics.cn + +<|ref|>text<|/ref|><|det|>[[194, 293, 444, 307]]<|/det|> +BCC: ananya.rastogi@nature.com + +<|ref|>text<|/ref|><|det|>[[152, 310, 844, 324]]<|/det|> +Subject: Decision on Nature Computational Science manuscript NATCOMPUTSCI- 21- 0438A + +<|ref|>text<|/ref|><|det|>[[152, 327, 848, 357]]<|/det|> +Message: \*\* Please ensure you delete the link to your author homepage in this e- mail if you wish to forward it to your co- authors. \*\* + +<|ref|>text<|/ref|><|det|>[[232, 369, 339, 384]]<|/det|> +Dear Dr Shen, + +<|ref|>text<|/ref|><|det|>[[232, 396, 872, 480]]<|/det|> +Your manuscript "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" has now been seen by the 3 referees that we had contacted earlier. In addition, we contacted 1 more reviewer for a more technical review. The reviewers' comments are appended below. You will see that while they find your work of interest, they have raised points that need to be addressed before we can make a decision on publication. + +<|ref|>text<|/ref|><|det|>[[231, 492, 858, 520]]<|/det|> +While we ask you to address all of the points raised, the following points need to be substantially worked on: + +<|ref|>text<|/ref|><|det|>[[231, 520, 880, 602]]<|/det|> +- Please provide more insight into the way indices are assigned to segments along with the effect this has on pool capacity. +- Please discuss the policy for what to do when a sequence fails to encode. +- Please provide a discussion on where the proposed codec fits in and how it could be used with other approaches. +- Please provide an insight into the observed poor performance of DNA Fountain. + +<|ref|>text<|/ref|><|det|>[[232, 616, 864, 660]]<|/det|> +Please use the following link to submit your revised manuscript and a point- by- point response to the referees' comments (which should be in a separate document to any cover letter): + +<|ref|>sub_title<|/ref|><|det|>[[232, 672, 327, 688]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[232, 700, 856, 743]]<|/det|> +\*\* This url links to your confidential homepage and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this e- mail to co- authors, please delete this link to your homepage first. \*\* + +<|ref|>text<|/ref|><|det|>[[232, 755, 878, 812]]<|/det|> +To aid in the review process, we would appreciate it if you could also provide a copy of your manuscript files that indicates your revisions by making use of Track Changes or similar mark- up tools. Please also ensure that all correspondence is marked with your Nature Computational Science reference number in the subject line. + +<|ref|>text<|/ref|><|det|>[[231, 824, 856, 853]]<|/det|> +In addition, please make sure to upload a Word Document or LaTeX version of your text, to assist us in the editorial stage. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[231, 159, 875, 272]]<|/det|> +To improve transparency in authorship, we request that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[231, 283, 880, 312]]<|/det|> +We hope to receive your revised paper within three weeks. If you cannot send it within this time, please let us know. + +<|ref|>text<|/ref|><|det|>[[232, 325, 551, 339]]<|/det|> +We look forward to hearing from you soon. + +<|ref|>text<|/ref|><|det|>[[232, 352, 331, 367]]<|/det|> +Best regards, + +<|ref|>text<|/ref|><|det|>[[231, 380, 458, 421]]<|/det|> +Ananya Rastogi, PhD Associate Editor Nature Computational Science + +<|ref|>text<|/ref|><|det|>[[232, 463, 396, 477]]<|/det|> +Reviewers comments: + +<|ref|>text<|/ref|><|det|>[[232, 490, 520, 504]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[231, 517, 810, 546]]<|/det|> +The points you raised in the previous round of review have been satisfactorily addressed. + +<|ref|>text<|/ref|><|det|>[[232, 546, 473, 560]]<|/det|> +The paper can be accepted now. + +<|ref|>text<|/ref|><|det|>[[232, 586, 520, 600]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[232, 613, 674, 628]]<|/det|> +The authors have adequately addressed all of my concerns. + +<|ref|>text<|/ref|><|det|>[[232, 655, 520, 669]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[231, 683, 863, 725]]<|/det|> +The authors addressed most of my comments as well as the ones by the other two reviewers. I still have several concerns with the paper presentation and my previous comments (I was reviewer #3). + +<|ref|>text<|/ref|><|det|>[[231, 726, 857, 780]]<|/det|> +- In my third comments, I asked about the use of some reconstruction algorithm. From your explanation it is implied that a voting strategy was applied to generate a consensus sequence. What exactly does it mean and why don't you use other algorithms for reconstruction. + +<|ref|>text<|/ref|><|det|>[[231, 781, 870, 836]]<|/det|> +- In comment 12, I still don't see the rationale behind the comparison with only DNA fountain codes. In general, you should mathematically describe the problem that is solved in the paper and why Yin-Yang codes are better than other known schemes for this problem. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[232, 157, 520, 172]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[232, 186, 378, 200]]<|/det|> +Reviewer Summary + +<|ref|>text<|/ref|><|det|>[[232, 213, 872, 284]]<|/det|> +This work describes a novel codec for DNA storage called the Yin- Yang Codec (YYC). It's based on the observation that it is difficult to achieve both theoretical information densities and sequences that meet critical biomolecular constraints, such as avoiding homopolymers, imbalanced GC content, or harmful structures. The YYC is effective at reaching high density because it supports a variety of encoding strategies. + +<|ref|>text<|/ref|><|det|>[[231, 296, 880, 574]]<|/det|> +Here's a brief summary of how it works. A file is divided into segments of a fixed length as binary strings; an index is added to each segment to mark its location in the file. Then, two segments, say a and b, are selected at random and sent through a two- step encoding process (Yin and Yang). One bit is taken from each of the two segments and is encoded into a single nucleotide. Using 2 bits to encode each nucleotide is what give it a high information density. The Yin step uses a[i] to select a set of possible encoding bases, which narrows it down to 2 of the 4 bases based on a look- up table, call this set A. The Yang step uses the b[i] bit and the previous nucleotide that was encoded to looks up its encoding, which is also a set of possible nucleotides, lets call it set B. Then, the intersection of A and B is emitted as the output nucleotide. The Yin and Yang coding tables are designed to ensure a unique nucleotide is emitted. This process repeats for all bits in a and b until the sequence is generated. Because two bits are used to produce each base, it has the potential to reach the information theoretical limit of 2 bits / nt. However, after the sequence is created, it's sent through a filter to weed out bad sequences based on GC content, homopolymers, and thermodynamic analysis. If it fails this step, the sequence is thrown out. This process of selecting segments, encoding them, and checking them is repeated until enough good sequences are created to enable decoding of the file. No additional logical redundancy is included since this process is only meant as a way of encoding the data and is not meant to provide error correction. + +<|ref|>text<|/ref|><|det|>[[232, 586, 875, 656]]<|/det|> +Experiments are conducted in silico, in vitro, and in vivo to understand its utility and verify its usefulness for DNA storage. The YYC approach is applied to a suite of files of various formats and shown to successfully encode and decode while achieving good information densities. Its effectiveness is compared primarily to DNA Fountain given their overall similarity in goals and approach. + +<|ref|>text<|/ref|><|det|>[[232, 669, 880, 725]]<|/det|> +The most interesting part of the evaluation is in how well the codec works in silico. The in vitro studies are expected to work since they largely follow proven experimental methodologies. The in vivo studies add some new analysis to the field concerning storage and retrieval of data in yeast. + +<|ref|>sub_title<|/ref|><|det|>[[232, 752, 321, 766]]<|/det|> +## Significance + +<|ref|>text<|/ref|><|det|>[[232, 779, 852, 849]]<|/det|> +This work aims to further the field by presenting a new codec that provides high information density while still avoiding problematic sequences. This codec bears significant similarity to the goals of DNA Fountain, and that's why they compare against DNA Fountain. However, this work is not a Fountain code, and that enables some simplifications while also creating potential weaknesses. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[232, 159, 325, 172]]<|/det|> +## Advantages: + +<|ref|>text<|/ref|><|det|>[[232, 173, 872, 243]]<|/det|> +\(+A\) potential advantage of this work is the straightforward encoding and decoding process with respect to segments and their indices. This work can embed the indices directly in the encoded segments and recover them through standard decoding, but fountain codes need to encode that information as separate meta- data or hard code a lookup table or enumerator function a priori in the encoder and decoder. + +<|ref|>text<|/ref|><|det|>[[232, 255, 868, 297]]<|/det|> +\(+\) Another potential advantage of this work is the large variety of Yin and Yang coding tables, up to 1536, that allow a wide variety of ways to encode data. However, this may be a weakness, as described below. + +<|ref|>sub_title<|/ref|><|det|>[[232, 311, 346, 325]]<|/det|> +## Disadvantages: + +<|ref|>text<|/ref|><|det|>[[232, 338, 872, 450]]<|/det|> +- A fountain code can pick an arbitrary number of segments to merge, but this can only pick 2. YYC makes up for this limitation to some degree by having non-unitary mapping rules, however, this is achieved using a trial and error process. The trial and error process is not described in the paper or in the supplementary material, as far as I could tell. While the YYC can allow up to 1536 different coding tables, it was not demonstrated in the work that all of these combinations are actually useful, and I suspect that many of the tables end up producing similar results and may not all be equally useful. + +<|ref|>text<|/ref|><|det|>[[232, 463, 872, 518]]<|/det|> +- Fountain codes and rateless codes, in general, can add an arbitrary number of additional symbols to the encoded file, but this work can pick from at most \(n^2\) combinations of segments, where n is the number of segments in the file, giving it far fewer combinations to work with to find usable sequences than Fountain codes. + +<|ref|>text<|/ref|><|det|>[[232, 531, 880, 629]]<|/det|> +- This work shares the disadvantage of DNA Fountain of needing to verify a sequence after its encoded, which means that either the pair of segments or the mapping tables could have been a poor choice. This can lead to large encode-time overheads and many failed attempts when encoding strands. The number of trials used to encode data and its compute time is not reported, but it should be for a fair assessment of the work. The work does report a limit of 100 attempts per strand, but the total number of attempts while encoding a file is not reported. + +<|ref|>text<|/ref|><|det|>[[232, 642, 880, 740]]<|/det|> +- The policy for what to do when a sequence fails to encode is not described in much detail. I am concerned with the computational complexity of choosing a suitable table - how many attempts are needed? Also, I'm concerned about what happens if there is no suitable encoding for some part of the data. If 100 attempts are made and all fail, at this point, is a suitable synthetic sequence created just to ensure encodability? Is this synthetic sequence somehow always guaranteed to succeed or might multiple attempts be needed here as well? It would be good to quantify this as well. + +<|ref|>sub_title<|/ref|><|det|>[[232, 752, 377, 766]]<|/det|> +## Clarity and Context + +<|ref|>text<|/ref|><|det|>[[232, 780, 878, 850]]<|/det|> +\* I think the work does not position itself as well as it could with respect to prior codecs or with respect to DNA Fountain. Many different codecs have been proposed to deal with various challenges of DNA storage. The presentation of where this one fits in and how it could be used with other approaches could be done with greater clarity. For example, this is really just part of the codec and doesn't include any new support for + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[232, 144, 881, 271]]<|/det|> +error correction. Also, this article takes a fairly limited view of what is relevant and does not discuss deeply how other codes were designed and what their advantages and disadvantages are. Organick et al. [Nature Biotech 2018] deal with these same issues but in different ways. Also, DNA Fountain, and fountain codes in general, could be configured and tuned to work potentially much better than the DNA Fountain work that is compared against, but this is not done or considered. The claimed advantages of YYC over DNA Fountain may be true for the specific implementation of DNA Fountain that was compared against, but those advantages likely do not extend to an optimized Fountain code for data storage. + +<|ref|>text<|/ref|><|det|>[[232, 283, 876, 368]]<|/det|> +\* The example of the Yin- Yang Codec given in the paper is hard to understand. I think you should move a similar example as in the video into the paper. Make it concrete so that readers can understand how one of the configurations actually works. You can always add more explanation on how to generalize it elsewhere. Without a good example, the paper is not self- contained and reviewers will need the supplementary material to make sense of the work, which is not ideal in my opinion. + +<|ref|>text<|/ref|><|det|>[[231, 380, 879, 589]]<|/det|> +- The way indices are assigned to segments is not explained in enough detail. Also, how segments are assigned to either the Yin or Yang rule is not explained. These are important details because they have a large bearing on the overall efficiency of the system. For example, suppose a file is partitioned into segments and each one is labeled with a unique binary index, of length k (2\*\*k total segments are possible). Now, suppose these segments are selected at random and passed arbitrarily into either the Yin or Yang rule. This means that k nucleotides are used to represent the index and 4\*\*k sequences are possible, but only 2\*\*k total indices are available in the file. This implies that indices have at most a coding density of 1 bit/base. Large files will need large indices, which substantially cuts into the claimed high density of the system since oligo synthesis has relatively hard limits on synthesized strand length. Other codecs which do not use a binary index will have a significant advantage in overall capacity and density. It's possible that I've misunderstood some aspect of how indices are assigned and used in this codec, so it would be good for this aspect of the paper to be improved. + +<|ref|>sub_title<|/ref|><|det|>[[232, 602, 370, 616]]<|/det|> +## Major Suggestions + +<|ref|>text<|/ref|><|det|>[[232, 642, 879, 809]]<|/det|> +1. The paper makes a strong claim about density that needs to be clarified. As mentioned earlier, the work does not explain well how indices are handled (as mentioned previously in my review), but the indices appear to achieve no better than a binary encoding (1 bit/base) density. One implication of this is that a high-density encoding is somewhat reliant on having small indices, which implies small file sizes and small capacity overall. This is an undesirable result for what should be a dense medium. Another implication of this is that the total capacity of the system (total unique strands) appears to be lower than those systems that achieve ternary indices, for example. While the claimed figures of merit for density are high, they hide the fact that the total capacity of a pool of DNA may be severely negatively impacted by binary indices. I would like to see a better explanation of how indices are handled and the effect this has on pool capacity. + +<|ref|>text<|/ref|><|det|>[[230, 822, 875, 850]]<|/det|> +2. The capabilities of the YYC codec with respect to the variety of mapping tables is not well justified. It's not clear that the ability to select one of the 1536 configurations + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[232, 144, 880, 201]]<|/det|> +actually helps or not. The work claims to leverage a combinatoric scheme, but that is not demonstrated through an experiment, except to some degree in the small one that analyzes strands with large fractions of 0 or 1 to see if any mapping tables can encode them satisfactorily. + +<|ref|>text<|/ref|><|det|>[[232, 214, 877, 368]]<|/det|> +To really demonstrate the advantage of all these combinations, several things need to be shown. (1) That having a choice among mapping tables is helpful and leads to less overhead as compared to DNA Fountain. (2) That the choice of mapping table can be made efficiently. It would be interesting to report the number of failed attempts at selecting segments and encoding them. (3) That the overhead of holding the choice of mapping table in meta- data is a reasonable cost, even if done electronically. If a mapping table selection needs to be remembered per strand, then that implies approximately 11 bits of overhead per segment- pair, which for an exabyte scale system would add up to a very large cost. If it only needs to be remembered per file, it's a lower meta- data cost but higher compute cost to find a mapping. These trade- offs need some further explanations. + +<|ref|>text<|/ref|><|det|>[[232, 380, 845, 408]]<|/det|> +If this analysis is prohibitive to conduct, then I would suggest softening the claims over how useful these tables are. + +<|ref|>text<|/ref|><|det|>[[232, 420, 880, 629]]<|/det|> +3. It's surprising that DNA Fountain does so poorly in the in silico experiment (Figure 2). I agree with the general arguments that DNA Fountain will have high degree packets that include many segments. However, I'm not convinced this is the entire answer unless DNA Fountain mostly selects high degree packets. Also, some important information is missing in this analysis. It appears that no error correction is used. In that case, what is done with strands that have insertions, deletions, and substitutions? Without error correction support, such problems cannot even be detected much less corrected. So, are they treated as correct and allowed to pollute the file with errors? This raises questions about how the DNA Fountain approach is utilized. Is the DNA Fountain code base used for this analysis? If so, is it possible that something is going wrong in how it handles these errors? For example, since segments are more likely repeated in multiple high degree packets, it may be detecting errors and throwing them out, whereas YYC has no such detection capability. Instead, YYC may be making a best-effort attempt to keep the data. More details of how this analysis is conducted are needed to fully explain DNA Fountain's poorer behavior. + +<|ref|>sub_title<|/ref|><|det|>[[232, 641, 370, 656]]<|/det|> +## Minor Suggestions + +<|ref|>text<|/ref|><|det|>[[232, 669, 881, 711]]<|/det|> +1. Perhaps add a brief explanation for a few things in the thermodynamic screening, such as at what temperature was the simulated free energy screening conducted? And, what other parameters were used, if any? Why did you pick -30 kcal/mol as the cutoff? + +<|ref|>text<|/ref|><|det|>[[231, 724, 875, 752]]<|/det|> +2. In the text regarding in vitro experiments, please make it clear which encoding was used for each pool. I think P2 and P3 were done using DNA Fountain. + +<|ref|>text<|/ref|><|det|>[[232, 765, 868, 821]]<|/det|> +3. On Page 9, line 242-244, it says that loss of one strand in YYC can lead to the loss of two segments. This is true. But, isn't it possible that a segment is repeatedly selected for pairing due to some good pattern in its data, decreasing the odds it is lost? Or, do you prevent selecting the same sequence many times? + +<|ref|>text<|/ref|><|det|>[[232, 834, 495, 849]]<|/det|> +Thank you for an interesting paper. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 255, 328, 274]]<|/det|> +Reviewers' comments: + +<|ref|>sub_title<|/ref|><|det|>[[115, 276, 492, 296]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 297, 883, 336]]<|/det|> +The points you raised in the previous round of review have been satisfactorily addressed. + +<|ref|>text<|/ref|><|det|>[[116, 337, 410, 357]]<|/det|> +The paper can be accepted now. + +<|ref|>text<|/ref|><|det|>[[115, 377, 852, 398]]<|/det|> +Response 1: We thank the reviewer for the significant help in improving our work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 415, 492, 435]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 436, 655, 456]]<|/det|> +The authors have adequately addressed all of my concerns. + +<|ref|>text<|/ref|><|det|>[[115, 475, 852, 496]]<|/det|> +Response 2: We thank the reviewer for the significant help in improving our work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 516, 492, 536]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 537, 882, 596]]<|/det|> +The authors addressed most of my comments as well as the ones by the other two reviewers. I still have several concerns with the paper presentation and my previous comments (I was reviewer #3). + +<|ref|>text<|/ref|><|det|>[[115, 597, 882, 678]]<|/det|> +- In my third comments, I asked about the use of some reconstruction algorithm. From your explanation it is implied that a voting strategy was applied to generate a consensus sequence. What exactly does it mean and why don't you use other algorithms for reconstruction. + +<|ref|>text<|/ref|><|det|>[[115, 696, 882, 814]]<|/det|> +Response 3: We thank the reviewer for the comment. The voting strategy here is the single- winner plurality voting strategy where each candidate sequence has the same weight. As this strategy is straightforward and effective with the stored data fully recovered, we chose this strategy over other algorithms to minimize complexity and avoid algorithmic bias. We have revised the coordinating manuscript on page 13 (line 376 to 378) to avoid confusion. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 882, 225]]<|/det|> +- In comment 12, I still don't see the rationale behind the comparison with only DNA fountain codes. In general, you should mathematically describe the problem that is solved in the paper and why Yin-Yang codes are better than other known schemes for this problem. + +<|ref|>text<|/ref|><|det|>[[114, 244, 882, 617]]<|/det|> +Response 4: We thank the reviewer for the comment. Excepting DNA fountain, early established coding schemes apply a single fixed rule for bit- to- base transcoding, in which no screening process is used. On the contrary, DNA Fountain and YYC are the only two known coding schemes that combine transcoding rules and screening as a whole process to make sure the generated DNA sequences can meet the biochemical constraints, such as GC content and maximum homopolymer length. Thus, we reason that direct mathematical analysis should be focused on the comparison between DNA Fountain and YYC due to the similarity of coding strategy between YYC and DNA Fountain. Both algorithms employ the strategy of incorporation of two or more binary segments and generate a corresponding DNA sequence/ information packet. The information packets generated by DNA fountain are topologically connected with each other and form a grid- like structure. For current information communication using cables or radio, this procedure is feasible because even if some packets are lost or with error, new packets can be immediately re- sent for successful data recovery. However, receiving information in the process of DNA storage is not synchronous. Thus, the errors or packets loss will lead to a domino effect or error propagation for DNA Fountain. In contrast, the information packets generated by YYC are mutually independent. The effect on data recovery caused by the errors or packets loss is greatly minimized for YYC. + +<|ref|>text<|/ref|><|det|>[[115, 616, 882, 714]]<|/det|> +In addition, as we explained in our previous response, we have included the performance comparison among all developed coding schemes by encoding 1GB data collection in our study for in silico simulation analysis (Table 1). And our result suggests that YYC shows superior performance in comparison with other existing coding schemes. + +<|ref|>sub_title<|/ref|><|det|>[[115, 772, 492, 792]]<|/det|> +## Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 794, 300, 812]]<|/det|> +Reviewer Summary + +<|ref|>text<|/ref|><|det|>[[115, 813, 882, 853]]<|/det|> +This work describes a novel codec for DNA storage called the Yin- Yang Codec (YYC). It's based on the observation that it is difficult to achieve both theoretical + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 883, 225]]<|/det|> +information densities and sequences that meet critical biomolecular constraints, such as avoiding homopolymers, imbalanced GC content, or harmful structures. The YYC is effective at reaching high density because it supports a variety of encoding strategies. + +<|ref|>text<|/ref|><|det|>[[114, 225, 883, 650]]<|/det|> +Here's a brief summary of how it works. A file is divided into segments of a fixed length as binary strings; an index is added to each segment to mark its location in the file. Then, two segments, say a and b, are selected at random and sent through a two- step encoding process (Yin and Yang). One bit is taken from each of the two segments and is encoded into a single nucleotide. Using 2 bits to encode each nucleotide is what give it a high information density. The Yin step uses a[i] to select a set of possible encoding bases, which narrows it down to 2 of the 4 bases based on a look- up table, call this set A. The Yang step uses the b[i] bit and the previous nucleotide that was encoded to looks up its encoding, which is also a set of possible nucleotides, lets call it set B. Then, the intersection of A and B is emitted as the output nucleotide. The Yin and Yang coding tables are designed to ensure a unique nucleotide is emitted. This process repeats for all bits in a and b until the sequence is generated. Because two bits are used to produce each base, it has the potential to reach the information theoretical limit of 2 bits / nt. However, after the sequence is created, it's sent through a filter to weed out bad sequences based on GC content, homopolymers, and thermodynamic analysis. If it fails this step, the sequence is thrown out. This process of selecting segments, encoding them, and checking them is repeated until enough good sequences are created to enable decoding of the file. No additional logical redundancy is included since this process is only meant as a way of encoding the data and is not meant to provide error correction. + +<|ref|>text<|/ref|><|det|>[[115, 652, 882, 752]]<|/det|> +Experiments are conducted in silico, in vitro, and in vivo to understand its utility and verify its usefulness for DNA storage. The YYC approach is applied to a suite of files of various formats and shown to successfully encode and decode while achieving good information densities. Its effectiveness is compared primarily to DNA Fountain given their overall similarity in goals and approach. + +<|ref|>text<|/ref|><|det|>[[115, 754, 882, 833]]<|/det|> +The most interesting part of the evaluation is in how well the codec works in silico. The in vitro studies are expected to work since they largely follow proven experimental methodologies. The in vivo studies add some new analysis to the field concerning storage and retrieval of data in yeast. + +<|ref|>text<|/ref|><|det|>[[115, 835, 231, 853]]<|/det|> +Significance + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 882, 247]]<|/det|> +This work aims to further the field by presenting a new codec that provides high information density while still avoiding problematic sequences. This codec bears significant similarity to the goals of DNA Fountain, and that's why they compare against DNA Fountain. However, this work is not a Fountain code, and that enables some simplifications while also creating potential weaknesses. + +<|ref|>text<|/ref|><|det|>[[115, 247, 226, 266]]<|/det|> +Advantages + +<|ref|>text<|/ref|><|det|>[[115, 266, 882, 387]]<|/det|> +\(+A\) potential advantage of this work is the straightforward encoding and decoding process with respect to segments and their indices. This work can embed the indices directly in the encoded segments and recover them through standard decoding, but fountain codes need to encode that information as separate meta- data or hard code a lookup table or enumerator function a priori in the encoder and decoder. + +<|ref|>text<|/ref|><|det|>[[115, 388, 882, 448]]<|/det|> +\(+\) Another potential advantage of this work is the large variety of Yin and Yang coding tables, up to 1536, that allow a wide variety of ways to encode data. However, this may be a weakness, as described below. + +<|ref|>text<|/ref|><|det|>[[115, 450, 257, 469]]<|/det|> +Disadvantages: + +<|ref|>text<|/ref|><|det|>[[115, 470, 882, 631]]<|/det|> +- A fountain code can pick an arbitrary number of segments to merge, but this can only pick 2. YYC makes up for this limitation to some degree by having non-unitary mapping rules, however, this is achieved using a trial and error process. The trial and error process is not described in the paper or in the supplementary material, as far as I could tell. While the YYC can allow up to 1536 different coding tables, it was not demonstrated in the work that all of these combinations are actually useful, and I suspect that many of the tables end up producing similar results and may not all be equally useful. + +<|ref|>text<|/ref|><|det|>[[115, 649, 882, 747]]<|/det|> +Response 5: We thank the reviewer for the comprehensive summary and recognition of our work. To briefly summarize the two major concerns/suggestions from the reviewer: 1) providing the detailed description of the trail- and- error process; 2) describing the differences of the proposed 1536 coding schemes in this study. To answer the questions: + +<|ref|>text<|/ref|><|det|>[[115, 748, 882, 846]]<|/det|> +For the trial- and- error process, it is the iteration process as the reviewer understands in the above summary part: "This process of selecting segments, encoding them, and checking them is repeated until enough good sequences are created to enable decoding of the file". We further revised the description to make it clearer and highlighted it in the manuscript on page 5 (line 144 to 151). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[549, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 883, 393]]<|/det|> +For the difference analysis of 1,536 combinatory coding schemes, we followed the reviewer's suggestion and performed further analysis on the difference of generated DNA sequences by using individual coding scheme to transcode various types of files. The DNA sequence difference are evaluated by the average hamming distance, which is the number of bit positions in which the two bits are different. Our result shows that for the same digital files, 1328 of the 1536 coding schemes can generate corresponding DNA sequences with identity less than \(40\%\) and only less than \(0.5\%\) of full coding scheme collections (7 coding schemes) generating DNA sequences with identity between \(80\%\) to \(91.85\%\) (Fig. S3). Our analysis suggests that the 1536 coding schemes can generate significantly different DNA sequences. We have revised the manuscript on page 7 (line 192 to 196) and supplementary information on Figure S3 to further clarify. + +<|ref|>text<|/ref|><|det|>[[114, 422, 883, 525]]<|/det|> +- Fountain codes and rateless codes, in general, can add an arbitrary number of additional symbols to the encoded file, but this work can pick from at most \(n^2\) combinations of segments, where n is the number of segments in the file, giving it far fewer combinations to work with to find usable sequences than Fountain codes. + +<|ref|>text<|/ref|><|det|>[[114, 525, 883, 740]]<|/det|> +Response 6: We thank the reviewer for the comment. We understand that the reviewer's concern is that \(n^2\) combinations of segments may not be sufficiently enough to generate valid DNA sequences. First, we would like to point out that in the general circumstance, rateless codes like LT codes, Raptor codes, etc., can generate an arbitrary number of packets from the information source and increase the redundancy correspondingly to find usable sequences. However, that doesn't apply if the digital information shows extreme data patterns. We have proved our point in our work by transcoding 5 different binary patterns in Table. S1 and the figures of 9 different national flags shown in Table. S6 of the supplementary information. For DNA Fountain, even with \(300\%\) redundancy being introduced, there is still no solution for successful transcoding. + +<|ref|>text<|/ref|><|det|>[[114, 740, 883, 858]]<|/det|> +We would also like to clarify that the maximum combinations of YYC can be much higher than \(n^2\) because YYC allows the introduction of additional "pseudo" binary segments to avoid the situation that there is no desired combination for existing segments (as stated in the manuscript on page 6 from line 165 to 167). Thus, the actual maximum number of combinations of YYC is \(n^* 2^k\) (k refers to the number of additionally added segments). The approach by incorporating + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 882, 243]]<|/det|> +additional binary segments is essentially useful and important for digital file with extreme data patterns. For the same examples we mentioned above that DNA Fountain failed to provide solution, using YYC, we successfully transcoded the figure into DNA sequences with high biocompatibility to DNA synthesis and sequencing processes. + +<|ref|>text<|/ref|><|det|>[[115, 242, 882, 380]]<|/det|> +Although archiving of the source digital file can balance the data pattern, however, as we described in the highlighted main text on page 14 (line 402- 407), it also brings significant challenges to data decoding because the errors introduced during DNA synthesis and sequencing will significantly affect the success rate of decoding. To summarize, our result suggests that YYC shows superior performance on the general coding/decoding processes by the proposed combination strategy with no preference on particular data patterns. + +<|ref|>text<|/ref|><|det|>[[115, 396, 882, 540]]<|/det|> +- This work shares the disadvantage of DNA Fountain of needing to verify a sequence after its encoded, which means that either the pair of segments or the mapping tables could have been a poor choice. This can lead to large encode-time overheads and many failed attempts when encoding strands. The number of trials used to encode data and its compute time is not reported, but it should be for a fair assessment of the work. The work does report a limit of 100 attempts per strand, but the total number of attempts while encoding a file is not reported. + +<|ref|>text<|/ref|><|det|>[[115, 557, 882, 617]]<|/det|> +Response 7: We thank the reviewer for the comment. We understand the reviewer concerns that whether the iteration cycle/attempts cost significant encoding- time overheads to generate valid DNA sequence. + +<|ref|>text<|/ref|><|det|>[[115, 617, 882, 850]]<|/det|> +We performed the evaluation of average iteration run required by transcoding ten different formats of files and have shown that the average number from 1 to 7 trails (Table S3). We further took the reviewer's suggestion and conducted further analysis by estimating the total number of trails while encoding the 1 GB data collection used in our study for in silico simulation. As shown in Fig. S4a, in general, 65% of the segment can be successfully incorporated with another segment with a single run of trail, and for files with balanced byte frequency (Fig. R1 shown below), the percentage further increase to \(\sim 77\%\) (Fig. S4b). From our observation, less than 0.3% of segments requires more than 10 runs of trail. Our results imply that for an arbitrary file, YYC encoding would not cost a large encode- time overheads. We have revised the manuscript accordingly to include these analysis results in the main text highlighted on page 6 (line 164 – 172), as well as supplementary (Figure S4). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>image<|/ref|><|det|>[[115, 163, 789, 696]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 714, 883, 748]]<|/det|> +
Statistics of byte frequency of all the files used in the simulation. According to Li et al., 2005, green ones were considered as files with balanced byte frequency. (For review usage only)
+ +<|ref|>text<|/ref|><|det|>[[115, 758, 883, 860]]<|/det|> +- The policy for what to do when a sequence fails to encode is not described in much detail. I am concerned with the computational complexity of choosing a suitable table -- how many attempts are needed? Also, I'm concerned about what happens if there is no suitable encoding for some part of the data. If 100 attempts are made and all fail, at this point, is a suitable synthetic sequence created just to + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 882, 204]]<|/det|> +ensure encodability? Is this synthetic sequence somehow always guaranteed to succeed or might multiple attempts be needed here as well? It would be good to quantify this as well. + +<|ref|>text<|/ref|><|det|>[[114, 222, 883, 499]]<|/det|> +Response 8: We thank the reviewer for the comment. We think there might be some misunderstanding on that poor choice is made when suitable encoding failed after 100 attempts. In the transcoding process of YYC, all the generated sequence must fulfill the constraints without any exception, and this is achieved by the incorporation of "pseudo" binary segment with random 0/1 but in balanced ratio as we mentioned in the response #6. This can make sure that a valid DNA sequence will be generated for each binary segment. The addition of "pseudo" segment will of course reduce the bit- to- base information density. But according to our simulation analysis using the 1GB data collection, less than \(0.002\%\) of overall segments need this "back- up" plan (Fig. S4). In the "worst" case we observed in Table S3, the additional information added to the source file for successful transcoding accounts for only \(19.25\%\) of the original file size, with the average number of trails at \(\sim 7\) and information density at \(\sim 1.45\) . We have updated the description in the manuscript accordingly on page 6 (line 164 to 172). + +<|ref|>sub_title<|/ref|><|det|>[[115, 516, 299, 535]]<|/det|> +## Clarity and Context + +<|ref|>text<|/ref|><|det|>[[114, 536, 883, 840]]<|/det|> +\* I think the work does not position itself as well as it could with respect to prior codecs or with respect to DNA Fountain. Many different codecs have been proposed to deal with various challenges of DNA storage. The presentation of where this one fits in and how it could be used with other approaches could be done with greater clarity. For example, this is really just part of the codec and doesn't include any new support for error correction. Also, this article takes a fairly limited view of what is relevant and does not discuss deeply how other codes were designed and what their advantages and disadvantages are. Organick et al. [Nature Biotech 2018] deal with these same issues but in different ways. Also, DNA Fountain, and fountain codes in general, could be configured and tuned to work potentially much better than the DNA Fountain work that is compared against, but this is not done or considered. The claimed advantages of YYC over DNA Fountain may be true for the specific implementation of DNA Fountain that was compared against, but those advantages likely do not extend to an optimized Fountain code for data storage. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 882, 243]]<|/det|> +Response 9: We thank the reviewer for the comment. To briefly summarize, we think there are two issues from the reviewer's view: 1) Comparison between YYC and other coding schemes apart from DNA fountain; relationship with other efforts (such as error correction) been made in the field of DNA storage; 2) Comparison towards DNA Fountain is limited at specific implementation. + +<|ref|>text<|/ref|><|det|>[[114, 241, 883, 673]]<|/det|> +For the first concern, as we described in the Response #4, excepting DNA fountain, early established coding schemes apply a single fixed rule for bit- to- base transcoding, in which no screening process is used. On the contrary, DNA Fountain and YYC are the only two coding schemes that combine transcoding rules and screening as a whole process to make sure the generated DNA sequences can meet the biochemical constraints, such as GC content and maximum homopolymer length. Thus, we reason that direct mathematical analysis should be focused on the comparison between DNA Fountain and YYC due to the similarity of coding strategy between YYC and DNA Fountain. Both algorithms employ the strategy of incorporation of two or more binary segments and generate a corresponding DNA sequence/ information packets. However, we did include the functional comparison with all developed coding scheme by encoding 1GB data collection in our study for in silico simulation analysis. Relative result is described in the "General principle and features of the Yin- Yang codec" part. From our point of view, the whole DNA storage process includes several function modules: bit- to- base encoding, error- correction, indices assignment, redundancy handling, etc. YYC is developed as a bit- to- base encoding algorithm for improving the practicality and robustness of DNA data storage. It can be used separately or in corporation with other developed function modules. For example, in this study we used RS code to implement the function of error correction. Future efforts can be performed to incorporate more functionalities and we proposed some of the orientations in the discussion part in main text, page 15 (line 418- 424). + +<|ref|>text<|/ref|><|det|>[[115, 672, 882, 860]]<|/det|> +For the second suggestion, the in silico simulation analysis and experimental validations were performed with recommended configuration and parameters of DNA Fountain claimed in their study. In addition, we agree with the reviewer that the configuration and parameter adjustment could improve the general performance of a coding scheme like DNA Fountain, but the improvement will be in a relatively limited range. As described in our manuscript, increasing logical redundancy could greatly improve the probability of successful decoding for all the coding schemes. However, we have proven that even with exceeding high redundancy at \(300\%\) (Table S6), for some digital files, DNA Fountain still failed to generate an encoding solution. And + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 880, 185]]<|/det|> +this is caused by the fundamental limitation of DNA Fountain rather than the selection of configuration and parameters. + +<|ref|>text<|/ref|><|det|>[[115, 221, 882, 365]]<|/det|> +\* The example of the Yin- Yang Codec given in the paper is hard to understand. I think you should move a similar example as in the video into the paper. Make it concrete so that readers can understand how one of the configurations actually works. You can always add more explanation on how to generalize it elsewhere. Without a good example, the paper is not self- contained and reviewers will need the supplementary material to make sense of the work, which is not ideal in my opinion. + +<|ref|>text<|/ref|><|det|>[[115, 365, 881, 424]]<|/det|> +Response 10: We thank the reviewer for the comment. We have revised the manuscript and provided a similar example as in the video to make the paper selfcontained (page 16 from line 469 to 481). + +<|ref|>text<|/ref|><|det|>[[114, 441, 882, 747]]<|/det|> +- The way indices are assigned to segments is not explained in enough detail. Also, how segments are assigned to either the Yin or Yang rule is not explained. These are important details because they have a large bearing on the overall efficiency of the system. For example, suppose a file is partitioned into segments and each one is labeled with a unique binary index, of length k (2\*\*k total segments are possible). Now, suppose these segments are selected at random and passed arbitrarily into either the Yin or Yang rule. This means that k nucleotides are used to represent the index and 4\*\*k sequences are possible, but only 2\*\*k total indices are available in the file. This implies that indices have at most a coding density of 1 bit/base. Large files will need large indices, which substantially cuts into the claimed high density of the system since oligo synthesis has relatively hard limits on synthesized strand length. Other codecs which do not use a binary index will have a significant advantage in overall capacity and density. It's possible that I've misunderstood some aspect of how indices are assigned and used in this codec, so it would be good for this aspect of the paper to be improved. + +<|ref|>text<|/ref|><|det|>[[115, 747, 882, 845]]<|/det|> +Response 11: We thank the reviewer for the comment. The reviewer suggested that: 1) Incorporation of index will decrease the coding density to 1 bit/base; 2) Indices for large file could be enormous and might further reduce the information density; 3) Other coding schemes avoiding the use of binary index have advantage in the overall capacity and density. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 143, 883, 352]]<|/det|> +For the first suggestion, we think there might be some misunderstanding about indices assignment. As the reviewer concluded, if a file is partitioned into \(2^{\wedge}k\) segments and each one is labeled with a unique binary index, the index length will be k. The index will be attached to the partitioned binary segment as a new segment (information + index) before encoding corporation. Therefore, for the k nucleotides representing index, they are the corporation product of two indices, which means each nucleotide will encode 2 bits of the indices' information at most rather than 1 bit/base. We understand that k nucleotide will give \(4^{\wedge}k\) possible sequences, but coding density refers to (total information / total base), rather than (total information / possible choices). + +<|ref|>text<|/ref|><|det|>[[114, 361, 883, 590]]<|/det|> +For the second suggestion, we agree with the reviewer that large files indeed need more indices only if the configuration and parameters remain defined. However, there are many alternative choices other than index itself for the application of DNA storage. For example, flanking region usually has a length of 16- 20 nucleotides for PCR amplification. And according to Organick et al., 2018, random access of DNA storage using flanking region can be one of the examples to expand the indexing. In addition, as the DNA synthesis technology keeps advancing, the length of synthetic DNA can be further increased to maintain a relatively high level of information density. In addition, using artificial data coding chromosome for storage further demonstrate the feasibility of reducing the number of indices and leads to a significant increase of coding capacity. + +<|ref|>text<|/ref|><|det|>[[114, 600, 883, 787]]<|/det|> +For the third suggestion, according to Shannon's information theory, there will be always overheads to record the addresses, or indices. For electrical devices, the address is the physical position of the spot, while for DNA storage the address is the index sequence. DNA fountain does not directly use a binary index. However, recording random seeds for segment trace- back can be also considered as indexing. Therefore, binary indices, or other forms for recording address, are indispensable elements especially for massive data storage by DNA. And in our study, we have demonstrated that YYC shows superior performance of information density in both in vitro and in vivo storage. + +<|ref|>sub_title<|/ref|><|det|>[[116, 797, 290, 817]]<|/det|> +## Major Suggestions + +<|ref|>text<|/ref|><|det|>[[116, 818, 883, 858]]<|/det|> +1. The paper makes a strong claim about density that needs to be clarified. As mentioned earlier, the work does not explain well how indices are handled (as + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 883, 347]]<|/det|> +mentioned previously in my review), but the indices appear to achieve no better than a binary encoding (1 bit /base) density. One implication of this is that a high- density encoding is somewhat reliant on having small indices, which implies small file sizes and small capacity overall. This is an undesirable result for what should be a dense medium. Another implication of this is that the total capacity of the system (total unique strands) appears to be lower than those systems that achieve ternary indices, for example. While the claimed figures of merit for density are high, they hide the fact that the total capacity of a pool of DNA may be severely negatively impacted by binary indices. I would like to see a better explanation of how indices are handled and the effect this has on pool capacity. + +<|ref|>text<|/ref|><|det|>[[115, 365, 883, 641]]<|/det|> +Response 12: We thank the reviewer for the comment. As described in response 11, the coding density refers to (total information / total base), rather than (total information / possible choices). Therefore, if one nucleotide encodes two binary digits of two different indices, the information density is 2 bits/base. In previous studies including Erlich et al., 2017, the density can be calculated in different ways. The coding potential (or information density) usually refers to (information stored/bases used to store information only). The coding density (or net information density) refers to (information stored/total bases used for information, indices, error- correction and flanking region). The physical density is related to experimental validation and refers to (information stored/total mass of DNA used). In this work, we used the consistent definition to calculate the information density. We believed that the 'pool capacity' the reviewer mentioned might refers to coding density (or net information density). Based on this, we have provided the statement of how indices would affect pool capacity and give some possible solution. + +<|ref|>text<|/ref|><|det|>[[115, 640, 882, 680]]<|/det|> +we have revised the effect of indices on pool capacity accordingly in the main text highlighted on page 6 (line 179 - 182). + +<|ref|>text<|/ref|><|det|>[[115, 697, 882, 820]]<|/det|> +2. The capabilities of the YYC codec with respect to the variety of mapping tables is not well justified. It's not clear that the ability to select one of the 1536 configurations actually helps or not. The work claims to leverage a combinatoric scheme, but that is not demonstrated through an experiment, except to some degree in the small one that analyzes strands with large fractions of 0 or 1 to see if any mapping tables can encode them satisfactorily. + +<|ref|>text<|/ref|><|det|>[[115, 819, 882, 860]]<|/det|> +To really demonstrate the advantage of all these combinations, several things need to be shown. (1) That having a choice among mapping tables is helpful and leads + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 883, 325]]<|/det|> +to less overhead as compared to DNA Fountain. (2) That the choice of mapping table can be made efficiently. It would be interesting to report the number of failed attempts at selecting segments and encoding them. (3) That the overhead of holding the choice of mapping table in meta- data is a reasonable cost, even if done electronically. If a mapping table selection needs to be remembered per strand, then that implies approximately 11 bits of overhead per segment- pair, which for an exabyte scale system would add up to a very large cost. If it only needs to be remembered per file, it's a lower meta- data cost but higher compute cost to find a mapping. These trade- offs need some further explanations. + +<|ref|>text<|/ref|><|det|>[[115, 327, 882, 366]]<|/det|> +If this analysis is prohibitive to conduct, then I would suggest softening the claims over how useful these tables are. + +<|ref|>text<|/ref|><|det|>[[115, 386, 700, 404]]<|/det|> +Response 13: We thank the reviewer for the instructive comment. + +<|ref|>text<|/ref|><|det|>[[115, 405, 882, 698]]<|/det|> +First of all, we would like to clarify that the 1536 coding schemes of YYC offer alternative choices for encoding process, meaning it is not mandatory requirement to use all coding schemes in one case, and therefore the 11 bits of overhead is not for each segment- pair. We have demonstrated in the Response #5 that the 1536 coding schemes can generate significantly different DNA sequences. Thus, it offers one of the advantages that for an individual arbitrary file, we can always find some scheme(s) that can generate higher information density than others (Table S4). We performed a benchmarking test by encoding different files using all the 1,536 coding schemes. As described in the Response #7, we counted the iteration runs of these coding schemes on encoding 1 GB of data by all the 1,536 coding schemes. The incorporation failure rate for segment pairing over 100 iteration runs is only at \(0.002\%\) . In our previous study, we also performed some benchmarking tests on encoding and decoding efficiency (https://doi.org/10.1101/2020.01.02.892588), showing that the transcoding overheads of YYC is less than that of DNA fountain, YYC is 2- 7 times faster. + +<|ref|>text<|/ref|><|det|>[[115, 700, 882, 855]]<|/det|> +For the efficiency of trail- and- error iteration, as we described in the Response #5 and 7, we performed the evaluation of average iteration run required by transcoding ten different formats of files and have shown that the average number from 1 to 7 trails (Table S3). We further took the reviewer's suggestion and conducted further analysis by estimating the total number of trails while encoding the 1 GB data collection used in our study for in silico simulation. As shown in Fig. S4a, in general, \(65\%\) of the segment can be successfully incorporated with another segment with a single run of trail, and for files with balanced byte frequency, the percentage further increase to + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 882, 203]]<|/det|> +\(\sim 77\%\) (Fig. S4b). From our observation, less than \(0.3\%\) of segments requires more than 10 runs of trail. Our results imply that for an arbitrary file, YYC encoding would not cost a large encode- time overheads. + +<|ref|>text<|/ref|><|det|>[[114, 220, 882, 546]]<|/det|> +3. It's surprising that DNA Fountain does so poorly in the in silico experiment (Figure 2). I agree with the general arguments that DNA Fountain will have high degree packets that include many segments. However, I'm not convinced this is the entire answer unless DNA Fountain mostly selects high degree packets. Also, some important information is missing in this analysis. It appears that no error correction is used. In that case, what is done with strands that have insertions, deletions, and substitutions? Without error correction support, such problems cannot even be detected much less corrected. So, are they treated as correct and allowed to pollute the file with errors? This raises questions about how the DNA Fountain approach is utilized. Is the DNA Fountain code base used for this analysis? If so, is it possible that something is going wrong in how it handles these errors? For example, since segments are more likely repeated in multiple high degree packets, it may be detecting errors and throwing them out, whereas YYC has no such detection capability. Instead, YYC may be making a best-effort attempt to keep the data. More details of how this analysis is conducted are needed to fully explain DNA Fountain's poorer behavior. + +<|ref|>text<|/ref|><|det|>[[114, 563, 882, 819]]<|/det|> +Response 14: We thank the reviewer for the comment. The reviewer suggests that DNA fountain may have no bias on generating high degree packets. For fountain code itself and balanced byte frequency data pattern, high degree packets and low degree packets should share equal odds to be selected. However, our observation is that the screening step of DNA Fountain offers an increased chance to pass the screening for high degree packets. We performed a few tests to encode different files using DNA Fountain with and without screening to estimate the corresponding ratio of high degree packets (as the figure R2 shown below). We used a bmp image (united nation flag) and its zip-compressed package as test file. For zip file, of which the byte frequency is balanced (upper), there was no significant difference with screening (middle). However, for the original bmp image itself, it turned out that among the encoded files with screening, the degree of packets generated is significantly biased without screening. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 145, 790, 556]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 560, 880, 594]]<|/det|> +
Figure R2. Distribution of degree of packets generated by DNA fountain with/without screening (For review usage only)
+ +<|ref|>text<|/ref|><|det|>[[114, 610, 883, 828]]<|/det|> +The second suggestion from the reviewer is that error- correction code should be used in the in- silico test. As described in the Response #9, error correction codes, such as Reed- Solomon code used in our study, can be used as one of the function modules in the whole DNA storage process to improve the robustness for all coding schemes, but the improvement is within limited range. The reason is that current error- correction code is capable of correcting substitution errors but not insertion and deletion errors. For almost all known coding schemes including DNA Fountain and YYC, the sequence with indels cannot be corrected and is discarded before decoding. This is also the reason why error- correction code cannot improve the robustness of DNA fountain significantly. In our experimental validation, we encoded files using the original package provided by Erlich et al. with error correction code applied. The + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 882, 184]]<|/det|> +result is consistent with in- silico simulation and proved our point of view. We have revised accordingly in the manuscript on page 9 (line 250- 258). + +<|ref|>sub_title<|/ref|><|det|>[[115, 202, 291, 221]]<|/det|> +## Minor Suggestions + +<|ref|>text<|/ref|><|det|>[[115, 222, 882, 302]]<|/det|> +1. Perhaps add a brief explanation for a few things in the thermodynamic screening, such as at what temperature was the simulated free energy screening conducted? And, what other parameters were used, if any? Why did you pick -30 kcal/mol as the cutoff? + +<|ref|>text<|/ref|><|det|>[[115, 323, 882, 443]]<|/det|> +Response 15: We thank the reviewer for the comment. The thermodynamic screening cut- off is defined based on previous studies (Noguera et. al., 2014 and Yilmaz et. al., 2004). The free energy cutoff for probe design was set as - 13 kcal/mol for \(\sim 20\) nt DNA sequence, and considering the length of data coding DNA at 160nt, we adjusted the cutoff to - 30 kcal/mol. We have revised the manuscript accordingly to further clarify on page 18 (line 515 to 517). + +<|ref|>text<|/ref|><|det|>[[115, 462, 882, 504]]<|/det|> +2. In the text regarding in vitro experiments, please make it clear which encoding was used for each pool. I think P2 and P3 were done using DNA Fountain. + +<|ref|>text<|/ref|><|det|>[[115, 522, 882, 563]]<|/det|> +Response 16: We thank the reviewer for the comment. we have revised this accordingly in the main text highlighted on page 10 (line 296 - 302). + +<|ref|>text<|/ref|><|det|>[[115, 582, 882, 682]]<|/det|> +3. On Page 9, line 242-244, it says that loss of one strand in YYC can lead to the loss of two segments. This is true. But, isn't it possible that a segment is repeatedly selected for pairing due to some good pattern in its data, decreasing the odds it is lost? Or, do you prevent selecting the same sequence many times? Thank you for an interesting paper. + +<|ref|>text<|/ref|><|det|>[[115, 704, 882, 860]]<|/det|> +Response 17: We thank the reviewer for the instructive comment and recognition of our work. We agree with the reviewer that repeated priority selection of segment with "good" pattern will increase the success rate of pairing. However, it will decrease the overall bit- to- base information density. In our study, we select each segment once and only once for the segment pairing process. The key difference between YYC and DNA Fountain is the segment incorporation strategy applied. For YYC each incorporation only involves two segments, so the loss of one segment will only affect the corresponding paired segment. However, for DNA Fountain the loss of one + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 883, 204]]<|/det|> +segment will affect all related paired segment. We have proven that without repeated selection of "good" pattern segments, YYC can greatly decrease the decoding failure caused by segment loss comparing to DNA Fountain. + +<|ref|>text<|/ref|><|det|>[[115, 256, 360, 272]]<|/det|> +Decision Letter, second revision: + +<|ref|>text<|/ref|><|det|>[[115, 312, 640, 455]]<|/det|> +Date: 8th February 22 17:18:31 Last Sent: 8th February 22 17:18:31 Triggered By: Ananya Rastogi From: ananya.rastogi@nature.com To: shenyue@genomics.cn CC: computationalscience@nature.com Subject: AIP Decision on Manuscript NATCOMPUTSCI- 21- 0438B Message: Our ref: NATCOMPUTSCI- 21- 0438B + +<|ref|>text<|/ref|><|det|>[[232, 464, 372, 479]]<|/det|> +8th February 2022 + +<|ref|>text<|/ref|><|det|>[[232, 492, 344, 506]]<|/det|> +Dear Dr. Shen, + +<|ref|>text<|/ref|><|det|>[[232, 518, 878, 616]]<|/det|> +Thank you for submitting your revised manuscript "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" (NATCOMPUTSCI- 21- 0438B). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Computational Science, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[232, 629, 854, 685]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>sub_title<|/ref|><|det|>[[232, 699, 450, 712]]<|/det|> +## TRANSPARENT PEER REVIEW + +<|ref|>text<|/ref|><|det|>[[232, 712, 880, 852]]<|/det|> +Nature Computational Science offers a transparent peer review option for new original research manuscripts submitted from 17th February 2021. We encourage increased transparency in peer review by publishing the reviewer comments, author rebuttal letters and editorial decision letters if the authors agree. Such peer review material is made available as a supplementary peer review file. Please state in the cover letter 'I wish to participate in transparent peer review' if you want to opt in, or 'I do not wish to participate in transparent peer review' if you don't. Failure to state your preference will result in delays in accepting your manuscript for publication. Please note: we allow redactions to authors' rebuttal and reviewer comments in the interest of confidentiality. If you are concerned about the release of confidential data, + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[232, 144, 882, 230]]<|/det|> +please let us know specifically what information you would like to have removed. Please note that we cannot incorporate redactions for any other reasons. Reviewer names will be published in the peer review files if the reviewer signed the comments to authors, or if reviewers explicitly agree to release their name. For more information, please refer to our FAQ page. + +<|ref|>text<|/ref|><|det|>[[232, 241, 835, 271]]<|/det|> +Thank you again for your interest in Nature Computational Science Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[232, 283, 305, 298]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[232, 311, 459, 353]]<|/det|> +Ananya Rastogi, PhD Associate Editor Nature Computational Science + +<|ref|>text<|/ref|><|det|>[[232, 366, 879, 464]]<|/det|> +ORCID IMPORTANT: Non- corresponding authors do not have to link their ORCIDs but are encouraged to do so. Please note that it will not be possible to add/modify ORCIDs at proof. Thus, please let your co- authors know that if they wish to have their ORCID added to the paper they must follow the procedure described in the following link prior to acceptance: https://www.springernature.com/gp/researchers/orcid/orcid- for- nature- research + +<|ref|>text<|/ref|><|det|>[[232, 476, 520, 491]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[232, 504, 772, 519]]<|/det|> +The authors addressed all my comments and the paper can be accepted. + +<|ref|>text<|/ref|><|det|>[[232, 545, 520, 560]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[232, 573, 855, 602]]<|/det|> +Thank you very much for the revisions and responses. You included some very nice analysis. Overall, they satisfy my concerns. I recommend acceptance. + +<|ref|>text<|/ref|><|det|>[[232, 614, 875, 726]]<|/det|> +I think there may be yet some misunderstanding between us about how indices are represented. I agree that you encode 2 bits per base for the indices. But, your approach appears to limit the total number of possible indices that fit into those k bases (k bases used for the index). This concerns me because it architecturally limits the pool capacity of the system. By pool capacity, I'm referring to the total amount of data in bytes that can be stored in the archive if this technique is employed. However, even if what I say is true, as you point out in your response, you can make up for it elsewhere with flanking primers, etc. So, I'm fine to accept the paper. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 144, 368, 160]]<|/det|> +Author Rebuttal, second revision: + +<|ref|>text<|/ref|><|det|>[[115, 199, 327, 218]]<|/det|> +Reviewer's comments: + +<|ref|>sub_title<|/ref|><|det|>[[115, 230, 492, 251]]<|/det|> +## Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 262, 861, 303]]<|/det|> +Thank you very much for the revisions and responses. You included some very nice analysis. Overall, they satisfy my concerns. I recommend acceptance. + +<|ref|>text<|/ref|><|det|>[[114, 314, 880, 484]]<|/det|> +I think there may be yet some misunderstanding between us about how indices are represented. I agree that you encode 2 bits per base for the indices. But, your approach appears to limit the total number of possible indices that fit into those k bases (k bases used for the index). This concerns me because it architecturally limits the pool capacity of the system. By pool capacity, I'm referring to the total amount of data in bytes that can be stored in the archive if this technique is employed. However, even if what I say is true, as you point out in your response, you can make up for it elsewhere with flanking primers, etc. So, I'm fine to accept the paper. + +<|ref|>text<|/ref|><|det|>[[114, 525, 872, 694]]<|/det|> +Response 1: We thank the reviewer for the significant help in improving our work. It is true that large files indeed need more indices, but there are many other approaches can be applied to expand the indexing. As we mentioned in our previous point- by- point reply, the application of flanking primer is just one of the choices. Also, as relative technologies keep advancing, increasing the length of DNA that encodes digital data can actually decrease the need of total indices number. Due to the word limit, we include a brief discussion in the Discussion section in the main text as highlighted at page 10, line 315- 318. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 162, 275, 178]]<|/det|> +Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[115, 200, 444, 288]]<|/det|> +Date: 18th March 22 17:19:05 Last Sent: 18th March 22 17:19:05 Triggered By: Ananya Rastogi From: ananya.rastogi@nature.com To: shenyue@genomics.cn + +<|ref|>text<|/ref|><|det|>[[144, 293, 842, 326]]<|/det|> +Subject: Decision on Nature Computational Science manuscript NATCOMPUTSCI- 21- 0438C Message: Dear Dr Shen, + +<|ref|>text<|/ref|><|det|>[[232, 337, 852, 381]]<|/det|> +We are pleased to inform you that your Article "Towards Practical and Robust DNA- Based Data Archiving Using 'Yin- Yang Codec' System" has now been accepted for publication in Nature Computational Science. + +<|ref|>text<|/ref|><|det|>[[232, 392, 867, 435]]<|/det|> +In approximately 10 business days you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. + +<|ref|>text<|/ref|><|det|>[[232, 447, 866, 545]]<|/det|> +Please note that Nature Computational Science is a Transformative Journal (TJ). 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If you have any questions please click here.\*\* + +<--- Page Split ---> diff --git a/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/images_list.json b/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..49daf2c8e8bf2df20480e05f6022e7140db5dade --- /dev/null +++ b/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,100 @@ +[ + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure R1 (Figure 2(c) in the main text). Measured (step horz curves) and calculated", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Figure R2 (Figure 5 in the main text). Intermolecular stretching of the N2-Ar dimer. a Reconstructed (blue curve) and calculated (red curve) time-dependent intermolecular stretching of the \\(\\mathrm{N}_2\\) -Ar dimer. b Power spectra of the reconstructed and calculated intermolecular stretching. c The energy levels are grouped by the approximate quantum numbers \\((j, J)\\) . The energy gaps related to the frequencies of rotation of \\(\\mathrm{N}_2\\) and intermolecular stretching are marked by red and green arrows, respectively.", + "footnote": [], + "bbox": [ + [ + 152, + 204, + 850, + 558 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R3. a Time evolution of the probability distribution of N₂-Ar for the distance between the atom and the center of mass of the N₂ molecule. b Same as a but for CH₃I-He.", + "footnote": [], + "bbox": [ + [ + 192, + 660, + 812, + 825 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_1.jpg", + "caption": "Figure R1 (Supplementary Figure 1) (a) Populations of \\(j\\) -states of eigenstates (b) Same as (a) but for the \\(L\\) -states. (c) Radical distributions along the stretch coordinate \\(r\\) of eigenstates. The eigenstates (Fig. 5(c) in the manuscript) are assigned by approximate quantum numbers (n, j, L) according to the nodes in the stretch coordinate \\(r\\) , and the most populated components of \\(j\\) and \\(L\\) .", + "footnote": [], + "bbox": [ + [ + 150, + 275, + 848, + 430 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Figure R2 (Figure 5 in the main text). Intermolecular stretching of the \\(\\mathbf{N}_2\\) -Ar dimer. a Reconstructed (blue curve) and calculated (red curve) time-dependent intermolecular stretching of the \\(\\mathbf{N}_2\\) -Ar dimer. b Power spectra of the reconstructed and calculated intermolecular stretching. c The energy levels, with the even parity \\(p = (-1)^{J + L + J}\\) and \\(J\\) \\(= 4\\) , are grouped by the approximate quantum numbers \\((n,j,L)\\) . The energy gaps related to the frequencies of rotation of \\(\\mathbf{N}_2\\) and intermolecular stretching are marked by red and green arrows, respectively.", + "footnote": [], + "bbox": [ + [ + 152, + 92, + 852, + 450 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R3. Calculated alignment traces of Ar-axis of \\(\\mathrm{N}_2\\) -Ar and \\(\\mathrm{Ar}_2\\) by the rigid model", + "footnote": [], + "bbox": [ + [ + 150, + 680, + 848, + 880 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure R3. Contour plot of potential energy surface for \\(\\mathrm{N}_2\\) -Ar [J. Chem. Phys. 121, 10419 (2004)]. Geometries are given in Å and degrees, and energies in \\(\\mathrm{cm}^{-1}\\) .", + "footnote": [], + "bbox": [ + [ + 293, + 102, + 666, + 286 + ] + ], + "page_idx": 26 + } +] \ No newline at end of file diff --git a/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b08278f01a2877ea6f271b2f6faf64ec87a95dc1 --- /dev/null +++ b/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,643 @@ + +# nature portfolio + +Peer Review File + +Intermolecular interactions probed by rotational dynamics in gas- phase clusters + +![](images/Figure_2.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Dear Editor, please find here enclosed my review of the manuscript entitled "Intermolecular interactions probed by rotational wavepackets in gas- phase clusters", submitted for publication in Nature Comm. + +This work investigates the experimental control of molecular rotation of \(\Phi \mathrm{N}_2\Phi\) molecules subjected to interaction with \(\Phi \mathrm{Ar}\Phi\) atoms. They observe that the alignment decays rapidly due to this interaction. They show that the decay rate depends on the relative position of \(\Phi \mathrm{Ar}\Phi\) atoms with respect to the molecular axis. Numerical simulations illustrate these experimental observations. + +Quantum control is currently a subject of increasing interest in chemistry, physics and mathematics but also for the development of quantum technologies. In this context, the control of molecular rotation is a well- established topic in molecular physics with a variety of applications extending from high harmonic generation to chemical reactivity. This paper focuses on the interaction of aligned molecules with their environment. The proposed method and the results are interesting. To the best of my knowledge, the investigation is original. I am not an experimentalist so I cannot directly judge the relevance of the experimental results. This paper seems sound numerically although I have some doubts about the model system used to reproduce the experimental results. + +Here is a series of questions about experiment modeling. The authors describe the quantum system as a pure state. This case corresponds to zero temperature. What is the experimental temperature of the supersonic gas jet? For a non- zero temperature, the system must be described by a density operator. What is the impact of this approximation? The authors consider the interaction of \(\Phi \mathrm{N}_2\Phi\) molecules with one or two \(\Phi \mathrm{Ar}\Phi\) atoms. Here again, how to justify this approximation when each \(\Phi \mathrm{N}_2\Phi\) molecule should interact with many atoms. In the literature, the interaction of linear molecules with its environment was described by a Redfield equation (see (1,2) for instance). Can this modeling be used in the case of this paper? This Redfield description also leads to a rapid degradation of molecular alignment. What are the advantages of direct modeling of molecule- atom interaction? + +\(\backslash (1)\) - M. Bournazel et al., \`emph\{Non- Markovian collisional dynamics probed with laser- aligned molecules\}, Phys. Rev. A \`textbf\{107\}, 023115 (2023)\}(2)- T. Viellard et al., \`emph\{Field- free molecular alignment for probing collisional relaxation dynamics\}, Phys. Rev. A \`textbf\{87\}, 023409 (2013) + +Reviewer #2 (Remarks to the Author): + +The manuscript "Intermolecular interactions probed by rotational wavepackets in gas- phase clusters" by Lu et al explores an internal- rotation wavepacket in N2- Ar to probe the dynamics, and potentially coupling, of large- amplitudes internal modes of the molecular system. + +Generally, this is a nice experiment that could likely deserves publication in Nat. Comm. following significant clarifications and improvements, mostly regarding the analysis but also with respect to experimental results on the overall rotation of the molecular system. + +Firstly, I am wondering if there is no overall- rotation dynamics induced in the N2- Ar system by the kick pulse? Obviously, this would be at longer timescales, but should be observable both in the experiment as well as the computations performed by the authors. + +<--- Page Split ---> + +Second, I fear in light of \(>50\) years of spectroscopic studies of floppy molecules and molecular clusters, the semantic description does not do justice to the problem. That is, the N2- Ar system has 3 low- frequency/large amplitude internal "intermolecular" vibrational modes, build up from the lost 3 degrees of translational freedom of the constituents, in addition to the N2 stretch and the overall rotation of the system. The authors use a cumbersome description of this, in which the N2- Ar stretch does not seem to occur at all and the two other (internal bending) modes are described as simple, maybe too simple, "perturbed 1D N2 rotations". + +Here, it is clear that these motions are coupled, esp. the various internal degrees of freedom and the overall rotation of the cluster. In fact, in an extremely simplified model the authors derive exactly the first glimpses of that. + +Moreover, it seems the overall N2- Ar stretch of the cluster was "forgotten" in the analysis? Is that justified by any means, i.e., what's the energy gaps and the coupling strengths of this mode to the internal rotations and to the overall rotation? + +I also wonder why the degree of alignment even for N2 itself is so low. Possibly this is due to a relatively large (rotational) temperature (?) What's the explanation of the authors? + +In that light and in any case, it is important to understand the "vibrational" temperature for the low- frequency modes of the cluster and in how far the modes are thermally excited before the kick pulse. + +Conceptionally, when comparing the out- of- plane and the in- plane rotation of the N2 in the N2- Ar dimer, how strongly are these modes coupled - to each other, to and via the intermolecular N2- Ar stretch, and via the overall rotation? Is it appropriate to discuss the results in such one- dimensional models as done in this manuscript? + +Are the energies of the relevant (populated) eigenstates in the wavepackets in fact bound states, barrier- modulated above- barrier states, or "free" above- barrier states? + +In fact, this question is relevant for both the initially populated states ("temperature") above and the kick- initiated populations. + +What's the polarizability anisotropy/tensor of the cluster and how does that change as a function of the intermolecular geometry? On the one hand, this would provide first hints at the overall- rotation dynamics induced by the kick as well as the coupling between internal modes and between internal modes and overall rotation. + +When comparing N2 rotational dynamics to the 1D- internal- rotation dynamics the reduction of dimensionality (1D to 2D) likely needs to be taken into account. + +To me, and in light of the very rich set of descriptions the simple model utilized by the authors does not seem to be appropriate. In + +fact, an analysis of the "intermolecular interactions probed by rotational wavepackets" would be highly appreciated and useful - if + +actually analyzed and described in the long- standing and proven models of intermolecular + +interactions. In the simple system + +presented here, that would require a 6D description (3 degrees of overall rotation and 3 degrees of intermolecular vibrations/internal + +rotations). This is clearly possible, both semantically as well as computationally. + +<--- Page Split ---> + +One of the important points to clarify is which of all these modes are actually directly Raman- excited in the experiment. + +Moreover, here it is really important to clarify also experimentally both the intermolecular stretch as well as the overall rotation - and their corresponding interaction with the internal rotations (same for thermal excitations of all these modes). + +The authors should also consider to refer to previous alignment experiments of floppy molecules and clusters, which is really what they are following up on here, e.g., PRL 102, (2009); JCP 148, 101103 (2018); PCCP 22, 3245- 3253 (2020), ... + +In the experimental section, how does a 7:3 splitting of the laser beam lead to intensities that differ by 2 orders of magnitude? Different focusing? Specify. Generally, some more details on the actual experiment should be provided in Methods. + +Also, details of the implementation of the computational approach by Zillich should be described. + +Re I. 117: No, (N2)- Ar axis motion can be internal rotation as well as overall rotation... + +/j/ is a "1D internal rotation" quantum number and should be treated as such. + +In the simulations: When the molecule is so floppy, why is it appropriate to use a single reduced mass \(\mu\) - instead of a coordinate/geometry depended one? + +Which pulse intensity and rotational temperature do the simulations yield? + +The N2- Ar2 cluster seems to be un- analyzed and superfluous. It's a nice experiment, but it does not provide any information in the current paper. Either leave away or clarify what you learn from this data. + +I. 148: "rotational deceleration of N2 induced by 149 the neighboring Ar in time domain" - is this actually a deceleration or simply a "slower dynamics"? Or is this simply a first dim hint at the coupling of various modes (vide supra)? + +Overall, to me this work requires very significant improvements, but I am looking forward to see this then published Nat. Comm. + +<--- Page Split ---> + +For clarity, we put the original comments in italics to distinguish them from our responses in blue. The text that has been changed or newly added is in red. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Dear Editor, please find here enclosed my review of the manuscript entitled "Intermolecular interactions probed by rotational wavepackets in gas- phase clusters", submitted for publication in Nature Comm. + +This work investigates the experimental control of molecular rotation of \(N_{2}\) molecules subjected to interaction with Ar atoms. They observe that the alignment decays rapidly due to this interaction. They show that the decay rate depends on the relative position of Ar atoms with respect to the molecular axis. Numerical simulations illustrate these experimental observations. + +Quantum control is currently a subject of increasing interest in chemistry, physics and mathematics but also for the development of quantum technologies. In this context, the control of molecular rotation is a well- established topic in molecular physics with a variety of applications extending from high harmonic generation to chemical reactivity. This paper focuses on the interaction of aligned molecules with their environment. The proposed method and the results are interesting. To the best of my knowledge, the investigation is original. I am not an experimentalist so I cannot directly judge the relevance of the experimental results. This paper seems sound numerically although I have some doubts about the model system used to reproduce the experimental results. + +Here is a series of questions about experiment modeling. The authors describe the quantum system as a pure state. This case corresponds to zero temperature. What is the experimental temperature of the supersonic gas jet? For a non- zero temperature, the system must be described by a density operator. What is the impact of this approximation? + +## Reply #1: + +In the experiment, the rotational temperatures of \(\mathrm{N}_{2}\) and \(\mathrm{N}_{2}\) - Ar are estimated to be 11 K and 7 K, respectively. + +To make it clear to readers, we have added the following sentences in the Methods: + +"The initial temperatures of \(\mathrm{N}_{2}\) and \(\mathrm{N}_{2}\) - Ar are estimated to be 11 K and 7 K, respectively, by approximation to their translational temperatures of \(T_{\mathrm{trans}} = \Delta p^{2} / [4\ln (4)k_{\mathrm{BM}}]\) [see Phys. Rev. Lett. 90, 233003 (2003); J. Chem. Phys. 118, 8699 (2003); Phys. Rev. A 83, 061403(R) (2011)], where \(k_{B}\) is the Boltzmann constant, and \(\Delta p\) and \(m\) are the full width + +<--- Page Split ---> + +at half maximum (FWHM) of the momentum distribution in the jet direction (Y- axis in our case) and mass of the singly ionized molecules of \(\mathrm{N}_{2}^{+}\) and \(\mathrm{N}_{2} - \mathrm{Ar}^{+}\) . In our experiment, we measure \(\Delta p \sim 3.2\) a.u. and \(\Delta p \sim 4.0\) a.u. for \(\mathrm{N}_{2}^{+}\) and \(\mathrm{N}_{2} - \mathrm{Ar}^{+}\) ions. The excellent agreement with the experiment is achieved in the simulation when using \(T = 9 \mathrm{~K}\) for isolated \(\mathrm{N}_{2}\) and \(T = 7 \mathrm{~K}\) for \(\mathrm{N}_{2} - \mathrm{Ar}\) molecule. (on page 11 line 263) + +In our simulation, the initial state is populated according to the measured temperature rather than 0. We also iterate the values used in simulation by comparing the simulation results with the measured alignment trace. + +Specifically, we obtain the time- dependent expectation value, \(\langle A\rangle_{i}(t) = \langle \Psi_{i}(t)|A|\Psi_{i}(t)\rangle\) for an initial state with the energy of \(E_{i}\) , where \(\Psi_{i}(t)\) is the time- dependent wave function for the \(i\) - th initial state. Subsequently, we consider thermal effects by averaging the expectation value over the different initial states with the relative weights given by the Boltzmann distribution, + +\[\langle A\rangle (t) = \frac{\Sigma_{i}\exp\left(-\frac{E_{i}}{k_{B}T}\right)\langle A\rangle_{i}(t)}{\Sigma_{i}\exp\left(-\frac{E_{i}}{k_{B}T}\right)},\] + +where \(k_{B}\) is the Boltzmann constant and \(T\) is the temperature. + +Considering the high coupling of the entire system (only the total angular momentum \(J\) and its projection \(N\) are good quantum numbers in field- free case), we use a collective temperature \(T\) to describe the system [J. Chem. Phys. 149, 124301 (2018)]. The excellent agreement with the experiment is achieved when using \(T = 9 \mathrm{~K}\) for isolated \(\mathrm{N}_{2}\) and \(T = 7 \mathrm{~K}\) for \(\mathrm{N}_{2} - \mathrm{Ar}\) molecule, which are in good agreement with the measurement. + +The authors consider the interaction of \(N_{2}\) molecules with one or two Ar atoms. Here again, how to justify this approximation when each \(N_{2}\) molecule should interact with many atoms. In the literature, the interaction of linear molecules with its environment was described by a Redfield equation (see (1,2) for instance). Can this modeling be used in the case of this paper? This Redfield description also leads to a rapid degradation of molecular alignment. What are the advantages of direct modeling of molecule- atom interaction? + +(1)- M. Bournazel et al., Non- Markovian collisional dynamics probed with laser- aligned molecules, Phys. Rev. A 107, 023115 (2023) (2)- T. Viellard et al., Field- free molecular alignment for probing collisional relaxation dynamics, Phys. Rev. A 87, 023409 (2013) + +## Reply #2: + +In this work, we focus on the interaction of the \(\mathrm{N}_{2}\) molecule with only one Ar atom both in the experiment and simulation. Although the interaction of the \(\mathrm{N}_{2}\) molecule with two Ar atoms is also measured in the experiment, we cannot simulate such case using our current code. In our work, the molecule- atom interaction is the van der Waals force + +<--- Page Split ---> + +formed under low temperature and low pressure, while the molecule- atom interaction in those studies mentioned by the referee is dominated by collisions. + +Those studies were performed in a gas cell with a high pressure and the gas density can be up to a few amagat [e.g., 5 amagat corresponding to the density of \(1.34 \times 10^{26} \mathrm{~m}^{- 3}\) in Phys. Rev. A 107, 023115 (2023)]. In contrast, for the supersonic jet we used, its density was pretty low, typically ranging from \(10^{16}\) to \(10^{18} \mathrm{~m}^{- 3}\) [Phys. Rev. A 68, 023406 (2003); Nat. Phy. 16, 328- 333 (2020)], ensuring neglectable collisions with neighboring atoms and molecules. Molecular alignment for typical linear molecules in this case can persist for more than hundreds of picoseconds [Phys. Rev. A 89, 023432 (2014); Phys. Chem. Chem. Phys 24, 11014 (2022); J. Phys. Chem. A 127, 4848 (2023)]. + +When collisions dominate as the gas density increases, the phenomena can be described by the Bloch- Redfield form of the Liouville- von Neumann equation [J. Chem. Phys. 124, 034101 (2006)]: + +\[\frac{d\rho(t)}{dt} = -\frac{i}{\hbar} [H_0 + H_i(t),\rho (t)] + \left(\frac{d\rho(t)}{dt}\right)_{diss},\] + +where \(\rho (t)\) is the density operator, \(H_0\) is the free rotational Hamiltonian of the rotating molecule, \(H_i(t)\) is the molecule- field interaction term. + +The collision is exhibited as a dissipative term \(\left(\frac{d\rho(t)}{dt}\right)_{diss}\) , including the rates of population transfer and elastic collision- induced dephasing. Since it is theoretically impossible to precisely consider numerous atoms/molecules, the collision is only approximated to be time- dependent in the view of the Redfield description. In our case, of only one atom and one molecule, the molecule- atom interaction provides a more comprehensive description as the radical and angular parts of the system are considered. + +According to the referee's comment, we briefly comment the difference in the manuscript: + +"Different from the case of high gas densities and temperatures where the collisions dominate the molecule- atom interactions [Phys. Rev. A 107, 023115 (2023), Phys. Rev. A 87, 023409 (2013)], we only consider the interaction of a single \(\mathrm{N}_2\) molecule with one Ar atom at low temperatures when the vdW bond is formed." (on page 7 line 175) + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +The manuscript "Intermolecular interactions probed by rotational wavepackets in gasphase clusters" by Lu et al explores an internal- rotation wavepacket in \(N_{2}\) - Ar to probe the dynamics, and potentially coupling, of large- amplitudes internal modes of the molecular system. + +Generally, this is a nice experiment that could likely deserves publication in Nat. Comm. following significant clarifications and improvements, mostly regarding the analysis but also with respect to experimental results on the overall rotation of the molecular system. + +Firstly, I am wondering if there is no overall- rotation dynamics induced in the \(N_{2}\) - Ar system by the kick pulse? Obviously, this would be at longer timescales, but should be observable both in the experiment as well as the computations performed by the authors. + +## Reply #1: + +Firstly, we want to clarify that if there was an overall rotation of the \(N_{2}\) - Ar dimer, the first alignment peak of the van der Waals axis should already appear within the current scanning time range (20 ps). Intuitively, the rotation of \(Ar_{2}\) dimers can be used as a reference because of their comparable rotational constants of \(0.05756 \mathrm{cm}^{- 1}\) and \(0.07 \mathrm{cm}^{- 1}\) for \(Ar_{2}\) and \(N_{2}\) - Ar dimers respectively [Phys. Rev. A 83, 061403(R) (2011); Mol. Phys. 27, 903 (1974)]. + +We have added the following content and a new plot in Fig. 2(c) in the manuscript: + +"...On the other hand, Figure 2(c) shows that the vdW axis between the \(N_{2}\) molecule and the Ar atom, termed as Ar- axis hereafter, hardly responds to the kick. It is worth to mention that our observation window is long enough if the Ar- axis shows an immediate post- pulse alignment. As a reference, the vdW axis of the \(Ar_{2}\) dimer with a similar rotational constant shows a clear alignment peak at \(\sim 3.5\) ps. The drastically different alignment response for the N- N axis and the Ar- axis inside the \(N_{2}\) - Ar dimer from that for isolated \(N_{2}\) molecule and \(Ar_{2}\) dimer indicates that the rotational dynamics can serve as a sensitive probe of the molecule- atom interaction." (on page 5 line 120) + +![](images/Figure_5.jpg) + +
Figure R1 (Figure 2(c) in the main text). Measured (step horz curves) and calculated
+ +<--- Page Split ---> + +(smooth curves) time- dependent alignment trace of the Ar- axis of Ar₂ and N₂- Ar dimers. + +To understand the underlying physics, we performed new simulations by simplifying the N₂- Ar dimer as a rigid asymmetric- top molecule. + +"To understand the underlying physics of the rotational dynamics of the N₂ molecule under the influence from the neighboring Ar atom, we performed rigid and floppy model simulations separately. In the rigid model, the N₂- Ar dimer is treated as a rigid asymmetric- top molecule. On the other hand, the vdW bonding nature of the N₂- Ar dimer is implemented by including the molecule- atom interaction potential in the floppy model, where the dynamics of N₂- Ar dimer is described by the internal rotation of N₂ as \(j\) , overall rotation \(L\) and intermolecular stretching (see Methods). Different from the case of high gas densities and temperatures where the collisions dominate the molecule- atom interactions [Phys. Rev. A 87, 023409 (2013), Phys. Rev. A 107, 023115 (2023)], we only consider the interaction of a single N₂ molecule with one Ar atom at low temperatures when the vdW bond is formed. + +Figure 2 shows the simulation results for both the rigid and floppy models. Although both results can repeat the decayed alignment traces, the rigid one shows alignment peaks mismatched from the measurement while the floppy model quantitatively agrees with the experiment. This indicates that the decayed alignment trace results from irregular energy spacing induced by the very unique asymmetric- top property of the N₂- Ar molecular structure, i.e. the moment of inertia of the Ar- axis differs drastically from the other two axes, as listed in Table. 1. However, such asymmetric- top property cannot fully account for the observed rotational dynamics. Figures 4(c) and (d) show the rotational spectra for the two models, which clearly illustrates that the rigid model fails to describe the influence of the neighboring Ar atom on the rotational energy of the N- N axis. Intuitively, the rigid model overestimates the red- shift because the Ar- axis is considered to completely corotate with the N- N axis which slows down its rotation in return. Only if the vdW interaction between the N₂ molecule and Ar atom is properly implemented in the floppy model, the rotational spectrum can be reproduced. The comparison between the two models unambiguously reveals that the rotational dynamics of N₂ molecule can serve as a sensitive probe of the neighboring environment. When it comes to the rotation of the Ar- axis, the rigid model considering the total polarizability shows a neglectable alignment response comparing with the Ar₂ dimer. Thus, the vanishing alignment of the Ar- axis stems from the large discrepancy in moments of inertia, i.e., approximately 30 times smaller moment of inertia along the Ar- axis than that along the other axes. The laser pulse induces the alignment of the N- N axis through the fast rotation about the Ar- axis. However, the large moments of inertia of the other two axes lead to the neglectable change in the angular velocities of rotation about the other two axes." (on page 7 line 169) + +Second, I fear in light of \(>50\) years of spectroscopic studies of floppy molecules and molecular clusters, the semantic description does not do justice to the problem. That is, the N₂- Ar system has 3 low- frequency/large amplitude internal "intermolecular" vibrational modes, build up from the lost 3 degrees of translational freedom of the + +<--- Page Split ---> + +constituents, in addition to the \(N_{2}\) stretch and the overall rotation of the system. The authors use a cumbersome description of this, in which the \(N_{2}\) —Ar stretch does not seem to occur at all and the two other (internal bending) modes are described as simple, maybe too simple, "perturbed 1D \(N_{2}\) rotations". + +Here, it is clear that these motions are coupled, esp. the various internal degrees of freedom and the overall rotation of the cluster. In fact, in an extremely simplified model the authors derive exactly the first glimpses of that. + +Moreover, it seems the overall \(N_{2}\) - Ar stretch of the cluster was "forgotten" in the analysis? Is that justified by any means, i.e., what's the energy gaps and the coupling strengths of this mode to the internal rotations and to the overall rotation? + +## Reply #2: + +We thank the referee for the instructive question. The vibration or stretching between the \(N_{2}\) molecule and the Ar atom is actually observed in our experimental data, as well as included in our simulation. We have added a new Discussion section and a new Fig. 5 to illustrate this issue. + +"For isolated diatomic molecules, the large discrepancy between the vibrational and rotational energies ensures decoupling between rotation and vibration. The vibration can be treated individually under an identical radial potential, resulting in orthogonal vibration states. However, this assumption does not hold any more when it comes to the \(N_{2}\) - Ar dimer since the radial and angular potential is entangled, i.e. the equilibrium distance between the \(N_{2}\) molecule and Ar atom changes with the relative angle between the Ar- axis and the N- N axis. By assuming the repulsive potential of the two- body fragment channel \(N_{2} - \mathrm{Ar} + n\hbar \omega \rightarrow N_{2}^{+} + \mathrm{Ar}^{+} + 2e\) as a simple Coulomb potential of \(1 / r\) , the intermolecular distance \(r\) as a function of time can be reconstructed. Figure 5(a) shows the expectation value \(< r>\) as a function of time, which indicates strong vibrational excitation. Although only the polarizability of \(N_{2}\) is considered in our floppy model, the simulation result well reproduces the intermolecular stretching and its frequency components, as shown in Figs. 5(a) and (b). This indicates that the intermolecular stretching is excited through the coupling with the internal rotation of the \(N_{2}\) molecule. As marked by the green arrows, states with energy gaps of 15.8 and \(20.2 \mathrm{cm}^{- 1}\) are assigned to the frequency components \(v_{1}\) and \(v_{2}\) , respectively. The superposition of these states results in the observed forth- back stretching in Fig. 5(a). + +Figure 5(c) displays the transition diagram of the ro- vibrational spectra. As the angular part is expanded onto the coupled basis in the floppy model, approximate quantum numbers \((j, J)\) are employed to label the eigenstates, where \(j\) represents the rotational quantum number of the N- N axis \((j\) is not a good quantum number), and only \(J\) is the good quantum number of the total angular momentum \(J = L + j\) . The eigenstates are not assigned to an approximate \(L\) - state because of its broad distribution. As numerous states are involved, for illustration, only several states with \(J = 4\) are + +<--- Page Split ---> + +displayed. For the internal rotation of \(\mathrm{N}_2\) , states with energy gaps of 9.27, 17.84 and \(26.13 \mathrm{cm}^{- 1}\) have been marked by red arrows in Fig. 5(c), which correspond to the observed rotational frequencies in Fig. 4. These frequencies relate to the ones of the \(\mathrm{N}_2\) monomer corresponding to the (0–2), (1–3) and (2–4) transitions. Thus, the red- shift of rotational frequencies results from smaller energy gaps for states of the \(\mathrm{N}_2\) - Ar than the \(\mathrm{N}_2\) monomer.” (on page 8 line 204) + +![](images/Figure_unknown_0.jpg) + +
Figure R2 (Figure 5 in the main text). Intermolecular stretching of the N2-Ar dimer. a Reconstructed (blue curve) and calculated (red curve) time-dependent intermolecular stretching of the \(\mathrm{N}_2\) -Ar dimer. b Power spectra of the reconstructed and calculated intermolecular stretching. c The energy levels are grouped by the approximate quantum numbers \((j, J)\) . The energy gaps related to the frequencies of rotation of \(\mathrm{N}_2\) and intermolecular stretching are marked by red and green arrows, respectively.
+ +I also wonder why the degree of alignment even for \(N_2\) itself is so low. Possibly this is due to a relatively large (rotational) temperature(?). What's the explanation of the authors? + +## Reply #3: + +The reason for the low degree of alignment for \(\mathrm{N}_2\) is we use low intensity \((7 \times 10^{12} \mathrm{W / cm}^2)\) and short duration (50 fs) of the pulse in this work. The temperatures of \(\mathrm{N}_2\) and \(\mathrm{N}_2\) - Ar of the supersonic jet are estimated to be 11 K and 7 K according to their translational temperatures (see Reply #1 of referee1). + +<--- Page Split ---> + +In that light and in any case, it is important to understand the "vibrational" temperature for the low-frequency modes of the cluster and in how far the modes are thermally excited before the kick pulse. + +## Reply #4: + +Considering the high coupling of various modes, we use a collective temperature of \(T = 7 \mathrm{~K}\) to describe the \(\mathrm{N}_{2}\) - Ar system [J. Chem. Phys. 149, 124301 (2018)] through which the initial thermal ensemble is given by the Boltzmann distribution \(P \sim \exp (- E_{j} / k_{B} T)\) with \(2 J + 1\) degeneracy, where \(E_{j}\) is the energy of an eigenstate state with total angular momentum \(J\) . \(87\%\) of thermally populated states are summarized in Table I (in the simulation, \(99.9\%\) of thermally populated states are involved). + +Table I. Thermally populations of eigenstates with \(2J + 1\) degeneracy. The states \((j,J)\) are labeled by the quantum numbers of the angular momentum of \(\mathrm{N}_{2}\) . \(j\) , and total angular momentum, \(J\) + +
(j, J)population(j, J)population
0, 00.005610, 80.03482
0, 10.016371, 80.0423
1, 10.01982, 80.0105
0, 20.02580, 90.03023
1, 20.031221, 90.03681
0, 30.03322, 90.00916
1, 30.040190, 100.02528
2, 30.009841, 100.03064
0, 40.038160, 110.01972
1, 40.046221, 110.02465
2, 40.011340, 120.01539
0, 50.040551, 120.01766
1, 50.04914
2, 50.01208
0, 60.04051
1, 60.04913
2, 60.01212
0, 70.03843
1, 70.04664
2, 70.01154
+ +<--- Page Split ---> + +Conceptionally, when comparing the out- of- plane and the in- plane rotation of the \(N_{2}\) in the \(N_{2}\) - Ar dimer, how strongly are these modes coupled – to each other, to and via the intermolecular \(N_{2}\) - Ar stretch, and via the overall rotation? Is it appropriate to discuss the results in such one- dimensional models as done in this manuscript? + +## Reply #5: + +We agree with the referee that the stronger the internal rotation of the N- N axis and the overall rotation are coupled, the more difficult it will be to distinguish between the in- and out of plane rotation of the internal rotation of N- N axis. We have properly illustrated the overall rotation as well as the stretching issue. To make it clearer, we have added the following sentences in the manuscript: + +"Benefiting from the statistically super weak alignment response of the Ar- axis, we found that the difference between the in- and out- of- plane rotations survives after selecting the relative angle between Ar- axis and the probe plane." (on page 6 line 130) + +Are the energies of the relevant (populated) eigenstates in the wavepackets in fact bound states, barrier- modulated above- barrier states, or "free" above- barrier states? + +In fact, this question is relevant for both the initially populated states ("temperature") above and the kick- initiated populations. + +## Reply #6: + +The initial thermal population has been answered in Reply #4. + +The time- dependent intermolecular distance during and after the laser kick is shown in Fig. R3. If there's any continuous state or above- barrier state, it will lead to increasing of the molecule- atom distance, i.e. dissociation. As a comparison, the above- barrier state of CH3I- He is shown. [J. Chem. Phys. 149, 124301 (2018)]. + +![](images/Supplementary_Figure_1.jpg) + +
Figure R3. a Time evolution of the probability distribution of N₂-Ar for the distance between the atom and the center of mass of the N₂ molecule. b Same as a but for CH₃I-He.
+ +<--- Page Split ---> + +What's the polarizability anisotropy/tensor of the cluster and how does that change as a function of the intermolecular geometry? On the one hand, this would provide first hints at the overall- rotation dynamics induced by the kick as well as the coupling between internal modes and between internal modes and overall rotation. + +## Reply #7: + +The polarizability components of the T- shape \(\mathrm{N}_2\) - Ar are listed in Table II, through which the rigid model is performed. In the floppy model, we only consider the polarizability of the isolated \(\mathrm{N}_2\) molecule, the polarizability components along and perpendicular to + +the molecular axis are set to be \(\alpha_{\parallel} = 2.38 \mathrm{\AA}^3\) and \(\alpha_{\perp} = 1.45 \mathrm{\AA}^3\) , respectively. + +Strictly speaking, the polarizability changes with the \(\mathrm{N}_2\) molecular rotation as well as the stretching. Although we cannot include such complex treatment in our current model, the floppy model still can well reproduce the experimental results, which in return indicates that the dynamical polarizability is not critical here. + +We attribute the success to the following reasons. The 50 fs pulse duration in our experiment is much shorter than the period of internal rotation and intermolecular vibration (magnitude of ps), such that the structure deformation during the pulse duration is not important. An improved model including a geometry- dependent polarizability may be required to describe the case of long kick pulse duration as the referee mentioned [e.g., 1.3 ps in Chem. Phys. Lett., 803, 139850 (2022); Phys. Chem. Chem. Phys. 24, 11014 (2022); 150 ps and 1.3 ps in Phys. Chem. Chem. Phys. 22, 3245 (2020)]. + +Table II. Moments of Inertia and Polarizabilities of the \(\mathrm{N}_2\) - Ar dimer under T- shape configuration. The \(a\) - axis and \(b\) - axis represent the axes parallel to the N- N axis and Ar- axis in the molecular frame, respectively. The \(c\) - axis is perpendicular to the \(a\) - and \(c\) - axes. + +
Moments of Inertia (amu Ų)Polarizability (ų)
Ia = 225.54αaa = 3.71
Ib = 8.47αbb = 3.32
Ic = 234.02αcc = 3.04
+ +When comparing \(N_2\) rotational dynamics to the 1D- internal- rotation dynamics the reduction of dimensionality (1D to 2D) likely needs to be taken into account. + +<--- Page Split ---> + +To me, and in light of the very rich set of descriptions the simple model utilized by the authors does not seem to be appropriate. In fact, an analysis of the "intermolecular interactions probed by rotational wavepackets" would be highly appreciated and useful – if actually analyzed and described in the long- standing and proven models of intermolecular interactions. In the simple system presented here, that would require a 6D description (3 degrees of overall rotation and 3 degrees of intermolecular vibrations/internal rotations). This is clearly possible, both semantically as well as computationally. + +## Reply #8: + +We have explained in Reply #1 and #2. Briefly, we considered internal rotation, overall rotation and intermolecular stretching, while we neglected the vibration between N- N atoms due to its strong interaction + +One of the important points to clarify is which of all these modes are actually directly Raman- excited in the experiment. + +## Reply #9: + +Our experimental results indicate that the internal rotation is directly excited through the polarizability of \(\mathrm{N}_2\) (Reply #19). For the overall rotation, the vanishing alignment stems from the large discrepancy in moments of inertia (Reply #1). The intermolecular vibration can be excited through coupling with the internal rotation (Reply #2). + +Moreover, here it is really important to clarify also experimentally both the intermolecular stretch as well as the overall rotation – and their corresponding interaction with the internal rotations (same for thermal excitations of all these modes). + +## Reply #10: + +We have explained in Reply #1 and #2. + +The authors should also consider to refer to previous alignment experiments of floppy molecules and clusters, which is really what they are following up on here, e.g., PRL 102, (2009); JCP 148, 101103 (2018); PCCP 22, 3245- 3253 (2020), ... + +## Reply #11: + +We have added the following sentences: + +"Recently, investigations on the rotational dynamics of such floppy molecule- atom clusters have been fueled due to their unique properties under the interaction with + +<--- Page Split ---> + +neighboring environment [Phys. Rev. Lett. 102, 023001 (2009); J. Chem. Phys. 148, 101103 (2018); Phys. Chem. Chem. Phys. 22, 3245 (2020)]; J. Phys. Chem. A 127, 4848 (2023); Phys. Rev. A 89, 023432 (2014)]." (on page 3, line 59) + +In the experimental section, how does a 7:3 splitting of the laser beam lead to intensities that differ by 2 orders of magnitude? Different focusing? Specify. Generally, some more details on the actual experiment should be provided in Methods. + +## Reply #12: + +For clarity, we have added the following sentences in the Method: + +"The intensities of them are adjustable using two neutral density filters and a quarter wave plate is placed in the arm of the probe pulse to make it circularly polarized. The probe pulse additionally passed through a telescope which increase its diameter by a factor of 1.5." (on page 11, line 251) + +Also, details of the implementation of the computational approach by Zillich should be described. + +## Reply #13: + +A more detailed description has been added in Method. + +Re l. 117: No, (N2)- Ar axis motion can be internal rotation as well as overall rotation... + +## Reply #14: + +To avoid misleading, we have removed the sentence "For simplicity, we refer to this joint pump probe induced observable as "rotation" ". + +Considering the neglectable alignment of overall rotation (Reply #1), for the rotation dynamics of \(\mathrm{N}_2\) - Ar, only the internal rotation is a good observable, therefore the rotation refers to the alignment of the N- N axis is caused by internal rotation currently. + +/j/ is a "1D internal rotation" quantum number and should be treated as such. + +## Reply #15: + +We have added the description of the floppy model in the revised version. The floppy model considers 3 rotational degrees of freedom and 2 vibrational degrees of freedom, while neglecting the vibration between N- N atoms due to its strong interaction. \(j\) is the + +<--- Page Split ---> + +angular momentum quantum number of the linear molecule. + +In the simulations: When the molecule is so floppy, why is it appropriate to use a single reduced mass \(\mu\) – instead of a coordinate/geometry depended one? + +## Reply #16: + +The reduced mass \(\mu\) is used to represent the relative motion of Ar and \(\mathrm{N}_2\) about their center of mass which is related to the overall rotation and intermolecular stretching. The relative distance (radical part) and rotation (angular part) are responsible for the geometry character of the floppy dimer rather than the reduced mass [J. Chem. Phys. 100, 2505 (1994)]. + +Thus, the reduced mass doesn't depend on the coordinate or geometry. + +Which pulse intensity and rotational temperature do the simulations yield? + +## Reply #17: + +In the simulation, the pulse intensity is set to be \(7 \times 10^{12} \mathrm{~W / cm}^2\) and the initial rotational temperature is set to be \(9 \mathrm{~K}\) and \(7 \mathrm{~K}\) for \(\mathrm{N}_2\) and \(\mathrm{N}_2\) - Ar, respectively. See Reply #1 for the first referee. + +The \(\mathrm{N}_2\) - Ar2 cluster seems to be un- analyzed and superfluous. It's a nice experiment, but it does not provide any information in the current paper. Either leave away or clarify what you learn from this data. + +## Reply #18: + +Under the same laser kick, the internal rotation is more severely hindered by two neighboring Ar atoms. Collaborating with the rotational dynamics of \(\mathrm{N}_2\) and \(\mathrm{N}_2\) - Ar, the absence of the alignment of the \(\mathrm{N}_2\) axis in \(\mathrm{N}_2\) - Ar2 directly indicates a quantity effect as the number of neighboring atoms increases that what we learned from the experiment. Though a deeper analysis of this complex rotational dynamics is not available currently, this result will be good to know. + +1. 148: "rotational deceleration of \(\mathrm{N}_2\) induced by 149 the neighboring Ar in time domain" – is this actually a deceleration or simply a "slower dynamics"? Or is this simply a first dim hint at the coupling of various modes (vide supra)? + +## Reply #19: + +<--- Page Split ---> + +For the rotation of \(\mathrm{N}_2\) , the central values of each spectral peak, 11.94, 19.9, and 27.86 \(\mathrm{cm}^{- 1}\) , are given by the frequency of a \((j - j + 2)\) coherence and described by the expression \(B(4j + 6)\) as a rigid rotor with the rotational constant \(B = 1.99 \mathrm{cm}^{- 1}\) . + +For the internal rotation of \(\mathrm{N}_2\) - Ar, similar to the intermolecular stretching, several states with \(J = 4\) have been marked by red arrows in Fig. R2(c). These states with energy gaps of 9.27, 17.84, and 26.13 \(\mathrm{cm}^{- 1}\) are close to the observed rotational frequencies in Fig. 4(b) in the manuscript. Collaborating with approximate labels, these frequencies can relate to the \(\mathrm{N}_2\) monomer corresponding to the (0- 2), (1- 3), and (2- 4) coherences. + +Thus, the red- shift of rotational frequencies and deceleration result from smaller energy gaps between states of the \(\mathrm{N}_2\) - Ar than the \(\mathrm{N}_2\) monomer and the quantum beatings of these states induce the slower rotation in the time domain. + +As previous studies have suggested, the faster the internal rotation is, the more it behaves like a free rotor, namely a weaker coupling and \(j\) becomes a good quantum number. So, the frequency shift directly reflects the coupling strength of the internal rotation with other modes. + +Overall, to me this work requires very significant improvements, but I am looking forward to see this then published Nat. Comm. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Dear Editor, since the authors adequately responded to all questions and comments of the referees, I support the publication of this paper. Best regards, + +Reviewer #2 (Remarks to the Author): + +Please see attached review. + +<--- Page Split ---> + +Review of "Intermolecular interactions probed by rotational dynamics in gas- phase clusters" by Chenxu Lu et al. + +Overall, the manuscript was strongly improved and all reviewer comments were addressed. Besides a few smaller comments, for clarity and accessibility the description of the molecular dynamics needs to be placed - numerically and semantically - in an the model that takes all relevant dimensions/motions into account. This should likely use the - extremely rich - traditional descriptions of intermolecular interactions in molecular clusters. + +I.e., the model of the authors should be correlated to, by explanation, or use traditional models which describe the lost translational degrees of freedom due complex formation as intermolecular vibrations, i.e., stretching, bending, or torsion/internal rotation modes. Textbook descriptions like chapter 9 of Kroto: Molecular Rotation Spectra (1975) or conceptional papers such as Molecular Physics 84, 853- 878 (1995) could be a good start for reference. I am convinced the authors can find more such relevant descriptions. + +This also includes a - also semantically - combined description of the "internal rotation" and the coupled stretching vibration. Btw. this new data in Fig. 5 is very nice and a strong addition to the paper. Fig. 5c and its description in the initial part of the discussion would strongly benefit from the advanced description sought for in this comment. That the \((j,J)\) nomenclature does not provide a good (supra)molecular frame description of the dynamics is also reflected when it averages the different motions - at least 2 bends and 1 stretch - into one \(j\) , which is not even a good quantum number (1. 224). + +Generally, a more "supermolecular" description of the cluster might be much clearer to describe the actual couplings and resulting dynamics. This would allow for a direct discussion of the relative contributions of the various mode- to- mode couplings and, furthermore, would allow to put these results into the context of the very many frequency- resolved investigations of such interactions. This would also c + +This should also seen in light of the authors insight that " \(j\) is not a good quantum number" + +It should be clarified what "properly implemented" in line 192 actually is. + +What are "frequency components \(\nu_{1}\) and \(\nu_{2}\) ?" + +Some further comments: + +When comparing the alignment of the "Ar axis" for N2- Ar and Ar- Ar (Fig 2c), were the corresponding interaction strengths and their anisotropies between the two experiments comparable? + +The N2- Ar2 results, as interesting they are, need further description, rationalizing, and discussion to be reasonably included in the manuscript. + +Approximating the rotational temperature based on translation can only provide a lower bound for the rotational temperature. In fact, they are often quite different for seeded beams - speed ratios of the beam \(>100\) but still rotational temperatures \(\sim 10 \mathrm{~K}\) . Even if the agreement is good here, this approximative approach ("lower bound") should probably be more clearly pointed out. + +Is the indeed relatively low- intensity short- pulse nature of the excitation also the reason for not exciting the overall rotation? Would be worth simulating at higher kick- energy and mentioning in the manuscript. + +It would be useful to clearly point out that all dynamics is in truly bound states. Also related to the weak kick strength used. + +To me, "deceleration" (reply #19) seems to be the inappropriate word, it seems to say "slower". + +What's "umbrella time breathing"? + +In line 208: Is this truly 'entanglement' in "radial and angular potential is entangled"? + +<--- Page Split ---> + +Re: NCOMMS- 23- 43274B + +" Intermolecular interactions probed by rotational dynamics in gas- phase clusters" by Chenxu Lu et al. + +For clarity, we put the original comments in italics to distinguish from our responses in blue. The text that has been changed or newly added is in red. + +Reviewer #2 (Remarks to the Author): + +Overall, the manuscript was strongly improved and all reviewer comments were addressed. Besides a few smaller comments, for clarity and accessibility the description of the molecular dynamics needs to be placed - numerically and semantically - in an the model that takes all relevant dimensions/motions into account. This should likely use the - extremely rich - traditional descriptions of intermolecular interactions in molecular clusters. + +I.e., the model of the authors should be correlated to, by explanation, or use traditional models which describe the lost translational degrees of freedom due complex formation as intermolecular vibrations, i.e., stretching, bending, or torsion/internal rotation modes. Textbook descriptions like chapter 9 of Kroto: Molecular Rotation Spectra (1975) or conceptional papers such as Molecular Physics 84, 853- 878 (1995) could be a good start for reference. I am convinced the authors can find more such relevant descriptions. + +This also includes a - also semantically - combined description of the "internal rotation" and the coupled stretching vibration. Btw. this new data in Fig. 5 is very nice and a strong addition to the paper. Fig. 5c and its description in the initial part of the discussion would strongly benefit from the advanced description sought for in this comment. That the (j, J) nomenclature does not provide a good (supra)molecular frame description of the dynamics is also reflected when it averages the different motions - at least 2 bends and 1 stretch - into one j, which is not even a good quantum number (l. 224). + +Generally, a more "supermolecular" description of the cluster might be much clearer to describe the actual couplings and resulting dynamics. This would allow for a direct discussion of the relative contributions of the various mode- to- mode couplings and, furthermore, would allow to put these results into the context of the very many frequency- resolved investigations of such interactions. This should also seen in light of the authors insight that "j is not a good quantum number" + +## Reply #1: + +The floppy model is performed under the space- fixed expression rather than the body + +<--- Page Split ---> + +fixed expression. These two expressions are equivalent, and they are both commonly used descriptions of noncovalent clusters [Chem. Rev., 94, 1931 (1994); Chem. Rev. 100, 4109 (2000)]. We chose the space- fixed (lab- frame) model since it makes us to have a direct comparison with the experimental observations. + +Based on the space- fixed expression, a more detailed description of all relevant dimensions (five degrees of freedom) has been added to the Methods + +"...The floppy model is conducted under the space- fixed scheme, where the rotation of \(\mathrm{N}_{2}\) and the translation motion are included, and the molecule- atom interaction is represented by an accurate potential surface [J. Chem. Phys. 121, 10419 (2004)]. Due to the complex formation, the angular part and the radical part of the translation motion are reduced to the rotation and intermolecular stretching of the vdW axis, respectively. With the rigid rotor approximation, the vibration of \(\mathrm{N}_{2}\) molecule is assumed to be neglected. Thus, the floppy model includes five degrees of freedom including two rotational degrees of \(\mathrm{N}_{2}\) , two rotational degrees and one vibrational degree of vdW axis, and the Hamiltonian in the space- fixed scheme takes the form of..."(on page 12 line 309) + +In our floppy model, two rotational degrees of \(\mathrm{N}_{2}\) and two rotational degrees of the vdW- axis are described in the lab frame which is consist with the experimental measurement of their angles with respect to the lab frame Z- axis (polarization direction of the kick pulse) [J. Chem. Phys. 78, 4025 (1983); Chem. Phys. Lett. 221, 161 (1994); Chem. Rev. 94, 1931 (1994); J. Chem. Phys. 108, 3554 (1998)]. For the body- fixed treatment of \(\mathrm{N}_{2}\) - Ar, it has been implemented by pioneering works, where the \(\mathrm{N}_{2}\) rotation is described by the angle with respect to the vdW axis in the molecular frame, termed as bending motions [Mol. Phys. 27, 903 (1974); J. Chem. Phys. 88, 578 (1988); J. Chem. Phys. 110, 8525 (1999); J. Chem. Phys. 121, 10419 (2004)]. + +The main difference of two expressions is the reference frame, and the Coulomb explosion imaging directly images the angular distribution in the lab frame rather than the molecular frame (both for the Ar- axis and N- N axis). Thus, a space- fixed description is more straightforward in our case, especially for the comparison with the isolated \(\mathrm{N}_{2}\) under the same reference frame. + +An eigenstate can be expressed as a superposition of different \(j\) and \(L\) components in the space- fixed scheme (see Methods for the expression of an eigenstate), namely couplings of these modes. Only the parity \(p = (- 1)^{j + L + J}\) , the total angular momentum \(J\) and its projection \(N\) onto Z- axis are rigorous. To get a qualitatively description about the degrees of freedom involved, approximate quantum numbers are instructive and required for both space- fixed and body- fixed expressions [Chem. Rev. 100, 4109 (2000)]. Collaborating with the approximate quantum number \(j\) of \(\mathrm{N}_{2}\) - Ar, the frequencies in Fig. 4 can relate to the ones of the \(\mathrm{N}_{2}\) monomer corresponding to the \((j - j + 2)\) transitions, i.e., (0- 2), (1- 3) and (2- 4). + +Now approximate quantum numbers \((n, j, L)\) are introduced corresponding to the intermolecular stretching, \(\mathrm{N}_{2}\) rotation and vdW rotation, respectively. Quantum + +<--- Page Split ---> + +numbers \(j\) and \(L\) are assigned according to their dominant components of an eigenstate. The quantum number \(n\) is used to represent the intermolecular stretch according to the nodes in the stretch coordinate \(r\) [J. Chem. Phys. 88, 578 (1988)]. + +Besides this qualitatively description, a direct knowledge about an eigenstate of its components from relative contributions of various \(j\) and \(L\) - states, and radical distributions along the stretch coordinate has been added to the Supplementary materials. It can be seen that as the increasing of energy, the quantum number \(j\) becomes nearly rigorous and the \(\mathrm{N}_2\) rotation behaves like a free rotor, while \(L\) still shows a wide distribution attributing to the small rotational energy of Ar- axis. + +![](images/Figure_5.jpg) + +
Figure R1 (Supplementary Figure 1) (a) Populations of \(j\) -states of eigenstates (b) Same as (a) but for the \(L\) -states. (c) Radical distributions along the stretch coordinate \(r\) of eigenstates. The eigenstates (Fig. 5(c) in the manuscript) are assigned by approximate quantum numbers (n, j, L) according to the nodes in the stretch coordinate \(r\) , and the most populated components of \(j\) and \(L\) .
+ +For the intermolecular stretching, we add the following contents to the manuscript: + +"...As marked by the green arrows, states with energy gaps of 15.8 and \(20.1 \mathrm{cm}^{- 1}\) are assigned to the frequency components \(v_{1}\) and \(v_{2}\) , respectively. The frequency \(v_{2}\) originating from the states beating between \(n = 0\) and 1 dominates the intermolecular stretching, where \(n\) is the approximate stretch quantum number representing the nodes in the stretch coordinate \(r\) [J. Chem. Phys. 88, 578 (1988)]. The frequency \(v_{1}\) originates from the identical approximate stretch quantum number \(n = 0\) of similar but different radial distributions (see Supplementary materials) as \(n\) is not rigorous, which results in the stretching with a relatively smaller amplitude as compared to \(v_{2}\) ." (on page 9 line 211) + +In the revised manuscript, we provide a more detailed description of relevant degrees of freedom of the observables and revise the label in Fig. 5. The pioneer works for \(\mathrm{N}_2\) - Ar under the body- fixed expression have been mentioned and cited properly. + +"Figure 5(c) displays the transition diagram of the ro- vibrational spectra carried out in the space- fixed expression [Chem. Rev., 94, 1931 (1994)]. Attributing to the low kick intensity which avoids the rotational dissociation [J. Chem. Phys. 147, 074304 (2017); J. Chem. Phys. 149, 124301 (2018)], the observed dynamics occurs in bound states of + +<--- Page Split ---> + +\(\mathrm{N}_{2}\) - Ar. As the angular part is expanded onto the coupled basis in the floppy model, approximate quantum numbers \((n, j, L)\) are employed to label the eigenstates corresponding to the intermolecular stretching, \(\mathrm{N}_{2}\) rotation and vdW rotation respectively, where \(j\) and \(L\) are the approximate rotational quantum numbers of \(\mathrm{N}_{2}\) and Ar-axis. An approximate quantum number which is not rigorous implies the involvement of multiple modes within this coordinate. Only the parity \(p = (- 1)^{j + L + J}\) , the total angular momentum \(J\) and its projection \(N\) are rigorous. As numerous states are involved, for illustration, only several states with even parity and \(J = 4\) are displayed. In the view of space- fixed expression, the quantum numbers \(j\) and \(L\) are not rigorous which means that an eigenstate of \(\mathrm{N}_{2}\) - Ar is a superposition of different rotational states of the N- N axis and Ar- axis (see Methods). For simplicity, the approximate quantum number \(j\) and \(L\) are assigned according to their most populated components (see Supplementary materials). The approximate quantum number is instructive as it builds up a connection between isolated \(\mathrm{N}_{2}\) and \(\mathrm{N}_{2}\) - Ar dimer, and reveals behaviors of the N- N axis with different angular momentum under the interaction of Ar. As the increase of \(j\) , the \(\mathrm{N}_{2}\) molecule behaves like a free rotor. Besides this space- fixed expression, a molecular frame knowledge about the internal bending of \(\mathrm{N}_{2}\) - Ar dimer can be obtained under the body- fixed expression [Mol. Phys. 27, 903 (1974); J. Chem. Phys. 88, 578 (1988); J. Chem. Phys. 110, 8525 (1999)]. For the rotation of \(\mathrm{N}_{2}\) , states with energy gaps of 9.27, 17.85 and 26.04 \(\mathrm{cm}^{- 1}\) have been marked by red arrows in Fig. 5(c), which correspond to the observed rotational frequencies in Fig. 4. Collaborating with the approximate quantum number \(j\) of \(\mathrm{N}_{2}\) - Ar, these frequencies can relate to the ones of the \(\mathrm{N}_{2}\) monomer corresponding to the (0–2), (1–3) and (2–4) transitions. Thus, the red- shift of rotational frequencies results from smaller energy gaps for states of the \(\mathrm{N}_{2}\) - Ar than the \(\mathrm{N}_{2}\) monomer.” (on page 9 line 220) + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Figure R2 (Figure 5 in the main text). Intermolecular stretching of the \(\mathbf{N}_2\) -Ar dimer. a Reconstructed (blue curve) and calculated (red curve) time-dependent intermolecular stretching of the \(\mathbf{N}_2\) -Ar dimer. b Power spectra of the reconstructed and calculated intermolecular stretching. c The energy levels, with the even parity \(p = (-1)^{J + L + J}\) and \(J\) \(= 4\) , are grouped by the approximate quantum numbers \((n,j,L)\) . The energy gaps related to the frequencies of rotation of \(\mathbf{N}_2\) and intermolecular stretching are marked by red and green arrows, respectively.
+ +It should be clarified what "properly implemented" in line 192 actually is. + +## Reply #2: + +For clarity, we have modified the corresponding statement: + +"Only if the molecule- atom interaction potential rather than a rigid connection between \(\mathbf{N}_2\) and Ar is added to describe their interaction (see Methods for details of the floppy model), the rotational spectrum can be reproduced." (on page 8 line 177) + +What are "frequency components \(\nu_1\) and \(\nu_2\) "? + +## Reply #3: + +We have explained in Reply #1. + +<--- Page Split ---> + +Some further comments: + +When comparing the alignment of the "Ar axis" for N2- Ar and Ar- Ar (Fig 2c), were the corresponding interaction strengths and their anisotropies between the two experiments comparable? + +## Reply #4: + +Both the interaction strengths and anisotropies of them are comparable. The fragments of Coulomb exploded \(\mathrm{Ar}_2\) dimer and \(\mathrm{N}_2\) - Ar dimer are collected in coincidence, ensuring the same kick intensity. + +The interaction energy of Ar- Ar has been calculated to be \(98.4\mathrm{cm}^{- 1}\) [J. Chem. Phys. 119, 2102 (2003)] which is close to the one of \(\mathrm{N}_2\) - Ar (about \(100\mathrm{cm}^{- 1}\) ) [J. Chem. Phys. 121, 10419 (2004)]. The polarizability anisotropy used in simulation for Ar- Ar is 0.45 \(\mathrm{\AA}^3\) [Phys. Rev. A 89, 023432 (2014)] which is comparable with the one about the Ar- axis in \(\mathrm{N}_2\) - Ar \((\Delta \alpha_{bc} = \alpha_{bb} - \alpha_{cc} = 0.28 \mathrm{\AA}^3)\) . + +To make it clearer, we have added the following sentences in the manuscript: + +"As a reference, the vdW axis of the \(\mathrm{Ar}_2\) dimer with a similar rotational constant, interaction strength and comparable polarizability anisotropy [J. Chem. Phys. 119, 2102 (2003); J. Chem. Phys. 121, 10419 (2004); Phys. Rev. A 89, 023432 (2014); Mol. Phys. 27, 903 (1974)] show a clear alignment peak at \(\sim 3.5\mathrm{ps}^*\) (on page 5 line 117) + +The N2- Ar2 results, as interesting they are, need further description, rationalizing, and discussion to be reasonably included in the manuscript. + +## Reply #5: + +As we have mentioned in the former reply, from current experiment results, we can obtain a quantity effect as the number of neighboring atoms increases. But currently we cannot simulate such case using our code which prevents us from a further analysis. + +To avoid an ambiguous description of \(\mathrm{N}_2\) - \(\mathrm{Ar}_2\) , we follow the referee's former suggestion that we no longer discuss it in the revised manuscript. + +Approximating the rotational temperature based on translation can only provide a lower bound for the rotational temperature. In fact, they are often quite different for seeded beams - speed ratios of the beam \(>100\) but still rotational temperatures \(\sim 10\mathrm{K}\) . Even if the agreement is good here, this approximative approach ("lower bound") should probably be more clearly pointed out. + +## Reply #6: + +<--- Page Split ---> + +We appreciate the reviewer's reminder. To make it clearer, we have added the following sentences in the manuscript: + +"The measured translation temperature results in an upper limit of the temperature of molecules in the supersonic gas jet." (on page 11 line 281) + +Is the indeed relatively low- intensity short- pulse nature of the excitation also the reason for not exciting the overall rotation? Would be worth simulating at higher kick- energy and mentioning in the manuscript. + +## Reply #7: + +The alignment signal for the asymmetric- top molecule depends on the molecular properties (polarizability and moments of inertia of three axes), temperature, and the laser parameters. Of course, higher kick intensity leads to higher alignment (see Fig. R3). + +However, as we have answered in Reply #4, since the Ar- axes in \(\mathrm{N}_2\) - Ar and Ar- Ar have similar interaction strengths and their anisotropies are comparable, as well as the kick intensities are the same, it is the large discrepancy of the three molecular axes of \(\mathrm{N}_2\) - Ar comparing with linear diatomic Ar- Ar that mainly leads to the weak alignment of the Ar- axis rather than the kick intensity. + +To make it clear to readers, we have added a corresponding statement + +"The kick intensity used here is very low, which might also be the reason that leads to neglectable overall rotation. However, since the Ar- axes in \(\mathrm{N}_2\) - Ar and Ar- Ar have similar interaction strengths and their anisotropies are comparable, as well as the kick intensities are the same, it is the large discrepancy of the three molecular axes of \(\mathrm{N}_2\) - Ar comparing with linear diatomic Ar- Ar that mainly leads to the weak alignment of the Ar- axis rather than the kick intensity. On the other hand, when increasing the kick intensity, the rotational dissociation happens [J. Chem. Phys. 147, 074304 (2017); J. Chem. Phys. 149, 124301 (2018)]." page 8 line 189) + +![](images/Figure_unknown_2.jpg) + +
Figure R3. Calculated alignment traces of Ar-axis of \(\mathrm{N}_2\) -Ar and \(\mathrm{Ar}_2\) by the rigid model
+ +<--- Page Split ---> + +with low intensity \((7 \times 10^{12} \mathrm{~W} / \mathrm{cm}^{2})\) and high intensity \((1.4 \times 10^{13} \mathrm{~W} / \mathrm{cm}^{2})\) . + +It would be useful to clearly point out that all dynamics is in truly bound states. Also related to the weak kick strength used. + +## Reply #8: + +To make it clearer, we have added the following sentences in the manuscript: + +"Attributing to the low kick intensity which avoids the rotational dissociation [J. Chem. Phys. 147, 074304 (2017); J. Chem. Phys. 149, 124301 (2018)], the observed dynamics occurs in bound states of \(\mathrm{N}_{2}\) - Ar." (on page 9 line 221) + +To me, "deceleration" (reply #19) seems to be the inappropriate word, it seems to say "slower" + +## Reply #9: + +We have replaced it with a proper description "slower rotation" in the manuscript. + +What's "umbrella time breathing"? + +## Reply #10: + +The umbrella time breathing means the evolution from alignment to anti- alignment resulting from the beats of the rotational states. + +In line 208: Is this truly 'entanglement' in "radial and angular potential is entangled"? + +## Reply #11: + +The intermolecular interaction can be described potential energy surface \(V(r, \theta_{r})\) (see Fig. R3) where \(\theta_{r}\) is the angle between the N- N axis and Ar- axis and \(r\) is the intermolecular distance between center of mass of the molecule and the atom. + +To make it clearer, we have added the following sentences in the manuscript: + +"...However, this assumption does not hold any more when it comes to the \(\mathrm{N}_{2}\) - Ar dimer since the molecule- atom interaction between \(\mathrm{N}_{2}\) and Ar relies on both their relative distance and angle..." (on page 8 line 200) + +<--- Page Split ---> +![PLACEHOLDER_28_0] + +
Figure R3. Contour plot of potential energy surface for \(\mathrm{N}_2\) -Ar [J. Chem. Phys. 121, 10419 (2004)]. Geometries are given in Å and degrees, and energies in \(\mathrm{cm}^{-1}\) .
+ +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #2 (Remarks to the Author): + +The authors clearly improved the manuscript regarding, and clarified all issues from, the reviews. I suggest to publish the manuscript in Nat. Comm. + +I suggest the authors to consider two small comments (without need for review): + +1. Regarding "The measured translation temperature results in an upper limit of the temperature of molecules in the supersonic gas jet." + +To my mind, the relevant "temperature of molecules" are the rotational and vibrational temperatures of the clusters, which are generally higher than the translational temperature of the beam. + +2. It would be useful if the authors or the editorial office could polish the English language of the text, e.g., the latest additions. + +<--- Page Split ---> + +Re: NCOMMS- 23- 43274B + +"Intermolecular interactions probed by rotational dynamics in gas- phase clusters" by Chenxu Lu et al. + +For clarity, we put the original comments in italics to distinguish from our responses in blue. The text that has been changed or newly added is in red. + +Reviewer #2 (Remarks to the Author): + +The authors clearly improved the manuscript regarding, and clarified all issues from, the reviews. I suggest to publish the manuscript in Nat. Comm. + +I suggest the authors to consider two small comments (without need for review): + +1. Regarding "The measured translation temperature results in an upper limit of the temperature of molecules in the supersonic gas jet." + +To my mind, the relevant "temperature of molecules" are the rotational and vibrational temperatures of the clusters, which are generally higher than the translational temperature of the beam. + +## Reply #1: + +To make it clear to the readers, we have rephrased the following sentences and corresponding references have been cited properly in the revised manuscript: + +"In our experiment, we measure \(\Delta p \sim 3.2\) a.u. and \(\Delta p \sim 4.0\) a.u. for \(\mathrm{N}_2^+\) and \(\mathrm{N}_2\mathrm{-Ar}^+\) ions. We expect the measured translation temperature is similar to the rotational and vibrational temperature of molecules in the supersonic gas jet [Phys. Rev. Lett. 90, 233003 (2003); J. Chem. Phys. 118, 8699 (2003); Nat. Phys. 16, 328 (2020)]. The excellent agreement with the experiment can be achieved in the simulation when using the temperatures of \(9\mathrm{K}\) for isolated \(\mathrm{N}_2\) and \(7\mathrm{K}\) for \(\mathrm{N}_2\mathrm{-Ar}\) molecules." (line 276 page 11) + +2. It would be useful if the authors or the editorial office could polish the English language of the text, e.g., the latest additions. + +Reply #2: + +We have improved the language of the manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..bf5fefe427c5ec4e80a076563ffb3d48f545a113 --- /dev/null +++ b/peer_reviews/78352ddf64be3a3e4b852e3cd1adbbbf54cf07c79fe43398e6d8e9cf1b03c2dd/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,890 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 111, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 162, 907, 219]]<|/det|> +Intermolecular interactions probed by rotational dynamics in gas- phase clusters + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 916, 800]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 295, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 111, 413, 125]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 140, 857, 197]]<|/det|> +Dear Editor, please find here enclosed my review of the manuscript entitled "Intermolecular interactions probed by rotational wavepackets in gas- phase clusters", submitted for publication in Nature Comm. + +<|ref|>text<|/ref|><|det|>[[119, 210, 877, 267]]<|/det|> +This work investigates the experimental control of molecular rotation of \(\Phi \mathrm{N}_2\Phi\) molecules subjected to interaction with \(\Phi \mathrm{Ar}\Phi\) atoms. They observe that the alignment decays rapidly due to this interaction. They show that the decay rate depends on the relative position of \(\Phi \mathrm{Ar}\Phi\) atoms with respect to the molecular axis. Numerical simulations illustrate these experimental observations. + +<|ref|>text<|/ref|><|det|>[[118, 280, 875, 406]]<|/det|> +Quantum control is currently a subject of increasing interest in chemistry, physics and mathematics but also for the development of quantum technologies. In this context, the control of molecular rotation is a well- established topic in molecular physics with a variety of applications extending from high harmonic generation to chemical reactivity. This paper focuses on the interaction of aligned molecules with their environment. The proposed method and the results are interesting. To the best of my knowledge, the investigation is original. I am not an experimentalist so I cannot directly judge the relevance of the experimental results. This paper seems sound numerically although I have some doubts about the model system used to reproduce the experimental results. + +<|ref|>text<|/ref|><|det|>[[117, 419, 872, 560]]<|/det|> +Here is a series of questions about experiment modeling. The authors describe the quantum system as a pure state. This case corresponds to zero temperature. What is the experimental temperature of the supersonic gas jet? For a non- zero temperature, the system must be described by a density operator. What is the impact of this approximation? The authors consider the interaction of \(\Phi \mathrm{N}_2\Phi\) molecules with one or two \(\Phi \mathrm{Ar}\Phi\) atoms. Here again, how to justify this approximation when each \(\Phi \mathrm{N}_2\Phi\) molecule should interact with many atoms. In the literature, the interaction of linear molecules with its environment was described by a Redfield equation (see (1,2) for instance). Can this modeling be used in the case of this paper? This Redfield description also leads to a rapid degradation of molecular alignment. What are the advantages of direct modeling of molecule- atom interaction? + +<|ref|>text<|/ref|><|det|>[[118, 560, 848, 616]]<|/det|> +\(\backslash (1)\) - M. Bournazel et al., \`emph\{Non- Markovian collisional dynamics probed with laser- aligned molecules\}, Phys. Rev. A \`textbf\{107\}, 023115 (2023)\}(2)- T. Viellard et al., \`emph\{Field- free molecular alignment for probing collisional relaxation dynamics\}, Phys. Rev. A \`textbf\{87\}, 023409 (2013) + +<|ref|>text<|/ref|><|det|>[[119, 671, 414, 685]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 699, 852, 770]]<|/det|> +The manuscript "Intermolecular interactions probed by rotational wavepackets in gas- phase clusters" by Lu et al explores an internal- rotation wavepacket in N2- Ar to probe the dynamics, and potentially coupling, of large- amplitudes internal modes of the molecular system. + +<|ref|>text<|/ref|><|det|>[[118, 784, 866, 855]]<|/det|> +Generally, this is a nice experiment that could likely deserves publication in Nat. Comm. following significant clarifications and improvements, mostly regarding the analysis but also with respect to experimental results on the overall rotation of the molecular system. + +<|ref|>text<|/ref|><|det|>[[117, 868, 874, 923]]<|/det|> +Firstly, I am wondering if there is no overall- rotation dynamics induced in the N2- Ar system by the kick pulse? Obviously, this would be at longer timescales, but should be observable both in the experiment as well as the computations performed by the authors. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 879, 225]]<|/det|> +Second, I fear in light of \(>50\) years of spectroscopic studies of floppy molecules and molecular clusters, the semantic description does not do justice to the problem. That is, the N2- Ar system has 3 low- frequency/large amplitude internal "intermolecular" vibrational modes, build up from the lost 3 degrees of translational freedom of the constituents, in addition to the N2 stretch and the overall rotation of the system. The authors use a cumbersome description of this, in which the N2- Ar stretch does not seem to occur at all and the two other (internal bending) modes are described as simple, maybe too simple, "perturbed 1D N2 rotations". + +<|ref|>text<|/ref|><|det|>[[118, 238, 866, 280]]<|/det|> +Here, it is clear that these motions are coupled, esp. the various internal degrees of freedom and the overall rotation of the cluster. In fact, in an extremely simplified model the authors derive exactly the first glimpses of that. + +<|ref|>text<|/ref|><|det|>[[118, 293, 866, 350]]<|/det|> +Moreover, it seems the overall N2- Ar stretch of the cluster was "forgotten" in the analysis? Is that justified by any means, i.e., what's the energy gaps and the coupling strengths of this mode to the internal rotations and to the overall rotation? + +<|ref|>text<|/ref|><|det|>[[118, 363, 846, 406]]<|/det|> +I also wonder why the degree of alignment even for N2 itself is so low. Possibly this is due to a relatively large (rotational) temperature (?) What's the explanation of the authors? + +<|ref|>text<|/ref|><|det|>[[118, 419, 852, 462]]<|/det|> +In that light and in any case, it is important to understand the "vibrational" temperature for the low- frequency modes of the cluster and in how far the modes are thermally excited before the kick pulse. + +<|ref|>text<|/ref|><|det|>[[118, 475, 866, 547]]<|/det|> +Conceptionally, when comparing the out- of- plane and the in- plane rotation of the N2 in the N2- Ar dimer, how strongly are these modes coupled - to each other, to and via the intermolecular N2- Ar stretch, and via the overall rotation? Is it appropriate to discuss the results in such one- dimensional models as done in this manuscript? + +<|ref|>text<|/ref|><|det|>[[118, 560, 864, 602]]<|/det|> +Are the energies of the relevant (populated) eigenstates in the wavepackets in fact bound states, barrier- modulated above- barrier states, or "free" above- barrier states? + +<|ref|>text<|/ref|><|det|>[[118, 615, 864, 644]]<|/det|> +In fact, this question is relevant for both the initially populated states ("temperature") above and the kick- initiated populations. + +<|ref|>text<|/ref|><|det|>[[118, 657, 877, 728]]<|/det|> +What's the polarizability anisotropy/tensor of the cluster and how does that change as a function of the intermolecular geometry? On the one hand, this would provide first hints at the overall- rotation dynamics induced by the kick as well as the coupling between internal modes and between internal modes and overall rotation. + +<|ref|>text<|/ref|><|det|>[[118, 742, 844, 784]]<|/det|> +When comparing N2 rotational dynamics to the 1D- internal- rotation dynamics the reduction of dimensionality (1D to 2D) likely needs to be taken into account. + +<|ref|>text<|/ref|><|det|>[[118, 798, 848, 829]]<|/det|> +To me, and in light of the very rich set of descriptions the simple model utilized by the authors does not seem to be appropriate. In + +<|ref|>text<|/ref|><|det|>[[118, 829, 856, 870]]<|/det|> +fact, an analysis of the "intermolecular interactions probed by rotational wavepackets" would be highly appreciated and useful - if + +<|ref|>text<|/ref|><|det|>[[118, 861, 808, 875]]<|/det|> +actually analyzed and described in the long- standing and proven models of intermolecular + +<|ref|>text<|/ref|><|det|>[[118, 875, 375, 888]]<|/det|> +interactions. In the simple system + +<|ref|>text<|/ref|><|det|>[[118, 885, 876, 914]]<|/det|> +presented here, that would require a 6D description (3 degrees of overall rotation and 3 degrees of intermolecular vibrations/internal + +<|ref|>text<|/ref|><|det|>[[118, 913, 730, 927]]<|/det|> +rotations). This is clearly possible, both semantically as well as computationally. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 97, 835, 125]]<|/det|> +One of the important points to clarify is which of all these modes are actually directly Raman- excited in the experiment. + +<|ref|>text<|/ref|><|det|>[[118, 139, 875, 198]]<|/det|> +Moreover, here it is really important to clarify also experimentally both the intermolecular stretch as well as the overall rotation - and their corresponding interaction with the internal rotations (same for thermal excitations of all these modes). + +<|ref|>text<|/ref|><|det|>[[118, 210, 857, 269]]<|/det|> +The authors should also consider to refer to previous alignment experiments of floppy molecules and clusters, which is really what they are following up on here, e.g., PRL 102, (2009); JCP 148, 101103 (2018); PCCP 22, 3245- 3253 (2020), ... + +<|ref|>text<|/ref|><|det|>[[118, 280, 840, 338]]<|/det|> +In the experimental section, how does a 7:3 splitting of the laser beam lead to intensities that differ by 2 orders of magnitude? Different focusing? Specify. Generally, some more details on the actual experiment should be provided in Methods. + +<|ref|>text<|/ref|><|det|>[[118, 350, 858, 366]]<|/det|> +Also, details of the implementation of the computational approach by Zillich should be described. + +<|ref|>text<|/ref|><|det|>[[118, 378, 781, 393]]<|/det|> +Re I. 117: No, (N2)- Ar axis motion can be internal rotation as well as overall rotation... + +<|ref|>text<|/ref|><|det|>[[118, 405, 715, 420]]<|/det|> +/j/ is a "1D internal rotation" quantum number and should be treated as such. + +<|ref|>text<|/ref|><|det|>[[118, 433, 857, 477]]<|/det|> +In the simulations: When the molecule is so floppy, why is it appropriate to use a single reduced mass \(\mu\) - instead of a coordinate/geometry depended one? + +<|ref|>text<|/ref|><|det|>[[118, 490, 688, 505]]<|/det|> +Which pulse intensity and rotational temperature do the simulations yield? + +<|ref|>text<|/ref|><|det|>[[118, 517, 857, 560]]<|/det|> +The N2- Ar2 cluster seems to be un- analyzed and superfluous. It's a nice experiment, but it does not provide any information in the current paper. Either leave away or clarify what you learn from this data. + +<|ref|>text<|/ref|><|det|>[[118, 573, 874, 616]]<|/det|> +I. 148: "rotational deceleration of N2 induced by 149 the neighboring Ar in time domain" - is this actually a deceleration or simply a "slower dynamics"? Or is this simply a first dim hint at the coupling of various modes (vide supra)? + +<|ref|>text<|/ref|><|det|>[[118, 629, 863, 658]]<|/det|> +Overall, to me this work requires very significant improvements, but I am looking forward to see this then published Nat. Comm. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 849, 120]]<|/det|> +For clarity, we put the original comments in italics to distinguish them from our responses in blue. The text that has been changed or newly added is in red. + +<|ref|>sub_title<|/ref|><|det|>[[149, 140, 363, 157]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[149, 178, 457, 195]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 216, 850, 287]]<|/det|> +Dear Editor, please find here enclosed my review of the manuscript entitled "Intermolecular interactions probed by rotational wavepackets in gas- phase clusters", submitted for publication in Nature Comm. + +<|ref|>text<|/ref|><|det|>[[148, 307, 850, 398]]<|/det|> +This work investigates the experimental control of molecular rotation of \(N_{2}\) molecules subjected to interaction with Ar atoms. They observe that the alignment decays rapidly due to this interaction. They show that the decay rate depends on the relative position of Ar atoms with respect to the molecular axis. Numerical simulations illustrate these experimental observations. + +<|ref|>text<|/ref|><|det|>[[147, 418, 850, 583]]<|/det|> +Quantum control is currently a subject of increasing interest in chemistry, physics and mathematics but also for the development of quantum technologies. In this context, the control of molecular rotation is a well- established topic in molecular physics with a variety of applications extending from high harmonic generation to chemical reactivity. This paper focuses on the interaction of aligned molecules with their environment. The proposed method and the results are interesting. To the best of my knowledge, the investigation is original. I am not an experimentalist so I cannot directly judge the relevance of the experimental results. This paper seems sound numerically although I have some doubts about the model system used to reproduce the experimental results. + +<|ref|>text<|/ref|><|det|>[[147, 603, 850, 694]]<|/det|> +Here is a series of questions about experiment modeling. The authors describe the quantum system as a pure state. This case corresponds to zero temperature. What is the experimental temperature of the supersonic gas jet? For a non- zero temperature, the system must be described by a density operator. What is the impact of this approximation? + +<|ref|>sub_title<|/ref|><|det|>[[148, 724, 232, 740]]<|/det|> +## Reply #1: + +<|ref|>text<|/ref|><|det|>[[148, 751, 848, 787]]<|/det|> +In the experiment, the rotational temperatures of \(\mathrm{N}_{2}\) and \(\mathrm{N}_{2}\) - Ar are estimated to be 11 K and 7 K, respectively. + +<|ref|>text<|/ref|><|det|>[[148, 797, 821, 814]]<|/det|> +To make it clear to readers, we have added the following sentences in the Methods: + +<|ref|>text<|/ref|><|det|>[[148, 825, 852, 898]]<|/det|> +"The initial temperatures of \(\mathrm{N}_{2}\) and \(\mathrm{N}_{2}\) - Ar are estimated to be 11 K and 7 K, respectively, by approximation to their translational temperatures of \(T_{\mathrm{trans}} = \Delta p^{2} / [4\ln (4)k_{\mathrm{BM}}]\) [see Phys. Rev. Lett. 90, 233003 (2003); J. Chem. Phys. 118, 8699 (2003); Phys. Rev. A 83, 061403(R) (2011)], where \(k_{B}\) is the Boltzmann constant, and \(\Delta p\) and \(m\) are the full width + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 852, 177]]<|/det|> +at half maximum (FWHM) of the momentum distribution in the jet direction (Y- axis in our case) and mass of the singly ionized molecules of \(\mathrm{N}_{2}^{+}\) and \(\mathrm{N}_{2} - \mathrm{Ar}^{+}\) . In our experiment, we measure \(\Delta p \sim 3.2\) a.u. and \(\Delta p \sim 4.0\) a.u. for \(\mathrm{N}_{2}^{+}\) and \(\mathrm{N}_{2} - \mathrm{Ar}^{+}\) ions. The excellent agreement with the experiment is achieved in the simulation when using \(T = 9 \mathrm{~K}\) for isolated \(\mathrm{N}_{2}\) and \(T = 7 \mathrm{~K}\) for \(\mathrm{N}_{2} - \mathrm{Ar}\) molecule. (on page 11 line 263) + +<|ref|>text<|/ref|><|det|>[[148, 187, 850, 241]]<|/det|> +In our simulation, the initial state is populated according to the measured temperature rather than 0. We also iterate the values used in simulation by comparing the simulation results with the measured alignment trace. + +<|ref|>text<|/ref|><|det|>[[148, 251, 850, 344]]<|/det|> +Specifically, we obtain the time- dependent expectation value, \(\langle A\rangle_{i}(t) = \langle \Psi_{i}(t)|A|\Psi_{i}(t)\rangle\) for an initial state with the energy of \(E_{i}\) , where \(\Psi_{i}(t)\) is the time- dependent wave function for the \(i\) - th initial state. Subsequently, we consider thermal effects by averaging the expectation value over the different initial states with the relative weights given by the Boltzmann distribution, + +<|ref|>equation<|/ref|><|det|>[[386, 358, 610, 405]]<|/det|> +\[\langle A\rangle (t) = \frac{\Sigma_{i}\exp\left(-\frac{E_{i}}{k_{B}T}\right)\langle A\rangle_{i}(t)}{\Sigma_{i}\exp\left(-\frac{E_{i}}{k_{B}T}\right)},\] + +<|ref|>text<|/ref|><|det|>[[148, 419, 640, 437]]<|/det|> +where \(k_{B}\) is the Boltzmann constant and \(T\) is the temperature. + +<|ref|>text<|/ref|><|det|>[[147, 447, 850, 539]]<|/det|> +Considering the high coupling of the entire system (only the total angular momentum \(J\) and its projection \(N\) are good quantum numbers in field- free case), we use a collective temperature \(T\) to describe the system [J. Chem. Phys. 149, 124301 (2018)]. The excellent agreement with the experiment is achieved when using \(T = 9 \mathrm{~K}\) for isolated \(\mathrm{N}_{2}\) and \(T = 7 \mathrm{~K}\) for \(\mathrm{N}_{2} - \mathrm{Ar}\) molecule, which are in good agreement with the measurement. + +<|ref|>text<|/ref|><|det|>[[147, 566, 850, 694]]<|/det|> +The authors consider the interaction of \(N_{2}\) molecules with one or two Ar atoms. Here again, how to justify this approximation when each \(N_{2}\) molecule should interact with many atoms. In the literature, the interaction of linear molecules with its environment was described by a Redfield equation (see (1,2) for instance). Can this modeling be used in the case of this paper? This Redfield description also leads to a rapid degradation of molecular alignment. What are the advantages of direct modeling of molecule- atom interaction? + +<|ref|>text<|/ref|><|det|>[[147, 696, 850, 768]]<|/det|> +(1)- M. Bournazel et al., Non- Markovian collisional dynamics probed with laser- aligned molecules, Phys. Rev. A 107, 023115 (2023) (2)- T. Viellard et al., Field- free molecular alignment for probing collisional relaxation dynamics, Phys. Rev. A 87, 023409 (2013) + +<|ref|>sub_title<|/ref|><|det|>[[148, 798, 232, 815]]<|/det|> +## Reply #2: + +<|ref|>text<|/ref|><|det|>[[147, 825, 850, 898]]<|/det|> +In this work, we focus on the interaction of the \(\mathrm{N}_{2}\) molecule with only one Ar atom both in the experiment and simulation. Although the interaction of the \(\mathrm{N}_{2}\) molecule with two Ar atoms is also measured in the experiment, we cannot simulate such case using our current code. In our work, the molecule- atom interaction is the van der Waals force + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 84, 849, 120]]<|/det|> +formed under low temperature and low pressure, while the molecule- atom interaction in those studies mentioned by the referee is dominated by collisions. + +<|ref|>text<|/ref|><|det|>[[148, 130, 850, 280]]<|/det|> +Those studies were performed in a gas cell with a high pressure and the gas density can be up to a few amagat [e.g., 5 amagat corresponding to the density of \(1.34 \times 10^{26} \mathrm{~m}^{- 3}\) in Phys. Rev. A 107, 023115 (2023)]. In contrast, for the supersonic jet we used, its density was pretty low, typically ranging from \(10^{16}\) to \(10^{18} \mathrm{~m}^{- 3}\) [Phys. Rev. A 68, 023406 (2003); Nat. Phy. 16, 328- 333 (2020)], ensuring neglectable collisions with neighboring atoms and molecules. Molecular alignment for typical linear molecules in this case can persist for more than hundreds of picoseconds [Phys. Rev. A 89, 023432 (2014); Phys. Chem. Chem. Phys 24, 11014 (2022); J. Phys. Chem. A 127, 4848 (2023)]. + +<|ref|>text<|/ref|><|det|>[[149, 288, 850, 344]]<|/det|> +When collisions dominate as the gas density increases, the phenomena can be described by the Bloch- Redfield form of the Liouville- von Neumann equation [J. Chem. Phys. 124, 034101 (2006)]: + +<|ref|>equation<|/ref|><|det|>[[312, 357, 683, 387]]<|/det|> +\[\frac{d\rho(t)}{dt} = -\frac{i}{\hbar} [H_0 + H_i(t),\rho (t)] + \left(\frac{d\rho(t)}{dt}\right)_{diss},\] + +<|ref|>text<|/ref|><|det|>[[149, 399, 850, 436]]<|/det|> +where \(\rho (t)\) is the density operator, \(H_0\) is the free rotational Hamiltonian of the rotating molecule, \(H_i(t)\) is the molecule- field interaction term. + +<|ref|>text<|/ref|><|det|>[[148, 450, 851, 576]]<|/det|> +The collision is exhibited as a dissipative term \(\left(\frac{d\rho(t)}{dt}\right)_{diss}\) , including the rates of population transfer and elastic collision- induced dephasing. Since it is theoretically impossible to precisely consider numerous atoms/molecules, the collision is only approximated to be time- dependent in the view of the Redfield description. In our case, of only one atom and one molecule, the molecule- atom interaction provides a more comprehensive description as the radical and angular parts of the system are considered. + +<|ref|>text<|/ref|><|det|>[[149, 585, 850, 621]]<|/det|> +According to the referee's comment, we briefly comment the difference in the manuscript: + +<|ref|>text<|/ref|><|det|>[[149, 631, 850, 705]]<|/det|> +"Different from the case of high gas densities and temperatures where the collisions dominate the molecule- atom interactions [Phys. Rev. A 107, 023115 (2023), Phys. Rev. A 87, 023409 (2013)], we only consider the interaction of a single \(\mathrm{N}_2\) molecule with one Ar atom at low temperatures when the vdW bond is formed." (on page 7 line 175) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 456, 101]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 121, 850, 195]]<|/det|> +The manuscript "Intermolecular interactions probed by rotational wavepackets in gasphase clusters" by Lu et al explores an internal- rotation wavepacket in \(N_{2}\) - Ar to probe the dynamics, and potentially coupling, of large- amplitudes internal modes of the molecular system. + +<|ref|>text<|/ref|><|det|>[[147, 214, 852, 288]]<|/det|> +Generally, this is a nice experiment that could likely deserves publication in Nat. Comm. following significant clarifications and improvements, mostly regarding the analysis but also with respect to experimental results on the overall rotation of the molecular system. + +<|ref|>text<|/ref|><|det|>[[148, 307, 851, 362]]<|/det|> +Firstly, I am wondering if there is no overall- rotation dynamics induced in the \(N_{2}\) - Ar system by the kick pulse? Obviously, this would be at longer timescales, but should be observable both in the experiment as well as the computations performed by the authors. + +<|ref|>sub_title<|/ref|><|det|>[[148, 382, 232, 399]]<|/det|> +## Reply #1: + +<|ref|>text<|/ref|><|det|>[[147, 408, 851, 520]]<|/det|> +Firstly, we want to clarify that if there was an overall rotation of the \(N_{2}\) - Ar dimer, the first alignment peak of the van der Waals axis should already appear within the current scanning time range (20 ps). Intuitively, the rotation of \(Ar_{2}\) dimers can be used as a reference because of their comparable rotational constants of \(0.05756 \mathrm{cm}^{- 1}\) and \(0.07 \mathrm{cm}^{- 1}\) for \(Ar_{2}\) and \(N_{2}\) - Ar dimers respectively [Phys. Rev. A 83, 061403(R) (2011); Mol. Phys. 27, 903 (1974)]. + +<|ref|>text<|/ref|><|det|>[[147, 529, 819, 548]]<|/det|> +We have added the following content and a new plot in Fig. 2(c) in the manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 557, 851, 705]]<|/det|> +"...On the other hand, Figure 2(c) shows that the vdW axis between the \(N_{2}\) molecule and the Ar atom, termed as Ar- axis hereafter, hardly responds to the kick. It is worth to mention that our observation window is long enough if the Ar- axis shows an immediate post- pulse alignment. As a reference, the vdW axis of the \(Ar_{2}\) dimer with a similar rotational constant shows a clear alignment peak at \(\sim 3.5\) ps. The drastically different alignment response for the N- N axis and the Ar- axis inside the \(N_{2}\) - Ar dimer from that for isolated \(N_{2}\) molecule and \(Ar_{2}\) dimer indicates that the rotational dynamics can serve as a sensitive probe of the molecule- atom interaction." (on page 5 line 120) + +<|ref|>image<|/ref|><|det|>[[150, 713, 850, 878]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 882, 850, 900]]<|/det|> +
Figure R1 (Figure 2(c) in the main text). Measured (step horz curves) and calculated
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 102]]<|/det|> +(smooth curves) time- dependent alignment trace of the Ar- axis of Ar₂ and N₂- Ar dimers. + +<|ref|>text<|/ref|><|det|>[[149, 113, 850, 149]]<|/det|> +To understand the underlying physics, we performed new simulations by simplifying the N₂- Ar dimer as a rigid asymmetric- top molecule. + +<|ref|>text<|/ref|><|det|>[[148, 158, 851, 361]]<|/det|> +"To understand the underlying physics of the rotational dynamics of the N₂ molecule under the influence from the neighboring Ar atom, we performed rigid and floppy model simulations separately. In the rigid model, the N₂- Ar dimer is treated as a rigid asymmetric- top molecule. On the other hand, the vdW bonding nature of the N₂- Ar dimer is implemented by including the molecule- atom interaction potential in the floppy model, where the dynamics of N₂- Ar dimer is described by the internal rotation of N₂ as \(j\) , overall rotation \(L\) and intermolecular stretching (see Methods). Different from the case of high gas densities and temperatures where the collisions dominate the molecule- atom interactions [Phys. Rev. A 87, 023409 (2013), Phys. Rev. A 107, 023115 (2023)], we only consider the interaction of a single N₂ molecule with one Ar atom at low temperatures when the vdW bond is formed. + +<|ref|>text<|/ref|><|det|>[[148, 364, 851, 806]]<|/det|> +Figure 2 shows the simulation results for both the rigid and floppy models. Although both results can repeat the decayed alignment traces, the rigid one shows alignment peaks mismatched from the measurement while the floppy model quantitatively agrees with the experiment. This indicates that the decayed alignment trace results from irregular energy spacing induced by the very unique asymmetric- top property of the N₂- Ar molecular structure, i.e. the moment of inertia of the Ar- axis differs drastically from the other two axes, as listed in Table. 1. However, such asymmetric- top property cannot fully account for the observed rotational dynamics. Figures 4(c) and (d) show the rotational spectra for the two models, which clearly illustrates that the rigid model fails to describe the influence of the neighboring Ar atom on the rotational energy of the N- N axis. Intuitively, the rigid model overestimates the red- shift because the Ar- axis is considered to completely corotate with the N- N axis which slows down its rotation in return. Only if the vdW interaction between the N₂ molecule and Ar atom is properly implemented in the floppy model, the rotational spectrum can be reproduced. The comparison between the two models unambiguously reveals that the rotational dynamics of N₂ molecule can serve as a sensitive probe of the neighboring environment. When it comes to the rotation of the Ar- axis, the rigid model considering the total polarizability shows a neglectable alignment response comparing with the Ar₂ dimer. Thus, the vanishing alignment of the Ar- axis stems from the large discrepancy in moments of inertia, i.e., approximately 30 times smaller moment of inertia along the Ar- axis than that along the other axes. The laser pulse induces the alignment of the N- N axis through the fast rotation about the Ar- axis. However, the large moments of inertia of the other two axes lead to the neglectable change in the angular velocities of rotation about the other two axes." (on page 7 line 169) + +<|ref|>text<|/ref|><|det|>[[149, 825, 850, 899]]<|/det|> +Second, I fear in light of \(>50\) years of spectroscopic studies of floppy molecules and molecular clusters, the semantic description does not do justice to the problem. That is, the N₂- Ar system has 3 low- frequency/large amplitude internal "intermolecular" vibrational modes, build up from the lost 3 degrees of translational freedom of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 159]]<|/det|> +constituents, in addition to the \(N_{2}\) stretch and the overall rotation of the system. The authors use a cumbersome description of this, in which the \(N_{2}\) —Ar stretch does not seem to occur at all and the two other (internal bending) modes are described as simple, maybe too simple, "perturbed 1D \(N_{2}\) rotations". + +<|ref|>text<|/ref|><|det|>[[148, 178, 850, 233]]<|/det|> +Here, it is clear that these motions are coupled, esp. the various internal degrees of freedom and the overall rotation of the cluster. In fact, in an extremely simplified model the authors derive exactly the first glimpses of that. + +<|ref|>text<|/ref|><|det|>[[148, 252, 850, 307]]<|/det|> +Moreover, it seems the overall \(N_{2}\) - Ar stretch of the cluster was "forgotten" in the analysis? Is that justified by any means, i.e., what's the energy gaps and the coupling strengths of this mode to the internal rotations and to the overall rotation? + +<|ref|>sub_title<|/ref|><|det|>[[148, 336, 232, 353]]<|/det|> +## Reply #2: + +<|ref|>text<|/ref|><|det|>[[148, 363, 850, 436]]<|/det|> +We thank the referee for the instructive question. The vibration or stretching between the \(N_{2}\) molecule and the Ar atom is actually observed in our experimental data, as well as included in our simulation. We have added a new Discussion section and a new Fig. 5 to illustrate this issue. + +<|ref|>text<|/ref|><|det|>[[147, 446, 851, 761]]<|/det|> +"For isolated diatomic molecules, the large discrepancy between the vibrational and rotational energies ensures decoupling between rotation and vibration. The vibration can be treated individually under an identical radial potential, resulting in orthogonal vibration states. However, this assumption does not hold any more when it comes to the \(N_{2}\) - Ar dimer since the radial and angular potential is entangled, i.e. the equilibrium distance between the \(N_{2}\) molecule and Ar atom changes with the relative angle between the Ar- axis and the N- N axis. By assuming the repulsive potential of the two- body fragment channel \(N_{2} - \mathrm{Ar} + n\hbar \omega \rightarrow N_{2}^{+} + \mathrm{Ar}^{+} + 2e\) as a simple Coulomb potential of \(1 / r\) , the intermolecular distance \(r\) as a function of time can be reconstructed. Figure 5(a) shows the expectation value \(< r>\) as a function of time, which indicates strong vibrational excitation. Although only the polarizability of \(N_{2}\) is considered in our floppy model, the simulation result well reproduces the intermolecular stretching and its frequency components, as shown in Figs. 5(a) and (b). This indicates that the intermolecular stretching is excited through the coupling with the internal rotation of the \(N_{2}\) molecule. As marked by the green arrows, states with energy gaps of 15.8 and \(20.2 \mathrm{cm}^{- 1}\) are assigned to the frequency components \(v_{1}\) and \(v_{2}\) , respectively. The superposition of these states results in the observed forth- back stretching in Fig. 5(a). + +<|ref|>text<|/ref|><|det|>[[148, 762, 850, 890]]<|/det|> +Figure 5(c) displays the transition diagram of the ro- vibrational spectra. As the angular part is expanded onto the coupled basis in the floppy model, approximate quantum numbers \((j, J)\) are employed to label the eigenstates, where \(j\) represents the rotational quantum number of the N- N axis \((j\) is not a good quantum number), and only \(J\) is the good quantum number of the total angular momentum \(J = L + j\) . The eigenstates are not assigned to an approximate \(L\) - state because of its broad distribution. As numerous states are involved, for illustration, only several states with \(J = 4\) are + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 852, 196]]<|/det|> +displayed. For the internal rotation of \(\mathrm{N}_2\) , states with energy gaps of 9.27, 17.84 and \(26.13 \mathrm{cm}^{- 1}\) have been marked by red arrows in Fig. 5(c), which correspond to the observed rotational frequencies in Fig. 4. These frequencies relate to the ones of the \(\mathrm{N}_2\) monomer corresponding to the (0–2), (1–3) and (2–4) transitions. Thus, the red- shift of rotational frequencies results from smaller energy gaps for states of the \(\mathrm{N}_2\) - Ar than the \(\mathrm{N}_2\) monomer.” (on page 8 line 204) + +<|ref|>image<|/ref|><|det|>[[152, 204, 850, 558]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 567, 852, 696]]<|/det|> +
Figure R2 (Figure 5 in the main text). Intermolecular stretching of the N2-Ar dimer. a Reconstructed (blue curve) and calculated (red curve) time-dependent intermolecular stretching of the \(\mathrm{N}_2\) -Ar dimer. b Power spectra of the reconstructed and calculated intermolecular stretching. c The energy levels are grouped by the approximate quantum numbers \((j, J)\) . The energy gaps related to the frequencies of rotation of \(\mathrm{N}_2\) and intermolecular stretching are marked by red and green arrows, respectively.
+ +<|ref|>text<|/ref|><|det|>[[148, 720, 850, 775]]<|/det|> +I also wonder why the degree of alignment even for \(N_2\) itself is so low. Possibly this is due to a relatively large (rotational) temperature(?). What's the explanation of the authors? + +<|ref|>sub_title<|/ref|><|det|>[[148, 805, 233, 822]]<|/det|> +## Reply #3: + +<|ref|>text<|/ref|><|det|>[[148, 831, 855, 905]]<|/det|> +The reason for the low degree of alignment for \(\mathrm{N}_2\) is we use low intensity \((7 \times 10^{12} \mathrm{W / cm}^2)\) and short duration (50 fs) of the pulse in this work. The temperatures of \(\mathrm{N}_2\) and \(\mathrm{N}_2\) - Ar of the supersonic jet are estimated to be 11 K and 7 K according to their translational temperatures (see Reply #1 of referee1). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 103, 850, 159]]<|/det|> +In that light and in any case, it is important to understand the "vibrational" temperature for the low-frequency modes of the cluster and in how far the modes are thermally excited before the kick pulse. + +<|ref|>sub_title<|/ref|><|det|>[[148, 188, 233, 204]]<|/det|> +## Reply #4: + +<|ref|>text<|/ref|><|det|>[[147, 215, 852, 362]]<|/det|> +Considering the high coupling of various modes, we use a collective temperature of \(T = 7 \mathrm{~K}\) to describe the \(\mathrm{N}_{2}\) - Ar system [J. Chem. Phys. 149, 124301 (2018)] through which the initial thermal ensemble is given by the Boltzmann distribution \(P \sim \exp (- E_{j} / k_{B} T)\) with \(2 J + 1\) degeneracy, where \(E_{j}\) is the energy of an eigenstate state with total angular momentum \(J\) . \(87\%\) of thermally populated states are summarized in Table I (in the simulation, \(99.9\%\) of thermally populated states are involved). + +<|ref|>table<|/ref|><|det|>[[147, 435, 850, 853]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[147, 372, 850, 426]]<|/det|> +Table I. Thermally populations of eigenstates with \(2J + 1\) degeneracy. The states \((j,J)\) are labeled by the quantum numbers of the angular momentum of \(\mathrm{N}_{2}\) . \(j\) , and total angular momentum, \(J\) + +
(j, J)population(j, J)population
0, 00.005610, 80.03482
0, 10.016371, 80.0423
1, 10.01982, 80.0105
0, 20.02580, 90.03023
1, 20.031221, 90.03681
0, 30.03322, 90.00916
1, 30.040190, 100.02528
2, 30.009841, 100.03064
0, 40.038160, 110.01972
1, 40.046221, 110.02465
2, 40.011340, 120.01539
0, 50.040551, 120.01766
1, 50.04914
2, 50.01208
0, 60.04051
1, 60.04913
2, 60.01212
0, 70.03843
1, 70.04664
2, 70.01154
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 159]]<|/det|> +Conceptionally, when comparing the out- of- plane and the in- plane rotation of the \(N_{2}\) in the \(N_{2}\) - Ar dimer, how strongly are these modes coupled – to each other, to and via the intermolecular \(N_{2}\) - Ar stretch, and via the overall rotation? Is it appropriate to discuss the results in such one- dimensional models as done in this manuscript? + +<|ref|>sub_title<|/ref|><|det|>[[149, 189, 232, 205]]<|/det|> +## Reply #5: + +<|ref|>text<|/ref|><|det|>[[149, 216, 850, 307]]<|/det|> +We agree with the referee that the stronger the internal rotation of the N- N axis and the overall rotation are coupled, the more difficult it will be to distinguish between the in- and out of plane rotation of the internal rotation of N- N axis. We have properly illustrated the overall rotation as well as the stretching issue. To make it clearer, we have added the following sentences in the manuscript: + +<|ref|>text<|/ref|><|det|>[[149, 317, 850, 372]]<|/det|> +"Benefiting from the statistically super weak alignment response of the Ar- axis, we found that the difference between the in- and out- of- plane rotations survives after selecting the relative angle between Ar- axis and the probe plane." (on page 6 line 130) + +<|ref|>text<|/ref|><|det|>[[149, 391, 850, 427]]<|/det|> +Are the energies of the relevant (populated) eigenstates in the wavepackets in fact bound states, barrier- modulated above- barrier states, or "free" above- barrier states? + +<|ref|>text<|/ref|><|det|>[[149, 447, 848, 483]]<|/det|> +In fact, this question is relevant for both the initially populated states ("temperature") above and the kick- initiated populations. + +<|ref|>sub_title<|/ref|><|det|>[[149, 512, 232, 529]]<|/det|> +## Reply #6: + +<|ref|>text<|/ref|><|det|>[[149, 540, 652, 557]]<|/det|> +The initial thermal population has been answered in Reply #4. + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 640]]<|/det|> +The time- dependent intermolecular distance during and after the laser kick is shown in Fig. R3. If there's any continuous state or above- barrier state, it will lead to increasing of the molecule- atom distance, i.e. dissociation. As a comparison, the above- barrier state of CH3I- He is shown. [J. Chem. Phys. 149, 124301 (2018)]. + +<|ref|>image<|/ref|><|det|>[[192, 660, 812, 825]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 839, 850, 891]]<|/det|> +
Figure R3. a Time evolution of the probability distribution of N₂-Ar for the distance between the atom and the center of mass of the N₂ molecule. b Same as a but for CH₃I-He.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 106, 850, 179]]<|/det|> +What's the polarizability anisotropy/tensor of the cluster and how does that change as a function of the intermolecular geometry? On the one hand, this would provide first hints at the overall- rotation dynamics induced by the kick as well as the coupling between internal modes and between internal modes and overall rotation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 209, 233, 225]]<|/det|> +## Reply #7: + +<|ref|>text<|/ref|><|det|>[[148, 236, 850, 293]]<|/det|> +The polarizability components of the T- shape \(\mathrm{N}_2\) - Ar are listed in Table II, through which the rigid model is performed. In the floppy model, we only consider the polarizability of the isolated \(\mathrm{N}_2\) molecule, the polarizability components along and perpendicular to + +<|ref|>text<|/ref|><|det|>[[148, 300, 805, 321]]<|/det|> +the molecular axis are set to be \(\alpha_{\parallel} = 2.38 \mathrm{\AA}^3\) and \(\alpha_{\perp} = 1.45 \mathrm{\AA}^3\) , respectively. + +<|ref|>text<|/ref|><|det|>[[148, 338, 850, 411]]<|/det|> +Strictly speaking, the polarizability changes with the \(\mathrm{N}_2\) molecular rotation as well as the stretching. Although we cannot include such complex treatment in our current model, the floppy model still can well reproduce the experimental results, which in return indicates that the dynamical polarizability is not critical here. + +<|ref|>text<|/ref|><|det|>[[148, 420, 850, 569]]<|/det|> +We attribute the success to the following reasons. The 50 fs pulse duration in our experiment is much shorter than the period of internal rotation and intermolecular vibration (magnitude of ps), such that the structure deformation during the pulse duration is not important. An improved model including a geometry- dependent polarizability may be required to describe the case of long kick pulse duration as the referee mentioned [e.g., 1.3 ps in Chem. Phys. Lett., 803, 139850 (2022); Phys. Chem. Chem. Phys. 24, 11014 (2022); 150 ps and 1.3 ps in Phys. Chem. Chem. Phys. 22, 3245 (2020)]. + +<|ref|>text<|/ref|><|det|>[[148, 578, 850, 651]]<|/det|> +Table II. Moments of Inertia and Polarizabilities of the \(\mathrm{N}_2\) - Ar dimer under T- shape configuration. The \(a\) - axis and \(b\) - axis represent the axes parallel to the N- N axis and Ar- axis in the molecular frame, respectively. The \(c\) - axis is perpendicular to the \(a\) - and \(c\) - axes. + +<|ref|>table<|/ref|><|det|>[[197, 660, 799, 806]]<|/det|> + +
Moments of Inertia (amu Ų)Polarizability (ų)
Ia = 225.54αaa = 3.71
Ib = 8.47αbb = 3.32
Ic = 234.02αcc = 3.04
+ +<|ref|>text<|/ref|><|det|>[[148, 844, 850, 880]]<|/det|> +When comparing \(N_2\) rotational dynamics to the 1D- internal- rotation dynamics the reduction of dimensionality (1D to 2D) likely needs to be taken into account. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 852, 233]]<|/det|> +To me, and in light of the very rich set of descriptions the simple model utilized by the authors does not seem to be appropriate. In fact, an analysis of the "intermolecular interactions probed by rotational wavepackets" would be highly appreciated and useful – if actually analyzed and described in the long- standing and proven models of intermolecular interactions. In the simple system presented here, that would require a 6D description (3 degrees of overall rotation and 3 degrees of intermolecular vibrations/internal rotations). This is clearly possible, both semantically as well as computationally. + +<|ref|>sub_title<|/ref|><|det|>[[148, 262, 232, 279]]<|/det|> +## Reply #8: + +<|ref|>text<|/ref|><|det|>[[149, 288, 850, 343]]<|/det|> +We have explained in Reply #1 and #2. Briefly, we considered internal rotation, overall rotation and intermolecular stretching, while we neglected the vibration between N- N atoms due to its strong interaction + +<|ref|>text<|/ref|><|det|>[[149, 372, 848, 408]]<|/det|> +One of the important points to clarify is which of all these modes are actually directly Raman- excited in the experiment. + +<|ref|>sub_title<|/ref|><|det|>[[148, 437, 232, 454]]<|/det|> +## Reply #9: + +<|ref|>text<|/ref|><|det|>[[148, 464, 850, 537]]<|/det|> +Our experimental results indicate that the internal rotation is directly excited through the polarizability of \(\mathrm{N}_2\) (Reply #19). For the overall rotation, the vanishing alignment stems from the large discrepancy in moments of inertia (Reply #1). The intermolecular vibration can be excited through coupling with the internal rotation (Reply #2). + +<|ref|>text<|/ref|><|det|>[[149, 566, 850, 621]]<|/det|> +Moreover, here it is really important to clarify also experimentally both the intermolecular stretch as well as the overall rotation – and their corresponding interaction with the internal rotations (same for thermal excitations of all these modes). + +<|ref|>sub_title<|/ref|><|det|>[[148, 642, 243, 659]]<|/det|> +## Reply #10: + +<|ref|>text<|/ref|><|det|>[[149, 668, 466, 686]]<|/det|> +We have explained in Reply #1 and #2. + +<|ref|>text<|/ref|><|det|>[[149, 715, 850, 769]]<|/det|> +The authors should also consider to refer to previous alignment experiments of floppy molecules and clusters, which is really what they are following up on here, e.g., PRL 102, (2009); JCP 148, 101103 (2018); PCCP 22, 3245- 3253 (2020), ... + +<|ref|>sub_title<|/ref|><|det|>[[148, 799, 241, 815]]<|/det|> +## Reply #11: + +<|ref|>text<|/ref|><|det|>[[149, 825, 475, 842]]<|/det|> +We have added the following sentences: + +<|ref|>text<|/ref|><|det|>[[148, 853, 850, 888]]<|/det|> +"Recently, investigations on the rotational dynamics of such floppy molecule- atom clusters have been fueled due to their unique properties under the interaction with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 84, 850, 140]]<|/det|> +neighboring environment [Phys. Rev. Lett. 102, 023001 (2009); J. Chem. Phys. 148, 101103 (2018); Phys. Chem. Chem. Phys. 22, 3245 (2020)]; J. Phys. Chem. A 127, 4848 (2023); Phys. Rev. A 89, 023432 (2014)]." (on page 3, line 59) + +<|ref|>text<|/ref|><|det|>[[149, 168, 850, 223]]<|/det|> +In the experimental section, how does a 7:3 splitting of the laser beam lead to intensities that differ by 2 orders of magnitude? Different focusing? Specify. Generally, some more details on the actual experiment should be provided in Methods. + +<|ref|>sub_title<|/ref|><|det|>[[149, 252, 243, 270]]<|/det|> +## Reply #12: + +<|ref|>text<|/ref|><|det|>[[149, 279, 683, 297]]<|/det|> +For clarity, we have added the following sentences in the Method: + +<|ref|>text<|/ref|><|det|>[[149, 307, 850, 380]]<|/det|> +"The intensities of them are adjustable using two neutral density filters and a quarter wave plate is placed in the arm of the probe pulse to make it circularly polarized. The probe pulse additionally passed through a telescope which increase its diameter by a factor of 1.5." (on page 11, line 251) + +<|ref|>text<|/ref|><|det|>[[149, 409, 850, 444]]<|/det|> +Also, details of the implementation of the computational approach by Zillich should be described. + +<|ref|>sub_title<|/ref|><|det|>[[149, 474, 243, 491]]<|/det|> +## Reply #13: + +<|ref|>text<|/ref|><|det|>[[149, 501, 596, 518]]<|/det|> +A more detailed description has been added in Method. + +<|ref|>text<|/ref|><|det|>[[149, 547, 848, 565]]<|/det|> +Re l. 117: No, (N2)- Ar axis motion can be internal rotation as well as overall rotation... + +<|ref|>sub_title<|/ref|><|det|>[[149, 595, 243, 612]]<|/det|> +## Reply #14: + +<|ref|>text<|/ref|><|det|>[[149, 621, 850, 657]]<|/det|> +To avoid misleading, we have removed the sentence "For simplicity, we refer to this joint pump probe induced observable as "rotation" ". + +<|ref|>text<|/ref|><|det|>[[149, 668, 850, 722]]<|/det|> +Considering the neglectable alignment of overall rotation (Reply #1), for the rotation dynamics of \(\mathrm{N}_2\) - Ar, only the internal rotation is a good observable, therefore the rotation refers to the alignment of the N- N axis is caused by internal rotation currently. + +<|ref|>text<|/ref|><|det|>[[147, 760, 781, 778]]<|/det|> +/j/ is a "1D internal rotation" quantum number and should be treated as such. + +<|ref|>sub_title<|/ref|><|det|>[[149, 808, 243, 825]]<|/det|> +## Reply #15: + +<|ref|>text<|/ref|><|det|>[[149, 834, 850, 889]]<|/det|> +We have added the description of the floppy model in the revised version. The floppy model considers 3 rotational degrees of freedom and 2 vibrational degrees of freedom, while neglecting the vibration between N- N atoms due to its strong interaction. \(j\) is the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 635, 103]]<|/det|> +angular momentum quantum number of the linear molecule. + +<|ref|>text<|/ref|><|det|>[[148, 140, 850, 177]]<|/det|> +In the simulations: When the molecule is so floppy, why is it appropriate to use a single reduced mass \(\mu\) – instead of a coordinate/geometry depended one? + +<|ref|>sub_title<|/ref|><|det|>[[148, 206, 243, 223]]<|/det|> +## Reply #16: + +<|ref|>text<|/ref|><|det|>[[148, 232, 850, 326]]<|/det|> +The reduced mass \(\mu\) is used to represent the relative motion of Ar and \(\mathrm{N}_2\) about their center of mass which is related to the overall rotation and intermolecular stretching. The relative distance (radical part) and rotation (angular part) are responsible for the geometry character of the floppy dimer rather than the reduced mass [J. Chem. Phys. 100, 2505 (1994)]. + +<|ref|>text<|/ref|><|det|>[[148, 335, 720, 353]]<|/det|> +Thus, the reduced mass doesn't depend on the coordinate or geometry. + +<|ref|>text<|/ref|><|det|>[[149, 381, 754, 399]]<|/det|> +Which pulse intensity and rotational temperature do the simulations yield? + +<|ref|>sub_title<|/ref|><|det|>[[148, 428, 243, 445]]<|/det|> +## Reply #17: + +<|ref|>text<|/ref|><|det|>[[148, 454, 850, 510]]<|/det|> +In the simulation, the pulse intensity is set to be \(7 \times 10^{12} \mathrm{~W / cm}^2\) and the initial rotational temperature is set to be \(9 \mathrm{~K}\) and \(7 \mathrm{~K}\) for \(\mathrm{N}_2\) and \(\mathrm{N}_2\) - Ar, respectively. See Reply #1 for the first referee. + +<|ref|>text<|/ref|><|det|>[[148, 539, 850, 593]]<|/det|> +The \(\mathrm{N}_2\) - Ar2 cluster seems to be un- analyzed and superfluous. It's a nice experiment, but it does not provide any information in the current paper. Either leave away or clarify what you learn from this data. + +<|ref|>sub_title<|/ref|><|det|>[[148, 622, 243, 639]]<|/det|> +## Reply #18: + +<|ref|>text<|/ref|><|det|>[[148, 649, 850, 760]]<|/det|> +Under the same laser kick, the internal rotation is more severely hindered by two neighboring Ar atoms. Collaborating with the rotational dynamics of \(\mathrm{N}_2\) and \(\mathrm{N}_2\) - Ar, the absence of the alignment of the \(\mathrm{N}_2\) axis in \(\mathrm{N}_2\) - Ar2 directly indicates a quantity effect as the number of neighboring atoms increases that what we learned from the experiment. Though a deeper analysis of this complex rotational dynamics is not available currently, this result will be good to know. + +<|ref|>text<|/ref|><|det|>[[147, 788, 860, 844]]<|/det|> +1. 148: "rotational deceleration of \(\mathrm{N}_2\) induced by 149 the neighboring Ar in time domain" – is this actually a deceleration or simply a "slower dynamics"? Or is this simply a first dim hint at the coupling of various modes (vide supra)? + +<|ref|>sub_title<|/ref|><|det|>[[148, 872, 243, 889]]<|/det|> +## Reply #19: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 84, 850, 140]]<|/det|> +For the rotation of \(\mathrm{N}_2\) , the central values of each spectral peak, 11.94, 19.9, and 27.86 \(\mathrm{cm}^{- 1}\) , are given by the frequency of a \((j - j + 2)\) coherence and described by the expression \(B(4j + 6)\) as a rigid rotor with the rotational constant \(B = 1.99 \mathrm{cm}^{- 1}\) . + +<|ref|>text<|/ref|><|det|>[[149, 149, 850, 243]]<|/det|> +For the internal rotation of \(\mathrm{N}_2\) - Ar, similar to the intermolecular stretching, several states with \(J = 4\) have been marked by red arrows in Fig. R2(c). These states with energy gaps of 9.27, 17.84, and 26.13 \(\mathrm{cm}^{- 1}\) are close to the observed rotational frequencies in Fig. 4(b) in the manuscript. Collaborating with approximate labels, these frequencies can relate to the \(\mathrm{N}_2\) monomer corresponding to the (0- 2), (1- 3), and (2- 4) coherences. + +<|ref|>text<|/ref|><|det|>[[149, 251, 850, 306]]<|/det|> +Thus, the red- shift of rotational frequencies and deceleration result from smaller energy gaps between states of the \(\mathrm{N}_2\) - Ar than the \(\mathrm{N}_2\) monomer and the quantum beatings of these states induce the slower rotation in the time domain. + +<|ref|>text<|/ref|><|det|>[[149, 316, 850, 389]]<|/det|> +As previous studies have suggested, the faster the internal rotation is, the more it behaves like a free rotor, namely a weaker coupling and \(j\) becomes a good quantum number. So, the frequency shift directly reflects the coupling strength of the internal rotation with other modes. + +<|ref|>text<|/ref|><|det|>[[147, 418, 848, 455]]<|/det|> +Overall, to me this work requires very significant improvements, but I am looking forward to see this then published Nat. Comm. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 295, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 112, 415, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 141, 864, 197]]<|/det|> +Dear Editor, since the authors adequately responded to all questions and comments of the referees, I support the publication of this paper. Best regards, + +<|ref|>text<|/ref|><|det|>[[119, 238, 415, 252]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 267, 330, 280]]<|/det|> +Please see attached review. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 66, 905, 81]]<|/det|> +Review of "Intermolecular interactions probed by rotational dynamics in gas- phase clusters" by Chenxu Lu et al. + +<|ref|>text<|/ref|><|det|>[[92, 87, 905, 145]]<|/det|> +Overall, the manuscript was strongly improved and all reviewer comments were addressed. Besides a few smaller comments, for clarity and accessibility the description of the molecular dynamics needs to be placed - numerically and semantically - in an the model that takes all relevant dimensions/motions into account. This should likely use the - extremely rich - traditional descriptions of intermolecular interactions in molecular clusters. + +<|ref|>text<|/ref|><|det|>[[92, 152, 905, 222]]<|/det|> +I.e., the model of the authors should be correlated to, by explanation, or use traditional models which describe the lost translational degrees of freedom due complex formation as intermolecular vibrations, i.e., stretching, bending, or torsion/internal rotation modes. Textbook descriptions like chapter 9 of Kroto: Molecular Rotation Spectra (1975) or conceptional papers such as Molecular Physics 84, 853- 878 (1995) could be a good start for reference. I am convinced the authors can find more such relevant descriptions. + +<|ref|>text<|/ref|><|det|>[[92, 229, 905, 315]]<|/det|> +This also includes a - also semantically - combined description of the "internal rotation" and the coupled stretching vibration. Btw. this new data in Fig. 5 is very nice and a strong addition to the paper. Fig. 5c and its description in the initial part of the discussion would strongly benefit from the advanced description sought for in this comment. That the \((j,J)\) nomenclature does not provide a good (supra)molecular frame description of the dynamics is also reflected when it averages the different motions - at least 2 bends and 1 stretch - into one \(j\) , which is not even a good quantum number (1. 224). + +<|ref|>text<|/ref|><|det|>[[92, 321, 905, 377]]<|/det|> +Generally, a more "supermolecular" description of the cluster might be much clearer to describe the actual couplings and resulting dynamics. This would allow for a direct discussion of the relative contributions of the various mode- to- mode couplings and, furthermore, would allow to put these results into the context of the very many frequency- resolved investigations of such interactions. This would also c + +<|ref|>text<|/ref|><|det|>[[92, 384, 768, 400]]<|/det|> +This should also seen in light of the authors insight that " \(j\) is not a good quantum number" + +<|ref|>text<|/ref|><|det|>[[92, 406, 636, 421]]<|/det|> +It should be clarified what "properly implemented" in line 192 actually is. + +<|ref|>text<|/ref|><|det|>[[92, 428, 430, 443]]<|/det|> +What are "frequency components \(\nu_{1}\) and \(\nu_{2}\) ?" + +<|ref|>text<|/ref|><|det|>[[92, 465, 272, 479]]<|/det|> +Some further comments: + +<|ref|>text<|/ref|><|det|>[[92, 486, 904, 515]]<|/det|> +When comparing the alignment of the "Ar axis" for N2- Ar and Ar- Ar (Fig 2c), were the corresponding interaction strengths and their anisotropies between the two experiments comparable? + +<|ref|>text<|/ref|><|det|>[[92, 520, 904, 550]]<|/det|> +The N2- Ar2 results, as interesting they are, need further description, rationalizing, and discussion to be reasonably included in the manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 556, 905, 614]]<|/det|> +Approximating the rotational temperature based on translation can only provide a lower bound for the rotational temperature. In fact, they are often quite different for seeded beams - speed ratios of the beam \(>100\) but still rotational temperatures \(\sim 10 \mathrm{~K}\) . Even if the agreement is good here, this approximative approach ("lower bound") should probably be more clearly pointed out. + +<|ref|>text<|/ref|><|det|>[[92, 620, 904, 650]]<|/det|> +Is the indeed relatively low- intensity short- pulse nature of the excitation also the reason for not exciting the overall rotation? Would be worth simulating at higher kick- energy and mentioning in the manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 655, 904, 684]]<|/det|> +It would be useful to clearly point out that all dynamics is in truly bound states. Also related to the weak kick strength used. + +<|ref|>text<|/ref|><|det|>[[92, 691, 797, 706]]<|/det|> +To me, "deceleration" (reply #19) seems to be the inappropriate word, it seems to say "slower". + +<|ref|>text<|/ref|><|det|>[[92, 712, 353, 727]]<|/det|> +What's "umbrella time breathing"? + +<|ref|>text<|/ref|><|det|>[[92, 734, 731, 749]]<|/det|> +In line 208: Is this truly 'entanglement' in "radial and angular potential is entangled"? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 90, 358, 106]]<|/det|> +Re: NCOMMS- 23- 43274B + +<|ref|>text<|/ref|><|det|>[[148, 118, 850, 162]]<|/det|> +" Intermolecular interactions probed by rotational dynamics in gas- phase clusters" by Chenxu Lu et al. + +<|ref|>text<|/ref|><|det|>[[149, 187, 848, 222]]<|/det|> +For clarity, we put the original comments in italics to distinguish from our responses in blue. The text that has been changed or newly added is in red. + +<|ref|>text<|/ref|><|det|>[[150, 242, 457, 259]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 279, 850, 389]]<|/det|> +Overall, the manuscript was strongly improved and all reviewer comments were addressed. Besides a few smaller comments, for clarity and accessibility the description of the molecular dynamics needs to be placed - numerically and semantically - in an the model that takes all relevant dimensions/motions into account. This should likely use the - extremely rich - traditional descriptions of intermolecular interactions in molecular clusters. + +<|ref|>text<|/ref|><|det|>[[148, 408, 850, 538]]<|/det|> +I.e., the model of the authors should be correlated to, by explanation, or use traditional models which describe the lost translational degrees of freedom due complex formation as intermolecular vibrations, i.e., stretching, bending, or torsion/internal rotation modes. Textbook descriptions like chapter 9 of Kroto: Molecular Rotation Spectra (1975) or conceptional papers such as Molecular Physics 84, 853- 878 (1995) could be a good start for reference. I am convinced the authors can find more such relevant descriptions. + +<|ref|>text<|/ref|><|det|>[[148, 557, 850, 704]]<|/det|> +This also includes a - also semantically - combined description of the "internal rotation" and the coupled stretching vibration. Btw. this new data in Fig. 5 is very nice and a strong addition to the paper. Fig. 5c and its description in the initial part of the discussion would strongly benefit from the advanced description sought for in this comment. That the (j, J) nomenclature does not provide a good (supra)molecular frame description of the dynamics is also reflected when it averages the different motions - at least 2 bends and 1 stretch - into one j, which is not even a good quantum number (l. 224). + +<|ref|>text<|/ref|><|det|>[[148, 723, 850, 835]]<|/det|> +Generally, a more "supermolecular" description of the cluster might be much clearer to describe the actual couplings and resulting dynamics. This would allow for a direct discussion of the relative contributions of the various mode- to- mode couplings and, furthermore, would allow to put these results into the context of the very many frequency- resolved investigations of such interactions. This should also seen in light of the authors insight that "j is not a good quantum number" + +<|ref|>sub_title<|/ref|><|det|>[[149, 864, 232, 880]]<|/det|> +## Reply #1: + +<|ref|>text<|/ref|><|det|>[[149, 890, 848, 908]]<|/det|> +The floppy model is performed under the space- fixed expression rather than the body + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 84, 850, 158]]<|/det|> +fixed expression. These two expressions are equivalent, and they are both commonly used descriptions of noncovalent clusters [Chem. Rev., 94, 1931 (1994); Chem. Rev. 100, 4109 (2000)]. We chose the space- fixed (lab- frame) model since it makes us to have a direct comparison with the experimental observations. + +<|ref|>text<|/ref|><|det|>[[149, 168, 850, 204]]<|/det|> +Based on the space- fixed expression, a more detailed description of all relevant dimensions (five degrees of freedom) has been added to the Methods + +<|ref|>text<|/ref|><|det|>[[148, 214, 851, 399]]<|/det|> +"...The floppy model is conducted under the space- fixed scheme, where the rotation of \(\mathrm{N}_{2}\) and the translation motion are included, and the molecule- atom interaction is represented by an accurate potential surface [J. Chem. Phys. 121, 10419 (2004)]. Due to the complex formation, the angular part and the radical part of the translation motion are reduced to the rotation and intermolecular stretching of the vdW axis, respectively. With the rigid rotor approximation, the vibration of \(\mathrm{N}_{2}\) molecule is assumed to be neglected. Thus, the floppy model includes five degrees of freedom including two rotational degrees of \(\mathrm{N}_{2}\) , two rotational degrees and one vibrational degree of vdW axis, and the Hamiltonian in the space- fixed scheme takes the form of..."(on page 12 line 309) + +<|ref|>text<|/ref|><|det|>[[148, 408, 852, 576]]<|/det|> +In our floppy model, two rotational degrees of \(\mathrm{N}_{2}\) and two rotational degrees of the vdW- axis are described in the lab frame which is consist with the experimental measurement of their angles with respect to the lab frame Z- axis (polarization direction of the kick pulse) [J. Chem. Phys. 78, 4025 (1983); Chem. Phys. Lett. 221, 161 (1994); Chem. Rev. 94, 1931 (1994); J. Chem. Phys. 108, 3554 (1998)]. For the body- fixed treatment of \(\mathrm{N}_{2}\) - Ar, it has been implemented by pioneering works, where the \(\mathrm{N}_{2}\) rotation is described by the angle with respect to the vdW axis in the molecular frame, termed as bending motions [Mol. Phys. 27, 903 (1974); J. Chem. Phys. 88, 578 (1988); J. Chem. Phys. 110, 8525 (1999); J. Chem. Phys. 121, 10419 (2004)]. + +<|ref|>text<|/ref|><|det|>[[148, 585, 850, 677]]<|/det|> +The main difference of two expressions is the reference frame, and the Coulomb explosion imaging directly images the angular distribution in the lab frame rather than the molecular frame (both for the Ar- axis and N- N axis). Thus, a space- fixed description is more straightforward in our case, especially for the comparison with the isolated \(\mathrm{N}_{2}\) under the same reference frame. + +<|ref|>text<|/ref|><|det|>[[148, 687, 850, 852]]<|/det|> +An eigenstate can be expressed as a superposition of different \(j\) and \(L\) components in the space- fixed scheme (see Methods for the expression of an eigenstate), namely couplings of these modes. Only the parity \(p = (- 1)^{j + L + J}\) , the total angular momentum \(J\) and its projection \(N\) onto Z- axis are rigorous. To get a qualitatively description about the degrees of freedom involved, approximate quantum numbers are instructive and required for both space- fixed and body- fixed expressions [Chem. Rev. 100, 4109 (2000)]. Collaborating with the approximate quantum number \(j\) of \(\mathrm{N}_{2}\) - Ar, the frequencies in Fig. 4 can relate to the ones of the \(\mathrm{N}_{2}\) monomer corresponding to the \((j - j + 2)\) transitions, i.e., (0- 2), (1- 3) and (2- 4). + +<|ref|>text<|/ref|><|det|>[[148, 862, 849, 899]]<|/det|> +Now approximate quantum numbers \((n, j, L)\) are introduced corresponding to the intermolecular stretching, \(\mathrm{N}_{2}\) rotation and vdW rotation, respectively. Quantum + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 140]]<|/det|> +numbers \(j\) and \(L\) are assigned according to their dominant components of an eigenstate. The quantum number \(n\) is used to represent the intermolecular stretch according to the nodes in the stretch coordinate \(r\) [J. Chem. Phys. 88, 578 (1988)]. + +<|ref|>text<|/ref|><|det|>[[148, 149, 850, 260]]<|/det|> +Besides this qualitatively description, a direct knowledge about an eigenstate of its components from relative contributions of various \(j\) and \(L\) - states, and radical distributions along the stretch coordinate has been added to the Supplementary materials. It can be seen that as the increasing of energy, the quantum number \(j\) becomes nearly rigorous and the \(\mathrm{N}_2\) rotation behaves like a free rotor, while \(L\) still shows a wide distribution attributing to the small rotational energy of Ar- axis. + +<|ref|>image<|/ref|><|det|>[[150, 275, 848, 430]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 438, 851, 530]]<|/det|> +
Figure R1 (Supplementary Figure 1) (a) Populations of \(j\) -states of eigenstates (b) Same as (a) but for the \(L\) -states. (c) Radical distributions along the stretch coordinate \(r\) of eigenstates. The eigenstates (Fig. 5(c) in the manuscript) are assigned by approximate quantum numbers (n, j, L) according to the nodes in the stretch coordinate \(r\) , and the most populated components of \(j\) and \(L\) .
+ +<|ref|>text<|/ref|><|det|>[[148, 566, 819, 584]]<|/det|> +For the intermolecular stretching, we add the following contents to the manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 594, 850, 761]]<|/det|> +"...As marked by the green arrows, states with energy gaps of 15.8 and \(20.1 \mathrm{cm}^{- 1}\) are assigned to the frequency components \(v_{1}\) and \(v_{2}\) , respectively. The frequency \(v_{2}\) originating from the states beating between \(n = 0\) and 1 dominates the intermolecular stretching, where \(n\) is the approximate stretch quantum number representing the nodes in the stretch coordinate \(r\) [J. Chem. Phys. 88, 578 (1988)]. The frequency \(v_{1}\) originates from the identical approximate stretch quantum number \(n = 0\) of similar but different radial distributions (see Supplementary materials) as \(n\) is not rigorous, which results in the stretching with a relatively smaller amplitude as compared to \(v_{2}\) ." (on page 9 line 211) + +<|ref|>text<|/ref|><|det|>[[148, 770, 849, 825]]<|/det|> +In the revised manuscript, we provide a more detailed description of relevant degrees of freedom of the observables and revise the label in Fig. 5. The pioneer works for \(\mathrm{N}_2\) - Ar under the body- fixed expression have been mentioned and cited properly. + +<|ref|>text<|/ref|><|det|>[[148, 835, 850, 908]]<|/det|> +"Figure 5(c) displays the transition diagram of the ro- vibrational spectra carried out in the space- fixed expression [Chem. Rev., 94, 1931 (1994)]. Attributing to the low kick intensity which avoids the rotational dissociation [J. Chem. Phys. 147, 074304 (2017); J. Chem. Phys. 149, 124301 (2018)], the observed dynamics occurs in bound states of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 851, 550]]<|/det|> +\(\mathrm{N}_{2}\) - Ar. As the angular part is expanded onto the coupled basis in the floppy model, approximate quantum numbers \((n, j, L)\) are employed to label the eigenstates corresponding to the intermolecular stretching, \(\mathrm{N}_{2}\) rotation and vdW rotation respectively, where \(j\) and \(L\) are the approximate rotational quantum numbers of \(\mathrm{N}_{2}\) and Ar-axis. An approximate quantum number which is not rigorous implies the involvement of multiple modes within this coordinate. Only the parity \(p = (- 1)^{j + L + J}\) , the total angular momentum \(J\) and its projection \(N\) are rigorous. As numerous states are involved, for illustration, only several states with even parity and \(J = 4\) are displayed. In the view of space- fixed expression, the quantum numbers \(j\) and \(L\) are not rigorous which means that an eigenstate of \(\mathrm{N}_{2}\) - Ar is a superposition of different rotational states of the N- N axis and Ar- axis (see Methods). For simplicity, the approximate quantum number \(j\) and \(L\) are assigned according to their most populated components (see Supplementary materials). The approximate quantum number is instructive as it builds up a connection between isolated \(\mathrm{N}_{2}\) and \(\mathrm{N}_{2}\) - Ar dimer, and reveals behaviors of the N- N axis with different angular momentum under the interaction of Ar. As the increase of \(j\) , the \(\mathrm{N}_{2}\) molecule behaves like a free rotor. Besides this space- fixed expression, a molecular frame knowledge about the internal bending of \(\mathrm{N}_{2}\) - Ar dimer can be obtained under the body- fixed expression [Mol. Phys. 27, 903 (1974); J. Chem. Phys. 88, 578 (1988); J. Chem. Phys. 110, 8525 (1999)]. For the rotation of \(\mathrm{N}_{2}\) , states with energy gaps of 9.27, 17.85 and 26.04 \(\mathrm{cm}^{- 1}\) have been marked by red arrows in Fig. 5(c), which correspond to the observed rotational frequencies in Fig. 4. Collaborating with the approximate quantum number \(j\) of \(\mathrm{N}_{2}\) - Ar, these frequencies can relate to the ones of the \(\mathrm{N}_{2}\) monomer corresponding to the (0–2), (1–3) and (2–4) transitions. Thus, the red- shift of rotational frequencies results from smaller energy gaps for states of the \(\mathrm{N}_{2}\) - Ar than the \(\mathrm{N}_{2}\) monomer.” (on page 9 line 220) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 92, 852, 450]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 464, 854, 595]]<|/det|> +
Figure R2 (Figure 5 in the main text). Intermolecular stretching of the \(\mathbf{N}_2\) -Ar dimer. a Reconstructed (blue curve) and calculated (red curve) time-dependent intermolecular stretching of the \(\mathbf{N}_2\) -Ar dimer. b Power spectra of the reconstructed and calculated intermolecular stretching. c The energy levels, with the even parity \(p = (-1)^{J + L + J}\) and \(J\) \(= 4\) , are grouped by the approximate quantum numbers \((n,j,L)\) . The energy gaps related to the frequencies of rotation of \(\mathbf{N}_2\) and intermolecular stretching are marked by red and green arrows, respectively.
+ +<|ref|>text<|/ref|><|det|>[[148, 621, 751, 640]]<|/det|> +It should be clarified what "properly implemented" in line 192 actually is. + +<|ref|>sub_title<|/ref|><|det|>[[148, 668, 233, 686]]<|/det|> +## Reply #2: + +<|ref|>text<|/ref|><|det|>[[148, 696, 632, 714]]<|/det|> +For clarity, we have modified the corresponding statement: + +<|ref|>text<|/ref|><|det|>[[148, 723, 850, 779]]<|/det|> +"Only if the molecule- atom interaction potential rather than a rigid connection between \(\mathbf{N}_2\) and Ar is added to describe their interaction (see Methods for details of the floppy model), the rotational spectrum can be reproduced." (on page 8 line 177) + +<|ref|>text<|/ref|><|det|>[[148, 807, 520, 825]]<|/det|> +What are "frequency components \(\nu_1\) and \(\nu_2\) "? + +<|ref|>sub_title<|/ref|><|det|>[[148, 854, 233, 871]]<|/det|> +## Reply #3: + +<|ref|>text<|/ref|><|det|>[[149, 881, 408, 899]]<|/det|> +We have explained in Reply #1. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 105, 347, 120]]<|/det|> +Some further comments: + +<|ref|>text<|/ref|><|det|>[[149, 141, 850, 195]]<|/det|> +When comparing the alignment of the "Ar axis" for N2- Ar and Ar- Ar (Fig 2c), were the corresponding interaction strengths and their anisotropies between the two experiments comparable? + +<|ref|>sub_title<|/ref|><|det|>[[149, 225, 234, 242]]<|/det|> +## Reply #4: + +<|ref|>text<|/ref|><|det|>[[149, 251, 850, 306]]<|/det|> +Both the interaction strengths and anisotropies of them are comparable. The fragments of Coulomb exploded \(\mathrm{Ar}_2\) dimer and \(\mathrm{N}_2\) - Ar dimer are collected in coincidence, ensuring the same kick intensity. + +<|ref|>text<|/ref|><|det|>[[149, 315, 850, 410]]<|/det|> +The interaction energy of Ar- Ar has been calculated to be \(98.4\mathrm{cm}^{- 1}\) [J. Chem. Phys. 119, 2102 (2003)] which is close to the one of \(\mathrm{N}_2\) - Ar (about \(100\mathrm{cm}^{- 1}\) ) [J. Chem. Phys. 121, 10419 (2004)]. The polarizability anisotropy used in simulation for Ar- Ar is 0.45 \(\mathrm{\AA}^3\) [Phys. Rev. A 89, 023432 (2014)] which is comparable with the one about the Ar- axis in \(\mathrm{N}_2\) - Ar \((\Delta \alpha_{bc} = \alpha_{bb} - \alpha_{cc} = 0.28 \mathrm{\AA}^3)\) . + +<|ref|>text<|/ref|><|det|>[[149, 418, 771, 436]]<|/det|> +To make it clearer, we have added the following sentences in the manuscript: + +<|ref|>text<|/ref|><|det|>[[149, 446, 850, 519]]<|/det|> +"As a reference, the vdW axis of the \(\mathrm{Ar}_2\) dimer with a similar rotational constant, interaction strength and comparable polarizability anisotropy [J. Chem. Phys. 119, 2102 (2003); J. Chem. Phys. 121, 10419 (2004); Phys. Rev. A 89, 023432 (2014); Mol. Phys. 27, 903 (1974)] show a clear alignment peak at \(\sim 3.5\mathrm{ps}^*\) (on page 5 line 117) + +<|ref|>text<|/ref|><|det|>[[149, 548, 850, 583]]<|/det|> +The N2- Ar2 results, as interesting they are, need further description, rationalizing, and discussion to be reasonably included in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 613, 234, 630]]<|/det|> +## Reply #5: + +<|ref|>text<|/ref|><|det|>[[149, 640, 850, 694]]<|/det|> +As we have mentioned in the former reply, from current experiment results, we can obtain a quantity effect as the number of neighboring atoms increases. But currently we cannot simulate such case using our code which prevents us from a further analysis. + +<|ref|>text<|/ref|><|det|>[[149, 704, 850, 740]]<|/det|> +To avoid an ambiguous description of \(\mathrm{N}_2\) - \(\mathrm{Ar}_2\) , we follow the referee's former suggestion that we no longer discuss it in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[149, 770, 850, 861]]<|/det|> +Approximating the rotational temperature based on translation can only provide a lower bound for the rotational temperature. In fact, they are often quite different for seeded beams - speed ratios of the beam \(>100\) but still rotational temperatures \(\sim 10\mathrm{K}\) . Even if the agreement is good here, this approximative approach ("lower bound") should probably be more clearly pointed out. + +<|ref|>sub_title<|/ref|><|det|>[[149, 891, 234, 907]]<|/det|> +## Reply #6: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 121]]<|/det|> +We appreciate the reviewer's reminder. To make it clearer, we have added the following sentences in the manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 131, 850, 168]]<|/det|> +"The measured translation temperature results in an upper limit of the temperature of molecules in the supersonic gas jet." (on page 11 line 281) + +<|ref|>text<|/ref|><|det|>[[147, 195, 850, 251]]<|/det|> +Is the indeed relatively low- intensity short- pulse nature of the excitation also the reason for not exciting the overall rotation? Would be worth simulating at higher kick- energy and mentioning in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 280, 233, 297]]<|/det|> +## Reply #7: + +<|ref|>text<|/ref|><|det|>[[148, 307, 850, 380]]<|/det|> +The alignment signal for the asymmetric- top molecule depends on the molecular properties (polarizability and moments of inertia of three axes), temperature, and the laser parameters. Of course, higher kick intensity leads to higher alignment (see Fig. R3). + +<|ref|>text<|/ref|><|det|>[[148, 390, 850, 483]]<|/det|> +However, as we have answered in Reply #4, since the Ar- axes in \(\mathrm{N}_2\) - Ar and Ar- Ar have similar interaction strengths and their anisotropies are comparable, as well as the kick intensities are the same, it is the large discrepancy of the three molecular axes of \(\mathrm{N}_2\) - Ar comparing with linear diatomic Ar- Ar that mainly leads to the weak alignment of the Ar- axis rather than the kick intensity. + +<|ref|>text<|/ref|><|det|>[[148, 493, 712, 511]]<|/det|> +To make it clear to readers, we have added a corresponding statement + +<|ref|>text<|/ref|><|det|>[[147, 520, 851, 669]]<|/det|> +"The kick intensity used here is very low, which might also be the reason that leads to neglectable overall rotation. However, since the Ar- axes in \(\mathrm{N}_2\) - Ar and Ar- Ar have similar interaction strengths and their anisotropies are comparable, as well as the kick intensities are the same, it is the large discrepancy of the three molecular axes of \(\mathrm{N}_2\) - Ar comparing with linear diatomic Ar- Ar that mainly leads to the weak alignment of the Ar- axis rather than the kick intensity. On the other hand, when increasing the kick intensity, the rotational dissociation happens [J. Chem. Phys. 147, 074304 (2017); J. Chem. Phys. 149, 124301 (2018)]." page 8 line 189) + +<|ref|>image<|/ref|><|det|>[[150, 680, 848, 880]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 891, 850, 909]]<|/det|> +
Figure R3. Calculated alignment traces of Ar-axis of \(\mathrm{N}_2\) -Ar and \(\mathrm{Ar}_2\) by the rigid model
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 734, 103]]<|/det|> +with low intensity \((7 \times 10^{12} \mathrm{~W} / \mathrm{cm}^{2})\) and high intensity \((1.4 \times 10^{13} \mathrm{~W} / \mathrm{cm}^{2})\) . + +<|ref|>text<|/ref|><|det|>[[148, 131, 849, 167]]<|/det|> +It would be useful to clearly point out that all dynamics is in truly bound states. Also related to the weak kick strength used. + +<|ref|>sub_title<|/ref|><|det|>[[148, 197, 233, 214]]<|/det|> +## Reply #8: + +<|ref|>text<|/ref|><|det|>[[148, 224, 770, 242]]<|/det|> +To make it clearer, we have added the following sentences in the manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 245, 849, 301]]<|/det|> +"Attributing to the low kick intensity which avoids the rotational dissociation [J. Chem. Phys. 147, 074304 (2017); J. Chem. Phys. 149, 124301 (2018)], the observed dynamics occurs in bound states of \(\mathrm{N}_{2}\) - Ar." (on page 9 line 221) + +<|ref|>text<|/ref|><|det|>[[149, 322, 849, 358]]<|/det|> +To me, "deceleration" (reply #19) seems to be the inappropriate word, it seems to say "slower" + +<|ref|>sub_title<|/ref|><|det|>[[148, 388, 233, 405]]<|/det|> +## Reply #9: + +<|ref|>text<|/ref|><|det|>[[149, 415, 815, 433]]<|/det|> +We have replaced it with a proper description "slower rotation" in the manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 456, 440, 473]]<|/det|> +What's "umbrella time breathing"? + +<|ref|>sub_title<|/ref|><|det|>[[148, 503, 243, 520]]<|/det|> +## Reply #10: + +<|ref|>text<|/ref|><|det|>[[149, 529, 849, 565]]<|/det|> +The umbrella time breathing means the evolution from alignment to anti- alignment resulting from the beats of the rotational states. + +<|ref|>text<|/ref|><|det|>[[148, 587, 849, 605]]<|/det|> +In line 208: Is this truly 'entanglement' in "radial and angular potential is entangled"? + +<|ref|>sub_title<|/ref|><|det|>[[148, 634, 241, 652]]<|/det|> +## Reply #11: + +<|ref|>text<|/ref|><|det|>[[149, 661, 850, 715]]<|/det|> +The intermolecular interaction can be described potential energy surface \(V(r, \theta_{r})\) (see Fig. R3) where \(\theta_{r}\) is the angle between the N- N axis and Ar- axis and \(r\) is the intermolecular distance between center of mass of the molecule and the atom. + +<|ref|>text<|/ref|><|det|>[[148, 726, 771, 744]]<|/det|> +To make it clearer, we have added the following sentences in the manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 754, 850, 809]]<|/det|> +"...However, this assumption does not hold any more when it comes to the \(\mathrm{N}_{2}\) - Ar dimer since the molecule- atom interaction between \(\mathrm{N}_{2}\) and Ar relies on both their relative distance and angle..." (on page 8 line 200) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[293, 102, 666, 286]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 298, 849, 335]]<|/det|> +
Figure R3. Contour plot of potential energy surface for \(\mathrm{N}_2\) -Ar [J. Chem. Phys. 121, 10419 (2004)]. Geometries are given in Å and degrees, and energies in \(\mathrm{cm}^{-1}\) .
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 310, 97]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 111, 415, 125]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 140, 720, 167]]<|/det|> +The authors clearly improved the manuscript regarding, and clarified all issues from, the reviews. I suggest to publish the manuscript in Nat. Comm. + +<|ref|>text<|/ref|><|det|>[[119, 181, 740, 195]]<|/det|> +I suggest the authors to consider two small comments (without need for review): + +<|ref|>text<|/ref|><|det|>[[119, 210, 733, 237]]<|/det|> +1. Regarding "The measured translation temperature results in an upper limit of the temperature of molecules in the supersonic gas jet." + +<|ref|>text<|/ref|><|det|>[[119, 252, 704, 293]]<|/det|> +To my mind, the relevant "temperature of molecules" are the rotational and vibrational temperatures of the clusters, which are generally higher than the translational temperature of the beam. + +<|ref|>text<|/ref|><|det|>[[118, 307, 675, 335]]<|/det|> +2. It would be useful if the authors or the editorial office could polish the English language of the text, e.g., the latest additions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 90, 371, 107]]<|/det|> +Re: NCOMMS- 23- 43274B + +<|ref|>text<|/ref|><|det|>[[148, 118, 850, 163]]<|/det|> +"Intermolecular interactions probed by rotational dynamics in gas- phase clusters" by Chenxu Lu et al. + +<|ref|>text<|/ref|><|det|>[[148, 187, 850, 223]]<|/det|> +For clarity, we put the original comments in italics to distinguish from our responses in blue. The text that has been changed or newly added is in red. + +<|ref|>text<|/ref|><|det|>[[149, 242, 457, 259]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[149, 288, 848, 325]]<|/det|> +The authors clearly improved the manuscript regarding, and clarified all issues from, the reviews. I suggest to publish the manuscript in Nat. Comm. + +<|ref|>text<|/ref|><|det|>[[148, 362, 798, 381]]<|/det|> +I suggest the authors to consider two small comments (without need for review): + +<|ref|>text<|/ref|><|det|>[[149, 390, 800, 437]]<|/det|> +1. Regarding "The measured translation temperature results in an upper limit of the temperature of molecules in the supersonic gas jet." + +<|ref|>text<|/ref|><|det|>[[149, 446, 850, 500]]<|/det|> +To my mind, the relevant "temperature of molecules" are the rotational and vibrational temperatures of the clusters, which are generally higher than the translational temperature of the beam. + +<|ref|>sub_title<|/ref|><|det|>[[149, 539, 230, 556]]<|/det|> +## Reply #1: + +<|ref|>text<|/ref|><|det|>[[149, 565, 850, 602]]<|/det|> +To make it clear to the readers, we have rephrased the following sentences and corresponding references have been cited properly in the revised manuscript: + +<|ref|>text<|/ref|><|det|>[[148, 612, 850, 741]]<|/det|> +"In our experiment, we measure \(\Delta p \sim 3.2\) a.u. and \(\Delta p \sim 4.0\) a.u. for \(\mathrm{N}_2^+\) and \(\mathrm{N}_2\mathrm{-Ar}^+\) ions. We expect the measured translation temperature is similar to the rotational and vibrational temperature of molecules in the supersonic gas jet [Phys. Rev. Lett. 90, 233003 (2003); J. Chem. Phys. 118, 8699 (2003); Nat. Phys. 16, 328 (2020)]. The excellent agreement with the experiment can be achieved in the simulation when using the temperatures of \(9\mathrm{K}\) for isolated \(\mathrm{N}_2\) and \(7\mathrm{K}\) for \(\mathrm{N}_2\mathrm{-Ar}\) molecules." (line 276 page 11) + +<|ref|>text<|/ref|><|det|>[[148, 779, 850, 815]]<|/det|> +2. It would be useful if the authors or the editorial office could polish the English language of the text, e.g., the latest additions. + +<|ref|>text<|/ref|><|det|>[[149, 826, 230, 843]]<|/det|> +Reply #2: + +<|ref|>text<|/ref|><|det|>[[149, 854, 560, 871]]<|/det|> +We have improved the language of the manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/images_list.json b/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..5f55183f1c9e4425de27d2bc6a2951f8b92a560d --- /dev/null +++ b/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,265 @@ + +# nature portfolio + +Peer Review File + +Hierarchical single- crystal- to- single- crystal transformations of a monomer to a 1D- polymer and then to a 2D- polymer + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +This is a wonderful piece of work. Finally, Sureshan and his co- workers realized the 2D polymer single crystal preparation via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. Sureshan is the key player in the topochemical azide- alkyne cycloaddition. Many excellent examples of 1D polymer single crystals have been reported by this group. In this work, they successfully realized the 2D polymer single crystals through the strategy developed by them. I am very glad and excited to read this work. As Sureshan suggested, the topochemically synthesized 2D polymers are mainly photo- triggered so far. Thermal polymerization is proven to be achievable in this work. This is significantly important in the preparation of 2D polymer area. Another highlight will be the step- by- step polymerization of the single crystal. This will provide guidance for the preparation of 2D polymer single crystal. Anyway, I will highly suggest the publication of this work in Nature Communications. + +Minioy suggestion. + +1. What is the role of the TFA play in the exfoliation of the 2DP single crystal? For example, the protonation? +2. What do the authors think about the advantages of the thermal-induced topochemical reaction compared to the photo-induced one? I am curious if the rule of thermal-induced topochemical reaction is less strict than the photo-induced topochemical reaction. For example, in a photoinduced topochemical reaction, the distance between the photo-active units has to be perfect for the photoreaction. However, it looks like the thermal-induced topochemical reaction allows more space in the arrangement of the monomer. If so, I would suggest adding a description of this advantage to the introduction. +3. Change the second Fig.2 to Fig.3. Type mistake. +4. What is the key to maintaining the single crystal state of the sample at a high temperature? The heating rate for example? +5. I would suggest to add two more related references. J. Am. Chem. Soc. 2021,143, 5636-5642; Chem. Lett. 2021, 50, 1015-1029. + +## Reviewer #2 (Remarks to the Author): + +In the present manuscript, the sequential polymerization of azide and alkyne moiety based monomeric system has been reported. The TFA exfoliated materials can be potentially applicable in many cases. Temperature is a key factor in such thermo responsive materials. This work provides some useful data for designing exfoliated materials, but it still needs improvements before I can suggest acceptance. My detailed comments are as follows: + +1. What could be the reason to check the monomer to be thermo-responsive? What could be the + +<--- Page Split ---> + +possibilities of polymerization with other stimuli? A details discussion is necessary; otherwise it looks like a routine work.2. How can the thermal polymerization be controlled? The temperature dependency needs to be explained with variable temperature experiment (e.g. PXRD).3. How can the mixture of product formation be eliminated during thermo-polymerization? Is it ok to heat azide based compound in high temperature?4. How do supramolecular interactions contribute to polymerization process in high temperature? How about the conversion rate onto cyclic product?5. It is mentioned that sonication of the crystals of 2D- P did not exfoliate it. How long the sonication has been performed? What about using common solvents (such as acetone, EtOH etc.)?6. What is the role of TFA in the exfoliation? TFA is a potentially toxic substance. Can it be done with other solvent?7. NMR plots should be depicted with corresponding structures and peak positions should be indicated properly.8. The mechanical property of crystal is not discussed properly. How about the softness of crystals? Authors should perform nano- indentation experiment [check example in Commun Chem 6, 150 (2023)].9. For practical application, solvent stabilities and pH stabilities of crystalline compounds need to be verified.10. How can the structure- to- property of exfoliated material be correlated? + +## Reviewer #3 (Remarks to the Author): + +The authors reported the synthesis of two- dimensional polymers via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. The design monomer linked with azide and alkyne groups was pre- arranged in the crystal, and the TAAC reaction can proceed in single crystal- to- single- crystal fashion. The reaction can be divided into two steps. The SCSC reaction to form a 1,5- triazolyl- linked 1- dimension polymer was the first step, and then after further heating, TAAC reaction for 1,4- triazolyl production was taken to link 1D polymer to 2D polymer. This process could be well verified by single- crystal X- ray diffraction. I think the work to fabricate 2D polymer through topochemical reaction was novel and of significant interests. However, there is still some room for improvement to further elucidate the mechanism of the assembly process and add more characterization for the 2D polymer to make some details clearer. I think the authors should make a major revision and add more experiments and discussion to make the manuscript better.1. The authors should review more results and cite more literature in 2D polymer and topochemical reaction, and make a more detailed discussion in Introduction part to state the significance and importance of this work to synthesize 2D polymer by topochemical reaction.2. Some works about 2D- P have been reported (doi.org/10.1038/nchem.2007; doi.org/10.1038/nchem.2008; doi.org/10.1038/nchem.1265). The sequential and hierarchical transformation might be novel in the 2D- P works. The author should add more information and + +<--- Page Split ---> + +discussion about this point in Introduction. + +3. In the introduction part, the authors states that it was a challenge of traditional on-surface/interfacial polymerization to realize the scalability. And the depolymerization in traditional method should be solved. However, these two aspects can not be solved in this manuscript. Particularly, the author also found the polymer will be depolymerized when heating to more than \(350^{\circ}C\) . Please adjust the statement to avoid the self-contradiction. + +4. The authors should make a simulation to compare the energy needed to 1,5-triazolyl and 1,4-triazolyl achieve state (doi.org/10.1039/C3CC46153J). It might help state the reason why the polymerization can be taken into two subsequent steps. + +5. The authors should add more experiments and discussions about the mechanism of the polymerization. + +a. The heating rate of \(5^{\circ}C / \min\) was used in DSC (Fig. 2), but the authors 1D-P was obtained by heating at a rate of \(2^{\circ}C / \min\) . How does the DSC curve heating look like with \(2^{\circ}C / \min\) ? What about the influence of heating rate to the DSC profile? Is there any specific reason for making the difference? + +b. More characterizations should be made for 1D-polymer. Maybe the authors can reduce the reaction time to obtain oligomer to make detailed discussion about the regioselectivity and the chemical structure of the products (GPC, NMR etc.). + +c. Maybe, with the studies in Q5b, the authors can make a detailed study about the kinetics and dynamics of the reaction (is it a step or chain polymerization?) + +d. I found that the peak around \(100 - 150^{\circ}C\) in DSC was broad, different from the peak around \(200^{\circ}C\) . Why the shapes of two peaks in DSC (which was assigned to the two-step polymerization) are different? Does it mean the mechanism or the kinetics of these two polymerization mechanism are different? + +6. The resolution in Fig. 2a and 4a should be improved. And the author should provide the POM image of the crystal along the direction of polarizer/analyzer to demonstrate the birefringence of crystal. Why did 2D-P have birefringence but the crystal was homogeneous? + +7. The authors should add the discussion about the IR in Figure 2e. Many new peaks were generated in the monomer heated till \(210^{\circ}C\) . In Figure 3e, I found that the peaks assigned to azide and alkyne was not disappeared. But it was not consistent with the results for the 2D polymer. Why? + +8. The authors should provide more characterization to demonstrate the formation of 2D-P. + +a. The authors might add AFM images of exfoliated sheets in main text (eg. + +https://doi.org/10.1038/nchem.1265) + +b. It that possible to peel one layer or several layer of 2D-P? Does the 2D-P have some more functional properties? + +9. the manuscript should be improved, as many mistakes and typos can be found in current state. eg. Page 2 "different type of monomer" + +<--- Page Split ---> + +## Please find below the point-by-point response to reviewer comments + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +This is a wonderful piece of work. Finally, Sureshan and his co- workers realized the 2D polymer single crystal preparation via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. Sureshan is the key player in the topochemical azide- alkyne cycloaddition. Many excellent examples of 1D polymer single crystals have been reported by this group. In this work, they successfully realized the 2D polymer single crystals through the strategy developed by them. I am very glad and excited to read this work. As Sureshan suggested, the topochemically synthesized 2D polymers are mainly phototriggered so far. Thermal polymerization is proven to be achievable in this work. This is significantly important in the preparation of 2D polymer area. Another highlight will be the step- by- step polymerization of the single crystal. This will provide guidance for the preparation of 2D polymer single crystal. Anyway, I will highly suggest the publication of this work in Nature Communications. + +Response: We thank this reviewer for these very positive remarks highlighting the novelty of our work and recommending publication. + +Minor suggestion. + +1. What is the role of the TFA play in the exfoliation of the 2DP single crystal? For example, the protonation? + +Response: The polymer sheets are stacked on top of each other via weak C- H...N hydrogen bonding and weak van der Waals contacts. As this reviewer guessed, strong acid such as TFA, can protonate triazole nitrogen and repulsion between positively charged triazolium ions could help in delamination of the sheets. We have proved this by exfoliation using 1N HCl. We have included this point in the main manuscript under the section 'Exfoliation of 2D- P crystals' and the supplementary Fig.18. + +2. What do the authors think about the advantages of the thermal-induced topochemical reaction compared to the photo-induced one? I am curious if the rule of thermal-induced topochemical reaction is less strict than the photo-induced topochemical reaction. For example, in a photo-induced topochemical reaction, the distance between the photo-active units has to be perfect for the photoreaction. However, it looks like the thermal-induced topochemical reaction allows more space in the arrangement of the monomer. If so, I would suggest adding a description of this advantage to the introduction. + +Response: We thank this reviewer for highlighting this point. We have added a description about the same in the revised manuscript in the introduction. + +3. Change the second Fig.2 to Fig.3. Type mistake. + +Response: The typographical error is corrected in the revised manuscript. + +4. What is the key to maintaining the single crystal state of the sample at a high temperature? The heating rate for example? + +Response: As the reviewer pointed out, preserving crystal integrity during heat-induced topochemical reactions is indeed challenging. We usually test the reactivity at different temperatures and to preserve + +<--- Page Split ---> + +the crystallinity, we generally conduct slow polymerization at a lowest possible temperature. Usually, the reactions are done at a constant temperature and hence heating rate is not relevant. But sometimes, reaction can be done by continuously heating from rt to a particular temperature and in such cases lower the heating rate is better to preserve the crystal integrity. We have clarified this point in the main manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of the monomer to 1D polymer'. + +5. I would suggest to add two more related references. J. Am. Chem. Soc. 2021,143, 5636-5642; Chem. Lett. 2021, 50, 1015-1029. + +Response: The first reference mentioned was already cited in the previous version of the manuscript (ref. 39). We have added the latter in the revised version (ref. 47). + +## Reviewer #2 (Remarks to the Author): + +In the present manuscript, the sequential polymerization of azide and alkyne moiety based monomeric system has been reported. The TFA exfoliated materials can be potentially applicable in many cases. Temperature is a key factor in such thermo responsive materials. This work provides some useful data for designing exfoliated materials, but it still needs improvements before I can suggest acceptance. My detailed comments are as follows: + +Response: We thank this reviewer for their positive comments about our manuscript. + +1. What could be the reason to check the monomer to be thermo-responsive? What could be the possibilities of polymerization with other stimuli? A details discussion is necessary; otherwise, it looks like a routine work. + +Response: The logic of our design has clearly been mentioned in the manuscript, which this reviewer has missed, we are afraid. We designed the monomer M for its thermal topochemical azide- alkyne cycloaddition (TAAC) polymerization. Azide- alkyne cycloaddition is a thermally allowed and photochemically forbidden reaction. When the distances between reacting groups are not close, pressure can also be used to induce reaction, but that is also a ground state (thermal) reaction. + +2. How can the thermal polymerization be controlled? The temperature dependency needs to be explained with variable temperature experiment (e.g. PXRD). + +Response: We have followed the reactions at different temperatures using DSC and PXRD (the details are added SI). We found that at higher temperature, higher is the reaction rate. At \(90^{\circ}C\) , the monomer to 1DP polymerization completes in 5h whereas at \(100^{\circ}C\) it takes only 2h. Similarly, 1DP to 2DP polymerization completes in 4h at \(140^{\circ}C\) and 2h at \(150^{\circ}C\) . However, to preserve the crystallinity, we generally conduct slow polymerization at a lowest possible temperature or low heating rate. We have detailed about the temperature dependency of the polymerizations in the main manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of the 1D- polymer to 2D- polymer' and the supplementary Figs. 10- 12 in the supporting information. + +3. How can the mixture of product formation be eliminated during thermo-polymerization? Is it ok to heat azide-based compound in high temperature? + +Response: We thank the reviewer for raising this important concern. In case of any topochemical reaction, the arrangement of the reactive groups in the crystal dictates the regioselectivity of the + +<--- Page Split ---> + +product. In order for the lattice arrangement to dictate regiochemistry, the reaction has to be done at a temperature below the melting point so that the crystal arrangement is not disturbed. + +The ratio of the number of atoms other than azide- nitrogen atoms and hydrogen atoms to the number of azide nitrogen atoms, often abbreviated as C/N ratio, is used to predict the safety of organic azides. Organic azides with a C/N ratio of less than 1 are potentially explosive, 1- 3 are safe to synthesize in quantities less than 5 grams and \(>3\) are very safe. In our case the ratio is 4.3. Also, as per rule of six, six carbons (or other atoms of about the same size) per azide group render organic azides safe to use. So our compounds are safe to use. + +4. How do supramolecular interactions contribute to polymerization process in high temperature? How about the conversion rate onto cyclic product? + +Response: While designing monomers for any topochemical reaction, various supramolecular synthons are used as the molecular glue, which facilitate self- assembly of the molecules placing reactive groups in proximity, making them topochemically reactive. Having stated this, during the polymerization process, particularly when heat is used as stimulus, molecules may undergo minor to significant movements, which can break or make non- covalent interactions. Post polymerization, we see many of the strong hydrogen bonds, such as N- H...O are intact. + +SCXRD analysis of the polymer did not show any monomer phase suggesting that the reaction is largely quantitative. However, there would be unreacted azide and alkyne at the sides (ends) of the 2D polymer (also observed in FT- IR spectrum). Also, there could be unreacted azide and alkyne at the defect sites within the crystal. As the polymer is insoluble, quantification by end group analysis is not possible. + +5. It is mentioned that sonication of the crystals of 2D- P did not exfoliate it. How long the sonication has been performed? What about using common solvents (such as acetone, EtOH etc.)? + +Response: We attempted exfoliation using various solvents including NMP, DMSO, acetone, IPA, MeOH, and EtOH, in addition to TFA. However, successful exfoliation was achieved only with TFA. We have added more details of exfoliation experiments in the main manuscript under the subheading 'Exfoliation of 2D- P crystals' and in the revised SI as supplementary Fig. 15. + +6. What is the role of TFA in the exfoliation? TFA is a potentially toxic substance. Can it be done with other solvent? + +Response: TFA can protonate triazole rings and repulsion between positively charged layers could be the reason for exfoliation. We agree to the reviewer's concern about the toxic nature of TFA. However, we use a minimal amount of the acid for the exfoliation process. We have tried the solvent- mediated exfoliation using other solvents such as NMP, DMSO, acetone, IPA, MeOH, and EtOH as well, but with no success as mentioned earlier. Also 1M HCl can be used for exfoliation but it takes longer time. We have added more details of exfoliation experiments in the main manuscript under the subheading 'Exfoliation of 2D- P crystals' and in the revised SI as supplementary Fig. 18. + +7. NMR plots should be depicted with corresponding structures and peak positions should be indicated properly. + +Response: We have updated the spectral data in the supporting information to include the changes recommended by the reviewer. + +<--- Page Split ---> + +8. The mechanical property of crystal is not discussed properly. How about the softness of crystals? Authors should perform nano-indentation experiment [check example in Commun Chem 6, 150 (2023)]. + +Response: We thank this reviewer for this suggestion. However, we believe that the study of mechanical properties of the crystals is beyond the scope of this manuscript. Here we are focussing on a method for the synthesis of 2D polymers. Though we synthesize them as crystals, they are further exfoliated as sheets for use. However, we will keep this advice for our further studies on the properties of polymer crystals. + +9. For practical application, solvent stabilities and pH stabilities of crystalline compounds need to be verified. + +Response: We have soaked the crystals in DMSO, DMF, Chloroform, 1M HCl for 12 h and then examined by PXRD. The 2D crystals were intact in all the solvents tested. However, the 1M HCl delaminated the crystal after 12 h. We have added these additional experimental results in the SI as supplementary Figs. 16 and 18. We have added this briefly, in the main manuscript, under subheading 'Exfoliation of 2D-P crystals'. + +10. How can the structure-to-property of exfoliated material be correlated? + +Response: Once again, the focus of the manuscript, including hypothesis and proof of concept, is a method to synthesise 2D polymers using a thermal reaction. Structure-property correlation requires syntheses of several such 2D polymers having different cavity size, linkage, core etc and study of their properties. Such studies, which will span for years, are beyond the scope of this manuscript. However, we would consider this referee's suggestion when we have different 2D polymers. + +## Reviewer #3 (Remarks to the Author): + +The authors reported the synthesis of two- dimensional polymers via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. The design monomer linked with azide and alkyne groups was pre- arranged in the crystal, and the TAAC reaction can proceed in single crystal- to- single- crystal fashion. The reaction can be divided into two steps. The SCSC reaction to form a 1,5- triazolyl- linked 1- dimension polymer was the first step, and then after further heating, TAAC reaction for 1,4- triazolyl production was taken to link 1D polymer to 2D polymer. This process could be well verified by single- crystal X- ray diffraction. I think the work to fabricate 2D polymer through topochemical reaction was novel and of significant interests. However, there is still some room for improvement to further elucidate the mechanism of the assembly process and add more characterization for the 2D polymer to make some details clearer. I think the authors should make a major revision and add more experiments and discussion to make the manuscript better. + +Response: We thank this reviewer for carefully evaluating our manuscript and for the constructive comments. + +1. The authors should review more results and cite more literature in 2D polymer and topochemical reaction, and make a more detailed discussion in Introduction part to state the significance and importance of this work to synthesize 2D polymer by topochemical reaction. + +Response: As per the advice of this reviewer, we have elaborated the introduction highlighting the importance of adopting topochemical reaction for the synthesis of 2D polymers. More literature references have been cited in the revised manuscript. + +<--- Page Split ---> + +2. Some works about 2D-P have been reported (doi.org/10.1038/nchem.2007; doi.org/10.1038/nchem.2008; doi.org/10.1038/nchem.1265). The sequential and hierarchical transformation might be novel in the 2D-P works. The author should add more information and discussion about this point in Introduction. + +Response: We have already cited these papers in the original version of the manuscript. We have elaborated the introduction further, as per the advice of this reviewer. + +3. In the introduction part, the authors states that it was a challenge of traditional on-surface/interfacial polymerization to realize the scalability. And the depolymerization in traditional method should be solved. However, these two aspects cannot be solved in this manuscript. Particularly, the author also found the polymer will be depolymerized when heating to more than 350 °C. Please adjust the statement to avoid the self-contradiction. + +Response: The reviewer is slightly mistaken here, we are afraid. 2D-polymers synthesized via light-induced reactions such as 4+4 and 2+2 cycloaddition undergo retro-cycloaddition reaction at higher temperature (150 °C- 200 °C) and converts back to the starting monomer. This thermal instability of polymer is due to the backward-reaction to monomers but not decomposition of the material. In the present manuscript we have employed a thermal 3+2 cycloaddition for the topochemical polymerization, which is an irreversible reaction. Thus, the synthesized 2D-polymer exhibits significantly enhanced thermal stability and never goes back to the monomer. At temperatures beyond 350 °C, the material decomposes (not depolymerizes). This has been clarified in the manuscript. + +4. The authors should make a simulation to compare the energy needed to 1,5-triazolyl and 1,4-triazolyl achieve state (doi.org/10.1039/C3CC46153J). It might help state the reason why the polymerization can be taken into two subsequent steps. + +Response: We thank this reviewer for this suggestion. However, these are lattice controlled reactions where preorganization (and its extent), crystal packing and cooperativity plays major roles. Simulations starting from the crystal geometry of a pair of azide and alkyne to make two different TS arrangements and comparing their relative energy would be of little relevance for reaction happening in an anisotropic, diffusion restricted state. In crystal, the kinetics (how well or badly preorganized) plays a prominent role than the thermodynamics. Gas phase calculation, using model molecules have already been done (J. Am. Chem. Soc. 2005, 127, 1, 210- 216) for the azide- alkyne cycloaddition which revealed similar activation energies for the TS of 1,5- and 1,4- isomers. + +5. The authors should add more experiments and discussions about the mechanism of the polymerization. + +a. The heating rate of \(5^{\circ}C / \min\) was used in DSC (Fig. 2), but the authors 1D-P was obtained by heating at a rate of \(2^{\circ}C / \min\) . How does the DSC curve heating look like with \(2^{\circ}C / \min\) ? What about the influence of heating rate to the DSC profile? Is there any specific reason for making the difference? + +Response: We thank this reviewer for this suggestion. We have recorded DSC thermogram from \(30^{\circ}C\) to \(250^{\circ}C\) at different heating rates (2 °C/min., 5 °C/min. and 10 °C/min.) using 0.5 mg of monomer M crystals in each case and are provided in the revised SI (Supplementary Fig 8). As the heating rates increased, the onset for both exothermic peaks shifted to higher temperatures. The onset temperatures for the first event are 90 °C, 110 °C and 115 °C at heating rates of 2 °C/min., 5 °C/min. and 10 °C/min. respectively and for the second event they are 169 °C, 190 °C and 191 °C. At higher heating rates, though the holder temperature increases quickly, the sample can have a temperature gradient from the holder-front to the bulk of the sample, in view of the poor thermal conductivity of + +<--- Page Split ---> + +the organic polymer (Saeed, Rami M., et al. "Uncertainty of thermal characterization of phase change material by differential scanning calorimetry analysis." Int. J. Eng. Res. Technol 5.1 (2016): 405- 412). The resultant thermal lag is the reason for shift in the onset temperature. + +We preferred a heating rate of \(2^{\circ}C / \min\) . for polymerization as the two thermal events are well resolved at this rate. This prevents the first polymerization process from interfering with the second. Also, slow heating prevents rigorous reaction leaving lesser strain in the crystal, thereby maintaining the crystallinity. We have briefly explained this in the manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of the monomer to 1D- polymer' and detailed in the supplementary section 4. + +b. More characterizations should be made for 1D-polymer. Maybe the authors can reduce the reaction time to obtain oligomer to make detailed discussion about the regioselectivity and the chemical structure of the products (GPC, NMR etc.). + +Response: We have tried out stop the 1D polymerization reaction before completion to obtain lower oligomers. Unfortunately, once the reaction proceeds the material becomes insoluble in all common organic solvents including DMSO and DMF, which prevented us from further characterization of any intermediate. We have unambiguously established regiosepecificity by solving the crystal structure of the 1D- P by SCXRD. + +c. Maybe, with the studies in Q5b, the authors can make a detailed study about the kinetics and dynamics of the reaction (is it a step or chain polymerization?) + +Response: We thank this reviewer for this comment. Deducing the dynamics of topochemical polymerisation is challenging especially when the oligomers are insoluble. First of all, labelling a topochemical polymerization as step growth or chain growth polymerization is difficult. Step growth or chain growth mechanisms are relevant only in isotropic free- diffusing solution- state polymerization, where the random molecular motion or collision is necessary for the polymerization. These mechanisms depend on the unreacted monomer concentration at any stage of polymerization and the viscosity of the medium (for free diffusion of monomer/oligomer molecules to find the reacting end), (J. Chem. Phys. 1998, 109, 2929- 2940). However, for a crystal, the term concentration and viscosity are irrelevant and extrapolation such mechanisms to an anisotropic diffusion- restricted crystal can be erroneous (J. Polym. Sci. A, 1964, 2, 2181- 2190). Crystal being anisotropic and ordered ensemble of molecules, wherein the monomer is preorganized in an orientation to form the polymer, cooperativity plays a role in the kinetics of topochemical reactions. + +However, Schluter et al. elegantly analyzed the plausible scenarios during the early stages of light- induced topochemical 2D- polymerization reactions and proposed three different mechanisms for lateral polymerization (Eur. J. Org. Chem. 2021, 5478- 5490). In all these three cases, at the intermediate stages, the monomers, 1D- oligomers/polymers and 2D polymers co- exist. The thermal 2D- polymerization reported here cannot be labelled as one of these three as it is mechanistically different and unique; it involves two discrete steps viz. monomer to 1DP followed by 1DP to 2DP, and at no stage the monomer coexists with 2DP. The insolubility of the reaction mixture (oligomers/1DP and 2DP) prevented any kinetic study. We have added these details in the main manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of 1D- polymer to 2D- polymer'. + +d. I found that the peak around \(100 - 150^{\circ}C\) in DSC was broad, different from the peak around \(200^{\circ}C\) . Why the shapes of two peaks in DSC (which was assigned to the two-step polymerization) are different? Does it mean the mechanism or the kinetics of these two-polymerization mechanism are different? + +<--- Page Split ---> + +Response: These topochemical reactions (rate, temperature) depend on how pre- organized the reacting groups are. Crystal structure of the monomer showed that one azide- alkyne pair is better preorganized (distance: 3.3 A) along the column than the other azide- alkyne pair, which is neither in a perfect orientation nor at a distance for TAAC polymerization. However, it can reach an antiparallel orientation after considerable rotation. It is expected that the first pair will react first to give 1,5- triazolyl- polymer along the column and with difficulty, the second one would react to give 1,4- triazolyl- linkage laterally. When monomer is heated from rt till \(300^{\circ}C\) at a heating rate of \(5^{\circ}C / \min\) , we observed two peaks with onset temperatures \(110^{\circ}C\) (range: \(110^{\circ}C - 160^{\circ}C\) ) and \(190^{\circ}C\) (range: \(190^{\circ}C - 205^{\circ}C\) ). In other words, the crystal is experiencing an average temperature of \(135^{\circ}C\) for 10 minutes for the first reaction and \(197^{\circ}C\) for 3 minutes for the second reaction. Obviously the second reaction happening at a high temperature is fast. This cannot be attributed to their difference in mechanism or kinetics. + +6. The resolution in Fig. 2a and 4a should be improved. And the author should provide the POM image of the crystal along the direction of polarizer/analyzer to demonstrate the birefringence of crystal. Why did 2D-P have birefringence but the crystal was homogeneous? + +Response: As suggested by this reviewer, we have added high resolution figures in the revised manuscript Fig. 2 and Fig.4a. Birefringence is a property of any anisotropic material including single crystals. Hence 2D-P single crystal is expected to exhibit birefringence. In thin crystals the interference colours are differentiated while in thick crystals this differentiation is not usually evident. POM images of 2D-P at different analyzer angles are added in the revised SI as supplementary Fig.9. + +7. The authors should add the discussion about the IR in Figure 2e. Many new peaks were generated in the monomer heated till \(210^{\circ}C\) . In Figure 3e, I found that the peaks assigned to azide and alkyne was not disappeared. But it was not consistent with the results for the 2D polymer. Why? + +Response: In Figure 2e, a gradual reduction in the peak attributed to asymmetric stretching of azide is evident. To make it clearer, we have normalized the peaks. Fig 2eii (heated to \(160^{\circ}C\) ) is the IR spectrum of the 1D- polymer. That means after consuming only half of the azide groups. This is the reason why there is considerable intensity of azide. But Fig. 2eiii is the IR spectrum of the 2D- P. The small residual azide peak seen in the 2D- P is due to the presence of terminal azide groups at the edges in the polymer. Also, the additional peaks in the IR spectrum in the previous version of the manuscript were due to background noise. We have repeated this experiment and provided better IR spectrum in the revised manuscript (Fig. 2e). + +8. The authors should provide more characterization to demonstrate the formation of 2D-P. + +Response: We have added Raman spectra (Supplementary Fig 13) and powder diffraction data (Supplementary Fig 12) to demonstrate the conversion of monomer to 1D-P and then to 2D-P. We have also added TEM images of the exfoliating/exfoliated 2D-P crystals as figure 5g in the main manuscript. Though we attempted to analyze the polymer by solids state NMR, we did not succeed. + +a. The authors might add AFM images of exfoliated sheets in main text (eg. https://doi.org/10.1038/nchem.1265) + +Response: AFM images are moved to the main text in the revised manuscript as Fig 5f. + +b. It that possible to peel one layer or several layer of 2D-P? Does the 2D-P have some more functional properties? + +Response: Our studies suggests that the 2D-P crystals can be exfoliated to monolayer as well as multilayered sheets (Fig. 5d-5g). + +<--- Page Split ---> + +9. the manuscript should be improved, as many mistakes and typos can be found in current state. + +eg. Page 2 "different type of monomer" + +Response: We carefully rechecked the manuscript to avoid such errors. The above- mentioned sentence has been rephrased in the revised manuscript. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The authors have satisfactorily addressed the points I raised before. The manuscript is now ready for publication. + +## Reviewer #2 (Remarks to the Author): + +The authors have successfully addressed most of the queries raised by the reviewers. Now the manuscript can be accepted for publication. + +## Reviewer #3 (Remarks to the Author): + +The manuscript has been revised well and is in a nice condition now. + +<--- Page Split ---> diff --git a/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1483674db6b662121ad373df33afb05200f0906c --- /dev/null +++ b/peer_reviews/7837dd87548c1c145a1dd183e20ac2444331115637cf9358f17109f921d5d4e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,367 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 917, 211]]<|/det|> +Hierarchical single- crystal- to- single- crystal transformations of a monomer to a 1D- polymer and then to a 2D- polymer + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 98, 323, 115]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 163, 416, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 199, 884, 400]]<|/det|> +This is a wonderful piece of work. Finally, Sureshan and his co- workers realized the 2D polymer single crystal preparation via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. Sureshan is the key player in the topochemical azide- alkyne cycloaddition. Many excellent examples of 1D polymer single crystals have been reported by this group. In this work, they successfully realized the 2D polymer single crystals through the strategy developed by them. I am very glad and excited to read this work. As Sureshan suggested, the topochemically synthesized 2D polymers are mainly photo- triggered so far. Thermal polymerization is proven to be achievable in this work. This is significantly important in the preparation of 2D polymer area. Another highlight will be the step- by- step polymerization of the single crystal. This will provide guidance for the preparation of 2D polymer single crystal. Anyway, I will highly suggest the publication of this work in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 402, 260, 418]]<|/det|> +Minioy suggestion. + +<|ref|>text<|/ref|><|det|>[[112, 420, 870, 675]]<|/det|> +1. What is the role of the TFA play in the exfoliation of the 2DP single crystal? For example, the protonation? +2. What do the authors think about the advantages of the thermal-induced topochemical reaction compared to the photo-induced one? I am curious if the rule of thermal-induced topochemical reaction is less strict than the photo-induced topochemical reaction. For example, in a photoinduced topochemical reaction, the distance between the photo-active units has to be perfect for the photoreaction. However, it looks like the thermal-induced topochemical reaction allows more space in the arrangement of the monomer. If so, I would suggest adding a description of this advantage to the introduction. +3. Change the second Fig.2 to Fig.3. Type mistake. +4. What is the key to maintaining the single crystal state of the sample at a high temperature? The heating rate for example? +5. I would suggest to add two more related references. J. Am. Chem. Soc. 2021,143, 5636-5642; Chem. Lett. 2021, 50, 1015-1029. + +<|ref|>sub_title<|/ref|><|det|>[[115, 731, 416, 748]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 766, 881, 857]]<|/det|> +In the present manuscript, the sequential polymerization of azide and alkyne moiety based monomeric system has been reported. The TFA exfoliated materials can be potentially applicable in many cases. Temperature is a key factor in such thermo responsive materials. This work provides some useful data for designing exfoliated materials, but it still needs improvements before I can suggest acceptance. My detailed comments are as follows: + +<|ref|>text<|/ref|><|det|>[[112, 876, 860, 894]]<|/det|> +1. What could be the reason to check the monomer to be thermo-responsive? What could be the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 95, 870, 465]]<|/det|> +possibilities of polymerization with other stimuli? A details discussion is necessary; otherwise it looks like a routine work.2. How can the thermal polymerization be controlled? The temperature dependency needs to be explained with variable temperature experiment (e.g. PXRD).3. How can the mixture of product formation be eliminated during thermo-polymerization? Is it ok to heat azide based compound in high temperature?4. How do supramolecular interactions contribute to polymerization process in high temperature? How about the conversion rate onto cyclic product?5. It is mentioned that sonication of the crystals of 2D- P did not exfoliate it. How long the sonication has been performed? What about using common solvents (such as acetone, EtOH etc.)?6. What is the role of TFA in the exfoliation? TFA is a potentially toxic substance. Can it be done with other solvent?7. NMR plots should be depicted with corresponding structures and peak positions should be indicated properly.8. The mechanical property of crystal is not discussed properly. How about the softness of crystals? Authors should perform nano- indentation experiment [check example in Commun Chem 6, 150 (2023)].9. For practical application, solvent stabilities and pH stabilities of crystalline compounds need to be verified.10. How can the structure- to- property of exfoliated material be correlated? + +<|ref|>sub_title<|/ref|><|det|>[[116, 546, 416, 562]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 581, 881, 900]]<|/det|> +The authors reported the synthesis of two- dimensional polymers via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. The design monomer linked with azide and alkyne groups was pre- arranged in the crystal, and the TAAC reaction can proceed in single crystal- to- single- crystal fashion. The reaction can be divided into two steps. The SCSC reaction to form a 1,5- triazolyl- linked 1- dimension polymer was the first step, and then after further heating, TAAC reaction for 1,4- triazolyl production was taken to link 1D polymer to 2D polymer. This process could be well verified by single- crystal X- ray diffraction. I think the work to fabricate 2D polymer through topochemical reaction was novel and of significant interests. However, there is still some room for improvement to further elucidate the mechanism of the assembly process and add more characterization for the 2D polymer to make some details clearer. I think the authors should make a major revision and add more experiments and discussion to make the manuscript better.1. The authors should review more results and cite more literature in 2D polymer and topochemical reaction, and make a more detailed discussion in Introduction part to state the significance and importance of this work to synthesize 2D polymer by topochemical reaction.2. Some works about 2D- P have been reported (doi.org/10.1038/nchem.2007; doi.org/10.1038/nchem.2008; doi.org/10.1038/nchem.1265). The sequential and hierarchical transformation might be novel in the 2D- P works. The author should add more information and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 448, 113]]<|/det|> +discussion about this point in Introduction. + +<|ref|>text<|/ref|><|det|>[[115, 116, 872, 205]]<|/det|> +3. In the introduction part, the authors states that it was a challenge of traditional on-surface/interfacial polymerization to realize the scalability. And the depolymerization in traditional method should be solved. However, these two aspects can not be solved in this manuscript. Particularly, the author also found the polymer will be depolymerized when heating to more than \(350^{\circ}C\) . Please adjust the statement to avoid the self-contradiction. + +<|ref|>text<|/ref|><|det|>[[115, 207, 852, 261]]<|/det|> +4. The authors should make a simulation to compare the energy needed to 1,5-triazolyl and 1,4-triazolyl achieve state (doi.org/10.1039/C3CC46153J). It might help state the reason why the polymerization can be taken into two subsequent steps. + +<|ref|>text<|/ref|><|det|>[[115, 262, 816, 297]]<|/det|> +5. The authors should add more experiments and discussions about the mechanism of the polymerization. + +<|ref|>text<|/ref|><|det|>[[115, 298, 866, 370]]<|/det|> +a. The heating rate of \(5^{\circ}C / \min\) was used in DSC (Fig. 2), but the authors 1D-P was obtained by heating at a rate of \(2^{\circ}C / \min\) . How does the DSC curve heating look like with \(2^{\circ}C / \min\) ? What about the influence of heating rate to the DSC profile? Is there any specific reason for making the difference? + +<|ref|>text<|/ref|><|det|>[[115, 371, 850, 425]]<|/det|> +b. More characterizations should be made for 1D-polymer. Maybe the authors can reduce the reaction time to obtain oligomer to make detailed discussion about the regioselectivity and the chemical structure of the products (GPC, NMR etc.). + +<|ref|>text<|/ref|><|det|>[[115, 426, 852, 462]]<|/det|> +c. Maybe, with the studies in Q5b, the authors can make a detailed study about the kinetics and dynamics of the reaction (is it a step or chain polymerization?) + +<|ref|>text<|/ref|><|det|>[[115, 463, 880, 535]]<|/det|> +d. I found that the peak around \(100 - 150^{\circ}C\) in DSC was broad, different from the peak around \(200^{\circ}C\) . Why the shapes of two peaks in DSC (which was assigned to the two-step polymerization) are different? Does it mean the mechanism or the kinetics of these two polymerization mechanism are different? + +<|ref|>text<|/ref|><|det|>[[115, 536, 858, 590]]<|/det|> +6. The resolution in Fig. 2a and 4a should be improved. And the author should provide the POM image of the crystal along the direction of polarizer/analyzer to demonstrate the birefringence of crystal. Why did 2D-P have birefringence but the crystal was homogeneous? + +<|ref|>text<|/ref|><|det|>[[115, 592, 880, 646]]<|/det|> +7. The authors should add the discussion about the IR in Figure 2e. Many new peaks were generated in the monomer heated till \(210^{\circ}C\) . In Figure 3e, I found that the peaks assigned to azide and alkyne was not disappeared. But it was not consistent with the results for the 2D polymer. Why? + +<|ref|>text<|/ref|><|det|>[[115, 647, 812, 664]]<|/det|> +8. The authors should provide more characterization to demonstrate the formation of 2D-P. + +<|ref|>text<|/ref|><|det|>[[115, 666, 686, 682]]<|/det|> +a. The authors might add AFM images of exfoliated sheets in main text (eg. + +<|ref|>text<|/ref|><|det|>[[115, 684, 405, 700]]<|/det|> +https://doi.org/10.1038/nchem.1265) + +<|ref|>text<|/ref|><|det|>[[115, 702, 820, 737]]<|/det|> +b. It that possible to peel one layer or several layer of 2D-P? Does the 2D-P have some more functional properties? + +<|ref|>text<|/ref|><|det|>[[115, 738, 866, 774]]<|/det|> +9. the manuscript should be improved, as many mistakes and typos can be found in current state. eg. Page 2 "different type of monomer" + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 110, 705, 128]]<|/det|> +## Please find below the point-by-point response to reviewer comments + +<|ref|>sub_title<|/ref|><|det|>[[119, 157, 298, 173]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[119, 184, 410, 200]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 210, 881, 383]]<|/det|> +This is a wonderful piece of work. Finally, Sureshan and his co- workers realized the 2D polymer single crystal preparation via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. Sureshan is the key player in the topochemical azide- alkyne cycloaddition. Many excellent examples of 1D polymer single crystals have been reported by this group. In this work, they successfully realized the 2D polymer single crystals through the strategy developed by them. I am very glad and excited to read this work. As Sureshan suggested, the topochemically synthesized 2D polymers are mainly phototriggered so far. Thermal polymerization is proven to be achievable in this work. This is significantly important in the preparation of 2D polymer area. Another highlight will be the step- by- step polymerization of the single crystal. This will provide guidance for the preparation of 2D polymer single crystal. Anyway, I will highly suggest the publication of this work in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[118, 393, 878, 426]]<|/det|> +Response: We thank this reviewer for these very positive remarks highlighting the novelty of our work and recommending publication. + +<|ref|>text<|/ref|><|det|>[[118, 437, 255, 452]]<|/det|> +Minor suggestion. + +<|ref|>text<|/ref|><|det|>[[118, 463, 878, 496]]<|/det|> +1. What is the role of the TFA play in the exfoliation of the 2DP single crystal? For example, the protonation? + +<|ref|>text<|/ref|><|det|>[[117, 507, 880, 593]]<|/det|> +Response: The polymer sheets are stacked on top of each other via weak C- H...N hydrogen bonding and weak van der Waals contacts. As this reviewer guessed, strong acid such as TFA, can protonate triazole nitrogen and repulsion between positively charged triazolium ions could help in delamination of the sheets. We have proved this by exfoliation using 1N HCl. We have included this point in the main manuscript under the section 'Exfoliation of 2D- P crystals' and the supplementary Fig.18. + +<|ref|>text<|/ref|><|det|>[[117, 603, 880, 723]]<|/det|> +2. What do the authors think about the advantages of the thermal-induced topochemical reaction compared to the photo-induced one? I am curious if the rule of thermal-induced topochemical reaction is less strict than the photo-induced topochemical reaction. For example, in a photo-induced topochemical reaction, the distance between the photo-active units has to be perfect for the photoreaction. However, it looks like the thermal-induced topochemical reaction allows more space in the arrangement of the monomer. If so, I would suggest adding a description of this advantage to the introduction. + +<|ref|>text<|/ref|><|det|>[[117, 733, 878, 767]]<|/det|> +Response: We thank this reviewer for highlighting this point. We have added a description about the same in the revised manuscript in the introduction. + +<|ref|>text<|/ref|><|det|>[[118, 778, 491, 794]]<|/det|> +3. Change the second Fig.2 to Fig.3. Type mistake. + +<|ref|>text<|/ref|><|det|>[[118, 805, 668, 820]]<|/det|> +Response: The typographical error is corrected in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 831, 878, 864]]<|/det|> +4. What is the key to maintaining the single crystal state of the sample at a high temperature? The heating rate for example? + +<|ref|>text<|/ref|><|det|>[[115, 875, 880, 908]]<|/det|> +Response: As the reviewer pointed out, preserving crystal integrity during heat-induced topochemical reactions is indeed challenging. We usually test the reactivity at different temperatures and to preserve + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 186]]<|/det|> +the crystallinity, we generally conduct slow polymerization at a lowest possible temperature. Usually, the reactions are done at a constant temperature and hence heating rate is not relevant. But sometimes, reaction can be done by continuously heating from rt to a particular temperature and in such cases lower the heating rate is better to preserve the crystal integrity. We have clarified this point in the main manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of the monomer to 1D polymer'. + +<|ref|>text<|/ref|><|det|>[[118, 197, 877, 230]]<|/det|> +5. I would suggest to add two more related references. J. Am. Chem. Soc. 2021,143, 5636-5642; Chem. Lett. 2021, 50, 1015-1029. + +<|ref|>text<|/ref|><|det|>[[118, 242, 880, 275]]<|/det|> +Response: The first reference mentioned was already cited in the previous version of the manuscript (ref. 39). We have added the latter in the revised version (ref. 47). + +<|ref|>sub_title<|/ref|><|det|>[[119, 312, 410, 327]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 338, 880, 423]]<|/det|> +In the present manuscript, the sequential polymerization of azide and alkyne moiety based monomeric system has been reported. The TFA exfoliated materials can be potentially applicable in many cases. Temperature is a key factor in such thermo responsive materials. This work provides some useful data for designing exfoliated materials, but it still needs improvements before I can suggest acceptance. My detailed comments are as follows: + +<|ref|>text<|/ref|><|det|>[[118, 434, 759, 450]]<|/det|> +Response: We thank this reviewer for their positive comments about our manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 461, 880, 511]]<|/det|> +1. What could be the reason to check the monomer to be thermo-responsive? What could be the possibilities of polymerization with other stimuli? A details discussion is necessary; otherwise, it looks like a routine work. + +<|ref|>text<|/ref|><|det|>[[118, 522, 880, 606]]<|/det|> +Response: The logic of our design has clearly been mentioned in the manuscript, which this reviewer has missed, we are afraid. We designed the monomer M for its thermal topochemical azide- alkyne cycloaddition (TAAC) polymerization. Azide- alkyne cycloaddition is a thermally allowed and photochemically forbidden reaction. When the distances between reacting groups are not close, pressure can also be used to induce reaction, but that is also a ground state (thermal) reaction. + +<|ref|>text<|/ref|><|det|>[[118, 617, 880, 650]]<|/det|> +2. How can the thermal polymerization be controlled? The temperature dependency needs to be explained with variable temperature experiment (e.g. PXRD). + +<|ref|>text<|/ref|><|det|>[[118, 660, 880, 798]]<|/det|> +Response: We have followed the reactions at different temperatures using DSC and PXRD (the details are added SI). We found that at higher temperature, higher is the reaction rate. At \(90^{\circ}C\) , the monomer to 1DP polymerization completes in 5h whereas at \(100^{\circ}C\) it takes only 2h. Similarly, 1DP to 2DP polymerization completes in 4h at \(140^{\circ}C\) and 2h at \(150^{\circ}C\) . However, to preserve the crystallinity, we generally conduct slow polymerization at a lowest possible temperature or low heating rate. We have detailed about the temperature dependency of the polymerizations in the main manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of the 1D- polymer to 2D- polymer' and the supplementary Figs. 10- 12 in the supporting information. + +<|ref|>text<|/ref|><|det|>[[118, 809, 880, 842]]<|/det|> +3. How can the mixture of product formation be eliminated during thermo-polymerization? Is it ok to heat azide-based compound in high temperature? + +<|ref|>text<|/ref|><|det|>[[118, 853, 880, 886]]<|/det|> +Response: We thank the reviewer for raising this important concern. In case of any topochemical reaction, the arrangement of the reactive groups in the crystal dictates the regioselectivity of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 117]]<|/det|> +product. In order for the lattice arrangement to dictate regiochemistry, the reaction has to be done at a temperature below the melting point so that the crystal arrangement is not disturbed. + +<|ref|>text<|/ref|><|det|>[[118, 128, 880, 230]]<|/det|> +The ratio of the number of atoms other than azide- nitrogen atoms and hydrogen atoms to the number of azide nitrogen atoms, often abbreviated as C/N ratio, is used to predict the safety of organic azides. Organic azides with a C/N ratio of less than 1 are potentially explosive, 1- 3 are safe to synthesize in quantities less than 5 grams and \(>3\) are very safe. In our case the ratio is 4.3. Also, as per rule of six, six carbons (or other atoms of about the same size) per azide group render organic azides safe to use. So our compounds are safe to use. + +<|ref|>text<|/ref|><|det|>[[118, 241, 880, 274]]<|/det|> +4. How do supramolecular interactions contribute to polymerization process in high temperature? How about the conversion rate onto cyclic product? + +<|ref|>text<|/ref|><|det|>[[118, 285, 880, 387]]<|/det|> +Response: While designing monomers for any topochemical reaction, various supramolecular synthons are used as the molecular glue, which facilitate self- assembly of the molecules placing reactive groups in proximity, making them topochemically reactive. Having stated this, during the polymerization process, particularly when heat is used as stimulus, molecules may undergo minor to significant movements, which can break or make non- covalent interactions. Post polymerization, we see many of the strong hydrogen bonds, such as N- H...O are intact. + +<|ref|>text<|/ref|><|det|>[[118, 397, 880, 483]]<|/det|> +SCXRD analysis of the polymer did not show any monomer phase suggesting that the reaction is largely quantitative. However, there would be unreacted azide and alkyne at the sides (ends) of the 2D polymer (also observed in FT- IR spectrum). Also, there could be unreacted azide and alkyne at the defect sites within the crystal. As the polymer is insoluble, quantification by end group analysis is not possible. + +<|ref|>text<|/ref|><|det|>[[118, 493, 880, 527]]<|/det|> +5. It is mentioned that sonication of the crystals of 2D- P did not exfoliate it. How long the sonication has been performed? What about using common solvents (such as acetone, EtOH etc.)? + +<|ref|>text<|/ref|><|det|>[[118, 537, 880, 605]]<|/det|> +Response: We attempted exfoliation using various solvents including NMP, DMSO, acetone, IPA, MeOH, and EtOH, in addition to TFA. However, successful exfoliation was achieved only with TFA. We have added more details of exfoliation experiments in the main manuscript under the subheading 'Exfoliation of 2D- P crystals' and in the revised SI as supplementary Fig. 15. + +<|ref|>text<|/ref|><|det|>[[118, 615, 880, 648]]<|/det|> +6. What is the role of TFA in the exfoliation? TFA is a potentially toxic substance. Can it be done with other solvent? + +<|ref|>text<|/ref|><|det|>[[118, 659, 880, 778]]<|/det|> +Response: TFA can protonate triazole rings and repulsion between positively charged layers could be the reason for exfoliation. We agree to the reviewer's concern about the toxic nature of TFA. However, we use a minimal amount of the acid for the exfoliation process. We have tried the solvent- mediated exfoliation using other solvents such as NMP, DMSO, acetone, IPA, MeOH, and EtOH as well, but with no success as mentioned earlier. Also 1M HCl can be used for exfoliation but it takes longer time. We have added more details of exfoliation experiments in the main manuscript under the subheading 'Exfoliation of 2D- P crystals' and in the revised SI as supplementary Fig. 18. + +<|ref|>text<|/ref|><|det|>[[118, 789, 880, 822]]<|/det|> +7. NMR plots should be depicted with corresponding structures and peak positions should be indicated properly. + +<|ref|>text<|/ref|><|det|>[[118, 833, 880, 866]]<|/det|> +Response: We have updated the spectral data in the supporting information to include the changes recommended by the reviewer. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 135]]<|/det|> +8. The mechanical property of crystal is not discussed properly. How about the softness of crystals? Authors should perform nano-indentation experiment [check example in Commun Chem 6, 150 (2023)]. + +<|ref|>text<|/ref|><|det|>[[118, 145, 880, 231]]<|/det|> +Response: We thank this reviewer for this suggestion. However, we believe that the study of mechanical properties of the crystals is beyond the scope of this manuscript. Here we are focussing on a method for the synthesis of 2D polymers. Though we synthesize them as crystals, they are further exfoliated as sheets for use. However, we will keep this advice for our further studies on the properties of polymer crystals. + +<|ref|>text<|/ref|><|det|>[[118, 241, 880, 274]]<|/det|> +9. For practical application, solvent stabilities and pH stabilities of crystalline compounds need to be verified. + +<|ref|>text<|/ref|><|det|>[[118, 284, 880, 369]]<|/det|> +Response: We have soaked the crystals in DMSO, DMF, Chloroform, 1M HCl for 12 h and then examined by PXRD. The 2D crystals were intact in all the solvents tested. However, the 1M HCl delaminated the crystal after 12 h. We have added these additional experimental results in the SI as supplementary Figs. 16 and 18. We have added this briefly, in the main manuscript, under subheading 'Exfoliation of 2D-P crystals'. + +<|ref|>text<|/ref|><|det|>[[118, 380, 685, 396]]<|/det|> +10. How can the structure-to-property of exfoliated material be correlated? + +<|ref|>text<|/ref|><|det|>[[118, 406, 880, 492]]<|/det|> +Response: Once again, the focus of the manuscript, including hypothesis and proof of concept, is a method to synthesise 2D polymers using a thermal reaction. Structure-property correlation requires syntheses of several such 2D polymers having different cavity size, linkage, core etc and study of their properties. Such studies, which will span for years, are beyond the scope of this manuscript. However, we would consider this referee's suggestion when we have different 2D polymers. + +<|ref|>sub_title<|/ref|><|det|>[[120, 529, 410, 545]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 555, 881, 744]]<|/det|> +The authors reported the synthesis of two- dimensional polymers via thermally induced topochemical azide- alkyne cycloaddition (TAAC) reaction. The design monomer linked with azide and alkyne groups was pre- arranged in the crystal, and the TAAC reaction can proceed in single crystal- to- single- crystal fashion. The reaction can be divided into two steps. The SCSC reaction to form a 1,5- triazolyl- linked 1- dimension polymer was the first step, and then after further heating, TAAC reaction for 1,4- triazolyl production was taken to link 1D polymer to 2D polymer. This process could be well verified by single- crystal X- ray diffraction. I think the work to fabricate 2D polymer through topochemical reaction was novel and of significant interests. However, there is still some room for improvement to further elucidate the mechanism of the assembly process and add more characterization for the 2D polymer to make some details clearer. I think the authors should make a major revision and add more experiments and discussion to make the manuscript better. + +<|ref|>text<|/ref|><|det|>[[118, 755, 880, 787]]<|/det|> +Response: We thank this reviewer for carefully evaluating our manuscript and for the constructive comments. + +<|ref|>text<|/ref|><|det|>[[118, 799, 880, 849]]<|/det|> +1. The authors should review more results and cite more literature in 2D polymer and topochemical reaction, and make a more detailed discussion in Introduction part to state the significance and importance of this work to synthesize 2D polymer by topochemical reaction. + +<|ref|>text<|/ref|><|det|>[[118, 860, 880, 910]]<|/det|> +Response: As per the advice of this reviewer, we have elaborated the introduction highlighting the importance of adopting topochemical reaction for the synthesis of 2D polymers. More literature references have been cited in the revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 153]]<|/det|> +2. Some works about 2D-P have been reported (doi.org/10.1038/nchem.2007; doi.org/10.1038/nchem.2008; doi.org/10.1038/nchem.1265). The sequential and hierarchical transformation might be novel in the 2D-P works. The author should add more information and discussion about this point in Introduction. + +<|ref|>text<|/ref|><|det|>[[118, 162, 880, 196]]<|/det|> +Response: We have already cited these papers in the original version of the manuscript. We have elaborated the introduction further, as per the advice of this reviewer. + +<|ref|>text<|/ref|><|det|>[[118, 206, 880, 291]]<|/det|> +3. In the introduction part, the authors states that it was a challenge of traditional on-surface/interfacial polymerization to realize the scalability. And the depolymerization in traditional method should be solved. However, these two aspects cannot be solved in this manuscript. Particularly, the author also found the polymer will be depolymerized when heating to more than 350 °C. Please adjust the statement to avoid the self-contradiction. + +<|ref|>text<|/ref|><|det|>[[118, 301, 881, 439]]<|/det|> +Response: The reviewer is slightly mistaken here, we are afraid. 2D-polymers synthesized via light-induced reactions such as 4+4 and 2+2 cycloaddition undergo retro-cycloaddition reaction at higher temperature (150 °C- 200 °C) and converts back to the starting monomer. This thermal instability of polymer is due to the backward-reaction to monomers but not decomposition of the material. In the present manuscript we have employed a thermal 3+2 cycloaddition for the topochemical polymerization, which is an irreversible reaction. Thus, the synthesized 2D-polymer exhibits significantly enhanced thermal stability and never goes back to the monomer. At temperatures beyond 350 °C, the material decomposes (not depolymerizes). This has been clarified in the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 448, 880, 500]]<|/det|> +4. The authors should make a simulation to compare the energy needed to 1,5-triazolyl and 1,4-triazolyl achieve state (doi.org/10.1039/C3CC46153J). It might help state the reason why the polymerization can be taken into two subsequent steps. + +<|ref|>text<|/ref|><|det|>[[118, 510, 881, 647]]<|/det|> +Response: We thank this reviewer for this suggestion. However, these are lattice controlled reactions where preorganization (and its extent), crystal packing and cooperativity plays major roles. Simulations starting from the crystal geometry of a pair of azide and alkyne to make two different TS arrangements and comparing their relative energy would be of little relevance for reaction happening in an anisotropic, diffusion restricted state. In crystal, the kinetics (how well or badly preorganized) plays a prominent role than the thermodynamics. Gas phase calculation, using model molecules have already been done (J. Am. Chem. Soc. 2005, 127, 1, 210- 216) for the azide- alkyne cycloaddition which revealed similar activation energies for the TS of 1,5- and 1,4- isomers. + +<|ref|>text<|/ref|><|det|>[[118, 657, 880, 690]]<|/det|> +5. The authors should add more experiments and discussions about the mechanism of the polymerization. + +<|ref|>text<|/ref|><|det|>[[118, 700, 880, 751]]<|/det|> +a. The heating rate of \(5^{\circ}C / \min\) was used in DSC (Fig. 2), but the authors 1D-P was obtained by heating at a rate of \(2^{\circ}C / \min\) . How does the DSC curve heating look like with \(2^{\circ}C / \min\) ? What about the influence of heating rate to the DSC profile? Is there any specific reason for making the difference? + +<|ref|>text<|/ref|><|det|>[[118, 761, 881, 899]]<|/det|> +Response: We thank this reviewer for this suggestion. We have recorded DSC thermogram from \(30^{\circ}C\) to \(250^{\circ}C\) at different heating rates (2 °C/min., 5 °C/min. and 10 °C/min.) using 0.5 mg of monomer M crystals in each case and are provided in the revised SI (Supplementary Fig 8). As the heating rates increased, the onset for both exothermic peaks shifted to higher temperatures. The onset temperatures for the first event are 90 °C, 110 °C and 115 °C at heating rates of 2 °C/min., 5 °C/min. and 10 °C/min. respectively and for the second event they are 169 °C, 190 °C and 191 °C. At higher heating rates, though the holder temperature increases quickly, the sample can have a temperature gradient from the holder-front to the bulk of the sample, in view of the poor thermal conductivity of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 879, 135]]<|/det|> +the organic polymer (Saeed, Rami M., et al. "Uncertainty of thermal characterization of phase change material by differential scanning calorimetry analysis." Int. J. Eng. Res. Technol 5.1 (2016): 405- 412). The resultant thermal lag is the reason for shift in the onset temperature. + +<|ref|>text<|/ref|><|det|>[[118, 145, 880, 249]]<|/det|> +We preferred a heating rate of \(2^{\circ}C / \min\) . for polymerization as the two thermal events are well resolved at this rate. This prevents the first polymerization process from interfering with the second. Also, slow heating prevents rigorous reaction leaving lesser strain in the crystal, thereby maintaining the crystallinity. We have briefly explained this in the manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of the monomer to 1D- polymer' and detailed in the supplementary section 4. + +<|ref|>text<|/ref|><|det|>[[118, 259, 879, 310]]<|/det|> +b. More characterizations should be made for 1D-polymer. Maybe the authors can reduce the reaction time to obtain oligomer to make detailed discussion about the regioselectivity and the chemical structure of the products (GPC, NMR etc.). + +<|ref|>text<|/ref|><|det|>[[118, 319, 880, 404]]<|/det|> +Response: We have tried out stop the 1D polymerization reaction before completion to obtain lower oligomers. Unfortunately, once the reaction proceeds the material becomes insoluble in all common organic solvents including DMSO and DMF, which prevented us from further characterization of any intermediate. We have unambiguously established regiosepecificity by solving the crystal structure of the 1D- P by SCXRD. + +<|ref|>text<|/ref|><|det|>[[118, 415, 878, 448]]<|/det|> +c. Maybe, with the studies in Q5b, the authors can make a detailed study about the kinetics and dynamics of the reaction (is it a step or chain polymerization?) + +<|ref|>text<|/ref|><|det|>[[117, 458, 880, 664]]<|/det|> +Response: We thank this reviewer for this comment. Deducing the dynamics of topochemical polymerisation is challenging especially when the oligomers are insoluble. First of all, labelling a topochemical polymerization as step growth or chain growth polymerization is difficult. Step growth or chain growth mechanisms are relevant only in isotropic free- diffusing solution- state polymerization, where the random molecular motion or collision is necessary for the polymerization. These mechanisms depend on the unreacted monomer concentration at any stage of polymerization and the viscosity of the medium (for free diffusion of monomer/oligomer molecules to find the reacting end), (J. Chem. Phys. 1998, 109, 2929- 2940). However, for a crystal, the term concentration and viscosity are irrelevant and extrapolation such mechanisms to an anisotropic diffusion- restricted crystal can be erroneous (J. Polym. Sci. A, 1964, 2, 2181- 2190). Crystal being anisotropic and ordered ensemble of molecules, wherein the monomer is preorganized in an orientation to form the polymer, cooperativity plays a role in the kinetics of topochemical reactions. + +<|ref|>text<|/ref|><|det|>[[118, 674, 880, 828]]<|/det|> +However, Schluter et al. elegantly analyzed the plausible scenarios during the early stages of light- induced topochemical 2D- polymerization reactions and proposed three different mechanisms for lateral polymerization (Eur. J. Org. Chem. 2021, 5478- 5490). In all these three cases, at the intermediate stages, the monomers, 1D- oligomers/polymers and 2D polymers co- exist. The thermal 2D- polymerization reported here cannot be labelled as one of these three as it is mechanistically different and unique; it involves two discrete steps viz. monomer to 1DP followed by 1DP to 2DP, and at no stage the monomer coexists with 2DP. The insolubility of the reaction mixture (oligomers/1DP and 2DP) prevented any kinetic study. We have added these details in the main manuscript under the subheading 'Single- crystal- to- single- crystal polymerization of 1D- polymer to 2D- polymer'. + +<|ref|>text<|/ref|><|det|>[[118, 838, 880, 905]]<|/det|> +d. I found that the peak around \(100 - 150^{\circ}C\) in DSC was broad, different from the peak around \(200^{\circ}C\) . Why the shapes of two peaks in DSC (which was assigned to the two-step polymerization) are different? Does it mean the mechanism or the kinetics of these two-polymerization mechanism are different? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 881, 274]]<|/det|> +Response: These topochemical reactions (rate, temperature) depend on how pre- organized the reacting groups are. Crystal structure of the monomer showed that one azide- alkyne pair is better preorganized (distance: 3.3 A) along the column than the other azide- alkyne pair, which is neither in a perfect orientation nor at a distance for TAAC polymerization. However, it can reach an antiparallel orientation after considerable rotation. It is expected that the first pair will react first to give 1,5- triazolyl- polymer along the column and with difficulty, the second one would react to give 1,4- triazolyl- linkage laterally. When monomer is heated from rt till \(300^{\circ}C\) at a heating rate of \(5^{\circ}C / \min\) , we observed two peaks with onset temperatures \(110^{\circ}C\) (range: \(110^{\circ}C - 160^{\circ}C\) ) and \(190^{\circ}C\) (range: \(190^{\circ}C - 205^{\circ}C\) ). In other words, the crystal is experiencing an average temperature of \(135^{\circ}C\) for 10 minutes for the first reaction and \(197^{\circ}C\) for 3 minutes for the second reaction. Obviously the second reaction happening at a high temperature is fast. This cannot be attributed to their difference in mechanism or kinetics. + +<|ref|>text<|/ref|><|det|>[[118, 283, 880, 335]]<|/det|> +6. The resolution in Fig. 2a and 4a should be improved. And the author should provide the POM image of the crystal along the direction of polarizer/analyzer to demonstrate the birefringence of crystal. Why did 2D-P have birefringence but the crystal was homogeneous? + +<|ref|>text<|/ref|><|det|>[[118, 344, 880, 430]]<|/det|> +Response: As suggested by this reviewer, we have added high resolution figures in the revised manuscript Fig. 2 and Fig.4a. Birefringence is a property of any anisotropic material including single crystals. Hence 2D-P single crystal is expected to exhibit birefringence. In thin crystals the interference colours are differentiated while in thick crystals this differentiation is not usually evident. POM images of 2D-P at different analyzer angles are added in the revised SI as supplementary Fig.9. + +<|ref|>text<|/ref|><|det|>[[118, 439, 880, 491]]<|/det|> +7. The authors should add the discussion about the IR in Figure 2e. Many new peaks were generated in the monomer heated till \(210^{\circ}C\) . In Figure 3e, I found that the peaks assigned to azide and alkyne was not disappeared. But it was not consistent with the results for the 2D polymer. Why? + +<|ref|>text<|/ref|><|det|>[[117, 500, 881, 638]]<|/det|> +Response: In Figure 2e, a gradual reduction in the peak attributed to asymmetric stretching of azide is evident. To make it clearer, we have normalized the peaks. Fig 2eii (heated to \(160^{\circ}C\) ) is the IR spectrum of the 1D- polymer. That means after consuming only half of the azide groups. This is the reason why there is considerable intensity of azide. But Fig. 2eiii is the IR spectrum of the 2D- P. The small residual azide peak seen in the 2D- P is due to the presence of terminal azide groups at the edges in the polymer. Also, the additional peaks in the IR spectrum in the previous version of the manuscript were due to background noise. We have repeated this experiment and provided better IR spectrum in the revised manuscript (Fig. 2e). + +<|ref|>text<|/ref|><|det|>[[115, 647, 802, 664]]<|/det|> +8. The authors should provide more characterization to demonstrate the formation of 2D-P. + +<|ref|>text<|/ref|><|det|>[[118, 674, 880, 743]]<|/det|> +Response: We have added Raman spectra (Supplementary Fig 13) and powder diffraction data (Supplementary Fig 12) to demonstrate the conversion of monomer to 1D-P and then to 2D-P. We have also added TEM images of the exfoliating/exfoliated 2D-P crystals as figure 5g in the main manuscript. Though we attempted to analyze the polymer by solids state NMR, we did not succeed. + +<|ref|>text<|/ref|><|det|>[[115, 753, 877, 787]]<|/det|> +a. The authors might add AFM images of exfoliated sheets in main text (eg. https://doi.org/10.1038/nchem.1265) + +<|ref|>text<|/ref|><|det|>[[118, 796, 765, 813]]<|/det|> +Response: AFM images are moved to the main text in the revised manuscript as Fig 5f. + +<|ref|>text<|/ref|><|det|>[[115, 823, 880, 857]]<|/det|> +b. It that possible to peel one layer or several layer of 2D-P? Does the 2D-P have some more functional properties? + +<|ref|>text<|/ref|><|det|>[[115, 867, 880, 901]]<|/det|> +Response: Our studies suggests that the 2D-P crystals can be exfoliated to monolayer as well as multilayered sheets (Fig. 5d-5g). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 84, 850, 101]]<|/det|> +9. the manuscript should be improved, as many mistakes and typos can be found in current state. + +<|ref|>text<|/ref|><|det|>[[118, 111, 417, 128]]<|/det|> +eg. Page 2 "different type of monomer" + +<|ref|>text<|/ref|><|det|>[[115, 138, 880, 172]]<|/det|> +Response: We carefully rechecked the manuscript to avoid such errors. The above- mentioned sentence has been rephrased in the revised manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 97, 340, 115]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 163, 417, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 200, 861, 235]]<|/det|> +The authors have satisfactorily addressed the points I raised before. The manuscript is now ready for publication. + +<|ref|>sub_title<|/ref|><|det|>[[115, 273, 417, 290]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 310, 841, 345]]<|/det|> +The authors have successfully addressed most of the queries raised by the reviewers. Now the manuscript can be accepted for publication. + +<|ref|>sub_title<|/ref|><|det|>[[115, 382, 417, 399]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 420, 642, 436]]<|/det|> +The manuscript has been revised well and is in a nice condition now. + +<--- Page Split ---> diff --git a/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..8410c6c017a73193d0a873ba48415e9e33847914 --- /dev/null +++ b/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,430 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "**Fig. R1. UV-Vis spectroscopy of electrolytes from coin cells (E/S = 4 \\(\\mu \\mathrm{L} \\mathrm{mg}^{-1}\\)) discharged to 2.1 V.**", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_3b.jpg", + "caption": "**Fig. 3b. Lewis acid-base reaction between multivalent metal ions and PSs. b, Correlation** between the pKa value of metal cations27 and the UV-vis absorbance at 425 nm (corresponding to \\(\\mathrm{S}_{4}^{2 - }\\) ) in electrolytes containing Lewis acidic additives after discharge to 2.1 V. Error bars denote the standard deviation from measurements obtained from four independent coin cells. The data are presented as mean values \\(\\pm\\) standard deviation.", + "footnote": [], + "bbox": [ + [ + 400, + 575, + 610, + 725 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_3a.jpg", + "caption": "Fig. 3a, b. Lewis acid-base reaction between multivalent metal ions and PSs. a, UV-vis spectra of electrolytes from the coin cells \\((E / S = 4 \\mu \\mathrm{L} \\mathrm{mg}^{-1})\\) after being discharged to 2.1 V. b, Correlation between the pKa value of metal cations \\(^{27}\\) and the UV-vis absorbance at 425 nm (corresponding to \\(\\mathrm{S}_4^{2 - }\\) ) in electrolytes containing Lewis acidic additives after discharge to 2.1 V. Error bars denote the standard deviation from measurements obtained from four independent coin cells. The data are presented as mean values \\(\\pm\\) standard deviation.", + "footnote": [], + "bbox": [ + [ + 283, + 490, + 712, + 643 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. R2. Cycle performance of Li-S cells with 1 M LiTFSI 2 wt% LiNO3 DOL:DME electrolyte. Cell capacity versus cycle number for a, 0.20C discharge/ 0.15C charge b, 0.30C discharge/ 0.20C charge.", + "footnote": [], + "bbox": [ + [ + 117, + 147, + 880, + 315 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. R3. Pouch-type Li-S bi-cell \\((E / S = 3.5 \\mu \\mathrm{L} \\mathrm{mg}^{-1})\\) cycling with the control and additive \\((\\mathrm{Sr}^{2 + }, \\mathrm{Ca}^{2 + }, \\mathrm{Mg}^{2 + }, \\mathrm{or} \\mathrm{Al}^{3 + })\\) -containing electrolytes.", + "footnote": [], + "bbox": [ + [ + 144, + 493, + 852, + 666 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. R4. Cycle performance of Li-S cells with Lewis acidic electrolyte additives.", + "footnote": [], + "bbox": [ + [ + 288, + 95, + 709, + 273 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. R5. Electrochemical performances of the Li-S pouch cells with Ca electrolyte. Li-S stack cell with an \\(E / S\\) ratio of \\(2.9 \\mu \\mathrm{L} \\mathrm{mg}^{-1}\\) (high power design) with \\(\\mathrm{Ca(OTf)_2}\\) additive showing stable cycling for over 350 cycles at \\(1.0 \\mathrm{C}\\) .", + "footnote": [], + "bbox": [ + [ + 165, + 336, + 824, + 513 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_2b.jpg", + "caption": "Fig. 2b-c. b, High-Energy design Li-S stack cell with an \\(E / S\\) ratio of \\(2.4~\\mu \\mathrm{L}\\mathrm{mg}^{-1}\\) in the presence of Lewis acidic metal cation additives. \\(\\mathrm{Ca(OTf)_2}\\) additive shows stable cycling for over 200 cycles at \\(0.3\\mathrm{C}\\) . Configuration of a high-energy cell with \\(25\\mu \\mathrm{m}\\) Li and sulfur loading of \\(2.26\\mathrm{mg}\\mathrm{cm}^{-2}\\) . c, High-Power design Li-S stack cell with an \\(E / S\\) ratio of \\(2.9\\mu \\mathrm{L}\\mathrm{mg}^{-1}\\) in the presence of Lewis acidic metal cation additives. \\(\\mathrm{Ca(OTf)_2}\\) additive shows stable cycling for over 350 cycles at \\(1.0\\mathrm{C}\\) . Configuration of a high-power cell with \\(20\\mu \\mathrm{m}\\) Li and sulfur loading of \\(1.81\\mathrm{mg}\\mathrm{cm}^{-2}\\) .", + "footnote": [], + "bbox": [ + [ + 120, + 99, + 875, + 404 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. R6. Raman spectroscopy of electrolytes and catholytes with varying lithium polysulfide concentrations. a, Raman spectra of electrolytes without lithium polysulfide. Different peak ranges are noted with arrows in the spectra. b, Raman spectra of supernatants from catholytes containing 1.6 M \\(\\mathrm{Li_2S_4}\\) (corresponding to full sulfur dissolution at \\(\\mathrm{E / S = 5\\mu Lmg^{-1}}\\) , \\(3.8\\mathrm{mgcm}^{-2}\\) sulfur loading). c, Raman spectra of supernatants from catholytes containing \\(0.2\\mathrm{M}\\mathrm{Li}_2\\mathrm{S}_4\\)", + "footnote": [], + "bbox": [ + [ + 115, + 99, + 880, + 555 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. R7. Cumulative distribution functions of \\(\\mathrm{Ca^{2 + }}\\) solvation in 0.1 M \\(\\mathrm{Ca(OTf)_2}\\) electrolyte.", + "footnote": [], + "bbox": [ + [ + 339, + 98, + 660, + 330 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Figure_2a.jpg", + "caption": "Fig. 2a-c. Electrochemical performances of the Li-S pouch cells with Lewis acidic multivalent metal additives. a, Pouch-type Li-S bi-cell \\((E / S = 3.5 \\mu \\mathrm{L} \\mathrm{mg}^{-1})\\) cycling with the control and additive \\((\\mathrm{Sr}^{2 + }\\) , \\(\\mathrm{Ca}^{2 + }\\) , \\(\\mathrm{Mg}^{2 + }\\) or \\(\\mathrm{Al}^{3 + }\\) )-containing electrolytes. b, High-Energy design Li-S stack cell with an \\(E / S\\) ratio of \\(2.4 \\mu \\mathrm{L} \\mathrm{mg}^{-1}\\) in the presence of Lewis acidic metal cation additives. \\(\\mathrm{Ca(OTf)_2}\\) additive shows stable cycling for over 200 cycles at \\(0.3 \\mathrm{C}\\) . Configuration of a high-energy cell with \\(25 \\mu \\mathrm{m} \\mathrm{Li}\\) and sulfur loading of \\(2.26 \\mathrm{mg} \\mathrm{cm}^{-2}\\) . c, High-Power design Li-S stack cell with an \\(E / S\\) ratio of \\(2.9 \\mu \\mathrm{L} \\mathrm{mg}^{-1}\\) in the presence of Lewis acidic metal cation additives. \\(\\mathrm{Ca(OTf)_2}\\) additive shows stable cycling for over 350 cycles at \\(1.0 \\mathrm{C}\\) . Configuration of a high-power cell with \\(20 \\mu \\mathrm{m} \\mathrm{Li}\\) and sulfur loading of \\(1.81 \\mathrm{mg} \\mathrm{cm}^{-2}\\) .", + "footnote": [], + "bbox": [ + [ + 118, + 320, + 830, + 748 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. R8. Molecular dynamics of the Ca catholyte. a, Coordination number of polysulfide with \\(\\mathrm{Li^{+}}\\) and \\(\\mathrm{Ca^{2 + }}\\) in the Ca catholyte. b, MD snapshots of the molecular distributions around \\(\\mathrm{Li^{+}}\\) , \\(\\mathrm{Ca^{2 + }}\\) , and \\(\\mathrm{S_{4}^{2 - }}\\) in the control catholyte (left) and 0.05 M Ca catholyte (right).", + "footnote": [], + "bbox": [ + [ + 128, + 100, + 870, + 293 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. R9. a, Cyclic voltammetry (CV) test of Li-S the coin cell with \\(0.5\\mathrm{M}\\) Ca electrolyte. b, Discharge voltage profiles of the coin cell with \\(0.5\\mathrm{M}\\) Ca electrolyte. c, XRD analysis of precipitates formed in \\(\\mathrm{Ca(OTf)_2}\\) containing solution. d, HAADF-STEM image and corresponding element mapping of the CNF cathode after discharge of the Li-S/CNF cell to \\(2.1\\mathrm{V}\\) , scale bar: \\(200\\mathrm{nm}\\) . e, Ca 2p XPS spectra of the cathode after \\(1^{\\mathrm{st}}\\) cycle discharge.", + "footnote": [], + "bbox": [ + [ + 135, + 99, + 875, + 428 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. R10. Oxidation of CaS during cell operation. a, Linear sweep voltammetry profiles of the carbon paper electrode, \\(\\mathrm{Li}_2\\mathrm{S}\\) -loaded carbon paper electrode, and CaS-loaded carbon paper electrode. b, Discharge voltage profiles of the Li-Carbon paper cells incorporating CaS or \\(\\mathrm{Li}_2\\mathrm{S}\\) in the carbon paper electrode.", + "footnote": [], + "bbox": [ + [ + 145, + 113, + 856, + 315 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Fig. R11. EIS analysis of Lean-electrolyte Li-S coin cells during 0.1C discharge. a, Discharge voltage profiles of Control and Ca electrolytes at the E/S ratio = 4 \\(\\mu \\mathrm{L} \\mathrm{mg}^{-1}\\) and 0.1 C. b-d, Nyquist plot during cycling at DOD of 10% (b), 30% (c), and 80% (d). f-h, Enlarged GITT data at DOD of 10% (e), 30% (f), and 80% (g).", + "footnote": [], + "bbox": [ + [ + 117, + 273, + 880, + 812 + ] + ], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Fig. R12. Decoupled ohmic, interfacial, and charge transfer polarization at a, DOD \\(10\\%\\) , b, \\(30\\%\\) , and c, \\(80\\%\\) .", + "footnote": [], + "bbox": [ + [ + 117, + 97, + 905, + 282 + ] + ], + "page_idx": 28 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Fig. R13. The relationship between \\(Z'\\) and square root of frequency \\((\\omega^{-1 / 2})\\) in the low-frequency region for at different densities of discharge.", + "footnote": [], + "bbox": [ + [ + 115, + 350, + 916, + 520 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Fig. R14. UV-Vis spectra of various catholytes with varying polysulfide species. Filtered Control and Ca electrolytes with a, \\(0.2 \\mathrm{M} \\mathrm{Li}_2\\mathrm{S}_8\\) , b, \\(\\mathrm{Li}_2\\mathrm{S}_6\\) , and c, \\(\\mathrm{Li}_2\\mathrm{S}_4\\) diluted by 0.01.", + "footnote": [], + "bbox": [ + [ + 117, + 391, + 916, + 560 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_14.jpg", + "caption": "Fig. R15. Voltage profile of pouch cells at 0.025C discharge with the multivalent cation additives.", + "footnote": [], + "bbox": [ + [ + 118, + 316, + 812, + 500 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_15.jpg", + "caption": "Fig. R16. UV-Vis spectra of various electrolytes. a, Control electrolytes with \\(0.2\\mathrm{M}\\mathrm{Li}_2\\mathrm{S}_8\\) , \\(\\mathrm{Li}_2\\mathrm{S}_6\\) , and \\(\\mathrm{Li}_2\\mathrm{S}_4\\) diluted by 0.01. b, Filtered \\(0.2\\mathrm{M}\\mathrm{Li}_2\\mathrm{S}_8\\) solution in Control and Ca electrolyte with solvent replaced by DMSO diluted by 0.005.", + "footnote": [], + "bbox": [ + [ + 145, + 317, + 850, + 526 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_5a.jpg", + "caption": "Supplementary Fig. 5a. Cycle performance of high sulfur loading, lean electrolyte coin cells.", + "footnote": [], + "bbox": [ + [ + 163, + 720, + 844, + 885 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_16.jpg", + "caption": "Fig. R17. Cycle performance of pouch cells with various LiOTf additive concentrations.", + "footnote": [], + "bbox": [ + [ + 330, + 120, + 668, + 298 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_17.jpg", + "caption": "Fig. R18. Ca 2p XPS Spectra of cathodes. a, Charged cathode after 1 cycle. b, Charged cathode after 40 cycles with periodic oxidation protocol.", + "footnote": [], + "bbox": [ + [ + 115, + 355, + 827, + 553 + ] + ], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_18.jpg", + "caption": "Fig. R19. Comparison of FSI⁻ and OTF⁻ anions with assistance of MD simulation and DFT calculations. a, Cumulative distribution functions of Li⁺ solvation with FSI⁻ and OTF⁻ anions in the Ca electrolyte. b, Highest occupied molecular orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels of the free and coordinated anions.", + "footnote": [], + "bbox": [ + [ + 155, + 446, + 857, + 648 + ] + ], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_19.jpg", + "caption": "Fig. R1 | Electrochemical performance of coin cells \\((E / S = 5 \\mu \\mathrm{L} \\mathrm{mg}^{-1})\\) with 0.75 M LiFSI/0.40 M LiNO3/0.05 M M(OH)2. (a) Cycle performance of diglyme-based electrolyte. (b) Voltage profile of coin cells with diglyme-based electrolytes at 0.2C discharge.", + "footnote": [], + "bbox": [ + [ + 118, + 97, + 880, + 293 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_20.jpg", + "caption": "Fig. R1 | Cycle performance of coin cells \\((E / S = 5 \\mu \\mathrm{L} \\mathrm{mg}^{-1})\\) with 0.75 M LiFSI/0.40 M LiNO3 in DME or DME:TTE (5:1). a, Voltage profile of cells at 0.05C discharge/charge. b, Cycle performance.", + "footnote": [], + "bbox": [ + [ + 128, + 387, + 864, + 599 + ] + ], + "page_idx": 40 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_1.jpg", + "caption": "Supplementary Fig. 1 | Compatibility of Lewis acidic cation additives in the electrolytes (a-b) Optical images of the control and metal additive (0.05 M)-containing electrolytes after standing for 7 days. X-ray diffraction (XRD) patterns of the precipitates in the (c) Mg and (d) Sr electrolytes, respectively. (e) Pouch-type Li-S bi-cell ( \\(E / S = 3.5 \\mu \\mathrm{L} \\mathrm{mg}^{-1}\\) ) cycling with the control and multivalent metal cation (Al \\(^{3 + }\\) , Mg \\(^{2 + }\\) , Ca \\(^{2 + }\\) , Sr \\(^{2 + }\\) ) additive-containing electrolytes.", + "footnote": [], + "bbox": [ + [ + 191, + 103, + 812, + 550 + ] + ], + "page_idx": 40 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_21.jpg", + "caption": "Fig. R3 | Optical images of 0.75 M LiFSI/0.40 M electrolytes with 0.05 M additives after dissolution. Electrolytes prepared using various solvents: (a) DMSO, (b) catholytes (0.2 M Li₂S₈) in DMSO, (c) 1-Methyl-1-Butylpyrrolidinium bis(fluorosulfonyl)imide (Pyr₁₄FSI), and (d) Diethylene glycol dimethyl ether (DEGDME).", + "footnote": [], + "bbox": [ + [ + 115, + 130, + 872, + 377 + ] + ], + "page_idx": 42 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_22.jpg", + "caption": "Fig. R4 | Voltage profile of coin cells \\((E / S = 5 \\mu \\mathrm{L} \\mathrm{mg}^{-1})\\) with 0.75 M LiFSI/0.40 M LiNO₃/0.05 M M(OTf) in DMSO.", + "footnote": [], + "bbox": [ + [ + 328, + 483, + 670, + 670 + ] + ], + "page_idx": 45 + } +] \ No newline at end of file diff --git a/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f79ddb6eb310ffdfb7021d3602e3db54c379760e --- /dev/null +++ b/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,683 @@ + +# Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries + +Corresponding Author: Professor Hee- Tak Kim + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +In their manuscript entitled "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," Cho et al. propose using \(\mathrm{Ca(OTf)_2}\) as an effective additive for lithium- sulfur batteries under lean electrolyte conditions. They claim that calcium ions mitigate polysulfide dissolution due to their high Lewis acidity, as well as the catalytic effects of CaS resulting from its interaction with LiPS. However, in my view, the publication of this manuscript is premature. Several additional experiments and essential experimental details are needed to substantiate the authors' claims. My specific comments are as follows: + +1. Primary Hypothesis: The core hypothesis of this work is that the "high" Lewis acidity of calcium ions mitigates polysulfide dissolution by forming Ca-PS complexes. If this hypothesis is accurate, electrolytes with \(\mathrm{Mg(OTf)_2}\) and \(\mathrm{Al(OTf)_3}\) , which have ions with significantly higher acidity than Ca, should show even better performance. Since the difference in acidity between Ca and Li ions is minimal, this oversight or lack of consideration raises doubts about the hypothesis's validity. +2. Experimental Descriptions: The manuscript contains many vague descriptions of experimental details, limiting the interpretability of the presented data. For example, in Fig. 5a, the electrolyte solutions for both the control and Ca experiments are described insufficiently, with only one line—"A viscometer (LVDV-2+P CP, BROOKFIELD) was used to measure the electrolyte viscosity"—included in the experimental section. What does "1.6M Li2S4 control" mean? What solvents and salts are in the control? It is questionable whether the authors can truly reduce the control electrolyte's viscosity by merely adding Ca salt. +3. Electrode Composition Details: Essential information about the electrodes, such as binder type, carbon materials, and sulfur loading percentage, is missing. These parameters are crucial for reproducing the results and should be included. +4. UV-Vis Study Protocols: The UV-Vis study requires a more detailed experimental procedure. Did the authors immerse all coin cell components in the control electrolyte? Given the small electrolyte volume in a coin cell, there may be significant experimental error. Providing at least three parallel experiment results would help confirm the data's consistency. +5. Control Setup in Fig. 3b: In Fig. 3b, the control should not solely consist of the control electrolyte; 0.05M Li(OTf) should also be added. Additionally, the authors must explain how they determined the pKa values in the experimental section. +6. Choice of Control Electrolyte: The authors' control choice of 0.75M LiFSI and 0.4M LiNO3 in DME differs from the conventional Li-S electrolyte (1M LiTFSI in DOL/DME with \(\sim 2\%\) LiNO3). The authors used a 0.5M LiTFSI and 0.2M LiNO3 DOL/DME electrolyte, and the large reduction in salt concentration likely exacerbates LiPS dissolution. +7. Cycling Performance: For Fig. 2a, the authors should provide parallel cycling performance for each cell to confirm repeatability and rule out cell-to-cell variations. +8. Additive Controls in Figs. 2b and 2c: The cycling results for the control electrolyte, as well as electrolytes with Al and Mg additives, should also be presented. +9. Electrolyte Solvation Analysis: The authors employed MD simulation and solid characterization techniques such as TEM and XPS. To thoroughly understand electrolyte solvation, additional FTIR/Raman and NMR data should be included. + +## Reviewer #2 + +(Remarks to the Author) Summary: This research paper entitled, "Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium + +<--- Page Split ---> + +sulfur batteries" reports a novel approach to designing and enhancing the performance of lean- electrolyte lithium- sulfur batteries by adding a small amount of calcium cations to the electrolyte. The calcium cations are reported that can effectively convert polysulfides into calcium sulfide and sulfur. This reaction prevents polysulfide shuttle and electrolyte jamming while mitigating lithium corrosion. The in situ formation of calcium sulfide acts as a catalyst, facilitating the reduction of polysulfides, and calcium cations are regenerated during charging, allowing sustainable cycling. The addition of calcium cations improves cycling stability and energy density, with pouch cells achieving 493 Wh kg \(^{- 1}\) and \(70\%\) capacity retention after 220 cycles, and 346 Wh kg \(^{- 1}\) with \(77\%\) retention after 360 cycles. + +## General comment: + +This study reports on the electrolyte additive for the lean- electrolyte lithium- sulfur cell to have an improved performance. Some minor revision is needed, and I hope the authors find the comment useful. + +## Comments: + +(1) The manuscript is well organized in both the writing and the data presentation. One minor suggestion is on the image layout in figures. Cycling performance data are not suggested to show an extended X axis for the cycle number. This gives an unreasonable cyclability. + +[Suggestion] Please organize and arrange the cycling performance data with a regular image layout. + +(2) The formation of CaS and S via the adsorbed polysulfides is the main finding of this research. It is suggested to focus on collecting direct experimental data as evidence. Then, the formation mechanism of CaS and the conversion from CaS to polysulfides is suggested to be studied and discussed. In addition, the polysulfide trapping mechanism is suggested to be explored. + +[Suggestion] Please conduct analysis and discussion on the formation mechanism of CaS, the conversion mechanism rom CaS to polysulfides, and the polysulfide-trapping mechanism of calcium cations together. + +(3) The sulfur cathode used in this research is necessary to be discussed and disclosed. The sulfur loading and sulfur content are suggested to be reported. The content of additional additives is necessary to be reported. These are necessary information, which controls the key experimental testing condition, E/S ratio. [Suggestion] Please report the necessary information on the cathode. + +(4) Lean-electrolyte lithium-sulfur cell suffers from poor reaction kinetics. It is suggested to show the electrochemical impedance analysis data that is used for showing the ohmic resistance. Besides the ohmic resistance, charge-transfer and interface impedances and the diffusion factor are important and are necessary to be reported and discussed in this research. [Suggestion] Please report the electrochemical impedance spectra data with the discussion on the ohmic, charge-transfer, and interface impedance values as well as the diffusion unit of the cell before and after cycling to tell the reaction the lean-electrolyte cell. + +## Reviewer #3 + +(Remarks to the Author) + +In this manuscript, the authors demonstrated that Lewis acidic \(\mathrm{Ca2 + }\) additive enables lean electrolyte and high energy density LSBs. The CaS readily adsorbs LiPSs and catalyzes SRR. With the addition of the \(\mathrm{Ca2 + }\) additive, the viscosity was reduced by \(70\%\) , and the ionic conductivity was enhanced by \(30\%\) . The electrolyte also enables an exceptional energy density of 493 Wh kg- 1. I am rather interested in this paper but have some specific questions listed as follow: + +1. The in situ formed CaS catalyst accelerates SRR throughout the discharging process, and is oxidized to form Ca2+ in the electrolyte during charging. Why does the conversion reaction require Li2S4 and not Li2S6? + +2. In Figure S3, please explain the reason of the higher 1st voltage plateau (>2.3 V) and provide the information about the current density. + +3. In Figure S7B, please analysis the absorbance from S62- not being observed in the UV-vis spectra of the supernatants. + +4. The author report that the cycle life of Li-S pouch cells was significantly extended by the addition of \(\mathrm{Ca(OTf)2}\) . On the other hand, we find that the Ca-based pouch cell demonstrated a low specific capacity at \(\mathrm{E / S = 8\mu L}\) mg-1 (Figure S5C) and a high specific capacity at \(\mathrm{E / S = 3.5\mu L}\) mg-1 (Figure 2a) under distinct electrolyte-starved conditions. Please address these inconsistencies. + +5. In Figure 4E, the CaS is not completely transformed into \(\mathrm{Ca2 + }\) at \(100\%\) charge. We believe that the \(\mathrm{Ca2 + }\) catalyst does not enable sustainable regulation of the PS concentration in the electrolyte during long cycle. The superior cycle life of \(\mathrm{Ca(OTf)2}\) electrolyte is related to the OTF- anion. We recommend adding the additive of \(\mathrm{Li(OTf)}\) electrolyte to the parallel experiment. + +6. In Figure 6B, the FSI- anion in the Li+ solvate promote the formation of anion-derived SEI. In actuality, the OTF- anion also break down. It is crucial to provide the mechanism of LiF-enriched SEI formation. + +Version 1: + +<--- Page Split ---> + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The revised manuscript, "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," shows notable improvements over its previous version. The authors provide additional details to support the effectiveness of the calcium additive. However, I remain unconvinced that their hypothesis—"the strong Lewis acidity of \(\mathrm{Ca^{2 + }}\) readily converts LiPSs into CaS and \(\mathrm{S_8}\) , preventing electrolyte jamming, polysulfide shuttle, and lithium corrosion"—is robustly supported by the presented data. Typically, if this hypothesis holds, the cycling performance of Li/S cells should correlate with the acidity of metal ions. Yet, the authors exclude three key data points (other metal ions) for unrelated reasons, leaving \(\mathrm{Ca^{2 + }}\) as the only additive for comparison, which weakens the case for a clear trend. They argue that the strong Lewis acidity of \(\mathrm{Mg^{2 + }}\) and \(\mathrm{Al^{3 + }}\) triggers polymerization of DOL and/or side reactions with DME, rendering the electrolyte unusable. While DOL gelation can occur even under mildly acidic conditions, this claim seems inconsistent with their ability to obtain UV- vis results and decent cycling performance for Li/S cells using \(\mathrm{Mg^{2 + }}\) and \(\mathrm{Al^{3 + }}\) additives. If solvent reactivity, particularly with DOL, is a concern, why didn't the authors test alternative solvents—such as DMSO, ionic liquids, or certain glymes—that are less reactive with Lewis acids and commonly used in Li- S battery electrolytes to better validate the acidity- performance trend? + +Reviewer #2 + +(Remarks to the Author) + +The authors have replied to my comments and made acceptable revision. Most of my concerns and queries have been addressed. Thus, I would suggest the consideration of acceptance of the revised manuscript. + +Reviewer #3 + +(Remarks to the Author) + +I think I like the author's revision and would be happy to recommend publication of the manuscript. + +Version 2: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors adequately addressed most reviewer questions but omitted experimental details for Supplementary Figure 6, which are critical for explaining why only the \(\mathrm{Ca^{2 + }}\) compound is effective, unlike the \(\mathrm{Al^{3 + }}\) , \(\mathrm{Mg^{2 + }}\) , and \(\mathrm{Sr^{2 + }}\) compounds. The authors mention "gel- like flocculent precipitates" as decomposition products of dimethoxythane (DME) induced by \(\mathrm{Al^{3 + }}\) ions, suggesting they used their standard electrolyte (i.e., 0.75 M LiFSI and 0.4 M LiNO3 in DME) for the gelation test, as using a DOL- containing electrolyte would invalidate the experiment. Nonetheless, including these experimental details is essential for clarity and reproducibility. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Point-to-Point Response to Reviewers' Comments + +Title: Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries + +Authors: Hannah Cho, Jinkwan Jung, Ilju Kim, Jinuk Kim, Sejin Kim, Jonghyun Hyun, Chang Hoon Lee, Hobeom Kwack, Wonsik Oh, Jinwoo Lee, and Hee- Tak Kim\* + +We greatly appreciate the reviewer's comments, which have been very helpful in improving our manuscript. Below, we provide responses of the revision made in response to the feedback. Reviewer questions are highlighted in blue, and any revisions made to the manuscript are highlighted to aid the reviewers. + +## Reviewer #1 (Remarks to the Author): + +In their manuscript entitled "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," Cho et al. propose using \(\mathrm{Ca(OTf)_2}\) as an effective additive for lithium- sulfur batteries under lean electrolyte conditions. They claim that calcium ions mitigate polysulfide dissolution due to their high Lewis acidity, as well as the catalytic effects of CaS resulting from its interaction with LiPS. However, in my view, the publication of this manuscript is premature. Several additional experiments and essential experimental details are needed to substantiate the authors' claims. My specific comments are as follows: + +RESPONSE: Thank you for your thoughtful and constructive feedback on our manuscript. The reviewer's detailed comments, based on your extensive knowledge, have been invaluable in refining our study. We especially appreciate the reviewer's suggestions, which have helped us enhance the precision of our data analysis and provide more comprehensive descriptions of the experimental methods. The manuscript has been carefully revised in accordance with the reviewer's comments and suggestions. Our point- by- point responses to the reviewer's comments are appended below. + +1. Primary Hypothesis: The core hypothesis of this work is that the "high" Lewis acidity of calcium ions mitigates polysulfide dissolution by forming Ca-PS complexes. If this hypothesis is accurate, electrolytes with \(\mathrm{Mg(OTf)_2}\) and \(\mathrm{Al(OTf)_3}\) , which have ions with significantly higher acidity than + +<--- Page Split ---> + +Ca, should show even better performance. Since the difference in acidity between Ca and Li ions is minimal, this oversight or lack of consideration raises doubts about the hypothesis's validity. + +RESPONSE: We sincerely appreciate the reviewer's constructive questions. In response, we have further refined our hypothesis to clarify the role of \(\mathrm{Ca^{2 + }}\) in polysulfide dissolution and to provide a more precise rationale for its selection. + +Although an electrolyte additive can regulate polysulfide solubility, its stability in the electrolyte must take priority for its use in lithium- sulfur batteries, particularly ensuring that it does not undergo unintended side reactions with Lewis basic salt anions and solvents. Our UV- Vis analysis (Figs. 3a and 3b in the revised manuscript) confirms that Lewis acidity of cations correlates with polysulfide solubility, but we also found that most cations, except for \(\mathrm{Ca^{2 + }}\) , exhibited poor compatibility with the electrolyte. + +As reported in our initial manuscript (Supplementary Fig. 2 in the revised manuscript), Al electrolyte was gelated and Mg electrolyte showed formation of precipitate, indicating severe instability. The strong Lewis acidity of \(\mathrm{Al^{3 + }}\) and \(\mathrm{Mg^{2 + }}\) ions is known to catalyze DOL polymerization, leading to gelation (Chem. Commun., 56, 4583- 4586 (2022)). Additionally, \(\mathrm{Al^{3 + }}\) has been reported to decompose DME when \(\mathrm{Al(OTf)_3}\) is added to LiFSI/DME electrolytes, forming gel- like flocculent precipitates (ACS Appl. Mater. Interfaces, 16, 47581- 47589 (2024)). These results suggest that a cation with excessively high Lewis acidity has detrimental effects rather than effectively regulating polysulfides. + +Thus, instead of choosing a cation that is significantly more acidic than \(\mathrm{Li^{+}}\) , we considered a moderate increase in Lewis acidity to be more appropriate. Although the difference in pKa between \(\mathrm{Ca^{2 + }}\) and \(\mathrm{Li^{+}}\) is not large, our experimental data demonstrate that \(\mathrm{Ca^{2 + }}\) effectively modifies the polysulfide solvation environment. When \(1.6\mathrm{M}\mathrm{Li}_2\mathrm{S}_4\) was dissolved in both the control and Ca- containing electrolytes, the saturated supernatant in the Ca electrolyte showed more than threefold decrease in the \(\mathrm{S_4^{2 - }}\) peak intensity in UV- Vis spectra. + +This level of polysulfide solubility alteration by \(\mathrm{Ca^{2 + }}\) was found to be optimal for our system. While the pKa difference alone may not seem substantial, the observed solubility differences indicate that \(\mathrm{Ca^{2 + }}\) sufficiently modifies the polysulfide environment without introducing the instability observed with \(\mathrm{Al^{3 + }}\) and \(\mathrm{Mg^{2 + }}\) . These results validate our hypothesis that a moderate increase in Lewis acidity, rather than an extreme shift, is the key to effective polysulfide regulation. + +<--- Page Split ---> + +2. Experimental Descriptions: The manuscript contains many vague descriptions of experimental details, limiting the interpretability of the presented data. For example, in Fig. 5a, the electrolyte solutions for both the control and Ca experiments are described insufficiently, with only one line—"A viscometer (LVDV-2+PC, BROOKFIELD) was used to measure the electrolyte viscosity"—included in the experimental section. What does "1.6M Li₂S₄ control" mean? What solvents and salts are in the control? It is questionable whether the authors can truly reduce the control electrolyte's viscosity by merely adding Ca salt. + +RESPONSE: The authors sincerely appreciate the reviewer's insightful comments regarding the need for greater clarity in the experimental descriptions. We fully acknowledge that providing additional details is essential for enhancing the interpretability and reproducibility of our data, particularly concerning the viscosity measurements and the electrolyte composition. To address the reviewer's concerns, we have provided a more detailed description of the catholyte preparation and measurement conditions in the revised manuscript. Specifically, the "1.6 M Li₂S₄- containing control electrolyte" refers to a solution prepared by dissolving 1.6 M Li₂S₄ into the Control electrolyte, which consists of 0.75 M LiFSI and 0.4 M LiNO₃ salts in DME solvent. The significant reduction in viscosity upon the addition of Ca salt is attributed to the interactions between Ca ions and polysulfide (PS) species. Ca²⁺ ions mitigate polysulfide dissolution by forming Ca-PS complexes and precipitating CaS, leading to a profound decrease in the polysulfide saturation concentration in the Ca electrolyte, as observed in Supplementary Fig. 24 in the revised manuscript. This effect of Ca²⁺ aligns with the strong influence of polysulfide concentration on electrolyte viscosity as previously reported in the literature (ACS Appl. Mater. Interfaces, 14, 46457–46470 (2022)). Increasing the Li₂S₈ concentration from 0.78 M to 3.9 M resulted in a three-order magnitude increase in viscosity, from 4.3 mPa·s to 1.8×10³ mPa·s. In our study, the threefold difference in UV-vis absorbance (Supplementary Fig. 24 in the revised manuscript) at 425 nm (corresponding to S₄²⁻) between the Li₂S₄-saturated control and Ca catholytes correlates well with the significant decrease in viscosity observed under the same conditions. + +Additionally, this PS- saturated environment mimics the conditions near the porous cathode at a depth of discharge (DOD) of \(\sim 30\%\) during the discharge process, where excessive polysulfide dissolution can lead to significant overpotential. The reduced viscosity in the Ca electrolyte + +<--- Page Split ---> + +mitigates this issue, lowering overpotential and improving both cell performance and reaction reversibility. + +In response to the reviewer's valuable suggestion, we have added details to experimental descriptions including catholyte preparation, viscosity measurements, source of LiTFSI, GITT protocols, Raman spectroscopy measurements and sample preparation in the methodology section of our revised manuscript. + +## [Revised manuscript] + +[Line 454- 463] + +To mimic the polysulfide- saturated environment, \(1.6\mathrm{M}\mathrm{Li}_2\mathrm{S}_4\) (equivalent to the \(E / S\) ratio of 5) was added to the Control electrolyte and Ca electrolyte, and the solutions were stirred for 72 hours at \(25^{\circ}\mathrm{C}\) . The catholytes were then rested for 24 hours to achieve equilibrium and filtrated through a syringe filter with a pore size of \(0.22\mu \mathrm{m}\) to obtain the saturated solution. The viscosity of the catholytes was measured using a viscometer (LVDV- 2+PC, BROOKFIELD) at \(25^{\circ}\mathrm{C}\) for 1 minute. To ensure accurate viscosity measurements for solutions with significantly different viscosities (7 cP vs. 2 cP), the torque values were maintained within the optimal range (60- 90%) by adjusting the rotational speed. For the Control catholyte, the rotational speed was set to 30- 40 RPM with a corresponding shear rate of \(225 - 300\mathrm{s}^{- 1}\) . For the Ca catholyte, the rotational speed was adjusted to 90- 95 RPM, with a shear rate of \(675 - 721.5\mathrm{s}^{- 1}\) . These adjustments ensured reliable viscosity readings while minimizing instrument- related errors. + +[Line 444] + +LiTFSI and DOL (anhydrous, \(99.5\%\) ) were purchased from 3M and Sigma- Aldrich, respectively. + +[Line 489- 492] + +The GITT experiments consist of a series of pulse currents at \(0.1\mathrm{C}\) for \(0.1\mathrm{h}\) , each followed by a \(0.4\mathrm{h}\) open- circuit period. The open- circuit relaxation time should be long enough that the voltage fluctuation is within a \(0.01\mathrm{V}\) range. The open circuit voltage (OCV) curves of the Li- S cells were constructed by connecting the voltage points after each relaxation period. + +[Line 481- 483] + +<--- Page Split ---> + +Samples for Raman spectroscopy were prepared by filling a sample vial, then were tightly sealed. Spectra were recorded using a dispersive Raman spectrometer (ARAMIS, JY Horiba) and sample excitation was carried out at \(514 \mathrm{nm}\) . + +![](images/Figure_unknown_0.jpg) + + +Supplementary Fig. 24 | Reduced PS saturation concentration at an \(E / S\) ratio of \(5 \mu \mathrm{L} \mathrm{mg}^{- 1}\) with the Ca electrolyte. a, Photograph of \(1.6 \mathrm{M} \mathrm{Li}_2 \mathrm{S}_4\) in the control electrolyte (left) and the Ca electrolyte (right). b, UV- vis spectroscopy of supernatants from (a). + +3. Electrode Composition Details: Essential information about the electrodes, such as binder type, carbon materials, and sulfur loading percentage, is missing. These parameters are crucial for reproducing the results and should be included. + +RESPONSE: The authors appreciate the reviewer's detailed comments. All electrodes used in this work were fabricated in a similar fashion as following information. CNT/S composite (75wt% elemental sulfur), and CMC/PAA/SBR binder (CMC:PAA:SBR = 3:1:4 by weight) were mixed well with a weight ratio of 96:4 in deionized water and the resulting slurry was casted onto Al foil with an areal loading of \(3.8 \mathrm{mg} \mathrm{cm}^{-2}\) unless otherwise specified. The information was added to the Method part of the revised manuscript. + +## [Revised manuscript] + +[Line 464- 468] + +Sulfur electrode preparation and materials characterization. For the preparation of the cathode, a CNT/S composite (75 wt% Sulfur) and the binder mixture (carboxymethyl cellulose (CMC)/poly(acrylic acid) (PAA)/styrene-butadiene rubber (SBR) binder = 3/1/4 by weight) were homogenized with a weight ratio of 96:4 in deionized water. The CNT/S composite was prepared by impregnating molten sulfur into a CNT micro-ball via melt-diffusion at 120 °C. Afterward, the + +<--- Page Split ---> + +resulting slurry was cast on the Al foil, followed by drying under \(80^{\circ}\mathrm{C}\) . For coin- type and pouch- type bi- cell, single- side coated cathodes were fabricated at sulfur loadings of 3.8 and \(2.25\mathrm{mg}\mathrm{cm}^{- 2}\) , respectively. For high- energy and high- power pouch cells, double side- coated cathodes were prepared at sulfur loadings of \(2.26\) and \(1.81\mathrm{mgcm}^{- 2}\) , respectively. + +4. UV-Vis Study Protocols: The UV-Vis study requires a more detailed experimental procedure. Did the authors immerse all coin cell components in the control electrolyte? Given the small electrolyte volume in a coin cell, there may be significant experimental error. Providing at least three parallel experiments would help confirm the data's consistency. + +RESPONSE: We thank the reviewer for raising this important point. The UV-Vis studies on both the catholyte and discharged cells were conducted to cross- validate the interaction between Lewis acidic cations and polysulfides. Beyond simply comparing the UV-Vis spectra of catholytes (Supplementary Fig. 11 in the revised manuscript) to evaluate polysulfide solubility, we focused on comparing the accommodative amount of polysulfides electrochemically reduced from \(\mathrm{S}_8\) in the presence of Lewis acidic additives. + +We apologize for the insufficient description of the experimental procedures in the original manuscript. To address the reviewer's point, we added the experimental details to the Methods section of the revised manuscript. Specifically, the procedure is as follows: Immediately after discharging the coin cells to \(2.1\mathrm{V}\) , the coin cell components, including the spacer, electrodes, and separator, were gently washed with \(2\mathrm{mL}\) of DME to wash off the dissolved polysulfides, particularly from the porous cathode and separator. The washed solution was filtered using a syringe filter with a pore size of \(0.22\mu \mathrm{m}\) . The solution was then diluted tenfold with the control electrolyte, which served as the baseline for UV- Vis spectroscopy. + +We ensured that this protocol was executed meticulously for all cells to minimize experimental error. Although dilution could introduce some variability under lean electrolyte conditions, the significant differences in the stability of electrochemically generated lithium polysulfides for each cation additive (as observed in parallel experiment on UV- Vis spectroscopy of catholytes) made these errors are negligible. As suggested by the reviewer, we repeated the experiments under the same conditions as Fig. 3a for three independent trials. The results, shown in Fig. R1, confirm the + +<--- Page Split ---> + +consistency of the data. Additionally, in response to the reviewer's suggestion in **Comment #5**, we replaced the control with \(0.05 \mathrm{M} \mathrm{Li}(\mathrm{OTf})\) in order to compare the polysulfide dissolution under different cation additives \((\mathrm{Li}^{+}, \mathrm{Sr}^{2 + }, \mathrm{Ca}^{2 + }, \mathrm{Mg}^{2 + }, \mathrm{Al}^{3 + })\) based on their Lewis acidity. The peak intensity at \(425 \mathrm{~nm}\) (corresponding to \(\mathrm{S}_{4}^{2 - }\) ) for four independent experiments, represented with error bars in the Revised **Fig. 3b**, shows minimal variability, demonstrating the reliability of the results. + +**Fig. R1** is now **Supplementary Fig. 6**. We hope this detailed explanation and additional data address the reviewer's concerns and provide confidence in the accuracy and reproducibility of our findings. + +![](images/Figure_3b.jpg) + +
**Fig. R1. UV-Vis spectroscopy of electrolytes from coin cells (E/S = 4 \(\mu \mathrm{L} \mathrm{mg}^{-1}\)) discharged to 2.1 V.**
+ +![](images/Figure_3a.jpg) + +
**Fig. 3b. Lewis acid-base reaction between multivalent metal ions and PSs. b, Correlation** between the pKa value of metal cations27 and the UV-vis absorbance at 425 nm (corresponding to \(\mathrm{S}_{4}^{2 - }\) ) in electrolytes containing Lewis acidic additives after discharge to 2.1 V. Error bars denote the standard deviation from measurements obtained from four independent coin cells. The data are presented as mean values \(\pm\) standard deviation.
+ +5. Control Setup in Fig. 3b: In Fig. 3b, the control should not solely consist of the control + +<--- Page Split ---> + +electrolyte; 0.05M Li(OTf) should also be added. Additionally, the authors must explain how they determined the pKa values in the experimental section. + +RESPONSE: The authors sincerely thank the reviewer for valuable suggestions. Following the reviewer's recommendation, we have revised the Control in Fig. 3b to 0.05 M Li(OTf), as the X-axis represents the pKa values of metal cation triflates. + +The pKa values of \([\mathrm{M(OH_2)_m}]^{n + }\) used in this study were referenced from "Perrin, D. D., Ionization Constants of Inorganic Acids and Bases in Aqueous Solution, Second Edition, Pergamon, Oxford, 1982". These pKa values of hydrated metal ion complexes are reported to be strongly correlated with Lewis acidity of metal triflates dissolved in organic solvents (Inorg. Chem., 60, 1107- 1115 (2021)). + +We have revised this content to the revised manuscript (Fig. 3a and b), as prompted by the reviewer's valuable suggestion. + +![](images/Figure_unknown_1.jpg) + +
Fig. 3a, b. Lewis acid-base reaction between multivalent metal ions and PSs. a, UV-vis spectra of electrolytes from the coin cells \((E / S = 4 \mu \mathrm{L} \mathrm{mg}^{-1})\) after being discharged to 2.1 V. b, Correlation between the pKa value of metal cations \(^{27}\) and the UV-vis absorbance at 425 nm (corresponding to \(\mathrm{S}_4^{2 - }\) ) in electrolytes containing Lewis acidic additives after discharge to 2.1 V. Error bars denote the standard deviation from measurements obtained from four independent coin cells. The data are presented as mean values \(\pm\) standard deviation.
+ +6. Choice of Control Electrolyte: The authors' control choice of 0.75M LiFSI and 0.4M LiNO₃ in DME differs from the conventional Li-S electrolyte (1M LiTFSI in DOL/DME with \(\sim 2\%\) LiNO₃). + +<--- Page Split ---> + +The authors used a 0.5M LiTFSI and 0.2M LiNO₃ DOL/DME electrolyte, and the large reduction in salt concentration likely exacerbates LiPS dissolution. + +RESPONSE: We thank the reviewer for suggesting the use of the conventional electrolyte (1 M LiTFSI in DOL/DME (1:1 v/v) with \(\sim 2\) wt% LiNO₃) as the Control electrolyte. To improve the performance of Li- S batteries under lean electrolyte conditions, alternative electrolyte engineering strategies from the conventional electrolyte have been actively explored. For instance, reducing the LiTFSI concentration from the conventional electrolytes has been reported to improve charge transfer kinetics, suppress the shuttle effect, and enhance lithium polysulfide conversion redox kinetics, ultimately leading to better overall Li- S battery performance (Chem, 8, 1- 20, (2022) / Adv. Funct. Mater., 32, 2205393 (2022)). Based on these findings, we selected 0.5 M LiTFSI electrolyte as an optimized system for achieving these benefits while maintaining compatibility with the conventional electrolyte framework. + +In case of LiFSI- based electrolytes, using LiFSI as main lithium salt has demonstrated advantages over LiTFSI especially under low E/S ratio, including lower resistance (J. Am. Chem. Soc., 145, 16449- 16457 (2023)) and the formation of a more stable LiF- based solid electrolyte interphase (SEI) (Nano- Micro Lett., 16, 35 (2024)). Given these benefits, we used 0.75 M LiFSI to achieve improved SEI stability and ionic transport properties. However, as the reviewer pointed out, it is essential to evaluate the effect of \(\mathrm{Ca^{2 + }}\) in the conventional LiTFSI- based electrolyte system for direct comparison with literature results. To address this, we conducted additional experiments incorporating \(\mathrm{Ca^{2 + }}\) into the conventional electrolyte. The results are discussed below. + +As shown in Fig. R2, the use of the conventional LiTFSI- based electrolyte as the Control electrolyte in lean electrolyte coin cells results in a significant increase in overpotential upon cycling, leading to a short cycle life of less than 50 cycles. In contrast, incorporating the Ca additive into the conventional electrolyte improved cycle life by more than twofold in different testing conditions. We have confirmed the effectiveness of the Ca additive not only in electrolyte systems with different main salts with different concentrations (e.g., 1 M LiTFSI, 0.5 M LiTFSI, LiFSI) but also across various co- solvents and E/S ratios under lean electrolyte conditions (Figs. 2a- c and Supplementary Fig. 5 in the revised manuscript). These results highlight the universal effectiveness of a small amount of Ca additive in modifying the solvation properties, enhancing interactions with polysulfide anions, and the formation of a CaS catalyst—a principle that extends to other electrolyte systems. These combined effects significantly reduce overpotential and extend + +<--- Page Split ---> + +the cycle life of lean electrolyte Li- S batteries. + +![](images/Figure_unknown_2.jpg) + +
Fig. R2. Cycle performance of Li-S cells with 1 M LiTFSI 2 wt% LiNO3 DOL:DME electrolyte. Cell capacity versus cycle number for a, 0.20C discharge/ 0.15C charge b, 0.30C discharge/ 0.20C charge.
+ +7. Cycling Performance: For Fig. 2a, the authors should provide parallel cycling performance for each cell to confirm repeatability and rule out cell-to-cell variations. + +RESPONSE: The authors thank the reviewer's valuable suggestion. We agree that confirming the repeatability of cycling performance is crucial, especially under lean electrolyte conditions where reaction inhomogeneity may cause cell-to-cell variations. + +To address this, we assembled pouch cells with the same configuration as in Fig. 2a, and these are currently undergoing cycling tests. Unfortunately, due to the low current density cycling conditions used in Fig. 2a (0.10C Discharge / 0.05C Charge), we were unable to fully replicate the complete cycling data at the time of this revision submission, except for the control electrolyte, for which an additional cell had been previously been tested. For instance, the pouch cell with Ca electrolyte required 150 days to reach 70% capacity retention. Nevertheless, we hope the following information convince you the consistency in the observed trends. + +For the replicated cells, cycling performance (Fig. R3) of Al and the Control electrolyte confirms consistency with the original data. The Al electrolyte, which exhibited significant overpotential and failed after 26 cycles in Fig. 2a, failed with same behavior at the \(28^{\text{th}}\) cycle in the replicated experiment. Additionally, the Control electrolyte exhibited a cycle life of 107 cycles (70% capacity retention) in the replicated cell, which closely matches the cell failure at \(103^{\text{th}}\) cycle observed in Fig. 2a. For the Mg, Ca, and Sr electrolytes, we observed similar trends in the ongoing cycles (~45 cycles), and we expect comparable cell performance to that shown in Fig. 2a. + +<--- Page Split ---> + +To further compare the performance of electrolytes with Lewis acidic additives, we tested coin cells with an \(E / S\) ratio of \(4 \mu \mathrm{L} \mathrm{mg}^{- 1}\) (Fig. R4). Although the cell format differs, we confirmed the similar trend in cycle life: the Ca electrolyte extends the cycle life compared to the control electrolyte, while Al, Mg, and Sr electrolytes show incompatibility. The inferior cell performance of coin cells in Fig. R4, despite higher \(E / S\) ratio, can be attributed to greater uniformity and higher stack pressure of pouch cells which positively impacts cycling stability (Nat. Energy, 4, 551 (2019)). + +To substantiate the reproducibility of the Ca electrolyte's superior performance under lean electrolyte pouch cell conditions, we tested additional pouch cell tests under faster discharging conditions as those shown in Fig. 2c. The performance of replicated cells (Fig. R5) confirm the consistency and highlight the cycling performance of the Ca electrolyte under extremely lean electrolyte conditions. We hope these additional data and comparisons address the reviewer's concerns regarding cycling performance and reinforce the reliability and reproducibility of our findings. + +![](images/Figure_unknown_3.jpg) + +
Fig. R3. Pouch-type Li-S bi-cell \((E / S = 3.5 \mu \mathrm{L} \mathrm{mg}^{-1})\) cycling with the control and additive \((\mathrm{Sr}^{2 + }, \mathrm{Ca}^{2 + }, \mathrm{Mg}^{2 + }, \mathrm{or} \mathrm{Al}^{3 + })\) -containing electrolytes.
+ +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
Fig. R4. Cycle performance of Li-S cells with Lewis acidic electrolyte additives.
+ +![](images/Figure_2b.jpg) + +
Fig. R5. Electrochemical performances of the Li-S pouch cells with Ca electrolyte. Li-S stack cell with an \(E / S\) ratio of \(2.9 \mu \mathrm{L} \mathrm{mg}^{-1}\) (high power design) with \(\mathrm{Ca(OTf)_2}\) additive showing stable cycling for over 350 cycles at \(1.0 \mathrm{C}\) .
+ +8. Additive Controls in Figs. 2b and 2c: The cycling results for the control electrolyte, as well as electrolytes with Al and Mg additives, should also be presented. + +RESPONSE: We appreciate the reviewer's helpful feedback, which has allowed us to improve the clarity of our study. In response to this suggestion, we have incorporated the cycling results for the control electrolyte as well as the electrolytes containing Al and Mg additives in Figs. 2b and 2c. These additional data provide a more comprehensive comparison of the cycling performance across different electrolyte formulations. + +The results confirm that the Ca electrolyte consistently outperforms the control electrolyte, while Al and Mg electrolytes show inferior cycling stability. + +<--- Page Split ---> +![](images/Figure_unknown_5.jpg) + +
Fig. 2b-c. b, High-Energy design Li-S stack cell with an \(E / S\) ratio of \(2.4~\mu \mathrm{L}\mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 200 cycles at \(0.3\mathrm{C}\) . Configuration of a high-energy cell with \(25\mu \mathrm{m}\) Li and sulfur loading of \(2.26\mathrm{mg}\mathrm{cm}^{-2}\) . c, High-Power design Li-S stack cell with an \(E / S\) ratio of \(2.9\mu \mathrm{L}\mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 350 cycles at \(1.0\mathrm{C}\) . Configuration of a high-power cell with \(20\mu \mathrm{m}\) Li and sulfur loading of \(1.81\mathrm{mg}\mathrm{cm}^{-2}\) .
+ +9. Electrolyte Solvation Analysis: The authors employed MD simulation and solid characterization techniques such as TEM and XPS. To thoroughly understand electrolyte solvation, additional FTIR/Raman and NMR data should be included. + +RESPONSE: We appreciate the reviewer's suggestion, which allowed us a more detailed analysis of \(\mathrm{Li^{+}}\) solvation behavior upon introducing the Ca additive. To address this, we performed Raman spectroscopy on the control and Ca electrolytes, as well as the catholytes. In the absence of lithium polysulfides, the addition of \(0.05\mathrm{M}\) or \(0.10\mathrm{M}\mathrm{Ca}^{2 + }\) does not affect \(\mathrm{Li^{+}}\) solvation. As shown in Fig. R6a, the Raman spectra exhibit no significant changes in the intensity or position of the \(\mathrm{Li^{+}}\) - FSI\({}^{-}\) and \(\mathrm{Li^{+}}\) - DME peaks upon the \(\mathrm{Ca}^{2 + }\) addition. This indicates negligible interaction between \(\mathrm{Ca}^{2 + }\) and FSI\({}^{-}\) anions or solvent molecules. Furthermore, the molecular dynamics (MD) simulations of the Ca electrolyte without polysulfides (Fig. R7) reveal that \(\mathrm{Ca}^{2 + }\) primarily coordinates with \(\mathrm{NO_3^{- }}\) anions, which possess a high donor number and dominate the solvation environment. + +<--- Page Split ---> + +In sharp contrast, a high- concentration catholyte (1.6 M \(\mathrm{Li_2S_4}\) , corresponding to full sulfur dissolution at \(\mathrm{E / S} = 5 \mu \mathrm{L} \mathrm{mg}^{- 1}\) ) showed clear differences upon the \(\mathrm{Ca^{2 + }}\) additions (Fig. R6b). Compared to the Control catholyte, the 0.05 M and 0.10 M Ca catholytes showed stronger signals for \(\mathrm{Li^{+}}\) - FSI, \(\mathrm{Li^{+}}\) - coordinated DME, and free DME. A same trend appeared even at a lower \(\mathrm{Li_2S_4}\) concentration of 0.2 M (Fig. R6c), where the Raman signals for \(\mathrm{Li^{+}}\) - FSI and \(\mathrm{Li^{+}}\) - DME were more distinct in the Ca electrolytes than in the control electrolyte. This can be explained by the strong Raman activity of polysulfides, which generate intense scattering signals that can hinder peaks from FSI or DME (Small Struct., 3, 2100170 (2022)). Since the Control electrolyte contains a higher concentration of solvated LiPS than the Ca electrolyte, the intense Raman scattering from polysulfides weakens the visibility of other species. These results indicate that \(\mathrm{Ca^{2 + }}\) modifies the solvation structure by decreasing the amount of solvated LiPS in the electrolyte. + +Regarding the reviewer's suggestion to include NMR analysis, distinguishing between \(\mathrm{Li^{+}}\) - FSI and \(\mathrm{Li^{+}}\) - PS interactions using \(^7\mathrm{Li}\) chemical shift would be difficult. The increase in \(\mathrm{Li^{+}}\) - FSI coordination in the Ca catholyte is counterbalanced by a decrease in \(\mathrm{Li^{+}}\) - PS interactions, resulting in little net change in the chemical shift. Also, \(^{19}\mathrm{F}\) NMR of FSI anions shows minimal variation, as \(\mathrm{Li^{+}}\) interacts primarily with the oxygen atoms of FSI rather than fluorine, making FSI chemical shifts less sensitive to solvation changes. + +The change of \(\mathrm{Li^{+}}\) solvation structure in polysulfide- containing electrolytes by \(\mathrm{Ca^{2 + }}\) additive is further supported by ToF- SIMS and XPS data, where an S- poor, F- rich SEI is formed in the Ca electrolyte. Additionally, linear sweep voltammetry (LSV) shows a lower LiPS reduction current, reinforcing the conclusion that \(\mathrm{Ca^{2 + }}\) influences the solvation environment. These results provide a clearer understanding of how \(\mathrm{Ca^{2 + }}\) affects \(\mathrm{Li^{+}}\) solvation in Li- S battery electrolytes, and we have incorporated the discussion into the revised manuscript, Fig. R7 is now Supplementary Fig. 26. + +<--- Page Split ---> +![](images/Figure_unknown_6.jpg) + +
Fig. R6. Raman spectroscopy of electrolytes and catholytes with varying lithium polysulfide concentrations. a, Raman spectra of electrolytes without lithium polysulfide. Different peak ranges are noted with arrows in the spectra. b, Raman spectra of supernatants from catholytes containing 1.6 M \(\mathrm{Li_2S_4}\) (corresponding to full sulfur dissolution at \(\mathrm{E / S = 5\mu Lmg^{-1}}\) , \(3.8\mathrm{mgcm}^{-2}\) sulfur loading). c, Raman spectra of supernatants from catholytes containing \(0.2\mathrm{M}\mathrm{Li}_2\mathrm{S}_4\)
+ +<--- Page Split ---> +![](images/Figure_2a.jpg) + +
Fig. R7. Cumulative distribution functions of \(\mathrm{Ca^{2 + }}\) solvation in 0.1 M \(\mathrm{Ca(OTf)_2}\) electrolyte.
+ +[Revised manuscript] [Line 383- 385] + +In parallel, Raman spectroscopy confirms the strengthened \(\mathrm{Li^{+}}\) - FSI coordination while the LiPS + +signal intensity decreases (Supplementary Fig. 26). + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +## Summary: + +This research paper entitled, "Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries" reports a novel approach to designing and enhancing the performance of lean- electrolyte lithium- sulfur batteries by adding a small amount of calcium cations to the electrolyte. The calcium cations are reported that can effectively convert polysulfides into calcium sulfide and sulfur. This reaction prevents polysulfide shuttle and electrolyte jamming while mitigating lithium corrosion. The in situ formation of calcium sulfide acts as a catalyst, facilitating the reduction of polysulfides, and calcium cations are regenerated during charging, allowing sustainable cycling. The addition of calcium cations improves cycling stability and energy density, with pouch cells achieving 493 Wh kg \(^{- 1}\) and \(70\%\) capacity retention after 220 cycles, and 346 Wh kg \(^{- 1}\) with \(77\%\) retention after 360 cycles. + +## General comment: + +This study reports on the electrolyte additive for the lean- electrolyte lithium- sulfur cell to have an improved performance. Some minor revision is needed, and I hope the authors find the comment useful. + +RESPONSE: We sincerely appreciate your thorough understanding and positive evaluation of our work, which has greatly encouraged us to refine the comprehensibility and design principles of the proposed electrolyte system. The reviewer's insightful comments and constructive suggestions have been instrumental in improving both the clarity and scientific rigor of our manuscript. In particular, we are grateful for the suggestions that prompted us to provide additional details regarding experimental methods, refine data presentation, and further explore the key mechanistic aspects of our study. These refinements have strengthened the manuscript and enhanced the robustness of our conclusions. The manuscript has been carefully revised in accordance with the reviewer's comments, and a point- by- point response detailing the modifications made is provided below. + +## Comments: + +(1) The manuscript is well organized in both the writing and the data presentation. One minor suggestion is on the image layout in figures. Cycling performance data are not suggested to show an extended X axis for the cycle number. This gives an unreasonable cyclability. [Suggestion] Please organize and arrange the cycling performance data with a regular image layout. + +<--- Page Split ---> + +**RESPONSE:** The authors sincerely appreciate the reviewer's positive evaluation of our work and the thoughtful suggestion regarding the image layout. Following the reviewer's recommendation, we have adjusted the X-axis range of **Figs. 2a–c** to present a more reasonable depiction of the cycling performance data. Additionally, we have included the configurations of the high-power and high-energy pouch cells in **Figs. 2b** and **2c** to enhance the clarity of the figure presentation. + +The revised manuscript now displays the cycling stability of the Ca electrolyte in pouch cells for up to \(\geq 200\) cycles, as shown in **Figs. 2a–c**. + +![](images/Figure_unknown_7.jpg) + +
Fig. 2a-c. Electrochemical performances of the Li-S pouch cells with Lewis acidic multivalent metal additives. a, Pouch-type Li-S bi-cell \((E / S = 3.5 \mu \mathrm{L} \mathrm{mg}^{-1})\) cycling with the control and additive \((\mathrm{Sr}^{2 + }\) , \(\mathrm{Ca}^{2 + }\) , \(\mathrm{Mg}^{2 + }\) or \(\mathrm{Al}^{3 + }\) )-containing electrolytes. b, High-Energy design Li-S stack cell with an \(E / S\) ratio of \(2.4 \mu \mathrm{L} \mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 200 cycles at \(0.3 \mathrm{C}\) . Configuration of a high-energy cell with \(25 \mu \mathrm{m} \mathrm{Li}\) and sulfur loading of \(2.26 \mathrm{mg} \mathrm{cm}^{-2}\) . c, High-Power design Li-S stack cell with an \(E / S\) ratio of \(2.9 \mu \mathrm{L} \mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 350 cycles at \(1.0 \mathrm{C}\) . Configuration of a high-power cell with \(20 \mu \mathrm{m} \mathrm{Li}\) and sulfur loading of \(1.81 \mathrm{mg} \mathrm{cm}^{-2}\) .
+ +<--- Page Split ---> + +(2) The formation of CaS and S via the adsorbed polysulfides is the main finding of this research. It is suggested to focus on collecting direct experimental data as evidence. Then, the formation mechanism of CaS and the conversion from CaS to polysulfides is suggested to be studied and discussed. In addition, the polysulfide trapping mechanism is suggested to be explored. [Suggestion] Please conduct analysis and discussion on the formation mechanism of CaS, the conversion mechanism from CaS to polysulfides, and the polysulfide-trapping mechanism of calcium cations together. + +RESPONSE: We thank the reviewer for these valuable insights. While our original manuscript presented various experimental and simulation results addressing the mechanisms in question (Fig. 3 and Fig. 4, Supplementary Figs. 8–18), these findings were dispersed throughout the manuscript, which may have made it difficult for readers to follow a cohesive narrative. To enhance clarity and provide a more structured discussion, we have compiled and consolidated these findings into a Supplementary Note that systematically outlines the mechanism. We acknowledge that our previous explanation may not have been sufficiently clear. In response, we provide a comprehensive discussion on the experimental evidence supporting the effects of \(\mathrm{Ca(OTf)_2}\) as an electrolyte additive, as well as its underlying mechanisms, which are summarized as follows. + +## 1. Polysulfide-trapping mechanism of the calcium cation: + +The strong electrostatic interaction between \(\mathrm{Ca^{2 + }}\) and polysulfides leads to the formation of tightly associated \(\mathrm{Ca^{2 + }}\) - PS complexes. As shown in Fig. R8a, \(\mathrm{Ca^{2 + }}\) ions coordinate with multiple polysulfide anions compared to \(\mathrm{Li^{+}}\) due to its stronger Lewis acidity, forming a stable \(\mathrm{Ca^{2 + }}\) - PS network in the electrolyte (Fig. R8a). A similar mechanism using Lewis acidic electrolyte additive has been reported in recent literature (Joule, 8, 3397–3411 (2024)), where \(\mathrm{LiBF_4}\) reacts with nucleophilic LiPS to form \(\mathrm{LiF}\) and \(\mathrm{BF_3}\) . The strong Lewis acidity of \(\mathrm{BF_3}\) subsequently leads to \(\mathrm{BF_3}\) - PS adduct formation, which lowers polysulfide solubility. By analogy, the interaction between \(\mathrm{Ca^{2 + }}\) and polysulfides is expected to play a critical role in reducing LiPS solubility within the electrolyte. + +<--- Page Split ---> +![](images/Figure_unknown_8.jpg) + +
Fig. R8. Molecular dynamics of the Ca catholyte. a, Coordination number of polysulfide with \(\mathrm{Li^{+}}\) and \(\mathrm{Ca^{2 + }}\) in the Ca catholyte. b, MD snapshots of the molecular distributions around \(\mathrm{Li^{+}}\) , \(\mathrm{Ca^{2 + }}\) , and \(\mathrm{S_{4}^{2 - }}\) in the control catholyte (left) and 0.05 M Ca catholyte (right).
+ +2. Formation mechanism of CaS and Ss: The \(\mathrm{Ca^{2 + }}\) -PS complex undergoes conversion via two possible pathways during discharge: + +1) Electrochemical Reduction: The Ca electrolyte used in our manuscript contains a relatively low concentration of \(\mathrm{Ca^{2 + }}\) compared to \(\mathrm{Li^{+}}\) , the electrochemical reduction of Ca-PS complexes was not apparent. However, when \(\mathrm{Ca(OTf)_2}\) concentration is increased to \(0.5\mathrm{M}\) , an additional peak appears at \(\sim 2.15\mathrm{V}\) in the cyclic voltammetry (CV) and also in the discharge voltage profiles following the \(1^{\mathrm{st}}\) plateau of \(\mathrm{S_8}\) to \(\mathrm{Li_2S_4}\) conversion (Fig. R9a and b). This peak aligns well with the electrochemical reduction potential of low-order Ca polysulfides ( \(\mathrm{CaS_n}\) , \(2 \leq n \leq 4\) ) to \(\mathrm{CaS_2}\) and \(\mathrm{CaS}\) ( \(\sim 2.2\mathrm{V}\) vs. \(\mathrm{Li / Li^{+}}\) ) (Small, 16, 2001806 (2020)). The persistence of this peak even after 20 cycles suggests that Ca-S redox process is reversible. + +2) Chemical Precipitation: The chemical precipitation reaction is expected to occur due to the strong electrostatic attraction between \(\mathrm{Ca^{2 + }}\) and the \(\mathrm{S^{2 - }}\) , leading to the spontaneous formation of thermodynamically stable CaS. Since CaS has extremely low solubility even in highly polar solvents like \(\mathrm{H_2O}\) , it cannot be solvated in DME, forming precipitates. This chemical reaction was confirmed through XRD (Fig. R9c) and XPS (Supplementary Figs. 11d, e) analysis of precipitates collected from \(\mathrm{Li_2S_8 + Ca(OTf)_2}\) in DME. + +As a result of this mechanism, the CaS precipitated on the cathode was experimentally analyzed using TEM (Fig. 9d) and XPS (Fig. R9e) of discharged cathodes. + +<--- Page Split ---> +![](images/Figure_unknown_9.jpg) + +
Fig. R9. a, Cyclic voltammetry (CV) test of Li-S the coin cell with \(0.5\mathrm{M}\) Ca electrolyte. b, Discharge voltage profiles of the coin cell with \(0.5\mathrm{M}\) Ca electrolyte. c, XRD analysis of precipitates formed in \(\mathrm{Ca(OTf)_2}\) containing solution. d, HAADF-STEM image and corresponding element mapping of the CNF cathode after discharge of the Li-S/CNF cell to \(2.1\mathrm{V}\) , scale bar: \(200\mathrm{nm}\) . e, Ca 2p XPS spectra of the cathode after \(1^{\mathrm{st}}\) cycle discharge.
+ +## 3. Conversion mechanism from CaS to \(\mathrm{Ca^{2 + }}\) : + +CaS undergoes oxidation back to \(\mathrm{Ca^{2 + }}\) because its oxidation potential within the operating voltage of Li- S batteries. Previous studies on Ca- S batteries (Small, 16, 2001806 (2020)/ Adv. Energy Mater., 9, (2019)) have shown that CaS is oxidized to \(\mathrm{CaS_n}\) and to \(\mathrm{S_8}\) at approximately 2.35 and \(2.47\mathrm{V}\) vs. \(\mathrm{Li / Li^{+}}\) , respectively (corresponding to \(2.18\mathrm{V}\) and \(2.3\mathrm{V}\) vs. \(\mathrm{Ca / Ca^{2 + }}\) ). In this study, we experimentally observed the oxidation of CaS to \(\mathrm{Ca^{2 + }}\) and \(\mathrm{S_8}\) by ICP- MS (Fig. 4f) analysis. Additionally, we directly observed the CaS oxidation using CaS- casted electrode (Fig. R10). Upon charging the Li- CaS cell, the oxidation peaks of CaS appeared, and subsequently discharging it, two distinct discharge plateaus were observed, indicating the formation of S8 from CaS when CaS was the only available sulfur source. + +<--- Page Split ---> +![](images/Figure_unknown_10.jpg) + +
Fig. R10. Oxidation of CaS during cell operation. a, Linear sweep voltammetry profiles of the carbon paper electrode, \(\mathrm{Li}_2\mathrm{S}\) -loaded carbon paper electrode, and CaS-loaded carbon paper electrode. b, Discharge voltage profiles of the Li-Carbon paper cells incorporating CaS or \(\mathrm{Li}_2\mathrm{S}\) in the carbon paper electrode.
+ +The above discussion was added to Supplementary Note 1. + +(3) The sulfur cathode used in this research is necessary to be discussed and disclosed. The sulfur loading and sulfur content are suggested to be reported. The content of additional additives is necessary to be reported. These are necessary information, which controls the key experimental testing condition, E/S ratio. + +[Suggestions] Please report the necessary information on the cathode. + +RESPONSE: The authors appreciate the reviewer's detailed comments and for highlighting the importance of disclosing key information. All electrodes used in this work were fabricated following a standardized procedure. CNT/S composite (containing 75wt% elemental sulfur) was mixed with Carboxymethyl cellulose (CMC) / Poly(acrylic acid) (PAA) / Styrene-butadiene rubber (SBR) binder (CMC:PAA:SBR = 3:1:4 by weight) in deionized water with a weight ratio of 96:4, then was cast onto Al foil with an areal loading of \(3.8\mathrm{mgcm}^{-2}\) unless otherwise specified. Regarding the additive content, we have further improved the clarity of the reported methods in the revised manuscript. The information has been incorporated into the Methods section of the revised manuscript to enhance visibility and reproducibility, as suggested by the reviewer. + +## [Revised manuscript] + +[Line 466- 470] + +<--- Page Split ---> + +Sulfur electrode preparation and materials characterization. For the preparation of the cathode, a CNT/S composite (75 wt% Sulfur) and the binder mixture (carboxymethyl cellulose (CMC)/poly(acrylic acid) (PAA)/styrene-butadiene rubber (SBR) binder = 3/1/4 by weight) were homogenized with a weight ratio of 96:4 in deionized water. The CNT/S composite was prepared by impregnating molten sulfur into a CNT micro- ball via melt- diffusion at 120 °C. Afterward, the resulting slurry was cast on the Al foil, followed by drying under 80 °C. For coin- type and pouch- type bi- cell, single- side coated cathodes were fabricated at sulfur loadings of 3.8 and 2.25 mg cm-2, respectively. For high- energy and high- power pouch cells, double side- coated cathodes were prepared at sulfur loadings of 2.26 and 1.81 mg cm-2, respectively. + +[Line 443- 444] + +Electrolyte characterization. In the argon- filled glove box, the control electrolyte was prepared by dissolving 0.75 M LiFSI (provided from LG Energy Solution Ltd.) and 0.4 M LiNO3 (Sigma- Aldrich) in DME (Sigma- Aldrich). Electrolytes denoted as Al, Mg, Ca, Sr, and Li were prepared by dissolving 0.05 M of Al(OTf)3, Mg(OTf)2, Ca(OTf)2, and Sr(TFSI)2 into the control electrolyte. + +(4) Lean-electrolyte lithium-sulfur cell suffers from poor reaction kinetics. It is suggested to show the electrochemical impedance analysis data that is used for showing the ohmic resistance. Besides the ohmic resistance, charge-transfer and interface impedances and the diffusion factor are important and are necessary to be reported and discussed in this research. [Suggestion] Please report the electrochemical impedance spectra data with the discussion on the ohmic, charge-transfer, and interface impedance values as well as the diffusion unit of the cell before and after cycling to tell the reaction the lean-electrolyte cell. + +RESPONSE: We sincerely thank the reviewer for the valuable suggestion regarding the detailed resistance analysis of low E/S ratio Li-S batteries. Following the reviewer's recommendation, we conducted a comprehensive discussion of resistance components through electrochemical impedance spectroscopy (EIS) measurements, combined with galvanostatic intermittent titration technique (GITT) and diffusion coefficient characteristics. The detailed responses are as follows: + +1. EIS analysis of Lean-electrolyte Li-S cell during discharge: Fig. R11a–d presents Nyquist plots of lean-electrolyte Li-S cells at different depths of discharge (DOD): 10%, 30%, and 80%, + +<--- Page Split ---> + +representing the stages of sulfur dissolution, \(\mathrm{Li}_2\mathrm{S}\) nucleation, and \(\mathrm{Li}_2\mathrm{S}\) growth, respectively. The lower- frequency semicircles in the Nyquist plots demonstrate that the charge- transfer resistance \((R_{\mathrm{ct}})\) is consistently lower for the Ca electrolyte compared to the control electrolyte ( \(6.5\mathrm{mV}\) vs.5.4 \(\mathrm{mV}\) at DOD \(10\%\) , \(44.0\mathrm{mV}\) vs. \(31.0\mathrm{mV}\) at DOD \(30\%\) , and \(46.0\mathrm{mV}\) vs. \(41.3\mathrm{mV}\) at DOD \(80\%\) ). This reduction in \(R_{\mathrm{ct}}\) can be attributed to the catalytic effect of CaS on polysulfide conversion reactions. + +Regarding diffusion characteristics, no significant differences were observed at a discharge rate of 0.1C. However, given that ionic diffusion at the cathode becomes more critical under higher C- rate conditions, we performed EIS analysis at 0.3C and compared the Warburg coefficients. This analysis is discussed in detail below. + +2. Decoupled resistance components: To provide further elucidate the resistance behavior of lean-electrolyte Li-S batteries under working conditions, we decoupled the total overpotentials into ohmic \((\eta_{\mathrm{ohm}})\) , charge-transfer \((\eta_{\mathrm{ct}})\) and interface \((\eta_{\mathrm{int}})\) by integrating GITT data in Fig. 5c with EIS measurements. Following the method described in J. Am. Chem. Soc., 145, 16449-16457 (2023), we separated current-dependent resistances (ohmic and charge-transfer resistance) and current-independent interfacial resistance, as shown in Fig. R11e-g. The \(\eta_{\mathrm{ohm}}\) was calculated using the ohmic resistance \((R_{\mathrm{ohm}})\) from Fig. 5b and Fig. R11b-d, multiplied by the applied discharge current according to Ohm's law. This allows us to decouple the total GITT overpotential into its three components, as depicted in Fig. R12. + +Under lean-electrolyte conditions, \(\mathrm{Ca}^{2 + }\) mitigates polysulfide gelation near the cathode, reducing electrolyte viscosity. According to the Stokes-Einstein equation, this leads to an increased diffusion coefficient of ionic species. Consequently, the \(\eta_{\mathrm{int}}\) , which depends on the concentration gradient of \(\mathrm{Li}^+\) and polysulfides at the electrode interface, is significantly reduced in the Ca electrolyte. Additionally, the charge-transfer overpotential \(\eta_{\mathrm{ct}}\) , which dominates the kinetic limitations in lean-electrolyte Li-S batteries, is substantially improved in the Ca electrolyte, particularly at DOD \(30\%\) , where the overpotential is highest. + +3. Diffusion characteristics: Given the importance of ionic diffusion at higher discharge rates, we compared the Warburg coefficients of the control and Ca electrolytes at three DODs during 0.3C discharge. As shown in Fig. R13, the slope of the linear fit in the Warburg region represents the Warburg coefficient, which is inversely proportional to the square root of the diffusion coefficient (J. Electrochem. Soc., 127, 343 (1980)). At DOD \(80\%\) , where active LiPS is consumed and + +<--- Page Split ---> + +concentration gradients become more pronounced, the control electrolyte shows a sharp increase in the Warburg coefficient, indicating a significant drop in diffusion. In contrast, the Ca electrolyte maintains a relatively low Warburg coefficient, demonstrating improved ion transport and higher diffusion coefficients even at high DODs, likely due to reduced LiPS gelation. + +A brief discussion was added in the revised manuscript and supplementary information. We reflected the figures in our revised manuscript (Figs. R11 and 12 is now Supplementary Fig. 20). + +![](images/Figure_unknown_11.jpg) + +
Fig. R11. EIS analysis of Lean-electrolyte Li-S coin cells during 0.1C discharge. a, Discharge voltage profiles of Control and Ca electrolytes at the E/S ratio = 4 \(\mu \mathrm{L} \mathrm{mg}^{-1}\) and 0.1 C. b-d, Nyquist plot during cycling at DOD of 10% (b), 30% (c), and 80% (d). f-h, Enlarged GITT data at DOD of 10% (e), 30% (f), and 80% (g).
+ +<--- Page Split ---> +![](images/Figure_unknown_12.jpg) + +
Fig. R12. Decoupled ohmic, interfacial, and charge transfer polarization at a, DOD \(10\%\) , b, \(30\%\) , and c, \(80\%\) .
+ +![](images/Figure_unknown_13.jpg) + +
Fig. R13. The relationship between \(Z'\) and square root of frequency \((\omega^{-1 / 2})\) in the low-frequency region for at different densities of discharge.
+ +## [Revised manuscript] + +[Line 334- 336] + +A combined analysis of \(R_{\text{ohm}}\) and GITT (Supplementary Fig. 20) revealed a reduction in ohmic, interfacial, and charge-transfer polarization in the Ca electrolyte throughout the discharge process. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +In this manuscript, the authors demonstrated that Lewis acidic \(\mathrm{Ca2 + }\) additive enables lean electrolyte and high energy density LSBs. The CaS readily adsorbs LiPSs and catalyzes SRR. With the addition of the \(\mathrm{Ca2 + }\) additive, the viscosity was reduced by \(70\%\) , and the ionic conductivity was enhanced by \(30\%\) . The electrolyte also enables an exceptional energy density of 493 Wh kg- 1. I am rather interested in this paper but have some specific questions listed as follow: + +RESPONSE: We sincerely appreciate the reviewer's detailed evaluation and interest in our work. The reviewer's insightful comments have been instrumental in refining our study and strengthening the clarity of our findings. In particular, we are grateful for the reviewer's constructive suggestions, which have allowed us to enhance our analysis of \(\mathrm{Ca^{2 + }}\) interactions with various species polysulfides and further investigate key mechanistic aspects such as anion effects of the additive. We have carefully revised the manuscript in accordance with the reviewer's recommendations, adding further experimental details and discussions where necessary. Below, we provide a point- by- point response addressing the reviewer's comments and outlining the modifications made in the manuscript. + +1. The in situ formed CaS catalyst accelerates SRR throughout the discharging process, and is oxidized to form \(\mathrm{Ca2 + }\) in the electrolyte during charging. Why does the conversion reaction require Li2S4 and not Li2S6? + +RESPONSE: We thank the reviewer for initiating this important discussion regarding the \(\mathrm{Ca^{2 + }}\) polysulfide interaction and CaS formation mechanism. While we used \(\mathrm{S_4^{2 - }}\) to represent the interaction between \(\mathrm{Ca^{2 + }}\) and polysulfides in our manuscript, our strategy based on multivalent additives has no limitation of polysulfide form. This contrasts with polysulfide-incompatible strategies, such as carbonate- based electrolytes, which highly relies on the use of short- chain polysulfides (Energy Storage Mater., 50, 197- 224 (2022)). + +As shown in Fig. R14, we prepared different types of LiPS (Li2S8, Li2S6, and Li2S4) catholytes by mixing stoichiometric amounts of Li2S and S8. The addition of the \(\mathrm{Ca(OTf)_2}\) additive to these + +<--- Page Split ---> + +catholytes induced conversion reactions, as confirmed by the reduction in polysulfide intensity observed in UV- Vis spectra. + +However, under a static environment that we simulated with catholytes—unlike the dynamic state during actual battery operation—exacerbated disproportionation of polysulfides occurs, which will be further discussed in our response to Comment #3 and UV- Vis intensity peaks are observed only at \(425 \mathrm{nm}\) ( \(\mathrm{S}_4^{2 - }\) ) and \(620 \mathrm{nm}\) ( \(\mathrm{S}_3^{2 - }\) ). This makes it challenging to directly compare the favorability of the conversion reaction involving \(\mathrm{Ca}^{2 + }\) across different polysulfide species. We hypothesize that short- chain polysulfides as \(\mathrm{S}_4^{2 - }\) , with lower negative charge density at their terminal sulfur atoms and a "harder base" character compared to long- chain polysulfides (e.g., \(\mathrm{S}_6^{2 - }\) ), are more effectively stabilized by \(\mathrm{Ca}^{2 + }\) . This interaction likely facilitates the formation of \(\mathrm{Ca}^{2 + }\) - short- chain PS complexes, which are more thermodynamically favorable in the electrolyte. + +![](images/Figure_unknown_14.jpg) + +
Fig. R14. UV-Vis spectra of various catholytes with varying polysulfide species. Filtered Control and Ca electrolytes with a, \(0.2 \mathrm{M} \mathrm{Li}_2\mathrm{S}_8\) , b, \(\mathrm{Li}_2\mathrm{S}_6\) , and c, \(\mathrm{Li}_2\mathrm{S}_4\) diluted by 0.01.
+ +2. In Figure S3, please explain the reason of the higher 1st voltage plateau (>2.3 V) and provide the information about the current density. + +RESPONSE: We appreciate the reviewer for this thought- provoking question. The voltage profiles in Supplementary Fig. 3 represent those of pouch cells discharged at 0.1C (0.38 mA \(\mathrm{cm}^{- 2}\) ). Regarding the 1st voltage plateau (>2.3 V), these profiles are after pre- cycling steps, so the overpotentials from various interfacial and kinetic factors obscure the direct comparison of voltage plateau among electrolytes. + +In order to make the overpotential negligible and the profiles to be reflective of the thermodynamic properties, we compared the discharge voltage profiles of the electrolytes a significantly lower + +<--- Page Split ---> + +discharge C- rate of C/40 (Fig. R15). We observe that with stronger Lewis acidity of additives, \(1^{\mathrm{st}}\) voltage plateau decreases. This trend can be attributed to the effect of Lewis acidic cations on the solubility and stability of polysulfides in the electrolyte. Stronger Lewis acidity enhances interactions with polysulfides, reducing their chemical potential and shifting the \(1^{\mathrm{st}}\) voltage plateau to lower values. The voltage plateau has been a strong parameter of polysulfide solubility in electrolytes, where the trend holds for the UV- Vis analyses in our study. We hope this explanation clarifies the observations in Supplementary Fig. 3 and provides a deeper understanding of the factors influencing the \(1^{\mathrm{st}}\) voltage plateau. + +![](images/Figure_unknown_15.jpg) + +
Fig. R15. Voltage profile of pouch cells at 0.025C discharge with the multivalent cation additives.
+ +3. In Figure S7B, please analysis the absorbance from S62- not being observed in the UV-vis spectra of the supernatants. + +RESPONSE: The authors appreciate the reviewer's detailed comments. As the reviewer mentioned, UV- Vis spectra of \(\mathrm{Li}_2\mathrm{S}_8\) solutions with metal cation additives (Supplementary Fig. 11b) exhibit peaks only at \(425\mathrm{nm}\) ( \(\mathrm{S}_4^{2 - }\) ) and \(620\mathrm{nm}\) ( \(\mathrm{S}_3^{2 - }\) ). To further validate this, we analyzed control electrolyte with \(0.2\mathrm{M}\) of different lithium polysulfide species, \(\mathrm{Li}_2\mathrm{S}_8\) , \(\mathrm{Li}_2\mathrm{S}_6\) , and \(\mathrm{Li}_2\mathrm{S}_4\) (Fig. R16a). The UV- Vis spectra of these solutions also showed peaks exclusively corresponding to \(\mathrm{S}_4^{2 - }\) and \(\mathrm{S}_3^{2 - }\) . + +This phenomenon can be attributed to the solvent's donor number (DN). As reported in previous studies (J. Electrochem. Soc., 165, A4027- A4033 (2018); J. Phys. Chem. Lett., 5, 1547 (2014)), \(\mathrm{Li}^+\) ions solvated in high- DN solvents (e.g., DMSO, TEGDME) tend to stabilize polysulfides with lower charge density (soft bases, e.g., \(\mathrm{S}_8^{2 - }\) , \(\mathrm{S}_6^{2 - }\) , \(\mathrm{S}_3^{2 - }\) ), whereas \(\mathrm{Li}^+\) ions in low- DN solvents (e.g., DME) preferentially stabilize polysulfides with higher charge density (hard bases, e.g., \(\mathrm{S}_4^{2 - }\) ). + +<--- Page Split ---> + +To confirm this, we replaced the solvent in the Control and Ca electrolytes from DME to DMSO and dissolved \(0.2\mathrm{M}\) of \(\mathrm{Li}_2\mathrm{S}_8\) . As shown in Fig. R16b, peaks corresponding to soft bases such as \(\mathrm{S}_6^{2 - }\) and \(\mathrm{S}_3^{+}\) were observed in the UV- Vis spectra. Interestingly, when using DMSO as the solvent, the Ca electrolyte exhibited lower polysulfide absorbance compared to the control, although the reduction was less pronounced than in DME. This behavior suggests that in high- DN solvents like DMSO, the tendency of the solvent to dissociate Ca- polysulfide complexes weakens the ability of \(\mathrm{Ca}^{2 + }\) to form stable complexes or precipitates (e.g., CaS), thereby reducing the polysulfide- capturing effect. + +![](images/Supplementary_Figure_5a.jpg) + +
Fig. R16. UV-Vis spectra of various electrolytes. a, Control electrolytes with \(0.2\mathrm{M}\mathrm{Li}_2\mathrm{S}_8\) , \(\mathrm{Li}_2\mathrm{S}_6\) , and \(\mathrm{Li}_2\mathrm{S}_4\) diluted by 0.01. b, Filtered \(0.2\mathrm{M}\mathrm{Li}_2\mathrm{S}_8\) solution in Control and Ca electrolyte with solvent replaced by DMSO diluted by 0.005.
+ +4. The author report that the cycle life of Li-S pouch cells was significantly extended by the addition of \(\mathrm{Ca(OTf)}_2\) . On the other hand, we find that the Ca-based pouch cell demonstrated a low specific capacity at \(\mathrm{E / S} = 8\mu \mathrm{L}\mathrm{mg} - 1\) (Figure S5C) and a high specific capacity at \(\mathrm{E / S} = 3.5\mu \mathrm{L}\) \(\mathrm{mg} - 1\) (Figure 2a) under distinct electrolyte-starved conditions. Please address these inconsistencies. + +RESPONSE: The authors sincerely appreciate the reviewer for highlighting this interesting observation with their meticulous attention to detail. The observed trend aligns with the general behavior of Li- S batteries, where higher \(E / S\) ratios typically lead to result in lower specific capacities (Supplementary Fig. 1). + +In conventional Li- S systems, an increase in \(E / S\) ratio reduces the polysulfide concentration in the electrolyte. In flooded electrolyte conditions, the local concentration of polysulfides near + +<--- Page Split ---> + +the active cathode surface decreases, which, while beneficial for long- term cyclability with slow capacity decay, results in lower sulfur utilization. When \(\mathrm{Ca^{2 + }}\) is introduced to the flooded electrolyte, its formation of \(\mathrm{Ca^{2 + }}\) - PS complexes further reduces the polysulfide concentration, exacerbating the decrease in sulfur utilization. + +In contrast, at low \(E / S\) ratios, the reduction in PS concentration does not necessarily lead to lower sulfur utilization. Instead, excessively high polysulfide concentrations in low \(E / S\) environments often cause detrimental effects such as electrolyte jamming and severe shuttle effects, which interfere with efficient redox reactions. The mitigation of these issues by \(\mathrm{Ca^{2 + }}\) rather leads to an enhancement in discharge capacity. + +As the underlying interfacial chemistries differ significantly depending on whether the cell is operating under flooded electrolyte (high E/S ratio) and lean electrolyte (low E/S ratio), the authors believe that the electrolyte engineering strategies must be tailored accordingly. Our research aimed at developing electrolytes for lean electrolyte and high energy- density battery systems. Given this object and in order to achieve high capacity (i.e. to utilize more amount of sulfur) at low E/S, we designed the electrolytes to exhibit following properties: (1) suppression of polysulfide gelation behavior, which is driven under lean electrolyte conditions and hinders sulfur utilization (Nat. Chem. Eng., 1, 563- 564 (2024)); (2) enhanced wettability of electrolytes to highly porous and tortuous cathodes for uniform ion and electron distribution throughout the electrode; and (3) prevention of capacity fading caused by lithium and sulfur loss due to the polysulfide shuttle effect. These design considerations reflect the primary objectives of our study and are the key factors contributing to the higher specific capacity of the \(\mathrm{Ca^{2 + }}\) electrolyte under lean electrolyte conditions compared to the control electrolyte. + +5. In Figure 4E, the CaS is not completely transformed into Ca2+ at 100% charge. We believe that the Ca2+ catalyst does not enable sustainable regulation of the PS concentration in the electrolyte during long cycle. The superior cycle life of Ca(OTf)2 electrolyte is related to the OTF- anion. We recommend adding the additive of Li(OTf) electrolyte to the parallel experiment. + +RESPONSE: The authors thank the reviewer for this insightful comment. In response to the reviewer's suggestion, we conducted additional experiments using Li(OTf) as an electrolyte additive to evaluate its effect. In lean electrolyte coin cell tests (Supplementary Fig. 5a), the addition of 0.1 M Li(OTf), which is the same OTF anion concentration of the Ca(OTf)2 + +<--- Page Split ---> + +electrolyte, extended the cycle life to \(\sim 80\) cycles, compared to \(\sim 60\) cycles for the control electrolyte. However, it cannot be compared with Ca electrolyte with stable operation \(>160\) cycles. Under harsher conditions in pouch cells (Fig. R17), the addition of Li(OTf) at various concentrations (0.05, 0.10, and 0.15 M) showed negligible improvement in performance compared to the reference electrolyte. These results allowed us to exclude the possibility that the superior cycle life observed in the Ca electrolyte is primarily due to the OTF anion. + +As noted by the reviewer, Fig. 4e shows that \(\mathrm{Ca^{2 + }}\) is not \(100\%\) rejuvenated after charge. This observation is based on the 0.05C discharge/charge cycle. In subsequent cycles, where the charge C- rate increases, the current- dependent ohmic and charge- transfer overpotentials increase, leading to the voltage to reach the oxidation potential of \(\mathrm{CaS}\) to \(\mathrm{CaS_n}\) (2.35 V vs. \(\mathrm{Li / Li^{+}}\) ) more readily. Specifically, 2.35 V is reached at SOC of \(73\%\) , \(68\%\) , and \(65\%\) for 0.05C, 0.10C, 0.20C charge rates, respectively. Thus, in the cycles following Fig. 4e, the thermodynamic driving force for \(\mathrm{CaS}\) oxidation at the cathode increases, promoting \(\mathrm{Ca^{2 + }}\) regeneration, as confirmed by ICP- MS of cathode and UV- Vis analyses after further cycles (Supplementary Fig. 17). + +Additionally, applying cycle protocols of periodically increasing the charge cutoff voltage to induce \(\mathrm{CaS}\) oxidation can further promote the rejuvenation of \(\mathrm{Ca^{2 + }}\) . To validate this hypothesis, we performed XPS analysis on cathodes after one cycle (SOC \(100\%\) in Fig. 4e) and after the \(40^{\mathrm{th}}\) charge with periodic oxidation up to 3.0 V every 10 cycles (Fig. R18). In the former case, the atomic percent of \(\mathrm{Ca}\) was 0.7, whereas in the latter, it decreased to 0.28, consistent with the rejuvenation of \(\mathrm{Ca^{2 + }}\) observed in Supplementary Fig.17a. These results demonstrate the enhanced regeneration of \(\mathrm{Ca^{2 + }}\) under higher charge rates and periodic oxidation protocols, providing further insight into the improved cycling performance of the Ca electrolyte. + +![](images/Figure_unknown_16.jpg) + +
Supplementary Fig. 5a. Cycle performance of high sulfur loading, lean electrolyte coin cells.
+ +<--- Page Split ---> +![](images/Figure_unknown_17.jpg) + +
Fig. R17. Cycle performance of pouch cells with various LiOTf additive concentrations.
+ +![](images/Figure_unknown_18.jpg) + +
Fig. R18. Ca 2p XPS Spectra of cathodes. a, Charged cathode after 1 cycle. b, Charged cathode after 40 cycles with periodic oxidation protocol.
+ +6. In Figure 6B, the FSI- anion in the \(\mathrm{Li + }\) solvate promote the formation of anion-derived SEI. In actuality, the OTF- anion also break down. It is crucial to provide the mechanism of LiF-enriched SEI formation. + +RESPONSE: We sincerely appreciate the reviewer for the constructive comments. As the reviewer pointed out, the OTF- anion can undergo reduction as well as the FSI- anion. To clarify the mechanism of LiF-enriched solid electrolyte interphase (SEI) formation, we focused on the reduction tendencies of the anions, as OTF- and FSI- are the only sources contributing to the inorganic fluoride component. + +In Fig. R19a, we compared the coordination number of two anions with \(\mathrm{Li^{+}}\) ions obtained by molecular dynamics (MD) simulation. Despite the higher electron donor number of OTF, the + +<--- Page Split ---> + +concentration difference between the electrolytes (0.75 M LiFSI vs. 0.05 M Ca(OTf)₂) results in a significantly higher coordination number of FSI⁻ with Li⁺ in the 1st solvation shell—over three times greater than that of OTF⁻. Additionally, as demonstrated by the density functional theory (DFT) simulation in Fig. R19b, the Lowest Unoccupied Molecular Orbital (LUMO) levels of the anions, when coordinated with Li⁺, are lower than those in their free states, indicating a higher tendency for cathodic decomposition. Specifically, the Li-FSI pair exhibits a lower LUMO level compared to the Li-OTf pair, which suggests that FSI⁻ decomposition is more likely to contribute to the formation of an F-rich SEI in the Ca electrolyte, given its higher coordination number. Furthermore, considering the relative weakness of S-F bonds (bond dissociation energy: 344 kJ mol⁻¹) in FSI⁻ compared to the stronger S-CF₃ bonds in OTF⁻ (514 kJ mol⁻¹), FSI is expected to exhibit a stronger tendency towards decomposition, leading to the formation of a more stable LiF-based SEI on the lithium metal surface (Nano-Micro Lett. 16, 35 (2024) and J. Power Sources 271, 291-297 (2014)). + +![](images/Figure_unknown_19.jpg) + +
Fig. R19. Comparison of FSI⁻ and OTF⁻ anions with assistance of MD simulation and DFT calculations. a, Cumulative distribution functions of Li⁺ solvation with FSI⁻ and OTF⁻ anions in the Ca electrolyte. b, Highest occupied molecular orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels of the free and coordinated anions.
+ +<--- Page Split ---> + +## Point-to-Point Response to Reviewers' Comments + +Title: Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries + +Authors: Hannah Cho, Jinkwan Jung, Ilju Kim, Jinuk Kim, Sejin Kim, Jonghyun Hyun, Chang Hoon Lee, Hobeom Kwack, Wonsik Oh, Jinwoo Lee, and Hee- Tak Kim\* + +We greatly appreciate the reviewer's comments, which have been very helpful in improving our manuscript. Below, we provide responses of the revision made in response to the feedback. Reviewer questions are highlighted in blue, and any revisions made to the manuscript are highlighted to aid the reviewers. + +## Reviewer #1 (Remarks to the Author): + +The revised manuscript, "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," shows notable improvements over its previous version. The authors provide additional details to support the effectiveness of the calcium additive. + +RESPONSE: We sincerely appreciate the reviewer's constructive and thoughtful questions. Also, we apologize that our previous revision may not have fully clarified the intent and scope of our hypothesis. We would like to take this opportunity to more precisely articulate the conceptual framework of our study and address the reviewer's concerns. + +However, I remain unconvinced that their hypothesis—"the strong Lewis acidity of \(\mathrm{Ca^{2 + }}\) readily converts LiPSs into CaS and \(\mathrm{S_8}\) , preventing electrolyte jamming, polysulfide shuttle, and lithium corrosion"—is robustly supported by the presented data. Typically, if this hypothesis holds, the cycling performance of Li/S cells should correlate with the acidity of metal ions. Yet, the authors exclude three key data points (other metal ions) for unrelated reasons, leaving \(\mathrm{Ca^{2 + }}\) as the only additive for comparison, which weakens the case for a clear trend. + +RESPONSE: We sincerely appreciate the reviewer for highlighting the unclear point in our previous manuscript. The point we want to deliver is the complex of strong Lewis acidic metal cations and weak Lewis basic polysulfide anions is decomposed into metal sulfide and sulfur as + +<--- Page Split ---> + +demonstrated in Supplementary Fig. 10. This tendency becomes strong as the Lewis acidity increases, which is supported by the decrease of LiPS solubility with increasing the Lewis acidity (Fig. 2a and b in the revised manuscript). + +While a systematic comparison across multiple cations would ideally clarify the correlation between the Lewis acidity and cycling performance, the instability of the electrolytes with stronger Lewis acidic cations (e.g., \(\mathrm{Mg^{2 + }}\) , \(\mathrm{Al^{3 + }}\) ) complicates such an analysis. As suggested by the reviewer, we explored alternative electrolytes with higher stability and found that diglyme- based electrolytes are stable with \(\mathrm{Mg^{2 + }}\) , \(\mathrm{Al^{3 + }}\) , and \(\mathrm{Ca^{2 + }}\) . The diglyme- based electrolyte exhibited performance trends similar to those of the DME- based electrolyte (Fig. R1): only the \(\mathrm{Ca^{2 + }}\) - based system showed a significantly enhanced electrochemical performance. This suggests that the relatively poor performance observed with \(\mathrm{Mg^{2 + }}\) and \(\mathrm{Al^{3 + }}\) compared to \(\mathrm{Ca^{2 + }}\) is not solely attributable to electrolyte degradation. + +According to previous studies on sparingly solvating electrolytes, the redox kinetics of sulfur species become markedly sluggish when polysulfide solubility falls below a critical threshold. Among various fluorinated diluents, those with excessively low LiPS solubility have been reported to result in unstable cell performance (Adv. Energy Mater., 15, 2403828 (2024) and Proc. Natl. Acad. Sci., 120, e2301260120 (2023)). Furthermore, high volume percent of diluents has been shown to aggravate kinetic limitations and reduce overall cell performance (J. Am. Chem. Soc., 21, 14754–14764 (2024) and Angew. Chem. Int. Ed., 62, e202309968 (2023)). These findings collectively suggest the existence of an optimal polysulfide- solvating power, where moderately solvating electrolytes are proposed to achieve a balance between suppressing the polysulfide shuttle and enabling efficient redox reactions. + +In line with previous literature, our experimental results (Fig. R2) show that under lean electrolyte conditions, Li- S cells with only 20 vol% TTE exhibit significantly increased discharge overpotentials compared to those with single- solvent DME electrolyte, to the extent that the second discharge plateau is completely suppressed. Similarly, the poor performance of Al and Mg electrolytes is not solely due to electrolyte instability, but also to the suppressed polysulfide solubility. In contrast, the Ca electrolyte appears to provide an appropriate level of polysulfide solubility—analogous to an optimal fluorination degree or diluent fraction in moderately solvating electrolytes—which allows it to achieve excellent cycling stability. + +<--- Page Split ---> +![](images/Figure_unknown_20.jpg) + +
Fig. R1 | Electrochemical performance of coin cells \((E / S = 5 \mu \mathrm{L} \mathrm{mg}^{-1})\) with 0.75 M LiFSI/0.40 M LiNO3/0.05 M M(OH)2. (a) Cycle performance of diglyme-based electrolyte. (b) Voltage profile of coin cells with diglyme-based electrolytes at 0.2C discharge.
+ +![](images/Supplementary_Figure_1.jpg) + +
Fig. R1 | Cycle performance of coin cells \((E / S = 5 \mu \mathrm{L} \mathrm{mg}^{-1})\) with 0.75 M LiFSI/0.40 M LiNO3 in DME or DME:TTE (5:1). a, Voltage profile of cells at 0.05C discharge/charge. b, Cycle performance.
+ +We appreciate the reviewers' insight, which made us recognize that our previous manuscript may have unintentionally conveyed the misleading notion that cations with stronger Lewis acidity universally enhance cycling performance and that Lewis acidity is the primary determinant of lithium sulfur battery performance. In reality, cell performance is influenced by multiple interrelated factors, including polysulfide regulation, redox kinetics, ion transport, and electrolyte stability. We have carefully revised our discussion to change any statements that might imply a direct correlation between Lewis acidity and cycling stability, in order to avoid potential misinterpretation. To enhance clarity, we explained the destabilization of polysulfide (PS) anions by using strongly Lewis acidic cations based on the Hard- Soft Acid- Base theory, providing a + +<--- Page Split ---> + +theoretical rationale for the decomposition of PS anions into metal sulfides and elemental sulfur—an effect clearly observed for various multivalent cations (Supplementary Fig. 10; \(\mathrm{Ca}^{2 + }\) , \(\mathrm{Al}^{3 + }\) , \(\mathrm{Mg}^{2 + }\) , and \(\mathrm{Sr}^{2 + }\) ). The instability of electrolytes containing \(\mathrm{Al}^{3 + }\) and \(\mathrm{Mg}^{2 + }\) , which we believe is useful information for readers, is collectively discussed in the Supplementary Fig. 6. + +## [Revised manuscript] + +[Line 153- 157] + +To investigate whether Lewis acidic metal cations can suppress the dissolution of polysulfides (PS) into the electrolyte during cell operation, we introduced these cations into the electrolyte and evaluated the relative PS concentration in lean electrolyte coin cells \((E / S = 4 \mu \mathrm{L} \mathrm{mg}^{- 1})\) using UV- vis spectra after discharging the cells to 2.1 V (Fig. 3a and Supplementary Fig. 4). + +[Line 223- 226] + +The disproportionation likely originates from the instability of PSs highly coordinated to \(\mathrm{Ca}^{2 + }\) , as complexes formed between strong Lewis acids (multivalent metal cations) and weak Lewis bases (PSs) are thermodynamically unstable. The increased precipitation observed at higher PS concentration (Supplementary Fig. 11) supports this consideration. + +<--- Page Split ---> +![](images/Figure_unknown_21.jpg) + +
Supplementary Fig. 1 | Compatibility of Lewis acidic cation additives in the electrolytes (a-b) Optical images of the control and metal additive (0.05 M)-containing electrolytes after standing for 7 days. X-ray diffraction (XRD) patterns of the precipitates in the (c) Mg and (d) Sr electrolytes, respectively. (e) Pouch-type Li-S bi-cell ( \(E / S = 3.5 \mu \mathrm{L} \mathrm{mg}^{-1}\) ) cycling with the control and multivalent metal cation (Al \(^{3 + }\) , Mg \(^{2 + }\) , Ca \(^{2 + }\) , Sr \(^{2 + }\) ) additive-containing electrolytes.
+ +Note) After being left for several days, gelation occurred in the Al electrolyte, while precipitates appeared in the Mg and Sr electrolytes. The gel- like flocculent precipitates are decomposed products from dimethoxvethane (DME) induced by \(\mathrm{Al}^{3 + }\) ion \(^{3}\) . The \(\mathrm{Mg(OTf)_2}\) precipitate in the Mg electrolyte, indicates the low solubility of \(\mathrm{Mg(OTf)_2}\) in the control electrolyte. The formation of \(\mathrm{Sr(NO_3)_2}\) in the Sr electrolyte is attributed to a detrimental Lewis acid- base reaction with \(\mathrm{NO_3}^{2 - }\) . Given that \(\mathrm{LiNO_3}\) is an indispensable component for mitigating the shuttle effect, \(\mathrm{Sr}^{2 + }\) cations are inadequate additives for LSB electrolytes. Similar phenomena occurred when Al, Mg, and Sr salts were added to the commonly- used LiTFSI- DOL- DME electrolyte. + +As seen in Supplementary Fig. 6e, except for the Ca electrolyte (control electrolyte with 0.05 M \(\mathrm{Ca(OTf)_2}\) ), electrolytes with the other cations demonstrated inferior cycling + +<--- Page Split ---> + +stability than the control electrolyte. This may be due to the extremely low solubility of polysulfides and/or their incompatibility with the electrolyte components. + +They argue that the strong Lewis acidity of \(\mathrm{Mg}^{2 + }\) and \(\mathrm{Al}^{3 + }\) triggers polymerization of DOL and/or side reactions with DME, rendering the electrolyte unusable. While DOL gelation can occur even under mildly acidic conditions, this claim seems inconsistent with their ability to obtain UV- vis results and decent cycling performance for Li/S cells using \(\mathrm{Al}^{3 + }\) and \(\mathrm{Mg}^{2 + }\) additives. + +RESPONSE: We conducted experiments using \(\mathrm{Al}^{3 + }\) , \(\mathrm{Mg}^{2 + }\) , and \(\mathrm{Sr}^{2 + }\) additives to explore how multivalent cations with different Lewis acidities influence polysulfide solubility. In the catholyte experiments shown in Fig. 3a of the manuscript, DME was used as the sole solvent, without DOL, to focus specifically on polysulfide- cation interactions. + +In the case of the Al- containing electrolyte, gel- like flocculent precipitates were observed after several days, which is in line with previous observations reported in the literature (ACS Appl. Mater. Interfaces, 16, 47581- 47589 (2024)). Similarly, for the Mg- containing electrolyte, the solution gradually became opaque and \(\mathrm{Mg(OTf)_2}\) precipitates appeared after a few days (Supplementary Fig. 7). + +We acknowledge that such electrolyte changes can occur during polysulfide solubility measurement or cycling stability test; however, the fact that these changes were only observed after a certain period suggests that, at least during polysulfide solubility measurements and the early stages of cycling, the primary effect was likely dominated by polysulfide- cation interactions rather than electrolyte decomposition. + +If solvent reactivity, particularly with DOL, is a concern, why didn't the authors test alternative solvents—such as DMSO, ionic liquids, or certain glymes—that are less reactive with Lewis acids and commonly used in Li- S battery electrolytes to better validate the acidity- performance trend? + +RESPONSE: We sincerely appreciate the reviewer's valuable suggestion, which offered a perspective we had not previously considered. In response to the reviewer's suggestion, we conducted additional experiments using alternative solvents: DMSO, an ionic liquid, and diethylene glycol dimethoxythane (diglyme). In the DMSO- based electrolyte, the addition of 0.05 M \(\mathrm{Al}^{3 + }\) and \(\mathrm{Mg}^{2 + }\) resulted in the formation of opaque solutions, both in the absence (Fig. R3a) and presence (Fig. R3b) of 0.2 M \(\mathrm{Li}_2\mathrm{S}_8\) , precluding reliable UV- Vis analysis. Notably, + +<--- Page Split ---> + +unlike in the DME- based electrolytes, no solid precipitates were observed. This suggests a shift in dominant interactions from cation- polysulfide toward cation- solvent coordination. This suppresses the desired mechanism of solid metal sulfide formation, highlighting that high- donor- number solvents alter the interaction mechanism rather than validating acidity effects. A similar outcome was observed when using an ionic liquid (1- Butyl- 1- methyl pyrrolidinium bis(fluorosulfonyl)imide) as the electrolyte solvent: the addition of \(0.05\mathrm{M}\mathrm{Al}^{3 + }\) or \(\mathrm{Mg^{2 + }}\) resulted in opaque solutions (Fig. R3c), likely due to limited solubility or side reactions with the solvent. + +In contrast, diglyme- based electrolytes did not exhibit any visible signs of side reactions or solution opaqueness upon the addition of \(0.05\mathrm{M}\mathrm{Al}^{3 + }\) , \(\mathrm{Mg^{2 + }}\) , or \(\mathrm{Ca^{2 + }}\) (Fig. R3d). \(\mathrm{Sr^{2 + }}\) remained poorly soluble, consistent with previous observations in DME. As discussed above, we evaluated the electrochemical performance of lean- electrolyte Li- S coin cells using diglyme- based electrolytes with metal additives (Control, Al, Mg, Ca, Sr) (Fig. R1). Consistent with our findings in DME- based electrolytes, the Ca- containing diglyme- based electrolyte exhibited significantly enhanced electrochemical performance, whereas the Control, Al, Mg, and Sr electrolytes displayed pronounced overpotentials and substantially reduced discharge capacities at \(0.2\mathrm{C}\) after precycling. As discussed earlier (page 2), electrochemical performance deteriorates when polysulfide solubility of the electrolyte falls below a critical threshold. This explains the relatively poor electrochemical performance of the Mg and Al electrolytes when solvent stability was ensured, as excessively low polysulfide solubility hindered efficient redox reactions. These results reinforce that the performance enhancement observed with \(\mathrm{Ca^{2 + }}\) is not solely due to the absence of side reactions with the solvent, but rather a result of the multiple effects demonstrated throughout the manuscript. + +Additionally, lean electrolyte coin cells assembled with DMSO and ionic liquid- based electrolytes (Control, Al, Mg, Ca, Sr) exhibited immediate overpotentials upon discharge and failed to operate properly (Fig. R4). Compared to DME, DMSO and ionic liquid showed poor wettability, high viscosity, and insufficient electrolyte penetration into the porous cathode structure, rendering them practically incompatible with our intended low \(E / S\) ratio electrolyte design and leading to fundamentally different operative mechanisms. In short, although alternative solvents may indeed mitigate solvent decomposition associated with strong Lewis acids, the resulting fundamental changes to solvation structure and interaction mechanisms prevent a direct comparison to our DME- based system and, consequently, do not allow for a fair validation of our core hypothesis. + +<--- Page Split ---> +![](images/Figure_unknown_22.jpg) + +
Fig. R3 | Optical images of 0.75 M LiFSI/0.40 M electrolytes with 0.05 M additives after dissolution. Electrolytes prepared using various solvents: (a) DMSO, (b) catholytes (0.2 M Li₂S₈) in DMSO, (c) 1-Methyl-1-Butylpyrrolidinium bis(fluorosulfonyl)imide (Pyr₁₄FSI), and (d) Diethylene glycol dimethyl ether (DEGDME).
+ +![PLACEHOLDER_45_1] + +
Fig. R4 | Voltage profile of coin cells \((E / S = 5 \mu \mathrm{L} \mathrm{mg}^{-1})\) with 0.75 M LiFSI/0.40 M LiNO₃/0.05 M M(OTf) in DMSO.
+ +We hope this explanation clarifies our rationale for \(\mathrm{Ca}^{2 + }\) , and addresses the reviewer's concerns regarding the correlation between Lewis acidity and electrochemical performance. + +[Revised manuscript] [Line 144- 146] + +<--- Page Split ---> + +Ca- S batteries22,23 exhibit lower PS concentration in the electrolytes during cell operation compared to LSBs due to the strong tendency to form ionic Ca- S bond. + +[Line 162- 165] + +Although these multivalent metal cations effectively suppress PS solubility, these do not improve cell performance except \(\mathrm{Ca}^{2 + }\) , likely attributed to the extremely low solubility of \(\mathrm{PSs}^{28 - 31}\) , gelation32, and/or precipitation observed in the corresponding electrolytes (Supplementary Fig. 6). + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +The authors have replied to my comments and made acceptable revision. Most of my concerns and queries have been addressed. Thus, I would suggest the consideration of acceptance of the revised manuscript. + +RESPONSE: We express our sincere gratitude to Reviewer#2 for conducting a thorough review of our revised manuscript. We are pleased to receive positive feedback from Reviewer #2 and appreciate their recommendation to publication. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +I think I like the author's revision and would be happy to recommend publication of the manuscript. + +RESPONSE: We deeply appreciate Reviewer #3's insightful assessment of our revised manuscript. Their thoughtful remarks and favorable evaluation have been both encouraging and instrumental in guiding our work toward potential publication. + +<--- Page Split ---> diff --git a/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c01bef8a699922317ffb09f9d6e3b5450829cbee --- /dev/null +++ b/peer_reviews/78460ec6d62f383dcddd6687a1394004b995667955d0dbc1ff5670b2bf67bfd7/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,880 @@ +<|ref|>title<|/ref|><|det|>[[72, 163, 856, 211]]<|/det|> +# Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries + +<|ref|>text<|/ref|><|det|>[[73, 224, 476, 241]]<|/det|> +Corresponding Author: Professor Hee- Tak Kim + +<|ref|>text<|/ref|><|det|>[[72, 275, 864, 290]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 327, 145, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 219, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 418, 916, 496]]<|/det|> +In their manuscript entitled "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," Cho et al. propose using \(\mathrm{Ca(OTf)_2}\) as an effective additive for lithium- sulfur batteries under lean electrolyte conditions. They claim that calcium ions mitigate polysulfide dissolution due to their high Lewis acidity, as well as the catalytic effects of CaS resulting from its interaction with LiPS. However, in my view, the publication of this manuscript is premature. Several additional experiments and essential experimental details are needed to substantiate the authors' claims. My specific comments are as follows: + +<|ref|>text<|/ref|><|det|>[[70, 508, 923, 850]]<|/det|> +1. Primary Hypothesis: The core hypothesis of this work is that the "high" Lewis acidity of calcium ions mitigates polysulfide dissolution by forming Ca-PS complexes. If this hypothesis is accurate, electrolytes with \(\mathrm{Mg(OTf)_2}\) and \(\mathrm{Al(OTf)_3}\) , which have ions with significantly higher acidity than Ca, should show even better performance. Since the difference in acidity between Ca and Li ions is minimal, this oversight or lack of consideration raises doubts about the hypothesis's validity. +2. Experimental Descriptions: The manuscript contains many vague descriptions of experimental details, limiting the interpretability of the presented data. For example, in Fig. 5a, the electrolyte solutions for both the control and Ca experiments are described insufficiently, with only one line—"A viscometer (LVDV-2+P CP, BROOKFIELD) was used to measure the electrolyte viscosity"—included in the experimental section. What does "1.6M Li2S4 control" mean? What solvents and salts are in the control? It is questionable whether the authors can truly reduce the control electrolyte's viscosity by merely adding Ca salt. +3. Electrode Composition Details: Essential information about the electrodes, such as binder type, carbon materials, and sulfur loading percentage, is missing. These parameters are crucial for reproducing the results and should be included. +4. UV-Vis Study Protocols: The UV-Vis study requires a more detailed experimental procedure. Did the authors immerse all coin cell components in the control electrolyte? Given the small electrolyte volume in a coin cell, there may be significant experimental error. Providing at least three parallel experiment results would help confirm the data's consistency. +5. Control Setup in Fig. 3b: In Fig. 3b, the control should not solely consist of the control electrolyte; 0.05M Li(OTf) should also be added. Additionally, the authors must explain how they determined the pKa values in the experimental section. +6. Choice of Control Electrolyte: The authors' control choice of 0.75M LiFSI and 0.4M LiNO3 in DME differs from the conventional Li-S electrolyte (1M LiTFSI in DOL/DME with \(\sim 2\%\) LiNO3). The authors used a 0.5M LiTFSI and 0.2M LiNO3 DOL/DME electrolyte, and the large reduction in salt concentration likely exacerbates LiPS dissolution. +7. Cycling Performance: For Fig. 2a, the authors should provide parallel cycling performance for each cell to confirm repeatability and rule out cell-to-cell variations. +8. Additive Controls in Figs. 2b and 2c: The cycling results for the control electrolyte, as well as electrolytes with Al and Mg additives, should also be presented. +9. Electrolyte Solvation Analysis: The authors employed MD simulation and solid characterization techniques such as TEM and XPS. To thoroughly understand electrolyte solvation, additional FTIR/Raman and NMR data should be included. + +<|ref|>sub_title<|/ref|><|det|>[[73, 874, 162, 887]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 899, 922, 939]]<|/det|> +(Remarks to the Author) Summary: This research paper entitled, "Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 140]]<|/det|> +sulfur batteries" reports a novel approach to designing and enhancing the performance of lean- electrolyte lithium- sulfur batteries by adding a small amount of calcium cations to the electrolyte. The calcium cations are reported that can effectively convert polysulfides into calcium sulfide and sulfur. This reaction prevents polysulfide shuttle and electrolyte jamming while mitigating lithium corrosion. The in situ formation of calcium sulfide acts as a catalyst, facilitating the reduction of polysulfides, and calcium cations are regenerated during charging, allowing sustainable cycling. The addition of calcium cations improves cycling stability and energy density, with pouch cells achieving 493 Wh kg \(^{- 1}\) and \(70\%\) capacity retention after 220 cycles, and 346 Wh kg \(^{- 1}\) with \(77\%\) retention after 360 cycles. + +<|ref|>sub_title<|/ref|><|det|>[[73, 152, 201, 164]]<|/det|> +## General comment: + +<|ref|>text<|/ref|><|det|>[[72, 164, 895, 191]]<|/det|> +This study reports on the electrolyte additive for the lean- electrolyte lithium- sulfur cell to have an improved performance. Some minor revision is needed, and I hope the authors find the comment useful. + +<|ref|>sub_title<|/ref|><|det|>[[73, 204, 153, 216]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[72, 216, 910, 256]]<|/det|> +(1) The manuscript is well organized in both the writing and the data presentation. One minor suggestion is on the image layout in figures. Cycling performance data are not suggested to show an extended X axis for the cycle number. This gives an unreasonable cyclability. + +<|ref|>text<|/ref|><|det|>[[72, 256, 758, 270]]<|/det|> +[Suggestion] Please organize and arrange the cycling performance data with a regular image layout. + +<|ref|>text<|/ref|><|det|>[[72, 281, 916, 334]]<|/det|> +(2) The formation of CaS and S via the adsorbed polysulfides is the main finding of this research. It is suggested to focus on collecting direct experimental data as evidence. Then, the formation mechanism of CaS and the conversion from CaS to polysulfides is suggested to be studied and discussed. In addition, the polysulfide trapping mechanism is suggested to be explored. + +<|ref|>text<|/ref|><|det|>[[72, 333, 911, 361]]<|/det|> +[Suggestion] Please conduct analysis and discussion on the formation mechanism of CaS, the conversion mechanism rom CaS to polysulfides, and the polysulfide-trapping mechanism of calcium cations together. + +<|ref|>text<|/ref|><|det|>[[72, 371, 913, 425]]<|/det|> +(3) The sulfur cathode used in this research is necessary to be discussed and disclosed. The sulfur loading and sulfur content are suggested to be reported. The content of additional additives is necessary to be reported. These are necessary information, which controls the key experimental testing condition, E/S ratio. [Suggestion] Please report the necessary information on the cathode. + +<|ref|>text<|/ref|><|det|>[[72, 436, 920, 517]]<|/det|> +(4) Lean-electrolyte lithium-sulfur cell suffers from poor reaction kinetics. It is suggested to show the electrochemical impedance analysis data that is used for showing the ohmic resistance. Besides the ohmic resistance, charge-transfer and interface impedances and the diffusion factor are important and are necessary to be reported and discussed in this research. [Suggestion] Please report the electrochemical impedance spectra data with the discussion on the ohmic, charge-transfer, and interface impedance values as well as the diffusion unit of the cell before and after cycling to tell the reaction the lean-electrolyte cell. + +<|ref|>sub_title<|/ref|><|det|>[[73, 541, 161, 555]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 567, 238, 580]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 580, 916, 633]]<|/det|> +In this manuscript, the authors demonstrated that Lewis acidic \(\mathrm{Ca2 + }\) additive enables lean electrolyte and high energy density LSBs. The CaS readily adsorbs LiPSs and catalyzes SRR. With the addition of the \(\mathrm{Ca2 + }\) additive, the viscosity was reduced by \(70\%\) , and the ionic conductivity was enhanced by \(30\%\) . The electrolyte also enables an exceptional energy density of 493 Wh kg- 1. I am rather interested in this paper but have some specific questions listed as follow: + +<|ref|>text<|/ref|><|det|>[[70, 644, 916, 673]]<|/det|> +1. The in situ formed CaS catalyst accelerates SRR throughout the discharging process, and is oxidized to form Ca2+ in the electrolyte during charging. Why does the conversion reaction require Li2S4 and not Li2S6? + +<|ref|>text<|/ref|><|det|>[[70, 684, 904, 712]]<|/det|> +2. In Figure S3, please explain the reason of the higher 1st voltage plateau (>2.3 V) and provide the information about the current density. + +<|ref|>text<|/ref|><|det|>[[70, 723, 908, 738]]<|/det|> +3. In Figure S7B, please analysis the absorbance from S62- not being observed in the UV-vis spectra of the supernatants. + +<|ref|>text<|/ref|><|det|>[[72, 749, 914, 803]]<|/det|> +4. The author report that the cycle life of Li-S pouch cells was significantly extended by the addition of \(\mathrm{Ca(OTf)2}\) . On the other hand, we find that the Ca-based pouch cell demonstrated a low specific capacity at \(\mathrm{E / S = 8\mu L}\) mg-1 (Figure S5C) and a high specific capacity at \(\mathrm{E / S = 3.5\mu L}\) mg-1 (Figure 2a) under distinct electrolyte-starved conditions. Please address these inconsistencies. + +<|ref|>text<|/ref|><|det|>[[72, 815, 904, 867]]<|/det|> +5. In Figure 4E, the CaS is not completely transformed into \(\mathrm{Ca2 + }\) at \(100\%\) charge. We believe that the \(\mathrm{Ca2 + }\) catalyst does not enable sustainable regulation of the PS concentration in the electrolyte during long cycle. The superior cycle life of \(\mathrm{Ca(OTf)2}\) electrolyte is related to the OTF- anion. We recommend adding the additive of \(\mathrm{Li(OTf)}\) electrolyte to the parallel experiment. + +<|ref|>text<|/ref|><|det|>[[70, 878, 900, 907]]<|/det|> +6. In Figure 6B, the FSI- anion in the Li+ solvate promote the formation of anion-derived SEI. In actuality, the OTF- anion also break down. It is crucial to provide the mechanism of LiF-enriched SEI formation. + +<|ref|>text<|/ref|><|det|>[[72, 919, 144, 931]]<|/det|> +Version 1: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 218, 60]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 73, 160, 86]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 99, 238, 112]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 112, 916, 283]]<|/det|> +The revised manuscript, "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," shows notable improvements over its previous version. The authors provide additional details to support the effectiveness of the calcium additive. However, I remain unconvinced that their hypothesis—"the strong Lewis acidity of \(\mathrm{Ca^{2 + }}\) readily converts LiPSs into CaS and \(\mathrm{S_8}\) , preventing electrolyte jamming, polysulfide shuttle, and lithium corrosion"—is robustly supported by the presented data. Typically, if this hypothesis holds, the cycling performance of Li/S cells should correlate with the acidity of metal ions. Yet, the authors exclude three key data points (other metal ions) for unrelated reasons, leaving \(\mathrm{Ca^{2 + }}\) as the only additive for comparison, which weakens the case for a clear trend. They argue that the strong Lewis acidity of \(\mathrm{Mg^{2 + }}\) and \(\mathrm{Al^{3 + }}\) triggers polymerization of DOL and/or side reactions with DME, rendering the electrolyte unusable. While DOL gelation can occur even under mildly acidic conditions, this claim seems inconsistent with their ability to obtain UV- vis results and decent cycling performance for Li/S cells using \(\mathrm{Mg^{2 + }}\) and \(\mathrm{Al^{3 + }}\) additives. If solvent reactivity, particularly with DOL, is a concern, why didn't the authors test alternative solvents—such as DMSO, ionic liquids, or certain glymes—that are less reactive with Lewis acids and commonly used in Li- S battery electrolytes to better validate the acidity- performance trend? + +<|ref|>text<|/ref|><|det|>[[73, 320, 161, 333]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 347, 238, 360]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 360, 881, 386]]<|/det|> +The authors have replied to my comments and made acceptable revision. Most of my concerns and queries have been addressed. Thus, I would suggest the consideration of acceptance of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 398, 161, 411]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 424, 238, 437]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 437, 741, 451]]<|/det|> +I think I like the author's revision and would be happy to recommend publication of the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 464, 144, 476]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 490, 218, 503]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 515, 160, 528]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 542, 238, 555]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 555, 901, 633]]<|/det|> +The authors adequately addressed most reviewer questions but omitted experimental details for Supplementary Figure 6, which are critical for explaining why only the \(\mathrm{Ca^{2 + }}\) compound is effective, unlike the \(\mathrm{Al^{3 + }}\) , \(\mathrm{Mg^{2 + }}\) , and \(\mathrm{Sr^{2 + }}\) compounds. The authors mention "gel- like flocculent precipitates" as decomposition products of dimethoxythane (DME) induced by \(\mathrm{Al^{3 + }}\) ions, suggesting they used their standard electrolyte (i.e., 0.75 M LiFSI and 0.4 M LiNO3 in DME) for the gelation test, as using a DOL- containing electrolyte would invalidate the experiment. Nonetheless, including these experimental details is essential for clarity and reproducibility. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[255, 100, 740, 120]]<|/det|> +## Point-to-Point Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[118, 151, 822, 195]]<|/det|> +Title: Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries + +<|ref|>text<|/ref|><|det|>[[118, 201, 853, 245]]<|/det|> +Authors: Hannah Cho, Jinkwan Jung, Ilju Kim, Jinuk Kim, Sejin Kim, Jonghyun Hyun, Chang Hoon Lee, Hobeom Kwack, Wonsik Oh, Jinwoo Lee, and Hee- Tak Kim\* + +<|ref|>text<|/ref|><|det|>[[118, 275, 860, 368]]<|/det|> +We greatly appreciate the reviewer's comments, which have been very helpful in improving our manuscript. Below, we provide responses of the revision made in response to the feedback. Reviewer questions are highlighted in blue, and any revisions made to the manuscript are highlighted to aid the reviewers. + +<|ref|>sub_title<|/ref|><|det|>[[119, 399, 421, 416]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 446, 876, 612]]<|/det|> +In their manuscript entitled "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," Cho et al. propose using \(\mathrm{Ca(OTf)_2}\) as an effective additive for lithium- sulfur batteries under lean electrolyte conditions. They claim that calcium ions mitigate polysulfide dissolution due to their high Lewis acidity, as well as the catalytic effects of CaS resulting from its interaction with LiPS. However, in my view, the publication of this manuscript is premature. Several additional experiments and essential experimental details are needed to substantiate the authors' claims. My specific comments are as follows: + +<|ref|>text<|/ref|><|det|>[[117, 643, 866, 809]]<|/det|> +RESPONSE: Thank you for your thoughtful and constructive feedback on our manuscript. The reviewer's detailed comments, based on your extensive knowledge, have been invaluable in refining our study. We especially appreciate the reviewer's suggestions, which have helped us enhance the precision of our data analysis and provide more comprehensive descriptions of the experimental methods. The manuscript has been carefully revised in accordance with the reviewer's comments and suggestions. Our point- by- point responses to the reviewer's comments are appended below. + +<|ref|>text<|/ref|><|det|>[[118, 839, 878, 907]]<|/det|> +1. Primary Hypothesis: The core hypothesis of this work is that the "high" Lewis acidity of calcium ions mitigates polysulfide dissolution by forming Ca-PS complexes. If this hypothesis is accurate, electrolytes with \(\mathrm{Mg(OTf)_2}\) and \(\mathrm{Al(OTf)_3}\) , which have ions with significantly higher acidity than + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 99, 866, 142]]<|/det|> +Ca, should show even better performance. Since the difference in acidity between Ca and Li ions is minimal, this oversight or lack of consideration raises doubts about the hypothesis's validity. + +<|ref|>text<|/ref|><|det|>[[118, 172, 879, 240]]<|/det|> +RESPONSE: We sincerely appreciate the reviewer's constructive questions. In response, we have further refined our hypothesis to clarify the role of \(\mathrm{Ca^{2 + }}\) in polysulfide dissolution and to provide a more precise rationale for its selection. + +<|ref|>text<|/ref|><|det|>[[117, 270, 876, 411]]<|/det|> +Although an electrolyte additive can regulate polysulfide solubility, its stability in the electrolyte must take priority for its use in lithium- sulfur batteries, particularly ensuring that it does not undergo unintended side reactions with Lewis basic salt anions and solvents. Our UV- Vis analysis (Figs. 3a and 3b in the revised manuscript) confirms that Lewis acidity of cations correlates with polysulfide solubility, but we also found that most cations, except for \(\mathrm{Ca^{2 + }}\) , exhibited poor compatibility with the electrolyte. + +<|ref|>text<|/ref|><|det|>[[115, 417, 864, 608]]<|/det|> +As reported in our initial manuscript (Supplementary Fig. 2 in the revised manuscript), Al electrolyte was gelated and Mg electrolyte showed formation of precipitate, indicating severe instability. The strong Lewis acidity of \(\mathrm{Al^{3 + }}\) and \(\mathrm{Mg^{2 + }}\) ions is known to catalyze DOL polymerization, leading to gelation (Chem. Commun., 56, 4583- 4586 (2022)). Additionally, \(\mathrm{Al^{3 + }}\) has been reported to decompose DME when \(\mathrm{Al(OTf)_3}\) is added to LiFSI/DME electrolytes, forming gel- like flocculent precipitates (ACS Appl. Mater. Interfaces, 16, 47581- 47589 (2024)). These results suggest that a cation with excessively high Lewis acidity has detrimental effects rather than effectively regulating polysulfides. + +<|ref|>text<|/ref|><|det|>[[115, 614, 840, 752]]<|/det|> +Thus, instead of choosing a cation that is significantly more acidic than \(\mathrm{Li^{+}}\) , we considered a moderate increase in Lewis acidity to be more appropriate. Although the difference in pKa between \(\mathrm{Ca^{2 + }}\) and \(\mathrm{Li^{+}}\) is not large, our experimental data demonstrate that \(\mathrm{Ca^{2 + }}\) effectively modifies the polysulfide solvation environment. When \(1.6\mathrm{M}\mathrm{Li}_2\mathrm{S}_4\) was dissolved in both the control and Ca- containing electrolytes, the saturated supernatant in the Ca electrolyte showed more than threefold decrease in the \(\mathrm{S_4^{2 - }}\) peak intensity in UV- Vis spectra. + +<|ref|>text<|/ref|><|det|>[[115, 758, 840, 904]]<|/det|> +This level of polysulfide solubility alteration by \(\mathrm{Ca^{2 + }}\) was found to be optimal for our system. While the pKa difference alone may not seem substantial, the observed solubility differences indicate that \(\mathrm{Ca^{2 + }}\) sufficiently modifies the polysulfide environment without introducing the instability observed with \(\mathrm{Al^{3 + }}\) and \(\mathrm{Mg^{2 + }}\) . These results validate our hypothesis that a moderate increase in Lewis acidity, rather than an extreme shift, is the key to effective polysulfide regulation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 123, 864, 290]]<|/det|> +2. Experimental Descriptions: The manuscript contains many vague descriptions of experimental details, limiting the interpretability of the presented data. For example, in Fig. 5a, the electrolyte solutions for both the control and Ca experiments are described insufficiently, with only one line—"A viscometer (LVDV-2+PC, BROOKFIELD) was used to measure the electrolyte viscosity"—included in the experimental section. What does "1.6M Li₂S₄ control" mean? What solvents and salts are in the control? It is questionable whether the authors can truly reduce the control electrolyte's viscosity by merely adding Ca salt. + +<|ref|>text<|/ref|><|det|>[[115, 317, 879, 820]]<|/det|> +RESPONSE: The authors sincerely appreciate the reviewer's insightful comments regarding the need for greater clarity in the experimental descriptions. We fully acknowledge that providing additional details is essential for enhancing the interpretability and reproducibility of our data, particularly concerning the viscosity measurements and the electrolyte composition. To address the reviewer's concerns, we have provided a more detailed description of the catholyte preparation and measurement conditions in the revised manuscript. Specifically, the "1.6 M Li₂S₄- containing control electrolyte" refers to a solution prepared by dissolving 1.6 M Li₂S₄ into the Control electrolyte, which consists of 0.75 M LiFSI and 0.4 M LiNO₃ salts in DME solvent. The significant reduction in viscosity upon the addition of Ca salt is attributed to the interactions between Ca ions and polysulfide (PS) species. Ca²⁺ ions mitigate polysulfide dissolution by forming Ca-PS complexes and precipitating CaS, leading to a profound decrease in the polysulfide saturation concentration in the Ca electrolyte, as observed in Supplementary Fig. 24 in the revised manuscript. This effect of Ca²⁺ aligns with the strong influence of polysulfide concentration on electrolyte viscosity as previously reported in the literature (ACS Appl. Mater. Interfaces, 14, 46457–46470 (2022)). Increasing the Li₂S₈ concentration from 0.78 M to 3.9 M resulted in a three-order magnitude increase in viscosity, from 4.3 mPa·s to 1.8×10³ mPa·s. In our study, the threefold difference in UV-vis absorbance (Supplementary Fig. 24 in the revised manuscript) at 425 nm (corresponding to S₄²⁻) between the Li₂S₄-saturated control and Ca catholytes correlates well with the significant decrease in viscosity observed under the same conditions. + +<|ref|>text<|/ref|><|det|>[[117, 825, 852, 893]]<|/det|> +Additionally, this PS- saturated environment mimics the conditions near the porous cathode at a depth of discharge (DOD) of \(\sim 30\%\) during the discharge process, where excessive polysulfide dissolution can lead to significant overpotential. The reduced viscosity in the Ca electrolyte + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 840, 142]]<|/det|> +mitigates this issue, lowering overpotential and improving both cell performance and reaction reversibility. + +<|ref|>text<|/ref|><|det|>[[117, 173, 875, 266]]<|/det|> +In response to the reviewer's valuable suggestion, we have added details to experimental descriptions including catholyte preparation, viscosity measurements, source of LiTFSI, GITT protocols, Raman spectroscopy measurements and sample preparation in the methodology section of our revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[118, 298, 297, 315]]<|/det|> +## [Revised manuscript] + +<|ref|>text<|/ref|><|det|>[[118, 322, 240, 338]]<|/det|> +[Line 454- 463] + +<|ref|>text<|/ref|><|det|>[[115, 345, 878, 635]]<|/det|> +To mimic the polysulfide- saturated environment, \(1.6\mathrm{M}\mathrm{Li}_2\mathrm{S}_4\) (equivalent to the \(E / S\) ratio of 5) was added to the Control electrolyte and Ca electrolyte, and the solutions were stirred for 72 hours at \(25^{\circ}\mathrm{C}\) . The catholytes were then rested for 24 hours to achieve equilibrium and filtrated through a syringe filter with a pore size of \(0.22\mu \mathrm{m}\) to obtain the saturated solution. The viscosity of the catholytes was measured using a viscometer (LVDV- 2+PC, BROOKFIELD) at \(25^{\circ}\mathrm{C}\) for 1 minute. To ensure accurate viscosity measurements for solutions with significantly different viscosities (7 cP vs. 2 cP), the torque values were maintained within the optimal range (60- 90%) by adjusting the rotational speed. For the Control catholyte, the rotational speed was set to 30- 40 RPM with a corresponding shear rate of \(225 - 300\mathrm{s}^{- 1}\) . For the Ca catholyte, the rotational speed was adjusted to 90- 95 RPM, with a shear rate of \(675 - 721.5\mathrm{s}^{- 1}\) . These adjustments ensured reliable viscosity readings while minimizing instrument- related errors. + +<|ref|>text<|/ref|><|det|>[[118, 666, 202, 682]]<|/det|> +[Line 444] + +<|ref|>text<|/ref|><|det|>[[118, 690, 870, 708]]<|/det|> +LiTFSI and DOL (anhydrous, \(99.5\%\) ) were purchased from 3M and Sigma- Aldrich, respectively. + +<|ref|>text<|/ref|><|det|>[[118, 739, 240, 755]]<|/det|> +[Line 489- 492] + +<|ref|>text<|/ref|><|det|>[[118, 763, 875, 855]]<|/det|> +The GITT experiments consist of a series of pulse currents at \(0.1\mathrm{C}\) for \(0.1\mathrm{h}\) , each followed by a \(0.4\mathrm{h}\) open- circuit period. The open- circuit relaxation time should be long enough that the voltage fluctuation is within a \(0.01\mathrm{V}\) range. The open circuit voltage (OCV) curves of the Li- S cells were constructed by connecting the voltage points after each relaxation period. + +<|ref|>text<|/ref|><|det|>[[118, 887, 238, 903]]<|/det|> +[Line 481- 483] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 100, 875, 166]]<|/det|> +Samples for Raman spectroscopy were prepared by filling a sample vial, then were tightly sealed. Spectra were recorded using a dispersive Raman spectrometer (ARAMIS, JY Horiba) and sample excitation was carried out at \(514 \mathrm{nm}\) . + +<|ref|>image<|/ref|><|det|>[[278, 200, 725, 339]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[117, 351, 880, 417]]<|/det|> +Supplementary Fig. 24 | Reduced PS saturation concentration at an \(E / S\) ratio of \(5 \mu \mathrm{L} \mathrm{mg}^{- 1}\) with the Ca electrolyte. a, Photograph of \(1.6 \mathrm{M} \mathrm{Li}_2 \mathrm{S}_4\) in the control electrolyte (left) and the Ca electrolyte (right). b, UV- vis spectroscopy of supernatants from (a). + +<|ref|>text<|/ref|><|det|>[[117, 455, 866, 523]]<|/det|> +3. Electrode Composition Details: Essential information about the electrodes, such as binder type, carbon materials, and sulfur loading percentage, is missing. These parameters are crucial for reproducing the results and should be included. + +<|ref|>text<|/ref|><|det|>[[117, 552, 880, 695]]<|/det|> +RESPONSE: The authors appreciate the reviewer's detailed comments. All electrodes used in this work were fabricated in a similar fashion as following information. CNT/S composite (75wt% elemental sulfur), and CMC/PAA/SBR binder (CMC:PAA:SBR = 3:1:4 by weight) were mixed well with a weight ratio of 96:4 in deionized water and the resulting slurry was casted onto Al foil with an areal loading of \(3.8 \mathrm{mg} \mathrm{cm}^{-2}\) unless otherwise specified. The information was added to the Method part of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[118, 726, 298, 744]]<|/det|> +## [Revised manuscript] + +<|ref|>text<|/ref|><|det|>[[118, 751, 240, 767]]<|/det|> +[Line 464- 468] + +<|ref|>text<|/ref|><|det|>[[117, 774, 875, 896]]<|/det|> +Sulfur electrode preparation and materials characterization. For the preparation of the cathode, a CNT/S composite (75 wt% Sulfur) and the binder mixture (carboxymethyl cellulose (CMC)/poly(acrylic acid) (PAA)/styrene-butadiene rubber (SBR) binder = 3/1/4 by weight) were homogenized with a weight ratio of 96:4 in deionized water. The CNT/S composite was prepared by impregnating molten sulfur into a CNT micro-ball via melt-diffusion at 120 °C. Afterward, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 101, 879, 204]]<|/det|> +resulting slurry was cast on the Al foil, followed by drying under \(80^{\circ}\mathrm{C}\) . For coin- type and pouch- type bi- cell, single- side coated cathodes were fabricated at sulfur loadings of 3.8 and \(2.25\mathrm{mg}\mathrm{cm}^{- 2}\) , respectively. For high- energy and high- power pouch cells, double side- coated cathodes were prepared at sulfur loadings of \(2.26\) and \(1.81\mathrm{mgcm}^{- 2}\) , respectively. + +<|ref|>text<|/ref|><|det|>[[117, 232, 857, 327]]<|/det|> +4. UV-Vis Study Protocols: The UV-Vis study requires a more detailed experimental procedure. Did the authors immerse all coin cell components in the control electrolyte? Given the small electrolyte volume in a coin cell, there may be significant experimental error. Providing at least three parallel experiments would help confirm the data's consistency. + +<|ref|>text<|/ref|><|det|>[[117, 355, 876, 499]]<|/det|> +RESPONSE: We thank the reviewer for raising this important point. The UV-Vis studies on both the catholyte and discharged cells were conducted to cross- validate the interaction between Lewis acidic cations and polysulfides. Beyond simply comparing the UV-Vis spectra of catholytes (Supplementary Fig. 11 in the revised manuscript) to evaluate polysulfide solubility, we focused on comparing the accommodative amount of polysulfides electrochemically reduced from \(\mathrm{S}_8\) in the presence of Lewis acidic additives. + +<|ref|>text<|/ref|><|det|>[[117, 527, 872, 721]]<|/det|> +We apologize for the insufficient description of the experimental procedures in the original manuscript. To address the reviewer's point, we added the experimental details to the Methods section of the revised manuscript. Specifically, the procedure is as follows: Immediately after discharging the coin cells to \(2.1\mathrm{V}\) , the coin cell components, including the spacer, electrodes, and separator, were gently washed with \(2\mathrm{mL}\) of DME to wash off the dissolved polysulfides, particularly from the porous cathode and separator. The washed solution was filtered using a syringe filter with a pore size of \(0.22\mu \mathrm{m}\) . The solution was then diluted tenfold with the control electrolyte, which served as the baseline for UV- Vis spectroscopy. + +<|ref|>text<|/ref|><|det|>[[117, 749, 875, 893]]<|/det|> +We ensured that this protocol was executed meticulously for all cells to minimize experimental error. Although dilution could introduce some variability under lean electrolyte conditions, the significant differences in the stability of electrochemically generated lithium polysulfides for each cation additive (as observed in parallel experiment on UV- Vis spectroscopy of catholytes) made these errors are negligible. As suggested by the reviewer, we repeated the experiments under the same conditions as Fig. 3a for three independent trials. The results, shown in Fig. R1, confirm the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 99, 878, 240]]<|/det|> +consistency of the data. Additionally, in response to the reviewer's suggestion in **Comment #5**, we replaced the control with \(0.05 \mathrm{M} \mathrm{Li}(\mathrm{OTf})\) in order to compare the polysulfide dissolution under different cation additives \((\mathrm{Li}^{+}, \mathrm{Sr}^{2 + }, \mathrm{Ca}^{2 + }, \mathrm{Mg}^{2 + }, \mathrm{Al}^{3 + })\) based on their Lewis acidity. The peak intensity at \(425 \mathrm{~nm}\) (corresponding to \(\mathrm{S}_{4}^{2 - }\) ) for four independent experiments, represented with error bars in the Revised **Fig. 3b**, shows minimal variability, demonstrating the reliability of the results. + +<|ref|>text<|/ref|><|det|>[[117, 246, 874, 313]]<|/det|> +**Fig. R1** is now **Supplementary Fig. 6**. We hope this detailed explanation and additional data address the reviewer's concerns and provide confidence in the accuracy and reproducibility of our findings. + +<|ref|>image<|/ref|><|det|>[[117, 343, 880, 500]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 505, 782, 542]]<|/det|> +
**Fig. R1. UV-Vis spectroscopy of electrolytes from coin cells (E/S = 4 \(\mu \mathrm{L} \mathrm{mg}^{-1}\)) discharged to 2.1 V.**
+ +<|ref|>image<|/ref|><|det|>[[400, 575, 610, 725]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 734, 876, 850]]<|/det|> +
**Fig. 3b. Lewis acid-base reaction between multivalent metal ions and PSs. b, Correlation** between the pKa value of metal cations27 and the UV-vis absorbance at 425 nm (corresponding to \(\mathrm{S}_{4}^{2 - }\) ) in electrolytes containing Lewis acidic additives after discharge to 2.1 V. Error bars denote the standard deviation from measurements obtained from four independent coin cells. The data are presented as mean values \(\pm\) standard deviation.
+ +<|ref|>text<|/ref|><|det|>[[117, 881, 797, 900]]<|/det|> +5. Control Setup in Fig. 3b: In Fig. 3b, the control should not solely consist of the control + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 99, 872, 142]]<|/det|> +electrolyte; 0.05M Li(OTf) should also be added. Additionally, the authors must explain how they determined the pKa values in the experimental section. + +<|ref|>text<|/ref|><|det|>[[118, 172, 864, 240]]<|/det|> +RESPONSE: The authors sincerely thank the reviewer for valuable suggestions. Following the reviewer's recommendation, we have revised the Control in Fig. 3b to 0.05 M Li(OTf), as the X-axis represents the pKa values of metal cation triflates. + +<|ref|>text<|/ref|><|det|>[[117, 270, 875, 388]]<|/det|> +The pKa values of \([\mathrm{M(OH_2)_m}]^{n + }\) used in this study were referenced from "Perrin, D. D., Ionization Constants of Inorganic Acids and Bases in Aqueous Solution, Second Edition, Pergamon, Oxford, 1982". These pKa values of hydrated metal ion complexes are reported to be strongly correlated with Lewis acidity of metal triflates dissolved in organic solvents (Inorg. Chem., 60, 1107- 1115 (2021)). + +<|ref|>text<|/ref|><|det|>[[118, 418, 816, 461]]<|/det|> +We have revised this content to the revised manuscript (Fig. 3a and b), as prompted by the reviewer's valuable suggestion. + +<|ref|>image<|/ref|><|det|>[[283, 490, 712, 643]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 653, 872, 794]]<|/det|> +
Fig. 3a, b. Lewis acid-base reaction between multivalent metal ions and PSs. a, UV-vis spectra of electrolytes from the coin cells \((E / S = 4 \mu \mathrm{L} \mathrm{mg}^{-1})\) after being discharged to 2.1 V. b, Correlation between the pKa value of metal cations \(^{27}\) and the UV-vis absorbance at 425 nm (corresponding to \(\mathrm{S}_4^{2 - }\) ) in electrolytes containing Lewis acidic additives after discharge to 2.1 V. Error bars denote the standard deviation from measurements obtained from four independent coin cells. The data are presented as mean values \(\pm\) standard deviation.
+ +<|ref|>text<|/ref|><|det|>[[118, 824, 875, 867]]<|/det|> +6. Choice of Control Electrolyte: The authors' control choice of 0.75M LiFSI and 0.4M LiNO₃ in DME differs from the conventional Li-S electrolyte (1M LiTFSI in DOL/DME with \(\sim 2\%\) LiNO₃). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 870, 142]]<|/det|> +The authors used a 0.5M LiTFSI and 0.2M LiNO₃ DOL/DME electrolyte, and the large reduction in salt concentration likely exacerbates LiPS dissolution. + +<|ref|>text<|/ref|><|det|>[[115, 172, 880, 411]]<|/det|> +RESPONSE: We thank the reviewer for suggesting the use of the conventional electrolyte (1 M LiTFSI in DOL/DME (1:1 v/v) with \(\sim 2\) wt% LiNO₃) as the Control electrolyte. To improve the performance of Li- S batteries under lean electrolyte conditions, alternative electrolyte engineering strategies from the conventional electrolyte have been actively explored. For instance, reducing the LiTFSI concentration from the conventional electrolytes has been reported to improve charge transfer kinetics, suppress the shuttle effect, and enhance lithium polysulfide conversion redox kinetics, ultimately leading to better overall Li- S battery performance (Chem, 8, 1- 20, (2022) / Adv. Funct. Mater., 32, 2205393 (2022)). Based on these findings, we selected 0.5 M LiTFSI electrolyte as an optimized system for achieving these benefits while maintaining compatibility with the conventional electrolyte framework. + +<|ref|>text<|/ref|><|det|>[[115, 417, 870, 612]]<|/det|> +In case of LiFSI- based electrolytes, using LiFSI as main lithium salt has demonstrated advantages over LiTFSI especially under low E/S ratio, including lower resistance (J. Am. Chem. Soc., 145, 16449- 16457 (2023)) and the formation of a more stable LiF- based solid electrolyte interphase (SEI) (Nano- Micro Lett., 16, 35 (2024)). Given these benefits, we used 0.75 M LiFSI to achieve improved SEI stability and ionic transport properties. However, as the reviewer pointed out, it is essential to evaluate the effect of \(\mathrm{Ca^{2 + }}\) in the conventional LiTFSI- based electrolyte system for direct comparison with literature results. To address this, we conducted additional experiments incorporating \(\mathrm{Ca^{2 + }}\) into the conventional electrolyte. The results are discussed below. + +<|ref|>text<|/ref|><|det|>[[115, 642, 872, 908]]<|/det|> +As shown in Fig. R2, the use of the conventional LiTFSI- based electrolyte as the Control electrolyte in lean electrolyte coin cells results in a significant increase in overpotential upon cycling, leading to a short cycle life of less than 50 cycles. In contrast, incorporating the Ca additive into the conventional electrolyte improved cycle life by more than twofold in different testing conditions. We have confirmed the effectiveness of the Ca additive not only in electrolyte systems with different main salts with different concentrations (e.g., 1 M LiTFSI, 0.5 M LiTFSI, LiFSI) but also across various co- solvents and E/S ratios under lean electrolyte conditions (Figs. 2a- c and Supplementary Fig. 5 in the revised manuscript). These results highlight the universal effectiveness of a small amount of Ca additive in modifying the solvation properties, enhancing interactions with polysulfide anions, and the formation of a CaS catalyst—a principle that extends to other electrolyte systems. These combined effects significantly reduce overpotential and extend + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 473, 117]]<|/det|> +the cycle life of lean electrolyte Li- S batteries. + +<|ref|>image<|/ref|><|det|>[[117, 147, 880, 315]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 322, 840, 374]]<|/det|> +
Fig. R2. Cycle performance of Li-S cells with 1 M LiTFSI 2 wt% LiNO3 DOL:DME electrolyte. Cell capacity versus cycle number for a, 0.20C discharge/ 0.15C charge b, 0.30C discharge/ 0.20C charge.
+ +<|ref|>text<|/ref|><|det|>[[118, 405, 860, 448]]<|/det|> +7. Cycling Performance: For Fig. 2a, the authors should provide parallel cycling performance for each cell to confirm repeatability and rule out cell-to-cell variations. + +<|ref|>text<|/ref|><|det|>[[117, 478, 878, 569]]<|/det|> +RESPONSE: The authors thank the reviewer's valuable suggestion. We agree that confirming the repeatability of cycling performance is crucial, especially under lean electrolyte conditions where reaction inhomogeneity may cause cell-to-cell variations. + +<|ref|>text<|/ref|><|det|>[[117, 550, 878, 719]]<|/det|> +To address this, we assembled pouch cells with the same configuration as in Fig. 2a, and these are currently undergoing cycling tests. Unfortunately, due to the low current density cycling conditions used in Fig. 2a (0.10C Discharge / 0.05C Charge), we were unable to fully replicate the complete cycling data at the time of this revision submission, except for the control electrolyte, for which an additional cell had been previously been tested. For instance, the pouch cell with Ca electrolyte required 150 days to reach 70% capacity retention. Nevertheless, we hope the following information convince you the consistency in the observed trends. + +<|ref|>text<|/ref|><|det|>[[117, 746, 880, 914]]<|/det|> +For the replicated cells, cycling performance (Fig. R3) of Al and the Control electrolyte confirms consistency with the original data. The Al electrolyte, which exhibited significant overpotential and failed after 26 cycles in Fig. 2a, failed with same behavior at the \(28^{\text{th}}\) cycle in the replicated experiment. Additionally, the Control electrolyte exhibited a cycle life of 107 cycles (70% capacity retention) in the replicated cell, which closely matches the cell failure at \(103^{\text{th}}\) cycle observed in Fig. 2a. For the Mg, Ca, and Sr electrolytes, we observed similar trends in the ongoing cycles (~45 cycles), and we expect comparable cell performance to that shown in Fig. 2a. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 123, 875, 292]]<|/det|> +To further compare the performance of electrolytes with Lewis acidic additives, we tested coin cells with an \(E / S\) ratio of \(4 \mu \mathrm{L} \mathrm{mg}^{- 1}\) (Fig. R4). Although the cell format differs, we confirmed the similar trend in cycle life: the Ca electrolyte extends the cycle life compared to the control electrolyte, while Al, Mg, and Sr electrolytes show incompatibility. The inferior cell performance of coin cells in Fig. R4, despite higher \(E / S\) ratio, can be attributed to greater uniformity and higher stack pressure of pouch cells which positively impacts cycling stability (Nat. Energy, 4, 551 (2019)). + +<|ref|>text<|/ref|><|det|>[[116, 298, 854, 465]]<|/det|> +To substantiate the reproducibility of the Ca electrolyte's superior performance under lean electrolyte pouch cell conditions, we tested additional pouch cell tests under faster discharging conditions as those shown in Fig. 2c. The performance of replicated cells (Fig. R5) confirm the consistency and highlight the cycling performance of the Ca electrolyte under extremely lean electrolyte conditions. We hope these additional data and comparisons address the reviewer's concerns regarding cycling performance and reinforce the reliability and reproducibility of our findings. + +<|ref|>image<|/ref|><|det|>[[144, 493, 852, 666]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 674, 880, 711]]<|/det|> +
Fig. R3. Pouch-type Li-S bi-cell \((E / S = 3.5 \mu \mathrm{L} \mathrm{mg}^{-1})\) cycling with the control and additive \((\mathrm{Sr}^{2 + }, \mathrm{Ca}^{2 + }, \mathrm{Mg}^{2 + }, \mathrm{or} \mathrm{Al}^{3 + })\) -containing electrolytes.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[288, 95, 709, 273]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 281, 797, 300]]<|/det|> +
Fig. R4. Cycle performance of Li-S cells with Lewis acidic electrolyte additives.
+ +<|ref|>image<|/ref|><|det|>[[165, 336, 824, 513]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[116, 519, 880, 567]]<|/det|> +
Fig. R5. Electrochemical performances of the Li-S pouch cells with Ca electrolyte. Li-S stack cell with an \(E / S\) ratio of \(2.9 \mu \mathrm{L} \mathrm{mg}^{-1}\) (high power design) with \(\mathrm{Ca(OTf)_2}\) additive showing stable cycling for over 350 cycles at \(1.0 \mathrm{C}\) .
+ +<|ref|>text<|/ref|><|det|>[[118, 599, 853, 641]]<|/det|> +8. Additive Controls in Figs. 2b and 2c: The cycling results for the control electrolyte, as well as electrolytes with Al and Mg additives, should also be presented. + +<|ref|>text<|/ref|><|det|>[[115, 671, 875, 789]]<|/det|> +RESPONSE: We appreciate the reviewer's helpful feedback, which has allowed us to improve the clarity of our study. In response to this suggestion, we have incorporated the cycling results for the control electrolyte as well as the electrolytes containing Al and Mg additives in Figs. 2b and 2c. These additional data provide a more comprehensive comparison of the cycling performance across different electrolyte formulations. + +<|ref|>text<|/ref|><|det|>[[118, 796, 864, 839]]<|/det|> +The results confirm that the Ca electrolyte consistently outperforms the control electrolyte, while Al and Mg electrolytes show inferior cycling stability. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 99, 875, 404]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 412, 881, 538]]<|/det|> +
Fig. 2b-c. b, High-Energy design Li-S stack cell with an \(E / S\) ratio of \(2.4~\mu \mathrm{L}\mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 200 cycles at \(0.3\mathrm{C}\) . Configuration of a high-energy cell with \(25\mu \mathrm{m}\) Li and sulfur loading of \(2.26\mathrm{mg}\mathrm{cm}^{-2}\) . c, High-Power design Li-S stack cell with an \(E / S\) ratio of \(2.9\mu \mathrm{L}\mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 350 cycles at \(1.0\mathrm{C}\) . Configuration of a high-power cell with \(20\mu \mathrm{m}\) Li and sulfur loading of \(1.81\mathrm{mg}\mathrm{cm}^{-2}\) .
+ +<|ref|>text<|/ref|><|det|>[[117, 570, 875, 637]]<|/det|> +9. Electrolyte Solvation Analysis: The authors employed MD simulation and solid characterization techniques such as TEM and XPS. To thoroughly understand electrolyte solvation, additional FTIR/Raman and NMR data should be included. + +<|ref|>text<|/ref|><|det|>[[115, 667, 878, 907]]<|/det|> +RESPONSE: We appreciate the reviewer's suggestion, which allowed us a more detailed analysis of \(\mathrm{Li^{+}}\) solvation behavior upon introducing the Ca additive. To address this, we performed Raman spectroscopy on the control and Ca electrolytes, as well as the catholytes. In the absence of lithium polysulfides, the addition of \(0.05\mathrm{M}\) or \(0.10\mathrm{M}\mathrm{Ca}^{2 + }\) does not affect \(\mathrm{Li^{+}}\) solvation. As shown in Fig. R6a, the Raman spectra exhibit no significant changes in the intensity or position of the \(\mathrm{Li^{+}}\) - FSI\({}^{-}\) and \(\mathrm{Li^{+}}\) - DME peaks upon the \(\mathrm{Ca}^{2 + }\) addition. This indicates negligible interaction between \(\mathrm{Ca}^{2 + }\) and FSI\({}^{-}\) anions or solvent molecules. Furthermore, the molecular dynamics (MD) simulations of the Ca electrolyte without polysulfides (Fig. R7) reveal that \(\mathrm{Ca}^{2 + }\) primarily coordinates with \(\mathrm{NO_3^{- }}\) anions, which possess a high donor number and dominate the solvation environment. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 880, 365]]<|/det|> +In sharp contrast, a high- concentration catholyte (1.6 M \(\mathrm{Li_2S_4}\) , corresponding to full sulfur dissolution at \(\mathrm{E / S} = 5 \mu \mathrm{L} \mathrm{mg}^{- 1}\) ) showed clear differences upon the \(\mathrm{Ca^{2 + }}\) additions (Fig. R6b). Compared to the Control catholyte, the 0.05 M and 0.10 M Ca catholytes showed stronger signals for \(\mathrm{Li^{+}}\) - FSI, \(\mathrm{Li^{+}}\) - coordinated DME, and free DME. A same trend appeared even at a lower \(\mathrm{Li_2S_4}\) concentration of 0.2 M (Fig. R6c), where the Raman signals for \(\mathrm{Li^{+}}\) - FSI and \(\mathrm{Li^{+}}\) - DME were more distinct in the Ca electrolytes than in the control electrolyte. This can be explained by the strong Raman activity of polysulfides, which generate intense scattering signals that can hinder peaks from FSI or DME (Small Struct., 3, 2100170 (2022)). Since the Control electrolyte contains a higher concentration of solvated LiPS than the Ca electrolyte, the intense Raman scattering from polysulfides weakens the visibility of other species. These results indicate that \(\mathrm{Ca^{2 + }}\) modifies the solvation structure by decreasing the amount of solvated LiPS in the electrolyte. + +<|ref|>text<|/ref|><|det|>[[116, 392, 870, 536]]<|/det|> +Regarding the reviewer's suggestion to include NMR analysis, distinguishing between \(\mathrm{Li^{+}}\) - FSI and \(\mathrm{Li^{+}}\) - PS interactions using \(^7\mathrm{Li}\) chemical shift would be difficult. The increase in \(\mathrm{Li^{+}}\) - FSI coordination in the Ca catholyte is counterbalanced by a decrease in \(\mathrm{Li^{+}}\) - PS interactions, resulting in little net change in the chemical shift. Also, \(^{19}\mathrm{F}\) NMR of FSI anions shows minimal variation, as \(\mathrm{Li^{+}}\) interacts primarily with the oxygen atoms of FSI rather than fluorine, making FSI chemical shifts less sensitive to solvation changes. + +<|ref|>text<|/ref|><|det|>[[116, 564, 872, 732]]<|/det|> +The change of \(\mathrm{Li^{+}}\) solvation structure in polysulfide- containing electrolytes by \(\mathrm{Ca^{2 + }}\) additive is further supported by ToF- SIMS and XPS data, where an S- poor, F- rich SEI is formed in the Ca electrolyte. Additionally, linear sweep voltammetry (LSV) shows a lower LiPS reduction current, reinforcing the conclusion that \(\mathrm{Ca^{2 + }}\) influences the solvation environment. These results provide a clearer understanding of how \(\mathrm{Ca^{2 + }}\) affects \(\mathrm{Li^{+}}\) solvation in Li- S battery electrolytes, and we have incorporated the discussion into the revised manuscript, Fig. R7 is now Supplementary Fig. 26. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 99, 880, 555]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 562, 870, 640]]<|/det|> +
Fig. R6. Raman spectroscopy of electrolytes and catholytes with varying lithium polysulfide concentrations. a, Raman spectra of electrolytes without lithium polysulfide. Different peak ranges are noted with arrows in the spectra. b, Raman spectra of supernatants from catholytes containing 1.6 M \(\mathrm{Li_2S_4}\) (corresponding to full sulfur dissolution at \(\mathrm{E / S = 5\mu Lmg^{-1}}\) , \(3.8\mathrm{mgcm}^{-2}\) sulfur loading). c, Raman spectra of supernatants from catholytes containing \(0.2\mathrm{M}\mathrm{Li}_2\mathrm{S}_4\)
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[339, 98, 660, 330]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 340, 797, 376]]<|/det|> +
Fig. R7. Cumulative distribution functions of \(\mathrm{Ca^{2 + }}\) solvation in 0.1 M \(\mathrm{Ca(OTf)_2}\) electrolyte.
+ +<|ref|>text<|/ref|><|det|>[[118, 410, 297, 450]]<|/det|> +[Revised manuscript] [Line 383- 385] + +<|ref|>text<|/ref|><|det|>[[118, 464, 875, 483]]<|/det|> +In parallel, Raman spectroscopy confirms the strengthened \(\mathrm{Li^{+}}\) - FSI coordination while the LiPS + +<|ref|>text<|/ref|><|det|>[[118, 497, 525, 515]]<|/det|> +signal intensity decreases (Supplementary Fig. 26). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 100, 421, 117]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[118, 139, 201, 154]]<|/det|> +## Summary: + +<|ref|>text<|/ref|><|det|>[[117, 156, 881, 344]]<|/det|> +This research paper entitled, "Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries" reports a novel approach to designing and enhancing the performance of lean- electrolyte lithium- sulfur batteries by adding a small amount of calcium cations to the electrolyte. The calcium cations are reported that can effectively convert polysulfides into calcium sulfide and sulfur. This reaction prevents polysulfide shuttle and electrolyte jamming while mitigating lithium corrosion. The in situ formation of calcium sulfide acts as a catalyst, facilitating the reduction of polysulfides, and calcium cations are regenerated during charging, allowing sustainable cycling. The addition of calcium cations improves cycling stability and energy density, with pouch cells achieving 493 Wh kg \(^{- 1}\) and \(70\%\) capacity retention after 220 cycles, and 346 Wh kg \(^{- 1}\) with \(77\%\) retention after 360 cycles. + +<|ref|>sub_title<|/ref|><|det|>[[118, 365, 262, 380]]<|/det|> +## General comment: + +<|ref|>text<|/ref|><|det|>[[118, 382, 872, 437]]<|/det|> +This study reports on the electrolyte additive for the lean- electrolyte lithium- sulfur cell to have an improved performance. Some minor revision is needed, and I hope the authors find the comment useful. + +<|ref|>text<|/ref|><|det|>[[115, 456, 879, 696]]<|/det|> +RESPONSE: We sincerely appreciate your thorough understanding and positive evaluation of our work, which has greatly encouraged us to refine the comprehensibility and design principles of the proposed electrolyte system. The reviewer's insightful comments and constructive suggestions have been instrumental in improving both the clarity and scientific rigor of our manuscript. In particular, we are grateful for the suggestions that prompted us to provide additional details regarding experimental methods, refine data presentation, and further explore the key mechanistic aspects of our study. These refinements have strengthened the manuscript and enhanced the robustness of our conclusions. The manuscript has been carefully revised in accordance with the reviewer's comments, and a point- by- point response detailing the modifications made is provided below. + +<|ref|>sub_title<|/ref|><|det|>[[118, 728, 209, 744]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[115, 751, 868, 867]]<|/det|> +(1) The manuscript is well organized in both the writing and the data presentation. One minor suggestion is on the image layout in figures. Cycling performance data are not suggested to show an extended X axis for the cycle number. This gives an unreasonable cyclability. [Suggestion] Please organize and arrange the cycling performance data with a regular image layout. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 100, 875, 217]]<|/det|> +**RESPONSE:** The authors sincerely appreciate the reviewer's positive evaluation of our work and the thoughtful suggestion regarding the image layout. Following the reviewer's recommendation, we have adjusted the X-axis range of **Figs. 2a–c** to present a more reasonable depiction of the cycling performance data. Additionally, we have included the configurations of the high-power and high-energy pouch cells in **Figs. 2b** and **2c** to enhance the clarity of the figure presentation. + +<|ref|>text<|/ref|><|det|>[[118, 246, 861, 289]]<|/det|> +The revised manuscript now displays the cycling stability of the Ca electrolyte in pouch cells for up to \(\geq 200\) cycles, as shown in **Figs. 2a–c**. + +<|ref|>image<|/ref|><|det|>[[118, 320, 830, 748]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[118, 762, 868, 890]]<|/det|> +
Fig. 2a-c. Electrochemical performances of the Li-S pouch cells with Lewis acidic multivalent metal additives. a, Pouch-type Li-S bi-cell \((E / S = 3.5 \mu \mathrm{L} \mathrm{mg}^{-1})\) cycling with the control and additive \((\mathrm{Sr}^{2 + }\) , \(\mathrm{Ca}^{2 + }\) , \(\mathrm{Mg}^{2 + }\) or \(\mathrm{Al}^{3 + }\) )-containing electrolytes. b, High-Energy design Li-S stack cell with an \(E / S\) ratio of \(2.4 \mu \mathrm{L} \mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 200 cycles at \(0.3 \mathrm{C}\) . Configuration of a high-energy cell with \(25 \mu \mathrm{m} \mathrm{Li}\) and sulfur loading of \(2.26 \mathrm{mg} \mathrm{cm}^{-2}\) . c, High-Power design Li-S stack cell with an \(E / S\) ratio of \(2.9 \mu \mathrm{L} \mathrm{mg}^{-1}\) in the presence of Lewis acidic metal cation additives. \(\mathrm{Ca(OTf)_2}\) additive shows stable cycling for over 350 cycles at \(1.0 \mathrm{C}\) . Configuration of a high-power cell with \(20 \mu \mathrm{m} \mathrm{Li}\) and sulfur loading of \(1.81 \mathrm{mg} \mathrm{cm}^{-2}\) .
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 123, 866, 290]]<|/det|> +(2) The formation of CaS and S via the adsorbed polysulfides is the main finding of this research. It is suggested to focus on collecting direct experimental data as evidence. Then, the formation mechanism of CaS and the conversion from CaS to polysulfides is suggested to be studied and discussed. In addition, the polysulfide trapping mechanism is suggested to be explored. [Suggestion] Please conduct analysis and discussion on the formation mechanism of CaS, the conversion mechanism from CaS to polysulfides, and the polysulfide-trapping mechanism of calcium cations together. + +<|ref|>text<|/ref|><|det|>[[115, 320, 877, 560]]<|/det|> +RESPONSE: We thank the reviewer for these valuable insights. While our original manuscript presented various experimental and simulation results addressing the mechanisms in question (Fig. 3 and Fig. 4, Supplementary Figs. 8–18), these findings were dispersed throughout the manuscript, which may have made it difficult for readers to follow a cohesive narrative. To enhance clarity and provide a more structured discussion, we have compiled and consolidated these findings into a Supplementary Note that systematically outlines the mechanism. We acknowledge that our previous explanation may not have been sufficiently clear. In response, we provide a comprehensive discussion on the experimental evidence supporting the effects of \(\mathrm{Ca(OTf)_2}\) as an electrolyte additive, as well as its underlying mechanisms, which are summarized as follows. + +<|ref|>sub_title<|/ref|><|det|>[[118, 590, 585, 609]]<|/det|> +## 1. Polysulfide-trapping mechanism of the calcium cation: + +<|ref|>text<|/ref|><|det|>[[115, 614, 880, 830]]<|/det|> +The strong electrostatic interaction between \(\mathrm{Ca^{2 + }}\) and polysulfides leads to the formation of tightly associated \(\mathrm{Ca^{2 + }}\) - PS complexes. As shown in Fig. R8a, \(\mathrm{Ca^{2 + }}\) ions coordinate with multiple polysulfide anions compared to \(\mathrm{Li^{+}}\) due to its stronger Lewis acidity, forming a stable \(\mathrm{Ca^{2 + }}\) - PS network in the electrolyte (Fig. R8a). A similar mechanism using Lewis acidic electrolyte additive has been reported in recent literature (Joule, 8, 3397–3411 (2024)), where \(\mathrm{LiBF_4}\) reacts with nucleophilic LiPS to form \(\mathrm{LiF}\) and \(\mathrm{BF_3}\) . The strong Lewis acidity of \(\mathrm{BF_3}\) subsequently leads to \(\mathrm{BF_3}\) - PS adduct formation, which lowers polysulfide solubility. By analogy, the interaction between \(\mathrm{Ca^{2 + }}\) and polysulfides is expected to play a critical role in reducing LiPS solubility within the electrolyte. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[128, 100, 870, 293]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 305, 864, 352]]<|/det|> +
Fig. R8. Molecular dynamics of the Ca catholyte. a, Coordination number of polysulfide with \(\mathrm{Li^{+}}\) and \(\mathrm{Ca^{2 + }}\) in the Ca catholyte. b, MD snapshots of the molecular distributions around \(\mathrm{Li^{+}}\) , \(\mathrm{Ca^{2 + }}\) , and \(\mathrm{S_{4}^{2 - }}\) in the control catholyte (left) and 0.05 M Ca catholyte (right).
+ +<|ref|>text<|/ref|><|det|>[[117, 383, 858, 426]]<|/det|> +2. Formation mechanism of CaS and Ss: The \(\mathrm{Ca^{2 + }}\) -PS complex undergoes conversion via two possible pathways during discharge: + +<|ref|>text<|/ref|><|det|>[[133, 432, 874, 624]]<|/det|> +1) Electrochemical Reduction: The Ca electrolyte used in our manuscript contains a relatively low concentration of \(\mathrm{Ca^{2 + }}\) compared to \(\mathrm{Li^{+}}\) , the electrochemical reduction of Ca-PS complexes was not apparent. However, when \(\mathrm{Ca(OTf)_2}\) concentration is increased to \(0.5\mathrm{M}\) , an additional peak appears at \(\sim 2.15\mathrm{V}\) in the cyclic voltammetry (CV) and also in the discharge voltage profiles following the \(1^{\mathrm{st}}\) plateau of \(\mathrm{S_8}\) to \(\mathrm{Li_2S_4}\) conversion (Fig. R9a and b). This peak aligns well with the electrochemical reduction potential of low-order Ca polysulfides ( \(\mathrm{CaS_n}\) , \(2 \leq n \leq 4\) ) to \(\mathrm{CaS_2}\) and \(\mathrm{CaS}\) ( \(\sim 2.2\mathrm{V}\) vs. \(\mathrm{Li / Li^{+}}\) ) (Small, 16, 2001806 (2020)). The persistence of this peak even after 20 cycles suggests that Ca-S redox process is reversible. + +<|ref|>text<|/ref|><|det|>[[133, 654, 875, 796]]<|/det|> +2) Chemical Precipitation: The chemical precipitation reaction is expected to occur due to the strong electrostatic attraction between \(\mathrm{Ca^{2 + }}\) and the \(\mathrm{S^{2 - }}\) , leading to the spontaneous formation of thermodynamically stable CaS. Since CaS has extremely low solubility even in highly polar solvents like \(\mathrm{H_2O}\) , it cannot be solvated in DME, forming precipitates. This chemical reaction was confirmed through XRD (Fig. R9c) and XPS (Supplementary Figs. 11d, e) analysis of precipitates collected from \(\mathrm{Li_2S_8 + Ca(OTf)_2}\) in DME. + +<|ref|>text<|/ref|><|det|>[[117, 826, 857, 870]]<|/det|> +As a result of this mechanism, the CaS precipitated on the cathode was experimentally analyzed using TEM (Fig. 9d) and XPS (Fig. R9e) of discharged cathodes. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[135, 99, 875, 428]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[116, 441, 875, 518]]<|/det|> +
Fig. R9. a, Cyclic voltammetry (CV) test of Li-S the coin cell with \(0.5\mathrm{M}\) Ca electrolyte. b, Discharge voltage profiles of the coin cell with \(0.5\mathrm{M}\) Ca electrolyte. c, XRD analysis of precipitates formed in \(\mathrm{Ca(OTf)_2}\) containing solution. d, HAADF-STEM image and corresponding element mapping of the CNF cathode after discharge of the Li-S/CNF cell to \(2.1\mathrm{V}\) , scale bar: \(200\mathrm{nm}\) . e, Ca 2p XPS spectra of the cathode after \(1^{\mathrm{st}}\) cycle discharge.
+ +<|ref|>sub_title<|/ref|><|det|>[[118, 550, 485, 567]]<|/det|> +## 3. Conversion mechanism from CaS to \(\mathrm{Ca^{2 + }}\) : + +<|ref|>text<|/ref|><|det|>[[115, 574, 872, 790]]<|/det|> +CaS undergoes oxidation back to \(\mathrm{Ca^{2 + }}\) because its oxidation potential within the operating voltage of Li- S batteries. Previous studies on Ca- S batteries (Small, 16, 2001806 (2020)/ Adv. Energy Mater., 9, (2019)) have shown that CaS is oxidized to \(\mathrm{CaS_n}\) and to \(\mathrm{S_8}\) at approximately 2.35 and \(2.47\mathrm{V}\) vs. \(\mathrm{Li / Li^{+}}\) , respectively (corresponding to \(2.18\mathrm{V}\) and \(2.3\mathrm{V}\) vs. \(\mathrm{Ca / Ca^{2 + }}\) ). In this study, we experimentally observed the oxidation of CaS to \(\mathrm{Ca^{2 + }}\) and \(\mathrm{S_8}\) by ICP- MS (Fig. 4f) analysis. Additionally, we directly observed the CaS oxidation using CaS- casted electrode (Fig. R10). Upon charging the Li- CaS cell, the oxidation peaks of CaS appeared, and subsequently discharging it, two distinct discharge plateaus were observed, indicating the formation of S8 from CaS when CaS was the only available sulfur source. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[145, 113, 856, 315]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 328, 874, 375]]<|/det|> +
Fig. R10. Oxidation of CaS during cell operation. a, Linear sweep voltammetry profiles of the carbon paper electrode, \(\mathrm{Li}_2\mathrm{S}\) -loaded carbon paper electrode, and CaS-loaded carbon paper electrode. b, Discharge voltage profiles of the Li-Carbon paper cells incorporating CaS or \(\mathrm{Li}_2\mathrm{S}\) in the carbon paper electrode.
+ +<|ref|>text<|/ref|><|det|>[[118, 408, 646, 427]]<|/det|> +The above discussion was added to Supplementary Note 1. + +<|ref|>text<|/ref|><|det|>[[117, 456, 866, 549]]<|/det|> +(3) The sulfur cathode used in this research is necessary to be discussed and disclosed. The sulfur loading and sulfur content are suggested to be reported. The content of additional additives is necessary to be reported. These are necessary information, which controls the key experimental testing condition, E/S ratio. + +<|ref|>text<|/ref|><|det|>[[118, 557, 645, 575]]<|/det|> +[Suggestions] Please report the necessary information on the cathode. + +<|ref|>text<|/ref|><|det|>[[116, 604, 876, 820]]<|/det|> +RESPONSE: The authors appreciate the reviewer's detailed comments and for highlighting the importance of disclosing key information. All electrodes used in this work were fabricated following a standardized procedure. CNT/S composite (containing 75wt% elemental sulfur) was mixed with Carboxymethyl cellulose (CMC) / Poly(acrylic acid) (PAA) / Styrene-butadiene rubber (SBR) binder (CMC:PAA:SBR = 3:1:4 by weight) in deionized water with a weight ratio of 96:4, then was cast onto Al foil with an areal loading of \(3.8\mathrm{mgcm}^{-2}\) unless otherwise specified. Regarding the additive content, we have further improved the clarity of the reported methods in the revised manuscript. The information has been incorporated into the Methods section of the revised manuscript to enhance visibility and reproducibility, as suggested by the reviewer. + +<|ref|>sub_title<|/ref|><|det|>[[118, 851, 297, 869]]<|/det|> +## [Revised manuscript] + +<|ref|>text<|/ref|><|det|>[[118, 877, 238, 893]]<|/det|> +[Line 466- 470] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 880, 343]]<|/det|> +Sulfur electrode preparation and materials characterization. For the preparation of the cathode, a CNT/S composite (75 wt% Sulfur) and the binder mixture (carboxymethyl cellulose (CMC)/poly(acrylic acid) (PAA)/styrene-butadiene rubber (SBR) binder = 3/1/4 by weight) were homogenized with a weight ratio of 96:4 in deionized water. The CNT/S composite was prepared by impregnating molten sulfur into a CNT micro- ball via melt- diffusion at 120 °C. Afterward, the resulting slurry was cast on the Al foil, followed by drying under 80 °C. For coin- type and pouch- type bi- cell, single- side coated cathodes were fabricated at sulfur loadings of 3.8 and 2.25 mg cm-2, respectively. For high- energy and high- power pouch cells, double side- coated cathodes were prepared at sulfur loadings of 2.26 and 1.81 mg cm-2, respectively. + +<|ref|>text<|/ref|><|det|>[[118, 370, 240, 388]]<|/det|> +[Line 443- 444] + +<|ref|>text<|/ref|><|det|>[[117, 394, 877, 490]]<|/det|> +Electrolyte characterization. In the argon- filled glove box, the control electrolyte was prepared by dissolving 0.75 M LiFSI (provided from LG Energy Solution Ltd.) and 0.4 M LiNO3 (Sigma- Aldrich) in DME (Sigma- Aldrich). Electrolytes denoted as Al, Mg, Ca, Sr, and Li were prepared by dissolving 0.05 M of Al(OTf)3, Mg(OTf)2, Ca(OTf)2, and Sr(TFSI)2 into the control electrolyte. + +<|ref|>text<|/ref|><|det|>[[115, 516, 880, 686]]<|/det|> +(4) Lean-electrolyte lithium-sulfur cell suffers from poor reaction kinetics. It is suggested to show the electrochemical impedance analysis data that is used for showing the ohmic resistance. Besides the ohmic resistance, charge-transfer and interface impedances and the diffusion factor are important and are necessary to be reported and discussed in this research. [Suggestion] Please report the electrochemical impedance spectra data with the discussion on the ohmic, charge-transfer, and interface impedance values as well as the diffusion unit of the cell before and after cycling to tell the reaction the lean-electrolyte cell. + +<|ref|>text<|/ref|><|det|>[[117, 713, 870, 833]]<|/det|> +RESPONSE: We sincerely thank the reviewer for the valuable suggestion regarding the detailed resistance analysis of low E/S ratio Li-S batteries. Following the reviewer's recommendation, we conducted a comprehensive discussion of resistance components through electrochemical impedance spectroscopy (EIS) measurements, combined with galvanostatic intermittent titration technique (GITT) and diffusion coefficient characteristics. The detailed responses are as follows: + +<|ref|>text<|/ref|><|det|>[[117, 860, 861, 906]]<|/det|> +1. EIS analysis of Lean-electrolyte Li-S cell during discharge: Fig. R11a–d presents Nyquist plots of lean-electrolyte Li-S cells at different depths of discharge (DOD): 10%, 30%, and 80%, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 877, 240]]<|/det|> +representing the stages of sulfur dissolution, \(\mathrm{Li}_2\mathrm{S}\) nucleation, and \(\mathrm{Li}_2\mathrm{S}\) growth, respectively. The lower- frequency semicircles in the Nyquist plots demonstrate that the charge- transfer resistance \((R_{\mathrm{ct}})\) is consistently lower for the Ca electrolyte compared to the control electrolyte ( \(6.5\mathrm{mV}\) vs.5.4 \(\mathrm{mV}\) at DOD \(10\%\) , \(44.0\mathrm{mV}\) vs. \(31.0\mathrm{mV}\) at DOD \(30\%\) , and \(46.0\mathrm{mV}\) vs. \(41.3\mathrm{mV}\) at DOD \(80\%\) ). This reduction in \(R_{\mathrm{ct}}\) can be attributed to the catalytic effect of CaS on polysulfide conversion reactions. + +<|ref|>text<|/ref|><|det|>[[117, 246, 881, 340]]<|/det|> +Regarding diffusion characteristics, no significant differences were observed at a discharge rate of 0.1C. However, given that ionic diffusion at the cathode becomes more critical under higher C- rate conditions, we performed EIS analysis at 0.3C and compared the Warburg coefficients. This analysis is discussed in detail below. + +<|ref|>text<|/ref|><|det|>[[115, 368, 881, 588]]<|/det|> +2. Decoupled resistance components: To provide further elucidate the resistance behavior of lean-electrolyte Li-S batteries under working conditions, we decoupled the total overpotentials into ohmic \((\eta_{\mathrm{ohm}})\) , charge-transfer \((\eta_{\mathrm{ct}})\) and interface \((\eta_{\mathrm{int}})\) by integrating GITT data in Fig. 5c with EIS measurements. Following the method described in J. Am. Chem. Soc., 145, 16449-16457 (2023), we separated current-dependent resistances (ohmic and charge-transfer resistance) and current-independent interfacial resistance, as shown in Fig. R11e-g. The \(\eta_{\mathrm{ohm}}\) was calculated using the ohmic resistance \((R_{\mathrm{ohm}})\) from Fig. 5b and Fig. R11b-d, multiplied by the applied discharge current according to Ohm's law. This allows us to decouple the total GITT overpotential into its three components, as depicted in Fig. R12. + +<|ref|>text<|/ref|><|det|>[[117, 593, 864, 760]]<|/det|> +Under lean-electrolyte conditions, \(\mathrm{Ca}^{2 + }\) mitigates polysulfide gelation near the cathode, reducing electrolyte viscosity. According to the Stokes-Einstein equation, this leads to an increased diffusion coefficient of ionic species. Consequently, the \(\eta_{\mathrm{int}}\) , which depends on the concentration gradient of \(\mathrm{Li}^+\) and polysulfides at the electrode interface, is significantly reduced in the Ca electrolyte. Additionally, the charge-transfer overpotential \(\eta_{\mathrm{ct}}\) , which dominates the kinetic limitations in lean-electrolyte Li-S batteries, is substantially improved in the Ca electrolyte, particularly at DOD \(30\%\) , where the overpotential is highest. + +<|ref|>text<|/ref|><|det|>[[117, 789, 877, 908]]<|/det|> +3. Diffusion characteristics: Given the importance of ionic diffusion at higher discharge rates, we compared the Warburg coefficients of the control and Ca electrolytes at three DODs during 0.3C discharge. As shown in Fig. R13, the slope of the linear fit in the Warburg region represents the Warburg coefficient, which is inversely proportional to the square root of the diffusion coefficient (J. Electrochem. Soc., 127, 343 (1980)). At DOD \(80\%\) , where active LiPS is consumed and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 100, 876, 192]]<|/det|> +concentration gradients become more pronounced, the control electrolyte shows a sharp increase in the Warburg coefficient, indicating a significant drop in diffusion. In contrast, the Ca electrolyte maintains a relatively low Warburg coefficient, demonstrating improved ion transport and higher diffusion coefficients even at high DODs, likely due to reduced LiPS gelation. + +<|ref|>text<|/ref|><|det|>[[117, 221, 875, 266]]<|/det|> +A brief discussion was added in the revised manuscript and supplementary information. We reflected the figures in our revised manuscript (Figs. R11 and 12 is now Supplementary Fig. 20). + +<|ref|>image<|/ref|><|det|>[[117, 273, 880, 812]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 818, 861, 879]]<|/det|> +
Fig. R11. EIS analysis of Lean-electrolyte Li-S coin cells during 0.1C discharge. a, Discharge voltage profiles of Control and Ca electrolytes at the E/S ratio = 4 \(\mu \mathrm{L} \mathrm{mg}^{-1}\) and 0.1 C. b-d, Nyquist plot during cycling at DOD of 10% (b), 30% (c), and 80% (d). f-h, Enlarged GITT data at DOD of 10% (e), 30% (f), and 80% (g).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 97, 905, 282]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 292, 833, 327]]<|/det|> +
Fig. R12. Decoupled ohmic, interfacial, and charge transfer polarization at a, DOD \(10\%\) , b, \(30\%\) , and c, \(80\%\) .
+ +<|ref|>image<|/ref|><|det|>[[115, 350, 916, 520]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 526, 853, 562]]<|/det|> +
Fig. R13. The relationship between \(Z'\) and square root of frequency \((\omega^{-1 / 2})\) in the low-frequency region for at different densities of discharge.
+ +<|ref|>sub_title<|/ref|><|det|>[[118, 595, 297, 612]]<|/det|> +## [Revised manuscript] + +<|ref|>text<|/ref|><|det|>[[118, 620, 243, 636]]<|/det|> +[Line 334- 336] + +<|ref|>text<|/ref|><|det|>[[118, 644, 870, 688]]<|/det|> +A combined analysis of \(R_{\text{ohm}}\) and GITT (Supplementary Fig. 20) revealed a reduction in ohmic, interfacial, and charge-transfer polarization in the Ca electrolyte throughout the discharge process. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 100, 421, 118]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 147, 873, 290]]<|/det|> +In this manuscript, the authors demonstrated that Lewis acidic \(\mathrm{Ca2 + }\) additive enables lean electrolyte and high energy density LSBs. The CaS readily adsorbs LiPSs and catalyzes SRR. With the addition of the \(\mathrm{Ca2 + }\) additive, the viscosity was reduced by \(70\%\) , and the ionic conductivity was enhanced by \(30\%\) . The electrolyte also enables an exceptional energy density of 493 Wh kg- 1. I am rather interested in this paper but have some specific questions listed as follow: + +<|ref|>text<|/ref|><|det|>[[115, 320, 874, 536]]<|/det|> +RESPONSE: We sincerely appreciate the reviewer's detailed evaluation and interest in our work. The reviewer's insightful comments have been instrumental in refining our study and strengthening the clarity of our findings. In particular, we are grateful for the reviewer's constructive suggestions, which have allowed us to enhance our analysis of \(\mathrm{Ca^{2 + }}\) interactions with various species polysulfides and further investigate key mechanistic aspects such as anion effects of the additive. We have carefully revised the manuscript in accordance with the reviewer's recommendations, adding further experimental details and discussions where necessary. Below, we provide a point- by- point response addressing the reviewer's comments and outlining the modifications made in the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 565, 837, 633]]<|/det|> +1. The in situ formed CaS catalyst accelerates SRR throughout the discharging process, and is oxidized to form \(\mathrm{Ca2 + }\) in the electrolyte during charging. Why does the conversion reaction require Li2S4 and not Li2S6? + +<|ref|>text<|/ref|><|det|>[[116, 663, 860, 807]]<|/det|> +RESPONSE: We thank the reviewer for initiating this important discussion regarding the \(\mathrm{Ca^{2 + }}\) polysulfide interaction and CaS formation mechanism. While we used \(\mathrm{S_4^{2 - }}\) to represent the interaction between \(\mathrm{Ca^{2 + }}\) and polysulfides in our manuscript, our strategy based on multivalent additives has no limitation of polysulfide form. This contrasts with polysulfide-incompatible strategies, such as carbonate- based electrolytes, which highly relies on the use of short- chain polysulfides (Energy Storage Mater., 50, 197- 224 (2022)). + +<|ref|>text<|/ref|><|det|>[[118, 835, 870, 880]]<|/det|> +As shown in Fig. R14, we prepared different types of LiPS (Li2S8, Li2S6, and Li2S4) catholytes by mixing stoichiometric amounts of Li2S and S8. The addition of the \(\mathrm{Ca(OTf)_2}\) additive to these + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 100, 848, 141]]<|/det|> +catholytes induced conversion reactions, as confirmed by the reduction in polysulfide intensity observed in UV- Vis spectra. + +<|ref|>text<|/ref|><|det|>[[115, 148, 877, 365]]<|/det|> +However, under a static environment that we simulated with catholytes—unlike the dynamic state during actual battery operation—exacerbated disproportionation of polysulfides occurs, which will be further discussed in our response to Comment #3 and UV- Vis intensity peaks are observed only at \(425 \mathrm{nm}\) ( \(\mathrm{S}_4^{2 - }\) ) and \(620 \mathrm{nm}\) ( \(\mathrm{S}_3^{2 - }\) ). This makes it challenging to directly compare the favorability of the conversion reaction involving \(\mathrm{Ca}^{2 + }\) across different polysulfide species. We hypothesize that short- chain polysulfides as \(\mathrm{S}_4^{2 - }\) , with lower negative charge density at their terminal sulfur atoms and a "harder base" character compared to long- chain polysulfides (e.g., \(\mathrm{S}_6^{2 - }\) ), are more effectively stabilized by \(\mathrm{Ca}^{2 + }\) . This interaction likely facilitates the formation of \(\mathrm{Ca}^{2 + }\) - short- chain PS complexes, which are more thermodynamically favorable in the electrolyte. + +<|ref|>image<|/ref|><|det|>[[117, 391, 916, 560]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 568, 856, 600]]<|/det|> +
Fig. R14. UV-Vis spectra of various catholytes with varying polysulfide species. Filtered Control and Ca electrolytes with a, \(0.2 \mathrm{M} \mathrm{Li}_2\mathrm{S}_8\) , b, \(\mathrm{Li}_2\mathrm{S}_6\) , and c, \(\mathrm{Li}_2\mathrm{S}_4\) diluted by 0.01.
+ +<|ref|>text<|/ref|><|det|>[[118, 633, 877, 674]]<|/det|> +2. In Figure S3, please explain the reason of the higher 1st voltage plateau (>2.3 V) and provide the information about the current density. + +<|ref|>text<|/ref|><|det|>[[117, 706, 878, 823]]<|/det|> +RESPONSE: We appreciate the reviewer for this thought- provoking question. The voltage profiles in Supplementary Fig. 3 represent those of pouch cells discharged at 0.1C (0.38 mA \(\mathrm{cm}^{- 2}\) ). Regarding the 1st voltage plateau (>2.3 V), these profiles are after pre- cycling steps, so the overpotentials from various interfacial and kinetic factors obscure the direct comparison of voltage plateau among electrolytes. + +<|ref|>text<|/ref|><|det|>[[118, 854, 880, 897]]<|/det|> +In order to make the overpotential negligible and the profiles to be reflective of the thermodynamic properties, we compared the discharge voltage profiles of the electrolytes a significantly lower + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 878, 291]]<|/det|> +discharge C- rate of C/40 (Fig. R15). We observe that with stronger Lewis acidity of additives, \(1^{\mathrm{st}}\) voltage plateau decreases. This trend can be attributed to the effect of Lewis acidic cations on the solubility and stability of polysulfides in the electrolyte. Stronger Lewis acidity enhances interactions with polysulfides, reducing their chemical potential and shifting the \(1^{\mathrm{st}}\) voltage plateau to lower values. The voltage plateau has been a strong parameter of polysulfide solubility in electrolytes, where the trend holds for the UV- Vis analyses in our study. We hope this explanation clarifies the observations in Supplementary Fig. 3 and provides a deeper understanding of the factors influencing the \(1^{\mathrm{st}}\) voltage plateau. + +<|ref|>image<|/ref|><|det|>[[118, 316, 812, 500]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 507, 861, 543]]<|/det|> +
Fig. R15. Voltage profile of pouch cells at 0.025C discharge with the multivalent cation additives.
+ +<|ref|>text<|/ref|><|det|>[[118, 576, 835, 618]]<|/det|> +3. In Figure S7B, please analysis the absorbance from S62- not being observed in the UV-vis spectra of the supernatants. + +<|ref|>text<|/ref|><|det|>[[115, 649, 877, 790]]<|/det|> +RESPONSE: The authors appreciate the reviewer's detailed comments. As the reviewer mentioned, UV- Vis spectra of \(\mathrm{Li}_2\mathrm{S}_8\) solutions with metal cation additives (Supplementary Fig. 11b) exhibit peaks only at \(425\mathrm{nm}\) ( \(\mathrm{S}_4^{2 - }\) ) and \(620\mathrm{nm}\) ( \(\mathrm{S}_3^{2 - }\) ). To further validate this, we analyzed control electrolyte with \(0.2\mathrm{M}\) of different lithium polysulfide species, \(\mathrm{Li}_2\mathrm{S}_8\) , \(\mathrm{Li}_2\mathrm{S}_6\) , and \(\mathrm{Li}_2\mathrm{S}_4\) (Fig. R16a). The UV- Vis spectra of these solutions also showed peaks exclusively corresponding to \(\mathrm{S}_4^{2 - }\) and \(\mathrm{S}_3^{2 - }\) . + +<|ref|>text<|/ref|><|det|>[[115, 797, 877, 915]]<|/det|> +This phenomenon can be attributed to the solvent's donor number (DN). As reported in previous studies (J. Electrochem. Soc., 165, A4027- A4033 (2018); J. Phys. Chem. Lett., 5, 1547 (2014)), \(\mathrm{Li}^+\) ions solvated in high- DN solvents (e.g., DMSO, TEGDME) tend to stabilize polysulfides with lower charge density (soft bases, e.g., \(\mathrm{S}_8^{2 - }\) , \(\mathrm{S}_6^{2 - }\) , \(\mathrm{S}_3^{2 - }\) ), whereas \(\mathrm{Li}^+\) ions in low- DN solvents (e.g., DME) preferentially stabilize polysulfides with higher charge density (hard bases, e.g., \(\mathrm{S}_4^{2 - }\) ). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 99, 875, 290]]<|/det|> +To confirm this, we replaced the solvent in the Control and Ca electrolytes from DME to DMSO and dissolved \(0.2\mathrm{M}\) of \(\mathrm{Li}_2\mathrm{S}_8\) . As shown in Fig. R16b, peaks corresponding to soft bases such as \(\mathrm{S}_6^{2 - }\) and \(\mathrm{S}_3^{+}\) were observed in the UV- Vis spectra. Interestingly, when using DMSO as the solvent, the Ca electrolyte exhibited lower polysulfide absorbance compared to the control, although the reduction was less pronounced than in DME. This behavior suggests that in high- DN solvents like DMSO, the tendency of the solvent to dissociate Ca- polysulfide complexes weakens the ability of \(\mathrm{Ca}^{2 + }\) to form stable complexes or precipitates (e.g., CaS), thereby reducing the polysulfide- capturing effect. + +<|ref|>image<|/ref|><|det|>[[145, 317, 850, 526]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 533, 880, 580]]<|/det|> +
Fig. R16. UV-Vis spectra of various electrolytes. a, Control electrolytes with \(0.2\mathrm{M}\mathrm{Li}_2\mathrm{S}_8\) , \(\mathrm{Li}_2\mathrm{S}_6\) , and \(\mathrm{Li}_2\mathrm{S}_4\) diluted by 0.01. b, Filtered \(0.2\mathrm{M}\mathrm{Li}_2\mathrm{S}_8\) solution in Control and Ca electrolyte with solvent replaced by DMSO diluted by 0.005.
+ +<|ref|>text<|/ref|><|det|>[[115, 611, 880, 727]]<|/det|> +4. The author report that the cycle life of Li-S pouch cells was significantly extended by the addition of \(\mathrm{Ca(OTf)}_2\) . On the other hand, we find that the Ca-based pouch cell demonstrated a low specific capacity at \(\mathrm{E / S} = 8\mu \mathrm{L}\mathrm{mg} - 1\) (Figure S5C) and a high specific capacity at \(\mathrm{E / S} = 3.5\mu \mathrm{L}\) \(\mathrm{mg} - 1\) (Figure 2a) under distinct electrolyte-starved conditions. Please address these inconsistencies. + +<|ref|>text<|/ref|><|det|>[[115, 758, 872, 850]]<|/det|> +RESPONSE: The authors sincerely appreciate the reviewer for highlighting this interesting observation with their meticulous attention to detail. The observed trend aligns with the general behavior of Li- S batteries, where higher \(E / S\) ratios typically lead to result in lower specific capacities (Supplementary Fig. 1). + +<|ref|>text<|/ref|><|det|>[[115, 856, 878, 900]]<|/det|> +In conventional Li- S systems, an increase in \(E / S\) ratio reduces the polysulfide concentration in the electrolyte. In flooded electrolyte conditions, the local concentration of polysulfides near + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 860, 193]]<|/det|> +the active cathode surface decreases, which, while beneficial for long- term cyclability with slow capacity decay, results in lower sulfur utilization. When \(\mathrm{Ca^{2 + }}\) is introduced to the flooded electrolyte, its formation of \(\mathrm{Ca^{2 + }}\) - PS complexes further reduces the polysulfide concentration, exacerbating the decrease in sulfur utilization. + +<|ref|>text<|/ref|><|det|>[[115, 198, 867, 315]]<|/det|> +In contrast, at low \(E / S\) ratios, the reduction in PS concentration does not necessarily lead to lower sulfur utilization. Instead, excessively high polysulfide concentrations in low \(E / S\) environments often cause detrimental effects such as electrolyte jamming and severe shuttle effects, which interfere with efficient redox reactions. The mitigation of these issues by \(\mathrm{Ca^{2 + }}\) rather leads to an enhancement in discharge capacity. + +<|ref|>text<|/ref|><|det|>[[115, 344, 875, 659]]<|/det|> +As the underlying interfacial chemistries differ significantly depending on whether the cell is operating under flooded electrolyte (high E/S ratio) and lean electrolyte (low E/S ratio), the authors believe that the electrolyte engineering strategies must be tailored accordingly. Our research aimed at developing electrolytes for lean electrolyte and high energy- density battery systems. Given this object and in order to achieve high capacity (i.e. to utilize more amount of sulfur) at low E/S, we designed the electrolytes to exhibit following properties: (1) suppression of polysulfide gelation behavior, which is driven under lean electrolyte conditions and hinders sulfur utilization (Nat. Chem. Eng., 1, 563- 564 (2024)); (2) enhanced wettability of electrolytes to highly porous and tortuous cathodes for uniform ion and electron distribution throughout the electrode; and (3) prevention of capacity fading caused by lithium and sulfur loss due to the polysulfide shuttle effect. These design considerations reflect the primary objectives of our study and are the key factors contributing to the higher specific capacity of the \(\mathrm{Ca^{2 + }}\) electrolyte under lean electrolyte conditions compared to the control electrolyte. + +<|ref|>text<|/ref|><|det|>[[117, 688, 875, 781]]<|/det|> +5. In Figure 4E, the CaS is not completely transformed into Ca2+ at 100% charge. We believe that the Ca2+ catalyst does not enable sustainable regulation of the PS concentration in the electrolyte during long cycle. The superior cycle life of Ca(OTf)2 electrolyte is related to the OTF- anion. We recommend adding the additive of Li(OTf) electrolyte to the parallel experiment. + +<|ref|>text<|/ref|><|det|>[[117, 811, 835, 904]]<|/det|> +RESPONSE: The authors thank the reviewer for this insightful comment. In response to the reviewer's suggestion, we conducted additional experiments using Li(OTf) as an electrolyte additive to evaluate its effect. In lean electrolyte coin cell tests (Supplementary Fig. 5a), the addition of 0.1 M Li(OTf), which is the same OTF anion concentration of the Ca(OTf)2 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 99, 881, 242]]<|/det|> +electrolyte, extended the cycle life to \(\sim 80\) cycles, compared to \(\sim 60\) cycles for the control electrolyte. However, it cannot be compared with Ca electrolyte with stable operation \(>160\) cycles. Under harsher conditions in pouch cells (Fig. R17), the addition of Li(OTf) at various concentrations (0.05, 0.10, and 0.15 M) showed negligible improvement in performance compared to the reference electrolyte. These results allowed us to exclude the possibility that the superior cycle life observed in the Ca electrolyte is primarily due to the OTF anion. + +<|ref|>text<|/ref|><|det|>[[117, 270, 880, 464]]<|/det|> +As noted by the reviewer, Fig. 4e shows that \(\mathrm{Ca^{2 + }}\) is not \(100\%\) rejuvenated after charge. This observation is based on the 0.05C discharge/charge cycle. In subsequent cycles, where the charge C- rate increases, the current- dependent ohmic and charge- transfer overpotentials increase, leading to the voltage to reach the oxidation potential of \(\mathrm{CaS}\) to \(\mathrm{CaS_n}\) (2.35 V vs. \(\mathrm{Li / Li^{+}}\) ) more readily. Specifically, 2.35 V is reached at SOC of \(73\%\) , \(68\%\) , and \(65\%\) for 0.05C, 0.10C, 0.20C charge rates, respectively. Thus, in the cycles following Fig. 4e, the thermodynamic driving force for \(\mathrm{CaS}\) oxidation at the cathode increases, promoting \(\mathrm{Ca^{2 + }}\) regeneration, as confirmed by ICP- MS of cathode and UV- Vis analyses after further cycles (Supplementary Fig. 17). + +<|ref|>text<|/ref|><|det|>[[117, 492, 881, 684]]<|/det|> +Additionally, applying cycle protocols of periodically increasing the charge cutoff voltage to induce \(\mathrm{CaS}\) oxidation can further promote the rejuvenation of \(\mathrm{Ca^{2 + }}\) . To validate this hypothesis, we performed XPS analysis on cathodes after one cycle (SOC \(100\%\) in Fig. 4e) and after the \(40^{\mathrm{th}}\) charge with periodic oxidation up to 3.0 V every 10 cycles (Fig. R18). In the former case, the atomic percent of \(\mathrm{Ca}\) was 0.7, whereas in the latter, it decreased to 0.28, consistent with the rejuvenation of \(\mathrm{Ca^{2 + }}\) observed in Supplementary Fig.17a. These results demonstrate the enhanced regeneration of \(\mathrm{Ca^{2 + }}\) under higher charge rates and periodic oxidation protocols, providing further insight into the improved cycling performance of the Ca electrolyte. + +<|ref|>image<|/ref|><|det|>[[163, 720, 844, 885]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 893, 870, 912]]<|/det|> +
Supplementary Fig. 5a. Cycle performance of high sulfur loading, lean electrolyte coin cells.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[330, 120, 668, 298]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[119, 307, 875, 326]]<|/det|> +
Fig. R17. Cycle performance of pouch cells with various LiOTf additive concentrations.
+ +<|ref|>image<|/ref|><|det|>[[115, 355, 827, 553]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 563, 872, 596]]<|/det|> +
Fig. R18. Ca 2p XPS Spectra of cathodes. a, Charged cathode after 1 cycle. b, Charged cathode after 40 cycles with periodic oxidation protocol.
+ +<|ref|>text<|/ref|><|det|>[[117, 628, 874, 694]]<|/det|> +6. In Figure 6B, the FSI- anion in the \(\mathrm{Li + }\) solvate promote the formation of anion-derived SEI. In actuality, the OTF- anion also break down. It is crucial to provide the mechanism of LiF-enriched SEI formation. + +<|ref|>text<|/ref|><|det|>[[115, 725, 860, 843]]<|/det|> +RESPONSE: We sincerely appreciate the reviewer for the constructive comments. As the reviewer pointed out, the OTF- anion can undergo reduction as well as the FSI- anion. To clarify the mechanism of LiF-enriched solid electrolyte interphase (SEI) formation, we focused on the reduction tendencies of the anions, as OTF- and FSI- are the only sources contributing to the inorganic fluoride component. + +<|ref|>text<|/ref|><|det|>[[117, 849, 840, 892]]<|/det|> +In Fig. R19a, we compared the coordination number of two anions with \(\mathrm{Li^{+}}\) ions obtained by molecular dynamics (MD) simulation. Despite the higher electron donor number of OTF, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 874, 413]]<|/det|> +concentration difference between the electrolytes (0.75 M LiFSI vs. 0.05 M Ca(OTf)₂) results in a significantly higher coordination number of FSI⁻ with Li⁺ in the 1st solvation shell—over three times greater than that of OTF⁻. Additionally, as demonstrated by the density functional theory (DFT) simulation in Fig. R19b, the Lowest Unoccupied Molecular Orbital (LUMO) levels of the anions, when coordinated with Li⁺, are lower than those in their free states, indicating a higher tendency for cathodic decomposition. Specifically, the Li-FSI pair exhibits a lower LUMO level compared to the Li-OTf pair, which suggests that FSI⁻ decomposition is more likely to contribute to the formation of an F-rich SEI in the Ca electrolyte, given its higher coordination number. Furthermore, considering the relative weakness of S-F bonds (bond dissociation energy: 344 kJ mol⁻¹) in FSI⁻ compared to the stronger S-CF₃ bonds in OTF⁻ (514 kJ mol⁻¹), FSI is expected to exhibit a stronger tendency towards decomposition, leading to the formation of a more stable LiF-based SEI on the lithium metal surface (Nano-Micro Lett. 16, 35 (2024) and J. Power Sources 271, 291-297 (2014)). + +<|ref|>image<|/ref|><|det|>[[155, 446, 857, 648]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 655, 879, 720]]<|/det|> +
Fig. R19. Comparison of FSI⁻ and OTF⁻ anions with assistance of MD simulation and DFT calculations. a, Cumulative distribution functions of Li⁺ solvation with FSI⁻ and OTF⁻ anions in the Ca electrolyte. b, Highest occupied molecular orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels of the free and coordinated anions.
+ +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[255, 100, 740, 120]]<|/det|> +## Point-to-Point Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[117, 152, 822, 195]]<|/det|> +Title: Interconvertible and rejuvenated Lewis acidic electrolyte additive for lean electrolyte lithium sulfur batteries + +<|ref|>text<|/ref|><|det|>[[118, 202, 854, 245]]<|/det|> +Authors: Hannah Cho, Jinkwan Jung, Ilju Kim, Jinuk Kim, Sejin Kim, Jonghyun Hyun, Chang Hoon Lee, Hobeom Kwack, Wonsik Oh, Jinwoo Lee, and Hee- Tak Kim\* + +<|ref|>text<|/ref|><|det|>[[118, 275, 860, 367]]<|/det|> +We greatly appreciate the reviewer's comments, which have been very helpful in improving our manuscript. Below, we provide responses of the revision made in response to the feedback. Reviewer questions are highlighted in blue, and any revisions made to the manuscript are highlighted to aid the reviewers. + +<|ref|>sub_title<|/ref|><|det|>[[119, 399, 421, 416]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 447, 875, 515]]<|/det|> +The revised manuscript, "Interconvertible and Rejuvenated Lewis Acidic Electrolyte Additive for Lean Electrolyte Lithium- Sulfur Batteries," shows notable improvements over its previous version. The authors provide additional details to support the effectiveness of the calcium additive. + +<|ref|>text<|/ref|><|det|>[[118, 545, 876, 637]]<|/det|> +RESPONSE: We sincerely appreciate the reviewer's constructive and thoughtful questions. Also, we apologize that our previous revision may not have fully clarified the intent and scope of our hypothesis. We would like to take this opportunity to more precisely articulate the conceptual framework of our study and address the reviewer's concerns. + +<|ref|>text<|/ref|><|det|>[[118, 667, 866, 810]]<|/det|> +However, I remain unconvinced that their hypothesis—"the strong Lewis acidity of \(\mathrm{Ca^{2 + }}\) readily converts LiPSs into CaS and \(\mathrm{S_8}\) , preventing electrolyte jamming, polysulfide shuttle, and lithium corrosion"—is robustly supported by the presented data. Typically, if this hypothesis holds, the cycling performance of Li/S cells should correlate with the acidity of metal ions. Yet, the authors exclude three key data points (other metal ions) for unrelated reasons, leaving \(\mathrm{Ca^{2 + }}\) as the only additive for comparison, which weakens the case for a clear trend. + +<|ref|>text<|/ref|><|det|>[[118, 840, 855, 907]]<|/det|> +RESPONSE: We sincerely appreciate the reviewer for highlighting the unclear point in our previous manuscript. The point we want to deliver is the complex of strong Lewis acidic metal cations and weak Lewis basic polysulfide anions is decomposed into metal sulfide and sulfur as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 99, 868, 167]]<|/det|> +demonstrated in Supplementary Fig. 10. This tendency becomes strong as the Lewis acidity increases, which is supported by the decrease of LiPS solubility with increasing the Lewis acidity (Fig. 2a and b in the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[117, 173, 870, 389]]<|/det|> +While a systematic comparison across multiple cations would ideally clarify the correlation between the Lewis acidity and cycling performance, the instability of the electrolytes with stronger Lewis acidic cations (e.g., \(\mathrm{Mg^{2 + }}\) , \(\mathrm{Al^{3 + }}\) ) complicates such an analysis. As suggested by the reviewer, we explored alternative electrolytes with higher stability and found that diglyme- based electrolytes are stable with \(\mathrm{Mg^{2 + }}\) , \(\mathrm{Al^{3 + }}\) , and \(\mathrm{Ca^{2 + }}\) . The diglyme- based electrolyte exhibited performance trends similar to those of the DME- based electrolyte (Fig. R1): only the \(\mathrm{Ca^{2 + }}\) - based system showed a significantly enhanced electrochemical performance. This suggests that the relatively poor performance observed with \(\mathrm{Mg^{2 + }}\) and \(\mathrm{Al^{3 + }}\) compared to \(\mathrm{Ca^{2 + }}\) is not solely attributable to electrolyte degradation. + +<|ref|>text<|/ref|><|det|>[[117, 394, 877, 633]]<|/det|> +According to previous studies on sparingly solvating electrolytes, the redox kinetics of sulfur species become markedly sluggish when polysulfide solubility falls below a critical threshold. Among various fluorinated diluents, those with excessively low LiPS solubility have been reported to result in unstable cell performance (Adv. Energy Mater., 15, 2403828 (2024) and Proc. Natl. Acad. Sci., 120, e2301260120 (2023)). Furthermore, high volume percent of diluents has been shown to aggravate kinetic limitations and reduce overall cell performance (J. Am. Chem. Soc., 21, 14754–14764 (2024) and Angew. Chem. Int. Ed., 62, e202309968 (2023)). These findings collectively suggest the existence of an optimal polysulfide- solvating power, where moderately solvating electrolytes are proposed to achieve a balance between suppressing the polysulfide shuttle and enabling efficient redox reactions. + +<|ref|>text<|/ref|><|det|>[[117, 638, 872, 831]]<|/det|> +In line with previous literature, our experimental results (Fig. R2) show that under lean electrolyte conditions, Li- S cells with only 20 vol% TTE exhibit significantly increased discharge overpotentials compared to those with single- solvent DME electrolyte, to the extent that the second discharge plateau is completely suppressed. Similarly, the poor performance of Al and Mg electrolytes is not solely due to electrolyte instability, but also to the suppressed polysulfide solubility. In contrast, the Ca electrolyte appears to provide an appropriate level of polysulfide solubility—analogous to an optimal fluorination degree or diluent fraction in moderately solvating electrolytes—which allows it to achieve excellent cycling stability. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 97, 880, 293]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 305, 832, 357]]<|/det|> +
Fig. R1 | Electrochemical performance of coin cells \((E / S = 5 \mu \mathrm{L} \mathrm{mg}^{-1})\) with 0.75 M LiFSI/0.40 M LiNO3/0.05 M M(OH)2. (a) Cycle performance of diglyme-based electrolyte. (b) Voltage profile of coin cells with diglyme-based electrolytes at 0.2C discharge.
+ +<|ref|>image<|/ref|><|det|>[[128, 387, 864, 599]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 608, 852, 659]]<|/det|> +
Fig. R1 | Cycle performance of coin cells \((E / S = 5 \mu \mathrm{L} \mathrm{mg}^{-1})\) with 0.75 M LiFSI/0.40 M LiNO3 in DME or DME:TTE (5:1). a, Voltage profile of cells at 0.05C discharge/charge. b, Cycle performance.
+ +<|ref|>text<|/ref|><|det|>[[117, 690, 875, 908]]<|/det|> +We appreciate the reviewers' insight, which made us recognize that our previous manuscript may have unintentionally conveyed the misleading notion that cations with stronger Lewis acidity universally enhance cycling performance and that Lewis acidity is the primary determinant of lithium sulfur battery performance. In reality, cell performance is influenced by multiple interrelated factors, including polysulfide regulation, redox kinetics, ion transport, and electrolyte stability. We have carefully revised our discussion to change any statements that might imply a direct correlation between Lewis acidity and cycling stability, in order to avoid potential misinterpretation. To enhance clarity, we explained the destabilization of polysulfide (PS) anions by using strongly Lewis acidic cations based on the Hard- Soft Acid- Base theory, providing a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 98, 875, 192]]<|/det|> +theoretical rationale for the decomposition of PS anions into metal sulfides and elemental sulfur—an effect clearly observed for various multivalent cations (Supplementary Fig. 10; \(\mathrm{Ca}^{2 + }\) , \(\mathrm{Al}^{3 + }\) , \(\mathrm{Mg}^{2 + }\) , and \(\mathrm{Sr}^{2 + }\) ). The instability of electrolytes containing \(\mathrm{Al}^{3 + }\) and \(\mathrm{Mg}^{2 + }\) , which we believe is useful information for readers, is collectively discussed in the Supplementary Fig. 6. + +<|ref|>sub_title<|/ref|><|det|>[[118, 222, 298, 240]]<|/det|> +## [Revised manuscript] + +<|ref|>text<|/ref|><|det|>[[118, 247, 240, 264]]<|/det|> +[Line 153- 157] + +<|ref|>text<|/ref|><|det|>[[117, 271, 880, 390]]<|/det|> +To investigate whether Lewis acidic metal cations can suppress the dissolution of polysulfides (PS) into the electrolyte during cell operation, we introduced these cations into the electrolyte and evaluated the relative PS concentration in lean electrolyte coin cells \((E / S = 4 \mu \mathrm{L} \mathrm{mg}^{- 1})\) using UV- vis spectra after discharging the cells to 2.1 V (Fig. 3a and Supplementary Fig. 4). + +<|ref|>text<|/ref|><|det|>[[118, 418, 240, 436]]<|/det|> +[Line 223- 226] + +<|ref|>text<|/ref|><|det|>[[117, 443, 872, 537]]<|/det|> +The disproportionation likely originates from the instability of PSs highly coordinated to \(\mathrm{Ca}^{2 + }\) , as complexes formed between strong Lewis acids (multivalent metal cations) and weak Lewis bases (PSs) are thermodynamically unstable. The increased precipitation observed at higher PS concentration (Supplementary Fig. 11) supports this consideration. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[191, 103, 812, 550]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 562, 881, 662]]<|/det|> +
Supplementary Fig. 1 | Compatibility of Lewis acidic cation additives in the electrolytes (a-b) Optical images of the control and metal additive (0.05 M)-containing electrolytes after standing for 7 days. X-ray diffraction (XRD) patterns of the precipitates in the (c) Mg and (d) Sr electrolytes, respectively. (e) Pouch-type Li-S bi-cell ( \(E / S = 3.5 \mu \mathrm{L} \mathrm{mg}^{-1}\) ) cycling with the control and multivalent metal cation (Al \(^{3 + }\) , Mg \(^{2 + }\) , Ca \(^{2 + }\) , Sr \(^{2 + }\) ) additive-containing electrolytes.
+ +<|ref|>text<|/ref|><|det|>[[117, 671, 882, 810]]<|/det|> +Note) After being left for several days, gelation occurred in the Al electrolyte, while precipitates appeared in the Mg and Sr electrolytes. The gel- like flocculent precipitates are decomposed products from dimethoxvethane (DME) induced by \(\mathrm{Al}^{3 + }\) ion \(^{3}\) . The \(\mathrm{Mg(OTf)_2}\) precipitate in the Mg electrolyte, indicates the low solubility of \(\mathrm{Mg(OTf)_2}\) in the control electrolyte. The formation of \(\mathrm{Sr(NO_3)_2}\) in the Sr electrolyte is attributed to a detrimental Lewis acid- base reaction with \(\mathrm{NO_3}^{2 - }\) . Given that \(\mathrm{LiNO_3}\) is an indispensable component for mitigating the shuttle effect, \(\mathrm{Sr}^{2 + }\) cations are inadequate additives for LSB electrolytes. Similar phenomena occurred when Al, Mg, and Sr salts were added to the commonly- used LiTFSI- DOL- DME electrolyte. + +<|ref|>text<|/ref|><|det|>[[118, 850, 870, 892]]<|/det|> +As seen in Supplementary Fig. 6e, except for the Ca electrolyte (control electrolyte with 0.05 M \(\mathrm{Ca(OTf)_2}\) ), electrolytes with the other cations demonstrated inferior cycling + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 100, 828, 143]]<|/det|> +stability than the control electrolyte. This may be due to the extremely low solubility of polysulfides and/or their incompatibility with the electrolyte components. + +<|ref|>text<|/ref|><|det|>[[118, 171, 870, 266]]<|/det|> +They argue that the strong Lewis acidity of \(\mathrm{Mg}^{2 + }\) and \(\mathrm{Al}^{3 + }\) triggers polymerization of DOL and/or side reactions with DME, rendering the electrolyte unusable. While DOL gelation can occur even under mildly acidic conditions, this claim seems inconsistent with their ability to obtain UV- vis results and decent cycling performance for Li/S cells using \(\mathrm{Al}^{3 + }\) and \(\mathrm{Mg}^{2 + }\) additives. + +<|ref|>text<|/ref|><|det|>[[118, 294, 877, 388]]<|/det|> +RESPONSE: We conducted experiments using \(\mathrm{Al}^{3 + }\) , \(\mathrm{Mg}^{2 + }\) , and \(\mathrm{Sr}^{2 + }\) additives to explore how multivalent cations with different Lewis acidities influence polysulfide solubility. In the catholyte experiments shown in Fig. 3a of the manuscript, DME was used as the sole solvent, without DOL, to focus specifically on polysulfide- cation interactions. + +<|ref|>text<|/ref|><|det|>[[118, 394, 875, 511]]<|/det|> +In the case of the Al- containing electrolyte, gel- like flocculent precipitates were observed after several days, which is in line with previous observations reported in the literature (ACS Appl. Mater. Interfaces, 16, 47581- 47589 (2024)). Similarly, for the Mg- containing electrolyte, the solution gradually became opaque and \(\mathrm{Mg(OTf)_2}\) precipitates appeared after a few days (Supplementary Fig. 7). + +<|ref|>text<|/ref|><|det|>[[118, 516, 875, 633]]<|/det|> +We acknowledge that such electrolyte changes can occur during polysulfide solubility measurement or cycling stability test; however, the fact that these changes were only observed after a certain period suggests that, at least during polysulfide solubility measurements and the early stages of cycling, the primary effect was likely dominated by polysulfide- cation interactions rather than electrolyte decomposition. + +<|ref|>text<|/ref|><|det|>[[118, 663, 876, 732]]<|/det|> +If solvent reactivity, particularly with DOL, is a concern, why didn't the authors test alternative solvents—such as DMSO, ionic liquids, or certain glymes—that are less reactive with Lewis acids and commonly used in Li- S battery electrolytes to better validate the acidity- performance trend? + +<|ref|>text<|/ref|><|det|>[[118, 760, 864, 904]]<|/det|> +RESPONSE: We sincerely appreciate the reviewer's valuable suggestion, which offered a perspective we had not previously considered. In response to the reviewer's suggestion, we conducted additional experiments using alternative solvents: DMSO, an ionic liquid, and diethylene glycol dimethoxythane (diglyme). In the DMSO- based electrolyte, the addition of 0.05 M \(\mathrm{Al}^{3 + }\) and \(\mathrm{Mg}^{2 + }\) resulted in the formation of opaque solutions, both in the absence (Fig. R3a) and presence (Fig. R3b) of 0.2 M \(\mathrm{Li}_2\mathrm{S}_8\) , precluding reliable UV- Vis analysis. Notably, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 98, 872, 289]]<|/det|> +unlike in the DME- based electrolytes, no solid precipitates were observed. This suggests a shift in dominant interactions from cation- polysulfide toward cation- solvent coordination. This suppresses the desired mechanism of solid metal sulfide formation, highlighting that high- donor- number solvents alter the interaction mechanism rather than validating acidity effects. A similar outcome was observed when using an ionic liquid (1- Butyl- 1- methyl pyrrolidinium bis(fluorosulfonyl)imide) as the electrolyte solvent: the addition of \(0.05\mathrm{M}\mathrm{Al}^{3 + }\) or \(\mathrm{Mg^{2 + }}\) resulted in opaque solutions (Fig. R3c), likely due to limited solubility or side reactions with the solvent. + +<|ref|>text<|/ref|><|det|>[[115, 295, 880, 658]]<|/det|> +In contrast, diglyme- based electrolytes did not exhibit any visible signs of side reactions or solution opaqueness upon the addition of \(0.05\mathrm{M}\mathrm{Al}^{3 + }\) , \(\mathrm{Mg^{2 + }}\) , or \(\mathrm{Ca^{2 + }}\) (Fig. R3d). \(\mathrm{Sr^{2 + }}\) remained poorly soluble, consistent with previous observations in DME. As discussed above, we evaluated the electrochemical performance of lean- electrolyte Li- S coin cells using diglyme- based electrolytes with metal additives (Control, Al, Mg, Ca, Sr) (Fig. R1). Consistent with our findings in DME- based electrolytes, the Ca- containing diglyme- based electrolyte exhibited significantly enhanced electrochemical performance, whereas the Control, Al, Mg, and Sr electrolytes displayed pronounced overpotentials and substantially reduced discharge capacities at \(0.2\mathrm{C}\) after precycling. As discussed earlier (page 2), electrochemical performance deteriorates when polysulfide solubility of the electrolyte falls below a critical threshold. This explains the relatively poor electrochemical performance of the Mg and Al electrolytes when solvent stability was ensured, as excessively low polysulfide solubility hindered efficient redox reactions. These results reinforce that the performance enhancement observed with \(\mathrm{Ca^{2 + }}\) is not solely due to the absence of side reactions with the solvent, but rather a result of the multiple effects demonstrated throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 664, 875, 905]]<|/det|> +Additionally, lean electrolyte coin cells assembled with DMSO and ionic liquid- based electrolytes (Control, Al, Mg, Ca, Sr) exhibited immediate overpotentials upon discharge and failed to operate properly (Fig. R4). Compared to DME, DMSO and ionic liquid showed poor wettability, high viscosity, and insufficient electrolyte penetration into the porous cathode structure, rendering them practically incompatible with our intended low \(E / S\) ratio electrolyte design and leading to fundamentally different operative mechanisms. In short, although alternative solvents may indeed mitigate solvent decomposition associated with strong Lewis acids, the resulting fundamental changes to solvation structure and interaction mechanisms prevent a direct comparison to our DME- based system and, consequently, do not allow for a fair validation of our core hypothesis. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 130, 872, 377]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 384, 872, 450]]<|/det|> +
Fig. R3 | Optical images of 0.75 M LiFSI/0.40 M electrolytes with 0.05 M additives after dissolution. Electrolytes prepared using various solvents: (a) DMSO, (b) catholytes (0.2 M Li₂S₈) in DMSO, (c) 1-Methyl-1-Butylpyrrolidinium bis(fluorosulfonyl)imide (Pyr₁₄FSI), and (d) Diethylene glycol dimethyl ether (DEGDME).
+ +<|ref|>image<|/ref|><|det|>[[328, 483, 670, 670]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 678, 812, 714]]<|/det|> +
Fig. R4 | Voltage profile of coin cells \((E / S = 5 \mu \mathrm{L} \mathrm{mg}^{-1})\) with 0.75 M LiFSI/0.40 M LiNO₃/0.05 M M(OTf) in DMSO.
+ +<|ref|>text<|/ref|><|det|>[[118, 750, 861, 794]]<|/det|> +We hope this explanation clarifies our rationale for \(\mathrm{Ca}^{2 + }\) , and addresses the reviewer's concerns regarding the correlation between Lewis acidity and electrochemical performance. + +<|ref|>text<|/ref|><|det|>[[118, 825, 297, 864]]<|/det|> +[Revised manuscript] [Line 144- 146] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 98, 845, 144]]<|/det|> +Ca- S batteries22,23 exhibit lower PS concentration in the electrolytes during cell operation compared to LSBs due to the strong tendency to form ionic Ca- S bond. + +<|ref|>text<|/ref|><|det|>[[118, 174, 238, 191]]<|/det|> +[Line 162- 165] + +<|ref|>text<|/ref|><|det|>[[118, 198, 870, 303]]<|/det|> +Although these multivalent metal cations effectively suppress PS solubility, these do not improve cell performance except \(\mathrm{Ca}^{2 + }\) , likely attributed to the extremely low solubility of \(\mathrm{PSs}^{28 - 31}\) , gelation32, and/or precipitation observed in the corresponding electrolytes (Supplementary Fig. 6). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 100, 421, 117]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 137, 880, 192]]<|/det|> +The authors have replied to my comments and made acceptable revision. Most of my concerns and queries have been addressed. Thus, I would suggest the consideration of acceptance of the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 217, 866, 285]]<|/det|> +RESPONSE: We express our sincere gratitude to Reviewer#2 for conducting a thorough review of our revised manuscript. We are pleased to receive positive feedback from Reviewer #2 and appreciate their recommendation to publication. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 100, 421, 117]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 148, 790, 191]]<|/det|> +I think I like the author's revision and would be happy to recommend publication of the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 221, 866, 286]]<|/det|> +RESPONSE: We deeply appreciate Reviewer #3's insightful assessment of our revised manuscript. Their thoughtful remarks and favorable evaluation have been both encouraging and instrumental in guiding our work toward potential publication. + +<--- Page Split ---> diff --git a/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/images_list.json b/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8f38a14fa25040287869dd3b18e521c4f170b9df --- /dev/null +++ b/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,688 @@ + +# nature portfolio + +Peer Review File + +Mycobacterium tuberculosis Cough Aerosol Culture Status Associates with Host Characteristics and Inflammatory Profiles + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +This is a very interesting paper, looking to identify markers of infectiousness of individuals with TB. The study is centred around the cough aerosol detection mechanism, and explores it's validity and potential markers. + +While this is interesting data, which should be certainly be published and feed into the wider discourse around Mtb transmission, there are a number of issues which make me unsure if the claims in the title, abstract and certain section headings are backed up sufficiently by the data. Some of these are clarifications and could be fine, others have to do with the study design and analytical approach, which may be harder to overcome. + +A major issue is lack of a control group of HH contacts, which would help to understand how the \(53\%\) IGRA+ in the CAC- population should be interpreted. This means that the findings can reflect on markers for 'higher' infectiousness, as suggested by CASS positivity. + +A key gap in the current methods is a lack of description of how the shift from 142 participants with TB to including 55 index cases in the HH contact study. It is mentioned in the results section, but is not described at all. Similarly, \(n = 58\) index cases were included in the transcriptomics, but their selection is not described. That needs to be clarified (see more detailed comments below). + +The analysis approach for the predictive models is a simple forward selection of variables. In the context of this well studied area, this seems too uninformed. The consequence is some strange findings which the authors do not pick up on. E.g. Why would MUAC be predictive but BMI would not? How should we interpret CASS predictive model mean where a dichotomised age variable is given equal importance as the sole bacteriological indicator (Xpert CT threshold)? While an uninformed approach to the cytokine/transcriptomics analysis seems OK given its novelty, this is not the case for associations for transmission or infectiousness, and this should be addressed, e.g. by discussing a conceptual framework, and exploring different predictive models with a- priori choices. + +The more conceptual issue is what space of infectiousness this paper addresses. The title, abstract and body text shift between scope. For example, the title and abstract reflect on 'TB infectiousness', suggesting it is about individuals that are either infectious or not. As clarified later in the abstract, the authors actually focus on a differentiation between more or less infectious individuals, based on CASS. They show that CASS+ individuals are likely more infectious with a nested household contact study (which is not a new finding), but there is no control group, so no statement about a binomial infectious yes/no status. For the transcriptomics they then look in a subgroup (which is not defined, see above), and find a number of associations with CASS+. I would agree that this provides data to 'suggest host inflammatory signatures are associated with Mtb aerosolization independent of bacillary load and cavitary lung disease.', as stated in the discussion. But what it does not show is 'Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles', which is the paper title, and as such much too broad. I think the authors should be more clear, and e.g. change the title, and any + +<--- Page Split ---> + +other statements regarding 'infectiousness' as a whole to reflect the more narrow scope. + +I have provided extensive detailed comments below, which hopefully will help improve the paper when the data is published here or in another journal. + +## Methods: + +While I understand why ignored trace+/culture- (given the low chance of being CASS pos), it would be good to state this explicitly, and state how the authors interpreted this group. (TB or not TB)? + +There is some reporting of results for BMI vs MUAC in the methods, this should be moved to the results. + +L314- 318 is results I think, should move there. + +It is not obvious from the methods that the HH contacts came from a subset \((n = 55,1352)\) of enrolled participants from the total population \((n = 142)\) . I did not see it in I185- I189), nor is it mentioned in I142- I144. Firstly, this should be made clear more clear. Secondly the rationale and method for this selection should be described explicitly (e.g. funding restrictions and random draw?). There is a similar selection for the host transcriptomic work (going down to \(n = 59\) index patients), which needs to be similarly explained. + +## RESULTS + +335: It seems odd that all of the participants were cough positive, as a percentage came from community screening. Given the difference in population and expected disease severity between ACF and PCF populations, these two populations should be described more in the text and supp materials. If the \(100\%\) cough positive holds, it is something to discuss, as it goes against most modern TB prevalence surveys where about \(50\%\) were found to be cough negative. + +Table 1: The MUAC result is odd (i.e. a higher MUAC means more \(\mathsf{CASS + }\) ). It seems counterintuitive, and the lack of an association with BMI makes me concerned the MUAC results are less reliable. The BMI/MUAC discrepancy should be discussed. + +Table 2: I am not clear what the OR and p- values are meant to show here. For the index case characteristics, those seem a near 1- 2- 1 repeat of table 1? I think those could be dropped, especially from the main body text. For e.g. the number of contacts per case - I think this is just a chi- square, but that is not the relevant finding. What we would like to know is whether the distribution of HH contacts is different by CAC+ and CAC-, which is currently unclear. + +What were reasons for missing QFT (N goes from 143 to 127)? These should be reported. + +Table 3: The results are quite stark, but not sure how superior the final model is. It makes sense that after one good measure of bacteriological burden is included in the model, the others are no longer adding enough value to be included. E.g. smear and cavitation seem to be quite useful explanatory/predictive variables by themselves. A simple forward stepwise modelling approach will not + +<--- Page Split ---> + +highlight those limitations. Given what we already know about infectiousness, this type of analysis would be better served with a formal DAG or at least conceptual framework, and then working through the various options or models. I suggest the authors explore this wider, and thereby enrich the insights that can be gained from the data. + +While the AUC for the scoring system for predicting \(\mathsf{CAC + } / -\) is high, I don't quite understand the results from Sup table 1. It seems to suggest that age and Xpert CT are equally valuable (both 7 'points')? But what does the model/score mean if the sole bacteriological indicator is removed? Are the authors suggesting that we could decide on \(\mathsf{CAC + } / -\) by age, CRP and MUAC alone? Could they provide an indication of how much value each individual characteristic adds, and how the model works if Xpert CT is not available. Could any other bacteriological indicator be switched in? I'd be surprised if the model functioned without a bacteriological indicator, and also not sure about the biological logic that would remain. It is also not clear if this predictive model is solely applicable for people who have bacteriologically positive TB? If so, that should be made clear. + +The variation in association pattern of the different cytokines is a bit strange. Would one not expect them to be elevated across the various indicators, also given that e.g. CT threshold and cavitation were themselves associated with CAC? The lack of stability makes me a bit concerned. The results are what they are, but potential explanations (including random noise across many comparisons that could affect the threshold for interpretation of p- values). + +## DISCUSSION + +L455- 457: these are results, and should be moved there. On a broader note, it would be good to place those observations in the context of the ongoing discussions around subclinical TB (see previous comment re cough positivity). + +L462: the statement about 'body mass' is strange, as BMI was not associated, but MUAC was. As mentioned before, this discrepancy needs discussion, and the statement should be adjusted accordingly. + +L473: this only interprets one of the cytokine findings, but ignored the conflicting results in the actual section (see above), where some cytokines were associated for one indicator, but not the other. Do the authors assume only 1 indicator is valid? If so, that is a stretch. If not, the discrepancies need to be addressed. + +L535: the suggestion that interventions (i.e. treatment) should target the most infectious is a bit strange. This approach was tried with the development of DOTS policies, where symptomatic smear positive individuals were targeted through PCF and 6m therapy. While saving lives, it has not interrupted transmission as expected, and it is not clear to me why this would work now? Shouldn't Identifying and treating all infectious individuals be the minimum target for all high burden countries, regardless of how infectious they are at the time of diagnosis? + +Furthermore, infectiousness is not static, and will likely vary over time. Finally, given the high Number Needed to Test to identify any person with low or high infectious disease, the cost of treatment is really not the limiting factor. It would be helpful if the authors reflected a bit more on this (also in the + +<--- Page Split ---> + +introduction). + +Minor pointsRef 33, 34 and 58 are the same I believe. Would be good to recheck references and make sure in order. + +Table 1: category 'Enrolled thru prevalence survey' – not appropriate language for scientific paper and not reflected in main text. Suggest something along lines of 'ACF- enrolled', as this is how it is described in methods. + +Table 3: the unit for Age is not given. From the OR I suspect it is year of age, but this should be made clear. Also note this assumes a linear association across the entire age range, which is unlikely to be true given what we know about age- dependent population ARI. This should be discussed. + +The section titles on 1397 and 1409 are phrased as interpretation rather than reporting of results. These should be adjusted. In addition, the last sentences in each of these sections is interpretation rather than result, and should be removed or put in discussion. + +Reviewer #2 (Remarks to the Author): + +The study "Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles" stands out for addressing a significant gap in tuberculosis research, focusing on individual infectiousness and biomarkers. It employs a prospective longitudinal study design, examining treatment- naive pulmonary TB patients in Nairobi, thereby providing valuable insights in a high TB burden setting. Methodological innovations, such as using the Cough Aerosol Sampling System (CASS) for measuring Mycobacterium tuberculosis aerosolization, the evaluation of sputum cytokine, and assessing household contacts through IGRA testing, add important epidemiological and molecular dimensions and adds novel knowledge and tools to predict Mtb transmission. Overall, the manuscript was well written. The incorporation of suggested improvements would enhance the paper's quality and ensure that concerns have been adequately addressed. + +#1 Introduction: The introduction section is well- written and effectively frames the context of TB infectiousness to its clinical and immunological aspects. It successfully outlines the importance of understanding individual variations in TB transmission and reviews relevant literature, thus situating the study within the broader field of TB research. I have no suggestions for improvement in this section. + +#2 Methods: The methods section is well- structured and thorough. However, consider breaking down the dense text into smaller paragraphs to improve readability (i.e. break the paragraph in line 262. "We assessed....". In addition: + +#2.1 – Methods (Line 203-204): The study does not address the issue of drug- resistant TB. On lines 203-204, the study mentions classifying rifampicin resistance as "positive," "negative," or "indeterminate," + +<--- Page Split ---> + +but this is not further elaborated in the text. I recommend including these data in the results and tables, even if \(100\%\) were susceptible, to provide a complete picture of the resistance profile among the study participants. + +#2.2 - Results (lines 222-228): It would be beneficial to provide a rationale for the decision to assess cytokines in sputum instead of blood; as well as the selection of the specific three cytokines studied. This is particularly important for readers who may have less experience in the field. Including one or two lines to explain these choices would greatly aid in comprehending the significance and implications of these methodological decisions. + +#2.3 - Methods (Data analysis section): To enhance reproducibility, I recommend adding a table in the supplementary material section. This table should list the names of the R packages used, their respective versions, and references. + +#3 Results: The results section provides a detailed and thorough presentation of the study's findings and analyses. The section appears to be well- organized and structured, with clear descriptions of the methods used and the outcomes observed. The use of tables, figures, and numerical values enhances the clarity of the presented results. However, there are a few areas where the clarity and objectivity could be further improved: + +#3.1 Results (lines 350-368): Considering that age emerged as a significant variable in the mixed methods bivariate & multivariable analysis, and the low median age reported, it is essential to have information on how many HHCs were children or adolescents. Furthermore, this aspect of age, including the distinction between adult and non- adult contacts, should be highlighted in the discussion section. + +#3.2 Results (lines 392-394): Please provide the sensitivity and specificity values of the ROC curve, with confident intervals. + +#3.3. Results (lines 397-437): In lines 397-437, all paragraphs finish with a phrase with the same structure that starts with "Together, these data suggest". I recommend rewriting some of them and evaluating if it is necessary. For example, I do not think that the phrase in lines 436-437 is fundamental for the text. + +#3.4. Results (Figures): The figures in the manuscript, particularly Figures 1c and d, Figure 2, and Supplementary Figure 4, need to be improved for better comprehension. A key enhancement is to include the legend for colours and shapes directly on the figure itself, rather than solely in the written legend. The absence of this information on the figures themselves can hinder interpretation and understanding. Providing these details directly on the figures would facilitate a more immediate and clear comprehension of the data being presented, especially for readers who might be quickly scanning through the figure. + +#4 Discussion: The discussion section demonstrates a good quality of scientific communication, with a thorough examination of the study's results and their implications. The section effectively contextualizes the findings within the existing literature and provides a balanced interpretation of the results. The limitations are acknowledged, and their potential impact on the study's conclusions is addressed. Minor comments: + +#4.1. It would be beneficial to discuss in more detail the age of the Household Contacts (HHCs), as well as the rationale behind using sputum to assess biomarkers. These discussions could provide deeper insights into the study's findings and their implications. + +#4.2 (lines 447-500): Breaking up the paragraphs could enhance the readability and clarity of + +<--- Page Split ---> + +information, making it easier for readers to digest and understand the key points being conveyed. + +Reviewer #3 (Remarks to the Author): + +The study is very interesting and opens new ways for understanding TB pathogenesis and proposing clinical management. Based on the reported findings and prior studies, cough aerosol cultures are superior to sputum smear analysis in predicting Mtb transmission events and are likely the best estimators of TB infectiousness. + +Few comments: + +Figure 1A: is any possibility of evaluating the correlation of WHITE BLOOD CELLS components as Lymphocytes, monocytes, or neutrophils with CAC?. Indeed interesting correlations were found in the past using different approaches (La Manna, 2017, PMID: 28208160; Chedid, 2020, PMID: 32920230; ). Moreover, it would be interesting to evaluate if there is an association between CAC score and platelets (La Manna, 2022 PMID: 35338775) + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +This is a very interesting paper, looking to identify markers of infectiousness of individuals with TB. The study is centered around the cough aerosol detection mechanism and explores its validity and potential markers. + +While this is interesting data, which should be certainly be published and feed into the wider discourse around Mtb transmission, there are a number of issues which make me unsure if the claims in the title, abstract and certain section headings are backed up sufficiently by the data. Some of these are clarifications and could be fine, others have to do with the study design and analytical approach, which may be harder to overcome. + +Response: We thank the reviewer for these positive comments and attempt to address all concerns in the replies below. + +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\* + +A major issue is lack of a control group of HH contacts, which would help to understand how the \(53\%\) IGRA+ in the CAC- population should be interpreted. This means that the findings can reflect on markers for 'higher' infectiousness, as suggested by CASS positivity. + +Response: We agree that providing a control group for the HH contacts is important to make population level claims regarding infectiousness. To address this concern, we include new data from two cohorts to estimate the frequency of QFT- positive tests among Nairobi residents without a known recent TB exposure (the "background" frequency of Mtb infection based on QFT result). For both cohorts, the rate of IGRA positivity was \(51\%\) and similar to rate of the household contacts of CASS- negative index cases \((54\%)\) . All of these rates are lower than the household contacts of CASS- positive index cases \((88\%)\) . These data suggest that CASS- positive pulmonary TB cases have a higher degree of infectiousness compared to those who are CASS- negative with evidence from multiple control groups. + +The following language has been added to the Methods section: + +"We estimated the frequency of positive interferon- gamma release assays in Nairobi residents who were not known to have active TB or recent close contact to a person with active pulmonary TB. Participants were enrolled through two studies. As part of a study of cough analysis for TB detection (38), we recruited adult outpatients \((n = 45)\) from the same TB and respiratory clinics as TBAIT participants with TB (described above) who were identified through passive case finding and presented with cough. All participants underwent sputum GeneXpert testing and chest X- rays to exclude pulmonary TB. Additionally, we report results from a study to evaluate treatment responses during isoniazid preventive therapy (39). From December 2019 to December 2020, we recruited adults with \((n = 121)\) and without \((n = 122)\) HIV from three HIV prevention and care centers in Nairobi. We assessed for TB using the WHO four- symptom screen, followed by sputum GeneXpert and chest X- rays among those with one or more symptoms. To calculate prevalence of QFT positive tests, we excluded indeterminate results." + +We added the following to the Results section: + +"To establish the background prevalence of QFT positive results in Nairobi residents, we evaluated QFT status in adult outpatients who presented for health care due to cough \((n = 45\) , median age 39 years (IQR, 34- 45)) and to HIV prevention and care centers \((n = 121\) PLWH; \(n = 122\) without HIV; overall median age 36 years (IQR, 28- 44). After excluding indeterminate results \((n = 2\) and \(n = 34\) , respectively), we found that the prevalence of QFT- positive results was, \(51\%\) \((n = 22)\) and \(51\%\) \((n = 121)\) , respectively. Among the 45 persons who presented to health care with a cough, QFT status did not differ by HIV status (PLWH = 17, + +<--- Page Split ---> + +p- value 0.66). In participants recruited at HIV care centers, QFT results differed by HIV status: \(43\%\) of PLWH (48 of 111) and \(60\%\) of persons without HIV (59 of 98) (p- value 0.01) were QFT positive. The estimated Nairobi background prevalence of QFT test positivity did not differ from contacts of cough aerosol culture- negative participants (p- value 0.33) but was significantly lower than contacts of cough aerosol culture- positive participants (p- value \(< 0.001\) )." + +A key gap in the current methods is a lack of description of how the shift from 142 participants with TB to including 55 index cases in the HH contact study. It is mentioned in the results section, but is not described at all. + +Response: Thank you for highlighting this concern. We added the following clarifying statements in the Results Section, + +"We next evaluated IGRA results in household contacts to determine whether cough aerosol culture status is associated with infectiousness. Of the 142 participants with TB, 30 lived alone and were not eligible for the household contact study and 57 had household members who could not be contacted or the household members declined enrollment. From the remaining 55 index participants, we enrolled 143 household contacts and obtained QFT tests on 127 (16 declined phlebotomy or had unsuccessful phlebotomy) (Table 2)." + +Similarly, \(n = 58\) index cases were included in the transcriptomics, but their selection is not described. That needs to be clarified (see more detailed comments below). + +Response: To clarify the selection of individuals for transcriptomic studies, we added the following information to the Methods section: + +"We selected 58 subjects for whole blood transcriptomic analysis which were a subgroup of the full cohort of 142. We initiated this experiment after 29 CAC+ and 29 CAC- subjects were available for analysis from the initial phase of enrollment (Supplementary Table 4)." + +The analysis approach for the predictive models is a simple forward selection of variables. In the context of this well studied area, this seems too uninformed. The consequence is some strange findings which the authors do not pick up on. E.g. Why would MUAC be predictive but BMI would not? + +Response: Thank you for this important question. While MUAC and BMI would seem to be two measurements of the same phenomenon (malnutrition) and therefore highly correlated, a body of findings from the literature demonstrates that there are differences between these biometrics. BMI measures the presence or loss of adipose tissue. MUAC assesses both adipose tissue and muscle mass. As such, MUAC reflects the presence of cachexia. + +We added the following to the Discussion with new references: + +"Our finding of a stronger association between cough aerosol status and MUAC than BMI may seem counterintuitive. However, MUAC and BMI measure related but different aspects of nutritional status: BMI reflects fat mass while MUAC measures fat and muscle mass. (51). Low MUAC was a better predictor than BMI of all- cause mortality in older adults (51- 53), and in persons with TB. MUAC (unlike BMI) was independently associated with cavitary lung disease (54). Cachexia, severe weight loss that results from muscle atrophy and the loss of adipose tissue, may correlate with differential immune cell responses (55). For example, using parasitic infections in the murine model, mice deficient for CD4+ T cells experienced muscle and fat wasting as opposed to CD8+ T cell- deficient mice which experienced only fat wasting (56)." + +How should we interpret CASS predictive model mean where a dichotomised age variable is given + +<--- Page Split ---> + +equal importance as the sole bacteriological indicator (Xpert CT threshold)? While an uninformed approach to the cytokine/transcriptomics analysis seems OK given its novelty, this is not the case for associations for transmission or infectiousness, and this should be addressed, e.g. by discussing a conceptual framework, and exploring different predictive models with a- priori choices. + +Response: Thank you for raising this important concern. We added a conceptual framework that is presented in Figure S1 as a Directed Acyclic Graph (DAG) to evaluate pulmonary TB host characteristics (predictors) associated with cough aerosol culture positive status (outcome). We included predictors (listed in methods section below), potential confounders (bacillary burden, HIV, and sex), mediators (health care engagement) and effect modifiers (Mtb strain), strengthening the rationale for our models' variable selection. We provide further details in the Methods section and Figure legend below. + +The following new language has been added to the following sections: + +## Methods: + +"We assessed associations between host TB characteristics and cough aerosol culture- positive status using bivariate and multivariable logistic regression models in which we evaluated predictor variables based on our conceptual model presented as a directed acyclic graph (DAG, Supplementary Figure 2) (45). Based on published studies of TB transmission and cough aerosol status (18, 25, 29), we categorized as predictors characteristics that we hypothesized as determining the cough aerosol culture- positive phenotype including younger age, functional status (body mass index (BMI), mid- upper arm circumference (MUAC), TB symptoms, cough duration, Leicester Cough Questionnaire (LCQ) score, prior history of TB, and cough peak flow) (29) and systemic inflammation (CRP, hemoglobin, white blood cell count and differential, hemoglobin A1C percent, and sputum appearance). In the DAG we categorized HIV status, bacillary burden (GeneXpert semi- quantitative grade, GeneXpert Ct value, AFB- smear grade, time to detection (TTD) of Mtb growth in liquid culture, presence of chest X- ray cavitation, and number of radiographic quadrants with TB- related changes), and sex as potential confounders due to their shared associations with the exposure and outcome (46). Health care engagement is considered a mediator, a node that is on the causal pathway from exposure to outcome and should not be controlled in models. Pathogen- related factors, which are not included in this study, would be considered effect modifiers as they may contribute to the outcome and modify the effect of other causes of the outcome. GeneXpert Ct values were assigned using the smallest Ct value from any of the probes targeting the rpoB gene; participants with Xpert Ultra trace positive results (for whom rpoB probe Ct values were 0) were assigned a Ct value of 35, near the highest detectable Ct value for Xpert Ultra." + +## Results: + +"We evaluated host characteristics associated with cough aerosol culture status based on a conceptual framework which included potential confounders (Table 1, Supplemental Figure 1)." + +Figure Legends: + +"Supplementary Figure 1: Directed acyclic graph (DAG) depicting conceptual framework of factors that determine cough aerosol culture status in persons with pulmonary TB. DAGs depict associations between an exposure (pulmonary tuberculosis), outcome (cough aerosols that are culture positive for M. tuberculosis), mediator (health care engagement), potential confounders (bacillary burden, HIV status, sex) and effect modifier (pathogen factors such as strain of M. tuberculosis)." + +The more conceptual issue is what space of infectiousness this paper addresses. The title, abstract and body text shift between scope. For example, the title and abstract reflect on 'TB infectiousness', suggesting it is about individuals that are either infectious or not. As clarified later in the abstract, the authors actually focus on a differentiation between more or less infectious + +<--- Page Split ---> + +individuals, based on CASS. They show that CASS+ individuals are likely more infectious with a nested household contact study (which is not a new finding), but there is no control group, so no statement about a binomial infectious yes/no status. For the transcriptomics they then look in a subgroup (which is not defined, see above), and find a number of associations with CASS+. I would agree that this provides data to 'suggest host inflammatory signatures are associated with Mtb aerosolization independent of bacillary load and cavitary lung disease.', as stated in the discussion. But what it does not show is 'Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles', which is the paper title, and as such much too broad. I think the authors should be more clear, and e.g. change the title, and any other statements regarding 'infectiousness' as a whole to reflect the more narrow scope. + +Response: Thank you for these suggestions. We added two control groups to provide an estimated level of Mtb infection (based on QFT results) in adult residents of Nairobi who are without a known recent TB exposure (please see detailed response above). We changed the title to, "Mycobacterium tuberculosis Cough Aerosol Culture Status is Associated with Host Clinical Characteristics, Host Inflammatory Profiles, and Infection in Close Contacts". We have clarified the group of participants who underwent transcriptional profiling (please see explanation above). + +Methods: + +While I understand why ignored trace+/culture- (given the low chance of being CASS pos), it would be good to state this explicitly, and state how the authors interpreted this group. (TB or not TB)? + +Response: We agree that more clarity is needed. The trace positive/culture negative individuals were identified through a prevalence survey where we used an active case finding method which is more likely to identify people with subclinical TB with minimal symptoms. We excluded individuals who were trace positive/culture negative as we do not consider them to have active TB. Participants in this category were identified only through active case- finding, were culture negative on four sputum samples that underwent MGIT culture and did not fit the eligibility of our CASS- study protocol. We added the following sentence to the Methods section, + +"We did not include persons in this study identified through active case finding who were trace positive/culture- negative as we concluded that they did not have active pulmonary based on four negative sputum cultures." + +There is some reporting of results for BMI vs MUAC in the methods, this should be moved to the results. + +Response: We are unable to find this in the text. + +L314- 318 is results I think, should move there. + +Response: We agree and moved the following from the Methods to Results: + +"While a strong majority of the genes (78%) were best fit by models including cough aerosol culture status alone, 16% of genes were best fit with the inclusion of bacillary load with a smaller percentage best explained by more complex models with age and cavitary disease (Supplemental Figure 3A)." + +It is not obvious from the methods that the HH contacts came from a subset (n=55, 1352) of enrolled participants from the total population (n=142). I did not see it in 1185- 1189), nor is it mentioned in 1142- 1144. Firstly, this should be made more clear. Secondly the rationale and method for this selection should be described explicitly (e.g. funding restrictions and random draw?). + +<--- Page Split ---> + +Response: Thank you. We added the following clarifying statements in the Results Section: "We next evaluated IGRA results in household contacts to determine whether cough aerosol culture status is associated with infectiousness. Of the 142 participants with TB, 30 lived alone and were not eligible for the household contact study and 57 had household members who could not be contacted, or the household members declined enrollment. From the remaining 55 index participants, we enrolled 143 household contacts and obtained QFT tests on 127 (16 declined phlebotomy or had unsuccessful phlebotomy) (Table 2)." + +There is a similar selection for the host transcriptomic work (going down to \(n = 59\) index patients), which needs to be similarly explained. + +Response: Thank you. Please see detailed responses above. + +## RESULTS + +335: It seems odd that all of the participants were cough positive, as a percentage came from community screening. Given the difference in population and expected disease severity between ACF and PCF populations, these two populations should be described more in the text and supp materials. If the \(100\%\) cough positive holds, it is something to discuss, as it goes against most modern TB prevalence surveys where about \(50\%\) were found to be cough negative. + +Response: Thank you for this suggestion. We agree that more description of these two populations is important for clarity. All participants identified through active case- finding were CAC- negative. As persons who presented for health care contributed entirely to CAC- positive participants (thus, \(100\%\) with cough) and contributed the majority of CAC- negatives, we see the high frequency of cough. Of the 26 participants enrolled through active case finding (all of whom were CAC- negative), 5 denied cough, for a cough frequency of \(81\%\) . In the community- based prevalence survey, \(42\%\) of people with prevalent TB denied cough. We did not enroll all people with prevalent TB into our CASS study as some were GeneXpert negative and later diagnosed with TB based on culture results, declined enrollment or were not available for recruitment (e.g. were diagnosed on a Saturday). We are not suggesting that the ACF participants are representative of prevalent TB in the community and have added text for clarification. We added the following clarifying language to the Methods section: + +"We did not include persons in this study identified through active case finding who were GeneXpert negative/culture- positive due to delays in their TB diagnosis, who were trace positive/culture- negative as we concluded that they did not have active pulmonary based on four negative sputum cultures, those who were diagnosed on weekends or those who declined enrollment." + +We added the following to the Results: + +"As compared to participants identified through passive case finding ( \(n = 116\) ), those identified through active case finding ( \(n = 26\) ) were older (mean 43 vs. 35 years, p- value 0.005), less likely to report a cough ( \(81\%\) vs. \(98\%\) , p- value \(< 0.001\) ), less likely to have cavitary disease on chest x- ray ( \(38\%\) vs \(77\%\) , p- value \(< 0.001\) ) and had higher mean GeneXpert Ct values (24.0 vs. 19.2, p- value \(< 0.001\) ); there was no difference in the frequency of women or PLWH." + +Table 1: The MUAC result is odd (i.e. a higher MUAC means more CASS+). It seems counterintuitive, and the lack of an association with BMI makes me concerned the MUAC results are less reliable. The BMI/MUAC discrepancy should be discussed. + +Response: Please see above response. + +Table 2: I am not clear what the OR and p- values are meant to show here. For the index case + +<--- Page Split ---> + +characteristics, those seem a near 1- 2- 1 repeat of table 1? I think those could be dropped, especially from the main body text. For e.g. the number of contacts per case – I think this is just a chi- square, but that is not the relevant finding. What we would like to know is whether the distribution of HH contacts is different by CAC+ and CAC-, which is currently unclear. + +Response: Table 2 contains a sub- set \((n = 55)\) of the index participants in Table 1 \((n = 142)\) . Since some of the index participants lived alone or had household contacts that were not enrolled (could not be reached, declined participation), there are differences in the included index participants. The purpose of Table 2 is to show variables of interest that may associate with differences in transmission risk and QFT result in order to assess for contributors to the differences in household contact QFT status by cough aerosol status of the index participant. Ultimately, we are offering data to support our hypothesis that cough aerosol status is the largest driver (risk factor) for TB transmission to close contacts. + +We have removed the odds ratio column from Table 2, clarified in Table 2 the number of index participants and their relation to household contacts, and removed the requested language from the main text. The p- value compares the size of households enrolled and shows a statistically significant difference. The number of contacts per household is larger for contacts of CAC- negative index participants: \(36\%\) of HHCs of CAC+ index participants were from households that enrolled 3 or more contacts compared to \(48\%\) of HHCs of CAC- index participants. We have clarified this by adding percents to the Table 2 cells. + +What were reasons for missing QFT (N goes from 143 to 127)? These should be reported. + +Response: The reasons for missing QFTs among enrolled HHCs was due to refusing phlebotomy or unsuccessful phlebotomy. We added the following text: + +"From the remaining 55 index participants, we enrolled 143 household contacts and obtained QFT tests on 127 (16 declined or had unsuccessful phlebotomy) (Table 2)." + +Table 3: The results are quite stark, but not sure how superior the final model is. It makes sense that after one good measure of bacteriological burden is included in the model, the others are no longer adding enough value to be included. E.g. smear and cavitation seem to be quite useful explanatory/predictive variables by themselves. A simple forward stepwise modelling approach will not highlight those limitations. Given what we already know about infectiousness, this type of analysis would be better served with a formal DAG or at least conceptual framework, and then working through the various options or models. I suggest the authors explore this wider, and thereby enrich the insights that can be gained from the data. + +Response: Thank you for this suggestion. We added a DAG as Figure S1 which includes the exposure, outcome, predictors, potential confounders and effect modifiers. The DAG includes variables that are known to have impact on infectiousness and were used in our model development when data was available. We added new text to the Methods, Results, and Figure legend as summarized above. + +While the AUC for the scoring system for predicting CAC+/- is high, I don't quite understand the results from Sup table 1. It seems to suggest that age and Xpert CT are equally valuable (both 7 'points')? But what does the model/score mean if the sole bacteriological indicator is removed? Are the authors suggesting that we could decide on CAC+/- by age, CRP and MUAC alone? Could they provide an indication of how much value each individual characteristic adds, and how the model works if Xpert CT is not available. Could any other bacteriological indicator be switched in? I'd be surprised if the model functioned without a bacteriological indicator, and also not sure about the biological logic that would remain. It is also not clear if this predictive model is solely applicable for people who have bacteriologically positive TB? If so, that should be made clear. + +Response: Thank you for these comments. We adjusted the model to have 3 categories for GeneXpert + +<--- Page Split ---> + +result based on semi- quantitative grade. The performance of this clinical prediction model is predicated on assessment of all the variables included in the tool. Thus, this tool should only be used for people who have bacteriologically positive TB. Supplementary Table 3 displays the changes in model sensitivity and specificity based on different cut- offs, which addresses aspects of the reviewer's questions regarding lack of access to data on model factors. Performance in other settings will need validation. + +We added the following to the Results: + +"We developed and evaluated the performance of a clinical prediction rule to predict cough aerosol culture- positive persons as a means to identify those who are likely to be highly infectiousness. We included predictors from our multivariable logistic regression model that are readily available to a clinician during the initial visit. For this reason, we removed time- to- detection of culture growth but kept CRP level as there are point- of- care versions of this test. (52) We also used Xpert Ultra semi- quantitative grade which is the result generally reported to clinicians and is derived from the Ct value. Using the coefficients obtained in the multivariable logistic regression analysis we derived the following prediction equation for cough aerosol culture- positive status where outcomes were coded according to weighted scores based on the beta coefficient: \(\mathrm{CRP > 42.9 + Age < 43.8}\) years + MUAC \(> 22.8\) cm + Xpert semi- quantitative grade (high, medium, or low/very low/trace). A total risk score is calculated by adding the risk points and has an optimum cut point of 15 points for predicting cough aerosol culture- positive status with estimated sensitivity of 0.86 (95% CI, 0.74 - 0.95) and specificity 0.65 (95% CI, 0.56 - 0.74). (Supplementary Tables 2 and 3) The prediction rule based on the calculated risk score had an area under the receiver operating curve (AUROC) of 0.84 (95% CI: 0.77- 0.91) (Supplementary Figure 3). The model's Somers' \(\mathrm{D_{xy}}\) index was 0.71; the equivalent in bootstrap validation was 0.66, with an optimism estimate of 0.051, indicating good stability of the model in internal validation." + + + +We added the following to the Discussion: + +"Like other clinical prediction rules, the model performance is predicated on having data for all of the characteristics that contribute to the risk score. While promising, the risk score that we present requires external validation and should not be used at this time for clinical (non- research) purposes." + +The variation in association pattern of the different cytokines is a bit strange. Would one not expect them to be elevated across the various indicators, also given that e.g. CT threshold and cavitation were themselves associated with CAC? The lack of stability makes me a bit concerned. The results are what they are, but potential explanations (including random noise across many comparisons that could affect the threshold for interpretation of p- values). + +Response: We agree that the sputum cytokine results contain variation in patterns of associations with different outcomes. Although these results are not consistent with a well- defined model of TB pathogenesis, each cytokine has distinct activation pathways and cellular sources that likely to contribute to the variation of results. For example, IL- 1B secretion is inflammasome- dependent while CXCL8 and IL6 secretion are primarily regulated by Toll- like Receptor and NOD- like receptor signaling pathways. All three cytokines are produced by several myeloid cells, but to different degrees. Finally, each has different autocrine and paracrine effects that likely get amplified at different stages of disease. For example, CXCL8 is a chemokine for neutrophil recruitment with potential for amplification of its levels during disease stages which are neutrophil predominant. At the suggestion of Reviewer #3 below, we examined leukocyte subsets and found that peripheral blood neutrophil counts are associated with CAC status, an association which is consistent with the higher levels of CXCL8 in CAC+ versus CAC- sputum cytokine analyses. + +To further address these cytokine observations, we collected more data and performed more analyses. First, we measured the same 4 cytokines in plasma to provide a parallel inflammatory profile in a different + +<--- Page Split ---> + +compartment. Second, we used a multivariate linear regression model to examine whether any of the associations were independently associated with CAC status. + +For the plasma cytokines, we were able to detect TNF and IL6, but not IL1B or CXCL8. In contrast, for our previous sputum cytokine results, we detected IL6, IL1B, and CXCL8 but not TNF. These results are consistent with compartmentalized immune responses and highlight the importance of analyzing inflammatory profiles in multiple sites. We then performed a multivariate logistic regression analysis to assess whether any of the sputum or plasma cytokines were associated with CAC independently of bacillary load. Interestingly, plasma TNF was the only cytokine associated with CAC in the adjusted analysis. These results provide additional evidence that inflammatory profiles are associated with CAC status and also highlight the importance of examining multiple sites of inflammation. However, we agree these cytokine observations are incomplete and not consistent with a fully developed or coherent model. Our RNASeq experiments were undertaken to attempt a more in- depth analysis of inflammatory pathways that are associated with aerosolization. + +We revised the Methods section and Figure 1 to include the plasma cytokines, added Supplementary Table 4 for the multivariate analysis, and added the following text to the Methods and Results sections: + +## Methods: + +"Four cytokines were examined in sputum and blood. TNF, IL6, IL1B, and CXCL8 were chosen based on their central roles in regulating inflammatory pathways and TB pathogenesis. (42) ... Plasma was tested directly. Sputum supernatants and plasma were tested for CXCL8 (IL- 8), Interleukin 1 beta (IL- 1β), Interleukin 6 (IL- 6), and TNF using sandwich ELISA according to the manufacturer's instructions. (R&D Systems Inc. Minneapolis, USA.). In pilot sputum cytokine studies, TNF was not detectable at high levels and was not examined further. In pilot plasma cytokine studies, CXCL8 and IL1B were not detectable at high levels and were not examined further." + +## Results: + +"To further examine the association of inflammatory markers with cough aerosol culture- positive status, we analyzed sputum and plasma levels of CXCL8 (IL- 8), IL- 1β, TNF, and IL- 6 (Figure 1B, Supplementary Table 5). TNF in sputum and IL- 1β and CXCL8 in plasma were nearly undetectable in preliminary subgroup testing and were not examined further. The sputum concentration of CXCL8 was significantly higher (p- value 0.03) among the cough aerosol culture- positive compared to cough aerosol culture- negative participants. Sputum IL- 1β (p- value 0.052) and IL- 6 were not different (p- value 0.36) (Figure 1B). In addition, higher IL- 6, CXCL8, and IL- 1β levels were associated with greater bacillary burden (measured by GeneXpert cycle threshold, p- value 0.0009, 0.007 and 0.00007, respectively, Figure 1C). IL- 1β, but not IL- 6 or CXCL8, was positively associated with cavitary lung disease (p- value 0.0007) across cough aerosol culture status. + +Plasma IL- 6 was associated with bacillary burden (p=1.69 x 10- 6) and cavitary disease (p=0.005) and was higher in CAC- positive compared CAC- negative participants (p=0.03). Plasma TNF was associated with cavitary disease (p=0.013), but not bacillary burden, and was lower in CAC- positive compared to CAC- negative participants (p- value 0.0007). For cytokines that had a significant association with cough aerosol status in bivariate models (sputum CXCL8, plasma TNF, plasma IL- 6), we evaluated associations in multivariate logistic regression models in which we adjusted for age, sex, cavitary disease on chest x- ray and GeneXpert Ct value. We found that plasma TNF was independently associated with CAC status (adjusted p- value 0.007, Supplementary Table 4)." + +Discussion (in the Limitations paragraph): + +"Fourth, sputum collection methods are not standardized and have more technical heterogeneity in + +<--- Page Split ---> + +comparison to other biologic samples. Despite this challenge, sputum provides a direct assessment of the primary site of TB disease where pulmonary immune responses are compartmentalized and differ from blood. In addition, sputum cytokines have been evaluated as biomarkers in the diagnosis of TB and treatment monitoring.(65- 67) However, to our knowledge no prior studies have evaluated their association with infectiousness measured by culturable aerosols." + +L455- 457: these are results and should be moved there. On a broader note, it would be good to place those observations in the context of the ongoing discussions around subclinical TB (see previous comment re cough positivity). + +Response: We agree that this sentence summarizes results, but the referenced statement ("In this study, a lower TB symptom score indicated a lower burden of findings attributable to TB disease as it is a summation of points for TB- related symptoms (cough, hemoptysis, dyspnea, chest pain, fever, night sweats), TB- related signs (anemia, tachycardia), lung auscultation findings, and malnutrition (low BMI, low MUAC).") refers to the study by Theron et al, not our findings. We have made it clear in the text that we are referring to findings from Theron's study and that this is in the context of our Discussion of the literature and findings suggestive of a CAC- positive phenotype. + +L462: the statement about 'body mass' is strange, as BMI was not associated, but MUAC was. As mentioned before, this discrepancy needs discussion, and the statement should be adjusted accordingly. + +Response: Thank you. We address this comment above. In addition, for line 462, we changed "body mass" to "muscle mass". + +L473: this only interprets one of the cytokine findings, but ignored the conflicting results in the actual section (see above), where some cytokines were associated for one indicator, but not the other. Do the authors assume only 1 indicator is valid? If so, that is a stretch. If not, the discrepancies need to be addressed. + +Response: Thank you for highlighting this issue which we partially address above including revision of the Results paragraph and addition of new data. Although the cytokine data has some level of association with CAC status, we do not claim to have a coherent model based on the limited scope of the cytokine analysis. We used the cytokine observations as a rationale for pursuing a more comprehensive analysis with whole blood RNAseq profiling. We considered how to revise Discussion section which includes line 473. Given the limited scope of the cytokine work, we would prefer to remove this sentence and focus the paragraph on discussion of the transcriptomic findings. We believe this modification adds more focus to the paragraph on the most important findings. + +In summary, we removed the following sentence from the Discussion paragraph: + +"Our results of significantly higher concentrations of sputum CXCL8 and 1L- 1β, as well as higher serum CRP, in participants with culturable aerosols support the role of systemic inflammation in TB infectiousness." + +L535: the suggestion that interventions (i.e. treatment) should target the most infectious is a bit strange. This approach was tried with the development of DOTS policies, where symptomatic smear positive individuals were targeted through PCF and 6m therapy. While saving lives, it has not interrupted transmission as expected, and it is not clear to me why this would work now? Shouldn't Identifying and treating all infectious individuals be the minimum target for all high burden countries, regardless of how infectious they are at the time of diagnosis? + +Furthermore, infectiousness is not static, and will likely vary over time. Finally, given the high + +<--- Page Split ---> + +Number Needed to Test to identify any person with low or high infectious disease, the cost of treatment is really not the limiting factor. It would be helpful if the authors reflected a bit more on this (also in the introduction). + +Response: Thank you for these suggestions and perspective for which we fully concur. Smear- based diagnosis is a crude and insensitive method for diagnosis and our statements are not intended to evoke that approach. "Targeted treatment interventions" is not meant to imply that treatment should only be provided to those who are most infectious. Rather, in resource constrained settings where enhanced treatment support such as "true" DOT is not commonly practiced, the most infectious persons could also be supported with true DOT, early drug susceptibility testing to ensure that treatment is appropriate, or other treatment support interventions. Also, as mentioned, more extensive contact investigations could be pursued to ensure evaluations for active TB and TB preventive therapy in contacts who are likely to have been recently infected. + +We edited the final Discussion paragraph to clarify our intended message, + +"While persons with pulmonary TB who are cough aerosol culture- negative patients may transmit Mtb, identifying the most infectious persons would allow targeted interventions to support TB control efforts such as isolation, true direct observation of treatment, and drug- susceptibility testing to confirm that treatment is effective. TB control could also be supported through enhanced investigations in contacts of the most infectious persons to evaluate for active TB and provide TB preventive therapy given higher likelihood of recent transmission and progression to disease." + +Minor points + +Ref 33, 34 and 58 are the same I believe. Would be good to recheck references and make sure in order. + +Response: Thank you. This has been corrected. All references were reviewed for accuracy and order. + +Table 1: category 'Enrolled thru prevalence survey' - not appropriate language for scientific paper and not reflected in main text. Suggest something along lines of 'ACF- enrolled', as this is how it is described in methods. + +Response: Thank you. We changed this category to "Enrolled through active case finding". + +Table 3: the unit for Age is not given. From the OR I suspect it is year of age, but this should be made clear. Also note this assumes a linear association across the entire age range, which is unlikely to be true given what we know about age- dependent population ARI. This should be discussed. + +Response: The units (years) has been added to the tables. is has been corrected. + +We added the following to the Discussion: + +"The annual risk of TB infection differs by age groups in high burden settings and notably, there was no difference in the ages of HHCs by CAC status. Among household contacts less than 10 years of age, who have a lower annual risk of infection compared to adolescents and adults, QFT positive results were also more common (p- value 0.01) among contacts of CAC- positive persons (9 of 10 participants, 90%) than contacts of CAC- negative persons (14 of 33 participants, 42%)." + +The section titles on 1397 and 1409 are phrased as interpretation rather than reporting of results. These should be adjusted. In addition, the last sentences in each of these sections is interpretation rather than result and should be removed or put in discussion. + +<--- Page Split ---> + +Response: Thank you for this suggestion. We edited the phrases and sentences to remove interpretation language from the Results section. + +The new section titles are: + +"Suptum cytokines and analysis of associations with cough aerosol culture positivity, bacterial load, cavitary lung disease, and extent of lung involvement." + +And + +"Whole blood transcriptomic signatures and analysis of associations with cough aerosol culture positivity and sputum bacterial load." + +In addition, we removed the summary sentence of these sections to avoid over- interpreting in the Results section. + +Reviewer #2 (Remarks to the Author): + +The study "Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles" stands out for addressing a significant gap in tuberculosis research, focusing on individual infectiousness and biomarkers. It employs a prospective longitudinal study design, examining treatment- naïve pulmonary TB patients in Nairobi, thereby providing valuable insights in a high TB burden setting. Methodological innovations, such as using the Cough Aerosol Sampling System (CASS) for measuring Mycobacterium tuberculosis aerosolization, the evaluation of sputum cytokine, and assessing household contacts through IGRA testing, add important epidemiological and molecular dimensions and adds novel knowledge and tools to predict Mtb transmission. Overall, the manuscript was well written. The incorporation of suggested improvements would enhance the paper's quality and ensure that concerns have been adequately addressed. + +#1 Introduction: The introduction section is well- written and effectively frames the context of TB infectiousness to its clinical and immunological aspects. It successfully outlines the importance of understanding individual variations in TB transmission and reviews relevant literature, thus situating the study within the broader field of TB research. I have no suggestions for improvement in this section. + +Response: We appreciate your kind words. + +#2 Methods: The methods section is well- structured and thorough. However, consider breaking down the dense text into smaller paragraphs to improve readability (i.e. break the paragraph in line 262.) + +Response: Thank you, we made the suggested edits. + +#2.1 – Methods (Line 203-204): The study does not address the issue of drug-resistant TB. On lines 203-204, the study mentions classifying rifampicin resistance as "positive", "negative", or "indeterminate", but this is not further elaborated in the text. I recommend including these data in the results and tables, even if 100% were susceptible, to provide a complete picture of the resistance profile among the study participants. + +Response: Thank you for pointing this out; it was an oversight on our part. One subject had rifampin resistance. We added information on detection of rifampin resistance to Table 1. + +#- 2 - Results (lines 222-228): It would be beneficial to provide a rationale for the decision to + +<--- Page Split ---> + +assess cytokines in sputum instead of blood; as well as the selection of the specific three cytokines studied. This is particularly important for readers who may have less experience in the field. Including one or two lines to explain these choices would greatly aid in comprehending the significance and implications of these methodological decisions. + +Response: We agree that adding more context around these issues will provide more clarity. We chose to analyze sputum cytokines due to our hypothesis that the inflammatory mediators and/or biomarkers of aerosolization are present in the lung and more likely to have a direct impact compared to the peripheral blood. In addition, the immune system is compartmentalized, and lung responses are often different than peripheral blood. However, there are technical challenges of collecting sputum in a standardized manner. In contrast, whole blood and plasma measurements are more standardized. To address this directly, we have now added cytokine measurements in plasma for comparison to sputum. We now have data for 4 cytokines in both sputum and blood. TNF was detectable at high levels in sputum and CXCL8 and IL1B were not present in plasma at high levels. These data support the compartmentalization of immune responses and the value of directly studying pulmonary immune responses when feasible. The rationale for studying IL6, TNF, and IL1B is based on their known role in TB pathogenesis. We chose to study CXCL8, due to its role as a chemokine involved in neutrophil recruitment, an important cell in TB pathogenesis, and previous studies documenting its presence in sputum. + +We added the following text with new references: + +## Methods: + +"Four cytokines were examined in sputum and blood. TNF, IL6, IL1B, and CXCL8 were chosen based on their central roles in regulating inflammatory pathways and TB pathogenesis. (42)" ... Plasma was tested directly. Sputum supernatants and plasma were tested for CXCL8 (IL- 8), Interleukin 1 beta (IL- 1β), Interleukin 6 (IL- 6), and TNF using sandwich ELISA according to the manufacturer's instructions. (R&D Systems Inc. Minneapolis, USA.). In pilot sputum cytokine studies, TNF was not detectable at high levels and was not examined further. In pilot plasma cytokine studies, CXCL8 and IL1B were not detectable at high levels and were not examined further." + +## Results: + +"To further examine the association of inflammatory markers with cough aerosol culture- positive status, we analyzed sputum and plasma levels of CXCL8 (IL- 8), IL- 1β, TNF, and IL- 6 (Figure 1B, Supplementary Table 5). TNF in sputum and IL- 1β and CXCL8 in plasma were nearly undetectable in preliminary subgroup testing and were not examined further. The sputum concentration of CXCL8 was significantly higher (p- value 0.03) among the cough aerosol culture- positive compared to cough aerosol culture- negative participants. Sputum IL- 1β (p- value 0.052) and IL- 6 were not different (p- value 0.36) (Figure 1B). In addition, higher IL- 6, CXCL8, and IL- 1β levels were associated with greater bacillary burden (measured by GeneXpert cycle threshold, p- value 0.0009, 0.007 and 0.00007, respectively, Figure 1C). IL- 1β, but not IL- 6 or CXCL8, was positively associated with cavitary lung disease (p- value 0.0007) across cough aerosol culture status. + +Plasma IL- 6 was associated with bacillary burden (p=1.69 x 10- 6) and cavitary disease (p=0.005) and was higher in CAC- positive compared CAC- negative participants (p=0.03). Plasma TNF was associated with cavitary disease (p=0.013), but not bacillary burden, and was lower in CAC- positive compared to CAC- negative participants (p- value 0.0007). For cytokines that had a significant association with cough aerosol status in bivariate models (sputum CXCL8, plasma TNF, plasma IL- 6), we evaluated associations in multivariate logistic regression models in which we adjusted for age, sex, cavitary disease on chest x- ray and GeneXpert Ct value. We found that plasma TNF was independently associated with CAC status (adjusted p- value 0.007, Supplementary Table 4)." + +Discussion (in the Limitations paragraph): "Fourth, sputum collection methods are not standardized and have more technical heterogeneity in + +<--- Page Split ---> + +comparison to other biologic samples. Despite this challenge, sputum provides a direct assessment of the primary site of TB disease where pulmonary immune responses are compartmentalized and differ from blood. In addition, sputum cytokines have been evaluated as biomarkers in the diagnosis of TB and treatment monitoring.(65- 67) However, to our knowledge no prior studies have evaluated their association with infectiousness measured by culturable aerosols." + +#2.3 – Methods (Data analysis section): To enhance reproducibility, I recommend adding a table in the supplementary material section. This table should list the names of the R packages used, their respective versions, and references. + +Response: Thank you for this suggestion. We added Supplementary Table 1 with the suggested information. + +#3 Results: The results section provides a detailed and thorough presentation of the study's findings and analyses. The section appears to be well- organized and structured, with clear descriptions of the methods used and the outcomes observed. The use of tables, figures, and numerical values enhances the clarity of the presented results. However, there are a few areas where the clarity and objectivity could be further improved: + +#3.1 Results (lines 350-368): Considering that age emerged as a significant variable in the mixed methods bivariate & multivariable analysis, and the low median age reported, it is essential to have information on how many HHCs were children or adolescents. Furthermore, this aspect of age, including the distinction between adult and non-adult contacts, should be highlighted in the discussion section. + +Responses: Thank you. We have added age groups to Table 2 for young children (<5 years of age), children (5- 10 years of age), and adolescents (10- 15 years of age). + +We added the following to the Results section: + +"Among household contacts less than 10 years of age, QFT positive results were also more common (p- value 0.01) among contacts of CAC- positive persons (9 of 10 participants, 90%) than contacts of CAC- negative persons (14 of 33 participants, 42%)." + +We added the following to the Discussion: + +"Third, we demonstrated that cough aerosol culture- positive status was strongly associated with evidence of TB transmission in household contacts based on QFT results, including child HHCs for whom a positive QFT result is more likely to represent recent infection." + +#3.2 Results (lines 392-394): Please provide the sensitivity and specificity values of the ROC curve, with confident intervals. + +Responses: Thank you. We have added estimated sensitivities and specificities at different cut points in Supplementary Table 3A. + +#3.3. Results (lines 397-437): In lines 397-437, all paragraphs finish with a phrase with the same structure that starts with "Together, these data suggest". I recommend rewriting some of them and evaluating if it is necessary. For example, I do not think that the phrase in lines 436-437 is fundamental for the text. + +Response: Thank you. We have made the suggested edits and removed these summary sentences. + +#3.4. Results (Figures): The figures in the manuscript, particularly Figures 1c and d, Figure 2, and + +<--- Page Split ---> + +Supplementary Figure 4, need to be improved for better comprehension. A key enhancement is to include the legend for colours and shapes directly on the figure itself, rather than solely in the written legend. The absence of this information on the figures themselves can hinder interpretation and understanding. Providing these details directly on the figures would facilitate a more immediate and clear comprehension of the data being presented, especially for readers who might be quickly scanning through the figure + +Response: Thank you for this suggestion. We made the suggested changes to Figures 1 and 2 and supplementary figure 4 (which is now supplementary figure 5. + +#4 Discussion: The discussion section demonstrates a good quality of scientific communication, with a thorough examination of the study's results and their implications. The section effectively contextualizes the findings within the existing literature and provides a balanced interpretation of the results. The limitations are acknowledged, and their potential impact on the study's conclusions is addressed. Minor comments: + +Response: Thank you, we appreciate the kind words. + +#4.1. It would be beneficial to discuss in more detail the age of the Household Contacts (HHCs) + +Response: Please see above response. + +as well as the rationale behind using sputum to assess biomarkers. These discussions could provide deeper insights into the study's findings and their implications + +Response: Thank you for this suggestion. As discussed above, our interest in studying sputum is to assess whether the compartmentalized immune response of the lung will generate novel insights compared to blood, especially with regards to the question of Mtb aerosolization. However, we fully acknowledge the methodologic challenges of working with sputum and the lack of standardization. We added more discussion of this in the limitations paragraph since we believe it is both a strength and a weakness due to these methodologic challenges. + +We added the following text to the Discussion: + +"Fourth, sputum collection methods are not standardized and have more technical heterogeneity in comparison to other biologic samples. Despite this challenge, sputum provides a direct assessment of the primary site of TB disease where pulmonary immune responses are compartmentalized and differ from blood. In addition, sputum cytokines have been evaluated as biomarkers in the diagnosis of TB and treatment monitoring.(57- 59) However, to our knowledge no prior studies have evaluated their association with infectiousness measured by culturable aerosols." + +#4.2 (lines 447-500): Breaking up the paragraphs could enhance the readability and clarity of information, making it easier for readers to digest and understand the key points being conveyed. + +Response: Thank you. We made the suggested edits. + +## Reviewer #3 (Remarks to the Author): + +The study is very interesting and opens new ways for understanding TB pathogenesis and proposing clinical management. Based on the reported findings and prior studies, cough aerosol cultures are superior to sputum smear analysis in predicting Mtb transmission events and are likely the best estimators of TB infectiousness. + +<--- Page Split ---> + +Figure 1A: is any possibility of evaluating the correlation of WHITE BLOOD CELLS components as Lymphocytes, monocytes, or neutrophils with CAC?. Indeed interesting correlations were found in the past using different approaches (La Manna, 2017, PMID: 28208160; Chedid, 2020, PMID: 32920230; ). Moreover, it would be interesting to evaluate if there is an association between CAC score and platelets (La Manna, 2022 PMID: 35338775) + +Response: Thank you for this suggestion. We evaluated associations between granulocyte, lymphocyte and monocyte counts and CAC status. While there was no association between the latter two white blood cell types and CAC status, the granulocyte count was significantly associated with CAC status (Table 1). We do not have platelet counts on study participants. The granulocyte odds ratio is very similar to the WBC count odds ratio; this is not unexpected as granulocytes are the largest number of WBCs and the two values (granulocyte count and WBC count) are highly correlated. + +We edited the following sentence in Results to incorporate this data: + +"Higher WBC counts (total and granulocyte count) and CRP levels were also associated with cough aerosol culture- positive status (Figure 1A)." + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +I thank the authors for their responses and the changes to the paper, which have addressed most of my major concerns. + +I remain sceptical of the sharp contrast between BMI and MUAC, and the suggested difference. We see the effects of nutrition on TB v clearly in BMI, as the recent RATIONS papers (Bhargava Lancet 2023, Bhargava Lancet GH 2023) and RePORT (Sinha preprint) papers have shown in terms of TB mortality and progression. For BMI to suddenly not matter in aerosol status seems more than a little odd. Also, MUAC is not solely driven by muscle mass, depending on the BMI, there is fat tissue as well. I suggest the text should be more open to the BMI vs MUAC findings reflecting artefact rather than fact and/or that the explanation is an hypothesis, rather than fact. + +The other point that needs more clarification is how these findings in almost solely cough reporting individuals contrast with the findings of other aerosol studies, such as the face masks and RASC groups. Simply mentioning them in 1558- 570 does not address this. It seems strange to suggest that only cough reporting individuals are infectious, where e.g. face mask positivity was not correlated with cough (Williams Lancet ID 2020) but was correlated with HH infections (Williams CID 2023). It's possible that both are true, but then restricting to cough- positive individuals in this study poses a limitation. + +I have some minor issues still, which the authors should also resolve in a final revision. + +- The path from 142 to 55 participants is useful. It would be good if the paper reflected whether this could affect the findings. In particular whether HHs that refused to participate are different in a way that is associated with QFT positivity + +- The explanation for how the 29 CAC+ and 29 CAC- is not sufficient. Is it a convenience sample (e.g. the first ones through the door). Again, anything that isn't random should be described and considered for analysis. + +- It should be made clear what age range was studied, and the age range the authors are comfortable for their prediction model to be valid for. + +- L298: With the 3 Xpert categories, variables are no longer all dichotomised, suggest to revise. + +Reviewer #2 (Remarks to the Author): + +The authors addressed all my questions and also the questions of the other reviewers. I am satisfied with the review and recommend the publication. + +Reviewer #3 (Remarks to the Author): + +<--- Page Split ---> + +the manuscript is interesting and great value scientifically and clinically, the authors answered the questions raised. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +I thank the authors for their responses and the changes to the paper, which have addressed most of my major concerns. + +I remain skeptical of the sharp contrast between BMI and MUAC, and the suggested difference. We see the effects of nutrition on TB v clearly in BMI, as the recent RATIONS papers (Bhargava Lancet 2023, Bhargava Lancet GH 2023) and RePORT (Sinha preprint) papers have shown in terms of TB mortality and progression. For BMI to suddenly not matter in aerosol status seems more than a little odd. Also, MUAC is not solely driven by muscle mass, depending on the BMI, there is fat tissue as well. I suggest the text should be more open to the BMI vs MUAC findings reflecting artefact rather than fact and/or that the explanation is an hypothesis, rather than fact. + +Response: Thank you for highlighting this concern and the citations. We agree that the association of MUAC, but not BMI, with aerosolization may be a statistical artefact and that our discussion of the finding is speculative. We also agree that MUAC represents both fat and muscle. + +We added more text to the Discussion to clarify that the BMI/MUAC differences may be a statistical artefact and that MUAC measures both fat and muscle mass: + +"Our finding of an association between cough aerosol status and MUAC, but not BMI, may seem counterintuitive and may represent a statistical artefact. Alternatively, we hypothesize that MUAC and BMI measure related but different aspects of nutritional status: BMI reflects fat mass while MUAC measures fat and muscle mass." + +The other point that needs more clarification is how these findings in almost solely cough reporting individuals contrast with the findings of other aerosol studies, such as the face masks and RASC groups. Simply mentioning them in 1558- 570 does not address this. It seems strange to suggest that only cough reporting individuals are infectious, where e.g. face mask positivity was not correlated with cough (Williams Lancet ID 2020) but was correlated with HH infections (Williams CID 2023). It's possible that both are true, but then restricting to cough- positive individuals in this study poses a limitation. + +Response: Thank you for highlighting this concern. We agree that there is exciting new information that is potentially paradigm shifting to the field of TB. We also believe that the findings from the face mask and RASC groups requires further study to understand the relationship to infectiousness. + +We added the following to limitations in the Discussion: + +"Second, \(95\%\) of participants reported cough and our findings may not apply to persons with TB without cough. Recent studies that have detected TB in exhaled breath call into question whether cough is essential and/or a primary driver of TB transmission. (33, 34, 67, 68)." + +33. Williams CM, Abdulwhhab M, Birring SS, De Kock E, Garton NJ, Townsend E, et al. Exhaled Mycobacterium tuberculosis output and detection of subclinical disease by face-mask sampling: prospective observational studies. Lancet Infect Dis. 2020;20(5):607-17. +34. Dinkele R, Gessner S, McKerry A, Leonard B, Leukes J, Seldon R, et al. Aerosolization of Mycobacterium tuberculosis by Tidal Breathing. Am J Respir Crit Care Med. 2022;206(2):206-16. +67. Williams CM, Muhammad AK, Sambou B, Bojang A, Jobe A, Daffeh GK, et al. Exhaled Mycobacterium tuberculosis Predicts Incident Infection in Household Contacts. Clin Infect Dis. 2023;76(3):e957-e64. +68. Patterson B, Dinkele R, Gessner S, Koch A, Hoosen Z, January V, et al. Aerosolization of viable Mycobacterium tuberculosis bacilli by tuberculosis clinic attendees independent of sputum-Xpert Ultra status. Proc Natl Acad Sci U S A. 2024;121(12):e2314813121. + +<--- Page Split ---> + +I have some minor issues still, which the authors should also resolve in a final revision. + +- The path from 142 to 55 participants is useful. It would be good if the paper reflected whether this could affect the findings. In particular whether HHs that refused to participate are different in a way that is associated with QFT positivity. + +Response: We agree that differences between those index participants and contacts who did or did not participate in the household contact analysis needs to be carefully evaluated to determine whether they reflect the characteristics of the entire cohort and are generalizable. To assess the characteristics of our subgroup analysis, we compared index participants with \((N = 48)\) and without \((N = 94)\) household members. These comparisons are presented in (new) Supplementary Table 5. We found 3 variables that differed between index participants with and without enrolled household contacts (sex, Xpert Ct, and cavitary CXR). Each of these variables was tested in the multivariate model. These results suggest that our subgroup had some differences from the full cohort (possibly related to female index participants being less likely to live alone than male index participants) and could lead to selection bias and/or decrease generalizability. Concerns around selection bias were addressed through use of random effects models clustered on index participant. (Bell A. Fixed and random effects models: making an informed choice". Qual Quant 53, 2019). We have added these concerns to the limitations section. + +We added the following to the Results: + +"Index participants \((N = 48)\) with enrolled household members compared to index participants \((N = 94)\) without enrolled household members did not differ by age (p- value 0.12), HIV status (p- value 0.74), MUAC (p- value 0.60), or CASS status (0.17). (Supplementary Table 5) However, there were differences in the proportion of women \((42\%\) vs. \(20\%\) , p- value 0.007), Xpert Ct values (20.5 vs. 18.1, p- value 0.01), and the frequency of cavitations on chest X- ray \((58\%\) vs. \(76\%\) , p- value 0.04) between those with and without enrolled household members, respectively. " + +We added the following to the limitations paragraph in the Discussion: + +"In addition, the index participants who contributed to our evaluations of risk factors for HHC IGRA results differed from index participants without enrolled HHCs which introduce selection bias and limit generalizability. Although our random effects models should address concerns around selection bias, generalizability of the HHC IGRA status remains a limitation." + +In the original submission, we included household contacts of both pulmonary TB cases and those investigated for TB who were determined to not have TB. In the revision, we removed the contacts \((n = 14)\) of subjects who were determined to not have pulmonary TB after investigation. The number of total pulmonary TB index participants \((n = 142)\) is unchanged. The number of HHCs decreased from 143 to 129. Our study findings are the same whether these household contacts are included or not. The revised numbers are in updated versions of Tables 2 and 3. + +- The explanation for how the 29 CAC+ and 29 CAC- is not sufficient. Is it a convenience sample (e.g. the first ones through the door). Again, anything that isn't random should be described and considered for analysis. + +Response: Thank you for asking for further clarification. The 29 CAC+ and 29 CAC- were a convenience sample due to being the first available participants for transcriptomic analysis. To assess whether these 58 individuals were representative of the full cohort, we compared the variables of CAC+ and CAC- groups in the transcriptomic subgroup analysis (new Supplementary Table 6, \(N = 29\) CAC+ and 29 CAC-) with the full cohort (Table 1, \(N = 43\) CAC+ vs 99 CAC- ). We found no differences in the participant characteristics of + +<--- Page Split ---> + +the CAC+ and CAC- groups when comparing age, sex, HIV status, Xpert Ct, Cavitary CXR, and degree of lung involvement (CXR quadrants). These analyses suggest that the subgroup used for the transcriptomic profiling is representative of the full cohort. + +We also included a new Supplementary Table 6 with a summary of these bivariate analyses (entitled "Comparison of participant characteristics of transcriptomic subgroup and full cohort") + +We added the following text to the Results section: + +"We found no differences in clinical and biologic variables (age, sex, HIV status, Xpert Ct, Cavitary CXR, and degree of lung involvement (CXR quadrants) when comparing participants included in the transcriptomic subgroups (CAC+ and CAC- ) with the remaining cohort (Supplementary Tables 6 and 7)." + +- It should be made clear what age range was studied, and the age range the authors are comfortable for their prediction model to be valid for. + +Response: For the entire study, we did not exclude any age groups and had a range of 18 to 100 years. For the predictive model, we also did not exclude any ages and included the same age range. + +We edited the Results to read as follows: + +"To examine the biology of Mtb aerosolization and transmission, we enrolled 142 individuals with microbiologically confirmed pulmonary TB in Nairobi, Kenya. The median age of participants was 35 years (interquartile range (IQR), 27- 44) and ranged from 18 to 100 years; 27% were women (Table 1)." + +In regards to questions about age and use of the prediction tool, we are not recommending its use as it requires external validation. As we have noted in the Discussion: + +"While promising, the risk score that we present requires external validation and should not be used at this time for clinical (non- research) purposes." + +- L298: With the 3 Xpert categories, variables are no longer all dichotomised, suggest to revise. + +Response: Thank you for this suggestion. We corrected the sentence to read as follows: + +"Included variables were categorized and the optimal cut- points were determined using Youden index (J) method," + +Reviewer #2 (Remarks to the Author): + +The authors addressed all my questions and also the questions of the other reviewers. I am satisfied with the review and recommend the publication. + +Response: We thank the reviewer for these positive comments. + +Reviewer #3 (Remarks to the Author): + +the manuscript is interesting and great value scientifically and clinically. the authors answered the questions raised. + +Response: We thank the reviewer for these positive comments. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +I thank the authors for working through the comments. It is an interesting study with results that should go into the wider scientific discourse, and I think has all the information that engaged readers need to judge the finding. + +Reviewer #4 (Remarks to the Author): + +I was asked only to review the X- ray component of this study. The team obtained posterior anterior chest x- rays from all participants (plus lateral for children \(< 10\) ), which were scored by one member of the study team who is a pulmonologist, according to: presence/absence of cavitations and number of quadrants with abnormalities. + +With regards to this, they found: + +- participants with TB identified through passive case finding were less likely to have cavitary TB (expected) +- cough aerosol culture positive patients were more likely to have cavitary TB +-TB-related abnormalities in more chest X-ray quadrants was associated with cough aerosol culture positivity + +These findings are expected and are clearly described. I have no major concerns with this. The only question is whether the reader was blind to the study results when assessing the chest x- rays, which should be the case. If so, they could clarify this in the methods. + +Unrelated to x- ray: + +Line 359- 360 "GeneXpert cycle threshold and semi- quantitative grade were significantly higher among cough aerosol- culture positive compared with cough aerosol culture- negative participants." - this should be GeneXpert cycle threshold was lower and semi- quantitative grade was higher." Lower PCR cycle thresholds correspond to higher semi- quantitative grade. They also on line 363 show that the Ct relationship was cough aerosol status was negative as expected as lower Ct values correspond to higher bacillary load. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +I thank the authors for working through the comments. It is an interesting study with results that should go into the wider scientific discourse, and I think has all the information that engaged readers need to judge the finding. + +Response: Thank you for your time, knowledge and insights in raising the quality of our manuscript. + +Reviewer #4 (Remarks to the Author): + +I was asked only to review the X- ray component of this study. The team obtained posterior anterior chest x- rays from all participants (plus lateral for children \(< 10\) ), which were scored by one member of the study team who is a pulmonologist, according to: presence/absence of cavitations and number of quadrants with abnormalities. + +With regards to this, they found: + +- participants with TB identified through passive case finding were less likely to have cavitary TB (expected) +- cough aerosol culture positive patients were more likely to have cavitary TB +-TB-related abnormalities in more chest X-ray quadrants was associated with cough aerosol culture positivity + +These findings are expected and are clearly described. I have no major concerns with this. The only question is whether the reader was blind to the study results when assessing the chest x-rays, which should be the case. If so, they could clarify this in the methods. + +Response: Thank you for your review. We have edited the manuscript to state, + +"DJH was blinded to CASS results in the review of chest x- rays." + +## Unrelated to x-ray: + +Line 359- 360 "GeneXpert cycle threshold and semi- quantitative grade were significantly higher among cough aerosol- culture positive compared with cough aerosol culture- negative participants." + +- this should be GeneXpert cycle threshold was lower and semi-quantitative grade was higher." Lower PCR cycle thresholds correspond to higher semi-quantitative grade. They also on line 363 show that the Ct relationship was cough aerosol status was negative as expected as lower Ct values correspond to higher bacillary load. + +Response: Thank you for identifying this error. We have edited the sentence to read, + +"GeneXpert cycle threshold was significantly lower and semi- quantitative grade significantly higher among cough aerosol culture- positive compared to cough aerosol culture- negative participants." + +<--- Page Split ---> diff --git a/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a1ab257c377b595cc3cf2d17ccbc7f56a82866c5 --- /dev/null +++ b/peer_reviews/7851b6ed1dd0d9efc3c42c3642a725b8f905f4e6d998cf18bb8bb6bd30395a08/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,967 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 930, 211]]<|/det|> +Mycobacterium tuberculosis Cough Aerosol Culture Status Associates with Host Characteristics and Inflammatory Profiles + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 290, 107]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 392, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 163, 870, 216]]<|/det|> +This is a very interesting paper, looking to identify markers of infectiousness of individuals with TB. The study is centred around the cough aerosol detection mechanism, and explores it's validity and potential markers. + +<|ref|>text<|/ref|><|det|>[[115, 236, 869, 326]]<|/det|> +While this is interesting data, which should be certainly be published and feed into the wider discourse around Mtb transmission, there are a number of issues which make me unsure if the claims in the title, abstract and certain section headings are backed up sufficiently by the data. Some of these are clarifications and could be fine, others have to do with the study design and analytical approach, which may be harder to overcome. + +<|ref|>text<|/ref|><|det|>[[115, 345, 874, 399]]<|/det|> +A major issue is lack of a control group of HH contacts, which would help to understand how the \(53\%\) IGRA+ in the CAC- population should be interpreted. This means that the findings can reflect on markers for 'higher' infectiousness, as suggested by CASS positivity. + +<|ref|>text<|/ref|><|det|>[[115, 418, 866, 490]]<|/det|> +A key gap in the current methods is a lack of description of how the shift from 142 participants with TB to including 55 index cases in the HH contact study. It is mentioned in the results section, but is not described at all. Similarly, \(n = 58\) index cases were included in the transcriptomics, but their selection is not described. That needs to be clarified (see more detailed comments below). + +<|ref|>text<|/ref|><|det|>[[114, 509, 878, 655]]<|/det|> +The analysis approach for the predictive models is a simple forward selection of variables. In the context of this well studied area, this seems too uninformed. The consequence is some strange findings which the authors do not pick up on. E.g. Why would MUAC be predictive but BMI would not? How should we interpret CASS predictive model mean where a dichotomised age variable is given equal importance as the sole bacteriological indicator (Xpert CT threshold)? While an uninformed approach to the cytokine/transcriptomics analysis seems OK given its novelty, this is not the case for associations for transmission or infectiousness, and this should be addressed, e.g. by discussing a conceptual framework, and exploring different predictive models with a- priori choices. + +<|ref|>text<|/ref|><|det|>[[114, 674, 876, 892]]<|/det|> +The more conceptual issue is what space of infectiousness this paper addresses. The title, abstract and body text shift between scope. For example, the title and abstract reflect on 'TB infectiousness', suggesting it is about individuals that are either infectious or not. As clarified later in the abstract, the authors actually focus on a differentiation between more or less infectious individuals, based on CASS. They show that CASS+ individuals are likely more infectious with a nested household contact study (which is not a new finding), but there is no control group, so no statement about a binomial infectious yes/no status. For the transcriptomics they then look in a subgroup (which is not defined, see above), and find a number of associations with CASS+. I would agree that this provides data to 'suggest host inflammatory signatures are associated with Mtb aerosolization independent of bacillary load and cavitary lung disease.', as stated in the discussion. But what it does not show is 'Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles', which is the paper title, and as such much too broad. I think the authors should be more clear, and e.g. change the title, and any + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 763, 125]]<|/det|> +other statements regarding 'infectiousness' as a whole to reflect the more narrow scope. + +<|ref|>text<|/ref|><|det|>[[114, 144, 870, 180]]<|/det|> +I have provided extensive detailed comments below, which hopefully will help improve the paper when the data is published here or in another journal. + +<|ref|>sub_title<|/ref|><|det|>[[115, 200, 188, 215]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[115, 218, 861, 253]]<|/det|> +While I understand why ignored trace+/culture- (given the low chance of being CASS pos), it would be good to state this explicitly, and state how the authors interpreted this group. (TB or not TB)? + +<|ref|>text<|/ref|><|det|>[[115, 272, 872, 290]]<|/det|> +There is some reporting of results for BMI vs MUAC in the methods, this should be moved to the results. + +<|ref|>text<|/ref|><|det|>[[115, 309, 452, 325]]<|/det|> +L314- 318 is results I think, should move there. + +<|ref|>text<|/ref|><|det|>[[115, 345, 869, 455]]<|/det|> +It is not obvious from the methods that the HH contacts came from a subset \((n = 55,1352)\) of enrolled participants from the total population \((n = 142)\) . I did not see it in I185- I189), nor is it mentioned in I142- I144. Firstly, this should be made clear more clear. Secondly the rationale and method for this selection should be described explicitly (e.g. funding restrictions and random draw?). There is a similar selection for the host transcriptomic work (going down to \(n = 59\) index patients), which needs to be similarly explained. + +<|ref|>sub_title<|/ref|><|det|>[[115, 475, 179, 490]]<|/det|> +## RESULTS + +<|ref|>text<|/ref|><|det|>[[115, 492, 874, 583]]<|/det|> +335: It seems odd that all of the participants were cough positive, as a percentage came from community screening. Given the difference in population and expected disease severity between ACF and PCF populations, these two populations should be described more in the text and supp materials. If the \(100\%\) cough positive holds, it is something to discuss, as it goes against most modern TB prevalence surveys where about \(50\%\) were found to be cough negative. + +<|ref|>text<|/ref|><|det|>[[115, 601, 872, 656]]<|/det|> +Table 1: The MUAC result is odd (i.e. a higher MUAC means more \(\mathsf{CASS + }\) ). It seems counterintuitive, and the lack of an association with BMI makes me concerned the MUAC results are less reliable. The BMI/MUAC discrepancy should be discussed. + +<|ref|>text<|/ref|><|det|>[[115, 675, 879, 765]]<|/det|> +Table 2: I am not clear what the OR and p- values are meant to show here. For the index case characteristics, those seem a near 1- 2- 1 repeat of table 1? I think those could be dropped, especially from the main body text. For e.g. the number of contacts per case - I think this is just a chi- square, but that is not the relevant finding. What we would like to know is whether the distribution of HH contacts is different by CAC+ and CAC-, which is currently unclear. + +<|ref|>text<|/ref|><|det|>[[115, 784, 763, 802]]<|/det|> +What were reasons for missing QFT (N goes from 143 to 127)? These should be reported. + +<|ref|>text<|/ref|><|det|>[[115, 821, 870, 894]]<|/det|> +Table 3: The results are quite stark, but not sure how superior the final model is. It makes sense that after one good measure of bacteriological burden is included in the model, the others are no longer adding enough value to be included. E.g. smear and cavitation seem to be quite useful explanatory/predictive variables by themselves. A simple forward stepwise modelling approach will not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 162]]<|/det|> +highlight those limitations. Given what we already know about infectiousness, this type of analysis would be better served with a formal DAG or at least conceptual framework, and then working through the various options or models. I suggest the authors explore this wider, and thereby enrich the insights that can be gained from the data. + +<|ref|>text<|/ref|><|det|>[[114, 181, 881, 345]]<|/det|> +While the AUC for the scoring system for predicting \(\mathsf{CAC + } / -\) is high, I don't quite understand the results from Sup table 1. It seems to suggest that age and Xpert CT are equally valuable (both 7 'points')? But what does the model/score mean if the sole bacteriological indicator is removed? Are the authors suggesting that we could decide on \(\mathsf{CAC + } / -\) by age, CRP and MUAC alone? Could they provide an indication of how much value each individual characteristic adds, and how the model works if Xpert CT is not available. Could any other bacteriological indicator be switched in? I'd be surprised if the model functioned without a bacteriological indicator, and also not sure about the biological logic that would remain. It is also not clear if this predictive model is solely applicable for people who have bacteriologically positive TB? If so, that should be made clear. + +<|ref|>text<|/ref|><|det|>[[115, 364, 872, 455]]<|/det|> +The variation in association pattern of the different cytokines is a bit strange. Would one not expect them to be elevated across the various indicators, also given that e.g. CT threshold and cavitation were themselves associated with CAC? The lack of stability makes me a bit concerned. The results are what they are, but potential explanations (including random noise across many comparisons that could affect the threshold for interpretation of p- values). + +<|ref|>sub_title<|/ref|><|det|>[[115, 475, 208, 490]]<|/det|> +## DISCUSSION + +<|ref|>text<|/ref|><|det|>[[115, 493, 861, 546]]<|/det|> +L455- 457: these are results, and should be moved there. On a broader note, it would be good to place those observations in the context of the ongoing discussions around subclinical TB (see previous comment re cough positivity). + +<|ref|>text<|/ref|><|det|>[[115, 565, 875, 600]]<|/det|> +L462: the statement about 'body mass' is strange, as BMI was not associated, but MUAC was. As mentioned before, this discrepancy needs discussion, and the statement should be adjusted accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 620, 870, 691]]<|/det|> +L473: this only interprets one of the cytokine findings, but ignored the conflicting results in the actual section (see above), where some cytokines were associated for one indicator, but not the other. Do the authors assume only 1 indicator is valid? If so, that is a stretch. If not, the discrepancies need to be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 711, 876, 820]]<|/det|> +L535: the suggestion that interventions (i.e. treatment) should target the most infectious is a bit strange. This approach was tried with the development of DOTS policies, where symptomatic smear positive individuals were targeted through PCF and 6m therapy. While saving lives, it has not interrupted transmission as expected, and it is not clear to me why this would work now? Shouldn't Identifying and treating all infectious individuals be the minimum target for all high burden countries, regardless of how infectious they are at the time of diagnosis? + +<|ref|>text<|/ref|><|det|>[[115, 840, 870, 893]]<|/det|> +Furthermore, infectiousness is not static, and will likely vary over time. Finally, given the high Number Needed to Test to identify any person with low or high infectious disease, the cost of treatment is really not the limiting factor. It would be helpful if the authors reflected a bit more on this (also in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 216, 106]]<|/det|> +introduction). + +<|ref|>text<|/ref|><|det|>[[115, 145, 862, 180]]<|/det|> +Minor pointsRef 33, 34 and 58 are the same I believe. Would be good to recheck references and make sure in order. + +<|ref|>text<|/ref|><|det|>[[115, 198, 881, 252]]<|/det|> +Table 1: category 'Enrolled thru prevalence survey' – not appropriate language for scientific paper and not reflected in main text. Suggest something along lines of 'ACF- enrolled', as this is how it is described in methods. + +<|ref|>text<|/ref|><|det|>[[115, 272, 876, 326]]<|/det|> +Table 3: the unit for Age is not given. From the OR I suspect it is year of age, but this should be made clear. Also note this assumes a linear association across the entire age range, which is unlikely to be true given what we know about age- dependent population ARI. This should be discussed. + +<|ref|>text<|/ref|><|det|>[[115, 345, 875, 400]]<|/det|> +The section titles on 1397 and 1409 are phrased as interpretation rather than reporting of results. These should be adjusted. In addition, the last sentences in each of these sections is interpretation rather than result, and should be removed or put in discussion. + +<|ref|>text<|/ref|><|det|>[[115, 455, 392, 472]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 508, 880, 691]]<|/det|> +The study "Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles" stands out for addressing a significant gap in tuberculosis research, focusing on individual infectiousness and biomarkers. It employs a prospective longitudinal study design, examining treatment- naive pulmonary TB patients in Nairobi, thereby providing valuable insights in a high TB burden setting. Methodological innovations, such as using the Cough Aerosol Sampling System (CASS) for measuring Mycobacterium tuberculosis aerosolization, the evaluation of sputum cytokine, and assessing household contacts through IGRA testing, add important epidemiological and molecular dimensions and adds novel knowledge and tools to predict Mtb transmission. Overall, the manuscript was well written. The incorporation of suggested improvements would enhance the paper's quality and ensure that concerns have been adequately addressed. + +<|ref|>text<|/ref|><|det|>[[115, 710, 875, 783]]<|/det|> +#1 Introduction: The introduction section is well- written and effectively frames the context of TB infectiousness to its clinical and immunological aspects. It successfully outlines the importance of understanding individual variations in TB transmission and reviews relevant literature, thus situating the study within the broader field of TB research. I have no suggestions for improvement in this section. + +<|ref|>text<|/ref|><|det|>[[115, 802, 870, 856]]<|/det|> +#2 Methods: The methods section is well- structured and thorough. However, consider breaking down the dense text into smaller paragraphs to improve readability (i.e. break the paragraph in line 262. "We assessed....". In addition: + +<|ref|>text<|/ref|><|det|>[[115, 857, 870, 893]]<|/det|> +#2.1 – Methods (Line 203-204): The study does not address the issue of drug- resistant TB. On lines 203-204, the study mentions classifying rifampicin resistance as "positive," "negative," or "indeterminate," + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 877, 143]]<|/det|> +but this is not further elaborated in the text. I recommend including these data in the results and tables, even if \(100\%\) were susceptible, to provide a complete picture of the resistance profile among the study participants. + +<|ref|>text<|/ref|><|det|>[[115, 144, 882, 235]]<|/det|> +#2.2 - Results (lines 222-228): It would be beneficial to provide a rationale for the decision to assess cytokines in sputum instead of blood; as well as the selection of the specific three cytokines studied. This is particularly important for readers who may have less experience in the field. Including one or two lines to explain these choices would greatly aid in comprehending the significance and implications of these methodological decisions. + +<|ref|>text<|/ref|><|det|>[[115, 236, 881, 290]]<|/det|> +#2.3 - Methods (Data analysis section): To enhance reproducibility, I recommend adding a table in the supplementary material section. This table should list the names of the R packages used, their respective versions, and references. + +<|ref|>text<|/ref|><|det|>[[115, 309, 879, 400]]<|/det|> +#3 Results: The results section provides a detailed and thorough presentation of the study's findings and analyses. The section appears to be well- organized and structured, with clear descriptions of the methods used and the outcomes observed. The use of tables, figures, and numerical values enhances the clarity of the presented results. However, there are a few areas where the clarity and objectivity could be further improved: + +<|ref|>text<|/ref|><|det|>[[115, 401, 880, 474]]<|/det|> +#3.1 Results (lines 350-368): Considering that age emerged as a significant variable in the mixed methods bivariate & multivariable analysis, and the low median age reported, it is essential to have information on how many HHCs were children or adolescents. Furthermore, this aspect of age, including the distinction between adult and non- adult contacts, should be highlighted in the discussion section. + +<|ref|>text<|/ref|><|det|>[[115, 475, 870, 510]]<|/det|> +#3.2 Results (lines 392-394): Please provide the sensitivity and specificity values of the ROC curve, with confident intervals. + +<|ref|>text<|/ref|><|det|>[[115, 511, 866, 583]]<|/det|> +#3.3. Results (lines 397-437): In lines 397-437, all paragraphs finish with a phrase with the same structure that starts with "Together, these data suggest". I recommend rewriting some of them and evaluating if it is necessary. For example, I do not think that the phrase in lines 436-437 is fundamental for the text. + +<|ref|>text<|/ref|><|det|>[[115, 584, 870, 712]]<|/det|> +#3.4. Results (Figures): The figures in the manuscript, particularly Figures 1c and d, Figure 2, and Supplementary Figure 4, need to be improved for better comprehension. A key enhancement is to include the legend for colours and shapes directly on the figure itself, rather than solely in the written legend. The absence of this information on the figures themselves can hinder interpretation and understanding. Providing these details directly on the figures would facilitate a more immediate and clear comprehension of the data being presented, especially for readers who might be quickly scanning through the figure. + +<|ref|>text<|/ref|><|det|>[[115, 730, 877, 820]]<|/det|> +#4 Discussion: The discussion section demonstrates a good quality of scientific communication, with a thorough examination of the study's results and their implications. The section effectively contextualizes the findings within the existing literature and provides a balanced interpretation of the results. The limitations are acknowledged, and their potential impact on the study's conclusions is addressed. Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 821, 866, 875]]<|/det|> +#4.1. It would be beneficial to discuss in more detail the age of the Household Contacts (HHCs), as well as the rationale behind using sputum to assess biomarkers. These discussions could provide deeper insights into the study's findings and their implications. + +<|ref|>text<|/ref|><|det|>[[115, 876, 793, 894]]<|/det|> +#4.2 (lines 447-500): Breaking up the paragraphs could enhance the readability and clarity of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 825, 107]]<|/det|> +information, making it easier for readers to digest and understand the key points being conveyed. + +<|ref|>text<|/ref|><|det|>[[116, 145, 393, 162]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 182, 844, 253]]<|/det|> +The study is very interesting and opens new ways for understanding TB pathogenesis and proposing clinical management. Based on the reported findings and prior studies, cough aerosol cultures are superior to sputum smear analysis in predicting Mtb transmission events and are likely the best estimators of TB infectiousness. + +<|ref|>text<|/ref|><|det|>[[115, 256, 233, 271]]<|/det|> +Few comments: + +<|ref|>text<|/ref|><|det|>[[115, 274, 872, 365]]<|/det|> +Figure 1A: is any possibility of evaluating the correlation of WHITE BLOOD CELLS components as Lymphocytes, monocytes, or neutrophils with CAC?. Indeed interesting correlations were found in the past using different approaches (La Manna, 2017, PMID: 28208160; Chedid, 2020, PMID: 32920230; ). Moreover, it would be interesting to evaluate if there is an association between CAC score and platelets (La Manna, 2022 PMID: 35338775) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[72, 67, 279, 84]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[72, 99, 375, 115]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[71, 130, 916, 180]]<|/det|> +This is a very interesting paper, looking to identify markers of infectiousness of individuals with TB. The study is centered around the cough aerosol detection mechanism and explores its validity and potential markers. + +<|ref|>text<|/ref|><|det|>[[71, 194, 886, 276]]<|/det|> +While this is interesting data, which should be certainly be published and feed into the wider discourse around Mtb transmission, there are a number of issues which make me unsure if the claims in the title, abstract and certain section headings are backed up sufficiently by the data. Some of these are clarifications and could be fine, others have to do with the study design and analytical approach, which may be harder to overcome. + +<|ref|>text<|/ref|><|det|>[[71, 290, 905, 323]]<|/det|> +Response: We thank the reviewer for these positive comments and attempt to address all concerns in the replies below. + +<|ref|>text<|/ref|><|det|>[[72, 339, 260, 350]]<|/det|> +\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*\*\\*\\*\\*\\*\\*\\*\\*\\*\\* + +<|ref|>text<|/ref|><|det|>[[71, 355, 909, 404]]<|/det|> +A major issue is lack of a control group of HH contacts, which would help to understand how the \(53\%\) IGRA+ in the CAC- population should be interpreted. This means that the findings can reflect on markers for 'higher' infectiousness, as suggested by CASS positivity. + +<|ref|>text<|/ref|><|det|>[[70, 417, 920, 547]]<|/det|> +Response: We agree that providing a control group for the HH contacts is important to make population level claims regarding infectiousness. To address this concern, we include new data from two cohorts to estimate the frequency of QFT- positive tests among Nairobi residents without a known recent TB exposure (the "background" frequency of Mtb infection based on QFT result). For both cohorts, the rate of IGRA positivity was \(51\%\) and similar to rate of the household contacts of CASS- negative index cases \((54\%)\) . All of these rates are lower than the household contacts of CASS- positive index cases \((88\%)\) . These data suggest that CASS- positive pulmonary TB cases have a higher degree of infectiousness compared to those who are CASS- negative with evidence from multiple control groups. + +<|ref|>text<|/ref|><|det|>[[71, 561, 581, 578]]<|/det|> +The following language has been added to the Methods section: + +<|ref|>text<|/ref|><|det|>[[70, 593, 920, 770]]<|/det|> +"We estimated the frequency of positive interferon- gamma release assays in Nairobi residents who were not known to have active TB or recent close contact to a person with active pulmonary TB. Participants were enrolled through two studies. As part of a study of cough analysis for TB detection (38), we recruited adult outpatients \((n = 45)\) from the same TB and respiratory clinics as TBAIT participants with TB (described above) who were identified through passive case finding and presented with cough. All participants underwent sputum GeneXpert testing and chest X- rays to exclude pulmonary TB. Additionally, we report results from a study to evaluate treatment responses during isoniazid preventive therapy (39). From December 2019 to December 2020, we recruited adults with \((n = 121)\) and without \((n = 122)\) HIV from three HIV prevention and care centers in Nairobi. We assessed for TB using the WHO four- symptom screen, followed by sputum GeneXpert and chest X- rays among those with one or more symptoms. To calculate prevalence of QFT positive tests, we excluded indeterminate results." + +<|ref|>text<|/ref|><|det|>[[70, 785, 442, 801]]<|/det|> +We added the following to the Results section: + +<|ref|>text<|/ref|><|det|>[[70, 816, 912, 913]]<|/det|> +"To establish the background prevalence of QFT positive results in Nairobi residents, we evaluated QFT status in adult outpatients who presented for health care due to cough \((n = 45\) , median age 39 years (IQR, 34- 45)) and to HIV prevention and care centers \((n = 121\) PLWH; \(n = 122\) without HIV; overall median age 36 years (IQR, 28- 44). After excluding indeterminate results \((n = 2\) and \(n = 34\) , respectively), we found that the prevalence of QFT- positive results was, \(51\%\) \((n = 22)\) and \(51\%\) \((n = 121)\) , respectively. Among the 45 persons who presented to health care with a cough, QFT status did not differ by HIV status (PLWH = 17, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 65, 882, 147]]<|/det|> +p- value 0.66). In participants recruited at HIV care centers, QFT results differed by HIV status: \(43\%\) of PLWH (48 of 111) and \(60\%\) of persons without HIV (59 of 98) (p- value 0.01) were QFT positive. The estimated Nairobi background prevalence of QFT test positivity did not differ from contacts of cough aerosol culture- negative participants (p- value 0.33) but was significantly lower than contacts of cough aerosol culture- positive participants (p- value \(< 0.001\) )." + +<|ref|>text<|/ref|><|det|>[[71, 161, 921, 211]]<|/det|> +A key gap in the current methods is a lack of description of how the shift from 142 participants with TB to including 55 index cases in the HH contact study. It is mentioned in the results section, but is not described at all. + +<|ref|>text<|/ref|><|det|>[[71, 226, 894, 259]]<|/det|> +Response: Thank you for highlighting this concern. We added the following clarifying statements in the Results Section, + +<|ref|>text<|/ref|><|det|>[[70, 273, 923, 370]]<|/det|> +"We next evaluated IGRA results in household contacts to determine whether cough aerosol culture status is associated with infectiousness. Of the 142 participants with TB, 30 lived alone and were not eligible for the household contact study and 57 had household members who could not be contacted or the household members declined enrollment. From the remaining 55 index participants, we enrolled 143 household contacts and obtained QFT tests on 127 (16 declined phlebotomy or had unsuccessful phlebotomy) (Table 2)." + +<|ref|>text<|/ref|><|det|>[[71, 384, 844, 418]]<|/det|> +Similarly, \(n = 58\) index cases were included in the transcriptomics, but their selection is not described. That needs to be clarified (see more detailed comments below). + +<|ref|>text<|/ref|><|det|>[[71, 432, 857, 465]]<|/det|> +Response: To clarify the selection of individuals for transcriptomic studies, we added the following information to the Methods section: + +<|ref|>text<|/ref|><|det|>[[71, 481, 915, 530]]<|/det|> +"We selected 58 subjects for whole blood transcriptomic analysis which were a subgroup of the full cohort of 142. We initiated this experiment after 29 CAC+ and 29 CAC- subjects were available for analysis from the initial phase of enrollment (Supplementary Table 4)." + +<|ref|>text<|/ref|><|det|>[[71, 544, 904, 608]]<|/det|> +The analysis approach for the predictive models is a simple forward selection of variables. In the context of this well studied area, this seems too uninformed. The consequence is some strange findings which the authors do not pick up on. E.g. Why would MUAC be predictive but BMI would not? + +<|ref|>text<|/ref|><|det|>[[71, 624, 911, 704]]<|/det|> +Response: Thank you for this important question. While MUAC and BMI would seem to be two measurements of the same phenomenon (malnutrition) and therefore highly correlated, a body of findings from the literature demonstrates that there are differences between these biometrics. BMI measures the presence or loss of adipose tissue. MUAC assesses both adipose tissue and muscle mass. As such, MUAC reflects the presence of cachexia. + +<|ref|>text<|/ref|><|det|>[[71, 720, 571, 736]]<|/det|> +We added the following to the Discussion with new references: + +<|ref|>text<|/ref|><|det|>[[70, 751, 923, 880]]<|/det|> +"Our finding of a stronger association between cough aerosol status and MUAC than BMI may seem counterintuitive. However, MUAC and BMI measure related but different aspects of nutritional status: BMI reflects fat mass while MUAC measures fat and muscle mass. (51). Low MUAC was a better predictor than BMI of all- cause mortality in older adults (51- 53), and in persons with TB. MUAC (unlike BMI) was independently associated with cavitary lung disease (54). Cachexia, severe weight loss that results from muscle atrophy and the loss of adipose tissue, may correlate with differential immune cell responses (55). For example, using parasitic infections in the murine model, mice deficient for CD4+ T cells experienced muscle and fat wasting as opposed to CD8+ T cell- deficient mice which experienced only fat wasting (56)." + +<|ref|>text<|/ref|><|det|>[[71, 895, 910, 912]]<|/det|> +How should we interpret CASS predictive model mean where a dichotomised age variable is given + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 66, 914, 147]]<|/det|> +equal importance as the sole bacteriological indicator (Xpert CT threshold)? While an uninformed approach to the cytokine/transcriptomics analysis seems OK given its novelty, this is not the case for associations for transmission or infectiousness, and this should be addressed, e.g. by discussing a conceptual framework, and exploring different predictive models with a- priori choices. + +<|ref|>text<|/ref|><|det|>[[71, 162, 921, 260]]<|/det|> +Response: Thank you for raising this important concern. We added a conceptual framework that is presented in Figure S1 as a Directed Acyclic Graph (DAG) to evaluate pulmonary TB host characteristics (predictors) associated with cough aerosol culture positive status (outcome). We included predictors (listed in methods section below), potential confounders (bacillary burden, HIV, and sex), mediators (health care engagement) and effect modifiers (Mtb strain), strengthening the rationale for our models' variable selection. We provide further details in the Methods section and Figure legend below. + +<|ref|>text<|/ref|><|det|>[[72, 274, 630, 291]]<|/det|> +The following new language has been added to the following sections: + +<|ref|>sub_title<|/ref|><|det|>[[72, 307, 147, 322]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[70, 338, 923, 643]]<|/det|> +"We assessed associations between host TB characteristics and cough aerosol culture- positive status using bivariate and multivariable logistic regression models in which we evaluated predictor variables based on our conceptual model presented as a directed acyclic graph (DAG, Supplementary Figure 2) (45). Based on published studies of TB transmission and cough aerosol status (18, 25, 29), we categorized as predictors characteristics that we hypothesized as determining the cough aerosol culture- positive phenotype including younger age, functional status (body mass index (BMI), mid- upper arm circumference (MUAC), TB symptoms, cough duration, Leicester Cough Questionnaire (LCQ) score, prior history of TB, and cough peak flow) (29) and systemic inflammation (CRP, hemoglobin, white blood cell count and differential, hemoglobin A1C percent, and sputum appearance). In the DAG we categorized HIV status, bacillary burden (GeneXpert semi- quantitative grade, GeneXpert Ct value, AFB- smear grade, time to detection (TTD) of Mtb growth in liquid culture, presence of chest X- ray cavitation, and number of radiographic quadrants with TB- related changes), and sex as potential confounders due to their shared associations with the exposure and outcome (46). Health care engagement is considered a mediator, a node that is on the causal pathway from exposure to outcome and should not be controlled in models. Pathogen- related factors, which are not included in this study, would be considered effect modifiers as they may contribute to the outcome and modify the effect of other causes of the outcome. GeneXpert Ct values were assigned using the smallest Ct value from any of the probes targeting the rpoB gene; participants with Xpert Ultra trace positive results (for whom rpoB probe Ct values were 0) were assigned a Ct value of 35, near the highest detectable Ct value for Xpert Ultra." + +<|ref|>sub_title<|/ref|><|det|>[[72, 658, 137, 673]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[71, 674, 891, 707]]<|/det|> +"We evaluated host characteristics associated with cough aerosol culture status based on a conceptual framework which included potential confounders (Table 1, Supplemental Figure 1)." + +<|ref|>text<|/ref|><|det|>[[72, 722, 202, 738]]<|/det|> +Figure Legends: + +<|ref|>text<|/ref|><|det|>[[71, 739, 912, 820]]<|/det|> +"Supplementary Figure 1: Directed acyclic graph (DAG) depicting conceptual framework of factors that determine cough aerosol culture status in persons with pulmonary TB. DAGs depict associations between an exposure (pulmonary tuberculosis), outcome (cough aerosols that are culture positive for M. tuberculosis), mediator (health care engagement), potential confounders (bacillary burden, HIV status, sex) and effect modifier (pathogen factors such as strain of M. tuberculosis)." + +<|ref|>text<|/ref|><|det|>[[71, 850, 919, 916]]<|/det|> +The more conceptual issue is what space of infectiousness this paper addresses. The title, abstract and body text shift between scope. For example, the title and abstract reflect on 'TB infectiousness', suggesting it is about individuals that are either infectious or not. As clarified later in the abstract, the authors actually focus on a differentiation between more or less infectious + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 65, 923, 228]]<|/det|> +individuals, based on CASS. They show that CASS+ individuals are likely more infectious with a nested household contact study (which is not a new finding), but there is no control group, so no statement about a binomial infectious yes/no status. For the transcriptomics they then look in a subgroup (which is not defined, see above), and find a number of associations with CASS+. I would agree that this provides data to 'suggest host inflammatory signatures are associated with Mtb aerosolization independent of bacillary load and cavitary lung disease.', as stated in the discussion. But what it does not show is 'Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles', which is the paper title, and as such much too broad. I think the authors should be more clear, and e.g. change the title, and any other statements regarding 'infectiousness' as a whole to reflect the more narrow scope. + +<|ref|>text<|/ref|><|det|>[[70, 243, 919, 340]]<|/det|> +Response: Thank you for these suggestions. We added two control groups to provide an estimated level of Mtb infection (based on QFT results) in adult residents of Nairobi who are without a known recent TB exposure (please see detailed response above). We changed the title to, "Mycobacterium tuberculosis Cough Aerosol Culture Status is Associated with Host Clinical Characteristics, Host Inflammatory Profiles, and Infection in Close Contacts". We have clarified the group of participants who underwent transcriptional profiling (please see explanation above). + +<|ref|>text<|/ref|><|det|>[[71, 355, 147, 370]]<|/det|> +Methods: + +<|ref|>text<|/ref|><|det|>[[70, 385, 919, 420]]<|/det|> +While I understand why ignored trace+/culture- (given the low chance of being CASS pos), it would be good to state this explicitly, and state how the authors interpreted this group. (TB or not TB)? + +<|ref|>text<|/ref|><|det|>[[70, 433, 912, 547]]<|/det|> +Response: We agree that more clarity is needed. The trace positive/culture negative individuals were identified through a prevalence survey where we used an active case finding method which is more likely to identify people with subclinical TB with minimal symptoms. We excluded individuals who were trace positive/culture negative as we do not consider them to have active TB. Participants in this category were identified only through active case- finding, were culture negative on four sputum samples that underwent MGIT culture and did not fit the eligibility of our CASS- study protocol. We added the following sentence to the Methods section, + +<|ref|>text<|/ref|><|det|>[[70, 562, 912, 610]]<|/det|> +"We did not include persons in this study identified through active case finding who were trace positive/culture- negative as we concluded that they did not have active pulmonary based on four negative sputum cultures." + +<|ref|>text<|/ref|><|det|>[[70, 625, 900, 658]]<|/det|> +There is some reporting of results for BMI vs MUAC in the methods, this should be moved to the results. + +<|ref|>text<|/ref|><|det|>[[70, 673, 460, 690]]<|/det|> +Response: We are unable to find this in the text. + +<|ref|>text<|/ref|><|det|>[[70, 720, 466, 737]]<|/det|> +L314- 318 is results I think, should move there. + +<|ref|>text<|/ref|><|det|>[[70, 752, 680, 769]]<|/det|> +Response: We agree and moved the following from the Methods to Results: + +<|ref|>text<|/ref|><|det|>[[70, 784, 916, 833]]<|/det|> +"While a strong majority of the genes (78%) were best fit by models including cough aerosol culture status alone, 16% of genes were best fit with the inclusion of bacillary load with a smaller percentage best explained by more complex models with age and cavitary disease (Supplemental Figure 3A)." + +<|ref|>text<|/ref|><|det|>[[70, 848, 921, 914]]<|/det|> +It is not obvious from the methods that the HH contacts came from a subset (n=55, 1352) of enrolled participants from the total population (n=142). I did not see it in 1185- 1189), nor is it mentioned in 1142- 1144. Firstly, this should be made more clear. Secondly the rationale and method for this selection should be described explicitly (e.g. funding restrictions and random draw?). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 82, 919, 196]]<|/det|> +Response: Thank you. We added the following clarifying statements in the Results Section: "We next evaluated IGRA results in household contacts to determine whether cough aerosol culture status is associated with infectiousness. Of the 142 participants with TB, 30 lived alone and were not eligible for the household contact study and 57 had household members who could not be contacted, or the household members declined enrollment. From the remaining 55 index participants, we enrolled 143 household contacts and obtained QFT tests on 127 (16 declined phlebotomy or had unsuccessful phlebotomy) (Table 2)." + +<|ref|>text<|/ref|><|det|>[[70, 210, 901, 245]]<|/det|> +There is a similar selection for the host transcriptomic work (going down to \(n = 59\) index patients), which needs to be similarly explained. + +<|ref|>text<|/ref|><|det|>[[71, 259, 565, 276]]<|/det|> +Response: Thank you. Please see detailed responses above. + +<|ref|>sub_title<|/ref|><|det|>[[71, 291, 157, 306]]<|/det|> +## RESULTS + +<|ref|>text<|/ref|><|det|>[[71, 307, 904, 388]]<|/det|> +335: It seems odd that all of the participants were cough positive, as a percentage came from community screening. Given the difference in population and expected disease severity between ACF and PCF populations, these two populations should be described more in the text and supp materials. If the \(100\%\) cough positive holds, it is something to discuss, as it goes against most modern TB prevalence surveys where about \(50\%\) were found to be cough negative. + +<|ref|>text<|/ref|><|det|>[[70, 402, 917, 579]]<|/det|> +Response: Thank you for this suggestion. We agree that more description of these two populations is important for clarity. All participants identified through active case- finding were CAC- negative. As persons who presented for health care contributed entirely to CAC- positive participants (thus, \(100\%\) with cough) and contributed the majority of CAC- negatives, we see the high frequency of cough. Of the 26 participants enrolled through active case finding (all of whom were CAC- negative), 5 denied cough, for a cough frequency of \(81\%\) . In the community- based prevalence survey, \(42\%\) of people with prevalent TB denied cough. We did not enroll all people with prevalent TB into our CASS study as some were GeneXpert negative and later diagnosed with TB based on culture results, declined enrollment or were not available for recruitment (e.g. were diagnosed on a Saturday). We are not suggesting that the ACF participants are representative of prevalent TB in the community and have added text for clarification. We added the following clarifying language to the Methods section: + +<|ref|>text<|/ref|><|det|>[[70, 593, 914, 658]]<|/det|> +"We did not include persons in this study identified through active case finding who were GeneXpert negative/culture- positive due to delays in their TB diagnosis, who were trace positive/culture- negative as we concluded that they did not have active pulmonary based on four negative sputum cultures, those who were diagnosed on weekends or those who declined enrollment." + +<|ref|>text<|/ref|><|det|>[[72, 673, 380, 690]]<|/det|> +We added the following to the Results: + +<|ref|>text<|/ref|><|det|>[[70, 704, 905, 785]]<|/det|> +"As compared to participants identified through passive case finding ( \(n = 116\) ), those identified through active case finding ( \(n = 26\) ) were older (mean 43 vs. 35 years, p- value 0.005), less likely to report a cough ( \(81\%\) vs. \(98\%\) , p- value \(< 0.001\) ), less likely to have cavitary disease on chest x- ray ( \(38\%\) vs \(77\%\) , p- value \(< 0.001\) ) and had higher mean GeneXpert Ct values (24.0 vs. 19.2, p- value \(< 0.001\) ); there was no difference in the frequency of women or PLWH." + +<|ref|>text<|/ref|><|det|>[[70, 800, 897, 850]]<|/det|> +Table 1: The MUAC result is odd (i.e. a higher MUAC means more CASS+). It seems counterintuitive, and the lack of an association with BMI makes me concerned the MUAC results are less reliable. The BMI/MUAC discrepancy should be discussed. + +<|ref|>text<|/ref|><|det|>[[72, 864, 390, 881]]<|/det|> +Response: Please see above response. + +<|ref|>text<|/ref|><|det|>[[70, 896, 861, 914]]<|/det|> +Table 2: I am not clear what the OR and p- values are meant to show here. For the index case + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 66, 910, 131]]<|/det|> +characteristics, those seem a near 1- 2- 1 repeat of table 1? I think those could be dropped, especially from the main body text. For e.g. the number of contacts per case – I think this is just a chi- square, but that is not the relevant finding. What we would like to know is whether the distribution of HH contacts is different by CAC+ and CAC-, which is currently unclear. + +<|ref|>text<|/ref|><|det|>[[70, 145, 922, 260]]<|/det|> +Response: Table 2 contains a sub- set \((n = 55)\) of the index participants in Table 1 \((n = 142)\) . Since some of the index participants lived alone or had household contacts that were not enrolled (could not be reached, declined participation), there are differences in the included index participants. The purpose of Table 2 is to show variables of interest that may associate with differences in transmission risk and QFT result in order to assess for contributors to the differences in household contact QFT status by cough aerosol status of the index participant. Ultimately, we are offering data to support our hypothesis that cough aerosol status is the largest driver (risk factor) for TB transmission to close contacts. + +<|ref|>text<|/ref|><|det|>[[70, 273, 919, 372]]<|/det|> +We have removed the odds ratio column from Table 2, clarified in Table 2 the number of index participants and their relation to household contacts, and removed the requested language from the main text. The p- value compares the size of households enrolled and shows a statistically significant difference. The number of contacts per household is larger for contacts of CAC- negative index participants: \(36\%\) of HHCs of CAC+ index participants were from households that enrolled 3 or more contacts compared to \(48\%\) of HHCs of CAC- index participants. We have clarified this by adding percents to the Table 2 cells. + +<|ref|>text<|/ref|><|det|>[[70, 384, 833, 403]]<|/det|> +What were reasons for missing QFT (N goes from 143 to 127)? These should be reported. + +<|ref|>text<|/ref|><|det|>[[70, 409, 870, 443]]<|/det|> +Response: The reasons for missing QFTs among enrolled HHCs was due to refusing phlebotomy or unsuccessful phlebotomy. We added the following text: + +<|ref|>text<|/ref|><|det|>[[70, 448, 920, 482]]<|/det|> +"From the remaining 55 index participants, we enrolled 143 household contacts and obtained QFT tests on 127 (16 declined or had unsuccessful phlebotomy) (Table 2)." + +<|ref|>text<|/ref|><|det|>[[70, 496, 923, 625]]<|/det|> +Table 3: The results are quite stark, but not sure how superior the final model is. It makes sense that after one good measure of bacteriological burden is included in the model, the others are no longer adding enough value to be included. E.g. smear and cavitation seem to be quite useful explanatory/predictive variables by themselves. A simple forward stepwise modelling approach will not highlight those limitations. Given what we already know about infectiousness, this type of analysis would be better served with a formal DAG or at least conceptual framework, and then working through the various options or models. I suggest the authors explore this wider, and thereby enrich the insights that can be gained from the data. + +<|ref|>text<|/ref|><|det|>[[71, 640, 894, 705]]<|/det|> +Response: Thank you for this suggestion. We added a DAG as Figure S1 which includes the exposure, outcome, predictors, potential confounders and effect modifiers. The DAG includes variables that are known to have impact on infectiousness and were used in our model development when data was available. We added new text to the Methods, Results, and Figure legend as summarized above. + +<|ref|>text<|/ref|><|det|>[[70, 735, 920, 882]]<|/det|> +While the AUC for the scoring system for predicting CAC+/- is high, I don't quite understand the results from Sup table 1. It seems to suggest that age and Xpert CT are equally valuable (both 7 'points')? But what does the model/score mean if the sole bacteriological indicator is removed? Are the authors suggesting that we could decide on CAC+/- by age, CRP and MUAC alone? Could they provide an indication of how much value each individual characteristic adds, and how the model works if Xpert CT is not available. Could any other bacteriological indicator be switched in? I'd be surprised if the model functioned without a bacteriological indicator, and also not sure about the biological logic that would remain. It is also not clear if this predictive model is solely applicable for people who have bacteriologically positive TB? If so, that should be made clear. + +<|ref|>text<|/ref|><|det|>[[70, 896, 888, 914]]<|/det|> +Response: Thank you for these comments. We adjusted the model to have 3 categories for GeneXpert + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 65, 921, 147]]<|/det|> +result based on semi- quantitative grade. The performance of this clinical prediction model is predicated on assessment of all the variables included in the tool. Thus, this tool should only be used for people who have bacteriologically positive TB. Supplementary Table 3 displays the changes in model sensitivity and specificity based on different cut- offs, which addresses aspects of the reviewer's questions regarding lack of access to data on model factors. Performance in other settings will need validation. + +<|ref|>text<|/ref|><|det|>[[72, 161, 379, 177]]<|/det|> +We added the following to the Results: + +<|ref|>text<|/ref|><|det|>[[68, 177, 925, 440]]<|/det|> +"We developed and evaluated the performance of a clinical prediction rule to predict cough aerosol culture- positive persons as a means to identify those who are likely to be highly infectiousness. We included predictors from our multivariable logistic regression model that are readily available to a clinician during the initial visit. For this reason, we removed time- to- detection of culture growth but kept CRP level as there are point- of- care versions of this test. (52) We also used Xpert Ultra semi- quantitative grade which is the result generally reported to clinicians and is derived from the Ct value. Using the coefficients obtained in the multivariable logistic regression analysis we derived the following prediction equation for cough aerosol culture- positive status where outcomes were coded according to weighted scores based on the beta coefficient: \(\mathrm{CRP > 42.9 + Age < 43.8}\) years + MUAC \(> 22.8\) cm + Xpert semi- quantitative grade (high, medium, or low/very low/trace). A total risk score is calculated by adding the risk points and has an optimum cut point of 15 points for predicting cough aerosol culture- positive status with estimated sensitivity of 0.86 (95% CI, 0.74 - 0.95) and specificity 0.65 (95% CI, 0.56 - 0.74). (Supplementary Tables 2 and 3) The prediction rule based on the calculated risk score had an area under the receiver operating curve (AUROC) of 0.84 (95% CI: 0.77- 0.91) (Supplementary Figure 3). The model's Somers' \(\mathrm{D_{xy}}\) index was 0.71; the equivalent in bootstrap validation was 0.66, with an optimism estimate of 0.051, indicating good stability of the model in internal validation." + +<|ref|>text<|/ref|><|det|>[[70, 436, 80, 444]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[72, 464, 407, 481]]<|/det|> +We added the following to the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 495, 894, 544]]<|/det|> +"Like other clinical prediction rules, the model performance is predicated on having data for all of the characteristics that contribute to the risk score. While promising, the risk score that we present requires external validation and should not be used at this time for clinical (non- research) purposes." + +<|ref|>text<|/ref|><|det|>[[70, 574, 907, 656]]<|/det|> +The variation in association pattern of the different cytokines is a bit strange. Would one not expect them to be elevated across the various indicators, also given that e.g. CT threshold and cavitation were themselves associated with CAC? The lack of stability makes me a bit concerned. The results are what they are, but potential explanations (including random noise across many comparisons that could affect the threshold for interpretation of p- values). + +<|ref|>text<|/ref|><|det|>[[70, 670, 920, 864]]<|/det|> +Response: We agree that the sputum cytokine results contain variation in patterns of associations with different outcomes. Although these results are not consistent with a well- defined model of TB pathogenesis, each cytokine has distinct activation pathways and cellular sources that likely to contribute to the variation of results. For example, IL- 1B secretion is inflammasome- dependent while CXCL8 and IL6 secretion are primarily regulated by Toll- like Receptor and NOD- like receptor signaling pathways. All three cytokines are produced by several myeloid cells, but to different degrees. Finally, each has different autocrine and paracrine effects that likely get amplified at different stages of disease. For example, CXCL8 is a chemokine for neutrophil recruitment with potential for amplification of its levels during disease stages which are neutrophil predominant. At the suggestion of Reviewer #3 below, we examined leukocyte subsets and found that peripheral blood neutrophil counts are associated with CAC status, an association which is consistent with the higher levels of CXCL8 in CAC+ versus CAC- sputum cytokine analyses. + +<|ref|>text<|/ref|><|det|>[[70, 878, 910, 911]]<|/det|> +To further address these cytokine observations, we collected more data and performed more analyses. First, we measured the same 4 cytokines in plasma to provide a parallel inflammatory profile in a different + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 66, 884, 99]]<|/det|> +compartment. Second, we used a multivariate linear regression model to examine whether any of the associations were independently associated with CAC status. + +<|ref|>text<|/ref|><|det|>[[70, 114, 920, 291]]<|/det|> +For the plasma cytokines, we were able to detect TNF and IL6, but not IL1B or CXCL8. In contrast, for our previous sputum cytokine results, we detected IL6, IL1B, and CXCL8 but not TNF. These results are consistent with compartmentalized immune responses and highlight the importance of analyzing inflammatory profiles in multiple sites. We then performed a multivariate logistic regression analysis to assess whether any of the sputum or plasma cytokines were associated with CAC independently of bacillary load. Interestingly, plasma TNF was the only cytokine associated with CAC in the adjusted analysis. These results provide additional evidence that inflammatory profiles are associated with CAC status and also highlight the importance of examining multiple sites of inflammation. However, we agree these cytokine observations are incomplete and not consistent with a fully developed or coherent model. Our RNASeq experiments were undertaken to attempt a more in- depth analysis of inflammatory pathways that are associated with aerosolization. + +<|ref|>text<|/ref|><|det|>[[70, 306, 890, 339]]<|/det|> +We revised the Methods section and Figure 1 to include the plasma cytokines, added Supplementary Table 4 for the multivariate analysis, and added the following text to the Methods and Results sections: + +<|ref|>sub_title<|/ref|><|det|>[[71, 355, 147, 370]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[70, 385, 914, 499]]<|/det|> +"Four cytokines were examined in sputum and blood. TNF, IL6, IL1B, and CXCL8 were chosen based on their central roles in regulating inflammatory pathways and TB pathogenesis. (42) ... Plasma was tested directly. Sputum supernatants and plasma were tested for CXCL8 (IL- 8), Interleukin 1 beta (IL- 1β), Interleukin 6 (IL- 6), and TNF using sandwich ELISA according to the manufacturer's instructions. (R&D Systems Inc. Minneapolis, USA.). In pilot sputum cytokine studies, TNF was not detectable at high levels and was not examined further. In pilot plasma cytokine studies, CXCL8 and IL1B were not detectable at high levels and were not examined further." + +<|ref|>sub_title<|/ref|><|det|>[[71, 530, 137, 545]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[70, 546, 922, 704]]<|/det|> +"To further examine the association of inflammatory markers with cough aerosol culture- positive status, we analyzed sputum and plasma levels of CXCL8 (IL- 8), IL- 1β, TNF, and IL- 6 (Figure 1B, Supplementary Table 5). TNF in sputum and IL- 1β and CXCL8 in plasma were nearly undetectable in preliminary subgroup testing and were not examined further. The sputum concentration of CXCL8 was significantly higher (p- value 0.03) among the cough aerosol culture- positive compared to cough aerosol culture- negative participants. Sputum IL- 1β (p- value 0.052) and IL- 6 were not different (p- value 0.36) (Figure 1B). In addition, higher IL- 6, CXCL8, and IL- 1β levels were associated with greater bacillary burden (measured by GeneXpert cycle threshold, p- value 0.0009, 0.007 and 0.00007, respectively, Figure 1C). IL- 1β, but not IL- 6 or CXCL8, was positively associated with cavitary lung disease (p- value 0.0007) across cough aerosol culture status. + +<|ref|>text<|/ref|><|det|>[[70, 720, 916, 850]]<|/det|> +Plasma IL- 6 was associated with bacillary burden (p=1.69 x 10- 6) and cavitary disease (p=0.005) and was higher in CAC- positive compared CAC- negative participants (p=0.03). Plasma TNF was associated with cavitary disease (p=0.013), but not bacillary burden, and was lower in CAC- positive compared to CAC- negative participants (p- value 0.0007). For cytokines that had a significant association with cough aerosol status in bivariate models (sputum CXCL8, plasma TNF, plasma IL- 6), we evaluated associations in multivariate logistic regression models in which we adjusted for age, sex, cavitary disease on chest x- ray and GeneXpert Ct value. We found that plasma TNF was independently associated with CAC status (adjusted p- value 0.007, Supplementary Table 4)." + +<|ref|>text<|/ref|><|det|>[[72, 865, 403, 881]]<|/det|> +Discussion (in the Limitations paragraph): + +<|ref|>text<|/ref|><|det|>[[70, 897, 857, 914]]<|/det|> +"Fourth, sputum collection methods are not standardized and have more technical heterogeneity in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 65, 919, 147]]<|/det|> +comparison to other biologic samples. Despite this challenge, sputum provides a direct assessment of the primary site of TB disease where pulmonary immune responses are compartmentalized and differ from blood. In addition, sputum cytokines have been evaluated as biomarkers in the diagnosis of TB and treatment monitoring.(65- 67) However, to our knowledge no prior studies have evaluated their association with infectiousness measured by culturable aerosols." + +<|ref|>text<|/ref|><|det|>[[71, 162, 886, 213]]<|/det|> +L455- 457: these are results and should be moved there. On a broader note, it would be good to place those observations in the context of the ongoing discussions around subclinical TB (see previous comment re cough positivity). + +<|ref|>text<|/ref|><|det|>[[70, 226, 921, 339]]<|/det|> +Response: We agree that this sentence summarizes results, but the referenced statement ("In this study, a lower TB symptom score indicated a lower burden of findings attributable to TB disease as it is a summation of points for TB- related symptoms (cough, hemoptysis, dyspnea, chest pain, fever, night sweats), TB- related signs (anemia, tachycardia), lung auscultation findings, and malnutrition (low BMI, low MUAC).") refers to the study by Theron et al, not our findings. We have made it clear in the text that we are referring to findings from Theron's study and that this is in the context of our Discussion of the literature and findings suggestive of a CAC- positive phenotype. + +<|ref|>text<|/ref|><|det|>[[71, 353, 902, 403]]<|/det|> +L462: the statement about 'body mass' is strange, as BMI was not associated, but MUAC was. As mentioned before, this discrepancy needs discussion, and the statement should be adjusted accordingly. + +<|ref|>text<|/ref|><|det|>[[71, 417, 888, 450]]<|/det|> +Response: Thank you. We address this comment above. In addition, for line 462, we changed "body mass" to "muscle mass". + +<|ref|>text<|/ref|><|det|>[[71, 464, 894, 530]]<|/det|> +L473: this only interprets one of the cytokine findings, but ignored the conflicting results in the actual section (see above), where some cytokines were associated for one indicator, but not the other. Do the authors assume only 1 indicator is valid? If so, that is a stretch. If not, the discrepancies need to be addressed. + +<|ref|>text<|/ref|><|det|>[[70, 544, 920, 673]]<|/det|> +Response: Thank you for highlighting this issue which we partially address above including revision of the Results paragraph and addition of new data. Although the cytokine data has some level of association with CAC status, we do not claim to have a coherent model based on the limited scope of the cytokine analysis. We used the cytokine observations as a rationale for pursuing a more comprehensive analysis with whole blood RNAseq profiling. We considered how to revise Discussion section which includes line 473. Given the limited scope of the cytokine work, we would prefer to remove this sentence and focus the paragraph on discussion of the transcriptomic findings. We believe this modification adds more focus to the paragraph on the most important findings. + +<|ref|>text<|/ref|><|det|>[[71, 688, 711, 705]]<|/det|> +In summary, we removed the following sentence from the Discussion paragraph: + +<|ref|>text<|/ref|><|det|>[[71, 720, 895, 768]]<|/det|> +"Our results of significantly higher concentrations of sputum CXCL8 and 1L- 1β, as well as higher serum CRP, in participants with culturable aerosols support the role of systemic inflammation in TB infectiousness." + +<|ref|>text<|/ref|><|det|>[[71, 784, 896, 881]]<|/det|> +L535: the suggestion that interventions (i.e. treatment) should target the most infectious is a bit strange. This approach was tried with the development of DOTS policies, where symptomatic smear positive individuals were targeted through PCF and 6m therapy. While saving lives, it has not interrupted transmission as expected, and it is not clear to me why this would work now? Shouldn't Identifying and treating all infectious individuals be the minimum target for all high burden countries, regardless of how infectious they are at the time of diagnosis? + +<|ref|>text<|/ref|><|det|>[[71, 896, 872, 913]]<|/det|> +Furthermore, infectiousness is not static, and will likely vary over time. Finally, given the high + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 66, 900, 115]]<|/det|> +Number Needed to Test to identify any person with low or high infectious disease, the cost of treatment is really not the limiting factor. It would be helpful if the authors reflected a bit more on this (also in the introduction). + +<|ref|>text<|/ref|><|det|>[[70, 130, 912, 275]]<|/det|> +Response: Thank you for these suggestions and perspective for which we fully concur. Smear- based diagnosis is a crude and insensitive method for diagnosis and our statements are not intended to evoke that approach. "Targeted treatment interventions" is not meant to imply that treatment should only be provided to those who are most infectious. Rather, in resource constrained settings where enhanced treatment support such as "true" DOT is not commonly practiced, the most infectious persons could also be supported with true DOT, early drug susceptibility testing to ensure that treatment is appropriate, or other treatment support interventions. Also, as mentioned, more extensive contact investigations could be pursued to ensure evaluations for active TB and TB preventive therapy in contacts who are likely to have been recently infected. + +<|ref|>text<|/ref|><|det|>[[71, 290, 660, 307]]<|/det|> +We edited the final Discussion paragraph to clarify our intended message, + +<|ref|>text<|/ref|><|det|>[[70, 322, 904, 418]]<|/det|> +"While persons with pulmonary TB who are cough aerosol culture- negative patients may transmit Mtb, identifying the most infectious persons would allow targeted interventions to support TB control efforts such as isolation, true direct observation of treatment, and drug- susceptibility testing to confirm that treatment is effective. TB control could also be supported through enhanced investigations in contacts of the most infectious persons to evaluate for active TB and provide TB preventive therapy given higher likelihood of recent transmission and progression to disease." + +<|ref|>text<|/ref|><|det|>[[70, 433, 171, 449]]<|/det|> +Minor points + +<|ref|>text<|/ref|><|det|>[[70, 449, 896, 482]]<|/det|> +Ref 33, 34 and 58 are the same I believe. Would be good to recheck references and make sure in order. + +<|ref|>text<|/ref|><|det|>[[70, 496, 891, 514]]<|/det|> +Response: Thank you. This has been corrected. All references were reviewed for accuracy and order. + +<|ref|>text<|/ref|><|det|>[[70, 528, 912, 577]]<|/det|> +Table 1: category 'Enrolled thru prevalence survey' - not appropriate language for scientific paper and not reflected in main text. Suggest something along lines of 'ACF- enrolled', as this is how it is described in methods. + +<|ref|>text<|/ref|><|det|>[[70, 592, 797, 609]]<|/det|> +Response: Thank you. We changed this category to "Enrolled through active case finding". + +<|ref|>text<|/ref|><|det|>[[70, 624, 888, 689]]<|/det|> +Table 3: the unit for Age is not given. From the OR I suspect it is year of age, but this should be made clear. Also note this assumes a linear association across the entire age range, which is unlikely to be true given what we know about age- dependent population ARI. This should be discussed. + +<|ref|>text<|/ref|><|det|>[[70, 704, 725, 721]]<|/det|> +Response: The units (years) has been added to the tables. is has been corrected. + +<|ref|>text<|/ref|><|det|>[[71, 736, 408, 752]]<|/det|> +We added the following to the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 768, 915, 849]]<|/det|> +"The annual risk of TB infection differs by age groups in high burden settings and notably, there was no difference in the ages of HHCs by CAC status. Among household contacts less than 10 years of age, who have a lower annual risk of infection compared to adolescents and adults, QFT positive results were also more common (p- value 0.01) among contacts of CAC- positive persons (9 of 10 participants, 90%) than contacts of CAC- negative persons (14 of 33 participants, 42%)." + +<|ref|>text<|/ref|><|det|>[[70, 864, 920, 913]]<|/det|> +The section titles on 1397 and 1409 are phrased as interpretation rather than reporting of results. These should be adjusted. In addition, the last sentences in each of these sections is interpretation rather than result and should be removed or put in discussion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 82, 916, 115]]<|/det|> +Response: Thank you for this suggestion. We edited the phrases and sentences to remove interpretation language from the Results section. + +<|ref|>text<|/ref|><|det|>[[72, 131, 283, 147]]<|/det|> +The new section titles are: + +<|ref|>text<|/ref|><|det|>[[72, 147, 860, 179]]<|/det|> +"Suptum cytokines and analysis of associations with cough aerosol culture positivity, bacterial load, cavitary lung disease, and extent of lung involvement." + +<|ref|>text<|/ref|><|det|>[[72, 195, 106, 210]]<|/det|> +And + +<|ref|>text<|/ref|><|det|>[[70, 226, 904, 259]]<|/det|> +"Whole blood transcriptomic signatures and analysis of associations with cough aerosol culture positivity and sputum bacterial load." + +<|ref|>text<|/ref|><|det|>[[70, 274, 907, 307]]<|/det|> +In addition, we removed the summary sentence of these sections to avoid over- interpreting in the Results section. + +<|ref|>text<|/ref|><|det|>[[72, 322, 374, 339]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 354, 916, 514]]<|/det|> +The study "Tuberculosis Infectiousness is Associated with Distinct Clinical and Inflammatory Profiles" stands out for addressing a significant gap in tuberculosis research, focusing on individual infectiousness and biomarkers. It employs a prospective longitudinal study design, examining treatment- naïve pulmonary TB patients in Nairobi, thereby providing valuable insights in a high TB burden setting. Methodological innovations, such as using the Cough Aerosol Sampling System (CASS) for measuring Mycobacterium tuberculosis aerosolization, the evaluation of sputum cytokine, and assessing household contacts through IGRA testing, add important epidemiological and molecular dimensions and adds novel knowledge and tools to predict Mtb transmission. Overall, the manuscript was well written. The incorporation of suggested improvements would enhance the paper's quality and ensure that concerns have been adequately addressed. + +<|ref|>text<|/ref|><|det|>[[70, 529, 917, 610]]<|/det|> +#1 Introduction: The introduction section is well- written and effectively frames the context of TB infectiousness to its clinical and immunological aspects. It successfully outlines the importance of understanding individual variations in TB transmission and reviews relevant literature, thus situating the study within the broader field of TB research. I have no suggestions for improvement in this section. + +<|ref|>text<|/ref|><|det|>[[72, 625, 420, 642]]<|/det|> +Response: We appreciate your kind words. + +<|ref|>text<|/ref|><|det|>[[70, 656, 916, 707]]<|/det|> +#2 Methods: The methods section is well- structured and thorough. However, consider breaking down the dense text into smaller paragraphs to improve readability (i.e. break the paragraph in line 262.) + +<|ref|>text<|/ref|><|det|>[[70, 721, 501, 738]]<|/det|> +Response: Thank you, we made the suggested edits. + +<|ref|>text<|/ref|><|det|>[[70, 752, 916, 835]]<|/det|> +#2.1 – Methods (Line 203-204): The study does not address the issue of drug-resistant TB. On lines 203-204, the study mentions classifying rifampicin resistance as "positive", "negative", or "indeterminate", but this is not further elaborated in the text. I recommend including these data in the results and tables, even if 100% were susceptible, to provide a complete picture of the resistance profile among the study participants. + +<|ref|>text<|/ref|><|det|>[[70, 849, 870, 882]]<|/det|> +Response: Thank you for pointing this out; it was an oversight on our part. One subject had rifampin resistance. We added information on detection of rifampin resistance to Table 1. + +<|ref|>text<|/ref|><|det|>[[70, 896, 860, 914]]<|/det|> +#- 2 - Results (lines 222-228): It would be beneficial to provide a rationale for the decision to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[71, 66, 901, 131]]<|/det|> +assess cytokines in sputum instead of blood; as well as the selection of the specific three cytokines studied. This is particularly important for readers who may have less experience in the field. Including one or two lines to explain these choices would greatly aid in comprehending the significance and implications of these methodological decisions. + +<|ref|>text<|/ref|><|det|>[[70, 146, 918, 355]]<|/det|> +Response: We agree that adding more context around these issues will provide more clarity. We chose to analyze sputum cytokines due to our hypothesis that the inflammatory mediators and/or biomarkers of aerosolization are present in the lung and more likely to have a direct impact compared to the peripheral blood. In addition, the immune system is compartmentalized, and lung responses are often different than peripheral blood. However, there are technical challenges of collecting sputum in a standardized manner. In contrast, whole blood and plasma measurements are more standardized. To address this directly, we have now added cytokine measurements in plasma for comparison to sputum. We now have data for 4 cytokines in both sputum and blood. TNF was detectable at high levels in sputum and CXCL8 and IL1B were not present in plasma at high levels. These data support the compartmentalization of immune responses and the value of directly studying pulmonary immune responses when feasible. The rationale for studying IL6, TNF, and IL1B is based on their known role in TB pathogenesis. We chose to study CXCL8, due to its role as a chemokine involved in neutrophil recruitment, an important cell in TB pathogenesis, and previous studies documenting its presence in sputum. + +<|ref|>text<|/ref|><|det|>[[72, 370, 463, 386]]<|/det|> +We added the following text with new references: + +<|ref|>sub_title<|/ref|><|det|>[[72, 403, 147, 417]]<|/det|> +## Methods: + +<|ref|>text<|/ref|><|det|>[[71, 418, 912, 530]]<|/det|> +"Four cytokines were examined in sputum and blood. TNF, IL6, IL1B, and CXCL8 were chosen based on their central roles in regulating inflammatory pathways and TB pathogenesis. (42)" ... Plasma was tested directly. Sputum supernatants and plasma were tested for CXCL8 (IL- 8), Interleukin 1 beta (IL- 1β), Interleukin 6 (IL- 6), and TNF using sandwich ELISA according to the manufacturer's instructions. (R&D Systems Inc. Minneapolis, USA.). In pilot sputum cytokine studies, TNF was not detectable at high levels and was not examined further. In pilot plasma cytokine studies, CXCL8 and IL1B were not detectable at high levels and were not examined further." + +<|ref|>sub_title<|/ref|><|det|>[[72, 547, 137, 561]]<|/det|> +## Results: + +<|ref|>text<|/ref|><|det|>[[70, 562, 923, 720]]<|/det|> +"To further examine the association of inflammatory markers with cough aerosol culture- positive status, we analyzed sputum and plasma levels of CXCL8 (IL- 8), IL- 1β, TNF, and IL- 6 (Figure 1B, Supplementary Table 5). TNF in sputum and IL- 1β and CXCL8 in plasma were nearly undetectable in preliminary subgroup testing and were not examined further. The sputum concentration of CXCL8 was significantly higher (p- value 0.03) among the cough aerosol culture- positive compared to cough aerosol culture- negative participants. Sputum IL- 1β (p- value 0.052) and IL- 6 were not different (p- value 0.36) (Figure 1B). In addition, higher IL- 6, CXCL8, and IL- 1β levels were associated with greater bacillary burden (measured by GeneXpert cycle threshold, p- value 0.0009, 0.007 and 0.00007, respectively, Figure 1C). IL- 1β, but not IL- 6 or CXCL8, was positively associated with cavitary lung disease (p- value 0.0007) across cough aerosol culture status. + +<|ref|>text<|/ref|><|det|>[[70, 735, 916, 866]]<|/det|> +Plasma IL- 6 was associated with bacillary burden (p=1.69 x 10- 6) and cavitary disease (p=0.005) and was higher in CAC- positive compared CAC- negative participants (p=0.03). Plasma TNF was associated with cavitary disease (p=0.013), but not bacillary burden, and was lower in CAC- positive compared to CAC- negative participants (p- value 0.0007). For cytokines that had a significant association with cough aerosol status in bivariate models (sputum CXCL8, plasma TNF, plasma IL- 6), we evaluated associations in multivariate logistic regression models in which we adjusted for age, sex, cavitary disease on chest x- ray and GeneXpert Ct value. We found that plasma TNF was independently associated with CAC status (adjusted p- value 0.007, Supplementary Table 4)." + +<|ref|>text<|/ref|><|det|>[[70, 882, 857, 915]]<|/det|> +Discussion (in the Limitations paragraph): "Fourth, sputum collection methods are not standardized and have more technical heterogeneity in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 66, 917, 147]]<|/det|> +comparison to other biologic samples. Despite this challenge, sputum provides a direct assessment of the primary site of TB disease where pulmonary immune responses are compartmentalized and differ from blood. In addition, sputum cytokines have been evaluated as biomarkers in the diagnosis of TB and treatment monitoring.(65- 67) However, to our knowledge no prior studies have evaluated their association with infectiousness measured by culturable aerosols." + +<|ref|>text<|/ref|><|det|>[[70, 162, 914, 211]]<|/det|> +#2.3 – Methods (Data analysis section): To enhance reproducibility, I recommend adding a table in the supplementary material section. This table should list the names of the R packages used, their respective versions, and references. + +<|ref|>text<|/ref|><|det|>[[70, 211, 850, 243]]<|/det|> +Response: Thank you for this suggestion. We added Supplementary Table 1 with the suggested information. + +<|ref|>text<|/ref|><|det|>[[70, 258, 917, 339]]<|/det|> +#3 Results: The results section provides a detailed and thorough presentation of the study's findings and analyses. The section appears to be well- organized and structured, with clear descriptions of the methods used and the outcomes observed. The use of tables, figures, and numerical values enhances the clarity of the presented results. However, there are a few areas where the clarity and objectivity could be further improved: + +<|ref|>text<|/ref|><|det|>[[70, 354, 917, 435]]<|/det|> +#3.1 Results (lines 350-368): Considering that age emerged as a significant variable in the mixed methods bivariate & multivariable analysis, and the low median age reported, it is essential to have information on how many HHCs were children or adolescents. Furthermore, this aspect of age, including the distinction between adult and non-adult contacts, should be highlighted in the discussion section. + +<|ref|>text<|/ref|><|det|>[[70, 450, 866, 483]]<|/det|> +Responses: Thank you. We have added age groups to Table 2 for young children (<5 years of age), children (5- 10 years of age), and adolescents (10- 15 years of age). + +<|ref|>text<|/ref|><|det|>[[70, 497, 442, 514]]<|/det|> +We added the following to the Results section: + +<|ref|>text<|/ref|><|det|>[[70, 529, 901, 578]]<|/det|> +"Among household contacts less than 10 years of age, QFT positive results were also more common (p- value 0.01) among contacts of CAC- positive persons (9 of 10 participants, 90%) than contacts of CAC- negative persons (14 of 33 participants, 42%)." + +<|ref|>text<|/ref|><|det|>[[70, 593, 406, 609]]<|/det|> +We added the following to the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 625, 914, 673]]<|/det|> +"Third, we demonstrated that cough aerosol culture- positive status was strongly associated with evidence of TB transmission in household contacts based on QFT results, including child HHCs for whom a positive QFT result is more likely to represent recent infection." + +<|ref|>text<|/ref|><|det|>[[70, 688, 916, 721]]<|/det|> +#3.2 Results (lines 392-394): Please provide the sensitivity and specificity values of the ROC curve, with confident intervals. + +<|ref|>text<|/ref|><|det|>[[70, 736, 899, 769]]<|/det|> +Responses: Thank you. We have added estimated sensitivities and specificities at different cut points in Supplementary Table 3A. + +<|ref|>text<|/ref|><|det|>[[70, 784, 917, 849]]<|/det|> +#3.3. Results (lines 397-437): In lines 397-437, all paragraphs finish with a phrase with the same structure that starts with "Together, these data suggest". I recommend rewriting some of them and evaluating if it is necessary. For example, I do not think that the phrase in lines 436-437 is fundamental for the text. + +<|ref|>text<|/ref|><|det|>[[70, 864, 872, 881]]<|/det|> +Response: Thank you. We have made the suggested edits and removed these summary sentences. + +<|ref|>text<|/ref|><|det|>[[70, 896, 904, 914]]<|/det|> +#3.4. Results (Figures): The figures in the manuscript, particularly Figures 1c and d, Figure 2, and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 66, 920, 166]]<|/det|> +Supplementary Figure 4, need to be improved for better comprehension. A key enhancement is to include the legend for colours and shapes directly on the figure itself, rather than solely in the written legend. The absence of this information on the figures themselves can hinder interpretation and understanding. Providing these details directly on the figures would facilitate a more immediate and clear comprehension of the data being presented, especially for readers who might be quickly scanning through the figure + +<|ref|>text<|/ref|><|det|>[[70, 179, 875, 213]]<|/det|> +Response: Thank you for this suggestion. We made the suggested changes to Figures 1 and 2 and supplementary figure 4 (which is now supplementary figure 5. + +<|ref|>text<|/ref|><|det|>[[70, 226, 907, 308]]<|/det|> +#4 Discussion: The discussion section demonstrates a good quality of scientific communication, with a thorough examination of the study's results and their implications. The section effectively contextualizes the findings within the existing literature and provides a balanced interpretation of the results. The limitations are acknowledged, and their potential impact on the study's conclusions is addressed. Minor comments: + +<|ref|>text<|/ref|><|det|>[[70, 322, 500, 339]]<|/det|> +Response: Thank you, we appreciate the kind words. + +<|ref|>text<|/ref|><|det|>[[70, 353, 884, 372]]<|/det|> +#4.1. It would be beneficial to discuss in more detail the age of the Household Contacts (HHCs) + +<|ref|>text<|/ref|><|det|>[[71, 386, 395, 403]]<|/det|> +Response: Please see above response. + +<|ref|>text<|/ref|><|det|>[[70, 417, 870, 451]]<|/det|> +as well as the rationale behind using sputum to assess biomarkers. These discussions could provide deeper insights into the study's findings and their implications + +<|ref|>text<|/ref|><|det|>[[70, 465, 890, 562]]<|/det|> +Response: Thank you for this suggestion. As discussed above, our interest in studying sputum is to assess whether the compartmentalized immune response of the lung will generate novel insights compared to blood, especially with regards to the question of Mtb aerosolization. However, we fully acknowledge the methodologic challenges of working with sputum and the lack of standardization. We added more discussion of this in the limitations paragraph since we believe it is both a strength and a weakness due to these methodologic challenges. + +<|ref|>text<|/ref|><|det|>[[70, 576, 441, 593]]<|/det|> +We added the following text to the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 608, 919, 706]]<|/det|> +"Fourth, sputum collection methods are not standardized and have more technical heterogeneity in comparison to other biologic samples. Despite this challenge, sputum provides a direct assessment of the primary site of TB disease where pulmonary immune responses are compartmentalized and differ from blood. In addition, sputum cytokines have been evaluated as biomarkers in the diagnosis of TB and treatment monitoring.(57- 59) However, to our knowledge no prior studies have evaluated their association with infectiousness measured by culturable aerosols." + +<|ref|>text<|/ref|><|det|>[[70, 720, 910, 755]]<|/det|> +#4.2 (lines 447-500): Breaking up the paragraphs could enhance the readability and clarity of information, making it easier for readers to digest and understand the key points being conveyed. + +<|ref|>text<|/ref|><|det|>[[70, 769, 504, 786]]<|/det|> +Response: Thank you. We made the suggested edits. + +<|ref|>sub_title<|/ref|><|det|>[[71, 800, 393, 818]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 832, 923, 898]]<|/det|> +The study is very interesting and opens new ways for understanding TB pathogenesis and proposing clinical management. Based on the reported findings and prior studies, cough aerosol cultures are superior to sputum smear analysis in predicting Mtb transmission events and are likely the best estimators of TB infectiousness. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 66, 916, 148]]<|/det|> +Figure 1A: is any possibility of evaluating the correlation of WHITE BLOOD CELLS components as Lymphocytes, monocytes, or neutrophils with CAC?. Indeed interesting correlations were found in the past using different approaches (La Manna, 2017, PMID: 28208160; Chedid, 2020, PMID: 32920230; ). Moreover, it would be interesting to evaluate if there is an association between CAC score and platelets (La Manna, 2022 PMID: 35338775) + +<|ref|>text<|/ref|><|det|>[[70, 162, 921, 261]]<|/det|> +Response: Thank you for this suggestion. We evaluated associations between granulocyte, lymphocyte and monocyte counts and CAC status. While there was no association between the latter two white blood cell types and CAC status, the granulocyte count was significantly associated with CAC status (Table 1). We do not have platelet counts on study participants. The granulocyte odds ratio is very similar to the WBC count odds ratio; this is not unexpected as granulocytes are the largest number of WBCs and the two values (granulocyte count and WBC count) are highly correlated. + +<|ref|>text<|/ref|><|det|>[[70, 274, 614, 292]]<|/det|> +We edited the following sentence in Results to incorporate this data: + +<|ref|>text<|/ref|><|det|>[[70, 306, 866, 340]]<|/det|> +"Higher WBC counts (total and granulocyte count) and CRP levels were also associated with cough aerosol culture- positive status (Figure 1A)." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 290, 107]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 392, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 163, 871, 199]]<|/det|> +I thank the authors for their responses and the changes to the paper, which have addressed most of my major concerns. + +<|ref|>text<|/ref|><|det|>[[114, 217, 878, 345]]<|/det|> +I remain sceptical of the sharp contrast between BMI and MUAC, and the suggested difference. We see the effects of nutrition on TB v clearly in BMI, as the recent RATIONS papers (Bhargava Lancet 2023, Bhargava Lancet GH 2023) and RePORT (Sinha preprint) papers have shown in terms of TB mortality and progression. For BMI to suddenly not matter in aerosol status seems more than a little odd. Also, MUAC is not solely driven by muscle mass, depending on the BMI, there is fat tissue as well. I suggest the text should be more open to the BMI vs MUAC findings reflecting artefact rather than fact and/or that the explanation is an hypothesis, rather than fact. + +<|ref|>text<|/ref|><|det|>[[114, 364, 869, 474]]<|/det|> +The other point that needs more clarification is how these findings in almost solely cough reporting individuals contrast with the findings of other aerosol studies, such as the face masks and RASC groups. Simply mentioning them in 1558- 570 does not address this. It seems strange to suggest that only cough reporting individuals are infectious, where e.g. face mask positivity was not correlated with cough (Williams Lancet ID 2020) but was correlated with HH infections (Williams CID 2023). It's possible that both are true, but then restricting to cough- positive individuals in this study poses a limitation. + +<|ref|>text<|/ref|><|det|>[[116, 493, 743, 510]]<|/det|> +I have some minor issues still, which the authors should also resolve in a final revision. + +<|ref|>text<|/ref|><|det|>[[114, 529, 878, 600]]<|/det|> +- The path from 142 to 55 participants is useful. It would be good if the paper reflected whether this could affect the findings. In particular whether HHs that refused to participate are different in a way that is associated with QFT positivity + +<|ref|>text<|/ref|><|det|>[[114, 581, 872, 636]]<|/det|> +- The explanation for how the 29 CAC+ and 29 CAC- is not sufficient. Is it a convenience sample (e.g. the first ones through the door). Again, anything that isn't random should be described and considered for analysis. + +<|ref|>text<|/ref|><|det|>[[114, 638, 875, 673]]<|/det|> +- It should be made clear what age range was studied, and the age range the authors are comfortable for their prediction model to be valid for. + +<|ref|>text<|/ref|><|det|>[[114, 674, 805, 692]]<|/det|> +- L298: With the 3 Xpert categories, variables are no longer all dichotomised, suggest to revise. + +<|ref|>text<|/ref|><|det|>[[116, 748, 392, 764]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 784, 881, 820]]<|/det|> +The authors addressed all my questions and also the questions of the other reviewers. I am satisfied with the review and recommend the publication. + +<|ref|>text<|/ref|><|det|>[[116, 858, 392, 875]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 830, 125]]<|/det|> +the manuscript is interesting and great value scientifically and clinically, the authors answered the questions raised. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[72, 67, 279, 84]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[72, 99, 375, 115]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 130, 905, 164]]<|/det|> +I thank the authors for their responses and the changes to the paper, which have addressed most of my major concerns. + +<|ref|>text<|/ref|><|det|>[[70, 179, 916, 291]]<|/det|> +I remain skeptical of the sharp contrast between BMI and MUAC, and the suggested difference. We see the effects of nutrition on TB v clearly in BMI, as the recent RATIONS papers (Bhargava Lancet 2023, Bhargava Lancet GH 2023) and RePORT (Sinha preprint) papers have shown in terms of TB mortality and progression. For BMI to suddenly not matter in aerosol status seems more than a little odd. Also, MUAC is not solely driven by muscle mass, depending on the BMI, there is fat tissue as well. I suggest the text should be more open to the BMI vs MUAC findings reflecting artefact rather than fact and/or that the explanation is an hypothesis, rather than fact. + +<|ref|>text<|/ref|><|det|>[[70, 306, 910, 355]]<|/det|> +Response: Thank you for highlighting this concern and the citations. We agree that the association of MUAC, but not BMI, with aerosolization may be a statistical artefact and that our discussion of the finding is speculative. We also agree that MUAC represents both fat and muscle. + +<|ref|>text<|/ref|><|det|>[[70, 370, 861, 402]]<|/det|> +We added more text to the Discussion to clarify that the BMI/MUAC differences may be a statistical artefact and that MUAC measures both fat and muscle mass: + +<|ref|>text<|/ref|><|det|>[[70, 417, 916, 482]]<|/det|> +"Our finding of an association between cough aerosol status and MUAC, but not BMI, may seem counterintuitive and may represent a statistical artefact. Alternatively, we hypothesize that MUAC and BMI measure related but different aspects of nutritional status: BMI reflects fat mass while MUAC measures fat and muscle mass." + +<|ref|>text<|/ref|><|det|>[[70, 498, 910, 609]]<|/det|> +The other point that needs more clarification is how these findings in almost solely cough reporting individuals contrast with the findings of other aerosol studies, such as the face masks and RASC groups. Simply mentioning them in 1558- 570 does not address this. It seems strange to suggest that only cough reporting individuals are infectious, where e.g. face mask positivity was not correlated with cough (Williams Lancet ID 2020) but was correlated with HH infections (Williams CID 2023). It's possible that both are true, but then restricting to cough- positive individuals in this study poses a limitation. + +<|ref|>text<|/ref|><|det|>[[70, 625, 916, 672]]<|/det|> +Response: Thank you for highlighting this concern. We agree that there is exciting new information that is potentially paradigm shifting to the field of TB. We also believe that the findings from the face mask and RASC groups requires further study to understand the relationship to infectiousness. + +<|ref|>text<|/ref|><|det|>[[70, 688, 511, 704]]<|/det|> +We added the following to limitations in the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 720, 900, 768]]<|/det|> +"Second, \(95\%\) of participants reported cough and our findings may not apply to persons with TB without cough. Recent studies that have detected TB in exhaled breath call into question whether cough is essential and/or a primary driver of TB transmission. (33, 34, 67, 68)." + +<|ref|>text<|/ref|><|det|>[[75, 768, 901, 914]]<|/det|> +33. Williams CM, Abdulwhhab M, Birring SS, De Kock E, Garton NJ, Townsend E, et al. Exhaled Mycobacterium tuberculosis output and detection of subclinical disease by face-mask sampling: prospective observational studies. Lancet Infect Dis. 2020;20(5):607-17. +34. Dinkele R, Gessner S, McKerry A, Leonard B, Leukes J, Seldon R, et al. Aerosolization of Mycobacterium tuberculosis by Tidal Breathing. Am J Respir Crit Care Med. 2022;206(2):206-16. +67. Williams CM, Muhammad AK, Sambou B, Bojang A, Jobe A, Daffeh GK, et al. Exhaled Mycobacterium tuberculosis Predicts Incident Infection in Household Contacts. Clin Infect Dis. 2023;76(3):e957-e64. +68. Patterson B, Dinkele R, Gessner S, Koch A, Hoosen Z, January V, et al. Aerosolization of viable Mycobacterium tuberculosis bacilli by tuberculosis clinic attendees independent of sputum-Xpert Ultra status. Proc Natl Acad Sci U S A. 2024;121(12):e2314813121. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 81, 820, 100]]<|/det|> +I have some minor issues still, which the authors should also resolve in a final revision. + +<|ref|>text<|/ref|><|det|>[[70, 113, 919, 164]]<|/det|> +- The path from 142 to 55 participants is useful. It would be good if the paper reflected whether this could affect the findings. In particular whether HHs that refused to participate are different in a way that is associated with QFT positivity. + +<|ref|>text<|/ref|><|det|>[[70, 179, 910, 371]]<|/det|> +Response: We agree that differences between those index participants and contacts who did or did not participate in the household contact analysis needs to be carefully evaluated to determine whether they reflect the characteristics of the entire cohort and are generalizable. To assess the characteristics of our subgroup analysis, we compared index participants with \((N = 48)\) and without \((N = 94)\) household members. These comparisons are presented in (new) Supplementary Table 5. We found 3 variables that differed between index participants with and without enrolled household contacts (sex, Xpert Ct, and cavitary CXR). Each of these variables was tested in the multivariate model. These results suggest that our subgroup had some differences from the full cohort (possibly related to female index participants being less likely to live alone than male index participants) and could lead to selection bias and/or decrease generalizability. Concerns around selection bias were addressed through use of random effects models clustered on index participant. (Bell A. Fixed and random effects models: making an informed choice". Qual Quant 53, 2019). We have added these concerns to the limitations section. + +<|ref|>text<|/ref|><|det|>[[72, 385, 380, 402]]<|/det|> +We added the following to the Results: + +<|ref|>text<|/ref|><|det|>[[70, 416, 917, 514]]<|/det|> +"Index participants \((N = 48)\) with enrolled household members compared to index participants \((N = 94)\) without enrolled household members did not differ by age (p- value 0.12), HIV status (p- value 0.74), MUAC (p- value 0.60), or CASS status (0.17). (Supplementary Table 5) However, there were differences in the proportion of women \((42\%\) vs. \(20\%\) , p- value 0.007), Xpert Ct values (20.5 vs. 18.1, p- value 0.01), and the frequency of cavitations on chest X- ray \((58\%\) vs. \(76\%\) , p- value 0.04) between those with and without enrolled household members, respectively. " + +<|ref|>text<|/ref|><|det|>[[70, 529, 627, 546]]<|/det|> +We added the following to the limitations paragraph in the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 560, 911, 626]]<|/det|> +"In addition, the index participants who contributed to our evaluations of risk factors for HHC IGRA results differed from index participants without enrolled HHCs which introduce selection bias and limit generalizability. Although our random effects models should address concerns around selection bias, generalizability of the HHC IGRA status remains a limitation." + +<|ref|>text<|/ref|><|det|>[[70, 640, 914, 737]]<|/det|> +In the original submission, we included household contacts of both pulmonary TB cases and those investigated for TB who were determined to not have TB. In the revision, we removed the contacts \((n = 14)\) of subjects who were determined to not have pulmonary TB after investigation. The number of total pulmonary TB index participants \((n = 142)\) is unchanged. The number of HHCs decreased from 143 to 129. Our study findings are the same whether these household contacts are included or not. The revised numbers are in updated versions of Tables 2 and 3. + +<|ref|>text<|/ref|><|det|>[[70, 766, 897, 816]]<|/det|> +- The explanation for how the 29 CAC+ and 29 CAC- is not sufficient. Is it a convenience sample (e.g. the first ones through the door). Again, anything that isn't random should be described and considered for analysis. + +<|ref|>text<|/ref|><|det|>[[70, 830, 920, 912]]<|/det|> +Response: Thank you for asking for further clarification. The 29 CAC+ and 29 CAC- were a convenience sample due to being the first available participants for transcriptomic analysis. To assess whether these 58 individuals were representative of the full cohort, we compared the variables of CAC+ and CAC- groups in the transcriptomic subgroup analysis (new Supplementary Table 6, \(N = 29\) CAC+ and 29 CAC-) with the full cohort (Table 1, \(N = 43\) CAC+ vs 99 CAC- ). We found no differences in the participant characteristics of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 66, 919, 115]]<|/det|> +the CAC+ and CAC- groups when comparing age, sex, HIV status, Xpert Ct, Cavitary CXR, and degree of lung involvement (CXR quadrants). These analyses suggest that the subgroup used for the transcriptomic profiling is representative of the full cohort. + +<|ref|>text<|/ref|><|det|>[[70, 130, 875, 164]]<|/det|> +We also included a new Supplementary Table 6 with a summary of these bivariate analyses (entitled "Comparison of participant characteristics of transcriptomic subgroup and full cohort") + +<|ref|>text<|/ref|><|det|>[[70, 179, 476, 196]]<|/det|> +We added the following text to the Results section: + +<|ref|>text<|/ref|><|det|>[[70, 210, 904, 260]]<|/det|> +"We found no differences in clinical and biologic variables (age, sex, HIV status, Xpert Ct, Cavitary CXR, and degree of lung involvement (CXR quadrants) when comparing participants included in the transcriptomic subgroups (CAC+ and CAC- ) with the remaining cohort (Supplementary Tables 6 and 7)." + +<|ref|>text<|/ref|><|det|>[[70, 274, 828, 308]]<|/det|> +- It should be made clear what age range was studied, and the age range the authors are comfortable for their prediction model to be valid for. + +<|ref|>text<|/ref|><|det|>[[70, 322, 900, 356]]<|/det|> +Response: For the entire study, we did not exclude any age groups and had a range of 18 to 100 years. For the predictive model, we also did not exclude any ages and included the same age range. + +<|ref|>text<|/ref|><|det|>[[70, 370, 399, 386]]<|/det|> +We edited the Results to read as follows: + +<|ref|>text<|/ref|><|det|>[[70, 400, 916, 450]]<|/det|> +"To examine the biology of Mtb aerosolization and transmission, we enrolled 142 individuals with microbiologically confirmed pulmonary TB in Nairobi, Kenya. The median age of participants was 35 years (interquartile range (IQR), 27- 44) and ranged from 18 to 100 years; 27% were women (Table 1)." + +<|ref|>text<|/ref|><|det|>[[70, 464, 893, 497]]<|/det|> +In regards to questions about age and use of the prediction tool, we are not recommending its use as it requires external validation. As we have noted in the Discussion: + +<|ref|>text<|/ref|><|det|>[[70, 512, 916, 545]]<|/det|> +"While promising, the risk score that we present requires external validation and should not be used at this time for clinical (non- research) purposes." + +<|ref|>text<|/ref|><|det|>[[70, 560, 884, 578]]<|/det|> +- L298: With the 3 Xpert categories, variables are no longer all dichotomised, suggest to revise. + +<|ref|>text<|/ref|><|det|>[[70, 592, 779, 609]]<|/det|> +Response: Thank you for this suggestion. We corrected the sentence to read as follows: + +<|ref|>text<|/ref|><|det|>[[70, 624, 904, 657]]<|/det|> +"Included variables were categorized and the optimal cut- points were determined using Youden index (J) method," + +<|ref|>text<|/ref|><|det|>[[70, 672, 394, 689]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 704, 857, 737]]<|/det|> +The authors addressed all my questions and also the questions of the other reviewers. I am satisfied with the review and recommend the publication. + +<|ref|>text<|/ref|><|det|>[[70, 751, 576, 768]]<|/det|> +Response: We thank the reviewer for these positive comments. + +<|ref|>text<|/ref|><|det|>[[70, 783, 394, 800]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 815, 916, 848]]<|/det|> +the manuscript is interesting and great value scientifically and clinically. the authors answered the questions raised. + +<|ref|>text<|/ref|><|det|>[[70, 863, 576, 880]]<|/det|> +Response: We thank the reviewer for these positive comments. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 303, 107]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 392, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 163, 876, 217]]<|/det|> +I thank the authors for working through the comments. It is an interesting study with results that should go into the wider scientific discourse, and I think has all the information that engaged readers need to judge the finding. + +<|ref|>text<|/ref|><|det|>[[116, 255, 392, 271]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 291, 883, 363]]<|/det|> +I was asked only to review the X- ray component of this study. The team obtained posterior anterior chest x- rays from all participants (plus lateral for children \(< 10\) ), which were scored by one member of the study team who is a pulmonologist, according to: presence/absence of cavitations and number of quadrants with abnormalities. + +<|ref|>text<|/ref|><|det|>[[116, 383, 355, 399]]<|/det|> +With regards to this, they found: + +<|ref|>text<|/ref|><|det|>[[115, 401, 852, 491]]<|/det|> +- participants with TB identified through passive case finding were less likely to have cavitary TB (expected) +- cough aerosol culture positive patients were more likely to have cavitary TB +-TB-related abnormalities in more chest X-ray quadrants was associated with cough aerosol culture positivity + +<|ref|>text<|/ref|><|det|>[[115, 510, 850, 564]]<|/det|> +These findings are expected and are clearly described. I have no major concerns with this. The only question is whether the reader was blind to the study results when assessing the chest x- rays, which should be the case. If so, they could clarify this in the methods. + +<|ref|>text<|/ref|><|det|>[[115, 584, 252, 599]]<|/det|> +Unrelated to x- ray: + +<|ref|>text<|/ref|><|det|>[[115, 601, 870, 710]]<|/det|> +Line 359- 360 "GeneXpert cycle threshold and semi- quantitative grade were significantly higher among cough aerosol- culture positive compared with cough aerosol culture- negative participants." - this should be GeneXpert cycle threshold was lower and semi- quantitative grade was higher." Lower PCR cycle thresholds correspond to higher semi- quantitative grade. They also on line 363 show that the Ct relationship was cough aerosol status was negative as expected as lower Ct values correspond to higher bacillary load. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[72, 67, 279, 84]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[72, 113, 379, 131]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[71, 145, 897, 197]]<|/det|> +I thank the authors for working through the comments. It is an interesting study with results that should go into the wider scientific discourse, and I think has all the information that engaged readers need to judge the finding. + +<|ref|>text<|/ref|><|det|>[[70, 210, 866, 228]]<|/det|> +Response: Thank you for your time, knowledge and insights in raising the quality of our manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 242, 379, 259]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[70, 273, 916, 340]]<|/det|> +I was asked only to review the X- ray component of this study. The team obtained posterior anterior chest x- rays from all participants (plus lateral for children \(< 10\) ), which were scored by one member of the study team who is a pulmonologist, according to: presence/absence of cavitations and number of quadrants with abnormalities. + +<|ref|>text<|/ref|><|det|>[[71, 355, 350, 371]]<|/det|> +With regards to this, they found: + +<|ref|>text<|/ref|><|det|>[[70, 371, 896, 450]]<|/det|> +- participants with TB identified through passive case finding were less likely to have cavitary TB (expected) +- cough aerosol culture positive patients were more likely to have cavitary TB +-TB-related abnormalities in more chest X-ray quadrants was associated with cough aerosol culture positivity + +<|ref|>text<|/ref|><|det|>[[70, 465, 884, 515]]<|/det|> +These findings are expected and are clearly described. I have no major concerns with this. The only question is whether the reader was blind to the study results when assessing the chest x-rays, which should be the case. If so, they could clarify this in the methods. + +<|ref|>text<|/ref|><|det|>[[71, 529, 702, 546]]<|/det|> +Response: Thank you for your review. We have edited the manuscript to state, + +<|ref|>text<|/ref|><|det|>[[71, 561, 585, 578]]<|/det|> +"DJH was blinded to CASS results in the review of chest x- rays." + +<|ref|>sub_title<|/ref|><|det|>[[71, 594, 232, 609]]<|/det|> +## Unrelated to x-ray: + +<|ref|>text<|/ref|><|det|>[[70, 610, 886, 655]]<|/det|> +Line 359- 360 "GeneXpert cycle threshold and semi- quantitative grade were significantly higher among cough aerosol- culture positive compared with cough aerosol culture- negative participants." + +<|ref|>text<|/ref|><|det|>[[70, 656, 900, 722]]<|/det|> +- this should be GeneXpert cycle threshold was lower and semi-quantitative grade was higher." Lower PCR cycle thresholds correspond to higher semi-quantitative grade. They also on line 363 show that the Ct relationship was cough aerosol status was negative as expected as lower Ct values correspond to higher bacillary load. + +<|ref|>text<|/ref|><|det|>[[70, 735, 749, 753]]<|/det|> +Response: Thank you for identifying this error. We have edited the sentence to read, + +<|ref|>text<|/ref|><|det|>[[70, 768, 912, 801]]<|/det|> +"GeneXpert cycle threshold was significantly lower and semi- quantitative grade significantly higher among cough aerosol culture- positive compared to cough aerosol culture- negative participants." + +<--- Page Split ---> diff --git a/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/images_list.json b/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e939e81d82d2f00bf8ac881996d061ea312b28fa --- /dev/null +++ b/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,17 @@ + +# nature portfolio + +Peer Review File + +Asgard archaea defense systems and their roles in the origin of eukaryotic immunity + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. The manuscript was considered suitable for publication without further review at Nature Communications. + +<--- Page Split ---> diff --git a/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a568d2feb9e249d794db3c6b7b96e08c3fec638a --- /dev/null +++ b/peer_reviews/786cc0aff51b737323e0accf1aee68245c9d2ac6e415706f6a5dbe416d4ca13a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,19 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 898, 211]]<|/det|> +Asgard archaea defense systems and their roles in the origin of eukaryotic immunity + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 156, 816, 209]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. The manuscript was considered suitable for publication without further review at Nature Communications. + +<--- Page Split ---> diff --git a/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..9e1ec3650939182506cb120e5a32a715c3803b39 --- /dev/null +++ b/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,280 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S12. Global maps of fractional tree cover from (a) GLOBMP and (b) Global Forest Change (GFC) datasets.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).", + "footnote": [], + "bbox": [ + [ + 280, + 469, + 722, + 735 + ] + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2. ...", + "footnote": [], + "bbox": [ + [ + 210, + 95, + 784, + 401 + ] + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S8. Flow chart of the remote sensing (RS)-based local temperature effect validation", + "footnote": [], + "bbox": [ + [ + 208, + 440, + 785, + 870 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. S1. Schematic representation of the methodology for estimating land surface temperature (Ts) or air temperature (Ta) sensitivity to tree cover change ( \\(\\delta T_{s}^{bph}\\) and \\(\\delta T_{a}^{bph}\\) ). (a–f) The example grid (59.75°–60°N, 63.5°–63.75°E) with positive \\(\\delta T_{s}^{bph}\\) and \\(\\delta T_{a}^{bph}\\) in January 2010. (a) True color image of the 0.25° grid. (b) GLOBMAP 2010 tree cover map. (c) Mean Ts of January 2010. (d) Mean \\(T_{a}\\) of January 2010. (e) Linear regression for estimating positive \\(\\delta T_{s}^{bph}\\) of the grid. (f) Linear regression for estimating positive \\(\\delta T_{a}^{bph}\\) of the grid. (g–l) Similar to (a–f), but for the other example grid (44.75°–45°N, 38°–38.25°E) with negative sensitives in July 2010.", + "footnote": [], + "bbox": [ + [ + 211, + 92, + 784, + 520 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).", + "footnote": [], + "bbox": [ + [ + 277, + 85, + 725, + 355 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. S8. Flow chart of the remote sensing (RS)-based local temperature effect validation using FLUXNET and gridded temperature data.", + "footnote": [], + "bbox": [ + [ + 210, + 131, + 785, + 562 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. S10. Validation of the monthly minimum land surface temperature and air temperature sensitivities. (a) Remote sensing-based relationships between minimum temperature sensitivities \\((\\delta T s_{min}^{b p h}\\) and \\(\\delta T a_{min}^{b p h}\\) ) and background shortwave radiation \\((SW_{d})\\) . (b) FLUXNET-based relationships between minimum temperature sensitivities \\((\\delta T s_{min}^{b p h *}\\) and \\(\\delta T a_{min}^{b p h *}\\) ) with SWd, using Climatic Research Unit (CRU) temperature data to exclude the impact of macro-climate background. (c) Same as (b), but the Berkeley Earth Surface Temperatures (BEST) data are used to exclude the impact of macro-climate background.", + "footnote": [], + "bbox": [ + [ + 260, + 503, + 736, + 758 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2. ...", + "footnote": [], + "bbox": [ + [ + 220, + 132, + 780, + 435 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure 3. ... (c) Bar plots of the mean air temperature sensitivity \\((\\delta T_{a}^{bph*})\\) , land surface temperature sensitivity \\((\\delta T_{b}^{bph*})\\) and their difference (Diff) contributed by variations in aerodynamic resistance \\((\\delta T^{ra})\\) , and sensible heat \\((\\delta T^{H})\\) ...", + "footnote": [], + "bbox": [ + [ + 228, + 93, + 761, + 358 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4. Comparison of the biophysical (bph) and biochemical (bchem) effects of potential tree cover gain. (a) Global pattern of the biochemical effect of potential tree cover gain ( \\(\\delta CO_2e^{bchem}\\) ). (b) Global and latitudinal means of biochemical and biophysical effects of potential tree cover gain. The Ts-based and Ta-based biophysical effects are shown as the equivalent \\(CO_2\\) uptake ( \\(\\delta CO_2e^{bph,TS}\\) and \\(\\delta CO_2e^{bph,TA}\\) ). The error bars indicate the uncertainty of the mean. (c–f) Monthly ratios of Ta-based and Ts-based biophysical effects to equivalent biochemical effects across northern high-latitudes (>50°N), northern mid-latitudes (20°–50°N), tropics (20°S–20°N) and southern mid-latitudes (>20°S). The shaded area indicates the uncertainty of the ratios.", + "footnote": [], + "bbox": [ + [ + 220, + 188, + 787, + 397 + ] + ], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. S12. Global maps of fractional tree cover from (a) GLOBMap and (b) Global", + "footnote": [], + "bbox": [ + [ + 284, + 572, + 692, + 846 + ] + ], + "page_idx": 27 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. S13. Validation of satellite monthly mean air temperature (Ta) of 2010. (a) Scatter plot between satellite monthly Ta and FLUXNET monthly \\(T_{\\mathrm{a}}\\) measurements in forest sites. (b) Similar to (a), but for non-forest sites. Abbreviation: RMSE, root mean squared error.", + "footnote": [], + "bbox": [ + [ + 270, + 430, + 727, + 593 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. R1. Comparison between max and min air temperature (Ta) and daily mean Ta using FLUXNET observations for (a) forest sites and (b) non-forest sites at the monthly scale.", + "footnote": [], + "bbox": [ + [ + 270, + 108, + 727, + 258 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Fig. R2. Fraction of excluded pixels due to water cover or elevation differences, defined as the number of abandoned forest pixels (tree cover \\(>10\\%\\) ) divided by the number of all forest pixels within each \\(0.25^{\\circ}\\) grid.", + "footnote": [], + "bbox": [ + [ + 315, + 679, + 692, + 819 + ] + ], + "page_idx": 34 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Fig. S1. Schematic representation of the methodology for estimating land surface temperature (Ts) or air temperature (Ta) sensitivity to tree cover change ( \\(\\delta T_{s}^{bph}\\) and \\(\\delta T_{a}^{bph}\\) ). (a–f) The example grid (59.75°–60°N, 63.5°–63.75°E) with positive \\(\\delta T_{s}^{bph}\\) and \\(\\delta T_{a}^{bph}\\) in January 2010. (a) True color image of the 0.25° grid. (b) GLOBMAP 2010 tree cover map. (c) Mean Ts of January 2010. (d) Mean \\(T_{a}\\) of January 2010. (e) Linear regression for estimating positive \\(\\delta T_{s}^{bph}\\) of the grid. (f) Linear regression for estimating positive \\(\\delta T_{a}^{bph}\\) of the grid. (g–l) Similar to (a–f), but for the other example grid (44.75°–45°N, 38°–38.25°E) with negative sensitives in July 2010.", + "footnote": [], + "bbox": [ + [ + 210, + 92, + 784, + 520 + ] + ], + "page_idx": 34 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).", + "footnote": [], + "bbox": [ + [ + 277, + 520, + 723, + 788 + ] + ], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4. Comparison of the biophysical (bph) and biochemical (bchem) effects of potential tree cover gain. (a) Global pattern of the biochemical effect of potential tree cover gain ( \\(\\delta C O_{2}e^{b c h e m}\\) ). (b) Global and latitudinal means of biochemical and biophysical effects of potential tree cover gain. The Ts-based and Ta-based biophysical effects are", + "footnote": [], + "bbox": [ + [ + 220, + 607, + 785, + 820 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_8.jpg", + "caption": "Supplementary Figure 8. Flow chart of the remote sensing (RS)-based local temperature effect validation using FLUXNET and gridded temperature data.", + "footnote": [], + "bbox": [ + [ + 207, + 90, + 784, + 523 + ] + ], + "page_idx": 41 + } +] \ No newline at end of file diff --git a/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9bfce24a719362c046d68e2a669403912331e2b0 --- /dev/null +++ b/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,1175 @@ + +# nature portfolio + +Peer Review File + +Lung megakaryocytes engulf inhaled airborne particles to promote intrapulmonary inflammation and extrapulmonary distribution + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to + +the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## Response to Reviewers' Comments + +We greatly appreciate the opportunity to revise our manuscript and thank all anonymous reviewers for their constructive comments. The manuscript has been revised and improved according to the reviewers' valuable comments and suggestions. We hope that the revision will make it more acceptable for publication. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in Italics and Arial) and the location of the revision. The line numbers referred to are for the clean version of the revised manuscript. + +## Reviewer #1 (Remarks to the Author): + +The authors analyse the biophysical feedback of forestation. For this they use observational data, comparing the feedback for surface and air temperature. The main finding of the first part is that air temperature is less sensitive to tree cover changes than surface temperature. After establishing this, the authors analyse this difference in sensitivity by using Monxin Obukhov and quantify the maximum local climate effect. Finally, a comparison is made with the biochemical feedback of forestation, which shows that in specific regions the biophysical feedback can outperform the biochemical feedback. + +The authors show an innovative approach of combining different data sources and analytical methods in order to be able to analyse the effect of forestation of air temperature using observational data. This is interesting, since such topics are usually tackled by using model data. I specifically enjoyed the analysis of the near surface temperature profiles and the decomposition of the air temperature sensitivity. + +That being said, it took me quite some time to understand which dataset was used for which analysis and how the different data sources were combined and analysed. In my opinion, clarifying this aspect would be a big help in improving the paper. If the authors choose to rewrite/reorganize parts of the paper, some questions that I had during reading (some of which got resolved, but were still confusing in the beginning) could maybe serve as a guideline as to which parts to clarify: + +Response: We appreciate the positive comments by the reviewer. We have carefully considered all the comments and suggestions and made corresponding point- by- point responses. In particular, we have revised the method section and clarified the usage of different datasets to improve the readability of the manuscript. Please see our detailed responses below. + +1) Line 230: I thought we were only looking at the difference between 0 and 100% tree cover? + +Response: Thanks for the comment. In the original manuscript, the section is based on the tree restoration potential (ATC), ranging from 0 to 100%. According to the comment of reviewer #3, we removed the analyses related to ATC and rewrote this section by comparing the biophysical and biochemical sensitivity of tree cover change from 0 to 100% (Line 246). This revision makes our results clearer that only local effects are evaluated and the non-local or global effects are not + +<--- Page Split ---> + +included. + +## Comparison of biophysical with biochemical effects based on two temperature metrics + +Most assessments of the climate benefits related to forestation have concentrated on the carbon sequestration (i.e., biochemical effect). Here, the biomass carbon stock sensitivity to tree cover is estimated by space- for- time analogy and converted to \(\mathrm{CO_2}\) absorption equivalents ( \(\delta \mathrm{CO_2e^{bchem}}\) ) to represent the biochemical effect. We also convert the biophysical Ts and Ta sensitivities to the metric of equivalent \(\mathrm{CO_2}\) uptake ( \(\delta \mathrm{CO_2e^{bph,Ts}}\) and \(\delta \mathrm{CO_2e^{bph,Ta}}\) ). These allow the comparison of the local biophysical and the biochemical climate effect and evaluate the relative importance of the former. + +2) Line 399: where do these radiation values come from, which dataset? Response: Thanks for raising this concern. Upward and downward longwave radiation data are from FLUXNET datasets. We have added the description of the data source (Line 470): + +\(\mathrm{LW_u}\) and \(\mathrm{LW_d}\) represent upward and downward longwave radiation from the FLUXNET2015 dataset, respectively; + +3) Figure 1: is this figure based on GLOBMP? I can't find that anywhere. Response: Thanks for the careful reading. Figure 1 is based on GLOBMP dataset. We have added the description in the figure caption (Line 129): + +The tree cover map for the sensitivity estimation is from the GLOBAMP dataset. + +4) Line 355: why this \(10\%\) As in, why at all, and why exactly 10? + +Response: Thank you for raising this question. Here, we set this threshold for two reasons. First, according to the definition from the Food and Agricultural Organization (FAO), forests are defined as land with a tree crown cover larger than \(10\%\) and an area of more than 0.5 hectares (ha). Second, the temperature variations in low tree cover (e.g. \(< 10\%\) ) pixels may be induced by the rest non- forest land cover components. Using these pixels for regression may reduce the reliability of estimated temperature sensitivity to tree cover changes. In the revised manuscript, we have added explanations of the threshold (Line 415): + +Specifically, for each \(0.25^{\circ}\times 0.25^{\circ}\) grid cell, we filter out pixels with more than \(1\%\) water body coverage or less than \(10\%\) tree cover according to the forest definition by the Food and Agricultural Organization79. This process is to reduce the impact of non- forest land cover types on the estimation of temperature sensitivity. + +79. Keenan, R. J. et al. Dynamics of global forest area: Results from the FAO Global Forest Resources Assessment 2015. Forest Ecology and Management vol. 352 9-20 (2015). + +5) The satellite based Ts and Ta are for 2010 whereas the potential tree cover map is for 2020 (lines 311-326). Is this difference in time what you correct for in lines 488-489? Unfortunately I don’t really understand what you’re trying + +<--- Page Split ---> + +to say here. + +Response: Thank you for raising this concern. In the original manuscript, we use tree cover data of 2010 to estimate sensitives, considering the data availability of both GLOBMP and GFC datasets. We also use tree cover data of 2020 from GLOBMP to calculate tree restoration potential (ATC) under the current stage. According to the comment of reviewer #3, the analyses based on ATC are removed, and only tree cover data of 2010 are used in the revised manuscript. + +We have rewritten the "Tree Cover Map" subsection to clarify this issue (Line 377): + +In this study, two tree canopy cover datasets derived from different sensors are used for the analysis, including the recently released GLOBMP fractional tree cover map with a spatial resolution of \(250 \mathrm{~m}\) , and the Global Forest Change (GFC) tree cover map with a spatial resolution of \(30 \mathrm{~m}\) . Considering the data availability, we use the tree cover maps of 2010 (TC2010) of both two products to calculate the biophysical temperature sensitivities to ensure robustness. Both TC2010 maps are preprocessed and spatially aggregated to a \(1 \mathrm{~km}\) resolution for further analysis (Supplementary Fig. 12). + +![](images/Figure_unknown_1.jpg) + +
Fig. S12. Global maps of fractional tree cover from (a) GLOBMP and (b) Global Forest Change (GFC) datasets.
+ +6) What I found most confusing is the different definitions/meanings/sources of Ts and Ta throughout the paper. When describing the satellite based Ts and Ta: ,Ts represent the mixture temperature of the tree canopy and the exposed soil at the observed angle ". So, Ts is at canopy height. Later is mentioned that Ta is located at screen height (line 339), what is screen height? Is that then above the canopy layer in the case of a forest? In line 430 and further, Ta is + +<--- Page Split ---> + +normalized to 2m height. Why is this not done right away? But also, are we then looking at a Ta inside the canopy, (heavily influenced by the microclimate in a forest) or is it 2m above the canopy? Unfortunately, I also don't really understand formulas 1 and 2 and where they come from (see also a later comment on why a linear relationship is assumed) so I have difficulty assessing if all these differences in meaning are problematic or not (since you're comparing deltas and not actual values). And then in line 396, "Ta is measured above the vegetation canopy, ranging from several decimeters to over ten meters", so which height is actually used for Ta? Clearing all this up would be extremely helpful. + +Response: Thank you very much for these important issues. First, the evaluated Ta, in both remote sensing- and site- based analyses, indicates the air temperature of about 2 m above the land surface. Here, "land surface" indicates the interface layer between different land surface components and the atmosphere (e.g., forest canopy, rooftops and soil). Thus, for forested areas, Ta refers to the air temperature of about 2 m above the tree canopy. For clarity, we have revised the "screen height" to "approximately 2 m above the land surface". We also added a schematic figure (Supplementary Fig. 2) and descriptions of the temperature metrics in the introduction section (Line 78): + +Notably, the evaluated Ts indicates the radiometric temperature of the land surface, and Ta indicates the air temperature at 2 m above the land surface (Supplementary Fig. 2). The land surface here refers to the interface layer between different land components and the atmosphere (e.g. vegetation canopy)44. + +![](images/Figure_2.jpg) + +
Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).
+ +## Reference: + +44. Reiners, P., Sobrino, J. & Kuenzer, C. Satellite-Derived Land Surface Temperature Dynamics in the Context of Global Change—A Review. Remote Sens. 15, (2023). + +We also added descriptions of the air temperature in the method section (Line 397): The other temperature metric used for assessment is Ta, the air temperature at + +<--- Page Split ---> + +approximately 2 m above the interface layer between land components and the atmosphere. Specifically, for forested areas, the reference plane is the canopy, whereas for openlands the reference plane is approximately the ground (Supplementary Fig. 2). + +Second, since Ta is measured above the vegetation canopy, ranging from several decimeters to over ten meters, we normalized FLUXNET Ta to explore the temperature profile from zero- plane displacement to the fixed 2- meter height above the canopy. + +Third, about Equations 1 and 2, please see the later response to your critical comment on the assumption of a linear relationship. + +Other comments: + +Line 28: „different biophysical characteristics “ → different than what? I suggest changing to „several biophysical characteristics “, or something along those lines. + +Response: Thanks for the suggestion. We have replaced the “different” with “several” (Line 36): + +Meanwhile, forests present several biophysical (bph) characteristics, such as lower albedo and greater roughness length, resulting in the local cooling or warming effect compared to their neighboring openlands. + +Line 32: what is a negative and what is a positive effect? Maybe use warming and cooling instead? + +Response: Thanks for the comment. We have changed “negative/positive” to “cooling/warming” (Line 40): + +The sign and magnitude of the local biophysical temperature effects can vary considerably based on spatial location and background climate, and are typically characterized by a shift from cooling effects in the tropics to warming effects in cold regions. + +Line 67: what does bgp actually stand for? (just out of curiosity, knowing this would help with reading) + +Response: Thanks for the suggestion. In the original manuscript, the superscript “bgp” is the abbreviation for “biogeophysical”. We have changed the superscript to “bph” as the abbreviation for biophysical for clarity (Line 36): + +Meanwhile, forests present several biophysical (bph) characteristics, such as lower albedo and greater roughness length, resulting in the local cooling or warming effect compared to their neighboring openlands. + +Line 85: only one other study is used in the figure for comparison? Response: Yes, we compare our result with Duveiller et al, which provides biophysical maximum, + +<--- Page Split ---> + +minimum and mean Ts effects of forestation. To avoid ambiguity, we have revised the sentence (Line 102): + +The estimated \(\delta T s^{b p h}\) aligns well with a previous study of the potential Ts effect of forestation based on the unmixing method46, suggesting the robustness to different analytical approaches. + +## Reference: + +46. Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64 - 75 (2018). + +Line 88: valueS + +Response: Thanks for the careful reading. We have corrected the mistake as the reviewer suggested (Line 105): + +In terms of the magnitude, \(\delta T a^{b p h}\) demonstrates much lower absolute values compared to \(\delta T s^{b p h}\) . + +Line 144- 147: please rewrite this sentence, or maybe it already works if the first „While“ is removed? + +Response: Thank you for the careful reading. We have rewritten the sentence and now it reads (Line 179): + +However, we show that the ratios of Ta sensitivity slopes to Ts sensitivity slopes are close in the RS- based (16.9%) and site- based (17.4%) results (Fig. 2c and d). This result suggests that site measurements corroborate the relative magnitude of the RS- based maximum temperature sensitivity. + +Figure 2: The text of the legend is very small, which makes it difficult to distinguish between Ts and Ta (the s and a look the same). If possible rearrange legend and panels to be able to increase font size (maybe the legend outside of the panel?) + +Response: We thank the reviewer for the helpful suggestion. To better distinguish the two temperatures, we have changed Ts and Ta to Ts and Ta. We also rearranged the panels to increase the font size of the legend (Fig. 2). + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Figure 2. ...
+ +Subsection starting at line 163: What could be a valuable addition is a short discussion on the differences between the sites. Why is the influence of a different between the three observed cases (Europe vs North America and Australia)? + +Response: Thanks for the suggestion. We have added an explanation of the higher contribution from H in European winter than North American or Australian summer (Line 226): + +We note that the contribution of H is greater in European winter than in North American or Australian summer. The possible reason is that H is more dominant in the turbulent flux exchange in winter (characterized by the higher Bowen ratio) than in summer51, thus contributing more to the temperature gradients between the land surface and the near- surface air, and further to the attenuation of the air temperature response. + +## Reference: + +51. Lin, H., Li, Y. & Zhao, L. Partitioning of Sensible and Latent Heat Fluxes in Different Vegetation Types and Their Spatiotemporal Variations Based on 203 FLUXNET Sites. J. Geophys. Res. Atmos. 127, (2022). + +Line 245: after how many years would this amount be reached? Compared to how fast trees grow and the biophysical effect will be apparent? Trees grow slow and biophysical and biochemical feedback act on different timescales, a sentences or two about this would be helpful I think. + +Response: Thanks for the professional suggestion. We have added a sentence to discuss the temporal scale of two effects (Line 320): + +<--- Page Split ---> + +Both evaluated biophysical and biochemical effects represent potential cumulative results. It may take a shorter period for biophysical processes (a single decade) to come into effect than biochemical processes, as the newly restored forests gradually absorb CO2 and reach equilibrium after several decades. + +Line 261: which regions? + +Response: Thanks for the careful reading. Following reviewer #3's comment, this section about the comparison between biophysical and biochemical effects has been rewritten. Please see the response below for the new content. + +Line 292: and A machine- learning model + +Response: Thanks for pointing out this and the following mistakes. According to the comment of reviewer #3, the analyses using the machine- learning model for sensitivity extrapolation are removed. Correspondingly, the related descriptions and discussions are deleted. + +Line 314: Both and two \(\rightarrow\) remove one + +Response: Revised as you suggested (Line 382): + +Both TC2010 maps from GLOBMP and GFC are preprocessed and spatially aggregated to the 1 km resolution for further analysis. + +Line 318: by A Random Forest model + +Response: Contents related to the random forest model are deleted for the same reason mentioned above. + +Line 323: annual precipitation is mentioned twice + +Response: This paragraph is deleted for the same reason mentioned above. + +Line 357: water coverage AND elevation data + +Response: Revised as you suggested (Line 420): + +The water coverage and elevation data are from Joint Research Center Global Surface Water Mapping Layers v1.4 and GMTED2010 datasets, respectively. + +Lines 360- 363: why do you assume the relation is linear? Do you have a reference for this (pretty strong) assumption? And about the formulas: what is the difference between TC T and TC? Also, deltaTsbgp and deltaTabgp are for 100% increase in forest cover (I thought?), how is this represented in formula 1 and 2? + +Response: Thanks for raising these concerns. The non- linear relationship is generally discussed in those studies at finer scales (Zhao et al., 2023) or inner- city scales (Yang et al., 2024). For most large- scale or global studies, the linear assumption is widely accepted and used (Alkama and Cescatti, 2016; Wang et al., 2023; Zhang et al., 2024). We add these references for the linear + +<--- Page Split ---> + +relationship between tree cover and temperature (Line 423): + +After the screening process, \(\delta T s^{b p h}\) and \(\delta T a^{b p h}\) can be estimated using a linear regression model between tree cover and corresponding temperature values for each \(0.25^{\circ}\) grid (Alkama and Cescatti, 2016; Wang et al., 2023; Zhang et al., 2024). + +Second, the original formulas 1 and 2 are the matrix representation of the ordinary least squares (OLS) method for estimating the slope, and the superscript "T" denotes the matrix transpose. We rewrite the formula 1 and 2 as the form or linear relationship for clarity, and it now reads (Line 425): + +\[\begin{array}{c}{{T s=\delta T s^{b p h}\times T C_{2010}+b_{s}}}\\ {{}}\\ {{T a=\delta T a^{b p h}\times T C_{2010}+b_{a}}}\end{array} \quad (1)\] + +where, \(b_{s}\) and \(b_{a}\) are the regression intercepts. + +## References: + +Alkama, R., Cescatti, A., 2016. Biophysical climate impacts of recent changes in global forest cover. Science (80- .). 351, 600 - 604. https://doi.org/10.1126/science.aac8083Wang, H., Yue, C., Luyssaert, S., 2023. Reconciling different approaches to quantifying land surface temperature impacts of afforestation using satellite observations. Biogeosciences 20, 75 - 92. https://doi.org/10.5194/bg- 20- 75- 2023Yang, L., Ge, J., Cao, Y., Liu, Y., Luo, X., Wang, S., Guo, W., 2024. Enhanced Cooling Efficiency of Urban Trees on Hotter Summer Days in 70 Cities of China. Adv. Atmos. Sci. 41, 2259 - 2275. https://doi.org/10.1007/s00376- 024- 3269- 9Zhang, Y., Wang, X., Lian, X., Li, S., Li, Y., Chen, C., Piao, S., 2024. Asymmetric impacts of forest gain and loss on tropical land surface temperature. Nat. Geosci. 13, 823 - 831. https://doi.org/10.1038/s41561- 024- 01423- 3Zhao, J., Zhao, X., Wu, D., Meili, N., Fatichi, S., 2023. Satellite - based evidence highlights a considerable increase of urban tree cooling benefits from 2000 to 2015. Glob. Chang. Biol. https://doi.org/10.1111/gcb.16667 + +Line 365: sample size of what? + +Response: Thanks for the comment. The sample size indicates the number of samples for the linear regression model. The sentence now reads (Line 427): + +To ensure the reliability of the results, biophysical sensitivity calculation is performed only when the total sample size of the linear regression model exceeds 90 (more than \(10\%\) of pixels within the \(0.25^{\circ}\) grid) and the difference between the highest and lowest tree cover is greater than \(40\%\) . + +Line 382: this is not entirely true though, is it? Because of the spatial autocorrelation and the fact that a forest influences it surroundings? Removing the forest could also change the temperature on the non- forest site. + +Response: Thanks for the valuable comment. We admit that forestation can affect the temperature of the surrounding area, by affecting heat advection or the circulation pattern. We have clarified that + +<--- Page Split ---> + +the paired site method can only be used to validate the "local" temperature effect derived from remote sensing data (Line 450): + +The RS- based local temperature sensitivity can be validated through the differences of measurements between spatially adjacent paired forest and non- forest sites. + +Line 401: why is the lack of spatial pairing a reason for this? I understood from the previous paragraph that no spatial pairing approach is used? As I understand from the formula, you simply average over all forest/open land sites anyway? + +Response: Thanks for pointing this out. The spatial pairing approach is not used here and we have removed this redundant description (Line 472): + +We bin the SWa with a fixed interval of \(10 \mathrm{w} / \mathrm{m}^2\) and calculate the mean \(\delta T s^{b p h *}\) or \(\delta T a^{b p h *}\) to explore the sensitivity variability under different background radiation conditions. + +Second, we average the forest and openland observations in different shortwave radiation bins, rather than all possible observations. We added a flow chart for the methodology for clarity (Supplementary Fig. 8). + +![](images/Figure_unknown_3.jpg) + +
Fig. S8. Flow chart of the remote sensing (RS)-based local temperature effect validation
+ +<--- Page Split ---> + +using FLUXNET and gridded temperature data. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +# Content of the paper + +In their paper, "The Overlooked Local Air Warming Mitigation of Potential Tree Restoration", the authors provide insights on the biophysical impacts of forestation. Namely, they compute the impacts of forestation on air temperature (as opposed to surface temperature) and compare these impacts with the often reported surface temperature changes, and with biogeochemical effects. + +For this, the authors train an RF model: From meteorological, soil, forest cover, and topographic data, this predicts the maximum forest cover under current climatic conditions across the globe. + +They correlate weather station air temperature \(T_{- }a\) to satellite- observed surface temperature \(T_{- }s\) , to get global coverage of \(T_{- }a\) . Then, after a filtering process to account for too- high elevation differences or too- low forest cover differences within that pixel, linear relationships between tree cover and the two temperatures are created, + +\[T_{-}s = \mathrm{TC\_2010x dT\_s\] \[T_{-}a = \mathrm{TC\_2010x dT\_a\] + +From this relationship, they can estimate the temperatures within that pixel if it contained the maximum possible forest cover. The authors validate their approach with site data. They finally compare their results with biogeochemical impacts of forestation. + +## # Remarks + +In general, I find this to be a relevant and well- crafted paper that could be suitable for publication within the journal Nature Communications. It offers substantial new contributions. The authors did a good job in using various data sources to back their claims and I enjoyed reading this paper. + +However, some more work needs to be invested to make the paper and its contribution clearer which is why I categorize this manuscript as needing "major revisions". + +For instance, it needs to be highlighted more what the new results are compared to existing knowledge, for instance compared to the study by Windisch et al. (2019), which the authors also cite. I found the state of current knowledge to be addressed, but not clear enough. Perhaps (only an idea), some more consolidation of current state of knowledge would be helpful, and the main results of this new manuscript should be made more prominent. + +Many points throughout the manuscript can be made clearer, it is sometimes not clear whether local impacts, or global impacts are talked about. And in various points (see my detailed comments below) the explanations need some more clarity. In the assessment of biogeochemical impacts, soil is neglected. + +Please find my detailed comments on the various sections below. + +Response: We appreciate your positive comments. We have revised our manuscript carefully and the detailed corrections are listed below. Specifically, we have invested more work to clarify the + +<--- Page Split ---> + +new contribution of this paper compared to previous Ts- based studies (e.g. Windisch, et al.). The state of current knowledge, such as global/local effects, the influence of soil carbon, and the widespread impact of forestation, have been introduced or discussed. We also revised explanations and technical terms to make the paper clearer. We hope the revised paper will be more suitable for publication. + +## Abstract + +1. 12-13: flatter temp profiles in forested areas \*compared to non-forested\* Response: Thanks for the comment. The sentence has been revised as suggested (Line 14): + +We further attribute the discrepancy in temperature responses to the reduced aerodynamic resistance and the resultant flatter near- surface temperature profiles in forests compared to non- forests. + +1. 14 the substantial climate benefits, could mention here how high they will get, how many K? How much is it compared to surface temperature? Also, what is the potential global impact? + +Response: Thanks for the suggestion. According to the comment of reviewer #3, we have updated the results of the comparison between biophysical and biochemical effects. The new results focus on the local biophysical and biochemical sensitivities, rather than the global biophysical and biochemical climate effects of potential tree restoration. Similar to Windisch, et al., the current comparisons are based on the equivalent \(\mathrm{CO_2}\) uptake, rather than the temperature effect (K). This revision makes our results clearer that only local effects are evaluated and the non- local or global effects are not included. Correspondingly, we have rewritten the abstract (Line 4): + +Forestation, as a key component of nature- based solutions, has the potential to cool or warm the local climate through biophysical processes, thereby enhancing or offsetting the global warming mitigation from carbon assimilation. Currently, the magnitude of such biophysical effects on local climate remains unconstrained, as most previous observational studies rely on land surface temperature (Ts), rather than the policy- relevant near surface air temperature (Ta). Based on satellite observations, we show that the Ta response to tree cover change is significantly lower, ranging from 15% to 30%, compared to Ts response. The relative magnitude of the two temperature effects is supported by independent evidence from site observations. We further attribute the discrepancy in temperature responses to the reduced aerodynamic resistance and the resultant flatter near- surface temperature profiles in forests compared to non- forests. Moreover, we show that at mid- or northern high- latitudes, the maximum seasonal biophysical Ta warming or cooling only accounts for approximately 10% of the equivalent climate effect of carbon sequestration in terms of magnitude, whereas the ratio for the biophysical Ts effect can reach 40%. These results highlight that Ts- based assessments may significantly overestimate the local climate impact of tree cover change. We also emphasize that when evaluating the biophysical effects of forestation or deforestation, the proper temperature metric should be specified and used in different cases to avoid misleading conclusions. + +<--- Page Split ---> + +1. 18: but the key message is not the strong potential, but quite contrarily, the much lower potential than what we anticipate, I think the wording needs to be a bit different (Line 14): + +Response: Thanks for the constructive comment. We've revised the wording according to the new results: + +Moreover, we show that at mid- or northern high- latitudes, the maximum seasonal biophysical Ta warming or cooling only accounts for approximately \(10\%\) of the equivalent climate effect of carbon sequestration in terms of magnitude, whereas the ratio for the biophysical Ts effect can reach \(40\%\) . These results highlight that Ts- based assessments may significantly overestimate the local climate impact of tree cover change. We also emphasize that when evaluating the biophysical effects of forestation or deforestation, the proper temperature metric should be specified and used in different cases to avoid misleading conclusions. + +### Introduction + +1. 26 - reference 5: there is a new version of this paper by the same authors: https://doi.org/10.1038/s41586-024-07602-x + +Response: Thanks for the careful reading. We have updated the reference (Line 598): + +Reference: + +5. Pan, Y. et al. The enduring world forest carbon sink. Nature 631, 563-569 (2024). + +1. 39 - some more introduction on local, non-local, and global effects would be nice. There is quite some work from the group of Julia Pongratz on this topic. + +Response: Thanks for the constructive comment. We added an introduction about non- local and global effects (Line 40): + +Forest changes also affect the temperature of spatial nearby regions through advective transport, and even global temperature via altering the large- scale circulation patterns14. The magnitude of this non- local effect depends on the area extent and the geolocation of the changes15,16. + +## Reference: + +14. Pongratz, J. et al. Land Use Effects on Climate: Current State, Recent Progress, and Emerging Topics. Curr. Clim. Chang. Reports 7, 99 - 120 (2021). + +15. Winckler, J., Lejeune, Q., Reick, C. H. & Pongratz, J. Nonlocal Effects Dominate the Global Mean Surface Temperature Response to the Biogeophysical Effects of Deforestation. Geophys. Res. Lett. 46, 745 - 755 (2019). + +16. Winckler, J., Reick, C. H. & Pongratz, J. Why does the locally induced temperature response to land cover change differ across scenarios? Geophys. Res. Lett. 44, 3833 - 3840 (2017). + +1. 54 - which limitations? + +Response: Thanks for the comment. We have revised the sentences to clarify the limitation (Line + +<--- Page Split ---> + +63): + +According to the report of the Intergovernmental Panel on Climate Change (IPCC), the indicator used to describe global land warming and frame climate change mitigation targets is near surface air temperature (Ta) rather than Ts36. Despite the strong correlation between Ts and Ta37, the Ts effect of forest change may significantly differ from the Ta effect38. Ts- based assessments are useful for model refinement or informing the sign of Ta effects, but the values cannot be directly considered in climate treaties or policies. + +## Reference: + +36. Intergovernmental Panel on Climate Change. Changing State of the Climate System. in Climate Change 2021 - The Physical Science Basis 287 - 422 (Cambridge University Press, 2023). doi:10.1017/9781009157896.004. + +37. Wang, Y. R., Hessen, D. O., Samset, B. H. & Stordal, F. Evaluating global and regional land warming trends in the past decades with both MODIS and ERA5-Land land surface temperature data. Remote Sens. Environ. 280, 113181 (2022). + +38. Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1-15 (2011). + +1. 57 - Note that the IPCC actually always talks about LSAT, land surface air temperature, and not surface temperature. + +Response: Thanks for pointing this out. We have highlighted the temperature used in IPCC reports (Line 64): + +According to the report of the Intergovernmental Panel on Climate Change (IPCC), the indicator used to describe global land warming and frame climate change mitigation targets is land surface air temperature (Ta) rather than Ts36. + +## Reference: + +36. Intergovernmental Panel on Climate Change. Changing State of the Climate System. in Climate Change 2021 - The Physical Science Basis 287 - 422 (Cambridge University Press, 2023). doi:10.1017/9781009157896.004. + +1. 58 - citation 34: there is a new report, also the citation seems wrong? at least the one I find has a different citation: https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_Chapter02_FIN AL.pdf + +Response: We thank the reviewer for the careful reading. We have updated the reference (Line 665): + +## Reference: + +36. Intergovernmental Panel on Climate Change. Changing State of the Climate System. in Climate Change 2021 - The Physical Science Basis 287 - 422 (Cambridge University Press, 2023). doi:10.1017/9781009157896.004. + +<--- Page Split ---> + +1.60 you criticize the sparse distribution of study sites in other studies, are the used study sites better distributed? + +Response: Thanks for this critical comment. The distribution of paired sites is limited in Europe and North America (Chen et al., 2018). Here, the proposed methodology makes full use of more than 100 sites spread across five continents. + +## Reference: + +Chen, L., Dirmeyer, P.A., Guo, Z., Schultz, N.M., 2018. Pairing FLUXNET sites to validate model representations of land- use/land- cover change. Hydrol. Earth Syst. Sci. 22, 111- 125. https://doi.org/10.5194/hess- 22- 111- 2018 + +We have highlighted the limitation of the current paired site in the revised manuscript (Line 68): + +Although a few studies have explored the different responses of these two temperatures in the context of forest change, their results may be affected by the uncertainties in numerical models or the sparse distribution of paired forest and non- forest sites. + +1. \(67 = 100\%\) increase in tree cover, what does that mean? What is the spatial moving window approach in that regard? + +Response: Thanks for the comments. First, the hypothetical tree cover gain from 0 to \(100\%\) indicates an ideal forest change. The evaluated \(\delta \mathrm{Ts}^{\mathrm{bph}}\) or \(\delta \mathrm{Ta}^{\mathrm{bph}}\) is based on this ideal change regardless of the existing tree cover. Second, according to your comment below, we used the "spatial- for- time analogy" to replace "the spatial moving window" for clarity (Line 76). We also added a schematic figure to show how the methodology works (Supplementary Fig. 1). + +We first estimated the biophysical Ts and Ta sensitivity to a hypothetical \(100\%\) increase in tree cover (denoted as \(\delta \mathrm{Ts}^{\mathrm{bph}}\) and \(\delta \mathrm{Ta}^{\mathrm{bph}}\) ) at the \(0.25^{\circ}\) scale, based on the space- for- time analogy (Supplementary Fig. 1) + +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
Fig. S1. Schematic representation of the methodology for estimating land surface temperature (Ts) or air temperature (Ta) sensitivity to tree cover change ( \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) ). (a–f) The example grid (59.75°–60°N, 63.5°–63.75°E) with positive \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) in January 2010. (a) True color image of the 0.25° grid. (b) GLOBMAP 2010 tree cover map. (c) Mean Ts of January 2010. (d) Mean \(T_{a}\) of January 2010. (e) Linear regression for estimating positive \(\delta T_{s}^{bph}\) of the grid. (f) Linear regression for estimating positive \(\delta T_{a}^{bph}\) of the grid. (g–l) Similar to (a–f), but for the other example grid (44.75°–45°N, 38°–38.25°E) with negative sensitives in July 2010.
+ +1. 67 not a big deal, but kind of strange that it's always "biophysical" but the abbreviation is "bgp" which I guess stands for biogeophysical + +Response: Thank you for pointing this out. We have changed the superscript to "bph" as the abbreviation for biophysical for clarity. + +1. 70 – globally distributed – you mean FLUXNET, right? Just mention this here. Globally distributed suggests that they are somewhat uniformly distributed across the globe, but Fluxnet has big biases towards certain regions (East Asia, North America, Europe). + +Response: Following your suggestion, we have revised the data statements (Line 84): Furthermore, we use the FLUXNET2015 dataset45 and two gridded temperature + +<--- Page Split ---> + +datasets to validate the differences between two sensitivities and elucidate the underlying biophysical mechanisms. + +Reference: + +45. Pastorello, G. et al. The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data. Sci. Data 7, 1 - 27 (2020). + +1. 72 - spatially gap fill: you mean to extrapolate to the globe? Response: Thanks for the comment. According to the suggestion of reviewer #3, the analyses based on sensitivity extrapolation are removed. The related descriptions and results are deleted. + +also not a big deal, but your use of tenses is inconsistent. Sometimes present, sometimes past. + +Response: Thanks for the careful reading. We have unified the tenses into the present tense. + +I am missing a clear definition of T_a which is, I assume, 2m above ground. + +Response: Thanks for raising this important question. The evaluated Ta is not exactly the air temperature 2 m above the ground, but the air temperature above the land surface (or underlying surface) (Zhang et al., 2022). Here, land surface indicates the interface layer between different land surface components and the atmosphere (e.g., tree canopy, rooftops and soil) (Reiners et al., 2023). Thus, for forested areas, Ta refers to the air temperature of about 2 m above the tree canopy; while for openlands, Ta is approximately air temperature 2 m above the ground. + +References: + +Reiners, P., Sobrino, J., Kuenzer, C., 2023. Satellite- Derived Land Surface Temperature Dynamics in the Context of Global Change — A Review. Remote Sens. 15. https://doi.org/10.3390/rs15071857 + +Zhang, T., Zhou, Y., Zhao, K., Zhu, Z., Chen, G., Hu, J., Wang, L., 2022. A global dataset of daily maximum and minimum near- surface air temperature at 1km resolution over land (2003- 2020). Earth Syst. Sci. Data 14, 5637 - 5649. https://doi.org/10.5194/essd- 14- 5637- 2022 + +In the revised manuscript, we gave the definition of Ta for clarity (Line 78): + +Notably, the evaluated Ts indicates the radiometric temperature of the land surface, and Ta indicates the air temperature at 2 m above the land surface (Supplementary Fig. 2). The land surface here refers to the interface layer between different land components and the atmosphere (e.g. vegetation canopy). + +<--- Page Split ---> +![](images/Figure_unknown_5.jpg) + +
Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).
+ +We also added descriptions of the air temperature in the method section (Line 397): + +The other temperature metric used for assessment is Ta, the air temperature at approximately \(2m\) above the interface layer between land components and the atmosphere. Specifically, for forested areas, the reference plane is the canopy, whereas for openlands the reference plane is approximately the ground. + +### Results + +1. 87 very nice, this comparison with the Duveiller paper. Response: Thanks for the positive comment. + +1. 89 why is it called the "local" effect here. + +Response: Thanks for the comment. We emphasize the effects "local" to distinguish them from non- local effects of tree restoration, which are not included in our RS- based analysis. We have rearranged the sentence for clarity (Line 105): + +In terms of the magnitude, \(\delta T a^{b p h}\) demonstrates much lower absolute values compared to \(\delta T s^{b p h}\) (- 0.14 K ± 0.40 K vs. - 0.65 ± 1.22 K, global mean ± standard deviation), indicating that the local Ta effect of tree restoration is approximately 22% of the Ts effect. + +1. 92 I am confused, should it be \(+0.17\mathrm{K}\) vs \(+0.53\mathrm{K}\) ? + +Response: Thanks for the careful reading. We have corrected the typo (Line 110): + +At northern high- latitudes, the Ta- based warming induced by tree cover change is 32% of the \(T_{s}\) - based warming (0.17 K vs. 0.53 K). + +<--- Page Split ---> + +1. 95 nice that you did this with multiple data products Response: Thank you for recognizing our work. + +1. 116 I like that you did this analysis for min and max Response: Thanks for the positive comment. + +1. 119 - I find it notable that for the max temp, even in boreal regions there is always cooling. This is important for applications / policy I believe + +Response: Thank you for pointing this out. We have emphasized this result in the discussion section (Line 341): + +In particular, the diurnal and seasonal changes in biophysical temperature effects should be considered when formulating comprehensive forest- based policies. For instance, we observe maximum temperature cooling and minimum temperature warming effects of forests at high- latitudes. This suggests that tree restoration in such cold regions may be a solution to reduce the risks or impacts of daytime warming on the ecosystem. + +1. 132 - why is this called the "ideal" temperature effect? Aren't you just doing the same exercise but now for observational data and not RS data? + +Response: We call the effect "ideal" because it is inferred from the observations from forest and non- forest sites, and the land cover changes do not actually occur. To avoid ambiguity, we have revised the sentence (Line 149): + +To ensure the robustness of our findings, especially the relative magnitude of Ta effects to Ts effects, we further validate the RS- based \(\delta \mathrm{T}s^{bph}\) and \(\delta \mathrm{T}a^{bph}\) against the temperature effects of forestation \((\delta \mathrm{T}s^{bph*}\) and \(\delta \mathrm{T}a^{bph*}\) ) inferred from the in- situ observations and gridded temperature data. + +Second, the validation based on FLUXNET observations is not exactly analogous to the method used for RS data. We provided a figure to illustrate how it works (Supplementary Fig. 8), which consists of the following steps: + +(1) We first subtract elevation-corrected gridded temperature data from FLUXNET Ts or Ta. Here, the gridded data mainly reflect the macro-climate; FLUXNET Ts or Ta are driven by both the macro-climate and the land use. Thus, their difference represent the relative impact of land cover on local Ts or Ta (Novick and Barnes, 2023). +(2) We then calculate the difference between corrected FLUXNET Ts or Ta in forest sites and non-forest sites ( \(\mathbf{x}_{\mathrm{f}}\) and \(\mathbf{x}_{\mathrm{o}}\) in Fig. S8). The difference values represent the impact of potential forestation on Ts or Ta (non-forest converting to forest). Notably, we calculate this difference at each \(10\mathrm{w / m}^2\) shortwave radiation (SWd) bin to represent the temperature effect of forestation under changing radiative conditions. +(3) We estimate the relationship between shortwave radiation and the Ts or Ta effects from both RS and in-situ data (e.g. Fig 2a and 2b). We compare the regression results to validate (a) whether the variation in RS-based Ts and Ta sensitivity with radiation are quantitatively aligned with the + +<--- Page Split ---> + +in- situ results. (b) whether the relative magnitude of RS- based Ta effects to Ts effects is supported by in- situ results. + +![](images/Figure_unknown_6.jpg) + +
Fig. S8. Flow chart of the remote sensing (RS)-based local temperature effect validation using FLUXNET and gridded temperature data.
+ +## Reference: + +Novick, K.A., Barnes, M.L., 2023. A practical exploration of land cover impacts on surface and air temperature when they are most consequential. Environ. Res. Clim. 2, 025007. https://doi.org/10.1088/2752- 5295/accdf9 + +## 1. 134 gradient? + +Response: Thanks for the careful reading. We have replaced "gradient" by "bins" for clarity (Line 153): + +Here, \(\delta T s^{b p h *}\) and \(\delta T a^{b p h *}\) are estimated in different shortwave radiation (SWd) bins to represent the relative changes with changing background radiation conditions (Methods, Supplementary Fig. 8). + +Fig 2b) provide n, and indicate that this is from fluxnet data. Is a line plot + +<--- Page Split ---> + +ok here? I think you should plot the actual data points, FLUXNET should be around 100- 200 data points if I am not mistaken. + +Response: Thanks for the suggestions. First, we noted that the date is from FLUXNET in the figure caption (Line 166). + +(b) FLUXNET-based relationships between the mean temperature sensitivities \((\delta T s^{b p h *}\) and \(\delta T a^{b p h *}\) ) and SWd. + +Second, the line plots in Fig.2b show the estimated \(\delta T s^{b p h *}\) or \(\delta T a^{b p h *}\) values rather than the original FLUXNET data. The forest and openland samples used to estimate each data point of the line plot have different sample sizes n. Hence, it is difficult to label n in the figure. For clarity, we here provide raw data (including forest n and openland n for each data point) for Figures 2b and 2d. The file, named "Raw_data_for_Fig2.xlsx", will be published with the article if the manuscript can be accepted. + +Why is it only mean and max, and not min? + +Response: Thank you for the comment. We have added minimum temperature results (Line 184): + +We also perform similar analyses to the site- based minimum Ta and Ts sensitivities \((\delta T s_{min}^{b p h *}\) and \(\delta T a_{min}^{b p h *}\) , Supplementary Fig. 10), which supports the lower Ta- based warming than Ts- based warming during the nighttime in the RS- based results. We note that the relationship between \(\delta T a_{min}^{b p h *}\) and SWd is not significant, which corresponds to the weak correlation between \(\delta T a_{min}^{b p h}\) and SWd in the RS- based results \((r = - 0.38)\) . + +![](images/Figure_2.jpg) + +
Fig. S10. Validation of the monthly minimum land surface temperature and air temperature sensitivities. (a) Remote sensing-based relationships between minimum temperature sensitivities \((\delta T s_{min}^{b p h}\) and \(\delta T a_{min}^{b p h}\) ) and background shortwave radiation \((SW_{d})\) . (b) FLUXNET-based relationships between minimum temperature sensitivities \((\delta T s_{min}^{b p h *}\) and \(\delta T a_{min}^{b p h *}\) ) with SWd, using Climatic Research Unit (CRU) temperature data to exclude the impact of macro-climate background. (c) Same as (b), but the Berkeley Earth Surface Temperatures (BEST) data are used to exclude the impact of macro-climate background.
+ +<--- Page Split ---> + +The usage of different y scales is quite misleading here. This should be changed. Response: Thank you for this comment. We have unified the y scales (Fig. 2). + +![](images/Figure_3.jpg) + +
Figure 2. ...
+ +Is this now monthly mean and max? + +Response: Thank you for this comment. Yes, the data for validation are at the monthly scale. We have declared the temporal scale in the figure caption (Line 164): + +Figure 2. Validation of the monthly land surface temperature and air temperature sensitivities. + +Why not a figure like 1c for the sites? This would be a convincing comparison between RS and site data. + +Response: Thank you for the suggestion about the visualization. Here, the FLUXNET- based sensitivities ( \(\delta \mathrm{T}\mathrm{s}^{\mathrm{bph}*}\) and \(\delta \mathrm{T}\mathrm{a}^{\mathrm{bph}*}\) ) are calculated at different radiation bins and thus do not represent the results of specific geo- locations or latitudes. Thus, these results are unlikely to be presented in the manner of Fig. 1c. + +1. 143 thank you for providing this disclaimer. can you also provide what the revisit times are? Is it from the MODIS with 4 visits per day? And here you mean occurrence of _daily_maximum temperature? + +Response: Thank you for the comments. We have added the overpass time and the word "daily" as you suggested (Line 176): + +The slopes derived from in- situ measurements are more pronounced than RS- based results, which may be due to the satellite overpass times (about 13:30, see Methods) not precisely coinciding with the occurrence of daily maximum temperatures. + +<--- Page Split ---> + +We also provide four overpass times of MODIS Ts in the method section (Line 390): + +Here, the monthly mean Ts data of 2010 is generated by the daily four observations from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua satellites (observed at 1:30, 10:30, 13:30 and 22:30). + +Section "Biophysical mechanisms..." is a very nice section but needs some more work to clear things up. + +Fig 3 - very interesting figure, unfortunately rather low n, but I guess there's nothing to do about that. I however still do not understand why it is now about 2m above the canopy. Should it not be 2m above the ground that is relevant? + +Response: Thanks for raising the concern. The evaluated Ta indicates the air temperature above the tree canopy in the forested area. Please refer to the response above about the definition of Ta. + +We admit that the air temperature 2 m above ground (usually below the tree canopy) is relevant for many organisms or processes within forests. However, the evaluated Ta is also important, because (a) Ta is close to the definition of 'Tas' in climate models (the inferred temperature at 2 m above zero- plane displacement height), which is used to assess climate change (Winckler et al., 2019). (b) Ta is more relevant to boundary layer dynamics, rainfall initiation, and interaction between the climate system and land surface (Novick and Katul, 2020). Therefore, we believe that the evaluated Ta is a highly relevant indicator for climate change and land- atmosphere interaction. + +## References: + +Winckler, J., Reick, C.H., Luyssaert, S., Cescatti, A., Stoy, P.C., Lejeune, Q., Raddatz, T., Chlond, A., Heidkamp, M., Pongratz, J., 2019. Different response of surface temperature and air temperature to deforestation in climate models. Earth Syst. Dyn. 10, 473 - 484. https://doi.org/10.5194/esd-10-473-2019 + +Novick, K.A., Katul, G.G., 2020. The Duality of Reforestation Impacts on Surface and Air Temperature. J. Geophys. Res. Biogeosciences 125, 1 - 15. https://doi.org/10.1029/2019JG005543 + +c) what is the Sum? The sum of all components? Why is it 0 then? Shouldn't it be the difference between 1.97 and 0.16K? + +Response: Thank you for pointing this out. In the original manuscript, "Sum" means the simulated \(\delta \mathrm{Ta}^{\mathrm{bph}}\) , represented by the sum of \(\delta \mathrm{T}\mathrm{s}^{\mathrm{bph}}\) , \(\delta \mathrm{T}^{\mathrm{Ta}}\) and \(\delta \mathrm{T}^{\mathrm{H}}\) . The estimated value is close to but not exactly zero. Following your suggestion, we have replaced the bar "Sum" with the difference between \(\delta \mathrm{Ta}^{\mathrm{bph}}\) and \(\delta \mathrm{T}\mathrm{s}^{\mathrm{bph}}\) ("Diff"). + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Figure 3. ... (c) Bar plots of the mean air temperature sensitivity \((\delta T_{a}^{bph*})\) , land surface temperature sensitivity \((\delta T_{b}^{bph*})\) and their difference (Diff) contributed by variations in aerodynamic resistance \((\delta T^{ra})\) , and sensible heat \((\delta T^{H})\) ...
+ +1. 169 but the 1.97 is so much higher than the reported 0.53 reported above? + +Response: Thanks for your comment. The most likely reason for this difference is that the reported 0.53 K indicates the annual warming in high-latitude regions, and 1.97 K (1.63 K in the revised version) here indicates the winter warming in Europe. In addition, differences in the observation scales may contribute to the mismatches between RS-based and site-based results. + +1. 173 - I am confused. Fig. 3a shows that the air temperature of forests is the same as the surface temperature for forests. Why then is the impact of forestation higher for surface temp compared to air temp (as was shown before)? + +Response: Thanks for your comment. The main reason is that the temperature impact of forestation relies on both status in non- forest openland (before forestation) and forest (after forestation). Although the vertical variation in the forest temperature profile is less pronounced, we find significant temperature gradients between Ts and Ta in non- forest openlands. This gradient weakens the strong surface warming effect in Europe (Fig. 3a) or the strong summer cooling in North America and Australia (Fig. 3d and 3g). + +1. 179 - steeper in openlands? In the figs, it is steeper in forests I would say? Response: Thank you for the valuable comment. We have revised the word "steeper" to avoid ambiguity (Line 208): + +These factors collectively result in more significant temperature gradients in openlands, ... + +1. 216 - where do the - 0.03K come from? More specifically, why is this not the + +<--- Page Split ---> + +- 0.14K as reported in the first section of the results in 1. 88? Is that the global average now? How does it compare to global average change in T_s? This should be a more prominent result. + +Response: Thanks for your comment. According to the comment of reviewer #3, the biophysical and biochemical climate effect analyses of the potential tree restoration are removed. We have rewritten this section by comparing the concept of sensitivity (Line 245). This revision makes our results clearer that only local effects are evaluated and the non- local or global effects are not included. Similar to Windisch, et al., the current comparisons are based on the equivalent \(\mathrm{CO_2}\) uptake, rather than the temperature effect (K). The new results allow us to investigate the relative importance of the biophysical effect and reveal the overestimation of the biophysical climate effect using Ts (rather than the more relevant Ta) as the metric. + +## Comparison of biophysical with biochemical effects based on two temperature metrics + +Most assessments of the climate benefits related to forestation have concentrated on the carbon sequestration (i.e., biochemical effects) \(^{52,53}\) . Here, the biomass carbon stock sensitivity to tree cover is estimated via space- for- time analogy and converted to \(\mathrm{CO_2}\) absorption equivalents \((\delta \mathrm{CO}_{2}e^{\mathrm{bchem}})\) to represent the biochemical effect. We also convert the biophysical Ts and Ta sensitivities to the metric of equivalent \(\mathrm{CO_2}\) uptake \((\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) and \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) , Supplementary Fig. 11). These allow the comparison of the local biophysical and biochemical climate effects and evaluation of the relative importance of the former. + +The spatial map shows that \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) in tropical rainforests can exceed 600 t/ha, which is much greater than temperate and boreal forests (Fig. 4a). This suggests that restoring damaged forests in tropical regions has the most carbon benefit. Latitudinally, \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) at low- latitudes is higher than that at mid- or high- latitudes, with global mean of \(268.2 \pm 37.8\) t/ha (mean \(\pm\) uncertainty) (Fig. 4b). In terms of the biophysical effect, \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) (41.7 \(\pm\) 9.3 t/ha) provides a global average of \(15.7\%\) additional benefits to \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) (Fig. 4b). However, if the more relevant biophysical Ta effect is considered, the ratio of \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) (9.3 \(\pm\) 2.9 t/ha) to \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) is only \(3.5\%\) . + +We then focus on northern high- latitudes, where tree restoration shows a biophysical warming effect. The resultant negative \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) could offset \(9.5\%\) of the \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) annually (Fig. 4b). The high- latitude biophysical warming is more pronounced in the cold season and can reduce the biochemical climate effect by \(42.4\%\) in March (Fig. 4c). However, when \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) is used as the indicator, the offset of biophysical to biochemical effects is only \(3.3\%\) at the annual scale, with the maximum monthly value of \(10.6\%\) (February) (Fig. 4b and 4c). In mid- latitudes, the seasonal \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) can enhance \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) by up to \(33.7\%\) (northern hemisphere) and \(40.5\%\) (southern hemisphere) during summer. However, these seasonal ratios are only about \(10\%\) considering \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) (Fig. 4d and 4f). In low- latitudes, annual positive \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) is equivalent to \(25.5\%\) of \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) , while the ratio for \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) is + +<--- Page Split ---> + +only \(6.2\%\) , with insignificant seasonal variations (Fig. 4b and 4e). These results suggest that the relative importance of biophysical effects largely depends on the evaluated temperature metric, and the role of biophysical effects in the overall climate effect (usually measured by Ta) may not be as important as estimated in previous Ts- based studies22,23. + +![](images/Figure_unknown_7.jpg) + +
Figure 4. Comparison of the biophysical (bph) and biochemical (bchem) effects of potential tree cover gain. (a) Global pattern of the biochemical effect of potential tree cover gain ( \(\delta CO_2e^{bchem}\) ). (b) Global and latitudinal means of biochemical and biophysical effects of potential tree cover gain. The Ts-based and Ta-based biophysical effects are shown as the equivalent \(CO_2\) uptake ( \(\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) ). The error bars indicate the uncertainty of the mean. (c–f) Monthly ratios of Ta-based and Ts-based biophysical effects to equivalent biochemical effects across northern high-latitudes (>50°N), northern mid-latitudes (20°–50°N), tropics (20°S–20°N) and southern mid-latitudes (>20°S). The shaded area indicates the uncertainty of the ratios.
+ +## References: + +22. Windisch, M. G., Davin, E. L. & Seneviratne, S. I. Prioritizing forestation based on biogeochemical and local biogeophysical impacts. Nat. Clim. Chang. 11, 867–871 (2021). +23. Zhu, L. et al. Comparable biophysical and biogeochemical feedbacks on warming from tropical moist forest degradation. Nat. Geosci. 16, 244–249 (2023). +52. Walker, W. S. et al. The global potential for increased storage of carbon on land. Proc. Natl. Acad. Sci. U. S. A. 119, 1–12 (2022). +53. Lewis, S. L., Wheeler, C. E., Mitchard, E. T. A. & Koch, A. Restoring natural forests is the best way to remove atmospheric carbon. Nature 568, 25–28 (2019). + +1. 214 – this gap-filling has not yet been explained, where do the gaps come from? + +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the revision. + +<--- Page Split ---> + +1. 224 - unclear, "reverses to be negative"? + +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the revision. + +Fig 4. e) instead of the ratio, it would be more understandable if you put the actual biochemical temperature effect. I am also confused why the ratio is always in the same direction. Why would forestation in Russia have a negative biochemical temperature impact? + +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the revision. + +1. 245 - what about soil? + +reforestation could potentially decrease soil carbon stocks (see, e.g., https://doi.org/10.1046/j.1354- 1013.2002.00486. x) + +In general, it is crucial that studies do not neglect soil, they often store more carbon than the biomass. I know this is not the main point of the paper, but I find it worrying that our community is writing paper after paper talking about changes in biomass and soil carbon is not mentioned even once. Please add some sort of discussion somewhere regarding soil carbon. Since you use the method of Windisch2019, why not include their soil aspect as well? + +Response: Thanks for raising this important issue regarding soil carbon. We admit that soil carbon is a crucial part when evaluating the biochemical effect of land cover changes. We did not include soil carbon like Windisch et al., because their analysis of relative SOC variation is based on the type conversion from forest to non- forest type (e.g. conversion of forest to cropland decreases SOC by \(26.6\% \pm 28.7\%\) ) (Sanderman et al., 2017), rather than the fractional tree cover changes. Since satellite observations do not provide direct estimations of soil carbon, we cannot obtain the soil carbon sensitivity to tree cover using the "space- for- time" method. Moreover, a recent study suggests that under the global tree restoration scenario, biomass change, rather than soil carbon change, is the main contributor to carbon sequestration (Veldman et al., 2019), despite the large amount of carbon stored in global soil. + +## Reference: + +Sanderman, J., Hengl, T., Fiske, G.J., 2017. Soil carbon debt of 12,000 years of human land use. Proc. Natl. Acad. Sci. U. S. A. 114, 9575 - 9580. https://doi.org/10.1073/pnas.1706103114Veldman, J.W., Aleman, J.C., Alvarado, S.T., Anderson, T.M., Archibald, S., Bond, W.J., Boutton, T.W., Buchmann, N., Buisson, E., Canadell, J.G., Dechoum, M. de S., Diaz- Toribio, M.H., Durigan, G., Ewel, J.J., Fernandes, G.W., Fidelis, A., Fleischman, F., Good, S.P., Griffith, D.M., Hermann, J.- M., Hoffmann, W.A., Le Stradic, S., Lehmann, C.E.R., Mahy, G., Nerlekar, A.N., Nippert, J.B., Noss, R.F., Osborne, C.P., Overbeck, G.E., Parr, C.L., Pausas, J.G., Pennington, R.T., Perring, M.P., Putz, F.E., Ratnam, J., Sankaran, M., Schmidt, I.B., Schmitt, C.B., Silveira, F.A.O., Staver, A.C., Stevens, N., Still, C.J., Strömberg, C.A.E., Temperton, V.M., Varner, J.M., Zaloumis, N.P., 2019. Comment on "The global tree restoration potential." + +<--- Page Split ---> + +Following your suggestion, we have added descriptions about soil carbon in the method section (Line 542): + +Notably, \(\delta CO_{2}e^{bchem}\) provides a simple estimation of the ideal carbon stock in biomass under current climate and disturbance regimes for further comparison with the biophysical effect. The period for restored forests to reach such carbon potential, and the role of changing climate and soil carbon flux in this process are neglected. + +We also added discussions about the impact of tree restoration on soil carbon (Line 323): + +In addition, potential variations in soil carbon are ignored in the biochemical part. In contrast to increases in biomass, tree restoration could have positive and negative effects on soil carbon, depending on the climate background and the ecosystem type \(^{58 - 60}\) . At the global scale, forestation can increase soil organic carbon, but the value is highly uncertain \(^{61}\) . Neglecting the potential change in soil carbon may lead to a slight underestimation of the biochemical effect \(^{62}\) . The evaluated change in biomass should be the main contributor to carbon sequestration \(^{63}\) . + +## Reference: + +58. Deng, L., Zhu, G. yu, Tang, Z. sheng & Shangguan, Z. ping. Global patterns of the effects of land-use changes on soil carbon stocks. Glob. Ecol. Conserv. 5, 127 - 138 (2016). +59. Sanderman, J., Hengl, T. & Fiske, G. J. Soil carbon debt of 12,000 years of human land use. Proc. Natl. Acad. Sci. U. S. A. 114, 9575 - 9580 (2017). +60. Guo, L. B. & Gifford, R. M. Soil carbon stocks and land use change: A meta analysis. Glob. Chang. Biol. 8, 345 - 360 (2002). +61. Mo, L. et al. Integrated global assessment of the natural forest carbon potential. Nature 624, 92 - 101 (2023). +62. Li, Y. et al. Prioritizing Forestation in China Through Incorporating Biogeochemical and Local Biogeophysical Effects. Earth 's Futur. 12, 1 - 18 (2024). +63. Veldman, J. W. et al. Comment on "The global tree restoration potential". Science (80. ). 366, 1 - 5 (2019). + +1. 248 - the -0.11K are now for air temperature? + +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the updated content. + +1. 251 - what do you mean with override? I think you mean a different word here. "exceed", maybe? + +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the updated content. + +## Discussion + +1. 1, 281 - should prob cite Winckler2019 here because the non-local effects can + +<--- Page Split ---> + +be even larger than local effects + +Response: Thank you for your professional suggestion. We have added a sentence about the nonlocal effect and cited the reference (Line 309): + +The non- local effect of forestation can even exceed the local effects in model simulations15. + +## Reference: + +15. Winckler, J., Lejeune, Q., Reick, C. H. & Pongratz, J. Nonlocal Effects Dominate the Global Mean Surface Temperature Response to the Biogeophysical Effects of Deforestation. Geophys. Res. Lett. 46, 745-755 (2019). + +295 - good that you provide this explanation. + +Response: Thanks for the positive comment. + +1. 302 - but they are not that substantial anymore when considering T_a instead of T_s right? Generally, I find the wording a bit too positive. Your paper shows that the climate impact of tree planting is lower when considering the air temperature instead of the surface temperature. + +Response: Thank you for the valuable suggestion. We have updated our results of comparison between Ts-based and Ta-based biophysical effects (please refer to the response above). We discussed the overestimation of biophysical climate effects based on Ts (Line 299): + +Through the comparison of biophysical and biochemical effects, we find that using Ts as the indicator may overestimate the role of biophysical processes in the overall climate effect of forestation. The evaluation based on the more relevant Ta can present better policy guidance for prioritizing the location of forestation. + +We also discussed the application for different temperature metrics (Line 329): + +In the context of global climate change, Ts and Ta show comparable variation patterns and trend values37. However, when assessing the temperature effects of afforestation or deforestation, the Ts- based values can be about five times higher than the Ta- based values. This significant difference in magnitude highlights that attention should be given to the evaluated temperature metrics and the application scenarios when interpreting the biophysical effects of land cover changes. For instance, Ts (i.e. canopy temperature) could be the more appropriate metric when considering the effects of biophysical processes on ecosystem metabolism of photosynthesis, respiration, and transpiration38,64. Meanwhile, the more relevant Ta should be used in analyses related to regional climate adaptation of tree restoration. We highlight that this issue should be considered in future RS- based studies focusing on the thermal buffering effects of forests. + +## Reference: + +37. Wang, Y. R., Hessen, D. O., Samset, B. H. & Stordal, F. Evaluating global and regional land warming trends in the past decades with both MODIS and ERA5- Land land surface temperature data. Remote Sens. Environ. 280, 113181 (2022). +38. Mldrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station + +<--- Page Split ---> + +air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1- 15 (2011). + +64. Guo, Z. et al. Does plant ecosystem thermoregulation occur? An extratropical assessment at different spatial and temporal scales. New Phytol. (2022) doi:10.1111/nph.18632. + +The discussion is missing the important point that forestation and forestry in general have numerous aspects outside of climate change mitigation that should not be forgotten over their climate impact because this can lead to bad strategies. The Bastin paper that you also base your research on was in part wrongly interpreted by the media, public, and politicians. It was understood in a way that we can simply plant our way out of the crisis. I therefore find it very important to briefly address this. + +Some examples that come to mind, no need to add them all, but just to point you to some aspects: + +- in many places, forests are not the ecosystem that "should be there" (see important work by Bond: https://10.1016/j.tree.2019.08.003, https://10.1126/science.aad5132) +- forests offer many ecosystem services, not only climate change mitigation +- tree planting can have negative ecological and economical impacts (e.g., https://doi.org/10.1126/science.abd3064 and https://10.1126/science.abc9892) + +Response: Thanks for the professional and helpful comments. We have added discussions about the widespread impacts of forestation (Line 360): + +Moreover, tree restoration can have numerous ecological, hydrological and economic impacts besides the assessed temperature effects. Restoration in inappropriate geolocations (e.g. tropical savannas) can have counterproductive consequences such as ecosystem degradation, biodiversity loss and water availability reduction68- 72. These impacts should be also taken into account in the development of comprehensive forest- related strategies to avoid the misconception that "restoring trees is the panacea for the current crisis". + +## References: + +68. Bond, W. J., Stevens, N., Midgley, G. F. & Lehmann, C. E. R. The Trouble with Trees: Afforestation Plans for Africa. Trends Ecol. Evol. 34, 963-965 (2019). +69. Bond, W. J. Ancient grasslands at risk. Science (80-). 351, 120-122 (2016). +70. Gómez-González, S., Ochoa-Hueso, R. & Pausas, J. G. Afforestation falls short as a biodiversity strategy. Science (80-). 368, 1439-1439 (2020). +71. Parr, C. L., te Beest, M. & Stevens, N. Conflation of reforestation with restoration is widespread. Science (80-). 383, 698-701 (2024). +72. Selva, N., Chylarecki, P., Jonsson, B.-G. & Ibisch, P. L. Misguided forest action in EU Biodiversity Strategy. Science (80-). 368, 1438-1439 (2020). + +<--- Page Split ---> + +The types of trees matter a lot, how is that accounted for? For instance, in temperate forests, if you reforest with broad- leafs, this will be much different then reforesting with needleleafs, especially regarding surface roughness in winter. How is that accounted for? + +Response: Thanks for this professional comment. Since the temperature sensitivity is estimated by the local regression between tree cover and temperature observations, our results reflect the potential consequence of tree restoration with the native tree species. We have added descriptions in the revised manuscript (Line 435): + +Notably, all the sensitivity results should be interpreted as the temperature consequences of restoration with native forest type, as the gridded tree cover data of existing species are used as inputs to the spatial regression model. + +1. 321 - soil is \(250\mathrm{m}\) how was this aggregated to the \(1\mathrm{km}^2\) + +Response: Thanks for the comment. This paragraph, describing how to estimate tree cover potential (ATC) using soil and climate data, is removed, since the tree cover potential related contents are no longer presented in the revised manuscript according to the comment of reviewer #3. + +1. 326 - Fig S8 - why is there only one such figure as there are two TC_2020 datasets? Also, which of the two is shown? + +Response: Thanks for raising this concern. In the original manuscript, we use tree cover data of 2020 to calculate tree restoration potential (ATC) under the current stage. According to the comment of reviewer #3, the analysis based on ATC is removed, and only tree cover data of 2010 are used for estimating the sensitivities (Supplementary Fig. 12). + +![](images/Figure_unknown_8.jpg) + +
Fig. S12. Global maps of fractional tree cover from (a) GLOBMap and (b) Global
+ +<--- Page Split ---> + +1. 339 - mention that screen height is \(1.25\mathrm{m}\) to \(2\mathrm{m}\) above ground, I had to look this up. + +Response: Thank you for the helpful suggestion. We have declared the physical meaning of assessed Ta here (Line 397): + +The other temperature metric used for assessment is Ta, the air temperature at \(2\mathrm{m}\) above the interface layer between the land components and the atmosphere. Specifically, for forested areas, the reference plane is the canopy, whereas for openlands, the reference plane is approximately the ground. + +1. 342 - can you provide a figure of the modeled vs observed Ta - a Response: Thanks for the suggestion. We have added the comparison between the satellite monthly mean Ta and FLUXNET monthly mean Ta measurements (Line 406): + +Satellite monthly mean Ta and FLUXNET monthly mean Ta show good agreement. Validation results for forest and non- forest sites show comparable accuracy (Supplementary Fig. 13). + +![](images/Figure_unknown_9.jpg) + +
Fig. S13. Validation of satellite monthly mean air temperature (Ta) of 2010. (a) Scatter plot between satellite monthly Ta and FLUXNET monthly \(T_{\mathrm{a}}\) measurements in forest sites. (b) Similar to (a), but for non-forest sites. Abbreviation: RMSE, root mean squared error.
+ +1. 345 - mean = average of min and max? this seems quite odd to me. Especially with strong differences in daylength vs nightlength this does not seem like a valid way to get the mean temperature. + +Response: Thanks for your comment. We compared the FLUXNET observations of (a) the mean of maximum and minimum Ta and (b) the daily mean Ta (Fig. R1). The comparison is performed at the monthly scale. The results show good overall agreement in either forest or non- forest sites (RMSE \(< 0.4\mathrm{K}\) ). In addition, for both cold months (with longer night length) and hot months (with longer day length), the scatter plots are also close to the 1:1 line, suggesting the method is robust to different day/night length conditions. + +<--- Page Split ---> +![](images/Figure_unknown_10.jpg) + +
Fig. R1. Comparison between max and min air temperature (Ta) and daily mean Ta using FLUXNET observations for (a) forest sites and (b) non-forest sites at the monthly scale.
+ +1. 353 - is it really moving window? Or is the globe just gridded into \(0.25^{\circ}\) pixels? If it is moving window, what is the step size? + +Response: Thanks for pointing this out. The regression is conducted for each \(0.25^{\circ}\) grid. We have removed the sentence about the moving window to avoid ambiguity. + +1. 355 what is the impact? how many pixels are excluded? If it's a lot then this has an important impact on the importance of the results. + +Response: Thank you for raising this concern. First, we set the threshold of tree cover \(>10\%\) for selecting the effective pixel for regression. This is because the temperature variations in low tree cover pixels may be induced by the rest non- forest land cover components. Using these pixels for regression may reduce the reliability of estimated temperature sensitivity. Second, for the pixels with tree cover \(>10\%\) , we exclude part of them with water cover \(>1\%\) and elevation difference \(>100 \mathrm{~m}\) . Here, we show the ratio of the excluded forest pixel number (due to water cover or elevation difference) to the total forest pixel number within each \(0.25^{\circ}\) grid (Fig. R2). Results show that the excluded pixel numbers are small across the globe ( \(< 5\%\) for most grids). Thus, the screening process may have limited impacts on our sensitivity results. + +![](images/Figure_unknown_11.jpg) + +
Fig. R2. Fraction of excluded pixels due to water cover or elevation differences, defined as the number of abandoned forest pixels (tree cover \(>10\%\) ) divided by the number of all forest pixels within each \(0.25^{\circ}\) grid.
+ +<--- Page Split ---> + +1. 357 I think there is an "and" missing + +Response: Thanks for your careful reading. We have added the word "and" (Line 420): + +The water coverage and elevation data are from Joint Research Center Global Surface Water Mapping Layers v1.4, and GMTED2010 datasets, respectively. + +1. 361: for each 0.25 pixel, right? + +Response: Thanks for pointing this out. We added the clarification about the scale (Line 424). + +After the screening process, \(\delta T s^{b p h}\) and \(\delta T a^{b p h}\) can be estimated using a linear regression model between tree cover and corresponding temperature values for each \(0.25^{\circ}\) grid: + +Formulas 1+2: Why not just write the formula of the linear model instead of the solution of the regression? + +Response: Thanks for the helpful suggestion. We have revised the formulas for clarity (Line 425): + +\[\begin{array}{c}{{T s=\delta T s^{b p h}\times T C_{2010}+b_{s}}}\\ {{{}}}\\ {{T a=\delta T a^{b p h}\times T C_{2010}+b_{a}}}\end{array} \quad (1)\] + +where, \(b_{s}\) and \(b_{a}\) are the regression intercepts. + +Formulas 1+2: provide a plot for a pixel in the supplements, to understand the relationship + +Response: Thank you for the valuable comment. We have added the schematic figure as you suggested (Supplementary Fig. 1). + +<--- Page Split ---> +![](images/Figure_unknown_12.jpg) + +
Fig. S1. Schematic representation of the methodology for estimating land surface temperature (Ts) or air temperature (Ta) sensitivity to tree cover change ( \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) ). (a–f) The example grid (59.75°–60°N, 63.5°–63.75°E) with positive \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) in January 2010. (a) True color image of the 0.25° grid. (b) GLOBMAP 2010 tree cover map. (c) Mean Ts of January 2010. (d) Mean \(T_{a}\) of January 2010. (e) Linear regression for estimating positive \(\delta T_{s}^{bph}\) of the grid. (f) Linear regression for estimating positive \(\delta T_{a}^{bph}\) of the grid. (g–l) Similar to (a–f), but for the other example grid (44.75°–45°N, 38°–38.25°E) with negative sensitives in July 2010.
+ +1. 364 – what robustness? you mean that the formula is solvable, i.e., the matrix is invertible? + +Response: Thanks for the comment. The small sample sizes may result in: (a) models that are sensitive to noise of the input data, and (b) estimated parameters that are unstable or have large uncertainties. We have revised the description for clarity (Line 427): + +To ensure the reliability of the results, .... + +1. 383 – "of" missing + +Response: Thanks for the careful reading. We have added the missing "of" (Line 450): + +The RS- based local temperature sensitivity can be validated through the differences of measurements between spatially adjacent paired forest and non- forest sites. + +<--- Page Split ---> + +1. 390 – BEST is at 1 degree resolution. So it’s not only land cover type impact but also elevation impact. How is that accounted for? + +Response: Thanks for the constructive comment. We have made the additional elevation correction for the gridded temperature using (a) the difference between grid mean and corresponding site elevations, and (b) the lapse rate of the grid. The lapse rate is estimated by the local regression between the gridded temperatures and elevations within \(5 \times 5\) window. Due to modifications made to the methodology, all the related results are also updated, and the systematic biases in site results are eliminated. We also revised descriptions for the elevation correction (Line 458): + +Here, we first make corrections to the gridded temperatures using the lapse rates to compensate for the elevation difference between the site and the corresponding grid. The lapse rate for the target grid is estimated by the regression slope of the gridded temperatures and elevations within the \(5 \times 5\) window. Then, by deducting the corrected gridded temperature data, the in- situ measurements can effectively represent the relative temperature effects attributable to different land cover types. + +1. 446 – why to 2m above the canopy? Isn’t the goal to estimate 2m above ground? A figure would generally be good to visualize the difference in the temperatures... Response: Thanks for the comment. The target variable is the 2 m air temperature above the land surface. We have added a schematic figure about the temperature metrics (Supplementary Fig. 2). Please refer to the above responses for the definition and the importance of the evaluated temperature. + +![](images/Figure_4.jpg) + +
Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).
+ +1. 471 – I am unsure how Fig S6 relates to that. Instead, can you provide a figure comparing the non-gap-filled and the gap-filled maps? + +<--- Page Split ---> + +Response: Thanks for the comment. According to the comment of reviewer #3, the analyses based on gap- filled sensitivity and the related figures are removed. + +1. 474 - why is this aggregation needed? + +Response: Thanks for the comment. This sub- section about sensitivity gap- filling is removed. + +1. 480 - how did you account for spatial auto- correlation? Training and testing data need to be independent, see https://www.nature.com/articles/s41467-022-29838-9 + +Response: Thanks for the comment. This sub- section about sensitivity gap- filling is removed. + +1. 504 - this is missing soil carbon + +Response: Thanks for raising this important issue. We have clarified in the methodology that soil carbon is ignored and discussed the possible consequences in the discussion section. Please refer to the response above for the modifications. + +### Code Availability + +Why is the code available only on request? This should be made public, we need to make results reproducible. + +Response: Thanks for raising this important issue. We have provided a Zenodo link to download the code (Line 561): + +## Code availability + +The Python codes used to generate all the results are available at https://zenodo.org/uploads/14215398 + +Reviewer #2 (Remarks on code availability): + +The code is hard to review. There are no comments or explanations. + +Response: Thanks for the careful reading. We have added a description file and comments to the code. + +What I found strange was, that the code to reproduce Figure 1 only reads in images that contain the temperature- forestcover relation and plots them. But there is no code that created these images. I assume these were generated in GEE, but this code should also be made available. + +Response: Thanks for the comment. We have uploaded the code file for the sensitivity estimation. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +This paper combines satellite data, and data from meteorological station and flux tower networks, to explore the extent to which reforestation confers a local air cooling benefit across the globe We have long known that reforestation leads to local surface cooling, at least in the tropic and temperate zones. So this adaptive benefit of reforestation is not exactly "overlooked" as the title of the paper suggests. However, because air temperature can not be directly measured from space, studies on the topic have tended to focus on patterns in surface temperature only, despite the fact that air temperature is arguably the more relevant target for adaptation. The authors acknowledge that some work has already attempted to address this knowledge gap, but I think that what the authors present in this paper is still a novel contribution. The show that forests likely lead to local air cooling, but the magnitude of the temperature change is less than the change in surface temperature. This is consistent with the other work done on the topic, including the nice study by Mildrexler et al. 2011 (which the authors don't cite but probably should, https://doi.org/10.1029/2010JG001486). + +I did, however, have some significant comments and concerns about the framing and the methods. + +Response: We appreciate the positive comments by the reviewer. We have carefully considered the critical comments, please see our detailed point- by- point responses below. In particular, we have updated the results and clarified the new contribution of this paper. Accordingly, we have revised the title to "Observed different impacts of potential tree restoration on local surface and air temperature". We also cited the reference as you suggested (Line 66): + +Despite the strong correlation between Ts and Ta, the Ts effect of forest change may significantly differ from the Ta effect38. + +38. Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1-15 (2011). + +[1] First, and perhaps most importantly, the air (or surface cooling) benefits of reforestation should not be referred to as "climate mitigation." Climate mitigation refers to efforts to reduce emissions and increase sinks for greenhouse gases. The direct modification of local temperature by forest restoration does neither of these. It can slow the pace of climate change in certain places by increasing sensible and latent heat fluxes. However, these mechanisms may simply represent the redistribution of energy within the climate system, and have the potential to enhance the pace of warming elsewhere. For example, energy used to evaporate water in a forested landscape is re- released when that water vapor condenses downwind. Likewise, greater sensible heat flux may increase lower temperatures near the surface but increase temperatures higher in the boundary layer. Thus, the direct local cooling benefits of reforestation + +<--- Page Split ---> + +should be described as "adaptation," not "mitigation," and discussion of the benefits should acknowledge the possibility for warming elsewhere. + +Response: Thanks for this critical comment. We have checked through our manuscript and replaced "mitigation" with "adaption" when discussing the local biophysical effect on climate. We also highlighted that our results should be related to adaption rather than mitigation in the discussion section (Line 355): + +From the perspective of the whole climate system, the non- radiative effects represent the redistribution of energy within the climate system and may lead to warming in downwind regions or the higher boundary layer67. Thus, our results concerning the biophysical effects should be treated as the reference for local climate adaptation rather than global climate mitigation. + +67. Barnes, M. L. et al. A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States. Earth's Futur. 12, (2024). + +[2] For this reason, it is also inappropriate to directly compare the change in LOCAL surface or air temperature associated with reforestation to the GLOBAL change in air temperature driven by the capacity of forests to enhance the global land carbon sink (specifically, the delta_TC metric which the authors present in Figure 4). They are not the same thing. Moreover, because the methods the authors used to calculate delta_TC do not appear to have been published elsewhere and are not clearly validated, I suggest the authors remove this part of the analysis from the manuscript. + +Response: Thanks for this critical comment. As you suggested, we have removed the analyses based on \(\Delta\) TC. We have rewritten this section by comparing the concept of sensitivity (Line 245). The revision makes our results clearer that only local effects are evaluated and the non- local or global effects are not included. Similar to the previous study (Windisch et al., 2021), the current comparisons are based on the equivalent \(\mathrm{CO_2}\) uptake, rather than the temperature effect (K). The new results allow us to investigate the relative importance of the biophysical effect and reveal the overestimation of the biophysical climate effect using Ts (rather than the more relevant Ta) as the metric. + +## References: + +Windisch, M. G., Davin, E. L. & Seneviratne, S. I. Prioritizing forestation based on biogeochemical and local biogeophysical impacts. Nat. Clim. Chang. 11, 867 - 871 (2021). + +## Comparison of biophysical with biochemical effects based on two temperature metrics + +Most assessments of the climate benefits related to forestation have concentrated on the carbon sequestration (i.e., biochemical effects) \(^{52,53}\) . Here, the biomass carbon stock sensitivity to tree cover is estimated via space- for- time analogy and converted to \(\mathrm{CO_2}\) absorption equivalents ( \(\delta \mathrm{CO_2e^{bchem}}\) ) to represent the biochemical effect. We also convert the biophysical Ts and Ta sensitivities to the metric of equivalent \(\mathrm{CO_2}\) uptake ( \(\delta \mathrm{CO_2e^{bph,Ts}}\) and \(\delta \mathrm{CO_2e^{bph,Ta}}\) , Supplementary Fig. 11). These allow the + +<--- Page Split ---> + +comparison of the local biophysical and biochemical climate effects and evaluation of the relative importance of the former. + +The spatial map shows that \(\delta C O_{2}e^{b c h e m}\) in tropical rainforests can exceed 600 t/ha, which is much greater than temperate and boreal forests (Fig. 4a). This suggests that restoring damaged forests in tropical regions has the most carbon benefit. Latitudinally, \(\delta C O_{2}e^{b c h e m}\) at low- latitudes is higher than that at mid- or high- latitudes, with global mean of \(268.2 \pm 37.8\) t/ha (mean \(\pm\) uncertainty) (Fig. 4b). In terms of the biophysical effect, \(\delta C O_{2}e^{b p h,T s}\) (41.7 \(\pm\) 9.3 t/ha) provides a global average of \(15.7\%\) additional benefits to \(\delta C O_{2}e^{b c h e m}\) (Fig. 4b). However, if the more relevant biophysical Ta effect is considered, the ratio of \(\delta C O_{2}e^{b p h,T a}\) (9.3 \(\pm\) 2.9 t/ha) to \(\delta C O_{2}e^{b c h e m}\) is only \(3.5\%\) . + +We then focus on northern high- latitudes, where tree restoration shows a biophysical warming effect. The resultant negative \(\delta C O_{2}e^{b p h,T s}\) could offset \(9.5\%\) of the \(\delta C O_{2}e^{b c h e m}\) annually (Fig. 4b). The high- latitude biophysical warming is more pronounced in the cold season and can reduce the biochemical climate effect by \(42.4\%\) in March (Fig. 4c). However, when \(\delta C O_{2}e^{b p h,T a}\) is used as the indicator, the offset of biophysical to biochemical effects is only \(3.3\%\) at the annual scale, with the maximum monthly value of \(10.6\%\) (February) (Fig. 4b and 4c). In mid- latitudes, the seasonal \(\delta C O_{2}e^{b p h,T s}\) can enhance \(\delta C O_{2}e^{b c h e m}\) by up to \(33.7\%\) (northern hemisphere) and \(40.5\%\) (southern hemisphere) during summer. However, these seasonal ratios are only about \(10\%\) considering \(\delta C O_{2}e^{b p h,T a}\) (Fig. 4d and 4f). In low- latitudes, annual positive \(\delta C O_{2}e^{b p h,T s}\) is equivalent to \(25.5\%\) of \(\delta C O_{2}e^{b c h e m}\) , while the ratio for \(\delta C O_{2}e^{b p h,T a}\) is only \(6.2\%\) , with insignificant seasonal variations (Fig. 4b and 4e). These results suggest that the relative importance of biophysical effects largely depends on the evaluated temperature metric, and the role of biophysical effects in the overall climate effect (usually measured by Ta) may not be as important as estimated in previous Ts- based studies22,23. + +![](images/Supplementary_Figure_8.jpg) + +
Figure 4. Comparison of the biophysical (bph) and biochemical (bchem) effects of potential tree cover gain. (a) Global pattern of the biochemical effect of potential tree cover gain ( \(\delta C O_{2}e^{b c h e m}\) ). (b) Global and latitudinal means of biochemical and biophysical effects of potential tree cover gain. The Ts-based and Ta-based biophysical effects are
+ +<--- Page Split ---> + +shown as the equivalent \(CO_2\) uptake \((\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) ). The error bars indicate the uncertainty of the mean. (c- f) Monthly ratios of Ta- based and Ts- based biophysical effects to equivalent biochemical effects across northern high- latitudes \((>50^{\circ}N)\) , northern mid- latitudes \((20^{\circ} - 50^{\circ}N)\) , tropics \((20^{\circ}S - 20^{\circ}N)\) and southern mid- latitudes \((>20^{\circ}S)\) . The shaded area indicates the uncertainty of the ratios. + +We also rewrite the corresponding method section (Line 535): + +## Comparison of biophysical and biochemical effects + +In addition to regulating the energy balance process, forestation can enhance the land carbon sink through vegetation photosynthesis, thereby generating negative biochemical feedback on the climate system \(^{92,93}\) . To quantify this biochemical impact, we first estimate the biomass carbon density sensitivity to ideal restoration, using Global Aboveground and Belowground Biomass Carbon Density Maps of 2010 (in t/ha) \(^{93}\) , along with \(TC_{2010}\) and the "space- for- time" strategy. We convert the biomass carbon stock sensitivity to \(CO_2\) absorption equivalents (i.e. \(\delta CO_2e^{bchem}\) ) based on the molar mass ratio. Notably, \(\delta CO_2e^{bchem}\) provides a simple estimation of the ideal carbon stock in biomass under current climate and disturbance regimes for further comparison with the biophysical effect. The period for restored forests to reach such carbon potential, and the role of changing climate and soil carbon flux in this process are neglected. + +The biophysical Ts and Ta sensitivities are also unified to the metric of \(CO_2\) equivalents \((\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) ) based on the transient climate response to cumulative emissions for both Ts ( \(TCRE^{Ts}\) ) and Ta ( \(TCRE^{TA}\) ) derived from Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations (Supplementary Fig. 11): + +\[\delta CO_2e^{bph,TS} = \frac{\delta TS^{bph}}{TCRE^{TS}}\times \frac{1}{A_E} \quad (11)\] + +\[\delta CO_2e^{bph,TA} = \frac{\delta TS^{bph}}{TCRE^{TA}}\times \frac{1}{A_E} \quad (12)\] + +where, \(A_E\) indicates the earth surface area (5.1x10 \(^8\) km \(^2\) ). The gridded \(TCRE^{TS}\) and \(TCRE^{TA}\) are estimated following the previous study \(^{22}\) , using 12 model simulations (ACCESS_ESM1- 5, CanESM5- 1, CMCC- ESM2, CNRM- ESM2- 1, FIO- ESM- 2- 0, GISS- E2- 1- H, INM- CM5- 0, IPSL- CM6A- LR, MIROC6, MPI- ESM1- 2- LR, MRI- ESM2- 0 and NESM3) of the "1 percent per year increase in carbon dioxide" experiment (1pctCO2). Notably, \(\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) calculated by equation (11) and (12) represent the \(CO_2\) emission equivalents. We further covert their signs to align with the \(\delta CO_2e^{bchem}\) , which represent the \(CO_2\) absorption equivalents. We compare the biophysical and biochemical effects based on the above metrics at both annual and monthly scales. + +## References: + +22. Windisch, M. G., Davin, E. L. & Seneviratne, S. I. Prioritizing forestation based + +<--- Page Split ---> + +on biogeochemical and local biogeophysical impacts. Nat. Clim. Chang. 11, 867- 871 (2021). + +23. Zhu, L. et al. Comparable biophysical and biogeochemical feedbacks on warming from tropical moist forest degradation. Nat. Geosci. 16, 244-249 (2023). + +52. Walker, W. S. et al. The global potential for increased storage of carbon on land. Proc. Natl. Acad. Sci. U. S. A. 119, 1-12 (2022). + +53. Lewis, S. L., Wheeler, C. E., Mitchard, E. T. A. & Koch, A. Restoring natural forests is the best way to remove atmospheric carbon. Nature 568, 25-28 (2019). + +92. Xu, H., Yue, C., Zhang, Y., Liu, D. & Piao, S. Forestation at the right time with the right species can generate persistent carbon benefits in China. Proc. Natl. Acad. Sci. 120, 2017 (2023). + +93. Spawn, S. A., Sullivan, C. C., Lark, T. J. & Gibbs, H. K. Harmonized global maps of above and belowground biomass carbon density in the year 2010. Sci. Data 7, 1-22 (2020). + +[3] Relatedly, the darkening of the land surface associated with the tendency for forests to lower albedo is a process that actually contributes to additional warming at regional and global scales, even if modifications to latent and sensible heat exchange tend to suppress temperature locally. This point, which is discussed in Barnes et al. (2024, https://doi.org/10.1029/2023EF003663) is important to make, because otherwise it is very hard to reconcile results from this paper with those that demonstrate that the climate mitigation potential of reforestation is reduced by the albedo impacts (including the paper by Hasler et al. published this year in Nature Communications, https://doi.org/10.1038/s41467-024-46577-1). + +Response: Thanks for the constructive comment. We have added discussions about the albedo effect of forestation to reconcile with previous studies (Line 350): + +The biophysical warming effects of boreal forests should be given specific attention in related mitigation policies, although our results of negative biophysical climate effects at high- latitudes may not be as strong as previous findings65,66. This is because those studies focus on the additional radiative forcing induced by the darker forest canopy but ignore the impact of turbulent fluxes. The overlooked non- radiative effects could partially offset the albedo effects, leading to the observed net warming in our results. From the perspective of the whole climate system, the non- radiative effects represent the redistribution of energy within the climate system and may lead to warming in downwind regions or the higher boundary layer67. Thus, our results concerning the biophysical effects should be treated as the reference for local climate adaptation rather than global climate mitigation. The fact that the mitigation potential of high- latitudes forestation could be reduced or even offset by the albedo impacts should be considered by forest- related global mitigation policies. + +# References: + +<--- Page Split ---> + +65. Hasler, N. et al. Accounting for albedo change to identify climate-positive tree cover restoration. Nat. Commun. 15, 2275 (2024). +66. Weber, J. et al. Chemistry-albedo feedbacks offset up to a third of forestation's CO 2 removal benefits. Science (80-). 383, 860-864 (2024). +67. Barnes, M. L. et al. A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States. Earth's Futur. 12, (2024). + +A few other comments: + +[4] The authors focus very strongly on the impacts of reforestation on roughness and sensible heat flux, but seem to ignore the impacts on latent heat flux (e.g. evapotranspiration). Other work on the topic (including papers cited by the authors already) make it clear that both processes are important for governing the local temperature impacts of reforestation. + +Response: Thanks for the professional comment. The enhancement in latent heat flux can strongly affect the local Ts effect of reforestation at low- latitudes. We have added related discussions in the revised manuscript (Line 287): + +Previous studies have demonstrated that in boreal regions, forests can warm local Ts because the tree canopy is darker than the snow background and absorbs more solar radiation; in tropical regions, forests show strong local Ts cooling, mainly due to the higher evapotranspiration rates than other vegetation or bare land; in temperate regions, the net Ts effect depends on the relative magnitude of these two processes \(^{10,12,29,31}\) . + +## References: + +10. Lawrence, D., Coe, M., Walker, W., Verchot, L. & Vandecar, K. The Unseen Effects of Deforestation: Biophysical Effects on Climate. Front. For. Glob. Chang. 5, 1-13 (2022). + +12. Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1-10 (2015). + +29. Duveiller, G. et al. Biophysics and vegetation cover change: A process-based evaluation framework for confronting land surface models with satellite observations. Earth Syst. Sci. Data 10, 1265-1279 (2018). + +31. Bright, R. M. et al. Local temperature response to land cover and management change driven by non-radiative processes. Nat. Clim. Chang. 7, 296-302 (2017). + +[5] I appreciate that the authors engaged in a robust effort to use data from eddy covariance flux towers to validate their approach of comparing land surface temperature measurements from satellites with gridded information on air temperature from meteorological station networks. However, this effort seems to compare the flux tower- derived information to a gridded air temperature product derived from CRU and BEST data. Why didn't the authors compare flux tower data to the air temperature product they actually use for the global mapping in the study (e.g. the dataset produced by Zhang et al 2022? + +Response: Thanks for the professional comment. The CRU or BEST data used here are interpolated + +<--- Page Split ---> + +temperature data, which represent the influence of the macroclimate. Therefore, their differences with site measurements reflect the relative influence of land cover on local temperature. Zhang et al's Ta data, on the other hand, are produced by a statistical method using satellite land surface temperature and thus contain both signals from macroclimate and land cover. The difference between Zhang et al. Ta data and site measurements may reflect systematic or random errors of the product rather than the information we are interested in. + +[6] The presentation of equations [1] and [2] is confusing. Not all of the terms in these equations are defined, and the math seems to simply considerably from what is shown (for example, as written, it seems the TC_2010\~T terms simply cancel out of the equations? + +Response: Thanks for raising this concern. The equations in the original manuscript are the solution of the linear model represented by the matrix operation form. The superscript "T" denotes the matrix transpose. We have revised the formulas for clarity (Line 425): + +\[\begin{array}{c}{{T s=\delta T s^{b p h}\times T C_{2010}+b_{s}}}\\ {{}}\\ {{T s=\delta T a^{b p h}\times T C_{2010}+b_{a}}}\end{array} \quad (1)\] + +where, \(b_{s}\) and \(b_{a}\) are the regression intercepts. + +[7] The relationship between surface temperature and outgoing long- wave radiation (equation 3) includes a correction for incident long- wave radiation. This is unusual...can the authors provide a reference or further justification for the approach? + +Response: Thanks for the comment. Equation 3 (Ts = [LW - (1- e)LW] has been widely used for land surface temperature retrieval from site longwave radiation measurements (Duan et al., 2019; Ma et al., 2021; Schultz et al., 2017). Here, the correction is made to exclude the reflected longwave radiation from the measured outgoing longwave radiation, and thereby obtain the actual value of emitted radiation. + +## References: + +Duan, S.B., Li, Z.L., Li, H., Gottsche, F.M., Wu, H., Zhao, W., Leng, P., Zhang, X., Coll, C., 2019. Validation of Collection 6 MODIS land surface temperature product using in situ measurements. Remote Sens. Environ. 225, 16 - 29. https://doi.org/10.1016/j.rse.2019.02.020Ma, J., Zhou, J., Liu, S., Gottsche, F.M., Zhang, X., Wang, S., Li, M., 2021. Continuous evaluation of the spatial representativeness of land surface temperature validation sites. Remote Sens. Environ. 265. https://doi.org/10.1016/j.rse.2021.112669Schultz, N.M., Lawrence, P.J., Lee, X., 2017. Global satellite data highlights the diurnal asymmetry of the surface temperature response to deforestation. J. Geophys. Res. Biogeosciences 122, 903 - 917. https://doi.org/10.1002/2016JG003653 + +We have added a reference for equation 3 (Line 781): + +<--- Page Split ---> + +87. Duan, S. B. et al. Validation of Collection 6 MODIS land surface temperature product using in situ measurements. Remote Sens. Environ. 225, 16 - 29 (2019). + +<--- Page Split ---> + +## Response to Reviewers' Comments + +We greatly appreciate the opportunity to revise our manuscript and thank all anonymous reviewers for their constructive comments. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in Italics and Arial) and the location of the revision. The line numbers referred to are for the clean version of the revised manuscript. + +## Reviewer #1 (Remarks to the Author): + +I thank the authors for the elaborate answers and thoughtful updates to the manuscript. I have no further comments. + +Response: We appreciate the constructive and valuable comments by the reviewer during the review process. + +## Reviewer #1 (Remarks on code availability): + +I could not access the code: "You do not have sufficient permissions to view this page." Response: We apologize for the data accessibility issue. We have confirmed that the Zenodo project is publicly accessible (https://zenodo.org/records/14633331). + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +The manuscript is now in much better shape, and I think it is a very interesting one and shows nice and relevant results. I especially like that the authors analyze the hypotheses both with remote sensing but also site information with FLUXNET data (they did so in the previous version already, but I still want to highlight this). + +My concerns from the first round were thoroughly addressed, but a few issues remain that I believe require minor revisions from the authors. + +Response: We thank the reviewer for the positive feedback. Based on the second- round comments, we mainly revised the methods section to make the manuscript clearer. Please see the point- by- point responses below. + +## ### Results + +- I now fully understand what you mean by "100% tree cover gain" and Fig S1 makes it very clear, thank you. But I think the term is misleading/confusing. It should be something like "full tree cover" or "full restoration" or something like that. Because a 100% gain would mean, if I have 5 hectares of forest in some area, and then you plant 5ha more, that is a 100% gain in tree cover. But that does not mean that the area is fully restored aka has 100% tree cover. I think this needs to be termed differently. + +Response: Thanks for pointing this out. We have revised "100% tree cover gain" to "the full tree cover restoration" to avoid ambiguity (Line 76). + +We first estimated the local biophysical Ts and Ta sensitivity to the full tree cover restoration (denoted as \(\delta T s^{bp}\) and \(\delta T a^{bp h}\) ) at the \(0.25^{\circ}\) scale, based on the space- for- time analogy. + +We have also revised the figure caption (Line 124). + +Figure 1. Annual mean temperature sensitivity to the full tree cover restoration. + +## ### Methods + +The procedure for the FLUXNET sites is now better explained, but still unclear. + +Response: Thanks for raising this concern. We rearranged the method section and hope the revision can make the procedure clearer (Line 464): + +The specific process of validation is as follows (Supplementary Fig. 8). In- situ data for Ta are measured above the vegetation canopy, whereas Ts is estimated using the longwave radiation measurements: + +\[T s = \left[\frac{L W_{u} - (1 - \epsilon)L W_{d}}{\epsilon \sigma}\right]^{\frac{1}{4}} \quad (3)\] + +where, \(L W_{u}\) and \(L W_{d}\) represent upward and downward longwave radiation from the FLUXNET2015 dataset, respectively; \(\sigma\) denotes the Stephan- Boltzmann constant \((5.67 \times 10^{- 8} W m^{- 2} K^{- 4})\) , and \(\epsilon\) is emissivity, estimated based on an empirical relationship with albedo88. For the gridded data, we first make corrections using the + +<--- Page Split ---> + +lapse rates to compensate for the elevation difference between the site and the corresponding grid. The lapse rate for the target grid is estimated by the regression slope of the gridded temperatures and elevations within the \(5 \times 5\) window. + +By deducting the corrected gridded temperature data, the in- situ measurements can effectively represent the land cover impacts on local Ts and Ta, assuming that macroclimate affects both temperature metrics similarly. Since the forest data cannot be directly matched with the openland data, we bin both forest and openland data points using the \(SW_d\) interval of \(10 \mathrm{~w} / \mathrm{m}^2\) . For each \(SW_d\) bin, we calculate the difference between mean values of forest and openland data points to represent the temperature effect of forestation (i.e. \(\delta T_s^{bph*}\) or \(\delta T_a^{bph*}\) ) under the specific radiation background: + +\[\delta T_s^{b p}~^{*} = \left(T_s^{s i t e} - T_f^{g r i d}\right) - \left(T_s^{s i t e} - T_o^{g r i d}\right) \qquad if S W_d\in (10k,10k + 10) \quad (4)\] + +\[\delta T_a^{b p h^{*}} = \left(T_a^{s i t e} - T_f^{g r i d}\right) - \left(T_a^{s i t e} - T_o^{g r i d}\right) \qquad if S W_d\in (10k,10k + 10) \quad (5)\] + +Here, \(T_s^{s i t e}\) and \(T_a^{s i t e}\) refer to Ts and Ta measured at forest sites, respectively; \(T_s^{s i t e}\) and \(T_a^{s i t e}\) refers to Ts and Ta measured at openland sites; \(T_f^{g r i d}\) and \(T_o^{g r i d}\) refer to the corresponding gridded temperatures after the elevation correction; \(k\) indicates counting of the \(SW_d\) bin. According to the metadata of the FLUXNET2015 dataset, forest sites include the following four IGBP landcover types: evergreen needleleaf forests, evergreen broadleaf forests, deciduous broadleaf forests, and mixed forests; openland sites are categorized as other non- forest vegetation types. + +Then, the relationships between two temperature sensitivities and \(SW_d\) are explored using the weighted least squares (WLS) regression model, in which the samples are \(\delta T_s^{b p h*}\) or \(\delta T_a^{b p h*}\) of all \(SW_d\) bins and the sample weights are defined as the inverse of the standard error of \(\delta T_s^{b p h*}\) or \(\delta T_a^{b p h*}\) . The derived relationships are then compared with those from RS- based results for validation. Here, the monthly ERA5- Land shortwave radiation data are used to build the relationships with RS- based sensitivities. We also compare and validate the maximum temperature sensitivities. + +- why is the binning necessary for the fluxnet sites? I looked at the data in the supplements and it seems you could just provide a plot with all data points as well. + +Response: Thanks for the valuable comment. First, we should note that the binning process is for all observations of forest (or openland) based on the shortwave radiation condition. In other words, the binning process is for observations rather than sites. + +Since the forest and openland observations may be spatially distant or temporally asynchronous, they cannot be directly matched with each other (here the data indicate the corrected FLUXNET observations by subtracting gridded temperature). Thus, the binning process is necessary to provide a similar radiation background for comparing the "temperature effects" of forests and openlands to represent the consequence of land cover conversion. We have added a sentence to illustrate the reason for the binning process (Line 476): + +<--- Page Split ---> + +Since the forest data cannot be directly matched with the openland data, we bin both forest and openland data points using the \(SW_{d}\) interval of \(10 \text{w/m}^2\) . + +- In equation 4 and 5, what is the mean taken over? is it the average over all forest sites, and then the average over all openland sites? This is not written out in a mathematically clear way and so I don't understand it. + +Response: Thanks for the valuable comment. The mean is taken over for all forest (or openland) observations within each shortwave radiation bin. We have revised the equations 4 and 5 for clarity (Line 477): + +For each \(SW_{d}\) bin, we calculate the difference between mean values of forest and openland data points to represent the temperature effect of forestation (i.e. \(\delta T s^{b p h *}\) or \(\delta T a^{b p h *}\) ) under the specific radiation background: + +\[\begin{array}{r l r l r l r l}{\delta T s^{b p h *} = \left(T s_{f}^{s i t e} - T_{f}^{g r i d}\right) - \left(T s_{o}^{s i t e} - T_{o}^{g r i d}\right)} & {} & & & & {i f S W_{d}\in (10k,10k + 10)}\\ {\delta T a^{b p h *} = \left(T a_{f}^{s i t e} - T_{f}^{g r i d}\right) - \left(T a_{o}^{s i t e} - T_{o}^{g r i d}\right)} & {} & & & {i f S W_{d}\in (10k,10k + 10)} \end{array} \quad (5)\] + +- why is it called a relative effect (e.g. in figure S8). You're doing a simple subtraction, so that's an absolute effect, it's not put in relation to anything else. + +Response: Thanks for the careful reading. We have revised the relative effect to "land cover impacts on Ta/Ts" for clarity (Line 474): + +By deducting the corrected gridded temperature data, the in-situ measurements can effectively represent the land cover impacts on local Ts and Ta + +We also modified the wording in fig.S8 by using the "quantitative metric of forest (openland) impacts on local Ta or Ts". + +<--- Page Split ---> +![PLACEHOLDER_51_0] + +
Supplementary Figure 8. Flow chart of the remote sensing (RS)-based local temperature effect validation using FLUXNET and gridded temperature data.
+ +- It is unclear for what values the regression is done. For all of the datapoints? For the means of the bins? + +Response: Thanks for the comment. The means of bins are used for regression. We have highlighted the regression data as you suggested (Line 489): + +Then, the relationships between two temperature sensitivities and \(SW_{d}\) are explored using the weighted least squares (WLS) regression model, in which the samples are \(\delta T_{a}^{bph*}\) or \(\delta T_{a}^{bph*}\) of all \(SW_{d}\) bins and the sample weights are defined as the inverse of the standard error of \(\delta T_{a}^{bph*}\) or \(\delta T_{a}^{bph*}\) . + +Fig S11 has inconsistent axes in a) and b), and a typo for b) in the caption (should be Ta) Response: Thanks for the careful reading. We have redrawn the supplementary figure with the same color bar and revised the figure caption. + +<--- Page Split ---> +![PLACEHOLDER_52_0] + + +Supplementary Figure 11. Equivalent \(\mathrm{CO_2}\) uptake induced by biophysical Ts and Ta effects of potential tree restoration ( \(\delta \mathrm{CO_2e^{bph,Ts}}\) and \(\delta \mathrm{CO_2e^{bph,Ta}}\) ). (a) Global map of \(\delta \mathrm{CO_2e^{bph,Ts}}\) . (b) Global map of \(\delta \mathrm{CO_2e^{bph,Ta}}\) . (c) Transient climate response to cumulative emissions (TCRE) of \(\mathrm{CO_2}\) for annual Ts. (d) Transient climate response to cumulative emissions (TCRE) of \(\mathrm{CO_2}^2\) for annual Ta. + +Just a suggestion: Put the 600 tC/ha in context, e.g. with Pan2024, stating how dense those biomes are currently (around 240 tC/ha if I recall correctly) + +Response: Thanks for the valuable comment. We should first note that the figure is \(\delta \mathrm{CO_2e}\) , which indicates the equivalent \(\mathrm{CO_2}\) densities (t/ha), rather than C densities. + +According to extended data table 2 of Pan et al., the mean biome- level C density of tropical intact forest is 293.1 tC/ha. Considering the ratio of living biomass to total C (living biomass, dead wood, litter and soil) derived from the table data, the estimated mean biomass C density is about 164.2 tC/ha. After converting the unit to \(\mathrm{CO_2}\) , the number is about 602.2 tCO2/ha, which is comparable to our result. Notably, we use the data of tropical intact forest rather than the tropical regrowth forest for comparison. This is because our density results are based on the full tree cover restoration, which is closer to the state of intact forest. + +Following your suggestion, we have added the context of our results (Line 253): + +The spatial map shows that \(\delta \mathrm{CO_2e^{bchem}}\) in tropical rainforest margins can exceed 600 t/ha (Fig. 4a), which is comparable to the previous estimation of tropical intact forests based on ecological research network observations. This value is greater than \(\delta \mathrm{CO_2e^{bch}}\) in temperate and boreal forests, suggesting the highest carbon benefit of restoring damaged or degraded tropical forests. + +5. Pan, Y. et al. The enduring world forest carbon sink. Nature 631, 563-569 (2024). + +## Reviewer #2 (Remarks on code availability): + +The code requires a small effort. First of all, the packages and versions with which to run this are not included. So I had to manually install packages one by one which is annoying. + +Response: Thanks for raising this concern. We have updated the Zenodo project (https://zenodo.org/records/14633331). The "environment.zip" file is uploaded, which contains the + +<--- Page Split ---> + +“yml” file and the python wheels of GDAL for both Linux and Windows systems. We also updated the “readme.md” file, which provides simple instructions about the environment installation. + +You should provide a conda environment.yml or something like that so one can just set up the environment and re- run the code. I managed to get the code running after I fixed some issues. + +Response: Please refer to the response above. The “yml” file is uploaded. + +BTW, the code does not directly run on Linux/Mac because of Windows- style file paths and sometimes wrong capitalization of filenames (that matters on Unix systems). Also, the names of the imports lib_image are wrong (should be function_image). But I was able to reproduce the figures in the end. + +Response: We apologize for the bugs in the code. We have checked through the code and debugged on both Windows and Linux. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +The authors have done a thorough job responding to comments raised during the first round of review. My particular concerns have been adequately addressed, and I do not have any others to raise at this point. + +Response: We thank the reviewer for the constructive comments during the review process. + +<--- Page Split ---> diff --git a/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..72188809797b6306357bf4444956c5708ed313c3 --- /dev/null +++ b/peer_reviews/786f982c72e4ca8408f270235d5844394c69723b525dd1a9aa654488705b8e7d/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1612 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 895, 240]]<|/det|> +Lung megakaryocytes engulf inhaled airborne particles to promote intrapulmonary inflammation and extrapulmonary distribution + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to + +<|ref|>text<|/ref|><|det|>[[57, 785, 933, 924]]<|/det|> +the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[348, 86, 649, 103]]<|/det|> +## Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[148, 113, 851, 223]]<|/det|> +We greatly appreciate the opportunity to revise our manuscript and thank all anonymous reviewers for their constructive comments. The manuscript has been revised and improved according to the reviewers' valuable comments and suggestions. We hope that the revision will make it more acceptable for publication. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in Italics and Arial) and the location of the revision. The line numbers referred to are for the clean version of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 257, 468, 273]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 292, 850, 438]]<|/det|> +The authors analyse the biophysical feedback of forestation. For this they use observational data, comparing the feedback for surface and air temperature. The main finding of the first part is that air temperature is less sensitive to tree cover changes than surface temperature. After establishing this, the authors analyse this difference in sensitivity by using Monxin Obukhov and quantify the maximum local climate effect. Finally, a comparison is made with the biochemical feedback of forestation, which shows that in specific regions the biophysical feedback can outperform the biochemical feedback. + +<|ref|>text<|/ref|><|det|>[[148, 440, 850, 550]]<|/det|> +The authors show an innovative approach of combining different data sources and analytical methods in order to be able to analyse the effect of forestation of air temperature using observational data. This is interesting, since such topics are usually tackled by using model data. I specifically enjoyed the analysis of the near surface temperature profiles and the decomposition of the air temperature sensitivity. + +<|ref|>text<|/ref|><|det|>[[148, 554, 850, 664]]<|/det|> +That being said, it took me quite some time to understand which dataset was used for which analysis and how the different data sources were combined and analysed. In my opinion, clarifying this aspect would be a big help in improving the paper. If the authors choose to rewrite/reorganize parts of the paper, some questions that I had during reading (some of which got resolved, but were still confusing in the beginning) could maybe serve as a guideline as to which parts to clarify: + +<|ref|>text<|/ref|><|det|>[[148, 668, 850, 740]]<|/det|> +Response: We appreciate the positive comments by the reviewer. We have carefully considered all the comments and suggestions and made corresponding point- by- point responses. In particular, we have revised the method section and clarified the usage of different datasets to improve the readability of the manuscript. Please see our detailed responses below. + +<|ref|>text<|/ref|><|det|>[[148, 766, 849, 800]]<|/det|> +1) Line 230: I thought we were only looking at the difference between 0 and 100% tree cover? + +<|ref|>text<|/ref|><|det|>[[148, 807, 850, 898]]<|/det|> +Response: Thanks for the comment. In the original manuscript, the section is based on the tree restoration potential (ATC), ranging from 0 to 100%. According to the comment of reviewer #3, we removed the analyses related to ATC and rewrote this section by comparing the biophysical and biochemical sensitivity of tree cover change from 0 to 100% (Line 246). This revision makes our results clearer that only local effects are evaluated and the non-local or global effects are not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 216, 100]]<|/det|> +included. + +<|ref|>sub_title<|/ref|><|det|>[[149, 112, 850, 147]]<|/det|> +## Comparison of biophysical with biochemical effects based on two temperature metrics + +<|ref|>text<|/ref|><|det|>[[183, 150, 851, 279]]<|/det|> +Most assessments of the climate benefits related to forestation have concentrated on the carbon sequestration (i.e., biochemical effect). Here, the biomass carbon stock sensitivity to tree cover is estimated by space- for- time analogy and converted to \(\mathrm{CO_2}\) absorption equivalents ( \(\delta \mathrm{CO_2e^{bchem}}\) ) to represent the biochemical effect. We also convert the biophysical Ts and Ta sensitivities to the metric of equivalent \(\mathrm{CO_2}\) uptake ( \(\delta \mathrm{CO_2e^{bph,Ts}}\) and \(\delta \mathrm{CO_2e^{bph,Ta}}\) ). These allow the comparison of the local biophysical and the biochemical climate effect and evaluate the relative importance of the former. + +<|ref|>text<|/ref|><|det|>[[148, 304, 850, 360]]<|/det|> +2) Line 399: where do these radiation values come from, which dataset? Response: Thanks for raising this concern. Upward and downward longwave radiation data are from FLUXNET datasets. We have added the description of the data source (Line 470): + +<|ref|>text<|/ref|><|det|>[[183, 372, 850, 407]]<|/det|> +\(\mathrm{LW_u}\) and \(\mathrm{LW_d}\) represent upward and downward longwave radiation from the FLUXNET2015 dataset, respectively; + +<|ref|>text<|/ref|><|det|>[[148, 433, 850, 490]]<|/det|> +3) Figure 1: is this figure based on GLOBMP? I can't find that anywhere. Response: Thanks for the careful reading. Figure 1 is based on GLOBMP dataset. We have added the description in the figure caption (Line 129): + +<|ref|>text<|/ref|><|det|>[[183, 495, 818, 511]]<|/det|> +The tree cover map for the sensitivity estimation is from the GLOBAMP dataset. + +<|ref|>text<|/ref|><|det|>[[148, 538, 725, 554]]<|/det|> +4) Line 355: why this \(10\%\) As in, why at all, and why exactly 10? + +<|ref|>text<|/ref|><|det|>[[148, 560, 851, 687]]<|/det|> +Response: Thank you for raising this question. Here, we set this threshold for two reasons. First, according to the definition from the Food and Agricultural Organization (FAO), forests are defined as land with a tree crown cover larger than \(10\%\) and an area of more than 0.5 hectares (ha). Second, the temperature variations in low tree cover (e.g. \(< 10\%\) ) pixels may be induced by the rest non- forest land cover components. Using these pixels for regression may reduce the reliability of estimated temperature sensitivity to tree cover changes. In the revised manuscript, we have added explanations of the threshold (Line 415): + +<|ref|>text<|/ref|><|det|>[[183, 698, 850, 771]]<|/det|> +Specifically, for each \(0.25^{\circ}\times 0.25^{\circ}\) grid cell, we filter out pixels with more than \(1\%\) water body coverage or less than \(10\%\) tree cover according to the forest definition by the Food and Agricultural Organization79. This process is to reduce the impact of non- forest land cover types on the estimation of temperature sensitivity. + +<|ref|>text<|/ref|><|det|>[[149, 775, 850, 829]]<|/det|> +79. Keenan, R. J. et al. Dynamics of global forest area: Results from the FAO Global Forest Resources Assessment 2015. Forest Ecology and Management vol. 352 9-20 (2015). + +<|ref|>text<|/ref|><|det|>[[148, 854, 850, 906]]<|/det|> +5) The satellite based Ts and Ta are for 2010 whereas the potential tree cover map is for 2020 (lines 311-326). Is this difference in time what you correct for in lines 488-489? Unfortunately I don’t really understand what you’re trying + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 87, 252, 100]]<|/det|> +to say here. + +<|ref|>text<|/ref|><|det|>[[148, 106, 852, 201]]<|/det|> +Response: Thank you for raising this concern. In the original manuscript, we use tree cover data of 2010 to estimate sensitives, considering the data availability of both GLOBMP and GFC datasets. We also use tree cover data of 2020 from GLOBMP to calculate tree restoration potential (ATC) under the current stage. According to the comment of reviewer #3, the analyses based on ATC are removed, and only tree cover data of 2010 are used in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[149, 205, 745, 221]]<|/det|> +We have rewritten the "Tree Cover Map" subsection to clarify this issue (Line 377): + +<|ref|>text<|/ref|><|det|>[[181, 226, 851, 375]]<|/det|> +In this study, two tree canopy cover datasets derived from different sensors are used for the analysis, including the recently released GLOBMP fractional tree cover map with a spatial resolution of \(250 \mathrm{~m}\) , and the Global Forest Change (GFC) tree cover map with a spatial resolution of \(30 \mathrm{~m}\) . Considering the data availability, we use the tree cover maps of 2010 (TC2010) of both two products to calculate the biophysical temperature sensitivities to ensure robustness. Both TC2010 maps are preprocessed and spatially aggregated to a \(1 \mathrm{~km}\) resolution for further analysis (Supplementary Fig. 12). + +<|ref|>image<|/ref|><|det|>[[283, 412, 692, 686]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[181, 729, 850, 765]]<|/det|> +
Fig. S12. Global maps of fractional tree cover from (a) GLOBMP and (b) Global Forest Change (GFC) datasets.
+ +<|ref|>text<|/ref|><|det|>[[147, 789, 850, 899]]<|/det|> +6) What I found most confusing is the different definitions/meanings/sources of Ts and Ta throughout the paper. When describing the satellite based Ts and Ta: ,Ts represent the mixture temperature of the tree canopy and the exposed soil at the observed angle ". So, Ts is at canopy height. Later is mentioned that Ta is located at screen height (line 339), what is screen height? Is that then above the canopy layer in the case of a forest? In line 430 and further, Ta is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 252]]<|/det|> +normalized to 2m height. Why is this not done right away? But also, are we then looking at a Ta inside the canopy, (heavily influenced by the microclimate in a forest) or is it 2m above the canopy? Unfortunately, I also don't really understand formulas 1 and 2 and where they come from (see also a later comment on why a linear relationship is assumed) so I have difficulty assessing if all these differences in meaning are problematic or not (since you're comparing deltas and not actual values). And then in line 396, "Ta is measured above the vegetation canopy, ranging from several decimeters to over ten meters", so which height is actually used for Ta? Clearing all this up would be extremely helpful. + +<|ref|>text<|/ref|><|det|>[[147, 256, 851, 383]]<|/det|> +Response: Thank you very much for these important issues. First, the evaluated Ta, in both remote sensing- and site- based analyses, indicates the air temperature of about 2 m above the land surface. Here, "land surface" indicates the interface layer between different land surface components and the atmosphere (e.g., forest canopy, rooftops and soil). Thus, for forested areas, Ta refers to the air temperature of about 2 m above the tree canopy. For clarity, we have revised the "screen height" to "approximately 2 m above the land surface". We also added a schematic figure (Supplementary Fig. 2) and descriptions of the temperature metrics in the introduction section (Line 78): + +<|ref|>text<|/ref|><|det|>[[182, 387, 851, 460]]<|/det|> +Notably, the evaluated Ts indicates the radiometric temperature of the land surface, and Ta indicates the air temperature at 2 m above the land surface (Supplementary Fig. 2). The land surface here refers to the interface layer between different land components and the atmosphere (e.g. vegetation canopy)44. + +<|ref|>image<|/ref|><|det|>[[280, 469, 722, 735]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[157, 745, 840, 780]]<|/det|> +
Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 793, 238, 807]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 811, 850, 845]]<|/det|> +44. Reiners, P., Sobrino, J. & Kuenzer, C. Satellite-Derived Land Surface Temperature Dynamics in the Context of Global Change—A Review. Remote Sens. 15, (2023). + +<|ref|>text<|/ref|><|det|>[[148, 869, 851, 905]]<|/det|> +We also added descriptions of the air temperature in the method section (Line 397): The other temperature metric used for assessment is Ta, the air temperature at + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[183, 85, 850, 159]]<|/det|> +approximately 2 m above the interface layer between land components and the atmosphere. Specifically, for forested areas, the reference plane is the canopy, whereas for openlands the reference plane is approximately the ground (Supplementary Fig. 2). + +<|ref|>text<|/ref|><|det|>[[148, 169, 850, 223]]<|/det|> +Second, since Ta is measured above the vegetation canopy, ranging from several decimeters to over ten meters, we normalized FLUXNET Ta to explore the temperature profile from zero- plane displacement to the fixed 2- meter height above the canopy. + +<|ref|>text<|/ref|><|det|>[[148, 234, 850, 269]]<|/det|> +Third, about Equations 1 and 2, please see the later response to your critical comment on the assumption of a linear relationship. + +<|ref|>text<|/ref|><|det|>[[148, 308, 281, 322]]<|/det|> +Other comments: + +<|ref|>text<|/ref|><|det|>[[148, 326, 850, 379]]<|/det|> +Line 28: „different biophysical characteristics “ → different than what? I suggest changing to „several biophysical characteristics “, or something along those lines. + +<|ref|>text<|/ref|><|det|>[[147, 384, 835, 401]]<|/det|> +Response: Thanks for the suggestion. We have replaced the “different” with “several” (Line 36): + +<|ref|>text<|/ref|><|det|>[[182, 406, 850, 460]]<|/det|> +Meanwhile, forests present several biophysical (bph) characteristics, such as lower albedo and greater roughness length, resulting in the local cooling or warming effect compared to their neighboring openlands. + +<|ref|>text<|/ref|><|det|>[[147, 486, 850, 520]]<|/det|> +Line 32: what is a negative and what is a positive effect? Maybe use warming and cooling instead? + +<|ref|>text<|/ref|><|det|>[[147, 526, 850, 561]]<|/det|> +Response: Thanks for the comment. We have changed “negative/positive” to “cooling/warming” (Line 40): + +<|ref|>text<|/ref|><|det|>[[182, 566, 850, 638]]<|/det|> +The sign and magnitude of the local biophysical temperature effects can vary considerably based on spatial location and background climate, and are typically characterized by a shift from cooling effects in the tropics to warming effects in cold regions. + +<|ref|>text<|/ref|><|det|>[[147, 665, 850, 700]]<|/det|> +Line 67: what does bgp actually stand for? (just out of curiosity, knowing this would help with reading) + +<|ref|>text<|/ref|><|det|>[[148, 705, 850, 758]]<|/det|> +Response: Thanks for the suggestion. In the original manuscript, the superscript “bgp” is the abbreviation for “biogeophysical”. We have changed the superscript to “bph” as the abbreviation for biophysical for clarity (Line 36): + +<|ref|>text<|/ref|><|det|>[[182, 770, 850, 823]]<|/det|> +Meanwhile, forests present several biophysical (bph) characteristics, such as lower albedo and greater roughness length, resulting in the local cooling or warming effect compared to their neighboring openlands. + +<|ref|>text<|/ref|><|det|>[[147, 861, 850, 900]]<|/det|> +Line 85: only one other study is used in the figure for comparison? Response: Yes, we compare our result with Duveiller et al, which provides biophysical maximum, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +minimum and mean Ts effects of forestation. To avoid ambiguity, we have revised the sentence (Line 102): + +<|ref|>text<|/ref|><|det|>[[183, 131, 851, 186]]<|/det|> +The estimated \(\delta T s^{b p h}\) aligns well with a previous study of the potential Ts effect of forestation based on the unmixing method46, suggesting the robustness to different analytical approaches. + +<|ref|>sub_title<|/ref|><|det|>[[148, 191, 237, 206]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 211, 850, 248]]<|/det|> +46. Duveiller, G., Hooker, J. & Cescatti, A. The mark of vegetation change on Earth's surface energy balance. Nat. Commun. 9, 64 - 75 (2018). + +<|ref|>text<|/ref|><|det|>[[148, 271, 284, 286]]<|/det|> +Line 88: valueS + +<|ref|>text<|/ref|><|det|>[[148, 292, 850, 327]]<|/det|> +Response: Thanks for the careful reading. We have corrected the mistake as the reviewer suggested (Line 105): + +<|ref|>text<|/ref|><|det|>[[180, 331, 850, 367]]<|/det|> +In terms of the magnitude, \(\delta T a^{b p h}\) demonstrates much lower absolute values compared to \(\delta T s^{b p h}\) . + +<|ref|>text<|/ref|><|det|>[[147, 392, 850, 427]]<|/det|> +Line 144- 147: please rewrite this sentence, or maybe it already works if the first „While“ is removed? + +<|ref|>text<|/ref|><|det|>[[147, 432, 850, 467]]<|/det|> +Response: Thank you for the careful reading. We have rewritten the sentence and now it reads (Line 179): + +<|ref|>text<|/ref|><|det|>[[181, 472, 850, 545]]<|/det|> +However, we show that the ratios of Ta sensitivity slopes to Ts sensitivity slopes are close in the RS- based (16.9%) and site- based (17.4%) results (Fig. 2c and d). This result suggests that site measurements corroborate the relative magnitude of the RS- based maximum temperature sensitivity. + +<|ref|>text<|/ref|><|det|>[[148, 570, 850, 643]]<|/det|> +Figure 2: The text of the legend is very small, which makes it difficult to distinguish between Ts and Ta (the s and a look the same). If possible rearrange legend and panels to be able to increase font size (maybe the legend outside of the panel?) + +<|ref|>text<|/ref|><|det|>[[148, 648, 850, 703]]<|/det|> +Response: We thank the reviewer for the helpful suggestion. To better distinguish the two temperatures, we have changed Ts and Ta to Ts and Ta. We also rearranged the panels to increase the font size of the legend (Fig. 2). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[210, 95, 784, 401]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[448, 422, 546, 438]]<|/det|> +
Figure 2. ...
+ +<|ref|>text<|/ref|><|det|>[[148, 464, 850, 536]]<|/det|> +Subsection starting at line 163: What could be a valuable addition is a short discussion on the differences between the sites. Why is the influence of a different between the three observed cases (Europe vs North America and Australia)? + +<|ref|>text<|/ref|><|det|>[[148, 542, 850, 576]]<|/det|> +Response: Thanks for the suggestion. We have added an explanation of the higher contribution from H in European winter than North American or Australian summer (Line 226): + +<|ref|>text<|/ref|><|det|>[[183, 582, 850, 672]]<|/det|> +We note that the contribution of H is greater in European winter than in North American or Australian summer. The possible reason is that H is more dominant in the turbulent flux exchange in winter (characterized by the higher Bowen ratio) than in summer51, thus contributing more to the temperature gradients between the land surface and the near- surface air, and further to the attenuation of the air temperature response. + +<|ref|>sub_title<|/ref|><|det|>[[148, 684, 238, 699]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 704, 841, 758]]<|/det|> +51. Lin, H., Li, Y. & Zhao, L. Partitioning of Sensible and Latent Heat Fluxes in Different Vegetation Types and Their Spatiotemporal Variations Based on 203 FLUXNET Sites. J. Geophys. Res. Atmos. 127, (2022). + +<|ref|>text<|/ref|><|det|>[[148, 785, 850, 856]]<|/det|> +Line 245: after how many years would this amount be reached? Compared to how fast trees grow and the biophysical effect will be apparent? Trees grow slow and biophysical and biochemical feedback act on different timescales, a sentences or two about this would be helpful I think. + +<|ref|>text<|/ref|><|det|>[[147, 863, 848, 897]]<|/det|> +Response: Thanks for the professional suggestion. We have added a sentence to discuss the temporal scale of two effects (Line 320): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[183, 84, 850, 158]]<|/det|> +Both evaluated biophysical and biochemical effects represent potential cumulative results. It may take a shorter period for biophysical processes (a single decade) to come into effect than biochemical processes, as the newly restored forests gradually absorb CO2 and reach equilibrium after several decades. + +<|ref|>text<|/ref|><|det|>[[148, 185, 364, 201]]<|/det|> +Line 261: which regions? + +<|ref|>text<|/ref|><|det|>[[148, 206, 850, 260]]<|/det|> +Response: Thanks for the careful reading. Following reviewer #3's comment, this section about the comparison between biophysical and biochemical effects has been rewritten. Please see the response below for the new content. + +<|ref|>text<|/ref|><|det|>[[148, 286, 485, 302]]<|/det|> +Line 292: and A machine- learning model + +<|ref|>text<|/ref|><|det|>[[148, 307, 851, 361]]<|/det|> +Response: Thanks for pointing out this and the following mistakes. According to the comment of reviewer #3, the analyses using the machine- learning model for sensitivity extrapolation are removed. Correspondingly, the related descriptions and discussions are deleted. + +<|ref|>text<|/ref|><|det|>[[148, 387, 470, 402]]<|/det|> +Line 314: Both and two \(\rightarrow\) remove one + +<|ref|>text<|/ref|><|det|>[[148, 408, 495, 424]]<|/det|> +Response: Revised as you suggested (Line 382): + +<|ref|>text<|/ref|><|det|>[[179, 429, 850, 464]]<|/det|> +Both TC2010 maps from GLOBMP and GFC are preprocessed and spatially aggregated to the 1 km resolution for further analysis. + +<|ref|>text<|/ref|><|det|>[[148, 491, 450, 507]]<|/det|> +Line 318: by A Random Forest model + +<|ref|>text<|/ref|><|det|>[[148, 513, 850, 548]]<|/det|> +Response: Contents related to the random forest model are deleted for the same reason mentioned above. + +<|ref|>text<|/ref|><|det|>[[148, 575, 585, 590]]<|/det|> +Line 323: annual precipitation is mentioned twice + +<|ref|>text<|/ref|><|det|>[[148, 596, 677, 612]]<|/det|> +Response: This paragraph is deleted for the same reason mentioned above. + +<|ref|>text<|/ref|><|det|>[[148, 639, 530, 655]]<|/det|> +Line 357: water coverage AND elevation data + +<|ref|>text<|/ref|><|det|>[[148, 660, 495, 676]]<|/det|> +Response: Revised as you suggested (Line 420): + +<|ref|>text<|/ref|><|det|>[[183, 681, 850, 716]]<|/det|> +The water coverage and elevation data are from Joint Research Center Global Surface Water Mapping Layers v1.4 and GMTED2010 datasets, respectively. + +<|ref|>text<|/ref|><|det|>[[148, 742, 850, 833]]<|/det|> +Lines 360- 363: why do you assume the relation is linear? Do you have a reference for this (pretty strong) assumption? And about the formulas: what is the difference between TC T and TC? Also, deltaTsbgp and deltaTabgp are for 100% increase in forest cover (I thought?), how is this represented in formula 1 and 2? + +<|ref|>text<|/ref|><|det|>[[148, 840, 850, 911]]<|/det|> +Response: Thanks for raising these concerns. The non- linear relationship is generally discussed in those studies at finer scales (Zhao et al., 2023) or inner- city scales (Yang et al., 2024). For most large- scale or global studies, the linear assumption is widely accepted and used (Alkama and Cescatti, 2016; Wang et al., 2023; Zhang et al., 2024). We add these references for the linear + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 577, 102]]<|/det|> +relationship between tree cover and temperature (Line 423): + +<|ref|>text<|/ref|><|det|>[[181, 112, 850, 168]]<|/det|> +After the screening process, \(\delta T s^{b p h}\) and \(\delta T a^{b p h}\) can be estimated using a linear regression model between tree cover and corresponding temperature values for each \(0.25^{\circ}\) grid (Alkama and Cescatti, 2016; Wang et al., 2023; Zhang et al., 2024). + +<|ref|>text<|/ref|><|det|>[[148, 178, 850, 233]]<|/det|> +Second, the original formulas 1 and 2 are the matrix representation of the ordinary least squares (OLS) method for estimating the slope, and the superscript "T" denotes the matrix transpose. We rewrite the formula 1 and 2 as the form or linear relationship for clarity, and it now reads (Line 425): + +<|ref|>equation<|/ref|><|det|>[[266, 245, 848, 295]]<|/det|> +\[\begin{array}{c}{{T s=\delta T s^{b p h}\times T C_{2010}+b_{s}}}\\ {{}}\\ {{T a=\delta T a^{b p h}\times T C_{2010}+b_{a}}}\end{array} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[182, 309, 562, 325]]<|/det|> +where, \(b_{s}\) and \(b_{a}\) are the regression intercepts. + +<|ref|>sub_title<|/ref|><|det|>[[148, 336, 234, 351]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 356, 850, 630]]<|/det|> +Alkama, R., Cescatti, A., 2016. Biophysical climate impacts of recent changes in global forest cover. Science (80- .). 351, 600 - 604. https://doi.org/10.1126/science.aac8083Wang, H., Yue, C., Luyssaert, S., 2023. Reconciling different approaches to quantifying land surface temperature impacts of afforestation using satellite observations. Biogeosciences 20, 75 - 92. https://doi.org/10.5194/bg- 20- 75- 2023Yang, L., Ge, J., Cao, Y., Liu, Y., Luo, X., Wang, S., Guo, W., 2024. Enhanced Cooling Efficiency of Urban Trees on Hotter Summer Days in 70 Cities of China. Adv. Atmos. Sci. 41, 2259 - 2275. https://doi.org/10.1007/s00376- 024- 3269- 9Zhang, Y., Wang, X., Lian, X., Li, S., Li, Y., Chen, C., Piao, S., 2024. Asymmetric impacts of forest gain and loss on tropical land surface temperature. Nat. Geosci. 13, 823 - 831. https://doi.org/10.1038/s41561- 024- 01423- 3Zhao, J., Zhao, X., Wu, D., Meili, N., Fatichi, S., 2023. Satellite - based evidence highlights a considerable increase of urban tree cooling benefits from 2000 to 2015. Glob. Chang. Biol. https://doi.org/10.1111/gcb.16667 + +<|ref|>text<|/ref|><|det|>[[148, 652, 420, 668]]<|/det|> +Line 365: sample size of what? + +<|ref|>text<|/ref|><|det|>[[148, 673, 850, 708]]<|/det|> +Response: Thanks for the comment. The sample size indicates the number of samples for the linear regression model. The sentence now reads (Line 427): + +<|ref|>text<|/ref|><|det|>[[183, 713, 850, 786]]<|/det|> +To ensure the reliability of the results, biophysical sensitivity calculation is performed only when the total sample size of the linear regression model exceeds 90 (more than \(10\%\) of pixels within the \(0.25^{\circ}\) grid) and the difference between the highest and lowest tree cover is greater than \(40\%\) . + +<|ref|>text<|/ref|><|det|>[[148, 811, 850, 866]]<|/det|> +Line 382: this is not entirely true though, is it? Because of the spatial autocorrelation and the fact that a forest influences it surroundings? Removing the forest could also change the temperature on the non- forest site. + +<|ref|>text<|/ref|><|det|>[[147, 870, 850, 906]]<|/det|> +Response: Thanks for the valuable comment. We admit that forestation can affect the temperature of the surrounding area, by affecting heat advection or the circulation pattern. We have clarified that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 849, 120]]<|/det|> +the paired site method can only be used to validate the "local" temperature effect derived from remote sensing data (Line 450): + +<|ref|>text<|/ref|><|det|>[[183, 131, 849, 167]]<|/det|> +The RS- based local temperature sensitivity can be validated through the differences of measurements between spatially adjacent paired forest and non- forest sites. + +<|ref|>text<|/ref|><|det|>[[148, 193, 850, 265]]<|/det|> +Line 401: why is the lack of spatial pairing a reason for this? I understood from the previous paragraph that no spatial pairing approach is used? As I understand from the formula, you simply average over all forest/open land sites anyway? + +<|ref|>text<|/ref|><|det|>[[148, 271, 850, 305]]<|/det|> +Response: Thanks for pointing this out. The spatial pairing approach is not used here and we have removed this redundant description (Line 472): + +<|ref|>text<|/ref|><|det|>[[183, 310, 850, 363]]<|/det|> +We bin the SWa with a fixed interval of \(10 \mathrm{w} / \mathrm{m}^2\) and calculate the mean \(\delta T s^{b p h *}\) or \(\delta T a^{b p h *}\) to explore the sensitivity variability under different background radiation conditions. + +<|ref|>text<|/ref|><|det|>[[148, 375, 850, 429]]<|/det|> +Second, we average the forest and openland observations in different shortwave radiation bins, rather than all possible observations. We added a flow chart for the methodology for clarity (Supplementary Fig. 8). + +<|ref|>image<|/ref|><|det|>[[208, 440, 785, 870]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[145, 881, 850, 898]]<|/det|> +
Fig. S8. Flow chart of the remote sensing (RS)-based local temperature effect validation
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 520, 101]]<|/det|> +using FLUXNET and gridded temperature data. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 99, 471, 115]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 134, 345, 149]]<|/det|> +# Content of the paper + +<|ref|>text<|/ref|><|det|>[[148, 151, 850, 243]]<|/det|> +In their paper, "The Overlooked Local Air Warming Mitigation of Potential Tree Restoration", the authors provide insights on the biophysical impacts of forestation. Namely, they compute the impacts of forestation on air temperature (as opposed to surface temperature) and compare these impacts with the often reported surface temperature changes, and with biogeochemical effects. + +<|ref|>text<|/ref|><|det|>[[148, 247, 848, 301]]<|/det|> +For this, the authors train an RF model: From meteorological, soil, forest cover, and topographic data, this predicts the maximum forest cover under current climatic conditions across the globe. + +<|ref|>text<|/ref|><|det|>[[148, 305, 850, 396]]<|/det|> +They correlate weather station air temperature \(T_{- }a\) to satellite- observed surface temperature \(T_{- }s\) , to get global coverage of \(T_{- }a\) . Then, after a filtering process to account for too- high elevation differences or too- low forest cover differences within that pixel, linear relationships between tree cover and the two temperatures are created, + +<|ref|>equation<|/ref|><|det|>[[148, 401, 328, 437]]<|/det|> +\[T_{-}s = \mathrm{TC\_2010x dT\_s\] \[T_{-}a = \mathrm{TC\_2010x dT\_a\] + +<|ref|>text<|/ref|><|det|>[[148, 439, 850, 511]]<|/det|> +From this relationship, they can estimate the temperatures within that pixel if it contained the maximum possible forest cover. The authors validate their approach with site data. They finally compare their results with biogeochemical impacts of forestation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 517, 231, 531]]<|/det|> +## # Remarks + +<|ref|>text<|/ref|><|det|>[[148, 534, 850, 606]]<|/det|> +In general, I find this to be a relevant and well- crafted paper that could be suitable for publication within the journal Nature Communications. It offers substantial new contributions. The authors did a good job in using various data sources to back their claims and I enjoyed reading this paper. + +<|ref|>text<|/ref|><|det|>[[148, 611, 850, 664]]<|/det|> +However, some more work needs to be invested to make the paper and its contribution clearer which is why I categorize this manuscript as needing "major revisions". + +<|ref|>text<|/ref|><|det|>[[148, 670, 850, 779]]<|/det|> +For instance, it needs to be highlighted more what the new results are compared to existing knowledge, for instance compared to the study by Windisch et al. (2019), which the authors also cite. I found the state of current knowledge to be addressed, but not clear enough. Perhaps (only an idea), some more consolidation of current state of knowledge would be helpful, and the main results of this new manuscript should be made more prominent. + +<|ref|>text<|/ref|><|det|>[[148, 784, 850, 857]]<|/det|> +Many points throughout the manuscript can be made clearer, it is sometimes not clear whether local impacts, or global impacts are talked about. And in various points (see my detailed comments below) the explanations need some more clarity. In the assessment of biogeochemical impacts, soil is neglected. + +<|ref|>text<|/ref|><|det|>[[148, 859, 702, 874]]<|/det|> +Please find my detailed comments on the various sections below. + +<|ref|>text<|/ref|><|det|>[[148, 878, 850, 911]]<|/det|> +Response: We appreciate your positive comments. We have revised our manuscript carefully and the detailed corrections are listed below. Specifically, we have invested more work to clarify the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 176]]<|/det|> +new contribution of this paper compared to previous Ts- based studies (e.g. Windisch, et al.). The state of current knowledge, such as global/local effects, the influence of soil carbon, and the widespread impact of forestation, have been introduced or discussed. We also revised explanations and technical terms to make the paper clearer. We hope the revised paper will be more suitable for publication. + +<|ref|>sub_title<|/ref|><|det|>[[148, 203, 256, 217]]<|/det|> +## Abstract + +<|ref|>text<|/ref|><|det|>[[148, 220, 825, 256]]<|/det|> +1. 12-13: flatter temp profiles in forested areas \*compared to non-forested\* Response: Thanks for the comment. The sentence has been revised as suggested (Line 14): + +<|ref|>text<|/ref|><|det|>[[183, 261, 850, 314]]<|/det|> +We further attribute the discrepancy in temperature responses to the reduced aerodynamic resistance and the resultant flatter near- surface temperature profiles in forests compared to non- forests. + +<|ref|>text<|/ref|><|det|>[[148, 341, 850, 394]]<|/det|> +1. 14 the substantial climate benefits, could mention here how high they will get, how many K? How much is it compared to surface temperature? Also, what is the potential global impact? + +<|ref|>text<|/ref|><|det|>[[147, 399, 851, 528]]<|/det|> +Response: Thanks for the suggestion. According to the comment of reviewer #3, we have updated the results of the comparison between biophysical and biochemical effects. The new results focus on the local biophysical and biochemical sensitivities, rather than the global biophysical and biochemical climate effects of potential tree restoration. Similar to Windisch, et al., the current comparisons are based on the equivalent \(\mathrm{CO_2}\) uptake, rather than the temperature effect (K). This revision makes our results clearer that only local effects are evaluated and the non- local or global effects are not included. Correspondingly, we have rewritten the abstract (Line 4): + +<|ref|>text<|/ref|><|det|>[[183, 532, 864, 882]]<|/det|> +Forestation, as a key component of nature- based solutions, has the potential to cool or warm the local climate through biophysical processes, thereby enhancing or offsetting the global warming mitigation from carbon assimilation. Currently, the magnitude of such biophysical effects on local climate remains unconstrained, as most previous observational studies rely on land surface temperature (Ts), rather than the policy- relevant near surface air temperature (Ta). Based on satellite observations, we show that the Ta response to tree cover change is significantly lower, ranging from 15% to 30%, compared to Ts response. The relative magnitude of the two temperature effects is supported by independent evidence from site observations. We further attribute the discrepancy in temperature responses to the reduced aerodynamic resistance and the resultant flatter near- surface temperature profiles in forests compared to non- forests. Moreover, we show that at mid- or northern high- latitudes, the maximum seasonal biophysical Ta warming or cooling only accounts for approximately 10% of the equivalent climate effect of carbon sequestration in terms of magnitude, whereas the ratio for the biophysical Ts effect can reach 40%. These results highlight that Ts- based assessments may significantly overestimate the local climate impact of tree cover change. We also emphasize that when evaluating the biophysical effects of forestation or deforestation, the proper temperature metric should be specified and used in different cases to avoid misleading conclusions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 139]]<|/det|> +1. 18: but the key message is not the strong potential, but quite contrarily, the much lower potential than what we anticipate, I think the wording needs to be a bit different (Line 14): + +<|ref|>text<|/ref|><|det|>[[149, 145, 850, 179]]<|/det|> +Response: Thanks for the constructive comment. We've revised the wording according to the new results: + +<|ref|>text<|/ref|><|det|>[[183, 185, 852, 330]]<|/det|> +Moreover, we show that at mid- or northern high- latitudes, the maximum seasonal biophysical Ta warming or cooling only accounts for approximately \(10\%\) of the equivalent climate effect of carbon sequestration in terms of magnitude, whereas the ratio for the biophysical Ts effect can reach \(40\%\) . These results highlight that Ts- based assessments may significantly overestimate the local climate impact of tree cover change. We also emphasize that when evaluating the biophysical effects of forestation or deforestation, the proper temperature metric should be specified and used in different cases to avoid misleading conclusions. + +<|ref|>text<|/ref|><|det|>[[149, 357, 294, 372]]<|/det|> +### Introduction + +<|ref|>text<|/ref|><|det|>[[149, 376, 850, 410]]<|/det|> +1. 26 - reference 5: there is a new version of this paper by the same authors: https://doi.org/10.1038/s41586-024-07602-x + +<|ref|>text<|/ref|><|det|>[[149, 413, 753, 429]]<|/det|> +Response: Thanks for the careful reading. We have updated the reference (Line 598): + +<|ref|>text<|/ref|><|det|>[[149, 434, 238, 448]]<|/det|> +Reference: + +<|ref|>text<|/ref|><|det|>[[149, 454, 824, 471]]<|/det|> +5. Pan, Y. et al. The enduring world forest carbon sink. Nature 631, 563-569 (2024). + +<|ref|>text<|/ref|><|det|>[[149, 498, 850, 532]]<|/det|> +1. 39 - some more introduction on local, non-local, and global effects would be nice. There is quite some work from the group of Julia Pongratz on this topic. + +<|ref|>text<|/ref|><|det|>[[149, 538, 850, 572]]<|/det|> +Response: Thanks for the constructive comment. We added an introduction about non- local and global effects (Line 40): + +<|ref|>text<|/ref|><|det|>[[183, 578, 850, 650]]<|/det|> +Forest changes also affect the temperature of spatial nearby regions through advective transport, and even global temperature via altering the large- scale circulation patterns14. The magnitude of this non- local effect depends on the area extent and the geolocation of the changes15,16. + +<|ref|>sub_title<|/ref|><|det|>[[149, 662, 238, 677]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 683, 839, 718]]<|/det|> +14. Pongratz, J. et al. Land Use Effects on Climate: Current State, Recent Progress, and Emerging Topics. Curr. Clim. Chang. Reports 7, 99 - 120 (2021). + +<|ref|>text<|/ref|><|det|>[[149, 722, 830, 775]]<|/det|> +15. Winckler, J., Lejeune, Q., Reick, C. H. & Pongratz, J. Nonlocal Effects Dominate the Global Mean Surface Temperature Response to the Biogeophysical Effects of Deforestation. Geophys. Res. Lett. 46, 745 - 755 (2019). + +<|ref|>text<|/ref|><|det|>[[149, 781, 820, 834]]<|/det|> +16. Winckler, J., Reick, C. H. & Pongratz, J. Why does the locally induced temperature response to land cover change differ across scenarios? Geophys. Res. Lett. 44, 3833 - 3840 (2017). + +<|ref|>text<|/ref|><|det|>[[150, 861, 380, 876]]<|/det|> +1. 54 - which limitations? + +<|ref|>text<|/ref|><|det|>[[147, 883, 850, 899]]<|/det|> +Response: Thanks for the comment. We have revised the sentences to clarify the limitation (Line + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 86, 179, 100]]<|/det|> +63): + +<|ref|>text<|/ref|><|det|>[[182, 106, 851, 236]]<|/det|> +According to the report of the Intergovernmental Panel on Climate Change (IPCC), the indicator used to describe global land warming and frame climate change mitigation targets is near surface air temperature (Ta) rather than Ts36. Despite the strong correlation between Ts and Ta37, the Ts effect of forest change may significantly differ from the Ta effect38. Ts- based assessments are useful for model refinement or informing the sign of Ta effects, but the values cannot be directly considered in climate treaties or policies. + +<|ref|>sub_title<|/ref|><|det|>[[149, 241, 237, 256]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 261, 851, 315]]<|/det|> +36. Intergovernmental Panel on Climate Change. Changing State of the Climate System. in Climate Change 2021 - The Physical Science Basis 287 - 422 (Cambridge University Press, 2023). doi:10.1017/9781009157896.004. + +<|ref|>text<|/ref|><|det|>[[149, 319, 851, 373]]<|/det|> +37. Wang, Y. R., Hessen, D. O., Samset, B. H. & Stordal, F. Evaluating global and regional land warming trends in the past decades with both MODIS and ERA5-Land land surface temperature data. Remote Sens. Environ. 280, 113181 (2022). + +<|ref|>text<|/ref|><|det|>[[149, 377, 851, 431]]<|/det|> +38. Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1-15 (2011). + +<|ref|>text<|/ref|><|det|>[[149, 454, 849, 490]]<|/det|> +1. 57 - Note that the IPCC actually always talks about LSAT, land surface air temperature, and not surface temperature. + +<|ref|>text<|/ref|><|det|>[[148, 495, 849, 530]]<|/det|> +Response: Thanks for pointing this out. We have highlighted the temperature used in IPCC reports (Line 64): + +<|ref|>text<|/ref|><|det|>[[181, 534, 849, 589]]<|/det|> +According to the report of the Intergovernmental Panel on Climate Change (IPCC), the indicator used to describe global land warming and frame climate change mitigation targets is land surface air temperature (Ta) rather than Ts36. + +<|ref|>sub_title<|/ref|><|det|>[[149, 594, 237, 608]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 614, 850, 669]]<|/det|> +36. Intergovernmental Panel on Climate Change. Changing State of the Climate System. in Climate Change 2021 - The Physical Science Basis 287 - 422 (Cambridge University Press, 2023). doi:10.1017/9781009157896.004. + +<|ref|>text<|/ref|><|det|>[[148, 694, 849, 767]]<|/det|> +1. 58 - citation 34: there is a new report, also the citation seems wrong? at least the one I find has a different citation: https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_Chapter02_FIN AL.pdf + +<|ref|>text<|/ref|><|det|>[[145, 778, 848, 795]]<|/det|> +Response: We thank the reviewer for the careful reading. We have updated the reference (Line 665): + +<|ref|>sub_title<|/ref|><|det|>[[149, 807, 237, 821]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 827, 850, 881]]<|/det|> +36. Intergovernmental Panel on Climate Change. Changing State of the Climate System. in Climate Change 2021 - The Physical Science Basis 287 - 422 (Cambridge University Press, 2023). doi:10.1017/9781009157896.004. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 120]]<|/det|> +1.60 you criticize the sparse distribution of study sites in other studies, are the used study sites better distributed? + +<|ref|>text<|/ref|><|det|>[[149, 125, 850, 179]]<|/det|> +Response: Thanks for this critical comment. The distribution of paired sites is limited in Europe and North America (Chen et al., 2018). Here, the proposed methodology makes full use of more than 100 sites spread across five continents. + +<|ref|>sub_title<|/ref|><|det|>[[149, 192, 227, 205]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 211, 820, 265]]<|/det|> +Chen, L., Dirmeyer, P.A., Guo, Z., Schultz, N.M., 2018. Pairing FLUXNET sites to validate model representations of land- use/land- cover change. Hydrol. Earth Syst. Sci. 22, 111- 125. https://doi.org/10.5194/hess- 22- 111- 2018 + +<|ref|>text<|/ref|><|det|>[[149, 271, 832, 287]]<|/det|> +We have highlighted the limitation of the current paired site in the revised manuscript (Line 68): + +<|ref|>text<|/ref|><|det|>[[184, 297, 850, 369]]<|/det|> +Although a few studies have explored the different responses of these two temperatures in the context of forest change, their results may be affected by the uncertainties in numerical models or the sparse distribution of paired forest and non- forest sites. + +<|ref|>text<|/ref|><|det|>[[149, 402, 848, 437]]<|/det|> +1. \(67 = 100\%\) increase in tree cover, what does that mean? What is the spatial moving window approach in that regard? + +<|ref|>text<|/ref|><|det|>[[148, 442, 850, 534]]<|/det|> +Response: Thanks for the comments. First, the hypothetical tree cover gain from 0 to \(100\%\) indicates an ideal forest change. The evaluated \(\delta \mathrm{Ts}^{\mathrm{bph}}\) or \(\delta \mathrm{Ta}^{\mathrm{bph}}\) is based on this ideal change regardless of the existing tree cover. Second, according to your comment below, we used the "spatial- for- time analogy" to replace "the spatial moving window" for clarity (Line 76). We also added a schematic figure to show how the methodology works (Supplementary Fig. 1). + +<|ref|>text<|/ref|><|det|>[[184, 538, 850, 592]]<|/det|> +We first estimated the biophysical Ts and Ta sensitivity to a hypothetical \(100\%\) increase in tree cover (denoted as \(\delta \mathrm{Ts}^{\mathrm{bph}}\) and \(\delta \mathrm{Ta}^{\mathrm{bph}}\) ) at the \(0.25^{\circ}\) scale, based on the space- for- time analogy (Supplementary Fig. 1) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[211, 92, 784, 520]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 533, 852, 660]]<|/det|> +
Fig. S1. Schematic representation of the methodology for estimating land surface temperature (Ts) or air temperature (Ta) sensitivity to tree cover change ( \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) ). (a–f) The example grid (59.75°–60°N, 63.5°–63.75°E) with positive \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) in January 2010. (a) True color image of the 0.25° grid. (b) GLOBMAP 2010 tree cover map. (c) Mean Ts of January 2010. (d) Mean \(T_{a}\) of January 2010. (e) Linear regression for estimating positive \(\delta T_{s}^{bph}\) of the grid. (f) Linear regression for estimating positive \(\delta T_{a}^{bph}\) of the grid. (g–l) Similar to (a–f), but for the other example grid (44.75°–45°N, 38°–38.25°E) with negative sensitives in July 2010.
+ +<|ref|>text<|/ref|><|det|>[[148, 686, 850, 721]]<|/det|> +1. 67 not a big deal, but kind of strange that it's always "biophysical" but the abbreviation is "bgp" which I guess stands for biogeophysical + +<|ref|>text<|/ref|><|det|>[[148, 727, 850, 761]]<|/det|> +Response: Thank you for pointing this out. We have changed the superscript to "bph" as the abbreviation for biophysical for clarity. + +<|ref|>text<|/ref|><|det|>[[148, 788, 850, 859]]<|/det|> +1. 70 – globally distributed – you mean FLUXNET, right? Just mention this here. Globally distributed suggests that they are somewhat uniformly distributed across the globe, but Fluxnet has big biases towards certain regions (East Asia, North America, Europe). + +<|ref|>text<|/ref|><|det|>[[148, 866, 855, 902]]<|/det|> +Response: Following your suggestion, we have revised the data statements (Line 84): Furthermore, we use the FLUXNET2015 dataset45 and two gridded temperature + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[183, 85, 850, 120]]<|/det|> +datasets to validate the differences between two sensitivities and elucidate the underlying biophysical mechanisms. + +<|ref|>text<|/ref|><|det|>[[149, 126, 238, 141]]<|/det|> +Reference: + +<|ref|>text<|/ref|><|det|>[[149, 146, 850, 182]]<|/det|> +45. Pastorello, G. et al. The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data. Sci. Data 7, 1 - 27 (2020). + +<|ref|>text<|/ref|><|det|>[[149, 208, 850, 262]]<|/det|> +1. 72 - spatially gap fill: you mean to extrapolate to the globe? Response: Thanks for the comment. According to the suggestion of reviewer #3, the analyses based on sensitivity extrapolation are removed. The related descriptions and results are deleted. + +<|ref|>text<|/ref|><|det|>[[149, 289, 845, 323]]<|/det|> +also not a big deal, but your use of tenses is inconsistent. Sometimes present, sometimes past. + +<|ref|>text<|/ref|><|det|>[[149, 326, 796, 342]]<|/det|> +Response: Thanks for the careful reading. We have unified the tenses into the present tense. + +<|ref|>text<|/ref|><|det|>[[149, 369, 808, 385]]<|/det|> +I am missing a clear definition of T_a which is, I assume, 2m above ground. + +<|ref|>text<|/ref|><|det|>[[148, 389, 851, 500]]<|/det|> +Response: Thanks for raising this important question. The evaluated Ta is not exactly the air temperature 2 m above the ground, but the air temperature above the land surface (or underlying surface) (Zhang et al., 2022). Here, land surface indicates the interface layer between different land surface components and the atmosphere (e.g., tree canopy, rooftops and soil) (Reiners et al., 2023). Thus, for forested areas, Ta refers to the air temperature of about 2 m above the tree canopy; while for openlands, Ta is approximately air temperature 2 m above the ground. + +<|ref|>text<|/ref|><|det|>[[149, 505, 234, 519]]<|/det|> +References: + +<|ref|>text<|/ref|><|det|>[[149, 525, 850, 578]]<|/det|> +Reiners, P., Sobrino, J., Kuenzer, C., 2023. Satellite- Derived Land Surface Temperature Dynamics in the Context of Global Change — A Review. Remote Sens. 15. https://doi.org/10.3390/rs15071857 + +<|ref|>text<|/ref|><|det|>[[149, 584, 852, 637]]<|/det|> +Zhang, T., Zhou, Y., Zhao, K., Zhu, Z., Chen, G., Hu, J., Wang, L., 2022. A global dataset of daily maximum and minimum near- surface air temperature at 1km resolution over land (2003- 2020). Earth Syst. Sci. Data 14, 5637 - 5649. https://doi.org/10.5194/essd- 14- 5637- 2022 + +<|ref|>text<|/ref|><|det|>[[149, 665, 688, 681]]<|/det|> +In the revised manuscript, we gave the definition of Ta for clarity (Line 78): + +<|ref|>text<|/ref|><|det|>[[183, 686, 850, 758]]<|/det|> +Notably, the evaluated Ts indicates the radiometric temperature of the land surface, and Ta indicates the air temperature at 2 m above the land surface (Supplementary Fig. 2). The land surface here refers to the interface layer between different land components and the atmosphere (e.g. vegetation canopy). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[277, 85, 725, 355]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[157, 365, 840, 401]]<|/det|> +
Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).
+ +<|ref|>text<|/ref|><|det|>[[150, 427, 743, 444]]<|/det|> +We also added descriptions of the air temperature in the method section (Line 397): + +<|ref|>text<|/ref|><|det|>[[183, 448, 851, 522]]<|/det|> +The other temperature metric used for assessment is Ta, the air temperature at approximately \(2m\) above the interface layer between land components and the atmosphere. Specifically, for forested areas, the reference plane is the canopy, whereas for openlands the reference plane is approximately the ground. + +<|ref|>text<|/ref|><|det|>[[148, 554, 249, 568]]<|/det|> +### Results + +<|ref|>text<|/ref|><|det|>[[148, 572, 658, 608]]<|/det|> +1. 87 very nice, this comparison with the Duveiller paper. Response: Thanks for the positive comment. + +<|ref|>text<|/ref|><|det|>[[148, 634, 561, 650]]<|/det|> +1. 89 why is it called the "local" effect here. + +<|ref|>text<|/ref|><|det|>[[148, 655, 850, 709]]<|/det|> +Response: Thanks for the comment. We emphasize the effects "local" to distinguish them from non- local effects of tree restoration, which are not included in our RS- based analysis. We have rearranged the sentence for clarity (Line 105): + +<|ref|>text<|/ref|><|det|>[[182, 714, 850, 787]]<|/det|> +In terms of the magnitude, \(\delta T a^{b p h}\) demonstrates much lower absolute values compared to \(\delta T s^{b p h}\) (- 0.14 K ± 0.40 K vs. - 0.65 ± 1.22 K, global mean ± standard deviation), indicating that the local Ta effect of tree restoration is approximately 22% of the Ts effect. + +<|ref|>text<|/ref|><|det|>[[148, 813, 610, 829]]<|/det|> +1. 92 I am confused, should it be \(+0.17\mathrm{K}\) vs \(+0.53\mathrm{K}\) ? + +<|ref|>text<|/ref|><|det|>[[148, 832, 728, 848]]<|/det|> +Response: Thanks for the careful reading. We have corrected the typo (Line 110): + +<|ref|>text<|/ref|><|det|>[[180, 852, 850, 888]]<|/det|> +At northern high- latitudes, the Ta- based warming induced by tree cover change is 32% of the \(T_{s}\) - based warming (0.17 K vs. 0.53 K). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 648, 123]]<|/det|> +1. 95 nice that you did this with multiple data products Response: Thank you for recognizing our work. + +<|ref|>text<|/ref|><|det|>[[147, 150, 647, 189]]<|/det|> +1. 116 I like that you did this analysis for min and max Response: Thanks for the positive comment. + +<|ref|>text<|/ref|><|det|>[[147, 214, 850, 250]]<|/det|> +1. 119 - I find it notable that for the max temp, even in boreal regions there is always cooling. This is important for applications / policy I believe + +<|ref|>text<|/ref|><|det|>[[147, 254, 850, 290]]<|/det|> +Response: Thank you for pointing this out. We have emphasized this result in the discussion section (Line 341): + +<|ref|>text<|/ref|><|det|>[[182, 293, 851, 404]]<|/det|> +In particular, the diurnal and seasonal changes in biophysical temperature effects should be considered when formulating comprehensive forest- based policies. For instance, we observe maximum temperature cooling and minimum temperature warming effects of forests at high- latitudes. This suggests that tree restoration in such cold regions may be a solution to reduce the risks or impacts of daytime warming on the ecosystem. + +<|ref|>text<|/ref|><|det|>[[148, 429, 850, 465]]<|/det|> +1. 132 - why is this called the "ideal" temperature effect? Aren't you just doing the same exercise but now for observational data and not RS data? + +<|ref|>text<|/ref|><|det|>[[148, 469, 851, 523]]<|/det|> +Response: We call the effect "ideal" because it is inferred from the observations from forest and non- forest sites, and the land cover changes do not actually occur. To avoid ambiguity, we have revised the sentence (Line 149): + +<|ref|>text<|/ref|><|det|>[[183, 528, 851, 601]]<|/det|> +To ensure the robustness of our findings, especially the relative magnitude of Ta effects to Ts effects, we further validate the RS- based \(\delta \mathrm{T}s^{bph}\) and \(\delta \mathrm{T}a^{bph}\) against the temperature effects of forestation \((\delta \mathrm{T}s^{bph*}\) and \(\delta \mathrm{T}a^{bph*}\) ) inferred from the in- situ observations and gridded temperature data. + +<|ref|>text<|/ref|><|det|>[[148, 611, 850, 666]]<|/det|> +Second, the validation based on FLUXNET observations is not exactly analogous to the method used for RS data. We provided a figure to illustrate how it works (Supplementary Fig. 8), which consists of the following steps: + +<|ref|>text<|/ref|><|det|>[[147, 670, 851, 900]]<|/det|> +(1) We first subtract elevation-corrected gridded temperature data from FLUXNET Ts or Ta. Here, the gridded data mainly reflect the macro-climate; FLUXNET Ts or Ta are driven by both the macro-climate and the land use. Thus, their difference represent the relative impact of land cover on local Ts or Ta (Novick and Barnes, 2023). +(2) We then calculate the difference between corrected FLUXNET Ts or Ta in forest sites and non-forest sites ( \(\mathbf{x}_{\mathrm{f}}\) and \(\mathbf{x}_{\mathrm{o}}\) in Fig. S8). The difference values represent the impact of potential forestation on Ts or Ta (non-forest converting to forest). Notably, we calculate this difference at each \(10\mathrm{w / m}^2\) shortwave radiation (SWd) bin to represent the temperature effect of forestation under changing radiative conditions. +(3) We estimate the relationship between shortwave radiation and the Ts or Ta effects from both RS and in-situ data (e.g. Fig 2a and 2b). We compare the regression results to validate (a) whether the variation in RS-based Ts and Ta sensitivity with radiation are quantitatively aligned with the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 850, 120]]<|/det|> +in- situ results. (b) whether the relative magnitude of RS- based Ta effects to Ts effects is supported by in- situ results. + +<|ref|>image<|/ref|><|det|>[[210, 131, 785, 562]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[152, 574, 845, 609]]<|/det|> +
Fig. S8. Flow chart of the remote sensing (RS)-based local temperature effect validation using FLUXNET and gridded temperature data.
+ +<|ref|>sub_title<|/ref|><|det|>[[149, 642, 227, 656]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 662, 850, 715]]<|/det|> +Novick, K.A., Barnes, M.L., 2023. A practical exploration of land cover impacts on surface and air temperature when they are most consequential. Environ. Res. Clim. 2, 025007. https://doi.org/10.1088/2752- 5295/accdf9 + +<|ref|>sub_title<|/ref|><|det|>[[150, 743, 293, 758]]<|/det|> +## 1. 134 gradient? + +<|ref|>text<|/ref|><|det|>[[149, 764, 850, 798]]<|/det|> +Response: Thanks for the careful reading. We have replaced "gradient" by "bins" for clarity (Line 153): + +<|ref|>text<|/ref|><|det|>[[183, 803, 850, 858]]<|/det|> +Here, \(\delta T s^{b p h *}\) and \(\delta T a^{b p h *}\) are estimated in different shortwave radiation (SWd) bins to represent the relative changes with changing background radiation conditions (Methods, Supplementary Fig. 8). + +<|ref|>text<|/ref|><|det|>[[145, 883, 848, 900]]<|/det|> +Fig 2b) provide n, and indicate that this is from fluxnet data. Is a line plot + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 120]]<|/det|> +ok here? I think you should plot the actual data points, FLUXNET should be around 100- 200 data points if I am not mistaken. + +<|ref|>text<|/ref|><|det|>[[148, 125, 850, 160]]<|/det|> +Response: Thanks for the suggestions. First, we noted that the date is from FLUXNET in the figure caption (Line 166). + +<|ref|>text<|/ref|><|det|>[[182, 164, 850, 201]]<|/det|> +(b) FLUXNET-based relationships between the mean temperature sensitivities \((\delta T s^{b p h *}\) and \(\delta T a^{b p h *}\) ) and SWd. + +<|ref|>text<|/ref|><|det|>[[148, 211, 851, 322]]<|/det|> +Second, the line plots in Fig.2b show the estimated \(\delta T s^{b p h *}\) or \(\delta T a^{b p h *}\) values rather than the original FLUXNET data. The forest and openland samples used to estimate each data point of the line plot have different sample sizes n. Hence, it is difficult to label n in the figure. For clarity, we here provide raw data (including forest n and openland n for each data point) for Figures 2b and 2d. The file, named "Raw_data_for_Fig2.xlsx", will be published with the article if the manuscript can be accepted. + +<|ref|>text<|/ref|><|det|>[[148, 347, 515, 363]]<|/det|> +Why is it only mean and max, and not min? + +<|ref|>text<|/ref|><|det|>[[147, 368, 840, 386]]<|/det|> +Response: Thank you for the comment. We have added minimum temperature results (Line 184): + +<|ref|>text<|/ref|><|det|>[[183, 387, 851, 488]]<|/det|> +We also perform similar analyses to the site- based minimum Ta and Ts sensitivities \((\delta T s_{min}^{b p h *}\) and \(\delta T a_{min}^{b p h *}\) , Supplementary Fig. 10), which supports the lower Ta- based warming than Ts- based warming during the nighttime in the RS- based results. We note that the relationship between \(\delta T a_{min}^{b p h *}\) and SWd is not significant, which corresponds to the weak correlation between \(\delta T a_{min}^{b p h}\) and SWd in the RS- based results \((r = - 0.38)\) . + +<|ref|>image<|/ref|><|det|>[[260, 503, 736, 758]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 767, 851, 895]]<|/det|> +
Fig. S10. Validation of the monthly minimum land surface temperature and air temperature sensitivities. (a) Remote sensing-based relationships between minimum temperature sensitivities \((\delta T s_{min}^{b p h}\) and \(\delta T a_{min}^{b p h}\) ) and background shortwave radiation \((SW_{d})\) . (b) FLUXNET-based relationships between minimum temperature sensitivities \((\delta T s_{min}^{b p h *}\) and \(\delta T a_{min}^{b p h *}\) ) with SWd, using Climatic Research Unit (CRU) temperature data to exclude the impact of macro-climate background. (c) Same as (b), but the Berkeley Earth Surface Temperatures (BEST) data are used to exclude the impact of macro-climate background.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 845, 125]]<|/det|> +The usage of different y scales is quite misleading here. This should be changed. Response: Thank you for this comment. We have unified the y scales (Fig. 2). + +<|ref|>image<|/ref|><|det|>[[220, 132, 780, 435]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[448, 447, 546, 463]]<|/det|> +
Figure 2. ...
+ +<|ref|>text<|/ref|><|det|>[[150, 489, 443, 504]]<|/det|> +Is this now monthly mean and max? + +<|ref|>text<|/ref|><|det|>[[148, 510, 850, 546]]<|/det|> +Response: Thank you for this comment. Yes, the data for validation are at the monthly scale. We have declared the temporal scale in the figure caption (Line 164): + +<|ref|>text<|/ref|><|det|>[[180, 550, 850, 585]]<|/det|> +Figure 2. Validation of the monthly land surface temperature and air temperature sensitivities. + +<|ref|>text<|/ref|><|det|>[[148, 611, 850, 647]]<|/det|> +Why not a figure like 1c for the sites? This would be a convincing comparison between RS and site data. + +<|ref|>text<|/ref|><|det|>[[148, 652, 850, 725]]<|/det|> +Response: Thank you for the suggestion about the visualization. Here, the FLUXNET- based sensitivities ( \(\delta \mathrm{T}\mathrm{s}^{\mathrm{bph}*}\) and \(\delta \mathrm{T}\mathrm{a}^{\mathrm{bph}*}\) ) are calculated at different radiation bins and thus do not represent the results of specific geo- locations or latitudes. Thus, these results are unlikely to be presented in the manner of Fig. 1c. + +<|ref|>text<|/ref|><|det|>[[148, 750, 850, 804]]<|/det|> +1. 143 thank you for providing this disclaimer. can you also provide what the revisit times are? Is it from the MODIS with 4 visits per day? And here you mean occurrence of _daily_maximum temperature? + +<|ref|>text<|/ref|><|det|>[[148, 809, 850, 844]]<|/det|> +Response: Thank you for the comments. We have added the overpass time and the word "daily" as you suggested (Line 176): + +<|ref|>text<|/ref|><|det|>[[183, 849, 850, 903]]<|/det|> +The slopes derived from in- situ measurements are more pronounced than RS- based results, which may be due to the satellite overpass times (about 13:30, see Methods) not precisely coinciding with the occurrence of daily maximum temperatures. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 752, 101]]<|/det|> +We also provide four overpass times of MODIS Ts in the method section (Line 390): + +<|ref|>text<|/ref|><|det|>[[181, 106, 850, 160]]<|/det|> +Here, the monthly mean Ts data of 2010 is generated by the daily four observations from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua satellites (observed at 1:30, 10:30, 13:30 and 22:30). + +<|ref|>text<|/ref|><|det|>[[149, 186, 848, 221]]<|/det|> +Section "Biophysical mechanisms..." is a very nice section but needs some more work to clear things up. + +<|ref|>text<|/ref|><|det|>[[149, 227, 850, 280]]<|/det|> +Fig 3 - very interesting figure, unfortunately rather low n, but I guess there's nothing to do about that. I however still do not understand why it is now about 2m above the canopy. Should it not be 2m above the ground that is relevant? + +<|ref|>text<|/ref|><|det|>[[149, 285, 850, 320]]<|/det|> +Response: Thanks for raising the concern. The evaluated Ta indicates the air temperature above the tree canopy in the forested area. Please refer to the response above about the definition of Ta. + +<|ref|>text<|/ref|><|det|>[[148, 325, 851, 454]]<|/det|> +We admit that the air temperature 2 m above ground (usually below the tree canopy) is relevant for many organisms or processes within forests. However, the evaluated Ta is also important, because (a) Ta is close to the definition of 'Tas' in climate models (the inferred temperature at 2 m above zero- plane displacement height), which is used to assess climate change (Winckler et al., 2019). (b) Ta is more relevant to boundary layer dynamics, rainfall initiation, and interaction between the climate system and land surface (Novick and Katul, 2020). Therefore, we believe that the evaluated Ta is a highly relevant indicator for climate change and land- atmosphere interaction. + +<|ref|>sub_title<|/ref|><|det|>[[149, 465, 234, 479]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[149, 483, 850, 555]]<|/det|> +Winckler, J., Reick, C.H., Luyssaert, S., Cescatti, A., Stoy, P.C., Lejeune, Q., Raddatz, T., Chlond, A., Heidkamp, M., Pongratz, J., 2019. Different response of surface temperature and air temperature to deforestation in climate models. Earth Syst. Dyn. 10, 473 - 484. https://doi.org/10.5194/esd-10-473-2019 + +<|ref|>text<|/ref|><|det|>[[149, 560, 850, 613]]<|/det|> +Novick, K.A., Katul, G.G., 2020. The Duality of Reforestation Impacts on Surface and Air Temperature. J. Geophys. Res. Biogeosciences 125, 1 - 15. https://doi.org/10.1029/2019JG005543 + +<|ref|>text<|/ref|><|det|>[[149, 640, 850, 674]]<|/det|> +c) what is the Sum? The sum of all components? Why is it 0 then? Shouldn't it be the difference between 1.97 and 0.16K? + +<|ref|>text<|/ref|><|det|>[[148, 680, 850, 752]]<|/det|> +Response: Thank you for pointing this out. In the original manuscript, "Sum" means the simulated \(\delta \mathrm{Ta}^{\mathrm{bph}}\) , represented by the sum of \(\delta \mathrm{T}\mathrm{s}^{\mathrm{bph}}\) , \(\delta \mathrm{T}^{\mathrm{Ta}}\) and \(\delta \mathrm{T}^{\mathrm{H}}\) . The estimated value is close to but not exactly zero. Following your suggestion, we have replaced the bar "Sum" with the difference between \(\delta \mathrm{Ta}^{\mathrm{bph}}\) and \(\delta \mathrm{T}\mathrm{s}^{\mathrm{bph}}\) ("Diff"). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[228, 93, 761, 358]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 364, 850, 418]]<|/det|> +
Figure 3. ... (c) Bar plots of the mean air temperature sensitivity \((\delta T_{a}^{bph*})\) , land surface temperature sensitivity \((\delta T_{b}^{bph*})\) and their difference (Diff) contributed by variations in aerodynamic resistance \((\delta T^{ra})\) , and sensible heat \((\delta T^{H})\) ...
+ +<|ref|>text<|/ref|><|det|>[[147, 446, 822, 464]]<|/det|> +1. 169 but the 1.97 is so much higher than the reported 0.53 reported above? + +<|ref|>text<|/ref|><|det|>[[147, 468, 850, 541]]<|/det|> +Response: Thanks for your comment. The most likely reason for this difference is that the reported 0.53 K indicates the annual warming in high-latitude regions, and 1.97 K (1.63 K in the revised version) here indicates the winter warming in Europe. In addition, differences in the observation scales may contribute to the mismatches between RS-based and site-based results. + +<|ref|>text<|/ref|><|det|>[[147, 566, 850, 620]]<|/det|> +1. 173 - I am confused. Fig. 3a shows that the air temperature of forests is the same as the surface temperature for forests. Why then is the impact of forestation higher for surface temp compared to air temp (as was shown before)? + +<|ref|>text<|/ref|><|det|>[[147, 625, 850, 736]]<|/det|> +Response: Thanks for your comment. The main reason is that the temperature impact of forestation relies on both status in non- forest openland (before forestation) and forest (after forestation). Although the vertical variation in the forest temperature profile is less pronounced, we find significant temperature gradients between Ts and Ta in non- forest openlands. This gradient weakens the strong surface warming effect in Europe (Fig. 3a) or the strong summer cooling in North America and Australia (Fig. 3d and 3g). + +<|ref|>text<|/ref|><|det|>[[147, 760, 850, 814]]<|/det|> +1. 179 - steeper in openlands? In the figs, it is steeper in forests I would say? Response: Thank you for the valuable comment. We have revised the word "steeper" to avoid ambiguity (Line 208): + +<|ref|>text<|/ref|><|det|>[[183, 819, 849, 855]]<|/det|> +These factors collectively result in more significant temperature gradients in openlands, ... + +<|ref|>text<|/ref|><|det|>[[147, 880, 849, 897]]<|/det|> +1. 216 - where do the - 0.03K come from? More specifically, why is this not the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 138]]<|/det|> +- 0.14K as reported in the first section of the results in 1. 88? Is that the global average now? How does it compare to global average change in T_s? This should be a more prominent result. + +<|ref|>text<|/ref|><|det|>[[148, 142, 851, 288]]<|/det|> +Response: Thanks for your comment. According to the comment of reviewer #3, the biophysical and biochemical climate effect analyses of the potential tree restoration are removed. We have rewritten this section by comparing the concept of sensitivity (Line 245). This revision makes our results clearer that only local effects are evaluated and the non- local or global effects are not included. Similar to Windisch, et al., the current comparisons are based on the equivalent \(\mathrm{CO_2}\) uptake, rather than the temperature effect (K). The new results allow us to investigate the relative importance of the biophysical effect and reveal the overestimation of the biophysical climate effect using Ts (rather than the more relevant Ta) as the metric. + +<|ref|>sub_title<|/ref|><|det|>[[164, 314, 850, 348]]<|/det|> +## Comparison of biophysical with biochemical effects based on two temperature metrics + +<|ref|>text<|/ref|><|det|>[[165, 366, 836, 515]]<|/det|> +Most assessments of the climate benefits related to forestation have concentrated on the carbon sequestration (i.e., biochemical effects) \(^{52,53}\) . Here, the biomass carbon stock sensitivity to tree cover is estimated via space- for- time analogy and converted to \(\mathrm{CO_2}\) absorption equivalents \((\delta \mathrm{CO}_{2}e^{\mathrm{bchem}})\) to represent the biochemical effect. We also convert the biophysical Ts and Ta sensitivities to the metric of equivalent \(\mathrm{CO_2}\) uptake \((\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) and \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) , Supplementary Fig. 11). These allow the comparison of the local biophysical and biochemical climate effects and evaluation of the relative importance of the former. + +<|ref|>text<|/ref|><|det|>[[165, 531, 853, 679]]<|/det|> +The spatial map shows that \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) in tropical rainforests can exceed 600 t/ha, which is much greater than temperate and boreal forests (Fig. 4a). This suggests that restoring damaged forests in tropical regions has the most carbon benefit. Latitudinally, \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) at low- latitudes is higher than that at mid- or high- latitudes, with global mean of \(268.2 \pm 37.8\) t/ha (mean \(\pm\) uncertainty) (Fig. 4b). In terms of the biophysical effect, \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) (41.7 \(\pm\) 9.3 t/ha) provides a global average of \(15.7\%\) additional benefits to \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) (Fig. 4b). However, if the more relevant biophysical Ta effect is considered, the ratio of \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) (9.3 \(\pm\) 2.9 t/ha) to \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) is only \(3.5\%\) . + +<|ref|>text<|/ref|><|det|>[[165, 694, 864, 897]]<|/det|> +We then focus on northern high- latitudes, where tree restoration shows a biophysical warming effect. The resultant negative \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) could offset \(9.5\%\) of the \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) annually (Fig. 4b). The high- latitude biophysical warming is more pronounced in the cold season and can reduce the biochemical climate effect by \(42.4\%\) in March (Fig. 4c). However, when \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) is used as the indicator, the offset of biophysical to biochemical effects is only \(3.3\%\) at the annual scale, with the maximum monthly value of \(10.6\%\) (February) (Fig. 4b and 4c). In mid- latitudes, the seasonal \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) can enhance \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) by up to \(33.7\%\) (northern hemisphere) and \(40.5\%\) (southern hemisphere) during summer. However, these seasonal ratios are only about \(10\%\) considering \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) (Fig. 4d and 4f). In low- latitudes, annual positive \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ts}}\) is equivalent to \(25.5\%\) of \(\delta \mathrm{CO}_{2}e^{\mathrm{bchem}}\) , while the ratio for \(\delta \mathrm{CO}_{2}e^{\mathrm{bph,Ta}}\) is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[165, 85, 852, 175]]<|/det|> +only \(6.2\%\) , with insignificant seasonal variations (Fig. 4b and 4e). These results suggest that the relative importance of biophysical effects largely depends on the evaluated temperature metric, and the role of biophysical effects in the overall climate effect (usually measured by Ta) may not be as important as estimated in previous Ts- based studies22,23. + +<|ref|>image<|/ref|><|det|>[[220, 188, 787, 397]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[161, 406, 852, 572]]<|/det|> +
Figure 4. Comparison of the biophysical (bph) and biochemical (bchem) effects of potential tree cover gain. (a) Global pattern of the biochemical effect of potential tree cover gain ( \(\delta CO_2e^{bchem}\) ). (b) Global and latitudinal means of biochemical and biophysical effects of potential tree cover gain. The Ts-based and Ta-based biophysical effects are shown as the equivalent \(CO_2\) uptake ( \(\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) ). The error bars indicate the uncertainty of the mean. (c–f) Monthly ratios of Ta-based and Ts-based biophysical effects to equivalent biochemical effects across northern high-latitudes (>50°N), northern mid-latitudes (20°–50°N), tropics (20°S–20°N) and southern mid-latitudes (>20°S). The shaded area indicates the uncertainty of the ratios.
+ +<|ref|>sub_title<|/ref|><|det|>[[163, 594, 260, 608]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[163, 611, 808, 814]]<|/det|> +22. Windisch, M. G., Davin, E. L. & Seneviratne, S. I. Prioritizing forestation based on biogeochemical and local biogeophysical impacts. Nat. Clim. Chang. 11, 867–871 (2021). +23. Zhu, L. et al. Comparable biophysical and biogeochemical feedbacks on warming from tropical moist forest degradation. Nat. Geosci. 16, 244–249 (2023). +52. Walker, W. S. et al. The global potential for increased storage of carbon on land. Proc. Natl. Acad. Sci. U. S. A. 119, 1–12 (2022). +53. Lewis, S. L., Wheeler, C. E., Mitchard, E. T. A. & Koch, A. Restoring natural forests is the best way to remove atmospheric carbon. Nature 568, 25–28 (2019). + +<|ref|>text<|/ref|><|det|>[[147, 836, 849, 870]]<|/det|> +1. 214 – this gap-filling has not yet been explained, where do the gaps come from? + +<|ref|>text<|/ref|><|det|>[[147, 874, 850, 908]]<|/det|> +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the revision. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 106, 540, 122]]<|/det|> +1. 224 - unclear, "reverses to be negative"? + +<|ref|>text<|/ref|><|det|>[[148, 128, 850, 163]]<|/det|> +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the revision. + +<|ref|>text<|/ref|><|det|>[[148, 189, 850, 261]]<|/det|> +Fig 4. e) instead of the ratio, it would be more understandable if you put the actual biochemical temperature effect. I am also confused why the ratio is always in the same direction. Why would forestation in Russia have a negative biochemical temperature impact? + +<|ref|>text<|/ref|><|det|>[[148, 265, 850, 299]]<|/det|> +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the revision. + +<|ref|>text<|/ref|><|det|>[[149, 325, 373, 340]]<|/det|> +1. 245 - what about soil? + +<|ref|>text<|/ref|><|det|>[[148, 347, 848, 381]]<|/det|> +reforestation could potentially decrease soil carbon stocks (see, e.g., https://doi.org/10.1046/j.1354- 1013.2002.00486. x) + +<|ref|>text<|/ref|><|det|>[[148, 386, 850, 495]]<|/det|> +In general, it is crucial that studies do not neglect soil, they often store more carbon than the biomass. I know this is not the main point of the paper, but I find it worrying that our community is writing paper after paper talking about changes in biomass and soil carbon is not mentioned even once. Please add some sort of discussion somewhere regarding soil carbon. Since you use the method of Windisch2019, why not include their soil aspect as well? + +<|ref|>text<|/ref|><|det|>[[147, 500, 851, 685]]<|/det|> +Response: Thanks for raising this important issue regarding soil carbon. We admit that soil carbon is a crucial part when evaluating the biochemical effect of land cover changes. We did not include soil carbon like Windisch et al., because their analysis of relative SOC variation is based on the type conversion from forest to non- forest type (e.g. conversion of forest to cropland decreases SOC by \(26.6\% \pm 28.7\%\) ) (Sanderman et al., 2017), rather than the fractional tree cover changes. Since satellite observations do not provide direct estimations of soil carbon, we cannot obtain the soil carbon sensitivity to tree cover using the "space- for- time" method. Moreover, a recent study suggests that under the global tree restoration scenario, biomass change, rather than soil carbon change, is the main contributor to carbon sequestration (Veldman et al., 2019), despite the large amount of carbon stored in global soil. + +<|ref|>sub_title<|/ref|><|det|>[[148, 698, 227, 711]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[147, 715, 853, 900]]<|/det|> +Sanderman, J., Hengl, T., Fiske, G.J., 2017. Soil carbon debt of 12,000 years of human land use. Proc. Natl. Acad. Sci. U. S. A. 114, 9575 - 9580. https://doi.org/10.1073/pnas.1706103114Veldman, J.W., Aleman, J.C., Alvarado, S.T., Anderson, T.M., Archibald, S., Bond, W.J., Boutton, T.W., Buchmann, N., Buisson, E., Canadell, J.G., Dechoum, M. de S., Diaz- Toribio, M.H., Durigan, G., Ewel, J.J., Fernandes, G.W., Fidelis, A., Fleischman, F., Good, S.P., Griffith, D.M., Hermann, J.- M., Hoffmann, W.A., Le Stradic, S., Lehmann, C.E.R., Mahy, G., Nerlekar, A.N., Nippert, J.B., Noss, R.F., Osborne, C.P., Overbeck, G.E., Parr, C.L., Pausas, J.G., Pennington, R.T., Perring, M.P., Putz, F.E., Ratnam, J., Sankaran, M., Schmidt, I.B., Schmitt, C.B., Silveira, F.A.O., Staver, A.C., Stevens, N., Still, C.J., Strömberg, C.A.E., Temperton, V.M., Varner, J.M., Zaloumis, N.P., 2019. Comment on "The global tree restoration potential." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 128, 850, 163]]<|/det|> +Following your suggestion, we have added descriptions about soil carbon in the method section (Line 542): + +<|ref|>text<|/ref|><|det|>[[183, 166, 850, 248]]<|/det|> +Notably, \(\delta CO_{2}e^{bchem}\) provides a simple estimation of the ideal carbon stock in biomass under current climate and disturbance regimes for further comparison with the biophysical effect. The period for restored forests to reach such carbon potential, and the role of changing climate and soil carbon flux in this process are neglected. + +<|ref|>text<|/ref|><|det|>[[148, 258, 781, 275]]<|/det|> +We also added discussions about the impact of tree restoration on soil carbon (Line 323): + +<|ref|>text<|/ref|><|det|>[[183, 279, 851, 408]]<|/det|> +In addition, potential variations in soil carbon are ignored in the biochemical part. In contrast to increases in biomass, tree restoration could have positive and negative effects on soil carbon, depending on the climate background and the ecosystem type \(^{58 - 60}\) . At the global scale, forestation can increase soil organic carbon, but the value is highly uncertain \(^{61}\) . Neglecting the potential change in soil carbon may lead to a slight underestimation of the biochemical effect \(^{62}\) . The evaluated change in biomass should be the main contributor to carbon sequestration \(^{63}\) . + +<|ref|>sub_title<|/ref|><|det|>[[148, 420, 238, 434]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[148, 437, 850, 679]]<|/det|> +58. Deng, L., Zhu, G. yu, Tang, Z. sheng & Shangguan, Z. ping. Global patterns of the effects of land-use changes on soil carbon stocks. Glob. Ecol. Conserv. 5, 127 - 138 (2016). +59. Sanderman, J., Hengl, T. & Fiske, G. J. Soil carbon debt of 12,000 years of human land use. Proc. Natl. Acad. Sci. U. S. A. 114, 9575 - 9580 (2017). +60. Guo, L. B. & Gifford, R. M. Soil carbon stocks and land use change: A meta analysis. Glob. Chang. Biol. 8, 345 - 360 (2002). +61. Mo, L. et al. Integrated global assessment of the natural forest carbon potential. Nature 624, 92 - 101 (2023). +62. Li, Y. et al. Prioritizing Forestation in China Through Incorporating Biogeochemical and Local Biogeophysical Effects. Earth 's Futur. 12, 1 - 18 (2024). +63. Veldman, J. W. et al. Comment on "The global tree restoration potential". Science (80. ). 366, 1 - 5 (2019). + +<|ref|>text<|/ref|><|det|>[[148, 697, 575, 712]]<|/det|> +1. 248 - the -0.11K are now for air temperature? + +<|ref|>text<|/ref|><|det|>[[148, 716, 850, 750]]<|/det|> +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the updated content. + +<|ref|>text<|/ref|><|det|>[[148, 776, 846, 810]]<|/det|> +1. 251 - what do you mean with override? I think you mean a different word here. "exceed", maybe? + +<|ref|>text<|/ref|><|det|>[[148, 816, 850, 850]]<|/det|> +Response: Thanks for your comment. We have rewritten this section. Please refer to the response above for the updated content. + +<|ref|>text<|/ref|><|det|>[[148, 877, 275, 892]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[148, 896, 850, 912]]<|/det|> +1. 1, 281 - should prob cite Winckler2019 here because the non-local effects can + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 86, 444, 100]]<|/det|> +be even larger than local effects + +<|ref|>text<|/ref|><|det|>[[149, 107, 850, 141]]<|/det|> +Response: Thank you for your professional suggestion. We have added a sentence about the nonlocal effect and cited the reference (Line 309): + +<|ref|>text<|/ref|><|det|>[[150, 146, 848, 163]]<|/det|> +The non- local effect of forestation can even exceed the local effects in model simulations15. + +<|ref|>sub_title<|/ref|><|det|>[[149, 175, 238, 190]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[150, 193, 845, 247]]<|/det|> +15. Winckler, J., Lejeune, Q., Reick, C. H. & Pongratz, J. Nonlocal Effects Dominate the Global Mean Surface Temperature Response to the Biogeophysical Effects of Deforestation. Geophys. Res. Lett. 46, 745-755 (2019). + +<|ref|>text<|/ref|><|det|>[[148, 274, 544, 290]]<|/det|> +295 - good that you provide this explanation. + +<|ref|>text<|/ref|><|det|>[[149, 296, 464, 311]]<|/det|> +Response: Thanks for the positive comment. + +<|ref|>text<|/ref|><|det|>[[149, 338, 850, 409]]<|/det|> +1. 302 - but they are not that substantial anymore when considering T_a instead of T_s right? Generally, I find the wording a bit too positive. Your paper shows that the climate impact of tree planting is lower when considering the air temperature instead of the surface temperature. + +<|ref|>text<|/ref|><|det|>[[149, 414, 850, 468]]<|/det|> +Response: Thank you for the valuable suggestion. We have updated our results of comparison between Ts-based and Ta-based biophysical effects (please refer to the response above). We discussed the overestimation of biophysical climate effects based on Ts (Line 299): + +<|ref|>text<|/ref|><|det|>[[184, 480, 850, 552]]<|/det|> +Through the comparison of biophysical and biochemical effects, we find that using Ts as the indicator may overestimate the role of biophysical processes in the overall climate effect of forestation. The evaluation based on the more relevant Ta can present better policy guidance for prioritizing the location of forestation. + +<|ref|>text<|/ref|><|det|>[[149, 563, 708, 579]]<|/det|> +We also discussed the application for different temperature metrics (Line 329): + +<|ref|>text<|/ref|><|det|>[[183, 584, 851, 805]]<|/det|> +In the context of global climate change, Ts and Ta show comparable variation patterns and trend values37. However, when assessing the temperature effects of afforestation or deforestation, the Ts- based values can be about five times higher than the Ta- based values. This significant difference in magnitude highlights that attention should be given to the evaluated temperature metrics and the application scenarios when interpreting the biophysical effects of land cover changes. For instance, Ts (i.e. canopy temperature) could be the more appropriate metric when considering the effects of biophysical processes on ecosystem metabolism of photosynthesis, respiration, and transpiration38,64. Meanwhile, the more relevant Ta should be used in analyses related to regional climate adaptation of tree restoration. We highlight that this issue should be considered in future RS- based studies focusing on the thermal buffering effects of forests. + +<|ref|>sub_title<|/ref|><|det|>[[149, 816, 237, 830]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[149, 833, 840, 905]]<|/det|> +37. Wang, Y. R., Hessen, D. O., Samset, B. H. & Stordal, F. Evaluating global and regional land warming trends in the past decades with both MODIS and ERA5- Land land surface temperature data. Remote Sens. Environ. 280, 113181 (2022). +38. Mldrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[201, 85, 850, 120]]<|/det|> +air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1- 15 (2011). + +<|ref|>text<|/ref|><|det|>[[150, 122, 812, 177]]<|/det|> +64. Guo, Z. et al. Does plant ecosystem thermoregulation occur? An extratropical assessment at different spatial and temporal scales. New Phytol. (2022) doi:10.1111/nph.18632. + +<|ref|>text<|/ref|><|det|>[[148, 200, 852, 328]]<|/det|> +The discussion is missing the important point that forestation and forestry in general have numerous aspects outside of climate change mitigation that should not be forgotten over their climate impact because this can lead to bad strategies. The Bastin paper that you also base your research on was in part wrongly interpreted by the media, public, and politicians. It was understood in a way that we can simply plant our way out of the crisis. I therefore find it very important to briefly address this. + +<|ref|>text<|/ref|><|det|>[[148, 333, 850, 368]]<|/det|> +Some examples that come to mind, no need to add them all, but just to point you to some aspects: + +<|ref|>text<|/ref|><|det|>[[147, 370, 850, 500]]<|/det|> +- in many places, forests are not the ecosystem that "should be there" (see important work by Bond: https://10.1016/j.tree.2019.08.003, https://10.1126/science.aad5132) +- forests offer many ecosystem services, not only climate change mitigation +- tree planting can have negative ecological and economical impacts (e.g., https://doi.org/10.1126/science.abd3064 and https://10.1126/science.abc9892) + +<|ref|>text<|/ref|><|det|>[[149, 503, 850, 538]]<|/det|> +Response: Thanks for the professional and helpful comments. We have added discussions about the widespread impacts of forestation (Line 360): + +<|ref|>text<|/ref|><|det|>[[183, 542, 852, 670]]<|/det|> +Moreover, tree restoration can have numerous ecological, hydrological and economic impacts besides the assessed temperature effects. Restoration in inappropriate geolocations (e.g. tropical savannas) can have counterproductive consequences such as ecosystem degradation, biodiversity loss and water availability reduction68- 72. These impacts should be also taken into account in the development of comprehensive forest- related strategies to avoid the misconception that "restoring trees is the panacea for the current crisis". + +<|ref|>sub_title<|/ref|><|det|>[[149, 683, 247, 697]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[165, 700, 848, 865]]<|/det|> +68. Bond, W. J., Stevens, N., Midgley, G. F. & Lehmann, C. E. R. The Trouble with Trees: Afforestation Plans for Africa. Trends Ecol. Evol. 34, 963-965 (2019). +69. Bond, W. J. Ancient grasslands at risk. Science (80-). 351, 120-122 (2016). +70. Gómez-González, S., Ochoa-Hueso, R. & Pausas, J. G. Afforestation falls short as a biodiversity strategy. Science (80-). 368, 1439-1439 (2020). +71. Parr, C. L., te Beest, M. & Stevens, N. Conflation of reforestation with restoration is widespread. Science (80-). 383, 698-701 (2024). +72. Selva, N., Chylarecki, P., Jonsson, B.-G. & Ibisch, P. L. Misguided forest action in EU Biodiversity Strategy. Science (80-). 368, 1438-1439 (2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 157]]<|/det|> +The types of trees matter a lot, how is that accounted for? For instance, in temperate forests, if you reforest with broad- leafs, this will be much different then reforesting with needleleafs, especially regarding surface roughness in winter. How is that accounted for? + +<|ref|>text<|/ref|><|det|>[[148, 163, 850, 235]]<|/det|> +Response: Thanks for this professional comment. Since the temperature sensitivity is estimated by the local regression between tree cover and temperature observations, our results reflect the potential consequence of tree restoration with the native tree species. We have added descriptions in the revised manuscript (Line 435): + +<|ref|>text<|/ref|><|det|>[[183, 240, 850, 293]]<|/det|> +Notably, all the sensitivity results should be interpreted as the temperature consequences of restoration with native forest type, as the gridded tree cover data of existing species are used as inputs to the spatial regression model. + +<|ref|>text<|/ref|><|det|>[[148, 320, 655, 336]]<|/det|> +1. 321 - soil is \(250\mathrm{m}\) how was this aggregated to the \(1\mathrm{km}^2\) + +<|ref|>text<|/ref|><|det|>[[148, 342, 850, 394]]<|/det|> +Response: Thanks for the comment. This paragraph, describing how to estimate tree cover potential (ATC) using soil and climate data, is removed, since the tree cover potential related contents are no longer presented in the revised manuscript according to the comment of reviewer #3. + +<|ref|>text<|/ref|><|det|>[[148, 421, 850, 455]]<|/det|> +1. 326 - Fig S8 - why is there only one such figure as there are two TC_2020 datasets? Also, which of the two is shown? + +<|ref|>text<|/ref|><|det|>[[147, 461, 851, 533]]<|/det|> +Response: Thanks for raising this concern. In the original manuscript, we use tree cover data of 2020 to calculate tree restoration potential (ATC) under the current stage. According to the comment of reviewer #3, the analysis based on ATC is removed, and only tree cover data of 2010 are used for estimating the sensitivities (Supplementary Fig. 12). + +<|ref|>image<|/ref|><|det|>[[284, 572, 692, 846]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[183, 891, 850, 907]]<|/det|> +
Fig. S12. Global maps of fractional tree cover from (a) GLOBMap and (b) Global
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 125, 849, 160]]<|/det|> +1. 339 - mention that screen height is \(1.25\mathrm{m}\) to \(2\mathrm{m}\) above ground, I had to look this up. + +<|ref|>text<|/ref|><|det|>[[148, 166, 849, 201]]<|/det|> +Response: Thank you for the helpful suggestion. We have declared the physical meaning of assessed Ta here (Line 397): + +<|ref|>text<|/ref|><|det|>[[183, 205, 850, 278]]<|/det|> +The other temperature metric used for assessment is Ta, the air temperature at \(2\mathrm{m}\) above the interface layer between the land components and the atmosphere. Specifically, for forested areas, the reference plane is the canopy, whereas for openlands, the reference plane is approximately the ground. + +<|ref|>text<|/ref|><|det|>[[148, 304, 850, 357]]<|/det|> +1. 342 - can you provide a figure of the modeled vs observed Ta - a Response: Thanks for the suggestion. We have added the comparison between the satellite monthly mean Ta and FLUXNET monthly mean Ta measurements (Line 406): + +<|ref|>text<|/ref|><|det|>[[183, 362, 850, 415]]<|/det|> +Satellite monthly mean Ta and FLUXNET monthly mean Ta show good agreement. Validation results for forest and non- forest sites show comparable accuracy (Supplementary Fig. 13). + +<|ref|>image<|/ref|><|det|>[[270, 430, 727, 593]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 608, 850, 663]]<|/det|> +
Fig. S13. Validation of satellite monthly mean air temperature (Ta) of 2010. (a) Scatter plot between satellite monthly Ta and FLUXNET monthly \(T_{\mathrm{a}}\) measurements in forest sites. (b) Similar to (a), but for non-forest sites. Abbreviation: RMSE, root mean squared error.
+ +<|ref|>text<|/ref|><|det|>[[148, 686, 850, 740]]<|/det|> +1. 345 - mean = average of min and max? this seems quite odd to me. Especially with strong differences in daylength vs nightlength this does not seem like a valid way to get the mean temperature. + +<|ref|>text<|/ref|><|det|>[[147, 745, 850, 855]]<|/det|> +Response: Thanks for your comment. We compared the FLUXNET observations of (a) the mean of maximum and minimum Ta and (b) the daily mean Ta (Fig. R1). The comparison is performed at the monthly scale. The results show good overall agreement in either forest or non- forest sites (RMSE \(< 0.4\mathrm{K}\) ). In addition, for both cold months (with longer night length) and hot months (with longer day length), the scatter plots are also close to the 1:1 line, suggesting the method is robust to different day/night length conditions. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[270, 108, 727, 258]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 274, 850, 309]]<|/det|> +
Fig. R1. Comparison between max and min air temperature (Ta) and daily mean Ta using FLUXNET observations for (a) forest sites and (b) non-forest sites at the monthly scale.
+ +<|ref|>text<|/ref|><|det|>[[147, 332, 840, 367]]<|/det|> +1. 353 - is it really moving window? Or is the globe just gridded into \(0.25^{\circ}\) pixels? If it is moving window, what is the step size? + +<|ref|>text<|/ref|><|det|>[[147, 371, 850, 407]]<|/det|> +Response: Thanks for pointing this out. The regression is conducted for each \(0.25^{\circ}\) grid. We have removed the sentence about the moving window to avoid ambiguity. + +<|ref|>text<|/ref|><|det|>[[147, 433, 850, 468]]<|/det|> +1. 355 what is the impact? how many pixels are excluded? If it's a lot then this has an important impact on the importance of the results. + +<|ref|>text<|/ref|><|det|>[[147, 472, 852, 640]]<|/det|> +Response: Thank you for raising this concern. First, we set the threshold of tree cover \(>10\%\) for selecting the effective pixel for regression. This is because the temperature variations in low tree cover pixels may be induced by the rest non- forest land cover components. Using these pixels for regression may reduce the reliability of estimated temperature sensitivity. Second, for the pixels with tree cover \(>10\%\) , we exclude part of them with water cover \(>1\%\) and elevation difference \(>100 \mathrm{~m}\) . Here, we show the ratio of the excluded forest pixel number (due to water cover or elevation difference) to the total forest pixel number within each \(0.25^{\circ}\) grid (Fig. R2). Results show that the excluded pixel numbers are small across the globe ( \(< 5\%\) for most grids). Thus, the screening process may have limited impacts on our sensitivity results. + +<|ref|>image<|/ref|><|det|>[[315, 679, 692, 819]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 832, 850, 885]]<|/det|> +
Fig. R2. Fraction of excluded pixels due to water cover or elevation differences, defined as the number of abandoned forest pixels (tree cover \(>10\%\) ) divided by the number of all forest pixels within each \(0.25^{\circ}\) grid.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 508, 101]]<|/det|> +1. 357 I think there is an "and" missing + +<|ref|>text<|/ref|><|det|>[[149, 106, 767, 123]]<|/det|> +Response: Thanks for your careful reading. We have added the word "and" (Line 420): + +<|ref|>text<|/ref|><|det|>[[183, 128, 850, 163]]<|/det|> +The water coverage and elevation data are from Joint Research Center Global Surface Water Mapping Layers v1.4, and GMTED2010 datasets, respectively. + +<|ref|>text<|/ref|><|det|>[[149, 189, 460, 205]]<|/det|> +1. 361: for each 0.25 pixel, right? + +<|ref|>text<|/ref|><|det|>[[149, 211, 812, 227]]<|/det|> +Response: Thanks for pointing this out. We added the clarification about the scale (Line 424). + +<|ref|>text<|/ref|><|det|>[[183, 232, 850, 286]]<|/det|> +After the screening process, \(\delta T s^{b p h}\) and \(\delta T a^{b p h}\) can be estimated using a linear regression model between tree cover and corresponding temperature values for each \(0.25^{\circ}\) grid: + +<|ref|>text<|/ref|><|det|>[[149, 312, 850, 346]]<|/det|> +Formulas 1+2: Why not just write the formula of the linear model instead of the solution of the regression? + +<|ref|>text<|/ref|><|det|>[[147, 352, 844, 370]]<|/det|> +Response: Thanks for the helpful suggestion. We have revised the formulas for clarity (Line 425): + +<|ref|>equation<|/ref|><|det|>[[320, 377, 848, 430]]<|/det|> +\[\begin{array}{c}{{T s=\delta T s^{b p h}\times T C_{2010}+b_{s}}}\\ {{{}}}\\ {{T a=\delta T a^{b p h}\times T C_{2010}+b_{a}}}\end{array} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[183, 440, 562, 457]]<|/det|> +where, \(b_{s}\) and \(b_{a}\) are the regression intercepts. + +<|ref|>text<|/ref|><|det|>[[147, 487, 850, 522]]<|/det|> +Formulas 1+2: provide a plot for a pixel in the supplements, to understand the relationship + +<|ref|>text<|/ref|><|det|>[[147, 527, 850, 562]]<|/det|> +Response: Thank you for the valuable comment. We have added the schematic figure as you suggested (Supplementary Fig. 1). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[210, 92, 784, 520]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 532, 852, 660]]<|/det|> +
Fig. S1. Schematic representation of the methodology for estimating land surface temperature (Ts) or air temperature (Ta) sensitivity to tree cover change ( \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) ). (a–f) The example grid (59.75°–60°N, 63.5°–63.75°E) with positive \(\delta T_{s}^{bph}\) and \(\delta T_{a}^{bph}\) in January 2010. (a) True color image of the 0.25° grid. (b) GLOBMAP 2010 tree cover map. (c) Mean Ts of January 2010. (d) Mean \(T_{a}\) of January 2010. (e) Linear regression for estimating positive \(\delta T_{s}^{bph}\) of the grid. (f) Linear regression for estimating positive \(\delta T_{a}^{bph}\) of the grid. (g–l) Similar to (a–f), but for the other example grid (44.75°–45°N, 38°–38.25°E) with negative sensitives in July 2010.
+ +<|ref|>text<|/ref|><|det|>[[149, 686, 849, 720]]<|/det|> +1. 364 – what robustness? you mean that the formula is solvable, i.e., the matrix is invertible? + +<|ref|>text<|/ref|><|det|>[[148, 727, 850, 780]]<|/det|> +Response: Thanks for the comment. The small sample sizes may result in: (a) models that are sensitive to noise of the input data, and (b) estimated parameters that are unstable or have large uncertainties. We have revised the description for clarity (Line 427): + +<|ref|>text<|/ref|><|det|>[[185, 786, 518, 802]]<|/det|> +To ensure the reliability of the results, .... + +<|ref|>text<|/ref|><|det|>[[149, 828, 338, 844]]<|/det|> +1. 383 – "of" missing + +<|ref|>text<|/ref|><|det|>[[149, 847, 762, 863]]<|/det|> +Response: Thanks for the careful reading. We have added the missing "of" (Line 450): + +<|ref|>text<|/ref|><|det|>[[181, 868, 850, 903]]<|/det|> +The RS- based local temperature sensitivity can be validated through the differences of measurements between spatially adjacent paired forest and non- forest sites. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 106, 848, 141]]<|/det|> +1. 390 – BEST is at 1 degree resolution. So it’s not only land cover type impact but also elevation impact. How is that accounted for? + +<|ref|>text<|/ref|><|det|>[[147, 146, 851, 257]]<|/det|> +Response: Thanks for the constructive comment. We have made the additional elevation correction for the gridded temperature using (a) the difference between grid mean and corresponding site elevations, and (b) the lapse rate of the grid. The lapse rate is estimated by the local regression between the gridded temperatures and elevations within \(5 \times 5\) window. Due to modifications made to the methodology, all the related results are also updated, and the systematic biases in site results are eliminated. We also revised descriptions for the elevation correction (Line 458): + +<|ref|>text<|/ref|><|det|>[[183, 261, 851, 370]]<|/det|> +Here, we first make corrections to the gridded temperatures using the lapse rates to compensate for the elevation difference between the site and the corresponding grid. The lapse rate for the target grid is estimated by the regression slope of the gridded temperatures and elevations within the \(5 \times 5\) window. Then, by deducting the corrected gridded temperature data, the in- situ measurements can effectively represent the relative temperature effects attributable to different land cover types. + +<|ref|>text<|/ref|><|det|>[[147, 395, 852, 511]]<|/det|> +1. 446 – why to 2m above the canopy? Isn’t the goal to estimate 2m above ground? A figure would generally be good to visualize the difference in the temperatures... Response: Thanks for the comment. The target variable is the 2 m air temperature above the land surface. We have added a schematic figure about the temperature metrics (Supplementary Fig. 2). Please refer to the above responses for the definition and the importance of the evaluated temperature. + +<|ref|>image<|/ref|><|det|>[[277, 520, 723, 788]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[157, 797, 840, 832]]<|/det|> +
Fig. S2. Schematic representation of evaluated land surface temperature (Ts) and near surface air temperature (Ta).
+ +<|ref|>text<|/ref|><|det|>[[147, 858, 848, 893]]<|/det|> +1. 471 – I am unsure how Fig S6 relates to that. Instead, can you provide a figure comparing the non-gap-filled and the gap-filled maps? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 121]]<|/det|> +Response: Thanks for the comment. According to the comment of reviewer #3, the analyses based on gap- filled sensitivity and the related figures are removed. + +<|ref|>text<|/ref|><|det|>[[148, 146, 504, 163]]<|/det|> +1. 474 - why is this aggregation needed? + +<|ref|>text<|/ref|><|det|>[[148, 168, 811, 185]]<|/det|> +Response: Thanks for the comment. This sub- section about sensitivity gap- filling is removed. + +<|ref|>text<|/ref|><|det|>[[148, 210, 850, 265]]<|/det|> +1. 480 - how did you account for spatial auto- correlation? Training and testing data need to be independent, see https://www.nature.com/articles/s41467-022-29838-9 + +<|ref|>text<|/ref|><|det|>[[148, 270, 811, 287]]<|/det|> +Response: Thanks for the comment. This sub- section about sensitivity gap- filling is removed. + +<|ref|>text<|/ref|><|det|>[[149, 312, 469, 328]]<|/det|> +1. 504 - this is missing soil carbon + +<|ref|>text<|/ref|><|det|>[[148, 334, 850, 388]]<|/det|> +Response: Thanks for raising this important issue. We have clarified in the methodology that soil carbon is ignored and discussed the possible consequences in the discussion section. Please refer to the response above for the modifications. + +<|ref|>text<|/ref|><|det|>[[148, 414, 336, 429]]<|/det|> +### Code Availability + +<|ref|>text<|/ref|><|det|>[[148, 433, 850, 468]]<|/det|> +Why is the code available only on request? This should be made public, we need to make results reproducible. + +<|ref|>text<|/ref|><|det|>[[148, 470, 850, 505]]<|/det|> +Response: Thanks for raising this important issue. We have provided a Zenodo link to download the code (Line 561): + +<|ref|>sub_title<|/ref|><|det|>[[168, 511, 309, 526]]<|/det|> +## Code availability + +<|ref|>text<|/ref|><|det|>[[165, 532, 850, 567]]<|/det|> +The Python codes used to generate all the results are available at https://zenodo.org/uploads/14215398 + +<|ref|>text<|/ref|><|det|>[[148, 592, 530, 608]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[149, 611, 728, 627]]<|/det|> +The code is hard to review. There are no comments or explanations. + +<|ref|>text<|/ref|><|det|>[[148, 633, 850, 668]]<|/det|> +Response: Thanks for the careful reading. We have added a description file and comments to the code. + +<|ref|>text<|/ref|><|det|>[[148, 694, 850, 766]]<|/det|> +What I found strange was, that the code to reproduce Figure 1 only reads in images that contain the temperature- forestcover relation and plots them. But there is no code that created these images. I assume these were generated in GEE, but this code should also be made available. + +<|ref|>text<|/ref|><|det|>[[147, 772, 840, 789]]<|/det|> +Response: Thanks for the comment. We have uploaded the code file for the sensitivity estimation. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 99, 471, 115]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 133, 851, 427]]<|/det|> +This paper combines satellite data, and data from meteorological station and flux tower networks, to explore the extent to which reforestation confers a local air cooling benefit across the globe We have long known that reforestation leads to local surface cooling, at least in the tropic and temperate zones. So this adaptive benefit of reforestation is not exactly "overlooked" as the title of the paper suggests. However, because air temperature can not be directly measured from space, studies on the topic have tended to focus on patterns in surface temperature only, despite the fact that air temperature is arguably the more relevant target for adaptation. The authors acknowledge that some work has already attempted to address this knowledge gap, but I think that what the authors present in this paper is still a novel contribution. The show that forests likely lead to local air cooling, but the magnitude of the temperature change is less than the change in surface temperature. This is consistent with the other work done on the topic, including the nice study by Mildrexler et al. 2011 (which the authors don't cite but probably should, https://doi.org/10.1029/2010JG001486). + +<|ref|>text<|/ref|><|det|>[[149, 429, 849, 463]]<|/det|> +I did, however, have some significant comments and concerns about the framing and the methods. + +<|ref|>text<|/ref|><|det|>[[148, 469, 851, 560]]<|/det|> +Response: We appreciate the positive comments by the reviewer. We have carefully considered the critical comments, please see our detailed point- by- point responses below. In particular, we have updated the results and clarified the new contribution of this paper. Accordingly, we have revised the title to "Observed different impacts of potential tree restoration on local surface and air temperature". We also cited the reference as you suggested (Line 66): + +<|ref|>text<|/ref|><|det|>[[180, 564, 849, 599]]<|/det|> +Despite the strong correlation between Ts and Ta, the Ts effect of forest change may significantly differ from the Ta effect38. + +<|ref|>text<|/ref|><|det|>[[150, 603, 850, 657]]<|/det|> +38. Mildrexler, D. J., Zhao, M. & Running, S. W. A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests. J. Geophys. Res. Biogeosciences 116, 1-15 (2011). + +<|ref|>text<|/ref|><|det|>[[148, 690, 851, 911]]<|/det|> +[1] First, and perhaps most importantly, the air (or surface cooling) benefits of reforestation should not be referred to as "climate mitigation." Climate mitigation refers to efforts to reduce emissions and increase sinks for greenhouse gases. The direct modification of local temperature by forest restoration does neither of these. It can slow the pace of climate change in certain places by increasing sensible and latent heat fluxes. However, these mechanisms may simply represent the redistribution of energy within the climate system, and have the potential to enhance the pace of warming elsewhere. For example, energy used to evaporate water in a forested landscape is re- released when that water vapor condenses downwind. Likewise, greater sensible heat flux may increase lower temperatures near the surface but increase temperatures higher in the boundary layer. Thus, the direct local cooling benefits of reforestation + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 850, 120]]<|/det|> +should be described as "adaptation," not "mitigation," and discussion of the benefits should acknowledge the possibility for warming elsewhere. + +<|ref|>text<|/ref|><|det|>[[148, 125, 850, 198]]<|/det|> +Response: Thanks for this critical comment. We have checked through our manuscript and replaced "mitigation" with "adaption" when discussing the local biophysical effect on climate. We also highlighted that our results should be related to adaption rather than mitigation in the discussion section (Line 355): + +<|ref|>text<|/ref|><|det|>[[183, 203, 850, 293]]<|/det|> +From the perspective of the whole climate system, the non- radiative effects represent the redistribution of energy within the climate system and may lead to warming in downwind regions or the higher boundary layer67. Thus, our results concerning the biophysical effects should be treated as the reference for local climate adaptation rather than global climate mitigation. + +<|ref|>text<|/ref|><|det|>[[149, 297, 838, 333]]<|/det|> +67. Barnes, M. L. et al. A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States. Earth's Futur. 12, (2024). + +<|ref|>text<|/ref|><|det|>[[148, 353, 850, 500]]<|/det|> +[2] For this reason, it is also inappropriate to directly compare the change in LOCAL surface or air temperature associated with reforestation to the GLOBAL change in air temperature driven by the capacity of forests to enhance the global land carbon sink (specifically, the delta_TC metric which the authors present in Figure 4). They are not the same thing. Moreover, because the methods the authors used to calculate delta_TC do not appear to have been published elsewhere and are not clearly validated, I suggest the authors remove this part of the analysis from the manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 505, 850, 650]]<|/det|> +Response: Thanks for this critical comment. As you suggested, we have removed the analyses based on \(\Delta\) TC. We have rewritten this section by comparing the concept of sensitivity (Line 245). The revision makes our results clearer that only local effects are evaluated and the non- local or global effects are not included. Similar to the previous study (Windisch et al., 2021), the current comparisons are based on the equivalent \(\mathrm{CO_2}\) uptake, rather than the temperature effect (K). The new results allow us to investigate the relative importance of the biophysical effect and reveal the overestimation of the biophysical climate effect using Ts (rather than the more relevant Ta) as the metric. + +<|ref|>sub_title<|/ref|><|det|>[[149, 657, 234, 671]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[149, 678, 849, 713]]<|/det|> +Windisch, M. G., Davin, E. L. & Seneviratne, S. I. Prioritizing forestation based on biogeochemical and local biogeophysical impacts. Nat. Clim. Chang. 11, 867 - 871 (2021). + +<|ref|>sub_title<|/ref|><|det|>[[164, 739, 849, 773]]<|/det|> +## Comparison of biophysical with biochemical effects based on two temperature metrics + +<|ref|>text<|/ref|><|det|>[[165, 792, 835, 903]]<|/det|> +Most assessments of the climate benefits related to forestation have concentrated on the carbon sequestration (i.e., biochemical effects) \(^{52,53}\) . Here, the biomass carbon stock sensitivity to tree cover is estimated via space- for- time analogy and converted to \(\mathrm{CO_2}\) absorption equivalents ( \(\delta \mathrm{CO_2e^{bchem}}\) ) to represent the biochemical effect. We also convert the biophysical Ts and Ta sensitivities to the metric of equivalent \(\mathrm{CO_2}\) uptake ( \(\delta \mathrm{CO_2e^{bph,Ts}}\) and \(\delta \mathrm{CO_2e^{bph,Ta}}\) , Supplementary Fig. 11). These allow the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[165, 85, 835, 120]]<|/det|> +comparison of the local biophysical and biochemical climate effects and evaluation of the relative importance of the former. + +<|ref|>text<|/ref|><|det|>[[165, 138, 852, 287]]<|/det|> +The spatial map shows that \(\delta C O_{2}e^{b c h e m}\) in tropical rainforests can exceed 600 t/ha, which is much greater than temperate and boreal forests (Fig. 4a). This suggests that restoring damaged forests in tropical regions has the most carbon benefit. Latitudinally, \(\delta C O_{2}e^{b c h e m}\) at low- latitudes is higher than that at mid- or high- latitudes, with global mean of \(268.2 \pm 37.8\) t/ha (mean \(\pm\) uncertainty) (Fig. 4b). In terms of the biophysical effect, \(\delta C O_{2}e^{b p h,T s}\) (41.7 \(\pm\) 9.3 t/ha) provides a global average of \(15.7\%\) additional benefits to \(\delta C O_{2}e^{b c h e m}\) (Fig. 4b). However, if the more relevant biophysical Ta effect is considered, the ratio of \(\delta C O_{2}e^{b p h,T a}\) (9.3 \(\pm\) 2.9 t/ha) to \(\delta C O_{2}e^{b c h e m}\) is only \(3.5\%\) . + +<|ref|>text<|/ref|><|det|>[[165, 302, 860, 595]]<|/det|> +We then focus on northern high- latitudes, where tree restoration shows a biophysical warming effect. The resultant negative \(\delta C O_{2}e^{b p h,T s}\) could offset \(9.5\%\) of the \(\delta C O_{2}e^{b c h e m}\) annually (Fig. 4b). The high- latitude biophysical warming is more pronounced in the cold season and can reduce the biochemical climate effect by \(42.4\%\) in March (Fig. 4c). However, when \(\delta C O_{2}e^{b p h,T a}\) is used as the indicator, the offset of biophysical to biochemical effects is only \(3.3\%\) at the annual scale, with the maximum monthly value of \(10.6\%\) (February) (Fig. 4b and 4c). In mid- latitudes, the seasonal \(\delta C O_{2}e^{b p h,T s}\) can enhance \(\delta C O_{2}e^{b c h e m}\) by up to \(33.7\%\) (northern hemisphere) and \(40.5\%\) (southern hemisphere) during summer. However, these seasonal ratios are only about \(10\%\) considering \(\delta C O_{2}e^{b p h,T a}\) (Fig. 4d and 4f). In low- latitudes, annual positive \(\delta C O_{2}e^{b p h,T s}\) is equivalent to \(25.5\%\) of \(\delta C O_{2}e^{b c h e m}\) , while the ratio for \(\delta C O_{2}e^{b p h,T a}\) is only \(6.2\%\) , with insignificant seasonal variations (Fig. 4b and 4e). These results suggest that the relative importance of biophysical effects largely depends on the evaluated temperature metric, and the role of biophysical effects in the overall climate effect (usually measured by Ta) may not be as important as estimated in previous Ts- based studies22,23. + +<|ref|>image<|/ref|><|det|>[[220, 607, 785, 820]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[161, 828, 852, 901]]<|/det|> +
Figure 4. Comparison of the biophysical (bph) and biochemical (bchem) effects of potential tree cover gain. (a) Global pattern of the biochemical effect of potential tree cover gain ( \(\delta C O_{2}e^{b c h e m}\) ). (b) Global and latitudinal means of biochemical and biophysical effects of potential tree cover gain. The Ts-based and Ta-based biophysical effects are
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[163, 84, 852, 177]]<|/det|> +shown as the equivalent \(CO_2\) uptake \((\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) ). The error bars indicate the uncertainty of the mean. (c- f) Monthly ratios of Ta- based and Ts- based biophysical effects to equivalent biochemical effects across northern high- latitudes \((>50^{\circ}N)\) , northern mid- latitudes \((20^{\circ} - 50^{\circ}N)\) , tropics \((20^{\circ}S - 20^{\circ}N)\) and southern mid- latitudes \((>20^{\circ}S)\) . The shaded area indicates the uncertainty of the ratios. + +<|ref|>text<|/ref|><|det|>[[150, 197, 590, 213]]<|/det|> +We also rewrite the corresponding method section (Line 535): + +<|ref|>sub_title<|/ref|><|det|>[[166, 230, 601, 247]]<|/det|> +## Comparison of biophysical and biochemical effects + +<|ref|>text<|/ref|><|det|>[[164, 251, 835, 472]]<|/det|> +In addition to regulating the energy balance process, forestation can enhance the land carbon sink through vegetation photosynthesis, thereby generating negative biochemical feedback on the climate system \(^{92,93}\) . To quantify this biochemical impact, we first estimate the biomass carbon density sensitivity to ideal restoration, using Global Aboveground and Belowground Biomass Carbon Density Maps of 2010 (in t/ha) \(^{93}\) , along with \(TC_{2010}\) and the "space- for- time" strategy. We convert the biomass carbon stock sensitivity to \(CO_2\) absorption equivalents (i.e. \(\delta CO_2e^{bchem}\) ) based on the molar mass ratio. Notably, \(\delta CO_2e^{bchem}\) provides a simple estimation of the ideal carbon stock in biomass under current climate and disturbance regimes for further comparison with the biophysical effect. The period for restored forests to reach such carbon potential, and the role of changing climate and soil carbon flux in this process are neglected. + +<|ref|>text<|/ref|><|det|>[[165, 480, 834, 554]]<|/det|> +The biophysical Ts and Ta sensitivities are also unified to the metric of \(CO_2\) equivalents \((\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) ) based on the transient climate response to cumulative emissions for both Ts ( \(TCRE^{Ts}\) ) and Ta ( \(TCRE^{TA}\) ) derived from Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations (Supplementary Fig. 11): + +<|ref|>equation<|/ref|><|det|>[[295, 563, 830, 595]]<|/det|> +\[\delta CO_2e^{bph,TS} = \frac{\delta TS^{bph}}{TCRE^{TS}}\times \frac{1}{A_E} \quad (11)\] + +<|ref|>equation<|/ref|><|det|>[[300, 608, 830, 639]]<|/det|> +\[\delta CO_2e^{bph,TA} = \frac{\delta TS^{bph}}{TCRE^{TA}}\times \frac{1}{A_E} \quad (12)\] + +<|ref|>text<|/ref|><|det|>[[164, 650, 834, 834]]<|/det|> +where, \(A_E\) indicates the earth surface area (5.1x10 \(^8\) km \(^2\) ). The gridded \(TCRE^{TS}\) and \(TCRE^{TA}\) are estimated following the previous study \(^{22}\) , using 12 model simulations (ACCESS_ESM1- 5, CanESM5- 1, CMCC- ESM2, CNRM- ESM2- 1, FIO- ESM- 2- 0, GISS- E2- 1- H, INM- CM5- 0, IPSL- CM6A- LR, MIROC6, MPI- ESM1- 2- LR, MRI- ESM2- 0 and NESM3) of the "1 percent per year increase in carbon dioxide" experiment (1pctCO2). Notably, \(\delta CO_2e^{bph,TS}\) and \(\delta CO_2e^{bph,TA}\) calculated by equation (11) and (12) represent the \(CO_2\) emission equivalents. We further covert their signs to align with the \(\delta CO_2e^{bchem}\) , which represent the \(CO_2\) absorption equivalents. We compare the biophysical and biochemical effects based on the above metrics at both annual and monthly scales. + +<|ref|>sub_title<|/ref|><|det|>[[150, 861, 246, 875]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[150, 879, 820, 895]]<|/det|> +22. Windisch, M. G., Davin, E. L. & Seneviratne, S. I. Prioritizing forestation based + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[202, 85, 797, 120]]<|/det|> +on biogeochemical and local biogeophysical impacts. Nat. Clim. Chang. 11, 867- 871 (2021). + +<|ref|>text<|/ref|><|det|>[[150, 123, 780, 176]]<|/det|> +23. Zhu, L. et al. Comparable biophysical and biogeochemical feedbacks on warming from tropical moist forest degradation. Nat. Geosci. 16, 244-249 (2023). + +<|ref|>text<|/ref|><|det|>[[150, 179, 793, 214]]<|/det|> +52. Walker, W. S. et al. The global potential for increased storage of carbon on land. Proc. Natl. Acad. Sci. U. S. A. 119, 1-12 (2022). + +<|ref|>text<|/ref|><|det|>[[150, 217, 800, 269]]<|/det|> +53. Lewis, S. L., Wheeler, C. E., Mitchard, E. T. A. & Koch, A. Restoring natural forests is the best way to remove atmospheric carbon. Nature 568, 25-28 (2019). + +<|ref|>text<|/ref|><|det|>[[150, 271, 813, 324]]<|/det|> +92. Xu, H., Yue, C., Zhang, Y., Liu, D. & Piao, S. Forestation at the right time with the right species can generate persistent carbon benefits in China. Proc. Natl. Acad. Sci. 120, 2017 (2023). + +<|ref|>text<|/ref|><|det|>[[150, 327, 825, 380]]<|/det|> +93. Spawn, S. A., Sullivan, C. C., Lark, T. J. & Gibbs, H. K. Harmonized global maps of above and belowground biomass carbon density in the year 2010. Sci. Data 7, 1-22 (2020). + +<|ref|>text<|/ref|><|det|>[[147, 403, 850, 586]]<|/det|> +[3] Relatedly, the darkening of the land surface associated with the tendency for forests to lower albedo is a process that actually contributes to additional warming at regional and global scales, even if modifications to latent and sensible heat exchange tend to suppress temperature locally. This point, which is discussed in Barnes et al. (2024, https://doi.org/10.1029/2023EF003663) is important to make, because otherwise it is very hard to reconcile results from this paper with those that demonstrate that the climate mitigation potential of reforestation is reduced by the albedo impacts (including the paper by Hasler et al. published this year in Nature Communications, https://doi.org/10.1038/s41467-024-46577-1). + +<|ref|>text<|/ref|><|det|>[[147, 591, 848, 626]]<|/det|> +Response: Thanks for the constructive comment. We have added discussions about the albedo effect of forestation to reconcile with previous studies (Line 350): + +<|ref|>text<|/ref|><|det|>[[182, 631, 851, 869]]<|/det|> +The biophysical warming effects of boreal forests should be given specific attention in related mitigation policies, although our results of negative biophysical climate effects at high- latitudes may not be as strong as previous findings65,66. This is because those studies focus on the additional radiative forcing induced by the darker forest canopy but ignore the impact of turbulent fluxes. The overlooked non- radiative effects could partially offset the albedo effects, leading to the observed net warming in our results. From the perspective of the whole climate system, the non- radiative effects represent the redistribution of energy within the climate system and may lead to warming in downwind regions or the higher boundary layer67. Thus, our results concerning the biophysical effects should be treated as the reference for local climate adaptation rather than global climate mitigation. The fact that the mitigation potential of high- latitudes forestation could be reduced or even offset by the albedo impacts should be considered by forest- related global mitigation policies. + +<|ref|>title<|/ref|><|det|>[[148, 882, 245, 896]]<|/det|> +# References: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 840, 196]]<|/det|> +65. Hasler, N. et al. Accounting for albedo change to identify climate-positive tree cover restoration. Nat. Commun. 15, 2275 (2024). +66. Weber, J. et al. Chemistry-albedo feedbacks offset up to a third of forestation's CO 2 removal benefits. Science (80-). 383, 860-864 (2024). +67. Barnes, M. L. et al. A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States. Earth's Futur. 12, (2024). + +<|ref|>text<|/ref|><|det|>[[149, 220, 334, 234]]<|/det|> +A few other comments: + +<|ref|>text<|/ref|><|det|>[[149, 240, 850, 330]]<|/det|> +[4] The authors focus very strongly on the impacts of reforestation on roughness and sensible heat flux, but seem to ignore the impacts on latent heat flux (e.g. evapotranspiration). Other work on the topic (including papers cited by the authors already) make it clear that both processes are important for governing the local temperature impacts of reforestation. + +<|ref|>text<|/ref|><|det|>[[149, 336, 850, 389]]<|/det|> +Response: Thanks for the professional comment. The enhancement in latent heat flux can strongly affect the local Ts effect of reforestation at low- latitudes. We have added related discussions in the revised manuscript (Line 287): + +<|ref|>text<|/ref|><|det|>[[182, 394, 851, 503]]<|/det|> +Previous studies have demonstrated that in boreal regions, forests can warm local Ts because the tree canopy is darker than the snow background and absorbs more solar radiation; in tropical regions, forests show strong local Ts cooling, mainly due to the higher evapotranspiration rates than other vegetation or bare land; in temperate regions, the net Ts effect depends on the relative magnitude of these two processes \(^{10,12,29,31}\) . + +<|ref|>sub_title<|/ref|><|det|>[[149, 515, 246, 529]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[149, 532, 836, 593]]<|/det|> +10. Lawrence, D., Coe, M., Walker, W., Verchot, L. & Vandecar, K. The Unseen Effects of Deforestation: Biophysical Effects on Climate. Front. For. Glob. Chang. 5, 1-13 (2022). + +<|ref|>text<|/ref|><|det|>[[150, 587, 780, 622]]<|/det|> +12. Li, Y. et al. Local cooling and warming effects of forests based on satellite observations. Nat. Commun. 6, 1-10 (2015). + +<|ref|>text<|/ref|><|det|>[[149, 624, 810, 677]]<|/det|> +29. Duveiller, G. et al. Biophysics and vegetation cover change: A process-based evaluation framework for confronting land surface models with satellite observations. Earth Syst. Sci. Data 10, 1265-1279 (2018). + +<|ref|>text<|/ref|><|det|>[[149, 679, 834, 715]]<|/det|> +31. Bright, R. M. et al. Local temperature response to land cover and management change driven by non-radiative processes. Nat. Clim. Chang. 7, 296-302 (2017). + +<|ref|>text<|/ref|><|det|>[[149, 738, 850, 885]]<|/det|> +[5] I appreciate that the authors engaged in a robust effort to use data from eddy covariance flux towers to validate their approach of comparing land surface temperature measurements from satellites with gridded information on air temperature from meteorological station networks. However, this effort seems to compare the flux tower- derived information to a gridded air temperature product derived from CRU and BEST data. Why didn't the authors compare flux tower data to the air temperature product they actually use for the global mapping in the study (e.g. the dataset produced by Zhang et al 2022? + +<|ref|>text<|/ref|><|det|>[[147, 890, 848, 907]]<|/det|> +Response: Thanks for the professional comment. The CRU or BEST data used here are interpolated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 851, 195]]<|/det|> +temperature data, which represent the influence of the macroclimate. Therefore, their differences with site measurements reflect the relative influence of land cover on local temperature. Zhang et al's Ta data, on the other hand, are produced by a statistical method using satellite land surface temperature and thus contain both signals from macroclimate and land cover. The difference between Zhang et al. Ta data and site measurements may reflect systematic or random errors of the product rather than the information we are interested in. + +<|ref|>text<|/ref|><|det|>[[148, 219, 850, 292]]<|/det|> +[6] The presentation of equations [1] and [2] is confusing. Not all of the terms in these equations are defined, and the math seems to simply considerably from what is shown (for example, as written, it seems the TC_2010\~T terms simply cancel out of the equations? + +<|ref|>text<|/ref|><|det|>[[148, 297, 850, 352]]<|/det|> +Response: Thanks for raising this concern. The equations in the original manuscript are the solution of the linear model represented by the matrix operation form. The superscript "T" denotes the matrix transpose. We have revised the formulas for clarity (Line 425): + +<|ref|>equation<|/ref|><|det|>[[276, 360, 848, 410]]<|/det|> +\[\begin{array}{c}{{T s=\delta T s^{b p h}\times T C_{2010}+b_{s}}}\\ {{}}\\ {{T s=\delta T a^{b p h}\times T C_{2010}+b_{a}}}\end{array} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[148, 421, 528, 439]]<|/det|> +where, \(b_{s}\) and \(b_{a}\) are the regression intercepts. + +<|ref|>text<|/ref|><|det|>[[148, 468, 850, 541]]<|/det|> +[7] The relationship between surface temperature and outgoing long- wave radiation (equation 3) includes a correction for incident long- wave radiation. This is unusual...can the authors provide a reference or further justification for the approach? + +<|ref|>text<|/ref|><|det|>[[147, 551, 850, 658]]<|/det|> +Response: Thanks for the comment. Equation 3 (Ts = [LW - (1- e)LW] has been widely used for land surface temperature retrieval from site longwave radiation measurements (Duan et al., 2019; Ma et al., 2021; Schultz et al., 2017). Here, the correction is made to exclude the reflected longwave radiation from the measured outgoing longwave radiation, and thereby obtain the actual value of emitted radiation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 670, 234, 684]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[147, 687, 850, 857]]<|/det|> +Duan, S.B., Li, Z.L., Li, H., Gottsche, F.M., Wu, H., Zhao, W., Leng, P., Zhang, X., Coll, C., 2019. Validation of Collection 6 MODIS land surface temperature product using in situ measurements. Remote Sens. Environ. 225, 16 - 29. https://doi.org/10.1016/j.rse.2019.02.020Ma, J., Zhou, J., Liu, S., Gottsche, F.M., Zhang, X., Wang, S., Li, M., 2021. Continuous evaluation of the spatial representativeness of land surface temperature validation sites. Remote Sens. Environ. 265. https://doi.org/10.1016/j.rse.2021.112669Schultz, N.M., Lawrence, P.J., Lee, X., 2017. Global satellite data highlights the diurnal asymmetry of the surface temperature response to deforestation. J. Geophys. Res. Biogeosciences 122, 903 - 917. https://doi.org/10.1002/2016JG003653 + +<|ref|>text<|/ref|><|det|>[[148, 884, 530, 900]]<|/det|> +We have added a reference for equation 3 (Line 781): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 837, 121]]<|/det|> +87. Duan, S. B. et al. Validation of Collection 6 MODIS land surface temperature product using in situ measurements. Remote Sens. Environ. 225, 16 - 29 (2019). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[348, 86, 649, 103]]<|/det|> +## Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[148, 113, 851, 186]]<|/det|> +We greatly appreciate the opportunity to revise our manuscript and thank all anonymous reviewers for their constructive comments. Below are the point- by- point responses to the comments, along with the revision of the manuscript (typed in Italics and Arial) and the location of the revision. The line numbers referred to are for the clean version of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 219, 451, 235]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 255, 850, 289]]<|/det|> +I thank the authors for the elaborate answers and thoughtful updates to the manuscript. I have no further comments. + +<|ref|>text<|/ref|><|det|>[[148, 295, 850, 330]]<|/det|> +Response: We appreciate the constructive and valuable comments by the reviewer during the review process. + +<|ref|>sub_title<|/ref|><|det|>[[148, 365, 498, 381]]<|/det|> +## Reviewer #1 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[147, 399, 851, 457]]<|/det|> +I could not access the code: "You do not have sufficient permissions to view this page." Response: We apologize for the data accessibility issue. We have confirmed that the Zenodo project is publicly accessible (https://zenodo.org/records/14633331). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 98, 451, 114]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 132, 850, 205]]<|/det|> +The manuscript is now in much better shape, and I think it is a very interesting one and shows nice and relevant results. I especially like that the authors analyze the hypotheses both with remote sensing but also site information with FLUXNET data (they did so in the previous version already, but I still want to highlight this). + +<|ref|>text<|/ref|><|det|>[[148, 210, 850, 244]]<|/det|> +My concerns from the first round were thoroughly addressed, but a few issues remain that I believe require minor revisions from the authors. + +<|ref|>text<|/ref|><|det|>[[148, 250, 850, 303]]<|/det|> +Response: We thank the reviewer for the positive feedback. Based on the second- round comments, we mainly revised the methods section to make the manuscript clearer. Please see the point- by- point responses below. + +<|ref|>sub_title<|/ref|><|det|>[[148, 330, 242, 345]]<|/det|> +## ### Results + +<|ref|>text<|/ref|><|det|>[[148, 351, 851, 460]]<|/det|> +- I now fully understand what you mean by "100% tree cover gain" and Fig S1 makes it very clear, thank you. But I think the term is misleading/confusing. It should be something like "full tree cover" or "full restoration" or something like that. Because a 100% gain would mean, if I have 5 hectares of forest in some area, and then you plant 5ha more, that is a 100% gain in tree cover. But that does not mean that the area is fully restored aka has 100% tree cover. I think this needs to be termed differently. + +<|ref|>text<|/ref|><|det|>[[148, 472, 850, 507]]<|/det|> +Response: Thanks for pointing this out. We have revised "100% tree cover gain" to "the full tree cover restoration" to avoid ambiguity (Line 76). + +<|ref|>text<|/ref|><|det|>[[163, 517, 850, 571]]<|/det|> +We first estimated the local biophysical Ts and Ta sensitivity to the full tree cover restoration (denoted as \(\delta T s^{bp}\) and \(\delta T a^{bp h}\) ) at the \(0.25^{\circ}\) scale, based on the space- for- time analogy. + +<|ref|>text<|/ref|><|det|>[[148, 576, 515, 592]]<|/det|> +We have also revised the figure caption (Line 124). + +<|ref|>text<|/ref|><|det|>[[163, 597, 780, 614]]<|/det|> +Figure 1. Annual mean temperature sensitivity to the full tree cover restoration. + +<|ref|>sub_title<|/ref|><|det|>[[148, 641, 256, 656]]<|/det|> +## ### Methods + +<|ref|>text<|/ref|><|det|>[[148, 662, 737, 679]]<|/det|> +The procedure for the FLUXNET sites is now better explained, but still unclear. + +<|ref|>text<|/ref|><|det|>[[148, 685, 850, 719]]<|/det|> +Response: Thanks for raising this concern. We rearranged the method section and hope the revision can make the procedure clearer (Line 464): + +<|ref|>text<|/ref|><|det|>[[183, 724, 850, 777]]<|/det|> +The specific process of validation is as follows (Supplementary Fig. 8). In- situ data for Ta are measured above the vegetation canopy, whereas Ts is estimated using the longwave radiation measurements: + +<|ref|>equation<|/ref|><|det|>[[432, 788, 848, 821]]<|/det|> +\[T s = \left[\frac{L W_{u} - (1 - \epsilon)L W_{d}}{\epsilon \sigma}\right]^{\frac{1}{4}} \quad (3)\] + +<|ref|>text<|/ref|><|det|>[[183, 830, 850, 903]]<|/det|> +where, \(L W_{u}\) and \(L W_{d}\) represent upward and downward longwave radiation from the FLUXNET2015 dataset, respectively; \(\sigma\) denotes the Stephan- Boltzmann constant \((5.67 \times 10^{- 8} W m^{- 2} K^{- 4})\) , and \(\epsilon\) is emissivity, estimated based on an empirical relationship with albedo88. For the gridded data, we first make corrections using the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[184, 84, 851, 139]]<|/det|> +lapse rates to compensate for the elevation difference between the site and the corresponding grid. The lapse rate for the target grid is estimated by the regression slope of the gridded temperatures and elevations within the \(5 \times 5\) window. + +<|ref|>text<|/ref|><|det|>[[184, 148, 852, 277]]<|/det|> +By deducting the corrected gridded temperature data, the in- situ measurements can effectively represent the land cover impacts on local Ts and Ta, assuming that macroclimate affects both temperature metrics similarly. Since the forest data cannot be directly matched with the openland data, we bin both forest and openland data points using the \(SW_d\) interval of \(10 \mathrm{~w} / \mathrm{m}^2\) . For each \(SW_d\) bin, we calculate the difference between mean values of forest and openland data points to represent the temperature effect of forestation (i.e. \(\delta T_s^{bph*}\) or \(\delta T_a^{bph*}\) ) under the specific radiation background: + +<|ref|>equation<|/ref|><|det|>[[200, 287, 848, 316]]<|/det|> +\[\delta T_s^{b p}~^{*} = \left(T_s^{s i t e} - T_f^{g r i d}\right) - \left(T_s^{s i t e} - T_o^{g r i d}\right) \qquad if S W_d\in (10k,10k + 10) \quad (4)\] + +<|ref|>equation<|/ref|><|det|>[[200, 333, 848, 362]]<|/det|> +\[\delta T_a^{b p h^{*}} = \left(T_a^{s i t e} - T_f^{g r i d}\right) - \left(T_a^{s i t e} - T_o^{g r i d}\right) \qquad if S W_d\in (10k,10k + 10) \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[183, 371, 850, 520]]<|/det|> +Here, \(T_s^{s i t e}\) and \(T_a^{s i t e}\) refer to Ts and Ta measured at forest sites, respectively; \(T_s^{s i t e}\) and \(T_a^{s i t e}\) refers to Ts and Ta measured at openland sites; \(T_f^{g r i d}\) and \(T_o^{g r i d}\) refer to the corresponding gridded temperatures after the elevation correction; \(k\) indicates counting of the \(SW_d\) bin. According to the metadata of the FLUXNET2015 dataset, forest sites include the following four IGBP landcover types: evergreen needleleaf forests, evergreen broadleaf forests, deciduous broadleaf forests, and mixed forests; openland sites are categorized as other non- forest vegetation types. + +<|ref|>text<|/ref|><|det|>[[183, 529, 851, 675]]<|/det|> +Then, the relationships between two temperature sensitivities and \(SW_d\) are explored using the weighted least squares (WLS) regression model, in which the samples are \(\delta T_s^{b p h*}\) or \(\delta T_a^{b p h*}\) of all \(SW_d\) bins and the sample weights are defined as the inverse of the standard error of \(\delta T_s^{b p h*}\) or \(\delta T_a^{b p h*}\) . The derived relationships are then compared with those from RS- based results for validation. Here, the monthly ERA5- Land shortwave radiation data are used to build the relationships with RS- based sensitivities. We also compare and validate the maximum temperature sensitivities. + +<|ref|>text<|/ref|><|det|>[[149, 704, 849, 740]]<|/det|> +- why is the binning necessary for the fluxnet sites? I looked at the data in the supplements and it seems you could just provide a plot with all data points as well. + +<|ref|>text<|/ref|><|det|>[[148, 745, 850, 800]]<|/det|> +Response: Thanks for the valuable comment. First, we should note that the binning process is for all observations of forest (or openland) based on the shortwave radiation condition. In other words, the binning process is for observations rather than sites. + +<|ref|>text<|/ref|><|det|>[[147, 804, 850, 914]]<|/det|> +Since the forest and openland observations may be spatially distant or temporally asynchronous, they cannot be directly matched with each other (here the data indicate the corrected FLUXNET observations by subtracting gridded temperature). Thus, the binning process is necessary to provide a similar radiation background for comparing the "temperature effects" of forests and openlands to represent the consequence of land cover conversion. We have added a sentence to illustrate the reason for the binning process (Line 476): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[182, 85, 850, 120]]<|/det|> +Since the forest data cannot be directly matched with the openland data, we bin both forest and openland data points using the \(SW_{d}\) interval of \(10 \text{w/m}^2\) . + +<|ref|>text<|/ref|><|det|>[[148, 146, 850, 200]]<|/det|> +- In equation 4 and 5, what is the mean taken over? is it the average over all forest sites, and then the average over all openland sites? This is not written out in a mathematically clear way and so I don't understand it. + +<|ref|>text<|/ref|><|det|>[[148, 205, 850, 259]]<|/det|> +Response: Thanks for the valuable comment. The mean is taken over for all forest (or openland) observations within each shortwave radiation bin. We have revised the equations 4 and 5 for clarity (Line 477): + +<|ref|>text<|/ref|><|det|>[[182, 263, 850, 319]]<|/det|> +For each \(SW_{d}\) bin, we calculate the difference between mean values of forest and openland data points to represent the temperature effect of forestation (i.e. \(\delta T s^{b p h *}\) or \(\delta T a^{b p h *}\) ) under the specific radiation background: + +<|ref|>equation<|/ref|><|det|>[[198, 325, 850, 399]]<|/det|> +\[\begin{array}{r l r l r l r l}{\delta T s^{b p h *} = \left(T s_{f}^{s i t e} - T_{f}^{g r i d}\right) - \left(T s_{o}^{s i t e} - T_{o}^{g r i d}\right)} & {} & & & & {i f S W_{d}\in (10k,10k + 10)}\\ {\delta T a^{b p h *} = \left(T a_{f}^{s i t e} - T_{f}^{g r i d}\right) - \left(T a_{o}^{s i t e} - T_{o}^{g r i d}\right)} & {} & & & {i f S W_{d}\in (10k,10k + 10)} \end{array} \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[148, 431, 850, 467]]<|/det|> +- why is it called a relative effect (e.g. in figure S8). You're doing a simple subtraction, so that's an absolute effect, it's not put in relation to anything else. + +<|ref|>text<|/ref|><|det|>[[148, 471, 850, 507]]<|/det|> +Response: Thanks for the careful reading. We have revised the relative effect to "land cover impacts on Ta/Ts" for clarity (Line 474): + +<|ref|>text<|/ref|><|det|>[[181, 511, 850, 547]]<|/det|> +By deducting the corrected gridded temperature data, the in-situ measurements can effectively represent the land cover impacts on local Ts and Ta + +<|ref|>text<|/ref|><|det|>[[148, 551, 850, 587]]<|/det|> +We also modified the wording in fig.S8 by using the "quantitative metric of forest (openland) impacts on local Ta or Ts". + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[207, 90, 784, 523]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 532, 850, 568]]<|/det|> +
Supplementary Figure 8. Flow chart of the remote sensing (RS)-based local temperature effect validation using FLUXNET and gridded temperature data.
+ +<|ref|>text<|/ref|><|det|>[[148, 594, 850, 628]]<|/det|> +- It is unclear for what values the regression is done. For all of the datapoints? For the means of the bins? + +<|ref|>text<|/ref|><|det|>[[148, 634, 850, 670]]<|/det|> +Response: Thanks for the comment. The means of bins are used for regression. We have highlighted the regression data as you suggested (Line 489): + +<|ref|>text<|/ref|><|det|>[[183, 674, 850, 748]]<|/det|> +Then, the relationships between two temperature sensitivities and \(SW_{d}\) are explored using the weighted least squares (WLS) regression model, in which the samples are \(\delta T_{a}^{bph*}\) or \(\delta T_{a}^{bph*}\) of all \(SW_{d}\) bins and the sample weights are defined as the inverse of the standard error of \(\delta T_{a}^{bph*}\) or \(\delta T_{a}^{bph*}\) . + +<|ref|>text<|/ref|><|det|>[[147, 772, 850, 829]]<|/det|> +Fig S11 has inconsistent axes in a) and b), and a typo for b) in the caption (should be Ta) Response: Thanks for the careful reading. We have redrawn the supplementary figure with the same color bar and revised the figure caption. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[216, 87, 780, 277]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 288, 852, 380]]<|/det|> +Supplementary Figure 11. Equivalent \(\mathrm{CO_2}\) uptake induced by biophysical Ts and Ta effects of potential tree restoration ( \(\delta \mathrm{CO_2e^{bph,Ts}}\) and \(\delta \mathrm{CO_2e^{bph,Ta}}\) ). (a) Global map of \(\delta \mathrm{CO_2e^{bph,Ts}}\) . (b) Global map of \(\delta \mathrm{CO_2e^{bph,Ta}}\) . (c) Transient climate response to cumulative emissions (TCRE) of \(\mathrm{CO_2}\) for annual Ts. (d) Transient climate response to cumulative emissions (TCRE) of \(\mathrm{CO_2}^2\) for annual Ta. + +<|ref|>text<|/ref|><|det|>[[148, 403, 849, 438]]<|/det|> +Just a suggestion: Put the 600 tC/ha in context, e.g. with Pan2024, stating how dense those biomes are currently (around 240 tC/ha if I recall correctly) + +<|ref|>text<|/ref|><|det|>[[148, 443, 849, 478]]<|/det|> +Response: Thanks for the valuable comment. We should first note that the figure is \(\delta \mathrm{CO_2e}\) , which indicates the equivalent \(\mathrm{CO_2}\) densities (t/ha), rather than C densities. + +<|ref|>text<|/ref|><|det|>[[147, 483, 851, 610]]<|/det|> +According to extended data table 2 of Pan et al., the mean biome- level C density of tropical intact forest is 293.1 tC/ha. Considering the ratio of living biomass to total C (living biomass, dead wood, litter and soil) derived from the table data, the estimated mean biomass C density is about 164.2 tC/ha. After converting the unit to \(\mathrm{CO_2}\) , the number is about 602.2 tCO2/ha, which is comparable to our result. Notably, we use the data of tropical intact forest rather than the tropical regrowth forest for comparison. This is because our density results are based on the full tree cover restoration, which is closer to the state of intact forest. + +<|ref|>text<|/ref|><|det|>[[148, 616, 720, 632]]<|/det|> +Following your suggestion, we have added the context of our results (Line 253): + +<|ref|>text<|/ref|><|det|>[[184, 637, 852, 728]]<|/det|> +The spatial map shows that \(\delta \mathrm{CO_2e^{bchem}}\) in tropical rainforest margins can exceed 600 t/ha (Fig. 4a), which is comparable to the previous estimation of tropical intact forests based on ecological research network observations. This value is greater than \(\delta \mathrm{CO_2e^{bch}}\) in temperate and boreal forests, suggesting the highest carbon benefit of restoring damaged or degraded tropical forests. + +<|ref|>text<|/ref|><|det|>[[183, 739, 839, 756]]<|/det|> +5. Pan, Y. et al. The enduring world forest carbon sink. Nature 631, 563-569 (2024). + +<|ref|>sub_title<|/ref|><|det|>[[149, 800, 498, 816]]<|/det|> +## Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[148, 834, 850, 869]]<|/det|> +The code requires a small effort. First of all, the packages and versions with which to run this are not included. So I had to manually install packages one by one which is annoying. + +<|ref|>text<|/ref|><|det|>[[147, 875, 850, 910]]<|/det|> +Response: Thanks for raising this concern. We have updated the Zenodo project (https://zenodo.org/records/14633331). The "environment.zip" file is uploaded, which contains the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 120]]<|/det|> +“yml” file and the python wheels of GDAL for both Linux and Windows systems. We also updated the “readme.md” file, which provides simple instructions about the environment installation. + +<|ref|>text<|/ref|><|det|>[[148, 146, 851, 200]]<|/det|> +You should provide a conda environment.yml or something like that so one can just set up the environment and re- run the code. I managed to get the code running after I fixed some issues. + +<|ref|>text<|/ref|><|det|>[[148, 205, 667, 221]]<|/det|> +Response: Please refer to the response above. The “yml” file is uploaded. + +<|ref|>text<|/ref|><|det|>[[147, 247, 851, 320]]<|/det|> +BTW, the code does not directly run on Linux/Mac because of Windows- style file paths and sometimes wrong capitalization of filenames (that matters on Unix systems). Also, the names of the imports lib_image are wrong (should be function_image). But I was able to reproduce the figures in the end. + +<|ref|>text<|/ref|><|det|>[[147, 326, 850, 360]]<|/det|> +Response: We apologize for the bugs in the code. We have checked through the code and debugged on both Windows and Linux. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 99, 451, 115]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 133, 850, 186]]<|/det|> +The authors have done a thorough job responding to comments raised during the first round of review. My particular concerns have been adequately addressed, and I do not have any others to raise at this point. + +<|ref|>text<|/ref|><|det|>[[147, 193, 795, 208]]<|/det|> +Response: We thank the reviewer for the constructive comments during the review process. + +<--- Page Split ---> diff --git a/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..424ee9e6e55ddab255b6fdbd15e3162e6b62c6fd --- /dev/null +++ b/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,317 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure S8. Structural unit conformation diagram of a) TPEI with one crosslink point and b) TPEI with two crosslink points. Among them, the blue hexagonal pyramid represents the location of the crosslinking point, while the green and red areas indicate the plane where the benzene ring of the diamine unit lies.", + "footnote": [], + "bbox": [ + [ + 152, + 88, + 840, + 300 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure S10. Structural formulas of PEI and TPEIu and the dihedral angles at the imide ring.", + "footnote": [], + "bbox": [ + [ + 252, + 88, + 759, + 374 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure S20 Leakage current density of TPEI as a function of electric field, compared with those of Kapton, FPE, and PEI-PSU at \\(150^{\\circ}\\mathrm{C}\\) a) and \\(200^{\\circ}\\mathrm{C}\\) b).", + "footnote": [], + "bbox": [ + [ + 150, + 85, + 913, + 344 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4. Analysis of mechanical performance and electrical insulation properties. DMA curves for a) PEI film and b) TPEI film. c) Comparison of the storage modulus of PEI and TPEI films. d) Leakage current density of polymer films as a function of electric field at \\(150^{\\circ}\\) C and e) \\(200^{\\circ}\\) C. f) Electrical conductivity of TPEI, PEI, FPE, Kapton, and PEI-PSU films at various temperatures.", + "footnote": [], + "bbox": [ + [ + 147, + 425, + 850, + 723 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure S21. The leakage current density of pristine PEI as a function of electric field at elevated temperatures is presented, with the solid curves denoting the SCLC model fit.", + "footnote": [], + "bbox": [ + [ + 310, + 87, + 690, + 321 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \\(150^{\\circ}\\mathrm{C}\\) and b) \\(200^{\\circ}\\mathrm{C}\\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \\(150^{\\circ}\\mathrm{C}\\) and BOPP at \\(120^{\\circ}\\mathrm{C}\\) , d) \\(200^{\\circ}\\mathrm{C}\\) and e) \\(250^{\\circ}\\mathrm{C}\\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \\(>90\\%\\) ) at \\(200^{\\circ}\\mathrm{C}^{10,11,17,18,24,25,38,39,40,41,42,43,44,45,46,47,48,49}\\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \\(250^{\\circ}\\mathrm{C}^{10,25,42,46,50}\\) for the TPEI and novel all-organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m-1 and 20 kΩ.", + "footnote": [], + "bbox": [ + [ + 147, + 85, + 850, + 510 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \\(150^{\\circ}\\mathrm{C}\\) and b) \\(200^{\\circ}\\mathrm{C}\\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \\(150^{\\circ}\\mathrm{C}\\) and BOPP at \\(120^{\\circ}\\mathrm{C}\\) , d) \\(200^{\\circ}\\mathrm{C}\\) and e) \\(250^{\\circ}\\mathrm{C}\\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \\(>90\\%\\) ) at \\(200^{\\circ}\\mathrm{C}^{10, 11, 17, 18, 24, 25, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49}\\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \\(250^{\\circ}\\mathrm{C}^{10, 25, 42, 46, 50}\\) for the TPEI and novel all-", + "footnote": [], + "bbox": [ + [ + 147, + 250, + 850, + 675 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure S19 Stress-strain curves of TPEI film.", + "footnote": [], + "bbox": [ + [ + 262, + 480, + 736, + 765 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Figure S18 Strain versus electric field (S-E) curves of TPEI at frequency of 100 Hz.", + "footnote": [], + "bbox": [ + [ + 152, + 92, + 850, + 355 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \\(150^{\\circ}\\mathrm{C}\\) and b) \\(200^{\\circ}\\mathrm{C}\\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \\(150^{\\circ}\\mathrm{C}\\) and BOPP at \\(120^{\\circ}\\mathrm{C}\\) , d) \\(200^{\\circ}\\mathrm{C}\\) and e) \\(250^{\\circ}\\mathrm{C}\\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \\(>90\\%\\) ) at \\(200^{\\circ}\\mathrm{C}^{10,11,17,18,24,25,38,39,40,41,42,43,44,45,46,47,48,49}\\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \\(250^{\\circ}\\mathrm{C}^{10,25,42,46,50}\\) for the TPEI and novel all-organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m-1 and 20 kΩ.", + "footnote": [], + "bbox": [ + [ + 147, + 85, + 850, + 510 + ] + ], + "page_idx": 38 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Figure S6. PEI a) and TPEI b) cells generated through molecular dynamics simulations. Blue regions denote the free volume and grey regions represent the volume occupied by polymer chains. c) Fractional free volume (FFV) and density data for PEI and TPEI.", + "footnote": [], + "bbox": [ + [ + 228, + 425, + 773, + 833 + ] + ], + "page_idx": 43 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Figure S7. Cleave plane of PEI a) and TPEI b) simulation cells. Green regions denote the free volume and grey regions represent the volume occupied by polymer chains. c) Average spacing around FFV in PEI and TPEI.", + "footnote": [], + "bbox": [ + [ + 148, + 87, + 848, + 656 + ] + ], + "page_idx": 44 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Figure S19 Stress-strain curves of TPEI film.", + "footnote": [], + "bbox": [ + [ + 260, + 174, + 737, + 459 + ] + ], + "page_idx": 46 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure 3. Characterization of the polymer films and the PLP structure. a) FT-IR spectra, b) TGA and DTG curves (Inset: partial enlarged detail of TGA), c) DSC curves, d) In-plane thermal expansion change curves (Inset: CET values) for PEI and TPEI films. Exploded view of the XRD pattern for e) PEI film and f) TPEI film. g) The WAXS patterns for TPEIu and TPEI films. The 2D GIWAXS patterns of h) TPEIu and i) TPEI films.", + "footnote": [], + "bbox": [ + [ + 149, + 111, + 848, + 592 + ] + ], + "page_idx": 48 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Figure S16. Schematic diagram of GIWAXS measurements of polymer film. \\(\\alpha_{f}\\) represents the exit angle of the X-ray beam relative to the film surface, and \\(2\\theta_{f}\\) denotes the exit angle relative to the plane of incidence. Meanwhile, \\(\\mathbf{q}_{\\mathrm{x}}\\) , \\(\\mathbf{q}_{\\mathrm{y}}\\) , and \\(\\mathbf{q}_{\\mathrm{z}}\\) is the components of the scattering vector \\(\\mathbf{q}\\) .", + "footnote": [], + "bbox": [ + [ + 260, + 85, + 734, + 285 + ] + ], + "page_idx": 49 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Figure S17. One-dimensional GIWAXS integration profile of polymer films.", + "footnote": [], + "bbox": [ + [ + 286, + 400, + 710, + 658 + ] + ], + "page_idx": 49 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Figure S12. Fluorescence emission spectra of PEI and TPEI samples.", + "footnote": [], + "bbox": [ + [ + 280, + 199, + 720, + 470 + ] + ], + "page_idx": 51 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Figure S3. Photos of un-crosslinked TPEI \\(u\\) and crosslinked TPEI films after soaking in NMP at \\(80^{\\circ}\\mathrm{C}\\) for 24h.", + "footnote": [], + "bbox": [ + [ + 272, + 92, + 725, + 352 + ] + ], + "page_idx": 59 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Figure S14. TGA and DTG curves of TPEI film.", + "footnote": [], + "bbox": [ + [ + 260, + 419, + 739, + 675 + ] + ], + "page_idx": 59 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_14.jpg", + "caption": "Figure S9. a) Solid-state UV-vis spectra and b) \\((a h\\nu)^{2} - h\\nu\\) plots of PEI and TPEI. Here, \\(\\alpha\\) represents the absorption coefficient, \\(h\\) corresponds to the Planck constant, and \\(\\nu\\) indicates the light frequency.", + "footnote": [], + "bbox": [ + [ + 150, + 115, + 848, + 348 + ] + ], + "page_idx": 61 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_15.jpg", + "caption": "Figure S3. Photos of un-crosslinked TPEI \\(u\\) and crosslinked TPEI films after soaking in NMP at \\(80^{\\circ}\\mathrm{C}\\) for \\(24\\mathrm{h}\\) .", + "footnote": [], + "bbox": [ + [ + 262, + 88, + 732, + 357 + ] + ], + "page_idx": 63 + } +] \ No newline at end of file diff --git a/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..926204b005cbac0355c2782e5a4f6e12909a989e --- /dev/null +++ b/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,771 @@ + +# nature portfolio + +Peer Review File + +# Decoupling thermal stability and insulation in dielectric polymers via donor acceptor rearrangement + +Corresponding Author: Professor Jun- Wei Zha + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors introduce a strategy to break the adverse correlation between thermal stability and electrical insulation of PEI dielectric by the effective rearrangement of short- range structural units. This work is innovative and meaningful for the advancement of dielectric polymers. Due to the suppressed electrical conductivity, the capacitive energy storage under high temperatures and electric fields is significantly improved. The following issues need to be addressed before the publication. (1) In Figure 2c(ii) and 2d(ii), the IFCT method calculated charge- transfer (CT) results indicate that the electron amount (0.14e) transferred from the donor unit to the acceptor in the molecular chain with two crosslinking points is significantly lower than that in the chain with one crosslinking point (0.87e). What accounts for this? + +(2) The authors confirmed the significant impact of the preferred layer packing (PLP) structure on inhibiting electron transfer through DFT calculations. How is the mentioned charge-transfer (CT) excitation determined? The related description in the DFT calculation section should be provided. + +(3) In Figure 3c, the specific heat capacity ((ΔCp) of TPEI is lower than that of PEI, indicating that the TPEI polymer chains are stretched. However, "Furthermore, the substituents on the benzene rings can influence the twisting of the molecular chain conformation..." The electrostatic potential distributions of PEI and TPEI reveal that TPEI exhibits weaker electrostatic interactions, which the authors attribute to the twisting of the molecular chain conformation. Is there a contradiction between the concepts of "polymer chains are stretched" and "the twisting of the molecular chain conformation" in these two contexts? (4) Here, "TPEI exhibits over an order of magnitude lower leakage current density than that of PEI and other heat-resistant polymers...", the authors reference "other heat-resistant polymers", but the leakage data for these materials are absent. Please provide examples of leakage data for "other heat-resistant polymers". + +(5) In figures 4d-e, the fitting mechanism of the leakage current for fresh PEI exhibits significant deviation. The authors should re-evaluate the leakage conduction mechanism and consider performing segmented fitting of the experimental results. + +(6) Please update the performance comparison charts in Figures 6e and 6f by including the most recent relevant reported results. + +(7) It is advisable for the author to incorporate a radar chart that compares the key performance parameters of TPEI and fresh PEI, emphasizing the advantages of the short-range structural rearrangement methods. + +(8) The authors discussed uncross-linked TPEI (TPEIu) during the research process. However, there is no characterization of its dielectric and energy storage performance. What accounts for this? + +(9) Some errors should be corrected, such as "(Tg ≈ 265 °C)" and "(Tg = 330 °C)" in the Materials section. + +## Reviewer #2 + +(Remarks to the Author) + +This work achieves the obstruction of long- range electron transport along polymer chain segments by rearranging the dianhydride and diamine units in polyimide, leading to the development of TPEI with both high thermal stability and high dielectric strength. Energy storage densities of 6.38 J/cm³ and 3.04 J/cm³ were obtained at 200 °C and 250 °C, respectively, while maintaining 90% efficiency. The manuscript is well- organized and provides valuable insights for researchers in the field. Therefore, I recommend its publication after minor revisions addressing the following points: + +<--- Page Split ---> + +1) The authors discuss electron transfer between the dianhydride and diamine units during excitation in lines 113-139. However, electron excitation typically involves transitions from the HOMO to the LUMO and higher energy levels. Does the reported charge transfer only consider transitions from HOMO to LUMO? I think analyzing a single energy level transition may not fully reveal the influence of electron excitation on the system. Therefore, I suggest also considering electron transitions to 3-5 energy levels near LUMO to obtain a more comprehensive understanding of the electronic excitation characteristics. + +2) The manuscript states in lines 182-193 that polymer thickness decreases with increasing electrostatic stress, which is an intriguing observation. While this effect is theoretically possible, it is rarely reported due to the generally high mechanical stability of polymers, especially for pure dielectric polymers under an applied electric field (excluding cases with piezoelectric or ferroelectric additives). Therefore, field-induced deformation of pure dielectric polymers is an interesting and meaningful topic. Perhaps, an experimental approach similar to those used for piezoelectric materials could be considered to measure polymer thickness changes under an external electric field to support this interesting hypothesis. + +3) In Figures 6e and 6f, the authors compare the performance of existing advanced energy storage materials. However, some of these materials are not purely organic polymers, as they contain fillers or ferroelectric components. To ensure a fair and consistent comparison, I recommend excluding these non-purely organic materials so that the advantages of the authors work can be more accurately highlighted. + +4) There are multiple formatting inconsistencies with the "C" unit in lines 350-385. + +5) The characterization section must be improved by providing a detailed description of each experimental technique used. For example, what mode was used in the AFM test? What amplitude was selected for the DMA test? Was preheating performed in the DSC test? In the D-E loop test, what were the electrode material and dimensions? + +6) In Figure 2, the author uses scan mode to explore the lowest energy points of two molecular chains. However, the structure of the polymer condensed matter is equally important, and I suggest that the free volume of the whole condensed matter structure should be calculated and analyzed. If you can, consider calculating statistics for the distance between this segment and the surrounding segment separately. The precision of the base group can be appropriately reduced to take into account the calculation speed and quality. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +I have carefully read the revised manuscript and relevant responses including the ones for mine and Reviewer 3. This manuscript is acceptable now. + +Reviewer #2 + +(Remarks to the Author) Can be accepted as it is. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Dear editors and reviewers, + +Dear editors and reviewers,Thank you for your valuable comments and constructive suggestions on our manuscript submitted to Nature Communications (Manuscript ID: NCOMMS- 25- 13172, Title: Breaking the adverse correlation between thermal stability and electrical insulation in polymer dielectrics by rearranging the donor and acceptor units). Based on these comments, we have carefully revised the manuscript to address all the concerns raised. A revised manuscript has been submitted, of which the modified sections are marked in red. The summary of the changes and a brief response to all recommendations and criticisms are listed as follows: + +Reviewer comment in BLACK. + +Reply in BLUE. + +New text in RED. + +Reviewer #1 (Remarks to the Author): + +The authors introduce a strategy to break the adverse correlation between thermal stability and electrical insulation of PEI dielectric by the effective rearrangement of short- range structural units. This work is innovative and meaningful for the advancement of dielectric polymers. Due to the suppressed electrical conductivity, the capacitive energy storage under high temperatures and electric fields is significantly improved. The following issues need to be addressed before the publication. + +Response: We thank the reviewer for the interest and the accurate summary of the results of the paper. + +(1) In Figure 2c(ii) and 2d(ii), the IFCT method calculated charge-transfer (CT) results indicate that the electron amount (0.14e) transferred from the donor unit to the acceptor in the molecular chain with two crosslinking points is significantly lower than that in the chain with one crosslinking point (0.87e). What accounts for this? + +Response: Thank you for your careful reading and considerate suggestions. IFCT calculation results demonstrate that the electron migration amount in TPEI containing + +<--- Page Split ---> + +two crosslinking points is significantly lower than that in TPEI with a single crosslinking point. This discrepancy is attributed to the enhanced face- to- face stacking of the two diamine units within the structural unit of TPEI with two crosslinking points, which leads to a more pronounced preferred layer packing (PLP) structure (Figure S8). In contrast, the two diamine units in the structural unit of TPEI with a crosslinking point predominantly exhibit partially misaligned stacking. This configuration likely induces a stacking mode resembling mixed layer packing (MLP), which significantly weakens the suppression of electron migration compared to the TPEI containing two crosslinking points. + +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). Notably, in the PLP structure induced by benzyl- induced crosslinking, the transfer of electrons from the diamine to the dianhydride during CT excitation is significantly diminished, with the amount of charge transfer nearly approaching 0 electrons between the two cross- linked molecular chains (Figures 2c- d(ii)). Moreover, the electron migration amount in TPEI containing two crosslinking points is significantly lower than that in TPEI with a crosslinking point. This difference arises from the enhanced face- to- face stacking of diamine units, which forms a more pronounced PLP structure. In contrast, TPEI with a crosslinking point exhibits partially misaligned stacking between diamine units, inducing a stacking more resembling MLP structure that weakens the suppression of electron migration (Figure S8, Supporting Information). + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Figure S8. Structural unit conformation diagram of a) TPEI with one crosslink point and b) TPEI with two crosslink points. Among them, the blue hexagonal pyramid represents the location of the crosslinking point, while the green and red areas indicate the plane where the benzene ring of the diamine unit lies.
+ +(2) The authors confirmed the significant impact of the preferred layer packing (PLP) structure on inhibiting electron transfer through DFT calculations. How is the mentioned charge-transfer (CT) excitation determined? The related description in the DFT calculation section should be provided. + +Response: Thank you for your important comments. From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge-transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +<--- Page Split ---> + +\[S_{r} \text { index } = \int S_{r}(\mathbf{r}) d\mathbf{r} \equiv \int \sqrt{\rho^{hole}(\mathbf{r}) \rho^{ele}(\mathbf{r})} d\mathbf{r} \quad (1)\] + +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +\[\begin{array}{c}{D_{x} = |X_{e l e} - X_{h o l e}|}\\ {D_{y} = |Y_{e l e} - Y_{h o l e}|}\\ {D_{z} = |Z_{e l e} - Z_{h o l e}|}\\ {D_{i n d e x} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}}} \end{array} \quad (2)\] + +Here, \(X_{ele}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +\[t_{index} = D_{index} - H_{CT} \quad (3)\] + +\[H_{CT} = |\pmb {H}\cdot \pmb{u}_{CT}| \quad (4)\] + +Here, \(H_{CT}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(\pmb{H}\) represents the vector composed of components \(\pmb{H_{x}}\) , \(\pmb{H_{y}}\) , and \(\pmb{H_{z}}\) , where \(\pmb{u}_{CT}\) denotes the unit vector along the CT direction. Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronically excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +Table S1 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
+ +<--- Page Split ---> + + +
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +Table S2 Analysis of the first 20 excited states of TPEI4 + +
Excited stateSr (a.u.)D (Angstrom)t(Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
+ +<--- Page Split ---> + + +
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +Table S3 Analysis of the first 20 excited states of TPEI with a crosslinking point + +
Excited stateSr(a.u.)D (Angstrom)t(Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
+ +<--- Page Split ---> + + +Table S3 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
+ +<--- Page Split ---> + + +
20th0.824871.009-0.582LE
+ +By analyzing the first 20 electronically excited states of PEI, TPEI \(u\) , TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +Revision: The interfragment CT (IFCT) method in Multiwfn \(^{26}\) revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). + +## DFT calculations + +The ground- state geometry optimizations and energy scanning of the polymer structural units were performed by Gaussian 16 with the B3LYP hybrid function and 6- 31G (d) basis function. The structure construction and the visualization of electrostatic potential distribution of polymer units was conducted by GaussView 6.1 and Multiwfn 3.8 \(^{51,52}\) . The model construction of polymer structural units for energy scanning was completed by dimerscan and xyz2QC \(^{54}\) . The first 20 excited states of polymer structural units were calculated using time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G functional \(^{55,56}\) . The interfragment charge- transfer (IFCT) method was implemented using the Multiwfn 3.8 program to analyze the electronic excitation behavior of the polymer molecule (see the Supporting Information for detailed analysis) \(^{57,58,59,60}\) . + +## DFT analysis + +From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent + +<--- Page Split ---> + +molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +\[S_{r} i n d e x = \int S_{r}(\pmb {r}) d\pmb {r} \equiv \int \sqrt{\rho^{h o l e}(\pmb {r})\rho^{e l e}(\pmb {r})} d\pmb {r}\] + +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +\[D_{x} = |X_{e l e} - X_{h o l e}|\] \[D_{y} = |Y_{e l e} - Y_{h o l e}|\] \[D_{z} = |Z_{e l e} - Z_{h o l e}|\] \[D_{i n d e x} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}}\] + +Here, \(X_{e l e}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +\[t_{i n d e x} = D_{i n d e x} - H_{c T}\] + +\[(3)\] + +\[H_{c T} = |H\cdot u_{c T}|\] + +Here, \(H_{c T}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(H\) represents the vector composed of components \(H_{x}\) , \(H_{y}\) , and \(H_{z}\) , where \(u_{c T}\) denotes the unit vector along the CT direction. + +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 + +<--- Page Split ---> + +electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +Table S2 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<--- Page Split ---> + +Table S3 Analysis of the first 20 excited states of TPEIu + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<--- Page Split ---> + +Table S4 Analysis of the first 20 excited states of TPEI with a crosslinking point + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<--- Page Split ---> + + +Table S5 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +By analyzing the first 20 electronically excited states of PEI, TPEI, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<--- Page Split ---> + +(3) In Figure 3c, the specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) of TPEI is lower than that of PEI, indicating that the TPEI polymer chains are stretched. However, "Furthermore, the substituents on the benzene rings can influence the twisting of the molecular chain conformation..." The electrostatic potential distributions of PEI and TPEI reveal that TPEI exhibits weaker electrostatic interactions, which the authors attribute to the twisting of the molecular chain conformation. Is there a contradiction between the concepts of "polymer chains are stretched" and "the twisting of the molecular chain conformation" in these two contexts? + +Response: Thank you for your careful reading and professional comment. The specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) of PEI and TPEI, obtained from differential scanning calorimetry (DSC), typically refers to the heat capacity change during the transition from the glassy state to the rubbery state. The \(\Delta C_{\mathrm{p}}\) value of TPEI is smaller than that of PEI, indicating that TPEI has more extended molecular chains compared to PEI. However, substituted methyl groups on the diamine benzene ring increase the dihedral angles at the imide ring of TPEI (Figure S10), inducing twisting at the donor-acceptor junctions within the molecular chains and thereby hindering electron transport. + +Revision: This strongly supports the idea that PLP structure effectively restricts electronic transport between polymer dielectrics. Furthermore, the substituent methyl groups on the diamine benzene rings increase the dihedral angles at the imide ring position of TPEI, inducing twisting at the donor-acceptor junctions within the molecular chains and thereby diminishing the electrostatic interactions within the molecular chains \(^{10}\) (Figures S10- 11, Supporting Information). + +The glass transition temperature ( \(\mathrm{T_g}\) ) increases from \(236.31^{\circ}\mathrm{C}\) for PEI to \(289.72^{\circ}\mathrm{C}\) for TPEI, suggesting that the movement of polymer chains is restrained by benzyl- induced crosslinking networks (Figure 3c). In addition, the variation in specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) during the glass transition, caused by changes in the conformation of polymer chains, was obtained from DSC data. \(\Delta C_{\mathrm{p}}\) is significantly reduced from 0.205 \(\mathrm{Jg^{- 1}°C^{- 1}}\) for PEI to \(0.119\mathrm{Jg^{- 1}°C^{- 1}}\) for TPEI, indicating that the polymer chains in the crosslinked films are more stretched compared to those in PEI, thereby minimizing voids and defects in the polymer films \(^{16,33}\) . + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Figure S10. Structural formulas of PEI and TPEIu and the dihedral angles at the imide ring.
+ +(4) Here, "TPEI exhibits over an order of magnitude lower leakage current density than that of PEI and other heat-resistant polymers...", the authors reference "other heat-resistant polymers", but the leakage data for these materials are absent. Please provide examples of leakage data for "other heat-resistant polymers". + +Response: Thank you for your professional comments. In response to the reviewer's kind suggestion, the leakage current density of conventional heat-resistant polymers (Kapton, FPE, and PEI-PSU) as a function of electric field was measured at elevated temperatures, as depicted in Figure S20. + +Revision: Another advantage of the TPEI film is its excellent electrical insulation performance at high temperatures. According to the tested results of leakage current density of the polymer films (Figures 4d-e and Figures S20-S22 in the Supporting Information), TPEI exhibits over an order of magnitude lower leakage current density than that of PEI and other heat-resistant polymers at high electric fields and elevated temperatures. + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Figure S20 Leakage current density of TPEI as a function of electric field, compared with those of Kapton, FPE, and PEI-PSU at \(150^{\circ}\mathrm{C}\) a) and \(200^{\circ}\mathrm{C}\) b).
+ +(5) In figures 4d-e, the fitting mechanism of the leakage current for fresh PEI exhibits significant deviation. The authors should re-evaluate the leakage conduction mechanism and consider performing segmented fitting of the experimental results. Response: Thank you for your valuable comment. In response to the reviewer's suggestion, we have re-evaluated the conduction mechanisms of PEI at \(150^{\circ}\mathrm{C}\) and \(200^{\circ}\mathrm{C}\) . During this evaluation, the Schottky emission mechanism was ruled out due to the mismatch between the theoretical and experimental dielectric constants. As shown in Figures 4d-e, the conduction mechanisms of PEI under elevated temperatures and specific electric fields aligns well with the hopping conduction model. Additionally, we analyzed the leakage current density versus electric field (J-E) curves of PEI at \(150^{\circ}\mathrm{C}\) and \(200^{\circ}\mathrm{C}\) using the space charge limited conduction (SCLC) mechanism. The SCLC mechanism exhibits three distinct stages as the electric field increases. First, at low electric fields, the concentration of electrons injected into the dielectric is significantly lower than that of thermally excited electrons within the bulk, where conduction follows the Ohmic law. Second, when the electric field increases to the first critical threshold, the injected electron concentration exceeds the thermally excited electron concentration. In this stage, injected electrons continuously fill the traps, and space charge remains + +<--- Page Split ---> + +localized rather than migrating through the sample. Here, the leakage current density \((J)\) is proportional to the square of the electric field \((E^{2})\) . Finally, as the electric field further increases to the second critical threshold, the traps become fully saturated. Excess electrons are no longer constrained, leading to a rapid increase in current density. The SCLC equation can be expressed as: + +\[J = \frac{9\mu\epsilon_0\epsilon_r}{8} E^2\] + +where \(\mu\) is the electron mobility, \(\epsilon_0\) represents the vacuum permittivity, and \(\epsilon_r\) denotes the relative dielectric permittivity of the material. As shown in Figure S21, the electrical conduction of PEI exhibits Ohmic conduction under high temperatures and low electric fields and follows the SCLC mechanism under high temperatures and high electric fields. + +![](images/Figure_4.jpg) + +
Figure 4. Analysis of mechanical performance and electrical insulation properties. DMA curves for a) PEI film and b) TPEI film. c) Comparison of the storage modulus of PEI and TPEI films. d) Leakage current density of polymer films as a function of electric field at \(150^{\circ}\) C and e) \(200^{\circ}\) C. f) Electrical conductivity of TPEI, PEI, FPE, Kapton, and PEI-PSU films at various temperatures.
+ +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Figure S21. The leakage current density of pristine PEI as a function of electric field at elevated temperatures is presented, with the solid curves denoting the SCLC model fit.
+ +(6) Please update the performance comparison charts in Figures 6e and 6f by including the most recent relevant reported results. + +Response: Thank you for your kind comments. Inspired by recent reports on the high- temperature capacitive energy storage performance of novel dielectric polymers and in response to the constructive suggestions from the second reviewer, we have supplemented and revised the performance comparison plots at \(200^{\circ}\mathrm{C}\) and \(250^{\circ}\mathrm{C}\) (Figures 6g-6h). These comparisons highlight the superior performance of TPEI in high-temperature capacitive energy storage. + +# Revision: + +<--- Page Split ---> +![](images/Figure_6.jpg) + +
Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \(150^{\circ}\mathrm{C}\) and b) \(200^{\circ}\mathrm{C}\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \(150^{\circ}\mathrm{C}\) and BOPP at \(120^{\circ}\mathrm{C}\) , d) \(200^{\circ}\mathrm{C}\) and e) \(250^{\circ}\mathrm{C}\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \(>90\%\) ) at \(200^{\circ}\mathrm{C}^{10,11,17,18,24,25,38,39,40,41,42,43,44,45,46,47,48,49}\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \(250^{\circ}\mathrm{C}^{10,25,42,46,50}\) for the TPEI and novel all-organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m-1 and 20 kΩ.
+ +(7) It is advisable for the author to incorporate a radar chart that compares the key performance parameters of TPEI and fresh PEI, emphasizing the advantages of the short-range structural rearrangement methods. + +<--- Page Split ---> + +Response: Thank you for your valuable comments. In response to the reviewer's kind suggestion, we constructed a radar chart to compare the key performance parameters of PEI and TPEI (Figure 6f). The results show that TPEI, modified via short- range structural rearrangement, exhibits unparalleled superiority over PEI in both thermal stability and electrical insulation. + +![](images/Figure_6.jpg) + +
Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \(150^{\circ}\mathrm{C}\) and b) \(200^{\circ}\mathrm{C}\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \(150^{\circ}\mathrm{C}\) and BOPP at \(120^{\circ}\mathrm{C}\) , d) \(200^{\circ}\mathrm{C}\) and e) \(250^{\circ}\mathrm{C}\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \(>90\%\) ) at \(200^{\circ}\mathrm{C}^{10, 11, 17, 18, 24, 25, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49}\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \(250^{\circ}\mathrm{C}^{10, 25, 42, 46, 50}\) for the TPEI and novel all-
+ +<--- Page Split ---> + +organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m- 1 and 20 kΩ. + +(8) The authors discussed uncross-linked TPEI (TPEIu) during the research process. However, there is no characterization of its dielectric and energy storage performance. What accounts for this? + +Response: Thank you for your thorough review of the experimental details. Firstly, non- crosslinked TPEI (TPEIu) fails to form a free- standing film due to the steric hindrance of the four methyl groups on the diamine's benzene ring, leading to severe film cracking. This structural instability prevents reliable measurements of its dielectric and capacitive properties. In contrast, TPEI modified via benzyl crosslinking- induced structural unit rearrangement forms a robust free- standing film while ensuring the mechanical properties of TPEI, as shown in Figure S19. + +# Revision: + +![](images/Figure_unknown_4.jpg) + +
Figure S19 Stress-strain curves of TPEI film.
+ +(9) Some errors should be corrected, such as " \(\mathrm{Tg} \approx 265^{\circ} \mathrm{C}\) " and " \(\mathrm{Tg} = 330^{\circ} \mathrm{C}\) " in the Materials section. + +Response: Thank you sincerely for your kindly reminder. We have reviewed the whole + +<--- Page Split ---> + +manuscript and revised the errors. + +## Revision: + +Copolymer of PEI with polysulfone (PEI- PSU) particles \(\mathrm{(T_g\approx 265~^\circ C)}\) , fluorene polyester (FPE) particles \(\mathrm{(T_g = 330~^\circ C)}\) and commercial biaxially oriented polypropylene (BOPP) films with a thickness of \(5.8\mu \mathrm{m}\) were provided by Polyk Technologies Company. PEI- PSU particles and FPE particles were dissolved in NMP, stirring at \(70^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Next, the viscous polymer solution was cast and baked at \(70^{\circ}\mathrm{C}\) for \(2\mathrm{h}\) , and then the sample films were dried in a vacuum oven at \(200^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Thermogravimetric analysis (TGA) curves were obtained from a NETZSCH TGA209F1 thermogravimetry under nitrogen (air) atmosphere at a heating rate of \(10^{\circ}\mathrm{C}\) \(\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(800^{\circ}\mathrm{C}\) . Differential scanning calorimetry (DSC) was performed on a TA Q10 DSC at a scan rate of \(10^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(300^{\circ}\mathrm{C}\) in a nitrogen atmosphere. The in- plane thermal expansion change curves of the films were recorded by a TMA Q400 from TA Instruments, with a force of \(0.02\mathrm{N}\) , under nitrogen flow at a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(350^{\circ}\mathrm{C}\) . + +Reviewer #2 (Remarks to the Author): + +This work achieves the obstruction of long- range electron transport along polymer chain segments by rearranging the dianhydride and diamine units in polyimide, leading to the development of TPEI with both high thermal stability and high dielectric strength. Energy storage densities of \(6.38\mathrm{J / cm^3}\) and \(3.04\mathrm{J / cm^3}\) were obtained at \(200^{\circ}\mathrm{C}\) and \(250^{\circ}\mathrm{C}\) , respectively, while maintaining \(90\%\) efficiency. The manuscript is well- organized and provides valuable insights for researchers in the field. Therefore, I recommend its publication after minor revisions addressing the following points: + +Response: We highly appreciate the reviewer's positive comment on our paper and we will try our best to address the questions raised. + +(1) The authors discuss electron transfer between the dianhydride and diamine units during excitation in lines 113-139. However, electron excitation typically involves transitions from the HOMO to the LUMO and higher energy levels. Does the reported + +<--- Page Split ---> + +charge transfer only consider transitions from HOMO to LUMO? I think analyzing a single energy level transition may not fully reveal the influence of electron excitation on the system. Therefore, I suggest also considering electron transitions to 3\~5 energy levels near LUMO to obtain a more comprehensive understanding of the electronic excitation characteristics. + +Response: Thank you for your careful reading and professional comments. We acknowledge the reviewer's point that analyzing single energy level transitions may not fully reveal the electronic excitation characteristics of polymer structural units. To address this concern, we applied time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G(d) method to analyze electron transitions in the first 20 excited states of the polymer structural units. As described in the DFT calculation validation section, the charge transfer processes we characterized were not limited to considering the energy level transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) in the first excited state. From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +\[S_{r} \text{index} = \int S_{r}(\mathbf{r}) d\mathbf{r} \equiv \int \sqrt{\rho^{hole}(\mathbf{r})\rho^{ele}(\mathbf{r})} d\mathbf{r} \quad (1)\] + +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify + +<--- Page Split ---> + +the distance between the centroids of the holes and electrons. + +\[D_{x} = |X_{ele} - X_{hole}|\] \[D_{y} = |Y_{ele} - Y_{hole}|\] \[D_{z} = |Z_{ele} - Z_{hole}|\] + +\[D_{index} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}} \quad (2)\] + +Here, \(X_{ele}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +\[t_{index} = D_{index} - H_{CT} \quad (3)\] \[H_{CT} = |H\cdot u_{CT}| \quad (4)\] + +Here, \(H_{CT}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(H\) represents the vector composed of components \(H_{x}\) , \(H_{y}\) , and \(H_{z}\) , where \(u_{CT}\) denotes the unit vector along the CT direction. + +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +Table S1 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
+ +<--- Page Split ---> + + +
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +Table S2 Analysis of the first 20 excited states of TPEIu + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
+ +<--- Page Split ---> + + +
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +Table S3 Analysis of the first 20 excited states of TPEI with a crosslinking point + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
+ +<--- Page Split ---> + + +
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +Table S3 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +By analyzing the first 20 electronically excited states of PEI, TPEIu, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations + +<--- Page Split ---> + +occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). + +## DFT calculations + +The ground- state geometry optimizations and energy scanning of the polymer structural units were performed by Gaussian 16 with the B3LYP hybrid function and 6- 31G (d) basis function. The structure construction and the visualization of electrostatic potential distribution of polymer units was conducted by GaussView 6.1 and Multiwfn 3.851, 52, 53. The model construction of polymer structural units for energy scanning was completed by dimerscan and xyz2QC54. The first 20 excited states of polymer structural units were calculated using time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G functional55, 56. The interfragment charge- transfer (IFCT) method was implemented using the Multiwfn 3.8 program to analyze the electronic excitation behavior of the polymer molecule (see the Supporting Information for detailed analysis)57, 58, 59, 60. + +## DFT analysis + +From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these + +<--- Page Split ---> + +results. The Sr function is integrated over the entire space as follows: + +\[S_{r} \text{index} = \int S_{r}(\mathbf{r}) \mathrm{d}\mathbf{r} \equiv \int \sqrt{\rho^{\text{hole}}(\mathbf{r}) \rho^{\text{ele}}(\mathbf{r})} \mathrm{d}\mathbf{r}\] + +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +\[D_{x} = |X_{e l e} - X_{h o l e}|\] \[D_{y} = |Y_{e l e} - Y_{h o l e}|\] \[D_{z} = |Z_{e l e} - Z_{h o l e}|\] \[D_{i n d e x} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}}\] + +Here, \(X_{e l e}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +\[t_{i n d e x} = D_{i n d e x} - H_{C T}\] + +\[(3)\] + +\[H_{C T} = |\pmb {H}\cdot \pmb{u}_{C T}|\] + +Here, \(H_{C T}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(\pmb{H}\) represents the vector composed of components \(\pmb{H_{x}}\) , \(\pmb{H_{y}}\) , and \(\pmb{H_{z}}\) , where \(\pmb{u}_{C T}\) denotes the unit vector along the CT direction. + +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding + +<--- Page Split ---> + +electronic excitation types for the first 20 excited states of the polymer molecules. + +Table S2 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<--- Page Split ---> + +Table S3 Analysis of the first 20 excited states of TPEIu + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<--- Page Split ---> + +Table S4 Analysis of the first 20 excited states of TPEI with a crosslinking point + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<--- Page Split ---> + + +Table S5 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +By analyzing the first 20 electronic excited states of PEI, TPEI, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<--- Page Split ---> + +(2) The manuscript states in lines 182-193 that polymer thickness decreases with increasing electrostatic stress, which is an intriguing observation. While this effect is theoretically possible, it is rarely reported due to the generally high mechanical stability of polymers, especially for pure dielectric polymers under an applied electric field (excluding cases with piezoelectric or ferroelectric additives). Therefore, field-induced deformation of pure dielectric polymers is an interesting and meaningful topic. Perhaps, an experimental approach similar to those used for piezoelectric materials could be considered to measure polymer thickness changes under an external electric field to support this interesting hypothesis. + +Response: Thank you for your valuable comments. Firstly, prior studies have shown that the breakdown electric field of polyethylene is correlated with its mechanical strength1. Secondly, based on the electromechanical breakdown mechanism of polymers and the working mechanisms of dielectric elastomers (both associated with the Maxwell stress under the applied electric field)2, 3, we hypothesize that the thickness of polymer films decreases with increasing electrostatic stress. Thus, we propose that pure dielectric polymers undergo electric field- induced deformation under applied electric fields. Furthermore, in response to the reviewer's suggestion, we tested the strain versus electric field (S- E) curve of TPEI, and the experimental results are consistent with our hypothesized conclusion (Figure S18). + +## Revision: + +As shown in Figure S18, the thickness of polymer films under an external electric field \((E)\) decreases due to the increasing electrostatic stress \((= \frac{1}{2}\epsilon_{0}\epsilon_{r}E^{2}\) , where \(\epsilon_{0}\) and \(\epsilon_{r}\) denote the dielectric permittivity of a vacuum and the dielectric constant of dielectrics, respectively), which is counterbalanced by the mechanical stress arising from elastic deformation \((= Ye\) , where \(Y\) is the modulus and \(e\) represents the elastic strain of the dielectric)7,36,37. + +<--- Page Split ---> +![](images/Figure_unknown_5.jpg) + +
Figure S18 Strain versus electric field (S-E) curves of TPEI at frequency of 100 Hz.
+ +(3) In Figures 6e and 6f, the authors compare the performance of existing advanced energy storage materials. However, some of these materials are not purely organic polymers, as they contain fillers or ferroelectric components. To ensure a fair and consistent comparison, I recommend excluding these non-purely organic materials so that the advantages of the authors work can be more accurately highlighted. + +Response: Thank you for your kind comments. Building on the latest advancements in high- temperature capacitive energy storage performance of novel dielectric polymers and incorporating suggestions from the first reviewer, we have supplemented and updated the performance comparison plots at \(200^{\circ}\mathrm{C}\) (Figure 6g) and \(250^{\circ}\mathrm{C}\) (Figure 6h). The updated results show that the polymer undergoing PLP structural rearrangement exhibits superior energy storage performance at \(200^{\circ}\mathrm{C}\) and \(250^{\circ}\mathrm{C}\) . This confirms the effectiveness of benzyl crosslinking in inducing short- range rearrangement of structural units within complexly packed polymer chains, thereby simultaneously enhancing thermal stability and electrical insulation at elevated temperatures. + +# Revision: + +<--- Page Split ---> +![](images/Figure_6.jpg) + +
Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \(150^{\circ}\mathrm{C}\) and b) \(200^{\circ}\mathrm{C}\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \(150^{\circ}\mathrm{C}\) and BOPP at \(120^{\circ}\mathrm{C}\) , d) \(200^{\circ}\mathrm{C}\) and e) \(250^{\circ}\mathrm{C}\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \(>90\%\) ) at \(200^{\circ}\mathrm{C}^{10,11,17,18,24,25,38,39,40,41,42,43,44,45,46,47,48,49}\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \(250^{\circ}\mathrm{C}^{10,25,42,46,50}\) for the TPEI and novel all-organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m-1 and 20 kΩ.
+ +(4) There are multiple formatting inconsistencies with the “°C” unit in lines 350–385. Response: Thank you sincerely for your kind reminder. We have reviewed the whole manuscript and revised the errors. + +<--- Page Split ---> + +## Revision: + +Copolymer of PEI with polysulfone (PEI- PSU) particles \(\mathrm{(T_g\approx 265~^\circ C)}\) , fluorene polyester (FPE) particles \(\mathrm{(T_g = 330~^\circ C)}\) and commercial biaxially oriented polypropylene (BOPP) films with a thickness of \(5.8\mu \mathrm{m}\) were provided by Polyk Technologies Company. PEI- PSU particles and FPE particles were dissolved in NMP, stirring at \(70^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Next, the viscous polymer solution was cast and baked at \(70^{\circ}\mathrm{C}\) for \(2\mathrm{h}\) , and then the sample films were dried in a vacuum oven at \(200^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Thermogravimetric analysis (TGA) curves were obtained from a NETZSCH TGA209F1 thermogravimetry under nitrogen (air) atmosphere at a heating rate of \(10^{\circ}\mathrm{C}\) \(\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(800^{\circ}\mathrm{C}\) . Differential scanning calorimetry (DSC) was performed on a TA Q10 DSC at a scan rate of \(10^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(300^{\circ}\mathrm{C}\) in a nitrogen atmosphere. The in- plane thermal expansion change curves of the films were recorded by a TMA Q400 from TA Instruments, with a force of \(0.02\mathrm{N}\) , under nitrogen flow at a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(350^{\circ}\mathrm{C}\) . + +(5) The characterization section must be improved by providing a detailed description of each experimental technique used. For example, what mode was used in the AFM test? What amplitude was selected for the DMA test? Was preheating performed in the DSC test? In the D-E loop test, what were the electrode material and dimensions? + +Response: Thank you for your valuable comments. We added these descriptions according to your suggestion. The surface morphology of the sample films was characterized using atomic force microscopy (AFM) in tapping mode. In tensile mode, dynamic mechanical analysis (DMA) of sample films was conducted at a load frequency of \(1\mathrm{Hz}\) , with a displacement amplitude of \(20\mu \mathrm{m}\) , a temperature ranges from \(50\) to \(350^{\circ}\mathrm{C}\) , and a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) . In differential scanning calorimetry (DSC) measurements, the glass transition temperature \((\mathrm{T_g})\) of the polymer films was determined from the inflection point of the second heating curve after an initial heating- cooling cycle, a protocol designed to eliminate thermal history and enhance data reliability. Gold electrodes with a diameter of \(3\mathrm{mm}\) were used as the electrode material for displacement- electric field (D- E) loop measurements. + +<--- Page Split ---> + +## Revision: + +## Characterization + +\(^1\mathrm{H}\) nuclear magnetic resonance (NMR) spectra of the prepolymers were recorded using a JNM- ECZ600R spectrometer in DMSO- \(d_{6}\) . The crosslinking degree of the films was determined by calculating the absorbance of the polymer solutions, which was recorded using a UV- vis spectrophotometer (UV- 2600i, Island Ferry, Japan). The morphologies of the polymer films were observed by a scanning electron microscope (SEM, TESCAN) and an atomic force microscope (AFM, NanomanTM VS, USA) operated in tapping mode. X- ray photoelectron spectroscopy (XPS) analysis was carried out by a Thermo Fisher K- Alpha spectroscopy with an Al source. Solid- state UV- vis absorption spectra were recorded using a Shimadzu UV- 3600 spectrophotometer. The steady- state/transient photoluminescence (PL) spectra of the polymer films were recorded using an Edinburgh FS5 spectrometer. Fourier transform infrared (FTIR) spectra of the samples were used to confirm their characteristic functional groups by a Nicolet iS50 FTIR spectrometer. X- ray diffraction (XRD) analysis was conducted with Cu radiation by a PANalytical Empyren diffractometer. The wide- angle X- ray scattering (WAXS) measurements were performed using a copper- target X- ray generator (Anton Paar) with operational parameters strictly controlled at \(\leq 40 \mathrm{kV}\) accelerating voltage and \(\leq 50 \mathrm{mA}\) tube current. Grazing incidence wide- angle X- ray scattering (GIWAXS) measurements were performed on a Rigaku Homelab system (Japan) equipped with a Cu Kα X- ray source (8.05 keV, \(\lambda = 1.54 \mathrm{\AA}\) ) and a HyPix- 6000 photon- counting detector. The sample- detector distance (SDD) was accurately calibrated using silicon standard sample data. The detector configuration included a pixel size of \(100 \mu \mathrm{m} \times 100 \mu \mathrm{m}\) , with an exposure time of 120 s per measurement. Thin films for GIWAXS analysis were prepared on a glass substrate by spin- coating. Thermogravimetric analysis (TGA) curves were obtained from a NETZSCH TGA209F1 thermogravimetry under nitrogen (air) atmosphere at a heating rate of \(10^{\circ}\mathrm{C min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(800^{\circ}\mathrm{C}\) . Differential scanning calorimetry (DSC) was performed on a TA Q10 DSC at a scan rate of \(10^{\circ}\mathrm{C min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(300^{\circ}\mathrm{C}\) in a nitrogen atmosphere. In DSC measurements, the glass transition temperature ( \(\mathrm{T_g}\) ) of the polymer films was determined from the + +<--- Page Split ---> + +inflection point of the second heating curve after an initial heating- cooling cycle, a protocol designed to eliminate thermal history and enhance data reliability. The in- plane thermal expansion change curves of the films were recorded by a TMA Q400 from TA Instruments, with a force of 0.02 N, under nitrogen flow at a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(350^{\circ}\mathrm{C}\) . Dynamic mechanical analysis (DMA) of samples was conducted in tensile mode using a DMA 850 (TA Instruments) at a load frequency of \(1\mathrm{Hz}\) , with a displacement amplitude of \(20\mu \mathrm{m}\) , a temperature ranges from 50 to \(350^{\circ}\mathrm{C}\) , a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , and under nitrogen flow. The stress- strain behavior of the crosslinked film was evaluated in tensile mode using a DMA 850 (TA Instruments, USA) with a preload force of \(0.1\mathrm{N}\) and a displacement ramp rate of 0.05 \(\mathrm{mm}\mathrm{min}^{- 1}\) . Gold electrodes with diameters of \(3\mathrm{mm}\) and \(8\mathrm{mm}\) were coated onto both sides of the films using a GVC- 2000 magnetron ion sputtering instrument for electrical testing under high electric field (D- E loop, breakdown strength and leakage current) and low electric field (dielectric spectra), respectively. The dielectric frequency spectrum and dielectric temperature spectrum of the samples were measured using a precision impedance analyzer (Agilent 4294A, Germany) and a DMS- 500 dielectric temperature spectroscopy measurement system (DMS- 500, China), respectively. The high- temperature- resistivity of the films was tested using a Tonghui TH2690A insulation resistance meter. The displacement- electric field hysteresis loop (D- E loop), breakdown strength and cyclic charge- discharge performance of the samples were measured by a TF Analyzer 3000 series (AixACT, Germany) at \(100\mathrm{Hz}\) . The leakage current density of sample films was measured using a TF Analyzer 3000 series (AixACT, Germany). A stepwise electric field increment mode was used, in which the electric field strength was increased by \(10\mathrm{MV}\mathrm{m}^{- 1}\) per step (each step maintained for 2 seconds) until reaching the preset electric field strength. The fast charge- discharge tests were performed using a DCQ- 20A measurement system (Polyk Technologies) with a load resistor (RL) of \(10\mathrm{k}\Omega\) . + +(6) In Figure 2, the author uses scan mode to explore the lowest energy points of two molecular chains. However, the structure of the polymer condensed matter is equally + +<--- Page Split ---> + +important, and I suggest that the free volume of the whole condensed matter structure should be calculated and analyzed. If you can, consider calculating statistics for the distance between this segment and the surrounding segment separately. The precision of the base group can be appropriately reduced to take into account the calculation speed and quality. + +Response: Thank you for your careful reading and professional suggestions. We employed molecular dynamics simulations to analyze the condensed- state structures of PEI and TPEI polymers (Figure S6). The simulation results reveal that despite the introduction of four methyl groups on diamine benzene to form benzyl groups (undergoing crosslinking under thermo- oxidative conditions) in TPEI, the cell of TPEI exhibits more free volume (blue regions) compared to PEI, resulting in a higher fractional free volume (FFV) for TPEI. Furthermore, we performed sectioning on the simulated cells of PEI and TPEI and conducted statistical analysis on the cavity contours of free volume within these planes to investigate distances around the polymer segments (Figure S7). The statistical analysis shows that the average interchain distance in TPEI (5.24 Å) significantly exceeds that in PEI (4.15 Å), a trend consistent with the findings from DFT calculations. Notably, the smaller interchain distance observed in PEI compared to the rigid scanning MLP results (5.1 Å) because the rigid scanning result was performed on two isolated polymer chains without considering the condensed- state structure of the polymer. + +## Revision: + +Additionally, the local interchain spacing in the polymer chains is increased by leveraging the electrostatic repulsion at the same positions between molecular chains, leading to difficulty in the transport of charge carriers within the polymer. The molecular dynamics (MD) simulations reveal that TPEI exhibits a higher fractional free volume (FFV = 23.48%) and greater interchain distance (5.24 Å) compared to those (FFV = 6.03%; interchain distance = 4.15 Å) of PEI (Figures S6- 7). + +## Molecular dynamics (MD) simulation + +<--- Page Split ---> + +Unit cells of PEI and TPEI were constructed using Materials Studio 20 software, both comprising 10 molecular chains with 20 repeat units per chain. Notably, 9 molecular chains in the TPEI system underwent crosslinking. Electrostatic interactions were handled by the Ewald summation technique, and van der Waals interactions were computed using an atom- based approach. A Nose- Hoover thermostat was used to control temperature, and pressure regulation was achieved through a Berendsen barostat. We use progressive relaxation and annealing methods to eliminate initial structural biases, enabling the system to reach thermodynamic equilibrium61. The fractional free volume (FFV) of a polymer is determined by the equation: + +\[FFV = \frac{V_{\mathrm{c}}}{V_{\mathrm{c}} + V_{0}}\] + +Where \(V_{c}\) corresponds to the unoccupied volume and \(V_{0}\) represents the volume occupied by polymer chains. + +![](images/Figure_unknown_6.jpg) + +
Figure S6. PEI a) and TPEI b) cells generated through molecular dynamics simulations. Blue regions denote the free volume and grey regions represent the volume occupied by polymer chains. c) Fractional free volume (FFV) and density data for PEI and TPEI.
+ +<--- Page Split ---> +![](images/Figure_unknown_7.jpg) + +
Figure S7. Cleave plane of PEI a) and TPEI b) simulation cells. Green regions denote the free volume and grey regions represent the volume occupied by polymer chains. c) Average spacing around FFV in PEI and TPEI.
+ +Reviewer #3 (Remarks to the Author): + +The reviewer had comments regarding a number of aspects, summarised below: We highly appreciate the reviewer's accurate comments on our paper and will try to address the questions raised. + +<--- Page Split ---> + +(1) The potential of the materials in future applications, due to changes in production methods. + +Response: Thank you for your valuable comments. Compared to conventional polyimide crosslinking requiring elevated temperature windows (300- 350 °C), the benzyl groups in TPEI undergo thermal- oxidative crosslinking under an air atmosphere at reduced temperatures (250- 290 °C), effectively inducing rearrangement of donor- acceptor units in TPEI. This process demonstrates significant energy- saving advantages in manufacturing. Regarding scalable manufacturing, the novel all- organic polymer (TPEI) eliminates filler dispersion challenges inherent in composite dielectrics incorporating organic/inorganic additives, thereby significantly enhancing production scalability. Finally, performance comparison plots reveal that the polyetherimide modified through a structural rearrangement strategy (TPEI) exhibits superior energy storage performance (Figure 6f). Collectively, these comparisons demonstrate that structurally rearranged dielectric polymers in this work exhibit substantial application potential in dielectric energy storage. + +(2) The mechanical properties of the crosslinked polyetherimides, with more characterization requested. + +Response: Appreciating your suggestion to further characterize the mechanical properties of the crosslinked polyetherimides, we performed tensile test on crosslinked TPEI films, with the corresponding stress-strain curves presented in Figure S19. The result indicates that TPEI exhibits a tensile strength of 80 MPa and an elongation at break of 3.4%. This is primarily attributed to the flexible ether linkages and alkane chains within the crosslinked network. Notably, the crosslinking method not only enhances the storage modulus of TPEI (Figures 4a-c) but also maintains its mechanical properties without compromise. + +## Revision: + +The increased breakdown strength of the polymer films can be attributed to their greater modulus. The storage modulus of TPEI (for example, 4.46 GPa at 150 °C, 3.97 GPa at 200 °C and 3.42 GPa at 250 °C) is greater than that of PEI (for example, 2.82 GPa at + +<--- Page Split ---> + +\(150~^\circ \mathrm{C}\) , 2.46 GPa at \(200~^\circ \mathrm{C}\) and 0 GPa at \(250~^\circ \mathrm{C}\) ), throughout a temperature range of \(35~^\circ \mathrm{C}\) to \(250~^\circ \mathrm{C}\) (Figures 4a- c). Notably, TPEI exhibits a tensile strength of 80 MPa and an elongation at break of \(3.4\%\) (Figure S19, Supporting Information). + +![](images/Figure_unknown_8.jpg) + +
Figure S19 Stress-strain curves of TPEI film.
+ +(3) The evidence provided to support the claim of preferred layer packing, compared to mixed layer packing, with more experimental results required. + +Response: Thank you for your constructive comment. Wide-angle X-ray scattering (WAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS) analyses were performed on TPEIu and TPEI samples. The WAXS patterns reveal significantly intensified and broadened diffraction peaks in TPEI compared to TPEIu, confirming the structural rearrangement into “ch-pack” packing structure (PLP structure) induced by benzyl crosslinking4 (Figure 3g). Furthermore, the 2D GIWAXS patterns reveal that TPEI exhibits broad and isotropic amorphous halos, contrasting sharply with the poorly defined amorphous scattering features observed in TPEIu (Figures 3h-i and Figure S16 in the Supporting Information). This stark difference indicates substantial alterations in molecular packing and arrangement induced by benzyl crosslinking, resulting in a heterogeneous microstructure comprising coexisting ordered domains and amorphous regions in TPEI. Furthermore, Analysis of one-dimensional intensity versus scattering + +<--- Page Split ---> + +vector (I- q) profiles derived from the 2D GIWAXS data reveals two characteristic scattering peaks for TPEI. The scattering peak of TPEI at a scattering vector \(\mathbf{q}\) of 1.01- 1.35 Å- 1 is attributed to the ordered "ch- pack" stacking structure (PLP structure; Figure S17). Additionally, the scattering peak of TPEI at \(\mathbf{q} = 1.35\text{- } 1.83\text{Å}^{- 1}\) is ascribed to "π- pack" interaction between imide rings and benzene rings in adjacent polymer chains. + +Revision: As shown in Figures 3e- f, the exploded views of the XRD patterns of the films indicate the presence of "ch- pack" ordered domains observed in TPEI compared with \(\mathrm{PEI^{34}}\) . The "ch- pack" packing structure of polymer chains, similar to the PLP structure, originates from liquid- crystalline- like ordered domains. Hence, the PLP structure formed by benzyl- induced crosslinking predominates in TPEI film, indicating an efficient reduction in electrical conduction loss. In contrast, the main ordered packing structure in PEI is a "π- stack" formation, which represents the π- π stacking of imide and phenyl rings in ordered domains, thereby largely promoting charge carrier transport in polymers. Notably, the variation in interchain spacing of polymer chains was calculated from the XRD data of PEI and TPEI films, which is consistent with the theoretical charge results from DFT calculations and MD simulations (Figure S15, Supporting Information). The WAXS patterns reveal significantly intensified and broadened diffraction peaks in TPEI compared to \(\mathrm{TPEI_u}\) , confirming the structural rearrangement into "ch- pack" packing structure (PLP structure) induced by benzyl crosslinking35 (Figure 3g). Furthermore, the 2D GIWAXS patterns reveal that TPEI exhibits broad and isotropic amorphous halos, contrasting sharply with the poorly defined amorphous scattering features observed in \(\mathrm{TPEI_u}\) (Figures 3h- i and Figure S16 in the Supporting Information). This stark difference indicates substantial alterations in molecular packing and arrangement induced by benzyl crosslinking, resulting in a heterogeneous microstructure comprising coexisting ordered domains and amorphous regions in TPEI. Furthermore, Analysis of one- dimensional intensity versus scattering vector (I- q) profiles derived from the 2D GIWAXS data reveals two characteristic scattering peaks for TPEI. The scattering peak of TPEI at a scattering vector \(\mathbf{q}\) of 1.01- 1.35 Å- 1 is attributed to the ordered "ch- pack" stacking structure (PLP structure; Figure S17). Additionally, the scattering peak of TPEI at \(\mathbf{q} = 1.35\text{- } 1.83\text{Å}^{- 1}\) is ascribed to "π- + +<--- Page Split ---> + +pack" interaction between imide rings and benzene rings in adjacent polymer chains. + +![](images/Figure_3.jpg) + +
Figure 3. Characterization of the polymer films and the PLP structure. a) FT-IR spectra, b) TGA and DTG curves (Inset: partial enlarged detail of TGA), c) DSC curves, d) In-plane thermal expansion change curves (Inset: CET values) for PEI and TPEI films. Exploded view of the XRD pattern for e) PEI film and f) TPEI film. g) The WAXS patterns for TPEIu and TPEI films. The 2D GIWAXS patterns of h) TPEIu and i) TPEI films.
+ +<--- Page Split ---> +![](images/Figure_unknown_9.jpg) + +
Figure S16. Schematic diagram of GIWAXS measurements of polymer film. \(\alpha_{f}\) represents the exit angle of the X-ray beam relative to the film surface, and \(2\theta_{f}\) denotes the exit angle relative to the plane of incidence. Meanwhile, \(\mathbf{q}_{\mathrm{x}}\) , \(\mathbf{q}_{\mathrm{y}}\) , and \(\mathbf{q}_{\mathrm{z}}\) is the components of the scattering vector \(\mathbf{q}\) .
+ +![](images/Figure_unknown_10.jpg) + +
Figure S17. One-dimensional GIWAXS integration profile of polymer films.
+ +(4) Additional experimental evidence for the possible charge transfer excitations, as well as the DFT calculations provided. + +Response: Thank you for your valuable comments. Through comparative analysis of fluorescence emission spectra between PEI and TPEI films combined with DFT calculations, we demonstrated that the benzyl-induced rearrangement of donor-acceptor units to form the PLP structure effectively suppresses both interchain and intrachain charge transfer. Notably, interchain charge transfer induces fluorescence quenching + +<--- Page Split ---> + +with intensity attenuation, while intrachain charge transfer promotes fluorescence redshift5, 6. As shown in Figure S12, the TPEI exhibits a significantly enhanced fluorescence signal with a blue- shifted peak compared to PEI, proving that the benzyl- induced PLP structure simultaneously inhibits interchain and intrachain charge transfer. Additionally, we employed time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G(d) method to analyze electron transitions in the first 20 excited states of the polymer structural units (see the Revision for detailed analysis). + +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). Notably, in the PLP structure induced by benzyl- induced crosslinking, the transfer of electrons from the diamine to the dianhydride during CT excitation is significantly diminished, with the amount of charge transfer nearly approaching 0 electrons between the two cross- linked molecular chains (Figures 2c- d(ii)). Moreover, the electron migration amount in TPEI containing two crosslinking points is significantly lower than that in TPEI with a crosslinking point. This difference arises from the enhanced face- to- face stacking of diamine units, which forms a more pronounced PLP structure. In contrast, TPEI with a crosslinking point exhibits partially misaligned stacking between diamine units, inducing a stacking more resembling MLP structure that weakens the suppression of electron migration (Figure S8, Supporting Information). Moreover, the optical bandgap (2.9 eV) of TPEI is narrower than that (3.1 eV) of PEI (Figure S9, Supporting Information). This result contrasts with conventional observations in dielectric polymers where a wider bandgap typically correlates with superior electrical insulation25, 27. This strongly supports the idea that PLP structure effectively restricts electronic transport between polymer dielectrics. Furthermore, the substituent methyl groups on the diamine benzene rings increase the dihedral angles at the imide ring position of TPEI, inducing twisting at the donor- acceptor junctions within the molecular chains and thereby diminishing the electrostatic interactions within the molecular chains10 (Figures S10- 11, Supporting + +<--- Page Split ---> + +Information). Based on the fluorescence emission spectra of PEI and TPEI, TPEI exhibits a significantly enhanced fluorescence signal with a blue- shifted peak compared to PEI, which proves that the benzyl- induced PLP structure simultaneously inhibits both interchain and intrachain charge transfer28, 29 (Figure S12, Supporting Information). + +![](images/Figure_unknown_11.jpg) + +
Figure S12. Fluorescence emission spectra of PEI and TPEI samples.
+ +## Measurement of gelation content of crosslinked TPEI film + +To evaluate the degree of chemical crosslinking in TPEI film, un- crosslinked (TPEIu) and crosslinked (TPEI) samples were immersed in N- methyl- 2- pyrrolidone (NMP) at \(80^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . The remaining TPEI polymer was rinsed with ethanol to remove residual solvent and dried in a vacuum oven at \(100^{\circ}\mathrm{C}\) for 24 hours. The gel content was calculated using the formula: + +\[\% \mathrm{gel~content} = \frac{M_f}{M_o}\times 100\%\] + +where \(M_{f}\) and \(M_{o}\) denote the residual and initial weights of the film samples, respectively. + +<--- Page Split ---> + + +Table S1. Test conditions during gel content testing and results. + +
SampleTemperature (°C)Original massFinal massRatio of gel
Time (h)(mg)(mg)
TPEIu80 °C &amp; 24 h31.500.000.00%
TPEI80 °C &amp; 24 h33.8027.8082.25%
+ +## DFT analysis + +From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +\[S_{r} i n d e x = \int S_{r}(\boldsymbol {r}) d\boldsymbol {r} \equiv \int \sqrt{\rho^{h o l e}(\boldsymbol {r})\rho^{e l e}(\boldsymbol {r})} d\boldsymbol {r}\] + +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +\[D_{x} = |X_{e l e} - X_{h o l e}|\] \[D_{y} = |Y_{e l e} - Y_{h o l e}|\] \[D_{z} = |Z_{e l e} - Z_{h o l e}|\] + +<--- Page Split ---> + +\[D_{i n d e x} = \sqrt{\left(D_{x}\right)^{2} + \left(D_{y}\right)^{2} + \left(D_{z}\right)^{2}}\] + +(2) + +Here, \(X_{e l e}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +\[t_{i n d e x} = D_{i n d e x} - H_{c T}\] + +(3) + +\[H_{c T} = |\pmb {H}\cdot \pmb{u}_{c T}|\] + +Here, \(H_{c T}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(H\) represents the vector composed of components \(\pmb{H_{x}}\) , \(\pmb{H_{y}}\) , and \(\pmb{H_{z}}\) , where \(\pmb{u}_{c T}\) denotes the unit vector along the CT direction. + +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +<--- Page Split ---> + +Table S2 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<--- Page Split ---> + +Table S3 Analysis of the first 20 excited states of TPEIu + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<--- Page Split ---> + +Table S4 Analysis of the first 20 excited states of TPEI with a crosslinking point + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<--- Page Split ---> + + +Table S5 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +By analyzing the first 20 electronically excited states of PEI, TPEI, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<--- Page Split ---> + +(5) Reason for the TPEI material not decomposing in different environments. + +Response: Thank you for your careful comment. The resistance of TPEI to decomposition under diverse environments arises from its rationally designed molecular structure. First, the rigid molecular skeleton containing aromatic and imine rings provides high bond energy and planar rigidity, effectively suppressing thermal decomposition of polymer chains at elevated temperatures (Figure S14). Second, the ether linkages and isopropyl groups in TPEI impart flexibility to the polymer chains, alleviating stress concentration to prevent brittle fracture and enhance mechanical stability. Third, benzyl-induced crosslinking forms a network through chemical crosslinks and physical entanglements, which significantly hinders solvent penetration into the polymer film and improves solvent resistance (Figure S3). Concurrently, this crosslinked network reinforces thermal stability and mechanical strength. Overall, the balanced integration of rigidity-flexibility in TPEI's molecular design endows the material with outstanding structural stability across various environments. + +Revision: The glass transition temperature ( \(\mathrm{T_g}\) ) increases from \(236.31^{\circ}\mathrm{C}\) for PEI to \(289.72^{\circ}\mathrm{C}\) for TPEI, suggesting that the movement of polymer chains is restrained by benzyl- induced crosslinking networks (Figure 3c). In addition, the variation in specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) during the glass transition, caused by changes in the conformation of polymer chains, was obtained from DSC data. \(\Delta C_{\mathrm{p}}\) is significantly reduced from \(0.205\mathrm{Jg}^{- 1}\mathrm{^\circ C^{- 1}}\) for PEI to \(0.119\mathrm{Jg}^{- 1}\mathrm{^\circ C^{- 1}}\) for TPEI, indicating that the polymer chains in the crosslinked films are more stretched compared to those in PEI, thereby minimizing voids and defects in the polymer films \(^{16,33}\) . Moreover, the results of the in- plane thermal dimension change curves show a lower coefficient of thermal expansion (CTE) in TPEI films compared to that of PEI films in a specific temperature range (Figure 3d). These results indicate that benzyl- induced crosslinking network effectively restricts movement of polymer chains, thereby improving the thermal stability of the polymer films. Furthermore, the TGA curve of the TPEI film exhibits only \(5\%\) weight loss at \(420^{\circ}\mathrm{C}\) , further confirming its superior structural stability (Figure S14, Supporting Information). + +<--- Page Split ---> +![](images/Figure_unknown_12.jpg) + +
Figure S3. Photos of un-crosslinked TPEI \(u\) and crosslinked TPEI films after soaking in NMP at \(80^{\circ}\mathrm{C}\) for 24h.
+ +![](images/Figure_unknown_13.jpg) + +
Figure S14. TGA and DTG curves of TPEI film.
+ +(6) A request for the optical bandgap of the TPEI material to be measured. + +Response: Thank you for your thorough review of the experimental details. Considering the effect of benzyl crosslinking- induced rearrangement of donor- acceptor unit on the experimental optical bandgap of polymer films, solid- state UV- vis spectra were performed on PEI and TPEI samples (Figure S9, Supporting Information). The + +<--- Page Split ---> + +optical bandgap of TPEI (2.9 eV) is narrower than that of PEI (3.1 eV). This result contrasts with conventional observations in dielectric polymers, where a wider bandgap typically correlates with superior electrical insulation. This indicates that the significant improvement in high- temperature electrical insulation properties of TPEI is primarily attributed to the formation of the benzyl crosslinking- induced PLP structure. + +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). Notably, in the PLP structure induced by benzyl- induced crosslinking, the transfer of electrons from the diamine to the dianhydride during CT excitation is significantly diminished, with the amount of charge transfer nearly approaching 0 electrons between the two cross- linked molecular chains (Figures 2c- d(ii)). Moreover, the electron migration amount in TPEI containing two crosslinking points is significantly lower than that in TPEI with a crosslinking point. This difference arises from the enhanced face- to- face stacking of diamine units, which forms a more pronounced PLP structure. In contrast, TPEI with a crosslinking point exhibits partially misaligned stacking between diamine units, inducing a stacking more resembling MLP structure that weakens the suppression of electron migration (Figure S8, Supporting Information). Moreover, the optical bandgap (2.9 eV) of TPEI is narrower than that (3.1 eV) of PEI (Figure S9, Supporting Information). This result contrasts with conventional observations in dielectric polymers where a wider bandgap typically correlates with superior electrical insulation25, 27. This strongly supports the idea that PLP structure effectively restricts electronic transport between polymer dielectrics. Furthermore, the substituent methyl groups on the diamine benzene rings increase the dihedral angles at the imide ring position of TPEI, inducing twisting at the donor- acceptor junctions within the molecular chains and thereby diminishing the electrostatic interactions within the molecular chains10 (Figures S10- 11, Supporting Information). Based on the fluorescence emission spectra of PEI and TPEI, TPEI exhibits a significantly enhanced fluorescence signal with a blue- shifted peak compared to PEI, which proves that the benzyl- induced PLP structure simultaneously inhibits both + +<--- Page Split ---> + +interchain and intrachain charge transfer \(^{28,29}\) (Figure S12, Supporting Information). + +![](images/Figure_unknown_14.jpg) + +
Figure S9. a) Solid-state UV-vis spectra and b) \((a h\nu)^{2} - h\nu\) plots of PEI and TPEI. Here, \(\alpha\) represents the absorption coefficient, \(h\) corresponds to the Planck constant, and \(\nu\) indicates the light frequency.
+ +(7) Use of only one method to measure crosslinking density – the use of additional methods is suggested. + +Response: Thank you for your kind comments. To assess the degree of chemical crosslinking in TPEI films, swelling experiments were conducted on un-crosslinked sample (TPEI \(_u\) ) and crosslinked sample (TPEI) using the strongly polar solvent N-methyl-2-pyrrolidone (NMP). After immersion in NMP at \(80^{\circ}\mathrm{C}\) for 24 hours, TPEI \(_u\) completely dissolved, whereas TPEI retained substantial residual polymer (Figure S3). The remaining TPEI polymer was rinsed with ethanol to remove residual solvent and dried in a vacuum oven at \(100^{\circ}\mathrm{C}\) for 24 hours. The gel content was calculated using the formula: + +\[\% \mathrm{gel~content} = \frac{M_f}{M_o}\times 100\%\] + +where \(M_f\) and \(M_o\) denote the residual and initial weights of the film samples, respectively. As shown in Table S1, TPEI exhibited a gel content of \(82.25\%\) , which is higher than the insoluble fraction measured via solution UV-Vis spectroscopy. This discrepancy arises because, in addition to crosslinked regions, polymer chain entanglements also contribute to the residual weight. + +<--- Page Split ---> + +## Revision: + +These polymer films were obtained through thermal imidization within a temperature range of \(70^{\circ} \mathrm{C}\) to \(290^{\circ} \mathrm{C}\) in air, during which the polymer film containing benzyl functional groups underwent a thermo-oxidation crosslinking reaction. The crosslinking degree of the obtained TPEI film was measured using UV- vis spectroscopy (Figure S2, Supporting Information), and the result was \(57.41\%\) . The crosslinked TPEI film cannot be dissolved in N- methyl- 2- pyrrolidone (NMP), whereas it exhibits swelling behavior with a gel content of \(82.25\%\) when immersed in NMP (Figures S3 and Table S1, Supporting Information). + +## Measurement of gelation content of crosslinked TPEI film + +To evaluate the degree of chemical crosslinking in TPEI film, un- crosslinked (TPEI \(u\) ) and crosslinked (TPEI) samples were immersed in N- methyl- 2- pyrrolidone (NMP) at \(80^{\circ} \mathrm{C}\) for \(24 \mathrm{~h}\) . The remaining TPEI polymer was rinsed with ethanol to remove residual solvent and dried in a vacuum oven at \(100^{\circ} \mathrm{C}\) for 24 hours. The gel content was calculated using the formula: + +\[\% \mathrm{gel} \mathrm{content} = \frac{M_{f}}{M_{o}} \times 100\%\] + +where \(M_{f}\) and \(M_{o}\) denote the residual and initial weights of the film samples, respectively. + +Table S1. Test conditions during gel content testing and results. + +
SampleTemperature (℃) Time (h)Original mass (mg)Final mass (mg)Ratio of gel
TPEIu80℃ &amp; 24 h31.500.000.00%
TPEI80℃ &amp; 24 h33.8027.8082.25%
+ +<--- Page Split ---> +![](images/Figure_unknown_15.jpg) + +
Figure S3. Photos of un-crosslinked TPEI \(u\) and crosslinked TPEI films after soaking in NMP at \(80^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) .
+ +(8) A request for more details for the measurement of Leakage current density. Response: Thank you for your kind reminder. The direct-current (DC) leakage current density of films with 3 mm-diameter gold electrodes was measured using a TF Analyzer 3000 series (AixACT, Germany). A stepwise electric field increment mode was used, in which the electric field strength was increased by \(10\mathrm{MV}\mathrm{m}^{-1}\) per step (each step maintained for 2 seconds) until reaching the preset electric field strength. + +## Revision: + +The dielectric frequency spectrum and dielectric temperature spectrum of the samples were measured using a precision impedance analyzer (Agilent 4294A, Germany) and a DMS- 500 dielectric temperature spectroscopy measurement system (DMS- 500, China), respectively. The high- temperature- resistivity of the films was tested using a Tonghui TH2690A insulation resistance meter. The displacement- electric field hysteresis loop (D- E loop), breakdown strength and cyclic charge- discharge performance of the samples were measured by a TF Analyzer 3000 series (AixACT, Germany) at \(100\mathrm{Hz}\) . The leakage current density of sample films was measured using a TF Analyzer 3000 series (AixACT, Germany). A stepwise electric field increment mode was used, in which the electric field strength was increased by \(10\mathrm{MV}\mathrm{m}^{-1}\) per step (each step + +<--- Page Split ---> + +maintained for 2 seconds) until reaching the preset electric field strength. The fast charge- discharge tests were proceeded using a DCQ- 20A measurement system (Polyk Technologies) with a load resistor (RL) of \(10\mathrm{k}\Omega\) . + +Thank you for your professional review work, constructive comments, and valuable suggestions. We hope the above replies and related revisions are acceptable for publication in Nature Communications. + +Sincerely yours, Prof. Dou Zhang & Prof. Hang Luo State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, P. R. China E- mail: dzhang@csu.edu.cn, hangluo@csu.edu.cn + +Prof. Jun- Wei Zha State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources School of Electrical and Electronic Engineering North China Electric Power University Beijing 102206, P. R. China E- mail: zhajw@ncepu.edu.cn + +<--- Page Split ---> + +## References + +1. Stark KH, et al. Electric strength of irradiated polythene. Nature 176, 1225-1226 (1955). +2. Shi Y, et al. A processable, high-performance dielectric elastomer and multilayering process. Science 377, 228-232 (2022). +3. Li Q, et al. High-temperature dielectric materials for electrical energy storage. Annu Rev Mater Res 48, 219-243 (2018). +4. Bai L, Zhai L, He M-H, Wang C-O, Mo S, Fan L. Thermal expansion behavior of poly(amide-imide) films with ultrahigh tensile strength and ultralow CTE. Chin J Polym Sci 38, 748-758 (2019). +5. Wang R, et al. Dielectric polymers with mechanical bonds for high-temperature capacitive energy storage. Nat Mater (2025). https://doi.org/10.1038/s41563-025-02130-z +6. Chen L, et al. Tuning second near-infrared fluorescence activation by regulating the excited-state charge transfer dynamics change ratio. J Am Chem Soc (2025). https://doi.org/10.1021/jacs.5c03763 + +<--- Page Split ---> diff --git a/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..86a2786a90415714cc2ec7bee06741679639a4fc --- /dev/null +++ b/peer_reviews/78702168b7e15fb5a93930d5267d619d43b6691e203603ef8f0686e13ae7a071/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1000 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 295, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 157, 897, 202]]<|/det|> +# Decoupling thermal stability and insulation in dielectric polymers via donor acceptor rearrangement + +<|ref|>text<|/ref|><|det|>[[73, 214, 475, 232]]<|/det|> +Corresponding Author: Professor Jun- Wei Zha + +<|ref|>text<|/ref|><|det|>[[72, 298, 864, 313]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 351, 142, 365]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 377, 219, 391]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 403, 160, 416]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 430, 238, 443]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 443, 919, 520]]<|/det|> +The authors introduce a strategy to break the adverse correlation between thermal stability and electrical insulation of PEI dielectric by the effective rearrangement of short- range structural units. This work is innovative and meaningful for the advancement of dielectric polymers. Due to the suppressed electrical conductivity, the capacitive energy storage under high temperatures and electric fields is significantly improved. The following issues need to be addressed before the publication. (1) In Figure 2c(ii) and 2d(ii), the IFCT method calculated charge- transfer (CT) results indicate that the electron amount (0.14e) transferred from the donor unit to the acceptor in the molecular chain with two crosslinking points is significantly lower than that in the chain with one crosslinking point (0.87e). What accounts for this? + +<|ref|>text<|/ref|><|det|>[[72, 520, 914, 572]]<|/det|> +(2) The authors confirmed the significant impact of the preferred layer packing (PLP) structure on inhibiting electron transfer through DFT calculations. How is the mentioned charge-transfer (CT) excitation determined? The related description in the DFT calculation section should be provided. + +<|ref|>text<|/ref|><|det|>[[72, 572, 920, 675]]<|/det|> +(3) In Figure 3c, the specific heat capacity ((ΔCp) of TPEI is lower than that of PEI, indicating that the TPEI polymer chains are stretched. However, "Furthermore, the substituents on the benzene rings can influence the twisting of the molecular chain conformation..." The electrostatic potential distributions of PEI and TPEI reveal that TPEI exhibits weaker electrostatic interactions, which the authors attribute to the twisting of the molecular chain conformation. Is there a contradiction between the concepts of "polymer chains are stretched" and "the twisting of the molecular chain conformation" in these two contexts? (4) Here, "TPEI exhibits over an order of magnitude lower leakage current density than that of PEI and other heat-resistant polymers...", the authors reference "other heat-resistant polymers", but the leakage data for these materials are absent. Please provide examples of leakage data for "other heat-resistant polymers". + +<|ref|>text<|/ref|><|det|>[[72, 675, 880, 714]]<|/det|> +(5) In figures 4d-e, the fitting mechanism of the leakage current for fresh PEI exhibits significant deviation. The authors should re-evaluate the leakage conduction mechanism and consider performing segmented fitting of the experimental results. + +<|ref|>text<|/ref|><|det|>[[72, 714, 904, 741]]<|/det|> +(6) Please update the performance comparison charts in Figures 6e and 6f by including the most recent relevant reported results. + +<|ref|>text<|/ref|><|det|>[[72, 741, 920, 768]]<|/det|> +(7) It is advisable for the author to incorporate a radar chart that compares the key performance parameters of TPEI and fresh PEI, emphasizing the advantages of the short-range structural rearrangement methods. + +<|ref|>text<|/ref|><|det|>[[72, 768, 911, 794]]<|/det|> +(8) The authors discussed uncross-linked TPEI (TPEIu) during the research process. However, there is no characterization of its dielectric and energy storage performance. What accounts for this? + +<|ref|>text<|/ref|><|det|>[[72, 794, 792, 808]]<|/det|> +(9) Some errors should be corrected, such as "(Tg ≈ 265 °C)" and "(Tg = 330 °C)" in the Materials section. + +<|ref|>sub_title<|/ref|><|det|>[[73, 833, 162, 846]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 860, 238, 873]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 873, 915, 939]]<|/det|> +This work achieves the obstruction of long- range electron transport along polymer chain segments by rearranging the dianhydride and diamine units in polyimide, leading to the development of TPEI with both high thermal stability and high dielectric strength. Energy storage densities of 6.38 J/cm³ and 3.04 J/cm³ were obtained at 200 °C and 250 °C, respectively, while maintaining 90% efficiency. The manuscript is well- organized and provides valuable insights for researchers in the field. Therefore, I recommend its publication after minor revisions addressing the following points: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 48, 912, 126]]<|/det|> +1) The authors discuss electron transfer between the dianhydride and diamine units during excitation in lines 113-139. However, electron excitation typically involves transitions from the HOMO to the LUMO and higher energy levels. Does the reported charge transfer only consider transitions from HOMO to LUMO? I think analyzing a single energy level transition may not fully reveal the influence of electron excitation on the system. Therefore, I suggest also considering electron transitions to 3-5 energy levels near LUMO to obtain a more comprehensive understanding of the electronic excitation characteristics. + +<|ref|>text<|/ref|><|det|>[[72, 127, 920, 203]]<|/det|> +2) The manuscript states in lines 182-193 that polymer thickness decreases with increasing electrostatic stress, which is an intriguing observation. While this effect is theoretically possible, it is rarely reported due to the generally high mechanical stability of polymers, especially for pure dielectric polymers under an applied electric field (excluding cases with piezoelectric or ferroelectric additives). Therefore, field-induced deformation of pure dielectric polymers is an interesting and meaningful topic. Perhaps, an experimental approach similar to those used for piezoelectric materials could be considered to measure polymer thickness changes under an external electric field to support this interesting hypothesis. + +<|ref|>text<|/ref|><|det|>[[72, 203, 923, 256]]<|/det|> +3) In Figures 6e and 6f, the authors compare the performance of existing advanced energy storage materials. However, some of these materials are not purely organic polymers, as they contain fillers or ferroelectric components. To ensure a fair and consistent comparison, I recommend excluding these non-purely organic materials so that the advantages of the authors work can be more accurately highlighted. + +<|ref|>text<|/ref|><|det|>[[72, 256, 645, 270]]<|/det|> +4) There are multiple formatting inconsistencies with the "C" unit in lines 350-385. + +<|ref|>text<|/ref|><|det|>[[72, 270, 920, 310]]<|/det|> +5) The characterization section must be improved by providing a detailed description of each experimental technique used. For example, what mode was used in the AFM test? What amplitude was selected for the DMA test? Was preheating performed in the DSC test? In the D-E loop test, what were the electrode material and dimensions? + +<|ref|>text<|/ref|><|det|>[[72, 310, 920, 375]]<|/det|> +6) In Figure 2, the author uses scan mode to explore the lowest energy points of two molecular chains. However, the structure of the polymer condensed matter is equally important, and I suggest that the free volume of the whole condensed matter structure should be calculated and analyzed. If you can, consider calculating statistics for the distance between this segment and the surrounding segment separately. The precision of the base group can be appropriately reduced to take into account the calculation speed and quality. + +<|ref|>text<|/ref|><|det|>[[72, 400, 145, 413]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 426, 219, 439]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 451, 160, 464]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 477, 238, 490]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 490, 875, 517]]<|/det|> +I have carefully read the revised manuscript and relevant responses including the ones for mine and Reviewer 3. This manuscript is acceptable now. + +<|ref|>text<|/ref|><|det|>[[72, 530, 161, 543]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 557, 242, 582]]<|/det|> +(Remarks to the Author) Can be accepted as it is. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 374, 107]]<|/det|> +Dear editors and reviewers, + +<|ref|>text<|/ref|><|det|>[[147, 117, 852, 330]]<|/det|> +Dear editors and reviewers,Thank you for your valuable comments and constructive suggestions on our manuscript submitted to Nature Communications (Manuscript ID: NCOMMS- 25- 13172, Title: Breaking the adverse correlation between thermal stability and electrical insulation in polymer dielectrics by rearranging the donor and acceptor units). Based on these comments, we have carefully revised the manuscript to address all the concerns raised. A revised manuscript has been submitted, of which the modified sections are marked in red. The summary of the changes and a brief response to all recommendations and criticisms are listed as follows: + +<|ref|>text<|/ref|><|det|>[[148, 367, 410, 384]]<|/det|> +Reviewer comment in BLACK. + +<|ref|>text<|/ref|><|det|>[[148, 395, 284, 412]]<|/det|> +Reply in BLUE. + +<|ref|>text<|/ref|><|det|>[[148, 422, 296, 439]]<|/det|> +New text in RED. + +<|ref|>text<|/ref|><|det|>[[148, 477, 460, 495]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 505, 852, 662]]<|/det|> +The authors introduce a strategy to break the adverse correlation between thermal stability and electrical insulation of PEI dielectric by the effective rearrangement of short- range structural units. This work is innovative and meaningful for the advancement of dielectric polymers. Due to the suppressed electrical conductivity, the capacitive energy storage under high temperatures and electric fields is significantly improved. The following issues need to be addressed before the publication. + +<|ref|>text<|/ref|><|det|>[[148, 672, 850, 718]]<|/det|> +Response: We thank the reviewer for the interest and the accurate summary of the results of the paper. + +<|ref|>text<|/ref|><|det|>[[147, 755, 852, 857]]<|/det|> +(1) In Figure 2c(ii) and 2d(ii), the IFCT method calculated charge-transfer (CT) results indicate that the electron amount (0.14e) transferred from the donor unit to the acceptor in the molecular chain with two crosslinking points is significantly lower than that in the chain with one crosslinking point (0.87e). What accounts for this? + +<|ref|>text<|/ref|><|det|>[[148, 867, 850, 912]]<|/det|> +Response: Thank you for your careful reading and considerate suggestions. IFCT calculation results demonstrate that the electron migration amount in TPEI containing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 853, 330]]<|/det|> +two crosslinking points is significantly lower than that in TPEI with a single crosslinking point. This discrepancy is attributed to the enhanced face- to- face stacking of the two diamine units within the structural unit of TPEI with two crosslinking points, which leads to a more pronounced preferred layer packing (PLP) structure (Figure S8). In contrast, the two diamine units in the structural unit of TPEI with a crosslinking point predominantly exhibit partially misaligned stacking. This configuration likely induces a stacking mode resembling mixed layer packing (MLP), which significantly weakens the suppression of electron migration compared to the TPEI containing two crosslinking points. + +<|ref|>text<|/ref|><|det|>[[147, 338, 855, 721]]<|/det|> +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). Notably, in the PLP structure induced by benzyl- induced crosslinking, the transfer of electrons from the diamine to the dianhydride during CT excitation is significantly diminished, with the amount of charge transfer nearly approaching 0 electrons between the two cross- linked molecular chains (Figures 2c- d(ii)). Moreover, the electron migration amount in TPEI containing two crosslinking points is significantly lower than that in TPEI with a crosslinking point. This difference arises from the enhanced face- to- face stacking of diamine units, which forms a more pronounced PLP structure. In contrast, TPEI with a crosslinking point exhibits partially misaligned stacking between diamine units, inducing a stacking more resembling MLP structure that weakens the suppression of electron migration (Figure S8, Supporting Information). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 88, 840, 300]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 311, 852, 414]]<|/det|> +
Figure S8. Structural unit conformation diagram of a) TPEI with one crosslink point and b) TPEI with two crosslink points. Among them, the blue hexagonal pyramid represents the location of the crosslinking point, while the green and red areas indicate the plane where the benzene ring of the diamine unit lies.
+ +<|ref|>text<|/ref|><|det|>[[147, 449, 852, 553]]<|/det|> +(2) The authors confirmed the significant impact of the preferred layer packing (PLP) structure on inhibiting electron transfer through DFT calculations. How is the mentioned charge-transfer (CT) excitation determined? The related description in the DFT calculation section should be provided. + +<|ref|>text<|/ref|><|det|>[[147, 561, 852, 886]]<|/det|> +Response: Thank you for your important comments. From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge-transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[282, 90, 848, 118]]<|/det|> +\[S_{r} \text { index } = \int S_{r}(\mathbf{r}) d\mathbf{r} \equiv \int \sqrt{\rho^{hole}(\mathbf{r}) \rho^{ele}(\mathbf{r})} d\mathbf{r} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[147, 126, 851, 230]]<|/det|> +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +<|ref|>equation<|/ref|><|det|>[[412, 236, 848, 355]]<|/det|> +\[\begin{array}{c}{D_{x} = |X_{e l e} - X_{h o l e}|}\\ {D_{y} = |Y_{e l e} - Y_{h o l e}|}\\ {D_{z} = |Z_{e l e} - Z_{h o l e}|}\\ {D_{i n d e x} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}}} \end{array} \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[147, 358, 850, 432]]<|/det|> +Here, \(X_{ele}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +<|ref|>equation<|/ref|><|det|>[[398, 440, 831, 462]]<|/det|> +\[t_{index} = D_{index} - H_{CT} \quad (3)\] + +<|ref|>equation<|/ref|><|det|>[[424, 468, 831, 489]]<|/det|> +\[H_{CT} = |\pmb {H}\cdot \pmb{u}_{CT}| \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[147, 496, 852, 802]]<|/det|> +Here, \(H_{CT}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(\pmb{H}\) represents the vector composed of components \(\pmb{H_{x}}\) , \(\pmb{H_{y}}\) , and \(\pmb{H_{z}}\) , where \(\pmb{u}_{CT}\) denotes the unit vector along the CT direction. Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronically excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +<|ref|>table<|/ref|><|det|>[[149, 833, 848, 893]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[280, 812, 715, 830]]<|/det|> +Table S1 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 81, 849, 625]]<|/det|> + +
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<|ref|>table_caption<|/ref|><|det|>[[271, 658, 720, 672]]<|/det|> +Table S2 Analysis of the first 20 excited states of TPEI4 + +<|ref|>table<|/ref|><|det|>[[150, 678, 848, 907]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t(Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 81, 848, 455]]<|/det|> + +
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<|ref|>table_caption<|/ref|><|det|>[[173, 489, 825, 503]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEI with a crosslinking point + +<|ref|>table<|/ref|><|det|>[[149, 509, 848, 907]]<|/det|> + +
Excited stateSr(a.u.)D (Angstrom)t(Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[149, 82, 849, 284]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[157, 317, 839, 334]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<|ref|>table<|/ref|><|det|>[[149, 336, 849, 910]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[150, 83, 848, 112]]<|/det|> + +
20th0.824871.009-0.582LE
+ +<|ref|>text<|/ref|><|det|>[[147, 145, 852, 276]]<|/det|> +By analyzing the first 20 electronically excited states of PEI, TPEI \(u\) , TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<|ref|>text<|/ref|><|det|>[[147, 284, 852, 388]]<|/det|> +Revision: The interfragment CT (IFCT) method in Multiwfn \(^{26}\) revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). + +<|ref|>sub_title<|/ref|><|det|>[[148, 397, 300, 415]]<|/det|> +## DFT calculations + +<|ref|>text<|/ref|><|det|>[[147, 424, 852, 720]]<|/det|> +The ground- state geometry optimizations and energy scanning of the polymer structural units were performed by Gaussian 16 with the B3LYP hybrid function and 6- 31G (d) basis function. The structure construction and the visualization of electrostatic potential distribution of polymer units was conducted by GaussView 6.1 and Multiwfn 3.8 \(^{51,52}\) . The model construction of polymer structural units for energy scanning was completed by dimerscan and xyz2QC \(^{54}\) . The first 20 excited states of polymer structural units were calculated using time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G functional \(^{55,56}\) . The interfragment charge- transfer (IFCT) method was implemented using the Multiwfn 3.8 program to analyze the electronic excitation behavior of the polymer molecule (see the Supporting Information for detailed analysis) \(^{57,58,59,60}\) . + +<|ref|>sub_title<|/ref|><|det|>[[148, 730, 265, 747]]<|/det|> +## DFT analysis + +<|ref|>text<|/ref|><|det|>[[147, 756, 852, 888]]<|/det|> +From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 247]]<|/det|> +molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +<|ref|>equation<|/ref|><|det|>[[318, 257, 748, 285]]<|/det|> +\[S_{r} i n d e x = \int S_{r}(\pmb {r}) d\pmb {r} \equiv \int \sqrt{\rho^{h o l e}(\pmb {r})\rho^{e l e}(\pmb {r})} d\pmb {r}\] + +<|ref|>text<|/ref|><|det|>[[148, 320, 851, 422]]<|/det|> +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +<|ref|>equation<|/ref|><|det|>[[350, 430, 648, 550]]<|/det|> +\[D_{x} = |X_{e l e} - X_{h o l e}|\] \[D_{y} = |Y_{e l e} - Y_{h o l e}|\] \[D_{z} = |Z_{e l e} - Z_{h o l e}|\] \[D_{i n d e x} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}}\] + +<|ref|>text<|/ref|><|det|>[[148, 580, 850, 654]]<|/det|> +Here, \(X_{e l e}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +<|ref|>equation<|/ref|><|det|>[[399, 662, 598, 684]]<|/det|> +\[t_{i n d e x} = D_{i n d e x} - H_{c T}\] + +<|ref|>equation<|/ref|><|det|>[[425, 692, 562, 711]]<|/det|> +\[(3)\] + +<|ref|>equation<|/ref|><|det|>[[425, 720, 562, 740]]<|/det|> +\[H_{c T} = |H\cdot u_{c T}|\] + +<|ref|>text<|/ref|><|det|>[[148, 774, 851, 885]]<|/det|> +Here, \(H_{c T}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(H\) represents the vector composed of components \(H_{x}\) , \(H_{y}\) , and \(H_{z}\) , where \(u_{c T}\) denotes the unit vector along the CT direction. + +<|ref|>text<|/ref|><|det|>[[147, 894, 850, 913]]<|/det|> +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 852, 247]]<|/det|> +electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +<|ref|>table<|/ref|><|det|>[[147, 275, 849, 877]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[280, 256, 718, 273]]<|/det|> +Table S2 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[270, 92, 728, 105]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEIu + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[172, 92, 826, 106]]<|/det|> +Table S4 Analysis of the first 20 excited states of TPEI with a crosslinking point + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[148, 110, 849, 711]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[156, 90, 839, 107]]<|/det|> +Table S5 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +<|ref|>text<|/ref|><|det|>[[147, 740, 851, 871]]<|/det|> +By analyzing the first 20 electronically excited states of PEI, TPEI, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 303]]<|/det|> +(3) In Figure 3c, the specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) of TPEI is lower than that of PEI, indicating that the TPEI polymer chains are stretched. However, "Furthermore, the substituents on the benzene rings can influence the twisting of the molecular chain conformation..." The electrostatic potential distributions of PEI and TPEI reveal that TPEI exhibits weaker electrostatic interactions, which the authors attribute to the twisting of the molecular chain conformation. Is there a contradiction between the concepts of "polymer chains are stretched" and "the twisting of the molecular chain conformation" in these two contexts? + +<|ref|>text<|/ref|><|det|>[[147, 311, 852, 525]]<|/det|> +Response: Thank you for your careful reading and professional comment. The specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) of PEI and TPEI, obtained from differential scanning calorimetry (DSC), typically refers to the heat capacity change during the transition from the glassy state to the rubbery state. The \(\Delta C_{\mathrm{p}}\) value of TPEI is smaller than that of PEI, indicating that TPEI has more extended molecular chains compared to PEI. However, substituted methyl groups on the diamine benzene ring increase the dihedral angles at the imide ring of TPEI (Figure S10), inducing twisting at the donor-acceptor junctions within the molecular chains and thereby hindering electron transport. + +<|ref|>text<|/ref|><|det|>[[147, 533, 852, 692]]<|/det|> +Revision: This strongly supports the idea that PLP structure effectively restricts electronic transport between polymer dielectrics. Furthermore, the substituent methyl groups on the diamine benzene rings increase the dihedral angles at the imide ring position of TPEI, inducing twisting at the donor-acceptor junctions within the molecular chains and thereby diminishing the electrostatic interactions within the molecular chains \(^{10}\) (Figures S10- 11, Supporting Information). + +<|ref|>text<|/ref|><|det|>[[147, 700, 852, 914]]<|/det|> +The glass transition temperature ( \(\mathrm{T_g}\) ) increases from \(236.31^{\circ}\mathrm{C}\) for PEI to \(289.72^{\circ}\mathrm{C}\) for TPEI, suggesting that the movement of polymer chains is restrained by benzyl- induced crosslinking networks (Figure 3c). In addition, the variation in specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) during the glass transition, caused by changes in the conformation of polymer chains, was obtained from DSC data. \(\Delta C_{\mathrm{p}}\) is significantly reduced from 0.205 \(\mathrm{Jg^{- 1}°C^{- 1}}\) for PEI to \(0.119\mathrm{Jg^{- 1}°C^{- 1}}\) for TPEI, indicating that the polymer chains in the crosslinked films are more stretched compared to those in PEI, thereby minimizing voids and defects in the polymer films \(^{16,33}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[252, 88, 759, 374]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 386, 850, 433]]<|/det|> +
Figure S10. Structural formulas of PEI and TPEIu and the dihedral angles at the imide ring.
+ +<|ref|>text<|/ref|><|det|>[[147, 468, 852, 572]]<|/det|> +(4) Here, "TPEI exhibits over an order of magnitude lower leakage current density than that of PEI and other heat-resistant polymers...", the authors reference "other heat-resistant polymers", but the leakage data for these materials are absent. Please provide examples of leakage data for "other heat-resistant polymers". + +<|ref|>text<|/ref|><|det|>[[147, 580, 852, 682]]<|/det|> +Response: Thank you for your professional comments. In response to the reviewer's kind suggestion, the leakage current density of conventional heat-resistant polymers (Kapton, FPE, and PEI-PSU) as a function of electric field was measured at elevated temperatures, as depicted in Figure S20. + +<|ref|>text<|/ref|><|det|>[[147, 690, 852, 849]]<|/det|> +Revision: Another advantage of the TPEI film is its excellent electrical insulation performance at high temperatures. According to the tested results of leakage current density of the polymer films (Figures 4d-e and Figures S20-S22 in the Supporting Information), TPEI exhibits over an order of magnitude lower leakage current density than that of PEI and other heat-resistant polymers at high electric fields and elevated temperatures. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 85, 913, 344]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 349, 850, 396]]<|/det|> +
Figure S20 Leakage current density of TPEI as a function of electric field, compared with those of Kapton, FPE, and PEI-PSU at \(150^{\circ}\mathrm{C}\) a) and \(200^{\circ}\mathrm{C}\) b).
+ +<|ref|>text<|/ref|><|det|>[[147, 430, 852, 900]]<|/det|> +(5) In figures 4d-e, the fitting mechanism of the leakage current for fresh PEI exhibits significant deviation. The authors should re-evaluate the leakage conduction mechanism and consider performing segmented fitting of the experimental results. Response: Thank you for your valuable comment. In response to the reviewer's suggestion, we have re-evaluated the conduction mechanisms of PEI at \(150^{\circ}\mathrm{C}\) and \(200^{\circ}\mathrm{C}\) . During this evaluation, the Schottky emission mechanism was ruled out due to the mismatch between the theoretical and experimental dielectric constants. As shown in Figures 4d-e, the conduction mechanisms of PEI under elevated temperatures and specific electric fields aligns well with the hopping conduction model. Additionally, we analyzed the leakage current density versus electric field (J-E) curves of PEI at \(150^{\circ}\mathrm{C}\) and \(200^{\circ}\mathrm{C}\) using the space charge limited conduction (SCLC) mechanism. The SCLC mechanism exhibits three distinct stages as the electric field increases. First, at low electric fields, the concentration of electrons injected into the dielectric is significantly lower than that of thermally excited electrons within the bulk, where conduction follows the Ohmic law. Second, when the electric field increases to the first critical threshold, the injected electron concentration exceeds the thermally excited electron concentration. In this stage, injected electrons continuously fill the traps, and space charge remains + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 854, 219]]<|/det|> +localized rather than migrating through the sample. Here, the leakage current density \((J)\) is proportional to the square of the electric field \((E^{2})\) . Finally, as the electric field further increases to the second critical threshold, the traps become fully saturated. Excess electrons are no longer constrained, leading to a rapid increase in current density. The SCLC equation can be expressed as: + +<|ref|>equation<|/ref|><|det|>[[434, 224, 561, 259]]<|/det|> +\[J = \frac{9\mu\epsilon_0\epsilon_r}{8} E^2\] + +<|ref|>text<|/ref|><|det|>[[147, 264, 852, 395]]<|/det|> +where \(\mu\) is the electron mobility, \(\epsilon_0\) represents the vacuum permittivity, and \(\epsilon_r\) denotes the relative dielectric permittivity of the material. As shown in Figure S21, the electrical conduction of PEI exhibits Ohmic conduction under high temperatures and low electric fields and follows the SCLC mechanism under high temperatures and high electric fields. + +<|ref|>image<|/ref|><|det|>[[147, 425, 850, 723]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 730, 850, 858]]<|/det|> +
Figure 4. Analysis of mechanical performance and electrical insulation properties. DMA curves for a) PEI film and b) TPEI film. c) Comparison of the storage modulus of PEI and TPEI films. d) Leakage current density of polymer films as a function of electric field at \(150^{\circ}\) C and e) \(200^{\circ}\) C. f) Electrical conductivity of TPEI, PEI, FPE, Kapton, and PEI-PSU films at various temperatures.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[310, 87, 690, 321]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 330, 850, 377]]<|/det|> +
Figure S21. The leakage current density of pristine PEI as a function of electric field at elevated temperatures is presented, with the solid curves denoting the SCLC model fit.
+ +<|ref|>text<|/ref|><|det|>[[148, 412, 850, 459]]<|/det|> +(6) Please update the performance comparison charts in Figures 6e and 6f by including the most recent relevant reported results. + +<|ref|>text<|/ref|><|det|>[[147, 468, 852, 627]]<|/det|> +Response: Thank you for your kind comments. Inspired by recent reports on the high- temperature capacitive energy storage performance of novel dielectric polymers and in response to the constructive suggestions from the second reviewer, we have supplemented and revised the performance comparison plots at \(200^{\circ}\mathrm{C}\) and \(250^{\circ}\mathrm{C}\) (Figures 6g-6h). These comparisons highlight the superior performance of TPEI in high-temperature capacitive energy storage. + +<|ref|>title<|/ref|><|det|>[[148, 637, 230, 653]]<|/det|> +# Revision: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[147, 85, 850, 510]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 516, 852, 784]]<|/det|> +
Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \(150^{\circ}\mathrm{C}\) and b) \(200^{\circ}\mathrm{C}\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \(150^{\circ}\mathrm{C}\) and BOPP at \(120^{\circ}\mathrm{C}\) , d) \(200^{\circ}\mathrm{C}\) and e) \(250^{\circ}\mathrm{C}\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \(>90\%\) ) at \(200^{\circ}\mathrm{C}^{10,11,17,18,24,25,38,39,40,41,42,43,44,45,46,47,48,49}\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \(250^{\circ}\mathrm{C}^{10,25,42,46,50}\) for the TPEI and novel all-organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m-1 and 20 kΩ.
+ +<|ref|>text<|/ref|><|det|>[[147, 820, 850, 895]]<|/det|> +(7) It is advisable for the author to incorporate a radar chart that compares the key performance parameters of TPEI and fresh PEI, emphasizing the advantages of the short-range structural rearrangement methods. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 218]]<|/det|> +Response: Thank you for your valuable comments. In response to the reviewer's kind suggestion, we constructed a radar chart to compare the key performance parameters of PEI and TPEI (Figure 6f). The results show that TPEI, modified via short- range structural rearrangement, exhibits unparalleled superiority over PEI in both thermal stability and electrical insulation. + +<|ref|>image<|/ref|><|det|>[[147, 250, 850, 675]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 680, 852, 896]]<|/det|> +
Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \(150^{\circ}\mathrm{C}\) and b) \(200^{\circ}\mathrm{C}\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \(150^{\circ}\mathrm{C}\) and BOPP at \(120^{\circ}\mathrm{C}\) , d) \(200^{\circ}\mathrm{C}\) and e) \(250^{\circ}\mathrm{C}\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \(>90\%\) ) at \(200^{\circ}\mathrm{C}^{10, 11, 17, 18, 24, 25, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49}\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \(250^{\circ}\mathrm{C}^{10, 25, 42, 46, 50}\) for the TPEI and novel all-
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 850, 135]]<|/det|> +organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m- 1 and 20 kΩ. + +<|ref|>text<|/ref|><|det|>[[147, 171, 850, 246]]<|/det|> +(8) The authors discussed uncross-linked TPEI (TPEIu) during the research process. However, there is no characterization of its dielectric and energy storage performance. What accounts for this? + +<|ref|>text<|/ref|><|det|>[[147, 255, 853, 441]]<|/det|> +Response: Thank you for your thorough review of the experimental details. Firstly, non- crosslinked TPEI (TPEIu) fails to form a free- standing film due to the steric hindrance of the four methyl groups on the diamine's benzene ring, leading to severe film cracking. This structural instability prevents reliable measurements of its dielectric and capacitive properties. In contrast, TPEI modified via benzyl crosslinking- induced structural unit rearrangement forms a robust free- standing film while ensuring the mechanical properties of TPEI, as shown in Figure S19. + +<|ref|>title<|/ref|><|det|>[[148, 450, 231, 467]]<|/det|> +# Revision: + +<|ref|>image<|/ref|><|det|>[[262, 480, 736, 765]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 775, 515, 793]]<|/det|> +
Figure S19 Stress-strain curves of TPEI film.
+ +<|ref|>text<|/ref|><|det|>[[147, 829, 850, 876]]<|/det|> +(9) Some errors should be corrected, such as " \(\mathrm{Tg} \approx 265^{\circ} \mathrm{C}\) " and " \(\mathrm{Tg} = 330^{\circ} \mathrm{C}\) " in the Materials section. + +<|ref|>text<|/ref|><|det|>[[147, 886, 850, 905]]<|/det|> +Response: Thank you sincerely for your kindly reminder. We have reviewed the whole + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 91, 424, 106]]<|/det|> +manuscript and revised the errors. + +<|ref|>sub_title<|/ref|><|det|>[[149, 118, 231, 134]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[147, 144, 852, 499]]<|/det|> +Copolymer of PEI with polysulfone (PEI- PSU) particles \(\mathrm{(T_g\approx 265~^\circ C)}\) , fluorene polyester (FPE) particles \(\mathrm{(T_g = 330~^\circ C)}\) and commercial biaxially oriented polypropylene (BOPP) films with a thickness of \(5.8\mu \mathrm{m}\) were provided by Polyk Technologies Company. PEI- PSU particles and FPE particles were dissolved in NMP, stirring at \(70^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Next, the viscous polymer solution was cast and baked at \(70^{\circ}\mathrm{C}\) for \(2\mathrm{h}\) , and then the sample films were dried in a vacuum oven at \(200^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Thermogravimetric analysis (TGA) curves were obtained from a NETZSCH TGA209F1 thermogravimetry under nitrogen (air) atmosphere at a heating rate of \(10^{\circ}\mathrm{C}\) \(\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(800^{\circ}\mathrm{C}\) . Differential scanning calorimetry (DSC) was performed on a TA Q10 DSC at a scan rate of \(10^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(300^{\circ}\mathrm{C}\) in a nitrogen atmosphere. The in- plane thermal expansion change curves of the films were recorded by a TMA Q400 from TA Instruments, with a force of \(0.02\mathrm{N}\) , under nitrogen flow at a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(350^{\circ}\mathrm{C}\) . + +<|ref|>text<|/ref|><|det|>[[149, 534, 460, 551]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 561, 852, 770]]<|/det|> +This work achieves the obstruction of long- range electron transport along polymer chain segments by rearranging the dianhydride and diamine units in polyimide, leading to the development of TPEI with both high thermal stability and high dielectric strength. Energy storage densities of \(6.38\mathrm{J / cm^3}\) and \(3.04\mathrm{J / cm^3}\) were obtained at \(200^{\circ}\mathrm{C}\) and \(250^{\circ}\mathrm{C}\) , respectively, while maintaining \(90\%\) efficiency. The manuscript is well- organized and provides valuable insights for researchers in the field. Therefore, I recommend its publication after minor revisions addressing the following points: + +<|ref|>text<|/ref|><|det|>[[148, 756, 848, 803]]<|/det|> +Response: We highly appreciate the reviewer's positive comment on our paper and we will try our best to address the questions raised. + +<|ref|>text<|/ref|><|det|>[[148, 839, 851, 915]]<|/det|> +(1) The authors discuss electron transfer between the dianhydride and diamine units during excitation in lines 113-139. However, electron excitation typically involves transitions from the HOMO to the LUMO and higher energy levels. Does the reported + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 219]]<|/det|> +charge transfer only consider transitions from HOMO to LUMO? I think analyzing a single energy level transition may not fully reveal the influence of electron excitation on the system. Therefore, I suggest also considering electron transitions to 3\~5 energy levels near LUMO to obtain a more comprehensive understanding of the electronic excitation characteristics. + +<|ref|>text<|/ref|><|det|>[[147, 225, 853, 777]]<|/det|> +Response: Thank you for your careful reading and professional comments. We acknowledge the reviewer's point that analyzing single energy level transitions may not fully reveal the electronic excitation characteristics of polymer structural units. To address this concern, we applied time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G(d) method to analyze electron transitions in the first 20 excited states of the polymer structural units. As described in the DFT calculation validation section, the charge transfer processes we characterized were not limited to considering the energy level transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) in the first excited state. From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +<|ref|>equation<|/ref|><|det|>[[281, 784, 848, 812]]<|/det|> +\[S_{r} \text{index} = \int S_{r}(\mathbf{r}) d\mathbf{r} \equiv \int \sqrt{\rho^{hole}(\mathbf{r})\rho^{ele}(\mathbf{r})} d\mathbf{r} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[147, 821, 850, 896]]<|/det|> +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 644, 107]]<|/det|> +the distance between the centroids of the holes and electrons. + +<|ref|>equation<|/ref|><|det|>[[415, 115, 583, 203]]<|/det|> +\[D_{x} = |X_{ele} - X_{hole}|\] \[D_{y} = |Y_{ele} - Y_{hole}|\] \[D_{z} = |Z_{ele} - Z_{hole}|\] + +<|ref|>equation<|/ref|><|det|>[[350, 199, 848, 237]]<|/det|> +\[D_{index} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}} \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[147, 239, 850, 312]]<|/det|> +Here, \(X_{ele}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +<|ref|>equation<|/ref|><|det|>[[400, 320, 831, 370]]<|/det|> +\[t_{index} = D_{index} - H_{CT} \quad (3)\] \[H_{CT} = |H\cdot u_{CT}| \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[147, 375, 850, 488]]<|/det|> +Here, \(H_{CT}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(H\) represents the vector composed of components \(H_{x}\) , \(H_{y}\) , and \(H_{z}\) , where \(u_{CT}\) denotes the unit vector along the CT direction. + +<|ref|>text<|/ref|><|det|>[[147, 495, 852, 683]]<|/det|> +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +<|ref|>table<|/ref|><|det|>[[148, 712, 849, 885]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[280, 692, 715, 710]]<|/det|> +Table S1 Analysis of the first 20 excited states of PEI + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 81, 848, 511]]<|/det|> + +
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<|ref|>table_caption<|/ref|><|det|>[[271, 545, 727, 558]]<|/det|> +Table S2 Analysis of the first 20 excited states of TPEIu + +<|ref|>table<|/ref|><|det|>[[149, 565, 848, 907]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 81, 849, 342]]<|/det|> + +
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<|ref|>table_caption<|/ref|><|det|>[[174, 376, 825, 390]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEI with a crosslinking point + +<|ref|>table<|/ref|><|det|>[[149, 395, 849, 907]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[149, 82, 848, 171]]<|/det|> + +
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<|ref|>table_caption<|/ref|><|det|>[[160, 205, 838, 219]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEI with two crosslinking points + +<|ref|>table<|/ref|><|det|>[[149, 225, 848, 824]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +<|ref|>text<|/ref|><|det|>[[147, 857, 850, 899]]<|/det|> +By analyzing the first 20 electronically excited states of PEI, TPEIu, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 851, 163]]<|/det|> +occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<|ref|>text<|/ref|><|det|>[[148, 172, 852, 275]]<|/det|> +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). + +<|ref|>sub_title<|/ref|><|det|>[[148, 285, 300, 302]]<|/det|> +## DFT calculations + +<|ref|>text<|/ref|><|det|>[[147, 311, 852, 607]]<|/det|> +The ground- state geometry optimizations and energy scanning of the polymer structural units were performed by Gaussian 16 with the B3LYP hybrid function and 6- 31G (d) basis function. The structure construction and the visualization of electrostatic potential distribution of polymer units was conducted by GaussView 6.1 and Multiwfn 3.851, 52, 53. The model construction of polymer structural units for energy scanning was completed by dimerscan and xyz2QC54. The first 20 excited states of polymer structural units were calculated using time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G functional55, 56. The interfragment charge- transfer (IFCT) method was implemented using the Multiwfn 3.8 program to analyze the electronic excitation behavior of the polymer molecule (see the Supporting Information for detailed analysis)57, 58, 59, 60. + +<|ref|>sub_title<|/ref|><|det|>[[148, 618, 265, 635]]<|/det|> +## DFT analysis + +<|ref|>text<|/ref|><|det|>[[147, 644, 852, 912]]<|/det|> +From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 710, 108]]<|/det|> +results. The Sr function is integrated over the entire space as follows: + +<|ref|>equation<|/ref|><|det|>[[318, 118, 750, 147]]<|/det|> +\[S_{r} \text{index} = \int S_{r}(\mathbf{r}) \mathrm{d}\mathbf{r} \equiv \int \sqrt{\rho^{\text{hole}}(\mathbf{r}) \rho^{\text{ele}}(\mathbf{r})} \mathrm{d}\mathbf{r}\] + +<|ref|>text<|/ref|><|det|>[[148, 182, 850, 284]]<|/det|> +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +<|ref|>equation<|/ref|><|det|>[[352, 290, 648, 410]]<|/det|> +\[D_{x} = |X_{e l e} - X_{h o l e}|\] \[D_{y} = |Y_{e l e} - Y_{h o l e}|\] \[D_{z} = |Z_{e l e} - Z_{h o l e}|\] \[D_{i n d e x} = \sqrt{(D_{x})^{2} + (D_{y})^{2} + (D_{z})^{2}}\] + +<|ref|>text<|/ref|><|det|>[[150, 440, 850, 515]]<|/det|> +Here, \(X_{e l e}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +<|ref|>equation<|/ref|><|det|>[[398, 524, 598, 545]]<|/det|> +\[t_{i n d e x} = D_{i n d e x} - H_{C T}\] + +<|ref|>equation<|/ref|><|det|>[[425, 552, 564, 571]]<|/det|> +\[(3)\] + +<|ref|>equation<|/ref|><|det|>[[425, 580, 562, 600]]<|/det|> +\[H_{C T} = |\pmb {H}\cdot \pmb{u}_{C T}|\] + +<|ref|>text<|/ref|><|det|>[[148, 635, 850, 746]]<|/det|> +Here, \(H_{C T}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(\pmb{H}\) represents the vector composed of components \(\pmb{H_{x}}\) , \(\pmb{H_{y}}\) , and \(\pmb{H_{z}}\) , where \(\pmb{u}_{C T}\) denotes the unit vector along the CT direction. + +<|ref|>text<|/ref|><|det|>[[148, 755, 852, 914]]<|/det|> +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 91, 811, 105]]<|/det|> +electronic excitation types for the first 20 excited states of the polymer molecules. + +<|ref|>table_caption<|/ref|><|det|>[[280, 120, 718, 133]]<|/det|> +Table S2 Analysis of the first 20 excited states of PEI + +<|ref|>table<|/ref|><|det|>[[150, 140, 848, 737]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[270, 92, 728, 105]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEIu + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[172, 91, 825, 106]]<|/det|> +Table S4 Analysis of the first 20 excited states of TPEI with a crosslinking point + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 110, 849, 711]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[156, 90, 839, 108]]<|/det|> +Table S5 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +<|ref|>text<|/ref|><|det|>[[147, 740, 851, 871]]<|/det|> +By analyzing the first 20 electronic excited states of PEI, TPEI, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 330]]<|/det|> +(2) The manuscript states in lines 182-193 that polymer thickness decreases with increasing electrostatic stress, which is an intriguing observation. While this effect is theoretically possible, it is rarely reported due to the generally high mechanical stability of polymers, especially for pure dielectric polymers under an applied electric field (excluding cases with piezoelectric or ferroelectric additives). Therefore, field-induced deformation of pure dielectric polymers is an interesting and meaningful topic. Perhaps, an experimental approach similar to those used for piezoelectric materials could be considered to measure polymer thickness changes under an external electric field to support this interesting hypothesis. + +<|ref|>text<|/ref|><|det|>[[147, 338, 852, 608]]<|/det|> +Response: Thank you for your valuable comments. Firstly, prior studies have shown that the breakdown electric field of polyethylene is correlated with its mechanical strength1. Secondly, based on the electromechanical breakdown mechanism of polymers and the working mechanisms of dielectric elastomers (both associated with the Maxwell stress under the applied electric field)2, 3, we hypothesize that the thickness of polymer films decreases with increasing electrostatic stress. Thus, we propose that pure dielectric polymers undergo electric field- induced deformation under applied electric fields. Furthermore, in response to the reviewer's suggestion, we tested the strain versus electric field (S- E) curve of TPEI, and the experimental results are consistent with our hypothesized conclusion (Figure S18). + +<|ref|>sub_title<|/ref|><|det|>[[148, 618, 231, 634]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[147, 643, 852, 812]]<|/det|> +As shown in Figure S18, the thickness of polymer films under an external electric field \((E)\) decreases due to the increasing electrostatic stress \((= \frac{1}{2}\epsilon_{0}\epsilon_{r}E^{2}\) , where \(\epsilon_{0}\) and \(\epsilon_{r}\) denote the dielectric permittivity of a vacuum and the dielectric constant of dielectrics, respectively), which is counterbalanced by the mechanical stress arising from elastic deformation \((= Ye\) , where \(Y\) is the modulus and \(e\) represents the elastic strain of the dielectric)7,36,37. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 92, 850, 355]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 367, 826, 386]]<|/det|> +
Figure S18 Strain versus electric field (S-E) curves of TPEI at frequency of 100 Hz.
+ +<|ref|>text<|/ref|><|det|>[[147, 421, 852, 555]]<|/det|> +(3) In Figures 6e and 6f, the authors compare the performance of existing advanced energy storage materials. However, some of these materials are not purely organic polymers, as they contain fillers or ferroelectric components. To ensure a fair and consistent comparison, I recommend excluding these non-purely organic materials so that the advantages of the authors work can be more accurately highlighted. + +<|ref|>text<|/ref|><|det|>[[147, 561, 852, 830]]<|/det|> +Response: Thank you for your kind comments. Building on the latest advancements in high- temperature capacitive energy storage performance of novel dielectric polymers and incorporating suggestions from the first reviewer, we have supplemented and updated the performance comparison plots at \(200^{\circ}\mathrm{C}\) (Figure 6g) and \(250^{\circ}\mathrm{C}\) (Figure 6h). The updated results show that the polymer undergoing PLP structural rearrangement exhibits superior energy storage performance at \(200^{\circ}\mathrm{C}\) and \(250^{\circ}\mathrm{C}\) . This confirms the effectiveness of benzyl crosslinking in inducing short- range rearrangement of structural units within complexly packed polymer chains, thereby simultaneously enhancing thermal stability and electrical insulation at elevated temperatures. + +<|ref|>title<|/ref|><|det|>[[148, 840, 231, 856]]<|/det|> +# Revision: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[147, 85, 850, 510]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 516, 852, 784]]<|/det|> +
Figure 6. High-temperature insulation properties. Discharge energy density and efficiency versus electric field of PEI and TPEI samples at a) \(150^{\circ}\mathrm{C}\) and b) \(200^{\circ}\mathrm{C}\) . Discharge energy density and efficiency versus electric field for TPEI and other polymers (Kapton, FPE, PEI-PSU) at c) \(150^{\circ}\mathrm{C}\) and BOPP at \(120^{\circ}\mathrm{C}\) , d) \(200^{\circ}\mathrm{C}\) and e) \(250^{\circ}\mathrm{C}\) . f) Radar chart comparing the key properties of PEI and TPEI. g) Comparison of discharge energy density (efficiency \(>90\%\) ) at \(200^{\circ}\mathrm{C}^{10,11,17,18,24,25,38,39,40,41,42,43,44,45,46,47,48,49}\) for the TPEI and novel all-organic polymer dielectrics. h) Comparison of maximum discharge energy density at \(250^{\circ}\mathrm{C}^{10,25,42,46,50}\) for the TPEI and novel all-organic polymers. i) Fast discharge testing of TPEI (200 °C) and BOPP (120 °C) at 200 MV m-1 and 20 kΩ.
+ +<|ref|>text<|/ref|><|det|>[[147, 819, 850, 894]]<|/det|> +(4) There are multiple formatting inconsistencies with the “°C” unit in lines 350–385. Response: Thank you sincerely for your kind reminder. We have reviewed the whole manuscript and revised the errors. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 90, 231, 106]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[147, 115, 853, 470]]<|/det|> +Copolymer of PEI with polysulfone (PEI- PSU) particles \(\mathrm{(T_g\approx 265~^\circ C)}\) , fluorene polyester (FPE) particles \(\mathrm{(T_g = 330~^\circ C)}\) and commercial biaxially oriented polypropylene (BOPP) films with a thickness of \(5.8\mu \mathrm{m}\) were provided by Polyk Technologies Company. PEI- PSU particles and FPE particles were dissolved in NMP, stirring at \(70^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Next, the viscous polymer solution was cast and baked at \(70^{\circ}\mathrm{C}\) for \(2\mathrm{h}\) , and then the sample films were dried in a vacuum oven at \(200^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . Thermogravimetric analysis (TGA) curves were obtained from a NETZSCH TGA209F1 thermogravimetry under nitrogen (air) atmosphere at a heating rate of \(10^{\circ}\mathrm{C}\) \(\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(800^{\circ}\mathrm{C}\) . Differential scanning calorimetry (DSC) was performed on a TA Q10 DSC at a scan rate of \(10^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(300^{\circ}\mathrm{C}\) in a nitrogen atmosphere. The in- plane thermal expansion change curves of the films were recorded by a TMA Q400 from TA Instruments, with a force of \(0.02\mathrm{N}\) , under nitrogen flow at a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(350^{\circ}\mathrm{C}\) . + +<|ref|>text<|/ref|><|det|>[[147, 505, 852, 602]]<|/det|> +(5) The characterization section must be improved by providing a detailed description of each experimental technique used. For example, what mode was used in the AFM test? What amplitude was selected for the DMA test? Was preheating performed in the DSC test? In the D-E loop test, what were the electrode material and dimensions? + +<|ref|>text<|/ref|><|det|>[[147, 612, 853, 914]]<|/det|> +Response: Thank you for your valuable comments. We added these descriptions according to your suggestion. The surface morphology of the sample films was characterized using atomic force microscopy (AFM) in tapping mode. In tensile mode, dynamic mechanical analysis (DMA) of sample films was conducted at a load frequency of \(1\mathrm{Hz}\) , with a displacement amplitude of \(20\mu \mathrm{m}\) , a temperature ranges from \(50\) to \(350^{\circ}\mathrm{C}\) , and a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) . In differential scanning calorimetry (DSC) measurements, the glass transition temperature \((\mathrm{T_g})\) of the polymer films was determined from the inflection point of the second heating curve after an initial heating- cooling cycle, a protocol designed to eliminate thermal history and enhance data reliability. Gold electrodes with a diameter of \(3\mathrm{mm}\) were used as the electrode material for displacement- electric field (D- E) loop measurements. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 91, 231, 107]]<|/det|> +## Revision: + +<|ref|>sub_title<|/ref|><|det|>[[148, 118, 298, 135]]<|/det|> +## Characterization + +<|ref|>text<|/ref|><|det|>[[147, 144, 853, 917]]<|/det|> +\(^1\mathrm{H}\) nuclear magnetic resonance (NMR) spectra of the prepolymers were recorded using a JNM- ECZ600R spectrometer in DMSO- \(d_{6}\) . The crosslinking degree of the films was determined by calculating the absorbance of the polymer solutions, which was recorded using a UV- vis spectrophotometer (UV- 2600i, Island Ferry, Japan). The morphologies of the polymer films were observed by a scanning electron microscope (SEM, TESCAN) and an atomic force microscope (AFM, NanomanTM VS, USA) operated in tapping mode. X- ray photoelectron spectroscopy (XPS) analysis was carried out by a Thermo Fisher K- Alpha spectroscopy with an Al source. Solid- state UV- vis absorption spectra were recorded using a Shimadzu UV- 3600 spectrophotometer. The steady- state/transient photoluminescence (PL) spectra of the polymer films were recorded using an Edinburgh FS5 spectrometer. Fourier transform infrared (FTIR) spectra of the samples were used to confirm their characteristic functional groups by a Nicolet iS50 FTIR spectrometer. X- ray diffraction (XRD) analysis was conducted with Cu radiation by a PANalytical Empyren diffractometer. The wide- angle X- ray scattering (WAXS) measurements were performed using a copper- target X- ray generator (Anton Paar) with operational parameters strictly controlled at \(\leq 40 \mathrm{kV}\) accelerating voltage and \(\leq 50 \mathrm{mA}\) tube current. Grazing incidence wide- angle X- ray scattering (GIWAXS) measurements were performed on a Rigaku Homelab system (Japan) equipped with a Cu Kα X- ray source (8.05 keV, \(\lambda = 1.54 \mathrm{\AA}\) ) and a HyPix- 6000 photon- counting detector. The sample- detector distance (SDD) was accurately calibrated using silicon standard sample data. The detector configuration included a pixel size of \(100 \mu \mathrm{m} \times 100 \mu \mathrm{m}\) , with an exposure time of 120 s per measurement. Thin films for GIWAXS analysis were prepared on a glass substrate by spin- coating. Thermogravimetric analysis (TGA) curves were obtained from a NETZSCH TGA209F1 thermogravimetry under nitrogen (air) atmosphere at a heating rate of \(10^{\circ}\mathrm{C min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(800^{\circ}\mathrm{C}\) . Differential scanning calorimetry (DSC) was performed on a TA Q10 DSC at a scan rate of \(10^{\circ}\mathrm{C min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(300^{\circ}\mathrm{C}\) in a nitrogen atmosphere. In DSC measurements, the glass transition temperature ( \(\mathrm{T_g}\) ) of the polymer films was determined from the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 87, 852, 833]]<|/det|> +inflection point of the second heating curve after an initial heating- cooling cycle, a protocol designed to eliminate thermal history and enhance data reliability. The in- plane thermal expansion change curves of the films were recorded by a TMA Q400 from TA Instruments, with a force of 0.02 N, under nitrogen flow at a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , ranging from \(30^{\circ}\mathrm{C}\) to \(350^{\circ}\mathrm{C}\) . Dynamic mechanical analysis (DMA) of samples was conducted in tensile mode using a DMA 850 (TA Instruments) at a load frequency of \(1\mathrm{Hz}\) , with a displacement amplitude of \(20\mu \mathrm{m}\) , a temperature ranges from 50 to \(350^{\circ}\mathrm{C}\) , a heating rate of \(5^{\circ}\mathrm{C}\mathrm{min}^{- 1}\) , and under nitrogen flow. The stress- strain behavior of the crosslinked film was evaluated in tensile mode using a DMA 850 (TA Instruments, USA) with a preload force of \(0.1\mathrm{N}\) and a displacement ramp rate of 0.05 \(\mathrm{mm}\mathrm{min}^{- 1}\) . Gold electrodes with diameters of \(3\mathrm{mm}\) and \(8\mathrm{mm}\) were coated onto both sides of the films using a GVC- 2000 magnetron ion sputtering instrument for electrical testing under high electric field (D- E loop, breakdown strength and leakage current) and low electric field (dielectric spectra), respectively. The dielectric frequency spectrum and dielectric temperature spectrum of the samples were measured using a precision impedance analyzer (Agilent 4294A, Germany) and a DMS- 500 dielectric temperature spectroscopy measurement system (DMS- 500, China), respectively. The high- temperature- resistivity of the films was tested using a Tonghui TH2690A insulation resistance meter. The displacement- electric field hysteresis loop (D- E loop), breakdown strength and cyclic charge- discharge performance of the samples were measured by a TF Analyzer 3000 series (AixACT, Germany) at \(100\mathrm{Hz}\) . The leakage current density of sample films was measured using a TF Analyzer 3000 series (AixACT, Germany). A stepwise electric field increment mode was used, in which the electric field strength was increased by \(10\mathrm{MV}\mathrm{m}^{- 1}\) per step (each step maintained for 2 seconds) until reaching the preset electric field strength. The fast charge- discharge tests were performed using a DCQ- 20A measurement system (Polyk Technologies) with a load resistor (RL) of \(10\mathrm{k}\Omega\) . + +<|ref|>text<|/ref|><|det|>[[148, 867, 850, 913]]<|/det|> +(6) In Figure 2, the author uses scan mode to explore the lowest energy points of two molecular chains. However, the structure of the polymer condensed matter is equally + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 220]]<|/det|> +important, and I suggest that the free volume of the whole condensed matter structure should be calculated and analyzed. If you can, consider calculating statistics for the distance between this segment and the surrounding segment separately. The precision of the base group can be appropriately reduced to take into account the calculation speed and quality. + +<|ref|>text<|/ref|><|det|>[[147, 228, 853, 636]]<|/det|> +Response: Thank you for your careful reading and professional suggestions. We employed molecular dynamics simulations to analyze the condensed- state structures of PEI and TPEI polymers (Figure S6). The simulation results reveal that despite the introduction of four methyl groups on diamine benzene to form benzyl groups (undergoing crosslinking under thermo- oxidative conditions) in TPEI, the cell of TPEI exhibits more free volume (blue regions) compared to PEI, resulting in a higher fractional free volume (FFV) for TPEI. Furthermore, we performed sectioning on the simulated cells of PEI and TPEI and conducted statistical analysis on the cavity contours of free volume within these planes to investigate distances around the polymer segments (Figure S7). The statistical analysis shows that the average interchain distance in TPEI (5.24 Å) significantly exceeds that in PEI (4.15 Å), a trend consistent with the findings from DFT calculations. Notably, the smaller interchain distance observed in PEI compared to the rigid scanning MLP results (5.1 Å) because the rigid scanning result was performed on two isolated polymer chains without considering the condensed- state structure of the polymer. + +<|ref|>sub_title<|/ref|><|det|>[[149, 647, 231, 662]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[148, 672, 852, 830]]<|/det|> +Additionally, the local interchain spacing in the polymer chains is increased by leveraging the electrostatic repulsion at the same positions between molecular chains, leading to difficulty in the transport of charge carriers within the polymer. The molecular dynamics (MD) simulations reveal that TPEI exhibits a higher fractional free volume (FFV = 23.48%) and greater interchain distance (5.24 Å) compared to those (FFV = 6.03%; interchain distance = 4.15 Å) of PEI (Figures S6- 7). + +<|ref|>sub_title<|/ref|><|det|>[[149, 867, 474, 885]]<|/det|> +## Molecular dynamics (MD) simulation + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 330]]<|/det|> +Unit cells of PEI and TPEI were constructed using Materials Studio 20 software, both comprising 10 molecular chains with 20 repeat units per chain. Notably, 9 molecular chains in the TPEI system underwent crosslinking. Electrostatic interactions were handled by the Ewald summation technique, and van der Waals interactions were computed using an atom- based approach. A Nose- Hoover thermostat was used to control temperature, and pressure regulation was achieved through a Berendsen barostat. We use progressive relaxation and annealing methods to eliminate initial structural biases, enabling the system to reach thermodynamic equilibrium61. The fractional free volume (FFV) of a polymer is determined by the equation: + +<|ref|>equation<|/ref|><|det|>[[432, 334, 567, 373]]<|/det|> +\[FFV = \frac{V_{\mathrm{c}}}{V_{\mathrm{c}} + V_{0}}\] + +<|ref|>text<|/ref|><|det|>[[147, 376, 850, 422]]<|/det|> +Where \(V_{c}\) corresponds to the unoccupied volume and \(V_{0}\) represents the volume occupied by polymer chains. + +<|ref|>image<|/ref|><|det|>[[228, 425, 773, 833]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 840, 850, 913]]<|/det|> +
Figure S6. PEI a) and TPEI b) cells generated through molecular dynamics simulations. Blue regions denote the free volume and grey regions represent the volume occupied by polymer chains. c) Fractional free volume (FFV) and density data for PEI and TPEI.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[148, 87, 848, 656]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 664, 851, 738]]<|/det|> +
Figure S7. Cleave plane of PEI a) and TPEI b) simulation cells. Green regions denote the free volume and grey regions represent the volume occupied by polymer chains. c) Average spacing around FFV in PEI and TPEI.
+ +<|ref|>text<|/ref|><|det|>[[148, 775, 460, 792]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 803, 850, 876]]<|/det|> +The reviewer had comments regarding a number of aspects, summarised below: We highly appreciate the reviewer's accurate comments on our paper and will try to address the questions raised. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 135]]<|/det|> +(1) The potential of the materials in future applications, due to changes in production methods. + +<|ref|>text<|/ref|><|det|>[[147, 144, 852, 499]]<|/det|> +Response: Thank you for your valuable comments. Compared to conventional polyimide crosslinking requiring elevated temperature windows (300- 350 °C), the benzyl groups in TPEI undergo thermal- oxidative crosslinking under an air atmosphere at reduced temperatures (250- 290 °C), effectively inducing rearrangement of donor- acceptor units in TPEI. This process demonstrates significant energy- saving advantages in manufacturing. Regarding scalable manufacturing, the novel all- organic polymer (TPEI) eliminates filler dispersion challenges inherent in composite dielectrics incorporating organic/inorganic additives, thereby significantly enhancing production scalability. Finally, performance comparison plots reveal that the polyetherimide modified through a structural rearrangement strategy (TPEI) exhibits superior energy storage performance (Figure 6f). Collectively, these comparisons demonstrate that structurally rearranged dielectric polymers in this work exhibit substantial application potential in dielectric energy storage. + +<|ref|>text<|/ref|><|det|>[[148, 533, 850, 579]]<|/det|> +(2) The mechanical properties of the crosslinked polyetherimides, with more characterization requested. + +<|ref|>text<|/ref|><|det|>[[147, 588, 852, 802]]<|/det|> +Response: Appreciating your suggestion to further characterize the mechanical properties of the crosslinked polyetherimides, we performed tensile test on crosslinked TPEI films, with the corresponding stress-strain curves presented in Figure S19. The result indicates that TPEI exhibits a tensile strength of 80 MPa and an elongation at break of 3.4%. This is primarily attributed to the flexible ether linkages and alkane chains within the crosslinked network. Notably, the crosslinking method not only enhances the storage modulus of TPEI (Figures 4a-c) but also maintains its mechanical properties without compromise. + +<|ref|>sub_title<|/ref|><|det|>[[148, 812, 231, 828]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[148, 839, 852, 914]]<|/det|> +The increased breakdown strength of the polymer films can be attributed to their greater modulus. The storage modulus of TPEI (for example, 4.46 GPa at 150 °C, 3.97 GPa at 200 °C and 3.42 GPa at 250 °C) is greater than that of PEI (for example, 2.82 GPa at + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 164]]<|/det|> +\(150~^\circ \mathrm{C}\) , 2.46 GPa at \(200~^\circ \mathrm{C}\) and 0 GPa at \(250~^\circ \mathrm{C}\) ), throughout a temperature range of \(35~^\circ \mathrm{C}\) to \(250~^\circ \mathrm{C}\) (Figures 4a- c). Notably, TPEI exhibits a tensile strength of 80 MPa and an elongation at break of \(3.4\%\) (Figure S19, Supporting Information). + +<|ref|>image<|/ref|><|det|>[[260, 174, 737, 459]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 469, 515, 488]]<|/det|> +
Figure S19 Stress-strain curves of TPEI film.
+ +<|ref|>text<|/ref|><|det|>[[147, 523, 850, 572]]<|/det|> +(3) The evidence provided to support the claim of preferred layer packing, compared to mixed layer packing, with more experimental results required. + +<|ref|>text<|/ref|><|det|>[[146, 580, 852, 906]]<|/det|> +Response: Thank you for your constructive comment. Wide-angle X-ray scattering (WAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS) analyses were performed on TPEIu and TPEI samples. The WAXS patterns reveal significantly intensified and broadened diffraction peaks in TPEI compared to TPEIu, confirming the structural rearrangement into “ch-pack” packing structure (PLP structure) induced by benzyl crosslinking4 (Figure 3g). Furthermore, the 2D GIWAXS patterns reveal that TPEI exhibits broad and isotropic amorphous halos, contrasting sharply with the poorly defined amorphous scattering features observed in TPEIu (Figures 3h-i and Figure S16 in the Supporting Information). This stark difference indicates substantial alterations in molecular packing and arrangement induced by benzyl crosslinking, resulting in a heterogeneous microstructure comprising coexisting ordered domains and amorphous regions in TPEI. Furthermore, Analysis of one-dimensional intensity versus scattering + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 220]]<|/det|> +vector (I- q) profiles derived from the 2D GIWAXS data reveals two characteristic scattering peaks for TPEI. The scattering peak of TPEI at a scattering vector \(\mathbf{q}\) of 1.01- 1.35 Å- 1 is attributed to the ordered "ch- pack" stacking structure (PLP structure; Figure S17). Additionally, the scattering peak of TPEI at \(\mathbf{q} = 1.35\text{- } 1.83\text{Å}^{- 1}\) is ascribed to "π- pack" interaction between imide rings and benzene rings in adjacent polymer chains. + +<|ref|>text<|/ref|><|det|>[[147, 222, 852, 920]]<|/det|> +Revision: As shown in Figures 3e- f, the exploded views of the XRD patterns of the films indicate the presence of "ch- pack" ordered domains observed in TPEI compared with \(\mathrm{PEI^{34}}\) . The "ch- pack" packing structure of polymer chains, similar to the PLP structure, originates from liquid- crystalline- like ordered domains. Hence, the PLP structure formed by benzyl- induced crosslinking predominates in TPEI film, indicating an efficient reduction in electrical conduction loss. In contrast, the main ordered packing structure in PEI is a "π- stack" formation, which represents the π- π stacking of imide and phenyl rings in ordered domains, thereby largely promoting charge carrier transport in polymers. Notably, the variation in interchain spacing of polymer chains was calculated from the XRD data of PEI and TPEI films, which is consistent with the theoretical charge results from DFT calculations and MD simulations (Figure S15, Supporting Information). The WAXS patterns reveal significantly intensified and broadened diffraction peaks in TPEI compared to \(\mathrm{TPEI_u}\) , confirming the structural rearrangement into "ch- pack" packing structure (PLP structure) induced by benzyl crosslinking35 (Figure 3g). Furthermore, the 2D GIWAXS patterns reveal that TPEI exhibits broad and isotropic amorphous halos, contrasting sharply with the poorly defined amorphous scattering features observed in \(\mathrm{TPEI_u}\) (Figures 3h- i and Figure S16 in the Supporting Information). This stark difference indicates substantial alterations in molecular packing and arrangement induced by benzyl crosslinking, resulting in a heterogeneous microstructure comprising coexisting ordered domains and amorphous regions in TPEI. Furthermore, Analysis of one- dimensional intensity versus scattering vector (I- q) profiles derived from the 2D GIWAXS data reveals two characteristic scattering peaks for TPEI. The scattering peak of TPEI at a scattering vector \(\mathbf{q}\) of 1.01- 1.35 Å- 1 is attributed to the ordered "ch- pack" stacking structure (PLP structure; Figure S17). Additionally, the scattering peak of TPEI at \(\mathbf{q} = 1.35\text{- } 1.83\text{Å}^{- 1}\) is ascribed to "π- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 835, 108]]<|/det|> +pack" interaction between imide rings and benzene rings in adjacent polymer chains. + +<|ref|>image<|/ref|><|det|>[[149, 111, 848, 592]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 600, 851, 756]]<|/det|> +
Figure 3. Characterization of the polymer films and the PLP structure. a) FT-IR spectra, b) TGA and DTG curves (Inset: partial enlarged detail of TGA), c) DSC curves, d) In-plane thermal expansion change curves (Inset: CET values) for PEI and TPEI films. Exploded view of the XRD pattern for e) PEI film and f) TPEI film. g) The WAXS patterns for TPEIu and TPEI films. The 2D GIWAXS patterns of h) TPEIu and i) TPEI films.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[260, 85, 734, 285]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 292, 852, 396]]<|/det|> +
Figure S16. Schematic diagram of GIWAXS measurements of polymer film. \(\alpha_{f}\) represents the exit angle of the X-ray beam relative to the film surface, and \(2\theta_{f}\) denotes the exit angle relative to the plane of incidence. Meanwhile, \(\mathbf{q}_{\mathrm{x}}\) , \(\mathbf{q}_{\mathrm{y}}\) , and \(\mathbf{q}_{\mathrm{z}}\) is the components of the scattering vector \(\mathbf{q}\) .
+ +<|ref|>image<|/ref|><|det|>[[286, 400, 710, 658]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 664, 772, 683]]<|/det|> +
Figure S17. One-dimensional GIWAXS integration profile of polymer films.
+ +<|ref|>text<|/ref|><|det|>[[147, 719, 850, 765]]<|/det|> +(4) Additional experimental evidence for the possible charge transfer excitations, as well as the DFT calculations provided. + +<|ref|>text<|/ref|><|det|>[[147, 774, 852, 905]]<|/det|> +Response: Thank you for your valuable comments. Through comparative analysis of fluorescence emission spectra between PEI and TPEI films combined with DFT calculations, we demonstrated that the benzyl-induced rearrangement of donor-acceptor units to form the PLP structure effectively suppresses both interchain and intrachain charge transfer. Notably, interchain charge transfer induces fluorescence quenching + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 303]]<|/det|> +with intensity attenuation, while intrachain charge transfer promotes fluorescence redshift5, 6. As shown in Figure S12, the TPEI exhibits a significantly enhanced fluorescence signal with a blue- shifted peak compared to PEI, proving that the benzyl- induced PLP structure simultaneously inhibits interchain and intrachain charge transfer. Additionally, we employed time- dependent density functional theory (TDDFT) combined with the CAM- B3LYP/6- 31G(d) method to analyze electron transitions in the first 20 excited states of the polymer structural units (see the Revision for detailed analysis). + +<|ref|>text<|/ref|><|det|>[[147, 308, 852, 917]]<|/det|> +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). Notably, in the PLP structure induced by benzyl- induced crosslinking, the transfer of electrons from the diamine to the dianhydride during CT excitation is significantly diminished, with the amount of charge transfer nearly approaching 0 electrons between the two cross- linked molecular chains (Figures 2c- d(ii)). Moreover, the electron migration amount in TPEI containing two crosslinking points is significantly lower than that in TPEI with a crosslinking point. This difference arises from the enhanced face- to- face stacking of diamine units, which forms a more pronounced PLP structure. In contrast, TPEI with a crosslinking point exhibits partially misaligned stacking between diamine units, inducing a stacking more resembling MLP structure that weakens the suppression of electron migration (Figure S8, Supporting Information). Moreover, the optical bandgap (2.9 eV) of TPEI is narrower than that (3.1 eV) of PEI (Figure S9, Supporting Information). This result contrasts with conventional observations in dielectric polymers where a wider bandgap typically correlates with superior electrical insulation25, 27. This strongly supports the idea that PLP structure effectively restricts electronic transport between polymer dielectrics. Furthermore, the substituent methyl groups on the diamine benzene rings increase the dihedral angles at the imide ring position of TPEI, inducing twisting at the donor- acceptor junctions within the molecular chains and thereby diminishing the electrostatic interactions within the molecular chains10 (Figures S10- 11, Supporting + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 192]]<|/det|> +Information). Based on the fluorescence emission spectra of PEI and TPEI, TPEI exhibits a significantly enhanced fluorescence signal with a blue- shifted peak compared to PEI, which proves that the benzyl- induced PLP structure simultaneously inhibits both interchain and intrachain charge transfer28, 29 (Figure S12, Supporting Information). + +<|ref|>image<|/ref|><|det|>[[280, 199, 720, 470]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 478, 712, 497]]<|/det|> +
Figure S12. Fluorescence emission spectra of PEI and TPEI samples.
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 506, 650, 525]]<|/det|> +## Measurement of gelation content of crosslinked TPEI film + +<|ref|>text<|/ref|><|det|>[[147, 533, 852, 664]]<|/det|> +To evaluate the degree of chemical crosslinking in TPEI film, un- crosslinked (TPEIu) and crosslinked (TPEI) samples were immersed in N- methyl- 2- pyrrolidone (NMP) at \(80^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) . The remaining TPEI polymer was rinsed with ethanol to remove residual solvent and dried in a vacuum oven at \(100^{\circ}\mathrm{C}\) for 24 hours. The gel content was calculated using the formula: + +<|ref|>equation<|/ref|><|det|>[[357, 670, 639, 707]]<|/det|> +\[\% \mathrm{gel~content} = \frac{M_f}{M_o}\times 100\%\] + +<|ref|>text<|/ref|><|det|>[[147, 710, 850, 756]]<|/det|> +where \(M_{f}\) and \(M_{o}\) denote the residual and initial weights of the film samples, respectively. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 115, 850, 290]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[238, 90, 756, 108]]<|/det|> +Table S1. Test conditions during gel content testing and results. + +
SampleTemperature (°C)Original massFinal massRatio of gel
Time (h)(mg)(mg)
TPEIu80 °C &amp; 24 h31.500.000.00%
TPEI80 °C &amp; 24 h33.8027.8082.25%
+ +<|ref|>sub_title<|/ref|><|det|>[[147, 323, 265, 340]]<|/det|> +## DFT analysis + +<|ref|>text<|/ref|><|det|>[[147, 350, 853, 650]]<|/det|> +From the perspective of charge transfer, electron excitation is primarily categorized into local excitation (LE) and charge- transfer excitation (CT). LE is characterized by negligible spatial redistribution of electrons before and after excitation. In contrast, CT involves a pronounced redistribution of electrons upon excitation, occurring either intramolecularly (within a single molecule) or intermolecularly (between adjacent molecules). Therefore, when analyzing the electronic excitation behavior of dielectric polymers, the first CT- dominated excited state serves as a critical indicator for evaluating electron migration between different molecular segments. To determine the nature of electronic excitation states, we calculated the first 20 excited states for each polymer molecule and then classified the electron excitation types based on these results. The Sr function is integrated over the entire space as follows: + +<|ref|>equation<|/ref|><|det|>[[318, 659, 750, 686]]<|/det|> +\[S_{r} i n d e x = \int S_{r}(\boldsymbol {r}) d\boldsymbol {r} \equiv \int \sqrt{\rho^{h o l e}(\boldsymbol {r})\rho^{e l e}(\boldsymbol {r})} d\boldsymbol {r}\] + +<|ref|>text<|/ref|><|det|>[[147, 720, 851, 822]]<|/det|> +The Sr index ranges between 0 and 1. A higher value indicates a stronger spatial overlap between the hole and electron distributions, whereas a lower value signifies more pronounced separation between them. Additionally, the D index is employed to quantify the distance between the centroids of the holes and electrons. + +<|ref|>equation<|/ref|><|det|>[[414, 830, 582, 910]]<|/det|> +\[D_{x} = |X_{e l e} - X_{h o l e}|\] \[D_{y} = |Y_{e l e} - Y_{h o l e}|\] \[D_{z} = |Z_{e l e} - Z_{h o l e}|\] + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[352, 85, 644, 123]]<|/det|> +\[D_{i n d e x} = \sqrt{\left(D_{x}\right)^{2} + \left(D_{y}\right)^{2} + \left(D_{z}\right)^{2}}\] + +<|ref|>text<|/ref|><|det|>[[651, 128, 680, 145]]<|/det|> +(2) + +<|ref|>text<|/ref|><|det|>[[147, 153, 850, 230]]<|/det|> +Here, \(X_{e l e}\) denotes the X- coordinate of the electron centroid. A larger D index indicates a more pronounced spatial separation between holes and electrons. Furthermore, the \(t\) index is employed to quantify the degree of hole- electron separation. + +<|ref|>equation<|/ref|><|det|>[[398, 238, 598, 260]]<|/det|> +\[t_{i n d e x} = D_{i n d e x} - H_{c T}\] + +<|ref|>text<|/ref|><|det|>[[484, 267, 512, 283]]<|/det|> +(3) + +<|ref|>equation<|/ref|><|det|>[[425, 293, 562, 313]]<|/det|> +\[H_{c T} = |\pmb {H}\cdot \pmb{u}_{c T}|\] + +<|ref|>text<|/ref|><|det|>[[148, 348, 850, 460]]<|/det|> +Here, \(H_{c T}\) quantifies the average spatial extension of the hole and electron distributions along the CT direction. In the equation (4), \(H\) represents the vector composed of components \(\pmb{H_{x}}\) , \(\pmb{H_{y}}\) , and \(\pmb{H_{z}}\) , where \(\pmb{u}_{c T}\) denotes the unit vector along the CT direction. + +<|ref|>text<|/ref|><|det|>[[147, 468, 852, 655]]<|/det|> +Using these indices (Sr, D and \(t\) ), we identified the first CT excitation from the first 20 electronic excited states of PEI and TPEI. Specifically, LE excitation is generally characterized by a large Sr index, a small D index, and a negative \(t\) index, whereas CT excitation is determined by a large D index, reflecting the inherent requirement for significant spatial separation between electrons and holes in CT excited states. Next, we list the aforementioned indices and preliminary classifications of the corresponding electronic excitation types for the first 20 excited states of the polymer molecules. + +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[280, 92, 717, 105]]<|/det|> +Table S2 Analysis of the first 20 excited states of PEI + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.516491.153-1.023LE
2nd0.520360.694-0.917LE
3rd0.522980.767-0.465LE
4th0.648991.607-0.408LE
5th0.521741.001-0.476LE
6th0.534710.598-1.032LE
7th0.741810.638-1.635LE
8th0.841460.855-1.015LE
9th0.783800.575-1.994LE
10th0.238163.9932.515CT
11th0.633553.8220.872CT
12th0.871030.603-2.815LE
13th0.835760.723-3.464LE
14th0.952670.153-1.674LE
15th0.752832.822-1.292LE
16th0.832690.752-3.195LE
17th0.830511.319-3.491LE
18th0.824840.219-3.130LE
19th0.757681.761-4.497LE
20th0.3569512.0157.386CT
+ +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[270, 92, 728, 105]]<|/det|> +Table S3 Analysis of the first 20 excited states of TPEIu + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.534091.085-0.526LE
2nd0.519520.718-0.651LE
3rd0.618490.086-2.234LE
4th0.646111.613-0.026LE
5th0.175384.132.698CT
6th0.531870.908-0.691LE
7th0.537470.617-0.819LE
8th0.614620.904-1.786LE
9th0.842620.84-0.66LE
10th0.747510.342-1.875LE
11th0.584014.2571.888CT
12th0.93380.35-1.402LE
13th0.808770.759-4.169LE
14th0.777191.585-2.361LE
15th0.912830.367-2.635LE
16th0.800110.65-3.56LE
17th0.0140320.7919.54CT
18th0.777380.493-4.332LE
19th0.82240.474-4.523LE
20th0.717443.939-1.345LE
+ +<--- Page Split ---> +<|ref|>table_caption<|/ref|><|det|>[[172, 91, 825, 106]]<|/det|> +Table S4 Analysis of the first 20 excited states of TPEI with a crosslinking point + +<|ref|>table<|/ref|><|det|>[[149, 111, 848, 710]]<|/det|> + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.53641.108-0.511LE
2nd0.509190.911-0.148LE
3rd0.544360.999-0.33LE
4th0.510581.051-0.318LE
5th0.634770.799-1.478LE
6th0.642991.193-1.665LE
7th0.640781.193-1.193LE
8th0.630421.358-0.617LE
9th0.227683.8252.101CT
10th0.523030.913-0.428LE
11th0.545830.887-0.757LE
12th0.251433.0830.953CT
13th0.480121.376-1.181LE
14th0.546660.896-1.015LE
15th0.533440.849-0.928LE
16th0.779150.533-1.178LE
17th0.158823.782.163CT
18th0.817740.881-0.8LE
19th0.834410.888-1.09LE
20th0.712960.983-0.841LE
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[147, 110, 849, 711]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[156, 90, 839, 107]]<|/det|> +Table S5 Analysis of the first 20 excited states of TPEI with two crosslinking points + +
Excited stateSr (a.u.)D (Angstrom)t (Angstrom)classification
1st0.520781.255-0.31LE
2nd0.567180.976-0.682LE
3rd0.517410.767-0.54LE
4th0.537320.75-0.645LE
5th0.297393.4161.444CT
6th0.61080.305-1.334LE
7th0.64421.426-2.574LE
8th0.610370.785-3.221LE
9th0.641961.433-0.14LE
10th0.204754.0732.527CT
11th0.441722.2520.571CT
12th0.479322.0990.122CT
13th0.535190.662-0.608LE
14th0.538370.923-0.684LE
15th0.604241.022-1.048LE
16th0.535060.804-0.671LE
17th0.325514.752.392CT
18th0.547382.637-0.073LE
19th0.479273.1420.761CT
20th0.824871.009-0.582LE
+ +<|ref|>text<|/ref|><|det|>[[147, 740, 851, 871]]<|/det|> +By analyzing the first 20 electronically excited states of PEI, TPEI, TPEI with one crosslinking point, and TPEI with two crosslinking points, their first CT excitations occur at the 10th, 5th, 9th, and 5th excited states, respectively. Subsequently, the electron transfer characteristics within these CT excitations were systematically analyzed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 773, 108]]<|/det|> +(5) Reason for the TPEI material not decomposing in different environments. + +<|ref|>text<|/ref|><|det|>[[147, 115, 853, 469]]<|/det|> +Response: Thank you for your careful comment. The resistance of TPEI to decomposition under diverse environments arises from its rationally designed molecular structure. First, the rigid molecular skeleton containing aromatic and imine rings provides high bond energy and planar rigidity, effectively suppressing thermal decomposition of polymer chains at elevated temperatures (Figure S14). Second, the ether linkages and isopropyl groups in TPEI impart flexibility to the polymer chains, alleviating stress concentration to prevent brittle fracture and enhance mechanical stability. Third, benzyl-induced crosslinking forms a network through chemical crosslinks and physical entanglements, which significantly hinders solvent penetration into the polymer film and improves solvent resistance (Figure S3). Concurrently, this crosslinked network reinforces thermal stability and mechanical strength. Overall, the balanced integration of rigidity-flexibility in TPEI's molecular design endows the material with outstanding structural stability across various environments. + +<|ref|>text<|/ref|><|det|>[[147, 477, 853, 888]]<|/det|> +Revision: The glass transition temperature ( \(\mathrm{T_g}\) ) increases from \(236.31^{\circ}\mathrm{C}\) for PEI to \(289.72^{\circ}\mathrm{C}\) for TPEI, suggesting that the movement of polymer chains is restrained by benzyl- induced crosslinking networks (Figure 3c). In addition, the variation in specific heat capacity ( \(\Delta C_{\mathrm{p}}\) ) during the glass transition, caused by changes in the conformation of polymer chains, was obtained from DSC data. \(\Delta C_{\mathrm{p}}\) is significantly reduced from \(0.205\mathrm{Jg}^{- 1}\mathrm{^\circ C^{- 1}}\) for PEI to \(0.119\mathrm{Jg}^{- 1}\mathrm{^\circ C^{- 1}}\) for TPEI, indicating that the polymer chains in the crosslinked films are more stretched compared to those in PEI, thereby minimizing voids and defects in the polymer films \(^{16,33}\) . Moreover, the results of the in- plane thermal dimension change curves show a lower coefficient of thermal expansion (CTE) in TPEI films compared to that of PEI films in a specific temperature range (Figure 3d). These results indicate that benzyl- induced crosslinking network effectively restricts movement of polymer chains, thereby improving the thermal stability of the polymer films. Furthermore, the TGA curve of the TPEI film exhibits only \(5\%\) weight loss at \(420^{\circ}\mathrm{C}\) , further confirming its superior structural stability (Figure S14, Supporting Information). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[272, 92, 725, 352]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 366, 831, 412]]<|/det|> +
Figure S3. Photos of un-crosslinked TPEI \(u\) and crosslinked TPEI films after soaking in NMP at \(80^{\circ}\mathrm{C}\) for 24h.
+ +<|ref|>image<|/ref|><|det|>[[260, 419, 739, 675]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 682, 541, 700]]<|/det|> +
Figure S14. TGA and DTG curves of TPEI film.
+ +<|ref|>text<|/ref|><|det|>[[147, 764, 748, 784]]<|/det|> +(6) A request for the optical bandgap of the TPEI material to be measured. + +<|ref|>text<|/ref|><|det|>[[147, 792, 852, 896]]<|/det|> +Response: Thank you for your thorough review of the experimental details. Considering the effect of benzyl crosslinking- induced rearrangement of donor- acceptor unit on the experimental optical bandgap of polymer films, solid- state UV- vis spectra were performed on PEI and TPEI samples (Figure S9, Supporting Information). The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 219]]<|/det|> +optical bandgap of TPEI (2.9 eV) is narrower than that of PEI (3.1 eV). This result contrasts with conventional observations in dielectric polymers, where a wider bandgap typically correlates with superior electrical insulation. This indicates that the significant improvement in high- temperature electrical insulation properties of TPEI is primarily attributed to the formation of the benzyl crosslinking- induced PLP structure. + +<|ref|>text<|/ref|><|det|>[[147, 222, 853, 917]]<|/det|> +Revision: The interfragment CT (IFCT) method in Multiwfn26 revealed that 0.92 electrons are transferred from the donor (diamine) to the acceptor (dianhydride) during charge- transfer (CT) excitation of PEI (Figure 2b(ii), the electronic excitation analysis of polymer units is shown in the Supporting Information). Notably, in the PLP structure induced by benzyl- induced crosslinking, the transfer of electrons from the diamine to the dianhydride during CT excitation is significantly diminished, with the amount of charge transfer nearly approaching 0 electrons between the two cross- linked molecular chains (Figures 2c- d(ii)). Moreover, the electron migration amount in TPEI containing two crosslinking points is significantly lower than that in TPEI with a crosslinking point. This difference arises from the enhanced face- to- face stacking of diamine units, which forms a more pronounced PLP structure. In contrast, TPEI with a crosslinking point exhibits partially misaligned stacking between diamine units, inducing a stacking more resembling MLP structure that weakens the suppression of electron migration (Figure S8, Supporting Information). Moreover, the optical bandgap (2.9 eV) of TPEI is narrower than that (3.1 eV) of PEI (Figure S9, Supporting Information). This result contrasts with conventional observations in dielectric polymers where a wider bandgap typically correlates with superior electrical insulation25, 27. This strongly supports the idea that PLP structure effectively restricts electronic transport between polymer dielectrics. Furthermore, the substituent methyl groups on the diamine benzene rings increase the dihedral angles at the imide ring position of TPEI, inducing twisting at the donor- acceptor junctions within the molecular chains and thereby diminishing the electrostatic interactions within the molecular chains10 (Figures S10- 11, Supporting Information). Based on the fluorescence emission spectra of PEI and TPEI, TPEI exhibits a significantly enhanced fluorescence signal with a blue- shifted peak compared to PEI, which proves that the benzyl- induced PLP structure simultaneously inhibits both + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 825, 108]]<|/det|> +interchain and intrachain charge transfer \(^{28,29}\) (Figure S12, Supporting Information). + +<|ref|>image<|/ref|><|det|>[[150, 115, 848, 348]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 357, 850, 431]]<|/det|> +
Figure S9. a) Solid-state UV-vis spectra and b) \((a h\nu)^{2} - h\nu\) plots of PEI and TPEI. Here, \(\alpha\) represents the absorption coefficient, \(h\) corresponds to the Planck constant, and \(\nu\) indicates the light frequency.
+ +<|ref|>text<|/ref|><|det|>[[148, 468, 850, 514]]<|/det|> +(7) Use of only one method to measure crosslinking density – the use of additional methods is suggested. + +<|ref|>text<|/ref|><|det|>[[147, 523, 852, 736]]<|/det|> +Response: Thank you for your kind comments. To assess the degree of chemical crosslinking in TPEI films, swelling experiments were conducted on un-crosslinked sample (TPEI \(_u\) ) and crosslinked sample (TPEI) using the strongly polar solvent N-methyl-2-pyrrolidone (NMP). After immersion in NMP at \(80^{\circ}\mathrm{C}\) for 24 hours, TPEI \(_u\) completely dissolved, whereas TPEI retained substantial residual polymer (Figure S3). The remaining TPEI polymer was rinsed with ethanol to remove residual solvent and dried in a vacuum oven at \(100^{\circ}\mathrm{C}\) for 24 hours. The gel content was calculated using the formula: + +<|ref|>equation<|/ref|><|det|>[[358, 740, 639, 778]]<|/det|> +\[\% \mathrm{gel~content} = \frac{M_f}{M_o}\times 100\%\] + +<|ref|>text<|/ref|><|det|>[[147, 782, 852, 914]]<|/det|> +where \(M_f\) and \(M_o\) denote the residual and initial weights of the film samples, respectively. As shown in Table S1, TPEI exhibited a gel content of \(82.25\%\) , which is higher than the insoluble fraction measured via solution UV-Vis spectroscopy. This discrepancy arises because, in addition to crosslinked regions, polymer chain entanglements also contribute to the residual weight. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 91, 231, 106]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[147, 117, 852, 330]]<|/det|> +These polymer films were obtained through thermal imidization within a temperature range of \(70^{\circ} \mathrm{C}\) to \(290^{\circ} \mathrm{C}\) in air, during which the polymer film containing benzyl functional groups underwent a thermo-oxidation crosslinking reaction. The crosslinking degree of the obtained TPEI film was measured using UV- vis spectroscopy (Figure S2, Supporting Information), and the result was \(57.41\%\) . The crosslinked TPEI film cannot be dissolved in N- methyl- 2- pyrrolidone (NMP), whereas it exhibits swelling behavior with a gel content of \(82.25\%\) when immersed in NMP (Figures S3 and Table S1, Supporting Information). + +<|ref|>sub_title<|/ref|><|det|>[[148, 340, 650, 358]]<|/det|> +## Measurement of gelation content of crosslinked TPEI film + +<|ref|>text<|/ref|><|det|>[[147, 367, 852, 497]]<|/det|> +To evaluate the degree of chemical crosslinking in TPEI film, un- crosslinked (TPEI \(u\) ) and crosslinked (TPEI) samples were immersed in N- methyl- 2- pyrrolidone (NMP) at \(80^{\circ} \mathrm{C}\) for \(24 \mathrm{~h}\) . The remaining TPEI polymer was rinsed with ethanol to remove residual solvent and dried in a vacuum oven at \(100^{\circ} \mathrm{C}\) for 24 hours. The gel content was calculated using the formula: + +<|ref|>equation<|/ref|><|det|>[[358, 500, 639, 539]]<|/det|> +\[\% \mathrm{gel} \mathrm{content} = \frac{M_{f}}{M_{o}} \times 100\%\] + +<|ref|>text<|/ref|><|det|>[[147, 542, 850, 589]]<|/det|> +where \(M_{f}\) and \(M_{o}\) denote the residual and initial weights of the film samples, respectively. + +<|ref|>table<|/ref|><|det|>[[147, 620, 850, 802]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[238, 599, 756, 617]]<|/det|> +Table S1. Test conditions during gel content testing and results. + +
SampleTemperature (℃) Time (h)Original mass (mg)Final mass (mg)Ratio of gel
TPEIu80℃ &amp; 24 h31.500.000.00%
TPEI80℃ &amp; 24 h33.8027.8082.25%
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[262, 88, 732, 357]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 367, 831, 413]]<|/det|> +
Figure S3. Photos of un-crosslinked TPEI \(u\) and crosslinked TPEI films after soaking in NMP at \(80^{\circ}\mathrm{C}\) for \(24\mathrm{h}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 449, 852, 608]]<|/det|> +(8) A request for more details for the measurement of Leakage current density. Response: Thank you for your kind reminder. The direct-current (DC) leakage current density of films with 3 mm-diameter gold electrodes was measured using a TF Analyzer 3000 series (AixACT, Germany). A stepwise electric field increment mode was used, in which the electric field strength was increased by \(10\mathrm{MV}\mathrm{m}^{-1}\) per step (each step maintained for 2 seconds) until reaching the preset electric field strength. + +<|ref|>sub_title<|/ref|><|det|>[[148, 618, 231, 634]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[147, 644, 853, 914]]<|/det|> +The dielectric frequency spectrum and dielectric temperature spectrum of the samples were measured using a precision impedance analyzer (Agilent 4294A, Germany) and a DMS- 500 dielectric temperature spectroscopy measurement system (DMS- 500, China), respectively. The high- temperature- resistivity of the films was tested using a Tonghui TH2690A insulation resistance meter. The displacement- electric field hysteresis loop (D- E loop), breakdown strength and cyclic charge- discharge performance of the samples were measured by a TF Analyzer 3000 series (AixACT, Germany) at \(100\mathrm{Hz}\) . The leakage current density of sample films was measured using a TF Analyzer 3000 series (AixACT, Germany). A stepwise electric field increment mode was used, in which the electric field strength was increased by \(10\mathrm{MV}\mathrm{m}^{-1}\) per step (each step + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 850, 164]]<|/det|> +maintained for 2 seconds) until reaching the preset electric field strength. The fast charge- discharge tests were proceeded using a DCQ- 20A measurement system (Polyk Technologies) with a load resistor (RL) of \(10\mathrm{k}\Omega\) . + +<|ref|>text<|/ref|><|det|>[[147, 172, 850, 248]]<|/det|> +Thank you for your professional review work, constructive comments, and valuable suggestions. We hope the above replies and related revisions are acceptable for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[147, 312, 559, 470]]<|/det|> +Sincerely yours, Prof. Dou Zhang & Prof. Hang Luo State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, P. R. China E- mail: dzhang@csu.edu.cn, hangluo@csu.edu.cn + +<|ref|>text<|/ref|><|det|>[[147, 505, 850, 693]]<|/det|> +Prof. Jun- Wei Zha State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources School of Electrical and Electronic Engineering North China Electric Power University Beijing 102206, P. R. China E- mail: zhajw@ncepu.edu.cn + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[147, 90, 245, 107]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[144, 123, 852, 534]]<|/det|> +1. Stark KH, et al. Electric strength of irradiated polythene. Nature 176, 1225-1226 (1955). +2. Shi Y, et al. A processable, high-performance dielectric elastomer and multilayering process. Science 377, 228-232 (2022). +3. Li Q, et al. High-temperature dielectric materials for electrical energy storage. Annu Rev Mater Res 48, 219-243 (2018). +4. Bai L, Zhai L, He M-H, Wang C-O, Mo S, Fan L. Thermal expansion behavior of poly(amide-imide) films with ultrahigh tensile strength and ultralow CTE. Chin J Polym Sci 38, 748-758 (2019). +5. Wang R, et al. Dielectric polymers with mechanical bonds for high-temperature capacitive energy storage. Nat Mater (2025). https://doi.org/10.1038/s41563-025-02130-z +6. Chen L, et al. Tuning second near-infrared fluorescence activation by regulating the excited-state charge transfer dynamics change ratio. J Am Chem Soc (2025). https://doi.org/10.1021/jacs.5c03763 + +<--- Page Split ---> diff --git a/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..b800944595e4d8ffe103794239e786a966c6eaec --- /dev/null +++ b/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,17 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_6.jpg", + "caption": "Supplementary Fig. 6: Hierarchical clustering of maximum growth rates of different strains. a Hierarchical clustering dendrogram based on maximum growth rates of different strains. Clustering was performed using Euclidean distance and Ward's minimum variance linkage method (ward.D2). Red rectangles delineate the clusters identified based on the silhouette analysis. Strains are color-coded at the base of the dendrogram according to trophic classifications. b Bar plot showing the average silhouette width for clusters \\((k = 2\\) to 5) with \\(k = 4\\) corresponding to the highest average width. Raw data can be found in Supplementary Data 5.", + "footnote": [], + "bbox": [ + [ + 114, + 87, + 884, + 405 + ] + ], + "page_idx": 8 + } +] \ No newline at end of file diff --git a/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c5cbd73bc9b4dc52bb594c8fea732f8ff4b48d85 --- /dev/null +++ b/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,730 @@ + +# Bringing the uncultivated microbial majority of freshwater ecosystems into culture + +Corresponding Author: Dr Michaela Salcher + +Editorial Note: Parts of this peer review file have been redacted as indicated to maintain the confidentiality of unpublished data. This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The paper by Salcher and colleagues describes a large effort to leverage dilution- to- extinction with defined media to isolate abundant prokaryotes in the epilimnia and metalimnia of lakes across central Europe, resulting in 627 pure cultures. The paper also sequences paired metagenomes and compares a metagenome- assembled genome (MAG) set to the isolate collection and compares the isolate and MAG collection to a large number of metagenomes from lakes worldwide. The paper shows that the isolate collection represents many of the most abundant and prevalent genera in lakes and includes two previously undescribed families and nine undescribed genera. Those novel taxa are named under the SeqCode. + +The paper tackles an important problem in microbiology at a large scale and generally delivers on the goal to isolate abundant and novel organisms. Some specific strengths are: large scale; paired isolate collection and metagenomes; analysis of growth rate and oligo/copiotrophy, high- quality of the isolate genomes; isolation of some interesting microorganisms including the first non- methanotrophic member of the Methylacidiphilales and some other difficult groups like Armatimonadota. I do have some critical comments for the authors' consideration. None of this is major, but I hope the authors take the comments seriously if they have a chance to resubmit. + +- In the title, please be aware that many scientists don't like the term "microbial dark matter". Also, I personally use the term only for higher ranks without cultured representatives (e.g., phyla, classes). But I'll leave the decision up to you. +- Line 18: evogonomic is not a standard word and is not a widely used term. Consider using evolutionary genomic. Also, please consider describing the importance of pure cultures more coherently. All scientist value pure samples (minerals, elements, spectra, etc.). It's easy to understand pure samples. Think of Koch's postulates for example. +- In the introduction, the discussion of auxotrophies and dependencies is a little off-target because this paper does not provide a solution to metabolic dependencies. The cells are diluted from the fresh samples into defined media with simple carbon sources and vitamins and other resources. Co-cultures are ignored, so this would prevent the study from growing microbes with metabolic dependencies (other than those supported by added media ingredients). Instead, I think the approach is very good at targeting slow-growing oligotrophs that can be outcompeted by copiotrophs during enrichment, which is not explicitly mentioned. +- Line 80, I suggest adding some text about novel biochemical pathways, cell ultrastructure, and other features here. The listed features are at least partly predictable from genomes (e.g., temperature optimum) and relatively boring. The paper would be improved by more creativity here. +- Line 108, what does "lineage-like taxa" mean? +- Line 124, how were the isolates divided into the three categories (oligotrophs, mesotrophs, copiotrophs)? Do the isolates form a continuum that was arbitrarily divided into thirds? Or were these discrete categories that were formed by a clustering method? +- Line 126, Fimbriicoccus appears to be a new genus that is first described here. For all such new taxa, please clearly communicate this the first time the new names are mentioned. +- Line 131, there is a poor transition here from discussing oligotrophs to copiotrophs. A separate paragraph with topic sentence would help. +- Line 139, what is NSY? +- Figure 1 A and B, please define all elements of the box and whisker plots and give precise p-values (per Nature guidelines). Do this throughout the paper. + +<--- Page Split ---> + +- Figure 1 B top, I don't understand what is plotted here. The labels refer to media but the legend refers to experiments with 18 different strains. So, was each strain only tested on one medium? There are only 18 data points (means presumably?) shown. Explain. Per Nature guidelines, show all data points and define all items on the graphs explicitly. + +- Line 166 "significantly similar results" is awkward but more importantly what statistical analysis is this referring to? I think you would report just a percent of strains with the same phylum assignment? I was confused about the methods here. + +- Line 170 and elsewhere (e.g., line 186, line 205), here you refer to genera as "taxa". Please try to be precise throughout the paper. In some cases, taxa is fine because a list transcends ranks, but please refer to genera or phyla or other specific ranks where possible. + +- Line 175, here you refer to species not listed in LPSN as not "cultivated before" but it's really better to be precise. Most probably have been cultivated in some way but this number refers to species names that have not been validated under the ICSP (and presumably there are no pure cultures or stable co-cultures). + +- Line 187 and elsewhere, the results are great but there's still a big cultivation bias toward Pseudomonas, which is displayed nicely in Figure S7 B and C. I suggest you point this out clearly. For example, you could mention how many of these abundant genera axenic cultures are from Pseudomonas and how many are from other phyla. I don't want to diminish the success of your work but just to communicate clearly that there's still a strong bias here and still a big problem with cultivation. Overall, as mentioned earlier, I think your study is very good for isolating oligotrophs that are outgrown in enrichment cultures or grow poorly on plates but it is poor at growing microbes with metabolic dependencies. It's ok, but it's good to be clear about the strengths of the study and where the study isn't so great (i.e., future directions). + +- Figure 2C top, what is "Diversity" here? I can't understand what this is given the two y-axis labels, figure legend, and text. +- Figure 2C bottom, does this graph include read recruitment to MAGs as described in the text (I think)? If so, I think this is really off-target. What you need to show is the same graph with your isolate genomes or ideally a comparison of your isolate genomes and the complete genome collection (isolate genomes plus MAGs). Making just one plot with isolate genomes and MAGs does not communicate the significance (abundance) of the isolate collection, which is what this paper is about. + +- Line 228 - beginning of the sentence needs fixing. + +- Line 234 - please cite a research paper (or proper review) instead of a Microbe article. You could use reference 97, for example. Also, please clarify in the text here what ANI and AAI levels were used to indicate novel species and genera - presumably 95% and 65%? + +- Line 240 - Use of the SeqCode is fine but please consider depositing the strain whose genome is the nomenclatural types into a culture collection because this could be an important resource for the research community. Please confirm in a response to reviewers that the entries in the SeqCode Registry have been pre-approved by curators. + +- Figure 3 legend - For the full figure, make sure you refer to cultures and MAGs. For panel A, make sure it's clear in the figure legend that this is isolates only. For panel B, "gained" should be "assembled". In B, it's ok I guess but some parts of the figure are unreadable. There are too many categories for bootstrap values, genome size, and GC%. Categories should be lumped so there's a chance to see something. That could be done for coverage too. I know it's hard to deal with so much data. It's up to you if you want to address this, but just a suggestion. + +- Line 282 - 287 - more abundant than what? What does the text about "a significant distinction" mean? I can't understand it. Do you mean that larger genomes encoded [flagellar] motility and a larger number of different secretion systems? In the supplemental figures, it looks like you're referring to some genomes without ANY secretion system but as far as I know, all organisms have at least one secretion system, often either Sec or SecA2. If you're inferring that some genomes have no secretion system, that would be an extraordinary claim that would require extraordinary evidence. + +- Line 288-312 is a repetition of the two preceding paragraphs. + +- Line 314 - 315. First, not all rhodopsins are light-driven ion pumps that can make ion gradients (see channelrhodopsins and sensory rhodopsins). Please consider trying to distinguish these or qualify your statement. Second, I notice a lot of cyanobacteria isolates. Is this right? What about those? + +- Line 316 - not "energy generation" but energy conservation - please. First Law of Thermodynamics. + +- Line 318 - not all RuBisCO homologs participate in the CBB cycle. Please clarify the type. + +- Line 321 - "organic carbon". + +- Line 322 - what about catalase? + +- Line 324 - Is this significant? Can you run a t-test for the endpoint? + +- line 370 = ranks + +- Line 406 - consider mentioning earlier in the main narrative that important tricks were used to increase cultivability, like catalase and pyruvate. I think these tricks aren't well known enough and it would be good to emphasize that you were careful and thoughtful and to help educate the community. + +- Line 419 - all additions after autoclaving were filter sterilized? Please explain. + +- Please check and confirm that the SeqCode Registry curators have provisionally accepted the proposed names and supporting data. + +Additional comments on figures + +Figure 1. the label "med3 (n=60)" was odd as shown in the figure; mention the statistical tests used. + +Figure 2. The figure labels are overlapping. For Panel A, mention what the thicker and darker colors represent. For Panel C, add statistical test information. + +Figure 3. The title "Diversity and phylogeny of genome- sequenced cultures" is not appropriate because the dataset also includes MAGs and other published genomes. + +Supplementary figures + +- Figure 1: Please show two-letter codes for lakes here and in Table S1. + +- Figure 12 - define the parts of the boxes and whiskers. What is "Diversity"? Just to confirm - these are based on the culture genomes only and not the MAGs? + +<--- Page Split ---> + +Very minor editorial suggestions + +Introduction + +Please check the citation formatting for the whole paper - there are extra spaces in some places. + +Line 38: When "however" connects two independent clauses (complete sentences), use a semicolon before it and a comma after it. + +Line 38: miniscule \(\rightarrow\) minuscule + +Line 46: nutrient rich \(\rightarrow\) nutrient- rich + +Line 48: nutrient rich \(\rightarrow\) nutrient- rich + +Line 69: the usage of \(\rightarrow\) the use of + +Line 86: missed a comma before "mimicking" + +Line 89: Spring, Autumn, Summer \(\rightarrow\) spring, autumn, summer + +Results and Discussion + +What are the differences between Supplementary Table 1 and Data S1? + +Line 98: 96- deep- well- plates \(\rightarrow\) 96- deep- well- plates + +Line 98: remove extra space after "one cell per well". + +Line 102: maintained further \(\rightarrow\) maintained thereafter + +Line 109: contained \(\rightarrow\) contain + +Line 113: failed in obtaining \(\rightarrow\) failed to obtain + +Lines 117- 121: the sentence is clunky; better to restructure. + +Line 127: use a multiplication sign \((\times)\) , not the letter "x". + +Line 131: write out the full name of NSY when it is first mentioned. + +Line 161: as used for \(\rightarrow\) used for + +Line 163: affiliated to \(\rightarrow\) affiliated with + +Line 213: of our culture collection \(\rightarrow\) from our culture collection + +Line 228: our the culture collection \(\rightarrow\) from our culture collection + +Line 232: the remaining ones \(\rightarrow\) the remaining genomes + +Line 225: a global presence \(\rightarrow\) their global distribution + +Line 234: Only six genomes could be assigned + +Line 290: how did you select the 324 genomes of the closest relatives from public databases? + +Line 293: Maybe you can highlight here that \(>83.9\%\) are novel/undescribed species. + +Line 376: differ to \(\rightarrow\) differ from + +Methods + +Line 544: as an outgroup + +Line 547: specify the number of bootstrap replicates + +Reviewer #2 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Reviewer #3 + +(Remarks to the Author) + +Salcher et al. present an innovative, high- throughput method to generate axenic cultures of aquatic prokaryotes. In doing so, they have addressed a major challenge in microbiology, i.e., "the great plate anomaly", that is the inability to cultivate a majority of microbial lineages. All the cultures presented here have been taxonomically annotated, and a subset had their genomes sequenced. The genome sequencing revealed diverse potential metabolisms, and as the cultures are now available, the genome- based predictions can be tested. Importantly, the cultured prokaryotes were among the most abundant in their environments, unlike many other, especially traditional cultivation techniques. Moreover, Salcher et al. used artificial media, which makes the cultures more transferable and easier to maintain as opposed to using autoclaved water. + +Major comment: + +As the authors correctly state in the Abstract, this study has resulted in a valuable collection of abundant freshwater microbes that holds significant potential as model systems for a wide array of studies. However, it is not stated how other researchers can get access to the isolates to perform such studies. This needs to be specified, otherwise this claim can hardly be made. + +Minor comments / suggested improvements: + +The detailed metabolic- capability map (Fig.4) for the 87 genome- sequenced strains could be combined with information on growth on the six media used in the study. The use of different media is a psychological experiment. Particularly, a medium + +<--- Page Split ---> + +with methanol and methylamine (MM- med) was used, and the potential for methylotrophy was analyzed based on the genomes. Comparing the growth on the medium and the genome- inferred metabolic potential would be a major addition both to the analysis of the inferred metabolism and to showcasing the potential of the cultivation approach presented here. + +The genomic comparison on page 10 and 11 is very informative and concise. An additional genomic feature interesting to compare would be CRISPRs. CRISPRs are known to be underrepresented in streamlined vs. non- streamlined genomes (for biological reasons) as well as in MAGs vs. isolates (for technical reasons), so comparing contents of CRISPR (eg proportion of genomes were CRISPRs are found) between your oligotrophic and copiotrophic isolates, as well as between your isolates and their closest MAG relatives (in cases were close MAG relatives exist) would be interesting. The latter comparison could also involve the number of CRISPR spacers found, since assembling MAGs may only recover the more conserved parts of the CRISPR within a population, as opposed to when assembling an isolate genome. + +Putting supplementary figure S2 (and potentially also S1) in the main is worth consideration, since there is space for extra display items. Fig. S2 visualizes the workflow, which is the key new development presented in the paper. This is a fully suggestive comment, and it is ultimately up to the authors how they want to present their work. + +Line 81: I find it very difficult to understand that phenotypic traits sometimes can be "not at all encoded in the genome". Of course, if, for example, there is a phage infection, the phenotype may differ from a non- infected population. But also propensity for infection by a specific phage is encoded in the genome. So please specify how you mean this might work. Line 89: It is unclear which year the spring and autumn samples come from (this is specified in the methods section and just requires a reformulation in the introduction for clarity). + +Line 122: "Most cultures showed stable growth for more than one year" - the information on which/how many cultures showed stable growth for more than one year is not in the figures. If the details of long- term survival and growth are in a supplementary table, they should be referred to. Otherwise, at least provide the percentage or number of stable long- term cultures (or which cultures were unstable and/or hard to maintain). + +Line 138: Please give the carbon source as concentration in the medium rather than as a mass. + +Lines 147- 156 (Fig. 3): The test used to obtain significance values is unspecified. + +Line 166: It's odd to provide the lower range of the p- values (">"), maybe the authors meant to write "<"? + +Lines 177- 178: It would be relevant here to write how many of the 30 genera (if any) overlap with the 48 previously cultivated genera mentioned on lines 174- 175. + +Line 189: Although I see what you mean, I guess the culture collection hasn't actually made a "contribution" to the diversity and abundance of taxa in the lakes. Consider rephrasing. + +Figure 2. Panel B includes so many taxa with similar colors that it is impossible to identify many taxa in the barplots. + +Consider only coloring a subset of the taxa with highest abundances. + +Line 218: I suggest you write "up to 117 x coverage per Gb mapped data" for clarity. + +Line 228: "Eighty- seven strains our the culture collection" - this sentence is agrammatical and thus hard to read. Should it be "in our" rather than "our the"? + +Lines 236- 237: What does "described species" mean here? Is it the species described according to the standards of ICNP, or, e.g., present in GTDB? Convention suggests the first option, but it would be beneficial to specify. The same applies to "undescribed genera" in line 237. + +Lines 265- 266: Is Data S11/S12 the same as Supplementary Table S11/S12? If yes, the cross- references should be consistent throughout the paper. + +Lines 268- 271: "In all but four cases" - do you mean "For all but four of the eighty- seven genomes"? And what does "closely related" MAG (95% ANI?) + +Line 270: Shouldn't it be "Fig. 3B" here? + +Line 280: Couldn't more TAA and less TGA/TAG simply reflect the general tendency of streamlined genes to have lower GC- content? + +Line 284: "significance distinction" could be reformulated to stress in what way these genomes were distinct (generally smaller/larger). + +Lines 288- 312: These two paragraphs are repeated. (I.e., these lines are almost exactly the same as lines 263- 287; the only difference between the two versions is the figures and supplementary material). + +Line 360: Should be "Fig. 4" + +Line 395: Was hypolimnion defined as deeper than 5m? + +Line 438: Since viability is a crucial statistic for the paper, it would be preferable to reiterate the formula in this study. + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +<--- Page Split ---> + +(Remarks to the Author) + +Thanks for your thoughtful responses to my suggestions and congratulations on a very nice study. I will endorse acceptance for publication, but if possible consider changing "72 distinct genus or lineage- like taxa" to something like "72 distinct genera or unnamed SILVA lineages". + +- Brian Hedlund + +Reviewer #3 + +(Remarks to the Author) The comments raised by us have all been well addressed in the revised version of the manuscript. + +Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The paper by Salcher and colleagues describes a large effort to leverage dilution- to- extinction with defined media to isolate abundant prokaryotes in the epilimnna and metalimnna of lakes across central Europe, resulting in 627 pure cultures. The paper also sequences paired metagenomes and compares a metagenome- assembled genome (MAG) set to the isolate collection and compares the isolate and MAG collection to a large number of metagenomes from lakes worldwide. The paper shows that the isolate collection represents many of the most abundant and prevalent genera in lakes and includes two previously undescribed families and nine undescribed genera. Those novel taxa are named under the SeqCode. + +The paper tackles an important problem in microbiology at a large scale and generally delivers on the goal to isolate abundant and novel organisms. Some specific strengths are: large scale; paired isolate collection and metagenomes; analysis of growth rate and oligo/copiotrophy, high- quality of the isolate genomes; isolation of some interesting microorganisms including the first non- methanotrophic member of the Methylacidiphilales and some other difficult groups like Armatimonadota. I do have some critical comments for the authors' consideration. None of this is major, but I hope the authors take the comments seriously if they have a chance to resubmit. + +RESPONSE: Thank you very much for your overall positive and encouraging review comments. Please find a detailed response to your individual comments below. + +- In the title, please be aware that many scientists don't like the term "microbial dark matter". Also, I personally use the term only for higher ranks without cultured representatives (e.g., phyla, classes). But I'll leave the decision up to you. RESPONSE: We thank the reviewer for this comment; we agree that the term "microbial dark matter" is mainly used for higher taxonomic ranks. We have changed the title of our manuscript to "Bringing the uncultivated microbial majority of freshwater ecosystems into culture". + +- Line 18: evogenomic is not a standard word and is not a widely used term. Consider using evolutionary genomic. Also, please consider describing the importance of pure cultures more coherently. All scientist value pure samples (minerals, elements, spectra, etc.). It's easy to understand pure samples. Think of Koch's postulates for example. + +<--- Page Split ---> + +RESPONSE: We changed "eco- and evo genomic investigations" to: "Axenic cultures are essential for studying microbial ecology, evolution, and genomics." We further changed "Despite their importance,..." to: "Despite the importance of pure cultures,...". (L 19- 20) + +- In the introduction, the discussion of auxotrophies and dependencies is a little off-target because this paper does not provide a solution to metabolic dependencies. The cells are diluted from the fresh samples into defined media with simple carbon sources and vitamins and other resources. Co-cultures are ignored, so this would prevent the study from growing microbes with metabolic dependencies (other than those supported by added media ingredients). Instead, I think the approach is very good at targeting slow-growing oligotrophs that can be outcompeted by copiotrophs during enrichment, which is not explicitly mentioned. + +RESPONSE: We thank the reviewer for this suggestion. We have rephrased this part to (L 57- 60): "Further, largely unknown growth requirements, adaptations to low nutrient and substrate concentrations, a tendency of being outcompeted by copiotrophs during enrichment, and a free- living lifestyle preventing growth on solid surfaces such as agar plates, make the isolation and cultivation of slowly growing aquatic oligotrophs challenging." + +- Line 80, I suggest adding some text about novel biochemical pathways, cell ultrastructure, and other features here. The listed features are at least partly predictable from genomes (e.g., temperature optimum) and relatively boring. The paper would be improved by more creativity here. + +RESPONSE: We thank the reviewer for this suggestion. We added a sentence listing additional features that rely on cultures (L 80- 85): "However, genomes alone are not sufficient to characterize the ecology of microbial taxa, as many phenotypic traits (e.g., cell size, temperature, pH, salinity, or substrate ranges and optima) are hard to identify or not at all encoded in the genome39. Further, cultures are a prerequisite to discover and characterize biochemical pathways25,40,41, cell ultrastructure42,43, growth requirements17,29, and microbial interactions15,44 and are the basis for genetic manipulations45,46. + +- Line 108, what does "lineage-like taxa" mean? + +RESPONSE: The SILVA database of 16S rRNA gene sequences assigns taxonomic ranks not always in a coherent way that follows the phylum- class- order- family- genus- species scheme. This is due to the many sequences obtained from uncultivated microbes that are included in this database. Hence, some important microbes are classified as clades or lineages, e.g., SAR11 clade I, II, or III (family or genus- level classifications within Pelagibacterales), hgcl (Nanopelagicales, i.e., order- level classification), GKS98 freshwater group (Zwartia, genus- level classification). We used a well- maintained and customized + +<--- Page Split ---> + +SILVA- ARB database with updated taxonomic ranks wherever possible (e.g., we split hgcl into the genera Planktophila, Nanopelagicus and other, so far undescribed Nanopelagicales, see Supplementary Data 3 and 9. However, some lineages assigned by SILVA are hard to split (e.g., NS11- 12 and OPS 17 seem to be orders), as 16S rRNA genes are often not discriminative enough to distinguish different genera and for many orders or families in SILVA, branches containing only environmental 16S rRNA sequences are simply grouped in uncultured lineages (e.g., Bacteria/Actinobacteria/Acidimicrobiiia/Microtrichales/uncultured or Bacteria/Proteobacteria/Alphaproteobacteria/Rhodobacterales_Rhodobacteraceae_1/uncultured). + +- Line 124, how were the isolates divided into the three categories (oligotrophs, mesotrophs, copiotrophs)? Do the isolates form a continuum that was arbitrarily divided into thirds? Or were these discrete categories that were formed by a clustering method? RESPONSE: The strains form a continuum that we arbitrarily divided into the three categories based on manual comparison of their growth rates. As suggested, we now did clustering of max. growth rates (based on Euclidean distance with Ward's method), however, the optimum number of clusters is 4, as one strain had extraordinarily fast growth (Flavobacterium rarum TH-1). For ease of comparison, we included this strain in the category "copiotrophs" as there is no such term as "ultracopiotroph" or "extracopiotroph". The clustering method also introduced slight changes in our manual division, as two strains that we initially thought to be copiotrophs are now in the group of mesotrophs. However, as mentioned above, the strains surely form a continuum with easily recognizable extremes (oligo- vs. copiotrophs). We still find significant differences between the three groups. We have included a new Figure (Suppl. Fig. 6, see also below) and modified the text accordingly to (L 131- 133): "Although the strains form a continuum in growth characteristics, they could be grouped into oligo- and copiotrophs and a group of strains with in- between features (mesotrophs) after clustering based on growth rates (Supplementary Fig. 6)." + +<--- Page Split ---> +![](images/Supplementary_Figure_6.jpg) + +
Supplementary Fig. 6: Hierarchical clustering of maximum growth rates of different strains. a Hierarchical clustering dendrogram based on maximum growth rates of different strains. Clustering was performed using Euclidean distance and Ward's minimum variance linkage method (ward.D2). Red rectangles delineate the clusters identified based on the silhouette analysis. Strains are color-coded at the base of the dendrogram according to trophic classifications. b Bar plot showing the average silhouette width for clusters \((k = 2\) to 5) with \(k = 4\) corresponding to the highest average width. Raw data can be found in Supplementary Data 5.
+ +- Line 126, Fimbriicoccus appears to be a new genus that is first described here. For all such new taxa, please clearly communicate this the first time the new names are mentioned. + +RESPONSE: We changed the sentence to (L 134- 138): "Oligotrophs affiliated with Planktopbila (Actinomycetota) and the newly proposed genera Acidimicrobicustris gen. nov. (Actinomycetota) and Fimbriicoccus gen. nov. (Armatimonadota) showed slow growth...". We further added fam. nov., gen. nov., and sp. nov. whenever we mention a newly proposed family, genus or species (e.g., L 145, 151, 207- 210, 218, 229- 233, 276, 286- 312) and throughout the Supplementary text. + +- Line 131, there is a poor transition here from discussing oligotrophs to copiotrophs. A separate paragraph with topic sentence would help. + +RESPONSE: We started the description of copiotrophs in a new paragraph. + +- Line 139, what is NSY? + +<--- Page Split ---> + +RESPONSE: NSY is a medium containing nutrient broth, soytone, and yeast extract. This information is now provided in brackets together with a reference (Hahn et al. 2004). + +- Figure 1 A and B, please define all elements of the box and whisker plots and give precise p-values (per Nature guidelines). Do this throughout the paper. RESPONSE: We added a description of the box plots of this figure (now Fig. 2) as follows: "Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, and individual values are displayed by open circles." We also included the results of all statistical tests in a new supplementary table (Supplementary Data 4) and refer to this in the figure legend. + +- Figure 1 B top, I don't understand what is plotted here. The labels refer to media but the legend refers to experiments with 18 different strains. So, was each strain only tested on one medium? There are only 18 data points (means presumably?) shown. Explain. Per Nature guidelines, show all data points and define all items on the graphs explicitly. RESPONSE: In this figure (now Fig. 2), we plotted average growth rates and growth rate ranges of oligo-, meso- and copiotrophic strains grown in different media. Every strain was tested in the six media, individual plots (growth curves, growth rates, max. abundances) are included as Supplementary Figs. 4 & 5. + +We changed the legend for clarification to: "b Maximum growth rates and abundances of 18 strains grown in six different media with low to high carbon and nutrient content. Strains were grouped in oligo-, meso- and copiotrophs according to growth characteristics. Averages and standard deviation of maximum growth rates for oligotrophs \((n = 6\) strains), mesotrophs \((n = 6)\) and copiotrophs \((n = 6\) ; upper panel) as well as boxplots of their maximum growth yields (lower panel) are shown. Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, and individual samples are displayed by open circles. Significant differences between these groups (t-tests) are indicated by asterisks \((***:p< 0.001)\) . Individual plots and growth curves of all strains are shown in Supplementary Figs. 4 and 5 and clustering of growth rates in Supplementary Fig. 6. Raw data are provided in Supplementary Data 3 and 5, and results of statistical tests in Supplementary Data 4." + +- Line 166 "significantly similar results" is awkward but more importantly what statistical analysis is this referring to? I think you would report just a percent of strains with the same phylum assignment? I was confused about the methods here. + +RESPONSE: We did a simple regression analysis between the results obtained by using 59 single copy marker genes (SingleM) and a single, commonly used marker gene (16S rRNA). We reformulated the sentence to make this clear (L163- 166): "Relative abundances based on taxonomic classification using 59 single copy marker genes were significantly correlated + +<--- Page Split ---> + +with results obtained by using 16S rRNA genes as taxonomic markers \((R^2 = 0.9725, p < 0.0001\) , Supplementary Notes, Supplementary Figs. 8- 10, Supplementary Data 4, 6, 8)." + +- Line 170 and elsewhere (e.g., line 186, line 205), here you refer to genera as "taxa". Please try to be precise throughout the paper. In some cases, taxa is fine because a list transcends ranks, but please refer to genera or phyla or other specific ranks where possible. RESPONSE: We changed "taxa" throughout the manuscript to genera, species or strains (e.g., 171, 173, 179). + +- Line 175, here you refer to species not listed in LPSN as not "cultivated before" but it's really better to be precise. Most probably have been cultivated in some way but this number refers to species names that have not been validated under the ICSP (and presumably there are no pure cultures or stable co-cultures). + +RESPONSE: We have rephrased this sentence accordingly to (L173- 176): "Only 39 of the 157 abundant genera have been validly published under the International Code of Nomenclature of Prokaryotes (ICNP) according to the List of Prokaryotic names with Standing in Nomenclature (LPSN) and another seven were proposed as Candidatus genera (Supplementary Data 7)." + +- Line 187 and elsewhere, the results are great but there's still a big cultivation bias toward Pseudomonas, which is displayed nicely in Figure S7 B and C. I suggest you point this out clearly. For example, you could mention how many of these abundant genera axenic cultures are from Pseudomonas and how many are from other phyla. I don't want to diminish the success of your work but just to communicate clearly that there's still a strong bias here and still a big problem with cultivation. Overall, as mentioned earlier, I think your study is very good for isolating oligotrophs that are outgrown in enrichment cultures or grow poorly on plates but it is poor at growing microbes with metabolic dependencies. It's ok, but it's good to be clear about the strengths of the study and where the study isn't so great (i.e., future directions). + +RESPONSE: We introduced the cultivation bias towards Pseudomonas in L 118 as follows: "Our culture collection was mainly dominated by Pseudomonas (50 out of 72 genera, many of them so far uncultivated), however, we failed to obtain isolates from several abundant bacterial (Chloroflexota, Planctomycetota) and archaeal (Thermoproteota) phyla that primarily inhabit the deep hypolimnion of freshwater lakes11,51." + +- Figure 2C top, what is "Diversity" here? I can't understand what this is given the two y-axis labels, figure legend, and text. + +RESPONSE: This figure (now Fig. 3c) is based on taxonomic assignment of metagenomic reads via SingleM (genus level classification) of the same water samples (original samples, + +<--- Page Split ---> + +\(\mathrm{n} = 67\) ) or in metagenomes from all over the world (global lakes, \(\mathrm{n} = 462\) ). The upper panel ("Diversity") is the proportion of genera that were represented by at least one strain of our culture collection. + +We modified the figure legend to make this more understandable: "c Proportion of genera from the culture collection relative to the total number of genera (diversity; upper panels) and their summed up relative abundances (abundance; lower panels) in the sampled lakes (original samples, \(n = 67\) ; left panels) and in 462 publicly available metagenomes from seven continents (global lakes, \(n = 462\) ; right panels). Metagenomic reads were taxonomy- assigned with SingleM, proportions of genera included in the culture collection are separately shown for different water layers (epi- and hypolimnion) and total. Boxes indicate the \(25^{\mathrm{th}}\) and \(75^{\mathrm{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\mathrm{th}}\) and \(95^{\mathrm{th}}\) quantiles, individual samples are displayed by open circles. Significant differences between epi- and hypolimnetic samples (t- tests) are indicated by asterisks (\\*\\*\\*: \(p < 0.001\) ). Raw data are provided in Supplementary Data 7 and 10, results of statistical test in Supplementary Data 4. " + +- Figure 2C bottom, does this graph include read recruitment to MAGs as described in the text (I think)? If so, I think this is really off-target. What you need to show is the same graph with your isolate genomes or ideally a comparison of your isolate genomes and the complete genome collection (isolate genomes plus MAGs). Making just one plot with isolate genomes and MAGs does not communicate the significance (abundance) of the isolate collection, which is what this paper is about. + +RESPONSE: Please see also our response to the comment above. Fig. 3c is based on taxonomic assignment of metagenomic reads via SingleM (genus level classification). SingleM provides the whole bacterial community composition present in each metagenome (here used to give the genus level community composition). We then determined how many of the identified genera are present in our culture collection (upper panel) and how abundant the isolated genera are in these samples (lower panel). + +- Line 228 +- beginning of the sentence needs fixing. + +RESPONSE: We changed the sentence to (L 217): "We selected 87 strains from our culture collection for whole-genome sequencing, including..." + +- Line 234 +- please cite a research paper (or proper review) instead of a Microbe article. You could use reference 97, for example. Also, please clarify in the text here what ANI and AAI levels were used to indicate novel species and genera +- presumably 95% and 65%? RESPONSE: Thank you for this suggestion. We removed the Microbe article and refer to Konstantinidis et al. 2017, ISMEJ instead (now reference 64). We also included the ANI and AAI cutoffs used in the text as follows (L 222-224): "GTDB classification and ANI and AAI comparisons (Supplementary Table S9-S10) indicated that the genomes represent 27 + +<--- Page Split ---> + +genera and 47 distinct species by using AAl cutoffs of \(65\%\) and ANI cutoffs of \(95\%\) , respectively." + +- Line 240 - Use of the SeqCode is fine but please consider depositing the strain whose genome is the nomenclatural types into a culture collection because this could be an important resource for the research community. Please confirm in a response to reviewers that the entries in the SeqCode Registry have been pre-approved by curators. RESPONSE: We plan to deposit some of the type strains in culture collections in the near future, however, this is not trivial as most strains are hard to maintain (no growth on agar plates, slow growth, low maximum cell yield [see Supplementary Figs. 4, 5] ruling out OD measurements). Meanwhile, we make strains available to the scientific community upon personal request by email. We amended the Data availability statement as follows: "Strains from the culture collection can be requested by email to Michaela M. Salcher (michaelasalcher@gmail.com)." We further confirm that the new taxa have been endorsed by the SeqCode curators, here are the confidential reviewer links: [redacted] + +[redacted] + +- Figure 3 legend – For the full figure, make sure you refer to cultures and MAGs. For panel A, make sure it’s clear in the figure legend that this is isolates only. For panel B, “gained” should be “assembled”. In B, it’s ok I guess but some parts of the figure are unreadable. There are too many categories for bootstrap values, genome size, and GC%. Categories should be lumped so there’s a chance to see something. That could be done for coverage too. I know it’s hard to deal with so much data. It’s up to you if you want to address this, but just a suggestion. + +RESPONSE: We thank the reviewer for these suggestions. We modified the figure legend (now Fig. 4) as follows: “Figure 4. Diversity and phylogeny of genome- sequenced cultures compared to metagenome- assembled genomes (MAGs) assembled from the same samples. a Number of genome- sequenced cultures with standing taxonomy and novel taxa on different phylogenetic levels (family, genus, species). b Phylogenomic tree of 120 single copy marker protein sequences of bacterial families containing cultures ( \(n = 87\) ), MAGs assembled from the same water samples ( \(n = 313\) ), and closely related published genomes ( \(n = 324\) ) from cultures (ref. culture), MAGs (ref. MAG), and SAGs (ref. SAG). Five genomes of Patescibacteria were used to root the tree. Clades are colored on a family level and genera containing cultures are marked in different colors and numbers (1: Leadbetterella; 2: Flavobacterium; 3: Fimbriicoccus gen. nov.; 4: Acidimicrobicalustris gen. nov.; 5: Mycobacterium; 6: Rhodoluna; 7: Planktophelia; 8: Verrucolacustris gen. nov.; 9: Fontibacterium; 10: Sphingobium; 11: Sphingorhabdus; 12: Rhabdaerophilum; 13: Aquidulcibacter; 14: Caulobacter; 15: Tabrizicola; 16: Allotabrizicola gen. nov.; 17: Novimethylotenera gen. nov.; 18: Methylotenera; 19: Methylopumilus; 20: Lacustribacter gen. nov.; 21: Hahnella gen. nov.; 22: Zwartia; 23: Hydrogenophaga; 24: Allorhodofexax + +<--- Page Split ---> + +gen. nov.; 25: Limnohabitans; 26: Perthalerella gen. nov.; 27: Polynucleobacter). Annotations of the rings from inside to outside: Genome source; genome size; genomic GC content; metagenomic fragment recruitment for 67 samples where cultures and MAGs were gained. The lakes are sorted from oligo- to eutrophic as in Fig. 3 and epi- and hypolimnetic samples are shown separately. See Supplementary Fig. 14 for a full tree with all 1,294 depreciated MAGs covering all families." + +- line 282 - 287 - more abundant than what? What does the text about "a significant distinction" mean? I can't understand it. Do you mean that larger genomes encoded [flagellar] motility and a larger number of different secretion systems? In the supplemental figures, it looks like you're referring to some genomes without ANY secretion system but as far as I know, all organisms have at least one secretion system, often either Sec or SecA2. If you're inferring that some genomes have no secretion system, that would be an extraordinary claim that would require extraordinary evidence. + +RESPONSE: We are sorry for this confusion and changed the text to make it clear that genome- streamlined microbes were more abundant than microbes with medium to large genomes. We also clarified that microbes with genes encoding motility (both flagellar motility and gliding motility) and secretion systems type II, IV, or VI were larger in genome size than those lacking these traits. All genomes contained genes encoding Sec and Tat secretion systems; we didn't specifically highlight this in the text, but this information can be found in Table S15. We changed the text to (L 256- 262): "Genome- streamlined bacteria were also clearly more abundant than microbes with larger genomes, both in the original water samples \((n = 67)\) and in freshwater metagenomes gained from six continents \((n = 250)\) . Further, microbes containing genes encoding motility and secretion systems type II, IV, or VI had significantly larger genome sizes (Supplementary Fig. 18, Supplementary Data 4, 18), except for two Zwartia strains with large genomes (3.6 and 4.5 Mbp) that lacked genes for flagella assembly and chemotaxis, congruent with previously described Zwartia strains67." We further added a sentence to the figure legend of Fig. 5 as follows: "Please note that general secretion systems Sec and Tat are not shown here as these were present in all strains." + +- Line 288-312 is a repetition of the two preceding paragraphs. + +RESPONSE: Thank you for identifying this mistake, it happened in the last round of revision before submission when we decided to shuffle some parts of the text. The duplicated paragraph has been deleted. + +- Line 314 - 315. First, not all rhodopsins are light-driven ion pumps that can make ion gradients (see channelrhodopsins and sensory rhodopsins). Please consider trying to distinguish these or qualify your statement. Second, I notice a lot of cyanobacteria isolates. Is this right? What about those? + +<--- Page Split ---> + +RESPONSE: We only searched for proton- pumping rhodopsins in this study and most taxa contained either actino- , proteo- or bacteriorhodopsins. We changed the text accordingly to (268- 270): "Most genome sequenced cultures can potentially utilize light as an energy source, either via proton- pumping rhodopsins \((n = 59)\) or by being anoxygenic aerobic phototrophs (AAPs, \(n = 15\) )." Regarding the second question, while we obtained many cyanobacterial strains, we did not genome- sequence them as this study focuses on heterotrophs. + +- Line 316 – not “energy generation” but energy conservation – please. First Law of Thermodynamics. + +RESPONSE: We are sorry for this rookie mistake; we changed the text accordingly. + +- Line 318 – not all RuBisCO homologs participate in the CBB cycle. Please clarify the type. RESPONSE: The five AAPs mentioned in the text contain RuBisCO type I, which is participating in the CBB cycle. Additionally, one strain (Tabrizicola rara LH-M10) contained RuBisCO type II, which is also participating in the CBB cycle and three strains contained RuBisCO-like proteins (RLP) type IV, which are not participating in CBB. We show only RuBisCO types I and II in Fig. 5. We added this information also in the text (L 273-275): “Interestingly, five AAPs additionally contained a carbon fixation pathway (Calvin cycle via RuBisCO type I), potentially leading to photoautotrophy that was so far only occasionally reported for sediment dwelling AAPs”72” + +- Line 321 – “organic carbon”. RESPONSE: Changed. + +- Line 322 – what about catalase? + +RESPONSE: We did not add catalase to the medium used for this experiment, only vitamins. + +- Line 324 – Is this significant? Can you run a t-test for the endpoint? + +RESPONSE: We ran a paired t-test for the endpoint; it was significantly different \((p = 0.0092\) , test results are given in Supplementary Data 4). We added this information in the text, it now reads (L 278-281): “While growth was observed in both dark and light:dark (12:12 h) conditions, L. simekii maintained significantly higher cell numbers during stationary phase in light:dark conditions \((p = 0.009175\) , Supplementary Data 4) hinting at photoautotrophic growth during starvation.” + +- line \(370 =\) ranks RESPONSE: Changed. + +- Line 406 – consider mentioning earlier in the main narrative that important tricks were used to increase cultivability, like catalase and pyruvate. I think these tricks aren’t well + +<--- Page Split ---> + +known enough and it would be good to emphasize that you were careful and thoughtful and to help educate the community. + +RESPONSE: We added this information in the last paragraph of the introduction (L 88- 92): "Here, we employed a high- throughput dilution- to- extinction approach with three defined artificial media containing either different carbohydrates, organic acids, catalase, vitamins, and other organic compounds in \(\mu M\) concentrations, mimicking carbon concentrations typically found in freshwater lakes (med2 and med3), or methanol, methylamine and vitamins (MM- med) as sole carbon sources (Supplementary Data 1)." We further included media components and preparation as Supplementary Data 1. + +- Line 419 – all additions after autoclaving were filter sterilized? Please explain. + +RESPONSE: Yes, we filtered all components through 0.1 \(\mu m\) filters, this information is now also mentioned in the methods as follows (L 368- 370): "After autoclaving, both media were amended with a filter-sterilized mix of the 20 proteinogenic amino acids (0.2 \(\mu M\) of each amino acid except for glutamate and glutamine which were added at 0.4 \(\mu M\) concentration), vitamins (0.593 \(\mu M\) thiamine, 0.08 \(\mu M\) niacin, 0.074 nM cobalamine, 0.005 \(\mu M\) para- amino benzoic acid, 0.074 \(\mu M\) pyridoxine, 0.081 \(\mu M\) pantothenic acid, 0.004 \(\mu M\) biotin, 0.004 \(\mu M\) folic acid, 0.555 \(\mu M\) myo- inositol), dipotassium phosphate (3.22 \(\mu M\) ) and catalase (10 U ml- 1)86." We further included media components and preparation as Supplementary Data 1. + +- Please check and confirm that the SeqCode Registry curators have provisionally accepted the proposed names and supporting data. + +RESPONSE: We confirm that the new taxa have been endorsed by the SeqCode curators (see above for confidential reviewer links) + +Additional comments on figures + +Figure 1. the label "med3 (n=60)" was odd as shown in the figure; mention the statistical tests used. + +RESPONSE: We updated the figure (now Fig. 2) as requested and mention the statistical tests (t- tests) in the figure legend. We further refer to Supplementary Data 4 for details on all statistical tests. + +Figure 2. The figure labels are overlapping. For Panel A, mention what the thicker and darker colors represent. For Panel C, add statistical test information. + +RESPONSE: We have reorganized this figure (now Fig. 3) to make it more appealing. For panel A, we specified that the thick lines are averages and the thin lines are maxima as follows: "a Rank- abundance curve (lower panel, averages are shown as thick lines, maxima as thin lines) and number of axenic cultures (upper panel) of abundant genera present in the sampled lakes (>1% of reads in at least one sample)." For panel C, we now included + +<--- Page Split ---> + +statistical test information as follows: c Proportion of genera from the culture collection relative to the total number of genera (diversity; upper panels) and their summed up relative abundances (abundance; lower panels) in the sampled lakes (original samples, \(n = 67\) ; left panels) and in 462 publicly available metagenomes from seven continents (global lakes, \(n = 462\) ; right panels). Metagenomic reads were taxonomy- assigned with SingleM, proportions of genera included in the culture collection are separately shown for different water layers (epi- and hypolimnion) and total. Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, individual samples are displayed by open circles. Significant differences between epi- and hypolimnetic samples (t- tests) are indicated by asterisks (\\*\\*: \(p < 0.001\) ). Raw data are provided in Supplementary Data 7 and 10, results of statistical tests in Supplementary Data 4. " + +Figure 3. The title "Diversity and phylogeny of genome- sequenced cultures" is not appropriate because the dataset also includes MAGs and other published genomes. RESPONSE: We changed the title of this figure (now Fig. 4) as follows: "Figure 4. Diversity and phylogeny of genome- sequenced cultures compared to metagenome- assembled genomes (MAGs) assembled from the same samples" + +## Supplementary figures + +- Figure 1: Please show two-letter codes for lakes here and in Table S1. + +RESPONSE: We added the two- letter codes also here and in the supplementary table (now Supplementary Data 2) + +- Figure 12 – define the parts of the boxes and whiskers. What is “Diversity”? Just to confirm – these are based on the culture genomes only and not the MAGs? + +RESPONSE: This figure is based on taxonomic assignment of metagenomic reads via SingleM (genus level classification) of water samples from all over the world (n=462). The upper panel (“Diversity”) is the proportion of genera that were represented by at least one strain of our culture collection. We modified the figure legend to make this more understandable: “Supplementary Figure 12. Contribution of cultures to the total number (diversity; upper panel) and summed up read counts (abundance, lower panel) of genera present in 462 freshwater metagenomic samples from seven different continents.” + +Very minor editorial suggestions + +Introduction + +Please check the citation formatting for the whole paper — there are extra spaces in some places. + +RESPONSE: We carefully checked all citations throughout the manuscript and supplementary text and removed all extra spaces. + +<--- Page Split ---> + +Line 38: When "however" connects two independent clauses (complete sentences), use a semicolon before it and a comma after it. + +RESPONSE: Changed. + +Line 38: miniscule \(\rightarrow\) minuscule RESPONSE: Changed. + +Line 46: nutrient rich \(\rightarrow\) nutrient- rich RESPONSE: Changed. + +Line 48: nutrient rich \(\rightarrow\) nutrient- rich RESPONSE: Changed. + +Line 69: the usage of \(\rightarrow\) the use of RESPONSE: Changed. + +Line 86: missed a comma before "mimicking" RESPONSE: Changed. + +Line 89: Spring, Autumn, Summer \(\rightarrow\) spring, autumn, summer RESPONSE: Changed. + +Results and Discussion + +What are the differences between Supplementary Table 1 and Data S1? + +RESPONSE: Supplementary Table S1 and Data S1 are the same, we apologize for this misnomer. We have now renamed all tables as Supplementary Data 1, 2, 3, etc. as per the formatting instructions of Nature Communications. + +Line 98: 96- deep- well- plates \(\rightarrow\) 96- deep- well plates RESPONSE: Changed. + +Line 98: remove extra space after "one cell per well". RESPONSE: Changed. + +Line 102: maintained further \(\rightarrow\) maintained thereafter RESPONSE: Changed. + +Line 109: contained \(\rightarrow\) contain RESPONSE: Changed. + +Line 113: failed in obtaining \(\rightarrow\) failed to obtain RESPONSE: Changed. + +Lines 117- 121: the sentence is clunky; better to restructure. RESPONSE: We have split this sentence in two (L124- 128): "The enrichment in a medium + +<--- Page Split ---> + +with methanol and methylamine as sole carbon sources resulted in an enhanced cultivation of methylotrophs (Methylopumulus, Methylotenera50,52). However, also other genera were able to grow in this C1 medium (e.g., Polynucleobacter, Limnohabitans) and might have survived by either being photoautotrophic, methylovorous, or by using catalase or vitamins as additional carbon sources." + +Line 127: use a multiplication sign \((\times)\) , not the letter "x". + +RESPONSE: Changed, also in lines 137, 140, 206, 210, 276, 357, 400, 402, 406- 407, 415, and throughout the Supplementary Text + +Line 131: write out the full name of NSY when it is first mentioned. + +RESPONSE: We wrote that NSY is a medium containing nutrient broth, soytone, and yeast extract in brackets. + +Line 161: as used for \(\Rightarrow\) used for RESPONSE: Changed. + +Line 163: affiliated to \(\Rightarrow\) affiliated with RESPONSE: Changed. + +Line 213: of our culture collection \(\Rightarrow\) from our culture collection RESPONSE: Changed. + +Line 228: our the culture collection \(\Rightarrow\) from our culture collection RESPONSE: Changed. + +Line 232: the remaining ones \(\Rightarrow\) the remaining genomes RESPONSE: Changed. + +Line 225: a global presence \(\Rightarrow\) their global distribution RESPONSE: Changed. + +Line 234: Only six genomes could be assigned RESPONSE: Changed. + +Line 290: how did you select the 324 genomes of the closest relatives from public databases? + +RESPONSE: We first looked for cultivated type strains in GTDB (gtdb.ecogenomics.org) by verbatim name matching of genus names assigned to genome- sequenced cultures (Advanced Search, match all of the following: "GTDB Type Material" IS "type strain of species" AND "GTDB Taxonomy" CONTAINS "genus taxonomy of genome- sequenced strain", e.g., g_Zwartia). We then added additional, not cultivated representative species in GTDB by verbatim name matching (Advanced Search, match all of the following: "GTDB + +<--- Page Split ---> + +Representative of Species" IS TRUE AND "GTDB Taxonomy" CONTAINS "genus taxonomy of genome- sequenced strain"). In the case of novel families that we described in this manuscript, we extended this search to additional, closely related families within the same order (e.g., Acidimicrobiates). This list was amended with additional genomes identified via literature research based on genus or family names. We added this information in the material and methods part as follows (L 492- 495): "Taxonomic classification was done with GTDB r220 as outlined above and the closest relatives of each culture genome ( \(n = 324\) ) were selected in GTDB by verbatim name matching of the assigned genus or family name and literature research and downloaded from NCBI." + +Line 293: Maybe you can highlight here that \(>83.9\%\) are novel/undescribed species. RESPONSE: We modified the sentence accordingly (L238- 240): Only seven MAGs could be assigned to a described species and another seven to Candidatus species (1.1% of the 1,294 MAGs), reiterating the high proportion of undescribed taxa in freshwater environments \(^{4,11}\) . + +Line 376: differ to \(\rightarrow\) differ from RESPONSE: Changed. + +Methods Line 544: as an outgroup RESPONSE: Changed. + +Line 547: specify the number of bootstrap replicates + +RESPONSE: We did 1000 ultrafast bootstrap replicates; this information is now included in the text (L 511). + +Reviewer #2 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +RESPONSE: Thank you very much for your review. We highly appreciate the Nature Communications initiative to facilitate training in peer review for Early Career Researchers. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +Salcher et al. present an innovative, high- throughput method to generate axenic cultures of aquatic prokaryotes. In doing so, they have addressed a major challenge in microbiology, i.e., "the great plate anomaly", that is the inability to cultivate a majority of microbial lineages. All the cultures presented here have been taxonomically annotated, and a subset had their genomes sequenced. The genome sequencing revealed diverse potential metabolisms, and as the cultures are now available, the genome- based predictions can be tested. Importantly, the cultured prokaryotes were among the most abundant in their environments, unlike many other, especially traditional cultivation techniques. Moreover, Salcher et al. used artificial media, which makes the cultures more transferable and easier to maintain as opposed to using autoclaved water. + +RESPONSE: Thank you very much for your overall positive and encouraging review comments. Please find a detailed response to your individual comments below. + +Major comment: + +As the authors correctly state in the Abstract, this study has resulted in a valuable collection of abundant freshwater microbes that holds significant potential as model systems for a wide array of studies. However, it is not stated how other researchers can get access to the isolates to perform such studies. This needs to be specified, otherwise this claim can hardly be made. + +RESPONSE: We thank the reviewer for this comment and apologize that we forgot to mention this information in the initial submission. All strains from our culture collection were cryopreserved and are available to other researchers by email request to the corresponding author (michaelasalcher@gmail.com). We have added this information to the Data availability statement as follows (L 532- 533): "Strains from the culture collection can be requested by email to Michaela M. Salcher (michaelasalcher@gmail.com)." + +Minor comments / suggested improvements: + +The detailed metabolic- capability map (Fig.4) for the 87 genome- sequenced strains could be combined with information on growth on the six media used in the study. The use of different media is a psychological experiment. Particularly, a medium with methanol and methylamine (MM- med) was used, and the potential for methylotrophy was analyzed based on the genomes. Comparing the growth on the medium and the genome- inferred + +<--- Page Split ---> + +metabolic potential would be a major addition both to the analysis of the inferred metabolism and to showcasing the potential of the cultivation approach presented here. RESPONSE: We did not use the MM- med in growth assays with known methylotrophs such as \*Methylopumilus\*, as this was already done in earlier studies (Salcher et al. 2015 ISMEJ, Layoun et al. 2024, ISMEJ). As for the other media used in the growth assays, it is not straightforward to match the carbon sources to growth patterns. For example, med2 and med3 are very similar in C composition, med3 additionally contains glycolate, polyamines and two carbohydrates compared to med2. We checked for the presence of glycolate oxidation in the genomes, but there was no obvious pattern connected to growth in med3, i.e., six strains grew better in med3 than in med2, but only two of them (\*Polynucleobacter hoetzingerianus\* RE- M21 and \*Allorhodofexax lacus\* MsE- M18) contained pathways for glycolate oxidation, while the others (\*Acidimicrobiloacustris europeus\* KE- 4, \*Planktophila versatilis\* MsE- 18, \*Fimbriicoccus planktonicus\* MsE- 15, \*Flavobacterium rarum\* TH- M1) did not. The same holds true for polyamines, only four of the strains that grew better in med3 contained membrane transporters for spermidine or putrescine (A. europeus KE- 4, P. versatilis MsE- 18, A. lacus MsE- M18, F. rarum TH- M1). We tried different versions of how to integrate the different media in this figure (Fig. 5), but none of them looked compelling, therefore we decided to keep it as is. + +The genomic comparison on page 10 and 11 is very informative and concise. An additional genomic feature interesting to compare would be CRISPRs. CRISPRs are known to be underrepresented in streamlined vs. non- streamlined genomes (for biological reasons) as well as in MAGs vs. isolates (for technical reasons), so comparing contents of CRISPR (eg proportion of genomes were CRISPRs are found) between your oligotrophic and copiotrophic isolates, as well as between your isolates and their closest MAG relatives (in cases were close MAG relatives exist) would be interesting. The latter comparison could also involve the number of CRISPR spacers found, since assembling MAGs may only recover the more conserved parts of the CRISPR within a population, as opposed to when assembling an isolate genome. + +RESPONSE: We thank the reviewer for this great suggestion. We predicted CRISPR- Cas systems in our culture collection, MAGs and reference genomes and found that only 5 strains (5% of the culture collection) with medium- large genome sizes contained this phage- defense system. In contrast, \(\sim 20\%\) of the reference genomes obtained from cultures and \(\sim 13\%\) of our MAGs contained CRISPR- Cas repeats. Further, as could be expected, there was a clear relationship between genome size and CRISPR system (with larger genomes being more likely to have CRISPR). We have made an additional Supplementary Figure (Suppl. Fig. 19, see below) and table (Supplementary Data 19) and included the following text in the manuscript (L 262- 267): "The phage- defense system CRISPR- Cas68,69 was present in only 5 strains with medium- large genome sizes (2.6- 5 Mbp, Supplementary Fig. 19, Supplementary Data 19). In contrast, 20.8% of the reference genomes obtained from cultures and 13.9% of MAGs contained on average 1.7 CRISPR + +<--- Page Split ---> + +arrays per genome. There was a clear relationship to genome size, as microbes containing CRISPR- Cas systems were significantly larger than those without \((p = 7.524E - 47\) , Supplementary Data 4).” + +![PLACEHOLDER_22_0] + + +Supplementary Figure 19. Occurrence of CRISPR- Cas arrays in cultures, MAGs and closely related cultivates references. a The same phylogenomic tree as in Fig. 4 including the number of CRISPR- Cas arrays per genome. b Number of genomes with CRISPR- Cas arrays and number of CRISPR- Cas arrays per genome separately shown for cultures, + +<--- Page Split ---> + +reference cultures, and MAGs or c different genome size classes. d Genome sizes of microbes with or without CRISPR- Cas arrays. \(***p < 0.0001\) for significant differences in genome sizes (t- test), results of statistical tests can be found in Supplementary Data 4. + +Putting supplementary figure S2 (and potentially also S1) in the main is worth consideration, since there is space for extra display items. Fig. S2 visualizes the workflow, which is the key new development presented in the paper. This is a fully suggestive comment, and it is ultimately up to the authors how they want to present their work. RESPONSE: We thank the reviewer for this valuable suggestion. We have now included Fig. S2 as a new main figure (new Fig. 1). + +Line 81: I find it very difficult to understand that phenotypic traits sometimes can be "not at all encoded in the genome". Of course, if, for example, there is a phage infection, the phenotype may differ from a non- infected population. But also propensity for infection by a specific phage is encoded in the genome. So please specify how you mean this might work. RESPONSE: Here, we argue that some traits can be very hard to infer from genomes without having cultures (e.g., cell size, temperature, pH, salinity, or substrate ranges and optima). We expanded this part as follows (L780- 85): "However, genomes alone are not sufficient to characterize the ecology of microbial taxa, as many phenotypic traits (e.g., cell size, temperature, pH, salinity, or substrate ranges and optima) are hard to identify or not at all encoded in the genome39. Further, cultures are a prerequisite to discover and characterize biochemical pathways25,40,41, cell ultrastructure42,43, growth requirements17,29, and microbial interactions15,44 and are the basis for genetic manipulations45,46." + +Line 89: It is unclear which year the spring and autumn samples come from (this is specified in the methods section and just requires a reformulation in the introduction for clarity). + +RESPONSE: The spring and autumn samples were also obtained in 2019. We have now included this information in the text (L 92- 94) as follows: "We sampled 14 lakes in Central Europe during spring and autumn 2019, and four lakes additionally in summer 2019 (Supplementary Fig. 1, Supplementary Data 2). + +Line 122: "Most cultures showed stable growth for more than one year" - the information on which/how many cultures showed stable growth for more than one year is not in the figures. If the details of long- term survival and growth are in a supplementary table, they should be referred to. Otherwise, at least provide the percentage or number of stable long- term cultures (or which cultures were unstable and/or hard to maintain). + +RESPONSE: We have included the information about unstable cultures in the beginning of the results section (L103- 106: "Screening resulted in 1,201 initial cultures, whereof 229 were identified as mixed by Sanger sequencing of 16S rRNA gene amplicons and 344 cultures showed no growth after several transfers and were discarded (Supplementary Fig. + +<--- Page Split ---> + +2, Supplementary Data 3)."), in Supplementary Fig. 2 and in a Supplementary table (Supplementary Data 3, row labeled as "# cultures with no growth after 3- 4 propagations"). However, it is very hard to reconstruct the exact time when we stopped propagating individual cultures, as we discontinued many strains from taxa for which we isolated multiple representatives after taxonomy assignment by 16S rRNA sequencing. This process took quite a long time (\~1 year) because of severe restrictions in lab work during COVID19 lockdowns, which was also a reason why we kept only a reduced number of strains in this period. Selected strains were kept until we obtained their genomes (>1 year). However, multiple strains are being maintained till today (e.g., the Fontibacterium and Planktophila strains) while some others have been revived several times from glycerol- stocks (e.g. for the growth assays). + +Line 138: Please give the carbon source as concentration in the medium rather than as a mass. + +RESPONSE: We have reformulated this sentence to (L 147- 150): "Copiotrophic strains grew to highest densities in the medium with highest nutrient content (1:10 diluted NSY containing 0.3 g complex carbon sources per liter), and several of these genera have been previously isolated by the filtration acclimatization method using NSY53." We further added an additional table (Supplementary Data 1) with details on all media used for isolation and for growth assays. + +Lines 147- 156 (Fig. 3): The test used to obtain significance values is unspecified. + +RESPONSE: We used t- tests to test for significant differences; this is now included in the figure legend. We further added all results of statistical test to a Supplementary Table (Supplementary Data 4). + +Line 166: It's odd to provide the lower range of the p- values (">"), maybe the authors meant to write "<"? + +RESPONSE: We thank the reviewers for finding this typo, it is changed to "<" now. + +Lines 177- 178: It would be relevant here to write how many of the 30 genera (if any) overlap with the 48 previously cultivated genera mentioned on lines 174- 175. + +RESPONSE: We have added this information to the text and also in Supplementary Data 7 as follows (L179- 180): "Only 16 of the 30 abundant genera of our culture collection have been validly described to date3." + +Line 189: Although I see what you mean, I guess the culture collection hasn't actually made a "contribution" to the diversity and abundance of taxa in the lakes. Consider rephrasing. + +RESPONSE: We rephrased the legend accordingly to: "Figure 3. Representation of the culture collection in lake samples. a Rank- abundance curve (lower panel, averages are + +<--- Page Split ---> + +shown as thick lines, maxima as thin lines) and number of axenic cultures (upper panel) of abundant genera present in the sampled lakes ( \(>1\%\) of reads in at least one sample). Metagenomic reads were taxonomy- assigned with SingleM. Asterisks below cultures indicate that at least one member of the genus was genome- sequenced. See Supplementary Fig. 11 and Supplementary Data 7 for all genera including rare taxa. b Summed up relative abundances of taxa with representatives in the culture collection in the epi- and hypolimnion of the sampled lakes. Samples are sorted from oligo- to eutrophic, abbreviations of lakes and sampling seasons are as in Supplementary Fig. 1. c Proportion of genera from the culture collection relative to the total number of genera (diversity; upper panels) and their summed up relative abundances (abundance; lower panels) in the sampled lakes (original samples, \(n = 67\) ; left panels) and in 462 publicly available metagenomes from seven continents (global lakes, \(n = 462\) ; right panels). Metagenomic reads were taxonomy- assigned with SingleM, proportions of genera included in the culture collection are separately shown for different water layers (epi- and hypolimnion) and total. Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, individual samples are displayed by open circles. Significant differences between epi- and hypolimnetic samples (t- tests) are indicated by asterisks (\\*\\*\\*: \(p < 0.001\) ). Raw data can be found as Supplementary Data 7 and 10, results of statistical test as Supplementary Data 4. " + +Figure 2. Panel B includes so many taxa with similar colors that it is impossible to identify many taxa in the barplots. Consider only coloring a subset of the taxa with highest abundances. + +RESPONSE: We agree that we used too many different colors in this figure. We summed up several taxa (e.g., Aquiluna & Rhodoluna, UBA2463 & UBA954, Limnohabitans & Limnohabitans_A,...) to make the figure less crowded. Please note that we have modified this figure (now Fig. 3) also based on suggestions by reviewer #1. + +Line 218: I suggest you write "up to \(117 \times\) coverage per Gb mapped data" for clarity. RESPONSE: Changed as suggested. + +Line 228: "Eighty- seven strains our the culture collection" - this sentence is agrammatical and thus hard to read. Should it be "in our" rather than "our the"? RESPONSE: Thank you for finding this mistake. We changed it to "We selected 87 strains from our culture collection for whole- genome sequencing" (L 217) + +Lines 236- 237: What does "described species" mean here? Is it the species described according to the standards of ICNP, or, e.g., present in GTDB? Convention suggests the first option, but it would be beneficial to specify. The same applies to "undescribed genera" in line 237. + +RESPONSE: We have modified the text to make the distinction between validly described and novel taxa. The text reads now as follows (L224- 228): "Only one genome could be + +<--- Page Split ---> + +assigned to a validly described species (Sphingobium curpiorestens \(^{65}\) ) and five more were previously proposed as \*Candidatus\* species by us \(^{24,52}\) (Supplementary Fig. 17). Moreover, genome- sequenced cultures contained nine novel genera and two novel families (Fig. 4a; Supplementary Data 11)." + +Lines 265- 266: Is Data S11/S12 the same as Supplementary Table S11/S12? If yes, the cross- references should be consistent throughout the paper. RESPONSE: Supplementary Table S11/S12 and Data S11/S12 are the same, we apologize for this misnomer. We have now unified the naming of all Supplementary tables to Supplementary Data 1- 21 as per the formatting instructions of Nature Communications. + +Lines 268- 271: "In all but four cases" - do you mean "For all but four of the eighty- seven genomes"? And what does "closely related" MAG (95% ANI?) + +RESPONSE: We calculated ANI values between our genome- sequenced strains and both the closest MAG and publicly available genome- sequenced culture. We have reanalyzed the data and have now included an additional figure that illustrates that the vast majority of our strains is closer related to environmental MAGs than to cultures (Suppl. Fig. 17, see also below). Moreover, by taking 95% ANI as species cutoff, we show that only one of our strains has a cultivated relative that is validly described and available in a strain collection (Sphingobium curpiorestens CCTCC AB 2011146), while another culture genome (Limnohabitans sp. B9- 3) was not validly described and five more \*Candidatus\* species were previously proposed by us (3 \*Methylopumilus\* species: Salcher et al. 2015 ISMEJ, Salcher et al. 2019 ISMEJ, 2 \*Planktophila\* species: Neuenschwander et al. 2018 ISMEJ). We rephrased this sentence to (L240- 244): "In the majority of cases, strains from our culture collection were phylogenetically closer to MAGs than to previously cultured species, and only one, \*Sphingobium curpiorestens\*, is validly described and available in a culture collection \(^{65}\) (Fig. 4b, Supplementary Figs. 14, 17), exemplifying that the genome- sequenced cultures were indeed novel and highly relevant." + +<--- Page Split ---> +![PLACEHOLDER_27_0] + +
Strains from culture collection next relative MAG next relative culture (described) next relative culture (not described) next relative culture (previously proposed as Candidatus by us)
+ +# Strain code: + +1 Acidimicrobicustrichus thunensis TE- 4 30 Sphingorhabdus communis GE- 11 59 Methylopulinus planktonicus MoH-M8 2 Acidimicrobicustrichus thunensis TE- 7 31 Sphingorhabdus communis ZE- 10 60 Methylopulinus planktonicus MsH-M18 3 Acidimicrobicustrichus europaeus KE- 4 32 Hydrogenophaga miladensis MiE- M28 61 Methylopulinus planktonicus MsH-M39 4 Rhodoluna miladensis MiE- 23b 33 Limnohabitans simeeki MiE- M12 62 Methylopulinus planktonicus MsH-M42 5 Rhodoluna miladensis MiE- 24b 34 Limnohabitans rimovensis RE- 1 63 Methylopulinus planktonicus TH-M4 6 Mycobacterium aquicola MaE- M6b 35 Limnohabitans kasalickyi MaE- M4 64 Methylopulinus planktonicus ZE- M7 7 Mycobacterium aquicola MiE- 22 36 Polynucleobacter hoezingerianus RE- M21 65 Methylopulinus planktonicus ZE- M8 8 Planktophila dulcis MaH- 2 37 Pernthalerella aquatica GE- M3 66 Methylopulinus rimovensis RE- M17 9 Planktophila dulcis MsH- 2 38 Pernthalerella lacunae MaE- M21 67 Methylopulinus rimovensis RE- M20 10 Planktophila dulcis TrE- 23 39 Pernthalerella communis MsE- 6 68 Methylopulinus rimovensis RE- M24 11 Planktophila grossartii RE- 3 40 Polynucleobacter hahni ZE- 4 69 Methylopulinus universalis GE- M14 12 Planktophila grossartii RH- 3 41 Allorhodofexar lacustis MiE- M13 70 Methylopulinus universalis GH- M24 13 Planktophila turicensis ZE- 9 42 Allorhodofexar lacus MsE- M18 71 Methylopulinus universalis GH- M4 14 Planktophila warnecki RE- 8 43 Allorhodofexar aquaticus MsE- M22 72 Methylopulinus universalis LE- M21 15 Planktophila versatilis MsE- 18 44 Allorhodofexar lacus MsH- M24 73 Methylopulinus universalis MaE- M17 16 Fimbriicoccus planktonicus MsE- 15 45 Allorhodofexar lacus ZE- M1 74 Methylopulinus universalis MH- M4 17 Leadbetterella lacustris RE- 19 46 Hahnella aquatica MiE- 11 75 Methylopulinus universalis MH- M5 18 Flavobacterium ruam TH- M1 47 Hahnella lacustris MsE- M47 76 Methylopulinus universalis MiE- M1 19 Flavobacterium neuenschwanderi GE- 10 48 Lacustribacter communis MsE- M52 77 Methylopulinus universalis RE- M9 20 Caulobacter lacus MiH- 16 49 Zwartia planktonica RE- 10 78 Methylopulinus universalis RH- M37 21 Aquidulcibacter rimovensis RH- 10 50 Zwartia lucis GE- 14 79 Methylopulinus universalis ZE- M6 22 Aquidulcibacter miladensis MiH- 15 51 Methylopulinus planktonicus KE- 4b 80 Methylopulinus universalis ZIE- M21 23 Fontibacterium abundans MiE- 29 52 Methylopulinus planktonicus LE- M7 81 Methylotenera profunda RE- M3 24 Fontibacterium medardense ME- 17 53 Methylopulinus planktonicus MaE- M16 82 Methylotenera profunda RH- M32 25 Rhodobacterophilum aquaticum MsE- M23 54 Methylopulinus planktonicus MaE- M22 83 Methylotenera hypolimnetica RH- M31 26 Tabrizicola rara LH- M10 55 Methylopulinus planktonicus MoH- M15 84 Methylotenera hypolimnetica ZIE- M10 27 Allotabrizicola aquatica RE- M30 56 Methylopulinus planktonicus MoH- M17 85 Nonimethylotenera aquatica ME- M6 28 Sphingobium cupriresistens MiE- 4 57 Methylopulinus planktonicus MoH- M19 86 Nonimethylotenera aquatica MsE- M29 29 Sphingorhabdus rara RE- M21a 58 Methylopulinus planktonicus MoH- M36 87 Verrucolacustris abundans MiH- 22 + +Supplementary Fig. 17: Average nucleotide identities (ANI) between strains from our culture collection and MAGs and previously cultivated species. The species border (95% ANI) is indicated with a solid line. Raw data is given in Supplementary Data 14. + +Line 270: Shouldn't it be "Fig. 3B" here? RESPONSE: This was indeed a typo, thank you for identifying it (now Fig. 4b). + +Line 280: Couldn't more TAA and less TGA/TAG simply reflect the general tendency of streamlined genomes to have lower GC- content? + +<--- Page Split ---> + +RESPONSE: This is certainly true, we have modified the text accordingly to (L 253- 256): "Genome- streamlined strains tended to use a different stop codon (TAA) indicative of nitrogen limitation \(^{52}\) , which is also reflected in a low GC content, and contained more membrane transporters (normalized per Mbp genome size) than strains with medium to large genomes. + +Line 284: "significance distinction" could be reformulated to stress in what way these genomes were distinct (generally smaller/larger). + +We are sorry for this confusion and changed the text to clarify that that microbes with genes encoding motility (both flagellar motility and gliding motility) and secretion systems type II, IV, or VI were larger in genome size than those lacking these traits. We changed the text to (L 258- 262): "Further, microbes containing genes encoding motility and secretion systems type II, IV, or VI had significantly larger genome sizes (Supplementary Fig. 18, Supplementary Data 4, 18), except for two Zwartia strains with large genomes (3.6 and 4.5 Mbp) that lacked genes for flagella assembly and chemotaxis, congruent with previously described Zwartia strains \(^{67}\) ." + +Lines 288- 312: These two paragraphs are repeated. (I.e., these lines are almost exactly the same as lines 263- 287; the only difference between the two versions is the figures and supplementary material). + +RESPONSE: Thank you for identifying this mistake, it happened in the last round of revision before submission when we decided to shuffle some parts of the text. The duplicated paragraph has been deleted. + +Line 360: Should be "Fig. 4" + +RESPONSE: Thank you for finding also this typo, we changed it accordingly (now Fig. 5). + +Line 395: Was hypolimnion defined as deeper than 5m? + +RESPONSE: The hypolimnion was defined based on thermal stratification (or - in the case of unstratified spring samples - based on previous data for the sampled lakes). We also took care not to sample anoxic water layers. + +Line 438: Since viability is a crucial statistic for the paper, it would be preferable to reiterate the formula in this study. + +RESPONSE: We included the formula in the methods as suggested (L 391- 394): "Isolation success expressed as Viability \((V)\) , i.e., probability that a cell selected at random is viable was calculated based on the formula by Button et al. \(^{49}\) as follows: + +\[V = \frac{\ln(1 - p)}{X}\] + +<--- Page Split ---> + +Where \(p\) is the number of wells or cultivation tubes, \(n\) , with growth \(z\) \((p = z / n)\) and \(X\) is the estimated number of cells inoculated per well." + +Reviewer #4 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +RESPONSE: Thank you very much for your review. We highly appreciate the Nature Communications initiative to facilitate training in peer review for Early Career Researchers. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Thanks for your thoughtful responses to my suggestions and congratulations on a very nice study. I will endorse acceptance for publication, but if possible consider changing "72 distinct genus or lineage- like taxa" to something like "72 distinct genera or unnamed SILVA lineages". + +- Brian Hedlund + +RESPONSE: Thank you very much for your supportive review with helpful comments that largely improve our manuscript. We changed "72 distinct genus or lineage- like taxa" to "72 distinct genera or alphanumerical SILVA lineages" (Line 113). + +Reviewer #3 (Remarks to the Author): + +The comments raised by us have all been well addressed in the revised version of the manuscript. + +RESPONSE: Thank you very much for your review. Your previous comments helped to improve our manuscript. + +Reviewer #4 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +RESPONSE: Thank you very much for your review. We highly appreciate the Nature Communications initiative to facilitate training in peer review for Early Career Researchers. + +<--- Page Split ---> diff --git a/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..06a94c2a112e78d5f739f4457026d217995cdba6 --- /dev/null +++ b/peer_reviews/78a8c21cdd9791d7482014494bf7a0733160407703519a18164d78699f714667/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1023 @@ +<|ref|>title<|/ref|><|det|>[[73, 161, 872, 210]]<|/det|> +# Bringing the uncultivated microbial majority of freshwater ecosystems into culture + +<|ref|>text<|/ref|><|det|>[[73, 224, 448, 241]]<|/det|> +Corresponding Author: Dr Michaela Salcher + +<|ref|>text<|/ref|><|det|>[[73, 246, 905, 290]]<|/det|> +Editorial Note: Parts of this peer review file have been redacted as indicated to maintain the confidentiality of unpublished data. This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 325, 144, 339]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 352, 220, 366]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 378, 160, 392]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 404, 238, 417]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 417, 914, 498]]<|/det|> +The paper by Salcher and colleagues describes a large effort to leverage dilution- to- extinction with defined media to isolate abundant prokaryotes in the epilimnia and metalimnia of lakes across central Europe, resulting in 627 pure cultures. The paper also sequences paired metagenomes and compares a metagenome- assembled genome (MAG) set to the isolate collection and compares the isolate and MAG collection to a large number of metagenomes from lakes worldwide. The paper shows that the isolate collection represents many of the most abundant and prevalent genera in lakes and includes two previously undescribed families and nine undescribed genera. Those novel taxa are named under the SeqCode. + +<|ref|>text<|/ref|><|det|>[[72, 509, 904, 589]]<|/det|> +The paper tackles an important problem in microbiology at a large scale and generally delivers on the goal to isolate abundant and novel organisms. Some specific strengths are: large scale; paired isolate collection and metagenomes; analysis of growth rate and oligo/copiotrophy, high- quality of the isolate genomes; isolation of some interesting microorganisms including the first non- methanotrophic member of the Methylacidiphilales and some other difficult groups like Armatimonadota. I do have some critical comments for the authors' consideration. None of this is major, but I hope the authors take the comments seriously if they have a chance to resubmit. + +<|ref|>text<|/ref|><|det|>[[70, 612, 910, 936]]<|/det|> +- In the title, please be aware that many scientists don't like the term "microbial dark matter". Also, I personally use the term only for higher ranks without cultured representatives (e.g., phyla, classes). But I'll leave the decision up to you. +- Line 18: evogonomic is not a standard word and is not a widely used term. Consider using evolutionary genomic. Also, please consider describing the importance of pure cultures more coherently. All scientist value pure samples (minerals, elements, spectra, etc.). It's easy to understand pure samples. Think of Koch's postulates for example. +- In the introduction, the discussion of auxotrophies and dependencies is a little off-target because this paper does not provide a solution to metabolic dependencies. The cells are diluted from the fresh samples into defined media with simple carbon sources and vitamins and other resources. Co-cultures are ignored, so this would prevent the study from growing microbes with metabolic dependencies (other than those supported by added media ingredients). Instead, I think the approach is very good at targeting slow-growing oligotrophs that can be outcompeted by copiotrophs during enrichment, which is not explicitly mentioned. +- Line 80, I suggest adding some text about novel biochemical pathways, cell ultrastructure, and other features here. The listed features are at least partly predictable from genomes (e.g., temperature optimum) and relatively boring. The paper would be improved by more creativity here. +- Line 108, what does "lineage-like taxa" mean? +- Line 124, how were the isolates divided into the three categories (oligotrophs, mesotrophs, copiotrophs)? Do the isolates form a continuum that was arbitrarily divided into thirds? Or were these discrete categories that were formed by a clustering method? +- Line 126, Fimbriicoccus appears to be a new genus that is first described here. For all such new taxa, please clearly communicate this the first time the new names are mentioned. +- Line 131, there is a poor transition here from discussing oligotrophs to copiotrophs. A separate paragraph with topic sentence would help. +- Line 139, what is NSY? +- Figure 1 A and B, please define all elements of the box and whisker plots and give precise p-values (per Nature guidelines). Do this throughout the paper. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 90]]<|/det|> +- Figure 1 B top, I don't understand what is plotted here. The labels refer to media but the legend refers to experiments with 18 different strains. So, was each strain only tested on one medium? There are only 18 data points (means presumably?) shown. Explain. Per Nature guidelines, show all data points and define all items on the graphs explicitly. + +<|ref|>text<|/ref|><|det|>[[72, 88, 920, 115]]<|/det|> +- Line 166 "significantly similar results" is awkward but more importantly what statistical analysis is this referring to? I think you would report just a percent of strains with the same phylum assignment? I was confused about the methods here. + +<|ref|>text<|/ref|><|det|>[[72, 113, 921, 153]]<|/det|> +- Line 170 and elsewhere (e.g., line 186, line 205), here you refer to genera as "taxa". Please try to be precise throughout the paper. In some cases, taxa is fine because a list transcends ranks, but please refer to genera or phyla or other specific ranks where possible. + +<|ref|>text<|/ref|><|det|>[[72, 152, 916, 193]]<|/det|> +- Line 175, here you refer to species not listed in LPSN as not "cultivated before" but it's really better to be precise. Most probably have been cultivated in some way but this number refers to species names that have not been validated under the ICSP (and presumably there are no pure cultures or stable co-cultures). + +<|ref|>text<|/ref|><|det|>[[72, 191, 916, 286]]<|/det|> +- Line 187 and elsewhere, the results are great but there's still a big cultivation bias toward Pseudomonas, which is displayed nicely in Figure S7 B and C. I suggest you point this out clearly. For example, you could mention how many of these abundant genera axenic cultures are from Pseudomonas and how many are from other phyla. I don't want to diminish the success of your work but just to communicate clearly that there's still a strong bias here and still a big problem with cultivation. Overall, as mentioned earlier, I think your study is very good for isolating oligotrophs that are outgrown in enrichment cultures or grow poorly on plates but it is poor at growing microbes with metabolic dependencies. It's ok, but it's good to be clear about the strengths of the study and where the study isn't so great (i.e., future directions). + +<|ref|>text<|/ref|><|det|>[[72, 284, 920, 352]]<|/det|> +- Figure 2C top, what is "Diversity" here? I can't understand what this is given the two y-axis labels, figure legend, and text. +- Figure 2C bottom, does this graph include read recruitment to MAGs as described in the text (I think)? If so, I think this is really off-target. What you need to show is the same graph with your isolate genomes or ideally a comparison of your isolate genomes and the complete genome collection (isolate genomes plus MAGs). Making just one plot with isolate genomes and MAGs does not communicate the significance (abundance) of the isolate collection, which is what this paper is about. + +<|ref|>text<|/ref|><|det|>[[72, 350, 430, 363]]<|/det|> +- Line 228 - beginning of the sentence needs fixing. + +<|ref|>text<|/ref|><|det|>[[72, 362, 900, 401]]<|/det|> +- Line 234 - please cite a research paper (or proper review) instead of a Microbe article. You could use reference 97, for example. Also, please clarify in the text here what ANI and AAI levels were used to indicate novel species and genera - presumably 95% and 65%? + +<|ref|>text<|/ref|><|det|>[[72, 400, 916, 440]]<|/det|> +- Line 240 - Use of the SeqCode is fine but please consider depositing the strain whose genome is the nomenclatural types into a culture collection because this could be an important resource for the research community. Please confirm in a response to reviewers that the entries in the SeqCode Registry have been pre-approved by curators. + +<|ref|>text<|/ref|><|det|>[[72, 438, 923, 505]]<|/det|> +- Figure 3 legend - For the full figure, make sure you refer to cultures and MAGs. For panel A, make sure it's clear in the figure legend that this is isolates only. For panel B, "gained" should be "assembled". In B, it's ok I guess but some parts of the figure are unreadable. There are too many categories for bootstrap values, genome size, and GC%. Categories should be lumped so there's a chance to see something. That could be done for coverage too. I know it's hard to deal with so much data. It's up to you if you want to address this, but just a suggestion. + +<|ref|>text<|/ref|><|det|>[[72, 503, 914, 569]]<|/det|> +- Line 282 - 287 - more abundant than what? What does the text about "a significant distinction" mean? I can't understand it. Do you mean that larger genomes encoded [flagellar] motility and a larger number of different secretion systems? In the supplemental figures, it looks like you're referring to some genomes without ANY secretion system but as far as I know, all organisms have at least one secretion system, often either Sec or SecA2. If you're inferring that some genomes have no secretion system, that would be an extraordinary claim that would require extraordinary evidence. + +<|ref|>text<|/ref|><|det|>[[72, 567, 491, 580]]<|/det|> +- Line 288-312 is a repetition of the two preceding paragraphs. + +<|ref|>text<|/ref|><|det|>[[72, 580, 900, 620]]<|/det|> +- Line 314 - 315. First, not all rhodopsins are light-driven ion pumps that can make ion gradients (see channelrhodopsins and sensory rhodopsins). Please consider trying to distinguish these or qualify your statement. Second, I notice a lot of cyanobacteria isolates. Is this right? What about those? + +<|ref|>text<|/ref|><|det|>[[72, 619, 765, 633]]<|/det|> +- Line 316 - not "energy generation" but energy conservation - please. First Law of Thermodynamics. + +<|ref|>text<|/ref|><|det|>[[72, 632, 652, 646]]<|/det|> +- Line 318 - not all RuBisCO homologs participate in the CBB cycle. Please clarify the type. + +<|ref|>text<|/ref|><|det|>[[72, 645, 290, 658]]<|/det|> +- Line 321 - "organic carbon". + +<|ref|>text<|/ref|><|det|>[[72, 658, 310, 671]]<|/det|> +- Line 322 - what about catalase? + +<|ref|>text<|/ref|><|det|>[[72, 671, 538, 685]]<|/det|> +- Line 324 - Is this significant? Can you run a t-test for the endpoint? + +<|ref|>text<|/ref|><|det|>[[72, 685, 193, 697]]<|/det|> +- line 370 = ranks + +<|ref|>text<|/ref|><|det|>[[72, 697, 896, 737]]<|/det|> +- Line 406 - consider mentioning earlier in the main narrative that important tricks were used to increase cultivability, like catalase and pyruvate. I think these tricks aren't well known enough and it would be good to emphasize that you were careful and thoughtful and to help educate the community. + +<|ref|>text<|/ref|><|det|>[[72, 736, 616, 750]]<|/det|> +- Line 419 - all additions after autoclaving were filter sterilized? Please explain. + +<|ref|>text<|/ref|><|det|>[[72, 749, 877, 777]]<|/det|> +- Please check and confirm that the SeqCode Registry curators have provisionally accepted the proposed names and supporting data. + +<|ref|>text<|/ref|><|det|>[[72, 790, 290, 802]]<|/det|> +Additional comments on figures + +<|ref|>text<|/ref|><|det|>[[72, 802, 750, 816]]<|/det|> +Figure 1. the label "med3 (n=60)" was odd as shown in the figure; mention the statistical tests used. + +<|ref|>text<|/ref|><|det|>[[72, 815, 916, 842]]<|/det|> +Figure 2. The figure labels are overlapping. For Panel A, mention what the thicker and darker colors represent. For Panel C, add statistical test information. + +<|ref|>text<|/ref|><|det|>[[72, 841, 888, 868]]<|/det|> +Figure 3. The title "Diversity and phylogeny of genome- sequenced cultures" is not appropriate because the dataset also includes MAGs and other published genomes. + +<|ref|>text<|/ref|><|det|>[[72, 894, 230, 907]]<|/det|> +Supplementary figures + +<|ref|>text<|/ref|><|det|>[[72, 907, 562, 920]]<|/det|> +- Figure 1: Please show two-letter codes for lakes here and in Table S1. + +<|ref|>text<|/ref|><|det|>[[72, 920, 920, 946]]<|/det|> +- Figure 12 - define the parts of the boxes and whiskers. What is "Diversity"? Just to confirm - these are based on the culture genomes only and not the MAGs? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 85, 296, 99]]<|/det|> +Very minor editorial suggestions + +<|ref|>text<|/ref|><|det|>[[72, 100, 156, 111]]<|/det|> +Introduction + +<|ref|>text<|/ref|><|det|>[[72, 112, 741, 125]]<|/det|> +Please check the citation formatting for the whole paper - there are extra spaces in some places. + +<|ref|>text<|/ref|><|det|>[[72, 125, 920, 152]]<|/det|> +Line 38: When "however" connects two independent clauses (complete sentences), use a semicolon before it and a comma after it. + +<|ref|>text<|/ref|><|det|>[[72, 153, 290, 165]]<|/det|> +Line 38: miniscule \(\rightarrow\) minuscule + +<|ref|>text<|/ref|><|det|>[[72, 166, 318, 178]]<|/det|> +Line 46: nutrient rich \(\rightarrow\) nutrient- rich + +<|ref|>text<|/ref|><|det|>[[72, 179, 318, 191]]<|/det|> +Line 48: nutrient rich \(\rightarrow\) nutrient- rich + +<|ref|>text<|/ref|><|det|>[[72, 192, 320, 204]]<|/det|> +Line 69: the usage of \(\rightarrow\) the use of + +<|ref|>text<|/ref|><|det|>[[72, 205, 380, 217]]<|/det|> +Line 86: missed a comma before "mimicking" + +<|ref|>text<|/ref|><|det|>[[72, 218, 494, 231]]<|/det|> +Line 89: Spring, Autumn, Summer \(\rightarrow\) spring, autumn, summer + +<|ref|>text<|/ref|><|det|>[[72, 231, 238, 243]]<|/det|> +Results and Discussion + +<|ref|>text<|/ref|><|det|>[[72, 244, 567, 257]]<|/det|> +What are the differences between Supplementary Table 1 and Data S1? + +<|ref|>text<|/ref|><|det|>[[72, 258, 430, 270]]<|/det|> +Line 98: 96- deep- well- plates \(\rightarrow\) 96- deep- well- plates + +<|ref|>text<|/ref|><|det|>[[72, 271, 435, 283]]<|/det|> +Line 98: remove extra space after "one cell per well". + +<|ref|>text<|/ref|><|det|>[[72, 284, 435, 296]]<|/det|> +Line 102: maintained further \(\rightarrow\) maintained thereafter + +<|ref|>text<|/ref|><|det|>[[72, 297, 288, 309]]<|/det|> +Line 109: contained \(\rightarrow\) contain + +<|ref|>text<|/ref|><|det|>[[72, 310, 430, 322]]<|/det|> +Line 113: failed in obtaining \(\rightarrow\) failed to obtain + +<|ref|>text<|/ref|><|det|>[[72, 323, 475, 335]]<|/det|> +Lines 117- 121: the sentence is clunky; better to restructure. + +<|ref|>text<|/ref|><|det|>[[72, 336, 448, 348]]<|/det|> +Line 127: use a multiplication sign \((\times)\) , not the letter "x". + +<|ref|>text<|/ref|><|det|>[[72, 349, 521, 362]]<|/det|> +Line 131: write out the full name of NSY when it is first mentioned. + +<|ref|>text<|/ref|><|det|>[[72, 363, 306, 375]]<|/det|> +Line 161: as used for \(\rightarrow\) used for + +<|ref|>text<|/ref|><|det|>[[72, 376, 330, 388]]<|/det|> +Line 163: affiliated to \(\rightarrow\) affiliated with + +<|ref|>text<|/ref|><|det|>[[72, 389, 507, 401]]<|/det|> +Line 213: of our culture collection \(\rightarrow\) from our culture collection + +<|ref|>text<|/ref|><|det|>[[72, 402, 510, 415]]<|/det|> +Line 228: our the culture collection \(\rightarrow\) from our culture collection + +<|ref|>text<|/ref|><|det|>[[72, 415, 460, 427]]<|/det|> +Line 232: the remaining ones \(\rightarrow\) the remaining genomes + +<|ref|>text<|/ref|><|det|>[[72, 428, 444, 440]]<|/det|> +Line 225: a global presence \(\rightarrow\) their global distribution + +<|ref|>text<|/ref|><|det|>[[72, 441, 400, 453]]<|/det|> +Line 234: Only six genomes could be assigned + +<|ref|>text<|/ref|><|det|>[[72, 454, 712, 466]]<|/det|> +Line 290: how did you select the 324 genomes of the closest relatives from public databases? + +<|ref|>text<|/ref|><|det|>[[72, 467, 650, 479]]<|/det|> +Line 293: Maybe you can highlight here that \(>83.9\%\) are novel/undescribed species. + +<|ref|>text<|/ref|><|det|>[[72, 480, 285, 492]]<|/det|> +Line 376: differ to \(\rightarrow\) differ from + +<|ref|>text<|/ref|><|det|>[[72, 504, 130, 515]]<|/det|> +Methods + +<|ref|>text<|/ref|><|det|>[[72, 517, 248, 529]]<|/det|> +Line 544: as an outgroup + +<|ref|>text<|/ref|><|det|>[[72, 530, 427, 543]]<|/det|> +Line 547: specify the number of bootstrap replicates + +<|ref|>text<|/ref|><|det|>[[72, 555, 162, 567]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[72, 580, 238, 592]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 593, 864, 633]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 645, 162, 658]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 671, 238, 683]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 684, 916, 789]]<|/det|> +Salcher et al. present an innovative, high- throughput method to generate axenic cultures of aquatic prokaryotes. In doing so, they have addressed a major challenge in microbiology, i.e., "the great plate anomaly", that is the inability to cultivate a majority of microbial lineages. All the cultures presented here have been taxonomically annotated, and a subset had their genomes sequenced. The genome sequencing revealed diverse potential metabolisms, and as the cultures are now available, the genome- based predictions can be tested. Importantly, the cultured prokaryotes were among the most abundant in their environments, unlike many other, especially traditional cultivation techniques. Moreover, Salcher et al. used artificial media, which makes the cultures more transferable and easier to maintain as opposed to using autoclaved water. + +<|ref|>text<|/ref|><|det|>[[72, 801, 184, 814]]<|/det|> +Major comment: + +<|ref|>text<|/ref|><|det|>[[72, 826, 896, 879]]<|/det|> +As the authors correctly state in the Abstract, this study has resulted in a valuable collection of abundant freshwater microbes that holds significant potential as model systems for a wide array of studies. However, it is not stated how other researchers can get access to the isolates to perform such studies. This needs to be specified, otherwise this claim can hardly be made. + +<|ref|>text<|/ref|><|det|>[[72, 892, 375, 905]]<|/det|> +Minor comments / suggested improvements: + +<|ref|>text<|/ref|><|det|>[[72, 917, 911, 945]]<|/det|> +The detailed metabolic- capability map (Fig.4) for the 87 genome- sequenced strains could be combined with information on growth on the six media used in the study. The use of different media is a psychological experiment. Particularly, a medium + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 905, 87]]<|/det|> +with methanol and methylamine (MM- med) was used, and the potential for methylotrophy was analyzed based on the genomes. Comparing the growth on the medium and the genome- inferred metabolic potential would be a major addition both to the analysis of the inferred metabolism and to showcasing the potential of the cultivation approach presented here. + +<|ref|>text<|/ref|><|det|>[[72, 98, 922, 192]]<|/det|> +The genomic comparison on page 10 and 11 is very informative and concise. An additional genomic feature interesting to compare would be CRISPRs. CRISPRs are known to be underrepresented in streamlined vs. non- streamlined genomes (for biological reasons) as well as in MAGs vs. isolates (for technical reasons), so comparing contents of CRISPR (eg proportion of genomes were CRISPRs are found) between your oligotrophic and copiotrophic isolates, as well as between your isolates and their closest MAG relatives (in cases were close MAG relatives exist) would be interesting. The latter comparison could also involve the number of CRISPR spacers found, since assembling MAGs may only recover the more conserved parts of the CRISPR within a population, as opposed to when assembling an isolate genome. + +<|ref|>text<|/ref|><|det|>[[72, 202, 905, 243]]<|/det|> +Putting supplementary figure S2 (and potentially also S1) in the main is worth consideration, since there is space for extra display items. Fig. S2 visualizes the workflow, which is the key new development presented in the paper. This is a fully suggestive comment, and it is ultimately up to the authors how they want to present their work. + +<|ref|>text<|/ref|><|det|>[[72, 268, 916, 333]]<|/det|> +Line 81: I find it very difficult to understand that phenotypic traits sometimes can be "not at all encoded in the genome". Of course, if, for example, there is a phage infection, the phenotype may differ from a non- infected population. But also propensity for infection by a specific phage is encoded in the genome. So please specify how you mean this might work. Line 89: It is unclear which year the spring and autumn samples come from (this is specified in the methods section and just requires a reformulation in the introduction for clarity). + +<|ref|>text<|/ref|><|det|>[[72, 333, 900, 386]]<|/det|> +Line 122: "Most cultures showed stable growth for more than one year" - the information on which/how many cultures showed stable growth for more than one year is not in the figures. If the details of long- term survival and growth are in a supplementary table, they should be referred to. Otherwise, at least provide the percentage or number of stable long- term cultures (or which cultures were unstable and/or hard to maintain). + +<|ref|>text<|/ref|><|det|>[[72, 386, 725, 400]]<|/det|> +Line 138: Please give the carbon source as concentration in the medium rather than as a mass. + +<|ref|>text<|/ref|><|det|>[[72, 400, 630, 413]]<|/det|> +Lines 147- 156 (Fig. 3): The test used to obtain significance values is unspecified. + +<|ref|>text<|/ref|><|det|>[[72, 413, 777, 426]]<|/det|> +Line 166: It's odd to provide the lower range of the p- values (">"), maybe the authors meant to write "<"? + +<|ref|>text<|/ref|><|det|>[[72, 426, 920, 452]]<|/det|> +Lines 177- 178: It would be relevant here to write how many of the 30 genera (if any) overlap with the 48 previously cultivated genera mentioned on lines 174- 175. + +<|ref|>text<|/ref|><|det|>[[72, 452, 910, 479]]<|/det|> +Line 189: Although I see what you mean, I guess the culture collection hasn't actually made a "contribution" to the diversity and abundance of taxa in the lakes. Consider rephrasing. + +<|ref|>text<|/ref|><|det|>[[72, 479, 864, 492]]<|/det|> +Figure 2. Panel B includes so many taxa with similar colors that it is impossible to identify many taxa in the barplots. + +<|ref|>text<|/ref|><|det|>[[72, 492, 592, 505]]<|/det|> +Consider only coloring a subset of the taxa with highest abundances. + +<|ref|>text<|/ref|><|det|>[[72, 505, 641, 518]]<|/det|> +Line 218: I suggest you write "up to 117 x coverage per Gb mapped data" for clarity. + +<|ref|>text<|/ref|><|det|>[[72, 518, 920, 544]]<|/det|> +Line 228: "Eighty- seven strains our the culture collection" - this sentence is agrammatical and thus hard to read. Should it be "in our" rather than "our the"? + +<|ref|>text<|/ref|><|det|>[[72, 544, 911, 584]]<|/det|> +Lines 236- 237: What does "described species" mean here? Is it the species described according to the standards of ICNP, or, e.g., present in GTDB? Convention suggests the first option, but it would be beneficial to specify. The same applies to "undescribed genera" in line 237. + +<|ref|>text<|/ref|><|det|>[[72, 584, 870, 610]]<|/det|> +Lines 265- 266: Is Data S11/S12 the same as Supplementary Table S11/S12? If yes, the cross- references should be consistent throughout the paper. + +<|ref|>text<|/ref|><|det|>[[72, 610, 911, 636]]<|/det|> +Lines 268- 271: "In all but four cases" - do you mean "For all but four of the eighty- seven genomes"? And what does "closely related" MAG (95% ANI?) + +<|ref|>text<|/ref|><|det|>[[72, 636, 352, 649]]<|/det|> +Line 270: Shouldn't it be "Fig. 3B" here? + +<|ref|>text<|/ref|><|det|>[[72, 649, 914, 675]]<|/det|> +Line 280: Couldn't more TAA and less TGA/TAG simply reflect the general tendency of streamlined genes to have lower GC- content? + +<|ref|>text<|/ref|><|det|>[[72, 675, 881, 701]]<|/det|> +Line 284: "significance distinction" could be reformulated to stress in what way these genomes were distinct (generally smaller/larger). + +<|ref|>text<|/ref|><|det|>[[72, 701, 916, 728]]<|/det|> +Lines 288- 312: These two paragraphs are repeated. (I.e., these lines are almost exactly the same as lines 263- 287; the only difference between the two versions is the figures and supplementary material). + +<|ref|>text<|/ref|><|det|>[[72, 728, 300, 740]]<|/det|> +Line 360: Should be "Fig. 4" + +<|ref|>text<|/ref|><|det|>[[72, 740, 457, 753]]<|/det|> +Line 395: Was hypolimnion defined as deeper than 5m? + +<|ref|>text<|/ref|><|det|>[[72, 753, 864, 767]]<|/det|> +Line 438: Since viability is a crucial statistic for the paper, it would be preferable to reiterate the formula in this study. + +<|ref|>sub_title<|/ref|><|det|>[[72, 779, 162, 792]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 805, 238, 817]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 818, 864, 856]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 868, 144, 881]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 895, 219, 908]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 921, 160, 934]]<|/det|> +Reviewer #1 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 238, 60]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 60, 924, 100]]<|/det|> +Thanks for your thoughtful responses to my suggestions and congratulations on a very nice study. I will endorse acceptance for publication, but if possible consider changing "72 distinct genus or lineage- like taxa" to something like "72 distinct genera or unnamed SILVA lineages". + +<|ref|>text<|/ref|><|det|>[[73, 100, 183, 112]]<|/det|> +- Brian Hedlund + +<|ref|>text<|/ref|><|det|>[[73, 126, 163, 139]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 152, 744, 180]]<|/det|> +(Remarks to the Author) The comments raised by us have all been well addressed in the revised version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 204, 163, 217]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 230, 238, 243]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 243, 864, 283]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[72, 636, 914, 690]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 689, 916, 757]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[73, 755, 620, 769]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 323, 108]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 133, 428, 150]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 174, 880, 366]]<|/det|> +The paper by Salcher and colleagues describes a large effort to leverage dilution- to- extinction with defined media to isolate abundant prokaryotes in the epilimnna and metalimnna of lakes across central Europe, resulting in 627 pure cultures. The paper also sequences paired metagenomes and compares a metagenome- assembled genome (MAG) set to the isolate collection and compares the isolate and MAG collection to a large number of metagenomes from lakes worldwide. The paper shows that the isolate collection represents many of the most abundant and prevalent genera in lakes and includes two previously undescribed families and nine undescribed genera. Those novel taxa are named under the SeqCode. + +<|ref|>text<|/ref|><|det|>[[114, 389, 884, 558]]<|/det|> +The paper tackles an important problem in microbiology at a large scale and generally delivers on the goal to isolate abundant and novel organisms. Some specific strengths are: large scale; paired isolate collection and metagenomes; analysis of growth rate and oligo/copiotrophy, high- quality of the isolate genomes; isolation of some interesting microorganisms including the first non- methanotrophic member of the Methylacidiphilales and some other difficult groups like Armatimonadota. I do have some critical comments for the authors' consideration. None of this is major, but I hope the authors take the comments seriously if they have a chance to resubmit. + +<|ref|>text<|/ref|><|det|>[[116, 560, 803, 600]]<|/det|> +RESPONSE: Thank you very much for your overall positive and encouraging review comments. Please find a detailed response to your individual comments below. + +<|ref|>text<|/ref|><|det|>[[114, 613, 875, 760]]<|/det|> +- In the title, please be aware that many scientists don't like the term "microbial dark matter". Also, I personally use the term only for higher ranks without cultured representatives (e.g., phyla, classes). But I'll leave the decision up to you. RESPONSE: We thank the reviewer for this comment; we agree that the term "microbial dark matter" is mainly used for higher taxonomic ranks. We have changed the title of our manuscript to "Bringing the uncultivated microbial majority of freshwater ecosystems into culture". + +<|ref|>text<|/ref|><|det|>[[114, 773, 877, 857]]<|/det|> +- Line 18: evogenomic is not a standard word and is not a widely used term. Consider using evolutionary genomic. Also, please consider describing the importance of pure cultures more coherently. All scientist value pure samples (minerals, elements, spectra, etc.). It's easy to understand pure samples. Think of Koch's postulates for example. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 850, 152]]<|/det|> +RESPONSE: We changed "eco- and evo genomic investigations" to: "Axenic cultures are essential for studying microbial ecology, evolution, and genomics." We further changed "Despite their importance,..." to: "Despite the importance of pure cultures,...". (L 19- 20) + +<|ref|>text<|/ref|><|det|>[[114, 163, 870, 333]]<|/det|> +- In the introduction, the discussion of auxotrophies and dependencies is a little off-target because this paper does not provide a solution to metabolic dependencies. The cells are diluted from the fresh samples into defined media with simple carbon sources and vitamins and other resources. Co-cultures are ignored, so this would prevent the study from growing microbes with metabolic dependencies (other than those supported by added media ingredients). Instead, I think the approach is very good at targeting slow-growing oligotrophs that can be outcompeted by copiotrophs during enrichment, which is not explicitly mentioned. + +<|ref|>text<|/ref|><|det|>[[114, 336, 855, 463]]<|/det|> +RESPONSE: We thank the reviewer for this suggestion. We have rephrased this part to (L 57- 60): "Further, largely unknown growth requirements, adaptations to low nutrient and substrate concentrations, a tendency of being outcompeted by copiotrophs during enrichment, and a free- living lifestyle preventing growth on solid surfaces such as agar plates, make the isolation and cultivation of slowly growing aquatic oligotrophs challenging." + +<|ref|>text<|/ref|><|det|>[[114, 474, 857, 558]]<|/det|> +- Line 80, I suggest adding some text about novel biochemical pathways, cell ultrastructure, and other features here. The listed features are at least partly predictable from genomes (e.g., temperature optimum) and relatively boring. The paper would be improved by more creativity here. + +<|ref|>text<|/ref|><|det|>[[114, 560, 882, 707]]<|/det|> +RESPONSE: We thank the reviewer for this suggestion. We added a sentence listing additional features that rely on cultures (L 80- 85): "However, genomes alone are not sufficient to characterize the ecology of microbial taxa, as many phenotypic traits (e.g., cell size, temperature, pH, salinity, or substrate ranges and optima) are hard to identify or not at all encoded in the genome39. Further, cultures are a prerequisite to discover and characterize biochemical pathways25,40,41, cell ultrastructure42,43, growth requirements17,29, and microbial interactions15,44 and are the basis for genetic manipulations45,46. + +<|ref|>text<|/ref|><|det|>[[114, 720, 515, 738]]<|/det|> +- Line 108, what does "lineage-like taxa" mean? + +<|ref|>text<|/ref|><|det|>[[114, 741, 880, 890]]<|/det|> +RESPONSE: The SILVA database of 16S rRNA gene sequences assigns taxonomic ranks not always in a coherent way that follows the phylum- class- order- family- genus- species scheme. This is due to the many sequences obtained from uncultivated microbes that are included in this database. Hence, some important microbes are classified as clades or lineages, e.g., SAR11 clade I, II, or III (family or genus- level classifications within Pelagibacterales), hgcl (Nanopelagicales, i.e., order- level classification), GKS98 freshwater group (Zwartia, genus- level classification). We used a well- maintained and customized + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 90, 879, 301]]<|/det|> +SILVA- ARB database with updated taxonomic ranks wherever possible (e.g., we split hgcl into the genera Planktophila, Nanopelagicus and other, so far undescribed Nanopelagicales, see Supplementary Data 3 and 9. However, some lineages assigned by SILVA are hard to split (e.g., NS11- 12 and OPS 17 seem to be orders), as 16S rRNA genes are often not discriminative enough to distinguish different genera and for many orders or families in SILVA, branches containing only environmental 16S rRNA sequences are simply grouped in uncultured lineages (e.g., Bacteria/Actinobacteria/Acidimicrobiiia/Microtrichales/uncultured or Bacteria/Proteobacteria/Alphaproteobacteria/Rhodobacterales_Rhodobacteraceae_1/uncultured). + +<|ref|>text<|/ref|><|det|>[[112, 313, 884, 697]]<|/det|> +- Line 124, how were the isolates divided into the three categories (oligotrophs, mesotrophs, copiotrophs)? Do the isolates form a continuum that was arbitrarily divided into thirds? Or were these discrete categories that were formed by a clustering method? RESPONSE: The strains form a continuum that we arbitrarily divided into the three categories based on manual comparison of their growth rates. As suggested, we now did clustering of max. growth rates (based on Euclidean distance with Ward's method), however, the optimum number of clusters is 4, as one strain had extraordinarily fast growth (Flavobacterium rarum TH-1). For ease of comparison, we included this strain in the category "copiotrophs" as there is no such term as "ultracopiotroph" or "extracopiotroph". The clustering method also introduced slight changes in our manual division, as two strains that we initially thought to be copiotrophs are now in the group of mesotrophs. However, as mentioned above, the strains surely form a continuum with easily recognizable extremes (oligo- vs. copiotrophs). We still find significant differences between the three groups. We have included a new Figure (Suppl. Fig. 6, see also below) and modified the text accordingly to (L 131- 133): "Although the strains form a continuum in growth characteristics, they could be grouped into oligo- and copiotrophs and a group of strains with in- between features (mesotrophs) after clustering based on growth rates (Supplementary Fig. 6)." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[114, 87, 884, 405]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 419, 877, 586]]<|/det|> +
Supplementary Fig. 6: Hierarchical clustering of maximum growth rates of different strains. a Hierarchical clustering dendrogram based on maximum growth rates of different strains. Clustering was performed using Euclidean distance and Ward's minimum variance linkage method (ward.D2). Red rectangles delineate the clusters identified based on the silhouette analysis. Strains are color-coded at the base of the dendrogram according to trophic classifications. b Bar plot showing the average silhouette width for clusters \((k = 2\) to 5) with \(k = 4\) corresponding to the highest average width. Raw data can be found in Supplementary Data 5.
+ +<|ref|>text<|/ref|><|det|>[[115, 599, 844, 660]]<|/det|> +- Line 126, Fimbriicoccus appears to be a new genus that is first described here. For all such new taxa, please clearly communicate this the first time the new names are mentioned. + +<|ref|>text<|/ref|><|det|>[[114, 664, 880, 790]]<|/det|> +RESPONSE: We changed the sentence to (L 134- 138): "Oligotrophs affiliated with Planktopbila (Actinomycetota) and the newly proposed genera Acidimicrobicustris gen. nov. (Actinomycetota) and Fimbriicoccus gen. nov. (Armatimonadota) showed slow growth...". We further added fam. nov., gen. nov., and sp. nov. whenever we mention a newly proposed family, genus or species (e.g., L 145, 151, 207- 210, 218, 229- 233, 276, 286- 312) and throughout the Supplementary text. + +<|ref|>text<|/ref|><|det|>[[115, 802, 841, 844]]<|/det|> +- Line 131, there is a poor transition here from discussing oligotrophs to copiotrophs. A separate paragraph with topic sentence would help. + +<|ref|>text<|/ref|><|det|>[[115, 846, 740, 864]]<|/det|> +RESPONSE: We started the description of copiotrophs in a new paragraph. + +<|ref|>text<|/ref|><|det|>[[116, 878, 318, 895]]<|/det|> +- Line 139, what is NSY? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 855, 130]]<|/det|> +RESPONSE: NSY is a medium containing nutrient broth, soytone, and yeast extract. This information is now provided in brackets together with a reference (Hahn et al. 2004). + +<|ref|>text<|/ref|><|det|>[[113, 142, 870, 290]]<|/det|> +- Figure 1 A and B, please define all elements of the box and whisker plots and give precise p-values (per Nature guidelines). Do this throughout the paper. RESPONSE: We added a description of the box plots of this figure (now Fig. 2) as follows: "Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, and individual values are displayed by open circles." We also included the results of all statistical tests in a new supplementary table (Supplementary Data 4) and refer to this in the figure legend. + +<|ref|>text<|/ref|><|det|>[[113, 301, 875, 470]]<|/det|> +- Figure 1 B top, I don't understand what is plotted here. The labels refer to media but the legend refers to experiments with 18 different strains. So, was each strain only tested on one medium? There are only 18 data points (means presumably?) shown. Explain. Per Nature guidelines, show all data points and define all items on the graphs explicitly. RESPONSE: In this figure (now Fig. 2), we plotted average growth rates and growth rate ranges of oligo-, meso- and copiotrophic strains grown in different media. Every strain was tested in the six media, individual plots (growth curves, growth rates, max. abundances) are included as Supplementary Figs. 4 & 5. + +<|ref|>text<|/ref|><|det|>[[113, 473, 881, 728]]<|/det|> +We changed the legend for clarification to: "b Maximum growth rates and abundances of 18 strains grown in six different media with low to high carbon and nutrient content. Strains were grouped in oligo-, meso- and copiotrophs according to growth characteristics. Averages and standard deviation of maximum growth rates for oligotrophs \((n = 6\) strains), mesotrophs \((n = 6)\) and copiotrophs \((n = 6\) ; upper panel) as well as boxplots of their maximum growth yields (lower panel) are shown. Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, and individual samples are displayed by open circles. Significant differences between these groups (t-tests) are indicated by asterisks \((***:p< 0.001)\) . Individual plots and growth curves of all strains are shown in Supplementary Figs. 4 and 5 and clustering of growth rates in Supplementary Fig. 6. Raw data are provided in Supplementary Data 3 and 5, and results of statistical tests in Supplementary Data 4." + +<|ref|>text<|/ref|><|det|>[[115, 740, 875, 802]]<|/det|> +- Line 166 "significantly similar results" is awkward but more importantly what statistical analysis is this referring to? I think you would report just a percent of strains with the same phylum assignment? I was confused about the methods here. + +<|ref|>text<|/ref|><|det|>[[115, 805, 881, 889]]<|/det|> +RESPONSE: We did a simple regression analysis between the results obtained by using 59 single copy marker genes (SingleM) and a single, commonly used marker gene (16S rRNA). We reformulated the sentence to make this clear (L163- 166): "Relative abundances based on taxonomic classification using 59 single copy marker genes were significantly correlated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 850, 130]]<|/det|> +with results obtained by using 16S rRNA genes as taxonomic markers \((R^2 = 0.9725, p < 0.0001\) , Supplementary Notes, Supplementary Figs. 8- 10, Supplementary Data 4, 6, 8)." + +<|ref|>text<|/ref|><|det|>[[113, 142, 881, 250]]<|/det|> +- Line 170 and elsewhere (e.g., line 186, line 205), here you refer to genera as "taxa". Please try to be precise throughout the paper. In some cases, taxa is fine because a list transcends ranks, but please refer to genera or phyla or other specific ranks where possible. RESPONSE: We changed "taxa" throughout the manuscript to genera, species or strains (e.g., 171, 173, 179). + +<|ref|>text<|/ref|><|det|>[[113, 259, 850, 344]]<|/det|> +- Line 175, here you refer to species not listed in LPSN as not "cultivated before" but it's really better to be precise. Most probably have been cultivated in some way but this number refers to species names that have not been validated under the ICSP (and presumably there are no pure cultures or stable co-cultures). + +<|ref|>text<|/ref|><|det|>[[113, 346, 883, 451]]<|/det|> +RESPONSE: We have rephrased this sentence accordingly to (L173- 176): "Only 39 of the 157 abundant genera have been validly published under the International Code of Nomenclature of Prokaryotes (ICNP) according to the List of Prokaryotic names with Standing in Nomenclature (LPSN) and another seven were proposed as Candidatus genera (Supplementary Data 7)." + +<|ref|>text<|/ref|><|det|>[[113, 462, 884, 675]]<|/det|> +- Line 187 and elsewhere, the results are great but there's still a big cultivation bias toward Pseudomonas, which is displayed nicely in Figure S7 B and C. I suggest you point this out clearly. For example, you could mention how many of these abundant genera axenic cultures are from Pseudomonas and how many are from other phyla. I don't want to diminish the success of your work but just to communicate clearly that there's still a strong bias here and still a big problem with cultivation. Overall, as mentioned earlier, I think your study is very good for isolating oligotrophs that are outgrown in enrichment cultures or grow poorly on plates but it is poor at growing microbes with metabolic dependencies. It's ok, but it's good to be clear about the strengths of the study and where the study isn't so great (i.e., future directions). + +<|ref|>text<|/ref|><|det|>[[113, 677, 864, 802]]<|/det|> +RESPONSE: We introduced the cultivation bias towards Pseudomonas in L 118 as follows: "Our culture collection was mainly dominated by Pseudomonas (50 out of 72 genera, many of them so far uncultivated), however, we failed to obtain isolates from several abundant bacterial (Chloroflexota, Planctomycetota) and archaeal (Thermoproteota) phyla that primarily inhabit the deep hypolimnion of freshwater lakes11,51." + +<|ref|>text<|/ref|><|det|>[[113, 816, 875, 856]]<|/det|> +- Figure 2C top, what is "Diversity" here? I can't understand what this is given the two y-axis labels, figure legend, and text. + +<|ref|>text<|/ref|><|det|>[[113, 867, 875, 904]]<|/det|> +RESPONSE: This figure (now Fig. 3c) is based on taxonomic assignment of metagenomic reads via SingleM (genus level classification) of the same water samples (original samples, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 867, 145]]<|/det|> +\(\mathrm{n} = 67\) ) or in metagenomes from all over the world (global lakes, \(\mathrm{n} = 462\) ). The upper panel ("Diversity") is the proportion of genera that were represented by at least one strain of our culture collection. + +<|ref|>text<|/ref|><|det|>[[113, 145, 884, 368]]<|/det|> +We modified the figure legend to make this more understandable: "c Proportion of genera from the culture collection relative to the total number of genera (diversity; upper panels) and their summed up relative abundances (abundance; lower panels) in the sampled lakes (original samples, \(n = 67\) ; left panels) and in 462 publicly available metagenomes from seven continents (global lakes, \(n = 462\) ; right panels). Metagenomic reads were taxonomy- assigned with SingleM, proportions of genera included in the culture collection are separately shown for different water layers (epi- and hypolimnion) and total. Boxes indicate the \(25^{\mathrm{th}}\) and \(75^{\mathrm{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\mathrm{th}}\) and \(95^{\mathrm{th}}\) quantiles, individual samples are displayed by open circles. Significant differences between epi- and hypolimnetic samples (t- tests) are indicated by asterisks (\\*\\*\\*: \(p < 0.001\) ). Raw data are provided in Supplementary Data 7 and 10, results of statistical test in Supplementary Data 4. " + +<|ref|>text<|/ref|><|det|>[[113, 382, 870, 508]]<|/det|> +- Figure 2C bottom, does this graph include read recruitment to MAGs as described in the text (I think)? If so, I think this is really off-target. What you need to show is the same graph with your isolate genomes or ideally a comparison of your isolate genomes and the complete genome collection (isolate genomes plus MAGs). Making just one plot with isolate genomes and MAGs does not communicate the significance (abundance) of the isolate collection, which is what this paper is about. + +<|ref|>text<|/ref|><|det|>[[113, 510, 867, 637]]<|/det|> +RESPONSE: Please see also our response to the comment above. Fig. 3c is based on taxonomic assignment of metagenomic reads via SingleM (genus level classification). SingleM provides the whole bacterial community composition present in each metagenome (here used to give the genus level community composition). We then determined how many of the identified genera are present in our culture collection (upper panel) and how abundant the isolated genera are in these samples (lower panel). + +<|ref|>text<|/ref|><|det|>[[115, 650, 541, 668]]<|/det|> +- Line 228 +- beginning of the sentence needs fixing. + +<|ref|>text<|/ref|><|det|>[[115, 670, 872, 710]]<|/det|> +RESPONSE: We changed the sentence to (L 217): "We selected 87 strains from our culture collection for whole-genome sequencing, including..." + +<|ref|>text<|/ref|><|det|>[[113, 723, 877, 870]]<|/det|> +- Line 234 +- please cite a research paper (or proper review) instead of a Microbe article. You could use reference 97, for example. Also, please clarify in the text here what ANI and AAI levels were used to indicate novel species and genera +- presumably 95% and 65%? RESPONSE: Thank you for this suggestion. We removed the Microbe article and refer to Konstantinidis et al. 2017, ISMEJ instead (now reference 64). We also included the ANI and AAI cutoffs used in the text as follows (L 222-224): "GTDB classification and ANI and AAI comparisons (Supplementary Table S9-S10) indicated that the genomes represent 27 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 805, 129]]<|/det|> +genera and 47 distinct species by using AAl cutoffs of \(65\%\) and ANI cutoffs of \(95\%\) , respectively." + +<|ref|>text<|/ref|><|det|>[[110, 141, 876, 418]]<|/det|> +- Line 240 - Use of the SeqCode is fine but please consider depositing the strain whose genome is the nomenclatural types into a culture collection because this could be an important resource for the research community. Please confirm in a response to reviewers that the entries in the SeqCode Registry have been pre-approved by curators. RESPONSE: We plan to deposit some of the type strains in culture collections in the near future, however, this is not trivial as most strains are hard to maintain (no growth on agar plates, slow growth, low maximum cell yield [see Supplementary Figs. 4, 5] ruling out OD measurements). Meanwhile, we make strains available to the scientific community upon personal request by email. We amended the Data availability statement as follows: "Strains from the culture collection can be requested by email to Michaela M. Salcher (michaelasalcher@gmail.com)." We further confirm that the new taxa have been endorsed by the SeqCode curators, here are the confidential reviewer links: [redacted] + +<|ref|>text<|/ref|><|det|>[[115, 420, 203, 437]]<|/det|> +[redacted] + +<|ref|>text<|/ref|><|det|>[[114, 473, 872, 604]]<|/det|> +- Figure 3 legend – For the full figure, make sure you refer to cultures and MAGs. For panel A, make sure it’s clear in the figure legend that this is isolates only. For panel B, “gained” should be “assembled”. In B, it’s ok I guess but some parts of the figure are unreadable. There are too many categories for bootstrap values, genome size, and GC%. Categories should be lumped so there’s a chance to see something. That could be done for coverage too. I know it’s hard to deal with so much data. It’s up to you if you want to address this, but just a suggestion. + +<|ref|>text<|/ref|><|det|>[[113, 604, 880, 900]]<|/det|> +RESPONSE: We thank the reviewer for these suggestions. We modified the figure legend (now Fig. 4) as follows: “Figure 4. Diversity and phylogeny of genome- sequenced cultures compared to metagenome- assembled genomes (MAGs) assembled from the same samples. a Number of genome- sequenced cultures with standing taxonomy and novel taxa on different phylogenetic levels (family, genus, species). b Phylogenomic tree of 120 single copy marker protein sequences of bacterial families containing cultures ( \(n = 87\) ), MAGs assembled from the same water samples ( \(n = 313\) ), and closely related published genomes ( \(n = 324\) ) from cultures (ref. culture), MAGs (ref. MAG), and SAGs (ref. SAG). Five genomes of Patescibacteria were used to root the tree. Clades are colored on a family level and genera containing cultures are marked in different colors and numbers (1: Leadbetterella; 2: Flavobacterium; 3: Fimbriicoccus gen. nov.; 4: Acidimicrobicalustris gen. nov.; 5: Mycobacterium; 6: Rhodoluna; 7: Planktophelia; 8: Verrucolacustris gen. nov.; 9: Fontibacterium; 10: Sphingobium; 11: Sphingorhabdus; 12: Rhabdaerophilum; 13: Aquidulcibacter; 14: Caulobacter; 15: Tabrizicola; 16: Allotabrizicola gen. nov.; 17: Novimethylotenera gen. nov.; 18: Methylotenera; 19: Methylopumilus; 20: Lacustribacter gen. nov.; 21: Hahnella gen. nov.; 22: Zwartia; 23: Hydrogenophaga; 24: Allorhodofexax + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 880, 202]]<|/det|> +gen. nov.; 25: Limnohabitans; 26: Perthalerella gen. nov.; 27: Polynucleobacter). Annotations of the rings from inside to outside: Genome source; genome size; genomic GC content; metagenomic fragment recruitment for 67 samples where cultures and MAGs were gained. The lakes are sorted from oligo- to eutrophic as in Fig. 3 and epi- and hypolimnetic samples are shown separately. See Supplementary Fig. 14 for a full tree with all 1,294 depreciated MAGs covering all families." + +<|ref|>text<|/ref|><|det|>[[113, 215, 882, 364]]<|/det|> +- line 282 - 287 - more abundant than what? What does the text about "a significant distinction" mean? I can't understand it. Do you mean that larger genomes encoded [flagellar] motility and a larger number of different secretion systems? In the supplemental figures, it looks like you're referring to some genomes without ANY secretion system but as far as I know, all organisms have at least one secretion system, often either Sec or SecA2. If you're inferring that some genomes have no secretion system, that would be an extraordinary claim that would require extraordinary evidence. + +<|ref|>text<|/ref|><|det|>[[113, 366, 875, 707]]<|/det|> +RESPONSE: We are sorry for this confusion and changed the text to make it clear that genome- streamlined microbes were more abundant than microbes with medium to large genomes. We also clarified that microbes with genes encoding motility (both flagellar motility and gliding motility) and secretion systems type II, IV, or VI were larger in genome size than those lacking these traits. All genomes contained genes encoding Sec and Tat secretion systems; we didn't specifically highlight this in the text, but this information can be found in Table S15. We changed the text to (L 256- 262): "Genome- streamlined bacteria were also clearly more abundant than microbes with larger genomes, both in the original water samples \((n = 67)\) and in freshwater metagenomes gained from six continents \((n = 250)\) . Further, microbes containing genes encoding motility and secretion systems type II, IV, or VI had significantly larger genome sizes (Supplementary Fig. 18, Supplementary Data 4, 18), except for two Zwartia strains with large genomes (3.6 and 4.5 Mbp) that lacked genes for flagella assembly and chemotaxis, congruent with previously described Zwartia strains67." We further added a sentence to the figure legend of Fig. 5 as follows: "Please note that general secretion systems Sec and Tat are not shown here as these were present in all strains." + +<|ref|>text<|/ref|><|det|>[[115, 718, 634, 737]]<|/det|> +- Line 288-312 is a repetition of the two preceding paragraphs. + +<|ref|>text<|/ref|><|det|>[[115, 740, 875, 802]]<|/det|> +RESPONSE: Thank you for identifying this mistake, it happened in the last round of revision before submission when we decided to shuffle some parts of the text. The duplicated paragraph has been deleted. + +<|ref|>text<|/ref|><|det|>[[115, 814, 835, 899]]<|/det|> +- Line 314 - 315. First, not all rhodopsins are light-driven ion pumps that can make ion gradients (see channelrhodopsins and sensory rhodopsins). Please consider trying to distinguish these or qualify your statement. Second, I notice a lot of cyanobacteria isolates. Is this right? What about those? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 870, 237]]<|/det|> +RESPONSE: We only searched for proton- pumping rhodopsins in this study and most taxa contained either actino- , proteo- or bacteriorhodopsins. We changed the text accordingly to (268- 270): "Most genome sequenced cultures can potentially utilize light as an energy source, either via proton- pumping rhodopsins \((n = 59)\) or by being anoxygenic aerobic phototrophs (AAPs, \(n = 15\) )." Regarding the second question, while we obtained many cyanobacterial strains, we did not genome- sequence them as this study focuses on heterotrophs. + +<|ref|>text<|/ref|><|det|>[[113, 249, 802, 290]]<|/det|> +- Line 316 – not “energy generation” but energy conservation – please. First Law of Thermodynamics. + +<|ref|>text<|/ref|><|det|>[[113, 291, 800, 311]]<|/det|> +RESPONSE: We are sorry for this rookie mistake; we changed the text accordingly. + +<|ref|>text<|/ref|><|det|>[[113, 322, 872, 514]]<|/det|> +- Line 318 – not all RuBisCO homologs participate in the CBB cycle. Please clarify the type. RESPONSE: The five AAPs mentioned in the text contain RuBisCO type I, which is participating in the CBB cycle. Additionally, one strain (Tabrizicola rara LH-M10) contained RuBisCO type II, which is also participating in the CBB cycle and three strains contained RuBisCO-like proteins (RLP) type IV, which are not participating in CBB. We show only RuBisCO types I and II in Fig. 5. We added this information also in the text (L 273-275): “Interestingly, five AAPs additionally contained a carbon fixation pathway (Calvin cycle via RuBisCO type I), potentially leading to photoautotrophy that was so far only occasionally reported for sediment dwelling AAPs”72” + +<|ref|>text<|/ref|><|det|>[[115, 528, 362, 567]]<|/det|> +- Line 321 – “organic carbon”. RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 580, 398, 598]]<|/det|> +- Line 322 – what about catalase? + +<|ref|>text<|/ref|><|det|>[[115, 601, 806, 641]]<|/det|> +RESPONSE: We did not add catalase to the medium used for this experiment, only vitamins. + +<|ref|>text<|/ref|><|det|>[[115, 653, 685, 672]]<|/det|> +- Line 324 – Is this significant? Can you run a t-test for the endpoint? + +<|ref|>text<|/ref|><|det|>[[113, 675, 861, 802]]<|/det|> +RESPONSE: We ran a paired t-test for the endpoint; it was significantly different \((p = 0.0092\) , test results are given in Supplementary Data 4). We added this information in the text, it now reads (L 278-281): “While growth was observed in both dark and light:dark (12:12 h) conditions, L. simekii maintained significantly higher cell numbers during stationary phase in light:dark conditions \((p = 0.009175\) , Supplementary Data 4) hinting at photoautotrophic growth during starvation.” + +<|ref|>text<|/ref|><|det|>[[115, 814, 303, 853]]<|/det|> +- line \(370 =\) ranks RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 866, 846, 907]]<|/det|> +- Line 406 – consider mentioning earlier in the main narrative that important tricks were used to increase cultivability, like catalase and pyruvate. I think these tricks aren’t well + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 880, 130]]<|/det|> +known enough and it would be good to emphasize that you were careful and thoughtful and to help educate the community. + +<|ref|>text<|/ref|><|det|>[[114, 133, 880, 280]]<|/det|> +RESPONSE: We added this information in the last paragraph of the introduction (L 88- 92): "Here, we employed a high- throughput dilution- to- extinction approach with three defined artificial media containing either different carbohydrates, organic acids, catalase, vitamins, and other organic compounds in \(\mu M\) concentrations, mimicking carbon concentrations typically found in freshwater lakes (med2 and med3), or methanol, methylamine and vitamins (MM- med) as sole carbon sources (Supplementary Data 1)." We further included media components and preparation as Supplementary Data 1. + +<|ref|>text<|/ref|><|det|>[[114, 292, 777, 311]]<|/det|> +- Line 419 – all additions after autoclaving were filter sterilized? Please explain. + +<|ref|>text<|/ref|><|det|>[[113, 313, 877, 504]]<|/det|> +RESPONSE: Yes, we filtered all components through 0.1 \(\mu m\) filters, this information is now also mentioned in the methods as follows (L 368- 370): "After autoclaving, both media were amended with a filter-sterilized mix of the 20 proteinogenic amino acids (0.2 \(\mu M\) of each amino acid except for glutamate and glutamine which were added at 0.4 \(\mu M\) concentration), vitamins (0.593 \(\mu M\) thiamine, 0.08 \(\mu M\) niacin, 0.074 nM cobalamine, 0.005 \(\mu M\) para- amino benzoic acid, 0.074 \(\mu M\) pyridoxine, 0.081 \(\mu M\) pantothenic acid, 0.004 \(\mu M\) biotin, 0.004 \(\mu M\) folic acid, 0.555 \(\mu M\) myo- inositol), dipotassium phosphate (3.22 \(\mu M\) ) and catalase (10 U ml- 1)86." We further included media components and preparation as Supplementary Data 1. + +<|ref|>text<|/ref|><|det|>[[114, 516, 881, 556]]<|/det|> +- Please check and confirm that the SeqCode Registry curators have provisionally accepted the proposed names and supporting data. + +<|ref|>text<|/ref|><|det|>[[114, 559, 872, 599]]<|/det|> +RESPONSE: We confirm that the new taxa have been endorsed by the SeqCode curators (see above for confidential reviewer links) + +<|ref|>text<|/ref|><|det|>[[115, 611, 387, 628]]<|/det|> +Additional comments on figures + +<|ref|>text<|/ref|><|det|>[[115, 631, 857, 670]]<|/det|> +Figure 1. the label "med3 (n=60)" was odd as shown in the figure; mention the statistical tests used. + +<|ref|>text<|/ref|><|det|>[[115, 673, 864, 734]]<|/det|> +RESPONSE: We updated the figure (now Fig. 2) as requested and mention the statistical tests (t- tests) in the figure legend. We further refer to Supplementary Data 4 for details on all statistical tests. + +<|ref|>text<|/ref|><|det|>[[115, 747, 827, 787]]<|/det|> +Figure 2. The figure labels are overlapping. For Panel A, mention what the thicker and darker colors represent. For Panel C, add statistical test information. + +<|ref|>text<|/ref|><|det|>[[114, 790, 881, 895]]<|/det|> +RESPONSE: We have reorganized this figure (now Fig. 3) to make it more appealing. For panel A, we specified that the thick lines are averages and the thin lines are maxima as follows: "a Rank- abundance curve (lower panel, averages are shown as thick lines, maxima as thin lines) and number of axenic cultures (upper panel) of abundant genera present in the sampled lakes (>1% of reads in at least one sample)." For panel C, we now included + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 879, 344]]<|/det|> +statistical test information as follows: c Proportion of genera from the culture collection relative to the total number of genera (diversity; upper panels) and their summed up relative abundances (abundance; lower panels) in the sampled lakes (original samples, \(n = 67\) ; left panels) and in 462 publicly available metagenomes from seven continents (global lakes, \(n = 462\) ; right panels). Metagenomic reads were taxonomy- assigned with SingleM, proportions of genera included in the culture collection are separately shown for different water layers (epi- and hypolimnion) and total. Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, individual samples are displayed by open circles. Significant differences between epi- and hypolimnetic samples (t- tests) are indicated by asterisks (\\*\\*: \(p < 0.001\) ). Raw data are provided in Supplementary Data 7 and 10, results of statistical tests in Supplementary Data 4. " + +<|ref|>text<|/ref|><|det|>[[113, 355, 861, 462]]<|/det|> +Figure 3. The title "Diversity and phylogeny of genome- sequenced cultures" is not appropriate because the dataset also includes MAGs and other published genomes. RESPONSE: We changed the title of this figure (now Fig. 4) as follows: "Figure 4. Diversity and phylogeny of genome- sequenced cultures compared to metagenome- assembled genomes (MAGs) assembled from the same samples" + +<|ref|>sub_title<|/ref|><|det|>[[115, 475, 310, 492]]<|/det|> +## Supplementary figures + +<|ref|>text<|/ref|><|det|>[[115, 495, 705, 514]]<|/det|> +- Figure 1: Please show two-letter codes for lakes here and in Table S1. + +<|ref|>text<|/ref|><|det|>[[115, 516, 876, 557]]<|/det|> +RESPONSE: We added the two- letter codes also here and in the supplementary table (now Supplementary Data 2) + +<|ref|>text<|/ref|><|det|>[[115, 569, 877, 609]]<|/det|> +- Figure 12 – define the parts of the boxes and whiskers. What is “Diversity”? Just to confirm – these are based on the culture genomes only and not the MAGs? + +<|ref|>text<|/ref|><|det|>[[113, 612, 868, 760]]<|/det|> +RESPONSE: This figure is based on taxonomic assignment of metagenomic reads via SingleM (genus level classification) of water samples from all over the world (n=462). The upper panel (“Diversity”) is the proportion of genera that were represented by at least one strain of our culture collection. We modified the figure legend to make this more understandable: “Supplementary Figure 12. Contribution of cultures to the total number (diversity; upper panel) and summed up read counts (abundance, lower panel) of genera present in 462 freshwater metagenomic samples from seven different continents.” + +<|ref|>text<|/ref|><|det|>[[115, 773, 388, 791]]<|/det|> +Very minor editorial suggestions + +<|ref|>text<|/ref|><|det|>[[115, 795, 223, 811]]<|/det|> +Introduction + +<|ref|>text<|/ref|><|det|>[[115, 815, 870, 855]]<|/det|> +Please check the citation formatting for the whole paper — there are extra spaces in some places. + +<|ref|>text<|/ref|><|det|>[[115, 858, 772, 899]]<|/det|> +RESPONSE: We carefully checked all citations throughout the manuscript and supplementary text and removed all extra spaces. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 871, 130]]<|/det|> +Line 38: When "however" connects two independent clauses (complete sentences), use a semicolon before it and a comma after it. + +<|ref|>text<|/ref|><|det|>[[115, 134, 303, 152]]<|/det|> +RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 165, 380, 203]]<|/det|> +Line 38: miniscule \(\rightarrow\) minuscule RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 217, 416, 256]]<|/det|> +Line 46: nutrient rich \(\rightarrow\) nutrient- rich RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 270, 416, 308]]<|/det|> +Line 48: nutrient rich \(\rightarrow\) nutrient- rich RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 322, 394, 361]]<|/det|> +Line 69: the usage of \(\rightarrow\) the use of RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 375, 499, 414]]<|/det|> +Line 86: missed a comma before "mimicking" RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 428, 629, 467]]<|/det|> +Line 89: Spring, Autumn, Summer \(\rightarrow\) spring, autumn, summer RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 481, 316, 499]]<|/det|> +Results and Discussion + +<|ref|>text<|/ref|><|det|>[[115, 503, 714, 521]]<|/det|> +What are the differences between Supplementary Table 1 and Data S1? + +<|ref|>text<|/ref|><|det|>[[115, 524, 871, 586]]<|/det|> +RESPONSE: Supplementary Table S1 and Data S1 are the same, we apologize for this misnomer. We have now renamed all tables as Supplementary Data 1, 2, 3, etc. as per the formatting instructions of Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 599, 548, 638]]<|/det|> +Line 98: 96- deep- well- plates \(\rightarrow\) 96- deep- well plates RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 651, 555, 690]]<|/det|> +Line 98: remove extra space after "one cell per well". RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 704, 559, 743]]<|/det|> +Line 102: maintained further \(\rightarrow\) maintained thereafter RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 757, 368, 796]]<|/det|> +Line 109: contained \(\rightarrow\) contain RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 810, 495, 849]]<|/det|> +Line 113: failed in obtaining \(\rightarrow\) failed to obtain RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 863, 868, 903]]<|/det|> +Lines 117- 121: the sentence is clunky; better to restructure. RESPONSE: We have split this sentence in two (L124- 128): "The enrichment in a medium + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 875, 194]]<|/det|> +with methanol and methylamine as sole carbon sources resulted in an enhanced cultivation of methylotrophs (Methylopumulus, Methylotenera50,52). However, also other genera were able to grow in this C1 medium (e.g., Polynucleobacter, Limnohabitans) and might have survived by either being photoautotrophic, methylovorous, or by using catalase or vitamins as additional carbon sources." + +<|ref|>text<|/ref|><|det|>[[114, 207, 576, 225]]<|/det|> +Line 127: use a multiplication sign \((\times)\) , not the letter "x". + +<|ref|>text<|/ref|><|det|>[[114, 229, 858, 269]]<|/det|> +RESPONSE: Changed, also in lines 137, 140, 206, 210, 276, 357, 400, 402, 406- 407, 415, and throughout the Supplementary Text + +<|ref|>text<|/ref|><|det|>[[114, 281, 666, 300]]<|/det|> +Line 131: write out the full name of NSY when it is first mentioned. + +<|ref|>text<|/ref|><|det|>[[114, 303, 866, 343]]<|/det|> +RESPONSE: We wrote that NSY is a medium containing nutrient broth, soytone, and yeast extract in brackets. + +<|ref|>text<|/ref|><|det|>[[114, 356, 380, 395]]<|/det|> +Line 161: as used for \(\Rightarrow\) used for RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 409, 428, 448]]<|/det|> +Line 163: affiliated to \(\Rightarrow\) affiliated with RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 461, 644, 501]]<|/det|> +Line 213: of our culture collection \(\Rightarrow\) from our culture collection RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 514, 655, 554]]<|/det|> +Line 228: our the culture collection \(\Rightarrow\) from our culture collection RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 567, 577, 606]]<|/det|> +Line 232: the remaining ones \(\Rightarrow\) the remaining genomes RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 620, 564, 659]]<|/det|> +Line 225: a global presence \(\Rightarrow\) their global distribution RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 673, 504, 712]]<|/det|> +Line 234: Only six genomes could be assigned RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[114, 725, 799, 765]]<|/det|> +Line 290: how did you select the 324 genomes of the closest relatives from public databases? + +<|ref|>text<|/ref|><|det|>[[114, 768, 866, 896]]<|/det|> +RESPONSE: We first looked for cultivated type strains in GTDB (gtdb.ecogenomics.org) by verbatim name matching of genus names assigned to genome- sequenced cultures (Advanced Search, match all of the following: "GTDB Type Material" IS "type strain of species" AND "GTDB Taxonomy" CONTAINS "genus taxonomy of genome- sequenced strain", e.g., g_Zwartia). We then added additional, not cultivated representative species in GTDB by verbatim name matching (Advanced Search, match all of the following: "GTDB + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 882, 280]]<|/det|> +Representative of Species" IS TRUE AND "GTDB Taxonomy" CONTAINS "genus taxonomy of genome- sequenced strain"). In the case of novel families that we described in this manuscript, we extended this search to additional, closely related families within the same order (e.g., Acidimicrobiates). This list was amended with additional genomes identified via literature research based on genus or family names. We added this information in the material and methods part as follows (L 492- 495): "Taxonomic classification was done with GTDB r220 as outlined above and the closest relatives of each culture genome ( \(n = 324\) ) were selected in GTDB by verbatim name matching of the assigned genus or family name and literature research and downloaded from NCBI." + +<|ref|>text<|/ref|><|det|>[[113, 292, 876, 397]]<|/det|> +Line 293: Maybe you can highlight here that \(>83.9\%\) are novel/undescribed species. RESPONSE: We modified the sentence accordingly (L238- 240): Only seven MAGs could be assigned to a described species and another seven to Candidatus species (1.1% of the 1,294 MAGs), reiterating the high proportion of undescribed taxa in freshwater environments \(^{4,11}\) . + +<|ref|>text<|/ref|><|det|>[[115, 410, 372, 450]]<|/det|> +Line 376: differ to \(\rightarrow\) differ from RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 464, 325, 523]]<|/det|> +Methods Line 544: as an outgroup RESPONSE: Changed. + +<|ref|>text<|/ref|><|det|>[[115, 537, 555, 555]]<|/det|> +Line 547: specify the number of bootstrap replicates + +<|ref|>text<|/ref|><|det|>[[115, 559, 874, 598]]<|/det|> +RESPONSE: We did 1000 ultrafast bootstrap replicates; this information is now included in the text (L 511). + +<|ref|>text<|/ref|><|det|>[[115, 675, 429, 693]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 717, 873, 800]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 814, 874, 854]]<|/det|> +RESPONSE: Thank you very much for your review. We highly appreciate the Nature Communications initiative to facilitate training in peer review for Early Career Researchers. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 428, 108]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 132, 881, 344]]<|/det|> +Salcher et al. present an innovative, high- throughput method to generate axenic cultures of aquatic prokaryotes. In doing so, they have addressed a major challenge in microbiology, i.e., "the great plate anomaly", that is the inability to cultivate a majority of microbial lineages. All the cultures presented here have been taxonomically annotated, and a subset had their genomes sequenced. The genome sequencing revealed diverse potential metabolisms, and as the cultures are now available, the genome- based predictions can be tested. Importantly, the cultured prokaryotes were among the most abundant in their environments, unlike many other, especially traditional cultivation techniques. Moreover, Salcher et al. used artificial media, which makes the cultures more transferable and easier to maintain as opposed to using autoclaved water. + +<|ref|>text<|/ref|><|det|>[[115, 377, 801, 418]]<|/det|> +RESPONSE: Thank you very much for your overall positive and encouraging review comments. Please find a detailed response to your individual comments below. + +<|ref|>text<|/ref|><|det|>[[115, 453, 256, 470]]<|/det|> +Major comment: + +<|ref|>text<|/ref|><|det|>[[113, 494, 877, 600]]<|/det|> +As the authors correctly state in the Abstract, this study has resulted in a valuable collection of abundant freshwater microbes that holds significant potential as model systems for a wide array of studies. However, it is not stated how other researchers can get access to the isolates to perform such studies. This needs to be specified, otherwise this claim can hardly be made. + +<|ref|>text<|/ref|><|det|>[[114, 602, 868, 729]]<|/det|> +RESPONSE: We thank the reviewer for this comment and apologize that we forgot to mention this information in the initial submission. All strains from our culture collection were cryopreserved and are available to other researchers by email request to the corresponding author (michaelasalcher@gmail.com). We have added this information to the Data availability statement as follows (L 532- 533): "Strains from the culture collection can be requested by email to Michaela M. Salcher (michaelasalcher@gmail.com)." + +<|ref|>text<|/ref|><|det|>[[115, 741, 494, 759]]<|/det|> +Minor comments / suggested improvements: + +<|ref|>text<|/ref|><|det|>[[114, 783, 870, 889]]<|/det|> +The detailed metabolic- capability map (Fig.4) for the 87 genome- sequenced strains could be combined with information on growth on the six media used in the study. The use of different media is a psychological experiment. Particularly, a medium with methanol and methylamine (MM- med) was used, and the potential for methylotrophy was analyzed based on the genomes. Comparing the growth on the medium and the genome- inferred + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 876, 473]]<|/det|> +metabolic potential would be a major addition both to the analysis of the inferred metabolism and to showcasing the potential of the cultivation approach presented here. RESPONSE: We did not use the MM- med in growth assays with known methylotrophs such as \*Methylopumilus\*, as this was already done in earlier studies (Salcher et al. 2015 ISMEJ, Layoun et al. 2024, ISMEJ). As for the other media used in the growth assays, it is not straightforward to match the carbon sources to growth patterns. For example, med2 and med3 are very similar in C composition, med3 additionally contains glycolate, polyamines and two carbohydrates compared to med2. We checked for the presence of glycolate oxidation in the genomes, but there was no obvious pattern connected to growth in med3, i.e., six strains grew better in med3 than in med2, but only two of them (\*Polynucleobacter hoetzingerianus\* RE- M21 and \*Allorhodofexax lacus\* MsE- M18) contained pathways for glycolate oxidation, while the others (\*Acidimicrobiloacustris europeus\* KE- 4, \*Planktophila versatilis\* MsE- 18, \*Fimbriicoccus planktonicus\* MsE- 15, \*Flavobacterium rarum\* TH- M1) did not. The same holds true for polyamines, only four of the strains that grew better in med3 contained membrane transporters for spermidine or putrescine (A. europeus KE- 4, P. versatilis MsE- 18, A. lacus MsE- M18, F. rarum TH- M1). We tried different versions of how to integrate the different media in this figure (Fig. 5), but none of them looked compelling, therefore we decided to keep it as is. + +<|ref|>text<|/ref|><|det|>[[114, 485, 875, 670]]<|/det|> +The genomic comparison on page 10 and 11 is very informative and concise. An additional genomic feature interesting to compare would be CRISPRs. CRISPRs are known to be underrepresented in streamlined vs. non- streamlined genomes (for biological reasons) as well as in MAGs vs. isolates (for technical reasons), so comparing contents of CRISPR (eg proportion of genomes were CRISPRs are found) between your oligotrophic and copiotrophic isolates, as well as between your isolates and their closest MAG relatives (in cases were close MAG relatives exist) would be interesting. The latter comparison could also involve the number of CRISPR spacers found, since assembling MAGs may only recover the more conserved parts of the CRISPR within a population, as opposed to when assembling an isolate genome. + +<|ref|>text<|/ref|><|det|>[[114, 672, 875, 891]]<|/det|> +RESPONSE: We thank the reviewer for this great suggestion. We predicted CRISPR- Cas systems in our culture collection, MAGs and reference genomes and found that only 5 strains (5% of the culture collection) with medium- large genome sizes contained this phage- defense system. In contrast, \(\sim 20\%\) of the reference genomes obtained from cultures and \(\sim 13\%\) of our MAGs contained CRISPR- Cas repeats. Further, as could be expected, there was a clear relationship between genome size and CRISPR system (with larger genomes being more likely to have CRISPR). We have made an additional Supplementary Figure (Suppl. Fig. 19, see below) and table (Supplementary Data 19) and included the following text in the manuscript (L 262- 267): "The phage- defense system CRISPR- Cas68,69 was present in only 5 strains with medium- large genome sizes (2.6- 5 Mbp, Supplementary Fig. 19, Supplementary Data 19). In contrast, 20.8% of the reference genomes obtained from cultures and 13.9% of MAGs contained on average 1.7 CRISPR + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 91, 879, 145]]<|/det|> +arrays per genome. There was a clear relationship to genome size, as microbes containing CRISPR- Cas systems were significantly larger than those without \((p = 7.524E - 47\) , Supplementary Data 4).” + +<|ref|>image<|/ref|><|det|>[[113, 152, 884, 816]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 820, 866, 894]]<|/det|> +Supplementary Figure 19. Occurrence of CRISPR- Cas arrays in cultures, MAGs and closely related cultivates references. a The same phylogenomic tree as in Fig. 4 including the number of CRISPR- Cas arrays per genome. b Number of genomes with CRISPR- Cas arrays and number of CRISPR- Cas arrays per genome separately shown for cultures, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 864, 149]]<|/det|> +reference cultures, and MAGs or c different genome size classes. d Genome sizes of microbes with or without CRISPR- Cas arrays. \(***p < 0.0001\) for significant differences in genome sizes (t- test), results of statistical tests can be found in Supplementary Data 4. + +<|ref|>text<|/ref|><|det|>[[113, 153, 878, 267]]<|/det|> +Putting supplementary figure S2 (and potentially also S1) in the main is worth consideration, since there is space for extra display items. Fig. S2 visualizes the workflow, which is the key new development presented in the paper. This is a fully suggestive comment, and it is ultimately up to the authors how they want to present their work. RESPONSE: We thank the reviewer for this valuable suggestion. We have now included Fig. S2 as a new main figure (new Fig. 1). + +<|ref|>text<|/ref|><|det|>[[113, 279, 883, 533]]<|/det|> +Line 81: I find it very difficult to understand that phenotypic traits sometimes can be "not at all encoded in the genome". Of course, if, for example, there is a phage infection, the phenotype may differ from a non- infected population. But also propensity for infection by a specific phage is encoded in the genome. So please specify how you mean this might work. RESPONSE: Here, we argue that some traits can be very hard to infer from genomes without having cultures (e.g., cell size, temperature, pH, salinity, or substrate ranges and optima). We expanded this part as follows (L780- 85): "However, genomes alone are not sufficient to characterize the ecology of microbial taxa, as many phenotypic traits (e.g., cell size, temperature, pH, salinity, or substrate ranges and optima) are hard to identify or not at all encoded in the genome39. Further, cultures are a prerequisite to discover and characterize biochemical pathways25,40,41, cell ultrastructure42,43, growth requirements17,29, and microbial interactions15,44 and are the basis for genetic manipulations45,46." + +<|ref|>text<|/ref|><|det|>[[114, 545, 860, 606]]<|/det|> +Line 89: It is unclear which year the spring and autumn samples come from (this is specified in the methods section and just requires a reformulation in the introduction for clarity). + +<|ref|>text<|/ref|><|det|>[[114, 609, 866, 692]]<|/det|> +RESPONSE: The spring and autumn samples were also obtained in 2019. We have now included this information in the text (L 92- 94) as follows: "We sampled 14 lakes in Central Europe during spring and autumn 2019, and four lakes additionally in summer 2019 (Supplementary Fig. 1, Supplementary Data 2). + +<|ref|>text<|/ref|><|det|>[[113, 705, 882, 808]]<|/det|> +Line 122: "Most cultures showed stable growth for more than one year" - the information on which/how many cultures showed stable growth for more than one year is not in the figures. If the details of long- term survival and growth are in a supplementary table, they should be referred to. Otherwise, at least provide the percentage or number of stable long- term cultures (or which cultures were unstable and/or hard to maintain). + +<|ref|>text<|/ref|><|det|>[[114, 811, 875, 895]]<|/det|> +RESPONSE: We have included the information about unstable cultures in the beginning of the results section (L103- 106: "Screening resulted in 1,201 initial cultures, whereof 229 were identified as mixed by Sanger sequencing of 16S rRNA gene amplicons and 344 cultures showed no growth after several transfers and were discarded (Supplementary Fig. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 880, 323]]<|/det|> +2, Supplementary Data 3)."), in Supplementary Fig. 2 and in a Supplementary table (Supplementary Data 3, row labeled as "# cultures with no growth after 3- 4 propagations"). However, it is very hard to reconstruct the exact time when we stopped propagating individual cultures, as we discontinued many strains from taxa for which we isolated multiple representatives after taxonomy assignment by 16S rRNA sequencing. This process took quite a long time (\~1 year) because of severe restrictions in lab work during COVID19 lockdowns, which was also a reason why we kept only a reduced number of strains in this period. Selected strains were kept until we obtained their genomes (>1 year). However, multiple strains are being maintained till today (e.g., the Fontibacterium and Planktophila strains) while some others have been revived several times from glycerol- stocks (e.g. for the growth assays). + +<|ref|>text<|/ref|><|det|>[[115, 335, 861, 375]]<|/det|> +Line 138: Please give the carbon source as concentration in the medium rather than as a mass. + +<|ref|>text<|/ref|><|det|>[[114, 378, 879, 504]]<|/det|> +RESPONSE: We have reformulated this sentence to (L 147- 150): "Copiotrophic strains grew to highest densities in the medium with highest nutrient content (1:10 diluted NSY containing 0.3 g complex carbon sources per liter), and several of these genera have been previously isolated by the filtration acclimatization method using NSY53." We further added an additional table (Supplementary Data 1) with details on all media used for isolation and for growth assays. + +<|ref|>text<|/ref|><|det|>[[115, 516, 789, 535]]<|/det|> +Lines 147- 156 (Fig. 3): The test used to obtain significance values is unspecified. + +<|ref|>text<|/ref|><|det|>[[115, 538, 860, 599]]<|/det|> +RESPONSE: We used t- tests to test for significant differences; this is now included in the figure legend. We further added all results of statistical test to a Supplementary Table (Supplementary Data 4). + +<|ref|>text<|/ref|><|det|>[[115, 611, 880, 651]]<|/det|> +Line 166: It's odd to provide the lower range of the p- values (">"), maybe the authors meant to write "<"? + +<|ref|>text<|/ref|><|det|>[[115, 654, 792, 674]]<|/det|> +RESPONSE: We thank the reviewers for finding this typo, it is changed to "<" now. + +<|ref|>text<|/ref|><|det|>[[115, 686, 875, 726]]<|/det|> +Lines 177- 178: It would be relevant here to write how many of the 30 genera (if any) overlap with the 48 previously cultivated genera mentioned on lines 174- 175. + +<|ref|>text<|/ref|><|det|>[[115, 729, 866, 790]]<|/det|> +RESPONSE: We have added this information to the text and also in Supplementary Data 7 as follows (L179- 180): "Only 16 of the 30 abundant genera of our culture collection have been validly described to date3." + +<|ref|>text<|/ref|><|det|>[[115, 804, 836, 861]]<|/det|> +Line 189: Although I see what you mean, I guess the culture collection hasn't actually made a "contribution" to the diversity and abundance of taxa in the lakes. Consider rephrasing. + +<|ref|>text<|/ref|><|det|>[[115, 862, 866, 899]]<|/det|> +RESPONSE: We rephrased the legend accordingly to: "Figure 3. Representation of the culture collection in lake samples. a Rank- abundance curve (lower panel, averages are + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 879, 442]]<|/det|> +shown as thick lines, maxima as thin lines) and number of axenic cultures (upper panel) of abundant genera present in the sampled lakes ( \(>1\%\) of reads in at least one sample). Metagenomic reads were taxonomy- assigned with SingleM. Asterisks below cultures indicate that at least one member of the genus was genome- sequenced. See Supplementary Fig. 11 and Supplementary Data 7 for all genera including rare taxa. b Summed up relative abundances of taxa with representatives in the culture collection in the epi- and hypolimnion of the sampled lakes. Samples are sorted from oligo- to eutrophic, abbreviations of lakes and sampling seasons are as in Supplementary Fig. 1. c Proportion of genera from the culture collection relative to the total number of genera (diversity; upper panels) and their summed up relative abundances (abundance; lower panels) in the sampled lakes (original samples, \(n = 67\) ; left panels) and in 462 publicly available metagenomes from seven continents (global lakes, \(n = 462\) ; right panels). Metagenomic reads were taxonomy- assigned with SingleM, proportions of genera included in the culture collection are separately shown for different water layers (epi- and hypolimnion) and total. Boxes indicate the \(25^{\text{th}}\) and \(75^{\text{th}}\) quantiles, medians are displayed by central lines, whiskers indicate the \(5^{\text{th}}\) and \(95^{\text{th}}\) quantiles, individual samples are displayed by open circles. Significant differences between epi- and hypolimnetic samples (t- tests) are indicated by asterisks (\\*\\*\\*: \(p < 0.001\) ). Raw data can be found as Supplementary Data 7 and 10, results of statistical test as Supplementary Data 4. " + +<|ref|>text<|/ref|><|det|>[[115, 455, 866, 517]]<|/det|> +Figure 2. Panel B includes so many taxa with similar colors that it is impossible to identify many taxa in the barplots. Consider only coloring a subset of the taxa with highest abundances. + +<|ref|>text<|/ref|><|det|>[[115, 520, 875, 604]]<|/det|> +RESPONSE: We agree that we used too many different colors in this figure. We summed up several taxa (e.g., Aquiluna & Rhodoluna, UBA2463 & UBA954, Limnohabitans & Limnohabitans_A,...) to make the figure less crowded. Please note that we have modified this figure (now Fig. 3) also based on suggestions by reviewer #1. + +<|ref|>text<|/ref|><|det|>[[115, 616, 808, 657]]<|/det|> +Line 218: I suggest you write "up to \(117 \times\) coverage per Gb mapped data" for clarity. RESPONSE: Changed as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 669, 867, 752]]<|/det|> +Line 228: "Eighty- seven strains our the culture collection" - this sentence is agrammatical and thus hard to read. Should it be "in our" rather than "our the"? RESPONSE: Thank you for finding this mistake. We changed it to "We selected 87 strains from our culture collection for whole- genome sequencing" (L 217) + +<|ref|>text<|/ref|><|det|>[[115, 764, 878, 847]]<|/det|> +Lines 236- 237: What does "described species" mean here? Is it the species described according to the standards of ICNP, or, e.g., present in GTDB? Convention suggests the first option, but it would be beneficial to specify. The same applies to "undescribed genera" in line 237. + +<|ref|>text<|/ref|><|det|>[[115, 850, 863, 891]]<|/det|> +RESPONSE: We have modified the text to make the distinction between validly described and novel taxa. The text reads now as follows (L224- 228): "Only one genome could be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 864, 174]]<|/det|> +assigned to a validly described species (Sphingobium curpiorestens \(^{65}\) ) and five more were previously proposed as \*Candidatus\* species by us \(^{24,52}\) (Supplementary Fig. 17). Moreover, genome- sequenced cultures contained nine novel genera and two novel families (Fig. 4a; Supplementary Data 11)." + +<|ref|>text<|/ref|><|det|>[[114, 186, 860, 290]]<|/det|> +Lines 265- 266: Is Data S11/S12 the same as Supplementary Table S11/S12? If yes, the cross- references should be consistent throughout the paper. RESPONSE: Supplementary Table S11/S12 and Data S11/S12 are the same, we apologize for this misnomer. We have now unified the naming of all Supplementary tables to Supplementary Data 1- 21 as per the formatting instructions of Nature Communications. + +<|ref|>text<|/ref|><|det|>[[114, 302, 870, 344]]<|/det|> +Lines 268- 271: "In all but four cases" - do you mean "For all but four of the eighty- seven genomes"? And what does "closely related" MAG (95% ANI?) + +<|ref|>text<|/ref|><|det|>[[113, 345, 882, 664]]<|/det|> +RESPONSE: We calculated ANI values between our genome- sequenced strains and both the closest MAG and publicly available genome- sequenced culture. We have reanalyzed the data and have now included an additional figure that illustrates that the vast majority of our strains is closer related to environmental MAGs than to cultures (Suppl. Fig. 17, see also below). Moreover, by taking 95% ANI as species cutoff, we show that only one of our strains has a cultivated relative that is validly described and available in a strain collection (Sphingobium curpiorestens CCTCC AB 2011146), while another culture genome (Limnohabitans sp. B9- 3) was not validly described and five more \*Candidatus\* species were previously proposed by us (3 \*Methylopumilus\* species: Salcher et al. 2015 ISMEJ, Salcher et al. 2019 ISMEJ, 2 \*Planktophila\* species: Neuenschwander et al. 2018 ISMEJ). We rephrased this sentence to (L240- 244): "In the majority of cases, strains from our culture collection were phylogenetically closer to MAGs than to previously cultured species, and only one, \*Sphingobium curpiorestens\*, is validly described and available in a culture collection \(^{65}\) (Fig. 4b, Supplementary Figs. 14, 17), exemplifying that the genome- sequenced cultures were indeed novel and highly relevant." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[112, 85, 880, 330]]<|/det|> +<|ref|>image_footnote<|/ref|><|det|>[[135, 312, 545, 350]]<|/det|> +
Strains from culture collection next relative MAG next relative culture (described) next relative culture (not described) next relative culture (previously proposed as Candidatus by us)
+ +<|ref|>title<|/ref|><|det|>[[135, 355, 216, 366]]<|/det|> +# Strain code: + +<|ref|>text<|/ref|><|det|>[[123, 365, 880, 720]]<|/det|> +1 Acidimicrobicustrichus thunensis TE- 4 30 Sphingorhabdus communis GE- 11 59 Methylopulinus planktonicus MoH-M8 2 Acidimicrobicustrichus thunensis TE- 7 31 Sphingorhabdus communis ZE- 10 60 Methylopulinus planktonicus MsH-M18 3 Acidimicrobicustrichus europaeus KE- 4 32 Hydrogenophaga miladensis MiE- M28 61 Methylopulinus planktonicus MsH-M39 4 Rhodoluna miladensis MiE- 23b 33 Limnohabitans simeeki MiE- M12 62 Methylopulinus planktonicus MsH-M42 5 Rhodoluna miladensis MiE- 24b 34 Limnohabitans rimovensis RE- 1 63 Methylopulinus planktonicus TH-M4 6 Mycobacterium aquicola MaE- M6b 35 Limnohabitans kasalickyi MaE- M4 64 Methylopulinus planktonicus ZE- M7 7 Mycobacterium aquicola MiE- 22 36 Polynucleobacter hoezingerianus RE- M21 65 Methylopulinus planktonicus ZE- M8 8 Planktophila dulcis MaH- 2 37 Pernthalerella aquatica GE- M3 66 Methylopulinus rimovensis RE- M17 9 Planktophila dulcis MsH- 2 38 Pernthalerella lacunae MaE- M21 67 Methylopulinus rimovensis RE- M20 10 Planktophila dulcis TrE- 23 39 Pernthalerella communis MsE- 6 68 Methylopulinus rimovensis RE- M24 11 Planktophila grossartii RE- 3 40 Polynucleobacter hahni ZE- 4 69 Methylopulinus universalis GE- M14 12 Planktophila grossartii RH- 3 41 Allorhodofexar lacustis MiE- M13 70 Methylopulinus universalis GH- M24 13 Planktophila turicensis ZE- 9 42 Allorhodofexar lacus MsE- M18 71 Methylopulinus universalis GH- M4 14 Planktophila warnecki RE- 8 43 Allorhodofexar aquaticus MsE- M22 72 Methylopulinus universalis LE- M21 15 Planktophila versatilis MsE- 18 44 Allorhodofexar lacus MsH- M24 73 Methylopulinus universalis MaE- M17 16 Fimbriicoccus planktonicus MsE- 15 45 Allorhodofexar lacus ZE- M1 74 Methylopulinus universalis MH- M4 17 Leadbetterella lacustris RE- 19 46 Hahnella aquatica MiE- 11 75 Methylopulinus universalis MH- M5 18 Flavobacterium ruam TH- M1 47 Hahnella lacustris MsE- M47 76 Methylopulinus universalis MiE- M1 19 Flavobacterium neuenschwanderi GE- 10 48 Lacustribacter communis MsE- M52 77 Methylopulinus universalis RE- M9 20 Caulobacter lacus MiH- 16 49 Zwartia planktonica RE- 10 78 Methylopulinus universalis RH- M37 21 Aquidulcibacter rimovensis RH- 10 50 Zwartia lucis GE- 14 79 Methylopulinus universalis ZE- M6 22 Aquidulcibacter miladensis MiH- 15 51 Methylopulinus planktonicus KE- 4b 80 Methylopulinus universalis ZIE- M21 23 Fontibacterium abundans MiE- 29 52 Methylopulinus planktonicus LE- M7 81 Methylotenera profunda RE- M3 24 Fontibacterium medardense ME- 17 53 Methylopulinus planktonicus MaE- M16 82 Methylotenera profunda RH- M32 25 Rhodobacterophilum aquaticum MsE- M23 54 Methylopulinus planktonicus MaE- M22 83 Methylotenera hypolimnetica RH- M31 26 Tabrizicola rara LH- M10 55 Methylopulinus planktonicus MoH- M15 84 Methylotenera hypolimnetica ZIE- M10 27 Allotabrizicola aquatica RE- M30 56 Methylopulinus planktonicus MoH- M17 85 Nonimethylotenera aquatica ME- M6 28 Sphingobium cupriresistens MiE- 4 57 Methylopulinus planktonicus MoH- M19 86 Nonimethylotenera aquatica MsE- M29 29 Sphingorhabdus rara RE- M21a 58 Methylopulinus planktonicus MoH- M36 87 Verrucolacustris abundans MiH- 22 + +<|ref|>text<|/ref|><|det|>[[114, 722, 857, 784]]<|/det|> +Supplementary Fig. 17: Average nucleotide identities (ANI) between strains from our culture collection and MAGs and previously cultivated species. The species border (95% ANI) is indicated with a solid line. Raw data is given in Supplementary Data 14. + +<|ref|>text<|/ref|><|det|>[[114, 797, 754, 840]]<|/det|> +Line 270: Shouldn't it be "Fig. 3B" here? RESPONSE: This was indeed a typo, thank you for identifying it (now Fig. 4b). + +<|ref|>text<|/ref|><|det|>[[114, 851, 830, 892]]<|/det|> +Line 280: Couldn't more TAA and less TGA/TAG simply reflect the general tendency of streamlined genomes to have lower GC- content? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 852, 194]]<|/det|> +RESPONSE: This is certainly true, we have modified the text accordingly to (L 253- 256): "Genome- streamlined strains tended to use a different stop codon (TAA) indicative of nitrogen limitation \(^{52}\) , which is also reflected in a low GC content, and contained more membrane transporters (normalized per Mbp genome size) than strains with medium to large genomes. + +<|ref|>text<|/ref|><|det|>[[114, 206, 833, 247]]<|/det|> +Line 284: "significance distinction" could be reformulated to stress in what way these genomes were distinct (generally smaller/larger). + +<|ref|>text<|/ref|><|det|>[[113, 249, 872, 418]]<|/det|> +We are sorry for this confusion and changed the text to clarify that that microbes with genes encoding motility (both flagellar motility and gliding motility) and secretion systems type II, IV, or VI were larger in genome size than those lacking these traits. We changed the text to (L 258- 262): "Further, microbes containing genes encoding motility and secretion systems type II, IV, or VI had significantly larger genome sizes (Supplementary Fig. 18, Supplementary Data 4, 18), except for two Zwartia strains with large genomes (3.6 and 4.5 Mbp) that lacked genes for flagella assembly and chemotaxis, congruent with previously described Zwartia strains \(^{67}\) ." + +<|ref|>text<|/ref|><|det|>[[114, 430, 872, 494]]<|/det|> +Lines 288- 312: These two paragraphs are repeated. (I.e., these lines are almost exactly the same as lines 263- 287; the only difference between the two versions is the figures and supplementary material). + +<|ref|>text<|/ref|><|det|>[[114, 495, 874, 558]]<|/det|> +RESPONSE: Thank you for identifying this mistake, it happened in the last round of revision before submission when we decided to shuffle some parts of the text. The duplicated paragraph has been deleted. + +<|ref|>text<|/ref|><|det|>[[115, 570, 349, 588]]<|/det|> +Line 360: Should be "Fig. 4" + +<|ref|>text<|/ref|><|det|>[[115, 590, 844, 610]]<|/det|> +RESPONSE: Thank you for finding also this typo, we changed it accordingly (now Fig. 5). + +<|ref|>text<|/ref|><|det|>[[114, 622, 583, 641]]<|/det|> +Line 395: Was hypolimnion defined as deeper than 5m? + +<|ref|>text<|/ref|><|det|>[[114, 643, 865, 705]]<|/det|> +RESPONSE: The hypolimnion was defined based on thermal stratification (or - in the case of unstratified spring samples - based on previous data for the sampled lakes). We also took care not to sample anoxic water layers. + +<|ref|>text<|/ref|><|det|>[[114, 718, 809, 756]]<|/det|> +Line 438: Since viability is a crucial statistic for the paper, it would be preferable to reiterate the formula in this study. + +<|ref|>text<|/ref|><|det|>[[114, 756, 867, 811]]<|/det|> +RESPONSE: We included the formula in the methods as suggested (L 391- 394): "Isolation success expressed as Viability \((V)\) , i.e., probability that a cell selected at random is viable was calculated based on the formula by Button et al. \(^{49}\) as follows: + +<|ref|>equation<|/ref|><|det|>[[434, 823, 562, 861]]<|/det|> +\[V = \frac{\ln(1 - p)}{X}\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 857, 128]]<|/det|> +Where \(p\) is the number of wells or cultivation tubes, \(n\) , with growth \(z\) \((p = z / n)\) and \(X\) is the estimated number of cells inoculated per well." + +<|ref|>text<|/ref|><|det|>[[115, 174, 428, 192]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 216, 872, 300]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 312, 875, 353]]<|/det|> +RESPONSE: Thank you very much for your review. We highly appreciate the Nature Communications initiative to facilitate training in peer review for Early Career Researchers. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 324, 108]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 133, 428, 151]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 175, 876, 258]]<|/det|> +Thanks for your thoughtful responses to my suggestions and congratulations on a very nice study. I will endorse acceptance for publication, but if possible consider changing "72 distinct genus or lineage- like taxa" to something like "72 distinct genera or unnamed SILVA lineages". + +<|ref|>text<|/ref|><|det|>[[115, 262, 250, 279]]<|/det|> +- Brian Hedlund + +<|ref|>text<|/ref|><|det|>[[115, 282, 874, 344]]<|/det|> +RESPONSE: Thank you very much for your supportive review with helpful comments that largely improve our manuscript. We changed "72 distinct genus or lineage- like taxa" to "72 distinct genera or alphanumerical SILVA lineages" (Line 113). + +<|ref|>text<|/ref|><|det|>[[115, 368, 428, 386]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 410, 830, 450]]<|/det|> +The comments raised by us have all been well addressed in the revised version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 454, 830, 494]]<|/det|> +RESPONSE: Thank you very much for your review. Your previous comments helped to improve our manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 539, 428, 557]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 581, 872, 664]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 667, 874, 708]]<|/det|> +RESPONSE: Thank you very much for your review. We highly appreciate the Nature Communications initiative to facilitate training in peer review for Early Career Researchers. + +<--- Page Split ---> diff --git a/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/images_list.json b/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..bc7a49065769ed89310adb3e54c8cc2ccca6a62d --- /dev/null +++ b/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/images_list.json @@ -0,0 +1,62 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1. Internal energy per lattice site \\(E\\) , specific heat per lattice site \\(C / k_{B}\\) , and a single Potts configuration sampled from a classical Monte-Carlo simulation on the chiral Potts model for a system of size \\(L = 10\\) . For the Potts configuration the black and purple circles label excited tetrahedra corresponding to a bion and a chiral charge, respectively.", + "footnote": [], + "bbox": [ + [ + 172, + 184, + 815, + 456 + ] + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2. Nearest-neighbor dot product (left) and single-triangle chirality (right) for a cool-down scheme on the upper row, and a warm-up scheme on the lower row. The black lines label the expected value of these quantities in an exact ground-state configuration, which is \\(-1 / 3\\) for the nearest-neighbor dot product and \\(-4 / (3\\sqrt{3})\\) for the chirality term.", + "footnote": [], + "bbox": [ + [ + 80, + 142, + 900, + 472 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure 3. Monte-Carlo unit cell with \\(L = 4\\) where only the \"up\" tetrahedra are shown. Here all the blue tetrahedra belong to a single infinite kagome plane which bisects the pyrochlore lattice. The apparent observation of three different planes is a consequence of the periodic boundary conditions of the system.", + "footnote": [], + "bbox": [ + [ + 355, + 132, + 675, + 350 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_9.jpg", + "caption": "Supplementary Figure 9. Specific heat for the chiral Hamiltonian in Eq. \\(\\sim \\text{eqref{eq:chiral\\_Hamiltonian}}\\) sampled through classical Monte-Carlo for three system sizes, namely \\(\\mathbb{S}\\mathbb{L} = 6,8,10\\mathbb{S}\\) .", + "footnote": [], + "bbox": [ + [ + 147, + 103, + 864, + 425 + ] + ], + "page_idx": 13 + } +] \ No newline at end of file diff --git a/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd b/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8d569b77c1a839fbfdcdf71bde0439b8b67bb7b5 --- /dev/null +++ b/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd @@ -0,0 +1,277 @@ + +# nature portfolio + +Peer Review File + +# A Classical Chiral Spin Liquid from Chiral Interactions on the Pyrochlore Lattice + +Corresponding Author: Dr Daniel Lozano- Gómez + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Lozano- Gomez and co- authors study a theoretical model of classical spins on pyrochlore lattice with three- spin interaction that induces a chirality. They show that ground state of model is equivalent to a four- color model with some special restrictions due to chirality. They claim it is a classical chiral spin liquid. They write a gauge theory for this model and discuss how excitations of this ground state may behave like classical fractons. They also discuss influence of Heisenberg interactions which is the main realistic perturbation of their model. They claim that Heisenberg interaction does not change a priori the nature of ground state. + +As cited by the authors in introduction, citation 24 studied a similar model but with biquadratic interaction instead of chirality interaction. The main difference is that model of citation 24 orders and is not a spin liquid. Indeed the cool down simulations done by the authors does not show a phase transition for their model. It suggests maybe spin liquid. But the energy of cool down and warm up simulations are different, and warm up simulations show a peak in specific heat in the supplemental material. This peak is called crossover in supplemental material, but it looks like a phase transition in figure S5. It means that at low temperature, simulations are either frozen in some form of order when warm up, or they are disordered in a phase that is not the ground state when cool down. It is interesting, but not entirely conclusive for the presence of spin liquid. + +As cited by the authors in page 6, citation 46 did the field theory with three gauge fields of four- color model on pyrochlore. The authors showed that chirality between spins of equation 1 becomes chirality in field theory in equation 9. + +Then the authors explain why a consequence of chirality is that excitations of ground state may be like fractons. This is maybe most interesting result because there is a lot of research on fractons and simple models for fractons are rare. But the authors "leave the study of these charges and a more detailed characterization of the model in Eq. (4) for future work" so it is not sure if there are fractons in simulations. + +Maybe fractons are responsible for the excited energy of simulations at low temperature when cool down ? + +The paper is easy to read and of interest to people in frustrated magnetism and maybe fracton physics. But some of the claims are not entirely established. For example, are cool down simulations metastable ? Do we really have fractons ? Also, compared to literature, the new results deserve to be published, but I am not sure they have enough impact for Nature Communications. + +Small comments + +Sometimes the paper is technical. For example, what is a pinch point and bow tie in structure factor ? A possible paper of interest to the author, Gia- Wei Chern and Congjun Wu, Four- Coloring Model and Frustrated Superfluidity in the Diamond Lattice, PRL 112, 020601 (2014) + +(Remarks on code availability) + +Reviewer #2 + +<--- Page Split ---> + +(Remarks to the Author) + +In this article, Lozano- Gomez et al. considered chiral interactions between classical spins defined on a pyrochlore lattice and found a classical spin liquid state captured by an effective gauge theory. Starting from the detailed analysis of the chiral interaction defined on a single tetrahedron, they identified 12 distinct ground state configurations. Then, using a classical Monte- Carlo simulation, thermodynamic properties of this model on larger systems were investigated. They further derived an effective 4- state (chiral) Potts model that has a ground state configuration corresponding to that of the original chiral model and developed an effective gauge theory based on an effective Potts model including chiral interactions. The existence of chiral interactions makes the chiral Potts model distinct from the regular Potts model, modifying the ground state manifold and the property of excitations. + +I think the authors are successful in describing the emergent gauge structure by chiral interactions, leading to a classical spin liquid state on a 3- dimensional pyrochlore lattice. The paper is written clearly and, therefore, could be published. However, I have a mixed feeling whether or not I should recommend the publication of this work in Nature Communications as explained below. + +Introducing chiral interactions on a pyrochlore lattice is a new way to realize a spin liquid state, both ingredients and consequence appear to be novel. However, the behavior of the proposed model does not seem to be so different from the other spin models, such as dipolar interactions on a pyrochlore lattice, showing two- fold pinch points in the spin structure factor and a Coulomb phase of bions. Is there fundamental difference between the different models and between the current classical spin liquid vs. a (quantum) spin ice? + +Since a chiral interaction on a triangle requires an (effective) magnetic field penetrating the triangle (Ref. 26), how the interactions are arranged appears to imply that magnetic fluxes are coming from the inside of a tetrahedron to the outside through all triangle surfaces, or vice versa, as if a magnetic monopole is located at the center of the tetrahedron. If I am correct, the physical realization of the current model is extremely difficult, while it may not be entirely impossible. Could this be realized in a physical system, or the current proposal is purely theoretical with no relevance to the real world? Because of the above points and considering how the paper is written (highly theoretical), the paper may not appeal to the broad audience of Nature Communications. The current manuscript may be better suited to other journal, where people specialized in the frustrated magnetism could enjoy it. Could the authors modify the manuscript so that broad audience could access? + +Other suggestions + +Some of the subsections may have alternative titles, such as "Regular Potts model" => "Gauge structure of the regular Potts model", "Chiral Potts model" => "Gauge structure of the chiral Potts model", "Chiral and Heisenberg interactions" => "Competition between Chiral and Heisenberg interactions" + +(Remarks on code availability) + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +I would like to thank the authors for their reply and their efforts. I find this new version clearer, especially related to the emergent physics of fractons, which is, as mentioned in my previous report, probably the most interesting aspect of this paper. + +There are still a few questions left unanswered, such as finite- size scaling of the specific heat (and other quantities), or the possibility for an order- by- disorder transition if an efficient non- local spin update were developed in order to thermalise this system at low temperatures (I realise that such an algorithm would be a technical challenge). + +But this manuscript has the advantage to present a relatively simple model that sits at the crossing point between chiral spin liquids, fractonic matter and out- of- equilibrium phenomena in a non- disordered magnet. The overall outcome is of sufficient interest that the unanswered questions may actually motivate further studies. It is difficult to say for sure, but this model could become a future toy model for fractons or chiral spin liquidity. + +Being easy to read and of interest to an active community of researchers, I would now recommend publication of this improved version of the manuscript. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +The authors responded to my questions appropriately and revised the manuscript. I think the paper is now accessible to the broader audience and, therefore, would like to recommend the publication in Nature Communications. + +<--- Page Split ---> + +(Remarks on code availability) + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS AND RESPONSE + +## Reviewer #1 (Remarks to the Author): + +Lozano- Gomez and co- authors study a theoretical model of classical spins on pyrochlore lattice with three- spin interaction that induces a chirality. They show that ground state of model is equivalent to a four- color model with some special restrictions due to chirality. They claim it is a classical chiral spin liquid. They write a gauge theory for this model and discuss how excitations of this ground state may behave like classical fractons. They also discuss influence of Heisenberg interactions which is the main realistic perturbation of their model. They claim that Heisenberg interaction does not change a priori the nature of ground state. + +As cited by the authors in introduction, citation 24 studied a similar model but with biquadratic interaction instead of chirality interaction. The main difference is that model of citation 24 orders and is not a spin liquid. Indeed the cool down simulations done by the authors does not show a phase transition for their model. It suggests maybe spin liquid. But the energy of cool down and warm up simulations are different, and warm up simulations show a peak in specific heat in the supplemental material. This peak is called crossover in supplemental material, but it looks like a phase transition in figure S5. It means that at low temperature, simulations are either frozen in some form of order when warm up, or they are disordered in a phase that is not the ground state when cool down. It is interesting, but not entirely conclusive for the presence of spin liquid. + +As cited by the authors in page 6, citation 46 did the field theory with three gauge fields of four- color model on pyrochlore. The authors showed that chirality between spins of equation 1 becomes chirality in field theory in equation 9. + +Then the authors explain why a consequence of chirality is that excitations of ground state may be like fractons. This is maybe most interesting result because there is a lot of research on fractons and simple models for fractons are rare. But the authors "leave the study of these charges and a more detailed characterization of the model in Eq. (4) for future work" so it is not sure if there are fractons in simulations. Maybe fractons are responsible for the excited energy of simulations at low temperature when cool down? + +We thank the reviewer #1 for his/her overall review of our results and for pointing out the connection between the fractonic excitations and the unusual thermodynamic behavior observed in our simulations. + +Indeed, and as the reviewer pointed out, the discrepancy between our warm- up and cool- down simulations is associated with fractonic excitations which are difficult to equilibrate. More specifically, as the temperature is lowered in a cool- down scheme, fractonic excitations tend to freeze in the lattice (due to their restricted mobility) and impede the system from fully accessing its low- energy manifold; this yields a higher internal energy from a cool- down scheme (as opposed to a warm- up scheme). This same behavior has been observed in other fracton systems with concomitant spin- glass- like behavior [R. M. Nandkishore and M. Hermele, Annu.Rev. Condens. Matter Phys. 10, 295 (2019)]. + +To illustrate this point let us consider the two cases we have studied, first the chiral potts model introduced in Eq. (4) of the main text, and then the chiral Hamilotnian in Eq. (1) of the main text, both which are described by the same effective gauge theory in Eq. (9) of the main text. + +## 1. The chiral Potts model + +As discussed in the main text, for the chiral potts model introduced in Eq. (4), the ground- state configurations have a vanishing energy, and the elementary excitations are bionic charges and chiral charges. We note that the mobility of these charges is severely restricted, as is discussed and characterized in the main text. + +<--- Page Split ---> + +In Fig. 1, we show the internal energy and specific heat per lattice site for both a cool-down and a warm-up scheme, and a single Potts configuration at low temperatures sampled from cool-down classical Monte-Carlo simulations. For the cool-down scheme, our simulations show a smooth evolution of the internal energy, and a Schottky-like peak in the specific heat. We note, however, that the low-temperature internal energy plateaus at a non-vanishing value as \(\mathrm{T} \rightarrow 0\) , implying that excitations are still present in the system. Indeed, by closely inspecting a low-temperature configuration (illustrated in Fig. 1), we see that both bins and chiral excitations are present. + +![](images/Figure_1.jpg) + +
Figure 1. Internal energy per lattice site \(E\) , specific heat per lattice site \(C / k_{B}\) , and a single Potts configuration sampled from a classical Monte-Carlo simulation on the chiral Potts model for a system of size \(L = 10\) . For the Potts configuration the black and purple circles label excited tetrahedra corresponding to a bion and a chiral charge, respectively.
+ +The presence of these charges at low temperatures is associated with their restricted mobility, which in turn lead to a freezing- in of the excitations as the temperature is lowered. A similar picture is seen if we now perform a warm- up scheme for the chiral Potts model starting from a ground- state configuration. In such a case the internal energy sampled by the classical Monte- Carlo does plateau at zero energy at low temperatures. However, and similar to the cool down- scheme, the warm- up scheme is frozen in the initial low- temperature configuration because thermal excitations cannot be easily generated. + +## 2. The chiral Hamiltonian + +As in the chiral Potts model, and as noted by the reviewer #1, the Monte- Carlo simulations of the chiral Hamiltonian in Eq. (4) present a similar discrepancy between the energy of the cool- down and warm- up schemes. In the chiral Hamiltonian, however, the bionic and chiral charges are not quantized but are instead continuous degrees of freedom due to the continuous nature of the underlying classical spins. Consequently, thermal spin fluctuations can thermally depopulate these charges. This effect may also be understood as the melting of a charge. A consequence of this thermal depopulation of the charges is that the internal energy of the system sampled from a cool- down scheme slowly decreases with temperature, although it remains above that of the internal energy sampled with a warm- up scheme, as shown in Fig. 7 of the main text. We note that the non- quantized character of the gauge charges for the chiral Hamiltonian refrains us from exactly locating their position in the lattice and producing an analysis similar to the one performed for the chiral Potts Hamiltonian [Flores- Calderon et al, arXiv:2402.03083 (2024)]. Instead, we can study the evolution of other statistical quantities which are directly associated with the ground- state manifold. Figure 2 illustrates the nearest- neighbor dot product and the single- triangle chirality for warm- up and cool- down schemes sampled at different temperatures and averaged over 200 configurations. At low temperatures all distributions are centered about the ground- state prediction, however, the distributions for the cool down scheme are consistently + +<--- Page Split ---> + +broader than those of the warm up schemes. This difference can be associated with non- vanishing excitations in the system. + +![](images/Figure_2.jpg) + +
Figure 2. Nearest-neighbor dot product (left) and single-triangle chirality (right) for a cool-down scheme on the upper row, and a warm-up scheme on the lower row. The black lines label the expected value of these quantities in an exact ground-state configuration, which is \(-1 / 3\) for the nearest-neighbor dot product and \(-4 / (3\sqrt{3})\) for the chirality term.
+ +We emphasize that in the warm- up simulations of both models, the system freezes in the initial configuration. Moreover, and as mentioned in our draft, there is an at- least sub- extensive number of ground states for these models which are associated by a cyclic permutation of all spins (or Potts degrees of freedom) in an infinite plane bisecting the pyrochlore lattice, see Fig. 3. We note that all of these ground states are equivalent and as such a warm- up simulation on these would also display the same freezing. In particular, and as shown in section "thermodynamics from warm- up and cool- down schemes" of the Supplement, such an equivalence is shown for the chiral Hamiltonian in Eq. (1) where we show warm- up simulations starting from three distinct ground- state configurations. + +<--- Page Split ---> +![](images/Figure_3.jpg) + +
Figure 3. Monte-Carlo unit cell with \(L = 4\) where only the "up" tetrahedra are shown. Here all the blue tetrahedra belong to a single infinite kagome plane which bisects the pyrochlore lattice. The apparent observation of three different planes is a consequence of the periodic boundary conditions of the system.
+ +Let us now comment on how this lack of proper equilibration could be resolved. As we pointed out for both the chiral Potts model and the chiral Hamiltonian, the discrepancy between their temperature- sweeping schemes is associated with remnant charges in the low- temperature phase. To avoid these charges from freezing out in the cool- down scheme and the freezing in a ground- state configuration in the warm- up scheme, a non- local update would be necessary, capable of moving these charges around with no additional energy cost and of connecting different ground- state configurations. In the main text we have discussed the pre- conditions this update must fulfill, however, due to the intricacy of the pyrochlore lattice geometry, we have not been able to implement such a non- local move in our simulations. + +Indeed, a recent work on a classical spin liquid with fractonic excitations showed that such an algorithm can radically improve the thermodynamic behavior of the simulation [B. Placke et al., arXiv:2306.13151 (2023)]. In that case, however, the fractonic excitations they identify are partially mobile which allows for the construction of such moves. This is not the case for the models we considered and therefore complicates the full identification and construction of such non- local updates. + +To summarize, we have studied two systems which are described by the same effective gauge theory at low temperatures. These systems possess fracton excitations with restricted mobility where the excitations are bions and chiral charges. In a cool down Monte- Carlo simulation, the restricted mobility of these charges results in freezing at low temperatures in both systems. The presence of these excitations is exposed by the study of the configuration in the Potts model and the distribution of the nearest- neighbor dot product and chirality term for the chiral Hamiltonian. Additionally, in a warm up Monte- Carlo simulation starting from a ground- state configuration, the restricted mobility results in the freezing of the system in the initial configuration at low temperatures. To overcome the discrepancy between the different temperature schemes, a non- local algorithm would be necessary. In the main text of our draft we have outlined what are the conditions such a non- local update must fulfill and showed a family of these non- local updates corresponds to the permutation of all spins (Potts degrees of freedom) in an infinite plane bisecting the system. + +In our efforts to clarify this point in our draft we have added the following text to the main text, + +"The restricted motion of these excitations results in glassy dynamics typically observed in fracton systems- \cite{Hermele_fractons_2019}. Indeed, performing a warm- up and cool- down classical Monte- Carlo + +<--- Page Split ---> + +simulation on the chiral Potts model exposes a similar behavior to the one observed in Fig.- \ref{fig:MC_warm_up_cool_down}: in the cool- down scheme, the restricted motion results in freezing of charges at low temperatures yielding a higher internal energy in these simulations. In the warm- up scheme, the restricted motion results in freezing of the simulations at low temperatures about the initial configuration, we refer the reader to the SI for further details on the chiral Potts model. Similarly, for the chiral model in Eq.- \ref{eq:chiral_Hamiltonian}, the fractonic nature of these charges is responsible for the disagreement between the internal energy illustrated in Fig.- \ref{fig:MC_warm_up_cool_down}, as well as the histograms of the nearest- neighbor spin correlation in Fig.- \ref{fig:MC_dot_product_warm_cool} measured in the warm- up and cool- down schemes. In the chiral Hamiltonian, however, the continuous nature of the spin degrees of freedom allows for a slow thermal depopulation of the gauge charges and therefore a decreasing internal energy with decreasing temperature. The presence of these charges however is reflected in the width of the histograms in Fig.- \ref{fig:MC_dot_product_warm_cool} which are consistently broader in the cool- down simulations. For more details regarding the difference between the cool- down and warm- up schemes for the chiral Hamiltonian in Eq.- \ref{eq:chiral_Hamiltonian} we refer the reader to the SI." + +In addition, we have modified two sections in the supplement. First, we have modified the section "Effective Potts Model" to include the warm- up Monte- Carlo for the Potts model shown in Fig. 1, along with the following text + +"A similar picture is seen when performing a warm- up scheme starting from a ground- state configuration, see red curve in Fig.- \ref{fig:Potts_model}(a) and (b). In such a case the internal energy sampled by the classical Monte- Carlo does plateau at zero energy at low temperatures. However, and similar to the cool- down scheme, the warm- up scheme is frozen in the initial low- temperature configuration due to the high cost associated with generating and moving the fractonic charges." + +and the section "Thermodynamics from warm- up and cool- down schemes" by including the chirality distributions shown in Fig. 2 along with the following text + +"... The peak in the specific heat observed in Fig.- \ref{fig:MC_warm_up_cool_down_E_and_C} in the warm- up simulations is associated with the freezing of the system into the initial partially ordered configuration. Indeed, our results suggest that the freezing observed in the warm- up scheme is bound to take place irrespective of the initial ground- state configuration selected. + +Similar to the chiral Potts model, the discrepancy between the warm- up and cool- down schemes can be associated with the presence of non- vanishing charges. In the chiral Hamiltonian, however, the bionic and chiral charges are not quantized but are instead continuous degrees of freedom which can be thermally depopulated by spin fluctuations. A consequence of such a thermal depopulation is that the internal energy of the system sampled from a cool- down scheme slowly decreases with temperature, although it remains above that of the internal energy sampled with a warm- up scheme, as shown in Fig.- \ref{fig:MC_warm_up_cool_down} of the main text. Furthermore, the non- quantize character of the gauge charges for the chiral Hamiltonian refrains us from exactly locating their position in the lattice and producing an analysis similar to the one performed for the chiral Potts Hamiltonian in Fig.- \ref{fig:Potts_model}- \text{cite{florescalderon2024irrational}}. Instead, we can study the evolution of other statistical quantities which are directly associated with the ground- state manifold. Figure- \ref{fig:MC_dot_product_warm_cool} in the main text and Figure- \ref{fig:MC_chirality_warm_cool} illustrates the nearest- neighbor dot product and the single triangle chirality for warm- up and cool- down schemes sampled at different temperatures and averaged over 200 configurations, respectively. At low temperatures, all distributions are centered about the ground- state prediction (this being \$- 1/3\$ for the nearest- neighbor dot product and \$- 4/(3\sqt{3})\$ for the chiral \$\$\chi_{chi\_{ijk}}\$ term). However, the distributions for the cool- down scheme are consistently broader than those of the warm- up schemes. This difference is associated with non- vanishing gauge charge excitations in the system. + +Lastly, we restate that a further study of both the chiral Hamiltonian in Eq.- \ref{eq:chiral_Hamiltonian} and the chiral Potts Hamiltonian in Eq.- \ref{eq:chiral_Hamiltonian} necessitates the implementation of a + +<--- Page Split ---> + +non- local update- \cite{placke2023ising} capable of avoiding the freezing observed in the simulations and characterized in the main text. However, we emphasize that the analysis performed in this work already characterizes the intricate and rich physics which are observed in this system." + +The paper is easy to read and of interest to people in frustrated magnetism and maybe fracton physics. But some of the claims are not entirely established. For example, are cool down simulations metastable ? Do we really have fractons ? Also, compared to literature, the new results deserve to be published, but I am not sure they have enough impact for Nature Communications. + +We thank the referee for his/her careful assessment of our work while pointing out the possible confusion on the fracton excitations. We have addressed this criticism above and modified the main text and supplementary information accordingly. + +We continue to believe that our work is of great interest to both the frustrated- magnetism and fracton communities. In particular, our work sits at the junction of these two fields and also represents a unique case where fracton excitations can be realized in a simple model with realistic spin exchange interactions. The novelty of our findings is two- fold, (i) it establishes an unforeseen and highly nontrivial connection between time- reversal symmetry breaking and fractons. It thus puts forth a novel mechanism for realizing fractons in a whole new class of spin models, a problem which is much in vogue, and (ii) it establishes a whole new genre of spin liquids by expanding to the classical regime, the paradigm of Kalmeyer- Laughlin chiral quantum spin liquids about three decades after they were introduced. The Kalmeyer- Laughlin chiral spin liquid (and the parent fractional quantum Hall state) introduced the notion of topological order and opened an entire field of research with classifying topological and quantum orders a la X.- G. Wen. In similar spirit, our model of a classical chiral spin liquid in the classical domain, along with its effective theory, opens exciting new avenues for further research. It calls for an exploration and development of a mathematical classification scheme and formalism which would enable distinguishing different types of classical chiral spin liquids and the associated orders. Thus, in addition to its impact, given the profoundness and broad character of the results, our work will be of appeal and kindle the interest of a large community of researchers. + +## Small comments + +Sometimes the paper is technical. For example, what is a pinch point and bow tie in structure factor ? A possible paper of interest to the author, Gia- Wei Chern and Congjun Wu, Four- Coloring Model and Frustrated Superfluidity in the Diamond Lattice, PRL 112, 020601 (2014) + +We thank the referee for pointing out this technical detail which may result in a confusion for a general reader. We have now added an explanation as follows: + +"As the temperature is decreased these features sharpen up leading to the observation of two- fold pinch points- \cite{lsakov- 2004, Pretko_ fractonsPhysRevB.98.115134, Pretko- 2017, yan2023classification_1, yan2023classification_2, Castelnovo- 2012, Benton_ topological_ PhysRevLett.127.107202, Davier_ spanish_group_ PhysRevB.108.054408, Chern2014fourColoring}, see Fig.- \ref{fig:Sq}(b), resulting in connected bow tie and diamond patterns in the \(\mathbb{S}[\mathrm{hh}|\mathrm{ell}]\mathbb{S}\) and \(\mathbb{S}[\mathrm{hk}0]\mathbb{S}\) planes, respectively. The two- fold pinch point features reflect dipolar correlations between the spin degrees of freedom and are indicative of an energetically imposed Gauss' law constraint on certain gauge field \(\mathbb{S}\mathrm{hm}\mathrm{B}^{\ast}(\mathrm{c})\mathbb{S}\) , namely \(\mathbb{S}\mathrm{nabla}\mathrm{l}\mathrm{c}\mathrm{dot}\mathrm{l}\mathrm{bm}\mathrm{B}^{\ast}(\mathrm{c})\mathrm{=}0\mathbb{S}\) , describing an effective low- temperature theory of the system- \cite{Chern2014fourColoring, Moessner- Chalker- 98)." + +## Reviewer #2 (Remarks to the Author): + +In this article, Lozano- Gomez et al. considered chiral interactions between classical spins defined on a pyrochlore lattice and found a classical spin liquid state captured by an effective gauge theory. Starting from the detailed analysis of the chiral interaction defined on a single tetrahedron, they identified 12 distinct ground state configurations. Then, using a classical Monte- Carlo simulation, thermodynamic properties of this model on larger systems were + +<--- Page Split ---> + +investigated. They further derived an effective 4- state (chiral) Potts model that has a ground state configuration corresponding to that of the original chiral model and developed an effective gauge theory based on an effective Potts model including chiral interactions. The existence of chiral interactions makes the chiral Potts model distinct from the regular Potts model, modifying the ground state manifold and the property of excitations. + +I think the authors are successful in describing the emergent gauge structure by chiral interactions, leading to a classical spin liquid state on a 3- dimensional pyrochlore lattice. The paper is written clearly and, therefore, could be published. However, I have a mixed feeling whether or not I should recommend the publication of this work in Nature Communications as explained below. + +Introducing chiral interactions on a pyrochlore lattice is a new way to realize a spin liquid state, both ingredients and consequence appear to be novel. However, the behavior of the proposed model does not seem to be so different from the other spin models, such as dipolar interactions on a pyrochlore lattice, showing two- fold pinch points in the spin structure factor and a Coulomb phase of bions. Is there fundamental difference between the different models and between the current classical spin liquid vs. a (quantum) spin ice? + +We thank the reviewer #2 for raising the important question on how "our" chiral spin liquid can be fundamentally differentiated from other spin liquids that have been previously realized in the pyrochlore lattice. As the reviewer pointed out, and not unlike in classical spin ice, the ground- state manifold of the novel chiral spin liquid is characterized by absence of bionic charges and the low- energy description based on divergence- free gauge fields, resulting in the observation of two- fold pinch points in the correlation functions. The chiral spin liquid, however, also possesses an additional constraint on the gauge fields which restricts the chirality of the total gauge flux in every tetrahedra; such a constraint is introduced by the chiral interaction in the Hamiltonian and is described by the second term in Eq. (9). Although this additional constraint seems rather harmless and inconsequential, it has severe ramifications in the gauge fields and its associated charges in the system. Indeed, and as pointed out in section "Excitations of the chiral Potts model" of our draft, this constraint identifies an additional excitation associated with having a left- hand chirality in the total gauge flux of a single tetrahedra even when no bionic charge is present. The inclusion of this charge results in the confinement of the bionic charges, which in the regular Potts model (and similar to the monopoles in classical spin ice) are free to move. Additionally, in section "Excitations of the chiral Potts model", we comment on how this new chiral constraint severely restricts the motion of both of these charges, which is one of the tell- tale signs we use to identify these as fractonic charges. Altogether, the inclusion of the left- hand chiral charge and its restricted mobility leads to a spin- liquid phase whose gauge charges are fundamentally different from those of the Coulomb spin liquids mentioned by the reviewer. + +To emphasize this point and to echo the fundamental distinction between this novel chiral spin liquid and formerly introduced spin liquids in the pyrochlore lattice, we have modified the following text in the discussion of our results. + +"We emphasize that the restriction on the chirality of the gauge fluxes and the restricted motion of the associated gauge charges fundamentally differentiate the chiral spin liquid realized for the model in Eq. (1) and (10) from previously identified spin liquid phases in the pyrochlore lattice. Additionally, and of particular interest for the study of fracton models, the realization of fractonic charges identifies the chiral Hamiltonian in Eq.\\~eqref{eq:chiral_Hamiltonian) on the pyrochlore lattice as a \\*simple" fracton model whose further study may shed light on the intricate physics associated with these systems." + +Since a chiral interaction on a triangle requires an (effective) magnetic field penetrating the triangle (Ref. 26), how the interactions are arranged appears to imply that magnetic fluxes are coming from the inside of a tetrahedron to the outside through all triangle surfaces, or vice versa, as if a magnetic monopole is located at the center of the tetrahedron. If I am correct, the physical realization of the current model is extremely difficult, while it may not be entirely impossible. Could this be realized in a physical system, or the current proposal is purely theoretical with no relevance to the real world? + +As the reviewer #2 pointed out, the chiral interaction we considered is partially motivated by its derivation on Ref. 26 of our paper, which derives the chiral interaction in a t/U expansion when an external magnetic field is applied. For + +<--- Page Split ---> + +the pyrochlore lattice, this interaction would indeed require a local magnetic field which points from every sublattice position into the center of every single up (or down) tetrahedron. Such a field configuration cannot be produced externally, however, such a field is known to occur internally in the family of the pyrochlore iridates \(A_{2}Ir_{2}O_{7}\) , with \(A\) a rare- earth ion. In this family of compounds, the \(Ir\) ions may undergo a phase transition into an all- in- all- out symmetry- breaking phase at elevated temperatures compared to the strength of the exchange interaction typically observed for the rare- earth ions in the \(A\) sites [Witczak- Krempa et al, Annu. Rev. Condens. Matter Phys. 5, 57 2014]. The magnetic order in the \(Ir\) ions results in an effective molecular field along the local \(z\) direction for the \(A\) sites. The manifestation of a weak local magnetic field on rare- earth ions on the \(A\) sites consequently identifies the family \(A_{2}Ir_{2}O_{7}\) compounds to be the natural candidates for the realization of the chiral spin liquid we have introduced and studied in our work. + +Because of the above points and considering how the paper is written (highly theoretical), the paper may not appeal to the broad audience of Nature Communications. The current manuscript may be better suited to other journal, where people specialized in the frustrated magnetism could enjoy it. Could the authors modify the manuscript so that broad audience could access? + +We thank the reviewer #2 for pointing out how the current presentation of our work may be missing an important connection to the experimental realization of the classical spin liquid we have uncovered. Based on our previous comment on the realization of this spin Hamiltonian in the pyrochlore iridates \(A_{2}Ir_{2}O_{7}\) , as well as the possible observation of associated thermodynamic features for systems in the proximity of this model, we have included the following text in the main body of our work to point out the possible candidate compounds to realize this novel chiral spin liquid. + +"As we have previously discussed, the chiral interaction in Eq.(1) descends from a t/U expansion where an external magnetic field is applied [ref. 26]. The realization of such an exchange term in the pyrochlore lattice would imply the presence of a local magnetic field pointing towards (away) the center of each tetrahedra. Such a local magnetic field is known to take place in the family of the pyrochlore iridates, described by the chemical formula \(A_{2}Ir_{2}O_{7}\) , where the \(A\) ions are typically rare earth elements, and both the \(A\) and the \(Ir\) ions occupy two interpenetrating pyrochlore lattices. In this family of compounds, the \(Ir\) ions may undergo a phase transition into an all- in- all- out symmetry- breaking phase at relatively high- temperatures compared to the strength of the exchange interaction typically observed for the rare- earth ions in the \(A\) sites [Witczak- Krempa et al, Annu. Rev. Condens. Matter Phys. 5, 57 2014]. The magnetic order in the \(Ir\) ions result in a relative weak effective molecular field along the local \(z\) direction for the rare- earth ions on the \(A\) sites [Witczak- Krempa et al, Annu. Rev. Condens. Matter Phys. 5, 57 2014]. Following Ref.[26], the introduction of a weak local magnetic field on rare- earth ions on the \(A\) sites may result in the chiral spin interactions we considered. Consequently, we identify the family \(A_{2}Ir_{2}O_{7}\) of compounds where the \(Ir\) ions order into an all- in- all- out symmetry breaking phase to be the natural candidates for the realization of the chiral interaction and therefore the chiral spin liquid we have introduced and studied in the present work." + +Furthermore, we note that even if the Hamiltonian for a candidate material in this family of compounds does not exactly match the interaction couplings considered in Eq. (10), the sole proximity to this spin liquid may yield remnant thermodynamic features associated with the spin liquid. Indeed, such remnant features behavior have been predicted and observed for other spin liquids in the pyrochlore lattice, this being the case for \(Yb_{2}Ti_{2}O_{7}\) [A. Scheie et al, Phys. Rev. Lett. 129, 217202 (2022)] and \(FeF_{3}\) [A. Sadeghi et al, Phys. Rev. B 91, 140407 (2015)], and even for other frustrated lattices as is the case for the recently synthetized trillium lattice compounds \(K_{2}Ni_{2}(SO_{4})_{3}\) [M. G. Gonzalez et al, Nature Communications 15, 7191 (2024)]." + +<--- Page Split ---> + +Other suggestions + +Some of the subsections may have alternative titles, such as "Regular Potts model" => "Gauge structure of the regular Potts model", "Chiral Potts model" => "Gauge structure of the chiral Potts model", "Chiral and Heisenberg interactions" => "Competition between Chiral and Heisenberg interactions" + +We thank the reviewer #2 for suggesting the alternative titles for the sections we have proposed in our draft. Accordingly, we have decided to update two of the three suggested titles, which are now implemented in the main text. + +"Regular Potts model" => "Gauge structure of the regular Potts model" "Chiral Potts model" => "Gauge structure of the chiral Potts model" + +## List of edits performed to the submitted draft: + +In the main text: + +1. Edits to "Results" section in the subsections "numerical results", "Excitations of the chiral Potts model". +2. Edits to the "Discussion" section. +3. Change to the title of subsections previously named "Regular Potts model" and "Chiral Potts model". + +In the Supplementary Information: + +1. Edits to the "Effective Potts model" and "Thermodynamics from warm-up and cool-down schemes" sections. +2. Additional Figure S.7. + +<--- Page Split ---> + +## REVIEWER COMMENTS AND RESPONSE + +## Reviewer #1 (Remarks to the Author): + +I would like to thank the authors for their reply and their efforts. I find this new version clearer, especially related to the emergent physics of fractons, which is, as mentioned in my previous report, probably the most interesting aspect of this paper. + +There are still a few questions left unanswered, such as finite- size scaling of the specific heat (and other quantities), or the possibility for an order- by- disorder transition if an efficient non- local spin update were developed in order to thermalise this system at low temperatures (I realise that such an algorithm would be a technical challenge). + +But this manuscript has the advantage to present a relatively simple model that sits at the crossing point between chiral spin liquids, fractonic matter and out- of- equilibrium phenomena in a non- disordered magnet. The overall outcome is of sufficient interest that the unanswered questions may actually motivate further studies. It is difficult to say for sure, but this model could become a future toy model for fractons or chiral spin liquidity. + +Being easy to read and of interest to an active community of researchers, I would now recommend publication of this improved version of the manuscript. + +We would like to thank reviewer #1 for his positive assessment of our revised manuscript, highlighting its long- term impact, and his/her recommendation for the publication of our work in Nature Communications. We agree with the reviewer regarding the importance of a finite size scaling illustrating the preservation of the classical chiral spin liquid in the thermodynamic limit. To address this remark we have included an additional appendix to the supplementary information stating the following + +"To ensure that the analysis that we have presented is valid in the thermodynamic limit, we have performed a cMC simulations of the chiral Hamiltonian in Eq.\\~\eqref{eq:chiral_Hamiltonian} for three distinct system sizes with \(\$ \mathsf{N} = 4\mathsf{L}^{\wedge}3\$ spins, namely\) \ \(L = 6,8,10\) . The specific heat obtained for these systems is illustrated in Fig.\\~\ref{fig:MC_chirality_finite_size} where the double bump feature in the specific heat is preserved for all the systems studied. The agreement of the specific heat between these three system sizes suggests that the classical chiral spin liquid is indeed the phase realized by the chiral Hamiltonian in the thermodynamic limit at low temperatures." + +<--- Page Split ---> +![](images/Supplementary_Figure_9.jpg) + +
Supplementary Figure 9. Specific heat for the chiral Hamiltonian in Eq. \(\sim \text{eqref{eq:chiral\_Hamiltonian}}\) sampled through classical Monte-Carlo for three system sizes, namely \(\mathbb{S}\mathbb{L} = 6,8,10\mathbb{S}\) .
+ +Reviewer #2 (Remarks to the Author): + +The authors responded to my questions appropriately and revised the manuscript. I think the paper is now accessible to the broader audience and, therefore, would like to recommend the publication in Nature Communications. + +We would like to thank reviewer #2 for his positive assessment of our work and his recommendation for publication. + +<--- Page Split ---> diff --git a/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd b/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0486fa5cba726f9543f0ab67e3c6790d477f8605 --- /dev/null +++ b/peer_reviews/7cb8b50be8c49026cf8ac13beb4569b43e06bb19f84fa579e3c9df37d35f2466/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd @@ -0,0 +1,381 @@ +<|ref|>title<|/ref|><|det|>[[72, 50, 295, 78]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 912, 210]]<|/det|> +# A Classical Chiral Spin Liquid from Chiral Interactions on the Pyrochlore Lattice + +<|ref|>text<|/ref|><|det|>[[73, 224, 494, 241]]<|/det|> +Corresponding Author: Dr Daniel Lozano- Gómez + +<|ref|>text<|/ref|><|det|>[[72, 274, 864, 289]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 326, 144, 339]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 353, 219, 366]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 379, 160, 392]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 404, 238, 417]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 417, 920, 496]]<|/det|> +Lozano- Gomez and co- authors study a theoretical model of classical spins on pyrochlore lattice with three- spin interaction that induces a chirality. They show that ground state of model is equivalent to a four- color model with some special restrictions due to chirality. They claim it is a classical chiral spin liquid. They write a gauge theory for this model and discuss how excitations of this ground state may behave like classical fractons. They also discuss influence of Heisenberg interactions which is the main realistic perturbation of their model. They claim that Heisenberg interaction does not change a priori the nature of ground state. + +<|ref|>text<|/ref|><|det|>[[72, 508, 919, 600]]<|/det|> +As cited by the authors in introduction, citation 24 studied a similar model but with biquadratic interaction instead of chirality interaction. The main difference is that model of citation 24 orders and is not a spin liquid. Indeed the cool down simulations done by the authors does not show a phase transition for their model. It suggests maybe spin liquid. But the energy of cool down and warm up simulations are different, and warm up simulations show a peak in specific heat in the supplemental material. This peak is called crossover in supplemental material, but it looks like a phase transition in figure S5. It means that at low temperature, simulations are either frozen in some form of order when warm up, or they are disordered in a phase that is not the ground state when cool down. It is interesting, but not entirely conclusive for the presence of spin liquid. + +<|ref|>text<|/ref|><|det|>[[72, 612, 900, 639]]<|/det|> +As cited by the authors in page 6, citation 46 did the field theory with three gauge fields of four- color model on pyrochlore. The authors showed that chirality between spins of equation 1 becomes chirality in field theory in equation 9. + +<|ref|>text<|/ref|><|det|>[[72, 652, 919, 704]]<|/det|> +Then the authors explain why a consequence of chirality is that excitations of ground state may be like fractons. This is maybe most interesting result because there is a lot of research on fractons and simple models for fractons are rare. But the authors "leave the study of these charges and a more detailed characterization of the model in Eq. (4) for future work" so it is not sure if there are fractons in simulations. + +<|ref|>text<|/ref|><|det|>[[70, 704, 800, 718]]<|/det|> +Maybe fractons are responsible for the excited energy of simulations at low temperature when cool down ? + +<|ref|>text<|/ref|><|det|>[[72, 730, 914, 783]]<|/det|> +The paper is easy to read and of interest to people in frustrated magnetism and maybe fracton physics. But some of the claims are not entirely established. For example, are cool down simulations metastable ? Do we really have fractons ? Also, compared to literature, the new results deserve to be published, but I am not sure they have enough impact for Nature Communications. + +<|ref|>text<|/ref|><|det|>[[72, 809, 189, 821]]<|/det|> +Small comments + +<|ref|>text<|/ref|><|det|>[[72, 821, 837, 860]]<|/det|> +Sometimes the paper is technical. For example, what is a pinch point and bow tie in structure factor ? A possible paper of interest to the author, Gia- Wei Chern and Congjun Wu, Four- Coloring Model and Frustrated Superfluidity in the Diamond Lattice, PRL 112, 020601 (2014) + +<|ref|>text<|/ref|><|det|>[[73, 887, 282, 900]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 925, 161, 938]]<|/det|> +Reviewer #2 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 60, 238, 73]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 73, 920, 179]]<|/det|> +In this article, Lozano- Gomez et al. considered chiral interactions between classical spins defined on a pyrochlore lattice and found a classical spin liquid state captured by an effective gauge theory. Starting from the detailed analysis of the chiral interaction defined on a single tetrahedron, they identified 12 distinct ground state configurations. Then, using a classical Monte- Carlo simulation, thermodynamic properties of this model on larger systems were investigated. They further derived an effective 4- state (chiral) Potts model that has a ground state configuration corresponding to that of the original chiral model and developed an effective gauge theory based on an effective Potts model including chiral interactions. The existence of chiral interactions makes the chiral Potts model distinct from the regular Potts model, modifying the ground state manifold and the property of excitations. + +<|ref|>text<|/ref|><|det|>[[72, 178, 916, 231]]<|/det|> +I think the authors are successful in describing the emergent gauge structure by chiral interactions, leading to a classical spin liquid state on a 3- dimensional pyrochlore lattice. The paper is written clearly and, therefore, could be published. However, I have a mixed feeling whether or not I should recommend the publication of this work in Nature Communications as explained below. + +<|ref|>text<|/ref|><|det|>[[72, 230, 920, 296]]<|/det|> +Introducing chiral interactions on a pyrochlore lattice is a new way to realize a spin liquid state, both ingredients and consequence appear to be novel. However, the behavior of the proposed model does not seem to be so different from the other spin models, such as dipolar interactions on a pyrochlore lattice, showing two- fold pinch points in the spin structure factor and a Coulomb phase of bions. Is there fundamental difference between the different models and between the current classical spin liquid vs. a (quantum) spin ice? + +<|ref|>text<|/ref|><|det|>[[72, 295, 920, 410]]<|/det|> +Since a chiral interaction on a triangle requires an (effective) magnetic field penetrating the triangle (Ref. 26), how the interactions are arranged appears to imply that magnetic fluxes are coming from the inside of a tetrahedron to the outside through all triangle surfaces, or vice versa, as if a magnetic monopole is located at the center of the tetrahedron. If I am correct, the physical realization of the current model is extremely difficult, while it may not be entirely impossible. Could this be realized in a physical system, or the current proposal is purely theoretical with no relevance to the real world? Because of the above points and considering how the paper is written (highly theoretical), the paper may not appeal to the broad audience of Nature Communications. The current manuscript may be better suited to other journal, where people specialized in the frustrated magnetism could enjoy it. Could the authors modify the manuscript so that broad audience could access? + +<|ref|>text<|/ref|><|det|>[[73, 410, 198, 423]]<|/det|> +Other suggestions + +<|ref|>text<|/ref|><|det|>[[73, 423, 914, 464]]<|/det|> +Some of the subsections may have alternative titles, such as "Regular Potts model" => "Gauge structure of the regular Potts model", "Chiral Potts model" => "Gauge structure of the chiral Potts model", "Chiral and Heisenberg interactions" => "Competition between Chiral and Heisenberg interactions" + +<|ref|>text<|/ref|><|det|>[[73, 476, 282, 490]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 515, 144, 528]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 541, 218, 554]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 565, 160, 579]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 592, 238, 605]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 605, 884, 647]]<|/det|> +I would like to thank the authors for their reply and their efforts. I find this new version clearer, especially related to the emergent physics of fractons, which is, as mentioned in my previous report, probably the most interesting aspect of this paper. + +<|ref|>text<|/ref|><|det|>[[72, 657, 916, 699]]<|/det|> +There are still a few questions left unanswered, such as finite- size scaling of the specific heat (and other quantities), or the possibility for an order- by- disorder transition if an efficient non- local spin update were developed in order to thermalise this system at low temperatures (I realise that such an algorithm would be a technical challenge). + +<|ref|>text<|/ref|><|det|>[[72, 698, 918, 752]]<|/det|> +But this manuscript has the advantage to present a relatively simple model that sits at the crossing point between chiral spin liquids, fractonic matter and out- of- equilibrium phenomena in a non- disordered magnet. The overall outcome is of sufficient interest that the unanswered questions may actually motivate further studies. It is difficult to say for sure, but this model could become a future toy model for fractons or chiral spin liquidity. + +<|ref|>text<|/ref|><|det|>[[72, 763, 867, 790]]<|/det|> +Being easy to read and of interest to an active community of researchers, I would now recommend publication of this improved version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 802, 282, 815]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 840, 161, 854]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 867, 238, 879]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 880, 875, 920]]<|/det|> +The authors responded to my questions appropriately and revised the manuscript. I think the paper is now accessible to the broader audience and, therefore, would like to recommend the publication in Nature Communications. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 49, 282, 62]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 426, 916, 480]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 481, 797, 495]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 495, 910, 548]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 548, 618, 561]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 88, 471, 106]]<|/det|> +## REVIEWER COMMENTS AND RESPONSE + +<|ref|>sub_title<|/ref|><|det|>[[115, 126, 379, 141]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 159, 882, 250]]<|/det|> +Lozano- Gomez and co- authors study a theoretical model of classical spins on pyrochlore lattice with three- spin interaction that induces a chirality. They show that ground state of model is equivalent to a four- color model with some special restrictions due to chirality. They claim it is a classical chiral spin liquid. They write a gauge theory for this model and discuss how excitations of this ground state may behave like classical fractons. They also discuss influence of Heisenberg interactions which is the main realistic perturbation of their model. They claim that Heisenberg interaction does not change a priori the nature of ground state. + +<|ref|>text<|/ref|><|det|>[[115, 268, 882, 387]]<|/det|> +As cited by the authors in introduction, citation 24 studied a similar model but with biquadratic interaction instead of chirality interaction. The main difference is that model of citation 24 orders and is not a spin liquid. Indeed the cool down simulations done by the authors does not show a phase transition for their model. It suggests maybe spin liquid. But the energy of cool down and warm up simulations are different, and warm up simulations show a peak in specific heat in the supplemental material. This peak is called crossover in supplemental material, but it looks like a phase transition in figure S5. It means that at low temperature, simulations are either frozen in some form of order when warm up, or they are disordered in a phase that is not the ground state when cool down. It is interesting, but not entirely conclusive for the presence of spin liquid. + +<|ref|>text<|/ref|><|det|>[[115, 404, 882, 450]]<|/det|> +As cited by the authors in page 6, citation 46 did the field theory with three gauge fields of four- color model on pyrochlore. The authors showed that chirality between spins of equation 1 becomes chirality in field theory in equation 9. + +<|ref|>text<|/ref|><|det|>[[115, 469, 882, 544]]<|/det|> +Then the authors explain why a consequence of chirality is that excitations of ground state may be like fractons. This is maybe most interesting result because there is a lot of research on fractons and simple models for fractons are rare. But the authors "leave the study of these charges and a more detailed characterization of the model in Eq. (4) for future work" so it is not sure if there are fractons in simulations. Maybe fractons are responsible for the excited energy of simulations at low temperature when cool down? + +<|ref|>text<|/ref|><|det|>[[115, 562, 880, 592]]<|/det|> +We thank the reviewer #1 for his/her overall review of our results and for pointing out the connection between the fractonic excitations and the unusual thermodynamic behavior observed in our simulations. + +<|ref|>text<|/ref|><|det|>[[115, 607, 882, 713]]<|/det|> +Indeed, and as the reviewer pointed out, the discrepancy between our warm- up and cool- down simulations is associated with fractonic excitations which are difficult to equilibrate. More specifically, as the temperature is lowered in a cool- down scheme, fractonic excitations tend to freeze in the lattice (due to their restricted mobility) and impede the system from fully accessing its low- energy manifold; this yields a higher internal energy from a cool- down scheme (as opposed to a warm- up scheme). This same behavior has been observed in other fracton systems with concomitant spin- glass- like behavior [R. M. Nandkishore and M. Hermele, Annu.Rev. Condens. Matter Phys. 10, 295 (2019)]. + +<|ref|>text<|/ref|><|det|>[[115, 728, 882, 773]]<|/det|> +To illustrate this point let us consider the two cases we have studied, first the chiral potts model introduced in Eq. (4) of the main text, and then the chiral Hamilotnian in Eq. (1) of the main text, both which are described by the same effective gauge theory in Eq. (9) of the main text. + +<|ref|>sub_title<|/ref|><|det|>[[116, 803, 304, 817]]<|/det|> +## 1. The chiral Potts model + +<|ref|>text<|/ref|><|det|>[[115, 833, 882, 877]]<|/det|> +As discussed in the main text, for the chiral potts model introduced in Eq. (4), the ground- state configurations have a vanishing energy, and the elementary excitations are bionic charges and chiral charges. We note that the mobility of these charges is severely restricted, as is discussed and characterized in the main text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 179]]<|/det|> +In Fig. 1, we show the internal energy and specific heat per lattice site for both a cool-down and a warm-up scheme, and a single Potts configuration at low temperatures sampled from cool-down classical Monte-Carlo simulations. For the cool-down scheme, our simulations show a smooth evolution of the internal energy, and a Schottky-like peak in the specific heat. We note, however, that the low-temperature internal energy plateaus at a non-vanishing value as \(\mathrm{T} \rightarrow 0\) , implying that excitations are still present in the system. Indeed, by closely inspecting a low-temperature configuration (illustrated in Fig. 1), we see that both bins and chiral excitations are present. + +<|ref|>image<|/ref|><|det|>[[172, 184, 815, 456]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[155, 460, 814, 529]]<|/det|> +
Figure 1. Internal energy per lattice site \(E\) , specific heat per lattice site \(C / k_{B}\) , and a single Potts configuration sampled from a classical Monte-Carlo simulation on the chiral Potts model for a system of size \(L = 10\) . For the Potts configuration the black and purple circles label excited tetrahedra corresponding to a bion and a chiral charge, respectively.
+ +<|ref|>text<|/ref|><|det|>[[115, 542, 883, 633]]<|/det|> +The presence of these charges at low temperatures is associated with their restricted mobility, which in turn lead to a freezing- in of the excitations as the temperature is lowered. A similar picture is seen if we now perform a warm- up scheme for the chiral Potts model starting from a ground- state configuration. In such a case the internal energy sampled by the classical Monte- Carlo does plateau at zero energy at low temperatures. However, and similar to the cool down- scheme, the warm- up scheme is frozen in the initial low- temperature configuration because thermal excitations cannot be easily generated. + +<|ref|>sub_title<|/ref|><|det|>[[116, 649, 304, 663]]<|/det|> +## 2. The chiral Hamiltonian + +<|ref|>text<|/ref|><|det|>[[114, 677, 883, 889]]<|/det|> +As in the chiral Potts model, and as noted by the reviewer #1, the Monte- Carlo simulations of the chiral Hamiltonian in Eq. (4) present a similar discrepancy between the energy of the cool- down and warm- up schemes. In the chiral Hamiltonian, however, the bionic and chiral charges are not quantized but are instead continuous degrees of freedom due to the continuous nature of the underlying classical spins. Consequently, thermal spin fluctuations can thermally depopulate these charges. This effect may also be understood as the melting of a charge. A consequence of this thermal depopulation of the charges is that the internal energy of the system sampled from a cool- down scheme slowly decreases with temperature, although it remains above that of the internal energy sampled with a warm- up scheme, as shown in Fig. 7 of the main text. We note that the non- quantized character of the gauge charges for the chiral Hamiltonian refrains us from exactly locating their position in the lattice and producing an analysis similar to the one performed for the chiral Potts Hamiltonian [Flores- Calderon et al, arXiv:2402.03083 (2024)]. Instead, we can study the evolution of other statistical quantities which are directly associated with the ground- state manifold. Figure 2 illustrates the nearest- neighbor dot product and the single- triangle chirality for warm- up and cool- down schemes sampled at different temperatures and averaged over 200 configurations. At low temperatures all distributions are centered about the ground- state prediction, however, the distributions for the cool down scheme are consistently + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 89, 881, 120]]<|/det|> +broader than those of the warm up schemes. This difference can be associated with non- vanishing excitations in the system. + +<|ref|>image<|/ref|><|det|>[[80, 142, 900, 472]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[171, 488, 799, 555]]<|/det|> +
Figure 2. Nearest-neighbor dot product (left) and single-triangle chirality (right) for a cool-down scheme on the upper row, and a warm-up scheme on the lower row. The black lines label the expected value of these quantities in an exact ground-state configuration, which is \(-1 / 3\) for the nearest-neighbor dot product and \(-4 / (3\sqrt{3})\) for the chirality term.
+ +<|ref|>text<|/ref|><|det|>[[115, 568, 882, 675]]<|/det|> +We emphasize that in the warm- up simulations of both models, the system freezes in the initial configuration. Moreover, and as mentioned in our draft, there is an at- least sub- extensive number of ground states for these models which are associated by a cyclic permutation of all spins (or Potts degrees of freedom) in an infinite plane bisecting the pyrochlore lattice, see Fig. 3. We note that all of these ground states are equivalent and as such a warm- up simulation on these would also display the same freezing. In particular, and as shown in section "thermodynamics from warm- up and cool- down schemes" of the Supplement, such an equivalence is shown for the chiral Hamiltonian in Eq. (1) where we show warm- up simulations starting from three distinct ground- state configurations. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[355, 132, 675, 350]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[155, 360, 815, 421]]<|/det|> +
Figure 3. Monte-Carlo unit cell with \(L = 4\) where only the "up" tetrahedra are shown. Here all the blue tetrahedra belong to a single infinite kagome plane which bisects the pyrochlore lattice. The apparent observation of three different planes is a consequence of the periodic boundary conditions of the system.
+ +<|ref|>text<|/ref|><|det|>[[115, 434, 882, 557]]<|/det|> +Let us now comment on how this lack of proper equilibration could be resolved. As we pointed out for both the chiral Potts model and the chiral Hamiltonian, the discrepancy between their temperature- sweeping schemes is associated with remnant charges in the low- temperature phase. To avoid these charges from freezing out in the cool- down scheme and the freezing in a ground- state configuration in the warm- up scheme, a non- local update would be necessary, capable of moving these charges around with no additional energy cost and of connecting different ground- state configurations. In the main text we have discussed the pre- conditions this update must fulfill, however, due to the intricacy of the pyrochlore lattice geometry, we have not been able to implement such a non- local move in our simulations. + +<|ref|>text<|/ref|><|det|>[[115, 571, 882, 647]]<|/det|> +Indeed, a recent work on a classical spin liquid with fractonic excitations showed that such an algorithm can radically improve the thermodynamic behavior of the simulation [B. Placke et al., arXiv:2306.13151 (2023)]. In that case, however, the fractonic excitations they identify are partially mobile which allows for the construction of such moves. This is not the case for the models we considered and therefore complicates the full identification and construction of such non- local updates. + +<|ref|>text<|/ref|><|det|>[[115, 661, 882, 828]]<|/det|> +To summarize, we have studied two systems which are described by the same effective gauge theory at low temperatures. These systems possess fracton excitations with restricted mobility where the excitations are bions and chiral charges. In a cool down Monte- Carlo simulation, the restricted mobility of these charges results in freezing at low temperatures in both systems. The presence of these excitations is exposed by the study of the configuration in the Potts model and the distribution of the nearest- neighbor dot product and chirality term for the chiral Hamiltonian. Additionally, in a warm up Monte- Carlo simulation starting from a ground- state configuration, the restricted mobility results in the freezing of the system in the initial configuration at low temperatures. To overcome the discrepancy between the different temperature schemes, a non- local algorithm would be necessary. In the main text of our draft we have outlined what are the conditions such a non- local update must fulfill and showed a family of these non- local updates corresponds to the permutation of all spins (Potts degrees of freedom) in an infinite plane bisecting the system. + +<|ref|>text<|/ref|><|det|>[[115, 842, 721, 857]]<|/det|> +In our efforts to clarify this point in our draft we have added the following text to the main text, + +<|ref|>text<|/ref|><|det|>[[171, 872, 882, 902]]<|/det|> +"The restricted motion of these excitations results in glassy dynamics typically observed in fracton systems- \cite{Hermele_fractons_2019}. Indeed, performing a warm- up and cool- down classical Monte- Carlo + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 89, 883, 300]]<|/det|> +simulation on the chiral Potts model exposes a similar behavior to the one observed in Fig.- \ref{fig:MC_warm_up_cool_down}: in the cool- down scheme, the restricted motion results in freezing of charges at low temperatures yielding a higher internal energy in these simulations. In the warm- up scheme, the restricted motion results in freezing of the simulations at low temperatures about the initial configuration, we refer the reader to the SI for further details on the chiral Potts model. Similarly, for the chiral model in Eq.- \ref{eq:chiral_Hamiltonian}, the fractonic nature of these charges is responsible for the disagreement between the internal energy illustrated in Fig.- \ref{fig:MC_warm_up_cool_down}, as well as the histograms of the nearest- neighbor spin correlation in Fig.- \ref{fig:MC_dot_product_warm_cool} measured in the warm- up and cool- down schemes. In the chiral Hamiltonian, however, the continuous nature of the spin degrees of freedom allows for a slow thermal depopulation of the gauge charges and therefore a decreasing internal energy with decreasing temperature. The presence of these charges however is reflected in the width of the histograms in Fig.- \ref{fig:MC_dot_product_warm_cool} which are consistently broader in the cool- down simulations. For more details regarding the difference between the cool- down and warm- up schemes for the chiral Hamiltonian in Eq.- \ref{eq:chiral_Hamiltonian} we refer the reader to the SI." + +<|ref|>text<|/ref|><|det|>[[117, 314, 881, 344]]<|/det|> +In addition, we have modified two sections in the supplement. First, we have modified the section "Effective Potts Model" to include the warm- up Monte- Carlo for the Potts model shown in Fig. 1, along with the following text + +<|ref|>text<|/ref|><|det|>[[173, 373, 882, 449]]<|/det|> +"A similar picture is seen when performing a warm- up scheme starting from a ground- state configuration, see red curve in Fig.- \ref{fig:Potts_model}(a) and (b). In such a case the internal energy sampled by the classical Monte- Carlo does plateau at zero energy at low temperatures. However, and similar to the cool- down scheme, the warm- up scheme is frozen in the initial low- temperature configuration due to the high cost associated with generating and moving the fractonic charges." + +<|ref|>text<|/ref|><|det|>[[116, 464, 880, 495]]<|/det|> +and the section "Thermodynamics from warm- up and cool- down schemes" by including the chirality distributions shown in Fig. 2 along with the following text + +<|ref|>text<|/ref|><|det|>[[173, 508, 882, 569]]<|/det|> +"... The peak in the specific heat observed in Fig.- \ref{fig:MC_warm_up_cool_down_E_and_C} in the warm- up simulations is associated with the freezing of the system into the initial partially ordered configuration. Indeed, our results suggest that the freezing observed in the warm- up scheme is bound to take place irrespective of the initial ground- state configuration selected. + +<|ref|>text<|/ref|><|det|>[[173, 583, 882, 855]]<|/det|> +Similar to the chiral Potts model, the discrepancy between the warm- up and cool- down schemes can be associated with the presence of non- vanishing charges. In the chiral Hamiltonian, however, the bionic and chiral charges are not quantized but are instead continuous degrees of freedom which can be thermally depopulated by spin fluctuations. A consequence of such a thermal depopulation is that the internal energy of the system sampled from a cool- down scheme slowly decreases with temperature, although it remains above that of the internal energy sampled with a warm- up scheme, as shown in Fig.- \ref{fig:MC_warm_up_cool_down} of the main text. Furthermore, the non- quantize character of the gauge charges for the chiral Hamiltonian refrains us from exactly locating their position in the lattice and producing an analysis similar to the one performed for the chiral Potts Hamiltonian in Fig.- \ref{fig:Potts_model}- \text{cite{florescalderon2024irrational}}. Instead, we can study the evolution of other statistical quantities which are directly associated with the ground- state manifold. Figure- \ref{fig:MC_dot_product_warm_cool} in the main text and Figure- \ref{fig:MC_chirality_warm_cool} illustrates the nearest- neighbor dot product and the single triangle chirality for warm- up and cool- down schemes sampled at different temperatures and averaged over 200 configurations, respectively. At low temperatures, all distributions are centered about the ground- state prediction (this being \$- 1/3\$ for the nearest- neighbor dot product and \$- 4/(3\sqt{3})\$ for the chiral \$\$\chi_{chi\_{ijk}}\$ term). However, the distributions for the cool- down scheme are consistently broader than those of the warm- up schemes. This difference is associated with non- vanishing gauge charge excitations in the system. + +<|ref|>text<|/ref|><|det|>[[172, 870, 882, 900]]<|/det|> +Lastly, we restate that a further study of both the chiral Hamiltonian in Eq.- \ref{eq:chiral_Hamiltonian} and the chiral Potts Hamiltonian in Eq.- \ref{eq:chiral_Hamiltonian} necessitates the implementation of a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 89, 882, 134]]<|/det|> +non- local update- \cite{placke2023ising} capable of avoiding the freezing observed in the simulations and characterized in the main text. However, we emphasize that the analysis performed in this work already characterizes the intricate and rich physics which are observed in this system." + +<|ref|>text<|/ref|><|det|>[[115, 152, 882, 212]]<|/det|> +The paper is easy to read and of interest to people in frustrated magnetism and maybe fracton physics. But some of the claims are not entirely established. For example, are cool down simulations metastable ? Do we really have fractons ? Also, compared to literature, the new results deserve to be published, but I am not sure they have enough impact for Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 230, 882, 275]]<|/det|> +We thank the referee for his/her careful assessment of our work while pointing out the possible confusion on the fracton excitations. We have addressed this criticism above and modified the main text and supplementary information accordingly. + +<|ref|>text<|/ref|><|det|>[[114, 290, 882, 500]]<|/det|> +We continue to believe that our work is of great interest to both the frustrated- magnetism and fracton communities. In particular, our work sits at the junction of these two fields and also represents a unique case where fracton excitations can be realized in a simple model with realistic spin exchange interactions. The novelty of our findings is two- fold, (i) it establishes an unforeseen and highly nontrivial connection between time- reversal symmetry breaking and fractons. It thus puts forth a novel mechanism for realizing fractons in a whole new class of spin models, a problem which is much in vogue, and (ii) it establishes a whole new genre of spin liquids by expanding to the classical regime, the paradigm of Kalmeyer- Laughlin chiral quantum spin liquids about three decades after they were introduced. The Kalmeyer- Laughlin chiral spin liquid (and the parent fractional quantum Hall state) introduced the notion of topological order and opened an entire field of research with classifying topological and quantum orders a la X.- G. Wen. In similar spirit, our model of a classical chiral spin liquid in the classical domain, along with its effective theory, opens exciting new avenues for further research. It calls for an exploration and development of a mathematical classification scheme and formalism which would enable distinguishing different types of classical chiral spin liquids and the associated orders. Thus, in addition to its impact, given the profoundness and broad character of the results, our work will be of appeal and kindle the interest of a large community of researchers. + +<|ref|>sub_title<|/ref|><|det|>[[115, 534, 226, 547]]<|/det|> +## Small comments + +<|ref|>text<|/ref|><|det|>[[115, 549, 882, 593]]<|/det|> +Sometimes the paper is technical. For example, what is a pinch point and bow tie in structure factor ? A possible paper of interest to the author, Gia- Wei Chern and Congjun Wu, Four- Coloring Model and Frustrated Superfluidity in the Diamond Lattice, PRL 112, 020601 (2014) + +<|ref|>text<|/ref|><|det|>[[115, 612, 882, 641]]<|/det|> +We thank the referee for pointing out this technical detail which may result in a confusion for a general reader. We have now added an explanation as follows: + +<|ref|>text<|/ref|><|det|>[[173, 658, 882, 777]]<|/det|> +"As the temperature is decreased these features sharpen up leading to the observation of two- fold pinch points- \cite{lsakov- 2004, Pretko_ fractonsPhysRevB.98.115134, Pretko- 2017, yan2023classification_1, yan2023classification_2, Castelnovo- 2012, Benton_ topological_ PhysRevLett.127.107202, Davier_ spanish_group_ PhysRevB.108.054408, Chern2014fourColoring}, see Fig.- \ref{fig:Sq}(b), resulting in connected bow tie and diamond patterns in the \(\mathbb{S}[\mathrm{hh}|\mathrm{ell}]\mathbb{S}\) and \(\mathbb{S}[\mathrm{hk}0]\mathbb{S}\) planes, respectively. The two- fold pinch point features reflect dipolar correlations between the spin degrees of freedom and are indicative of an energetically imposed Gauss' law constraint on certain gauge field \(\mathbb{S}\mathrm{hm}\mathrm{B}^{\ast}(\mathrm{c})\mathbb{S}\) , namely \(\mathbb{S}\mathrm{nabla}\mathrm{l}\mathrm{c}\mathrm{dot}\mathrm{l}\mathrm{bm}\mathrm{B}^{\ast}(\mathrm{c})\mathrm{=}0\mathbb{S}\) , describing an effective low- temperature theory of the system- \cite{Chern2014fourColoring, Moessner- Chalker- 98)." + +<|ref|>sub_title<|/ref|><|det|>[[115, 811, 378, 825]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 844, 882, 904]]<|/det|> +In this article, Lozano- Gomez et al. considered chiral interactions between classical spins defined on a pyrochlore lattice and found a classical spin liquid state captured by an effective gauge theory. Starting from the detailed analysis of the chiral interaction defined on a single tetrahedron, they identified 12 distinct ground state configurations. Then, using a classical Monte- Carlo simulation, thermodynamic properties of this model on larger systems were + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 148]]<|/det|> +investigated. They further derived an effective 4- state (chiral) Potts model that has a ground state configuration corresponding to that of the original chiral model and developed an effective gauge theory based on an effective Potts model including chiral interactions. The existence of chiral interactions makes the chiral Potts model distinct from the regular Potts model, modifying the ground state manifold and the property of excitations. + +<|ref|>text<|/ref|><|det|>[[115, 150, 881, 209]]<|/det|> +I think the authors are successful in describing the emergent gauge structure by chiral interactions, leading to a classical spin liquid state on a 3- dimensional pyrochlore lattice. The paper is written clearly and, therefore, could be published. However, I have a mixed feeling whether or not I should recommend the publication of this work in Nature Communications as explained below. + +<|ref|>text<|/ref|><|det|>[[115, 224, 882, 300]]<|/det|> +Introducing chiral interactions on a pyrochlore lattice is a new way to realize a spin liquid state, both ingredients and consequence appear to be novel. However, the behavior of the proposed model does not seem to be so different from the other spin models, such as dipolar interactions on a pyrochlore lattice, showing two- fold pinch points in the spin structure factor and a Coulomb phase of bions. Is there fundamental difference between the different models and between the current classical spin liquid vs. a (quantum) spin ice? + +<|ref|>text<|/ref|><|det|>[[114, 314, 882, 570]]<|/det|> +We thank the reviewer #2 for raising the important question on how "our" chiral spin liquid can be fundamentally differentiated from other spin liquids that have been previously realized in the pyrochlore lattice. As the reviewer pointed out, and not unlike in classical spin ice, the ground- state manifold of the novel chiral spin liquid is characterized by absence of bionic charges and the low- energy description based on divergence- free gauge fields, resulting in the observation of two- fold pinch points in the correlation functions. The chiral spin liquid, however, also possesses an additional constraint on the gauge fields which restricts the chirality of the total gauge flux in every tetrahedra; such a constraint is introduced by the chiral interaction in the Hamiltonian and is described by the second term in Eq. (9). Although this additional constraint seems rather harmless and inconsequential, it has severe ramifications in the gauge fields and its associated charges in the system. Indeed, and as pointed out in section "Excitations of the chiral Potts model" of our draft, this constraint identifies an additional excitation associated with having a left- hand chirality in the total gauge flux of a single tetrahedra even when no bionic charge is present. The inclusion of this charge results in the confinement of the bionic charges, which in the regular Potts model (and similar to the monopoles in classical spin ice) are free to move. Additionally, in section "Excitations of the chiral Potts model", we comment on how this new chiral constraint severely restricts the motion of both of these charges, which is one of the tell- tale signs we use to identify these as fractonic charges. Altogether, the inclusion of the left- hand chiral charge and its restricted mobility leads to a spin- liquid phase whose gauge charges are fundamentally different from those of the Coulomb spin liquids mentioned by the reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 584, 881, 614]]<|/det|> +To emphasize this point and to echo the fundamental distinction between this novel chiral spin liquid and formerly introduced spin liquids in the pyrochlore lattice, we have modified the following text in the discussion of our results. + +<|ref|>text<|/ref|><|det|>[[173, 629, 882, 720]]<|/det|> +"We emphasize that the restriction on the chirality of the gauge fluxes and the restricted motion of the associated gauge charges fundamentally differentiate the chiral spin liquid realized for the model in Eq. (1) and (10) from previously identified spin liquid phases in the pyrochlore lattice. Additionally, and of particular interest for the study of fracton models, the realization of fractonic charges identifies the chiral Hamiltonian in Eq.\\~eqref{eq:chiral_Hamiltonian) on the pyrochlore lattice as a \\*simple" fracton model whose further study may shed light on the intricate physics associated with these systems." + +<|ref|>text<|/ref|><|det|>[[115, 764, 882, 854]]<|/det|> +Since a chiral interaction on a triangle requires an (effective) magnetic field penetrating the triangle (Ref. 26), how the interactions are arranged appears to imply that magnetic fluxes are coming from the inside of a tetrahedron to the outside through all triangle surfaces, or vice versa, as if a magnetic monopole is located at the center of the tetrahedron. If I am correct, the physical realization of the current model is extremely difficult, while it may not be entirely impossible. Could this be realized in a physical system, or the current proposal is purely theoretical with no relevance to the real world? + +<|ref|>text<|/ref|><|det|>[[115, 870, 882, 900]]<|/det|> +As the reviewer #2 pointed out, the chiral interaction we considered is partially motivated by its derivation on Ref. 26 of our paper, which derives the chiral interaction in a t/U expansion when an external magnetic field is applied. For + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 252]]<|/det|> +the pyrochlore lattice, this interaction would indeed require a local magnetic field which points from every sublattice position into the center of every single up (or down) tetrahedron. Such a field configuration cannot be produced externally, however, such a field is known to occur internally in the family of the pyrochlore iridates \(A_{2}Ir_{2}O_{7}\) , with \(A\) a rare- earth ion. In this family of compounds, the \(Ir\) ions may undergo a phase transition into an all- in- all- out symmetry- breaking phase at elevated temperatures compared to the strength of the exchange interaction typically observed for the rare- earth ions in the \(A\) sites [Witczak- Krempa et al, Annu. Rev. Condens. Matter Phys. 5, 57 2014]. The magnetic order in the \(Ir\) ions results in an effective molecular field along the local \(z\) direction for the \(A\) sites. The manifestation of a weak local magnetic field on rare- earth ions on the \(A\) sites consequently identifies the family \(A_{2}Ir_{2}O_{7}\) compounds to be the natural candidates for the realization of the chiral spin liquid we have introduced and studied in our work. + +<|ref|>text<|/ref|><|det|>[[114, 281, 882, 342]]<|/det|> +Because of the above points and considering how the paper is written (highly theoretical), the paper may not appeal to the broad audience of Nature Communications. The current manuscript may be better suited to other journal, where people specialized in the frustrated magnetism could enjoy it. Could the authors modify the manuscript so that broad audience could access? + +<|ref|>text<|/ref|><|det|>[[114, 356, 882, 454]]<|/det|> +We thank the reviewer #2 for pointing out how the current presentation of our work may be missing an important connection to the experimental realization of the classical spin liquid we have uncovered. Based on our previous comment on the realization of this spin Hamiltonian in the pyrochlore iridates \(A_{2}Ir_{2}O_{7}\) , as well as the possible observation of associated thermodynamic features for systems in the proximity of this model, we have included the following text in the main body of our work to point out the possible candidate compounds to realize this novel chiral spin liquid. + +<|ref|>text<|/ref|><|det|>[[173, 466, 883, 706]]<|/det|> +"As we have previously discussed, the chiral interaction in Eq.(1) descends from a t/U expansion where an external magnetic field is applied [ref. 26]. The realization of such an exchange term in the pyrochlore lattice would imply the presence of a local magnetic field pointing towards (away) the center of each tetrahedra. Such a local magnetic field is known to take place in the family of the pyrochlore iridates, described by the chemical formula \(A_{2}Ir_{2}O_{7}\) , where the \(A\) ions are typically rare earth elements, and both the \(A\) and the \(Ir\) ions occupy two interpenetrating pyrochlore lattices. In this family of compounds, the \(Ir\) ions may undergo a phase transition into an all- in- all- out symmetry- breaking phase at relatively high- temperatures compared to the strength of the exchange interaction typically observed for the rare- earth ions in the \(A\) sites [Witczak- Krempa et al, Annu. Rev. Condens. Matter Phys. 5, 57 2014]. The magnetic order in the \(Ir\) ions result in a relative weak effective molecular field along the local \(z\) direction for the rare- earth ions on the \(A\) sites [Witczak- Krempa et al, Annu. Rev. Condens. Matter Phys. 5, 57 2014]. Following Ref.[26], the introduction of a weak local magnetic field on rare- earth ions on the \(A\) sites may result in the chiral spin interactions we considered. Consequently, we identify the family \(A_{2}Ir_{2}O_{7}\) of compounds where the \(Ir\) ions order into an all- in- all- out symmetry breaking phase to be the natural candidates for the realization of the chiral interaction and therefore the chiral spin liquid we have introduced and studied in the present work." + +<|ref|>text<|/ref|><|det|>[[173, 720, 882, 833]]<|/det|> +Furthermore, we note that even if the Hamiltonian for a candidate material in this family of compounds does not exactly match the interaction couplings considered in Eq. (10), the sole proximity to this spin liquid may yield remnant thermodynamic features associated with the spin liquid. Indeed, such remnant features behavior have been predicted and observed for other spin liquids in the pyrochlore lattice, this being the case for \(Yb_{2}Ti_{2}O_{7}\) [A. Scheie et al, Phys. Rev. Lett. 129, 217202 (2022)] and \(FeF_{3}\) [A. Sadeghi et al, Phys. Rev. B 91, 140407 (2015)], and even for other frustrated lattices as is the case for the recently synthetized trillium lattice compounds \(K_{2}Ni_{2}(SO_{4})_{3}\) [M. G. Gonzalez et al, Nature Communications 15, 7191 (2024)]." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 237, 103]]<|/det|> +Other suggestions + +<|ref|>text<|/ref|><|det|>[[115, 104, 850, 149]]<|/det|> +Some of the subsections may have alternative titles, such as "Regular Potts model" => "Gauge structure of the regular Potts model", "Chiral Potts model" => "Gauge structure of the chiral Potts model", "Chiral and Heisenberg interactions" => "Competition between Chiral and Heisenberg interactions" + +<|ref|>text<|/ref|><|det|>[[115, 167, 856, 211]]<|/det|> +We thank the reviewer #2 for suggesting the alternative titles for the sections we have proposed in our draft. Accordingly, we have decided to update two of the three suggested titles, which are now implemented in the main text. + +<|ref|>text<|/ref|><|det|>[[172, 212, 632, 241]]<|/det|> +"Regular Potts model" => "Gauge structure of the regular Potts model" "Chiral Potts model" => "Gauge structure of the chiral Potts model" + +<|ref|>sub_title<|/ref|><|det|>[[115, 298, 507, 315]]<|/det|> +## List of edits performed to the submitted draft: + +<|ref|>text<|/ref|><|det|>[[115, 331, 221, 344]]<|/det|> +In the main text: + +<|ref|>text<|/ref|><|det|>[[144, 346, 840, 390]]<|/det|> +1. Edits to "Results" section in the subsections "numerical results", "Excitations of the chiral Potts model". +2. Edits to the "Discussion" section. +3. Change to the title of subsections previously named "Regular Potts model" and "Chiral Potts model". + +<|ref|>text<|/ref|><|det|>[[115, 405, 338, 419]]<|/det|> +In the Supplementary Information: + +<|ref|>text<|/ref|><|det|>[[140, 420, 875, 450]]<|/det|> +1. Edits to the "Effective Potts model" and "Thermodynamics from warm-up and cool-down schemes" sections. +2. Additional Figure S.7. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 125, 472, 143]]<|/det|> +## REVIEWER COMMENTS AND RESPONSE + +<|ref|>sub_title<|/ref|><|det|>[[115, 162, 438, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 199, 857, 254]]<|/det|> +I would like to thank the authors for their reply and their efforts. I find this new version clearer, especially related to the emergent physics of fractons, which is, as mentioned in my previous report, probably the most interesting aspect of this paper. + +<|ref|>text<|/ref|><|det|>[[115, 273, 881, 345]]<|/det|> +There are still a few questions left unanswered, such as finite- size scaling of the specific heat (and other quantities), or the possibility for an order- by- disorder transition if an efficient non- local spin update were developed in order to thermalise this system at low temperatures (I realise that such an algorithm would be a technical challenge). + +<|ref|>text<|/ref|><|det|>[[115, 347, 879, 437]]<|/det|> +But this manuscript has the advantage to present a relatively simple model that sits at the crossing point between chiral spin liquids, fractonic matter and out- of- equilibrium phenomena in a non- disordered magnet. The overall outcome is of sufficient interest that the unanswered questions may actually motivate further studies. It is difficult to say for sure, but this model could become a future toy model for fractons or chiral spin liquidity. + +<|ref|>text<|/ref|><|det|>[[115, 456, 801, 492]]<|/det|> +Being easy to read and of interest to an active community of researchers, I would now recommend publication of this improved version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 510, 870, 620]]<|/det|> +We would like to thank reviewer #1 for his positive assessment of our revised manuscript, highlighting its long- term impact, and his/her recommendation for the publication of our work in Nature Communications. We agree with the reviewer regarding the importance of a finite size scaling illustrating the preservation of the classical chiral spin liquid in the thermodynamic limit. To address this remark we have included an additional appendix to the supplementary information stating the following + +<|ref|>text<|/ref|><|det|>[[115, 657, 880, 803]]<|/det|> +"To ensure that the analysis that we have presented is valid in the thermodynamic limit, we have performed a cMC simulations of the chiral Hamiltonian in Eq.\\~\eqref{eq:chiral_Hamiltonian} for three distinct system sizes with \(\$ \mathsf{N} = 4\mathsf{L}^{\wedge}3\$ spins, namely\) \ \(L = 6,8,10\) . The specific heat obtained for these systems is illustrated in Fig.\\~\ref{fig:MC_chirality_finite_size} where the double bump feature in the specific heat is preserved for all the systems studied. The agreement of the specific heat between these three system sizes suggests that the classical chiral spin liquid is indeed the phase realized by the chiral Hamiltonian in the thermodynamic limit at low temperatures." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[147, 103, 864, 425]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[137, 427, 861, 483]]<|/det|> +
Supplementary Figure 9. Specific heat for the chiral Hamiltonian in Eq. \(\sim \text{eqref{eq:chiral\_Hamiltonian}}\) sampled through classical Monte-Carlo for three system sizes, namely \(\mathbb{S}\mathbb{L} = 6,8,10\mathbb{S}\) .
+ +<|ref|>text<|/ref|><|det|>[[115, 519, 420, 538]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 556, 813, 611]]<|/det|> +The authors responded to my questions appropriately and revised the manuscript. I think the paper is now accessible to the broader audience and, therefore, would like to recommend the publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 648, 774, 684]]<|/det|> +We would like to thank reviewer #2 for his positive assessment of our work and his recommendation for publication. + +<--- Page Split ---> diff --git a/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/images_list.json b/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..1fe8f1f5c4db6bf5d72cf3f87e8b67c6cb8baf7f --- /dev/null +++ b/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/images_list.json @@ -0,0 +1,482 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S33 (a) XRD patterns of the fresh catalysts. DF-TEM, HRTEM images and corresponding particle distribution of the fresh (b) 5Pt/P25, (c) 5Pd/P25, and (d) 5Cu/P25 catalysts.", + "footnote": [], + "bbox": [ + [ + 240, + 455, + 760, + 787 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. S34 (a) Methanol conversion and product selectivity of the 0.2Pt/P25, 0.2Pd/P25, and 0.2Cu/P25 catalysts; (b) Corresponding H₂ production rates and TOF; (c-f) HAADF-STEM images of the fresh 0.2Pt/P25 catalyst. Reaction conditions: 290 °C, a S/C ratio of 3/1, 0.1 MPa pressure, and a feed rate of 3 mL g⁻¹ h⁻¹.", + "footnote": [], + "bbox": [ + [ + 147, + 228, + 835, + 515 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S6 Feed rate dependence of methanol conversion and \\(\\mathrm{H}_2\\) production rates over 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts. Reaction conditions: catalyst \\(0.1\\mathrm{g} + \\mathrm{SiO}_2 0.2\\mathrm{g}\\) ; liquid feed of \\(\\mathrm{S / C} = 3\\) at \\(6 - 45\\mathrm{mL}\\mathrm{g}^{-1}\\mathrm{h}^{-1}\\) ; \\(\\mathrm{N}_2\\) carrier at \\(20\\mathrm{mL}\\mathrm{min}^{-1}\\) ; temperature: \\(290^{\\circ}\\mathrm{C}\\) .", + "footnote": [], + "bbox": [ + [ + 149, + 94, + 949, + 247 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig. 1 Catalytic performance and structural characteristics of catalysts in the MSR reaction. d, Apparent activation energy evaluation (methanol conversion less than 10%).", + "footnote": [], + "bbox": [ + [ + 363, + 85, + 636, + 247 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. S4 Catalytic performance as a function of varying Cd loadings on the P25 support. Reaction conditions: \\(290^{\\circ}\\mathrm{C}\\) , S/C ratio of 3/1, 0.1 MPa pressure, and \\(3\\mathrm{mL}\\mathrm{g}^{-1}\\mathrm{h}^{-1}\\) feed rate.", + "footnote": [], + "bbox": [ + [ + 147, + 90, + 857, + 283 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. S20 XRD patterns of (a) fresh and (b) spent catalysts with different Cd loadings. (c) Cd K-edge XANES spectra of fresh catalysts with different Cd loadings. (d) \\(\\mathrm{K}^{3}\\) -weighted \\(\\chi\\) (k) function of EXAFS spectra.", + "footnote": [], + "bbox": [ + [ + 163, + 95, + 835, + 505 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. S2 Comparison of catalytic performance between 5Cd/P25 and mixtures composed of varying ratios of 5Cd/A and 5Cd/R. Reaction conditions: 290 °C, S/C ratio of 3/1, 0.1 MPa pressure, and 3 mL g-1 h-1 feed rate.", + "footnote": [], + "bbox": [ + [ + 234, + 506, + 760, + 774 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. S36 (a) XRD patterns of fresh catalysts. (b) Catalytic performance. (c and d) HAADF-STEM images of the 5Cd/A-700Air catalyst. Reaction conditions: 290 $^{\\circ }C$ , a S/C ratio of 3/1, 0.1 MPa pressure, and a feed rate of 3 mL g-1 h-1.", + "footnote": [], + "bbox": [ + [ + 268, + 223, + 733, + 551 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Figure R1 XPS spectra of the Cd 3d orbitals for pure supports and fresh catalysts.", + "footnote": [], + "bbox": [ + [ + 155, + 131, + 848, + 268 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. S26 Quasi-in situ XPS spectrum of the 5Cd/P25 catalyst during the MSR reaction at \\(290^{\\circ}\\mathrm{C}\\) and a S/C ratio of 3/1.", + "footnote": [], + "bbox": [ + [ + 200, + 88, + 792, + 374 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. S40 (a) \\(\\mathrm{CH_3OH}\\) conversion in MD and CO conversion in WGS. (b) Product selectivity for MSR, MD, and WGS. (c) Corresponding \\(\\mathrm{H_2}\\) production rates.", + "footnote": [], + "bbox": [ + [ + 178, + 587, + 881, + 727 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Figure R2 In situ DRIFTS of (a) A, (b) R, (c) P25, (d) 5Cd/A, (e) 5Cd/R, and (f) 5Cd/P25.", + "footnote": [], + "bbox": [ + [ + 179, + 255, + 916, + 505 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Figure R3 (a) KIE measurements on the 5Cd/P25 catalyst by modulating the isotopic composition of the feed gas. (b) Reaction rate equation and reaction order of \\(\\mathrm{CH_3OH}\\) on the 5Cd/P25 catalyst.", + "footnote": [], + "bbox": [ + [ + 186, + 90, + 873, + 300 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Figure R4 HAADF-STEM images of (a, b) interface Cd single atoms on the 5Cd/P25 catalyst and (c, d) CdTiO3 on the 10Cd/P25 catalyst.", + "footnote": [], + "bbox": [ + [ + 275, + 85, + 722, + 396 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Figure R5 (a) Cd K-edge XANES spectra of fresh catalysts. (b) \\(\\mathrm{K}^{3}\\) -weighted \\(\\chi\\) (k) function of", + "footnote": [], + "bbox": [ + [ + 155, + 727, + 850, + 875 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_14.jpg", + "caption": "Fig. S23 Structural characterizations of the 5Cd/P25 catalysts after reduction at \\(400^{\\circ}\\mathrm{C}\\) (denoted", + "footnote": [], + "bbox": [ + [ + 147, + 570, + 832, + 877 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig. 1 i-k, HAADF-STEM and EDS mapping images for 5Cd/A (i), 5Cd/R (j), and 5Cd/P25 (k)", + "footnote": [], + "bbox": [ + [ + 248, + 219, + 627, + 891 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_15.jpg", + "caption": "Fig. S13 Structural characterization of the 5Cd/A catalyst. (a) Low-magnification HAADF-STEM image. (b) High-resolution EDS elemental mapping of Cd distribution. (c) Atomic-scale EELS analysis. (d-f) Atomic-resolution HAADF-STEM images showing isolated Cd single atoms (indicated by yellow circles).", + "footnote": [], + "bbox": [ + [ + 149, + 106, + 839, + 430 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_16.jpg", + "caption": "Fig. S14 Structural characterization of the 5Cd/R catalyst. (a) Low-magnification HAADF-STEM image. (b) High-resolution EDS elemental mapping of Cd distribution. (c) Atomic-scale EELS analysis. (d-f) Atomic-resolution HAADF-STEM images showing isolated Cd single atoms (indicated by yellow circles).", + "footnote": [], + "bbox": [ + [ + 149, + 509, + 844, + 825 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_17.jpg", + "caption": "Fig. S12 HAADF-STEM images of the 5Cd/P25 catalyst, showing Cd single atoms anchored between the A (101) and R (110) facets (yellow arrow and orange markers); scale bars: \\(100\\mathrm{nm}\\) (a), \\(50\\mathrm{nm}\\) (b), \\(20\\mathrm{nm}\\) (c), \\(5\\mathrm{nm}\\) (d). (e and f) Phase interface EDX elemental mapping images. (g-h) HAADF-STEM images of phase interface at a scale of \\(1\\mathrm{nm}\\) (bright spots correspond to Cd single atoms).", + "footnote": [], + "bbox": [ + [ + 180, + 92, + 816, + 540 + ] + ], + "page_idx": 34 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_18.jpg", + "caption": "Fig. S6 Feed rate dependence of methanol conversion and \\(\\mathrm{H}_2\\) production rates over 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts. Reaction conditions: catalyst \\(0.1\\mathrm{g} + \\mathrm{SiO}_2 0.2\\mathrm{g}\\) ; liquid feed of \\(\\mathrm{S / C} = 3\\) at \\(6 - 45\\mathrm{mL}\\mathrm{g}^{-1}\\mathrm{h}^{-1}\\) ; \\(\\mathrm{N}_2\\) carrier at \\(20\\mathrm{mL}\\mathrm{min}^{-1}\\) ; temperature: \\(290^{\\circ}\\mathrm{C}\\)", + "footnote": [], + "bbox": [ + [ + 147, + 355, + 951, + 508 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig. 1 Catalytic performance and structural characteristics of catalysts in the MSR reaction. d, Apparent activation energy evaluation (methanol conversion less than \\(10\\%\\) ).", + "footnote": [], + "bbox": [ + [ + 364, + 567, + 636, + 732 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_19.jpg", + "caption": "Figure R7 (a) XRD patterns of the amorphous \\(\\mathrm{TiO_2}\\) , 5Cd/amorphous \\(\\mathrm{TiO_2}\\) , and spent amorphous \\(\\mathrm{TiO_2}\\) catalysts. (b) Comparative catalytic performance. Reaction conditions: \\(290^{\\circ}\\mathrm{C}\\) , S/C ratio of 3/1, 0.1 MPa pressure, carrier gas of \\(30\\mathrm{mL} / \\mathrm{min}\\mathrm{N}_2\\) , and \\(3\\mathrm{mL}\\mathrm{g}^{-1}\\mathrm{h}^{-1}\\) feed rate.", + "footnote": [], + "bbox": [ + [ + 149, + 450, + 845, + 646 + ] + ], + "page_idx": 39 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_20.jpg", + "caption": "Fig. S40 (a) CH\\(_3\\)OH conversion in MD and CO conversion in WGS. (b) Product selectivity for MSR, MD, and WGS. (c) Corresponding H\\(_2\\) production rates.", + "footnote": [], + "bbox": [ + [ + 148, + 280, + 870, + 425 + ] + ], + "page_idx": 40 + }, + { + "type": "image", + "img_path": "images/Figure_4e.jpg", + "caption": "Fig. 4e Reaction orders on CH3OH in the 0.9-3.8 kPa range.", + "footnote": [], + "bbox": [ + [ + 352, + 471, + 645, + 639 + ] + ], + "page_idx": 43 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_21.jpg", + "caption": "Fig. S21 Structural characterizations of the 5Cd/P25 catalysts after reduction at \\(290^{\\circ}\\mathrm{C}\\) . (a) XRD patterns. (b) XPS spectra of the Cd 3d orbitals. (c) Cd K-edge XANES spectra. (d) \\(\\mathrm{K}^{3}\\) -weighted \\(\\chi\\) (k) function of EXAFS spectra.", + "footnote": [], + "bbox": [ + [ + 185, + 323, + 812, + 678 + ] + ], + "page_idx": 50 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig. 1 i-k, HAADF-STEM and EDS mapping images for 5Cd/A (i), 5Cd/R (j), and 5Cd/P25 (k) catalysts.", + "footnote": [], + "bbox": [ + [ + 268, + 90, + 645, + 768 + ] + ], + "page_idx": 52 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_22.jpg", + "caption": "Figure R9 XRD patterns of CdTiO₃ and CdTiO₃/TiO₂.", + "footnote": [], + "bbox": [ + [ + 293, + 286, + 706, + 514 + ] + ], + "page_idx": 53 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_23.jpg", + "caption": "Fig. S23 Structural characterizations of the 5Cd/P25 catalysts after reduction at \\(400^{\\circ}\\mathrm{C}\\) (denoted as 5Cd/P25-400H2). (a) XRD patterns. (b and c) HAADF-STEM images of the 5Cd/P25-400H2. (d) Cd K-edge XANES spectra. (e) \\(\\mathrm{K}^{3}\\) -weighted \\(\\chi\\) (k) function of EXAFS spectra. (f) XPS and AES spectra.", + "footnote": [], + "bbox": [ + [ + 155, + 88, + 837, + 395 + ] + ], + "page_idx": 55 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_24.jpg", + "caption": "Fig. S29 CH3OH-TPD profiles of three samples (CH3OH was decomposed with the increase of temperature).", + "footnote": [], + "bbox": [ + [ + 128, + 92, + 890, + 250 + ] + ], + "page_idx": 56 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_25.jpg", + "caption": "Figure R1 XANES and EXAFS spectra of 0.1Pt/P25 (a, b), 0.1Pd/P25 (c, d), and 0.1Cu/P25 (e, f)", + "footnote": [], + "bbox": [ + [ + 175, + 629, + 827, + 874 + ] + ], + "page_idx": 60 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_26.jpg", + "caption": "Figure R2 Comparative catalytic performance of various single atoms catalysts. (a) Methanol conversion, selectivity, and \\(\\mathrm{H}_2\\) production rate. (b) Apparent TOF. Reaction conditions: \\(290^{\\circ}\\mathrm{C}\\) , S/C molar ratio \\(= 3 / 1\\) , 0.1 MPa, and liquid feed rate \\(= 3 \\mathrm{mL g^{- 1} h^{- 1}}\\) .", + "footnote": [], + "bbox": [ + [ + 148, + 562, + 850, + 738 + ] + ], + "page_idx": 61 + } +] \ No newline at end of file diff --git a/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd b/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b991d72c7551f5e2acb079ef912a08df697250fc --- /dev/null +++ b/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File.mmd @@ -0,0 +1,891 @@ + +# nature portfolio + +# Peer Review File + +# Phase-interface-anchored cadmium single-atom catalysts for efficient methanol steam reforming + +Corresponding Author: Professor Hui Wang + +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Zhang et al. reported the development of a phase- interface- anchored Cd SAC for methanol steam reforming. The catalyst demonstrated exceptional performance, achieving \(100\%\) methanol conversion with CO selectivity below \(0.1\%\) . Additionally, it showed excellent stability, maintaining activity for more than 150 hrs. To assess the scalability of this process, the authors explored 3D printing techniques to produce monolithic catalysts on a Kg scale. While this work is fundamentally interesting, the area of methanol steam reforming is already well- explored, and the scalability of non- noble metal- based catalysts has been extensively studied. Furthermore, the use of Cd, a toxic element, raises concerns about the industrial viability and environmental acceptability of this approach. Several important aspects of the study require clarification and further investigation. + +1. The study compares Cd SAC with Cu, Pd, and Pt. However, it remains unclear whether all the compared metals are present as single atoms and located at the phase interface. This information is critical, as the localization and atomic dispersion of metal sites significantly influence catalytic performance. Detailed structural and surface characterizations, should be provided to confirm these aspects for each catalyst. + +2. Ea for 5Cd/P25 is reported to be \(82.7\mathrm{kJ / mol}\) , which is nearly half of that for 5Cd/A. The reasons behind this substantial difference should be thoroughly investigated. Additionally, it would be insightful to compare this Ea value with those of state-of-the-art catalysts for methanol steam reforming. Detailed explanations of how Ea was calculated, including the experimental methods and assumptions, should also be included to enhance the transparency and reproducibility of the findings. + +3. The authors observed that increasing the Cd loading up to 5 wt% enhanced the catalyst's reactivity, while further increases resulted in a decline. Authors should compare the turnover frequency (TOF) of catalysts with varying Cd loadings. This analysis would provide direct evidence of SAC-driven catalysis and clarify the relationship between Cd loading and catalytic performance. + +4. The authors claim that a mixture of anatase and rutile phases is not effective for catalysis. To strengthen this conclusion, more control experiments should be performed to find out the optimum balance between anatase and rutile. Anatase could be subjected to controlled heating to partially convert it into the rutile phase, and the catalytic activity of the resulting material could be tested. Optimizing the anatase-to-rutile phase ratio would provide valuable insights into the specific phase-change requirements for Cd SAC catalysis. + +5. The O1s XPS data presented in the study lacks sufficient detail to support the proposed active sites. The authors should provide a more thorough deconvolution of the O1s peaks to identify the types of oxygen species present and their roles in the catalytic process. + +6. The reaction mechanism proposed in the study requires further elaboration. Identifying the rate-determining step (RDS) is crucial to understanding the catalytic process and design of the next generation of catalysts. + +<--- Page Split ---> + +(Remarks to the Author) + +In this work, Wang et. al, selectively decorated isolated Cd atoms to the interface of the P25 where heterogeneous structures of anatase and rutile coexist and the promoted H2 production rate has been achieved at \(\sim 292.9\) mmol gcat- 1 h- 1, which is about 15- fold and 8- fold higher than that of anatase and rutile dispersed Cd active components. The superior reaction performance has been attributed to the Cd- O- Ti interfacial structures. And this specific active component has been systematically probed by HRTEM, XAFS, EPR etc. A formate decomposition reaction pathway has been systematically discussed and was taken as the reaction mechanism for the hydrogen production. Finally, 3D printing has been introduced to produce the catalyst and this reaction system does show some potential in industrial applications. Generally, this is a good work and shows some interesting results, however, some of them are still under debate and might be critical to the overall conclusions. I suggest to reject this paper and give the author the opportunity to resubmit the work and hopefully the concerns listed bellow could be answered during the re- submission. + +(1) First of all, the authors suggest that there is CdTiO3 at the interfacial site and it does not contribute to the hydrogen formation. I agree that, however, the Cd/CdOx does not show good activity either as comparisons. How can you explain that? And this CdTiO3 structure coexists with the real active components, is that possible most of the characterization is simply against this in-active structures (c.a. CdTiO3) rather than the real ones. + +(2) The authors suggest that the Cd is isolated, however, there is only one evidence from EXAFS, even the HAADF-STEM characterizations are not very clear. Is that possible the Cd are clusters rather than isolated site? Then it still gives advanced reaction performance, well the actually active component is not the isolated Cd. + +(3) The author shows the selectivity of H2, CO, CO2 and CH4, and hydrogen dominants in the products, however, this is not correct. In this way, none of the product could reach 100%. The selectivity should be classified into carbonaceous species and hydrogen, which should be more reasonable, during which time, CO selectivity won't be as low as it is for right now. + +(4) For the activation energy determined, it looks that 82.7 KJ/mol is almost half the value of 152.1 KJ/mol, which may suggest that the system of Cd/P25 is suffering from diffusion limitations and it gives half the value of the real one and the superior reaction performance is not originated from the reduced activation energies. Well, this is only based on my assumption and the author definitely should exclude the mass/heat transfer limitations (both internal and outside channel diffusion limitations) before determining the apparent activation energies. + +(5) If the real active component is the Cd-O-Ti structure, no matter which TiO2 phase it connects to, the Cd/P25 should gives similar activities with either Cd/anatase or Cd/rutile. This is not very clear, this reviewer suggests the author put more effort on explaining that. For example, the highly dispersed Cd on amorphous TiO2 might be also good for this reaction. + +(6) There is contradictory assessment in elucidating the reaction mechanism of hydrogen production. Clearly, the C-H bond rupture within methanol is the rate determining step based on the KIE values determined. And usually, CO could be easily generated from methanol decomposition. Negligible CO determined would be attributed to the strong WGS reaction in the system, and it was not mentioned. This reviewer suggests the author to clarify that by determining the reaction rate and equilibrium constant on WGS at the relative conditions. + +(7) I cannot quite follow why the overall reaction rate could be influenced by the electronic properties determined in figure 2, then I suggest the author move these results to the ESI. + +(8) I don't know why the HAADF-STEM images were given twice in Figure 1 and Figure 3. I hope the author could re- organize the results and make it easy to read. + +(9) From the reaction coordinate, it looks that the hydrogen formation over Cd1/A(101) is quite difficult, while it is not quite the situation for Cd/P25. This might be the main difference among these samples. And it is not well discussed. This reviewer suggests the author to clarify that. + +## Reviewer #3 + +(Remarks to the Author) + +This research presents a phase- interface- stabilized Cd/P25 single- atom catalysts, which demonstrate much higher MSR performance than other Cd/TiO2 counterparts. The authors uncovered Cd- O- Ti phase interface site that dominates the high MSR activity and low CO selectivity. They also show that the densities of phase interface/sites can be regulated. Additionally, the fundamental mechanism of enhanced MSR performance on Cd/P25 SACs is clearly revealed by the combination of experimental and theoretical studies. This manuscript is well structured and demonstrated. I am willing to recommend its publication in Nature Communications. However, I would like to see the following concerns addressed before it can be further considered. + +Main concerns: + +1. In the Abstract, the statement "The formed Cd-O-Ti phase interface sites exhibit asymmetric geometric and electronic properties that achieve 100% methanol conversion, minimal CO selectivity (<0.1%), and sustained stability exceeding 150 hours" leads to misunderstanding. 100% methanol conversion and <0.1% CO selectivity are not achieved by interface sites solely. + +2. In Supplementary Fig. 2, it is interesting and surprising that Cd catalysts exhibit similar MSR performance. This means that Cd catalysts after air calculation at 500°C and H2 reduction at 290C probably have the same active site. It is important to identify the properties of the catalysts at two states. + +3. In Fig. 1, it is recommended to only display Cd element distribution on TiO2-A and -R in EDS-mapping results, for a better comparison with Cd-P25. It is unclear to identify Cd dispersion (blue spots) now. + +4. A significant amount of CdTiO3 exists in Cd/P25. What is the MSR performance of CdTiO3/TiO2? + +5. In Supplementary Fig. 18, it is necessary to identify the chemical state of Cd for Cd/P25 after H2 reduction at 400 C with XPS, rather than H2-TPR. + +6. In Supplementary Fig 24., it seems that 5Cd/A displays a stronger CH3OH adsorption than 5Cd/P25. + +<--- Page Split ---> + +7. DFT parts need to involve more discussion about the comparison with other models and highlight the advantage of Cd/A-R model. + +8. In conclusion, when elucidating catalysis mechanism of Cd-O-Ti interface site, the authors need to make it clearer. Why is substantially lowering the energy barriers for formate decomposition important for complete methanol conversion? It is not clear to readers. + +9. Some discussion in the manuscript is not accurate. For example, on Page 9, "This suggests that the Cd-O-Ti configuration is the most effective active site, particularly at phase interfaces" should be revised to "This suggests that the Cd-O-Ti configuration is a more efficient active site, particularly at phase interfaces". + +10. The format of the font should be consistent throughout the manuscript. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Zhang et al. have revised the manuscript in response to the suggestions and questions raised during the review process. I agree that Cd could be a promising catalyst at the phase interface. However, I am still not fully convinced by the comparison with other metals. For a fair evaluation, Cd single atoms should be compared under similar conditions with single atoms of other metals. + +Overall, the remaining comments have been addressed well. After adequately responding to this remaining concern, the manuscript can be considered suitable for publication in Nature Communications. + +Reviewer #2 + +(Remarks to the Author) + +The authors addressed most questions raised, even there is still some concerns on the formate reaction pathways. I feel that this work is not mainly focusing on reaction mechanism investigations. I decide to accept this paper without further modifications. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + + +<--- Page Split ---> + +## RESPONSES TO REVIEWERS' COMMENTS + +Many thanks for the reviewers' insightful comments and questions, we have addressed the point- by- point responses below and believe the revised manuscript provides a more detailed, clear, and accurate description of the catalytic system. + +Reviewer: 1 + +## Response to Reviewer #1: + +Comments: + +Zhang et al. reported the development of a phase- interface- anchored Cd SAC for methanol steam reforming. The catalyst demonstrated exceptional performance, achieving \(100\%\) methanol conversion with CO selectivity below \(0.1\%\) . Additionally, it showed excellent stability, maintaining activity for more than 150 hrs. To assess the scalability of this process, the authors explored 3D printing techniques to produce monolithic catalysts on a Kg scale. While this work is fundamentally interesting, the area of methanol steam reforming is already well- explored, and the scalability of non- noble metal- based catalysts has been extensively studied. Furthermore, the use of Cd, a toxic element, raises concerns about the industrial viability and environmental acceptability of this approach. Several important aspects of the study require clarification and further investigation. + +Response: Thank you for your insightful comments. We acknowledge the concerns regarding the safety and environmental issues associated with the use of Cd. However, our investigation revealed for the first time a scientifically compelling phenomenon: the preferential anchoring of Cd single atoms at the phase interface of P25. This unique interfacial coordination configuration demonstrated remarkable catalytic performance in MSR, presenting fundamental scientific significance for understanding structure- property relationships in single- atom catalysts (SACs). While pursuing mechanistic studies to elucidate the formation dynamics and functional characteristics of this interfacial structure, we have made parallel efforts to develop + +<--- Page Split ---> + +next- generation SACs using environmentally benign alternatives. This pursuit aligns with our broader research goals and forms the core of our ongoing work, where we aim to leverage more abundant and non- toxic metals to develop catalysts with enhanced performance based on this intriguing structural framework. We are committed to addressing these challenges and advancing the field of sustainable catalysis through our research efforts. + +1. The study compares Cd SAC with Cu, Pd, and Pt. However, it remains unclear whether all the compared metals are present as single atoms and located at the phase interface. This information is critical, as the localization and atomic dispersion of metal sites significantly influence catalytic performance. Detailed structural and surface characterizations should be provided to confirm these aspects for each catalyst. + +![](images/Figure_unknown_0.jpg) + +
Fig. S33 (a) XRD patterns of the fresh catalysts. DF-TEM, HRTEM images and corresponding particle distribution of the fresh (b) 5Pt/P25, (c) 5Pd/P25, and (d) 5Cu/P25 catalysts.
+ +Response: We are grateful for your insightful comment. In response, we have enhanced the structural characterization of the corresponding Cu-, Pd-, and Pt- based + +<--- Page Split ---> + +catalysts (Fig. S33). At a loading of 5 wt.%, XRD analysis identified diffraction peaks corresponding to PdO and CuO on the 5Pd/P25 and 5Cu/P25 catalysts, respectively, suggesting the formation of oxide nanoparticles. TEM further confirmed the formation of nanoparticles, revealing average sizes of 1.2 nm for PtO₂, 8.7 nm for PdO, and 2.2 nm for CuO when deposited at 5 wt.% on P25. + +![](images/Figure_unknown_1.jpg) + +
Fig. S34 (a) Methanol conversion and product selectivity of the 0.2Pt/P25, 0.2Pd/P25, and 0.2Cu/P25 catalysts; (b) Corresponding H₂ production rates and TOF; (c-f) HAADF-STEM images of the fresh 0.2Pt/P25 catalyst. Reaction conditions: 290 °C, a S/C ratio of 3/1, 0.1 MPa pressure, and a feed rate of 3 mL g⁻¹ h⁻¹.
+ +To obtain single- atom catalysts, we synthesized 0.2 wt.% Pt/P25, 0.2 wt.% Pd/P25, and 0.2 wt.% Cu/P25 catalysts. Comparative performance analysis revealed that under low- loading conditions, the Pt- based catalyst exhibited the higher methanol conversion (33.1%), H₂ production rates (25.0 mmol g⁻¹ h⁻¹), and TOF (1406.1 h⁻¹) compared to its Pd and Cu counterparts. However, it showed an undesirably high CO selectivity of 61.6%. HAADF- STEM imaging revealed that in the 0.2Pt/P25 catalyst, Pt single atoms and nanoclusters coexist on its surface, with no single atoms detected at the P25 phase interface. This phenomenon implies that the formation of interfacial single atoms requires specific conditions, mainly determined by the match between the metal's properties (e.g., surface energy and coordination preference) and interfacial thermodynamics, as elaborated in the main text. Therefore, the properties + +<--- Page Split ---> + +of Cd single atoms and the phase interface of P25 are well- matched compared with other metals. + +## Manuscript Revision: + +"Notably, other active metals (e.g., Pt, Pd, Cu) deposited on P25 at equivalent concentrations (5 wt.%) exhibited nanoparticle aggregation on its surface (Supplementary Fig. 33). However, single- atom formation of transition metals (e.g., Pt) on the P25 phase interface remained unattainable even at 0.2 wt.% loading, concomitant with a marked decline in catalytic performance (Supplementary Fig. 34). These findings suggest that the formation of single atoms at the interface necessitates a favorable match between the metal's properties and the interfacial energy. The ionic radius of Cd differs more markedly from that of Ti than those of Pd, Pt and Cu. Moreover, the electronegativity of Cd is most analogous to that of Ti (Supplementary Table 7). These characteristics may endow Cd atoms with a significant difference in average internal energy between the lattice and phase interface, rendering them particularly prone to segregation and anchoring at Ti defect sites within the interface, thereby minimizing the interfacial energy. This attribute elucidates the challenge faced by other metals in achieving single- atom dispersion at the P25 interface." + +2. Ea for 5Cd/P25 is reported to be 82.7 kJ/mol, which is nearly half of that for 5Cd/A. The reasons behind this substantial difference should be thoroughly investigated. Additionally, it would be insightful to compare this Ea value with those of state-of-the-art catalysts for methanol steam reforming. Detailed explanations of how Ea was calculated, including the experimental methods and assumptions, should also be included to enhance the transparency and reproducibility of the findings. + +Response: Thanks for pointing this out. In light of the significant difference in activation energy you highlighted, we have thoroughly re- examined and analyzed our experimental data. We acknowledge that the influence of mass transfer cannot be entirely ruled out during the testing process. Specifically, the conversion rate was + +<--- Page Split ---> + +relatively high ( \(\sim 20\%\) ) during the tests, which could potentially lead to a small activation energy. This is because, at higher conversion rates, the rate- limiting step may shift from the intrinsic catalytic activity to the mass transfer of reactants to the catalyst surface. Therefore, we re- tested the apparent activation energy of the catalyst. + +First, to eliminate the effect of external diffusion, we increased the space velocity (feed rate). As depicted in Fig. S6, for the three catalysts (5Cd/A, 5Cd/R, and 5Cd/P25), the conversion rate showed an inverse relationship with feed rate as the feed rate increased. Concurrently, the \(\mathrm{H}_2\) production rate gradually increased, and the curve tended to stabilize. This behavior suggests that the reaction on these catalysts is analogous to a first- order kinetic model. Under high feed rate conditions ( \(>30 \mathrm{mL} \mathrm{g}^{- 1}\) \(\mathrm{h}^{- 1}\) ), when the conversion rate was below \(10\%\) , the impact of feed rates on the \(\mathrm{H}_2\) production rate was minimal, indicating that the effect of external diffusion could be neglected. Therefore, we opted to conduct our activation energy tests at a feed rate corresponding to a conversion rate of less than \(10\%\) . This selection ensured that the influence of external diffusion was minimized, allowing for a more accurate assessment of the intrinsic catalytic activity and the apparent activation energy of the catalyst. + +To determine whether the effect of internal diffusion was negligible, we applied the Weisz- Prater criterion for calculation, as shown in Equations (1- 3). + +\[\begin{array}{l}\mathrm{WP} = \frac{\mathrm{r}\times\mathrm{R}^2}{\mathrm{C}_\mathrm{S}\times\mathrm{D}_\mathrm{e}}\\ \frac{1}{\mathrm{D}_\mathrm{e}} = \frac{\tau}{\epsilon} (\frac{1}{\mathrm{D}_\mathrm{m}} +\frac{1}{\mathrm{D}_\mathrm{k}})\\ \mathrm{D}_\mathrm{k} = \frac{2}{3}\mathrm{d}_\mathrm{p}\sqrt{\frac{8\mathrm{RT}}{\pi\mathrm{M}}} \end{array} \quad (1)\] + +\(\mathrm{r}\) represents the reaction rate, \(\mathrm{R}\) represents the particle radius, \(\mathrm{C}_\mathrm{s}\) represents the reactant concentration at the catalyst surface, \(\mathrm{D}_\mathrm{e}\) represents the effective diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\tau\) represents the pore tortuosity, \(\epsilon\) represents the porosity, \(\mathrm{D}_\mathrm{m}\) represents the molecular diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{D}_\mathrm{k}\) represents the Knudsen diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{d}_\mathrm{p}\) represents the average pore diameter \((\mathrm{m})\) , \(\mathrm{M}\) represents the molar mass of the diffusing species \((\mathrm{kg} / \mathrm{mol})\) , \(\mathrm{R}\) represents the gas constant, and \(\mathrm{T}\) represents the temperature \((\mathrm{K})\) . + +<--- Page Split ---> + +Under the conditions of \(290^{\circ}\mathrm{C}\) , \(\mathrm{S / C} = 3 / 1\) , 0.1 MPa, and methanol conversion below \(10\%\) , the Weisz-Prater (WP) values for 5Cd/A, 5Cd/R, and 5Cd/P25 were \(1.0 \times 10^{- 7}\) , \(2.4 \times 10^{- 9}\) , and \(7.3 \times 10^{- 10}\) , respectively. All of them are much less than 1, so the internal diffusion limitation can be excluded. In addition, we added inert \(\mathrm{SiO}_2\) to the catalyst to promote heat transfer during the reaction process, ensuring no temperature gradient in the reaction zone and excluding the impact of heat transfer. Finally, we tested the \(\mathrm{H}_2\) production rate at every \(10^{\circ}\mathrm{C}\) intervals in the temperature range of \(250 - 290^{\circ}\mathrm{C}\) and calculated the corresponding activation energy by substituting it into the Arrhenius equation (as shown in Equation 4). The apparent activation energies of the 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts were \(146.6\mathrm{KJ / mol}\) , \(121.9\mathrm{KJ / mol}\) , and \(107.3\mathrm{KJ / mol}\) , respectively. In comparison, the apparent activation energy of the 5Cd/P25 catalyst was still the lowest, which did not affect the original conclusion that the interfacial Cd single atom sites with their unique interfacial structure and electronic properties had relatively excellent catalytic performance. + +\[\ln \mathbf{k} = \ln \mathbf{A} - \frac{\mathbf{B}_{\mathbf{a}}}{\mathbf{R}\mathbf{T}} \quad (4)\] + +Regarding the comparison of apparent activation energy, we have reviewed a substantial amount of literature and found that few studies calculated or tested the apparent activation energy. Instead, the \(\mathrm{H}_2\) production rate is commonly used as the basis for comparison. Therefore, we have not made a horizontal comparison of apparent activation energy in this study. + +To enhance the transparency and reproducibility of the findings, we have added Fig. S6 and the calculation process of activation energy in the SI section of the revised manuscript, and the corresponding content is as follows. + +Supplementary Information Revision: + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Fig. S6 Feed rate dependence of methanol conversion and \(\mathrm{H}_2\) production rates over 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts. Reaction conditions: catalyst \(0.1\mathrm{g} + \mathrm{SiO}_2 0.2\mathrm{g}\) ; liquid feed of \(\mathrm{S / C} = 3\) at \(6 - 45\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) ; \(\mathrm{N}_2\) carrier at \(20\mathrm{mL}\mathrm{min}^{-1}\) ; temperature: \(290^{\circ}\mathrm{C}\) .
+ +Note: For the three catalysts (5Cd/A, 5Cd/R, and 5Cd/P25), the conversion rate showed an inverse relationship with feed rate as the feed rate increased. Concurrently, the \(\mathrm{H}_2\) production rate gradually rised, and the curve tended to stabilize. This behavior indicates that the reaction on these catalysts follows a first- order kinetics model, and the impact of external diffusion can be disregarded under high feed rate conditions. Consequently, methanol conversion maintained below \(10\%\) during the activation energy test. Under these reaction conditions, the impact of internal diffusion was assessed using the Weisz- Prater criterion, and the specific calculation formula was as follows (Equations 1- 3): + +\[\mathrm{WP} = \frac{r\times\mathrm{R}^2}{\mathrm{C}_\mathrm{S}\times\mathrm{D}_\mathrm{e}} \quad (1)\] + +\[\frac{1}{\mathrm{D}_{\mathrm{e}}} = \frac{\tau}{\epsilon}\left(\frac{1}{\mathrm{D}_{\mathrm{m}}} +\frac{1}{\mathrm{D}_{\mathrm{k}}}\right) \quad (2)\] + +\[\mathrm{D}_{\mathrm{k}} = \frac{2}{3}\mathrm{d}_{\mathrm{p}}\sqrt{\frac{8\mathrm{R}\mathrm{T}}{\pi\mathrm{M}}} \quad (3)\] + +r represents the reaction rate, R represents the particle radius, \(\mathrm{C}_\mathrm{s}\) represents the reactant concentration at the catalyst surface, \(\mathrm{D}_{\mathrm{e}}\) represents the effective diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\tau\) represents the pore tortuosity, \(\epsilon\) represents the porosity, \(\mathrm{D}_{\mathrm{m}}\) represents the molecular diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{D}_{\mathrm{k}}\) represents the Knudsen diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{d}_{\mathrm{p}}\) represents the average pore diameter (m), M represents the molar mass of the diffusing species (kg/mol), R represents the gas constant, and T represents the temperature (K). + +The calculated WP values for 5Cd/A, 5Cd/R, and 5Cd/P25 were \(1.0 \times 10^{- 7}, 2.4 \times 10^{- 9}\) , and \(7.3 \times 10^{- 10}\) , respectively. Given that all these values are significantly less than 1, the influence of internal diffusion limitations could be excluded. Additionally, inert \(\mathrm{SiO}_2\) was incorporated into the catalyst to enhance heat transfer during the reaction process, ensuring a uniform temperature profile within the reaction zone and thereby eliminating the impact of heat transfer. The activation energy was determined using the following equation (Reaction conditions: catalyst \(0.1 \mathrm{g} + \mathrm{SiO}_2 0.2 \mathrm{g}\) ; liquid feed of \(\mathrm{S / C} = 3\) at \(15 - 45 \mathrm{mL} \mathrm{g}^{- 1} \mathrm{h}^{- 1}\) ; \(\mathrm{N}_2\) carrier at \(20 \mathrm{mL} \mathrm{min}^{- 1}\) ; temperature: \(250 - 290^{\circ}\mathrm{C}\) ; methanol conversion less than \(10\%\) ): + +\[\mathrm{lnk} = \mathrm{lnA} - \frac{\mathrm{E}_{\mathrm{a}}}{\mathrm{RT}} \quad (4)\] + +<--- Page Split ---> +![](images/Figure_1.jpg) + +
Fig. 1 Catalytic performance and structural characteristics of catalysts in the MSR reaction. d, Apparent activation energy evaluation (methanol conversion less than 10%).
+ +3. The authors observed that increasing the Cd loading up to 5 wt% enhanced the catalyst's reactivity, while further increases resulted in a decline. Authors should compare the turnover frequency (TOF) of catalysts with varying Cd loadings. This analysis would provide direct evidence of SAC-driven catalysis and clarify the relationship between Cd loading and catalytic performance. + +Response: Thank you for your constructive suggestions. In response to this valuable comment, we have conducted detailed TOF calculations for catalysts with varying Cd loadings. The results are presented in the revised Fig. S4. The TOF was found to decrease significantly with the increase in Cd loadings, which was inconsistent with the trend of \(\mathrm{H}_2\) production rates. This result provides compelling evidence of SAC- driven catalysis at low Cd loadings, while also indicating that the structure of active sites changes with varying Cd loadings, leading to a decrease in the efficiency of the single Cd active sites. + +Supplementary Information Revision: + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Fig. S4 Catalytic performance as a function of varying Cd loadings on the P25 support. Reaction conditions: \(290^{\circ}\mathrm{C}\) , S/C ratio of 3/1, 0.1 MPa pressure, and \(3\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) feed rate.
+ +XRD patterns of the fresh and spent catalysts with varying Cd loadings revealed the emergence of \(\mathrm{CdTiO_3}\) species at a Cd loading of 5 wt. \(\%\) (Figs. S20a and b). Further XAFS spectroscopy was conducted to reveal the Cd species with varying loadings. As shown in Fig. S20c, the white line of the Cd K- edge XANES spectra for these samples was positioned between that of the Cd foil and CdO reference, with the white line of the 10Cd/P25 catalyst nearly overlapping with that of the \(\mathrm{CdTiO_3}\) reference. This finding further confirmed the presence of \(\mathrm{CdTiO_3}\) at high Cd loadings. The fitting results of the EXAFS spectrum indicated the absence of a Cd- Cd coordination structure in all samples, suggesting that neither metallic Cd nor CdO clusters formed as the Cd loading increased. However, as indicated in Table S4, the \(\mathrm{CdTiO_3}\) species, which were inactive for MSR, have been identified, and the \(\mathrm{H_2}\) production rate decreased with the increase of \(\mathrm{CdTiO_3}\) (Fig. S4b). Therefore, the decrease in TOF can be attributed to the presence of \(\mathrm{CdTiO_3}\) . With the increase in Cd loadings, although the number or density of Cd single atoms (active sites), particularly those anchored at the phase interface, increased nonlinearly, which could enhance the \(\mathrm{H_2}\) production rate, the efficiency of the single atom sites (TOF) decreased because some Cd species formed \(\mathrm{CdTiO_3}\) . + +## Supplementary Information Revision: + +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
Fig. S20 XRD patterns of (a) fresh and (b) spent catalysts with different Cd loadings. (c) Cd K-edge XANES spectra of fresh catalysts with different Cd loadings. (d) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of EXAFS spectra.
+ +Note: As the Cd loading varied, the \(\mathrm{CdTiO_3}\) species emerged when the Cd loading exceeded 5 wt.%. The fitting results of the EXAFS spectrum indicated the absence of a Cd-Cd coordination structure in all samples, suggesting that neither metallic Cd nor CdO clusters formed as the Cd loading increased. + +Table S4 Catalytic performance of homemade reference catalysts. + +
CatalystConversion (%)SCO2SCOSCH4
CdTiO30000
CdTiO3/TiO20.584.515.50
CdO0.101000
Cd0000
+ +Reaction conditions: \(290^{\circ}C\) , 0.1 MPa, a S/C ratio of 3/1, and a feed rate of \(3\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) + +<--- Page Split ---> + +4. The authors claim that a mixture of anatase and rutile phases is not effective for catalysis. To strengthen this conclusion, more control experiments should be performed to find out the optimum balance between anatase and rutile. Anatase could be subjected to controlled heating to partially convert it into the rutile phase, and the catalytic activity of the resulting material could be tested. Optimizing the anatase-to-rutile phase ratio would provide valuable insights into the specific phase-change requirements for Cd SAC catalysis. + +Response: Thank you for your constructive suggestions. We evaluated the combined performance of 5Cd/A and 5Cd/R catalysts at ratios of 80/20, 50/50, and 20/80. As the proportion of 5Cd/R increased, methanol conversion increased from 18.1% to 33.7%, nearing the performance of sole 5Cd/R but remaining inferior to that of 5Cd/P25 (Fig. S2). This strongly suggests that single- atom Cd at the phase interface is far more effective than the synergistic interaction of single atoms on two separate phase surfaces. + +![](images/Figure_unknown_5.jpg) + +
Fig. S2 Comparison of catalytic performance between 5Cd/P25 and mixtures composed of varying ratios of 5Cd/A and 5Cd/R. Reaction conditions: 290 °C, S/C ratio of 3/1, 0.1 MPa pressure, and 3 mL g-1 h-1 feed rate.
+ +In accordance with the reviewers' opinions, we also supplemented the experiments of calcining anatase (A) at different temperatures to control the phase + +<--- Page Split ---> + +transformation and form different ratios of A to R. A was calcined at \(600^{\circ}\mathrm{C}\) , \(700^{\circ}\mathrm{C}\) , and \(800^{\circ}\mathrm{C}\) for 2 hours respectively, and then 5 wt.% Cd was loaded, which were denoted as 5Cd/A- XAir (X represents the temperature) (Fig. S36a). As shown in Fig. S36b, with the increase of calcination temperature, the methanol conversion and \(\mathrm{H}_{2}\) production rate exhibited a volcanic profile. At \(700^{\circ}\mathrm{C}\) , the methanol conversion significantly increased from \(21.6\%\) to \(94.5\%\) , and the \(\mathrm{H}_{2}\) production rate reached 92.3 mmol \(\mathrm{g}^{- 1} \mathrm{h}^{- 1}\) , with a CO selectivity of \(0.7\%\) , which was close to the performance of the 5Cd/P25 catalyst (97.7 mmol \(\mathrm{g}^{- 1} \mathrm{h}^{- 1}\) ). HAADF- STEM images of the 5Cd/A- 700Air catalyst revealed that Cd single atoms anchored at the A-R phase interface, consistent with the 5Cd/P25 catalyst (Figs. S36c and d). This underscored that the phase interface formed by phase transition was conducive to the formation of Cd single atoms. However, at \(800^{\circ}\mathrm{C}\) , methanol conversion dropped sharply to \(12.1\%\) . XRD Rietveld analysis showed the calcination temperature primarily affected the A/R ratio and crystallite size. As the temperature increased, A gradually transformed to R, and the crystallite size increased, altering the interfacial density (Table S8). Upon calcination at \(700^{\circ}\mathrm{C}\) , the ratio of A and R ( \(80.2\% /19.8\%\) ) closely resembled that of P25, accompanied by an elevated interfacial density ( \(4.7 \mathrm{m}^{2} \mathrm{g}^{- 1}\) ) relative to other calcination temperatures, thereby conferring enhanced \(\mathrm{H}_{2}\) production rates. However, due to the larger crystallite size of A and R after calcination, the performance remained inferior to that of 5Cd/P25. + +Table S8 Data for interface density calculations following the pretreatments of A and P25. + +
Pretre atmentTemperature /TimeWA /%WR /%crystal /nmsize CNmaxN (A) /1015 g-1N (R) /1015 g-1N (A) / N (R)/ Amax /m2 g-1
A R
Air a600 °C/2h90.19.931.641.710.47.50.325.0
700 °C/2h80.219.844.260.811.42.40.212.0
800 °C/2h57.442.649.177.214.81.30.26.5
N2 b500 °C/2h79.620.419.236.721.929.60.930.1
600 °C/2h69.930.121.736.917.318.01.412.6
700 °C/2h29.670.433.048.412.92.21.51.5
+ +<--- Page Split ---> + + +
\(H_{2}^{c}\)500℃/2h73.626.419.621.67.325.76.24.19.9
500℃/4h68.431.617.924.811.531.44.96.410.1
500℃/8h51.348.721.522.56.613.610.21.36.3
+ +a Pure A was calcined at \(600–800^{\circ }C\) for 2 hours in static air. + +b Pure P25 was calcined at \(500–700^{\circ }C\) for 2 hours in a flow of \(N_{2}(100mL/min).\) + +c Pure P25 was reduced at \(500^{\circ }C\) for 2 hours in a flow of \(H_{2}(100mL/min).\) + +![](images/Figure_unknown_6.jpg) + +
Fig. S36 (a) XRD patterns of fresh catalysts. (b) Catalytic performance. (c and d) HAADF-STEM images of the 5Cd/A-700Air catalyst. Reaction conditions: 290 $^{\circ }C$ , a S/C ratio of 3/1, 0.1 MPa pressure, and a feed rate of 3 mL g-1 h-1.
+ +In the manuscript, we have systematically modulated the phase interface density via \(N_{2}/H_{2}\) -pretreated P25 to optimize catalytic performance. Fig. 3f revealed a volcano-shaped correlation between interfacial density and \(H_{2}\) production rates, with the peak density \((8.5m^{2}g^{-1})\) and maximum \(H_{2}\) production rate \((266.0mmolg_{cat}^{-1}h^{-1})\) observed at 600 $^{\circ }C$ . To further enhance interfacial density, \(H_{2}\) -pretreated P25 was subjected to varying durations at 500 $^{\circ }C$ , maintaining identical crystallite size. After 4-hour \(H_{2}\) pretreatment, the A/R ratio reached \(68.4\%/31.6\%\) , obtaining the highest interface density \((m^{2}g^{-1})\) and \(H_{2}\) production rate \((292.9mmolg_{cat}^{-1}h^{-1})\) + +# Manuscript Revision: + +Lines 100-102: + +*Additionally, adjusting the mixture ratio still failed to achieve reaction performance comparable + +<--- Page Split ---> + +to that of 5Cd/P25 (Supplementary Fig. 2), underscoring the unique catalytic properties of this catalyst." + +Lines 333- 339: + +"To validate this hypothesis, we systematically investigated the phase transformation by calcining A under static- air conditions at varying temperatures (Supplementary Fig. 36 and Supplementary Table 8). At a calcination temperature of \(700^{\circ}\mathrm{C}\) , the A/R weight fraction ratio of \(80.2 / 19.8\%\) and corresponding catalytic performance closely mirrored those of 5Cd/P25. HAADF- STEM images revealed the formation of Cd single atoms at the phase interface, which corroborated the formation of Ti defects through the in- situ phase transformation." + +Lines 344- 347: + +"Although calcining A in air regulated phase weight fractions, the resulting interfacial density was limited to \(4.7\mathrm{m}^2\mathrm{g}^{- 1}\) due to the enlarged crystallite size, which was lower than that of 5Cd/P25 ( \(7.9\mathrm{m}^2\mathrm{g}^{- 1}\) ). Consequently, we implemented \(\mathrm{N}_2\) pretreatment (500- 700 °C) on P25 to enhance interface density prior to Cd loading." + +5. The O1s XPS data presented in the study lacks sufficient detail to support the proposed active sites. The authors should provide a more thorough deconvolution of the O1s peaks to identify the types of oxygen species present and their roles in the catalytic process. + +Response: We appreciate your constructive advice. To support the identification of the proposed active sites, we have added the O1s spectrum with deconvoluted peaks for both the pure supports and the catalysts loaded with Cd species (Figure R1). The peaks at around \(530.0\mathrm{eV}\) , \(531.2\mathrm{eV}\) , and \(532.2\mathrm{eV}\) are attributed to the lattice oxygen (O\(_{\text{lattice}}\)) of TiO\(_2\), the adsorbed oxygen at oxygen vacancies (O\(_v\)), and the surface adsorbed hydroxyl group (*OH), respectively. When Cd was loaded on the pure supports, the binding energy of O\(_{\text{lattice}}\) decreased \(0.1\mathrm{eV}\) for all samples, which indicated that the electron of Cd species transferred to O\(_{\text{lattice}}\). The findings also indirectly demonstrated that Cd atoms anchored at the Ti vacancies of TiO\(_2\) and bound + +<--- Page Split ---> + +with O\(_{lattice}\) to form the active sites of Cd- O- Ti. + +![](images/Figure_unknown_7.jpg) + +
Figure R1 XPS spectra of the Cd 3d orbitals for pure supports and fresh catalysts.
+ +The O1s spectrum in the quasi in situ XPS was also subjected to a thorough deconvolution (Fig. S26). The binding energies of O\(_{lattice}\), O\(_{v}\), and \*OH remained unchanged during the MSR reaction. Moreover, the peak area of O\(_{v}\) stayed within the range of 10\~12%, suggesting that O\(_{v}\) had a negligible impact on the reaction process. These results were consistent with the EPR and DFT calculations. Since the quasi in situ XPS differs from the near atmospheric pressure XPS (NAP- XPS), it cannot capture the surface adsorbed intermediates and the reaction process. This leads to difficulties in directly elucidating the types and roles of surface oxygen species during the reaction through this characterization technique. However, the role of Cd- O- Ti sites during the reaction can be elucidated through DFT calculations (Figs. S44- 46). The Cd atoms played a crucial role in the adsorption of CH\(_{3}\)OH and the intermediate reaction steps (\*CH\(_{3}\)OH\->\*CH\(_{3}\)O\->\*CH\(_{2}\)O\->\*CH\(_{2}\)OOH\->\*CHOOH\->\*CHO\(_{2}\)O\->\*CO\(_{2}\)). The O atoms within the Cd- O- Ti sites assisted the Cd atoms in dissociating the H atoms in CH\(_{3}\)OH and CH\(_{3}\)O intermediates. Meanwhile, the Ti atoms are responsible for the adsorption and dissociation of H\(_{2}\)O into \*H and \*OH species. This reaction process follows the Langmuir- Hinshelwood mechanism. + +## Supplementary Information Revision: + +<--- Page Split ---> +![](images/Figure_unknown_8.jpg) + +
Fig. S26 Quasi-in situ XPS spectrum of the 5Cd/P25 catalyst during the MSR reaction at \(290^{\circ}\mathrm{C}\) and a S/C ratio of 3/1.
+ +Note: The \(\mathrm{Cd3d_{5 / 2}}\) binding energy at \(405.6\mathrm{eV}\) was characteristic of \(\mathrm{Cd^{2 + }}\) species, while the Ti \(2\mathrm{p}^{3 / 2}\) peak centered at \(458.8\mathrm{eV}\) corresponded to \(\mathrm{Ti^{4 + }}\) in the \(\mathrm{TiO_2}\) matrix. Deconvolution of the O1s spectrum revealed three chemically distinct oxygen species: the primary component at \(530.1\mathrm{eV}\) originated from lattice oxygen (Olatice) in \(\mathrm{TiO_2}\) , the intermediate peak at \(531.5\mathrm{eV}\) was associated with oxygen vacancies (Ov), and the high- binding- energy component at \(532.7\mathrm{eV}\) resulted from surface- adsorbed hydroxyl groups (\*OH). Notably, comparative analysis throughout the catalytic process showed that (i) the cadmium valence state remained unchanged and (ii) the oxygen vacancy concentration maintained relative stability (10- 12% area ratio). These observations indicate that the catalytically active centers are predominantly Cd- O- Ti interface sites rather than oxygen vacancy- mediated mechanisms. + +6. The reaction mechanism proposed in the study requires further elaboration. Identifying the rate-determining step (RDS) is crucial to understanding the catalytic process and design of the next generation of catalysts. + +Response: Thank you for your kind advice. In our initial submission, the mechanistic discussion was condensed due to word limit constraints. In response to your insightful comments, we have now conducted additional kinetic experiments and comprehensively revised the reaction mechanism analysis. Our response focuses on clarifying the research logic underlying mechanistic investigations and presenting the + +<--- Page Split ---> + +newly incorporated experimental validations. Detailed modifications are systematically documented in the revised manuscript (Section Reaction Mechanism Studies) and Supplementary Information (Scheme 1). + +(1) To elucidate the MSR mechanism among three proposed pathways (MD-WGS, methyl formate hydrolysis, and formate degradation), we first conducted independent MD and WGS reaction analyses (Fig. S40). Under MD conditions at \(290^{\circ}\mathrm{C}\) , methanol conversion reached merely \(1.7\%\) with \(\mathrm{CO_2}\) as the dominant product (\~77% selectivity). Notably, the conversion progressively declined below \(1.0\%\) over time, suggesting \(\mathrm{CO_2}\) formation through intermediates reacting with surface hydroxyl groups (\*OH) until deactivation via \*OH depletion and intermediate accumulation. This observation demonstrates that MD is thermodynamically favorable but kinetically restricted. Parallel WGS evaluations under identical conditions (290 °C, \(\mathrm{P_{H_2O}} = 20 \mathrm{kPa}\) , \(\mathrm{CO / H_2O} = 1 / 1\) ) revealed limited CO conversion (\<5%) and negligible \(\mathrm{H_2}\) production rates (1.6 mmol \(\mathrm{g^{-1}}\) \(\mathrm{h^{-1}}\) ), contrasting sharply with the superior MSR performance (264.7 mmol \(\mathrm{g^{-1} h^{-1}}\) \(\mathrm{H_2}\) production rate under equivalent \(\mathrm{CH_3OH / H_2O}\) partial pressures). These findings conclusively exclude the MD-WGS pathway as the operative MSR mechanism. + +![](images/Figure_unknown_9.jpg) + +
Fig. S40 (a) \(\mathrm{CH_3OH}\) conversion in MD and CO conversion in WGS. (b) Product selectivity for MSR, MD, and WGS. (c) Corresponding \(\mathrm{H_2}\) production rates.
+ +(2) To gain deeper insight into the reaction mechanism, in situ DRIFTS was employed (Figure R2). Results indicated that the support exhibited weak methanol adsorption, primarily functioning in water adsorption and dissociation. However, in the presence of single-atom Cd, strong adsorption peaks of methoxy and formate species emerged. As temperature increased, these species were rapidly + +<--- Page Split ---> + +consumed, coinciding with the appearance of \(\mathrm{CO_2}\) , indicating that \(\mathrm{CO_2}\) and \(\mathrm{H}_2\) generation occurred via formate decomposition. Neither methyl formate nor CO was detected during the reaction or Ar blow- off stage. TPSR analysis also confirmed formate as the main intermediate, with no methyl formate formation. These findings suggest that the MSR reaction proceeds through formate decomposition. + +![](images/Figure_unknown_10.jpg) + +
Figure R2 In situ DRIFTS of (a) A, (b) R, (c) P25, (d) 5Cd/A, (e) 5Cd/R, and (f) 5Cd/P25.
+ +(3) KIE experiment showed that C-H dissociation of methanol was more difficult than O-H bond dissociation (Figure R3a). To verify which step in C-H bond dissociation was the RDS, we derived the rate equation. Assuming methoxy dehydrogenation was the RDS, the derived rate equation showed first-order dependence on methanol partial pressures (The detailed derivation of the rate equation is provided in Scheme 1 in the SI or the response to reviewer 2's sixth question). Given competitive adsorption of methanol and water, the reaction order for methanol should be less than 1. The experimentally determined reaction order of 0.72 aligned with the kinetic equation, confirming methoxy dehydrogenation as the RDS (Figure R3b). + +<--- Page Split ---> +![](images/Figure_unknown_11.jpg) + +
Figure R3 (a) KIE measurements on the 5Cd/P25 catalyst by modulating the isotopic composition of the feed gas. (b) Reaction rate equation and reaction order of \(\mathrm{CH_3OH}\) on the 5Cd/P25 catalyst.
+ +(4) DFT calculations further explored the formate decomposition mechanism. Calculations of adsorption energies for methanol decomposition and formate formation intermediates revealed that \(\mathrm{Cd_1 / A}\) (101) and \(\mathrm{Cd_1 / R}\) (110) have low \(\mathrm{*CHO}\) adsorption energies, favoring CO formation thermodynamically. In contrast, \(\mathrm{Cd_1 / A}\) (101)-R (110) exhibited low adsorption energies for key intermediates ( \(\mathrm{*CH_2O}\) - \(\mathrm{*OH}\) , \(\mathrm{*CHOO}\) , and \(\mathrm{*CHOO}\) ), making the formate pathway more thermodynamically favorable. Transition-state calculations showed that water dissociation and activation on \(\mathrm{Cd_1 / A}\) (101)-R (110) have the lowest energy barriers, promoting formate formation and its subsequent decomposition into \(\mathrm{CO_2}\) and \(\mathrm{H_2}\) . This is attributed to the asymmetric coordination structure and high charge density of phase interface. Additionally, the high energy barrier for methoxy dehydrogenation confirmed it as the RDS. + +## Manuscript Revision: + +## "Reaction mechanism studies + +Since the reaction mechanism determines the product selectivity, we scrutinized various proposed reaction mechanisms for the novel catalysts, including methanol decomposition- water gas shift (MD- WGS), methyl formate hydrolysis, and formate decomposition (Supplementary Fig. 39). The MD reaction was initially investigated over the 5Cd/P25 catalyst at \(290^{\circ}\mathrm{C}\) under a methanol partial pressure of \(20\mathrm{kPa}\) with a feed rate of \(12\mathrm{mL}\mathrm{g}^{- 1}\mathrm{h}^{- 1}\) . \(\mathrm{CH_3OH}\) conversion was limited at \(1.7\%\) , with \(\mathrm{CO_2}\) constituting \(\sim 77\%\) of the products, accompanied by \(\mathrm{CO}\) ( \(\sim 10\%\) ) and + +<--- Page Split ---> + +\(\mathrm{CH}_4\) (\~13%) (Supplementary Fig. 40). The formation of \(\mathrm{CO}_2\) was proposed to originate from reactions between transient intermediates and hydroxyl groups (OH) on the catalyst support. Progressive depletion of surface OH species and accumulation of adsorbed intermediates correlated with the observed decline in methanol conversion to \(\leq 1.0\%\) over time. This finding indicates that, although thermodynamically favorable at high temperatures, MD is kinetically disfavored. Furthermore, comparative evaluation of WGS activity under equivalent conditions (290 °C, \(\mathrm{CO / H_2O} = 1 / 1\) , \(\mathrm{P_{H2O}} = 20 \mathrm{kPa}\) ) revealed limited catalytic performance, with CO conversion decaying from \(9.0\%\) to \(4.5\%\) over 10 hours and a correspondingly low \(\mathrm{H}_2\) production rate of \(1.6 \mathrm{mmol g^{- 1} h^{- 1}}\) . Strikingly, MSR under identical \(\mathrm{CH}_3\mathrm{OH}\) and \(\mathrm{H}_2\mathrm{O}\) partial pressures (20 kPa each) demonstrated a two- order- of- magnitude enhancement in \(\mathrm{H}_2\) production rates (264.7 mmol \(\mathrm{g^{- 1} h^{- 1}}\) ). These findings suggest that WGS contributes negligibly to \(\mathrm{H}_2\) generation, confirming that the MD- WGS pathway is unlikely to be viable for the Cd- based catalysts. + +In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was conducted to elucidate the reaction mechanism. When exposed to \(\mathrm{CH}_3\mathrm{OH} / \mathrm{H}_2\mathrm{O}\) between 50 and \(320^{\circ}\mathrm{C}\) , only weak methanol physisorbed peaks ( \(\mathrm{u}\) (CO) at \(1000–1100 \mathrm{cm}^{- 1}\) , \(\delta\) (CH) at \(1300–1500 \mathrm{cm}^{- 1}\) , and \(\mathrm{u}\) (CH) at \(2800–3000 \mathrm{cm}^{- 1}\) ) were observed on A, R, and P25, aside from \(\mathrm{H}_2\mathrm{O}\) adsorption and \*OH peaks ( \(\delta\) ( \(\mathrm{H}_2\mathrm{O}\) ) at \(1651 \mathrm{cm}^{- 1}\) and \(\mathrm{u}\) (OH) at \(3710 \mathrm{cm}^{- 1}\) ) (Supplementary Fig. 41 and Supplementary Table 10). These findings demonstrate that the functionality of supports is limited to facilitating \(\mathrm{H}_2\mathrm{O}\) adsorption and dissociation. In stark contrast, after loading Cd single atoms, distinct methoxy (\* \(\mathrm{CH}_3\mathrm{O}\) , \(\delta\) (CH) at \(1431 \mathrm{cm}^{- 1}\) ) and bidentate formate (b- \* \(\mathrm{HCOO}^-\) , \(\mathrm{u}_s\) (OCO) at \(1336 \mathrm{cm}^{- 1}\) , \(\mathrm{u}_{as}\) (OCO) at \(1554 \mathrm{cm}^{- 1}\) ) species emerged \(^{5,29}\) , which indicated that Cd single atoms were responsible for \(\mathrm{CH}_3\mathrm{OH}\) adsorption and dissociation (Figs. 4a- c). As the reaction temperature increased, the \* \(\mathrm{CH}_3\mathrm{O}\) and b- \* \(\mathrm{HCOO}^-\) were rapidly consumed, coinciding with the emergence of gaseous \(\mathrm{CO}_2\) peaks at \(2308\) and \(2375 \mathrm{cm}^{- 1}\) , indicating that \(\mathrm{H}_2\) generation resulted from formate transformation. Notably, on 5Cd/P25, \* \(\mathrm{CH}_3\mathrm{O}\) and b- \* \(\mathrm{HCOO}^-\) were transformed more rapidly at a lower temperature (200 °C) compared to 5Cd/A (260 °C) and 5Cd/R (320 °C) (Fig. 4d). This trend aligns with the catalytic performance, implying that interfacial Cd single atoms are more conducive to intermediates transformation. Additionally, no characteristic peaks indicative of methyl formate (\* \(\mathrm{HCOOCH}_3\) ) were detected in the \(1700–1800 \mathrm{cm}^{- 1}\) range during the reaction and the Ar sweeping stage \(^{30}\) . Similarly, temperature- programmed surface reaction (TPSR) analyses + +<--- Page Split ---> + +exclusively identified formate species, with no indication of HCOOCH3 (Fig. 4e and Supplementary Fig. 42). These findings rule out mechanism pathways involving methyl formate hydrolysis via esterification of formic acid with methanol, followed by its hydrolysis to yield CO2 and H2. Therefore, we propose that the formate decomposition pathway dominates the reaction mechanism on the SACs, where methanol initially decomposes into \(*CH_3O\) , subsequently dehydrogenates to \(*H_2CO\) , and reacts with \(*OH\) groups from dissociated H2O to form \(*HCOO^-\) . This intermediate then further dehydrogenates, yielding H2 and CO2. + +The kinetic isotope effect (KIE) experiments were conducted on the 5Cd/P25 catalyst to reveal the reaction kinetics. Switching the feedstock from CH3OH/H2O to CH3OD/H2O resulted in essentially unchanged H2 generation rates, yielding a KIE value (K/H/KD) of 1.1 (Fig. 4f). In contrast, substituting CH3OH/H2O with CD3OD/H2O caused a dramatic 4- fold decline in H2 production rates, corresponding to a significantly elevated KIE of 3.7. These findings establish that C- H bond cleavage exhibits substantially greater kinetic resistance than O- H bond scission, potentially identifying the rate- determining step (RDS) in the MSR reaction. To identify the specific RDS in elementary reactions, we derived the reaction rate equation based on established formate mechanism. According to previous reports, assuming that methoxy dehydrogenation \((*CH_3O \rightarrow *CH_2O + *H)\) was RDS, the derived rate equation showed a first- order dependence on CH3OH pressures (Supplementary scheme 1). Considering competitive adsorption between CH3OH and H2O on active sites, the theoretical CH3OH reaction order was predicted to be less than unity (<1). The experimentally determined CH3OH reaction order of 0.72 demonstrated excellent agreement with the kinetic model (Fig. 4g), providing conclusive evidence that methoxy dehydrogenation constitutes the RDS in this pathway. + +DFT calculations based on the established Cd1/A (101), Cd1/R (110), and Cd1/A (101)- R (110) models provided complementary theoretical insights into the MSR reaction pathway. The computed energy landscape revealed distinct adsorption energy profiles: \(*CHO\) exhibited significantly lower adsorption energies on Cd1/A (101) (- 1.45 eV) and Cd1/R (110) (- 1.18 eV) compared to the C1/A (101)- R (110) model (4.1 eV) (Supplementary Fig. 43). This energy disparity implies preferential CO generation pathways on Cd1/A (101) and Cd1/R (110) surfaces. Conversely, critical intermediates such as \(*CH_2O - *OH\) , \(*CHOOH\) and \(*CHO\) displayed substantially reduced adsorption energies on the Cd1/A (101)- R (110) surface. These findings + +<--- Page Split ---> + +demonstrate that the formate decomposition pathway is thermodynamically more favorable on the Cd1/A (101)-R (110) catalyst, attributable to its asymmetric coordination environment and enhanced charge density at the interface Cd single-atom sites. + +The transition states of the formate decomposition pathway were further investigated (Fig. 4h and Supplementary Figs. 44- 46). Consistent with in situ DRIFTS observations, DFT calculations revealed that both the adsorption and the stepwise dehydrogenation of CH3OH occurred at the Cd active site. The activation energy barriers for CH3OH dehydrogenation (TS1: 0.64 eV) were significantly lower than those for \*CH3O dehydrogenation (TS2: 0.87 eV) on the Cd1/A (101)-R (110) surface. This clearly demonstrates that the C-H bond cleavage encounters higher kinetic resistance than O-H bond scission, aligning with the experimental KIE results. Following \*CH3O dehydrogenation to \*CH2O, H2O adsorption and dissociation on adjacent Ti atoms generated \*H and \*OH species (TS3: 0.37 eV). Subsequent CH2O/OH recombination formed CH2OOH (TS4: 0.43 eV), which further dehydrogenated to produce CO2 and H2. Although TS1 and TS2 barriers on Cd1/A (101)-R (110) were modestly elevated relative to Cd1/A (101) (TS3/TS4: 1.07/0.60 eV) and Cd1/R (110) (TS3/TS4: 0.57/0.53 eV), the dissociation of H2O (TS3) and CH2OOH formation (TS4) exhibited significantly lower energy barriers in the phase interface model. These results demonstrated that the unique structural properties of the interfacial structure enhanced the dissociation and activation of H2O, thereby facilitating the subsequent formation of formate and H2. Consequently, these observations rationalized the high activity and low CO selectivity of the 5Cd/P25 catalyst. Additionally, the highest activation energy barrier (TS2: 0.87 eV) confirmed \*CH3O dehydrogenation as the RDS on the Cd1/A (101)-R (110), consistent with previous kinetic analysis." + +<--- Page Split ---> + +Reviewer: 2 + +## Response to Reviewer #2: + +Comments: + +In this work, Wang et. al, selectively decorated isolated Cd atoms to the interface of the P25 where heterogeneous structures of anatase and rutile coexist and the promoted H2 production rate has been achieved at \(\sim 292.9 \mathrm{mmol}\) gcat- 1 h- 1, which is about 15- fold and 8- fold higher than that of anatase and rutile dispersed Cd active components. The superior reaction performance has been attributed to the Cd- O- Ti interfacial structures. And this specific active component has been systematically probed by HRTEM, XAFS, EPR etc. A formate decomposition reaction pathway has been systematically discussed and was taken as the reaction mechanism for the hydrogen production. Finally, 3D printing has been introduced to produce the catalyst and this reaction system does show some potential in industrial applications. Generally, this is a good work and shows some interesting results, however, some of them are still under debate and might be critical to the overall conclusions. I suggest to reject this paper and give the author the opportunity to resubmit the work and hopefully the concerns listed bellow could be answered during the re- submission. + +1. First of all, the authors suggest that there is CdTiO3 at the interfacial site and it does not contribute to the hydrogen formation. I agree that, however, the Cd/CdOx does not show good activity either as comparisons. How can you explain that? And this CdTiO3 structure coexists with the real active components, is that possible most of the characterization is simply against this in-active structures (c.a. CdTiO3) rather than the real ones. + +Response: Thank you for raising this critical issue. We included CdTiO3, metallic Cd, and CdO nanoparticles in our studies to exclude their contribution to the reaction + +<--- Page Split ---> + +performance and to further demonstrate and emphasize that the active sites were Cd single atoms, particularly at the phase interface of P25. The poor catalytic performance of Cd/CdOx species resembled the subpar performance of clusters and nanoparticles observed in SACs studies. For instance, in CO oxidation and olefin hydroformylation reactions, atomically dispersed Au species demonstrated exceptional activity, whereas Au nanoparticles/clusters remained catalytically inert (J. Am. Chem. Soc. 2018, 140, 13808–13816; Chem Catal. 2022, 2, 1–11). The superior performance of single-atom configurations arises from their unique electronic structures that enable precisely tuned adsorption/desorption energetics of key intermediates—a fundamental advantage over nanometer-scale counterparts. + +The distinct coordination environments of Cd species critically determine their catalytic functionality. Metallic Cd nanoparticles exhibit symmetric Cd- Cd coordination, while CdO nanoparticles maintain regular Cd- O octahedral geometry. In stark contrast, interfacial Cd single- atom catalysts display exclusive Cd- O coordination with pronounced asymmetry. This structural distortion induces localized charge redistribution, creating polarized electronic domains fundamentally distinct from the delocalized electron clouds in metallic Cd and CdO. Such electronic configuration enables the Cd SACs to stabilize key reaction intermediates through enhanced orbital hybridization, rationalizing the superior activity over conventional Cd/CdO systems. + +## The location of CdTiO3 formed on the catalysts + +Our manuscript does not assert the interfacial localization of CdTiO3. As an ilmenite- type compound, CdTiO3 can be detected by XRD, which implies that its content is sufficient to be visualized in HAADF- STEM images. However, the lattice fringe of CdTiO3 was not observed at the phase interface of P25 (Fig. S15). Notably, combined XRD and Raman analyses demonstrated the CdTiO3 formation exclusively in R- phase- containing systems (5Cd/R and 5Cd/P25), with complete suppression in 5Cd/A (Figs. 1e, and S17). Meanwhile, crystallographic parameter analysis revealed a critical mechanistic insight: the R- phase/CdO lattice mismatch (2.4%) facilitated + +<--- Page Split ---> + +coherent heteroepitaxy, whereas anatase- CdO exhibited prohibitive mismatch (24.1%) that kinetically hindered phase transformation. This confirmed that limited CdTiO₃ formation in 5Cd/P25 originated from atomic migration of surface- isolated Cd species, which preferentially anchored on the R- phase domains of P25. + +## - Distinctions of active sites + +To distinguish the inert phase CdTiO₃ from the actual active sites (interface Cd single atoms), we also took this into consideration in advance during the research process and conducted an in- depth analysis. The results indicated that they can be clearly differentiated from each other. + +(1) Crystallographic structure analysis: + +XRD patterns identify CdTiO₃ (R- 3 space group, JCPDS#00- 052- 1436) as a hexagonally ordered ilmenite structure (Fig. S20). Therefore, HAADF- STEM images should display distinct lattice fringes, with atoms arranged in an ordered periodic pattern. In contrast, the interface single- atom Cd should appear as isolated, disordered bright spots due to the Z- contrast differentiation between Cd (Z=48) and Ti (Z=22), as shown in the 5Cd/P25 catalyst (Figures R4a and b). Taking 10Cd/P25 (Cd: 10 wt%) as an example, which exhibited more pronounced CdTiO₃ features, we observed CdTiO₃ particles of approximately 2 nm in size from HAADF- TEM images, with lattice fringes of 2.56 Å corresponding to the (110) crystal face of CdTiO₃ (Figures R4c and d). Therefore, the CdTiO₃ and Cd single atoms can be significantly differentiated based on structure characterizations. + +<--- Page Split ---> +![](images/Figure_unknown_12.jpg) + +
Figure R4 HAADF-STEM images of (a, b) interface Cd single atoms on the 5Cd/P25 catalyst and (c, d) CdTiO3 on the 10Cd/P25 catalyst.
+ +(2) Local coordination and electronic properties + +XANES revealed a downward shift in the near- edge absorption threshold for CdTiO3 compared to Cd SACs, indicating distinct electronic configurations (Figure R5a). EXAFS fitting demonstrated significantly shorter Cd- O bond lengths in CdTiO3 (2.05 Å) than in SACs (2.23 Å), confirming differential coordination environments (Figure R5b). In addition, XPS analysis further corroborated this differentiation: The coordination- saturated Cd atoms in CdTiO3 exhibited a 0.3- 0.7 eV lower Cd3d binding energy (404.8 eV) compared to undercoordinated single- atom Cd (Figure R5c). Therefore, the aforementioned characterizations can distinguish the inert active phase (CdTiO3) from the single- atom Cd active sites. + +![](images/Figure_unknown_13.jpg) + +
Figure R5 (a) Cd K-edge XANES spectra of fresh catalysts. (b) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of
+ +<--- Page Split ---> + +2. The authors suggest that the Cd is isolated, however, there is only one evidence from EXAFS, even the HAADF-STEM characterizations are not very clear. Is that possible the Cd are clusters rather than isolated site? Then it still gives advanced reaction performance, well the actually active component is not the isolated Cd. + +Response: We appreciate the reviewer's insightful comments. To more clearly show the Cd single atoms via HAADF- STEM, we have re- photographed them as much as possible (given the limitations of the instrumental resolution and the beam- sensitive nature of samples, this is the highest resolution we can achieve) and updated the figures in both the manuscript and the Supplementary Information (Fig. 1 and Figs. S13- 15). Since the atomic number of Cd is higher than that of Ti, it appears as a brighter point in the HAADF- STEM images. In addition, no clustered bright spots were observed across \(>20\) randomly sampled regions, excluding the formation of Cd cluster and nanoparticles. + +We believe that the presence of Cd clusters can be ruled out. Firstly, our samples were only calcined in air and not reduced in a reductive atmosphere (such as \(\mathrm{H}_2\) ), making the formation of metallic clusters highly unlikely. Secondly, based on the EXAFS data, if Cd clusters were present, Cd- Cd coordination would be evident. For instance, in the low- Cd- content catalysts developed by Wang et al. (Chinese J. Catal., 2022, 43,767- 770), the formation of Cd clusters after the reaction led to the detection of significant Cd- Cd coordination in the EXAFS spectra (Figure R6). + +<--- Page Split ---> + +Figure R6 EXAFS spectra with \(\mathrm{k^3}\) - weighted data obtained from low- Cd- content catalysts (Chinese J. Catal., 2022, 43,767- 770). + +To delineate the structural distinction between Cd single atoms and clusters, we synthesized a cluster- containing catalyst via \(\mathrm{H}_2\) reduction of the 5Cd/P25 at \(400^{\circ}\mathrm{C}\) (denoted as 5Cd/P25- 400H2). XRD analysis detected no metallic Cd diffraction peaks (Fig. S23a), suggesting the absence of crystalline Cd nanoparticles. Intriguingly, HAADF- STEM revealed the existence of sub- nanometer Cd clusters (Fig. S23b), which were further corroborated by EXAFS spectra showing prominent Cd- Cd coordination at \(\sim 2.8 \mathrm{\AA}\) (Fig. S23c). XPS analysis indicated a \(0.4 \mathrm{eV}\) downward shift in the Cd \(3\mathrm{d}_{5 / 2}\) binding energy for 5Cd/P25- 400H2 relative to 5Cd/P25, concurrent with the transformation of the Cd MNN Auger peak into a broadened feature characteristic of metallic clusters (Fig. S23d). + +Catalytic evaluation under identical reaction conditions revealed that cluster formation drastically impaired performance: Methanol conversion decreased from \(100\%\) to \(33.6\%\) , the \(\mathrm{H}_2\) production rate dropped from 97.7 to \(32.6 \mathrm{mmol} \mathrm{g}^{- 1} \mathrm{h}^{- 1}\) , and CO selectivity increased from \(0.5\%\) to \(2.6\%\) (Fig. S22). The results clearly differentiate between Cd clusters and single atoms, pinpointing the phase- interface Cd single atoms as actual active sites. + +![](images/Figure_unknown_14.jpg) + +
Fig. S23 Structural characterizations of the 5Cd/P25 catalysts after reduction at \(400^{\circ}\mathrm{C}\) (denoted
+ +<--- Page Split ---> + +as 5Cd/P25- 400H₂). (a) XRD patterns. (b and c) HAADF- STEM images of the 5Cd/P25- 400H₂. (d) Cd K-edge XANES spectra. (e) K³- weighted χ (k) function of EXAFS spectra. (f) XPS and AES spectra. + +The content as mentioned above was supplemented into the Fig. S23 in Supplementary Information. + +# Manuscript Revision: + +![](images/Figure_1.jpg) + +
Fig. 1 i-k, HAADF-STEM and EDS mapping images for 5Cd/A (i), 5Cd/R (j), and 5Cd/P25 (k)
+ +<--- Page Split ---> + +catalysts. + +![](images/Figure_unknown_15.jpg) + +
Fig. S13 Structural characterization of the 5Cd/A catalyst. (a) Low-magnification HAADF-STEM image. (b) High-resolution EDS elemental mapping of Cd distribution. (c) Atomic-scale EELS analysis. (d-f) Atomic-resolution HAADF-STEM images showing isolated Cd single atoms (indicated by yellow circles).
+ +![](images/Figure_unknown_16.jpg) + +
Fig. S14 Structural characterization of the 5Cd/R catalyst. (a) Low-magnification HAADF-STEM image. (b) High-resolution EDS elemental mapping of Cd distribution. (c) Atomic-scale EELS analysis. (d-f) Atomic-resolution HAADF-STEM images showing isolated Cd single atoms (indicated by yellow circles).
+ +<--- Page Split ---> +![](images/Figure_unknown_17.jpg) + +
Fig. S12 HAADF-STEM images of the 5Cd/P25 catalyst, showing Cd single atoms anchored between the A (101) and R (110) facets (yellow arrow and orange markers); scale bars: \(100\mathrm{nm}\) (a), \(50\mathrm{nm}\) (b), \(20\mathrm{nm}\) (c), \(5\mathrm{nm}\) (d). (e and f) Phase interface EDX elemental mapping images. (g-h) HAADF-STEM images of phase interface at a scale of \(1\mathrm{nm}\) (bright spots correspond to Cd single atoms).
+ +3. The author shows the selectivity of \(H_{2}\) , \(CO\) , \(CO_{2}\) and \(CH_{4}\) , and hydrogen dominants in the products, however, this is not correct. In this way, none of the product could reach \(100\%\) . The selectivity should be classified into carbonaceous species and hydrogen, which should be more reasonable, during which time, \(CO\) selectivity won't be as low as it is for right now. + +Response: We sincerely appreciate the rigorous technical evaluation and constructive + +<--- Page Split ---> + +guidance. In accordance with the reviewer's suggestions on product selectivity, we have implemented the following revisions throughout the manuscript (Figs. 1a-c, 5b, and Supplementary Figs. S1-S9, S22, S34-36). The CO selectivity of the optimal catalyst remained at a low level of \(0.3\%\) . + +The corresponding calculation equation has been revised as follows: + +\[\mathrm{CO~Selectivity~(\%) = \frac{n(CO,outlet)}{n(CO,outlet) + n(CO_2,outlet) + n(CH_4,outlet)}\times 100\%}\] \[\mathrm{CO_2~Selectivity~(\%) = \frac{n(CO_2,outlet)}{n(CO,outlet) + n(CO_2,outlet) + n(CH_4,outlet)}\times 100\%}\] \[\mathrm{CH_4~Selectivity~(\%) = \frac{n(CO_2,outlet)}{n(CO,outlet) + n(CO_2,outlet) + n(CH_4,outlet)}\times 100\%}\] + +4. For the activation energy determined, it looks that 82.7 KJ/mol is almost half the value of 152.1 KJ/mol, which may suggest that the system of Cd/P25 is suffering from diffusion limitations and it gives half the value of the real one and the superior reaction performance is not originated from the reduced activation energies. Well, this is only based on my assumption and the author definitely should exclude the mass/heat transfer limitations (both internal and outside channel diffusion limitations) before determining the apparent activation energies. + +Response: Thanks for pointing this out. We have thoroughly re- examined and analyzed our experimental data in light of your comments. We acknowledge that the influence of mass transfer cannot be entirely ruled out during the testing process. Specifically, the conversion rate was relatively high ( \(\sim 20\%\) ) in the previous tests, which potentially led to an underestimation of the apparent activation energy. + +To eliminate the effect of external diffusion, we increased the space velocity (liquid feed rate). As depicted in Fig. S6, for the three catalysts (5Cd/A, 5Cd/R, and 5Cd/P25), the methanol conversion shows an inverse relationship with increasing feed rate. Concurrently, the \(\mathrm{H}_2\) production rate gradually rises, and the curve tends to stabilize. This behavior suggests that the reaction on these catalysts is analogous to a + +<--- Page Split ---> + +first- order reaction kinetics model. Under high feed rate conditions, when the conversion rate was below \(10\%\) , the impact of feed rates on the \(\mathrm{H}_2\) production rate is minimal, indicating that the effect of external diffusion can be neglected. Therefore, we opted to conduct our activation energy tests at a high feed rate corresponding to a methanol conversion of less than \(10\%\) . This selection ensures that the influence of external diffusion is minimized, allowing for a more accurate assessment of the intrinsic catalytic activity and the apparent activation energy of the catalyst. + +To determine whether the effect of internal diffusion was negligible, we applied the Weisz- Prater criterion for calculation, as shown in Equations (1- 3). + +\[\begin{array}{l}\mathrm{WP} = \frac{\mathrm{r}\times\mathrm{R}^2}{\mathrm{C}_\mathrm{S}\times\mathrm{D}_\mathrm{e}}\\ \displaystyle \frac{1}{\mathrm{D}_\mathrm{e}} = \frac{\tau}{\epsilon}\left(\frac{1}{\mathrm{D}_\mathrm{m}} +\frac{1}{\mathrm{D}_\mathrm{k}}\right)\\ \displaystyle \mathrm{D}_\mathrm{k} = \frac{2}{3}\mathrm{d}_\mathrm{p}\sqrt{\frac{8\mathrm{R}\mathrm{T}}{\pi\mathrm{M}}} \end{array} \quad (1)\] + +\(\mathrm{r}\) represents the reaction rate, \(\mathrm{R}\) represents the particle radius, \(\mathrm{C}_\mathrm{s}\) represents the reactant concentration at the catalyst surface, \(\mathrm{D}_\mathrm{e}\) represents the effective diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\tau\) represents the pore tortuosity, \(\epsilon\) represents the porosity, \(\mathrm{D}_\mathrm{m}\) represents the molecular diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{D}_\mathrm{k}\) represents the Knudsen diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{d}_\mathrm{p}\) represents the average pore diameter \((\mathrm{m})\) , \(\mathrm{M}\) represents the molar mass of the diffusing species \((\mathrm{kg} / \mathrm{mol})\) , \(\mathrm{R}\) represents the gas constant, and \(\mathrm{T}\) represents the temperature \((\mathrm{K})\) . + +Under the conditions of \(290^{\circ}\mathrm{C}\) , \(\mathrm{S / C} = 3 / 1\) , \(0.1 \mathrm{MPa}\) , and methanol conversion below \(10\%\) , the Weisz- Prater (WP) values for \(5\mathrm{Cd / A}\) , \(5\mathrm{Cd / R}\) , and \(5\mathrm{Cd / P25}\) were \(1.0 \times 10^{- 7}\) , \(2.4 \times 10^{- 9}\) , and \(7.3 \times 10^{- 10}\) , respectively. All of them were much less than 1, so the internal diffusion limitation could be excluded. In addition, we added inert \(\mathrm{SiO}_2\) to the catalyst to promote heat transfer during the reaction process, ensuring no temperature gradient in the reaction zone and excluding the impact of heat transfer. Finally, we tested the \(\mathrm{H}_2\) production rate at every \(10^{\circ}\mathrm{C}\) intervals in the temperature range of \(250 - 290^{\circ}\mathrm{C}\) and calculated the corresponding apparent activation energy by substituting it into the Arrhenius equation (as shown in Equation 4). The apparent activation energies of the three catalysts \(5\mathrm{Cd / A}\) , \(5\mathrm{Cd / R}\) , and \(5\mathrm{Cd / P25}\) + +<--- Page Split ---> + +were 146.6 KJ/mol, 121.9 KJ/mol, and 107.3 KJ/mol, respectively (Fig. 1d). In comparison, the activation energy of the 5Cd/P25 catalyst was still the lowest, which did not affect the original conclusion that the interfacial Cd single atom sites with their unique interfacial structure and electronic properties had relatively excellent catalytic performance. + +\[\ln \mathbf{k} = \ln \mathbf{A} - \frac{\mathbf{E}_{\mathrm{a}}}{\mathrm{RT}} \quad (4)\] + +To enhance the transparency and reproducibility of the findings, we have added Fig. S6 and the calculation process of apparent activation energy in the SI section of the revised manuscript, and the corresponding content is as follows. + +![](images/Figure_unknown_18.jpg) + +
Fig. S6 Feed rate dependence of methanol conversion and \(\mathrm{H}_2\) production rates over 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts. Reaction conditions: catalyst \(0.1\mathrm{g} + \mathrm{SiO}_2 0.2\mathrm{g}\) ; liquid feed of \(\mathrm{S / C} = 3\) at \(6 - 45\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) ; \(\mathrm{N}_2\) carrier at \(20\mathrm{mL}\mathrm{min}^{-1}\) ; temperature: \(290^{\circ}\mathrm{C}\)
+ +![](images/Figure_1.jpg) + +
Fig. 1 Catalytic performance and structural characteristics of catalysts in the MSR reaction. d, Apparent activation energy evaluation (methanol conversion less than \(10\%\) ).
+ +5. If the real active component is the Cd-O-Ti structure, no matter which TiO₂ phase it connects to, the Cd/P25 should gives similar activities with either Cd/anatase or Cd/rutile. This is not very clear, this reviewer suggests the author put more effort on + +<--- Page Split ---> + +explaining that. For example, the highly dispersed Cd on amorphous \(\mathrm{TiO_2}\) might be also good for this reaction. + +Response: Thank you for your comment. As is well- known, the unique structure or electronic properties of single- atom catalysts is a significant factor determining reaction performance. Our characterizations and DFT calculations showed that although Cd- Ti- O coordination sites were fundamental active centers, differences in their microenvironment (structural and electronic properties) significantly affected catalytic performance. Therefore, the unique Cd- Ti- O sites at P25 anatase/rutile phase interfaces exhibit superior catalytic performance compared to those on individual phase surfaces. This is systematically demonstrated in the manuscript: + +In terms of structure, the atomic arrangement at the anatase- rutile phase interface in P25, which contained Ti vacancies, was disordered (Figs. 3a and b). Therefore, the Cd- Ti- O sites formed at the phase interface have an asymmetric structure, which is different from the symmetric structure of surface sites (Fig. S16). This special asymmetric structure also leads to its unique electronic properties. The oxidation state of Cd atoms at the interface was between that of the surface atoms of anatase or rutile. DFT calculations revealed that, compared with the Cd- Ti- O sites on the surface of anatase and rutile, the phase- interface Cd- Ti- O sites possessed a polar electronic domain and exhibit a higher electron density of states (Fig. 2e and Fig. S28). These characteristics decreased the adsorption and activation energies of reactants (Fig. 2f). In addition, electrochemical cyclic voltammetry proved that the Cd- Ti- O sites at the phase interface were more conducive to electron transfer to the reactants (Fig. 2d). \(\mathrm{CH_3OH - TPD}\) and TPSR experiments further revealed their strong adsorption and activation ability (Figs. 4e, S29, and S42). Therefore, the Cd- Ti- O sites formed at the phase interface had optimal performance. + +In accordance with the reviewer's suggestion, amorphous \(\mathrm{TiO_2}\) with a specific surface area of \(242 \mathrm{m^2 / g}\) was synthesized following the methodology established by Xu et al (J. Colloid Interface Sci., 2024, 653, 1006- 1017). As evidenced by the XRD + +<--- Page Split ---> + +patterns in Figure R7a, the \(\mathrm{TiO_2}\) support retained its amorphous nature after Cd loading, with no detectable diffraction peaks corresponding to crystalline Cd species, indicating their high dispersion. However, under MSR conditions ( \(290^{\circ}\mathrm{C}\) , S/C ratio of 3/1, 0.1 MPa pressure, and \(3\mathrm{mL}\cdot \mathrm{g}^{- 1}\cdot \mathrm{h}^{- 1}\) feed rate), distinct anatase- phase diffraction peaks emerged after the reaction. This structural evolution demonstrated the thermodynamic instability of the amorphous \(\mathrm{TiO_2}\) under MSR conditions. Catalytic performance evaluations revealed substantially lower methanol conversion ( \(0.8\%\) ) for this catalyst compared to 5Cd/A, 5Cd/R, and 5Cd/P25 benchmarks (Figure R7b). These results collectively suggested that the crystallographic form and specific surface area of \(\mathrm{TiO_2}\) were not the determining factor for the catalytic activity of Cd- O- Ti sites. Rather, the exceptional catalytic performance originated from the unique local coordination environment and electronic interactions within the Cd- Ti- O asymmetric structures at phase interfaces. + +![](images/Figure_unknown_19.jpg) + +
Figure R7 (a) XRD patterns of the amorphous \(\mathrm{TiO_2}\) , 5Cd/amorphous \(\mathrm{TiO_2}\) , and spent amorphous \(\mathrm{TiO_2}\) catalysts. (b) Comparative catalytic performance. Reaction conditions: \(290^{\circ}\mathrm{C}\) , S/C ratio of 3/1, 0.1 MPa pressure, carrier gas of \(30\mathrm{mL} / \mathrm{min}\mathrm{N}_2\) , and \(3\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) feed rate.
+ +6. There is contradictory assessment in elucidating the reaction mechanism of hydrogen production. Clearly, the C-H bond rupture within methanol is the rate determining step based on the KIE values determined. And usually, CO could be easily generated from methanol decomposition. Negligible CO determined would be attributed to the strong WGS reaction in the system, and it was not mentioned. This + +<--- Page Split ---> + +reviewer suggests the author to clarify that by determining the reaction rate and equilibrium constant on WGS at the relative conditions. + +Response: We appreciate the reviewer's insightful comments regarding the possible role of the WGS reaction in consuming CO. Below we clarify why the WGS reaction is not dominant in our system, supporting the formate decomposition pathway as the primary mechanism. + +![](images/Figure_unknown_20.jpg) + +
Fig. S40 (a) CH\(_3\)OH conversion in MD and CO conversion in WGS. (b) Product selectivity for MSR, MD, and WGS. (c) Corresponding H\(_2\) production rates.
+ +We performed methanol decomposition (MD) experiments. When only CH\(_3\)OH was introduced (with a partial pressure of 20 kPa), the CH\(_3\)OH conversion was just 1.7%, and the CO\(_2\) selectivity in the products was as high as \(\sim\) 80%, with CO and CH\(_4\) selectivity at 10% each (Fig. S40a and b). As the reaction proceeded, the CH\(_3\)OH conversion progressively declined to below 1%. These observations suggest that the direct C-H bond cleavage of CH\(_3\)OH to form CO is kinetically hindered. This could be attributed to methanol adsorption and dissociation on the catalyst surface, forming \(*CH_3O\) or \(*CH_2O\) intermediates. While a small fraction of these intermediates dissociates to CO, the majority react with surface \(*OH\) to form formate ( \(*HCOO\) ), which subsequently decomposes to CO\(_2\), or with \(*H\) to produce CH\(_4\). In-situ DRIFTS confirmed the appearance of strong \(*HCOO\) and \(*CH_3O\) adsorption after methanol adsorption (Fig. 4a-c). As the reaction proceeds, the \(*OH\) on the catalyst surface is consumed. The surface intermediates ( \(*CH_3O\) and \(*CHO\) ) gradually accumulate due to the lack of \(*OH\) from water, making the formate reaction path difficult and leading to a drop in CH\(_3\)OH conversion. This shows that although MD is thermodynamically favorable at high temperatures, it is kinetically unfavorable in our catalytic system (If + +<--- Page Split ---> + +MD is favorable, the CO selectivity should be \(100\%\) . We also conducted WGS reactions to verify the reaction mechanism. Under conditions of \(20\mathrm{kPa}\) water partial pressure, \(\mathrm{CO / H_2O} = 1 / 1\) , and \(290^{\circ}\mathrm{C}\) , the CO conversion decreased from \(9\%\) to \(5\%\) , with a \(\mathrm{H}_2\) production rate of only \(\sim 2\mathrm{mmol}\mathrm{g}^{- 1}\mathrm{h}^{- 1}\) , indicating kinetic hindrance. In contrast, under the same methanol and water partial pressures, the MSR reaction had a high \(\mathrm{H}_2\) production rate of \(264.7\mathrm{mmol}\mathrm{g}^{- 1}\mathrm{h}^{- 1}\) (Fig. 40c). Comparison of MD, WGS, and MSR reactions thus showed that \(\mathrm{MD} + \mathrm{WGS}\) was not the reaction mechanism. In addition, in the \(\mathrm{MD} + \mathrm{WGS}\) mechanism, prior studies suggested that in TPSR experiments, methanol and water consumption would lag behind: methanol was first converted to CO at a lower temperature, which then reacted with water to form \(\mathrm{CO}_2\) at a higher temperature (Figure R8). However, this tandem process was not observed in our experiment (Fig. 4e). Instead, \(\mathrm{CO}_2\) generation coincided with formate production, further confirming that formate decomposition is the mechanism of our catalytic system. + +Figure R8 TPSR experiments in previous reports (Appl. Catal. B: Environ., 2010, 95, 87- 92; Chem. Eng. J., 2023, 473, 145458). + +In prior studies of Pt- and Cu- based systems, C- H bond cleavage as the rate- determining step (RDS) has been extensively reported, with methoxy dehydrogenation considered the RDS for the mechanism of \(\mathrm{MD} + \mathrm{WGS}\) and formate decomposition (J. Am. Chem. Soc., 2023, 145, 905- 918; Nat. Commun., 2023, 14, 7980; Nat. Catal., 2022, 5, 99- 108). To verify if methoxy dehydrogenation in elementary reactions is the RDS, we derived a kinetic rate equation. + +Formate mechanism elementary steps: + +(1) Methanol adsorption and dissociation: + +<--- Page Split ---> + +\[\mathrm{CH_3OH(g)} + 2*\stackrel {k_1}{\rightleftharpoons}*\mathrm{CH_3O} + *\mathrm{H} \quad (1)\] + +(2) Methoxy dehydrogenation: + +\[* \mathrm{CH_3O} \xrightarrow{k} \mathrm{CH_2O} + * \mathrm{H} \quad (\mathrm{R.D.S}) \quad (2)\] + +(3) Water dissociates to form hydroxyl groups: + +\[\mathrm{H_2O} + *\stackrel {k_2}{\rightleftharpoons}*\mathrm{OH} + *\mathrm{H} \quad (3)\] + +(4) Formaldehyde oxidizes to form formates: + +\[* \mathrm{CH_2O} + * \mathrm{OH} \xrightarrow{k_3} * \mathrm{HCOO} + \mathrm{H_2} \quad (4)\] + +(5) Formates decompose to produce \(\mathrm{CO_2}\) : + +\[* \mathrm{HCOO} \xrightarrow{k_4} \mathrm{CO_2} + * \mathrm{H} + * \quad (5)\] + +(6) Hydrogen atoms desorption to \(\mathrm{H_2}\) : + +\[* 2\mathrm{H} \xrightarrow{k_5} \mathrm{H_2} + 2 * \quad (6)\] + +Assume that all steps except the RDS are in equilibrium, and the coverage \((\theta)\) is determined by the equilibrium constant. + +\[k_{1} = \frac{\theta_{CH_{3}O}\cdot\theta_{H}}{P_{CH_{3}OH}\cdot\theta_{*}^{2}} \quad (7)\] + +\[k_{2} = \frac{\theta_{OH}\cdot\theta_{H}}{P_{H_{2}O}\cdot\theta_{*}} \quad (9)\] + +\[k_{5} = \frac{P_{H_{2}}\cdot\theta_{*}^{2}}{\theta_{H}^{2}} \quad (11)\] + +Substitute equation (12) into equation (8): + +\[\theta_{CH_3O} = k_1 \cdot \sqrt{\frac{k_5}{P_{H_2}}} \cdot P_{CH_3OH} \cdot \theta_* \quad (13)\] + +Substitute equation (12) into equation (10): + +\[\theta_{OH} = k_2 \cdot \sqrt{\frac{k_5}{P_{H_2}}} \cdot P_{H_2O} \cdot \theta_* \quad (14)\] + +The intermediate product coverage is assumed to be negligible \((\theta_{CH_2O} \approx 0, \theta_{\mathrm{HCOO}} \approx 0)\) . + +Conservation of total active sites: + +\[\theta_{*} + \theta_{H} + \theta_{CH_{3}O} + \theta_{OH} = 1 \quad (15)\] + +<--- Page Split ---> + +\[\theta_{*} = \frac{1}{1 + \sqrt{\frac{P_{H_{2}}}{k_{5}} + k_{1}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{CH_{3}OH} + k_{2}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{H_{2}O}}} \quad (16)\] + +RDS: + +\[r = k\cdot \theta_{CH_{3}O}\cdot \theta_{*} \quad (17)\] + +\[r = \frac{k k_{1}\sqrt{k_{5}P_{CH_{3}OH}}}{\sqrt{P_{H_{2}}}\left(1 + \sqrt{\frac{P_{H_{2}}}{k_{5}} + k_{1}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{CH_{3}OH} + k_{2}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{H_{2}O}}}\right)^{2}} \quad (18)\] + +At low partial pressure of methanol \((k_{1}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{CH_{3}OH}}\ll 1,P_{CH_{3}OH}\to 0)\) : + +\[r\propto P_{CH_{3}OH}\left(\text{first order reaction}\right)\] + +As experimental findings showed competitive adsorption between water and methanol, the water adsorption term \(k_{2}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{H_{2}O}}\) cannot be ignored. Considering the minor impact of \(\mathrm{H}_{2}\) partial pressure, the methanol reaction order becomes less than 1, approximating a first- order reaction. + +![](images/Figure_4e.jpg) + +
Fig. 4e Reaction orders on CH3OH in the 0.9-3.8 kPa range.
+ +The experimental reaction order of methanol was 0.72 at low partial pressure (0.9- 3.8 kPa), consistent with the rate equation. This indicates the reaction mechanism is formate decomposition. + +7. I cannot quite follow why the overall reaction rate could be influenced by the electronic properties determined in figure 2, then I suggest the author move these results to the ESI. + +<--- Page Split ---> + +Response: Thank you for your comment. The impact of electronic properties on performance mainly stems from two aspects. Firstly, EELS analysis revealed that electrons from Cd atoms were transferred to Ti atoms at the interface (Fig. 2c). Low- temperature EPR further indicated that electrons from the distorted \(\mathrm{Ti^{4 + }}\) tetrahedra at the interface were readily transferred to Cd atoms (Fig. 3c). These inter- atomic electron transfers enhance the strong interactions at the interface, as evidenced by the \(\mathrm{H}_2\) - TPR results (Fig. S27). Consequently, the resulting interfacial Cd- O- Ti sites exhibited high stability, ensuring consistent performance during prolonged operation (Fig. 1c). + +On the other hand, the impact of electronic properties on the adsorption and activation of reactants was significant. The asymmetric structure at the interface resulted in a coordination number and oxidation state of Cd that were intermediate between those of Cd/A and Cd/R catalysts (Fig. 2b). Compared to the surfaces of A and R, the charge distribution exhibited asymmetry (polar electronic domain) and had a higher electron density of states (Figs. 2e and S28), which was conducive to the adsorption and activation of reactants (a high electron density of states in polar electronic domains facilitates the polarization of reactant molecules). Additionally, previous studies have shown that phase interfaces facilitated electron transfer from rutile to anatase, thereby affecting the adsorption and activation of reactants (Nat. Mater., 2013, 12, 798- 801). Our CV results directly demonstrated that the interfacial Cd- O- Ti sites facilitated rapid electron transfer to the reactants (Fig. 2d), making them more favorable for the quick adsorption and activation of reactants. DFT calculations and \(\mathrm{CH}_3\mathrm{OH}\) - TPD further confirmed that the adsorption energy of \(\mathrm{CH}_3\mathrm{OH}\) and \(\mathrm{H}_2\mathrm{O}\) was lowest at the interfacial Cd- O- Ti sites and that their activation was easiest. DFT calculations also indicated that electronic properties significantly reduced the transition- state energy barrier, thereby determining its high activity. + +Therefore, we propose that electronic properties are intrinsically linked to the reaction kinetics through a cascade mechanism involving asymmetric charge distribution, elevated charge density, and rapid charge transfer, which collectively facilitate reactant adsorption/activation and lower the reaction energy barrier, thereby + +<--- Page Split ---> + +enhancing catalytic activity and reaction rates. This mechanistic interpretation is supported by the detailed analyses in Figure 2 and the accompanying discussions in the main text. + +8. I don't know why the HAADF-STEM images were given twice in Figure 1 and Figure 3. I hope the author could re-organize the results and make it easy to read. + +Response: Thank you for your comments. HAADF- STEM images in Figure 1 are used to demonstrate the formation of Cd single- atom sites at the anatase (101)/rutile (110) phase interfaces in P25, highlighting the phase- interface confined anchoring configuration. Figure 3 systematically elucidates the driving forces for preferential Cd single- atom anchoring at P25 phase interfaces and the structure- performance relationship under the modulation of phase interface densities. Specifically, the atomic- resolution images in Figs. 3a- b reveal non- equilibrium phase interfaces of P25 characterized by irregular topography and disordered atomic configurations with abundant atomic- level defects, which thermodynamically favor Cd anchoring. Fig. 3g (left) demonstrates that after reducing P25 with \(\mathrm{H}_2\) for 4 hours, the phase- interface density is increased to \(10.1\mathrm{m}^2\mathrm{g}^{-1}\) . After loading Cd, more and brighter contrast bands are observed at the interface, indicating that more single atoms are positioned at the phase interface. This observation is consistent with the Cd contents detected by ICP after the reaction. This suggests that phase- interface density can increase the loading of single atoms at the interface, thereby potentially enhancing the \(\mathrm{H}_2\) production rate. However, when the reduction time was too long, such as 8 hours, obvious aggregation of particles occurred, possibly due to the destruction of the phase- interface structure, making it less favorable for single- atom formation. + +To enhance conceptual clarity, we have revised the manuscript with improved textual organization to ensure logical progression of the key findings. + +# Manuscript Revision: + +<--- Page Split ---> + +Lines 160- 166: + +"High- angle annular dark field scanning transmission electron microscopy (HAADF- STEM) further revealed atomically dispersed Cd atoms (bright contrast spots) on A (101) and R (110) facets of 5Cd/A and 5Cd/R (Supplementary Figs. 13 and 14). Notably, in the 5Cd/P25 catalyst, Cd single atoms were primarily anchored at the anatase (101)/rutile (110) phase interface, as evidenced by the distinct bright contrast band observed along the interfacial boundary in Fig. 1k and Supplementary Fig. 15." + +Lines 279- 288: + +"HAADF- STEM further elucidated the microstructure of the phase interface in pure P25. Lattice discontinuities and irregularities were clearly identified at the interface between the A (101) and R (110) facets, as shown by the gray line in Fig. 3a, indicating the presence of interface defects. Atomic- resolution characterization further revealed that subtle disorder in the interfacial atomic arrangement was confined to a narrow region at the interface, as highlighted by the white circle in Fig. 3b. These observations were likely due to surface atom rearrangements resulting from the lattice mismatch between the A (101) and R (110) facets, leading to the formation of abundant Ti defects at the incoherent phase interface (asymmetric structure)." + +Lines 353- 367: + +"Prolonged pretreatment was found to increase the interface density. Notably, the phase interface region appeared brighter after a 4- hour \(\mathrm{H}_2\) pretreatment, and the number of bright interface bands significantly increased in the HAADF- STEM images (Fig. 3g left and Supplementary Fig. 38). Atomic resolution analysis further revealed that the distinct bright interface bands correspond to dispersed Cd single atoms (Supplementary Fig. 38). Moreover, ICP- OES results showed that the Cd loss rate of the spent catalysts substantially decreased with the increase of the interface density (Fig. 3h). This trend suggested an increased number of single atoms stably anchored at the interface, thereby leading to a higher interface site density. A 4- hour \(\mathrm{H}_2\) pretreatment yielded the highest interface density \((10.1 \mathrm{m}^2 \mathrm{g}^{-1})\) and a remarkable \(\mathrm{H}_2\) production rate of \(292.9 \mathrm{mmol} \mathrm{g}_{\mathrm{cat}}^{-1} \mathrm{h}^{-1}\) (Fig. 3h), surpassing conventional MSR catalysts (Supplementary Table 9). An 8- hour pretreatment, however, resulted in the formation of small Cd particles (1- 2.5 nm) (Fig. 3g right), led to increased Cd loss after the reaction, and compromised catalytic performance. This was likely attributed to the disruption of the phase interface structure." + +<--- Page Split ---> + +9. From the reaction coordinate, it looks that the hydrogen formation over Cd1/A(101) is quite difficult, while it is not quite the situation for Cd/P25. This might be the main difference among these samples. And it is not well discussed. This reviewer suggests the author to clarify that. + +Response: Thank you for your comment. The formation of \(\mathrm{H}_2\) on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110) surfaces was thermodynamically unfavorable. Adsorption energy calculations revealed that critical intermediates such as \(* \mathrm{CH}_2 \mathrm{COOH}\) , \(* \mathrm{CH}_2 \mathrm{OH}\) , and \(* \mathrm{CHO}\) exhibit strong endothermic adsorption characteristics, with adsorption energies on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110) exceeding those on the \(\mathrm{Cd}_1 / \mathrm{A}\) (101)- R (110) model by significant margins (Table R1). Transition state analyses further demonstrate substantially increased activation energies of \(* \mathrm{H}_2 \mathrm{O}\) dissociation and \(* \mathrm{CH}_2 \mathrm{OH}\) formation on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110) compared to \(\mathrm{Cd}_1 / \mathrm{A}\) (101)- R (110). These combined thermodynamic and kinetic limitations collectively impeded \(\mathrm{H}_2\) generation on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110). The origin of these differences lies in the asymmetric interfacial structure of \(\mathrm{Cd}_1 / \mathrm{A}\) (101)- R (110), which exhibits enhanced electron density at the interface, facilitating intermediate stabilization and activation. + +Table R1 Adsorption energies of critical intermediates. + +
*CH2OOH*CHOOH*CHOO
Cd1/A (101)2.49 eV3.16 eV1.8 eV
Cd1/R (110)2.50 eV2.75 eV2.82 eV
Cd1/A (101)-R (110)0.96 eV0.60 eV0.19 eV
+ +During our initial submission, we were constrained by word limit requirements and provided only a concise description of the DFT calculations, which limited our ability to elaborate on the underlying mechanistic distinctions. To address this, we have comprehensively revised the DFT section in the present work to systematically elucidate how structural differences among catalyst models influence activation energies and catalytic performance. The revised content is presented below: + +Lines 444- 476: + +<--- Page Split ---> + +(110) models provided complementary theoretical insights into the MSR reaction pathway. The computed energy landscape revealed distinct adsorption energy profiles: \*CHO exhibited significantly lower adsorption energies on Cd\(_1\)/A (101) (-1.45 eV) and Cd\(_1\)/R (110) (-1.18 eV) compared to the C\(_1\)/A (101)-R (110) model (4.1 eV) (Supplementary Fig. 43). This energy disparity implies preferential CO generation pathways on Cd\(_1\)/A (101) and Cd\(_1\)/R (110) surfaces. Conversely, critical intermediates such as \*CH\(_2\)O-\*OH, \*CHOOH and \*CHOO displayed substantially reduced adsorption energies on the Cd\(_1\)/A (101)-R (110) surface. These findings demonstrate that the formate decomposition pathway is thermodynamically more favorable on the Cd\(_1\)/A (101)-R (110) catalyst, attributable to its asymmetric coordination environment and enhanced charge density at the interface Cd single-atom sites. + +The transition states of the formate decomposition pathway were further investigated (Fig. 4h and Supplementary Figs. 44- 46). Consistent with in situ DRIFTS observations, DFT calculations revealed that both the adsorption and the stepwise dehydrogenation of CH\(_3\)OH occurred at the Cd active site. The activation energy barriers for CH\(_3\)OH dehydrogenation (TS1: 0.64 eV) were significantly lower than those for \*CH\(_3\)O dehydrogenation (TS2: 0.87 eV) on the Cd\(_1\)/A (101)-R (110) surface. This clearly demonstrates that the C-H bond cleavage encounters higher kinetic resistance than O-H bond scission, aligning with the experimental KIE results. Following \*CH\(_3\)O dehydrogenation to \*CH\(_2\)O, H\(_2\)O adsorption and dissociation on adjacent Ti atoms generated \*H and \*OH species (TS3: 0.37 eV). Subsequent CH\(_2\)O/H recombination formed CH\(_2\)OOH (TS4: 0.43 eV), which further dehydrogenated to produce CO\(_2\) and H\(_2\). Although TS1 and TS2 barriers on Cd\(_1\)/A (101)-R (110) were modestly elevated relative to Cd1/A (101) (TS3/TS4: 1.07/0.60 eV) and Cd1/R (110) (TS3/TS4: 0.57/0.53 eV), the dissociation of H\(_2\)O (TS3) and CH\(_2\)OOH formation (TS4) exhibited significantly lower energy barriers in the phase interface model. These results demonstrated that the unique structural properties of the interfacial structure enhanced the dissociation and activation of H\(_2\)O, thereby facilitating the subsequent formation of formate and H\(_2\). Consequently, these observations rationalized the high activity and low CO selectivity of the 5Cd/P25 catalyst. Additionally, the highest activation energy barrier (TS2: 0.87 eV) confirmed \*CH\(_3\)O dehydrogenation as the RDS on the Cd\(_1\)/A (101)-R (110), consistent with previous kinetic analysis." + +<--- Page Split ---> + +Reviewer: 3 + +## Response to Reviewer #3 + +Comments: + +This research presents a phase- interface- stabilized Cd/P25 single- atom catalyst, which demonstrates much higher MSR performance than other Cd/TiO₂ counterparts. The authors uncovered Cd- O- Ti phase interface site that dominates the high MSR activity and low CO selectivity. They also show that the densities of phase interface/sites can be regulated. Additionally, the fundamental mechanism of enhanced MSR performance on Cd/P25 SACs is clearly revealed by the combination of experimental and theoretical studies. This manuscript is well structured and demonstrated. I am willing to recommend its publication in Nature Communications. However, I would like to see the following concerns addressed before they can be further considered. + +Main concerns: + +1. In the Abstract, the statement "The formed Cd-O-Ti phase interface sites exhibit asymmetric geometric and electronic properties that achieve 100% methanol conversion, minimal CO selectivity (<0.1%), and sustained stability exceeding 150 hours" leads to misunderstanding. 100% methanol conversion and <0.1% CO selectivity are not achieved by interface sites solely. + +Response: Thank you for pointing this out. You are correct; the formation of interfacial sites can achieve 100% methanol conversion and 0.13% CO selectivity, but the <0.1% CO selectivity requires further optimization of 3D printing to be achieved. To avoid any misunderstanding, we have removed this value from the abstract. + +## Manuscript Revision: + +Lines 20- 22 + +"The formed Cd-O-Ti phase interface sites exhibit asymmetric geometric and electronic properties that achieve 100% methanol conversion, a low CO concentration (<0.1 mol%) in the + +<--- Page Split ---> + +2. In Supplementary Fig. 2, it is interesting and surprising that Cd catalysts exhibit similar MSR performance. This means that Cd catalysts after air calculation at \(500^{\circ}\mathrm{C}\) and \(H_{2}\) reduction at \(290^{\circ}\mathrm{C}\) probably have the same active site. It is important to identify the properties of the catalysts at two states. + +![](images/Figure_unknown_21.jpg) + +
Fig. S21 Structural characterizations of the 5Cd/P25 catalysts after reduction at \(290^{\circ}\mathrm{C}\) . (a) XRD patterns. (b) XPS spectra of the Cd 3d orbitals. (c) Cd K-edge XANES spectra. (d) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of EXAFS spectra.
+ +Response: We appreciate the insightful feedback. Taking the 5Cd/P25 catalyst as an example, we compared the differences between the catalyst calcined at \(500^{\circ}\mathrm{C}\) and reduced at \(290^{\circ}\mathrm{C}\) (Fig. S21). No significant differences were observed in the XRD patterns before and after reduction, and the peaks of Cd species were still not detected, indicating that the catalyst remained highly dispersed after the reduction. XPS + +<--- Page Split ---> + +analysis indicated a \(0.1\mathrm{eV}\) shift in \(\mathrm{Cd3ds_2}\) binding energy following reduction. XANES spectral comparisons showed near- identical white line position, demonstrating unchanged oxidation states of isolated Cd atoms. Moreover, EXAFS spectra showed that only Cd- O bonds were present after reduction, indicating that the reduction at \(290^{\circ}\mathrm{C}\) did not affect the microstructure and electronic properties of the Cd single atoms. It could be known from \(\mathrm{H_2}\) - TPR results that the reduction of Cd species required a temperature exceeding \(400^{\circ}\mathrm{C}\) (Fig. S27). + +3. In Fig. 1, it is recommended to only display Cd element distribution on \(\mathrm{TiO_2}\) -A and -R in EDS-mapping results, for a better comparison with Cd-P25. It is unclear to identify Cd dispersion (blue spots) now. + +Response: We are very grateful for your excellent suggestion. We attempted to re- acquire the EDS- mapping. However, due to the limitations of the instrumental equipment and the sensitivity of the samples, the results were similar to the original ones. Therefore, for better comparison, only the distribution of the Cd element is presented for \(\mathrm{TiO_2}\) - A and \(\mathrm{TiO_2}\) - R. The specific changes are presented below: + +<--- Page Split ---> +![](images/Figure_1.jpg) + +
Fig. 1 i-k, HAADF-STEM and EDS mapping images for 5Cd/A (i), 5Cd/R (j), and 5Cd/P25 (k) catalysts.
+ +4. A significant amount of CdTiO₃ exists in Cd/P25. What is the MSR performance of CdTiO₃/TiO₂? + +<--- Page Split ---> + +**Response:** We are very grateful for your suggestion. Since CdTiO₃ primarily formed on R, we prepared CdTiO₃ catalysts by increasing the Cd loading (20%) on R. As shown in Figure R9, the diffraction peaks of CdTiO₃ can be clearly detected in the XRD pattern. Performance studies revealed that the activity of CdTiO₃/TiO₂ was almost negligible, similar to that of pure CdTiO₃. Therefore, it can be concluded that CdTiO₃ is an inert phase. This result has been added to Table S4. + +![](images/Figure_unknown_22.jpg) + +
Figure R9 XRD patterns of CdTiO₃ and CdTiO₃/TiO₂.
+ +Table S4 Catalytic performance of homemade reference catalysts. + +
CatalystConversion (%)\(S_{CO2}\)\(S_{CO}\)\(S_{CH4}\)
CdTiO₃0000
CdTiO₃/TiO₂0.584.515.50
CdO0.101000
Cd0000
+ +Reaction conditions: 290 °C, 0.1 MPa, a S/C ratio of 3/1, and a feed rate of 3 mL g-1 h-1 + +# Manuscript Revision: + +“Moreover, the synthesized CdTiO₃ and CdTiO₃/TiO₂ demonstrated negligible catalytic activity under identical reaction conditions, effectively ruling out CdTiO₃ as an active species (Supplementary Table 4).” + +<--- Page Split ---> + +Synthesis of CdTiO3. \(\mathrm{Cd(NO_3)_2\cdot 4H_2O}\) (0.617 g) and P25 powder (0.160 g) were homogenously mixed through a rotary evaporation process at \(65^{\circ}\mathrm{C}\) . The mixture was then dried at \(80^{\circ}\mathrm{C}\) for \(12\mathrm{h}\) and ground thoroughly with an agate mortar. The resulting samples were calcined at \(650^{\circ}\mathrm{C}\) for \(8\mathrm{h}\) under static air, then immersed in \(200\mathrm{mL}\) of \(1\mathrm{mol / L}\) \(\mathrm{HNO_3}\) aqueous solution and stirred magnetically for \(3\mathrm{h}\) . Solid- liquid separation was achieved through six cycles of centrifugation (8,000 rpm, \(10\mathrm{min}\) each) with deionized water washing. The purified precipitate was dried at \(80^{\circ}\mathrm{C}\) for \(12\mathrm{h}\) to obtain phase- pure CdTiO3 powder. + +Synthesis of CdTiO3/TiO2. \(1\mathrm{g}\) of rutile was dispersed in \(80\mathrm{mL}\) of deionized water, followed by the addition of \(0.08\mathrm{mmol / mL}\) \(\mathrm{Cd(NO_3)_2\cdot 4H_2O}\) . The mixture was stirred for 12 hours and then dried at \(60^{\circ}\mathrm{C}\) for 1 hour using a vacuum rotary evaporator. The product was subsequently calcined at \(700^{\circ}\mathrm{C}\) for 3 hours in static air. + +5. In Supplementary Fig. 18, it is necessary to identify the chemical state of Cd for Cd/P25 after \(H_2\) reduction at \(400^{\circ}\mathrm{C}\) with XPS, rather than \(H_2\) -TPR. + +Response: We are very grateful for your constructive suggestion. To identify the structure and chemical state of Cd species after \(H_2\) reduction at \(400^{\circ}\mathrm{C}\) (denoted as 5Cd/P25- 400H2), we have added the characterizations of XRD, HAADF- STEM, XAFS, XPS, and AES. + +XRD analysis detected no metallic Cd diffraction peaks (Fig. S23a), suggesting the absence of crystalline Cd nanoparticles. Intriguingly, HAADF- STEM revealed the existence of sub- nanometer metallic Cd clusters (Fig. S23b), corroborated by EXAFS spectra showing prominent Cd- Cd coordination at \(\sim 2.8\mathrm{\AA}\) (Fig. S23c). XPS analysis indicated a \(0.4\mathrm{eV}\) downward shift in the Cd \(3\mathrm{d}_{5 / 2}\) binding energy for 5Cd/P25- 400H2 relative to 5Cd/P25, concurrent with the transformation of the Cd MNN Auger peak into a broadened feature characteristic of metallic clusters (Fig. S23d). These results strongly indicate that sub- nanometer Cd clusters or Cd nanoparticles are unfavorable to catalytic performance. The supplementary information has been added to the revised version. + +<--- Page Split ---> +![](images/Figure_unknown_23.jpg) + +
Fig. S23 Structural characterizations of the 5Cd/P25 catalysts after reduction at \(400^{\circ}\mathrm{C}\) (denoted as 5Cd/P25-400H2). (a) XRD patterns. (b and c) HAADF-STEM images of the 5Cd/P25-400H2. (d) Cd K-edge XANES spectra. (e) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of EXAFS spectra. (f) XPS and AES spectra.
+ +## Manuscript Revision: + +Lines 207- 210 + +“HAADF- STEM revealed the formation of sub- nanometer Cd clusters, corroborated by EXAFS spectra showing prominent Cd- Cd coordination at \(\sim 2.8 \mathrm{\AA}\) , suggesting that metallic Cd or clusters were detrimental to catalytic activity (Supplementary Fig. 23).” + +6. In Supplementary Fig 24., it seems that 5Cd/A displays a stronger CH3OH adsorption than 5Cd/P25. + +Response: Thank you for pointing this out. Due to the differences in catalysts, we initially did not standardize the y- axis range in order to make the weaker signal peaks more visible. This led to a misunderstanding of the data by the reviewer. Therefore, we have now standardized the y- axis range and added a scale for easy comparison. The results were consistent with the performance. + +<--- Page Split ---> +![](images/Figure_unknown_24.jpg) + +
Fig. S29 CH3OH-TPD profiles of three samples (CH3OH was decomposed with the increase of temperature).
+ +7. DFT parts need to involve more discussion about the comparison with other models and highlight the advantage of Cd/A-R model. + +Response: We sincerely appreciate your insightful comments and constructive suggestions, which significantly enhance the scientific rigor and clarity of our manuscript. In our initial submission, we were restricted by the word limit and provided a brief overview of the DFT calculations, preventing us from fully elaborating on the underlying mechanistic distinctions. To address this limitation, we have thoroughly revised the DFT section in the current manuscript to systematically investigate how structural differences between catalyst models dictate activation energy and catalytic performance. The revised analysis is presented below: + +Lines 442- 472: + +"DFT calculations based on the established Cd/A (101), Cd/R (110), and Cd/A (101)- R (110) models provided complementary theoretical insights into the MSR reaction pathway. The computed energy landscape revealed distinct adsorption energy profiles: \*CHO exhibited significantly lower adsorption energies on Cd/A (101) (- 1.45 eV) and Cd/R (110) (- 1.18 eV) compared to the C1/A (101)- R (110) model (4.1 eV) (Supplementary Fig. 43). This energy disparity implies preferential CO generation pathways on Cd/A (101) and Cd/R (110) surfaces. Conversely, critical intermediates such as \*CHO- \*OH, \*CHOH and \*CHOO displayed substantially reduced adsorption energies on the Cd/A (101)- R (110) surface. These findings + +<--- Page Split ---> + +demonstrate that the formate decomposition pathway is thermodynamically more favorable on the Cd1/A (101)-R (110) catalyst, attributable to its asymmetric coordination environment and enhanced charge density at the interface Cd single-atom sites. + +The transition states of the formate decomposition pathway were further investigated (Fig. 4h and Supplementary Figs. 44- 46). Consistent with in situ DRIFTS observations, DFT calculations revealed that both the adsorption and the stepwise dehydrogenation of CH3OH occurred at the Cd active site. The activation energy barriers for CH3OH dehydrogenation (TS1: 0.64 eV) were significantly lower than those for \*CH3O dehydrogenation (TS2: 0.87 eV) on the Cd1/A (101)-R (110) surface. This clearly demonstrates that the C-H bond cleavage encounters higher kinetic resistance than O-H bond scission, aligning with the experimental KIE results. Following \*CH3O dehydrogenation to \*CH2O, H2O adsorption and dissociation on adjacent Ti atoms generated \*H and \*OH species (TS3: 0.37 eV). Subsequent CH2O/OH recombination formed CH2OOH (TS4: 0.43 eV), which further dehydrogenated to produce CO2 and H2. Although TS1 and TS2 barriers on Cd1/A (101)-R (110) were modestly elevated relative to Cd1/A (101) (TS3/TS4: 1.07/0.60 eV) and Cd1/R (110) (TS3/TS4: 0.57/0.53 eV), the dissociation of H2O (TS3) and CH2OOH formation (TS4) exhibited significantly lower energy barriers in the phase interface model. These results demonstrated that the unique structural properties of the interfacial structure enhanced the dissociation and activation of H2O, thereby facilitating the subsequent formation of formate and H2. Consequently, these observations rationalized the high activity and low CO selectivity of the 5Cd/P25 catalyst. Additionally, the highest activation energy barrier (TS2: 0.87 eV) confirmed \*CH3O dehydrogenation as the RDS on the Cd1/A (101)-R (110), consistent with previous kinetic analysis." + +8. In conclusion, when elucidating catalysis mechanism of Cd-O-Ti interface site, the authors need to make it clearer. Why is substantially lowering the energy barriers for formate decomposition important for complete methanol conversion? It is not clear to readers. + +<--- Page Split ---> + +Response: We sincerely appreciate your valuable suggestions. We have revised the conclusions to clarify the catalytic mechanism of the Cd- O- Ti interfacial sites and their structure- performance relationship, with specific revisions presented below: + +Lines 505- 510: + +"The resultant unique Cd- O- Ti interface sites, featuring asymmetric coordination geometry and elevated charge density, enable enhanced adsorption of reactants/intermediates. These structural attributes further reduce the energy barrier for both water dissociation and its activation within the formate decomposition pathway, thereby achieving complete methanol conversion with suppressed CO selectivity." + +9. Some discussion in the manuscript is not accurate. For example, on Page 9, "This suggests that the Cd-O-Ti configuration is the most effective active site, particularly at phase interfaces" should be revised to "This suggests that the Cd-O-Ti configuration is a more efficient active site, particularly at phase interfaces". + +Response: We sincerely appreciate the reviewers' insightful comments. In response to this constructive feedback, we have systematically revised ambiguous expressions throughout the manuscript to ensure terminological precision. Specific corrections are detailed below: + +Lines 212- 214: + +"This suggests that the Cd- O- Ti configuration is the most effective active site, particularly at phase interfaces" \(\rightarrow\) "This suggests that the Cd- O- Ti configuration is a more efficient active site, particularly at phase interfaces." + +Lines 252- 255: + +"In general, the distinctive and asymmetric geometric and electronic properties of the + +<--- Page Split ---> + +Cd- O- Ti sites at the phase interface are instrumental in elucidating the superior catalytic performance observed in the 5Cd/P25 catalyst." → "In general, the distinctive and asymmetric geometric and electronic properties of the Cd- O- Ti sites at the phase interface are instrumental in elucidating the enhanced catalytic performance observed in the 5Cd/P25 catalyst." + +Lines 361- 362: + +"...remarkable \(\mathrm{H}_{2}\) production rate of \(292.9 \mathrm{mmol} \mathrm{g}_{\mathrm{cat}}^{- 1} \mathrm{h}^{- 1}\) (Fig. 3h), surpassing conventional MSR catalysts" → "...remarkable \(\mathrm{H}_{2}\) production rate of \(292.9 \mathrm{mmol} \mathrm{g}_{\mathrm{cat}}^{- 1} \mathrm{h}^{- 1}\) (Fig. 3h), surpassing conventional Cu- and Pt- based catalysts" + +Lines 501- 502: + +"The resultant unique Cd- O- Ti interface sites [...] enable efficient adsorption of reactants/intermediates." → "The resultant unique Cd- O- Ti interface sites [...] enable enhanced adsorption of reactants/intermediates." + +10. The format of the font should be consistent throughout the manuscript. + +Response: We appreciate your valuable suggestions. Following your recommendations, we have revised the font format throughout the manuscript. + +<--- Page Split ---> + +## Responses to reviewers' comments + +Many thanks for the reviewers' insightful comments and questions, we have addressed the point- by- point responses below and believe the revised manuscript provides a more detailed, clear, and accurate description of the catalytic system. + +Reviewer #1 (Remarks to the Author): + +Zhang et al. have revised the manuscript in response to the suggestions and questions raised during the review process. I agree that Cd could be a promising catalyst at the phase interface. However, I am still not fully convinced by the comparison with other metals. For a fair evaluation, Cd single atoms should be compared under similar conditions with single atoms of other metals. + +Overall, the remaining comments have been addressed well. After adequately responding to this remaining concern, the manuscript can be considered suitable for publication in Nature Communications. + +Response: We sincerely appreciate your insightful feedback, which has greatly strengthened our manuscript. + +![](images/Figure_unknown_25.jpg) + +
Figure R1 XANES and EXAFS spectra of 0.1Pt/P25 (a, b), 0.1Pd/P25 (c, d), and 0.1Cu/P25 (e, f)
+ +<--- Page Split ---> + +catalysts. + +As previously stated, forming Pt/Pd/Cu single atoms on P25 is infeasible at high loadings. Therefore, to ensure fair comparison of the catalytic performance among these metals, the metal loading was reduced to \(0.1\%\) in accordance with the reported preparation strategy (J. Am. Chem. Soc.2019, 141, 17995- 17999) to achieve single- atom dispersion. As shown in Figure R1, EXAFS spectra confirm exclusive M- O coordination for Pt, Pd, and Cu, verifying their single- atom configurations. Under identical thermocatalytic conditions (290 °C, S/C molar ratio \(= 3 / 1\) , 0.1 MPa, N2 carrier gas flow \(= 30 \mathrm{mL min^{- 1}}\) , and liquid feed rate \(= 3 \mathrm{mL g^{- 1} h^{- 1}}\) ), methanol conversion remained below \(5\%\) for Pd and Cu single- atom catalysts, whereas Pt single atoms achieved the highest conversion (25.2%) (Figure R2). In terms of apparent TOF, although Pt SAC exhibited 2.3 times higher methanol activity than Cd SAC at equivalent loadings (0.1%), it demonstrated a higher CO selectivity (61.6%). In contrast, under optimal Cd loading (5%), methanol selectivity reached 100% with only 0.5% CO byproduct, while \(\mathrm{H}_2\) production rate surged to 97.7 mmol \(\mathrm{g^{- 1} h^{- 1}} - 5.0\) times greater than Pt (19.6 mmol \(\mathrm{g^{- 1} h^{- 1}}\) ). This might indicate that the synergistic effect between Cd and P25 is better than that of Pt/Pd/Cu single- atom systems. + +![](images/Figure_unknown_26.jpg) + +
Figure R2 Comparative catalytic performance of various single atoms catalysts. (a) Methanol conversion, selectivity, and \(\mathrm{H}_2\) production rate. (b) Apparent TOF. Reaction conditions: \(290^{\circ}\mathrm{C}\) , S/C molar ratio \(= 3 / 1\) , 0.1 MPa, and liquid feed rate \(= 3 \mathrm{mL g^{- 1} h^{- 1}}\) .
+ +We do not deny that high activity can be achieved with other single- atom metals, which may relate to selected supports or promoters. For example, Ma et al. reported single- atom catalyst systems including \(\mathrm{Pt_1 / a - MoC}\) (Nature 2017, 544, 80- 83), + +<--- Page Split ---> + +\(\mathrm{Pt_1 / NiAl_2O_4}\) (J. Am. Chem. Soc. 2023, 145, 905- 918), and \(\mathrm{Ni_1 / \alpha - MoC}\) (J. Am. Chem. Soc. 2021, 143, 309- 317), where Pt or Ni single atoms form interfaces with MoC or \(\mathrm{NiAl_2O_4}\) that efficiently promote \(\mathrm{H_2O}\) dissociation, enhancing catalytic performance. Additionally, Li et al. (ACS Catal. 2014, 4, 3886- 3890) described \(\mathrm{Pt_1 / ZnO}\) systems exhibiting significant \(\mathrm{Pt_1 - ZnO}\) synergy that enhances activity. Qu et al. demonstrated \(\mathrm{Pt_1 / PN - CeO_2}\) configurations featuring frustrated Lewis pairs at \(\mathrm{Pt - CeO_2}\) interfaces to substantially boost \(\mathrm{H_2}\) production rates (Nat. Commun. 2022, 13, 5527). + +This work focuses on elucidating why Cd single atoms preferentially locate at phase interfaces and outperform surface- adsorbed Cd SACs, while probing the reaction mechanism of this novel catalyst. Therefore, we do not emphasize comparative analysis or mechanistic interpretation of the performance of other metallic systems (whether supported on P25 or alternative carriers) configured as single- atom catalysts. Despite exhaustive synthesis attempts, Pt, Pd, and Cu cannot be anchored at P25 phase interfaces. We have initiated efforts to develop universal phase- interface SAC synthesis strategies in the next research, actively pursuing innovative pathways for diverse metals on P25 and other metal oxides. As investigated in our study, interfacial single- atom formation necessitates both matched electronegativity between active metal and titanium atoms and a substantial mean internal energy differential between surface and phase- interface sites, thus driving preferential metal anchoring at titanium vacancies within P25 phase interfaces. + +Reviewer #2 (Remarks to the Author): + +The authors addressed most questions raised, even there is still some concerns on the formate reaction pathways. I feel that this work is not mainly focusing on reaction mechanism investigations. I decide to accept this paper without further modifications. + +Response: Thank you for your valuable suggestions, which significantly improved our manuscript. Current characterization limitations make certain elementary + +<--- Page Split ---> + +steps/intermediates challenging to detect. Therefore, our subsequent research will continue to delve deeper into the study of the reaction mechanism and further refine the kinetic research, aiming to reveal the complete reaction pathway. + +<--- Page Split ---> diff --git a/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd b/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b642fbcab9f8771b3d6c68e0ad5936e4c35c79c3 --- /dev/null +++ b/peer_reviews/7d7dc4f356570fff9c84034e10f5607a82c00fe9ee90ed6dcfd23d92819d60ca/supplementary_0_Transparent Peer Review File/supplementary_0_Transparent Peer Review File_det.mmd @@ -0,0 +1,1164 @@ +<|ref|>title<|/ref|><|det|>[[72, 50, 295, 78]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +# Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 919, 210]]<|/det|> +# Phase-interface-anchored cadmium single-atom catalysts for efficient methanol steam reforming + +<|ref|>text<|/ref|><|det|>[[73, 224, 449, 241]]<|/det|> +Corresponding Author: Professor Hui Wang + +<|ref|>text<|/ref|><|det|>[[72, 275, 712, 290]]<|/det|> +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +<|ref|>text<|/ref|><|det|>[[72, 301, 866, 316]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 353, 144, 367]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 379, 220, 393]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 404, 160, 418]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 431, 238, 444]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 443, 917, 550]]<|/det|> +Zhang et al. reported the development of a phase- interface- anchored Cd SAC for methanol steam reforming. The catalyst demonstrated exceptional performance, achieving \(100\%\) methanol conversion with CO selectivity below \(0.1\%\) . Additionally, it showed excellent stability, maintaining activity for more than 150 hrs. To assess the scalability of this process, the authors explored 3D printing techniques to produce monolithic catalysts on a Kg scale. While this work is fundamentally interesting, the area of methanol steam reforming is already well- explored, and the scalability of non- noble metal- based catalysts has been extensively studied. Furthermore, the use of Cd, a toxic element, raises concerns about the industrial viability and environmental acceptability of this approach. Several important aspects of the study require clarification and further investigation. + +<|ref|>text<|/ref|><|det|>[[72, 561, 886, 615]]<|/det|> +1. The study compares Cd SAC with Cu, Pd, and Pt. However, it remains unclear whether all the compared metals are present as single atoms and located at the phase interface. This information is critical, as the localization and atomic dispersion of metal sites significantly influence catalytic performance. Detailed structural and surface characterizations, should be provided to confirm these aspects for each catalyst. + +<|ref|>text<|/ref|><|det|>[[72, 626, 900, 693]]<|/det|> +2. Ea for 5Cd/P25 is reported to be \(82.7\mathrm{kJ / mol}\) , which is nearly half of that for 5Cd/A. The reasons behind this substantial difference should be thoroughly investigated. Additionally, it would be insightful to compare this Ea value with those of state-of-the-art catalysts for methanol steam reforming. Detailed explanations of how Ea was calculated, including the experimental methods and assumptions, should also be included to enhance the transparency and reproducibility of the findings. + +<|ref|>text<|/ref|><|det|>[[72, 704, 917, 757]]<|/det|> +3. The authors observed that increasing the Cd loading up to 5 wt% enhanced the catalyst's reactivity, while further increases resulted in a decline. Authors should compare the turnover frequency (TOF) of catalysts with varying Cd loadings. This analysis would provide direct evidence of SAC-driven catalysis and clarify the relationship between Cd loading and catalytic performance. + +<|ref|>text<|/ref|><|det|>[[72, 769, 919, 835]]<|/det|> +4. The authors claim that a mixture of anatase and rutile phases is not effective for catalysis. To strengthen this conclusion, more control experiments should be performed to find out the optimum balance between anatase and rutile. Anatase could be subjected to controlled heating to partially convert it into the rutile phase, and the catalytic activity of the resulting material could be tested. Optimizing the anatase-to-rutile phase ratio would provide valuable insights into the specific phase-change requirements for Cd SAC catalysis. + +<|ref|>text<|/ref|><|det|>[[72, 847, 910, 887]]<|/det|> +5. The O1s XPS data presented in the study lacks sufficient detail to support the proposed active sites. The authors should provide a more thorough deconvolution of the O1s peaks to identify the types of oxygen species present and their roles in the catalytic process. + +<|ref|>text<|/ref|><|det|>[[70, 899, 915, 927]]<|/det|> +6. The reaction mechanism proposed in the study requires further elaboration. Identifying the rate-determining step (RDS) is crucial to understanding the catalytic process and design of the next generation of catalysts. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 87, 238, 100]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 100, 920, 228]]<|/det|> +In this work, Wang et. al, selectively decorated isolated Cd atoms to the interface of the P25 where heterogeneous structures of anatase and rutile coexist and the promoted H2 production rate has been achieved at \(\sim 292.9\) mmol gcat- 1 h- 1, which is about 15- fold and 8- fold higher than that of anatase and rutile dispersed Cd active components. The superior reaction performance has been attributed to the Cd- O- Ti interfacial structures. And this specific active component has been systematically probed by HRTEM, XAFS, EPR etc. A formate decomposition reaction pathway has been systematically discussed and was taken as the reaction mechanism for the hydrogen production. Finally, 3D printing has been introduced to produce the catalyst and this reaction system does show some potential in industrial applications. Generally, this is a good work and shows some interesting results, however, some of them are still under debate and might be critical to the overall conclusions. I suggest to reject this paper and give the author the opportunity to resubmit the work and hopefully the concerns listed bellow could be answered during the re- submission. + +<|ref|>text<|/ref|><|det|>[[72, 228, 918, 280]]<|/det|> +(1) First of all, the authors suggest that there is CdTiO3 at the interfacial site and it does not contribute to the hydrogen formation. I agree that, however, the Cd/CdOx does not show good activity either as comparisons. How can you explain that? And this CdTiO3 structure coexists with the real active components, is that possible most of the characterization is simply against this in-active structures (c.a. CdTiO3) rather than the real ones. + +<|ref|>text<|/ref|><|det|>[[72, 280, 920, 319]]<|/det|> +(2) The authors suggest that the Cd is isolated, however, there is only one evidence from EXAFS, even the HAADF-STEM characterizations are not very clear. Is that possible the Cd are clusters rather than isolated site? Then it still gives advanced reaction performance, well the actually active component is not the isolated Cd. + +<|ref|>text<|/ref|><|det|>[[72, 319, 916, 358]]<|/det|> +(3) The author shows the selectivity of H2, CO, CO2 and CH4, and hydrogen dominants in the products, however, this is not correct. In this way, none of the product could reach 100%. The selectivity should be classified into carbonaceous species and hydrogen, which should be more reasonable, during which time, CO selectivity won't be as low as it is for right now. + +<|ref|>text<|/ref|><|det|>[[72, 358, 901, 422]]<|/det|> +(4) For the activation energy determined, it looks that 82.7 KJ/mol is almost half the value of 152.1 KJ/mol, which may suggest that the system of Cd/P25 is suffering from diffusion limitations and it gives half the value of the real one and the superior reaction performance is not originated from the reduced activation energies. Well, this is only based on my assumption and the author definitely should exclude the mass/heat transfer limitations (both internal and outside channel diffusion limitations) before determining the apparent activation energies. + +<|ref|>text<|/ref|><|det|>[[72, 422, 915, 461]]<|/det|> +(5) If the real active component is the Cd-O-Ti structure, no matter which TiO2 phase it connects to, the Cd/P25 should gives similar activities with either Cd/anatase or Cd/rutile. This is not very clear, this reviewer suggests the author put more effort on explaining that. For example, the highly dispersed Cd on amorphous TiO2 might be also good for this reaction. + +<|ref|>text<|/ref|><|det|>[[72, 461, 912, 526]]<|/det|> +(6) There is contradictory assessment in elucidating the reaction mechanism of hydrogen production. Clearly, the C-H bond rupture within methanol is the rate determining step based on the KIE values determined. And usually, CO could be easily generated from methanol decomposition. Negligible CO determined would be attributed to the strong WGS reaction in the system, and it was not mentioned. This reviewer suggests the author to clarify that by determining the reaction rate and equilibrium constant on WGS at the relative conditions. + +<|ref|>text<|/ref|><|det|>[[72, 526, 911, 553]]<|/det|> +(7) I cannot quite follow why the overall reaction rate could be influenced by the electronic properties determined in figure 2, then I suggest the author move these results to the ESI. + +<|ref|>text<|/ref|><|det|>[[72, 553, 870, 580]]<|/det|> +(8) I don't know why the HAADF-STEM images were given twice in Figure 1 and Figure 3. I hope the author could re- organize the results and make it easy to read. + +<|ref|>text<|/ref|><|det|>[[72, 580, 920, 620]]<|/det|> +(9) From the reaction coordinate, it looks that the hydrogen formation over Cd1/A(101) is quite difficult, while it is not quite the situation for Cd/P25. This might be the main difference among these samples. And it is not well discussed. This reviewer suggests the author to clarify that. + +<|ref|>sub_title<|/ref|><|det|>[[72, 632, 161, 645]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 659, 238, 671]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 671, 914, 760]]<|/det|> +This research presents a phase- interface- stabilized Cd/P25 single- atom catalysts, which demonstrate much higher MSR performance than other Cd/TiO2 counterparts. The authors uncovered Cd- O- Ti phase interface site that dominates the high MSR activity and low CO selectivity. They also show that the densities of phase interface/sites can be regulated. Additionally, the fundamental mechanism of enhanced MSR performance on Cd/P25 SACs is clearly revealed by the combination of experimental and theoretical studies. This manuscript is well structured and demonstrated. I am willing to recommend its publication in Nature Communications. However, I would like to see the following concerns addressed before it can be further considered. + +<|ref|>text<|/ref|><|det|>[[72, 760, 185, 772]]<|/det|> +Main concerns: + +<|ref|>text<|/ref|><|det|>[[72, 773, 916, 826]]<|/det|> +1. In the Abstract, the statement "The formed Cd-O-Ti phase interface sites exhibit asymmetric geometric and electronic properties that achieve 100% methanol conversion, minimal CO selectivity (<0.1%), and sustained stability exceeding 150 hours" leads to misunderstanding. 100% methanol conversion and <0.1% CO selectivity are not achieved by interface sites solely. + +<|ref|>text<|/ref|><|det|>[[72, 826, 920, 865]]<|/det|> +2. In Supplementary Fig. 2, it is interesting and surprising that Cd catalysts exhibit similar MSR performance. This means that Cd catalysts after air calculation at 500°C and H2 reduction at 290C probably have the same active site. It is important to identify the properties of the catalysts at two states. + +<|ref|>text<|/ref|><|det|>[[72, 865, 918, 892]]<|/det|> +3. In Fig. 1, it is recommended to only display Cd element distribution on TiO2-A and -R in EDS-mapping results, for a better comparison with Cd-P25. It is unclear to identify Cd dispersion (blue spots) now. + +<|ref|>text<|/ref|><|det|>[[72, 892, 911, 917]]<|/det|> +4. A significant amount of CdTiO3 exists in Cd/P25. What is the MSR performance of CdTiO3/TiO2? + +<|ref|>text<|/ref|><|det|>[[72, 907, 905, 933]]<|/det|> +5. In Supplementary Fig. 18, it is necessary to identify the chemical state of Cd for Cd/P25 after H2 reduction at 400 C with XPS, rather than H2-TPR. + +<|ref|>text<|/ref|><|det|>[[72, 933, 777, 947]]<|/det|> +6. In Supplementary Fig 24., it seems that 5Cd/A displays a stronger CH3OH adsorption than 5Cd/P25. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 920, 75]]<|/det|> +7. DFT parts need to involve more discussion about the comparison with other models and highlight the advantage of Cd/A-R model. + +<|ref|>text<|/ref|><|det|>[[70, 73, 920, 112]]<|/det|> +8. In conclusion, when elucidating catalysis mechanism of Cd-O-Ti interface site, the authors need to make it clearer. Why is substantially lowering the energy barriers for formate decomposition important for complete methanol conversion? It is not clear to readers. + +<|ref|>text<|/ref|><|det|>[[70, 112, 920, 152]]<|/det|> +9. Some discussion in the manuscript is not accurate. For example, on Page 9, "This suggests that the Cd-O-Ti configuration is the most effective active site, particularly at phase interfaces" should be revised to "This suggests that the Cd-O-Ti configuration is a more efficient active site, particularly at phase interfaces". + +<|ref|>text<|/ref|><|det|>[[73, 152, 575, 165]]<|/det|> +10. The format of the font should be consistent throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 178, 144, 191]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 204, 219, 217]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 230, 160, 243]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 257, 238, 270]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 270, 918, 321]]<|/det|> +Zhang et al. have revised the manuscript in response to the suggestions and questions raised during the review process. I agree that Cd could be a promising catalyst at the phase interface. However, I am still not fully convinced by the comparison with other metals. For a fair evaluation, Cd single atoms should be compared under similar conditions with single atoms of other metals. + +<|ref|>text<|/ref|><|det|>[[70, 333, 896, 360]]<|/det|> +Overall, the remaining comments have been addressed well. After adequately responding to this remaining concern, the manuscript can be considered suitable for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 372, 161, 385]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 399, 238, 411]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 411, 920, 451]]<|/det|> +The authors addressed most questions raised, even there is still some concerns on the formate reaction pathways. I feel that this work is not mainly focusing on reaction mechanism investigations. I decide to accept this paper without further modifications. + +<|ref|>text<|/ref|><|det|>[[72, 805, 916, 857]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 857, 796, 870]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 870, 911, 922]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 922, 618, 936]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[0, 0, 997, 997]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[290, 89, 705, 108]]<|/det|> +## RESPONSES TO REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[147, 117, 851, 191]]<|/det|> +Many thanks for the reviewers' insightful comments and questions, we have addressed the point- by- point responses below and believe the revised manuscript provides a more detailed, clear, and accurate description of the catalytic system. + +<|ref|>text<|/ref|><|det|>[[148, 224, 248, 240]]<|/det|> +Reviewer: 1 + +<|ref|>sub_title<|/ref|><|det|>[[149, 265, 363, 283]]<|/det|> +## Response to Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[148, 308, 244, 325]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[147, 348, 852, 645]]<|/det|> +Zhang et al. reported the development of a phase- interface- anchored Cd SAC for methanol steam reforming. The catalyst demonstrated exceptional performance, achieving \(100\%\) methanol conversion with CO selectivity below \(0.1\%\) . Additionally, it showed excellent stability, maintaining activity for more than 150 hrs. To assess the scalability of this process, the authors explored 3D printing techniques to produce monolithic catalysts on a Kg scale. While this work is fundamentally interesting, the area of methanol steam reforming is already well- explored, and the scalability of non- noble metal- based catalysts has been extensively studied. Furthermore, the use of Cd, a toxic element, raises concerns about the industrial viability and environmental acceptability of this approach. Several important aspects of the study require clarification and further investigation. + +<|ref|>text<|/ref|><|det|>[[147, 672, 853, 914]]<|/det|> +Response: Thank you for your insightful comments. We acknowledge the concerns regarding the safety and environmental issues associated with the use of Cd. However, our investigation revealed for the first time a scientifically compelling phenomenon: the preferential anchoring of Cd single atoms at the phase interface of P25. This unique interfacial coordination configuration demonstrated remarkable catalytic performance in MSR, presenting fundamental scientific significance for understanding structure- property relationships in single- atom catalysts (SACs). While pursuing mechanistic studies to elucidate the formation dynamics and functional characteristics of this interfacial structure, we have made parallel efforts to develop + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 247]]<|/det|> +next- generation SACs using environmentally benign alternatives. This pursuit aligns with our broader research goals and forms the core of our ongoing work, where we aim to leverage more abundant and non- toxic metals to develop catalysts with enhanced performance based on this intriguing structural framework. We are committed to addressing these challenges and advancing the field of sustainable catalysis through our research efforts. + +<|ref|>text<|/ref|><|det|>[[147, 273, 853, 432]]<|/det|> +1. The study compares Cd SAC with Cu, Pd, and Pt. However, it remains unclear whether all the compared metals are present as single atoms and located at the phase interface. This information is critical, as the localization and atomic dispersion of metal sites significantly influence catalytic performance. Detailed structural and surface characterizations should be provided to confirm these aspects for each catalyst. + +<|ref|>image<|/ref|><|det|>[[240, 455, 760, 787]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 790, 850, 825]]<|/det|> +
Fig. S33 (a) XRD patterns of the fresh catalysts. DF-TEM, HRTEM images and corresponding particle distribution of the fresh (b) 5Pt/P25, (c) 5Pd/P25, and (d) 5Cu/P25 catalysts.
+ +<|ref|>text<|/ref|><|det|>[[148, 849, 850, 895]]<|/det|> +Response: We are grateful for your insightful comment. In response, we have enhanced the structural characterization of the corresponding Cu-, Pd-, and Pt- based + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 219]]<|/det|> +catalysts (Fig. S33). At a loading of 5 wt.%, XRD analysis identified diffraction peaks corresponding to PdO and CuO on the 5Pd/P25 and 5Cu/P25 catalysts, respectively, suggesting the formation of oxide nanoparticles. TEM further confirmed the formation of nanoparticles, revealing average sizes of 1.2 nm for PtO₂, 8.7 nm for PdO, and 2.2 nm for CuO when deposited at 5 wt.% on P25. + +<|ref|>image<|/ref|><|det|>[[147, 228, 835, 515]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 520, 850, 594]]<|/det|> +
Fig. S34 (a) Methanol conversion and product selectivity of the 0.2Pt/P25, 0.2Pd/P25, and 0.2Cu/P25 catalysts; (b) Corresponding H₂ production rates and TOF; (c-f) HAADF-STEM images of the fresh 0.2Pt/P25 catalyst. Reaction conditions: 290 °C, a S/C ratio of 3/1, 0.1 MPa pressure, and a feed rate of 3 mL g⁻¹ h⁻¹.
+ +<|ref|>text<|/ref|><|det|>[[147, 599, 852, 896]]<|/det|> +To obtain single- atom catalysts, we synthesized 0.2 wt.% Pt/P25, 0.2 wt.% Pd/P25, and 0.2 wt.% Cu/P25 catalysts. Comparative performance analysis revealed that under low- loading conditions, the Pt- based catalyst exhibited the higher methanol conversion (33.1%), H₂ production rates (25.0 mmol g⁻¹ h⁻¹), and TOF (1406.1 h⁻¹) compared to its Pd and Cu counterparts. However, it showed an undesirably high CO selectivity of 61.6%. HAADF- STEM imaging revealed that in the 0.2Pt/P25 catalyst, Pt single atoms and nanoclusters coexist on its surface, with no single atoms detected at the P25 phase interface. This phenomenon implies that the formation of interfacial single atoms requires specific conditions, mainly determined by the match between the metal's properties (e.g., surface energy and coordination preference) and interfacial thermodynamics, as elaborated in the main text. Therefore, the properties + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 850, 135]]<|/det|> +of Cd single atoms and the phase interface of P25 are well- matched compared with other metals. + +<|ref|>sub_title<|/ref|><|det|>[[149, 173, 336, 191]]<|/det|> +## Manuscript Revision: + +<|ref|>text<|/ref|><|det|>[[147, 200, 852, 552]]<|/det|> +"Notably, other active metals (e.g., Pt, Pd, Cu) deposited on P25 at equivalent concentrations (5 wt.%) exhibited nanoparticle aggregation on its surface (Supplementary Fig. 33). However, single- atom formation of transition metals (e.g., Pt) on the P25 phase interface remained unattainable even at 0.2 wt.% loading, concomitant with a marked decline in catalytic performance (Supplementary Fig. 34). These findings suggest that the formation of single atoms at the interface necessitates a favorable match between the metal's properties and the interfacial energy. The ionic radius of Cd differs more markedly from that of Ti than those of Pd, Pt and Cu. Moreover, the electronegativity of Cd is most analogous to that of Ti (Supplementary Table 7). These characteristics may endow Cd atoms with a significant difference in average internal energy between the lattice and phase interface, rendering them particularly prone to segregation and anchoring at Ti defect sites within the interface, thereby minimizing the interfacial energy. This attribute elucidates the challenge faced by other metals in achieving single- atom dispersion at the P25 interface." + +<|ref|>text<|/ref|><|det|>[[147, 616, 852, 775]]<|/det|> +2. Ea for 5Cd/P25 is reported to be 82.7 kJ/mol, which is nearly half of that for 5Cd/A. The reasons behind this substantial difference should be thoroughly investigated. Additionally, it would be insightful to compare this Ea value with those of state-of-the-art catalysts for methanol steam reforming. Detailed explanations of how Ea was calculated, including the experimental methods and assumptions, should also be included to enhance the transparency and reproducibility of the findings. + +<|ref|>text<|/ref|><|det|>[[148, 810, 852, 913]]<|/det|> +Response: Thanks for pointing this out. In light of the significant difference in activation energy you highlighted, we have thoroughly re- examined and analyzed our experimental data. We acknowledge that the influence of mass transfer cannot be entirely ruled out during the testing process. Specifically, the conversion rate was + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 192]]<|/det|> +relatively high ( \(\sim 20\%\) ) during the tests, which could potentially lead to a small activation energy. This is because, at higher conversion rates, the rate- limiting step may shift from the intrinsic catalytic activity to the mass transfer of reactants to the catalyst surface. Therefore, we re- tested the apparent activation energy of the catalyst. + +<|ref|>text<|/ref|><|det|>[[146, 199, 853, 555]]<|/det|> +First, to eliminate the effect of external diffusion, we increased the space velocity (feed rate). As depicted in Fig. S6, for the three catalysts (5Cd/A, 5Cd/R, and 5Cd/P25), the conversion rate showed an inverse relationship with feed rate as the feed rate increased. Concurrently, the \(\mathrm{H}_2\) production rate gradually increased, and the curve tended to stabilize. This behavior suggests that the reaction on these catalysts is analogous to a first- order kinetic model. Under high feed rate conditions ( \(>30 \mathrm{mL} \mathrm{g}^{- 1}\) \(\mathrm{h}^{- 1}\) ), when the conversion rate was below \(10\%\) , the impact of feed rates on the \(\mathrm{H}_2\) production rate was minimal, indicating that the effect of external diffusion could be neglected. Therefore, we opted to conduct our activation energy tests at a feed rate corresponding to a conversion rate of less than \(10\%\) . This selection ensured that the influence of external diffusion was minimized, allowing for a more accurate assessment of the intrinsic catalytic activity and the apparent activation energy of the catalyst. + +<|ref|>text<|/ref|><|det|>[[147, 561, 850, 609]]<|/det|> +To determine whether the effect of internal diffusion was negligible, we applied the Weisz- Prater criterion for calculation, as shown in Equations (1- 3). + +<|ref|>equation<|/ref|><|det|>[[368, 614, 627, 725]]<|/det|> +\[\begin{array}{l}\mathrm{WP} = \frac{\mathrm{r}\times\mathrm{R}^2}{\mathrm{C}_\mathrm{S}\times\mathrm{D}_\mathrm{e}}\\ \frac{1}{\mathrm{D}_\mathrm{e}} = \frac{\tau}{\epsilon} (\frac{1}{\mathrm{D}_\mathrm{m}} +\frac{1}{\mathrm{D}_\mathrm{k}})\\ \mathrm{D}_\mathrm{k} = \frac{2}{3}\mathrm{d}_\mathrm{p}\sqrt{\frac{8\mathrm{RT}}{\pi\mathrm{M}}} \end{array} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[146, 728, 852, 916]]<|/det|> +\(\mathrm{r}\) represents the reaction rate, \(\mathrm{R}\) represents the particle radius, \(\mathrm{C}_\mathrm{s}\) represents the reactant concentration at the catalyst surface, \(\mathrm{D}_\mathrm{e}\) represents the effective diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\tau\) represents the pore tortuosity, \(\epsilon\) represents the porosity, \(\mathrm{D}_\mathrm{m}\) represents the molecular diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{D}_\mathrm{k}\) represents the Knudsen diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{d}_\mathrm{p}\) represents the average pore diameter \((\mathrm{m})\) , \(\mathrm{M}\) represents the molar mass of the diffusing species \((\mathrm{kg} / \mathrm{mol})\) , \(\mathrm{R}\) represents the gas constant, and \(\mathrm{T}\) represents the temperature \((\mathrm{K})\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 88, 853, 470]]<|/det|> +Under the conditions of \(290^{\circ}\mathrm{C}\) , \(\mathrm{S / C} = 3 / 1\) , 0.1 MPa, and methanol conversion below \(10\%\) , the Weisz-Prater (WP) values for 5Cd/A, 5Cd/R, and 5Cd/P25 were \(1.0 \times 10^{- 7}\) , \(2.4 \times 10^{- 9}\) , and \(7.3 \times 10^{- 10}\) , respectively. All of them are much less than 1, so the internal diffusion limitation can be excluded. In addition, we added inert \(\mathrm{SiO}_2\) to the catalyst to promote heat transfer during the reaction process, ensuring no temperature gradient in the reaction zone and excluding the impact of heat transfer. Finally, we tested the \(\mathrm{H}_2\) production rate at every \(10^{\circ}\mathrm{C}\) intervals in the temperature range of \(250 - 290^{\circ}\mathrm{C}\) and calculated the corresponding activation energy by substituting it into the Arrhenius equation (as shown in Equation 4). The apparent activation energies of the 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts were \(146.6\mathrm{KJ / mol}\) , \(121.9\mathrm{KJ / mol}\) , and \(107.3\mathrm{KJ / mol}\) , respectively. In comparison, the apparent activation energy of the 5Cd/P25 catalyst was still the lowest, which did not affect the original conclusion that the interfacial Cd single atom sites with their unique interfacial structure and electronic properties had relatively excellent catalytic performance. + +<|ref|>equation<|/ref|><|det|>[[379, 478, 616, 506]]<|/det|> +\[\ln \mathbf{k} = \ln \mathbf{A} - \frac{\mathbf{B}_{\mathbf{a}}}{\mathbf{R}\mathbf{T}} \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[147, 515, 853, 646]]<|/det|> +Regarding the comparison of apparent activation energy, we have reviewed a substantial amount of literature and found that few studies calculated or tested the apparent activation energy. Instead, the \(\mathrm{H}_2\) production rate is commonly used as the basis for comparison. Therefore, we have not made a horizontal comparison of apparent activation energy in this study. + +<|ref|>text<|/ref|><|det|>[[147, 654, 852, 728]]<|/det|> +To enhance the transparency and reproducibility of the findings, we have added Fig. S6 and the calculation process of activation energy in the SI section of the revised manuscript, and the corresponding content is as follows. + +<|ref|>text<|/ref|><|det|>[[148, 737, 478, 756]]<|/det|> +Supplementary Information Revision: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[149, 94, 949, 247]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 252, 851, 306]]<|/det|> +
Fig. S6 Feed rate dependence of methanol conversion and \(\mathrm{H}_2\) production rates over 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts. Reaction conditions: catalyst \(0.1\mathrm{g} + \mathrm{SiO}_2 0.2\mathrm{g}\) ; liquid feed of \(\mathrm{S / C} = 3\) at \(6 - 45\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) ; \(\mathrm{N}_2\) carrier at \(20\mathrm{mL}\mathrm{min}^{-1}\) ; temperature: \(290^{\circ}\mathrm{C}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 329, 850, 476]]<|/det|> +Note: For the three catalysts (5Cd/A, 5Cd/R, and 5Cd/P25), the conversion rate showed an inverse relationship with feed rate as the feed rate increased. Concurrently, the \(\mathrm{H}_2\) production rate gradually rised, and the curve tended to stabilize. This behavior indicates that the reaction on these catalysts follows a first- order kinetics model, and the impact of external diffusion can be disregarded under high feed rate conditions. Consequently, methanol conversion maintained below \(10\%\) during the activation energy test. Under these reaction conditions, the impact of internal diffusion was assessed using the Weisz- Prater criterion, and the specific calculation formula was as follows (Equations 1- 3): + +<|ref|>equation<|/ref|><|det|>[[384, 479, 621, 510]]<|/det|> +\[\mathrm{WP} = \frac{r\times\mathrm{R}^2}{\mathrm{C}_\mathrm{S}\times\mathrm{D}_\mathrm{e}} \quad (1)\] + +<|ref|>equation<|/ref|><|det|>[[368, 517, 627, 543]]<|/det|> +\[\frac{1}{\mathrm{D}_{\mathrm{e}}} = \frac{\tau}{\epsilon}\left(\frac{1}{\mathrm{D}_{\mathrm{m}}} +\frac{1}{\mathrm{D}_{\mathrm{k}}}\right) \quad (2)\] + +<|ref|>equation<|/ref|><|det|>[[370, 550, 624, 584]]<|/det|> +\[\mathrm{D}_{\mathrm{k}} = \frac{2}{3}\mathrm{d}_{\mathrm{p}}\sqrt{\frac{8\mathrm{R}\mathrm{T}}{\pi\mathrm{M}}} \quad (3)\] + +<|ref|>text<|/ref|><|det|>[[147, 588, 850, 698]]<|/det|> +r represents the reaction rate, R represents the particle radius, \(\mathrm{C}_\mathrm{s}\) represents the reactant concentration at the catalyst surface, \(\mathrm{D}_{\mathrm{e}}\) represents the effective diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\tau\) represents the pore tortuosity, \(\epsilon\) represents the porosity, \(\mathrm{D}_{\mathrm{m}}\) represents the molecular diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{D}_{\mathrm{k}}\) represents the Knudsen diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{d}_{\mathrm{p}}\) represents the average pore diameter (m), M represents the molar mass of the diffusing species (kg/mol), R represents the gas constant, and T represents the temperature (K). + +<|ref|>text<|/ref|><|det|>[[147, 700, 850, 846]]<|/det|> +The calculated WP values for 5Cd/A, 5Cd/R, and 5Cd/P25 were \(1.0 \times 10^{- 7}, 2.4 \times 10^{- 9}\) , and \(7.3 \times 10^{- 10}\) , respectively. Given that all these values are significantly less than 1, the influence of internal diffusion limitations could be excluded. Additionally, inert \(\mathrm{SiO}_2\) was incorporated into the catalyst to enhance heat transfer during the reaction process, ensuring a uniform temperature profile within the reaction zone and thereby eliminating the impact of heat transfer. The activation energy was determined using the following equation (Reaction conditions: catalyst \(0.1 \mathrm{g} + \mathrm{SiO}_2 0.2 \mathrm{g}\) ; liquid feed of \(\mathrm{S / C} = 3\) at \(15 - 45 \mathrm{mL} \mathrm{g}^{- 1} \mathrm{h}^{- 1}\) ; \(\mathrm{N}_2\) carrier at \(20 \mathrm{mL} \mathrm{min}^{- 1}\) ; temperature: \(250 - 290^{\circ}\mathrm{C}\) ; methanol conversion less than \(10\%\) ): + +<|ref|>equation<|/ref|><|det|>[[412, 852, 618, 878]]<|/det|> +\[\mathrm{lnk} = \mathrm{lnA} - \frac{\mathrm{E}_{\mathrm{a}}}{\mathrm{RT}} \quad (4)\] + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[363, 85, 636, 247]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 251, 848, 287]]<|/det|> +
Fig. 1 Catalytic performance and structural characteristics of catalysts in the MSR reaction. d, Apparent activation energy evaluation (methanol conversion less than 10%).
+ +<|ref|>text<|/ref|><|det|>[[147, 347, 852, 490]]<|/det|> +3. The authors observed that increasing the Cd loading up to 5 wt% enhanced the catalyst's reactivity, while further increases resulted in a decline. Authors should compare the turnover frequency (TOF) of catalysts with varying Cd loadings. This analysis would provide direct evidence of SAC-driven catalysis and clarify the relationship between Cd loading and catalytic performance. + +<|ref|>text<|/ref|><|det|>[[147, 525, 852, 738]]<|/det|> +Response: Thank you for your constructive suggestions. In response to this valuable comment, we have conducted detailed TOF calculations for catalysts with varying Cd loadings. The results are presented in the revised Fig. S4. The TOF was found to decrease significantly with the increase in Cd loadings, which was inconsistent with the trend of \(\mathrm{H}_2\) production rates. This result provides compelling evidence of SAC- driven catalysis at low Cd loadings, while also indicating that the structure of active sites changes with varying Cd loadings, leading to a decrease in the efficiency of the single Cd active sites. + +<|ref|>text<|/ref|><|det|>[[148, 748, 478, 766]]<|/det|> +Supplementary Information Revision: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[147, 90, 857, 283]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 289, 850, 325]]<|/det|> +
Fig. S4 Catalytic performance as a function of varying Cd loadings on the P25 support. Reaction conditions: \(290^{\circ}\mathrm{C}\) , S/C ratio of 3/1, 0.1 MPa pressure, and \(3\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) feed rate.
+ +<|ref|>text<|/ref|><|det|>[[147, 330, 852, 794]]<|/det|> +XRD patterns of the fresh and spent catalysts with varying Cd loadings revealed the emergence of \(\mathrm{CdTiO_3}\) species at a Cd loading of 5 wt. \(\%\) (Figs. S20a and b). Further XAFS spectroscopy was conducted to reveal the Cd species with varying loadings. As shown in Fig. S20c, the white line of the Cd K- edge XANES spectra for these samples was positioned between that of the Cd foil and CdO reference, with the white line of the 10Cd/P25 catalyst nearly overlapping with that of the \(\mathrm{CdTiO_3}\) reference. This finding further confirmed the presence of \(\mathrm{CdTiO_3}\) at high Cd loadings. The fitting results of the EXAFS spectrum indicated the absence of a Cd- Cd coordination structure in all samples, suggesting that neither metallic Cd nor CdO clusters formed as the Cd loading increased. However, as indicated in Table S4, the \(\mathrm{CdTiO_3}\) species, which were inactive for MSR, have been identified, and the \(\mathrm{H_2}\) production rate decreased with the increase of \(\mathrm{CdTiO_3}\) (Fig. S4b). Therefore, the decrease in TOF can be attributed to the presence of \(\mathrm{CdTiO_3}\) . With the increase in Cd loadings, although the number or density of Cd single atoms (active sites), particularly those anchored at the phase interface, increased nonlinearly, which could enhance the \(\mathrm{H_2}\) production rate, the efficiency of the single atom sites (TOF) decreased because some Cd species formed \(\mathrm{CdTiO_3}\) . + +<|ref|>sub_title<|/ref|><|det|>[[149, 831, 477, 849]]<|/det|> +## Supplementary Information Revision: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[163, 95, 835, 505]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 511, 850, 565]]<|/det|> +
Fig. S20 XRD patterns of (a) fresh and (b) spent catalysts with different Cd loadings. (c) Cd K-edge XANES spectra of fresh catalysts with different Cd loadings. (d) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of EXAFS spectra.
+ +<|ref|>text<|/ref|><|det|>[[149, 585, 850, 658]]<|/det|> +Note: As the Cd loading varied, the \(\mathrm{CdTiO_3}\) species emerged when the Cd loading exceeded 5 wt.%. The fitting results of the EXAFS spectrum indicated the absence of a Cd-Cd coordination structure in all samples, suggesting that neither metallic Cd nor CdO clusters formed as the Cd loading increased. + +<|ref|>table<|/ref|><|det|>[[100, 696, 870, 845]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[149, 679, 616, 694]]<|/det|> +Table S4 Catalytic performance of homemade reference catalysts. + +
CatalystConversion (%)SCO2SCOSCH4
CdTiO30000
CdTiO3/TiO20.584.515.50
CdO0.101000
Cd0000
+ +<|ref|>table_footnote<|/ref|><|det|>[[147, 844, 768, 860]]<|/det|> +Reaction conditions: \(290^{\circ}C\) , 0.1 MPa, a S/C ratio of 3/1, and a feed rate of \(3\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 88, 852, 275]]<|/det|> +4. The authors claim that a mixture of anatase and rutile phases is not effective for catalysis. To strengthen this conclusion, more control experiments should be performed to find out the optimum balance between anatase and rutile. Anatase could be subjected to controlled heating to partially convert it into the rutile phase, and the catalytic activity of the resulting material could be tested. Optimizing the anatase-to-rutile phase ratio would provide valuable insights into the specific phase-change requirements for Cd SAC catalysis. + +<|ref|>text<|/ref|><|det|>[[146, 310, 852, 496]]<|/det|> +Response: Thank you for your constructive suggestions. We evaluated the combined performance of 5Cd/A and 5Cd/R catalysts at ratios of 80/20, 50/50, and 20/80. As the proportion of 5Cd/R increased, methanol conversion increased from 18.1% to 33.7%, nearing the performance of sole 5Cd/R but remaining inferior to that of 5Cd/P25 (Fig. S2). This strongly suggests that single- atom Cd at the phase interface is far more effective than the synergistic interaction of single atoms on two separate phase surfaces. + +<|ref|>image<|/ref|><|det|>[[234, 506, 760, 774]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 781, 850, 836]]<|/det|> +
Fig. S2 Comparison of catalytic performance between 5Cd/P25 and mixtures composed of varying ratios of 5Cd/A and 5Cd/R. Reaction conditions: 290 °C, S/C ratio of 3/1, 0.1 MPa pressure, and 3 mL g-1 h-1 feed rate.
+ +<|ref|>text<|/ref|><|det|>[[148, 840, 850, 886]]<|/det|> +In accordance with the reviewers' opinions, we also supplemented the experiments of calcining anatase (A) at different temperatures to control the phase + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 90, 852, 656]]<|/det|> +transformation and form different ratios of A to R. A was calcined at \(600^{\circ}\mathrm{C}\) , \(700^{\circ}\mathrm{C}\) , and \(800^{\circ}\mathrm{C}\) for 2 hours respectively, and then 5 wt.% Cd was loaded, which were denoted as 5Cd/A- XAir (X represents the temperature) (Fig. S36a). As shown in Fig. S36b, with the increase of calcination temperature, the methanol conversion and \(\mathrm{H}_{2}\) production rate exhibited a volcanic profile. At \(700^{\circ}\mathrm{C}\) , the methanol conversion significantly increased from \(21.6\%\) to \(94.5\%\) , and the \(\mathrm{H}_{2}\) production rate reached 92.3 mmol \(\mathrm{g}^{- 1} \mathrm{h}^{- 1}\) , with a CO selectivity of \(0.7\%\) , which was close to the performance of the 5Cd/P25 catalyst (97.7 mmol \(\mathrm{g}^{- 1} \mathrm{h}^{- 1}\) ). HAADF- STEM images of the 5Cd/A- 700Air catalyst revealed that Cd single atoms anchored at the A-R phase interface, consistent with the 5Cd/P25 catalyst (Figs. S36c and d). This underscored that the phase interface formed by phase transition was conducive to the formation of Cd single atoms. However, at \(800^{\circ}\mathrm{C}\) , methanol conversion dropped sharply to \(12.1\%\) . XRD Rietveld analysis showed the calcination temperature primarily affected the A/R ratio and crystallite size. As the temperature increased, A gradually transformed to R, and the crystallite size increased, altering the interfacial density (Table S8). Upon calcination at \(700^{\circ}\mathrm{C}\) , the ratio of A and R ( \(80.2\% /19.8\%\) ) closely resembled that of P25, accompanied by an elevated interfacial density ( \(4.7 \mathrm{m}^{2} \mathrm{g}^{- 1}\) ) relative to other calcination temperatures, thereby conferring enhanced \(\mathrm{H}_{2}\) production rates. However, due to the larger crystallite size of A and R after calcination, the performance remained inferior to that of 5Cd/P25. + +<|ref|>table<|/ref|><|det|>[[135, 677, 952, 904]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[146, 660, 787, 676]]<|/det|> +Table S8 Data for interface density calculations following the pretreatments of A and P25. + +
Pretre atmentTemperature /TimeWA /%WR /%crystal /nmsize CNmaxN (A) /1015 g-1N (R) /1015 g-1N (A) / N (R)/ Amax /m2 g-1
A R
Air a600 °C/2h90.19.931.641.710.47.50.325.0
700 °C/2h80.219.844.260.811.42.40.212.0
800 °C/2h57.442.649.177.214.81.30.26.5
N2 b500 °C/2h79.620.419.236.721.929.60.930.1
600 °C/2h69.930.121.736.917.318.01.412.6
700 °C/2h29.670.433.048.412.92.21.51.5
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[135, 83, 950, 157]]<|/det|> + +
\(H_{2}^{c}\)500℃/2h73.626.419.621.67.325.76.24.19.9
500℃/4h68.431.617.924.811.531.44.96.410.1
500℃/8h51.348.721.522.56.613.610.21.36.3
+ +<|ref|>text<|/ref|><|det|>[[147, 159, 576, 172]]<|/det|> +a Pure A was calcined at \(600–800^{\circ }C\) for 2 hours in static air. + +<|ref|>text<|/ref|><|det|>[[147, 178, 734, 192]]<|/det|> +b Pure P25 was calcined at \(500–700^{\circ }C\) for 2 hours in a flow of \(N_{2}(100mL/min).\) + +<|ref|>text<|/ref|><|det|>[[147, 201, 690, 214]]<|/det|> +c Pure P25 was reduced at \(500^{\circ }C\) for 2 hours in a flow of \(H_{2}(100mL/min).\) + +<|ref|>image<|/ref|><|det|>[[268, 223, 733, 551]]<|/det|> + +<|ref|>image_caption<|/ref|><|det|>[[147, 558, 850, 608]]<|/det|> +
Fig. S36 (a) XRD patterns of fresh catalysts. (b) Catalytic performance. (c and d) HAADF-STEM images of the 5Cd/A-700Air catalyst. Reaction conditions: 290 $^{\circ }C$ , a S/C ratio of 3/1, 0.1 MPa pressure, and a feed rate of 3 mL g-1 h-1.
+ +<|ref|>text<|/ref|><|det|>[[147, 619, 850, 828]]<|/det|> +In the manuscript, we have systematically modulated the phase interface density via \(N_{2}/H_{2}\) -pretreated P25 to optimize catalytic performance. Fig. 3f revealed a volcano-shaped correlation between interfacial density and \(H_{2}\) production rates, with the peak density \((8.5m^{2}g^{-1})\) and maximum \(H_{2}\) production rate \((266.0mmolg_{cat}^{-1}h^{-1})\) observed at 600 $^{\circ }C$ . To further enhance interfacial density, \(H_{2}\) -pretreated P25 was subjected to varying durations at 500 $^{\circ }C$ , maintaining identical crystallite size. After 4-hour \(H_{2}\) pretreatment, the A/R ratio reached \(68.4\%/31.6\%\) , obtaining the highest interface density \((m^{2}g^{-1})\) and \(H_{2}\) production rate \((292.9mmolg_{cat}^{-1}h^{-1})\) + +<|ref|>title<|/ref|><|det|>[[147, 841, 338, 853]]<|/det|> +# Manuscript Revision: + +<|ref|>text<|/ref|><|det|>[[147, 869, 260, 879]]<|/det|> +Lines 100-102: + +<|ref|>text<|/ref|><|det|>[[147, 896, 850, 908]]<|/det|> +*Additionally, adjusting the mixture ratio still failed to achieve reaction performance comparable + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 135]]<|/det|> +to that of 5Cd/P25 (Supplementary Fig. 2), underscoring the unique catalytic properties of this catalyst." + +<|ref|>text<|/ref|><|det|>[[148, 145, 258, 161]]<|/det|> +Lines 333- 339: + +<|ref|>text<|/ref|><|det|>[[147, 172, 852, 330]]<|/det|> +"To validate this hypothesis, we systematically investigated the phase transformation by calcining A under static- air conditions at varying temperatures (Supplementary Fig. 36 and Supplementary Table 8). At a calcination temperature of \(700^{\circ}\mathrm{C}\) , the A/R weight fraction ratio of \(80.2 / 19.8\%\) and corresponding catalytic performance closely mirrored those of 5Cd/P25. HAADF- STEM images revealed the formation of Cd single atoms at the phase interface, which corroborated the formation of Ti defects through the in- situ phase transformation." + +<|ref|>text<|/ref|><|det|>[[148, 340, 258, 356]]<|/det|> +Lines 344- 347: + +<|ref|>text<|/ref|><|det|>[[147, 367, 852, 469]]<|/det|> +"Although calcining A in air regulated phase weight fractions, the resulting interfacial density was limited to \(4.7\mathrm{m}^2\mathrm{g}^{- 1}\) due to the enlarged crystallite size, which was lower than that of 5Cd/P25 ( \(7.9\mathrm{m}^2\mathrm{g}^{- 1}\) ). Consequently, we implemented \(\mathrm{N}_2\) pretreatment (500- 700 °C) on P25 to enhance interface density prior to Cd loading." + +<|ref|>text<|/ref|><|det|>[[147, 524, 853, 627]]<|/det|> +5. The O1s XPS data presented in the study lacks sufficient detail to support the proposed active sites. The authors should provide a more thorough deconvolution of the O1s peaks to identify the types of oxygen species present and their roles in the catalytic process. + +<|ref|>text<|/ref|><|det|>[[147, 662, 853, 905]]<|/det|> +Response: We appreciate your constructive advice. To support the identification of the proposed active sites, we have added the O1s spectrum with deconvoluted peaks for both the pure supports and the catalysts loaded with Cd species (Figure R1). The peaks at around \(530.0\mathrm{eV}\) , \(531.2\mathrm{eV}\) , and \(532.2\mathrm{eV}\) are attributed to the lattice oxygen (O\(_{\text{lattice}}\)) of TiO\(_2\), the adsorbed oxygen at oxygen vacancies (O\(_v\)), and the surface adsorbed hydroxyl group (*OH), respectively. When Cd was loaded on the pure supports, the binding energy of O\(_{\text{lattice}}\) decreased \(0.1\mathrm{eV}\) for all samples, which indicated that the electron of Cd species transferred to O\(_{\text{lattice}}\). The findings also indirectly demonstrated that Cd atoms anchored at the Ti vacancies of TiO\(_2\) and bound + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 94, 536, 111]]<|/det|> +with O\(_{lattice}\) to form the active sites of Cd- O- Ti. + +<|ref|>image<|/ref|><|det|>[[155, 131, 848, 268]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 276, 732, 293]]<|/det|> +
Figure R1 XPS spectra of the Cd 3d orbitals for pure supports and fresh catalysts.
+ +<|ref|>text<|/ref|><|det|>[[146, 303, 853, 768]]<|/det|> +The O1s spectrum in the quasi in situ XPS was also subjected to a thorough deconvolution (Fig. S26). The binding energies of O\(_{lattice}\), O\(_{v}\), and \*OH remained unchanged during the MSR reaction. Moreover, the peak area of O\(_{v}\) stayed within the range of 10\~12%, suggesting that O\(_{v}\) had a negligible impact on the reaction process. These results were consistent with the EPR and DFT calculations. Since the quasi in situ XPS differs from the near atmospheric pressure XPS (NAP- XPS), it cannot capture the surface adsorbed intermediates and the reaction process. This leads to difficulties in directly elucidating the types and roles of surface oxygen species during the reaction through this characterization technique. However, the role of Cd- O- Ti sites during the reaction can be elucidated through DFT calculations (Figs. S44- 46). The Cd atoms played a crucial role in the adsorption of CH\(_{3}\)OH and the intermediate reaction steps (\*CH\(_{3}\)OH\->\*CH\(_{3}\)O\->\*CH\(_{2}\)O\->\*CH\(_{2}\)OOH\->\*CHOOH\->\*CHO\(_{2}\)O\->\*CO\(_{2}\)). The O atoms within the Cd- O- Ti sites assisted the Cd atoms in dissociating the H atoms in CH\(_{3}\)OH and CH\(_{3}\)O intermediates. Meanwhile, the Ti atoms are responsible for the adsorption and dissociation of H\(_{2}\)O into \*H and \*OH species. This reaction process follows the Langmuir- Hinshelwood mechanism. + +<|ref|>sub_title<|/ref|><|det|>[[149, 803, 478, 821]]<|/det|> +## Supplementary Information Revision: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[200, 88, 792, 374]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 381, 848, 416]]<|/det|> +
Fig. S26 Quasi-in situ XPS spectrum of the 5Cd/P25 catalyst during the MSR reaction at \(290^{\circ}\mathrm{C}\) and a S/C ratio of 3/1.
+ +<|ref|>text<|/ref|><|det|>[[147, 435, 850, 620]]<|/det|> +Note: The \(\mathrm{Cd3d_{5 / 2}}\) binding energy at \(405.6\mathrm{eV}\) was characteristic of \(\mathrm{Cd^{2 + }}\) species, while the Ti \(2\mathrm{p}^{3 / 2}\) peak centered at \(458.8\mathrm{eV}\) corresponded to \(\mathrm{Ti^{4 + }}\) in the \(\mathrm{TiO_2}\) matrix. Deconvolution of the O1s spectrum revealed three chemically distinct oxygen species: the primary component at \(530.1\mathrm{eV}\) originated from lattice oxygen (Olatice) in \(\mathrm{TiO_2}\) , the intermediate peak at \(531.5\mathrm{eV}\) was associated with oxygen vacancies (Ov), and the high- binding- energy component at \(532.7\mathrm{eV}\) resulted from surface- adsorbed hydroxyl groups (\*OH). Notably, comparative analysis throughout the catalytic process showed that (i) the cadmium valence state remained unchanged and (ii) the oxygen vacancy concentration maintained relative stability (10- 12% area ratio). These observations indicate that the catalytically active centers are predominantly Cd- O- Ti interface sites rather than oxygen vacancy- mediated mechanisms. + +<|ref|>text<|/ref|><|det|>[[147, 662, 850, 737]]<|/det|> +6. The reaction mechanism proposed in the study requires further elaboration. Identifying the rate-determining step (RDS) is crucial to understanding the catalytic process and design of the next generation of catalysts. + +<|ref|>text<|/ref|><|det|>[[147, 780, 851, 912]]<|/det|> +Response: Thank you for your kind advice. In our initial submission, the mechanistic discussion was condensed due to word limit constraints. In response to your insightful comments, we have now conducted additional kinetic experiments and comprehensively revised the reaction mechanism analysis. Our response focuses on clarifying the research logic underlying mechanistic investigations and presenting the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 164]]<|/det|> +newly incorporated experimental validations. Detailed modifications are systematically documented in the revised manuscript (Section Reaction Mechanism Studies) and Supplementary Information (Scheme 1). + +<|ref|>text<|/ref|><|det|>[[147, 172, 853, 580]]<|/det|> +(1) To elucidate the MSR mechanism among three proposed pathways (MD-WGS, methyl formate hydrolysis, and formate degradation), we first conducted independent MD and WGS reaction analyses (Fig. S40). Under MD conditions at \(290^{\circ}\mathrm{C}\) , methanol conversion reached merely \(1.7\%\) with \(\mathrm{CO_2}\) as the dominant product (\~77% selectivity). Notably, the conversion progressively declined below \(1.0\%\) over time, suggesting \(\mathrm{CO_2}\) formation through intermediates reacting with surface hydroxyl groups (\*OH) until deactivation via \*OH depletion and intermediate accumulation. This observation demonstrates that MD is thermodynamically favorable but kinetically restricted. Parallel WGS evaluations under identical conditions (290 °C, \(\mathrm{P_{H_2O}} = 20 \mathrm{kPa}\) , \(\mathrm{CO / H_2O} = 1 / 1\) ) revealed limited CO conversion (\<5%) and negligible \(\mathrm{H_2}\) production rates (1.6 mmol \(\mathrm{g^{-1}}\) \(\mathrm{h^{-1}}\) ), contrasting sharply with the superior MSR performance (264.7 mmol \(\mathrm{g^{-1} h^{-1}}\) \(\mathrm{H_2}\) production rate under equivalent \(\mathrm{CH_3OH / H_2O}\) partial pressures). These findings conclusively exclude the MD-WGS pathway as the operative MSR mechanism. + +<|ref|>image<|/ref|><|det|>[[178, 587, 881, 727]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[178, 733, 848, 769]]<|/det|> +
Fig. S40 (a) \(\mathrm{CH_3OH}\) conversion in MD and CO conversion in WGS. (b) Product selectivity for MSR, MD, and WGS. (c) Corresponding \(\mathrm{H_2}\) production rates.
+ +<|ref|>text<|/ref|><|det|>[[148, 775, 852, 905]]<|/det|> +(2) To gain deeper insight into the reaction mechanism, in situ DRIFTS was employed (Figure R2). Results indicated that the support exhibited weak methanol adsorption, primarily functioning in water adsorption and dissociation. However, in the presence of single-atom Cd, strong adsorption peaks of methoxy and formate species emerged. As temperature increased, these species were rapidly + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 88, 852, 247]]<|/det|> +consumed, coinciding with the appearance of \(\mathrm{CO_2}\) , indicating that \(\mathrm{CO_2}\) and \(\mathrm{H}_2\) generation occurred via formate decomposition. Neither methyl formate nor CO was detected during the reaction or Ar blow- off stage. TPSR analysis also confirmed formate as the main intermediate, with no methyl formate formation. These findings suggest that the MSR reaction proceeds through formate decomposition. + +<|ref|>image<|/ref|><|det|>[[179, 255, 916, 505]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[178, 516, 825, 533]]<|/det|> +
Figure R2 In situ DRIFTS of (a) A, (b) R, (c) P25, (d) 5Cd/A, (e) 5Cd/R, and (f) 5Cd/P25.
+ +<|ref|>text<|/ref|><|det|>[[147, 542, 852, 813]]<|/det|> +(3) KIE experiment showed that C-H dissociation of methanol was more difficult than O-H bond dissociation (Figure R3a). To verify which step in C-H bond dissociation was the RDS, we derived the rate equation. Assuming methoxy dehydrogenation was the RDS, the derived rate equation showed first-order dependence on methanol partial pressures (The detailed derivation of the rate equation is provided in Scheme 1 in the SI or the response to reviewer 2's sixth question). Given competitive adsorption of methanol and water, the reaction order for methanol should be less than 1. The experimentally determined reaction order of 0.72 aligned with the kinetic equation, confirming methoxy dehydrogenation as the RDS (Figure R3b). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[186, 90, 873, 300]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[180, 308, 850, 360]]<|/det|> +
Figure R3 (a) KIE measurements on the 5Cd/P25 catalyst by modulating the isotopic composition of the feed gas. (b) Reaction rate equation and reaction order of \(\mathrm{CH_3OH}\) on the 5Cd/P25 catalyst.
+ +<|ref|>text<|/ref|><|det|>[[149, 367, 852, 692]]<|/det|> +(4) DFT calculations further explored the formate decomposition mechanism. Calculations of adsorption energies for methanol decomposition and formate formation intermediates revealed that \(\mathrm{Cd_1 / A}\) (101) and \(\mathrm{Cd_1 / R}\) (110) have low \(\mathrm{*CHO}\) adsorption energies, favoring CO formation thermodynamically. In contrast, \(\mathrm{Cd_1 / A}\) (101)-R (110) exhibited low adsorption energies for key intermediates ( \(\mathrm{*CH_2O}\) - \(\mathrm{*OH}\) , \(\mathrm{*CHOO}\) , and \(\mathrm{*CHOO}\) ), making the formate pathway more thermodynamically favorable. Transition-state calculations showed that water dissociation and activation on \(\mathrm{Cd_1 / A}\) (101)-R (110) have the lowest energy barriers, promoting formate formation and its subsequent decomposition into \(\mathrm{CO_2}\) and \(\mathrm{H_2}\) . This is attributed to the asymmetric coordination structure and high charge density of phase interface. Additionally, the high energy barrier for methoxy dehydrogenation confirmed it as the RDS. + +<|ref|>sub_title<|/ref|><|det|>[[149, 701, 336, 718]]<|/det|> +## Manuscript Revision: + +<|ref|>sub_title<|/ref|><|det|>[[150, 731, 404, 748]]<|/det|> +## "Reaction mechanism studies + +<|ref|>text<|/ref|><|det|>[[147, 755, 851, 912]]<|/det|> +Since the reaction mechanism determines the product selectivity, we scrutinized various proposed reaction mechanisms for the novel catalysts, including methanol decomposition- water gas shift (MD- WGS), methyl formate hydrolysis, and formate decomposition (Supplementary Fig. 39). The MD reaction was initially investigated over the 5Cd/P25 catalyst at \(290^{\circ}\mathrm{C}\) under a methanol partial pressure of \(20\mathrm{kPa}\) with a feed rate of \(12\mathrm{mL}\mathrm{g}^{- 1}\mathrm{h}^{- 1}\) . \(\mathrm{CH_3OH}\) conversion was limited at \(1.7\%\) , with \(\mathrm{CO_2}\) constituting \(\sim 77\%\) of the products, accompanied by \(\mathrm{CO}\) ( \(\sim 10\%\) ) and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 90, 852, 412]]<|/det|> +\(\mathrm{CH}_4\) (\~13%) (Supplementary Fig. 40). The formation of \(\mathrm{CO}_2\) was proposed to originate from reactions between transient intermediates and hydroxyl groups (OH) on the catalyst support. Progressive depletion of surface OH species and accumulation of adsorbed intermediates correlated with the observed decline in methanol conversion to \(\leq 1.0\%\) over time. This finding indicates that, although thermodynamically favorable at high temperatures, MD is kinetically disfavored. Furthermore, comparative evaluation of WGS activity under equivalent conditions (290 °C, \(\mathrm{CO / H_2O} = 1 / 1\) , \(\mathrm{P_{H2O}} = 20 \mathrm{kPa}\) ) revealed limited catalytic performance, with CO conversion decaying from \(9.0\%\) to \(4.5\%\) over 10 hours and a correspondingly low \(\mathrm{H}_2\) production rate of \(1.6 \mathrm{mmol g^{- 1} h^{- 1}}\) . Strikingly, MSR under identical \(\mathrm{CH}_3\mathrm{OH}\) and \(\mathrm{H}_2\mathrm{O}\) partial pressures (20 kPa each) demonstrated a two- order- of- magnitude enhancement in \(\mathrm{H}_2\) production rates (264.7 mmol \(\mathrm{g^{- 1} h^{- 1}}\) ). These findings suggest that WGS contributes negligibly to \(\mathrm{H}_2\) generation, confirming that the MD- WGS pathway is unlikely to be viable for the Cd- based catalysts. + +<|ref|>text<|/ref|><|det|>[[145, 421, 852, 916]]<|/det|> +In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was conducted to elucidate the reaction mechanism. When exposed to \(\mathrm{CH}_3\mathrm{OH} / \mathrm{H}_2\mathrm{O}\) between 50 and \(320^{\circ}\mathrm{C}\) , only weak methanol physisorbed peaks ( \(\mathrm{u}\) (CO) at \(1000–1100 \mathrm{cm}^{- 1}\) , \(\delta\) (CH) at \(1300–1500 \mathrm{cm}^{- 1}\) , and \(\mathrm{u}\) (CH) at \(2800–3000 \mathrm{cm}^{- 1}\) ) were observed on A, R, and P25, aside from \(\mathrm{H}_2\mathrm{O}\) adsorption and \*OH peaks ( \(\delta\) ( \(\mathrm{H}_2\mathrm{O}\) ) at \(1651 \mathrm{cm}^{- 1}\) and \(\mathrm{u}\) (OH) at \(3710 \mathrm{cm}^{- 1}\) ) (Supplementary Fig. 41 and Supplementary Table 10). These findings demonstrate that the functionality of supports is limited to facilitating \(\mathrm{H}_2\mathrm{O}\) adsorption and dissociation. In stark contrast, after loading Cd single atoms, distinct methoxy (\* \(\mathrm{CH}_3\mathrm{O}\) , \(\delta\) (CH) at \(1431 \mathrm{cm}^{- 1}\) ) and bidentate formate (b- \* \(\mathrm{HCOO}^-\) , \(\mathrm{u}_s\) (OCO) at \(1336 \mathrm{cm}^{- 1}\) , \(\mathrm{u}_{as}\) (OCO) at \(1554 \mathrm{cm}^{- 1}\) ) species emerged \(^{5,29}\) , which indicated that Cd single atoms were responsible for \(\mathrm{CH}_3\mathrm{OH}\) adsorption and dissociation (Figs. 4a- c). As the reaction temperature increased, the \* \(\mathrm{CH}_3\mathrm{O}\) and b- \* \(\mathrm{HCOO}^-\) were rapidly consumed, coinciding with the emergence of gaseous \(\mathrm{CO}_2\) peaks at \(2308\) and \(2375 \mathrm{cm}^{- 1}\) , indicating that \(\mathrm{H}_2\) generation resulted from formate transformation. Notably, on 5Cd/P25, \* \(\mathrm{CH}_3\mathrm{O}\) and b- \* \(\mathrm{HCOO}^-\) were transformed more rapidly at a lower temperature (200 °C) compared to 5Cd/A (260 °C) and 5Cd/R (320 °C) (Fig. 4d). This trend aligns with the catalytic performance, implying that interfacial Cd single atoms are more conducive to intermediates transformation. Additionally, no characteristic peaks indicative of methyl formate (\* \(\mathrm{HCOOCH}_3\) ) were detected in the \(1700–1800 \mathrm{cm}^{- 1}\) range during the reaction and the Ar sweeping stage \(^{30}\) . Similarly, temperature- programmed surface reaction (TPSR) analyses + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 851, 273]]<|/det|> +exclusively identified formate species, with no indication of HCOOCH3 (Fig. 4e and Supplementary Fig. 42). These findings rule out mechanism pathways involving methyl formate hydrolysis via esterification of formic acid with methanol, followed by its hydrolysis to yield CO2 and H2. Therefore, we propose that the formate decomposition pathway dominates the reaction mechanism on the SACs, where methanol initially decomposes into \(*CH_3O\) , subsequently dehydrogenates to \(*H_2CO\) , and reacts with \(*OH\) groups from dissociated H2O to form \(*HCOO^-\) . This intermediate then further dehydrogenates, yielding H2 and CO2. + +<|ref|>text<|/ref|><|det|>[[147, 284, 851, 690]]<|/det|> +The kinetic isotope effect (KIE) experiments were conducted on the 5Cd/P25 catalyst to reveal the reaction kinetics. Switching the feedstock from CH3OH/H2O to CH3OD/H2O resulted in essentially unchanged H2 generation rates, yielding a KIE value (K/H/KD) of 1.1 (Fig. 4f). In contrast, substituting CH3OH/H2O with CD3OD/H2O caused a dramatic 4- fold decline in H2 production rates, corresponding to a significantly elevated KIE of 3.7. These findings establish that C- H bond cleavage exhibits substantially greater kinetic resistance than O- H bond scission, potentially identifying the rate- determining step (RDS) in the MSR reaction. To identify the specific RDS in elementary reactions, we derived the reaction rate equation based on established formate mechanism. According to previous reports, assuming that methoxy dehydrogenation \((*CH_3O \rightarrow *CH_2O + *H)\) was RDS, the derived rate equation showed a first- order dependence on CH3OH pressures (Supplementary scheme 1). Considering competitive adsorption between CH3OH and H2O on active sites, the theoretical CH3OH reaction order was predicted to be less than unity (<1). The experimentally determined CH3OH reaction order of 0.72 demonstrated excellent agreement with the kinetic model (Fig. 4g), providing conclusive evidence that methoxy dehydrogenation constitutes the RDS in this pathway. + +<|ref|>text<|/ref|><|det|>[[147, 701, 851, 912]]<|/det|> +DFT calculations based on the established Cd1/A (101), Cd1/R (110), and Cd1/A (101)- R (110) models provided complementary theoretical insights into the MSR reaction pathway. The computed energy landscape revealed distinct adsorption energy profiles: \(*CHO\) exhibited significantly lower adsorption energies on Cd1/A (101) (- 1.45 eV) and Cd1/R (110) (- 1.18 eV) compared to the C1/A (101)- R (110) model (4.1 eV) (Supplementary Fig. 43). This energy disparity implies preferential CO generation pathways on Cd1/A (101) and Cd1/R (110) surfaces. Conversely, critical intermediates such as \(*CH_2O - *OH\) , \(*CHOOH\) and \(*CHO\) displayed substantially reduced adsorption energies on the Cd1/A (101)- R (110) surface. These findings + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 162]]<|/det|> +demonstrate that the formate decomposition pathway is thermodynamically more favorable on the Cd1/A (101)-R (110) catalyst, attributable to its asymmetric coordination environment and enhanced charge density at the interface Cd single-atom sites. + +<|ref|>text<|/ref|><|det|>[[146, 170, 852, 692]]<|/det|> +The transition states of the formate decomposition pathway were further investigated (Fig. 4h and Supplementary Figs. 44- 46). Consistent with in situ DRIFTS observations, DFT calculations revealed that both the adsorption and the stepwise dehydrogenation of CH3OH occurred at the Cd active site. The activation energy barriers for CH3OH dehydrogenation (TS1: 0.64 eV) were significantly lower than those for \*CH3O dehydrogenation (TS2: 0.87 eV) on the Cd1/A (101)-R (110) surface. This clearly demonstrates that the C-H bond cleavage encounters higher kinetic resistance than O-H bond scission, aligning with the experimental KIE results. Following \*CH3O dehydrogenation to \*CH2O, H2O adsorption and dissociation on adjacent Ti atoms generated \*H and \*OH species (TS3: 0.37 eV). Subsequent CH2O/OH recombination formed CH2OOH (TS4: 0.43 eV), which further dehydrogenated to produce CO2 and H2. Although TS1 and TS2 barriers on Cd1/A (101)-R (110) were modestly elevated relative to Cd1/A (101) (TS3/TS4: 1.07/0.60 eV) and Cd1/R (110) (TS3/TS4: 0.57/0.53 eV), the dissociation of H2O (TS3) and CH2OOH formation (TS4) exhibited significantly lower energy barriers in the phase interface model. These results demonstrated that the unique structural properties of the interfacial structure enhanced the dissociation and activation of H2O, thereby facilitating the subsequent formation of formate and H2. Consequently, these observations rationalized the high activity and low CO selectivity of the 5Cd/P25 catalyst. Additionally, the highest activation energy barrier (TS2: 0.87 eV) confirmed \*CH3O dehydrogenation as the RDS on the Cd1/A (101)-R (110), consistent with previous kinetic analysis." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 250, 107]]<|/det|> +Reviewer: 2 + +<|ref|>sub_title<|/ref|><|det|>[[149, 146, 363, 163]]<|/det|> +## Response to Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[148, 201, 245, 217]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[147, 226, 853, 617]]<|/det|> +In this work, Wang et. al, selectively decorated isolated Cd atoms to the interface of the P25 where heterogeneous structures of anatase and rutile coexist and the promoted H2 production rate has been achieved at \(\sim 292.9 \mathrm{mmol}\) gcat- 1 h- 1, which is about 15- fold and 8- fold higher than that of anatase and rutile dispersed Cd active components. The superior reaction performance has been attributed to the Cd- O- Ti interfacial structures. And this specific active component has been systematically probed by HRTEM, XAFS, EPR etc. A formate decomposition reaction pathway has been systematically discussed and was taken as the reaction mechanism for the hydrogen production. Finally, 3D printing has been introduced to produce the catalyst and this reaction system does show some potential in industrial applications. Generally, this is a good work and shows some interesting results, however, some of them are still under debate and might be critical to the overall conclusions. I suggest to reject this paper and give the author the opportunity to resubmit the work and hopefully the concerns listed bellow could be answered during the re- submission. + +<|ref|>text<|/ref|><|det|>[[147, 653, 853, 812]]<|/det|> +1. First of all, the authors suggest that there is CdTiO3 at the interfacial site and it does not contribute to the hydrogen formation. I agree that, however, the Cd/CdOx does not show good activity either as comparisons. How can you explain that? And this CdTiO3 structure coexists with the real active components, is that possible most of the characterization is simply against this in-active structures (c.a. CdTiO3) rather than the real ones. + +<|ref|>text<|/ref|><|det|>[[147, 848, 850, 895]]<|/det|> +Response: Thank you for raising this critical issue. We included CdTiO3, metallic Cd, and CdO nanoparticles in our studies to exclude their contribution to the reaction + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 371]]<|/det|> +performance and to further demonstrate and emphasize that the active sites were Cd single atoms, particularly at the phase interface of P25. The poor catalytic performance of Cd/CdOx species resembled the subpar performance of clusters and nanoparticles observed in SACs studies. For instance, in CO oxidation and olefin hydroformylation reactions, atomically dispersed Au species demonstrated exceptional activity, whereas Au nanoparticles/clusters remained catalytically inert (J. Am. Chem. Soc. 2018, 140, 13808–13816; Chem Catal. 2022, 2, 1–11). The superior performance of single-atom configurations arises from their unique electronic structures that enable precisely tuned adsorption/desorption energetics of key intermediates—a fundamental advantage over nanometer-scale counterparts. + +<|ref|>text<|/ref|><|det|>[[147, 385, 852, 655]]<|/det|> +The distinct coordination environments of Cd species critically determine their catalytic functionality. Metallic Cd nanoparticles exhibit symmetric Cd- Cd coordination, while CdO nanoparticles maintain regular Cd- O octahedral geometry. In stark contrast, interfacial Cd single- atom catalysts display exclusive Cd- O coordination with pronounced asymmetry. This structural distortion induces localized charge redistribution, creating polarized electronic domains fundamentally distinct from the delocalized electron clouds in metallic Cd and CdO. Such electronic configuration enables the Cd SACs to stabilize key reaction intermediates through enhanced orbital hybridization, rationalizing the superior activity over conventional Cd/CdO systems. + +<|ref|>sub_title<|/ref|><|det|>[[149, 664, 595, 682]]<|/det|> +## The location of CdTiO3 formed on the catalysts + +<|ref|>text<|/ref|><|det|>[[147, 692, 852, 906]]<|/det|> +Our manuscript does not assert the interfacial localization of CdTiO3. As an ilmenite- type compound, CdTiO3 can be detected by XRD, which implies that its content is sufficient to be visualized in HAADF- STEM images. However, the lattice fringe of CdTiO3 was not observed at the phase interface of P25 (Fig. S15). Notably, combined XRD and Raman analyses demonstrated the CdTiO3 formation exclusively in R- phase- containing systems (5Cd/R and 5Cd/P25), with complete suppression in 5Cd/A (Figs. 1e, and S17). Meanwhile, crystallographic parameter analysis revealed a critical mechanistic insight: the R- phase/CdO lattice mismatch (2.4%) facilitated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 855, 191]]<|/det|> +coherent heteroepitaxy, whereas anatase- CdO exhibited prohibitive mismatch (24.1%) that kinetically hindered phase transformation. This confirmed that limited CdTiO₃ formation in 5Cd/P25 originated from atomic migration of surface- isolated Cd species, which preferentially anchored on the R- phase domains of P25. + +<|ref|>sub_title<|/ref|><|det|>[[150, 201, 410, 218]]<|/det|> +## - Distinctions of active sites + +<|ref|>text<|/ref|><|det|>[[147, 228, 852, 330]]<|/det|> +To distinguish the inert phase CdTiO₃ from the actual active sites (interface Cd single atoms), we also took this into consideration in advance during the research process and conducted an in- depth analysis. The results indicated that they can be clearly differentiated from each other. + +<|ref|>text<|/ref|><|det|>[[149, 340, 465, 358]]<|/det|> +(1) Crystallographic structure analysis: + +<|ref|>text<|/ref|><|det|>[[146, 367, 853, 664]]<|/det|> +XRD patterns identify CdTiO₃ (R- 3 space group, JCPDS#00- 052- 1436) as a hexagonally ordered ilmenite structure (Fig. S20). Therefore, HAADF- STEM images should display distinct lattice fringes, with atoms arranged in an ordered periodic pattern. In contrast, the interface single- atom Cd should appear as isolated, disordered bright spots due to the Z- contrast differentiation between Cd (Z=48) and Ti (Z=22), as shown in the 5Cd/P25 catalyst (Figures R4a and b). Taking 10Cd/P25 (Cd: 10 wt%) as an example, which exhibited more pronounced CdTiO₃ features, we observed CdTiO₃ particles of approximately 2 nm in size from HAADF- TEM images, with lattice fringes of 2.56 Å corresponding to the (110) crystal face of CdTiO₃ (Figures R4c and d). Therefore, the CdTiO₃ and Cd single atoms can be significantly differentiated based on structure characterizations. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[275, 85, 722, 396]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 401, 850, 437]]<|/det|> +
Figure R4 HAADF-STEM images of (a, b) interface Cd single atoms on the 5Cd/P25 catalyst and (c, d) CdTiO3 on the 10Cd/P25 catalyst.
+ +<|ref|>text<|/ref|><|det|>[[148, 442, 538, 460]]<|/det|> +(2) Local coordination and electronic properties + +<|ref|>text<|/ref|><|det|>[[147, 469, 852, 710]]<|/det|> +XANES revealed a downward shift in the near- edge absorption threshold for CdTiO3 compared to Cd SACs, indicating distinct electronic configurations (Figure R5a). EXAFS fitting demonstrated significantly shorter Cd- O bond lengths in CdTiO3 (2.05 Å) than in SACs (2.23 Å), confirming differential coordination environments (Figure R5b). In addition, XPS analysis further corroborated this differentiation: The coordination- saturated Cd atoms in CdTiO3 exhibited a 0.3- 0.7 eV lower Cd3d binding energy (404.8 eV) compared to undercoordinated single- atom Cd (Figure R5c). Therefore, the aforementioned characterizations can distinguish the inert active phase (CdTiO3) from the single- atom Cd active sites. + +<|ref|>image<|/ref|><|det|>[[155, 727, 850, 875]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 882, 850, 900]]<|/det|> +
Figure R5 (a) Cd K-edge XANES spectra of fresh catalysts. (b) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 163, 852, 266]]<|/det|> +2. The authors suggest that the Cd is isolated, however, there is only one evidence from EXAFS, even the HAADF-STEM characterizations are not very clear. Is that possible the Cd are clusters rather than isolated site? Then it still gives advanced reaction performance, well the actually active component is not the isolated Cd. + +<|ref|>text<|/ref|><|det|>[[147, 302, 852, 543]]<|/det|> +Response: We appreciate the reviewer's insightful comments. To more clearly show the Cd single atoms via HAADF- STEM, we have re- photographed them as much as possible (given the limitations of the instrumental resolution and the beam- sensitive nature of samples, this is the highest resolution we can achieve) and updated the figures in both the manuscript and the Supplementary Information (Fig. 1 and Figs. S13- 15). Since the atomic number of Cd is higher than that of Ti, it appears as a brighter point in the HAADF- STEM images. In addition, no clustered bright spots were observed across \(>20\) randomly sampled regions, excluding the formation of Cd cluster and nanoparticles. + +<|ref|>text<|/ref|><|det|>[[147, 552, 852, 739]]<|/det|> +We believe that the presence of Cd clusters can be ruled out. Firstly, our samples were only calcined in air and not reduced in a reductive atmosphere (such as \(\mathrm{H}_2\) ), making the formation of metallic clusters highly unlikely. Secondly, based on the EXAFS data, if Cd clusters were present, Cd- Cd coordination would be evident. For instance, in the low- Cd- content catalysts developed by Wang et al. (Chinese J. Catal., 2022, 43,767- 770), the formation of Cd clusters after the reaction led to the detection of significant Cd- Cd coordination in the EXAFS spectra (Figure R6). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 121]]<|/det|> +Figure R6 EXAFS spectra with \(\mathrm{k^3}\) - weighted data obtained from low- Cd- content catalysts (Chinese J. Catal., 2022, 43,767- 770). + +<|ref|>text<|/ref|><|det|>[[147, 126, 853, 397]]<|/det|> +To delineate the structural distinction between Cd single atoms and clusters, we synthesized a cluster- containing catalyst via \(\mathrm{H}_2\) reduction of the 5Cd/P25 at \(400^{\circ}\mathrm{C}\) (denoted as 5Cd/P25- 400H2). XRD analysis detected no metallic Cd diffraction peaks (Fig. S23a), suggesting the absence of crystalline Cd nanoparticles. Intriguingly, HAADF- STEM revealed the existence of sub- nanometer Cd clusters (Fig. S23b), which were further corroborated by EXAFS spectra showing prominent Cd- Cd coordination at \(\sim 2.8 \mathrm{\AA}\) (Fig. S23c). XPS analysis indicated a \(0.4 \mathrm{eV}\) downward shift in the Cd \(3\mathrm{d}_{5 / 2}\) binding energy for 5Cd/P25- 400H2 relative to 5Cd/P25, concurrent with the transformation of the Cd MNN Auger peak into a broadened feature characteristic of metallic clusters (Fig. S23d). + +<|ref|>text<|/ref|><|det|>[[147, 404, 866, 561]]<|/det|> +Catalytic evaluation under identical reaction conditions revealed that cluster formation drastically impaired performance: Methanol conversion decreased from \(100\%\) to \(33.6\%\) , the \(\mathrm{H}_2\) production rate dropped from 97.7 to \(32.6 \mathrm{mmol} \mathrm{g}^{- 1} \mathrm{h}^{- 1}\) , and CO selectivity increased from \(0.5\%\) to \(2.6\%\) (Fig. S22). The results clearly differentiate between Cd clusters and single atoms, pinpointing the phase- interface Cd single atoms as actual active sites. + +<|ref|>image<|/ref|><|det|>[[147, 570, 832, 877]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 882, 848, 899]]<|/det|> +
Fig. S23 Structural characterizations of the 5Cd/P25 catalysts after reduction at \(400^{\circ}\mathrm{C}\) (denoted
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 849, 140]]<|/det|> +as 5Cd/P25- 400H₂). (a) XRD patterns. (b and c) HAADF- STEM images of the 5Cd/P25- 400H₂. (d) Cd K-edge XANES spectra. (e) K³- weighted χ (k) function of EXAFS spectra. (f) XPS and AES spectra. + +<|ref|>text<|/ref|><|det|>[[148, 145, 850, 191]]<|/det|> +The content as mentioned above was supplemented into the Fig. S23 in Supplementary Information. + +<|ref|>title<|/ref|><|det|>[[148, 197, 336, 213]]<|/det|> +# Manuscript Revision: + +<|ref|>image<|/ref|><|det|>[[248, 219, 627, 891]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 894, 848, 910]]<|/det|> +
Fig. 1 i-k, HAADF-STEM and EDS mapping images for 5Cd/A (i), 5Cd/R (j), and 5Cd/P25 (k)
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 87, 214, 100]]<|/det|> +catalysts. + +<|ref|>image<|/ref|><|det|>[[149, 106, 839, 430]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 436, 850, 508]]<|/det|> +
Fig. S13 Structural characterization of the 5Cd/A catalyst. (a) Low-magnification HAADF-STEM image. (b) High-resolution EDS elemental mapping of Cd distribution. (c) Atomic-scale EELS analysis. (d-f) Atomic-resolution HAADF-STEM images showing isolated Cd single atoms (indicated by yellow circles).
+ +<|ref|>image<|/ref|><|det|>[[149, 509, 844, 825]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 826, 850, 899]]<|/det|> +
Fig. S14 Structural characterization of the 5Cd/R catalyst. (a) Low-magnification HAADF-STEM image. (b) High-resolution EDS elemental mapping of Cd distribution. (c) Atomic-scale EELS analysis. (d-f) Atomic-resolution HAADF-STEM images showing isolated Cd single atoms (indicated by yellow circles).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[180, 92, 816, 540]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 547, 852, 640]]<|/det|> +
Fig. S12 HAADF-STEM images of the 5Cd/P25 catalyst, showing Cd single atoms anchored between the A (101) and R (110) facets (yellow arrow and orange markers); scale bars: \(100\mathrm{nm}\) (a), \(50\mathrm{nm}\) (b), \(20\mathrm{nm}\) (c), \(5\mathrm{nm}\) (d). (e and f) Phase interface EDX elemental mapping images. (g-h) HAADF-STEM images of phase interface at a scale of \(1\mathrm{nm}\) (bright spots correspond to Cd single atoms).
+ +<|ref|>text<|/ref|><|det|>[[147, 700, 852, 840]]<|/det|> +3. The author shows the selectivity of \(H_{2}\) , \(CO\) , \(CO_{2}\) and \(CH_{4}\) , and hydrogen dominants in the products, however, this is not correct. In this way, none of the product could reach \(100\%\) . The selectivity should be classified into carbonaceous species and hydrogen, which should be more reasonable, during which time, \(CO\) selectivity won't be as low as it is for right now. + +<|ref|>text<|/ref|><|det|>[[147, 877, 848, 896]]<|/det|> +Response: We sincerely appreciate the rigorous technical evaluation and constructive + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 191]]<|/det|> +guidance. In accordance with the reviewer's suggestions on product selectivity, we have implemented the following revisions throughout the manuscript (Figs. 1a-c, 5b, and Supplementary Figs. S1-S9, S22, S34-36). The CO selectivity of the optimal catalyst remained at a low level of \(0.3\%\) . + +<|ref|>text<|/ref|><|det|>[[148, 200, 702, 219]]<|/det|> +The corresponding calculation equation has been revised as follows: + +<|ref|>equation<|/ref|><|det|>[[202, 225, 792, 355]]<|/det|> +\[\mathrm{CO~Selectivity~(\%) = \frac{n(CO,outlet)}{n(CO,outlet) + n(CO_2,outlet) + n(CH_4,outlet)}\times 100\%}\] \[\mathrm{CO_2~Selectivity~(\%) = \frac{n(CO_2,outlet)}{n(CO,outlet) + n(CO_2,outlet) + n(CH_4,outlet)}\times 100\%}\] \[\mathrm{CH_4~Selectivity~(\%) = \frac{n(CO_2,outlet)}{n(CO,outlet) + n(CO_2,outlet) + n(CH_4,outlet)}\times 100\%}\] + +<|ref|>text<|/ref|><|det|>[[147, 421, 857, 610]]<|/det|> +4. For the activation energy determined, it looks that 82.7 KJ/mol is almost half the value of 152.1 KJ/mol, which may suggest that the system of Cd/P25 is suffering from diffusion limitations and it gives half the value of the real one and the superior reaction performance is not originated from the reduced activation energies. Well, this is only based on my assumption and the author definitely should exclude the mass/heat transfer limitations (both internal and outside channel diffusion limitations) before determining the apparent activation energies. + +<|ref|>text<|/ref|><|det|>[[147, 644, 852, 775]]<|/det|> +Response: Thanks for pointing this out. We have thoroughly re- examined and analyzed our experimental data in light of your comments. We acknowledge that the influence of mass transfer cannot be entirely ruled out during the testing process. Specifically, the conversion rate was relatively high ( \(\sim 20\%\) ) in the previous tests, which potentially led to an underestimation of the apparent activation energy. + +<|ref|>text<|/ref|><|det|>[[147, 783, 852, 914]]<|/det|> +To eliminate the effect of external diffusion, we increased the space velocity (liquid feed rate). As depicted in Fig. S6, for the three catalysts (5Cd/A, 5Cd/R, and 5Cd/P25), the methanol conversion shows an inverse relationship with increasing feed rate. Concurrently, the \(\mathrm{H}_2\) production rate gradually rises, and the curve tends to stabilize. This behavior suggests that the reaction on these catalysts is analogous to a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 853, 275]]<|/det|> +first- order reaction kinetics model. Under high feed rate conditions, when the conversion rate was below \(10\%\) , the impact of feed rates on the \(\mathrm{H}_2\) production rate is minimal, indicating that the effect of external diffusion can be neglected. Therefore, we opted to conduct our activation energy tests at a high feed rate corresponding to a methanol conversion of less than \(10\%\) . This selection ensures that the influence of external diffusion is minimized, allowing for a more accurate assessment of the intrinsic catalytic activity and the apparent activation energy of the catalyst. + +<|ref|>text<|/ref|><|det|>[[147, 284, 850, 329]]<|/det|> +To determine whether the effect of internal diffusion was negligible, we applied the Weisz- Prater criterion for calculation, as shown in Equations (1- 3). + +<|ref|>equation<|/ref|><|det|>[[366, 336, 628, 444]]<|/det|> +\[\begin{array}{l}\mathrm{WP} = \frac{\mathrm{r}\times\mathrm{R}^2}{\mathrm{C}_\mathrm{S}\times\mathrm{D}_\mathrm{e}}\\ \displaystyle \frac{1}{\mathrm{D}_\mathrm{e}} = \frac{\tau}{\epsilon}\left(\frac{1}{\mathrm{D}_\mathrm{m}} +\frac{1}{\mathrm{D}_\mathrm{k}}\right)\\ \displaystyle \mathrm{D}_\mathrm{k} = \frac{2}{3}\mathrm{d}_\mathrm{p}\sqrt{\frac{8\mathrm{R}\mathrm{T}}{\pi\mathrm{M}}} \end{array} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[146, 449, 852, 635]]<|/det|> +\(\mathrm{r}\) represents the reaction rate, \(\mathrm{R}\) represents the particle radius, \(\mathrm{C}_\mathrm{s}\) represents the reactant concentration at the catalyst surface, \(\mathrm{D}_\mathrm{e}\) represents the effective diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\tau\) represents the pore tortuosity, \(\epsilon\) represents the porosity, \(\mathrm{D}_\mathrm{m}\) represents the molecular diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{D}_\mathrm{k}\) represents the Knudsen diffusion coefficient \((\mathrm{m}^2 \mathrm{s}^{- 1})\) , \(\mathrm{d}_\mathrm{p}\) represents the average pore diameter \((\mathrm{m})\) , \(\mathrm{M}\) represents the molar mass of the diffusing species \((\mathrm{kg} / \mathrm{mol})\) , \(\mathrm{R}\) represents the gas constant, and \(\mathrm{T}\) represents the temperature \((\mathrm{K})\) . + +<|ref|>text<|/ref|><|det|>[[146, 644, 853, 914]]<|/det|> +Under the conditions of \(290^{\circ}\mathrm{C}\) , \(\mathrm{S / C} = 3 / 1\) , \(0.1 \mathrm{MPa}\) , and methanol conversion below \(10\%\) , the Weisz- Prater (WP) values for \(5\mathrm{Cd / A}\) , \(5\mathrm{Cd / R}\) , and \(5\mathrm{Cd / P25}\) were \(1.0 \times 10^{- 7}\) , \(2.4 \times 10^{- 9}\) , and \(7.3 \times 10^{- 10}\) , respectively. All of them were much less than 1, so the internal diffusion limitation could be excluded. In addition, we added inert \(\mathrm{SiO}_2\) to the catalyst to promote heat transfer during the reaction process, ensuring no temperature gradient in the reaction zone and excluding the impact of heat transfer. Finally, we tested the \(\mathrm{H}_2\) production rate at every \(10^{\circ}\mathrm{C}\) intervals in the temperature range of \(250 - 290^{\circ}\mathrm{C}\) and calculated the corresponding apparent activation energy by substituting it into the Arrhenius equation (as shown in Equation 4). The apparent activation energies of the three catalysts \(5\mathrm{Cd / A}\) , \(5\mathrm{Cd / R}\) , and \(5\mathrm{Cd / P25}\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 219]]<|/det|> +were 146.6 KJ/mol, 121.9 KJ/mol, and 107.3 KJ/mol, respectively (Fig. 1d). In comparison, the activation energy of the 5Cd/P25 catalyst was still the lowest, which did not affect the original conclusion that the interfacial Cd single atom sites with their unique interfacial structure and electronic properties had relatively excellent catalytic performance. + +<|ref|>equation<|/ref|><|det|>[[378, 226, 616, 255]]<|/det|> +\[\ln \mathbf{k} = \ln \mathbf{A} - \frac{\mathbf{E}_{\mathrm{a}}}{\mathrm{RT}} \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[147, 264, 852, 340]]<|/det|> +To enhance the transparency and reproducibility of the findings, we have added Fig. S6 and the calculation process of apparent activation energy in the SI section of the revised manuscript, and the corresponding content is as follows. + +<|ref|>image<|/ref|><|det|>[[147, 355, 951, 508]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 512, 852, 565]]<|/det|> +
Fig. S6 Feed rate dependence of methanol conversion and \(\mathrm{H}_2\) production rates over 5Cd/A, 5Cd/R, and 5Cd/P25 catalysts. Reaction conditions: catalyst \(0.1\mathrm{g} + \mathrm{SiO}_2 0.2\mathrm{g}\) ; liquid feed of \(\mathrm{S / C} = 3\) at \(6 - 45\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) ; \(\mathrm{N}_2\) carrier at \(20\mathrm{mL}\mathrm{min}^{-1}\) ; temperature: \(290^{\circ}\mathrm{C}\)
+ +<|ref|>image<|/ref|><|det|>[[364, 567, 636, 732]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 735, 848, 771]]<|/det|> +
Fig. 1 Catalytic performance and structural characteristics of catalysts in the MSR reaction. d, Apparent activation energy evaluation (methanol conversion less than \(10\%\) ).
+ +<|ref|>text<|/ref|><|det|>[[147, 816, 852, 896]]<|/det|> +5. If the real active component is the Cd-O-Ti structure, no matter which TiO₂ phase it connects to, the Cd/P25 should gives similar activities with either Cd/anatase or Cd/rutile. This is not very clear, this reviewer suggests the author put more effort on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 136]]<|/det|> +explaining that. For example, the highly dispersed Cd on amorphous \(\mathrm{TiO_2}\) might be also good for this reaction. + +<|ref|>text<|/ref|><|det|>[[147, 172, 852, 387]]<|/det|> +Response: Thank you for your comment. As is well- known, the unique structure or electronic properties of single- atom catalysts is a significant factor determining reaction performance. Our characterizations and DFT calculations showed that although Cd- Ti- O coordination sites were fundamental active centers, differences in their microenvironment (structural and electronic properties) significantly affected catalytic performance. Therefore, the unique Cd- Ti- O sites at P25 anatase/rutile phase interfaces exhibit superior catalytic performance compared to those on individual phase surfaces. This is systematically demonstrated in the manuscript: + +<|ref|>text<|/ref|><|det|>[[147, 395, 852, 802]]<|/det|> +In terms of structure, the atomic arrangement at the anatase- rutile phase interface in P25, which contained Ti vacancies, was disordered (Figs. 3a and b). Therefore, the Cd- Ti- O sites formed at the phase interface have an asymmetric structure, which is different from the symmetric structure of surface sites (Fig. S16). This special asymmetric structure also leads to its unique electronic properties. The oxidation state of Cd atoms at the interface was between that of the surface atoms of anatase or rutile. DFT calculations revealed that, compared with the Cd- Ti- O sites on the surface of anatase and rutile, the phase- interface Cd- Ti- O sites possessed a polar electronic domain and exhibit a higher electron density of states (Fig. 2e and Fig. S28). These characteristics decreased the adsorption and activation energies of reactants (Fig. 2f). In addition, electrochemical cyclic voltammetry proved that the Cd- Ti- O sites at the phase interface were more conducive to electron transfer to the reactants (Fig. 2d). \(\mathrm{CH_3OH - TPD}\) and TPSR experiments further revealed their strong adsorption and activation ability (Figs. 4e, S29, and S42). Therefore, the Cd- Ti- O sites formed at the phase interface had optimal performance. + +<|ref|>text<|/ref|><|det|>[[147, 811, 850, 888]]<|/det|> +In accordance with the reviewer's suggestion, amorphous \(\mathrm{TiO_2}\) with a specific surface area of \(242 \mathrm{m^2 / g}\) was synthesized following the methodology established by Xu et al (J. Colloid Interface Sci., 2024, 653, 1006- 1017). As evidenced by the XRD + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 853, 442]]<|/det|> +patterns in Figure R7a, the \(\mathrm{TiO_2}\) support retained its amorphous nature after Cd loading, with no detectable diffraction peaks corresponding to crystalline Cd species, indicating their high dispersion. However, under MSR conditions ( \(290^{\circ}\mathrm{C}\) , S/C ratio of 3/1, 0.1 MPa pressure, and \(3\mathrm{mL}\cdot \mathrm{g}^{- 1}\cdot \mathrm{h}^{- 1}\) feed rate), distinct anatase- phase diffraction peaks emerged after the reaction. This structural evolution demonstrated the thermodynamic instability of the amorphous \(\mathrm{TiO_2}\) under MSR conditions. Catalytic performance evaluations revealed substantially lower methanol conversion ( \(0.8\%\) ) for this catalyst compared to 5Cd/A, 5Cd/R, and 5Cd/P25 benchmarks (Figure R7b). These results collectively suggested that the crystallographic form and specific surface area of \(\mathrm{TiO_2}\) were not the determining factor for the catalytic activity of Cd- O- Ti sites. Rather, the exceptional catalytic performance originated from the unique local coordination environment and electronic interactions within the Cd- Ti- O asymmetric structures at phase interfaces. + +<|ref|>image<|/ref|><|det|>[[149, 450, 845, 646]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 652, 851, 705]]<|/det|> +
Figure R7 (a) XRD patterns of the amorphous \(\mathrm{TiO_2}\) , 5Cd/amorphous \(\mathrm{TiO_2}\) , and spent amorphous \(\mathrm{TiO_2}\) catalysts. (b) Comparative catalytic performance. Reaction conditions: \(290^{\circ}\mathrm{C}\) , S/C ratio of 3/1, 0.1 MPa pressure, carrier gas of \(30\mathrm{mL} / \mathrm{min}\mathrm{N}_2\) , and \(3\mathrm{mL}\mathrm{g}^{-1}\mathrm{h}^{-1}\) feed rate.
+ +<|ref|>text<|/ref|><|det|>[[147, 765, 853, 896]]<|/det|> +6. There is contradictory assessment in elucidating the reaction mechanism of hydrogen production. Clearly, the C-H bond rupture within methanol is the rate determining step based on the KIE values determined. And usually, CO could be easily generated from methanol decomposition. Negligible CO determined would be attributed to the strong WGS reaction in the system, and it was not mentioned. This + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 136]]<|/det|> +reviewer suggests the author to clarify that by determining the reaction rate and equilibrium constant on WGS at the relative conditions. + +<|ref|>text<|/ref|><|det|>[[147, 172, 852, 274]]<|/det|> +Response: We appreciate the reviewer's insightful comments regarding the possible role of the WGS reaction in consuming CO. Below we clarify why the WGS reaction is not dominant in our system, supporting the formate decomposition pathway as the primary mechanism. + +<|ref|>image<|/ref|><|det|>[[148, 280, 870, 425]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 428, 850, 464]]<|/det|> +
Fig. S40 (a) CH\(_3\)OH conversion in MD and CO conversion in WGS. (b) Product selectivity for MSR, MD, and WGS. (c) Corresponding H\(_2\) production rates.
+ +<|ref|>text<|/ref|><|det|>[[147, 470, 852, 906]]<|/det|> +We performed methanol decomposition (MD) experiments. When only CH\(_3\)OH was introduced (with a partial pressure of 20 kPa), the CH\(_3\)OH conversion was just 1.7%, and the CO\(_2\) selectivity in the products was as high as \(\sim\) 80%, with CO and CH\(_4\) selectivity at 10% each (Fig. S40a and b). As the reaction proceeded, the CH\(_3\)OH conversion progressively declined to below 1%. These observations suggest that the direct C-H bond cleavage of CH\(_3\)OH to form CO is kinetically hindered. This could be attributed to methanol adsorption and dissociation on the catalyst surface, forming \(*CH_3O\) or \(*CH_2O\) intermediates. While a small fraction of these intermediates dissociates to CO, the majority react with surface \(*OH\) to form formate ( \(*HCOO\) ), which subsequently decomposes to CO\(_2\), or with \(*H\) to produce CH\(_4\). In-situ DRIFTS confirmed the appearance of strong \(*HCOO\) and \(*CH_3O\) adsorption after methanol adsorption (Fig. 4a-c). As the reaction proceeds, the \(*OH\) on the catalyst surface is consumed. The surface intermediates ( \(*CH_3O\) and \(*CHO\) ) gradually accumulate due to the lack of \(*OH\) from water, making the formate reaction path difficult and leading to a drop in CH\(_3\)OH conversion. This shows that although MD is thermodynamically favorable at high temperatures, it is kinetically unfavorable in our catalytic system (If + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 88, 853, 469]]<|/det|> +MD is favorable, the CO selectivity should be \(100\%\) . We also conducted WGS reactions to verify the reaction mechanism. Under conditions of \(20\mathrm{kPa}\) water partial pressure, \(\mathrm{CO / H_2O} = 1 / 1\) , and \(290^{\circ}\mathrm{C}\) , the CO conversion decreased from \(9\%\) to \(5\%\) , with a \(\mathrm{H}_2\) production rate of only \(\sim 2\mathrm{mmol}\mathrm{g}^{- 1}\mathrm{h}^{- 1}\) , indicating kinetic hindrance. In contrast, under the same methanol and water partial pressures, the MSR reaction had a high \(\mathrm{H}_2\) production rate of \(264.7\mathrm{mmol}\mathrm{g}^{- 1}\mathrm{h}^{- 1}\) (Fig. 40c). Comparison of MD, WGS, and MSR reactions thus showed that \(\mathrm{MD} + \mathrm{WGS}\) was not the reaction mechanism. In addition, in the \(\mathrm{MD} + \mathrm{WGS}\) mechanism, prior studies suggested that in TPSR experiments, methanol and water consumption would lag behind: methanol was first converted to CO at a lower temperature, which then reacted with water to form \(\mathrm{CO}_2\) at a higher temperature (Figure R8). However, this tandem process was not observed in our experiment (Fig. 4e). Instead, \(\mathrm{CO}_2\) generation coincided with formate production, further confirming that formate decomposition is the mechanism of our catalytic system. + +<|ref|>text<|/ref|><|det|>[[147, 600, 810, 636]]<|/det|> +Figure R8 TPSR experiments in previous reports (Appl. Catal. B: Environ., 2010, 95, 87- 92; Chem. Eng. J., 2023, 473, 145458). + +<|ref|>text<|/ref|><|det|>[[147, 681, 852, 833]]<|/det|> +In prior studies of Pt- and Cu- based systems, C- H bond cleavage as the rate- determining step (RDS) has been extensively reported, with methoxy dehydrogenation considered the RDS for the mechanism of \(\mathrm{MD} + \mathrm{WGS}\) and formate decomposition (J. Am. Chem. Soc., 2023, 145, 905- 918; Nat. Commun., 2023, 14, 7980; Nat. Catal., 2022, 5, 99- 108). To verify if methoxy dehydrogenation in elementary reactions is the RDS, we derived a kinetic rate equation. + +<|ref|>text<|/ref|><|det|>[[148, 850, 460, 866]]<|/det|> +Formate mechanism elementary steps: + +<|ref|>text<|/ref|><|det|>[[148, 877, 487, 894]]<|/det|> +(1) Methanol adsorption and dissociation: + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[285, 92, 712, 116]]<|/det|> +\[\mathrm{CH_3OH(g)} + 2*\stackrel {k_1}{\rightleftharpoons}*\mathrm{CH_3O} + *\mathrm{H} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[147, 127, 399, 144]]<|/det|> +(2) Methoxy dehydrogenation: + +<|ref|>equation<|/ref|><|det|>[[281, 153, 712, 183]]<|/det|> +\[* \mathrm{CH_3O} \xrightarrow{k} \mathrm{CH_2O} + * \mathrm{H} \quad (\mathrm{R.D.S}) \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[147, 192, 528, 210]]<|/det|> +(3) Water dissociates to form hydroxyl groups: + +<|ref|>equation<|/ref|><|det|>[[293, 220, 712, 247]]<|/det|> +\[\mathrm{H_2O} + *\stackrel {k_2}{\rightleftharpoons}*\mathrm{OH} + *\mathrm{H} \quad (3)\] + +<|ref|>text<|/ref|><|det|>[[147, 257, 515, 275]]<|/det|> +(4) Formaldehyde oxidizes to form formates: + +<|ref|>equation<|/ref|><|det|>[[281, 284, 712, 312]]<|/det|> +\[* \mathrm{CH_2O} + * \mathrm{OH} \xrightarrow{k_3} * \mathrm{HCOO} + \mathrm{H_2} \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[147, 322, 491, 339]]<|/det|> +(5) Formates decompose to produce \(\mathrm{CO_2}\) : + +<|ref|>equation<|/ref|><|det|>[[280, 348, 712, 378]]<|/det|> +\[* \mathrm{HCOO} \xrightarrow{k_4} \mathrm{CO_2} + * \mathrm{H} + * \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[147, 387, 457, 404]]<|/det|> +(6) Hydrogen atoms desorption to \(\mathrm{H_2}\) : + +<|ref|>equation<|/ref|><|det|>[[275, 413, 720, 443]]<|/det|> +\[* 2\mathrm{H} \xrightarrow{k_5} \mathrm{H_2} + 2 * \quad (6)\] + +<|ref|>text<|/ref|><|det|>[[147, 451, 850, 497]]<|/det|> +Assume that all steps except the RDS are in equilibrium, and the coverage \((\theta)\) is determined by the equilibrium constant. + +<|ref|>equation<|/ref|><|det|>[[305, 503, 820, 541]]<|/det|> +\[k_{1} = \frac{\theta_{CH_{3}O}\cdot\theta_{H}}{P_{CH_{3}OH}\cdot\theta_{*}^{2}} \quad (7)\] + +<|ref|>equation<|/ref|><|det|>[[305, 544, 821, 574]]<|/det|> +\[k_{2} = \frac{\theta_{OH}\cdot\theta_{H}}{P_{H_{2}O}\cdot\theta_{*}} \quad (9)\] + +<|ref|>equation<|/ref|><|det|>[[305, 577, 821, 615]]<|/det|> +\[k_{5} = \frac{P_{H_{2}}\cdot\theta_{*}^{2}}{\theta_{H}^{2}} \quad (11)\] + +<|ref|>text<|/ref|><|det|>[[147, 619, 488, 636]]<|/det|> +Substitute equation (12) into equation (8): + +<|ref|>equation<|/ref|><|det|>[[305, 640, 702, 678]]<|/det|> +\[\theta_{CH_3O} = k_1 \cdot \sqrt{\frac{k_5}{P_{H_2}}} \cdot P_{CH_3OH} \cdot \theta_* \quad (13)\] + +<|ref|>text<|/ref|><|det|>[[147, 683, 498, 700]]<|/det|> +Substitute equation (12) into equation (10): + +<|ref|>equation<|/ref|><|det|>[[305, 706, 702, 742]]<|/det|> +\[\theta_{OH} = k_2 \cdot \sqrt{\frac{k_5}{P_{H_2}}} \cdot P_{H_2O} \cdot \theta_* \quad (14)\] + +<|ref|>text<|/ref|><|det|>[[147, 747, 850, 792]]<|/det|> +The intermediate product coverage is assumed to be negligible \((\theta_{CH_2O} \approx 0, \theta_{\mathrm{HCOO}} \approx 0)\) . + +<|ref|>text<|/ref|><|det|>[[147, 803, 421, 820]]<|/det|> +Conservation of total active sites: + +<|ref|>equation<|/ref|><|det|>[[270, 833, 727, 853]]<|/det|> +\[\theta_{*} + \theta_{H} + \theta_{CH_{3}O} + \theta_{OH} = 1 \quad (15)\] + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[269, 85, 725, 135]]<|/det|> +\[\theta_{*} = \frac{1}{1 + \sqrt{\frac{P_{H_{2}}}{k_{5}} + k_{1}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{CH_{3}OH} + k_{2}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{H_{2}O}}} \quad (16)\] + +<|ref|>text<|/ref|><|det|>[[147, 145, 196, 161]]<|/det|> +RDS: + +<|ref|>equation<|/ref|><|det|>[[366, 177, 727, 196]]<|/det|> +\[r = k\cdot \theta_{CH_{3}O}\cdot \theta_{*} \quad (17)\] + +<|ref|>equation<|/ref|><|det|>[[264, 210, 727, 270]]<|/det|> +\[r = \frac{k k_{1}\sqrt{k_{5}P_{CH_{3}OH}}}{\sqrt{P_{H_{2}}}\left(1 + \sqrt{\frac{P_{H_{2}}}{k_{5}} + k_{1}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{CH_{3}OH} + k_{2}}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{H_{2}O}}}\right)^{2}} \quad (18)\] + +<|ref|>text<|/ref|><|det|>[[147, 280, 732, 315]]<|/det|> +At low partial pressure of methanol \((k_{1}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{CH_{3}OH}}\ll 1,P_{CH_{3}OH}\to 0)\) : + +<|ref|>equation<|/ref|><|det|>[[350, 323, 650, 344]]<|/det|> +\[r\propto P_{CH_{3}OH}\left(\text{first order reaction}\right)\] + +<|ref|>text<|/ref|><|det|>[[147, 356, 854, 469]]<|/det|> +As experimental findings showed competitive adsorption between water and methanol, the water adsorption term \(k_{2}\sqrt{\frac{k_{5}}{P_{H_{2}}}P_{H_{2}O}}\) cannot be ignored. Considering the minor impact of \(\mathrm{H}_{2}\) partial pressure, the methanol reaction order becomes less than 1, approximating a first- order reaction. + +<|ref|>image<|/ref|><|det|>[[352, 471, 645, 639]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[252, 646, 742, 665]]<|/det|> +
Fig. 4e Reaction orders on CH3OH in the 0.9-3.8 kPa range.
+ +<|ref|>text<|/ref|><|det|>[[147, 674, 851, 748]]<|/det|> +The experimental reaction order of methanol was 0.72 at low partial pressure (0.9- 3.8 kPa), consistent with the rate equation. This indicates the reaction mechanism is formate decomposition. + +<|ref|>text<|/ref|><|det|>[[147, 811, 851, 886]]<|/det|> +7. I cannot quite follow why the overall reaction rate could be influenced by the electronic properties determined in figure 2, then I suggest the author move these results to the ESI. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 330]]<|/det|> +Response: Thank you for your comment. The impact of electronic properties on performance mainly stems from two aspects. Firstly, EELS analysis revealed that electrons from Cd atoms were transferred to Ti atoms at the interface (Fig. 2c). Low- temperature EPR further indicated that electrons from the distorted \(\mathrm{Ti^{4 + }}\) tetrahedra at the interface were readily transferred to Cd atoms (Fig. 3c). These inter- atomic electron transfers enhance the strong interactions at the interface, as evidenced by the \(\mathrm{H}_2\) - TPR results (Fig. S27). Consequently, the resulting interfacial Cd- O- Ti sites exhibited high stability, ensuring consistent performance during prolonged operation (Fig. 1c). + +<|ref|>text<|/ref|><|det|>[[147, 339, 852, 803]]<|/det|> +On the other hand, the impact of electronic properties on the adsorption and activation of reactants was significant. The asymmetric structure at the interface resulted in a coordination number and oxidation state of Cd that were intermediate between those of Cd/A and Cd/R catalysts (Fig. 2b). Compared to the surfaces of A and R, the charge distribution exhibited asymmetry (polar electronic domain) and had a higher electron density of states (Figs. 2e and S28), which was conducive to the adsorption and activation of reactants (a high electron density of states in polar electronic domains facilitates the polarization of reactant molecules). Additionally, previous studies have shown that phase interfaces facilitated electron transfer from rutile to anatase, thereby affecting the adsorption and activation of reactants (Nat. Mater., 2013, 12, 798- 801). Our CV results directly demonstrated that the interfacial Cd- O- Ti sites facilitated rapid electron transfer to the reactants (Fig. 2d), making them more favorable for the quick adsorption and activation of reactants. DFT calculations and \(\mathrm{CH}_3\mathrm{OH}\) - TPD further confirmed that the adsorption energy of \(\mathrm{CH}_3\mathrm{OH}\) and \(\mathrm{H}_2\mathrm{O}\) was lowest at the interfacial Cd- O- Ti sites and that their activation was easiest. DFT calculations also indicated that electronic properties significantly reduced the transition- state energy barrier, thereby determining its high activity. + +<|ref|>text<|/ref|><|det|>[[148, 811, 851, 913]]<|/det|> +Therefore, we propose that electronic properties are intrinsically linked to the reaction kinetics through a cascade mechanism involving asymmetric charge distribution, elevated charge density, and rapid charge transfer, which collectively facilitate reactant adsorption/activation and lower the reaction energy barrier, thereby + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 851, 163]]<|/det|> +enhancing catalytic activity and reaction rates. This mechanistic interpretation is supported by the detailed analyses in Figure 2 and the accompanying discussions in the main text. + +<|ref|>text<|/ref|><|det|>[[147, 230, 851, 284]]<|/det|> +8. I don't know why the HAADF-STEM images were given twice in Figure 1 and Figure 3. I hope the author could re-organize the results and make it easy to read. + +<|ref|>text<|/ref|><|det|>[[146, 319, 852, 812]]<|/det|> +Response: Thank you for your comments. HAADF- STEM images in Figure 1 are used to demonstrate the formation of Cd single- atom sites at the anatase (101)/rutile (110) phase interfaces in P25, highlighting the phase- interface confined anchoring configuration. Figure 3 systematically elucidates the driving forces for preferential Cd single- atom anchoring at P25 phase interfaces and the structure- performance relationship under the modulation of phase interface densities. Specifically, the atomic- resolution images in Figs. 3a- b reveal non- equilibrium phase interfaces of P25 characterized by irregular topography and disordered atomic configurations with abundant atomic- level defects, which thermodynamically favor Cd anchoring. Fig. 3g (left) demonstrates that after reducing P25 with \(\mathrm{H}_2\) for 4 hours, the phase- interface density is increased to \(10.1\mathrm{m}^2\mathrm{g}^{-1}\) . After loading Cd, more and brighter contrast bands are observed at the interface, indicating that more single atoms are positioned at the phase interface. This observation is consistent with the Cd contents detected by ICP after the reaction. This suggests that phase- interface density can increase the loading of single atoms at the interface, thereby potentially enhancing the \(\mathrm{H}_2\) production rate. However, when the reduction time was too long, such as 8 hours, obvious aggregation of particles occurred, possibly due to the destruction of the phase- interface structure, making it less favorable for single- atom formation. + +<|ref|>text<|/ref|><|det|>[[148, 821, 850, 867]]<|/det|> +To enhance conceptual clarity, we have revised the manuscript with improved textual organization to ensure logical progression of the key findings. + +<|ref|>title<|/ref|><|det|>[[148, 877, 336, 894]]<|/det|> +# Manuscript Revision: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 258, 105]]<|/det|> +Lines 160- 166: + +<|ref|>text<|/ref|><|det|>[[147, 118, 852, 275]]<|/det|> +"High- angle annular dark field scanning transmission electron microscopy (HAADF- STEM) further revealed atomically dispersed Cd atoms (bright contrast spots) on A (101) and R (110) facets of 5Cd/A and 5Cd/R (Supplementary Figs. 13 and 14). Notably, in the 5Cd/P25 catalyst, Cd single atoms were primarily anchored at the anatase (101)/rutile (110) phase interface, as evidenced by the distinct bright contrast band observed along the interfacial boundary in Fig. 1k and Supplementary Fig. 15." + +<|ref|>text<|/ref|><|det|>[[148, 285, 258, 300]]<|/det|> +Lines 279- 288: + +<|ref|>text<|/ref|><|det|>[[147, 312, 852, 524]]<|/det|> +"HAADF- STEM further elucidated the microstructure of the phase interface in pure P25. Lattice discontinuities and irregularities were clearly identified at the interface between the A (101) and R (110) facets, as shown by the gray line in Fig. 3a, indicating the presence of interface defects. Atomic- resolution characterization further revealed that subtle disorder in the interfacial atomic arrangement was confined to a narrow region at the interface, as highlighted by the white circle in Fig. 3b. These observations were likely due to surface atom rearrangements resulting from the lattice mismatch between the A (101) and R (110) facets, leading to the formation of abundant Ti defects at the incoherent phase interface (asymmetric structure)." + +<|ref|>text<|/ref|><|det|>[[148, 535, 258, 550]]<|/det|> +Lines 353- 367: + +<|ref|>text<|/ref|><|det|>[[147, 562, 852, 912]]<|/det|> +"Prolonged pretreatment was found to increase the interface density. Notably, the phase interface region appeared brighter after a 4- hour \(\mathrm{H}_2\) pretreatment, and the number of bright interface bands significantly increased in the HAADF- STEM images (Fig. 3g left and Supplementary Fig. 38). Atomic resolution analysis further revealed that the distinct bright interface bands correspond to dispersed Cd single atoms (Supplementary Fig. 38). Moreover, ICP- OES results showed that the Cd loss rate of the spent catalysts substantially decreased with the increase of the interface density (Fig. 3h). This trend suggested an increased number of single atoms stably anchored at the interface, thereby leading to a higher interface site density. A 4- hour \(\mathrm{H}_2\) pretreatment yielded the highest interface density \((10.1 \mathrm{m}^2 \mathrm{g}^{-1})\) and a remarkable \(\mathrm{H}_2\) production rate of \(292.9 \mathrm{mmol} \mathrm{g}_{\mathrm{cat}}^{-1} \mathrm{h}^{-1}\) (Fig. 3h), surpassing conventional MSR catalysts (Supplementary Table 9). An 8- hour pretreatment, however, resulted in the formation of small Cd particles (1- 2.5 nm) (Fig. 3g right), led to increased Cd loss after the reaction, and compromised catalytic performance. This was likely attributed to the disruption of the phase interface structure." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 856, 191]]<|/det|> +9. From the reaction coordinate, it looks that the hydrogen formation over Cd1/A(101) is quite difficult, while it is not quite the situation for Cd/P25. This might be the main difference among these samples. And it is not well discussed. This reviewer suggests the author to clarify that. + +<|ref|>text<|/ref|><|det|>[[147, 228, 853, 555]]<|/det|> +Response: Thank you for your comment. The formation of \(\mathrm{H}_2\) on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110) surfaces was thermodynamically unfavorable. Adsorption energy calculations revealed that critical intermediates such as \(* \mathrm{CH}_2 \mathrm{COOH}\) , \(* \mathrm{CH}_2 \mathrm{OH}\) , and \(* \mathrm{CHO}\) exhibit strong endothermic adsorption characteristics, with adsorption energies on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110) exceeding those on the \(\mathrm{Cd}_1 / \mathrm{A}\) (101)- R (110) model by significant margins (Table R1). Transition state analyses further demonstrate substantially increased activation energies of \(* \mathrm{H}_2 \mathrm{O}\) dissociation and \(* \mathrm{CH}_2 \mathrm{OH}\) formation on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110) compared to \(\mathrm{Cd}_1 / \mathrm{A}\) (101)- R (110). These combined thermodynamic and kinetic limitations collectively impeded \(\mathrm{H}_2\) generation on \(\mathrm{Cd}_1 / \mathrm{A}\) (101) and \(\mathrm{Cd}_1 / \mathrm{R}\) (110). The origin of these differences lies in the asymmetric interfacial structure of \(\mathrm{Cd}_1 / \mathrm{A}\) (101)- R (110), which exhibits enhanced electron density at the interface, facilitating intermediate stabilization and activation. + +<|ref|>table<|/ref|><|det|>[[140, 583, 858, 688]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[147, 565, 540, 580]]<|/det|> +Table R1 Adsorption energies of critical intermediates. + +
*CH2OOH*CHOOH*CHOO
Cd1/A (101)2.49 eV3.16 eV1.8 eV
Cd1/R (110)2.50 eV2.75 eV2.82 eV
Cd1/A (101)-R (110)0.96 eV0.60 eV0.19 eV
+ +<|ref|>text<|/ref|><|det|>[[147, 692, 853, 850]]<|/det|> +During our initial submission, we were constrained by word limit requirements and provided only a concise description of the DFT calculations, which limited our ability to elaborate on the underlying mechanistic distinctions. To address this, we have comprehensively revised the DFT section in the present work to systematically elucidate how structural differences among catalyst models influence activation energies and catalytic performance. The revised content is presented below: + +<|ref|>text<|/ref|><|det|>[[148, 860, 258, 874]]<|/det|> +Lines 444- 476: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 852, 357]]<|/det|> +(110) models provided complementary theoretical insights into the MSR reaction pathway. The computed energy landscape revealed distinct adsorption energy profiles: \*CHO exhibited significantly lower adsorption energies on Cd\(_1\)/A (101) (-1.45 eV) and Cd\(_1\)/R (110) (-1.18 eV) compared to the C\(_1\)/A (101)-R (110) model (4.1 eV) (Supplementary Fig. 43). This energy disparity implies preferential CO generation pathways on Cd\(_1\)/A (101) and Cd\(_1\)/R (110) surfaces. Conversely, critical intermediates such as \*CH\(_2\)O-\*OH, \*CHOOH and \*CHOO displayed substantially reduced adsorption energies on the Cd\(_1\)/A (101)-R (110) surface. These findings demonstrate that the formate decomposition pathway is thermodynamically more favorable on the Cd\(_1\)/A (101)-R (110) catalyst, attributable to its asymmetric coordination environment and enhanced charge density at the interface Cd single-atom sites. + +<|ref|>text<|/ref|><|det|>[[147, 365, 852, 887]]<|/det|> +The transition states of the formate decomposition pathway were further investigated (Fig. 4h and Supplementary Figs. 44- 46). Consistent with in situ DRIFTS observations, DFT calculations revealed that both the adsorption and the stepwise dehydrogenation of CH\(_3\)OH occurred at the Cd active site. The activation energy barriers for CH\(_3\)OH dehydrogenation (TS1: 0.64 eV) were significantly lower than those for \*CH\(_3\)O dehydrogenation (TS2: 0.87 eV) on the Cd\(_1\)/A (101)-R (110) surface. This clearly demonstrates that the C-H bond cleavage encounters higher kinetic resistance than O-H bond scission, aligning with the experimental KIE results. Following \*CH\(_3\)O dehydrogenation to \*CH\(_2\)O, H\(_2\)O adsorption and dissociation on adjacent Ti atoms generated \*H and \*OH species (TS3: 0.37 eV). Subsequent CH\(_2\)O/H recombination formed CH\(_2\)OOH (TS4: 0.43 eV), which further dehydrogenated to produce CO\(_2\) and H\(_2\). Although TS1 and TS2 barriers on Cd\(_1\)/A (101)-R (110) were modestly elevated relative to Cd1/A (101) (TS3/TS4: 1.07/0.60 eV) and Cd1/R (110) (TS3/TS4: 0.57/0.53 eV), the dissociation of H\(_2\)O (TS3) and CH\(_2\)OOH formation (TS4) exhibited significantly lower energy barriers in the phase interface model. These results demonstrated that the unique structural properties of the interfacial structure enhanced the dissociation and activation of H\(_2\)O, thereby facilitating the subsequent formation of formate and H\(_2\). Consequently, these observations rationalized the high activity and low CO selectivity of the 5Cd/P25 catalyst. Additionally, the highest activation energy barrier (TS2: 0.87 eV) confirmed \*CH\(_3\)O dehydrogenation as the RDS on the Cd\(_1\)/A (101)-R (110), consistent with previous kinetic analysis." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 91, 249, 106]]<|/det|> +Reviewer: 3 + +<|ref|>sub_title<|/ref|><|det|>[[149, 146, 356, 163]]<|/det|> +## Response to Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[148, 201, 245, 217]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[147, 227, 852, 480]]<|/det|> +This research presents a phase- interface- stabilized Cd/P25 single- atom catalyst, which demonstrates much higher MSR performance than other Cd/TiO₂ counterparts. The authors uncovered Cd- O- Ti phase interface site that dominates the high MSR activity and low CO selectivity. They also show that the densities of phase interface/sites can be regulated. Additionally, the fundamental mechanism of enhanced MSR performance on Cd/P25 SACs is clearly revealed by the combination of experimental and theoretical studies. This manuscript is well structured and demonstrated. I am willing to recommend its publication in Nature Communications. However, I would like to see the following concerns addressed before they can be further considered. + +<|ref|>text<|/ref|><|det|>[[148, 489, 275, 505]]<|/det|> +Main concerns: + +<|ref|>text<|/ref|><|det|>[[147, 518, 852, 655]]<|/det|> +1. In the Abstract, the statement "The formed Cd-O-Ti phase interface sites exhibit asymmetric geometric and electronic properties that achieve 100% methanol conversion, minimal CO selectivity (<0.1%), and sustained stability exceeding 150 hours" leads to misunderstanding. 100% methanol conversion and <0.1% CO selectivity are not achieved by interface sites solely. + +<|ref|>text<|/ref|><|det|>[[147, 691, 852, 793]]<|/det|> +Response: Thank you for pointing this out. You are correct; the formation of interfacial sites can achieve 100% methanol conversion and 0.13% CO selectivity, but the <0.1% CO selectivity requires further optimization of 3D printing to be achieved. To avoid any misunderstanding, we have removed this value from the abstract. + +<|ref|>sub_title<|/ref|><|det|>[[148, 803, 337, 820]]<|/det|> +## Manuscript Revision: + +<|ref|>text<|/ref|><|det|>[[148, 831, 237, 846]]<|/det|> +Lines 20- 22 + +<|ref|>text<|/ref|><|det|>[[147, 857, 850, 904]]<|/det|> +"The formed Cd-O-Ti phase interface sites exhibit asymmetric geometric and electronic properties that achieve 100% methanol conversion, a low CO concentration (<0.1 mol%) in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 172, 852, 284]]<|/det|> +2. In Supplementary Fig. 2, it is interesting and surprising that Cd catalysts exhibit similar MSR performance. This means that Cd catalysts after air calculation at \(500^{\circ}\mathrm{C}\) and \(H_{2}\) reduction at \(290^{\circ}\mathrm{C}\) probably have the same active site. It is important to identify the properties of the catalysts at two states. + +<|ref|>image<|/ref|><|det|>[[185, 323, 812, 678]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 687, 850, 742]]<|/det|> +
Fig. S21 Structural characterizations of the 5Cd/P25 catalysts after reduction at \(290^{\circ}\mathrm{C}\) . (a) XRD patterns. (b) XPS spectra of the Cd 3d orbitals. (c) Cd K-edge XANES spectra. (d) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of EXAFS spectra.
+ +<|ref|>text<|/ref|><|det|>[[147, 774, 854, 905]]<|/det|> +Response: We appreciate the insightful feedback. Taking the 5Cd/P25 catalyst as an example, we compared the differences between the catalyst calcined at \(500^{\circ}\mathrm{C}\) and reduced at \(290^{\circ}\mathrm{C}\) (Fig. S21). No significant differences were observed in the XRD patterns before and after reduction, and the peaks of Cd species were still not detected, indicating that the catalyst remained highly dispersed after the reduction. XPS + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 275]]<|/det|> +analysis indicated a \(0.1\mathrm{eV}\) shift in \(\mathrm{Cd3ds_2}\) binding energy following reduction. XANES spectral comparisons showed near- identical white line position, demonstrating unchanged oxidation states of isolated Cd atoms. Moreover, EXAFS spectra showed that only Cd- O bonds were present after reduction, indicating that the reduction at \(290^{\circ}\mathrm{C}\) did not affect the microstructure and electronic properties of the Cd single atoms. It could be known from \(\mathrm{H_2}\) - TPR results that the reduction of Cd species required a temperature exceeding \(400^{\circ}\mathrm{C}\) (Fig. S27). + +<|ref|>text<|/ref|><|det|>[[147, 339, 851, 413]]<|/det|> +3. In Fig. 1, it is recommended to only display Cd element distribution on \(\mathrm{TiO_2}\) -A and -R in EDS-mapping results, for a better comparison with Cd-P25. It is unclear to identify Cd dispersion (blue spots) now. + +<|ref|>text<|/ref|><|det|>[[147, 449, 852, 581]]<|/det|> +Response: We are very grateful for your excellent suggestion. We attempted to re- acquire the EDS- mapping. However, due to the limitations of the instrumental equipment and the sensitivity of the samples, the results were similar to the original ones. Therefore, for better comparison, only the distribution of the Cd element is presented for \(\mathrm{TiO_2}\) - A and \(\mathrm{TiO_2}\) - R. The specific changes are presented below: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[268, 90, 645, 768]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 769, 848, 803]]<|/det|> +
Fig. 1 i-k, HAADF-STEM and EDS mapping images for 5Cd/A (i), 5Cd/R (j), and 5Cd/P25 (k) catalysts.
+ +<|ref|>text<|/ref|><|det|>[[147, 864, 852, 909]]<|/det|> +4. A significant amount of CdTiO₃ exists in Cd/P25. What is the MSR performance of CdTiO₃/TiO₂? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 117, 852, 275]]<|/det|> +**Response:** We are very grateful for your suggestion. Since CdTiO₃ primarily formed on R, we prepared CdTiO₃ catalysts by increasing the Cd loading (20%) on R. As shown in Figure R9, the diffraction peaks of CdTiO₃ can be clearly detected in the XRD pattern. Performance studies revealed that the activity of CdTiO₃/TiO₂ was almost negligible, similar to that of pure CdTiO₃. Therefore, it can be concluded that CdTiO₃ is an inert phase. This result has been added to Table S4. + +<|ref|>image<|/ref|><|det|>[[293, 286, 706, 514]]<|/det|> + +<|ref|>image_caption<|/ref|><|det|>[[147, 528, 540, 541]]<|/det|> +
Figure R9 XRD patterns of CdTiO₃ and CdTiO₃/TiO₂.
+ +<|ref|>table_caption<|/ref|><|det|>[[147, 579, 618, 591]]<|/det|> +Table S4 Catalytic performance of homemade reference catalysts. + +<|ref|>table<|/ref|><|det|>[[101, 595, 870, 740]]<|/det|> + +
CatalystConversion (%)\(S_{CO2}\)\(S_{CO}\)\(S_{CH4}\)
CdTiO₃0000
CdTiO₃/TiO₂0.584.515.50
CdO0.101000
Cd0000
+ +<|ref|>text<|/ref|><|det|>[[147, 744, 769, 757]]<|/det|> +Reaction conditions: 290 °C, 0.1 MPa, a S/C ratio of 3/1, and a feed rate of 3 mL g-1 h-1 + +<|ref|>title<|/ref|><|det|>[[147, 796, 338, 809]]<|/det|> +# Manuscript Revision: + +<|ref|>text<|/ref|><|det|>[[147, 823, 850, 892]]<|/det|> +“Moreover, the synthesized CdTiO₃ and CdTiO₃/TiO₂ demonstrated negligible catalytic activity under identical reaction conditions, effectively ruling out CdTiO₃ as an active species (Supplementary Table 4).” + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 112, 850, 243]]<|/det|> +Synthesis of CdTiO3. \(\mathrm{Cd(NO_3)_2\cdot 4H_2O}\) (0.617 g) and P25 powder (0.160 g) were homogenously mixed through a rotary evaporation process at \(65^{\circ}\mathrm{C}\) . The mixture was then dried at \(80^{\circ}\mathrm{C}\) for \(12\mathrm{h}\) and ground thoroughly with an agate mortar. The resulting samples were calcined at \(650^{\circ}\mathrm{C}\) for \(8\mathrm{h}\) under static air, then immersed in \(200\mathrm{mL}\) of \(1\mathrm{mol / L}\) \(\mathrm{HNO_3}\) aqueous solution and stirred magnetically for \(3\mathrm{h}\) . Solid- liquid separation was achieved through six cycles of centrifugation (8,000 rpm, \(10\mathrm{min}\) each) with deionized water washing. The purified precipitate was dried at \(80^{\circ}\mathrm{C}\) for \(12\mathrm{h}\) to obtain phase- pure CdTiO3 powder. + +<|ref|>text<|/ref|><|det|>[[147, 261, 850, 335]]<|/det|> +Synthesis of CdTiO3/TiO2. \(1\mathrm{g}\) of rutile was dispersed in \(80\mathrm{mL}\) of deionized water, followed by the addition of \(0.08\mathrm{mmol / mL}\) \(\mathrm{Cd(NO_3)_2\cdot 4H_2O}\) . The mixture was stirred for 12 hours and then dried at \(60^{\circ}\mathrm{C}\) for 1 hour using a vacuum rotary evaporator. The product was subsequently calcined at \(700^{\circ}\mathrm{C}\) for 3 hours in static air. + +<|ref|>text<|/ref|><|det|>[[148, 394, 850, 441]]<|/det|> +5. In Supplementary Fig. 18, it is necessary to identify the chemical state of Cd for Cd/P25 after \(H_2\) reduction at \(400^{\circ}\mathrm{C}\) with XPS, rather than \(H_2\) -TPR. + +<|ref|>text<|/ref|><|det|>[[147, 478, 851, 580]]<|/det|> +Response: We are very grateful for your constructive suggestion. To identify the structure and chemical state of Cd species after \(H_2\) reduction at \(400^{\circ}\mathrm{C}\) (denoted as 5Cd/P25- 400H2), we have added the characterizations of XRD, HAADF- STEM, XAFS, XPS, and AES. + +<|ref|>text<|/ref|><|det|>[[147, 589, 852, 858]]<|/det|> +XRD analysis detected no metallic Cd diffraction peaks (Fig. S23a), suggesting the absence of crystalline Cd nanoparticles. Intriguingly, HAADF- STEM revealed the existence of sub- nanometer metallic Cd clusters (Fig. S23b), corroborated by EXAFS spectra showing prominent Cd- Cd coordination at \(\sim 2.8\mathrm{\AA}\) (Fig. S23c). XPS analysis indicated a \(0.4\mathrm{eV}\) downward shift in the Cd \(3\mathrm{d}_{5 / 2}\) binding energy for 5Cd/P25- 400H2 relative to 5Cd/P25, concurrent with the transformation of the Cd MNN Auger peak into a broadened feature characteristic of metallic clusters (Fig. S23d). These results strongly indicate that sub- nanometer Cd clusters or Cd nanoparticles are unfavorable to catalytic performance. The supplementary information has been added to the revised version. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[155, 88, 837, 395]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 401, 850, 473]]<|/det|> +
Fig. S23 Structural characterizations of the 5Cd/P25 catalysts after reduction at \(400^{\circ}\mathrm{C}\) (denoted as 5Cd/P25-400H2). (a) XRD patterns. (b and c) HAADF-STEM images of the 5Cd/P25-400H2. (d) Cd K-edge XANES spectra. (e) \(\mathrm{K}^{3}\) -weighted \(\chi\) (k) function of EXAFS spectra. (f) XPS and AES spectra.
+ +<|ref|>sub_title<|/ref|><|det|>[[148, 507, 336, 524]]<|/det|> +## Manuscript Revision: + +<|ref|>text<|/ref|><|det|>[[148, 535, 269, 551]]<|/det|> +Lines 207- 210 + +<|ref|>text<|/ref|><|det|>[[147, 562, 850, 636]]<|/det|> +“HAADF- STEM revealed the formation of sub- nanometer Cd clusters, corroborated by EXAFS spectra showing prominent Cd- Cd coordination at \(\sim 2.8 \mathrm{\AA}\) , suggesting that metallic Cd or clusters were detrimental to catalytic activity (Supplementary Fig. 23).” + +<|ref|>text<|/ref|><|det|>[[147, 700, 850, 746]]<|/det|> +6. In Supplementary Fig 24., it seems that 5Cd/A displays a stronger CH3OH adsorption than 5Cd/P25. + +<|ref|>text<|/ref|><|det|>[[147, 784, 851, 914]]<|/det|> +Response: Thank you for pointing this out. Due to the differences in catalysts, we initially did not standardize the y- axis range in order to make the weaker signal peaks more visible. This led to a misunderstanding of the data by the reviewer. Therefore, we have now standardized the y- axis range and added a scale for easy comparison. The results were consistent with the performance. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[128, 92, 890, 250]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 253, 852, 299]]<|/det|> +
Fig. S29 CH3OH-TPD profiles of three samples (CH3OH was decomposed with the increase of temperature).
+ +<|ref|>text<|/ref|><|det|>[[148, 364, 850, 411]]<|/det|> +7. DFT parts need to involve more discussion about the comparison with other models and highlight the advantage of Cd/A-R model. + +<|ref|>text<|/ref|><|det|>[[147, 447, 852, 662]]<|/det|> +Response: We sincerely appreciate your insightful comments and constructive suggestions, which significantly enhance the scientific rigor and clarity of our manuscript. In our initial submission, we were restricted by the word limit and provided a brief overview of the DFT calculations, preventing us from fully elaborating on the underlying mechanistic distinctions. To address this limitation, we have thoroughly revised the DFT section in the current manuscript to systematically investigate how structural differences between catalyst models dictate activation energy and catalytic performance. The revised analysis is presented below: + +<|ref|>text<|/ref|><|det|>[[148, 671, 258, 686]]<|/det|> +Lines 442- 472: + +<|ref|>text<|/ref|><|det|>[[147, 698, 852, 911]]<|/det|> +"DFT calculations based on the established Cd/A (101), Cd/R (110), and Cd/A (101)- R (110) models provided complementary theoretical insights into the MSR reaction pathway. The computed energy landscape revealed distinct adsorption energy profiles: \*CHO exhibited significantly lower adsorption energies on Cd/A (101) (- 1.45 eV) and Cd/R (110) (- 1.18 eV) compared to the C1/A (101)- R (110) model (4.1 eV) (Supplementary Fig. 43). This energy disparity implies preferential CO generation pathways on Cd/A (101) and Cd/R (110) surfaces. Conversely, critical intermediates such as \*CHO- \*OH, \*CHOH and \*CHOO displayed substantially reduced adsorption energies on the Cd/A (101)- R (110) surface. These findings + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 850, 163]]<|/det|> +demonstrate that the formate decomposition pathway is thermodynamically more favorable on the Cd1/A (101)-R (110) catalyst, attributable to its asymmetric coordination environment and enhanced charge density at the interface Cd single-atom sites. + +<|ref|>text<|/ref|><|det|>[[146, 172, 852, 692]]<|/det|> +The transition states of the formate decomposition pathway were further investigated (Fig. 4h and Supplementary Figs. 44- 46). Consistent with in situ DRIFTS observations, DFT calculations revealed that both the adsorption and the stepwise dehydrogenation of CH3OH occurred at the Cd active site. The activation energy barriers for CH3OH dehydrogenation (TS1: 0.64 eV) were significantly lower than those for \*CH3O dehydrogenation (TS2: 0.87 eV) on the Cd1/A (101)-R (110) surface. This clearly demonstrates that the C-H bond cleavage encounters higher kinetic resistance than O-H bond scission, aligning with the experimental KIE results. Following \*CH3O dehydrogenation to \*CH2O, H2O adsorption and dissociation on adjacent Ti atoms generated \*H and \*OH species (TS3: 0.37 eV). Subsequent CH2O/OH recombination formed CH2OOH (TS4: 0.43 eV), which further dehydrogenated to produce CO2 and H2. Although TS1 and TS2 barriers on Cd1/A (101)-R (110) were modestly elevated relative to Cd1/A (101) (TS3/TS4: 1.07/0.60 eV) and Cd1/R (110) (TS3/TS4: 0.57/0.53 eV), the dissociation of H2O (TS3) and CH2OOH formation (TS4) exhibited significantly lower energy barriers in the phase interface model. These results demonstrated that the unique structural properties of the interfacial structure enhanced the dissociation and activation of H2O, thereby facilitating the subsequent formation of formate and H2. Consequently, these observations rationalized the high activity and low CO selectivity of the 5Cd/P25 catalyst. Additionally, the highest activation energy barrier (TS2: 0.87 eV) confirmed \*CH3O dehydrogenation as the RDS on the Cd1/A (101)-R (110), consistent with previous kinetic analysis." + +<|ref|>text<|/ref|><|det|>[[146, 760, 852, 868]]<|/det|> +8. In conclusion, when elucidating catalysis mechanism of Cd-O-Ti interface site, the authors need to make it clearer. Why is substantially lowering the energy barriers for formate decomposition important for complete methanol conversion? It is not clear to readers. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 851, 165]]<|/det|> +Response: We sincerely appreciate your valuable suggestions. We have revised the conclusions to clarify the catalytic mechanism of the Cd- O- Ti interfacial sites and their structure- performance relationship, with specific revisions presented below: + +<|ref|>text<|/ref|><|det|>[[148, 174, 258, 189]]<|/det|> +Lines 505- 510: + +<|ref|>text<|/ref|><|det|>[[147, 201, 851, 330]]<|/det|> +"The resultant unique Cd- O- Ti interface sites, featuring asymmetric coordination geometry and elevated charge density, enable enhanced adsorption of reactants/intermediates. These structural attributes further reduce the energy barrier for both water dissociation and its activation within the formate decomposition pathway, thereby achieving complete methanol conversion with suppressed CO selectivity." + +<|ref|>text<|/ref|><|det|>[[147, 397, 852, 530]]<|/det|> +9. Some discussion in the manuscript is not accurate. For example, on Page 9, "This suggests that the Cd-O-Ti configuration is the most effective active site, particularly at phase interfaces" should be revised to "This suggests that the Cd-O-Ti configuration is a more efficient active site, particularly at phase interfaces". + +<|ref|>text<|/ref|><|det|>[[147, 570, 852, 672]]<|/det|> +Response: We sincerely appreciate the reviewers' insightful comments. In response to this constructive feedback, we have systematically revised ambiguous expressions throughout the manuscript to ensure terminological precision. Specific corrections are detailed below: + +<|ref|>text<|/ref|><|det|>[[148, 682, 273, 699]]<|/det|> +Lines 212- 214: + +<|ref|>text<|/ref|><|det|>[[147, 713, 851, 802]]<|/det|> +"This suggests that the Cd- O- Ti configuration is the most effective active site, particularly at phase interfaces" \(\rightarrow\) "This suggests that the Cd- O- Ti configuration is a more efficient active site, particularly at phase interfaces." + +<|ref|>text<|/ref|><|det|>[[148, 840, 273, 857]]<|/det|> +Lines 252- 255: + +<|ref|>text<|/ref|><|det|>[[147, 867, 850, 886]]<|/det|> +"In general, the distinctive and asymmetric geometric and electronic properties of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 92, 852, 237]]<|/det|> +Cd- O- Ti sites at the phase interface are instrumental in elucidating the superior catalytic performance observed in the 5Cd/P25 catalyst." → "In general, the distinctive and asymmetric geometric and electronic properties of the Cd- O- Ti sites at the phase interface are instrumental in elucidating the enhanced catalytic performance observed in the 5Cd/P25 catalyst." + +<|ref|>text<|/ref|><|det|>[[148, 247, 274, 264]]<|/det|> +Lines 361- 362: + +<|ref|>text<|/ref|><|det|>[[147, 274, 852, 350]]<|/det|> +"...remarkable \(\mathrm{H}_{2}\) production rate of \(292.9 \mathrm{mmol} \mathrm{g}_{\mathrm{cat}}^{- 1} \mathrm{h}^{- 1}\) (Fig. 3h), surpassing conventional MSR catalysts" → "...remarkable \(\mathrm{H}_{2}\) production rate of \(292.9 \mathrm{mmol} \mathrm{g}_{\mathrm{cat}}^{- 1} \mathrm{h}^{- 1}\) (Fig. 3h), surpassing conventional Cu- and Pt- based catalysts" + +<|ref|>text<|/ref|><|det|>[[148, 386, 273, 402]]<|/det|> +Lines 501- 502: + +<|ref|>text<|/ref|><|det|>[[147, 413, 852, 488]]<|/det|> +"The resultant unique Cd- O- Ti interface sites [...] enable efficient adsorption of reactants/intermediates." → "The resultant unique Cd- O- Ti interface sites [...] enable enhanced adsorption of reactants/intermediates." + +<|ref|>text<|/ref|><|det|>[[148, 525, 748, 544]]<|/det|> +10. The format of the font should be consistent throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 580, 850, 626]]<|/det|> +Response: We appreciate your valuable suggestions. Following your recommendations, we have revised the font format throughout the manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[349, 90, 648, 108]]<|/det|> +## Responses to reviewers' comments + +<|ref|>text<|/ref|><|det|>[[147, 117, 851, 191]]<|/det|> +Many thanks for the reviewers' insightful comments and questions, we have addressed the point- by- point responses below and believe the revised manuscript provides a more detailed, clear, and accurate description of the catalytic system. + +<|ref|>text<|/ref|><|det|>[[148, 238, 460, 255]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 292, 852, 423]]<|/det|> +Zhang et al. have revised the manuscript in response to the suggestions and questions raised during the review process. I agree that Cd could be a promising catalyst at the phase interface. However, I am still not fully convinced by the comparison with other metals. For a fair evaluation, Cd single atoms should be compared under similar conditions with single atoms of other metals. + +<|ref|>text<|/ref|><|det|>[[147, 459, 850, 535]]<|/det|> +Overall, the remaining comments have been addressed well. After adequately responding to this remaining concern, the manuscript can be considered suitable for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[147, 570, 849, 617]]<|/det|> +Response: We sincerely appreciate your insightful feedback, which has greatly strengthened our manuscript. + +<|ref|>image<|/ref|><|det|>[[175, 629, 827, 874]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[145, 882, 850, 900]]<|/det|> +
Figure R1 XANES and EXAFS spectra of 0.1Pt/P25 (a, b), 0.1Pd/P25 (c, d), and 0.1Cu/P25 (e, f)
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 215, 101]]<|/det|> +catalysts. + +<|ref|>text<|/ref|><|det|>[[147, 108, 854, 555]]<|/det|> +As previously stated, forming Pt/Pd/Cu single atoms on P25 is infeasible at high loadings. Therefore, to ensure fair comparison of the catalytic performance among these metals, the metal loading was reduced to \(0.1\%\) in accordance with the reported preparation strategy (J. Am. Chem. Soc.2019, 141, 17995- 17999) to achieve single- atom dispersion. As shown in Figure R1, EXAFS spectra confirm exclusive M- O coordination for Pt, Pd, and Cu, verifying their single- atom configurations. Under identical thermocatalytic conditions (290 °C, S/C molar ratio \(= 3 / 1\) , 0.1 MPa, N2 carrier gas flow \(= 30 \mathrm{mL min^{- 1}}\) , and liquid feed rate \(= 3 \mathrm{mL g^{- 1} h^{- 1}}\) ), methanol conversion remained below \(5\%\) for Pd and Cu single- atom catalysts, whereas Pt single atoms achieved the highest conversion (25.2%) (Figure R2). In terms of apparent TOF, although Pt SAC exhibited 2.3 times higher methanol activity than Cd SAC at equivalent loadings (0.1%), it demonstrated a higher CO selectivity (61.6%). In contrast, under optimal Cd loading (5%), methanol selectivity reached 100% with only 0.5% CO byproduct, while \(\mathrm{H}_2\) production rate surged to 97.7 mmol \(\mathrm{g^{- 1} h^{- 1}} - 5.0\) times greater than Pt (19.6 mmol \(\mathrm{g^{- 1} h^{- 1}}\) ). This might indicate that the synergistic effect between Cd and P25 is better than that of Pt/Pd/Cu single- atom systems. + +<|ref|>image<|/ref|><|det|>[[148, 562, 850, 738]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 745, 850, 797]]<|/det|> +
Figure R2 Comparative catalytic performance of various single atoms catalysts. (a) Methanol conversion, selectivity, and \(\mathrm{H}_2\) production rate. (b) Apparent TOF. Reaction conditions: \(290^{\circ}\mathrm{C}\) , S/C molar ratio \(= 3 / 1\) , 0.1 MPa, and liquid feed rate \(= 3 \mathrm{mL g^{- 1} h^{- 1}}\) .
+ +<|ref|>text<|/ref|><|det|>[[147, 820, 850, 896]]<|/det|> +We do not deny that high activity can be achieved with other single- atom metals, which may relate to selected supports or promoters. For example, Ma et al. reported single- atom catalyst systems including \(\mathrm{Pt_1 / a - MoC}\) (Nature 2017, 544, 80- 83), + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 275]]<|/det|> +\(\mathrm{Pt_1 / NiAl_2O_4}\) (J. Am. Chem. Soc. 2023, 145, 905- 918), and \(\mathrm{Ni_1 / \alpha - MoC}\) (J. Am. Chem. Soc. 2021, 143, 309- 317), where Pt or Ni single atoms form interfaces with MoC or \(\mathrm{NiAl_2O_4}\) that efficiently promote \(\mathrm{H_2O}\) dissociation, enhancing catalytic performance. Additionally, Li et al. (ACS Catal. 2014, 4, 3886- 3890) described \(\mathrm{Pt_1 / ZnO}\) systems exhibiting significant \(\mathrm{Pt_1 - ZnO}\) synergy that enhances activity. Qu et al. demonstrated \(\mathrm{Pt_1 / PN - CeO_2}\) configurations featuring frustrated Lewis pairs at \(\mathrm{Pt - CeO_2}\) interfaces to substantially boost \(\mathrm{H_2}\) production rates (Nat. Commun. 2022, 13, 5527). + +<|ref|>text<|/ref|><|det|>[[147, 283, 852, 636]]<|/det|> +This work focuses on elucidating why Cd single atoms preferentially locate at phase interfaces and outperform surface- adsorbed Cd SACs, while probing the reaction mechanism of this novel catalyst. Therefore, we do not emphasize comparative analysis or mechanistic interpretation of the performance of other metallic systems (whether supported on P25 or alternative carriers) configured as single- atom catalysts. Despite exhaustive synthesis attempts, Pt, Pd, and Cu cannot be anchored at P25 phase interfaces. We have initiated efforts to develop universal phase- interface SAC synthesis strategies in the next research, actively pursuing innovative pathways for diverse metals on P25 and other metal oxides. As investigated in our study, interfacial single- atom formation necessitates both matched electronegativity between active metal and titanium atoms and a substantial mean internal energy differential between surface and phase- interface sites, thus driving preferential metal anchoring at titanium vacancies within P25 phase interfaces. + +<|ref|>text<|/ref|><|det|>[[149, 700, 460, 718]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 755, 850, 831]]<|/det|> +The authors addressed most questions raised, even there is still some concerns on the formate reaction pathways. I feel that this work is not mainly focusing on reaction mechanism investigations. I decide to accept this paper without further modifications. + +<|ref|>text<|/ref|><|det|>[[148, 867, 850, 913]]<|/det|> +Response: Thank you for your valuable suggestions, which significantly improved our manuscript. Current characterization limitations make certain elementary + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 851, 164]]<|/det|> +steps/intermediates challenging to detect. Therefore, our subsequent research will continue to delve deeper into the study of the reaction mechanism and further refine the kinetic research, aiming to reveal the complete reaction pathway. + +<--- Page Split ---> diff --git a/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/images_list.json b/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..d1caeb2c20c0010ccdd274939277c8ee009d3632 --- /dev/null +++ b/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,132 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_22.jpg", + "caption": "Supplementary Figure 22. FAD autofluorescence in high magnification brain region of zebrafish embryo", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Figure 5 from Maltas et al (https://doi.org/10.1021/ac504386x): Figure 5. Spectral detection of NADH protein binding. Sequential additions of MDH, MDH, and LDH to solutions of NADH (left column) or NADPH (right column). In all plots, the color or symbol shape corresponds to times before protein is added (red, square), after adding MDH once (blue, circle), after adding MDH twice (orange, triangle), and after adding LDH (green, inverted triangle). (a) Integrated-gate spectra. The spectrum taken before protein addition was scaled to its maximum intensity, with all other spectra scaled to minimize least-squares differences. Fractional-difference spectra are calculated using the spectrum before protein addition as the reference spectrum. (b) Spectral phasor plots. Shifts due to MDH addition to the NADH solution (left) are collinear (best fit line is shown). The shift due to LDH addition is not collinear with MDH-induced shifts, evidencing that protein-bound NADH conformations are spectrally distinguishable. As a negative control, no shift is observed when proteins are added to the NADPH solution (right). (c) Spectrum shape", + "footnote": [], + "bbox": [ + [ + 378, + 297, + 617, + 572 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_15.jpg", + "caption": "Supplementary Figure 15. HyU unmixing on low concentration signals using customized independent spectra", + "footnote": [], + "bbox": [], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_16.jpg", + "caption": "Supplementary Figure 16. RMSE improvement for simulated fluorescent spectral combinations highlights increased HyU performance across multiple denoising filters.", + "footnote": [], + "bbox": [ + [ + 130, + 486, + 880, + 805 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_29.jpg", + "caption": "Supplementary Figure 29. Intrinsic fluorescent signatures in fresh mouse tissue", + "footnote": [], + "bbox": [], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_30.jpg", + "caption": "Supplementary Figure 30. Extrinsic fluorescent signatures in fixed mouse tissue", + "footnote": [], + "bbox": [ + [ + 174, + 88, + 812, + 512 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_23.jpg", + "caption": "Supplementary Figure 23. Phasor analysis on signal distortion in deep tissue", + "footnote": [], + "bbox": [ + [ + 177, + 245, + 707, + 696 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_28.jpg", + "caption": "Supplementary Figure 28:", + "footnote": [], + "bbox": [], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_19.jpg", + "caption": "Supplementary Figure 19. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels", + "footnote": [], + "bbox": [ + [ + 128, + 554, + 875, + 808 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_29.jpg", + "caption": "Supplementary Figure 29:", + "footnote": [], + "bbox": [], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_30.jpg", + "caption": "Supplementary Figure 30. Extrinsic fluorescent signatures in fixed mouse tissue", + "footnote": [], + "bbox": [ + [ + 172, + 125, + 812, + 551 + ] + ], + "page_idx": 23 + } +] \ No newline at end of file diff --git a/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..59f6b0536516d6c108db79a9d9f0028fd1c9bb17 --- /dev/null +++ b/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,1327 @@ + +# nature portfolio + +Peer Review File + +# HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence + +![](images/Supplementary_Figure_22.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to + +the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author: Overall significance): + +The paper by Chiang et al titled "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence" has a lot of details that are really attractive. This includes the possibility of multiplexing using a combination of Phasor and linear unmixing and potential for understanding the distribution pattern for multiple fluorophores, both endogenous and exogenous ones in the live system. The authors provide software based on this principle and detailed instruction to run the system. This is really attractive for the biological community as this does not require a specialized instrument and can use a hyperspectral detector with a linear array which is more commonly available to the researchers. + +However, there is a major flaw that concerns me the most. The authors use only one harmonics to do phasor transformation and then linear unmixing, as stated in their mathematical arguments. This should be fine up to three components. For two components a pixel which has contribution of those components, it's phasor position is along the line joining those two components. In case of three it will be inside the triangle created by the three individual components. This isn't true for four components or higher. In four components, the position of an image phasor point can be either contributed to all four components or just three - as it will always be within a triangle. This has been shown previously by Dr. Enrico Gratton's group (PMID: 32235070). In that case another harmonic needs to be calculated to identify and explain if there are three or four components. The examples and analysis provided in this paper only involve a single harmonic - and that makes it impossible to specify the difference between image phasor points in the middle of the phasor cloud with multiple species (Fig 5F). My main concern is that use of a single harmonic assume that all of the components are present in an image pixel whose phasor coordinate is within the pentagon with the vertices occupied by the five components. It may be a very small contribution based on the fractional intensity - but it is there. This may or may not be true depending on pixel size, presence of components and basically the type of the sample. This argument needs to be resolved as I feel this is a fundamental approach to phasor and its limitation when only one harmonic is calculated. + +Other comments and concerns follow below: + +1. The authors provide a spectra.txt files for the unmixing. How was that obtained. How to calculate and save the data from samples having only one fluorophores? +2. I did not see any mention of collagen fluorescence when excited at \(740~\mathrm{nm}\) . That should be a component in the autofluorescence category. +3. What happens to FAD? That can be excited at \(740~\mathrm{nm}\) (PMID: 11964266). +4. About Bound NADH - does the spectra change based on the proteins it binds to? +5. What is the distance of separation of the pure components in the phasor space that allow for successful linear unmixing. I presume at some point the S/N will make it difficult if the spectra of the components are too close. +6. What about when the linear unmixing won't work? For example, a case where the individual components lie in line in the phasor space. +7. Coming back to Q1. - Prior knowledge of the components - How are they calculated? Where are the coordinates stored? Are only the center of the phasor cloud used or the whole distribution? +8. I do like the point mentioned in lines 10-20 in page 2. Spectral imaging and deconvolution is absolutely necessary. +9. Lines 30-40, page 2 - missing references about the different noise. +10. The linear deconvolution of the phasor space involves fractional intensity and not the actual fraction - something that I found missing in the discussion. +11. How do 5 photons/spectra work with Poisson statistics and associated uncertainty? +12. Does the Elastin spectrum change on crosslinking in a tissue compared to the solution? +13. Td-Tomato (PMID 19127988) and mRuby (PMID 23459413) can be excited with a \(740~\mathrm{nm}\) two-photon excitation. I am curious how the authors did not observe that in Figure 6. +14. What determines how much spatial denoising needs to be used? Spatial denoising indeed doesn't affect the intensity image - but it does affect the phasor mapped image - something that hasn't been discussed at all. + +<--- Page Split ---> + +15. Figure 1 D-E – this is strictly not true. Once you transfer to phasor – the information remaining for the spectra is the FWHM and the peak/center – so how does the proper spectra being calculated in figure E? +16. The reduction of data from \(10^{A7}\) to \(10^{A4}\) . How much of that is related to spectral denoising and how much is related to the transformation to phasor? +17. Page 4 line 19 – after two-components – what happens with three/four and their possible combinations? +18. One of the uses of HyU is for low light level and long term imaging. What happens to the deconvolution if there is bleaching? This is a minor concern. +19. How to create the spectral libraries in the software provided by the authors (page 15, line 29-30)? +20. I do feel the references can be expanded for the phasor analysis of the multicomponent systems from other labs. + +Reviewer #1 (Remarks to the Author: Impact): + +The paper will influence the community - but the discrepancies need to be cleared and explained. + +Reviewer #1 (Remarks to the Author: Strength of the claims): + +The main concern is the linear additivity of phasor space and their implementation in this paper. Use of a single harmonic should not be enough for anything more than three components. + +Reviewer #1 (Remarks to the Author: Reproducibility): + +I do think the data is reproducible as the imaging is done using a commercial microscope and the authors provide an software to do so. There are details that is missing that need to be provided for the use. This includes calculation and storage of single components for the analysis. + +Reviewer #2 (Remarks to the Author: Overall significance): + +The manuscript of Hsiao Ju Chang et al (from the lab of Prof Cultrale) deals with dynamic (time- lapse) multiplexed imaging and offers a global- based solution for spectral unmixing of hyperspectral imaging data. Therefore, the authors improve the previously published algorithm HySP (Cultrale et al, Nat. Meth. 2017), which uses dimensionality reduction via the phasor approach (normalized discrete Fourier transformation of the hyperspectral 4D fluorescence data). They achieve this improvement by integrating in HySP a linear unmixing of the expected spectral signatures in the phase domain (HyU) - including both extrinsic signals (fluorescence proteins) and intrinsic signals (NAD(P)H, retinol, elastin, etc.). The dimensionality reduction of the phasor approach implies also a global analysis of the spectra (i.e. appreciates similarities of the spectra per voxel) and by that better deals with low signals. A thorough characterization of the laser, detector, read background noise and of their distribution type (Poisson, Gaussian, etc.) and implementation for denoising and additional reference- based preprocessing (SEER, Shi et al, Nat. Commun. 2020) improves not only the image quality but also the success of the hyperspectral unmixing of 8 or 9 emission (intrinsic and extrinsic) signals, at high computation speeds, as impressively demonstrated on simulated data and on time- lapse imaging data of multiple- reporter zebra fish larvae. While being of great interest for the live imaging community, in my opinion, the manuscript needs additional experimental, algorithmic and background (citation of previous work) information to unfold the full potential, as described in detail in the following. + +Reviewer #2 (Remarks to the Author: Impact): + +The relevance of the question/need for simultaneous spectrally multiplexed fluorescent microscopy to allow dynamic (time- lapse) multi- color imaging is tremendous, however, certainly going far beyond the field of developmental biology and zebra fish larvae imaging. This need has been previously recognized in the frame of + +<--- Page Split ---> + +intravital multi- photon imaging (not hyperspectral), with impact for cancer research (Entenberg et al, 2011), immunology and neurosciences/neuroimaging, just to mention a few examples. Specifically, there have been solutions proposed and demonstrated for dynamic in vivo fluorescence imaging, including unmixing algorithms apart of the state- of- the- art linear unmixing (Rakhymzhan et al, Sci Rep 2017), in which up to 8 extrinsic and intrinsic signals are simultaneously distinguished, while dealing with low SNRs of multi- photon microscopy still remained a challenge. Including this information in the introduction is key, in order to demonstrate the potential general relevance of the present work and to awake a real interest for a broad readership. + +In line with this, it is crucial to demonstrate the power of the presented algorithm for unmixing also intravital multi- photon imaging data in optically more challenging tissues and organisms, which need to deal with much lower signals and SNR values, especially due to massive scattering and wave- front distortions in mammal tissue. + +Referring to the algorithm itself and to its characterization, the evolution from hyperspectral multiplexed imaging using the phasor approach HySP (Cultrale et al, 2017, Nat Meth), enhanced by preprocessing the data to account for various experimental noise via SEER (2020, Nat Commun) and finally by applying linear unmixing in the hyperspectral phase space, bringing additional significant accuracy to the unmixing capacity of the data is currently not clear in the manuscript and needs to be elaborated in the introduction, to emphasize the novelty of the present work. + +Reviewer #2 (Remarks to the Author: Strength of the claims): + +A. Referring to the broad applicability of the algorithm and the interest for a large community: + +A.1. As previously mentioned, in order to prove the value of the approach presented in this manuscript, multiplexed time-lapse imaging in a mammal (adult mouse or rat or human) tissue is key and experimental data on this need to be added to the manuscript. I believe, one 4D (3D + time) imaging example showing 8-9 distinct emission signals would be absolutely convincing. + +B. Referring to the unmixing approach: + +B.1. In order to judge the added value of the integration of linear unmixing and of reference extrinsic and intrinsic spectral signatures on the performance of unmixing, a thorough comparison with the previously available HySP (Cultrale et al, 2017) needs to be provided, additionally to the comparison to state-of-the-art linear unmixing algorithms already included in the manuscript. + +B.2. A central advantage of the here presented approach is the capacity of dealing even with low signals, i.e. unmixing even low endogenous signals, such as NAD(P)H, even free and bound - having extremely similar emission spectra (one reason why their fluorescence lifetime has been used to resolve the two states). The authors show the improvement referring to number of photons per spectrum, however, in order to judge the true improvement brought by the algorithm for real imaging data (which includes background with diverse types of noise distributions), the unmixing quality needs to be related to the signal-to-noise (SNR) ratio per voxel. While mentioning SNR in the text, no values or comparison are provided in this sense - it is important to mention how the SNR as such (not only the number of photons per spectrum) impacts on the spectral resolution, i.e. how similar can be two spectra at a certain SNR to be able to still resolve them? + +B.3. A corner stone in acquiring better unmixing is the availability of appropriate reference spectral signatures. Whereas the current software provides the spectra necessary for the data shown in the manuscript and gives the opportunity for the users to identify signatures in their own data, the manuscript remains elusive of how the user can differentiate between a real spectral signature and different types of optical or electronical background and interferences - as well known from the use of the phasor approach in fluorescence lifetime imaging, a major challenge when dealing with experimental noisy imaging data in the frequency (phase) domain. The manuscript would benefit from including such a guide to validate the capacity for external use of the algorithm. + +<--- Page Split ---> + +B.4. Finally, fully agreeing with the authors that the number of detectors may be varied, depending on the imaged sample type and on the excitation strategy, in order to acquire an emission signal at all, an analysis of how the number of detectors (channels) impacts on the resolution between different signatures (spectra) is needed also for less than 32 detectors (4 to 6 channels being the reality in many labs due to truly low fluorescence signals in deep tissue, e.g. of mice or of humans). + +Reviewer #2 (Remarks to the Author: Reproducibility): + +The current version of the HySP platform was easy to use and the provided sample data delivered similar results as those shown in the manuscript. + +Reviewer #3 (Remarks to the Author: Overall significance): + +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. However, I found that there are some confusing points to be addressed clearly to publish this manuscript in Nature Portfolio. + +Comments: + +1) Hyperspectral phasor compresses spectral dimension by exploiting real and imaginary parts of Fourier transformation. Moreover, there were reports that hyperspectral phasor could be applied for multiplexed fluorescence imaging. If there are any advantages of combining phasor and spectral unmixing methods, please describe them clearly in the Introduction. + +2) If I understood correctly, numbers of photons (For instance, 5 photons per spectral in the last paragraph in Introduction) were calculated from the computer simulation. If so, this quantitative value is significantly affected by the noise levels used in the simulation. Therefore, it would be good to add these values were obtained from the simulation for clarity. + +3) The authors addressed that the HyU method is more computationally efficient than the linear spectral unmixing method. This is true as the spectral dimension was reduced in Hyperspectral Phasors and histogram binning. However, these spectral compression and denoising also require computational power. Does the proposed method is more efficient when the entire process is considered? + +4) For spectral unmixing, it seems to use the reference signals obtained from pure fluorophores. What happens if there are unknown fluorescence signals? Can the proposed method be applied for blind spectral separation? +5) Following the previous question, I wonder about the effect of light scattering on the accuracy of the proposed method. In fig4, the proposed method can be applied for volumetric imaging. I wonder there are consistent fluorescence signals over the depth of tissue. Fluorescence signals occurred in deep tissue regions experience more light scattering, which might occur in spectral distortions. + +Reviewer #3 (Remarks to the Author: Strength of the claims): + +This work demonstrates the superiority of the proposed method using computer simulation and experimental data. The authors clearly claim that the proposed method is more efficient and robust than conventional linear spectral unmixing methods. + +Reviewer #3 (Remarks to the Author: Reproducibility): + +The authors provide the code and data used in the manuscript. This allows other people to reproduce these + +<--- Page Split ---> + +results. And the dataset used in this work is appropriate for the purpose of the study. + +## Response to Reviewers' Comments + +We appreciated the positive response to our manuscript submission. We would like to thank the reviewers and editors for constructive comments and suggestions that helped improve the manuscript. We have addressed the comments, performed additional quantifications and experiments and revised the re- submission accordingly. + +## Reviewer #1 (Remarks to the Author: Overall significance): + +The paper by Chiang et al titled "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence" has a lot of details that are really attractive. This includes the possibility of multiplexing using a combination of Phasor and linear unmixing and potential for understanding the distribution pattern for multiple fluorophores, both endogenous and exogenous ones in the live system. The authors provide software based on this principle and detailed instruction to run the system. This is really attractive for the biological community as this does not require a specialized instrument and can use a hyperspectral detector with a linear array which is more commonly available to the researchers. + +However, there is a major flaw that concerns me the most. The authors use only one harmonic to do phasor transformation and then linear unmixing, as stated in their mathematical arguments. This should be fine up to three components. For two components a pixel which has contribution of those components, it's phasor position is along the line joining those two components. In case of three it will be inside the triangle created by the three individual components. This isn't true for four components or higher. In four components, the position of an image phasor point can be either contributed to all four components or just three - as it will always be within a triangle. This has been shown previously by Dr. Enrico Gratton's group (PMID: 32235070). In that case another harmonic needs to be calculated to identify and explain if there are three or four components. The examples and analysis provided in this paper only involve a single harmonic - and that makes it impossible to specify the difference between + +<--- Page Split ---> + +image phasor points in the middle of the phasor cloud with multiple species (Fig 5F). My main concern is that use of a single harmonic assume that all of the components are present in an image pixel whose phasor coordinate is within the pentagon with the vertices occupied by the five components. It may be a very small contribution based on the fractional intensity – but it is there. This may or may not be true depending on pixel size, presence of components and basically the type of the sample. This argument needs to be resolved as I feel this is a fundamental approach to phasor and its limitation when only one harmonic is calculated. + +<--- Page Split ---> + +ANSWER: We thank the reviewer for the insightful comments and for providing us an opportunity to clarify. In regard to the major concern, the use of a single harmonic, this hybrid approach uses the phasor as an aggregator of similar spectra while maintaining the wavelength dimension of the original data. + +Spectral similarity unmixing. The unmixing is performed over the spectral dimension (in this case 32 channels), by aggregating similar spectra of the original data, as explained in Supplementary Material "Hybrid Unmixing - Linear Unmixing" and further demonstrated in the pseudo- code in "HyU Algorithm". The spectra are not calculated from phasor, rather aggregated from the original spectral cube dataset. Our strategy is less phasor- esque than the traditional geometry based phasor approach (PMID: 32235070 and 22714302) where the approach uses the phasor geometry to unmix the components. The geometrical phasor approach only uses the coordinates G, S at a specific harmonic, omitting the wavelength dimension in the final unmixing process. As such, like the reviewer correctly states, it is a limiting strategy that makes it impossible to specify the difference between image phasor points in the middle of the phasor cloud with multiple species, requiring multiple harmonics. + +With HyU, we utilized the phasor as an encoder, to aggregate similar spectra, because of our familiarity with the approach, but, in principle, other encoding strategies could be utilized. The relative positions and geometry of phasor bin coordinates, from the unmixing algorithm perspective, do not directly matter, as the unmixing is performed with a 32 channel endmember over a 32 channel experimental spectrum ("Linear Unmixing" in Supp. Material). + +We improved the text in the last paragraph of the Introduction to clarify this aspect: + +Line 13 "HyU utilizes phasor processing as an encoder to aggregate similar spectra and applies unmixing algorithms, such as LU, on them to provide unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity." + +Information loss and noise. We are aware that the phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original "pure" data. This is evident in the scenario of very high quality signals, but in the case of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data makes phasor a valuable tool for fluorescence microscopy (FLIM/spectral alike); this point is reported by multiple groups using phasors (Gratton: https://www.pnas.org/doi/full/10.1073/pnas.1108161108, https://escholarship.org/content/qt5g279175/qt5g279175.pdf, Vicidomini: https://www.nature.com/articles/ncomms7701, Gerritsen: https://pubmed.ncbi.nlm.nih.gov/22714302/, Fraser: https://pubmed.ncbi.nlm.nih.gov/28068315/), and more recently nicely described in the work of Scipioni et al ( https://www.nature.com/articles/s41592-021-01108-4 ) "However, + +<--- Page Split ---> + +microscopy data are affected by a number of other detrimental factors, [...] which results in decreased signal- to- background ratio (SBR). [...] the phasor approach shows increased precision (Fig. 1f,i), decreased bias (Fig. 1e,h) and a three orders of magnitude lower execution time (Fig. 1g,j) with respect to the least mean square (LMS) fitting procedure". + +To support the validity of this hybrid unmixing approach, we have assembled a complex simulation matrix representing the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built on top of the complex simulation we designed (further described below in our answer to this reviewer's question 14), which is soon to be published in a separate manuscript. This simulation accounts for a multitude of real- world noises in experimental samples that are regularly imaged (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). The results of applying our approach on an array of simulations under different conditions of SNR, number of filters applied, in comparison to standard Linear Unmixing are now reported in Supplementary Figures 16, 17, 18, and 19. We further describe how multiple components are affected by our hybrid unmixing approach in our answer to question 17 for this reviewer. + +Other comments and concerns follow below: + +1. The authors provide a spectra.txt files for the unmixing. How was that obtained. How to calculate and save the data from samples having only one fluorophores? + +ANSWER: The "Independent Spectral Signatures" subsection of the Image analysis section of the supplementary text now provides an expanded description on this topic. Briefly, we obtain spectra from samples or pure solutions and validate with spectra reported in literature. The edited section "Independent Spectral Signatures" now states: + +Independent spectral fingerprints can be obtained through samples, solutions, literatures, or spectral viewer websites (Thermo fisher, BD spectral viewer, Spectra analyzer). Fluorescent signals used in this paper were obtained by imaging single labeled samples in areas morphologically and physiologically known to express the specific fluorescence, see Supplementary Figure 21. For each dataset a phasor plot was computed. The 32- channel spectral fingerprint was extracted from the phasor- bin at the counts- weighted average position of the phasor cluster. Those fingerprints were compared with literature fingerprints and manually corrected to reduce noise. Further descriptions for how to identify new components can be found in Supplementary Note 1 and Supplementary Figure 11, 27. + +To further clarify, we have added a Supplementary Figure 27 that shows a step- by- step example on how to obtain single spectral endmember from samples using the attached software: + +<--- Page Split ---> +![](images/Figure_5.jpg) + + +Supplementary Figure 27. Endmember Spectrum selection process + +(A) Phasor map shows the spectral distribution of the data for a single fluorescent labelled sample, in this case an 18 hpf transgenic Tg(ubiq:lyn-tdTomato) zebrafish. (B) The average spectrum corresponding to a phasor bin selection (red point in A) can be visualized using our software, which plots (C) the corresponding average spectrum with relative (top) and absolute (bottom) intensity. The save button allows exporting of spectral data as a txt file that can be re-loaded for unmixing other data. (D) Unmixing result. More step-by-step information is available in the README file associated with the software in this publication. + +We then expanded Supplementary Note 1 to further clarify: + +In our experience, obtaining fluorescence spectra from experimental samples has some advantages compared to utilizing spectra from an existing library, as they account for a multitude of experimental and instrumental settings. Imaging settings such as different types of lenses or optical filters (Sup. Figure 4, C and D) together with factors within the microenvironment of samples, such as pH or temperature have the potential to alter the fluorescence spectral emissions15. In the presence of unexpected fluorescent signals, spectra can also be selected and visualized directly from the phasor. Phasors facilitate the identification of unexpected independent components and their distinction from the multiple system noises. A noise- free spectrum will appear as a single point on the phasor plot, while a spectrum affected by instrument and electronic noises will mainly appear as a gaussian distribution, centered on the original spectral signal8. Conversely, a randomized noise across the multiple spectral channels will not produce a clustered aggregate of spectra on the phasor. A constant spectral noise, with a distinct spectrum (e.g. a constant light leakage into the system), would produce a distinct phasor cluster and could be selected for unmixing. The phasor plot representation is a 2D- histogram and provides insights into the frequency of + +<--- Page Split ---> + +occurrence for these signals. These unexpected independent components in samples often appear as "tails" on the phasor distributions (Sup. Figure 11, C). In our HyU graphical interface, clicking on the phasor visualizes the spectra within a small area (9x9 bins by default, with size adjustable from the interface) of the phasor histogram (Figure 1 D). + +Pre- identified phasor locations can be displayed in the software; we have also recreated their positions here in Supplementary Figure 21: + +![](images/Supplementary_Figure_15.jpg) + + +Supplementary Figure 21. Pre- identified positions for common fluorophores on the phasor map + +(A) Pre-identified extrinsic label positions (g,s) are denoted on the phasor plot for the first harmonic and (B) second harmonic. (C) Intrinsic label locations are further added on the phasor plot for the first harmonic and (D) second harmonic. Second harmonic generally covers a larger portion of the phasor space compared to the first harmonic. However, in the case of intrinsic signals, the locations of the pure autofluorescence spectra are on average more separated when utilizing the first harmonic. Details on the source of the pure spectra for these locations are reported in Methods – Independent Spectral Signatures. + +We have compiled a database of 32- channel spectra which have been gathered from literature, retrieved from commercially available resources (spectral viewer for fluorophores such as Alexas), and measured from both pure solutions and fusion proteins with our confocal + +<--- Page Split ---> + +microscopes. The spectra.txt files are organized as space delimited files with columns denoting independent spectral signature and rows denoting the channel. A spectra.txt file containing a single column (and so, the spectra for a single fluorophore) can be utilized as shown in the demo for single fluorophore samples (Supplementary Figure 27); this would maximize the contribution of that single spectrum. Exploration of the phasor plot can provide visual indication of unexpected contributing spectral endmembers. Such spectra can be included as a component, as we denoted in Supplementary Note 1. Further instructions on how to build/format and utilize the spectra.txt file have been added to the README.docx. + +Step 2 of README.docx: + +\* spectra.txt is a text file with the input spectra needed for unmixing with HyU. The file describes a 2D numpy array outputted using numpy's savetxt function. The file is formatted as a space delimited text file with the rows denoting the channels and the columns denoting the independent spectral signatures. Each row must have the same number of entries, and the values in each entry should be formatted as either integers, floats, or floats in scientific notation (#e±#). The values for the channels of each spectra represent the values corresponding to each spectral bin of uniform size within the detection wavelength range. The spectra.txt file linked in this README serves as an example for this formatting and contains 5 spectra of 32 channels, respectively mko2, tdtomato, mruby, citrine, and an unknown spectral signature chosen for HyU_demo- 02- fishtail.lsm. + +2. I did not see any mention of collagen fluorescence when excited at 740 nm. That should be a component in the autofluorescence category. + +ANSWER: We thank the reviewer for the insight. From the analysis of our experimental data, we do not detect measurable collagen signals with our imaging conditions, in the context of the many other fluorescent signals in the sample. Multiple references in literature (PMC4337962 / PMID: 22402635, PMC123202 / PMID: 12177437, PMC4337962 / PMID: 22402635) report 2- photon fluorescence of collagen to be very low at 740 nm and suggest instead the use of Second Harmonic Generation (SHG). At 2- photon 740 nm, the SHG detection would be at around 375 nm, outside of our detection range. + +3. What happens to FAD? That can be excited at 740 nm (PMID: 11964266). + +ANSWER: The reviewer is correct that FAD can be excited at 740 nm. However, for our imaging conditions, we used low 2P excitation (3% power, 9 mW) at relatively low magnification (pixel size 0.259x0.259\~1.38x1.38μm), and therefore, FAD was not sufficiently contributing to the autofluorescence in the datasets shown in the manuscript. We believe the reason to be related to three main factors: + +<--- Page Split ---> + +First: According to Huang et al. (Huang et al., 2002 / PMC1302068 / PMID: 11964266), the lower concentration of FAD compared to NADH is known to create a "shadowing" effect of FAD in autofluorescent imaging experiments "because of the predominantly 2P- NAD(P)H fluorescence excited at 750 nm due to its much higher cellular concentration (Guezennec et al., 1991; Kunz and Gellerich, 1993" leading to the use of 890- 900nm excitation for exciting FAD to eliminate the contribution of NADH (Stringari et al, 2011; Skala et al, 2007) + +Second: the magnification level in most of our data is relatively low, with pixel size \(0.259 \times 1.38 \mu m\) , contributing to an apparent reduction of the relative concentration of FAD with respect to NADH. Third: the 2P excitation used here is intentionally maintained at a considerably low power (3- 4% which corresponds to 9- 12mW) to minimize the inevitable photobleaching of the autofluorescent molecules and photodamage of the sample. This, combined with the lower magnification level, produces a low wattage/ \(\mathrm{cm}^2\) that further reduces the amount of signal emitted by the low- concentrated FAD to levels we cannot detect. Our estimate of power density for the sample in Figure 5 and Figure 6 are approximately \(4.7 \times 10^{- 6} \mathrm{mW / mm}^2\) compared to the zoomed- in sample in Supplementary Figure 22 that was \(1.4 \times 10^{- 3} \mathrm{mW / mm}^2\) . + +To further confirm, we performed imaging of a wildtype zebrafish hindbrain, at least 11 times higher magnification (pixel size \(= 0.078 \times 0.078 \mu m\) ) and a slightly lower laser power at \(2.8\%\) ; at which point, we were able to observe FAD. Under these imaging conditions, the amount of 2P power deployed on the sample was 10- fold higher than the images shown in the manuscript. This is in agreement with other published works (https://www.pnas.org/content/104/49/19494. long). We summarized the results in Supplementary Figure 22: + +![](images/Supplementary_Figure_16.jpg) + +
Supplementary Figure 22. FAD autofluorescence in high magnification brain region of zebrafish embryo
+ +<--- Page Split ---> + +(A) Phasor analysis reveals a distinct autofluorescence spectral component (magenta dot) when utilizing 740 nm 2-photon excitation to image a 22 hpf wild type zebrafish brain with high magnification (pixel size = 0.078x0.078μm) and high power (Table S1). (B) The corresponding emission spectra from the phasor selections in A. The spectrum corresponding to the magenta phasor selection in A closely matches the spectral signal of FAD obtained from in vitro solutions (Methods – Independent Spectral Signatures) and accounting for local environment changes14. (C) FAD unmixing channel highlights the FAD cluster in the head region of zebrafish. (D) Composite image rendering of the unmixing results for the intrinsic signals: NADH bound, NADH free, Retinoid, Retinoic Acid, FAD, and Elastin. + +We expanded Supplementary Note 2 to further describe these details: + +"A map of the phasor position for common autofluorescence from pure solutions is reported in Sup. Figure 21 B. Imaging autofluorescent data, with regard to cell metabolism, requires accounting for complex and dynamic changes of metabolic pathways which can occur in a broad range of times, from seconds to years. These autofluorescent signals are often weak in nature and do not rapidly replenish after photobleaching. In our work we utilize reduced laser power to avoid rapid autofluorescence spectral signal bleaching, as well to reduce photo- damage. Additional factors known to affect emission spectra include pH and temperature, pixel- wise concentration of the fluorophore, excitation power, developmental stage and region of the sample imaged. An example for the latter is reported in Sup. Figure 12, where signals in the sample present strong localized differences. One example of the effects of different 2- photon excitation power and different levels of pixel- wise concentration is reported in Figure 5, Figure 6. In these images, samples at similar developmental stages are imaged utilizing different pixel size (0.259 μm and 0.923 μm lateral resolutions) and laser power (4% and 3% @740nm 2- photon) resulting in laser power densities of \(\sim 4.7 \cdot 10^{- 6} \text{mW/mm}^2\) . This different laser power causes some lower- concentration intrinsic fluorophores to not be excited, in this case mRuby is visible in Figure 5 but not in Figure 6. In both of these images, FAD is not excited in measurable quantity, whereas in Sup. Figure 22, where the laser power density is \(1.4 \cdot 10^{- 3} \text{mW/mm}^2\), FAD contribution is measurable and unmixed. HyU is well posed for the analysis of intrinsically low autofluorescence owing to its ability to operate at low SNR. In Sup. Figure 12, we visualize unmixing of multiple autofluorescent signals based on spectra acquired from in vitro solutions. Sup. Figures 17, 19 present a simulated overview of the improvement of HyU over Linear Unmixing for autofluorescence data, as a function of number of labels, percentage of pixels containing mixed ratio of fluorophores, number of denoising filters applied and number of channels under different levels of Signal to Noise." + +<--- Page Split ---> + +ANSWER: We appreciate the explorative nature of this question with regard to the behavior of NADH. While we do not believe that this is in line with the purpose of this manuscript, a literature search shows interesting information about this subject. + +In figure 5 of Maltas et al ( https://doi.org/10.1021/ac504386x ), the authors report spectra and spectral phasors of NADH bound to LDH and MDH. Maltas et al conclude that "protein- bound NADH conformations are spectrally distinguishable" in solution when measured with 1024 channels at 2nm resolution. From their Figure 5, it appears the spectra have differences, although these differences are not resolvable with the 32 channel PMT utilized in commercial confocal microscopes. For simplicity, we are copying the figure below with its original caption (from Maltas et al ( https://doi.org/10.1021/ac504386x ) + +![](images/Supplementary_Figure_29.jpg) + +
Figure 5 from Maltas et al (https://doi.org/10.1021/ac504386x): Figure 5. Spectral detection of NADH protein binding. Sequential additions of MDH, MDH, and LDH to solutions of NADH (left column) or NADPH (right column). In all plots, the color or symbol shape corresponds to times before protein is added (red, square), after adding MDH once (blue, circle), after adding MDH twice (orange, triangle), and after adding LDH (green, inverted triangle). (a) Integrated-gate spectra. The spectrum taken before protein addition was scaled to its maximum intensity, with all other spectra scaled to minimize least-squares differences. Fractional-difference spectra are calculated using the spectrum before protein addition as the reference spectrum. (b) Spectral phasor plots. Shifts due to MDH addition to the NADH solution (left) are collinear (best fit line is shown). The shift due to LDH addition is not collinear with MDH-induced shifts, evidencing that protein-bound NADH conformations are spectrally distinguishable. As a negative control, no shift is observed when proteins are added to the NADPH solution (right). (c) Spectrum shape
+ +<--- Page Split ---> + +plots for the same data as in (b). For (b) and (c), analysis is performed over the first 512 pixels (400- 530 nm wavelength range). + +5. What is the distance of separation of the pure components in the phasor space that allow for successful linear unmixing. I presume at some point the S/N will make it difficult if the spectra of the components are too close. + +ANSWER: In general, a good rule would be for pure spectral endmembers to be separated by at least one phasor scatter error, between center of scatter (endmember 1) to center of scatter (endmember 2), based on the definition introduced in the previous work (PMID: 28068315). + +For our experimental conditions, the phasor scatter error is \(\sim 0.09\) ; hence, that would be a threshold distance between pure endmembers for a reliable linear unmixing. However, it should be noted that multiple factors contribute to this "minimal distance". + +1. Number of histogram bins utilized: in this work, we utilize the phasor as an encoder/aggregator for the spectra in the raw dataset. We do not use the geometry of phasor for unmixing. The phasor transformed data is discretized as a 2D histogram which is then used to sort and average the raw spectra in wavelength space. Both the number of bins used to discretize the phasor plot and the actual (G,S) locations of the pure components on the phasor plot will affect the quality of the unmixing result. + +2. Instrument noise: instruments are characterized by noise that differs in quantity across wavelengths. The parameter we estimate above can be used as reference for a Quasar Detector (Zeiss 710-780 series). A better sensor (e.g. the cooled version of Quasar in Zeiss 880-above series) will have lower noise than our current instrument. Any later generation emCCD or BSI-SCMOS camera based spectral detector would have considerably lower noise. + +6. What about when the linear unmixing won't work? For example, a case where the individual components lie in line in the phasor space. + +ANSWER: We believe that the reviewer is referring to the case where multiple independent components lie exactly on a line within the phasor plot such that multiple combinations of different fluorophores will occupy the exact same location on the phasor plot. + +Example of this scenario: a sample with 3 endmembers, A, B, C, where \(\mathrm{A} = \mathrm{B} / 2 + \mathrm{C} / 2\) . + +Mathematically, it is true that in this extreme case, the unmixing will have unpredictable results. The likely reason behind this unpredictability is that this scenario breaks one of the general constraints of Linear Mixing Models where endmember spectral signatures need to be linearly independent, making standard linear unmixing or fully constrained linear unmixing an ill posed problem. In practice, however, in such a case, one might argue if A is really an endmember or simply a combination of two spectra present in the sample. In our experience, we have found that it is highly unlikely for this condition to occur in spectral fluorescence of biomedical samples. As demonstrated in Supplementary Figure 16, the chances of the phasor locations of different fluorophores to line up exactly on the same line is very small. + +<--- Page Split ---> + +Though it may appear very close to a single line, there is sufficient non- linearity to create an offset that this case does not happen. It is much more likely for different combinations of many fluorophores \((>4)\) to somehow occupy the same phasor location. However, we have demonstrated in our reply to the first comment and in the numerous additional simulations (Supplemental Figure 16, 17, 18, 19) that noise affects the unmixing results much more than the encoding loss of the phasor method. + +7. Coming back to Q1. – Prior knowledge of the components – How are they calculated? Where are the coordinates stored? Are only the center of the phasor cloud used or the whole distribution? + +ANSWER: We believe our answer to Q1 addresses the majority of this question. We have expanded details on this subject in the Image analysis “Independent Spectral Signatures” subsection of the Image analysis section of the supplementary text and our expanded Supplementary Note 1 as well as added Supplementary Figures 21, 27. + +We utilized the 32- channel spectrum contained in the phasor- bin at the weighted average position of the phasor cluster following the method described in the updated “Independent Spectral Signatures” subsection: + +Independent spectral fingerprints can be obtained through samples, solutions, literatures, or spectral viewer websites (Thermo fisher, BD spectral viewer, Spectra analyzer). Fluorescent signals used in this paper were obtained by imaging single labelled samples in areas morphologically and physiologically known to express the specific fluorescence, see Supplementary Figure 21. For each dataset a phasor plot was computed. The 32- channel spectral fingerprint was extracted from the phasor- bin at the counts- weighted average position of the phasor cluster. Those fingerprints were compared with literature fingerprints and manually corrected to reduce noise. Further descriptions for how to identify new components can be found in Supplementary Note 1 and Supplementary Figure 11, 27. + +The phasor coordinates, obtained from the prior experiments, are saved/embedded in the software. New spectral signatures can be imported using a correctly formatted text file (see answer to Question 1 and README.docx). We added Supplementary Figure 21 to demonstrate phasor positions of common fluorophores (corresponding emission spectra can be found in Supplementary Figure 20). + +8. I do like the point mentioned in lines 10-20 in page 2. Spectral imaging and deconvolution is absolutely necessary. + +<--- Page Split ---> + +ANSWER: We thank the reviewer for this comment. + +9. Lines 30-40, page 2 – missing references about the different noise. + +ANSWER: We have included the following references to the main text and bibliography: + +22. Bass, M. Handbook of Optics, vol 3. Geometric Optics, General Principles Spherical Surfaces, 2nd ed., Optical Society of America, New York (1995). +23. Hamamatsu Photonics, K. K. P. T. H. PHOTOMULTIPLIER TUBES Basics and Applications FOURTH EDITION. (1994). +24. Pawley, J. B. Confocal and two-photon microscopy: Foundations, applications and advances. Microscopy Research and Technique 59, (2002). +25. Huang, F. et al. Video-rate nanoscopy using sCMOS camera-specific single-molecule localization algorithms. Nature Methods 10, (2013). + +10. The linear deconvolution of the phasor space involves fractional intensity and not the actual fraction – something that I found missing in the discussion. + +ANSWER: The reviewer is correct, however we are not utilizing or calculating fractional intensity on phasor. We utilize linear unmixing on the aggregated corresponding spectra in wavelength space. We believe the initial answer to this reviewer addresses this question in completeness. + +11. How do 5 photons/spectra work with Poisson statistics and associated uncertainty? + +ANSWER: Utilizing 5 photons per spectra results in very noisy data. As we demonstrate in the figures below, which represent both simulated single spectrum and simulated combined multiple spectra data, there is a considerable amount of obfuscation between the ideal spectral shape and the combined signal of the stochastically emitted spectra with the background noise. Averaging of the spectra using the phasor does provide a more spectrally similar array of values, but still results in a very noisy spectra, with deteriorated unmixing results. + +<--- Page Split ---> +![](images/Supplementary_Figure_30.jpg) + + +Simulation of tdTomato spectral fluorescent emission with max 5 photons. + +Simulations are performed starting from a reference spectrum for tdTomato (black dash line), acquired from a pure solution and matched with values reported in literature. (A) Spectra are shown for 3 randomly selected pixels (orange, blue, green lines) within the phasor histogram bin with maximum number of counts. (B) Average of the spectra (blue line) belonging to all pixels inside the phasor histogram bin with maximum number of pixel counts. In both plots, the reference spectrum scaled to the max of the simulated spectra is delineated with a black dashed line. + +![](images/Supplementary_Figure_23.jpg) + + +![](images/Supplementary_Figure_28.jpg) + + +Simulation of multiple spectral fluorescent emission with max 5 photons per spectra. Simulations are performed by combining four reference spectra (mKO2, Citrine, mRuby, tdTomato) at 5 photons per spectra. (A) Spectra are shown for 3 randomly selected pixels (orange, blue, green lines) within the phasor histogram bin with the maximum number of counts. (B) Average of the spectra belonging to all pixels inside the phasor histogram bin with + +<--- Page Split ---> + +maximum number of pixel counts. In both plots, the dashed lines represent the reference spectrum, scaled to the maximum value of the simulated spectra. + +12. Does the Elastin spectrum change on crosslinking in a tissue compared to the solution? + +ANSWER: This is an interesting question that we have not yet addressed. While we believe this to be outside the focus of this paper, we found answers in literature. Richards- Kortum et al (DOI: 10.1146/annurev.physchem.47.1.555) state that collagen and elastin fluorescence is associated with cross- links and report differences in fluorescence emission maxima between elastin in powdered form, in skin and in load bearing structures (https://doi.org/10.1016/0584- 8539(89)80031- 5). These differences were echoed by Eyre et al (10.1146/annurev.bi.53.070184.003441) and more recently by Croce et al (10.4081/ejh.2014.2461). + +13. Td-Tomato (PMID 19127988) and mRuby (PMID 23459413) can be excited with a 740 nm two-photon excitation. I am curious how the authors did not observe that in Figure 6. + +ANSWER: The reviewer is correct, both tdTomato and mRuby can be excited with 740 nm. Our main purpose in Figure 6 was to demonstrate the different extrinsic and intrinsic signal profiles when excited by either 1-photon or 2-photon. Since our focus for this sample is in the autofluorescence for two- photon 740 nm excitation, we purposely chose samples with reduced extrinsic fluorescence expression to prevent a suppressing effect that we experimentally found to interfere with measurement of autofluorescence signals. Although the fluorescence signals are still visible, we decided to not include the tdTomato and mRuby channels from the 740nm section of the figure owing to the large amount of signals to display. We have now added Supplementary Figure 15 with both signals from 740 nm two- photon excitation. + +Note that Figure 5 and Figure 6 data come from the same sample. tdTomato expression is observed in figure 5 because of the imaging setting. The imaging area in Figure 5 is \(2.59 \times 2.59 \mu m\) versus \(9.23 \times 9.23 \mu m\) in Figure 6. The image area in Figure 6 is 12 times larger for each pixel while using \(1\%\) lower laser power. Laser power was intentionally reduced to avoid photo- bleaching and photo- damage as well as to minimize disturbance of the system during longer time series imaging, with the expectation of reduced excitation of extrinsic fluorescent signals. We added this data in Supplementary Figure 15 and observed low intensity results showing a low expression level. + +Supplementary Figure 15: + +<--- Page Split ---> +![](images/Supplementary_Figure_19.jpg) + +
Supplementary Figure 15. HyU unmixing on low concentration signals using customized independent spectra
+ +Results from unmixing intrinsic and extrinsic signals of a quadra- transgenic zebrafish: Gt(cltca- citrine); Tg(ubiq:lyn- tdTomato; ubig:Lifeact- mRuby;fli1:mKO2) at a single timepoint of the dataset presented in Figure 6 provide further information and highlight the weak expression of some extrinsic signals in this dataset. (A) Input spectra for the intrinsic signatures were directly acquired by selection of the endmembers in the phasor plot. Input spectra for the extrinsic signatures were acquired from other datasets of samples expressing those signatures individually and excited at 740 nm with 2- photon, since these extrinsic signals are not strongly expressed within this dataset. (B) Renderings of unmixing results were automatically adjusted to show the best contrast. Unmixing can still be performed with spectra from weak input signatures. (C) Histogram counts of each unmixed independent spectral signature demonstrate the low signals of the extrinsic fluorescence signatures compared to the intrinsic ones. The median values of the mRuby and tdTomato channels are 57 and 77 Digital Levels respectively, considerably lower than those of the other signals. + +<--- Page Split ---> + +14. What determines how much spatial denoising needs to be used? Spatial denoising indeed doesn't affect the intensity image – but it does affect the phasor mapped image – something that hasn't been discussed at all. + +ANSWER: This question has been answered in our previous paper (Cutrale et.al., Nature Methods). It was determined that the spatial denoising plateaus after 5 applications. Still, we have added multiple simulations to better quantify the performance improvement of HyU with respect to LU for multiple denoising filters (Supplementary Figure 16 and 17) in terms of Relative Mean Squared Error (RMSE) (as defined in the Methods section, Mean Square Error). The new figures show a matrix of RMSE values for a number of fluorophores over the percentage of overlap. Each RMSE value is calculated as average from a simulation that has n fluorophores and a specific percentage of pixels containing randomized ratios of n fluorophores, where n is the number of fluorophores in the specific matrix position. For example, the RMSE value for 6 fluorophores at \(50\%\) overlap is calculated from a simulated dataset with 6 fluorophores where \(50\%\) of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. Further details on these newer simulations have been added to the Methods section Hyperspectral Fluorescence Image Simulation. + +## Hyperspectral Fluorescence Image Simulation + +The model simulates spectral fluorescent emission by generating a stochastic distribution of photons with profile equivalent to the pure reference spectra (as described in Sup. Note 1). The effect of photon starvation, commonly observed on microscopes, is synthetically obtained by manually reducing the number of photons in this stochastic distribution. Detection, Poisson and signal transfer noises are then added to produce 32- channel fluorescence emission spectra that closely resemble those acquired on microscopes. The simulations include accurate integration of dichroic mirrors and imaging settings. + +## Simulation Types: + +## Biologically comparable simulations + +To quantify the performance of HyU vs LU for microscopy data acquired experimentally, we generated synthetic data where each input spectra was organized with intensity distributions taken from experimental data of fluorescently labeled biological samples. We calibrated the analog (Digital Levels) to photon counting rate based on existing literature \(^{5,6}\) . Experimental data was discretized to photons to produce biologically relevant photon masks with distributions of signals highly resembling those of the samples. This provided intensities and ratios which closely resemble those acquired from a confocal microscope while allowing control over the effects of photon starvation. + +Spatially and spectrally overlapping simulations + +<--- Page Split ---> + +We also included simulations to quantify the performance of HyU vs LU with respect to the number of spectral combinations and of endmembers. The results are summarized in Supplementary Figures 16- 19 in the form of matrices of spectral overlap (0 to \(100\%\) , steps of \(10\%\) , X- axis) by number of endmembers (2 to 8 endmembers, Y- axis) representing the Relative Mean Squared Error (RMSE) (Supplementary Methods, Performance quantification). Each RMSE value reported in a matrix is the average of analysis of a 1024x1024 pixels image simulation with a spectral dimension of 32- channels matching the spectral range and bandwidth of the detectors in commercial confocal microscopes (LSM 780, Carl Zeiss). These simulations were created with artificial intensity distributions so that a simulation with X% overlap and n fluorophores would have X percentage of pixels with a randomized ratio of n input spectra. As an example, for a simulation with 6 fluorophores and 50% overlap, the simulated dataset would have 50% of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. This allowed us to investigate the effects of an increasing number of spectral combinations on the compressive nature of the phasor method for HyU. + +Supplementary Figure 16 is simulated utilizing only extrinsic fluorophores and Supplementary Figure 17 is simulated using a combination of intrinsic and extrinsic fluorophores: + +![](images/Supplementary_Figure_29.jpg) + +
Supplementary Figure 16. RMSE improvement for simulated fluorescent spectral combinations highlights increased HyU performance across multiple denoising filters.
+ +<--- Page Split ---> + +Twelve matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Different columns in the figure report the RMSE improvement matrices with different numbers of denoising filters (0x, 1x, 3x, 5x) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. In the absence of denoising filters, the improvement of HyU overall is less than \(8\%\) . Denoising filters improve RMSE by over \(80\%\) . Spectra utilized for this simulation are reported in Sup. Figure 20A. + +![](images/Supplementary_Figure_30.jpg) + + +Supplementary Figure 17. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights increased HyU performance across multiple denoising filters + +Twelve matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic and intrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel + +<--- Page Split ---> + +corresponds to a single fluorophore, while simulations with \(100\%\) overlap have, in every pixel, a randomized ratio of the n extrinsic and intrinsic fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Different columns in the figure report the RMSE improvement matrices with different numbers of denoising filters (0x, 1x, 3x, 5x) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. In the absence of denoising filters, the improvement of HyU overall is less than \(25\%\) . Denoising filters improve RMSE by over \(100\%\) . Spectra utilized for this simulation are reported in Sup. Figure 20B. + +15. Figure 1 D-E – this is strictly not true. Once you transfer to phasor – the information remaining for the spectra is the FWHM and the peak/center – so how does the proper spectra being calculated in figure E? + +ANSWER: The reviewer is correct that full spectra cannot be calculated from the first harmonic components without major loss of information. We are not calculating the spectra from the phasor; instead, we are preserving them in wavelength space from the original input data (32 channel) that was used to calculate the phasor components. The unmixing is performed over the spectral dimension (in this case, 32 channels) on aggregated similar spectra from the original data (in 32 channels), as explained in Supplementary Material “Hybrid Unmixing - Linear Unmixing” and further demonstrated in the pseudo-code in “HyU Algorithm”. + +We improved Figure 1 D-E, changing the connecting arrow to be “Phasor Aggregation”. + +![PLACEHOLDER_24_0] + + +<--- Page Split ---> + +16. The reduction of data from \(10^{A7}\) to \(10^{A4}\) . How much of that is related to spectral denoising and how much is related to the transformation to phasor? + +ANSWER: The majority of the data reduction occurs when transforming the raw data to the phasor. The initial transformation reduces the data by approximately two orders of magnitude, from \(10^{A7}\) to \(10^{A5}\) . Successive spectral denoising filters further reduce the data in much smaller increments, staying within \(10^{A4}\) elements. + +17. Page 4 line 19 – after two-components – what happens with three/four and their possible combinations? + +ANSWER: Line 19 is meant to provide an overview of the standard phasor approach, with a simple example of one of the advantages of phasors. HyU does not utilize the geometry of phasor for performing the unmixing, circumventing in most cases the challenges related to phasor ratiometric unmixing of more than 3 components. + +The unmixing is performed over the spectral dimension (in this case, 32 channels), by aggregating similar spectra of the original data, as explained in Supplementary Material "Hybrid Unmixing - Linear Unmixing" and further demonstrated in the pseudo- code in "HyU Algorithm". The spectra are not calculated from phasor; rather, they are aggregated from the original spectral cube dataset. HyU strategy is less phasor- esque than the traditional geometry based phasor approach (PMID: 32235070 and 22714302) where the approach uses the phasor geometry to unmix the components. The phasor geometrical approach only uses the coordinates G, S at a specific harmonic, omitting the wavelength dimension in the final unmixing process. As such, like the reviewer correctly states, it is a limiting strategy that makes it impossible to specify the difference between image phasor points in the middle of the phasor cloud with multiple species, requiring multiple harmonics. + +With HyU, we utilized the phasor as an encoder, to aggregate similar spectra, because of our familiarity with the approach, but, in principle, other encoding strategies could be utilized. The relative positions and geometry of phasor bin coordinates, from the unmixing algorithm perspective, do not directly matter, as the unmixing is performed with a 32 channel endmember over a 32 channel experimental spectrum ("Linear Unmixing" in Supp. Material). + +The phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original data. This is evident in the scenario of very strong signals (e.g. in hyperspectral reflectance), but in the case of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less impactful on the results compared to the noise of the fluorescent signals. This fundamental advantage of phasor in increasing SNR in noisy data makes phasor a valuable tool for fluorescence microscopy (FLIM/spectral alike); this point is reported by multiple groups using phasors: + +<--- Page Split ---> + +Gratton: https://www.pnas.org/doi/full/10.1073/pnas.1108161108, https://escholarship.org/content/qt5g279175/qt5g279175. pdf, + +Vicidomini: https://www.nature.com/articles/ncomms7701, Gerritsen: + +https://pubmed.ncbi.nlm.nih.gov/22714302/, + +Fraser: https://pubmed.ncbi.nlm.nih.gov/28068315/ + +and more recently nicely described in the work of Scipioni at al ( https://www.nature.com/articles/s41592- 021- 01108- 4) "However, microscopy data are affected by a number of other detrimental factors, [...] which results in decreased signal- to- background ratio (SBR). [...] the phasor approach shows increased precision (Fig. 1f,i), decreased bias (Fig. 1e,h) and a three orders of magnitude lower execution time (Fig. 1g,j) with respect to the least mean square (LMS) fitting procedure". + +We characterize the encoding loss of the Hybrid Unmixing approach owing to phasor and show that HyU still outperforms the standard LU. We performed simulations following the description provided in answer 14 to this reviewer, assembling a matrix of performance improvement with respect to Linear Unmixing by utilizing Relative Mean Squared Error (also described in Supplementary Methods) across the number of fluorophores and percentage of pixels with randomized overlap. This complex simulation matrix represents the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built from a complex simulation soon to be published in a separate manuscript that accounts for a multitude of real- world noises that occur in imaging of experimental samples (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). + +In Supplementary Figures 16- 19, we explore this matrix of fluorophores/overlap with the following parameters: + +- Number of denoising filters- Different values of SNR- Fluorescent or Autofluorescent labels- Number of channels detected + +Supplementary Figures 16 and 17 are reported above in question 14 of this reviewer. Supplementary Figures 18 and 19: + +<--- Page Split ---> +![PLACEHOLDER_27_0] + + +# Supplementary Figure 18. RMSE improvement for simulated fluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels + +Fifteen matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU with \(3x\) denoising filters. Columns in the figure represent RMSE improvement matrices across an increasingly binned number of spectral channels (32, 16, 8, 6, 4) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. When utilizing 32 spectral channels data, RMSE improvements reach above the previously reported \(80\%\) for highly overlapping fluorophores. Successively increasing the binning across the wavelength dimension (and therefore decreasing the number of spectral channels) shows a slow downward trend of the RMSE improvement until the 4 spectral channels matrices, where the RMSE improvement drops drastically down to below \(8\%\) , especially for more than 6 labels. Spectra utilized for this simulation are reported in Sup. Figure 20A. + +<--- Page Split ---> +![PLACEHOLDER_28_0] + + +# Supplementary Figure 19. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels + +Fifteen matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic and intrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n extrinsic and intrinsic fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Columns in the figure represent RMSE improvement matrices with 3x denoising filters across an increasingly binned number of spectral channels (32, 16, 8, 6, 4) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. When utilizing 32 spectral channel data, RMSE improvements reach up to the previously reported \(100\%\) for highly overlapping fluorophores. Successively increasing the binning across the wavelength dimension (and therefore decreasing the number of channels) shows a slow downward trend of the RMSE improvement until the 4 spectral channel matrices, where the RMSE improvement drops drastically down to below \(25\%\) , especially for more than 3 labels. Spectra utilized for this simulation are reported in Sup. Figure 20B. + +With regard to the simulations, the Supplementary Methods section "Hyperspectral Fluorescence Image Simulation" has been updated to include descriptions of the new simulations as reported in our reply to question 14 of this reviewer. + +<--- Page Split ---> + +With regard to the encoding, the Discussion in the main text was updated to state: + +Due to the initial computational overhead for encoding spectra in phasors, there is a 2- fold speed reduction for HyU in comparison to standard LU. However, this may be improved with further optimizations of the HyU implementation or by implementing different types of encoding. + +We added a new Supplementary Note 4 that details aspects of phasors and encoding loss. The note reads: + +Supplementary Note 4: Improvements of HyU over the standard phasor analysis + +Linearity of combinations is the general assumption for most of the spectral analysis algorithms in Hyperspectral Fluorescence Imaging (HFI). Each pixel is assumed to contain a linear combination of the independent spectral signatures, or endmembers, contained in the sample. This assumption requires knowledge, or identification, of the independent spectra within the sample. In standard linear unmixing algorithms, the extraction of relative amounts of spectra (ratios) is conducted on a pixel- by- pixel basis, at the expense of computational costs. Disrupted experimental signals, in the case of lower Signal to Noise Ratio (SNR) spectra, complicate the detection of spectral endmembers and reduce the accuracy of ratio determination. These standard unmixing algorithms, however, have the advantage of being unsupervised with the possibility of automating the analysis process. + +The phasor approach has become a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis \(^{13 - 15}\) . Phasors provide key advantages, including spectral compression, denoising, and computational reduction for both preprocessing \(^{3}\) and unmixing \(^{8,16,17}\) of HFI datasets. Phasor analysis overcomes the challenge of low SNR data analysis that limits standard unmixing algorithms, providing a multiplexing solution to a need. The phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original clean data \(^{18}\) . In the imaging of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data has made the phasor method a valuable tool for fluorescence microscopy, both for Lifetime and Spectral Fluorescence Microscopy. This point is reported by multiple groups using phasors \(^{18 - 21}\) and, more recently, nicely described in the work of Scipioni et al \(^{22}\) . Standard Phasor analysis \(^{23 - 25}\) is fully supervised and requires a manual selection of + +<--- Page Split ---> + +regions or points on a graphical representation of the transformed spectra, called the phasor plot. Each selection of a region in the phasor plot associates pixels containing similar spectra to the same fluorophore, forming an output channel that contains wavelength integral of intensities with unitary ratiometric value. This "winner takes all" approach is suitable when fluorophores for each single excitation light are spectrally overlapping and spatially disperse (Sup. Figure 24), but requires separate acquisition of different excitation wavelengths for demultiplexing spatially and spectrally overlapping fluorophores (Sup. Figure 25). + +HyU uses the phasor transform to group pixels with similar spectral shape within each phasor histogram bin. This approach maintains the advantage of compressing, denoising and simplifying identification of clean endmember fluorescent spectra. However, HyU improves on the robustness of the analysis. The denoised signals are maintained in a hybrid phasor and wavelength domain, and therefore can be unmixed with a multitude of standard unmixing algorithms (Sup. Figure 13), such as Linear Unmixing or Fully Constrained Least Squares. These standard unmixing approaches can operate without supervision and provide for each pixel the ratios for a set of spectral signals, overcoming some of the limitations of phasor, but generally do not perform well in experimental conditions with reduced and compromised signals, such as in fluorescence, and require extensive computational time for high spectral- count datasets. HyU provides wavelength- based denoised spectra that enable these standard algorithms to outperform their pixel- by- pixel typical application, both in quality of the results (Sup. Figures 16- 19), owing to cleaner and better defined fluorescent spectra in each phasor bin, and, generally, in speed, owing to the phasor dimensionality reduction. HyU performs well for single excitation light when fluorophores are spectrally overlapping both when they are spatially disperse or co- localized, providing a ratio for each independent spectrum currently unmixed. Our data suggests HyU has reasonable performance for up to 8 different fluorophores per dataset, for each single excitation wavelength. In an experiment with a carefully chosen palette of labels, where octuples of fluorophores can be excited by a single wavelength, with an instrument capable of spectral acquisition with 5 standard and sufficiently spectrally separated excitation wavelengths in 5 sequential acquisitions (one for each excitation light), HyU could, in principle, unmix 40 signals. This performance however decreases with the number of channels (Sup. Figures 18, 19) showing a small deterioration at 8 channels and limitations at 4. + +Figures 18, 19) showing a small deterioration at 8 channels and limitations at 4. + +18. One of the uses of HyU is for low light level and long term imaging. What happens to the deconvolution if there is bleaching? This is a minor concern. + +ANSWER: The effects of phasor denoising with respect to photobleaching have been characterized in our previous work ( https://www.nature.com/articles/s41467- 020- 14486- 8 ) in: + +<--- Page Split ---> + +- Supplementary Figure 26 (https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-020-14486-8/MediaObjects/41467_2020_14486_MOESM1_ESM.pdf) and +- Supplementary Movie 3 (https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-020-14486-8/MediaObjects/41467_2020_14486_MOESM6_ESM.mov) + +For simplicity, we copy paste Supplementary Figure 26 from Shi et al 2020: + +![PLACEHOLDER_31_0] + + +from Shi et al 2020: + +"Supplementary Figure 26. Visualization of photobleaching with SEER. Photo- bleaching experiments were performed on a 24 hpf zebrafish embryo Gt(cltca- citrine); Tg(fli1:mKO2); Tg(ubiq:memTdTomato), labeling clathrin, pan- endothelial and membrane respectively. The experiments were performed utilizing the "bleaching" modality in the Zeiss Zen 780 inverted confocal, where single z positions were acquired in lambda mode. Frames are acquired every 13.7 sec, with 5 intermediate bleaching frames (not acquired) at high laser power until image intensity reached 90% bleaching. The SEER RGB mask represents the values of colors associated to each pixel, independent from the intensity values. The map used here is Radial map in Center of Mass mode. In this modality the map will adjust its position on the shifting center of mass of the phasor clusters, visually compensating for the decrease in intensity. (a) In the initial frame the cltca- citrine is associated to a magenta color, membrane to cerulean, pan- endothelial is not in frame and background to yellow. (b) Frame 10 shows consistent colors with the initial bleaching; the colors are maintained (c) at frame 40 and (d) frame 70 where most of the signal has bleached and most colors have switched to yellow (here, background). (e) Final frame shows the 90% bleached sample. The Alpha Color rendering adds the information of intensity to the image visualization. Here we show for comparison (f) frame 1, (g) frame 10, (h) frame 40 and (i) frame 70. Scale bar 10um. (j) Average total intensity plot as a function of frame, calculated from the sum of 32 channels, shows evident bleaching in the sample. Further visualization is provided in Supplementary Movie 3 + +<--- Page Split ---> + +19. How to create the spectral libraries in the software provided by the authors (page 15, line 29-30)? + +ANSWER: We refer the reviewer to the answer to Q1, where we explain how to obtain the spectra from samples or literature and how to format them to fit the spectra.txt library in our example. Correspondingly, we updated the manuscript in the section "Independent Spectral Signatures" under Image analysis in Supplementary Information, added Supplementary Figures 21 and 27, and edited the README document. + +20. I do feel the references can be expanded for the phasor analysis of the multicomponent systems from other labs. + +ANSWER: We expanded the reference list with respect to phasor analysis, preprocessing hyperspectral data, and unmixing hyperspectral data by including the following: + +26. Digman, M. A., Caiolfa, V. R., Zamai, M. & Gratton, E. The Phasor Approach to Fluorescence Lifetime Imaging Analysis. Biophysical Journal 94, L14–L16 (2008). +27. Fereidouni, F., Bader, A. N., Colonna, A. & Gerritsen, H. C. Phasor analysis of multiphoton spectral images distinguishes autofluorescence components of in vivo human skin. Journal of Biophotonics 7, 589–596 (2014). +28. Scipioni, L., Rossetta, A., Tedeschi, G. & Gratton, E. Phasor S-FLIM: a new paradigm for fast and robust spectral fluorescence lifetime imaging. Nature Methods 18, 542–550 (2021). +29. Ranjit, S., Malacrida, L., Jameson, D. M. & Gratton, E. Fit-free analysis of fluorescence lifetime imaging data using the phasor approach. Nature Protocols 13, 1979–2004 (2018). +30. Shi, W. et al. Pre-processing visualization of hyperspectral fluorescent data with Spectrally Encoded Enhanced Representations. Nature Communications 11, 1–15 (2020). +31. Keshava, N. & Mustard, J. F. Spectral unmixing. IEEE Signal Processing Magazine 19, 44–57 (2002). +32. Dobigeon, N., Altmann, Y., Brun, N. & Moussaoui, S. Linear and Nonlinear Unmixing in Hyperspectral Imaging. in Data Handling in Science and Technology vol. 30 (2016). +33. Zeiss, C. & Online, M. Introduction to Spectral Imaging and Linear Unmixing. Imaging 1, 1–13 (2010). +34. Hedde, P. N., Cinco, R., Malacrida, L., Kamaid, A. & Gratton, E. 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International Journal of Molecular Sciences 14, (2013). + +15. Islam, M. S., Honma, M., Nakabayashi, T., Kinjo, M. & Ohta, N. pH dependence of the fluorescence lifetime of FAD in solution and in cells. International Journal of Molecular Sciences 14, (2013). + +16. Andrews, L. M., Jones, M. R., Digman, M. A. & Gratton, E. Spectral phasor analysis of Pyronin Y labeled RNA microenvironments in living cells. Biomedical Optics Express 4, (2013). + +17. Fereidouni, F., Bader, A. N. & Gerritsen, H. C. Spectral phasor analysis allows rapid and reliable unmixing of fluorescence microscopy spectral images. Optics Express 20, (2012). + +18. Cutrale, F. et al. Hyperspectral phasor analysis enables multiplexed 5D in vivo imaging. Nature Methods 14, (2017). + +19. Stringari, C. et al. Phasor approach to fluorescence lifetime microscopy distinguishes different metabolic states of germ cells in a live tissue. Proc Natl Acad Sci U S A 108, 13582-7 (2011). + +20. Lanzano, L. et al. Encoding and decoding spatio-temporal information for super-resolution microscopy. Nature Communications 6, (2015). + +21. Fereidouni, F., Bader, A. N. & Gerritsen, H. C. Spectral phasor analysis allows rapid and reliable unmixing of fluorescence microscopy spectral images. Opt Express 20, 12729-12741 (2012). + +22. Scipioni, L., Rossetta, A., Tedeschi, G. & Gratton, E. Phasor S-FLIM: a new paradigm for fast and robust spectral fluorescence lifetime imaging. Nature Methods 18, (2021). + +<--- Page Split ---> + +23. Malacrida, L., Ranjit, S., Jameson, D. M. & Gratton, E. The Phasor Plot: A Universal Circle to Advance Fluorescence Lifetime Analysis and Interpretation. Annual Review of Biophysics vol. 50 Preprint at https://doi.org/10.1146/annurev-biophys-062920-063631 (2021). +24. Ranjit, S., Malacrida, L., Jameson, D. M. & Gratton, E. Fit-free analysis of fluorescence lifetime imaging data using the phasor approach. Nature Protocols 13, 1979–2004 (2018). +25. Digman, M. A., Caiolfa, V. R., Zamai, M. & Gratton, E. The Phasor Approach to Fluorescence Lifetime Imaging Analysis. Biophysical Journal 94, L14–L16 (2008). + +Reviewer #1 (Remarks to the Author: Impact): + +The paper will influence the community - but the discrepancies need to be cleared and explained. + +ANSWER: We thank the reviewer for this comment and all the constructive criticism. We believe we addressed all of this reviewer's comments in the answers above and the edits in the manuscript considerably improved the quality of the work. + +Reviewer #1 (Remarks to the Author: Strength of the claims): + +The main concern is the linear additivity of phasor space and their implementation in this paper. Use of a single harmonic should not be enough for anything more than three components. + +ANSWER: We believe we addressed this reviewer's specific comment in the answer to question 17 above and in the introductory answer. + +Reviewer #1 (Remarks to the Author: Reproducibility): + +I do think the data is reproducible as the imaging is done using a commercial microscope and the authors provide an software to do so. There are details that is missing that need to be provided for the use. This includes calculation and storage of single components for the analysis. + +ANSWER: We thank the reviewer for helping us improve this aspect of the manuscript. We believe we addressed this specific comment in answers 1 and 19 above. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author: Overall significance): + +The manuscript of Hsiao Ju Chang et al (from the lab of Prof Cultrale) deals with dynamic (time- lapse) multiplexed imaging and offers a global- based solution for spectral unmixing of hyperspectral imaging data. Therefore, the authors improve the previously published algorithm HySP (Cultrale et al, Nat. Meth. 2017), which uses dimensionality reduction via the phasor approach (normalized discrete Fourier transformation of the hyperspectral 4D fluorescence data). They achieve this improvement by integrating in HySP a linear unmixing of the expected spectral signatures in the phase domain (HyU) - including both extrinsic signals (fluorescence proteins) and intrinsic signals (NAD(P)H, retinol, elastin, etc.). The dimensionality reduction of the phasor approach implies also a global analysis of the spectra (i.e. appreciates similarities of the spectra per voxel) and by that better deals with low signals. A thorough characterization of the laser, detector, read background noise and of their distribution type (Poisson, Gaussian, etc.) and implementation for denoising and additional reference- based preprocessing (SEER, Shi et al, Nat. Commun. 2020) improves not only the image quality but also the success of the hyperspectral unmixing of 8 or 9 emission (intrinsic and extrinsic) signals, at high computation speeds, as impressively demonstrated on simulated data and on time- lapse imaging data of multiple- reporter zebrafish larvae. + +While being of great interest for the live imaging community, in my opinion, the manuscript needs additional experimental, algorithmic and background (citation of previous work) information to unfold the full potential, as described in detail in the following. + +ANSWER: We thank the reviewer for the constructive comments and for providing us an opportunity to considerably improve this work. + +Reviewer #2 (Remarks to the Author: Impact): + +The relevance of the question/need for simultaneous spectrally multiplexed fluorescent microscopy to allow dynamic (time- lapse) multi- color imaging is tremendous, however, certainly going far beyond the field of developmental biology and zebrafish larvae imaging. This need has been previously recognized in the frame of intravital multi- photon imaging (not hyperspectral), with impact for cancer research (Entenberg et al, 2011), immunology and neurosciences/neuroimaging, just to mention a few examples. Specifically, there have been solutions proposed and demonstrated for dynamic in vivo fluorescence imaging, including unmixing algorithms apart of the state- of- the- art linear unmixing (Rakhymzhan et al, Sci Rep 2017), in which up to 8 extrinsic and intrinsic signals are simultaneously distinguished, while dealing with low SNRs of multi- photon microscopy still remained a challenge. Including this information in the introduction is key, in order to demonstrate the potential general relevance of the present work and to awake a real interest for a broad readership. + +ANSWER: This is a very good point. We have edited the introduction to broaden the impact of this work. The introduction now reads: + +<--- Page Split ---> + +Standard fluorescence microscopes collect multiple images sequentially, employing different excitation and detection bandpass filters for each label. Recently developed techniques allow for massive multiplexing by utilizing sequential labeling of fixed samples but are not suitable for in vivo imaging. \(^{12,13}\) Unfortunately, these approaches are ill- suited to separating overlapping fluorescence emission signals, and the narrow bandpass optical filters used to increase selectivity, decrease the photon efficiency of the imaging. (Figs. S1, S2) These limitations have restricted the number of imaged fluorophores per sample (usually 3- 4) and risks exposing the specimen to damaging levels of exciting light. This has been a significant obstacle for the dynamic imaging, preventing in vivo and intravital imaging from reaching its full potential, with broad impact on research, from developmental biology \(^{14}\) , cancer research \(^{15}\) and immunology \(^{2}\) to neuroimaging \(^{16}\) . + +Hyperspectral Fluorescent Imaging (HFI) potentially overcomes the limitations of overlapping emissions by expanding signal detection into the spectral domain. \(^{14}\) HFI captures a spectral profile from each pixel, resulting in a hyperspectral cube (x,y, wavelength) of data, that can be processed to deduce the labels present in that pixel. Linear unmixing (LU) has been widely utilized to analyze HFI data, and has performed well with bright samples emitting strong signals from fully- characterized, extrinsic fluorophores such as fluorescent proteins and dyes \(^{15 - 17}\) . However, in vivo fluorescence microscopy is almost always limited in the number of photons collected per pixel (due to the expression levels, the bio- physical fluorescent properties, and the sensitivity of the detection system), which reduces the quality of the spectra acquired. While solutions beyond the standard LU have been proposed \(^{21}\) , the challenge of analyzing low intensity spectral signals remains. + +In line with this, it is crucial to demonstrate the power of the presented algorithm for unmixing also intravital multi- photon imaging data in optically more challenging tissues and organisms, which need to deal with much lower signals and SNR values, especially due to massive scattering and wave- front distortions in mammal tissue. + +ANSWER: We understand the reviewer's concern on challenging tissues with respect to scattering and wavefront distortions. However, we believe that the underlying physics for combining fluorescent signals and the mathematical requirements for applying our unmixing method should be valid independently from the type of tissue and the depth of the imaging. + +<--- Page Split ---> + +With regard to the reviewer's concern for HyU to "deal with much lower signals and SNR values", the now updated plots for the unmixing performance covers a wide range of photon counts and SNR, which will likely to cover a wide range of biological applications. + +With regard to "to massive scattering and wave- front distortions in mammal tissue", the reviewer is correct; in principle, highly scattering tissues might affect the fluorescent spectra. However, it should be noted that, in most cases, such massive distortions would require particularly deep imaging. Generally, fluorescent signals decrease greatly in intensity and are lost (scattering/absorption) before reaching such depth, long before these massive wavefront distortions are visible. Undoubtedly, there have to be some spectral distortions caused by the light traveling across a non- uniform biological medium; however, at the relatively shallow sample depths reached before losing signal, these distortions were not measurable at the spectral sampling resolution available on the most common confocal spectral fluorescent microscopes (32 channels, each with 8.9nm bandwidth). + +From our previous experience in working with hyperspectral images and utilizing the phasor method ( https://www.nature.com/articles/nmeth.4134 , https://www.nature.com/articles/s41467- 020- 14486- 8 ) in both deep and scattering tissue, we have demonstrated that as long as the signal is not completely indistinguishable from the noise (for \(\mathrm{SNR} > = 2\) ), the phasor method proves reliable in categorizing signals (shown in Supplementary Figures 21, 22, 23, 24 of https://www.nature.com/articles/s41467- 020- 14486- 8 available at Nature Comm. link https://static- content.springer.com/esm/art%3A10.1038%2Fs41467- 020- 14486- 8/MediaObjects/41467_2020_14486_MOESM1_ESM.pdf ). + +This correct phasor categorization enables HyU to perform averaging and denoising of spectral signals for unmixing. When working with scattered signals, in our experience, fluorescent signals drop below \(\mathrm{SNR} = 2\) before sufficient scattering and spectral distortions affect the unmixing method. This physical limitation of diffusion of fluorescent signal across scattering and absorbing tissues, at least for the biological samples we imaged (cells, zebrafish, mouse), prevented us from encountering sufficiently distorted spectra to induce major errors in the phasor transform or in the unmixing. + +An example of this is shown in Supplementary Figure 28 of https://www.nature.com/articles/s41467- 020- 14486- 8 available at Nature Comm. link https://static- content.springer.com/esm/art%3A10.1038%2Fs41467- 020- 14486- 8/MediaObjects/41467_2020_14486_MOESM1_ESM.pdf . A very similar discussion with additional figures, experiments, and descriptions is reported in the Peer Review File (pgs 47- 49) of https://www.nature.com/articles/s41467- 020- 14486- 8 available at Nature Comm. link https://static- content.springer.com/esm/art%3A10.1038%2Fs41467- 020- 14486- 8/MediaObjects/41467_2020_14486_MOESM2_ESM.pdf. The image in this discussion shows how stable the signal position on the phasor remains when acquiring fluorescent spectra at deeper parts of the sample. + +<--- Page Split ---> + +However, we understand that providing an example of our method in more scattering mammal tissue would facilitate any adopter in their decision making. We have performed the following additional changes to address this point: + +1. We have added experiments performed on both freshly excised and fixed mouse tissue. (Supplementary Figures 29, 30) +2. We have included unmixing results from deep imaging performed on zebrafish embryos for further comparison. (Supplementary Figure 23) +3. We expanded the Supplementary Information with details on mouse lines, fluorescent silica beads characterization, mouse tissue samples preparation, and imaging. + +1. For mouse experiments, we have included two examples of application for the Hybrid Unmixing method: fresh tissue autofluorescence metabolic imaging and fixed tissue fluorescence imaging. + +The first experiment involved unmixing autofluorescent signals in freshly excised mouse kidney tissue. The unmixed signals include NADH bound, NADH free, Retinol, Retinoic acid, and Elastin, in correspondence to the intrinsic signals previously unmixed in the zebrafish experiments. In Supplementary Figure 29, we demonstrate that the same independant autofluorescent signatures used in the zebrafish to perform HyU can be utilized in the fresh mouse tissue. Even as the intensities of the autofluorescent signatures drop rapidly within the first \(75 \mu \mathrm{m}\) of tissue, we demonstrate that HyU performs as previously shown in zebrafish. The unmixed autofluorescent signals within the mouse tissue yield spatial patterns (Sup. Fig 29 A, B, C, E) corresponding to those described in literature (https://doi.org/10.1117/1.JBO.19.2.020901, https://doi.org/10.1681/ASN.2016101153, https://doi.org/10.1021/cr900343z) and to those previously shown in zebrafish. Cross- section visualizations (Sup. Fig 29 B and E) show consistency in the unmixed autofluorescence patterns along the depth of the sample (z- direction) until signal drops to noise level. For these notoriously weak autofluorescent signals, intensities fade out at approximately \(75 \mu \mathrm{m}\) depth. + +In the presence of massive wavefront distortions in the fluorescent spectra, the expected and most likely behavior of the HyU would be a deterioration of the unmixing quality. This generally results in a non- organized, more uniform re- assignment of intensities across the unmixed channels. When this scenario happens, severe cross- talk is visible across channels. If one were to visualize these results in a 2- D image, it would result in a "white" color where multiple signals are shown together in the same image. + +Supplementary Figure 29 panels B and E are single slices of the volume, representing a 1- pixel wide cross- section of the volume, along the XZ and YZ planes respectively. In these cross sections, there is no visible confounding of signals or "white" color, delineating the overlap of multiple fluorescent signals. This suggests that the algorithm, under reasonable imaging conditions, performs as characterized (Sup. Figures + +<--- Page Split ---> + +16,17,18,19). This is mainly because fluorescent signals fade to dark before any appreciable distortion affects the system. + +Supplementary Figure 29: + +![PLACEHOLDER_41_0] + +
Supplementary Figure 29. Intrinsic fluorescent signatures in fresh mouse tissue
+ +Intrinsic fluorescent signatures in fresh kidney tissue of a 7 months Balb- c mouse imaged with 2- photon excitation at \(740~\mathrm{nm}\) in a \(150~\mu \mathrm{m}\) deep volume. Despite the increasing scattering effect of this mammal tissue with increasing depth, HyU can perform unmixing of intrinsic fluorescent signals. (A) Volumetric rendering of the unmixing results of five intrinsic fluorescent signatures shows results consistent with literature, as visible in the (B- E) orthogonal views of (C) an unmixed (x,y) cross- section of the volume at \(30~\mu \mathrm{m}\) + +<--- Page Split ---> + +depth in the sample and its corresponding (B) (x,z) and (E) (y,z) projections. (D) Averaged autofluorescent signals for each acquired spectral (x,y) section over the \(150\mu m\) depth of the volume show a sharp decrease of intensities after \(75\mu m\) depth as visible in E, the corresponding (y,z) projection. + +The second experiment involved unmixing a known fluorescent signal among the background signals within the highly scattering mouse tissue by imaging Cy3 beads injected (described in the new Mouse Sample Preparation section below) into fixed mouse tissue. The ground truth spectra of the Cy3 beads is known, measured in pure bead solution (described in the new Fluorescent silica bead characterization section). With this known constant Cy3 fluorescent spectrum, we can demonstrate: + +a. The efficacy of HyU even when fluorescent signatures are buried deep within highly scattering tissue. +b. The effect of tissue scattering on the known Cy3 fluorescent spectrum. + +Supplementary Figure 30 below shows that the Cy3 beads (magenta) are unmixed with the proper spatial profiles (spherical shape) from the autofluorescent (yellow), background (green), and structural signatures (light blue) of the fixed mouse tissue. Similarly to Supplementary Figure 29 B,C,E, there is no evident confounding overlap of signals when imaging deeper in the sample. In this case, with stronger autofluorescent (fixative- related) and fluorescent (beads) signals, signals started fading at \(110\mu m\) depth in the sample. + +In support of our observation that fluorescent spectra, as measured in our commercial instrument, are not excessively distorted in their shape, we plot the spectra corresponding to the Cy3 beads at multiple depths (Supplementary Figure 30 F, G), up to \(130\mu m\) deep in the sample, in absolute (Sup. Fig 30 F) and relative (Sup. Fig 30 G) intensity. Absolute peak intensity for some of the deeper spectra is around \(\sim 1300\) Digital Levels, corresponding to \(2\%\) of the full 16 bit dynamic range of the detector, close to the noise level of the instrument. This translates to visibly noisy spectra for deeper z- planes of the sample, as shown in the relative intensity plots (panel G), but does not show massive spectral distortions. + +In regards to the performance of HyU, the unmixed fluorescent signatures remain consistent with expected spatial patterns within the scattering mouse tissue even as the overall intensity drops. Within the imaging depth we could reach in our instrument, the highly scattering nature of the mouse tissue does not affect the performance of HyU, similar to what we previously demonstrated in zebrafish. + +Supplementary Figure 30: + +<--- Page Split ---> +![PLACEHOLDER_43_0] + +
Supplementary Figure 30. Extrinsic fluorescent signatures in fixed mouse tissue
+ +We evaluate the performance of HyU in imaging fluorescent signals in a highly scattering fixed kidney tissue of a 7- month- old Balb- c mouse with embedded Cy3 fluorescent beads (Methods) imaged with 2- photon 850nm excitation up to \(150 \mu \mathrm{m}\) deep. (A) Volumetric rendering of the unmixing results of the signals from fixative autofluorescence (autoFL), Cy3 beads, background, and Second Harmonic Generation (SHG). (B- E) Orthogonal views of the same volume for (C) single (x,y) plane of the volume at a depth of \(90 \mu \mathrm{m}\) with cross- sections (yellow hairlines in C). (B) (z,x) of \(18 \mu \mathrm{m}\) and (E) (y,z) of \(4 \mu \mathrm{m}\) respectively showing sections of the unmixed volume containing Cy3 beads at different depths up to \(140 \mu \mathrm{m}\) . (D) Average intensity value for each acquired (x,y) spectral image slice as a function of depth reveals considerable loss of fluorescent signal deeper than \(110 \mu \mathrm{m}\) . (F) Average spectra for each z- plane containing pixels with Cy3 beads signal plotted with absolute intensity (Digital Levels, DL) show decreasing intensity with depth as demonstrated by the area under each spectrum. (G) The same averaged spectra are normalized and plotted with Relative Intensity to show the consistency in the spectral shape as a function of depth in reference to Cy3 beads in solution (dashed line). + +<--- Page Split ---> + +2. For completion, we added an example of deep imaging in zebrafish, to demonstrate the similarities in signal attenuation that occurs in this model when compared to highly scattering mouse tissue (Supplementary Figure 23). The phasor plot of the signals provides a consistent distribution, centered at the same coordinates, even for images acquired deeper into the tissue where the detected spectra decrease in intensity and increase in noise. The signal attenuation and noise increase match those seen for the spectra detected in both mouse examples (Sup. Fig 29 and 30). + +![PLACEHOLDER_44_0] + +
Supplementary Figure 23. Phasor analysis on signal distortion in deep tissue
+ +Images at different Z- positions of a 3D (x,y,z) dataset of 19 hpf Tg(ubiq:lyn- tdTomato) zebrafish acquired from 0 um to 80 um (relative to the object) depth displaying at every 13 z- slices. (A- D) Phasors calculated from the single slices at 0 \(\mu \mathrm{m}\) , 26 \(\mu \mathrm{m}\) , 52 \(\mu \mathrm{m}\) , and 78 \(\mu \mathrm{m}\) depth. (E- H) Corresponding average intensity images (across the 32 spectral channels) for each z- slice show an expected decrease in fluorescence intensity with depth. (I) Average spectra of the pixels linked to the phasor position bin for the tdTomato fluorescent signature for each of the four presented z- slices (0, 26, 52, 78 \(\mu \mathrm{m}\) ) show a decrease in the spectral area without change in spectral shape as shown by (J) + +<--- Page Split ---> + +normalizing the average spectra shown in I to each spectrum's maximum value. This demonstrates the spectral shape does not change across different depths (z- planes), while the overall intensity decreases. (K) Randomly selected spectra from the raw spectral image at 0 \(\mu \mathrm{m}\) (blue) and 26 \(\mu \mathrm{m}\) (red), five spectra for each image and similarly (L) for 52 \(\mu \mathrm{m}\) (green) and 78 \(\mu \mathrm{m}\) (yellow). Two yellow and three green spectra are not clearly visible because of low signal intensity. + +3. We expanded the supplementary information to include details on mouse lines, fluorescent silica beads characterization, mouse tissue sample preparation, and imaging: + +## Mouse lines + +Mice imaging was approved by the Institutional Animal Care and Use Committee (IACUC) of University of Southern California, Protocol #21311. Experimental research on vertebrates complied with institutional, national and international ethical guidelines. Animals were kept on a 13:11 hours light:dark cycle. Animals were breathing double filtered air, temperature in the room was kept at 68- 73 F, and cage bedding was changed weekly. All these factors contributed to minimize intra- and inter- experiment variability. Adult Balb- c mice were euthanized via overdose of isoflurane followed by cardiac puncture. Kidneys were quickly harvested from the mouse, washed in PBS, and cut longitudinally alongside the midsection in order to expose the inner part of the organ. The two halves of the organ were arranged onto a microscope slide for imaging. + +## Fluorescent silica beads characterization + +One fluorescent silica beads solution (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, 1% solid, lot# 1608BRX5) was characterized in its spectral fluorescence emission and physical size. + +10x dilution in PBS of the beads was placed on a no. 1.5 imaging coverglass and spectrally characterized using spectral mode on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using 40x/1.1 W LD C- Apochromat Korr UV- VIS- IR lens utilizing a 2- photon laser at 740 nm to excite fluorescence from the beads, using a 690 nm lowpass filter to separate excitation and fluorescence. Spectra obtained from multiple beads with the same label were averaged, producing the reference spectrum reported in Sup. Figure 30 G (dashed line). Fluorescent silica bead size and concentration were determined via nanoparticle tracking analysis (NTA) on the Nanosight NS300 (Malvern Panalytical). Samples were run 5 times and results averaged for final size and concentration values reported. + +<--- Page Split ---> + +## Mouse Sample preparation + +For autofluorescent measurements, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in Phosphate Buffered Saline (PBS) to remove residual blood and kept in PBS until imaging preparation. Organs were sectioned in order to image the internal architecture and mounted on a glass imaging dish with sufficient PBS to avoid dehydration of the sample. Following imaging, all samples were fixed in a \(10\%\) Neutral Buffered Formalin solution at \(4 - 9C\) + +For ex vivo bead characterization in tissue, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in PBS followed by incubation for at least 24 hours in \(10\%\) buffered formalin. The kidney was then removed from the fixative and sectioned into smaller \(\sim 5\times 5\times 5\mathrm{mm}\) pieces for imaging. A fluorescent silica beads stock (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, \(1\%\) solid, lot# 1608BRX5) and previously characterized was prepared using a \(10x\) dilution of the fluorescent beads from their stock concentration. Beads were injected in the sample using 50ul of these solutions loaded into a \(0.5\mathrm{mL}\) syringe with a \(28g\) needle. The kidney sections were then placed in imaging dishes with a small volume of PBS to keep the samples hydrated prior to imaging. + +## Image Acquisition. + +Images were acquired on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using \(40x / 1.1\) W LD C- Apochromat Korr UV- VIS- IR lens at \(28 - 9C\) + +Samples of Gt(cltca- Citrine), Tg(ubiq:lyn- tdTomato), Tg(fli1::mKO2), and Tg(ubiq:Lifeact- mRuby), were simultaneously imaged with 488 nm and 561 nm laser excitation, for citrine, tdTomato, mKO2, and mRuby. A narrow 488 nm/561 nm dichroic mirror was used to separate excitation and fluorescence emission. Samples were imaged with a 2- photon laser at 740 nm to excite autofluorescence, using a 690 nm lowpass filter to separate excitation and fluorescence. + +Samples of mouse kidney tissue were imaged in 2- photon exciting at 740 nm or 850 nm with a \(690+\) nm lowpass filter, at 37C incubation. + +For all samples, detection was performed at the full available range (410.5- 694.9nm) with 8.9nm spectral binning. + +<--- Page Split ---> + +Referring to the algorithm itself and to its characterization, the evolution from hyperspectral multiplexed imaging using the phasor approach HySP (Cultrale et al, 2017, Nat Meth), enhanced by preprocessing the data to account for various experimental noise via SEER (2020, Nat Commun) and finally by applying linear unmixing in the hyperspectral phase space, bringing additional significant accuracy to the unmixing capacity of the data is currently not clear in the manuscript and needs to be elaborated in the introduction, to emphasize the novelty of the present work. + +ANSWER: We have improved the introduction to emphasize the novelty of HyU with respect to previously published work: + +We have developed Hybrid Unmixing (HyU) as an answer to the challenges that have limited the wider acceptance of HFI for in vivo imaging. HyU employs the phasor approach26 merged with traditional unmixing algorithms to untangle the fluorescent signals more rapidly and more accurately from multiple exogenous and endogenous labels. The phasor approach26, a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis27- 29 has been shown to provides key advantages to HyU, including spectral compression, denoising, and computational reduction for both pre- processing30 and unmixing31- 33 of HFI datasets. + +Standard Phasor analysis26,27,34- 41 is fully supervised and requires a manual selection of regions or points on a graphical representation of the transformed spectra, called the phasor plot. HyU utilizes phasor processing as an encoder to aggregate similar spectra and applies unmixing algorithms, such as LU, on them to provide unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity. Our results show that HyU offers three key advantages: (1) improved unmixing over conventional LU, especially for low intensity images, down to 5 photons per spectra; (2) simplified identification of independent spectral components; (3) dramatically faster processing of large datasets, overcoming the typical unmixing bottleneck for in vivo fluorescence microscopy. + +We further clarified the advantages of HyU over our previous work HySP in a Supplementary Note 4. + +Supplementary Note 4: Improvements of HyU over the standard phasor analysis + +Linearity of combinations is the general assumption for most of the spectral analysis algorithms in Hyperspectral Fluorescence Imaging (HFI). Each pixel is assumed to contain a linear combination of the independent spectral signatures, or endmembers, + +<--- Page Split ---> + +contained in the sample. This assumption requires knowledge, or identification, of the independent spectra within the sample. In standard linear unmixing algorithms, the extraction of relative amounts of spectra (ratios) is conducted on a pixel- by- pixel basis, at the expense of computational costs. Disrupted experimental signals, in the case of lower Signal to Noise Ratio (SNR) spectra, complicate the detection of spectral endmembers and reduce the accuracy of ratio determination. These standard unmixing algorithms, however, have the advantage of being unsupervised with the possibility of automating the analysis process. + +The phasor approach has become a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis13- 15. Phasors provide key advantages, including spectral compression, denoising, and computational reduction for both pre- processing3 and unmixing8,16,17 of HFI datasets. Phasor analysis overcomes the challenge of low SNR data analysis that limits standard unmixing algorithms, providing a multiplexing solution to a need. The phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original clean data18. In the imaging of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data has made the phasor method a valuable tool for fluorescence microscopy, both for Lifetime and Spectral Fluorescence Microscopy. This point is reported by multiple groups using phasors18- 21 and, more recently, nicely described in the work of Scipioni et al22. Standard Phasor analysis23- 25 is fully supervised and requires a manual selection of regions or points on a graphical representation of the transformed spectra, called the phasor plot. Each selection of a region in the phasor plot associates pixels containing similar spectra to the same fluorophore, forming an output channel that contains wavelength integral of intensities with unitary ratiometric value. This “winner takes all” approach is suitable when fluorophores for each single excitation light are spectrally overlapping and spatially disperse (Sup. Figure 24), but requires separate acquisition of different excitation wavelengths for demultiplexing spatially and spectrally overlapping fluorophores (Sup. Figure 25). + +HyU uses the phasor transform to group pixels with similar spectral shape within each phasor histogram bin. This approach maintains the advantage of compressing, denoising and simplifying identification of clean endmember fluorescent spectra. However, HyU improves on the robustness of the analysis. The denoised signals are maintained in a hybrid phasor and wavelength domain, and therefore can be unmixed with a multitude of standard unmixing algorithms (Sup. Figure 13), such as Linear Unmixing or Fully Constrained Least Squares. These standard unmixing approaches can operate without supervision and provide for each pixel the ratios for a set of spectral signals, overcoming some of the limitations of phasor, but generally do not perform well in experimental + +<--- Page Split ---> + +conditions with reduced and compromised signals, such as in fluorescence, and require extensive computational time for high spectral- count datasets. HyU provides wavelength- based denoised spectra that enable these standard algorithms to outperform their pixel- by- pixel typical application, both in quality of the results (Sup. Figures 16- 19), owing to cleaner and better defined fluorescent spectra in each phasor bin, and, generally, in speed, owing to the phasor dimensionality reduction. HyU performs well for single excitation light when fluorophores are spectrally overlapping both when they are spatially disperse or co- localized, providing a ratio for each independent spectrum currently unmixed. Our data suggests HyU has reasonable performance for up to 8 different fluorophores per dataset, for each single excitation wavelength. In an experiment with a carefully chosen palette of labels, where octuples of fluorophores can be excited by a single wavelength, with an instrument capable of spectral acquisition with 5 standard and sufficiently spectrally separated excitation wavelengths in 5 sequential acquisitions (one for each excitation light), HyU could, in principle, unmix 40 signals. This performance however decreases with the number of channels (Sup. Figures 18, 19) showing a small deterioration at 8 channels and limitations at 4. + +<--- Page Split ---> + +A. Referring to the broad applicability of the algorithm and the interest for a large community: +A.1. As previously mentioned, in order to prove the value of the approach presented in this manuscript, multiplexed time-lapse imaging in a mammal (adult mouse or rat or human) tissue is key and experimental data on this need to be added to the manuscript. I believe, one 4D (3D + time) imaging example showing 8-9 distinct emission signals would be absolutely convincing. + +ANSWER: We agree with this reviewer that a multiplexed time- lapse imaging in a mammal (adult mouse or rat or human) tissue showing 8- 9 distinct emission signals would absolutely be convincing. However, such an experiment would require a specialized team with expertise in mouse/rat multicolor labeling, a dedicated mouse/rat colony, specialized equipment for both anesthesia and imaging of the samples, and a complex survival imaging animal protocol. We currently do not have such expertise in our group, which mainly uses zebrafish, lack the compliant instrumentation for performing mammal timelapse imaging under anesthesia as regulated by IACUC of USC, and do not have active mouse protocols that would allow such imaging. Performing such a complex experiment would require 2- 3 years of work, after securing the necessary funding for additional personnel and instrumentation, while, arguably, there likely is a very limited number of laboratories with the capability and equipment of routinely performing 4D imaging of mouse/rat samples with 8- 9 labels. For these reasons we believe such an experiment would, itself, be worthy of an independent publication. However, it would not further the demonstration of the method in this manuscript. + +As such, we believe this experiment to be beyond the scope of this manuscript, which presents a fluorescence unmixing method for the broader audience. We agree with the reviewer that example applications in mouse should be part of this manuscript (as we stated above) with respect to the concerns of distortions of spectra in scattering tissues. We have included additional mouse tissue experiments in this revision that we believe address the performance of the method when applied to mammalian samples. We kindly refer to the above answer to this reviewer (Remarks to the Author: Impact) for details of the additional experiments. + +B. Referring to the unmixing approach: + +B. Referring to the unmixing approach: +B.1. In order to judge the added value of the integration of linear unmixing and of reference extrinsic and intrinsic spectral signatures on the performance of unmixing, a thorough comparison with the previously available HySP (Cultrale et al, 2017) needs to be provided, additionally to the comparison to state-of-the-art linear unmixing algorithms already included in teh manuscript. + +ANSWER: To address this point: + +<--- Page Split ---> + +1. We have improved the introduction to emphasize the novelty of HyU with respect to previously published work (see answer above for in-line text). +2. We included a full comparison with different types of samples in Supplementary Figures 24 and 25. +3. We added an extensive discussion that outlines the advantages of HyU over the previously available HySP in the new Supplementary Note 4. + +1. The introduction now refers to our previous work and overviews the improvements of HyU over it. The excerpt is copied for reference in the last answer to this reviewer's "Impact" section. +2. We included comparisons of HyU vs HySP with different sample types, where for each laser excitation, the sample contains spectrally overlapping spatially disperse labels or both spectrally and spatially overlapping fluorophores. + +Supplementary Figure 24: + +![PLACEHOLDER_51_0] + + +<--- Page Split ---> + +Supplementary Figure 24. Comparison of HyU vs HySP results from a spectrally overlapping and spatially disperse sample + +Results are presented for unmixing using HyU and Hyperspectral Phasors (HySP) on a spectrally overlapping spatially disperse dataset collected from a tri- labeled transgenic zebrafish embryo obtained by injecting mRNA- encoding H2B- cerulean (cyan) in double transgenic embryos Gt(desm- citrine) ct122a/+;Tg(kdrl:eGFP) (magenta and yellow, respectively) (A- F) HyU unmixing results and (G- L) HySP unmixing results renderings for the dataset. Line profiles of (F) HySP (L) HyU analysis results (B, H dashed line) show the similarity in signal between the two methods for all channels within a non- overlapping sample. (A,F) Volumetric images show a similarity between the HyU and HySP results. This is further demonstrated for the results in a (B,H) single z- slice, for just the (C,I) Citrine channel, the (D,J) Cerulean channel, and the (E,K) mCherry channel. (F,L) Line profiles for the lines shown in B and H, respectively, also demonstrate the similar results of HyU and HySP for spatially non- overlapping samples. + +Supplementary Figure 25: + +![PLACEHOLDER_52_0] + + +<--- Page Split ---> + +Supplementary Figure 25. Comparison of HyU vs HySP results from a spectrally overlapping and spatially non- disperse sample + +Results for unmixing using HyU and HySP on a spectrally overlapping and spatially non- disperse dataset collected from a 5 dpf dual- labeled transgenic zebrafish embryo: Gt(cltca- citrine); Tg(fli1:mKO2), presenting frequent combinations of signals in pixels across the dataset. (A- E) HyU unmixing results and (F- K) HySP unmixing results for the dataset. (A,F) Volumetric images show the expected signal overlaps between channels for the HyU result and a more distinct separation in the HySP result. This is further demonstrated for the results in a (B,G) single z- slice, for just the (C,H) mKO2 channel, and the (D,I) Citrine channel. (E,J) Line profiles for the lines shown in B and G, respectively, demonstrate the fractional nature of HyU results compared to the winner- takes- all analysis of HySP. + +3. Supplementary Note 4, replicated in our first answer to this reviewer, furthers the discussion. + +B.2. A central advantage of the here presented approach is the capacity of dealing even with low signals, i.e. unmixing even low endogenous signals, such as NAD(P)H, even free and bound – having extremely similar emission spectra (one reason why their fluorescence lifetime has been used to resolve the two states). The authors show the improvement referring to number of photons per spectrum, however, in order to judge the true improvement brought by the algorithm for real imaging data (which includes background with diverse types of noise distributions), the unmixing quality needs to be related to the signal-to-noise (SNR) ratio per voxel. While mentioning SNR in the text, no values or comparison are provided in this sense – it is important to mention how the SNR as such (not only the number of photons per spectrum) impacts on the spectral resolution, i.e. how similar can be two spectra at a certain SNR to be able to still resolve them? + +ANSWER: We thank the reviewer for this very good point. To address this comment we prepared: + +1. A plot correlating the SNR as a function of spectrum-type and photons/spectrum +2. A definition of the Spectral SNR + +1. The plot represents how photons per spectra translate to a more standardized definition of SNR, utilizing the fluorophores' spectra from this manuscript. We provide these plots to show the direct relationship between photons per spectrum and the SNR of a single spectra. The reason for demonstrating the relationship between photons per spectra and SNR instead of directly calculating and presenting the SNR values is because the exact description and quantification of SNR becomes highly convoluted and unintuitive for + +<--- Page Split ---> + +combinations of multiple spectra. It is important to notice the differences in Spectral SNR between fluorophores as the result of the different spectra shapes which cover different numbers of channels in our instrument- simulating algorithm (410- 692nm spectral detection range, 32 bands each with 8.8nm bandwidth). + +![PLACEHOLDER_54_0] + +
Supplementary Figure 28:
+ +Supplementary Figure 28. Relationship between Spectral SNR and Photon/SpectrumThe direct relationship between SNR and photons per spectrum is shown here using the calculation of Spectral SNR for varying levels of photons per spectrum. The spectral SNR has a general trend of increased values with increasing photons per spectrum, but it is not a truly monotonic function. This non- monotonicity demonstrates the limitations of SNR when analyzing spectral images. (A) Absolute Spectral SNR and (B) Relative Spectral SNR follow the same trends of higher values with increasing photons per spectrum. However, the Relative Spectral SNR better differentiates the effects of the differing spectral shapes on the SNR. Citrine, mKO2, mRuby, and tdTomato each have easily distinguished values for the slope of the regression in ascending order. tdTomato has a spectral shape which provides the best SNR while Citrine provides the worst SNR, even with the same number of photons per spectrum. + +2. For this simulated hyperspectral (multispectral/multichannel) fluorescent data, the term of Spectral SNR is calculated inclusively of the spectral dimension. We define the criteria used for calculating Spectral SNR in a new section in Supplementary Methods. Briefly, these Spectral SNR calculations are designed to also include the noise resulting from the stochastic emission of fluorescent photons which disrupts the shape of spectra, therefore compromising the unmixing analysis. The additional section in Supplementary Methods reads: + +<--- Page Split ---> + +## Spectral Signal to Noise Ratio + +Since each synthetic dataset has a ground truth, the SNR can be calculated by comparing the simulated image to the ground truth. Since these are hyperspectral images, we extend the definition of SNR to the wavelength dimension of the data and use the term Spectral SNR. We define two types of Spectral SNR, Absolute Spectral SNR and Relative Spectral SNR. + +Spectral SNR is calculated as follows for each single spectrum simulation. First, for each pixel and channel, the absolute value of the difference is taken between the ground truth intensity and the simulated intensity. Then the mean is calculated over all of the pixels for each channel. Finally, the sum is taken over all of the channels and divided by either 32 for the absolute SNR, or the number of channels with signal for the relative SNR. The number of channels with signal is calculated by checking if there is a statistically significative number of pixels in a single channel with a pixel SNR value greater than zero. + +\[\mathrm{Absolute~SNR} = \frac{\sum_{c = 1}^{P}\frac{t_{gnd}}{t_{sim} - t_{gnd}}}{32} \quad (23)\] \[\mathrm{Relative~SNR} = \frac{\sum_{c = 1}^{P}\frac{t_{gnd}}{t_{sim} - t_{gnd}}}{c} \quad (24)\] + +Where ignd is the intensity per pixel per channel for the ground truth data, isim is the intensity per pixel per channel for the simulated (noisy) data, \(P\) is the total number of pixels, and \(C\) is the number of channels with signal. + +B.3. A corner stone in acquiring better unmixing is the availability of appropriate reference spectral signatures. Whereas the current software provides the spectra necessary for the data shown in the manuscript and gives the opportunity for the users to identify signatures in their own data, the manuscript remains elusive of how the user can differentiate between a real spectral signature and different types of optical or electronical background and interferences – as well known from the use of the phasor approach in fluorescence lifetime imaging, a major challenge when dealing with experimental noisy imaging data in the frequency (phase) domain. The manuscript would benefit from including such a guide to validate the capacity for external use of the algorithm. + +ANSWER: We have expanded Supplementary Note 1 titled “Identification of spectra and new components with HyU” with further clarifications, insights and references on how to distinguish + +<--- Page Split ---> + +independent spectral signatures from various types of noise. Supplementary Note 1 now reads: + +Supplementary Note 1: Identification of spectra and new components with HyU + +Identification of independent spectral components has been an adversity for unmixing hyperspectral data. First, the collected spectra may be distorted by reduced SNR. Secondly, excitation of intrinsic signals causes uncertainty of biological sample. Favorably, HyU simplifies this process by adapting Phasor approach and achieving semi- or full- automation process for spectra identification and selection. In HyU spectra can be loaded from an existing library, virtually automating the analysis process. Pre- identified cursors are generated from common fluorophores such as mKO2, tdTomato, mRuby, Citrine. In our experience, obtaining fluorescence spectra from experimental samples has some advantages compared to utilizing spectra from existing library, as they account for a multitude of experimental and instrumental settings. Imaging settings such as different types of lenses or optical filters (Sup. Figure 4, C and D) together with factors within the microenvironment of samples, such as pH or temperature have the potential to alter the fluorescence spectral emissions12. In the presence of unexpected fluorescent signals, spectra can also be selected and visualized directly from the phasor. Phasors facilitate the identification of unexpected independent components and their distinction from the multiple system noises. A noise- free spectrum will appear as a single point on the phasor plot, while a spectrum affected by instrument and electronic noises will mainly appear as a gaussian distribution, centered on the original spectral signal6. Conversely, a randomized noise across the multiple spectral channels will not produce a clustered aggregate of spectra on the phasor. A constant spectral noise, with a distinct spectrum (e.g. a constant light leakage into the system), would produce a distinct phasor cluster and could be selected for unmixing. The phasor plot representation is a 2D- histogram and provides insights into the frequency of occurrence for these signals. These unexpected independent components in samples often appear as "tails" on the phasor distributions (Sup. Figure 11, C). In our HyU graphical interface, clicking on the phasor visualizes the spectra within a small area (9x9 bins by default, with size adjustable from the interface) of the phasor histogram (Figure 1 D). In the example in Sup. Figure 9- 11 we identify 5 distinct endmembers on the Phasor (Sup. Figure 10, C), visualize their spectra identifying Citrine, mRuby, Td- Tomato, mKO2, and one strong autofluorescence signature. The use of Residual Phasor Map (Sup. Figure 11, B) allows for identification of areas in the phasor with high amount of residuals, likely corresponding to a missing endmember in the unmixing. Residual Image Maps (Sup. Figure 11, C) provide a rapid overview of residuals in the image data, for identification of location in the dataset of the missing endmember. + +<--- Page Split ---> + +B.4. Finally, fully agreeing with the authors that the number of detectors may be varied, depending on the imaged sample type and on the excitation strategy, in order to acquire an emission signal at all, an analysis of how the number of detectors (channels) impacts on the resolution between different signatures (spectra) is needed also for less than 32 detectors (4 to 6 channels being the reality in many labs due to truly low fluorescence signals in deep tissue, e.g. of mice or of humans). + +ANSWER: To characterize how the number of channels affects the hybrid unmixing analysis, we have assembled a complex simulation matrix representing the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built on top of the complex simulation we designed (further expanded in the Hyperspectral Fluorescence Image Simulation section of the supplementary methods), which is soon to be published in a separate manuscript. This simulation accounts for a multitude of real-world noises in experimental samples that are regularly imaged (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). + +We replicate the expanded Hyperspectral Fluorescence Image Simulation section: + +## Hyperspectral Fluorescence Image Simulation + +The model simulates spectral fluorescent emission by generating a stochastic distribution of photons with profile equivalent to the pure reference spectra (as described in Sup. Note 1). The effect of photon starvation, commonly observed on microscopes, is synthetically obtained by manually reducing the number of photons in this stochastic distribution. Detection, Poisson and signal transfer noises are then added to produce 32- channel fluorescence emission spectra that closely resemble those acquired on microscopes. The simulations include accurate integration of dichroic mirrors and imaging settings. + +## Simulation Types: + +## Biologically comparable simulations + +To quantify the performance of HyU vs LU for microscopy data acquired experimentally, we generated synthetic data where each input spectra was organized with intensity distributions taken from experimental data of fluorescently labeled biological samples. We calibrated the analog (Digital Levels) to photon counting rate based on existing literature \(^{5,6}\) . Experimental data was discretized to photons to produce biologically relevant photon masks with distributions of signals highly resembling those of the samples. This provided intensities and ratios which closely resemble those acquired from a confocal microscope while allowing control over the effects of photon starvation. + +<--- Page Split ---> + +## Spatially and spectrally overlapping simulations + +We also included simulations to quantify the performance of HyU vs LU with respect to the number of spectral combinations and of endmembers. The results are summarized in Supplementary Figures 16- 19 in the form of matrices of spectral overlap (0 to \(100\%\) , steps of \(10\%\) , X- axis) by number of endmembers (2 to 8 endmembers, Y- axis) representing the Relative Mean Squared Error (RMSE) (Supplementary Methods, Performance quantification). Each RMSE value reported in a matrix is the average of analysis of a \(1024 \times 1024\) pixels image simulation with a spectral dimension of \(32:\) channels matching the spectral range and bandwidth of the detectors in commercial confocal microscopes (LSM 780, Carl Zeiss). These simulations were created with artificial intensity distributions so that a simulation with \(X\%\) overlap and n fluorophores would have X percentage of pixels with a randomized ratio of n input spectra. As an example, for a simulation with 6 fluorophores and \(50\%\) overlap, the simulated dataset would have \(50\%\) of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. This allowed us to investigate the effects of an increasing number of spectral combinations on the compressive nature of the phasor method for HyU. + +The results are reported in Supplementary Figure 19 and described in Supplementary Note 4 (reported above): + +![PLACEHOLDER_58_0] + +
Supplementary Figure 19. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels
+ +<--- Page Split ---> + +Fifteen matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic and intrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n extrinsic and intrinsic fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Columns in the figure represent RMSE improvement matrices with 3x denoising filters across an increasingly binned number of spectral channels (32, 16, 8, 6, 4) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. When utilizing 32 spectral channel data, RMSE improvements reach up to the previously reported \(100\%\) for highly overlapping fluorophores. Successively increasing the binning across the wavelength dimension (and therefore decreasing the number of channels) shows a slow downward trend of the RMSE improvement until the 4 spectral channel matrices, where the RMSE improvement drops drastically down to below \(25\%\) , especially for more than 3 labels. Spectra utilized for this simulation are reported in Sup. Figure 20B. + +The excerpt of Supplementary Note 4 clarifying the performance / number of channels: + +In an experiment with a carefully chosen palette of labels, where octuples of fluorophores can be excited by a single wavelength, with an instrument capable of spectral acquisition with 5 standard and sufficiently spectrally separated excitation wavelengths in 5 sequential acquisitions (one for each excitation light), HyU could in principle unmix 40 signals. This performance however decreases with the number of channels (Sup. Figure 25) showing a small deterioration at 8 channels and limitations at 4. + +Reviewer #2 (Remarks to the Author: Reproducibility): + +The current version of the HySP platform was easy to use and the provided sample data delivered similar results as those shown in the manuscript. + +ANSWER: We thank the reviewer for the constructive feedback and for helping us improve the quality of the work presented here. + +<--- Page Split ---> + +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. However, I found that there are some confusing points to be addressed clearly to publish this manuscript in Nature Portfolio. + +ANSWER: We thank the reviewer for the valuable comments on the manuscript. Following the reviewer's comments we have: + +1. improved the explanation of the advantages of HyU by modifying our introduction and adding a new Supplementary Note 4 +2. extended the description of the simulations with more detail, providing our reasoning and multiple figures to demonstrate why they provide a realistic replication of standard experimental conditions and are reliable as standards to compare our results with our unmixing methods +3. expanded our Supplementary Note 1 with further clarifications, insights, and references on how to distinguish both known and unknown independent spectral signatures within the phasor plot +4. demonstrated our unmixing method in both scattering and non-optically clear tissue by performing hyperspectral fluorescence experiments in both freshly excised and fixed mouse tissue, summarizing the HyU unmixing results in two new supplementary figures as well as demonstrating the unmixing method for deep imaging in zebrafish. + +## Comments: + +1) Hyperspectral phasor compresses spectral dimension by exploiting real and imaginary parts of Fourier transformation. Moreover, there were reports that hyperspectral phasor could be applied for multiplexed fluorescence imaging. If there are any advantages of combining phasor and spectral unmixing methods, please describe them clearly in the Introduction. + +ANSWER: To address this comment we have: + +1. modified the introduction to clarify the advantages of combining phasor and spectral unmixing +2. added a Supplementary Note 4 to further the clarification of the advantages for HyU compared to previous reports of hyperspectral phasors + +<--- Page Split ---> + +1. The introduction now reads: + +1. The introduction now reads:HyU employs the phasor approach26 merged with traditional unmixing algorithms to untangle the fluorescent signals more rapidly and more accurately from multiple exogenous and endogenous labels. The phasor approach26, a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis27-29 has been shown to provides key advantages to HyU, including spectral compression, denoising, and computational reduction for both pre-processing30 and unmixing31-33 of HFI datasets. Standard Phasor analysis26,27,34-41 is fully supervised and requires a manual selection of regions or points on a graphical representation of the transformed spectra, called the phasor plot. HyU utilizes phasor processing as an encoder to aggregate similar spectra and applies unmixing algorithms, such as LU, on them to provide unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity. Our results show that HyU offers three key advantages: (1) improved unmixing over conventional LU, especially for low intensity images, down to 5 photons per spectra; (2) simplified identification of independent spectral components; (3) dramatically faster processing of large datasets, overcoming the typical unmixing bottleneck for in vivo fluorescence microscopy. + +2. We have added Supplementary Note 4 to directly address the improvements of HyU over previously published works on spectral phasors, particularly in this portion of the note: + +HyU uses the phasor transform to group pixels with similar spectral shape within each phasor histogram bin. This approach maintains the advantage of compressing, denoising and simplifying identification of clean endmember fluorescent spectra. However, HyU improves on the robustness of the analysis. The denoised signals are maintained in a hybrid phasor and wavelength domain, and therefore can be unmixed with a multitude of standard unmixing algorithms (Sup. Figure 13), such as Linear Unmixing or Fully Constrained Least Squares. These standard unmixing approaches can operate without supervision and provide for each pixel the ratios for a set of spectral signals, overcoming some of the limitations of phasor, but generally do not perform well in experimental conditions with reduced and compromised signals, such as in fluorescence, and require extensive computational time for high spectral-count datasets. HyU provides wavelength-based denoised spectra that enable these standard algorithms to outperform their pixel-by-pixel typical application, both in quality of the results (Sup. Figures 16- 19), owing to cleaner and better defined fluorescent spectra in each phasor bin, and, generally, in speed, owing to the phasor dimensionality reduction. HyU performs well for single excitation light when fluorophores are spectrally overlapping both when they are spatially disperse or co-localized, providing a ratio for each independent spectrum currently unmixed. + +<--- Page Split ---> + +2) If I understood correctly, numbers of photons (For instance, 5 photons per spectral in the last paragraph in Introduction) were calculated from the computer simulation. If so, this quantitative value is significantly affected by the noise levels used in the simulation. Therefore, it would be good to add these values were obtained from the simulation for clarity. + +## ANSWER: + +We have edited the Section "Hyperspectral Fluorescence Image Simulation" in the Supplementary Materials to include more details on the simulations: + +## Hyperspectral Fluorescence Image Simulation + +The model simulates spectral fluorescent emission by generating a stochastic distribution of photons with profile equivalent to the pure reference spectra (as described in Sup. Note 1). The effect of photon starvation, commonly observed on microscopes, is synthetically obtained by manually reducing the number of photons in this stochastic distribution. Detection, Poisson and signal transfer noises are then added to produce 32- channel fluorescence emission spectra that closely resemble those acquired on microscopes. The simulations include accurate integration of dichroic mirrors and imaging settings. + +## Simulation Types: + +## Biologically comparable simulations + +To quantify the performance of HyU vs LU for microscopy data acquired experimentally, we generated synthetic data where each input spectra was organized with intensity distributions taken from experimental data of fluorescently labeled biological samples. We calibrated the analog (Digital Levels) to photon counting rate based on existing literature \(^{5,6}\) . Experimental data was discretized to photons to produce biologically relevant photon masks with distributions of signals highly resembling those of the samples. This provided intensities and ratios which closely resemble those acquired from a confocal microscope while allowing control over the effects of photon starvation. + +## Spatially and spectrally overlapping simulations + +We also included simulations to quantify the performance of HyU vs LU with respect to the number of spectral combinations and of endmembers. The results are summarized in Supplementary Figures 16- 19 in the form of matrices of spectral overlap (0 to 100%, steps of 10%, X- axis) by number of endmembers (2 to 8 endmembers, Y- axis) representing the Relative Mean Squared Error (RMSE) (Supplementary Methods, Performance quantification). Each RMSE value reported in a matrix is the average of analysis of a 1024x1024 pixels image simulation with a spectral dimension of 32: channels matching the spectral range and bandwidth of the detectors in commercial confocal microscopes (LSM 780, Carl Zeiss). These simulations were created with artificial intensity distributions so that a simulation with X% overlap and n fluorophores would have X percentage of pixels with a randomized ratio of n input spectra. As an example, for a simulation with 6 fluorophores and 50% overlap, the simulated dataset + +<--- Page Split ---> + +would have \(50\%\) of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. This allowed us to investigate the effects of an increasing number of spectral combinations on the compressive nature of the phasor method for HyU. + +The simulation algorithm is soon to be published in a separate manuscript. It includes extensive characterization of instrument noise and produces distributions of signals that closely resemble the corresponding images acquired from the fluorescent microscope with analog mode detection. We provide the reviewer with a link to the GitHub repository with the version of the simulation used for the paper to demonstrate the complexity of the simulation. https://github.com/TranslationalImagingCenter/fluoroSim- HyU + +Here, we show some images that will be part of the separate publication with an example of a simulated uniform signal (a Chroma Slide) recreated using our simulation framework after acquiring the experimental signal using a confocal fluorescent microscope. The distribution of intensities between the experimental and simulated signals (A, B) present similar characteristics, even accounting for the stochasticity of photon emission and multiple noise contributions. The average spectrum of each dataset (C, D) shows close resemblance in both shape and intensity. + +<--- Page Split ---> +![PLACEHOLDER_64_0] + + +Comparison of microscope measured uniform signal and corresponding simulation: In this example, a yellow Chroma Slide is imaged using a 780 Zeiss Inverted in spectral mode (32 channels). (A,C) The top row shows images, histogram intensities, and the average spectrum for experimental data, focusing on two significant channels (468 nm and 548 nm). (B, D) The bottom row shows the corresponding results created by the simulation. + +We further characterized the performance of the hyperspectral fluorescent simulation with respect to noise, detectors, and fluorescence characteristics. In the following image, we show the plots of mean vs variance of intensity for a constant fluorescent signal (in this case a Chroma Slide) deriving from experimental (blue lines) and simulated (orange lines) data. The mean/variance plot is expected to be linear when the detector gain is within the linear response range. The plots below show only 6 different channels, but for all 32 channels the data was acquired at a gain of 740, well within the linear gain response range. Each data point in all plots is the (mean, variance) of a 1024x1024 pixels image for that specific channel. We acquired 7 datasets, each with an increasing laser power excitation (constant gain). As expected, the experimental data shows linearity in the mean/variance (blue lines). Similarly, + +<--- Page Split ---> + +simulated data where we increased the number of stochastically emitted fluorescence photons to mimic the increase in laser power, also provides a linear mean/variance (orange lines). The plots show consistent similarity between simulations and experimentally acquired data at both high and low intensities, suggesting a good replication of the multiple system noises. + +![PLACEHOLDER_65_0] + + +High similarity of mean vs variance plots between experimental and simulated images. + +Mean vs Variance plots are provided for experimental and simulated data in analog mode at low photon emissions for a constant fluorescent signal. Linearity in mean/variance is expected within the gain's linear response range. In this image, experimental data was acquired sequentially at increasing laser power, while simulated data was created by increasing the average statistically emitted fluorescent photons, effectively simulating an "increasing laser power". Results show a linear mean/variance relation for experimental data and a similar linear relation for simulated data. Slope values are reported in each plot's legend. + +Finally, we show the simulation's ability to reconstruct a biologically relevant hyperspectral image, replicating the spatial characteristics and most typical noises of fluorescent signals acquired through a confocal microscope lens and detectors. A comparison between the individual channel images of the (A) experimental hyperspectral dataset and (B) its synthetic counterpart demonstrates the realism of the computationally generated hyperspectral image. In (C), we compare the intensity profiles of a section of each pair of images (yellow line in A and B), showing, within the stochasticity of noise, how similar the synthetic data pattern (C, orange line) is to the experimental (C, blue line). + +<--- Page Split ---> +![PLACEHOLDER_66_0] + + +## Simulations recapitulate spatial intensity distributions across all channels + +(A) 2D intensity images of the experimental data for channels 18 (566 nm), 25 (629 nm), and 30 (673 nm) each with 8.9nm bandwidth, provide a baseline comparison for the simulations. (B) Corresponding images of the simulated data for channels 18 (566 nm), 25 (629 nm), and 30 (673 nm) show visually similar images for each channel, considering the stochasticity of noise. (C) Line profiles for experimental (blue) and simulated (orange) data corresponding to the yellow lines in A and B provide a comparison for the spatial distribution of intensity values and present a high degree of similarity for the distributions across multiple channels even accounting for stochastic noise. + +<--- Page Split ---> + +3) The authors addressed that the HyU method is more computationally efficient than the linear spectral unmixing method. This is true as the spectral dimension was reduced in Hyperspectral Phasors and histogram binning. However, these spectral compression and denoising also require computational power. Does the proposed method is more efficient when the entire process is considered? + +ANSWER: This comment was addressed in Supplementary Note 3 and Supplementary Figure 13. We noted that due to the highly efficient and optimized algorithms for matrix inversion, LU is strictly faster than hybrid unmixing overall, but our comment of the greatly decreased computational costs of hybrid unmixing are demonstrated with the usage of fitting algorithms instead of LU. We have edited the main text for clarity, which now reads: + +Speed tests with iterative fitting unmixing algorithms demonstrate a speed increase of up to 500- fold when the HyU compressive strategy is applied. (Fig. S13, Supplementary Note 3). Due to the initial computational overhead for encoding spectra in phasors, there is a 2- fold speed reduction for HyU in comparison to standard LU. However, this may be improved with further optimizations of the HyU implementation or by implementing different types of encoding. + +4) For spectral unmixing, it seems to use the reference signals obtained from pure fluorophores. What happens if there are unknown fluorescence signals? Can the proposed method be applied for blind spectral separation? + +ANSWER: In principle, yes, HyU could be implemented with blind spectral separation. However, in this current iteration of the approach, applying HyU to unknown fluorescence signals requires manual inspection of the phasor plot and is not automatic. The biggest advantage of HyU is the capability to visualize the spectra of endmembers on phasor. + +- The example reported in Figure 5 B shows how we identified the spectrum from an unidentified component by observing a separate cluster on the phasor. After a literature search, we determined that its spectral shape and anatomical location suggest that the signature is from blood cells.- Supplementary Figure 11 shows an example of utilizing residual maps as a strategy for identifying unexpected spectral contributions using the phasor by color-coding phasor bins with low unmixing performance, which provide a quantitative clue to which phasor areas may contain an unexpected independent spectral signature.- Phasor-based blind spectral separation such as those described in the work of Scipioni et al (https://www.nature.com/articles/s41592-021-01108-4) could be directly applied to HyU. + +<--- Page Split ---> + +We have expanded Supplementary Note 1 titled "Identification of spectra and new components with HyU" with further clarifications, insights, and references on how to distinguish independent spectral signatures from various types of noise. Supplementary Note 1 now reads: + +Supplementary Note 1: Identification of spectra and new components with HyU + +Identification of independent spectral components has been an adversity for unmixing hyperspectral data. First, the collected spectra may be distorted by reduced SNR. Secondly, excitation of intrinsic signals causes uncertainty of biological sample. Favorably, HyU simplifies this process by adapting Phasor approach and achieving semi- or full- automation process for spectra identification and selection. In HyU spectra can be loaded from an existing library, virtually automating the analysis process. Pre- identified cursors are generated from common fluorophores such as mKO2, tdTomato, mRuby, Citrine. In our experience, obtaining fluorescence spectra from experimental samples has some advantages compared to utilizing spectra from an existing library, as they account for a multitude of experimental and instrumental settings. Imaging settings such as different types of lenses or optical filters (Sup. Figure 4, C and D) together with factors within the microenvironment of samples, such as pH or temperature have the potential to alter the fluorescence spectral emissions12. In the presence of unexpected fluorescent signals, spectra can also be selected and visualized directly from the phasor. Phasors facilitate the identification of unexpected independent components and their distinction from the multiple system noises. A noise- free spectrum will appear as a single point on the phasor plot, while a spectrum affected by instrument and electronic noises will mainly appear as a gaussian distribution, centered on the original spectral signal6. Conversely, a randomized noise across the multiple spectral channels will not produce a clustered aggregate of spectra on the phasor. A constant spectral noise, with a distinct spectrum (e.g. a constant light leakage into the system), would produce a distinct phasor cluster and could be selected for unmixing. The phasor plot representation is a 2D- histogram and provides insights into the frequency of occurrence for these signals. These unexpected independent components in samples often appear as "tails" on the phasor distributions (Sup. Figure 11, C). In our HyU graphical interface, clicking on the phasor visualizes the spectra within a small area (9x9 bins by default, with size adjustable from the interface) of the phasor histogram (Figure 1 D). In the example in Sup. Figure 9- 11 we identify 5 distinct endmembers on the Phasor (Sup. Figure 10, C), visualize their spectra identifying Citrine, mRuby, Td- Tomato, mKO2, and one strong autofluorescence signature. The use of Residual Phasor Map (Sup. Figure 11, B) allows for identification of areas in the phasor with high amount of residuals, likely corresponding to a missing endmember in the unmixing. Residual Image Maps (Sup. Figure 11, C) provide a rapid overview of residuals in the image data, for identification of location in the dataset of the missing endmember. + +<--- Page Split ---> + +5) Following the previous question, I wonder about the effect of light scattering on the accuracy of the proposed method. In fig4, the proposed method can be applied for volumetric imaging. I wonder there are consistent fluorescence signals over the depth of tissue. Fluorescence signals occurred in deep tissue regions experience more light scattering, which might occur in spectral distortions. + +ANSWER: We have performed the following additional changes to address this point: + +1. We have added unmixing results from deep imaging performed on zebrafish embryos. (Supplementary Figure 23) +2. We have also added experiments performed on both freshly excised and fixed mouse tissue for further comparison to more highly scattering tissue. (Supplementary Figures 29, 30) +3. We expanded the Supplementary Information with details on mouse lines, fluorescent silica beads characterization, mouse tissue samples preparation, and imaging. + +1. To address the question of light scattering in deep tissue, we added an example of deep imaging in zebrafish, to demonstrate that scattering distortions due to increased depth do not affect the signal and therefore the unmixing, even with signal attenuation (Supplementary Figure 23). As seen in Supplementary Figure 23, the phasor plots of the signals demonstrate a consistent distribution, centered at the same coordinates, even for images acquired deeper into the tissue where the detected spectra decrease in intensity and increase in noise. Following the trend of the absolute intensity average spectra (I) within the center bin shows the attenuation of the signal over depth as the area under the curve decreases. Even with that attenuation, (J) the normalized forms of the average spectra display no difference in shape. The consistency of the average spectra is a strength of the phasor method, which allows for grouping of the similar spectra even with the signal attenuation and noise increase seen in the (K,L) random individual spectra of the pixels across different depths. + +<--- Page Split ---> +![PLACEHOLDER_70_0] + + +## Supplementary Figure 23. Phasor analysis on signal distortion in deep tissue + +Images at different Z- positions of a 3D (x,y,z) dataset of 19 hpf Tg(ubiq:lyn- tdTomato) zebrafish acquired from 0 um to 80 um (relative to the dataset) depth displaying at every 13 z- slices. (A- D) Phasors calculated from the single slices at 0 um, 26 um, 52 um, and 78 um depth. (E- H) Corresponding average intensity images (across the 32 spectral channels) for each z- slice show an expected decrease in fluorescence intensity with depth. (I) Average spectra of the pixels linked to the phasor position bin for the tdTomato fluorescent signature for each of the four presented z- slices (0, 26, 52, 78 um) show a decrease in the spectral area without change in spectral shape as shown by (J) normalizing the average spectra shown in I to each spectrum's maximum value. This demonstrates the spectral shape does not change across different depths (z- planes), while the overall intensity decreases. (K) Randomly selected spectra from the raw spectral image at 0 um (blue) and 26um (red), five spectra for each image and similarly (L) for 52 um (green) and 78um (yellow). Two yellow and three green spectra are not clearly visible because of low signal intensity. + +<--- Page Split ---> + +2. Mouse experiments: we have included two examples of application for the Hybrid Unmixing method: fresh tissue autofluorescence metabolic imaging and fixed tissue fluorescence imaging. These experiments provide support for the reliability of HyU even in tissue that are even more scattering than that of the zebrafish. + +The first experiment involved unmixing autofluorescent signals in freshly excised mouse kidney tissue. The unmixed signals include NADH bound, NADH free, Retinol, Retinoic acid, and Elastin, in correspondence to the intrinsic signals previously unmixed in the zebrafish experiments. In Supplementary Figure 29, we demonstrate that the same independant autofluorescent signatures used in the zebrafish to perform HyU can be utilized in the fresh mouse tissue. Even as the intensities of the autofluorescent signatures drop rapidly within the first \(75 \mu \mathrm{m}\) of tissue, we demonstrate that HyU performs as previously shown in zebrafish. The unmixed autofluorescent signals within the mouse tissue yield spatial patterns (Sup. Fig 29 A, B, C, E) corresponding to those described in literature (https://doi.org/10.1117/1.JBO.19.2.020901, https://doi.org/10.1681/ASN.2016101153, https://doi.org/10.1021/cr900343z) and to those previously shown in zebrafish. Cross- section visualizations (Sup. Fig 29 B and E) show consistency in the unmixed autofluorescence patterns along the depth of the sample (z- direction) until signal drops to noise level. For these notoriously weak autofluorescent signals, intensities fade out at approximately \(75 \mu \mathrm{m}\) depth. + +In the presence of wavefront distortions in the fluorescent spectra, the expected and most likely behavior of the HyU would be a deterioration of the unmixing quality. This deterioration generally results in a non- organized, more uniform re- assignment of intensities across the unmixed channels. When this scenario happens, severe cross- talk is visible across channels. If one were to visualize these results in a 2- D image, it would result in a "white" color where multiple signals are shown together in the same image, due to how multiple colors are combined in the rendering algorithms used for visualizing fluorescence microscopy data. Supplementary Figure 29 panels B and E are single slices of the volume, representing a 1- pixel wide cross- section of the volume, along the XZ and YZ planes respectively. In these cross sections, there is no visible confounding of signals or "white" color, delineating the overlap of multiple fluorescent signals. This suggests that the algorithm, under reasonable imaging conditions, performs as characterized (Sup. Figures 16,17,18,19). This is mainly because fluorescent signals fade to dark before any appreciable distortion affects the system. + +<--- Page Split ---> +![PLACEHOLDER_72_0] + +
Supplementary Figure 29:
+ +Intrinsic fluorescent signatures in fresh kidney tissue of a 7 months Balb- c mouse imaged with 2- photon excitation at \(740\mathrm{nm}\) in a \(150\mu \mathrm{m}\) deep volume. Despite the increasing scattering effect of this mammal tissue with increasing depth, HyU can perform unmixing of intrinsic fluorescent signals. (A) Volumetric rendering of the unmixing results of five intrinsic fluorescent signatures shows results consistent with literature, as visible in the (B- E) orthogonal views of (C) an unmixed (x,y) cross- section of the volume at \(30\mu \mathrm{m}\) depth in the sample and its corresponding (B) (x,z) and (E) (y,z) projections. (D) Averaged autofluorescent signals for each acquired spectral (x,y) section over the \(150\mu \mathrm{m}\) depth of the volume show a sharp decrease of intensities after 75 \(\mu \mathrm{m}\) depth as visible in E, the corresponding (y,z) projection. + +<--- Page Split ---> + +The second experiment involved unmixing a known fluorescent signal among the background signals within the highly scattering mouse tissue by imaging Cy3 beads injected (described in the new Mouse Sample Preparation section below) into fixed mouse tissue. The ground truth spectra of the Cy3 beads is known, measured in pure bead solution (described in the new Fluorescent silica bead characterization section). With this known constant Cy3 fluorescent spectrum, we can demonstrate: + +a. The efficacy of HyU even when fluorescent signatures are buried deep within highly scattering tissue. +b. The effect of tissue scattering on the known Cy3 fluorescent spectrum. + +Supplementary Figure 30 below shows that the Cy3 beads (magenta) are unmixed with the proper spatial profiles (spherical shape) from the autofluorescent (yellow), background (green), and structural signatures (light blue) of the fixed mouse tissue. Similarly to Supplementary Figure 29 B,C,E, there is no evident confounding overlap of signals when imaging deeper in the sample. In this case, with stronger autofluorescent (fixative- related) and fluorescent (beads) signals, signals started fading at \(110\mu m\) depth in the sample. + +In support of our observation that fluorescent spectra, as measured in our commercial instrument, for scattering mammalian samples, are not excessively distorted in their shape, we plot the spectra corresponding to the Cy3 beads at multiple depths (Supplementary Figure 30 F, G), up to \(130\mu m\) deep in the sample, in absolute (Sup. Fig 30 F) and relative (Sup. Fig 30 G) intensity. Absolute peak intensity for some of the deeper spectra is around \(\sim 1300\) Digital Levels, corresponding to \(2\%\) of the full 16 bit dynamic range of the detector, close to the noise level of the instrument. This translates to visibly noisy spectra for deeper z- planes of the sample, as shown in the relative intensity plots (panel G), but does not show evident spectral distortions. + +In regards to the performance of HyU, the unmixed fluorescent signatures remain consistent with expected spatial patterns within the scattering mouse tissue even as the overall intensity drops. Within the imaging depth we could reach in our instrument, the highly scattering nature of the mouse tissue does not affect the performance of HyU, similar to what we previously demonstrated in zebrafish. + +<--- Page Split ---> +![PLACEHOLDER_74_0] + +
Supplementary Figure 30. Extrinsic fluorescent signatures in fixed mouse tissue
+ +We evaluate the performance of HyU in imaging fluorescent signals in a highly scattering fixed kidney tissue of a 7- month- old Balb- c mouse with embedded Cy3 fluorescent beads (Methods) imaged with 2- photon 850nm excitation up to \(150~\mu \mathrm{m}\) deep. (A) Volumetric rendering of the unmixing results of the signals from fixative autofluorescence (autoFL), Cy3 beads, background, and Second Harmonic Generation (SHG). (B- E) Orthogonal views of the same volume for (C) single (x,y) plane of the volume at a depth of \(90~\mu \mathrm{m}\) with cross- sections (yellow hairlines in C) (B) (z,x) of \(18~\mu \mathrm{m}\) and (E) (y,z) of \(4~\mu \mathrm{m}\) respectively showing sections of the unmixed volume containing Cy3 beads at different depths up to \(140~\mu \mathrm{m}\) . (D) Average intensity value for each acquired (x,y) spectral image slice as a function of depth reveals considerable loss of fluorescent signal deeper than \(110~\mu \mathrm{m}\) . (F) Average spectra for each z- plane containing pixels with Cy3 beads signal plotted with absolute intensity (Digital Levels, DL) show decreasing intensity with depth as visible by the area under spectrum. (G) The same averaged spectra are normalized and plotted with Relative Intensity to show the consistency in the spectral shape as a function of depth in reference to Cy3 beads in solution (dashed line). + +<--- Page Split ---> + +3. We expanded the supplementary information to include details on mouse lines, fluorescent silica beads characterization, mouse tissue sample preparation, and imaging: + +## Mouse lines + +Mouse linesMice imaging was approved by the Institutional Animal Care and Use Committee (IACUC) of University of Southern California, Protocol #21311. Experimental research on vertebrates complied with institutional, national and international ethical guidelines. Animals were kept on a 13:11 hours light:dark cycle. Animals were breathing double filtered air, temperature in the room was kept at 68–73 F, and cage bedding was changed weekly. All these factors contributed to minimize intra- and inter- experiment variability. Adult Balb- c mice were euthanized via overdose of isoflurane followed by cardiac puncture. Kidneys were quickly harvested from the mouse, washed in PBS, and cut longitudinally alongside the midsection in order to expose the inner part of the organ. The two halves of the organ were arranged onto a microscope slide for imaging. + +## Fluorescent silica beads characterization + +One fluorescent silica beads solution (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, 1% solid, lot# 1608BRX5) was characterized in its spectral fluorescence emission and physical size. + +10x dilution in PBS of the beads was placed on a no. 1.5 imaging coverglass and spectrally characterized using spectral mode on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using 40x/1.1 W LD C- Apochromat Korr UV- VIS- IR lens utilizing a 2- photon laser at 740 nm to excite fluorescence from the beads, using a 690nm lowpass filter to separate excitation and fluorescence. Spectra obtained from multiple beads with the same label were averaged, producing the reference spectrum reported in Sup. Figure 30 G (dashed line). Fluorescent silica bead size and concentration were determined via nanoparticle tracking analysis (NTA) on the Nanosight NS300 (Malvern Panalytical). Samples were run 5 times and results averaged for final size and concentration values reported. + +## Mouse Sample preparation + +Mouse Sample preparationFor autofluorescent measurements, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in Phosphate Buffered Saline (PBS) to remove residual blood and kept in PBS until imaging preparation. Organs were sectioned in order to image the internal architecture and mounted on a glass imaging dish with sufficient PBS to avoid dehydration of the sample. Following imaging, all samples were fixed in a 10% Neutral Buffered Formalin solution at 4- °C. + +<--- Page Split ---> + +For ex vivo bead characterization in tissue, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in PBS followed by incubation for + +<--- Page Split ---> + +at least 24 hours in \(10\%\) buffered formalin. The kidney was then removed from the fixative and sectioned into smaller \(\sim 5 \times 5 \times 5 \mathrm{mm}\) pieces for imaging. A fluorescent silica beads stock (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, \(1\%\) solid, lot# 1608BRX5) and previously characterized was prepared using a 10x dilution of the fluorescent beads from their stock concentration. Beads were injected in the sample using 50ul of these solutions loaded into a 0.5mL syringe with a 28g needle. The kidney sections were then placed in imaging dishes with a small volume of PBS to keep the samples hydrated prior to imaging. + +## Image Acquisition. + +Images were acquired on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using \(40 \times / 1.1 \mathrm{W}\) LD C- Apochromat Korr UV- VIS- IR lens at \(28 - 0C\) . + +Samples of Gt(cltca- Citrine), Tg(ubiq:lyn- tdTomato), Tg(fli1::mKO2), and Tg(ubiq:Lifeact- mRuby), were simultaneously imaged with 488 nm and 561 nm laser excitation, for citrine, tdTomato, mKO2, and mRuby. A narrow 488 nm/561 nm dichroic mirror was used to separate excitation and fluorescence emission. Samples were imaged with a 2- photon laser at 740 nm to excite autofluorescence, using a 690nm lowpass filter to separate excitation and fluorescence. + +Samples of mouse kidney tissue were imaged with 2- photon excitation at 740 nm or 850 nm with a \(690 +\) nm lowpass filter, at \(37 - 9C\) incubation. + +For all samples, detection was performed at the full available range (410.5- 694.9nm) with 8.9nm spectral binning. + +Reviewer #3 (Remarks to the Author: Strength of the claims): + +This work demonstrates the superiority of the proposed method using computer simulation and experimental data. The authors clearly claim that the proposed method is more efficient and robust than conventional linear spectral unmixing methods. + +ANSWER: We thank this reviewer for the constructive comments and helping us improve the manuscript. + +Reviewer #3 (Remarks to the Author: Reproducibility): + +The authors provide the code and data used in the manuscript. This allows other people to reproduce these results. And the dataset used in this work is appropriate for the purpose of the study. + +ANSWER: We thank this reviewer for the insightful remarks. + +<--- Page Split ---> + +Reviewers comments: + +Reviewer #1: + +Remarks to the Author: Overall significance: + +The results are significant and as a new method of analysis of hyperspectral data - it adds to the community. The authors have replied to most of my questions. I do think they need to add a little more to explain how this method is different from the phasor and linear combination method. I am a bit conflicted as to usual readers - the difference between phasor as analysis method and phasor as encoder as to decrease the data from \(10^{\wedge}7\) to \(10^{\wedge}4\) may not be clear. The authors comment about collage autofluorescence - while SHG is certainly true for collagen 1 it is not for other types of collagens - some of them can be highly fluorescent. About question 6 - While I agree that mathematically a point on the line between the position of two other phasor points may be unlikely. That is true for the center of the distribution. It is definitely not true when S/N creates a distribution. In that case the points can be along that line. If the authors propose only using the center of the distribution - that needs to be mentioned clearly. About FAD - I can see why laser power can be a valid argument. I do not agree with the effect of zooming. Lets say an area has a particular NADH/FAD distribution. Why would it matter if we zoom into a smaller part of that or a larger area? Unless zooming in separates the areas of high NADH and high FAD spatially and they appear at different phasor positions. That brings out a separate problem. If HyU is zoom dependent - then how will anyone know if they are getting the proper distribution or not? Finally I do like the new figures. + +Remarks to the Author: Impact: + +I would suggest Nature communications or Scientific reports. The authors use phasor- but not to it's full capacity. The paper will indeed influence the field. However, I do feel publication in Nature methods can influence it in a way that may not be the best for the field. + +Remarks to the Author: Strength of the claims: The work is convincing. + +Remarks to the Author: Reproducibility: The paper is very detailed and can be reproducible. + +Reviewer #2: + +Remarks to the Author: Overall significance: + +In their revised manuscript "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence", the authors convincingly highlight the achievements/unique features of the further- developed + +<--- Page Split ---> + +algorithm for multiplexed imaging of hyperspectral data, expanding its use to low signal- to- noise ratio of real data, moving towards two- photon microscopy. Especially, they made particular efforts in demonstrating the power and the limitations of the algorithm when applied in highly- scattering tissue or when the number of detection channels is limited, providing an excellent and useful benchmarking for a broad life sciences audience interested in imaging and microscopy. + +Although, I think, of high interest and definitely an important next step, I do agree with the authors that intravital imaging of highly scattering organs is a major challenge and can be the subject of future work. I fully recommend the present manuscript for publication in its present form. + +Remarks to the Author: Impact: + +As mentioned above, with the new added data, the presented algorithm will find broad applicability for all sorts of data, which typically need to deal with low signals. + +Remarks to the Author: Strength of the claims: + +In the current form, the revised manuscript provides all necessary evidence for the unique power of the HyU algorithm. + +Remarks to the Author: Reproducibility: + +Beyond of statistics, I find the broad range of applications, excitation schemes and microscopy types particularly important to emphasize the general validity of the algorithm. + +Reviewer #3: + +Remarks to the Author: Overall significance: + +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. And the authors appropriately discussed the proposed method by comparing previous techniques. + +Remarks to the Author: Strength of the claims: + +The revised manuscript has clearly addressed all of my previous comments and concerns. + +Reviewers comments: + +We would like to thank all Reviewers for their constructive criticism that helped considerably to improve the quality of this manuscript. + +Reviewer #1 (Remarks to the Author: Overall significance): + +The results are significant and as a new method of analysis of hyperspectral data - it adds to the community. + +We thank the reviewer for this comment. + +The authors have replied to most of my questions. I do think they need to add a little more to explain how this method is different from the phasor and linear combination method. I am a bit conflicted as to + +<--- Page Split ---> + +usual readers – the difference between phasor as analysis method and phasor as encoder as to decrease the data from \(10^4\) to \(10^4\) may not be clear. + +We have refined our previous explanation (yellow highlight) of the differences between the Standard Phasor analysis method and the Hybrid Unmixing method in the introduction. We have now expanded this (green highlighted portions) to address the specific concern about the difference between the phasor method as an analysis and as an encoder: + +We have developed Hybrid Unmixing (HyU) as an answer to the challenges that have limited the wider acceptance of HFI for in vivo imaging. HyU combines our previous phasor hyperspectral approach26 with traditional unmixing algorithms to untangle the fluorescent signals more rapidly and more accurately from multiple exogenous and endogenous labels. The phasor approach26 is a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis27- 29. In HyU, the phasor approach provides spectral compression, denoising, and computational reduction that simplifies both pre- processing30 and unmixing31- 33 of HFI datasets. Standard Phasor analysis26,27,34- 41 is fully supervised and requires a manual selection of regions or points on the phasor plot, a graphical representation of the transformed spectra. In contrast, HyU utilizes phasor processing as an encoder to aggregate similar spectra onto the phasor plot, reducing even the largest volumetric datasets so that unmixing algorithms, such as LU, can be applied on a far smaller number of elements (the number of pixels on the phasor plot). Furthermore HyU provides unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity. Our results show that HyU offers three key advantages: (1) improved unmixing over conventional LU, especially for low intensity images, down to 5 photons per spectra; (2) simplified identification of independent spectral components; (3) dramatically faster processing of large datasets, overcoming the typical unmixing bottleneck for in vivo fluorescence microscopy. + +<--- Page Split ---> + +We believe this further extended description, obeying the limited word count of the manuscript sufficiently clarifies the difference between Standard Phasor analysis and HyU. The graphical representation in Figure 1 clarifies this: notice the absence of any typical selection on the phasor plot, either in the form of Region of Interest processing or in the form of linear geometric unmixing, both factors that are essential for Standard Phasor analysis. + +This combination of description and Fig 1 (and absence of Standard Phasor indicators) should be sufficient to avoid any confusion in the reader. + +![PLACEHOLDER_81_0] + + +The authors comment about collage autofluorescence – while SHG is certainly true for collagen 1 it is not for other types of collagens – some of them can be highly fluorescent. + +We thank the reviewer for this insight. While we agree that some types of collagen can be highly fluorescent, the references we cited in our previous answer (duplicated below) demonstrate that depending on the imaging conditions, collagen may not be visible. We did not observe any such signal within the regions of the specific samples imaged in this work, under our imaging conditions (reported in Table S1 supplementary). + +Multiple references in literature (PMC4337962 / PMID: 22402635, PMC123202 / PMID: 12177437, PMC4337962 / PMID: 22402635) report 2- photon fluorescence of collagen to be very low at 740 nm... + +<--- Page Split ---> + +About question 6 – While I agree that mathematically a point on the line between the position of two other phasor points may be unlikely. That is true for the center of the distribution. It is definitely not true when S/N creates a distribution. In that case the points can be along that line. If the authors propose only using the center of the distribution – that needs to be mentioned clearly. + +Owing to the extended length of the Response to Referees, we tried summarizing the common points to the questions of each reviewer, where possible, in the first comment. In this case, the noise aspect in question was expansively described in the initial comment “Information loss and noise”. + +We do not propose only using the center of the distribution and we account for noise as explained when presenting the “3.3 billion simulations used to assemble Supplemental Figures 16, 17, 18, 19. + +Our answer to question 6 covers two main subjects: + +i) acknowledging that there are specific cases where mathematically, linear unmixing would not workii) acknowledging the likelihood of many fluorophores and their combinations to occupy the same location (whether or not we are referring to the center or the full distribution corresponding to a fluorescent signature). In this scenario, where multiple components may be present in the exact same phasor location, we comment that the amount of error that may arise from this situation (encoding loss) is most likely overwhelmed by the error introduced by the noise instead. + +We report here the second part of question 6: + +However, we have demonstrated in our reply to the first comment and in the numerous additional simulations (Supplemental Figure 16, 17, 18, 19) that noise affects the unmixing results much more than the encoding loss of the phasor method. + +The first comment here referenced states: + +Information loss and noise. We are aware that the phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original “pure” data. This is evident in the scenario of very high- quality signals, but in the case of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data makes phasor a valuable tool for fluorescence microscopy (both FLIM and hyperspectral); this point is reported by multiple groups using phasors (Gratton: + +<--- Page Split ---> + +https://www.pnas.org/doi/full/10.1073/pnas.1108161108, https://escholarship.org/content/qt5g279175/qt5g279175. pdf, Vicidomini: https://www.nature.com/articles/ncomms7701, Gerritsen: https://pubmed.ncbi.nlm.nih.gov/22714302/, Fraser: https://pubmed.ncbi.nlm.nih.gov/28068315/), and more recently nicely described in the work of Scipioni et al ( https://www.nature.com/articles/s41592- 021- 01108- 4 ) "However, microscopy data are affected by a number of other detrimental factors, [...] which results in decreased signal- to- background ratio (SBR). [...] the phasor approach shows increased precision (Fig. 1f,i), decreased bias (Fig. 1e,h) and a three orders of magnitude lower execution time (Fig. 1g,j) with respect to the least mean square (LMS) fitting procedure". + +To support the validity of this hybrid unmixing approach, we have assembled a complex simulation matrix representing the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built on top of the complex simulation we designed (further described below in our answer to this reviewer's question 14), which is soon to be published in a separate manuscript. This simulation accounts for a multitude of real- world noises in experimental samples that are regularly imaged (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). The results of applying our approach on an array of simulations under different conditions of SNR, number of filters applied, in comparison to standard Linear Unmixing are now reported in Supplementary Figures 16, 17, 18, and 19. We further describe how multiple components are affected by our hybrid unmixing approach in our answer to question 17 for this reviewer. + +About FAD – I can see why laser power can be a valid argument. I do not agree with the effect of zooming. Lets say an area has a particular NADH/FAD distribution. Why would it matter if we zoom into a smaller part of that or a larger area? Unless zooming in separates the areas of high NADH and high FAD spatially and they appear at different phasor positions. That brings out a separate problem. If HyU is zoom dependent – then how will anyone know if they are getting the proper distribution or not? + +We worry that the reviewer is misunderstanding our intended meaning of "zooming in to image a smaller region". It is not merely cropping the large image to display a smaller field of view (FoV), in which case the reviewer would be correct. Instead, in the optics of confocal laser scanning microscope, "zooming" by using a higher magnification objective or by scanning a smaller region of the specimen delivers more exciting light to the FoV, increasing it by the square of the zoom or magnification of the objective lens. Thus, zooming in by two- fold would increase the fluorescence excitation by four- fold for one- photon excitation, and by 16- fold for two- photon excitation. + +<--- Page Split ---> + +We hope that this clarifies the issue, but if the reviewer would like to explore this further, we direct them to the excellent book, Principles of Fluorescence Spectroscopy (Lakowicz), section 18.2 + +"The physical origin of the 2PE cross-sections can be understood by some simple considerations. For one- photon absorption the number of photons absorbed per second \((NA_{1})\) is given by \(NA_{1}(photon / s) \sigma_{1}(cm^{2})I(photon / cm^{2}s)\) (18.1) where \(I\) is the intensity and \(\sigma_{1}\) is the cross- section for one- photon absorption. The units are given within the parentheses. The cross- section in \(cm^{2}\) is multiplied by the number of photons passing near the molecule per second to yield the number of photons absorbed per second. To obtain NA1 in photons per second the cross- section must be in units of \(cm^{2}\) . Now consider two- photon absorption. The number of photons absorbed per second by 2PE \((NA_{2})\) is given by \(NA_{2}(photons / s) \sigma^{2}I^{2}(photons / cm^{2}s)^{2}\) (18.2) In order for the units to match on both sides of eq. 18.2 the units of \(\sigma_{2}\) must be \(cm^{4}s / photon\) . Similarly, for 3PE, \(NA_{3}(photons / s) \sigma_{3}I^{3}(photons / cm^{2}s)^{3}\) (18.3) and the units of a three- photon cross- section are \(cm^{6}s^{2} / photon^{2}\) . + +We quote the Principles of Fluorescence Spectroscopy (Lakowicz), section 1.7: "The steady- state intensity (of the fluorophore) is given by + +\[I_{SS} = \int_{0}^{\infty}I_{0}e^{-t / \tau}dt = I_{0}\tau \quad (1.16)\] + +The value of 10 can be considered to be a parameter that depends on the fluorophore concentration and a number of instrumental parameters." + +While it is true that the true spectral signature should not change depending on the zoom or power, the amount of signal depends not only on the concentration of the fluorophores, and the excitation wavelength used, but also on the zoom and excitation power. + +These factors are major contributors to the measured intensity of the fluorophore, which can alter both the SNR and could alter the resulting analysis. The chief advantage of our method is to overcome the low signal that occurs during these types of acquisitions. If signal cannot be detected clearly (signal approaches the noise), it is extremely challenging if not impossible to perform any kind of analysis. + +The reviewer goes on to ask: That brings out a separate problem. If HyU is zoom dependent – then how will anyone know if they are getting the proper distribution or not? + +<--- Page Split ---> + +HyU, like any fluorescent microscopy imaging experiment, requires proper experimental settings based on the scientific/experimental scope and probes utilized. The absence of a signal cannot be taken as the absence of an analyte in HyU or any other analysis approach. + +To obtain more meaningful results, in fluorescence microscopy, imaging area (zoom), pixel dwell time and laser power will need to be properly set. There are multiple strategies for validating if experimental settings are proper. In the manuscript, we show the pipeline for using phasors to identify presence of fluorophores with practical examples to assist the readership in proper experimental design (see Supplementary Figure 11 and more extensively in Supplementary Note 1: Identification of spectra and new components with HyU). + +Finally I do like the new figures. + +We thank the reviewer for this comment. + +Reviewer #1 (Remarks to the Author: Impact): + +I would suggest Nature communications or Scientific reports. The authors use phasor- but not to it's full capacity. The paper will indeed influence the field. However, I do feel publication in Nature methods can influence it in a way that may not be the best for the field. + +We thank the reviewer for this comment. + +Reviewer #1 (Remarks to the Author: Strength of the claims): The + +work is convincing. + +We thank the reviewer for this comment. + +Reviewer #1 (Remarks to the Author: Reproducibility): The + +paper is very detailed and can be reproducible. + +We thank the reviewer for this comment. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author: Overall significance): + +In their revised manuscript "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence", the authors convincingly highlight the achievements/unique features of the further- developed algorithm for multiplexed imaging of hyperspectral data, expanding its use to low signal- to- noise ratio of real data, moving towards two- photon microscopy. Especially, they made particular efforts in demonstrating the power and the limitations of the algorithm when applied in highly- scattering tissue or when the number of detection channels is limited, providing an excellent and useful benchmarking for a broad life sciences audience interested in imaging and microscopy. + +Although, I think, of high interest and definitely an important next step, I do agree with the authors that intravital imaging of highly scattering organs is a major challenge and can be the subject of future work. I fully recommend the present manuscript for publication in its present form. + +We thank this reviewer for this comment. Reviewer + +#2 (Remarks to the Author: Impact): + +As mentioned above, with the new added data, the presented algorithm will find broad applicability for all sorts of data, which typically need to deal with low signals. + +Reviewer #2 (Remarks to the Author: Strength of the claims): + +In the current form, the revised manuscript provides all necessary evidence for the unique power of the HyU algorithm. + +Reviewer #2 (Remarks to the Author: Reproducibility): + +Beyond of statistics, I find the broad range of applications, excitation schemes and microscopy types particularly important to emphasize the general validity of the algorithm. + +Reviewer #3 (Remarks to the Author: Overall significance): + +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the + +<--- Page Split ---> + +conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. And the authors appropriately discussed the proposed method by comparing previous techniques. + +We thank the reviewer for this comment. + +Reviewer #3 (Remarks to the Author: Strength of the claims): + +The revised manuscript has clearly addressed all of my previous comments and concerns. + +We thank the reviewer for this comment. + +<--- Page Split ---> diff --git a/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..475612e9edcf4fca5906a4ba221acd58411bdea8 --- /dev/null +++ b/peer_reviews/98a7f7399d69c3b07697f2560f446c1e043a7929fa7b8d85ef58b7cf97af6536/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1739 @@ +<|ref|>title<|/ref|><|det|>[[60, 35, 510, 88]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[62, 123, 330, 150]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[57, 225, 937, 291]]<|/det|> +# HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence + +<|ref|>image<|/ref|><|det|>[[57, 653, 240, 700]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 650, 953, 697]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to + +<|ref|>text<|/ref|><|det|>[[57, 697, 944, 825]]<|/det|> +the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 122, 533, 139]]<|/det|> +Reviewer #1 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[105, 154, 945, 274]]<|/det|> +The paper by Chiang et al titled "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence" has a lot of details that are really attractive. This includes the possibility of multiplexing using a combination of Phasor and linear unmixing and potential for understanding the distribution pattern for multiple fluorophores, both endogenous and exogenous ones in the live system. The authors provide software based on this principle and detailed instruction to run the system. This is really attractive for the biological community as this does not require a specialized instrument and can use a hyperspectral detector with a linear array which is more commonly available to the researchers. + +<|ref|>text<|/ref|><|det|>[[104, 289, 949, 544]]<|/det|> +However, there is a major flaw that concerns me the most. The authors use only one harmonics to do phasor transformation and then linear unmixing, as stated in their mathematical arguments. This should be fine up to three components. For two components a pixel which has contribution of those components, it's phasor position is along the line joining those two components. In case of three it will be inside the triangle created by the three individual components. This isn't true for four components or higher. In four components, the position of an image phasor point can be either contributed to all four components or just three - as it will always be within a triangle. This has been shown previously by Dr. Enrico Gratton's group (PMID: 32235070). In that case another harmonic needs to be calculated to identify and explain if there are three or four components. The examples and analysis provided in this paper only involve a single harmonic - and that makes it impossible to specify the difference between image phasor points in the middle of the phasor cloud with multiple species (Fig 5F). My main concern is that use of a single harmonic assume that all of the components are present in an image pixel whose phasor coordinate is within the pentagon with the vertices occupied by the five components. It may be a very small contribution based on the fractional intensity - but it is there. This may or may not be true depending on pixel size, presence of components and basically the type of the sample. This argument needs to be resolved as I feel this is a fundamental approach to phasor and its limitation when only one harmonic is calculated. + +<|ref|>text<|/ref|><|det|>[[106, 560, 437, 576]]<|/det|> +Other comments and concerns follow below: + +<|ref|>text<|/ref|><|det|>[[102, 577, 936, 968]]<|/det|> +1. The authors provide a spectra.txt files for the unmixing. How was that obtained. How to calculate and save the data from samples having only one fluorophores? +2. I did not see any mention of collagen fluorescence when excited at \(740~\mathrm{nm}\) . That should be a component in the autofluorescence category. +3. What happens to FAD? That can be excited at \(740~\mathrm{nm}\) (PMID: 11964266). +4. About Bound NADH - does the spectra change based on the proteins it binds to? +5. What is the distance of separation of the pure components in the phasor space that allow for successful linear unmixing. I presume at some point the S/N will make it difficult if the spectra of the components are too close. +6. What about when the linear unmixing won't work? For example, a case where the individual components lie in line in the phasor space. +7. Coming back to Q1. - Prior knowledge of the components - How are they calculated? Where are the coordinates stored? Are only the center of the phasor cloud used or the whole distribution? +8. I do like the point mentioned in lines 10-20 in page 2. Spectral imaging and deconvolution is absolutely necessary. +9. Lines 30-40, page 2 - missing references about the different noise. +10. The linear deconvolution of the phasor space involves fractional intensity and not the actual fraction - something that I found missing in the discussion. +11. How do 5 photons/spectra work with Poisson statistics and associated uncertainty? +12. Does the Elastin spectrum change on crosslinking in a tissue compared to the solution? +13. Td-Tomato (PMID 19127988) and mRuby (PMID 23459413) can be excited with a \(740~\mathrm{nm}\) two-photon excitation. I am curious how the authors did not observe that in Figure 6. +14. What determines how much spatial denoising needs to be used? Spatial denoising indeed doesn't affect the intensity image - but it does affect the phasor mapped image - something that hasn't been discussed at all. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[101, 85, 940, 257]]<|/det|> +15. Figure 1 D-E – this is strictly not true. Once you transfer to phasor – the information remaining for the spectra is the FWHM and the peak/center – so how does the proper spectra being calculated in figure E? +16. The reduction of data from \(10^{A7}\) to \(10^{A4}\) . How much of that is related to spectral denoising and how much is related to the transformation to phasor? +17. Page 4 line 19 – after two-components – what happens with three/four and their possible combinations? +18. One of the uses of HyU is for low light level and long term imaging. What happens to the deconvolution if there is bleaching? This is a minor concern. +19. How to create the spectral libraries in the software provided by the authors (page 15, line 29-30)? +20. I do feel the references can be expanded for the phasor analysis of the multicomponent systems from other labs. + +<|ref|>text<|/ref|><|det|>[[106, 290, 443, 307]]<|/det|> +Reviewer #1 (Remarks to the Author: Impact): + +<|ref|>text<|/ref|><|det|>[[105, 323, 820, 341]]<|/det|> +The paper will influence the community - but the discrepancies need to be cleared and explained. + +<|ref|>text<|/ref|><|det|>[[106, 357, 552, 374]]<|/det|> +Reviewer #1 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[105, 390, 920, 425]]<|/det|> +The main concern is the linear additivity of phasor space and their implementation in this paper. Use of a single harmonic should not be enough for anything more than three components. + +<|ref|>text<|/ref|><|det|>[[105, 441, 501, 458]]<|/det|> +Reviewer #1 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[106, 475, 934, 526]]<|/det|> +I do think the data is reproducible as the imaging is done using a commercial microscope and the authors provide an software to do so. There are details that is missing that need to be provided for the use. This includes calculation and storage of single components for the analysis. + +<|ref|>text<|/ref|><|det|>[[105, 560, 533, 576]]<|/det|> +Reviewer #2 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[103, 593, 940, 864]]<|/det|> +The manuscript of Hsiao Ju Chang et al (from the lab of Prof Cultrale) deals with dynamic (time- lapse) multiplexed imaging and offers a global- based solution for spectral unmixing of hyperspectral imaging data. Therefore, the authors improve the previously published algorithm HySP (Cultrale et al, Nat. Meth. 2017), which uses dimensionality reduction via the phasor approach (normalized discrete Fourier transformation of the hyperspectral 4D fluorescence data). They achieve this improvement by integrating in HySP a linear unmixing of the expected spectral signatures in the phase domain (HyU) - including both extrinsic signals (fluorescence proteins) and intrinsic signals (NAD(P)H, retinol, elastin, etc.). The dimensionality reduction of the phasor approach implies also a global analysis of the spectra (i.e. appreciates similarities of the spectra per voxel) and by that better deals with low signals. A thorough characterization of the laser, detector, read background noise and of their distribution type (Poisson, Gaussian, etc.) and implementation for denoising and additional reference- based preprocessing (SEER, Shi et al, Nat. Commun. 2020) improves not only the image quality but also the success of the hyperspectral unmixing of 8 or 9 emission (intrinsic and extrinsic) signals, at high computation speeds, as impressively demonstrated on simulated data and on time- lapse imaging data of multiple- reporter zebra fish larvae. While being of great interest for the live imaging community, in my opinion, the manuscript needs additional experimental, algorithmic and background (citation of previous work) information to unfold the full potential, as described in detail in the following. + +<|ref|>text<|/ref|><|det|>[[105, 881, 443, 897]]<|/det|> +Reviewer #2 (Remarks to the Author: Impact): + +<|ref|>text<|/ref|><|det|>[[106, 915, 916, 966]]<|/det|> +The relevance of the question/need for simultaneous spectrally multiplexed fluorescent microscopy to allow dynamic (time- lapse) multi- color imaging is tremendous, however, certainly going far beyond the field of developmental biology and zebra fish larvae imaging. This need has been previously recognized in the frame of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 85, 931, 204]]<|/det|> +intravital multi- photon imaging (not hyperspectral), with impact for cancer research (Entenberg et al, 2011), immunology and neurosciences/neuroimaging, just to mention a few examples. Specifically, there have been solutions proposed and demonstrated for dynamic in vivo fluorescence imaging, including unmixing algorithms apart of the state- of- the- art linear unmixing (Rakhymzhan et al, Sci Rep 2017), in which up to 8 extrinsic and intrinsic signals are simultaneously distinguished, while dealing with low SNRs of multi- photon microscopy still remained a challenge. Including this information in the introduction is key, in order to demonstrate the potential general relevance of the present work and to awake a real interest for a broad readership. + +<|ref|>text<|/ref|><|det|>[[105, 222, 930, 273]]<|/det|> +In line with this, it is crucial to demonstrate the power of the presented algorithm for unmixing also intravital multi- photon imaging data in optically more challenging tissues and organisms, which need to deal with much lower signals and SNR values, especially due to massive scattering and wave- front distortions in mammal tissue. + +<|ref|>text<|/ref|><|det|>[[105, 290, 943, 391]]<|/det|> +Referring to the algorithm itself and to its characterization, the evolution from hyperspectral multiplexed imaging using the phasor approach HySP (Cultrale et al, 2017, Nat Meth), enhanced by preprocessing the data to account for various experimental noise via SEER (2020, Nat Commun) and finally by applying linear unmixing in the hyperspectral phase space, bringing additional significant accuracy to the unmixing capacity of the data is currently not clear in the manuscript and needs to be elaborated in the introduction, to emphasize the novelty of the present work. + +<|ref|>text<|/ref|><|det|>[[105, 424, 552, 441]]<|/det|> +Reviewer #2 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[105, 459, 796, 476]]<|/det|> +A. Referring to the broad applicability of the algorithm and the interest for a large community: + +<|ref|>text<|/ref|><|det|>[[105, 477, 945, 544]]<|/det|> +A.1. As previously mentioned, in order to prove the value of the approach presented in this manuscript, multiplexed time-lapse imaging in a mammal (adult mouse or rat or human) tissue is key and experimental data on this need to be added to the manuscript. I believe, one 4D (3D + time) imaging example showing 8-9 distinct emission signals would be absolutely convincing. + +<|ref|>text<|/ref|><|det|>[[106, 562, 389, 577]]<|/det|> +B. Referring to the unmixing approach: + +<|ref|>text<|/ref|><|det|>[[105, 579, 940, 645]]<|/det|> +B.1. In order to judge the added value of the integration of linear unmixing and of reference extrinsic and intrinsic spectral signatures on the performance of unmixing, a thorough comparison with the previously available HySP (Cultrale et al, 2017) needs to be provided, additionally to the comparison to state-of-the-art linear unmixing algorithms already included in the manuscript. + +<|ref|>text<|/ref|><|det|>[[105, 662, 948, 814]]<|/det|> +B.2. A central advantage of the here presented approach is the capacity of dealing even with low signals, i.e. unmixing even low endogenous signals, such as NAD(P)H, even free and bound - having extremely similar emission spectra (one reason why their fluorescence lifetime has been used to resolve the two states). The authors show the improvement referring to number of photons per spectrum, however, in order to judge the true improvement brought by the algorithm for real imaging data (which includes background with diverse types of noise distributions), the unmixing quality needs to be related to the signal-to-noise (SNR) ratio per voxel. While mentioning SNR in the text, no values or comparison are provided in this sense - it is important to mention how the SNR as such (not only the number of photons per spectrum) impacts on the spectral resolution, i.e. how similar can be two spectra at a certain SNR to be able to still resolve them? + +<|ref|>text<|/ref|><|det|>[[105, 832, 935, 950]]<|/det|> +B.3. A corner stone in acquiring better unmixing is the availability of appropriate reference spectral signatures. Whereas the current software provides the spectra necessary for the data shown in the manuscript and gives the opportunity for the users to identify signatures in their own data, the manuscript remains elusive of how the user can differentiate between a real spectral signature and different types of optical or electronical background and interferences - as well known from the use of the phasor approach in fluorescence lifetime imaging, a major challenge when dealing with experimental noisy imaging data in the frequency (phase) domain. The manuscript would benefit from including such a guide to validate the capacity for external use of the algorithm. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 86, 947, 172]]<|/det|> +B.4. Finally, fully agreeing with the authors that the number of detectors may be varied, depending on the imaged sample type and on the excitation strategy, in order to acquire an emission signal at all, an analysis of how the number of detectors (channels) impacts on the resolution between different signatures (spectra) is needed also for less than 32 detectors (4 to 6 channels being the reality in many labs due to truly low fluorescence signals in deep tissue, e.g. of mice or of humans). + +<|ref|>text<|/ref|><|det|>[[105, 205, 503, 221]]<|/det|> +Reviewer #2 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[105, 240, 945, 273]]<|/det|> +The current version of the HySP platform was easy to use and the provided sample data delivered similar results as those shown in the manuscript. + +<|ref|>text<|/ref|><|det|>[[105, 306, 533, 322]]<|/det|> +Reviewer #3 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[105, 340, 943, 459]]<|/det|> +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. However, I found that there are some confusing points to be addressed clearly to publish this manuscript in Nature Portfolio. + +<|ref|>text<|/ref|><|det|>[[105, 461, 191, 475]]<|/det|> +Comments: + +<|ref|>text<|/ref|><|det|>[[105, 477, 916, 544]]<|/det|> +1) Hyperspectral phasor compresses spectral dimension by exploiting real and imaginary parts of Fourier transformation. Moreover, there were reports that hyperspectral phasor could be applied for multiplexed fluorescence imaging. If there are any advantages of combining phasor and spectral unmixing methods, please describe them clearly in the Introduction. + +<|ref|>text<|/ref|><|det|>[[105, 545, 944, 612]]<|/det|> +2) If I understood correctly, numbers of photons (For instance, 5 photons per spectral in the last paragraph in Introduction) were calculated from the computer simulation. If so, this quantitative value is significantly affected by the noise levels used in the simulation. Therefore, it would be good to add these values were obtained from the simulation for clarity. + +<|ref|>text<|/ref|><|det|>[[105, 612, 943, 679]]<|/det|> +3) The authors addressed that the HyU method is more computationally efficient than the linear spectral unmixing method. This is true as the spectral dimension was reduced in Hyperspectral Phasors and histogram binning. However, these spectral compression and denoising also require computational power. Does the proposed method is more efficient when the entire process is considered? + +<|ref|>text<|/ref|><|det|>[[105, 680, 936, 780]]<|/det|> +4) For spectral unmixing, it seems to use the reference signals obtained from pure fluorophores. What happens if there are unknown fluorescence signals? Can the proposed method be applied for blind spectral separation? +5) Following the previous question, I wonder about the effect of light scattering on the accuracy of the proposed method. In fig4, the proposed method can be applied for volumetric imaging. I wonder there are consistent fluorescence signals over the depth of tissue. Fluorescence signals occurred in deep tissue regions experience more light scattering, which might occur in spectral distortions. + +<|ref|>text<|/ref|><|det|>[[105, 815, 552, 831]]<|/det|> +Reviewer #3 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[105, 850, 918, 900]]<|/det|> +This work demonstrates the superiority of the proposed method using computer simulation and experimental data. The authors clearly claim that the proposed method is more efficient and robust than conventional linear spectral unmixing methods. + +<|ref|>text<|/ref|><|det|>[[105, 917, 503, 933]]<|/det|> +Reviewer #3 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[102, 951, 895, 968]]<|/det|> +The authors provide the code and data used in the manuscript. This allows other people to reproduce these + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 87, 728, 103]]<|/det|> +results. And the dataset used in this work is appropriate for the purpose of the study. + +<|ref|>sub_title<|/ref|><|det|>[[115, 379, 375, 395]]<|/det|> +## Response to Reviewers' Comments + +<|ref|>text<|/ref|><|det|>[[114, 445, 870, 522]]<|/det|> +We appreciated the positive response to our manuscript submission. We would like to thank the reviewers and editors for constructive comments and suggestions that helped improve the manuscript. We have addressed the comments, performed additional quantifications and experiments and revised the re- submission accordingly. + +<|ref|>sub_title<|/ref|><|det|>[[231, 575, 667, 592]]<|/det|> +## Reviewer #1 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[114, 626, 875, 760]]<|/det|> +The paper by Chiang et al titled "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence" has a lot of details that are really attractive. This includes the possibility of multiplexing using a combination of Phasor and linear unmixing and potential for understanding the distribution pattern for multiple fluorophores, both endogenous and exogenous ones in the live system. The authors provide software based on this principle and detailed instruction to run the system. This is really attractive for the biological community as this does not require a specialized instrument and can use a hyperspectral detector with a linear array which is more commonly available to the researchers. + +<|ref|>text<|/ref|><|det|>[[114, 780, 875, 973]]<|/det|> +However, there is a major flaw that concerns me the most. The authors use only one harmonic to do phasor transformation and then linear unmixing, as stated in their mathematical arguments. This should be fine up to three components. For two components a pixel which has contribution of those components, it's phasor position is along the line joining those two components. In case of three it will be inside the triangle created by the three individual components. This isn't true for four components or higher. In four components, the position of an image phasor point can be either contributed to all four components or just three - as it will always be within a triangle. This has been shown previously by Dr. Enrico Gratton's group (PMID: 32235070). In that case another harmonic needs to be calculated to identify and explain if there are three or four components. The examples and analysis provided in this paper only involve a single harmonic - and that makes it impossible to specify the difference between + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 85, 874, 219]]<|/det|> +image phasor points in the middle of the phasor cloud with multiple species (Fig 5F). My main concern is that use of a single harmonic assume that all of the components are present in an image pixel whose phasor coordinate is within the pentagon with the vertices occupied by the five components. It may be a very small contribution based on the fractional intensity – but it is there. This may or may not be true depending on pixel size, presence of components and basically the type of the sample. This argument needs to be resolved as I feel this is a fundamental approach to phasor and its limitation when only one harmonic is calculated. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 147, 877, 223]]<|/det|> +ANSWER: We thank the reviewer for the insightful comments and for providing us an opportunity to clarify. In regard to the major concern, the use of a single harmonic, this hybrid approach uses the phasor as an aggregator of similar spectra while maintaining the wavelength dimension of the original data. + +<|ref|>text<|/ref|><|det|>[[140, 242, 866, 456]]<|/det|> +Spectral similarity unmixing. The unmixing is performed over the spectral dimension (in this case 32 channels), by aggregating similar spectra of the original data, as explained in Supplementary Material "Hybrid Unmixing - Linear Unmixing" and further demonstrated in the pseudo- code in "HyU Algorithm". The spectra are not calculated from phasor, rather aggregated from the original spectral cube dataset. Our strategy is less phasor- esque than the traditional geometry based phasor approach (PMID: 32235070 and 22714302) where the approach uses the phasor geometry to unmix the components. The geometrical phasor approach only uses the coordinates G, S at a specific harmonic, omitting the wavelength dimension in the final unmixing process. As such, like the reviewer correctly states, it is a limiting strategy that makes it impossible to specify the difference between image phasor points in the middle of the phasor cloud with multiple species, requiring multiple harmonics. + +<|ref|>text<|/ref|><|det|>[[144, 469, 882, 566]]<|/det|> +With HyU, we utilized the phasor as an encoder, to aggregate similar spectra, because of our familiarity with the approach, but, in principle, other encoding strategies could be utilized. The relative positions and geometry of phasor bin coordinates, from the unmixing algorithm perspective, do not directly matter, as the unmixing is performed with a 32 channel endmember over a 32 channel experimental spectrum ("Linear Unmixing" in Supp. Material). + +<|ref|>text<|/ref|><|det|>[[144, 584, 754, 602]]<|/det|> +We improved the text in the last paragraph of the Introduction to clarify this aspect: + +<|ref|>text<|/ref|><|det|>[[144, 622, 833, 681]]<|/det|> +Line 13 "HyU utilizes phasor processing as an encoder to aggregate similar spectra and applies unmixing algorithms, such as LU, on them to provide unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity." + +<|ref|>text<|/ref|><|det|>[[130, 700, 876, 952]]<|/det|> +Information loss and noise. We are aware that the phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original "pure" data. This is evident in the scenario of very high quality signals, but in the case of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data makes phasor a valuable tool for fluorescence microscopy (FLIM/spectral alike); this point is reported by multiple groups using phasors (Gratton: https://www.pnas.org/doi/full/10.1073/pnas.1108161108, https://escholarship.org/content/qt5g279175/qt5g279175.pdf, Vicidomini: https://www.nature.com/articles/ncomms7701, Gerritsen: https://pubmed.ncbi.nlm.nih.gov/22714302/, Fraser: https://pubmed.ncbi.nlm.nih.gov/28068315/), and more recently nicely described in the work of Scipioni et al ( https://www.nature.com/articles/s41592-021-01108-4 ) "However, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[143, 90, 876, 166]]<|/det|> +microscopy data are affected by a number of other detrimental factors, [...] which results in decreased signal- to- background ratio (SBR). [...] the phasor approach shows increased precision (Fig. 1f,i), decreased bias (Fig. 1e,h) and a three orders of magnitude lower execution time (Fig. 1g,j) with respect to the least mean square (LMS) fitting procedure". + +<|ref|>text<|/ref|><|det|>[[113, 184, 879, 397]]<|/det|> +To support the validity of this hybrid unmixing approach, we have assembled a complex simulation matrix representing the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built on top of the complex simulation we designed (further described below in our answer to this reviewer's question 14), which is soon to be published in a separate manuscript. This simulation accounts for a multitude of real- world noises in experimental samples that are regularly imaged (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). The results of applying our approach on an array of simulations under different conditions of SNR, number of filters applied, in comparison to standard Linear Unmixing are now reported in Supplementary Figures 16, 17, 18, and 19. We further describe how multiple components are affected by our hybrid unmixing approach in our answer to question 17 for this reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 450, 444, 467]]<|/det|> +Other comments and concerns follow below: + +<|ref|>text<|/ref|><|det|>[[115, 470, 777, 507]]<|/det|> +1. The authors provide a spectra.txt files for the unmixing. How was that obtained. How to calculate and save the data from samples having only one fluorophores? + +<|ref|>text<|/ref|><|det|>[[115, 525, 852, 602]]<|/det|> +ANSWER: The "Independent Spectral Signatures" subsection of the Image analysis section of the supplementary text now provides an expanded description on this topic. Briefly, we obtain spectra from samples or pure solutions and validate with spectra reported in literature. The edited section "Independent Spectral Signatures" now states: + +<|ref|>text<|/ref|><|det|>[[142, 610, 870, 787]]<|/det|> +Independent spectral fingerprints can be obtained through samples, solutions, literatures, or spectral viewer websites (Thermo fisher, BD spectral viewer, Spectra analyzer). Fluorescent signals used in this paper were obtained by imaging single labeled samples in areas morphologically and physiologically known to express the specific fluorescence, see Supplementary Figure 21. For each dataset a phasor plot was computed. The 32- channel spectral fingerprint was extracted from the phasor- bin at the counts- weighted average position of the phasor cluster. Those fingerprints were compared with literature fingerprints and manually corrected to reduce noise. Further descriptions for how to identify new components can be found in Supplementary Note 1 and Supplementary Figure 11, 27. + +<|ref|>text<|/ref|><|det|>[[128, 821, 828, 858]]<|/det|> +To further clarify, we have added a Supplementary Figure 27 that shows a step- by- step example on how to obtain single spectral endmember from samples using the attached software: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[338, 88, 686, 325]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 346, 630, 364]]<|/det|> +Supplementary Figure 27. Endmember Spectrum selection process + +<|ref|>text<|/ref|><|det|>[[143, 384, 872, 523]]<|/det|> +(A) Phasor map shows the spectral distribution of the data for a single fluorescent labelled sample, in this case an 18 hpf transgenic Tg(ubiq:lyn-tdTomato) zebrafish. (B) The average spectrum corresponding to a phasor bin selection (red point in A) can be visualized using our software, which plots (C) the corresponding average spectrum with relative (top) and absolute (bottom) intensity. The save button allows exporting of spectral data as a txt file that can be re-loaded for unmixing other data. (D) Unmixing result. More step-by-step information is available in the README file associated with the software in this publication. + +<|ref|>text<|/ref|><|det|>[[119, 558, 555, 575]]<|/det|> +We then expanded Supplementary Note 1 to further clarify: + +<|ref|>text<|/ref|><|det|>[[142, 596, 881, 869]]<|/det|> +In our experience, obtaining fluorescence spectra from experimental samples has some advantages compared to utilizing spectra from an existing library, as they account for a multitude of experimental and instrumental settings. Imaging settings such as different types of lenses or optical filters (Sup. Figure 4, C and D) together with factors within the microenvironment of samples, such as pH or temperature have the potential to alter the fluorescence spectral emissions15. In the presence of unexpected fluorescent signals, spectra can also be selected and visualized directly from the phasor. Phasors facilitate the identification of unexpected independent components and their distinction from the multiple system noises. A noise- free spectrum will appear as a single point on the phasor plot, while a spectrum affected by instrument and electronic noises will mainly appear as a gaussian distribution, centered on the original spectral signal8. Conversely, a randomized noise across the multiple spectral channels will not produce a clustered aggregate of spectra on the phasor. A constant spectral noise, with a distinct spectrum (e.g. a constant light leakage into the system), would produce a distinct phasor cluster and could be selected for unmixing. The phasor plot representation is a 2D- histogram and provides insights into the frequency of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 868, 167]]<|/det|> +occurrence for these signals. These unexpected independent components in samples often appear as "tails" on the phasor distributions (Sup. Figure 11, C). In our HyU graphical interface, clicking on the phasor visualizes the spectra within a small area (9x9 bins by default, with size adjustable from the interface) of the phasor histogram (Figure 1 D). + +<|ref|>text<|/ref|><|det|>[[130, 218, 812, 256]]<|/det|> +Pre- identified phasor locations can be displayed in the software; we have also recreated their positions here in Supplementary Figure 21: + +<|ref|>image<|/ref|><|det|>[[277, 277, 745, 530]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 564, 841, 583]]<|/det|> +Supplementary Figure 21. Pre- identified positions for common fluorophores on the phasor map + +<|ref|>text<|/ref|><|det|>[[144, 606, 877, 743]]<|/det|> +(A) Pre-identified extrinsic label positions (g,s) are denoted on the phasor plot for the first harmonic and (B) second harmonic. (C) Intrinsic label locations are further added on the phasor plot for the first harmonic and (D) second harmonic. Second harmonic generally covers a larger portion of the phasor space compared to the first harmonic. However, in the case of intrinsic signals, the locations of the pure autofluorescence spectra are on average more separated when utilizing the first harmonic. Details on the source of the pure spectra for these locations are reported in Methods – Independent Spectral Signatures. + +<|ref|>text<|/ref|><|det|>[[129, 811, 880, 868]]<|/det|> +We have compiled a database of 32- channel spectra which have been gathered from literature, retrieved from commercially available resources (spectral viewer for fluorophores such as Alexas), and measured from both pure solutions and fusion proteins with our confocal + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[129, 88, 866, 244]]<|/det|> +microscopes. The spectra.txt files are organized as space delimited files with columns denoting independent spectral signature and rows denoting the channel. A spectra.txt file containing a single column (and so, the spectra for a single fluorophore) can be utilized as shown in the demo for single fluorophore samples (Supplementary Figure 27); this would maximize the contribution of that single spectrum. Exploration of the phasor plot can provide visual indication of unexpected contributing spectral endmembers. Such spectra can be included as a component, as we denoted in Supplementary Note 1. Further instructions on how to build/format and utilize the spectra.txt file have been added to the README.docx. + +<|ref|>text<|/ref|><|det|>[[129, 263, 306, 279]]<|/det|> +Step 2 of README.docx: + +<|ref|>text<|/ref|><|det|>[[142, 281, 872, 456]]<|/det|> +\* spectra.txt is a text file with the input spectra needed for unmixing with HyU. The file describes a 2D numpy array outputted using numpy's savetxt function. The file is formatted as a space delimited text file with the rows denoting the channels and the columns denoting the independent spectral signatures. Each row must have the same number of entries, and the values in each entry should be formatted as either integers, floats, or floats in scientific notation (#e±#). The values for the channels of each spectra represent the values corresponding to each spectral bin of uniform size within the detection wavelength range. The spectra.txt file linked in this README serves as an example for this formatting and contains 5 spectra of 32 channels, respectively mko2, tdtomato, mruby, citrine, and an unknown spectral signature chosen for HyU_demo- 02- fishtail.lsm. + +<|ref|>text<|/ref|><|det|>[[115, 508, 810, 546]]<|/det|> +2. I did not see any mention of collagen fluorescence when excited at 740 nm. That should be a component in the autofluorescence category. + +<|ref|>text<|/ref|><|det|>[[115, 564, 875, 700]]<|/det|> +ANSWER: We thank the reviewer for the insight. From the analysis of our experimental data, we do not detect measurable collagen signals with our imaging conditions, in the context of the many other fluorescent signals in the sample. Multiple references in literature (PMC4337962 / PMID: 22402635, PMC123202 / PMID: 12177437, PMC4337962 / PMID: 22402635) report 2- photon fluorescence of collagen to be very low at 740 nm and suggest instead the use of Second Harmonic Generation (SHG). At 2- photon 740 nm, the SHG detection would be at around 375 nm, outside of our detection range. + +<|ref|>text<|/ref|><|det|>[[115, 752, 664, 770]]<|/det|> +3. What happens to FAD? That can be excited at 740 nm (PMID: 11964266). + +<|ref|>text<|/ref|><|det|>[[115, 786, 850, 881]]<|/det|> +ANSWER: The reviewer is correct that FAD can be excited at 740 nm. However, for our imaging conditions, we used low 2P excitation (3% power, 9 mW) at relatively low magnification (pixel size 0.259x0.259\~1.38x1.38μm), and therefore, FAD was not sufficiently contributing to the autofluorescence in the datasets shown in the manuscript. We believe the reason to be related to three main factors: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[130, 89, 857, 204]]<|/det|> +First: According to Huang et al. (Huang et al., 2002 / PMC1302068 / PMID: 11964266), the lower concentration of FAD compared to NADH is known to create a "shadowing" effect of FAD in autofluorescent imaging experiments "because of the predominantly 2P- NAD(P)H fluorescence excited at 750 nm due to its much higher cellular concentration (Guezennec et al., 1991; Kunz and Gellerich, 1993" leading to the use of 890- 900nm excitation for exciting FAD to eliminate the contribution of NADH (Stringari et al, 2011; Skala et al, 2007) + +<|ref|>text<|/ref|><|det|>[[130, 206, 860, 380]]<|/det|> +Second: the magnification level in most of our data is relatively low, with pixel size \(0.259 \times 1.38 \mu m\) , contributing to an apparent reduction of the relative concentration of FAD with respect to NADH. Third: the 2P excitation used here is intentionally maintained at a considerably low power (3- 4% which corresponds to 9- 12mW) to minimize the inevitable photobleaching of the autofluorescent molecules and photodamage of the sample. This, combined with the lower magnification level, produces a low wattage/ \(\mathrm{cm}^2\) that further reduces the amount of signal emitted by the low- concentrated FAD to levels we cannot detect. Our estimate of power density for the sample in Figure 5 and Figure 6 are approximately \(4.7 \times 10^{- 6} \mathrm{mW / mm}^2\) compared to the zoomed- in sample in Supplementary Figure 22 that was \(1.4 \times 10^{- 3} \mathrm{mW / mm}^2\) . + +<|ref|>text<|/ref|><|det|>[[129, 399, 871, 515]]<|/det|> +To further confirm, we performed imaging of a wildtype zebrafish hindbrain, at least 11 times higher magnification (pixel size \(= 0.078 \times 0.078 \mu m\) ) and a slightly lower laser power at \(2.8\%\) ; at which point, we were able to observe FAD. Under these imaging conditions, the amount of 2P power deployed on the sample was 10- fold higher than the images shown in the manuscript. This is in agreement with other published works (https://www.pnas.org/content/104/49/19494. long). We summarized the results in Supplementary Figure 22: + +<|ref|>image<|/ref|><|det|>[[235, 533, 770, 840]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[156, 847, 852, 884]]<|/det|> +
Supplementary Figure 22. FAD autofluorescence in high magnification brain region of zebrafish embryo
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[156, 88, 865, 265]]<|/det|> +(A) Phasor analysis reveals a distinct autofluorescence spectral component (magenta dot) when utilizing 740 nm 2-photon excitation to image a 22 hpf wild type zebrafish brain with high magnification (pixel size = 0.078x0.078μm) and high power (Table S1). (B) The corresponding emission spectra from the phasor selections in A. The spectrum corresponding to the magenta phasor selection in A closely matches the spectral signal of FAD obtained from in vitro solutions (Methods – Independent Spectral Signatures) and accounting for local environment changes14. (C) FAD unmixing channel highlights the FAD cluster in the head region of zebrafish. (D) Composite image rendering of the unmixing results for the intrinsic signals: NADH bound, NADH free, Retinoid, Retinoic Acid, FAD, and Elastin. + +<|ref|>text<|/ref|><|det|>[[130, 298, 640, 316]]<|/det|> +We expanded Supplementary Note 2 to further describe these details: + +<|ref|>text<|/ref|><|det|>[[156, 353, 872, 825]]<|/det|> +"A map of the phasor position for common autofluorescence from pure solutions is reported in Sup. Figure 21 B. Imaging autofluorescent data, with regard to cell metabolism, requires accounting for complex and dynamic changes of metabolic pathways which can occur in a broad range of times, from seconds to years. These autofluorescent signals are often weak in nature and do not rapidly replenish after photobleaching. In our work we utilize reduced laser power to avoid rapid autofluorescence spectral signal bleaching, as well to reduce photo- damage. Additional factors known to affect emission spectra include pH and temperature, pixel- wise concentration of the fluorophore, excitation power, developmental stage and region of the sample imaged. An example for the latter is reported in Sup. Figure 12, where signals in the sample present strong localized differences. One example of the effects of different 2- photon excitation power and different levels of pixel- wise concentration is reported in Figure 5, Figure 6. In these images, samples at similar developmental stages are imaged utilizing different pixel size (0.259 μm and 0.923 μm lateral resolutions) and laser power (4% and 3% @740nm 2- photon) resulting in laser power densities of \(\sim 4.7 \cdot 10^{- 6} \text{mW/mm}^2\) . This different laser power causes some lower- concentration intrinsic fluorophores to not be excited, in this case mRuby is visible in Figure 5 but not in Figure 6. In both of these images, FAD is not excited in measurable quantity, whereas in Sup. Figure 22, where the laser power density is \(1.4 \cdot 10^{- 3} \text{mW/mm}^2\), FAD contribution is measurable and unmixed. HyU is well posed for the analysis of intrinsically low autofluorescence owing to its ability to operate at low SNR. In Sup. Figure 12, we visualize unmixing of multiple autofluorescent signals based on spectra acquired from in vitro solutions. Sup. Figures 17, 19 present a simulated overview of the improvement of HyU over Linear Unmixing for autofluorescence data, as a function of number of labels, percentage of pixels containing mixed ratio of fluorophores, number of denoising filters applied and number of channels under different levels of Signal to Noise." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 125, 857, 175]]<|/det|> +ANSWER: We appreciate the explorative nature of this question with regard to the behavior of NADH. While we do not believe that this is in line with the purpose of this manuscript, a literature search shows interesting information about this subject. + +<|ref|>text<|/ref|><|det|>[[128, 175, 867, 295]]<|/det|> +In figure 5 of Maltas et al ( https://doi.org/10.1021/ac504386x ), the authors report spectra and spectral phasors of NADH bound to LDH and MDH. Maltas et al conclude that "protein- bound NADH conformations are spectrally distinguishable" in solution when measured with 1024 channels at 2nm resolution. From their Figure 5, it appears the spectra have differences, although these differences are not resolvable with the 32 channel PMT utilized in commercial confocal microscopes. For simplicity, we are copying the figure below with its original caption (from Maltas et al ( https://doi.org/10.1021/ac504386x ) + +<|ref|>image<|/ref|><|det|>[[378, 297, 617, 572]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[128, 585, 877, 766]]<|/det|> +
Figure 5 from Maltas et al (https://doi.org/10.1021/ac504386x): Figure 5. Spectral detection of NADH protein binding. Sequential additions of MDH, MDH, and LDH to solutions of NADH (left column) or NADPH (right column). In all plots, the color or symbol shape corresponds to times before protein is added (red, square), after adding MDH once (blue, circle), after adding MDH twice (orange, triangle), and after adding LDH (green, inverted triangle). (a) Integrated-gate spectra. The spectrum taken before protein addition was scaled to its maximum intensity, with all other spectra scaled to minimize least-squares differences. Fractional-difference spectra are calculated using the spectrum before protein addition as the reference spectrum. (b) Spectral phasor plots. Shifts due to MDH addition to the NADH solution (left) are collinear (best fit line is shown). The shift due to LDH addition is not collinear with MDH-induced shifts, evidencing that protein-bound NADH conformations are spectrally distinguishable. As a negative control, no shift is observed when proteins are added to the NADPH solution (right). (c) Spectrum shape
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 94, 764, 135]]<|/det|> +plots for the same data as in (b). For (b) and (c), analysis is performed over the first 512 pixels (400- 530 nm wavelength range). + +<|ref|>text<|/ref|><|det|>[[115, 137, 850, 194]]<|/det|> +5. What is the distance of separation of the pure components in the phasor space that allow for successful linear unmixing. I presume at some point the S/N will make it difficult if the spectra of the components are too close. + +<|ref|>text<|/ref|><|det|>[[115, 212, 868, 268]]<|/det|> +ANSWER: In general, a good rule would be for pure spectral endmembers to be separated by at least one phasor scatter error, between center of scatter (endmember 1) to center of scatter (endmember 2), based on the definition introduced in the previous work (PMID: 28068315). + +<|ref|>text<|/ref|><|det|>[[130, 270, 848, 327]]<|/det|> +For our experimental conditions, the phasor scatter error is \(\sim 0.09\) ; hence, that would be a threshold distance between pure endmembers for a reliable linear unmixing. However, it should be noted that multiple factors contribute to this "minimal distance". + +<|ref|>text<|/ref|><|det|>[[144, 329, 860, 444]]<|/det|> +1. Number of histogram bins utilized: in this work, we utilize the phasor as an encoder/aggregator for the spectra in the raw dataset. We do not use the geometry of phasor for unmixing. The phasor transformed data is discretized as a 2D histogram which is then used to sort and average the raw spectra in wavelength space. Both the number of bins used to discretize the phasor plot and the actual (G,S) locations of the pure components on the phasor plot will affect the quality of the unmixing result. + +<|ref|>text<|/ref|><|det|>[[144, 445, 876, 542]]<|/det|> +2. Instrument noise: instruments are characterized by noise that differs in quantity across wavelengths. The parameter we estimate above can be used as reference for a Quasar Detector (Zeiss 710-780 series). A better sensor (e.g. the cooled version of Quasar in Zeiss 880-above series) will have lower noise than our current instrument. Any later generation emCCD or BSI-SCMOS camera based spectral detector would have considerably lower noise. + +<|ref|>text<|/ref|><|det|>[[115, 577, 809, 614]]<|/det|> +6. What about when the linear unmixing won't work? For example, a case where the individual components lie in line in the phasor space. + +<|ref|>text<|/ref|><|det|>[[117, 632, 845, 690]]<|/det|> +ANSWER: We believe that the reviewer is referring to the case where multiple independent components lie exactly on a line within the phasor plot such that multiple combinations of different fluorophores will occupy the exact same location on the phasor plot. + +<|ref|>text<|/ref|><|det|>[[130, 708, 748, 727]]<|/det|> +Example of this scenario: a sample with 3 endmembers, A, B, C, where \(\mathrm{A} = \mathrm{B} / 2 + \mathrm{C} / 2\) . + +<|ref|>text<|/ref|><|det|>[[130, 743, 874, 917]]<|/det|> +Mathematically, it is true that in this extreme case, the unmixing will have unpredictable results. The likely reason behind this unpredictability is that this scenario breaks one of the general constraints of Linear Mixing Models where endmember spectral signatures need to be linearly independent, making standard linear unmixing or fully constrained linear unmixing an ill posed problem. In practice, however, in such a case, one might argue if A is really an endmember or simply a combination of two spectra present in the sample. In our experience, we have found that it is highly unlikely for this condition to occur in spectral fluorescence of biomedical samples. As demonstrated in Supplementary Figure 16, the chances of the phasor locations of different fluorophores to line up exactly on the same line is very small. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 89, 875, 204]]<|/det|> +Though it may appear very close to a single line, there is sufficient non- linearity to create an offset that this case does not happen. It is much more likely for different combinations of many fluorophores \((>4)\) to somehow occupy the same phasor location. However, we have demonstrated in our reply to the first comment and in the numerous additional simulations (Supplemental Figure 16, 17, 18, 19) that noise affects the unmixing results much more than the encoding loss of the phasor method. + +<|ref|>text<|/ref|><|det|>[[115, 240, 870, 279]]<|/det|> +7. Coming back to Q1. – Prior knowledge of the components – How are they calculated? Where are the coordinates stored? Are only the center of the phasor cloud used or the whole distribution? + +<|ref|>text<|/ref|><|det|>[[118, 295, 870, 374]]<|/det|> +ANSWER: We believe our answer to Q1 addresses the majority of this question. We have expanded details on this subject in the Image analysis “Independent Spectral Signatures” subsection of the Image analysis section of the supplementary text and our expanded Supplementary Note 1 as well as added Supplementary Figures 21, 27. + +<|ref|>text<|/ref|><|det|>[[129, 408, 850, 465]]<|/det|> +We utilized the 32- channel spectrum contained in the phasor- bin at the weighted average position of the phasor cluster following the method described in the updated “Independent Spectral Signatures” subsection: + +<|ref|>text<|/ref|><|det|>[[142, 474, 872, 650]]<|/det|> +Independent spectral fingerprints can be obtained through samples, solutions, literatures, or spectral viewer websites (Thermo fisher, BD spectral viewer, Spectra analyzer). Fluorescent signals used in this paper were obtained by imaging single labelled samples in areas morphologically and physiologically known to express the specific fluorescence, see Supplementary Figure 21. For each dataset a phasor plot was computed. The 32- channel spectral fingerprint was extracted from the phasor- bin at the counts- weighted average position of the phasor cluster. Those fingerprints were compared with literature fingerprints and manually corrected to reduce noise. Further descriptions for how to identify new components can be found in Supplementary Note 1 and Supplementary Figure 11, 27. + +<|ref|>text<|/ref|><|det|>[[128, 667, 876, 744]]<|/det|> +The phasor coordinates, obtained from the prior experiments, are saved/embedded in the software. New spectral signatures can be imported using a correctly formatted text file (see answer to Question 1 and README.docx). We added Supplementary Figure 21 to demonstrate phasor positions of common fluorophores (corresponding emission spectra can be found in Supplementary Figure 20). + +<|ref|>text<|/ref|><|det|>[[113, 796, 805, 834]]<|/det|> +8. I do like the point mentioned in lines 10-20 in page 2. Spectral imaging and deconvolution is absolutely necessary. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 490, 107]]<|/det|> +ANSWER: We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[115, 124, 617, 142]]<|/det|> +9. Lines 30-40, page 2 – missing references about the different noise. + +<|ref|>text<|/ref|><|det|>[[115, 158, 750, 177]]<|/det|> +ANSWER: We have included the following references to the main text and bibliography: + +<|ref|>text<|/ref|><|det|>[[164, 209, 884, 362]]<|/det|> +22. Bass, M. Handbook of Optics, vol 3. Geometric Optics, General Principles Spherical Surfaces, 2nd ed., Optical Society of America, New York (1995). +23. Hamamatsu Photonics, K. K. P. T. H. PHOTOMULTIPLIER TUBES Basics and Applications FOURTH EDITION. (1994). +24. Pawley, J. B. Confocal and two-photon microscopy: Foundations, applications and advances. Microscopy Research and Technique 59, (2002). +25. Huang, F. et al. Video-rate nanoscopy using sCMOS camera-specific single-molecule localization algorithms. Nature Methods 10, (2013). + +<|ref|>text<|/ref|><|det|>[[115, 412, 817, 450]]<|/det|> +10. The linear deconvolution of the phasor space involves fractional intensity and not the actual fraction – something that I found missing in the discussion. + +<|ref|>text<|/ref|><|det|>[[115, 486, 880, 543]]<|/det|> +ANSWER: The reviewer is correct, however we are not utilizing or calculating fractional intensity on phasor. We utilize linear unmixing on the aggregated corresponding spectra in wavelength space. We believe the initial answer to this reviewer addresses this question in completeness. + +<|ref|>text<|/ref|><|det|>[[115, 579, 750, 597]]<|/det|> +11. How do 5 photons/spectra work with Poisson statistics and associated uncertainty? + +<|ref|>text<|/ref|><|det|>[[115, 613, 853, 730]]<|/det|> +ANSWER: Utilizing 5 photons per spectra results in very noisy data. As we demonstrate in the figures below, which represent both simulated single spectrum and simulated combined multiple spectra data, there is a considerable amount of obfuscation between the ideal spectral shape and the combined signal of the stochastically emitted spectra with the background noise. Averaging of the spectra using the phasor does provide a more spectrally similar array of values, but still results in a very noisy spectra, with deteriorated unmixing results. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[171, 108, 797, 314]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[128, 342, 682, 359]]<|/det|> +Simulation of tdTomato spectral fluorescent emission with max 5 photons. + +<|ref|>text<|/ref|><|det|>[[128, 361, 867, 476]]<|/det|> +Simulations are performed starting from a reference spectrum for tdTomato (black dash line), acquired from a pure solution and matched with values reported in literature. (A) Spectra are shown for 3 randomly selected pixels (orange, blue, green lines) within the phasor histogram bin with maximum number of counts. (B) Average of the spectra (blue line) belonging to all pixels inside the phasor histogram bin with maximum number of pixel counts. In both plots, the reference spectrum scaled to the max of the simulated spectra is delineated with a black dashed line. + +<|ref|>image<|/ref|><|det|>[[130, 536, 475, 770]]<|/det|> + +<|ref|>image<|/ref|><|det|>[[504, 536, 850, 770]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[128, 795, 870, 891]]<|/det|> +Simulation of multiple spectral fluorescent emission with max 5 photons per spectra. Simulations are performed by combining four reference spectra (mKO2, Citrine, mRuby, tdTomato) at 5 photons per spectra. (A) Spectra are shown for 3 randomly selected pixels (orange, blue, green lines) within the phasor histogram bin with the maximum number of counts. (B) Average of the spectra belonging to all pixels inside the phasor histogram bin with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 90, 864, 127]]<|/det|> +maximum number of pixel counts. In both plots, the dashed lines represent the reference spectrum, scaled to the maximum value of the simulated spectra. + +<|ref|>text<|/ref|><|det|>[[115, 197, 775, 214]]<|/det|> +12. Does the Elastin spectrum change on crosslinking in a tissue compared to the solution? + +<|ref|>text<|/ref|><|det|>[[115, 230, 867, 365]]<|/det|> +ANSWER: This is an interesting question that we have not yet addressed. While we believe this to be outside the focus of this paper, we found answers in literature. Richards- Kortum et al (DOI: 10.1146/annurev.physchem.47.1.555) state that collagen and elastin fluorescence is associated with cross- links and report differences in fluorescence emission maxima between elastin in powdered form, in skin and in load bearing structures (https://doi.org/10.1016/0584- 8539(89)80031- 5). These differences were echoed by Eyre et al (10.1146/annurev.bi.53.070184.003441) and more recently by Croce et al (10.4081/ejh.2014.2461). + +<|ref|>text<|/ref|><|det|>[[115, 435, 833, 471]]<|/det|> +13. Td-Tomato (PMID 19127988) and mRuby (PMID 23459413) can be excited with a 740 nm two-photon excitation. I am curious how the authors did not observe that in Figure 6. + +<|ref|>text<|/ref|><|det|>[[124, 491, 880, 664]]<|/det|> +ANSWER: The reviewer is correct, both tdTomato and mRuby can be excited with 740 nm. Our main purpose in Figure 6 was to demonstrate the different extrinsic and intrinsic signal profiles when excited by either 1-photon or 2-photon. Since our focus for this sample is in the autofluorescence for two- photon 740 nm excitation, we purposely chose samples with reduced extrinsic fluorescence expression to prevent a suppressing effect that we experimentally found to interfere with measurement of autofluorescence signals. Although the fluorescence signals are still visible, we decided to not include the tdTomato and mRuby channels from the 740nm section of the figure owing to the large amount of signals to display. We have now added Supplementary Figure 15 with both signals from 740 nm two- photon excitation. + +<|ref|>text<|/ref|><|det|>[[129, 683, 881, 818]]<|/det|> +Note that Figure 5 and Figure 6 data come from the same sample. tdTomato expression is observed in figure 5 because of the imaging setting. The imaging area in Figure 5 is \(2.59 \times 2.59 \mu m\) versus \(9.23 \times 9.23 \mu m\) in Figure 6. The image area in Figure 6 is 12 times larger for each pixel while using \(1\%\) lower laser power. Laser power was intentionally reduced to avoid photo- bleaching and photo- damage as well as to minimize disturbance of the system during longer time series imaging, with the expectation of reduced excitation of extrinsic fluorescent signals. We added this data in Supplementary Figure 15 and observed low intensity results showing a low expression level. + +<|ref|>text<|/ref|><|det|>[[130, 839, 317, 855]]<|/det|> +Supplementary Figure 15: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[277, 95, 715, 504]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[144, 521, 783, 559]]<|/det|> +
Supplementary Figure 15. HyU unmixing on low concentration signals using customized independent spectra
+ +<|ref|>text<|/ref|><|det|>[[142, 560, 875, 794]]<|/det|> +Results from unmixing intrinsic and extrinsic signals of a quadra- transgenic zebrafish: Gt(cltca- citrine); Tg(ubiq:lyn- tdTomato; ubig:Lifeact- mRuby;fli1:mKO2) at a single timepoint of the dataset presented in Figure 6 provide further information and highlight the weak expression of some extrinsic signals in this dataset. (A) Input spectra for the intrinsic signatures were directly acquired by selection of the endmembers in the phasor plot. Input spectra for the extrinsic signatures were acquired from other datasets of samples expressing those signatures individually and excited at 740 nm with 2- photon, since these extrinsic signals are not strongly expressed within this dataset. (B) Renderings of unmixing results were automatically adjusted to show the best contrast. Unmixing can still be performed with spectra from weak input signatures. (C) Histogram counts of each unmixed independent spectral signature demonstrate the low signals of the extrinsic fluorescence signatures compared to the intrinsic ones. The median values of the mRuby and tdTomato channels are 57 and 77 Digital Levels respectively, considerably lower than those of the other signals. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 861, 145]]<|/det|> +14. What determines how much spatial denoising needs to be used? Spatial denoising indeed doesn't affect the intensity image – but it does affect the phasor mapped image – something that hasn't been discussed at all. + +<|ref|>text<|/ref|><|det|>[[123, 165, 876, 416]]<|/det|> +ANSWER: This question has been answered in our previous paper (Cutrale et.al., Nature Methods). It was determined that the spatial denoising plateaus after 5 applications. Still, we have added multiple simulations to better quantify the performance improvement of HyU with respect to LU for multiple denoising filters (Supplementary Figure 16 and 17) in terms of Relative Mean Squared Error (RMSE) (as defined in the Methods section, Mean Square Error). The new figures show a matrix of RMSE values for a number of fluorophores over the percentage of overlap. Each RMSE value is calculated as average from a simulation that has n fluorophores and a specific percentage of pixels containing randomized ratios of n fluorophores, where n is the number of fluorophores in the specific matrix position. For example, the RMSE value for 6 fluorophores at \(50\%\) overlap is calculated from a simulated dataset with 6 fluorophores where \(50\%\) of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. Further details on these newer simulations have been added to the Methods section Hyperspectral Fluorescence Image Simulation. + +<|ref|>sub_title<|/ref|><|det|>[[106, 455, 440, 472]]<|/det|> +## Hyperspectral Fluorescence Image Simulation + +<|ref|>text<|/ref|><|det|>[[172, 482, 875, 617]]<|/det|> +The model simulates spectral fluorescent emission by generating a stochastic distribution of photons with profile equivalent to the pure reference spectra (as described in Sup. Note 1). The effect of photon starvation, commonly observed on microscopes, is synthetically obtained by manually reducing the number of photons in this stochastic distribution. Detection, Poisson and signal transfer noises are then added to produce 32- channel fluorescence emission spectra that closely resemble those acquired on microscopes. The simulations include accurate integration of dichroic mirrors and imaging settings. + +<|ref|>sub_title<|/ref|><|det|>[[174, 627, 307, 643]]<|/det|> +## Simulation Types: + +<|ref|>sub_title<|/ref|><|det|>[[175, 654, 434, 670]]<|/det|> +## Biologically comparable simulations + +<|ref|>text<|/ref|><|det|>[[172, 679, 870, 833]]<|/det|> +To quantify the performance of HyU vs LU for microscopy data acquired experimentally, we generated synthetic data where each input spectra was organized with intensity distributions taken from experimental data of fluorescently labeled biological samples. We calibrated the analog (Digital Levels) to photon counting rate based on existing literature \(^{5,6}\) . Experimental data was discretized to photons to produce biologically relevant photon masks with distributions of signals highly resembling those of the samples. This provided intensities and ratios which closely resemble those acquired from a confocal microscope while allowing control over the effects of photon starvation. + +<|ref|>text<|/ref|><|det|>[[174, 876, 518, 892]]<|/det|> +Spatially and spectrally overlapping simulations + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[171, 88, 864, 381]]<|/det|> +We also included simulations to quantify the performance of HyU vs LU with respect to the number of spectral combinations and of endmembers. The results are summarized in Supplementary Figures 16- 19 in the form of matrices of spectral overlap (0 to \(100\%\) , steps of \(10\%\) , X- axis) by number of endmembers (2 to 8 endmembers, Y- axis) representing the Relative Mean Squared Error (RMSE) (Supplementary Methods, Performance quantification). Each RMSE value reported in a matrix is the average of analysis of a 1024x1024 pixels image simulation with a spectral dimension of 32- channels matching the spectral range and bandwidth of the detectors in commercial confocal microscopes (LSM 780, Carl Zeiss). These simulations were created with artificial intensity distributions so that a simulation with X% overlap and n fluorophores would have X percentage of pixels with a randomized ratio of n input spectra. As an example, for a simulation with 6 fluorophores and 50% overlap, the simulated dataset would have 50% of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. This allowed us to investigate the effects of an increasing number of spectral combinations on the compressive nature of the phasor method for HyU. + +<|ref|>text<|/ref|><|det|>[[130, 442, 861, 481]]<|/det|> +Supplementary Figure 16 is simulated utilizing only extrinsic fluorophores and Supplementary Figure 17 is simulated using a combination of intrinsic and extrinsic fluorophores: + +<|ref|>image<|/ref|><|det|>[[130, 486, 880, 805]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[104, 825, 872, 864]]<|/det|> +
Supplementary Figure 16. RMSE improvement for simulated fluorescent spectral combinations highlights increased HyU performance across multiple denoising filters.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[171, 88, 878, 339]]<|/det|> +Twelve matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Different columns in the figure report the RMSE improvement matrices with different numbers of denoising filters (0x, 1x, 3x, 5x) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. In the absence of denoising filters, the improvement of HyU overall is less than \(8\%\) . Denoising filters improve RMSE by over \(80\%\) . Spectra utilized for this simulation are reported in Sup. Figure 20A. + +<|ref|>image<|/ref|><|det|>[[128, 408, 875, 728]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[173, 771, 872, 810]]<|/det|> +Supplementary Figure 17. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights increased HyU performance across multiple denoising filters + +<|ref|>text<|/ref|><|det|>[[173, 833, 870, 930]]<|/det|> +Twelve matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic and intrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 88, 872, 245]]<|/det|> +corresponds to a single fluorophore, while simulations with \(100\%\) overlap have, in every pixel, a randomized ratio of the n extrinsic and intrinsic fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Different columns in the figure report the RMSE improvement matrices with different numbers of denoising filters (0x, 1x, 3x, 5x) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. In the absence of denoising filters, the improvement of HyU overall is less than \(25\%\) . Denoising filters improve RMSE by over \(100\%\) . Spectra utilized for this simulation are reported in Sup. Figure 20B. + +<|ref|>text<|/ref|><|det|>[[115, 314, 864, 369]]<|/det|> +15. Figure 1 D-E – this is strictly not true. Once you transfer to phasor – the information remaining for the spectra is the FWHM and the peak/center – so how does the proper spectra being calculated in figure E? + +<|ref|>text<|/ref|><|det|>[[115, 389, 877, 525]]<|/det|> +ANSWER: The reviewer is correct that full spectra cannot be calculated from the first harmonic components without major loss of information. We are not calculating the spectra from the phasor; instead, we are preserving them in wavelength space from the original input data (32 channel) that was used to calculate the phasor components. The unmixing is performed over the spectral dimension (in this case, 32 channels) on aggregated similar spectra from the original data (in 32 channels), as explained in Supplementary Material “Hybrid Unmixing - Linear Unmixing” and further demonstrated in the pseudo-code in “HyU Algorithm”. + +<|ref|>text<|/ref|><|det|>[[128, 526, 760, 545]]<|/det|> +We improved Figure 1 D-E, changing the connecting arrow to be “Phasor Aggregation”. + +<|ref|>image<|/ref|><|det|>[[129, 555, 866, 880]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 844, 145]]<|/det|> +16. The reduction of data from \(10^{A7}\) to \(10^{A4}\) . How much of that is related to spectral denoising and how much is related to the transformation to phasor? + +<|ref|>text<|/ref|><|det|>[[115, 163, 879, 240]]<|/det|> +ANSWER: The majority of the data reduction occurs when transforming the raw data to the phasor. The initial transformation reduces the data by approximately two orders of magnitude, from \(10^{A7}\) to \(10^{A5}\) . Successive spectral denoising filters further reduce the data in much smaller increments, staying within \(10^{A4}\) elements. + +<|ref|>text<|/ref|><|det|>[[115, 276, 800, 312]]<|/det|> +17. Page 4 line 19 – after two-components – what happens with three/four and their possible combinations? + +<|ref|>text<|/ref|><|det|>[[115, 349, 857, 426]]<|/det|> +ANSWER: Line 19 is meant to provide an overview of the standard phasor approach, with a simple example of one of the advantages of phasors. HyU does not utilize the geometry of phasor for performing the unmixing, circumventing in most cases the challenges related to phasor ratiometric unmixing of more than 3 components. + +<|ref|>text<|/ref|><|det|>[[128, 444, 877, 638]]<|/det|> +The unmixing is performed over the spectral dimension (in this case, 32 channels), by aggregating similar spectra of the original data, as explained in Supplementary Material "Hybrid Unmixing - Linear Unmixing" and further demonstrated in the pseudo- code in "HyU Algorithm". The spectra are not calculated from phasor; rather, they are aggregated from the original spectral cube dataset. HyU strategy is less phasor- esque than the traditional geometry based phasor approach (PMID: 32235070 and 22714302) where the approach uses the phasor geometry to unmix the components. The phasor geometrical approach only uses the coordinates G, S at a specific harmonic, omitting the wavelength dimension in the final unmixing process. As such, like the reviewer correctly states, it is a limiting strategy that makes it impossible to specify the difference between image phasor points in the middle of the phasor cloud with multiple species, requiring multiple harmonics. + +<|ref|>text<|/ref|><|det|>[[129, 652, 876, 747]]<|/det|> +With HyU, we utilized the phasor as an encoder, to aggregate similar spectra, because of our familiarity with the approach, but, in principle, other encoding strategies could be utilized. The relative positions and geometry of phasor bin coordinates, from the unmixing algorithm perspective, do not directly matter, as the unmixing is performed with a 32 channel endmember over a 32 channel experimental spectrum ("Linear Unmixing" in Supp. Material). + +<|ref|>text<|/ref|><|det|>[[129, 761, 869, 898]]<|/det|> +The phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original data. This is evident in the scenario of very strong signals (e.g. in hyperspectral reflectance), but in the case of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less impactful on the results compared to the noise of the fluorescent signals. This fundamental advantage of phasor in increasing SNR in noisy data makes phasor a valuable tool for fluorescence microscopy (FLIM/spectral alike); this point is reported by multiple groups using phasors: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[171, 90, 672, 127]]<|/det|> +Gratton: https://www.pnas.org/doi/full/10.1073/pnas.1108161108, https://escholarship.org/content/qt5g279175/qt5g279175. pdf, + +<|ref|>text<|/ref|><|det|>[[171, 142, 696, 159]]<|/det|> +Vicidomini: https://www.nature.com/articles/ncomms7701, Gerritsen: + +<|ref|>text<|/ref|><|det|>[[172, 175, 512, 192]]<|/det|> +https://pubmed.ncbi.nlm.nih.gov/22714302/, + +<|ref|>text<|/ref|><|det|>[[172, 207, 555, 224]]<|/det|> +Fraser: https://pubmed.ncbi.nlm.nih.gov/28068315/ + +<|ref|>text<|/ref|><|det|>[[128, 241, 849, 357]]<|/det|> +and more recently nicely described in the work of Scipioni at al ( https://www.nature.com/articles/s41592- 021- 01108- 4) "However, microscopy data are affected by a number of other detrimental factors, [...] which results in decreased signal- to- background ratio (SBR). [...] the phasor approach shows increased precision (Fig. 1f,i), decreased bias (Fig. 1e,h) and a three orders of magnitude lower execution time (Fig. 1g,j) with respect to the least mean square (LMS) fitting procedure". + +<|ref|>text<|/ref|><|det|>[[128, 375, 874, 568]]<|/det|> +We characterize the encoding loss of the Hybrid Unmixing approach owing to phasor and show that HyU still outperforms the standard LU. We performed simulations following the description provided in answer 14 to this reviewer, assembling a matrix of performance improvement with respect to Linear Unmixing by utilizing Relative Mean Squared Error (also described in Supplementary Methods) across the number of fluorophores and percentage of pixels with randomized overlap. This complex simulation matrix represents the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built from a complex simulation soon to be published in a separate manuscript that accounts for a multitude of real- world noises that occur in imaging of experimental samples (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). + +<|ref|>text<|/ref|><|det|>[[128, 587, 850, 623]]<|/det|> +In Supplementary Figures 16- 19, we explore this matrix of fluorophores/overlap with the following parameters: + +<|ref|>text<|/ref|><|det|>[[157, 644, 448, 718]]<|/det|> +- Number of denoising filters- Different values of SNR- Fluorescent or Autofluorescent labels- Number of channels detected + +<|ref|>text<|/ref|><|det|>[[128, 736, 866, 773]]<|/det|> +Supplementary Figures 16 and 17 are reported above in question 14 of this reviewer. Supplementary Figures 18 and 19: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[125, 88, 855, 343]]<|/det|> + +<|ref|>title<|/ref|><|det|>[[173, 401, 871, 456]]<|/det|> +# Supplementary Figure 18. RMSE improvement for simulated fluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels + +<|ref|>text<|/ref|><|det|>[[172, 481, 880, 792]]<|/det|> +Fifteen matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU with \(3x\) denoising filters. Columns in the figure represent RMSE improvement matrices across an increasingly binned number of spectral channels (32, 16, 8, 6, 4) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. When utilizing 32 spectral channels data, RMSE improvements reach above the previously reported \(80\%\) for highly overlapping fluorophores. Successively increasing the binning across the wavelength dimension (and therefore decreasing the number of spectral channels) shows a slow downward trend of the RMSE improvement until the 4 spectral channels matrices, where the RMSE improvement drops drastically down to below \(8\%\) , especially for more than 6 labels. Spectra utilized for this simulation are reported in Sup. Figure 20A. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[125, 88, 866, 345]]<|/det|> + +<|ref|>title<|/ref|><|det|>[[173, 370, 870, 426]]<|/det|> +# Supplementary Figure 19. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels + +<|ref|>text<|/ref|><|det|>[[172, 450, 877, 760]]<|/det|> +Fifteen matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic and intrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n extrinsic and intrinsic fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Columns in the figure represent RMSE improvement matrices with 3x denoising filters across an increasingly binned number of spectral channels (32, 16, 8, 6, 4) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. When utilizing 32 spectral channel data, RMSE improvements reach up to the previously reported \(100\%\) for highly overlapping fluorophores. Successively increasing the binning across the wavelength dimension (and therefore decreasing the number of channels) shows a slow downward trend of the RMSE improvement until the 4 spectral channel matrices, where the RMSE improvement drops drastically down to below \(25\%\) , especially for more than 3 labels. Spectra utilized for this simulation are reported in Sup. Figure 20B. + +<|ref|>text<|/ref|><|det|>[[130, 812, 875, 869]]<|/det|> +With regard to the simulations, the Supplementary Methods section "Hyperspectral Fluorescence Image Simulation" has been updated to include descriptions of the new simulations as reported in our reply to question 14 of this reviewer. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[130, 137, 728, 154]]<|/det|> +With regard to the encoding, the Discussion in the main text was updated to state: + +<|ref|>text<|/ref|><|det|>[[173, 181, 857, 260]]<|/det|> +Due to the initial computational overhead for encoding spectra in phasors, there is a 2- fold speed reduction for HyU in comparison to standard LU. However, this may be improved with further optimizations of the HyU implementation or by implementing different types of encoding. + +<|ref|>text<|/ref|><|det|>[[128, 294, 856, 332]]<|/det|> +We added a new Supplementary Note 4 that details aspects of phasors and encoding loss. The note reads: + +<|ref|>text<|/ref|><|det|>[[108, 371, 694, 390]]<|/det|> +Supplementary Note 4: Improvements of HyU over the standard phasor analysis + +<|ref|>text<|/ref|><|det|>[[171, 398, 875, 593]]<|/det|> +Linearity of combinations is the general assumption for most of the spectral analysis algorithms in Hyperspectral Fluorescence Imaging (HFI). Each pixel is assumed to contain a linear combination of the independent spectral signatures, or endmembers, contained in the sample. This assumption requires knowledge, or identification, of the independent spectra within the sample. In standard linear unmixing algorithms, the extraction of relative amounts of spectra (ratios) is conducted on a pixel- by- pixel basis, at the expense of computational costs. Disrupted experimental signals, in the case of lower Signal to Noise Ratio (SNR) spectra, complicate the detection of spectral endmembers and reduce the accuracy of ratio determination. These standard unmixing algorithms, however, have the advantage of being unsupervised with the possibility of automating the analysis process. + +<|ref|>text<|/ref|><|det|>[[171, 601, 872, 855]]<|/det|> +The phasor approach has become a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis \(^{13 - 15}\) . Phasors provide key advantages, including spectral compression, denoising, and computational reduction for both preprocessing \(^{3}\) and unmixing \(^{8,16,17}\) of HFI datasets. Phasor analysis overcomes the challenge of low SNR data analysis that limits standard unmixing algorithms, providing a multiplexing solution to a need. The phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original clean data \(^{18}\) . In the imaging of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data has made the phasor method a valuable tool for fluorescence microscopy, both for Lifetime and Spectral Fluorescence Microscopy. This point is reported by multiple groups using phasors \(^{18 - 21}\) and, more recently, nicely described in the work of Scipioni et al \(^{22}\) . Standard Phasor analysis \(^{23 - 25}\) is fully supervised and requires a manual selection of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[171, 88, 875, 225]]<|/det|> +regions or points on a graphical representation of the transformed spectra, called the phasor plot. Each selection of a region in the phasor plot associates pixels containing similar spectra to the same fluorophore, forming an output channel that contains wavelength integral of intensities with unitary ratiometric value. This "winner takes all" approach is suitable when fluorophores for each single excitation light are spectrally overlapping and spatially disperse (Sup. Figure 24), but requires separate acquisition of different excitation wavelengths for demultiplexing spatially and spectrally overlapping fluorophores (Sup. Figure 25). + +<|ref|>text<|/ref|><|det|>[[171, 232, 875, 666]]<|/det|> +HyU uses the phasor transform to group pixels with similar spectral shape within each phasor histogram bin. This approach maintains the advantage of compressing, denoising and simplifying identification of clean endmember fluorescent spectra. However, HyU improves on the robustness of the analysis. The denoised signals are maintained in a hybrid phasor and wavelength domain, and therefore can be unmixed with a multitude of standard unmixing algorithms (Sup. Figure 13), such as Linear Unmixing or Fully Constrained Least Squares. These standard unmixing approaches can operate without supervision and provide for each pixel the ratios for a set of spectral signals, overcoming some of the limitations of phasor, but generally do not perform well in experimental conditions with reduced and compromised signals, such as in fluorescence, and require extensive computational time for high spectral- count datasets. HyU provides wavelength- based denoised spectra that enable these standard algorithms to outperform their pixel- by- pixel typical application, both in quality of the results (Sup. Figures 16- 19), owing to cleaner and better defined fluorescent spectra in each phasor bin, and, generally, in speed, owing to the phasor dimensionality reduction. HyU performs well for single excitation light when fluorophores are spectrally overlapping both when they are spatially disperse or co- localized, providing a ratio for each independent spectrum currently unmixed. Our data suggests HyU has reasonable performance for up to 8 different fluorophores per dataset, for each single excitation wavelength. In an experiment with a carefully chosen palette of labels, where octuples of fluorophores can be excited by a single wavelength, with an instrument capable of spectral acquisition with 5 standard and sufficiently spectrally separated excitation wavelengths in 5 sequential acquisitions (one for each excitation light), HyU could, in principle, unmix 40 signals. This performance however decreases with the number of channels (Sup. Figures 18, 19) showing a small deterioration at 8 channels and limitations at 4. + +<|ref|>text<|/ref|><|det|>[[170, 666, 755, 683]]<|/det|> +Figures 18, 19) showing a small deterioration at 8 channels and limitations at 4. + +<|ref|>text<|/ref|><|det|>[[115, 737, 790, 773]]<|/det|> +18. One of the uses of HyU is for low light level and long term imaging. What happens to the deconvolution if there is bleaching? This is a minor concern. + +<|ref|>text<|/ref|><|det|>[[115, 794, 857, 831]]<|/det|> +ANSWER: The effects of phasor denoising with respect to photobleaching have been characterized in our previous work ( https://www.nature.com/articles/s41467- 020- 14486- 8 ) in: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[137, 90, 633, 205]]<|/det|> +- Supplementary Figure 26 (https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-020-14486-8/MediaObjects/41467_2020_14486_MOESM1_ESM.pdf) and +- Supplementary Movie 3 (https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-020-14486-8/MediaObjects/41467_2020_14486_MOESM6_ESM.mov) + +<|ref|>text<|/ref|><|det|>[[130, 230, 672, 247]]<|/det|> +For simplicity, we copy paste Supplementary Figure 26 from Shi et al 2020: + +<|ref|>image<|/ref|><|det|>[[130, 258, 872, 485]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[128, 510, 275, 526]]<|/det|> +from Shi et al 2020: + +<|ref|>text<|/ref|><|det|>[[125, 530, 876, 881]]<|/det|> +"Supplementary Figure 26. Visualization of photobleaching with SEER. Photo- bleaching experiments were performed on a 24 hpf zebrafish embryo Gt(cltca- citrine); Tg(fli1:mKO2); Tg(ubiq:memTdTomato), labeling clathrin, pan- endothelial and membrane respectively. The experiments were performed utilizing the "bleaching" modality in the Zeiss Zen 780 inverted confocal, where single z positions were acquired in lambda mode. Frames are acquired every 13.7 sec, with 5 intermediate bleaching frames (not acquired) at high laser power until image intensity reached 90% bleaching. The SEER RGB mask represents the values of colors associated to each pixel, independent from the intensity values. The map used here is Radial map in Center of Mass mode. In this modality the map will adjust its position on the shifting center of mass of the phasor clusters, visually compensating for the decrease in intensity. (a) In the initial frame the cltca- citrine is associated to a magenta color, membrane to cerulean, pan- endothelial is not in frame and background to yellow. (b) Frame 10 shows consistent colors with the initial bleaching; the colors are maintained (c) at frame 40 and (d) frame 70 where most of the signal has bleached and most colors have switched to yellow (here, background). (e) Final frame shows the 90% bleached sample. The Alpha Color rendering adds the information of intensity to the image visualization. Here we show for comparison (f) frame 1, (g) frame 10, (h) frame 40 and (i) frame 70. Scale bar 10um. (j) Average total intensity plot as a function of frame, calculated from the sum of 32 channels, shows evident bleaching in the sample. Further visualization is provided in Supplementary Movie 3 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 826, 127]]<|/det|> +19. How to create the spectral libraries in the software provided by the authors (page 15, line 29-30)? + +<|ref|>text<|/ref|><|det|>[[115, 145, 877, 241]]<|/det|> +ANSWER: We refer the reviewer to the answer to Q1, where we explain how to obtain the spectra from samples or literature and how to format them to fit the spectra.txt library in our example. Correspondingly, we updated the manuscript in the section "Independent Spectral Signatures" under Image analysis in Supplementary Information, added Supplementary Figures 21 and 27, and edited the README document. + +<|ref|>text<|/ref|><|det|>[[115, 260, 787, 297]]<|/det|> +20. I do feel the references can be expanded for the phasor analysis of the multicomponent systems from other labs. + +<|ref|>text<|/ref|><|det|>[[115, 316, 865, 354]]<|/det|> +ANSWER: We expanded the reference list with respect to phasor analysis, preprocessing hyperspectral data, and unmixing hyperspectral data by including the following: + +<|ref|>text<|/ref|><|det|>[[163, 387, 866, 821]]<|/det|> +26. Digman, M. A., Caiolfa, V. R., Zamai, M. & Gratton, E. The Phasor Approach to Fluorescence Lifetime Imaging Analysis. Biophysical Journal 94, L14–L16 (2008). +27. Fereidouni, F., Bader, A. N., Colonna, A. & Gerritsen, H. C. Phasor analysis of multiphoton spectral images distinguishes autofluorescence components of in vivo human skin. Journal of Biophotonics 7, 589–596 (2014). +28. Scipioni, L., Rossetta, A., Tedeschi, G. & Gratton, E. Phasor S-FLIM: a new paradigm for fast and robust spectral fluorescence lifetime imaging. Nature Methods 18, 542–550 (2021). +29. Ranjit, S., Malacrida, L., Jameson, D. M. & Gratton, E. Fit-free analysis of fluorescence lifetime imaging data using the phasor approach. Nature Protocols 13, 1979–2004 (2018). +30. Shi, W. et al. Pre-processing visualization of hyperspectral fluorescent data with Spectrally Encoded Enhanced Representations. Nature Communications 11, 1–15 (2020). +31. Keshava, N. & Mustard, J. F. Spectral unmixing. IEEE Signal Processing Magazine 19, 44–57 (2002). +32. Dobigeon, N., Altmann, Y., Brun, N. & Moussaoui, S. Linear and Nonlinear Unmixing in Hyperspectral Imaging. in Data Handling in Science and Technology vol. 30 (2016). +33. Zeiss, C. & Online, M. Introduction to Spectral Imaging and Linear Unmixing. Imaging 1, 1–13 (2010). +34. Hedde, P. N., Cinco, R., Malacrida, L., Kamaid, A. & Gratton, E. Phasor-based hyperspectral snapshot microscopy allows fast imaging of live, three-dimensional tissues for biomedical applications. Communications Biology 4, (2021). +35. Cutrale, F. et al. Hyperspectral phasor analysis enables multi-plexed 5D in vivo imaging. Nature Publishing Group (2017) doi:10.1038/nmeth.4134. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[163, 88, 860, 125]]<|/det|> +36. Stringari, C. et al. Metabolic trajectory of cellular differentiation in small intestine by Phasor Fluorescence Lifetime Microscopy of NADH. Scientific Reports 2, (2012). + +<|ref|>text<|/ref|><|det|>[[164, 127, 861, 184]]<|/det|> +37. Ranjit, S., Datta, R., Dvornikov, A. & Gratton, E. Multicomponent Analysis of Phasor Plot in a Single Pixel to Calculate Changes of Metabolic Trajectory in Biological Systems. Journal of Physical Chemistry A 123, (2019). + +<|ref|>text<|/ref|><|det|>[[164, 186, 852, 243]]<|/det|> +38. Jeong, S. et al. Time-resolved fluorescence microscopy with phasor analysis for visualizing multicomponent topical drug distribution within human skin. Scientific Reports 10, (2020). + +<|ref|>text<|/ref|><|det|>[[164, 245, 743, 301]]<|/det|> +39. Haas, K. T., Fries, M. W., Venkitaraman, A. R. & Esposito, A. Single-Cell Biochemical Multiplexing by Multidimensional Phasor Demixing and Spectral Fluorescence Lifetime Imaging Microscopy. Frontiers in Physics 9, (2021). + +<|ref|>text<|/ref|><|det|>[[164, 303, 816, 341]]<|/det|> +40. Lanzano, L. et al. Encoding and decoding spatio-temporal information for super-resolution microscopy. Nature Communications 6, (2015). + +<|ref|>text<|/ref|><|det|>[[164, 343, 773, 379]]<|/det|> +41. Yao, Z. et al. Multiplexed bioluminescence microscopy via phasor analysis. Nature Methods 2022 19:7 19, 893-898 (2022). + +<|ref|>text<|/ref|><|det|>[[164, 381, 816, 400]]<|/det|> +42. Depasquale, J. A. Actin Microridges. Anat Rec (Hoboken) 301, 2037-2050 (2018). + +<|ref|>text<|/ref|><|det|>[[164, 401, 850, 438]]<|/det|> +43. Okuda, K. S., Hogan, B. M., Cantelmo, A. R. & Hogan, B. M. 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An orthologue of the kit-related gene fms is required for development of neural crest-derived xanthophores and a subpopulation of adult melanocytes in the zebrafish, Danio rerio. Development (2000).5. Digman, M. A., Dalal, R., Horwitz, A. F. & Gratton, E. Mapping the number of molecules and brightness in the laser scanning microscope. Biophys J 94, 2320-2332 (2008).6. Dalal, R. B., Digman, M. A., Horwitz, A. F., Vetri, V. & Gratton, E. Determination of particle number and brightness using a laser scanning confocal microscope operating in the analog mode. Microsc Res Tech 71, 69-81 (2008).7. Wagnieres, G. A., Star, W. M. & Wilson, B. C. Invited Review In Vivo Fluorescence Spectroscopy and Imaging for Oncological Applications. 68, 603-632 (1998). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[163, 90, 860, 127]]<|/det|> +8. Cutrale, F. et al. Hyperspectral phasor analysis enables multi-plexed 5D in vivo imaging. Nature Publishing Group (2017) doi:10.1038/nmeth.4134. + +<|ref|>text<|/ref|><|det|>[[163, 130, 868, 167]]<|/det|> +9. Taylor, R. C. Experiments in physical chemistry (Shoemaker, David P.; Garland, Carl W.). Journal of Chemical Education 45, (1968). + +<|ref|>text<|/ref|><|det|>[[163, 170, 777, 207]]<|/det|> +10. Févotte, C. & Dobigeon, N. Nonlinear hyperspectral unmixing with robust nonnegative matrix factorization. IEEE Transactions on Image Processing 24, (2015). + +<|ref|>text<|/ref|><|det|>[[163, 210, 844, 247]]<|/det|> +11. Parslow, A., Cardona, A. & Bryson-Richardson, R. J. Sample drift correction following 4D confocal time-lapse Imaging. Journal of Visualized Experiments (2014) doi:10.3791/51086. + +<|ref|>text<|/ref|><|det|>[[163, 250, 800, 268]]<|/det|> +12. Schindelin, J. et al. Fiji: An open-source platform for biological-image analysis. + +<|ref|>text<|/ref|><|det|>[[163, 270, 744, 287]]<|/det|> +Nature Methods vol. 9 Preprint at https://doi.org/10.1038/nmeth.2019 (2012). + +<|ref|>text<|/ref|><|det|>[[163, 290, 755, 308]]<|/det|> +13. Shimozono, S., Iimura, T., Kitaguchi, T., Higashijima, S. I. & Miyawaki, A. + +<|ref|>text<|/ref|><|det|>[[163, 310, 790, 327]]<|/det|> +Visualization of an endogenous retinoic acid gradient across embryonic development. + +<|ref|>text<|/ref|><|det|>[[163, 330, 380, 346]]<|/det|> +Nature 496, 363- 366 (2013). + +<|ref|>text<|/ref|><|det|>[[163, 350, 865, 406]]<|/det|> +14. Islam, M. S., Honma, M., Nakabayashi, T., Kinjo, M. & Ohta, N. pH dependence of the fluorescence lifetime of FAD in solution and in cells. International Journal of Molecular Sciences 14, (2013). + +<|ref|>text<|/ref|><|det|>[[163, 409, 865, 465]]<|/det|> +15. Islam, M. S., Honma, M., Nakabayashi, T., Kinjo, M. & Ohta, N. pH dependence of the fluorescence lifetime of FAD in solution and in cells. International Journal of Molecular Sciences 14, (2013). + +<|ref|>text<|/ref|><|det|>[[163, 468, 852, 506]]<|/det|> +16. Andrews, L. M., Jones, M. R., Digman, M. A. & Gratton, E. Spectral phasor analysis of Pyronin Y labeled RNA microenvironments in living cells. Biomedical Optics Express 4, (2013). + +<|ref|>text<|/ref|><|det|>[[163, 508, 844, 546]]<|/det|> +17. Fereidouni, F., Bader, A. N. & Gerritsen, H. C. Spectral phasor analysis allows rapid and reliable unmixing of fluorescence microscopy spectral images. Optics Express 20, (2012). + +<|ref|>text<|/ref|><|det|>[[163, 548, 797, 585]]<|/det|> +18. Cutrale, F. et al. Hyperspectral phasor analysis enables multiplexed 5D in vivo imaging. Nature Methods 14, (2017). + +<|ref|>text<|/ref|><|det|>[[163, 589, 852, 644]]<|/det|> +19. Stringari, C. et al. Phasor approach to fluorescence lifetime microscopy distinguishes different metabolic states of germ cells in a live tissue. Proc Natl Acad Sci U S A 108, 13582-7 (2011). + +<|ref|>text<|/ref|><|det|>[[163, 648, 816, 684]]<|/det|> +20. Lanzano, L. et al. Encoding and decoding spatio-temporal information for super-resolution microscopy. Nature Communications 6, (2015). + +<|ref|>text<|/ref|><|det|>[[163, 687, 865, 744]]<|/det|> +21. Fereidouni, F., Bader, A. N. & Gerritsen, H. C. Spectral phasor analysis allows rapid and reliable unmixing of fluorescence microscopy spectral images. Opt Express 20, 12729-12741 (2012). + +<|ref|>text<|/ref|><|det|>[[163, 747, 865, 784]]<|/det|> +22. Scipioni, L., Rossetta, A., Tedeschi, G. & Gratton, E. Phasor S-FLIM: a new paradigm for fast and robust spectral fluorescence lifetime imaging. Nature Methods 18, (2021). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[164, 90, 875, 228]]<|/det|> +23. Malacrida, L., Ranjit, S., Jameson, D. M. & Gratton, E. The Phasor Plot: A Universal Circle to Advance Fluorescence Lifetime Analysis and Interpretation. Annual Review of Biophysics vol. 50 Preprint at https://doi.org/10.1146/annurev-biophys-062920-063631 (2021). +24. Ranjit, S., Malacrida, L., Jameson, D. M. & Gratton, E. Fit-free analysis of fluorescence lifetime imaging data using the phasor approach. Nature Protocols 13, 1979–2004 (2018). +25. Digman, M. A., Caiolfa, V. R., Zamai, M. & Gratton, E. The Phasor Approach to Fluorescence Lifetime Imaging Analysis. Biophysical Journal 94, L14–L16 (2008). + +<|ref|>text<|/ref|><|det|>[[115, 280, 450, 297]]<|/det|> +Reviewer #1 (Remarks to the Author: Impact): + +<|ref|>text<|/ref|><|det|>[[115, 314, 825, 332]]<|/det|> +The paper will influence the community - but the discrepancies need to be cleared and explained. + +<|ref|>text<|/ref|><|det|>[[115, 350, 844, 408]]<|/det|> +ANSWER: We thank the reviewer for this comment and all the constructive criticism. We believe we addressed all of this reviewer's comments in the answers above and the edits in the manuscript considerably improved the quality of the work. + +<|ref|>text<|/ref|><|det|>[[115, 426, 559, 444]]<|/det|> +Reviewer #1 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[115, 461, 880, 499]]<|/det|> +The main concern is the linear additivity of phasor space and their implementation in this paper. Use of a single harmonic should not be enough for anything more than three components. + +<|ref|>text<|/ref|><|det|>[[115, 516, 880, 554]]<|/det|> +ANSWER: We believe we addressed this reviewer's specific comment in the answer to question 17 above and in the introductory answer. + +<|ref|>text<|/ref|><|det|>[[115, 573, 508, 591]]<|/det|> +Reviewer #1 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[115, 607, 870, 665]]<|/det|> +I do think the data is reproducible as the imaging is done using a commercial microscope and the authors provide an software to do so. There are details that is missing that need to be provided for the use. This includes calculation and storage of single components for the analysis. + +<|ref|>text<|/ref|><|det|>[[115, 683, 860, 720]]<|/det|> +ANSWER: We thank the reviewer for helping us improve this aspect of the manuscript. We believe we addressed this specific comment in answers 1 and 19 above. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[231, 86, 667, 102]]<|/det|> +## Reviewer #2 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[113, 136, 878, 425]]<|/det|> +The manuscript of Hsiao Ju Chang et al (from the lab of Prof Cultrale) deals with dynamic (time- lapse) multiplexed imaging and offers a global- based solution for spectral unmixing of hyperspectral imaging data. Therefore, the authors improve the previously published algorithm HySP (Cultrale et al, Nat. Meth. 2017), which uses dimensionality reduction via the phasor approach (normalized discrete Fourier transformation of the hyperspectral 4D fluorescence data). They achieve this improvement by integrating in HySP a linear unmixing of the expected spectral signatures in the phase domain (HyU) - including both extrinsic signals (fluorescence proteins) and intrinsic signals (NAD(P)H, retinol, elastin, etc.). The dimensionality reduction of the phasor approach implies also a global analysis of the spectra (i.e. appreciates similarities of the spectra per voxel) and by that better deals with low signals. A thorough characterization of the laser, detector, read background noise and of their distribution type (Poisson, Gaussian, etc.) and implementation for denoising and additional reference- based preprocessing (SEER, Shi et al, Nat. Commun. 2020) improves not only the image quality but also the success of the hyperspectral unmixing of 8 or 9 emission (intrinsic and extrinsic) signals, at high computation speeds, as impressively demonstrated on simulated data and on time- lapse imaging data of multiple- reporter zebrafish larvae. + +<|ref|>text<|/ref|><|det|>[[115, 428, 867, 485]]<|/det|> +While being of great interest for the live imaging community, in my opinion, the manuscript needs additional experimental, algorithmic and background (citation of previous work) information to unfold the full potential, as described in detail in the following. + +<|ref|>text<|/ref|><|det|>[[115, 520, 870, 558]]<|/det|> +ANSWER: We thank the reviewer for the constructive comments and for providing us an opportunity to considerably improve this work. + +<|ref|>text<|/ref|><|det|>[[115, 578, 449, 594]]<|/det|> +Reviewer #2 (Remarks to the Author: Impact): + +<|ref|>text<|/ref|><|det|>[[114, 611, 880, 824]]<|/det|> +The relevance of the question/need for simultaneous spectrally multiplexed fluorescent microscopy to allow dynamic (time- lapse) multi- color imaging is tremendous, however, certainly going far beyond the field of developmental biology and zebrafish larvae imaging. This need has been previously recognized in the frame of intravital multi- photon imaging (not hyperspectral), with impact for cancer research (Entenberg et al, 2011), immunology and neurosciences/neuroimaging, just to mention a few examples. Specifically, there have been solutions proposed and demonstrated for dynamic in vivo fluorescence imaging, including unmixing algorithms apart of the state- of- the- art linear unmixing (Rakhymzhan et al, Sci Rep 2017), in which up to 8 extrinsic and intrinsic signals are simultaneously distinguished, while dealing with low SNRs of multi- photon microscopy still remained a challenge. Including this information in the introduction is key, in order to demonstrate the potential general relevance of the present work and to awake a real interest for a broad readership. + +<|ref|>text<|/ref|><|det|>[[115, 840, 872, 877]]<|/det|> +ANSWER: This is a very good point. We have edited the introduction to broaden the impact of this work. The introduction now reads: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 114, 876, 328]]<|/det|> +Standard fluorescence microscopes collect multiple images sequentially, employing different excitation and detection bandpass filters for each label. Recently developed techniques allow for massive multiplexing by utilizing sequential labeling of fixed samples but are not suitable for in vivo imaging. \(^{12,13}\) Unfortunately, these approaches are ill- suited to separating overlapping fluorescence emission signals, and the narrow bandpass optical filters used to increase selectivity, decrease the photon efficiency of the imaging. (Figs. S1, S2) These limitations have restricted the number of imaged fluorophores per sample (usually 3- 4) and risks exposing the specimen to damaging levels of exciting light. This has been a significant obstacle for the dynamic imaging, preventing in vivo and intravital imaging from reaching its full potential, with broad impact on research, from developmental biology \(^{14}\) , cancer research \(^{15}\) and immunology \(^{2}\) to neuroimaging \(^{16}\) . + +<|ref|>text<|/ref|><|det|>[[172, 380, 878, 593]]<|/det|> +Hyperspectral Fluorescent Imaging (HFI) potentially overcomes the limitations of overlapping emissions by expanding signal detection into the spectral domain. \(^{14}\) HFI captures a spectral profile from each pixel, resulting in a hyperspectral cube (x,y, wavelength) of data, that can be processed to deduce the labels present in that pixel. Linear unmixing (LU) has been widely utilized to analyze HFI data, and has performed well with bright samples emitting strong signals from fully- characterized, extrinsic fluorophores such as fluorescent proteins and dyes \(^{15 - 17}\) . However, in vivo fluorescence microscopy is almost always limited in the number of photons collected per pixel (due to the expression levels, the bio- physical fluorescent properties, and the sensitivity of the detection system), which reduces the quality of the spectra acquired. While solutions beyond the standard LU have been proposed \(^{21}\) , the challenge of analyzing low intensity spectral signals remains. + +<|ref|>text<|/ref|><|det|>[[114, 629, 872, 705]]<|/det|> +In line with this, it is crucial to demonstrate the power of the presented algorithm for unmixing also intravital multi- photon imaging data in optically more challenging tissues and organisms, which need to deal with much lower signals and SNR values, especially due to massive scattering and wave- front distortions in mammal tissue. + +<|ref|>text<|/ref|><|det|>[[115, 724, 864, 801]]<|/det|> +ANSWER: We understand the reviewer's concern on challenging tissues with respect to scattering and wavefront distortions. However, we believe that the underlying physics for combining fluorescent signals and the mathematical requirements for applying our unmixing method should be valid independently from the type of tissue and the depth of the imaging. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 857, 147]]<|/det|> +With regard to the reviewer's concern for HyU to "deal with much lower signals and SNR values", the now updated plots for the unmixing performance covers a wide range of photon counts and SNR, which will likely to cover a wide range of biological applications. + +<|ref|>text<|/ref|><|det|>[[115, 156, 877, 330]]<|/det|> +With regard to "to massive scattering and wave- front distortions in mammal tissue", the reviewer is correct; in principle, highly scattering tissues might affect the fluorescent spectra. However, it should be noted that, in most cases, such massive distortions would require particularly deep imaging. Generally, fluorescent signals decrease greatly in intensity and are lost (scattering/absorption) before reaching such depth, long before these massive wavefront distortions are visible. Undoubtedly, there have to be some spectral distortions caused by the light traveling across a non- uniform biological medium; however, at the relatively shallow sample depths reached before losing signal, these distortions were not measurable at the spectral sampling resolution available on the most common confocal spectral fluorescent microscopes (32 channels, each with 8.9nm bandwidth). + +<|ref|>text<|/ref|><|det|>[[115, 339, 872, 494]]<|/det|> +From our previous experience in working with hyperspectral images and utilizing the phasor method ( https://www.nature.com/articles/nmeth.4134 , https://www.nature.com/articles/s41467- 020- 14486- 8 ) in both deep and scattering tissue, we have demonstrated that as long as the signal is not completely indistinguishable from the noise (for \(\mathrm{SNR} > = 2\) ), the phasor method proves reliable in categorizing signals (shown in Supplementary Figures 21, 22, 23, 24 of https://www.nature.com/articles/s41467- 020- 14486- 8 available at Nature Comm. link https://static- content.springer.com/esm/art%3A10.1038%2Fs41467- 020- 14486- 8/MediaObjects/41467_2020_14486_MOESM1_ESM.pdf ). + +<|ref|>text<|/ref|><|det|>[[115, 502, 878, 618]]<|/det|> +This correct phasor categorization enables HyU to perform averaging and denoising of spectral signals for unmixing. When working with scattered signals, in our experience, fluorescent signals drop below \(\mathrm{SNR} = 2\) before sufficient scattering and spectral distortions affect the unmixing method. This physical limitation of diffusion of fluorescent signal across scattering and absorbing tissues, at least for the biological samples we imaged (cells, zebrafish, mouse), prevented us from encountering sufficiently distorted spectra to induce major errors in the phasor transform or in the unmixing. + +<|ref|>text<|/ref|><|det|>[[142, 627, 860, 840]]<|/det|> +An example of this is shown in Supplementary Figure 28 of https://www.nature.com/articles/s41467- 020- 14486- 8 available at Nature Comm. link https://static- content.springer.com/esm/art%3A10.1038%2Fs41467- 020- 14486- 8/MediaObjects/41467_2020_14486_MOESM1_ESM.pdf . A very similar discussion with additional figures, experiments, and descriptions is reported in the Peer Review File (pgs 47- 49) of https://www.nature.com/articles/s41467- 020- 14486- 8 available at Nature Comm. link https://static- content.springer.com/esm/art%3A10.1038%2Fs41467- 020- 14486- 8/MediaObjects/41467_2020_14486_MOESM2_ESM.pdf. The image in this discussion shows how stable the signal position on the phasor remains when acquiring fluorescent spectra at deeper parts of the sample. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 870, 147]]<|/det|> +However, we understand that providing an example of our method in more scattering mammal tissue would facilitate any adopter in their decision making. We have performed the following additional changes to address this point: + +<|ref|>text<|/ref|><|det|>[[142, 156, 845, 270]]<|/det|> +1. We have added experiments performed on both freshly excised and fixed mouse tissue. (Supplementary Figures 29, 30) +2. We have included unmixing results from deep imaging performed on zebrafish embryos for further comparison. (Supplementary Figure 23) +3. We expanded the Supplementary Information with details on mouse lines, fluorescent silica beads characterization, mouse tissue samples preparation, and imaging. + +<|ref|>text<|/ref|><|det|>[[146, 324, 800, 380]]<|/det|> +1. For mouse experiments, we have included two examples of application for the Hybrid Unmixing method: fresh tissue autofluorescence metabolic imaging and fixed tissue fluorescence imaging. + +<|ref|>text<|/ref|><|det|>[[172, 399, 876, 670]]<|/det|> +The first experiment involved unmixing autofluorescent signals in freshly excised mouse kidney tissue. The unmixed signals include NADH bound, NADH free, Retinol, Retinoic acid, and Elastin, in correspondence to the intrinsic signals previously unmixed in the zebrafish experiments. In Supplementary Figure 29, we demonstrate that the same independant autofluorescent signatures used in the zebrafish to perform HyU can be utilized in the fresh mouse tissue. Even as the intensities of the autofluorescent signatures drop rapidly within the first \(75 \mu \mathrm{m}\) of tissue, we demonstrate that HyU performs as previously shown in zebrafish. The unmixed autofluorescent signals within the mouse tissue yield spatial patterns (Sup. Fig 29 A, B, C, E) corresponding to those described in literature (https://doi.org/10.1117/1.JBO.19.2.020901, https://doi.org/10.1681/ASN.2016101153, https://doi.org/10.1021/cr900343z) and to those previously shown in zebrafish. Cross- section visualizations (Sup. Fig 29 B and E) show consistency in the unmixed autofluorescence patterns along the depth of the sample (z- direction) until signal drops to noise level. For these notoriously weak autofluorescent signals, intensities fade out at approximately \(75 \mu \mathrm{m}\) depth. + +<|ref|>text<|/ref|><|det|>[[172, 689, 866, 805]]<|/det|> +In the presence of massive wavefront distortions in the fluorescent spectra, the expected and most likely behavior of the HyU would be a deterioration of the unmixing quality. This generally results in a non- organized, more uniform re- assignment of intensities across the unmixed channels. When this scenario happens, severe cross- talk is visible across channels. If one were to visualize these results in a 2- D image, it would result in a "white" color where multiple signals are shown together in the same image. + +<|ref|>text<|/ref|><|det|>[[173, 806, 861, 902]]<|/det|> +Supplementary Figure 29 panels B and E are single slices of the volume, representing a 1- pixel wide cross- section of the volume, along the XZ and YZ planes respectively. In these cross sections, there is no visible confounding of signals or "white" color, delineating the overlap of multiple fluorescent signals. This suggests that the algorithm, under reasonable imaging conditions, performs as characterized (Sup. Figures + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 90, 844, 127]]<|/det|> +16,17,18,19). This is mainly because fluorescent signals fade to dark before any appreciable distortion affects the system. + +<|ref|>text<|/ref|><|det|>[[173, 181, 362, 197]]<|/det|> +Supplementary Figure 29: + +<|ref|>image<|/ref|><|det|>[[272, 216, 787, 735]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[172, 748, 759, 766]]<|/det|> +
Supplementary Figure 29. Intrinsic fluorescent signatures in fresh mouse tissue
+ +<|ref|>text<|/ref|><|det|>[[172, 787, 877, 904]]<|/det|> +Intrinsic fluorescent signatures in fresh kidney tissue of a 7 months Balb- c mouse imaged with 2- photon excitation at \(740~\mathrm{nm}\) in a \(150~\mu \mathrm{m}\) deep volume. Despite the increasing scattering effect of this mammal tissue with increasing depth, HyU can perform unmixing of intrinsic fluorescent signals. (A) Volumetric rendering of the unmixing results of five intrinsic fluorescent signatures shows results consistent with literature, as visible in the (B- E) orthogonal views of (C) an unmixed (x,y) cross- section of the volume at \(30~\mu \mathrm{m}\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 88, 880, 167]]<|/det|> +depth in the sample and its corresponding (B) (x,z) and (E) (y,z) projections. (D) Averaged autofluorescent signals for each acquired spectral (x,y) section over the \(150\mu m\) depth of the volume show a sharp decrease of intensities after \(75\mu m\) depth as visible in E, the corresponding (y,z) projection. + +<|ref|>text<|/ref|><|det|>[[173, 201, 881, 317]]<|/det|> +The second experiment involved unmixing a known fluorescent signal among the background signals within the highly scattering mouse tissue by imaging Cy3 beads injected (described in the new Mouse Sample Preparation section below) into fixed mouse tissue. The ground truth spectra of the Cy3 beads is known, measured in pure bead solution (described in the new Fluorescent silica bead characterization section). With this known constant Cy3 fluorescent spectrum, we can demonstrate: + +<|ref|>text<|/ref|><|det|>[[184, 327, 820, 383]]<|/det|> +a. The efficacy of HyU even when fluorescent signatures are buried deep within highly scattering tissue. +b. The effect of tissue scattering on the known Cy3 fluorescent spectrum. + +<|ref|>text<|/ref|><|det|>[[173, 399, 874, 515]]<|/det|> +Supplementary Figure 30 below shows that the Cy3 beads (magenta) are unmixed with the proper spatial profiles (spherical shape) from the autofluorescent (yellow), background (green), and structural signatures (light blue) of the fixed mouse tissue. Similarly to Supplementary Figure 29 B,C,E, there is no evident confounding overlap of signals when imaging deeper in the sample. In this case, with stronger autofluorescent (fixative- related) and fluorescent (beads) signals, signals started fading at \(110\mu m\) depth in the sample. + +<|ref|>text<|/ref|><|det|>[[173, 533, 880, 686]]<|/det|> +In support of our observation that fluorescent spectra, as measured in our commercial instrument, are not excessively distorted in their shape, we plot the spectra corresponding to the Cy3 beads at multiple depths (Supplementary Figure 30 F, G), up to \(130\mu m\) deep in the sample, in absolute (Sup. Fig 30 F) and relative (Sup. Fig 30 G) intensity. Absolute peak intensity for some of the deeper spectra is around \(\sim 1300\) Digital Levels, corresponding to \(2\%\) of the full 16 bit dynamic range of the detector, close to the noise level of the instrument. This translates to visibly noisy spectra for deeper z- planes of the sample, as shown in the relative intensity plots (panel G), but does not show massive spectral distortions. + +<|ref|>text<|/ref|><|det|>[[173, 705, 872, 800]]<|/det|> +In regards to the performance of HyU, the unmixed fluorescent signatures remain consistent with expected spatial patterns within the scattering mouse tissue even as the overall intensity drops. Within the imaging depth we could reach in our instrument, the highly scattering nature of the mouse tissue does not affect the performance of HyU, similar to what we previously demonstrated in zebrafish. + +<|ref|>text<|/ref|><|det|>[[174, 821, 362, 837]]<|/det|> +Supplementary Figure 30: + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[174, 88, 812, 512]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[173, 537, 760, 555]]<|/det|> +
Supplementary Figure 30. Extrinsic fluorescent signatures in fixed mouse tissue
+ +<|ref|>text<|/ref|><|det|>[[172, 576, 875, 848]]<|/det|> +We evaluate the performance of HyU in imaging fluorescent signals in a highly scattering fixed kidney tissue of a 7- month- old Balb- c mouse with embedded Cy3 fluorescent beads (Methods) imaged with 2- photon 850nm excitation up to \(150 \mu \mathrm{m}\) deep. (A) Volumetric rendering of the unmixing results of the signals from fixative autofluorescence (autoFL), Cy3 beads, background, and Second Harmonic Generation (SHG). (B- E) Orthogonal views of the same volume for (C) single (x,y) plane of the volume at a depth of \(90 \mu \mathrm{m}\) with cross- sections (yellow hairlines in C). (B) (z,x) of \(18 \mu \mathrm{m}\) and (E) (y,z) of \(4 \mu \mathrm{m}\) respectively showing sections of the unmixed volume containing Cy3 beads at different depths up to \(140 \mu \mathrm{m}\) . (D) Average intensity value for each acquired (x,y) spectral image slice as a function of depth reveals considerable loss of fluorescent signal deeper than \(110 \mu \mathrm{m}\) . (F) Average spectra for each z- plane containing pixels with Cy3 beads signal plotted with absolute intensity (Digital Levels, DL) show decreasing intensity with depth as demonstrated by the area under each spectrum. (G) The same averaged spectra are normalized and plotted with Relative Intensity to show the consistency in the spectral shape as a function of depth in reference to Cy3 beads in solution (dashed line). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[143, 90, 863, 223]]<|/det|> +2. For completion, we added an example of deep imaging in zebrafish, to demonstrate the similarities in signal attenuation that occurs in this model when compared to highly scattering mouse tissue (Supplementary Figure 23). The phasor plot of the signals provides a consistent distribution, centered at the same coordinates, even for images acquired deeper into the tissue where the detected spectra decrease in intensity and increase in noise. The signal attenuation and noise increase match those seen for the spectra detected in both mouse examples (Sup. Fig 29 and 30). + +<|ref|>image<|/ref|><|det|>[[177, 245, 707, 696]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[173, 714, 737, 732]]<|/det|> +
Supplementary Figure 23. Phasor analysis on signal distortion in deep tissue
+ +<|ref|>text<|/ref|><|det|>[[172, 754, 874, 909]]<|/det|> +Images at different Z- positions of a 3D (x,y,z) dataset of 19 hpf Tg(ubiq:lyn- tdTomato) zebrafish acquired from 0 um to 80 um (relative to the object) depth displaying at every 13 z- slices. (A- D) Phasors calculated from the single slices at 0 \(\mu \mathrm{m}\) , 26 \(\mu \mathrm{m}\) , 52 \(\mu \mathrm{m}\) , and 78 \(\mu \mathrm{m}\) depth. (E- H) Corresponding average intensity images (across the 32 spectral channels) for each z- slice show an expected decrease in fluorescence intensity with depth. (I) Average spectra of the pixels linked to the phasor position bin for the tdTomato fluorescent signature for each of the four presented z- slices (0, 26, 52, 78 \(\mu \mathrm{m}\) ) show a decrease in the spectral area without change in spectral shape as shown by (J) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 88, 875, 205]]<|/det|> +normalizing the average spectra shown in I to each spectrum's maximum value. This demonstrates the spectral shape does not change across different depths (z- planes), while the overall intensity decreases. (K) Randomly selected spectra from the raw spectral image at 0 \(\mu \mathrm{m}\) (blue) and 26 \(\mu \mathrm{m}\) (red), five spectra for each image and similarly (L) for 52 \(\mu \mathrm{m}\) (green) and 78 \(\mu \mathrm{m}\) (yellow). Two yellow and three green spectra are not clearly visible because of low signal intensity. + +<|ref|>text<|/ref|><|det|>[[144, 257, 759, 315]]<|/det|> +3. We expanded the supplementary information to include details on mouse lines, fluorescent silica beads characterization, mouse tissue sample preparation, and imaging: + +<|ref|>sub_title<|/ref|><|det|>[[174, 356, 264, 372]]<|/det|> +## Mouse lines + +<|ref|>text<|/ref|><|det|>[[172, 395, 874, 589]]<|/det|> +Mice imaging was approved by the Institutional Animal Care and Use Committee (IACUC) of University of Southern California, Protocol #21311. Experimental research on vertebrates complied with institutional, national and international ethical guidelines. Animals were kept on a 13:11 hours light:dark cycle. Animals were breathing double filtered air, temperature in the room was kept at 68- 73 F, and cage bedding was changed weekly. All these factors contributed to minimize intra- and inter- experiment variability. Adult Balb- c mice were euthanized via overdose of isoflurane followed by cardiac puncture. Kidneys were quickly harvested from the mouse, washed in PBS, and cut longitudinally alongside the midsection in order to expose the inner part of the organ. The two halves of the organ were arranged onto a microscope slide for imaging. + +<|ref|>sub_title<|/ref|><|det|>[[174, 630, 473, 647]]<|/det|> +## Fluorescent silica beads characterization + +<|ref|>text<|/ref|><|det|>[[174, 670, 872, 727]]<|/det|> +One fluorescent silica beads solution (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, 1% solid, lot# 1608BRX5) was characterized in its spectral fluorescence emission and physical size. + +<|ref|>text<|/ref|><|det|>[[172, 751, 860, 926]]<|/det|> +10x dilution in PBS of the beads was placed on a no. 1.5 imaging coverglass and spectrally characterized using spectral mode on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using 40x/1.1 W LD C- Apochromat Korr UV- VIS- IR lens utilizing a 2- photon laser at 740 nm to excite fluorescence from the beads, using a 690 nm lowpass filter to separate excitation and fluorescence. Spectra obtained from multiple beads with the same label were averaged, producing the reference spectrum reported in Sup. Figure 30 G (dashed line). Fluorescent silica bead size and concentration were determined via nanoparticle tracking analysis (NTA) on the Nanosight NS300 (Malvern Panalytical). Samples were run 5 times and results averaged for final size and concentration values reported. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[175, 123, 377, 140]]<|/det|> +## Mouse Sample preparation + +<|ref|>text<|/ref|><|det|>[[173, 161, 866, 280]]<|/det|> +For autofluorescent measurements, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in Phosphate Buffered Saline (PBS) to remove residual blood and kept in PBS until imaging preparation. Organs were sectioned in order to image the internal architecture and mounted on a glass imaging dish with sufficient PBS to avoid dehydration of the sample. Following imaging, all samples were fixed in a \(10\%\) Neutral Buffered Formalin solution at \(4 - 9C\) + +<|ref|>text<|/ref|><|det|>[[173, 302, 874, 477]]<|/det|> +For ex vivo bead characterization in tissue, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in PBS followed by incubation for at least 24 hours in \(10\%\) buffered formalin. The kidney was then removed from the fixative and sectioned into smaller \(\sim 5\times 5\times 5\mathrm{mm}\) pieces for imaging. A fluorescent silica beads stock (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, \(1\%\) solid, lot# 1608BRX5) and previously characterized was prepared using a \(10x\) dilution of the fluorescent beads from their stock concentration. Beads were injected in the sample using 50ul of these solutions loaded into a \(0.5\mathrm{mL}\) syringe with a \(28g\) needle. The kidney sections were then placed in imaging dishes with a small volume of PBS to keep the samples hydrated prior to imaging. + +<|ref|>sub_title<|/ref|><|det|>[[175, 529, 310, 545]]<|/det|> +## Image Acquisition. + +<|ref|>text<|/ref|><|det|>[[175, 561, 861, 599]]<|/det|> +Images were acquired on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using \(40x / 1.1\) W LD C- Apochromat Korr UV- VIS- IR lens at \(28 - 9C\) + +<|ref|>text<|/ref|><|det|>[[173, 622, 870, 718]]<|/det|> +Samples of Gt(cltca- Citrine), Tg(ubiq:lyn- tdTomato), Tg(fli1::mKO2), and Tg(ubiq:Lifeact- mRuby), were simultaneously imaged with 488 nm and 561 nm laser excitation, for citrine, tdTomato, mKO2, and mRuby. A narrow 488 nm/561 nm dichroic mirror was used to separate excitation and fluorescence emission. Samples were imaged with a 2- photon laser at 740 nm to excite autofluorescence, using a 690 nm lowpass filter to separate excitation and fluorescence. + +<|ref|>text<|/ref|><|det|>[[173, 742, 860, 780]]<|/det|> +Samples of mouse kidney tissue were imaged in 2- photon exciting at 740 nm or 850 nm with a \(690+\) nm lowpass filter, at 37C incubation. + +<|ref|>text<|/ref|><|det|>[[173, 801, 876, 839]]<|/det|> +For all samples, detection was performed at the full available range (410.5- 694.9nm) with 8.9nm spectral binning. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 860, 223]]<|/det|> +Referring to the algorithm itself and to its characterization, the evolution from hyperspectral multiplexed imaging using the phasor approach HySP (Cultrale et al, 2017, Nat Meth), enhanced by preprocessing the data to account for various experimental noise via SEER (2020, Nat Commun) and finally by applying linear unmixing in the hyperspectral phase space, bringing additional significant accuracy to the unmixing capacity of the data is currently not clear in the manuscript and needs to be elaborated in the introduction, to emphasize the novelty of the present work. + +<|ref|>text<|/ref|><|det|>[[117, 242, 808, 279]]<|/det|> +ANSWER: We have improved the introduction to emphasize the novelty of HyU with respect to previously published work: + +<|ref|>text<|/ref|><|det|>[[172, 298, 880, 451]]<|/det|> +We have developed Hybrid Unmixing (HyU) as an answer to the challenges that have limited the wider acceptance of HFI for in vivo imaging. HyU employs the phasor approach26 merged with traditional unmixing algorithms to untangle the fluorescent signals more rapidly and more accurately from multiple exogenous and endogenous labels. The phasor approach26, a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis27- 29 has been shown to provides key advantages to HyU, including spectral compression, denoising, and computational reduction for both pre- processing30 and unmixing31- 33 of HFI datasets. + +<|ref|>text<|/ref|><|det|>[[172, 453, 880, 630]]<|/det|> +Standard Phasor analysis26,27,34- 41 is fully supervised and requires a manual selection of regions or points on a graphical representation of the transformed spectra, called the phasor plot. HyU utilizes phasor processing as an encoder to aggregate similar spectra and applies unmixing algorithms, such as LU, on them to provide unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity. Our results show that HyU offers three key advantages: (1) improved unmixing over conventional LU, especially for low intensity images, down to 5 photons per spectra; (2) simplified identification of independent spectral components; (3) dramatically faster processing of large datasets, overcoming the typical unmixing bottleneck for in vivo fluorescence microscopy. + +<|ref|>text<|/ref|><|det|>[[128, 680, 860, 699]]<|/det|> +We further clarified the advantages of HyU over our previous work HySP in a Supplementary Note 4. + +<|ref|>text<|/ref|><|det|>[[106, 739, 694, 758]]<|/det|> +Supplementary Note 4: Improvements of HyU over the standard phasor analysis + +<|ref|>text<|/ref|><|det|>[[172, 779, 870, 837]]<|/det|> +Linearity of combinations is the general assumption for most of the spectral analysis algorithms in Hyperspectral Fluorescence Imaging (HFI). Each pixel is assumed to contain a linear combination of the independent spectral signatures, or endmembers, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 88, 870, 224]]<|/det|> +contained in the sample. This assumption requires knowledge, or identification, of the independent spectra within the sample. In standard linear unmixing algorithms, the extraction of relative amounts of spectra (ratios) is conducted on a pixel- by- pixel basis, at the expense of computational costs. Disrupted experimental signals, in the case of lower Signal to Noise Ratio (SNR) spectra, complicate the detection of spectral endmembers and reduce the accuracy of ratio determination. These standard unmixing algorithms, however, have the advantage of being unsupervised with the possibility of automating the analysis process. + +<|ref|>text<|/ref|><|det|>[[172, 248, 872, 638]]<|/det|> +The phasor approach has become a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis13- 15. Phasors provide key advantages, including spectral compression, denoising, and computational reduction for both pre- processing3 and unmixing8,16,17 of HFI datasets. Phasor analysis overcomes the challenge of low SNR data analysis that limits standard unmixing algorithms, providing a multiplexing solution to a need. The phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original clean data18. In the imaging of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data has made the phasor method a valuable tool for fluorescence microscopy, both for Lifetime and Spectral Fluorescence Microscopy. This point is reported by multiple groups using phasors18- 21 and, more recently, nicely described in the work of Scipioni et al22. Standard Phasor analysis23- 25 is fully supervised and requires a manual selection of regions or points on a graphical representation of the transformed spectra, called the phasor plot. Each selection of a region in the phasor plot associates pixels containing similar spectra to the same fluorophore, forming an output channel that contains wavelength integral of intensities with unitary ratiometric value. This “winner takes all” approach is suitable when fluorophores for each single excitation light are spectrally overlapping and spatially disperse (Sup. Figure 24), but requires separate acquisition of different excitation wavelengths for demultiplexing spatially and spectrally overlapping fluorophores (Sup. Figure 25). + +<|ref|>text<|/ref|><|det|>[[173, 660, 870, 835]]<|/det|> +HyU uses the phasor transform to group pixels with similar spectral shape within each phasor histogram bin. This approach maintains the advantage of compressing, denoising and simplifying identification of clean endmember fluorescent spectra. However, HyU improves on the robustness of the analysis. The denoised signals are maintained in a hybrid phasor and wavelength domain, and therefore can be unmixed with a multitude of standard unmixing algorithms (Sup. Figure 13), such as Linear Unmixing or Fully Constrained Least Squares. These standard unmixing approaches can operate without supervision and provide for each pixel the ratios for a set of spectral signals, overcoming some of the limitations of phasor, but generally do not perform well in experimental + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 88, 868, 384]]<|/det|> +conditions with reduced and compromised signals, such as in fluorescence, and require extensive computational time for high spectral- count datasets. HyU provides wavelength- based denoised spectra that enable these standard algorithms to outperform their pixel- by- pixel typical application, both in quality of the results (Sup. Figures 16- 19), owing to cleaner and better defined fluorescent spectra in each phasor bin, and, generally, in speed, owing to the phasor dimensionality reduction. HyU performs well for single excitation light when fluorophores are spectrally overlapping both when they are spatially disperse or co- localized, providing a ratio for each independent spectrum currently unmixed. Our data suggests HyU has reasonable performance for up to 8 different fluorophores per dataset, for each single excitation wavelength. In an experiment with a carefully chosen palette of labels, where octuples of fluorophores can be excited by a single wavelength, with an instrument capable of spectral acquisition with 5 standard and sufficiently spectrally separated excitation wavelengths in 5 sequential acquisitions (one for each excitation light), HyU could, in principle, unmix 40 signals. This performance however decreases with the number of channels (Sup. Figures 18, 19) showing a small deterioration at 8 channels and limitations at 4. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 136, 857, 232]]<|/det|> +A. Referring to the broad applicability of the algorithm and the interest for a large community: +A.1. As previously mentioned, in order to prove the value of the approach presented in this manuscript, multiplexed time-lapse imaging in a mammal (adult mouse or rat or human) tissue is key and experimental data on this need to be added to the manuscript. I believe, one 4D (3D + time) imaging example showing 8-9 distinct emission signals would be absolutely convincing. + +<|ref|>text<|/ref|><|det|>[[125, 265, 870, 517]]<|/det|> +ANSWER: We agree with this reviewer that a multiplexed time- lapse imaging in a mammal (adult mouse or rat or human) tissue showing 8- 9 distinct emission signals would absolutely be convincing. However, such an experiment would require a specialized team with expertise in mouse/rat multicolor labeling, a dedicated mouse/rat colony, specialized equipment for both anesthesia and imaging of the samples, and a complex survival imaging animal protocol. We currently do not have such expertise in our group, which mainly uses zebrafish, lack the compliant instrumentation for performing mammal timelapse imaging under anesthesia as regulated by IACUC of USC, and do not have active mouse protocols that would allow such imaging. Performing such a complex experiment would require 2- 3 years of work, after securing the necessary funding for additional personnel and instrumentation, while, arguably, there likely is a very limited number of laboratories with the capability and equipment of routinely performing 4D imaging of mouse/rat samples with 8- 9 labels. For these reasons we believe such an experiment would, itself, be worthy of an independent publication. However, it would not further the demonstration of the method in this manuscript. + +<|ref|>text<|/ref|><|det|>[[128, 535, 872, 670]]<|/det|> +As such, we believe this experiment to be beyond the scope of this manuscript, which presents a fluorescence unmixing method for the broader audience. We agree with the reviewer that example applications in mouse should be part of this manuscript (as we stated above) with respect to the concerns of distortions of spectra in scattering tissues. We have included additional mouse tissue experiments in this revision that we believe address the performance of the method when applied to mammalian samples. We kindly refer to the above answer to this reviewer (Remarks to the Author: Impact) for details of the additional experiments. + +<|ref|>text<|/ref|><|det|>[[115, 725, 405, 742]]<|/det|> +B. Referring to the unmixing approach: + +<|ref|>text<|/ref|><|det|>[[115, 744, 866, 820]]<|/det|> +B. Referring to the unmixing approach: +B.1. In order to judge the added value of the integration of linear unmixing and of reference extrinsic and intrinsic spectral signatures on the performance of unmixing, a thorough comparison with the previously available HySP (Cultrale et al, 2017) needs to be provided, additionally to the comparison to state-of-the-art linear unmixing algorithms already included in teh manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 840, 346, 856]]<|/det|> +ANSWER: To address this point: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[142, 90, 870, 207]]<|/det|> +1. We have improved the introduction to emphasize the novelty of HyU with respect to previously published work (see answer above for in-line text). +2. We included a full comparison with different types of samples in Supplementary Figures 24 and 25. +3. We added an extensive discussion that outlines the advantages of HyU over the previously available HySP in the new Supplementary Note 4. + +<|ref|>text<|/ref|><|det|>[[143, 258, 850, 375]]<|/det|> +1. The introduction now refers to our previous work and overviews the improvements of HyU over it. The excerpt is copied for reference in the last answer to this reviewer's "Impact" section. +2. We included comparisons of HyU vs HySP with different sample types, where for each laser excitation, the sample contains spectrally overlapping spatially disperse labels or both spectrally and spatially overlapping fluorophores. + +<|ref|>text<|/ref|><|det|>[[174, 394, 362, 410]]<|/det|> +Supplementary Figure 24: + +<|ref|>image<|/ref|><|det|>[[360, 410, 689, 899]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[108, 90, 866, 127]]<|/det|> +Supplementary Figure 24. Comparison of HyU vs HySP results from a spectrally overlapping and spatially disperse sample + +<|ref|>text<|/ref|><|det|>[[172, 152, 876, 366]]<|/det|> +Results are presented for unmixing using HyU and Hyperspectral Phasors (HySP) on a spectrally overlapping spatially disperse dataset collected from a tri- labeled transgenic zebrafish embryo obtained by injecting mRNA- encoding H2B- cerulean (cyan) in double transgenic embryos Gt(desm- citrine) ct122a/+;Tg(kdrl:eGFP) (magenta and yellow, respectively) (A- F) HyU unmixing results and (G- L) HySP unmixing results renderings for the dataset. Line profiles of (F) HySP (L) HyU analysis results (B, H dashed line) show the similarity in signal between the two methods for all channels within a non- overlapping sample. (A,F) Volumetric images show a similarity between the HyU and HySP results. This is further demonstrated for the results in a (B,H) single z- slice, for just the (C,I) Citrine channel, the (D,J) Cerulean channel, and the (E,K) mCherry channel. (F,L) Line profiles for the lines shown in B and H, respectively, also demonstrate the similar results of HyU and HySP for spatially non- overlapping samples. + +<|ref|>text<|/ref|><|det|>[[174, 402, 362, 418]]<|/det|> +Supplementary Figure 25: + +<|ref|>image<|/ref|><|det|>[[333, 444, 710, 876]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[104, 90, 904, 127]]<|/det|> +Supplementary Figure 25. Comparison of HyU vs HySP results from a spectrally overlapping and spatially non- disperse sample + +<|ref|>text<|/ref|><|det|>[[171, 128, 881, 323]]<|/det|> +Results for unmixing using HyU and HySP on a spectrally overlapping and spatially non- disperse dataset collected from a 5 dpf dual- labeled transgenic zebrafish embryo: Gt(cltca- citrine); Tg(fli1:mKO2), presenting frequent combinations of signals in pixels across the dataset. (A- E) HyU unmixing results and (F- K) HySP unmixing results for the dataset. (A,F) Volumetric images show the expected signal overlaps between channels for the HyU result and a more distinct separation in the HySP result. This is further demonstrated for the results in a (B,G) single z- slice, for just the (C,H) mKO2 channel, and the (D,I) Citrine channel. (E,J) Line profiles for the lines shown in B and G, respectively, demonstrate the fractional nature of HyU results compared to the winner- takes- all analysis of HySP. + +<|ref|>text<|/ref|><|det|>[[143, 340, 772, 378]]<|/det|> +3. Supplementary Note 4, replicated in our first answer to this reviewer, furthers the discussion. + +<|ref|>text<|/ref|><|det|>[[113, 440, 880, 635]]<|/det|> +B.2. A central advantage of the here presented approach is the capacity of dealing even with low signals, i.e. unmixing even low endogenous signals, such as NAD(P)H, even free and bound – having extremely similar emission spectra (one reason why their fluorescence lifetime has been used to resolve the two states). The authors show the improvement referring to number of photons per spectrum, however, in order to judge the true improvement brought by the algorithm for real imaging data (which includes background with diverse types of noise distributions), the unmixing quality needs to be related to the signal-to-noise (SNR) ratio per voxel. While mentioning SNR in the text, no values or comparison are provided in this sense – it is important to mention how the SNR as such (not only the number of photons per spectrum) impacts on the spectral resolution, i.e. how similar can be two spectra at a certain SNR to be able to still resolve them? + +<|ref|>text<|/ref|><|det|>[[115, 670, 828, 688]]<|/det|> +ANSWER: We thank the reviewer for this very good point. To address this comment we prepared: + +<|ref|>text<|/ref|><|det|>[[143, 690, 765, 727]]<|/det|> +1. A plot correlating the SNR as a function of spectrum-type and photons/spectrum +2. A definition of the Spectral SNR + +<|ref|>text<|/ref|><|det|>[[144, 760, 864, 876]]<|/det|> +1. The plot represents how photons per spectra translate to a more standardized definition of SNR, utilizing the fluorophores' spectra from this manuscript. We provide these plots to show the direct relationship between photons per spectrum and the SNR of a single spectra. The reason for demonstrating the relationship between photons per spectra and SNR instead of directly calculating and presenting the SNR values is because the exact description and quantification of SNR becomes highly convoluted and unintuitive for + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 90, 850, 166]]<|/det|> +combinations of multiple spectra. It is important to notice the differences in Spectral SNR between fluorophores as the result of the different spectra shapes which cover different numbers of channels in our instrument- simulating algorithm (410- 692nm spectral detection range, 32 bands each with 8.8nm bandwidth). + +<|ref|>image<|/ref|><|det|>[[175, 208, 901, 438]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[173, 185, 362, 201]]<|/det|> +
Supplementary Figure 28:
+ +<|ref|>text<|/ref|><|det|>[[108, 446, 881, 660]]<|/det|> +Supplementary Figure 28. Relationship between Spectral SNR and Photon/SpectrumThe direct relationship between SNR and photons per spectrum is shown here using the calculation of Spectral SNR for varying levels of photons per spectrum. The spectral SNR has a general trend of increased values with increasing photons per spectrum, but it is not a truly monotonic function. This non- monotonicity demonstrates the limitations of SNR when analyzing spectral images. (A) Absolute Spectral SNR and (B) Relative Spectral SNR follow the same trends of higher values with increasing photons per spectrum. However, the Relative Spectral SNR better differentiates the effects of the differing spectral shapes on the SNR. Citrine, mKO2, mRuby, and tdTomato each have easily distinguished values for the slope of the regression in ascending order. tdTomato has a spectral shape which provides the best SNR while Citrine provides the worst SNR, even with the same number of photons per spectrum. + +<|ref|>text<|/ref|><|det|>[[144, 712, 877, 828]]<|/det|> +2. For this simulated hyperspectral (multispectral/multichannel) fluorescent data, the term of Spectral SNR is calculated inclusively of the spectral dimension. We define the criteria used for calculating Spectral SNR in a new section in Supplementary Methods. Briefly, these Spectral SNR calculations are designed to also include the noise resulting from the stochastic emission of fluorescent photons which disrupts the shape of spectra, therefore compromising the unmixing analysis. The additional section in Supplementary Methods reads: + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[203, 90, 417, 107]]<|/det|> +## Spectral Signal to Noise Ratio + +<|ref|>text<|/ref|><|det|>[[202, 128, 870, 227]]<|/det|> +Since each synthetic dataset has a ground truth, the SNR can be calculated by comparing the simulated image to the ground truth. Since these are hyperspectral images, we extend the definition of SNR to the wavelength dimension of the data and use the term Spectral SNR. We define two types of Spectral SNR, Absolute Spectral SNR and Relative Spectral SNR. + +<|ref|>text<|/ref|><|det|>[[202, 248, 877, 385]]<|/det|> +Spectral SNR is calculated as follows for each single spectrum simulation. First, for each pixel and channel, the absolute value of the difference is taken between the ground truth intensity and the simulated intensity. Then the mean is calculated over all of the pixels for each channel. Finally, the sum is taken over all of the channels and divided by either 32 for the absolute SNR, or the number of channels with signal for the relative SNR. The number of channels with signal is calculated by checking if there is a statistically significative number of pixels in a single channel with a pixel SNR value greater than zero. + +<|ref|>equation<|/ref|><|det|>[[365, 401, 658, 496]]<|/det|> +\[\mathrm{Absolute~SNR} = \frac{\sum_{c = 1}^{P}\frac{t_{gnd}}{t_{sim} - t_{gnd}}}{32} \quad (23)\] \[\mathrm{Relative~SNR} = \frac{\sum_{c = 1}^{P}\frac{t_{gnd}}{t_{sim} - t_{gnd}}}{c} \quad (24)\] + +<|ref|>text<|/ref|><|det|>[[202, 531, 875, 591]]<|/det|> +Where ignd is the intensity per pixel per channel for the ground truth data, isim is the intensity per pixel per channel for the simulated (noisy) data, \(P\) is the total number of pixels, and \(C\) is the number of channels with signal. + +<|ref|>text<|/ref|><|det|>[[113, 658, 870, 814]]<|/det|> +B.3. A corner stone in acquiring better unmixing is the availability of appropriate reference spectral signatures. Whereas the current software provides the spectra necessary for the data shown in the manuscript and gives the opportunity for the users to identify signatures in their own data, the manuscript remains elusive of how the user can differentiate between a real spectral signature and different types of optical or electronical background and interferences – as well known from the use of the phasor approach in fluorescence lifetime imaging, a major challenge when dealing with experimental noisy imaging data in the frequency (phase) domain. The manuscript would benefit from including such a guide to validate the capacity for external use of the algorithm. + +<|ref|>text<|/ref|><|det|>[[113, 848, 928, 888]]<|/det|> +ANSWER: We have expanded Supplementary Note 1 titled “Identification of spectra and new components with HyU” with further clarifications, insights and references on how to distinguish + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 91, 828, 108]]<|/det|> +independent spectral signatures from various types of noise. Supplementary Note 1 now reads: + +<|ref|>text<|/ref|><|det|>[[104, 130, 686, 147]]<|/det|> +Supplementary Note 1: Identification of spectra and new components with HyU + +<|ref|>text<|/ref|><|det|>[[171, 153, 883, 780]]<|/det|> +Identification of independent spectral components has been an adversity for unmixing hyperspectral data. First, the collected spectra may be distorted by reduced SNR. Secondly, excitation of intrinsic signals causes uncertainty of biological sample. Favorably, HyU simplifies this process by adapting Phasor approach and achieving semi- or full- automation process for spectra identification and selection. In HyU spectra can be loaded from an existing library, virtually automating the analysis process. Pre- identified cursors are generated from common fluorophores such as mKO2, tdTomato, mRuby, Citrine. In our experience, obtaining fluorescence spectra from experimental samples has some advantages compared to utilizing spectra from existing library, as they account for a multitude of experimental and instrumental settings. Imaging settings such as different types of lenses or optical filters (Sup. Figure 4, C and D) together with factors within the microenvironment of samples, such as pH or temperature have the potential to alter the fluorescence spectral emissions12. In the presence of unexpected fluorescent signals, spectra can also be selected and visualized directly from the phasor. Phasors facilitate the identification of unexpected independent components and their distinction from the multiple system noises. A noise- free spectrum will appear as a single point on the phasor plot, while a spectrum affected by instrument and electronic noises will mainly appear as a gaussian distribution, centered on the original spectral signal6. Conversely, a randomized noise across the multiple spectral channels will not produce a clustered aggregate of spectra on the phasor. A constant spectral noise, with a distinct spectrum (e.g. a constant light leakage into the system), would produce a distinct phasor cluster and could be selected for unmixing. The phasor plot representation is a 2D- histogram and provides insights into the frequency of occurrence for these signals. These unexpected independent components in samples often appear as "tails" on the phasor distributions (Sup. Figure 11, C). In our HyU graphical interface, clicking on the phasor visualizes the spectra within a small area (9x9 bins by default, with size adjustable from the interface) of the phasor histogram (Figure 1 D). In the example in Sup. Figure 9- 11 we identify 5 distinct endmembers on the Phasor (Sup. Figure 10, C), visualize their spectra identifying Citrine, mRuby, Td- Tomato, mKO2, and one strong autofluorescence signature. The use of Residual Phasor Map (Sup. Figure 11, B) allows for identification of areas in the phasor with high amount of residuals, likely corresponding to a missing endmember in the unmixing. Residual Image Maps (Sup. Figure 11, C) provide a rapid overview of residuals in the image data, for identification of location in the dataset of the missing endmember. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 136, 868, 252]]<|/det|> +B.4. Finally, fully agreeing with the authors that the number of detectors may be varied, depending on the imaged sample type and on the excitation strategy, in order to acquire an emission signal at all, an analysis of how the number of detectors (channels) impacts on the resolution between different signatures (spectra) is needed also for less than 32 detectors (4 to 6 channels being the reality in many labs due to truly low fluorescence signals in deep tissue, e.g. of mice or of humans). + +<|ref|>text<|/ref|><|det|>[[115, 268, 860, 423]]<|/det|> +ANSWER: To characterize how the number of channels affects the hybrid unmixing analysis, we have assembled a complex simulation matrix representing the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built on top of the complex simulation we designed (further expanded in the Hyperspectral Fluorescence Image Simulation section of the supplementary methods), which is soon to be published in a separate manuscript. This simulation accounts for a multitude of real-world noises in experimental samples that are regularly imaged (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). + +<|ref|>text<|/ref|><|det|>[[128, 458, 722, 476]]<|/det|> +We replicate the expanded Hyperspectral Fluorescence Image Simulation section: + +<|ref|>sub_title<|/ref|><|det|>[[106, 512, 439, 529]]<|/det|> +## Hyperspectral Fluorescence Image Simulation + +<|ref|>text<|/ref|><|det|>[[172, 538, 875, 673]]<|/det|> +The model simulates spectral fluorescent emission by generating a stochastic distribution of photons with profile equivalent to the pure reference spectra (as described in Sup. Note 1). The effect of photon starvation, commonly observed on microscopes, is synthetically obtained by manually reducing the number of photons in this stochastic distribution. Detection, Poisson and signal transfer noises are then added to produce 32- channel fluorescence emission spectra that closely resemble those acquired on microscopes. The simulations include accurate integration of dichroic mirrors and imaging settings. + +<|ref|>sub_title<|/ref|><|det|>[[174, 683, 306, 700]]<|/det|> +## Simulation Types: + +<|ref|>sub_title<|/ref|><|det|>[[175, 710, 434, 726]]<|/det|> +## Biologically comparable simulations + +<|ref|>text<|/ref|><|det|>[[172, 735, 870, 891]]<|/det|> +To quantify the performance of HyU vs LU for microscopy data acquired experimentally, we generated synthetic data where each input spectra was organized with intensity distributions taken from experimental data of fluorescently labeled biological samples. We calibrated the analog (Digital Levels) to photon counting rate based on existing literature \(^{5,6}\) . Experimental data was discretized to photons to produce biologically relevant photon masks with distributions of signals highly resembling those of the samples. This provided intensities and ratios which closely resemble those acquired from a confocal microscope while allowing control over the effects of photon starvation. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[174, 115, 518, 133]]<|/det|> +## Spatially and spectrally overlapping simulations + +<|ref|>text<|/ref|><|det|>[[172, 140, 861, 435]]<|/det|> +We also included simulations to quantify the performance of HyU vs LU with respect to the number of spectral combinations and of endmembers. The results are summarized in Supplementary Figures 16- 19 in the form of matrices of spectral overlap (0 to \(100\%\) , steps of \(10\%\) , X- axis) by number of endmembers (2 to 8 endmembers, Y- axis) representing the Relative Mean Squared Error (RMSE) (Supplementary Methods, Performance quantification). Each RMSE value reported in a matrix is the average of analysis of a \(1024 \times 1024\) pixels image simulation with a spectral dimension of \(32:\) channels matching the spectral range and bandwidth of the detectors in commercial confocal microscopes (LSM 780, Carl Zeiss). These simulations were created with artificial intensity distributions so that a simulation with \(X\%\) overlap and n fluorophores would have X percentage of pixels with a randomized ratio of n input spectra. As an example, for a simulation with 6 fluorophores and \(50\%\) overlap, the simulated dataset would have \(50\%\) of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. This allowed us to investigate the effects of an increasing number of spectral combinations on the compressive nature of the phasor method for HyU. + +<|ref|>text<|/ref|><|det|>[[128, 495, 878, 533]]<|/det|> +The results are reported in Supplementary Figure 19 and described in Supplementary Note 4 (reported above): + +<|ref|>image<|/ref|><|det|>[[128, 554, 875, 808]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[103, 812, 857, 851]]<|/det|> +
Supplementary Figure 19. RMSE improvement for simulated fluorescent and autofluorescent spectral combinations highlights decreasing overall performance across decreased number of spectral channels
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[171, 88, 877, 400]]<|/det|> +Fifteen matrices demonstrate the RMSE improvement of HyU with respect to LU when unmixing a collection of synthetic data with 2 to 8 extrinsic and intrinsic labels (Y axis of each matrix) as a function of the spatial overlap of these labels in a sample (X axis of each matrix). In the matrix, \(0\%\) overlap denotes simulations with spatially distinct fluorophores, where each pixel corresponds to a single fluorophore, while simulations with \(100\%\) overlap contain, in every pixel, a randomized ratio of the n extrinsic and intrinsic fluorophores. Each one of the values reported in a matrix is the average of a \(1024 \times 1024 \times 32\) pixels simulation and shows the RMSE improvement of HyU to LU. Columns in the figure represent RMSE improvement matrices with 3x denoising filters across an increasingly binned number of spectral channels (32, 16, 8, 6, 4) applied with a total number of photons per pixel at (A) 16 (B) 32 (C) 48. When utilizing 32 spectral channel data, RMSE improvements reach up to the previously reported \(100\%\) for highly overlapping fluorophores. Successively increasing the binning across the wavelength dimension (and therefore decreasing the number of channels) shows a slow downward trend of the RMSE improvement until the 4 spectral channel matrices, where the RMSE improvement drops drastically down to below \(25\%\) , especially for more than 3 labels. Spectra utilized for this simulation are reported in Sup. Figure 20B. + +<|ref|>text<|/ref|><|det|>[[130, 449, 763, 468]]<|/det|> +The excerpt of Supplementary Note 4 clarifying the performance / number of channels: + +<|ref|>text<|/ref|><|det|>[[172, 495, 870, 612]]<|/det|> +In an experiment with a carefully chosen palette of labels, where octuples of fluorophores can be excited by a single wavelength, with an instrument capable of spectral acquisition with 5 standard and sufficiently spectrally separated excitation wavelengths in 5 sequential acquisitions (one for each excitation light), HyU could in principle unmix 40 signals. This performance however decreases with the number of channels (Sup. Figure 25) showing a small deterioration at 8 channels and limitations at 4. + +<|ref|>text<|/ref|><|det|>[[115, 683, 508, 700]]<|/det|> +Reviewer #2 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[115, 717, 880, 754]]<|/det|> +The current version of the HySP platform was easy to use and the provided sample data delivered similar results as those shown in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 807, 877, 844]]<|/det|> +ANSWER: We thank the reviewer for the constructive feedback and for helping us improve the quality of the work presented here. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 137, 869, 272]]<|/det|> +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. However, I found that there are some confusing points to be addressed clearly to publish this manuscript in Nature Portfolio. + +<|ref|>text<|/ref|><|det|>[[115, 290, 806, 328]]<|/det|> +ANSWER: We thank the reviewer for the valuable comments on the manuscript. Following the reviewer's comments we have: + +<|ref|>text<|/ref|><|det|>[[142, 346, 876, 600]]<|/det|> +1. improved the explanation of the advantages of HyU by modifying our introduction and adding a new Supplementary Note 4 +2. extended the description of the simulations with more detail, providing our reasoning and multiple figures to demonstrate why they provide a realistic replication of standard experimental conditions and are reliable as standards to compare our results with our unmixing methods +3. expanded our Supplementary Note 1 with further clarifications, insights, and references on how to distinguish both known and unknown independent spectral signatures within the phasor plot +4. demonstrated our unmixing method in both scattering and non-optically clear tissue by performing hyperspectral fluorescence experiments in both freshly excised and fixed mouse tissue, summarizing the HyU unmixing results in two new supplementary figures as well as demonstrating the unmixing method for deep imaging in zebrafish. + +<|ref|>sub_title<|/ref|><|det|>[[115, 655, 200, 669]]<|/det|> +## Comments: + +<|ref|>text<|/ref|><|det|>[[115, 672, 857, 747]]<|/det|> +1) Hyperspectral phasor compresses spectral dimension by exploiting real and imaginary parts of Fourier transformation. Moreover, there were reports that hyperspectral phasor could be applied for multiplexed fluorescence imaging. If there are any advantages of combining phasor and spectral unmixing methods, please describe them clearly in the Introduction. + +<|ref|>text<|/ref|><|det|>[[115, 784, 443, 800]]<|/det|> +ANSWER: To address this comment we have: + +<|ref|>text<|/ref|><|det|>[[144, 818, 792, 894]]<|/det|> +1. modified the introduction to clarify the advantages of combining phasor and spectral unmixing +2. added a Supplementary Note 4 to further the clarification of the advantages for HyU compared to previous reports of hyperspectral phasors + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[146, 90, 381, 106]]<|/det|> +1. The introduction now reads: + +<|ref|>text<|/ref|><|det|>[[171, 108, 879, 400]]<|/det|> +1. The introduction now reads:HyU employs the phasor approach26 merged with traditional unmixing algorithms to untangle the fluorescent signals more rapidly and more accurately from multiple exogenous and endogenous labels. The phasor approach26, a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis27-29 has been shown to provides key advantages to HyU, including spectral compression, denoising, and computational reduction for both pre-processing30 and unmixing31-33 of HFI datasets. Standard Phasor analysis26,27,34-41 is fully supervised and requires a manual selection of regions or points on a graphical representation of the transformed spectra, called the phasor plot. HyU utilizes phasor processing as an encoder to aggregate similar spectra and applies unmixing algorithms, such as LU, on them to provide unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity. Our results show that HyU offers three key advantages: (1) improved unmixing over conventional LU, especially for low intensity images, down to 5 photons per spectra; (2) simplified identification of independent spectral components; (3) dramatically faster processing of large datasets, overcoming the typical unmixing bottleneck for in vivo fluorescence microscopy. + +<|ref|>text<|/ref|><|det|>[[144, 468, 830, 505]]<|/det|> +2. We have added Supplementary Note 4 to directly address the improvements of HyU over previously published works on spectral phasors, particularly in this portion of the note: + +<|ref|>text<|/ref|><|det|>[[230, 508, 880, 858]]<|/det|> +HyU uses the phasor transform to group pixels with similar spectral shape within each phasor histogram bin. This approach maintains the advantage of compressing, denoising and simplifying identification of clean endmember fluorescent spectra. However, HyU improves on the robustness of the analysis. The denoised signals are maintained in a hybrid phasor and wavelength domain, and therefore can be unmixed with a multitude of standard unmixing algorithms (Sup. Figure 13), such as Linear Unmixing or Fully Constrained Least Squares. These standard unmixing approaches can operate without supervision and provide for each pixel the ratios for a set of spectral signals, overcoming some of the limitations of phasor, but generally do not perform well in experimental conditions with reduced and compromised signals, such as in fluorescence, and require extensive computational time for high spectral-count datasets. HyU provides wavelength-based denoised spectra that enable these standard algorithms to outperform their pixel-by-pixel typical application, both in quality of the results (Sup. Figures 16- 19), owing to cleaner and better defined fluorescent spectra in each phasor bin, and, generally, in speed, owing to the phasor dimensionality reduction. HyU performs well for single excitation light when fluorophores are spectrally overlapping both when they are spatially disperse or co-localized, providing a ratio for each independent spectrum currently unmixed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 868, 166]]<|/det|> +2) If I understood correctly, numbers of photons (For instance, 5 photons per spectral in the last paragraph in Introduction) were calculated from the computer simulation. If so, this quantitative value is significantly affected by the noise levels used in the simulation. Therefore, it would be good to add these values were obtained from the simulation for clarity. + +<|ref|>sub_title<|/ref|><|det|>[[115, 186, 186, 201]]<|/det|> +## ANSWER: + +<|ref|>text<|/ref|><|det|>[[115, 204, 833, 241]]<|/det|> +We have edited the Section "Hyperspectral Fluorescence Image Simulation" in the Supplementary Materials to include more details on the simulations: + +<|ref|>sub_title<|/ref|><|det|>[[106, 264, 439, 281]]<|/det|> +## Hyperspectral Fluorescence Image Simulation + +<|ref|>text<|/ref|><|det|>[[172, 290, 875, 425]]<|/det|> +The model simulates spectral fluorescent emission by generating a stochastic distribution of photons with profile equivalent to the pure reference spectra (as described in Sup. Note 1). The effect of photon starvation, commonly observed on microscopes, is synthetically obtained by manually reducing the number of photons in this stochastic distribution. Detection, Poisson and signal transfer noises are then added to produce 32- channel fluorescence emission spectra that closely resemble those acquired on microscopes. The simulations include accurate integration of dichroic mirrors and imaging settings. + +<|ref|>sub_title<|/ref|><|det|>[[174, 435, 306, 451]]<|/det|> +## Simulation Types: + +<|ref|>sub_title<|/ref|><|det|>[[175, 462, 433, 478]]<|/det|> +## Biologically comparable simulations + +<|ref|>text<|/ref|><|det|>[[172, 487, 880, 641]]<|/det|> +To quantify the performance of HyU vs LU for microscopy data acquired experimentally, we generated synthetic data where each input spectra was organized with intensity distributions taken from experimental data of fluorescently labeled biological samples. We calibrated the analog (Digital Levels) to photon counting rate based on existing literature \(^{5,6}\) . Experimental data was discretized to photons to produce biologically relevant photon masks with distributions of signals highly resembling those of the samples. This provided intensities and ratios which closely resemble those acquired from a confocal microscope while allowing control over the effects of photon starvation. + +<|ref|>sub_title<|/ref|><|det|>[[174, 684, 518, 701]]<|/det|> +## Spatially and spectrally overlapping simulations + +<|ref|>text<|/ref|><|det|>[[172, 710, 866, 943]]<|/det|> +We also included simulations to quantify the performance of HyU vs LU with respect to the number of spectral combinations and of endmembers. The results are summarized in Supplementary Figures 16- 19 in the form of matrices of spectral overlap (0 to 100%, steps of 10%, X- axis) by number of endmembers (2 to 8 endmembers, Y- axis) representing the Relative Mean Squared Error (RMSE) (Supplementary Methods, Performance quantification). Each RMSE value reported in a matrix is the average of analysis of a 1024x1024 pixels image simulation with a spectral dimension of 32: channels matching the spectral range and bandwidth of the detectors in commercial confocal microscopes (LSM 780, Carl Zeiss). These simulations were created with artificial intensity distributions so that a simulation with X% overlap and n fluorophores would have X percentage of pixels with a randomized ratio of n input spectra. As an example, for a simulation with 6 fluorophores and 50% overlap, the simulated dataset + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 88, 863, 166]]<|/det|> +would have \(50\%\) of the pixels contain a randomized combination of the 6 fluorophores, while the remaining pixels contain a single fluorophore. This allowed us to investigate the effects of an increasing number of spectral combinations on the compressive nature of the phasor method for HyU. + +<|ref|>text<|/ref|><|det|>[[128, 184, 865, 300]]<|/det|> +The simulation algorithm is soon to be published in a separate manuscript. It includes extensive characterization of instrument noise and produces distributions of signals that closely resemble the corresponding images acquired from the fluorescent microscope with analog mode detection. We provide the reviewer with a link to the GitHub repository with the version of the simulation used for the paper to demonstrate the complexity of the simulation. https://github.com/TranslationalImagingCenter/fluoroSim- HyU + +<|ref|>text<|/ref|><|det|>[[128, 324, 862, 440]]<|/det|> +Here, we show some images that will be part of the separate publication with an example of a simulated uniform signal (a Chroma Slide) recreated using our simulation framework after acquiring the experimental signal using a confocal fluorescent microscope. The distribution of intensities between the experimental and simulated signals (A, B) present similar characteristics, even accounting for the stochasticity of photon emission and multiple noise contributions. The average spectrum of each dataset (C, D) shows close resemblance in both shape and intensity. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 90, 870, 530]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[173, 556, 881, 653]]<|/det|> +Comparison of microscope measured uniform signal and corresponding simulation: In this example, a yellow Chroma Slide is imaged using a 780 Zeiss Inverted in spectral mode (32 channels). (A,C) The top row shows images, histogram intensities, and the average spectrum for experimental data, focusing on two significant channels (468 nm and 548 nm). (B, D) The bottom row shows the corresponding results created by the simulation. + +<|ref|>text<|/ref|><|det|>[[128, 705, 877, 899]]<|/det|> +We further characterized the performance of the hyperspectral fluorescent simulation with respect to noise, detectors, and fluorescence characteristics. In the following image, we show the plots of mean vs variance of intensity for a constant fluorescent signal (in this case a Chroma Slide) deriving from experimental (blue lines) and simulated (orange lines) data. The mean/variance plot is expected to be linear when the detector gain is within the linear response range. The plots below show only 6 different channels, but for all 32 channels the data was acquired at a gain of 740, well within the linear gain response range. Each data point in all plots is the (mean, variance) of a 1024x1024 pixels image for that specific channel. We acquired 7 datasets, each with an increasing laser power excitation (constant gain). As expected, the experimental data shows linearity in the mean/variance (blue lines). Similarly, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 90, 856, 166]]<|/det|> +simulated data where we increased the number of stochastically emitted fluorescence photons to mimic the increase in laser power, also provides a linear mean/variance (orange lines). The plots show consistent similarity between simulations and experimentally acquired data at both high and low intensities, suggesting a good replication of the multiple system noises. + +<|ref|>image<|/ref|><|det|>[[120, 235, 866, 528]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[170, 541, 820, 560]]<|/det|> +High similarity of mean vs variance plots between experimental and simulated images. + +<|ref|>text<|/ref|><|det|>[[171, 561, 880, 696]]<|/det|> +Mean vs Variance plots are provided for experimental and simulated data in analog mode at low photon emissions for a constant fluorescent signal. Linearity in mean/variance is expected within the gain's linear response range. In this image, experimental data was acquired sequentially at increasing laser power, while simulated data was created by increasing the average statistically emitted fluorescent photons, effectively simulating an "increasing laser power". Results show a linear mean/variance relation for experimental data and a similar linear relation for simulated data. Slope values are reported in each plot's legend. + +<|ref|>text<|/ref|><|det|>[[128, 730, 877, 866]]<|/det|> +Finally, we show the simulation's ability to reconstruct a biologically relevant hyperspectral image, replicating the spatial characteristics and most typical noises of fluorescent signals acquired through a confocal microscope lens and detectors. A comparison between the individual channel images of the (A) experimental hyperspectral dataset and (B) its synthetic counterpart demonstrates the realism of the computationally generated hyperspectral image. In (C), we compare the intensity profiles of a section of each pair of images (yellow line in A and B), showing, within the stochasticity of noise, how similar the synthetic data pattern (C, orange line) is to the experimental (C, blue line). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[130, 130, 870, 670]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[171, 675, 718, 693]]<|/det|> +## Simulations recapitulate spatial intensity distributions across all channels + +<|ref|>text<|/ref|><|det|>[[171, 695, 870, 850]]<|/det|> +(A) 2D intensity images of the experimental data for channels 18 (566 nm), 25 (629 nm), and 30 (673 nm) each with 8.9nm bandwidth, provide a baseline comparison for the simulations. (B) Corresponding images of the simulated data for channels 18 (566 nm), 25 (629 nm), and 30 (673 nm) show visually similar images for each channel, considering the stochasticity of noise. (C) Line profiles for experimental (blue) and simulated (orange) data corresponding to the yellow lines in A and B provide a comparison for the spatial distribution of intensity values and present a high degree of similarity for the distributions across multiple channels even accounting for stochastic noise. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 108, 874, 185]]<|/det|> +3) The authors addressed that the HyU method is more computationally efficient than the linear spectral unmixing method. This is true as the spectral dimension was reduced in Hyperspectral Phasors and histogram binning. However, these spectral compression and denoising also require computational power. Does the proposed method is more efficient when the entire process is considered? + +<|ref|>text<|/ref|><|det|>[[115, 204, 874, 299]]<|/det|> +ANSWER: This comment was addressed in Supplementary Note 3 and Supplementary Figure 13. We noted that due to the highly efficient and optimized algorithms for matrix inversion, LU is strictly faster than hybrid unmixing overall, but our comment of the greatly decreased computational costs of hybrid unmixing are demonstrated with the usage of fitting algorithms instead of LU. We have edited the main text for clarity, which now reads: + +<|ref|>text<|/ref|><|det|>[[172, 318, 874, 414]]<|/det|> +Speed tests with iterative fitting unmixing algorithms demonstrate a speed increase of up to 500- fold when the HyU compressive strategy is applied. (Fig. S13, Supplementary Note 3). Due to the initial computational overhead for encoding spectra in phasors, there is a 2- fold speed reduction for HyU in comparison to standard LU. However, this may be improved with further optimizations of the HyU implementation or by implementing different types of encoding. + +<|ref|>text<|/ref|><|det|>[[114, 449, 881, 506]]<|/det|> +4) For spectral unmixing, it seems to use the reference signals obtained from pure fluorophores. What happens if there are unknown fluorescence signals? Can the proposed method be applied for blind spectral separation? + +<|ref|>text<|/ref|><|det|>[[115, 541, 866, 618]]<|/det|> +ANSWER: In principle, yes, HyU could be implemented with blind spectral separation. However, in this current iteration of the approach, applying HyU to unknown fluorescence signals requires manual inspection of the phasor plot and is not automatic. The biggest advantage of HyU is the capability to visualize the spectra of endmembers on phasor. + +<|ref|>text<|/ref|><|det|>[[142, 620, 864, 815]]<|/det|> +- The example reported in Figure 5 B shows how we identified the spectrum from an unidentified component by observing a separate cluster on the phasor. After a literature search, we determined that its spectral shape and anatomical location suggest that the signature is from blood cells.- Supplementary Figure 11 shows an example of utilizing residual maps as a strategy for identifying unexpected spectral contributions using the phasor by color-coding phasor bins with low unmixing performance, which provide a quantitative clue to which phasor areas may contain an unexpected independent spectral signature.- Phasor-based blind spectral separation such as those described in the work of Scipioni et al (https://www.nature.com/articles/s41592-021-01108-4) could be directly applied to HyU. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[129, 90, 868, 147]]<|/det|> +We have expanded Supplementary Note 1 titled "Identification of spectra and new components with HyU" with further clarifications, insights, and references on how to distinguish independent spectral signatures from various types of noise. Supplementary Note 1 now reads: + +<|ref|>text<|/ref|><|det|>[[105, 168, 686, 186]]<|/det|> +Supplementary Note 1: Identification of spectra and new components with HyU + +<|ref|>text<|/ref|><|det|>[[170, 195, 879, 751]]<|/det|> +Identification of independent spectral components has been an adversity for unmixing hyperspectral data. First, the collected spectra may be distorted by reduced SNR. Secondly, excitation of intrinsic signals causes uncertainty of biological sample. Favorably, HyU simplifies this process by adapting Phasor approach and achieving semi- or full- automation process for spectra identification and selection. In HyU spectra can be loaded from an existing library, virtually automating the analysis process. Pre- identified cursors are generated from common fluorophores such as mKO2, tdTomato, mRuby, Citrine. In our experience, obtaining fluorescence spectra from experimental samples has some advantages compared to utilizing spectra from an existing library, as they account for a multitude of experimental and instrumental settings. Imaging settings such as different types of lenses or optical filters (Sup. Figure 4, C and D) together with factors within the microenvironment of samples, such as pH or temperature have the potential to alter the fluorescence spectral emissions12. In the presence of unexpected fluorescent signals, spectra can also be selected and visualized directly from the phasor. Phasors facilitate the identification of unexpected independent components and their distinction from the multiple system noises. A noise- free spectrum will appear as a single point on the phasor plot, while a spectrum affected by instrument and electronic noises will mainly appear as a gaussian distribution, centered on the original spectral signal6. Conversely, a randomized noise across the multiple spectral channels will not produce a clustered aggregate of spectra on the phasor. A constant spectral noise, with a distinct spectrum (e.g. a constant light leakage into the system), would produce a distinct phasor cluster and could be selected for unmixing. The phasor plot representation is a 2D- histogram and provides insights into the frequency of occurrence for these signals. These unexpected independent components in samples often appear as "tails" on the phasor distributions (Sup. Figure 11, C). In our HyU graphical interface, clicking on the phasor visualizes the spectra within a small area (9x9 bins by default, with size adjustable from the interface) of the phasor histogram (Figure 1 D). In the example in Sup. Figure 9- 11 we identify 5 distinct endmembers on the Phasor (Sup. Figure 10, C), visualize their spectra identifying Citrine, mRuby, Td- Tomato, mKO2, and one strong autofluorescence signature. The use of Residual Phasor Map (Sup. Figure 11, B) allows for identification of areas in the phasor with high amount of residuals, likely corresponding to a missing endmember in the unmixing. Residual Image Maps (Sup. Figure 11, C) provide a rapid overview of residuals in the image data, for identification of location in the dataset of the missing endmember. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 221, 877, 298]]<|/det|> +5) Following the previous question, I wonder about the effect of light scattering on the accuracy of the proposed method. In fig4, the proposed method can be applied for volumetric imaging. I wonder there are consistent fluorescence signals over the depth of tissue. Fluorescence signals occurred in deep tissue regions experience more light scattering, which might occur in spectral distortions. + +<|ref|>text<|/ref|><|det|>[[113, 317, 731, 335]]<|/det|> +ANSWER: We have performed the following additional changes to address this point: + +<|ref|>text<|/ref|><|det|>[[143, 352, 850, 467]]<|/det|> +1. We have added unmixing results from deep imaging performed on zebrafish embryos. (Supplementary Figure 23) +2. We have also added experiments performed on both freshly excised and fixed mouse tissue for further comparison to more highly scattering tissue. (Supplementary Figures 29, 30) +3. We expanded the Supplementary Information with details on mouse lines, fluorescent silica beads characterization, mouse tissue samples preparation, and imaging. + +<|ref|>text<|/ref|><|det|>[[144, 535, 877, 768]]<|/det|> +1. To address the question of light scattering in deep tissue, we added an example of deep imaging in zebrafish, to demonstrate that scattering distortions due to increased depth do not affect the signal and therefore the unmixing, even with signal attenuation (Supplementary Figure 23). As seen in Supplementary Figure 23, the phasor plots of the signals demonstrate a consistent distribution, centered at the same coordinates, even for images acquired deeper into the tissue where the detected spectra decrease in intensity and increase in noise. Following the trend of the absolute intensity average spectra (I) within the center bin shows the attenuation of the signal over depth as the area under the curve decreases. Even with that attenuation, (J) the normalized forms of the average spectra display no difference in shape. The consistency of the average spectra is a strength of the phasor method, which allows for grouping of the similar spectra even with the signal attenuation and noise increase seen in the (K,L) random individual spectra of the pixels across different depths. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[177, 90, 707, 540]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[171, 566, 737, 584]]<|/det|> +## Supplementary Figure 23. Phasor analysis on signal distortion in deep tissue + +<|ref|>text<|/ref|><|det|>[[171, 604, 880, 857]]<|/det|> +Images at different Z- positions of a 3D (x,y,z) dataset of 19 hpf Tg(ubiq:lyn- tdTomato) zebrafish acquired from 0 um to 80 um (relative to the dataset) depth displaying at every 13 z- slices. (A- D) Phasors calculated from the single slices at 0 um, 26 um, 52 um, and 78 um depth. (E- H) Corresponding average intensity images (across the 32 spectral channels) for each z- slice show an expected decrease in fluorescence intensity with depth. (I) Average spectra of the pixels linked to the phasor position bin for the tdTomato fluorescent signature for each of the four presented z- slices (0, 26, 52, 78 um) show a decrease in the spectral area without change in spectral shape as shown by (J) normalizing the average spectra shown in I to each spectrum's maximum value. This demonstrates the spectral shape does not change across different depths (z- planes), while the overall intensity decreases. (K) Randomly selected spectra from the raw spectral image at 0 um (blue) and 26um (red), five spectra for each image and similarly (L) for 52 um (green) and 78um (yellow). Two yellow and three green spectra are not clearly visible because of low signal intensity. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 877, 166]]<|/det|> +2. Mouse experiments: we have included two examples of application for the Hybrid Unmixing method: fresh tissue autofluorescence metabolic imaging and fixed tissue fluorescence imaging. These experiments provide support for the reliability of HyU even in tissue that are even more scattering than that of the zebrafish. + +<|ref|>text<|/ref|><|det|>[[171, 201, 876, 473]]<|/det|> +The first experiment involved unmixing autofluorescent signals in freshly excised mouse kidney tissue. The unmixed signals include NADH bound, NADH free, Retinol, Retinoic acid, and Elastin, in correspondence to the intrinsic signals previously unmixed in the zebrafish experiments. In Supplementary Figure 29, we demonstrate that the same independant autofluorescent signatures used in the zebrafish to perform HyU can be utilized in the fresh mouse tissue. Even as the intensities of the autofluorescent signatures drop rapidly within the first \(75 \mu \mathrm{m}\) of tissue, we demonstrate that HyU performs as previously shown in zebrafish. The unmixed autofluorescent signals within the mouse tissue yield spatial patterns (Sup. Fig 29 A, B, C, E) corresponding to those described in literature (https://doi.org/10.1117/1.JBO.19.2.020901, https://doi.org/10.1681/ASN.2016101153, https://doi.org/10.1021/cr900343z) and to those previously shown in zebrafish. Cross- section visualizations (Sup. Fig 29 B and E) show consistency in the unmixed autofluorescence patterns along the depth of the sample (z- direction) until signal drops to noise level. For these notoriously weak autofluorescent signals, intensities fade out at approximately \(75 \mu \mathrm{m}\) depth. + +<|ref|>text<|/ref|><|det|>[[172, 491, 875, 744]]<|/det|> +In the presence of wavefront distortions in the fluorescent spectra, the expected and most likely behavior of the HyU would be a deterioration of the unmixing quality. This deterioration generally results in a non- organized, more uniform re- assignment of intensities across the unmixed channels. When this scenario happens, severe cross- talk is visible across channels. If one were to visualize these results in a 2- D image, it would result in a "white" color where multiple signals are shown together in the same image, due to how multiple colors are combined in the rendering algorithms used for visualizing fluorescence microscopy data. Supplementary Figure 29 panels B and E are single slices of the volume, representing a 1- pixel wide cross- section of the volume, along the XZ and YZ planes respectively. In these cross sections, there is no visible confounding of signals or "white" color, delineating the overlap of multiple fluorescent signals. This suggests that the algorithm, under reasonable imaging conditions, performs as characterized (Sup. Figures 16,17,18,19). This is mainly because fluorescent signals fade to dark before any appreciable distortion affects the system. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[300, 125, 816, 644]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[173, 97, 362, 112]]<|/det|> +
Supplementary Figure 29:
+ +<|ref|>text<|/ref|><|det|>[[173, 697, 880, 872]]<|/det|> +Intrinsic fluorescent signatures in fresh kidney tissue of a 7 months Balb- c mouse imaged with 2- photon excitation at \(740\mathrm{nm}\) in a \(150\mu \mathrm{m}\) deep volume. Despite the increasing scattering effect of this mammal tissue with increasing depth, HyU can perform unmixing of intrinsic fluorescent signals. (A) Volumetric rendering of the unmixing results of five intrinsic fluorescent signatures shows results consistent with literature, as visible in the (B- E) orthogonal views of (C) an unmixed (x,y) cross- section of the volume at \(30\mu \mathrm{m}\) depth in the sample and its corresponding (B) (x,z) and (E) (y,z) projections. (D) Averaged autofluorescent signals for each acquired spectral (x,y) section over the \(150\mu \mathrm{m}\) depth of the volume show a sharp decrease of intensities after 75 \(\mu \mathrm{m}\) depth as visible in E, the corresponding (y,z) projection. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 107, 880, 223]]<|/det|> +The second experiment involved unmixing a known fluorescent signal among the background signals within the highly scattering mouse tissue by imaging Cy3 beads injected (described in the new Mouse Sample Preparation section below) into fixed mouse tissue. The ground truth spectra of the Cy3 beads is known, measured in pure bead solution (described in the new Fluorescent silica bead characterization section). With this known constant Cy3 fluorescent spectrum, we can demonstrate: + +<|ref|>text<|/ref|><|det|>[[173, 226, 815, 282]]<|/det|> +a. The efficacy of HyU even when fluorescent signatures are buried deep within highly scattering tissue. +b. The effect of tissue scattering on the known Cy3 fluorescent spectrum. + +<|ref|>text<|/ref|><|det|>[[173, 297, 875, 413]]<|/det|> +Supplementary Figure 30 below shows that the Cy3 beads (magenta) are unmixed with the proper spatial profiles (spherical shape) from the autofluorescent (yellow), background (green), and structural signatures (light blue) of the fixed mouse tissue. Similarly to Supplementary Figure 29 B,C,E, there is no evident confounding overlap of signals when imaging deeper in the sample. In this case, with stronger autofluorescent (fixative- related) and fluorescent (beads) signals, signals started fading at \(110\mu m\) depth in the sample. + +<|ref|>text<|/ref|><|det|>[[173, 430, 880, 585]]<|/det|> +In support of our observation that fluorescent spectra, as measured in our commercial instrument, for scattering mammalian samples, are not excessively distorted in their shape, we plot the spectra corresponding to the Cy3 beads at multiple depths (Supplementary Figure 30 F, G), up to \(130\mu m\) deep in the sample, in absolute (Sup. Fig 30 F) and relative (Sup. Fig 30 G) intensity. Absolute peak intensity for some of the deeper spectra is around \(\sim 1300\) Digital Levels, corresponding to \(2\%\) of the full 16 bit dynamic range of the detector, close to the noise level of the instrument. This translates to visibly noisy spectra for deeper z- planes of the sample, as shown in the relative intensity plots (panel G), but does not show evident spectral distortions. + +<|ref|>text<|/ref|><|det|>[[173, 603, 874, 698]]<|/det|> +In regards to the performance of HyU, the unmixed fluorescent signatures remain consistent with expected spatial patterns within the scattering mouse tissue even as the overall intensity drops. Within the imaging depth we could reach in our instrument, the highly scattering nature of the mouse tissue does not affect the performance of HyU, similar to what we previously demonstrated in zebrafish. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[172, 125, 812, 551]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[172, 564, 760, 581]]<|/det|> +
Supplementary Figure 30. Extrinsic fluorescent signatures in fixed mouse tissue
+ +<|ref|>text<|/ref|><|det|>[[172, 601, 875, 875]]<|/det|> +We evaluate the performance of HyU in imaging fluorescent signals in a highly scattering fixed kidney tissue of a 7- month- old Balb- c mouse with embedded Cy3 fluorescent beads (Methods) imaged with 2- photon 850nm excitation up to \(150~\mu \mathrm{m}\) deep. (A) Volumetric rendering of the unmixing results of the signals from fixative autofluorescence (autoFL), Cy3 beads, background, and Second Harmonic Generation (SHG). (B- E) Orthogonal views of the same volume for (C) single (x,y) plane of the volume at a depth of \(90~\mu \mathrm{m}\) with cross- sections (yellow hairlines in C) (B) (z,x) of \(18~\mu \mathrm{m}\) and (E) (y,z) of \(4~\mu \mathrm{m}\) respectively showing sections of the unmixed volume containing Cy3 beads at different depths up to \(140~\mu \mathrm{m}\) . (D) Average intensity value for each acquired (x,y) spectral image slice as a function of depth reveals considerable loss of fluorescent signal deeper than \(110~\mu \mathrm{m}\) . (F) Average spectra for each z- plane containing pixels with Cy3 beads signal plotted with absolute intensity (Digital Levels, DL) show decreasing intensity with depth as visible by the area under spectrum. (G) The same averaged spectra are normalized and plotted with Relative Intensity to show the consistency in the spectral shape as a function of depth in reference to Cy3 beads in solution (dashed line). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 759, 147]]<|/det|> +3. We expanded the supplementary information to include details on mouse lines, fluorescent silica beads characterization, mouse tissue sample preparation, and imaging: + +<|ref|>sub_title<|/ref|><|det|>[[174, 206, 264, 221]]<|/det|> +## Mouse lines + +<|ref|>text<|/ref|><|det|>[[172, 243, 875, 438]]<|/det|> +Mouse linesMice imaging was approved by the Institutional Animal Care and Use Committee (IACUC) of University of Southern California, Protocol #21311. Experimental research on vertebrates complied with institutional, national and international ethical guidelines. Animals were kept on a 13:11 hours light:dark cycle. Animals were breathing double filtered air, temperature in the room was kept at 68–73 F, and cage bedding was changed weekly. All these factors contributed to minimize intra- and inter- experiment variability. Adult Balb- c mice were euthanized via overdose of isoflurane followed by cardiac puncture. Kidneys were quickly harvested from the mouse, washed in PBS, and cut longitudinally alongside the midsection in order to expose the inner part of the organ. The two halves of the organ were arranged onto a microscope slide for imaging. + +<|ref|>sub_title<|/ref|><|det|>[[175, 479, 473, 496]]<|/det|> +## Fluorescent silica beads characterization + +<|ref|>text<|/ref|><|det|>[[174, 518, 872, 575]]<|/det|> +One fluorescent silica beads solution (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, 1% solid, lot# 1608BRX5) was characterized in its spectral fluorescence emission and physical size. + +<|ref|>text<|/ref|><|det|>[[173, 600, 860, 774]]<|/det|> +10x dilution in PBS of the beads was placed on a no. 1.5 imaging coverglass and spectrally characterized using spectral mode on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using 40x/1.1 W LD C- Apochromat Korr UV- VIS- IR lens utilizing a 2- photon laser at 740 nm to excite fluorescence from the beads, using a 690nm lowpass filter to separate excitation and fluorescence. Spectra obtained from multiple beads with the same label were averaged, producing the reference spectrum reported in Sup. Figure 30 G (dashed line). Fluorescent silica bead size and concentration were determined via nanoparticle tracking analysis (NTA) on the Nanosight NS300 (Malvern Panalytical). Samples were run 5 times and results averaged for final size and concentration values reported. + +<|ref|>sub_title<|/ref|><|det|>[[175, 799, 377, 816]]<|/det|> +## Mouse Sample preparation + +<|ref|>text<|/ref|><|det|>[[173, 838, 864, 954]]<|/det|> +Mouse Sample preparationFor autofluorescent measurements, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in Phosphate Buffered Saline (PBS) to remove residual blood and kept in PBS until imaging preparation. Organs were sectioned in order to image the internal architecture and mounted on a glass imaging dish with sufficient PBS to avoid dehydration of the sample. Following imaging, all samples were fixed in a 10% Neutral Buffered Formalin solution at 4- °C. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[173, 85, 875, 121]]<|/det|> +For ex vivo bead characterization in tissue, mouse organ samples were collected from Balb- c mice. Following euthanasia, organs were resected and washed in PBS followed by incubation for + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 88, 839, 224]]<|/det|> +at least 24 hours in \(10\%\) buffered formalin. The kidney was then removed from the fixative and sectioned into smaller \(\sim 5 \times 5 \times 5 \mathrm{mm}\) pieces for imaging. A fluorescent silica beads stock (Nanocs, Inc.) labeled with Cy3 (Si500- S3- 1, 0.5mL, 0.5um, \(1\%\) solid, lot# 1608BRX5) and previously characterized was prepared using a 10x dilution of the fluorescent beads from their stock concentration. Beads were injected in the sample using 50ul of these solutions loaded into a 0.5mL syringe with a 28g needle. The kidney sections were then placed in imaging dishes with a small volume of PBS to keep the samples hydrated prior to imaging. + +<|ref|>sub_title<|/ref|><|det|>[[175, 244, 312, 260]]<|/det|> +## Image Acquisition. + +<|ref|>text<|/ref|><|det|>[[175, 278, 820, 333]]<|/det|> +Images were acquired on a Zeiss LSM 780 laser confocal scanning microscope equipped with a 32- channel detector using \(40 \times / 1.1 \mathrm{W}\) LD C- Apochromat Korr UV- VIS- IR lens at \(28 - 0C\) . + +<|ref|>text<|/ref|><|det|>[[174, 358, 847, 475]]<|/det|> +Samples of Gt(cltca- Citrine), Tg(ubiq:lyn- tdTomato), Tg(fli1::mKO2), and Tg(ubiq:Lifeact- mRuby), were simultaneously imaged with 488 nm and 561 nm laser excitation, for citrine, tdTomato, mKO2, and mRuby. A narrow 488 nm/561 nm dichroic mirror was used to separate excitation and fluorescence emission. Samples were imaged with a 2- photon laser at 740 nm to excite autofluorescence, using a 690nm lowpass filter to separate excitation and fluorescence. + +<|ref|>text<|/ref|><|det|>[[175, 499, 847, 537]]<|/det|> +Samples of mouse kidney tissue were imaged with 2- photon excitation at 740 nm or 850 nm with a \(690 +\) nm lowpass filter, at \(37 - 9C\) incubation. + +<|ref|>text<|/ref|><|det|>[[175, 557, 830, 593]]<|/det|> +For all samples, detection was performed at the full available range (410.5- 694.9nm) with 8.9nm spectral binning. + +<|ref|>text<|/ref|><|det|>[[116, 646, 560, 663]]<|/det|> +Reviewer #3 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[116, 681, 848, 737]]<|/det|> +This work demonstrates the superiority of the proposed method using computer simulation and experimental data. The authors clearly claim that the proposed method is more efficient and robust than conventional linear spectral unmixing methods. + +<|ref|>text<|/ref|><|det|>[[116, 756, 794, 792]]<|/det|> +ANSWER: We thank this reviewer for the constructive comments and helping us improve the manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 812, 510, 829]]<|/det|> +Reviewer #3 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[116, 847, 816, 902]]<|/det|> +The authors provide the code and data used in the manuscript. This allows other people to reproduce these results. And the dataset used in this work is appropriate for the purpose of the study. + +<|ref|>text<|/ref|><|det|>[[116, 922, 551, 939]]<|/det|> +ANSWER: We thank this reviewer for the insightful remarks. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[108, 340, 269, 354]]<|/det|> +Reviewers comments: + +<|ref|>text<|/ref|><|det|>[[108, 374, 203, 388]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[108, 390, 430, 405]]<|/det|> +Remarks to the Author: Overall significance: + +<|ref|>text<|/ref|><|det|>[[106, 406, 916, 660]]<|/det|> +The results are significant and as a new method of analysis of hyperspectral data - it adds to the community. The authors have replied to most of my questions. I do think they need to add a little more to explain how this method is different from the phasor and linear combination method. I am a bit conflicted as to usual readers - the difference between phasor as analysis method and phasor as encoder as to decrease the data from \(10^{\wedge}7\) to \(10^{\wedge}4\) may not be clear. The authors comment about collage autofluorescence - while SHG is certainly true for collagen 1 it is not for other types of collagens - some of them can be highly fluorescent. About question 6 - While I agree that mathematically a point on the line between the position of two other phasor points may be unlikely. That is true for the center of the distribution. It is definitely not true when S/N creates a distribution. In that case the points can be along that line. If the authors propose only using the center of the distribution - that needs to be mentioned clearly. About FAD - I can see why laser power can be a valid argument. I do not agree with the effect of zooming. Lets say an area has a particular NADH/FAD distribution. Why would it matter if we zoom into a smaller part of that or a larger area? Unless zooming in separates the areas of high NADH and high FAD spatially and they appear at different phasor positions. That brings out a separate problem. If HyU is zoom dependent - then how will anyone know if they are getting the proper distribution or not? Finally I do like the new figures. + +<|ref|>text<|/ref|><|det|>[[108, 679, 339, 694]]<|/det|> +Remarks to the Author: Impact: + +<|ref|>text<|/ref|><|det|>[[108, 696, 872, 744]]<|/det|> +I would suggest Nature communications or Scientific reports. The authors use phasor- but not to it's full capacity. The paper will indeed influence the field. However, I do feel publication in Nature methods can influence it in a way that may not be the best for the field. + +<|ref|>text<|/ref|><|det|>[[108, 763, 449, 796]]<|/det|> +Remarks to the Author: Strength of the claims: The work is convincing. + +<|ref|>text<|/ref|><|det|>[[108, 815, 483, 847]]<|/det|> +Remarks to the Author: Reproducibility: The paper is very detailed and can be reproducible. + +<|ref|>text<|/ref|><|det|>[[108, 899, 203, 912]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[108, 915, 430, 930]]<|/det|> +Remarks to the Author: Overall significance: + +<|ref|>text<|/ref|><|det|>[[108, 932, 907, 965]]<|/det|> +In their revised manuscript "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence", the authors convincingly highlight the achievements/unique features of the further- developed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[107, 85, 904, 170]]<|/det|> +algorithm for multiplexed imaging of hyperspectral data, expanding its use to low signal- to- noise ratio of real data, moving towards two- photon microscopy. Especially, they made particular efforts in demonstrating the power and the limitations of the algorithm when applied in highly- scattering tissue or when the number of detection channels is limited, providing an excellent and useful benchmarking for a broad life sciences audience interested in imaging and microscopy. + +<|ref|>text<|/ref|><|det|>[[108, 170, 870, 221]]<|/det|> +Although, I think, of high interest and definitely an important next step, I do agree with the authors that intravital imaging of highly scattering organs is a major challenge and can be the subject of future work. I fully recommend the present manuscript for publication in its present form. + +<|ref|>text<|/ref|><|det|>[[108, 238, 339, 254]]<|/det|> +Remarks to the Author: Impact: + +<|ref|>text<|/ref|><|det|>[[108, 255, 888, 289]]<|/det|> +As mentioned above, with the new added data, the presented algorithm will find broad applicability for all sorts of data, which typically need to deal with low signals. + +<|ref|>text<|/ref|><|det|>[[108, 306, 450, 322]]<|/det|> +Remarks to the Author: Strength of the claims: + +<|ref|>text<|/ref|><|det|>[[108, 323, 901, 357]]<|/det|> +In the current form, the revised manuscript provides all necessary evidence for the unique power of the HyU algorithm. + +<|ref|>text<|/ref|><|det|>[[108, 374, 400, 390]]<|/det|> +Remarks to the Author: Reproducibility: + +<|ref|>text<|/ref|><|det|>[[108, 391, 840, 425]]<|/det|> +Beyond of statistics, I find the broad range of applications, excitation schemes and microscopy types particularly important to emphasize the general validity of the algorithm. + +<|ref|>text<|/ref|><|det|>[[108, 476, 204, 490]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[108, 493, 430, 508]]<|/det|> +Remarks to the Author: Overall significance: + +<|ref|>text<|/ref|><|det|>[[107, 509, 907, 628]]<|/det|> +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. And the authors appropriately discussed the proposed method by comparing previous techniques. + +<|ref|>text<|/ref|><|det|>[[108, 645, 450, 660]]<|/det|> +Remarks to the Author: Strength of the claims: + +<|ref|>text<|/ref|><|det|>[[108, 662, 759, 679]]<|/det|> +The revised manuscript has clearly addressed all of my previous comments and concerns. + +<|ref|>text<|/ref|><|det|>[[116, 735, 275, 750]]<|/det|> +Reviewers comments: + +<|ref|>text<|/ref|><|det|>[[115, 768, 904, 805]]<|/det|> +We would like to thank all Reviewers for their constructive criticism that helped considerably to improve the quality of this manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 825, 539, 841]]<|/det|> +Reviewer #1 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[115, 860, 901, 876]]<|/det|> +The results are significant and as a new method of analysis of hyperspectral data - it adds to the community. + +<|ref|>text<|/ref|><|det|>[[144, 896, 446, 912]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[115, 930, 872, 966]]<|/det|> +The authors have replied to most of my questions. I do think they need to add a little more to explain how this method is different from the phasor and linear combination method. I am a bit conflicted as to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 85, 877, 121]]<|/det|> +usual readers – the difference between phasor as analysis method and phasor as encoder as to decrease the data from \(10^4\) to \(10^4\) may not be clear. + +<|ref|>text<|/ref|><|det|>[[142, 140, 855, 217]]<|/det|> +We have refined our previous explanation (yellow highlight) of the differences between the Standard Phasor analysis method and the Hybrid Unmixing method in the introduction. We have now expanded this (green highlighted portions) to address the specific concern about the difference between the phasor method as an analysis and as an encoder: + +<|ref|>text<|/ref|><|det|>[[130, 235, 920, 546]]<|/det|> +We have developed Hybrid Unmixing (HyU) as an answer to the challenges that have limited the wider acceptance of HFI for in vivo imaging. HyU combines our previous phasor hyperspectral approach26 with traditional unmixing algorithms to untangle the fluorescent signals more rapidly and more accurately from multiple exogenous and endogenous labels. The phasor approach26 is a popular dimensionality reduction approach for the analysis of both fluorescence lifetime and spectral image analysis27- 29. In HyU, the phasor approach provides spectral compression, denoising, and computational reduction that simplifies both pre- processing30 and unmixing31- 33 of HFI datasets. Standard Phasor analysis26,27,34- 41 is fully supervised and requires a manual selection of regions or points on the phasor plot, a graphical representation of the transformed spectra. In contrast, HyU utilizes phasor processing as an encoder to aggregate similar spectra onto the phasor plot, reducing even the largest volumetric datasets so that unmixing algorithms, such as LU, can be applied on a far smaller number of elements (the number of pixels on the phasor plot). Furthermore HyU provides unsupervised analysis of the HFI data, simplifying the data processing and removing user subjectivity. Our results show that HyU offers three key advantages: (1) improved unmixing over conventional LU, especially for low intensity images, down to 5 photons per spectra; (2) simplified identification of independent spectral components; (3) dramatically faster processing of large datasets, overcoming the typical unmixing bottleneck for in vivo fluorescence microscopy. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 107, 872, 205]]<|/det|> +We believe this further extended description, obeying the limited word count of the manuscript sufficiently clarifies the difference between Standard Phasor analysis and HyU. The graphical representation in Figure 1 clarifies this: notice the absence of any typical selection on the phasor plot, either in the form of Region of Interest processing or in the form of linear geometric unmixing, both factors that are essential for Standard Phasor analysis. + +<|ref|>text<|/ref|><|det|>[[144, 206, 848, 243]]<|/det|> +This combination of description and Fig 1 (and absence of Standard Phasor indicators) should be sufficient to avoid any confusion in the reader. + +<|ref|>image<|/ref|><|det|>[[152, 252, 910, 585]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 611, 852, 648]]<|/det|> +The authors comment about collage autofluorescence – while SHG is certainly true for collagen 1 it is not for other types of collagens – some of them can be highly fluorescent. + +<|ref|>text<|/ref|><|det|>[[144, 667, 866, 764]]<|/det|> +We thank the reviewer for this insight. While we agree that some types of collagen can be highly fluorescent, the references we cited in our previous answer (duplicated below) demonstrate that depending on the imaging conditions, collagen may not be visible. We did not observe any such signal within the regions of the specific samples imaged in this work, under our imaging conditions (reported in Table S1 supplementary). + +<|ref|>text<|/ref|><|det|>[[172, 799, 876, 855]]<|/det|> +Multiple references in literature (PMC4337962 / PMID: 22402635, PMC123202 / PMID: 12177437, PMC4337962 / PMID: 22402635) report 2- photon fluorescence of collagen to be very low at 740 nm... + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 853, 166]]<|/det|> +About question 6 – While I agree that mathematically a point on the line between the position of two other phasor points may be unlikely. That is true for the center of the distribution. It is definitely not true when S/N creates a distribution. In that case the points can be along that line. If the authors propose only using the center of the distribution – that needs to be mentioned clearly. + +<|ref|>text<|/ref|><|det|>[[144, 185, 848, 260]]<|/det|> +Owing to the extended length of the Response to Referees, we tried summarizing the common points to the questions of each reviewer, where possible, in the first comment. In this case, the noise aspect in question was expansively described in the initial comment “Information loss and noise”. + +<|ref|>text<|/ref|><|det|>[[144, 280, 844, 336]]<|/det|> +We do not propose only using the center of the distribution and we account for noise as explained when presenting the “3.3 billion simulations used to assemble Supplemental Figures 16, 17, 18, 19. + +<|ref|>text<|/ref|><|det|>[[144, 356, 523, 372]]<|/det|> +Our answer to question 6 covers two main subjects: + +<|ref|>text<|/ref|><|det|>[[171, 390, 863, 544]]<|/det|> +i) acknowledging that there are specific cases where mathematically, linear unmixing would not workii) acknowledging the likelihood of many fluorophores and their combinations to occupy the same location (whether or not we are referring to the center or the full distribution corresponding to a fluorescent signature). In this scenario, where multiple components may be present in the exact same phasor location, we comment that the amount of error that may arise from this situation (encoding loss) is most likely overwhelmed by the error introduced by the noise instead. + +<|ref|>text<|/ref|><|det|>[[144, 564, 481, 580]]<|/det|> +We report here the second part of question 6: + +<|ref|>text<|/ref|><|det|>[[173, 614, 836, 670]]<|/det|> +However, we have demonstrated in our reply to the first comment and in the numerous additional simulations (Supplemental Figure 16, 17, 18, 19) that noise affects the unmixing results much more than the encoding loss of the phasor method. + +<|ref|>text<|/ref|><|det|>[[145, 708, 454, 723]]<|/det|> +The first comment here referenced states: + +<|ref|>text<|/ref|><|det|>[[173, 758, 872, 912]]<|/det|> +Information loss and noise. We are aware that the phasor transform is a lossy encoder that in principle carries a reduced percentage of the information compared to the original “pure” data. This is evident in the scenario of very high- quality signals, but in the case of fluorescent signals, where signal to noise often decreases to lower digits, the encoding loss is less relevant compared to the noise of the fluorescent signals. This fundamental advantage of increasing SNR in noisy data makes phasor a valuable tool for fluorescence microscopy (both FLIM and hyperspectral); this point is reported by multiple groups using phasors (Gratton: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[186, 90, 881, 283]]<|/det|> +https://www.pnas.org/doi/full/10.1073/pnas.1108161108, https://escholarship.org/content/qt5g279175/qt5g279175. pdf, Vicidomini: https://www.nature.com/articles/ncomms7701, Gerritsen: https://pubmed.ncbi.nlm.nih.gov/22714302/, Fraser: https://pubmed.ncbi.nlm.nih.gov/28068315/), and more recently nicely described in the work of Scipioni et al ( https://www.nature.com/articles/s41592- 021- 01108- 4 ) "However, microscopy data are affected by a number of other detrimental factors, [...] which results in decreased signal- to- background ratio (SBR). [...] the phasor approach shows increased precision (Fig. 1f,i), decreased bias (Fig. 1e,h) and a three orders of magnitude lower execution time (Fig. 1g,j) with respect to the least mean square (LMS) fitting procedure". + +<|ref|>text<|/ref|><|det|>[[187, 301, 876, 534]]<|/det|> +To support the validity of this hybrid unmixing approach, we have assembled a complex simulation matrix representing the performance of HyU in unmixing 2 to 8 labels as a function of the spatial overlap in the sample. This simulation matrix is built on top of the complex simulation we designed (further described below in our answer to this reviewer's question 14), which is soon to be published in a separate manuscript. This simulation accounts for a multitude of real- world noises in experimental samples that are regularly imaged (stochasticity of fluorescence spectral emission, poisson, readout noise, electronics transfer noise, detector sensitivity at different wavelength). The results of applying our approach on an array of simulations under different conditions of SNR, number of filters applied, in comparison to standard Linear Unmixing are now reported in Supplementary Figures 16, 17, 18, and 19. We further describe how multiple components are affected by our hybrid unmixing approach in our answer to question 17 for this reviewer. + +<|ref|>text<|/ref|><|det|>[[114, 602, 880, 699]]<|/det|> +About FAD – I can see why laser power can be a valid argument. I do not agree with the effect of zooming. Lets say an area has a particular NADH/FAD distribution. Why would it matter if we zoom into a smaller part of that or a larger area? Unless zooming in separates the areas of high NADH and high FAD spatially and they appear at different phasor positions. That brings out a separate problem. If HyU is zoom dependent – then how will anyone know if they are getting the proper distribution or not? + +<|ref|>text<|/ref|><|det|>[[144, 717, 874, 852]]<|/det|> +We worry that the reviewer is misunderstanding our intended meaning of "zooming in to image a smaller region". It is not merely cropping the large image to display a smaller field of view (FoV), in which case the reviewer would be correct. Instead, in the optics of confocal laser scanning microscope, "zooming" by using a higher magnification objective or by scanning a smaller region of the specimen delivers more exciting light to the FoV, increasing it by the square of the zoom or magnification of the objective lens. Thus, zooming in by two- fold would increase the fluorescence excitation by four- fold for one- photon excitation, and by 16- fold for two- photon excitation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 106, 870, 144]]<|/det|> +We hope that this clarifies the issue, but if the reviewer would like to explore this further, we direct them to the excellent book, Principles of Fluorescence Spectroscopy (Lakowicz), section 18.2 + +<|ref|>text<|/ref|><|det|>[[201, 147, 875, 432]]<|/det|> +"The physical origin of the 2PE cross-sections can be understood by some simple considerations. For one- photon absorption the number of photons absorbed per second \((NA_{1})\) is given by \(NA_{1}(photon / s) \sigma_{1}(cm^{2})I(photon / cm^{2}s)\) (18.1) where \(I\) is the intensity and \(\sigma_{1}\) is the cross- section for one- photon absorption. The units are given within the parentheses. The cross- section in \(cm^{2}\) is multiplied by the number of photons passing near the molecule per second to yield the number of photons absorbed per second. To obtain NA1 in photons per second the cross- section must be in units of \(cm^{2}\) . Now consider two- photon absorption. The number of photons absorbed per second by 2PE \((NA_{2})\) is given by \(NA_{2}(photons / s) \sigma^{2}I^{2}(photons / cm^{2}s)^{2}\) (18.2) In order for the units to match on both sides of eq. 18.2 the units of \(\sigma_{2}\) must be \(cm^{4}s / photon\) . Similarly, for 3PE, \(NA_{3}(photons / s) \sigma_{3}I^{3}(photons / cm^{2}s)^{3}\) (18.3) and the units of a three- photon cross- section are \(cm^{6}s^{2} / photon^{2}\) . + +<|ref|>text<|/ref|><|det|>[[144, 449, 751, 488]]<|/det|> +We quote the Principles of Fluorescence Spectroscopy (Lakowicz), section 1.7: "The steady- state intensity (of the fluorophore) is given by + +<|ref|>equation<|/ref|><|det|>[[219, 491, 555, 555]]<|/det|> +\[I_{SS} = \int_{0}^{\infty}I_{0}e^{-t / \tau}dt = I_{0}\tau \quad (1.16)\] + +<|ref|>text<|/ref|><|det|>[[201, 579, 730, 616]]<|/det|> +The value of 10 can be considered to be a parameter that depends on the fluorophore concentration and a number of instrumental parameters." + +<|ref|>text<|/ref|><|det|>[[144, 652, 872, 709]]<|/det|> +While it is true that the true spectral signature should not change depending on the zoom or power, the amount of signal depends not only on the concentration of the fluorophores, and the excitation wavelength used, but also on the zoom and excitation power. + +<|ref|>text<|/ref|><|det|>[[144, 728, 875, 824]]<|/det|> +These factors are major contributors to the measured intensity of the fluorophore, which can alter both the SNR and could alter the resulting analysis. The chief advantage of our method is to overcome the low signal that occurs during these types of acquisitions. If signal cannot be detected clearly (signal approaches the noise), it is extremely challenging if not impossible to perform any kind of analysis. + +<|ref|>text<|/ref|><|det|>[[144, 843, 870, 900]]<|/det|> +The reviewer goes on to ask: That brings out a separate problem. If HyU is zoom dependent – then how will anyone know if they are getting the proper distribution or not? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 107, 863, 165]]<|/det|> +HyU, like any fluorescent microscopy imaging experiment, requires proper experimental settings based on the scientific/experimental scope and probes utilized. The absence of a signal cannot be taken as the absence of an analyte in HyU or any other analysis approach. + +<|ref|>text<|/ref|><|det|>[[144, 184, 870, 300]]<|/det|> +To obtain more meaningful results, in fluorescence microscopy, imaging area (zoom), pixel dwell time and laser power will need to be properly set. There are multiple strategies for validating if experimental settings are proper. In the manuscript, we show the pipeline for using phasors to identify presence of fluorophores with practical examples to assist the readership in proper experimental design (see Supplementary Figure 11 and more extensively in Supplementary Note 1: Identification of spectra and new components with HyU). + +<|ref|>text<|/ref|><|det|>[[116, 336, 344, 352]]<|/det|> +Finally I do like the new figures. + +<|ref|>text<|/ref|><|det|>[[144, 370, 446, 387]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[115, 421, 451, 438]]<|/det|> +Reviewer #1 (Remarks to the Author: Impact): + +<|ref|>text<|/ref|><|det|>[[115, 455, 880, 512]]<|/det|> +I would suggest Nature communications or Scientific reports. The authors use phasor- but not to it's full capacity. The paper will indeed influence the field. However, I do feel publication in Nature methods can influence it in a way that may not be the best for the field. + +<|ref|>text<|/ref|><|det|>[[144, 531, 446, 548]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[115, 600, 591, 617]]<|/det|> +Reviewer #1 (Remarks to the Author: Strength of the claims): The + +<|ref|>text<|/ref|><|det|>[[115, 640, 255, 656]]<|/det|> +work is convincing. + +<|ref|>text<|/ref|><|det|>[[144, 677, 446, 694]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[115, 744, 541, 761]]<|/det|> +Reviewer #1 (Remarks to the Author: Reproducibility): The + +<|ref|>text<|/ref|><|det|>[[115, 784, 460, 800]]<|/det|> +paper is very detailed and can be reproducible. + +<|ref|>text<|/ref|><|det|>[[144, 823, 446, 839]]<|/det|> +We thank the reviewer for this comment. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 539, 107]]<|/det|> +Reviewer #2 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[113, 123, 880, 259]]<|/det|> +In their revised manuscript "HyU: Hybrid Unmixing for longitudinal in vivo imaging of low signal to noise fluorescence", the authors convincingly highlight the achievements/unique features of the further- developed algorithm for multiplexed imaging of hyperspectral data, expanding its use to low signal- to- noise ratio of real data, moving towards two- photon microscopy. Especially, they made particular efforts in demonstrating the power and the limitations of the algorithm when applied in highly- scattering tissue or when the number of detection channels is limited, providing an excellent and useful benchmarking for a broad life sciences audience interested in imaging and microscopy. + +<|ref|>text<|/ref|><|det|>[[115, 260, 876, 317]]<|/det|> +Although, I think, of high interest and definitely an important next step, I do agree with the authors that intravital imaging of highly scattering organs is a major challenge and can be the subject of future work. I fully recommend the present manuscript for publication in its present form. + +<|ref|>text<|/ref|><|det|>[[144, 333, 524, 350]]<|/det|> +We thank this reviewer for this comment. Reviewer + +<|ref|>text<|/ref|><|det|>[[115, 372, 378, 389]]<|/det|> +#2 (Remarks to the Author: Impact): + +<|ref|>text<|/ref|><|det|>[[115, 410, 870, 448]]<|/det|> +As mentioned above, with the new added data, the presented algorithm will find broad applicability for all sorts of data, which typically need to deal with low signals. + +<|ref|>text<|/ref|><|det|>[[115, 483, 559, 501]]<|/det|> +Reviewer #2 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[115, 517, 872, 555]]<|/det|> +In the current form, the revised manuscript provides all necessary evidence for the unique power of the HyU algorithm. + +<|ref|>text<|/ref|><|det|>[[115, 609, 510, 626]]<|/det|> +Reviewer #2 (Remarks to the Author: Reproducibility): + +<|ref|>text<|/ref|><|det|>[[115, 643, 847, 681]]<|/det|> +Beyond of statistics, I find the broad range of applications, excitation schemes and microscopy types particularly important to emphasize the general validity of the algorithm. + +<|ref|>text<|/ref|><|det|>[[115, 750, 539, 767]]<|/det|> +Reviewer #3 (Remarks to the Author: Overall significance): + +<|ref|>text<|/ref|><|det|>[[115, 784, 866, 861]]<|/det|> +In this report, Chiang and co- workers presented the Hybrid Unmixing (HyU) method for the efficient and robust analysis of multiple fluorescent signals. The authors employ the spectral phasor method for reducing spectral data dimension and denoising noises in the imaging system. The superiority of the proposed method has been demonstrated compared to the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[37, 118, 900, 172]]<|/det|> +conventional linear unmixing method by exploiting computer simulation and experimental results. This article seems to be timely the report as increasing the biomedical applications using hyperspectral imaging methods. And the authors appropriately discussed the proposed method by comparing previous techniques. + +<|ref|>text<|/ref|><|det|>[[67, 190, 378, 205]]<|/det|> +We thank the reviewer for this comment. + +<|ref|>text<|/ref|><|det|>[[37, 222, 494, 237]]<|/det|> +Reviewer #3 (Remarks to the Author: Strength of the claims): + +<|ref|>text<|/ref|><|det|>[[37, 255, 705, 270]]<|/det|> +The revised manuscript has clearly addressed all of my previous comments and concerns. + +<|ref|>text<|/ref|><|det|>[[67, 287, 378, 302]]<|/det|> +We thank the reviewer for this comment. + +<--- Page Split ---> diff --git a/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/images_list.json b/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a35055858a511ede88e8752d3a6c6ec4893743d7 --- /dev/null +++ b/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,642 @@ + +# nature portfolio + +Peer Review File + +# MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior + +Corresponding Author: Dr Matthew Isaacson + +This file contains all editorial decision letters in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Decision Letter: + +22nd Nov 2023 + +Dear Dr Isaacson, + +Thank you for your patience. Your Brief Communication, "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior", has now been seen by three reviewers. As you will see from their comments below, although the reviewers find your work of considerable potential interest, they have raised a number of concerns. We are interested in the possibility of publishing your paper in Nature Methods, but would like to consider your response to these concerns before we reach a final decision on publication. + +We therefore invite you to revise your manuscript to address these concerns. Specifically, please be sure to demonstrate the advantages over standard VR systems more thoroughly and discuss the limitations of your system. It won't be necessary to conduct experiments with a large number of animals. + +Importantly, please discuss the similarities and differences of your system with that described in https://www.researchsquare.com/article/rs- 3352160/v1 and https://patents.justia.com/patent/20220295743. You will need to make a strong case for the uniqueness of your system. + +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +When revising your paper: + +\* include a point- by- point response to the reviewers and to any editorial suggestions + +\* please underline/highlight any additions to the text or areas with other significant changes to facilitate review of the revised manuscript + +\* address the points listed described below to conform to our open science requirements + +\* ensure it complies with our general format requirements as set out in our guide to authors at www.nature.com/naturemethods + +\* resubmit all the necessary files electronically by using the link below to access your home page + +Link Redacted + +Note: This URL links to your confidential home page and associated information about manuscripts you may have + +<--- Page Split ---> + +submitted, or that you are reviewing for us. 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For more guidance on how to write this section please see: http://www.nature.com/authors/policies/data/data- availability- statements- data- citations.pdf + +## CODE AVAILABILITY + +Please include a "Code Availability" subsection in the Online Methods which details how your custom code is made available. Only in rare cases (where code is not central to the main conclusions of the paper) is the statement "available + +<--- Page Split ---> + +upon request" allowed (and reasons should be specified). + +We request that you deposit code in a DOI- minting repository such as Zenodo, Gigantum or Code Ocean and cite the DOI in the Reference list. We also request that you use code versioning and provide a license. + +For more information on our code sharing policy and requirements, please see: https://www.nature.com/nature- research/editorial- policies/reporting- standards#availability- of- computer- code + +## MATERIALS AVAILABILITY + +As a condition of publication in Nature Methods, authors are required to make unique materials promptly available to others without undue qualifications. + +Authors reporting new chemical compounds must provide chemical structure, synthesis and characterization details. Authors reporting mutant strains and cell lines are strongly encouraged to use established public repositories. + +More details about our materials availability policy can be found at https://www.nature.com/nature- portfolio/editorial- policies/reporting- standards#availability- of- materials + +## ORCID + +Nature Methods is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please do not hesitate to contact me if you have any questions or would like to discuss these revisions further. We look forward to seeing the revised manuscript and thank you for the opportunity to consider your work. + +Best regards, Nina + +Nina Vogt, PhD Senior Editor Nature Methods + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: + +In this manuscript, Isaacson and colleagues present a novel version of the VR system for head- fixed mice that features a miniature contraption (hence entitled MouseGoggles), easy and cheap design, direct stimulation of the eyes with minimal stray light, and independent control of each eye stimulus. MouseGoggles VR functionality is illustrated using 2PM visual cortex and hippocampal electrophysiology experiments, as well as spatial reward association and innate looming fear paradigms. This work is certainly going to lower the bar for the use of VR in many labs with limited budgets due to the price, eliminate shortcomings of the conventional HD VR, as well as will enable VR experiments that are currently not possible. Hardware is built on inexpensive and widely available components, both optical, mechanical, and electronic designs and software are made open source. Experiments are performed at a high level of quality and the data and results are convincing. I have a few comments listed below. While the new form factor, low cost, stereo- ability, and compactness make this system clearly novel and show great premise, the present form of the manuscript doesn't demonstrate or elaborate on any of these advantages. + +The minimalistic and low- cost hardware/software used in the MouseGoggles clearly leads to some compromises on the flexibility and performance of the VR implementation. Maximal frame rate, latency, and richness of the 3D cues will surely be limited compared to setups that rely on high- speed and high- resolution projector(s), GPU cards, and performant VR engines (e.g Unity). It would be good if the authors laid out the cons of such a system for animal experiments and possible future directions for circumventing them. + +A natural and important advance in the setup is the possibility to independently render images to both eyes thus enabling stereo- VR. However, unfortunately, the authors do not include such experiments. While testing V1 and CA1 cell tuning simply confirms that MouseGoggles is performing comparably to the existing conventional HF VR setups, these experiments + +<--- Page Split ---> + +do not demonstrate the advantages of the new system and do not make the case why it should be published in this journal as a major advance of the technology. Some experiments contrasting mono vs stereo- VR would demonstrate this key advance in the technology that is missing in the neuroscience toolbox. + +Innate behavior, such as startle response in response to looming stimulus, even though possibly recapitulating natural avoidance behavior observed in freely- moving rodents, is hardly making a decisive showcase for the system distinguishing it from the conventional ones. It is not clear from the methods section describing conventional projector VR that authors compare to if that system has used all possible means to increase projection surfaces at the lower visual field, including the floor (e.g. as done by labs of Mehta and Tank) by adding a cutout floor disk all around the ball. As many groups implemented this innate fear response with a simple overhead screen or sound, this paper doesn't put forward a distinct use- case for studying flight response to the looming stimulus under head- fixed conditions that could not be done in freely- moving animals. + +Stray light measurements make the case for the clear improvement in that parameter over plain- vanilla imaging setup in which the optical axis is not shielded from the light. However, similar to the enclosure protecting the 2PM from the monitor light, it is possible (and done by some scientists) to design and 3D print an enclosure protecting the cranial window from the external stray light. The use of blue light is another option (e.g Kuznetsova et al JNM 2021), which, I assume, authors refer to as "filtering". Besides, a significant amount of stray light reaches the brain through the eye, which would mean that if imaging was performed in more frontal regions, high- intensity eye stimulation might cause more stray light diverted through this pathway than in a conventional setup. Could authors measure that? What is the functional consequence of the difference in the stray light for the performance of 2PM imaging? Arguably somatic high- SNR Ca imaging will likely not be affected. I suggest that to make this feature a decisive one that sets this setup apart from the conventional one, there needs to be a clear demonstration of the functional advantages. + +What appears to be the top point setting the system apart is that, in addition to enabling stereo VR, it is inexpensive and compact. Inexpensive - means that scalable, high- throughput parallel VR setups would allow training the large batches of mice, something that, clearly was not possible so far. However obvious, this feature is not emphasized in the manuscript. Compactness of the setup is only slightly outlined by the authors, but not exploited. Rotations of the miniaturized setup allow easy implementation of the proper 2D VR (similar to Chen et al eLife 2018). Rotations around other than the vertical axis allow for so far impossible experiments testing vestibular input contributions. Realistic vestibular inputs could be added by implementing appropriate movements of the apparatus using hexapods. + +## Reviewer #2: + +Remarks to the Author: + +Mouse Goggles is a novel VR display device for the binocular visual stimulation of mice. Together with its online documentation this is to be a fully documented open- source tool that others can replicate. The results of MouseGoggle experimental testing confirm that it functions at least as well as traditionally used surround screens with visual stimuli or VR scenes. The experimental testing for MouseGoggles has been done comprehensively. The report is brief, to the point, well written, and complete. + +The usefulness of the method will depend on the possibility that it can actually be used as an open source tool and replicated by others. + +Authors should discuss how their relatively simple optical solution could potentially be improved. In this context they should cite the publicly accessible manuscript about Moculus doi.org/10.21203/rs.3.rs- 3352160/v1. + +Authors should discuss if patent PCT HU2020/050029 published under WO2021009526A1 covers or is different from their method as it may affect its use as an open source tool (accessible e.g. at https://patents.justia.com/patent/20220295743). + +The authors should improve the online documentation that is cited in the manuscript in order to better facilitate replication of this open source method. + +## Mechanics, CAD: + +Mechanics, CAD:1. Please upload not only the STL files but also the STP files or IPT drawing of the CAD designs for easier modification2. The bill of materials mentions all parts in [cm] however Figure 2 shows them in [mm] – please update the bill of materials and use only one unit of measurement to avoid confusion3. Recommendation for a future revision: Reconsider the material that was used in the printing. If the parts will be adjustable or moveable at some point, resin material will become brittle quickly. + +## Electronics: + +Electronics:1. Upload not only gerber files but also the schematic and PCB file for easier modification2. Include the fabrication specifications for the PCBs: board thickness, copper thickness and surface finish3. In MinibrdV1, the copper to copper spacing is only 0.06 mm – for a future revision I recommend updating the layout to increase the minimum copper to copper spacing to at least 0.2 mm; this simplifies demands on production.4. In MinihatV1, there are 90 degree traces and these will form acid traps that cause corrosion – for a future revision I recommend updating the layout with traces only at 45 degrees + +## Software: + +Software:a. The driver for sending the images via SPI to two small screens is from an external project (fbcp- ili9341 and fbcp- st7789) which seems to be well documented, no action required. + +<--- Page Split ---> + +b. Drivers for detecting the movement of the ball. + +The movement is transmitted to the PC/RasPi as if it were a PC mouse. The ADNS3080 sensor is used. "mouseVRheadset_controller_V4. ino" is not commented in detail. This is so small that this is not of great importance. Action: add a few explanatory sentences to facilitate faster orientation. + +The purpose and use of the files in the "ADNS3080 debugging" folder must be explained. While these are only for debugging, how and what they are used for is not clear. This is also because these data have no comments. Action required: Explain and comment. + +c. The experiments with 3D glasses use the Godot engine. Some examples are provided. But you need some knowledge about this engine, especially because the experiments run completely within the engine. This engine is not only responsible for the representation of the 3D world, but also for the process and the logging of the data. The examples make it easier to get started, but still require some familiarisation with Godot. Recommended action: the authors might think about how they could further facilitate getting familiar with this part of the code. + +d. The glasses are also available in a variant for "Monocular Display". This uses the Teensy board to control a small display. "GC9307_teensy_GFX.ino" has a lot of comments on single lines, but a more general documentation to understand the context of the parameters would be nice. Especially because there are so many parameters. Action required: provide a better general documentation and include a table of all parameters and their use. + +While the software is neither very large nor a complex project, with its current level of documentation it still poses a challenge to find ones way around. This does not apply to the external SPI monitor driver. This part alone is much larger and more complex than MouseGoggles. + +## Minor comments + +Minor comments551 check sentence for completeness: ... last bin excluded due the mouse's constrained position ... 555 For ease of understanding change: "All kicks not occurring following a reward delivery were defined as "exploratory licks". TO Licks at other times than after a reward delivery ... 619 a 2nd cohort of mice were tested -> was tested + +## Reviewer #3: + +Remarks to the Author: + +Virtual reality has become a powerful tool for studying a variety of brain functions in head- fixed rodents. Current implementations of rodent VR involve large displays that not only create difficulties for the experimenter, but also do not provide an immersive experience for the animal, largely due to their expansive visual field. Isaacson, Chang, et al. designed a head- set based VR system to overcome current constraints. They provide evidence that their system solves many of the practical issues with VR, including reduced light pollution for imaging methods and reduced cost. They use neural recordings to show that the visual tuning properties of neurons are comparable to results obtained with standard techniques, supporting the quality of image presentation. Finally, they provide evidence that the VR experience for the mouse is immersive through effective behavioral training in reward and innate fear behaviors. + +This work represents a very useful advance for both the quality of rodent VR experience and the ability of individual laboratories to implement VR systems, especially given the low- cost and open source design. Overall, the authors provide a straightforward and convincing case for the improvements this system makes over traditional rodent VR systems. The manuscript could be substantially improved by addressing the following points: + +The system provides 230 deg of field coverage in the horizontal azimuth, with 140 deg per eye and 25 deg of binocular overlap. The authors should report measured values of the mouse visual field from previous studies in the main text, and discuss the limitations of the system in obtaining full coverage in the Discussion. Also, the approximate elevation covered by the system should be reported in the main text. + +- How does the 130 ms input to display latency compare to other rodent VR systems? My understanding is that latencies greater than 20ms are detectable to humans, so it seems possible this relatively long latency may limit the immersive experience for the mouse. The authors should discuss this. + +- The measurements in 1b-d are in the range of 0-70 deg, but the authors report monocular coverage of 130 deg. Is there some reason why they did not model the full coverage, which is nearly twice the range in the figure? + +- The modeling of the light reaching the eye from the screen/lens is very useful. It would also be useful to have a measurement of the performance of the actual system, e.g., by projecting onto a model or real mouse eye. + +- The comparison of light pollution between the monitor and monocular display is quite striking. It would be ideal to see a similar direct comparison of the two systems for the visual tuning properties in Fig2d-i, especially since the stimulus used for receptive field mapping is different from the referenced study (Niell & Stryker, 2008). + +- How do the tuning properties of CA1 place cells compare to other mouse VR studies and freely moving mouse studies (e.g. place field width)? + +- In comparing the behavioral responses to looming stimuli on MouseGoggles vs. a traditional projector system, was the + +<--- Page Split ---> + +projector system oriented above the mouse? Based on the methods, it appears the projector reached a maximum of only 64 deg elevation, so is this the presumed reason that a response was not elicited? The ability to adjust elevation with MouseGoggles is indeed useful, but ideally the behavior would be compared to a projector system with similar visual field coverage. If it is experimentally infeasible to adjust the projector system to cover a comparable region of the visual field, the authors should state this. Otherwise, the experiment should be conducted with comparable overhead coverage between the two systems. + +- It appears that video of the mouse was acquired during the looming stimulus presentation (Fig3f and methods). The methods clearly state the responses were manually scored, but the main text and figure do not mention this, and the line fit to the mouse's back in Fig3f might lead the reader to assume the quantification of behavior was achieved with computational video analysis. Is the resolution of the video sufficient to perform the startle analysis? If so, the authors should quantify the behavior using image analysis methods or markerless pose estimation. If not, the authors should clearly state that in the text/Fig3g that the quantification was performed by two human observers. The authors could also plot the velocity of the animal measured via the spherical treadmill aligned to the onset of the looming stimulus. + +- Does this system permit the measurement of eye movements? Given that mice move their eyes (though somewhat infrequently) while head-fixed, it would be ideal to measure these movements during stimulus presentation. The authors mention that pupil tracking would be feasible with this system; how would this be achieved? + +- Face/whisker movements contribute significantly to neural activity. Does this system allow for these measurements, or do the MouseGoggles fully obstruct the view? + +- If possible, the experimenters should quantify whisker contact with the system. Do any of the whiskers touch the system, and if so with what frequency? Extensive whisker contact with the system would presumably degrade any immersive experience the mouse may have, and would make it difficult to perform some of the multisensory experiments the authors propose in the Discussion. + +- How do the authors calibrate the system with each individual mouse, given e.g., the inherent variability in headplate placement? + +- Given that monocular cues should be sufficient for most experiments performed in the manuscript (formation of place cells, responses to looming stimuli, reinforcement learning), an "immersive" experience may not be requisite for the results obtained here. A more convincing test that the animal is having an immersive experience would be ideal, e.g., behavior with a virtual cliff showing that animals stop to avoid falling over the edge. + +Version 1: + +Decision Letter: + +Our ref: NMETH- A53654A + +31st Jul 2024 + +Dear Dr. Isaacson, + +Thank you for your patience during this period and for submitting your revised manuscript "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior" (NMETH- A53654A). It has been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Methods, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements within two weeks or so. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +## TRANSPARENT PEER REVIEW + +Nature Methods offers a transparent peer review option for new original research manuscripts submitted from 17th February 2021. We encourage increased transparency in peer review by publishing the reviewer comments, author rebuttal letters and editorial decision letters if the authors agree. Such peer review material is made available as a supplementary peer review file. Please state in the cover letter 'I wish to participate in transparent peer review' if you want to opt in, or 'I do not wish to participate in transparent peer review' if you don't. Failure to state your preference will result in delays in accepting your manuscript for publication. + +Please note: we allow redactions to authors' rebuttal and reviewer comments in the interest of confidentiality. If you are concerned about the release of confidential data, please let us know specifically what information you would like to have removed. Please note that we cannot incorporate redactions for any other reasons. Reviewer names will be published in the + +<--- Page Split ---> + +peer review files if the reviewer signed the comments to authors, or if reviewers explicitly agree to release their name. For more information, please refer to our FAQ page. + +## ORCID + +IMPORTANT: Non- corresponding authors do not have to link their ORCIDs but are encouraged to do so. Please note that it will not be possible to add/modify ORCIDs at proof. Thus, please let your co- authors know that if they wish to have their ORCID added to the paper they must follow the procedure described in the following link prior to acceptance: https://www.springermature.com/gp/researchers/orcid/orcid- for- nature- research + +Thank you again for your interest in Nature Methods. Please do not hesitate to contact me if you have any questions. We will be in touch again soon. + +Best regards, Nina + +Nina Vogt, PhD Senior Editor Nature Methods + +Reviewer #1 (Remarks to the Author): + +Authors addressed all my comments, I would fully support publishing this paper. + +Reviewer #1 (Remarks on code availability): + +Software and hardware are well- documented and all open- source. + +Reviewer #2 (Remarks to the Author): + +The authors have made quite some effort to respond to my concerns. + +## Comment 14 + +The "Hardware" directory has been renamed to "Other Hardware". This was a good decision, as it helps to differentiate between MouseGoggles and other hardware mentioned in paper. The added documentation should now enable and simplify the initial setup of treadmill and the sensors. + +Comment 15 + +Still no comments in the code. But now it is explained how these files should be used and their purpose. Since the files are small, this seems fine now. + +Comment 16 + +The new short "Introduction to Godot" should indeed make it a little easier to get started. Even if there is still a relatively large hurdle here, as Godot has to be learned. But the experiments seem to be both very small and very similar, so that customisation should be possible. + +Small note and suggestion for a further small change: it should be noted which version of Godot is used here. I opened the project with 4.2.2 and had some error messages in the script editor. This happened although the documentation explicitly calls for the last version of Godot. However, this probably refers to the latest 3. x version. + +## Comment 17 + +The description of the hardware and the hardware assembly instructions should now be sufficient to build the system. And the software description/documentation should help to setup the system. + +Comment 18 + +I agree. + +Reviewer #3 (Remarks to the Author): + +The updated manuscript provided by Isaacson, Chang et al. entitled "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior" represents a substantial improvement over the initial manuscript submission. The authors responded to the reviewer comments with a significant amount of work that addresses the issues with the original manuscript, including: + +Relationship of the system to the total visual field Discussion of latency and steps toward reducing it Measured the light reaching the eye Clarification on visual stimuli + +<--- Page Split ---> + +Quantification of place cell properties Improved behavioral measures during looming behavior Characterization of whisker obstruction + +The heroic addition of pupillometry also sets this system apart from other emerging immersive mouse VR systems, making this system particularly useful to neuroscientists who also want to track pupil position and size. + +I have only a minor comment, which is that the authors should consider mentioning a finding from Meyer et al., Curr Bio 2020, that might explain the eye movements in response to the looming stimulus. Eye movements in headfixed mice appear to result primarily from attempted head movements (see Fig S5 in that paper), so one interpretation of the results here is that the animals are attempting to escape by moving their heads, which results in a saccade. While a subtle point, the authors' interpretation that the animal's gaze is being directed toward the stimulus is more likely due to an artifact of the animal's inability to move its head freely. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +Dear Dr. Vogt, + +Dear Dr. Vogt,We thank you for the opportunity to submit our revised manuscript, "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior", to Nature Methods. We appreciate the time taken by you and the reviewers to comment and make suggestions on both the technical and experimental aspects of our approach, and in responding to these comments we have made substantial improvements to our manuscript. These improvements include a more comprehensive comparison of our MouseGoggles system to existing VR technologies and recently developed headset- based systems, an improved online repository to enhance the reproducibility and modifiability of our technology, and the addition of a substantial new capability to our VR system – binocular eye and pupil tracking during VR – which has been our most requested new feature and sets MouseGoggles apart from other recently reported headset- based mouse VR systems. These improvements are demonstrated with the addition of 13 main figure panels, 14 supplemental figure panels, 2 supplementary videos, new results, discussion, and methods text, and substantial additions to the public online repository. These changes are outlined in our point- by- point response to all comments below. + +## Comments from the Editor: + +Comment 1: Specifically, please be sure to demonstrate the advantages over standard VR systems more thoroughly and discuss the limitations of your system. + +Comment 1: Specifically, please be sure to demonstrate the advantages over standard VR systems more thoroughly and discuss the limitations of your system. Response: Thank you very much for this suggestion. We have added new details and results to the main text and methods sections expanding on the advantages of our system over traditional panoramic VR systems. These advantages include a substantially reduced form factor and lowered computational requirements (enabling low- cost VR in a small footprint and a greater ability to scale up experiments, detailed on lines 167- 169), increased immersivity and ability to study innate behaviors during head- fixation (lines 148- 152), and the ability to perform binocular eye and pupil tracking during VR (lines 127- 142, 169- 170, and demonstrated in Fig. 4 and Supplementary Video 3). We have also added some discussion of the limitations of our system, including the relatively low resolution displays used which are well- suited for mouse visual acuity but could be difficult to be directly used on other animals models with higher visual acuity, the 130 ms input- to- display latency which may be problematic during closed- loop feedback of fast behaviors or neural events, and the occlusion of many of the mouse's whiskers by the headset which may confound the sensory experience of a mouse navigating virtual environments (lines 154- 165). We also discuss potential future hardware and software improvements that could increase display resolution and lower latency (lines 158- 165), while a new supplemental figure characterizes the amount of whisker contact at different headset positions to provide guidance on minimizing this potential sensory conflict (Supplementary Fig. 7). + +Comment 2: Importantly, please discuss the similarities and differences of your system with that described in https://www.researchsquare.com/article/rs- 3352160/v1 and https://patents.justia.com/patent/20220295743. You will need to make a strong case for the uniqueness of your system. + +Response: Since our submission of this manuscript in Aug. 2023, two new mouse VR headset systems have been described in the literature. The 1st system, named "Moculus," was released as a preprint on Research Square in Oct. 2023 (https://www.researchsquare.com/article/rs- 3352160/v1) and cited patent applications from previous years. The 2nd system, named "iMRSIV," was published in Dec. 2023 in Neuron (https://www.cell.com/neuron/fulltext/S0896- + +<--- Page Split ---> + +6273(23)00893- 0) and built using the same software platform as Moculus but using a different display and lens configuration to support a larger field of view. In our manuscript, we now compare our MouseGoggles system with these two new mouse VR headsets. There are several similarities: small form factor, greater accessibility and scalability of head- fixed mouse VR, and evidence of experimental benefits from increased mouse immersion in the virtual world with headset- based systems (lines 148- 152). We have also added new discussion and results on the uniqueness of our system compared to these other approaches, including the ability to perform binocular eye and pupil tracking during VR, the open hardware and software platforms used by MouseGoggles (Raspberry Pi and Godot game engine; all details for replication of hardware and software on GitHub), reduced cost and computational requirements, simplified optical design requiring no custom lenses or precise eye alignment protocols, and the greater mobility of the miniature headset to accommodate rotating head mounts. These discussion points are detailed in the main text (lines 154- 170), with headset mobility and rotation demonstrated in Supplementary Video 4 and binocular eye and pupil tracking demonstrated in Fig. 4 and Supplementary Video 3. Taken together, our and other headset- based VR systems have shown increased immersion, as well as reduced form factor and cost relative to panoramic systems. These benefits will be salient for nearly all neuroscience researchers using VR systems, and rapid adoption is likely. + +Our MouseGoggles system is distinct from the other two systems demonstrated so far primarily in having the ability to track eye gaze direction (to assess what part of the VR space the mouse is looking at) and pupil diameter (a reliable indicator of arousal), with many additional minor differences. This eye tracking capability has been, by far, the most requested addition to MouseGoggles that we have heard from other researchers when they learn about our system. We are happy that we were challenged to make this addition to the system now by both a Reviewer and the need to make a strong case for the uniqueness of our system. + +## Comments from Reviewer 1: + +Comment 1: In this manuscript, Isaacson and colleagues present a novel version of the VR system for head- fixed mice that features a miniature contraption (hence entitled MouseGoggles), easy and cheap design, direct stimulation of the eyes with minimal stray light, and independent control of each eye stimulus. MouseGoggles VR functionality is illustrated using 2PM visual cortex and hippocampal electrophysiology experiments, as well as spatial reward association and innate looming fear paradigms. This work is certainly going to lower the bar for the use of VR in many labs with limited budgets due to the price, eliminate shortcomings of the conventional HD VR, as well as will enable VR experiments that are currently not possible. Hardware is built on inexpensive and widely available components, both optical, mechanical, and electronic designs and software are made open source. Experiments are performed at a high level of quality and the data and results are convincing. + +Response: We thank the reviewer for this positive assessment of our open- source system's advancements over traditional VR technology (e.g. increased accessibility, reduced technical shortcomings, and utility in enabling new VR experiments) and in the high quality of data demonstrating its use. + +Comment 2: I have a few comments listed below. While the new form factor, low cost, stere- ability, and compactness make this system clearly novel and show great premise, the present form of the manuscript doesn't demonstrate or elaborate on any of these advantages. + +Response: As detailed in responses to the specific comments below, we have added additional results and discussion points that explicitly describe these advantages of the system. This includes discussion of the ability to investigate binocular integration and stereo vision with + +<--- Page Split ---> + +independent eye stimulus control (response to comment 4), to scale up VR experiments due to our system's low cost and small size (response to comment 8), and to rotate the VR system around or with the animal to engage the animal's vestibular system (response to comment 9). + +Comment 3: The minimalistic and low- cost hardware/software used in the MouseGoggles clearly leads to some compromises on the flexibility and performance of the VR implementation. Maximal frame rate, latency, and richness of the 3D cues will surely be limited compared to setups that rely on high- speed and high- resolution projector(s), GPU cards, and performant VR engines (e.g Unity). It would be good if the authors laid out the cons of such a system for animal experiments and possible future directions for circumventing them. + +Response: We thank the reviewer for this comment and apologize for not discussing these limitations in more depth in the original manuscript. The primary technical compromise of MouseGoggles relative to other systems (including human VR systems, traditional panoramic mouse VR systems, and the two other headset- based mouse VR systems) is in display resolution, though we are confident this does not hinder mouse visual neuroscience applications. We used small 240x210 or 240x240 pixel circular displays that contain approximately 1/50th the number of pixels as a single 1080p HD monitor, which substantially reduces the smallest simulated objects and features that can be resolved on screen. However, as prior literature suggests and our experiments have demonstrated (Fig. 2), this reduction in resolution is not a detriment to stimulating the mouse visual system due to the mouse's relatively poor visual acuity, being approximately 1/100th that of humans (~60 cpd maximum for humans vs \~0.5 cpd for mice, reported in Sinex et al, Vision Res. 1979). To better demonstrate this poor visual acuity of the mouse visual system, inserted below is an example image demonstrating how a high- resolution image (left) and a low resolution MouseGoggles image (right) might appear to the mouse (bottom row): + +<--- Page Split ---> +![PLACEHOLDER_11_0] + + +Low resolution displays would be a limitation if MouseGoggles were to be adapted for a different animal model with higher visual acuity (rats or tree shrews, for example – ongoing in our lab), and would need to be circumvented with the use of higher- resolution displays, and potentially heftier computational resources. On the other hand, because we do not need higher resolution due to the poor visual acuity of mice, an added benefit is a substantial reduction in the computer processing power and data transfer rates required to render 3D scenes and stream images to the displays. With the display resolution we use, complex 3D environments can be rendered at high frame rate on a Raspberry Pi 4, which only has a simple onboard GPU, and frames can be streamed at up to 80 fps using a simple SPI interface. To achieve a similar result, other VR systems require an expensive desktop computer and powerful GPU (e.g. Nvidia RTX3070 used by iMRSIV). Our low- cost solution makes VR research more accessible and promotes high- throughput VR experiments. + +As the reviewer noted, many VR systems used in neuroscience use the Unity game engine to generate 3D scenes and create experiments. Compared to very high- performance game engines (e.g. Unreal Engine), Unity is a beginner- friendly engine more popular among researchers. For MouseGoggles, we opted for the game engine “Godot”, in part due to the ethos of our project relying on open- source tools (unlike Unity, Godot is a fully free and open- source engine). Additionally, despite being lightweight and beginner- friendly, Godot is a full- featured 3D game engine, capable of complex lighting, shaders, particles, and physics simulations, which we are confident is more than powerful enough to support all mouse neuroscience use cases. Researchers may find Godot even easier to work with than Unity as it uses a node- based graphical user interface to create 3D scenes and uses Python- like scripts for game design, instead of Unity’s C# programming. To assist researchers in developing with the + +<--- Page Split ---> + +Godot game engine, we have added an "Introduction to Godot" document along with a Godot project file containing seven example VR experiments in the online repository + +Notes on the motivation to use the Godot game engine and on VR environment development have been added to the main text and methods (lines 165- 167, 399- 403). + +Comment 4: A natural and important advance in the setup is the possibility to independently render images to both eyes thus enabling stereo- VR. However, unfortunately, the authors do not include such experiments. While testing V1 and CA1 cell tuning simply confirms that MouseGoggles is performing comparably to the existing conventional HF VR setups, these experiments do not demonstrate the advantages of the new system and do not make the case why it should be published in this journal as a major advance of the technology. Some experiments contrasting mono vs stereo- VR would demonstrate this key advance in the technology that is missing in the neuroscience toolbox. + +Response: The reviewer is correct in that we have not demonstrated an experiment that utilizes stereo VR over mono VR, although all VR scenes were rendered stereoscopically. We have put considerable thought into the possibility of a convincing mono vs stereo VR demonstration experiment, but our reading of the literature on stereoscopic vision in mice suggests that a meaningful stereo VR experiment is beyond the scope of this manuscript due to ongoing uncertainty about the role of stereoscopy in natural mouse behavior. + +Some limited aspects of stereo vision have been previously reported in mice using custom stereo displays: visual cortical neurons show some stereo- disparity selectivity (Chioma et al, J Neurosci 2020: https://pubmed.ncbi.nlm.nih.gov/33051348/), mice can be trained to use this information to discriminate "near" and "far" surfaces in random dot stereograms (Samonds et al, J Neurosci 2019: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786824/), and there has even been a report describing the innate use of stereo cues in a novel angled pole descent test (Boone et al, Cur Bio 2021: https://www.cell.com/current- biology/fulltext/S0960- 9822(21)00272- 4). In sum, however, these reports describe rather limited mouse stereo vision capabilities: mice don't use vergence eye movements to fixate by depth like primates do, and the neural selectivity to stereo disparity was relatively weak and only relevant over a narrow range of disparities. Other animal models such as tree shrews show comparably more selective responses to stereo disparity (Tanabe et al, Curr Bio 2022: https://pubmed.ncbi.nlm.nih.gov/36417902/) and may be better models to study stereo vision (this has motivated us to begin development of a larger, higher- resolution version of MouseGoggles suitable for rats and tree shrews). Nonetheless, stereoscopy is a fascinating topic in mouse neuroscience, and MouseGoggles could be helpful in future VR experiments that explore stereoscopic vision in mice. For example, one could develop a stereo vs. mono VR version of the angled pole descent test, which is necessary over a standard flat visual cliff as the downward angle of the descent shifts the view of the cliff into the binocular overlap region where stereo vision might contribute to depth perception. + +Because prior studies have already described custom stereo displays to study stereoscopy in mice, our manuscript focuses on more novel aspects of our method, such as the greater immersivity as well as eye and pupil tracking in VR. But we fully agree that the stereoscopic capabilities of MouseGoggles is another important advance of our method that should be valuable to the neuroscience community, so we have highlighted this feature in the discussion (line 149). + +Comment 5: Innate behavior, such as startle response in response to looming stimulus, even though possibly recapitulating natural avoidance behavior observed in freely- moving rodents, is hardly making a decisive showcase for the system distinguishing it from the conventional ones. It is not clear from the methods section describing conventional projector VR that authors compare to if that system has used all possible means to increase projection surfaces at the + +<--- Page Split ---> + +lower visual field, including the floor (e.g. as done by labs of Mehta and Tank) by adding a cutout floor disk all around the ball. As many groups implemented this innate fear response with a simple overhead screen or sound, this paper doesn't put forward a distinct use- case for studying flight response to the looming stimulus under head- fixed conditions that could not be done in freely- moving animals. + +Response: The reviewer is correct that innate fear reactions to looming visual stimuli have been observed using VR setups in freely- moving rodents. However, the primary goal of this experiment in our manuscript was to determine if looming reactions could also be elicited in head- fixed conditions, which is necessary for many setups that use neural recording systems not amenable to free- walking. The panoramic VR system we used is state- of- the- art and covers a very wide field- of- view, leaving only a small cutout above the mouse to accommodate a microscope objective and a larger gap below the mouse to fit a spherical treadmill. This projector setup did not include the cutout floor disk approach the reviewer describes, though because the looming object approached at an angle from overhead and did not produce a ground shadow, this may not be a meaningful difference. As reviewer 3 (in comment 8) pointed out, the projector also did not have quite the same vertical extent as MouseGoggles, though in new looming stimulus experiments with eye and pupil tracking (Fig. 4), we blacked out the top of the MouseGoggles displays to match the projector's vertical extent and startle reactions were still observed, suggesting that the extent of visual field coverage does not explain the difference. To our knowledge, only our manuscript and the recent publication on the iMRSIV headset system report fear- based reactions to looming stimuli in head- fixed mice, and neither could replicate this startle reaction in a panoramic VR setup. Thus, we believe that the prior and new data on mouse responses to looming stimuli with headset VR does demonstrate increased immersion in the VR environment, which could be broadly helpful for VR- based experiments. + +Beyond head- fixed neural recording, there are other benefits to being able to perform this task during head- fixation, such being able to use precise behavioral monitoring systems that are more effective in stationary animals. In our revision we have added a new demonstration of one such system: binocular eye and pupil tracking. By building eye tracking cameras into the VR headset, we monitored eye and pupil dynamics in both eyes simultaneously during the presentation of looming stimuli. We observed consistent eye tracking in the direction of the overhead approaching virtual object, and an increase in pupil diameter following the looming stimulus that diminishes with further repetitions of the stimulus, similar to the diminishing startle response we reported in the original manuscript. The ability to elicit fear responses in head- fixed setups where not only neural activity but also eye and pupil dynamics can be recorded, thus enabling assessment of the mouse's attention, arousal, and memory encoding is a substantial advance for mouse neuroscience, in particular the study of emotional circuits. This new MouseGoggles design with eye tracking and application to the head- fixed looming experiment is described in the main text (lines 127- 142) and shown in Fig. 4 and Supplementary Video 3. + +Comment 6: Stray light measurements make the case for the clear improvement in that parameter over plain- vanilla imaging setup in which the optical axis is not shielded from the light. However, similar to the enclosure protecting the 2PM from the monitor light, it is possible (and done by some scientists) to design and 3D print an enclosure protecting the cranial window from the external stray light. The use of blue light is another option (e.g Kuznetsova et al JNM 2021), which, I assume, authors refer to as "filtering". + +Response: On the issue of stray light contamination into sensitive imaging applications, the reviewer accurately points out that shielding the cranial window (or what we described as "shielding the objective" in the manuscript) or filtering out display light (e.g. using blue light with a short- pass color filter, since blue LEDs used in commercial displays typically emit small amounts of longer wavelength light) can be effective in enabling imaging during high intensity visual stimulation. The main advantage of using our MouseGoggles display is that this additional + +<--- Page Split ---> + +shielding or filtering is not necessary. This point could range from being irrelevant for setups that already have appropriate shielding solutions in place, to a significant advantage for setups that would otherwise have to create and test new strategies appropriate for their equipment and experiment. Some imaging setups feature components that make shielding and filtering more difficult, such as those that use multiple different microscope objectives or use blue/green fluorescent probes, so having a visual stimulation system which produces minimal stray light to begin with can be a benefit. Because our display system was designed with the goal that it could simply be "dropped in" to most existing experimental setups, we believe that this issue of stray light reduction is important in that context, though we agree with the reviewer's point that this is otherwise a surmountable problem. We have adjusted the main text so that this feature is described as an improvement over a standard off- the- shelf monitor, and equivalent to a monitor with substantial added shielding (lines 82- 85, see also our response to the next comment). New data on the comparison to a shielded monitor is demonstrated in Supplementary Fig. 4 and described in the methods section (line 573- 578). + +Comment 7: Besides, a significant amount of stray light reaches the brain through the eye, which would mean that if imaging was performed in more frontal regions, high- intensity eye stimulation might cause more stray light diverted through this pathway than in a conventional setup. Could authors measure that? What is the functional consequence of the difference in the stray light for the performance of 2PM imaging? Arguably somatic high- SNR Ca imaging will likely not be affected. I suggest that to make this feature a decisive one that sets this setup apart from the conventional one, there needs to be a clear demonstration of the functional advantages. + +Response: The reviewer brings up an excellent point that a small amount of light from the displays may reach imaging cameras or PMTs by passing through the pupil and scattering through the brain, and while the overall amount of light generated by a MouseGoggles display is substantially less than that of a full- sized monitor or projector, it is not immediately clear whether MouseGoggles would focus more or less light through the eye than traditional displays. + +To investigate this possibility, we recorded light levels from both a MouseGoggles monocular display and a traditional flat screen with and without shielding the cranial window. In anesthetized mice, we imaged in both visual area 1, where visual stimulus- evoked neural activity could be seen from GCaMP6f fluorescence, and in somatosensory area 1, where no stimulus- evoked GCaMP activity was seen and the contribution from stray light could be quantified. To determine whether this measured stray light was acquired through an external pathway or an internal one (i.e., through the pupil and scattering through the skull), we compared recorded light levels with the cranial window either unblocked, where light could be collected from both internal and external pathways, or blocked, where light is only collected from external pathways. We found that using MouseGoggles or a substantially shielded traditional monitor, we could eliminate nearly all of the external stray light, where only minimal external stray light was recorded at maximum display brightness, far less than the intensity of typical GCaMP6s- labeled cell baseline fluorescence. In addition, we did not detect any additional light from the display reaching our detectors when the cranial window was unblocked relative to the open cranial window condition, suggesting that the internal pathway is not contributing any detectable stray light in our imaging setup, at least in the brain regions we imaged. We thus conclude that light contamination through the eye is not a major issue with MouseGoggles, and that total stray light from MouseGoggles is comparable to a highly shielded traditional monitor. These new results have now been included in Supplementary Fig. 4 and referred to in the main text (lines 82- 85). + +Comment 8: What appears to be the top point setting the system apart is that, in addition to enabling stereo VR, it is inexpensive and compact. Inexpensive - means that scalable, high + +<--- Page Split ---> + +throughput parallel VR setups would allow training the large batches of mice, something that, clearly was not possible so far. However obvious, this feature is not emphasized in the manuscript. + +Response: We thank the reviewer for this helpful perspective and suggestion. Since the MouseGoggles system is even more compact and inexpensive than other recent mouse VR headset systems (Moculus and iMRSIV) and has substantially reduced computational requirements (only needing a Raspberry Pi 4 with no GPU), our system is particularly well suited to the scaled- up VR training the reviewer contemplates. We have added an additional discussion point highlighting this benefit (lines 165- 169). To further demonstrate the ability to scale up VR experiments with small- footprint VR systems, we have added a description of a VR setup using a linear treadmill (lines 651- 658) that fits within a \(14 \times 14 \text{cm}\) footprint (Fig. 4b) and added new documentation to the online repository with assembly instructions and code for this setup. We have also included instructions in our online repository for controlling the VR system with VNC, so that multiple VR setups can be controlled from a single host computer, which may be the desired solution for running VR experiments in parallel. + +Comment 9: Compactness of the setup is only slightly outlined by the authors, but not exploited. Rotations of the miniaturized setup allow easy implementation of the proper 2D VR (similar to Chen et al eLife 2018). Rotations around other than the vertical axis allow for so far impossible experiments testing vestibular input contributions. Realistic vestibular inputs could be added by implementing appropriate movements of the apparatus using hexapods. + +Response: We agree with the reviewer that the compact size of MouseGoggles could allow rotations of the headset during use. Rotating the VR setup to test vestibular inputs is a fascinating possibility, though beyond the scope of this manuscript to thoroughly implement. We have added new discussion points about this possibility in the main text (lines 172- 173). Additionally, since relatively recent evidence has shown that rotatable head mounts improve 2D navigation in VR (such as in Chen et al, eLife 2018; this citation has been added to our manuscript), we believe this could be a very important feature for future MouseGoggles implementations. To demonstrate how headset rotations could be measured for closed- loop experiments, we have added a new supplementary video demonstrating headset rotation, using an integrated sensor (accelerometer and gyroscope) and magnetometer. The accelerometer provided feedback for headset roll and the magnetometer worked well for yaw feedback (Supplementary Video 4). We have added details on this modification to the methods section and online repository for building and controlling these setups. We hope this addition will enable interested researchers to take on the scientific questions the reviewer mentions. + +## Comments from Reviewer 2: + +Comment 1: Mouse Goggles is a novel VR display device for the binocular visual stimulation of mice. Together with its online documentation this is to be a fully documented open- source tool that others can replicate. The results of MouseGoggle experimental testing confirm that it functions at least as well as traditionally used surround screens with visual stimuli or VR scenes. The experimental testing for MouseGoggles has been done comprehensively. The report is brief, to the point, well written, and complete. + +Response: We thank the reviewer for this positive assessment of our work. + +Comment 2: The usefullness of the method will depend on the possibility that it can actually be used as an open source tool and replicated by others. + +<--- Page Split ---> + +Response: This is an excellent point, and we are in full agreement with the reviewer. One of our primary goals in this project is that not only is it possible for others to replicate this method, but that it be simple and easy for non- experts to do. To that end, we have opted for off- the- shelf parts wherever possible (e.g. no custom lenses), have created a comprehensive parts list, and provide simple assembly and installation instructions that have all necessary details for replication. We have also verified that this system has been successfully replicated by multiple external labs through the online resources, though we acknowledge that our open- source documentation at the time of submission still had significant room for improvement. As detailed in response to many comments below (comments 6- 18), we have made significant improvements to the online repository to facilitate further replication and modification by the research community. + +Comment 3: Authors should discuss how their relatively simple optical solution could potentially be improved. In this context they should cite the publicly accessible manuscript about Moculus doi.org/10.21203/rs.3.rs- 3352160/v1. + +Response: Since the submission of our MouseGoggles manuscript, there are now two other headset- based mouse VR systems in the literature: Moculus (Rozsa et al, Research Square 2023; preprint: https://www.researchsquare.com/article/rs- 3352160/v1) and iMRSIV (Pinke et al, Neuron 2023; published: https://www.cell.com/neuron/fulltext/S0896- 6273(23)00893- 0). We have added new discussion points commenting on the different optical design strategies used and their pros/cons. Importantly, the optical design we chose is in service of a primary goal of our project: that MouseGoggles is simple and easy to replicate and use. By using just a single off- the- shelf Fresnel lens, no custom lenses have to be ordered or cut to size. Also, because of our use of a display system positioned at infinity focus from the perspective of the mouse, no complicated eye positioning protocols (such as those used by Moculus and iMRSIV) are needed. To add a new test and demonstration of the performance of our optical design, we imaged the display's projection on the back plane of an enucleated mouse eye, confirming that our design produces a clear image of the display that is robust to small changes in eye position within the allowed space of the eyepiece. These new results are shown in Supplementary Fig. 1 and referenced in the main text (lines 50- 52) and described in the methods section (lines 425- 439). The primary disadvantage of this simple optical design is that the field of view coverage of our eyepieces is limited to 140 deg, whereas more complex optical designs (e.g. iMRSIV) can support increased field of view coverage up to 180 deg. However, this enhanced field of view comes at the expense of necessitating more precise eye positioning. These pros and cons are now detailed in the discussion (lines 159- 162). + +Comment 4: Authors should discuss if patent PCT HU2020/050029 published under WO2021009526A1 covers or is different from their method as it may affect its use as an open source tool (accessible e.g. at https://patents.justia.com/patent/20220295743). + +Response: As it currently stands, the Moculus patent application was given a non- final rejection in Nov, 2023 (https://patentcenter.uspto.gov/applications/17626700/ifw/docs?application=). While we are not qualified to comment on the legal aspects of the differences between our method and the currently rejected patent, in terms of engineering and scientific differences, our method differs in significant ways from the Moculus system as described both in the patent and in the preprint. + +Moculus is a stereoscopic VR simulator composed of separate display "wings" that are individually positioned for each eye and secured to the animal head- clamping mechanism, distinguishing itself from prior VR designs that are single- piece headsets and that can be attached to freely- walking animals. MouseGoggles on the other hand is a single piece design similar to prior VR/AR headsets and that is not attached to the head- clamp. MouseGoggles is also built on entirely different hardware and software platforms than Moculus (MouseGoggles + +<--- Page Split ---> + +with a Raspberry Pi computer, Godot game engine, and SPI- based displays, compared to Moculus with a Windows PC, Unity engine, and HDMI- based displays); in fact, there is not a single piece of hardware or software in common between the two systems. We further successfully demonstrate in situ tracking of eye gaze direction and pupil diameter, a feature the neuroscience community has explicitly requested from us. In this manuscript, our focus is reporting on the design and results from our mouse VR system, and we must leave questions about the impact of this patent to the US Patent and Trademark Office, and comparable entities in other countries. + +Comment 5: The authors should improve the online documentation that is cited in the manuscript in order to better facilitate replication of this open source method. Response: We thank the reviewer for such detailed and helpful notes regarding the online documentation. We have updated the repository with all details requested and listed in the following comments. + +Comment 6: Please upload not only the STL files but also the STP files or IPT drawing of the CAD designs for easier modification + +Response: For all custom 3D designed parts, both .stl files and .step files have been uploaded to facilitate modification. + +Comment 7: The bill of materials mentions all parts in [cm] however Figure 2 shows them in [mm] - please update the bill of materials and use only one unit of measurement to avoid confusion + +Response: The bill of materials has been updated to show 3D print sizes in mm to stay consistent with the rest of the repository and manuscript. + +Comment 8: Recommendation for a future revision: Reconsider the material that was used in the printing. If the parts will be adjustable or moveable at some point, resin material will become brittle quickly. + +Response: We thank the reviewer for this recommendation. In our online assembly instructions, we have added new recommendations for different materials, 3D printers, and print settings to use. To successfully print the small features of our eyepiece enclosure, we recommend high resolution printers capable of \(< 0.2 \text{mm}\) layer resolution. Low- cost SLA printers (e.g. Photon Mono X) using standard UV- cured resin can be very cost- effective and successfully print all parts used by MouseGoggles. Parts produced this way have remained intact after over 2 years of use in our hands. For more rigid and longer- lasting parts, a high resolution FDM printer (e.g. Ultimaker) can be used with stronger and tougher thermoplastics such as PLA, PETG, or ABS. + +Comment 9: Upload not only gerber files but also the schematic and PCB file for easier modification + +Response: For all custom PCBs, both the schematic and layout files as well as the Autodesk Eagle project file have been added to the online repository to facilitate modification. + +Comment 10: Include the fabrication specifications for the PCBs: board thickness, copper thickness and surface finish + +Response: Fabrication specifications for custom PCBs have been added to the online repository, including the number of layers (2), board material (FR- 4), board thickness (1.6 mm), copper thickness (0.0348 mm), and surface finish (HASL with lead). + +<--- Page Split ---> + +Comment 11: In MinibrdV1, the copper to copper spacing is only \(0.06 \text{mm}\) – for a future revision I recommend updating the layout to increase the minimum copper to copper spacing to at least \(0.2 \text{mm}\) ; this simplifies demands on production. + +Response: In MinibrdV1 (now renamed to MouseGoggles MiniBrdAA 1.1 as part of a comprehensive version naming structure), the minimum copper to copper spacing has been adjusted to \(0.2 \text{mm}\) . All other PCB layout files have been verified to fit this requirement as well. Thank you for this valuable suggestion. + +Comment 12: In MinihatV1, there are 90 degree traces and these will form acid traps that cause corrosion – for a future revision I recommend updating the layout with traces only at 45 degrees + +Response: In MinihatV1 (now renamed to MouseGoggles MiniHataAA 1.1), all 90- degree traces have been removed and replaced with 45- degree traces. Other layout files have been checked for these as well. Thank you again for helping us with these PCB design subtleties. + +Comment 13: The driver for sending the images via SPI to two small screens is from an external project (fbcp- ili9341 and fbcp- st7789) which seems to be well documented, no action required. + +Response: We thank the reviewer for this comment, and again for thoroughly checking the open documentation. Our selection of this driver was in keeping with the open- source, well- documented ethos of this project. + +Comment 14: Drivers for detecting the movement of the ball. + +The movement is transmitted to the PC/RasPi as if it were a PC mouse. The ADNS3080 sensor is used. "mouseVRheadset_controller_V4. ino" is not commented in detail. This is so small that this is not of great importance. Action: add a few explanatory sentences to facilitate faster orientation. + +Response: We thank the reviewer for pointing out our lack of documentation on the treadmill system. Since our focus has been on the development of visual display hardware and software, we mistakenly omitted some documentation on the treadmill system software we've developed for MouseGoggles compatibility. We have now added new documentation describing the software for two treadmill systems: the spherical treadmill system originally from Harvey et al, Nature 2009 (https://www.nature.com/articles/nature08499) that was described in our original manuscript, as well as a linear treadmill from Arnold, JRC, 2023 (https://www.janelia.org/open- science/low- friction- rodent- driven- belt- treadmill) which we have recently implemented with MouseGoggles, and is included in our revision (Fig. 4). Our new documentation describes where the treadmill hardware is described and/or can be purchased, and details how to update the treadmill's microcontroller firmware for compatibility with the MouseGoggles system. + +Comment 15: The purpose and use of the files in the "ADNS3080 debugging" folder must be explained. While these are only for debugging, how and what they are used for is not clear. This is also because these data have no comments. Action required: Explain and comment. + +Response: A description of this debugging folder has been added to the spherical treadmill documentation described above, and additional in- code comments have been added to the scripts within that folder. + +Comment 16: The experiments with 3D glasses use the Godot engine. Some examples are provided. But you need some knowledge about this engine, especially because the experiments run completely within the engine. This engine is not only responsible for the representation of the 3D world, but also for the process and the logging of the data. The examples make it easier + +<--- Page Split ---> + +to get started, but still require some familiarisation with Godot. Recommended action: the authors might think about how they could further facilitate getting familiar with this part of the code. + +Response: Since the Godot game engine has not been previously used in neuroscience applications (unlike Unity), adding a tutorial or familiarization document for the Game engine is an excellent suggestion. To the online repository, we have added a new document to function as both a general 'Introduction to Godot' as well as an overview of the specific Godot files created and used for MouseGoggles experiments. This includes walking the reader through the Godot game engine editor and scripting environment, organization of different types of game files, highlighting some commonly used features and settings, and walking through a typical experiment script and logged data file. We also include seven example VR environments that can help get users started. + +Comment 17: The glasses are also available in a variant for "Monocular Display". This uses the Teensy board to control a small display. "GC9307_teensy_GFX.ino" has a lot of comments on single lines, but a more general documentation to understand the context of the parameters would be nice. Especially because there are so many parameters. Action required: provide a better general documentation and include a table of all parameters and their use. + +Response: Since the Monocular Display (now referred to as MouseGoggles Mono) is built on a different hardware and software platform as the binocular MouseGoggles Duo (Arduino graphics library + Teensy microcontroller, vs Godot game engine + Raspberry Pi computer), we agree that it makes sense to have comprehensive documentation for the MouseGoggles Mono code and control system. We have added new documentation which describes a general overview of the system, the different operational modes of the system, and describes and lists the commands and parameters which can be sent to the microcontroller to display patterns on the monocular display. + +Comment 18: While the software is neither very large nor a complex project, with its current level of documentation it still poses a challenge to find ones way around. This does not apply to the external SPI monitor driver. This part alone is much larger and more complex than MouseGoggles. + +Response: With the extensive documentation added and described above, including both specific technical details as well as general overviews of the software and systems, we believe that the online repository is now easier to navigate and understand, and users will be better able to replicate and modify this tool for their own purposes. + +Comment 19: 551 check sentence for completeness: ... last bin excluded due the mouse's constrained position ... + +Response: We have rewritten this sentence for completeness: "All licking data was binned by location into 5- cm wide bins, with the first and last bin were excluded due to the mouse's constrained position away from the walls". (line 739- 741). + +Comment 20: 555 For ease of understanding change: "All licks not occurring following a reward delivery were defined as "exploratory licks". TO Licks at other times than after a reward delivery ... + +Response: This suggested change has been made (line 744- 745): "All licks occurring at other times than after a reward delivery were defined as "exploratory licks". + +Comment 21: 619 a 2nd cohort of mice were tested -> was tested Response: This typo has been fixed (line 808). + +<--- Page Split ---> + +Related to the typographical errors mentioned above, we have made additional corrections to our methods section after identifying missing or confusing information: + +Missing information about post- operative analgesia after the surgical procedure for head- fixed behavior has been added (lines 530- 531). Missing information about the concentration of AAV- GCaMP6s bolus injection for V1 calcium imaging has been added (lines 538). The section on habituation for head- fixed behavior has been rewritten for clarity, with added details for habituation on our newly included linear treadmill (lines 660- 671). + +## Comments from Reviewer 3: + +Comment 1: Virtual reality has become a powerful tool for studying a variety of brain functions in head- fixed rodents. Current implementations of rodent VR involve large displays that not only create difficulties for the experimenter, but also do not provide an immersive experience for the animal, largely due to their expansive visual field. Isaacson, Chang, et al. designed a head- set based VR system to overcome current constraints. They provide evidence that their system solves many of the practical issues with VR, including reduced light pollution for imaging methods and reduced cost. They use neural recordings to show that the visual tuning properties of neurons are comparable to results obtained with standard techniques, supporting the quality of image presentation. Finally, they provide evidence that the VR experience for the mouse is immersive through effective behavioral training in reward and innate fear behaviors. + +This work represents a very useful advance for both the quality of rodent VR experience and the ability of individual laboratories to implement VR systems, especially given the low- cost and open source design. Overall, the authors provide a straightforward and convincing case for the improvements this system makes over traditional rodent VR systems. + +Response: We thank the reviewer for these positive comments. + +Comment 2: The manuscript could be substantially improved by addressing the following points: The system provides 230 deg of field coverage in the horizontal azimuth, with 140 deg per eye and 25 deg of binocular overlap. The authors should report measured values of the mouse visual field from previous studies in the main text, and discuss the limitations of the system in obtaining full coverage in the Discussion. Also, the approximate elevation covered by the system should be reported in the main text. + +Response: We agree with this suggested change and have moved information on mouse visual field estimates and our coverage of that field from the methods to the main text. We also report approximate elevation covered by the system (140 deg) and the headset configuration that was predominantly used in this manuscript (15 deg pitch, for - 55 to +85 deg maximum stimulated elevation relative to the horizon). These details have been added on lines 55- 58. Details on different pitch positions of the headset and the estimated visual field coverage of each position has been added in Supplementary Fig. 7. Relating to this, we noticed an error in our plotting of the estimated mouse visual field, which is now correctly plotted as a 180x140 deg ellipse (Fig. 1e, Supplementary Fig. 6d, and Supplementary Fig. 7c). + +We have also added discussion on the strengths and limitations of our relatively simple optical design (lines 159- 162). The main limitation being that FOV coverage is limited to 140 deg, whereas the main strengths are a simple, inexpensive build requiring no custom lenses, and a system which is robust to eye position variations and does not require precise eye + +<--- Page Split ---> + +alignment protocols. We have added a new supplementary figure demonstrating the system's performance by imaging gratings through the back of an enucleated mouse eye, showing similar performance to a traditional flat monitor (Supplementary Fig. 1). + +Comment 3: How does the 130 ms input to display latency compare to other rodent VR systems? My understanding is that latencies greater than 20ms are detectable to humans, so it seems possible this relatively long latency may limit the immersive experience for the mouse. The authors should discuss this. + +Response: We believe that total system latency is an important consideration for any closedloop system. To our knowledge, most existing rodent VR systems do not report end- to- end latency, thus it can be difficult to compare. Among modern, high- end human VR headset systems, mean total latency has been reported to range from 21- 42 ms (https://pubmed.ncbi.nlm.nih.gov/36217006/), where the longest latencies were found during periods of rapid movements. Among VR systems used in animal model neuroscience (specifically, those that report total latency), total latency ranges more broadly, with values as small as 2 ms under restrictive conditions (Isaacson et al, BioRxiv 2022: https://www.biorxiv.org/content/10.1101/2022.08.02.502550v1) to \(\sim 100\) ms for general- purpose VR (Madhav et al, J Neurosci Methods 2022: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9178503/). Our panoramic projector VR system, after optimization, measured at \(\sim 90\) ms latency. As for what latencies are needed or desired for head- fixed animals to be "immersed" in the VR world, we aren't able to say, as to our knowledge very little has been published on the effects of latency on neuroscience VR applications. One might speculate that long latencies are workable for closed- loop feedback from slow behaviors, such as mice walking on a treadmill, but could be problematic with fast behaviors such as eye movements. + +Without optimization, we measured MouseGoggles latency at \(\sim 130\) ms. However, there are opportunities to substantially reduce this latency in the display driver. Using "adaptive display stream updates", where only pixels which changed from the previous frame are updated, total latency can be drastically reduced. This feature is supported by the display driver used by MouseGoggles, and has been demonstrated to reduce total latency on a single display comparable to that used by MouseGoggles to under 20 ms (https://github.com/juj/fbcp- ili9341#about- input- latency). This feature has not yet been implemented for dual displays, though this is an area we are actively working on, and we hope to have this feature implemented and latency reduced in the near future (we will update our online repository accordingly). We have added these details on total latency and potential future optimization in the main text (lines 156- 159) and the methods (lines 417- 420). + +Comment 4: The measurements in 1b- d are in the range of 0- 70 deg, but the authors report monocular coverage of 130 deg. Is there some reason why they did not model the full coverage, which is nearly twice the range in the figure? + +Response: We thank the reviewer for pointing out this confusion. The 130 deg value comes from the total horizontal extent of the visual field coverage, which includes both left and right directions from straight ahead (70 deg in one direction and 60 deg in the other due to the "chipped edge" of the 240x210 circular display). In Fig. 1b- d, we modeled the viewing angle in a single direction up to 70 deg; since the display and lens configuration is radially symmetric, this modeling will be identical in all other directions. We have reworded the text of the figure legend (lines 196- 197), referring to the viewing angle as one side of the total maximum field of view coverage (140 deg) to reduce this confusion. + +<--- Page Split ---> + +Comment 5: The modeling of the light reaching the eye from the screen/lens is very useful. It would also be useful to have a measurement of the performance of the actual system, e.g., by projecting onto a model or real mouse eye. + +Comment 5: The modeling of the light reaching the eye from the screen/lens is very useful. It would also be useful to have a measurement of the performance of the actual system, e.g., by projecting onto a model or real mouse eye. Response: As suggested, we have now imaged the display's projection on the back of enucleated mouse eyes during the presentation of drifting gratings, comparing the image generated by a MouseGoggles eyepiece to that of a traditional flat monitor positioned further away (10 cm). We found that the image produced onto the plane of the retina by MouseGoggles is qualitatively comparable to that of the monitor, except that MouseGoggles is able to cover a much larger area of the eye's FOV. Furthermore, since one theoretical benefit of our relatively simple optical design is that the eye is not required to be precisely positioned relative to the lens (with the display positioned at the lens' focal distance, rays extending from the lens to the eye should be close to parallel), we measured the robustness of the system to minor changes in eye position by shifting the eye relative to the eyepiece and imaging the projection. We found that changes in position of up to \(\sim 2\) mm orthogonal to the optical axis of the lens and produced no clear distortion of the image projection on the back of the eye adding experimental support to the theoretical robustness of our design. These results are shown in Supplementary Fig. 1 and referenced in the main text (lines 50- 52) and methods (lines 425- 439). + +Comment 6: The comparison of light pollution between the monitor and monocular display is quite striking. It would be ideal to see a similar direct comparison of the two systems for the visual tuning properties in Fig2d- i, especially since the stimulus used for receptive field mapping is different from the referenced study (Niell & Stryker, 2008). + +Comment 6: The comparison of light pollution between the monitor and monocular display is quite striking. It would be ideal to see a similar direct comparison of the two systems for the visual tuning properties in Fig2d- i, especially since the stimulus used for receptive field mapping is different from the referenced study (Niell & Stryker, 2008).Response: Related to this comment, we describe new experiments and analyses on light pollution comparing MouseGoggles to a traditional monitor in response to Reviewer 1, Comment 6, above. Regarding differences in stimuli used to map visual responses, the stimuli we used to measure visual tuning properties (Fig. 2d- i) were designed to closely match prior studies so that they could be considered close to direct comparisons. We do agree with the reviewer that our receptive field mapping stimuli is somewhat different than that of the referenced study, though we believe this is not a significant difference and our original description of our stimuli could give the impression that the stimuli were more different than they actually were. The study we designed this receptive field mapping test on (Niell & Stryker, 2008) used a 4x8 deg bright bar sweeping across the visual field, repeated in 4 directions and at 8 different azimuths and elevations. Our study used a 3.8x7.6 deg bright bar (the closest we could get with our display's resolution), repeated across 5 different azimuths and elevations to reduce the total experiment time required – since our experiments began with a search to locate receptive field centers, a 5x5 grid was sufficient in our experiments to capture many neurons' receptive fields. There were minor differences in the presentation order of the stimuli across the visual field: Niell and Stryker presented a continuous sweep in one direction across 8 positions before switching to a new direction and position, while we presented sweeps in 4 directions at a single position before switching to a new position. The amount of the visual field stimulated in each data bin was nearly identical to the study from Niell and Stryker, which is expected to be the main determining factor in the receptive field size measurement. A likely source of confusion in our original description of the stimuli was that we described our stimuli as gratings rather than bar sweeps. However, each of these "gratings" had a 7.6 deg spatial wavelength and was presented at 1 Hz for 0.5 s, which is essentially just a bright bar sweep across the 7.6 deg position, similar to the study from Niell and Stryker. We apologize for this confusing description and have now adjusted the text to describe this stimulus as a bar sweep (lines 85, 587- 589), but if there are still any concerns about this comparison, we are happy to revisit or repeat this experiment with a new protocol. + +<--- Page Split ---> + +Comment 7: How do the tuning properties of CA1 place cells compare to other mouse VR studies and freely moving mouse studies (e.g. place field width)? + +Response: Since the properties of place fields in rodent dorsal CA1 are known to be modulated by the size of the virtual environment (e.g. Harland et al, Curr Bio 2021: https://www.sciencedirect.com/science/article/pii/S0960982221003420#bib8) and richness of the local visual cues (Tanni et al, Curr Bio 2022: + +https://www.sciencedirect.com/science/article/pii/S0960982222010089#bib16), and since our virtual linear track was visually distinct from those in prior studies, a direct comparison may be difficult to interpret. However, we agree that CA1 place cell tuning properties are useful for interpreting how the VR experiment was encoded by place cells, so we have added new quantifications to our manuscript: proportion of neurons that exhibited place- like characteristics for each session, place field width in the virtual space, and information rate for each place cell. These quantifications have been added to Fig. 2 (panel n), and references to these properties have been added to the main text (lines 99- 102). Details on how these new properties were quantified have been added to the methods (lines 702- 707). + +Comment 8: In comparing the behavioral responses to looming stimuli on MouseGoggles vs. a traditional projector system, was the projector system oriented above the mouse? Based on the methods, it appears the projector reached a maximum of only 64 deg elevation, so is this the presumed reason that a response was not elicited? The ability to adjust elevation with MouseGoggles is indeed useful, but ideally the behavior would be compared to a projector system with similar visual field coverage. If it is experimentally infeasible to adjust the projector system to cover a comparable region of the visual field, the authors should state this. Otherwise, the experiment should be conducted with comparable overhead coverage between the two systems. + +Response: The projector- based VR system we used featured a custom conical screen that extended significantly above the horizon, with only a circular cutout above the mouse to fit a microscope objective for 2- photon imaging. Even though the projector had a large vertical extent, the reviewer is correct that the FOV coverage of MouseGoggles extends even further. This increased overhead coverage was likely not meaningful for the looming experiment since the looming object approached from a 45 deg elevation, which is easily covered by the 64 deg elevation of the projector screen. However, to be sure, during the newer looming experiments with eye and pupil tracking (shown in Fig. 4 and Supplementary Video 3) we blacked out the top section of the screen (above 64 deg elevation) and we observed similar startle responses from these mice. This detail on the restricted elevation has been added to the methods section (lines 819- 821). + +Comment 9: It appears that video of the mouse was acquired during the looming stimulus presentation (Fig3f and methods). The methods clearly state the responses were manually scored, but the main text and figure do not mention this, and the line fit to the mouse's back in Fig3f might lead the reader to assume the quantification of behavior was achieved with computational video analysis. Is the resolution of the video sufficient to perform the startle analysis? If so, the authors should quantify the behavior using image analysis methods or markerless pose estimation. If not, the authors should clearly state that in the text/Fig3g that the quantification was performed by two human observers. The authors could also plot the velocity of the animal measured via the spherical treadmill aligned to the onset of the looming stimulus. Response: We thank the reviewer for pointing out this omission in our text. One complication we observed during early attempts at automatic quantification and detection of looming reactions is the significant variability in mouse behavior prior to the looming stimulus; head- fixed mice may be stopped, walking, running, or grooming immediately prior to the loom. Therefore, we determined that identifying reactions to looming stimuli are most clearly assessed through + +<--- Page Split ---> + +manual behavior scoring. We have clarified this approach in the main text and Fig. 3 legend (lines 121, 249- 252). + +In inspecting and plotting the spherical treadmill velocity aligned to the looming stimulus, we found it impossible to detect startle responses in terms of treadmill movements, seemingly due to the near- constant movement of the low- friction treadmill and the relatively small startle- movement transferred to the ball. However, in the new looming experiments with eye and pupil tracking which were performed on a more stable linear treadmill, plotting the linear treadmill velocity showed a clearer response from the looming stimuli (mice back up a bit!). This new data is shown in Fig. 4, referenced in the main text and described in the methods section (lines 137- 142, 815- 839). + +Comment 10: Does this system permit the measurement of eye movements? Given that mice move their eyes (though somewhat infrequently) while head- fixed, it would be ideal to measure these movements during stimulus presentation. The authors mention that pupil tracking would be feasible with this system; how would this be achieved? + +Response: Although it was a lot of work, we thank the reviewer for challenging us to achieve this goal. The ability to measure eye and pupil dynamics during head- fixed VR has been the most requested feature for future versions of the MouseGoggles system, and we are excited to add this capability in our revised manuscript. As we show in new figure panels (Fig. 4), the MouseGoggles system does indeed permit eye and pupil measurement during VR presentation through the use of fully- integrated infrared imaging inside the eyepiece. Due to the simple optical design of MouseGoggles, enough space exists within the eyepiece to fit an angled hot mirror, which allows visible display light to pass from the VR display to the mouse eye while IR illumination can reflect to the eye and back toward a mini- IR camera. This new design, which still only uses off- the- shelf parts, enables clear imaging of the mouse eye and pupil during visual stimulus presentation. This optical strategy for simultaneous eye/pupil monitoring and VR presentation might not be possible with the other recent mouse VR headsets, Moculus and iMRSIV, due to their more complex optical design and reduced space within the eyepiece enclosure to fit additional lenses or mirrors. The iMRSIV publication specifically identifies a lack of eyepiece space as a hindrance to simultaneous eye monitoring in their system, and notes that eye tracking would be highly beneficial for future VR headsets. + +To demonstrate this new feature, we performed infrared eye imaging of head- fixed mice walking on a linear treadmill during the looming visual stimulus experiment. Position of points along the eye and pupil were tracked using Deeplabcut to enable measurement of both eye orientation and pupil diameter. From this experiment, we observed clear eye tracking towards the overhead looming objects and noted a pupil dilation response following the looming stimulus that diminished with additional repetitions of the stimulus, similar to the habituating startle responses. These new results are shown in Fig. 4 and discussed in the main text and detailed in the methods section (lines 127- 142, 441- 489, 815- 839). + +Comment 11: Face/whisker movements contribute significantly to neural activity. Does this system allow for these measurements, or do the MouseGoggles fully obstruct the view? Response: Face movements can indeed be seen with the MouseGoggles system if a camera is mounted in front of the mouse and below the headset (e.g. supplementary Video 1), where views of the nose, mouth, and many lower whiskers are unobstructed. However, upper whisker movements are significantly impaired as many upper whiskers during whisking behavior cross in front of and near the eyes. These details have been added to the main text (lines 154- 156). + +Comment 12: If possible, the experimenters should quantify whisker contact with the system. Do any of the whiskers touch the system, and if so with what frequency? Extensive whisker + +<--- Page Split ---> + +contact with the system would presumably degrade any immersive experience the mouse may have, and would make it difficult to perform some of the multisensory experiments the authors propose in the Discussion. + +Response: We thank the reviewer for this excellent suggestion, we agree that quantifying whisker contact is important to characterize our system and its limitations. We have added a new supplementary figure quantifying the whisker contact depending on different orientations of the headset. Depending on the headset pitch, slightly more or less of the head- fixed mouse's whiskers will be occluded by the headset. In a near- flat position, where the headset is pitched 15 degrees upward from the horizon (a typical orientation used in this study), approximately \(60\%\) of whiskers are blocked by the headset. With significantly increased positive headset pitch (e.g. 45 deg), where more of the visual field above the horizon is covered, some frontal whiskers become unblocked. These considerations should assist future users in selecting a headset position that will enable their desired experiments. These new results are shown in Supplementary Fig. 7 and referenced in the main text (lines 154- 156). + +Comment 13: How do the authors calibrate the system with each individual mouse, given e.g., the inherent variability in headplate placement? + +Response: Due to the simple optical design of the MouseGoggles headset, the system is robust to minor offsets of the mouse eye from the center of the lens. To demonstrate this feature more clearly, we have added Supplementary Fig. 1 showing the performance of the optical design by viewing the display's projection on the back of an enucleated mouse eye. By adjusting the position of the eye relative to the Fresnel lens surface center, we found that small lateral eye displacements ( \(< 2 \text{mm}\) ) caused little noticeable distortion of the display image. In our experience, manual adjustment of the optical posts and angled post clamps until both eyes were roughly centered inside each eyepiece routinely achieves binocular eye positioning well within this range. This may be a unique benefit of the MouseGoggles system compared to the Moculus and iMRSIV systems which use more complex lens arrays and are described as being sensitive to eye position, and whose methods describe a more precise eye alignment protocol. We have added a discussion on this issue to the main text and to the methods section (lines 159- 162). + +In our surgical preparations the headplate placement did not significantly vary in tilt, therefore the only adjustment necessary for accurate positioning of mice relative to the headset was manually translating the headset up to the mouse's eyes, with no sideways tilt required to roughly center both eyes inside the eyepieces. We have added this detail on headset positioning to the methods section (lines 666- 670). In the case that a surgical preparation results in a significantly tilted headplate (either in pitch or roll directions), a further calibration might be needed in the VR software if it is desired to match the virtual "eyes" to the headset orientation and position. While we did not have to make this kind of adjustment in our experiments, we have updated the VR experiment scripts in the online repository + +so that both headset pitch and roll tilt angles can be easily matched by the game engine. + +Comment 14: Given that monocular cues should be sufficient for most experiments performed in the manuscript (formation of place cells, responses to looming stimuli, reinforcement learning), an "immersive" experience may not be requisite for the results obtained here. A more convincing test that the animal is having an immersive experience would be ideal, e.g., behavior with a virtual cliff showing that animals stop to avoid falling over the edge. + +Response: Due to the lack of startle responses to looming visual stimuli from head- fixed mice in our panoramic projector- based VR system, we believe that even wide- field binocular visual cues are insufficient to cause startle responses, and monocular cues have not been shown, to our knowledge, to generate a startle response. Thus, an immersive virtual experience seems to be necessary and is successfully demonstrated by our MouseGoggles system. However, we + +<--- Page Split ---> + +agree with the reviewer that a visual cliff experiment may be an excellent test that only a binocular, immersive, and stereoscopic VR system could replicate. As we detailed more fully in response to reviewer 1, comment 4, the current understanding of the salience of stereoscopic vision in mice is limited, making this more a topic for exploration with stereoscopic VR systems than a robust testbed for establishing the degree of immersion. The only experiment we are aware of that demonstrates mouse's innate use of stereo cues is in the angled pole descent test (Boone et al, Curr Bio 2021: https://www.cell.com/current- biology/fulltext/S0960- 9822(21)00272- 4). This test is required over a typical flat visual cliff experiment as the downward angle ensures that the cliff appears well within the mouse's binocular overlap region, where stereo vision has been shown to apply. MouseGoggles, combined with a custom pitching treadmill, could provide an excellent toolkit for testing the salience of stereoscopic vision in mice, but is beyond the scope of this manuscript. Our additions, in this revision, of implementation with a compact linear treadmill (Fig. 4) and with closed- loop feedback from headset rotation (Supplementary Video 4), should facilitate the development of this kind of VR experiment in the future. + +<--- Page Split ---> + +Dear Dr. Vogt, + +Dear Dr. Vogt,We thank you and the reviewers for providing feedback on our revised manuscript, "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior". We appreciate all the positive feedback on our recent changes and the final comments to ready the manuscript for publication. Below is our point- by- point response to the remaining reviewer comments. + +## Comments from Reviewer 1: + +Comment 1: Authors addressed all my comments, I would fully support publishing this paper. + +Thank you for your positive feedback and support for the publication of our paper, and for the excellent suggestions in the previous comments. + +## Comments from Reviewer 2: + +Comment 1: The authors have made quite some effort to respond to my concerns. [referencing previous comment 14] The "Hardware" directory has been renamed to "Other Hardware". This was a good decision, as it helps to differentiate between MouseGoggles and other hardware mentioned in paper. The added documentation should now enable and simplify the initial setup of treadmill and the sensors. Thank you for your positive feedback. + +Comment 2: [referencing previous comment 15] Still no comments in the code. But now it is explained how these files should be used and their purpose. Since the files are small, this seems fine now. + +In addition to the explanation of the purpose of the debugging files in our online repository, we have now added comments to the "ADNS3080 debugging" code for each file individually, as requested earlier. Sorry for the omission, we mistakenly had not pushed an update after our last response, but it has now been updated and verified. + +Comment 3: [referencing previous comment 16] The new short "Introduction to Godot" should indeed make it a little easier to get started. Even if there is still a relatively large hurdle here, as Godot has to be learned. But the experiments seem to be both very small and very similar, so that customisation should be possible. + +Thank you for your feedback on the "Introduction to Godot" file. We understand that there is still a learning curve, as there will be with any experiment design program or game engine, but we hope that our aim to keep the example 3D experiments simple will also make them [relatively] easy to understand and customize. + +Comment 4: Small note and suggestion for a further small change: it should be noted which version of Godot is used here. I opened the project with 4.2.2 and had some error messages in the script editor. This happend although the documentation explicitly calls for the last version of Godot. However, this probably refers to the latest 3. x version. The version of game engine software used by in this manuscript (Godot 3.2) has now been added to the "Introduction to godot" document in our online repository. + +<--- Page Split ---> + +Comment 5: [referencing previous comment 17] The description of the hardware and the hardware assembly instructions should now be sufficient to build the system. And the software description/documentation should help to setup the system. [referencing previous comment 18] I agree. + +Thank you for your agreement and positive feedback on the hardware and software documentation, and for all your help in improving the online resource. + +## Comments from Reviewer 3: + +Comment 1: The updated manuscript provided by Isaacson, Chang et al. entitled "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior" represents a substantial improvement over the initial manuscript submission. The authors responded to the reviewer comments with a significant amount of work that addresses the issues with the original manuscript, including: + +Relationship of the system to the total visual field Discussion of latency and steps toward reducing it Measured the light reaching the eye Clarification on visual stimuli Quantification of place cell properties Improved behavioral measures during looming behavior Characterization of whisker obstruction + +The heroic addition of pupillometry also sets this system apart from other emerging immersive mouse VR systems, making this system particularly useful to neuroscientists who also want to track pupil position and size. + +We are grateful for your thorough and positive evaluation of our manuscript. We appreciate the acknowledgment of our revisions and additions, including the incorporation of pupillometry which was a particular challenge but one we also believe will be highly useful for behavioral neuroscientists. Thank you for the earlier feedback which motivated these improvements. + +Comment 2: I have only a minor comment, which is that the authors should consider mentioning a finding from Meyer et al., Curr Bio 2020, that might explain the eye movements in response to the looming stimulus. Eye movements in headfixed mice appear to result primarily from attempted head movements (see Fig S5 in that paper), so one interpretation of the results here is that the animals are attempting to escape by moving their heads, which results in a saccade. While a subtle point, the authors' interpretation that the animal's gaze is being directed toward the stimulus is more likely due to an artifact of the animal's inability to move its head freely. + +Thank you for this insightful suggestion. Since head- fixed eye movements have been shown to be related to attempted head movements, we have added this suggested interpretation of eye movements during our virtual looming experiment and added a reference to Meyer et al., Curr Bio 2020 (lines 152- 154). + +We appreciate the valuable feedback from all reviewers and hope that these revisions address all remaining concerns. + +Sincerely, Matthew Isaacson On behalf of all authors + +<--- Page Split ---> diff --git a/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..acded5e40eaa0b6509f43be8fdee4a3cdad1f9c4 --- /dev/null +++ b/peer_reviews/98b704278f6d767e6385ffbdfa5eb54b8328ed33ec101bd20c275f46757c7b95/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,904 @@ +<|ref|>title<|/ref|><|det|>[[108, 53, 312, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[110, 96, 313, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[110, 161, 810, 210]]<|/det|> +# MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior + +<|ref|>text<|/ref|><|det|>[[110, 224, 461, 241]]<|/det|> +Corresponding Author: Dr Matthew Isaacson + +<|ref|>text<|/ref|><|det|>[[110, 274, 884, 290]]<|/det|> +This file contains all editorial decision letters in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[110, 326, 175, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[110, 353, 210, 366]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[110, 378, 208, 392]]<|/det|> +22nd Nov 2023 + +<|ref|>text<|/ref|><|det|>[[110, 417, 223, 431]]<|/det|> +Dear Dr Isaacson, + +<|ref|>text<|/ref|><|det|>[[110, 443, 877, 510]]<|/det|> +Thank you for your patience. Your Brief Communication, "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior", has now been seen by three reviewers. As you will see from their comments below, although the reviewers find your work of considerable potential interest, they have raised a number of concerns. We are interested in the possibility of publishing your paper in Nature Methods, but would like to consider your response to these concerns before we reach a final decision on publication. + +<|ref|>text<|/ref|><|det|>[[110, 521, 883, 563]]<|/det|> +We therefore invite you to revise your manuscript to address these concerns. Specifically, please be sure to demonstrate the advantages over standard VR systems more thoroughly and discuss the limitations of your system. It won't be necessary to conduct experiments with a large number of animals. + +<|ref|>text<|/ref|><|det|>[[110, 574, 880, 615]]<|/det|> +Importantly, please discuss the similarities and differences of your system with that described in https://www.researchsquare.com/article/rs- 3352160/v1 and https://patents.justia.com/patent/20220295743. You will need to make a strong case for the uniqueness of your system. + +<|ref|>text<|/ref|><|det|>[[110, 664, 880, 692]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. + +<|ref|>text<|/ref|><|det|>[[110, 704, 276, 718]]<|/det|> +When revising your paper: + +<|ref|>text<|/ref|><|det|>[[110, 729, 636, 744]]<|/det|> +\* include a point- by- point response to the reviewers and to any editorial suggestions + +<|ref|>text<|/ref|><|det|>[[110, 755, 884, 784]]<|/det|> +\* please underline/highlight any additions to the text or areas with other significant changes to facilitate review of the revised manuscript + +<|ref|>text<|/ref|><|det|>[[110, 795, 661, 809]]<|/det|> +\* address the points listed described below to conform to our open science requirements + +<|ref|>text<|/ref|><|det|>[[110, 821, 692, 848]]<|/det|> +\* ensure it complies with our general format requirements as set out in our guide to authors at www.nature.com/naturemethods + +<|ref|>text<|/ref|><|det|>[[110, 860, 714, 874]]<|/det|> +\* resubmit all the necessary files electronically by using the link below to access your home page + +<|ref|>text<|/ref|><|det|>[[110, 900, 202, 913]]<|/det|> +Link Redacted + +<|ref|>text<|/ref|><|det|>[[110, 924, 823, 939]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[110, 46, 848, 75]]<|/det|> +submitted, or that you are reviewing for us. 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We look forward to seeing the revised manuscript and thank you for the opportunity to consider your work. + +<|ref|>text<|/ref|><|det|>[[110, 490, 194, 515]]<|/det|> +Best regards, Nina + +<|ref|>text<|/ref|><|det|>[[110, 527, 210, 566]]<|/det|> +Nina Vogt, PhD Senior Editor Nature Methods + +<|ref|>text<|/ref|><|det|>[[110, 604, 255, 618]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[110, 630, 255, 657]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[109, 669, 880, 815]]<|/det|> +In this manuscript, Isaacson and colleagues present a novel version of the VR system for head- fixed mice that features a miniature contraption (hence entitled MouseGoggles), easy and cheap design, direct stimulation of the eyes with minimal stray light, and independent control of each eye stimulus. MouseGoggles VR functionality is illustrated using 2PM visual cortex and hippocampal electrophysiology experiments, as well as spatial reward association and innate looming fear paradigms. This work is certainly going to lower the bar for the use of VR in many labs with limited budgets due to the price, eliminate shortcomings of the conventional HD VR, as well as will enable VR experiments that are currently not possible. Hardware is built on inexpensive and widely available components, both optical, mechanical, and electronic designs and software are made open source. Experiments are performed at a high level of quality and the data and results are convincing. I have a few comments listed below. While the new form factor, low cost, stereo- ability, and compactness make this system clearly novel and show great premise, the present form of the manuscript doesn't demonstrate or elaborate on any of these advantages. + +<|ref|>text<|/ref|><|det|>[[110, 826, 884, 892]]<|/det|> +The minimalistic and low- cost hardware/software used in the MouseGoggles clearly leads to some compromises on the flexibility and performance of the VR implementation. Maximal frame rate, latency, and richness of the 3D cues will surely be limited compared to setups that rely on high- speed and high- resolution projector(s), GPU cards, and performant VR engines (e.g Unity). It would be good if the authors laid out the cons of such a system for animal experiments and possible future directions for circumventing them. + +<|ref|>text<|/ref|><|det|>[[110, 904, 884, 945]]<|/det|> +A natural and important advance in the setup is the possibility to independently render images to both eyes thus enabling stereo- VR. However, unfortunately, the authors do not include such experiments. While testing V1 and CA1 cell tuning simply confirms that MouseGoggles is performing comparably to the existing conventional HF VR setups, these experiments + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[109, 46, 872, 87]]<|/det|> +do not demonstrate the advantages of the new system and do not make the case why it should be published in this journal as a major advance of the technology. Some experiments contrasting mono vs stereo- VR would demonstrate this key advance in the technology that is missing in the neuroscience toolbox. + +<|ref|>text<|/ref|><|det|>[[109, 98, 886, 206]]<|/det|> +Innate behavior, such as startle response in response to looming stimulus, even though possibly recapitulating natural avoidance behavior observed in freely- moving rodents, is hardly making a decisive showcase for the system distinguishing it from the conventional ones. It is not clear from the methods section describing conventional projector VR that authors compare to if that system has used all possible means to increase projection surfaces at the lower visual field, including the floor (e.g. as done by labs of Mehta and Tank) by adding a cutout floor disk all around the ball. As many groups implemented this innate fear response with a simple overhead screen or sound, this paper doesn't put forward a distinct use- case for studying flight response to the looming stimulus under head- fixed conditions that could not be done in freely- moving animals. + +<|ref|>text<|/ref|><|det|>[[109, 216, 884, 348]]<|/det|> +Stray light measurements make the case for the clear improvement in that parameter over plain- vanilla imaging setup in which the optical axis is not shielded from the light. However, similar to the enclosure protecting the 2PM from the monitor light, it is possible (and done by some scientists) to design and 3D print an enclosure protecting the cranial window from the external stray light. The use of blue light is another option (e.g Kuznetsova et al JNM 2021), which, I assume, authors refer to as "filtering". Besides, a significant amount of stray light reaches the brain through the eye, which would mean that if imaging was performed in more frontal regions, high- intensity eye stimulation might cause more stray light diverted through this pathway than in a conventional setup. Could authors measure that? What is the functional consequence of the difference in the stray light for the performance of 2PM imaging? Arguably somatic high- SNR Ca imaging will likely not be affected. I suggest that to make this feature a decisive one that sets this setup apart from the conventional one, there needs to be a clear demonstration of the functional advantages. + +<|ref|>text<|/ref|><|det|>[[109, 359, 875, 453]]<|/det|> +What appears to be the top point setting the system apart is that, in addition to enabling stereo VR, it is inexpensive and compact. Inexpensive - means that scalable, high- throughput parallel VR setups would allow training the large batches of mice, something that, clearly was not possible so far. However obvious, this feature is not emphasized in the manuscript. Compactness of the setup is only slightly outlined by the authors, but not exploited. Rotations of the miniaturized setup allow easy implementation of the proper 2D VR (similar to Chen et al eLife 2018). Rotations around other than the vertical axis allow for so far impossible experiments testing vestibular input contributions. Realistic vestibular inputs could be added by implementing appropriate movements of the apparatus using hexapods. + +<|ref|>sub_title<|/ref|><|det|>[[110, 490, 195, 502]]<|/det|> +## Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[110, 503, 255, 515]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[109, 515, 877, 580]]<|/det|> +Mouse Goggles is a novel VR display device for the binocular visual stimulation of mice. Together with its online documentation this is to be a fully documented open- source tool that others can replicate. The results of MouseGoggle experimental testing confirm that it functions at least as well as traditionally used surround screens with visual stimuli or VR scenes. The experimental testing for MouseGoggles has been done comprehensively. The report is brief, to the point, well written, and complete. + +<|ref|>text<|/ref|><|det|>[[110, 580, 830, 608]]<|/det|> +The usefulness of the method will depend on the possibility that it can actually be used as an open source tool and replicated by others. + +<|ref|>text<|/ref|><|det|>[[110, 608, 880, 636]]<|/det|> +Authors should discuss how their relatively simple optical solution could potentially be improved. In this context they should cite the publicly accessible manuscript about Moculus doi.org/10.21203/rs.3.rs- 3352160/v1. + +<|ref|>text<|/ref|><|det|>[[110, 635, 875, 662]]<|/det|> +Authors should discuss if patent PCT HU2020/050029 published under WO2021009526A1 covers or is different from their method as it may affect its use as an open source tool (accessible e.g. at https://patents.justia.com/patent/20220295743). + +<|ref|>text<|/ref|><|det|>[[110, 672, 880, 699]]<|/det|> +The authors should improve the online documentation that is cited in the manuscript in order to better facilitate replication of this open source method. + +<|ref|>sub_title<|/ref|><|det|>[[110, 711, 221, 723]]<|/det|> +## Mechanics, CAD: + +<|ref|>text<|/ref|><|det|>[[110, 724, 880, 789]]<|/det|> +Mechanics, CAD:1. Please upload not only the STL files but also the STP files or IPT drawing of the CAD designs for easier modification2. The bill of materials mentions all parts in [cm] however Figure 2 shows them in [mm] – please update the bill of materials and use only one unit of measurement to avoid confusion3. Recommendation for a future revision: Reconsider the material that was used in the printing. If the parts will be adjustable or moveable at some point, resin material will become brittle quickly. + +<|ref|>sub_title<|/ref|><|det|>[[110, 802, 185, 814]]<|/det|> +## Electronics: + +<|ref|>text<|/ref|><|det|>[[110, 815, 857, 894]]<|/det|> +Electronics:1. Upload not only gerber files but also the schematic and PCB file for easier modification2. Include the fabrication specifications for the PCBs: board thickness, copper thickness and surface finish3. In MinibrdV1, the copper to copper spacing is only 0.06 mm – for a future revision I recommend updating the layout to increase the minimum copper to copper spacing to at least 0.2 mm; this simplifies demands on production.4. In MinihatV1, there are 90 degree traces and these will form acid traps that cause corrosion – for a future revision I recommend updating the layout with traces only at 45 degrees + +<|ref|>sub_title<|/ref|><|det|>[[110, 907, 170, 919]]<|/det|> +## Software: + +<|ref|>text<|/ref|><|det|>[[110, 919, 870, 946]]<|/det|> +Software:a. The driver for sending the images via SPI to two small screens is from an external project (fbcp- ili9341 and fbcp- st7789) which seems to be well documented, no action required. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[110, 60, 410, 73]]<|/det|> +b. Drivers for detecting the movement of the ball. + +<|ref|>text<|/ref|><|det|>[[110, 73, 888, 113]]<|/det|> +The movement is transmitted to the PC/RasPi as if it were a PC mouse. The ADNS3080 sensor is used. "mouseVRheadset_controller_V4. ino" is not commented in detail. This is so small that this is not of great importance. Action: add a few explanatory sentences to facilitate faster orientation. + +<|ref|>text<|/ref|><|det|>[[110, 112, 888, 153]]<|/det|> +The purpose and use of the files in the "ADNS3080 debugging" folder must be explained. While these are only for debugging, how and what they are used for is not clear. This is also because these data have no comments. Action required: Explain and comment. + +<|ref|>text<|/ref|><|det|>[[108, 164, 888, 241]]<|/det|> +c. The experiments with 3D glasses use the Godot engine. Some examples are provided. But you need some knowledge about this engine, especially because the experiments run completely within the engine. This engine is not only responsible for the representation of the 3D world, but also for the process and the logging of the data. The examples make it easier to get started, but still require some familiarisation with Godot. Recommended action: the authors might think about how they could further facilitate getting familiar with this part of the code. + +<|ref|>text<|/ref|><|det|>[[108, 230, 888, 285]]<|/det|> +d. The glasses are also available in a variant for "Monocular Display". This uses the Teensy board to control a small display. "GC9307_teensy_GFX.ino" has a lot of comments on single lines, but a more general documentation to understand the context of the parameters would be nice. Especially because there are so many parameters. Action required: provide a better general documentation and include a table of all parameters and their use. + +<|ref|>text<|/ref|><|det|>[[108, 283, 888, 323]]<|/det|> +While the software is neither very large nor a complex project, with its current level of documentation it still poses a challenge to find ones way around. This does not apply to the external SPI monitor driver. This part alone is much larger and more complex than MouseGoggles. + +<|ref|>sub_title<|/ref|><|det|>[[108, 335, 215, 348]]<|/det|> +## Minor comments + +<|ref|>text<|/ref|><|det|>[[108, 348, 855, 400]]<|/det|> +Minor comments551 check sentence for completeness: ... last bin excluded due the mouse's constrained position ... 555 For ease of understanding change: "All kicks not occurring following a reward delivery were defined as "exploratory licks". TO Licks at other times than after a reward delivery ... 619 a 2nd cohort of mice were tested -> was tested + +<|ref|>sub_title<|/ref|><|det|>[[108, 438, 195, 450]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[108, 451, 255, 463]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[108, 463, 885, 567]]<|/det|> +Virtual reality has become a powerful tool for studying a variety of brain functions in head- fixed rodents. Current implementations of rodent VR involve large displays that not only create difficulties for the experimenter, but also do not provide an immersive experience for the animal, largely due to their expansive visual field. Isaacson, Chang, et al. designed a head- set based VR system to overcome current constraints. They provide evidence that their system solves many of the practical issues with VR, including reduced light pollution for imaging methods and reduced cost. They use neural recordings to show that the visual tuning properties of neurons are comparable to results obtained with standard techniques, supporting the quality of image presentation. Finally, they provide evidence that the VR experience for the mouse is immersive through effective behavioral training in reward and innate fear behaviors. + +<|ref|>text<|/ref|><|det|>[[108, 579, 884, 633]]<|/det|> +This work represents a very useful advance for both the quality of rodent VR experience and the ability of individual laboratories to implement VR systems, especially given the low- cost and open source design. Overall, the authors provide a straightforward and convincing case for the improvements this system makes over traditional rodent VR systems. The manuscript could be substantially improved by addressing the following points: + +<|ref|>text<|/ref|><|det|>[[108, 644, 886, 698]]<|/det|> +The system provides 230 deg of field coverage in the horizontal azimuth, with 140 deg per eye and 25 deg of binocular overlap. The authors should report measured values of the mouse visual field from previous studies in the main text, and discuss the limitations of the system in obtaining full coverage in the Discussion. Also, the approximate elevation covered by the system should be reported in the main text. + +<|ref|>text<|/ref|><|det|>[[108, 709, 857, 750]]<|/det|> +- How does the 130 ms input to display latency compare to other rodent VR systems? My understanding is that latencies greater than 20ms are detectable to humans, so it seems possible this relatively long latency may limit the immersive experience for the mouse. The authors should discuss this. + +<|ref|>text<|/ref|><|det|>[[108, 761, 857, 789]]<|/det|> +- The measurements in 1b-d are in the range of 0-70 deg, but the authors report monocular coverage of 130 deg. Is there some reason why they did not model the full coverage, which is nearly twice the range in the figure? + +<|ref|>text<|/ref|><|det|>[[108, 801, 805, 829]]<|/det|> +- The modeling of the light reaching the eye from the screen/lens is very useful. It would also be useful to have a measurement of the performance of the actual system, e.g., by projecting onto a model or real mouse eye. + +<|ref|>text<|/ref|><|det|>[[108, 840, 884, 880]]<|/det|> +- The comparison of light pollution between the monitor and monocular display is quite striking. It would be ideal to see a similar direct comparison of the two systems for the visual tuning properties in Fig2d-i, especially since the stimulus used for receptive field mapping is different from the referenced study (Niell & Stryker, 2008). + +<|ref|>text<|/ref|><|det|>[[108, 891, 881, 919]]<|/det|> +- How do the tuning properties of CA1 place cells compare to other mouse VR studies and freely moving mouse studies (e.g. place field width)? + +<|ref|>text<|/ref|><|det|>[[108, 930, 852, 945]]<|/det|> +- In comparing the behavioral responses to looming stimuli on MouseGoggles vs. a traditional projector system, was the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[108, 45, 883, 128]]<|/det|> +projector system oriented above the mouse? Based on the methods, it appears the projector reached a maximum of only 64 deg elevation, so is this the presumed reason that a response was not elicited? The ability to adjust elevation with MouseGoggles is indeed useful, but ideally the behavior would be compared to a projector system with similar visual field coverage. If it is experimentally infeasible to adjust the projector system to cover a comparable region of the visual field, the authors should state this. Otherwise, the experiment should be conducted with comparable overhead coverage between the two systems. + +<|ref|>text<|/ref|><|det|>[[108, 138, 886, 232]]<|/det|> +- It appears that video of the mouse was acquired during the looming stimulus presentation (Fig3f and methods). The methods clearly state the responses were manually scored, but the main text and figure do not mention this, and the line fit to the mouse's back in Fig3f might lead the reader to assume the quantification of behavior was achieved with computational video analysis. Is the resolution of the video sufficient to perform the startle analysis? If so, the authors should quantify the behavior using image analysis methods or markerless pose estimation. If not, the authors should clearly state that in the text/Fig3g that the quantification was performed by two human observers. The authors could also plot the velocity of the animal measured via the spherical treadmill aligned to the onset of the looming stimulus. + +<|ref|>text<|/ref|><|det|>[[108, 242, 860, 283]]<|/det|> +- Does this system permit the measurement of eye movements? Given that mice move their eyes (though somewhat infrequently) while head-fixed, it would be ideal to measure these movements during stimulus presentation. The authors mention that pupil tracking would be feasible with this system; how would this be achieved? + +<|ref|>text<|/ref|><|det|>[[108, 294, 870, 322]]<|/det|> +- Face/whisker movements contribute significantly to neural activity. Does this system allow for these measurements, or do the MouseGoggles fully obstruct the view? + +<|ref|>text<|/ref|><|det|>[[108, 333, 866, 386]]<|/det|> +- If possible, the experimenters should quantify whisker contact with the system. Do any of the whiskers touch the system, and if so with what frequency? Extensive whisker contact with the system would presumably degrade any immersive experience the mouse may have, and would make it difficult to perform some of the multisensory experiments the authors propose in the Discussion. + +<|ref|>text<|/ref|><|det|>[[108, 397, 836, 425]]<|/det|> +- How do the authors calibrate the system with each individual mouse, given e.g., the inherent variability in headplate placement? + +<|ref|>text<|/ref|><|det|>[[108, 436, 881, 490]]<|/det|> +- Given that monocular cues should be sufficient for most experiments performed in the manuscript (formation of place cells, responses to looming stimuli, reinforcement learning), an "immersive" experience may not be requisite for the results obtained here. A more convincing test that the animal is having an immersive experience would be ideal, e.g., behavior with a virtual cliff showing that animals stop to avoid falling over the edge. + +<|ref|>text<|/ref|><|det|>[[108, 501, 173, 514]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[108, 526, 208, 540]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[108, 552, 275, 566]]<|/det|> +Our ref: NMETH- A53654A + +<|ref|>text<|/ref|><|det|>[[108, 578, 196, 592]]<|/det|> +31st Jul 2024 + +<|ref|>text<|/ref|><|det|>[[108, 604, 228, 618]]<|/det|> +Dear Dr. Isaacson, + +<|ref|>text<|/ref|><|det|>[[108, 630, 876, 697]]<|/det|> +Thank you for your patience during this period and for submitting your revised manuscript "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior" (NMETH- A53654A). It has been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Methods, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[108, 708, 877, 750]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements within two weeks or so. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>sub_title<|/ref|><|det|>[[108, 800, 323, 814]]<|/det|> +## TRANSPARENT PEER REVIEW + +<|ref|>text<|/ref|><|det|>[[108, 814, 881, 894]]<|/det|> +Nature Methods offers a transparent peer review option for new original research manuscripts submitted from 17th February 2021. We encourage increased transparency in peer review by publishing the reviewer comments, author rebuttal letters and editorial decision letters if the authors agree. Such peer review material is made available as a supplementary peer review file. Please state in the cover letter 'I wish to participate in transparent peer review' if you want to opt in, or 'I do not wish to participate in transparent peer review' if you don't. Failure to state your preference will result in delays in accepting your manuscript for publication. + +<|ref|>text<|/ref|><|det|>[[108, 905, 884, 947]]<|/det|> +Please note: we allow redactions to authors' rebuttal and reviewer comments in the interest of confidentiality. If you are concerned about the release of confidential data, please let us know specifically what information you would like to have removed. Please note that we cannot incorporate redactions for any other reasons. Reviewer names will be published in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[109, 46, 866, 88]]<|/det|> +peer review files if the reviewer signed the comments to authors, or if reviewers explicitly agree to release their name. For more information, please refer to our FAQ page. + +<|ref|>sub_title<|/ref|><|det|>[[109, 100, 157, 112]]<|/det|> +## ORCID + +<|ref|>text<|/ref|><|det|>[[109, 112, 880, 166]]<|/det|> +IMPORTANT: Non- corresponding authors do not have to link their ORCIDs but are encouraged to do so. Please note that it will not be possible to add/modify ORCIDs at proof. Thus, please let your co- authors know that if they wish to have their ORCID added to the paper they must follow the procedure described in the following link prior to acceptance: https://www.springermature.com/gp/researchers/orcid/orcid- for- nature- research + +<|ref|>text<|/ref|><|det|>[[108, 176, 886, 205]]<|/det|> +Thank you again for your interest in Nature Methods. Please do not hesitate to contact me if you have any questions. We will be in touch again soon. + +<|ref|>text<|/ref|><|det|>[[109, 216, 195, 243]]<|/det|> +Best regards, Nina + +<|ref|>text<|/ref|><|det|>[[109, 255, 211, 295]]<|/det|> +Nina Vogt, PhD Senior Editor Nature Methods + +<|ref|>text<|/ref|><|det|>[[110, 345, 346, 360]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[109, 371, 608, 386]]<|/det|> +Authors addressed all my comments, I would fully support publishing this paper. + +<|ref|>text<|/ref|><|det|>[[110, 397, 388, 411]]<|/det|> +Reviewer #1 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[109, 423, 525, 437]]<|/det|> +Software and hardware are well- documented and all open- source. + +<|ref|>text<|/ref|><|det|>[[110, 461, 346, 476]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[109, 488, 538, 503]]<|/det|> +The authors have made quite some effort to respond to my concerns. + +<|ref|>sub_title<|/ref|><|det|>[[109, 515, 192, 527]]<|/det|> +## Comment 14 + +<|ref|>text<|/ref|><|det|>[[109, 527, 852, 568]]<|/det|> +The "Hardware" directory has been renamed to "Other Hardware". This was a good decision, as it helps to differentiate between MouseGoggles and other hardware mentioned in paper. The added documentation should now enable and simplify the initial setup of treadmill and the sensors. + +<|ref|>text<|/ref|><|det|>[[109, 568, 192, 580]]<|/det|> +Comment 15 + +<|ref|>text<|/ref|><|det|>[[108, 580, 875, 607]]<|/det|> +Still no comments in the code. But now it is explained how these files should be used and their purpose. Since the files are small, this seems fine now. + +<|ref|>text<|/ref|><|det|>[[109, 608, 192, 619]]<|/det|> +Comment 16 + +<|ref|>text<|/ref|><|det|>[[109, 619, 886, 660]]<|/det|> +The new short "Introduction to Godot" should indeed make it a little easier to get started. Even if there is still a relatively large hurdle here, as Godot has to be learned. But the experiments seem to be both very small and very similar, so that customisation should be possible. + +<|ref|>text<|/ref|><|det|>[[109, 670, 875, 711]]<|/det|> +Small note and suggestion for a further small change: it should be noted which version of Godot is used here. I opened the project with 4.2.2 and had some error messages in the script editor. This happened although the documentation explicitly calls for the last version of Godot. However, this probably refers to the latest 3. x version. + +<|ref|>sub_title<|/ref|><|det|>[[109, 723, 192, 735]]<|/det|> +## Comment 17 + +<|ref|>text<|/ref|><|det|>[[108, 735, 870, 763]]<|/det|> +The description of the hardware and the hardware assembly instructions should now be sufficient to build the system. And the software description/documentation should help to setup the system. + +<|ref|>text<|/ref|><|det|>[[109, 763, 192, 775]]<|/det|> +Comment 18 + +<|ref|>text<|/ref|><|det|>[[109, 776, 158, 788]]<|/det|> +I agree. + +<|ref|>text<|/ref|><|det|>[[110, 813, 346, 827]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[109, 839, 886, 892]]<|/det|> +The updated manuscript provided by Isaacson, Chang et al. entitled "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior" represents a substantial improvement over the initial manuscript submission. The authors responded to the reviewer comments with a significant amount of work that addresses the issues with the original manuscript, including: + +<|ref|>text<|/ref|><|det|>[[109, 892, 425, 944]]<|/det|> +Relationship of the system to the total visual field Discussion of latency and steps toward reducing it Measured the light reaching the eye Clarification on visual stimuli + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[109, 48, 462, 88]]<|/det|> +Quantification of place cell properties Improved behavioral measures during looming behavior Characterization of whisker obstruction + +<|ref|>text<|/ref|><|det|>[[108, 100, 872, 127]]<|/det|> +The heroic addition of pupillometry also sets this system apart from other emerging immersive mouse VR systems, making this system particularly useful to neuroscientists who also want to track pupil position and size. + +<|ref|>text<|/ref|><|det|>[[108, 139, 883, 218]]<|/det|> +I have only a minor comment, which is that the authors should consider mentioning a finding from Meyer et al., Curr Bio 2020, that might explain the eye movements in response to the looming stimulus. Eye movements in headfixed mice appear to result primarily from attempted head movements (see Fig S5 in that paper), so one interpretation of the results here is that the animals are attempting to escape by moving their heads, which results in a saccade. While a subtle point, the authors' interpretation that the animal's gaze is being directed toward the stimulus is more likely due to an artifact of the animal's inability to move its head freely. + +<|ref|>text<|/ref|><|det|>[[108, 558, 880, 610]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[110, 610, 770, 624]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[108, 623, 875, 675]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[110, 675, 608, 689]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 230, 106]]<|/det|> +Dear Dr. Vogt, + +<|ref|>text<|/ref|><|det|>[[114, 121, 881, 347]]<|/det|> +Dear Dr. Vogt,We thank you for the opportunity to submit our revised manuscript, "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior", to Nature Methods. We appreciate the time taken by you and the reviewers to comment and make suggestions on both the technical and experimental aspects of our approach, and in responding to these comments we have made substantial improvements to our manuscript. These improvements include a more comprehensive comparison of our MouseGoggles system to existing VR technologies and recently developed headset- based systems, an improved online repository to enhance the reproducibility and modifiability of our technology, and the addition of a substantial new capability to our VR system – binocular eye and pupil tracking during VR – which has been our most requested new feature and sets MouseGoggles apart from other recently reported headset- based mouse VR systems. These improvements are demonstrated with the addition of 13 main figure panels, 14 supplemental figure panels, 2 supplementary videos, new results, discussion, and methods text, and substantial additions to the public online repository. These changes are outlined in our point- by- point response to all comments below. + +<|ref|>sub_title<|/ref|><|det|>[[116, 379, 370, 398]]<|/det|> +## Comments from the Editor: + +<|ref|>text<|/ref|><|det|>[[115, 414, 844, 448]]<|/det|> +Comment 1: Specifically, please be sure to demonstrate the advantages over standard VR systems more thoroughly and discuss the limitations of your system. + +<|ref|>text<|/ref|><|det|>[[113, 446, 880, 737]]<|/det|> +Comment 1: Specifically, please be sure to demonstrate the advantages over standard VR systems more thoroughly and discuss the limitations of your system. Response: Thank you very much for this suggestion. We have added new details and results to the main text and methods sections expanding on the advantages of our system over traditional panoramic VR systems. These advantages include a substantially reduced form factor and lowered computational requirements (enabling low- cost VR in a small footprint and a greater ability to scale up experiments, detailed on lines 167- 169), increased immersivity and ability to study innate behaviors during head- fixation (lines 148- 152), and the ability to perform binocular eye and pupil tracking during VR (lines 127- 142, 169- 170, and demonstrated in Fig. 4 and Supplementary Video 3). We have also added some discussion of the limitations of our system, including the relatively low resolution displays used which are well- suited for mouse visual acuity but could be difficult to be directly used on other animals models with higher visual acuity, the 130 ms input- to- display latency which may be problematic during closed- loop feedback of fast behaviors or neural events, and the occlusion of many of the mouse's whiskers by the headset which may confound the sensory experience of a mouse navigating virtual environments (lines 154- 165). We also discuss potential future hardware and software improvements that could increase display resolution and lower latency (lines 158- 165), while a new supplemental figure characterizes the amount of whisker contact at different headset positions to provide guidance on minimizing this potential sensory conflict (Supplementary Fig. 7). + +<|ref|>text<|/ref|><|det|>[[115, 751, 852, 816]]<|/det|> +Comment 2: Importantly, please discuss the similarities and differences of your system with that described in https://www.researchsquare.com/article/rs- 3352160/v1 and https://patents.justia.com/patent/20220295743. You will need to make a strong case for the uniqueness of your system. + +<|ref|>text<|/ref|><|det|>[[115, 816, 875, 896]]<|/det|> +Response: Since our submission of this manuscript in Aug. 2023, two new mouse VR headset systems have been described in the literature. The 1st system, named "Moculus," was released as a preprint on Research Square in Oct. 2023 (https://www.researchsquare.com/article/rs- 3352160/v1) and cited patent applications from previous years. The 2nd system, named "iMRSIV," was published in Dec. 2023 in Neuron (https://www.cell.com/neuron/fulltext/S0896- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 881, 378]]<|/det|> +6273(23)00893- 0) and built using the same software platform as Moculus but using a different display and lens configuration to support a larger field of view. In our manuscript, we now compare our MouseGoggles system with these two new mouse VR headsets. There are several similarities: small form factor, greater accessibility and scalability of head- fixed mouse VR, and evidence of experimental benefits from increased mouse immersion in the virtual world with headset- based systems (lines 148- 152). We have also added new discussion and results on the uniqueness of our system compared to these other approaches, including the ability to perform binocular eye and pupil tracking during VR, the open hardware and software platforms used by MouseGoggles (Raspberry Pi and Godot game engine; all details for replication of hardware and software on GitHub), reduced cost and computational requirements, simplified optical design requiring no custom lenses or precise eye alignment protocols, and the greater mobility of the miniature headset to accommodate rotating head mounts. These discussion points are detailed in the main text (lines 154- 170), with headset mobility and rotation demonstrated in Supplementary Video 4 and binocular eye and pupil tracking demonstrated in Fig. 4 and Supplementary Video 3. Taken together, our and other headset- based VR systems have shown increased immersion, as well as reduced form factor and cost relative to panoramic systems. These benefits will be salient for nearly all neuroscience researchers using VR systems, and rapid adoption is likely. + +<|ref|>text<|/ref|><|det|>[[115, 377, 881, 490]]<|/det|> +Our MouseGoggles system is distinct from the other two systems demonstrated so far primarily in having the ability to track eye gaze direction (to assess what part of the VR space the mouse is looking at) and pupil diameter (a reliable indicator of arousal), with many additional minor differences. This eye tracking capability has been, by far, the most requested addition to MouseGoggles that we have heard from other researchers when they learn about our system. We are happy that we were challenged to make this addition to the system now by both a Reviewer and the need to make a strong case for the uniqueness of our system. + +<|ref|>sub_title<|/ref|><|det|>[[117, 507, 386, 526]]<|/det|> +## Comments from Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[113, 541, 876, 720]]<|/det|> +Comment 1: In this manuscript, Isaacson and colleagues present a novel version of the VR system for head- fixed mice that features a miniature contraption (hence entitled MouseGoggles), easy and cheap design, direct stimulation of the eyes with minimal stray light, and independent control of each eye stimulus. MouseGoggles VR functionality is illustrated using 2PM visual cortex and hippocampal electrophysiology experiments, as well as spatial reward association and innate looming fear paradigms. This work is certainly going to lower the bar for the use of VR in many labs with limited budgets due to the price, eliminate shortcomings of the conventional HD VR, as well as will enable VR experiments that are currently not possible. Hardware is built on inexpensive and widely available components, both optical, mechanical, and electronic designs and software are made open source. Experiments are performed at a high level of quality and the data and results are convincing. + +<|ref|>text<|/ref|><|det|>[[115, 719, 857, 783]]<|/det|> +Response: We thank the reviewer for this positive assessment of our open- source system's advancements over traditional VR technology (e.g. increased accessibility, reduced technical shortcomings, and utility in enabling new VR experiments) and in the high quality of data demonstrating its use. + +<|ref|>text<|/ref|><|det|>[[115, 799, 870, 866]]<|/det|> +Comment 2: I have a few comments listed below. While the new form factor, low cost, stere- ability, and compactness make this system clearly novel and show great premise, the present form of the manuscript doesn't demonstrate or elaborate on any of these advantages. + +<|ref|>text<|/ref|><|det|>[[115, 844, 880, 895]]<|/det|> +Response: As detailed in responses to the specific comments below, we have added additional results and discussion points that explicitly describe these advantages of the system. This includes discussion of the ability to investigate binocular integration and stereo vision with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 870, 139]]<|/det|> +independent eye stimulus control (response to comment 4), to scale up VR experiments due to our system's low cost and small size (response to comment 8), and to rotate the VR system around or with the animal to engage the animal's vestibular system (response to comment 9). + +<|ref|>text<|/ref|><|det|>[[115, 155, 879, 252]]<|/det|> +Comment 3: The minimalistic and low- cost hardware/software used in the MouseGoggles clearly leads to some compromises on the flexibility and performance of the VR implementation. Maximal frame rate, latency, and richness of the 3D cues will surely be limited compared to setups that rely on high- speed and high- resolution projector(s), GPU cards, and performant VR engines (e.g Unity). It would be good if the authors laid out the cons of such a system for animal experiments and possible future directions for circumventing them. + +<|ref|>text<|/ref|><|det|>[[114, 252, 876, 490]]<|/det|> +Response: We thank the reviewer for this comment and apologize for not discussing these limitations in more depth in the original manuscript. The primary technical compromise of MouseGoggles relative to other systems (including human VR systems, traditional panoramic mouse VR systems, and the two other headset- based mouse VR systems) is in display resolution, though we are confident this does not hinder mouse visual neuroscience applications. We used small 240x210 or 240x240 pixel circular displays that contain approximately 1/50th the number of pixels as a single 1080p HD monitor, which substantially reduces the smallest simulated objects and features that can be resolved on screen. However, as prior literature suggests and our experiments have demonstrated (Fig. 2), this reduction in resolution is not a detriment to stimulating the mouse visual system due to the mouse's relatively poor visual acuity, being approximately 1/100th that of humans (~60 cpd maximum for humans vs \~0.5 cpd for mice, reported in Sinex et al, Vision Res. 1979). To better demonstrate this poor visual acuity of the mouse visual system, inserted below is an example image demonstrating how a high- resolution image (left) and a low resolution MouseGoggles image (right) might appear to the mouse (bottom row): + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[211, 88, 782, 520]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 537, 880, 732]]<|/det|> +Low resolution displays would be a limitation if MouseGoggles were to be adapted for a different animal model with higher visual acuity (rats or tree shrews, for example – ongoing in our lab), and would need to be circumvented with the use of higher- resolution displays, and potentially heftier computational resources. On the other hand, because we do not need higher resolution due to the poor visual acuity of mice, an added benefit is a substantial reduction in the computer processing power and data transfer rates required to render 3D scenes and stream images to the displays. With the display resolution we use, complex 3D environments can be rendered at high frame rate on a Raspberry Pi 4, which only has a simple onboard GPU, and frames can be streamed at up to 80 fps using a simple SPI interface. To achieve a similar result, other VR systems require an expensive desktop computer and powerful GPU (e.g. Nvidia RTX3070 used by iMRSIV). Our low- cost solution makes VR research more accessible and promotes high- throughput VR experiments. + +<|ref|>text<|/ref|><|det|>[[115, 730, 880, 907]]<|/det|> +As the reviewer noted, many VR systems used in neuroscience use the Unity game engine to generate 3D scenes and create experiments. Compared to very high- performance game engines (e.g. Unreal Engine), Unity is a beginner- friendly engine more popular among researchers. For MouseGoggles, we opted for the game engine “Godot”, in part due to the ethos of our project relying on open- source tools (unlike Unity, Godot is a fully free and open- source engine). Additionally, despite being lightweight and beginner- friendly, Godot is a full- featured 3D game engine, capable of complex lighting, shaders, particles, and physics simulations, which we are confident is more than powerful enough to support all mouse neuroscience use cases. Researchers may find Godot even easier to work with than Unity as it uses a node- based graphical user interface to create 3D scenes and uses Python- like scripts for game design, instead of Unity’s C# programming. To assist researchers in developing with the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 864, 126]]<|/det|> +Godot game engine, we have added an "Introduction to Godot" document along with a Godot project file containing seven example VR experiments in the online repository + +<|ref|>text<|/ref|><|det|>[[115, 123, 870, 172]]<|/det|> +Notes on the motivation to use the Godot game engine and on VR environment development have been added to the main text and methods (lines 165- 167, 399- 403). + +<|ref|>text<|/ref|><|det|>[[115, 188, 866, 315]]<|/det|> +Comment 4: A natural and important advance in the setup is the possibility to independently render images to both eyes thus enabling stereo- VR. However, unfortunately, the authors do not include such experiments. While testing V1 and CA1 cell tuning simply confirms that MouseGoggles is performing comparably to the existing conventional HF VR setups, these experiments do not demonstrate the advantages of the new system and do not make the case why it should be published in this journal as a major advance of the technology. Some experiments contrasting mono vs stereo- VR would demonstrate this key advance in the technology that is missing in the neuroscience toolbox. + +<|ref|>text<|/ref|><|det|>[[115, 315, 880, 411]]<|/det|> +Response: The reviewer is correct in that we have not demonstrated an experiment that utilizes stereo VR over mono VR, although all VR scenes were rendered stereoscopically. We have put considerable thought into the possibility of a convincing mono vs stereo VR demonstration experiment, but our reading of the literature on stereoscopic vision in mice suggests that a meaningful stereo VR experiment is beyond the scope of this manuscript due to ongoing uncertainty about the role of stereoscopy in natural mouse behavior. + +<|ref|>text<|/ref|><|det|>[[114, 411, 881, 714]]<|/det|> +Some limited aspects of stereo vision have been previously reported in mice using custom stereo displays: visual cortical neurons show some stereo- disparity selectivity (Chioma et al, J Neurosci 2020: https://pubmed.ncbi.nlm.nih.gov/33051348/), mice can be trained to use this information to discriminate "near" and "far" surfaces in random dot stereograms (Samonds et al, J Neurosci 2019: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786824/), and there has even been a report describing the innate use of stereo cues in a novel angled pole descent test (Boone et al, Cur Bio 2021: https://www.cell.com/current- biology/fulltext/S0960- 9822(21)00272- 4). In sum, however, these reports describe rather limited mouse stereo vision capabilities: mice don't use vergence eye movements to fixate by depth like primates do, and the neural selectivity to stereo disparity was relatively weak and only relevant over a narrow range of disparities. Other animal models such as tree shrews show comparably more selective responses to stereo disparity (Tanabe et al, Curr Bio 2022: https://pubmed.ncbi.nlm.nih.gov/36417902/) and may be better models to study stereo vision (this has motivated us to begin development of a larger, higher- resolution version of MouseGoggles suitable for rats and tree shrews). Nonetheless, stereoscopy is a fascinating topic in mouse neuroscience, and MouseGoggles could be helpful in future VR experiments that explore stereoscopic vision in mice. For example, one could develop a stereo vs. mono VR version of the angled pole descent test, which is necessary over a standard flat visual cliff as the downward angle of the descent shifts the view of the cliff into the binocular overlap region where stereo vision might contribute to depth perception. + +<|ref|>text<|/ref|><|det|>[[115, 714, 876, 811]]<|/det|> +Because prior studies have already described custom stereo displays to study stereoscopy in mice, our manuscript focuses on more novel aspects of our method, such as the greater immersivity as well as eye and pupil tracking in VR. But we fully agree that the stereoscopic capabilities of MouseGoggles is another important advance of our method that should be valuable to the neuroscience community, so we have highlighted this feature in the discussion (line 149). + +<|ref|>text<|/ref|><|det|>[[115, 827, 875, 908]]<|/det|> +Comment 5: Innate behavior, such as startle response in response to looming stimulus, even though possibly recapitulating natural avoidance behavior observed in freely- moving rodents, is hardly making a decisive showcase for the system distinguishing it from the conventional ones. It is not clear from the methods section describing conventional projector VR that authors compare to if that system has used all possible means to increase projection surfaces at the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 877, 170]]<|/det|> +lower visual field, including the floor (e.g. as done by labs of Mehta and Tank) by adding a cutout floor disk all around the ball. As many groups implemented this innate fear response with a simple overhead screen or sound, this paper doesn't put forward a distinct use- case for studying flight response to the looming stimulus under head- fixed conditions that could not be done in freely- moving animals. + +<|ref|>text<|/ref|><|det|>[[114, 170, 881, 473]]<|/det|> +Response: The reviewer is correct that innate fear reactions to looming visual stimuli have been observed using VR setups in freely- moving rodents. However, the primary goal of this experiment in our manuscript was to determine if looming reactions could also be elicited in head- fixed conditions, which is necessary for many setups that use neural recording systems not amenable to free- walking. The panoramic VR system we used is state- of- the- art and covers a very wide field- of- view, leaving only a small cutout above the mouse to accommodate a microscope objective and a larger gap below the mouse to fit a spherical treadmill. This projector setup did not include the cutout floor disk approach the reviewer describes, though because the looming object approached at an angle from overhead and did not produce a ground shadow, this may not be a meaningful difference. As reviewer 3 (in comment 8) pointed out, the projector also did not have quite the same vertical extent as MouseGoggles, though in new looming stimulus experiments with eye and pupil tracking (Fig. 4), we blacked out the top of the MouseGoggles displays to match the projector's vertical extent and startle reactions were still observed, suggesting that the extent of visual field coverage does not explain the difference. To our knowledge, only our manuscript and the recent publication on the iMRSIV headset system report fear- based reactions to looming stimuli in head- fixed mice, and neither could replicate this startle reaction in a panoramic VR setup. Thus, we believe that the prior and new data on mouse responses to looming stimuli with headset VR does demonstrate increased immersion in the VR environment, which could be broadly helpful for VR- based experiments. + +<|ref|>text<|/ref|><|det|>[[114, 473, 884, 699]]<|/det|> +Beyond head- fixed neural recording, there are other benefits to being able to perform this task during head- fixation, such being able to use precise behavioral monitoring systems that are more effective in stationary animals. In our revision we have added a new demonstration of one such system: binocular eye and pupil tracking. By building eye tracking cameras into the VR headset, we monitored eye and pupil dynamics in both eyes simultaneously during the presentation of looming stimuli. We observed consistent eye tracking in the direction of the overhead approaching virtual object, and an increase in pupil diameter following the looming stimulus that diminishes with further repetitions of the stimulus, similar to the diminishing startle response we reported in the original manuscript. The ability to elicit fear responses in head- fixed setups where not only neural activity but also eye and pupil dynamics can be recorded, thus enabling assessment of the mouse's attention, arousal, and memory encoding is a substantial advance for mouse neuroscience, in particular the study of emotional circuits. This new MouseGoggles design with eye tracking and application to the head- fixed looming experiment is described in the main text (lines 127- 142) and shown in Fig. 4 and Supplementary Video 3. + +<|ref|>text<|/ref|><|det|>[[115, 714, 882, 811]]<|/det|> +Comment 6: Stray light measurements make the case for the clear improvement in that parameter over plain- vanilla imaging setup in which the optical axis is not shielded from the light. However, similar to the enclosure protecting the 2PM from the monitor light, it is possible (and done by some scientists) to design and 3D print an enclosure protecting the cranial window from the external stray light. The use of blue light is another option (e.g Kuznetsova et al JNM 2021), which, I assume, authors refer to as "filtering". + +<|ref|>text<|/ref|><|det|>[[115, 811, 880, 907]]<|/det|> +Response: On the issue of stray light contamination into sensitive imaging applications, the reviewer accurately points out that shielding the cranial window (or what we described as "shielding the objective" in the manuscript) or filtering out display light (e.g. using blue light with a short- pass color filter, since blue LEDs used in commercial displays typically emit small amounts of longer wavelength light) can be effective in enabling imaging during high intensity visual stimulation. The main advantage of using our MouseGoggles display is that this additional + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 880, 315]]<|/det|> +shielding or filtering is not necessary. This point could range from being irrelevant for setups that already have appropriate shielding solutions in place, to a significant advantage for setups that would otherwise have to create and test new strategies appropriate for their equipment and experiment. Some imaging setups feature components that make shielding and filtering more difficult, such as those that use multiple different microscope objectives or use blue/green fluorescent probes, so having a visual stimulation system which produces minimal stray light to begin with can be a benefit. Because our display system was designed with the goal that it could simply be "dropped in" to most existing experimental setups, we believe that this issue of stray light reduction is important in that context, though we agree with the reviewer's point that this is otherwise a surmountable problem. We have adjusted the main text so that this feature is described as an improvement over a standard off- the- shelf monitor, and equivalent to a monitor with substantial added shielding (lines 82- 85, see also our response to the next comment). New data on the comparison to a shielded monitor is demonstrated in Supplementary Fig. 4 and described in the methods section (line 573- 578). + +<|ref|>text<|/ref|><|det|>[[114, 330, 877, 460]]<|/det|> +Comment 7: Besides, a significant amount of stray light reaches the brain through the eye, which would mean that if imaging was performed in more frontal regions, high- intensity eye stimulation might cause more stray light diverted through this pathway than in a conventional setup. Could authors measure that? What is the functional consequence of the difference in the stray light for the performance of 2PM imaging? Arguably somatic high- SNR Ca imaging will likely not be affected. I suggest that to make this feature a decisive one that sets this setup apart from the conventional one, there needs to be a clear demonstration of the functional advantages. + +<|ref|>text<|/ref|><|det|>[[114, 459, 882, 540]]<|/det|> +Response: The reviewer brings up an excellent point that a small amount of light from the displays may reach imaging cameras or PMTs by passing through the pupil and scattering through the brain, and while the overall amount of light generated by a MouseGoggles display is substantially less than that of a full- sized monitor or projector, it is not immediately clear whether MouseGoggles would focus more or less light through the eye than traditional displays. + +<|ref|>text<|/ref|><|det|>[[114, 539, 880, 858]]<|/det|> +To investigate this possibility, we recorded light levels from both a MouseGoggles monocular display and a traditional flat screen with and without shielding the cranial window. In anesthetized mice, we imaged in both visual area 1, where visual stimulus- evoked neural activity could be seen from GCaMP6f fluorescence, and in somatosensory area 1, where no stimulus- evoked GCaMP activity was seen and the contribution from stray light could be quantified. To determine whether this measured stray light was acquired through an external pathway or an internal one (i.e., through the pupil and scattering through the skull), we compared recorded light levels with the cranial window either unblocked, where light could be collected from both internal and external pathways, or blocked, where light is only collected from external pathways. We found that using MouseGoggles or a substantially shielded traditional monitor, we could eliminate nearly all of the external stray light, where only minimal external stray light was recorded at maximum display brightness, far less than the intensity of typical GCaMP6s- labeled cell baseline fluorescence. In addition, we did not detect any additional light from the display reaching our detectors when the cranial window was unblocked relative to the open cranial window condition, suggesting that the internal pathway is not contributing any detectable stray light in our imaging setup, at least in the brain regions we imaged. We thus conclude that light contamination through the eye is not a major issue with MouseGoggles, and that total stray light from MouseGoggles is comparable to a highly shielded traditional monitor. These new results have now been included in Supplementary Fig. 4 and referred to in the main text (lines 82- 85). + +<|ref|>text<|/ref|><|det|>[[114, 875, 850, 908]]<|/det|> +Comment 8: What appears to be the top point setting the system apart is that, in addition to enabling stereo VR, it is inexpensive and compact. Inexpensive - means that scalable, high + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 857, 138]]<|/det|> +throughput parallel VR setups would allow training the large batches of mice, something that, clearly was not possible so far. However obvious, this feature is not emphasized in the manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 138, 877, 330]]<|/det|> +Response: We thank the reviewer for this helpful perspective and suggestion. Since the MouseGoggles system is even more compact and inexpensive than other recent mouse VR headset systems (Moculus and iMRSIV) and has substantially reduced computational requirements (only needing a Raspberry Pi 4 with no GPU), our system is particularly well suited to the scaled- up VR training the reviewer contemplates. We have added an additional discussion point highlighting this benefit (lines 165- 169). To further demonstrate the ability to scale up VR experiments with small- footprint VR systems, we have added a description of a VR setup using a linear treadmill (lines 651- 658) that fits within a \(14 \times 14 \text{cm}\) footprint (Fig. 4b) and added new documentation to the online repository with assembly instructions and code for this setup. We have also included instructions in our online repository for controlling the VR system with VNC, so that multiple VR setups can be controlled from a single host computer, which may be the desired solution for running VR experiments in parallel. + +<|ref|>text<|/ref|><|det|>[[114, 346, 882, 425]]<|/det|> +Comment 9: Compactness of the setup is only slightly outlined by the authors, but not exploited. Rotations of the miniaturized setup allow easy implementation of the proper 2D VR (similar to Chen et al eLife 2018). Rotations around other than the vertical axis allow for so far impossible experiments testing vestibular input contributions. Realistic vestibular inputs could be added by implementing appropriate movements of the apparatus using hexapods. + +<|ref|>text<|/ref|><|det|>[[114, 425, 880, 650]]<|/det|> +Response: We agree with the reviewer that the compact size of MouseGoggles could allow rotations of the headset during use. Rotating the VR setup to test vestibular inputs is a fascinating possibility, though beyond the scope of this manuscript to thoroughly implement. We have added new discussion points about this possibility in the main text (lines 172- 173). Additionally, since relatively recent evidence has shown that rotatable head mounts improve 2D navigation in VR (such as in Chen et al, eLife 2018; this citation has been added to our manuscript), we believe this could be a very important feature for future MouseGoggles implementations. To demonstrate how headset rotations could be measured for closed- loop experiments, we have added a new supplementary video demonstrating headset rotation, using an integrated sensor (accelerometer and gyroscope) and magnetometer. The accelerometer provided feedback for headset roll and the magnetometer worked well for yaw feedback (Supplementary Video 4). We have added details on this modification to the methods section and online repository for building and controlling these setups. We hope this addition will enable interested researchers to take on the scientific questions the reviewer mentions. + +<|ref|>sub_title<|/ref|><|det|>[[116, 683, 385, 701]]<|/det|> +## Comments from Reviewer 2: + +<|ref|>text<|/ref|><|det|>[[115, 718, 881, 814]]<|/det|> +Comment 1: Mouse Goggles is a novel VR display device for the binocular visual stimulation of mice. Together with its online documentation this is to be a fully documented open- source tool that others can replicate. The results of MouseGoggle experimental testing confirm that it functions at least as well as traditionally used surround screens with visual stimuli or VR scenes. The experimental testing for MouseGoggles has been done comprehensively. The report is brief, to the point, well written, and complete. + +<|ref|>text<|/ref|><|det|>[[115, 814, 716, 831]]<|/det|> +Response: We thank the reviewer for this positive assessment of our work. + +<|ref|>text<|/ref|><|det|>[[115, 847, 874, 880]]<|/det|> +Comment 2: The usefullness of the method will depend on the possibility that it can actually be used as an open source tool and replicated by others. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 877, 268]]<|/det|> +Response: This is an excellent point, and we are in full agreement with the reviewer. One of our primary goals in this project is that not only is it possible for others to replicate this method, but that it be simple and easy for non- experts to do. To that end, we have opted for off- the- shelf parts wherever possible (e.g. no custom lenses), have created a comprehensive parts list, and provide simple assembly and installation instructions that have all necessary details for replication. We have also verified that this system has been successfully replicated by multiple external labs through the online resources, though we acknowledge that our open- source documentation at the time of submission still had significant room for improvement. As detailed in response to many comments below (comments 6- 18), we have made significant improvements to the online repository to facilitate further replication and modification by the research community. + +<|ref|>text<|/ref|><|det|>[[114, 282, 880, 330]]<|/det|> +Comment 3: Authors should discuss how their relatively simple optical solution could potentially be improved. In this context they should cite the publicly accessible manuscript about Moculus doi.org/10.21203/rs.3.rs- 3352160/v1. + +<|ref|>text<|/ref|><|det|>[[114, 330, 880, 650]]<|/det|> +Response: Since the submission of our MouseGoggles manuscript, there are now two other headset- based mouse VR systems in the literature: Moculus (Rozsa et al, Research Square 2023; preprint: https://www.researchsquare.com/article/rs- 3352160/v1) and iMRSIV (Pinke et al, Neuron 2023; published: https://www.cell.com/neuron/fulltext/S0896- 6273(23)00893- 0). We have added new discussion points commenting on the different optical design strategies used and their pros/cons. Importantly, the optical design we chose is in service of a primary goal of our project: that MouseGoggles is simple and easy to replicate and use. By using just a single off- the- shelf Fresnel lens, no custom lenses have to be ordered or cut to size. Also, because of our use of a display system positioned at infinity focus from the perspective of the mouse, no complicated eye positioning protocols (such as those used by Moculus and iMRSIV) are needed. To add a new test and demonstration of the performance of our optical design, we imaged the display's projection on the back plane of an enucleated mouse eye, confirming that our design produces a clear image of the display that is robust to small changes in eye position within the allowed space of the eyepiece. These new results are shown in Supplementary Fig. 1 and referenced in the main text (lines 50- 52) and described in the methods section (lines 425- 439). The primary disadvantage of this simple optical design is that the field of view coverage of our eyepieces is limited to 140 deg, whereas more complex optical designs (e.g. iMRSIV) can support increased field of view coverage up to 180 deg. However, this enhanced field of view comes at the expense of necessitating more precise eye positioning. These pros and cons are now detailed in the discussion (lines 159- 162). + +<|ref|>text<|/ref|><|det|>[[115, 666, 864, 715]]<|/det|> +Comment 4: Authors should discuss if patent PCT HU2020/050029 published under WO2021009526A1 covers or is different from their method as it may affect its use as an open source tool (accessible e.g. at https://patents.justia.com/patent/20220295743). + +<|ref|>text<|/ref|><|det|>[[115, 715, 880, 812]]<|/det|> +Response: As it currently stands, the Moculus patent application was given a non- final rejection in Nov, 2023 (https://patentcenter.uspto.gov/applications/17626700/ifw/docs?application=). While we are not qualified to comment on the legal aspects of the differences between our method and the currently rejected patent, in terms of engineering and scientific differences, our method differs in significant ways from the Moculus system as described both in the patent and in the preprint. + +<|ref|>text<|/ref|><|det|>[[115, 812, 865, 908]]<|/det|> +Moculus is a stereoscopic VR simulator composed of separate display "wings" that are individually positioned for each eye and secured to the animal head- clamping mechanism, distinguishing itself from prior VR designs that are single- piece headsets and that can be attached to freely- walking animals. MouseGoggles on the other hand is a single piece design similar to prior VR/AR headsets and that is not attached to the head- clamp. MouseGoggles is also built on entirely different hardware and software platforms than Moculus (MouseGoggles + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 876, 219]]<|/det|> +with a Raspberry Pi computer, Godot game engine, and SPI- based displays, compared to Moculus with a Windows PC, Unity engine, and HDMI- based displays); in fact, there is not a single piece of hardware or software in common between the two systems. We further successfully demonstrate in situ tracking of eye gaze direction and pupil diameter, a feature the neuroscience community has explicitly requested from us. In this manuscript, our focus is reporting on the design and results from our mouse VR system, and we must leave questions about the impact of this patent to the US Patent and Trademark Office, and comparable entities in other countries. + +<|ref|>text<|/ref|><|det|>[[114, 234, 860, 315]]<|/det|> +Comment 5: The authors should improve the online documentation that is cited in the manuscript in order to better facilitate replication of this open source method. Response: We thank the reviewer for such detailed and helpful notes regarding the online documentation. We have updated the repository with all details requested and listed in the following comments. + +<|ref|>text<|/ref|><|det|>[[114, 330, 864, 364]]<|/det|> +Comment 6: Please upload not only the STL files but also the STP files or IPT drawing of the CAD designs for easier modification + +<|ref|>text<|/ref|><|det|>[[114, 364, 870, 397]]<|/det|> +Response: For all custom 3D designed parts, both .stl files and .step files have been uploaded to facilitate modification. + +<|ref|>text<|/ref|><|det|>[[114, 412, 854, 460]]<|/det|> +Comment 7: The bill of materials mentions all parts in [cm] however Figure 2 shows them in [mm] - please update the bill of materials and use only one unit of measurement to avoid confusion + +<|ref|>text<|/ref|><|det|>[[114, 460, 815, 494]]<|/det|> +Response: The bill of materials has been updated to show 3D print sizes in mm to stay consistent with the rest of the repository and manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 510, 877, 558]]<|/det|> +Comment 8: Recommendation for a future revision: Reconsider the material that was used in the printing. If the parts will be adjustable or moveable at some point, resin material will become brittle quickly. + +<|ref|>text<|/ref|><|det|>[[114, 558, 880, 688]]<|/det|> +Response: We thank the reviewer for this recommendation. In our online assembly instructions, we have added new recommendations for different materials, 3D printers, and print settings to use. To successfully print the small features of our eyepiece enclosure, we recommend high resolution printers capable of \(< 0.2 \text{mm}\) layer resolution. Low- cost SLA printers (e.g. Photon Mono X) using standard UV- cured resin can be very cost- effective and successfully print all parts used by MouseGoggles. Parts produced this way have remained intact after over 2 years of use in our hands. For more rigid and longer- lasting parts, a high resolution FDM printer (e.g. Ultimaker) can be used with stronger and tougher thermoplastics such as PLA, PETG, or ABS. + +<|ref|>text<|/ref|><|det|>[[114, 703, 816, 736]]<|/det|> +Comment 9: Upload not only gerber files but also the schematic and PCB file for easier modification + +<|ref|>text<|/ref|><|det|>[[114, 736, 861, 769]]<|/det|> +Response: For all custom PCBs, both the schematic and layout files as well as the Autodesk Eagle project file have been added to the online repository to facilitate modification. + +<|ref|>text<|/ref|><|det|>[[114, 784, 835, 817]]<|/det|> +Comment 10: Include the fabrication specifications for the PCBs: board thickness, copper thickness and surface finish + +<|ref|>text<|/ref|><|det|>[[114, 817, 872, 866]]<|/det|> +Response: Fabrication specifications for custom PCBs have been added to the online repository, including the number of layers (2), board material (FR- 4), board thickness (1.6 mm), copper thickness (0.0348 mm), and surface finish (HASL with lead). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 875, 138]]<|/det|> +Comment 11: In MinibrdV1, the copper to copper spacing is only \(0.06 \text{mm}\) – for a future revision I recommend updating the layout to increase the minimum copper to copper spacing to at least \(0.2 \text{mm}\) ; this simplifies demands on production. + +<|ref|>text<|/ref|><|det|>[[115, 138, 868, 202]]<|/det|> +Response: In MinibrdV1 (now renamed to MouseGoggles MiniBrdAA 1.1 as part of a comprehensive version naming structure), the minimum copper to copper spacing has been adjusted to \(0.2 \text{mm}\) . All other PCB layout files have been verified to fit this requirement as well. Thank you for this valuable suggestion. + +<|ref|>text<|/ref|><|det|>[[115, 218, 864, 267]]<|/det|> +Comment 12: In MinihatV1, there are 90 degree traces and these will form acid traps that cause corrosion – for a future revision I recommend updating the layout with traces only at 45 degrees + +<|ref|>text<|/ref|><|det|>[[115, 267, 875, 315]]<|/det|> +Response: In MinihatV1 (now renamed to MouseGoggles MiniHataAA 1.1), all 90- degree traces have been removed and replaced with 45- degree traces. Other layout files have been checked for these as well. Thank you again for helping us with these PCB design subtleties. + +<|ref|>text<|/ref|><|det|>[[115, 331, 863, 379]]<|/det|> +Comment 13: The driver for sending the images via SPI to two small screens is from an external project (fbcp- ili9341 and fbcp- st7789) which seems to be well documented, no action required. + +<|ref|>text<|/ref|><|det|>[[115, 380, 844, 428]]<|/det|> +Response: We thank the reviewer for this comment, and again for thoroughly checking the open documentation. Our selection of this driver was in keeping with the open- source, well- documented ethos of this project. + +<|ref|>text<|/ref|><|det|>[[115, 445, 602, 460]]<|/det|> +Comment 14: Drivers for detecting the movement of the ball. + +<|ref|>text<|/ref|><|det|>[[115, 461, 876, 523]]<|/det|> +The movement is transmitted to the PC/RasPi as if it were a PC mouse. The ADNS3080 sensor is used. "mouseVRheadset_controller_V4. ino" is not commented in detail. This is so small that this is not of great importance. Action: add a few explanatory sentences to facilitate faster orientation. + +<|ref|>text<|/ref|><|det|>[[114, 525, 875, 700]]<|/det|> +Response: We thank the reviewer for pointing out our lack of documentation on the treadmill system. Since our focus has been on the development of visual display hardware and software, we mistakenly omitted some documentation on the treadmill system software we've developed for MouseGoggles compatibility. We have now added new documentation describing the software for two treadmill systems: the spherical treadmill system originally from Harvey et al, Nature 2009 (https://www.nature.com/articles/nature08499) that was described in our original manuscript, as well as a linear treadmill from Arnold, JRC, 2023 (https://www.janelia.org/open- science/low- friction- rodent- driven- belt- treadmill) which we have recently implemented with MouseGoggles, and is included in our revision (Fig. 4). Our new documentation describes where the treadmill hardware is described and/or can be purchased, and details how to update the treadmill's microcontroller firmware for compatibility with the MouseGoggles system. + +<|ref|>text<|/ref|><|det|>[[115, 717, 878, 763]]<|/det|> +Comment 15: The purpose and use of the files in the "ADNS3080 debugging" folder must be explained. While these are only for debugging, how and what they are used for is not clear. This is also because these data have no comments. Action required: Explain and comment. + +<|ref|>text<|/ref|><|det|>[[115, 765, 846, 813]]<|/det|> +Response: A description of this debugging folder has been added to the spherical treadmill documentation described above, and additional in- code comments have been added to the scripts within that folder. + +<|ref|>text<|/ref|><|det|>[[115, 830, 878, 894]]<|/det|> +Comment 16: The experiments with 3D glasses use the Godot engine. Some examples are provided. But you need some knowledge about this engine, especially because the experiments run completely within the engine. This engine is not only responsible for the representation of the 3D world, but also for the process and the logging of the data. The examples make it easier + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 852, 138]]<|/det|> +to get started, but still require some familiarisation with Godot. Recommended action: the authors might think about how they could further facilitate getting familiar with this part of the code. + +<|ref|>text<|/ref|><|det|>[[115, 138, 877, 283]]<|/det|> +Response: Since the Godot game engine has not been previously used in neuroscience applications (unlike Unity), adding a tutorial or familiarization document for the Game engine is an excellent suggestion. To the online repository, we have added a new document to function as both a general 'Introduction to Godot' as well as an overview of the specific Godot files created and used for MouseGoggles experiments. This includes walking the reader through the Godot game engine editor and scripting environment, organization of different types of game files, highlighting some commonly used features and settings, and walking through a typical experiment script and logged data file. We also include seven example VR environments that can help get users started. + +<|ref|>text<|/ref|><|det|>[[115, 299, 880, 377]]<|/det|> +Comment 17: The glasses are also available in a variant for "Monocular Display". This uses the Teensy board to control a small display. "GC9307_teensy_GFX.ino" has a lot of comments on single lines, but a more general documentation to understand the context of the parameters would be nice. Especially because there are so many parameters. Action required: provide a better general documentation and include a table of all parameters and their use. + +<|ref|>text<|/ref|><|det|>[[115, 378, 881, 507]]<|/det|> +Response: Since the Monocular Display (now referred to as MouseGoggles Mono) is built on a different hardware and software platform as the binocular MouseGoggles Duo (Arduino graphics library + Teensy microcontroller, vs Godot game engine + Raspberry Pi computer), we agree that it makes sense to have comprehensive documentation for the MouseGoggles Mono code and control system. We have added new documentation which describes a general overview of the system, the different operational modes of the system, and describes and lists the commands and parameters which can be sent to the microcontroller to display patterns on the monocular display. + +<|ref|>text<|/ref|><|det|>[[115, 522, 876, 587]]<|/det|> +Comment 18: While the software is neither very large nor a complex project, with its current level of documentation it still poses a challenge to find ones way around. This does not apply to the external SPI monitor driver. This part alone is much larger and more complex than MouseGoggles. + +<|ref|>text<|/ref|><|det|>[[115, 588, 881, 653]]<|/det|> +Response: With the extensive documentation added and described above, including both specific technical details as well as general overviews of the software and systems, we believe that the online repository is now easier to navigate and understand, and users will be better able to replicate and modify this tool for their own purposes. + +<|ref|>text<|/ref|><|det|>[[115, 669, 844, 701]]<|/det|> +Comment 19: 551 check sentence for completeness: ... last bin excluded due the mouse's constrained position ... + +<|ref|>text<|/ref|><|det|>[[115, 702, 866, 749]]<|/det|> +Response: We have rewritten this sentence for completeness: "All licking data was binned by location into 5- cm wide bins, with the first and last bin were excluded due to the mouse's constrained position away from the walls". (line 739- 741). + +<|ref|>text<|/ref|><|det|>[[115, 765, 880, 816]]<|/det|> +Comment 20: 555 For ease of understanding change: "All licks not occurring following a reward delivery were defined as "exploratory licks". TO Licks at other times than after a reward delivery ... + +<|ref|>text<|/ref|><|det|>[[115, 816, 867, 847]]<|/det|> +Response: This suggested change has been made (line 744- 745): "All licks occurring at other times than after a reward delivery were defined as "exploratory licks". + +<|ref|>text<|/ref|><|det|>[[115, 863, 645, 896]]<|/det|> +Comment 21: 619 a 2nd cohort of mice were tested -> was tested Response: This typo has been fixed (line 808). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 106, 860, 140]]<|/det|> +Related to the typographical errors mentioned above, we have made additional corrections to our methods section after identifying missing or confusing information: + +<|ref|>text<|/ref|><|det|>[[144, 140, 852, 237]]<|/det|> +Missing information about post- operative analgesia after the surgical procedure for head- fixed behavior has been added (lines 530- 531). Missing information about the concentration of AAV- GCaMP6s bolus injection for V1 calcium imaging has been added (lines 538). The section on habituation for head- fixed behavior has been rewritten for clarity, with added details for habituation on our newly included linear treadmill (lines 660- 671). + +<|ref|>sub_title<|/ref|><|det|>[[116, 285, 386, 305]]<|/det|> +## Comments from Reviewer 3: + +<|ref|>text<|/ref|><|det|>[[114, 320, 880, 481]]<|/det|> +Comment 1: Virtual reality has become a powerful tool for studying a variety of brain functions in head- fixed rodents. Current implementations of rodent VR involve large displays that not only create difficulties for the experimenter, but also do not provide an immersive experience for the animal, largely due to their expansive visual field. Isaacson, Chang, et al. designed a head- set based VR system to overcome current constraints. They provide evidence that their system solves many of the practical issues with VR, including reduced light pollution for imaging methods and reduced cost. They use neural recordings to show that the visual tuning properties of neurons are comparable to results obtained with standard techniques, supporting the quality of image presentation. Finally, they provide evidence that the VR experience for the mouse is immersive through effective behavioral training in reward and innate fear behaviors. + +<|ref|>text<|/ref|><|det|>[[115, 497, 880, 562]]<|/det|> +This work represents a very useful advance for both the quality of rodent VR experience and the ability of individual laboratories to implement VR systems, especially given the low- cost and open source design. Overall, the authors provide a straightforward and convincing case for the improvements this system makes over traditional rodent VR systems. + +<|ref|>text<|/ref|><|det|>[[116, 562, 626, 578]]<|/det|> +Response: We thank the reviewer for these positive comments. + +<|ref|>text<|/ref|><|det|>[[115, 595, 875, 692]]<|/det|> +Comment 2: The manuscript could be substantially improved by addressing the following points: The system provides 230 deg of field coverage in the horizontal azimuth, with 140 deg per eye and 25 deg of binocular overlap. The authors should report measured values of the mouse visual field from previous studies in the main text, and discuss the limitations of the system in obtaining full coverage in the Discussion. Also, the approximate elevation covered by the system should be reported in the main text. + +<|ref|>text<|/ref|><|det|>[[115, 692, 880, 835]]<|/det|> +Response: We agree with this suggested change and have moved information on mouse visual field estimates and our coverage of that field from the methods to the main text. We also report approximate elevation covered by the system (140 deg) and the headset configuration that was predominantly used in this manuscript (15 deg pitch, for - 55 to +85 deg maximum stimulated elevation relative to the horizon). These details have been added on lines 55- 58. Details on different pitch positions of the headset and the estimated visual field coverage of each position has been added in Supplementary Fig. 7. Relating to this, we noticed an error in our plotting of the estimated mouse visual field, which is now correctly plotted as a 180x140 deg ellipse (Fig. 1e, Supplementary Fig. 6d, and Supplementary Fig. 7c). + +<|ref|>text<|/ref|><|det|>[[115, 835, 867, 900]]<|/det|> +We have also added discussion on the strengths and limitations of our relatively simple optical design (lines 159- 162). The main limitation being that FOV coverage is limited to 140 deg, whereas the main strengths are a simple, inexpensive build requiring no custom lenses, and a system which is robust to eye position variations and does not require precise eye + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 140]]<|/det|> +alignment protocols. We have added a new supplementary figure demonstrating the system's performance by imaging gratings through the back of an enucleated mouse eye, showing similar performance to a traditional flat monitor (Supplementary Fig. 1). + +<|ref|>text<|/ref|><|det|>[[115, 155, 875, 220]]<|/det|> +Comment 3: How does the 130 ms input to display latency compare to other rodent VR systems? My understanding is that latencies greater than 20ms are detectable to humans, so it seems possible this relatively long latency may limit the immersive experience for the mouse. The authors should discuss this. + +<|ref|>text<|/ref|><|det|>[[113, 220, 878, 490]]<|/det|> +Response: We believe that total system latency is an important consideration for any closedloop system. To our knowledge, most existing rodent VR systems do not report end- to- end latency, thus it can be difficult to compare. Among modern, high- end human VR headset systems, mean total latency has been reported to range from 21- 42 ms (https://pubmed.ncbi.nlm.nih.gov/36217006/), where the longest latencies were found during periods of rapid movements. Among VR systems used in animal model neuroscience (specifically, those that report total latency), total latency ranges more broadly, with values as small as 2 ms under restrictive conditions (Isaacson et al, BioRxiv 2022: https://www.biorxiv.org/content/10.1101/2022.08.02.502550v1) to \(\sim 100\) ms for general- purpose VR (Madhav et al, J Neurosci Methods 2022: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9178503/). Our panoramic projector VR system, after optimization, measured at \(\sim 90\) ms latency. As for what latencies are needed or desired for head- fixed animals to be "immersed" in the VR world, we aren't able to say, as to our knowledge very little has been published on the effects of latency on neuroscience VR applications. One might speculate that long latencies are workable for closed- loop feedback from slow behaviors, such as mice walking on a treadmill, but could be problematic with fast behaviors such as eye movements. + +<|ref|>text<|/ref|><|det|>[[114, 490, 881, 668]]<|/det|> +Without optimization, we measured MouseGoggles latency at \(\sim 130\) ms. However, there are opportunities to substantially reduce this latency in the display driver. Using "adaptive display stream updates", where only pixels which changed from the previous frame are updated, total latency can be drastically reduced. This feature is supported by the display driver used by MouseGoggles, and has been demonstrated to reduce total latency on a single display comparable to that used by MouseGoggles to under 20 ms (https://github.com/juj/fbcp- ili9341#about- input- latency). This feature has not yet been implemented for dual displays, though this is an area we are actively working on, and we hope to have this feature implemented and latency reduced in the near future (we will update our online repository accordingly). We have added these details on total latency and potential future optimization in the main text (lines 156- 159) and the methods (lines 417- 420). + +<|ref|>text<|/ref|><|det|>[[115, 682, 880, 731]]<|/det|> +Comment 4: The measurements in 1b- d are in the range of 0- 70 deg, but the authors report monocular coverage of 130 deg. Is there some reason why they did not model the full coverage, which is nearly twice the range in the figure? + +<|ref|>text<|/ref|><|det|>[[115, 732, 879, 860]]<|/det|> +Response: We thank the reviewer for pointing out this confusion. The 130 deg value comes from the total horizontal extent of the visual field coverage, which includes both left and right directions from straight ahead (70 deg in one direction and 60 deg in the other due to the "chipped edge" of the 240x210 circular display). In Fig. 1b- d, we modeled the viewing angle in a single direction up to 70 deg; since the display and lens configuration is radially symmetric, this modeling will be identical in all other directions. We have reworded the text of the figure legend (lines 196- 197), referring to the viewing angle as one side of the total maximum field of view coverage (140 deg) to reduce this confusion. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 866, 138]]<|/det|> +Comment 5: The modeling of the light reaching the eye from the screen/lens is very useful. It would also be useful to have a measurement of the performance of the actual system, e.g., by projecting onto a model or real mouse eye. + +<|ref|>text<|/ref|><|det|>[[114, 138, 881, 363]]<|/det|> +Comment 5: The modeling of the light reaching the eye from the screen/lens is very useful. It would also be useful to have a measurement of the performance of the actual system, e.g., by projecting onto a model or real mouse eye. Response: As suggested, we have now imaged the display's projection on the back of enucleated mouse eyes during the presentation of drifting gratings, comparing the image generated by a MouseGoggles eyepiece to that of a traditional flat monitor positioned further away (10 cm). We found that the image produced onto the plane of the retina by MouseGoggles is qualitatively comparable to that of the monitor, except that MouseGoggles is able to cover a much larger area of the eye's FOV. Furthermore, since one theoretical benefit of our relatively simple optical design is that the eye is not required to be precisely positioned relative to the lens (with the display positioned at the lens' focal distance, rays extending from the lens to the eye should be close to parallel), we measured the robustness of the system to minor changes in eye position by shifting the eye relative to the eyepiece and imaging the projection. We found that changes in position of up to \(\sim 2\) mm orthogonal to the optical axis of the lens and produced no clear distortion of the image projection on the back of the eye adding experimental support to the theoretical robustness of our design. These results are shown in Supplementary Fig. 1 and referenced in the main text (lines 50- 52) and methods (lines 425- 439). + +<|ref|>text<|/ref|><|det|>[[115, 378, 878, 442]]<|/det|> +Comment 6: The comparison of light pollution between the monitor and monocular display is quite striking. It would be ideal to see a similar direct comparison of the two systems for the visual tuning properties in Fig2d- i, especially since the stimulus used for receptive field mapping is different from the referenced study (Niell & Stryker, 2008). + +<|ref|>text<|/ref|><|det|>[[114, 443, 881, 874]]<|/det|> +Comment 6: The comparison of light pollution between the monitor and monocular display is quite striking. It would be ideal to see a similar direct comparison of the two systems for the visual tuning properties in Fig2d- i, especially since the stimulus used for receptive field mapping is different from the referenced study (Niell & Stryker, 2008).Response: Related to this comment, we describe new experiments and analyses on light pollution comparing MouseGoggles to a traditional monitor in response to Reviewer 1, Comment 6, above. Regarding differences in stimuli used to map visual responses, the stimuli we used to measure visual tuning properties (Fig. 2d- i) were designed to closely match prior studies so that they could be considered close to direct comparisons. We do agree with the reviewer that our receptive field mapping stimuli is somewhat different than that of the referenced study, though we believe this is not a significant difference and our original description of our stimuli could give the impression that the stimuli were more different than they actually were. The study we designed this receptive field mapping test on (Niell & Stryker, 2008) used a 4x8 deg bright bar sweeping across the visual field, repeated in 4 directions and at 8 different azimuths and elevations. Our study used a 3.8x7.6 deg bright bar (the closest we could get with our display's resolution), repeated across 5 different azimuths and elevations to reduce the total experiment time required – since our experiments began with a search to locate receptive field centers, a 5x5 grid was sufficient in our experiments to capture many neurons' receptive fields. There were minor differences in the presentation order of the stimuli across the visual field: Niell and Stryker presented a continuous sweep in one direction across 8 positions before switching to a new direction and position, while we presented sweeps in 4 directions at a single position before switching to a new position. The amount of the visual field stimulated in each data bin was nearly identical to the study from Niell and Stryker, which is expected to be the main determining factor in the receptive field size measurement. A likely source of confusion in our original description of the stimuli was that we described our stimuli as gratings rather than bar sweeps. However, each of these "gratings" had a 7.6 deg spatial wavelength and was presented at 1 Hz for 0.5 s, which is essentially just a bright bar sweep across the 7.6 deg position, similar to the study from Niell and Stryker. We apologize for this confusing description and have now adjusted the text to describe this stimulus as a bar sweep (lines 85, 587- 589), but if there are still any concerns about this comparison, we are happy to revisit or repeat this experiment with a new protocol. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 835, 123]]<|/det|> +Comment 7: How do the tuning properties of CA1 place cells compare to other mouse VR studies and freely moving mouse studies (e.g. place field width)? + +<|ref|>text<|/ref|><|det|>[[115, 123, 876, 168]]<|/det|> +Response: Since the properties of place fields in rodent dorsal CA1 are known to be modulated by the size of the virtual environment (e.g. Harland et al, Curr Bio 2021: https://www.sciencedirect.com/science/article/pii/S0960982221003420#bib8) and richness of the local visual cues (Tanni et al, Curr Bio 2022: + +<|ref|>text<|/ref|><|det|>[[115, 168, 870, 330]]<|/det|> +https://www.sciencedirect.com/science/article/pii/S0960982222010089#bib16), and since our virtual linear track was visually distinct from those in prior studies, a direct comparison may be difficult to interpret. However, we agree that CA1 place cell tuning properties are useful for interpreting how the VR experiment was encoded by place cells, so we have added new quantifications to our manuscript: proportion of neurons that exhibited place- like characteristics for each session, place field width in the virtual space, and information rate for each place cell. These quantifications have been added to Fig. 2 (panel n), and references to these properties have been added to the main text (lines 99- 102). Details on how these new properties were quantified have been added to the methods (lines 702- 707). + +<|ref|>text<|/ref|><|det|>[[115, 346, 880, 490]]<|/det|> +Comment 8: In comparing the behavioral responses to looming stimuli on MouseGoggles vs. a traditional projector system, was the projector system oriented above the mouse? Based on the methods, it appears the projector reached a maximum of only 64 deg elevation, so is this the presumed reason that a response was not elicited? The ability to adjust elevation with MouseGoggles is indeed useful, but ideally the behavior would be compared to a projector system with similar visual field coverage. If it is experimentally infeasible to adjust the projector system to cover a comparable region of the visual field, the authors should state this. Otherwise, the experiment should be conducted with comparable overhead coverage between the two systems. + +<|ref|>text<|/ref|><|det|>[[115, 490, 880, 666]]<|/det|> +Response: The projector- based VR system we used featured a custom conical screen that extended significantly above the horizon, with only a circular cutout above the mouse to fit a microscope objective for 2- photon imaging. Even though the projector had a large vertical extent, the reviewer is correct that the FOV coverage of MouseGoggles extends even further. This increased overhead coverage was likely not meaningful for the looming experiment since the looming object approached from a 45 deg elevation, which is easily covered by the 64 deg elevation of the projector screen. However, to be sure, during the newer looming experiments with eye and pupil tracking (shown in Fig. 4 and Supplementary Video 3) we blacked out the top section of the screen (above 64 deg elevation) and we observed similar startle responses from these mice. This detail on the restricted elevation has been added to the methods section (lines 819- 821). + +<|ref|>text<|/ref|><|det|>[[115, 682, 880, 905]]<|/det|> +Comment 9: It appears that video of the mouse was acquired during the looming stimulus presentation (Fig3f and methods). The methods clearly state the responses were manually scored, but the main text and figure do not mention this, and the line fit to the mouse's back in Fig3f might lead the reader to assume the quantification of behavior was achieved with computational video analysis. Is the resolution of the video sufficient to perform the startle analysis? If so, the authors should quantify the behavior using image analysis methods or markerless pose estimation. If not, the authors should clearly state that in the text/Fig3g that the quantification was performed by two human observers. The authors could also plot the velocity of the animal measured via the spherical treadmill aligned to the onset of the looming stimulus. Response: We thank the reviewer for pointing out this omission in our text. One complication we observed during early attempts at automatic quantification and detection of looming reactions is the significant variability in mouse behavior prior to the looming stimulus; head- fixed mice may be stopped, walking, running, or grooming immediately prior to the loom. Therefore, we determined that identifying reactions to looming stimuli are most clearly assessed through + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 848, 123]]<|/det|> +manual behavior scoring. We have clarified this approach in the main text and Fig. 3 legend (lines 121, 249- 252). + +<|ref|>text<|/ref|><|det|>[[115, 122, 881, 251]]<|/det|> +In inspecting and plotting the spherical treadmill velocity aligned to the looming stimulus, we found it impossible to detect startle responses in terms of treadmill movements, seemingly due to the near- constant movement of the low- friction treadmill and the relatively small startle- movement transferred to the ball. However, in the new looming experiments with eye and pupil tracking which were performed on a more stable linear treadmill, plotting the linear treadmill velocity showed a clearer response from the looming stimuli (mice back up a bit!). This new data is shown in Fig. 4, referenced in the main text and described in the methods section (lines 137- 142, 815- 839). + +<|ref|>text<|/ref|><|det|>[[115, 266, 872, 330]]<|/det|> +Comment 10: Does this system permit the measurement of eye movements? Given that mice move their eyes (though somewhat infrequently) while head- fixed, it would be ideal to measure these movements during stimulus presentation. The authors mention that pupil tracking would be feasible with this system; how would this be achieved? + +<|ref|>text<|/ref|><|det|>[[115, 330, 878, 586]]<|/det|> +Response: Although it was a lot of work, we thank the reviewer for challenging us to achieve this goal. The ability to measure eye and pupil dynamics during head- fixed VR has been the most requested feature for future versions of the MouseGoggles system, and we are excited to add this capability in our revised manuscript. As we show in new figure panels (Fig. 4), the MouseGoggles system does indeed permit eye and pupil measurement during VR presentation through the use of fully- integrated infrared imaging inside the eyepiece. Due to the simple optical design of MouseGoggles, enough space exists within the eyepiece to fit an angled hot mirror, which allows visible display light to pass from the VR display to the mouse eye while IR illumination can reflect to the eye and back toward a mini- IR camera. This new design, which still only uses off- the- shelf parts, enables clear imaging of the mouse eye and pupil during visual stimulus presentation. This optical strategy for simultaneous eye/pupil monitoring and VR presentation might not be possible with the other recent mouse VR headsets, Moculus and iMRSIV, due to their more complex optical design and reduced space within the eyepiece enclosure to fit additional lenses or mirrors. The iMRSIV publication specifically identifies a lack of eyepiece space as a hindrance to simultaneous eye monitoring in their system, and notes that eye tracking would be highly beneficial for future VR headsets. + +<|ref|>text<|/ref|><|det|>[[115, 586, 881, 714]]<|/det|> +To demonstrate this new feature, we performed infrared eye imaging of head- fixed mice walking on a linear treadmill during the looming visual stimulus experiment. Position of points along the eye and pupil were tracked using Deeplabcut to enable measurement of both eye orientation and pupil diameter. From this experiment, we observed clear eye tracking towards the overhead looming objects and noted a pupil dilation response following the looming stimulus that diminished with additional repetitions of the stimulus, similar to the habituating startle responses. These new results are shown in Fig. 4 and discussed in the main text and detailed in the methods section (lines 127- 142, 441- 489, 815- 839). + +<|ref|>text<|/ref|><|det|>[[115, 730, 881, 844]]<|/det|> +Comment 11: Face/whisker movements contribute significantly to neural activity. Does this system allow for these measurements, or do the MouseGoggles fully obstruct the view? Response: Face movements can indeed be seen with the MouseGoggles system if a camera is mounted in front of the mouse and below the headset (e.g. supplementary Video 1), where views of the nose, mouth, and many lower whiskers are unobstructed. However, upper whisker movements are significantly impaired as many upper whiskers during whisking behavior cross in front of and near the eyes. These details have been added to the main text (lines 154- 156). + +<|ref|>text<|/ref|><|det|>[[115, 860, 860, 893]]<|/det|> +Comment 12: If possible, the experimenters should quantify whisker contact with the system. Do any of the whiskers touch the system, and if so with what frequency? Extensive whisker + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 867, 138]]<|/det|> +contact with the system would presumably degrade any immersive experience the mouse may have, and would make it difficult to perform some of the multisensory experiments the authors propose in the Discussion. + +<|ref|>text<|/ref|><|det|>[[114, 138, 882, 314]]<|/det|> +Response: We thank the reviewer for this excellent suggestion, we agree that quantifying whisker contact is important to characterize our system and its limitations. We have added a new supplementary figure quantifying the whisker contact depending on different orientations of the headset. Depending on the headset pitch, slightly more or less of the head- fixed mouse's whiskers will be occluded by the headset. In a near- flat position, where the headset is pitched 15 degrees upward from the horizon (a typical orientation used in this study), approximately \(60\%\) of whiskers are blocked by the headset. With significantly increased positive headset pitch (e.g. 45 deg), where more of the visual field above the horizon is covered, some frontal whiskers become unblocked. These considerations should assist future users in selecting a headset position that will enable their desired experiments. These new results are shown in Supplementary Fig. 7 and referenced in the main text (lines 154- 156). + +<|ref|>text<|/ref|><|det|>[[115, 330, 870, 363]]<|/det|> +Comment 13: How do the authors calibrate the system with each individual mouse, given e.g., the inherent variability in headplate placement? + +<|ref|>text<|/ref|><|det|>[[114, 363, 884, 555]]<|/det|> +Response: Due to the simple optical design of the MouseGoggles headset, the system is robust to minor offsets of the mouse eye from the center of the lens. To demonstrate this feature more clearly, we have added Supplementary Fig. 1 showing the performance of the optical design by viewing the display's projection on the back of an enucleated mouse eye. By adjusting the position of the eye relative to the Fresnel lens surface center, we found that small lateral eye displacements ( \(< 2 \text{mm}\) ) caused little noticeable distortion of the display image. In our experience, manual adjustment of the optical posts and angled post clamps until both eyes were roughly centered inside each eyepiece routinely achieves binocular eye positioning well within this range. This may be a unique benefit of the MouseGoggles system compared to the Moculus and iMRSIV systems which use more complex lens arrays and are described as being sensitive to eye position, and whose methods describe a more precise eye alignment protocol. We have added a discussion on this issue to the main text and to the methods section (lines 159- 162). + +<|ref|>text<|/ref|><|det|>[[114, 555, 875, 700]]<|/det|> +In our surgical preparations the headplate placement did not significantly vary in tilt, therefore the only adjustment necessary for accurate positioning of mice relative to the headset was manually translating the headset up to the mouse's eyes, with no sideways tilt required to roughly center both eyes inside the eyepieces. We have added this detail on headset positioning to the methods section (lines 666- 670). In the case that a surgical preparation results in a significantly tilted headplate (either in pitch or roll directions), a further calibration might be needed in the VR software if it is desired to match the virtual "eyes" to the headset orientation and position. While we did not have to make this kind of adjustment in our experiments, we have updated the VR experiment scripts in the online repository + +<|ref|>text<|/ref|><|det|>[[115, 700, 872, 730]]<|/det|> +so that both headset pitch and roll tilt angles can be easily matched by the game engine. + +<|ref|>text<|/ref|><|det|>[[115, 746, 877, 826]]<|/det|> +Comment 14: Given that monocular cues should be sufficient for most experiments performed in the manuscript (formation of place cells, responses to looming stimuli, reinforcement learning), an "immersive" experience may not be requisite for the results obtained here. A more convincing test that the animal is having an immersive experience would be ideal, e.g., behavior with a virtual cliff showing that animals stop to avoid falling over the edge. + +<|ref|>text<|/ref|><|det|>[[115, 827, 875, 907]]<|/det|> +Response: Due to the lack of startle responses to looming visual stimuli from head- fixed mice in our panoramic projector- based VR system, we believe that even wide- field binocular visual cues are insufficient to cause startle responses, and monocular cues have not been shown, to our knowledge, to generate a startle response. Thus, an immersive virtual experience seems to be necessary and is successfully demonstrated by our MouseGoggles system. However, we + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 880, 312]]<|/det|> +agree with the reviewer that a visual cliff experiment may be an excellent test that only a binocular, immersive, and stereoscopic VR system could replicate. As we detailed more fully in response to reviewer 1, comment 4, the current understanding of the salience of stereoscopic vision in mice is limited, making this more a topic for exploration with stereoscopic VR systems than a robust testbed for establishing the degree of immersion. The only experiment we are aware of that demonstrates mouse's innate use of stereo cues is in the angled pole descent test (Boone et al, Curr Bio 2021: https://www.cell.com/current- biology/fulltext/S0960- 9822(21)00272- 4). This test is required over a typical flat visual cliff experiment as the downward angle ensures that the cliff appears well within the mouse's binocular overlap region, where stereo vision has been shown to apply. MouseGoggles, combined with a custom pitching treadmill, could provide an excellent toolkit for testing the salience of stereoscopic vision in mice, but is beyond the scope of this manuscript. Our additions, in this revision, of implementation with a compact linear treadmill (Fig. 4) and with closed- loop feedback from headset rotation (Supplementary Video 4), should facilitate the development of this kind of VR experiment in the future. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 231, 107]]<|/det|> +Dear Dr. Vogt, + +<|ref|>text<|/ref|><|det|>[[115, 121, 876, 203]]<|/det|> +Dear Dr. Vogt,We thank you and the reviewers for providing feedback on our revised manuscript, "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior". We appreciate all the positive feedback on our recent changes and the final comments to ready the manuscript for publication. Below is our point- by- point response to the remaining reviewer comments. + +<|ref|>sub_title<|/ref|><|det|>[[117, 219, 386, 239]]<|/det|> +## Comments from Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[115, 254, 861, 288]]<|/det|> +Comment 1: Authors addressed all my comments, I would fully support publishing this paper. + +<|ref|>text<|/ref|><|det|>[[115, 288, 860, 321]]<|/det|> +Thank you for your positive feedback and support for the publication of our paper, and for the excellent suggestions in the previous comments. + +<|ref|>sub_title<|/ref|><|det|>[[117, 335, 386, 355]]<|/det|> +## Comments from Reviewer 2: + +<|ref|>text<|/ref|><|det|>[[115, 369, 825, 468]]<|/det|> +Comment 1: The authors have made quite some effort to respond to my concerns. [referencing previous comment 14] The "Hardware" directory has been renamed to "Other Hardware". This was a good decision, as it helps to differentiate between MouseGoggles and other hardware mentioned in paper. The added documentation should now enable and simplify the initial setup of treadmill and the sensors. Thank you for your positive feedback. + +<|ref|>text<|/ref|><|det|>[[115, 481, 867, 530]]<|/det|> +Comment 2: [referencing previous comment 15] Still no comments in the code. But now it is explained how these files should be used and their purpose. Since the files are small, this seems fine now. + +<|ref|>text<|/ref|><|det|>[[115, 530, 879, 594]]<|/det|> +In addition to the explanation of the purpose of the debugging files in our online repository, we have now added comments to the "ADNS3080 debugging" code for each file individually, as requested earlier. Sorry for the omission, we mistakenly had not pushed an update after our last response, but it has now been updated and verified. + +<|ref|>text<|/ref|><|det|>[[115, 608, 876, 673]]<|/det|> +Comment 3: [referencing previous comment 16] The new short "Introduction to Godot" should indeed make it a little easier to get started. Even if there is still a relatively large hurdle here, as Godot has to be learned. But the experiments seem to be both very small and very similar, so that customisation should be possible. + +<|ref|>text<|/ref|><|det|>[[115, 673, 876, 737]]<|/det|> +Thank you for your feedback on the "Introduction to Godot" file. We understand that there is still a learning curve, as there will be with any experiment design program or game engine, but we hope that our aim to keep the example 3D experiments simple will also make them [relatively] easy to understand and customize. + +<|ref|>text<|/ref|><|det|>[[115, 752, 868, 850]]<|/det|> +Comment 4: Small note and suggestion for a further small change: it should be noted which version of Godot is used here. I opened the project with 4.2.2 and had some error messages in the script editor. This happend although the documentation explicitly calls for the last version of Godot. However, this probably refers to the latest 3. x version. The version of game engine software used by in this manuscript (Godot 3.2) has now been added to the "Introduction to godot" document in our online repository. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 155]]<|/det|> +Comment 5: [referencing previous comment 17] The description of the hardware and the hardware assembly instructions should now be sufficient to build the system. And the software description/documentation should help to setup the system. [referencing previous comment 18] I agree. + +<|ref|>text<|/ref|><|det|>[[115, 155, 780, 188]]<|/det|> +Thank you for your agreement and positive feedback on the hardware and software documentation, and for all your help in improving the online resource. + +<|ref|>sub_title<|/ref|><|det|>[[116, 205, 386, 224]]<|/det|> +## Comments from Reviewer 3: + +<|ref|>text<|/ref|><|det|>[[115, 239, 874, 321]]<|/det|> +Comment 1: The updated manuscript provided by Isaacson, Chang et al. entitled "MouseGoggles: an immersive virtual reality headset for mouse neuroscience and behavior" represents a substantial improvement over the initial manuscript submission. The authors responded to the reviewer comments with a significant amount of work that addresses the issues with the original manuscript, including: + +<|ref|>text<|/ref|><|det|>[[143, 335, 658, 455]]<|/det|> +Relationship of the system to the total visual field Discussion of latency and steps toward reducing it Measured the light reaching the eye Clarification on visual stimuli Quantification of place cell properties Improved behavioral measures during looming behavior Characterization of whisker obstruction + +<|ref|>text<|/ref|><|det|>[[115, 469, 872, 519]]<|/det|> +The heroic addition of pupillometry also sets this system apart from other emerging immersive mouse VR systems, making this system particularly useful to neuroscientists who also want to track pupil position and size. + +<|ref|>text<|/ref|><|det|>[[115, 518, 872, 582]]<|/det|> +We are grateful for your thorough and positive evaluation of our manuscript. We appreciate the acknowledgment of our revisions and additions, including the incorporation of pupillometry which was a particular challenge but one we also believe will be highly useful for behavioral neuroscientists. Thank you for the earlier feedback which motivated these improvements. + +<|ref|>text<|/ref|><|det|>[[115, 597, 872, 727]]<|/det|> +Comment 2: I have only a minor comment, which is that the authors should consider mentioning a finding from Meyer et al., Curr Bio 2020, that might explain the eye movements in response to the looming stimulus. Eye movements in headfixed mice appear to result primarily from attempted head movements (see Fig S5 in that paper), so one interpretation of the results here is that the animals are attempting to escape by moving their heads, which results in a saccade. While a subtle point, the authors' interpretation that the animal's gaze is being directed toward the stimulus is more likely due to an artifact of the animal's inability to move its head freely. + +<|ref|>text<|/ref|><|det|>[[115, 727, 870, 790]]<|/det|> +Thank you for this insightful suggestion. Since head- fixed eye movements have been shown to be related to attempted head movements, we have added this suggested interpretation of eye movements during our virtual looming experiment and added a reference to Meyer et al., Curr Bio 2020 (lines 152- 154). + +<|ref|>text<|/ref|><|det|>[[115, 804, 869, 838]]<|/det|> +We appreciate the valuable feedback from all reviewers and hope that these revisions address all remaining concerns. + +<|ref|>text<|/ref|><|det|>[[115, 853, 303, 901]]<|/det|> +Sincerely, Matthew Isaacson On behalf of all authors + +<--- Page Split ---> diff --git a/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/images_list.json b/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..5915fdee077ccb387bb579ce9ea98e9f8ccecde4 --- /dev/null +++ b/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,362 @@ + +# nature portfolio + +Peer Review File + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Qi Zhang and colleagues investigated the role of heparin sulphate (HS) in SARS- CoV- 2 spike mediated fusion and syncytium formation. They started by testing newly generated MTAN- related drugs to investigate their effect on SARS- CoV- 2 infection and their toxicity. They selected PIXN (LC1541) as their best candidate. It binds specific sulphate groups on HS and inhibits SARS- CoV- 2 entry and replication in different systems including primary air- liquid cells and K18- hACE2 mice. Next, they showed that HS depletion inhibits spike mediated cell- cell fusion using both drugs and knock- out cells. They investigated the mechanism underlying HS- mediated increased fusion, showing that HS does not promote Spike- ACE2 binding or S2' cleavage. Using cell- cell fusion and in vitro techniques they show that HS induce clustering of ACE2 and promotion of fusion pore formation. + +Overall, the article is clear and provides interesting mechanistic data on the action of HS on ACE2 and SARS- CoV- 2 fusion. + +Main comments + +1. Fig 1. H. For the mouse experiments it would have been interesting to include data on the clinical score for SARS-CoV-2 infections and comment on the toxicity of the drug in vivo. + +2. Fig. 3 - Cell line infection experiments are indicated being done at 4h post infection at relatively high MOIs (MOI of 0.5 or 0.1 was calculated on Vero TMPRSS2 cells) using Vero cells overexpressing both human ACE2 and TMPRSS2. At 4h post-infection the authors observed large syncytia and clear N staining (Fig. 3). 4h post infection seems like a very early timepoint to detect extended cell-cell fusion. According to published data (for instance Koch et al. EMBO, 2021) there is no significant detection of N after 4h of infection in Vero cells and from our experience, syncytia formation generally starts only as early as 6-7h post infection in highly permissive cell lines. Is this observation due to the usage of VeroE6 expressing both human ACE2 and TMPRSS2 making them highly fusogenic? Could the cell-cell fusion observed be due to fusion from without? + +3. The authors should comment on the choice of this 4h timepoint. The results should be confirmed at lower MOIs, possibly including a drug blocking viral replication to distinguish fusion from without and de-novo produced spike. + +4. Fig. 6. The authors identified a region of ACE2 promoting HS mediated receptor clustering. It would have been interesting to test if this region of ACE2 also plays a role if viral entry in addition to its role on cell-cell fusion. As in figure 1 and 3 the authors used virus and pseudotypes to show that HS modulating drugs impact viral entry, it may be worth testing if the phenotype for cell-cell fusion with this ACE2 mutant also translates to differential viral entry. + +Reviewer #2 (Remarks to the Author): + +This submission provides interesting findings to support the hypothesis that heparin and HSPGs facilitate the coalescence of target- cell ACE2 with effector- cell spikes. This coalescence correlates with higher levels of spike- directed cell- cell fusion. The authors suggest that this higher cell- cell fusion correlates with more severe COVID, and thus hypothesize that drugs interfering with this HSPG activity could be useful in mitigating COVID. They test new HSPG- binding agents as SARS- CoV- 2 antivirals and find that one, PIXN, is moderately antiviral at nontoxic concentrations. + +The significance of the findings appears moderate but with additional research there may be potential for HSPG interference as an antiviral measure. + +The findings are sophisticated and high quality. These include results in medicinal chemistry, + +<--- Page Split ---> + +biochemistry and virology, and they include excellent imaging data. However, even with the abundant data, the mechanism by which heparin and HSPGs facilitate viral fusion seems unclear. The summary models of ACE2 clustering in Fig 7 are only partially supported by the data. + +The major issues in this review are centered on authors' rationales, i.e., justifications for experiments, and on authors' interpretations of findings. The minor issues include suggestions for additional experiments and modifications of the text. + +## Major points: + +1. The model is that HSPGs facilitate coalescence of ACE2 on target cells. However, when HSPGs are not present or are inhibited by bound PIXN, there are still some ACE2-spike synapses and also cell-cell fusions. This may arise because spikes themselves are clustered on surfaces of effector cells, independent of whether the spikes are opposed next to adjacent ACE2 on target cells. Spikes coalesce in lipid rafts in plasma membranes of infected cells and spike-transfected cells. The investigators should image the positions of spike proteins on plasma membranes both before and after co-cultivation of spike-expressing cells with target cells. Clustered spikes will likely cluster ACE2 upon contact of spike-expressing and ACE2-expressing cells. + +2. The finding that ACE2 lacking the dimerization domain (ACE2-GS) fails to coalesce in response to HSPGs is interesting. However, the interpretation of the result should be broadened. One spike trimer can bind more than one ACE2, generating ACE2 coalescence. If ACE2 is dimeric, then higher-order spike trimer: ACE2 dimer zippering (coalescence) seems likely. Alternative models for ACE2 clustering should be put forward. + +3. Premise – justification for the study appeals to the need for durably active spikes as syncytia expand, even in the face of spike “dilution” on the ever-increasing plasma membrane surface areas of syncytia. This is an interesting idea but it does not have any any experimental support and it may not be correct to assume that spikes are not continuously synthesized as syncytia expand. There could be plenty enough continued spike synthesis to generate large syncytia. This appeal to spike dilution appears prominently in the intro and discussion sections and this reviewer feels it should be tempered or communicated in context of other equally or more credible views about syncytial developments. + +## Minor points: + +1. Fig. 1H; very modest in vivo antiviral activity in K18-hACE2 mice; does PIXN reduce pathogenicity of infections in this model? +2. Fig. 3B; the assay is not specifically measuring "virus entry"; y-axis should be relabeled as "infection" +3. Fig 3CD; need to emphasize when PIXN was added (added after virus entry or before?) If before, the smaller syncytia could merely be a result of reduced infection at entry stage, not actually blockade of syncytia per se. +4. Fig 4, what specifically is "semi-fusion"? Is it different than hemi-fusion? +5. Fig 5E (and elsewhere); "HS is required..." One can agree that HS facilitates ACE2 clustering but is not "required", consider rephrasing. +6. Fig. 6; ACE2-GS; should test whether ACE2-GS confers SARS-CoV-2 susceptibility to ACE2-negative cells, quantifying ACE2-GS receptor activity relative to ACE2-WT. +7. Fig. 7A and 7E; depictions may be communicating inaccurately; a single S trimer may bind more than one ACE2 dimer, resulting in ACE2 clustering. Consider revising the images to account for this possibility. +8. Line 161; there is no evidence that N punctae are virions, they could be aggregates of intracellular N protein. +9. Lines 166-170; syncytia come from free S proteins going to cell surfaces, and likely far less so from "fusion of viral envelope with plasma membrane" (line 167); this part of text is not interpreting findings in the conventional and well-known ways. +10. Lines 286-287; there is no rationale stated for the test to determine whether LS is critical for cell-cell fusion. Consider major point #2 as a possible rationale. +11. Fig 7; should incubate the immobilized ACE2 with both soluble RBD monomers and soluble spike trimers, to determine whether trimerized state of spike is needed for ACE2 clustering. + +<--- Page Split ---> + +We thank the reviewers for their positive and constructive suggestions. We have done many additional experiments to address these comments, as explained below point- by- point. + +Reviewer #1 (Remarks to the Author): + +Qi Zhang and colleagues investigated the role of heparan sulphate (HS) in SARS- CoV- 2 spike mediated fusion and syncytium formation. They started by testing newly generated MTAN- related drugs to investigate their effect on SARS- CoV- 2 infection and their toxicity. They selected PIXN (LC1541) as their best candidate. It binds specific sulphate groups on HS and inhibits SARS- CoV- 2 entry and replication in different systems including primary air- liquid cells and K18- hACE2 mice. Next, they showed that HS depletion inhibits spike mediated cell- cell fusion using both drugs and knock- out cells. They investigated the mechanism underlying HS- mediated increased fusion, showing that HS does not promote Spike- ACE2 binding or S2' cleavage. Using cell- cell fusion and in vitro techniques they show that HS induce clustering of ACE2 and promotion of fusion pore formation. + +Overall, the article is clear and provides interesting mechanistic data on the action of HS on ACE2 and SARS- CoV- 2 fusion. + +Response: We thank this reviewer for his/her enthusiasm in our study. + +Main comments + +1. Fig 1. H. For the mouse experiments it would have been interesting to include data on the clinical score for SARS-CoV-2 infections and comment on the toxicity of the drug in vivo. + +Response: When we examined the viral titer in the lungs of mice treated with PIXN or untreated after infection, we did weight the lungs. We noticed a small reduction in lung weight in mice treated with PIXN (see below), suggesting that the drug might have some side effect on the lung. Because of this, and also because pathology- based scoring is less quantitative and has a narrower dynamic range compared to viral titer measurement, we chose the latter to determine the effect of drug treatment on viral entry and replication in mice. + +From the drug development perspective, the reviewer raised an excellent point. However, we would like to emphasize that the significance of our finding is the mechanism underlying spike- induced membrane fusion, which reveals how the virus co- opts a cell surface molecule to enhance spike's membrane fusion activity. We now add a sentence on page 6 to clarify this, which reads as "The low in vivo anti- SARS- CoV- 2 activity may be due to PIXN binding to HS in non- targeting tissues, which would reduce its effective concentration in the lung, suggesting that further optimizations are required to advance HS inhibitors into clinics as an anti- viral agent." + +The toxicity of Pixantrone (PIXN) has been extensively evaluated in animals and in clinics (PMID: 31997425; ref 32 in the manuscript). To confirm this, we treated mice with PIXN and + +<--- Page Split ---> + +analyzed the serum aspartate aminotransferase (AST) level as an indicator of liver toxicity 3 days after drug injection. We did not notice any increase in the AST level in the serum (Supplementary Fig. 1c), consistent with the known safety profile of this drug. + +2. Fig. 3 - Cell line infection experiments are indicated being done at 4h post infection at relatively high MOIs (MOI of 0.5 or 0.1 was calculated on Vero TMPRSS2 cells) using Vero cells overexpressing both human ACE2 and TMPRSS2. At 4h post-infection the authors observed large syncytia and clear N staining (Fig. 3). 4h post infection seems like a very early timepoint to detect extended cell-cell fusion. According to published data (for instance Koch et al. EMBO, 2021) there is no significant detection of N after 4h of infection in Vero cells and from our experience, syncytia formation generally starts only as early as 6-7h post infection in highly permissive cell lines. Is this observation due to the usage of VeroE6 expressing both human ACE2 and TMPRSS2 making them highly fusogenic? Could the cell-cell fusion observed be due to fusion from without? + +Response: The reviewer is correct that we chose 4- hour post infection (hpi) because we could not detect significant de novo spike synthesis at this time point, yet the infection- induced cell- cell fusion could be observed (Supplementary Fig. 3d). When we stained cells with a spike antibody, we could detect some spike signal as clustered dots on the surface 4 hpi (Supplementary Fig. 3d, Video 1), whereas de novo synthesized spike at 6 hpi is mostly localized at a peri- nuclear ERGIC compartment (Supplementary Fig. 3d). This difference suggests that the spike positive signal on the cell surface 4 hpi is derived from viral membrane during viral entry. + +As for the MOI chosen in this study, we used MOI of 0.1- 0.5, which is in line with published studies. For example, the study by Koch et al. EMBO 2021 used a MOI of 0.2. The paper by Braga L et al. (Nature 2021, https://doi.org/10.1038/s41586- 021- 03491- 6, Figure 3) used a MOI of 0.5. In the study by Blanco- Melo, D. and colleagues (Cell 2020), the authors used 0.2 as low MOI and 2 as high MOI. + +One key difference between our study and previous studies on SARS- CoV- 2- induced syncytia is in the viral strain. Apparently, most studies published before 2021 used early strains such as the Washington strain or a closely related one. In our hand, only the Delta strain generates giant syncytia 4 h post infection, whereas the Washington strain only generates medium size syncytia after a much longer incubation (9 h) (Supplementary Fig. 3b). We never observed any syncytia with more than 2 nuclei per cell without infection, suggesting that the cell- cell fusion cannot be due to fusion from without. A few cells with two nuclei in uninfected cells are apparently caused by cell division. + +3. The authors should comment on the choice of this 4h time points. The results should be confirmed at lower MOIs, possibly including a drug blocking viral replication to distinguish fusion from without and de-novo produced spike. + +<--- Page Split ---> + +Response: We now add a sentence on page 8 to explain the choice of this time point (no significant de novo spike synthesis at this early time point). We repeated the infection experiment at a low MOI (0.01) for 4 and 6 hours, respectively, and in both Vero E6 cells and the highly permissive Vero TA6 cells (expressing ACE2 and TMPRSS2). As expected, we saw very few syncytia. Nevertheless, there seems to be a trend that is consistent with Delta being more potent in inducing cell- cell fusion and TA6 being more permissive than Vero E6 cells in cell- cell fusion (Supplementary Fig. 3c). + +4. Fig. 6. The authors identified a region of ACE2 promoting HS mediated receptor clustering. It would have been interesting to test if this region of ACE2 also plays a role if viral entry in addition to its role on cell-cell fusion. As in figure 1 and 3 the authors used virus and pseudotypes to show that HS modulating drugs impact viral entry, it may be worth testing if the phenotype for cell-cell fusion with this ACE2 mutant also translates to differential viral entry. + +Response: We tested the entry of pseudovirus-coated with the spike of the Washington strain, which is mediated primarily by ACE2-mediated endocytosis. In ACE2-GS-GFP cells, the entry of this virus appears identical to that in WT ACE2-GFP cells (Supplementary Fig. 6e), suggesting that this loop is not required for ACE2-mediated endocytosis of SARS-CoV-2. + +Reviewer #2 (Remarks to the Author): + +This submission provides interesting findings to support the hypothesis that heparin and HSPGs facilitate the coalescence of target- cell ACE2 with effector- cell spikes. This coalescence correlates with higher levels of spike- directed cell- cell fusion. The authors suggest that this higher cell- cell fusion correlates with more severe COVID, and thus hypothesize that drugs interfering with this HSPG activity could be useful in mitigating COVID. They test new HSPG- binding agents as SARS- CoV- 2 antivirals and find that one, PIXN, is moderately antiviral at nontoxic concentrations. + +The significance of the findings appears moderate but with additional research there may be potential for HSPG interference as an antiviral measure. + +The findings are sophisticated and high quality. These include results in medicinal chemistry, biochemistry and virology, and they include excellent imaging data. However, even with the abundant data, the mechanism by which heparin and HSPGs facilitate viral fusion seems unclear. The summary models of ACE2 clustering in Fig 7 are only partially supported by the data. + +Response: We agree with this reviewer that from a drug development perspective, the potency of PIXN may not be significant enough to warrant clinical testing at this points. However, it is worth noting that the most important finding of our study is about the unexpected role of heparan sulfate in promoting spike- mediated cell- cell fusion. We show that 1) ACE2 forms a super- cluster upon spike engagement, which is dependent on heparan sulfate; 2) ACE2 super- clustering concentrates the spike at the membrane contact site, which + +<--- Page Split ---> + +facilitates fusion pore formation; 3) Heparan sulfate acts through a conserved loop in ACE2 to promote receptor super- clustering. All these findings are novel, which significantly advance our understanding on the mechanism of spike- mediated membrane fusion. + +The major issues in this review are centered on authors' rationales, i.e., justifications for experiments, and on authors' interpretations of findings. The minor issues include suggestions for additional experiments and modifications of the text. + +Major points: + +1. The model is that HSPGs facilitate coalescence of ACE2 on target cells. However, when HSPGs are not present or are inhibited by bound PIXN, there are still some ACE2-spike synapses and also cell-cell fusions. This may arise because spikes themselves are clustered on surfaces of effector cells, independent of whether the spikes are opposed next to adjacent ACE2 on target cells. Spikes coalesce in lipid rafts in plasma membranes of infected cells and spike-transfected cells. The investigators should image the positions of spike proteins on plasma membranes both before and after co-cultivation of spike-expressing cells with target cells. Clustered spikes will likely cluster ACE2 upon contact of spike-expressing and ACE2-expressing cells. + +Response: We thank the reviewer for this excellent suggestion. We have done the suggested experiment (Supplementary Fig. 5a). We stained spike transfected cells with a spike specific antibody either without or after co- culturing with ACE2 WT- or ACE2 GS- GFP cells. As pointed out by the reviewer, spike does form small coalesces on the cell surface, but these small puncta are uniformly distributed throughout the surface. By contrast, when spike cells encounter ACE2- GFP cells, the spike forms giant super- clusters that are co- localized with ACE2- GFP. Interestingly, when spike cells contact ACE2 GS- GFP cells, the spike clustering is significantly reduced (Supplementary Fig. 5a). This experiment suggests that it is ACE2 clustering that drives spike super- cluster formation, but not the other way around. + +2. The finding that ACE2 lacking the dimerization domain (ACE2-GS) fails to coalesce in response to HSPGs is interesting. However, the interpretation of the result should be broadened. One spike trimer can bind more than one ACE2, generating ACE2 coalescence. If ACE2 is dimeric, then higher-order spike trimer: ACE2 dimer zippering (coalescence) seems likely. Alternative models for ACE2 clustering should be put forward. + +Response: We agree with the reviewer that our data does not suggest how exactly ACE2 super- clusters are formed. We have now added more discussions on this point including a brief mentioning of the previous study on the role of heparan sulfate in facilitating FGF2 receptor dimerization (page 17). In this case, a structural study suggests that heparan sulfate can bind two FGF2 receptors to facilitate its dimerization. The linker segment may be involved in heparan sulfate- mediated ACE2 oligomerization in a similar way, but we do point out that "other alternative models cannot be excluded." + +The zippering model suggested by the reviewer is also possible. However, in our initial attempt, we tried to reconstitute ACE2 super- clustering in solution, but failed to detect any + +<--- Page Split ---> + +clustered ACE2 despite the use of a trimeric spike. This argues against a simple zippering model. Only after we attached the ACE2 receptor to lipid bilayers, did we see ACE2 clustering in the presence of the spike and heparan sulfate. + +3. Premise – justification for the study appeals to the need for durably active spikes as syncytia expand, even in the face of spike “dilution” on the ever-increasing plasma membrane surface areas of syncytia. This is an interesting idea but it does not have any any experimental support and it may not be correct to assume that spikes are not continuously synthesized as syncytia expand. There could be plenty enough continued spike synthesis to generate large syncytia. This appeal to spike dilution appears prominently in the intro and discussion sections and this reviewer feels it should be tempered or communicated in context of other equally or more credible views about syncytial developments. + +Response: The reviewer is correct that during prolonged infection, there will be de novo synthesis of the spike. According to our time-course studies, we could not detect any spike expression in cells 4 hpi, yet in cells infected with the Delta strain, massive cell- cell fusion was seen, which is dependent on the viral concentration. At around 6 hours, we started to detect spike expression, which is mostly localized to the endoplasmic reticulum (ER) and some post ER vesicles (the ERGIC compartment), consistent with the presence of an ER retention signal in the C terminus of the spike. Given that the virus is assembled in a post- Golgi compartment akin to endolysosomes (PMID: 33157038), it is not surprising that most de novo synthesized spikes are localized to this compartment. In fact, it has been suggested by several studies that the deletion of the C- terminal 19 amino acids is necessary to re- distribute the spike to the cell surface (PMID: 32738193), which is the version widely used in cell- cell fusion studies including our study. Thus, under viral infection conditions, particularly during early stages of infection, there should be very little spike signal on the cell surface. We have revised the introduction to better explain this point on page 4. We also rephrase the question as “How spike maintains high fusogenic activities at low surface concentrations remains unclear”. + +Additionally, we added more discussions (page 17). We specifically elaborate on the two- stage fusion model based on reviewer's suggestion: the early phase induced by retribution of the viral spike to the cell surface during viral entry, and a second phase supported by de novo spike synthesis. Our data suggest that even for cell- cell fusion induced by de novo synthesized spike, as shown in HEK293T cell- based fusion assays (Figure 3), heparan sulfate is still involved and can function as a fusion enhancer. Thus, in either stage, concentrating spike at the fusion site, as facilitated by heparan sulfate, is a critical factor in spike- induced membrane fusion. + +Minor points: + +1. Fig. 1H; very modest in vivo antiviral activity in K18-hACE2 mice; does PIXN reduce pathogenicity of infections in this model? + +Response: We agree with the reviewer that the effect of PIXN on viral entry and replication in vivo is modest, highlighting the necessity to further understand the PD and PK properties of + +<--- Page Split ---> + +the drug. Given the relatively weak in vivo antiviral activity, it will be extremely difficult to demonstrate any significant improvement in lung morphology as this type of study is only semi- quantitative (See response to point 1 reviewer 1). + +2. Fig. 3B; the assay is not specifically measuring "virus entry"; y-axis should be relabeled as "infection" + +Response: We have changed the label to "Relative NP level (%)". + +3. Fig 3CD; need to emphasize when PIXN was added (added after virus entry or before?) If before, the smaller syncytia could merely be a result of reduced infection at entry stage, not actually blockade of syncytia per se. + +Response: The drug was added together with the virus. We agree that this experiment by itself does not prove that heparan sulfate regulates cell- cell fusion per se. We change our conclusion to "our results raise the possibility that HS might enhance the fusogenic activities of the spike on the cell surface, which PIXN and MTAN antagonize". + +4. Fig 4, what specifically is "semi-fusion"? Is it different than hemi-fusion? + +Response: hemi- fusion in general refers to a fusion stage in which the lipids in the outer leaflet of the donor and acceptor membranes are mixed, but fusion pore has not formed yet. This stage can either proceed towards the fusion if a fusion pore is formed or relax back to the unfused state. We used semi- fusion to refer to a subsequent stage in which a fusion pore is in forming, although it is not visible by our microscope. It is only indicated by the diffusion of the mCherry signal from the spike cells to ACE2 cells. We now revise the test to clarify this point on page 11. + +5. Fig 5E (and elsewhere); "HS is required..." One can agree that HS facilitates ACE2 clustering but is not "required", consider rephrasing. + +Response: We have rephrased the sentence as suggested. + +6. Fig. 6; ACE2- GS; should test whether ACE2- GS confers SARS-CoV-2 susceptibility to ACE2- negative cells, quantifying ACE2- GS receptor activity relative to ACE2- WT. + +Response: We did show in the Supplementary Fig. 6c that ACE2- GS binds spike with a similar affinity as WT ACE2. To address the reviewer's comment, we tested whether ACE- GS cells allow the entry of spike- coated pseudovirus. As shown in Supplementary Fig. 6e, the endocytosis- mediated entry of pseudovirus- coated by the spike was unaffected in ACE2- GS cells, suggesting that the dimerization function of this loop is only involved in membrane fusion, but dispensable for receptor- mediated endocytosis. + +<--- Page Split ---> + +7. Fig. 7A and 7E; depictions may be communicating inaccurately; a single S trimer may bind more than one ACE2 dimer, resulting in ACE2 clustering. Consider revising the images to account for this possibility. + +Response: As we do not know how exactly ACE2 forms super-clusters, we explain in the figure legend that the drawing only reflects one hypothetical model for simplicity, which does not exclude other modes of ACE2 oligomerization. + +8. Line 161; there is no evidence that N punctae are virions, they could be aggregates of intracellular N protein. + +Response: We have revised the text to clarify this point on page 8. + +9. Lines 166-170; syncytia come from free S proteins going to cell surfaces, and likely far less so from "fusion of viral envelope with plasma membrane" (line 167); this part of text is not interpreting findings in the conventional and well-known ways. + +Response: As explained above, our experimental design allows detection of infection-induced syncytia without significant de novo spike synthesis. Our data also suggest that regardless of the source of the spike (de novo synthesized vs. virally transferred), HS plays a critical role, enhancing the fusion efficiency. The text has been extensively revised to clarify this point. + +10. Lines 286-287; there is no rationale stated for the test to determine whether LS is critical for cell-cell fusion. Consider major point #2 as a possible rationale. + +Response: The rationale to test this domain in cell-cell fusion was simply because the sequence is so conserved evolutionarily, suggesting that it may have an unknown function that could be potentially exploited by the virus. + +11. Fig 7; should incubate the immobilized ACE2 with both soluble RBD monomers and soluble spike trimers, to determine whether trimerized state of spike is needed for ACE2 clustering. + +Response: We performed the proposed experiment and found that the RBD monomers are not capable of inducing ACE2 clustering in the presence of HS (Supplementary Fig. 7a). + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have adressed my concerns + +Reviewer #2 (Remarks to the Author): + +This resubmission contains some valuable findings that support a role for heparin and heparin sulfate in facilitating SARS- CoV- 2 spike- mediated cell- cell fusion. Many of the experiments are sophisticated and the data quality are high. There are interesting findings that cell- cell fusion takes place at large micron- diameter areas in which spikes and receptors are opposed and clustered. There is evidence that heparin and HS can facilitate this clustering. There are data showing that a portion of ACE2, once changed, will eliminate the facilitating effect of ACE2. This is interesting. However, there are still many additional concerns about this paper. Several of the concerns are minor but collectively they indicate that more work and more revision would be needed to improve the report. Similar to the issues during the first round of review, this re- review has questions about the authors' interpretations of findings and their support for the statements made in the text. The concerns are listed below in the order in which they appear in the text. + +1. Line 29, the mechanism of syncytium formation is not "largely unclear". There are many excellent papers describing the mechanisms. +2. Lines 37-38, "the interaction of HS with spike allosterically enables a conserved ACE2 linker..." Readers will be unclear about the meaning of this sentence in the abstract. +3. Lines 39, fusion is targeted by the HS-binding drug, but not "effectively". +4. Line 49, S1 and S2 are not covalently linked. +5. Line 52, the fusion peptide does not "drive fusion...". It is the collapse of the S2 fusion intermediates into helical bundles that drives fusion. +6. Line 70, what is the evidence that viruses, after fusion with plasma membranes, leave behind a cluster of fusion-active spikes? +7. Line 72, what is the evidence that spikes are redistributed on plasma membranes during virus entry, causing spike dilution? These statements are put forward as though they are known, but where are the supporting data? +8. Line 75, even if spikes were deposited on plasma membranes after virion-host cell membrane fusion, they would not then "limit the cell surface spike level". Further clarify. +9. Line 78, it is not known how "low" the spike concentrations are... many unsupported assumptions are here in the introduction. +10. Line 109, Fig 1d data appear to show that PIXN reduces the binding of virions to cells. How can it be claimed that PIXN suppresses endocytic virus entry? +11. Lines 110-116, Fig 1f and 1g show that PIXN is only antiviral at the highest 20 micromolar dose, but at this dose, the PIXN is cytotoxic, so the antiviral effect is likely due to direct PXIN cytotoxicity. This finding does not "show that PIXN has a favorable anti-SARS-CoV-2 activity in vitro". +12. Lines 117-128, PIXN in vivo antiviral activity is so weak that it is difficult to see the value of the findings here. +13. Lines 164-165, it does not appear that investigators "have established PIXN and MTAN as HS-binding drugs that block endocytosis-mediated entry of SARS-CoV-2". Precisely where is the evidence for this statement? +14. Lines 173-174, delta entry by plasma membrane is assumed but not shown, the statement on these lines should be tempered. +15. Line 176, you mean de novo "spike" synthesis, not synthesis in general. +16. Line 185-188, why would multiple rounds of fusion be required to fuse up to 80 cells? Were inoculated virions rinsed away after a 4C binding period? If not, then virions in media could keep binding to cells, generating syncytia via fusion-from-without. +17. Line 186-187, is it known that the spike molecules are "transferred from the viral particles"? Might virions bind between cells, forming virion bridges between cells, which then offer an intercellular fusion to occur via virions? +18. Line 191-192, does PXIN and MTAN reduce the binding of virions to cells, in possibly doing so, reducing the level of virion-based "fusion-from-without"? This would be an interpretation of findings + +<--- Page Split ---> + +that does not raise the possibility that HS enhances the fusogenic activation to the spike on the cell surface. + +19. Lines 261-262, how can it be claimed that the red arrow is pointing to a fusion event? In the figure legend it is stated as though this is a fact, but in the text, one reads that the red arrow "probably points to a fusion event. + +20. Lines 359-360, do spike antibodies block syncytia, if yes, then how do syncytia allow viruses to escape antibody-mediated neutralization? + +21. Lines 365-367, what is the evidence that membrane fusion activity of spike can sustain over multiple rounds? Were virions bound to cells at 4C, then cells rinsed extensively, then incubated to the 4 hpi time point without residual inoculum in the media, or were virions applied to cells, leaving residual inoculum to continue binding to cells, allowing for continued fusion from without to occur? + +22. Lines 380-381, what alternative models are envisioned? Consider expanding here. + +23. ACE2-GS, does the portion of ACE2 replaced by GS include the ADAM17/TACE and TMPRSS2 cleavage site? Is this relevant to ACE2-GS activity? + +24. Can there be some discussion of the findings in this paper with those in this recent paper that has been getting some press? Eiring et al, Coronavirus Use ACE2 Monomers as Entry-Receptors, Angewandte Chemie International Edition(2023). DOI: 10.1002/anie.202300821 + +<--- Page Split ---> + +We thank this reviewer for careful reviewing of our manuscript. We have made changes to the text to clarify all the points. + +1. Line 29, the mechanism of syncytium formation is not "largely unclear". There are many excellent papers describing the mechanisms. + +Response: We have revised the text. It now reads as "To better elucidate the mechanism of syncytium formation associated severe COVID- 19, we...." + +2. Lines 37-38, "the interaction of HS with spike allosterically enables a conserved ACE2 linker...." Readers will be unclear about the meaning of this sentence in the abstract. Response: Since the spike binds ACE2 at a site distal from the linker segment, we assumed that the activation of this linker segment during ACE2 clustering must occur by an allosteric mechanism. We agree that it may not be easy to get this point without reviewing the data. We removed the word "allosterically" from the abstract. + +3. Lines 39, fusion is targeted by the HS-binding drug, but not "effectively". Response: We removed "effectively". + +4. Line 49, S1 and S2 are not covalently linked. Response: We have corrected the text on page 3. + +5. Line 52, the fusion peptide does not "drive fusion..". It is the collapse of the S2 fusion intermediates into helical bundles that drives fusion. + +Response: We changed the text to "inducing TMPRSS2- mediated cleavage of the S2 fragment that ultimately leads to the collapse of an S2 fusion intermediate into a helical bundle to drive the fusion of viral membranes with the plasma membrane." + +6. Line 70, what is the evidence that viruses, after fusion with plasma membranes, leave behind a cluster of fusion-active spikes? + +Response: If all spike molecules were cleaved by TMPRSS2 during viral entry, given the short time window of the viral entry, the cleavage should be extremely efficient. This is INCONSISTENT with the fact that the virus has constantly evolved in a direction that allows the spike to be cleaved more and more efficiently by TMPRSS2 (Rajah, 2021, EMBO), suggesting that the S2 cleavage by TMPRSS2 is far from optimal. We now add a sentence on page 3 to highlight this point. Additionally, a recent study showed that even when both spike and TMPRSS2 are co- expressed in the same cell, the cleavage only occurs to a small population of spike (PMID: 32703818). Likewise, in our cell- cell fusion assay, we measured the cleavage of S2 by a chase experiment (Figure S5d, e). Even after 2 hours of incubation (all cells have fused at least once), only a small fraction of the S2 fragment was converted to S2'. Note that this experiment was conducted with the spike from the Delta variant. Thus, even for spike with a strong fusion activity, it is still cleaved very inefficiently. These observations all suggest that membrane fusion can take place with only a small fraction of spike being consumed by cleavage. + +<--- Page Split ---> + +We added a sentence on page 3 to highlight the evolution of the virus, which is associated with increased spike cleavage efficiency. + +7. Line 72, what is the evidence that spikes are redistributed on plasma membranes during virus entry, causing spike dilution? These statements are put forward as though they are known, but where are the supporting data? + +Response: When a membrane- encircled virus fuses with host cells, the viral membrane would become part of the plasma membrane. This is a well- accepted concept in the membrane fusion field (see the cited review by Harrison, S. 2008 Nat. Strul. Mol. Biol. PMID: 18596815). Since spike is a membrane protein, it should be free to distribute to the entire cell surface by diffusion. We now add a sentence on page 4 to clarify this point. It reads as "Strikingly, when the virus fuses with the plasma membrane, the viral membrane becomes part of the cell membrane, leading to a drastic expansion of the spike- containing membranes...." + +8. Line 75, even if spikes were deposited on plasma membranes after virion-host cell membrane fusion, they would not then "limit the cell surface spike level". Further clarify. + +Response: What we meant was that the expansion of the spike- containing membranes during viral entry and the retention of the newly synthesized spike to the cell surface by the ER retention signal collectively limit the cell surface spike level. We have re- worded the sentences to avoid the confusion. + +9. Line 78, it is not known how "low" the spike concentrations are... many unsupported assumptions are here in the introduction. + +Response: We removed the phrase "at low surface concentration". + +10. Line 109, Fig 1d data appear to show that PIXN reduces the binding of virions to cells. How can it be claimed that PIXN suppresses endocytic virus entry? + +Response: The reviewer is correct that we did not detect significant accumulation of the viral particles on the lateral cell surface in these confocal images of PIXN-treated cells (Fig. 1d). However, since we detected no effect of these drugs on the interaction of spike with ACE2 (Fig. S4c) and also because the interaction of spike- expressing cells with ACE2 cells was not affected by PIXN (Fig. S4d, e), we believe that PIXN does not disrupt the spike (and therefore the virus) binding to ACE2 cells. The lack of cell surface spike staining in drug- treated cells was most likely caused by a detection sensitivity issue or by our initial focus on confocal sections around endolysosomes. As we later revealed in Fig. S3d by 3D reconstruction, the viral particles on the cell surface are usually clustered on apical surface of the cell, which would escape detection by deeper confocal sections in Fig. 1d. + +To avoid potential overinterpretation of the data, we have tempered our conclusion. The sentence reads as "suggesting that the drug inhibits viral entry at a step upstream of endocytosis". + +11. Lines 110-116, Fig 1f and 1g show that PIXN is only antiviral at the highest 20 micromolar dose, but at this dose, the PIXN is cytotoxic, so the antiviral effect is likely due to direct PIXN + +<--- Page Split ---> + +cytotoxicity. This finding does not "show that PIXN has a favorable anti- SARS- CoV- 2 activity in vitro". + +Response: Please note that even at the lowest dose chosen (200 nM), there was a significant inhibition of viral replication when compared to the vehicle controls (the dotted lines). We have changed the text to make this point clear. + +12. Lines 117-128, PIXN in vivo antiviral activity is so weak that it is difficult to see the value of the findings here. + +Response: We agree with the reviewer that the in vivo efficacy of PIXN is not very strong. However, we feel that it is important to include the data to make the study complete. The result may provide a base for future optimization studies. Considering the reviewer's criticism, we now move this data to supplementary Fig. 1d, e. + +13. Lines 164-165, it does not appear that investigators "have established PIXN and MTAN as HSbinding drugs that block endocytosis-mediated entry of SARS-CoV-2". Precisely where is the evidence for this statement? + +Response: The binding of PIXN and MTAN to HS was shown in Figure 2 and related supplementary figures. The inhibition of SARS-CoV-2 entry was shown in Figure 1d. We now refer to these figures in the text. + +14. Lines 173-174, delta entry by plasma membrane is assumed but not shown, the statement on these lines should be tempered. + +Response: We now add an additional reference that shows increased membrane fusion activity of Delta spike. This study (Rajah, 2021, EMBO), combined with the paper cited in the previous version (Zhang, 2022 Science), suggests that delta strain should primarily use the plasma membrane as the entry site provided sufficient TMPRSS2 expression. We also point out that in our immunostaining experiment (Fig. 3a), the viral protein NP is not localized to the endolysosome, consistent with the notion that it uses the plasma membrane as the entry site. + +15. Line 176, you mean de novo "spike" synthesis, not synthesis in general. + +Response: The reviewer is correct. We have added "Spike" to the sentence. + +16. Line 185-188, why would multiple rounds of fusion be required to fuse up to 80 cells? Were inoculated virions rinsed away after a 4C binding period? If not, then virions in media could keep binding to cells, generating syncytia via fusion-from-without. + +Response: We now include a brief discussion about "fusion-from-without", a relatively uncommon mechanism for virus-induced cell-cell fusion. Specifically, we cited a recent paper in iScience (Theuerkauf, 2021 iScience), which demonstrate that for virus-like particles containing spike, it needs very high concentrations to induce fusion-from-without (5,000 VLP/cell). This would not happen under our experimental condition given that relatively low viral titer used. + +17. Line 186-187, is it known that the spike molecules are "transferred from the viral particles"? + +<--- Page Split ---> + +Might virions bind between cells, forming virion bridges between cells, which then offer an inter- cellular fusion to occur via virions? + +Response: Again, the scenario described here (also referred to as fusion- from- without) should not happen under our experimental conditions as explained for point 16. + +18. Line 191-192, does PXIN and MTAN reduce the binding of virions to cells, in possibly doing so, reducing the level of virion- based "fusion- from- without"? This would be an interpretation of findings that does not raise the possibility that HS enhances the fusogenic activation to the spike on the cell surface. + +Response: We show in Supplementary Fig. 4c, d, e that neither PXIN nor MTAN affects the binding of spike to ACE2 or ACE2-expressing cells. Thus, these drugs should not affect virus binding to the cells. Additionally, as pointed out above, "fusion- from- without" does not happen under our experimental conditions. + +19. Lines 261-262, how can it be claimed that the red arrow is pointing to a fusion event? In the figure legend it is stated as though this is a fact, but in the text, one reads that the red arrow "probably points to a fusion event. + +Response: We added probably to the figure legend. + +20. Lines 359-360, do spike antibodies block syncytia, if yes, then how do syncytia allow viruses to escape antibody-mediated neutralization? + +Response: The statement here is based on the following article, which shows that viral spreading via syncytia is more resistant to neutralizing antibodies (Zeng 2022, PNAS). We have revised text. It now reads as "it was proposed that this transmission route allows the virus to escape immune surveillance and antibody-mediated neutralization". + +21. Lines 365-367, what is the evidence that membrane fusion activity of spike can sustain over multiple rounds? Were virions bound to cells at 4C, then cells rinsed extensively, then incubated to the 4 hpi time point without residual inoculum in the media, or were virions applied to cells, leaving residual inoculum to continue binding to cells, allowing for continued fusion from without to occur? + +Response: We have removed this speculative statement from the discussion. + +22. Lines 380-381, what alternative models are envisioned? Consider expanding here. Response: We mentioned that "How HS facilitates ACE2 super-cluster formation remains to be determined" on page 18. At this point, any models would be speculative in nature. We only mentioned one possibility based on previous structural studies on the role of HS in regulating FGF receptor oligomerization. The analogy raises the possibility that a similar mechanism may be applied to ACE2 oligomerization. + +23. ACE2-GS, does the portion of ACE2 replaced by GS include the ADAM17/TACE and TMPRSS2 cleavage site? Is this relevant to ACE2-GS activity? + +Response: The answer is No. The linker segment is from 721- 740. The TMPRSS2 and ADAM17/TACE-mediated cleavage occurs between 697- 716 (PMID: 24227843). + +<--- Page Split ---> + +24. Can there be some discussion of the findings in this paper with those in this recent paper that has been getting some press? Eiring et al, Coronavirus Uses ACE2 Monomers as Entry-Receptors, Angewandte Chemie International Edition(2023). DOI: 10.1002/anie.202300821 Response: We now mentioned the article that suggests the possibility of ACE2 being a monomer, which if true would certainly impact our model. However, this new study challenges a well-established dogma in the field with only limited evidence (entirely imaging-based). The controversy certainly will require more studies to resolve. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #2 (Remarks to the Author): + +The authors adequately responded to second- round reviewer questions. + +<--- Page Split ---> diff --git a/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b6f540ebb0d13b4838fd50bdec83ad167c3f55fe --- /dev/null +++ b/peer_reviews/98cec2f23ed2985ed8a2bd919f3ccd9e34bc3cf9e1771a61b8dd869f34c4e876/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,491 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 505, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[67, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 783]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 88, 305, 104]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 117, 404, 132]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 144, 876, 270]]<|/det|> +Qi Zhang and colleagues investigated the role of heparin sulphate (HS) in SARS- CoV- 2 spike mediated fusion and syncytium formation. They started by testing newly generated MTAN- related drugs to investigate their effect on SARS- CoV- 2 infection and their toxicity. They selected PIXN (LC1541) as their best candidate. It binds specific sulphate groups on HS and inhibits SARS- CoV- 2 entry and replication in different systems including primary air- liquid cells and K18- hACE2 mice. Next, they showed that HS depletion inhibits spike mediated cell- cell fusion using both drugs and knock- out cells. They investigated the mechanism underlying HS- mediated increased fusion, showing that HS does not promote Spike- ACE2 binding or S2' cleavage. Using cell- cell fusion and in vitro techniques they show that HS induce clustering of ACE2 and promotion of fusion pore formation. + +<|ref|>text<|/ref|><|det|>[[115, 282, 872, 310]]<|/det|> +Overall, the article is clear and provides interesting mechanistic data on the action of HS on ACE2 and SARS- CoV- 2 fusion. + +<|ref|>text<|/ref|><|det|>[[116, 325, 234, 339]]<|/det|> +Main comments + +<|ref|>text<|/ref|><|det|>[[115, 365, 864, 394]]<|/det|> +1. Fig 1. H. For the mouse experiments it would have been interesting to include data on the clinical score for SARS-CoV-2 infections and comment on the toxicity of the drug in vivo. + +<|ref|>text<|/ref|><|det|>[[115, 406, 879, 531]]<|/det|> +2. Fig. 3 - Cell line infection experiments are indicated being done at 4h post infection at relatively high MOIs (MOI of 0.5 or 0.1 was calculated on Vero TMPRSS2 cells) using Vero cells overexpressing both human ACE2 and TMPRSS2. At 4h post-infection the authors observed large syncytia and clear N staining (Fig. 3). 4h post infection seems like a very early timepoint to detect extended cell-cell fusion. According to published data (for instance Koch et al. EMBO, 2021) there is no significant detection of N after 4h of infection in Vero cells and from our experience, syncytia formation generally starts only as early as 6-7h post infection in highly permissive cell lines. Is this observation due to the usage of VeroE6 expressing both human ACE2 and TMPRSS2 making them highly fusogenic? Could the cell-cell fusion observed be due to fusion from without? + +<|ref|>text<|/ref|><|det|>[[115, 544, 876, 587]]<|/det|> +3. The authors should comment on the choice of this 4h timepoint. The results should be confirmed at lower MOIs, possibly including a drug blocking viral replication to distinguish fusion from without and de-novo produced spike. + +<|ref|>text<|/ref|><|det|>[[115, 600, 876, 670]]<|/det|> +4. Fig. 6. The authors identified a region of ACE2 promoting HS mediated receptor clustering. It would have been interesting to test if this region of ACE2 also plays a role if viral entry in addition to its role on cell-cell fusion. As in figure 1 and 3 the authors used virus and pseudotypes to show that HS modulating drugs impact viral entry, it may be worth testing if the phenotype for cell-cell fusion with this ACE2 mutant also translates to differential viral entry. + +<|ref|>text<|/ref|><|det|>[[116, 725, 404, 740]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 752, 876, 835]]<|/det|> +This submission provides interesting findings to support the hypothesis that heparin and HSPGs facilitate the coalescence of target- cell ACE2 with effector- cell spikes. This coalescence correlates with higher levels of spike- directed cell- cell fusion. The authors suggest that this higher cell- cell fusion correlates with more severe COVID, and thus hypothesize that drugs interfering with this HSPG activity could be useful in mitigating COVID. They test new HSPG- binding agents as SARS- CoV- 2 antivirals and find that one, PIXN, is moderately antiviral at nontoxic concentrations. + +<|ref|>text<|/ref|><|det|>[[115, 847, 872, 876]]<|/det|> +The significance of the findings appears moderate but with additional research there may be potential for HSPG interference as an antiviral measure. + +<|ref|>text<|/ref|><|det|>[[115, 889, 805, 905]]<|/det|> +The findings are sophisticated and high quality. These include results in medicinal chemistry, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 875, 133]]<|/det|> +biochemistry and virology, and they include excellent imaging data. However, even with the abundant data, the mechanism by which heparin and HSPGs facilitate viral fusion seems unclear. The summary models of ACE2 clustering in Fig 7 are only partially supported by the data. + +<|ref|>text<|/ref|><|det|>[[115, 145, 876, 188]]<|/det|> +The major issues in this review are centered on authors' rationales, i.e., justifications for experiments, and on authors' interpretations of findings. The minor issues include suggestions for additional experiments and modifications of the text. + +<|ref|>sub_title<|/ref|><|det|>[[115, 201, 213, 215]]<|/det|> +## Major points: + +<|ref|>text<|/ref|><|det|>[[115, 215, 880, 325]]<|/det|> +1. The model is that HSPGs facilitate coalescence of ACE2 on target cells. However, when HSPGs are not present or are inhibited by bound PIXN, there are still some ACE2-spike synapses and also cell-cell fusions. This may arise because spikes themselves are clustered on surfaces of effector cells, independent of whether the spikes are opposed next to adjacent ACE2 on target cells. Spikes coalesce in lipid rafts in plasma membranes of infected cells and spike-transfected cells. The investigators should image the positions of spike proteins on plasma membranes both before and after co-cultivation of spike-expressing cells with target cells. Clustered spikes will likely cluster ACE2 upon contact of spike-expressing and ACE2-expressing cells. + +<|ref|>text<|/ref|><|det|>[[115, 325, 880, 393]]<|/det|> +2. The finding that ACE2 lacking the dimerization domain (ACE2-GS) fails to coalesce in response to HSPGs is interesting. However, the interpretation of the result should be broadened. One spike trimer can bind more than one ACE2, generating ACE2 coalescence. If ACE2 is dimeric, then higher-order spike trimer: ACE2 dimer zippering (coalescence) seems likely. Alternative models for ACE2 clustering should be put forward. + +<|ref|>text<|/ref|><|det|>[[115, 393, 877, 492]]<|/det|> +3. Premise – justification for the study appeals to the need for durably active spikes as syncytia expand, even in the face of spike “dilution” on the ever-increasing plasma membrane surface areas of syncytia. This is an interesting idea but it does not have any any experimental support and it may not be correct to assume that spikes are not continuously synthesized as syncytia expand. There could be plenty enough continued spike synthesis to generate large syncytia. This appeal to spike dilution appears prominently in the intro and discussion sections and this reviewer feels it should be tempered or communicated in context of other equally or more credible views about syncytial developments. + +<|ref|>sub_title<|/ref|><|det|>[[115, 504, 213, 517]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[111, 517, 880, 850]]<|/det|> +1. Fig. 1H; very modest in vivo antiviral activity in K18-hACE2 mice; does PIXN reduce pathogenicity of infections in this model? +2. Fig. 3B; the assay is not specifically measuring "virus entry"; y-axis should be relabeled as "infection" +3. Fig 3CD; need to emphasize when PIXN was added (added after virus entry or before?) If before, the smaller syncytia could merely be a result of reduced infection at entry stage, not actually blockade of syncytia per se. +4. Fig 4, what specifically is "semi-fusion"? Is it different than hemi-fusion? +5. Fig 5E (and elsewhere); "HS is required..." One can agree that HS facilitates ACE2 clustering but is not "required", consider rephrasing. +6. Fig. 6; ACE2-GS; should test whether ACE2-GS confers SARS-CoV-2 susceptibility to ACE2-negative cells, quantifying ACE2-GS receptor activity relative to ACE2-WT. +7. Fig. 7A and 7E; depictions may be communicating inaccurately; a single S trimer may bind more than one ACE2 dimer, resulting in ACE2 clustering. Consider revising the images to account for this possibility. +8. Line 161; there is no evidence that N punctae are virions, they could be aggregates of intracellular N protein. +9. Lines 166-170; syncytia come from free S proteins going to cell surfaces, and likely far less so from "fusion of viral envelope with plasma membrane" (line 167); this part of text is not interpreting findings in the conventional and well-known ways. +10. Lines 286-287; there is no rationale stated for the test to determine whether LS is critical for cell-cell fusion. Consider major point #2 as a possible rationale. +11. Fig 7; should incubate the immobilized ACE2 with both soluble RBD monomers and soluble spike trimers, to determine whether trimerized state of spike is needed for ACE2 clustering. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 874, 127]]<|/det|> +We thank the reviewers for their positive and constructive suggestions. We have done many additional experiments to address these comments, as explained below point- by- point. + +<|ref|>text<|/ref|><|det|>[[116, 144, 419, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 179, 866, 365]]<|/det|> +Qi Zhang and colleagues investigated the role of heparan sulphate (HS) in SARS- CoV- 2 spike mediated fusion and syncytium formation. They started by testing newly generated MTAN- related drugs to investigate their effect on SARS- CoV- 2 infection and their toxicity. They selected PIXN (LC1541) as their best candidate. It binds specific sulphate groups on HS and inhibits SARS- CoV- 2 entry and replication in different systems including primary air- liquid cells and K18- hACE2 mice. Next, they showed that HS depletion inhibits spike mediated cell- cell fusion using both drugs and knock- out cells. They investigated the mechanism underlying HS- mediated increased fusion, showing that HS does not promote Spike- ACE2 binding or S2' cleavage. Using cell- cell fusion and in vitro techniques they show that HS induce clustering of ACE2 and promotion of fusion pore formation. + +<|ref|>text<|/ref|><|det|>[[116, 382, 844, 419]]<|/det|> +Overall, the article is clear and provides interesting mechanistic data on the action of HS on ACE2 and SARS- CoV- 2 fusion. + +<|ref|>text<|/ref|><|det|>[[116, 437, 690, 455]]<|/det|> +Response: We thank this reviewer for his/her enthusiasm in our study. + +<|ref|>text<|/ref|><|det|>[[116, 474, 248, 490]]<|/det|> +Main comments + +<|ref|>text<|/ref|><|det|>[[116, 492, 853, 528]]<|/det|> +1. Fig 1. H. For the mouse experiments it would have been interesting to include data on the clinical score for SARS-CoV-2 infections and comment on the toxicity of the drug in vivo. + +<|ref|>text<|/ref|><|det|>[[114, 545, 875, 675]]<|/det|> +Response: When we examined the viral titer in the lungs of mice treated with PIXN or untreated after infection, we did weight the lungs. We noticed a small reduction in lung weight in mice treated with PIXN (see below), suggesting that the drug might have some side effect on the lung. Because of this, and also because pathology- based scoring is less quantitative and has a narrower dynamic range compared to viral titer measurement, we chose the latter to determine the effect of drug treatment on viral entry and replication in mice. + +<|ref|>text<|/ref|><|det|>[[114, 692, 870, 840]]<|/det|> +From the drug development perspective, the reviewer raised an excellent point. However, we would like to emphasize that the significance of our finding is the mechanism underlying spike- induced membrane fusion, which reveals how the virus co- opts a cell surface molecule to enhance spike's membrane fusion activity. We now add a sentence on page 6 to clarify this, which reads as "The low in vivo anti- SARS- CoV- 2 activity may be due to PIXN binding to HS in non- targeting tissues, which would reduce its effective concentration in the lung, suggesting that further optimizations are required to advance HS inhibitors into clinics as an anti- viral agent." + +<|ref|>text<|/ref|><|det|>[[116, 858, 867, 895]]<|/det|> +The toxicity of Pixantrone (PIXN) has been extensively evaluated in animals and in clinics (PMID: 31997425; ref 32 in the manuscript). To confirm this, we treated mice with PIXN and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 863, 145]]<|/det|> +analyzed the serum aspartate aminotransferase (AST) level as an indicator of liver toxicity 3 days after drug injection. We did not notice any increase in the AST level in the serum (Supplementary Fig. 1c), consistent with the known safety profile of this drug. + +<|ref|>text<|/ref|><|det|>[[114, 162, 879, 346]]<|/det|> +2. Fig. 3 - Cell line infection experiments are indicated being done at 4h post infection at relatively high MOIs (MOI of 0.5 or 0.1 was calculated on Vero TMPRSS2 cells) using Vero cells overexpressing both human ACE2 and TMPRSS2. At 4h post-infection the authors observed large syncytia and clear N staining (Fig. 3). 4h post infection seems like a very early timepoint to detect extended cell-cell fusion. According to published data (for instance Koch et al. EMBO, 2021) there is no significant detection of N after 4h of infection in Vero cells and from our experience, syncytia formation generally starts only as early as 6-7h post infection in highly permissive cell lines. Is this observation due to the usage of VeroE6 expressing both human ACE2 and TMPRSS2 making them highly fusogenic? Could the cell-cell fusion observed be due to fusion from without? + +<|ref|>text<|/ref|><|det|>[[114, 364, 881, 512]]<|/det|> +Response: The reviewer is correct that we chose 4- hour post infection (hpi) because we could not detect significant de novo spike synthesis at this time point, yet the infection- induced cell- cell fusion could be observed (Supplementary Fig. 3d). When we stained cells with a spike antibody, we could detect some spike signal as clustered dots on the surface 4 hpi (Supplementary Fig. 3d, Video 1), whereas de novo synthesized spike at 6 hpi is mostly localized at a peri- nuclear ERGIC compartment (Supplementary Fig. 3d). This difference suggests that the spike positive signal on the cell surface 4 hpi is derived from viral membrane during viral entry. + +<|ref|>text<|/ref|><|det|>[[114, 529, 864, 621]]<|/det|> +As for the MOI chosen in this study, we used MOI of 0.1- 0.5, which is in line with published studies. For example, the study by Koch et al. EMBO 2021 used a MOI of 0.2. The paper by Braga L et al. (Nature 2021, https://doi.org/10.1038/s41586- 021- 03491- 6, Figure 3) used a MOI of 0.5. In the study by Blanco- Melo, D. and colleagues (Cell 2020), the authors used 0.2 as low MOI and 2 as high MOI. + +<|ref|>text<|/ref|><|det|>[[114, 639, 877, 787]]<|/det|> +One key difference between our study and previous studies on SARS- CoV- 2- induced syncytia is in the viral strain. Apparently, most studies published before 2021 used early strains such as the Washington strain or a closely related one. In our hand, only the Delta strain generates giant syncytia 4 h post infection, whereas the Washington strain only generates medium size syncytia after a much longer incubation (9 h) (Supplementary Fig. 3b). We never observed any syncytia with more than 2 nuclei per cell without infection, suggesting that the cell- cell fusion cannot be due to fusion from without. A few cells with two nuclei in uninfected cells are apparently caused by cell division. + +<|ref|>text<|/ref|><|det|>[[115, 820, 837, 875]]<|/det|> +3. The authors should comment on the choice of this 4h time points. The results should be confirmed at lower MOIs, possibly including a drug blocking viral replication to distinguish fusion from without and de-novo produced spike. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 878, 220]]<|/det|> +Response: We now add a sentence on page 8 to explain the choice of this time point (no significant de novo spike synthesis at this early time point). We repeated the infection experiment at a low MOI (0.01) for 4 and 6 hours, respectively, and in both Vero E6 cells and the highly permissive Vero TA6 cells (expressing ACE2 and TMPRSS2). As expected, we saw very few syncytia. Nevertheless, there seems to be a trend that is consistent with Delta being more potent in inducing cell- cell fusion and TA6 being more permissive than Vero E6 cells in cell- cell fusion (Supplementary Fig. 3c). + +<|ref|>text<|/ref|><|det|>[[114, 236, 880, 329]]<|/det|> +4. Fig. 6. The authors identified a region of ACE2 promoting HS mediated receptor clustering. It would have been interesting to test if this region of ACE2 also plays a role if viral entry in addition to its role on cell-cell fusion. As in figure 1 and 3 the authors used virus and pseudotypes to show that HS modulating drugs impact viral entry, it may be worth testing if the phenotype for cell-cell fusion with this ACE2 mutant also translates to differential viral entry. + +<|ref|>text<|/ref|><|det|>[[115, 346, 877, 420]]<|/det|> +Response: We tested the entry of pseudovirus-coated with the spike of the Washington strain, which is mediated primarily by ACE2-mediated endocytosis. In ACE2-GS-GFP cells, the entry of this virus appears identical to that in WT ACE2-GFP cells (Supplementary Fig. 6e), suggesting that this loop is not required for ACE2-mediated endocytosis of SARS-CoV-2. + +<|ref|>text<|/ref|><|det|>[[116, 438, 419, 455]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 473, 877, 602]]<|/det|> +This submission provides interesting findings to support the hypothesis that heparin and HSPGs facilitate the coalescence of target- cell ACE2 with effector- cell spikes. This coalescence correlates with higher levels of spike- directed cell- cell fusion. The authors suggest that this higher cell- cell fusion correlates with more severe COVID, and thus hypothesize that drugs interfering with this HSPG activity could be useful in mitigating COVID. They test new HSPG- binding agents as SARS- CoV- 2 antivirals and find that one, PIXN, is moderately antiviral at nontoxic concentrations. + +<|ref|>text<|/ref|><|det|>[[115, 620, 857, 656]]<|/det|> +The significance of the findings appears moderate but with additional research there may be potential for HSPG interference as an antiviral measure. + +<|ref|>text<|/ref|><|det|>[[115, 674, 855, 766]]<|/det|> +The findings are sophisticated and high quality. These include results in medicinal chemistry, biochemistry and virology, and they include excellent imaging data. However, even with the abundant data, the mechanism by which heparin and HSPGs facilitate viral fusion seems unclear. The summary models of ACE2 clustering in Fig 7 are only partially supported by the data. + +<|ref|>text<|/ref|><|det|>[[114, 784, 874, 896]]<|/det|> +Response: We agree with this reviewer that from a drug development perspective, the potency of PIXN may not be significant enough to warrant clinical testing at this points. However, it is worth noting that the most important finding of our study is about the unexpected role of heparan sulfate in promoting spike- mediated cell- cell fusion. We show that 1) ACE2 forms a super- cluster upon spike engagement, which is dependent on heparan sulfate; 2) ACE2 super- clustering concentrates the spike at the membrane contact site, which + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 878, 145]]<|/det|> +facilitates fusion pore formation; 3) Heparan sulfate acts through a conserved loop in ACE2 to promote receptor super- clustering. All these findings are novel, which significantly advance our understanding on the mechanism of spike- mediated membrane fusion. + +<|ref|>text<|/ref|><|det|>[[115, 163, 870, 218]]<|/det|> +The major issues in this review are centered on authors' rationales, i.e., justifications for experiments, and on authors' interpretations of findings. The minor issues include suggestions for additional experiments and modifications of the text. + +<|ref|>text<|/ref|><|det|>[[115, 238, 224, 254]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[115, 255, 882, 402]]<|/det|> +1. The model is that HSPGs facilitate coalescence of ACE2 on target cells. However, when HSPGs are not present or are inhibited by bound PIXN, there are still some ACE2-spike synapses and also cell-cell fusions. This may arise because spikes themselves are clustered on surfaces of effector cells, independent of whether the spikes are opposed next to adjacent ACE2 on target cells. Spikes coalesce in lipid rafts in plasma membranes of infected cells and spike-transfected cells. The investigators should image the positions of spike proteins on plasma membranes both before and after co-cultivation of spike-expressing cells with target cells. Clustered spikes will likely cluster ACE2 upon contact of spike-expressing and ACE2-expressing cells. + +<|ref|>text<|/ref|><|det|>[[114, 419, 877, 585]]<|/det|> +Response: We thank the reviewer for this excellent suggestion. We have done the suggested experiment (Supplementary Fig. 5a). We stained spike transfected cells with a spike specific antibody either without or after co- culturing with ACE2 WT- or ACE2 GS- GFP cells. As pointed out by the reviewer, spike does form small coalesces on the cell surface, but these small puncta are uniformly distributed throughout the surface. By contrast, when spike cells encounter ACE2- GFP cells, the spike forms giant super- clusters that are co- localized with ACE2- GFP. Interestingly, when spike cells contact ACE2 GS- GFP cells, the spike clustering is significantly reduced (Supplementary Fig. 5a). This experiment suggests that it is ACE2 clustering that drives spike super- cluster formation, but not the other way around. + +<|ref|>text<|/ref|><|det|>[[115, 603, 881, 696]]<|/det|> +2. The finding that ACE2 lacking the dimerization domain (ACE2-GS) fails to coalesce in response to HSPGs is interesting. However, the interpretation of the result should be broadened. One spike trimer can bind more than one ACE2, generating ACE2 coalescence. If ACE2 is dimeric, then higher-order spike trimer: ACE2 dimer zippering (coalescence) seems likely. Alternative models for ACE2 clustering should be put forward. + +<|ref|>text<|/ref|><|det|>[[114, 713, 874, 842]]<|/det|> +Response: We agree with the reviewer that our data does not suggest how exactly ACE2 super- clusters are formed. We have now added more discussions on this point including a brief mentioning of the previous study on the role of heparan sulfate in facilitating FGF2 receptor dimerization (page 17). In this case, a structural study suggests that heparan sulfate can bind two FGF2 receptors to facilitate its dimerization. The linker segment may be involved in heparan sulfate- mediated ACE2 oligomerization in a similar way, but we do point out that "other alternative models cannot be excluded." + +<|ref|>text<|/ref|><|det|>[[115, 861, 862, 898]]<|/det|> +The zippering model suggested by the reviewer is also possible. However, in our initial attempt, we tried to reconstitute ACE2 super- clustering in solution, but failed to detect any + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 875, 145]]<|/det|> +clustered ACE2 despite the use of a trimeric spike. This argues against a simple zippering model. Only after we attached the ACE2 receptor to lipid bilayers, did we see ACE2 clustering in the presence of the spike and heparan sulfate. + +<|ref|>text<|/ref|><|det|>[[114, 162, 875, 310]]<|/det|> +3. Premise – justification for the study appeals to the need for durably active spikes as syncytia expand, even in the face of spike “dilution” on the ever-increasing plasma membrane surface areas of syncytia. This is an interesting idea but it does not have any any experimental support and it may not be correct to assume that spikes are not continuously synthesized as syncytia expand. There could be plenty enough continued spike synthesis to generate large syncytia. This appeal to spike dilution appears prominently in the intro and discussion sections and this reviewer feels it should be tempered or communicated in context of other equally or more credible views about syncytial developments. + +<|ref|>text<|/ref|><|det|>[[114, 328, 882, 605]]<|/det|> +Response: The reviewer is correct that during prolonged infection, there will be de novo synthesis of the spike. According to our time-course studies, we could not detect any spike expression in cells 4 hpi, yet in cells infected with the Delta strain, massive cell- cell fusion was seen, which is dependent on the viral concentration. At around 6 hours, we started to detect spike expression, which is mostly localized to the endoplasmic reticulum (ER) and some post ER vesicles (the ERGIC compartment), consistent with the presence of an ER retention signal in the C terminus of the spike. Given that the virus is assembled in a post- Golgi compartment akin to endolysosomes (PMID: 33157038), it is not surprising that most de novo synthesized spikes are localized to this compartment. In fact, it has been suggested by several studies that the deletion of the C- terminal 19 amino acids is necessary to re- distribute the spike to the cell surface (PMID: 32738193), which is the version widely used in cell- cell fusion studies including our study. Thus, under viral infection conditions, particularly during early stages of infection, there should be very little spike signal on the cell surface. We have revised the introduction to better explain this point on page 4. We also rephrase the question as “How spike maintains high fusogenic activities at low surface concentrations remains unclear”. + +<|ref|>text<|/ref|><|det|>[[114, 622, 879, 770]]<|/det|> +Additionally, we added more discussions (page 17). We specifically elaborate on the two- stage fusion model based on reviewer's suggestion: the early phase induced by retribution of the viral spike to the cell surface during viral entry, and a second phase supported by de novo spike synthesis. Our data suggest that even for cell- cell fusion induced by de novo synthesized spike, as shown in HEK293T cell- based fusion assays (Figure 3), heparan sulfate is still involved and can function as a fusion enhancer. Thus, in either stage, concentrating spike at the fusion site, as facilitated by heparan sulfate, is a critical factor in spike- induced membrane fusion. + +<|ref|>text<|/ref|><|det|>[[115, 789, 225, 805]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[115, 808, 792, 844]]<|/det|> +1. Fig. 1H; very modest in vivo antiviral activity in K18-hACE2 mice; does PIXN reduce pathogenicity of infections in this model? + +<|ref|>text<|/ref|><|det|>[[115, 862, 879, 899]]<|/det|> +Response: We agree with the reviewer that the effect of PIXN on viral entry and replication in vivo is modest, highlighting the necessity to further understand the PD and PK properties of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 857, 145]]<|/det|> +the drug. Given the relatively weak in vivo antiviral activity, it will be extremely difficult to demonstrate any significant improvement in lung morphology as this type of study is only semi- quantitative (See response to point 1 reviewer 1). + +<|ref|>text<|/ref|><|det|>[[115, 163, 847, 199]]<|/det|> +2. Fig. 3B; the assay is not specifically measuring "virus entry"; y-axis should be relabeled as "infection" + +<|ref|>text<|/ref|><|det|>[[115, 218, 641, 236]]<|/det|> +Response: We have changed the label to "Relative NP level (%)". + +<|ref|>text<|/ref|><|det|>[[115, 254, 853, 309]]<|/det|> +3. Fig 3CD; need to emphasize when PIXN was added (added after virus entry or before?) If before, the smaller syncytia could merely be a result of reduced infection at entry stage, not actually blockade of syncytia per se. + +<|ref|>text<|/ref|><|det|>[[115, 327, 870, 400]]<|/det|> +Response: The drug was added together with the virus. We agree that this experiment by itself does not prove that heparan sulfate regulates cell- cell fusion per se. We change our conclusion to "our results raise the possibility that HS might enhance the fusogenic activities of the spike on the cell surface, which PIXN and MTAN antagonize". + +<|ref|>text<|/ref|><|det|>[[115, 418, 710, 436]]<|/det|> +4. Fig 4, what specifically is "semi-fusion"? Is it different than hemi-fusion? + +<|ref|>text<|/ref|><|det|>[[114, 454, 871, 584]]<|/det|> +Response: hemi- fusion in general refers to a fusion stage in which the lipids in the outer leaflet of the donor and acceptor membranes are mixed, but fusion pore has not formed yet. This stage can either proceed towards the fusion if a fusion pore is formed or relax back to the unfused state. We used semi- fusion to refer to a subsequent stage in which a fusion pore is in forming, although it is not visible by our microscope. It is only indicated by the diffusion of the mCherry signal from the spike cells to ACE2 cells. We now revise the test to clarify this point on page 11. + +<|ref|>text<|/ref|><|det|>[[115, 601, 860, 637]]<|/det|> +5. Fig 5E (and elsewhere); "HS is required..." One can agree that HS facilitates ACE2 clustering but is not "required", consider rephrasing. + +<|ref|>text<|/ref|><|det|>[[115, 656, 585, 674]]<|/det|> +Response: We have rephrased the sentence as suggested. + +<|ref|>text<|/ref|><|det|>[[115, 692, 844, 728]]<|/det|> +6. Fig. 6; ACE2- GS; should test whether ACE2- GS confers SARS-CoV-2 susceptibility to ACE2- negative cells, quantifying ACE2- GS receptor activity relative to ACE2- WT. + +<|ref|>text<|/ref|><|det|>[[115, 745, 868, 856]]<|/det|> +Response: We did show in the Supplementary Fig. 6c that ACE2- GS binds spike with a similar affinity as WT ACE2. To address the reviewer's comment, we tested whether ACE- GS cells allow the entry of spike- coated pseudovirus. As shown in Supplementary Fig. 6e, the endocytosis- mediated entry of pseudovirus- coated by the spike was unaffected in ACE2- GS cells, suggesting that the dimerization function of this loop is only involved in membrane fusion, but dispensable for receptor- mediated endocytosis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 850, 145]]<|/det|> +7. Fig. 7A and 7E; depictions may be communicating inaccurately; a single S trimer may bind more than one ACE2 dimer, resulting in ACE2 clustering. Consider revising the images to account for this possibility. + +<|ref|>text<|/ref|><|det|>[[115, 162, 881, 218]]<|/det|> +Response: As we do not know how exactly ACE2 forms super-clusters, we explain in the figure legend that the drawing only reflects one hypothetical model for simplicity, which does not exclude other modes of ACE2 oligomerization. + +<|ref|>text<|/ref|><|det|>[[115, 236, 819, 272]]<|/det|> +8. Line 161; there is no evidence that N punctae are virions, they could be aggregates of intracellular N protein. + +<|ref|>text<|/ref|><|det|>[[115, 290, 655, 309]]<|/det|> +Response: We have revised the text to clarify this point on page 8. + +<|ref|>text<|/ref|><|det|>[[115, 326, 875, 381]]<|/det|> +9. Lines 166-170; syncytia come from free S proteins going to cell surfaces, and likely far less so from "fusion of viral envelope with plasma membrane" (line 167); this part of text is not interpreting findings in the conventional and well-known ways. + +<|ref|>text<|/ref|><|det|>[[115, 398, 879, 473]]<|/det|> +Response: As explained above, our experimental design allows detection of infection-induced syncytia without significant de novo spike synthesis. Our data also suggest that regardless of the source of the spike (de novo synthesized vs. virally transferred), HS plays a critical role, enhancing the fusion efficiency. The text has been extensively revised to clarify this point. + +<|ref|>text<|/ref|><|det|>[[115, 490, 879, 526]]<|/det|> +10. Lines 286-287; there is no rationale stated for the test to determine whether LS is critical for cell-cell fusion. Consider major point #2 as a possible rationale. + +<|ref|>text<|/ref|><|det|>[[115, 544, 853, 599]]<|/det|> +Response: The rationale to test this domain in cell-cell fusion was simply because the sequence is so conserved evolutionarily, suggesting that it may have an unknown function that could be potentially exploited by the virus. + +<|ref|>text<|/ref|><|det|>[[115, 617, 826, 672]]<|/det|> +11. Fig 7; should incubate the immobilized ACE2 with both soluble RBD monomers and soluble spike trimers, to determine whether trimerized state of spike is needed for ACE2 clustering. + +<|ref|>text<|/ref|><|det|>[[115, 690, 860, 727]]<|/det|> +Response: We performed the proposed experiment and found that the RBD monomers are not capable of inducing ACE2 clustering in the presence of HS (Supplementary Fig. 7a). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 305, 105]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 118, 404, 133]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 145, 416, 160]]<|/det|> +The authors have adressed my concerns + +<|ref|>text<|/ref|><|det|>[[116, 186, 404, 201]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 213, 880, 366]]<|/det|> +This resubmission contains some valuable findings that support a role for heparin and heparin sulfate in facilitating SARS- CoV- 2 spike- mediated cell- cell fusion. Many of the experiments are sophisticated and the data quality are high. There are interesting findings that cell- cell fusion takes place at large micron- diameter areas in which spikes and receptors are opposed and clustered. There is evidence that heparin and HS can facilitate this clustering. There are data showing that a portion of ACE2, once changed, will eliminate the facilitating effect of ACE2. This is interesting. However, there are still many additional concerns about this paper. Several of the concerns are minor but collectively they indicate that more work and more revision would be needed to improve the report. Similar to the issues during the first round of review, this re- review has questions about the authors' interpretations of findings and their support for the statements made in the text. The concerns are listed below in the order in which they appear in the text. + +<|ref|>text<|/ref|><|det|>[[112, 378, 880, 910]]<|/det|> +1. Line 29, the mechanism of syncytium formation is not "largely unclear". There are many excellent papers describing the mechanisms. +2. Lines 37-38, "the interaction of HS with spike allosterically enables a conserved ACE2 linker..." Readers will be unclear about the meaning of this sentence in the abstract. +3. Lines 39, fusion is targeted by the HS-binding drug, but not "effectively". +4. Line 49, S1 and S2 are not covalently linked. +5. Line 52, the fusion peptide does not "drive fusion...". It is the collapse of the S2 fusion intermediates into helical bundles that drives fusion. +6. Line 70, what is the evidence that viruses, after fusion with plasma membranes, leave behind a cluster of fusion-active spikes? +7. Line 72, what is the evidence that spikes are redistributed on plasma membranes during virus entry, causing spike dilution? These statements are put forward as though they are known, but where are the supporting data? +8. Line 75, even if spikes were deposited on plasma membranes after virion-host cell membrane fusion, they would not then "limit the cell surface spike level". Further clarify. +9. Line 78, it is not known how "low" the spike concentrations are... many unsupported assumptions are here in the introduction. +10. Line 109, Fig 1d data appear to show that PIXN reduces the binding of virions to cells. How can it be claimed that PIXN suppresses endocytic virus entry? +11. Lines 110-116, Fig 1f and 1g show that PIXN is only antiviral at the highest 20 micromolar dose, but at this dose, the PIXN is cytotoxic, so the antiviral effect is likely due to direct PXIN cytotoxicity. This finding does not "show that PIXN has a favorable anti-SARS-CoV-2 activity in vitro". +12. Lines 117-128, PIXN in vivo antiviral activity is so weak that it is difficult to see the value of the findings here. +13. Lines 164-165, it does not appear that investigators "have established PIXN and MTAN as HS-binding drugs that block endocytosis-mediated entry of SARS-CoV-2". Precisely where is the evidence for this statement? +14. Lines 173-174, delta entry by plasma membrane is assumed but not shown, the statement on these lines should be tempered. +15. Line 176, you mean de novo "spike" synthesis, not synthesis in general. +16. Line 185-188, why would multiple rounds of fusion be required to fuse up to 80 cells? Were inoculated virions rinsed away after a 4C binding period? If not, then virions in media could keep binding to cells, generating syncytia via fusion-from-without. +17. Line 186-187, is it known that the spike molecules are "transferred from the viral particles"? Might virions bind between cells, forming virion bridges between cells, which then offer an intercellular fusion to occur via virions? +18. Line 191-192, does PXIN and MTAN reduce the binding of virions to cells, in possibly doing so, reducing the level of virion-based "fusion-from-without"? This would be an interpretation of findings + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 860, 120]]<|/det|> +that does not raise the possibility that HS enhances the fusogenic activation to the spike on the cell surface. + +<|ref|>text<|/ref|><|det|>[[113, 118, 864, 163]]<|/det|> +19. Lines 261-262, how can it be claimed that the red arrow is pointing to a fusion event? In the figure legend it is stated as though this is a fact, but in the text, one reads that the red arrow "probably points to a fusion event. + +<|ref|>text<|/ref|><|det|>[[113, 161, 864, 190]]<|/det|> +20. Lines 359-360, do spike antibodies block syncytia, if yes, then how do syncytia allow viruses to escape antibody-mediated neutralization? + +<|ref|>text<|/ref|><|det|>[[113, 189, 880, 245]]<|/det|> +21. Lines 365-367, what is the evidence that membrane fusion activity of spike can sustain over multiple rounds? Were virions bound to cells at 4C, then cells rinsed extensively, then incubated to the 4 hpi time point without residual inoculum in the media, or were virions applied to cells, leaving residual inoculum to continue binding to cells, allowing for continued fusion from without to occur? + +<|ref|>text<|/ref|><|det|>[[115, 244, 777, 258]]<|/det|> +22. Lines 380-381, what alternative models are envisioned? Consider expanding here. + +<|ref|>text<|/ref|><|det|>[[115, 257, 835, 285]]<|/det|> +23. ACE2-GS, does the portion of ACE2 replaced by GS include the ADAM17/TACE and TMPRSS2 cleavage site? Is this relevant to ACE2-GS activity? + +<|ref|>text<|/ref|><|det|>[[115, 284, 875, 327]]<|/det|> +24. Can there be some discussion of the findings in this paper with those in this recent paper that has been getting some press? Eiring et al, Coronavirus Use ACE2 Monomers as Entry-Receptors, Angewandte Chemie International Edition(2023). DOI: 10.1002/anie.202300821 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 127]]<|/det|> +We thank this reviewer for careful reviewing of our manuscript. We have made changes to the text to clarify all the points. + +<|ref|>text<|/ref|><|det|>[[115, 145, 840, 180]]<|/det|> +1. Line 29, the mechanism of syncytium formation is not "largely unclear". There are many excellent papers describing the mechanisms. + +<|ref|>text<|/ref|><|det|>[[115, 182, 844, 218]]<|/det|> +Response: We have revised the text. It now reads as "To better elucidate the mechanism of syncytium formation associated severe COVID- 19, we...." + +<|ref|>text<|/ref|><|det|>[[115, 237, 875, 349]]<|/det|> +2. Lines 37-38, "the interaction of HS with spike allosterically enables a conserved ACE2 linker...." Readers will be unclear about the meaning of this sentence in the abstract. Response: Since the spike binds ACE2 at a site distal from the linker segment, we assumed that the activation of this linker segment during ACE2 clustering must occur by an allosteric mechanism. We agree that it may not be easy to get this point without reviewing the data. We removed the word "allosterically" from the abstract. + +<|ref|>text<|/ref|><|det|>[[115, 367, 708, 404]]<|/det|> +3. Lines 39, fusion is targeted by the HS-binding drug, but not "effectively". Response: We removed "effectively". + +<|ref|>text<|/ref|><|det|>[[115, 422, 506, 459]]<|/det|> +4. Line 49, S1 and S2 are not covalently linked. Response: We have corrected the text on page 3. + +<|ref|>text<|/ref|><|det|>[[115, 477, 815, 513]]<|/det|> +5. Line 52, the fusion peptide does not "drive fusion..". It is the collapse of the S2 fusion intermediates into helical bundles that drives fusion. + +<|ref|>text<|/ref|><|det|>[[115, 515, 864, 569]]<|/det|> +Response: We changed the text to "inducing TMPRSS2- mediated cleavage of the S2 fragment that ultimately leads to the collapse of an S2 fusion intermediate into a helical bundle to drive the fusion of viral membranes with the plasma membrane." + +<|ref|>text<|/ref|><|det|>[[115, 588, 877, 624]]<|/det|> +6. Line 70, what is the evidence that viruses, after fusion with plasma membranes, leave behind a cluster of fusion-active spikes? + +<|ref|>text<|/ref|><|det|>[[113, 625, 881, 866]]<|/det|> +Response: If all spike molecules were cleaved by TMPRSS2 during viral entry, given the short time window of the viral entry, the cleavage should be extremely efficient. This is INCONSISTENT with the fact that the virus has constantly evolved in a direction that allows the spike to be cleaved more and more efficiently by TMPRSS2 (Rajah, 2021, EMBO), suggesting that the S2 cleavage by TMPRSS2 is far from optimal. We now add a sentence on page 3 to highlight this point. Additionally, a recent study showed that even when both spike and TMPRSS2 are co- expressed in the same cell, the cleavage only occurs to a small population of spike (PMID: 32703818). Likewise, in our cell- cell fusion assay, we measured the cleavage of S2 by a chase experiment (Figure S5d, e). Even after 2 hours of incubation (all cells have fused at least once), only a small fraction of the S2 fragment was converted to S2'. Note that this experiment was conducted with the spike from the Delta variant. Thus, even for spike with a strong fusion activity, it is still cleaved very inefficiently. These observations all suggest that membrane fusion can take place with only a small fraction of spike being consumed by cleavage. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 127]]<|/det|> +We added a sentence on page 3 to highlight the evolution of the virus, which is associated with increased spike cleavage efficiency. + +<|ref|>text<|/ref|><|det|>[[115, 145, 879, 201]]<|/det|> +7. Line 72, what is the evidence that spikes are redistributed on plasma membranes during virus entry, causing spike dilution? These statements are put forward as though they are known, but where are the supporting data? + +<|ref|>text<|/ref|><|det|>[[115, 202, 880, 331]]<|/det|> +Response: When a membrane- encircled virus fuses with host cells, the viral membrane would become part of the plasma membrane. This is a well- accepted concept in the membrane fusion field (see the cited review by Harrison, S. 2008 Nat. Strul. Mol. Biol. PMID: 18596815). Since spike is a membrane protein, it should be free to distribute to the entire cell surface by diffusion. We now add a sentence on page 4 to clarify this point. It reads as "Strikingly, when the virus fuses with the plasma membrane, the viral membrane becomes part of the cell membrane, leading to a drastic expansion of the spike- containing membranes...." + +<|ref|>text<|/ref|><|det|>[[115, 350, 880, 386]]<|/det|> +8. Line 75, even if spikes were deposited on plasma membranes after virion-host cell membrane fusion, they would not then "limit the cell surface spike level". Further clarify. + +<|ref|>text<|/ref|><|det|>[[115, 387, 875, 460]]<|/det|> +Response: What we meant was that the expansion of the spike- containing membranes during viral entry and the retention of the newly synthesized spike to the cell surface by the ER retention signal collectively limit the cell surface spike level. We have re- worded the sentences to avoid the confusion. + +<|ref|>text<|/ref|><|det|>[[115, 479, 808, 515]]<|/det|> +9. Line 78, it is not known how "low" the spike concentrations are... many unsupported assumptions are here in the introduction. + +<|ref|>text<|/ref|><|det|>[[115, 516, 649, 534]]<|/det|> +Response: We removed the phrase "at low surface concentration". + +<|ref|>text<|/ref|><|det|>[[115, 552, 866, 589]]<|/det|> +10. Line 109, Fig 1d data appear to show that PIXN reduces the binding of virions to cells. How can it be claimed that PIXN suppresses endocytic virus entry? + +<|ref|>text<|/ref|><|det|>[[115, 590, 872, 774]]<|/det|> +Response: The reviewer is correct that we did not detect significant accumulation of the viral particles on the lateral cell surface in these confocal images of PIXN-treated cells (Fig. 1d). However, since we detected no effect of these drugs on the interaction of spike with ACE2 (Fig. S4c) and also because the interaction of spike- expressing cells with ACE2 cells was not affected by PIXN (Fig. S4d, e), we believe that PIXN does not disrupt the spike (and therefore the virus) binding to ACE2 cells. The lack of cell surface spike staining in drug- treated cells was most likely caused by a detection sensitivity issue or by our initial focus on confocal sections around endolysosomes. As we later revealed in Fig. S3d by 3D reconstruction, the viral particles on the cell surface are usually clustered on apical surface of the cell, which would escape detection by deeper confocal sections in Fig. 1d. + +<|ref|>text<|/ref|><|det|>[[115, 792, 821, 847]]<|/det|> +To avoid potential overinterpretation of the data, we have tempered our conclusion. The sentence reads as "suggesting that the drug inhibits viral entry at a step upstream of endocytosis". + +<|ref|>text<|/ref|><|det|>[[115, 866, 853, 903]]<|/det|> +11. Lines 110-116, Fig 1f and 1g show that PIXN is only antiviral at the highest 20 micromolar dose, but at this dose, the PIXN is cytotoxic, so the antiviral effect is likely due to direct PIXN + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 860, 126]]<|/det|> +cytotoxicity. This finding does not "show that PIXN has a favorable anti- SARS- CoV- 2 activity in vitro". + +<|ref|>text<|/ref|><|det|>[[115, 127, 880, 182]]<|/det|> +Response: Please note that even at the lowest dose chosen (200 nM), there was a significant inhibition of viral replication when compared to the vehicle controls (the dotted lines). We have changed the text to make this point clear. + +<|ref|>text<|/ref|><|det|>[[115, 202, 870, 238]]<|/det|> +12. Lines 117-128, PIXN in vivo antiviral activity is so weak that it is difficult to see the value of the findings here. + +<|ref|>text<|/ref|><|det|>[[115, 239, 883, 312]]<|/det|> +Response: We agree with the reviewer that the in vivo efficacy of PIXN is not very strong. However, we feel that it is important to include the data to make the study complete. The result may provide a base for future optimization studies. Considering the reviewer's criticism, we now move this data to supplementary Fig. 1d, e. + +<|ref|>text<|/ref|><|det|>[[115, 331, 881, 385]]<|/det|> +13. Lines 164-165, it does not appear that investigators "have established PIXN and MTAN as HSbinding drugs that block endocytosis-mediated entry of SARS-CoV-2". Precisely where is the evidence for this statement? + +<|ref|>text<|/ref|><|det|>[[115, 387, 857, 441]]<|/det|> +Response: The binding of PIXN and MTAN to HS was shown in Figure 2 and related supplementary figures. The inhibition of SARS-CoV-2 entry was shown in Figure 1d. We now refer to these figures in the text. + +<|ref|>text<|/ref|><|det|>[[115, 460, 867, 496]]<|/det|> +14. Lines 173-174, delta entry by plasma membrane is assumed but not shown, the statement on these lines should be tempered. + +<|ref|>text<|/ref|><|det|>[[115, 497, 872, 608]]<|/det|> +Response: We now add an additional reference that shows increased membrane fusion activity of Delta spike. This study (Rajah, 2021, EMBO), combined with the paper cited in the previous version (Zhang, 2022 Science), suggests that delta strain should primarily use the plasma membrane as the entry site provided sufficient TMPRSS2 expression. We also point out that in our immunostaining experiment (Fig. 3a), the viral protein NP is not localized to the endolysosome, consistent with the notion that it uses the plasma membrane as the entry site. + +<|ref|>text<|/ref|><|det|>[[115, 644, 710, 661]]<|/det|> +15. Line 176, you mean de novo "spike" synthesis, not synthesis in general. + +<|ref|>text<|/ref|><|det|>[[115, 663, 715, 680]]<|/det|> +Response: The reviewer is correct. We have added "Spike" to the sentence. + +<|ref|>text<|/ref|><|det|>[[115, 700, 875, 754]]<|/det|> +16. Line 185-188, why would multiple rounds of fusion be required to fuse up to 80 cells? Were inoculated virions rinsed away after a 4C binding period? If not, then virions in media could keep binding to cells, generating syncytia via fusion-from-without. + +<|ref|>text<|/ref|><|det|>[[115, 756, 879, 847]]<|/det|> +Response: We now include a brief discussion about "fusion-from-without", a relatively uncommon mechanism for virus-induced cell-cell fusion. Specifically, we cited a recent paper in iScience (Theuerkauf, 2021 iScience), which demonstrate that for virus-like particles containing spike, it needs very high concentrations to induce fusion-from-without (5,000 VLP/cell). This would not happen under our experimental condition given that relatively low viral titer used. + +<|ref|>text<|/ref|><|det|>[[115, 866, 880, 884]]<|/det|> +17. Line 186-187, is it known that the spike molecules are "transferred from the viral particles"? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 840, 126]]<|/det|> +Might virions bind between cells, forming virion bridges between cells, which then offer an inter- cellular fusion to occur via virions? + +<|ref|>text<|/ref|><|det|>[[115, 127, 864, 164]]<|/det|> +Response: Again, the scenario described here (also referred to as fusion- from- without) should not happen under our experimental conditions as explained for point 16. + +<|ref|>text<|/ref|><|det|>[[115, 182, 882, 256]]<|/det|> +18. Line 191-192, does PXIN and MTAN reduce the binding of virions to cells, in possibly doing so, reducing the level of virion- based "fusion- from- without"? This would be an interpretation of findings that does not raise the possibility that HS enhances the fusogenic activation to the spike on the cell surface. + +<|ref|>text<|/ref|><|det|>[[115, 256, 880, 330]]<|/det|> +Response: We show in Supplementary Fig. 4c, d, e that neither PXIN nor MTAN affects the binding of spike to ACE2 or ACE2-expressing cells. Thus, these drugs should not affect virus binding to the cells. Additionally, as pointed out above, "fusion- from- without" does not happen under our experimental conditions. + +<|ref|>text<|/ref|><|det|>[[115, 349, 876, 404]]<|/det|> +19. Lines 261-262, how can it be claimed that the red arrow is pointing to a fusion event? In the figure legend it is stated as though this is a fact, but in the text, one reads that the red arrow "probably points to a fusion event. + +<|ref|>text<|/ref|><|det|>[[115, 405, 525, 422]]<|/det|> +Response: We added probably to the figure legend. + +<|ref|>text<|/ref|><|det|>[[115, 441, 872, 477]]<|/det|> +20. Lines 359-360, do spike antibodies block syncytia, if yes, then how do syncytia allow viruses to escape antibody-mediated neutralization? + +<|ref|>text<|/ref|><|det|>[[115, 479, 870, 552]]<|/det|> +Response: The statement here is based on the following article, which shows that viral spreading via syncytia is more resistant to neutralizing antibodies (Zeng 2022, PNAS). We have revised text. It now reads as "it was proposed that this transmission route allows the virus to escape immune surveillance and antibody-mediated neutralization". + +<|ref|>text<|/ref|><|det|>[[115, 571, 879, 664]]<|/det|> +21. Lines 365-367, what is the evidence that membrane fusion activity of spike can sustain over multiple rounds? Were virions bound to cells at 4C, then cells rinsed extensively, then incubated to the 4 hpi time point without residual inoculum in the media, or were virions applied to cells, leaving residual inoculum to continue binding to cells, allowing for continued fusion from without to occur? + +<|ref|>text<|/ref|><|det|>[[115, 664, 725, 682]]<|/det|> +Response: We have removed this speculative statement from the discussion. + +<|ref|>text<|/ref|><|det|>[[115, 701, 866, 811]]<|/det|> +22. Lines 380-381, what alternative models are envisioned? Consider expanding here. Response: We mentioned that "How HS facilitates ACE2 super-cluster formation remains to be determined" on page 18. At this point, any models would be speculative in nature. We only mentioned one possibility based on previous structural studies on the role of HS in regulating FGF receptor oligomerization. The analogy raises the possibility that a similar mechanism may be applied to ACE2 oligomerization. + +<|ref|>text<|/ref|><|det|>[[115, 830, 875, 866]]<|/det|> +23. ACE2-GS, does the portion of ACE2 replaced by GS include the ADAM17/TACE and TMPRSS2 cleavage site? Is this relevant to ACE2-GS activity? + +<|ref|>text<|/ref|><|det|>[[115, 867, 792, 904]]<|/det|> +Response: The answer is No. The linker segment is from 721- 740. The TMPRSS2 and ADAM17/TACE-mediated cleavage occurs between 697- 716 (PMID: 24227843). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 107, 870, 238]]<|/det|> +24. Can there be some discussion of the findings in this paper with those in this recent paper that has been getting some press? Eiring et al, Coronavirus Uses ACE2 Monomers as Entry-Receptors, Angewandte Chemie International Edition(2023). DOI: 10.1002/anie.202300821 Response: We now mentioned the article that suggests the possibility of ACE2 being a monomer, which if true would certainly impact our model. However, this new study challenges a well-established dogma in the field with only limited evidence (entirely imaging-based). The controversy certainly will require more studies to resolve. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 89, 321, 105]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 117, 405, 133]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 145, 650, 161]]<|/det|> +The authors adequately responded to second- round reviewer questions. + +<--- Page Split ---> diff --git a/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/images_list.json b/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..98430590e14d21f2a2063663ff693586292ba892 --- /dev/null +++ b/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,191 @@ + +# nature portfolio + +Peer Review File + +# Interplay between disorder and electronic correlations in compositionally complex alloys + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The paper describes a highly impressive and thorough investigation of properties of the high entropy Cantor- Wu alloy, CrMnFeCoNi, via photoemission spectroscopy, optical conductivity and electrical resistivity experiments, all of which are analysed with detailed, quantitative theoretical calculations. The work is a fine case study of the rich links between electron correlations, nature of self energy effects and multicomponent disorder. + +Element- specific information extracted from resonant PES and X- ray absorption data show the effects on these data of localised electron correlations in concert with chemical disorder and magnetic fluctuations. Electron correlation effects are modelled effectively by DFT+DMFT within a KKR- CPA framework using prescribed U values for local onsite correlations. Element- specific information such as quasi- particle lifetimes is also extracted from optical conductivity measurements and appropriate rigorous theoretical analysis. Finally the authors show that localised correlation effects appear to have less effect on the temperature- dependent electrical resistivity calculations which undershoot the experimental measured values. They identify important aspects such as atomic short- range order and Anderson- type localisation effects that require further study. + +The paper is very interesting and suitable for publication in Nature Communications. The manuscript, however, could be improved by some further proof- reading and also making the figure captions more accessible and easier to follow - the reader could be reminded about what some of the acronyms stand for (e.g. CST, TR- 2PPE) and directed to note certain features. + +Reviewer #2 (Remarks to the Author): + +This manuscript delves into the exploration of disorder and electronic correlations within the CrMnFeCoNi high- entropy alloy using photoemission spectroscopy, and the results are + +<--- Page Split ---> + +compared with DFT/DMFT calculations. This is a timely piece of work because detailed investigations into the electronic structure of these alloys, particularly with regard to the elemental contributions to the valence band structure, is still very rare. While the quality of the work is commendable, this reviewer suggests that the manuscript may find a better fit in a specialized journal with a stronger physics focus. The findings, while of importance, may lack the broader impact required for publication in a top- tier journal like this. + +Reviewer #3 (Remarks to the Author): + +In this manuscript, the authors investigated the electron correlation effect on the band structure and transport properties in HEA- CrMnFeCoNi using both experimental and theoretical methods. The authors found that the KKR- CPA+DMFT method explains the experimental results well, showing the importance of electron correlation even in HEAs. The authors also discuss the differences between LDA and LDA+DMFT in detail by comparing low- energy and high- energy electronic transport properties, emphasizing the importance of strong correlation effects, especially in the high- energy regime. This study advances the understanding of electronic states in HEAs and provides significant information to those working in this field. + +I have the following comments regarding this manuscript: + +(1) In the Methods section, while the element dependence of U is discussed in detail, the Hund coupling J is treated as element-independent. The authors should explain the reason for this. + +(2) The effect of J on the electronic states should be discussed. + +(3) In Fig. 4(a), the LDA+DMFT calculation results should also be included. + +<--- Page Split ---> + +Based on the above, I think that this manuscript is suitable for publication in Nature Communications after addressing my concerns. + +<--- Page Split ---> + +## Response to Reviewer's remarks on the manuscript entitled "Interplay between disorder and electronic correlations in compositionally complex alloys" (NCOMMS-24-11440) + +We sincerely appreciate the valuable feedback and constructive comments provided by the Reviewers. The consistently positive feedback on the quality and results of our work is very pleasing. The manuscript has been revised to address all of the concerns and suggestions raised. Below is a summary of the changes made, followed by specific responses to each Reviewer. + +All changes to the manuscript and Supplementary Information are highlighted: new text in blue color, and old, removed text in red color and crossed out. + +## Main Manuscript: + +- The abstract has been modified to be more appealing and to better generalize the scope of the work.- The final section of the introduction has been revised to more effectively guide the reader through the paper and present the generalizable results.- Two sentences have been appended to the conclusion in order to enhance its efficacy.- In order to facilitate the reading of the manuscript regarding the ResPES analysis for the reader, the corresponding section has been optimized. In addition to a few minor changes, including a reference to a new section in the supplement, some sentences have been added to clarify the theoretical background.- In order to address the issue raised by Reviewer 3, a sentence redirecting the reader to the Supplemental Information for the analysis of the role played the Hund exchange \(J\) has been added to the Methods section.- The x label in Figure 1 has been changed from BE to EB to correct a minor inconsistency.- Figure 2 has been reformatted from a single-column layout to a two-column layout to improve the visibility of the spectra displayed, thus improving accessibility. The subfigures have not been changed.- LDA+DMFT results for electrical resistivity have been added to Figure 4(a) as suggested by Reviewer 3. An appropriate sentence has been added to the main text.- All figure captions have been revised to improve clarity and accessibility, as requested by Reviewer 1.- Thorough proofreading was performed to correct inconsistencies and irregularities.- Eduardo Bonini Guedes has been added as a co-author, as he was overlooked in the initial submission. He was involved in the ResPES measurements. His contribution has been updated in "Author Contributions". He has been given the latest version of the manuscript to review, like the other authors.- The current address of Trpimir Ivšić has been added.- A code availability statement has been added. + +## Supplementary Information: + +- A new section (1) has been added to provide more detailed plots on the ResPES data.- A new section (3) has been added to discuss the influence of J in our calculations, including relevant new references.- All figures and sections were renumbered to accommodate the new sections.- All figure captions have been refined at the request of Reviewer 1.- Eduardo Bonini Guedes has been added as a co-author (see above).- The current address of Trpimir Ivšić has been added. + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +The paper describes a highly impressive and thorough investigation of properties of the high entropy Cantor- Wu alloy, CrMnFeCoNi, via photoemission spectroscopy, optical conductivity and electrical resistivity experiments, all of which are analysed with detailed, quantitative theoretical calculations. The work is a fine case study of the rich links between electron correlations, nature of self energy effects and multicomponent disorder. + +Element- specific information extracted from resonant PES and X- ray absorption data show the effects on these data of localised electron correlations in concert with chemical disorder and magnetic fluctuations. Electron correlation effects are modelled effectively by DFT+DMFT within a KKR- CPA framework using prescribed U values for local onsite correlations. Element- specific information such as quasi- particle lifetimes is also extracted from optical conductivity measurements and appropriate rigorous theoretical analysis. Finally the authors show that localised correlation effects appear to have less effect on the temperature- dependent electrical resistivity calculations which undershoot the experimental measured values. They identify important aspects such as atomic short- range order and Anderson- type localisation effects that require further study. + +The paper is very interesting and suitable for publication in Nature Communications. The manuscript, however, could be improved by some further proof- reading and also making the figure captions more accessible and easier to follow - the reader could be reminded about what some of the acronyms stand for (e.g. CST, TR- 2PPE) and directed to note certain features. + +## Authors: + +We sincerely appreciate Reviewer 1's detailed and positive feedback on our manuscript. We have carefully addressed all the points raised, including proof- reading and enhancing the figure captions for clarity and accessibility. We defined all abbreviations in the captions, pointed out important features and added physical explanations (if they are not too long). We believe these revisions have significantly improved the quality of the manuscript. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +This manuscript delves into the exploration of disorder and electronic correlations within the CrMnFeCoNi high- entropy alloy using photoemission spectroscopy, and the results are compared with DFT/DMFT calculations. This is a timely piece of work because detailed investigations into the electronic structure of these alloys, particularly with regard to the elemental contributions to the valence band structure, is still very rare. While the quality of the work is commendable, this reviewer suggests that the manuscript may find a better fit in a specialized journal with a stronger physics focus. The findings, while of importance, may lack the broader impact required for publication in a top- tier journal like this. + +## Authors: + +We would like to thank Reviewer 2 for the invested time and positive scientific evaluation of our work. However, we respectfully disagree with the assertion that our manuscript "may lack the broader impact required for publication in a top- tier journal like this." We believe that our study is highly suitable for Nature Communications, and we would like to highlight a few points: + +We think that our study represents a significant advancement as it provides, to our knowledge, the first quantitative comparison of the influence of disorder and correlated many- body effects on electronic structure- driven properties in CCAs/HEAs. Based on the results, we are able to make clear statements regarding electronic spectra, transport and optics. In principle, these can be generalized to other multi- principal element alloys and are therefore suitable for many other technically important advanced materials. + +Building on recent findings on CCAs, such as studies on short- range order [Nature 624, 564- 569 (2023); Nat. Commun, 13, 1021 (2022); Nat. Commun. 581, 283- 287 (2020)], or nano- structure induced mechanical properties [Nat. Commun. 15, 4599 (2024), Nat. Commun. 14, 2516 (2023)], we describe an additional physical mechanism that influences key material properties. Further, we want to highlight that some papers were recently published in Nature Communications regarding electronic and phononic transport [Nat. Commun. 15, 4554 (2024), Nat. Commun. 13, 7509 (2022)], utilizing specific HEAs as model materials and providing generalizable results. We would also like to emphasize the potential of the results to extend DFT- based machine learning models [Science 378, 6615, 78- 85 (2022)] to account for many- body correlation effects. From our perspective, this appears to be crucial for the further development of alloys with improved transport and optical properties. + +Regarding optical properties, our findings are also interesting for the photonics industry, which operates largely in the visible and near- infrared spectral regions. Alloys are of decisive importance for these applications, especially in laser processing, where the initial absorption of laser radiation is the central part of the process. Here we can clearly demonstrate that through the implementation of correlated many- body effects, the predicted optical spectra are improved. + +Another point is that the KKR- CPA approach is extremely valuable for disordered alloys and is attracting increasing interest from the materials science community, especially for HEA calculations. We also wish to emphasize the extremely positive feedback from the other two Reviewers, including their suggestion for publication. + +Finally, we understand that the broader implications of our study were not immediately apparent in the previous version of our manuscript, due to the specific and concise nature of our abstract and conclusion. Therefore, we have added some sentences at the beginning of the summary and at the end of the conclusion to attract the interest of a wider audience. + +We hope these revisions and clarifications will convince the Reviewer of the broader impact and significance of our work. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +## Reviewer: + +In this manuscript, the authors investigated the electron correlation effect on the band structure and transport properties in HEA- CrMnFeCoNi using both experimental and theoretical methods. The authors found that the KKR- CPA+DMFT method explains the experimental results well, showing the importance of electron correlation even in HEAs. The authors also discuss the differences between LDA and LDA+DMFT in detail by comparing low- energy and high- energy electronic transport properties, emphasizing the importance of strong correlation effects, especially in the high- energy regime. This study advances the understanding of electronic states in HEAs and provides significant information to those working in this field. + +I have the following comments regarding this manuscript: + +## Authors: + +The authors would like to thank Reviewer 3 for his time and valuable comments. We are also very pleased to receive positive feedback on our work. We have addressed all the points raised and are confident that our revisions have improved the quality of the manuscript. + +## Reviewer: + +(1) In the Methods section, while the element dependence of U is discussed in detail, the Hund coupling J is treated as element-independent. The authors should explain the reason for this. + +## Authors: + +In principle, we could have introduced a small variation of the Hund exchange to mimic what has been reported for the 3d elemental series. Calculations based on constrained random-phase approximation (cRPA) show that the Hund exchange changes of about 0.1 eV when going from Cr to Ni [Phys. Rev. B 77, 085122 (2008)]. This variation may be \(50\%\) larger in our case, accounting for differences in the local orbitals [see also Ref. 49 in the manuscript]. There are, however, two main reasons why this variation is not fully meaningful in our case. First, our study is focused on a high-entropy alloy and not on pure elements. Cr, Fe and Co have a different crystal structure than the one investigated here, with a different number of neighbors and a different screening. Second, a change of \(J\) of about 0.1 or 0.2 eV would have no visible + +![PLACEHOLDER_7_0] + + +effect on our calculations. This is due to the particular computational scheme we use for our study, where the DMFT self- energy acts as a correction to a spin- polarized DFT solution. In this approach, which is the most common way to apply DFT+DMFT to magnetic materials, the major effect associated to \(J\) , i.e. the renormalization of the exchange splitting, is completely canceled by the double- counting term [see e.g. Phys. Rev. B 97, 184404 (2018) for the analysis of the consequences on the effective magnetic coupling]. A detailed investigation of these methodological subtleties has been provided for DFT+U, in Phys. Rev. B 98, 125126 (2018). On the left, we show Fig. 2 of this work, focused on + +<--- Page Split ---> + +LaMnO3. In panel (a), various exchange splittings are defined. In panel (b), these values are plotted with respect to the variation of the Hund exchange J. Variations of the order of 0.1 or 0.2 eV cause minor changes in the splitting and thus in the spectrum. These changes are due to the fact that J also determines the anisotropic effects among the different orbitals of the 3d shell. To restore a more significant dependence, one should work with a non- spin- polarized DFT solution and let the whole magnetism arise from the local problem in DMFT or DFT+U. This is illustrated by the data plotted in panel (c). Although these data are for DFT+U, similar trends are expected for DFT+DMFT. The presence of higher order terms beyond Hartree- Fock is likely to be compensated by the reduction of the effective interaction due to dynamical screening [see e.g. discussions in Phys. Rev. B 90, 165130 (2014)]. + +## Reviewer: + +(2) The effect of J on the electronic states should be discussed. + +## Authors: + +In the previous answer, we have explained why a small variation of \(J\) is expected to have a negligible effect on the final spectra. We now aim to demonstrate this, as suggested by the referee, on systems related to our study. For this purpose, we calculated the influence of a \(J\) variation on the electronic spectra for ferromagnetic (FM) Ni and paramagnetic (DLM) FeNi, using the SPRKKR package. \(J\) is changed at both Fe and Ni sites, while the U values arekept to the same values as those reported in the paper. The density of states (DOS) resulting from these calculations is shown in the following figure, panels (a) to (c). + +![PLACEHOLDER_8_0] + + +Even a variation of \(J\) as large as \(\pm 0.4 \mathrm{eV}\) (from \(J = 0.5 \mathrm{eV}\) to \(1.3 \mathrm{eV}\) ) does not lead to a significant shift in the spectral weight of the d- bands for FM Ni (see excitation energies between - 5 eV and 0 eV). The most visible effect is a slight shift of the split- off satellites. For ferromagnetic Ni, majority (up) channel, the satellite shifts from - 8.2 eV to - 8.7 eV as \(J\) increases from 0.5 eV to 1.3 eV. This corresponds to a shift of \(\Delta P_s / \Delta J = - 0.6\) ( \(P_s\) is the position of the spectral weight of the satellites). For the minority (down) spin channel, the satellite is less marked and appears as a shoulder- like feature between - 5 and - 10 eV. Increasing \(J\) causes a + +<--- Page Split ---> + +farther attenuation. For paramagnetic FeNi, even smaller changes in the electronic spectra are observed for J variations from 0.6 eV to 1.2 eV. As for the minority spin channel of FM Ni, a slight influence on the shoulders around - 8 eV is found. No changes in the bandwidth or shift of the d- block are observed upon a variation of \(J\) . + +Finally, in panel (d), we show how the results of the calculations for paramagnetic (DLM) CrMnFeCoNi depend on varying \(J\) . The \(U\) values again correspond to those in the main manuscript. Unlike FeNi, we find no influence on the shoulder features at - 8 eV, which means that the simultaneous variation of \(J\) at the various sites leads to compensating effects. The main peak position remains unchanged at - 1 eV for all \(J\) , while its height only slightly decreases from 2.01 states/eV/atom to 1.97 when \(J\) goes from the lowest to the largest value. The DOS at \(E_{\mathrm{F}}\) is completely unaffected. The spectral width of the d- band block does not change, but the spectral weight shifts slightly towards higher binding energies with increasing \(J\) . This is observed in the flanks of the \(d\) - band block, which shift approximately with \(\Delta P_{\mathrm{f}} / \Delta J = - 0.3\) ( \(P_{\mathrm{f}}\) is the position of the \(d\) - band flanks). Compared to the effect induced by a variation of \(U\) , as shown in Figure 2(a) of the main manuscript or Figure 3(b) in the supplementary materials, the uncertainty of \(J\) is negligible. An increase of \(U\) for Ni from 3 eV to 4 eV in CrMnFeCoNi induces a direct and isolated shift of the Ni satellite from - 8 eV to - 10 eV. This corresponds to \(\Delta P_{\mathrm{s}} / \Delta U = - 2\) . Considering that the expected variation of \(J\) is of 0.1 eV to 0.2 eV, as discussed in the previous question, we can safely ignore this effect. + +We agree with the referee that these issues should be addressed in our manuscript. Therefore, we have summarized the main points of the previous discussions in the Supplementary Information, where we also included the previous results. In the main manuscript, we added a reminder to this discussion in the Methods section, just after mentioning our choice of keeping the Hund exchange constant for all the elements considered. + +## Reviewer: + +(3) In Fig. 4(a), the LDA+DMFT calculation results should also be included. + +## Authors: + +Figure 4(a) shows the experiments on the electrical resistivity of various alloys, ranging from Ni to CrMnFeCoNi. Due to the lack of short- range order in our CPA- based calculations, we observed a larger offset between measurements and calculations. This issue has already been discussed in the manuscript. In response to the referee's suggestion, we have now included the LDA+DMFT calculations (see dashed line in the revised manuscript). + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have satisfactorily addressed points raised in my first report and have improved the manuscript. The paper is suitable for publication in Nature Communications. + +Reviewer #2 (Remarks to the Author): + +Like I mentioned in my previous review, the manuscript is of good quality and provides important missing data in the current understanding of CCAs. My concern about this manuscript lies in its limited broader impact. More specifically, the new data on the electronic structure of this model alloy does not seem to bring significant new insights or enhance our general knowledge of how CCAs differ from conventional alloys. The authors attempt to address this in their revised manuscript, but the connection between the new data and new insights remains unclear to me. However, as scientific importance is somewhat subjective, I will leave the final decision to the editor. + +Reviewer #3 (Remarks to the Author): + +The authors have provided a satisfactory response to my comments. Therefore, I have no further concerns, and I believe that this manuscript is suitable for publication in Nature Communications. + +<--- Page Split ---> + +## Response to Reviewer's remarks on the manuscript entitled "Interplay between disorder and electronic correlations in compositionally complex alloys" (NCOMMS-24-11440) + +We sincerely thank the reviewers for their thorough evaluation and positive feedback on our revised manuscript. The constructive comments have undoubtedly improved the manuscript and we are pleased that it is now suitable for publication in Nature Communications. + +As the reviewers did not raise further questions or suggest any additional changes, we have not revised the manuscript further. + +We greatly appreciate your time and effort in reviewing our work. + +On behalf of all coauthors, + +Jan Minár + +<--- Page Split ---> diff --git a/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..67b9826eb6073d72e809bf71e4e08e76b4013c73 --- /dev/null +++ b/peer_reviews/98e188d197f798d498e66156851783607bd993dcbb8ac0d0cb28a16b4678777a/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,255 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[65, 111, 360, 139]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[92, 164, 870, 231]]<|/det|> +# Interplay between disorder and electronic correlations in compositionally complex alloys + +<|ref|>image<|/ref|><|det|>[[57, 712, 238, 760]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 711, 909, 761]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 315, 108]]<|/det|> +REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 152, 428, 170]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 214, 880, 320]]<|/det|> +The paper describes a highly impressive and thorough investigation of properties of the high entropy Cantor- Wu alloy, CrMnFeCoNi, via photoemission spectroscopy, optical conductivity and electrical resistivity experiments, all of which are analysed with detailed, quantitative theoretical calculations. The work is a fine case study of the rich links between electron correlations, nature of self energy effects and multicomponent disorder. + +<|ref|>text<|/ref|><|det|>[[114, 363, 880, 577]]<|/det|> +Element- specific information extracted from resonant PES and X- ray absorption data show the effects on these data of localised electron correlations in concert with chemical disorder and magnetic fluctuations. Electron correlation effects are modelled effectively by DFT+DMFT within a KKR- CPA framework using prescribed U values for local onsite correlations. Element- specific information such as quasi- particle lifetimes is also extracted from optical conductivity measurements and appropriate rigorous theoretical analysis. Finally the authors show that localised correlation effects appear to have less effect on the temperature- dependent electrical resistivity calculations which undershoot the experimental measured values. They identify important aspects such as atomic short- range order and Anderson- type localisation effects that require further study. + +<|ref|>text<|/ref|><|det|>[[115, 619, 861, 724]]<|/det|> +The paper is very interesting and suitable for publication in Nature Communications. The manuscript, however, could be improved by some further proof- reading and also making the figure captions more accessible and easier to follow - the reader could be reminded about what some of the acronyms stand for (e.g. CST, TR- 2PPE) and directed to note certain features. + +<|ref|>text<|/ref|><|det|>[[115, 800, 428, 818]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 862, 877, 903]]<|/det|> +This manuscript delves into the exploration of disorder and electronic correlations within the CrMnFeCoNi high- entropy alloy using photoemission spectroscopy, and the results are + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 878, 216]]<|/det|> +compared with DFT/DMFT calculations. This is a timely piece of work because detailed investigations into the electronic structure of these alloys, particularly with regard to the elemental contributions to the valence band structure, is still very rare. While the quality of the work is commendable, this reviewer suggests that the manuscript may find a better fit in a specialized journal with a stronger physics focus. The findings, while of importance, may lack the broader impact required for publication in a top- tier journal like this. + +<|ref|>text<|/ref|><|det|>[[115, 291, 428, 309]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 353, 857, 544]]<|/det|> +In this manuscript, the authors investigated the electron correlation effect on the band structure and transport properties in HEA- CrMnFeCoNi using both experimental and theoretical methods. The authors found that the KKR- CPA+DMFT method explains the experimental results well, showing the importance of electron correlation even in HEAs. The authors also discuss the differences between LDA and LDA+DMFT in detail by comparing low- energy and high- energy electronic transport properties, emphasizing the importance of strong correlation effects, especially in the high- energy regime. This study advances the understanding of electronic states in HEAs and provides significant information to those working in this field. + +<|ref|>text<|/ref|><|det|>[[115, 589, 598, 608]]<|/det|> +I have the following comments regarding this manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 652, 877, 712]]<|/det|> +(1) In the Methods section, while the element dependence of U is discussed in detail, the Hund coupling J is treated as element-independent. The authors should explain the reason for this. + +<|ref|>text<|/ref|><|det|>[[115, 757, 642, 776]]<|/det|> +(2) The effect of J on the electronic states should be discussed. + +<|ref|>text<|/ref|><|det|>[[115, 820, 735, 839]]<|/det|> +(3) In Fig. 4(a), the LDA+DMFT calculation results should also be included. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 816, 130]]<|/det|> +Based on the above, I think that this manuscript is suitable for publication in Nature Communications after addressing my concerns. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 83, 894, 117]]<|/det|> +## Response to Reviewer's remarks on the manuscript entitled "Interplay between disorder and electronic correlations in compositionally complex alloys" (NCOMMS-24-11440) + +<|ref|>text<|/ref|><|det|>[[92, 127, 894, 195]]<|/det|> +We sincerely appreciate the valuable feedback and constructive comments provided by the Reviewers. The consistently positive feedback on the quality and results of our work is very pleasing. The manuscript has been revised to address all of the concerns and suggestions raised. Below is a summary of the changes made, followed by specific responses to each Reviewer. + +<|ref|>text<|/ref|><|det|>[[92, 205, 894, 239]]<|/det|> +All changes to the manuscript and Supplementary Information are highlighted: new text in blue color, and old, removed text in red color and crossed out. + +<|ref|>sub_title<|/ref|><|det|>[[92, 250, 231, 265]]<|/det|> +## Main Manuscript: + +<|ref|>text<|/ref|><|det|>[[91, 268, 896, 670]]<|/det|> +- The abstract has been modified to be more appealing and to better generalize the scope of the work.- The final section of the introduction has been revised to more effectively guide the reader through the paper and present the generalizable results.- Two sentences have been appended to the conclusion in order to enhance its efficacy.- In order to facilitate the reading of the manuscript regarding the ResPES analysis for the reader, the corresponding section has been optimized. In addition to a few minor changes, including a reference to a new section in the supplement, some sentences have been added to clarify the theoretical background.- In order to address the issue raised by Reviewer 3, a sentence redirecting the reader to the Supplemental Information for the analysis of the role played the Hund exchange \(J\) has been added to the Methods section.- The x label in Figure 1 has been changed from BE to EB to correct a minor inconsistency.- Figure 2 has been reformatted from a single-column layout to a two-column layout to improve the visibility of the spectra displayed, thus improving accessibility. The subfigures have not been changed.- LDA+DMFT results for electrical resistivity have been added to Figure 4(a) as suggested by Reviewer 3. An appropriate sentence has been added to the main text.- All figure captions have been revised to improve clarity and accessibility, as requested by Reviewer 1.- Thorough proofreading was performed to correct inconsistencies and irregularities.- Eduardo Bonini Guedes has been added as a co-author, as he was overlooked in the initial submission. He was involved in the ResPES measurements. His contribution has been updated in "Author Contributions". He has been given the latest version of the manuscript to review, like the other authors.- The current address of Trpimir Ivšić has been added.- A code availability statement has been added. + +<|ref|>sub_title<|/ref|><|det|>[[92, 681, 313, 696]]<|/det|> +## Supplementary Information: + +<|ref|>text<|/ref|><|det|>[[91, 699, 896, 822]]<|/det|> +- A new section (1) has been added to provide more detailed plots on the ResPES data.- A new section (3) has been added to discuss the influence of J in our calculations, including relevant new references.- All figures and sections were renumbered to accommodate the new sections.- All figure captions have been refined at the request of Reviewer 1.- Eduardo Bonini Guedes has been added as a co-author (see above).- The current address of Trpimir Ivšić has been added. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 83, 384, 98]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[92, 109, 894, 194]]<|/det|> +The paper describes a highly impressive and thorough investigation of properties of the high entropy Cantor- Wu alloy, CrMnFeCoNi, via photoemission spectroscopy, optical conductivity and electrical resistivity experiments, all of which are analysed with detailed, quantitative theoretical calculations. The work is a fine case study of the rich links between electron correlations, nature of self energy effects and multicomponent disorder. + +<|ref|>text<|/ref|><|det|>[[92, 205, 894, 358]]<|/det|> +Element- specific information extracted from resonant PES and X- ray absorption data show the effects on these data of localised electron correlations in concert with chemical disorder and magnetic fluctuations. Electron correlation effects are modelled effectively by DFT+DMFT within a KKR- CPA framework using prescribed U values for local onsite correlations. Element- specific information such as quasi- particle lifetimes is also extracted from optical conductivity measurements and appropriate rigorous theoretical analysis. Finally the authors show that localised correlation effects appear to have less effect on the temperature- dependent electrical resistivity calculations which undershoot the experimental measured values. They identify important aspects such as atomic short- range order and Anderson- type localisation effects that require further study. + +<|ref|>text<|/ref|><|det|>[[92, 368, 893, 437]]<|/det|> +The paper is very interesting and suitable for publication in Nature Communications. The manuscript, however, could be improved by some further proof- reading and also making the figure captions more accessible and easier to follow - the reader could be reminded about what some of the acronyms stand for (e.g. CST, TR- 2PPE) and directed to note certain features. + +<|ref|>sub_title<|/ref|><|det|>[[92, 448, 161, 462]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 473, 894, 560]]<|/det|> +We sincerely appreciate Reviewer 1's detailed and positive feedback on our manuscript. We have carefully addressed all the points raised, including proof- reading and enhancing the figure captions for clarity and accessibility. We defined all abbreviations in the captions, pointed out important features and added physical explanations (if they are not too long). We believe these revisions have significantly improved the quality of the manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 83, 384, 98]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[92, 109, 894, 230]]<|/det|> +This manuscript delves into the exploration of disorder and electronic correlations within the CrMnFeCoNi high- entropy alloy using photoemission spectroscopy, and the results are compared with DFT/DMFT calculations. This is a timely piece of work because detailed investigations into the electronic structure of these alloys, particularly with regard to the elemental contributions to the valence band structure, is still very rare. While the quality of the work is commendable, this reviewer suggests that the manuscript may find a better fit in a specialized journal with a stronger physics focus. The findings, while of importance, may lack the broader impact required for publication in a top- tier journal like this. + +<|ref|>sub_title<|/ref|><|det|>[[92, 241, 161, 255]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 266, 893, 335]]<|/det|> +We would like to thank Reviewer 2 for the invested time and positive scientific evaluation of our work. However, we respectfully disagree with the assertion that our manuscript "may lack the broader impact required for publication in a top- tier journal like this." We believe that our study is highly suitable for Nature Communications, and we would like to highlight a few points: + +<|ref|>text<|/ref|><|det|>[[92, 344, 893, 447]]<|/det|> +We think that our study represents a significant advancement as it provides, to our knowledge, the first quantitative comparison of the influence of disorder and correlated many- body effects on electronic structure- driven properties in CCAs/HEAs. Based on the results, we are able to make clear statements regarding electronic spectra, transport and optics. In principle, these can be generalized to other multi- principal element alloys and are therefore suitable for many other technically important advanced materials. + +<|ref|>text<|/ref|><|det|>[[92, 457, 894, 627]]<|/det|> +Building on recent findings on CCAs, such as studies on short- range order [Nature 624, 564- 569 (2023); Nat. Commun, 13, 1021 (2022); Nat. Commun. 581, 283- 287 (2020)], or nano- structure induced mechanical properties [Nat. Commun. 15, 4599 (2024), Nat. Commun. 14, 2516 (2023)], we describe an additional physical mechanism that influences key material properties. Further, we want to highlight that some papers were recently published in Nature Communications regarding electronic and phononic transport [Nat. Commun. 15, 4554 (2024), Nat. Commun. 13, 7509 (2022)], utilizing specific HEAs as model materials and providing generalizable results. We would also like to emphasize the potential of the results to extend DFT- based machine learning models [Science 378, 6615, 78- 85 (2022)] to account for many- body correlation effects. From our perspective, this appears to be crucial for the further development of alloys with improved transport and optical properties. + +<|ref|>text<|/ref|><|det|>[[92, 638, 893, 724]]<|/det|> +Regarding optical properties, our findings are also interesting for the photonics industry, which operates largely in the visible and near- infrared spectral regions. Alloys are of decisive importance for these applications, especially in laser processing, where the initial absorption of laser radiation is the central part of the process. Here we can clearly demonstrate that through the implementation of correlated many- body effects, the predicted optical spectra are improved. + +<|ref|>text<|/ref|><|det|>[[92, 734, 893, 802]]<|/det|> +Another point is that the KKR- CPA approach is extremely valuable for disordered alloys and is attracting increasing interest from the materials science community, especially for HEA calculations. We also wish to emphasize the extremely positive feedback from the other two Reviewers, including their suggestion for publication. + +<|ref|>text<|/ref|><|det|>[[92, 812, 893, 880]]<|/det|> +Finally, we understand that the broader implications of our study were not immediately apparent in the previous version of our manuscript, due to the specific and concise nature of our abstract and conclusion. Therefore, we have added some sentences at the beginning of the summary and at the end of the conclusion to attract the interest of a wider audience. + +<|ref|>text<|/ref|><|det|>[[92, 890, 893, 923]]<|/det|> +We hope these revisions and clarifications will convince the Reviewer of the broader impact and significance of our work. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 83, 385, 98]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[93, 110, 172, 123]]<|/det|> +## Reviewer: + +<|ref|>text<|/ref|><|det|>[[92, 136, 895, 272]]<|/det|> +In this manuscript, the authors investigated the electron correlation effect on the band structure and transport properties in HEA- CrMnFeCoNi using both experimental and theoretical methods. The authors found that the KKR- CPA+DMFT method explains the experimental results well, showing the importance of electron correlation even in HEAs. The authors also discuss the differences between LDA and LDA+DMFT in detail by comparing low- energy and high- energy electronic transport properties, emphasizing the importance of strong correlation effects, especially in the high- energy regime. This study advances the understanding of electronic states in HEAs and provides significant information to those working in this field. + +<|ref|>text<|/ref|><|det|>[[92, 283, 528, 298]]<|/det|> +I have the following comments regarding this manuscript: + +<|ref|>sub_title<|/ref|><|det|>[[92, 310, 161, 324]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 336, 894, 386]]<|/det|> +The authors would like to thank Reviewer 3 for his time and valuable comments. We are also very pleased to receive positive feedback on our work. We have addressed all the points raised and are confident that our revisions have improved the quality of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[92, 398, 172, 412]]<|/det|> +## Reviewer: + +<|ref|>text<|/ref|><|det|>[[92, 424, 894, 457]]<|/det|> +(1) In the Methods section, while the element dependence of U is discussed in detail, the Hund coupling J is treated as element-independent. The authors should explain the reason for this. + +<|ref|>sub_title<|/ref|><|det|>[[92, 469, 161, 483]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 494, 895, 633]]<|/det|> +In principle, we could have introduced a small variation of the Hund exchange to mimic what has been reported for the 3d elemental series. Calculations based on constrained random-phase approximation (cRPA) show that the Hund exchange changes of about 0.1 eV when going from Cr to Ni [Phys. Rev. B 77, 085122 (2008)]. This variation may be \(50\%\) larger in our case, accounting for differences in the local orbitals [see also Ref. 49 in the manuscript]. There are, however, two main reasons why this variation is not fully meaningful in our case. First, our study is focused on a high-entropy alloy and not on pure elements. Cr, Fe and Co have a different crystal structure than the one investigated here, with a different number of neighbors and a different screening. Second, a change of \(J\) of about 0.1 or 0.2 eV would have no visible + +<|ref|>image<|/ref|><|det|>[[108, 644, 528, 916]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[559, 633, 895, 924]]<|/det|> +effect on our calculations. This is due to the particular computational scheme we use for our study, where the DMFT self- energy acts as a correction to a spin- polarized DFT solution. In this approach, which is the most common way to apply DFT+DMFT to magnetic materials, the major effect associated to \(J\) , i.e. the renormalization of the exchange splitting, is completely canceled by the double- counting term [see e.g. Phys. Rev. B 97, 184404 (2018) for the analysis of the consequences on the effective magnetic coupling]. A detailed investigation of these methodological subtleties has been provided for DFT+U, in Phys. Rev. B 98, 125126 (2018). On the left, we show Fig. 2 of this work, focused on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 895, 237]]<|/det|> +LaMnO3. In panel (a), various exchange splittings are defined. In panel (b), these values are plotted with respect to the variation of the Hund exchange J. Variations of the order of 0.1 or 0.2 eV cause minor changes in the splitting and thus in the spectrum. These changes are due to the fact that J also determines the anisotropic effects among the different orbitals of the 3d shell. To restore a more significant dependence, one should work with a non- spin- polarized DFT solution and let the whole magnetism arise from the local problem in DMFT or DFT+U. This is illustrated by the data plotted in panel (c). Although these data are for DFT+U, similar trends are expected for DFT+DMFT. The presence of higher order terms beyond Hartree- Fock is likely to be compensated by the reduction of the effective interaction due to dynamical screening [see e.g. discussions in Phys. Rev. B 90, 165130 (2014)]. + +<|ref|>sub_title<|/ref|><|det|>[[92, 248, 172, 262]]<|/det|> +## Reviewer: + +<|ref|>text<|/ref|><|det|>[[92, 274, 564, 290]]<|/det|> +(2) The effect of J on the electronic states should be discussed. + +<|ref|>sub_title<|/ref|><|det|>[[92, 302, 161, 316]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 327, 895, 430]]<|/det|> +In the previous answer, we have explained why a small variation of \(J\) is expected to have a negligible effect on the final spectra. We now aim to demonstrate this, as suggested by the referee, on systems related to our study. For this purpose, we calculated the influence of a \(J\) variation on the electronic spectra for ferromagnetic (FM) Ni and paramagnetic (DLM) FeNi, using the SPRKKR package. \(J\) is changed at both Fe and Ni sites, while the U values arekept to the same values as those reported in the paper. The density of states (DOS) resulting from these calculations is shown in the following figure, panels (a) to (c). + +<|ref|>image<|/ref|><|det|>[[98, 446, 864, 797]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[92, 825, 895, 928]]<|/det|> +Even a variation of \(J\) as large as \(\pm 0.4 \mathrm{eV}\) (from \(J = 0.5 \mathrm{eV}\) to \(1.3 \mathrm{eV}\) ) does not lead to a significant shift in the spectral weight of the d- bands for FM Ni (see excitation energies between - 5 eV and 0 eV). The most visible effect is a slight shift of the split- off satellites. For ferromagnetic Ni, majority (up) channel, the satellite shifts from - 8.2 eV to - 8.7 eV as \(J\) increases from 0.5 eV to 1.3 eV. This corresponds to a shift of \(\Delta P_s / \Delta J = - 0.6\) ( \(P_s\) is the position of the spectral weight of the satellites). For the minority (down) spin channel, the satellite is less marked and appears as a shoulder- like feature between - 5 and - 10 eV. Increasing \(J\) causes a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 82, 893, 150]]<|/det|> +farther attenuation. For paramagnetic FeNi, even smaller changes in the electronic spectra are observed for J variations from 0.6 eV to 1.2 eV. As for the minority spin channel of FM Ni, a slight influence on the shoulders around - 8 eV is found. No changes in the bandwidth or shift of the d- block are observed upon a variation of \(J\) . + +<|ref|>text<|/ref|><|det|>[[92, 160, 894, 384]]<|/det|> +Finally, in panel (d), we show how the results of the calculations for paramagnetic (DLM) CrMnFeCoNi depend on varying \(J\) . The \(U\) values again correspond to those in the main manuscript. Unlike FeNi, we find no influence on the shoulder features at - 8 eV, which means that the simultaneous variation of \(J\) at the various sites leads to compensating effects. The main peak position remains unchanged at - 1 eV for all \(J\) , while its height only slightly decreases from 2.01 states/eV/atom to 1.97 when \(J\) goes from the lowest to the largest value. The DOS at \(E_{\mathrm{F}}\) is completely unaffected. The spectral width of the d- band block does not change, but the spectral weight shifts slightly towards higher binding energies with increasing \(J\) . This is observed in the flanks of the \(d\) - band block, which shift approximately with \(\Delta P_{\mathrm{f}} / \Delta J = - 0.3\) ( \(P_{\mathrm{f}}\) is the position of the \(d\) - band flanks). Compared to the effect induced by a variation of \(U\) , as shown in Figure 2(a) of the main manuscript or Figure 3(b) in the supplementary materials, the uncertainty of \(J\) is negligible. An increase of \(U\) for Ni from 3 eV to 4 eV in CrMnFeCoNi induces a direct and isolated shift of the Ni satellite from - 8 eV to - 10 eV. This corresponds to \(\Delta P_{\mathrm{s}} / \Delta U = - 2\) . Considering that the expected variation of \(J\) is of 0.1 eV to 0.2 eV, as discussed in the previous question, we can safely ignore this effect. + +<|ref|>text<|/ref|><|det|>[[92, 394, 894, 479]]<|/det|> +We agree with the referee that these issues should be addressed in our manuscript. Therefore, we have summarized the main points of the previous discussions in the Supplementary Information, where we also included the previous results. In the main manuscript, we added a reminder to this discussion in the Methods section, just after mentioning our choice of keeping the Hund exchange constant for all the elements considered. + +<|ref|>sub_title<|/ref|><|det|>[[92, 490, 172, 504]]<|/det|> +## Reviewer: + +<|ref|>text<|/ref|><|det|>[[92, 515, 644, 532]]<|/det|> +(3) In Fig. 4(a), the LDA+DMFT calculation results should also be included. + +<|ref|>sub_title<|/ref|><|det|>[[92, 543, 161, 558]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 569, 894, 656]]<|/det|> +Figure 4(a) shows the experiments on the electrical resistivity of various alloys, ranging from Ni to CrMnFeCoNi. Due to the lack of short- range order in our CPA- based calculations, we observed a larger offset between measurements and calculations. This issue has already been discussed in the manuscript. In response to the referee's suggestion, we have now included the LDA+DMFT calculations (see dashed line in the revised manuscript). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 331, 107]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 152, 428, 170]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 215, 877, 255]]<|/det|> +The authors have satisfactorily addressed points raised in my first report and have improved the manuscript. The paper is suitable for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 332, 428, 350]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 394, 867, 565]]<|/det|> +Like I mentioned in my previous review, the manuscript is of good quality and provides important missing data in the current understanding of CCAs. My concern about this manuscript lies in its limited broader impact. More specifically, the new data on the electronic structure of this model alloy does not seem to bring significant new insights or enhance our general knowledge of how CCAs differ from conventional alloys. The authors attempt to address this in their revised manuscript, but the connection between the new data and new insights remains unclear to me. However, as scientific importance is somewhat subjective, I will leave the final decision to the editor. + +<|ref|>text<|/ref|><|det|>[[115, 640, 428, 658]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 702, 860, 763]]<|/det|> +The authors have provided a satisfactory response to my comments. Therefore, I have no further concerns, and I believe that this manuscript is suitable for publication in Nature Communications. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 83, 880, 117]]<|/det|> +## Response to Reviewer's remarks on the manuscript entitled "Interplay between disorder and electronic correlations in compositionally complex alloys" (NCOMMS-24-11440) + +<|ref|>text<|/ref|><|det|>[[116, 127, 881, 177]]<|/det|> +We sincerely thank the reviewers for their thorough evaluation and positive feedback on our revised manuscript. The constructive comments have undoubtedly improved the manuscript and we are pleased that it is now suitable for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 189, 880, 221]]<|/det|> +As the reviewers did not raise further questions or suggest any additional changes, we have not revised the manuscript further. + +<|ref|>text<|/ref|><|det|>[[116, 233, 613, 248]]<|/det|> +We greatly appreciate your time and effort in reviewing our work. + +<|ref|>text<|/ref|><|det|>[[116, 260, 316, 275]]<|/det|> +On behalf of all coauthors, + +<|ref|>text<|/ref|><|det|>[[116, 287, 192, 301]]<|/det|> +Jan Minár + +<--- Page Split ---> diff --git a/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..297e4a694b5bec5a54fb7871ecc16d4cf5e4b475 --- /dev/null +++ b/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,388 @@ + +# Multi-trait association analysis reveals shared genetic loci between Alzheimer's disease and cardiovascular traits + +Corresponding Author: Dr Fotios Koskeridis + +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The manuscript's exploration of genetic risk factors common to Alzheimer's disease and cardiovascular diseases is of significant interest due to the potential implications for understanding disease mechanisms and informing therapeutic strategies. However, the manuscript primarily recounts experimental methodologies and fails to provide substantial interpretation or discussion of the results. Moreover, the proposed shared risk factors, PLEC and C1Q, lack sufficient validation within the study. As it stands, I cannot endorse this manuscript for publication in Nature Communications. + +To improve the manuscript, the authors should consider the following: + +First of all, the GWAS database used for the analysis should be defined and interpretated carefully in the manuscript. 1. The author used published GWAS data from Alzheimer's diseases for the extraction of AD traits (62 AD genetic loci). The author should compare their analysis and the result with the original publication. 2. To extract cardiovascular traits, the author used diverse GWAS data from five different publications; atrial fibrillation, coronary artery disease, stroke, carotid intima- media thickness, systolic and diastolic blood pressure. 'Intima- media thickness' and 'systolic and diastolic blood pressure' are not terms of disease condition. Their inclusion in cardiovascular trait extraction necessitates a clear exposition of their connection to atrial fibrillation, coronary artery disease, and stroke. 3. The justification for using a diverse range of GWAS data to extract cardiovascular traits must be elaborated upon. The authors should demonstrate the advantage of this diversity and whether it led to definitive conclusions about cardiovascular traits. 4. A discussion on the 740 cardiovascular loci identified should be provided to underscore their relevance and significance. 5. The manuscript must critically examine the heterogeneity of the phenotypes in the GWAS datasets, especially considering the comorbidity of AD and cardiovascular symptoms, and delineate how these datasets were selected and utilized in light of the study's objectives + +Regarding the identification of PLEC and C1Q as shared risk factors: + +6. The significance of PLEC, HSPG2, and APOE, which were implicated based on the multi-trait colocalization method, must be contextualized with previous GWAS findings on AD and cardiovascular disease (CVD) traits. +7. The shared risk factors for AD and CVD indicated by genetic variants rs11786896 (PLEC) and rs7529220 (HSPG2) should be reassessed, as the observed odds ratios do not robustly categorize them as high-risk factors for Alzheimer's disease or atrial fibrillation. +8. The relevance of the identified loci to other cardiovascular traits should be discussed. If no correlation exists, the study should narrow its focus to the relationship between AD and atrial fibrillation, avoiding unnecessary data and analyses. Finally, while the single-nuclei transcriptome and protein-protein interaction analyses involving PLEC, NDUFS3, and C1Q on AD brain tissues are noted, the study fails to elucidate a clear pathogenic connection of these targets to Alzheimer's disease and atrial fibrillation. + +Reviewer #2 + +(Remarks to the Author) + +<--- Page Split ---> + +## Overview + +OverviewThe work uses MTAG to examine AD with cardiovascular traits. The motivation is the long- standing association between cardiovascular disease and AD, and the method harnesses the genetic correlation to improve power for detecting genetic associations. The authors use eQTLs identified from a range of tissues from the GTEx project plus their results to perform colocalization analyses and hone in on two sites, and follow up some of those findings with analysis of gene expression. Overall, the manuscript was clear and interesting. The methods are well- described and approach seems sound, but it looked like there might be a disagreement between figure 3 and text and figure 2 does not share enough detail so it cannot be used to check against the text, which were my most important concerns. I had some specific comments below but I also wondered 1) if the authors could examine genetic correlation between AD and the traits in addition to sharing the MTAG results; and, 2) whether the authors considered testing colocalization with multiple traits at loci that seemed like they had \(= 2\) signal with several cardiovascular traits. + +## Major Comments + +Major Comments1. Title – at best, these data let you say that there is evidence consistent with what you'd observe with pleiotrophy. Also, there are more genes implicated than just PLEC and C1Q, unless I missed something.2. Figure 1 would be helped by sharing the sample sizes for each GWAS used to let the reader understand their magnitudes.3. Figure 2 is difficult to read - can it just be made into a horizontal plot with labeled axes?4. Figure 3 seems to present different p-values compared to the text (lines 112-115) that should be checked.5. Please provide manhattan and qq plots for each trait combination.6. Discussion - lines 218-221. The authors claim the results of their study disentangles the relationship between AD and AF. This is beyond what I think they can say with these data since the outcome in the Jansen paper is mainly from the UKB that infers case status using a question about whether the parent had dementia. This introduces a substantial amount of heterogeneity as to the underlying cause of dementia that ranges from cerebrovascular disease to a purely neurodegenerative cause, which preclude the kind of conclusion the authors made. Using Kunkle et al., 2018, which relies on a clinical diagnosis, might help this. Regardless of the specific cause of dementia, it's clear that there's a relationship between dementia and AF.7. Using gene expression from tissues that are not likely directly relevant for the pathogenesis of AD or one of the CVD traits rests on an assumption that the eQTLs in that tissue are generalizable. It could be that they are false positives in one tissue and are correctly null in other tissues. + +## Minor Comments + +Minor Comments1. Consider adding the limitation that not all GWAS summary results are complete so signal that is not present in one of the dataset pairs would not be tested using MTAG.2. Figure 3 – the eQTL line plot is confusing. Why not stack the two tissues and use dots? Either way, the association between the eQTL signal and other traits (i.e., AD, atrial fib) are not striking.3. Unlike CVD traits, AD has one region, the APOE locus, that has an outsized effect compared to other genetic loci. I would guess the results from APOC1 were driven by the association between AD and APOE.4. Discussion - lines 204-5 (grammer/phrasing) - "rs11786896 expressed via PLEC and rs7529220 expressed via C1QA, C1QB, and C1QC" sounds odd. I'd phrase it something like rs1179686 is an eQTL for PLEC. + +## Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have fully addressed reviewers' comments and the revised version is worth being accepted for publication as it is. + +Reviewer #2 + +(Remarks to the Author) + +No matter how AD is commonly defined (e.g., clinically or pathologically), it often co- occurring with evidence of cerebrovascular disease yet whether this is pleiotropic or causal relationship is unknown -- although there is some work that suggests a direct link https://pubmed.ncbi.nlm.nih.gov/35772923/. The current work focuses on finding shared genetic risk using MTAG, which uses genetic correlation to boost power for multi- trait gwas. The most interesting portion of the work is the MTAG results along with the SMR analysis. By contrast the differential expression and network- based analysis was descriptive without addressing the most interesting question of the work -- the shared risk for CV traits and AD dementia. Overall, the revised manuscript nicely addressed my comments. + +## Minor Comments + +1. line 297 - AD-proxy status was inferred based on whether the parent was diagnosed with dementia (not AD per se). + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The manuscript's exploration of genetic risk factors common to Alzheimer's disease and cardiovascular diseases is of significant interest due to the potential implications for understanding disease mechanisms and informing therapeutic strategies. However, the manuscript primarily recounts experimental methodologies and fails to provide substantial interpretation or discussion of the results. Moreover, the proposed shared risk factors, PLEC and C1Q, lack sufficient validation within the study. As it stands, I cannot endorse this manuscript for publication in Nature Communications. To improve the manuscript, the authors should consider the following: + +Reply: Thank you for your feedback and insightful comments. We have carefully revised our manuscript to address them, ensuring a cautious and robust interpretation of our results. Further details on your specific comments are provided below. + +1.1 First of all, the GWAS database used for the analysis should be defined and interpretated carefully in the manuscript. + +Reply1.1: We have provided detailed descriptions of the GWAS datasets in the methods section, including citations, sources, and characteristics (new Supplementary Table 18). + +In lines 327- 332 (p.14) we now explain "We restricted our study to a population of European ancestry. We used the summary statistics from seven GWAS on the following diseases: AD, AF, CAD, cIMT, stroke, SBP, and DBP. We selected these datasets based on the sample size (with preference for larger GWAS), the quality of the phenotypic data, the date of publication (favouring more recent studies), and their relevance to our research questions. Supplementary Table 18 lists basic characteristics of all included GWAS datasets." + +<--- Page Split ---> + +1.2 The author used published GWAS data from Alzheimer's diseases for the extraction of AD traits (62 AD genetic loci). The author should compare their analysis and the result with the original publication. + +Reply 1.2: The primary focus of our results was the investigation of pleiotropic loci between AD and CVD rather than the description of novel findings stemming from MTAG. We acknowledge that the latter is also of interest to the readers. In this revised version, we have included a comprehensive comparison between novel and previous findings for all examined traits. We provided Manhattan plots and QQplots for each trait, comparing MTAG results with those from the original GWAS (Supplementary Figures 1- 6) and reported novel loci for each trait (Table 1). We also provided new analysis to support the validity of novel findings in relation to AD. + +To ensure robust findings and to facilitate a rigorous comparison, we implemented strict criteria to define MTAG loci. Specifically, we considered only loci that were at least 500kb distant and independent (LD < 0.1) from previously reported signals. Next to the genome- wide significant p- value in MTAG results, these loci also had to exhibit nominal significant association (P < 0.01) in the original GWAS with concordant direction of effect. To reflect these updates, we have thoroughly revised our manuscript accordingly. We have included a detailed explanation in the methods. For example: + +"To ensure the robustness of our findings, we considered only MTAG loci if the respective top variants were also associated with the examined trait (P < 0.01) in the corresponding original GWAS with a concordant direction of effect (between MTAG and the original GWAS)." (p.15, lines 361- 363) + +Moreover, to identify novel signals, we compared the MTAG findings with those from previously published GWAS. Specifically for AD, we assessed previously identified loci from three key GWAS studies (Jansen et al., Kunkle et al., and Bellenguez et al.). A dedicated section in the methods has been included to elaborate on how novel signals were defined. + +<--- Page Split ---> + +"A signal indicated by MTAG was considered novel if its top variant achieved genome- wide significance \((P< 5\times 10^{- 8})\) in MTAG results and was also statistically significant \((P< 0.01)\) in the included original univariate GWAS with a concordant direction of effect (between MTAG and the original GWAS). Additionally, the top variant should not be located within \(\pm 500kb\) or in LD \((r^{2} > 0.1)\) with previously reported loci. For AD, in addition to the included GWAS study, novel loci were compared to two previously published key GWAS studies." (p.16, lines 368- 373) + +In the results section we highlight novel findings, for example: + +"Across all pairwise MTAG analyses, we identified 27 unique genetic loci associated with AD at genome- wide significance (GWS) level \((P< 5\times 10^{- 8})\) corresponding to 114 unique single- nucleotide polymorphisms (SNPs) (Supplementary Table 2). Out of the 27 AD loci, 5 were novel (not within \(\pm 500\) kilobases (kb) of the previously known AD loci) and among them rs73069394 (ULK4) displayed the strongest association (Table 1). + +To further validate the associations of the novel AD loci, we applied summary data- based Mendelian randomisation (SMR) and heterogeneity in dependent instruments (HEIDI) using gene expression data in relevant brain tissues. SMR analysis suggested a potentially causal association between ULK4 expression in the hippocampus and AD risk \((\beta_{SMR} = 0.04, P_{SMR} = 3.4\times 10^{- 10}, P_{HEIDI} > 0.05)\) . SMR was not possible for the remaining loci due to unavailability of gene expression data. + +Furthermore, we found 1,222 top signals associated with different CV traits at GWS level in 740 genetic loci (Supplementary Table 3). Of these, 13 novel loci were highlighted for CAD \((N = 4)\) , cIMT \((N = 8)\) and stroke \((N = 1)\) (Table 1). Overall, 15 of the unique AD SNPs (9 loci) were additionally associated at GWS level with at least one of the examined CV traits (Supplementary Table 4)." (p.2- 3, lines 47- 63) + +Of note, these refinements, which ensure our manuscript presents findings with robust evidence, do not alter the highlighted results or conclusions of our initial manuscript, as we had already applied these criteria in the subsequent analyses following MTAG. + +Finally, we discuss novel findings: + +<--- Page Split ---> + +"Our study highlighted 5 not previously reported AD loci including SNPs located in or near HSPG2, AC019055.1, ULK4, KRT18P16 and ACTN4. Of them, the intronic variant rs73069394 (ULK4) showed the strongest association with AD and was also GWS associated with DBP. The locus did not show evidence for colocalization between AD and DBP suggesting this variant is not likely the causal one for both traits. Apart from DBP, GWAS studies have shown associations between this locus and schizophrenia and bipolar disorder. The role of the ULK4 in relation to neurodegeneration is little studied but the gene function shows biological plausibility to AD. ULK4 protein is involved in the regulation of autophagy and plays multiple roles in brain function including neuronal growth, endocytosis and myelination which are pathways implicated to AD pathology. Here, we also provided additional evidence from SMR analysis supporting a potentially causal association between expression levels of ULK4 and AD." (p.9, lines 196- 207) + +1.3 To extract cardiovascular traits, the author used diverse GWAS data from five different publications; atrial fibrillation, coronary artery disease, stroke, carotid intima- media thickness, systolic and diastolic blood pressure. 'Intima- media thickness' and 'systolic and diastolic blood pressure' are not terms of disease condition. Their inclusion in cardiovascular trait extraction necessitates a clear exposition of their connection to atrial fibrillation, coronary artery disease, and stroke. + +Reply 1.3: Our objective was to systematically explore the interconnection between AD and CVDs by covering a broad spectrum of cardiovascular conditions and associated traits, which is now stated more clearly throughout the manuscript: + +"AD has been considered a brain- specific disease whose primary pathology is confined to the brain. However, accumulating evidence suggests mechanistic links between a wide range of cardiovascular (CV) abnormalities and AD. Epidemiological studies and experimental data have shown consistent associations between manifestations of clinical CV diseases such as coronary heart disease (CHD), atrial fibrillation (AF) and stroke, with higher risk of AD. Several hypotheses have been proposed to explain this. Indeed, atherosclerosis, the main underlying cause of cardiovascular diseases, also has profound consequences on the cerebrovascular system. These include reduced blood flow and potential vascular damage in the + +<--- Page Split ---> + +brain, impaired cerebral perfusion, and associations with inflammation and oxidative stress, all of which are factors that can contribute to neurodegenerative pathology and increase the risk of AD. Beyond atherosclerosis, other hemodynamic effects associated with hypertension, arteriosclerosis and subsequent aortic stiffening have been associated with cerebrovascular damage and cognitive function, potentially accelerating the onset and progression of AD." (p.1, lines 4- 17) + +"Here, we further investigated the commonalities in the genetic architecture of AD and CV traits and identified pleiotropic loci affecting multiple traits aiming to define common targets for therapeutic modulation. We explored a wide range of CV abnormalities and two common main risk factors, atherosclerosis and blood pressure, proposed to underlie both CV and AD, to investigate different molecular pathways that may link different CV manifestations to AD." (p.2, lines 29- 33) + +1.4 The justification for using a diverse range of GWAS data to extract cardiovascular traits must be elaborated upon. The authors should demonstrate the advantage of this diversity and whether it led to definitive conclusions about cardiovascular traits. + +Reply 1.4: We selected a diverse range of GWAS datasets to encompass a broad spectrum of cardiovascular traits, given the unclear connection with AD. This approach allowed a thorough exploration of how genetic factors contribute to the interconnection between AD and CV conditions, offering a more comprehensive understanding than focusing solely on a single CV trait. + +In the introduction, we have added a paragraph explaining this: + +"Here, we further investigated the commonalities in the genetic architecture of AD and CV traits and identified pleiotropic loci affecting multiple traits aiming to define common targets for therapeutic modulation. We explored a wide range of CV abnormalities and two common main risk factors, atherosclerosis and blood pressure, proposed to underlie both CV and AD, to investigate different molecular pathways that may link different CV manifestations to AD." (p.2, lines 29- 33) + +<--- Page Split ---> + +## In the discussion, we further mention: + +"Third, exploring a wide spectrum of CV diseases pairwise enabled a comprehensive investigation into the diverse shared mechanisms underlying the relationship between different manifestations of CV conditions and AD." (p.12, lines 275- 277) + +1.5 A discussion on the 740 cardiovascular loci identified should be provided to underscore their relevance and significance. + +Reply 1.5: Thank you for the suggestion. The primary aim of our study was to identify pleiotropic genes linking AD and CVDs. The genetic architecture of CV conditions has been much more extensively studied with large scale GWAS compared to AD. Here, we aimed to leverage the co- occurrence of CV conditions with AD to increase the power of AD GWAS studies and identify shared loci including novel loci related to AD. Following your suggestion, we now compared the reported loci for all examined traits (see response to comment 1.2). The vast majority of the 740 loci (727 loci) were already reported loci for CVD and the new ones are highlighted in Table 1. + +1.6 The manuscript must critically examine the heterogeneity of the phenotypes in the GWAS datasets, especially considering the comorbidity of AD and cardiovascular symptoms, and delineate how these datasets were selected and utilized in light of the study's objectives + +Reply 1.6: Our study utilised summary statistics derived from publicly available GWAS datasets, which precluded us from examining the heterogeneity in the original GWAS datasets. We acknowledge that any potential heterogeneity present in these datasets could affect the results of our study. We included this limitation in our manuscript. + +"GWAS compares the cases we are studying with controls, but due to comorbidity, the number of other diseases might be higher in cases than in controls. As we used summary statistics + +<--- Page Split ---> + +without access to individual- level data, we couldn't examine or address this heterogeneity. Despite this limitation, the identified shared genes remain valid and important for understanding their genetic connections." (p.12, lines 286- 291) + +To mitigate this limitation, we employed a bivariate analysis approach, examining the shared associations between AD and each CV trait separately. We used MTAG, which accounts for phenotypic heterogeneity from diverse populations and studies by leveraging the genetic correlation among the examined traits. Furthermore, MTAG provides trait- specific summary statistics and therefore we were able to explore the potential influence of other CV traits on our observed associations between AD and specific CV traits, by systematically comparing our findings across all examined CV traits. This approach provided insights into the complex interrelationships among these traits and their potential impact on AD. Our discussion now states: + +"Out of the several CV traits and diseases examined with AD, the largest number of pleiotropic signals with AD was observed for AF and BP highlighting the importance of pathways related to these CV traits in explaining comorbidities with AD. Numerous observational studies, provide growing evidence that BP and AF are associated with cognitive impairment, risk of AD and other dementias. The suggested mechanistic links between these traits and AD involve a combination of cerebrovascular damage, neuroinflammation, amyloid- beta accumulation, oxidative stress, and endothelial dysfunction. However, it is unclear whether the diseases have a shared pathophysiology or whether the relationship arises as downstream consequences of BP and AF (e.g., stroke)." (p.9, lines 208- 216) + +Finally, in response to your suggestion, we have provided a description in the methods outlining the criteria used for selecting and utilising the GWAS datasets relevant to our study objectives. + +"We selected these datasets based on the sample size (with preference for larger GWAS), the quality of the phenotypic data, the date of publication (favouring more recent studies), and their relevance to our research questions." (p.14, lines 329- 332) + +<--- Page Split ---> + +Regarding the identification of PLEC and C1Q as shared risk factors: + +1.7 The significance of PLEC, HSPG2, and APOE, which were implicated based on the multi- trait colocalization method, must be contextualized with previous GWAS findings on AD and cardiovascular disease (CVD) traits. + +Reply 1.7: Thank you for your comment. PLEC and HSPG2 are among our most highlighted findings, and we have discussed their importance in the context of previous studies. For instance, we state in the discussion: + +"A low- frequency missense variant in PLEC has been previously associated with atrial fibrillation in whole- genome sequencing data whereas another missense variant has been linked to structural brain connectivity. The intronic variant highlighted in this analysis has been previously associated with right ventricular structure and function but has not been identified in GWAS studies as an AD or AF signal." (p.10, lines 222- 226) + +"Previous studies of human tissues or preclinical models provide independent evidence for an association of plectin with diseases including AD and AF." (p.10, lines 229- 231) + +We also included in the discussion regarding HSPG2: + +"Another colocalised variant between AD and AF, the intergenic rs7529220, which is located 19k upstream from Heparan Sulfate Proteoglycan 2 (HSPG2) ... and is a previously unreported locus for AD." (p.11, lines 252- 257) + +APOE is a well- established gene associated with AD, and previous studies have supported its involvement in cardiovascular traits. Although our initial colocalisation analysis provided considerable evidence for its possible pleiotropic effect on AD and coronary artery disease (PP = 0.57), our subsequent eQTL colocalisation analysis could not replicate this association. This suggests that our study could not prioritise any shared gene within the locus between the two traits expressed in the examined tissues. Given the robust evidence from several independent studies linking APOE to both traits, it is plausible that the locus affects the two traits independently through different pathways (horizontal pleiotropy). + +<--- Page Split ---> + +Alternatively, there may be a shared gene expressed in tissues other than those we examined in our study. We added in the discussion: + +"The variant rs429358, located within APOE, showed evidence for colocalisation between AD and CAD. However, further investigation using eQTL could not prioritise any shared gene within the locus expressed in the examined tissues. Given APOE's well- established role in AD and its potential involvement in other CV traits, including CAD, it is plausible that the locus affects the two traits independently through different pathways (horizontal pleiotropy) or through a shared gene expressed in tissues other than those examined in our study." (p.11, lines 264- 269) + +1.8 The shared risk factors for AD and CVD indicated by genetic variants rs11786896 (PLEC) and rs7529220 (HSPG2) should be reassessed, as the observed odds ratios do not robustly categorize them as high- risk factors for Alzheimer's disease or atrial fibrillation. + +Reply 1.8: We appreciate your notice. In the revised manuscript, we present the odds ratios (OR) and p- values from the MTAG analysis, which show that HSPG2 is associated with both traits at a GWS level, while PLEC is associated with AD at a GWS level and associated with AF ( \(P < 5 \times 10^{- 6}\) ). Indeed, the reported ORs are small (e.g. OR=1.02 for PLEC); however, it is not uncommon in GWAS studies to observe associations of variants with small effect sizes, which nonetheless can have significant biological importance. In support, the genetic colocalisation as well as other subsequent analyses consistently showed that these loci are associated with both AD and AF with the same causal variant, suggesting a pleiotropic effect. Figure 3 in our manuscript demonstrates a signal for both traits at the PLEC locus, underscoring the shared genetic architecture. + +1.9 The relevance of the identified loci to other cardiovascular traits should be discussed. If no correlation exists, the study should narrow its focus to the relationship between AD and atrial fibrillation, avoiding unnecessary data and analyses. + +<--- Page Split ---> + +Reply 1.9: Thank you for your comment. As previously mentioned, we compared our findings across diverse CV traits that is thoroughly discussed in the revised version of our manuscript. + +We aimed to look at several CV conditions in pairwise comparisons to explore the different pathways that may link different manifestations of AD with CV traits. For example, atrial fibrillation and coronary heart disease have different pathophysiology and therefore their cooccurrence with AD may be due to different shared mechanisms. Our study involved a series of sequential analyses, with each phase building upon the findings of the previous one to avoid unnecessary data and analyses. For instance, the colocalisation analysis was performed only for significant MTAG findings and identified 53 variant- gene- tissue associations with only four different CV traits involving 43 unique genes. We subsequently prioritised additional analyses for the indicated genes. Our gene expression analysis provided evidence of differential expression only for PLEC and C1Q, prompting further investigation into their pathways and interactions with other proteins. + +We have revised our manuscript to provide clearer explanations of our methodology and findings (See reply to 1.2). + +1.10 Finally, while the single- nuclei transcriptome and protein- protein interaction analyses involving PLEC, NDUFS3, and C1Q on AD brain tissues are noted, the study fails to elucidate a clear pathogenic connection of these targets to Alzheimer's disease and atrial fibrillation. + +Reply 1.10: Thank you for your comment. We have provided a comprehensive set of analyses to draw conclusion on the potential mechanisms linking the highlighted genes with AD and AF. For example, we discuss the functions of PLEC and C1Q, aiming to elucidate their roles in the pathogenicity of AD and AF. Our study suggests that PLEC, a critical structural protein in the cytoskeleton, and its interactions with intermediate filaments may contribute to dysfunctions in astrocytes, potentially increasing the risk of AD. Similarly, these interactions in + +<--- Page Split ---> + +cardiomyocytes could lead to dysfunctions associated with heart failure, thereby linking PLEC to both AD and CV disorders. Additionally, our findings suggest that higher expression of C1Q may enhance activity within the complement system, potentially leading to synapse loss in early AD and contributing to the formation of atherosclerotic plaques and elevated inflammatory responses in cardiomyocytes. These insights are detailed in our discussion and we have revised our manuscript to make this clearer. + +"Plectin is highly expressed in the central nervous system, especially at the interfaces between glia and pial cells and between glia and endothelial cells, and is thought to be important to blood- brain barrier and pial surface integrity. Plectin deficiency in mice has been associated with diminished learning capabilities and reduced long- term memory compared to wild- type littermates. Here we provide evidence that the risk of AD may be affected via functions of plectin in astrocytes. Astrocytes play multiple roles, central to the pathology of AD, including metabolic support for neurons, modulation of brain microvascular function and, through activities associated with those of microglia, inflammatory responses. We hypothesise that these functional roles are mediated in part by interactions of plectin with intermediate filaments (IFs), microtubules and actin filaments." (p.10, lines 232- 241) + +"The role of PLEC in AF has been largely hypothesised to act via structural effects on the heart and cause electrophysiological abnormalities. Here, we also show evidence for upregulation of PLEC in cardiomyocytes of HF patients. Therefore, in accordance with the hypothesised mechanisms linking PLEC to AD above, PLEC may play related roles in cardiomyocytes for assembling and mobilising the intermediate filaments and their networks. These effects further modulate contractile function in cardiomyocytes and inflammatory responses in macrophages which may further contribute to AF." (p.11, lines 245- 251) + +"The complement system plays a central role in synaptic remodelling in the brain and in cellular damage response more generally in the body. We hypothesise that greater expression of C1Q may lead to higher activity of the complement system which in turn may potentiate synapse loss in early AD. Similarly, C1Q has roles in the genesis of atherosclerotic plaques and in the regulation of early stages of inflammatory responses to the cardiomyocyte injury associated with a range of cardiac traits." (p.11, lines 258- 263) + +<--- Page Split ---> + +Additionally, we provide a schematic overview illustrating the pathogenic connection suggested by our study (Figure 1). + +[figure redacted] + +However, it is important to note that epidemiological data often face limitations in elucidating clear pathogenic pathways. While we provided additional mechanistic evidence, the precise biological mechanisms cannot be inferred. Consequently, additional research approaches are essential to complement epidemiological findings and provide deeper insights into disease pathogenesis. + +We added this as a limitation: + +"Finally, epidemiological data frequently encounter challenges in clarifying pathogenic mechanisms. Although we provided evidence from mechanistic experiments, the exact biological processes involved cannot be inferred. Further work is needed to validate our findings and the suggested disease pathways." (p.13- 14, lines 314- 317) + +Reviewer #2 (Remarks to the Author): + +<--- Page Split ---> + +## Overview + +The work uses MTAG to examine AD with cardiovascular traits. The motivation is the long- standing association between cardiovascular disease and AD, and the method harnesses the genetic correlation to improve power for detecting genetic associations. The authors use eQTLs identified from a range of tissues from the GTEx project plus their results to perform colocalization analyses and hone in on two sites, and follow up some of those findings with analysis of gene expression. Overall, the manuscript was clear and interesting. The methods are well- described and approach seems sound, but it looked like there might be a disagreement between figure 3 and text and figure 2 does not share enough detail so it cannot be used to check against the text, which were my most important concerns. I had some specific comments below but I also wondered 1) if the authors could examine genetic correlation between AD and the traits in addition to sharing the MTAG results; and, 2) whether the authors considered testing colocalization with multiple traits at loci that seemed like they had \(> = 2\) signal with several cardiovascular traits. + +Reply: Thank you for your positive feedback on the clarity and interest of our manuscript and for your suggestions. We apologise for any confusion. We have carefully revised both the text and figures to ensure consistency and clarity throughout. We addressed each of your specific concerns and provided additional details to clarify any discrepancies you noted. + +We provide the genetic correlation results in Supplementary Table 1. + +Regarding the comment on colocalisation of multiple traits, we only performed bivariate (pairwise) MTAG analysis between AD and CV traits. Subsequently, this study design did not allow us to perform colocalisation across multiple CV traits as the MTAG AD GWAS results were different from each bivariate MTAG analysis. We opted for bivariate analysis to explore different pathways that may link different CV traits with AD (e.g. different shared pathways linking AF to AD and CAD to AD). However, in the case of systolic and diastolic blood pressure, as those two traits are correlated and reflect similar pathways, we analysed the traits in a single MTAG between AD, systolic and diastolic blood pressure and the subsequent + +<--- Page Split ---> + +colocalisation was performed across these three traits. Additionally, our results did not highlight the same loci with evidence for colocalisation between different AD- CV pairs. The regions with evidence of colocalisation with multiple CV traits in Figure 2 (chromosomes 8 and 10), were associated with CV traits through different and independent signals ( \(R^2 < 0.1\) ). Thus, these loci likely do not affect the different CV traits through the same mechanism. + +Major Comments + +2.1. Title – at best, these data let you say that there is evidence consistent with what you’d observe with pleiotrophy. Also, there are more genes implicated than just PLEC and C1Q, unless I missed something. + +Reply 2.1: Thank you for your comment. We agree and have now changed the title of our manuscript to: + +“Multi- trait association analysis reveals shared genetic loci between Alzheimer's disease and cardiovascular traits”. + +2.2 Figure 1 would be helped by sharing the sample sizes for each GWAS used to let the reader understand their magnitudes. + +Reply 2.2: Thank you for your suggestion. We modified Figure 1 accordingly and now show the sample sizes for each GWAS. + +<--- Page Split ---> + +2.3 Figure 2 is difficult to read - can it just be made into a horizontal plot with labeled axes? + +Reply 2.3: We apologise for this. Figure 2 presents the regional plots for the colocalised loci. Our intention with this plot was to highlight the significant results from our colocalisation analysis in a summarised format, believing that a circular form of the plot would do so more efficiently. We provide the suggested horizontal orientation in Supplementary Figure 7. Nevertheless, to address reviewer's concerns regarding the complexity of Figure 2, we applied a few modifications to simplify the plot. More specifically, we removed the outer circles corresponding to eQTL information, erased the coordinates from the x- axis and enlarged the text for the annotated genes. Finally, we removed the trait annotations from the plots and replaced them with a simpler legend. + +<--- Page Split ---> +![PLACEHOLDER_18_0] + + +We also made a few changes to the Figure legend, which now says: + +"Fig. 2: Circular figure visualising regional plots on the colocalised loci between Alzheimer's disease (AD) and cardiovascular traits (CV). + +The figure presents the distribution of P- values (- log10P) from MTAG with inner orientation. The annotations show the mapped genes of the AD/CV top lead SNPs on the colocalised loci." + +2.4 Figure 3 seems to present different p- values compared to the text (lines 112- 115) that should be checked. + +Reply 2.4: Thank you for noticing this and apologies for the confusion. We modified our manuscript accordingly and now present the correct OR and p- values from the + +<--- Page Split ---> + +MTAG analysis. The p-values in Figure 3 are now concordant with those mentioned in the text (p.4, lines 84- 85) + +2.5 Please provide manhattan and qq plots for each trait combination. + +Reply 2.5: We provided Manhattan plots and QQ- plots for each trait (Supplementary Figures 1- 6). In those plots, we compare MTAG results with those from the respective univariate GWAS. We have revised the results section appropriately: + +"We examined the bivariate genetic correlation between AD and the examined CV traits (Supplementary Table 1) and visually illustrated the MTAG results alongside those from the original GWAS (Supplementary Fig. 1- 6)." (p.2, lines 45- 47) + +2.6 Discussion - lines 218- 221. The authors claim the results of their study disentangles the relationship between AD and AF. This is beyond what I think they can say with these data since the outcome in the Jansen paper is mainly from the UKB that infers case status using a question about whether the parent had dementia. This introduces a substantial amount of heterogeneity as to the underlying cause of dementia that ranges from cerebrovascular disease to a purely neurodegenerative cause, which preclude the kind of conclusion the authors made. Using Kunkle et al., 2018, which relies on a clinical diagnosis, might help this. Regardless of the specific cause of dementia, it's clear that there's a relationship between dementia and AF. + +Reply 2.6: Thank you for your detailed and insightful comment. We also share the reviewer's view that there is a link between dementia and AF. Our study focused on AD, the most prevalent type of dementia, to identify genetic regions with pleiotropic effects that could indicate shared biological mechanisms contributing to their observed comorbidity. We utilised the largest available GWAS from Jansen et al. at the time of our analysis. This GWAS combined clinically diagnosed cases of AD with proxies (AD- by- proxy- individuals whose parents were diagnosed with dementia). The authors provide evidence that the correlation between the GWAS + +<--- Page Split ---> + +with and without the 'AD- by- proxy' cases was high adding to the validity of this approach, especially regarding sample size improvement which is critical for AD GWAS. However, we agree that 'AD- by- proxy' may introduce heterogeneity in the results and highlight associations which may be driven by other types of dementia. We acknowledge this as a limitation of our study (see below). The revised text now more accurately represents the conclusions that can be drawn from our data. + +“Here we provide evidence suggesting a shared genetic determinant that may contribute to the pathophysiology of AF and AD.” (p.10, lines 217- 218) + +“The GWAS for AD combined clinically diagnosed cases of AD with proxies (AD- by- proxy, individuals whose parents were diagnosed with AD). The correlation between the GWAS with and without the ‘AD- by- proxy’ cases was high adding to the validity of this approach. Nonetheless, the inclusion of individuals with parental AD diagnoses in the original GWAS may have introduced greater heterogeneity and increased probability of misclassification, suggesting that some of our observed associations might be misclassified or influenced by other types of dementia.” (p.13, lines 296- 302) + +2.7 Using gene expression from tissues that are not likely directly relevant for the pathogenesis of AD or one of the CVD traits rests on an assumption that the eQTLs in that tissue are generalizable. It could be that they are false positives in one tissue and are correctly null in other tissues. + +Reply 2.7: We appreciate your comment. Emerging evidence suggests that AD is a systemic disease with widespread effects beyond the central nervous system. In this work, we aimed to further study the systemic nature of the disease by studying the interconnectedness of vascular health and neurodegeneration. We therefore opted to investigate agnostically all available tissues to also capture potential effects beyond the nervous system. Additionally, by studying all tissues, the analysis is not restricted to specific tissues with very small sample sizes (139 to 255 samples in brain tissues). Many eQTLs are correlated across different tissues, potentially adding to the generalizability of our findings. + +<--- Page Split ---> + +However, we acknowledge that the possibility of false positive findings remains. To address this, we aimed to validate our findings through additional analyses on different populations using single- cell and single- nuclei data from brain tissue of AD cases and cardiac tissue from heart failure cases. + +We believe that our approach is comprehensive, even though it comes with the limitations mentioned above. This consideration has been added to our manuscript, which now states: + +"Considering the systemic nature of AD, which encompasses multiple pathways and various tissues, our study conducted a thorough investigation across all tissues, assuming correlations among many eQTLs across different tissues. However, it is important to acknowledge that some eQTLs from tissues not directly linked to AD or CV traits could represent false positive associations. To mitigate this, we validated our findings using single- cell and single- nuclei data obtained from brain tissue samples of AD cases and cardiac tissue samples from individuals with HF." (p.13, lines 302- 308) + +Minor Comments + +2.8 Consider adding the limitation that not all GWAS summary results are complete so signal that is not present in one of the dataset pairs would not be tested using MTAG. + +Reply 2.8: Thank you for your suggestion. We modified the limitations as suggested. In the discussion, we mention: + +"Additionally, we did not investigate a considerable portion of the genetic predisposition coming from rare variants (MAF < 1%) as we excluded them from our analyses. This exclusion is a restriction of the MTAG method, in order to mitigate the risk of false- positive findings and biased results. Another limitation of using MTAG is that genetic variants that are not present in at least one GWAS dataset of each AD- CV pair were excluded from the corresponding pairwise MTAG analysis and therefore some variants tested in one pairwise MTAG may not be tested in another." (p.12, lines 280- 286) + +<--- Page Split ---> + +2.9 Figure 3 – the eQTL line plot is confusing. Why not stack the two tissues and use dots? Either way, the association between the eQTL signal and other traits (i.e., AD, atrial fib) are not striking. + +Reply 2.9: We apologise for the confusion initially caused by Figure 3. We have carefully revised the figure as suggested to enhance the illustration of the eQTL results. + +Regarding your concern on the association between the eQTL signal and other traits, we now provide further clarification. This locus was identified through MTAG analysis between AD and AF and further colocalisation analysis yielded robust evidence of colocalisation, as detailed in our manuscript: + +"The intronic variant rs11786896 (PLEC) explained the colocalisation of AD and AF with expression levels of PLEC in the cardiac left ventricle (PP = 0.99, %PP explained by \(SNP = 99\%\) ) and skeletal muscle (PP = 0.92, %PP explained by \(SNP = 98\%\) ) (Fig. 3)." (p.4, lines 91- 94) + +Additionally, we have conducted several post- GWAS analyses including gene expression, pathway analysis, and protein- protein interaction, providing supplementary evidence which strengthens the association of these traits with the identified locus. + +2.10 Unlike CVD traits, AD has one region, the APOE locus, that has an outsized effect compared to other genetic loci. I would guess the results from APOC1 were driven by the association between AD and APOE. + +Reply 2.10: Thank you for your insightful comment. Regarding our findings related to the APOC1 locus, we acknowledge that APOE is one of the major genetic regions associated with AD, and it is indeed closely located to APOC1. Our MTAG analysis indicated a variant mapped to APOC1 (rs438811). However, in our trait- trait colocalization analysis, another variant in APOE (rs429358) was highlighted as the + +<--- Page Split ---> + +candidate causal variant. The evidence for colocalization was sufficient but not very strong (PP = 0.57). + +It is important to note that the two aforementioned SNPs are in linkage disequilibrium (LD, \(r^2 = 0.63\) ). Based on this, it is very likely that the observed association with APOC1 is driven by the influence of the APOE locus. Additionally, the eQTL colocalization analysis did not show sufficient evidence for colocalization at this locus. Given the insufficient support for colocalization (see study design in Figure 1), we did not pursue further investigation into this association. However, we added the following to the discussion: + +"The variant rs429358, located within APOE, showed evidence for colocalisation between AD and CAD. However, further investigation using eQTL could not prioritise any shared gene within the locus expressed in the examined tissues. Given APOE's well- established role in AD and its potential involvement in other CV traits, including CAD, it is plausible that the locus affects the two traits independently through different pathways (horizontal pleiotropy) or through a shared gene expressed in tissues other than those examined in our study." (p.11- 12, lines 264- 269) + +2.11 Discussion - lines 204-5 (grammer/phrasing) - "rs11786896 expressed via PLEC and rs7529220 expressed via C1QA, C1QB, and C1QC" sounds odd. I'd phrase it something like rs1179686 is an eQTL for PLEC. + +Reply 2.11: We rephrased the sentence as suggested: + +"rs11786896 which was an eQTL for PLEC and rs7529220 which was an eQTL for C1QA, C1QB, and C1QC" (p.8, lines 184- 185) + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have fully addressed reviewers' comments and the revised version is worth being accepted for publication as it is. + +Reply: We thank the reviewer for suggesting the publication of our manuscript + +Reviewer #2 (Remarks to the Author): + +No matter how AD is commonly defined (e.g., clinically or pathologically), it often co- occurring with evidence of cerebrovascular disease yet whether this is pleiotropic or causal relationship is unknown - - although there is some work that suggests a direct link https://pubmed.ncbi.nlm.nih.gov/35772923/. + +The current work focuses on finding shared genetic risk using MTAG, which uses genetic correlation to boost power for multi- trait gwas. + +The most interesting portion of the work is the MTAG results along with the SMR analysis. + +By contrast the differential expression and network- based analysis was descriptive without addressing the most interesting question of the work - - the shared risk for CV traits and AD dementia. + +Overall, the revised manuscript nicely addressed my comments. + +## ## Minor Comments + +1. line 297 - AD-proxy status was inferred based on whether the parent was diagnosed with dementia (not AD per se). + +Reply: We thank the reviewer for the comment. We have clarified this distinction in the revised manuscript as suggested: + +"The GWAS for AD combined clinically diagnosed cases of AD with AD-proxy status (inferred based on whether the parent was diagnosed with dementia)." (p.13, lines 296- 298) + +<--- Page Split ---> diff --git a/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a04747c8f9741eed7e94b0dad97421c41e1dcfd8 --- /dev/null +++ b/peer_reviews/98fb4ba88f0a70c557260983cb2ed2862bd0594a0769ba577bb3fceecc0025a3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,530 @@ +<|ref|>title<|/ref|><|det|>[[73, 163, 878, 211]]<|/det|> +# Multi-trait association analysis reveals shared genetic loci between Alzheimer's disease and cardiovascular traits + +<|ref|>text<|/ref|><|det|>[[73, 225, 448, 241]]<|/det|> +Corresponding Author: Dr Fotios Koskeridis + +<|ref|>text<|/ref|><|det|>[[73, 275, 712, 289]]<|/det|> +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +<|ref|>text<|/ref|><|det|>[[72, 301, 866, 315]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 354, 144, 368]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 380, 219, 394]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 405, 160, 419]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 432, 238, 445]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 444, 878, 511]]<|/det|> +The manuscript's exploration of genetic risk factors common to Alzheimer's disease and cardiovascular diseases is of significant interest due to the potential implications for understanding disease mechanisms and informing therapeutic strategies. However, the manuscript primarily recounts experimental methodologies and fails to provide substantial interpretation or discussion of the results. Moreover, the proposed shared risk factors, PLEC and C1Q, lack sufficient validation within the study. As it stands, I cannot endorse this manuscript for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 523, 550, 537]]<|/det|> +To improve the manuscript, the authors should consider the following: + +<|ref|>text<|/ref|><|det|>[[72, 536, 918, 720]]<|/det|> +First of all, the GWAS database used for the analysis should be defined and interpretated carefully in the manuscript. 1. The author used published GWAS data from Alzheimer's diseases for the extraction of AD traits (62 AD genetic loci). The author should compare their analysis and the result with the original publication. 2. To extract cardiovascular traits, the author used diverse GWAS data from five different publications; atrial fibrillation, coronary artery disease, stroke, carotid intima- media thickness, systolic and diastolic blood pressure. 'Intima- media thickness' and 'systolic and diastolic blood pressure' are not terms of disease condition. Their inclusion in cardiovascular trait extraction necessitates a clear exposition of their connection to atrial fibrillation, coronary artery disease, and stroke. 3. The justification for using a diverse range of GWAS data to extract cardiovascular traits must be elaborated upon. The authors should demonstrate the advantage of this diversity and whether it led to definitive conclusions about cardiovascular traits. 4. A discussion on the 740 cardiovascular loci identified should be provided to underscore their relevance and significance. 5. The manuscript must critically examine the heterogeneity of the phenotypes in the GWAS datasets, especially considering the comorbidity of AD and cardiovascular symptoms, and delineate how these datasets were selected and utilized in light of the study's objectives + +<|ref|>text<|/ref|><|det|>[[72, 731, 545, 744]]<|/det|> +Regarding the identification of PLEC and C1Q as shared risk factors: + +<|ref|>text<|/ref|><|det|>[[72, 744, 890, 875]]<|/det|> +6. The significance of PLEC, HSPG2, and APOE, which were implicated based on the multi-trait colocalization method, must be contextualized with previous GWAS findings on AD and cardiovascular disease (CVD) traits. +7. The shared risk factors for AD and CVD indicated by genetic variants rs11786896 (PLEC) and rs7529220 (HSPG2) should be reassessed, as the observed odds ratios do not robustly categorize them as high-risk factors for Alzheimer's disease or atrial fibrillation. +8. The relevance of the identified loci to other cardiovascular traits should be discussed. If no correlation exists, the study should narrow its focus to the relationship between AD and atrial fibrillation, avoiding unnecessary data and analyses. Finally, while the single-nuclei transcriptome and protein-protein interaction analyses involving PLEC, NDUFS3, and C1Q on AD brain tissues are noted, the study fails to elucidate a clear pathogenic connection of these targets to Alzheimer's disease and atrial fibrillation. + +<|ref|>text<|/ref|><|det|>[[73, 899, 161, 912]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 925, 237, 938]]<|/det|> +(Remarks to the Author) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[73, 48, 139, 60]]<|/det|> +## Overview + +<|ref|>text<|/ref|><|det|>[[72, 73, 925, 203]]<|/det|> +OverviewThe work uses MTAG to examine AD with cardiovascular traits. The motivation is the long- standing association between cardiovascular disease and AD, and the method harnesses the genetic correlation to improve power for detecting genetic associations. The authors use eQTLs identified from a range of tissues from the GTEx project plus their results to perform colocalization analyses and hone in on two sites, and follow up some of those findings with analysis of gene expression. Overall, the manuscript was clear and interesting. The methods are well- described and approach seems sound, but it looked like there might be a disagreement between figure 3 and text and figure 2 does not share enough detail so it cannot be used to check against the text, which were my most important concerns. I had some specific comments below but I also wondered 1) if the authors could examine genetic correlation between AD and the traits in addition to sharing the MTAG results; and, 2) whether the authors considered testing colocalization with multiple traits at loci that seemed like they had \(= 2\) signal with several cardiovascular traits. + +<|ref|>sub_title<|/ref|><|det|>[[73, 216, 192, 230]]<|/det|> +## Major Comments + +<|ref|>text<|/ref|><|det|>[[70, 241, 920, 455]]<|/det|> +Major Comments1. Title – at best, these data let you say that there is evidence consistent with what you'd observe with pleiotrophy. Also, there are more genes implicated than just PLEC and C1Q, unless I missed something.2. Figure 1 would be helped by sharing the sample sizes for each GWAS used to let the reader understand their magnitudes.3. Figure 2 is difficult to read - can it just be made into a horizontal plot with labeled axes?4. Figure 3 seems to present different p-values compared to the text (lines 112-115) that should be checked.5. Please provide manhattan and qq plots for each trait combination.6. Discussion - lines 218-221. The authors claim the results of their study disentangles the relationship between AD and AF. This is beyond what I think they can say with these data since the outcome in the Jansen paper is mainly from the UKB that infers case status using a question about whether the parent had dementia. This introduces a substantial amount of heterogeneity as to the underlying cause of dementia that ranges from cerebrovascular disease to a purely neurodegenerative cause, which preclude the kind of conclusion the authors made. Using Kunkle et al., 2018, which relies on a clinical diagnosis, might help this. Regardless of the specific cause of dementia, it's clear that there's a relationship between dementia and AF.7. Using gene expression from tissues that are not likely directly relevant for the pathogenesis of AD or one of the CVD traits rests on an assumption that the eQTLs in that tissue are generalizable. It could be that they are false positives in one tissue and are correctly null in other tissues. + +<|ref|>sub_title<|/ref|><|det|>[[73, 465, 192, 478]]<|/det|> +## Minor Comments + +<|ref|>text<|/ref|><|det|>[[70, 490, 916, 595]]<|/det|> +Minor Comments1. Consider adding the limitation that not all GWAS summary results are complete so signal that is not present in one of the dataset pairs would not be tested using MTAG.2. Figure 3 – the eQTL line plot is confusing. Why not stack the two tissues and use dots? Either way, the association between the eQTL signal and other traits (i.e., AD, atrial fib) are not striking.3. Unlike CVD traits, AD has one region, the APOE locus, that has an outsized effect compared to other genetic loci. I would guess the results from APOC1 were driven by the association between AD and APOE.4. Discussion - lines 204-5 (grammer/phrasing) - "rs11786896 expressed via PLEC and rs7529220 expressed via C1QA, C1QB, and C1QC" sounds odd. I'd phrase it something like rs1179686 is an eQTL for PLEC. + +<|ref|>sub_title<|/ref|><|det|>[[73, 607, 145, 620]]<|/det|> +## Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 633, 218, 647]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 658, 156, 671]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 684, 238, 697]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 697, 916, 725]]<|/det|> +The authors have fully addressed reviewers' comments and the revised version is worth being accepted for publication as it is. + +<|ref|>text<|/ref|><|det|>[[73, 738, 161, 751]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 764, 238, 777]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 777, 920, 884]]<|/det|> +No matter how AD is commonly defined (e.g., clinically or pathologically), it often co- occurring with evidence of cerebrovascular disease yet whether this is pleiotropic or causal relationship is unknown -- although there is some work that suggests a direct link https://pubmed.ncbi.nlm.nih.gov/35772923/. The current work focuses on finding shared genetic risk using MTAG, which uses genetic correlation to boost power for multi- trait gwas. The most interesting portion of the work is the MTAG results along with the SMR analysis. By contrast the differential expression and network- based analysis was descriptive without addressing the most interesting question of the work -- the shared risk for CV traits and AD dementia. Overall, the revised manuscript nicely addressed my comments. + +<|ref|>text<|/ref|><|det|>[[73, 905, 213, 918]]<|/det|> +## Minor Comments + +<|ref|>text<|/ref|><|det|>[[70, 930, 875, 946]]<|/det|> +1. line 297 - AD-proxy status was inferred based on whether the parent was diagnosed with dementia (not AD per se). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 414, 916, 468]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 468, 916, 535]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 533, 618, 547]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 88, 342, 108]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 125, 466, 145]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 160, 884, 365]]<|/det|> +The manuscript's exploration of genetic risk factors common to Alzheimer's disease and cardiovascular diseases is of significant interest due to the potential implications for understanding disease mechanisms and informing therapeutic strategies. However, the manuscript primarily recounts experimental methodologies and fails to provide substantial interpretation or discussion of the results. Moreover, the proposed shared risk factors, PLEC and C1Q, lack sufficient validation within the study. As it stands, I cannot endorse this manuscript for publication in Nature Communications. To improve the manuscript, the authors should consider the following: + +<|ref|>text<|/ref|><|det|>[[113, 379, 884, 479]]<|/det|> +Reply: Thank you for your feedback and insightful comments. We have carefully revised our manuscript to address them, ensuring a cautious and robust interpretation of our results. Further details on your specific comments are provided below. + +<|ref|>text<|/ref|><|det|>[[115, 530, 883, 577]]<|/det|> +1.1 First of all, the GWAS database used for the analysis should be defined and interpretated carefully in the manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 592, 883, 666]]<|/det|> +Reply1.1: We have provided detailed descriptions of the GWAS datasets in the methods section, including citations, sources, and characteristics (new Supplementary Table 18). + +<|ref|>text<|/ref|><|det|>[[113, 681, 884, 858]]<|/det|> +In lines 327- 332 (p.14) we now explain "We restricted our study to a population of European ancestry. We used the summary statistics from seven GWAS on the following diseases: AD, AF, CAD, cIMT, stroke, SBP, and DBP. We selected these datasets based on the sample size (with preference for larger GWAS), the quality of the phenotypic data, the date of publication (favouring more recent studies), and their relevance to our research questions. Supplementary Table 18 lists basic characteristics of all included GWAS datasets." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 161]]<|/det|> +1.2 The author used published GWAS data from Alzheimer's diseases for the extraction of AD traits (62 AD genetic loci). The author should compare their analysis and the result with the original publication. + +<|ref|>text<|/ref|><|det|>[[113, 177, 884, 381]]<|/det|> +Reply 1.2: The primary focus of our results was the investigation of pleiotropic loci between AD and CVD rather than the description of novel findings stemming from MTAG. We acknowledge that the latter is also of interest to the readers. In this revised version, we have included a comprehensive comparison between novel and previous findings for all examined traits. We provided Manhattan plots and QQplots for each trait, comparing MTAG results with those from the original GWAS (Supplementary Figures 1- 6) and reported novel loci for each trait (Table 1). We also provided new analysis to support the validity of novel findings in relation to AD. + +<|ref|>text<|/ref|><|det|>[[113, 395, 884, 599]]<|/det|> +To ensure robust findings and to facilitate a rigorous comparison, we implemented strict criteria to define MTAG loci. Specifically, we considered only loci that were at least 500kb distant and independent (LD < 0.1) from previously reported signals. Next to the genome- wide significant p- value in MTAG results, these loci also had to exhibit nominal significant association (P < 0.01) in the original GWAS with concordant direction of effect. To reflect these updates, we have thoroughly revised our manuscript accordingly. We have included a detailed explanation in the methods. For example: + +<|ref|>text<|/ref|><|det|>[[114, 615, 884, 714]]<|/det|> +"To ensure the robustness of our findings, we considered only MTAG loci if the respective top variants were also associated with the examined trait (P < 0.01) in the corresponding original GWAS with a concordant direction of effect (between MTAG and the original GWAS)." (p.15, lines 361- 363) + +<|ref|>text<|/ref|><|det|>[[114, 729, 884, 855]]<|/det|> +Moreover, to identify novel signals, we compared the MTAG findings with those from previously published GWAS. Specifically for AD, we assessed previously identified loci from three key GWAS studies (Jansen et al., Kunkle et al., and Bellenguez et al.). A dedicated section in the methods has been included to elaborate on how novel signals were defined. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 886, 240]]<|/det|> +"A signal indicated by MTAG was considered novel if its top variant achieved genome- wide significance \((P< 5\times 10^{- 8})\) in MTAG results and was also statistically significant \((P< 0.01)\) in the included original univariate GWAS with a concordant direction of effect (between MTAG and the original GWAS). Additionally, the top variant should not be located within \(\pm 500kb\) or in LD \((r^{2} > 0.1)\) with previously reported loci. For AD, in addition to the included GWAS study, novel loci were compared to two previously published key GWAS studies." (p.16, lines 368- 373) + +<|ref|>text<|/ref|><|det|>[[115, 255, 699, 276]]<|/det|> +In the results section we highlight novel findings, for example: + +<|ref|>text<|/ref|><|det|>[[113, 291, 886, 416]]<|/det|> +"Across all pairwise MTAG analyses, we identified 27 unique genetic loci associated with AD at genome- wide significance (GWS) level \((P< 5\times 10^{- 8})\) corresponding to 114 unique single- nucleotide polymorphisms (SNPs) (Supplementary Table 2). Out of the 27 AD loci, 5 were novel (not within \(\pm 500\) kilobases (kb) of the previously known AD loci) and among them rs73069394 (ULK4) displayed the strongest association (Table 1). + +<|ref|>text<|/ref|><|det|>[[113, 432, 886, 584]]<|/det|> +To further validate the associations of the novel AD loci, we applied summary data- based Mendelian randomisation (SMR) and heterogeneity in dependent instruments (HEIDI) using gene expression data in relevant brain tissues. SMR analysis suggested a potentially causal association between ULK4 expression in the hippocampus and AD risk \((\beta_{SMR} = 0.04, P_{SMR} = 3.4\times 10^{- 10}, P_{HEIDI} > 0.05)\) . SMR was not possible for the remaining loci due to unavailability of gene expression data. + +<|ref|>text<|/ref|><|det|>[[113, 599, 886, 723]]<|/det|> +Furthermore, we found 1,222 top signals associated with different CV traits at GWS level in 740 genetic loci (Supplementary Table 3). Of these, 13 novel loci were highlighted for CAD \((N = 4)\) , cIMT \((N = 8)\) and stroke \((N = 1)\) (Table 1). Overall, 15 of the unique AD SNPs (9 loci) were additionally associated at GWS level with at least one of the examined CV traits (Supplementary Table 4)." (p.2- 3, lines 47- 63) + +<|ref|>text<|/ref|><|det|>[[113, 739, 884, 837]]<|/det|> +Of note, these refinements, which ensure our manuscript presents findings with robust evidence, do not alter the highlighted results or conclusions of our initial manuscript, as we had already applied these criteria in the subsequent analyses following MTAG. + +<|ref|>text<|/ref|><|det|>[[115, 854, 439, 873]]<|/det|> +Finally, we discuss novel findings: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 87, 885, 397]]<|/det|> +"Our study highlighted 5 not previously reported AD loci including SNPs located in or near HSPG2, AC019055.1, ULK4, KRT18P16 and ACTN4. Of them, the intronic variant rs73069394 (ULK4) showed the strongest association with AD and was also GWS associated with DBP. The locus did not show evidence for colocalization between AD and DBP suggesting this variant is not likely the causal one for both traits. Apart from DBP, GWAS studies have shown associations between this locus and schizophrenia and bipolar disorder. The role of the ULK4 in relation to neurodegeneration is little studied but the gene function shows biological plausibility to AD. ULK4 protein is involved in the regulation of autophagy and plays multiple roles in brain function including neuronal growth, endocytosis and myelination which are pathways implicated to AD pathology. Here, we also provided additional evidence from SMR analysis supporting a potentially causal association between expression levels of ULK4 and AD." (p.9, lines 196- 207) + +<|ref|>text<|/ref|><|det|>[[114, 411, 885, 563]]<|/det|> +1.3 To extract cardiovascular traits, the author used diverse GWAS data from five different publications; atrial fibrillation, coronary artery disease, stroke, carotid intima- media thickness, systolic and diastolic blood pressure. 'Intima- media thickness' and 'systolic and diastolic blood pressure' are not terms of disease condition. Their inclusion in cardiovascular trait extraction necessitates a clear exposition of their connection to atrial fibrillation, coronary artery disease, and stroke. + +<|ref|>text<|/ref|><|det|>[[114, 614, 884, 689]]<|/det|> +Reply 1.3: Our objective was to systematically explore the interconnection between AD and CVDs by covering a broad spectrum of cardiovascular conditions and associated traits, which is now stated more clearly throughout the manuscript: + +<|ref|>text<|/ref|><|det|>[[113, 704, 885, 907]]<|/det|> +"AD has been considered a brain- specific disease whose primary pathology is confined to the brain. However, accumulating evidence suggests mechanistic links between a wide range of cardiovascular (CV) abnormalities and AD. Epidemiological studies and experimental data have shown consistent associations between manifestations of clinical CV diseases such as coronary heart disease (CHD), atrial fibrillation (AF) and stroke, with higher risk of AD. Several hypotheses have been proposed to explain this. Indeed, atherosclerosis, the main underlying cause of cardiovascular diseases, also has profound consequences on the cerebrovascular system. These include reduced blood flow and potential vascular damage in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 240]]<|/det|> +brain, impaired cerebral perfusion, and associations with inflammation and oxidative stress, all of which are factors that can contribute to neurodegenerative pathology and increase the risk of AD. Beyond atherosclerosis, other hemodynamic effects associated with hypertension, arteriosclerosis and subsequent aortic stiffening have been associated with cerebrovascular damage and cognitive function, potentially accelerating the onset and progression of AD." (p.1, lines 4- 17) + +<|ref|>text<|/ref|><|det|>[[113, 255, 884, 407]]<|/det|> +"Here, we further investigated the commonalities in the genetic architecture of AD and CV traits and identified pleiotropic loci affecting multiple traits aiming to define common targets for therapeutic modulation. We explored a wide range of CV abnormalities and two common main risk factors, atherosclerosis and blood pressure, proposed to underlie both CV and AD, to investigate different molecular pathways that may link different CV manifestations to AD." (p.2, lines 29- 33) + +<|ref|>text<|/ref|><|det|>[[114, 458, 883, 532]]<|/det|> +1.4 The justification for using a diverse range of GWAS data to extract cardiovascular traits must be elaborated upon. The authors should demonstrate the advantage of this diversity and whether it led to definitive conclusions about cardiovascular traits. + +<|ref|>text<|/ref|><|det|>[[113, 546, 884, 672]]<|/det|> +Reply 1.4: We selected a diverse range of GWAS datasets to encompass a broad spectrum of cardiovascular traits, given the unclear connection with AD. This approach allowed a thorough exploration of how genetic factors contribute to the interconnection between AD and CV conditions, offering a more comprehensive understanding than focusing solely on a single CV trait. + +<|ref|>text<|/ref|><|det|>[[114, 687, 707, 708]]<|/det|> +In the introduction, we have added a paragraph explaining this: + +<|ref|>text<|/ref|><|det|>[[113, 723, 884, 875]]<|/det|> +"Here, we further investigated the commonalities in the genetic architecture of AD and CV traits and identified pleiotropic loci affecting multiple traits aiming to define common targets for therapeutic modulation. We explored a wide range of CV abnormalities and two common main risk factors, atherosclerosis and blood pressure, proposed to underlie both CV and AD, to investigate different molecular pathways that may link different CV manifestations to AD." (p.2, lines 29- 33) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[114, 90, 471, 108]]<|/det|> +## In the discussion, we further mention: + +<|ref|>text<|/ref|><|det|>[[114, 125, 884, 199]]<|/det|> +"Third, exploring a wide spectrum of CV diseases pairwise enabled a comprehensive investigation into the diverse shared mechanisms underlying the relationship between different manifestations of CV conditions and AD." (p.12, lines 275- 277) + +<|ref|>text<|/ref|><|det|>[[115, 248, 883, 295]]<|/det|> +1.5 A discussion on the 740 cardiovascular loci identified should be provided to underscore their relevance and significance. + +<|ref|>text<|/ref|><|det|>[[113, 311, 885, 543]]<|/det|> +Reply 1.5: Thank you for the suggestion. The primary aim of our study was to identify pleiotropic genes linking AD and CVDs. The genetic architecture of CV conditions has been much more extensively studied with large scale GWAS compared to AD. Here, we aimed to leverage the co- occurrence of CV conditions with AD to increase the power of AD GWAS studies and identify shared loci including novel loci related to AD. Following your suggestion, we now compared the reported loci for all examined traits (see response to comment 1.2). The vast majority of the 740 loci (727 loci) were already reported loci for CVD and the new ones are highlighted in Table 1. + +<|ref|>text<|/ref|><|det|>[[114, 592, 884, 692]]<|/det|> +1.6 The manuscript must critically examine the heterogeneity of the phenotypes in the GWAS datasets, especially considering the comorbidity of AD and cardiovascular symptoms, and delineate how these datasets were selected and utilized in light of the study's objectives + +<|ref|>text<|/ref|><|det|>[[114, 707, 884, 833]]<|/det|> +Reply 1.6: Our study utilised summary statistics derived from publicly available GWAS datasets, which precluded us from examining the heterogeneity in the original GWAS datasets. We acknowledge that any potential heterogeneity present in these datasets could affect the results of our study. We included this limitation in our manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 849, 884, 896]]<|/det|> +"GWAS compares the cases we are studying with controls, but due to comorbidity, the number of other diseases might be higher in cases than in controls. As we used summary statistics + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 162]]<|/det|> +without access to individual- level data, we couldn't examine or address this heterogeneity. Despite this limitation, the identified shared genes remain valid and important for understanding their genetic connections." (p.12, lines 286- 291) + +<|ref|>text<|/ref|><|det|>[[113, 177, 885, 432]]<|/det|> +To mitigate this limitation, we employed a bivariate analysis approach, examining the shared associations between AD and each CV trait separately. We used MTAG, which accounts for phenotypic heterogeneity from diverse populations and studies by leveraging the genetic correlation among the examined traits. Furthermore, MTAG provides trait- specific summary statistics and therefore we were able to explore the potential influence of other CV traits on our observed associations between AD and specific CV traits, by systematically comparing our findings across all examined CV traits. This approach provided insights into the complex interrelationships among these traits and their potential impact on AD. Our discussion now states: + +<|ref|>text<|/ref|><|det|>[[113, 448, 886, 678]]<|/det|> +"Out of the several CV traits and diseases examined with AD, the largest number of pleiotropic signals with AD was observed for AF and BP highlighting the importance of pathways related to these CV traits in explaining comorbidities with AD. Numerous observational studies, provide growing evidence that BP and AF are associated with cognitive impairment, risk of AD and other dementias. The suggested mechanistic links between these traits and AD involve a combination of cerebrovascular damage, neuroinflammation, amyloid- beta accumulation, oxidative stress, and endothelial dysfunction. However, it is unclear whether the diseases have a shared pathophysiology or whether the relationship arises as downstream consequences of BP and AF (e.g., stroke)." (p.9, lines 208- 216) + +<|ref|>text<|/ref|><|det|>[[114, 693, 884, 766]]<|/det|> +Finally, in response to your suggestion, we have provided a description in the methods outlining the criteria used for selecting and utilising the GWAS datasets relevant to our study objectives. + +<|ref|>text<|/ref|><|det|>[[114, 781, 884, 855]]<|/det|> +"We selected these datasets based on the sample size (with preference for larger GWAS), the quality of the phenotypic data, the date of publication (favouring more recent studies), and their relevance to our research questions." (p.14, lines 329- 332) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 714, 109]]<|/det|> +Regarding the identification of PLEC and C1Q as shared risk factors: + +<|ref|>text<|/ref|><|det|>[[115, 124, 883, 198]]<|/det|> +1.7 The significance of PLEC, HSPG2, and APOE, which were implicated based on the multi- trait colocalization method, must be contextualized with previous GWAS findings on AD and cardiovascular disease (CVD) traits. + +<|ref|>text<|/ref|><|det|>[[115, 213, 884, 287]]<|/det|> +Reply 1.7: Thank you for your comment. PLEC and HSPG2 are among our most highlighted findings, and we have discussed their importance in the context of previous studies. For instance, we state in the discussion: + +<|ref|>text<|/ref|><|det|>[[113, 301, 884, 427]]<|/det|> +"A low- frequency missense variant in PLEC has been previously associated with atrial fibrillation in whole- genome sequencing data whereas another missense variant has been linked to structural brain connectivity. The intronic variant highlighted in this analysis has been previously associated with right ventricular structure and function but has not been identified in GWAS studies as an AD or AF signal." (p.10, lines 222- 226) + +<|ref|>text<|/ref|><|det|>[[115, 442, 883, 490]]<|/det|> +"Previous studies of human tissues or preclinical models provide independent evidence for an association of plectin with diseases including AD and AF." (p.10, lines 229- 231) + +<|ref|>text<|/ref|><|det|>[[115, 504, 617, 525]]<|/det|> +We also included in the discussion regarding HSPG2: + +<|ref|>text<|/ref|><|det|>[[115, 541, 884, 614]]<|/det|> +"Another colocalised variant between AD and AF, the intergenic rs7529220, which is located 19k upstream from Heparan Sulfate Proteoglycan 2 (HSPG2) ... and is a previously unreported locus for AD." (p.11, lines 252- 257) + +<|ref|>text<|/ref|><|det|>[[113, 629, 884, 860]]<|/det|> +APOE is a well- established gene associated with AD, and previous studies have supported its involvement in cardiovascular traits. Although our initial colocalisation analysis provided considerable evidence for its possible pleiotropic effect on AD and coronary artery disease (PP = 0.57), our subsequent eQTL colocalisation analysis could not replicate this association. This suggests that our study could not prioritise any shared gene within the locus between the two traits expressed in the examined tissues. Given the robust evidence from several independent studies linking APOE to both traits, it is plausible that the locus affects the two traits independently through different pathways (horizontal pleiotropy). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 135]]<|/det|> +Alternatively, there may be a shared gene expressed in tissues other than those we examined in our study. We added in the discussion: + +<|ref|>text<|/ref|><|det|>[[113, 150, 885, 329]]<|/det|> +"The variant rs429358, located within APOE, showed evidence for colocalisation between AD and CAD. However, further investigation using eQTL could not prioritise any shared gene within the locus expressed in the examined tissues. Given APOE's well- established role in AD and its potential involvement in other CV traits, including CAD, it is plausible that the locus affects the two traits independently through different pathways (horizontal pleiotropy) or through a shared gene expressed in tissues other than those examined in our study." (p.11, lines 264- 269) + +<|ref|>text<|/ref|><|det|>[[114, 379, 884, 478]]<|/det|> +1.8 The shared risk factors for AD and CVD indicated by genetic variants rs11786896 (PLEC) and rs7529220 (HSPG2) should be reassessed, as the observed odds ratios do not robustly categorize them as high- risk factors for Alzheimer's disease or atrial fibrillation. + +<|ref|>text<|/ref|><|det|>[[113, 493, 885, 777]]<|/det|> +Reply 1.8: We appreciate your notice. In the revised manuscript, we present the odds ratios (OR) and p- values from the MTAG analysis, which show that HSPG2 is associated with both traits at a GWS level, while PLEC is associated with AD at a GWS level and associated with AF ( \(P < 5 \times 10^{- 6}\) ). Indeed, the reported ORs are small (e.g. OR=1.02 for PLEC); however, it is not uncommon in GWAS studies to observe associations of variants with small effect sizes, which nonetheless can have significant biological importance. In support, the genetic colocalisation as well as other subsequent analyses consistently showed that these loci are associated with both AD and AF with the same causal variant, suggesting a pleiotropic effect. Figure 3 in our manuscript demonstrates a signal for both traits at the PLEC locus, underscoring the shared genetic architecture. + +<|ref|>text<|/ref|><|det|>[[114, 827, 883, 901]]<|/det|> +1.9 The relevance of the identified loci to other cardiovascular traits should be discussed. If no correlation exists, the study should narrow its focus to the relationship between AD and atrial fibrillation, avoiding unnecessary data and analyses. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 161]]<|/det|> +Reply 1.9: Thank you for your comment. As previously mentioned, we compared our findings across diverse CV traits that is thoroughly discussed in the revised version of our manuscript. + +<|ref|>text<|/ref|><|det|>[[113, 177, 885, 485]]<|/det|> +We aimed to look at several CV conditions in pairwise comparisons to explore the different pathways that may link different manifestations of AD with CV traits. For example, atrial fibrillation and coronary heart disease have different pathophysiology and therefore their cooccurrence with AD may be due to different shared mechanisms. Our study involved a series of sequential analyses, with each phase building upon the findings of the previous one to avoid unnecessary data and analyses. For instance, the colocalisation analysis was performed only for significant MTAG findings and identified 53 variant- gene- tissue associations with only four different CV traits involving 43 unique genes. We subsequently prioritised additional analyses for the indicated genes. Our gene expression analysis provided evidence of differential expression only for PLEC and C1Q, prompting further investigation into their pathways and interactions with other proteins. + +<|ref|>text<|/ref|><|det|>[[114, 500, 884, 547]]<|/det|> +We have revised our manuscript to provide clearer explanations of our methodology and findings (See reply to 1.2). + +<|ref|>text<|/ref|><|det|>[[114, 598, 884, 696]]<|/det|> +1.10 Finally, while the single- nuclei transcriptome and protein- protein interaction analyses involving PLEC, NDUFS3, and C1Q on AD brain tissues are noted, the study fails to elucidate a clear pathogenic connection of these targets to Alzheimer's disease and atrial fibrillation. + +<|ref|>text<|/ref|><|det|>[[113, 712, 885, 891]]<|/det|> +Reply 1.10: Thank you for your comment. We have provided a comprehensive set of analyses to draw conclusion on the potential mechanisms linking the highlighted genes with AD and AF. For example, we discuss the functions of PLEC and C1Q, aiming to elucidate their roles in the pathogenicity of AD and AF. Our study suggests that PLEC, a critical structural protein in the cytoskeleton, and its interactions with intermediate filaments may contribute to dysfunctions in astrocytes, potentially increasing the risk of AD. Similarly, these interactions in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 87, 885, 265]]<|/det|> +cardiomyocytes could lead to dysfunctions associated with heart failure, thereby linking PLEC to both AD and CV disorders. Additionally, our findings suggest that higher expression of C1Q may enhance activity within the complement system, potentially leading to synapse loss in early AD and contributing to the formation of atherosclerotic plaques and elevated inflammatory responses in cardiomyocytes. These insights are detailed in our discussion and we have revised our manuscript to make this clearer. + +<|ref|>text<|/ref|><|det|>[[112, 281, 885, 538]]<|/det|> +"Plectin is highly expressed in the central nervous system, especially at the interfaces between glia and pial cells and between glia and endothelial cells, and is thought to be important to blood- brain barrier and pial surface integrity. Plectin deficiency in mice has been associated with diminished learning capabilities and reduced long- term memory compared to wild- type littermates. Here we provide evidence that the risk of AD may be affected via functions of plectin in astrocytes. Astrocytes play multiple roles, central to the pathology of AD, including metabolic support for neurons, modulation of brain microvascular function and, through activities associated with those of microglia, inflammatory responses. We hypothesise that these functional roles are mediated in part by interactions of plectin with intermediate filaments (IFs), microtubules and actin filaments." (p.10, lines 232- 241) + +<|ref|>text<|/ref|><|det|>[[113, 553, 885, 729]]<|/det|> +"The role of PLEC in AF has been largely hypothesised to act via structural effects on the heart and cause electrophysiological abnormalities. Here, we also show evidence for upregulation of PLEC in cardiomyocytes of HF patients. Therefore, in accordance with the hypothesised mechanisms linking PLEC to AD above, PLEC may play related roles in cardiomyocytes for assembling and mobilising the intermediate filaments and their networks. These effects further modulate contractile function in cardiomyocytes and inflammatory responses in macrophages which may further contribute to AF." (p.11, lines 245- 251) + +<|ref|>text<|/ref|><|det|>[[113, 744, 885, 898]]<|/det|> +"The complement system plays a central role in synaptic remodelling in the brain and in cellular damage response more generally in the body. We hypothesise that greater expression of C1Q may lead to higher activity of the complement system which in turn may potentiate synapse loss in early AD. Similarly, C1Q has roles in the genesis of atherosclerotic plaques and in the regulation of early stages of inflammatory responses to the cardiomyocyte injury associated with a range of cardiac traits." (p.11, lines 258- 263) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 882, 135]]<|/det|> +Additionally, we provide a schematic overview illustrating the pathogenic connection suggested by our study (Figure 1). + +<|ref|>text<|/ref|><|det|>[[400, 310, 538, 328]]<|/det|> +[figure redacted] + +<|ref|>text<|/ref|><|det|>[[113, 544, 884, 670]]<|/det|> +However, it is important to note that epidemiological data often face limitations in elucidating clear pathogenic pathways. While we provided additional mechanistic evidence, the precise biological mechanisms cannot be inferred. Consequently, additional research approaches are essential to complement epidemiological findings and provide deeper insights into disease pathogenesis. + +<|ref|>text<|/ref|><|det|>[[115, 686, 393, 705]]<|/det|> +We added this as a limitation: + +<|ref|>text<|/ref|><|det|>[[113, 722, 884, 820]]<|/det|> +"Finally, epidemiological data frequently encounter challenges in clarifying pathogenic mechanisms. Although we provided evidence from mechanistic experiments, the exact biological processes involved cannot be inferred. Further work is needed to validate our findings and the suggested disease pathways." (p.13- 14, lines 314- 317) + +<|ref|>text<|/ref|><|det|>[[113, 872, 466, 891]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 205, 108]]<|/det|> +## Overview + +<|ref|>text<|/ref|><|det|>[[113, 124, 884, 485]]<|/det|> +The work uses MTAG to examine AD with cardiovascular traits. The motivation is the long- standing association between cardiovascular disease and AD, and the method harnesses the genetic correlation to improve power for detecting genetic associations. The authors use eQTLs identified from a range of tissues from the GTEx project plus their results to perform colocalization analyses and hone in on two sites, and follow up some of those findings with analysis of gene expression. Overall, the manuscript was clear and interesting. The methods are well- described and approach seems sound, but it looked like there might be a disagreement between figure 3 and text and figure 2 does not share enough detail so it cannot be used to check against the text, which were my most important concerns. I had some specific comments below but I also wondered 1) if the authors could examine genetic correlation between AD and the traits in addition to sharing the MTAG results; and, 2) whether the authors considered testing colocalization with multiple traits at loci that seemed like they had \(> = 2\) signal with several cardiovascular traits. + +<|ref|>text<|/ref|><|det|>[[113, 500, 884, 625]]<|/det|> +Reply: Thank you for your positive feedback on the clarity and interest of our manuscript and for your suggestions. We apologise for any confusion. We have carefully revised both the text and figures to ensure consistency and clarity throughout. We addressed each of your specific concerns and provided additional details to clarify any discrepancies you noted. + +<|ref|>text<|/ref|><|det|>[[115, 641, 755, 662]]<|/det|> +We provide the genetic correlation results in Supplementary Table 1. + +<|ref|>text<|/ref|><|det|>[[113, 677, 884, 907]]<|/det|> +Regarding the comment on colocalisation of multiple traits, we only performed bivariate (pairwise) MTAG analysis between AD and CV traits. Subsequently, this study design did not allow us to perform colocalisation across multiple CV traits as the MTAG AD GWAS results were different from each bivariate MTAG analysis. We opted for bivariate analysis to explore different pathways that may link different CV traits with AD (e.g. different shared pathways linking AF to AD and CAD to AD). However, in the case of systolic and diastolic blood pressure, as those two traits are correlated and reflect similar pathways, we analysed the traits in a single MTAG between AD, systolic and diastolic blood pressure and the subsequent + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 886, 240]]<|/det|> +colocalisation was performed across these three traits. Additionally, our results did not highlight the same loci with evidence for colocalisation between different AD- CV pairs. The regions with evidence of colocalisation with multiple CV traits in Figure 2 (chromosomes 8 and 10), were associated with CV traits through different and independent signals ( \(R^2 < 0.1\) ). Thus, these loci likely do not affect the different CV traits through the same mechanism. + +<|ref|>text<|/ref|><|det|>[[115, 292, 267, 310]]<|/det|> +Major Comments + +<|ref|>text<|/ref|><|det|>[[114, 364, 884, 436]]<|/det|> +2.1. Title – at best, these data let you say that there is evidence consistent with what you’d observe with pleiotrophy. Also, there are more genes implicated than just PLEC and C1Q, unless I missed something. + +<|ref|>text<|/ref|><|det|>[[114, 451, 884, 499]]<|/det|> +Reply 2.1: Thank you for your comment. We agree and have now changed the title of our manuscript to: + +<|ref|>text<|/ref|><|det|>[[114, 515, 884, 561]]<|/det|> +“Multi- trait association analysis reveals shared genetic loci between Alzheimer's disease and cardiovascular traits”. + +<|ref|>text<|/ref|><|det|>[[114, 614, 883, 659]]<|/det|> +2.2 Figure 1 would be helped by sharing the sample sizes for each GWAS used to let the reader understand their magnitudes. + +<|ref|>text<|/ref|><|det|>[[114, 675, 884, 722]]<|/det|> +Reply 2.2: Thank you for your suggestion. We modified Figure 1 accordingly and now show the sample sizes for each GWAS. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 483, 883, 526]]<|/det|> +2.3 Figure 2 is difficult to read - can it just be made into a horizontal plot with labeled axes? + +<|ref|>text<|/ref|><|det|>[[112, 544, 885, 800]]<|/det|> +Reply 2.3: We apologise for this. Figure 2 presents the regional plots for the colocalised loci. Our intention with this plot was to highlight the significant results from our colocalisation analysis in a summarised format, believing that a circular form of the plot would do so more efficiently. We provide the suggested horizontal orientation in Supplementary Figure 7. Nevertheless, to address reviewer's concerns regarding the complexity of Figure 2, we applied a few modifications to simplify the plot. More specifically, we removed the outer circles corresponding to eQTL information, erased the coordinates from the x- axis and enlarged the text for the annotated genes. Finally, we removed the trait annotations from the plots and replaced them with a simpler legend. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 88, 850, 556]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 575, 746, 595]]<|/det|> +We also made a few changes to the Figure legend, which now says: + +<|ref|>text<|/ref|><|det|>[[115, 611, 883, 658]]<|/det|> +"Fig. 2: Circular figure visualising regional plots on the colocalised loci between Alzheimer's disease (AD) and cardiovascular traits (CV). + +<|ref|>text<|/ref|><|det|>[[115, 673, 881, 720]]<|/det|> +The figure presents the distribution of P- values (- log10P) from MTAG with inner orientation. The annotations show the mapped genes of the AD/CV top lead SNPs on the colocalised loci." + +<|ref|>text<|/ref|><|det|>[[115, 772, 883, 817]]<|/det|> +2.4 Figure 3 seems to present different p- values compared to the text (lines 112- 115) that should be checked. + +<|ref|>text<|/ref|><|det|>[[115, 834, 883, 881]]<|/det|> +Reply 2.4: Thank you for noticing this and apologies for the confusion. We modified our manuscript accordingly and now present the correct OR and p- values from the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 136]]<|/det|> +MTAG analysis. The p-values in Figure 3 are now concordant with those mentioned in the text (p.4, lines 84- 85) + +<|ref|>text<|/ref|><|det|>[[114, 187, 720, 207]]<|/det|> +2.5 Please provide manhattan and qq plots for each trait combination. + +<|ref|>text<|/ref|><|det|>[[114, 222, 884, 297]]<|/det|> +Reply 2.5: We provided Manhattan plots and QQ- plots for each trait (Supplementary Figures 1- 6). In those plots, we compare MTAG results with those from the respective univariate GWAS. We have revised the results section appropriately: + +<|ref|>text<|/ref|><|det|>[[114, 312, 884, 386]]<|/det|> +"We examined the bivariate genetic correlation between AD and the examined CV traits (Supplementary Table 1) and visually illustrated the MTAG results alongside those from the original GWAS (Supplementary Fig. 1- 6)." (p.2, lines 45- 47) + +<|ref|>text<|/ref|><|det|>[[113, 435, 884, 666]]<|/det|> +2.6 Discussion - lines 218- 221. The authors claim the results of their study disentangles the relationship between AD and AF. This is beyond what I think they can say with these data since the outcome in the Jansen paper is mainly from the UKB that infers case status using a question about whether the parent had dementia. This introduces a substantial amount of heterogeneity as to the underlying cause of dementia that ranges from cerebrovascular disease to a purely neurodegenerative cause, which preclude the kind of conclusion the authors made. Using Kunkle et al., 2018, which relies on a clinical diagnosis, might help this. Regardless of the specific cause of dementia, it's clear that there's a relationship between dementia and AF. + +<|ref|>text<|/ref|><|det|>[[113, 681, 884, 886]]<|/det|> +Reply 2.6: Thank you for your detailed and insightful comment. We also share the reviewer's view that there is a link between dementia and AF. Our study focused on AD, the most prevalent type of dementia, to identify genetic regions with pleiotropic effects that could indicate shared biological mechanisms contributing to their observed comorbidity. We utilised the largest available GWAS from Jansen et al. at the time of our analysis. This GWAS combined clinically diagnosed cases of AD with proxies (AD- by- proxy- individuals whose parents were diagnosed with dementia). The authors provide evidence that the correlation between the GWAS + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 87, 884, 239]]<|/det|> +with and without the 'AD- by- proxy' cases was high adding to the validity of this approach, especially regarding sample size improvement which is critical for AD GWAS. However, we agree that 'AD- by- proxy' may introduce heterogeneity in the results and highlight associations which may be driven by other types of dementia. We acknowledge this as a limitation of our study (see below). The revised text now more accurately represents the conclusions that can be drawn from our data. + +<|ref|>text<|/ref|><|det|>[[113, 255, 884, 303]]<|/det|> +“Here we provide evidence suggesting a shared genetic determinant that may contribute to the pathophysiology of AF and AD.” (p.10, lines 217- 218) + +<|ref|>text<|/ref|><|det|>[[113, 318, 886, 496]]<|/det|> +“The GWAS for AD combined clinically diagnosed cases of AD with proxies (AD- by- proxy, individuals whose parents were diagnosed with AD). The correlation between the GWAS with and without the ‘AD- by- proxy’ cases was high adding to the validity of this approach. Nonetheless, the inclusion of individuals with parental AD diagnoses in the original GWAS may have introduced greater heterogeneity and increased probability of misclassification, suggesting that some of our observed associations might be misclassified or influenced by other types of dementia.” (p.13, lines 296- 302) + +<|ref|>text<|/ref|><|det|>[[113, 546, 884, 645]]<|/det|> +2.7 Using gene expression from tissues that are not likely directly relevant for the pathogenesis of AD or one of the CVD traits rests on an assumption that the eQTLs in that tissue are generalizable. It could be that they are false positives in one tissue and are correctly null in other tissues. + +<|ref|>text<|/ref|><|det|>[[113, 661, 884, 892]]<|/det|> +Reply 2.7: We appreciate your comment. Emerging evidence suggests that AD is a systemic disease with widespread effects beyond the central nervous system. In this work, we aimed to further study the systemic nature of the disease by studying the interconnectedness of vascular health and neurodegeneration. We therefore opted to investigate agnostically all available tissues to also capture potential effects beyond the nervous system. Additionally, by studying all tissues, the analysis is not restricted to specific tissues with very small sample sizes (139 to 255 samples in brain tissues). Many eQTLs are correlated across different tissues, potentially adding to the generalizability of our findings. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 187]]<|/det|> +However, we acknowledge that the possibility of false positive findings remains. To address this, we aimed to validate our findings through additional analyses on different populations using single- cell and single- nuclei data from brain tissue of AD cases and cardiac tissue from heart failure cases. + +<|ref|>text<|/ref|><|det|>[[114, 202, 884, 275]]<|/det|> +We believe that our approach is comprehensive, even though it comes with the limitations mentioned above. This consideration has been added to our manuscript, which now states: + +<|ref|>text<|/ref|><|det|>[[113, 291, 885, 469]]<|/det|> +"Considering the systemic nature of AD, which encompasses multiple pathways and various tissues, our study conducted a thorough investigation across all tissues, assuming correlations among many eQTLs across different tissues. However, it is important to acknowledge that some eQTLs from tissues not directly linked to AD or CV traits could represent false positive associations. To mitigate this, we validated our findings using single- cell and single- nuclei data obtained from brain tissue samples of AD cases and cardiac tissue samples from individuals with HF." (p.13, lines 302- 308) + +<|ref|>text<|/ref|><|det|>[[114, 521, 267, 540]]<|/det|> +Minor Comments + +<|ref|>text<|/ref|><|det|>[[114, 591, 884, 640]]<|/det|> +2.8 Consider adding the limitation that not all GWAS summary results are complete so signal that is not present in one of the dataset pairs would not be tested using MTAG. + +<|ref|>text<|/ref|><|det|>[[114, 654, 884, 703]]<|/det|> +Reply 2.8: Thank you for your suggestion. We modified the limitations as suggested. In the discussion, we mention: + +<|ref|>text<|/ref|><|det|>[[113, 717, 885, 896]]<|/det|> +"Additionally, we did not investigate a considerable portion of the genetic predisposition coming from rare variants (MAF < 1%) as we excluded them from our analyses. This exclusion is a restriction of the MTAG method, in order to mitigate the risk of false- positive findings and biased results. Another limitation of using MTAG is that genetic variants that are not present in at least one GWAS dataset of each AD- CV pair were excluded from the corresponding pairwise MTAG analysis and therefore some variants tested in one pairwise MTAG may not be tested in another." (p.12, lines 280- 286) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 124, 883, 198]]<|/det|> +2.9 Figure 3 – the eQTL line plot is confusing. Why not stack the two tissues and use dots? Either way, the association between the eQTL signal and other traits (i.e., AD, atrial fib) are not striking. + +<|ref|>text<|/ref|><|det|>[[114, 213, 883, 286]]<|/det|> +Reply 2.9: We apologise for the confusion initially caused by Figure 3. We have carefully revised the figure as suggested to enhance the illustration of the eQTL results. + +<|ref|>text<|/ref|><|det|>[[114, 300, 884, 401]]<|/det|> +Regarding your concern on the association between the eQTL signal and other traits, we now provide further clarification. This locus was identified through MTAG analysis between AD and AF and further colocalisation analysis yielded robust evidence of colocalisation, as detailed in our manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 415, 884, 515]]<|/det|> +"The intronic variant rs11786896 (PLEC) explained the colocalisation of AD and AF with expression levels of PLEC in the cardiac left ventricle (PP = 0.99, %PP explained by \(SNP = 99\%\) ) and skeletal muscle (PP = 0.92, %PP explained by \(SNP = 98\%\) ) (Fig. 3)." (p.4, lines 91- 94) + +<|ref|>text<|/ref|><|det|>[[114, 530, 884, 629]]<|/det|> +Additionally, we have conducted several post- GWAS analyses including gene expression, pathway analysis, and protein- protein interaction, providing supplementary evidence which strengthens the association of these traits with the identified locus. + +<|ref|>text<|/ref|><|det|>[[114, 682, 883, 753]]<|/det|> +2.10 Unlike CVD traits, AD has one region, the APOE locus, that has an outsized effect compared to other genetic loci. I would guess the results from APOC1 were driven by the association between AD and APOE. + +<|ref|>text<|/ref|><|det|>[[114, 769, 884, 896]]<|/det|> +Reply 2.10: Thank you for your insightful comment. Regarding our findings related to the APOC1 locus, we acknowledge that APOE is one of the major genetic regions associated with AD, and it is indeed closely located to APOC1. Our MTAG analysis indicated a variant mapped to APOC1 (rs438811). However, in our trait- trait colocalization analysis, another variant in APOE (rs429358) was highlighted as the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 136]]<|/det|> +candidate causal variant. The evidence for colocalization was sufficient but not very strong (PP = 0.57). + +<|ref|>text<|/ref|><|det|>[[113, 150, 884, 329]]<|/det|> +It is important to note that the two aforementioned SNPs are in linkage disequilibrium (LD, \(r^2 = 0.63\) ). Based on this, it is very likely that the observed association with APOC1 is driven by the influence of the APOE locus. Additionally, the eQTL colocalization analysis did not show sufficient evidence for colocalization at this locus. Given the insufficient support for colocalization (see study design in Figure 1), we did not pursue further investigation into this association. However, we added the following to the discussion: + +<|ref|>text<|/ref|><|det|>[[113, 344, 885, 522]]<|/det|> +"The variant rs429358, located within APOE, showed evidence for colocalisation between AD and CAD. However, further investigation using eQTL could not prioritise any shared gene within the locus expressed in the examined tissues. Given APOE's well- established role in AD and its potential involvement in other CV traits, including CAD, it is plausible that the locus affects the two traits independently through different pathways (horizontal pleiotropy) or through a shared gene expressed in tissues other than those examined in our study." (p.11- 12, lines 264- 269) + +<|ref|>text<|/ref|><|det|>[[114, 572, 883, 645]]<|/det|> +2.11 Discussion - lines 204-5 (grammer/phrasing) - "rs11786896 expressed via PLEC and rs7529220 expressed via C1QA, C1QB, and C1QC" sounds odd. I'd phrase it something like rs1179686 is an eQTL for PLEC. + +<|ref|>text<|/ref|><|det|>[[114, 661, 618, 682]]<|/det|> +Reply 2.11: We rephrased the sentence as suggested: + +<|ref|>text<|/ref|><|det|>[[114, 697, 883, 744]]<|/det|> +"rs11786896 which was an eQTL for PLEC and rs7529220 which was an eQTL for C1QA, C1QB, and C1QC" (p.8, lines 184- 185) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 370, 101]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 128, 459, 145]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 172, 850, 207]]<|/det|> +The authors have fully addressed reviewers' comments and the revised version is worth being accepted for publication as it is. + +<|ref|>text<|/ref|><|det|>[[117, 233, 819, 252]]<|/det|> +Reply: We thank the reviewer for suggesting the publication of our manuscript + +<|ref|>text<|/ref|><|det|>[[119, 300, 459, 318]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 344, 872, 411]]<|/det|> +No matter how AD is commonly defined (e.g., clinically or pathologically), it often co- occurring with evidence of cerebrovascular disease yet whether this is pleiotropic or causal relationship is unknown - - although there is some work that suggests a direct link https://pubmed.ncbi.nlm.nih.gov/35772923/. + +<|ref|>text<|/ref|><|det|>[[117, 411, 844, 445]]<|/det|> +The current work focuses on finding shared genetic risk using MTAG, which uses genetic correlation to boost power for multi- trait gwas. + +<|ref|>text<|/ref|><|det|>[[117, 444, 840, 478]]<|/det|> +The most interesting portion of the work is the MTAG results along with the SMR analysis. + +<|ref|>text<|/ref|><|det|>[[117, 478, 875, 528]]<|/det|> +By contrast the differential expression and network- based analysis was descriptive without addressing the most interesting question of the work - - the shared risk for CV traits and AD dementia. + +<|ref|>text<|/ref|><|det|>[[119, 527, 690, 545]]<|/det|> +Overall, the revised manuscript nicely addressed my comments. + +<|ref|>sub_title<|/ref|><|det|>[[119, 560, 301, 577]]<|/det|> +## ## Minor Comments + +<|ref|>text<|/ref|><|det|>[[119, 592, 794, 626]]<|/det|> +1. line 297 - AD-proxy status was inferred based on whether the parent was diagnosed with dementia (not AD per se). + +<|ref|>text<|/ref|><|det|>[[117, 653, 860, 687]]<|/det|> +Reply: We thank the reviewer for the comment. We have clarified this distinction in the revised manuscript as suggested: + +<|ref|>text<|/ref|><|det|>[[117, 691, 870, 741]]<|/det|> +"The GWAS for AD combined clinically diagnosed cases of AD with AD-proxy status (inferred based on whether the parent was diagnosed with dementia)." (p.13, lines 296- 298) + +<--- Page Split ---> diff --git a/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/images_list.json b/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c6996ea84bfcf16a0f1e352284c7b7829c14102c --- /dev/null +++ b/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,201 @@ + +# nature portfolio + +Peer Review File + +Spectroscape Enables Real- time Query and Visualization of a Spectral Archive in Proteomics + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this revised version of the manuscript the authors have in my view addressed my previous comments: (i) they provide a larger benchmarking study (trying to get closer to a repository size dataset); (ii) they have improved documentation, including videos, and (iii) have tried to compare the performance of the tool with other previously published approaches. + +I also find that the manuscript has now improved quite a lot in terms of scope and clarifying some aspects that maybe were not completely clear to me after my first review. + +I agree with the authors that Spectroscape can indeed be a useful tool, but its real future impact cannot really be assessed at this point. A possible collaboration with a proteomics repository would also be key for the future although of course this is outside the current scope of this work. + +Reviewer #2 (Remarks to the Author): + +Wu et al. present an updated version of their manuscript presenting Spectroscape as a novel visualization tool for spectral archives. + +The authors strongly argue, that their tool must not be viewed as another spectrum clustering algorithm, but a tool to investigate individual spectra. + +I believe, that this argument falls short as it is necessary to show that the used method to group spectra compares to existing methods. Nevertheless, I follow the authors argument for this review. + +<--- Page Split ---> + +I am surprised to see that all benchmarks etc were put in the supplementary methods. Therefore, the manuscript itself holds very limited information that would be relevant to a wider audience. + +## 1) Novelty + +The idea to create a visualization tool on top of a spectrum grouping / ANN network is nice, but not novel. This was done as part of previous PRIDE associated resources (although static and not scalable). + +The methods used by the authors also were introduced by others before. Adapting the training process is innovative, but something I consider incremental improvement. Therefore, overall, the novelty of the proposed work is in my opinion limited. + +## 2) Software + +The state of the software was improved but is still below expectations. The installation works. Nevertheless, building an archive with only one 750 MB mzXML file failed with a segmentation fault on a 16 core machine with 32 GB RAM (again using a docker container and ubuntu:22.04). The mzXML file was taken from PXD016673. + +The website to test the live version at http://omics.ust.hk:8709/index.html was not accessible during the time of the review (tested from multiple networks). + +Overall, I therefore have severe reservations whether this tool will provide the simple and high usage of spectrum clustering or similar methods. It also raises grave concerns whether the authors hold the required expertise to develop an end- user ready piece of software and maintain it for a relevant amount of time. The original version contained severe and obvious errors and highlighted that the software was not tested properly. Apparently, the software still has not reached a stable version. + +## 3) Theoretical usability + +The tool (if it works) will only serve one question in proteomics research, to validate specific PSMs. The authors are correct, that some findings center on specific proteoforms / PTMs. Nevertheless, a vast number of literature centers on large- scale characterisations of proteomics samples. These will not profit from this tool. + +<--- Page Split ---> + +As a mere proof of concept, this work is interesting, but not to the wide community addressed by this Journal. I therefore suggest this work to be submitted to a field- specific one. + +Reviewer #3 (Remarks to the Author): + +The authors have clarified the scope of the current work and have offered a compelling defense of the current capabilities of Spectroscape. There will be researchers looking at novel proteoforms or other non- standard identifications, and Spectroscape provides a unique tool for quickly exploring possible hypotheses regarding these discoveries. Additionally, the new analyses provided by the authors go a long way towards suggesting future developments for the technology. + +In their rebuttal, the authors offered the following argument in defense of Spectroscape: + +We believe that as a field we have gone too far down the road of controlling errors at a global level (e.g., by estimating FDR by target- decoy searching), while side- stepping the more fundamental question of what makes an individual PSM believable in the first place. Automatic "black box" approach to validation appeals to researchers who would rather focus on the biology, but we pay for this convenience with our credibility in the eyes of other life scientists. In a perfect world, the global error control we do today should only be viewed as the first step to filter away unpromising leads, but we should not be content to accept everything that passes the filter as truth. In just about every other discipline, scientists would not embark on expensive independent validation experiments until technical validation is done first and the data is deemed trustworthy. In proteomics, many researchers do not bother to even look at a spectrum that underpins our hypothesis, but are all too willing to embark on expensive and tedious biological validation experiments. With the right tool, checking even hundreds of PSMs perhaps take a matter of hours; in contrast, biological validation experiments often take months. + +I would suggest adding something along these lines to the main manuscript. The argument against global FDR control is not new. Many papers have been written about the differences between global + +<--- Page Split ---> + +FDR and local FDR or the False Positive Rate of a spectrum. For example, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689316/ + +These issues take on added importance when discovering novel proteoforms or searching non- standard databases. Even simple phospho enrichment experiments typically have different empirical FDR rates when subsetting the data to modifications on tyrosine. Referencing the known failures of global FDR control would bolster the argument in favor of using Spectroscape as a validation step. + +Regarding the main manuscript, my only new suggestion is that it would be nice for references to the Supplement to include a specific section identifier. In the current form it is somewhat inconvenient to match the main text with the relevant section of the supplement. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +In this revised version of the manuscript the authors have in my view addressed my previous comments: (i) they provide a larger benchmarking study (trying to get closer to a repository size dataset); (ii) they have improved documentation, including videos, and (iii) have tried to compare the performance of the tool with other previously published approaches. + +I also find that the manuscript has now improved quite a lot in terms of scope and clarifying some aspects that maybe were not completely clear to me after my first review. + +I agree with the authors that Spectroscape can indeed be a useful tool, but its real future impact cannot really be assessed at this point. A possible collaboration with a proteomics repository would also be key for the future although of course this is outside the current scope of this work. + +## Response: + +Thank you for the supportive comments on our manuscript. Yes, we are planning to make Spectroscape available over PeptideAtlas as a first step, and have been in touch with the engineers at ISB about this. However, it will take us months to sort out the technical (in particular hardware) issues within the ISB infrastructure, and we feel that we should not delay the dissemination of this work any longer. We hope that the Spectroscape tool can be easily accessible to everyone in the future, including researchers who want to build their own specialized spectral archives. Recently, we have also purchased a domain name, spectroscape.cc to host a demo spectral archive persistently to promote the idea to the community. + +## Reviewer #2 (Remarks to the Author): + +Wu et al. present an updated version of their manuscript presenting Spectroscape as a novel visualization tool for spectral archives. + +The authors strongly argue, that their tool must not be viewed as another spectrum clustering algorithm, but a tool to investigate individual spectra. + +I believe, that this argument falls short as it is necessary to show that the used method to group spectra compares to existing methods. Nevertheless, I follow the authors argument for this review. + +## Response: + +<--- Page Split ---> + +Thanks for the supportive comments. As we have described in the manuscript, Spectroscape is not a clustering tool. It does not "group spectra" ahead of time, nor does it outputs the list of clusters of the entire spectral archive. So we struggle to see how we can show a comparison of how Spectroscape "group spectra" as compared to existing methods (e.g., MS- Cluster, MaRaCluster, GLEAMS, etc.). Rather, we must emphasize that Spectroscape is a retrieval and visualization tool. It will respond to each individual query spectra (ignoring precursor information), find the nearest neighbors, and compute the connectivity graph among the neighbors on the fly. It is then up to the user to interpret such "local" cluster information. (Of course, this retrieval algorithm can be leveraged to compute the global adjacency matrix efficiently, but that is not the intended application of Spectroscape. Even if we have the adjacency matrix, it would still require a subsequent step to determine the cluster boundaries in an unsupervised manner, before one can compare to the outputs of other clustering tools. This unsupervised clustering function is not part of Spectroscape.) In our view, the performance evaluation of Spectroscape should be in terms of query retrieval, not clustering outcome. We provided evidence to show that the indexing and retrieval method of Spectroscape provides for very high recall, and that the index was designed effectively such that the distances between the 17- byte addresses are well- correlated with the true distances of the corresponding spectra. + +I am surprised to see that all benchmarks etc were put in the supplementary methods. Therefore, the manuscript itself holds very limited information that would be relevant to a wider audience. + +## Response: + +Thanks for this constructive comment. Actually, we put them into the Supplementary Information to adhere to the typical length of Nature Communication articles. We felt that the technical details are perhaps only of interest to the real computational experts, which may be a minority of our audience. In any case, we have modified the manuscript to include the comparison to GLEAMS (in terms of approximate nearest neighbor retrieval) in the main text. + +## 1) Novelty + +The idea to create a visualization tool on top of a spectrum grouping / ANN network is nice, but not novel. This was done as part of previous PRIDE associated resources (although static and not scalable). + +## Response: + +Thanks for this insightful comment. Yes, we agree that providing a visual representation of clusters is not in itself novel. (We were unable to find the PRIDE cluster visualization alluded to by the reviewer, however.) On the other hand, as the reviewer recognized, Spectroscape is dynamic and scalable, unlike previous tools. Spectroscape did not cluster at all before the neighboring spectra are retrieved. What Spectroscape enabled is the ability to see the neighborhood of a query spectrum, in real time, without any prior offline clustering. Besides, it does not use the precursor m/z to filter for neighbors, meaning that it is effectively performing an "open" search. Since it does not rely on peptide annotations to "train" the index, it is more general + +<--- Page Split ---> + +and adaptable to other fields in mass spectrometry. The calculation of the detailed cluster structure (by complete pair- wise similarity calculations among retrieved neighbors) and its display using a force- directed graph, is also unique to Spectroscape. + +The methods used by the authors also were introduced by others before. Adapting the training process is innovative, but something I consider incremental improvement. Therefore, overall, the novelty of the proposed work is in my opinion limited. + +## Response: + +We would respectfully disagree with this assessment. Since no example of such similar work was mentioned, we were unable to offer our rebuttal in detail. However, please allow us to state our case in general terms here. + +Spectroscape's underlying algorithm, IVF- PQ, was developed by others (Facebook), but the adaptation of it to proteomics in our hands is no doubt novel. (Adapting an algorithm developed by others has also enabled many recent advances in proteomics, e.g., applications of deep learning.) It is important to emphasize that the FAISS library provides many indexing algorithms, of which IVF- PQ is only one of many. It is unfair to suggest that any work that uses the FAISS library is not novel because someone else has used the FAISS library before. On the contrary, precisely because there are so many possible indexing algorithms to choose from, the selection of the specific indexing algorithm and its adaptation and optimization for the task at hand is not trivial. + +Perhaps the reviewer was taking a broader view that any method that relies on some dimensionality reduction to speed up the search of neighbors in high- dimensional space should be considered "similar" and therefore not novel or merely "incremental." But if this is the case, the novelty bar is set unreasonably high. For example, we would argue that GLEAMS, which was published recently in Nature Methods, also adopts a similar conceptual approach. Its novelty, as in our case, lies in the choice of the exact dimensionality reduction algorithm (i.e., in how the "embedding" was trained) to suit its particular application. Moreover, we have shown that the approximate nearest neighbor retrieval of Spectroscape is more effective and general than GLEAMS's, not to mention that Spectroscape enables real- time and dynamic visualization of the complete cluster structure among neighbors, a feature that no other tool can boast. + +## 2) Software + +The state of the software was improved but is still below expectations. The installation works. Nevertheless, building an archive with only one 750 MB mzXML file failed with a segmentation fault on a 16 core machine with 32 GB RAM (again using a docker container and ubuntu:22.04). The mzXML filwas taken from PXD016673. + +<--- Page Split ---> + +## Response: + +Thanks for pointing out this issue. We apologize for forgetting to mention that a minimum of 100,000 spectra is required to initialize the Spectroscape index. One mzXML file is not sufficient for the k- means algorithms to initialize the "buckets". In our demo, we use 24 mzXML files, and we do not observe the error. We have updated the user manual to explain this, and provide a clear error message if the user fails to provide enough training data. We also uploaded a test dataset so that users can try out the tool more easily. + +The website to test the live version at http://omics.ust.hk:8709/index.html was not accessible during the time of the review (tested from multiple networks). + +## Response: + +Thanks for pointing out this issue. Our server was down for several days during the time of review due to electricity suspension and hardware upgrade in our institution, which was out of our control. (We did make an announcement on GitHub around that time to warn potential users; nonetheless, we fully accept that it is our responsibility to keep it running.) To make the web demo works more persistently, we recently purchased an domain name spectroscape.cc and a server instance in AWS, which connects to multiple mirror servers to provide a bit more redundancy. We are confident that our new web interface (spectroscape.cc) will always be online during the period of the review and beyond. + +Overall, I therefore have severe reservations whether this tool will provide the simple and high usage of spectrum clustering or similar methods. It also raises grave concerns whether the authors hold the required expertise to develop an end- user ready piece of software and maintain it for a relevant amount of time. The original version contained severe and obvious errors and highlighted that the software was not tested properly. Apparently, the software still has not reached a stable version. + +## Response: + +We again apologize for the web interface issues, which are now fixed. We will continue to maintain the software and ensure its usability. + +## 3) Theoretical usability + +The tool (if it works) will only serve one question in proteomics research, to validate specific PSMs. The authors are correct, that some findings center on specific proteoforms / PTMs. Nevertheless, a vast number of literature centers on large- scale characterisations of proteomics samples. These will not profit from this tool. + +## Response: + +<--- Page Split ---> + +Yes, we agree that the large- scale characterization of proteomics samples will always be important. However, we do not lack tools (e.g. database search engines) for that purpose. Spectroscape serves a different purpose: for validating biological findings that critically depend on the identification/quantification of specific genes/proteins (which could be discovered by database search engines initially). Clearly, the credibility of a single PSM or a few selected PSMs cannot be established by current approaches of global FDR control approach at the dataset level. Spectroscape helps in the validation of such findings with information that is not readily accessible to the researcher now. Spectroscape is therefore complementary to, and not competing with, existing tools for high- throughput characterization. We have added a paragraph in the revision to clarify this point. + +As a mere proof of concept, this work is interesting, but not to the wide community addressed by this Journal. I therefore suggest this work to be submitted to a field- specific one. + +## Response: + +We do not dispute that this is a proof of concept at this stage, but Spectroscape is a one- of- a- kind addition to our toolkit that may have long- lasting impact to our field. In the manuscript we have articulated a vision of how proteomics data analysis should be more collaborative and better integrated with data sharing, with Spectroscape being the interface between the user and the repository. Although this will require the active participation of many stakeholders and cannot be realized now, we believe that getting the word out is the critical first step. Of course, whether this step is "big" enough for this journal is a question for the editorial leadership of Nature Communications. On the other hand, we have also seen many publications in journals with broad readership that are proof of concept in nature, or target audience in a specific field exclusively. In our field, for example, we can think of many recent examples, such as MSFragger (2017 Nat Methods), DeepNovo (2017 PNAS), Prosit (2019 Nat Methods), AlphaPeptDeep (2022 Nat Comm), GLEAMS (2022 Nat Methods), etc. + +## Reviewer #3 (Remarks to the Author): + +The authors have clarified the scope of the current work and have offered a compelling defense of the current capabilities of Spectroscape. There will be researchers looking at novel proteoforms or other non- standard identifications, and Spectroscape provides a unique tool for quickly exploring possible hypotheses regarding these discoveries. Additionally, the new analyses provided by the authors go a long way towards suggesting future developments for the technology. + +## Response: + +Thank you very much for the supportive comments. We believe the Spectroscape tool has the potential to shed light on the unidentified spectra and verify new identifications against the massive amount of existing data, which we cannot easily do right now. + +<--- Page Split ---> + +In their rebuttal, the authors offered the following argument in defense of Spectroscape: + +We believe that as a field we have gone too far down the road of controlling errors at a global level (e.g., by estimating FDR by target- decoy searching), while side- stepping the more fundamental question of what makes an individual PSM believable in the first place. Automatic "black box" approach to validation appeals to researchers who would rather focus on the biology, but we pay for this convenience with our credibility in the eyes of other life scientists. In a perfect world, the global error control we do today should only be viewed as the first step to filter away unpromising leads, but we should not be content to accept everything that passes the filter as truth. In just about every other discipline, scientists would not embark on expensive independent validation experiments until technical validation is done first and the data is deemed trustworthy. In proteomics, many researchers do not bother to even look at a spectrum that underpins our hypothesis, but are all too willing to embark on expensive and tedious biological validation experiments. With the right tool, checking even hundreds of PSMs perhaps take a matter of hours; in contrast, biological validation experiments often take months. + +I would suggest adding something along these lines to the main manuscript. The argument against global FDR control is not new. Many papers have been written about the differences between global FDR and local FDR or the False Positive Rate of a spectrum. For example, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689316/. These issues take on added importance when discovering novel proteoforms or searching non- standard databases. Even simple phospho enrichment experiments typically have different empirical FDR rates when subsetting the data to modifications on tyrosine. Referencing the known failures of global FDR control would bolster the argument in favor of using Spectroscape as a validation step. + +## Response: + +Thanks for the suggestions. We have modified the main text to include discussion of how global FDR control is not sufficient to establish the credibility of a small subset of the data, and why the ability to validate individual PSMs will always have an important place in proteomics. + +Regarding the main manuscript, my only new suggestion is that it would be nice for references to the Supplement to include a specific section identifier. In the current form it is somewhat inconvenient to match the main text with the relevant section of the supplement. + +## Response: + +Thanks for the suggestion. We have assigned specific identifiers to different sections of the Supplementary Information. + +<--- Page Split ---> diff --git a/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b126a2898d1dbf25be89edf0fc3413c775a91554 --- /dev/null +++ b/peer_reviews/990b6b7a4019afa38768bea301e6129480c22c61c21e3e2575ba8092b42152e6/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,277 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 900, 211]]<|/det|> +Spectroscape Enables Real- time Query and Visualization of a Spectral Archive in Proteomics + +<|ref|>image<|/ref|><|det|>[[57, 732, 239, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 844, 163]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[115, 204, 288, 219]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 260, 393, 277]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 317, 877, 389]]<|/det|> +In this revised version of the manuscript the authors have in my view addressed my previous comments: (i) they provide a larger benchmarking study (trying to get closer to a repository size dataset); (ii) they have improved documentation, including videos, and (iii) have tried to compare the performance of the tool with other previously published approaches. + +<|ref|>text<|/ref|><|det|>[[115, 428, 833, 464]]<|/det|> +I also find that the manuscript has now improved quite a lot in terms of scope and clarifying some aspects that maybe were not completely clear to me after my first review. + +<|ref|>text<|/ref|><|det|>[[115, 503, 875, 558]]<|/det|> +I agree with the authors that Spectroscape can indeed be a useful tool, but its real future impact cannot really be assessed at this point. A possible collaboration with a proteomics repository would also be key for the future although of course this is outside the current scope of this work. + +<|ref|>text<|/ref|><|det|>[[115, 626, 393, 642]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 682, 794, 717]]<|/det|> +Wu et al. present an updated version of their manuscript presenting Spectroscape as a novel visualization tool for spectral archives. + +<|ref|>text<|/ref|><|det|>[[115, 757, 805, 792]]<|/det|> +The authors strongly argue, that their tool must not be viewed as another spectrum clustering algorithm, but a tool to investigate individual spectra. + +<|ref|>text<|/ref|><|det|>[[115, 832, 875, 867]]<|/det|> +I believe, that this argument falls short as it is necessary to show that the used method to group spectra compares to existing methods. Nevertheless, I follow the authors argument for this review. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 860, 125]]<|/det|> +I am surprised to see that all benchmarks etc were put in the supplementary methods. Therefore, the manuscript itself holds very limited information that would be relevant to a wider audience. + +<|ref|>sub_title<|/ref|><|det|>[[115, 165, 193, 181]]<|/det|> +## 1) Novelty + +<|ref|>text<|/ref|><|det|>[[115, 220, 864, 256]]<|/det|> +The idea to create a visualization tool on top of a spectrum grouping / ANN network is nice, but not novel. This was done as part of previous PRIDE associated resources (although static and not scalable). + +<|ref|>text<|/ref|><|det|>[[115, 296, 873, 350]]<|/det|> +The methods used by the authors also were introduced by others before. Adapting the training process is innovative, but something I consider incremental improvement. Therefore, overall, the novelty of the proposed work is in my opinion limited. + +<|ref|>sub_title<|/ref|><|det|>[[115, 390, 202, 406]]<|/det|> +## 2) Software + +<|ref|>text<|/ref|><|det|>[[115, 445, 880, 518]]<|/det|> +The state of the software was improved but is still below expectations. The installation works. Nevertheless, building an archive with only one 750 MB mzXML file failed with a segmentation fault on a 16 core machine with 32 GB RAM (again using a docker container and ubuntu:22.04). The mzXML file was taken from PXD016673. + +<|ref|>text<|/ref|><|det|>[[115, 557, 857, 592]]<|/det|> +The website to test the live version at http://omics.ust.hk:8709/index.html was not accessible during the time of the review (tested from multiple networks). + +<|ref|>text<|/ref|><|det|>[[115, 632, 880, 723]]<|/det|> +Overall, I therefore have severe reservations whether this tool will provide the simple and high usage of spectrum clustering or similar methods. It also raises grave concerns whether the authors hold the required expertise to develop an end- user ready piece of software and maintain it for a relevant amount of time. The original version contained severe and obvious errors and highlighted that the software was not tested properly. Apparently, the software still has not reached a stable version. + +<|ref|>sub_title<|/ref|><|det|>[[115, 763, 283, 779]]<|/det|> +## 3) Theoretical usability + +<|ref|>text<|/ref|><|det|>[[115, 819, 868, 890]]<|/det|> +The tool (if it works) will only serve one question in proteomics research, to validate specific PSMs. The authors are correct, that some findings center on specific proteoforms / PTMs. Nevertheless, a vast number of literature centers on large- scale characterisations of proteomics samples. These will not profit from this tool. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 860, 154]]<|/det|> +As a mere proof of concept, this work is interesting, but not to the wide community addressed by this Journal. I therefore suggest this work to be submitted to a field- specific one. + +<|ref|>text<|/ref|><|det|>[[116, 222, 393, 238]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 277, 864, 370]]<|/det|> +The authors have clarified the scope of the current work and have offered a compelling defense of the current capabilities of Spectroscape. There will be researchers looking at novel proteoforms or other non- standard identifications, and Spectroscape provides a unique tool for quickly exploring possible hypotheses regarding these discoveries. Additionally, the new analyses provided by the authors go a long way towards suggesting future developments for the technology. + +<|ref|>text<|/ref|><|det|>[[115, 408, 765, 426]]<|/det|> +In their rebuttal, the authors offered the following argument in defense of Spectroscape: + +<|ref|>text<|/ref|><|det|>[[113, 463, 825, 826]]<|/det|> +We believe that as a field we have gone too far down the road of controlling errors at a global level (e.g., by estimating FDR by target- decoy searching), while side- stepping the more fundamental question of what makes an individual PSM believable in the first place. Automatic "black box" approach to validation appeals to researchers who would rather focus on the biology, but we pay for this convenience with our credibility in the eyes of other life scientists. In a perfect world, the global error control we do today should only be viewed as the first step to filter away unpromising leads, but we should not be content to accept everything that passes the filter as truth. In just about every other discipline, scientists would not embark on expensive independent validation experiments until technical validation is done first and the data is deemed trustworthy. In proteomics, many researchers do not bother to even look at a spectrum that underpins our hypothesis, but are all too willing to embark on expensive and tedious biological validation experiments. With the right tool, checking even hundreds of PSMs perhaps take a matter of hours; in contrast, biological validation experiments often take months. + +<|ref|>text<|/ref|><|det|>[[115, 862, 852, 899]]<|/det|> +I would suggest adding something along these lines to the main manuscript. The argument against global FDR control is not new. Many papers have been written about the differences between global + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 645, 126]]<|/det|> +FDR and local FDR or the False Positive Rate of a spectrum. For example, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689316/ + +<|ref|>text<|/ref|><|det|>[[115, 137, 875, 209]]<|/det|> +These issues take on added importance when discovering novel proteoforms or searching non- standard databases. Even simple phospho enrichment experiments typically have different empirical FDR rates when subsetting the data to modifications on tyrosine. Referencing the known failures of global FDR control would bolster the argument in favor of using Spectroscape as a validation step. + +<|ref|>text<|/ref|><|det|>[[115, 248, 861, 302]]<|/det|> +Regarding the main manuscript, my only new suggestion is that it would be nice for references to the Supplement to include a specific section identifier. In the current form it is somewhat inconvenient to match the main text with the relevant section of the supplement. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 316, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 127, 411, 143]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 163, 882, 235]]<|/det|> +In this revised version of the manuscript the authors have in my view addressed my previous comments: (i) they provide a larger benchmarking study (trying to get closer to a repository size dataset); (ii) they have improved documentation, including videos, and (iii) have tried to compare the performance of the tool with other previously published approaches. + +<|ref|>text<|/ref|><|det|>[[115, 255, 882, 290]]<|/det|> +I also find that the manuscript has now improved quite a lot in terms of scope and clarifying some aspects that maybe were not completely clear to me after my first review. + +<|ref|>text<|/ref|><|det|>[[115, 310, 882, 363]]<|/det|> +I agree with the authors that Spectroscape can indeed be a useful tool, but its real future impact cannot really be assessed at this point. A possible collaboration with a proteomics repository would also be key for the future although of course this is outside the current scope of this work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 383, 202, 400]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 419, 883, 565]]<|/det|> +Thank you for the supportive comments on our manuscript. Yes, we are planning to make Spectroscape available over PeptideAtlas as a first step, and have been in touch with the engineers at ISB about this. However, it will take us months to sort out the technical (in particular hardware) issues within the ISB infrastructure, and we feel that we should not delay the dissemination of this work any longer. We hope that the Spectroscape tool can be easily accessible to everyone in the future, including researchers who want to build their own specialized spectral archives. Recently, we have also purchased a domain name, spectroscape.cc to host a demo spectral archive persistently to promote the idea to the community. + +<|ref|>sub_title<|/ref|><|det|>[[115, 658, 411, 675]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 696, 882, 730]]<|/det|> +Wu et al. present an updated version of their manuscript presenting Spectroscape as a novel visualization tool for spectral archives. + +<|ref|>text<|/ref|><|det|>[[115, 751, 882, 785]]<|/det|> +The authors strongly argue, that their tool must not be viewed as another spectrum clustering algorithm, but a tool to investigate individual spectra. + +<|ref|>text<|/ref|><|det|>[[115, 805, 882, 840]]<|/det|> +I believe, that this argument falls short as it is necessary to show that the used method to group spectra compares to existing methods. Nevertheless, I follow the authors argument for this review. + +<|ref|>sub_title<|/ref|><|det|>[[115, 860, 202, 876]]<|/det|> +## Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 401]]<|/det|> +Thanks for the supportive comments. As we have described in the manuscript, Spectroscape is not a clustering tool. It does not "group spectra" ahead of time, nor does it outputs the list of clusters of the entire spectral archive. So we struggle to see how we can show a comparison of how Spectroscape "group spectra" as compared to existing methods (e.g., MS- Cluster, MaRaCluster, GLEAMS, etc.). Rather, we must emphasize that Spectroscape is a retrieval and visualization tool. It will respond to each individual query spectra (ignoring precursor information), find the nearest neighbors, and compute the connectivity graph among the neighbors on the fly. It is then up to the user to interpret such "local" cluster information. (Of course, this retrieval algorithm can be leveraged to compute the global adjacency matrix efficiently, but that is not the intended application of Spectroscape. Even if we have the adjacency matrix, it would still require a subsequent step to determine the cluster boundaries in an unsupervised manner, before one can compare to the outputs of other clustering tools. This unsupervised clustering function is not part of Spectroscape.) In our view, the performance evaluation of Spectroscape should be in terms of query retrieval, not clustering outcome. We provided evidence to show that the indexing and retrieval method of Spectroscape provides for very high recall, and that the index was designed effectively such that the distances between the 17- byte addresses are well- correlated with the true distances of the corresponding spectra. + +<|ref|>text<|/ref|><|det|>[[116, 420, 883, 455]]<|/det|> +I am surprised to see that all benchmarks etc were put in the supplementary methods. Therefore, the manuscript itself holds very limited information that would be relevant to a wider audience. + +<|ref|>sub_title<|/ref|><|det|>[[116, 475, 203, 491]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[116, 510, 883, 602]]<|/det|> +Thanks for this constructive comment. Actually, we put them into the Supplementary Information to adhere to the typical length of Nature Communication articles. We felt that the technical details are perhaps only of interest to the real computational experts, which may be a minority of our audience. In any case, we have modified the manuscript to include the comparison to GLEAMS (in terms of approximate nearest neighbor retrieval) in the main text. + +<|ref|>sub_title<|/ref|><|det|>[[116, 622, 195, 638]]<|/det|> +## 1) Novelty + +<|ref|>text<|/ref|><|det|>[[116, 658, 882, 694]]<|/det|> +The idea to create a visualization tool on top of a spectrum grouping / ANN network is nice, but not novel. This was done as part of previous PRIDE associated resources (although static and not scalable). + +<|ref|>sub_title<|/ref|><|det|>[[116, 714, 203, 730]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 749, 884, 896]]<|/det|> +Thanks for this insightful comment. Yes, we agree that providing a visual representation of clusters is not in itself novel. (We were unable to find the PRIDE cluster visualization alluded to by the reviewer, however.) On the other hand, as the reviewer recognized, Spectroscape is dynamic and scalable, unlike previous tools. Spectroscape did not cluster at all before the neighboring spectra are retrieved. What Spectroscape enabled is the ability to see the neighborhood of a query spectrum, in real time, without any prior offline clustering. Besides, it does not use the precursor m/z to filter for neighbors, meaning that it is effectively performing an "open" search. Since it does not rely on peptide annotations to "train" the index, it is more general + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 144]]<|/det|> +and adaptable to other fields in mass spectrometry. The calculation of the detailed cluster structure (by complete pair- wise similarity calculations among retrieved neighbors) and its display using a force- directed graph, is also unique to Spectroscape. + +<|ref|>text<|/ref|><|det|>[[115, 181, 883, 236]]<|/det|> +The methods used by the authors also were introduced by others before. Adapting the training process is innovative, but something I consider incremental improvement. Therefore, overall, the novelty of the proposed work is in my opinion limited. + +<|ref|>sub_title<|/ref|><|det|>[[116, 255, 202, 271]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[116, 290, 883, 345]]<|/det|> +We would respectfully disagree with this assessment. Since no example of such similar work was mentioned, we were unable to offer our rebuttal in detail. However, please allow us to state our case in general terms here. + +<|ref|>text<|/ref|><|det|>[[115, 364, 883, 530]]<|/det|> +Spectroscape's underlying algorithm, IVF- PQ, was developed by others (Facebook), but the adaptation of it to proteomics in our hands is no doubt novel. (Adapting an algorithm developed by others has also enabled many recent advances in proteomics, e.g., applications of deep learning.) It is important to emphasize that the FAISS library provides many indexing algorithms, of which IVF- PQ is only one of many. It is unfair to suggest that any work that uses the FAISS library is not novel because someone else has used the FAISS library before. On the contrary, precisely because there are so many possible indexing algorithms to choose from, the selection of the specific indexing algorithm and its adaptation and optimization for the task at hand is not trivial. + +<|ref|>text<|/ref|><|det|>[[115, 548, 883, 732]]<|/det|> +Perhaps the reviewer was taking a broader view that any method that relies on some dimensionality reduction to speed up the search of neighbors in high- dimensional space should be considered "similar" and therefore not novel or merely "incremental." But if this is the case, the novelty bar is set unreasonably high. For example, we would argue that GLEAMS, which was published recently in Nature Methods, also adopts a similar conceptual approach. Its novelty, as in our case, lies in the choice of the exact dimensionality reduction algorithm (i.e., in how the "embedding" was trained) to suit its particular application. Moreover, we have shown that the approximate nearest neighbor retrieval of Spectroscape is more effective and general than GLEAMS's, not to mention that Spectroscape enables real- time and dynamic visualization of the complete cluster structure among neighbors, a feature that no other tool can boast. + +<|ref|>sub_title<|/ref|><|det|>[[115, 770, 202, 786]]<|/det|> +## 2) Software + +<|ref|>text<|/ref|><|det|>[[115, 805, 883, 877]]<|/det|> +The state of the software was improved but is still below expectations. The installation works. Nevertheless, building an archive with only one 750 MB mzXML file failed with a segmentation fault on a 16 core machine with 32 GB RAM (again using a docker container and ubuntu:22.04). The mzXML filwas taken from PXD016673. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 203, 106]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 125, 884, 236]]<|/det|> +Thanks for pointing out this issue. We apologize for forgetting to mention that a minimum of 100,000 spectra is required to initialize the Spectroscape index. One mzXML file is not sufficient for the k- means algorithms to initialize the "buckets". In our demo, we use 24 mzXML files, and we do not observe the error. We have updated the user manual to explain this, and provide a clear error message if the user fails to provide enough training data. We also uploaded a test dataset so that users can try out the tool more easily. + +<|ref|>text<|/ref|><|det|>[[115, 272, 883, 309]]<|/det|> +The website to test the live version at http://omics.ust.hk:8709/index.html was not accessible during the time of the review (tested from multiple networks). + +<|ref|>sub_title<|/ref|><|det|>[[116, 328, 203, 345]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 363, 884, 512]]<|/det|> +Thanks for pointing out this issue. Our server was down for several days during the time of review due to electricity suspension and hardware upgrade in our institution, which was out of our control. (We did make an announcement on GitHub around that time to warn potential users; nonetheless, we fully accept that it is our responsibility to keep it running.) To make the web demo works more persistently, we recently purchased an domain name spectroscape.cc and a server instance in AWS, which connects to multiple mirror servers to provide a bit more redundancy. We are confident that our new web interface (spectroscape.cc) will always be online during the period of the review and beyond. + +<|ref|>text<|/ref|><|det|>[[115, 547, 883, 639]]<|/det|> +Overall, I therefore have severe reservations whether this tool will provide the simple and high usage of spectrum clustering or similar methods. It also raises grave concerns whether the authors hold the required expertise to develop an end- user ready piece of software and maintain it for a relevant amount of time. The original version contained severe and obvious errors and highlighted that the software was not tested properly. Apparently, the software still has not reached a stable version. + +<|ref|>sub_title<|/ref|><|det|>[[116, 658, 203, 675]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 694, 883, 731]]<|/det|> +We again apologize for the web interface issues, which are now fixed. We will continue to maintain the software and ensure its usability. + +<|ref|>sub_title<|/ref|><|det|>[[116, 750, 285, 767]]<|/det|> +## 3) Theoretical usability + +<|ref|>text<|/ref|><|det|>[[115, 786, 883, 858]]<|/det|> +The tool (if it works) will only serve one question in proteomics research, to validate specific PSMs. The authors are correct, that some findings center on specific proteoforms / PTMs. Nevertheless, a vast number of literature centers on large- scale characterisations of proteomics samples. These will not profit from this tool. + +<|ref|>sub_title<|/ref|><|det|>[[116, 879, 203, 895]]<|/det|> +## Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 106, 883, 291]]<|/det|> +Yes, we agree that the large- scale characterization of proteomics samples will always be important. However, we do not lack tools (e.g. database search engines) for that purpose. Spectroscape serves a different purpose: for validating biological findings that critically depend on the identification/quantification of specific genes/proteins (which could be discovered by database search engines initially). Clearly, the credibility of a single PSM or a few selected PSMs cannot be established by current approaches of global FDR control approach at the dataset level. Spectroscape helps in the validation of such findings with information that is not readily accessible to the researcher now. Spectroscape is therefore complementary to, and not competing with, existing tools for high- throughput characterization. We have added a paragraph in the revision to clarify this point. + +<|ref|>text<|/ref|><|det|>[[115, 310, 883, 346]]<|/det|> +As a mere proof of concept, this work is interesting, but not to the wide community addressed by this Journal. I therefore suggest this work to be submitted to a field- specific one. + +<|ref|>sub_title<|/ref|><|det|>[[116, 365, 203, 381]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 400, 883, 620]]<|/det|> +We do not dispute that this is a proof of concept at this stage, but Spectroscape is a one- of- a- kind addition to our toolkit that may have long- lasting impact to our field. In the manuscript we have articulated a vision of how proteomics data analysis should be more collaborative and better integrated with data sharing, with Spectroscape being the interface between the user and the repository. Although this will require the active participation of many stakeholders and cannot be realized now, we believe that getting the word out is the critical first step. Of course, whether this step is "big" enough for this journal is a question for the editorial leadership of Nature Communications. On the other hand, we have also seen many publications in journals with broad readership that are proof of concept in nature, or target audience in a specific field exclusively. In our field, for example, we can think of many recent examples, such as MSFragger (2017 Nat Methods), DeepNovo (2017 PNAS), Prosit (2019 Nat Methods), AlphaPeptDeep (2022 Nat Comm), GLEAMS (2022 Nat Methods), etc. + +<|ref|>sub_title<|/ref|><|det|>[[116, 658, 411, 675]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 694, 883, 787]]<|/det|> +The authors have clarified the scope of the current work and have offered a compelling defense of the current capabilities of Spectroscape. There will be researchers looking at novel proteoforms or other non- standard identifications, and Spectroscape provides a unique tool for quickly exploring possible hypotheses regarding these discoveries. Additionally, the new analyses provided by the authors go a long way towards suggesting future developments for the technology. + +<|ref|>sub_title<|/ref|><|det|>[[116, 806, 203, 822]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[116, 841, 883, 895]]<|/det|> +Thank you very much for the supportive comments. We believe the Spectroscape tool has the potential to shed light on the unidentified spectra and verify new identifications against the massive amount of existing data, which we cannot easily do right now. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 748, 125]]<|/det|> +In their rebuttal, the authors offered the following argument in defense of Spectroscape: + +<|ref|>text<|/ref|><|det|>[[158, 144, 884, 381]]<|/det|> +We believe that as a field we have gone too far down the road of controlling errors at a global level (e.g., by estimating FDR by target- decoy searching), while side- stepping the more fundamental question of what makes an individual PSM believable in the first place. Automatic "black box" approach to validation appeals to researchers who would rather focus on the biology, but we pay for this convenience with our credibility in the eyes of other life scientists. In a perfect world, the global error control we do today should only be viewed as the first step to filter away unpromising leads, but we should not be content to accept everything that passes the filter as truth. In just about every other discipline, scientists would not embark on expensive independent validation experiments until technical validation is done first and the data is deemed trustworthy. In proteomics, many researchers do not bother to even look at a spectrum that underpins our hypothesis, but are all too willing to embark on expensive and tedious biological validation experiments. With the right tool, checking even hundreds of PSMs perhaps take a matter of hours; in contrast, biological validation experiments often take months. + +<|ref|>text<|/ref|><|det|>[[114, 400, 883, 548]]<|/det|> +I would suggest adding something along these lines to the main manuscript. The argument against global FDR control is not new. Many papers have been written about the differences between global FDR and local FDR or the False Positive Rate of a spectrum. For example, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689316/. These issues take on added importance when discovering novel proteoforms or searching non- standard databases. Even simple phospho enrichment experiments typically have different empirical FDR rates when subsetting the data to modifications on tyrosine. Referencing the known failures of global FDR control would bolster the argument in favor of using Spectroscape as a validation step. + +<|ref|>sub_title<|/ref|><|det|>[[115, 566, 203, 583]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 602, 882, 657]]<|/det|> +Thanks for the suggestions. We have modified the main text to include discussion of how global FDR control is not sufficient to establish the credibility of a small subset of the data, and why the ability to validate individual PSMs will always have an important place in proteomics. + +<|ref|>text<|/ref|><|det|>[[115, 676, 882, 730]]<|/det|> +Regarding the main manuscript, my only new suggestion is that it would be nice for references to the Supplement to include a specific section identifier. In the current form it is somewhat inconvenient to match the main text with the relevant section of the supplement. + +<|ref|>sub_title<|/ref|><|det|>[[115, 750, 203, 766]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 786, 882, 822]]<|/det|> +Thanks for the suggestion. We have assigned specific identifiers to different sections of the Supplementary Information. + +<--- Page Split ---> diff --git a/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/images_list.json b/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..f889519df50d0d34c8bde5a1989eb3736a34569f --- /dev/null +++ b/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_9.jpg", + "caption": "Supplementary Fig.9: Histone modification levels of the egg-sperm DMRs in the parental lines.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S6: DNA methylation levels of the hybrid parental gametes DMR in paternal reproductive cells and tissues.", + "footnote": [], + "bbox": [ + [ + 161, + 95, + 839, + 451 + ] + ], + "page_idx": 15 + } +] \ No newline at end of file diff --git a/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..964fa2c4c44a43104b4e658c600ceeabe1af17ff --- /dev/null +++ b/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,425 @@ + +# nature portfolio + +Peer Review File + +Paternal DNA methylation is remodeled to maternal levels in rice zygote + +![](images/Supplementary_Figure_9.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The manuscript by Liu et al reports the results of epigenomic and transcriptomic experiments on rice eggs, sperm, zygotes, and hybrid zygotes and globular embryos resulting from crosses of the MH63 and ZS97 varieties. Using bisulfite sequencing of eggs, sperm, zygotes, and hybrid zygotes, the authors provide evidence that the methylome of the paternal genome is remodeled in the zygote to a methylation status similar to the maternal genome. Interestingly, the authors provide evidence that, by the globular stage, the methylation patterns of the maternal and paternal genomes return to their overall patterns at the time of fertilization, ie. to the methylation patterns in the gametes. The authors then correlate differentially methylated regions between maternal and paternal genomes with histone marks found in seedling tissues, providing a nice association between parent- of- origin methylation status in hybrid zygotes and histone marks in the respective parental lines. Finally, the authors produce transcriptomes from eggs and sperm of the MH63 and ZS97 varieties, as well as hybrid zygotes and globular embryos from crosses in both directions. The authors compare the transcript levels from the maternal and paternal alleles with epigenetic marks in the egg, sperm and zygote, finding correlations between parent- of- origin gene expression and different contexts of cytosine methylation. + +This manuscript describes novel experiments conducted on epigenetic regulation of parent- of- origin gene expression in plant embryogenesis. The field of early embryogenesis in plants has been waiting for this combination of epigenomic and transcriptomic data of gametes and hybrid zygotes for a long time. This manuscript is absolutely appropriate for publication in Nature Communications, if not Nature. The manuscript would benefit from some light editing for language style. Below I list comments and suggestions for improving the manuscript. + +Stewart Gillmor Langebio, CINVESTAV, Mexico + +Figure 1C: why is there a clear bi- modal distribution (some genes lose methylation and some gain methylation) but only in the CHH context? Are these genes enriched for some GO term or in a particular region of the genome like near centromeres or transposons? + +Extended Data Figure 10a: Reads are shown only as \(\%\) maternal or \(\%\) paternal, without regard to how many genes these reads map to. The authors should also show how many genes were called as having statistically significant maternal or paternal bias. + +Figure 5a The authors should show how many genes do not show maternal or paternal bias (i.e. how many genes are represented by a grey point). + +line 18 'DNA methylation' + +line 22 'reprogramming' + +line 31- 32 for a more in- depth review on parent- of- origin contributions to early plant embryogenesis which includes a discussion of genetic as well as transcriptomic studies, the authors might consider also citing Armenta- Medina and Gillmor https://doi.org/10.1016/bs.ctdb.2018.11.008 + +lines 34- 35 when discussing the contrasting results in Arabidopsis on parent- of- origin studies of hybrid zygote and early embryo transcriptomes, the authors should cite Alaniz- Fabian et al 2022 https://doi.org/10.1242/dev.201025, who reanalyzed the Col/Ler zygote transcriptomes originally described in Zhao et al (2019) Dev Cell and Zhao et al (2020) Nature Plants. This reanalysis showed that on an gene- by- gene bases, Col/Ler zygotes do not show equal parental transcriptome contributions; thousands of genes in Col/Ler zygotes are represented by transcripts from either the maternal or paternal allele, but not both. Thus, previous conclusions on parent- of- origin transcript contributions are oversimplified, and the evidence for equal transcript contributions in Col/Ler zygotes is not as strong as originally presented. + +Consistent with Liu et al's finding that maternal transcripts dominate in rice zygotes, previous work + +<--- Page Split ---> + +in Arabidopsis by Alaniz- Fabian et al (2022) Development as well as Del Toro De Leon et al (2014) Nature presented genetic evidence that maternal allies of most EMB genes make a more important contribution functional to early embryogenesis than paternal alleles, and that hybridization itself can affect parental genome contributions to early embryogenesis. Adding a sentence about this genetic evidence for parental genome contributions in Arabidopsis would provide a fuller picture of work on parent- of- origin regulation of early embryogenesis in plants, and would put the experiments presented by Liu et al in a more complete context. + +lines 61- 63 'DNA methylomes data were obtained from 25 eggs or zygotes and 150 sperm cells, two biological replicates were performed with a sequencing depth of about \(24.7 - 75.4 \times\) genome coverage (Supplementary Table 1).' Question: Is this 25x Coverage from 25 eggs? After excluding duplicates? + +lines 64- 64 'sperm methylome more distal from that of egg or zygote' An inspection of Extended Data Figure 1a does not support this statement. Only for mCHH of the ZS97 variety is sperm methylation separated from egg and zygote, for other methylation types and the other variety they are not separated. The authors should remove this statement. + +Lines 66- 67 'Boxplots indicated that sperm cells showed globally higher CG methylation (mCG) but lower CHG methylation (mCHG) than egg cells' An inspection of Extended Data Figure 2a does not fully support this statement. Only MH63 apparently has higher CG for sperm than egg. Also, are the differences shown by the box plots statistically significant, even when the median looks different? The authors should do statistical analysis to determine if the results in the box plots in Extended Data Figure 2 and in Figure 1 really are different. + +Lines 70- 71 'In the zygote mCG and mCHH levels were lower than in the sperm, while the mCHG was at the intermediate levels of the egg and sperm cells' Same as my previous comment- are the differences in box plots statistically significant? + +line 85 I find the notation that the authors use to describe the different hybrids confusing. The MH63 x ZS97 hybrid is notated as MZ; this makes sense. But the ZS97 x MH63 hybrid is notated as SY63. I understand that this is a standard hybrid in rice and that is its name, but perhaps for the purposes of simplicity in the manuscript the authors could refer to the SY63 hybrid as ZM? + +Lines 86- 88 'In the hybrid zygotes, the methylation levels appeared higher than in the male and female gametes, particularly at CG and CHG sites (Fig. 1)' As I mentioned above, the authors should conduct statistical tests to determine if the data represented in the box plots in Figure 1 are statistically significantly different. + +Lines 117- 118 'indicating that the maternal- controlled remodeling of paternal allele- specific methylation in the zygote persisted till at least the 2- cell embryo stage.' The authors do not formally show that the remodeling that occurs is maternally controlled. All they show is that the remodeling makes the paternal genome similar to the maternal genome. They should soften this statement. + +Lines 191- 193 'Several genes such as plasma membrane protein gene GEX1, RALF- like secreted peptide RALF3, and Arabinogalactan protein 7 (AGP7) were shown to function in male gametophyte development and during early embryogenesis 39- 41'. Alaniz- Fabian (2022) Development showed that gex1 mutants condition both maternal and paternal effects in early embryogenesis. This is genetic evidence that paternal GEX1 transcripts have a function in early embryos, consisted with GEX1 being a PEG. The authors might consider citing Alaniz- Fabian (2022) here. + +Lines 207- 209 'indicating an increased paternal contribution to gene expression in GE, as observation in Arabidopsis 11, which was consistent with the reestablishment of the parental allelic- specific DNA methylome in GE'. In addition to citing the transcriptomic data of Autran et al that indicates equal maternal and paternal transcriptome contributions at the globular stage, the authors might consider also citing Del Toro De Leon (2014) Nature and Alaniz- Fabian (2022) Development, which provide functional evidence for increased paternal allele contributions from + +<--- Page Split ---> + +EMB genes by the globular stage of embryogenesis in Arabidopsis. + +Reviewer #2 (Remarks to the Author): + +The manuscript entitled "Maternal- based paternal DNA methylation remodeling in rice zygote" aims to decipher how DNA methylation (DNAme) is remodeled after fertilization. The authors provide a very comprehensive experimental dataset of DNAme on egg, sperm, zygote and globular embryos. Results described here provide evidence of how DNAme in the zygote changes after fertilization to match a pattern that closely resembles the maternal genome. The data also shows how hybridization has immediate effects on DNAme in a subset of loci in zygotes and globular embryos. + +Bellow you can find a summary of my comments by sections of the present manuscript. + +"Predominant remodeling of the male methylome in the rice zygote upon fertilization" This first section of the manuscript describes global comparisons of DNA methylation in S, E and Z. However, the title and the conclusions drawn refer to a remodeling of the male methylome. This is indeed suggested by the data, but convincingly demonstrated later in the manuscript with parent- specific DNA methylation. I suggest changing the title of this section to more accurately reflect the findings described in it. + +Line 72: "Density plots revealed higher methylation variations between zygote and sperm than between zygote and egg (Extended Data Fig. 2b)." Results and interpretations on this part feel disjointed. For clarity, please rephrase by explaining the quantitative differences observed in the density plots that support the statements. + +"A number of given loci tend to be remodeled in the zygote" In this section, the authors highlight that in zygotes, "DNA methylation at a number of specific loci tends to be enhanced upon fertilization," which is particularly true in hybrid zygotes. What are these loci? Do they have anything in common? And how this reflects on gene expression? Line 88: "(Fig. 1)", what part of the panel is this referring to? + +"Parental allele- specific methylation was restored during embryogenesis and stably maintained in the hybrids" + +Here the authors nicely show that although the DMRs between egg and sperm are closer to the maternal genome in hybrids, they recover the parent- specific profile by the globular stage. I wonder if this is consistent with the activity of the RdDM pathway during embryogenesis? The authors have RNAseq data that can help answer this question. Figure 3. Label x axis. + +"Parental methylation difference was associated with distinct histone modifications" Figure 4. I suggest including at least in the extended data a representation of the data using box plots, which are more quantitative and less sensitive to bias from individual loci. + +"Parental DNA methylation remodeling mirrors parental contribution to zygotic gene expression" Whether DNA methylation reprogramming after fertilization has an effect on ZGA is still unclear and not discussed by the authors. The fact that DNA methylation of the paternal genome is reprogrammed to reach levels similar to the maternal genome, and yet most genes show predominant maternal expression, suggests that the mechanism by which this maternal- allele preferential expression occurs is independent from DNA methylation, or that it occurs at an earlier time when the zygote still maintains parental asymmetry in DNA methylation. + +Line 179: Not clear. What do they mean with "most of the reads were maternal allelic- specific and about \(1.5\% \sim 4.1\%\) of the reads was paternal allelic- specific"? I find hard to reconcile this statement with figure 5a where most genes are biallelic (with a level of maternal bias expression) while a small subset of genes shows either maternal (1063) or paternal (28) specific expression. + +<--- Page Split ---> + +The authors here refer to Extended Data Figure 10a, which shows a Venn diagram showing, I believe, the parental reads for MEGs in zygotes or for the entire transcriptome? Please rephrase this paragraph for clarity. In the Extended Data Figure 10a. include the total number in Venn diagrams. + +Line 18: DNA + +Reviewer #3 (Remarks to the Author): + +In the manuscript "Maternal- based paternal DNA methylation remodeling in rice zygote", authors Liu et al investigate changes in DNA methylation that occur in early rice zygotes. They observe that in regions of the genome with differential methylation between egg and sperm, zygotes show more similarity to the egg cell methylation levels resulting from changes in paternal methylation. As observed in the literature previously, DNA methylation patterns are consistent across development, with a major exception being the sperm cell, so remodeling of paternal methylation is expected. + +The authors hypothesized that the maternal genome is acting to "control" the remodeling of the paternal genome, however none of the experiments or analyses demonstrated active involvement of the maternal genome. This is important because although the zygote is more correlated with the maternal than paternal epigenome, so is the DNA methylation profile of all vegetative tissue in the plant. Sperm cells have active remodeling of methylation during development, so the change in paternal methylation is necessary to regain the methylation pattern typical of vegetative cells. In order to make the claim that "paternal DNA methylation remodeling" is "maternal- based" as stated in the title and throughout the manuscript, the authors would need to somehow distinguish between paternal methylation reverting to vegetative levels vs. changing to maternal levels. While some cases of trans- acting epi- alleles exist in plants (i.e. paramutation), DNA methylation is also inherited trans- generationally and many alleles maintain methylation patterns consistent with the genetic origin of that sequence, as demonstrated in this paper as well. + +In order to make the claim that DNA methylation remodeling is maternal- based, the authors need to exclude the more likely possibility that DNA methylation is simply being re- established to vegetative levels based on cis- regulatory information coded in the DNA. A cis- regulatory mechanism of DNA methylation reestablishment would also explain why the maternal shift occurs for CG and CHG but not CHH methylation which depends on trans- acting factors. The genotype- dependent methylation patterns are demonstrated in Figure 3, however, the authors label this as parental effects instead of genotype effects. Excluding re- establishment of vegetative methylation could potentially be performed with additional analyses of existing data, however it may require additional experiments to demonstrate persuasively. + +In addition to the major problem of the data not matching the main point of the paper, there are several smaller cases of the text of the manuscript not matching or oversimplifying the results shown on figures. I have listed these examples below. + +Line 64 - PCA shows separation by genotype before cell type. Please rewrite to reflect observations. + +Line 66 - Boxplots show slightly lower CG for sperm in one genotype but higher CG in the other genotype. CHG is very similar. + +Line 78 - Only some of the bars show that "more than half of DMRs concerned non- TE regions. + +Line 87 - Methylation was higher for genes but not TEs. + +Line 200 - The figures do not look "overall higher" in all regions, but does look marginally higher in upstream and downstream regions. Error bars or other stats on the metaplots would help clarify if the signal here is significant. + +<--- Page Split ---> + +Line 206 – What is meant by "comparable numbers"? It looks like fewer MEGs and PEGs than zygotes. + +Finally, the authors analyze parent- of- origin biased gene expression and conclude that expression patterns are dynamic and shift between MEGs, PEGs, and non- imprint. However, these calls are only described as discreet data. The problem with this is that imprinting calls are typically based on a small number of allele- specific reads, and a change from, for example, MEG to not imprinted can reflect a real change in allelic expression, a loss of expression of the expressed allele, or most often, it can reflect a subtle change that is no longer called significant without necessarily reflecting the biology. In order to conclude that imprinting is dynamic in these early stages, the authors need to demonstrate that the change in patterns is real and not an artifact of small numbers of reads. + +<--- Page Split ---> + +## Point-by-point response to the reviewers + +## Reviewer #1 (Remarks to the Author): + +The manuscript by Liu et al reports the results of epigenomic and transcriptomic experiments on rice eggs, sperm, zygotes, and hybrid zygotes and globular embryos resulting from crosses of the MH63 and ZS97 varieties. Using bisulfite sequencing of eggs, sperm, zygotes, and hybrid zygotes, the authors provide evidence that the methylome of the paternal genome is remodeled in the zygote to a methylation status similar to the maternal genome. Interestingly, the authors provide evidence that, by the globular stage, the methylation patterns of the maternal and paternal genomes return to their overall patterns at the time of fertilization, ie. to the methylation patterns in the gametes. The authors then correlate differentially methylated regions between maternal and paternal genomes with histone marks found in seedling tissues, providing a nice association between parent- of- origin methylation status in hybrid zygotes and histone marks in the respective parental lines. Finally, the authors produce transcriptomes from eggs and sperm of the MH63 and ZS97 varieties, as well as hybrid zygotes and globular embryos from crosses in both directions. The authors compare the transcript levels from the maternal and paternal alleles with epigenetic marks in the egg, sperm and zygote, finding correlations between parent- of- origin gene expression and different contexts of cytosine methylation. + +This manuscript describes novel experiments conducted on epigenetic regulation of parent- of- origin gene expression in plant embryogenesis. The field of early embryogenesis in plants has been waiting for this combination of epigenomic and transcriptomic data of gametes and hybrid zygotes for a long time. This manuscript is absolutely appropriate for publication in Nature Communications, if not Nature. The manuscript would benefit from some light editing for language style. Below I list comments and suggestions for improving the manuscript. + +<--- Page Split ---> + +Stewart GillmorLangebio, CINVESTAV, Mexico + +Figure 1C: why is there a clear bi- modal distribution (some genes lose methylation and some gain methylation) but only in the CHH context? Are these genes enriched for some GO term or in a particular region of the genome like near centromeres or transposons? + +Response: Thank you for the comments. As suggested, we analyzed the genomic distribution of the CHH DMRs in zygotes vs the gametes and found that the hyper- DMRs were mainly enriched in genic regions, and the hypo- DMRs enriched in TE regions, which is consistent with the observations that sperm and egg show high levels of mCHH in long TEs. The GO enrichment indicates that the concerned genes are mainly enriched in RNA silencing, defense and developmental pathways. + +The analysis is presented in Supplementary Fig. 4 and commented in the results section: + +"Density plots revealed a clear bimodal distribution pattern of CHH DMR between zygote and sperm (Z - S) or between zygote and egg (Z - E) (Figure 1c), indicating a fraction of loci showed clearly increased (hyper) or decreased (hypo) methylation at CHH sites in the zygote genome. Further analysis indicated that the hyper methylated CHH sites were enriched in genic regions whereas the hypo- methylated sites were mainly located in TE regions (Supplementary Fig. 4a). Genes with the CHH DMRs were mainly enriched in RNA silencing, defense and developmental pathways" (Supplementary Fig. 4b). + +Extended Data Figure 10a: Reads are shown only as \(\%\) maternal or \(\%\) paternal, without regard to how many genes these reads map to. The authors should also show how many genes were called as having statistically significant maternal or paternal + +<--- Page Split ---> + +bias. + +Response: Thanks for the comments. As suggested, we have added the informative sequencing reads and the numbers of expressed SNP genes (maternal and paternal) in the Supplementary Fig. 14a) in the revised version. + +Figure 5a The authors should show how many genes do not show maternal or paternal bias (i.e. how many genes are represented by a grey point). + +Response: Thanks for the suggestion. We have reanalyzed the zygotic genes. The gene number (2569) represented by the grey points is added in Fig.5a in the revised version. + +line 18 'DNA methylation' + +Response: Thanks, we have corrected the typo. + +line 22 'reprogramming' + +Response: Corrected. + +line 31- 32 for a more in- depth review on parent- of- origin contributions to early plant embryogenesis which includes a discussion of genetic as well as transcriptomic studies, the authors might consider also citing Armenta- Medina and Gillmor https://doi.org/10.1016/bs.ctdb.2018.11.008 + +Response: Thank you for the point. We have included the sentence "Parent- of- origin contributions to plant early embryogenesis have been studied at genetic and transcriptomic levels10" and cited the reference in the revised version. + +lines 34- 35 when discussing the contrasting results in Arabidopsis on parent- of- origin studies of hybrid zygote and early embryo transcriptomes, the authors should cite + +<--- Page Split ---> + +Alaniz- Fabián et al 2022 https://doi.org/10.1242/dev.201025, who reanalyzed the Col/Ler zygote transcriptomes originally described in Zhao et al (2019) Dev Cell and Zhao et al (2020) Nature Plants. This reanalysis showed that on an gene- by- gene bases, Col/Ler zygotes do not show equal parental transcriptome contributions; thousands of genes in Col/Ler zygotes are represented by transcripts from either the maternal or paternal allele, but not both. Thus, previous conclusions on parent- of- origin transcript contributions are oversimplified, and the evidence for equal transcript contributions in Col/Ler zygotes is not as strong as originally presented. + +Response: Thank you for the comments. We have mentioned the results of reanalysis and cited the references in the revised version. + +"However, a reanalysis of the published data6,7 showed that, on a gene- by- gene basis, the Arabidopsis hybrid (Col/Ler) zygotes do not show equal parental transcriptome contributions; thousands of genes in hybrid zygotes are represented by transcripts from either the maternal or paternal allele, but not both13." + +Consistent with Liu et al's finding that maternal transcripts dominate in rice zygotes, previous work in Arabidopsis by Alaniz- Fabián et al (2022) Development as well as Del Toro De León et al (2014) Nature presented genetic evidence that maternal alleles of most EMB genes make a more important contribution functional to early embryogenesis than paternal alleles, and that hybridization itself can affect parental genome contributions to early embryogenesis. Adding a sentence about this genetic evidence for parental genome contributions in Arabidopsis would provide a fuller picture of work on parent- of- origin regulation of early embryogenesis in plants, and would put the experiments presented by Liu et al in a more complete context. + +Response: Thanks for the suggestion. We have added the context in the revised Introduction and cited the related references. + +"There is also genetic evidence that maternal alleles of most embryo genes make a more important contribution functional to early embryogenesis than paternal alleles, + +<--- Page Split ---> + +and that hybridization itself can affect parental genome contributions to early embryogenesis \(^{13,15}\) ." + +lines 61- 63 'DNA methylomes data were obtained from 25 eggs or zygotes and 150 sperm cells, two biological replicates were performed with a sequencing depth of about \(24.7 - 75.4 \times\) genome coverage (Supplementary Table 1).' Question: Is this \(25x\) Coverage from 25 eggs? After excluding duplicates? + +Response: Genome coverage was calculated per replicate (25 cells). We have clarified this in the MS. + +"DNA methylomes data were obtained from 25 eggs or zygotes and 150 sperm cells, two biological replicates were performed with a sequencing depth of about \(24.7 - 75.4 \times\) genome coverage per replicate." + +lines 64- 64 'sperm methylome more distal from that of egg or zygote' An inspection of Extended Data Figure 1a does not support this statement. Only for mCHH of the ZS97 variety is sperm methylation separated from egg and zygote, for other methylation types and the other variety they are not separated. The authors should remove this statement. + +Response: Thanks for the point. We have rephrased the statement: "Principal component analysis revealed a high reproducibility of the replicates and a clear difference between the two parental lines". + +Lines 66- 67 'Boxplots indicated that sperm cells showed globally higher CG methylation (mCG) but lower CHG methylation (mCHG) than egg cells' An inspection of Extended Data Figure 2a does not fully support this statement. Only MH63 apparently has higher CG for sperm than egg. Also, are the differences shown by the box plots statistically significant, even when the median looks different? The + +<--- Page Split ---> + +authors should do statistical analysis to determine if the results in the box plots in Extended Data Figure 2 and in Figure 1 really are different. + +Response: Thanks for the comments. We have reentenced the statement and added the statistical significance of the boxplots in the revised version. "Boxplots indicated that sperm cells showed globally lower CHG methylation (mCHG) than egg cells in TEs." + +Lines 70- 71 'In the zygote mCG and mCHH levels were lower than in the sperm, while the mCHG was at the intermediate levels of the egg and sperm cells' Same as my previous comment- are the differences in box plots statistically significant? + +Response: We have added the statistical significance of the boxplots in the revised Figures. + +line 85 I find the notation that the authors use to describe the different hybrids confusing. The MH63 x ZS97 hybrid is notated as MZ; this makes sense. But the ZS97 x MH63 hybrid is notated as SY63. I understand that this is a standard hybrid in rice and that is its name, but perhaps for the purposes of simplicity in the manuscript the authors could refer to the SY63 hybrid as ZM? + +Response: We have changed SY63 to ZM as advised. + +Lines 86- 88 'In the hybrid zygotes, the methylation levels appeared higher than in the male and female gametes, particularly at CG and CHG sites (Fig. 1)' As I mentioned above, the authors should conduct statistical tests to determine if the data represented in the box plots in Figure 1 are statistically significantly different. + +Response: We have added statistical significance of the boxplots in the revised Figures. + +Lines 117- 118 'indicating that the maternal- controlled remodeling of paternal + +<--- Page Split ---> + +allele- specific methylation in the zygote persisted till at least the 2- cell embryo stage.' The authors do not formally show that the remodeling that occurs is maternally controlled. All they show is that the remodeling makes the paternal genome similar to the maternal genome. They should soften this statement. + +Response: We have rewritten the statement in the revised version. "The data together indicated that the paternal allele- specific methylation is remodeled to the levels similar to the maternal alleles in the zygote, which persists till at least the 2- cell embryo stage." + +Lines 191- 193 'Several genes such as plasma membrane protein gene GEX1, RALF- like secreted peptide RALF3, and Arabinogalactan protein 7 (AGP7) were shown to function in male gametophyte development and during early embryogenesis 39- 41'. Alaniz- Fabian (2022) Development showed that gex1 mutants condition both maternal and paternal effects in early embryogenesis. This is genetic evidence that paternal GEX1 transcripts have a function in early embryos, consisted with GEX1 being a PEG. The authors might consider citing Alaniz- Fabian (2022) here. + +Response: Thanks for the suggestion. We have discussed the point and cited the reference in the revised version. + +"Recent results showed that gex1 mutants condition both maternal and paternal effects in early embryogenesis13, providing genetic evidence that paternal GEX1 transcripts have a function in early embryos." + +Lines 207- 209 'indicating an increased paternal contribution to gene expression in GE, as observation in Arabidopsis 11, which was consistent with the reestablishment of the parental allelic- specific DNA methylome in GE'. In addition to citing the transcriptomic data of Autran et al that indicates equal maternal and paternal transcriptome contributions at the globular stage, the authors might consider also citing Del Toro De León (2014) Nature and Alaniz- Fabian (2022) Development, + +<--- Page Split ---> + +which provide functional evidence for increased paternal allele contributions from EMB genes by the globular stage of embryogenesis in Arabidopsis. + +Response: Thanks for the suggestion. We have discussed the finding and cited the references in the revised version: + +"It is shown that increased paternal allele contributions from embryo genes by the globular stage have functional significance in Arabidopsis embryogenesis13,15." + +Reviewer #2 (Remarks to the Author): + +The manuscript entitled "Maternal- based paternal DNA methylation remodeling in rice zygote" aims to decipher how DNA methylation (DNAme) is remodeled after fertilization. The authors provide a very comprehensive experimental dataset of DNAme on egg, sperm, zygote and globular embryos. Results described here provide evidence of how DNAme in the zygote changes after fertilization to match a pattern that closely resembles the maternal genome. The data also shows how hybridization has immediate effects on DNAme in a subset of loci in zygotes and globular embryos. + +"Predominant remodeling of the male methylome in the rice zygote upon fertilization" + +This first section of the manuscript describes global comparisons of DNA methylation in S, E and Z. However, the title and the conclusions drawn refer to a remodeling of the male methylome. This is indeed suggested by the data, but convincingly demonstrated later in the manuscript with parent- specific DNA methylation. I suggest changing the title of this section to more accurately reflect the findings described in it. + +Response: Thank you for the comments. As suggested, we have changed the title of this section in the revised version to: + +<--- Page Split ---> + +"Remodeling of the rice gamete methylomes in the zygote upon fertilization" + +Line 72: "Density plots revealed higher methylation variations between zygote and sperm than between zygote and egg (Extended Data Fig. 2b)." Results and interpretations on this part feel disjointed. For clarity, please rephrase by explaining the quantitative differences observed in the density plots that support the statements. + +Response: Thanks for the point. We have rewritten the statements in the revised version: + +"Density plots revealed lower mCG in zygote relative to both sperm and egg, and lower mCHH but higher mCHG in zygote versus sperm" + +"A number of given loci tend to be remodeled in the zygote" In this section, the authors highlight that in zygotes, "DNA methylation at a number of specific loci tends to be enhanced upon fertilization," which is particularly true in hybrid zygotes. What are these loci? Do they have anything in common? And how this reflects on gene expression? + +Response: Thank for comments. We have analyzed the overlapping hyper DMRs between hybrid and inbred zygote relative sperm/egg and found many genes are associated with the DMRs. GO enrichment indicates that the genes are of diverse function, many of which are expressed in sperm but repressed in the zygotes. We have included the data in Fig S3 and dataset1 and commented in the text: "Genes with diverse functions were associated the hyper DMRs in the hybrid and inbred zygotes versus sperm (Supplementary Fig. 3c-f; Supplementary Dataset 1). Most of the genes were lowly expressed or repressed in both sperm and zygotes, while a number of genes were expressed in sperm but repressed in the zygotes (Supplementary Dataset 1, labeled in red)" + +Line 88: "(Fig. 1)", what part of the panel is this referring to? + +<--- Page Split ---> + +Response: It is referring to the Fig. 1a, b, specified now in the text. + +"Parental allele- specific methylation was restored during embryogenesis and stably maintained in the hybrids" + +Here the authors nicely show that although the DMRs between egg and sperm are closer to the maternal genome in hybrids, they recover the parent- specific profile by the globular stage. I wonder if this is consistent with the activity of the RdDM pathway during embryogenesis? The authors have RNAseq data that can help answer this question. + +Response: Thanks for the comments. We have analyzed transcript levels of RdDM genes in zygote and GE (Fig S7) + +![](images/Figure_unknown_0.jpg) + + +and commented the data in the text: + +"Transcript levels of genes involved in CHH methylation (e.g. AGO4, DCL3, DRM2, and Pol IV) were lower in the GE than in the zygote (Supplementary Fig. 7). + +Figure 3. Label x axis. + +Response: Thanks. We have added the x- axis in Fig.3 in the revised version. + +"Parental methylation difference was associated with distinct histone modifications" Figure 4. I suggest including at least in the extended data a representation of the data using box plots, which are more quantitative and less sensitive to bias from individual + +<--- Page Split ---> + +loci. + +Response: Thanks for the suggestion. We have included boxplots in the Supplementary Fig. 9 in the revised version. + +![PLACEHOLDER_16_0] + +
Supplementary Fig.9: Histone modification levels of the egg-sperm DMRs in the parental lines.
+ +"Parental DNA methylation remodeling mirrors parental contribution to zygotic gene expression" + +Whether DNA methylation reprogramming after fertilization has an effect on ZGA is still unclear and not discussed by the authors. The fact that DNA methylation of the paternal genome is reprogrammed to reach levels similar to the maternal genome, and yet most genes show predominant maternal expression, suggests that the mechanism by which this maternal- allele preferential expression occurs is independent from DNA methylation, or that it occurs at an earlier time when the zygote still maintains parental asymmetry in DNA methylation. + +Response: Thanks for the comments. We have discussed the point in the Discussion section: + +<--- Page Split ---> + +"The observations that DNA methylation of the paternal genome was reprogrammed to reach levels similar to the maternal genome, and yet most genes showed predominant maternal expression, suggest that the mechanism by which this maternal- allele preferential expression occurs at an earlier time when the zygote still maintains parental asymmetry in DNA methylation and that the paternal methylation remodeling may contribute to paternal alleles expression in later stages during zygote development." + +Line 179: Not clear. What do they mean with "most of the reads were maternal allelic- specific and about \(1.5\% \sim 4.1\%\) of the reads was paternal allelic- specific"? I find hard to reconciliate this statement with figure 5a where most genes are biallelic (with a level of maternal bias expression) while a small subset of genes shows either maternal (1063) or paternal (28) specific expression. The authors here refer to Extended Data Figure 10a, which shows a Venn diagram showing, I believe, the parental reads for MEGs in zygotes or for the entire transcriptome? Please rephrase this paragraph for clarity. In the Extended Data Figure 10a. include the total number in Venn diagrams. + +Response: Thanks for the comment. We recognize that the presentation and the explanation were not sufficiently clear. We have added the numbers of the SNP reads (maternal and paternal) and expressed SNP genes (maternal and paternal) in the figure (Fig S14a) as well as the overlapping SNP genes between the reciprocal hybrid zygotes. We have rewritten the description of the data for clarity. "we analyzed parental SNP reads (2.66 to \(6 \times 10^{6}\) ) from the reciprocal hybrid zygote transcriptomes and found that most of the reads were of maternal origin and about \(1.5\% \sim 4.1\%\) of the reads were of paternal origin (Supplementary Fig. 14a).".... + +"From the SNP reads, we identified 6245 expressed SNP genes (2221 maternal biased, 219 paternal biased) in the MZ zygote and 7116 expressed SNP genes (1666 maternal biased, 262 paternal biased) in the ZM zygote (Supplementary Fig. 14a). Among the + +<--- Page Split ---> + +SNP genes, 3765 overlapped in the reciprocal hybrids (Supplementary Fig. 14a), of which 1063 were maternal, 28 genes were paternal (Figure 5a). A number of genes were parental sequence- specific genes. The other genes are mostly enriched in maternal reads in either ZM or MZ zygote, as shown by the density plots (Figure 5a)." + +Line 18: DNA + +Response: Thanks. corrected. + +Reviewer #3 (Remarks to the Author): + +In the manuscript "Maternal- based paternal DNA methylation remodeling in rice zygote", authors Liu et al investigate changes in DNA methylation that occur in early rice zygotes. They observe that in regions of the genome with differential methylation between egg and sperm, zygotes show more similarity to the egg cell methylation levels resulting from changes in paternal methylation. As observed in the literature previously, DNA methylation patterns are consistent across development, with a major exception being the sperm cell, so remodeling of paternal methylation is expected. + +The authors hypothesized that the maternal genome is acting to "control" the remodeling of the paternal genome, however none of the experiments or analyses demonstrated active involvement of the maternal genome. This is important because although the zygote is more correlated with the maternal than paternal epigenome, so is the DNA methylation profile of all vegetative tissue in the plant. Sperm cells have active remodeling of methylation during development, so the change in paternal methylation is necessary to regain the methylation pattern typical of vegetative cells. In order to make the claim that "paternal DNA methylation remodeling" is "maternal- based" as stated in the title and throughout the manuscript, the authors would need to somehow distinguish between paternal methylation reverting to vegetative levels vs. changing to maternal levels. While some cases of trans- acting + +<--- Page Split ---> + +epi- alleles exist in plants (i.e. paramutation), DNA methylation is also inherited trans- generationally and many alleles maintain methylation patterns consistent with the genetic origin of that sequence, as demonstrated in this paper as well. + +Response: Thank you for the comments. We recognize that the term "control" was inappropriate; we have revised the relevant sentences throughout the MS text. We understand the reviewer's concern about the paternal remodeling in the zygote to maternal pattern or just vegetative pattern. The later possibility seems unlikely in the context of hybrid zygotes, as the paternal alleles of the E- S DMRs have different DNA sequence than the maternal line. As advised, we have performed additional analysis to compare methylation levels of the E- S DMRs in sperm, egg, zygote, seedling and panicle of the paternal lines (Fig S6). The sperm methylation of the E- S DMRs (in the hybrid context) is already close to the vegetative (shoot and panicle) tissues of the paternal line. DNA methylations in egg and sperm are differentially remodeled as shown in Fig S1 of this work and in Zhou et al 2021 Mol Plant, which can be also observed in the present Fig S6 (where only the E- S DMRs are considered). The data confirm that in the zygote the paternal methylation of the DMRs is remodeled to match the maternal allele levels rather than the levels in vegetative tissues of the parental line. + +<--- Page Split ---> +![PLACEHOLDER_20_0] + +
Fig. S6: DNA methylation levels of the hybrid parental gametes DMR in paternal reproductive cells and tissues.
+ +We have revised the MS text: + +"To distinguish between paternal methylation reverting to vegetative levels vs. changing to maternal levels in the hybrid zygote, we analyzed the methylation levels of the E – S DMRs in sperm, egg, zygote, shoot and panicles of the paternal lines used to produce the three hybrids (ZM, MZ and ZHM). We observed that the methylation levels of the DMRs in sperm were similar to shoot and panicle of the 3 paternal lines (Supplementary Fig. 6a-c). DNA methylations in egg and sperm of inbred lines are differentially remodeled (Supplementary Figure 1) \(^{20}\) . These observations suggested that the paternal alleles of the E – S CG and CHG DMRs were remodeled to match the levels of the maternal alleles rather than to restore to the vegetative levels in the zygote." + +<--- Page Split ---> + +In order to make the claim that DNA methylation remodeling is maternal- based, the authors need to exclude the more likely possibility that DNA methylation is simply being re- established to vegetative levels based on cis- regulatory information coded in the DNA. A cis- regulatory mechanism of DNA methylation reestablishment would also explain why the maternal shift occurs for CG and CHG but not CHH methylation which depends on trans- acting factors. The genotype- dependent methylation patterns are demonstrated in Figure 3, however, the authors label this as parental effects instead of genotype effects. Excluding re- establishment of vegetative methylation could potentially be performed with additional analyses of existing data, however it may require additional experiments to demonstrate persuasively. + +Response: We thank the reviewer for the comments. In our reply to the previous comment of the reviewer we have provide data confirming the results (shown in Fig 2) that in the hybrid zygote, the paternal methylation of the E- S DMRs are remodeled to the levels of the maternal alleles (Fig 2). In Fig 3 we show that at Globular Embryo (GE) stage, the parental methylation difference (or E- S DMR) is reestablished. We agree that the reestablishment at GE stage may be based on a cis- regulatory mechanism, as we mentioned in the last part of the discussion section. In the context of hybrid, 'parental allelic difference' is in fact 'DNA sequence difference'. We have changed 'parental allelic- specific' to 'parental allelic or sequence- specific' in the discussion section. + +In addition to the major problem of the data not matching the main point of the paper, there are several smaller cases of the text of the manuscript not matching or oversimplifying the results shown on figures. I have listed these examples below. + +Line 64 – PCA shows separation by genotype before cell type. Please rewrite to reflect observations. + +Response: Thanks for the point. We have rewritten the statement in the revised + +<--- Page Split ---> + +version. + +"Principal component analysis revealed a high reproducibility of the replicates and a clear difference between the two parental lines" + +Line 66 – Boxplots show slightly lower CG for sperm in one genotype but higher CG in the other genotype. CHG is very similar. + +Response: Thanks. We have rewritten the statement in the revised version. "Boxplots indicated that sperm cells showed globally lower CHG methylation (mCHG) than egg cells in TEs" + +Line 78 – Only some of the bars show that “more than half of DMRs concerned non- TE regions. + +Response: We have revised the statement in the revised version. "Scanning differentially methylated regions (DMRs, within 50- bp windows with the cutoff of methylation difference at \(\mathrm{CG} > 0.5\) , \(\mathrm{CHG} > 0.3\) , and \(\mathrm{CHH} > 0.1\) , \(P < 0.05\) ) between the gametes and zygotes revealed that about a third or more of the DMRs concerned non- transposable element (non- TE) regions" + +Line 87 – Methylation was higher for genes but not TEs. + +Response: We have revised the statement in the revised version. "In the hybrid zygotes, the methylation levels appeared higher than in the male and female gametes, particularly at genic CG and CHG sites" + +Line 200 – The figures do not look “overall higher” in all regions, but does look marginally higher in upstream and downstream regions. Error bars or other stats on the metaplots would help clarify if the signal here is significant. + +<--- Page Split ---> + +Response: Thanks for the comments. We have rewritten the sentence in the revised version. + +"and displayed lower mCHH in egg than in sperm in the upstream region" + +Line 206 – What is meant by “comparable numbers”? It looks like fewer MEGs and PEGs than zygotes. + +Response: The “comparable numbers” is referring to the numbers of paternal allelic- specific (P- ASEGs: ZM [n = 903], MZ [n = 1150]) or maternal allelic- specific expressed genes (M- ASEGs; ZM [n = 1883], MZ [n = 1680]) in ZM and MZ GE. We have revised the statement in the revised version. + +"similar numbers" + +Finally, the authors analyze parent- of- origin biased gene expression and conclude that expression patterns are dynamic and shift between MEGs, PEGs, and non- imprint. However, these calls are only described as discreet data. The problem with this is that imprinting calls are typically based on a small number of allele- specific reads, and a change from, for example, MEG to not imprinted can reflect a real change in allelic expression, a loss of expression of the expressed allele, or most often, it can reflect a subtle change that is no longer called significant without necessarily reflecting the biology. In order to conclude that imprinting is dynamic in these early stages, the authors need to demonstrate that the change in patterns is real and not an artifact of small numbers of reads. + +Response: We have deleted the sentence. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The results and analysis reported in this manuscript constitute a major advance in our understanding of the epigenetic regulation of parent- of- origin contributions to early embryogenesis. I am satisfied with the authors' response to my comments and I recommend publication of this manuscript. + +While I was reading the manuscript, I noticed that reference 13 is incomplete, the complete reference should be: + +(13) Alaniz-Fabián J, Orozco-Nieto A, Abreu-Goodger C, Gillmor CS. Hybridization alters maternal and paternal genome contributions to early plant embryogenesis. Development (2022) 149 (22): dev201025. + +Reviewer #3 (Remarks to the Author): + +The authors have adequately addressed my concerns. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The results and analysis reported in this manuscript constitute a major advance in our understanding of the epigenetic regulation of parent- of- origin contributions to early embryogenesis. I am satisfied with the authors' response to my comments and I recommend publication of this manuscript. + +While I was reading the manuscript, I noticed that reference 13 is incomplete, the complete reference should be: + +(13) Alaniz-Fabian J, Orozco-Nieto A, Abreu-Goodger C, Gillmor CS. Hybridization alters maternal and paternal genome contributions to early plant embryogenesis. Development (2022) 149 (22): dev201025. + +Response: Thanks, we have completed the reference information. + +Reviewer #3 (Remarks to the Author): + +The authors have adequately addressed my concerns. + +Response: Thank you for the comments! + +<--- Page Split ---> diff --git a/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6de0f34c11e42bb2c7932c075e18cf71fbf8ba2d --- /dev/null +++ b/peer_reviews/99250fe0d3b688404183e3322e58722cd45a80f64d480bc394d9cc031ae737bf/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,578 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 505, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[80, 154, 916, 211]]<|/det|> +Paternal DNA methylation is remodeled to maternal levels in rice zygote + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 415, 98]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 111, 877, 323]]<|/det|> +The manuscript by Liu et al reports the results of epigenomic and transcriptomic experiments on rice eggs, sperm, zygotes, and hybrid zygotes and globular embryos resulting from crosses of the MH63 and ZS97 varieties. Using bisulfite sequencing of eggs, sperm, zygotes, and hybrid zygotes, the authors provide evidence that the methylome of the paternal genome is remodeled in the zygote to a methylation status similar to the maternal genome. Interestingly, the authors provide evidence that, by the globular stage, the methylation patterns of the maternal and paternal genomes return to their overall patterns at the time of fertilization, ie. to the methylation patterns in the gametes. The authors then correlate differentially methylated regions between maternal and paternal genomes with histone marks found in seedling tissues, providing a nice association between parent- of- origin methylation status in hybrid zygotes and histone marks in the respective parental lines. Finally, the authors produce transcriptomes from eggs and sperm of the MH63 and ZS97 varieties, as well as hybrid zygotes and globular embryos from crosses in both directions. The authors compare the transcript levels from the maternal and paternal alleles with epigenetic marks in the egg, sperm and zygote, finding correlations between parent- of- origin gene expression and different contexts of cytosine methylation. + +<|ref|>text<|/ref|><|det|>[[119, 336, 877, 421]]<|/det|> +This manuscript describes novel experiments conducted on epigenetic regulation of parent- of- origin gene expression in plant embryogenesis. The field of early embryogenesis in plants has been waiting for this combination of epigenomic and transcriptomic data of gametes and hybrid zygotes for a long time. This manuscript is absolutely appropriate for publication in Nature Communications, if not Nature. The manuscript would benefit from some light editing for language style. Below I list comments and suggestions for improving the manuscript. + +<|ref|>text<|/ref|><|det|>[[119, 434, 351, 463]]<|/det|> +Stewart Gillmor Langebio, CINVESTAV, Mexico + +<|ref|>text<|/ref|><|det|>[[119, 476, 870, 519]]<|/det|> +Figure 1C: why is there a clear bi- modal distribution (some genes lose methylation and some gain methylation) but only in the CHH context? Are these genes enriched for some GO term or in a particular region of the genome like near centromeres or transposons? + +<|ref|>text<|/ref|><|det|>[[119, 531, 869, 575]]<|/det|> +Extended Data Figure 10a: Reads are shown only as \(\%\) maternal or \(\%\) paternal, without regard to how many genes these reads map to. The authors should also show how many genes were called as having statistically significant maternal or paternal bias. + +<|ref|>text<|/ref|><|det|>[[118, 588, 852, 617]]<|/det|> +Figure 5a The authors should show how many genes do not show maternal or paternal bias (i.e. how many genes are represented by a grey point). + +<|ref|>text<|/ref|><|det|>[[119, 630, 313, 644]]<|/det|> +line 18 'DNA methylation' + +<|ref|>text<|/ref|><|det|>[[119, 658, 300, 672]]<|/det|> +line 22 'reprogramming' + +<|ref|>text<|/ref|><|det|>[[119, 686, 816, 744]]<|/det|> +line 31- 32 for a more in- depth review on parent- of- origin contributions to early plant embryogenesis which includes a discussion of genetic as well as transcriptomic studies, the authors might consider also citing Armenta- Medina and Gillmor https://doi.org/10.1016/bs.ctdb.2018.11.008 + +<|ref|>text<|/ref|><|det|>[[118, 756, 878, 883]]<|/det|> +lines 34- 35 when discussing the contrasting results in Arabidopsis on parent- of- origin studies of hybrid zygote and early embryo transcriptomes, the authors should cite Alaniz- Fabian et al 2022 https://doi.org/10.1242/dev.201025, who reanalyzed the Col/Ler zygote transcriptomes originally described in Zhao et al (2019) Dev Cell and Zhao et al (2020) Nature Plants. This reanalysis showed that on an gene- by- gene bases, Col/Ler zygotes do not show equal parental transcriptome contributions; thousands of genes in Col/Ler zygotes are represented by transcripts from either the maternal or paternal allele, but not both. Thus, previous conclusions on parent- of- origin transcript contributions are oversimplified, and the evidence for equal transcript contributions in Col/Ler zygotes is not as strong as originally presented. + +<|ref|>text<|/ref|><|det|>[[118, 896, 876, 911]]<|/det|> +Consistent with Liu et al's finding that maternal transcripts dominate in rice zygotes, previous work + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 876, 182]]<|/det|> +in Arabidopsis by Alaniz- Fabian et al (2022) Development as well as Del Toro De Leon et al (2014) Nature presented genetic evidence that maternal allies of most EMB genes make a more important contribution functional to early embryogenesis than paternal alleles, and that hybridization itself can affect parental genome contributions to early embryogenesis. Adding a sentence about this genetic evidence for parental genome contributions in Arabidopsis would provide a fuller picture of work on parent- of- origin regulation of early embryogenesis in plants, and would put the experiments presented by Liu et al in a more complete context. + +<|ref|>text<|/ref|><|det|>[[118, 196, 872, 252]]<|/det|> +lines 61- 63 'DNA methylomes data were obtained from 25 eggs or zygotes and 150 sperm cells, two biological replicates were performed with a sequencing depth of about \(24.7 - 75.4 \times\) genome coverage (Supplementary Table 1).' Question: Is this 25x Coverage from 25 eggs? After excluding duplicates? + +<|ref|>text<|/ref|><|det|>[[118, 266, 860, 322]]<|/det|> +lines 64- 64 'sperm methylome more distal from that of egg or zygote' An inspection of Extended Data Figure 1a does not support this statement. Only for mCHH of the ZS97 variety is sperm methylation separated from egg and zygote, for other methylation types and the other variety they are not separated. The authors should remove this statement. + +<|ref|>text<|/ref|><|det|>[[118, 336, 875, 420]]<|/det|> +Lines 66- 67 'Boxplots indicated that sperm cells showed globally higher CG methylation (mCG) but lower CHG methylation (mCHG) than egg cells' An inspection of Extended Data Figure 2a does not fully support this statement. Only MH63 apparently has higher CG for sperm than egg. Also, are the differences shown by the box plots statistically significant, even when the median looks different? The authors should do statistical analysis to determine if the results in the box plots in Extended Data Figure 2 and in Figure 1 really are different. + +<|ref|>text<|/ref|><|det|>[[118, 433, 875, 476]]<|/det|> +Lines 70- 71 'In the zygote mCG and mCHH levels were lower than in the sperm, while the mCHG was at the intermediate levels of the egg and sperm cells' Same as my previous comment- are the differences in box plots statistically significant? + +<|ref|>text<|/ref|><|det|>[[118, 490, 864, 546]]<|/det|> +line 85 I find the notation that the authors use to describe the different hybrids confusing. The MH63 x ZS97 hybrid is notated as MZ; this makes sense. But the ZS97 x MH63 hybrid is notated as SY63. I understand that this is a standard hybrid in rice and that is its name, but perhaps for the purposes of simplicity in the manuscript the authors could refer to the SY63 hybrid as ZM? + +<|ref|>text<|/ref|><|det|>[[118, 560, 877, 616]]<|/det|> +Lines 86- 88 'In the hybrid zygotes, the methylation levels appeared higher than in the male and female gametes, particularly at CG and CHG sites (Fig. 1)' As I mentioned above, the authors should conduct statistical tests to determine if the data represented in the box plots in Figure 1 are statistically significantly different. + +<|ref|>text<|/ref|><|det|>[[118, 630, 860, 700]]<|/det|> +Lines 117- 118 'indicating that the maternal- controlled remodeling of paternal allele- specific methylation in the zygote persisted till at least the 2- cell embryo stage.' The authors do not formally show that the remodeling that occurs is maternally controlled. All they show is that the remodeling makes the paternal genome similar to the maternal genome. They should soften this statement. + +<|ref|>text<|/ref|><|det|>[[118, 714, 857, 813]]<|/det|> +Lines 191- 193 'Several genes such as plasma membrane protein gene GEX1, RALF- like secreted peptide RALF3, and Arabinogalactan protein 7 (AGP7) were shown to function in male gametophyte development and during early embryogenesis 39- 41'. Alaniz- Fabian (2022) Development showed that gex1 mutants condition both maternal and paternal effects in early embryogenesis. This is genetic evidence that paternal GEX1 transcripts have a function in early embryos, consisted with GEX1 being a PEG. The authors might consider citing Alaniz- Fabian (2022) here. + +<|ref|>text<|/ref|><|det|>[[118, 827, 863, 911]]<|/det|> +Lines 207- 209 'indicating an increased paternal contribution to gene expression in GE, as observation in Arabidopsis 11, which was consistent with the reestablishment of the parental allelic- specific DNA methylome in GE'. In addition to citing the transcriptomic data of Autran et al that indicates equal maternal and paternal transcriptome contributions at the globular stage, the authors might consider also citing Del Toro De Leon (2014) Nature and Alaniz- Fabian (2022) Development, which provide functional evidence for increased paternal allele contributions from + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 625, 99]]<|/det|> +EMB genes by the globular stage of embryogenesis in Arabidopsis. + +<|ref|>text<|/ref|><|det|>[[120, 166, 415, 180]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 195, 877, 295]]<|/det|> +The manuscript entitled "Maternal- based paternal DNA methylation remodeling in rice zygote" aims to decipher how DNA methylation (DNAme) is remodeled after fertilization. The authors provide a very comprehensive experimental dataset of DNAme on egg, sperm, zygote and globular embryos. Results described here provide evidence of how DNAme in the zygote changes after fertilization to match a pattern that closely resembles the maternal genome. The data also shows how hybridization has immediate effects on DNAme in a subset of loci in zygotes and globular embryos. + +<|ref|>text<|/ref|><|det|>[[120, 308, 788, 322]]<|/det|> +Bellow you can find a summary of my comments by sections of the present manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 336, 876, 420]]<|/det|> +"Predominant remodeling of the male methylome in the rice zygote upon fertilization" This first section of the manuscript describes global comparisons of DNA methylation in S, E and Z. However, the title and the conclusions drawn refer to a remodeling of the male methylome. This is indeed suggested by the data, but convincingly demonstrated later in the manuscript with parent- specific DNA methylation. I suggest changing the title of this section to more accurately reflect the findings described in it. + +<|ref|>text<|/ref|><|det|>[[118, 433, 860, 490]]<|/det|> +Line 72: "Density plots revealed higher methylation variations between zygote and sperm than between zygote and egg (Extended Data Fig. 2b)." Results and interpretations on this part feel disjointed. For clarity, please rephrase by explaining the quantitative differences observed in the density plots that support the statements. + +<|ref|>text<|/ref|><|det|>[[118, 504, 875, 574]]<|/det|> +"A number of given loci tend to be remodeled in the zygote" In this section, the authors highlight that in zygotes, "DNA methylation at a number of specific loci tends to be enhanced upon fertilization," which is particularly true in hybrid zygotes. What are these loci? Do they have anything in common? And how this reflects on gene expression? Line 88: "(Fig. 1)", what part of the panel is this referring to? + +<|ref|>text<|/ref|><|det|>[[118, 587, 864, 612]]<|/det|> +"Parental allele- specific methylation was restored during embryogenesis and stably maintained in the hybrids" + +<|ref|>text<|/ref|><|det|>[[118, 614, 850, 684]]<|/det|> +Here the authors nicely show that although the DMRs between egg and sperm are closer to the maternal genome in hybrids, they recover the parent- specific profile by the globular stage. I wonder if this is consistent with the activity of the RdDM pathway during embryogenesis? The authors have RNAseq data that can help answer this question. Figure 3. Label x axis. + +<|ref|>text<|/ref|><|det|>[[118, 699, 861, 741]]<|/det|> +"Parental methylation difference was associated with distinct histone modifications" Figure 4. I suggest including at least in the extended data a representation of the data using box plots, which are more quantitative and less sensitive to bias from individual loci. + +<|ref|>text<|/ref|><|det|>[[118, 756, 870, 855]]<|/det|> +"Parental DNA methylation remodeling mirrors parental contribution to zygotic gene expression" Whether DNA methylation reprogramming after fertilization has an effect on ZGA is still unclear and not discussed by the authors. The fact that DNA methylation of the paternal genome is reprogrammed to reach levels similar to the maternal genome, and yet most genes show predominant maternal expression, suggests that the mechanism by which this maternal- allele preferential expression occurs is independent from DNA methylation, or that it occurs at an earlier time when the zygote still maintains parental asymmetry in DNA methylation. + +<|ref|>text<|/ref|><|det|>[[118, 855, 870, 911]]<|/det|> +Line 179: Not clear. What do they mean with "most of the reads were maternal allelic- specific and about \(1.5\% \sim 4.1\%\) of the reads was paternal allelic- specific"? I find hard to reconcile this statement with figure 5a where most genes are biallelic (with a level of maternal bias expression) while a small subset of genes shows either maternal (1063) or paternal (28) specific expression. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 853, 141]]<|/det|> +The authors here refer to Extended Data Figure 10a, which shows a Venn diagram showing, I believe, the parental reads for MEGs in zygotes or for the entire transcriptome? Please rephrase this paragraph for clarity. In the Extended Data Figure 10a. include the total number in Venn diagrams. + +<|ref|>text<|/ref|><|det|>[[118, 154, 221, 168]]<|/det|> +Line 18: DNA + +<|ref|>text<|/ref|><|det|>[[119, 209, 415, 223]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 237, 870, 336]]<|/det|> +In the manuscript "Maternal- based paternal DNA methylation remodeling in rice zygote", authors Liu et al investigate changes in DNA methylation that occur in early rice zygotes. They observe that in regions of the genome with differential methylation between egg and sperm, zygotes show more similarity to the egg cell methylation levels resulting from changes in paternal methylation. As observed in the literature previously, DNA methylation patterns are consistent across development, with a major exception being the sperm cell, so remodeling of paternal methylation is expected. + +<|ref|>text<|/ref|><|det|>[[117, 349, 875, 519]]<|/det|> +The authors hypothesized that the maternal genome is acting to "control" the remodeling of the paternal genome, however none of the experiments or analyses demonstrated active involvement of the maternal genome. This is important because although the zygote is more correlated with the maternal than paternal epigenome, so is the DNA methylation profile of all vegetative tissue in the plant. Sperm cells have active remodeling of methylation during development, so the change in paternal methylation is necessary to regain the methylation pattern typical of vegetative cells. In order to make the claim that "paternal DNA methylation remodeling" is "maternal- based" as stated in the title and throughout the manuscript, the authors would need to somehow distinguish between paternal methylation reverting to vegetative levels vs. changing to maternal levels. While some cases of trans- acting epi- alleles exist in plants (i.e. paramutation), DNA methylation is also inherited trans- generationally and many alleles maintain methylation patterns consistent with the genetic origin of that sequence, as demonstrated in this paper as well. + +<|ref|>text<|/ref|><|det|>[[117, 532, 870, 658]]<|/det|> +In order to make the claim that DNA methylation remodeling is maternal- based, the authors need to exclude the more likely possibility that DNA methylation is simply being re- established to vegetative levels based on cis- regulatory information coded in the DNA. A cis- regulatory mechanism of DNA methylation reestablishment would also explain why the maternal shift occurs for CG and CHG but not CHH methylation which depends on trans- acting factors. The genotype- dependent methylation patterns are demonstrated in Figure 3, however, the authors label this as parental effects instead of genotype effects. Excluding re- establishment of vegetative methylation could potentially be performed with additional analyses of existing data, however it may require additional experiments to demonstrate persuasively. + +<|ref|>text<|/ref|><|det|>[[118, 672, 861, 714]]<|/det|> +In addition to the major problem of the data not matching the main point of the paper, there are several smaller cases of the text of the manuscript not matching or oversimplifying the results shown on figures. I have listed these examples below. + +<|ref|>text<|/ref|><|det|>[[118, 728, 778, 756]]<|/det|> +Line 64 - PCA shows separation by genotype before cell type. Please rewrite to reflect observations. + +<|ref|>text<|/ref|><|det|>[[118, 770, 853, 799]]<|/det|> +Line 66 - Boxplots show slightly lower CG for sperm in one genotype but higher CG in the other genotype. CHG is very similar. + +<|ref|>text<|/ref|><|det|>[[118, 812, 845, 826]]<|/det|> +Line 78 - Only some of the bars show that "more than half of DMRs concerned non- TE regions. + +<|ref|>text<|/ref|><|det|>[[118, 840, 546, 854]]<|/det|> +Line 87 - Methylation was higher for genes but not TEs. + +<|ref|>text<|/ref|><|det|>[[118, 868, 874, 910]]<|/det|> +Line 200 - The figures do not look "overall higher" in all regions, but does look marginally higher in upstream and downstream regions. Error bars or other stats on the metaplots would help clarify if the signal here is significant. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 97, 833, 125]]<|/det|> +Line 206 – What is meant by "comparable numbers"? It looks like fewer MEGs and PEGs than zygotes. + +<|ref|>text<|/ref|><|det|>[[118, 138, 870, 266]]<|/det|> +Finally, the authors analyze parent- of- origin biased gene expression and conclude that expression patterns are dynamic and shift between MEGs, PEGs, and non- imprint. However, these calls are only described as discreet data. The problem with this is that imprinting calls are typically based on a small number of allele- specific reads, and a change from, for example, MEG to not imprinted can reflect a real change in allelic expression, a loss of expression of the expressed allele, or most often, it can reflect a subtle change that is no longer called significant without necessarily reflecting the biology. In order to conclude that imprinting is dynamic in these early stages, the authors need to demonstrate that the change in patterns is real and not an artifact of small numbers of reads. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[293, 94, 702, 113]]<|/det|> +## Point-by-point response to the reviewers + +<|ref|>sub_title<|/ref|><|det|>[[148, 163, 463, 180]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 190, 853, 655]]<|/det|> +The manuscript by Liu et al reports the results of epigenomic and transcriptomic experiments on rice eggs, sperm, zygotes, and hybrid zygotes and globular embryos resulting from crosses of the MH63 and ZS97 varieties. Using bisulfite sequencing of eggs, sperm, zygotes, and hybrid zygotes, the authors provide evidence that the methylome of the paternal genome is remodeled in the zygote to a methylation status similar to the maternal genome. Interestingly, the authors provide evidence that, by the globular stage, the methylation patterns of the maternal and paternal genomes return to their overall patterns at the time of fertilization, ie. to the methylation patterns in the gametes. The authors then correlate differentially methylated regions between maternal and paternal genomes with histone marks found in seedling tissues, providing a nice association between parent- of- origin methylation status in hybrid zygotes and histone marks in the respective parental lines. Finally, the authors produce transcriptomes from eggs and sperm of the MH63 and ZS97 varieties, as well as hybrid zygotes and globular embryos from crosses in both directions. The authors compare the transcript levels from the maternal and paternal alleles with epigenetic marks in the egg, sperm and zygote, finding correlations between parent- of- origin gene expression and different contexts of cytosine methylation. + +<|ref|>text<|/ref|><|det|>[[147, 690, 852, 876]]<|/det|> +This manuscript describes novel experiments conducted on epigenetic regulation of parent- of- origin gene expression in plant embryogenesis. The field of early embryogenesis in plants has been waiting for this combination of epigenomic and transcriptomic data of gametes and hybrid zygotes for a long time. This manuscript is absolutely appropriate for publication in Nature Communications, if not Nature. The manuscript would benefit from some light editing for language style. Below I list comments and suggestions for improving the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 90, 419, 135]]<|/det|> +Stewart GillmorLangebio, CINVESTAV, Mexico + +<|ref|>text<|/ref|><|det|>[[147, 226, 852, 330]]<|/det|> +Figure 1C: why is there a clear bi- modal distribution (some genes lose methylation and some gain methylation) but only in the CHH context? Are these genes enriched for some GO term or in a particular region of the genome like near centromeres or transposons? + +<|ref|>text<|/ref|><|det|>[[147, 366, 852, 525]]<|/det|> +Response: Thank you for the comments. As suggested, we analyzed the genomic distribution of the CHH DMRs in zygotes vs the gametes and found that the hyper- DMRs were mainly enriched in genic regions, and the hypo- DMRs enriched in TE regions, which is consistent with the observations that sperm and egg show high levels of mCHH in long TEs. The GO enrichment indicates that the concerned genes are mainly enriched in RNA silencing, defense and developmental pathways. + +<|ref|>text<|/ref|><|det|>[[148, 533, 850, 579]]<|/det|> +The analysis is presented in Supplementary Fig. 4 and commented in the results section: + +<|ref|>text<|/ref|><|det|>[[147, 588, 852, 802]]<|/det|> +"Density plots revealed a clear bimodal distribution pattern of CHH DMR between zygote and sperm (Z - S) or between zygote and egg (Z - E) (Figure 1c), indicating a fraction of loci showed clearly increased (hyper) or decreased (hypo) methylation at CHH sites in the zygote genome. Further analysis indicated that the hyper methylated CHH sites were enriched in genic regions whereas the hypo- methylated sites were mainly located in TE regions (Supplementary Fig. 4a). Genes with the CHH DMRs were mainly enriched in RNA silencing, defense and developmental pathways" (Supplementary Fig. 4b). + +<|ref|>text<|/ref|><|det|>[[148, 838, 850, 913]]<|/det|> +Extended Data Figure 10a: Reads are shown only as \(\%\) maternal or \(\%\) paternal, without regard to how many genes these reads map to. The authors should also show how many genes were called as having statistically significant maternal or paternal + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 92, 187, 106]]<|/det|> +bias. + +<|ref|>text<|/ref|><|det|>[[147, 144, 851, 220]]<|/det|> +Response: Thanks for the comments. As suggested, we have added the informative sequencing reads and the numbers of expressed SNP genes (maternal and paternal) in the Supplementary Fig. 14a) in the revised version. + +<|ref|>text<|/ref|><|det|>[[147, 255, 850, 303]]<|/det|> +Figure 5a The authors should show how many genes do not show maternal or paternal bias (i.e. how many genes are represented by a grey point). + +<|ref|>text<|/ref|><|det|>[[147, 338, 851, 413]]<|/det|> +Response: Thanks for the suggestion. We have reanalyzed the zygotic genes. The gene number (2569) represented by the grey points is added in Fig.5a in the revised version. + +<|ref|>text<|/ref|><|det|>[[148, 450, 363, 468]]<|/det|> +line 18 'DNA methylation' + +<|ref|>text<|/ref|><|det|>[[147, 478, 535, 497]]<|/det|> +Response: Thanks, we have corrected the typo. + +<|ref|>text<|/ref|><|det|>[[148, 533, 344, 551]]<|/det|> +line 22 'reprogramming' + +<|ref|>text<|/ref|><|det|>[[148, 561, 327, 579]]<|/det|> +Response: Corrected. + +<|ref|>text<|/ref|><|det|>[[147, 615, 852, 719]]<|/det|> +line 31- 32 for a more in- depth review on parent- of- origin contributions to early plant embryogenesis which includes a discussion of genetic as well as transcriptomic studies, the authors might consider also citing Armenta- Medina and Gillmor https://doi.org/10.1016/bs.ctdb.2018.11.008 + +<|ref|>text<|/ref|><|det|>[[147, 754, 851, 830]]<|/det|> +Response: Thank you for the point. We have included the sentence "Parent- of- origin contributions to plant early embryogenesis have been studied at genetic and transcriptomic levels10" and cited the reference in the revised version. + +<|ref|>text<|/ref|><|det|>[[147, 865, 851, 913]]<|/det|> +lines 34- 35 when discussing the contrasting results in Arabidopsis on parent- of- origin studies of hybrid zygote and early embryo transcriptomes, the authors should cite + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 303]]<|/det|> +Alaniz- Fabián et al 2022 https://doi.org/10.1242/dev.201025, who reanalyzed the Col/Ler zygote transcriptomes originally described in Zhao et al (2019) Dev Cell and Zhao et al (2020) Nature Plants. This reanalysis showed that on an gene- by- gene bases, Col/Ler zygotes do not show equal parental transcriptome contributions; thousands of genes in Col/Ler zygotes are represented by transcripts from either the maternal or paternal allele, but not both. Thus, previous conclusions on parent- of- origin transcript contributions are oversimplified, and the evidence for equal transcript contributions in Col/Ler zygotes is not as strong as originally presented. + +<|ref|>text<|/ref|><|det|>[[147, 339, 850, 386]]<|/det|> +Response: Thank you for the comments. We have mentioned the results of reanalysis and cited the references in the revised version. + +<|ref|>text<|/ref|><|det|>[[147, 394, 851, 497]]<|/det|> +"However, a reanalysis of the published data6,7 showed that, on a gene- by- gene basis, the Arabidopsis hybrid (Col/Ler) zygotes do not show equal parental transcriptome contributions; thousands of genes in hybrid zygotes are represented by transcripts from either the maternal or paternal allele, but not both13." + +<|ref|>text<|/ref|><|det|>[[147, 532, 852, 775]]<|/det|> +Consistent with Liu et al's finding that maternal transcripts dominate in rice zygotes, previous work in Arabidopsis by Alaniz- Fabián et al (2022) Development as well as Del Toro De León et al (2014) Nature presented genetic evidence that maternal alleles of most EMB genes make a more important contribution functional to early embryogenesis than paternal alleles, and that hybridization itself can affect parental genome contributions to early embryogenesis. Adding a sentence about this genetic evidence for parental genome contributions in Arabidopsis would provide a fuller picture of work on parent- of- origin regulation of early embryogenesis in plants, and would put the experiments presented by Liu et al in a more complete context. + +<|ref|>text<|/ref|><|det|>[[147, 810, 850, 856]]<|/det|> +Response: Thanks for the suggestion. We have added the context in the revised Introduction and cited the related references. + +<|ref|>text<|/ref|><|det|>[[148, 866, 850, 912]]<|/det|> +"There is also genetic evidence that maternal alleles of most embryo genes make a more important contribution functional to early embryogenesis than paternal alleles, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 849, 135]]<|/det|> +and that hybridization itself can affect parental genome contributions to early embryogenesis \(^{13,15}\) ." + +<|ref|>text<|/ref|><|det|>[[147, 171, 852, 275]]<|/det|> +lines 61- 63 'DNA methylomes data were obtained from 25 eggs or zygotes and 150 sperm cells, two biological replicates were performed with a sequencing depth of about \(24.7 - 75.4 \times\) genome coverage (Supplementary Table 1).' Question: Is this \(25x\) Coverage from 25 eggs? After excluding duplicates? + +<|ref|>text<|/ref|><|det|>[[147, 311, 851, 357]]<|/det|> +Response: Genome coverage was calculated per replicate (25 cells). We have clarified this in the MS. + +<|ref|>text<|/ref|><|det|>[[147, 367, 851, 441]]<|/det|> +"DNA methylomes data were obtained from 25 eggs or zygotes and 150 sperm cells, two biological replicates were performed with a sequencing depth of about \(24.7 - 75.4 \times\) genome coverage per replicate." + +<|ref|>text<|/ref|><|det|>[[147, 477, 852, 608]]<|/det|> +lines 64- 64 'sperm methylome more distal from that of egg or zygote' An inspection of Extended Data Figure 1a does not support this statement. Only for mCHH of the ZS97 variety is sperm methylation separated from egg and zygote, for other methylation types and the other variety they are not separated. The authors should remove this statement. + +<|ref|>text<|/ref|><|det|>[[147, 644, 837, 718]]<|/det|> +Response: Thanks for the point. We have rephrased the statement: "Principal component analysis revealed a high reproducibility of the replicates and a clear difference between the two parental lines". + +<|ref|>text<|/ref|><|det|>[[147, 770, 852, 900]]<|/det|> +Lines 66- 67 'Boxplots indicated that sperm cells showed globally higher CG methylation (mCG) but lower CHG methylation (mCHG) than egg cells' An inspection of Extended Data Figure 2a does not fully support this statement. Only MH63 apparently has higher CG for sperm than egg. Also, are the differences shown by the box plots statistically significant, even when the median looks different? The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 850, 135]]<|/det|> +authors should do statistical analysis to determine if the results in the box plots in Extended Data Figure 2 and in Figure 1 really are different. + +<|ref|>text<|/ref|><|det|>[[147, 172, 850, 273]]<|/det|> +Response: Thanks for the comments. We have reentenced the statement and added the statistical significance of the boxplots in the revised version. "Boxplots indicated that sperm cells showed globally lower CHG methylation (mCHG) than egg cells in TEs." + +<|ref|>text<|/ref|><|det|>[[147, 310, 850, 384]]<|/det|> +Lines 70- 71 'In the zygote mCG and mCHH levels were lower than in the sperm, while the mCHG was at the intermediate levels of the egg and sperm cells' Same as my previous comment- are the differences in box plots statistically significant? + +<|ref|>text<|/ref|><|det|>[[147, 394, 850, 440]]<|/det|> +Response: We have added the statistical significance of the boxplots in the revised Figures. + +<|ref|>text<|/ref|><|det|>[[147, 477, 851, 608]]<|/det|> +line 85 I find the notation that the authors use to describe the different hybrids confusing. The MH63 x ZS97 hybrid is notated as MZ; this makes sense. But the ZS97 x MH63 hybrid is notated as SY63. I understand that this is a standard hybrid in rice and that is its name, but perhaps for the purposes of simplicity in the manuscript the authors could refer to the SY63 hybrid as ZM? + +<|ref|>text<|/ref|><|det|>[[147, 644, 585, 663]]<|/det|> +Response: We have changed SY63 to ZM as advised. + +<|ref|>text<|/ref|><|det|>[[147, 700, 851, 802]]<|/det|> +Lines 86- 88 'In the hybrid zygotes, the methylation levels appeared higher than in the male and female gametes, particularly at CG and CHG sites (Fig. 1)' As I mentioned above, the authors should conduct statistical tests to determine if the data represented in the box plots in Figure 1 are statistically significantly different. + +<|ref|>text<|/ref|><|det|>[[147, 811, 850, 857]]<|/det|> +Response: We have added statistical significance of the boxplots in the revised Figures. + +<|ref|>text<|/ref|><|det|>[[145, 895, 848, 913]]<|/det|> +Lines 117- 118 'indicating that the maternal- controlled remodeling of paternal + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 851, 191]]<|/det|> +allele- specific methylation in the zygote persisted till at least the 2- cell embryo stage.' The authors do not formally show that the remodeling that occurs is maternally controlled. All they show is that the remodeling makes the paternal genome similar to the maternal genome. They should soften this statement. + +<|ref|>text<|/ref|><|det|>[[147, 228, 851, 330]]<|/det|> +Response: We have rewritten the statement in the revised version. "The data together indicated that the paternal allele- specific methylation is remodeled to the levels similar to the maternal alleles in the zygote, which persists till at least the 2- cell embryo stage." + +<|ref|>text<|/ref|><|det|>[[147, 366, 852, 552]]<|/det|> +Lines 191- 193 'Several genes such as plasma membrane protein gene GEX1, RALF- like secreted peptide RALF3, and Arabinogalactan protein 7 (AGP7) were shown to function in male gametophyte development and during early embryogenesis 39- 41'. Alaniz- Fabian (2022) Development showed that gex1 mutants condition both maternal and paternal effects in early embryogenesis. This is genetic evidence that paternal GEX1 transcripts have a function in early embryos, consisted with GEX1 being a PEG. The authors might consider citing Alaniz- Fabian (2022) here. + +<|ref|>text<|/ref|><|det|>[[147, 588, 850, 635]]<|/det|> +Response: Thanks for the suggestion. We have discussed the point and cited the reference in the revised version. + +<|ref|>text<|/ref|><|det|>[[147, 644, 850, 719]]<|/det|> +"Recent results showed that gex1 mutants condition both maternal and paternal effects in early embryogenesis13, providing genetic evidence that paternal GEX1 transcripts have a function in early embryos." + +<|ref|>text<|/ref|><|det|>[[147, 755, 852, 913]]<|/det|> +Lines 207- 209 'indicating an increased paternal contribution to gene expression in GE, as observation in Arabidopsis 11, which was consistent with the reestablishment of the parental allelic- specific DNA methylome in GE'. In addition to citing the transcriptomic data of Autran et al that indicates equal maternal and paternal transcriptome contributions at the globular stage, the authors might consider also citing Del Toro De León (2014) Nature and Alaniz- Fabian (2022) Development, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 850, 136]]<|/det|> +which provide functional evidence for increased paternal allele contributions from EMB genes by the globular stage of embryogenesis in Arabidopsis. + +<|ref|>text<|/ref|><|det|>[[148, 172, 850, 220]]<|/det|> +Response: Thanks for the suggestion. We have discussed the finding and cited the references in the revised version: + +<|ref|>text<|/ref|><|det|>[[148, 229, 814, 275]]<|/det|> +"It is shown that increased paternal allele contributions from embryo genes by the globular stage have functional significance in Arabidopsis embryogenesis13,15." + +<|ref|>text<|/ref|><|det|>[[148, 316, 463, 334]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 357, 852, 600]]<|/det|> +The manuscript entitled "Maternal- based paternal DNA methylation remodeling in rice zygote" aims to decipher how DNA methylation (DNAme) is remodeled after fertilization. The authors provide a very comprehensive experimental dataset of DNAme on egg, sperm, zygote and globular embryos. Results described here provide evidence of how DNAme in the zygote changes after fertilization to match a pattern that closely resembles the maternal genome. The data also shows how hybridization has immediate effects on DNAme in a subset of loci in zygotes and globular embryos. + +<|ref|>text<|/ref|><|det|>[[148, 625, 850, 670]]<|/det|> +"Predominant remodeling of the male methylome in the rice zygote upon fertilization" + +<|ref|>text<|/ref|><|det|>[[147, 681, 852, 812]]<|/det|> +This first section of the manuscript describes global comparisons of DNA methylation in S, E and Z. However, the title and the conclusions drawn refer to a remodeling of the male methylome. This is indeed suggested by the data, but convincingly demonstrated later in the manuscript with parent- specific DNA methylation. I suggest changing the title of this section to more accurately reflect the findings described in it. + +<|ref|>text<|/ref|><|det|>[[148, 848, 850, 894]]<|/det|> +Response: Thank you for the comments. As suggested, we have changed the title of this section in the revised version to: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 90, 774, 108]]<|/det|> +"Remodeling of the rice gamete methylomes in the zygote upon fertilization" + +<|ref|>text<|/ref|><|det|>[[147, 151, 852, 255]]<|/det|> +Line 72: "Density plots revealed higher methylation variations between zygote and sperm than between zygote and egg (Extended Data Fig. 2b)." Results and interpretations on this part feel disjointed. For clarity, please rephrase by explaining the quantitative differences observed in the density plots that support the statements. + +<|ref|>text<|/ref|><|det|>[[147, 290, 850, 336]]<|/det|> +Response: Thanks for the point. We have rewritten the statements in the revised version: + +<|ref|>text<|/ref|><|det|>[[148, 346, 850, 393]]<|/det|> +"Density plots revealed lower mCG in zygote relative to both sperm and egg, and lower mCHH but higher mCHG in zygote versus sperm" + +<|ref|>text<|/ref|><|det|>[[147, 420, 850, 551]]<|/det|> +"A number of given loci tend to be remodeled in the zygote" In this section, the authors highlight that in zygotes, "DNA methylation at a number of specific loci tends to be enhanced upon fertilization," which is particularly true in hybrid zygotes. What are these loci? Do they have anything in common? And how this reflects on gene expression? + +<|ref|>text<|/ref|><|det|>[[147, 586, 852, 856]]<|/det|> +Response: Thank for comments. We have analyzed the overlapping hyper DMRs between hybrid and inbred zygote relative sperm/egg and found many genes are associated with the DMRs. GO enrichment indicates that the genes are of diverse function, many of which are expressed in sperm but repressed in the zygotes. We have included the data in Fig S3 and dataset1 and commented in the text: "Genes with diverse functions were associated the hyper DMRs in the hybrid and inbred zygotes versus sperm (Supplementary Fig. 3c-f; Supplementary Dataset 1). Most of the genes were lowly expressed or repressed in both sperm and zygotes, while a number of genes were expressed in sperm but repressed in the zygotes (Supplementary Dataset 1, labeled in red)" + +<|ref|>text<|/ref|><|det|>[[147, 892, 645, 911]]<|/det|> +Line 88: "(Fig. 1)", what part of the panel is this referring to? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 117, 694, 135]]<|/det|> +Response: It is referring to the Fig. 1a, b, specified now in the text. + +<|ref|>text<|/ref|><|det|>[[147, 172, 850, 218]]<|/det|> +"Parental allele- specific methylation was restored during embryogenesis and stably maintained in the hybrids" + +<|ref|>text<|/ref|><|det|>[[147, 227, 851, 358]]<|/det|> +Here the authors nicely show that although the DMRs between egg and sperm are closer to the maternal genome in hybrids, they recover the parent- specific profile by the globular stage. I wonder if this is consistent with the activity of the RdDM pathway during embryogenesis? The authors have RNAseq data that can help answer this question. + +<|ref|>text<|/ref|><|det|>[[147, 394, 850, 441]]<|/det|> +Response: Thanks for the comments. We have analyzed transcript levels of RdDM genes in zygote and GE (Fig S7) + +<|ref|>image<|/ref|><|det|>[[149, 451, 458, 604]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 618, 440, 634]]<|/det|> +and commented the data in the text: + +<|ref|>text<|/ref|><|det|>[[148, 644, 849, 691]]<|/det|> +"Transcript levels of genes involved in CHH methylation (e.g. AGO4, DCL3, DRM2, and Pol IV) were lower in the GE than in the zygote (Supplementary Fig. 7). + +<|ref|>text<|/ref|><|det|>[[148, 728, 332, 745]]<|/det|> +Figure 3. Label x axis. + +<|ref|>text<|/ref|><|det|>[[147, 782, 768, 801]]<|/det|> +Response: Thanks. We have added the x- axis in Fig.3 in the revised version. + +<|ref|>text<|/ref|><|det|>[[147, 837, 851, 914]]<|/det|> +"Parental methylation difference was associated with distinct histone modifications" Figure 4. I suggest including at least in the extended data a representation of the data using box plots, which are more quantitative and less sensitive to bias from individual + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 91, 185, 106]]<|/det|> +loci. + +<|ref|>text<|/ref|><|det|>[[147, 144, 850, 191]]<|/det|> +Response: Thanks for the suggestion. We have included boxplots in the Supplementary Fig. 9 in the revised version. + +<|ref|>image<|/ref|><|det|>[[241, 200, 755, 525]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[145, 535, 825, 552]]<|/det|> +
Supplementary Fig.9: Histone modification levels of the egg-sperm DMRs in the parental lines.
+ +<|ref|>text<|/ref|><|det|>[[147, 589, 850, 635]]<|/det|> +"Parental DNA methylation remodeling mirrors parental contribution to zygotic gene expression" + +<|ref|>text<|/ref|><|det|>[[147, 644, 852, 830]]<|/det|> +Whether DNA methylation reprogramming after fertilization has an effect on ZGA is still unclear and not discussed by the authors. The fact that DNA methylation of the paternal genome is reprogrammed to reach levels similar to the maternal genome, and yet most genes show predominant maternal expression, suggests that the mechanism by which this maternal- allele preferential expression occurs is independent from DNA methylation, or that it occurs at an earlier time when the zygote still maintains parental asymmetry in DNA methylation. + +<|ref|>text<|/ref|><|det|>[[147, 867, 850, 912]]<|/det|> +Response: Thanks for the comments. We have discussed the point in the Discussion section: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 275]]<|/det|> +"The observations that DNA methylation of the paternal genome was reprogrammed to reach levels similar to the maternal genome, and yet most genes showed predominant maternal expression, suggest that the mechanism by which this maternal- allele preferential expression occurs at an earlier time when the zygote still maintains parental asymmetry in DNA methylation and that the paternal methylation remodeling may contribute to paternal alleles expression in later stages during zygote development." + +<|ref|>text<|/ref|><|det|>[[147, 317, 852, 560]]<|/det|> +Line 179: Not clear. What do they mean with "most of the reads were maternal allelic- specific and about \(1.5\% \sim 4.1\%\) of the reads was paternal allelic- specific"? I find hard to reconciliate this statement with figure 5a where most genes are biallelic (with a level of maternal bias expression) while a small subset of genes shows either maternal (1063) or paternal (28) specific expression. The authors here refer to Extended Data Figure 10a, which shows a Venn diagram showing, I believe, the parental reads for MEGs in zygotes or for the entire transcriptome? Please rephrase this paragraph for clarity. In the Extended Data Figure 10a. include the total number in Venn diagrams. + +<|ref|>text<|/ref|><|det|>[[147, 569, 852, 780]]<|/det|> +Response: Thanks for the comment. We recognize that the presentation and the explanation were not sufficiently clear. We have added the numbers of the SNP reads (maternal and paternal) and expressed SNP genes (maternal and paternal) in the figure (Fig S14a) as well as the overlapping SNP genes between the reciprocal hybrid zygotes. We have rewritten the description of the data for clarity. "we analyzed parental SNP reads (2.66 to \(6 \times 10^{6}\) ) from the reciprocal hybrid zygote transcriptomes and found that most of the reads were of maternal origin and about \(1.5\% \sim 4.1\%\) of the reads were of paternal origin (Supplementary Fig. 14a).".... + +<|ref|>text<|/ref|><|det|>[[148, 817, 852, 893]]<|/det|> +"From the SNP reads, we identified 6245 expressed SNP genes (2221 maternal biased, 219 paternal biased) in the MZ zygote and 7116 expressed SNP genes (1666 maternal biased, 262 paternal biased) in the ZM zygote (Supplementary Fig. 14a). Among the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 852, 219]]<|/det|> +SNP genes, 3765 overlapped in the reciprocal hybrids (Supplementary Fig. 14a), of which 1063 were maternal, 28 genes were paternal (Figure 5a). A number of genes were parental sequence- specific genes. The other genes are mostly enriched in maternal reads in either ZM or MZ zygote, as shown by the density plots (Figure 5a)." + +<|ref|>text<|/ref|><|det|>[[148, 229, 267, 245]]<|/det|> +Line 18: DNA + +<|ref|>text<|/ref|><|det|>[[149, 280, 392, 297]]<|/det|> +Response: Thanks. corrected. + +<|ref|>text<|/ref|><|det|>[[148, 335, 463, 352]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 357, 852, 571]]<|/det|> +In the manuscript "Maternal- based paternal DNA methylation remodeling in rice zygote", authors Liu et al investigate changes in DNA methylation that occur in early rice zygotes. They observe that in regions of the genome with differential methylation between egg and sperm, zygotes show more similarity to the egg cell methylation levels resulting from changes in paternal methylation. As observed in the literature previously, DNA methylation patterns are consistent across development, with a major exception being the sperm cell, so remodeling of paternal methylation is expected. + +<|ref|>text<|/ref|><|det|>[[147, 606, 852, 905]]<|/det|> +The authors hypothesized that the maternal genome is acting to "control" the remodeling of the paternal genome, however none of the experiments or analyses demonstrated active involvement of the maternal genome. This is important because although the zygote is more correlated with the maternal than paternal epigenome, so is the DNA methylation profile of all vegetative tissue in the plant. Sperm cells have active remodeling of methylation during development, so the change in paternal methylation is necessary to regain the methylation pattern typical of vegetative cells. In order to make the claim that "paternal DNA methylation remodeling" is "maternal- based" as stated in the title and throughout the manuscript, the authors would need to somehow distinguish between paternal methylation reverting to vegetative levels vs. changing to maternal levels. While some cases of trans- acting + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 852, 164]]<|/det|> +epi- alleles exist in plants (i.e. paramutation), DNA methylation is also inherited trans- generationally and many alleles maintain methylation patterns consistent with the genetic origin of that sequence, as demonstrated in this paper as well. + +<|ref|>text<|/ref|><|det|>[[146, 199, 853, 608]]<|/det|> +Response: Thank you for the comments. We recognize that the term "control" was inappropriate; we have revised the relevant sentences throughout the MS text. We understand the reviewer's concern about the paternal remodeling in the zygote to maternal pattern or just vegetative pattern. The later possibility seems unlikely in the context of hybrid zygotes, as the paternal alleles of the E- S DMRs have different DNA sequence than the maternal line. As advised, we have performed additional analysis to compare methylation levels of the E- S DMRs in sperm, egg, zygote, seedling and panicle of the paternal lines (Fig S6). The sperm methylation of the E- S DMRs (in the hybrid context) is already close to the vegetative (shoot and panicle) tissues of the paternal line. DNA methylations in egg and sperm are differentially remodeled as shown in Fig S1 of this work and in Zhou et al 2021 Mol Plant, which can be also observed in the present Fig S6 (where only the E- S DMRs are considered). The data confirm that in the zygote the paternal methylation of the DMRs is remodeled to match the maternal allele levels rather than the levels in vegetative tissues of the parental line. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[161, 95, 839, 451]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 475, 820, 519]]<|/det|> +
Fig. S6: DNA methylation levels of the hybrid parental gametes DMR in paternal reproductive cells and tissues.
+ +<|ref|>text<|/ref|><|det|>[[149, 544, 388, 560]]<|/det|> +We have revised the MS text: + +<|ref|>text<|/ref|><|det|>[[147, 571, 852, 841]]<|/det|> +"To distinguish between paternal methylation reverting to vegetative levels vs. changing to maternal levels in the hybrid zygote, we analyzed the methylation levels of the E – S DMRs in sperm, egg, zygote, shoot and panicles of the paternal lines used to produce the three hybrids (ZM, MZ and ZHM). We observed that the methylation levels of the DMRs in sperm were similar to shoot and panicle of the 3 paternal lines (Supplementary Fig. 6a-c). DNA methylations in egg and sperm of inbred lines are differentially remodeled (Supplementary Figure 1) \(^{20}\) . These observations suggested that the paternal alleles of the E – S CG and CHG DMRs were remodeled to match the levels of the maternal alleles rather than to restore to the vegetative levels in the zygote." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 88, 853, 358]]<|/det|> +In order to make the claim that DNA methylation remodeling is maternal- based, the authors need to exclude the more likely possibility that DNA methylation is simply being re- established to vegetative levels based on cis- regulatory information coded in the DNA. A cis- regulatory mechanism of DNA methylation reestablishment would also explain why the maternal shift occurs for CG and CHG but not CHH methylation which depends on trans- acting factors. The genotype- dependent methylation patterns are demonstrated in Figure 3, however, the authors label this as parental effects instead of genotype effects. Excluding re- establishment of vegetative methylation could potentially be performed with additional analyses of existing data, however it may require additional experiments to demonstrate persuasively. + +<|ref|>text<|/ref|><|det|>[[147, 394, 855, 663]]<|/det|> +Response: We thank the reviewer for the comments. In our reply to the previous comment of the reviewer we have provide data confirming the results (shown in Fig 2) that in the hybrid zygote, the paternal methylation of the E- S DMRs are remodeled to the levels of the maternal alleles (Fig 2). In Fig 3 we show that at Globular Embryo (GE) stage, the parental methylation difference (or E- S DMR) is reestablished. We agree that the reestablishment at GE stage may be based on a cis- regulatory mechanism, as we mentioned in the last part of the discussion section. In the context of hybrid, 'parental allelic difference' is in fact 'DNA sequence difference'. We have changed 'parental allelic- specific' to 'parental allelic or sequence- specific' in the discussion section. + +<|ref|>text<|/ref|><|det|>[[148, 700, 851, 774]]<|/det|> +In addition to the major problem of the data not matching the main point of the paper, there are several smaller cases of the text of the manuscript not matching or oversimplifying the results shown on figures. I have listed these examples below. + +<|ref|>text<|/ref|><|det|>[[148, 792, 850, 838]]<|/det|> +Line 64 – PCA shows separation by genotype before cell type. Please rewrite to reflect observations. + +<|ref|>text<|/ref|><|det|>[[147, 876, 848, 894]]<|/det|> +Response: Thanks for the point. We have rewritten the statement in the revised + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 92, 214, 106]]<|/det|> +version. + +<|ref|>text<|/ref|><|det|>[[148, 117, 850, 163]]<|/det|> +"Principal component analysis revealed a high reproducibility of the replicates and a clear difference between the two parental lines" + +<|ref|>text<|/ref|><|det|>[[148, 200, 850, 247]]<|/det|> +Line 66 – Boxplots show slightly lower CG for sperm in one genotype but higher CG in the other genotype. CHG is very similar. + +<|ref|>text<|/ref|><|det|>[[148, 283, 852, 358]]<|/det|> +Response: Thanks. We have rewritten the statement in the revised version. "Boxplots indicated that sperm cells showed globally lower CHG methylation (mCHG) than egg cells in TEs" + +<|ref|>text<|/ref|><|det|>[[148, 394, 850, 440]]<|/det|> +Line 78 – Only some of the bars show that “more than half of DMRs concerned non- TE regions. + +<|ref|>text<|/ref|><|det|>[[148, 477, 852, 608]]<|/det|> +Response: We have revised the statement in the revised version. "Scanning differentially methylated regions (DMRs, within 50- bp windows with the cutoff of methylation difference at \(\mathrm{CG} > 0.5\) , \(\mathrm{CHG} > 0.3\) , and \(\mathrm{CHH} > 0.1\) , \(P < 0.05\) ) between the gametes and zygotes revealed that about a third or more of the DMRs concerned non- transposable element (non- TE) regions" + +<|ref|>text<|/ref|><|det|>[[148, 644, 608, 662]]<|/det|> +Line 87 – Methylation was higher for genes but not TEs. + +<|ref|>text<|/ref|><|det|>[[148, 700, 850, 774]]<|/det|> +Response: We have revised the statement in the revised version. "In the hybrid zygotes, the methylation levels appeared higher than in the male and female gametes, particularly at genic CG and CHG sites" + +<|ref|>text<|/ref|><|det|>[[148, 810, 850, 885]]<|/det|> +Line 200 – The figures do not look “overall higher” in all regions, but does look marginally higher in upstream and downstream regions. Error bars or other stats on the metaplots would help clarify if the signal here is significant. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 89, 850, 135]]<|/det|> +Response: Thanks for the comments. We have rewritten the sentence in the revised version. + +<|ref|>text<|/ref|><|det|>[[148, 145, 750, 164]]<|/det|> +"and displayed lower mCHH in egg than in sperm in the upstream region" + +<|ref|>text<|/ref|><|det|>[[148, 199, 850, 246]]<|/det|> +Line 206 – What is meant by “comparable numbers”? It looks like fewer MEGs and PEGs than zygotes. + +<|ref|>text<|/ref|><|det|>[[147, 282, 852, 380]]<|/det|> +Response: The “comparable numbers” is referring to the numbers of paternal allelic- specific (P- ASEGs: ZM [n = 903], MZ [n = 1150]) or maternal allelic- specific expressed genes (M- ASEGs; ZM [n = 1883], MZ [n = 1680]) in ZM and MZ GE. We have revised the statement in the revised version. + +<|ref|>text<|/ref|><|det|>[[149, 390, 350, 408]]<|/det|> +"similar numbers" + +<|ref|>text<|/ref|><|det|>[[147, 448, 853, 720]]<|/det|> +Finally, the authors analyze parent- of- origin biased gene expression and conclude that expression patterns are dynamic and shift between MEGs, PEGs, and non- imprint. However, these calls are only described as discreet data. The problem with this is that imprinting calls are typically based on a small number of allele- specific reads, and a change from, for example, MEG to not imprinted can reflect a real change in allelic expression, a loss of expression of the expressed allele, or most often, it can reflect a subtle change that is no longer called significant without necessarily reflecting the biology. In order to conclude that imprinting is dynamic in these early stages, the authors need to demonstrate that the change in patterns is real and not an artifact of small numbers of reads. + +<|ref|>text<|/ref|><|det|>[[148, 756, 483, 774]]<|/det|> +Response: We have deleted the sentence. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 415, 97]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 112, 832, 168]]<|/det|> +The results and analysis reported in this manuscript constitute a major advance in our understanding of the epigenetic regulation of parent- of- origin contributions to early embryogenesis. I am satisfied with the authors' response to my comments and I recommend publication of this manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 182, 822, 210]]<|/det|> +While I was reading the manuscript, I noticed that reference 13 is incomplete, the complete reference should be: + +<|ref|>text<|/ref|><|det|>[[119, 224, 864, 265]]<|/det|> +(13) Alaniz-Fabián J, Orozco-Nieto A, Abreu-Goodger C, Gillmor CS. Hybridization alters maternal and paternal genome contributions to early plant embryogenesis. Development (2022) 149 (22): dev201025. + +<|ref|>text<|/ref|><|det|>[[119, 294, 415, 308]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 322, 530, 336]]<|/det|> +The authors have adequately addressed my concerns. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 89, 406, 108]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[148, 145, 461, 162]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 199, 851, 301]]<|/det|> +The results and analysis reported in this manuscript constitute a major advance in our understanding of the epigenetic regulation of parent- of- origin contributions to early embryogenesis. I am satisfied with the authors' response to my comments and I recommend publication of this manuscript. + +<|ref|>text<|/ref|><|det|>[[147, 339, 850, 385]]<|/det|> +While I was reading the manuscript, I noticed that reference 13 is incomplete, the complete reference should be: + +<|ref|>text<|/ref|><|det|>[[147, 421, 850, 496]]<|/det|> +(13) Alaniz-Fabian J, Orozco-Nieto A, Abreu-Goodger C, Gillmor CS. Hybridization alters maternal and paternal genome contributions to early plant embryogenesis. Development (2022) 149 (22): dev201025. + +<|ref|>text<|/ref|><|det|>[[147, 533, 682, 551]]<|/det|> +Response: Thanks, we have completed the reference information. + +<|ref|>text<|/ref|><|det|>[[148, 590, 460, 606]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 644, 579, 662]]<|/det|> +The authors have adequately addressed my concerns. + +<|ref|>text<|/ref|><|det|>[[147, 700, 483, 717]]<|/det|> +Response: Thank you for the comments! + +<--- Page Split ---> diff --git a/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/images_list.json b/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..4298b49cb4e92fd58a57eff3bc628f51ece22182 --- /dev/null +++ b/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,312 @@ + +# nature portfolio + +Peer Review File + +Light- triggered and phosphorylation- dependent 14- 3- 3 association with NON- PHOTOTROPIC HYPOCOTYL 3 is required for hypocotyl phototropism + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The paper by Reuter et al. presents impressive work aimed at the characterization of NPH3 functioning in seedlings. Two major findings, the nature of NPH3 interaction with the plasma membrane and light- dependent phosphorylation of NPH3 followed by 14- 3- 3 binding are of primary interest to the researcher community. + +Microscopic observations are of primary importance for conclusions raised in this paper. However, some panels lack images showing the localization patterns of wild- type NPH3 in particular experiments. This is important as transient transformation of N. benthamiana is sensitive to the state of plants and thus the control line should be always included as a reference to show that the observed differences in localization stem from mutagenesis of the protein itself. I would also like to ask for three biological replicates of physiological assays using the NPH3 expressing lines. + +Before I recommend this paper for publishing, I would like to ask for a rearrangement of figure panels. The story presented in the paper is consistent, however extremely difficult to follow, due to figure panels inconsistency. It very inconvenient to follow the data presented in several figures simultaneously. The figures should be prepared in such a way that the reader can refer to them in a sequence and does not need to jump between their fragments. Figure numbering should in general match the text of the manuscript. Also, figure legends are not clear enough to me, as the description tends to merge quite different experiments. Descriptions should also refer in detail to what is presented on figures and be self- explanatory. The word antepenultimate is not intuitive and I would like to ask for a different expression. + +Detailed comments: + +Fig.1,A,D Please provide control images. + +Fig 1B. Please indicate GST: NPH3- S774D in the figure legend. + +Line 115. Please refer in the full name to the analyzed fusion proteins for example GST: NPH3- C51 so it is easier to refer to the figures. + +Line 140. Were the mutations in the replacement variants of NPH3 introduced into the whole mutated proteins or only the C51 fragment? Please clarify the description in the text and the figure legend. + +Line 146. Please refer precisely to mutesins used. + +Fig.2B. Were the proteins tagged with GST (figure legend) or HA (marked on the figure)? + +Fig.2D. Please indicate the localization of wild- type NPH3 in the appropriate control lines. I do not like the idea of comparing the localization of proteins fused with different fluorescent protein tags, as in our hands GFP and RFP show different expression levels and sensitivity to photobleaching which affects the signal intensities. I am afraid that comparing the localization of proteins fused with different fluorescent protein tags may lead to biased assessments. + +<--- Page Split ---> + +Line 159. Why interactions with omega 14- 3- 3 are shown in figure 3A, but 14- 3- 3 epsilon: GFP is further analyzed by MS? The IP experiments are done for the 14- 3- 3 omega, but this is not indicated in the text + +Fig.3B, D. Please indicate the type of 14- 3- 3 in the figure and in the text. + +Line 190. Please comment on why phosphomimic variants do not allow for 14- 3- 3 binding. + +Line 219- 220. Please rephrase this sentence. + +Line 224. Please indicate the wavelength for the GFP laser. + +Line 269- 270. Please indicate the reference. + +Fig. 4A. Please provide data from 3 biological replicates. Similarly for Fig. S3A. + +Fig. 4F, G. Please indicate the number of analyzed cells. + +Fig.6B. Please add GFP- NPH3 localization in the control line. + +Fig.6D. Please indicate what unbound/bound means in the figure legend. + +Line 470- 471. Please describe the treatments in the M and M sections as well. + +Fig. S2. For colocalization studies please provide images also from separate channels. + +Reviewer #2 (Remarks to the Author): + +The authors present truly outstanding results. Their work revolutionises out current understanding of the molecular basis for phototropism. They present results that not only solve the long standing mystery of how NPH3 attaches to membranes, but go on to show is exquisite detail how NPH3- membrane localisation is regulated and how this impacts on NPH3 function. This MS will have a profound impact on the field. The MS is already looking great, but as a reviewer it is my role to point out some areas that I think could be improved and so I detail these below. + +The methodology in the paper is innovative and yet sound. In the methods section, several techniques are cited, rather than described. To ensure reproducibility, please describe these methods. In some instances, inappropriate statistical tests are used. The statistical tests used do not correct for multiple testing and so other tests (e.g. 1- way ANOVA with a post hoc test) may be more appropriate. Some continuous data are presented as histograms, where violin/ box plots would give the reader a better understanding of the variation in these experiments. + +<--- Page Split ---> + +Most of the conclusions in the MS are completely well founded. I did however find a few areas where language could be tightened or a more appropriate control could have been used: + +Figure 2D: Why did the authors use different FP for these experiments? As the authors note, laser excitation of GFP also effects NPH3 localisation. To make comparisons between the localisation of these truncated proteins it would be beneficial to use the same FP. + +Fig 3A. It's interesting that the binding of 14:3:3 to NPH3 also occurs in yeast. Do the authors have any suggestions of how plant- specific NPH3 (presumably) becomes phosphorylated in the absence of phot1? + +Line 311: "General' dephosphorylation of NPH3 is thus not coupled to PM dissociation. Moreover, it is neither a prerequisite nor a consequence of condensate assembly, rather it seems to require prior light- triggered and S744 phosphorylation- dependent 14- 3- 3 association". While I am sympathetic to the hypothesis put forward by the authors, strictly speaking they do not show that association of 14:3:3 is required for NPH3 de- phosphorylation. Rather they show that BL- dependent phosphorylation of S744 is required for general de- phosphorylation AND for the association of 14:3:3. If they want to make the current conclusion they need to show that general de- phos does not occur in the absence of 14:3:3s. Given the highly redundant function of 14:3:3s, this is no small task. The easiest solution would be to moderate this conclusion (also for the statements in line 347, 399 and the general conclusions). + +Figure 6C. GFP:NPH3- 4K/A appears to run on the gel as a 'general dephosphorylated' NPH3. Does that not imply that cytosolic localisation is sufficient for general dephosphorylation? How does this square with the results presented in Figure 5D? + +Line 377: I don't follow how the residual function of NPH3- S744A can be explained by redundancy with RPT2. The NPH3- S744A construct rescues phototropism in the nph3- 7 background. The most simple explanation is that NPH3- S744A still retains some function. + +In addition to these remarks, I also had a few suggestions for where I think that the MS could be modified to enhance fullness and readability: + +Line 42: The authors should cite studies showing phot1 transphosphorylation ie. BLUS1, CBC1, ABCD19 and PSK4 + +Line 119: I this is referring to RFP- constructs (1D) and GFP constructs (S2A)? + +<--- Page Split ---> + +The figure legends could be simplified. Currently, several sub- figures are referred to within the same heading. For example: "(Figure 3. B, D) In vivo interaction of mCherry: NPH3 variants and 14- 3- 3 omega:mEGFP in transiently transformed N. benthamiana leaves. Expression of transgenes was driven by the 35S promoter. Freshly transformed tobacco plants were either kept under constant light for 42 h (B) or kept under constant light for 24 h and subsequently transferred to darkness for 17h with (BL) or without (D) blue light treatment (5 μmol m- 2 sec- 1 912 ) for the last 40 minutes (D)". It would be a lot easier for the reader to follow if the legend for B and D was separated. This will inevitably require some repetition, but the legend will become much clearer as a result. + +Line 179: mostly + +Line 200: suggesting (indicating is too strong) + +Line 305: neither NPH3 variant? + +It took my a little while to understand summary figure 6E. It might help to clearly separate the 3 panels and to label them as wild type NPH3 and constitutive membrane- bound / unbound variants. + +Line 397: 'also in plants' is not necessary (any more than also in bacteria, also in animals etc)! + +Best wishes, + +Scott Hayes + +<--- Page Split ---> + +We would like to thank the Referees for constructive comments that helped us to improve our MS. Below are point- by- point replies to all Referee queries and explanations for changes we have made to the original MS. To facilitate assessment, we have copied reviewer's queries (Q) ahead of our replies (R): + +## Reply to comments of Referee 1: + +Q1: Microscopic observations are of primary importance for conclusions raised in this paper. However, some panels lack images showing the localization patterns of wild- type NPH3 in particular experiments. This is important as transient transformation of N. benthamiana is sensitive to the state of plants and thus the control line should be always included as a reference to show that the observed differences in localization stem from mutagenesis of the protein itself. + +R1: We now included images showing the localization pattern of the respective NPH3 control in all figure panels displaying CLSM analyses (Fig 1, 2, 4, 5, 7, Supplementary Fig. 2, 3, 4). + +Q2: I would also like to ask for three biological replicates of physiological assays using the NPH3 expressing lines. + +R2: We performed a third biological replicate of the analysis of the phototropic response in all control and transgenic lines expressing GFP:NPH3 variants under control of the 35S promoter (endogenous promoter see below). The data as well as the data analysis are available in a separate source data Excel document referred to as 'source data phototropism' (sheet I to III: 35S nph3- 7 phototropism). We, however, faced a germination problem with nph3- 7 line #5 expressing GFP:NPH3- S744A under control of the endogenous promoter (see previous Fig. S3 A). We therefore have chosen another transgenic nph3- 7 line expressing pNPH3::GFP:NPH3- S744A (# 13, see Supplementary Fig. 4 in the revised manuscript) for further analysis. The subcellular localization of the transgene both in darkness and upon blue light treatment was examined. Furthermore, three biological replicates with the transgenic nph3- 7 lines expressing pNPH3 driven constructs, alongside with the controls were performed. The data as well as the data analysis are available in the abovementioned source data Excel document (sheet IV to VI: pNPH3 nph3- 7 phototropism). + +Q3: Before I recommend this paper for publishing, I would like to ask for a rearrangement of figure panels. The story presented in the paper is consistent, however extremely difficult to follow, due to figure panels inconsistency. It very inconvenient to follow the data presented in several figures simultaneously. The figures should be prepared in such a way that the reader can refer to them in a sequence and does not need to jump between their fragments. Figure numbering should in general match the text of the manuscript. + +R3: Figures and figure panels were completely rearranged so that Figure numbering matches the text of the main manuscript. + +Q4: Also, figure legends are not clear enough to me, as the description tends to merge quite different experiments. Descriptions should also refer in detail to what is presented on figures and be self- explanatory. + +R4: Figure legends were separated and simplified, including enough information to understand the figure without referring to the main text. + +Q5: The word antepenultimate is not intuitive and I would like to ask for a different expression. + +R5: The word antepenultimate was replaced by 'third last'. + +<--- Page Split ---> + +## Detailed comments Referee 1: + +Q6: Fig.1,A,D Please provide control images. + +R6: Control images are now shown in Fig. 1a and Fig. 1d (see R1). + +Q7: Fig 1B. Please indicate GST: NPH3- S774D in the figure legend. + +R7: Due to figure rearrangement (see R3) the lipid overlay assay performed with GST:NPH3- C51- S744D is now shown in Fig. 4c. The analyzed protein is mentioned in the figure legend. + +Q8: Line 115. Please refer in the full name to the analyzed fusion proteins for example GST: NPH3- C51 so it is easier to refer to the figures. + +R8: In all cases, we now referred to the full name of the studied fusion proteins. For instance, GST:NPH3- C51 is mentioned in line 121. + +Q9: Line 140. Were the mutations in the replacement variants of NPH3 introduced into the whole mutated proteins or only the C51 fragment? Please clarify the description in the text and the figure legend. Line 146. Please refer precisely to mutiens used. + +Fig.2B. Were the proteins tagged with GST (figure legend) or HA (marked on the figure)? + +R9: Thanks for pointing this out. We realized that the previous figure legend 2(B) was not correct. In fact, the mutations were introduced in both the HA- tagged full- length NPH3 protein and the GST- NPH3- C51 fusion protein. While the first- mentioned protein was used for lipid overlay assays (Fig. 2b), liposome binding assays were performed by using the GST- NPH3- C51 variants (Fig. 2c). This is now clearly indicated in the main text (line 146) as well as the legend of Fig. 2. + +Q10: Fig.2D. Please indicate the localization of wild- type NPH3 in the appropriate control lines. I do not like the idea of comparing the localization of proteins fused with different fluorescent protein tags, as in our hands GFP and RFP show different expression levels and sensitivity to photobleaching which affects the signal intensities. I am afraid that comparing the localization of proteins fused with different fluorescent protein tags may lead to biased assessments. + +R10: As already mentioned (R1) we now included images showing the localization pattern of the respective NPH3 control in all figure panels displaying CLSM analyses. Furthermore, we analyzed the localization of 35S::RFP:NPH3- 5KR/A in darkness - a representative image is now shown for comparison with other RFP- tagged NPH3 variants in Fig. 2d. + +Q11: Line 159. Why interactions with omega 14- 3- 3 are shown in figure 3A, but 14- 3- 3 epsilon: GFP is further analyzed by MS? The IP experiments are done for the 14- 3- 3 omega, but this is not indicated in the text Fig.3B, D. Please indicate the type of 14- 3- 3 in the figure and in the text. + +R11: We now included yeast two hybrid assays performed with the 14- 3- 3 isoform epsilon (belonging to the epsilon group) to demonstrate that members of both phylogenetic 14- 3- 3 groups (isoform omega belongs to the non- epsilon group, Fig. 3a, Supplementary Fig. 5a) interact with NPH3 (Supplementary Fig. 4a) as well as other NRL proteins (Supplementary Fig. 5b). In each case, the type of 14- 3- 3 isoform is indicated in the figure and in the text. Within the main text, we inserted the following statement (lines 170- 174): 'A yeast two hybrid screen performed in our lab (see 39) identified NPH3 as putative interactor of several Arabidopsis 14- 3- 3 isoforms, among those representatives of both phylogenetic 14- 3- 3 groups, the non- epsilon group (isoform omega, Fig. 3a) and the epsilon group (isoform epsilon, Supplementary Fig. 4a)'. In contrast to phot1 8 14- 3- 3 isoform specificity was thus not observed for binding to NPH3.' + +<--- Page Split ---> + +Q12: Line 190. Please comment on why phosphomimic variants do not allow for 14- 3- 3 binding. + +R12: The requested information has been added (lines 204- 207): 'Phosphomimic variants (NPH3- S744D/S744E), however, do not allow for 14- 3- 3 binding (Fig. 3a, Supplementary Fig. 4a), consistent with the general finding that aspartate and glutamate do not provide good phosphomimetic residues with respect to 14- 3- 3 binding 45. ' + +Q13: Line 219- 220. Please rephrase this sentence. + +R13: The sentence was rephrased (lines 238- 241): 'Altogether, the C- terminal domain serves a dual function in determining the subcellular localization of NPH3 since it comprises both the amphipathic helix required for phospholipid- dependent PM association in darkness and the 14- 3- 3 binding motif mediating BL- triggered PM dissociation.' + +Q14: Line 224. Please indicate the wavelength for the GFP laser. + +R14: The wavelength is indicated (line 244- 246). + +Q15: Line 269- 270. Please indicate the reference. + +R15: The reference is indicated (line 295). + +Q16: Fig. 4A. Please provide data from 3 biological replicates. Similarly for Fig.S3A. + +R16: We performed three biological replicates for the analysis of the phototropic response (see R2). The graphs shown in Fig. 4a, Fig. 7a (previous Fig. 6A) and Supplementary Fig. 4b represent data from a single experiment. Source data for all biological replicates including data analysis are provided with this paper (separate source data Excel document 'source data phototropism', see R2). + +Q17: Fig. 4F, G. Please indicate the number of analyzed cells. + +R17: As (already) indicated in the figure legend (now Fig. 5 d- f) a single cell time lapse imaging of RFP: NPH3 condensation was performed. This single cell experiment was repeated five times and is described in the 'Material and Methods' section as follows (lines 706- 710): 'PM- detachment was induced by means of the GFP- laser (488 nm) and image acquisition (RFP- laser) was done for the duration of 32 min by scanning 30 consecutive planes along the Z axis covering the entire thickness of an epidermal cell. Z- projection was done for each 3.5 min interval. Five replicates were performed.' + +Q18: Fig.6B. Please add GFP- NPH3 localization in the control line. + +R18: GFP: NPH3 localization in the control line has been added (now Fig. 7 b) (see R1). + +Q19: Fig.6D. Please indicate what unbound/bound means in the figure legend. + +R19: We exchanged unbound/bound for flowthrough/precipitate (IP) and indicated the meaning in the figure legend (now Fig. 7d). + +Q20: Line 470- 471. Please describe the treatments in the M and M sections as well. + +R20: The light treatments are now described in the M and M section as well (lines 500- 503 for transgenic Arabidopsis seedlings, lines 510- 514 for N. benthamiana). + +<--- Page Split ---> + +Q21: Fig. S2. For colocalization studies please provide images also from separate channels. + +R21: The colocalization studies shown in the previous Fig. S2 are now available in Supplementary Fig. 3, alongside with the separate channels. + +## Reply to comments of Referee 2: + +Q1: The methodology in the paper is innovative and yet sound. In the methods section, several techniques are cited, rather than described. To ensure reproducibility, please describe these methods. + +R1: We now described the majority of methods in detail. + +In rare cases we, however, precisely followed a step- by- step protocol (i.e. data analysis of single cell time lapse imaging). On that condition, we just cited the corresponding protocol. + +Q2: In some instances, inappropriate statistical tests are used. The statistical tests used do not correct for multiple testing and so other tests (e.g. 1- way ANOVA with a post hoc test) may be more appropriate. Some continuous data are presented as histograms, where violin/ box plots would give the reader a better understanding of the variation in these experiments. + +R2: With respect to the analysis of the phototropic response (Fig. 4a, Fig. 7a, Supplementary Fig. 4b in the revised manuscript) we now performed one- way ANOVA with Tukey's post hoc test and presented the data as box plots. The data as well as the data analysis are available in a separate source data Excel document referred to as 'source data phototropism'. + +Q3: Most of the conclusions in the MS are completely well founded. I did however find a few areas where language could be tightened or a more appropriate control could have been used: Figure 2D: Why did the authors use different FP for these experiments? As the authors note, laser excitation of GFP also effects NPH3 localisation. To make comparisons between the localisation of these truncated proteins it would be beneficial to use the same FP. + +R3: We completely agree and thus analyzed the localization of 35S::RFP:NPH3- 5KR/A in darkness - a representative image is now shown for comparison with other RFP- tagged NPH3 variants in Fig. 2d. + +Q4: Fig 3A. It's interesting that the binding of 14:3:3 to NPH3 also occurs in yeast. Do the authors have any suggestions of how plant- specific NPH3 (presumably) becomes phosphorylated in the absence of phot1? + +R4: Beyond any doubt, this is an interesting observation and here, we just can speculate. We now discuss this issue as follows (lines 207- 211): 'Considering that constitutive 14- 3- 3 complex formation of other plant targets characterized by a C- terminal binding site, such as the H+-ATPase or the transcription factor FD, has been observed in yeast 46, 47, light- independent NPH3:14- 3- 3 interaction in yeast (Fig. 3a, Supplementary Fig. 4a) might arise from a promiscuous kinase with a certain preference for terminal motifs.' + +Q5: Line 311: "General' dephosphorylation of NPH3 is thus not coupled to PM dissociation. Moreover, it is neither a prerequisite nor a consequence of condensate assembly, rather it seems to require prior light- triggered and S744 phosphorylation- dependent 14- 3- 3 association". While I am sympathetic to the hypothesis put forward by the authors, strictly speaking they do not show that association of 14:3:3 is required for NPH3 de- phosphorylation. Rather they show that BL- dependent phosphorylation of S744 is required for general de- phosphorylation AND for the association of 14:3:3. If they want to make the current conclusion they need to show that general de- phos does not occur in the absence of 14:3:3s. Given the highly redundant function of 14:3:3s, this is no small task. The easiest solution would be to moderate this conclusion (also for the statements in line 347, 399 and the general conclusions). + +<--- Page Split ---> + +R5: Yes, from a strict point of view, this is absolutely correct! We therefore moderated our conclusion. Lines 334- 340: 'Moreover, it is neither a prerequisite nor a consequence of condensate assembly, rather it requires prior light- triggered S744 phosphorylation and potentially 14- 3- 3 association (Fig. 6a, d). Taken together, we suggest that BL- induced phosphorylation of S744 provokes (i) 14- 3- 3 association which releases NPH3 from the PM into the cytosol and (ii) 'general' dephosphorylation of NPH3'. + +Q6: Figure 6C. GFP:NPH3- 4K/A appears to run on the gel as a 'general dephosphorylated' NPH3. Does that not imply that cytosolic localisation is sufficient for general dephosphorylation? How does this square with the results presented in Figure 5D? + +R6: This observation puzzled us as well. Nevertheless, provided that 'general dephosphorylation' is not coupled to PM dissociation (Q5, see above) there is another explanation for the electrophoretic mobility of this NPH3 mutant that most likely is incapable of PM association following translation: 'general' phosphorylation of NPH3 might take place at the PM! This possibility is now mentioned in lines 350- 353: 'Worth mentioning, the electrophoretic mobility of GFP:NPH3- 4K/A corresponded to the dephosphorylated version of NPH3 and was not modified by light treatment (Fig. 7c), suggesting that 'general' phosphorylation of NPH3 might take place at the PM.' + +Q7: Line 377: I don't follow how the residual function of NPH3- S744A can be explained by redundancy with RPT2. The NPH3- S744A construct rescues phototropism in the nph3- 7 background. The most simple explanation is that NPH3- S744A still retains some function. + +R7: I am sorry for this! Of course, residual activity of NPH3- S744A cannot be explained by redundancy with RPT2! We, however, have to keep in mind, that NPH3- S744A is permanently present at the PM. Therefore, the possibility exists that it functions together with RPT2 or other NRL family members. We now rephrased the sentence (lines 406- 408): 'Residual functionality might be due to co- action of this constitutively PM- associated NPH3 mutant with certain members of the NRL protein family.' + +Q8: In addition to these remarks, I also had a few suggestions for where I think that the MS could be modified to enhance fullness and readability: Line 42: The authors should cite studies showing phot1 transphosphorylation ie. BLUS1, CBC1, ABCD19 and PSK4 + +R8: The phot1 substrates known so far are now mentioned in the Introduction (lines 42- 46). + +Q9: Line 119: I this is referring to RFP- constructs (1D) and GFP constructs (S2A)? + +R9: In fact, the (previously misleading) statement should refer to both constructs. This has been rephrased (lines 127- 129): 'As expected, transient expression of RFP/GFP:NPH3ΔC51 in N. benthamiana (35S or native promoter) revealed loss of PM recruitment in the dark, as evident by the presence of discrete bodies in the cytosol (Fig. 1d, Supplementary Fig. 2c). + +Q10: The figure legends could be simplified. Currently, several sub- figures are referred to within the same heading. For example: "(Figure 3. B, D) In vivo interaction of mCherry:NPH3 variants and 14- 3- 3 omega:mEGFP in transiently transformed N. benthamiana leaves. Expression of transgenes was driven by the 35S promoter. Freshly transformed tobacco plants were either kept under constant light for 42 h (B) or kept under constant light for 24 h and subsequently transferred to darkness for 17h with (BL) or without (D) blue light treatment (5 μmol m- 2 sec- 1 912 ) for the last 40 minutes (D)". It would be a lot easier for the reader to follow if the legend for B and D was separated. This will inevitably require some repetition, but the legend will become much clearer as a result. + +R10: Figure legends were separated and simplified, including enough information to understand the figure without referring to the main text. + +<--- Page Split ---> + +Q11: Line 179: mostly + +R11: This has been modified (line 193). + +Q12: Line 200: suggesting (indicating is too strong) + +R12: 'Indicating' has been exchanged for 'suggesting' (line 220). + +Q13: Line 305: neither NPH3 variant? + +R13: NO, definitively not! To avoid confusion the sentence was rephrased (line 330): 'Despite the fact that both NPH3 variants constitutively localized to cytosolic condensates (Fig. 1a, Fig. 5c)....' + +Q14: It took my a little while to understand summary figure 6E. It might help to clearly separate the 3 panels and to label them as wild type NPH3 and constitutive membrane- bound / unbound variants. + +R14: Thanks for pointing this out! We now (Fig. 7e) separated the 3 panels and listed the appropriate NPH3 variants at the bottom of the individual panels. + +Q15: Line 397: 'also in plants' is not necessary (any more than also in bacteria, also in animals etc)! + +R15: We deleted it (line 427). + +With best regards, also on behalf of my co- authors, Claudia Oecking + +![PLACEHOLDER_10_0] + + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +I would like to thank the Authors for providing answers to my questions. I appreciate the time and effort they have taken to improve the manuscript. I admire the comprehensive attitude to the science presented in this study. I fully recommend this paper for publishing in Nature Communications. + +If possible, I would like to ask for small additions during the manuscript processing: + +Lines 42- 45, please add the abbreviated names of proteins. + +Fig.4F Please show also the green channel separately. + +M&M Please provide the Catalog Numbers for antibodies. + +Reviewer #2 (Remarks to the Author): + +The authors have taken my comments on board and I am pleased the new format of the MS. I would therefore like to recommend this MS for publication. + +Apologies for not noticing it in the previous MS, but I just spotted something in Figure 7C. GFP- NPH3- 4K/A does unexpectedly show some phosphorylation of S744, despite it being located in the cytoplasm. I guess that PM localised phot1 still is still able to phosphorylate a small proportion of cytosolic NPH3, thus explaining the partial phosphorylation. The fact that GFP- NPH3- 4K/A is phosphorylated and cytoplasmic and yet still not functional actually lends even more weight to the authors hypothesis that it is the cycling is of NPH3 is essential for its function. Please note that I'm only raising this observation because I have the opportunity to do so. The authors shouldn't feel at all obliged to discuss it in the MS if they feel that it is not warranted! + +Again, congratulations on the MS, really nice work! + +Best wishes, + +Scott Hayes + +<--- Page Split ---> diff --git a/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..05e6eb0222559b1f1162663027febc615803dc29 --- /dev/null +++ b/peer_reviews/9937ad734a3858e02f648619b966cc973f874dbf719528959aedd62faea1712d/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,439 @@ +<|ref|>title<|/ref|><|det|>[[99, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[106, 161, 894, 250]]<|/det|> +Light- triggered and phosphorylation- dependent 14- 3- 3 association with NON- PHOTOTROPIC HYPOCOTYL 3 is required for hypocotyl phototropism + +<|ref|>image<|/ref|><|det|>[[93, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[270, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 350, 106]]<|/det|> +REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 147, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 870, 275]]<|/det|> +The paper by Reuter et al. presents impressive work aimed at the characterization of NPH3 functioning in seedlings. Two major findings, the nature of NPH3 interaction with the plasma membrane and light- dependent phosphorylation of NPH3 followed by 14- 3- 3 binding are of primary interest to the researcher community. + +<|ref|>text<|/ref|><|det|>[[115, 286, 880, 395]]<|/det|> +Microscopic observations are of primary importance for conclusions raised in this paper. However, some panels lack images showing the localization patterns of wild- type NPH3 in particular experiments. This is important as transient transformation of N. benthamiana is sensitive to the state of plants and thus the control line should be always included as a reference to show that the observed differences in localization stem from mutagenesis of the protein itself. I would also like to ask for three biological replicates of physiological assays using the NPH3 expressing lines. + +<|ref|>text<|/ref|><|det|>[[114, 406, 880, 570]]<|/det|> +Before I recommend this paper for publishing, I would like to ask for a rearrangement of figure panels. The story presented in the paper is consistent, however extremely difficult to follow, due to figure panels inconsistency. It very inconvenient to follow the data presented in several figures simultaneously. The figures should be prepared in such a way that the reader can refer to them in a sequence and does not need to jump between their fragments. Figure numbering should in general match the text of the manuscript. Also, figure legends are not clear enough to me, as the description tends to merge quite different experiments. Descriptions should also refer in detail to what is presented on figures and be self- explanatory. The word antepenultimate is not intuitive and I would like to ask for a different expression. + +<|ref|>text<|/ref|><|det|>[[115, 581, 265, 597]]<|/det|> +Detailed comments: + +<|ref|>text<|/ref|><|det|>[[115, 609, 410, 625]]<|/det|> +Fig.1,A,D Please provide control images. + +<|ref|>text<|/ref|><|det|>[[115, 637, 564, 654]]<|/det|> +Fig 1B. Please indicate GST: NPH3- S774D in the figure legend. + +<|ref|>text<|/ref|><|det|>[[115, 665, 880, 700]]<|/det|> +Line 115. Please refer in the full name to the analyzed fusion proteins for example GST: NPH3- C51 so it is easier to refer to the figures. + +<|ref|>text<|/ref|><|det|>[[115, 712, 870, 747]]<|/det|> +Line 140. Were the mutations in the replacement variants of NPH3 introduced into the whole mutated proteins or only the C51 fragment? Please clarify the description in the text and the figure legend. + +<|ref|>text<|/ref|><|det|>[[115, 758, 470, 775]]<|/det|> +Line 146. Please refer precisely to mutesins used. + +<|ref|>text<|/ref|><|det|>[[115, 787, 761, 804]]<|/det|> +Fig.2B. Were the proteins tagged with GST (figure legend) or HA (marked on the figure)? + +<|ref|>text<|/ref|><|det|>[[115, 815, 878, 906]]<|/det|> +Fig.2D. Please indicate the localization of wild- type NPH3 in the appropriate control lines. I do not like the idea of comparing the localization of proteins fused with different fluorescent protein tags, as in our hands GFP and RFP show different expression levels and sensitivity to photobleaching which affects the signal intensities. I am afraid that comparing the localization of proteins fused with different fluorescent protein tags may lead to biased assessments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 90, 875, 127]]<|/det|> +Line 159. Why interactions with omega 14- 3- 3 are shown in figure 3A, but 14- 3- 3 epsilon: GFP is further analyzed by MS? The IP experiments are done for the 14- 3- 3 omega, but this is not indicated in the text + +<|ref|>text<|/ref|><|det|>[[115, 137, 643, 155]]<|/det|> +Fig.3B, D. Please indicate the type of 14- 3- 3 in the figure and in the text. + +<|ref|>text<|/ref|><|det|>[[115, 165, 775, 183]]<|/det|> +Line 190. Please comment on why phosphomimic variants do not allow for 14- 3- 3 binding. + +<|ref|>text<|/ref|><|det|>[[115, 194, 441, 210]]<|/det|> +Line 219- 220. Please rephrase this sentence. + +<|ref|>text<|/ref|><|det|>[[115, 221, 545, 238]]<|/det|> +Line 224. Please indicate the wavelength for the GFP laser. + +<|ref|>text<|/ref|><|det|>[[115, 250, 441, 266]]<|/det|> +Line 269- 270. Please indicate the reference. + +<|ref|>text<|/ref|><|det|>[[115, 277, 677, 295]]<|/det|> +Fig. 4A. Please provide data from 3 biological replicates. Similarly for Fig. S3A. + +<|ref|>text<|/ref|><|det|>[[115, 306, 520, 323]]<|/det|> +Fig. 4F, G. Please indicate the number of analyzed cells. + +<|ref|>text<|/ref|><|det|>[[115, 334, 553, 351]]<|/det|> +Fig.6B. Please add GFP- NPH3 localization in the control line. + +<|ref|>text<|/ref|><|det|>[[115, 363, 650, 380]]<|/det|> +Fig.6D. Please indicate what unbound/bound means in the figure legend. + +<|ref|>text<|/ref|><|det|>[[115, 391, 686, 408]]<|/det|> +Line 470- 471. Please describe the treatments in the M and M sections as well. + +<|ref|>text<|/ref|><|det|>[[115, 419, 738, 437]]<|/det|> +Fig. S2. For colocalization studies please provide images also from separate channels. + +<|ref|>text<|/ref|><|det|>[[115, 561, 393, 578]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 617, 881, 727]]<|/det|> +The authors present truly outstanding results. Their work revolutionises out current understanding of the molecular basis for phototropism. They present results that not only solve the long standing mystery of how NPH3 attaches to membranes, but go on to show is exquisite detail how NPH3- membrane localisation is regulated and how this impacts on NPH3 function. This MS will have a profound impact on the field. The MS is already looking great, but as a reviewer it is my role to point out some areas that I think could be improved and so I detail these below. + +<|ref|>text<|/ref|><|det|>[[115, 766, 864, 876]]<|/det|> +The methodology in the paper is innovative and yet sound. In the methods section, several techniques are cited, rather than described. To ensure reproducibility, please describe these methods. In some instances, inappropriate statistical tests are used. The statistical tests used do not correct for multiple testing and so other tests (e.g. 1- way ANOVA with a post hoc test) may be more appropriate. Some continuous data are presented as histograms, where violin/ box plots would give the reader a better understanding of the variation in these experiments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 860, 125]]<|/det|> +Most of the conclusions in the MS are completely well founded. I did however find a few areas where language could be tightened or a more appropriate control could have been used: + +<|ref|>text<|/ref|><|det|>[[115, 165, 877, 218]]<|/det|> +Figure 2D: Why did the authors use different FP for these experiments? As the authors note, laser excitation of GFP also effects NPH3 localisation. To make comparisons between the localisation of these truncated proteins it would be beneficial to use the same FP. + +<|ref|>text<|/ref|><|det|>[[115, 258, 880, 294]]<|/det|> +Fig 3A. It's interesting that the binding of 14:3:3 to NPH3 also occurs in yeast. Do the authors have any suggestions of how plant- specific NPH3 (presumably) becomes phosphorylated in the absence of phot1? + +<|ref|>text<|/ref|><|det|>[[114, 333, 878, 497]]<|/det|> +Line 311: "General' dephosphorylation of NPH3 is thus not coupled to PM dissociation. Moreover, it is neither a prerequisite nor a consequence of condensate assembly, rather it seems to require prior light- triggered and S744 phosphorylation- dependent 14- 3- 3 association". While I am sympathetic to the hypothesis put forward by the authors, strictly speaking they do not show that association of 14:3:3 is required for NPH3 de- phosphorylation. Rather they show that BL- dependent phosphorylation of S744 is required for general de- phosphorylation AND for the association of 14:3:3. If they want to make the current conclusion they need to show that general de- phos does not occur in the absence of 14:3:3s. Given the highly redundant function of 14:3:3s, this is no small task. The easiest solution would be to moderate this conclusion (also for the statements in line 347, 399 and the general conclusions). + +<|ref|>text<|/ref|><|det|>[[115, 535, 864, 590]]<|/det|> +Figure 6C. GFP:NPH3- 4K/A appears to run on the gel as a 'general dephosphorylated' NPH3. Does that not imply that cytosolic localisation is sufficient for general dephosphorylation? How does this square with the results presented in Figure 5D? + +<|ref|>text<|/ref|><|det|>[[115, 628, 869, 683]]<|/det|> +Line 377: I don't follow how the residual function of NPH3- S744A can be explained by redundancy with RPT2. The NPH3- S744A construct rescues phototropism in the nph3- 7 background. The most simple explanation is that NPH3- S744A still retains some function. + +<|ref|>text<|/ref|><|det|>[[115, 722, 820, 758]]<|/det|> +In addition to these remarks, I also had a few suggestions for where I think that the MS could be modified to enhance fullness and readability: + +<|ref|>text<|/ref|><|det|>[[115, 797, 867, 832]]<|/det|> +Line 42: The authors should cite studies showing phot1 transphosphorylation ie. BLUS1, CBC1, ABCD19 and PSK4 + +<|ref|>text<|/ref|><|det|>[[115, 872, 670, 890]]<|/det|> +Line 119: I this is referring to RFP- constructs (1D) and GFP constructs (S2A)? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 117, 875, 264]]<|/det|> +The figure legends could be simplified. Currently, several sub- figures are referred to within the same heading. For example: "(Figure 3. B, D) In vivo interaction of mCherry: NPH3 variants and 14- 3- 3 omega:mEGFP in transiently transformed N. benthamiana leaves. Expression of transgenes was driven by the 35S promoter. Freshly transformed tobacco plants were either kept under constant light for 42 h (B) or kept under constant light for 24 h and subsequently transferred to darkness for 17h with (BL) or without (D) blue light treatment (5 μmol m- 2 sec- 1 912 ) for the last 40 minutes (D)". It would be a lot easier for the reader to follow if the legend for B and D was separated. This will inevitably require some repetition, but the legend will become much clearer as a result. + +<|ref|>text<|/ref|><|det|>[[115, 303, 237, 319]]<|/det|> +Line 179: mostly + +<|ref|>text<|/ref|><|det|>[[115, 359, 447, 376]]<|/det|> +Line 200: suggesting (indicating is too strong) + +<|ref|>text<|/ref|><|det|>[[115, 415, 350, 431]]<|/det|> +Line 305: neither NPH3 variant? + +<|ref|>text<|/ref|><|det|>[[115, 471, 870, 507]]<|/det|> +It took my a little while to understand summary figure 6E. It might help to clearly separate the 3 panels and to label them as wild type NPH3 and constitutive membrane- bound / unbound variants. + +<|ref|>text<|/ref|><|det|>[[115, 546, 797, 564]]<|/det|> +Line 397: 'also in plants' is not necessary (any more than also in bacteria, also in animals etc)! + +<|ref|>text<|/ref|><|det|>[[115, 604, 207, 620]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[115, 661, 203, 677]]<|/det|> +Scott Hayes + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 175, 907, 244]]<|/det|> +We would like to thank the Referees for constructive comments that helped us to improve our MS. Below are point- by- point replies to all Referee queries and explanations for changes we have made to the original MS. To facilitate assessment, we have copied reviewer's queries (Q) ahead of our replies (R): + +<|ref|>sub_title<|/ref|><|det|>[[94, 261, 381, 277]]<|/det|> +## Reply to comments of Referee 1: + +<|ref|>text<|/ref|><|det|>[[92, 297, 905, 368]]<|/det|> +Q1: Microscopic observations are of primary importance for conclusions raised in this paper. However, some panels lack images showing the localization patterns of wild- type NPH3 in particular experiments. This is important as transient transformation of N. benthamiana is sensitive to the state of plants and thus the control line should be always included as a reference to show that the observed differences in localization stem from mutagenesis of the protein itself. + +<|ref|>text<|/ref|><|det|>[[92, 380, 900, 413]]<|/det|> +R1: We now included images showing the localization pattern of the respective NPH3 control in all figure panels displaying CLSM analyses (Fig 1, 2, 4, 5, 7, Supplementary Fig. 2, 3, 4). + +<|ref|>text<|/ref|><|det|>[[92, 427, 901, 457]]<|/det|> +Q2: I would also like to ask for three biological replicates of physiological assays using the NPH3 expressing lines. + +<|ref|>text<|/ref|><|det|>[[91, 470, 911, 653]]<|/det|> +R2: We performed a third biological replicate of the analysis of the phototropic response in all control and transgenic lines expressing GFP:NPH3 variants under control of the 35S promoter (endogenous promoter see below). The data as well as the data analysis are available in a separate source data Excel document referred to as 'source data phototropism' (sheet I to III: 35S nph3- 7 phototropism). We, however, faced a germination problem with nph3- 7 line #5 expressing GFP:NPH3- S744A under control of the endogenous promoter (see previous Fig. S3 A). We therefore have chosen another transgenic nph3- 7 line expressing pNPH3::GFP:NPH3- S744A (# 13, see Supplementary Fig. 4 in the revised manuscript) for further analysis. The subcellular localization of the transgene both in darkness and upon blue light treatment was examined. Furthermore, three biological replicates with the transgenic nph3- 7 lines expressing pNPH3 driven constructs, alongside with the controls were performed. The data as well as the data analysis are available in the abovementioned source data Excel document (sheet IV to VI: pNPH3 nph3- 7 phototropism). + +<|ref|>text<|/ref|><|det|>[[92, 667, 904, 737]]<|/det|> +Q3: Before I recommend this paper for publishing, I would like to ask for a rearrangement of figure panels. The story presented in the paper is consistent, however extremely difficult to follow, due to figure panels inconsistency. It very inconvenient to follow the data presented in several figures simultaneously. The figures should be prepared in such a way that the reader can refer to them in a sequence and does not need to jump between their fragments. Figure numbering should in general match the text of the manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 752, 890, 782]]<|/det|> +R3: Figures and figure panels were completely rearranged so that Figure numbering matches the text of the main manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 797, 897, 827]]<|/det|> +Q4: Also, figure legends are not clear enough to me, as the description tends to merge quite different experiments. Descriptions should also refer in detail to what is presented on figures and be self- explanatory. + +<|ref|>text<|/ref|><|det|>[[92, 842, 900, 873]]<|/det|> +R4: Figure legends were separated and simplified, including enough information to understand the figure without referring to the main text. + +<|ref|>text<|/ref|><|det|>[[92, 888, 794, 903]]<|/det|> +Q5: The word antepenultimate is not intuitive and I would like to ask for a different expression. + +<|ref|>text<|/ref|><|det|>[[92, 919, 575, 935]]<|/det|> +R5: The word antepenultimate was replaced by 'third last'. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[94, 158, 358, 174]]<|/det|> +## Detailed comments Referee 1: + +<|ref|>text<|/ref|><|det|>[[93, 188, 434, 204]]<|/det|> +Q6: Fig.1,A,D Please provide control images. + +<|ref|>text<|/ref|><|det|>[[92, 218, 642, 234]]<|/det|> +R6: Control images are now shown in Fig. 1a and Fig. 1d (see R1). + +<|ref|>text<|/ref|><|det|>[[92, 250, 604, 266]]<|/det|> +Q7: Fig 1B. Please indicate GST: NPH3- S774D in the figure legend. + +<|ref|>text<|/ref|><|det|>[[92, 280, 899, 312]]<|/det|> +R7: Due to figure rearrangement (see R3) the lipid overlay assay performed with GST:NPH3- C51- S744D is now shown in Fig. 4c. The analyzed protein is mentioned in the figure legend. + +<|ref|>text<|/ref|><|det|>[[92, 325, 904, 355]]<|/det|> +Q8: Line 115. Please refer in the full name to the analyzed fusion proteins for example GST: NPH3- C51 so it is easier to refer to the figures. + +<|ref|>text<|/ref|><|det|>[[92, 369, 857, 400]]<|/det|> +R8: In all cases, we now referred to the full name of the studied fusion proteins. For instance, GST:NPH3- C51 is mentioned in line 121. + +<|ref|>text<|/ref|><|det|>[[92, 400, 884, 445]]<|/det|> +Q9: Line 140. Were the mutations in the replacement variants of NPH3 introduced into the whole mutated proteins or only the C51 fragment? Please clarify the description in the text and the figure legend. Line 146. Please refer precisely to mutiens used. + +<|ref|>text<|/ref|><|det|>[[92, 444, 755, 459]]<|/det|> +Fig.2B. Were the proteins tagged with GST (figure legend) or HA (marked on the figure)? + +<|ref|>text<|/ref|><|det|>[[92, 473, 909, 549]]<|/det|> +R9: Thanks for pointing this out. We realized that the previous figure legend 2(B) was not correct. In fact, the mutations were introduced in both the HA- tagged full- length NPH3 protein and the GST- NPH3- C51 fusion protein. While the first- mentioned protein was used for lipid overlay assays (Fig. 2b), liposome binding assays were performed by using the GST- NPH3- C51 variants (Fig. 2c). This is now clearly indicated in the main text (line 146) as well as the legend of Fig. 2. + +<|ref|>text<|/ref|><|det|>[[92, 563, 905, 633]]<|/det|> +Q10: Fig.2D. Please indicate the localization of wild- type NPH3 in the appropriate control lines. I do not like the idea of comparing the localization of proteins fused with different fluorescent protein tags, as in our hands GFP and RFP show different expression levels and sensitivity to photobleaching which affects the signal intensities. I am afraid that comparing the localization of proteins fused with different fluorescent protein tags may lead to biased assessments. + +<|ref|>text<|/ref|><|det|>[[92, 648, 897, 710]]<|/det|> +R10: As already mentioned (R1) we now included images showing the localization pattern of the respective NPH3 control in all figure panels displaying CLSM analyses. Furthermore, we analyzed the localization of 35S::RFP:NPH3- 5KR/A in darkness - a representative image is now shown for comparison with other RFP- tagged NPH3 variants in Fig. 2d. + +<|ref|>text<|/ref|><|det|>[[92, 724, 911, 768]]<|/det|> +Q11: Line 159. Why interactions with omega 14- 3- 3 are shown in figure 3A, but 14- 3- 3 epsilon: GFP is further analyzed by MS? The IP experiments are done for the 14- 3- 3 omega, but this is not indicated in the text Fig.3B, D. Please indicate the type of 14- 3- 3 in the figure and in the text. + +<|ref|>text<|/ref|><|det|>[[92, 782, 909, 928]]<|/det|> +R11: We now included yeast two hybrid assays performed with the 14- 3- 3 isoform epsilon (belonging to the epsilon group) to demonstrate that members of both phylogenetic 14- 3- 3 groups (isoform omega belongs to the non- epsilon group, Fig. 3a, Supplementary Fig. 5a) interact with NPH3 (Supplementary Fig. 4a) as well as other NRL proteins (Supplementary Fig. 5b). In each case, the type of 14- 3- 3 isoform is indicated in the figure and in the text. Within the main text, we inserted the following statement (lines 170- 174): 'A yeast two hybrid screen performed in our lab (see 39) identified NPH3 as putative interactor of several Arabidopsis 14- 3- 3 isoforms, among those representatives of both phylogenetic 14- 3- 3 groups, the non- epsilon group (isoform omega, Fig. 3a) and the epsilon group (isoform epsilon, Supplementary Fig. 4a)'. In contrast to phot1 8 14- 3- 3 isoform specificity was thus not observed for binding to NPH3.' + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 174, 808, 190]]<|/det|> +Q12: Line 190. Please comment on why phosphomimic variants do not allow for 14- 3- 3 binding. + +<|ref|>text<|/ref|><|det|>[[92, 204, 912, 263]]<|/det|> +R12: The requested information has been added (lines 204- 207): 'Phosphomimic variants (NPH3- S744D/S744E), however, do not allow for 14- 3- 3 binding (Fig. 3a, Supplementary Fig. 4a), consistent with the general finding that aspartate and glutamate do not provide good phosphomimetic residues with respect to 14- 3- 3 binding 45. ' + +<|ref|>text<|/ref|><|det|>[[92, 276, 477, 291]]<|/det|> +Q13: Line 219- 220. Please rephrase this sentence. + +<|ref|>text<|/ref|><|det|>[[92, 307, 911, 367]]<|/det|> +R13: The sentence was rephrased (lines 238- 241): 'Altogether, the C- terminal domain serves a dual function in determining the subcellular localization of NPH3 since it comprises both the amphipathic helix required for phospholipid- dependent PM association in darkness and the 14- 3- 3 binding motif mediating BL- triggered PM dissociation.' + +<|ref|>text<|/ref|><|det|>[[92, 380, 627, 397]]<|/det|> +Q14: Line 224. Please indicate the wavelength for the GFP laser. + +<|ref|>text<|/ref|><|det|>[[92, 411, 525, 428]]<|/det|> +R14: The wavelength is indicated (line 244- 246). + +<|ref|>text<|/ref|><|det|>[[92, 444, 473, 460]]<|/det|> +Q15: Line 269- 270. Please indicate the reference. + +<|ref|>text<|/ref|><|det|>[[92, 475, 440, 491]]<|/det|> +R15: The reference is indicated (line 295). + +<|ref|>text<|/ref|><|det|>[[92, 506, 720, 522]]<|/det|> +Q16: Fig. 4A. Please provide data from 3 biological replicates. Similarly for Fig.S3A. + +<|ref|>text<|/ref|><|det|>[[92, 536, 911, 599]]<|/det|> +R16: We performed three biological replicates for the analysis of the phototropic response (see R2). The graphs shown in Fig. 4a, Fig. 7a (previous Fig. 6A) and Supplementary Fig. 4b represent data from a single experiment. Source data for all biological replicates including data analysis are provided with this paper (separate source data Excel document 'source data phototropism', see R2). + +<|ref|>text<|/ref|><|det|>[[92, 612, 560, 628]]<|/det|> +Q17: Fig. 4F, G. Please indicate the number of analyzed cells. + +<|ref|>text<|/ref|><|det|>[[92, 643, 910, 732]]<|/det|> +R17: As (already) indicated in the figure legend (now Fig. 5 d- f) a single cell time lapse imaging of RFP: NPH3 condensation was performed. This single cell experiment was repeated five times and is described in the 'Material and Methods' section as follows (lines 706- 710): 'PM- detachment was induced by means of the GFP- laser (488 nm) and image acquisition (RFP- laser) was done for the duration of 32 min by scanning 30 consecutive planes along the Z axis covering the entire thickness of an epidermal cell. Z- projection was done for each 3.5 min interval. Five replicates were performed.' + +<|ref|>text<|/ref|><|det|>[[92, 745, 595, 761]]<|/det|> +Q18: Fig.6B. Please add GFP- NPH3 localization in the control line. + +<|ref|>text<|/ref|><|det|>[[92, 776, 809, 792]]<|/det|> +R18: GFP: NPH3 localization in the control line has been added (now Fig. 7 b) (see R1). + +<|ref|>text<|/ref|><|det|>[[92, 806, 682, 822]]<|/det|> +Q19: Fig.6D. Please indicate what unbound/bound means in the figure legend. + +<|ref|>text<|/ref|><|det|>[[92, 837, 891, 869]]<|/det|> +R19: We exchanged unbound/bound for flowthrough/precipitate (IP) and indicated the meaning in the figure legend (now Fig. 7d). + +<|ref|>text<|/ref|><|det|>[[92, 882, 722, 898]]<|/det|> +Q20: Line 470- 471. Please describe the treatments in the M and M sections as well. + +<|ref|>text<|/ref|><|det|>[[92, 913, 863, 945]]<|/det|> +R20: The light treatments are now described in the M and M section as well (lines 500- 503 for transgenic Arabidopsis seedlings, lines 510- 514 for N. benthamiana). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 174, 784, 190]]<|/det|> +Q21: Fig. S2. For colocalization studies please provide images also from separate channels. + +<|ref|>text<|/ref|><|det|>[[92, 203, 899, 238]]<|/det|> +R21: The colocalization studies shown in the previous Fig. S2 are now available in Supplementary Fig. 3, alongside with the separate channels. + +<|ref|>sub_title<|/ref|><|det|>[[94, 273, 381, 290]]<|/det|> +## Reply to comments of Referee 2: + +<|ref|>text<|/ref|><|det|>[[92, 308, 890, 339]]<|/det|> +Q1: The methodology in the paper is innovative and yet sound. In the methods section, several techniques are cited, rather than described. To ensure reproducibility, please describe these methods. + +<|ref|>text<|/ref|><|det|>[[92, 349, 552, 366]]<|/det|> +R1: We now described the majority of methods in detail. + +<|ref|>text<|/ref|><|det|>[[92, 365, 886, 397]]<|/det|> +In rare cases we, however, precisely followed a step- by- step protocol (i.e. data analysis of single cell time lapse imaging). On that condition, we just cited the corresponding protocol. + +<|ref|>text<|/ref|><|det|>[[92, 410, 895, 468]]<|/det|> +Q2: In some instances, inappropriate statistical tests are used. The statistical tests used do not correct for multiple testing and so other tests (e.g. 1- way ANOVA with a post hoc test) may be more appropriate. Some continuous data are presented as histograms, where violin/ box plots would give the reader a better understanding of the variation in these experiments. + +<|ref|>text<|/ref|><|det|>[[92, 480, 890, 543]]<|/det|> +R2: With respect to the analysis of the phototropic response (Fig. 4a, Fig. 7a, Supplementary Fig. 4b in the revised manuscript) we now performed one- way ANOVA with Tukey's post hoc test and presented the data as box plots. The data as well as the data analysis are available in a separate source data Excel document referred to as 'source data phototropism'. + +<|ref|>text<|/ref|><|det|>[[92, 556, 880, 627]]<|/det|> +Q3: Most of the conclusions in the MS are completely well founded. I did however find a few areas where language could be tightened or a more appropriate control could have been used: Figure 2D: Why did the authors use different FP for these experiments? As the authors note, laser excitation of GFP also effects NPH3 localisation. To make comparisons between the localisation of these truncated proteins it would be beneficial to use the same FP. + +<|ref|>text<|/ref|><|det|>[[92, 638, 905, 685]]<|/det|> +R3: We completely agree and thus analyzed the localization of 35S::RFP:NPH3- 5KR/A in darkness - a representative image is now shown for comparison with other RFP- tagged NPH3 variants in Fig. 2d. + +<|ref|>text<|/ref|><|det|>[[92, 699, 895, 730]]<|/det|> +Q4: Fig 3A. It's interesting that the binding of 14:3:3 to NPH3 also occurs in yeast. Do the authors have any suggestions of how plant- specific NPH3 (presumably) becomes phosphorylated in the absence of phot1? + +<|ref|>text<|/ref|><|det|>[[92, 741, 897, 815]]<|/det|> +R4: Beyond any doubt, this is an interesting observation and here, we just can speculate. We now discuss this issue as follows (lines 207- 211): 'Considering that constitutive 14- 3- 3 complex formation of other plant targets characterized by a C- terminal binding site, such as the H+-ATPase or the transcription factor FD, has been observed in yeast 46, 47, light- independent NPH3:14- 3- 3 interaction in yeast (Fig. 3a, Supplementary Fig. 4a) might arise from a promiscuous kinase with a certain preference for terminal motifs.' + +<|ref|>text<|/ref|><|det|>[[92, 826, 907, 952]]<|/det|> +Q5: Line 311: "General' dephosphorylation of NPH3 is thus not coupled to PM dissociation. Moreover, it is neither a prerequisite nor a consequence of condensate assembly, rather it seems to require prior light- triggered and S744 phosphorylation- dependent 14- 3- 3 association". While I am sympathetic to the hypothesis put forward by the authors, strictly speaking they do not show that association of 14:3:3 is required for NPH3 de- phosphorylation. Rather they show that BL- dependent phosphorylation of S744 is required for general de- phosphorylation AND for the association of 14:3:3. If they want to make the current conclusion they need to show that general de- phos does not occur in the absence of 14:3:3s. Given the highly redundant function of 14:3:3s, this is no small task. The easiest solution would be to moderate this conclusion (also for the statements in line 347, 399 and the general conclusions). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 171, 904, 247]]<|/det|> +R5: Yes, from a strict point of view, this is absolutely correct! We therefore moderated our conclusion. Lines 334- 340: 'Moreover, it is neither a prerequisite nor a consequence of condensate assembly, rather it requires prior light- triggered S744 phosphorylation and potentially 14- 3- 3 association (Fig. 6a, d). Taken together, we suggest that BL- induced phosphorylation of S744 provokes (i) 14- 3- 3 association which releases NPH3 from the PM into the cytosol and (ii) 'general' dephosphorylation of NPH3'. + +<|ref|>text<|/ref|><|det|>[[92, 259, 905, 303]]<|/det|> +Q6: Figure 6C. GFP:NPH3- 4K/A appears to run on the gel as a 'general dephosphorylated' NPH3. Does that not imply that cytosolic localisation is sufficient for general dephosphorylation? How does this square with the results presented in Figure 5D? + +<|ref|>text<|/ref|><|det|>[[92, 313, 908, 418]]<|/det|> +R6: This observation puzzled us as well. Nevertheless, provided that 'general dephosphorylation' is not coupled to PM dissociation (Q5, see above) there is another explanation for the electrophoretic mobility of this NPH3 mutant that most likely is incapable of PM association following translation: 'general' phosphorylation of NPH3 might take place at the PM! This possibility is now mentioned in lines 350- 353: 'Worth mentioning, the electrophoretic mobility of GFP:NPH3- 4K/A corresponded to the dephosphorylated version of NPH3 and was not modified by light treatment (Fig. 7c), suggesting that 'general' phosphorylation of NPH3 might take place at the PM.' + +<|ref|>text<|/ref|><|det|>[[92, 431, 896, 476]]<|/det|> +Q7: Line 377: I don't follow how the residual function of NPH3- S744A can be explained by redundancy with RPT2. The NPH3- S744A construct rescues phototropism in the nph3- 7 background. The most simple explanation is that NPH3- S744A still retains some function. + +<|ref|>text<|/ref|><|det|>[[92, 487, 908, 576]]<|/det|> +R7: I am sorry for this! Of course, residual activity of NPH3- S744A cannot be explained by redundancy with RPT2! We, however, have to keep in mind, that NPH3- S744A is permanently present at the PM. Therefore, the possibility exists that it functions together with RPT2 or other NRL family members. We now rephrased the sentence (lines 406- 408): 'Residual functionality might be due to co- action of this constitutively PM- associated NPH3 mutant with certain members of the NRL protein family.' + +<|ref|>text<|/ref|><|det|>[[92, 589, 910, 648]]<|/det|> +Q8: In addition to these remarks, I also had a few suggestions for where I think that the MS could be modified to enhance fullness and readability: Line 42: The authors should cite studies showing phot1 transphosphorylation ie. BLUS1, CBC1, ABCD19 and PSK4 + +<|ref|>text<|/ref|><|det|>[[90, 658, 840, 675]]<|/det|> +R8: The phot1 substrates known so far are now mentioned in the Introduction (lines 42- 46). + +<|ref|>text<|/ref|><|det|>[[92, 688, 710, 705]]<|/det|> +Q9: Line 119: I this is referring to RFP- constructs (1D) and GFP constructs (S2A)? + +<|ref|>text<|/ref|><|det|>[[92, 717, 904, 777]]<|/det|> +R9: In fact, the (previously misleading) statement should refer to both constructs. This has been rephrased (lines 127- 129): 'As expected, transient expression of RFP/GFP:NPH3ΔC51 in N. benthamiana (35S or native promoter) revealed loss of PM recruitment in the dark, as evident by the presence of discrete bodies in the cytosol (Fig. 1d, Supplementary Fig. 2c). + +<|ref|>text<|/ref|><|det|>[[92, 789, 907, 903]]<|/det|> +Q10: The figure legends could be simplified. Currently, several sub- figures are referred to within the same heading. For example: "(Figure 3. B, D) In vivo interaction of mCherry:NPH3 variants and 14- 3- 3 omega:mEGFP in transiently transformed N. benthamiana leaves. Expression of transgenes was driven by the 35S promoter. Freshly transformed tobacco plants were either kept under constant light for 42 h (B) or kept under constant light for 24 h and subsequently transferred to darkness for 17h with (BL) or without (D) blue light treatment (5 μmol m- 2 sec- 1 912 ) for the last 40 minutes (D)". It would be a lot easier for the reader to follow if the legend for B and D was separated. This will inevitably require some repetition, but the legend will become much clearer as a result. + +<|ref|>text<|/ref|><|det|>[[92, 914, 905, 945]]<|/det|> +R10: Figure legends were separated and simplified, including enough information to understand the figure without referring to the main text. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 174, 264, 190]]<|/det|> +Q11: Line 179: mostly + +<|ref|>text<|/ref|><|det|>[[92, 202, 418, 218]]<|/det|> +R11: This has been modified (line 193). + +<|ref|>text<|/ref|><|det|>[[92, 232, 480, 248]]<|/det|> +Q12: Line 200: suggesting (indicating is too strong) + +<|ref|>text<|/ref|><|det|>[[92, 260, 620, 277]]<|/det|> +R12: 'Indicating' has been exchanged for 'suggesting' (line 220). + +<|ref|>text<|/ref|><|det|>[[92, 290, 380, 306]]<|/det|> +Q13: Line 305: neither NPH3 variant? + +<|ref|>text<|/ref|><|det|>[[92, 320, 910, 351]]<|/det|> +R13: NO, definitively not! To avoid confusion the sentence was rephrased (line 330): 'Despite the fact that both NPH3 variants constitutively localized to cytosolic condensates (Fig. 1a, Fig. 5c)....' + +<|ref|>text<|/ref|><|det|>[[92, 365, 900, 395]]<|/det|> +Q14: It took my a little while to understand summary figure 6E. It might help to clearly separate the 3 panels and to label them as wild type NPH3 and constitutive membrane- bound / unbound variants. + +<|ref|>text<|/ref|><|det|>[[92, 407, 825, 439]]<|/det|> +R14: Thanks for pointing this out! We now (Fig. 7e) separated the 3 panels and listed the appropriate NPH3 variants at the bottom of the individual panels. + +<|ref|>text<|/ref|><|det|>[[90, 451, 839, 468]]<|/det|> +Q15: Line 397: 'also in plants' is not necessary (any more than also in bacteria, also in animals etc)! + +<|ref|>text<|/ref|><|det|>[[92, 484, 353, 501]]<|/det|> +R15: We deleted it (line 427). + +<|ref|>text<|/ref|><|det|>[[92, 522, 550, 558]]<|/det|> +With best regards, also on behalf of my co- authors, Claudia Oecking + +<|ref|>image<|/ref|><|det|>[[92, 576, 310, 650]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 361, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 147, 394, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 880, 256]]<|/det|> +I would like to thank the Authors for providing answers to my questions. I appreciate the time and effort they have taken to improve the manuscript. I admire the comprehensive attitude to the science presented in this study. I fully recommend this paper for publishing in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 268, 723, 285]]<|/det|> +If possible, I would like to ask for small additions during the manuscript processing: + +<|ref|>text<|/ref|><|det|>[[115, 296, 549, 312]]<|/det|> +Lines 42- 45, please add the abbreviated names of proteins. + +<|ref|>text<|/ref|><|det|>[[115, 325, 508, 341]]<|/det|> +Fig.4F Please show also the green channel separately. + +<|ref|>text<|/ref|><|det|>[[115, 353, 540, 370]]<|/det|> +M&M Please provide the Catalog Numbers for antibodies. + +<|ref|>text<|/ref|><|det|>[[115, 439, 394, 455]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 495, 853, 530]]<|/det|> +The authors have taken my comments on board and I am pleased the new format of the MS. I would therefore like to recommend this MS for publication. + +<|ref|>text<|/ref|><|det|>[[114, 570, 882, 715]]<|/det|> +Apologies for not noticing it in the previous MS, but I just spotted something in Figure 7C. GFP- NPH3- 4K/A does unexpectedly show some phosphorylation of S744, despite it being located in the cytoplasm. I guess that PM localised phot1 still is still able to phosphorylate a small proportion of cytosolic NPH3, thus explaining the partial phosphorylation. The fact that GFP- NPH3- 4K/A is phosphorylated and cytoplasmic and yet still not functional actually lends even more weight to the authors hypothesis that it is the cycling is of NPH3 is essential for its function. Please note that I'm only raising this observation because I have the opportunity to do so. The authors shouldn't feel at all obliged to discuss it in the MS if they feel that it is not warranted! + +<|ref|>text<|/ref|><|det|>[[115, 755, 490, 771]]<|/det|> +Again, congratulations on the MS, really nice work! + +<|ref|>text<|/ref|><|det|>[[115, 812, 206, 828]]<|/det|> +Best wishes, + +<|ref|>text<|/ref|><|det|>[[115, 869, 203, 884]]<|/det|> +Scott Hayes + +<--- Page Split ---> diff --git a/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/images_list.json b/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1d6014d6f979f5149d6a2fe1c4cbf1b8cd964a46 --- /dev/null +++ b/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,171 @@ + +# nature portfolio + +Peer Review File + +Quantitative proteomics defines mechanisms of antiviral defence and cell death during modified vaccinia Ankara infection + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to + +the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +Reviewers' Comments: + +Reviewer #2: + +Remarks to the Author: + +In the revision of Quantitative temporal proteomic analysis of modified vaccinia Ankara, a monkeypox virus vaccine by Albarraza et al., the authors provide address many of the concerns of the reviewers. I continue to believe that the dataset is novel, important, and likely be a critical resource for the community. However, the study remains descriptive, and the lack of orthogonal validation and demonstration of therapeutic relevance continues to hamper the overall potential impact of this study + +Major points: + +1) The authors performed quantitative temporal viromics (QTV) of modified vaccinia Ankara (MVA) whose variant strain is used for as a vaccine against smallpox and monkeypox. They found nucleoporins as one of the key elements for MVA antagonism. Investigation of the mechanism and functional consequences of the downregulation of those factors would be critical and the data would improve their manuscript. The study was done in immortalized cell lines, and thus the therapeutic/physiological/in vivo importance of the findings is not clear. Providing functional validation of at least a subset of the dataset would provide confidence that these findings are relevant to vaccine biology and thus worth the time and attention of the community to follow up on. + +2) I appreciate the authors repeated the proteomic analysis in PMA-differentiated THP-1 macrophage-like cells. The manuscript will greatly benefit from a more comprehensive analysis comparing the data generated in HFFF-TERTs and THP-1 to elucidate potential common and cell type-specific virus-regulated proteins. + +3) While they analyzed similarities and difference carefully between the cell types as well as previous similar studies, it seems to end in a list of their observation. The discussion lacks significance of factors they found from the perspective of vaccine design and development. + +4) Systematic errors and incorrect peptide assignment increasing the false peptide identification can occur in high-throughput analysis due MS/MS fragmentation patterns. The authors suggested to maximize coverage, the dataset was not filtered to eliminate proteins with single peptide quantification. Since this manuscript is the first global view of the impacts of MVA infection on the host proteome, and low number of biological replicates, to avoid false positive rates, more conservative criteria should be applied \(\geq 2\) unique peptides to be identified within a single protein for its positive identification. + +Minor points: + +1) TMT reagents have different isotope impurities that need to be include for database search to correct the reporter ion ratio interference across different TMT channels. + +Reviewer #6: + +Remarks to the Author: + +In this manuscript, the authors conducted a multiplexed proteomic analysis of MVA and host at five time points throughout MVA infection of human cells. The experiment included inactivated controls to reveal the contribution of the viral particle with no- or limited viral gene expression, and might provide a global view of the impact of MVA infection on the host proteome. + +<--- Page Split ---> + +As for the major points mentioned by reviewer #4 that the low number of biological replicates were used, a further proteomic analysis in differentiated THP- 1 cells was performed in revision, and differences in regulation between cell types were discussed. As for the minor points mentioned by reviewer #4, appropriate modifications have been made in this revision. Furthermore, the meaning of the dots color should be presented clearly in the legends of Figure 2d and 4d. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #2 (Remarks to the Author): + +In the revision of Quantitative temporal proteomic analysis of modified vaccinia Ankara, a monkeypox virus vaccine by Albarraza et al., the authors provide address many of the concerns of the reviewers. I continue to believe that the dataset is novel, important, and likely be a critical resource for the community. However, the study remains descriptive, and the lack of orthogonal validation and demonstration of therapeutic relevance continues to hamper the overall potential impact of this study + +Thank you for the positive evaluation of our revised manuscript. We have now addressed the lack of orthogonal validation in two different ways. + +Firstly, we have included a gain- of- function screen of (i) selected proteins that were down- regulated during MVA infection of HFF- TERTs and (ii) selected proteins whose induction was suppressed in comparison to infection in presence of DNA replication inhibitor or heat- killed virions. This revealed that one interferon- inducible effector, ISG20, can limit viral gene expression (new Figure 2e, Extended Data Figure 4). We discuss this finding in the context of the well- characterised capacity of MVA vectors to attain high levels of heterologous gene expression under the control viral promoters: + +## Results + +"To gauge the functional significance of the host proteomic changes during MVA infection, we performed a small- scale gain- of- function screen via ectopic expression in HFF- TERTs (Extended data Fig. 4a, b). We included a selection of proteins that were downregulated during MVA infection (GLE1, NSA2, NUP54, NUP62, NUP88, RBM28). We also examined IFN- stimulated proteins whose induction was suppressed by infection, but not by heat- inactivated virions or upon inhibition of viral DNA replication (ISG20, OASL, ZNFX1). Cells were infected with an MVA strain expressing GFP under the control a viral early/late promoter (MVA- GFP) \(^{30}\) as proxy of viral gene expression. Out of the nine selected proteins, only ISG20 significantly altered MVA- GFP infection (Fig. 2e). Of note, it is possible that other proteins expressed in this screen at a level lower than ISG20 including GLE1, NSA2 and ZNFX1 might nevertheless exhibit an effect (Extended data Fig. 4a, b)." + +## Discussion + +"Suppression of the IFN response might represent one of the mechanisms responsible for the capacity of MVA vectors to attain high levels of heterologous gene expression under the control of viral promoters \(^{50}\) . Of three ISGs included in our gain- of- function screen, we could confidently conclude that ectopic ISG20 can limit MVA gene expression whereas ectopic OASL cannot. A \(3' - 5'\) exonuclease with strong preference for RNA, ISG20 can also degrade deaminated viral DNA (reviewed in \(^{58}\) ). Genomic analyses support that APOBEC3- mediated deamination of the viral genome is a key mutational driver in the MPXV strain that emerged globally in 2022 \(^{1}\) . A plausible hypothesis is that the degradation APOBEC3- deaminated viral DNA by ISG20 might constitute another host defence against poxviruses. In light of the recent proposal that subset of "dominant" ISGs may confer most of the inhibition of a given virus by IFNs \(^{59}\) , it is not surprising that, out of three ISGs, only ISG20 exerted significant antiviral activity against MVA." + +<--- Page Split ---> + +Secondly, we followed up the observation that IL- 1β is down- regulated from whole cell lysates following infection of THP- 1 macrophages, an indication that pyroptosis is induced by MVA. We confirmed this hypothesis with three different approaches: (i) lactate dehydrogenase (LDH) release assay in presence of different inhibitors of necroptosis, pyroptosis and apoptosis; (ii) immunoblotting of gasdermin D (GSDMD), the pore- forming effector of pyroptotic cell death; and (iii) fluorescence microscopy of a reporter cell line expressing caspase- 1 CARD fused to GFP and immunostaining of ASC, the inflammasome adapter protein (new Figure 4, Extended Data Figure 8). Combined, these approaches confirmed that MVA infection of THP- 1 macrophages activates the inflammasome which leads to caspase- 1- dependent processing of GSDMD and cell death. We discuss these findings in the context of vaccine immunogenicity, since inflammasome- dependent release of cytokines and antigens derived from pyroptotic cells shape adaptive antigen- specific immunity. However, demonstration of the importance of inflammasome and pyroptosis to the immunogenicity of MVA- based vaccines in vivo would require extensive experimentation in mouse models and is beyond the scope of this study. + +## Results + +"Inflammasomes are multimeric protein complexes that assemble in response to infectious or cellular damage stimuli and activate pro- inflammatory caspases, most notably caspase- 1. Active caspase- 1 cleaves pro- IL- 1β, pro- IL- 18, and gasdermin D (GSDMD) (Deets & Vance 2021). To determine whether inflammasomes are indeed activated during MVA infection of THP- 1s, we first measured cell death by lactate dehydrogenase (LDH) release assay. Infection of THP- 1s with MVA induced a sharp increase in cell death, which was reversed by treatment with a caspase- 1 inhibitor (VX- 765) and, to a lesser extent, the pan- caspase inhibitor (zVAD- fmk) (Fig. 4a). Conversely, inhibitors of the necroptosis mediators RIPK1, RIPK3, and MLKL did not affect MVA- induced cell death at concentrations that blocked necroptosis in HFF- TERTs (Fig. 4a, Extended data Fig. 8a). Next, we sought to visualize and quantify inflammasome assembly in infected THP- 1 macrophages engineered to express caspase- 1 caspase recruitment domain (CARD) fused to EGFP (C1C- EGFP) \(^{40}\) . Following infection with MVA in the presence of VX- 765 to avoid cell loss due to pyroptosis, C1C- GFP redistributed to single specks in each cell at 4 and 8 h p.i. (Fig. 4b, c; Extended data Fig. 8a). Co- localisation with the adaptor protein apoptosis- associated speck- like protein containing a CARD (ASC) confirmed the identity of the specks as inflammasomes (Fig. 4b; Extended data Fig. 8a). ASC specks were also observed following infection of parental THP- 1s with MVA (Extended Data Fig 8b, c). Lastly, we also observed cleavage of GSDMD downstream of inflammasome activation by MVA infection. VX- 765, as well as zVAD- fmk, prevented GSDMD cleavage, indicating its caspase- 1- dependence (Fig. 4d, e)." + +## Discussion + +"Other than corroborating previous observations, our proteomic analysis also provided multiple novel insights into the interactions between MVA and antigen- presenting myeloid cells. The downregulation of IL- 1β and the modulation of the abundance of proteins involved in NLRP3 inflammasome activation implicates this immune sensing pathway and inflammatory, pyroptotic cell death in detection of and response to MVA infection in human macrophages. Our data supports that caspase- 1- dependent pyroptosis is the dominant mechanism of cell death of MVA- infected macrophages. Notably, MVA lacks a functional orthologue of B13, a viral antagonist of caspase- 1 but still encodes F1, an apoptosis and inflammasome inhibitor, and A47, a homologue of gasdermins that counteracts IL- 1β secretion and pyroptosis \(^{57,74,75}\) . Therefore, we predict that F1 and A47 are largely non- functional during MVA infection because we observed inflammasome assembly, GSDMD processing, IL- 1β secretion and pyroptotic cell death in MVA- infected macrophages. MVA also lacks C1, a viral protein recently shown to enhance inflammasome activation \(^{74}\) . It is likely that viral DNA triggers inflammasome activation and pyroptosis via the absent in melanoma 2 (AIM2) inflammasome \(^{76}\) and/or NLRP3 inflammasome + +<--- Page Split ---> + +downstream of STING activation77,78. Inflammasome- dependent release of cytokines and antigens derived from pyrotopic cells shape adaptive antigen- specific immunity39,79. It remains to be determined how activation of the inflammasome and pyroptosis contribute to the immunogenicity and protection of MVA- based vaccines in vivo." + +We have additionally edited both the abstract and the title to reflect this substantial new data. + +## Major points: + +1) The authors performed quantitative temporal viromics (QTV) of modified vaccinia Ankara (MVA) whose variant strain is used for as a vaccine against smallpox and monkeypox. They found nucleoprins as one of the key elements for MVA antagonism. Investigation of the mechanism and functional consequences of the downregulation of those factors would be critical and the data would improve their manuscript. The study was done in immortalized cell lines, and thus the therapeutic/physiological/in vivo importance of the findings is not clear. Providing functional validation of at least a subset of the dataset would provide confidence that these findings are relevant to vaccine biology and thus worth the time and attention of the community to follow up on. + +Please see our response to the comment above. + +2) I appreciate the authors repeated the proteomic analysis in PMA-differentiated THP-1 macrophage-like cells. The manuscript will greatly benefit from a more comprehensive analysis comparing the data generated in HFFF-TERTs and THP-1 to elucidate potential common and cell type-specific virus-regulated proteins. + +Many thanks for this point. We have already provided a comprehensive analysis comparing data generated in HFFF-TERTs and THP-1s. Presently, this is in the form of: (a) detailed comparison of proteins that change commonly in both cell types and cell-type specific changes (Figures 3d, 3f); (b) enrichment analysis of the types of protein that change in both scenarios (Figure 3d, Supplementary tables 2-3); (c) detailed analysis of both of the above in the main text and discussion. However, for maximal value to the community, we agree that it would be useful to highlight the comparison between these cell types, and have generated a new section of results "Comparison of protein changes during MVA infection in fibroblasts and macrophages". In this, we now incorporate a new table identifying the specific proteins that change commonly or in a cell-type specific manner (Supplementary Table 7). + +3) While they analyzed similarities and difference carefully between the cell types as well as previous similar studies, it seems to end in a list of their observation. The discussion lacks significance of factors they found from the perspective of vaccine design and development. + +Many thanks for this suggestion. We have now addressed this point comprehensively as discussed above. In the discussion, we specifically refer to the significance of our findings with regards to vaccine design in two ways. First, we discuss the finding about ISG20 restriction of viral gene expression in the context of the well- characterised capacity of MVA vectors to attain high levels of heterologous gene expression under the control viral promoters. Second, we discuss the findings related to pyroptosis in the context of vaccine immunogenicity, since inflammasome- dependent release of cytokines and antigens derived from pyrotopic cells shape adaptive antigen- specific immunity. + +<--- Page Split ---> + +4) Systematic errors and incorrect peptide assignment increasing the false peptide identification can occur in high-throughput analysis due MS/MS fragmentation patterns. The authors suggested to maximize coverage, the dataset was not filtered to eliminate proteins with single peptide quantification. Since this manuscript is the first global view of the impacts of MVA infection on the host proteome, and low number of biological replicates, to avoid false positive rates, more conservative criteria should be applied \(\geq 2\) unique peptides to be identified within a single protein for its positive identification. + +Many thanks for this point. We agree with the reviewer that it is important to consider the confidence in protein identifications. Our Supplementary Table 1 already includes the number of independent peptide sequencing events for each protein (across the two replicates, \(1 - 2088\) peptides/protein, with \(89\%\) of proteins quantified by 2 or more peptides). We have also included an additional supplemental table 5 showing the sequences, SEQUEST XCorr scores and signal:noise values for all peptides that were quantified. Of note, since each protein identification is generally a result of multiple peptide identifications, it is correspondingly less likely that any given ID will be incorrect. Furthermore, as we employ additional quantitation-level filtering, our false discovery rate for protein identification was actually \(0.57\%\) , which is less than the prevailing standard in the field of \(1\%\) . This was calculated from the number of quantified reverse hits / total number of proteins quantified. We already provide details of filtering criteria according to XCorr score and signal:noise ratio in the Methods section. + +Whilst we agree that the most confidently identified proteins are identified by \(\geq 2\) peptides, there is nevertheless value in the quantification of proteins identified by fewer peptides, both as potential 'hits' where applicable, to support changes identified in enrichment analysis, and to provide as comprehensive as possible a resource to the community. Furthermore, another disadvantage of completely removing single peptide identifications is the consequent bias against including smaller proteins (since they produce fewer peptides eligible for detection). As such, we have now highlighted proteins quantified by single peptides only in Table S1. Additionally, in our 'plotter', when a protein is only quantified by a single peptide, we highlight this to warn readers that there is a small increase in the potential for an incorrect identification or suboptimal quantitation. + +## Minor points: + +1) TMT reagents have different isotope impurities that need to be include for database search to correct the reporter ion ratio interference across different TMT channels. + +Many thanks for this point – we have now included these values in Supplementary Table 6. + +## Reviewer #6 (Remarks to the Author): + +In this manuscript, the authors conducted a multiplexed proteomic analysis of MVA and host at five time points throughout MVA infection of human cells. The experiment included inactivated controls to reveal the contribution of the viral particle with no-, or limited viral gene expression, and might provide a global view of the impact of MVA infection on the host proteome. + +<--- Page Split ---> + +As for the major points mentioned by reviewer #4 that the low number of biological replicates were used, a further proteomic analysis in differentiated THP- 1 cells was performed in revision, and differences in regulation between cell types were discussed. As for the minor points mentioned by reviewer #4, appropriate modifications have been made in this revision. Furthermore, the meaning of the dots color should be presented clearly in the legends of Figure 2d and 4d. + +Many thanks for this point – we have now addressed the meaning of the dot colour in the relevant legends. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #2: + +Remarks to the Author: + +I appreciate the author's attempt to address the concerns from the last revision. While some of these new analyses are compelling, including comparison between THP- 1 and HFFF- TERTs, the study still lacks significant mechanistic insights, including how deregulated proteins impact replication and response to vaccine/protection. The validation studies cited by the authors remain superficial, and do not provide any concrete insights on the importance of these proteins either in the context of host- pathogen interactions are immune responses to vaccines. + +Specific comments: + +1) The small gain of function screen only finds 1 protein that might be important for replication (ISG20). No further insight into how it is regulated (besides a plausible hypothesis), how it restricts replication (both life cycle staging and mechanism of inhibitor), or how this regulation impacts vaccine induced protection is provided. Loss of function studies should also be conducted to confirm these findings2) No further data is provided on the NUPs, which did not have a readout in the GOF screens. There is no validation that these factors (or any besides ISG20) are important for replication or vaccine mediated protection3) The induction of the inflammasome is a relatively trivial finding. Molecular insights into how the virus induces this pathway, and its contribution to vaccine induced protect would be important to understand the role of this pathway in immune protection. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #2 (Remarks to the Author): + +I appreciate the author's attempt to address the concerns from the last revision. While some of these new analyses are compelling, including comparison between THP- 1 and HFFF- TERTs, the study still lacks significant mechanistic insights, including how deregulated proteins impact replication and response to vaccine/protection. The validation studies cited by the authors remain superficial, and do not provide any concrete insights on the importance of these proteins either in the context of host- pathogen interactions are immune responses to vaccines. + +Specific comments: + +1) The small gain of function screen only finds 1 protein that might be important for replication (ISG20). No further insight into how it is regulated (besides a plausible hypothesis), how it restricts replication (both life cycle staging and mechanism of inhibitor), or how this regulation impacts vaccine induced protection is provided. Loss of function studies should also be conducted to confirm these findings + +Reply: We have added further detail to acknowledge the limitations of our findings in the results section: + +"Although ectopic expression of ISG20 limited virus-driven GFP expression, loss- of- function studies will need to be conducted to confirm this phenotype." + +2) No further data is provided on the NUPs, which did not have a readout in the GOF screens. There is no validation that these factors (or any besides ISG20) are important for replication or vaccine mediated protection + +Reply: We dedicate an entire paragraph in the discussion for the implications of NUP downregulation for MVA infection. The detailed investigation of the implications of NUP downregulation for vaccine-mediated protection is beyond the scope of this study because it would require in vivo experiments. Regarding the importance of NUPs for MVA replication, testing this in human cells is challenging in human cells that do not support the productive replication of MVA. It is unlikely the gain- of- function or loss- of- function of single host factors account for MVA restriction in human cells. The paragraph states: + +"A total of 101 proteins were downregulated during MVA, but not VACV- WR infection. These included multiple components of the nuclear pore complex, whose downregulation is likely to disrupt nucleocytoplasmic transport60. The innate immune response to virus infection requires an intact NPC to mediate nucleocytoplasmic transport of transcription factors and mRNAs and therefore, downregulation/degradation of NPC proteins may be a viral immune evasion strategy. Although some viral proteases inactivate nucleoporins (NUPs) by cleavage, NUP abundance did not vary substantially during infection by multiple human pathogenic viruses, such as human cytomegalovirus, herpes simplex virus type, influenza A virus, Epstein- Barr virus, SARS- CoV- 2 and HIV. Three of the NUPs down- regulated by MVA (NUP54, NUP62, NUP88) were identified as host factors necessary for VACV- WR morphogenesis, raising the possibility that NUP downregulation contributes to arrested virion maturation during MVA infection of human cells. It remains to be determined whether this MVA- induced modulation is shared with the parental strain (CVA) or was acquired during the serial passage in chicken embryo fibroblasts. The molecular mechanisms underpinning restriction of MVA in human cells are not fully understood but are largely attributed to the loss or disruption of genes encoding host- range factors. Nucleoporins have been implicated in antiviral defences, including as co- factors in the MX2- mediated restriction of HIV- 1 or as substrates for proteolytic cleavage by the antiviral restriction + +<--- Page Split ---> + +factor FAM111A, which restricts SV40 by disrupting the nuclear pore complex. In line with our observations, a recent report confirmed that FAM111A cleaves NUP62 and disrupts nuclear barrier during MVA infection, in addition to inducing the degradation of the viral single- stranded DNA- binding (SSB) protein I3. The antiviral functions of FAM111A are antagonized by the poxvirus host- range factor SPI- 1, which is missing in MVA. Restoration of SPI- 1 in MVA rescues virus replication in human cells. In our gain- of- function screen, ectopic expression of NUP54, NUP62 or NUP88 did not significantly affect MVA gene expression, possibly because the rescue of individual nucleoporins is insufficient to restore the functional consequence of the simultaneous downregulation of several nuclear pore complex components." + +Because this already provides a significant amount of detail, we have not extended this discussion further. + +3) The induction of the inflammasome is a relatively trivial finding. Molecular insights into how the virus induces this pathway, and its contribution to vaccine induced protect would be important to understand the role of this pathway in immune protection. Reply: We disagree that these findings are relatively trivial. Indeed, presentation of our data at the "Infectious Diseases Through an Evolutionary Lens" conference held just earlier this week in London provoked a significant amount of interest from multiple conference participants, and we have detailed why this is of particular interest in the text already. To fully test the implications of inflammasome activation on vaccine efficacy would require in vivo experiments that are beyond the scope of our study. However, we have already covered this point in the discussion and highlighted that "it remains to be determined how activation of the inflammasome and pyroptosis contribute to the immunogenicity and protection of MVA-based vaccines in vivo." + +<--- Page Split ---> diff --git a/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b3059c8eeb9620ff44262ef3df553fb56a0daa76 --- /dev/null +++ b/peer_reviews/996236fe7bcffb4d384731573a4c082ea4a44831dd06c020baf33b3c539e363c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,232 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 850, 240]]<|/det|> +Quantitative proteomics defines mechanisms of antiviral defence and cell death during modified vaccinia Ankara infection + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to + +<|ref|>text<|/ref|><|det|>[[57, 785, 936, 924]]<|/det|> +the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 867, 134]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[119, 145, 293, 159]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 174, 223, 187]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 189, 298, 201]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 202, 877, 286]]<|/det|> +In the revision of Quantitative temporal proteomic analysis of modified vaccinia Ankara, a monkeypox virus vaccine by Albarraza et al., the authors provide address many of the concerns of the reviewers. I continue to believe that the dataset is novel, important, and likely be a critical resource for the community. However, the study remains descriptive, and the lack of orthogonal validation and demonstration of therapeutic relevance continues to hamper the overall potential impact of this study + +<|ref|>text<|/ref|><|det|>[[119, 328, 220, 341]]<|/det|> +Major points: + +<|ref|>text<|/ref|><|det|>[[118, 341, 874, 465]]<|/det|> +1) The authors performed quantitative temporal viromics (QTV) of modified vaccinia Ankara (MVA) whose variant strain is used for as a vaccine against smallpox and monkeypox. They found nucleoporins as one of the key elements for MVA antagonism. Investigation of the mechanism and functional consequences of the downregulation of those factors would be critical and the data would improve their manuscript. The study was done in immortalized cell lines, and thus the therapeutic/physiological/in vivo importance of the findings is not clear. Providing functional validation of at least a subset of the dataset would provide confidence that these findings are relevant to vaccine biology and thus worth the time and attention of the community to follow up on. + +<|ref|>text<|/ref|><|det|>[[118, 466, 855, 522]]<|/det|> +2) I appreciate the authors repeated the proteomic analysis in PMA-differentiated THP-1 macrophage-like cells. The manuscript will greatly benefit from a more comprehensive analysis comparing the data generated in HFFF-TERTs and THP-1 to elucidate potential common and cell type-specific virus-regulated proteins. + +<|ref|>text<|/ref|><|det|>[[118, 522, 825, 565]]<|/det|> +3) While they analyzed similarities and difference carefully between the cell types as well as previous similar studies, it seems to end in a list of their observation. The discussion lacks significance of factors they found from the perspective of vaccine design and development. + +<|ref|>text<|/ref|><|det|>[[118, 592, 867, 692]]<|/det|> +4) Systematic errors and incorrect peptide assignment increasing the false peptide identification can occur in high-throughput analysis due MS/MS fragmentation patterns. The authors suggested to maximize coverage, the dataset was not filtered to eliminate proteins with single peptide quantification. Since this manuscript is the first global view of the impacts of MVA infection on the host proteome, and low number of biological replicates, to avoid false positive rates, more conservative criteria should be applied \(\geq 2\) unique peptides to be identified within a single protein for its positive identification. + +<|ref|>text<|/ref|><|det|>[[118, 733, 220, 747]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[118, 748, 857, 776]]<|/det|> +1) TMT reagents have different isotope impurities that need to be include for database search to correct the reporter ion ratio interference across different TMT channels. + +<|ref|>text<|/ref|><|det|>[[118, 818, 220, 831]]<|/det|> +Reviewer #6: + +<|ref|>text<|/ref|><|det|>[[118, 833, 299, 845]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 846, 854, 901]]<|/det|> +In this manuscript, the authors conducted a multiplexed proteomic analysis of MVA and host at five time points throughout MVA infection of human cells. The experiment included inactivated controls to reveal the contribution of the viral particle with no- or limited viral gene expression, and might provide a global view of the impact of MVA infection on the host proteome. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 97, 874, 168]]<|/det|> +As for the major points mentioned by reviewer #4 that the low number of biological replicates were used, a further proteomic analysis in differentiated THP- 1 cells was performed in revision, and differences in regulation between cell types were discussed. As for the minor points mentioned by reviewer #4, appropriate modifications have been made in this revision. Furthermore, the meaning of the dots color should be presented clearly in the legends of Figure 2d and 4d. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[152, 86, 315, 100]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[152, 139, 418, 154]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[150, 191, 848, 275]]<|/det|> +In the revision of Quantitative temporal proteomic analysis of modified vaccinia Ankara, a monkeypox virus vaccine by Albarraza et al., the authors provide address many of the concerns of the reviewers. I continue to believe that the dataset is novel, important, and likely be a critical resource for the community. However, the study remains descriptive, and the lack of orthogonal validation and demonstration of therapeutic relevance continues to hamper the overall potential impact of this study + +<|ref|>text<|/ref|><|det|>[[150, 287, 848, 319]]<|/det|> +Thank you for the positive evaluation of our revised manuscript. We have now addressed the lack of orthogonal validation in two different ways. + +<|ref|>text<|/ref|><|det|>[[150, 330, 848, 432]]<|/det|> +Firstly, we have included a gain- of- function screen of (i) selected proteins that were down- regulated during MVA infection of HFF- TERTs and (ii) selected proteins whose induction was suppressed in comparison to infection in presence of DNA replication inhibitor or heat- killed virions. This revealed that one interferon- inducible effector, ISG20, can limit viral gene expression (new Figure 2e, Extended Data Figure 4). We discuss this finding in the context of the well- characterised capacity of MVA vectors to attain high levels of heterologous gene expression under the control viral promoters: + +<|ref|>sub_title<|/ref|><|det|>[[150, 444, 203, 457]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[149, 469, 848, 641]]<|/det|> +"To gauge the functional significance of the host proteomic changes during MVA infection, we performed a small- scale gain- of- function screen via ectopic expression in HFF- TERTs (Extended data Fig. 4a, b). We included a selection of proteins that were downregulated during MVA infection (GLE1, NSA2, NUP54, NUP62, NUP88, RBM28). We also examined IFN- stimulated proteins whose induction was suppressed by infection, but not by heat- inactivated virions or upon inhibition of viral DNA replication (ISG20, OASL, ZNFX1). Cells were infected with an MVA strain expressing GFP under the control a viral early/late promoter (MVA- GFP) \(^{30}\) as proxy of viral gene expression. Out of the nine selected proteins, only ISG20 significantly altered MVA- GFP infection (Fig. 2e). Of note, it is possible that other proteins expressed in this screen at a level lower than ISG20 including GLE1, NSA2 and ZNFX1 might nevertheless exhibit an effect (Extended data Fig. 4a, b)." + +<|ref|>sub_title<|/ref|><|det|>[[150, 653, 228, 667]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[149, 679, 848, 866]]<|/det|> +"Suppression of the IFN response might represent one of the mechanisms responsible for the capacity of MVA vectors to attain high levels of heterologous gene expression under the control of viral promoters \(^{50}\) . Of three ISGs included in our gain- of- function screen, we could confidently conclude that ectopic ISG20 can limit MVA gene expression whereas ectopic OASL cannot. A \(3' - 5'\) exonuclease with strong preference for RNA, ISG20 can also degrade deaminated viral DNA (reviewed in \(^{58}\) ). Genomic analyses support that APOBEC3- mediated deamination of the viral genome is a key mutational driver in the MPXV strain that emerged globally in 2022 \(^{1}\) . A plausible hypothesis is that the degradation APOBEC3- deaminated viral DNA by ISG20 might constitute another host defence against poxviruses. In light of the recent proposal that subset of "dominant" ISGs may confer most of the inhibition of a given virus by IFNs \(^{59}\) , it is not surprising that, out of three ISGs, only ISG20 exerted significant antiviral activity against MVA." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 849, 306]]<|/det|> +Secondly, we followed up the observation that IL- 1β is down- regulated from whole cell lysates following infection of THP- 1 macrophages, an indication that pyroptosis is induced by MVA. We confirmed this hypothesis with three different approaches: (i) lactate dehydrogenase (LDH) release assay in presence of different inhibitors of necroptosis, pyroptosis and apoptosis; (ii) immunoblotting of gasdermin D (GSDMD), the pore- forming effector of pyroptotic cell death; and (iii) fluorescence microscopy of a reporter cell line expressing caspase- 1 CARD fused to GFP and immunostaining of ASC, the inflammasome adapter protein (new Figure 4, Extended Data Figure 8). Combined, these approaches confirmed that MVA infection of THP- 1 macrophages activates the inflammasome which leads to caspase- 1- dependent processing of GSDMD and cell death. We discuss these findings in the context of vaccine immunogenicity, since inflammasome- dependent release of cytokines and antigens derived from pyroptotic cells shape adaptive antigen- specific immunity. However, demonstration of the importance of inflammasome and pyroptosis to the immunogenicity of MVA- based vaccines in vivo would require extensive experimentation in mouse models and is beyond the scope of this study. + +<|ref|>sub_title<|/ref|><|det|>[[151, 319, 204, 332]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[150, 344, 849, 654]]<|/det|> +"Inflammasomes are multimeric protein complexes that assemble in response to infectious or cellular damage stimuli and activate pro- inflammatory caspases, most notably caspase- 1. Active caspase- 1 cleaves pro- IL- 1β, pro- IL- 18, and gasdermin D (GSDMD) (Deets & Vance 2021). To determine whether inflammasomes are indeed activated during MVA infection of THP- 1s, we first measured cell death by lactate dehydrogenase (LDH) release assay. Infection of THP- 1s with MVA induced a sharp increase in cell death, which was reversed by treatment with a caspase- 1 inhibitor (VX- 765) and, to a lesser extent, the pan- caspase inhibitor (zVAD- fmk) (Fig. 4a). Conversely, inhibitors of the necroptosis mediators RIPK1, RIPK3, and MLKL did not affect MVA- induced cell death at concentrations that blocked necroptosis in HFF- TERTs (Fig. 4a, Extended data Fig. 8a). Next, we sought to visualize and quantify inflammasome assembly in infected THP- 1 macrophages engineered to express caspase- 1 caspase recruitment domain (CARD) fused to EGFP (C1C- EGFP) \(^{40}\) . Following infection with MVA in the presence of VX- 765 to avoid cell loss due to pyroptosis, C1C- GFP redistributed to single specks in each cell at 4 and 8 h p.i. (Fig. 4b, c; Extended data Fig. 8a). Co- localisation with the adaptor protein apoptosis- associated speck- like protein containing a CARD (ASC) confirmed the identity of the specks as inflammasomes (Fig. 4b; Extended data Fig. 8a). ASC specks were also observed following infection of parental THP- 1s with MVA (Extended Data Fig 8b, c). Lastly, we also observed cleavage of GSDMD downstream of inflammasome activation by MVA infection. VX- 765, as well as zVAD- fmk, prevented GSDMD cleavage, indicating its caspase- 1- dependence (Fig. 4d, e)." + +<|ref|>sub_title<|/ref|><|det|>[[151, 665, 226, 679]]<|/det|> +## Discussion + +<|ref|>text<|/ref|><|det|>[[150, 690, 849, 912]]<|/det|> +"Other than corroborating previous observations, our proteomic analysis also provided multiple novel insights into the interactions between MVA and antigen- presenting myeloid cells. The downregulation of IL- 1β and the modulation of the abundance of proteins involved in NLRP3 inflammasome activation implicates this immune sensing pathway and inflammatory, pyroptotic cell death in detection of and response to MVA infection in human macrophages. Our data supports that caspase- 1- dependent pyroptosis is the dominant mechanism of cell death of MVA- infected macrophages. Notably, MVA lacks a functional orthologue of B13, a viral antagonist of caspase- 1 but still encodes F1, an apoptosis and inflammasome inhibitor, and A47, a homologue of gasdermins that counteracts IL- 1β secretion and pyroptosis \(^{57,74,75}\) . Therefore, we predict that F1 and A47 are largely non- functional during MVA infection because we observed inflammasome assembly, GSDMD processing, IL- 1β secretion and pyroptotic cell death in MVA- infected macrophages. MVA also lacks C1, a viral protein recently shown to enhance inflammasome activation \(^{74}\) . It is likely that viral DNA triggers inflammasome activation and pyroptosis via the absent in melanoma 2 (AIM2) inflammasome \(^{76}\) and/or NLRP3 inflammasome + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[151, 84, 848, 152]]<|/det|> +downstream of STING activation77,78. Inflammasome- dependent release of cytokines and antigens derived from pyrotopic cells shape adaptive antigen- specific immunity39,79. It remains to be determined how activation of the inflammasome and pyroptosis contribute to the immunogenicity and protection of MVA- based vaccines in vivo." + +<|ref|>text<|/ref|><|det|>[[150, 163, 802, 179]]<|/det|> +We have additionally edited both the abstract and the title to reflect this substantial new data. + +<|ref|>sub_title<|/ref|><|det|>[[151, 218, 245, 233]]<|/det|> +## Major points: + +<|ref|>text<|/ref|><|det|>[[150, 243, 849, 379]]<|/det|> +1) The authors performed quantitative temporal viromics (QTV) of modified vaccinia Ankara (MVA) whose variant strain is used for as a vaccine against smallpox and monkeypox. They found nucleoprins as one of the key elements for MVA antagonism. Investigation of the mechanism and functional consequences of the downregulation of those factors would be critical and the data would improve their manuscript. The study was done in immortalized cell lines, and thus the therapeutic/physiological/in vivo importance of the findings is not clear. Providing functional validation of at least a subset of the dataset would provide confidence that these findings are relevant to vaccine biology and thus worth the time and attention of the community to follow up on. + +<|ref|>text<|/ref|><|det|>[[151, 390, 481, 404]]<|/det|> +Please see our response to the comment above. + +<|ref|>text<|/ref|><|det|>[[150, 442, 848, 511]]<|/det|> +2) I appreciate the authors repeated the proteomic analysis in PMA-differentiated THP-1 macrophage-like cells. The manuscript will greatly benefit from a more comprehensive analysis comparing the data generated in HFFF-TERTs and THP-1 to elucidate potential common and cell type-specific virus-regulated proteins. + +<|ref|>text<|/ref|><|det|>[[150, 522, 849, 693]]<|/det|> +Many thanks for this point. We have already provided a comprehensive analysis comparing data generated in HFFF-TERTs and THP-1s. Presently, this is in the form of: (a) detailed comparison of proteins that change commonly in both cell types and cell-type specific changes (Figures 3d, 3f); (b) enrichment analysis of the types of protein that change in both scenarios (Figure 3d, Supplementary tables 2-3); (c) detailed analysis of both of the above in the main text and discussion. However, for maximal value to the community, we agree that it would be useful to highlight the comparison between these cell types, and have generated a new section of results "Comparison of protein changes during MVA infection in fibroblasts and macrophages". In this, we now incorporate a new table identifying the specific proteins that change commonly or in a cell-type specific manner (Supplementary Table 7). + +<|ref|>text<|/ref|><|det|>[[150, 730, 848, 780]]<|/det|> +3) While they analyzed similarities and difference carefully between the cell types as well as previous similar studies, it seems to end in a list of their observation. The discussion lacks significance of factors they found from the perspective of vaccine design and development. + +<|ref|>text<|/ref|><|det|>[[150, 791, 848, 910]]<|/det|> +Many thanks for this suggestion. We have now addressed this point comprehensively as discussed above. In the discussion, we specifically refer to the significance of our findings with regards to vaccine design in two ways. First, we discuss the finding about ISG20 restriction of viral gene expression in the context of the well- characterised capacity of MVA vectors to attain high levels of heterologous gene expression under the control viral promoters. Second, we discuss the findings related to pyroptosis in the context of vaccine immunogenicity, since inflammasome- dependent release of cytokines and antigens derived from pyrotopic cells shape adaptive antigen- specific immunity. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 110, 848, 230]]<|/det|> +4) Systematic errors and incorrect peptide assignment increasing the false peptide identification can occur in high-throughput analysis due MS/MS fragmentation patterns. The authors suggested to maximize coverage, the dataset was not filtered to eliminate proteins with single peptide quantification. Since this manuscript is the first global view of the impacts of MVA infection on the host proteome, and low number of biological replicates, to avoid false positive rates, more conservative criteria should be applied \(\geq 2\) unique peptides to be identified within a single protein for its positive identification. + +<|ref|>text<|/ref|><|det|>[[150, 240, 848, 428]]<|/det|> +Many thanks for this point. We agree with the reviewer that it is important to consider the confidence in protein identifications. Our Supplementary Table 1 already includes the number of independent peptide sequencing events for each protein (across the two replicates, \(1 - 2088\) peptides/protein, with \(89\%\) of proteins quantified by 2 or more peptides). We have also included an additional supplemental table 5 showing the sequences, SEQUEST XCorr scores and signal:noise values for all peptides that were quantified. Of note, since each protein identification is generally a result of multiple peptide identifications, it is correspondingly less likely that any given ID will be incorrect. Furthermore, as we employ additional quantitation-level filtering, our false discovery rate for protein identification was actually \(0.57\%\) , which is less than the prevailing standard in the field of \(1\%\) . This was calculated from the number of quantified reverse hits / total number of proteins quantified. We already provide details of filtering criteria according to XCorr score and signal:noise ratio in the Methods section. + +<|ref|>text<|/ref|><|det|>[[150, 438, 848, 592]]<|/det|> +Whilst we agree that the most confidently identified proteins are identified by \(\geq 2\) peptides, there is nevertheless value in the quantification of proteins identified by fewer peptides, both as potential 'hits' where applicable, to support changes identified in enrichment analysis, and to provide as comprehensive as possible a resource to the community. Furthermore, another disadvantage of completely removing single peptide identifications is the consequent bias against including smaller proteins (since they produce fewer peptides eligible for detection). As such, we have now highlighted proteins quantified by single peptides only in Table S1. Additionally, in our 'plotter', when a protein is only quantified by a single peptide, we highlight this to warn readers that there is a small increase in the potential for an incorrect identification or suboptimal quantitation. + +<|ref|>sub_title<|/ref|><|det|>[[150, 604, 245, 618]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[150, 630, 848, 662]]<|/det|> +1) TMT reagents have different isotope impurities that need to be include for database search to correct the reporter ion ratio interference across different TMT channels. + +<|ref|>text<|/ref|><|det|>[[150, 674, 775, 690]]<|/det|> +Many thanks for this point – we have now included these values in Supplementary Table 6. + +<|ref|>sub_title<|/ref|><|det|>[[152, 728, 418, 743]]<|/det|> +## Reviewer #6 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[150, 781, 848, 849]]<|/det|> +In this manuscript, the authors conducted a multiplexed proteomic analysis of MVA and host at five time points throughout MVA infection of human cells. The experiment included inactivated controls to reveal the contribution of the viral particle with no-, or limited viral gene expression, and might provide a global view of the impact of MVA infection on the host proteome. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 848, 170]]<|/det|> +As for the major points mentioned by reviewer #4 that the low number of biological replicates were used, a further proteomic analysis in differentiated THP- 1 cells was performed in revision, and differences in regulation between cell types were discussed. As for the minor points mentioned by reviewer #4, appropriate modifications have been made in this revision. Furthermore, the meaning of the dots color should be presented clearly in the legends of Figure 2d and 4d. + +<|ref|>text<|/ref|><|det|>[[150, 179, 848, 213]]<|/det|> +Many thanks for this point – we have now addressed the meaning of the dot colour in the relevant legends. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 223, 125]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 139]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 140, 866, 223]]<|/det|> +I appreciate the author's attempt to address the concerns from the last revision. While some of these new analyses are compelling, including comparison between THP- 1 and HFFF- TERTs, the study still lacks significant mechanistic insights, including how deregulated proteins impact replication and response to vaccine/protection. The validation studies cited by the authors remain superficial, and do not provide any concrete insights on the importance of these proteins either in the context of host- pathogen interactions are immune responses to vaccines. + +<|ref|>text<|/ref|><|det|>[[119, 238, 267, 252]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[117, 265, 868, 420]]<|/det|> +1) The small gain of function screen only finds 1 protein that might be important for replication (ISG20). No further insight into how it is regulated (besides a plausible hypothesis), how it restricts replication (both life cycle staging and mechanism of inhibitor), or how this regulation impacts vaccine induced protection is provided. Loss of function studies should also be conducted to confirm these findings2) No further data is provided on the NUPs, which did not have a readout in the GOF screens. There is no validation that these factors (or any besides ISG20) are important for replication or vaccine mediated protection3) The induction of the inflammasome is a relatively trivial finding. Molecular insights into how the virus induces this pathway, and its contribution to vaccine induced protect would be important to understand the role of this pathway in immune protection. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 88, 338, 106]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 121, 417, 138]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 153, 877, 250]]<|/det|> +I appreciate the author's attempt to address the concerns from the last revision. While some of these new analyses are compelling, including comparison between THP- 1 and HFFF- TERTs, the study still lacks significant mechanistic insights, including how deregulated proteins impact replication and response to vaccine/protection. The validation studies cited by the authors remain superficial, and do not provide any concrete insights on the importance of these proteins either in the context of host- pathogen interactions are immune responses to vaccines. + +<|ref|>text<|/ref|><|det|>[[116, 265, 271, 281]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[115, 296, 864, 377]]<|/det|> +1) The small gain of function screen only finds 1 protein that might be important for replication (ISG20). No further insight into how it is regulated (besides a plausible hypothesis), how it restricts replication (both life cycle staging and mechanism of inhibitor), or how this regulation impacts vaccine induced protection is provided. Loss of function studies should also be conducted to confirm these findings + +<|ref|>text<|/ref|><|det|>[[115, 377, 872, 409]]<|/det|> +Reply: We have added further detail to acknowledge the limitations of our findings in the results section: + +<|ref|>text<|/ref|><|det|>[[115, 408, 845, 441]]<|/det|> +"Although ectopic expression of ISG20 limited virus-driven GFP expression, loss- of- function studies will need to be conducted to confirm this phenotype." + +<|ref|>text<|/ref|><|det|>[[115, 455, 865, 504]]<|/det|> +2) No further data is provided on the NUPs, which did not have a readout in the GOF screens. There is no validation that these factors (or any besides ISG20) are important for replication or vaccine mediated protection + +<|ref|>text<|/ref|><|det|>[[115, 504, 852, 617]]<|/det|> +Reply: We dedicate an entire paragraph in the discussion for the implications of NUP downregulation for MVA infection. The detailed investigation of the implications of NUP downregulation for vaccine-mediated protection is beyond the scope of this study because it would require in vivo experiments. Regarding the importance of NUPs for MVA replication, testing this in human cells is challenging in human cells that do not support the productive replication of MVA. It is unlikely the gain- of- function or loss- of- function of single host factors account for MVA restriction in human cells. The paragraph states: + +<|ref|>text<|/ref|><|det|>[[113, 632, 877, 904]]<|/det|> +"A total of 101 proteins were downregulated during MVA, but not VACV- WR infection. These included multiple components of the nuclear pore complex, whose downregulation is likely to disrupt nucleocytoplasmic transport60. The innate immune response to virus infection requires an intact NPC to mediate nucleocytoplasmic transport of transcription factors and mRNAs and therefore, downregulation/degradation of NPC proteins may be a viral immune evasion strategy. Although some viral proteases inactivate nucleoporins (NUPs) by cleavage, NUP abundance did not vary substantially during infection by multiple human pathogenic viruses, such as human cytomegalovirus, herpes simplex virus type, influenza A virus, Epstein- Barr virus, SARS- CoV- 2 and HIV. Three of the NUPs down- regulated by MVA (NUP54, NUP62, NUP88) were identified as host factors necessary for VACV- WR morphogenesis, raising the possibility that NUP downregulation contributes to arrested virion maturation during MVA infection of human cells. It remains to be determined whether this MVA- induced modulation is shared with the parental strain (CVA) or was acquired during the serial passage in chicken embryo fibroblasts. The molecular mechanisms underpinning restriction of MVA in human cells are not fully understood but are largely attributed to the loss or disruption of genes encoding host- range factors. Nucleoporins have been implicated in antiviral defences, including as co- factors in the MX2- mediated restriction of HIV- 1 or as substrates for proteolytic cleavage by the antiviral restriction + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 880, 234]]<|/det|> +factor FAM111A, which restricts SV40 by disrupting the nuclear pore complex. In line with our observations, a recent report confirmed that FAM111A cleaves NUP62 and disrupts nuclear barrier during MVA infection, in addition to inducing the degradation of the viral single- stranded DNA- binding (SSB) protein I3. The antiviral functions of FAM111A are antagonized by the poxvirus host- range factor SPI- 1, which is missing in MVA. Restoration of SPI- 1 in MVA rescues virus replication in human cells. In our gain- of- function screen, ectopic expression of NUP54, NUP62 or NUP88 did not significantly affect MVA gene expression, possibly because the rescue of individual nucleoporins is insufficient to restore the functional consequence of the simultaneous downregulation of several nuclear pore complex components." + +<|ref|>text<|/ref|><|det|>[[115, 248, 808, 281]]<|/det|> +Because this already provides a significant amount of detail, we have not extended this discussion further. + +<|ref|>text<|/ref|><|det|>[[115, 295, 875, 472]]<|/det|> +3) The induction of the inflammasome is a relatively trivial finding. Molecular insights into how the virus induces this pathway, and its contribution to vaccine induced protect would be important to understand the role of this pathway in immune protection. Reply: We disagree that these findings are relatively trivial. Indeed, presentation of our data at the "Infectious Diseases Through an Evolutionary Lens" conference held just earlier this week in London provoked a significant amount of interest from multiple conference participants, and we have detailed why this is of particular interest in the text already. To fully test the implications of inflammasome activation on vaccine efficacy would require in vivo experiments that are beyond the scope of our study. However, we have already covered this point in the discussion and highlighted that "it remains to be determined how activation of the inflammasome and pyroptosis contribute to the immunogenicity and protection of MVA-based vaccines in vivo." + +<--- Page Split ---> diff --git a/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/images_list.json b/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..de03b6bcd28d3d00686da5da5c12431f39c14153 --- /dev/null +++ b/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,49 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Rebuttal Fig. 1 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Rebuttal Fig. 2 | The seed germination rate of Arabidopsis plants.", + "footnote": [], + "bbox": [ + [ + 290, + 112, + 725, + 440 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Rebuttal Fig. 2 | The seed germination rate of Arabidopsis plants.", + "footnote": [], + "bbox": [], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Rebuttal Fig. 6 SnRK2.3/2.3N323A interact with STT3A.", + "footnote": [], + "bbox": [], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_10.jpg", + "caption": "Rebuttal Fig. 10 Subcellular localization of STT3A and GIIβ.", + "footnote": [], + "bbox": [], + "page_idx": 18 + } +] \ No newline at end of file diff --git a/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..607d346bac91172702d0bb934c83c5aaf45675b1 --- /dev/null +++ b/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,1272 @@ + +# nature portfolio + +Peer Review File + +N- glycosylation of SnRK2s affects NADPH maintenance in peroxisomes during prolonged ABA signalling + +![](images/Figure_1.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +This manuscript provides evidence that N- glycosylation of SnRK2s controls NADPH maintenance in peroxisomes, and this relates to the desensitization of plants to repeated ABA signalling. It is founded on discovery of a hypersensitivity to ABA- mediated repression in a mutant of \(\beta\) - subunit of glucosidase II (glβ- 2). + +The fact of this hypersensitivity would imply some non- compensatory need for this specific glucoside directly. However, oddly the authors find the same hypersensitivity when they individually knockout other glucosidases - STT3A, GIIa and three other N- glucosidases (CGL1, GMII, FUT11) - so why cant they compensate for the glβ- 2 mutant? Its not clear. I never saw any real exploration how each of these could in a non- compensatory manner effect the same pathway to SnRK2. + +The manuscript then uses experiments on glβ- 2 or STT3A mutants interchangeably to then explore the mechanism of this desensitization of plants to repeated ABA signalling. The yeast 2 hybrid assays are implied to show an exclusive interaction between glβ- 2 and SnRK2.2/2/3/2.6 but this was a set of pairwise interactions, not a yeast- 2 hybrid screen, so its not reasonable to call it exclusive - they only tested what they tested. Same with the LCl assays - "GIIβ, STT3A, GIIa, CGL1 and FUT11 all exclusively bind to SnRK2s" its just amongst the assay done - its not exclusive of other targets of these glucosidases. + +Critical to the claims of the paper is that SnRKs are glycosylated by these glucosidases - this is claimed by, "PNGase F and Endo H digestions confirmed that the band shift was due to N- glycan modification" this band shift seems to be the only evidence that this modification is occurring and the later genetic studies to mutate residues and show an absence of band shift - while in themselves compelling - are not independent of this method. There are a wide variety of other independent methods to prove N- glycan modification as well as MS and MRM methods to independently confirm the claim at the site on the SnRKs - none of these are used but really should be to independently confirm this central claim of the paper. + +The apparent translocation of SnRK2 to the peroxisome is proposed, but then recanted in the text, because nuclear export inhibition did not block it. Instead it seemed more likely the nuclear SnRK2 is degraded and a peroxisome targeted version is generated, so authors need to ensure they don't continue to claim 'translocation' in the text in other passages and also Fig 3 legend. + +When we get to peroxisomes and what SnRK2 interacts with, we see another selective process "we investigated the potential SnRK2- interacting partners among peroxisomal isozymes involved in H2O2- + +<--- Page Split ---> + +scavenging and NADPH generation" so again the link to GPT1 is really achieved by analysis of a small subset of hand picked targets. + +The claim of changes in NADPH and ROS in peroxisomes require detailed time- lapse measurements to be performed. The claimed errors bars in Fig 4 and extended Fig 11 are noted to be based on mean plus or minus sd, no n value is provided for either in the legends. But the reporting summary suggested - "All experiments were repeated two- three biologically independent experiments as mentioned in figure legends and methods". Having done these sorts of assays myself I find those errors (just a few percent in many cases) just inconceivably small for independent experiments. Throughout the paper these small n value experiments are just showing mean and sd, not data points on graphs to show means for each rep. + +These very small errors are essential for the claims made as the H2O2 and NADPH changes in Figure 4 are very small. I would want to see further evidence that the errors are accurately reported across independent experiments. + +Overall the biological case surrounding this mutant is extensively explored and links of the mutants effects back into ABA processes are extensive and involve a large amount of work and come to novel conclusions for the field. My main concern is that the biochemical pathway to the claim involves a series of selective choices that need to be acknowledged along the way and key points such as the glycosylation evidence and the clarification of how such small errors can be recorded need to be resolved. + +Reviewer #2 (Remarks to the Author): + +Pretreating plants with mild abiotic stresses helps them to adapt to harsh conditions, and the adaptation process is enhanced by ABA treatment. Revealing the underlying mechanism would have practical implications. This paper reports that ABA causes the subcellular redistribution and target change of SnRK2.2/2.3, two key regulators of ABA signaling. SnRK2.2/2.3 are localized in the nucleus and activate transcriptional responses at the initial ABA signaling stage, but during prolonged ABA treatment, they are N- glycosylated in the ER- Golgi network and sent to the peroxisomes. On the peroxisomal membrane, SnRK2.2/2.3 phosphorylate and activate Glucose- 6- Phosphate Transporter 1 (GPT1), which helps maintain NADPH homeostasis and suppress H2O2 over- accumulation. Plants that have undergone such changes become less responsive to ABA (desensitized) and may better tolerate stress conditions (becoming acclimated). + +<--- Page Split ---> + +The data presented in this paper are sound, the logic is clear, and the finding represents a significant step toward understanding the molecular mechanisms of plant acclimation. + +Minor comments: + +1. Labeling errors: in Extended Data Fig. 1, the labels "e" and "f" are misplaced; the "Fig. 1f" is mislabeled. + +2. Labeling errors: Main text lines 65 – 67, the Extended Data Fig. 2c-e, 2f, and 2g should be Extended Data Fig. 1c-e, 1f, and 1g. + +3. Labeling error: Main text line 92, the Fig. 1j should be Fig. 1j, k. + +4. Labeling error: Main text line 148, the Extended Data Fig. 6e should be Extended Data Fig. 6f. + +5. About the term "translocation": This term may mislead readers and should be considered revision. Throughout the paper, the authors use "translocate/translocation" to describe the change of SnRK2s localization patterns: SnRK2s are normally localized in the nucleus, and during prolonged ABA treatment, they are N-glycosylated and localized on the peroxisomal membrane. Although they disappear from the nucleus and reappear on the peroxisome, the SnRK2s proteins do not physically move 'from the nucleus to the peroxisomes'; this is supported by the experiment presented in Extended Data Fig. 10f, g (main text lines 188-190). Therefore, the term "translocate/translocation" does not accurately describe the process and can be misleading. + +For example, in the Abstract, line 11 reads, "...which promotes their gradual translocation from the nucleus to the peroxisomes...." Immediately following this sentence, line 13 reads, "After moving to the peroxisomal membrane, SnRK2s directly interact with...." This combination will almost surely make readers mistakenly think that SnRK2s physically move between the two organelles. + +A possible substitute for "translocation" is "redistribution." The term "redistribution" better describes the phenomenon, avoids misunderstanding, and inspires people to wonder. People may ask where SnRK2s proteins are synthesized and precisely what triggers the switch from targeting SnRK2s to the nucleus to targeting them to peroxisomes. The answers to such questions may expand the current finding and lead to the development of application strategies. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +This study presents a putative mechanism for the desensitization and transition of ABA signaling during prolonged treatment, involving N- glycosylation of SnRK2s. Under prolonged ABA signaling, the key regulator SnRK2.2/2.3 undergoes N- glycosylation in the ER- Golgi network, which leads to its translocation to the peroxisome. In the peroxisome, SnRK2s regulate NADPH generation by phosphorylating the transporter GPT1 during NADPH synthesis, suggesting a new module of redox homeostasis for adapting to long- term stress conditions during prolonged ABA signaling. The findings are interesting and provide insights into plant responses under prolonged stress conditions. However, there are several major issues in the manuscript that need to be addressed, before it could be considered by Nat Commun. + +Major Points: + +1. It is common to assay ABA responses through germination, cotyledon greening, and post-germination growth using different concentrations of ABA. In this study, the authors chose to germinate the seeds in a very high concentration of ABA (3 μM) and measured the root length at a later stage. Please explain the rationale for this choice and provide results from other assays. + +2. The major discovery in this work is that N-glycosylation of SnRK2s leads to the desensitization of prolonged ABA signaling through translocation. However, the relationship between these two processes remains unclear. Does N-glycosylation of SnRK2s occur before or after their translocation? Does N-glycosylation cause translocation, or does translocation lead to N-glycosylation? It would be helpful to design a subcellular-fixed mode of SnRK2s that can only be located in the nucleus or peroxisome to investigate the effects. + +3. The introduction of this paper focuses mainly on plant ABA signaling but lacks information about N-glucosidases, especially those mentioned in this work. + +4. Why the authors chose to study STT3A instead of the GIIβ, the mutant initially screened in most experiments? + +5. The authors performed a time course RNA-seq analysis to investigate the effects of N-glucosidases, but the stt3a-2 results were analyzed using Col-0 as a control instead of using no ABA-treated stt3a-2 as a control. Additionally, the results do not seem to match the expression pattern shown in Figure 1g-i, as the expression of stress response genes in stt3a-2 would be expected to be stronger and longer than in Col-0. Address these inconsistencies and provide a proper control for the analysis. + +6. In Figure 2, based on the results of co-expressed SnRK2.2/2.3 and STT3A in tobacco, the western blot results need to include a control without co-expression and ABA treatment to confirm the band as N-glycosylated SnRK2s. Additionally, the western blot results in snrk2.6 mutants require a control using + +<--- Page Split ---> + +snrk2.2/2.3/2.6 mutants to eliminate non- specific bands. Include these controls for a more accurate interpretation of the results. + +7. To confirm the N-glycosylated point Asp323 on SnRK2.3, include at least one additional point mutant in Figure 2k as a negative control to provide more solid evidence. + +Regarding the translocation of SnRK2.2/2.3- GFP in Arabidopsis, both SnRK2.2 and SnRK2.3 need to complete this evidence. Choose one of them to show the results instead of showing SnRK2.2 translocation with SnRK2.3 (Fig 3d) and performing a mutation assay with SnRK2.3N323A (Fig 3f). The results in Figure 3f indicate that a small amount of SnRK2.3N323A can still export from the nucleus, while SnRK2.2 cannot translocate in the stt3a- 2 mutant. This suggests that other factors may be involved in SnRK2.3 translocation besides N- glycosylation at N323, but it is difficult to confirm due to the unequal comparison. To address this, extract nuclear and cytoplasmic proteins separately for western blot analysis to check the N- glycosylation of SnRK2.2/2.3 after ABA treatment. + +8. In most experiments, the authors used SnRK2.3N323A, a mutant with abolished N-glycosylation of SnRK2.3 (Fig 2k). However, SnRK2.3 still exists in both the nucleus and peroxisome (Fig 3f), which may explain the weak or inconsistent results in Fig. 4 and Extended Data 16. To overcome this issue, delete the nuclear localization signal and peroxisome targeting signal separately to generate SnRK2.2/3 specifically located in the peroxisome and nucleus, and assess the function of SnRK2.2/3 translocation. Additionally, include snrk2.2/snrk2.3 as controls in all assays of SnRK2.32WT and SnRK2.3N323A to demonstrate the role of SnRK2s in these processes. + +9. This study shows the interaction and regulation between SnRK2s and GPT1, but mainly focuses on SnRK2.2 and GPT1, neglecting SnRK2.2 and 2.3. To verify the function of the phosphorylation site, stable transgenic plants would provide more solid evidence than transient expression. + +10. Explain why the SnRK2.2- and 2.3-GFP proteins showed a dramatic increase (more than 10-fold) after ABA treatment in Fig 9c. However, in Fig 9e, the 2.2-GFP protein only increased less than 1.5-fold after ABA treatment, leading to inconsistency. Generally, the protein abundance of SnRK2s should decline after ABA treatment. Provide an explanation for this discrepancy. + +In Extended Data Fig. 11, clarify the location of ROS affected by the stt3a mutation, rather than focusing on the amount. + +## Additional issues: + +11. In Line 65 to Line 67, the reference to Extended Data Figure should be corrected to Extended Data Figure 1. + +12. In Figure 4d, the legend describes a Co-IP assay using 4-day-old seedlings, but the results show a different pattern compared to Figure 4b, which also shows a Co-IP assay using the same material. Additionally, Figure 4d indicates a \(3 \mu M\) ABA treatment, but the legend describes it as \(50 \mu M\) ABA. Please address these inconsistencies. + +13. The results in Figure 2l and m demonstrate the phenotype of the triple mutant stt3a-2/snrk2.2/2.3 to confirm the epistasis of SnRK2.2/2.3 to STT3A. However, Figure 2l shows a slightly longer primary root in + +<--- Page Split ---> + +snrk2.2/2.3 compared to the triple mutant, whereas Figure 2m shows the reverse result, with the triple mutant having a slightly longer root. This discrepancy may be due to the selection of seedlings for photography. Clarify this issue. + +14. In Figure 3a and 3b, the intensity of SnRK2.2-GFP appears to increase after 2 hours of treatment, but Figure 3d shows a similar fluorescence intensity. Although this does not directly relate to the conclusion, please address this inconsistency. Additionally, for Figure 3c, a larger scale view may be more suitable to clearly show the cytosol, nuclear, and peroxisome localization of SnRK2.2-GFP. + +15. Ensure that the growth conditions described in the text match those depicted in Figure 1a, 1c, and 1e, as there appears to be a significant difference in root lengths of Col-0 plants. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +This manuscript provides evidence that N- glycosylation of SnRK2s controls NADPH maintenance in peroxisomes, and this relates to the desensitization of plants to repeated ABA signalling. + +It is founded on discovery of a hypersensitivity to ABA- mediated repression in a mutant of \(\beta\) - subunit of glucosidase II (glβ- 2). The fact of this hypersensitivity would imply some non- compensatory need for this specific glucoside directly. However, oddly the authors find the same hypersensitivity when they individually knockout other glucosidases – STT3A, GIIα and three other N- glucosidases (CGL1, GMII, FUT11) – so why can't they compensate for the glβ- 2 mutant? Its not clear. I never saw any real exploration how each of these could in a non- compensatory manner effect the same pathway to SnRK2. + +Reply 1: We thank the reviewer for the comments. For N- glycosylation modification, a nascent protein is attached a GlcManGlcNAc2 N- glycan on a specific asparagine (N) residue (NX(S/T) motif) by an oligosaccharide transferase complex when it enters the ER lumen. Subsequently, N- glucosidase I (GI) and GIIα/GIIβ heterodimer remove the outmost two glucose residues. GII- trimmed glycoprotein (N- glycan, GlcManGlcNAc2) is captured by calnexin/calreticulin (CNX/CRT) for quality control. Successfully folded glycoprotein (ManGlcNAc2) can be further processed by mannose- removing enzymes (α- mannosidase, MNSs), β1,2- N- acetylglucosaminyltransferase I (GnTI), Golgi- α- mannosidase II (GMII), fucosyltransferases (FUT), etc. sequentially in the ER- Golgi network, to form characteristic complex- type N- glycans (Nagashima et al., 2018; Strasser, 2016). + +The importance of this sequential actions of N- glycan processing enzymes (NPEs) was supported by Farid's study (Farid et al., 2011). Severe defects of gl mutant can be suppressed by additional mutation of ALG10 which is responsible for biosynthesis of the outmost glucose residue, suggesting that trimming of the Glc by GI is a prerequisite for further processing by GII (Farid et al., 2011). In our report, we provided rich data such as protein- protein assays and genetic interactions between NPEs and SnRK2s, showing that NPEs regulate ABA signalling through common substrate SnRK2 kinases. So, these npe mutants (stt3a, glIα, glIIβ, cglI, hglI, futII) exhibit similar ABA- sensitivities to each other, as well as similar high salt- hypersensitivity previously reported (Strasser, 2016). + +Based on suggestions from you and reviewer #3, more detailed information about N- glycosylation was added to introduction of the revised manuscript. + +## Reference + +Farid, A., Pabst, M., Schoberer, J., Altmann, F., Glossl, J., and Strasser, R. (2011). Arabidopsis thaliana alpha1,2- glucosyltransferase (ALG10) is required for efficient N- glycosylation and leaf growth. Plant J 68, 314- 325. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +The manuscript then uses experiments on glβ- 2 or stt3a mutants interchangeably to then explore the mechanism of this desensitization of plants to repeated ABA signalling. + +Reply 2: We thank the reviewer for the comments. As GIIβ and STT3A act in the same N- glycosylation pathway to co/post- modify SnRK2.2/2.3, and their mutants exhibit similar hypersensitivity to ABA treatment, they were used in our study to double- check the effect of N- + +<--- Page Split ---> + +glycosylation on ABA signalling in some experiments such as protein- protein binding, and genetic assays. But for N- glycosylation assay, STT3A can cause about 2- 3 kDa molecular mass difference of SnRK2.2/2.3 (one N- glycan), whereas GIIa/β induce only one glucose difference ( \(\sim 0.18\) kDa). It's easy to distinguish the N- glycosylated SnRK2.2/2.3 with STT3A. So the STT3A and its' mutant were chosen in N- glycosylation assays. We are sorry about making some confusion sometimes. + +The yeast 2 hybrid assays are implied to show an exclusive interaction between glβ- 2 and SnRK2.2/2/3/2.6 but this was a set of pairwise interactions, not a yeast- 2 hybrid screen, so its not reasonable to call it exclusive – they only tested what they tested. Same with the LCI assays – “GIIβ, STT3A, GIIα, CGL1 and FUT11 all exclusively bind to SnRK2s” its just amongst the assay done – its not exclusive of other targets of these glucosidases. + +Reply 3: We understand the reviewer's concern and removed the word “exclusively” according to the suggestions in the revised manuscript. + +Critical to the claims of the paper is that SnRK2s are glycosylated by these glucosidases – this is claimed by, “PNGase F and Endo H digestions confirmed that the band shift was due to N- glycan modification” this band shift seems to be the only evidence that this modification is occurring and the later genetic studies to mutate residues and show an absence of band shift – while in themselves compelling – are not independent of this method. There are a wide variety of other independent methods to prove N- glycan modification as well as MS and MRM methods to independently confirm the claim at the site on the SnRK2s – none of these are used but really should be to independently confirm this central claim of the paper. + +Reply 4: We thank the reviewer for careful evaluation and for encouraging us to improve our manuscript. + +Based on the reviewer's suggestion, we have carried out the LC- MS/MS analysis of SnRK2.3 (Zielinska et al., 2012). Our general procedure is to firstly enrich N- glycosylated SnRK2.3 with immunoprecipitation (IP), followed by N- glycosylation site identification with LC- MS/MS. We collected roots of SnRK2.3- GFP OE- line treated with \(50~\mu \mathrm{M}\) , followed by enrichment of the N- glycosylated SnRK2.3 from total protein extracts with GFP- trap and ConA Sequentially, then carried out MS analysis (see additional method below). Unfortunately, the MS results failed to show the N- glycosylation of SnRK2.3, even no any fragment of SnRK2.3- GFP was shown. The reason may be due to small amount of SnRK2.3- GFP enriched. After multiple attempts with a large amount of roots collected, we still failed in MS analysis. The enrichment of SnRK2.3- GFP was shown in Rebuttal Fig. 1a and b. We also tried other strategy to improve the expression level of SnRK2.3. The 35S::SnRK2.3- His and 35S::STT3- mCherry were constructed on a same vector and transiently expressed in tobacco, which can increase the expression level of N- glycosylated SnRK2.3 as we did in Fig. 2d- f. But the MS results still failed to detect any SnRK2.3. The Rebuttal Fig. 1c, d showed the enrichment of SnRK2.3- His after IPs. + +In our manuscript, we firstly applied band- shift assays to show SnRK2.2/2.3 are N- glycosylated in tobacco and Arabidopsis (a N- glycan gives rise to a larger band shift ( \(\sim 2\) kD plus) which can be removed by PNGase F or Endo H, Fig. 2d- i). Secondly, we found that N- glycosylation promotes nuclear export of SnRK2.2 and SnRK2.3 in tobacco leaves. To identify the N- glycosylation site, we mutated a total of 11 N (asparagine) sites of SnRK2.3 individually and the results showed that only SnRK2.3N323A is retained in the nucleus when co- expressed with STT3A- mCherry, suggesting the + +<--- Page Split ---> + +N323 site is responsible for the N- glycosylation. Finally, this N- glycosylation site was further confirmed by band- shift assay with site mutation. Therefore, we concluded that SnRK2.3N323 is a real N- glycosylation site. The method "band shift assays followed by PNGase F and Endo H digestions" we used, was a classical method widely used for identification of N- glycosylation in publications (Liu et al., 2015; Sato et al., 2012; Shen et al., 2014; Yamamoto et al., 2014). We think we provided strong evidences to show that SnRK2.3 is really N- glycosylated in our manuscript. + +We agree with the reviewer that MS and MRM analyses would more enhance our conclusion of N- glycosylation of SnRK2.2/2.3, and we also tried many times of MS analysis, but failed due to a tiny amount of N- glycosylated SnRK2s expressed in plants. It must be admitted that there are still many unsolved mysteries regarding the N- glycosylation modification of SnRK2s. We will continue to explore this field in the future and use more methods to detect this phenomenon. Thanks the reviewer again for valuable comments. + +![](images/Figure_2.jpg) + +
Rebuttal Fig. 1 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His.
+ +a, Enrichment of N- glycosylated SnRK2.3- GFP before MS analysis. SnRK2.3- GFP overexpression plants were treated with \(50\mu \mathrm{M}\) ABA for 48 h after seven days of growth and the roots were collected. After IP with GFP- Trap and ConA (concanavalin A, a plant lectin can bind to mannose on the glycoproteins), the enrichment was determined by western blot. Input, total protein extract; GFP- Trap, enrichment of SnRK2.3- GFP by GFP- Trap beads; ConA- IP, enrichment of N- glycosylated SnRK2.3- GFP by ConA bead after GFP- Trap- IP. The white arrowhead denotes the N- glycosylated SnRK2.3- GFP. b, Coomassie brilliant blue staining after PNGase F digestion of N- glycosylated SnRK2.3- GFP enriched by ConA. The dashed white frame denotes the gel cut for LC- MS/MS. c, Enrichment of N- glycosylated SnRK2.3. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in tobacco leaves with \(50\mu \mathrm{M}\) ABA for 48 h and N- glycosylated SnRK2.3 were enriched with Ni- NTA and ConA beads sequentially. No signal was shown after ConA enrichment (right line). So only Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. His- IP, enrichment of SnRK2.3- His by Ni- NTA; PNGase F, PNGase F digestion. N- SnRK2.3- His, N- glycosylated SnRK2.3- His. d, Coomassie brilliant blue staining after PNGase F digestion of His- antibody enriched SnRK2.3- His. The dashed white frame denotes the gel cut for LC- MS/MS. + +## Additional method: + +## Enrichment of N-glycosylated SnRK2.3 + +Plant tissues were grounded to powder in the frozen state and homogenized in extraction buffer (50 mM Tris- HCl, pH 7.4, 150 mM NaCl, 1 mM MgCl2, 10 μM EDTA, 1% NP- 40, 1×protease inhibitor, 5 + +<--- Page Split ---> + +\(\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with GFP- Trap agarose (Chromotek) or nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(4\mathrm{h}\) , beads were washed five times with ice- cold washing buffer (50 mM Tris- HCl, pH 7.4, \(400\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) \(\mathrm{MgCl}_2\) , \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins were eluted with acidic buffer (200 mM glycine, pH 2.5) and immediately neutralized the eluate fraction with neutralization buffer ( \(100\mathrm{mM}\) Tris- HCl, pH 10.4). The eluted proteins were then incubated with ConA (concanavalin A, a plant lectin can bind to mannose on the glycoproteins) beads (Beyotime) at \(4^{\circ}\mathrm{C}\) , After \(4\mathrm{h}\) , beads were washed five times with washing buffer ( \(20\mathrm{mM}\) Hepes, \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) \(\mathrm{MgCl}_2\) , \(1\mathrm{mM}\) \(\mathrm{MnCl}_2\) , \(1\mathrm{mM}\) \(\mathrm{CaCl}_2\) , \(0.1\%\) Tween- 20). The proteins were eluted with elution buffer ( \(5\mathrm{mM}\) Tris- HCl, pH 8.0, \(150\mathrm{mM}\) NaCl, \(1\mathrm{M}\) Glucose). + +## PNGase F digestion + +For PNGase F treatment, referring to the manufacturer's protocol, \(10\times\) glycoprotein denaturing buffer was added to IP- purified proteins and heated at \(100^{\circ}\mathrm{C}\) for \(10\mathrm{min}\) . After returning to room temperature, the reaction buffer (containing \(\mathrm{H}_2^{18}\mathrm{O}\) ) and PNGase F (New England Biolabs) were added to sample. The mixture was incubated for \(1\mathrm{h}\) at \(37^{\circ}\mathrm{C}\) before boiled in \(5\times\) SDS loading buffer. N- glycation of SnRK2.3 was detected by immunoblot analyses using by anti- GFP and anti- His antibodies after \(6\%\) SDS- PAGE. The sample was subjected to mass spectrometry detection after immunoblot analyses. + +## LC-MS/MS for identification of N-glycosylation site of SnRK2.3 + +For mass spectrometry analysis, protein samples were separated using SDS- PAGE electrophoresis and detected by coomassie brilliant blue staining. The SDS- PAGE gel at \(70\mathrm{kD}\) or \(40\mathrm{kD}\) was collected into a clean centrifuge tube. \(500\mu \mathrm{l}\) destain solution were added to a centrifuge tube and shaken at room temperature until the gel discolored. After discarding the supernatant, \(75\%\) acetonitrile ( \(200\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature. After \(30\mathrm{min}\) , \(500\mu \mathrm{l}\) H2O were added to the centrifuge tube and shaken at room temperature for \(1\mathrm{h}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) ( \(300\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) ( \(20\mu \mathrm{l}\) ) and \(2\mu \mathrm{l}\) trypsin ( \(1\mu \mathrm{g / \mu l}\) , Promega) were added to the centrifuge tube, and gel was crushed. After centrifugation ( \(1000\mathrm{rpm}\) , 1min), the sample was digested at \(37^{\circ}\mathrm{C}\) . After \(8\mathrm{min}\) , \(200\mu \mathrm{l}\) acetonitrile were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After centrifugation ( \(1000\mathrm{rpm}\) , 1min), the supernatant was transferred to a new centrifuge tube. This step was repeated once, ultimately resulting in \(400\mu \mathrm{l}\) supernatant. The obtained supernatant was vacuum dried at \(60^{\circ}\mathrm{C}\) and dissolved in \(0.1\%\) formic acid ( \(100\mu \mathrm{l}\) ). Samples were subjected to mass spectrometry detection by using mass spectrometer (Orbitrap Fusion™ Lumos™ Tribrid™, Thermo Scientific). The N- glycation site of SnRK2.3 was analyzed using software (Proteome Discoverer 2.3). + +## Reference + +Liu, Y., Zhang, C., Wang, D., Su, W., Liu, L., Wang, M., and Li, J. (2015). EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated degradation system in Arabidopsis. Proc Natl Acad Sci U S A 112, 12205- 12210. Sato, T., Sako, Y., Sho, M., Momohara, M., Suico, M.A., Shuto, T., Nishitoh, H., Okiyoneeda, T., Kokame, K., Kaneko, M., et al. (2012). STT3B- dependent posttranslational N- glycosylation as a surveillance system for secretory protein. Mol Cell 47, 99- 110. Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M.E., and Nasrallah, J.B. (2014). Site- specific N- glycosylation of the S- locus receptor kinase and its role in the self- incompatibility response of the brassicaceae. Plant Cell 26, 4749- 4762. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +The apparent translocation of SnRK2 to the peroxisome is proposed, but then recanted in the text, because nuclear export inhibition did not block it. Instead it seemed more likely the nuclear SnRK2 is degraded and a peroxisome targeted version is generated, so authors need to ensure they don't continue + +<--- Page Split ---> + +to claim 'translocation' in the text in other passages and also Fig 3 legend. + +Reply 5: We thank the reviewer for the comments. According to the suggestions from you and reviewer #2, we have replaced "translocate/translocation" with "redistribute/ redistribution" to illustrate the movement of SnRK2 in the revised manuscript. + +When we get to peroxisomes and what SnRK2 interacts with, we see another selective process "we investigated the potential SnRK2- interacting partners among peroxisomal isozymes involved in \(\mathrm{H}_2\mathrm{O}_2\) - scavenging and NADPH generation" so again the link to GPT1 is really achieved by analysis of a small subset of hand picked targets. + +Reply 6: We thank the reviewer for the comments. In our study, we did not search the potential peroxisomal SnRK2 binding proteins in genome- wide. One of the reasons is that it is hard to construct a gene library encoding all the peroxisomal isozymes for SnRK2- partner screening. Another reason is that it is hard to get only peroxisome- localized SnRK2s for IP- MS/MS analysis (some SnRK2s in the nuclei, and some on the peroxisomal membrane during prolonged ABA signalling). Instead, for quick identification of SnRK2 partners, we cloned 13 published genes of peroxisomal isozymes required for NADPH- generation on the peroxisomal membrane (Extended Data Fig. 14a), and identified GPT1 as a SnRK2 binding protein with ABA- dependent manner. Based on the reviewer #3's comments, we have constructed peroxisome- fixed SnRK2.3 (SnRK2.3- mPTSPEX26, with SnRK2.3- NLS as a control, see revised Fig. 4 i,j, and Extended Data Fig. 17), and we are trying to make transgenic Arabidopsis for SnRK2- binding protein screening in genome- wide via IP- MS/MS in the future. Thanks again for your valuable comments. + +In all honesty, the claim of changes in NADPH and ROS in peroxisomes require detailed time- lapse measurements to be performed. The claimed errors bars in Fig 4 and extended Fig 11 are noted to be based on mean plus or minus sd, no n value is provided for either in the legends. But the reporting summary suggested - "All experiments were repeated two- three biologically independent experiments as mentioned in figure legends and methods". Having done these sorts of assays myself I find those errors (just a few percent in many cases) just inconceivably small for independent experiments. Throughout the paper these small n value experiments are just showing mean and sd, not data points on graphs to show means for each rep. + +These very small errors are essential for the claims made as the \(\mathrm{H}_2\mathrm{O}_2\) and NADPH changes in Figure 4 are very small. I would want to see further evidence that the errors are accurately reported across independent experiments. + +Reply 7: We thank the reviewer for the comments. According to the reviewer's suggestions, we re- investigated the accumulations of \(\mathrm{H}_2\mathrm{O}_2\) and NADPH with three biological replicates in revised Fig. 4 a, and d. The "n value" in the figure legends of Extended data Fig. 11 and all the other figures were checked in our revised manuscript. + +Overall the biological case surrounding this mutant is extensively explored and links of the mutants effects back into ABA processes are extensive and involve a large amount of work and come to novel conclusions for the field. My main concern is that the biochemical pathway to the claim involves a series of selective choices that need to be acknowledged along the way and key points such as the glycosylation evidence and the clarification of how such small errors can be recorded need to be resolved. + +Reply 8: We would like to thank the reviewer for the careful evaluation and for encouraging us + +<--- Page Split ---> + +to improve our manuscript. Above, we have provided our responses to all the comments point- by- point. We answered the comments about “a series of selective choices” in Reply 3 and 6. The N- glycosylation modification of SnRK2.3 was further elucidated in Reply 4. To address the small error bars, we re- investigated the accumulation levels of NADPH, and \(\mathrm{H}_2\mathrm{O}_2\) with three independent biological replicates (Reply 7). + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +Reviewer #2 (Remarks to the Author):Pretreating plants with mild abiotic stresses helps them to adapt to harsh conditions, and the adaptation process is enhanced by ABA treatment. Revealing the underlying mechanism would have practical implications. This paper reports that ABA causes the subcellular redistribution and target change of SnRK2.2/2.3, two key regulators of ABA signaling. SnRK2.2/2.3 are localized in the nucleus and activate transcriptional responses at the initial ABA signaling stage, but during prolonged ABA treatment, they are N- glycosylated in the ER- Golgi network and sent to the peroxisomes. On the peroxisomal membrane, SnRK2.2/2.3 phosphorylate and activate Glucose- 6- Phosphate Transporter 1 (GPT1), which helps maintain NADPH homeostasis and suppress \(\mathrm{H}_2\mathrm{O}_2\) over- accumulation. Plants that have undergone such changes become less responsive to ABA (desensitized) and may better tolerate stress conditions (becoming acclimated). + +The data presented in this paper are sound, the logic is clear, and the finding represents a significant step toward understanding the molecular mechanisms of plant acclimation. + +We great appreciate the reviewer for positive comments on our manuscript. + +Minor comments: + +1. Labeling errors: in Extended Data Fig. 1, the labels "e" and "f" are misplaced; the "Fig. 1f" is mislabeled. + +Reply 1: That's correct. Done. + +2. Labeling errors: Main text lines 65 - 67, the Extended Data Fig. 2c-e, 2f, and 2g should be Extended Data Fig. 1c-e, 1f, and 1g. + +Reply 2: Done. + +3. Labeling error: Main text line 92, the Fig. 1j should be Fig. 1j, k. + +Reply 3: Done + +4. Labeling error: Main text line 148, the Extended Data Fig. 6e should be Extended Data Fig. 6f. + +Reply 4: Done + +5. About the term "translocation": This term may mislead readers and should be considered revision. Throughout the paper, the authors use "translocate/translocation" to describe the change of SnRK2s localization patterns: SnRK2s are normally localized in the nucleus, and during prolonged ABA treatment, they are N-glycosylated and localized on the peroxisomal membrane. Although they disappear from the nucleus and reappear on the peroxisome, the SnRK2s proteins do not physically move 'from the nucleus to the peroxisomes'; this is supported by the experiment presented in Extended Data Fig. 10f, g (main text lines 188-190). Therefore, the term "translocate/translocation" does not accurately describe the process and can be misleading. For example, in the Abstract, line 11 reads, "...which promotes their gradual translocation from the nucleus to the peroxisomes...." Immediately following this sentence, line 13 reads, "After moving to the peroxisomal membrane, SnRK2s directly interact with...." This combination will almost surely make readers mistakenly think that SnRK2s physically move between the two organelles. A possible substitute for "translocation" is "redistribution." The term "redistribution" better describes the phenomenon, avoids misunderstanding, and inspires people to wonder. + +Reply 5: The comments are greatly appreciated. We have replaced the term "translocate/translocation" with "redistribute/redistribution" in the revised manuscript. + +In the abstract (line 11- 13), both "translocation" and "After moving to" have been replaced with "redistribution" and "On", respectively. + +<--- Page Split ---> + +People may ask where SnRK2s proteins are synthesized and precisely what triggers the switch from targeting SnRK2s to the nucleus to targeting them to peroxisomes. The answers to such questions may expand the current finding and lead to the development of application strategies. + +Reply 6: We would like to thank the referee for the valuable suggestion. Our study revealed that SnRK2s are modified with a N- glycan on the ER- Golgi networks, and are redistributed on the peroxisomal membrane finally. As non- secretory proteins, how SnRK2s are located on the ER- Golgi networks; Where they are synthesized. They are translated on the rough ER and then enter the ER lumen, or they are synthesized in the cytosol and then translocated on the ER- Golgi. What triggers the ER- Golgi localization of them. The answers to these questions would deepen our understanding of the molecular mechanisms of ABA signalling. We are trying to answer some of these questions now. In our another project, we found a protein channel which may be responsible for the ER- Golgi- loading of SnRK2s, but now we need to collect more solid evidences to support this notion. + +Reviewer #3 (Remarks to the Author): + +This study presents a putative mechanism for the desensitization and transition of ABA signaling during prolonged treatment, involving N- glycosylation of SnRK2s. Under prolonged ABA signaling, the key regulator SnRK2.2/2.3 undergoes N- glycosylation in the ER- Golgi network, which leads to its translocation to the peroxisome. In the peroxisome, SnRK2s regulate NADPH generation by phosphorylating the transporter GPT1 during NADPH synthesis, suggesting a new module of redox homeostasis for adapting to long- term stress conditions during prolonged ABA signaling. The findings are interesting and provide insights into plant responses under prolonged stress conditions. However, there are several major issues in the manuscript that need to be addressed, before it could be considered by Nat Commun. + +We thank the reviewer for positive evaluation of the manuscript. + +Major Points: + +1. It is common to assay ABA responses through germination, cotyledon greening, and post-germination growth using different concentrations of ABA. In this study, the authors chose to germinate the seeds in a very high concentration of ABA (3 μM) and measured the root length at a later stage. Please explain the rationale for this choice and provide results from other assays. + +Reply 1: The comments are greatly appreciated. At the beginning of our project, we carried out morphological assays of gIIβ- 2 with 1, 3, 5 (μM) ABA, and the results showed that 3 μM ABA induced more significant difference in gIIβ- 2, OE- GIIβ compared with WT in terms of germination rate (Rebuttal Fig. 2). Hereafter, 3 μM ABA was chosen for phenotypical assays of all mutants of N- glycosylation processing enzymes (NPEs). we apologize for not including these results due to space limitation in our first submission. + +<--- Page Split ---> +![](images/Figure_2.jpg) + +
Rebuttal Fig. 2 | The seed germination rate of Arabidopsis plants.
+ +a- d, The germination rate of Col- 0, glβ- 2 and OE- Glβ- 16 were determined with different concentrations of ABA. The germination rate was calculated every half day until the fifth day (after stratification at \(4^{\circ}\mathrm{C}\) for 2 days). In each petri dish, approximately 60 seeds were counted for each Arabidopsis genotype. + +2. The major discovery in this work is that N-glycosylation of SnRK2s leads to the desensitization of prolonged ABA signaling through translocation. However, the relationship between these two processes remains unclear. Does N-glycosylation of SnRK2s occur before or after their translocation? Does N-glycosylation cause translocation, or does translocation lead to N-glycosylation? It would be helpful to design a subcellular-fixed mode of SnRK2s that can only be located in the nucleus or peroxisome to investigate the effects. + +Reply 2: We thank the reviewer for the valuable comments. In our purposed working model (revised Extended Data Fig. 18), SnRK2s appear to be N-glycosylated on the ER-Golgi networks, then to be redistributed to the peroxisome membrane, which is supported by evidences from N-glycosylation assays (Fig. 2d-j) and time-course confocal microscopy observations of SnRK2.2/2.3- GFP (Fig. 3a-g). The peroxisomal localization of SnRK2.2- GFP was inhibited by stt3a- 2, and was enhanced by STT3A overexpression (Fig. 3d); mutation of N-glycosylation site of SnRK2.3N323A suppress its peroxisomal redistribution (Fig. 3f). The findings indicate that N-glycosylation is one of the key factors to determine the peroxisomal redistribution of SnRK2.2/2.3. + +Based on the reviewer's suggestions, we constructed fixed SnRK2.3s with SV40 nuclear location signal (NLS) and PEX26 c- terminal end (mPTSPEX26) (Wright and Bartel, 2020) specifically located in the nucleus and on the peroxisomal membrane respectively. As shown in revised Extended Data + +<--- Page Split ---> + +Fig. 17, the SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 showed the fixed subcellular localizations and normal kinase activities. To investigate the N- glycosylation, we transiently expressed them in the Arabidopsis roots. After treatment with ABA, the total protein extracts were co- immunoprecipitated with GFP- trap beads, and the N- glycosylation of fixed SnRK2.3s was determined by ConA- HRP (ConA, concanavalin A, a plant lectin can bind to mannose on the glycoproteins; ConA- HRP, HRP conjugated ConA (Sigma- Aldrich, L6397); HRP, horseradish peroxidase). + +We proposed that the nuclear SnRK2.3 is not N- glycosylated, whereas peroxisomal SnRK2.3 should possess a N- glycan. Unexpectedly, our results showed that only wild type SnRK2.3 is N- glycosylated, but both SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 are not (Rebuttal Fig. 3). The absence of N- glycan of peroxisomal SnRK2.3 may be due to deferent targeting pathways of native SnRK2.3 and fixed SnRK2.3. The SnRK2.3- mPTSPEX26 may directly target to the peroxisomal membrane, whereas native SnRK2.3 redistribute to the peroxisomes through ER- Golgi networks. + +![](images/Figure_6.jpg) + + +Rebuttal Fig. 3 | N- glycosylation assays of SnRK2.3WT, SnRK2.3- NLS, SnRK2.3- mPTSPEX26 with ConA- HRP. Total proteins were extracted from ABA- treated transgenic hair roots of SnRK2.3WT/snrk2.2/2.3, SnRK2.3- NLS/snrk2.2/2.3, and SnRK2.3- mPTSPEX26/snrk2.2/2.3, followed by immunoprecipitation with GFP- Trap agarose and detection with the anti- GFP antibody and ConA- HRP. The white arrowhead indicates the N- glycosylated SnRK2.3WT- GFP. + +## Reference + +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +The introduction of this paper focuses mainly on plant ABA signaling but lacks information about N- glucosidases, especially those mentioned in this work. + +Reply 3: We thank the reviewer for the comments. Based on the reviewer's suggestion, detailed information about N- glycosylation has been added to the introduction of the revised manuscript with highlight of the roles of STT3A, GIIa, GIIβ, CGL1, GMII, and FUT11 used in our study. + +Why the authors chose to study STT3A instead of the GIIβ, the mutant initially screened in most experiments? + +Reply 4: We thank the reviewer for the comments. N- glycosylation involves sequential actions of an array of enzymes, such as STT3A, GIIa, GIIβ, and FUT11 used in our study, which function in transfer and modification of sugar moieties in ER and Golgi networks (Strasser, 2016; Zielinska et al., 2012). STT3A is a catalytic subunit of oligosaccharide transferase complex, whereas GIIβ is involved in GIIα/β- heterodimer- mediated glucose trimming of N- glycans. For the N- glycosylation + +<--- Page Split ---> + +assays, GIIβ would cause about 0.18 kDa molecular mass difference (one glucose) of SnRK2.2/2.3, but this molecular mass difference would be enlarged to 2- 3 kDa (one N- glycan) made by STT3A (Shen et al., 2014). Similar ABA- sensitive phenotype, but easy test for N- glycosylation assay of SnRK2.2/2.3, STT3A was chosen for further works instead of GIIβ. We apologize for making some confusion in our manuscript. We added a reasonable sentence in the revised manuscript at line 173. + +## Reference + +Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +5. The authors performed a time course RNA-seq analysis to investigate the effects of N-glucosidases, but the stt3a-2 results were analyzed using Col-0 as a control instead of using no ABA-treated stt3a-2 as a control. + +Reply 5: We thank the reviewer for the comments. We have 0 h ABA-treated stt3a-2 which is a no ABA-treated control. When analyzed datasets, we first carried out k-means clustering analysis to determine the ABA-responsive genes (well overlap with previously reported ABA-responsive genes), and their time-course expression pattern in ABA-treated Col-0 group with 0 h - ABA-Col-0 as a control. Then we retrieved the expression profiles of these ABA-responsive genes from no-ABA-treated Col-0 group (0-72 h), to show their basal expression level during 72 h-ABA treatment. Finally, we retrieved the expression data of the ABA-responsive genes from ABA-treated stt3a-2 with 0 h- stt3a-2 as a control, to show the desensitization of ABA-responsive genes is delayed in stt3a-2 compared with ABA-treated Col-0. Detailed information was added in revised manuscript line 115 and 121. + +Additionally, the results do not seem to match the expression pattern shown in Figure 1g- i, as the expression of stress response genes in stt3a-2 would be expected to be stronger and longer than in Col- 0. Address these inconsistencies and provide a proper control for the analysis. + +Reply 6: For ABA- induced cluster 18 in (previous) Fig. 1k (now in revised Extended Data Fig. 3a), the biphasic inflection timepoint is delayed from 1 h in Col- 0 to 2 h in stt3a- 2. However, the expression level of these genes in stt3a- 2 appears not stronger and longer than that in Col- 0. This phenomena may be due to its special expression pattern with the rapid induction (peak at 1 h) and followed by a rapid reduction (4- 6 h to basal level, (previous) Fig. 1j (now in revised Extended Data Fig. 3a)), whereas, the expression of NCED3, P5CS1, and RAB18 all peak at 3 h, and decline to basal level at 48 h for NCED3 and RAB18 (Fig. 1g- i). Our study also revealed that N- glycosylation mainly function in prolonged ABA signalling. Taken together, our results may suggest the weaker effects of N- glycosylation/STT3A on these rapidly induced ABA- responsive genes in cluster 18. + +For the left 3 ABA- induced clusters (cluster 1, 8 and 13 in Extended Data Fig.3a), the expression peaks of them are 4- 6 h, 6 h, 2- 3 h in ABA- treated Col- 0 respectively, which are similar to that of NCED3, P5CS1, and RAB18 in Fig. 1g- i. the expression of genes in cluster 1, 8, and 13 is stronger and longer in stt3a- 2 than that in Col- 0. We put cluster 1 in Fig.1j, k in exchange of cluster 18, and related text also was corrected in our revised manuscript. + +<--- Page Split ---> + +In Figure 2, based on the results of co- expressed SnRK2.2/2.3 and STT3A in tobacco, the western blot results need to include a control without co- expression and ABA treatment to confirm the band as N- glycosylated SnRK2s. + +Reply 7: We thank the reviewer for the comments. That's correct. Done. The results were shown in revised Fig. 2f. + +Additionally, the western blot results in snrk2.6 mutants require a control using snrk2.2/2.3/2.6 mutants to eliminate non- specific bands. Include these controls for a more accurate interpretation of the results. + +Reply 8: Done. See revised Fig.2h and i. + +We also checked the specificity of the antibody used (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +![](images/Figure_10.jpg) + + +Rebuttal Fig. 3 The anti- SnRK2.2/2.3/2.6 used in our study. + +The 10- day seedlings of snrk2.6 single mutant, snrk2.2/2.3 double mutant, and snrk2.2/2.3/2.6 triple mutant were used here. (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +To confirm the N- glycosylated point Asp323 on SnRK2.3, include at least one additional point mutant in Figure 2k as a negative control to provide more solid evidence. + +Reply 9: We thank the reviewer for the comments. Another point mutation SnRK2.3N288A has been included in the N- glycosylation assay (see revised Fig.2k). + +Regarding the translocation of SnRK2.2/2.3- GFP in Arabidopsis, both SnRK2.2 and SnRK2.3 need to complete this evidence. Choose one of them to show the results instead of showing SnRK2.2 translocation with SnRK2.3 (Fig 3d) and performing a mutation assay with SnRK2.3N323A (Fig 3f). The results in Figure 3f indicate that a small amount of SnRK2.3N323A can still export from the nucleus, while SnRK2.2 cannot translocate in the stt3a- 2 mutant. This suggests that other factors may be involved in SnRK2.3 translocation besides N- glycosylation at N323, but it is difficult to confirm due to the unequal comparison. To address this, extract nuclear and cytoplasmic proteins separately for western blot analysis to check the N- glycosylation of SnRK2.2/2.3 after ABA treatment. + +Reply 10: We thank the reviewer for the careful evaluation. We are sorry for misunderstanding of redistribution of SnRK2.2 and SnRK2.3 due to lacking full evidences of both of them. Actually, there is no any significant difference between SnRK2.2 and SnRK2.3 in their subcellular dynamics. In stt3a- 2 background, peroxisomal redistribution of SnRK2.2- GFP is repressed, but few amount of SnRK2.2- GFP still locate on the peroxisomes like SnRK2.3N323A (see 48 h ABA in (previous) Fig. 3d). + +Based on the reviewer's suggestions, to avoid misunderstanding, we have completed the observation of both SnRK2.2- GFP and SnRK2.3- GFP in the revised Fig. 3a. We also re- investigated SnRK2.2- GFP subcellular dynamics under stt3a- 2, and STT3A- OE backgrounds in + +<--- Page Split ---> + +revised Fig. 3d and 3e. For N- glycosylation of SnRK2.2 and SnRK2.3, they are also similar to each other (Fig. 2d-f, and Extended Data Fig. 7) + +8. In most experiments, the authors used SnRK2.3N323A, a mutant with abolished N-glycosylation of SnRK2.3 (Fig 2k). However, SnRK2.3 still exists in both the nucleus and peroxisome (Fig 3f), which may explain the weak or inconsistent results in Fig. 4 and Extended Data 16. To overcome this issue, delete the nuclear localization signal and peroxisome targeting signal separately to generate SnRK2.2/3 specifically located in the peroxisome and nucleus, and assess the function of SnRK2.2/3 translocation. Additionally, include snrk2.2/snrk2.3 as controls in all assays of SnRK2.32WT and SnRK2.3N323A to demonstrate the role of SnRK2s in these processes. + +Reply 11: We thank the reviewer for the valuable comments. We agree with the reviewer that N- glycosylation is not the only effector in the regulation of SnRK2.2/2.3's redistribution, as SnRK2.3N323A with mutated N-glycosylation site can still presents on the peroxisomes. However, our studies also showed that N-glycosylation is a crucial effector for SnRK2-redistribution during prolonged ABA signalling. Firstly, genetic analysis showed that N-glycosylation is a key regulator in ABA signalling (ABA-hypersensitivity of npe mutants and SnRK2.3N323A/snrk2.2/2.3 transgenic lines (Fig. 1a-f, Extended Data Fig. 8). Secondly, the subcellular dynamics of SnRK2.2/2.3 in Fig. 3d,e and Fig. 3f,g showed that significantly less SnRK2.3/2.3 locate on the peroxisomes when N- glycosylation is defective. Finally, ABA-induced NADH maintenance and H2O2 clearance are significantly affected by N-glycosylation (stt3a-2 vs. Col-0; SnRK2.3N323A vs. SnRK2.3WTin snrk2.2/2.3 double mutant background) during prolonged ABA signalling (Fig. 4a, d and Extended Data Fig. 11, 13, 15c-f, and 16a-d). Totally, our results suggested strong correlation between N- glycosylation and peroxisomal localization of SnRK2.2/2.3. + +To confirm whether the effect of N- glycosylation on ABA signalling is due to the peroxisomal targeting of SnRK2.2/2.3, based on the reviewer's suggestion, we constructed the fixed SnRK2.3s that specifically locate in the nucleus (SnRK2.3- NLS) and the peroxisomal membrane (SnRK2.3- mPTSPEX26), and expressed them in the snrk2.2/2.3 double mutant background (Wright and Bartel, 2020). As shown in revised Extended Data Fig. 17, and Fig. 4i, j, both of them possess normal kinase activities, and the SnRK2.3- mPTSPEX26 possesses higher NADPH level (NADPH/NADP+) and lower H2O2 than SnRK2.3WT during prolonged ABA signalling, whereas SnRK2.3- NLS has the highest H2O2 level. We also investigated the ABA- transcriptional response, and the results showed that SnRK2.3- NLS strongly enhance the expression of ABA- responsive genes, but SnRK2.3- mPTSPEX26 not. Our findings support the notion that SnRK2.3 activates the ABA- transcriptional response, whereas the peroxisomal SnRK2.3 for NADPH maintenance during prolonged ABA signalling. In all these experiments, snrk2.2/2.3 double mutant was included as a control. See revised manuscript line 437- 468. + +The SnRK2.3N323A, SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 were expressed under the snrk2.2/2.3 double mutant background, and the SnRK2.3WT/snrk2.2/2.3 was used as a strict control in these analyses. + +## Reference + +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intralumenal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +<--- Page Split ---> + +This study shows the interaction and regulation between SnRK2s and GPT1, but mainly focuses on SnRK2.2 and GPT1, neglecting SnRK2.2 and 2.3. + +Reply 12: We thank the reviewer for the comments. According to the reviewer's suggestion, the interaction assay between SnRK2.3 and GPT1 has been added in revised Fig. 4c. Phosphorylation analysis of GPT1 by SnRK2.3 has been added in revised Fig. 4e. Interaction assay of GPT1 and SnRK2.2, and phosphorylation analysis of GPT1 by SnRK2.2 have been moved to Extended Data Fig. 14c, f. + +The time- course expression pattern of GPT1 protein, and identification of GPT1 phosphorylation sites by LC- MS/MS have been moved to Extended Data Fig. 14d, e. + +To verify the function of the phosphorylation site, stable transgenic plants would provide more solid evidence than transient expression. + +Reply 13: We thank the reviewer for the comments and we agree with the reviewer that GPT1- stable transgenic plants would provide more strong support to our manuscript. We have obtained gpt1- 1 mutant from prof. Juan Xu (Zhe Jiang University)(Zheng et al., 2018), and are trying to introduce the GPT1WT, GPT1S324, and GPT1S320 constructs into gpt1- 1(- /-) background, but it appears a hard and long- time work. gpt1- 1 mutant is a T- DNA insertion line and the homozygous gpt1- 1 (- /-) is embryo lethal, so we had to introduce GPT1- constructs into gpt1- 1 (- /+) background. it would need a long time to screen GPT1WT, GPT1S324, and GPT1S320 transgenic lines with gpt1- 1 (- /-) background. On the other hand, our transient expression data of GPT1- constructs in Fig. 4g and h, appears to work well. It showed significantly difference for GPT1S324 and GPT1S320, compared with GPT1WT. Without a doubt, the stable transgenic plants would provide more strong evidences to our conclusions, and we will continue to screen the GPT1- transgenic plants, and collect more comprehensive evidences to support the conclusions. + +## Reference + +Zheng, Y., Deng, X., Qu, A., Zhang, M., Tao, Y., Yang, L., Liu, Y., Xu, J., and Zhang, S. (2018). Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis. PLoS Genet 14, e1007880. + +Explain why the SnRK2.2- and SnRK2.3- GFP proteins showed a dramatic increase (more than 10- fold) after ABA treatment in Extended Data Fig. 9c. However, in Extended Data Fig 9e, the SnRK2.2- GFP protein only increased less than 1.5- fold after ABA treatment, leading to inconsistency. Generally, the protein abundance of SnRK2s should decline after ABA treatment. Provide an explanation for this discrepancy. (in Extended Data Fig 9e, the 35S:: SnRK2.2- GFP, error bar value) + +Reply 14: We investigated temporal dynamics of endogenous SnRK2.2/2.3/2.6 over prolonged ABA treatment with antibody (Agrisera AS142783) in our manuscript, and the results showed that the SnRK2.2/2.3/2.6 are induced by short- term ABA treatments (peak at 4- 6 h), then following degradation (Extended Data Fig. 9c), which is consistent with previous report (Ali et al., 2019). SnRK2.2- GFP, even through driven by 35S promoter, has a similar expression pattern over ABA treatment, indicating SnRK2s are tightly regulated by ABA in protein level (Extended Data Fig. 9d). However, the fold- change of SnRK2.2- GFP induced by short- term ABA is less than endogenous SnRK2.2/2.3 compared with 0 h ABA. This difference may caused by 35S promoter, which elevates the basal expression level of SnRK2.2 without ABA treatment. This hypothesis was also supported by the temporal expression pattern of 35S:: SnRK2.3- GFP in revised Extended Data + +<--- Page Split ---> + +## Fig. 9e. + +## Reference + +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. + +In Extended Data Fig. 11, clarify the location of ROS affected by the stt3a mutation, rather than focusing on the amount. + +Reply 15: We thank the reviewer for the comments. It was previously reported that SnRK2.2/2.3 mainly are expressed in root tip (Fujii et al., 2007). In our study, we found that the redistribution of SnRK2.2/2.3 induced by prolonged ABA also mainly occurs in root meristem which is consistent with the ROS location affected by stt3a and mutation of N- glycosylation site of SnRK2.3 (SnRK2.3N323A). we have clarified that the root meristem or root tips are the main region of ROS affected by stt3a and N- glycosylation of SnRK2.2/2.3 (revised manuscript line 330, and line 345; Extended Data Fig.11 and 13) + +## Reference + +Fujii, H., Verslues, P.E., and Zhu, J.K. (2007). Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell 19, 485- 494. + +## Additional issues: + +11. In Line 65 to Line 67, the reference to Extended Data Figure should be corrected to Extended Data Figure 1. + +Reply 16: That's correct. Done. + +12. In Figure 4d, the legend describes a Co-IP assay using 4-day-old seedlings, but the results show a different pattern compared to Figure 4b, which also shows a Co-IP assay using the same material. + +Reply 17: Thanks the viewer for the comments. (previous) Fig. 4d is not a Co-IP assay, it is a western blot analysis using total protein extracts to determine the temporal expression pattern during prolonged ABA treatment. The figure legend has been corrected (Now in Extended Data Fig. 14d). + +Additionally, Figure 4d indicates a \(3\mu \mathrm{M}\) ABA treatment, but the legend describes it as \(50\mu \mathrm{M}\) ABA. Please address these inconsistencies. + +Reply 18: Actually, \(3\mu \mathrm{M}\) ABA was used in (previous) Fig. 4d, and the figure legend has been corrected (Now in Extended Data Fig. 14d). + +13. The results in Figure 21 and m demonstrate the phenotype of the triple mutant stt3a-2/snrk2.2/2.3 to confirm the epistasis of SnRK2.2/2.3 to STT3A. However, Figure 21 shows a slightly longer primary root in the triple mutant, whereas Figure 2m shows the reverse result, with the triple mutant having a slightly longer root. This discrepancy may be due to the selection of seedlings for photography. Clarify this issue. + +Reply 19: Thanks the referee for the comments. The quantification data is a relative root length (ABA+/- ) in Fig. 2m. The ratio (ABA+/- ) of WT was designated as 1, and the relative ratio to WT was shown for double and triple mutants. Although Fig. 21 showed a little bit longer roots for triple mutant with and without ABA treatment, the relative ratio is slightly smaller. We are sorry for this confusion due to lacking detailed information. The figure legend of Fig. 21, m, has been described + +<--- Page Split ---> + +in details. + +14. In Figure 3a and 3b, the intensity of SnRK2.2-GFP appears to increase after 2 hours of treatment, but Figure 3d shows a similar fluorescence intensity. Although this does not directly relate to the conclusion, please address this inconsistency. + +Reply 20: We thank the reviewer for the careful evaluation. In (previous) Fig. 3d, we mainly focus on the subcellular changes of SnRK2.2-GFP under different backgrounds. In order to observe the peroxisomes more clearly, the fluorescence intensity was appropriately enhanced in some photographs. Based on the reviewer's suggestion, we have re-investigated SnRK2.2-GFP subcellular dynamics under Col-0, stt3a-2, and STT3A-OE backgrounds, and have replaced them with more suitable photographs in revised Fig. 3d and 3e. + +Additionally, for Figure 3c, a larger scale view may be more suitable to clearly show the cytosol, nuclear, and peroxisome localization of SnRK2.2- GFP. + +Reply 21: We thank the reviewer for the comments. The overlap between SnRK2.2/2.3- GFP and peroxisomal marker gene has been re- investigated, and the photographs with higher quality and a larger view have been replaced for revised Fig. 3c. + +15. Ensure that the growth conditions described in the text match those depicted in Figure 1a, 1c, and 1e, as there appears to be a significant difference in root lengths of Col-0 plants. + +Reply 22: We thank the viewer for the comment. The detailed information about growth conditions has been clarified in revised figure legend of Fig.1a, 1c, and 1e. + +## Additional corrections: + +As the enzymes of N- glycosylation pathway used in our study include transferase (STT3A), glucosidase (GIIα, and GIIβ), acetylglucosaminyltransferase (CGL1), mannosidase (GMII), and fucosyltransferase (FUT). The term "N- glucosidases" can not represent all these enzymes. So we have replaced "N- glucosidases" with "NPEs" (N- glycan processing enzymes) in the revised manuscript. + +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. Farid, A., Pabst, M., Schoberer, J., Altmann, F., Glossl, J., and Strasser, R. (2011). Arabidopsis thaliana alpha1, 2- glucosyltransferase (ALG10) is required for efficient N- glycosylation and leaf growth. Plant J 68, 314- 325. Fujii, H., Verslues, P.E., and Zhu, J.K. (2007). Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell 19, 485- 494. Liu, Y., Zhang, C., Wang, D., Su, W., Liu, L., Wang, M., and Li, J. (2015). EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated + +<--- Page Split ---> + +degradation system in Arabidopsis. Proc Natl Acad Sci U S A 112, 12205- 12210. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Sato, T., Sako, Y., Sho, M., Momohara, M., Suico, M.A., Shuto, T., Nishitoh, H., Okiyoneda, T., Kokame, K., Kaneko, M., et al. (2012). STT3B- dependent posttranslational N- glycosylation as a surveillance system for secretory protein. Mol Cell 47, 99- 110. Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M.E., and Nasrallah, J.B. (2014). Site- specific N- glycosylation of the S- locus receptor kinase and its role in the self- incompatibility response of the brassicaceae. Plant Cell 26, 4749- 4762. Zheng, Y., Deng, X., Qu, A., Zhang, M., Tao, Y., Yang, L., Liu, Y., Xu, J., and Zhang, S. (2018). Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis. PLoS Genet 14, e1007880. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<--- Page Split ---> + +Reviewer #4 (Remarks to the Author): + +This is a highly interesting manuscript and I would like to see that story published. However, I am not convinced that all the conclusions are supported by the shown data. Therefore, I would ask the authors for additional experiments and explanations. + +## Major points + +The general concept: + +How do you think does this transport and glycosylation process work (see statement in Abstract lines 11- 12)? How do you think that STT3A- mCherry (a protein with numerous transmembrane domains) localizes to the cytoplasm - see statement in lines 142- 144 - without a membrane it would immediately aggregate. How can glycosylation in the lumen of the ER affect the nuclear localization of another protein (processes taking place in completely different subcellular compartments)? Based on your model in Extended Data Fig. 17, the SnRK2 proteins are transported to the ER lumen for glycosylation, if it is like this than glycosylation is not involved in transport from the nucleus/cytoplasm to the ER lumen and another process mediates this transport. Then glycosylation of SnRK2.2/2.3 might be involved in transport from the ER to the peroxisomes, but this is not clearly shown and glycosylation would then not be involved in desensitization of the transcriptional response in the nucleus. Do you think that the folded SnRK2.2/2.3 proteins are taken up into the ER where they are glycosylated by a complex that normally glycosylates unfolded proteins? Which complex is involved in the uptake into the ER? Glycosylation mutants are pleiotropic and typically affect many proteins, how likely is it that there are indirect effects from other glycoproteins that are related to the ABA sensitivity? + +The protein- protein interaction data: + +In the Y2H assay SnRKs is not glycosylated and an interaction with Gilbeta therefore shows that the interaction is not N- glycan dependent. Gilbeta has a lectin domain for carbohydrate binding, so binding to a non- glycosylated protein shows a glycosylation- independent process or hints at an unspecific binding event. Panel a from the Extended Data Fig. 5 (and also Fig. 2b and comment below) confirms that because the GST- tagged protein is produced in E.coli and therefore not glycosylated. + +The luciferase assay shows interaction of all tested SnRKs with all tested glycosylation related enzymes. This is suspicious, especially because the tested glycosylation related enzymes are located in different subcellular compartments, have a different membrane topology and most have only a few amino acids facing the cytosol where the interaction with SnRKs would likely occur. Moreover, glycosylation related enzymes often interact with the glycan and not the protein and the interaction is only transient. + +I would like to see additional controls for the luciferase assay and additional experiments showing the interaction, like additional co- IP data. Why did the authors characterize a specific set of glycosylation related enzymes, the rationale for choosing them is not clear. Did they also test others like FUT12 or + +<--- Page Split ---> + +XylT? Related to that and their main claim that N- glycosylation plays a role, how sure are the authors that the used mutants lead to changes in N- glycosylation. Has this been shown for Arabidopsis Gllbeta and FUT11 knockout? + +The confocal data: + +I am sorry, but in the shown images a clear reticular ER network is not visible (e.g. Fig. 2j, Fig. 4c, Fig. 5g, Fig. 6b, e and f). The used ER- marker seems not appropriate in these experiments and is not frequently used to label the ER in tobacco in literature. In the shown images the cellular morphology appears altered, either because of the used marker or overexpressed proteins and often cellular structures are visible that look like aggregates. As a consequence, conclusions directly linked the ER localization data are questionable and BiFC data could represent false positives. The authors should provide better images, where the ER is clearly visible. Please provide also the subcellular localization of STT3A- mCherry and Gllbeta- GFP without any co- expressed other protein to see if they reside in the ER. + +In Extended Data Fig. 6b the authors show images of Gllbeta co- expression with SnRK2.2- GFP or SnRK2.3- GFP and show a diffuse signal in the cell. This looks more like a cell undergoing cell death than cytosolic localization. Please comment on that. How many cells show this type of fluorescence? Is it only visible with Gllbeta? Which Gllbeta was used for co- expression, is it also tagged with a fluorescent protein and leads to a diffuse labelling of the cell? Please provide co- localization data with Gllbeta- mCherry or at least with an ER- marker. + +In general, the confocal images are quite small, larger images should be provided and the quality of the images should be improved. + +The peroxisomal uptake should also be supported by more data clearer confocal images. In lines 188- 190 it is stated that translocation of SnRK2.2 might consist of two steps SnRK degradation and peroxisomal targeting. This is unclear. Do you mean that the protein in the nucleus is degraded and that new SnRK protein is translated in the cytoplasm that is then transported to the ER and further to the peroxisome? Is there any evidence for nuclear degradation? Which machinery would be involved in the degradation in the nucleus? Did you test proteasome inhibitors? Did you do any experiments with protein synthesis inhibitors to see if synthesis of new proteins is involved in the process. Additional experiments should be provided to support the claims. + +## The SnRK glycosylation: + +The overexpression of STT3A- mCherry results in an additional SnRK2.2- His/SnRK2.3- His band that is also detectable when treated with ABA. This raises a number of questions. This suggests, for example, that STT3A activity is limited in plants and its overexpression is sufficient to increase the glycosylation of proteins. Is there any additional evidence for that? STT3A is part of a larger protein complex and one would expect that other proteins in this complex are also required for the activity which were not overexpressed. Please comment on that. + +Given the fact, that the authors are familiar with peptide analysis by LC- MS/MS (Fig. 4f), they should try to purify the transiently expressed His- or GFP- tagged SnRK2.2/2.3 and confirm the presence of the glycan linked to N323 by MS analysis. + +<--- Page Split ---> + +The data from 2d suggest that ABA has the same effect as STT3A overexpression? How can this be explained? Do the authors suggest that ABA induces STT3A expression which leads to SnRK2.2/2.3 glycosylation. Is this process specific for SnRK2.2/2.3 or is protein glycosylation generally increased by ABA? + +The glycosylation of the transiently expressed His- tagged protein is obviously different from the endogenous protein because the His- tagged protein is fully sensitive to Endo H and PNG F in the presence of ABA. What would be the explanation for this difference? Please digest the His- tagged protein co- expressed with STT3A- mCherry also int the absence of ABA. + +In Fig. 2i, the anti- SnRK2.2/2.3/2.6 antibody is used to show glycosylation of the endogenous SnRKs proteins. This is an important experiment, but not entirely convincing because neither Endo H nor PNG F give a complete shift. Can the authors do the Endo H/PNG F digestion experiment in a glycosylation knockout, for example, in cgl1 plants where all glycans should be sensitive to Endo H and PNG F. The presence of the PNG F resistant band could be related to fucosylation which takes place in the Golgi and is catalyzed by FUT11. Is there any evidence that SnRKs are located in the Golgi? In which cellular compartment would FUT11 decorated the SnRK glycan with a fucose? Please do the same experiment from Fig. 2i also without ABA. + +Does Gilbeta- GFP coexpression also result in the occurrence of the glycosylated band on immunoblots with the His- antibody? What is the proposed molecular function of Gilbeta in the overall process? + +Other issues: + +In Fig.2b - please do the same experiment with the N323A protein. No glycosylated SnRK2.2/2.3 band is visible in the blot indicating that Gilbeta does not interact with the glycan on SnRK2.2/2.3. How is this then a glycosylation dependent process? Can the authors purify Gilbeta from the snrk2.6 mutant plants in the presence/absence of ABA and see if glycosylated SnRK2.2/2.3 come along? + +Fig.2f: please do the same experiment without ABA. + +Fig 2h: please provide quantitative data from several repetitions. + +In Fig. 2j the authors state that N323A coexpression disrupts its nuclear export. Why not the opposite - block of nuclear import in by SnRK2.3 expression? Can the authors provide a time series of images showing a transport process? + +Extended data Fig.5a: do the same with GST- SnRK2.3- N323A + +Extended data Fig.9c: show a time course experiment in the snrk2.6 background with anti- SnRK2.2/2.3/2.6 antibody for comparison. To see also if the glycosylated band increases with prolonged ABA incubation. Based on Extended Data Fig. 1f one would expect the highest STT3a expression after 6 h of ABA treatment and this should correlate with the increase of N- glycosylated SnRK2.2/2.3. + +Minor point + +<--- Page Split ---> + +The term N- glucosidase is not correct in the description of the glycosylated related enzymes. Some of the characterized proteins are transferases (STT3A, CGL1, FUT11) others are glycosidases (GMII) and only Glialpha and beta are glucosidases. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +This manuscript provides evidence that N- glycosylation of SnRK2s controls NADPH maintenance in peroxisomes, and this relates to the desensitization of plants to repeated ABA signalling. + +It is founded on discovery of a hypersensitivity to ABA- mediated repression in a mutant of \(\beta\) - subunit of glucosidase II (glIβ- 2). The fact of this hypersensitivity would imply some non- compensatory need for this specific glucoside directly. However, oddly the authors find the same hypersensitivity when they individually knockout other glucosidases - STT3A, GIIα and three other N- glucosidases (CGL1, GMII, FUT11) - so why can't they compensate for the glIβ- 2 mutant? Its not clear. I never saw any real exploration how each of these could in a non- compensatory manner effect the same pathway to SnRK2. + +Reply 1: We thank the reviewer for the valuable comments. For N- glycosylation modification, a nascent protein is attached a GlcManGlcNAc N- glycan on a specific asparagine (N) residue (NX(S/T) motif) by an oligosaccharide transferase complex when it enters the ER lumen. Subsequently, N- glucosidase I (GI) and GIIα/GIIβ heterodimer remove the outmost two glucose residues. GII- trimmed glycoprotein (N- glycan, GlcManGlcNAc) is captured by calnexin/calreticulin (CNX/CRT) for quality control. Successfully folded glycoprotein (ManGlcNAc) can be further processed by mannose- removing enzymes (α- mannosidase, MNSs), β1,2- N- acetylglucosaminyltransferase I (GntI), Golgi- α- mannosidase II (GMII), fucosyltransferases (FUT), etc. sequentially in the ER- Golgi network, to form characteristic complex- type N- glycans (Nagashima et al., 2018; Strasser, 2016). + +The importance of this sequential actions of N- glycan processing enzymes (NPEs) was supported by Farid's study (Farid et al., 2011). Severe defects of \(gl\) mutant can be suppressed by additional mutation of ALG10 which is responsible for biosynthesis of the outmost glucose residue, suggesting that trimming of the Glc by GI is a prerequisite for further processing by GII (Farid et al., 2011). In our manuscript, we provided rich data such as protein- protein assays and genetic interactions between NPEs and SnRK2s, showing that NPEs regulate ABA signalling through common substrate SnRK2 kinases. The similar ABA- hypersensitivity of these npe mutants (stt3a, glIα, glIIβ, cgl1, hgl1, fut1) imply the importance of the mature structure of N- glycan for the SnRK2s' biological roles. The similar high- salt- hypersensitivity of these npe mutants were also reported previously and reviewed by Richard Strasser (Strasser, 2016). + +Based on suggestions from you and reviewer #3, more detailed information about N- glycosylation was added to introduction of the revised manuscript. + +## Reference + +Farid, A., Pabst, M., Schoberer, J., Altmann, F., Glossl, J., and Strasser, R. (2011). Arabidopsis thaliana alpha1,2- glucosyltransferase (ALG10) is required for efficient N- glycosylation and leaf growth. Plant J 68, 314- 325. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +The manuscript then uses experiments on glIβ- 2 or stt3a mutants interchangeably to then explore the mechanism of this desensitization of plants to repeated ABA signalling. + +Reply 2: We thank the reviewer for the comments. As GIIβ and STT3A act in the same N- glycosylation pathway to co/post- modify SnRK2.2/2.3, and their mutants exhibit similar + +<--- Page Split ---> + +hypersensitivity to ABA, they were used in our study to double- check the effect of N- glycosylation on ABA signalling in some experiments such as protein- protein binding, and genetic assays. But for N- glycosylation assay, STT3A can cause about 2- 3 kDa molecular mass difference of SnRK2.2/2.3 (one N- glycan difference), whereas GIIα/β induce only one glucose difference ( \(\sim 0.18\) kDa). It's easy to distinguish the N- glycosylated SnRK2.2/2.3 with STT3A. So the STT3A and its' mutant were chosen in N- glycosylation assays. We are sorry about making some confusion sometimes. + +The yeast 2 hybrid assays are implied to show an exclusive interaction between glβ- 2 and SnRK2.2/2/3/2.6 but this was a set of pairwise interactions, not a yeast- 2 hybrid screen, so its not reasonable to call it exclusive – they only tested what they tested. Same with the LCI assays – "GIIβ, STT3A, GIIα, CGL1 and FUT11 all exclusively bind to SnRK2s" its just amongst the assay done – its not exclusive of other targets of these glucosidases. + +Reply 3: We understand the reviewer's concern and removed the word "exclusively" according to the suggestions in the revised manuscript. + +Critical to the claims of the paper is that SnRK2s are glycosylated by these glucosidases – this is claimed by, "PNGase F and Endo H digestions confirmed that the band shift was due to N- glycan modification" this band shift seems to be the only evidence that this modification is occurring and the later genetic studies to mutate residues and show an absence of band shift – while in themselves compelling – are not independent of this method. There are a wide variety of other independent methods to prove N- glycan modification as well as MS and MRM methods to independently confirm the claim at the site on the SnRK2s – none of these are used but really should be to independently confirm this central claim of the paper. + +Reply 4: We thank the reviewer for careful evaluation and for encouraging us to improve our manuscript. We agree with the reviewer that MS (mass spectrometry) assay will be better for confirmation of SnRK2.2/2.3 N- glycosylation. Based on the reviewer's suggestion, we have carried out the LC- MS/MS analysis of SnRK2.3 N- glycosylation (Zielinska et al., 2012). Unfortunately, in the past few months, we tried no less than five times with SnRK2.3- GFP transgenic plants or SnRK2.3- His transgenic BY- 2 cells (bright yellow tobacco cell), but all failed. We presume that the failure may be due to the tiny amount of N- glycosylated SnRK2.3. only a few SnRK2s are N- glycosylated in Arabidopsis and transgenic tobacco cells (see Fig. 2d- i, k, and Rebuttal Fig. 1). + +In our manuscript, we have provide rich data to show the SnRK2.2/2.3 N- glycosylation and the crucial roles in ABA signalling. We mutated total 11 N sites (asparagine residues) individually, and identified the N- glycosylation site SnRK2.3N323 (Fig. 2j, Extended Data Fig. 6f- i). this site mutation can block SnRK2.3 N- glycosylation (Fig. 2k), can inhibit SnRK2.3 subcellular change (Fig. 2j, Fig. 3a- f), can enhance the expression of ABA- induced genes (Fig. 3i, j), and can change phenotype of snrk2.2/2.3 double mutant from ABA- hyposensitivity to ABA- hypersensitivity (Fig. 2l,m). + +Additionally, the method "band shift assays followed by PNGase F and Endo H digestions" we used, was a classical method widely used for identification of N- glycosylation in publications (Liu et al., 2015; Sato et al., 2012; Shen et al., 2014; Yamamoto et al., 2014). + +We will continue to explore this field in the future and use more methods to detect this phenomenon. Thanks the reviewer again for valuable comments. + +<--- Page Split ---> +![PLACEHOLDER_30_0] + + +## Rebuttal Fig. 1 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His. + +a, Enrichment of N- glycosylated SnRK2.3- GFP before MS analysis. SnRK2.3- GFP overexpression plants were treated with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) after seven days of growth and the roots were collected. After IP with GFP- Trap and ConA (concanaalvin A, a plant lectin can bind to mannose on the glycoproteins), the enrichment was determined by western blot. Input, total protein extract; GFP- Trap, enrichment of SnRK2.3- GFP by GFP- Trap beads; ConA- IP, enrichment of N- glycosylated SnRK2.3- GFP by ConA bead after GFP- Trap- IP. The white arrowhead denotes the N- glycosylated SnRK2.3- GFP. b, Coomassie brilliant blue staining after PNGase F digestion of N- glycosylated SnRK2.3- GFP enriched by ConA. The dashed white frame denotes the gel cut for LC- MS/MS. c, Enrichment of N- glycosylated SnRK2.3. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in tobacco leaves with 50 \(\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and N- glycosylated SnRK2.3 were enriched with Ni- NTA and ConA beads sequentially. No signal was shown after ConA enrichment (right line). So only Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. His- IP, enrichment of SnRK2.3- His by Ni- NTA; PNGase F, PNGase F digestion. N- SnRK2.3- His, N- glycosylated SnRK2.3- His. d, Coomassie brilliant blue staining after PNGase F digestion of His- antibody enriched SnRK2.3- His. The dashed white frame denotes the gel cut for LC- MS/MS. e, g, i, Coomassie brilliant blue staining after His- antibody enriched SnRK2.3- His. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in BY- 2 cells with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and SnRK2.3- His were enriched with Ni- NTA. The dashed white frame denotes the location of SnRK2.3- His. Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. f, h, j, After IP with Ni- NTA, the enrichment was determined by western blot. CK, total protein extract of wide type BY- 2 cells; Input, total protein extract of transgenic BY- 2 cells; His- IP, enrichment of SnRK2.3- His by Ni- NTA. + +## Additional method: + +## Enrichment of N-glycosylated SnRK2.3 + +Plant tissues were grounded to powder in the frozen state and homogenized in extraction buffer (50 mM Tris- HCl, pH 7.4, \(150\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, 5 mM DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with GFP- Trap agarose (Chromotek) or nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(4\mathrm{h}\) , beads were washed five times with ice- cold washing buffer (50 mM Tris- HCl, pH 7.4, \(400\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins were eluted with acidic buffer (200 mM glycine, pH 2.5) and immediately neutralized the eluate fraction with neutralization buffer ( \(100\mathrm{mM}\) Tris- HCl, pH 10.4). The eluted proteins were then incubated with ConA (concanaalvin A, a plant lectin can bind to mannose on + +<--- Page Split ---> + +the glycoproteins) beads (Beyotime) at \(4^{\circ}\mathrm{C}\) , After \(4\mathrm{h}\) , beads were washed five times with washing buffer ( \(20\mathrm{mM}\) Heps, \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl2, \(1\mathrm{mM}\) MnCl2, \(1\mathrm{mM}\) CaCl2, \(0.1\%\) Tween- 20). The proteins were eluted with elution buffer ( \(5\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}8.0\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{M}\) Glucose). + +After treatment with \(50\mu \mathrm{M}\) ABA for 48 hours, BY- 2 cells were collected by centrifugation. Cells were grounded to powder in the frozen state and homogenized in extraction buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl2, \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(8\mathrm{h}\) , beads were washed five times with ice- cold washing buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(400\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl2, \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins are boiled in boiling water for \(10\mathrm{min}\) after adding \(1\times\) glycoprotein denaturing buffer ( \(0.5\%\) SDS, \(40\mathrm{mM}\) DTT, \(\mathrm{H}_{2}^{18}\mathrm{O}\) ). + +## PNGase F digestion + +For PNGase F treatment, referring to the manufacturer's protocol, the reaction buffer (containing \(\mathrm{H}_{2}^{18}\mathrm{O}\) ) and PNGase F (New England Biolabs) were added to sample. The mixture was incubated for \(4\mathrm{h}\) at \(37^{\circ}\mathrm{C}\) before boiled in \(5\times\) SDS loading buffer. N- glycation of SnRK2.3 was detected by immunoblot analyses using by anti- GFP or anti- His antibodies after \(6\%\) SDS- PAGE. The sample was subjected to mass spectrometry detection after immunoblot analyses. + +## LC-MS/MS for identification of N-glycosylation site of SnRK2.3 + +For mass spectrometry analysis, protein samples were separated using SDS- PAGE electrophoresis and detected by coomassie brilliant blue staining. The SDS- PAGE gel at \(70\mathrm{kD}\) or \(40\mathrm{kD}\) was collected into a clean centrifuge tube. \(500\mu \mathrm{l}\) destain solution were added to a centrifuge tube and shaken at room temperature until the gel discolored. After discarding the supernatant, \(75\%\) acetonitrile ( \(200\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature. After \(30\mathrm{min}\) , \(500\mu \mathrm{l}\) \(\mathrm{H}_{2}\mathrm{O}\) were added to the centrifuge tube and shaken at room temperature for \(1\mathrm{h}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH}_{4}\mathrm{HCO}_{3}\) ( \(300\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH}_{4}\mathrm{HCO}_{3}\) ( \(20\mu \mathrm{l}\) ) and \(2\mu \mathrm{l}\) trypsin ( \(1\mu \mathrm{g / \mu l}\) , Promega) were added to the centrifuge tube, and gel was crushed. After centrifugation ( \(1000\mathrm{rpm}\) , \(1\mathrm{min}\) ), the sample was digested at \(37^{\circ}\mathrm{C}\) . After \(8\mathrm{min}\) , \(200\mu \mathrm{l}\) acetonitrile were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After centrifugation ( \(1000\mathrm{rpm}\) , \(1\mathrm{min}\) ), the supernatant was transferred to a new centrifuge tube. This step was repeated once, ultimately resulting in \(400\mu \mathrm{l}\) supernatant. The obtained supernatant was vacuum dried at \(60^{\circ}\mathrm{C}\) and dissolved in \(0.1\%\) formic acid ( \(100\mu \mathrm{l}\) ). Samples were subjected to mass spectrometry detection by using mass spectrometer (Orbitrap Fusion™ Lumos™ Tribrid™, Thermo Scientific). The N- glycation site of SnRK2.3 was analyzed using software (Proteome Discoverer 2.3). + +## Reference + +Liu, Y., Zhang, C., Wang, D., Su, W., Liu, L., Wang, M., and Li, J. (2015). EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated degradation system in Arabidopsis. Proc Natl Acad Sci U S A 112, 12205- 12210. Sato, T., Sako, Y., Sho, M., Momohara, M., Suico, M.A., Shuto, T., Nishitoh, H., Okiyoneda, T., Kokame, K., Kaneko, M., et al. (2012). STT3B- dependent posttranslational N- glycosylation as a surveillance system for secretory protein. Mol Cell 47, 99- 110. Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M.E., and Nasrallah, J.B. (2014). Site- specific N- glycosylation of the S- locus receptor kinase and its role in the self- incompatibility response of the brassicaceae. Plant Cell 26, 4749- 4762. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +The apparent translocation of SnRK2 to the peroxisome is proposed, but then recanted in the text, because nuclear export inhibition did not block it. Instead it seemed more likely the nuclear SnRK2 is degraded + +<--- Page Split ---> + +and a peroxisome targeted version is generated, so authors need to ensure they don't continue to claim 'translocation' in the text in other passages and also Fig 3 legend. + +Reply 5: We thank the reviewer for the comments. According to the suggestions from you and reviewer #2, we have replaced "translocate/translocation" with "redistribute/redistribution" to describe the movement of SnRK2 in the revised manuscript. + +When we get to peroxisomes and what SnRK2 interacts with, we see another selective process "we investigated the potential SnRK2- interacting partners among peroxisomal isozymes involved in \(\mathrm{H}_2\mathrm{O}_2\) - scavenging and NADPH generation" so again the link to GPT1 is really achieved by analysis of a small subset of hand picked targets. + +Reply 6: We thank the reviewer for the comments. In our study, we did not search the potential peroxisomal SnRK2 binding proteins genome- widely. One of the reasons is that it is hard to construct a gene library encoding all the peroxisomal isozymes for SnRK2- partner screening. Another reason is that it is hard to get the sole peroxisome- localized SnRK2 for IP- MS/MS analysis (some SnRK2s in the nuclei, and some on the peroxisomal membrane during prolonged ABA signalling). Instead, for quick identification of SnRK2 partners, we cloned 13 published genes of peroxisomal isozymes required for NADPH- generation on the peroxisomal membrane (Extended Data Fig. 14a), and identified GPT1 as a SnRK2 binding protein with ABA- dependent manner. Based on the reviewer #3's comments, we have constructed peroxisome- fixed SnRK2.3 (SnRK2.3- mPTSPEX26, with nuclear SnRK2.3- NLS as a control, see revised Fig. 4 i, j, and Extended Data Fig. 17), and we are trying to make transgenic Arabidopsis for SnRK2- binding protein screening in genome- wide via IP- MS/MS in the future. Thanks again for your valuable comments. + +In all honesty, the claim of changes in NADPH and ROS in peroxisomes require detailed time- lapse measurements to be performed. The claimed errors bars in Fig 4 and extended Fig 11 are noted to be based on mean plus or minus sd, no n value is provided for either in the legends. But the reporting summary suggested – “All experiments were repeated two- three biologically independent experiments as mentioned in figure legends and methods”. Having done these sorts of assays myself I find those errors (just a few percent in many cases) just inconceivably small for independent experiments. Throughout the paper these small n value experiments are just showing mean and sd, not data points on graphs to show means for each rep. + +These very small errors are essential for the claims made as the \(\mathrm{H}_2\mathrm{O}_2\) and NADPH changes in Figure 4 are very small. I would want to see further evidence that the errors are accurately reported across independent experiments. + +Reply 7: We thank the reviewer for the comments. According to the reviewer's suggestions, we re- quantified the level of \(\mathrm{H}_2\mathrm{O}_2\) and NADPH accumulation with three biological replicates in revised Fig. 4 a, and d. The “n value” in the figure legends of Extended data Fig. 11 and all the other figures were checked in our revised manuscript. + +Overall the biological case surrounding this mutant is extensively explored and links of the mutants effects back into ABA processes are extensive and involve a large amount of work and come to novel conclusions for the field. My main concern is that the biochemical pathway to the claim involves a series of selective choices that need to be acknowledged along the way and key points such as the glycosylation evidence and the clarification of how such small errors can be recorded need to be resolved. + +<--- Page Split ---> + +Reply 8: We would like to thank the reviewer for the careful evaluation and for encouraging us to improve our manuscript. we have provided our responses to all the comments point- by- point. We answered the comments about "a series of selective choices" in Reply 3 and 6. The N- glycosylation site of SnRK2.3 was re- identified with LC- MS/MS in Reply 4. To address the small error bars, we re- investigated the accumulation of NADPH, and \(\mathrm{H}_2\mathrm{O}_2\) levels with three independent biological replicates in Reply 7. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +Pretreating plants with mild abiotic stresses helps them to adapt to harsh conditions, and the adaptation process is enhanced by ABA treatment. Revealing the underlying mechanism would have practical implications. This paper reports that ABA causes the subcellular redistribution and target change of SnRK2.2/2.3, two key regulators of ABA signaling. SnRK2.2/2.3 are localized in the nucleus and activate transcriptional responses at the initial ABA signaling stage, but during prolonged ABA treatment, they are N- glycosylated in the ER- Golgi network and sent to the peroxisomes. On the peroxisomal membrane, SnRK2.2/2.3 phosphorylate and activate Glucose- 6- Phosphate Transporter 1 (GPT1), which helps maintain NADPH homeostasis and suppress \(\mathrm{H}_2\mathrm{O}_2\) over- accumulation. Plants that have undergone such changes become less responsive to ABA (desensitized) and may better tolerate stress conditions (becoming acclimated). + +The data presented in this paper are sound, the logic is clear, and the finding represents a significant step toward understanding the molecular mechanisms of plant acclimation. + +We greatly appreciate the reviewer for positive comments on our manuscript. + +Minor comments: + +1. Labeling errors: in Extended Data Fig. 1, the labels "e" and "f" are misplaced; the "Fig. 1f" is mislabeled. + +Reply 1: That's correct. Done. + +2. Labeling errors: Main text lines 65 - 67, the Extended Data Fig. 2c-e, 2f, and 2g should be Extended Data Fig. 1c-e, 1f, and 1g. + +Reply 2: Done. + +3. Labeling error: Main text line 92, the Fig. 1j should be Fig. 1j, k. + +Reply 3: Done + +4. Labeling error: Main text line 148, the Extended Data Fig. 6e should be Extended Data Fig. 6f. Reply 4: Done + +5. About the term "translocation": This term may mislead readers and should be considered revision. Throughout the paper, the authors use "translocate/translocation" to describe the change of SnRK2s localization patterns: SnRK2s are normally localized in the nucleus, and during prolonged ABA treatment, they are N-glycosylated and localized on the peroxisomal membrane. Although they disappear from the nucleus and reappear on the peroxisome, the SnRK2s proteins do not physically move 'from the nucleus to the peroxisomes'; this is supported by the experiment presented in Extended Data Fig. 10f, g (main text lines 188-190). Therefore, the term "translocate/translocation" does not accurately describe the process and can be misleading. For example, in the Abstract, line 11 reads, "...which promotes their gradual translocation from the nucleus to the peroxisomes...." Immediately following this sentence, line 13 reads, "After moving to the peroxisomal membrane, SnRK2s directly interact with...." This + +<--- Page Split ---> + +combination will almost surely make readers mistakenly think that SnRK2s physically move between the two organelles. A possible substitute for "translocation" is "redistribution." The term "redistribution" better describes the phenomenon, avoids misunderstanding, and inspires people to wonder. + +Reply 5: The comments are greatly appreciated. We have replaced the terms "translocate/ translocation" with "redistribute/redistribution" in the revised manuscript. + +In the abstract (line 11- 13), both "translocation" and "After moving to" have been replaced with "redistribution" and "On", respectively. + +People may ask where SnRK2s proteins are synthesized and precisely what triggers the switch from targeting SnRK2s to the nucleus to targeting them to peroxisomes. The answers to such questions may expand the current finding and lead to the development of application strategies. + +Reply 6: We would like to thank the referee for the valuable suggestions. Our study revealed that SnRK2s are modified with a N- glycan on the ER- Golgi networks, and are redistributed on the peroxisomal membrane finally. As non- secretory proteins, how are SnRK2s located on the ER- Golgi networks? Where are they synthesised? Are they translated on the rough ER and then enter the ER lumen? or they are synthesised in the cytosol and then translocated on the ER- Golgi? or they are directly translated on the surface of the peroxisomes (Dahan et al., 2022)? What triggers the ER- Golgi localization of them? The answers to these questions would deepen our understanding of the molecular mechanisms of ABA signalling. We are trying to answer some of these questions now. In our another project, we found a protein channel (homolog of TMED10 (Zhang et al., 2020)) which may be responsible for the ER- Golgi- loading of SnRK2s, but now we need time to collect more solid evidences to support this notion. + +## Reference + +Dahan, N., Bykov, Y.S., Boydston, E.A., Fadel, A., Gazi, Z., Hochberg- Laufer, H., Martenson, J., Denic, V., Shav- Tal, Y., Weissman, J.S., et al. (2022). Peroxisome function relies on organelle- associated mRNA translation. Sci Adv 8, eabk2141. + +Zhang, M., Liu, L., Lin, X., Wang, Y., Li, Y., Guo, Q., Li, S., Sun, Y., Tao, X., Zhang, D., et al. (2020). A Translocation Pathway for Vesicle- Mediated Unconventional Protein Secretion. Cell 181, 637- 652 e615. + +## Reviewer #3 (Remarks to the Author): + +This study presents a putative mechanism for the desensitization and transition of ABA signaling during prolonged treatment, involving N- glycosylation of SnRK2s. Under prolonged ABA signaling, the key regulator SnRK2.2/2.3 undergoes N- glycosylation in the ER- Golgi network, which leads to its translocation to the peroxisome. In the peroxisome, SnRK2s regulate NADPH generation by phosphorylating the transporter GPT1 during NADPH synthesis, suggesting a new module of redox homeostasis for adapting to long- term stress conditions during prolonged ABA signaling. The findings are interesting and provide insights into plant responses under prolonged stress conditions. However, there are several major issues in the manuscript that need to be addressed, before it could be considered by Nat Commun. + +<--- Page Split ---> + +Major Points: + +1. It is common to assay ABA responses through germination, cotyledon greening, and post-germination growth using different concentrations of ABA. In this study, the authors chose to germinate the seeds in a very high concentration of ABA (3 \(\mu \mathrm{M}\) ) and measured the root length at a later stage. Please explain the rationale for this choice and provide results from other assays. + +Reply 1: The comments are greatly appreciated. Actually, at the beginning of our project, we carried out morphological assays of gIIβ- 2 with 1, 3, 5 (μM) ABA, and the results showed that 3 \(\mu \mathrm{M}\) ABA induced more significant difference in gIIβ- 2, OE- GIIβ compared with WT in terms of germination rate (Rebuttal Fig. 2). Hereafter, 3 \(\mu \mathrm{M}\) ABA was chosen for phenotypical assays of all mutants of N- glycosylation processing enzymes (NPEs). we apologize for not including these results due to space limitation in our first submission. + +![PLACEHOLDER_36_0] + +
Rebuttal Fig. 2 | The seed germination rate of Arabidopsis plants.
+ +a- d, The germination rate of Col- 0, gIIβ- 2 and OE- GIIβ- 16 were determined with different concentrations of ABA. The germination rate was calculated every half day until the fifth day (after stratification at \(4^{\circ}\mathrm{C}\) for 2 days). In each petri dish, about 60 seeds were counted for each Arabidopsis genotype. + +2. The major discovery in this work is that N-glycosylation of SnRK2s leads to the desensitization of prolonged ABA signaling through translocation. However, the relationship between these two processes remains unclear. Does N-glycosylation of SnRK2s occur before or after their translocation? Does N-glycosylation cause translocation, or does translocation lead to N-glycosylation? It would be helpful to + +<--- Page Split ---> + +design a subcellular- fixed mode of SnRK2s that can only be located in the nucleus or peroxisome to investigate the effects. + +Reply 2: We thank the reviewer for the valuable comments. In our purposed working model (revised Extended Data Fig. 18), SnRK2s appear to be N- glycosylated on the ER- Golgi networks, then to be redistributed to the peroxisome membrane, which is supported by evidences from N- glycosylation assays (Fig. 2d- j) and time- course confocal microscopy observations of SnRK2.2/2.3- GFP (Fig. 3a- g). The peroxisomal localization of SnRK2.2- GFP was inhibited by stt3a mutant, and was enhanced by STT3A overexpression (Fig. 3d); mutation of N- glycosylation site of SnRK2.3N323A delayed its peroxisomal redistribution (Fig. 3f). The findings indicate that N- glycosylation is one of the key factors to determine the peroxisomal redistribution of SnRK2.2/2.3. + +Based on the reviewer's suggestions, we constructed fixed SnRK2.3s with SV40 nuclear location signal (NLS) and PEX26 c- terminal end (mPTSPEX26) specifically located in the nucleus and on the peroxisomal membrane respectively (Wright and Bartel, 2020). As shown in revised Extended Data Fig. 17, the SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 showed the fixed subcellular localizations and normal kinase activities. However, they were not N- glycosylated (SnRK2.3WT as a positive control in Rebuttal Fig. 3). The absence of N- glycan on SnRK2.3- mPTSPEX26 may be due to different targeting pathways of native SnRK2.3 and fixed peroxisomal SnRK2.3. Our findings support the notion that N- glycosylation cause translocation, but translocation does not lead to N- glycosylation of SnRK2.3. + +![PLACEHOLDER_37_0] + + +Rebuttal Fig. 3 | N- glycosylation assays of SnRK2.3WT, SnRK2.3- NLS, SnRK2.3- mPTSPEX26 with ConA- HRP. Constructs SnRK2.3::SnRK2.3WT- GFP (SnRK2.3WT), SnRK2.3::SnRK2.3- NLS- GFP (SnRK2.3- NLS), and SnRK2.3::SnRK2.3- GFP- mPTSPEX26 (SnRK2.3- mPTSPEX26) were expressed in Arabidopsis root hair of snrk2.2/2.3. Total proteins were extracted from ABA- treated transgenic hair roots of SnRK2.3WT, SnRK2.3- NLS- GFP, and SnRK2.3- GFP- mPTSPEX2, followed by immunoprecipitation with GFP- Trap agarose and detection with the anti- GFP antibody and ConA- HRP. The white arrowhead indicates the N- glycosylated SnRK2.3WT- GFP. ConA, concanavalin A, a plant lectin can bind to mannose on the glycoproteins; ConA- HRP, HRP conjugated ConA (Sigma- Aldrich, L6397) for glycoprotein detection; HRP, horseradish peroxidase. + +## Reference + +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +The introduction of this paper focuses mainly on plant ABA signaling but lacks information about N- glucosidases, especially those mentioned in this work. + +<--- Page Split ---> + +Reply 3: We thank the reviewer for the careful evaluation. Based on the reviewer's suggestion, detailed information of N- glycosylation has been added to the introduction of the revised manuscript, highlighting the roles of STT3A, GIIα, GIIβ, CGL1, GMII, and FUT11 used in our study. + +Why the authors chose to study STT3A instead of the GIIβ, the mutant initially screened in most experiments? + +Reply 4: We thank the reviewer for the comments. N- glycosylation involves sequential actions of an array of enzymes, such as STT3A, GIIα, GIIβ, and FUT11 used in our study, which function in transfer and modification of sugar moieties in ER and Golgi networks (Strasser, 2016; Zielinska et al., 2012). STT3A is a catalytic subunit of oligosaccharide transferase complex, whereas GIIβ is involved in GIIα/β- heterodimer- mediated glucose trimming of N- glycans. For the N- glycosylation assays, GIIβ would cause about 0.18 kDa molecular mass difference (one glucose) of SnRK2.2/2.3, but this molecular mass difference would be enlarged to 2- 3 kDa (one N- glycan) made by STT3A (Shen et al., 2014). Similar ABA- hypersensitive phenotype, but easy test for N- glycosylation assay of SnRK2.2/2.3, STT3A was chosen for further works instead of GIIβ. We apologize for making some confusion in our manuscript. We added a reasonable sentence in the revised manuscript at line 176. + +## Reference + +Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. + +Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +5. The authors performed a time course RNA-seq analysis to investigate the effects of N-glucosidases, but the stt3a-2 results were analyzed using Col-0 as a control instead of using no ABA-treated stt3a-2 as a control. + +Reply 5: We thank the reviewer for the comments. We have 0 h ABA- treated stt3a-2 which is a no ABA- treated control. When analyzed datasets, we first carried out k- means clustering analysis to determine the ABA- responsive genes, and their time- course expression pattern in ABA- treated Col-0 group with 0 h - ABA- Col-0 as a control. Then we retrieved the expression profiles of these ABA- responsive genes from no- ABA- treated Col-0 group (0- 72 h), to show their basal expression level during 72 h period (no ABA induction). Finally, we retrieved the expression data of the ABA- responsive genes from ABA- treated stt3a-2 with 0 h- stt3a-2 as a control, to show the desensitization of ABA- responsive genes is delayed in stt3a-2 compared with ABA- treated Col-0. The manuscript has been revised in line 121 and 137. + +Additionally, the results do not seem to match the expression pattern shown in Figure 1g- i, as the expression of stress response genes in stt3a- 2 would be expected to be stronger and longer than in Col- 0. Address these inconsistencies and provide a proper control for the analysis. + +Reply 6: We thank the reviewer for the careful evaluation. We agree with the reviewer. The expression of ABA- induced genes in cluster 18 in Fig. 1k (now in revised Extended Data Fig. 3a), + +<--- Page Split ---> + +is not obviously stronger and longer in st3a- 2 than that in Col- 0. This phenomena may be due to its rapid induction (peak at 1 h) and followed by a rapid reduction (4- 6 h to basal level). But ABA- induced cluster 1, 8 and 13 appear to have stronger and longer expression in st3a- 2 than that in Col- 0 (Extended Data Fig.3a), and the expression pattern of them is similar to that of NCED3, P5CS1, and RAB18 (peak at 3 h, and decline gradually and slowly) in Fig. 1g- i. For these reasons, we put cluster 1 in Fig.1j, k in exchange for cluster 18, and the related text was corrected in our revised manuscript. + +In Figure 2, based on the results of co- expressed SnRK2.2/2.3 and STT3A in tobacco, the western blot results need to include a control without co- expression and ABA treatment to confirm the band as N- glycosylated SnRK2s. + +Reply 7: We thank the reviewer for the comments. That's correct. Done. The results were shown in revised Fig. 2f. + +Additionally, the western blot results in snrk2.6 mutants require a control using snrk2.2/2.3/2.6 mutants to eliminate non- specific bands. Include these controls for a more accurate interpretation of the results. + +Reply 8: Done. See revised Fig.2h and i. + +We also checked the specificity of the antibody used (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +![PLACEHOLDER_39_0] + + +Rebuttal Fig. 4 The anti- SnRK2.2/2.3/2.6 used in our study. + +The 10- day seedlings of snrk2.6 mutant, snrk2.2/2.3 double mutant, and snrk2.2/2.3/2.6 triple mutant were used here (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +To confirm the N- glycosylated point Asp323 on SnRK2.3, include at least one additional point mutant in Figure 2k as a negative control to provide more solid evidence. + +Reply 9: We thank the reviewer for the comments. Another point mutation SnRK2.3N288A has been included in the N- glycosylation assay (see revised Fig.2k). + +Regarding the translocation of SnRK2.2/2.3- GFP in Arabidopsis, both SnRK2.2 and SnRK2.3 need to complete this evidence. Choose one of them to show the results instead of showing SnRK2.2 translocation with SnRK2.3 (Fig 3d) and performing a mutation assay with SnRK2.3N323A (Fig 3f). The results in Figure 3f indicate that a small amount of SnRK2.3N323A can still export from the nucleus, while SnRK2.2 cannot translocate in the st3a- 2 mutant. This suggests that other factors may be involved in SnRK2.3 translocation besides N- glycosylation at N323, but it is difficult to confirm due to the unequal comparison. To address this, extract nuclear and cytoplasmic proteins separately for western blot analysis to check the N- glycosylation of SnRK2.2/2.3 after ABA treatment. + +Reply 10: We thank the reviewer for the careful evaluation. We are sorry for misunderstanding + +<--- Page Split ---> + +of redistribution of SnRK2.2 and SnRK2.3 due to lacking full evidences of both of them. Actually, there is no any significant difference between SnRK2.2 and SnRK2.3 in their subcellular dynamics. In stt3a- 2 background, peroxisomal redistribution of SnRK2.2- GFP is repressed, but few amount of SnRK2.2- GFP still locate on the peroxisomes like SnRK2.3N323A, suggesting that N- glycosylation is not the only one factor to determine redistribution of SnRK2s as the reviewer commented. + +Based on the reviewer's suggestions, to avoid misunderstanding, we have completed the observation of both SnRK2.2- GFP and SnRK2.3- GFP in the revised Fig. 3a. We also re- investigated SnRK2.2- GFP subcellular dynamics under stt3a- 2, and STT3A- OE backgrounds in revised Fig. 3d and 3e. + +Additionally, the N- glycosylation of SnRK2.2 and SnRK2.3 is also similar to each other (Fig. 2d- f, and Extended Data Fig. 7) + +8. In most experiments, the authors used SnRK2.3N323A, a mutant with abolished N-glycosylation of SnRK2.3 (Fig 2k). However, SnRK2.3 still exists in both the nucleus and peroxisome (Fig 3f), which may explain the weak or inconsistent results in Fig. 4 and Extended Data 16. To overcome this issue, delete the nuclear localization signal and peroxisome targeting signal separately to generate SnRK2.2/3 specifically located in the peroxisome and nucleus, and assess the function of SnRK2.2/3 translocation. Additionally, include snrk2.2/snrk2.3 as controls in all assays of SnRK2.32WT and SnRK2.3N323A to demonstrate the role of SnRK2s in these processes. + +Reply 11: We thank the reviewer for the valuable comments. We agree with the reviewer that N- glycosylation is not the sole effector in the regulation of SnRK2.2/2.3's redistribution, as SnRK2.3N323A with mutated N- glycosylation site can still presents on the peroxisomes. However, our studies also showed that N- glycosylation is a crucial effector for SnRK2- redistribution during prolonged ABA signalling. Firstly, genetic analysis showed that N- glycosylation is a key regulator in ABA signalling (ABA- hypersensitivity of npe mutants and SnRK2.3N323A/snrk2.2/2.3 transgenic lines (Fig. 1a- f, Extended Data Fig. 8). Secondly, the subcellular dynamics of SnRK2.2/2.3 in Fig. 3d,e and Fig. 3f,g showed that significantly less SnRK2.3/2.3 locate on the peroxisomes when N- glycosylation is defective. Finally, ABA- induced NADH maintenance and H2O2 clearance are significantly affected by N- glycosylation (stt3a- 2 vs. Col- 0; SnRK2.3N323A vs. SnRK2.3WTin snrk2.2/2.3 double mutant background) during prolonged ABA signalling (Fig. 4a, d and Extended Data Fig. 11, 13, 15c- f, and 16a- d). Totally, our results suggested strong correlation between N- glycosylation and peroxisomal localization of SnRK2.2/2.3. + +To confirm whether the effect of N- glycosylation on ABA signalling is due to the peroxisomal targeting of SnRK2.2/2.3, based on the reviewer's suggestion, we constructed the fixed SnRK2.3s that specifically locate in the nucleus (SnRK2.3- NLS) and the peroxisomal membrane (SnRK2.3- mPTSPEX26), and expressed them in the snrk2.2/2.3 double mutant background (Wright and Bartel, 2020). As shown in revised Extended Data Fig. 17, and Fig. 4i, j, both of them possess normal kinase activities, and the SnRK2.3- mPTSPEX26 possesses higher NADPH level (NADPH/NADP+) and lower H2O2 than SnRK2.3WT during prolonged ABA signalling, whereas SnRK2.3- NLS has the highest H2O2 level. We also investigated the ABA- transcriptional response, and the results showed that SnRK2.3- NLS strongly enhance the expression of ABA- responsive genes, but SnRK2.3- mPTSPEX26 not. Our findings support the notion that nuclear SnRK2.3 activates the ABA- transcriptional + +<--- Page Split ---> + +response, whereas the peroxisomal SnRK2.3 acts on NADPH maintenance during prolonged ABA signalling. In all these experiments, snrk2.2/2.3 double mutant was included as a control. See revised manuscript line 567- 568. The SnRK2.33323A, SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 were expressed under the snrk2.2/2.3 double mutant background, and the SnRK2.3WT/snrk2.2/2.3 was used as a strict control in these analyses. + +## Reference + +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +This study shows the interaction and regulation between SnRK2s and GPT1, but mainly focuses on SnRK2.2 and GPT1, neglecting SnRK2.2 and 2.3. + +Reply 12: We thank the reviewer for the comments. According to the reviewer's suggestion, the interaction assay between SnRK2.3 and GPT1 has been added in revised Fig. 4c. Phosphorylation analysis of GPT1 by SnRK2.3 has been added in revised Fig. 4e. Interaction assay of GPT1 and SnRK2.2, and phosphorylation analysis of GPT1 by SnRK2.2 have been moved to Extended Data Fig. 14c, f. + +The time- course expression pattern of GPT1 protein, and identification of GPT1 phosphorylation sites by LC- MS/MS have been moved to Extended Data Fig. 14d, e. + +To verify the function of the phosphorylation site, stable transgenic plants would provide more solid evidence than transient expression. + +Reply 13: We thank the reviewer for the valuable comments and we agree with the reviewer that GPT1- stable transgenic plants would provide more strong support to our manuscript. We have obtained gpt1- 1 mutant from prof. Xu in Zhejiang University (Zheng et al., 2018), and are trying to introduce the GPT1WT, GPT13324, and GPT1532D constructs into gpt1- 1(- /-) background, but it appears a hard and long- time work. gpt1- 1 mutant is a T- DNA insertion line and the homozygous gpt1- 1 (- /-) is embryo lethal, so we had to introduce GPT1- constructs into gpt1- 1 (- /+) background. it would need a long time to screen GPT1WT, GPT15324, and GPT1532D transgenic lines with gpt1- 1 (- /-) background. On the other hand, our transient expression data of GPT1- constructs in Fig. 4g and h, appears to work well. It showed significantly difference in GPT15324 and GPT1532D, compared with GPT1WT. Without a doubt, the stable transgenic plants would provide more strong evidences to our conclusions, and we will continue to screen the GPT1- transgenic plants, and collect more comprehensive evidences to support the conclusions in the future. + +## Reference + +Zheng, Y., Deng, X., Qu, A., Zhang, M., Tao, Y., Yang, L., Liu, Y., Xu, J., and Zhang, S. (2018). Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis. PLoS Genet 14, e1007880. + +Explain why the SnRK2.2- and SnRK2.3- GFP proteins showed a dramatic increase (more than 10- fold) after ABA treatment in Extended Data Fig. 9c. However, in Extended Data Fig 9e, the SnRK2.2- GFP protein only increased less than 1.5- fold after ABA treatment, leading to inconsistency. Generally, the protein abundance of SnRK2s should decline after ABA treatment. Provide an explanation for this discrepancy. (in Extended Data Fig 9e, the 35S:: SnRK2.2- GFP, error bar value) + +Reply 14: We thank the reviewer for the comments. In our manuscript, we investigated temporal dynamics of endogenous SnRK2.2/2.3/2.6 over prolonged ABA treatment with antibody (Agrisera + +<--- Page Split ---> + +AS142783), and the results showed that the SnRK2.2/2.3/2.6 are induced by short- term ABA treatments (peak at 4- 6 h), then following degradation (Extended Data Fig. 9c), which is consistent with previous report (Ali et al., 2019). SnRK2.2- GFP, even through driven by 35S promoter, has a similar expression pattern over ABA treatment, indicating SnRK2s are tightly regulated by ABA in protein level (Extended Data Fig. 9d). However, the fold- change of SnRK2.2- GFP induced by short- term ABA is less than endogenous SnRK2.2/2.3 compared with 0 h ABA. This difference may caused by 35S promoter, which elevates the basal expression level of SnRK2.2 without ABA treatment. This hypothesis was also supported by the temporal expression pattern of 35S::SnRK2.3- GFP in revised Extended Data Fig. 9e. + +## Reference + +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. + +In Extended Data Fig. 11, clarify the location of ROS affected by the stt3a mutation, rather than focusing on the amount. + +Reply 15: We thank the reviewer for the comments. It was previously reported that SnRK2.2/2.3 mainly are expressed in root tip (Fujii et al., 2007). In our study, we found that the redistribution of SnRK2.2/2.3 induced by prolonged ABA also mainly occurs in root meristem which is consistent with the ROS location affected by stt3a and mutation of N- glycosylation site of SnRK2.3 (SnRK2.3N323A). we have clarified that the root meristem or root tips are the main region of ROS affected by stt3a and N- glycosylation of SnRK2.2/2.3 (revised Extended Data Fig.11 and 13) + +## Reference + +Fujii, H., Verslues, P.E., and Zhu, J.K. (2007). Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell 19, 485- 494. + +## Additional issues: + +11. In Line 65 to Line 67, the reference to Extended Data Figure should be corrected to Extended Data Figure 1. + +Reply 16: That's correct. Done. + +12. In Figure 4d, the legend describes a Co-IP assay using 4-day-old seedlings, but the results show a different pattern compared to Figure 4b, which also shows a Co-IP assay using the same material. + +Reply 17: Thanks the viewer for the comments. (previous) Fig. 4d is not a Co-IP assay, it is a western blot analysis using total protein extracts to determine the temporal expression pattern during prolonged ABA treatment. The figure legend has been corrected (Now in Extended Data Fig. 14d). + +Additionally, Figure 4d indicates a \(3\mu \mathrm{M}\) ABA treatment, but the legend describes it as \(50\mu \mathrm{M}\) ABA. Please address these inconsistencies. + +Reply 18: Actually, \(3\mu \mathrm{M}\) ABA was used in (previous) Fig. 4d, and the figure legend has been corrected (Now in Extended Data Fig. 14d). + +13. The results in Figure 2l and m demonstrate the phenotype of the triple mutant stt3a-2/snrk2.2/2.3 to confirm the epistasis of SnRK2.2/2.3 to STT3A. However, Figure 2l shows a slightly longer primary root + +<--- Page Split ---> + +in the triple mutant compared to snrk2.2/2.3, whereas Figure 2m shows the reverse result, with the triple mutant having a slightly longer root. This discrepancy may be due to the selection of seedlings for photography. Clarify this issue. + +Reply 19: Thanks the referee for the comments. The quantification data is a relative root length (ABA+/- ) in Fig. 2m. The ratio (ABA+/- ) of WT was designated as 1, and the relative ratio to WT was shown for double and triple mutants. Although Fig. 21 showed a little bit longer roots for triple mutant with and without ABA treatment, the relative ratio is slightly smaller. We are sorry for this confusion due to lacking detailed information. The figure legend of Fig. 21, m, has been described in details. + +14. In Figure 3a and 3b, the intensity of SnRK2.2-GFP appears to increase after 2 hours of treatment, but Figure 3d shows a similar fluorescence intensity. Although this does not directly relate to the conclusion, please address this inconsistency. + +Reply 20: We thank the reviewer for the careful evaluation. In (previous) Fig. 3d, we mainly focus on the subcellular changes of SnRK2.2-GFP under different backgrounds. In order to observe the peroxisomes more clearly, the fluorescence intensity was appropriately enhanced in some photographs. Based on the reviewer's suggestion, we have re-investigated SnRK2.2-GFP subcellular dynamics under Col-0, st3a-2, and STT3A-OE backgrounds, and have replaced them with more suitable photographs in revised Fig. 3d and 3e. + +Additionally, for Figure 3c, a larger scale view may be more suitable to clearly show the cytosol, nuclear, and peroxisome localization of SnRK2.2- GFP. + +Reply 21: We thank the reviewer for the comments. The overlap between SnRK2.2/2.3- GFP and peroxisomal marker gene has been re- investigated, and the photographs with higher quality and a larger view have been replaced for revised Fig. 3c. + +15. Ensure that the growth conditions described in the text match those depicted in Figure 1a, 1c, and 1e, as there appears to be a significant difference in root lengths of Col-0 plants. + +Reply 22: We thank the viewer for the comment. The detailed information about growth conditions has been clarified in revised figure legend of Fig.1a, 1c, and 1e. + +<--- Page Split ---> + +Reviewer #4 (Remarks to the Author): + +This is a highly interesting manuscript and I would like to see that story published. However, I am not convinced that all the conclusions are supported by the shown data. Therefore, I would ask the authors for additional experiments and explanations. + +We greatly appreciate the reviewer for positive comments on our manuscript. + +Major points + +The general concept: + +How do you think does this transport and glycosylation process work (see statement in Abstract lines 11- 12)? + +Reply 1: We thank the reviewer for the comment. The abstract statement in line 11- 12 has been revised according to the working model (revised Extended Data Fig. 18). + +How do you think that STT3A- mCherry (a protein with numerous transmembrane domains) localizes to the cytoplasm - see statement in lines 142- 144 - without a membrane it would immediately aggregate. + +Reply 2: We agree with the reviewer. As no organellar marker was used previously, we concluded that "co- expression of STT3A- mCherry leads to SnRK2.2/2.3- GFP nuclear export and their colocalization in cytoplasm". Based on the reviewer's suggestion, we re- observed their subcellular dynamics with ER- marker CFP- HDEL, and the results showed that they co- localized in the ER (revised Fig. 2j and Extended Data Fig. 6f- i). The manuscript has been revised in line 196. + +How can glycosylation in the lumen of the ER affect the nuclear localization of another protein (processes taking place in completely different subcellular compartments)? Based on your model in Extended Data Fig. 17, the SnRK2 proteins are transported to the ER lumen for glycosylation, if it is like this than glycosylation is not involved in transport from the nucleus/cytoplasm to the ER lumen and another process mediates this transport. Then glycosylation of SnRK2.2/2.3 might be involved in transport from the ER to the peroxisomes, but this is not clearly shown and glycosylation would then not be involved in desensitization of the transcriptional response in the nucleus. + +Reply 3: We thank the reviewer for the valuable comments. In the working model (revised Extended Data Fig. 18), we proposed that synthesised SnRK2.2/2.3 in the cytoplasm, are distributed into the nucleus during short- term ABA treatment (such as 2 h), and then some of them are redistributed onto the peroxisome membrane through ER- Golgi networks, which indirectly leads to less nuclear SnRK2s distribution, desensitizing ABA- transcriptional response (another factor leading to decrease of nuclear SnRK2s is ubiquitination- mediated protein degradation (Ali et al., 2019; Cheng et al., 2017)). Fig. 3i,j showed that SnRK2.3N232A mutation did affect the transcript level of ABA- responsive genes. + +Our results showed that overexpression of STT3A sufficiently led to the full ER- location of SnRK2.2/2.3- GFP in tobacco leaves, supporting the hypothesis that STT3A is essential to SnRK2s ER- localization (Fig. 2j, Extended Data Fig. 6f- i), although the molecular mechanism is unknown. Moreover, N- glycosylation/STT3A did desensitize ABA- transcriptional response (Fig. 1f- k). + +Based on the reviewer's comments, the working model has been revised, highlighting the SnRK2s' synthesis in cytoplasm, then targeting to the nucleus and the peroxisomes respectively (see revised Extended Data Fig. 18). + +<--- Page Split ---> + +## Reference + +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. + +Cheng, C., Wang, Z., Ren, Z., Zhi, L., Yao, B., Su, C., Liu, L., and Li, X. (2017). SCFATPP2- B11 modulates ABA signaling by facilitating SnRK2.3 degradation in Arabidopsis thaliana. PLoS Genet 13, e1006947. + +Do you think that the folded SnRK2.2/2.3 proteins are taken up into the ER where they are glycosylated by a complex that normally glycosylates unfolded proteins? Which complex is involved in the uptake into the ER? + +Reply 4: We agree with the reviewer that a N- glycan is attached on an unfolded protein (or unfolded domain) in the ER lumen (Nagashima et al., 2018; Ruiz- Canada et al., 2009). Here, we supposed that SnRK2.2/2.3 N- glycosylation obeys this rule. Firstly, N- glycosylation site is present in the C- terminal domain II of SnRK2s, an extended conformation protruding outside of the three- dimensional protein structure (Extended Data Fig. 7a), indicating that the N- glycosylation site of SnRK2s is always "unfolded" for N- glycan attaching (Ng et al., 2011; Xie et al., 2012). Secondly, it was recently reported that TMED10 channel protein mediated uptake of unconventional secretory proteins into ER- Golgi intermediate compartment (ERGIC in mammals, cis- most Golgi structure in plants). We proposed that SnRK2's localization in the ER may be mediated by Arabidopsis homologs of TMED10 (our unpublished data showed they function in ABA signalling and interact with SnRK2s). If this is true, SnRK2.2/2.3 may also be unfolded, as TMED10 cargoes were unfolded by HSP90A during transport (Zhang et al., 2020). This hypothesis need more evidences to be collected in the future. + +## Reference + +Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. + +Ruiz- Canada, C., Kelleher, D.J., and Gilmore, R. (2009). Cotranslational and posttranslational N- glycosylation of polypeptides by distinct mammalian OST isoforms. Cell 136, 272- 283. + +Glycosylation mutants are pleiotropic and typically affect many proteins, how likely is it that there are indirect effects from other glycoproteins that are related to the ABA sensitivity? + +Reply 5: We agree with the reviewer that N- glycosylation mutants are pleiotropic and many glycoproteins may be affected during ABA treatment. However, in our manuscript, only SnRK2s glycosylation was tested and the results showed its dominant roles in prolonged ABA signalling. Further research works need to be carried out to show the important roles of other glycoproteins in ABA signalling in the future. + +The protein- protein interaction data: + +In the Y2H assay SnRK2s is not glycosylated and an interaction with GIIbeta therefore shows that the interaction is not N- glycan dependent. GIIbeta has a lectin domain for carbohydrate binding, so binding to a non- glycosylated protein shows a glycosylation- independent process or hints at an unspecific binding event. Panel a from the Extended Data Fig. 5 (and also Fig. 2b and comment below) confirms that because the GST- tagged protein is produced in E.coli and therefore not glycosylated. + +<--- Page Split ---> + +Reply 6: We thank the reviewer for the comments. To distinguish whether interactions between N- glycan processing enzymes (NPEs) and SnRK2s are N- glycan dependent or not, we carried out a pull- down assay with SnRK2.3N323A and GIIβ. as shown in Rebuttal Fig.5, SnRK2.3N323A still interacts directly with GIIβ, suggesting that SnRK2s- NPEs interaction is N- glycan independent. However, further LCI assays showed that the binding activity of SnRK2.3N323A to STT3A was weaker than SnRK2.3WT(Rebuttal Fig.6). The findings suggested that the interaction between SnRK2s and NPEs are both dependent and independent on N- glycan. Moreover, Our results did show that N- glycosylation of SnRK2.2/2.3 plays crucial roles in subcellular dynamics of SnRK2.2/2.3 and desensitization of ABA- transcriptional response (Fig. 3a- j) + +![PLACEHOLDER_46_0] + + +Rebuttal Fig. 5 SnRK2.3N323A interacts with GIIβ. + +The pull- down assay was carried out with GST- SnRK2.3N323A and GIIβ- 3×FLAG expressed in E. coli. GST- SnRK2.3N323A and GIIβ- 3×FLAG were mixed together and incubated for 4 hours, followed by Western blot analysis using indicated antibodies. GST was used as a control. + +![PLACEHOLDER_46_1] + +
Rebuttal Fig. 6 SnRK2.3/2.3N323A interact with STT3A.
+ +The LCI assays showed the interactions between STT3A and SnRK2.3/2.3N323A. For ABA treatment, \(50 \mu \mathrm{M}\) ABA was injected into tobacco leaves after 12 hours of GV3101 infection. After 2.5 days, 1mM luciferin solution was sprayed on the leaves. Then, luciferase activity was detected. Three leaves were three replicates. + +The luciferase assay shows interaction of all tested SnRK2s with all tested glycosylation related enzymes. This is suspicious, especially because the tested glycosylation related enzymes are located in different subcellular compartments, have a different membrane topology and most have only a few amino acids facing the cytosol where the interaction with SnRK2s would likely occur. Moreover, glycosylation related enzymes often interact with the glycan and not the protein and the interaction is only transient. I would like to see additional controls for the luciferase assay and additional experiments showing the interaction, like additional co- IP data. + +Reply 7: We thank the reviewer for the comments. As discussed above, NPEs can bind to SnRK2s + +<--- Page Split ---> + +with both glycan- dependent and - independent manners. The Firefly luciferase complementation imaging (LCI) assays showed that STT3A, GIIα, GIIβ, CGL1, and FUT11 interacted with SnRK2s, and ABA treatment enhanced this binding activities in tobacco leaves (Fig. 2c). As negative controls, these NPEs cannot interact with ABA receptor PYLs, ABI1, ABI2, ABI5 and ABF2 in our LCI assays (Extended Data Fig. 5b- f). Moreover, the Co- IP assay showed GIIβ bound to SnRK2s in Arabidopsis (Fig. 2b). + +Why did the authors characterize a specific set of glycosylation related enzymes, the rationale for choosing them is not clear. Did they also test others like FUT12 or XylT? + +Reply 8: It was reported that loss- of- function mutants of STT3A, GIIα, CGL1, and FUT11 exhibited hypersensitivity to high salt (Strasser, 2016). In our manuscript, they were found to be hypersensitive to ABA (Fig. 1a- f). + +Based on the reviewer's comment, the rationale has been added to our manuscript. Moreover, we also tested the FUT12, and the results showed that FUT12 interact with SnRK2.2/2.3 with ABA- dependent manner (Rebuttal Fig. 7). + +![PLACEHOLDER_47_0] + + +Rebuttal Fig. 7 SnRK2.2/2.3 interact with FUT12. + +The LCI assays showed the interactions between FUT12 and SnRK2.2/2.3. For ABA treatment, 50 μM ABA was injected into tobacco leaves after 12 hours of GV3101 infection (0.05% DMSO as control). After 2.5 days, 1mM luciferin solution was sprayed on the leaves. Then, luciferase activity was detected. Two leaves were two replicates. + +## Reference + +Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +Related to that and their main claim that N- glycosylation plays a role, how sure are the authors that the used mutants lead to changes in N- glycosylation. Has this been shown for Arabidopsis GIIbeta and FUT11 knockouts? + +Reply 9: Based on the reviewer's comment, we investigated the N- glycosylation in stt3a- 2 background, as deficiency of STT3A would induce larger molecular weight difference than other NPEs. The result showed that the band shift of SnRK2.3 (N- glycosylated SnRK2.3) was abolished in stt3a- 2 (Rebuttal Fig. 8) + +<--- Page Split ---> +![PLACEHOLDER_48_0] + + +Rebuttal Fig. 8 N- glycosylation assay of SnRK2.3 in Col- 0 and stt3a- 2. + +SnRK2.3- His were expressed in Arabidopsis hair roots of Col- 0 and stt3a- 2, followed by immunoprecipitation with anti- His antibodies. N- SnRK2.3- His means N- glycosylated SnRK2.3- His. + +The confocal data: + +I am sorry, but in the shown images a clear reticular ER network is not visible (e.g. Fig. 2j, Fig. 4c, Fig. 5g, Fig. 6b, e and f). The used ER- marker seems not appropriate in these experiments and is not frequently used to label the ER in tobacco in literature. In the shown images the cellular morphology appears altered, either because of the used marker or overexpressed proteins and often cellular structures are visible that look like aggregates. As a consequence, conclusions directly linked the ER localization data are questionable and BiFC data could represent false positives. The authors should provide better images, where the ER is clearly visible. Please provide also the subcellular localization of STT3A- mCherry and GlIBeta- GFP without any co- expressed other protein to see if they reside in the ER. + +Reply 10: We thank the reviewer for the careful evaluation. As reviewer suggested, we re- investigated the ER structure and obtained high- quality figures with clear ER network in Fig. 2j, Fig. 4c, Extended Data Fig. 5g, Extended Data Fig. 6e, g and h. + +For ER- marker, we used CFP- HDEL, and CD3- 959 reported by Nelson et al. (Nelson et al., 2007). Subcellular localization of STT3A- mCherry, GlIP- mCherry and GlIP- GFP was shown in Rebuttal Fig. 9. + +![PLACEHOLDER_48_1] + + +Rebuttal Fig. 9 Subcellular localization of STT3A and GlIP. + +a, STT3A- mCherry was expressed in N. benthamiana leaves with \(50~\mu \mathrm{M}\) ABA treatment for \(48\mathrm{h}\) (0.05% DMSO as control). CFP- HDEL was as ER marker. Scale bars, \(10\mu \mathrm{m}\) . b, GlIP- mCherry was expressed in N. benthamiana leaves (left) and GlIP- GFP was stably expressed in glIP- 2 (right) treated with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) (0.05% DMSO as control). CFP (CFP- HDEL) and mCherry (CD3- 959) were used as ER marker. Scale bars, \(10\mu \mathrm{m}\) . + +## Reference + +Nelson, B.K., Cai, X., and Nebenfuhr, A. (2007). A multicolored set of in vivo organelle markers for co- localization studies in Arabidopsis and other plants. Plant J 51, 1126- 1136. + +<--- Page Split ---> + +In Extended Data Fig. 6b the authors show images of GlBeta co- expression with SnRK2.2- GFP or SnRK2.3- GFP and show a diffuse signal in the cell. This looks more like a cell undergoing cell death than cytosolic localization. Please comment on that. How many cells show this type of fluorescence? Is it only visible with GlBeta? Which GlBeta was used for co- expression, is it also tagged with a fluorescent protein and leads to a diffuse labelling of the cell? Please provide co- localization data with GlBeta- mCherry or at least with an ER- marker. + +In general, the confocal images are quite small, larger images should be provided and the quality of the images should be improved. + +Reply 11: We thank the reviewer for the comments. Our results showed that STT3A- coexpression induced SnRK2.2/2.3 ER- localization and overlap with each other (Extended Data revised Fig. 6f- i); GIIβ- coexpression led cytoplasmic diffusing of SnRK2.2/2.3 (most of the cells displayed this kind of diffusing as shown in Extended Data Fig. 6b). To answer the reviewer if it is due to cell death, we re- investigated this experiment with GIIβ- mCherry, and the enlarged view showed that SnRK2.3- GFP still diffused in cytoplasm, but did not overlap with GIIβ- mCherry (revised Extended Data Fig. 6e). Clear shape of organelles, such as nucleus, GIIβ- mCherry ER- structure (GIIβ contains a HDEL end), suggested that they were not dead cells (revised Extended Data Fig. 6e). + +The peroxisomal uptake should also be supported by more data clearer confocal images. In lines 188- 190 it is stated that translocation of SnRK2.2 might consist of two steps SnRK2 degradation and peroxisomal targeting. This is unclear. Do you mean that the protein in the nucleus is degraded and that new SnRK2 protein is translated in the cytoplasm that is then transported to the ER and further to the peroxisome? Is there any evidence for nuclear degradation? Which machinery would be involved in the degradation in the nucleus? Did you test proteasome inhibitors? Did you do any experiments with protein synthesis inhibitors to see if synthesis of new proteins is involved in the process. Additional experiments should be provided to support the claims. + +Reply 12: We thank the reviewer for the comments. Based on the reviewer's suggestions, we employed translation inhibitor CHX (Cycloheximide) and proteasome inhibitor MG132 to further investigate the subcellular dynamics of SnRK2.2/2.3 during prolonged ABA signalling. As shown in Extended Data Fig.10f, CHX repressed accumulation of peroxisomal SnRK2.3- GFP, supporting the notion that peroxisomal SnRK2.3 is from new synthesised protein; MG132 treatment obviously increased accumulation of nuclear SnRK2.3- GFP, which was consistent with previous reports, suggesting 26S proteasome mediates degradation of SnRK2.3 in the nucleus (Ali et al., 2019; Cheng et al., 2017). Our manuscript showed that N- glycosylation did affect nuclear SnRK2.2/2.3 decrease (more peroxisomal SnRK2s, less nuclear SnRK2s, as discussed in working model) in addition to proteasome- mediated degradation. + +## Reference + +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. Baena- Gonzalez, E., Rolland, F., Thevelein, J.M., and Sheen, J. (2007). A central integrator of transcription networks in plant stress and energy signalling. Nature 448, 938- 942. Cheng, C., Wang, Z., Ren, Z., Zhi, L., Yao, B., Su, C., Liu, L., and Li, X. (2017). SCFAtPP2- B11 + +<--- Page Split ---> + +modulates ABA signaling by facilitating SnRK2.3 degradation in Arabidopsis thaliana. PLoS Genet 13, e1006947. + +The SnRK2 glycosylation: + +The overexpression of STT3A- mCherry results in an additional SnRK2.2- His/SnRK2.3- His band that is also detectable when treated with ABA. This raises a number of questions. This suggests, for example, that STT3A activity is limited in plants and its overexpression is sufficient to increase the glycosylation of proteins. Is there any additional evidence for that? STT3A is part of a larger protein complex and one would expect that other proteins in this complex are also required for the activity which were not overexpressed. Please comment on that. + +Reply 13: We thank the reviewer for the comments. Our results showed that the sole STT3A- overexpression caused N- glycosylation of SnRK2.2/2.3 in tobacco leaves (35S::STT3A, 35S::SnRK2.2/2.3 constructed on a same vector; see revised Fig. 2d- f). We made many biological replicates, and all showed the N- glycosylation of SnRK2.2/2.3 when coexpressed with STT3A (Rebuttal Fig.11). Moreover, the sole STT3A- coexpression also affected subcellular localization of SnRK2s (revised Fig. 2j, Extended Data Fig 6. f- i). Our findings suggest the sole overexpression of STT3A is sufficient for N- glycosylation of SnRK2.2/2.3. + +Oligosaccharyltransferase complex (OST) consists of one catalytically active subunit, STT3 (staurosporine and temperature sensitivity 3), and several different non- catalytic subunits. Arabidopsis genome has two paralogs, STT3A and STT3B (Strasser, 2016). Overexpression of STT3A subunit is sufficient for N- glycosylation of SnRK2.2/2.3 in our manuscript, suggesting its default activation with complex- independent activity, which is similar to the overexpression of SnRK1, a catalytic subunit involved in heteromeric complex (Baena- Gonzalez et al., 2007). + +Additionally, the sole ABA treatment can occasionally induce N- glycosylation and subcellular change of SnRK2s when transiently expressed in tobacco leaves. Most of the time, the sole ABA cannot or very weakly induce SnRK2s' N- glycosylation and subcellular change in tobacco leaves (See revised Fig. 2d- f). As shown in Rebuttal Fig.10, SnRK2.3- GFP was mainly located in the nucleus with or without ABA treatment in tobacco leaves. + +![PLACEHOLDER_50_0] + +
Rebuttal Fig. 10 Subcellular localization of STT3A and GIIβ.
+ +SnRK2.3WT- GFP and SnRK2.3N323A- GFP were expressed in N. benthamiana leaves with 50 μM ABA treatment for 48 h (0.05% DMSO as control). DAPI was a nuclear dye. Scale bars, 10 μm. + +<--- Page Split ---> +![PLACEHOLDER_51_0] + + +Rebuttal Fig. 11 N- glycosylation of SnRK2.2/2.3. + +a, b, SnRK2.2- His and SnRK2.3- His were coexpressed with STT3A- mCherry (constructed on the same vector) in the tobacco leaves respectively. Total protein was extracted and followed by \(6\%\) SDS- PAGE separation and detection with the anti- His antibodies. Endo H and PNG F digestion confirmed that the band shift was due to N- glycosylation. N- SnRK2s- His means N- glycosylated SnRK2s- His. + +## Reference + +Baena- Gonzalez, E., Rolland, F., Thevelein, J.M., and Sheen, J. (2007). A central integrator of transcription networks in plant stress and energy signalling. Nature 448, 938- 942. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +Given the fact, that the authors are familiar with peptide analysis by LC- MS/MS (Fig. 4f), they should try to purify the transiently expressed His- or GFP- tagged SnRK2.2/2.3 and confirm the presence of the glycan linked to N323 by MS analysis. + +Reply 14: We thank the reviewer for careful evaluation and for encouraging us to improve our manuscript. We agree with the reviewer that MS (mass spectrometry) assay will be better for confirmation of SnRK2.2/2.3 N- glycosylation. Based on the reviewer's suggestion, we have carried out the LC- MS/MS analysis of SnRK2.3 N- glycosylation (Zielinska et al., 2012). Unfortunately, in the past few months, we tried no less than five times with SnRK2.3- GFP transgenic plants or SnRK2.3- His transgenic BY- 2 cells (bright yellow tobacco cell), but all failed. We presume that the failure may be due to the tiny amount of N- glycosylated SnRK2.3. only a few SnRK2s are N- glycosylated in Arabidopsis and transgenic tobacco cells (see Fig. 2d- i, k, and Rebuttal Fig. 11). + +In our manuscript, we have provide rich data to show the SnRK2.2/2.3 N- glycosylation and the crucial roles in ABA signalling. We mutated total 11 N sites (asparagine residues) individually, and identified the N- glycosylation site SnRK2.3N323 (Fig. 2j, Extended Data Fig. 6f- i). this site mutation can block SnRK2.3 N- glycosylation (Fig. 2k), can inhibit SnRK2.3 subcellular change (Fig. 2j, Fig. 3a- f), can enhance the expression of ABA- induced genes (Fig. 3i, j), and can change phenotype of snrk2.2/2.3 double mutant from ABA- hyposensitivity to ABA- hypersensitivity (Extended Data Fig. 9l,m). + +We will continue to explore this field in the future and use more methods to detect this phenomenon. Thanks the reviewer again for valuable comments. + +<--- Page Split ---> +![PLACEHOLDER_52_0] + + +## Rebuttal Fig. 12 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His. + +a, Enrichment of N- glycosylated SnRK2.3- GFP before MS analysis. SnRK2.3- GFP overexpression plants were treated with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) after seven days of growth and the roots were collected. After IP with GFP- Trap and ConA (concanavalin A, a plant lectin can bind to mannose on the glycoproteins), the enrichment was determined by western blot. Input, total protein extract; GFP- Trap, enrichment of SnRK2.3- GFP by GFP- Trap beads; ConA- IP, enrichment of N- glycosylated SnRK2.3- GFP by ConA bead after GFP- Trap- IP. The white arrowhead denotes the N- glycosylated SnRK2.3- GFP. b, Coomassie brilliant blue staining after PNGase F digestion of N- glycosylated SnRK2.3- GFP enriched by ConA. The dashed white frame denotes the gel cut for LC- MS/MS. c, Enrichment of N- glycosylated SnRK2.3. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in tobacco leaves with 50 \(\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and N- glycosylated SnRK2.3 were enriched with Ni- NTA and ConA beads sequentially. No signal was shown after ConA enrichment (right line). So only Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. His- IP, enrichment of SnRK2.3- His by Ni- NTA; PNGase F, PNGase F digestion. N- SnRK2.3- His, N- glycosylated SnRK2.3- His. d, Coomassie brilliant blue staining after PNGase F digestion of His- antibody enriched SnRK2.3- His. The dashed white frame denotes the gel cut for LC- MS/MS. e, g, i, Coomassie brilliant blue staining after His- antibody enriched SnRK2.3- His. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in BY- 2 cells with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and SnRK2.3- His were enriched with Ni- NTA. The dashed white frame denotes the location of SnRK2.3- His. Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. f, h, j, After IP with Ni- NTA, the enrichment was determined by western blot. CK, total protein extract of wide type BY- 2 cells; Input, total protein extract of transgenic BY- 2 cells; His- IP, enrichment of SnRK2.3- His by Ni- NTA. + +## Additional method: + +## Enrichment of N-glycosylated SnRK2.3 + +Plant tissues were grounded to powder in the frozen state and homogenized in extraction buffer (50 mM Tris- HCl, pH 7.4, \(150\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, 5 mM DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with GFP- Trap agarose (Chromotek) or nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(4\mathrm{h}\) , beads were washed five times with ice- cold washing buffer (50 mM Tris- HCl, pH 7.4, \(400\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins were eluted with acidic buffer (200 mM glycine, pH 2.5) and immediately neutralized the eluate fraction with neutralization buffer ( \(100\mathrm{mM}\) Tris- HCl, pH 10.4). The eluted proteins were then incubated with ConA (concanavalin A, a plant lectin can bind to mannose on + +<--- Page Split ---> + +the glycoproteins) beads (Beyotime) at \(4^{\circ}\mathrm{C}\) , After \(4\mathrm{h}\) , beads were washed five times with washing buffer ( \(20\mathrm{mM}\) Heps, \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl \(_2\) , \(1\mathrm{mM}\) MnCl \(_2\) , \(1\mathrm{mM}\) CaCl \(_2\) , \(0.1\%\) Tween- 20). The proteins were eluted with elution buffer ( \(5\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}8.0\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{M}\) Glucose). + +After treatment with \(50\mu \mathrm{M}\) ABA for 48 hours, BY- 2 cells were collected by centrifugation. Cells were grounded to powder in the frozen state and homogenized in extraction buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl \(_2\) , \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(8\mathrm{h}\) , beads were washed five times with ice- cold washing buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(400\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl \(_2\) , \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins are boiled in boiling water for \(10\mathrm{min}\) after adding \(1\times\) glycoprotein denaturing buffer ( \(0.5\%\) SDS, \(40\mathrm{mM}\) DTT, \(\mathrm{H}_2^{18}\mathrm{O}\) ). + +## PNGase F digestion + +For PNGase F treatment, referring to the manufacturer's protocol, the reaction buffer (containing \(\mathrm{H}_2^{18}\mathrm{O}\) ) and PNGase F (New England Biolabs) were added to sample. The mixture was incubated for \(4\mathrm{h}\) at \(37^{\circ}\mathrm{C}\) before boiled in \(5\times\) SDS loading buffer. N- glycation of SnRK2.3 was detected by immunoblot analyses using by anti- GFP or anti- His antibodies after \(6\%\) SDS- PAGE. The sample was subjected to mass spectrometry detection after immunoblot analyses. + +## LC-MS/MS for identification of N-glycosylation site of SnRK2.3 + +For mass spectrometry analysis, protein samples were separated using SDS- PAGE electrophoresis and detected by coomassie brilliant blue staining. The SDS- PAGE gel at \(70\mathrm{kD}\) or \(40\mathrm{kD}\) was collected into a clean centrifuge tube. \(500\mu \mathrm{l}\) destain solution were added to a centrifuge tube and shaken at room temperature until the gel discolored. After discarding the supernatant, \(75\%\) acetonitrile \((200\mu \mathrm{l})\) were added to the centrifuge tube and shaken at room temperature. After \(30\mathrm{min}\) , \(500\mu \mathrm{l}\) \(\mathrm{H}_2\mathrm{O}\) were added to the centrifuge tube and shaken at room temperature for \(1\mathrm{h}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) \((300\mu \mathrm{l})\) were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) \((20\mu \mathrm{l})\) and \(2\mu \mathrm{l}\) trypsin \((1\mu \mathrm{g / \mu l}\) , Promega) were added to the centrifuge tube, and gel was crushed. After centrifugation \((1000\mathrm{rpm},1\mathrm{min})\) , the sample was digested at \(37^{\circ}\mathrm{C}\) . After \(8\mathrm{min}\) , \(200\mu \mathrm{l}\) acetonitrile were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After centrifugation \((1000\mathrm{rpm},1\mathrm{min})\) , the supernatant was transferred to a new centrifuge tube. This step was repeated once, ultimately resulting in \(400\mu \mathrm{l}\) supernatant. The obtained supernatant was vacuum dried at \(60^{\circ}\mathrm{C}\) and dissolved in \(0.1\%\) formic acid \((100\mu \mathrm{l})\) . Samples were subjected to mass spectrometry detection by using mass spectrometer (Orbitrap Fusion™ Lumos™ Tribrid™, Thermo Scientific). The N- glycation site of SnRK2.3 was analyzed using software (Proteome Discoverer 2.3). + +## Reference + +Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +The data from 2d suggest that ABA has the same effect as STT3A overexpression? How can this be explained? Do the authors suggest that ABA induces STT3A expression which leads to SnRK2.2/2.3 glycosylation. Is this process specific for SnRK2.2/2.3 or is protein glycosylation generally increased by ABA? + +Reply 15: We thank the reviewer for the valuable comments. We have carefully re- tested the N- glycosylation of SnRK2.2/2.3 transiently expressed in tobacco leaves (Rebuttal Fig. 11). The results showed that the sole STT3A- overexpression did produce obviously N- glycosylated band of SnRK2.2/2.3. However, the sole ABA treatment occasionally or very weakly produced glycosylated SnRK2.2/2.3 which can not be obviously detected in most of our biological replicates (revised Fig. 2d- f, Rebuttal Fig. 11). The reason may be due to no enough NPEs are induced by ABA in tobacco leaves, as ABA- induced N- glycosylation and subcellular dynamics of SnRK2.2/2.3 were mainly + +<--- Page Split ---> + +The glycosylation of the transiently expressed His- tagged protein is obviously different from the endogenous protein because the His- tagged protein is fully sensitive to Endo H and PNG F in the presence of ABA. What would be the explanation for this difference? + +Reply 16: We thank the reviewer for the comments. As discussed above, the N- glycosylation and related subcellular dynamics of SnRK2.2/2.3 were mainly found in heterotrophic root tissue, so, we proposed that the sole STT3A- overexpression it can lead to N- glycosylation of SnRK2s, however, the N- glycan can not be further processed to form mature structure in tobacco leaves (Arabidopsis roots can form mature N- glycan). + +Please digest the His- tagged protein co- expressed with STT3A- mCherry also in the absence of ABA. + +Reply 17: We thank the reviewer for the comments. This has been done in revised Fig. 2d,f, and Rebuttal Fig. 13. + +![PLACEHOLDER_54_0] + + +Rebuttal Fig. 13 N- glycosylation assay of SnRK2.2/2.3 without ABA treatment. + +SnRK2.2- His and SnRK2.3- His were coexpressed with STT3A- mCherry in the tobacco leaves respectively, followed by immunoprecipitation with anti- His antibodies. Endo H and PNG F treatments confirmed that the band shift was due to N- glycosylation. N- SnRK2s- His means N- glycosylated SnRK2s- His. + +In Fig. 2i, the anti- SnRK2.2/2.3/2.6 antibody is used to show glycosylation of the endogenous SnRK2s proteins. This is an important experiment, but not entirely convincing because neither Endo H nor PNG F give a complete shift. Can the authors do the Endo H/PNG F digestion experiment in a glycosylation knockout, for example, in cgl1 plants where all glycans should be sensitive to Endo H and PNG F. + +Reply 18: We thank the reviewer for the comments. As the molecular weights of SnRK2.6 and N- glycosylated SnRK2.2/2.3 are similar to each other, the N- glycosylation assay of endogenous SnRK2.2/2.3 in cgl1 mutant should be carried out in cgl1/snrk2.6 double mutant background. So far, we have no such double mutant yet. + +To answer the reviewer's comment, we expressed SnRK2.3- His in cgl1 hairy root (mediated by Agrobacterium rhizogenes, see method of manuscript). The results showed that the N- glycosylated band of SnRK2.3- His can be fully digested by PNGF and Endo H in cgl1- T background (Rebuttal Fig. 14). + +![PLACEHOLDER_54_1] + + +<--- Page Split ---> + +## Rebuttal Fig. 14 N-glycosylation assay of SnRK2.3 in Col-0 and cgl1-T. + +SnRK2.3- His were expressed in hair roots of Col- 0 and cgl1- T with ABA treatment, followed by immunoprecipitation with anti- His antibodies. Endo H and PNG F treatments confirmed that the band shift was due to N- glycosylation. N- SnRK2.3- His means N- glycosylated SnRK2.3- His. + +The presence of the PNG F resistant band could be related to fucosylation which takes place in the Golgi and is catalyzed by FUT11. Is there any evidence that SnRK2s are located in the Golgi? In which cellular compartment would FUT11 decorated the SnRK2 glycan with a fucose? + +Reply 19: We thank the reviewer for the comments. The subcellular localization of FUT11's action was proposed mainly in trans- Golgi (Nagashima et al., 2018; Strasser, 2016). In our previous report, TPST (tyrosylprotein sulfotransferase), an integral membrane protein of the trans- Golgi network (Beisswanger et al., 1998), was found to interact with and to sulfate SnRK2s (Wang et al., 2023). + +## Reference + +Beisswanger, R., Corbeil, D., Vannier, C., Thiele, C., Dohrmann, U., Kellner, R., Ashman, K., Niehrs, C., and Huttner, W.B. (1998). Existence of distinct tyrosylprotein sulfotransferase genes: molecular characterization of tyrosylprotein sulfotransferase- 2. Proc Natl Acad Sci U S A 95, 11134- 11139. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. Wang, J., Wang, C., Wang, T., Zhang, S., Yan, K., Yang, G., Wu, C., Zheng, C., and Huang, J. (2023). Tyrosylprotein sulfotransferase suppresses ABAsignaling via sulfation of SnRK2.2/2.3/2.6. J Integr Plant Biol 65, 1846- 1851. + +Please do the same experiment from Fig. 2i also without ABA. + +Reply 20: We thank the reviewer for the comment. Without ABA treatment, the N- glycosylation level of SnRK2.2/2.3 was very low (Fig. 2h), it is hard to do N- glycosylation assay (PNGase F or Endo H digestion). Rebuttal Fig. 15 showed another two replicates of Fig. 2i. + +![PLACEHOLDER_55_0] + + +Rebuttal Fig. 15 N- glycosylation assay of SnRK2.2/2.3 in snrk2.6. + +Total proteins were extracted from snrk2.6 after treatment with \(50~\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) , followed by \(6\%\) SDS- PAGE separation and detection with the anti- SnRK2.2/2.3/2.6 antibodies. The snrk2.2/2.3/2.6 triple mutant was used as a negative control. + +Does GIIbeta- GFP coexpression also result in the occurrence of the glycosylated band on immunoblots with the His- antibody? What is the proposed molecular function of GIIbeta in the overall process? + +Reply 21: We thank the reviewer for the comments. Based on the current working model of N- glycosylation, GIIβ (also known as α- glucosidases II, GCSII) catalyzes the second outmost glucose + +<--- Page Split ---> + +residue after GIIa, which is crucial to formation of mature N- glycan complex of SnRK2s (Nagashima et al., 2018; Strasser, 2016). Our manuscript did not test the SnRK2s' N- glycosylation with GIIβ- coexpression. Instead, we tested it with STT3A which can produce a significant molecular mass difference for glycosylated protein. Like STT3A, GIIβ bound to SnRK2s and affected its subcellular localization in tobacco leaves. However, STT3A overlapped with coexpressed SnRK2 in ER, whereas GIIβ did not. Investigation of SnRK2s glycosylation with GIIβ would also be very interesting, and we will focus on this question in the future. + +Other issues: + +In Fig.2b - please do the same experiment with the N323A protein. No glycosylated SnRK2.2/2.3 band is visible in the blot indicating that GIIbeta does not interact with the glycan on SnRK2.2/2.3. How is this then a glycosylation dependent process? Can the authors purify GIIbeta from the snrk2.6 mutant plants in the presence/absence of ABA and see if glycosylated SnRK2.2/2.3 come along? + +Reply 22: We thank the reviewer for the comment. The interactions between SnRK2.2/2.3 and GIIβ or other NPEs have been discussed in "Reply 6". They bind to SnRK2.2/2.3 with both N- glycan dependent and independent manners. We have provided a pull- down assay with SnRK2.3N323A (Rebuttal Fig. 5 in Reply 6). + +Fig.2f: please do the same experiment without ABA. + +Reply 23: Done. + +Fig 2h: please provide quantitative data from several repetitions. + +Reply 24: Done. Another replicate of Fig. 2h see Rebuttal Fig. 16 below. + +![PLACEHOLDER_56_0] + + +Rebuttal Fig. 16 N- glycosylation assay of SnRK2.2/2.3 in snrk2.6. + +Total proteins were extracted from snrk2.6 after treatment with \(50~\mu \mathrm{M}\) ABA for different time periods, followed by \(6\%\) SDS- PAGE separation and detection with the anti- SnRK2.2/2.3/2.6 antibodies. The snrk2.2/2.3/2.6 triple mutant was used as a negative control. + +In Fig. 2j the authors state that N323A coexpression disrupts its nuclear export. Why not the opposite - block of nuclear import in by SnRK2.3 expression? Can the authors provide a time series of images showing a transport process? + +Reply 25: We agree with the reviewer and We have revised the Fig. 2j legend and main text in line 192- 197. + +Extended data Fig.5a: do the same with GST- SnRK2.3- N323A + +Reply 26: We thank the reviewer for the comment. We have re- done the pull- down assay with SnRK2.3N323A in Rebuttal Fig. 5 in reply 6. The results also showed the interaction between SnRK2.3N323A and GIIβ. + +<--- Page Split ---> + +Extended data Fig.9c: show a time course experiment in the snrk2.6 background with anti- SnRK2.2/2.3/2.6 antibody for comparison. To see also if the glycosylated band increases with prolonged ABA incubation. Based on Extended Data Fig. 1f one would expect the highest STT3a expression after 6 h of ABA treatment and this should correlate with the increase of N- glycosylated SnRK2.2/2.3. + +Reply 27: We thank the reviewer for the comment. A time course expression pattern of endogenous N- glycosylated SnRK2.2/2.3 has been done in snrk2.6 background, and the results showed that a gradual increase of N- glycosylated SnRK2.2/2.3 after 6 h during prolonged ABA treatment (revised Fig. 2h). + +Minor point: + +The term N- glucosidase is not correct in the description of the glycosylated related enzymes. Some of the characterized proteins are transferases (STT3A, CGL1, FUT11) others are glycosidases (GMII) and only GIIalpha and beta are glucosidases. + +Reply 28: We thank the reviewer for the valuable comment. As the enzymes of N- glycosylation pathway used in our study include oligosaccharide transferase (STT3A), glucosidase (GIIα, and GIIβ), acetylglucosaminyltransferase (CGL1), mannosidase (GMII), and fucosyltransferase (FUT). The term "N- glucosidases" can not represent all these enzymes. So we have replaced "N- glucosidases" with "NPEs" (N- glycan processing enzymes) in the revised manuscript. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +All my concerns have been addressed in the revision. I have no more concerns this time. + +Reviewer #3 (Remarks to the Author): + +The authors have addressed most of my questions; however, I still have lingering concerns regarding the data presented in both the manuscript and the response to reviewers. + +1 As previously mentioned, my primary concern lies in the notably high concentration of ABA used in the germination assay. In the rebuttal Fig. 2, the authors demonstrate that all tested varieties could germinate in 2- 3 days, even on the medium containing 3 or \(5 \mu M\) ABA. It is essential to note that even \(1.0 \mu M\) ABA is a concentration known to almost totally inhibit seed germination in the Col- 0 wild type. Fuji et al. (2007) used \(0.6 \mu M\) ABA in their assay of the snrk2.2snrk2.3 double mutant (Plant Cell, 2007). For reference, please consult Fujita et al., 2009, Plant Cell Physiol; Fuji et al., 2009, PNAS; Gonzalez- Guzman et al., Plant Cell, 2012, etc. I recommend that the authors double- check the chemical concentrations used and ensure that the related results presented in the manuscript are accurate to avoid any potential misinterpretation in this field. + +2 Another concern relates to the SnRK2.2/3/6 antibody used in Figure 2B and Rebuttal Fig. 4. Although we routinely use this antibody, I have not observed its ability to distinguish SnRK2.6 from SnRK2.2 and SnRK2.3. Please provide the unaltered image in response to the reviewers' comments and include supplementary materials for clarity. + +3 I concur with reviewer 4 regarding the LC- MS/MS identification of N323 glycosylation, which is crucial to this manuscript. The authors reported the failure to detect this glycosylation in more than five LC- MS/MS assays, explaining that only a tiny amount of SnRK2.3 proteins undergo S- glycosylation. However, it remains unclear how the authors can demonstrate that such a small portion of glycosylated SnRK2.3 significantly contributes to the desensitization of ABA. + +Actually, almost all reviewers questioned the importance or the exact role of the glycosylation of SnRK2.2/2.3 in ABA and stress signaling, if indeed it exists, which is not fully addressed by the authors in this revision. + +<--- Page Split ---> + +Reviewer #4 (Remarks to the Author): + +The authors have made a lot of effort to improve the manuscript. They have provided additional experimental data and most of my main points have been answered. + +There are still a number of open questions related to the glycosylation of SnRKs and ER localisation or uptake from the nucleus/cytosol that need to be answered. However, this is something that should be addressed in future studies. + +The story is of great interest and should be published. + +<--- Page Split ---> + +We would like to thank all the reviewers for their insightful comments and suggestions and for encouraging us to improve our manuscript. + +Reviewer's Comments: + +## Reviewer #2 (Remarks to the Author) + +All my concerns have been addressed in the revision. I have no more concerns this time. + +We thank the reviewer for the positive evaluation of the manuscript. + +## Reviewer #3 (Remarks to the Author) + +The authors have addressed most of my questions; however, I still have lingering concerns regarding the data presented in both the manuscript and the response to reviewers. 1. As previously mentioned, my primary concern lies in the notably high concentration of ABA used in the germination assay. In the rebuttal Fig. 2, the authors demonstrate that all tested varieties could germinate in 2- 3 days, even on the medium containing 3 or \(5\mu \mathrm{M}\) ABA. It is essential to note that even \(1.0\mu \mathrm{M}\) ABA is a concentration known to almost totally inhibit seed germination in the Col- 0 wild type. Fuji et al. (2007) used \(0.6\mu \mathrm{M}\) ABA in their assay of the snrk2.2snrk2.3 double mutant (Plant Cell, 2007). For reference, please consult Fujita et al., 2009, Plant Cell Physiol; Fuji et al., 2009, PNAS; Gonzalez- Guzman et al., Plant Cell, 2012, etc. I recommend that the authors double- check the chemical concentrations used and ensure that the related results presented in the manuscript are accurate to avoid any potential misinterpretation in this field. + +We thank the reviewer for careful evaluation. We agree with the reviewer that Arabidopsis is more sensitive to exogenous ABA treatment during seed germination than during vegetative growth. In general, high concentrations of ABA, such as \(50\mu \mathrm{M}\) ABA (Fujii et al., 2007) \(^1\) , have been used to inhibit seedling growth (Fujita et al., 2009; Fujii and Zhu, 2009) \(^2,3\) , whereas even \(0.6\mu \mathrm{M}\) ABA can well suppress seed germination as suggested by the reviewer. Our results showed a higher germination rate at high ABA application, which may be due to the different experimental conditions used in our experiments compared to the publications. For example, it was reported (Fujii and Zhu, 2009) \(^2\) that seeds were plated on MS medium without sucrose for germination (with \(1.5\%\) sucrose applied in our experiment). In fact, most of the germinated seeds with high concentration of ABA in our tests have very small radicles and grow slowly and weakly. In our future work we would be very careful to choose a lower concentration of ABA for seed germination analysis. + +2. Another concern relates to the SnRK2.2/3/6 antibody used in Figure 2B and Rebuttal Fig. 4. Although we routinely use this antibody, I have not observed its ability to distinguish SnRK2.6 from SnRK2.2 and SnRK2.3. Please provide the unaltered image in response to the reviewers' comments and include supplementary materials for clarity. + +We thank the reviewer for comments. It is really hard to distinguish SnRK2.6 from SnRK2.2/2.3 in most cases because they are very close in molecular weight. In our work, we validated the specificity of the SnRK2.2/2.3/2.6 antibody with Col- 0, snrk2.6, snrk2.2/2.3, and snrk2.2/2.3/2.6 triple mutant, and the results showed that it can produce two close bands for SnRK2.6 and SnRK2.2/2.3 in Col- 0 compared to mutants (better distinguishable in Rebuttal Fig. 17a, but they are very close in Rebuttal Fig. 17b), as tested by the manufacturer Agrisera (Rebuttal Fig. 1c, from Agrisera website). To make it easier to distinguish between the two bands, we run the gel for a + +<--- Page Split ---> + +longer time (until 35 kD protein band is almost out of the gel), and cut the gel to remove proteins larger than 55 kD (Rebuttal Fig. 17d, e), as a huge amount of 55 kD bands make the SnRK2 bands very weak (Rebuttal Fig. 17a). The Rebuttal Fig. 17 d and e showed the unaltered images (after gel cut) for Rebuttal Fig. 4 and Figure 2b respectively. + +![PLACEHOLDER_61_0] + + +<--- Page Split ---> + +## Rebuttal Fig. 17 The SnRK2.2/2.3/2.6 antibody used in our study. + +a- b. The 7- day seedlings of Col- 0, snrk2.6 mutant, snrk2.2/2.3 double mutant, and snrk2.2/2.3/2.6 triple mutant were used here. Total protein extracted with SDS buffer was separated on \(10\%\) SDS- PAGE. The blot was incubated with the primary antibody (anti- SnRK2.2/2.3/2.6, Agrisera, AS142783). a and b show two biological replicates. a, replicate 1; b, replicate 2; bottom of b, upper figure merged with protein ladder. + +c. WB result from the manufacturer. From the website (https://www.agrisera.com/en/artiklar/srk-ser-thr-protein-kinase-snrk.html). + +d. Unaltered image of Rebuttal Fig. 4. From top to bottom: image without protein ladder, the same image with protein ladder, excision of \(55\mathrm{kD}\) miscellaneous bands without protein ladder, and excision of \(55\mathrm{kD}\) miscellaneous bands with protein ladder. + +e. The unaltered image of Fig.2b. + +The red triangle indicates the SnRK2.6 band, and the black triangle indicates the SnRK2.2/2.3 band. There are some other unrelated samples in d and e. + +3. concur with reviewer 4 regarding the LC-MS/MS identification of N323 glycosylation, which is crucial to this manuscript. The authors reported the failure to detect this glycosylation in more than five LC-MS/MS assays, explaining that only a tiny amount of SnRK2.3 proteins undergo N-glycosylation. However, it remains unclear how the authors can demonstrate that such a small portion of glycosylated SnRK2.3 significantly contributes to the desensitization of ABA. + +Actually, almost all reviewers questioned the importance or the exact role of the glycosylation of SnRK2.2/2.3 in ABA and stress signaling, if indeed it exists, which is not fully addressed by the authors in this revision. + +We thank the reviewer for the valuable comments. We agree with the reviewer that the confirmation of SnRK2.3N323 glycosylation by LC- MS/MC is important, and we will do it by trial and error in the future. We believe that our manuscript provides strong evidence for the N- glycosylation of SnRK2.2/2.3. Our manuscript determined the N- glycosylation of SnRK2.2/2.3 in tobacco leaves and Arabidopsis (Fig. 2d- i) using "band shift assays followed by PNGase F and Endo H digestions", which is a classical method widely used to identify N- glycosylation 4-15. Furthermore, our manuscript identified the N323 N- glycosylation site within a total of 11 point mutations of asparagine residues in SnRK2.3 (Fig. 2j, and Extended Data Fig. 6), and reconfirmed the N323 N- glycosylation site with "band shift assay" (Fig. 2k). + +Regarding the question "small portion of glycosylation of SnRK2.3, big roles", on the one hand, our results showed that only a small part of SnRK2.2/2.3 are N- glycosylated in transiently expressed tobacco leaves (Fig. 2d- f, k) and in Arabidopsis (even treated with 50 ABA for 48 h, Fig. 2h, i). On the other hand, we provided strong evidence for the significant role of N- glycosylation in the desensitization of ABA transcriptional response (Fig. 1f- k, Fig. 3i, j, and Extended Data Fig 3, 4), the positive regulation of high- salt adaptation (Extended Data Fig. 9f- m), the positive function in the subcellular dynamics of SnRK2.2/2.3 (Fig. 3a- h, Extended Data Fig. 10), and the crucial role in the regulation of NADPH and \(\mathrm{H}_2\mathrm{O}_2\) homeostasis (Fig. 4, Extended Data Fig. 15, 16). However, the molecular mechanism underlying the question "small portion of glycosylation of SnRK2.3, big roles" remains unclear as suggested by the reviewer. The small proportion of N- glycosylation of SnRK2.2/2.3 indicates that N- glycosylated SnRK2.2/2.3 may act as an inducer of its peroxisomal + +<--- Page Split ---> + +localisation, and more SnRK2.2/2.3 may be directly recruited from the cytosol to the peroxisomal membrane by the inducer. + +Although our manuscript provided strong evidence for the N- glycosylation of SnRK2.2/2.3, and its important role in ABA signalling, there are still some open questions in this field to be answered, as suggested by the reviewer #3 and #4. (1) How SnRK2.2/2.3, as non- secretory proteins, are transported into the ER lumen for N- glycosylation; (2) How SnRK2.2/2.3 are redistributed from the ER to the peroxisomes; (3) whether all the peroxisomal SnRK2.2/2.3 are transported from ER, or whether some of them are recruited directly from the cytosol as hypothesised above. These questions are very interesting and worthy of further investigation, and we will do our best to address them in the future. + +## Reviewer #4 (Remarks to the Author) + +The authors have made a lot of effort to improve the manuscript. They have provided additional experimental data and most of my main points have been answered. + +There are still a number of open questions related to the glycosylation of SnRKs and ER localisation or uptake from the nucleus/cytosol that need to be answered. However, this is something that should be addressed in future studies. + +The story is of great interest and should be published. + +We thank the reviewer for the positive evaluation of the manuscript. + +## Reference + +1 Fujii, H., Versluus, P. E. & Zhu, J.- K. Identification of Two Protein Kinases Required for Abscisic Acid Regulation of Seed Germination, Root Growth, and Gene Expression in Arabidopsis. The Plant Cell 19, 485- 494, doi:10.1105/tpc.106.048538 (2007). 2 Fujii, H. & Zhu, J.- K. Arabidopsis mutant deficient in 3 abscisic acid- activated protein kinases reveals critical roles in growth, reproduction, and stress. Proceedings of the National Academy of Sciences 106, 8380- 8385, doi:10.1073/pnas.0903144106 (2009). 3 Fujita, Y. et al. Three SnRK2 Protein Kinases are the Main Positive Regulators of Abscisic Acid Signaling in Response to Water Stress in Arabidopsis. Plant and Cell Physiology 50, 2123- 2132, doi:10.1093/pcp/pcp147 (2009). 4 Ruiz- Canada, C., Kelleher, D. J. & Gilmore, R. Cotranslational and Posttranslational N- Glycosylation of Polypeptides by Distinct Mammalian OST Isoforms. Cell 136, 272- 283, doi:10.1016/j.cell.2008.11.047 (2009). 5 Tsachaki, M. et al. Glycosylation of BRI2 on asparagine 170 is involved in its trafficking to the cell surface but not in its processing by furin or ADAM10. Glycobiology 21, 1382- 1388, doi:10.1093/glycob/cwr097 (2011). 6 Sato, T. et al. STT3B- Dependent Posttranslational N- Glycosylation as a Surveillance System for Secretory Protein. Molecular Cell 47, 99- 110, doi:10.1016/j.molcel.2012.04.015 (2012). 7 Chen, X.- L. et al. N- Glycosylation of Effector Proteins by an \(\alpha - 1,3-\) + +<--- Page Split ---> + +Mannosyltransferase Is Required for the Rice Blast Fungus to Evade Host Innate Immunity. The Plant Cell 26, 1360- 1376, doi:10.1105/tpc.114.123588 (2014). Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M. E. & Nasrallah, J. B. Site- Specific- Glycosylation of the S- Locus Receptor Kinase and Its Role in the Self- Incompatibility Response of the Brassicaceae. Plant Cell 26, 4749- 4762, doi:10.1105/tpc.114.131987 (2014). Shen, J., Ding, Y., Gao, C., Rojo, E. & Jiang, L. N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. The Plant Journal 80, 977- 992, doi:10.1111/tpj.12696 (2014). Voss, M. et al. Shedding of glycan - modifying enzymes by signal peptide peptidase - like 3 (SPPL3) regulates cellular N - glycosylation. The EMBO Journal 33, 2890- 2905, doi:10.15252/embj.201488375 (2014). Liu, Y. D. et al. EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated degradation system in. P Nat1 Acad Sci USA 112, 12205- 12210, doi:10.1073/pnas.1511724112 (2015). Stevens, K. L. P. et al. Diminished Ost3- dependent N- glycosylation of the BiP nucleotide exchange factor Sill is an adaptive response to reductive ER stress. P Nat1 Acad Sci USA 114, 12489- 12494, doi:10.1073/pnas.1705641114 (2017). Wang, H. et al. N- glycosylation in the protease domain of trypsin- like serine proteases mediates calnexin- assisted protein folding. eLife 7, doi:10.7554/eLife.35672 (2018). Phoomak, C. et al. The translocon- associated protein (TRAP) complex regulates quality control of N- linked glycosylation during ER stress. Science Advances 7, doi:10.1126/sciadv.abc6364 (2021). de la Morena- Barrio, M. E. et al. Two SERPINC1 variants affecting N- glycosylation of Asn224 cause severe thrombophilia not detected by functional assays. Blood 140, 140- 151, doi:10.1182/blood.2021014708 (2022). + +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #3 (Remarks to the Author): + +The authors responded to my comments as much as possible, and I have no more concerns about this manuscript. I agree with reviewer 4 that the remaining open questions could be addressed in future studies. In my opinion, the current version is ready to publish in Nature Communications. + +<--- Page Split ---> diff --git a/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7c39772137bbf1f947c1e4feb2e633ac7782460d --- /dev/null +++ b/peer_reviews/996a335d085336dc9880221475d34358c76bcd769e11a6cc725b14a00ca20246/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1731 @@ +<|ref|>title<|/ref|><|det|>[[61, 41, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 854, 212]]<|/det|> +N- glycosylation of SnRK2s affects NADPH maintenance in peroxisomes during prolonged ABA signalling + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 392, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 880, 275]]<|/det|> +This manuscript provides evidence that N- glycosylation of SnRK2s controls NADPH maintenance in peroxisomes, and this relates to the desensitization of plants to repeated ABA signalling. It is founded on discovery of a hypersensitivity to ABA- mediated repression in a mutant of \(\beta\) - subunit of glucosidase II (glβ- 2). + +<|ref|>text<|/ref|><|det|>[[115, 286, 882, 377]]<|/det|> +The fact of this hypersensitivity would imply some non- compensatory need for this specific glucoside directly. However, oddly the authors find the same hypersensitivity when they individually knockout other glucosidases - STT3A, GIIa and three other N- glucosidases (CGL1, GMII, FUT11) - so why cant they compensate for the glβ- 2 mutant? Its not clear. I never saw any real exploration how each of these could in a non- compensatory manner effect the same pathway to SnRK2. + +<|ref|>text<|/ref|><|det|>[[115, 415, 880, 525]]<|/det|> +The manuscript then uses experiments on glβ- 2 or STT3A mutants interchangeably to then explore the mechanism of this desensitization of plants to repeated ABA signalling. The yeast 2 hybrid assays are implied to show an exclusive interaction between glβ- 2 and SnRK2.2/2/3/2.6 but this was a set of pairwise interactions, not a yeast- 2 hybrid screen, so its not reasonable to call it exclusive - they only tested what they tested. Same with the LCl assays - "GIIβ, STT3A, GIIa, CGL1 and FUT11 all exclusively bind to SnRK2s" its just amongst the assay done - its not exclusive of other targets of these glucosidases. + +<|ref|>text<|/ref|><|det|>[[115, 564, 883, 710]]<|/det|> +Critical to the claims of the paper is that SnRKs are glycosylated by these glucosidases - this is claimed by, "PNGase F and Endo H digestions confirmed that the band shift was due to N- glycan modification" this band shift seems to be the only evidence that this modification is occurring and the later genetic studies to mutate residues and show an absence of band shift - while in themselves compelling - are not independent of this method. There are a wide variety of other independent methods to prove N- glycan modification as well as MS and MRM methods to independently confirm the claim at the site on the SnRKs - none of these are used but really should be to independently confirm this central claim of the paper. + +<|ref|>text<|/ref|><|det|>[[115, 749, 850, 820]]<|/det|> +The apparent translocation of SnRK2 to the peroxisome is proposed, but then recanted in the text, because nuclear export inhibition did not block it. Instead it seemed more likely the nuclear SnRK2 is degraded and a peroxisome targeted version is generated, so authors need to ensure they don't continue to claim 'translocation' in the text in other passages and also Fig 3 legend. + +<|ref|>text<|/ref|><|det|>[[115, 860, 855, 895]]<|/det|> +When we get to peroxisomes and what SnRK2 interacts with, we see another selective process "we investigated the potential SnRK2- interacting partners among peroxisomal isozymes involved in H2O2- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 848, 125]]<|/det|> +scavenging and NADPH generation" so again the link to GPT1 is really achieved by analysis of a small subset of hand picked targets. + +<|ref|>text<|/ref|><|det|>[[115, 164, 881, 293]]<|/det|> +The claim of changes in NADPH and ROS in peroxisomes require detailed time- lapse measurements to be performed. The claimed errors bars in Fig 4 and extended Fig 11 are noted to be based on mean plus or minus sd, no n value is provided for either in the legends. But the reporting summary suggested - "All experiments were repeated two- three biologically independent experiments as mentioned in figure legends and methods". Having done these sorts of assays myself I find those errors (just a few percent in many cases) just inconceivably small for independent experiments. Throughout the paper these small n value experiments are just showing mean and sd, not data points on graphs to show means for each rep. + +<|ref|>text<|/ref|><|det|>[[115, 303, 864, 357]]<|/det|> +These very small errors are essential for the claims made as the H2O2 and NADPH changes in Figure 4 are very small. I would want to see further evidence that the errors are accurately reported across independent experiments. + +<|ref|>text<|/ref|><|det|>[[115, 396, 878, 504]]<|/det|> +Overall the biological case surrounding this mutant is extensively explored and links of the mutants effects back into ABA processes are extensive and involve a large amount of work and come to novel conclusions for the field. My main concern is that the biochemical pathway to the claim involves a series of selective choices that need to be acknowledged along the way and key points such as the glycosylation evidence and the clarification of how such small errors can be recorded need to be resolved. + +<|ref|>text<|/ref|><|det|>[[115, 601, 392, 617]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 657, 884, 840]]<|/det|> +Pretreating plants with mild abiotic stresses helps them to adapt to harsh conditions, and the adaptation process is enhanced by ABA treatment. Revealing the underlying mechanism would have practical implications. This paper reports that ABA causes the subcellular redistribution and target change of SnRK2.2/2.3, two key regulators of ABA signaling. SnRK2.2/2.3 are localized in the nucleus and activate transcriptional responses at the initial ABA signaling stage, but during prolonged ABA treatment, they are N- glycosylated in the ER- Golgi network and sent to the peroxisomes. On the peroxisomal membrane, SnRK2.2/2.3 phosphorylate and activate Glucose- 6- Phosphate Transporter 1 (GPT1), which helps maintain NADPH homeostasis and suppress H2O2 over- accumulation. Plants that have undergone such changes become less responsive to ABA (desensitized) and may better tolerate stress conditions (becoming acclimated). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 125]]<|/det|> +The data presented in this paper are sound, the logic is clear, and the finding represents a significant step toward understanding the molecular mechanisms of plant acclimation. + +<|ref|>text<|/ref|><|det|>[[115, 166, 247, 182]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 194, 803, 228]]<|/det|> +1. Labeling errors: in Extended Data Fig. 1, the labels "e" and "f" are misplaced; the "Fig. 1f" is mislabeled. + +<|ref|>text<|/ref|><|det|>[[115, 268, 857, 304]]<|/det|> +2. Labeling errors: Main text lines 65 – 67, the Extended Data Fig. 2c-e, 2f, and 2g should be Extended Data Fig. 1c-e, 1f, and 1g. + +<|ref|>text<|/ref|><|det|>[[115, 343, 591, 360]]<|/det|> +3. Labeling error: Main text line 92, the Fig. 1j should be Fig. 1j, k. + +<|ref|>text<|/ref|><|det|>[[115, 399, 810, 416]]<|/det|> +4. Labeling error: Main text line 148, the Extended Data Fig. 6e should be Extended Data Fig. 6f. + +<|ref|>text<|/ref|><|det|>[[114, 455, 880, 602]]<|/det|> +5. About the term "translocation": This term may mislead readers and should be considered revision. Throughout the paper, the authors use "translocate/translocation" to describe the change of SnRK2s localization patterns: SnRK2s are normally localized in the nucleus, and during prolonged ABA treatment, they are N-glycosylated and localized on the peroxisomal membrane. Although they disappear from the nucleus and reappear on the peroxisome, the SnRK2s proteins do not physically move 'from the nucleus to the peroxisomes'; this is supported by the experiment presented in Extended Data Fig. 10f, g (main text lines 188-190). Therefore, the term "translocate/translocation" does not accurately describe the process and can be misleading. + +<|ref|>text<|/ref|><|det|>[[115, 641, 868, 712]]<|/det|> +For example, in the Abstract, line 11 reads, "...which promotes their gradual translocation from the nucleus to the peroxisomes...." Immediately following this sentence, line 13 reads, "After moving to the peroxisomal membrane, SnRK2s directly interact with...." This combination will almost surely make readers mistakenly think that SnRK2s physically move between the two organelles. + +<|ref|>text<|/ref|><|det|>[[115, 752, 857, 842]]<|/det|> +A possible substitute for "translocation" is "redistribution." The term "redistribution" better describes the phenomenon, avoids misunderstanding, and inspires people to wonder. People may ask where SnRK2s proteins are synthesized and precisely what triggers the switch from targeting SnRK2s to the nucleus to targeting them to peroxisomes. The answers to such questions may expand the current finding and lead to the development of application strategies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 392, 134]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 174, 880, 339]]<|/det|> +This study presents a putative mechanism for the desensitization and transition of ABA signaling during prolonged treatment, involving N- glycosylation of SnRK2s. Under prolonged ABA signaling, the key regulator SnRK2.2/2.3 undergoes N- glycosylation in the ER- Golgi network, which leads to its translocation to the peroxisome. In the peroxisome, SnRK2s regulate NADPH generation by phosphorylating the transporter GPT1 during NADPH synthesis, suggesting a new module of redox homeostasis for adapting to long- term stress conditions during prolonged ABA signaling. The findings are interesting and provide insights into plant responses under prolonged stress conditions. However, there are several major issues in the manuscript that need to be addressed, before it could be considered by Nat Commun. + +<|ref|>text<|/ref|><|det|>[[115, 378, 214, 394]]<|/det|> +Major Points: + +<|ref|>text<|/ref|><|det|>[[115, 434, 875, 507]]<|/det|> +1. It is common to assay ABA responses through germination, cotyledon greening, and post-germination growth using different concentrations of ABA. In this study, the authors chose to germinate the seeds in a very high concentration of ABA (3 μM) and measured the root length at a later stage. Please explain the rationale for this choice and provide results from other assays. + +<|ref|>text<|/ref|><|det|>[[114, 517, 874, 626]]<|/det|> +2. The major discovery in this work is that N-glycosylation of SnRK2s leads to the desensitization of prolonged ABA signaling through translocation. However, the relationship between these two processes remains unclear. Does N-glycosylation of SnRK2s occur before or after their translocation? Does N-glycosylation cause translocation, or does translocation lead to N-glycosylation? It would be helpful to design a subcellular-fixed mode of SnRK2s that can only be located in the nucleus or peroxisome to investigate the effects. + +<|ref|>text<|/ref|><|det|>[[114, 637, 860, 673]]<|/det|> +3. The introduction of this paper focuses mainly on plant ABA signaling but lacks information about N-glucosidases, especially those mentioned in this work. + +<|ref|>text<|/ref|><|det|>[[114, 684, 835, 720]]<|/det|> +4. Why the authors chose to study STT3A instead of the GIIβ, the mutant initially screened in most experiments? + +<|ref|>text<|/ref|><|det|>[[114, 730, 883, 821]]<|/det|> +5. The authors performed a time course RNA-seq analysis to investigate the effects of N-glucosidases, but the stt3a-2 results were analyzed using Col-0 as a control instead of using no ABA-treated stt3a-2 as a control. Additionally, the results do not seem to match the expression pattern shown in Figure 1g-i, as the expression of stress response genes in stt3a-2 would be expected to be stronger and longer than in Col-0. Address these inconsistencies and provide a proper control for the analysis. + +<|ref|>text<|/ref|><|det|>[[115, 833, 871, 887]]<|/det|> +6. In Figure 2, based on the results of co-expressed SnRK2.2/2.3 and STT3A in tobacco, the western blot results need to include a control without co-expression and ABA treatment to confirm the band as N-glycosylated SnRK2s. Additionally, the western blot results in snrk2.6 mutants require a control using + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 845, 125]]<|/det|> +snrk2.2/2.3/2.6 mutants to eliminate non- specific bands. Include these controls for a more accurate interpretation of the results. + +<|ref|>text<|/ref|><|det|>[[115, 137, 870, 172]]<|/det|> +7. To confirm the N-glycosylated point Asp323 on SnRK2.3, include at least one additional point mutant in Figure 2k as a negative control to provide more solid evidence. + +<|ref|>text<|/ref|><|det|>[[114, 183, 884, 329]]<|/det|> +Regarding the translocation of SnRK2.2/2.3- GFP in Arabidopsis, both SnRK2.2 and SnRK2.3 need to complete this evidence. Choose one of them to show the results instead of showing SnRK2.2 translocation with SnRK2.3 (Fig 3d) and performing a mutation assay with SnRK2.3N323A (Fig 3f). The results in Figure 3f indicate that a small amount of SnRK2.3N323A can still export from the nucleus, while SnRK2.2 cannot translocate in the stt3a- 2 mutant. This suggests that other factors may be involved in SnRK2.3 translocation besides N- glycosylation at N323, but it is difficult to confirm due to the unequal comparison. To address this, extract nuclear and cytoplasmic proteins separately for western blot analysis to check the N- glycosylation of SnRK2.2/2.3 after ABA treatment. + +<|ref|>text<|/ref|><|det|>[[114, 340, 866, 466]]<|/det|> +8. In most experiments, the authors used SnRK2.3N323A, a mutant with abolished N-glycosylation of SnRK2.3 (Fig 2k). However, SnRK2.3 still exists in both the nucleus and peroxisome (Fig 3f), which may explain the weak or inconsistent results in Fig. 4 and Extended Data 16. To overcome this issue, delete the nuclear localization signal and peroxisome targeting signal separately to generate SnRK2.2/3 specifically located in the peroxisome and nucleus, and assess the function of SnRK2.2/3 translocation. Additionally, include snrk2.2/snrk2.3 as controls in all assays of SnRK2.32WT and SnRK2.3N323A to demonstrate the role of SnRK2s in these processes. + +<|ref|>text<|/ref|><|det|>[[115, 478, 875, 531]]<|/det|> +9. This study shows the interaction and regulation between SnRK2s and GPT1, but mainly focuses on SnRK2.2 and GPT1, neglecting SnRK2.2 and 2.3. To verify the function of the phosphorylation site, stable transgenic plants would provide more solid evidence than transient expression. + +<|ref|>text<|/ref|><|det|>[[115, 542, 879, 614]]<|/det|> +10. Explain why the SnRK2.2- and 2.3-GFP proteins showed a dramatic increase (more than 10-fold) after ABA treatment in Fig 9c. However, in Fig 9e, the 2.2-GFP protein only increased less than 1.5-fold after ABA treatment, leading to inconsistency. Generally, the protein abundance of SnRK2s should decline after ABA treatment. Provide an explanation for this discrepancy. + +<|ref|>text<|/ref|><|det|>[[115, 625, 872, 660]]<|/det|> +In Extended Data Fig. 11, clarify the location of ROS affected by the stt3a mutation, rather than focusing on the amount. + +<|ref|>sub_title<|/ref|><|det|>[[115, 700, 245, 716]]<|/det|> +## Additional issues: + +<|ref|>text<|/ref|><|det|>[[115, 729, 860, 763]]<|/det|> +11. In Line 65 to Line 67, the reference to Extended Data Figure should be corrected to Extended Data Figure 1. + +<|ref|>text<|/ref|><|det|>[[115, 776, 880, 847]]<|/det|> +12. In Figure 4d, the legend describes a Co-IP assay using 4-day-old seedlings, but the results show a different pattern compared to Figure 4b, which also shows a Co-IP assay using the same material. Additionally, Figure 4d indicates a \(3 \mu M\) ABA treatment, but the legend describes it as \(50 \mu M\) ABA. Please address these inconsistencies. + +<|ref|>text<|/ref|><|det|>[[115, 860, 880, 894]]<|/det|> +13. The results in Figure 2l and m demonstrate the phenotype of the triple mutant stt3a-2/snrk2.2/2.3 to confirm the epistasis of SnRK2.2/2.3 to STT3A. However, Figure 2l shows a slightly longer primary root in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 144]]<|/det|> +snrk2.2/2.3 compared to the triple mutant, whereas Figure 2m shows the reverse result, with the triple mutant having a slightly longer root. This discrepancy may be due to the selection of seedlings for photography. Clarify this issue. + +<|ref|>text<|/ref|><|det|>[[115, 155, 876, 227]]<|/det|> +14. In Figure 3a and 3b, the intensity of SnRK2.2-GFP appears to increase after 2 hours of treatment, but Figure 3d shows a similar fluorescence intensity. Although this does not directly relate to the conclusion, please address this inconsistency. Additionally, for Figure 3c, a larger scale view may be more suitable to clearly show the cytosol, nuclear, and peroxisome localization of SnRK2.2-GFP. + +<|ref|>text<|/ref|><|det|>[[115, 238, 861, 274]]<|/det|> +15. Ensure that the growth conditions described in the text match those depicted in Figure 1a, 1c, and 1e, as there appears to be a significant difference in root lengths of Col-0 plants. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[179, 86, 362, 101]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[179, 123, 416, 138]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[179, 159, 820, 194]]<|/det|> +This manuscript provides evidence that N- glycosylation of SnRK2s controls NADPH maintenance in peroxisomes, and this relates to the desensitization of plants to repeated ABA signalling. + +<|ref|>text<|/ref|><|det|>[[178, 196, 821, 304]]<|/det|> +It is founded on discovery of a hypersensitivity to ABA- mediated repression in a mutant of \(\beta\) - subunit of glucosidase II (glβ- 2). The fact of this hypersensitivity would imply some non- compensatory need for this specific glucoside directly. However, oddly the authors find the same hypersensitivity when they individually knockout other glucosidases – STT3A, GIIα and three other N- glucosidases (CGL1, GMII, FUT11) – so why can't they compensate for the glβ- 2 mutant? Its not clear. I never saw any real exploration how each of these could in a non- compensatory manner effect the same pathway to SnRK2. + +<|ref|>text<|/ref|><|det|>[[178, 308, 821, 490]]<|/det|> +Reply 1: We thank the reviewer for the comments. For N- glycosylation modification, a nascent protein is attached a GlcManGlcNAc2 N- glycan on a specific asparagine (N) residue (NX(S/T) motif) by an oligosaccharide transferase complex when it enters the ER lumen. Subsequently, N- glucosidase I (GI) and GIIα/GIIβ heterodimer remove the outmost two glucose residues. GII- trimmed glycoprotein (N- glycan, GlcManGlcNAc2) is captured by calnexin/calreticulin (CNX/CRT) for quality control. Successfully folded glycoprotein (ManGlcNAc2) can be further processed by mannose- removing enzymes (α- mannosidase, MNSs), β1,2- N- acetylglucosaminyltransferase I (GnTI), Golgi- α- mannosidase II (GMII), fucosyltransferases (FUT), etc. sequentially in the ER- Golgi network, to form characteristic complex- type N- glycans (Nagashima et al., 2018; Strasser, 2016). + +<|ref|>text<|/ref|><|det|>[[178, 493, 821, 656]]<|/det|> +The importance of this sequential actions of N- glycan processing enzymes (NPEs) was supported by Farid's study (Farid et al., 2011). Severe defects of gl mutant can be suppressed by additional mutation of ALG10 which is responsible for biosynthesis of the outmost glucose residue, suggesting that trimming of the Glc by GI is a prerequisite for further processing by GII (Farid et al., 2011). In our report, we provided rich data such as protein- protein assays and genetic interactions between NPEs and SnRK2s, showing that NPEs regulate ABA signalling through common substrate SnRK2 kinases. So, these npe mutants (stt3a, glIα, glIIβ, cglI, hglI, futII) exhibit similar ABA- sensitivities to each other, as well as similar high salt- hypersensitivity previously reported (Strasser, 2016). + +<|ref|>text<|/ref|><|det|>[[179, 660, 820, 694]]<|/det|> +Based on suggestions from you and reviewer #3, more detailed information about N- glycosylation was added to introduction of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[179, 699, 246, 711]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[191, 714, 820, 802]]<|/det|> +Farid, A., Pabst, M., Schoberer, J., Altmann, F., Glossl, J., and Strasser, R. (2011). Arabidopsis thaliana alpha1,2- glucosyltransferase (ALG10) is required for efficient N- glycosylation and leaf growth. Plant J 68, 314- 325. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +<|ref|>text<|/ref|><|det|>[[179, 820, 820, 854]]<|/det|> +The manuscript then uses experiments on glβ- 2 or stt3a mutants interchangeably to then explore the mechanism of this desensitization of plants to repeated ABA signalling. + +<|ref|>text<|/ref|><|det|>[[179, 857, 820, 909]]<|/det|> +Reply 2: We thank the reviewer for the comments. As GIIβ and STT3A act in the same N- glycosylation pathway to co/post- modify SnRK2.2/2.3, and their mutants exhibit similar hypersensitivity to ABA treatment, they were used in our study to double- check the effect of N- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 86, 820, 175]]<|/det|> +glycosylation on ABA signalling in some experiments such as protein- protein binding, and genetic assays. But for N- glycosylation assay, STT3A can cause about 2- 3 kDa molecular mass difference of SnRK2.2/2.3 (one N- glycan), whereas GIIa/β induce only one glucose difference ( \(\sim 0.18\) kDa). It's easy to distinguish the N- glycosylated SnRK2.2/2.3 with STT3A. So the STT3A and its' mutant were chosen in N- glycosylation assays. We are sorry about making some confusion sometimes. + +<|ref|>text<|/ref|><|det|>[[178, 197, 821, 286]]<|/det|> +The yeast 2 hybrid assays are implied to show an exclusive interaction between glβ- 2 and SnRK2.2/2/3/2.6 but this was a set of pairwise interactions, not a yeast- 2 hybrid screen, so its not reasonable to call it exclusive – they only tested what they tested. Same with the LCI assays – “GIIβ, STT3A, GIIα, CGL1 and FUT11 all exclusively bind to SnRK2s” its just amongst the assay done – its not exclusive of other targets of these glucosidases. + +<|ref|>text<|/ref|><|det|>[[179, 289, 820, 323]]<|/det|> +Reply 3: We understand the reviewer's concern and removed the word “exclusively” according to the suggestions in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 344, 821, 490]]<|/det|> +Critical to the claims of the paper is that SnRK2s are glycosylated by these glucosidases – this is claimed by, “PNGase F and Endo H digestions confirmed that the band shift was due to N- glycan modification” this band shift seems to be the only evidence that this modification is occurring and the later genetic studies to mutate residues and show an absence of band shift – while in themselves compelling – are not independent of this method. There are a wide variety of other independent methods to prove N- glycan modification as well as MS and MRM methods to independently confirm the claim at the site on the SnRK2s – none of these are used but really should be to independently confirm this central claim of the paper. + +<|ref|>text<|/ref|><|det|>[[179, 494, 820, 527]]<|/det|> +Reply 4: We thank the reviewer for careful evaluation and for encouraging us to improve our manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 530, 821, 787]]<|/det|> +Based on the reviewer's suggestion, we have carried out the LC- MS/MS analysis of SnRK2.3 (Zielinska et al., 2012). Our general procedure is to firstly enrich N- glycosylated SnRK2.3 with immunoprecipitation (IP), followed by N- glycosylation site identification with LC- MS/MS. We collected roots of SnRK2.3- GFP OE- line treated with \(50~\mu \mathrm{M}\) , followed by enrichment of the N- glycosylated SnRK2.3 from total protein extracts with GFP- trap and ConA Sequentially, then carried out MS analysis (see additional method below). Unfortunately, the MS results failed to show the N- glycosylation of SnRK2.3, even no any fragment of SnRK2.3- GFP was shown. The reason may be due to small amount of SnRK2.3- GFP enriched. After multiple attempts with a large amount of roots collected, we still failed in MS analysis. The enrichment of SnRK2.3- GFP was shown in Rebuttal Fig. 1a and b. We also tried other strategy to improve the expression level of SnRK2.3. The 35S::SnRK2.3- His and 35S::STT3- mCherry were constructed on a same vector and transiently expressed in tobacco, which can increase the expression level of N- glycosylated SnRK2.3 as we did in Fig. 2d- f. But the MS results still failed to detect any SnRK2.3. The Rebuttal Fig. 1c, d showed the enrichment of SnRK2.3- His after IPs. + +<|ref|>text<|/ref|><|det|>[[178, 789, 821, 898]]<|/det|> +In our manuscript, we firstly applied band- shift assays to show SnRK2.2/2.3 are N- glycosylated in tobacco and Arabidopsis (a N- glycan gives rise to a larger band shift ( \(\sim 2\) kD plus) which can be removed by PNGase F or Endo H, Fig. 2d- i). Secondly, we found that N- glycosylation promotes nuclear export of SnRK2.2 and SnRK2.3 in tobacco leaves. To identify the N- glycosylation site, we mutated a total of 11 N (asparagine) sites of SnRK2.3 individually and the results showed that only SnRK2.3N323A is retained in the nucleus when co- expressed with STT3A- mCherry, suggesting the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 195]]<|/det|> +N323 site is responsible for the N- glycosylation. Finally, this N- glycosylation site was further confirmed by band- shift assay with site mutation. Therefore, we concluded that SnRK2.3N323 is a real N- glycosylation site. The method "band shift assays followed by PNGase F and Endo H digestions" we used, was a classical method widely used for identification of N- glycosylation in publications (Liu et al., 2015; Sato et al., 2012; Shen et al., 2014; Yamamoto et al., 2014). We think we provided strong evidences to show that SnRK2.3 is really N- glycosylated in our manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 197, 821, 305]]<|/det|> +We agree with the reviewer that MS and MRM analyses would more enhance our conclusion of N- glycosylation of SnRK2.2/2.3, and we also tried many times of MS analysis, but failed due to a tiny amount of N- glycosylated SnRK2s expressed in plants. It must be admitted that there are still many unsolved mysteries regarding the N- glycosylation modification of SnRK2s. We will continue to explore this field in the future and use more methods to detect this phenomenon. Thanks the reviewer again for valuable comments. + +<|ref|>image<|/ref|><|det|>[[270, 325, 740, 580]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[194, 594, 722, 610]]<|/det|> +
Rebuttal Fig. 1 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His.
+ +<|ref|>text<|/ref|><|det|>[[178, 611, 821, 825]]<|/det|> +a, Enrichment of N- glycosylated SnRK2.3- GFP before MS analysis. SnRK2.3- GFP overexpression plants were treated with \(50\mu \mathrm{M}\) ABA for 48 h after seven days of growth and the roots were collected. After IP with GFP- Trap and ConA (concanavalin A, a plant lectin can bind to mannose on the glycoproteins), the enrichment was determined by western blot. Input, total protein extract; GFP- Trap, enrichment of SnRK2.3- GFP by GFP- Trap beads; ConA- IP, enrichment of N- glycosylated SnRK2.3- GFP by ConA bead after GFP- Trap- IP. The white arrowhead denotes the N- glycosylated SnRK2.3- GFP. b, Coomassie brilliant blue staining after PNGase F digestion of N- glycosylated SnRK2.3- GFP enriched by ConA. The dashed white frame denotes the gel cut for LC- MS/MS. c, Enrichment of N- glycosylated SnRK2.3. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in tobacco leaves with \(50\mu \mathrm{M}\) ABA for 48 h and N- glycosylated SnRK2.3 were enriched with Ni- NTA and ConA beads sequentially. No signal was shown after ConA enrichment (right line). So only Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. His- IP, enrichment of SnRK2.3- His by Ni- NTA; PNGase F, PNGase F digestion. N- SnRK2.3- His, N- glycosylated SnRK2.3- His. d, Coomassie brilliant blue staining after PNGase F digestion of His- antibody enriched SnRK2.3- His. The dashed white frame denotes the gel cut for LC- MS/MS. + +<|ref|>sub_title<|/ref|><|det|>[[179, 837, 308, 851]]<|/det|> +## Additional method: + +<|ref|>sub_title<|/ref|><|det|>[[195, 863, 455, 877]]<|/det|> +## Enrichment of N-glycosylated SnRK2.3 + +<|ref|>text<|/ref|><|det|>[[179, 878, 820, 907]]<|/det|> +Plant tissues were grounded to powder in the frozen state and homogenized in extraction buffer (50 mM Tris- HCl, pH 7.4, 150 mM NaCl, 1 mM MgCl2, 10 μM EDTA, 1% NP- 40, 1×protease inhibitor, 5 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 820, 227]]<|/det|> +\(\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with GFP- Trap agarose (Chromotek) or nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(4\mathrm{h}\) , beads were washed five times with ice- cold washing buffer (50 mM Tris- HCl, pH 7.4, \(400\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) \(\mathrm{MgCl}_2\) , \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins were eluted with acidic buffer (200 mM glycine, pH 2.5) and immediately neutralized the eluate fraction with neutralization buffer ( \(100\mathrm{mM}\) Tris- HCl, pH 10.4). The eluted proteins were then incubated with ConA (concanavalin A, a plant lectin can bind to mannose on the glycoproteins) beads (Beyotime) at \(4^{\circ}\mathrm{C}\) , After \(4\mathrm{h}\) , beads were washed five times with washing buffer ( \(20\mathrm{mM}\) Hepes, \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) \(\mathrm{MgCl}_2\) , \(1\mathrm{mM}\) \(\mathrm{MnCl}_2\) , \(1\mathrm{mM}\) \(\mathrm{CaCl}_2\) , \(0.1\%\) Tween- 20). The proteins were eluted with elution buffer ( \(5\mathrm{mM}\) Tris- HCl, pH 8.0, \(150\mathrm{mM}\) NaCl, \(1\mathrm{M}\) Glucose). + +<|ref|>sub_title<|/ref|><|det|>[[195, 236, 323, 250]]<|/det|> +## PNGase F digestion + +<|ref|>text<|/ref|><|det|>[[179, 250, 820, 337]]<|/det|> +For PNGase F treatment, referring to the manufacturer's protocol, \(10\times\) glycoprotein denaturing buffer was added to IP- purified proteins and heated at \(100^{\circ}\mathrm{C}\) for \(10\mathrm{min}\) . After returning to room temperature, the reaction buffer (containing \(\mathrm{H}_2^{18}\mathrm{O}\) ) and PNGase F (New England Biolabs) were added to sample. The mixture was incubated for \(1\mathrm{h}\) at \(37^{\circ}\mathrm{C}\) before boiled in \(5\times\) SDS loading buffer. N- glycation of SnRK2.3 was detected by immunoblot analyses using by anti- GFP and anti- His antibodies after \(6\%\) SDS- PAGE. The sample was subjected to mass spectrometry detection after immunoblot analyses. + +<|ref|>sub_title<|/ref|><|det|>[[195, 345, 615, 359]]<|/det|> +## LC-MS/MS for identification of N-glycosylation site of SnRK2.3 + +<|ref|>text<|/ref|><|det|>[[178, 360, 820, 587]]<|/det|> +For mass spectrometry analysis, protein samples were separated using SDS- PAGE electrophoresis and detected by coomassie brilliant blue staining. The SDS- PAGE gel at \(70\mathrm{kD}\) or \(40\mathrm{kD}\) was collected into a clean centrifuge tube. \(500\mu \mathrm{l}\) destain solution were added to a centrifuge tube and shaken at room temperature until the gel discolored. After discarding the supernatant, \(75\%\) acetonitrile ( \(200\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature. After \(30\mathrm{min}\) , \(500\mu \mathrm{l}\) H2O were added to the centrifuge tube and shaken at room temperature for \(1\mathrm{h}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) ( \(300\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) ( \(20\mu \mathrm{l}\) ) and \(2\mu \mathrm{l}\) trypsin ( \(1\mu \mathrm{g / \mu l}\) , Promega) were added to the centrifuge tube, and gel was crushed. After centrifugation ( \(1000\mathrm{rpm}\) , 1min), the sample was digested at \(37^{\circ}\mathrm{C}\) . After \(8\mathrm{min}\) , \(200\mu \mathrm{l}\) acetonitrile were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After centrifugation ( \(1000\mathrm{rpm}\) , 1min), the supernatant was transferred to a new centrifuge tube. This step was repeated once, ultimately resulting in \(400\mu \mathrm{l}\) supernatant. The obtained supernatant was vacuum dried at \(60^{\circ}\mathrm{C}\) and dissolved in \(0.1\%\) formic acid ( \(100\mu \mathrm{l}\) ). Samples were subjected to mass spectrometry detection by using mass spectrometer (Orbitrap Fusion™ Lumos™ Tribrid™, Thermo Scientific). The N- glycation site of SnRK2.3 was analyzed using software (Proteome Discoverer 2.3). + +<|ref|>sub_title<|/ref|><|det|>[[178, 608, 246, 620]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[177, 622, 820, 824]]<|/det|> +Liu, Y., Zhang, C., Wang, D., Su, W., Liu, L., Wang, M., and Li, J. (2015). EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated degradation system in Arabidopsis. Proc Natl Acad Sci U S A 112, 12205- 12210. Sato, T., Sako, Y., Sho, M., Momohara, M., Suico, M.A., Shuto, T., Nishitoh, H., Okiyoneeda, T., Kokame, K., Kaneko, M., et al. (2012). STT3B- dependent posttranslational N- glycosylation as a surveillance system for secretory protein. Mol Cell 47, 99- 110. Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M.E., and Nasrallah, J.B. (2014). Site- specific N- glycosylation of the S- locus receptor kinase and its role in the self- incompatibility response of the brassicaceae. Plant Cell 26, 4749- 4762. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<|ref|>text<|/ref|><|det|>[[178, 843, 819, 895]]<|/det|> +The apparent translocation of SnRK2 to the peroxisome is proposed, but then recanted in the text, because nuclear export inhibition did not block it. Instead it seemed more likely the nuclear SnRK2 is degraded and a peroxisome targeted version is generated, so authors need to ensure they don't continue + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 86, 636, 101]]<|/det|> +to claim 'translocation' in the text in other passages and also Fig 3 legend. + +<|ref|>text<|/ref|><|det|>[[178, 105, 820, 156]]<|/det|> +Reply 5: We thank the reviewer for the comments. According to the suggestions from you and reviewer #2, we have replaced "translocate/translocation" with "redistribute/ redistribution" to illustrate the movement of SnRK2 in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 179, 820, 249]]<|/det|> +When we get to peroxisomes and what SnRK2 interacts with, we see another selective process "we investigated the potential SnRK2- interacting partners among peroxisomal isozymes involved in \(\mathrm{H}_2\mathrm{O}_2\) - scavenging and NADPH generation" so again the link to GPT1 is really achieved by analysis of a small subset of hand picked targets. + +<|ref|>text<|/ref|><|det|>[[177, 253, 821, 471]]<|/det|> +Reply 6: We thank the reviewer for the comments. In our study, we did not search the potential peroxisomal SnRK2 binding proteins in genome- wide. One of the reasons is that it is hard to construct a gene library encoding all the peroxisomal isozymes for SnRK2- partner screening. Another reason is that it is hard to get only peroxisome- localized SnRK2s for IP- MS/MS analysis (some SnRK2s in the nuclei, and some on the peroxisomal membrane during prolonged ABA signalling). Instead, for quick identification of SnRK2 partners, we cloned 13 published genes of peroxisomal isozymes required for NADPH- generation on the peroxisomal membrane (Extended Data Fig. 14a), and identified GPT1 as a SnRK2 binding protein with ABA- dependent manner. Based on the reviewer #3's comments, we have constructed peroxisome- fixed SnRK2.3 (SnRK2.3- mPTSPEX26, with SnRK2.3- NLS as a control, see revised Fig. 4 i,j, and Extended Data Fig. 17), and we are trying to make transgenic Arabidopsis for SnRK2- binding protein screening in genome- wide via IP- MS/MS in the future. Thanks again for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[178, 493, 821, 637]]<|/det|> +In all honesty, the claim of changes in NADPH and ROS in peroxisomes require detailed time- lapse measurements to be performed. The claimed errors bars in Fig 4 and extended Fig 11 are noted to be based on mean plus or minus sd, no n value is provided for either in the legends. But the reporting summary suggested - "All experiments were repeated two- three biologically independent experiments as mentioned in figure legends and methods". Having done these sorts of assays myself I find those errors (just a few percent in many cases) just inconceivably small for independent experiments. Throughout the paper these small n value experiments are just showing mean and sd, not data points on graphs to show means for each rep. + +<|ref|>text<|/ref|><|det|>[[179, 640, 820, 693]]<|/det|> +These very small errors are essential for the claims made as the \(\mathrm{H}_2\mathrm{O}_2\) and NADPH changes in Figure 4 are very small. I would want to see further evidence that the errors are accurately reported across independent experiments. + +<|ref|>text<|/ref|><|det|>[[179, 697, 820, 768]]<|/det|> +Reply 7: We thank the reviewer for the comments. According to the reviewer's suggestions, we re- investigated the accumulations of \(\mathrm{H}_2\mathrm{O}_2\) and NADPH with three biological replicates in revised Fig. 4 a, and d. The "n value" in the figure legends of Extended data Fig. 11 and all the other figures were checked in our revised manuscript. + +<|ref|>text<|/ref|><|det|>[[179, 790, 820, 879]]<|/det|> +Overall the biological case surrounding this mutant is extensively explored and links of the mutants effects back into ABA processes are extensive and involve a large amount of work and come to novel conclusions for the field. My main concern is that the biochemical pathway to the claim involves a series of selective choices that need to be acknowledged along the way and key points such as the glycosylation evidence and the clarification of how such small errors can be recorded need to be resolved. + +<|ref|>text<|/ref|><|det|>[[191, 883, 820, 898]]<|/det|> +Reply 8: We would like to thank the reviewer for the careful evaluation and for encouraging us + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 176]]<|/det|> +to improve our manuscript. Above, we have provided our responses to all the comments point- by- point. We answered the comments about “a series of selective choices” in Reply 3 and 6. The N- glycosylation modification of SnRK2.3 was further elucidated in Reply 4. To address the small error bars, we re- investigated the accumulation levels of NADPH, and \(\mathrm{H}_2\mathrm{O}_2\) with three independent biological replicates (Reply 7). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 86, 416, 100]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 104, 821, 287]]<|/det|> +Reviewer #2 (Remarks to the Author):Pretreating plants with mild abiotic stresses helps them to adapt to harsh conditions, and the adaptation process is enhanced by ABA treatment. Revealing the underlying mechanism would have practical implications. This paper reports that ABA causes the subcellular redistribution and target change of SnRK2.2/2.3, two key regulators of ABA signaling. SnRK2.2/2.3 are localized in the nucleus and activate transcriptional responses at the initial ABA signaling stage, but during prolonged ABA treatment, they are N- glycosylated in the ER- Golgi network and sent to the peroxisomes. On the peroxisomal membrane, SnRK2.2/2.3 phosphorylate and activate Glucose- 6- Phosphate Transporter 1 (GPT1), which helps maintain NADPH homeostasis and suppress \(\mathrm{H}_2\mathrm{O}_2\) over- accumulation. Plants that have undergone such changes become less responsive to ABA (desensitized) and may better tolerate stress conditions (becoming acclimated). + +<|ref|>text<|/ref|><|det|>[[179, 308, 820, 341]]<|/det|> +The data presented in this paper are sound, the logic is clear, and the finding represents a significant step toward understanding the molecular mechanisms of plant acclimation. + +<|ref|>text<|/ref|><|det|>[[194, 346, 690, 360]]<|/det|> +We great appreciate the reviewer for positive comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[179, 383, 290, 397]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[179, 401, 820, 433]]<|/det|> +1. Labeling errors: in Extended Data Fig. 1, the labels "e" and "f" are misplaced; the "Fig. 1f" is mislabeled. + +<|ref|>text<|/ref|><|det|>[[179, 438, 378, 453]]<|/det|> +Reply 1: That's correct. Done. + +<|ref|>text<|/ref|><|det|>[[178, 457, 820, 490]]<|/det|> +2. Labeling errors: Main text lines 65 - 67, the Extended Data Fig. 2c-e, 2f, and 2g should be Extended Data Fig. 1c-e, 1f, and 1g. + +<|ref|>text<|/ref|><|det|>[[179, 494, 277, 508]]<|/det|> +Reply 2: Done. + +<|ref|>text<|/ref|><|det|>[[179, 512, 593, 527]]<|/det|> +3. Labeling error: Main text line 92, the Fig. 1j should be Fig. 1j, k. + +<|ref|>text<|/ref|><|det|>[[179, 531, 275, 545]]<|/det|> +Reply 3: Done + +<|ref|>text<|/ref|><|det|>[[179, 549, 780, 564]]<|/det|> +4. Labeling error: Main text line 148, the Extended Data Fig. 6e should be Extended Data Fig. 6f. + +<|ref|>text<|/ref|><|det|>[[179, 568, 275, 581]]<|/det|> +Reply 4: Done + +<|ref|>text<|/ref|><|det|>[[178, 586, 821, 824]]<|/det|> +5. About the term "translocation": This term may mislead readers and should be considered revision. Throughout the paper, the authors use "translocate/translocation" to describe the change of SnRK2s localization patterns: SnRK2s are normally localized in the nucleus, and during prolonged ABA treatment, they are N-glycosylated and localized on the peroxisomal membrane. Although they disappear from the nucleus and reappear on the peroxisome, the SnRK2s proteins do not physically move 'from the nucleus to the peroxisomes'; this is supported by the experiment presented in Extended Data Fig. 10f, g (main text lines 188-190). Therefore, the term "translocate/translocation" does not accurately describe the process and can be misleading. For example, in the Abstract, line 11 reads, "...which promotes their gradual translocation from the nucleus to the peroxisomes...." Immediately following this sentence, line 13 reads, "After moving to the peroxisomal membrane, SnRK2s directly interact with...." This combination will almost surely make readers mistakenly think that SnRK2s physically move between the two organelles. A possible substitute for "translocation" is "redistribution." The term "redistribution" better describes the phenomenon, avoids misunderstanding, and inspires people to wonder. + +<|ref|>text<|/ref|><|det|>[[179, 827, 820, 860]]<|/det|> +Reply 5: The comments are greatly appreciated. We have replaced the term "translocate/translocation" with "redistribute/redistribution" in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[179, 864, 820, 897]]<|/det|> +In the abstract (line 11- 13), both "translocation" and "After moving to" have been replaced with "redistribution" and "On", respectively. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 103, 820, 157]]<|/det|> +People may ask where SnRK2s proteins are synthesized and precisely what triggers the switch from targeting SnRK2s to the nucleus to targeting them to peroxisomes. The answers to such questions may expand the current finding and lead to the development of application strategies. + +<|ref|>text<|/ref|><|det|>[[178, 160, 821, 342]]<|/det|> +Reply 6: We would like to thank the referee for the valuable suggestion. Our study revealed that SnRK2s are modified with a N- glycan on the ER- Golgi networks, and are redistributed on the peroxisomal membrane finally. As non- secretory proteins, how SnRK2s are located on the ER- Golgi networks; Where they are synthesized. They are translated on the rough ER and then enter the ER lumen, or they are synthesized in the cytosol and then translocated on the ER- Golgi. What triggers the ER- Golgi localization of them. The answers to these questions would deepen our understanding of the molecular mechanisms of ABA signalling. We are trying to answer some of these questions now. In our another project, we found a protein channel which may be responsible for the ER- Golgi- loading of SnRK2s, but now we need to collect more solid evidences to support this notion. + +<|ref|>text<|/ref|><|det|>[[179, 438, 416, 453]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 474, 821, 638]]<|/det|> +This study presents a putative mechanism for the desensitization and transition of ABA signaling during prolonged treatment, involving N- glycosylation of SnRK2s. Under prolonged ABA signaling, the key regulator SnRK2.2/2.3 undergoes N- glycosylation in the ER- Golgi network, which leads to its translocation to the peroxisome. In the peroxisome, SnRK2s regulate NADPH generation by phosphorylating the transporter GPT1 during NADPH synthesis, suggesting a new module of redox homeostasis for adapting to long- term stress conditions during prolonged ABA signaling. The findings are interesting and provide insights into plant responses under prolonged stress conditions. However, there are several major issues in the manuscript that need to be addressed, before it could be considered by Nat Commun. + +<|ref|>text<|/ref|><|det|>[[179, 660, 601, 675]]<|/det|> +We thank the reviewer for positive evaluation of the manuscript. + +<|ref|>text<|/ref|><|det|>[[179, 698, 263, 712]]<|/det|> +Major Points: + +<|ref|>text<|/ref|><|det|>[[179, 716, 820, 787]]<|/det|> +1. It is common to assay ABA responses through germination, cotyledon greening, and post-germination growth using different concentrations of ABA. In this study, the authors chose to germinate the seeds in a very high concentration of ABA (3 μM) and measured the root length at a later stage. Please explain the rationale for this choice and provide results from other assays. + +<|ref|>text<|/ref|><|det|>[[178, 799, 821, 907]]<|/det|> +Reply 1: The comments are greatly appreciated. At the beginning of our project, we carried out morphological assays of gIIβ- 2 with 1, 3, 5 (μM) ABA, and the results showed that 3 μM ABA induced more significant difference in gIIβ- 2, OE- GIIβ compared with WT in terms of germination rate (Rebuttal Fig. 2). Hereafter, 3 μM ABA was chosen for phenotypical assays of all mutants of N- glycosylation processing enzymes (NPEs). we apologize for not including these results due to space limitation in our first submission. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[290, 112, 725, 440]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[210, 465, 640, 481]]<|/det|> +
Rebuttal Fig. 2 | The seed germination rate of Arabidopsis plants.
+ +<|ref|>text<|/ref|><|det|>[[203, 483, 821, 555]]<|/det|> +a- d, The germination rate of Col- 0, glβ- 2 and OE- Glβ- 16 were determined with different concentrations of ABA. The germination rate was calculated every half day until the fifth day (after stratification at \(4^{\circ}\mathrm{C}\) for 2 days). In each petri dish, approximately 60 seeds were counted for each Arabidopsis genotype. + +<|ref|>text<|/ref|><|det|>[[178, 575, 822, 685]]<|/det|> +2. The major discovery in this work is that N-glycosylation of SnRK2s leads to the desensitization of prolonged ABA signaling through translocation. However, the relationship between these two processes remains unclear. Does N-glycosylation of SnRK2s occur before or after their translocation? Does N-glycosylation cause translocation, or does translocation lead to N-glycosylation? It would be helpful to design a subcellular-fixed mode of SnRK2s that can only be located in the nucleus or peroxisome to investigate the effects. + +<|ref|>text<|/ref|><|det|>[[178, 696, 821, 842]]<|/det|> +Reply 2: We thank the reviewer for the valuable comments. In our purposed working model (revised Extended Data Fig. 18), SnRK2s appear to be N-glycosylated on the ER-Golgi networks, then to be redistributed to the peroxisome membrane, which is supported by evidences from N-glycosylation assays (Fig. 2d-j) and time-course confocal microscopy observations of SnRK2.2/2.3- GFP (Fig. 3a-g). The peroxisomal localization of SnRK2.2- GFP was inhibited by stt3a- 2, and was enhanced by STT3A overexpression (Fig. 3d); mutation of N-glycosylation site of SnRK2.3N323A suppress its peroxisomal redistribution (Fig. 3f). The findings indicate that N-glycosylation is one of the key factors to determine the peroxisomal redistribution of SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[178, 854, 820, 907]]<|/det|> +Based on the reviewer's suggestions, we constructed fixed SnRK2.3s with SV40 nuclear location signal (NLS) and PEX26 c- terminal end (mPTSPEX26) (Wright and Bartel, 2020) specifically located in the nucleus and on the peroxisomal membrane respectively. As shown in revised Extended Data + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 212]]<|/det|> +Fig. 17, the SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 showed the fixed subcellular localizations and normal kinase activities. To investigate the N- glycosylation, we transiently expressed them in the Arabidopsis roots. After treatment with ABA, the total protein extracts were co- immunoprecipitated with GFP- trap beads, and the N- glycosylation of fixed SnRK2.3s was determined by ConA- HRP (ConA, concanavalin A, a plant lectin can bind to mannose on the glycoproteins; ConA- HRP, HRP conjugated ConA (Sigma- Aldrich, L6397); HRP, horseradish peroxidase). + +<|ref|>text<|/ref|><|det|>[[178, 224, 821, 333]]<|/det|> +We proposed that the nuclear SnRK2.3 is not N- glycosylated, whereas peroxisomal SnRK2.3 should possess a N- glycan. Unexpectedly, our results showed that only wild type SnRK2.3 is N- glycosylated, but both SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 are not (Rebuttal Fig. 3). The absence of N- glycan of peroxisomal SnRK2.3 may be due to deferent targeting pathways of native SnRK2.3 and fixed SnRK2.3. The SnRK2.3- mPTSPEX26 may directly target to the peroxisomal membrane, whereas native SnRK2.3 redistribute to the peroxisomes through ER- Golgi networks. + +<|ref|>image<|/ref|><|det|>[[195, 345, 710, 471]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[178, 482, 821, 574]]<|/det|> +Rebuttal Fig. 3 | N- glycosylation assays of SnRK2.3WT, SnRK2.3- NLS, SnRK2.3- mPTSPEX26 with ConA- HRP. Total proteins were extracted from ABA- treated transgenic hair roots of SnRK2.3WT/snrk2.2/2.3, SnRK2.3- NLS/snrk2.2/2.3, and SnRK2.3- mPTSPEX26/snrk2.2/2.3, followed by immunoprecipitation with GFP- Trap agarose and detection with the anti- GFP antibody and ConA- HRP. The white arrowhead indicates the N- glycosylated SnRK2.3WT- GFP. + +<|ref|>sub_title<|/ref|><|det|>[[178, 588, 246, 601]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 611, 820, 642]]<|/det|> +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +<|ref|>text<|/ref|><|det|>[[178, 670, 820, 704]]<|/det|> +The introduction of this paper focuses mainly on plant ABA signaling but lacks information about N- glucosidases, especially those mentioned in this work. + +<|ref|>text<|/ref|><|det|>[[178, 707, 820, 760]]<|/det|> +Reply 3: We thank the reviewer for the comments. Based on the reviewer's suggestion, detailed information about N- glycosylation has been added to the introduction of the revised manuscript with highlight of the roles of STT3A, GIIa, GIIβ, CGL1, GMII, and FUT11 used in our study. + +<|ref|>text<|/ref|><|det|>[[178, 781, 820, 814]]<|/det|> +Why the authors chose to study STT3A instead of the GIIβ, the mutant initially screened in most experiments? + +<|ref|>text<|/ref|><|det|>[[178, 818, 821, 908]]<|/det|> +Reply 4: We thank the reviewer for the comments. N- glycosylation involves sequential actions of an array of enzymes, such as STT3A, GIIa, GIIβ, and FUT11 used in our study, which function in transfer and modification of sugar moieties in ER and Golgi networks (Strasser, 2016; Zielinska et al., 2012). STT3A is a catalytic subunit of oligosaccharide transferase complex, whereas GIIβ is involved in GIIα/β- heterodimer- mediated glucose trimming of N- glycans. For the N- glycosylation + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 180]]<|/det|> +assays, GIIβ would cause about 0.18 kDa molecular mass difference (one glucose) of SnRK2.2/2.3, but this molecular mass difference would be enlarged to 2- 3 kDa (one N- glycan) made by STT3A (Shen et al., 2014). Similar ABA- sensitive phenotype, but easy test for N- glycosylation assay of SnRK2.2/2.3, STT3A was chosen for further works instead of GIIβ. We apologize for making some confusion in our manuscript. We added a reasonable sentence in the revised manuscript at line 173. + +<|ref|>sub_title<|/ref|><|det|>[[179, 183, 247, 196]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[184, 196, 820, 280]]<|/det|> +Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<|ref|>text<|/ref|><|det|>[[178, 300, 820, 352]]<|/det|> +5. The authors performed a time course RNA-seq analysis to investigate the effects of N-glucosidases, but the stt3a-2 results were analyzed using Col-0 as a control instead of using no ABA-treated stt3a-2 as a control. + +<|ref|>text<|/ref|><|det|>[[178, 356, 821, 539]]<|/det|> +Reply 5: We thank the reviewer for the comments. We have 0 h ABA-treated stt3a-2 which is a no ABA-treated control. When analyzed datasets, we first carried out k-means clustering analysis to determine the ABA-responsive genes (well overlap with previously reported ABA-responsive genes), and their time-course expression pattern in ABA-treated Col-0 group with 0 h - ABA-Col-0 as a control. Then we retrieved the expression profiles of these ABA-responsive genes from no-ABA-treated Col-0 group (0-72 h), to show their basal expression level during 72 h-ABA treatment. Finally, we retrieved the expression data of the ABA-responsive genes from ABA-treated stt3a-2 with 0 h- stt3a-2 as a control, to show the desensitization of ABA-responsive genes is delayed in stt3a-2 compared with ABA-treated Col-0. Detailed information was added in revised manuscript line 115 and 121. + +<|ref|>text<|/ref|><|det|>[[180, 560, 820, 612]]<|/det|> +Additionally, the results do not seem to match the expression pattern shown in Figure 1g- i, as the expression of stress response genes in stt3a-2 would be expected to be stronger and longer than in Col- 0. Address these inconsistencies and provide a proper control for the analysis. + +<|ref|>text<|/ref|><|det|>[[186, 615, 821, 797]]<|/det|> +Reply 6: For ABA- induced cluster 18 in (previous) Fig. 1k (now in revised Extended Data Fig. 3a), the biphasic inflection timepoint is delayed from 1 h in Col- 0 to 2 h in stt3a- 2. However, the expression level of these genes in stt3a- 2 appears not stronger and longer than that in Col- 0. This phenomena may be due to its special expression pattern with the rapid induction (peak at 1 h) and followed by a rapid reduction (4- 6 h to basal level, (previous) Fig. 1j (now in revised Extended Data Fig. 3a)), whereas, the expression of NCED3, P5CS1, and RAB18 all peak at 3 h, and decline to basal level at 48 h for NCED3 and RAB18 (Fig. 1g- i). Our study also revealed that N- glycosylation mainly function in prolonged ABA signalling. Taken together, our results may suggest the weaker effects of N- glycosylation/STT3A on these rapidly induced ABA- responsive genes in cluster 18. + +<|ref|>text<|/ref|><|det|>[[186, 801, 821, 890]]<|/det|> +For the left 3 ABA- induced clusters (cluster 1, 8 and 13 in Extended Data Fig.3a), the expression peaks of them are 4- 6 h, 6 h, 2- 3 h in ABA- treated Col- 0 respectively, which are similar to that of NCED3, P5CS1, and RAB18 in Fig. 1g- i. the expression of genes in cluster 1, 8, and 13 is stronger and longer in stt3a- 2 than that in Col- 0. We put cluster 1 in Fig.1j, k in exchange of cluster 18, and related text also was corrected in our revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 138]]<|/det|> +In Figure 2, based on the results of co- expressed SnRK2.2/2.3 and STT3A in tobacco, the western blot results need to include a control without co- expression and ABA treatment to confirm the band as N- glycosylated SnRK2s. + +<|ref|>text<|/ref|><|det|>[[178, 142, 820, 175]]<|/det|> +Reply 7: We thank the reviewer for the comments. That's correct. Done. The results were shown in revised Fig. 2f. + +<|ref|>text<|/ref|><|det|>[[178, 197, 820, 230]]<|/det|> +Additionally, the western blot results in snrk2.6 mutants require a control using snrk2.2/2.3/2.6 mutants to eliminate non- specific bands. Include these controls for a more accurate interpretation of the results. + +<|ref|>text<|/ref|><|det|>[[191, 234, 455, 248]]<|/det|> +Reply 8: Done. See revised Fig.2h and i. + +<|ref|>text<|/ref|><|det|>[[191, 252, 820, 268]]<|/det|> +We also checked the specificity of the antibody used (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +<|ref|>image<|/ref|><|det|>[[336, 298, 678, 393]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[193, 400, 584, 415]]<|/det|> +Rebuttal Fig. 3 The anti- SnRK2.2/2.3/2.6 used in our study. + +<|ref|>text<|/ref|><|det|>[[178, 419, 820, 452]]<|/det|> +The 10- day seedlings of snrk2.6 single mutant, snrk2.2/2.3 double mutant, and snrk2.2/2.3/2.6 triple mutant were used here. (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +<|ref|>text<|/ref|><|det|>[[178, 492, 820, 526]]<|/det|> +To confirm the N- glycosylated point Asp323 on SnRK2.3, include at least one additional point mutant in Figure 2k as a negative control to provide more solid evidence. + +<|ref|>text<|/ref|><|det|>[[178, 530, 820, 564]]<|/det|> +Reply 9: We thank the reviewer for the comments. Another point mutation SnRK2.3N288A has been included in the N- glycosylation assay (see revised Fig.2k). + +<|ref|>text<|/ref|><|det|>[[178, 585, 821, 730]]<|/det|> +Regarding the translocation of SnRK2.2/2.3- GFP in Arabidopsis, both SnRK2.2 and SnRK2.3 need to complete this evidence. Choose one of them to show the results instead of showing SnRK2.2 translocation with SnRK2.3 (Fig 3d) and performing a mutation assay with SnRK2.3N323A (Fig 3f). The results in Figure 3f indicate that a small amount of SnRK2.3N323A can still export from the nucleus, while SnRK2.2 cannot translocate in the stt3a- 2 mutant. This suggests that other factors may be involved in SnRK2.3 translocation besides N- glycosylation at N323, but it is difficult to confirm due to the unequal comparison. To address this, extract nuclear and cytoplasmic proteins separately for western blot analysis to check the N- glycosylation of SnRK2.2/2.3 after ABA treatment. + +<|ref|>text<|/ref|><|det|>[[178, 733, 821, 841]]<|/det|> +Reply 10: We thank the reviewer for the careful evaluation. We are sorry for misunderstanding of redistribution of SnRK2.2 and SnRK2.3 due to lacking full evidences of both of them. Actually, there is no any significant difference between SnRK2.2 and SnRK2.3 in their subcellular dynamics. In stt3a- 2 background, peroxisomal redistribution of SnRK2.2- GFP is repressed, but few amount of SnRK2.2- GFP still locate on the peroxisomes like SnRK2.3N323A (see 48 h ABA in (previous) Fig. 3d). + +<|ref|>text<|/ref|><|det|>[[178, 845, 820, 897]]<|/det|> +Based on the reviewer's suggestions, to avoid misunderstanding, we have completed the observation of both SnRK2.2- GFP and SnRK2.3- GFP in the revised Fig. 3a. We also re- investigated SnRK2.2- GFP subcellular dynamics under stt3a- 2, and STT3A- OE backgrounds in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 819, 120]]<|/det|> +revised Fig. 3d and 3e. For N- glycosylation of SnRK2.2 and SnRK2.3, they are also similar to each other (Fig. 2d-f, and Extended Data Fig. 7) + +<|ref|>text<|/ref|><|det|>[[178, 150, 821, 278]]<|/det|> +8. In most experiments, the authors used SnRK2.3N323A, a mutant with abolished N-glycosylation of SnRK2.3 (Fig 2k). However, SnRK2.3 still exists in both the nucleus and peroxisome (Fig 3f), which may explain the weak or inconsistent results in Fig. 4 and Extended Data 16. To overcome this issue, delete the nuclear localization signal and peroxisome targeting signal separately to generate SnRK2.2/3 specifically located in the peroxisome and nucleus, and assess the function of SnRK2.2/3 translocation. Additionally, include snrk2.2/snrk2.3 as controls in all assays of SnRK2.32WT and SnRK2.3N323A to demonstrate the role of SnRK2s in these processes. + +<|ref|>text<|/ref|><|det|>[[178, 289, 821, 527]]<|/det|> +Reply 11: We thank the reviewer for the valuable comments. We agree with the reviewer that N- glycosylation is not the only effector in the regulation of SnRK2.2/2.3's redistribution, as SnRK2.3N323A with mutated N-glycosylation site can still presents on the peroxisomes. However, our studies also showed that N-glycosylation is a crucial effector for SnRK2-redistribution during prolonged ABA signalling. Firstly, genetic analysis showed that N-glycosylation is a key regulator in ABA signalling (ABA-hypersensitivity of npe mutants and SnRK2.3N323A/snrk2.2/2.3 transgenic lines (Fig. 1a-f, Extended Data Fig. 8). Secondly, the subcellular dynamics of SnRK2.2/2.3 in Fig. 3d,e and Fig. 3f,g showed that significantly less SnRK2.3/2.3 locate on the peroxisomes when N- glycosylation is defective. Finally, ABA-induced NADH maintenance and H2O2 clearance are significantly affected by N-glycosylation (stt3a-2 vs. Col-0; SnRK2.3N323A vs. SnRK2.3WTin snrk2.2/2.3 double mutant background) during prolonged ABA signalling (Fig. 4a, d and Extended Data Fig. 11, 13, 15c-f, and 16a-d). Totally, our results suggested strong correlation between N- glycosylation and peroxisomal localization of SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[178, 530, 821, 767]]<|/det|> +To confirm whether the effect of N- glycosylation on ABA signalling is due to the peroxisomal targeting of SnRK2.2/2.3, based on the reviewer's suggestion, we constructed the fixed SnRK2.3s that specifically locate in the nucleus (SnRK2.3- NLS) and the peroxisomal membrane (SnRK2.3- mPTSPEX26), and expressed them in the snrk2.2/2.3 double mutant background (Wright and Bartel, 2020). As shown in revised Extended Data Fig. 17, and Fig. 4i, j, both of them possess normal kinase activities, and the SnRK2.3- mPTSPEX26 possesses higher NADPH level (NADPH/NADP+) and lower H2O2 than SnRK2.3WT during prolonged ABA signalling, whereas SnRK2.3- NLS has the highest H2O2 level. We also investigated the ABA- transcriptional response, and the results showed that SnRK2.3- NLS strongly enhance the expression of ABA- responsive genes, but SnRK2.3- mPTSPEX26 not. Our findings support the notion that SnRK2.3 activates the ABA- transcriptional response, whereas the peroxisomal SnRK2.3 for NADPH maintenance during prolonged ABA signalling. In all these experiments, snrk2.2/2.3 double mutant was included as a control. See revised manuscript line 437- 468. + +<|ref|>text<|/ref|><|det|>[[179, 770, 820, 823]]<|/det|> +The SnRK2.3N323A, SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 were expressed under the snrk2.2/2.3 double mutant background, and the SnRK2.3WT/snrk2.2/2.3 was used as a strict control in these analyses. + +<|ref|>sub_title<|/ref|><|det|>[[179, 837, 246, 850]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[179, 861, 820, 890]]<|/det|> +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intralumenal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 120]]<|/det|> +This study shows the interaction and regulation between SnRK2s and GPT1, but mainly focuses on SnRK2.2 and GPT1, neglecting SnRK2.2 and 2.3. + +<|ref|>text<|/ref|><|det|>[[178, 123, 820, 213]]<|/det|> +Reply 12: We thank the reviewer for the comments. According to the reviewer's suggestion, the interaction assay between SnRK2.3 and GPT1 has been added in revised Fig. 4c. Phosphorylation analysis of GPT1 by SnRK2.3 has been added in revised Fig. 4e. Interaction assay of GPT1 and SnRK2.2, and phosphorylation analysis of GPT1 by SnRK2.2 have been moved to Extended Data Fig. 14c, f. + +<|ref|>text<|/ref|><|det|>[[178, 216, 820, 250]]<|/det|> +The time- course expression pattern of GPT1 protein, and identification of GPT1 phosphorylation sites by LC- MS/MS have been moved to Extended Data Fig. 14d, e. + +<|ref|>text<|/ref|><|det|>[[178, 270, 820, 305]]<|/det|> +To verify the function of the phosphorylation site, stable transgenic plants would provide more solid evidence than transient expression. + +<|ref|>text<|/ref|><|det|>[[177, 307, 821, 529]]<|/det|> +Reply 13: We thank the reviewer for the comments and we agree with the reviewer that GPT1- stable transgenic plants would provide more strong support to our manuscript. We have obtained gpt1- 1 mutant from prof. Juan Xu (Zhe Jiang University)(Zheng et al., 2018), and are trying to introduce the GPT1WT, GPT1S324, and GPT1S320 constructs into gpt1- 1(- /-) background, but it appears a hard and long- time work. gpt1- 1 mutant is a T- DNA insertion line and the homozygous gpt1- 1 (- /-) is embryo lethal, so we had to introduce GPT1- constructs into gpt1- 1 (- /+) background. it would need a long time to screen GPT1WT, GPT1S324, and GPT1S320 transgenic lines with gpt1- 1 (- /-) background. On the other hand, our transient expression data of GPT1- constructs in Fig. 4g and h, appears to work well. It showed significantly difference for GPT1S324 and GPT1S320, compared with GPT1WT. Without a doubt, the stable transgenic plants would provide more strong evidences to our conclusions, and we will continue to screen the GPT1- transgenic plants, and collect more comprehensive evidences to support the conclusions. + +<|ref|>sub_title<|/ref|><|det|>[[178, 560, 246, 572]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 574, 820, 619]]<|/det|> +Zheng, Y., Deng, X., Qu, A., Zhang, M., Tao, Y., Yang, L., Liu, Y., Xu, J., and Zhang, S. (2018). Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis. PLoS Genet 14, e1007880. + +<|ref|>text<|/ref|><|det|>[[178, 637, 821, 727]]<|/det|> +Explain why the SnRK2.2- and SnRK2.3- GFP proteins showed a dramatic increase (more than 10- fold) after ABA treatment in Extended Data Fig. 9c. However, in Extended Data Fig 9e, the SnRK2.2- GFP protein only increased less than 1.5- fold after ABA treatment, leading to inconsistency. Generally, the protein abundance of SnRK2s should decline after ABA treatment. Provide an explanation for this discrepancy. (in Extended Data Fig 9e, the 35S:: SnRK2.2- GFP, error bar value) + +<|ref|>text<|/ref|><|det|>[[178, 730, 821, 913]]<|/det|> +Reply 14: We investigated temporal dynamics of endogenous SnRK2.2/2.3/2.6 over prolonged ABA treatment with antibody (Agrisera AS142783) in our manuscript, and the results showed that the SnRK2.2/2.3/2.6 are induced by short- term ABA treatments (peak at 4- 6 h), then following degradation (Extended Data Fig. 9c), which is consistent with previous report (Ali et al., 2019). SnRK2.2- GFP, even through driven by 35S promoter, has a similar expression pattern over ABA treatment, indicating SnRK2s are tightly regulated by ABA in protein level (Extended Data Fig. 9d). However, the fold- change of SnRK2.2- GFP induced by short- term ABA is less than endogenous SnRK2.2/2.3 compared with 0 h ABA. This difference may caused by 35S promoter, which elevates the basal expression level of SnRK2.2 without ABA treatment. This hypothesis was also supported by the temporal expression pattern of 35S:: SnRK2.3- GFP in revised Extended Data + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[178, 87, 228, 100]]<|/det|> +## Fig. 9e. + +<|ref|>sub_title<|/ref|><|det|>[[178, 105, 246, 118]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 120, 820, 164]]<|/det|> +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. + +<|ref|>text<|/ref|><|det|>[[178, 185, 820, 218]]<|/det|> +In Extended Data Fig. 11, clarify the location of ROS affected by the stt3a mutation, rather than focusing on the amount. + +<|ref|>text<|/ref|><|det|>[[178, 222, 821, 348]]<|/det|> +Reply 15: We thank the reviewer for the comments. It was previously reported that SnRK2.2/2.3 mainly are expressed in root tip (Fujii et al., 2007). In our study, we found that the redistribution of SnRK2.2/2.3 induced by prolonged ABA also mainly occurs in root meristem which is consistent with the ROS location affected by stt3a and mutation of N- glycosylation site of SnRK2.3 (SnRK2.3N323A). we have clarified that the root meristem or root tips are the main region of ROS affected by stt3a and N- glycosylation of SnRK2.2/2.3 (revised manuscript line 330, and line 345; Extended Data Fig.11 and 13) + +<|ref|>sub_title<|/ref|><|det|>[[178, 370, 246, 383]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 386, 820, 430]]<|/det|> +Fujii, H., Verslues, P.E., and Zhu, J.K. (2007). Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell 19, 485- 494. + +<|ref|>sub_title<|/ref|><|det|>[[178, 451, 290, 465]]<|/det|> +## Additional issues: + +<|ref|>text<|/ref|><|det|>[[178, 468, 820, 501]]<|/det|> +11. In Line 65 to Line 67, the reference to Extended Data Figure should be corrected to Extended Data Figure 1. + +<|ref|>text<|/ref|><|det|>[[194, 506, 400, 521]]<|/det|> +Reply 16: That's correct. Done. + +<|ref|>text<|/ref|><|det|>[[178, 542, 820, 576]]<|/det|> +12. In Figure 4d, the legend describes a Co-IP assay using 4-day-old seedlings, but the results show a different pattern compared to Figure 4b, which also shows a Co-IP assay using the same material. + +<|ref|>text<|/ref|><|det|>[[178, 579, 820, 649]]<|/det|> +Reply 17: Thanks the viewer for the comments. (previous) Fig. 4d is not a Co-IP assay, it is a western blot analysis using total protein extracts to determine the temporal expression pattern during prolonged ABA treatment. The figure legend has been corrected (Now in Extended Data Fig. 14d). + +<|ref|>text<|/ref|><|det|>[[178, 653, 820, 686]]<|/det|> +Additionally, Figure 4d indicates a \(3\mu \mathrm{M}\) ABA treatment, but the legend describes it as \(50\mu \mathrm{M}\) ABA. Please address these inconsistencies. + +<|ref|>text<|/ref|><|det|>[[178, 690, 820, 723]]<|/det|> +Reply 18: Actually, \(3\mu \mathrm{M}\) ABA was used in (previous) Fig. 4d, and the figure legend has been corrected (Now in Extended Data Fig. 14d). + +<|ref|>text<|/ref|><|det|>[[178, 745, 821, 815]]<|/det|> +13. The results in Figure 21 and m demonstrate the phenotype of the triple mutant stt3a-2/snrk2.2/2.3 to confirm the epistasis of SnRK2.2/2.3 to STT3A. However, Figure 21 shows a slightly longer primary root in the triple mutant, whereas Figure 2m shows the reverse result, with the triple mutant having a slightly longer root. This discrepancy may be due to the selection of seedlings for photography. Clarify this issue. + +<|ref|>text<|/ref|><|det|>[[178, 819, 821, 908]]<|/det|> +Reply 19: Thanks the referee for the comments. The quantification data is a relative root length (ABA+/- ) in Fig. 2m. The ratio (ABA+/- ) of WT was designated as 1, and the relative ratio to WT was shown for double and triple mutants. Although Fig. 21 showed a little bit longer roots for triple mutant with and without ABA treatment, the relative ratio is slightly smaller. We are sorry for this confusion due to lacking detailed information. The figure legend of Fig. 21, m, has been described + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 88, 243, 100]]<|/det|> +in details. + +<|ref|>text<|/ref|><|det|>[[179, 140, 820, 194]]<|/det|> +14. In Figure 3a and 3b, the intensity of SnRK2.2-GFP appears to increase after 2 hours of treatment, but Figure 3d shows a similar fluorescence intensity. Although this does not directly relate to the conclusion, please address this inconsistency. + +<|ref|>text<|/ref|><|det|>[[178, 197, 821, 306]]<|/det|> +Reply 20: We thank the reviewer for the careful evaluation. In (previous) Fig. 3d, we mainly focus on the subcellular changes of SnRK2.2-GFP under different backgrounds. In order to observe the peroxisomes more clearly, the fluorescence intensity was appropriately enhanced in some photographs. Based on the reviewer's suggestion, we have re-investigated SnRK2.2-GFP subcellular dynamics under Col-0, stt3a-2, and STT3A-OE backgrounds, and have replaced them with more suitable photographs in revised Fig. 3d and 3e. + +<|ref|>text<|/ref|><|det|>[[179, 325, 822, 360]]<|/det|> +Additionally, for Figure 3c, a larger scale view may be more suitable to clearly show the cytosol, nuclear, and peroxisome localization of SnRK2.2- GFP. + +<|ref|>text<|/ref|><|det|>[[179, 363, 820, 416]]<|/det|> +Reply 21: We thank the reviewer for the comments. The overlap between SnRK2.2/2.3- GFP and peroxisomal marker gene has been re- investigated, and the photographs with higher quality and a larger view have been replaced for revised Fig. 3c. + +<|ref|>text<|/ref|><|det|>[[179, 437, 820, 472]]<|/det|> +15. Ensure that the growth conditions described in the text match those depicted in Figure 1a, 1c, and 1e, as there appears to be a significant difference in root lengths of Col-0 plants. + +<|ref|>text<|/ref|><|det|>[[179, 475, 820, 509]]<|/det|> +Reply 22: We thank the viewer for the comment. The detailed information about growth conditions has been clarified in revised figure legend of Fig.1a, 1c, and 1e. + +<|ref|>sub_title<|/ref|><|det|>[[179, 549, 333, 563]]<|/det|> +## Additional corrections: + +<|ref|>text<|/ref|><|det|>[[178, 567, 821, 657]]<|/det|> +As the enzymes of N- glycosylation pathway used in our study include transferase (STT3A), glucosidase (GIIα, and GIIβ), acetylglucosaminyltransferase (CGL1), mannosidase (GMII), and fucosyltransferase (FUT). The term "N- glucosidases" can not represent all these enzymes. So we have replaced "N- glucosidases" with "NPEs" (N- glycan processing enzymes) in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[177, 696, 820, 896]]<|/det|> +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. Farid, A., Pabst, M., Schoberer, J., Altmann, F., Glossl, J., and Strasser, R. (2011). Arabidopsis thaliana alpha1, 2- glucosyltransferase (ALG10) is required for efficient N- glycosylation and leaf growth. Plant J 68, 314- 325. Fujii, H., Verslues, P.E., and Zhu, J.K. (2007). Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell 19, 485- 494. Liu, Y., Zhang, C., Wang, D., Su, W., Liu, L., Wang, M., and Li, J. (2015). EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 85, 822, 517]]<|/det|> +degradation system in Arabidopsis. Proc Natl Acad Sci U S A 112, 12205- 12210. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Sato, T., Sako, Y., Sho, M., Momohara, M., Suico, M.A., Shuto, T., Nishitoh, H., Okiyoneda, T., Kokame, K., Kaneko, M., et al. (2012). STT3B- dependent posttranslational N- glycosylation as a surveillance system for secretory protein. Mol Cell 47, 99- 110. Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M.E., and Nasrallah, J.B. (2014). Site- specific N- glycosylation of the S- locus receptor kinase and its role in the self- incompatibility response of the brassicaceae. Plant Cell 26, 4749- 4762. Zheng, Y., Deng, X., Qu, A., Zhang, M., Tao, Y., Yang, L., Liu, Y., Xu, J., and Zhang, S. (2018). Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis. PLoS Genet 14, e1007880. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 147, 392, 163]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 175, 869, 228]]<|/det|> +This is a highly interesting manuscript and I would like to see that story published. However, I am not convinced that all the conclusions are supported by the shown data. Therefore, I would ask the authors for additional experiments and explanations. + +<|ref|>sub_title<|/ref|><|det|>[[116, 269, 211, 285]]<|/det|> +## Major points + +<|ref|>text<|/ref|><|det|>[[116, 297, 270, 313]]<|/det|> +The general concept: + +<|ref|>text<|/ref|><|det|>[[113, 324, 883, 581]]<|/det|> +How do you think does this transport and glycosylation process work (see statement in Abstract lines 11- 12)? How do you think that STT3A- mCherry (a protein with numerous transmembrane domains) localizes to the cytoplasm - see statement in lines 142- 144 - without a membrane it would immediately aggregate. How can glycosylation in the lumen of the ER affect the nuclear localization of another protein (processes taking place in completely different subcellular compartments)? Based on your model in Extended Data Fig. 17, the SnRK2 proteins are transported to the ER lumen for glycosylation, if it is like this than glycosylation is not involved in transport from the nucleus/cytoplasm to the ER lumen and another process mediates this transport. Then glycosylation of SnRK2.2/2.3 might be involved in transport from the ER to the peroxisomes, but this is not clearly shown and glycosylation would then not be involved in desensitization of the transcriptional response in the nucleus. Do you think that the folded SnRK2.2/2.3 proteins are taken up into the ER where they are glycosylated by a complex that normally glycosylates unfolded proteins? Which complex is involved in the uptake into the ER? Glycosylation mutants are pleiotropic and typically affect many proteins, how likely is it that there are indirect effects from other glycoproteins that are related to the ABA sensitivity? + +<|ref|>text<|/ref|><|det|>[[116, 620, 385, 636]]<|/det|> +The protein- protein interaction data: + +<|ref|>text<|/ref|><|det|>[[115, 648, 870, 739]]<|/det|> +In the Y2H assay SnRKs is not glycosylated and an interaction with Gilbeta therefore shows that the interaction is not N- glycan dependent. Gilbeta has a lectin domain for carbohydrate binding, so binding to a non- glycosylated protein shows a glycosylation- independent process or hints at an unspecific binding event. Panel a from the Extended Data Fig. 5 (and also Fig. 2b and comment below) confirms that because the GST- tagged protein is produced in E.coli and therefore not glycosylated. + +<|ref|>text<|/ref|><|det|>[[115, 749, 866, 839]]<|/det|> +The luciferase assay shows interaction of all tested SnRKs with all tested glycosylation related enzymes. This is suspicious, especially because the tested glycosylation related enzymes are located in different subcellular compartments, have a different membrane topology and most have only a few amino acids facing the cytosol where the interaction with SnRKs would likely occur. Moreover, glycosylation related enzymes often interact with the glycan and not the protein and the interaction is only transient. + +<|ref|>text<|/ref|><|det|>[[115, 850, 858, 904]]<|/det|> +I would like to see additional controls for the luciferase assay and additional experiments showing the interaction, like additional co- IP data. Why did the authors characterize a specific set of glycosylation related enzymes, the rationale for choosing them is not clear. Did they also test others like FUT12 or + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 861, 143]]<|/det|> +XylT? Related to that and their main claim that N- glycosylation plays a role, how sure are the authors that the used mutants lead to changes in N- glycosylation. Has this been shown for Arabidopsis Gllbeta and FUT11 knockout? + +<|ref|>text<|/ref|><|det|>[[116, 156, 250, 171]]<|/det|> +The confocal data: + +<|ref|>text<|/ref|><|det|>[[114, 183, 877, 329]]<|/det|> +I am sorry, but in the shown images a clear reticular ER network is not visible (e.g. Fig. 2j, Fig. 4c, Fig. 5g, Fig. 6b, e and f). The used ER- marker seems not appropriate in these experiments and is not frequently used to label the ER in tobacco in literature. In the shown images the cellular morphology appears altered, either because of the used marker or overexpressed proteins and often cellular structures are visible that look like aggregates. As a consequence, conclusions directly linked the ER localization data are questionable and BiFC data could represent false positives. The authors should provide better images, where the ER is clearly visible. Please provide also the subcellular localization of STT3A- mCherry and Gllbeta- GFP without any co- expressed other protein to see if they reside in the ER. + +<|ref|>text<|/ref|><|det|>[[114, 339, 877, 448]]<|/det|> +In Extended Data Fig. 6b the authors show images of Gllbeta co- expression with SnRK2.2- GFP or SnRK2.3- GFP and show a diffuse signal in the cell. This looks more like a cell undergoing cell death than cytosolic localization. Please comment on that. How many cells show this type of fluorescence? Is it only visible with Gllbeta? Which Gllbeta was used for co- expression, is it also tagged with a fluorescent protein and leads to a diffuse labelling of the cell? Please provide co- localization data with Gllbeta- mCherry or at least with an ER- marker. + +<|ref|>text<|/ref|><|det|>[[115, 460, 870, 495]]<|/det|> +In general, the confocal images are quite small, larger images should be provided and the quality of the images should be improved. + +<|ref|>text<|/ref|><|det|>[[114, 506, 882, 651]]<|/det|> +The peroxisomal uptake should also be supported by more data clearer confocal images. In lines 188- 190 it is stated that translocation of SnRK2.2 might consist of two steps SnRK degradation and peroxisomal targeting. This is unclear. Do you mean that the protein in the nucleus is degraded and that new SnRK protein is translated in the cytoplasm that is then transported to the ER and further to the peroxisome? Is there any evidence for nuclear degradation? Which machinery would be involved in the degradation in the nucleus? Did you test proteasome inhibitors? Did you do any experiments with protein synthesis inhibitors to see if synthesis of new proteins is involved in the process. Additional experiments should be provided to support the claims. + +<|ref|>sub_title<|/ref|><|det|>[[116, 692, 287, 708]]<|/det|> +## The SnRK glycosylation: + +<|ref|>text<|/ref|><|det|>[[114, 719, 877, 826]]<|/det|> +The overexpression of STT3A- mCherry results in an additional SnRK2.2- His/SnRK2.3- His band that is also detectable when treated with ABA. This raises a number of questions. This suggests, for example, that STT3A activity is limited in plants and its overexpression is sufficient to increase the glycosylation of proteins. Is there any additional evidence for that? STT3A is part of a larger protein complex and one would expect that other proteins in this complex are also required for the activity which were not overexpressed. Please comment on that. + +<|ref|>text<|/ref|><|det|>[[115, 839, 872, 892]]<|/det|> +Given the fact, that the authors are familiar with peptide analysis by LC- MS/MS (Fig. 4f), they should try to purify the transiently expressed His- or GFP- tagged SnRK2.2/2.3 and confirm the presence of the glycan linked to N323 by MS analysis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 857, 161]]<|/det|> +The data from 2d suggest that ABA has the same effect as STT3A overexpression? How can this be explained? Do the authors suggest that ABA induces STT3A expression which leads to SnRK2.2/2.3 glycosylation. Is this process specific for SnRK2.2/2.3 or is protein glycosylation generally increased by ABA? + +<|ref|>text<|/ref|><|det|>[[115, 173, 830, 245]]<|/det|> +The glycosylation of the transiently expressed His- tagged protein is obviously different from the endogenous protein because the His- tagged protein is fully sensitive to Endo H and PNG F in the presence of ABA. What would be the explanation for this difference? Please digest the His- tagged protein co- expressed with STT3A- mCherry also int the absence of ABA. + +<|ref|>text<|/ref|><|det|>[[114, 283, 878, 429]]<|/det|> +In Fig. 2i, the anti- SnRK2.2/2.3/2.6 antibody is used to show glycosylation of the endogenous SnRKs proteins. This is an important experiment, but not entirely convincing because neither Endo H nor PNG F give a complete shift. Can the authors do the Endo H/PNG F digestion experiment in a glycosylation knockout, for example, in cgl1 plants where all glycans should be sensitive to Endo H and PNG F. The presence of the PNG F resistant band could be related to fucosylation which takes place in the Golgi and is catalyzed by FUT11. Is there any evidence that SnRKs are located in the Golgi? In which cellular compartment would FUT11 decorated the SnRK glycan with a fucose? Please do the same experiment from Fig. 2i also without ABA. + +<|ref|>text<|/ref|><|det|>[[115, 469, 864, 505]]<|/det|> +Does Gilbeta- GFP coexpression also result in the occurrence of the glycosylated band on immunoblots with the His- antibody? What is the proposed molecular function of Gilbeta in the overall process? + +<|ref|>text<|/ref|><|det|>[[115, 517, 212, 532]]<|/det|> +Other issues: + +<|ref|>text<|/ref|><|det|>[[115, 544, 875, 617]]<|/det|> +In Fig.2b - please do the same experiment with the N323A protein. No glycosylated SnRK2.2/2.3 band is visible in the blot indicating that Gilbeta does not interact with the glycan on SnRK2.2/2.3. How is this then a glycosylation dependent process? Can the authors purify Gilbeta from the snrk2.6 mutant plants in the presence/absence of ABA and see if glycosylated SnRK2.2/2.3 come along? + +<|ref|>text<|/ref|><|det|>[[115, 628, 496, 644]]<|/det|> +Fig.2f: please do the same experiment without ABA. + +<|ref|>text<|/ref|><|det|>[[115, 656, 587, 673]]<|/det|> +Fig 2h: please provide quantitative data from several repetitions. + +<|ref|>text<|/ref|><|det|>[[115, 685, 870, 738]]<|/det|> +In Fig. 2j the authors state that N323A coexpression disrupts its nuclear export. Why not the opposite - block of nuclear import in by SnRK2.3 expression? Can the authors provide a time series of images showing a transport process? + +<|ref|>text<|/ref|><|det|>[[115, 750, 558, 766]]<|/det|> +Extended data Fig.5a: do the same with GST- SnRK2.3- N323A + +<|ref|>text<|/ref|><|det|>[[115, 778, 879, 849]]<|/det|> +Extended data Fig.9c: show a time course experiment in the snrk2.6 background with anti- SnRK2.2/2.3/2.6 antibody for comparison. To see also if the glycosylated band increases with prolonged ABA incubation. Based on Extended Data Fig. 1f one would expect the highest STT3a expression after 6 h of ABA treatment and this should correlate with the increase of N- glycosylated SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[115, 862, 205, 877]]<|/det|> +Minor point + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 143]]<|/det|> +The term N- glucosidase is not correct in the description of the glycosylated related enzymes. Some of the characterized proteins are transferases (STT3A, CGL1, FUT11) others are glycosidases (GMII) and only Glialpha and beta are glucosidases. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[210, 86, 395, 100]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[179, 123, 431, 138]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 159, 820, 194]]<|/det|> +This manuscript provides evidence that N- glycosylation of SnRK2s controls NADPH maintenance in peroxisomes, and this relates to the desensitization of plants to repeated ABA signalling. + +<|ref|>text<|/ref|><|det|>[[178, 196, 821, 304]]<|/det|> +It is founded on discovery of a hypersensitivity to ABA- mediated repression in a mutant of \(\beta\) - subunit of glucosidase II (glIβ- 2). The fact of this hypersensitivity would imply some non- compensatory need for this specific glucoside directly. However, oddly the authors find the same hypersensitivity when they individually knockout other glucosidases - STT3A, GIIα and three other N- glucosidases (CGL1, GMII, FUT11) - so why can't they compensate for the glIβ- 2 mutant? Its not clear. I never saw any real exploration how each of these could in a non- compensatory manner effect the same pathway to SnRK2. + +<|ref|>text<|/ref|><|det|>[[178, 308, 821, 490]]<|/det|> +Reply 1: We thank the reviewer for the valuable comments. For N- glycosylation modification, a nascent protein is attached a GlcManGlcNAc N- glycan on a specific asparagine (N) residue (NX(S/T) motif) by an oligosaccharide transferase complex when it enters the ER lumen. Subsequently, N- glucosidase I (GI) and GIIα/GIIβ heterodimer remove the outmost two glucose residues. GII- trimmed glycoprotein (N- glycan, GlcManGlcNAc) is captured by calnexin/calreticulin (CNX/CRT) for quality control. Successfully folded glycoprotein (ManGlcNAc) can be further processed by mannose- removing enzymes (α- mannosidase, MNSs), β1,2- N- acetylglucosaminyltransferase I (GntI), Golgi- α- mannosidase II (GMII), fucosyltransferases (FUT), etc. sequentially in the ER- Golgi network, to form characteristic complex- type N- glycans (Nagashima et al., 2018; Strasser, 2016). + +<|ref|>text<|/ref|><|det|>[[178, 493, 821, 675]]<|/det|> +The importance of this sequential actions of N- glycan processing enzymes (NPEs) was supported by Farid's study (Farid et al., 2011). Severe defects of \(gl\) mutant can be suppressed by additional mutation of ALG10 which is responsible for biosynthesis of the outmost glucose residue, suggesting that trimming of the Glc by GI is a prerequisite for further processing by GII (Farid et al., 2011). In our manuscript, we provided rich data such as protein- protein assays and genetic interactions between NPEs and SnRK2s, showing that NPEs regulate ABA signalling through common substrate SnRK2 kinases. The similar ABA- hypersensitivity of these npe mutants (stt3a, glIα, glIIβ, cgl1, hgl1, fut1) imply the importance of the mature structure of N- glycan for the SnRK2s' biological roles. The similar high- salt- hypersensitivity of these npe mutants were also reported previously and reviewed by Richard Strasser (Strasser, 2016). + +<|ref|>text<|/ref|><|det|>[[178, 679, 820, 713]]<|/det|> +Based on suggestions from you and reviewer #3, more detailed information about N- glycosylation was added to introduction of the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[179, 717, 247, 730]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 733, 820, 820]]<|/det|> +Farid, A., Pabst, M., Schoberer, J., Altmann, F., Glossl, J., and Strasser, R. (2011). Arabidopsis thaliana alpha1,2- glucosyltransferase (ALG10) is required for efficient N- glycosylation and leaf growth. Plant J 68, 314- 325. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +<|ref|>text<|/ref|><|det|>[[178, 840, 820, 873]]<|/det|> +The manuscript then uses experiments on glIβ- 2 or stt3a mutants interchangeably to then explore the mechanism of this desensitization of plants to repeated ABA signalling. + +<|ref|>text<|/ref|><|det|>[[178, 876, 820, 910]]<|/det|> +Reply 2: We thank the reviewer for the comments. As GIIβ and STT3A act in the same N- glycosylation pathway to co/post- modify SnRK2.2/2.3, and their mutants exhibit similar + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 213]]<|/det|> +hypersensitivity to ABA, they were used in our study to double- check the effect of N- glycosylation on ABA signalling in some experiments such as protein- protein binding, and genetic assays. But for N- glycosylation assay, STT3A can cause about 2- 3 kDa molecular mass difference of SnRK2.2/2.3 (one N- glycan difference), whereas GIIα/β induce only one glucose difference ( \(\sim 0.18\) kDa). It's easy to distinguish the N- glycosylated SnRK2.2/2.3 with STT3A. So the STT3A and its' mutant were chosen in N- glycosylation assays. We are sorry about making some confusion sometimes. + +<|ref|>text<|/ref|><|det|>[[178, 234, 821, 323]]<|/det|> +The yeast 2 hybrid assays are implied to show an exclusive interaction between glβ- 2 and SnRK2.2/2/3/2.6 but this was a set of pairwise interactions, not a yeast- 2 hybrid screen, so its not reasonable to call it exclusive – they only tested what they tested. Same with the LCI assays – "GIIβ, STT3A, GIIα, CGL1 and FUT11 all exclusively bind to SnRK2s" its just amongst the assay done – its not exclusive of other targets of these glucosidases. + +<|ref|>text<|/ref|><|det|>[[178, 326, 820, 360]]<|/det|> +Reply 3: We understand the reviewer's concern and removed the word "exclusively" according to the suggestions in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[177, 382, 821, 528]]<|/det|> +Critical to the claims of the paper is that SnRK2s are glycosylated by these glucosidases – this is claimed by, "PNGase F and Endo H digestions confirmed that the band shift was due to N- glycan modification" this band shift seems to be the only evidence that this modification is occurring and the later genetic studies to mutate residues and show an absence of band shift – while in themselves compelling – are not independent of this method. There are a wide variety of other independent methods to prove N- glycan modification as well as MS and MRM methods to independently confirm the claim at the site on the SnRK2s – none of these are used but really should be to independently confirm this central claim of the paper. + +<|ref|>text<|/ref|><|det|>[[178, 530, 821, 675]]<|/det|> +Reply 4: We thank the reviewer for careful evaluation and for encouraging us to improve our manuscript. We agree with the reviewer that MS (mass spectrometry) assay will be better for confirmation of SnRK2.2/2.3 N- glycosylation. Based on the reviewer's suggestion, we have carried out the LC- MS/MS analysis of SnRK2.3 N- glycosylation (Zielinska et al., 2012). Unfortunately, in the past few months, we tried no less than five times with SnRK2.3- GFP transgenic plants or SnRK2.3- His transgenic BY- 2 cells (bright yellow tobacco cell), but all failed. We presume that the failure may be due to the tiny amount of N- glycosylated SnRK2.3. only a few SnRK2s are N- glycosylated in Arabidopsis and transgenic tobacco cells (see Fig. 2d- i, k, and Rebuttal Fig. 1). + +<|ref|>text<|/ref|><|det|>[[178, 678, 821, 803]]<|/det|> +In our manuscript, we have provide rich data to show the SnRK2.2/2.3 N- glycosylation and the crucial roles in ABA signalling. We mutated total 11 N sites (asparagine residues) individually, and identified the N- glycosylation site SnRK2.3N323 (Fig. 2j, Extended Data Fig. 6f- i). this site mutation can block SnRK2.3 N- glycosylation (Fig. 2k), can inhibit SnRK2.3 subcellular change (Fig. 2j, Fig. 3a- f), can enhance the expression of ABA- induced genes (Fig. 3i, j), and can change phenotype of snrk2.2/2.3 double mutant from ABA- hyposensitivity to ABA- hypersensitivity (Fig. 2l,m). + +<|ref|>text<|/ref|><|det|>[[178, 808, 820, 860]]<|/det|> +Additionally, the method "band shift assays followed by PNGase F and Endo H digestions" we used, was a classical method widely used for identification of N- glycosylation in publications (Liu et al., 2015; Sato et al., 2012; Shen et al., 2014; Yamamoto et al., 2014). + +<|ref|>text<|/ref|><|det|>[[178, 863, 820, 897]]<|/det|> +We will continue to explore this field in the future and use more methods to detect this phenomenon. Thanks the reviewer again for valuable comments. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[181, 90, 816, 409]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[194, 427, 722, 443]]<|/det|> +## Rebuttal Fig. 1 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His. + +<|ref|>text<|/ref|><|det|>[[179, 444, 821, 732]]<|/det|> +a, Enrichment of N- glycosylated SnRK2.3- GFP before MS analysis. SnRK2.3- GFP overexpression plants were treated with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) after seven days of growth and the roots were collected. After IP with GFP- Trap and ConA (concanaalvin A, a plant lectin can bind to mannose on the glycoproteins), the enrichment was determined by western blot. Input, total protein extract; GFP- Trap, enrichment of SnRK2.3- GFP by GFP- Trap beads; ConA- IP, enrichment of N- glycosylated SnRK2.3- GFP by ConA bead after GFP- Trap- IP. The white arrowhead denotes the N- glycosylated SnRK2.3- GFP. b, Coomassie brilliant blue staining after PNGase F digestion of N- glycosylated SnRK2.3- GFP enriched by ConA. The dashed white frame denotes the gel cut for LC- MS/MS. c, Enrichment of N- glycosylated SnRK2.3. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in tobacco leaves with 50 \(\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and N- glycosylated SnRK2.3 were enriched with Ni- NTA and ConA beads sequentially. No signal was shown after ConA enrichment (right line). So only Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. His- IP, enrichment of SnRK2.3- His by Ni- NTA; PNGase F, PNGase F digestion. N- SnRK2.3- His, N- glycosylated SnRK2.3- His. d, Coomassie brilliant blue staining after PNGase F digestion of His- antibody enriched SnRK2.3- His. The dashed white frame denotes the gel cut for LC- MS/MS. e, g, i, Coomassie brilliant blue staining after His- antibody enriched SnRK2.3- His. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in BY- 2 cells with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and SnRK2.3- His were enriched with Ni- NTA. The dashed white frame denotes the location of SnRK2.3- His. Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. f, h, j, After IP with Ni- NTA, the enrichment was determined by western blot. CK, total protein extract of wide type BY- 2 cells; Input, total protein extract of transgenic BY- 2 cells; His- IP, enrichment of SnRK2.3- His by Ni- NTA. + +<|ref|>sub_title<|/ref|><|det|>[[180, 742, 308, 755]]<|/det|> +## Additional method: + +<|ref|>sub_title<|/ref|><|det|>[[195, 768, 455, 782]]<|/det|> +## Enrichment of N-glycosylated SnRK2.3 + +<|ref|>text<|/ref|><|det|>[[180, 782, 820, 911]]<|/det|> +Plant tissues were grounded to powder in the frozen state and homogenized in extraction buffer (50 mM Tris- HCl, pH 7.4, \(150\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, 5 mM DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with GFP- Trap agarose (Chromotek) or nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(4\mathrm{h}\) , beads were washed five times with ice- cold washing buffer (50 mM Tris- HCl, pH 7.4, \(400\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins were eluted with acidic buffer (200 mM glycine, pH 2.5) and immediately neutralized the eluate fraction with neutralization buffer ( \(100\mathrm{mM}\) Tris- HCl, pH 10.4). The eluted proteins were then incubated with ConA (concanaalvin A, a plant lectin can bind to mannose on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 84, 819, 127]]<|/det|> +the glycoproteins) beads (Beyotime) at \(4^{\circ}\mathrm{C}\) , After \(4\mathrm{h}\) , beads were washed five times with washing buffer ( \(20\mathrm{mM}\) Heps, \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl2, \(1\mathrm{mM}\) MnCl2, \(1\mathrm{mM}\) CaCl2, \(0.1\%\) Tween- 20). The proteins were eluted with elution buffer ( \(5\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}8.0\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{M}\) Glucose). + +<|ref|>text<|/ref|><|det|>[[179, 127, 820, 242]]<|/det|> +After treatment with \(50\mu \mathrm{M}\) ABA for 48 hours, BY- 2 cells were collected by centrifugation. Cells were grounded to powder in the frozen state and homogenized in extraction buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl2, \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(8\mathrm{h}\) , beads were washed five times with ice- cold washing buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(400\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl2, \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins are boiled in boiling water for \(10\mathrm{min}\) after adding \(1\times\) glycoprotein denaturing buffer ( \(0.5\%\) SDS, \(40\mathrm{mM}\) DTT, \(\mathrm{H}_{2}^{18}\mathrm{O}\) ). + +<|ref|>sub_title<|/ref|><|det|>[[195, 251, 325, 264]]<|/det|> +## PNGase F digestion + +<|ref|>text<|/ref|><|det|>[[179, 265, 820, 336]]<|/det|> +For PNGase F treatment, referring to the manufacturer's protocol, the reaction buffer (containing \(\mathrm{H}_{2}^{18}\mathrm{O}\) ) and PNGase F (New England Biolabs) were added to sample. The mixture was incubated for \(4\mathrm{h}\) at \(37^{\circ}\mathrm{C}\) before boiled in \(5\times\) SDS loading buffer. N- glycation of SnRK2.3 was detected by immunoblot analyses using by anti- GFP or anti- His antibodies after \(6\%\) SDS- PAGE. The sample was subjected to mass spectrometry detection after immunoblot analyses. + +<|ref|>sub_title<|/ref|><|det|>[[195, 345, 615, 359]]<|/det|> +## LC-MS/MS for identification of N-glycosylation site of SnRK2.3 + +<|ref|>text<|/ref|><|det|>[[179, 360, 820, 586]]<|/det|> +For mass spectrometry analysis, protein samples were separated using SDS- PAGE electrophoresis and detected by coomassie brilliant blue staining. The SDS- PAGE gel at \(70\mathrm{kD}\) or \(40\mathrm{kD}\) was collected into a clean centrifuge tube. \(500\mu \mathrm{l}\) destain solution were added to a centrifuge tube and shaken at room temperature until the gel discolored. After discarding the supernatant, \(75\%\) acetonitrile ( \(200\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature. After \(30\mathrm{min}\) , \(500\mu \mathrm{l}\) \(\mathrm{H}_{2}\mathrm{O}\) were added to the centrifuge tube and shaken at room temperature for \(1\mathrm{h}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH}_{4}\mathrm{HCO}_{3}\) ( \(300\mu \mathrm{l}\) ) were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH}_{4}\mathrm{HCO}_{3}\) ( \(20\mu \mathrm{l}\) ) and \(2\mu \mathrm{l}\) trypsin ( \(1\mu \mathrm{g / \mu l}\) , Promega) were added to the centrifuge tube, and gel was crushed. After centrifugation ( \(1000\mathrm{rpm}\) , \(1\mathrm{min}\) ), the sample was digested at \(37^{\circ}\mathrm{C}\) . After \(8\mathrm{min}\) , \(200\mu \mathrm{l}\) acetonitrile were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After centrifugation ( \(1000\mathrm{rpm}\) , \(1\mathrm{min}\) ), the supernatant was transferred to a new centrifuge tube. This step was repeated once, ultimately resulting in \(400\mu \mathrm{l}\) supernatant. The obtained supernatant was vacuum dried at \(60^{\circ}\mathrm{C}\) and dissolved in \(0.1\%\) formic acid ( \(100\mu \mathrm{l}\) ). Samples were subjected to mass spectrometry detection by using mass spectrometer (Orbitrap Fusion™ Lumos™ Tribrid™, Thermo Scientific). The N- glycation site of SnRK2.3 was analyzed using software (Proteome Discoverer 2.3). + +<|ref|>sub_title<|/ref|><|det|>[[179, 608, 246, 620]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[179, 623, 820, 835]]<|/det|> +Liu, Y., Zhang, C., Wang, D., Su, W., Liu, L., Wang, M., and Li, J. (2015). EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated degradation system in Arabidopsis. Proc Natl Acad Sci U S A 112, 12205- 12210. Sato, T., Sako, Y., Sho, M., Momohara, M., Suico, M.A., Shuto, T., Nishitoh, H., Okiyoneda, T., Kokame, K., Kaneko, M., et al. (2012). STT3B- dependent posttranslational N- glycosylation as a surveillance system for secretory protein. Mol Cell 47, 99- 110. Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M.E., and Nasrallah, J.B. (2014). Site- specific N- glycosylation of the S- locus receptor kinase and its role in the self- incompatibility response of the brassicaceae. Plant Cell 26, 4749- 4762. Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<|ref|>text<|/ref|><|det|>[[179, 866, 820, 899]]<|/det|> +The apparent translocation of SnRK2 to the peroxisome is proposed, but then recanted in the text, because nuclear export inhibition did not block it. Instead it seemed more likely the nuclear SnRK2 is degraded + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 86, 819, 120]]<|/det|> +and a peroxisome targeted version is generated, so authors need to ensure they don't continue to claim 'translocation' in the text in other passages and also Fig 3 legend. + +<|ref|>text<|/ref|><|det|>[[178, 123, 820, 176]]<|/det|> +Reply 5: We thank the reviewer for the comments. According to the suggestions from you and reviewer #2, we have replaced "translocate/translocation" with "redistribute/redistribution" to describe the movement of SnRK2 in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 197, 820, 268]]<|/det|> +When we get to peroxisomes and what SnRK2 interacts with, we see another selective process "we investigated the potential SnRK2- interacting partners among peroxisomal isozymes involved in \(\mathrm{H}_2\mathrm{O}_2\) - scavenging and NADPH generation" so again the link to GPT1 is really achieved by analysis of a small subset of hand picked targets. + +<|ref|>text<|/ref|><|det|>[[177, 272, 821, 492]]<|/det|> +Reply 6: We thank the reviewer for the comments. In our study, we did not search the potential peroxisomal SnRK2 binding proteins genome- widely. One of the reasons is that it is hard to construct a gene library encoding all the peroxisomal isozymes for SnRK2- partner screening. Another reason is that it is hard to get the sole peroxisome- localized SnRK2 for IP- MS/MS analysis (some SnRK2s in the nuclei, and some on the peroxisomal membrane during prolonged ABA signalling). Instead, for quick identification of SnRK2 partners, we cloned 13 published genes of peroxisomal isozymes required for NADPH- generation on the peroxisomal membrane (Extended Data Fig. 14a), and identified GPT1 as a SnRK2 binding protein with ABA- dependent manner. Based on the reviewer #3's comments, we have constructed peroxisome- fixed SnRK2.3 (SnRK2.3- mPTSPEX26, with nuclear SnRK2.3- NLS as a control, see revised Fig. 4 i, j, and Extended Data Fig. 17), and we are trying to make transgenic Arabidopsis for SnRK2- binding protein screening in genome- wide via IP- MS/MS in the future. Thanks again for your valuable comments. + +<|ref|>text<|/ref|><|det|>[[178, 511, 821, 656]]<|/det|> +In all honesty, the claim of changes in NADPH and ROS in peroxisomes require detailed time- lapse measurements to be performed. The claimed errors bars in Fig 4 and extended Fig 11 are noted to be based on mean plus or minus sd, no n value is provided for either in the legends. But the reporting summary suggested – “All experiments were repeated two- three biologically independent experiments as mentioned in figure legends and methods”. Having done these sorts of assays myself I find those errors (just a few percent in many cases) just inconceivably small for independent experiments. Throughout the paper these small n value experiments are just showing mean and sd, not data points on graphs to show means for each rep. + +<|ref|>text<|/ref|><|det|>[[178, 660, 820, 712]]<|/det|> +These very small errors are essential for the claims made as the \(\mathrm{H}_2\mathrm{O}_2\) and NADPH changes in Figure 4 are very small. I would want to see further evidence that the errors are accurately reported across independent experiments. + +<|ref|>text<|/ref|><|det|>[[178, 716, 820, 787]]<|/det|> +Reply 7: We thank the reviewer for the comments. According to the reviewer's suggestions, we re- quantified the level of \(\mathrm{H}_2\mathrm{O}_2\) and NADPH accumulation with three biological replicates in revised Fig. 4 a, and d. The “n value” in the figure legends of Extended data Fig. 11 and all the other figures were checked in our revised manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 808, 820, 899]]<|/det|> +Overall the biological case surrounding this mutant is extensively explored and links of the mutants effects back into ABA processes are extensive and involve a large amount of work and come to novel conclusions for the field. My main concern is that the biochemical pathway to the claim involves a series of selective choices that need to be acknowledged along the way and key points such as the glycosylation evidence and the clarification of how such small errors can be recorded need to be resolved. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 195]]<|/det|> +Reply 8: We would like to thank the reviewer for the careful evaluation and for encouraging us to improve our manuscript. we have provided our responses to all the comments point- by- point. We answered the comments about "a series of selective choices" in Reply 3 and 6. The N- glycosylation site of SnRK2.3 was re- identified with LC- MS/MS in Reply 4. To address the small error bars, we re- investigated the accumulation of NADPH, and \(\mathrm{H}_2\mathrm{O}_2\) levels with three independent biological replicates in Reply 7. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[178, 86, 430, 100]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[177, 122, 821, 305]]<|/det|> +Pretreating plants with mild abiotic stresses helps them to adapt to harsh conditions, and the adaptation process is enhanced by ABA treatment. Revealing the underlying mechanism would have practical implications. This paper reports that ABA causes the subcellular redistribution and target change of SnRK2.2/2.3, two key regulators of ABA signaling. SnRK2.2/2.3 are localized in the nucleus and activate transcriptional responses at the initial ABA signaling stage, but during prolonged ABA treatment, they are N- glycosylated in the ER- Golgi network and sent to the peroxisomes. On the peroxisomal membrane, SnRK2.2/2.3 phosphorylate and activate Glucose- 6- Phosphate Transporter 1 (GPT1), which helps maintain NADPH homeostasis and suppress \(\mathrm{H}_2\mathrm{O}_2\) over- accumulation. Plants that have undergone such changes become less responsive to ABA (desensitized) and may better tolerate stress conditions (becoming acclimated). + +<|ref|>text<|/ref|><|det|>[[178, 326, 820, 360]]<|/det|> +The data presented in this paper are sound, the logic is clear, and the finding represents a significant step toward understanding the molecular mechanisms of plant acclimation. + +<|ref|>text<|/ref|><|det|>[[184, 364, 692, 378]]<|/det|> +We greatly appreciate the reviewer for positive comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 419, 290, 433]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[178, 455, 820, 488]]<|/det|> +1. Labeling errors: in Extended Data Fig. 1, the labels "e" and "f" are misplaced; the "Fig. 1f" is mislabeled. + +<|ref|>text<|/ref|><|det|>[[185, 494, 385, 508]]<|/det|> +Reply 1: That's correct. Done. + +<|ref|>text<|/ref|><|det|>[[177, 529, 820, 563]]<|/det|> +2. Labeling errors: Main text lines 65 - 67, the Extended Data Fig. 2c-e, 2f, and 2g should be Extended Data Fig. 1c-e, 1f, and 1g. + +<|ref|>text<|/ref|><|det|>[[193, 567, 293, 581]]<|/det|> +Reply 2: Done. + +<|ref|>text<|/ref|><|det|>[[178, 604, 593, 619]]<|/det|> +3. Labeling error: Main text line 92, the Fig. 1j should be Fig. 1j, k. + +<|ref|>text<|/ref|><|det|>[[193, 623, 290, 637]]<|/det|> +Reply 3: Done + +<|ref|>text<|/ref|><|det|>[[178, 659, 820, 693]]<|/det|> +4. Labeling error: Main text line 148, the Extended Data Fig. 6e should be Extended Data Fig. 6f. Reply 4: Done + +<|ref|>text<|/ref|><|det|>[[178, 715, 822, 899]]<|/det|> +5. About the term "translocation": This term may mislead readers and should be considered revision. Throughout the paper, the authors use "translocate/translocation" to describe the change of SnRK2s localization patterns: SnRK2s are normally localized in the nucleus, and during prolonged ABA treatment, they are N-glycosylated and localized on the peroxisomal membrane. Although they disappear from the nucleus and reappear on the peroxisome, the SnRK2s proteins do not physically move 'from the nucleus to the peroxisomes'; this is supported by the experiment presented in Extended Data Fig. 10f, g (main text lines 188-190). Therefore, the term "translocate/translocation" does not accurately describe the process and can be misleading. For example, in the Abstract, line 11 reads, "...which promotes their gradual translocation from the nucleus to the peroxisomes...." Immediately following this sentence, line 13 reads, "After moving to the peroxisomal membrane, SnRK2s directly interact with...." This + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 139]]<|/det|> +combination will almost surely make readers mistakenly think that SnRK2s physically move between the two organelles. A possible substitute for "translocation" is "redistribution." The term "redistribution" better describes the phenomenon, avoids misunderstanding, and inspires people to wonder. + +<|ref|>text<|/ref|><|det|>[[178, 142, 820, 175]]<|/det|> +Reply 5: The comments are greatly appreciated. We have replaced the terms "translocate/ translocation" with "redistribute/redistribution" in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 180, 820, 213]]<|/det|> +In the abstract (line 11- 13), both "translocation" and "After moving to" have been replaced with "redistribution" and "On", respectively. + +<|ref|>text<|/ref|><|det|>[[178, 234, 820, 286]]<|/det|> +People may ask where SnRK2s proteins are synthesized and precisely what triggers the switch from targeting SnRK2s to the nucleus to targeting them to peroxisomes. The answers to such questions may expand the current finding and lead to the development of application strategies. + +<|ref|>text<|/ref|><|det|>[[178, 290, 821, 490]]<|/det|> +Reply 6: We would like to thank the referee for the valuable suggestions. Our study revealed that SnRK2s are modified with a N- glycan on the ER- Golgi networks, and are redistributed on the peroxisomal membrane finally. As non- secretory proteins, how are SnRK2s located on the ER- Golgi networks? Where are they synthesised? Are they translated on the rough ER and then enter the ER lumen? or they are synthesised in the cytosol and then translocated on the ER- Golgi? or they are directly translated on the surface of the peroxisomes (Dahan et al., 2022)? What triggers the ER- Golgi localization of them? The answers to these questions would deepen our understanding of the molecular mechanisms of ABA signalling. We are trying to answer some of these questions now. In our another project, we found a protein channel (homolog of TMED10 (Zhang et al., 2020)) which may be responsible for the ER- Golgi- loading of SnRK2s, but now we need time to collect more solid evidences to support this notion. + +<|ref|>sub_title<|/ref|><|det|>[[178, 495, 247, 508]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 512, 821, 560]]<|/det|> +Dahan, N., Bykov, Y.S., Boydston, E.A., Fadel, A., Gazi, Z., Hochberg- Laufer, H., Martenson, J., Denic, V., Shav- Tal, Y., Weissman, J.S., et al. (2022). Peroxisome function relies on organelle- associated mRNA translation. Sci Adv 8, eabk2141. + +<|ref|>text<|/ref|><|det|>[[178, 564, 820, 618]]<|/det|> +Zhang, M., Liu, L., Lin, X., Wang, Y., Li, Y., Guo, Q., Li, S., Sun, Y., Tao, X., Zhang, D., et al. (2020). A Translocation Pathway for Vesicle- Mediated Unconventional Protein Secretion. Cell 181, 637- 652 e615. + +<|ref|>sub_title<|/ref|><|det|>[[179, 679, 430, 694]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 715, 821, 878]]<|/det|> +This study presents a putative mechanism for the desensitization and transition of ABA signaling during prolonged treatment, involving N- glycosylation of SnRK2s. Under prolonged ABA signaling, the key regulator SnRK2.2/2.3 undergoes N- glycosylation in the ER- Golgi network, which leads to its translocation to the peroxisome. In the peroxisome, SnRK2s regulate NADPH generation by phosphorylating the transporter GPT1 during NADPH synthesis, suggesting a new module of redox homeostasis for adapting to long- term stress conditions during prolonged ABA signaling. The findings are interesting and provide insights into plant responses under prolonged stress conditions. However, there are several major issues in the manuscript that need to be addressed, before it could be considered by Nat Commun. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 125, 264, 139]]<|/det|> +Major Points: + +<|ref|>text<|/ref|><|det|>[[178, 142, 821, 213]]<|/det|> +1. It is common to assay ABA responses through germination, cotyledon greening, and post-germination growth using different concentrations of ABA. In this study, the authors chose to germinate the seeds in a very high concentration of ABA (3 \(\mu \mathrm{M}\) ) and measured the root length at a later stage. Please explain the rationale for this choice and provide results from other assays. + +<|ref|>text<|/ref|><|det|>[[177, 225, 821, 333]]<|/det|> +Reply 1: The comments are greatly appreciated. Actually, at the beginning of our project, we carried out morphological assays of gIIβ- 2 with 1, 3, 5 (μM) ABA, and the results showed that 3 \(\mu \mathrm{M}\) ABA induced more significant difference in gIIβ- 2, OE- GIIβ compared with WT in terms of germination rate (Rebuttal Fig. 2). Hereafter, 3 \(\mu \mathrm{M}\) ABA was chosen for phenotypical assays of all mutants of N- glycosylation processing enzymes (NPEs). we apologize for not including these results due to space limitation in our first submission. + +<|ref|>image<|/ref|><|det|>[[194, 370, 630, 700]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[208, 725, 640, 740]]<|/det|> +
Rebuttal Fig. 2 | The seed germination rate of Arabidopsis plants.
+ +<|ref|>text<|/ref|><|det|>[[203, 743, 821, 814]]<|/det|> +a- d, The germination rate of Col- 0, gIIβ- 2 and OE- GIIβ- 16 were determined with different concentrations of ABA. The germination rate was calculated every half day until the fifth day (after stratification at \(4^{\circ}\mathrm{C}\) for 2 days). In each petri dish, about 60 seeds were counted for each Arabidopsis genotype. + +<|ref|>text<|/ref|><|det|>[[177, 835, 821, 907]]<|/det|> +2. The major discovery in this work is that N-glycosylation of SnRK2s leads to the desensitization of prolonged ABA signaling through translocation. However, the relationship between these two processes remains unclear. Does N-glycosylation of SnRK2s occur before or after their translocation? Does N-glycosylation cause translocation, or does translocation lead to N-glycosylation? It would be helpful to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 820, 120]]<|/det|> +design a subcellular- fixed mode of SnRK2s that can only be located in the nucleus or peroxisome to investigate the effects. + +<|ref|>text<|/ref|><|det|>[[178, 131, 821, 280]]<|/det|> +Reply 2: We thank the reviewer for the valuable comments. In our purposed working model (revised Extended Data Fig. 18), SnRK2s appear to be N- glycosylated on the ER- Golgi networks, then to be redistributed to the peroxisome membrane, which is supported by evidences from N- glycosylation assays (Fig. 2d- j) and time- course confocal microscopy observations of SnRK2.2/2.3- GFP (Fig. 3a- g). The peroxisomal localization of SnRK2.2- GFP was inhibited by stt3a mutant, and was enhanced by STT3A overexpression (Fig. 3d); mutation of N- glycosylation site of SnRK2.3N323A delayed its peroxisomal redistribution (Fig. 3f). The findings indicate that N- glycosylation is one of the key factors to determine the peroxisomal redistribution of SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[178, 280, 821, 444]]<|/det|> +Based on the reviewer's suggestions, we constructed fixed SnRK2.3s with SV40 nuclear location signal (NLS) and PEX26 c- terminal end (mPTSPEX26) specifically located in the nucleus and on the peroxisomal membrane respectively (Wright and Bartel, 2020). As shown in revised Extended Data Fig. 17, the SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 showed the fixed subcellular localizations and normal kinase activities. However, they were not N- glycosylated (SnRK2.3WT as a positive control in Rebuttal Fig. 3). The absence of N- glycan on SnRK2.3- mPTSPEX26 may be due to different targeting pathways of native SnRK2.3 and fixed peroxisomal SnRK2.3. Our findings support the notion that N- glycosylation cause translocation, but translocation does not lead to N- glycosylation of SnRK2.3. + +<|ref|>image<|/ref|><|det|>[[193, 475, 710, 602]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[178, 611, 821, 778]]<|/det|> +Rebuttal Fig. 3 | N- glycosylation assays of SnRK2.3WT, SnRK2.3- NLS, SnRK2.3- mPTSPEX26 with ConA- HRP. Constructs SnRK2.3::SnRK2.3WT- GFP (SnRK2.3WT), SnRK2.3::SnRK2.3- NLS- GFP (SnRK2.3- NLS), and SnRK2.3::SnRK2.3- GFP- mPTSPEX26 (SnRK2.3- mPTSPEX26) were expressed in Arabidopsis root hair of snrk2.2/2.3. Total proteins were extracted from ABA- treated transgenic hair roots of SnRK2.3WT, SnRK2.3- NLS- GFP, and SnRK2.3- GFP- mPTSPEX2, followed by immunoprecipitation with GFP- Trap agarose and detection with the anti- GFP antibody and ConA- HRP. The white arrowhead indicates the N- glycosylated SnRK2.3WT- GFP. ConA, concanavalin A, a plant lectin can bind to mannose on the glycoproteins; ConA- HRP, HRP conjugated ConA (Sigma- Aldrich, L6397) for glycoprotein detection; HRP, horseradish peroxidase. + +<|ref|>sub_title<|/ref|><|det|>[[178, 790, 247, 803]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 806, 820, 837]]<|/det|> +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +<|ref|>text<|/ref|><|det|>[[178, 864, 819, 899]]<|/det|> +The introduction of this paper focuses mainly on plant ABA signaling but lacks information about N- glucosidases, especially those mentioned in this work. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 158]]<|/det|> +Reply 3: We thank the reviewer for the careful evaluation. Based on the reviewer's suggestion, detailed information of N- glycosylation has been added to the introduction of the revised manuscript, highlighting the roles of STT3A, GIIα, GIIβ, CGL1, GMII, and FUT11 used in our study. + +<|ref|>text<|/ref|><|det|>[[178, 179, 820, 213]]<|/det|> +Why the authors chose to study STT3A instead of the GIIβ, the mutant initially screened in most experiments? + +<|ref|>text<|/ref|><|det|>[[177, 216, 821, 414]]<|/det|> +Reply 4: We thank the reviewer for the comments. N- glycosylation involves sequential actions of an array of enzymes, such as STT3A, GIIα, GIIβ, and FUT11 used in our study, which function in transfer and modification of sugar moieties in ER and Golgi networks (Strasser, 2016; Zielinska et al., 2012). STT3A is a catalytic subunit of oligosaccharide transferase complex, whereas GIIβ is involved in GIIα/β- heterodimer- mediated glucose trimming of N- glycans. For the N- glycosylation assays, GIIβ would cause about 0.18 kDa molecular mass difference (one glucose) of SnRK2.2/2.3, but this molecular mass difference would be enlarged to 2- 3 kDa (one N- glycan) made by STT3A (Shen et al., 2014). Similar ABA- hypersensitive phenotype, but easy test for N- glycosylation assay of SnRK2.2/2.3, STT3A was chosen for further works instead of GIIβ. We apologize for making some confusion in our manuscript. We added a reasonable sentence in the revised manuscript at line 176. + +<|ref|>sub_title<|/ref|><|det|>[[178, 419, 247, 433]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 437, 820, 470]]<|/det|> +Shen, J., Ding, Y., Gao, C., Rojo, E., and Jiang, L. (2014). N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. Plant J 80, 977- 992. + +<|ref|>text<|/ref|><|det|>[[178, 473, 644, 489]]<|/det|> +Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +<|ref|>text<|/ref|><|det|>[[178, 492, 820, 545]]<|/det|> +Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<|ref|>text<|/ref|><|det|>[[178, 566, 820, 618]]<|/det|> +5. The authors performed a time course RNA-seq analysis to investigate the effects of N-glucosidases, but the stt3a-2 results were analyzed using Col-0 as a control instead of using no ABA-treated stt3a-2 as a control. + +<|ref|>text<|/ref|><|det|>[[178, 622, 821, 787]]<|/det|> +Reply 5: We thank the reviewer for the comments. We have 0 h ABA- treated stt3a-2 which is a no ABA- treated control. When analyzed datasets, we first carried out k- means clustering analysis to determine the ABA- responsive genes, and their time- course expression pattern in ABA- treated Col-0 group with 0 h - ABA- Col-0 as a control. Then we retrieved the expression profiles of these ABA- responsive genes from no- ABA- treated Col-0 group (0- 72 h), to show their basal expression level during 72 h period (no ABA induction). Finally, we retrieved the expression data of the ABA- responsive genes from ABA- treated stt3a-2 with 0 h- stt3a-2 as a control, to show the desensitization of ABA- responsive genes is delayed in stt3a-2 compared with ABA- treated Col-0. The manuscript has been revised in line 121 and 137. + +<|ref|>text<|/ref|><|det|>[[178, 808, 820, 860]]<|/det|> +Additionally, the results do not seem to match the expression pattern shown in Figure 1g- i, as the expression of stress response genes in stt3a- 2 would be expected to be stronger and longer than in Col- 0. Address these inconsistencies and provide a proper control for the analysis. + +<|ref|>text<|/ref|><|det|>[[185, 863, 820, 898]]<|/det|> +Reply 6: We thank the reviewer for the careful evaluation. We agree with the reviewer. The expression of ABA- induced genes in cluster 18 in Fig. 1k (now in revised Extended Data Fig. 3a), + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[185, 85, 821, 213]]<|/det|> +is not obviously stronger and longer in st3a- 2 than that in Col- 0. This phenomena may be due to its rapid induction (peak at 1 h) and followed by a rapid reduction (4- 6 h to basal level). But ABA- induced cluster 1, 8 and 13 appear to have stronger and longer expression in st3a- 2 than that in Col- 0 (Extended Data Fig.3a), and the expression pattern of them is similar to that of NCED3, P5CS1, and RAB18 (peak at 3 h, and decline gradually and slowly) in Fig. 1g- i. For these reasons, we put cluster 1 in Fig.1j, k in exchange for cluster 18, and the related text was corrected in our revised manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 234, 820, 288]]<|/det|> +In Figure 2, based on the results of co- expressed SnRK2.2/2.3 and STT3A in tobacco, the western blot results need to include a control without co- expression and ABA treatment to confirm the band as N- glycosylated SnRK2s. + +<|ref|>text<|/ref|><|det|>[[178, 290, 820, 325]]<|/det|> +Reply 7: We thank the reviewer for the comments. That's correct. Done. The results were shown in revised Fig. 2f. + +<|ref|>text<|/ref|><|det|>[[178, 345, 820, 380]]<|/det|> +Additionally, the western blot results in snrk2.6 mutants require a control using snrk2.2/2.3/2.6 mutants to eliminate non- specific bands. Include these controls for a more accurate interpretation of the results. + +<|ref|>text<|/ref|><|det|>[[194, 383, 456, 398]]<|/det|> +Reply 8: Done. See revised Fig.2h and i. + +<|ref|>text<|/ref|><|det|>[[194, 401, 819, 417]]<|/det|> +We also checked the specificity of the antibody used (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +<|ref|>image<|/ref|><|det|>[[198, 444, 540, 545]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[193, 549, 584, 565]]<|/det|> +Rebuttal Fig. 4 The anti- SnRK2.2/2.3/2.6 used in our study. + +<|ref|>text<|/ref|><|det|>[[178, 567, 820, 602]]<|/det|> +The 10- day seedlings of snrk2.6 mutant, snrk2.2/2.3 double mutant, and snrk2.2/2.3/2.6 triple mutant were used here (anti- SnRK2.2/2.3/2.6, Agrisera, AS14 2783). + +<|ref|>text<|/ref|><|det|>[[178, 640, 820, 675]]<|/det|> +To confirm the N- glycosylated point Asp323 on SnRK2.3, include at least one additional point mutant in Figure 2k as a negative control to provide more solid evidence. + +<|ref|>text<|/ref|><|det|>[[178, 678, 820, 713]]<|/det|> +Reply 9: We thank the reviewer for the comments. Another point mutation SnRK2.3N288A has been included in the N- glycosylation assay (see revised Fig.2k). + +<|ref|>text<|/ref|><|det|>[[178, 732, 821, 880]]<|/det|> +Regarding the translocation of SnRK2.2/2.3- GFP in Arabidopsis, both SnRK2.2 and SnRK2.3 need to complete this evidence. Choose one of them to show the results instead of showing SnRK2.2 translocation with SnRK2.3 (Fig 3d) and performing a mutation assay with SnRK2.3N323A (Fig 3f). The results in Figure 3f indicate that a small amount of SnRK2.3N323A can still export from the nucleus, while SnRK2.2 cannot translocate in the st3a- 2 mutant. This suggests that other factors may be involved in SnRK2.3 translocation besides N- glycosylation at N323, but it is difficult to confirm due to the unequal comparison. To address this, extract nuclear and cytoplasmic proteins separately for western blot analysis to check the N- glycosylation of SnRK2.2/2.3 after ABA treatment. + +<|ref|>text<|/ref|><|det|>[[191, 883, 820, 899]]<|/det|> +Reply 10: We thank the reviewer for the careful evaluation. We are sorry for misunderstanding + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 820, 194]]<|/det|> +of redistribution of SnRK2.2 and SnRK2.3 due to lacking full evidences of both of them. Actually, there is no any significant difference between SnRK2.2 and SnRK2.3 in their subcellular dynamics. In stt3a- 2 background, peroxisomal redistribution of SnRK2.2- GFP is repressed, but few amount of SnRK2.2- GFP still locate on the peroxisomes like SnRK2.3N323A, suggesting that N- glycosylation is not the only one factor to determine redistribution of SnRK2s as the reviewer commented. + +<|ref|>text<|/ref|><|det|>[[178, 197, 820, 268]]<|/det|> +Based on the reviewer's suggestions, to avoid misunderstanding, we have completed the observation of both SnRK2.2- GFP and SnRK2.3- GFP in the revised Fig. 3a. We also re- investigated SnRK2.2- GFP subcellular dynamics under stt3a- 2, and STT3A- OE backgrounds in revised Fig. 3d and 3e. + +<|ref|>text<|/ref|><|det|>[[178, 272, 820, 306]]<|/det|> +Additionally, the N- glycosylation of SnRK2.2 and SnRK2.3 is also similar to each other (Fig. 2d- f, and Extended Data Fig. 7) + +<|ref|>text<|/ref|><|det|>[[178, 336, 821, 462]]<|/det|> +8. In most experiments, the authors used SnRK2.3N323A, a mutant with abolished N-glycosylation of SnRK2.3 (Fig 2k). However, SnRK2.3 still exists in both the nucleus and peroxisome (Fig 3f), which may explain the weak or inconsistent results in Fig. 4 and Extended Data 16. To overcome this issue, delete the nuclear localization signal and peroxisome targeting signal separately to generate SnRK2.2/3 specifically located in the peroxisome and nucleus, and assess the function of SnRK2.2/3 translocation. Additionally, include snrk2.2/snrk2.3 as controls in all assays of SnRK2.32WT and SnRK2.3N323A to demonstrate the role of SnRK2s in these processes. + +<|ref|>text<|/ref|><|det|>[[178, 475, 821, 713]]<|/det|> +Reply 11: We thank the reviewer for the valuable comments. We agree with the reviewer that N- glycosylation is not the sole effector in the regulation of SnRK2.2/2.3's redistribution, as SnRK2.3N323A with mutated N- glycosylation site can still presents on the peroxisomes. However, our studies also showed that N- glycosylation is a crucial effector for SnRK2- redistribution during prolonged ABA signalling. Firstly, genetic analysis showed that N- glycosylation is a key regulator in ABA signalling (ABA- hypersensitivity of npe mutants and SnRK2.3N323A/snrk2.2/2.3 transgenic lines (Fig. 1a- f, Extended Data Fig. 8). Secondly, the subcellular dynamics of SnRK2.2/2.3 in Fig. 3d,e and Fig. 3f,g showed that significantly less SnRK2.3/2.3 locate on the peroxisomes when N- glycosylation is defective. Finally, ABA- induced NADH maintenance and H2O2 clearance are significantly affected by N- glycosylation (stt3a- 2 vs. Col- 0; SnRK2.3N323A vs. SnRK2.3WTin snrk2.2/2.3 double mutant background) during prolonged ABA signalling (Fig. 4a, d and Extended Data Fig. 11, 13, 15c- f, and 16a- d). Totally, our results suggested strong correlation between N- glycosylation and peroxisomal localization of SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[178, 716, 821, 899]]<|/det|> +To confirm whether the effect of N- glycosylation on ABA signalling is due to the peroxisomal targeting of SnRK2.2/2.3, based on the reviewer's suggestion, we constructed the fixed SnRK2.3s that specifically locate in the nucleus (SnRK2.3- NLS) and the peroxisomal membrane (SnRK2.3- mPTSPEX26), and expressed them in the snrk2.2/2.3 double mutant background (Wright and Bartel, 2020). As shown in revised Extended Data Fig. 17, and Fig. 4i, j, both of them possess normal kinase activities, and the SnRK2.3- mPTSPEX26 possesses higher NADPH level (NADPH/NADP+) and lower H2O2 than SnRK2.3WT during prolonged ABA signalling, whereas SnRK2.3- NLS has the highest H2O2 level. We also investigated the ABA- transcriptional response, and the results showed that SnRK2.3- NLS strongly enhance the expression of ABA- responsive genes, but SnRK2.3- mPTSPEX26 not. Our findings support the notion that nuclear SnRK2.3 activates the ABA- transcriptional + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 175]]<|/det|> +response, whereas the peroxisomal SnRK2.3 acts on NADPH maintenance during prolonged ABA signalling. In all these experiments, snrk2.2/2.3 double mutant was included as a control. See revised manuscript line 567- 568. The SnRK2.33323A, SnRK2.3- NLS, and SnRK2.3- mPTSPEX26 were expressed under the snrk2.2/2.3 double mutant background, and the SnRK2.3WT/snrk2.2/2.3 was used as a strict control in these analyses. + +<|ref|>sub_title<|/ref|><|det|>[[178, 188, 247, 201]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 204, 820, 234]]<|/det|> +Wright, Z.J., and Bartel, B. (2020). Peroxisomes form intraluminal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis. Nat Commun 11, 6221. + +<|ref|>text<|/ref|><|det|>[[178, 252, 820, 286]]<|/det|> +This study shows the interaction and regulation between SnRK2s and GPT1, but mainly focuses on SnRK2.2 and GPT1, neglecting SnRK2.2 and 2.3. + +<|ref|>text<|/ref|><|det|>[[178, 289, 820, 379]]<|/det|> +Reply 12: We thank the reviewer for the comments. According to the reviewer's suggestion, the interaction assay between SnRK2.3 and GPT1 has been added in revised Fig. 4c. Phosphorylation analysis of GPT1 by SnRK2.3 has been added in revised Fig. 4e. Interaction assay of GPT1 and SnRK2.2, and phosphorylation analysis of GPT1 by SnRK2.2 have been moved to Extended Data Fig. 14c, f. + +<|ref|>text<|/ref|><|det|>[[178, 383, 819, 417]]<|/det|> +The time- course expression pattern of GPT1 protein, and identification of GPT1 phosphorylation sites by LC- MS/MS have been moved to Extended Data Fig. 14d, e. + +<|ref|>text<|/ref|><|det|>[[178, 437, 820, 471]]<|/det|> +To verify the function of the phosphorylation site, stable transgenic plants would provide more solid evidence than transient expression. + +<|ref|>text<|/ref|><|det|>[[178, 475, 821, 695]]<|/det|> +Reply 13: We thank the reviewer for the valuable comments and we agree with the reviewer that GPT1- stable transgenic plants would provide more strong support to our manuscript. We have obtained gpt1- 1 mutant from prof. Xu in Zhejiang University (Zheng et al., 2018), and are trying to introduce the GPT1WT, GPT13324, and GPT1532D constructs into gpt1- 1(- /-) background, but it appears a hard and long- time work. gpt1- 1 mutant is a T- DNA insertion line and the homozygous gpt1- 1 (- /-) is embryo lethal, so we had to introduce GPT1- constructs into gpt1- 1 (- /+) background. it would need a long time to screen GPT1WT, GPT15324, and GPT1532D transgenic lines with gpt1- 1 (- /-) background. On the other hand, our transient expression data of GPT1- constructs in Fig. 4g and h, appears to work well. It showed significantly difference in GPT15324 and GPT1532D, compared with GPT1WT. Without a doubt, the stable transgenic plants would provide more strong evidences to our conclusions, and we will continue to screen the GPT1- transgenic plants, and collect more comprehensive evidences to support the conclusions in the future. + +<|ref|>sub_title<|/ref|><|det|>[[178, 709, 247, 721]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 724, 819, 768]]<|/det|> +Zheng, Y., Deng, X., Qu, A., Zhang, M., Tao, Y., Yang, L., Liu, Y., Xu, J., and Zhang, S. (2018). Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis. PLoS Genet 14, e1007880. + +<|ref|>text<|/ref|><|det|>[[178, 787, 820, 875]]<|/det|> +Explain why the SnRK2.2- and SnRK2.3- GFP proteins showed a dramatic increase (more than 10- fold) after ABA treatment in Extended Data Fig. 9c. However, in Extended Data Fig 9e, the SnRK2.2- GFP protein only increased less than 1.5- fold after ABA treatment, leading to inconsistency. Generally, the protein abundance of SnRK2s should decline after ABA treatment. Provide an explanation for this discrepancy. (in Extended Data Fig 9e, the 35S:: SnRK2.2- GFP, error bar value) + +<|ref|>text<|/ref|><|det|>[[178, 880, 820, 913]]<|/det|> +Reply 14: We thank the reviewer for the comments. In our manuscript, we investigated temporal dynamics of endogenous SnRK2.2/2.3/2.6 over prolonged ABA treatment with antibody (Agrisera + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 821, 250]]<|/det|> +AS142783), and the results showed that the SnRK2.2/2.3/2.6 are induced by short- term ABA treatments (peak at 4- 6 h), then following degradation (Extended Data Fig. 9c), which is consistent with previous report (Ali et al., 2019). SnRK2.2- GFP, even through driven by 35S promoter, has a similar expression pattern over ABA treatment, indicating SnRK2s are tightly regulated by ABA in protein level (Extended Data Fig. 9d). However, the fold- change of SnRK2.2- GFP induced by short- term ABA is less than endogenous SnRK2.2/2.3 compared with 0 h ABA. This difference may caused by 35S promoter, which elevates the basal expression level of SnRK2.2 without ABA treatment. This hypothesis was also supported by the temporal expression pattern of 35S::SnRK2.3- GFP in revised Extended Data Fig. 9e. + +<|ref|>sub_title<|/ref|><|det|>[[178, 254, 247, 267]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 269, 820, 313]]<|/det|> +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. + +<|ref|>text<|/ref|><|det|>[[178, 332, 820, 366]]<|/det|> +In Extended Data Fig. 11, clarify the location of ROS affected by the stt3a mutation, rather than focusing on the amount. + +<|ref|>text<|/ref|><|det|>[[178, 369, 821, 477]]<|/det|> +Reply 15: We thank the reviewer for the comments. It was previously reported that SnRK2.2/2.3 mainly are expressed in root tip (Fujii et al., 2007). In our study, we found that the redistribution of SnRK2.2/2.3 induced by prolonged ABA also mainly occurs in root meristem which is consistent with the ROS location affected by stt3a and mutation of N- glycosylation site of SnRK2.3 (SnRK2.3N323A). we have clarified that the root meristem or root tips are the main region of ROS affected by stt3a and N- glycosylation of SnRK2.2/2.3 (revised Extended Data Fig.11 and 13) + +<|ref|>sub_title<|/ref|><|det|>[[178, 500, 247, 512]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 515, 820, 560]]<|/det|> +Fujii, H., Verslues, P.E., and Zhu, J.K. (2007). Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell 19, 485- 494. + +<|ref|>sub_title<|/ref|><|det|>[[178, 580, 290, 593]]<|/det|> +## Additional issues: + +<|ref|>text<|/ref|><|det|>[[178, 597, 820, 630]]<|/det|> +11. In Line 65 to Line 67, the reference to Extended Data Figure should be corrected to Extended Data Figure 1. + +<|ref|>text<|/ref|><|det|>[[193, 634, 400, 649]]<|/det|> +Reply 16: That's correct. Done. + +<|ref|>text<|/ref|><|det|>[[178, 670, 820, 705]]<|/det|> +12. In Figure 4d, the legend describes a Co-IP assay using 4-day-old seedlings, but the results show a different pattern compared to Figure 4b, which also shows a Co-IP assay using the same material. + +<|ref|>text<|/ref|><|det|>[[178, 708, 820, 779]]<|/det|> +Reply 17: Thanks the viewer for the comments. (previous) Fig. 4d is not a Co-IP assay, it is a western blot analysis using total protein extracts to determine the temporal expression pattern during prolonged ABA treatment. The figure legend has been corrected (Now in Extended Data Fig. 14d). + +<|ref|>text<|/ref|><|det|>[[178, 782, 820, 815]]<|/det|> +Additionally, Figure 4d indicates a \(3\mu \mathrm{M}\) ABA treatment, but the legend describes it as \(50\mu \mathrm{M}\) ABA. Please address these inconsistencies. + +<|ref|>text<|/ref|><|det|>[[178, 819, 820, 853]]<|/det|> +Reply 18: Actually, \(3\mu \mathrm{M}\) ABA was used in (previous) Fig. 4d, and the figure legend has been corrected (Now in Extended Data Fig. 14d). + +<|ref|>text<|/ref|><|det|>[[178, 875, 820, 909]]<|/det|> +13. The results in Figure 2l and m demonstrate the phenotype of the triple mutant stt3a-2/snrk2.2/2.3 to confirm the epistasis of SnRK2.2/2.3 to STT3A. However, Figure 2l shows a slightly longer primary root + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 820, 138]]<|/det|> +in the triple mutant compared to snrk2.2/2.3, whereas Figure 2m shows the reverse result, with the triple mutant having a slightly longer root. This discrepancy may be due to the selection of seedlings for photography. Clarify this issue. + +<|ref|>text<|/ref|><|det|>[[178, 141, 820, 250]]<|/det|> +Reply 19: Thanks the referee for the comments. The quantification data is a relative root length (ABA+/- ) in Fig. 2m. The ratio (ABA+/- ) of WT was designated as 1, and the relative ratio to WT was shown for double and triple mutants. Although Fig. 21 showed a little bit longer roots for triple mutant with and without ABA treatment, the relative ratio is slightly smaller. We are sorry for this confusion due to lacking detailed information. The figure legend of Fig. 21, m, has been described in details. + +<|ref|>text<|/ref|><|det|>[[178, 270, 820, 323]]<|/det|> +14. In Figure 3a and 3b, the intensity of SnRK2.2-GFP appears to increase after 2 hours of treatment, but Figure 3d shows a similar fluorescence intensity. Although this does not directly relate to the conclusion, please address this inconsistency. + +<|ref|>text<|/ref|><|det|>[[178, 326, 820, 435]]<|/det|> +Reply 20: We thank the reviewer for the careful evaluation. In (previous) Fig. 3d, we mainly focus on the subcellular changes of SnRK2.2-GFP under different backgrounds. In order to observe the peroxisomes more clearly, the fluorescence intensity was appropriately enhanced in some photographs. Based on the reviewer's suggestion, we have re-investigated SnRK2.2-GFP subcellular dynamics under Col-0, st3a-2, and STT3A-OE backgrounds, and have replaced them with more suitable photographs in revised Fig. 3d and 3e. + +<|ref|>text<|/ref|><|det|>[[178, 455, 820, 489]]<|/det|> +Additionally, for Figure 3c, a larger scale view may be more suitable to clearly show the cytosol, nuclear, and peroxisome localization of SnRK2.2- GFP. + +<|ref|>text<|/ref|><|det|>[[178, 493, 820, 545]]<|/det|> +Reply 21: We thank the reviewer for the comments. The overlap between SnRK2.2/2.3- GFP and peroxisomal marker gene has been re- investigated, and the photographs with higher quality and a larger view have been replaced for revised Fig. 3c. + +<|ref|>text<|/ref|><|det|>[[178, 566, 820, 600]]<|/det|> +15. Ensure that the growth conditions described in the text match those depicted in Figure 1a, 1c, and 1e, as there appears to be a significant difference in root lengths of Col-0 plants. + +<|ref|>text<|/ref|><|det|>[[178, 603, 820, 637]]<|/det|> +Reply 22: We thank the viewer for the comment. The detailed information about growth conditions has been clarified in revised figure legend of Fig.1a, 1c, and 1e. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 86, 416, 101]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[178, 104, 820, 157]]<|/det|> +This is a highly interesting manuscript and I would like to see that story published. However, I am not convinced that all the conclusions are supported by the shown data. Therefore, I would ask the authors for additional experiments and explanations. + +<|ref|>text<|/ref|><|det|>[[178, 161, 711, 177]]<|/det|> +We greatly appreciate the reviewer for positive comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[178, 198, 260, 212]]<|/det|> +Major points + +<|ref|>text<|/ref|><|det|>[[178, 216, 309, 230]]<|/det|> +The general concept: + +<|ref|>text<|/ref|><|det|>[[178, 234, 820, 267]]<|/det|> +How do you think does this transport and glycosylation process work (see statement in Abstract lines 11- 12)? + +<|ref|>text<|/ref|><|det|>[[178, 271, 820, 305]]<|/det|> +Reply 1: We thank the reviewer for the comment. The abstract statement in line 11- 12 has been revised according to the working model (revised Extended Data Fig. 18). + +<|ref|>text<|/ref|><|det|>[[178, 325, 820, 360]]<|/det|> +How do you think that STT3A- mCherry (a protein with numerous transmembrane domains) localizes to the cytoplasm - see statement in lines 142- 144 - without a membrane it would immediately aggregate. + +<|ref|>text<|/ref|><|det|>[[178, 363, 820, 453]]<|/det|> +Reply 2: We agree with the reviewer. As no organellar marker was used previously, we concluded that "co- expression of STT3A- mCherry leads to SnRK2.2/2.3- GFP nuclear export and their colocalization in cytoplasm". Based on the reviewer's suggestion, we re- observed their subcellular dynamics with ER- marker CFP- HDEL, and the results showed that they co- localized in the ER (revised Fig. 2j and Extended Data Fig. 6f- i). The manuscript has been revised in line 196. + +<|ref|>text<|/ref|><|det|>[[178, 474, 821, 600]]<|/det|> +How can glycosylation in the lumen of the ER affect the nuclear localization of another protein (processes taking place in completely different subcellular compartments)? Based on your model in Extended Data Fig. 17, the SnRK2 proteins are transported to the ER lumen for glycosylation, if it is like this than glycosylation is not involved in transport from the nucleus/cytoplasm to the ER lumen and another process mediates this transport. Then glycosylation of SnRK2.2/2.3 might be involved in transport from the ER to the peroxisomes, but this is not clearly shown and glycosylation would then not be involved in desensitization of the transcriptional response in the nucleus. + +<|ref|>text<|/ref|><|det|>[[178, 604, 821, 749]]<|/det|> +Reply 3: We thank the reviewer for the valuable comments. In the working model (revised Extended Data Fig. 18), we proposed that synthesised SnRK2.2/2.3 in the cytoplasm, are distributed into the nucleus during short- term ABA treatment (such as 2 h), and then some of them are redistributed onto the peroxisome membrane through ER- Golgi networks, which indirectly leads to less nuclear SnRK2s distribution, desensitizing ABA- transcriptional response (another factor leading to decrease of nuclear SnRK2s is ubiquitination- mediated protein degradation (Ali et al., 2019; Cheng et al., 2017)). Fig. 3i,j showed that SnRK2.3N232A mutation did affect the transcript level of ABA- responsive genes. + +<|ref|>text<|/ref|><|det|>[[178, 752, 821, 823]]<|/det|> +Our results showed that overexpression of STT3A sufficiently led to the full ER- location of SnRK2.2/2.3- GFP in tobacco leaves, supporting the hypothesis that STT3A is essential to SnRK2s ER- localization (Fig. 2j, Extended Data Fig. 6f- i), although the molecular mechanism is unknown. Moreover, N- glycosylation/STT3A did desensitize ABA- transcriptional response (Fig. 1f- k). + +<|ref|>text<|/ref|><|det|>[[178, 826, 820, 879]]<|/det|> +Based on the reviewer's comments, the working model has been revised, highlighting the SnRK2s' synthesis in cytoplasm, then targeting to the nucleus and the peroxisomes respectively (see revised Extended Data Fig. 18). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[178, 87, 247, 100]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 104, 820, 152]]<|/det|> +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. + +<|ref|>text<|/ref|><|det|>[[178, 157, 820, 211]]<|/det|> +Cheng, C., Wang, Z., Ren, Z., Zhi, L., Yao, B., Su, C., Liu, L., and Li, X. (2017). SCFATPP2- B11 modulates ABA signaling by facilitating SnRK2.3 degradation in Arabidopsis thaliana. PLoS Genet 13, e1006947. + +<|ref|>text<|/ref|><|det|>[[178, 234, 820, 286]]<|/det|> +Do you think that the folded SnRK2.2/2.3 proteins are taken up into the ER where they are glycosylated by a complex that normally glycosylates unfolded proteins? Which complex is involved in the uptake into the ER? + +<|ref|>text<|/ref|><|det|>[[178, 290, 821, 527]]<|/det|> +Reply 4: We agree with the reviewer that a N- glycan is attached on an unfolded protein (or unfolded domain) in the ER lumen (Nagashima et al., 2018; Ruiz- Canada et al., 2009). Here, we supposed that SnRK2.2/2.3 N- glycosylation obeys this rule. Firstly, N- glycosylation site is present in the C- terminal domain II of SnRK2s, an extended conformation protruding outside of the three- dimensional protein structure (Extended Data Fig. 7a), indicating that the N- glycosylation site of SnRK2s is always "unfolded" for N- glycan attaching (Ng et al., 2011; Xie et al., 2012). Secondly, it was recently reported that TMED10 channel protein mediated uptake of unconventional secretory proteins into ER- Golgi intermediate compartment (ERGIC in mammals, cis- most Golgi structure in plants). We proposed that SnRK2's localization in the ER may be mediated by Arabidopsis homologs of TMED10 (our unpublished data showed they function in ABA signalling and interact with SnRK2s). If this is true, SnRK2.2/2.3 may also be unfolded, as TMED10 cargoes were unfolded by HSP90A during transport (Zhang et al., 2020). This hypothesis need more evidences to be collected in the future. + +<|ref|>sub_title<|/ref|><|det|>[[179, 532, 247, 545]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 549, 820, 582]]<|/det|> +Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. + +<|ref|>text<|/ref|><|det|>[[178, 586, 820, 620]]<|/det|> +Ruiz- Canada, C., Kelleher, D.J., and Gilmore, R. (2009). Cotranslational and posttranslational N- glycosylation of polypeptides by distinct mammalian OST isoforms. Cell 136, 272- 283. + +<|ref|>text<|/ref|><|det|>[[178, 641, 820, 675]]<|/det|> +Glycosylation mutants are pleiotropic and typically affect many proteins, how likely is it that there are indirect effects from other glycoproteins that are related to the ABA sensitivity? + +<|ref|>text<|/ref|><|det|>[[178, 678, 820, 767]]<|/det|> +Reply 5: We agree with the reviewer that N- glycosylation mutants are pleiotropic and many glycoproteins may be affected during ABA treatment. However, in our manuscript, only SnRK2s glycosylation was tested and the results showed its dominant roles in prolonged ABA signalling. Further research works need to be carried out to show the important roles of other glycoproteins in ABA signalling in the future. + +<|ref|>text<|/ref|><|det|>[[179, 790, 404, 804]]<|/det|> +The protein- protein interaction data: + +<|ref|>text<|/ref|><|det|>[[178, 808, 821, 898]]<|/det|> +In the Y2H assay SnRK2s is not glycosylated and an interaction with GIIbeta therefore shows that the interaction is not N- glycan dependent. GIIbeta has a lectin domain for carbohydrate binding, so binding to a non- glycosylated protein shows a glycosylation- independent process or hints at an unspecific binding event. Panel a from the Extended Data Fig. 5 (and also Fig. 2b and comment below) confirms that because the GST- tagged protein is produced in E.coli and therefore not glycosylated. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 822, 250]]<|/det|> +Reply 6: We thank the reviewer for the comments. To distinguish whether interactions between N- glycan processing enzymes (NPEs) and SnRK2s are N- glycan dependent or not, we carried out a pull- down assay with SnRK2.3N323A and GIIβ. as shown in Rebuttal Fig.5, SnRK2.3N323A still interacts directly with GIIβ, suggesting that SnRK2s- NPEs interaction is N- glycan independent. However, further LCI assays showed that the binding activity of SnRK2.3N323A to STT3A was weaker than SnRK2.3WT(Rebuttal Fig.6). The findings suggested that the interaction between SnRK2s and NPEs are both dependent and independent on N- glycan. Moreover, Our results did show that N- glycosylation of SnRK2.2/2.3 plays crucial roles in subcellular dynamics of SnRK2.2/2.3 and desensitization of ABA- transcriptional response (Fig. 3a- j) + +<|ref|>image<|/ref|><|det|>[[303, 256, 583, 430]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[194, 438, 520, 454]]<|/det|> +Rebuttal Fig. 5 SnRK2.3N323A interacts with GIIβ. + +<|ref|>text<|/ref|><|det|>[[178, 456, 820, 510]]<|/det|> +The pull- down assay was carried out with GST- SnRK2.3N323A and GIIβ- 3×FLAG expressed in E. coli. GST- SnRK2.3N323A and GIIβ- 3×FLAG were mixed together and incubated for 4 hours, followed by Western blot analysis using indicated antibodies. GST was used as a control. + +<|ref|>image<|/ref|><|det|>[[198, 532, 777, 633]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[195, 643, 553, 658]]<|/det|> +
Rebuttal Fig. 6 SnRK2.3/2.3N323A interact with STT3A.
+ +<|ref|>text<|/ref|><|det|>[[178, 660, 820, 732]]<|/det|> +The LCI assays showed the interactions between STT3A and SnRK2.3/2.3N323A. For ABA treatment, \(50 \mu \mathrm{M}\) ABA was injected into tobacco leaves after 12 hours of GV3101 infection. After 2.5 days, 1mM luciferin solution was sprayed on the leaves. Then, luciferase activity was detected. Three leaves were three replicates. + +<|ref|>text<|/ref|><|det|>[[178, 752, 821, 879]]<|/det|> +The luciferase assay shows interaction of all tested SnRK2s with all tested glycosylation related enzymes. This is suspicious, especially because the tested glycosylation related enzymes are located in different subcellular compartments, have a different membrane topology and most have only a few amino acids facing the cytosol where the interaction with SnRK2s would likely occur. Moreover, glycosylation related enzymes often interact with the glycan and not the protein and the interaction is only transient. I would like to see additional controls for the luciferase assay and additional experiments showing the interaction, like additional co- IP data. + +<|ref|>text<|/ref|><|det|>[[193, 882, 820, 898]]<|/det|> +Reply 7: We thank the reviewer for the comments. As discussed above, NPEs can bind to SnRK2s + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 823, 195]]<|/det|> +with both glycan- dependent and - independent manners. The Firefly luciferase complementation imaging (LCI) assays showed that STT3A, GIIα, GIIβ, CGL1, and FUT11 interacted with SnRK2s, and ABA treatment enhanced this binding activities in tobacco leaves (Fig. 2c). As negative controls, these NPEs cannot interact with ABA receptor PYLs, ABI1, ABI2, ABI5 and ABF2 in our LCI assays (Extended Data Fig. 5b- f). Moreover, the Co- IP assay showed GIIβ bound to SnRK2s in Arabidopsis (Fig. 2b). + +<|ref|>text<|/ref|><|det|>[[178, 215, 820, 250]]<|/det|> +Why did the authors characterize a specific set of glycosylation related enzymes, the rationale for choosing them is not clear. Did they also test others like FUT12 or XylT? + +<|ref|>text<|/ref|><|det|>[[178, 252, 820, 305]]<|/det|> +Reply 8: It was reported that loss- of- function mutants of STT3A, GIIα, CGL1, and FUT11 exhibited hypersensitivity to high salt (Strasser, 2016). In our manuscript, they were found to be hypersensitive to ABA (Fig. 1a- f). + +<|ref|>text<|/ref|><|det|>[[178, 308, 820, 360]]<|/det|> +Based on the reviewer's comment, the rationale has been added to our manuscript. Moreover, we also tested the FUT12, and the results showed that FUT12 interact with SnRK2.2/2.3 with ABA- dependent manner (Rebuttal Fig. 7). + +<|ref|>image<|/ref|><|det|>[[339, 368, 672, 523]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[194, 532, 521, 546]]<|/det|> +Rebuttal Fig. 7 SnRK2.2/2.3 interact with FUT12. + +<|ref|>text<|/ref|><|det|>[[178, 549, 820, 620]]<|/det|> +The LCI assays showed the interactions between FUT12 and SnRK2.2/2.3. For ABA treatment, 50 μM ABA was injected into tobacco leaves after 12 hours of GV3101 infection (0.05% DMSO as control). After 2.5 days, 1mM luciferin solution was sprayed on the leaves. Then, luciferase activity was detected. Two leaves were two replicates. + +<|ref|>sub_title<|/ref|><|det|>[[178, 625, 246, 637]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 640, 642, 656]]<|/det|> +Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +<|ref|>text<|/ref|><|det|>[[178, 694, 820, 745]]<|/det|> +Related to that and their main claim that N- glycosylation plays a role, how sure are the authors that the used mutants lead to changes in N- glycosylation. Has this been shown for Arabidopsis GIIbeta and FUT11 knockouts? + +<|ref|>text<|/ref|><|det|>[[178, 750, 820, 820]]<|/det|> +Reply 9: Based on the reviewer's comment, we investigated the N- glycosylation in stt3a- 2 background, as deficiency of STT3A would induce larger molecular weight difference than other NPEs. The result showed that the band shift of SnRK2.3 (N- glycosylated SnRK2.3) was abolished in stt3a- 2 (Rebuttal Fig. 8) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[300, 93, 592, 168]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[193, 179, 653, 194]]<|/det|> +Rebuttal Fig. 8 N- glycosylation assay of SnRK2.3 in Col- 0 and stt3a- 2. + +<|ref|>text<|/ref|><|det|>[[179, 198, 820, 231]]<|/det|> +SnRK2.3- His were expressed in Arabidopsis hair roots of Col- 0 and stt3a- 2, followed by immunoprecipitation with anti- His antibodies. N- SnRK2.3- His means N- glycosylated SnRK2.3- His. + +<|ref|>text<|/ref|><|det|>[[179, 254, 295, 268]]<|/det|> +The confocal data: + +<|ref|>text<|/ref|><|det|>[[178, 272, 821, 417]]<|/det|> +I am sorry, but in the shown images a clear reticular ER network is not visible (e.g. Fig. 2j, Fig. 4c, Fig. 5g, Fig. 6b, e and f). The used ER- marker seems not appropriate in these experiments and is not frequently used to label the ER in tobacco in literature. In the shown images the cellular morphology appears altered, either because of the used marker or overexpressed proteins and often cellular structures are visible that look like aggregates. As a consequence, conclusions directly linked the ER localization data are questionable and BiFC data could represent false positives. The authors should provide better images, where the ER is clearly visible. Please provide also the subcellular localization of STT3A- mCherry and GlIBeta- GFP without any co- expressed other protein to see if they reside in the ER. + +<|ref|>text<|/ref|><|det|>[[178, 438, 820, 491]]<|/det|> +Reply 10: We thank the reviewer for the careful evaluation. As reviewer suggested, we re- investigated the ER structure and obtained high- quality figures with clear ER network in Fig. 2j, Fig. 4c, Extended Data Fig. 5g, Extended Data Fig. 6e, g and h. + +<|ref|>text<|/ref|><|det|>[[178, 494, 821, 546]]<|/det|> +For ER- marker, we used CFP- HDEL, and CD3- 959 reported by Nelson et al. (Nelson et al., 2007). Subcellular localization of STT3A- mCherry, GlIP- mCherry and GlIP- GFP was shown in Rebuttal Fig. 9. + +<|ref|>image<|/ref|><|det|>[[205, 592, 790, 704]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[193, 717, 588, 732]]<|/det|> +Rebuttal Fig. 9 Subcellular localization of STT3A and GlIP. + +<|ref|>text<|/ref|><|det|>[[178, 735, 821, 824]]<|/det|> +a, STT3A- mCherry was expressed in N. benthamiana leaves with \(50~\mu \mathrm{M}\) ABA treatment for \(48\mathrm{h}\) (0.05% DMSO as control). CFP- HDEL was as ER marker. Scale bars, \(10\mu \mathrm{m}\) . b, GlIP- mCherry was expressed in N. benthamiana leaves (left) and GlIP- GFP was stably expressed in glIP- 2 (right) treated with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) (0.05% DMSO as control). CFP (CFP- HDEL) and mCherry (CD3- 959) were used as ER marker. Scale bars, \(10\mu \mathrm{m}\) . + +<|ref|>sub_title<|/ref|><|det|>[[179, 828, 247, 841]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[179, 845, 820, 879]]<|/det|> +Nelson, B.K., Cai, X., and Nebenfuhr, A. (2007). A multicolored set of in vivo organelle markers for co- localization studies in Arabidopsis and other plants. Plant J 51, 1126- 1136. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 195]]<|/det|> +In Extended Data Fig. 6b the authors show images of GlBeta co- expression with SnRK2.2- GFP or SnRK2.3- GFP and show a diffuse signal in the cell. This looks more like a cell undergoing cell death than cytosolic localization. Please comment on that. How many cells show this type of fluorescence? Is it only visible with GlBeta? Which GlBeta was used for co- expression, is it also tagged with a fluorescent protein and leads to a diffuse labelling of the cell? Please provide co- localization data with GlBeta- mCherry or at least with an ER- marker. + +<|ref|>text<|/ref|><|det|>[[178, 198, 820, 231]]<|/det|> +In general, the confocal images are quite small, larger images should be provided and the quality of the images should be improved. + +<|ref|>text<|/ref|><|det|>[[178, 235, 821, 398]]<|/det|> +Reply 11: We thank the reviewer for the comments. Our results showed that STT3A- coexpression induced SnRK2.2/2.3 ER- localization and overlap with each other (Extended Data revised Fig. 6f- i); GIIβ- coexpression led cytoplasmic diffusing of SnRK2.2/2.3 (most of the cells displayed this kind of diffusing as shown in Extended Data Fig. 6b). To answer the reviewer if it is due to cell death, we re- investigated this experiment with GIIβ- mCherry, and the enlarged view showed that SnRK2.3- GFP still diffused in cytoplasm, but did not overlap with GIIβ- mCherry (revised Extended Data Fig. 6e). Clear shape of organelles, such as nucleus, GIIβ- mCherry ER- structure (GIIβ contains a HDEL end), suggested that they were not dead cells (revised Extended Data Fig. 6e). + +<|ref|>text<|/ref|><|det|>[[178, 418, 821, 565]]<|/det|> +The peroxisomal uptake should also be supported by more data clearer confocal images. In lines 188- 190 it is stated that translocation of SnRK2.2 might consist of two steps SnRK2 degradation and peroxisomal targeting. This is unclear. Do you mean that the protein in the nucleus is degraded and that new SnRK2 protein is translated in the cytoplasm that is then transported to the ER and further to the peroxisome? Is there any evidence for nuclear degradation? Which machinery would be involved in the degradation in the nucleus? Did you test proteasome inhibitors? Did you do any experiments with protein synthesis inhibitors to see if synthesis of new proteins is involved in the process. Additional experiments should be provided to support the claims. + +<|ref|>text<|/ref|><|det|>[[178, 568, 821, 749]]<|/det|> +Reply 12: We thank the reviewer for the comments. Based on the reviewer's suggestions, we employed translation inhibitor CHX (Cycloheximide) and proteasome inhibitor MG132 to further investigate the subcellular dynamics of SnRK2.2/2.3 during prolonged ABA signalling. As shown in Extended Data Fig.10f, CHX repressed accumulation of peroxisomal SnRK2.3- GFP, supporting the notion that peroxisomal SnRK2.3 is from new synthesised protein; MG132 treatment obviously increased accumulation of nuclear SnRK2.3- GFP, which was consistent with previous reports, suggesting 26S proteasome mediates degradation of SnRK2.3 in the nucleus (Ali et al., 2019; Cheng et al., 2017). Our manuscript showed that N- glycosylation did affect nuclear SnRK2.2/2.3 decrease (more peroxisomal SnRK2s, less nuclear SnRK2s, as discussed in working model) in addition to proteasome- mediated degradation. + +<|ref|>sub_title<|/ref|><|det|>[[179, 772, 246, 785]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 789, 821, 899]]<|/det|> +Ali, A., Kim, J.K., Jan, M., Khan, H.A., Khan, I.U., Shen, M., Park, J., Lim, C.J., Hussain, S., Baek, D., et al. (2019). Rheostatic Control of ABA Signaling through HOS15- Mediated OST1 Degradation. Mol Plant 12, 1447- 1462. Baena- Gonzalez, E., Rolland, F., Thevelein, J.M., and Sheen, J. (2007). A central integrator of transcription networks in plant stress and energy signalling. Nature 448, 938- 942. Cheng, C., Wang, Z., Ren, Z., Zhi, L., Yao, B., Su, C., Liu, L., and Li, X. (2017). SCFAtPP2- B11 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[208, 86, 820, 120]]<|/det|> +modulates ABA signaling by facilitating SnRK2.3 degradation in Arabidopsis thaliana. PLoS Genet 13, e1006947. + +<|ref|>text<|/ref|><|det|>[[179, 142, 345, 157]]<|/det|> +The SnRK2 glycosylation: + +<|ref|>text<|/ref|><|det|>[[178, 160, 822, 268]]<|/det|> +The overexpression of STT3A- mCherry results in an additional SnRK2.2- His/SnRK2.3- His band that is also detectable when treated with ABA. This raises a number of questions. This suggests, for example, that STT3A activity is limited in plants and its overexpression is sufficient to increase the glycosylation of proteins. Is there any additional evidence for that? STT3A is part of a larger protein complex and one would expect that other proteins in this complex are also required for the activity which were not overexpressed. Please comment on that. + +<|ref|>text<|/ref|><|det|>[[178, 272, 822, 398]]<|/det|> +Reply 13: We thank the reviewer for the comments. Our results showed that the sole STT3A- overexpression caused N- glycosylation of SnRK2.2/2.3 in tobacco leaves (35S::STT3A, 35S::SnRK2.2/2.3 constructed on a same vector; see revised Fig. 2d- f). We made many biological replicates, and all showed the N- glycosylation of SnRK2.2/2.3 when coexpressed with STT3A (Rebuttal Fig.11). Moreover, the sole STT3A- coexpression also affected subcellular localization of SnRK2s (revised Fig. 2j, Extended Data Fig 6. f- i). Our findings suggest the sole overexpression of STT3A is sufficient for N- glycosylation of SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[178, 401, 822, 508]]<|/det|> +Oligosaccharyltransferase complex (OST) consists of one catalytically active subunit, STT3 (staurosporine and temperature sensitivity 3), and several different non- catalytic subunits. Arabidopsis genome has two paralogs, STT3A and STT3B (Strasser, 2016). Overexpression of STT3A subunit is sufficient for N- glycosylation of SnRK2.2/2.3 in our manuscript, suggesting its default activation with complex- independent activity, which is similar to the overexpression of SnRK1, a catalytic subunit involved in heteromeric complex (Baena- Gonzalez et al., 2007). + +<|ref|>text<|/ref|><|det|>[[178, 512, 822, 600]]<|/det|> +Additionally, the sole ABA treatment can occasionally induce N- glycosylation and subcellular change of SnRK2s when transiently expressed in tobacco leaves. Most of the time, the sole ABA cannot or very weakly induce SnRK2s' N- glycosylation and subcellular change in tobacco leaves (See revised Fig. 2d- f). As shown in Rebuttal Fig.10, SnRK2.3- GFP was mainly located in the nucleus with or without ABA treatment in tobacco leaves. + +<|ref|>image<|/ref|><|det|>[[202, 628, 700, 775]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[194, 789, 595, 805]]<|/det|> +
Rebuttal Fig. 10 Subcellular localization of STT3A and GIIβ.
+ +<|ref|>text<|/ref|><|det|>[[179, 808, 820, 841]]<|/det|> +SnRK2.3WT- GFP and SnRK2.3N323A- GFP were expressed in N. benthamiana leaves with 50 μM ABA treatment for 48 h (0.05% DMSO as control). DAPI was a nuclear dye. Scale bars, 10 μm. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[256, 90, 775, 285]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[194, 290, 515, 305]]<|/det|> +Rebuttal Fig. 11 N- glycosylation of SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[180, 308, 821, 379]]<|/det|> +a, b, SnRK2.2- His and SnRK2.3- His were coexpressed with STT3A- mCherry (constructed on the same vector) in the tobacco leaves respectively. Total protein was extracted and followed by \(6\%\) SDS- PAGE separation and detection with the anti- His antibodies. Endo H and PNG F digestion confirmed that the band shift was due to N- glycosylation. N- SnRK2s- His means N- glycosylated SnRK2s- His. + +<|ref|>sub_title<|/ref|><|det|>[[179, 401, 247, 414]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[179, 419, 821, 471]]<|/det|> +Baena- Gonzalez, E., Rolland, F., Thevelein, J.M., and Sheen, J. (2007). A central integrator of transcription networks in plant stress and energy signalling. Nature 448, 938- 942. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. + +<|ref|>text<|/ref|><|det|>[[179, 528, 820, 583]]<|/det|> +Given the fact, that the authors are familiar with peptide analysis by LC- MS/MS (Fig. 4f), they should try to purify the transiently expressed His- or GFP- tagged SnRK2.2/2.3 and confirm the presence of the glycan linked to N323 by MS analysis. + +<|ref|>text<|/ref|><|det|>[[179, 586, 820, 732]]<|/det|> +Reply 14: We thank the reviewer for careful evaluation and for encouraging us to improve our manuscript. We agree with the reviewer that MS (mass spectrometry) assay will be better for confirmation of SnRK2.2/2.3 N- glycosylation. Based on the reviewer's suggestion, we have carried out the LC- MS/MS analysis of SnRK2.3 N- glycosylation (Zielinska et al., 2012). Unfortunately, in the past few months, we tried no less than five times with SnRK2.3- GFP transgenic plants or SnRK2.3- His transgenic BY- 2 cells (bright yellow tobacco cell), but all failed. We presume that the failure may be due to the tiny amount of N- glycosylated SnRK2.3. only a few SnRK2s are N- glycosylated in Arabidopsis and transgenic tobacco cells (see Fig. 2d- i, k, and Rebuttal Fig. 11). + +<|ref|>text<|/ref|><|det|>[[179, 734, 820, 861]]<|/det|> +In our manuscript, we have provide rich data to show the SnRK2.2/2.3 N- glycosylation and the crucial roles in ABA signalling. We mutated total 11 N sites (asparagine residues) individually, and identified the N- glycosylation site SnRK2.3N323 (Fig. 2j, Extended Data Fig. 6f- i). this site mutation can block SnRK2.3 N- glycosylation (Fig. 2k), can inhibit SnRK2.3 subcellular change (Fig. 2j, Fig. 3a- f), can enhance the expression of ABA- induced genes (Fig. 3i, j), and can change phenotype of snrk2.2/2.3 double mutant from ABA- hyposensitivity to ABA- hypersensitivity (Extended Data Fig. 9l,m). + +<|ref|>text<|/ref|><|det|>[[179, 863, 819, 898]]<|/det|> +We will continue to explore this field in the future and use more methods to detect this phenomenon. Thanks the reviewer again for valuable comments. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[181, 90, 816, 409]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[194, 427, 728, 443]]<|/det|> +## Rebuttal Fig. 12 | Enrichment of N-glycosylated SnRK2.3-GFP and SnRK2.3-His. + +<|ref|>text<|/ref|><|det|>[[178, 444, 821, 732]]<|/det|> +a, Enrichment of N- glycosylated SnRK2.3- GFP before MS analysis. SnRK2.3- GFP overexpression plants were treated with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) after seven days of growth and the roots were collected. After IP with GFP- Trap and ConA (concanavalin A, a plant lectin can bind to mannose on the glycoproteins), the enrichment was determined by western blot. Input, total protein extract; GFP- Trap, enrichment of SnRK2.3- GFP by GFP- Trap beads; ConA- IP, enrichment of N- glycosylated SnRK2.3- GFP by ConA bead after GFP- Trap- IP. The white arrowhead denotes the N- glycosylated SnRK2.3- GFP. b, Coomassie brilliant blue staining after PNGase F digestion of N- glycosylated SnRK2.3- GFP enriched by ConA. The dashed white frame denotes the gel cut for LC- MS/MS. c, Enrichment of N- glycosylated SnRK2.3. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in tobacco leaves with 50 \(\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and N- glycosylated SnRK2.3 were enriched with Ni- NTA and ConA beads sequentially. No signal was shown after ConA enrichment (right line). So only Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. His- IP, enrichment of SnRK2.3- His by Ni- NTA; PNGase F, PNGase F digestion. N- SnRK2.3- His, N- glycosylated SnRK2.3- His. d, Coomassie brilliant blue staining after PNGase F digestion of His- antibody enriched SnRK2.3- His. The dashed white frame denotes the gel cut for LC- MS/MS. e, g, i, Coomassie brilliant blue staining after His- antibody enriched SnRK2.3- His. STT3A- mCherry and SnRK2.3- His were transiently co- expressed in BY- 2 cells with \(50\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) and SnRK2.3- His were enriched with Ni- NTA. The dashed white frame denotes the location of SnRK2.3- His. Ni- NTA enriched SnRK2.3 was analyzed for LC- MS/MS. f, h, j, After IP with Ni- NTA, the enrichment was determined by western blot. CK, total protein extract of wide type BY- 2 cells; Input, total protein extract of transgenic BY- 2 cells; His- IP, enrichment of SnRK2.3- His by Ni- NTA. + +<|ref|>sub_title<|/ref|><|det|>[[180, 742, 308, 756]]<|/det|> +## Additional method: + +<|ref|>sub_title<|/ref|><|det|>[[195, 768, 455, 782]]<|/det|> +## Enrichment of N-glycosylated SnRK2.3 + +<|ref|>text<|/ref|><|det|>[[179, 782, 820, 911]]<|/det|> +Plant tissues were grounded to powder in the frozen state and homogenized in extraction buffer (50 mM Tris- HCl, pH 7.4, \(150\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, 5 mM DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with GFP- Trap agarose (Chromotek) or nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(4\mathrm{h}\) , beads were washed five times with ice- cold washing buffer (50 mM Tris- HCl, pH 7.4, \(400\mathrm{mMNaCl}\) , \(1\mathrm{mM}\) MgCl2, \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins were eluted with acidic buffer (200 mM glycine, pH 2.5) and immediately neutralized the eluate fraction with neutralization buffer ( \(100\mathrm{mM}\) Tris- HCl, pH 10.4). The eluted proteins were then incubated with ConA (concanavalin A, a plant lectin can bind to mannose on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 819, 127]]<|/det|> +the glycoproteins) beads (Beyotime) at \(4^{\circ}\mathrm{C}\) , After \(4\mathrm{h}\) , beads were washed five times with washing buffer ( \(20\mathrm{mM}\) Heps, \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl \(_2\) , \(1\mathrm{mM}\) MnCl \(_2\) , \(1\mathrm{mM}\) CaCl \(_2\) , \(0.1\%\) Tween- 20). The proteins were eluted with elution buffer ( \(5\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}8.0\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{M}\) Glucose). + +<|ref|>text<|/ref|><|det|>[[179, 128, 820, 242]]<|/det|> +After treatment with \(50\mu \mathrm{M}\) ABA for 48 hours, BY- 2 cells were collected by centrifugation. Cells were grounded to powder in the frozen state and homogenized in extraction buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(150\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl \(_2\) , \(10\mu \mathrm{M}\) EDTA, \(1\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF). Centrifugation (12,000 rpm, \(10\mathrm{min}\) , \(4^{\circ}\mathrm{C}\) ) was performed and supernatant were incubated with nickel- nitrilotriacetic acid (Ni- NTA) agarose beads (for anti- His) at \(4^{\circ}\mathrm{C}\) . After \(8\mathrm{h}\) , beads were washed five times with ice- cold washing buffer ( \(50\mathrm{mM}\) Tris- HCl, \(\mathrm{pH}7.4\) , \(400\mathrm{mM}\) NaCl, \(1\mathrm{mM}\) MgCl \(_2\) , \(0.02\%\) NP- 40, \(1\times\) protease inhibitor, \(5\mathrm{mM}\) DTT and \(0.5\mathrm{mM}\) PMSF) and the proteins are boiled in boiling water for \(10\mathrm{min}\) after adding \(1\times\) glycoprotein denaturing buffer ( \(0.5\%\) SDS, \(40\mathrm{mM}\) DTT, \(\mathrm{H}_2^{18}\mathrm{O}\) ). + +<|ref|>sub_title<|/ref|><|det|>[[195, 251, 325, 264]]<|/det|> +## PNGase F digestion + +<|ref|>text<|/ref|><|det|>[[179, 265, 820, 336]]<|/det|> +For PNGase F treatment, referring to the manufacturer's protocol, the reaction buffer (containing \(\mathrm{H}_2^{18}\mathrm{O}\) ) and PNGase F (New England Biolabs) were added to sample. The mixture was incubated for \(4\mathrm{h}\) at \(37^{\circ}\mathrm{C}\) before boiled in \(5\times\) SDS loading buffer. N- glycation of SnRK2.3 was detected by immunoblot analyses using by anti- GFP or anti- His antibodies after \(6\%\) SDS- PAGE. The sample was subjected to mass spectrometry detection after immunoblot analyses. + +<|ref|>sub_title<|/ref|><|det|>[[195, 345, 615, 359]]<|/det|> +## LC-MS/MS for identification of N-glycosylation site of SnRK2.3 + +<|ref|>text<|/ref|><|det|>[[179, 360, 820, 589]]<|/det|> +For mass spectrometry analysis, protein samples were separated using SDS- PAGE electrophoresis and detected by coomassie brilliant blue staining. The SDS- PAGE gel at \(70\mathrm{kD}\) or \(40\mathrm{kD}\) was collected into a clean centrifuge tube. \(500\mu \mathrm{l}\) destain solution were added to a centrifuge tube and shaken at room temperature until the gel discolored. After discarding the supernatant, \(75\%\) acetonitrile \((200\mu \mathrm{l})\) were added to the centrifuge tube and shaken at room temperature. After \(30\mathrm{min}\) , \(500\mu \mathrm{l}\) \(\mathrm{H}_2\mathrm{O}\) were added to the centrifuge tube and shaken at room temperature for \(1\mathrm{h}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) \((300\mu \mathrm{l})\) were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After discarding the supernatant, \(50\mathrm{mM}\) \(\mathrm{NH_4HCO_3}\) \((20\mu \mathrm{l})\) and \(2\mu \mathrm{l}\) trypsin \((1\mu \mathrm{g / \mu l}\) , Promega) were added to the centrifuge tube, and gel was crushed. After centrifugation \((1000\mathrm{rpm},1\mathrm{min})\) , the sample was digested at \(37^{\circ}\mathrm{C}\) . After \(8\mathrm{min}\) , \(200\mu \mathrm{l}\) acetonitrile were added to the centrifuge tube and shaken at room temperature for \(5\mathrm{min}\) . After centrifugation \((1000\mathrm{rpm},1\mathrm{min})\) , the supernatant was transferred to a new centrifuge tube. This step was repeated once, ultimately resulting in \(400\mu \mathrm{l}\) supernatant. The obtained supernatant was vacuum dried at \(60^{\circ}\mathrm{C}\) and dissolved in \(0.1\%\) formic acid \((100\mu \mathrm{l})\) . Samples were subjected to mass spectrometry detection by using mass spectrometer (Orbitrap Fusion™ Lumos™ Tribrid™, Thermo Scientific). The N- glycation site of SnRK2.3 was analyzed using software (Proteome Discoverer 2.3). + +<|ref|>sub_title<|/ref|><|det|>[[179, 609, 246, 621]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[179, 626, 819, 677]]<|/det|> +Zielinska, D.F., Gnad, F., Schropp, K., Wisniewski, J.R., and Mann, M. (2012). Mapping N- glycosylation sites across seven evolutionarily distant species reveals a divergent substrate proteome despite a common core machinery. Mol Cell 46, 542- 548. + +<|ref|>text<|/ref|><|det|>[[179, 700, 820, 770]]<|/det|> +The data from 2d suggest that ABA has the same effect as STT3A overexpression? How can this be explained? Do the authors suggest that ABA induces STT3A expression which leads to SnRK2.2/2.3 glycosylation. Is this process specific for SnRK2.2/2.3 or is protein glycosylation generally increased by ABA? + +<|ref|>text<|/ref|><|det|>[[179, 775, 820, 900]]<|/det|> +Reply 15: We thank the reviewer for the valuable comments. We have carefully re- tested the N- glycosylation of SnRK2.2/2.3 transiently expressed in tobacco leaves (Rebuttal Fig. 11). The results showed that the sole STT3A- overexpression did produce obviously N- glycosylated band of SnRK2.2/2.3. However, the sole ABA treatment occasionally or very weakly produced glycosylated SnRK2.2/2.3 which can not be obviously detected in most of our biological replicates (revised Fig. 2d- f, Rebuttal Fig. 11). The reason may be due to no enough NPEs are induced by ABA in tobacco leaves, as ABA- induced N- glycosylation and subcellular dynamics of SnRK2.2/2.3 were mainly + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 123, 820, 175]]<|/det|> +The glycosylation of the transiently expressed His- tagged protein is obviously different from the endogenous protein because the His- tagged protein is fully sensitive to Endo H and PNG F in the presence of ABA. What would be the explanation for this difference? + +<|ref|>text<|/ref|><|det|>[[178, 179, 822, 268]]<|/det|> +Reply 16: We thank the reviewer for the comments. As discussed above, the N- glycosylation and related subcellular dynamics of SnRK2.2/2.3 were mainly found in heterotrophic root tissue, so, we proposed that the sole STT3A- overexpression it can lead to N- glycosylation of SnRK2s, however, the N- glycan can not be further processed to form mature structure in tobacco leaves (Arabidopsis roots can form mature N- glycan). + +<|ref|>text<|/ref|><|det|>[[178, 289, 803, 305]]<|/det|> +Please digest the His- tagged protein co- expressed with STT3A- mCherry also in the absence of ABA. + +<|ref|>text<|/ref|><|det|>[[178, 308, 820, 341]]<|/det|> +Reply 17: We thank the reviewer for the comments. This has been done in revised Fig. 2d,f, and Rebuttal Fig. 13. + +<|ref|>image<|/ref|><|det|>[[262, 365, 704, 450]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[195, 455, 707, 471]]<|/det|> +Rebuttal Fig. 13 N- glycosylation assay of SnRK2.2/2.3 without ABA treatment. + +<|ref|>text<|/ref|><|det|>[[178, 474, 820, 545]]<|/det|> +SnRK2.2- His and SnRK2.3- His were coexpressed with STT3A- mCherry in the tobacco leaves respectively, followed by immunoprecipitation with anti- His antibodies. Endo H and PNG F treatments confirmed that the band shift was due to N- glycosylation. N- SnRK2s- His means N- glycosylated SnRK2s- His. + +<|ref|>text<|/ref|><|det|>[[178, 566, 820, 638]]<|/det|> +In Fig. 2i, the anti- SnRK2.2/2.3/2.6 antibody is used to show glycosylation of the endogenous SnRK2s proteins. This is an important experiment, but not entirely convincing because neither Endo H nor PNG F give a complete shift. Can the authors do the Endo H/PNG F digestion experiment in a glycosylation knockout, for example, in cgl1 plants where all glycans should be sensitive to Endo H and PNG F. + +<|ref|>text<|/ref|><|det|>[[178, 642, 820, 712]]<|/det|> +Reply 18: We thank the reviewer for the comments. As the molecular weights of SnRK2.6 and N- glycosylated SnRK2.2/2.3 are similar to each other, the N- glycosylation assay of endogenous SnRK2.2/2.3 in cgl1 mutant should be carried out in cgl1/snrk2.6 double mutant background. So far, we have no such double mutant yet. + +<|ref|>text<|/ref|><|det|>[[178, 716, 820, 787]]<|/det|> +To answer the reviewer's comment, we expressed SnRK2.3- His in cgl1 hairy root (mediated by Agrobacterium rhizogenes, see method of manuscript). The results showed that the N- glycosylated band of SnRK2.3- His can be fully digested by PNGF and Endo H in cgl1- T background (Rebuttal Fig. 14). + +<|ref|>image<|/ref|><|det|>[[247, 815, 734, 888]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[194, 86, 660, 101]]<|/det|> +## Rebuttal Fig. 14 N-glycosylation assay of SnRK2.3 in Col-0 and cgl1-T. + +<|ref|>text<|/ref|><|det|>[[179, 104, 820, 157]]<|/det|> +SnRK2.3- His were expressed in hair roots of Col- 0 and cgl1- T with ABA treatment, followed by immunoprecipitation with anti- His antibodies. Endo H and PNG F treatments confirmed that the band shift was due to N- glycosylation. N- SnRK2.3- His means N- glycosylated SnRK2.3- His. + +<|ref|>text<|/ref|><|det|>[[179, 179, 820, 231]]<|/det|> +The presence of the PNG F resistant band could be related to fucosylation which takes place in the Golgi and is catalyzed by FUT11. Is there any evidence that SnRK2s are located in the Golgi? In which cellular compartment would FUT11 decorated the SnRK2 glycan with a fucose? + +<|ref|>text<|/ref|><|det|>[[178, 234, 821, 323]]<|/det|> +Reply 19: We thank the reviewer for the comments. The subcellular localization of FUT11's action was proposed mainly in trans- Golgi (Nagashima et al., 2018; Strasser, 2016). In our previous report, TPST (tyrosylprotein sulfotransferase), an integral membrane protein of the trans- Golgi network (Beisswanger et al., 1998), was found to interact with and to sulfate SnRK2s (Wang et al., 2023). + +<|ref|>sub_title<|/ref|><|det|>[[179, 346, 247, 359]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[178, 363, 821, 528]]<|/det|> +Beisswanger, R., Corbeil, D., Vannier, C., Thiele, C., Dohrmann, U., Kellner, R., Ashman, K., Niehrs, C., and Huttner, W.B. (1998). Existence of distinct tyrosylprotein sulfotransferase genes: molecular characterization of tyrosylprotein sulfotransferase- 2. Proc Natl Acad Sci U S A 95, 11134- 11139. Nagashima, Y., von Schaewen, A., and Koiwa, H. (2018). Function of N- glycosylation in plants. Plant Sci 274, 70- 79. Strasser, R. (2016). Plant protein glycosylation. Glycobiology 26, 926- 939. Wang, J., Wang, C., Wang, T., Zhang, S., Yan, K., Yang, G., Wu, C., Zheng, C., and Huang, J. (2023). Tyrosylprotein sulfotransferase suppresses ABAsignaling via sulfation of SnRK2.2/2.3/2.6. J Integr Plant Biol 65, 1846- 1851. + +<|ref|>text<|/ref|><|det|>[[179, 567, 566, 583]]<|/det|> +Please do the same experiment from Fig. 2i also without ABA. + +<|ref|>text<|/ref|><|det|>[[179, 587, 820, 639]]<|/det|> +Reply 20: We thank the reviewer for the comment. Without ABA treatment, the N- glycosylation level of SnRK2.2/2.3 was very low (Fig. 2h), it is hard to do N- glycosylation assay (PNGase F or Endo H digestion). Rebuttal Fig. 15 showed another two replicates of Fig. 2i. + +<|ref|>image<|/ref|><|det|>[[191, 650, 767, 725]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[193, 734, 620, 749]]<|/det|> +Rebuttal Fig. 15 N- glycosylation assay of SnRK2.2/2.3 in snrk2.6. + +<|ref|>text<|/ref|><|det|>[[179, 753, 820, 805]]<|/det|> +Total proteins were extracted from snrk2.6 after treatment with \(50~\mu \mathrm{M}\) ABA for \(48\mathrm{h}\) , followed by \(6\%\) SDS- PAGE separation and detection with the anti- SnRK2.2/2.3/2.6 antibodies. The snrk2.2/2.3/2.6 triple mutant was used as a negative control. + +<|ref|>text<|/ref|><|det|>[[179, 826, 820, 860]]<|/det|> +Does GIIbeta- GFP coexpression also result in the occurrence of the glycosylated band on immunoblots with the His- antibody? What is the proposed molecular function of GIIbeta in the overall process? + +<|ref|>text<|/ref|><|det|>[[179, 864, 820, 898]]<|/det|> +Reply 21: We thank the reviewer for the comments. Based on the current working model of N- glycosylation, GIIβ (also known as α- glucosidases II, GCSII) catalyzes the second outmost glucose + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 213]]<|/det|> +residue after GIIa, which is crucial to formation of mature N- glycan complex of SnRK2s (Nagashima et al., 2018; Strasser, 2016). Our manuscript did not test the SnRK2s' N- glycosylation with GIIβ- coexpression. Instead, we tested it with STT3A which can produce a significant molecular mass difference for glycosylated protein. Like STT3A, GIIβ bound to SnRK2s and affected its subcellular localization in tobacco leaves. However, STT3A overlapped with coexpressed SnRK2 in ER, whereas GIIβ did not. Investigation of SnRK2s glycosylation with GIIβ would also be very interesting, and we will focus on this question in the future. + +<|ref|>text<|/ref|><|det|>[[178, 235, 260, 249]]<|/det|> +Other issues: + +<|ref|>text<|/ref|><|det|>[[178, 252, 821, 323]]<|/det|> +In Fig.2b - please do the same experiment with the N323A protein. No glycosylated SnRK2.2/2.3 band is visible in the blot indicating that GIIbeta does not interact with the glycan on SnRK2.2/2.3. How is this then a glycosylation dependent process? Can the authors purify GIIbeta from the snrk2.6 mutant plants in the presence/absence of ABA and see if glycosylated SnRK2.2/2.3 come along? + +<|ref|>text<|/ref|><|det|>[[178, 326, 820, 397]]<|/det|> +Reply 22: We thank the reviewer for the comment. The interactions between SnRK2.2/2.3 and GIIβ or other NPEs have been discussed in "Reply 6". They bind to SnRK2.2/2.3 with both N- glycan dependent and independent manners. We have provided a pull- down assay with SnRK2.3N323A (Rebuttal Fig. 5 in Reply 6). + +<|ref|>text<|/ref|><|det|>[[178, 419, 504, 435]]<|/det|> +Fig.2f: please do the same experiment without ABA. + +<|ref|>text<|/ref|><|det|>[[194, 439, 300, 452]]<|/det|> +Reply 23: Done. + +<|ref|>text<|/ref|><|det|>[[178, 456, 577, 472]]<|/det|> +Fig 2h: please provide quantitative data from several repetitions. + +<|ref|>text<|/ref|><|det|>[[194, 475, 662, 491]]<|/det|> +Reply 24: Done. Another replicate of Fig. 2h see Rebuttal Fig. 16 below. + +<|ref|>image<|/ref|><|det|>[[194, 513, 535, 597]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[193, 605, 620, 620]]<|/det|> +Rebuttal Fig. 16 N- glycosylation assay of SnRK2.2/2.3 in snrk2.6. + +<|ref|>text<|/ref|><|det|>[[178, 624, 820, 675]]<|/det|> +Total proteins were extracted from snrk2.6 after treatment with \(50~\mu \mathrm{M}\) ABA for different time periods, followed by \(6\%\) SDS- PAGE separation and detection with the anti- SnRK2.2/2.3/2.6 antibodies. The snrk2.2/2.3/2.6 triple mutant was used as a negative control. + +<|ref|>text<|/ref|><|det|>[[178, 697, 820, 749]]<|/det|> +In Fig. 2j the authors state that N323A coexpression disrupts its nuclear export. Why not the opposite - block of nuclear import in by SnRK2.3 expression? Can the authors provide a time series of images showing a transport process? + +<|ref|>text<|/ref|><|det|>[[178, 753, 820, 786]]<|/det|> +Reply 25: We agree with the reviewer and We have revised the Fig. 2j legend and main text in line 192- 197. + +<|ref|>text<|/ref|><|det|>[[178, 809, 568, 824]]<|/det|> +Extended data Fig.5a: do the same with GST- SnRK2.3- N323A + +<|ref|>text<|/ref|><|det|>[[178, 828, 820, 879]]<|/det|> +Reply 26: We thank the reviewer for the comment. We have re- done the pull- down assay with SnRK2.3N323A in Rebuttal Fig. 5 in reply 6. The results also showed the interaction between SnRK2.3N323A and GIIβ. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 821, 157]]<|/det|> +Extended data Fig.9c: show a time course experiment in the snrk2.6 background with anti- SnRK2.2/2.3/2.6 antibody for comparison. To see also if the glycosylated band increases with prolonged ABA incubation. Based on Extended Data Fig. 1f one would expect the highest STT3a expression after 6 h of ABA treatment and this should correlate with the increase of N- glycosylated SnRK2.2/2.3. + +<|ref|>text<|/ref|><|det|>[[178, 160, 821, 232]]<|/det|> +Reply 27: We thank the reviewer for the comment. A time course expression pattern of endogenous N- glycosylated SnRK2.2/2.3 has been done in snrk2.6 background, and the results showed that a gradual increase of N- glycosylated SnRK2.2/2.3 after 6 h during prolonged ABA treatment (revised Fig. 2h). + +<|ref|>text<|/ref|><|det|>[[178, 253, 258, 268]]<|/det|> +Minor point: + +<|ref|>text<|/ref|><|det|>[[178, 271, 821, 323]]<|/det|> +The term N- glucosidase is not correct in the description of the glycosylated related enzymes. Some of the characterized proteins are transferases (STT3A, CGL1, FUT11) others are glycosidases (GMII) and only GIIalpha and beta are glucosidases. + +<|ref|>text<|/ref|><|det|>[[178, 326, 821, 415]]<|/det|> +Reply 28: We thank the reviewer for the valuable comment. As the enzymes of N- glycosylation pathway used in our study include oligosaccharide transferase (STT3A), glucosidase (GIIα, and GIIβ), acetylglucosaminyltransferase (CGL1), mannosidase (GMII), and fucosyltransferase (FUT). The term "N- glucosidases" can not represent all these enzymes. So we have replaced "N- glucosidases" with "NPEs" (N- glycan processing enzymes) in the revised manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 393, 161]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 203, 757, 220]]<|/det|> +All my concerns have been addressed in the revision. I have no more concerns this time. + +<|ref|>text<|/ref|><|det|>[[115, 289, 393, 305]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 345, 875, 381]]<|/det|> +The authors have addressed most of my questions; however, I still have lingering concerns regarding the data presented in both the manuscript and the response to reviewers. + +<|ref|>text<|/ref|><|det|>[[114, 392, 877, 555]]<|/det|> +1 As previously mentioned, my primary concern lies in the notably high concentration of ABA used in the germination assay. In the rebuttal Fig. 2, the authors demonstrate that all tested varieties could germinate in 2- 3 days, even on the medium containing 3 or \(5 \mu M\) ABA. It is essential to note that even \(1.0 \mu M\) ABA is a concentration known to almost totally inhibit seed germination in the Col- 0 wild type. Fuji et al. (2007) used \(0.6 \mu M\) ABA in their assay of the snrk2.2snrk2.3 double mutant (Plant Cell, 2007). For reference, please consult Fujita et al., 2009, Plant Cell Physiol; Fuji et al., 2009, PNAS; Gonzalez- Guzman et al., Plant Cell, 2012, etc. I recommend that the authors double- check the chemical concentrations used and ensure that the related results presented in the manuscript are accurate to avoid any potential misinterpretation in this field. + +<|ref|>text<|/ref|><|det|>[[115, 566, 865, 638]]<|/det|> +2 Another concern relates to the SnRK2.2/3/6 antibody used in Figure 2B and Rebuttal Fig. 4. Although we routinely use this antibody, I have not observed its ability to distinguish SnRK2.6 from SnRK2.2 and SnRK2.3. Please provide the unaltered image in response to the reviewers' comments and include supplementary materials for clarity. + +<|ref|>text<|/ref|><|det|>[[115, 649, 880, 740]]<|/det|> +3 I concur with reviewer 4 regarding the LC- MS/MS identification of N323 glycosylation, which is crucial to this manuscript. The authors reported the failure to detect this glycosylation in more than five LC- MS/MS assays, explaining that only a tiny amount of SnRK2.3 proteins undergo S- glycosylation. However, it remains unclear how the authors can demonstrate that such a small portion of glycosylated SnRK2.3 significantly contributes to the desensitization of ABA. + +<|ref|>text<|/ref|><|det|>[[115, 752, 875, 805]]<|/det|> +Actually, almost all reviewers questioned the importance or the exact role of the glycosylation of SnRK2.2/2.3 in ABA and stress signaling, if indeed it exists, which is not fully addressed by the authors in this revision. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 392, 107]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 146, 818, 182]]<|/det|> +The authors have made a lot of effort to improve the manuscript. They have provided additional experimental data and most of my main points have been answered. + +<|ref|>text<|/ref|><|det|>[[115, 221, 860, 275]]<|/det|> +There are still a number of open questions related to the glycosylation of SnRKs and ER localisation or uptake from the nucleus/cytosol that need to be answered. However, this is something that should be addressed in future studies. + +<|ref|>text<|/ref|><|det|>[[115, 315, 508, 332]]<|/det|> +The story is of great interest and should be published. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 828, 120]]<|/det|> +We would like to thank all the reviewers for their insightful comments and suggestions and for encouraging us to improve our manuscript. + +<|ref|>text<|/ref|><|det|>[[149, 142, 316, 156]]<|/det|> +Reviewer's Comments: + +<|ref|>sub_title<|/ref|><|det|>[[150, 160, 435, 175]]<|/det|> +## Reviewer #2 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[163, 179, 790, 194]]<|/det|> +All my concerns have been addressed in the revision. I have no more concerns this time. + +<|ref|>text<|/ref|><|det|>[[163, 198, 655, 212]]<|/det|> +We thank the reviewer for the positive evaluation of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[150, 234, 435, 249]]<|/det|> +## Reviewer #3 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[147, 252, 840, 470]]<|/det|> +The authors have addressed most of my questions; however, I still have lingering concerns regarding the data presented in both the manuscript and the response to reviewers. 1. As previously mentioned, my primary concern lies in the notably high concentration of ABA used in the germination assay. In the rebuttal Fig. 2, the authors demonstrate that all tested varieties could germinate in 2- 3 days, even on the medium containing 3 or \(5\mu \mathrm{M}\) ABA. It is essential to note that even \(1.0\mu \mathrm{M}\) ABA is a concentration known to almost totally inhibit seed germination in the Col- 0 wild type. Fuji et al. (2007) used \(0.6\mu \mathrm{M}\) ABA in their assay of the snrk2.2snrk2.3 double mutant (Plant Cell, 2007). For reference, please consult Fujita et al., 2009, Plant Cell Physiol; Fuji et al., 2009, PNAS; Gonzalez- Guzman et al., Plant Cell, 2012, etc. I recommend that the authors double- check the chemical concentrations used and ensure that the related results presented in the manuscript are accurate to avoid any potential misinterpretation in this field. + +<|ref|>text<|/ref|><|det|>[[147, 474, 849, 695]]<|/det|> +We thank the reviewer for careful evaluation. We agree with the reviewer that Arabidopsis is more sensitive to exogenous ABA treatment during seed germination than during vegetative growth. In general, high concentrations of ABA, such as \(50\mu \mathrm{M}\) ABA (Fujii et al., 2007) \(^1\) , have been used to inhibit seedling growth (Fujita et al., 2009; Fujii and Zhu, 2009) \(^2,3\) , whereas even \(0.6\mu \mathrm{M}\) ABA can well suppress seed germination as suggested by the reviewer. Our results showed a higher germination rate at high ABA application, which may be due to the different experimental conditions used in our experiments compared to the publications. For example, it was reported (Fujii and Zhu, 2009) \(^2\) that seeds were plated on MS medium without sucrose for germination (with \(1.5\%\) sucrose applied in our experiment). In fact, most of the germinated seeds with high concentration of ABA in our tests have very small radicles and grow slowly and weakly. In our future work we would be very careful to choose a lower concentration of ABA for seed germination analysis. + +<|ref|>text<|/ref|><|det|>[[148, 705, 820, 777]]<|/det|> +2. Another concern relates to the SnRK2.2/3/6 antibody used in Figure 2B and Rebuttal Fig. 4. Although we routinely use this antibody, I have not observed its ability to distinguish SnRK2.6 from SnRK2.2 and SnRK2.3. Please provide the unaltered image in response to the reviewers' comments and include supplementary materials for clarity. + +<|ref|>text<|/ref|><|det|>[[148, 780, 852, 906]]<|/det|> +We thank the reviewer for comments. It is really hard to distinguish SnRK2.6 from SnRK2.2/2.3 in most cases because they are very close in molecular weight. In our work, we validated the specificity of the SnRK2.2/2.3/2.6 antibody with Col- 0, snrk2.6, snrk2.2/2.3, and snrk2.2/2.3/2.6 triple mutant, and the results showed that it can produce two close bands for SnRK2.6 and SnRK2.2/2.3 in Col- 0 compared to mutants (better distinguishable in Rebuttal Fig. 17a, but they are very close in Rebuttal Fig. 17b), as tested by the manufacturer Agrisera (Rebuttal Fig. 1c, from Agrisera website). To make it easier to distinguish between the two bands, we run the gel for a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 86, 850, 156]]<|/det|> +longer time (until 35 kD protein band is almost out of the gel), and cut the gel to remove proteins larger than 55 kD (Rebuttal Fig. 17d, e), as a huge amount of 55 kD bands make the SnRK2 bands very weak (Rebuttal Fig. 17a). The Rebuttal Fig. 17 d and e showed the unaltered images (after gel cut) for Rebuttal Fig. 4 and Figure 2b respectively. + +<|ref|>image<|/ref|><|det|>[[164, 156, 822, 900]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[164, 86, 636, 101]]<|/det|> +## Rebuttal Fig. 17 The SnRK2.2/2.3/2.6 antibody used in our study. + +<|ref|>text<|/ref|><|det|>[[147, 104, 851, 194]]<|/det|> +a- b. The 7- day seedlings of Col- 0, snrk2.6 mutant, snrk2.2/2.3 double mutant, and snrk2.2/2.3/2.6 triple mutant were used here. Total protein extracted with SDS buffer was separated on \(10\%\) SDS- PAGE. The blot was incubated with the primary antibody (anti- SnRK2.2/2.3/2.6, Agrisera, AS142783). a and b show two biological replicates. a, replicate 1; b, replicate 2; bottom of b, upper figure merged with protein ladder. + +<|ref|>text<|/ref|><|det|>[[147, 197, 850, 230]]<|/det|> +c. WB result from the manufacturer. From the website (https://www.agrisera.com/en/artiklar/srk-ser-thr-protein-kinase-snrk.html). + +<|ref|>text<|/ref|><|det|>[[147, 234, 850, 286]]<|/det|> +d. Unaltered image of Rebuttal Fig. 4. From top to bottom: image without protein ladder, the same image with protein ladder, excision of \(55\mathrm{kD}\) miscellaneous bands without protein ladder, and excision of \(55\mathrm{kD}\) miscellaneous bands with protein ladder. + +<|ref|>text<|/ref|><|det|>[[164, 290, 390, 304]]<|/det|> +e. The unaltered image of Fig.2b. + +<|ref|>text<|/ref|><|det|>[[150, 308, 848, 342]]<|/det|> +The red triangle indicates the SnRK2.6 band, and the black triangle indicates the SnRK2.2/2.3 band. There are some other unrelated samples in d and e. + +<|ref|>text<|/ref|><|det|>[[147, 362, 844, 453]]<|/det|> +3. concur with reviewer 4 regarding the LC-MS/MS identification of N323 glycosylation, which is crucial to this manuscript. The authors reported the failure to detect this glycosylation in more than five LC-MS/MS assays, explaining that only a tiny amount of SnRK2.3 proteins undergo N-glycosylation. However, it remains unclear how the authors can demonstrate that such a small portion of glycosylated SnRK2.3 significantly contributes to the desensitization of ABA. + +<|ref|>text<|/ref|><|det|>[[147, 455, 829, 508]]<|/det|> +Actually, almost all reviewers questioned the importance or the exact role of the glycosylation of SnRK2.2/2.3 in ABA and stress signaling, if indeed it exists, which is not fully addressed by the authors in this revision. + +<|ref|>text<|/ref|><|det|>[[147, 511, 850, 675]]<|/det|> +We thank the reviewer for the valuable comments. We agree with the reviewer that the confirmation of SnRK2.3N323 glycosylation by LC- MS/MC is important, and we will do it by trial and error in the future. We believe that our manuscript provides strong evidence for the N- glycosylation of SnRK2.2/2.3. Our manuscript determined the N- glycosylation of SnRK2.2/2.3 in tobacco leaves and Arabidopsis (Fig. 2d- i) using "band shift assays followed by PNGase F and Endo H digestions", which is a classical method widely used to identify N- glycosylation 4-15. Furthermore, our manuscript identified the N323 N- glycosylation site within a total of 11 point mutations of asparagine residues in SnRK2.3 (Fig. 2j, and Extended Data Fig. 6), and reconfirmed the N323 N- glycosylation site with "band shift assay" (Fig. 2k). + +<|ref|>text<|/ref|><|det|>[[147, 678, 850, 879]]<|/det|> +Regarding the question "small portion of glycosylation of SnRK2.3, big roles", on the one hand, our results showed that only a small part of SnRK2.2/2.3 are N- glycosylated in transiently expressed tobacco leaves (Fig. 2d- f, k) and in Arabidopsis (even treated with 50 ABA for 48 h, Fig. 2h, i). On the other hand, we provided strong evidence for the significant role of N- glycosylation in the desensitization of ABA transcriptional response (Fig. 1f- k, Fig. 3i, j, and Extended Data Fig 3, 4), the positive regulation of high- salt adaptation (Extended Data Fig. 9f- m), the positive function in the subcellular dynamics of SnRK2.2/2.3 (Fig. 3a- h, Extended Data Fig. 10), and the crucial role in the regulation of NADPH and \(\mathrm{H}_2\mathrm{O}_2\) homeostasis (Fig. 4, Extended Data Fig. 15, 16). However, the molecular mechanism underlying the question "small portion of glycosylation of SnRK2.3, big roles" remains unclear as suggested by the reviewer. The small proportion of N- glycosylation of SnRK2.2/2.3 indicates that N- glycosylated SnRK2.2/2.3 may act as an inducer of its peroxisomal + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 86, 850, 120]]<|/det|> +localisation, and more SnRK2.2/2.3 may be directly recruited from the cytosol to the peroxisomal membrane by the inducer. + +<|ref|>text<|/ref|><|det|>[[148, 123, 852, 268]]<|/det|> +Although our manuscript provided strong evidence for the N- glycosylation of SnRK2.2/2.3, and its important role in ABA signalling, there are still some open questions in this field to be answered, as suggested by the reviewer #3 and #4. (1) How SnRK2.2/2.3, as non- secretory proteins, are transported into the ER lumen for N- glycosylation; (2) How SnRK2.2/2.3 are redistributed from the ER to the peroxisomes; (3) whether all the peroxisomal SnRK2.2/2.3 are transported from ER, or whether some of them are recruited directly from the cytosol as hypothesised above. These questions are very interesting and worthy of further investigation, and we will do our best to address them in the future. + +<|ref|>sub_title<|/ref|><|det|>[[150, 290, 434, 306]]<|/det|> +## Reviewer #4 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[149, 326, 848, 361]]<|/det|> +The authors have made a lot of effort to improve the manuscript. They have provided additional experimental data and most of my main points have been answered. + +<|ref|>text<|/ref|><|det|>[[149, 363, 792, 416]]<|/det|> +There are still a number of open questions related to the glycosylation of SnRKs and ER localisation or uptake from the nucleus/cytosol that need to be answered. However, this is something that should be addressed in future studies. + +<|ref|>text<|/ref|><|det|>[[166, 419, 546, 435]]<|/det|> +The story is of great interest and should be published. + +<|ref|>text<|/ref|><|det|>[[165, 438, 655, 453]]<|/det|> +We thank the reviewer for the positive evaluation of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[148, 482, 231, 496]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[147, 507, 846, 911]]<|/det|> +1 Fujii, H., Versluus, P. E. & Zhu, J.- K. Identification of Two Protein Kinases Required for Abscisic Acid Regulation of Seed Germination, Root Growth, and Gene Expression in Arabidopsis. The Plant Cell 19, 485- 494, doi:10.1105/tpc.106.048538 (2007). 2 Fujii, H. & Zhu, J.- K. Arabidopsis mutant deficient in 3 abscisic acid- activated protein kinases reveals critical roles in growth, reproduction, and stress. Proceedings of the National Academy of Sciences 106, 8380- 8385, doi:10.1073/pnas.0903144106 (2009). 3 Fujita, Y. et al. Three SnRK2 Protein Kinases are the Main Positive Regulators of Abscisic Acid Signaling in Response to Water Stress in Arabidopsis. Plant and Cell Physiology 50, 2123- 2132, doi:10.1093/pcp/pcp147 (2009). 4 Ruiz- Canada, C., Kelleher, D. J. & Gilmore, R. Cotranslational and Posttranslational N- Glycosylation of Polypeptides by Distinct Mammalian OST Isoforms. Cell 136, 272- 283, doi:10.1016/j.cell.2008.11.047 (2009). 5 Tsachaki, M. et al. Glycosylation of BRI2 on asparagine 170 is involved in its trafficking to the cell surface but not in its processing by furin or ADAM10. Glycobiology 21, 1382- 1388, doi:10.1093/glycob/cwr097 (2011). 6 Sato, T. et al. STT3B- Dependent Posttranslational N- Glycosylation as a Surveillance System for Secretory Protein. Molecular Cell 47, 99- 110, doi:10.1016/j.molcel.2012.04.015 (2012). 7 Chen, X.- L. et al. N- Glycosylation of Effector Proteins by an \(\alpha - 1,3-\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 85, 843, 620]]<|/det|> +Mannosyltransferase Is Required for the Rice Blast Fungus to Evade Host Innate Immunity. The Plant Cell 26, 1360- 1376, doi:10.1105/tpc.114.123588 (2014). Yamamoto, M., Tantikanjana, T., Nishio, T., Nasrallah, M. E. & Nasrallah, J. B. Site- Specific- Glycosylation of the S- Locus Receptor Kinase and Its Role in the Self- Incompatibility Response of the Brassicaceae. Plant Cell 26, 4749- 4762, doi:10.1105/tpc.114.131987 (2014). Shen, J., Ding, Y., Gao, C., Rojo, E. & Jiang, L. N- linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. The Plant Journal 80, 977- 992, doi:10.1111/tpj.12696 (2014). Voss, M. et al. Shedding of glycan - modifying enzymes by signal peptide peptidase - like 3 (SPPL3) regulates cellular N - glycosylation. The EMBO Journal 33, 2890- 2905, doi:10.15252/embj.201488375 (2014). Liu, Y. D. et al. EBS7 is a plant- specific component of a highly conserved endoplasmic reticulum- associated degradation system in. P Nat1 Acad Sci USA 112, 12205- 12210, doi:10.1073/pnas.1511724112 (2015). Stevens, K. L. P. et al. Diminished Ost3- dependent N- glycosylation of the BiP nucleotide exchange factor Sill is an adaptive response to reductive ER stress. P Nat1 Acad Sci USA 114, 12489- 12494, doi:10.1073/pnas.1705641114 (2017). Wang, H. et al. N- glycosylation in the protease domain of trypsin- like serine proteases mediates calnexin- assisted protein folding. eLife 7, doi:10.7554/eLife.35672 (2018). Phoomak, C. et al. The translocon- associated protein (TRAP) complex regulates quality control of N- linked glycosylation during ER stress. Science Advances 7, doi:10.1126/sciadv.abc6364 (2021). de la Morena- Barrio, M. E. et al. Two SERPINC1 variants affecting N- glycosylation of Asn224 cause severe thrombophilia not detected by functional assays. Blood 140, 140- 151, doi:10.1182/blood.2021014708 (2022). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 300, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 147, 392, 163]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 203, 860, 257]]<|/det|> +The authors responded to my comments as much as possible, and I have no more concerns about this manuscript. I agree with reviewer 4 that the remaining open questions could be addressed in future studies. In my opinion, the current version is ready to publish in Nature Communications. + +<--- Page Split ---> diff --git a/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/images_list.json b/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..34ad5d05b436857cde88718ec5dad4ea5aa110f5 --- /dev/null +++ b/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,174 @@ + +# nature portfolio + +Peer Review File + +CD4 expression in effector T cells depends on DNA demethylation over a developmentally established stimulus- responsive element + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this manuscript Teghanemt and colleagues present a detailed and compelling story involving developmental epigenetic programming of the Cd4 locus that maintains CD4 expression in effector CD4 T cells. The data support a model in which H3K4me3 blocks de novo DNA methylation at critical CREs in the Cd4 locus to maintain CD4 expression. The molecular work is elegant, and demonstrating using cutting- edge in vivo technologies is impactful. I have only a few relatively minor comments: + +1) The authors state, "our study provides one of the very few demonstrations of the potential for early epigenetically transmitted transcriptional programs that have significant relevance for T cell physiology post-developmentally." While I agree that it is important to conceptually link developmental with maintenance steady state biology, as this study does, there are numerous examples of these phenomena in T cell subsets. I would soften the language here. +2) I applaud the authors for testing their mechanisms in an integrated in vivo model, but it is not clear that Leshmaniasis represents the best choice given the relatively unimpressive readouts in Fig 6A-C. I would recommend complementing this in vivo model with some straightforward classic T cell skewing assays in vitro, for example Th2, Th17, and iTreg induction using naive CD4 T cells from the Cd4E4mD/D and E4aD/D mice. +3) Figure 7 seems tacked on or at least out of place. I would consider moving this figure to the supplement. +4) In the Discussion the authors may want to review the mechanisms demonstrated in Nat Genet. 2020 Jun;52(6):615-625. + +Reviewer #2 (Remarks to the Author): + +This is an elegant study showing that DNA demethylation during thymic development is critical for the licensing of, E4a, a novel stimulus- responsive cis- regulatory element (CRE) that serves to maintain CD4 gene expression in effector T cells. E4a and E4m act in concert to maintain transcriptional activity at the CD4 locus and, thereby, prevent de novo DNA methylation during CD4 T cell proliferation. In absence of thymic demethylation, the authors find that E4a and E4m are less active and CD4 downregulation ensues upon T cell proliferation. Strikingly, this downregulation leads to impaired Th1 differentiation and reduced control of Leishmania infection. This reviewer lacks expertise with respect to the technical validity of some of the assays used by the authors for investigating epigenetic regulation. Still, the experiments appear to be overall very well performed and the conclusions drawn seem valid. In the eyes of this reviewer, the finding that infection control is substantially reduced by joint deletion of E4a and E4m is exciting, as is the association to the Th1 phenotype. And, at least to my knowledge, nothing comparable has been previously shown. + +Major Concern: + +From an immunological point of view, I think this manuscript would benefit from an additional evaluation of Th2 differentiation and of TCR binding strength to peptide MHCII complexes in E4a/E4m- deficient vs. WT mice. + +The Th1/Th2 topic could be tackled via an in vitro differentiation assay using presentation of actual peptide- MHCII complexes for stimulation (and not CD3) or by using a Th2 infection model in addition to the Th1- controlled Leishmania model or by asking, whether during Leishmania infection there is suddenly aberrant Th2- cytokine production. + +The binding strength topic could be investigated (at least roughly) by measuring functional avidity through peptide titration upon T cell restitution in the Leishmania system and then calculating an EC50 for IFNg secretion, or in absence of this cytokine of CD107 degranulation of of CD69 upregulation. + +The concept to be tested would be: Does CD4 downregulation reduce TCR binding strength to peptide MHCII complexes and, thereby, favor Th2 vs. Th1 differentiation. See e.g. (Van Panhuys et al., 2014). + +Van Panhuys, N., Klauschen, F., and Germain, R.N. (2014). T- cell- receptor- dependent signal intensity dominantly controls CD4(+) T cell polarization In Vivo. Immunity 41, 63- 74. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +It is not uncommon to hear the term epigenetic regulation of gene expression used to describe chromatin effects on gene activity. Yet, epigenetic effects typically imply an inducible change in the activation or repression of a gene that can be heritably and stably transmitted across the space and time of cell division and cell migration; often transcending the inductive signal itself. How such signaling behaviors are remembered through development, especially in mobile cells, has remained obscure. Teghanemt et al. demonstrate that a cis- acting regulatory element of the Cd4 locus undergoes programmed demethylation during thymic development of \(\mathrm{CD4 + }\) T cells. The primary function of this inductive event in the thymus is to pre- configure a permissive chromatin landscape such that the cellular descendants of a naive CD4 T cell maintain gene activity and function after the naive cell's cell's bona fide antigen activation and the subsequent dispatch of those daughter cells to peripheral tissues. The novel cis- acting regulatory element (E4a) works in concert with with a developmentally important cis- acting regulatory element (E4m) to heritably maintain CD4 expression in the descendant of the antigen- activated naive T cell. Mechanistically, the authors demonstrate that TET1/3 induces the DNA demethylation in the thymus and without this developmental activation, peripheral CD4 T cells undergo de novo methylation and silencing of the Cd4 locus during their post- antigen- activation cell divisions. The data quality is excellent and the conclusions are supported by the results. This study will be an important new paradigm in understanding epigenetic gene regulation. + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +In this manuscript Teghanemt and colleagues present a detailed and compelling story involving developmental epigenetic programming of the Cd4 locus that maintains CD4 expression in effector CD4 T cells. The data support a model in which H3K4me3 blocks de novo DNA methylation at critical CREs in the Cd4 locus to maintain CD4 expression. The molecular work is elegant, and demonstrating using cutting- edge in vivo technologies is impactful. I have only a few relatively minor comments: + +## Response: + +We thank the reviewer for the positive feedback on our work. + +1) The authors state, "our study provides one of the very few demonstrations of the potential for early epigenetically transmitted transcriptional programs that have significant relevance for T cell physiology post-developmentally." While I agree that it is important to conceptually link developmental with maintenance steady state biology, as this study does, there are numerous examples of these phenomena in T cell subsets. I would soften the language here. + +## Response: + +In response to the reviewer's comment, we have edited the aforementioned statement to read as "our study provides a mechanistic demonstration of the potential for early epigenetically transmitted transcriptional programs that have significant relevance for T cell physiology post-developmentally". + +2) I applaud the authors for testing their mechanisms in an integrated in vivo model, but it is not clear that Leishmaniasis represents the best choice given the relatively unimpressive readouts in Fig 6A-C. I would recommend complementing this in vivo model with some straightforward classic T cell skewing assays in vitro, for example Th2, Th17, and iTreg induction using naive CD4 T cells from the Cd4E4mD/D and E4aD/D mice. + +## Response: + +We are thankful for the reviewer's suggestion. Given that in vitro T cell skewing assays require the use of anti- CD3/anti- CD28- mediated TCR activation and bypass CD4 co- engagement, we did not anticipate any differences between WT and E4a nor E4a/E4m- deficient T cells when driven to differentiate into T helper subsets. Nonetheless, in the event of an unexpected contribution for CD4 in that system, we have performed such assays but did not find any differences in Th1, Th2, Treg nor Th17 differentiation, as assessed by master transcription factor expression of the respective lineages. To keep our study focused, we have only included Th1 and Th2 differentiation results in the manuscript (Supplementary Fig. 6j, k). Moreover, in addition to the Leishmaniasis + +<--- Page Split ---> + +system, we have now included a second model of Th1 differentiation using an acute viral pathogen (LCMV Armstrong), which triggers a robust Th1 effector response (Supplementary Fig. 6f), and uncovered a similar defect in Th1 differentiation (Supplementary Fig. 6g), as observed in the Leishmaniasis system. Together, we hope the reviewer's concerns are adequately addressed. + +3) Figure 7 seems tacked on or at least out of place. I would consider moving this figure to the supplement. + +## Response: + +We believe that Figure 7, together with Supplementary Figure 7, extend the idea that many genes in \(\mathrm{CD4^{+}}\) T cells, beyond the dissected example of the \(\mathrm{Cd4}\) gene, undergo similar patterns of regulation during thymic development and is relevant to the general audience. We strongly believe that it adds significant value to our working paradigm and moving this entire figure to a supplementary will be a pity as it may be overlooked by the readership. + +4) In the Discussion the authors may want to review the mechanisms demonstrated in Nat Genet. 2020 Jun;52(6):615-625. + +## Response: + +We sincerely thank the reviewer for bringing our attention to this elegant work and agree that the mechanisms proposed are highly relevant and compatible with our working model that H3K4me3 does not dictate coding gene transcription per say but has an instructional role in preventing repression of gene expression via DNA methylation. We have now included this reference to our discussion in the manuscript. + +## Reviewer #2 (Remarks to the Author): + +This is an elegant study showing that DNA demethylation during thymic development is critical for the licensing of, E4a, a novel stimulus- responsive cis- regulatory element (CRE) that serves to maintain CD4 gene expression in effector T cells. E4a and E4m act in concert to maintain transcriptional activity at the CD4 locus and, thereby, prevent de novo DNA methylation during CD4 T cell proliferation. In absence of thymic demethylation, the authors find that E4a and E4m are less active and CD4 downregulation ensues upon T cell proliferation. Strikingly, this downregulation leads to impaired Th1 differentiation and reduced control of Leishmania infection. + +This reviewer lacks expertise with respect to the technical validity of some of the assays used by the authors for investigating epigenetic regulation. Still, the experiments appear to be overall very well performed and the conclusions drawn seem valid. In the eyes of this reviewer, the finding that infection control is + +<--- Page Split ---> + +substantially reduced by joint deletion of E4a and E4m is exciting, as is the association to the Th1 phenotype. And, at least to my knowledge, nothing comparable has been previously shown. + +## Response: + +We thank the reviewer for the positive feedback on our work. + +## Major Concern: + +From an immunological point of view, I think this manuscript would benefit from an additional evaluation of Th2 differentiation and of TCR binding strength to peptide MHCI complexes in E4a/E4m- deficient vs. WT mice. + +The Th1/Th2 topic could be tackled via an in vitro differentiation assay using presentation of actual peptide- MHCI complexes for stimulation (and not CD3) or by using a Th2 infection model in addition to the Th1- controlled Leishmania model or by asking, whether during Leishmania infection there is suddenly aberrant Th2- cytokine production. + +The binding strength topic could be investigated (at least roughly) by measuring functional avidity through peptide titration upon T cell restitution in the Leishmania system and then calculating an EC50 for IFNg secretion, or in absence of this cytokine of CD107 degranulation of of CD69 upregulation. The concept to be tested would be: Does CD4 downregulation reduce TCR binding strength to peptide MHCI complexes and, thereby, favor Th2 vs. Th1 differentiation. See e.g. (Van Panhuys et al., 2014). Van Panhuys, N., Klauschen, F., and Germain, R.N. (2014). T- cell- receptor- dependent signal intensity dominantly controls CD4(+) T cell polarization In Vivo. Immunity 41, 63- 74. + +## Response: + +We thank the reviewer for the questions posed and recommendations to tackle them. We wanted to evaluate the consequences of reduced CD4 expression on TCR binding and downstream signaling, to support the presented evidence that TCR signaling strength is decreased in antigen- experienced E4a/E4m- deficient T cells during Leishmaniasis, by virtue of CD5 and Nur77 expression levels. However, in the absence of a transgenic system (e.g. an OTII- TCR Tg system), it is challenging to test the question of functional avidity directly. Using such an in vitro TCR Tg system is best suited for robust conclusions because we would be able to a) bypass any differences in helper T cell differentiation that happens between WT and E4a/E4m- deficient mice during infection b) then specifically assess the contribution of CD4 expression on functional avidity through peptide titration and assess an EC50 value for cytokine responses such as IL- 2. We were not successful in establishing a reliable dose- response using crude soluble leishmania antigen (SLA) extracts in a WT setting, as the + +<--- Page Split ---> + +response was too variable, highlighting the need for defined antigen epitopes and specific TCR strategies. + +Nevertheless, we have addressed some aspects of the questions raised using a different approach. We have challenged E4a/E4m- deficient and WT mice with an LCMV Armstrong strain, which induces an acute Th1 CD4 response in addition to a cytotoxic CD8 response. We chose to do so because of the well- characterized expansion of a dominant MHC- Class II- restricted (IA \(^{\mathsf{b}}\) - restricted) CD4 T cell clone (SMARTA- TCR) that recognizes a specific LCMV glycoprotein epitope GP 61- 80. Using tetramer tools (GP 66- 77) and a peptide specific to this TCR clone to then engage stimulation, we were then able to ask a) does reduced CD4 expression result in a compromised ability to bind to antigen b) is there an impact on Th1 differentiation c) is there a diversion to a Th2 response. To summarize, we found that while a reduction in CD4 expression did not significantly impair the ability of CD4 T cells to bind to GP66- 77 tetramers, a complete loss of CD4 expression had a modest but significant impact (Fig. 6i, j, k). We found a significant reduction in Tbet \(^+\) CD4 \(^+\) T cells in LCMV- infected E4a/E4m- deficient mice but no significant increase in Gata3 \(^+\) CD4 \(^+\) T cells (Supplementary Fig. 6g, h). Accordingly, E4m/E4a- deficient antigen- experienced CD4 \(^+\) T cells mounted a less robust IFN- g response upon antigen re- stimulation (Fig. 6i) but we detected no significant IL- 4 production (data not shown). Together, these findings indicate that reduced TCR signaling mediated via CD4 impairs Th1 differentiation but does not result in preferential Th2 differentiation and are in agreement with our findings in the Leishmaniasis model, where we did not observe an increase in Gata3 \(^+\) T cells nor an increase in IL- 4 production in the footpads (Supplementary Fig. 6b, d, e). + +These results may highlight important differences in modulating TCR signaling via alterations in CD4 levels (which in our model is mostly affected during T cell replication) versus pMHC density as demonstrated by Van Panhuys et al., 2014 and/or other environmental/ cellular factors. We agree that it would be exciting to test whether CD4 expression has an impact on Th2 differentiation in the context of a Th2- dominant infection model. However, we hope the reviewer agrees this merit a future study. + +## Reviewer #3 (Remarks to the Author): + +It is not uncommon to hear the term epigenetic regulation of gene expression used to describe chromatin effects on gene activity. Yet, epigenetic effects typically imply an inducible change in the activation or repression of a gene that can be heritably and stably transmitted across the space and time of cell division and cell migration; often transcending the inductive signal itself. How such signaling behaviors are remembered through development, especially in mobile cells, has remained obscure. Teghanemt et al. demonstrate that a cis- acting regulatory element of the Cd4 locus undergoes programmed demethylation during thymic development of CD4 \(^+\) T cells. The primary function of this inductive event in the thymus is to pre- configure a permissive chromatin landscape such + +<--- Page Split ---> + +that the cellular descendants of a naive CD4 T cell maintain gene activity and function after the naive cell's cell's bona fide antigen activation and the subsequent dispatch of those daughter cells to peripheral tissues. The novel cis- acting regulatory element (E4a) works in concert with with a developmentally important cis- acting regulatory element (E4m) to heritably maintain CD4 expression in the descendant of the antigen- activated naive T cell. Mechanistically, the authors demonstrate that TET1/3 induces the DNA demethylation in the thymus and without this developmental activation, peripheral CD4 T cells undergo de novo methylation and silencing of the Cd4 locus during their post- antigen- activation cell divisions. The data quality is excellent and the conclusions are supported by the results. This study will be an important new paradigm in understanding epigenetic gene regulation. + +## Response: + +We are sincerely thankful to the reviewer for the positive and insightful remarks on our work. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have satisfactorily addressed my comments. I congratulate the team on a beautiful paper. + +Reviewer #2 (Remarks to the Author): + +The authors have sufficiently addressed my concerns. I do not have any further comments. + +Reviewer #3 (Remarks to the Author): + +All 3 reviewers acknowledged the elegance and importance of this study and the revised manuscript has been highly responsive to the critiques. This will be an important contribution to the field. + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +The authors have satisfactorily addressed my comments. I congratulate the team on a beautiful paper. + +## Response: + +We thank the reviewer for their time and positive remark on our work. + +## Reviewer #2 (Remarks to the Author): + +The authors have sufficiently addressed my concerns. I do not have any further comments. + +## Response: + +We are thankful to the reviewer for their time and pleased that we were able to address all their concerns. + +## Reviewer #3 (Remarks to the Author): + +All 3 reviewers acknowledged the elegance and importance of this study and the revised manuscript has been highly responsive to the critiques. This will be an important contribution to the field. + +## Response: + +We are thankful to the reviewer for their time and are greatly invigorated by their positive outlook on our study. + +<--- Page Split ---> diff --git a/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..124f02132e4318ee8742568b88151f09795786c2 --- /dev/null +++ b/peer_reviews/997e5f0f499f9ebc5785fbd5a774b236c8d5864696c4e29e1300bc006f7cf440/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,237 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 161, 768, 248]]<|/det|> +CD4 expression in effector T cells depends on DNA demethylation over a developmentally established stimulus- responsive element + +<|ref|>image<|/ref|><|det|>[[56, 732, 239, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 295, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 112, 415, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 140, 874, 224]]<|/det|> +In this manuscript Teghanemt and colleagues present a detailed and compelling story involving developmental epigenetic programming of the Cd4 locus that maintains CD4 expression in effector CD4 T cells. The data support a model in which H3K4me3 blocks de novo DNA methylation at critical CREs in the Cd4 locus to maintain CD4 expression. The molecular work is elegant, and demonstrating using cutting- edge in vivo technologies is impactful. I have only a few relatively minor comments: + +<|ref|>text<|/ref|><|det|>[[117, 238, 870, 433]]<|/det|> +1) The authors state, "our study provides one of the very few demonstrations of the potential for early epigenetically transmitted transcriptional programs that have significant relevance for T cell physiology post-developmentally." While I agree that it is important to conceptually link developmental with maintenance steady state biology, as this study does, there are numerous examples of these phenomena in T cell subsets. I would soften the language here. +2) I applaud the authors for testing their mechanisms in an integrated in vivo model, but it is not clear that Leshmaniasis represents the best choice given the relatively unimpressive readouts in Fig 6A-C. I would recommend complementing this in vivo model with some straightforward classic T cell skewing assays in vitro, for example Th2, Th17, and iTreg induction using naive CD4 T cells from the Cd4E4mD/D and E4aD/D mice. +3) Figure 7 seems tacked on or at least out of place. I would consider moving this figure to the supplement. +4) In the Discussion the authors may want to review the mechanisms demonstrated in Nat Genet. 2020 Jun;52(6):615-625. + +<|ref|>text<|/ref|><|det|>[[120, 462, 415, 476]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 490, 878, 675]]<|/det|> +This is an elegant study showing that DNA demethylation during thymic development is critical for the licensing of, E4a, a novel stimulus- responsive cis- regulatory element (CRE) that serves to maintain CD4 gene expression in effector T cells. E4a and E4m act in concert to maintain transcriptional activity at the CD4 locus and, thereby, prevent de novo DNA methylation during CD4 T cell proliferation. In absence of thymic demethylation, the authors find that E4a and E4m are less active and CD4 downregulation ensues upon T cell proliferation. Strikingly, this downregulation leads to impaired Th1 differentiation and reduced control of Leishmania infection. This reviewer lacks expertise with respect to the technical validity of some of the assays used by the authors for investigating epigenetic regulation. Still, the experiments appear to be overall very well performed and the conclusions drawn seem valid. In the eyes of this reviewer, the finding that infection control is substantially reduced by joint deletion of E4a and E4m is exciting, as is the association to the Th1 phenotype. And, at least to my knowledge, nothing comparable has been previously shown. + +<|ref|>text<|/ref|><|det|>[[119, 675, 238, 687]]<|/det|> +Major Concern: + +<|ref|>text<|/ref|><|det|>[[118, 688, 840, 728]]<|/det|> +From an immunological point of view, I think this manuscript would benefit from an additional evaluation of Th2 differentiation and of TCR binding strength to peptide MHCII complexes in E4a/E4m- deficient vs. WT mice. + +<|ref|>text<|/ref|><|det|>[[118, 728, 878, 784]]<|/det|> +The Th1/Th2 topic could be tackled via an in vitro differentiation assay using presentation of actual peptide- MHCII complexes for stimulation (and not CD3) or by using a Th2 infection model in addition to the Th1- controlled Leishmania model or by asking, whether during Leishmania infection there is suddenly aberrant Th2- cytokine production. + +<|ref|>text<|/ref|><|det|>[[118, 784, 872, 840]]<|/det|> +The binding strength topic could be investigated (at least roughly) by measuring functional avidity through peptide titration upon T cell restitution in the Leishmania system and then calculating an EC50 for IFNg secretion, or in absence of this cytokine of CD107 degranulation of of CD69 upregulation. + +<|ref|>text<|/ref|><|det|>[[118, 840, 860, 881]]<|/det|> +The concept to be tested would be: Does CD4 downregulation reduce TCR binding strength to peptide MHCII complexes and, thereby, favor Th2 vs. Th1 differentiation. See e.g. (Van Panhuys et al., 2014). + +<|ref|>text<|/ref|><|det|>[[118, 882, 830, 910]]<|/det|> +Van Panhuys, N., Klauschen, F., and Germain, R.N. (2014). T- cell- receptor- dependent signal intensity dominantly controls CD4(+) T cell polarization In Vivo. Immunity 41, 63- 74. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 99, 415, 112]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 126, 880, 386]]<|/det|> +It is not uncommon to hear the term epigenetic regulation of gene expression used to describe chromatin effects on gene activity. Yet, epigenetic effects typically imply an inducible change in the activation or repression of a gene that can be heritably and stably transmitted across the space and time of cell division and cell migration; often transcending the inductive signal itself. How such signaling behaviors are remembered through development, especially in mobile cells, has remained obscure. Teghanemt et al. demonstrate that a cis- acting regulatory element of the Cd4 locus undergoes programmed demethylation during thymic development of \(\mathrm{CD4 + }\) T cells. The primary function of this inductive event in the thymus is to pre- configure a permissive chromatin landscape such that the cellular descendants of a naive CD4 T cell maintain gene activity and function after the naive cell's cell's bona fide antigen activation and the subsequent dispatch of those daughter cells to peripheral tissues. The novel cis- acting regulatory element (E4a) works in concert with with a developmentally important cis- acting regulatory element (E4m) to heritably maintain CD4 expression in the descendant of the antigen- activated naive T cell. Mechanistically, the authors demonstrate that TET1/3 induces the DNA demethylation in the thymus and without this developmental activation, peripheral CD4 T cells undergo de novo methylation and silencing of the Cd4 locus during their post- antigen- activation cell divisions. The data quality is excellent and the conclusions are supported by the results. This study will be an important new paradigm in understanding epigenetic gene regulation. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 124, 466, 142]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 159, 872, 282]]<|/det|> +In this manuscript Teghanemt and colleagues present a detailed and compelling story involving developmental epigenetic programming of the Cd4 locus that maintains CD4 expression in effector CD4 T cells. The data support a model in which H3K4me3 blocks de novo DNA methylation at critical CREs in the Cd4 locus to maintain CD4 expression. The molecular work is elegant, and demonstrating using cutting- edge in vivo technologies is impactful. I have only a few relatively minor comments: + +<|ref|>sub_title<|/ref|><|det|>[[115, 299, 216, 315]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 316, 642, 332]]<|/det|> +We thank the reviewer for the positive feedback on our work. + +<|ref|>text<|/ref|><|det|>[[115, 350, 863, 456]]<|/det|> +1) The authors state, "our study provides one of the very few demonstrations of the potential for early epigenetically transmitted transcriptional programs that have significant relevance for T cell physiology post-developmentally." While I agree that it is important to conceptually link developmental with maintenance steady state biology, as this study does, there are numerous examples of these phenomena in T cell subsets. I would soften the language here. + +<|ref|>sub_title<|/ref|><|det|>[[115, 474, 216, 490]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 491, 870, 560]]<|/det|> +In response to the reviewer's comment, we have edited the aforementioned statement to read as "our study provides a mechanistic demonstration of the potential for early epigenetically transmitted transcriptional programs that have significant relevance for T cell physiology post-developmentally". + +<|ref|>text<|/ref|><|det|>[[114, 594, 878, 699]]<|/det|> +2) I applaud the authors for testing their mechanisms in an integrated in vivo model, but it is not clear that Leishmaniasis represents the best choice given the relatively unimpressive readouts in Fig 6A-C. I would recommend complementing this in vivo model with some straightforward classic T cell skewing assays in vitro, for example Th2, Th17, and iTreg induction using naive CD4 T cells from the Cd4E4mD/D and E4aD/D mice. + +<|ref|>sub_title<|/ref|><|det|>[[115, 717, 216, 733]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[114, 734, 875, 890]]<|/det|> +We are thankful for the reviewer's suggestion. Given that in vitro T cell skewing assays require the use of anti- CD3/anti- CD28- mediated TCR activation and bypass CD4 co- engagement, we did not anticipate any differences between WT and E4a nor E4a/E4m- deficient T cells when driven to differentiate into T helper subsets. Nonetheless, in the event of an unexpected contribution for CD4 in that system, we have performed such assays but did not find any differences in Th1, Th2, Treg nor Th17 differentiation, as assessed by master transcription factor expression of the respective lineages. To keep our study focused, we have only included Th1 and Th2 differentiation results in the manuscript (Supplementary Fig. 6j, k). Moreover, in addition to the Leishmaniasis + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 844, 177]]<|/det|> +system, we have now included a second model of Th1 differentiation using an acute viral pathogen (LCMV Armstrong), which triggers a robust Th1 effector response (Supplementary Fig. 6f), and uncovered a similar defect in Th1 differentiation (Supplementary Fig. 6g), as observed in the Leishmaniasis system. Together, we hope the reviewer's concerns are adequately addressed. + +<|ref|>text<|/ref|><|det|>[[114, 194, 875, 230]]<|/det|> +3) Figure 7 seems tacked on or at least out of place. I would consider moving this figure to the supplement. + +<|ref|>sub_title<|/ref|><|det|>[[115, 247, 216, 264]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[114, 264, 881, 369]]<|/det|> +We believe that Figure 7, together with Supplementary Figure 7, extend the idea that many genes in \(\mathrm{CD4^{+}}\) T cells, beyond the dissected example of the \(\mathrm{Cd4}\) gene, undergo similar patterns of regulation during thymic development and is relevant to the general audience. We strongly believe that it adds significant value to our working paradigm and moving this entire figure to a supplementary will be a pity as it may be overlooked by the readership. + +<|ref|>text<|/ref|><|det|>[[114, 402, 759, 438]]<|/det|> +4) In the Discussion the authors may want to review the mechanisms demonstrated in Nat Genet. 2020 Jun;52(6):615-625. + +<|ref|>sub_title<|/ref|><|det|>[[115, 455, 216, 472]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 473, 881, 560]]<|/det|> +We sincerely thank the reviewer for bringing our attention to this elegant work and agree that the mechanisms proposed are highly relevant and compatible with our working model that H3K4me3 does not dictate coding gene transcription per say but has an instructional role in preventing repression of gene expression via DNA methylation. We have now included this reference to our discussion in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 629, 465, 647]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 663, 876, 820]]<|/det|> +This is an elegant study showing that DNA demethylation during thymic development is critical for the licensing of, E4a, a novel stimulus- responsive cis- regulatory element (CRE) that serves to maintain CD4 gene expression in effector T cells. E4a and E4m act in concert to maintain transcriptional activity at the CD4 locus and, thereby, prevent de novo DNA methylation during CD4 T cell proliferation. In absence of thymic demethylation, the authors find that E4a and E4m are less active and CD4 downregulation ensues upon T cell proliferation. Strikingly, this downregulation leads to impaired Th1 differentiation and reduced control of Leishmania infection. + +<|ref|>text<|/ref|><|det|>[[115, 821, 873, 891]]<|/det|> +This reviewer lacks expertise with respect to the technical validity of some of the assays used by the authors for investigating epigenetic regulation. Still, the experiments appear to be overall very well performed and the conclusions drawn seem valid. In the eyes of this reviewer, the finding that infection control is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 818, 143]]<|/det|> +substantially reduced by joint deletion of E4a and E4m is exciting, as is the association to the Th1 phenotype. And, at least to my knowledge, nothing comparable has been previously shown. + +<|ref|>sub_title<|/ref|><|det|>[[115, 160, 216, 176]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 177, 642, 194]]<|/det|> +We thank the reviewer for the positive feedback on our work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 229, 260, 246]]<|/det|> +## Major Concern: + +<|ref|>text<|/ref|><|det|>[[115, 247, 866, 300]]<|/det|> +From an immunological point of view, I think this manuscript would benefit from an additional evaluation of Th2 differentiation and of TCR binding strength to peptide MHCI complexes in E4a/E4m- deficient vs. WT mice. + +<|ref|>text<|/ref|><|det|>[[115, 315, 867, 404]]<|/det|> +The Th1/Th2 topic could be tackled via an in vitro differentiation assay using presentation of actual peptide- MHCI complexes for stimulation (and not CD3) or by using a Th2 infection model in addition to the Th1- controlled Leishmania model or by asking, whether during Leishmania infection there is suddenly aberrant Th2- cytokine production. + +<|ref|>text<|/ref|><|det|>[[113, 420, 870, 595]]<|/det|> +The binding strength topic could be investigated (at least roughly) by measuring functional avidity through peptide titration upon T cell restitution in the Leishmania system and then calculating an EC50 for IFNg secretion, or in absence of this cytokine of CD107 degranulation of of CD69 upregulation. The concept to be tested would be: Does CD4 downregulation reduce TCR binding strength to peptide MHCI complexes and, thereby, favor Th2 vs. Th1 differentiation. See e.g. (Van Panhuys et al., 2014). Van Panhuys, N., Klauschen, F., and Germain, R.N. (2014). T- cell- receptor- dependent signal intensity dominantly controls CD4(+) T cell polarization In Vivo. Immunity 41, 63- 74. + +<|ref|>sub_title<|/ref|><|det|>[[115, 629, 216, 646]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[113, 647, 876, 874]]<|/det|> +We thank the reviewer for the questions posed and recommendations to tackle them. We wanted to evaluate the consequences of reduced CD4 expression on TCR binding and downstream signaling, to support the presented evidence that TCR signaling strength is decreased in antigen- experienced E4a/E4m- deficient T cells during Leishmaniasis, by virtue of CD5 and Nur77 expression levels. However, in the absence of a transgenic system (e.g. an OTII- TCR Tg system), it is challenging to test the question of functional avidity directly. Using such an in vitro TCR Tg system is best suited for robust conclusions because we would be able to a) bypass any differences in helper T cell differentiation that happens between WT and E4a/E4m- deficient mice during infection b) then specifically assess the contribution of CD4 expression on functional avidity through peptide titration and assess an EC50 value for cytokine responses such as IL- 2. We were not successful in establishing a reliable dose- response using crude soluble leishmania antigen (SLA) extracts in a WT setting, as the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 824, 125]]<|/det|> +response was too variable, highlighting the need for defined antigen epitopes and specific TCR strategies. + +<|ref|>text<|/ref|><|det|>[[113, 142, 883, 510]]<|/det|> +Nevertheless, we have addressed some aspects of the questions raised using a different approach. We have challenged E4a/E4m- deficient and WT mice with an LCMV Armstrong strain, which induces an acute Th1 CD4 response in addition to a cytotoxic CD8 response. We chose to do so because of the well- characterized expansion of a dominant MHC- Class II- restricted (IA \(^{\mathsf{b}}\) - restricted) CD4 T cell clone (SMARTA- TCR) that recognizes a specific LCMV glycoprotein epitope GP 61- 80. Using tetramer tools (GP 66- 77) and a peptide specific to this TCR clone to then engage stimulation, we were then able to ask a) does reduced CD4 expression result in a compromised ability to bind to antigen b) is there an impact on Th1 differentiation c) is there a diversion to a Th2 response. To summarize, we found that while a reduction in CD4 expression did not significantly impair the ability of CD4 T cells to bind to GP66- 77 tetramers, a complete loss of CD4 expression had a modest but significant impact (Fig. 6i, j, k). We found a significant reduction in Tbet \(^+\) CD4 \(^+\) T cells in LCMV- infected E4a/E4m- deficient mice but no significant increase in Gata3 \(^+\) CD4 \(^+\) T cells (Supplementary Fig. 6g, h). Accordingly, E4m/E4a- deficient antigen- experienced CD4 \(^+\) T cells mounted a less robust IFN- g response upon antigen re- stimulation (Fig. 6i) but we detected no significant IL- 4 production (data not shown). Together, these findings indicate that reduced TCR signaling mediated via CD4 impairs Th1 differentiation but does not result in preferential Th2 differentiation and are in agreement with our findings in the Leishmaniasis model, where we did not observe an increase in Gata3 \(^+\) T cells nor an increase in IL- 4 production in the footpads (Supplementary Fig. 6b, d, e). + +<|ref|>text<|/ref|><|det|>[[115, 525, 875, 630]]<|/det|> +These results may highlight important differences in modulating TCR signaling via alterations in CD4 levels (which in our model is mostly affected during T cell replication) versus pMHC density as demonstrated by Van Panhuys et al., 2014 and/or other environmental/ cellular factors. We agree that it would be exciting to test whether CD4 expression has an impact on Th2 differentiation in the context of a Th2- dominant infection model. However, we hope the reviewer agrees this merit a future study. + +<|ref|>sub_title<|/ref|><|det|>[[115, 682, 465, 700]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 716, 880, 891]]<|/det|> +It is not uncommon to hear the term epigenetic regulation of gene expression used to describe chromatin effects on gene activity. Yet, epigenetic effects typically imply an inducible change in the activation or repression of a gene that can be heritably and stably transmitted across the space and time of cell division and cell migration; often transcending the inductive signal itself. How such signaling behaviors are remembered through development, especially in mobile cells, has remained obscure. Teghanemt et al. demonstrate that a cis- acting regulatory element of the Cd4 locus undergoes programmed demethylation during thymic development of CD4 \(^+\) T cells. The primary function of this inductive event in the thymus is to pre- configure a permissive chromatin landscape such + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 881, 318]]<|/det|> +that the cellular descendants of a naive CD4 T cell maintain gene activity and function after the naive cell's cell's bona fide antigen activation and the subsequent dispatch of those daughter cells to peripheral tissues. The novel cis- acting regulatory element (E4a) works in concert with with a developmentally important cis- acting regulatory element (E4m) to heritably maintain CD4 expression in the descendant of the antigen- activated naive T cell. Mechanistically, the authors demonstrate that TET1/3 induces the DNA demethylation in the thymus and without this developmental activation, peripheral CD4 T cells undergo de novo methylation and silencing of the Cd4 locus during their post- antigen- activation cell divisions. The data quality is excellent and the conclusions are supported by the results. This study will be an important new paradigm in understanding epigenetic gene regulation. + +<|ref|>sub_title<|/ref|><|det|>[[115, 350, 216, 367]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 367, 864, 403]]<|/det|> +We are sincerely thankful to the reviewer for the positive and insightful remarks on our work. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 310, 97]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 112, 416, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 140, 854, 169]]<|/det|> +The authors have satisfactorily addressed my comments. I congratulate the team on a beautiful paper. + +<|ref|>text<|/ref|><|det|>[[119, 196, 416, 210]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 224, 816, 238]]<|/det|> +The authors have sufficiently addressed my concerns. I do not have any further comments. + +<|ref|>text<|/ref|><|det|>[[119, 266, 416, 280]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 294, 855, 336]]<|/det|> +All 3 reviewers acknowledged the elegance and importance of this study and the revised manuscript has been highly responsive to the critiques. This will be an important contribution to the field. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 438, 108]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 124, 861, 161]]<|/det|> +The authors have satisfactorily addressed my comments. I congratulate the team on a beautiful paper. + +<|ref|>sub_title<|/ref|><|det|>[[115, 179, 202, 196]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 212, 669, 230]]<|/det|> +We thank the reviewer for their time and positive remark on our work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 263, 439, 282]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 298, 828, 317]]<|/det|> +The authors have sufficiently addressed my concerns. I do not have any further comments. + +<|ref|>sub_title<|/ref|><|det|>[[115, 334, 202, 351]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 368, 866, 404]]<|/det|> +We are thankful to the reviewer for their time and pleased that we were able to address all their concerns. + +<|ref|>sub_title<|/ref|><|det|>[[115, 420, 439, 439]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 455, 872, 508]]<|/det|> +All 3 reviewers acknowledged the elegance and importance of this study and the revised manuscript has been highly responsive to the critiques. This will be an important contribution to the field. + +<|ref|>sub_title<|/ref|><|det|>[[115, 526, 202, 543]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[115, 560, 824, 596]]<|/det|> +We are thankful to the reviewer for their time and are greatly invigorated by their positive outlook on our study. + +<--- Page Split ---> diff --git a/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..a3bd02357eb529b633ded5fb02cb485f846c6278 --- /dev/null +++ b/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,17 @@ +[ + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1. Clusters identified with the inclusion of 47 variants genome-wide significant for fasting insulin or a related glycemic trait", + "footnote": [], + "bbox": [ + [ + 115, + 88, + 884, + 428 + ] + ], + "page_idx": 4 + } +] \ No newline at end of file diff --git a/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..4c5ae73011c64534824bc15696e8490513c928dc --- /dev/null +++ b/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,239 @@ + +# nature portfolio + +Peer Review File + +# Heterogeneous effects of genetic variants and traits associated with fasting insulin on cardiometabolic outcomes + +Corresponding Author: Dr Alisa Manning + +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Communications. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +I feel that the authors could have explored in more depth some of the reviewers' suggestions. I have two outstanding points which overlap with comments from the other reviewers: + +1. To what extent are these clusters robust? The authors include many variants at sub GWAS significance but did not attempt to justify this or test it other than stating that they need more variants for the clustering to work. This reason seems sub optimal given the aim of the paper is to characterize variants associated with fasting insulin into more homogeneous pathways. This will probably result in the inclusion of many variants that are not real. This is testable relatively easily by performing a sensitivity analysis with only variants that reach \(p< 5\times 10 - 8\) for insulin. And or in the follow up work, seeing if genetic risk scores consisting of only the \(p< 5\times 10 - 8\) variants or only the \(p>5\times 10 - 8\) variants produce similar results. + +2. What are the reasons T2D variants with well established robust insulin secretion effects flip for fasting insulin? It is important to understand more about why an allele that results in higher insulin secretion is associated with lower insulin sensitivity and vice versa. If this is an artefact it will have resulted in the wrong inferences being made about the "no diabetes" clusters. One explanation is that the data come from people without diabetes and they "need" to be more insulin sensitive if they are genetically more prone to poorer insulin secretion - in other words a bias is introduced towards people who have some other reason for being insulin sensitive. This does not require individual level data to test but only summary stats. If there is such an artefact in the data there will be a simple dose response relationship between insulin secretion effect and insulin resistance effect. Or perhaps a dose response relationship that follows a classic hyperbolic curve of secretion vs resistance. Also the authors could test the results excluding any variants where the FI increasing allele is also a well known insulin secretion increasing allele. + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +In this MS, the authors applied their previously developed bioinformatic pipeline for identifying clusters of SNP- phenotype associations for fasting insulin- related SNPs. The work attempts to disentangle multiple genetic mechanisms modulating fasting insulin levels alongside the phenotypic context they are also associated with. The analysis yielded 7 clusters, 3 of which associated with fasting insulin without being associated with an increased T2D risk. These clusters could highlight biologically reasonable pathway groups, such as the visceral adiposity cluster, which is jointly associated with higher visceral fat, waist circumference, HOMA- B but lower "corrected insulin response", and associates with hypertension among the outcomes and in males with MI. + +Points of criticism: + +<--- Page Split ---> + +1. Many of the variants used from the fasting insulin aspect are known diabetes-associated variants, of which in some clusters the protective alleles are referred to. For a better readability, it would be important to note which allele is specifically referred to (allele with higher/lower insulin levels, alleles associating with or protecting from diabetes) in the main figures. This would thus set a reference allele direction. For example, the PIS cluster features TCF7L2 as one of the included variants. Is the lower plasma insulin in this cluster associated with the diabetes-related allele of the variant, and the association of the whole cluster with lower fasting glucose thus a consequence of the aggregate effects of all variants comprised in the cluster? Or is the diabetes-protective allele in this variant associating with a lower fasting insulin level with similar mechanisms? Similarly, it would be nice to see clearly, whether for the HIR/liver lipid cluster, the diabetes-associated effect direction really aligns with higher fasting glucose but lower 2-hour-glucose and lower triglycerides. + +2. Some interesting constellations of end-point-associations are not discussed. For example, while the HIR cluster associates with lower MI (which could fit to findings from mendelian randomization analyses about hepatic fat and CV outcomes), it is associated with lower eGFR, suggesting that this mechanism could underly diabetic nephropathy to some extent. + +3. Some of the cluster denominations seem to be rather arbitrary, and difficult to explain. E.g. the stressed beta-cell cluster is associated with higher gGT and CRP, which positions it closer to inflammatory/hepatic mechanisms. Also, cluster denominations seem to be left from the working titles in the Suppl Fig 3, it's better to align these to the main MS. I liked liver-lipid better than HIR anyway. + +4. The authors use the word "ectopic fat" synonymously with visceral fat. This is not correct. Ectopic fat refers to triglyceride accumulation in cell types not dedicated for triglyceride storage such as hepatocytes or myocytes. Visceral fat is just a dysfunctional adipose tissue distribution, but not ectopic fat. + +5. I couldn't find a listing of the 43 traits which were fed to the bNMF algorithm according to Fig 1 + +(Remarks on code availability) I didn't try to reproduce the results, it would require much work, but the code seems to be well documented and reasonable to be reused by others. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have had a much better go at attempting to unravel what are I believe a complex set of variants and clusters of variants. They should be congratulated for tackling a tricky subject. However, I do think that two main concerns should be more explicitly acknowledged in the discussion. + +First, the inclusion of \(80\%\) of the variants not reaching genome wide significance adds complexity and confusion in my opinion. I believe most if not all previous papers using clustering approaches of variants have limited the analyses to variants associated with the primary trait in question, at \(p< 5\times 10 - 8\) . For sure some of these variants are associated with other metabolic traits at \(p< 5\times 10 - 8\) and are likely affecting FI, but most likely via a more proximal trait, such as BMI, or as an artefact of being primarily an insulin secretion allele, and it is better to characterise these by looking first at the trait they are most strongly associated with - then it will become much clearer as to the mechanism. This point is partly clarified when the new analyses limited to the 47 / 230 variants reaching \(p< 5\times 10 - 8\) reveals only 4 not 7 clusters. I feel the discussion skirts around this issue a little and the authors should more explicitly state something like "Only \(20\%\) of the variants we included reach GWS significance for FI. Of the remaining \(80\%\) NN are GWAS for another metabolic trait, and these associations will likely provide greater clarity as to how the allele alters FI, compared to trying to clustering algorithms. When limited to the 47 GWAS significant variants we observed 4 not 7 clusters" + +Second, the discussion on lines 458 and 501 is a nice addition but skirts around the strong possibility that many of the alleles in the preserved insulin secretion cluster may have no effect on FI at all. Four of the 8 FI increasing alleles in this cluster are simply the opposite alleles to well known alleles associated with type 2 risk through reduced insulin secretion from the beta cell. (ST6). So I think important to be explicit about "these alleles" association with FI being an artefact of the FI GWAS being performed in people without diabetes, thus inducing subtle but false associations between insulin secretion increasing/T2D protective alleles and higher FI". + +(Remarks on code availability) + +Reviewer #2 + +(Remarks to the Author) + +The authors have done a great job in responding to all critiques from my side and appropriately amended the MS. + +<--- Page Split ---> + +(Remarks on code availability) + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +We appreciate the reviewer's suggestions and comments, as addressing them has resulted in a clearer and more refined paper. + +## Reviewer #1 (Remarks to the Author): + +I feel that the authors could have explored in more depth some of the reviewers' suggestions. I have two outstanding points which overlap with comments from the other reviewers: + +1. To what extent are these clusters robust? The authors include many variants at sub GWAS significance but did not attempt to justify this or test it other than stating that they need more variants for the clustering to work. This reason seems sub optimal given the aim of the paper is to characterize variants associated with fasting insulin into more homogeneous pathways. This will probably result in the inclusion of many variants that are not real. This is testable relatively easily by performing a sensitivity analysis with only variants that reach \(p< 5\times 10^{-8}\) for insulin. And or in the follow up work, seeing if genetic risk scores consisting of only the \(p< 5\times 10^{-8}\) variants or only the \(p > 5\times 10^{-8}\) variants produce similar results. + +We thank the reviewer for this insightful comment and agree that it is critical to confirm that inclusion of sub- GWAS variants does not lead to meaningless results. In response to this, we have 1) conducted a sensitivity analysis using only variants that meet the more stringent threshold of \(p<\) \(5\times 10^{- 8}\) and 2) performed cross- study validation of the variants with \(p > 5\times 10^{- 8}\) . + +## Sensitivity Analysis of variants meeting genome-wide significance threshold: + +As recommended by the reviewer, we conducted a sensitivity analysis using only variants that met the more stringent threshold of \(p< 5\times 10^{- 8}\) . This analysis included 47 variants derived either from European (N=39) or multi- ancestry (N=8) GWAS studies on fasting insulin. + +The clustering of these high- confidence variants resulted in four distinct clusters that closely resembled clusters presented in our manuscript (Figure 1): + +Cluster 1, similar to the VAT cluster, was characterized by higher levels of visceral adiposity and included variants in COBLL1 and VEGFA. + +Cluster 2, which closely resembles the Preserved Insulin Secretion cluster (PIS), included the rs7903146 variant in TCF7L2 and was associated with lower proinsulin and 2h glucose levels. + +Cluster 3, akin to the FI- Liver Lipid cluster, featured GCKR as a top- weighted locus and was associated with lower triglycerides, albumin and GGT. + +Cluster 4 contains very similar features than the Adiposity cluster, with FTO as top weighted locus and several anthropometric and body composition traits with positive associations. + +<--- Page Split ---> +![](images/Figure_1.jpg) + +
Figure 1. Clusters identified with the inclusion of 47 variants genome-wide significant for fasting insulin or a related glycemic trait
+ +These results support the findings from our manuscript. + +## Cross-Study Validation of Variant Significance + +To assess whether the \(p > 5\times 10 - 8\) variants have cardiometabolic relevance, we validated their association across GWAS for related glycemic and metabolic traits. Of the 101 variants highly weighted in at least one cluster, 38 reached genome- wide significance \((p< 5\times 10 - 8)\) in either European only or multi- ancestry GWAS studies for fasting insulin. Additionally, 89 variants \((88\%)\) which included the prior 38, were associated with at least one metabolic trait at genome- wide significance, supporting their relevance in metabolic regulation. + +We have incorporated these changes into the Methods and Discussion sections of our Manuscript + +Methods Line 174: Additionally, we conducted a sensitivity analysis using a more stringent threshold, including only variants with \(p< 5\times 10^{- 8}\) for FI in European \((N = 39)\) or Multi- ancestry \((N = 8)\) GWAS. + +Discussion Line 510: Another limitation of our study is the inclusion of variants with subthreshold GWAS significance levels. However, to address this concern, we conducted a sensitivity analysis focusing on variants meeting the stringent criterion of \(p< 5\times 10 - 8\) . This analysis led to the identification of four clusters—PIS, Adiposity, VAT, and FI- Liver/Lipid—that closely correspond to four of the original seven clusters, reinforcing the robustness of our findings (Supplementary Figure 4). Additionally, we confirmed that \(88\%\) of the full set of the 101 variants highly weighted in at least one cluster were associated with at least one metabolic trait at genome- wide significance, supporting their relevance in metabolic regulation. + +2. What are the reasons T2D variants with well-established robust insulin secretion effects flip for fasting insulin? It is important to understand more about why an allele that results in higher insulin secretion is associated with lower insulin sensitivity and vice versa. If this is an artefact it will have resulted in the wrong inferences being made about the "no diabetes" clusters. One explanation is that the data come from people without diabetes and they "need" + +<--- Page Split ---> + +to be more insulin sensitive if they are genetically more prone to poorer insulin secretion – in other words a bias is introduced towards people who have some other reason for being insulin sensitive. This does not require individual level data to test but only summary stats. If there is such an artefact in the data there will be a simple dose response relationship between insulin secretion effect and insulin resistance effect. Or perhaps a dose response relationship that follows a classic hyperbolic curve of secretion vs resistance. Also, the authors could test the results excluding any variants where the FI increasing allele is also a well- known insulin secretion increasing allele. + +We thank the reviewer for highlighting this important issue. Although we hypothesize that the nondiabetogenic clusters are associated with insulin secretion, we acknowledge that these clusters may not necessarily be linked to lower insulin sensitivity. + +We are aware of the well- established hyperbolic relationship between insulin secretion and insulin sensitivity in individuals without diabetes. This relationship can complicate the interpretation of associations between genetic variants and fasting insulin, particularly due to the inherent biases introduced by this hyperbolic association. Summary statistics may also be influenced by these biases. + +We revised the discussion of these limitations in the discussion section of our manuscript to provide a clearer understanding of how these factors might affect our findings. + +Line 458: "The non- diabetogenic clusters, characterized by alleles associated with increased FI and decreased risk of T2D, suggest mechanisms involving increased insulin resistance coupled with compensatory insulin production. In particular, the preserved beta- insulin secretion cluster may be influenced by the gene expression of ADCY5, which is known to regulate insulin secretion from human islets 52. This cluster features the opposite allele (rs11708067- G) compared to the T2D beta- cell cluster identified by Udler et al. 8 (rs11708067- A), which contains the rs11708067- A allele. The rs11708067- A allele is linked to reduced function of an islet enhancer, leading to decreased ADCY5 expression and impaired insulin secretion 53. Similarly, the rs7903146- T allele in TCF7L2 is associated with compromised beta- cell function 54. The alleles in the preserved beta- insulin secretion cluster (rs11708067- G, rs7903146- C, and rs11039290- A) contribute to incremental increases in insulin production. This increased production may enhance or preserve beta- cell function, potentially leading to lower blood glucose levels and reduced cardiometabolic risk. Alternatively, these findings could reflect an early compensatory response when glycemia is normal or only slightly elevated. 2,55,56. " + +Line 501: "The study also has some limitations; we acknowledge the potential bias stemming from the hyperbolic association, where elevated insulin secretion might be driven by insulin resistance as a compensatory mechanism rather than by genetic factors alone. Insulin responses, which reflect basal beta cell function, are inversely related to insulin action across varying degrees of glucose intolerance53,54,60. This physiological complexity complicates the task of isolating these two mechanisms, making it difficult to disentangle their individual genetic contributions." + +## Reviewer #2 (Remarks to the Author): + +In this MS, the authors applied their previously developed bioinformatic pipeline for identifying clusters of SNP- phenotype associations for fasting insulin- related SNPs. The work attempts to disentangle multiple genetic mechanisms modulating fasting insulin levels alongside the phenotypic context they are also associated with. The analysis yielded 7 clusters, 3 of which associated with fasting insulin without being associated with an increased T2D risk. These clusters could highlight biologically reasonable pathway groups, such as the visceral adiposity cluster, which is jointly + +<--- Page Split ---> + +associated with higher visceral fat, waist circumference, HOMA- B but lower “corrected insulin response”, and associates with hypertension among the outcomes and in males with MI. + +Points of criticism: + +1. Many of the variants used from the fasting insulin aspect are known diabetes-associated variants, of which in some clusters the protective alleles are referred to. For a better readability, it would be important to note which allele is specifically referred to (allele with higher/lower insulin levels, alleles associating with or protecting from diabetes) in the main figures. This would thus set a reference allele direction. For example, the PIS cluster features TCF7L2 as one of the included variants. Is the lower plasma insulin in this cluster associated with the diabetes-related allele of the variant, and the association of the whole cluster with lower fasting glucose thus a consequence of the aggregate effects of all variants comprised in the cluster? Or is the diabetes-protective allele in this variant associating with a lower fasting insulin level with similar mechanisms? Similarly, it would be nice to see clearly, whether for the HIR/liver lipid cluster, the diabetes-associated effect direction really aligns with higher fasting glucose but lower 2-hour-glucose and lower triglycerides. + +To improve the readability of our results, we have revised Figure 2 to include annotations indicating the main association with type 2 diabetes (T2D) at the top, which will guide interpretation. + +In the figure, all alleles are aligned to show the direction of effect on fasting insulin. Specifically for the PIS cluster, we clarify that the diabetes-protective allele of TCF7L2 is associated with lower fasting insulin levels, which contributes to a reduced T2D risk. + +For the HIR/liver lipid cluster, the T2D association at the top clarifies whether the diabetes- associated effect direction aligns with higher fasting glucose, but lower 2- hour glucose and triglycerides. + +We believe these changes will enhance the interpretability of our figures and better convey the relationships between alleles, fasting insulin, and diabetes risk. + +Figure 2 + +<--- Page Split ---> +![PLACEHOLDER_7_0] + + +2. Some interesting constellations of end-point-associations are not discussed. For example, while the HIR cluster associates with lower MI (which could fit to findings from mendelian randomization analyses about hepatic fat and CV outcomes), it is associated with lower eGFR, suggesting that this mechanism could underly diabetic nephropathy to some extent. + +We appreciate the reviewer's insightful observation regarding the interesting constellations of endpoint associations. In response, we have included a dedicated section in the manuscript to discuss these associations in greater depth. Specifically, we now address the relationship between the HIR cluster and its associations with both lower MI risk and reduced eGFR. This section explores how these findings align with recent Mendelian randomization analyses and discusses the potential implications for understanding the complex mechanisms underlying these associations. We also outline the future work necessary to further investigate these connections. Thank you for highlighting this important aspect of our study. + +Line 484: "Our study reveals several noteworthy associations that merit further examination. Notably, the HIR cluster demonstrates a significant association with a lower risk of MI. This finding is consistent with recent research by Ahmed et al59, which identified 13 genetic variants associated with impaired hepatic triglyceride export. Their study showed that liver fat-increasing alleles were correlated with a reduced risk of coronary artery disease and MI but an elevated risk of type 2 diabetes, underscoring the heterogeneous effects of liver fat on health outcomes. Additionally, the HIR cluster is associated with a reduced eGFR, a marker of kidney function. The connection between lower MI risk and reduced eGFR within the HIR cluster suggests that mechanisms implicated in diabetogenic pathways related to hepatic function may influence multiple disease outcomes through complex and interrelated mechanisms. This emphasizes the need for further + +<--- Page Split ---> + +research to elucidate the pathways linking insulin resistance with cardiovascular and renal diseases and to explore how these associations might inform personalized intervention strategies." + +3. Some of the cluster denominations seem to be rather arbitrary, and difficult to explain. E.g. the stressed beta-cell cluster is associated with higher gGT and CRP, which positions it closer to inflammatory/hepatic mechanisms. Also, cluster denominations seem to be left from the working titles in the Suppl Fig 3, it's better to align these to the main MS. I liked liver-lipid better than HIR anyway. + +We thank the reviewer for the detailed feedback. In response, we have revised the cluster names to better reflect the traits they represent and to avoid potential misinterpretations. The revised cluster names are as follows: Proinsulin (formerly Stressed Beta-Cell), FI-Liver/Lipid (formerly HIR), and FI- Lipodystrophy (formerly Lipodystrophy). We have updated all figures, tables, and the manuscript to ensure consistency with these new names. We believe these changes better align with the underlying biological mechanisms and improve the clarity of our presentation. + +4. The authors use the word "ectopic fat" synonymously with visceral fat. This is not correct. Ectopic fat refers to triglyceride accumulation in cell types not dedicated for triglyceride storage such as hepatocytes or myocytes. Visceral fat is just a dysfunctional adipose tissue distribution, but not ectopic fat. + +We thank the reviewer for pointing out this important distinction. To correct this, we have revised the manuscript to use the term "visceral fat" where appropriate and ensured that the term "ectopic fat" is used correctly to describe triglyceride accumulation in non-adipose tissues. + +We appreciate the reviewer's attention to this detail, which improves the accuracy of our terminology. + +## 5. I couldn't find a listing of the 43 traits which were fed to the bNMF algorithm according to Fig 1 + +A comprehensive listing of the 43 traits that were input into the bNMF algorithm, as well as the reasons for excluding certain traits, is provided in Supplementary Table 3. We have updated the manuscript to ensure that this information is clearly referenced. + +Reviewer #2 (Remarks on code availability): + +I didn't try to reproduce the results, it would require much work, but the code seems to be well documented and reasonable to be reused by others. + +We appreciate the reviewer's comment. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors have had a much better go at attempting to unravel what are I believe a complex set of variants and clusters of variants. They should be congratulated for tackling a tricky subject. However, I do think that two main concerns should be more explicitly acknowledged in the discussion. + +First, the inclusion of \(80\%\) of the variants not reaching genome wide significance adds complexity and confusion in my opinion. I believe most if not all previous papers using clustering approaches of variants have limited the analyses to variants associated with the primary trait in question, at \(p< 5\times 10 - 8\) . For sure some of these variants are associated with other metabolic traits at \(p< 5\times 10 - 8\) and are likely affecting FI, but most likely via a more proximal trait, such as BMI, or as an artefact of being primarily an insulin secretion allele, and it is better to characterise these by looking first at the trait they are most strongly associated with - then it will become much clearer as to the mechanism. This point is partly clarified when the new analyses limited to the 47 / 230 variants reaching \(p< 5\times 10 - 8\) reveals only 4 not 7 clusters. I feel the discussion skirts around this issue a little and the authors should more explicitly state something like "Only \(20\%\) of the variants we included reach GWS significance for FI. Of the remaining \(80\%\) NN are GWAS for another metabolic trait, and these associations will likely provide greater clarity as to how the allele alters FI, compared to trying to clustering algorithms. When limited to the 47 GWAS significant variants we observed 4 not 7 clusters" + +false associations between insulin secretion increasing/T2D protective alleles and higher FI". + +We thank the reviewer for their constructive suggestions. We have incorporated the required clarifications in the last version of the manuscript: + +## First comment + +## Previous version: + +Line 509: "Another limitation of our study is the inclusion of variants with subthreshold GWAS significance levels. However, to address this concern, we conducted a sensitivity analysis focusing on variants meeting the stringent criterion of \(p< 5\times 10^{- 8}\) . This analysis led to the identification of four clusters—PIS, Adiposity, VAT, and FI- Liver/Lipid—that closely correspond to four of the original seven clusters, reinforcing the robustness of our findings (Supplementary Figure 4). Additionally, we confirmed that \(88\%\) of the full set of the 101 variants highly weighted in at least one cluster were associated with at least one metabolic trait at genome- wide significance, supporting their relevance in metabolic regulation." + +## Updated paragraph: + +Line 380: "Another limitation of our study is the inclusion of variants with subthreshold GWAS significance levels, with only \(20.43\%\) reaching genome- wide significance for FI (N=47). However, to address this concern, we conducted a sensitivity analysis focusing on variants meeting the stringent criterion of \(p< 5\times 10^{- 8}\) . This stricter selection led to the identification of + +<--- Page Split ---> + +four clusters—PIS, Adiposity, VAT, and FI- Liver/Lipid—from a subset of 47 GWAS- significant variants, which corresponds closely to four of the original seven clusters, thereby reinforcing the robustness of our findings (Supplementary Figure 4). Moreover, 88% of the full set of 101 variants highly weighted in at least one cluster were associated with at least one metabolic trait at genome- wide significance. This supports their relevance in metabolic regulation and provides clarity on how these alleles potentially influence FI, demonstrating that broader metabolic associations beyond FI are integral to understanding the allelic impact on metabolic traits." + +## Second comment: + +Previous version: + +Line 457: "The non- diabetogenic clusters, characterized by alleles associated with increased FI and decreased risk of T2D, suggest mechanisms involving increased insulin resistance coupled with compensatory insulin production. In particular, the preserved beta- insulin secretion cluster may be influenced by the gene expression of ADCY5, which is known to regulate insulin secretion from human islets \(^{52}\) . This cluster features the opposite allele (rs11708067- G) compared to the T2D beta- cell cluster identified by Udler et al. \(^{8}\) (rs11708067- A), which contains the rs11708067- A allele. The rs11708067- A allele is linked to reduced function of an islet enhancer, leading to decreased ADCY5 expression and impaired insulin secretion \(^{53}\) . Similarly, the rs7903146- T allele in TCF7L2 is associated with compromised beta- cell function \(^{54}\) . The alleles in the preserved beta- insulin secretion cluster (rs11708067- G, rs7903146- C, and rs11039290- A) contribute to incremental increases in insulin production. This increased production may enhance or preserve beta- cell function, potentially leading to lower blood glucose levels and reduced cardiometabolic risk. Alternatively, these findings could reflect an early compensatory response when glycemia is normal or only slightly elevated. \(^{2,55,56}\) ." + +## Updated version: + +Line 324: "The non- diabetogenic clusters, characterized by alleles associated with increased FI and decreased risk of T2D, suggest mechanisms involving increased insulin resistance coupled with compensatory insulin production. In particular, the PIS cluster may be influenced by the gene expression of ADCY5, which is known to regulate insulin secretion from human islets \(^{52}\) . This cluster features the opposite allele (rs11708067- G) compared to the T2D beta- cell cluster identified by Udler et al. \(^{8}\) , which contains the rs11708067- A allele. The rs11708067- A allele is linked to reduced function of an islet enhancer, leading to decreased ADCY5 expression and impaired insulin secretion \(^{53}\) . Similarly, the rs7903146- T allele in TCF7L2 is associated with compromised beta- cell function \(^{54}\) . The alleles in the preserved beta- insulin secretion cluster (rs11708067- G, rs7903146- C, and rs11039290- A) contribute to incremental increases in insulin production. This increased production may enhance or preserve beta- cell function, potentially leading to lower blood glucose levels and reduced cardiometabolic risk. Alternatively, these findings could reflect an early compensatory response when glycemia is normal or only slightly elevated. \(^{2,55,56}\) . Furthermore, it is crucial to acknowledge that the alleles within the PIS cluster were selected for this analysis due to their association with increased FI levels, and they exhibit a decreased risk for T2D; as noted above, the alternative alleles increase T2D risk and are associated with reduced insulin secretion. The observed effects of the T2D- reducing alleles may be attributed to collider bias, particularly since the FI GWAS were conducted in individuals without T2D + +<--- Page Split ---> diff --git a/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d74566943e96231608eec0a34a68a9fbf46942a6 --- /dev/null +++ b/peer_reviews/997f07f04b39548fa714645ea9bb31d84ed0ec8d5a169ee966fa024983bf7046/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,335 @@ +<|ref|>title<|/ref|><|det|>[[73, 50, 295, 78]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 912, 210]]<|/det|> +# Heterogeneous effects of genetic variants and traits associated with fasting insulin on cardiometabolic outcomes + +<|ref|>text<|/ref|><|det|>[[75, 224, 421, 240]]<|/det|> +Corresponding Author: Dr Alisa Manning + +<|ref|>text<|/ref|><|det|>[[72, 274, 874, 301]]<|/det|> +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[72, 313, 866, 328]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 365, 144, 378]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 391, 219, 404]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 417, 160, 430]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 444, 238, 456]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 457, 914, 484]]<|/det|> +I feel that the authors could have explored in more depth some of the reviewers' suggestions. I have two outstanding points which overlap with comments from the other reviewers: + +<|ref|>text<|/ref|><|det|>[[72, 508, 902, 589]]<|/det|> +1. To what extent are these clusters robust? The authors include many variants at sub GWAS significance but did not attempt to justify this or test it other than stating that they need more variants for the clustering to work. This reason seems sub optimal given the aim of the paper is to characterize variants associated with fasting insulin into more homogeneous pathways. This will probably result in the inclusion of many variants that are not real. This is testable relatively easily by performing a sensitivity analysis with only variants that reach \(p< 5\times 10 - 8\) for insulin. And or in the follow up work, seeing if genetic risk scores consisting of only the \(p< 5\times 10 - 8\) variants or only the \(p>5\times 10 - 8\) variants produce similar results. + +<|ref|>text<|/ref|><|det|>[[71, 600, 923, 730]]<|/det|> +2. What are the reasons T2D variants with well established robust insulin secretion effects flip for fasting insulin? It is important to understand more about why an allele that results in higher insulin secretion is associated with lower insulin sensitivity and vice versa. If this is an artefact it will have resulted in the wrong inferences being made about the "no diabetes" clusters. One explanation is that the data come from people without diabetes and they "need" to be more insulin sensitive if they are genetically more prone to poorer insulin secretion - in other words a bias is introduced towards people who have some other reason for being insulin sensitive. This does not require individual level data to test but only summary stats. If there is such an artefact in the data there will be a simple dose response relationship between insulin secretion effect and insulin resistance effect. Or perhaps a dose response relationship that follows a classic hyperbolic curve of secretion vs resistance. Also the authors could test the results excluding any variants where the FI increasing allele is also a well known insulin secretion increasing allele. + +<|ref|>text<|/ref|><|det|>[[73, 743, 282, 757]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 781, 161, 794]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 808, 238, 821]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 821, 912, 912]]<|/det|> +In this MS, the authors applied their previously developed bioinformatic pipeline for identifying clusters of SNP- phenotype associations for fasting insulin- related SNPs. The work attempts to disentangle multiple genetic mechanisms modulating fasting insulin levels alongside the phenotypic context they are also associated with. The analysis yielded 7 clusters, 3 of which associated with fasting insulin without being associated with an increased T2D risk. These clusters could highlight biologically reasonable pathway groups, such as the visceral adiposity cluster, which is jointly associated with higher visceral fat, waist circumference, HOMA- B but lower "corrected insulin response", and associates with hypertension among the outcomes and in males with MI. + +<|ref|>text<|/ref|><|det|>[[73, 925, 198, 938]]<|/det|> +Points of criticism: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 60, 922, 179]]<|/det|> +1. Many of the variants used from the fasting insulin aspect are known diabetes-associated variants, of which in some clusters the protective alleles are referred to. For a better readability, it would be important to note which allele is specifically referred to (allele with higher/lower insulin levels, alleles associating with or protecting from diabetes) in the main figures. This would thus set a reference allele direction. For example, the PIS cluster features TCF7L2 as one of the included variants. Is the lower plasma insulin in this cluster associated with the diabetes-related allele of the variant, and the association of the whole cluster with lower fasting glucose thus a consequence of the aggregate effects of all variants comprised in the cluster? Or is the diabetes-protective allele in this variant associating with a lower fasting insulin level with similar mechanisms? Similarly, it would be nice to see clearly, whether for the HIR/liver lipid cluster, the diabetes-associated effect direction really aligns with higher fasting glucose but lower 2-hour-glucose and lower triglycerides. + +<|ref|>text<|/ref|><|det|>[[72, 190, 907, 242]]<|/det|> +2. Some interesting constellations of end-point-associations are not discussed. For example, while the HIR cluster associates with lower MI (which could fit to findings from mendelian randomization analyses about hepatic fat and CV outcomes), it is associated with lower eGFR, suggesting that this mechanism could underly diabetic nephropathy to some extent. + +<|ref|>text<|/ref|><|det|>[[72, 255, 918, 308]]<|/det|> +3. Some of the cluster denominations seem to be rather arbitrary, and difficult to explain. E.g. the stressed beta-cell cluster is associated with higher gGT and CRP, which positions it closer to inflammatory/hepatic mechanisms. Also, cluster denominations seem to be left from the working titles in the Suppl Fig 3, it's better to align these to the main MS. I liked liver-lipid better than HIR anyway. + +<|ref|>text<|/ref|><|det|>[[72, 319, 911, 360]]<|/det|> +4. The authors use the word "ectopic fat" synonymously with visceral fat. This is not correct. Ectopic fat refers to triglyceride accumulation in cell types not dedicated for triglyceride storage such as hepatocytes or myocytes. Visceral fat is just a dysfunctional adipose tissue distribution, but not ectopic fat. + +<|ref|>text<|/ref|><|det|>[[72, 371, 728, 386]]<|/det|> +5. I couldn't find a listing of the 43 traits which were fed to the bNMF algorithm according to Fig 1 + +<|ref|>text<|/ref|><|det|>[[73, 411, 919, 451]]<|/det|> +(Remarks on code availability) I didn't try to reproduce the results, it would require much work, but the code seems to be well documented and reasonable to be reused by others. + +<|ref|>text<|/ref|><|det|>[[73, 463, 144, 476]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 489, 219, 502]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 514, 160, 527]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 540, 237, 554]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 554, 911, 593]]<|/det|> +The authors have had a much better go at attempting to unravel what are I believe a complex set of variants and clusters of variants. They should be congratulated for tackling a tricky subject. However, I do think that two main concerns should be more explicitly acknowledged in the discussion. + +<|ref|>text<|/ref|><|det|>[[72, 605, 923, 746]]<|/det|> +First, the inclusion of \(80\%\) of the variants not reaching genome wide significance adds complexity and confusion in my opinion. I believe most if not all previous papers using clustering approaches of variants have limited the analyses to variants associated with the primary trait in question, at \(p< 5\times 10 - 8\) . For sure some of these variants are associated with other metabolic traits at \(p< 5\times 10 - 8\) and are likely affecting FI, but most likely via a more proximal trait, such as BMI, or as an artefact of being primarily an insulin secretion allele, and it is better to characterise these by looking first at the trait they are most strongly associated with - then it will become much clearer as to the mechanism. This point is partly clarified when the new analyses limited to the 47 / 230 variants reaching \(p< 5\times 10 - 8\) reveals only 4 not 7 clusters. I feel the discussion skirts around this issue a little and the authors should more explicitly state something like "Only \(20\%\) of the variants we included reach GWS significance for FI. Of the remaining \(80\%\) NN are GWAS for another metabolic trait, and these associations will likely provide greater clarity as to how the allele alters FI, compared to trying to clustering algorithms. When limited to the 47 GWAS significant variants we observed 4 not 7 clusters" + +<|ref|>text<|/ref|><|det|>[[72, 747, 920, 827]]<|/det|> +Second, the discussion on lines 458 and 501 is a nice addition but skirts around the strong possibility that many of the alleles in the preserved insulin secretion cluster may have no effect on FI at all. Four of the 8 FI increasing alleles in this cluster are simply the opposite alleles to well known alleles associated with type 2 risk through reduced insulin secretion from the beta cell. (ST6). So I think important to be explicit about "these alleles" association with FI being an artefact of the FI GWAS being performed in people without diabetes, thus inducing subtle but false associations between insulin secretion increasing/T2D protective alleles and higher FI". + +<|ref|>text<|/ref|><|det|>[[73, 840, 282, 854]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[73, 880, 160, 893]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 906, 237, 919]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 919, 850, 934]]<|/det|> +The authors have done a great job in responding to all critiques from my side and appropriately amended the MS. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 49, 283, 62]]<|/det|> +(Remarks on code availability) + +<|ref|>text<|/ref|><|det|>[[72, 426, 916, 480]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 481, 796, 495]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 495, 911, 546]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 546, 618, 559]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 314, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 114, 844, 146]]<|/det|> +We appreciate the reviewer's suggestions and comments, as addressing them has resulted in a clearer and more refined paper. + +<|ref|>sub_title<|/ref|><|det|>[[116, 161, 423, 178]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 193, 875, 225]]<|/det|> +I feel that the authors could have explored in more depth some of the reviewers' suggestions. I have two outstanding points which overlap with comments from the other reviewers: + +<|ref|>text<|/ref|><|det|>[[114, 240, 878, 368]]<|/det|> +1. To what extent are these clusters robust? The authors include many variants at sub GWAS significance but did not attempt to justify this or test it other than stating that they need more variants for the clustering to work. This reason seems sub optimal given the aim of the paper is to characterize variants associated with fasting insulin into more homogeneous pathways. This will probably result in the inclusion of many variants that are not real. This is testable relatively easily by performing a sensitivity analysis with only variants that reach \(p< 5\times 10^{-8}\) for insulin. And or in the follow up work, seeing if genetic risk scores consisting of only the \(p< 5\times 10^{-8}\) variants or only the \(p > 5\times 10^{-8}\) variants produce similar results. + +<|ref|>text<|/ref|><|det|>[[115, 374, 876, 439]]<|/det|> +We thank the reviewer for this insightful comment and agree that it is critical to confirm that inclusion of sub- GWAS variants does not lead to meaningless results. In response to this, we have 1) conducted a sensitivity analysis using only variants that meet the more stringent threshold of \(p<\) \(5\times 10^{- 8}\) and 2) performed cross- study validation of the variants with \(p > 5\times 10^{- 8}\) . + +<|ref|>sub_title<|/ref|><|det|>[[116, 446, 748, 463]]<|/det|> +## Sensitivity Analysis of variants meeting genome-wide significance threshold: + +<|ref|>text<|/ref|><|det|>[[115, 470, 864, 518]]<|/det|> +As recommended by the reviewer, we conducted a sensitivity analysis using only variants that met the more stringent threshold of \(p< 5\times 10^{- 8}\) . This analysis included 47 variants derived either from European (N=39) or multi- ancestry (N=8) GWAS studies on fasting insulin. + +<|ref|>text<|/ref|><|det|>[[115, 525, 815, 557]]<|/det|> +The clustering of these high- confidence variants resulted in four distinct clusters that closely resembled clusters presented in our manuscript (Figure 1): + +<|ref|>text<|/ref|><|det|>[[115, 563, 853, 596]]<|/det|> +Cluster 1, similar to the VAT cluster, was characterized by higher levels of visceral adiposity and included variants in COBLL1 and VEGFA. + +<|ref|>text<|/ref|><|det|>[[115, 603, 833, 636]]<|/det|> +Cluster 2, which closely resembles the Preserved Insulin Secretion cluster (PIS), included the rs7903146 variant in TCF7L2 and was associated with lower proinsulin and 2h glucose levels. + +<|ref|>text<|/ref|><|det|>[[115, 643, 824, 675]]<|/det|> +Cluster 3, akin to the FI- Liver Lipid cluster, featured GCKR as a top- weighted locus and was associated with lower triglycerides, albumin and GGT. + +<|ref|>text<|/ref|><|det|>[[115, 682, 864, 714]]<|/det|> +Cluster 4 contains very similar features than the Adiposity cluster, with FTO as top weighted locus and several anthropometric and body composition traits with positive associations. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 884, 428]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 435, 836, 469]]<|/det|> +
Figure 1. Clusters identified with the inclusion of 47 variants genome-wide significant for fasting insulin or a related glycemic trait
+ +<|ref|>text<|/ref|><|det|>[[115, 475, 536, 492]]<|/det|> +These results support the findings from our manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 498, 496, 515]]<|/det|> +## Cross-Study Validation of Variant Significance + +<|ref|>text<|/ref|><|det|>[[115, 521, 857, 618]]<|/det|> +To assess whether the \(p > 5\times 10 - 8\) variants have cardiometabolic relevance, we validated their association across GWAS for related glycemic and metabolic traits. Of the 101 variants highly weighted in at least one cluster, 38 reached genome- wide significance \((p< 5\times 10 - 8)\) in either European only or multi- ancestry GWAS studies for fasting insulin. Additionally, 89 variants \((88\%)\) which included the prior 38, were associated with at least one metabolic trait at genome- wide significance, supporting their relevance in metabolic regulation. + +<|ref|>text<|/ref|><|det|>[[115, 624, 863, 641]]<|/det|> +We have incorporated these changes into the Methods and Discussion sections of our Manuscript + +<|ref|>text<|/ref|><|det|>[[115, 647, 879, 681]]<|/det|> +Methods Line 174: Additionally, we conducted a sensitivity analysis using a more stringent threshold, including only variants with \(p< 5\times 10^{- 8}\) for FI in European \((N = 39)\) or Multi- ancestry \((N = 8)\) GWAS. + +<|ref|>text<|/ref|><|det|>[[115, 687, 880, 815]]<|/det|> +Discussion Line 510: Another limitation of our study is the inclusion of variants with subthreshold GWAS significance levels. However, to address this concern, we conducted a sensitivity analysis focusing on variants meeting the stringent criterion of \(p< 5\times 10 - 8\) . This analysis led to the identification of four clusters—PIS, Adiposity, VAT, and FI- Liver/Lipid—that closely correspond to four of the original seven clusters, reinforcing the robustness of our findings (Supplementary Figure 4). Additionally, we confirmed that \(88\%\) of the full set of the 101 variants highly weighted in at least one cluster were associated with at least one metabolic trait at genome- wide significance, supporting their relevance in metabolic regulation. + +<|ref|>text<|/ref|><|det|>[[115, 821, 880, 903]]<|/det|> +2. What are the reasons T2D variants with well-established robust insulin secretion effects flip for fasting insulin? It is important to understand more about why an allele that results in higher insulin secretion is associated with lower insulin sensitivity and vice versa. If this is an artefact it will have resulted in the wrong inferences being made about the "no diabetes" clusters. One explanation is that the data come from people without diabetes and they "need" + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 879, 219]]<|/det|> +to be more insulin sensitive if they are genetically more prone to poorer insulin secretion – in other words a bias is introduced towards people who have some other reason for being insulin sensitive. This does not require individual level data to test but only summary stats. If there is such an artefact in the data there will be a simple dose response relationship between insulin secretion effect and insulin resistance effect. Or perhaps a dose response relationship that follows a classic hyperbolic curve of secretion vs resistance. Also, the authors could test the results excluding any variants where the FI increasing allele is also a well- known insulin secretion increasing allele. + +<|ref|>text<|/ref|><|det|>[[115, 240, 876, 289]]<|/det|> +We thank the reviewer for highlighting this important issue. Although we hypothesize that the nondiabetogenic clusters are associated with insulin secretion, we acknowledge that these clusters may not necessarily be linked to lower insulin sensitivity. + +<|ref|>text<|/ref|><|det|>[[115, 295, 861, 375]]<|/det|> +We are aware of the well- established hyperbolic relationship between insulin secretion and insulin sensitivity in individuals without diabetes. This relationship can complicate the interpretation of associations between genetic variants and fasting insulin, particularly due to the inherent biases introduced by this hyperbolic association. Summary statistics may also be influenced by these biases. + +<|ref|>text<|/ref|><|det|>[[115, 382, 872, 415]]<|/det|> +We revised the discussion of these limitations in the discussion section of our manuscript to provide a clearer understanding of how these factors might affect our findings. + +<|ref|>text<|/ref|><|det|>[[114, 421, 880, 647]]<|/det|> +Line 458: "The non- diabetogenic clusters, characterized by alleles associated with increased FI and decreased risk of T2D, suggest mechanisms involving increased insulin resistance coupled with compensatory insulin production. In particular, the preserved beta- insulin secretion cluster may be influenced by the gene expression of ADCY5, which is known to regulate insulin secretion from human islets 52. This cluster features the opposite allele (rs11708067- G) compared to the T2D beta- cell cluster identified by Udler et al. 8 (rs11708067- A), which contains the rs11708067- A allele. The rs11708067- A allele is linked to reduced function of an islet enhancer, leading to decreased ADCY5 expression and impaired insulin secretion 53. Similarly, the rs7903146- T allele in TCF7L2 is associated with compromised beta- cell function 54. The alleles in the preserved beta- insulin secretion cluster (rs11708067- G, rs7903146- C, and rs11039290- A) contribute to incremental increases in insulin production. This increased production may enhance or preserve beta- cell function, potentially leading to lower blood glucose levels and reduced cardiometabolic risk. Alternatively, these findings could reflect an early compensatory response when glycemia is normal or only slightly elevated. 2,55,56. " + +<|ref|>text<|/ref|><|det|>[[115, 652, 875, 749]]<|/det|> +Line 501: "The study also has some limitations; we acknowledge the potential bias stemming from the hyperbolic association, where elevated insulin secretion might be driven by insulin resistance as a compensatory mechanism rather than by genetic factors alone. Insulin responses, which reflect basal beta cell function, are inversely related to insulin action across varying degrees of glucose intolerance53,54,60. This physiological complexity complicates the task of isolating these two mechanisms, making it difficult to disentangle their individual genetic contributions." + +<|ref|>sub_title<|/ref|><|det|>[[116, 779, 422, 795]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 811, 872, 906]]<|/det|> +In this MS, the authors applied their previously developed bioinformatic pipeline for identifying clusters of SNP- phenotype associations for fasting insulin- related SNPs. The work attempts to disentangle multiple genetic mechanisms modulating fasting insulin levels alongside the phenotypic context they are also associated with. The analysis yielded 7 clusters, 3 of which associated with fasting insulin without being associated with an increased T2D risk. These clusters could highlight biologically reasonable pathway groups, such as the visceral adiposity cluster, which is jointly + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 825, 122]]<|/det|> +associated with higher visceral fat, waist circumference, HOMA- B but lower “corrected insulin response”, and associates with hypertension among the outcomes and in males with MI. + +<|ref|>text<|/ref|><|det|>[[115, 137, 255, 153]]<|/det|> +Points of criticism: + +<|ref|>text<|/ref|><|det|>[[113, 168, 877, 360]]<|/det|> +1. Many of the variants used from the fasting insulin aspect are known diabetes-associated variants, of which in some clusters the protective alleles are referred to. For a better readability, it would be important to note which allele is specifically referred to (allele with higher/lower insulin levels, alleles associating with or protecting from diabetes) in the main figures. This would thus set a reference allele direction. For example, the PIS cluster features TCF7L2 as one of the included variants. Is the lower plasma insulin in this cluster associated with the diabetes-related allele of the variant, and the association of the whole cluster with lower fasting glucose thus a consequence of the aggregate effects of all variants comprised in the cluster? Or is the diabetes-protective allele in this variant associating with a lower fasting insulin level with similar mechanisms? Similarly, it would be nice to see clearly, whether for the HIR/liver lipid cluster, the diabetes-associated effect direction really aligns with higher fasting glucose but lower 2-hour-glucose and lower triglycerides. + +<|ref|>text<|/ref|><|det|>[[115, 382, 870, 415]]<|/det|> +To improve the readability of our results, we have revised Figure 2 to include annotations indicating the main association with type 2 diabetes (T2D) at the top, which will guide interpretation. + +<|ref|>text<|/ref|><|det|>[[115, 421, 861, 470]]<|/det|> +In the figure, all alleles are aligned to show the direction of effect on fasting insulin. Specifically for the PIS cluster, we clarify that the diabetes-protective allele of TCF7L2 is associated with lower fasting insulin levels, which contributes to a reduced T2D risk. + +<|ref|>text<|/ref|><|det|>[[115, 476, 805, 525]]<|/det|> +For the HIR/liver lipid cluster, the T2D association at the top clarifies whether the diabetes- associated effect direction aligns with higher fasting glucose, but lower 2- hour glucose and triglycerides. + +<|ref|>text<|/ref|><|det|>[[115, 532, 835, 564]]<|/det|> +We believe these changes will enhance the interpretability of our figures and better convey the relationships between alleles, fasting insulin, and diabetes risk. + +<|ref|>text<|/ref|><|det|>[[115, 572, 185, 588]]<|/det|> +Figure 2 + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 90, 790, 470]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 495, 875, 561]]<|/det|> +2. Some interesting constellations of end-point-associations are not discussed. For example, while the HIR cluster associates with lower MI (which could fit to findings from mendelian randomization analyses about hepatic fat and CV outcomes), it is associated with lower eGFR, suggesting that this mechanism could underly diabetic nephropathy to some extent. + +<|ref|>text<|/ref|><|det|>[[114, 568, 877, 697]]<|/det|> +We appreciate the reviewer's insightful observation regarding the interesting constellations of endpoint associations. In response, we have included a dedicated section in the manuscript to discuss these associations in greater depth. Specifically, we now address the relationship between the HIR cluster and its associations with both lower MI risk and reduced eGFR. This section explores how these findings align with recent Mendelian randomization analyses and discusses the potential implications for understanding the complex mechanisms underlying these associations. We also outline the future work necessary to further investigate these connections. Thank you for highlighting this important aspect of our study. + +<|ref|>text<|/ref|><|det|>[[114, 718, 878, 878]]<|/det|> +Line 484: "Our study reveals several noteworthy associations that merit further examination. Notably, the HIR cluster demonstrates a significant association with a lower risk of MI. This finding is consistent with recent research by Ahmed et al59, which identified 13 genetic variants associated with impaired hepatic triglyceride export. Their study showed that liver fat-increasing alleles were correlated with a reduced risk of coronary artery disease and MI but an elevated risk of type 2 diabetes, underscoring the heterogeneous effects of liver fat on health outcomes. Additionally, the HIR cluster is associated with a reduced eGFR, a marker of kidney function. The connection between lower MI risk and reduced eGFR within the HIR cluster suggests that mechanisms implicated in diabetogenic pathways related to hepatic function may influence multiple disease outcomes through complex and interrelated mechanisms. This emphasizes the need for further + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 122]]<|/det|> +research to elucidate the pathways linking insulin resistance with cardiovascular and renal diseases and to explore how these associations might inform personalized intervention strategies." + +<|ref|>text<|/ref|><|det|>[[114, 144, 880, 226]]<|/det|> +3. Some of the cluster denominations seem to be rather arbitrary, and difficult to explain. E.g. the stressed beta-cell cluster is associated with higher gGT and CRP, which positions it closer to inflammatory/hepatic mechanisms. Also, cluster denominations seem to be left from the working titles in the Suppl Fig 3, it's better to align these to the main MS. I liked liver-lipid better than HIR anyway. + +<|ref|>text<|/ref|><|det|>[[114, 232, 875, 328]]<|/det|> +We thank the reviewer for the detailed feedback. In response, we have revised the cluster names to better reflect the traits they represent and to avoid potential misinterpretations. The revised cluster names are as follows: Proinsulin (formerly Stressed Beta-Cell), FI-Liver/Lipid (formerly HIR), and FI- Lipodystrophy (formerly Lipodystrophy). We have updated all figures, tables, and the manuscript to ensure consistency with these new names. We believe these changes better align with the underlying biological mechanisms and improve the clarity of our presentation. + +<|ref|>text<|/ref|><|det|>[[114, 342, 874, 408]]<|/det|> +4. The authors use the word "ectopic fat" synonymously with visceral fat. This is not correct. Ectopic fat refers to triglyceride accumulation in cell types not dedicated for triglyceride storage such as hepatocytes or myocytes. Visceral fat is just a dysfunctional adipose tissue distribution, but not ectopic fat. + +<|ref|>text<|/ref|><|det|>[[114, 414, 876, 462]]<|/det|> +We thank the reviewer for pointing out this important distinction. To correct this, we have revised the manuscript to use the term "visceral fat" where appropriate and ensured that the term "ectopic fat" is used correctly to describe triglyceride accumulation in non-adipose tissues. + +<|ref|>text<|/ref|><|det|>[[114, 469, 785, 502]]<|/det|> +We appreciate the reviewer's attention to this detail, which improves the accuracy of our terminology. + +<|ref|>sub_title<|/ref|><|det|>[[114, 524, 864, 558]]<|/det|> +## 5. I couldn't find a listing of the 43 traits which were fed to the bNMF algorithm according to Fig 1 + +<|ref|>text<|/ref|><|det|>[[115, 572, 847, 620]]<|/det|> +A comprehensive listing of the 43 traits that were input into the bNMF algorithm, as well as the reasons for excluding certain traits, is provided in Supplementary Table 3. We have updated the manuscript to ensure that this information is clearly referenced. + +<|ref|>text<|/ref|><|det|>[[115, 644, 452, 660]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[114, 675, 850, 708]]<|/det|> +I didn't try to reproduce the results, it would require much work, but the code seems to be well documented and reasonable to be reused by others. + +<|ref|>text<|/ref|><|det|>[[115, 732, 418, 747]]<|/det|> +We appreciate the reviewer's comment. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 418, 106]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 121, 870, 186]]<|/det|> +The authors have had a much better go at attempting to unravel what are I believe a complex set of variants and clusters of variants. They should be congratulated for tackling a tricky subject. However, I do think that two main concerns should be more explicitly acknowledged in the discussion. + +<|ref|>text<|/ref|><|det|>[[113, 201, 881, 512]]<|/det|> +First, the inclusion of \(80\%\) of the variants not reaching genome wide significance adds complexity and confusion in my opinion. I believe most if not all previous papers using clustering approaches of variants have limited the analyses to variants associated with the primary trait in question, at \(p< 5\times 10 - 8\) . For sure some of these variants are associated with other metabolic traits at \(p< 5\times 10 - 8\) and are likely affecting FI, but most likely via a more proximal trait, such as BMI, or as an artefact of being primarily an insulin secretion allele, and it is better to characterise these by looking first at the trait they are most strongly associated with - then it will become much clearer as to the mechanism. This point is partly clarified when the new analyses limited to the 47 / 230 variants reaching \(p< 5\times 10 - 8\) reveals only 4 not 7 clusters. I feel the discussion skirts around this issue a little and the authors should more explicitly state something like "Only \(20\%\) of the variants we included reach GWS significance for FI. Of the remaining \(80\%\) NN are GWAS for another metabolic trait, and these associations will likely provide greater clarity as to how the allele alters FI, compared to trying to clustering algorithms. When limited to the 47 GWAS significant variants we observed 4 not 7 clusters" + +<|ref|>text<|/ref|><|det|>[[116, 512, 857, 546]]<|/det|> +false associations between insulin secretion increasing/T2D protective alleles and higher FI". + +<|ref|>text<|/ref|><|det|>[[116, 553, 852, 586]]<|/det|> +We thank the reviewer for their constructive suggestions. We have incorporated the required clarifications in the last version of the manuscript: + +<|ref|>sub_title<|/ref|><|det|>[[116, 601, 241, 617]]<|/det|> +## First comment + +<|ref|>sub_title<|/ref|><|det|>[[117, 633, 256, 649]]<|/det|> +## Previous version: + +<|ref|>text<|/ref|><|det|>[[115, 663, 880, 794]]<|/det|> +Line 509: "Another limitation of our study is the inclusion of variants with subthreshold GWAS significance levels. However, to address this concern, we conducted a sensitivity analysis focusing on variants meeting the stringent criterion of \(p< 5\times 10^{- 8}\) . This analysis led to the identification of four clusters—PIS, Adiposity, VAT, and FI- Liver/Lipid—that closely correspond to four of the original seven clusters, reinforcing the robustness of our findings (Supplementary Figure 4). Additionally, we confirmed that \(88\%\) of the full set of the 101 variants highly weighted in at least one cluster were associated with at least one metabolic trait at genome- wide significance, supporting their relevance in metabolic regulation." + +<|ref|>sub_title<|/ref|><|det|>[[117, 809, 277, 825]]<|/det|> +## Updated paragraph: + +<|ref|>text<|/ref|><|det|>[[116, 840, 856, 904]]<|/det|> +Line 380: "Another limitation of our study is the inclusion of variants with subthreshold GWAS significance levels, with only \(20.43\%\) reaching genome- wide significance for FI (N=47). However, to address this concern, we conducted a sensitivity analysis focusing on variants meeting the stringent criterion of \(p< 5\times 10^{- 8}\) . This stricter selection led to the identification of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 877, 218]]<|/det|> +four clusters—PIS, Adiposity, VAT, and FI- Liver/Lipid—from a subset of 47 GWAS- significant variants, which corresponds closely to four of the original seven clusters, thereby reinforcing the robustness of our findings (Supplementary Figure 4). Moreover, 88% of the full set of 101 variants highly weighted in at least one cluster were associated with at least one metabolic trait at genome- wide significance. This supports their relevance in metabolic regulation and provides clarity on how these alleles potentially influence FI, demonstrating that broader metabolic associations beyond FI are integral to understanding the allelic impact on metabolic traits." + +<|ref|>sub_title<|/ref|><|det|>[[116, 248, 272, 265]]<|/det|> +## Second comment: + +<|ref|>text<|/ref|><|det|>[[117, 281, 256, 297]]<|/det|> +Previous version: + +<|ref|>text<|/ref|><|det|>[[115, 312, 882, 539]]<|/det|> +Line 457: "The non- diabetogenic clusters, characterized by alleles associated with increased FI and decreased risk of T2D, suggest mechanisms involving increased insulin resistance coupled with compensatory insulin production. In particular, the preserved beta- insulin secretion cluster may be influenced by the gene expression of ADCY5, which is known to regulate insulin secretion from human islets \(^{52}\) . This cluster features the opposite allele (rs11708067- G) compared to the T2D beta- cell cluster identified by Udler et al. \(^{8}\) (rs11708067- A), which contains the rs11708067- A allele. The rs11708067- A allele is linked to reduced function of an islet enhancer, leading to decreased ADCY5 expression and impaired insulin secretion \(^{53}\) . Similarly, the rs7903146- T allele in TCF7L2 is associated with compromised beta- cell function \(^{54}\) . The alleles in the preserved beta- insulin secretion cluster (rs11708067- G, rs7903146- C, and rs11039290- A) contribute to incremental increases in insulin production. This increased production may enhance or preserve beta- cell function, potentially leading to lower blood glucose levels and reduced cardiometabolic risk. Alternatively, these findings could reflect an early compensatory response when glycemia is normal or only slightly elevated. \(^{2,55,56}\) ." + +<|ref|>sub_title<|/ref|><|det|>[[117, 553, 253, 569]]<|/det|> +## Updated version: + +<|ref|>text<|/ref|><|det|>[[115, 584, 882, 888]]<|/det|> +Line 324: "The non- diabetogenic clusters, characterized by alleles associated with increased FI and decreased risk of T2D, suggest mechanisms involving increased insulin resistance coupled with compensatory insulin production. In particular, the PIS cluster may be influenced by the gene expression of ADCY5, which is known to regulate insulin secretion from human islets \(^{52}\) . This cluster features the opposite allele (rs11708067- G) compared to the T2D beta- cell cluster identified by Udler et al. \(^{8}\) , which contains the rs11708067- A allele. The rs11708067- A allele is linked to reduced function of an islet enhancer, leading to decreased ADCY5 expression and impaired insulin secretion \(^{53}\) . Similarly, the rs7903146- T allele in TCF7L2 is associated with compromised beta- cell function \(^{54}\) . The alleles in the preserved beta- insulin secretion cluster (rs11708067- G, rs7903146- C, and rs11039290- A) contribute to incremental increases in insulin production. This increased production may enhance or preserve beta- cell function, potentially leading to lower blood glucose levels and reduced cardiometabolic risk. Alternatively, these findings could reflect an early compensatory response when glycemia is normal or only slightly elevated. \(^{2,55,56}\) . Furthermore, it is crucial to acknowledge that the alleles within the PIS cluster were selected for this analysis due to their association with increased FI levels, and they exhibit a decreased risk for T2D; as noted above, the alternative alleles increase T2D risk and are associated with reduced insulin secretion. The observed effects of the T2D- reducing alleles may be attributed to collider bias, particularly since the FI GWAS were conducted in individuals without T2D + +<--- Page Split ---> diff --git a/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/images_list.json b/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..01f9e5d5c99297cb6af1138bee29dfd6d8e9bf64 --- /dev/null +++ b/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,177 @@ +[ + { + "type": "image", + "img_path": "images/Figure_6d.jpg", + "caption": "*Supplemental Fig. 6d", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_3a.jpg", + "caption": "*Fig. 3a-c and Fig. 4f.", + "footnote": [], + "bbox": [ + [ + 89, + 410, + 790, + 840 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_3e.jpg", + "caption": "*Supplemental Fig. 3e", + "footnote": [], + "bbox": [ + [ + 308, + 45, + 610, + 230 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_11.jpg", + "caption": "*Supplemental Fig. 11", + "footnote": [], + "bbox": [], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_3g.jpg", + "caption": "\\\\*Supplemental Fig. 3g-i", + "footnote": [], + "bbox": [ + [ + 160, + 72, + 839, + 475 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_9e.jpg", + "caption": "\\*Supplemental Fig. 9e-g", + "footnote": [], + "bbox": [], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_3a.jpg", + "caption": "*Fig. 3a-c", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_4f.jpg", + "caption": "\\\\*Fig. 4f", + "footnote": [], + "bbox": [ + [ + 63, + 43, + 446, + 214 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "4. As shown in Fig. 3, NCLK-1 flies display elevated immune responses and shortened lifespan and demonstrated that disrupting neuronal CLK function elevates systemic immune responses. Later the authors have demonstrated that this is also eye-driven (Fig. 3c, d). For these experiments, the authors have used fly bodies, instead of heads. Why expression was not tested in the head/eyes?", + "footnote": [], + "bbox": [ + [ + 158, + 690, + 707, + 844 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_4a.jpg", + "caption": "*Fig. 4a and Supplemental Fig. 5f", + "footnote": [], + "bbox": [ + [ + 66, + 120, + 840, + 300 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_5d.jpg", + "caption": "*Supplemental Fig. 5d and Fig. 4d", + "footnote": [], + "bbox": [ + [ + 57, + 316, + 797, + 504 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_7.jpg", + "caption": "Fig. 7", + "footnote": [], + "bbox": [ + [ + 113, + 736, + 480, + 920 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_1m.jpg", + "caption": "*Supplemental Fig. 1m and 7c", + "footnote": [], + "bbox": [ + [ + 58, + 288, + 920, + 522 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1: trpl-gal4>Clk-DN1 cross-section at day 2.", + "footnote": [], + "bbox": [], + "page_idx": 13 + } +] \ No newline at end of file diff --git a/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..de1366cc551c90bf4ceb265676e556da9722ee3f --- /dev/null +++ b/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,498 @@ + +# nature portfolio + +Peer Review File + +Dietary restriction and the transcription factor clock delay eye aging to extend lifespan in Drosophila melanogaster + +![](images/Figure_6d.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +Previous studies have shown a two- ways interaction between dietary restriction (DR) and the circadian clocks. In flies, the DR- induced lifespan extension is decreased when peripheral (non- brain) circadian clocks are stopped and DR increases the amplitude of clock protein cycling (Katewa et al. 2016). Building on these data Hodge et al. investigate the effects of clock disruption in the eye and retinal degeneration on lifespan in DR or ad libitum feeding conditions. They conclude that flies expressing the dominant- negative CLOCK protein show accelerated retinal senescence and shortened lifespan. They show that photoreceptor activation and subsequent retinal senescence shorten lifespan and that DR protects against this effect. + +The idea that photoreception activation shortens lifespan and is prevented by DR is very interesting and the possibility that the eye circadian clock protects from these effects exciting. The conclusions of this study are definitely important. The data are rather convincing although I have some concerns with the tools that are used to disrupt the clock and I would recommend using classical clock mutants to confirm the results, as detailed below. + +1- Since CLK affects the anatomy of at least some clock neurons, the CLK- delta dominant- negative might have related effects in other cells including photoreceptors. It would thus be important to use an independent way of abolishing the clock function. perO or timO flies do not have reported developmental effects, including in the eye. I think that the authors need to confirm the CLK- delta experiments for at least the phenotypes phototaxis assay during aging in AL and DR conditions, to conclude that the absence of a functional clock prevents + +2- It is clear from the present study that CLK- delta flies have a strongly reduced lifespan in both AL and DR conditions and it is not clear to me that it is the case of perO flies. As indicated for photoreceptor degeneration, perO or timO flies need to be used in the lifespan assay in AL and DR to decipher between the effects of expressing the CLK- delta protein and the absence of a functional clock. + +3- p17. The three CLK- controlled genes (Gb76c, retinin, sunglasses) whose downregulation causes phototaxis defects and shortening of lifespan under DR (Fig 5e- f) should show circadian oscillations of their mRNAs with larger amplitude in DR versus AL conditions if the proposed model is correct. Is it the case ? + +4- I notice some tendency to mix known results from mammals and flies to draw general conclusions. I would suggest to be more cautious about this since rather strong differences exist, for example in the phototransduction pathway. Please be more precise about the model system when citing published data and provide appropriate references. + +## Minor points + +- p8. "These findings provide a potential mechanistic explanation for the rhythmic response pattern in light-sensitivity observed in Drosophila photoreceptors". It is well documented in vertebrates but is it + +<--- Page Split ---> + +clearly shown in flies? Please provide references. + +Reviewer #2 (Remarks to the Author): + +The manuscript by Hodge and colleagues demonstrates that the circadian clock regulates phototransduction in such a manner as to increase lifespan, visual function, and lower systematic inflammation. The data in the paper are convincing and support the conclusion of the authors. + +I am having some trouble with the connections that are made in the paper. For example, it is not clear to me why photoreceptor degeneration would cause an increase in systemic inflammation and a decrease in lifespan. I am not questioning the data in the paper. I just think that the authors need to connect the dots for the reader more carefully. + +I am also not sure I understand how the dietary restriction plays into the study. I think the authors could just look at defective retinal clocks and the effect that it has on the fly. Especially since flies are not normally going to encounter dietary restrictive conditions out in the wild. + +I also think that the authors need to focus on one of the effects that the eye clock has on the fly. It could be visual function, inflammation, or lifespan but it I think the paper will benefit from a single idea. + +Just my two cents - I think the strongest part of the paper is the effect the eye clock has on phototransduction and visual function. I think that a revised paper in which the authors focus exclusively on this connection will be very exciting and would be appropriate for Nature Communications. + +The effect on systematic inflammation and lifespan, while both interesting, are hard to connect to the state of photoreceptor health and, to me, make a much less interesting story. + +If the authors focus on visual function I would suggest that they combine their clock mutants with all known phototransduction mutants to gain a comprehensive view of how the clock is affecting degeneration and visual function. + +I would also suggest that the authors do experiments in complete darkness, a light:dark cycle, and constant light. + +Reviewer #3 (Remarks to the Author): + +Using Drosophila models, in this study Hodge et al. demonstrated that dietary restriction (DR) extends lifespan by promoting circadian homoeostatic processes that protect the visual system from age- and light- associated damage. The authors have further demonstrated that disrupting circadian rhythms in the eye by inhibiting the transcription factor, Clock (CLK), or CLK- output genes, accelerated visual + +<--- Page Split ---> + +senescence, induced a systemic immune response, and shortened lifespan. Moreover, flies subjected to dietary restriction were protected from the lifespan- shortening effects of photoreceptor activation. Inversely, photoreceptor inactivation, achieved via mutating rhodopsin or housing flies in constant darkness, primarily extended lifespan in flies reared on a high- nutrient diet. Overall, their findings establish the eye as a diet- sensitive modulator of lifespan and indicate that vision is an antagonistically pleiotropic process that contributes to organismal aging. + +Using multiple assays this is a very detail, systemic, and well- designed mechanistic study to demonstrate the linkage to DR and circadian rhythms to protect the visual system from age- and light- associated damage. Overall, findings from this study are quite interesting, however, require more clarity, specification, and justifications. In my assessment with some clarity and justification, this might become suitable for publication in Nature Communications. The following questions/concerns need to be addressed for this consideration. + +1. The authors have used multiple drivers to express/knockdown various genes in multiple tissues, however, the focus is limited to visual-aging. The authors need to provide a table using all the drivers/genes used in this manuscript for all the genetic modulations with clear/concise justifications. This is essential to justify the authors' hypothesis and potential outcome. This will be also useful for the general audience in understanding the power of Drosophila genetics for addressing cell-autonomous functions. + +2. Related to my concern 1, the authors frequently use ELAV and GMR drivers however, did not differentiate clock-mediated neuroprotective functions vs photoreceptors/visual system. When using a Pan-neuronal driver like ELAV, how modulation of circadian clock or DR affecting the neuronal system? Based upon their findings, it is clear that the life-span and phototaxis performance will be affected by the para-neuronal ELAV driver. Therefore, most of the outcomes shown by the authors could be neuronal as well. Therefore, it will be essential to differentiate neuronal vs visual systems in the entire manuscript. Also, as shown in Fig.5, it is important to clarify how knock-down of GMR-driven DR-sensitive eye-specific Clk-output genes reduces survival and affects phototaxis performance? Recent studies have shown that GMR-expression is not limited to the visual system therefore, most of these genes knock-down, including reduces survival and affects phototaxis performance might be not limited to the visual system. + +3. It is well known that GMR-driver mediated expression/knock-down directly affects ommatidia organization/degeneration. Did the authors see any defects in ommatidia organization/degeneration with the ocular expression of CLK-delta1 and CLK-delta or ocular knock-down of ATP or other genes shown in listed in Fig. 5? It will be also important to know if this was impacted by DR or other genetic modulations. + +4. As shown in Fig. 3, NCLK-1 flies display elevated immune responses and shortened lifespan and demonstrated that disrupting neuronal CLK function elevates systemic immune responses. Later the authors have demonstrated that this is also eye-driven (Fig. 3c, d). For these experiments, the authors have used fly bodies, instead of heads. Why expression was not tested in the head/eyes? + +5. Similarly, in Fig 5e, why the experiment is limited to the whole fly? Relative mRNA expression of immune genes (AttaA, DiptB, and Dro) calculated by RT-qPCR with mRNA isolated from bodies of w1118 and rhodopsin mutant flies housed in 12:12h LD. + +6. As I mentioned before, different drivers used for different experiments, however, the conclusion is limited to eye aging? The authors need to justify how the expression of different tissues leads to eyes aging? A clear cell-autonomous vs non-cell-autonomous justification will be required including editing + +<--- Page Split ---> + +Fig. 6. If neuronal damage signals propagate throughout the body to drive systemic immune responses, the authors need to find basal expression of these genes responsible for immune response in the neuronal and visual tissue/system. + +7. Again, the authors have argued that neuronal CLK function is required for the full lifespan extension mediated by DR and indicate that photoreceptor clocks are essential for the maintenance of visual function with age and organismal survival? I think these are confusing statements and need more clarity and justification. Despite several pieces of evidence provided by authors for the neurological role, I am not sure how the outcome is limited to visual function/system? + +8. DR-protection against lifespan shortening downstream of light and/or rhodopsin-mediated signaling in a manner that requires light-adaptation, and by extension, arr1-mediated rhodopsin endocytosis. This justification needs more clarification. + +9. Despite the noticeable difference of immune system and photoreceptors cells between, Drosophila with the mammalian visual system, the authors did not indicate the limitations of their finding. + +10. The discussion section of the main text needs a significant improvement including clarity about the above-mentioned comments. The authors have also used discussion/significance of their findings in the SI section without any clarification. + +<--- Page Split ---> + +Dear Editor, + +Thank you for considering our manuscript in your esteemed journal and allowing us to respond to the reviewer's comments. We thank the reviewers for their thoughtful comments and I hope you will find that our responses have significantly improved the manuscript. We have made appropriate changes in the text and figures and here is our point- by- point response to the comments. + +We have provided the following new data and updates to address the reviewer comments: + +New Figures/Data: + +
FigureData
3a-cprCLK-DN1 and prCLK-OE phototaxis, ERG, trangenial cross-sections.
S. 1b, d-f, 1Tim01 circadian transcriptome analyses.
S. 4bprCLK-DN1 and prCLK-OE ERG traces.
S. 7carr1 expression from nCLK-DN1 RNA-Seq.
S. 8a-bCone-cell specific ATPalpha-RNAi knockdown phototaxis and lifespan.
S. Data 12Rationale and strengths/weakness of lines used in study.
+ +Updated Figures/Data: + +
FigureData
4fprCLK-DN1 lifespan (N=3).
S. 7dEye-specific arr1 knockdown phototaxis.
S. Data 1AL and DR circadian transcriptome analyses in wild-type and circadian mutant flies
S. Data 7Survival analyses.
S. Data 9Positive phototaxis responses and statistics.
S Data 10Electroretinogram analyses and statistics.
S. Table 2Drosophila strains used in this study.
+ +## Reviewer #1 (Remarks to the Author): + +Previous studies have shown a two- ways interaction between dietary restriction (DR) and the circadian clocks. In flies, the DR- induced lifespan extension is decreased when peripheral (non- brain) circadian clocks are stopped and DR increases the amplitude of clock protein cycling (Katewa et al., 2016, PMID: 26626459). Building on these data Hodge et al. investigate the effects of clock disruption in the eye and retinal degeneration on lifespan in DR or ad libitum feeding conditions. They conclude that flies expressing the dominant- negative CLOCK protein show accelerated retinal senescence and shortened lifespan. They show that photoreceptor activation and subsequent retinal senescence shorten lifespan and that DR protects against this effect. + +The idea that photoreception activation shortens lifespan and is prevented by DR is very interesting and the possibility that the eye circadian clock protects from these effects exciting. The conclusions of this study are definitely important. The data are rather convincing although I have some concerns with the tools that are used to disrupt the clock and I would recommend using classical clock mutants to confirm the results, as detailed below. + +1- Since CLK affects the anatomy of at least some clock neurons, the CLK- delta dominant- negative might have related effects in other cells including photoreceptors. It would thus be important to use an independent way of abolishing the clock function. per0 or tim0 flies do not have reported developmental effects, including in the eye. I think that the authors need to confirm the CLK- delta experiments for at least the phenotypes phototaxis assay during aging in AL and DR conditions, to conclude that the absence of a functional clock prevents + +We agree with the concern that over- expressing CLK- \(\Delta 1\) might influence the function of non- photoreceptor neurons, especially when we utilizing the pan- neuronal Elav- gene- switch- GAL4 driver system. We would like to point out that with the GeneSwitch system we induce GAL4- mediated expression with the addition of RU486 in 4- day old adult, mated female flies, post- development. Therefore, we can avoid developmental defects associated with the expression of CLK- \(\Delta 1\) . Furthermore, the positive phototaxis and ERG data with the CLK- \(\Delta 1\) lines, elav- GS- GAL4>CLK- \(\Delta 1\) and CLK- \(\Delta 2\) , are indistinguishable from control at the earliest time- point recorded (day 2 post induction), indicating that the photoreceptor cells have developed normally. An additional strength of Gene- Switch system is that the control flies are from the same F1 generation and have the same genotype (but are reared on vehicle treated food vs food with RU486). We also note that although we used a pan- neuronal driver (elav- GS- GAL4), Clk is enriched 5- fold within the photoreceptor cells vs the rest of the neurons in the brain (see Supplemental Fig. 6d). Furthermore, within the brain, clk expression is confined to a small population of approximately 150 neurons. Therefore, it is likely that over- expressing a dominant- negative CLK protein with a pan- neuronal driver may only affect this minor population of neurons in the brain. To demonstrate cell- intrinsic function of CLK we have included new data with photoreceptor- specific disruption to Clk, which we describe in greater detail below. + +<--- Page Split ---> +![](images/Figure_3a.jpg) + +
*Supplemental Fig. 6d
+ +- To directly test the role of CLK function in adult photoreceptors (post-developmental), we combined the Trpl-Gal4 driver (which narrowly expresses GAL4 in the photoreceptor cells) with temperature-sensitive Gal80 (which strongly represses Gal4 activity at \(18^{\circ}\mathrm{C}\) ) and crossed these flies to UAS-Clk-Δ1 (Trpl-gal4; gal80>Clk-Δ1, denoted prCLK-Δ1). To suppress the expression of Clk-Δ1 during development, we housed these flies (prCLK-Δ1) at \(18^{\circ}\mathrm{C}\) . Upon occlusion, we then sorted the flies (prCLK-Δ1) onto AL or DR food and then transferred them to \(30^{\circ}\mathrm{C}\) to de-repress GAL4 and induce the expression of Clk-Δ1. To limit confusion, the data generated with Elav-GS-GAL4 remain in Figure 2, while new data generated with the photoreceptor specific GAL4 line was placed into a new Figure 3. Similar to Elav-Gs>Clk-Δ1, Trpl-gal4; gal80>Clk-Δ1 flies also display accelerated photoreceptor aging, as is apparent via phototaxis (Fig. 3a), ERG amplitude (Fig. 3b), and tangential cross-sections of the ommatidia (Fig. 3c). Trpl-gal4; gal80>Clk-Δ1 flies also display a lifespan shortening in comparison to their outcrossed controls (w/+,Trpl-Gal4/+; Gal80/+) (Fig. 4f). This further demonstrates that CLK function within photoreceptors influences lifespan and visual senescence. Lastly, we have included several Clk overexpression experiments (w;Trpl-Gal4/+;UAS-Clk/Gal80) and demonstrate that increasing the expression of CLK within the photoreceptor cells is sufficient to delay visual senescence and rescue AL-mediated declines, as we observed with phototaxis (Fig. 3a), ERG amplitude (Fig. 3b), and cross-sections of the ommatidia (Fig. 3c). **See Supplemental Fig. 4b for the averaged ERG traces between the control, prCLK-Δ1, and prCLK-OE lines. + +![](images/Figure_3e.jpg) + +
*Fig. 3a-c and Fig. 4f.
+ +- In addition to using the CLK-Δ1 lines, we have also tested flies homozygous for a separate null clk allele, CLKout. Consistent with the CLK-Δ1 data, in CLKout flies, we found that that DR failed to delay visual senescence in comparison to AL-fed flies (now in Supplemental Fig. 3e). + +<--- Page Split ---> +![](images/Figure_11.jpg) + +
*Supplemental Fig. 3e
+ +We agree that testing additional circadian mutants may help support our claim that CLK influences photoreceptor aging and mediates the beneficial effects of DR on the eye. In addition to the wild- type circadian time- course microarray (Canton- S flies), we also performed the same time- course in \(\text{tim}^{01}\) mutant flies (and have now included these data in Supplemental Fig. 1b, d, e- f, and 1) \\*\\*We also deposited the raw and processed files for the \(\text{tim}^{01}\) circadian time- course microarray at GEO: GSE158286. Interestingly, we found that DR failed to amplify the number of circadian genes in \(\text{tim}^{01}\) mutants (Supplemental Fig. 1d), indicating that normal circadian function is required. + +![](images/Figure_3g.jpg) + + +For both \(\text{per}^{01}\) and \(\text{tim}^{01}\) mutants, the negative feedback loop that represses CLK/CYC heterodimers is disrupted, resulting in low but constitutive transcriptional activity by CLK/CYC (Glossop et al., 1999. PMID:10531060). Because of this caveat—and our model that CLK- output genes mediate DR's ability to delay eye aging—we decided not to move forward with testing phototaxis in either \(\text{per}^{01}\) or \(\text{tim}^{01}\) flies. In agreement with the observation that CLK/CYC activity exists in mutants of the repressive limb of the molecular clock, we found that photoreceptor genes were still upregulated in expression upon DR in \(\text{tim}^{01}\) flies, although they failed to display a circadian oscillation (Supplemental Fig. 1l). + +![](images/Figure_9e.jpg) + +
*Supplemental Fig. 11
+ +Instead of utilizing \(\text{per}^{01}\) and \(\text{tim}^{01}\) mutants (for the reasons described above) we did decide to test the role of cryptochrome (CRY), a core clock component that is a direct light sensor and aids in photoentrainment. We found that three cry mutants \(\text{(cry}^{B}, \text{cry}^{01}\) , and \(\text{cry}^{02}\) ) all demonstrated clear enhancements in phototaxis on DR compared to AL (see Supplemental Fig. 3g- i). This suggests that circadian timing, and/or photoentrainment, may not be as important for mediating the diet- dependent responses in eye aging compared to proper CLK function. Our final reason for not testing \(\text{per}^{01}\) or \(\text{tim}^{01}\) mutants is because they harbor null, full- body mutations in period and timeless. + +<--- Page Split ---> + +Therefore, any phototaxis defect we might observe in these flies could be attributable to either developmental abnormalities or the loss of these genes in extra- ocular tissues. + +![](images/Figure_3a.jpg) + +
\\*Supplemental Fig. 3g-i
+ +2- It is clear from the present study that CLK- delta flies have a strongly reduced lifespan in both AL and DR conditions and it is not clear to me that it is the case of per0 flies. As indicated for photoreceptor degeneration, per0 or tim0 flies need to be used in the lifespan assay in AL and DR to decipher between the effects of expressing the CLK- delta protein and the absence of a functional clock. + +We thank you for your concern regarding potential different circadian mutants may yield variable effects on lifespan in the context of DR. As mentioned in the response to your first questions, we believe that neither the \(tim^{0l}\) nor \(per^{0l}\) mutant flies serve as a strong model for accessing the absence of functional CLK. Additionally, it is becoming increasingly apparent that disrupting circadian function, or losing CLK activity, can have tissue- specific effects on aging. In turn, lifespan may reflect a summation and/or differences in the individual contributions of aging across cell- types/tissues. For example, loss of \(per^{0l}\) function in the gut appears to extend lifespan in Drosophila (Ulgherait et al., 2020. PMID: 32317636). Our goal in this study was to elucidate the role of CLK function within the photoreceptors and determine its effect on aging and lifespan. Therefore, we feel it is appropriate to confine our efforts to transgenic lines that manipulate CLK activity in a tissue- specific fashion, namely in the photoreceptors and neurons. Also, we would like to highlight that \(per^{0l}\) mutant lifespans were performed on AL and DR diets in a previous publication from our lab (Subhash et al, 2016. PMID: 26626459) and that \(per^{0l}\) and \(tim^{0l}\) failed to display DR- mediated lifespan extension. These results were subsequently refuted by another lab observed that DR extended lifespan in these lines (Ulgherait et al., 2016. PMID: 27916531). It is unclear why there was a discrepancy between the period and timeless mutant lifespans, but these may be explained by lab- specific differences in lighting conditions (LUX, and LEDs used) or the microbiomes. Again, given that CLK activity can persist in \(per^{0l}\) and \(tim^{0l}\) mutants, we believe that these lines are suboptimal for studying CLK's role in modulating the rate of aging of adult photoreceptor cells. + +3- p17. The three CLK- controlled genes (Gb76c, retinin, sunglasses) whose downregulation causes phototaxis defects and shortening of lifespan under DR (Fig 5e- f) should show circadian oscillations of their mRNAs with larger amplitude in DR versus AL conditions if the proposed model is correct. Is it the case ? + +- The CLK-output genes we decided to analyze in this study (Gbeta76c, retinin, and sunglasses) were chosen based on our bioinformatics approach (Supplemental Fig. 9a): they were enriched in photoreceptors (public dataset, Charlton-Perkins et al, 2017. GSE93782), show circadian mRNA expression in young wild-type heads (public dataset, Kuintzle et al, 2017. GSE81100), are down-regulated with age, upregulated on DR vs AL (our data), and are down-regulated in nCLK-Δ1 vs control flies (our data). We did not observe a circadian oscillation (JTK CYCLE p-value<0.05) with Gbeta76c, retinin, and sunglasses in our AL and DR circadian transcriptome analysis, although these genes are all highly rhythmic in wild-type heads (Supplemental Fig. 9b-d). We likely failed to observe a circadian oscillation in these genes in our dataset because our transcriptome analyses incorporated pooled RNA from whole-fly lysates, whereas the circadian RNA sequencing experiment we reference extracted RNA from heads only. + +<--- Page Split ---> +![](images/Figure_4f.jpg) + + +![](images/Figure_3.jpg) + + +\*Supplemental Fig. 9b- d + +- Since we performed our nCLK-Δ1 RNA-Seq analysis at ZT 0 and ZT 12 (the peak and trough of their expression, respectively) we were able to observe time-of-day and diet-dependent changes in the expression of Gbeta76c, retinin, and sunglasses from RNA isolated from heads (Supplemental Fig. 9e-g). Our bulk analysis of circadian transcripts that oscillate on both AL and DR revealed that, on average, these transcripts display a more robust amplitude on DR vs AL (Supplementary Fig. 1j). Analysis of our RNA-Seq data from ZT0 and ZT12 indicate that the amplitude (difference in expression fold-change over time) was more robust for Gbeta76c (AL: 1.57, DR: 1.77) and retinin (AL: 0.93, DR 1.17), but not for sunglasses although the amplitudes were similar (AL: 1.19, DR: 1.15). Although we demonstrate that on average circadian amplitude is elevated on DR vs AL, our model that DR promotes the circadian expression of CLK-output genes does not rely solely on increases in circadian amplitude. It is possible that for several CLK-output genes that are elevated in expression by DR are also more rhythmic in their pattern of oscillation (i.e., their expression more closely fits a sine wave) while not elevating their overall amplitude. Alternatively, it is possible that DR-CLK mediated benefits to the aging photoreceptor are more dependant on overall expression changes to CLK-output genes, rather than their amplitude or rhythmicity. + +![](images/Figure_4a.jpg) + +
\*Supplemental Fig. 9e-g
+ +4- I notice some tendency to mix known results from mammals and flies to draw general conclusions. I would suggest to be more cautious about this since rather strong differences exist, for example in the phototransduction pathway. Please be more precise about the model system when citing published data and provide appropriate references. + +- We thank the reviewer for this concern and would like to highlight that we have included the following section in the Supplemental Discussion 1 section to help clarify potential differences between flies and mammals: + +<--- Page Split ---> + +"In mammals, light- activated rhodopsin in rod and cone photoreceptor neurons couples to, and inactivates, cyclic nucleotide gated channels, hyperpolarizing the cell [17]. This is distinctly different from what occurs in the fly, where light- activated rhodopsin couples to a TRP channel, which when activated depolarizes the cell [18]. However, in a third class of mammalian photoreceptors, the intrinsically- photosensitive retinal ganglion cells (ipRGCs), there is a nearly identical mechanism of phototransduction to Drosophila [19]. The ipRGCs play a role in non- image forming light sensation, effecting pupillary constriction and the entrainment of the central circadian clock to light. There is some evidence that eliminating Bmal1 in mice (either specifically in their ipRGCs or throughout their entire body) impairs the functionality of the ipRGCs [20]. This is consistent with what we observed when we disrupted clk in the Drosophila photoreceptors. Together, this suggests that there may be a conserved mechanism through which circadian clocks mediate the health of photoreceptor cells." + +## Minor points + +- p8. "These findings provide a potential mechanistic explanation for the rhythmic response pattern in light-sensitivity observed in Drosophila photoreceptors". It is well documented in vertebrates but is it clearly shown in flies? Please provide references. + +- It appears we accidentally neglected to include the reference within the main text, as it was only referenced in the supplemental discussion (ref #25). We have now included that reference within the main text: Nippe, O.M., et al., Circadian Rhythms in Visual Responsiveness in the Behaviorally Arrhythmic Drosophila Clock Mutant Clk(Jrk). J Biol Rhythms, 2017. 32(6): p. 583-592. + +## Reviewer #2 (Remarks to the Author): + +The manuscript by Hodge and colleagues demonstrates that the circadian clock regulates phototransduction in such a manner as to increase lifespan, visual function, and lower systematic inflammation. The data in the paper are convincing and support the conclusion of the authors. + +I am having some trouble with the connections that are made in the paper. For example, it is not clear to me why photoreceptor degeneration would cause an increase in systemic inflammation and a decrease in lifespan. I am not questioning the data in the paper. I just think that the authors need to connect the dots for the reader more carefully. + +- We thank the reviewer for their comment. In our current manuscript we believe we provide sufficient evidence that the photoreceptor is both a modulator of local and systemic inflammation as well as Drosophila lifespan. We believe that further studies are needed to elucidate the actual mechanism(s) by which photoreceptor's influence the health of other cell-types and modulate lifespan, but we feel that these studies are not within the scope of this current study. Herein, our focus was to identify the downstream CLK-controlled processes that are upregulated on DR, and to determine how they regulate aging and longevity, which we believe we have provided sufficient evidence. + +I am also not sure I understand how the dietary restriction plays into the study. I think the authors could just look at defective retinal clocks and the effect that it has on the fly. Especially since flies are not normally going to encounter dietary restrictive conditions out in the wild. + +- Given the observations that circadian clocks decline with age and that restrictive diets such as dietary restriction or calorie restriction enhance core molecular clock rhythms, we set out to identify which processes and tissues displayed clear DR-dependent improvements in circadian oscillation. Our time-course circadian transcriptome data on DR and AL led us to identify light-response genes as circadian and being selectively amplified by DR. We do believe that circadian clocks play important roles even in standard diets, or those that would be consumed in the wild, but our goal was to elucidate the circadian processes downstream of DR that help to slow aging and extend lifespan. + +I also think that the authors need to focus on one of the effects that the eye clock has on the fly. It could be visual function, inflammation, or lifespan but it I think the paper will benefit from a single idea. + +- We and the editor disagree with the critique that the manuscript will benefit by changing the focus or scope, and therefore we will not comment here. + +Just my two cents - I think the strongest part of the paper is the effect the eye clock has on phototransduction and visual function. I think that a revised paper in which the authors focus exclusively on this connection will be very exciting and would be appropriate for Nature Communications. + +- Please refer to our previous statement. + +The effect on systematic inflammation and lifespan, while both interesting, are hard to connect to the state of photoreceptor health and, to me, make a much less interesting story. + +- We found through an unbiased analysis of the genes that were upregulated with loss of CLK function that there were significant enrichments in inflammatory genes (i.e., AMPs). Furthermore, housing flies in LD vs DD also increases the expression of inflammatory markers. We then demonstrate that forcing photoreceptor degeneration (eye-specific ATPalpha knockdown) was sufficient to drive a systemic inflammatory response, while reducing rhodopsin mediated signaling (Rhodopsin null lines) suppressed this response. Given that chronic inflammation is now considered a hallmark of aging, we believe it is important to demonstrate that the photoreceptor could be a critical regulator of inflammation in the fly, and although the lifespan and inflammation findings are highly correlated, we are careful to refrain from claiming that photoreceptor derived inflammation is a main driver of lifespan shortening. We believe future studies are needed to develop a likely complex, mechanistic understanding of the interplay of diet, circadian rhythms, photoreceptor physiology, inflammation, and lifespan. + +If the authors focus on visual function I would suggest that they combine their clock mutants with all known phototransduction mutants to gain a comprehensive view of how the clock is affecting degeneration and visual function. + +<--- Page Split ---> + +- We thank the reviewer for this suggestion. Although we agree that a deeper understanding of how functionally circadian clocks may influence photoreceptor degeneration in varying phototransduction mutants, we believe that these experiments would not change the overall interpretations made in this manuscript and are therefore out of our current scope. Additionally, there are many phototransduction mutants (n>25 different lines) and there is not a clear rationale as to why we should screen these different mutants in the context of our circadian mutants. + +## I would also suggest that the authors do experiments in complete darkness, a light:dark cycle, and constant light. + +- We have performed lifespans in flies in either LD vs DD and demonstrated that the \(w^{1118}\) flies display a clear diet-dependent lifespan shortening in LD (Fig. 5a) that is rescued in DD. Alternatively, we found that red-eyed Canton-S flies did not display a clear lifespan shortening in LD (Supp. Fig. 7a). We reasoned since w1118 flies lack red-pigment in their pigment cells, they are known to be more susceptible to light-mediated photoreceptor degeneration that is likely exacerbated in AL. We also performed the LD vs DD lifespan analysis in flies that lack photoreceptors (TRP\(^{365}\)) and demonstrate that these flies are not long-lived in DD (Supp. Fig. 7b). Our lab previously demonstrated that wildtype Canton-S flies are short-lived when reared in constant light vs LD (Katewa et al., 2016, PMID: 26626459), and therefore did not feel the need to repeat these experiments in the current manuscript. + +![](images/Figure_5d.jpg) + + +<--- Page Split ---> + +Using Drosophila models, in this study Hodge et al. demonstrated that dietary restriction (DR) extends lifespan by promoting circadian homeostatic processes that protect the visual system from age- and light- associated damage. The authors have further demonstrated that disrupting circadian rhythms in the eye by inhibiting the transcription factor, Clock (CLK), or CLK- output genes, accelerated visual senescence, induced a systemic immune response, and shortened lifespan. Moreover, flies subjected to dietary restriction were protected from the lifespan- shortening effects of photoreceptor activation. Inversely, photoreceptor inactivation, achieved via mutating rhodopsin or housing flies in constant darkness, primarily extended lifespan in flies reared on a high- nutrient diet. Overall, their findings establish the eye as a diet- sensitive modulator of lifespan and indicate that vision is an antagonistically pleiotropic process that contributes to organismal aging. + +Using multiple assays this is a very detail, systemic, and well- designed mechanistic study to demonstrate the linkage to DR and circadian rhythms to protect the visual system from age- and light- associated damage. Overall, findings from this study are quite interesting, however, require more clarity, specification, and justifications. In my assessment with some clarity and justification, this might become suitable for publication in Nature Communications. The following questions/concerns need to be addressed for this consideration. + +1. The authors have used multiple drivers to express/knockdown various genes in multiple tissues, however, the focus is limited to visualaging. The authors need to provide a table using all the drivers/genes used in this manuscript for all the genetic modulations with clear/concise justifications. This is essential to justify the authors' hypothesis and potential outcome. This will be also useful for the general audience in understanding the power of Drosophila genetics for addressing cell-autonomous functions. + +Thank you for your comment. To clarify our approach and help aide the audience in the design of our study we have generated a new supplemental data file (Supplemental Data 12). Herein, we provide a clear description of the lines used within each figure and include pertinent information regarding the strains (mutant line, GAL4 driver, UAS- line, etc), our rationale for utilizing each line, and a description of the strengths and potential limitations of each line. + +2. Related to my concern 1, the authors frequently use ELAV and GMR drivers however, did not differentiate clock-mediated neuroprotective functions vs photoreceptors/visual system. When using a Pan-neuronal driver like ELAV, how modulation of circadian clock or DR affecting the neuronal system? Based upon their findings, it is clear that the life-span and phototaxis performance will be affected by the para-neuronal ELAV driver. Therefore, most of the outcomes shown by the authors could be neuronal as well. Therefore, it will be essential to differentiate neuronal vs visual systems in the entire manuscript. Also, as shown in Fig.5, it is important to clarify how knock-down of GMR-driven DR-sensitive eye-specific Clk-output genes reduces survival and affects phototaxis performance? Recent studies have shown that GMR-expression is not limited to the visual system therefore, most of these genes knock-down, including reduces survival and affects phototaxis performance might be not limited to the visual system. + +We agree that a major limitation of utilizing the Elav- GS- GAL4 driver to over- express the CLK- \(\Delta 1 / 2\) lines is the inability to decipher whether the outcomes on eye- aging and/or lifespan are confounded by potential changes in extra- ocular neuronal subtypes. To directly test the role of photoreceptor clocks in diet- mediated changes in visual function and lifespan, we crossed a photoreceptor- specific GAL4 driver (trpl- GAL4;GAL80) with the UAS- CLK- \(\Delta 1\) line (prCLK- \(\Delta 1\) ). Additionally, we crossed the Trpl- GAL4;GAL80 line with a UAS- Clk line (prCLK- OE) to test the effects of over- expressing wild- type Clk specifically in photoreceptors. \\*Note: The Trpl- GAL4;GAL80 line is temperature sensitive and allows for a repression of GAL4 throughout development by housing the flies at \(18^{\circ}C\) Once the flies are sorted onto the food they are moved to \(30^{\circ}C\) to de- repress the GAL4 for the remainder of their lifespan. To avoid potential confusion between the pan- neuronal Elav- GS- GAL4 (nCLK- \(\Delta 1\) ) and photoreceptor specific lines (prCLK- \(\Delta 1\) and prCLK- OE), we placed the eye- specific Clk data in its own figure (Fig. 3). Within Figure 3, we now show that prCLK- \(\Delta 1\) display accelerated declines in positive phototaxis (3a), reduced ERG amplitude (3b), and massive photoreceptor degeneration by day 10 (3c). Inversely, prCLK- OE improved positive phototaxis (3a) and increased ERG amplitude(3b) in comparison to control flies. Additionally, we found that prCLK- \(\Delta 1\) flies displayed significant reductions in median lifespan on both AL and DR, as compared to controls (Fig. 4f). This indicates that reducing CLK function within photoreceptor cells is sufficient to decrease lifespan. + +![](images/Figure_7.jpg) + +
*Fig. 3a-c
+ +<--- Page Split ---> +![](images/Figure_1m.jpg) + +
\\*Fig. 4f
+ +- We thank the reviewers for their concern per utilizing the GMR-GAL4 driver. Our rationale for using GMR-gal4 for our knockdown experiments with retinin, Gbeta76c, and Sunglasses was the strength of the driver. Namely, we sought to utilize a strong GAL4 driver to promote efficient RNAi-mediated knockdown of these genes within the eye. Additionally, we chose to study retinin, Gbeta76c, and sunglasses based on our bioinformatic analyses demonstrating them to be photoreceptor enriched genes, and because they have clearly defined functional roles within the Drosophila eye literature. Therefore, it is our belief that the phototaxis and lifespan changes observed with GMR-GAL4 crossed to retinin-RNAi, Gbeta76c-RNAi, and sunglasses-RNAi is primarily due to their knockdown within the eye. + +3. It is well known that GMR-driver mediated expression/knock-down directly affects ommatidia organization/degeneration. Did the authors see any defects in ommatidia organization/degeneration with the ocular expression of CLK-delta1 and CLK- delta or ocular knock-down of ATP or other genes shown in listed in Fig. 5? It will be also important to know if this was impacted by DR or other genetic modulations. + +- We agree and are aware of previous studies demonstrating that the GMR-GAL4 driver can induce photoreceptor degeneration due to toxicity from excessive amounts of intracellular GAL4 protein. Although we cannot rule out the possibility that GAL4 toxicity could influence the phenotypes we reported, it is our belief that our findings and conclusions were made with the proper controls. For each of our GMR-GAL4 experiments, we used a control RNAi group: GMR-GAL4>UAS-RNAi control (UAS-mCherry-RNAi, from BDSC) and GMR-GAL4>UAS-RNAi control (UAS-empty vector, from VDRC). The F1 generations from the GMR-GAL4 crosses are GMR heterozygotes, as are the experimental groups. Therefore, it is our assumption that all GMR-GAL4 F1 generations within our experimental RNAi groups (retinin, Gbeta76c, ATPalpha, etc) express a similar amount of GAL4 protein as compared to the RNAi control flies, and thus it is unlikely that GAL4 toxicity differs among our experimental and control groups. Furthermore, we chose our RNAi controls because they share the same genetic background as our experimental UAS-lines. Although others have demonstrated GAL4 toxicity, we do not believe this is a major concern given that our GMR-GAL4>RNAi control groups display normal phototaxis behavior and lifespan compared to wildtype lines (e.g., Canton-S etc.). + +- When we crossed the GMR-GAL4 to UAS-CLK-Δ1 or UAS-CLK-Δ2, we found that these flies develop to pupae but never eclose. This is likely caused by developmental toxicity from expressing dominant negative CLK. We observed a similar result with both the Trpl-GAL4 (photoreceptor driver, \\*without temperature-sensitive Gal80) and Spa-GAL4 (a cone-cell driver) when they were crossed to the UAS-CLK-Δ1/2 lines. Therefore, we combined the Trpl-GAL4 driver with the temperature-sensitive GAL80 line to make a photoreceptor-specific, temperature controlled GAL4 driver: The prCLK-Δ1 and prCLK-OE flies allowed us to assess how loss or gain of CLK function (post-developmentally) influenced photoreceptor function and degeneration (as described above). + +- Given that ATPalpha is highly expressed in cone-cells in addition to photoreceptor cells, we also knocked down ATPalpha with the cone-cell specific driver Spa-GAL4. We found that these flies also have reduced phototaxis and lifespan, albeit to a lesser extent compared to GMR-GAL4>ATPalpha-RNAi (Supplemental Fig. 8a-b). These data are in support of our initial claim that forcing photoreceptor degeneration by altering ATPalpha levels is sufficient to shorten lifespan. We do not have the ability to tease out whether the difference in lifespan with ATPalpha knocked down in GMR-GAL4 vs Spa-GAL4 is due to differences in tissue expression patterns (knockdown in all eye cells vs cone-cells), GAL4 toxicity, knockdown strength, or developmental expression patterns. + +![](images/Figure_1.jpg) + +
4. As shown in Fig. 3, NCLK-1 flies display elevated immune responses and shortened lifespan and demonstrated that disrupting neuronal CLK function elevates systemic immune responses. Later the authors have demonstrated that this is also eye-driven (Fig. 3c, d). For these experiments, the authors have used fly bodies, instead of heads. Why expression was not tested in the head/eyes?
+ +- We initially observed and reported that there was a significant enrichment in immune markers in the nCLK-Δ1 RNA-Seq. which was performed exclusively within heads (Fig. 4a). Additionally, when we analyzed a publicly available microarray dataset comparing gene expression in the heads of wildtype flies \((y,w)\) reared in different lighting conditions, we also observed a significant elevation of immune markers within the heads of flies reared in 12:12hr light dark as compared to constant dark conditions (Supp. Fig. 5f). Taken together, + +<--- Page Split ---> + +these results led us to question whether the photoreceptor itself could influence systemic inflammation in the fly. Given that the mammalian literature has extensively documented that retinal degeneration can strongly induce local inflammatory responses in the eye, our main objective with these experiments was to ask whether manipulating photoreceptor homeostasis in the fly could influence systemic inflammation (in the bodies); This is the main reason we decided to quantified AMP expression within bodies while only manipulating processes within the eye/neurons. We found that forcing photoreceptor degeneration (ATPalpha knockdown, Supp. Fig. 5d) promoted AMP gene expression, while reducing phototransduction (Rhodopsin null lines, Fig. 4d) reduced AMP gene expression to varying degrees. + +![PLACEHOLDER_14_0] + +
*Fig. 4a and Supplemental Fig. 5f
+ +![PLACEHOLDER_14_1] + +
*Supplemental Fig. 5d and Fig. 4d
+ +5. Similarly, in Fig 5e, why the experiment is limited to the whole fly? Relative mRNA expression of immune genes (AttaA, DiptB, and Dro) calculated by RT-qPCR with mRNA isolated from bodies of w1118 and rhodopsin mutant flies housed in 12:12h LD. + +Please see previous response to 4. + +6. As I mentioned before, different drivers used for different experiments, however, the conclusion is limited to eye aging? The authors need to justify how the expression of different tissues leads to eyes aging? A clear cell-autonomous vs non-cell-autonomous justification will be required including editing Fig. 6. If neuronal damage signals propagate throughout the body to drive systemic immune responses, the authors need to find basal expression of these genes responsible for immune response in the neuronal and visual tissue/system. + +As mentioned above, the inclusion of the prCLK- \(\Delta 1\) and prCLK- OE data now demonstrate a clear cell- intrinsic role for CLK in modulating photoreceptor (eye) aging. + +To limit any potential confusion or overstatement of our findings, we have removed the "Systemic Inflammation" from the summary figure (now Fig. 7) and have made changes to the discussion. + +![PLACEHOLDER_14_2] + +
Fig. 7
+ +<--- Page Split ---> + +7. Again, the authors have argued that neuronal CLK function is required for the full lifespan extension mediated by DR and indicate that photoreceptor clocks are essential for the maintenance of visual function with age and organismal survival? I think these are confusing statements and need more clarity and justification. Despite several pieces of evidence provided by authors for the neurological role, I am not sure how the outcome is limited to visual function/system? + +- We thank the reviewers for their concern. We believe the addition of the new prCLK-DN1 and prCLK-OE data indicate a clear role for CLK function in photoreceptor function and degeneration with age (Fig. 3 and Supplemental Fig. 4). Furthermore, the lifespan shortening observed in prCLK-Δ1 flies (Fig. 4f) indicates that loss of CLK function only within photoreceptors (and post-developmental) is sufficient to reduce lifespan. + +8. DR-protection against lifespan shortening downstream of light and/or rhodopsin-mediated signaling in a manner that requires light-adaptation, and by extension, arr1-mediated rhodopsin endocytosis. This justification needs more clarification. + +- We apologize for any confusion as to our rationale for analyzing phototaxis responses and lifespan with knockdown of arr1. We have added the follow sentence within the main text to help clarify: "Arr1 mRNA is circadian in wildtype heads (Supplemental Fig. 1m) and is also a direct CLK target (CLK ChIP-Seq., Supplemental Table 1). Additionally, arr1 expression was significantly downregulated in heads of nCLK-DN1 flies compared to controls (Supplemental Fig. 7e)." \*Note, we have generated Supplemental Fig. 7c for this revision. + +![PLACEHOLDER_15_0] + +
*Supplemental Fig. 1m and 7c
+ +- Additionally, since we ourselves have not quantitively measured Arr1-mediated rhodopsin endocytosis in flies reared on either AL or DR we agree that our initial statement may have overstated our findings. Therefore, we decided to replace the concluding sentence that is in question with: "Together, these data suggest that modulation of rhodopsin-mediated signaling is sufficient to regulate lifespan in Drosophila." + +9. Despite the noticeable difference of immune system and photoreceptors cells between, Drosophila with the mammalian visual system, the authors did not indicate the limitations of their finding. + +- As mentioned above, we have listed specific limitations of the individual lines used within this study in Supplemental Data 12. Although, we have attempted to highlight potential similarities and differences between our findings and those previously published in the mammalian literature in our Supplemental Discussion 1 section, we do not believe that our utilization of Drosophila is in any way a limitation of our study and/or findings. + +10. The discussion section of the main text needs a significant improvement including clarity about the above-mentioned comments. The authors have also used discussion/significance of their findings in the SI section without any clarification. + +- We have re-worded portions of our main text to improve clarity. The additional discussion text was included within the supplemental section in accordance with Nature Communications guidelines and to adhere to the sizing/formatting of the manuscript. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have significantly improved the manuscript. However, I believe that there is still a major problem with the conclusion that the CLK- DN effect that is reported here is related with the circadian clock, as detailed below. + +## p5-6 and Sup Fig 1 + +The authors indicate that cycling genes experiment made in light- dark (LD) conditions are circadianly- regulated. I am afraid that there is some misunderstanding here. In LD cycles, cycling genes might be either circadianly- regulated genes or light- regulated genes. I thus do not understand why the term circadian is used here. A DD experiment would be required to show that circadian control is involved here. + +This is particularly relevant for the timO mutants where no circadian transcription is known to occur, in contrast to light- regulated transcription (see Wijnen et al., PLoS Genet 2006). Thus, finding 480- 490 genes cycling in LD conditions does not mean that there are under circadian regulation. Having a circadian transcription in timO flies would be highly surprising and goes against all previous work, to my knowledge. + +This is a key point that needs to be clarified since the effect of DR could well be on light- regulated transcription more than on circadianly- regulated transcription. + +## Figure 1 and sup fig3e + +The above comment brings back the question of the CLK- DN effect. I understand that the RU486 conditional expression system that is use here and that is confirmed by the TS- gal80 system supports a non- developmental effect, and the use of the clkout mutant is also a good control for non- specific CLK- DN effects. However, it is known that CLK affects the transcription of non- circadianly controlled genes (McDonald et al., Cell 2001, Abruzzi et al., Genes Dev 2011), possibly including light- controlled genes. I would thus suggest to interpret the data differently, with DR affecting reinforcing light- regulated transcription and not circadian transcription. + +In the rebuttal letter, the authors indicate that because TIM/PER repress CLK- dependent transcription, the corresponding mutants cannot be used here to confirm the circadian function of clk. I disagree with this, constitutive clk expression in the perO and timO mutants does not change the fact that the clock function is abolished. I still would like to see a phototaxis experiment with timO or perO mutants to really make the difference between a function of the CLK transcription factor and the circadian clock. + +Reviewer #2 (Remarks to the Author): + +the authors have addressed my concerns. As such I support the publication of the manuscript. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The authors did a really good job in addressing most of the concerns/questions I raised in the previous version. In addition to addressing questions, the authors have provided additional supporting data for their findings. However, a couple of important questions still need some clarification/justification with the data support. Therefore, addressing the following questions will make this study suitable for publications in the prestigious Nature Communications Journal. + +1. The authors have indicated that the GMR-GAL4 driver can induce photoreceptor degeneration due to toxicity from excessive amounts of intracellular GAL4 protein. This justification is very poor. It is well established for several neurological disease models that GMR-Gal4 specific expression of mutant, not wild-type associated with ommatidia organization/degeneration. Instead of going through this intracellular toxicity theory, the authors should directly if they have received any ommatidia organization/degeneration or not? + +2. The authors mentioned that when they crossed the GMR-GAL4 to UAS-CLK-delta1 or UAS-CLK-delta 2, they found that these flies develop to pupae but never eclose. How expression of UAS-CLK-delta1 or UAS-CLK-delta2 with GMR-Gal4 driver caused pupae stage lethality. It is hard to believe ocular-specific expression leads to developmental toxicity from expressing dominant-negative CLK. In my opinion, the lethality is caused because GMR-driver is not specific to ocular and is shown to express in other tissues as well. Did the authors check the expression of GMR-GAL4 in other tissues as indicated in the other tissues? https://pubmed.ncbi.nlm.nih.gov/22911584/ https://pubmed.ncbi.nlm.nih.gov/26440079/ Related to this the authors have indicated that they have similar results with both the Trpl-GAL4 (photoreceptor driver, \*without temperature-sensitive Gal80). Therefore, the authors need to explain how photoreceptor-specific expression of UAS-CLK-delta1 or UAS-CLK-delta 2 caused developmental lethality? + +3. It is still hard to understand how eye-specific expression of leads to elevates systemic immune responses beyond the head as in the updated Fig.7, the authors did not explain that (including elevated AMP expression within bodies). They still need to justify the elevated level of immune response beyond ocular tissue. + +4. In general, the author needs to say that some of the lethality/immune response could be due to the expression of UAS-CLK-delta1 or UAS-CLK-delta 2 expression of these dominant negative in other tissues, beyond their ocular (eye)-specific expression. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +The authors have significantly improved the manuscript. However, I believe that there is still a major problem with the conclusion that the CLK- DN effect that is reported here is related with the circadian clock, as detailed below. + +## p5-6 and Sup Fig 1 + +The authors indicate that cycling genes experiment made in light- dark (LD) conditions are circadianlyregulated. I am afraid that there is some misunderstanding here. In LD cycles, cycling genes might be either circadianly- regulated genes or light- regulated genes. I thus do not understand why the term circadian is used here. A DD experiment would be required to show that circadian control is involved here. + +This is particularly relevant for the tim0 mutants where no circadian transcription is known to occur, in contrast to light- regulated transcription (see Wijnen et al., PLoS Genet 2006). Thus, finding 480- 490 genes cycling in LD conditions does not mean that there are under circadian regulation. Having a circadian transcription in tim0 flies would be highly surprising and goes against all previous work, to my knowledge. + +This is a key point that needs to be clarified since the effect of DR could well be on light- regulated transcription more than on circadianly- regulated transcription. + +We thank the reviewer for the comments to improve our manuscript. In our previous submission we reported that roughly 480- 490 transcripts oscillate in a circadian fashion in \(\text{tim}^{01}\) flies. We did not intend to argue, or make the distinction, that the oscillating genes we reported for the \(\text{tim}^{01}\) flies were driven by "circadian" vs "light- driven" mechanisms. Our only intention was to state the number of transcripts that displayed a circadian expression pattern on AL or DR according to our JTK_CYCLE parameters. + +We appreciate the reviewer's concern that the oscillating transcripts reported for CantonS wildtype flies may be influenced by light- dark cycles, as we did not perform additional time- course microarrays in free- running conditions (DD). Our laboratory has a long history of characterizing DR- mediated lifespan benefits while housing flies in LD, and we designed our time- course microarray experiments to identify the circadian processes that are enriched on AL and DR diets in this context. It is well established that \(\text{tim}^{01}\) mutant flies are behaviorally arrhythmic in constant conditions (DD) but retain some ability to entrain to light- dark cycles due to masking effects. It is our assumption that any transcripts that display a circadian expression pattern in the \(\text{tim}^{01}\) flies housed in 12:12h LD are most likely "light- driven". + +To classify which genes are circadianly- regulated in wildtype flies we subtracted the light- driven transcripts (i.e., also circadian in \(\text{tim}^{01}\) ) from the transcripts that comprise the AL and DR circadian microarrays in wildtype CantonS flies. By controlling for the potential confounding variable of light, we believe that the remaining genes (circadian in CantonS but not in \(\text{tim}^{01}\) ) are clock controlled. However, it is possible that these circadianly- regulated transcripts are also reinforced by lighting signals/cues. For instance, light- mediated intracellular signaling cascades (e.g., photoentrainment by Cry) may impinge on the circadian transcription factor CLK to influence timing (i.e., phase shifts) and/or amounts of transcriptional activation of downstream targets (i.e., amplitude). Furthermore, light- and nutrient- signals from the diet may independently or synergistically converge on the core- clock machinery to influence the transcription of clock- controlled genes/processes within photoreceptors. + +We have provided the following statements to clarify these concerns within the text: + +<--- Page Split ---> + +"In LD conditions, circadian transcripts may be driven by the core-molecular clock or by rhythmic lighting cues. We performed time-course microarrays under similar conditions in arrhythmic tim \(^{01}\) mutant flies which lack circadian transcriptional rhythms, as we reasoned that the circadian transcripts identified in these mutants are primarily light-driven. Circadianly-regulated transcripts (clock-output genes) were identified as those which oscillate only in wildtype flies and not in tim \(^{01}\) mutants (Supplementary Fig. 1a)." + +The following figures and datasets have been updated to reflect our new analyses: Fig. 1a- f, Supplementary Fig. 1a- b, f- g, j- k and Supplementary Data 1. + +## Figure 1 and sup fig3e + +The above comment brings back the question of the CLK- DN effect. I understand that the RU486 conditional expression system that is use here and that is confirmed by the TS- gal80 system supports a non- developmental effect, and the use of the clkout mutant is also a good control for non- specific CLK- DN effects. However, it is known that CLK affects the transcription of non- circadianly controlled genes (McDonald et al., Cell 2001, Abruzzi et al., Genes Dev 2011), possibly including light- controlled genes. I would thus suggest to interpret the data differently, with DR reinforcing light- regulated transcription and not circadian transcription. + +We agree with the reviewer on being cautious in the interpretation of our experiments and have modified the text to reflect this. In any experiment where CLK function is perturbed, there will always be the possibility that the phenotypic observations reported are due to changes in the expression of downstream circadian genes, non- circadian genes, or a combination of both gene sets. Regarding our analyses of CLK's role in mediating the beneficial effects of DR on photoreceptor physiology with age, we believe that the effects are more- likely due to changes in circadian vs non- circadian gene expression. Our initial analyses of the AL/DR circadian transcriptomes led us to identify many light and eye- related circadian transcripts. We found that the circadian phototransduction genes displayed increased expression and circadian amplitude in CantonS flies on DR but were no longer rhythmic in tim \(^{01}\) flies, suggesting that their circadian expression pattern in wildtype flies is regulated downstream of the molecular clock as opposed to light. + +This argument was strengthened by our nCLK- \(\Delta 1\) RNA- Seq. experiments: We found that genes that were significantly downregulated in expression in nCLK- \(\Delta 1\) heads (DR) and were also circadian in wildtype flies displayed a significant enrichment for biological processes related to light- sensing and homeostatic processes within the eye (Supplemental Fig. 2c). Genes that were significantly downregulated in expression in nCLK- \(\Delta 1\) heads but were non- circadian in wildtype flies failed to display a significant enrichment for light- responsive pathways or eye homeostasis. Below is a table comparing the gene- ontology enrichment scores for genes that were significantly down- regulated in nCLK- \(\Delta 1\) (on DR) and are either circadian ("Circadian_Enrichment") or non- circadian ("Non- Circadian_Enrichment") in wildtype flies. Therefore, it is our interpretation that DR and CLK primarily influence eye aging via downstream regulation of circadian genes, and not non- circadian genes. + +<--- Page Split ---> + + +
TermIDTermCircadian_EnrichmentNon-
Circadian_Enrichment
GO:0009416response to light stimulus3.32E-060.7968651
GO:0009642response to light intensity1.27E-050.5084995
GO:0071482cellular response to light stimulus2.60E-050.91390436
GO:0016059deactivation of rhodopsin mediated signaling2.64E-050.71738834
GO:0022400regulation of rhodopsin mediated signaling pathway2.64E-050.71738834
GO:0007602phototransduction5.98E-050.43081234
GO:0009583detection of light stimulus8.65E-050.46534368
GO:0007603phototransduction, visible light0.0001110580.79408137
GO:0006874cellular calcium ion homeostasis0.0005615180.13304433
GO:0009584detection of visible light0.0009962150.65752068
GO:0050953sensory perception of light stimulus0.0013655510.48052537
GO:0001895retina homeostasis0.00151571
GO:0016056rhodopsin mediated signaling pathway0.00151570.64171047
GO:0002032desensitization of G protein-coupled receptor signaling pathway by arrestin0.0017040441
GO:0050962detection of light stimulus involved in sensory perception0.0021596271
GO:0007601visual perception0.0034988330.34515896
GO:0071484cellular response to light intensity0.0049724451
GO:0045494photoreceptor cell maintenance0.0090035861
GO:0016062adaptation of rhodopsin mediated signaling0.0096740641
GO:0036367light adaption0.0096740641
GO:0050908detection of light stimulus involved in visual perception0.0096740641
GO:0046154rhodopsin metabolic process0.0116433871
GO:0042052rhabdomee development0.0136231660.75601232
+ +It is possible that DR reinforces CLK- mediated output by influencing light- sensing. Alternatively, light- mediated signals may influence DR's ability to regulate CLK- mediated transcriptional output. In other words, DR may promote CLK- mediated circadian transcription by reinforcing light- mediated signals. + +We have updated Supplemental Data 4 has to include the gene- ontology enrichment scores for the genes that are non- circadian in wildtype flies and down- regulated in nCLK- \(\Delta 1\) RNA- Seq. (Supplemental Data 4c). We have denoted the changes in the text: + +"Additionally, genes that were both circadian in wild- type heads and downregulated in nCLK- \(\Delta 1\) were highly enriched for homeostatic processes related to eye function, while downregulated genes in nCLK- \(\Delta 1\) that were non- circadian in wildtype heads displayed no such enrichment (Supplementary Fig. 2c and Supplemental Data 4)." And, in the discussion: "Given that CLK transcriptionally regulates circadian and + +<--- Page Split ---> + +non- circadian transcripts, future studies may determine whether the time- of- day regulation of these genes by CLK is germane to promoting eye health with age." + +In the rebuttal letter, the authors indicate that because TIM/PER repress CLK- dependent transcription, the corresponding mutants cannot be used here to confirm the circadian function of clk. I disagree with this, constitutive clk expression in the per0 and tim0 mutants does not change the fact that the clock function is abolished. I still would like to see a phototaxis experiment with tim0 or per0 mutants to really make the difference between a function of the CLK transcription factor and the circadian clock. + +We have edited our conclusions according to the comments made by the reviewer and no longer state that circadian regulation is required for the DR- or CLK- mediated effects within our study. Thus, the additional \(per^{01} / \mathrm{tim}^{01}\) phototaxis experiments are not required to support our conclusions or interpretations. + +## Reviewer #2 (Remarks to the Author): + +the authors have addressed my concerns. As such I support the publication of the manuscript. + +## Reviewer #3 (Remarks to the Author): + +The authors did a really good job in addressing most of the concerns/questions I raised in the previous version. In addition to addressing questions, the authors have provided additional supporting data for their findings. However, a couple of important questions still need some clarification/justification with the data support. Therefore, addressing the following questions will make this study suitable for publications in the prestigious Nature Communications Journal. + +1. The authors have indicated that the GMR-GAL4 driver can induce photoreceptor degeneration due to toxicity from excessive amounts of intracellular GAL4 protein. This justification is very poor. It is well established for several neurological disease models that GMR-Gal4 specific expression of mutant, not wild-type associated with ommatidia organization/degeneration. Instead of going through this intracellular toxicity theory, the authors should directly if they have received any ommatidia organization/degeneration or not? + +We did not observe overt changes to ommatidia organization/degeneration in any of our GMR- GAL4 crosses utilized in this manuscript. Below we have crossed GMR- GAL4 with UAS- mCD8- GFP which express green fluorescent protein on the cell surface and did not observe any disorganization or degeneration of the ommatidia. + +<--- Page Split ---> +![PLACEHOLDER_22_0] + + +2. The authors mentioned that when they crossed the GMR-GAL4 to UAS-CLK-delta1 or UAS-CLK-delta 2, they found that these flies develop to pupae but never eclipse. How expression of UAS-CLK-delta1 or UAS-CLK-delta2 with GMR-Gal4 driver caused pupae stage lethality. It is hard to believe ocular-specific expression leads to developmental toxicity from expressing dominant-negative CLK. In my opinion, the lethality is caused because GMR-driver is not specific to ocular and is shown to express in other tissues as well. Did the authors check the expression of GMR-GAL4 in other tissues as indicated in the other tissues? https://pubmed.ncbi.nlm.nih.gov/22911584/ https://pubmed.ncbi.nlm.nih.gov/26440079/ Related to this the authors have indicated that they have similar results with both the Trpl-GAL4 (photoreceptor driver, \*without temperature-sensitive Gal80). Therefore, the authors need to explain how photoreceptor-specific expression of UAS-CLK-delta1 or UAS-CLK-delta 2 caused developmental lethality? + +We agree with the reviewer's comment that the observed developmental lethality in crossing the GMR- GAL4 to either UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) is surprising and may be due to mis- expression of the GAL4 in non- ocular tissues. Since others have extensively characterized the mis- expression of GMR- GAL4 in non- ocular tissues we did not feel it was necessary for us to recapitulate those studies here, especially as we were able to utilize the Trpl- GAL80- GAL4 line which allowed us to examine the effects of modulating CLK specifically in adult photoreceptors. We did however observe a similar pupae stage lethality when crossing the UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) with the SPA- GAL4 driver (a commonly used cone- cell specific driver) and the RDGA- GAL4 driver (an additional eye driver). We do note that it is possible that the developmental lethality observed with SPA or RDGA driver lines may also be caused by mis- expression in extra- ocular tissues. + +We would like to clarify our previous response where we stated that the non- temperature- sensitive photoreceptor driver, Trpl- GAL4, flies were 'similar' to the GMR- GAL4 flies when crossed to UAS- CLK- \(\Delta 1\) or - CLK- \(\Delta 2\) , as this statement may have been unintentionally misleading. To be clear, we did not observe any developmental lethality when crossing Trpl- GAL4 flies with either UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) ; these flies eclosed normally. However, we found that upon eclosion, Trpl- GAL4>UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) flies displayed very low positive phototaxis responses, and overt disruption to their photoreceptors, measured by transverse sections of the eye (below). These observations suggest that CLK is required for proper development of photoreceptors. Furthermore, these findings were central in our reasoning for using the temperature sensitive Trpl;GAL80- GAL4 line for further analysis. + +<--- Page Split ---> +![PLACEHOLDER_23_0] + +
Figure 1: trpl-gal4>Clk-DN1 cross-section at day 2.
+ +![PLACEHOLDER_23_1] + + +3. It is still hard to understand how eye-specific expression of leads to elevates systemic immune responses beyond the head as in the updated Fig.7, the authors did not explain that (including elevated AMP expression within bodies). They still need to justify the elevated level of immune response beyond ocular tissue. + +We thank the reviewer for their comments to improve our study. Our main reasoning for assessing systemic immune responses and providing those data within this manuscript were due to the fact that we observed large elevations in anti-microbial peptide (AMP) expression when manipulating CLK (nCLK- \(\Delta 1\) ) and when forcing photoreceptor degeneration (GMR- GAL4>UAS- ATPalpha- RNAi). AMP expression has been shown to result from local damage responses, but they are primarily upregulated within the fat- body. We do not fully understand the mechanisms by which the Drosophila eye and more specifically, the photoreceptors influence systemic immune responses. However, we can speculate on several potential explanations, including: 1. A retinal- blood barrier exists to keep the hemolymph separate from the ommatidia such that the extracellular space surrounding the photoreceptors can maintain a proper ion balance required for photoreceptor viability and the ion gradient required for phototransduction to occur. With age and neurodegeneration, there is leakiness of both the retinal/brain and blood/brain barrier in Drosophila. Interestingly, recent reports have indicated that the blood- brain barrier is under direct circadian control. The upregulation of the AMPs in the body, which is indicative of a systemic immune response, may indicate that photoreceptor degeneration can lead to a + +<--- Page Split ---> + +breakdown of the retinal brain barrier and damage signals propagating throughout the hemolymph may then activate the fat body to increase the expression of AMPs. 2. An additional explanation may be that as photoreceptors degenerate they do so in a necrotic fashion vs apoptosis. Previous reports have indicated that promoting photoreceptor degeneration by over- expressing a leaky channel can drive local neuronal death in other wise healthy cells. As the photoreceptors degenerate due to age and \(\mathtt{Ca2 + }\) induced toxicity from light exposure, they may promote a feed- forward cycle of neuronal cell death and inflammation that ultimately leads to systemic inflammatory responses. + +Since we have only demonstrated the correlations between photoreceptor degeneration and systemic inflammation with age and have not directly claimed that these systemic immune responses are causal for the phenotypes we described (visual function, lifespan). We have added some of these explanation in the revised submission in the discussion + +We have provided the following text within the discussion to address these concerns: + +"Among the more interesting and unexpecting observations of this study is that the Drosophila eye can influence systemic immune responses, as we observed elevated AMP expression in the bodies of flies overexpressing CLK- \(\Delta 1\) pan- neuronally and in flies with forced photoreceptor degeneration (ATPalpha- RNAi). It is possible that GAL4 mis- expression may promote inflammatory responses in the fly bodies, although we found a reduction in systemic inflammation in the rhodopsin- null lines indicating that this phenomenon can originate at the photoreceptor. We also found that these systemic immune responses correlate with lifespan changes (increased body AMP expression is associated with declines in longevity, and vise- versa), similar to what is reported with chronic inflammation or "inflammaging" in other models. However, we cannot conclude whether neuronal or eye- mediated increases in systemic inflammation are at all causal to aging in other tissues. Furthermore, we do not fully understand the mechanisms by which the Drosophila eye and more specifically, the photoreceptor influences systemic immune responses although we speculate that photoreceptor degeneration may disrupt the retinal- blood barrier such that damage signals from the eye may propagate through the hemolymph to activate AMP expression in distal tissues. Future studies are aimed at elucidating the mechanisms by which the eye influences systemic inflammation and its relation to aging and longevity." + +4. In general, the author needs to say that some of the lethality/immune response could be due to the expression of UAS-CLK-delta1 or UAS-CLK- delta 2 expression of these dominant negative in other tissues, beyond their ocular (eye)-specific expression. + +To address this potential limitation, we have provided the follow text within the manuscript: "However, as with all tissue- specific driver systems, we cannot rule of the possibility that our ELAV- GS- GAL4 driver expresses in a small population of non- neuronal cell- types, which, in theory, could contribute to the elevated systemic inflammatory responses and/or influence lifespan." + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The changes made in the new revised version of the manuscript addresses my concerns. I have one last request about the circadian versus non- circadian 24h oscillations: + +The authors now define circadian transcripts as LD cycling transcripts that do not cycle in tim0 clockless flies and I think that it is a very reasonable estimation for a circadian control. In the modified sentence "In LD conditions, circadian transcripts may be driven by the core- molecular clock or by rhythmic lighting cues...", please do not use circadian for cycling transcripts in LD. I would suggest "In LD conditions, transcripts showing 24h oscillations..." This should be applied to the other instances of the word circadian in the text, please keep circadian when speaking about clock- dependent expression otherwise it is confusing for the reader. + +Reviewer #3 (Remarks to the Author): + +All the previous concerns have been appropriately addressed and this should be now suitable for publication in Nature Communications. Best wishes + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The changes made in the new revised version of the manuscript addresses my concerns. I have one last request about the circadian versus non- circadian 24h oscillations: + +The authors now define circadian transcripts as LD cycling transcripts that do not cycle in tim0 clockless flies and I think that it is a very reasonable estimation for a circadian control. + +In the modified sentence "In LD conditions, circadian transcripts may be driven by the core- molecular clock or by rhythmic lighting cues...", please do not use circadian for cycling transcripts in LD. I would suggest "In LD conditions, transcripts showing 24h oscillations..." + +This should be applied to the other instances of the word circadian in the text, please keep circadian when speaking about clock- dependent expression otherwise it is confusing for the reader. + +We thank the reviewer for their comment and have made the appropriate changes to the text: "In LD conditions, transcripts displaying 24h oscillations may be driven by the core- molecular clock ("circadian") or by rhythmic lighting cues [13]." + +Reviewer #3 (Remarks to the Author): + +All the previous concerns have been appropriately addressed and this should be now suitable for publication in Nature Communications. Best wishes + +We appreciate the reviewers' comments and suggestions throughout this review process. + +<--- Page Split ---> diff --git a/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..bf75c4b2637b8452e4bbb748c5b7010aff8afe9f --- /dev/null +++ b/peer_reviews/9989c1e3af8040541872be14a54793ebca3bf6a961f8907b5f56fa9d883c7c67/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,656 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 922, 211]]<|/det|> +Dietary restriction and the transcription factor clock delay eye aging to extend lifespan in Drosophila melanogaster + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 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To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 288, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 393, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 162, 879, 308]]<|/det|> +Previous studies have shown a two- ways interaction between dietary restriction (DR) and the circadian clocks. In flies, the DR- induced lifespan extension is decreased when peripheral (non- brain) circadian clocks are stopped and DR increases the amplitude of clock protein cycling (Katewa et al. 2016). Building on these data Hodge et al. investigate the effects of clock disruption in the eye and retinal degeneration on lifespan in DR or ad libitum feeding conditions. They conclude that flies expressing the dominant- negative CLOCK protein show accelerated retinal senescence and shortened lifespan. They show that photoreceptor activation and subsequent retinal senescence shorten lifespan and that DR protects against this effect. + +<|ref|>text<|/ref|><|det|>[[114, 309, 877, 400]]<|/det|> +The idea that photoreception activation shortens lifespan and is prevented by DR is very interesting and the possibility that the eye circadian clock protects from these effects exciting. The conclusions of this study are definitely important. The data are rather convincing although I have some concerns with the tools that are used to disrupt the clock and I would recommend using classical clock mutants to confirm the results, as detailed below. + +<|ref|>text<|/ref|><|det|>[[114, 418, 877, 527]]<|/det|> +1- Since CLK affects the anatomy of at least some clock neurons, the CLK- delta dominant- negative might have related effects in other cells including photoreceptors. It would thus be important to use an independent way of abolishing the clock function. perO or timO flies do not have reported developmental effects, including in the eye. I think that the authors need to confirm the CLK- delta experiments for at least the phenotypes phototaxis assay during aging in AL and DR conditions, to conclude that the absence of a functional clock prevents + +<|ref|>text<|/ref|><|det|>[[114, 545, 875, 618]]<|/det|> +2- It is clear from the present study that CLK- delta flies have a strongly reduced lifespan in both AL and DR conditions and it is not clear to me that it is the case of perO flies. As indicated for photoreceptor degeneration, perO or timO flies need to be used in the lifespan assay in AL and DR to decipher between the effects of expressing the CLK- delta protein and the absence of a functional clock. + +<|ref|>text<|/ref|><|det|>[[114, 637, 870, 710]]<|/det|> +3- p17. The three CLK- controlled genes (Gb76c, retinin, sunglasses) whose downregulation causes phototaxis defects and shortening of lifespan under DR (Fig 5e- f) should show circadian oscillations of their mRNAs with larger amplitude in DR versus AL conditions if the proposed model is correct. Is it the case ? + +<|ref|>text<|/ref|><|det|>[[114, 729, 881, 802]]<|/det|> +4- I notice some tendency to mix known results from mammals and flies to draw general conclusions. I would suggest to be more cautious about this since rather strong differences exist, for example in the phototransduction pathway. Please be more precise about the model system when citing published data and provide appropriate references. + +<|ref|>sub_title<|/ref|><|det|>[[115, 822, 212, 838]]<|/det|> +## Minor points + +<|ref|>text<|/ref|><|det|>[[114, 857, 863, 893]]<|/det|> +- p8. "These findings provide a potential mechanistic explanation for the rhythmic response pattern in light-sensitivity observed in Drosophila photoreceptors". It is well documented in vertebrates but is it + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 473, 106]]<|/det|> +clearly shown in flies? Please provide references. + +<|ref|>text<|/ref|><|det|>[[116, 163, 393, 179]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 199, 830, 253]]<|/det|> +The manuscript by Hodge and colleagues demonstrates that the circadian clock regulates phototransduction in such a manner as to increase lifespan, visual function, and lower systematic inflammation. The data in the paper are convincing and support the conclusion of the authors. + +<|ref|>text<|/ref|><|det|>[[115, 273, 881, 345]]<|/det|> +I am having some trouble with the connections that are made in the paper. For example, it is not clear to me why photoreceptor degeneration would cause an increase in systemic inflammation and a decrease in lifespan. I am not questioning the data in the paper. I just think that the authors need to connect the dots for the reader more carefully. + +<|ref|>text<|/ref|><|det|>[[115, 364, 879, 418]]<|/det|> +I am also not sure I understand how the dietary restriction plays into the study. I think the authors could just look at defective retinal clocks and the effect that it has on the fly. Especially since flies are not normally going to encounter dietary restrictive conditions out in the wild. + +<|ref|>text<|/ref|><|det|>[[115, 437, 880, 473]]<|/det|> +I also think that the authors need to focus on one of the effects that the eye clock has on the fly. It could be visual function, inflammation, or lifespan but it I think the paper will benefit from a single idea. + +<|ref|>text<|/ref|><|det|>[[115, 492, 881, 546]]<|/det|> +Just my two cents - I think the strongest part of the paper is the effect the eye clock has on phototransduction and visual function. I think that a revised paper in which the authors focus exclusively on this connection will be very exciting and would be appropriate for Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 565, 864, 600]]<|/det|> +The effect on systematic inflammation and lifespan, while both interesting, are hard to connect to the state of photoreceptor health and, to me, make a much less interesting story. + +<|ref|>text<|/ref|><|det|>[[115, 620, 854, 673]]<|/det|> +If the authors focus on visual function I would suggest that they combine their clock mutants with all known phototransduction mutants to gain a comprehensive view of how the clock is affecting degeneration and visual function. + +<|ref|>text<|/ref|><|det|>[[115, 694, 835, 728]]<|/det|> +I would also suggest that the authors do experiments in complete darkness, a light:dark cycle, and constant light. + +<|ref|>text<|/ref|><|det|>[[116, 786, 393, 802]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 822, 863, 894]]<|/det|> +Using Drosophila models, in this study Hodge et al. demonstrated that dietary restriction (DR) extends lifespan by promoting circadian homoeostatic processes that protect the visual system from age- and light- associated damage. The authors have further demonstrated that disrupting circadian rhythms in the eye by inhibiting the transcription factor, Clock (CLK), or CLK- output genes, accelerated visual + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 877, 199]]<|/det|> +senescence, induced a systemic immune response, and shortened lifespan. Moreover, flies subjected to dietary restriction were protected from the lifespan- shortening effects of photoreceptor activation. Inversely, photoreceptor inactivation, achieved via mutating rhodopsin or housing flies in constant darkness, primarily extended lifespan in flies reared on a high- nutrient diet. Overall, their findings establish the eye as a diet- sensitive modulator of lifespan and indicate that vision is an antagonistically pleiotropic process that contributes to organismal aging. + +<|ref|>text<|/ref|><|det|>[[114, 200, 880, 308]]<|/det|> +Using multiple assays this is a very detail, systemic, and well- designed mechanistic study to demonstrate the linkage to DR and circadian rhythms to protect the visual system from age- and light- associated damage. Overall, findings from this study are quite interesting, however, require more clarity, specification, and justifications. In my assessment with some clarity and justification, this might become suitable for publication in Nature Communications. The following questions/concerns need to be addressed for this consideration. + +<|ref|>text<|/ref|><|det|>[[114, 310, 874, 418]]<|/det|> +1. The authors have used multiple drivers to express/knockdown various genes in multiple tissues, however, the focus is limited to visual-aging. The authors need to provide a table using all the drivers/genes used in this manuscript for all the genetic modulations with clear/concise justifications. This is essential to justify the authors' hypothesis and potential outcome. This will be also useful for the general audience in understanding the power of Drosophila genetics for addressing cell-autonomous functions. + +<|ref|>text<|/ref|><|det|>[[114, 419, 872, 618]]<|/det|> +2. Related to my concern 1, the authors frequently use ELAV and GMR drivers however, did not differentiate clock-mediated neuroprotective functions vs photoreceptors/visual system. When using a Pan-neuronal driver like ELAV, how modulation of circadian clock or DR affecting the neuronal system? Based upon their findings, it is clear that the life-span and phototaxis performance will be affected by the para-neuronal ELAV driver. Therefore, most of the outcomes shown by the authors could be neuronal as well. Therefore, it will be essential to differentiate neuronal vs visual systems in the entire manuscript. Also, as shown in Fig.5, it is important to clarify how knock-down of GMR-driven DR-sensitive eye-specific Clk-output genes reduces survival and affects phototaxis performance? Recent studies have shown that GMR-expression is not limited to the visual system therefore, most of these genes knock-down, including reduces survival and affects phototaxis performance might be not limited to the visual system. + +<|ref|>text<|/ref|><|det|>[[114, 620, 860, 710]]<|/det|> +3. It is well known that GMR-driver mediated expression/knock-down directly affects ommatidia organization/degeneration. Did the authors see any defects in ommatidia organization/degeneration with the ocular expression of CLK-delta1 and CLK-delta or ocular knock-down of ATP or other genes shown in listed in Fig. 5? It will be also important to know if this was impacted by DR or other genetic modulations. + +<|ref|>text<|/ref|><|det|>[[114, 711, 866, 784]]<|/det|> +4. As shown in Fig. 3, NCLK-1 flies display elevated immune responses and shortened lifespan and demonstrated that disrupting neuronal CLK function elevates systemic immune responses. Later the authors have demonstrated that this is also eye-driven (Fig. 3c, d). For these experiments, the authors have used fly bodies, instead of heads. Why expression was not tested in the head/eyes? + +<|ref|>text<|/ref|><|det|>[[114, 785, 877, 838]]<|/det|> +5. Similarly, in Fig 5e, why the experiment is limited to the whole fly? Relative mRNA expression of immune genes (AttaA, DiptB, and Dro) calculated by RT-qPCR with mRNA isolated from bodies of w1118 and rhodopsin mutant flies housed in 12:12h LD. + +<|ref|>text<|/ref|><|det|>[[114, 840, 861, 893]]<|/det|> +6. As I mentioned before, different drivers used for different experiments, however, the conclusion is limited to eye aging? The authors need to justify how the expression of different tissues leads to eyes aging? A clear cell-autonomous vs non-cell-autonomous justification will be required including editing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 874, 145]]<|/det|> +Fig. 6. If neuronal damage signals propagate throughout the body to drive systemic immune responses, the authors need to find basal expression of these genes responsible for immune response in the neuronal and visual tissue/system. + +<|ref|>text<|/ref|><|det|>[[113, 145, 879, 237]]<|/det|> +7. Again, the authors have argued that neuronal CLK function is required for the full lifespan extension mediated by DR and indicate that photoreceptor clocks are essential for the maintenance of visual function with age and organismal survival? I think these are confusing statements and need more clarity and justification. Despite several pieces of evidence provided by authors for the neurological role, I am not sure how the outcome is limited to visual function/system? + +<|ref|>text<|/ref|><|det|>[[113, 237, 880, 291]]<|/det|> +8. DR-protection against lifespan shortening downstream of light and/or rhodopsin-mediated signaling in a manner that requires light-adaptation, and by extension, arr1-mediated rhodopsin endocytosis. This justification needs more clarification. + +<|ref|>text<|/ref|><|det|>[[113, 291, 875, 327]]<|/det|> +9. Despite the noticeable difference of immune system and photoreceptors cells between, Drosophila with the mammalian visual system, the authors did not indicate the limitations of their finding. + +<|ref|>text<|/ref|><|det|>[[113, 328, 875, 382]]<|/det|> +10. The discussion section of the main text needs a significant improvement including clarity about the above-mentioned comments. The authors have also used discussion/significance of their findings in the SI section without any clarification. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[56, 44, 139, 57]]<|/det|> +Dear Editor, + +<|ref|>text<|/ref|><|det|>[[56, 72, 937, 117]]<|/det|> +Thank you for considering our manuscript in your esteemed journal and allowing us to respond to the reviewer's comments. We thank the reviewers for their thoughtful comments and I hope you will find that our responses have significantly improved the manuscript. We have made appropriate changes in the text and figures and here is our point- by- point response to the comments. + +<|ref|>text<|/ref|><|det|>[[56, 131, 644, 145]]<|/det|> +We have provided the following new data and updates to address the reviewer comments: + +<|ref|>table<|/ref|><|det|>[[56, 160, 642, 295]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[56, 146, 180, 158]]<|/det|> +New Figures/Data: + +
FigureData
3a-cprCLK-DN1 and prCLK-OE phototaxis, ERG, trangenial cross-sections.
S. 1b, d-f, 1Tim01 circadian transcriptome analyses.
S. 4bprCLK-DN1 and prCLK-OE ERG traces.
S. 7carr1 expression from nCLK-DN1 RNA-Seq.
S. 8a-bCone-cell specific ATPalpha-RNAi knockdown phototaxis and lifespan.
S. Data 12Rationale and strengths/weakness of lines used in study.
+ +<|ref|>table<|/ref|><|det|>[[56, 306, 752, 437]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[56, 295, 201, 307]]<|/det|> +Updated Figures/Data: + +
FigureData
4fprCLK-DN1 lifespan (N=3).
S. 7dEye-specific arr1 knockdown phototaxis.
S. Data 1AL and DR circadian transcriptome analyses in wild-type and circadian mutant flies
S. Data 7Survival analyses.
S. Data 9Positive phototaxis responses and statistics.
S Data 10Electroretinogram analyses and statistics.
S. Table 2Drosophila strains used in this study.
+ +<|ref|>sub_title<|/ref|><|det|>[[56, 448, 300, 461]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[55, 474, 933, 555]]<|/det|> +Previous studies have shown a two- ways interaction between dietary restriction (DR) and the circadian clocks. In flies, the DR- induced lifespan extension is decreased when peripheral (non- brain) circadian clocks are stopped and DR increases the amplitude of clock protein cycling (Katewa et al., 2016, PMID: 26626459). Building on these data Hodge et al. investigate the effects of clock disruption in the eye and retinal degeneration on lifespan in DR or ad libitum feeding conditions. They conclude that flies expressing the dominant- negative CLOCK protein show accelerated retinal senescence and shortened lifespan. They show that photoreceptor activation and subsequent retinal senescence shorten lifespan and that DR protects against this effect. + +<|ref|>text<|/ref|><|det|>[[55, 553, 940, 606]]<|/det|> +The idea that photoreception activation shortens lifespan and is prevented by DR is very interesting and the possibility that the eye circadian clock protects from these effects exciting. The conclusions of this study are definitely important. The data are rather convincing although I have some concerns with the tools that are used to disrupt the clock and I would recommend using classical clock mutants to confirm the results, as detailed below. + +<|ref|>text<|/ref|><|det|>[[55, 616, 940, 672]]<|/det|> +1- Since CLK affects the anatomy of at least some clock neurons, the CLK- delta dominant- negative might have related effects in other cells including photoreceptors. It would thus be important to use an independent way of abolishing the clock function. per0 or tim0 flies do not have reported developmental effects, including in the eye. I think that the authors need to confirm the CLK- delta experiments for at least the phenotypes phototaxis assay during aging in AL and DR conditions, to conclude that the absence of a functional clock prevents + +<|ref|>text<|/ref|><|det|>[[85, 684, 936, 843]]<|/det|> +We agree with the concern that over- expressing CLK- \(\Delta 1\) might influence the function of non- photoreceptor neurons, especially when we utilizing the pan- neuronal Elav- gene- switch- GAL4 driver system. We would like to point out that with the GeneSwitch system we induce GAL4- mediated expression with the addition of RU486 in 4- day old adult, mated female flies, post- development. Therefore, we can avoid developmental defects associated with the expression of CLK- \(\Delta 1\) . Furthermore, the positive phototaxis and ERG data with the CLK- \(\Delta 1\) lines, elav- GS- GAL4>CLK- \(\Delta 1\) and CLK- \(\Delta 2\) , are indistinguishable from control at the earliest time- point recorded (day 2 post induction), indicating that the photoreceptor cells have developed normally. An additional strength of Gene- Switch system is that the control flies are from the same F1 generation and have the same genotype (but are reared on vehicle treated food vs food with RU486). We also note that although we used a pan- neuronal driver (elav- GS- GAL4), Clk is enriched 5- fold within the photoreceptor cells vs the rest of the neurons in the brain (see Supplemental Fig. 6d). Furthermore, within the brain, clk expression is confined to a small population of approximately 150 neurons. Therefore, it is likely that over- expressing a dominant- negative CLK protein with a pan- neuronal driver may only affect this minor population of neurons in the brain. To demonstrate cell- intrinsic function of CLK we have included new data with photoreceptor- specific disruption to Clk, which we describe in greater detail below. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[297, 55, 597, 210]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[608, 208, 745, 222]]<|/det|> +
*Supplemental Fig. 6d
+ +<|ref|>text<|/ref|><|det|>[[85, 232, 941, 410]]<|/det|> +- To directly test the role of CLK function in adult photoreceptors (post-developmental), we combined the Trpl-Gal4 driver (which narrowly expresses GAL4 in the photoreceptor cells) with temperature-sensitive Gal80 (which strongly represses Gal4 activity at \(18^{\circ}\mathrm{C}\) ) and crossed these flies to UAS-Clk-Δ1 (Trpl-gal4; gal80>Clk-Δ1, denoted prCLK-Δ1). To suppress the expression of Clk-Δ1 during development, we housed these flies (prCLK-Δ1) at \(18^{\circ}\mathrm{C}\) . Upon occlusion, we then sorted the flies (prCLK-Δ1) onto AL or DR food and then transferred them to \(30^{\circ}\mathrm{C}\) to de-repress GAL4 and induce the expression of Clk-Δ1. To limit confusion, the data generated with Elav-GS-GAL4 remain in Figure 2, while new data generated with the photoreceptor specific GAL4 line was placed into a new Figure 3. Similar to Elav-Gs>Clk-Δ1, Trpl-gal4; gal80>Clk-Δ1 flies also display accelerated photoreceptor aging, as is apparent via phototaxis (Fig. 3a), ERG amplitude (Fig. 3b), and tangential cross-sections of the ommatidia (Fig. 3c). Trpl-gal4; gal80>Clk-Δ1 flies also display a lifespan shortening in comparison to their outcrossed controls (w/+,Trpl-Gal4/+; Gal80/+) (Fig. 4f). This further demonstrates that CLK function within photoreceptors influences lifespan and visual senescence. Lastly, we have included several Clk overexpression experiments (w;Trpl-Gal4/+;UAS-Clk/Gal80) and demonstrate that increasing the expression of CLK within the photoreceptor cells is sufficient to delay visual senescence and rescue AL-mediated declines, as we observed with phototaxis (Fig. 3a), ERG amplitude (Fig. 3b), and cross-sections of the ommatidia (Fig. 3c). **See Supplemental Fig. 4b for the averaged ERG traces between the control, prCLK-Δ1, and prCLK-OE lines. + +<|ref|>image<|/ref|><|det|>[[89, 410, 790, 840]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[88, 841, 221, 856]]<|/det|> +
*Fig. 3a-c and Fig. 4f.
+ +<|ref|>text<|/ref|><|det|>[[86, 891, 905, 935]]<|/det|> +- In addition to using the CLK-Δ1 lines, we have also tested flies homozygous for a separate null clk allele, CLKout. Consistent with the CLK-Δ1 data, in CLKout flies, we found that that DR failed to delay visual senescence in comparison to AL-fed flies (now in Supplemental Fig. 3e). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[308, 45, 610, 230]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[620, 220, 756, 234]]<|/det|> +
*Supplemental Fig. 3e
+ +<|ref|>text<|/ref|><|det|>[[85, 233, 927, 303]]<|/det|> +We agree that testing additional circadian mutants may help support our claim that CLK influences photoreceptor aging and mediates the beneficial effects of DR on the eye. In addition to the wild- type circadian time- course microarray (Canton- S flies), we also performed the same time- course in \(\text{tim}^{01}\) mutant flies (and have now included these data in Supplemental Fig. 1b, d, e- f, and 1) \\*\\*We also deposited the raw and processed files for the \(\text{tim}^{01}\) circadian time- course microarray at GEO: GSE158286. Interestingly, we found that DR failed to amplify the number of circadian genes in \(\text{tim}^{01}\) mutants (Supplemental Fig. 1d), indicating that normal circadian function is required. + +<|ref|>image<|/ref|><|det|>[[130, 301, 860, 540]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[85, 556, 920, 637]]<|/det|> +For both \(\text{per}^{01}\) and \(\text{tim}^{01}\) mutants, the negative feedback loop that represses CLK/CYC heterodimers is disrupted, resulting in low but constitutive transcriptional activity by CLK/CYC (Glossop et al., 1999. PMID:10531060). Because of this caveat—and our model that CLK- output genes mediate DR's ability to delay eye aging—we decided not to move forward with testing phototaxis in either \(\text{per}^{01}\) or \(\text{tim}^{01}\) flies. In agreement with the observation that CLK/CYC activity exists in mutants of the repressive limb of the molecular clock, we found that photoreceptor genes were still upregulated in expression upon DR in \(\text{tim}^{01}\) flies, although they failed to display a circadian oscillation (Supplemental Fig. 1l). + +<|ref|>image<|/ref|><|det|>[[297, 633, 565, 852]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[570, 848, 702, 863]]<|/det|> +
*Supplemental Fig. 11
+ +<|ref|>text<|/ref|><|det|>[[85, 874, 933, 942]]<|/det|> +Instead of utilizing \(\text{per}^{01}\) and \(\text{tim}^{01}\) mutants (for the reasons described above) we did decide to test the role of cryptochrome (CRY), a core clock component that is a direct light sensor and aids in photoentrainment. We found that three cry mutants \(\text{(cry}^{B}, \text{cry}^{01}\) , and \(\text{cry}^{02}\) ) all demonstrated clear enhancements in phototaxis on DR compared to AL (see Supplemental Fig. 3g- i). This suggests that circadian timing, and/or photoentrainment, may not be as important for mediating the diet- dependent responses in eye aging compared to proper CLK function. Our final reason for not testing \(\text{per}^{01}\) or \(\text{tim}^{01}\) mutants is because they harbor null, full- body mutations in period and timeless. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 43, 927, 70]]<|/det|> +Therefore, any phototaxis defect we might observe in these flies could be attributable to either developmental abnormalities or the loss of these genes in extra- ocular tissues. + +<|ref|>image<|/ref|><|det|>[[160, 72, 839, 475]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[427, 468, 572, 482]]<|/det|> +
\\*Supplemental Fig. 3g-i
+ +<|ref|>text<|/ref|><|det|>[[56, 504, 936, 546]]<|/det|> +2- It is clear from the present study that CLK- delta flies have a strongly reduced lifespan in both AL and DR conditions and it is not clear to me that it is the case of per0 flies. As indicated for photoreceptor degeneration, per0 or tim0 flies need to be used in the lifespan assay in AL and DR to decipher between the effects of expressing the CLK- delta protein and the absence of a functional clock. + +<|ref|>text<|/ref|><|det|>[[85, 546, 940, 729]]<|/det|> +We thank you for your concern regarding potential different circadian mutants may yield variable effects on lifespan in the context of DR. As mentioned in the response to your first questions, we believe that neither the \(tim^{0l}\) nor \(per^{0l}\) mutant flies serve as a strong model for accessing the absence of functional CLK. Additionally, it is becoming increasingly apparent that disrupting circadian function, or losing CLK activity, can have tissue- specific effects on aging. In turn, lifespan may reflect a summation and/or differences in the individual contributions of aging across cell- types/tissues. For example, loss of \(per^{0l}\) function in the gut appears to extend lifespan in Drosophila (Ulgherait et al., 2020. PMID: 32317636). Our goal in this study was to elucidate the role of CLK function within the photoreceptors and determine its effect on aging and lifespan. Therefore, we feel it is appropriate to confine our efforts to transgenic lines that manipulate CLK activity in a tissue- specific fashion, namely in the photoreceptors and neurons. Also, we would like to highlight that \(per^{0l}\) mutant lifespans were performed on AL and DR diets in a previous publication from our lab (Subhash et al, 2016. PMID: 26626459) and that \(per^{0l}\) and \(tim^{0l}\) failed to display DR- mediated lifespan extension. These results were subsequently refuted by another lab observed that DR extended lifespan in these lines (Ulgherait et al., 2016. PMID: 27916531). It is unclear why there was a discrepancy between the period and timeless mutant lifespans, but these may be explained by lab- specific differences in lighting conditions (LUX, and LEDs used) or the microbiomes. Again, given that CLK activity can persist in \(per^{0l}\) and \(tim^{0l}\) mutants, we believe that these lines are suboptimal for studying CLK's role in modulating the rate of aging of adult photoreceptor cells. + +<|ref|>text<|/ref|><|det|>[[58, 754, 910, 796]]<|/det|> +3- p17. The three CLK- controlled genes (Gb76c, retinin, sunglasses) whose downregulation causes phototaxis defects and shortening of lifespan under DR (Fig 5e- f) should show circadian oscillations of their mRNAs with larger amplitude in DR versus AL conditions if the proposed model is correct. Is it the case ? + +<|ref|>text<|/ref|><|det|>[[86, 808, 925, 916]]<|/det|> +- The CLK-output genes we decided to analyze in this study (Gbeta76c, retinin, and sunglasses) were chosen based on our bioinformatics approach (Supplemental Fig. 9a): they were enriched in photoreceptors (public dataset, Charlton-Perkins et al, 2017. GSE93782), show circadian mRNA expression in young wild-type heads (public dataset, Kuintzle et al, 2017. GSE81100), are down-regulated with age, upregulated on DR vs AL (our data), and are down-regulated in nCLK-Δ1 vs control flies (our data). We did not observe a circadian oscillation (JTK CYCLE p-value<0.05) with Gbeta76c, retinin, and sunglasses in our AL and DR circadian transcriptome analysis, although these genes are all highly rhythmic in wild-type heads (Supplemental Fig. 9b-d). We likely failed to observe a circadian oscillation in these genes in our dataset because our transcriptome analyses incorporated pooled RNA from whole-fly lysates, whereas the circadian RNA sequencing experiment we reference extracted RNA from heads only. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[70, 45, 496, 496]]<|/det|> + +<|ref|>image<|/ref|><|det|>[[525, 48, 936, 270]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[540, 483, 687, 497]]<|/det|> +\*Supplemental Fig. 9b- d + +<|ref|>text<|/ref|><|det|>[[85, 508, 936, 653]]<|/det|> +- Since we performed our nCLK-Δ1 RNA-Seq analysis at ZT 0 and ZT 12 (the peak and trough of their expression, respectively) we were able to observe time-of-day and diet-dependent changes in the expression of Gbeta76c, retinin, and sunglasses from RNA isolated from heads (Supplemental Fig. 9e-g). Our bulk analysis of circadian transcripts that oscillate on both AL and DR revealed that, on average, these transcripts display a more robust amplitude on DR vs AL (Supplementary Fig. 1j). Analysis of our RNA-Seq data from ZT0 and ZT12 indicate that the amplitude (difference in expression fold-change over time) was more robust for Gbeta76c (AL: 1.57, DR: 1.77) and retinin (AL: 0.93, DR 1.17), but not for sunglasses although the amplitudes were similar (AL: 1.19, DR: 1.15). Although we demonstrate that on average circadian amplitude is elevated on DR vs AL, our model that DR promotes the circadian expression of CLK-output genes does not rely solely on increases in circadian amplitude. It is possible that for several CLK-output genes that are elevated in expression by DR are also more rhythmic in their pattern of oscillation (i.e., their expression more closely fits a sine wave) while not elevating their overall amplitude. Alternatively, it is possible that DR-CLK mediated benefits to the aging photoreceptor are more dependant on overall expression changes to CLK-output genes, rather than their amplitude or rhythmicity. + +<|ref|>image<|/ref|><|det|>[[85, 655, 897, 814]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[60, 817, 205, 831]]<|/det|> +
\*Supplemental Fig. 9e-g
+ +<|ref|>text<|/ref|><|det|>[[58, 842, 916, 884]]<|/det|> +4- I notice some tendency to mix known results from mammals and flies to draw general conclusions. I would suggest to be more cautious about this since rather strong differences exist, for example in the phototransduction pathway. Please be more precise about the model system when citing published data and provide appropriate references. + +<|ref|>text<|/ref|><|det|>[[85, 895, 893, 924]]<|/det|> +- We thank the reviewer for this concern and would like to highlight that we have included the following section in the Supplemental Discussion 1 section to help clarify potential differences between flies and mammals: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 44, 936, 164]]<|/det|> +"In mammals, light- activated rhodopsin in rod and cone photoreceptor neurons couples to, and inactivates, cyclic nucleotide gated channels, hyperpolarizing the cell [17]. This is distinctly different from what occurs in the fly, where light- activated rhodopsin couples to a TRP channel, which when activated depolarizes the cell [18]. However, in a third class of mammalian photoreceptors, the intrinsically- photosensitive retinal ganglion cells (ipRGCs), there is a nearly identical mechanism of phototransduction to Drosophila [19]. The ipRGCs play a role in non- image forming light sensation, effecting pupillary constriction and the entrainment of the central circadian clock to light. There is some evidence that eliminating Bmal1 in mice (either specifically in their ipRGCs or throughout their entire body) impairs the functionality of the ipRGCs [20]. This is consistent with what we observed when we disrupted clk in the Drosophila photoreceptors. Together, this suggests that there may be a conserved mechanism through which circadian clocks mediate the health of photoreceptor cells." + +<|ref|>sub_title<|/ref|><|det|>[[57, 188, 141, 201]]<|/det|> +## Minor points + +<|ref|>text<|/ref|><|det|>[[60, 213, 875, 241]]<|/det|> +- p8. "These findings provide a potential mechanistic explanation for the rhythmic response pattern in light-sensitivity observed in Drosophila photoreceptors". It is well documented in vertebrates but is it clearly shown in flies? Please provide references. + +<|ref|>text<|/ref|><|det|>[[85, 243, 933, 285]]<|/det|> +- It appears we accidentally neglected to include the reference within the main text, as it was only referenced in the supplemental discussion (ref #25). We have now included that reference within the main text: Nippe, O.M., et al., Circadian Rhythms in Visual Responsiveness in the Behaviorally Arrhythmic Drosophila Clock Mutant Clk(Jrk). J Biol Rhythms, 2017. 32(6): p. 583-592. + +<|ref|>sub_title<|/ref|><|det|>[[58, 310, 298, 323]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[57, 335, 937, 376]]<|/det|> +The manuscript by Hodge and colleagues demonstrates that the circadian clock regulates phototransduction in such a manner as to increase lifespan, visual function, and lower systematic inflammation. The data in the paper are convincing and support the conclusion of the authors. + +<|ref|>text<|/ref|><|det|>[[57, 387, 935, 428]]<|/det|> +I am having some trouble with the connections that are made in the paper. For example, it is not clear to me why photoreceptor degeneration would cause an increase in systemic inflammation and a decrease in lifespan. I am not questioning the data in the paper. I just think that the authors need to connect the dots for the reader more carefully. + +<|ref|>text<|/ref|><|det|>[[85, 427, 937, 494]]<|/det|> +- We thank the reviewer for their comment. In our current manuscript we believe we provide sufficient evidence that the photoreceptor is both a modulator of local and systemic inflammation as well as Drosophila lifespan. We believe that further studies are needed to elucidate the actual mechanism(s) by which photoreceptor's influence the health of other cell-types and modulate lifespan, but we feel that these studies are not within the scope of this current study. Herein, our focus was to identify the downstream CLK-controlled processes that are upregulated on DR, and to determine how they regulate aging and longevity, which we believe we have provided sufficient evidence. + +<|ref|>text<|/ref|><|det|>[[60, 506, 933, 534]]<|/det|> +I am also not sure I understand how the dietary restriction plays into the study. I think the authors could just look at defective retinal clocks and the effect that it has on the fly. Especially since flies are not normally going to encounter dietary restrictive conditions out in the wild. + +<|ref|>text<|/ref|><|det|>[[85, 534, 935, 600]]<|/det|> +- Given the observations that circadian clocks decline with age and that restrictive diets such as dietary restriction or calorie restriction enhance core molecular clock rhythms, we set out to identify which processes and tissues displayed clear DR-dependent improvements in circadian oscillation. Our time-course circadian transcriptome data on DR and AL led us to identify light-response genes as circadian and being selectively amplified by DR. We do believe that circadian clocks play important roles even in standard diets, or those that would be consumed in the wild, but our goal was to elucidate the circadian processes downstream of DR that help to slow aging and extend lifespan. + +<|ref|>text<|/ref|><|det|>[[60, 612, 933, 640]]<|/det|> +I also think that the authors need to focus on one of the effects that the eye clock has on the fly. It could be visual function, inflammation, or lifespan but it I think the paper will benefit from a single idea. + +<|ref|>text<|/ref|><|det|>[[85, 640, 911, 667]]<|/det|> +- We and the editor disagree with the critique that the manuscript will benefit by changing the focus or scope, and therefore we will not comment here. + +<|ref|>text<|/ref|><|det|>[[57, 692, 919, 732]]<|/det|> +Just my two cents - I think the strongest part of the paper is the effect the eye clock has on phototransduction and visual function. I think that a revised paper in which the authors focus exclusively on this connection will be very exciting and would be appropriate for Nature Communications. + +<|ref|>text<|/ref|><|det|>[[86, 732, 342, 744]]<|/det|> +- Please refer to our previous statement. + +<|ref|>text<|/ref|><|det|>[[60, 757, 925, 784]]<|/det|> +The effect on systematic inflammation and lifespan, while both interesting, are hard to connect to the state of photoreceptor health and, to me, make a much less interesting story. + +<|ref|>text<|/ref|><|det|>[[85, 784, 936, 904]]<|/det|> +- We found through an unbiased analysis of the genes that were upregulated with loss of CLK function that there were significant enrichments in inflammatory genes (i.e., AMPs). Furthermore, housing flies in LD vs DD also increases the expression of inflammatory markers. We then demonstrate that forcing photoreceptor degeneration (eye-specific ATPalpha knockdown) was sufficient to drive a systemic inflammatory response, while reducing rhodopsin mediated signaling (Rhodopsin null lines) suppressed this response. Given that chronic inflammation is now considered a hallmark of aging, we believe it is important to demonstrate that the photoreceptor could be a critical regulator of inflammation in the fly, and although the lifespan and inflammation findings are highly correlated, we are careful to refrain from claiming that photoreceptor derived inflammation is a main driver of lifespan shortening. We believe future studies are needed to develop a likely complex, mechanistic understanding of the interplay of diet, circadian rhythms, photoreceptor physiology, inflammation, and lifespan. + +<|ref|>text<|/ref|><|det|>[[60, 916, 927, 943]]<|/det|> +If the authors focus on visual function I would suggest that they combine their clock mutants with all known phototransduction mutants to gain a comprehensive view of how the clock is affecting degeneration and visual function. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[85, 45, 926, 111]]<|/det|> +- We thank the reviewer for this suggestion. Although we agree that a deeper understanding of how functionally circadian clocks may influence photoreceptor degeneration in varying phototransduction mutants, we believe that these experiments would not change the overall interpretations made in this manuscript and are therefore out of our current scope. Additionally, there are many phototransduction mutants (n>25 different lines) and there is not a clear rationale as to why we should screen these different mutants in the context of our circadian mutants. + +<|ref|>sub_title<|/ref|><|det|>[[58, 124, 764, 139]]<|/det|> +## I would also suggest that the authors do experiments in complete darkness, a light:dark cycle, and constant light. + +<|ref|>text<|/ref|><|det|>[[85, 139, 907, 230]]<|/det|> +- We have performed lifespans in flies in either LD vs DD and demonstrated that the \(w^{1118}\) flies display a clear diet-dependent lifespan shortening in LD (Fig. 5a) that is rescued in DD. Alternatively, we found that red-eyed Canton-S flies did not display a clear lifespan shortening in LD (Supp. Fig. 7a). We reasoned since w1118 flies lack red-pigment in their pigment cells, they are known to be more susceptible to light-mediated photoreceptor degeneration that is likely exacerbated in AL. We also performed the LD vs DD lifespan analysis in flies that lack photoreceptors (TRP\(^{365}\)) and demonstrate that these flies are not long-lived in DD (Supp. Fig. 7b). Our lab previously demonstrated that wildtype Canton-S flies are short-lived when reared in constant light vs LD (Katewa et al., 2016, PMID: 26626459), and therefore did not feel the need to repeat these experiments in the current manuscript. + +<|ref|>image<|/ref|><|det|>[[100, 241, 900, 888]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[55, 44, 940, 150]]<|/det|> +Using Drosophila models, in this study Hodge et al. demonstrated that dietary restriction (DR) extends lifespan by promoting circadian homeostatic processes that protect the visual system from age- and light- associated damage. The authors have further demonstrated that disrupting circadian rhythms in the eye by inhibiting the transcription factor, Clock (CLK), or CLK- output genes, accelerated visual senescence, induced a systemic immune response, and shortened lifespan. Moreover, flies subjected to dietary restriction were protected from the lifespan- shortening effects of photoreceptor activation. Inversely, photoreceptor inactivation, achieved via mutating rhodopsin or housing flies in constant darkness, primarily extended lifespan in flies reared on a high- nutrient diet. Overall, their findings establish the eye as a diet- sensitive modulator of lifespan and indicate that vision is an antagonistically pleiotropic process that contributes to organismal aging. + +<|ref|>text<|/ref|><|det|>[[56, 148, 937, 202]]<|/det|> +Using multiple assays this is a very detail, systemic, and well- designed mechanistic study to demonstrate the linkage to DR and circadian rhythms to protect the visual system from age- and light- associated damage. Overall, findings from this study are quite interesting, however, require more clarity, specification, and justifications. In my assessment with some clarity and justification, this might become suitable for publication in Nature Communications. The following questions/concerns need to be addressed for this consideration. + +<|ref|>text<|/ref|><|det|>[[56, 213, 928, 267]]<|/det|> +1. The authors have used multiple drivers to express/knockdown various genes in multiple tissues, however, the focus is limited to visualaging. The authors need to provide a table using all the drivers/genes used in this manuscript for all the genetic modulations with clear/concise justifications. This is essential to justify the authors' hypothesis and potential outcome. This will be also useful for the general audience in understanding the power of Drosophila genetics for addressing cell-autonomous functions. + +<|ref|>text<|/ref|><|det|>[[85, 266, 916, 320]]<|/det|> +Thank you for your comment. To clarify our approach and help aide the audience in the design of our study we have generated a new supplemental data file (Supplemental Data 12). Herein, we provide a clear description of the lines used within each figure and include pertinent information regarding the strains (mutant line, GAL4 driver, UAS- line, etc), our rationale for utilizing each line, and a description of the strengths and potential limitations of each line. + +<|ref|>text<|/ref|><|det|>[[56, 331, 940, 437]]<|/det|> +2. Related to my concern 1, the authors frequently use ELAV and GMR drivers however, did not differentiate clock-mediated neuroprotective functions vs photoreceptors/visual system. When using a Pan-neuronal driver like ELAV, how modulation of circadian clock or DR affecting the neuronal system? Based upon their findings, it is clear that the life-span and phototaxis performance will be affected by the para-neuronal ELAV driver. Therefore, most of the outcomes shown by the authors could be neuronal as well. Therefore, it will be essential to differentiate neuronal vs visual systems in the entire manuscript. Also, as shown in Fig.5, it is important to clarify how knock-down of GMR-driven DR-sensitive eye-specific Clk-output genes reduces survival and affects phototaxis performance? Recent studies have shown that GMR-expression is not limited to the visual system therefore, most of these genes knock-down, including reduces survival and affects phototaxis performance might be not limited to the visual system. + +<|ref|>text<|/ref|><|det|>[[85, 449, 936, 624]]<|/det|> +We agree that a major limitation of utilizing the Elav- GS- GAL4 driver to over- express the CLK- \(\Delta 1 / 2\) lines is the inability to decipher whether the outcomes on eye- aging and/or lifespan are confounded by potential changes in extra- ocular neuronal subtypes. To directly test the role of photoreceptor clocks in diet- mediated changes in visual function and lifespan, we crossed a photoreceptor- specific GAL4 driver (trpl- GAL4;GAL80) with the UAS- CLK- \(\Delta 1\) line (prCLK- \(\Delta 1\) ). Additionally, we crossed the Trpl- GAL4;GAL80 line with a UAS- Clk line (prCLK- OE) to test the effects of over- expressing wild- type Clk specifically in photoreceptors. \\*Note: The Trpl- GAL4;GAL80 line is temperature sensitive and allows for a repression of GAL4 throughout development by housing the flies at \(18^{\circ}C\) Once the flies are sorted onto the food they are moved to \(30^{\circ}C\) to de- repress the GAL4 for the remainder of their lifespan. To avoid potential confusion between the pan- neuronal Elav- GS- GAL4 (nCLK- \(\Delta 1\) ) and photoreceptor specific lines (prCLK- \(\Delta 1\) and prCLK- OE), we placed the eye- specific Clk data in its own figure (Fig. 3). Within Figure 3, we now show that prCLK- \(\Delta 1\) display accelerated declines in positive phototaxis (3a), reduced ERG amplitude (3b), and massive photoreceptor degeneration by day 10 (3c). Inversely, prCLK- OE improved positive phototaxis (3a) and increased ERG amplitude(3b) in comparison to control flies. Additionally, we found that prCLK- \(\Delta 1\) flies displayed significant reductions in median lifespan on both AL and DR, as compared to controls (Fig. 4f). This indicates that reducing CLK function within photoreceptor cells is sufficient to decrease lifespan. + +<|ref|>image<|/ref|><|det|>[[70, 625, 835, 828]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[57, 831, 121, 844]]<|/det|> +
*Fig. 3a-c
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[63, 43, 446, 214]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[393, 206, 444, 219]]<|/det|> +
\\*Fig. 4f
+ +<|ref|>text<|/ref|><|det|>[[85, 229, 925, 310]]<|/det|> +- We thank the reviewers for their concern per utilizing the GMR-GAL4 driver. Our rationale for using GMR-gal4 for our knockdown experiments with retinin, Gbeta76c, and Sunglasses was the strength of the driver. Namely, we sought to utilize a strong GAL4 driver to promote efficient RNAi-mediated knockdown of these genes within the eye. Additionally, we chose to study retinin, Gbeta76c, and sunglasses based on our bioinformatic analyses demonstrating them to be photoreceptor enriched genes, and because they have clearly defined functional roles within the Drosophila eye literature. Therefore, it is our belief that the phototaxis and lifespan changes observed with GMR-GAL4 crossed to retinin-RNAi, Gbeta76c-RNAi, and sunglasses-RNAi is primarily due to their knockdown within the eye. + +<|ref|>text<|/ref|><|det|>[[56, 320, 940, 363]]<|/det|> +3. It is well known that GMR-driver mediated expression/knock-down directly affects ommatidia organization/degeneration. Did the authors see any defects in ommatidia organization/degeneration with the ocular expression of CLK-delta1 and CLK- delta or ocular knock-down of ATP or other genes shown in listed in Fig. 5? It will be also important to know if this was impacted by DR or other genetic modulations. + +<|ref|>text<|/ref|><|det|>[[85, 373, 936, 519]]<|/det|> +- We agree and are aware of previous studies demonstrating that the GMR-GAL4 driver can induce photoreceptor degeneration due to toxicity from excessive amounts of intracellular GAL4 protein. Although we cannot rule out the possibility that GAL4 toxicity could influence the phenotypes we reported, it is our belief that our findings and conclusions were made with the proper controls. For each of our GMR-GAL4 experiments, we used a control RNAi group: GMR-GAL4>UAS-RNAi control (UAS-mCherry-RNAi, from BDSC) and GMR-GAL4>UAS-RNAi control (UAS-empty vector, from VDRC). The F1 generations from the GMR-GAL4 crosses are GMR heterozygotes, as are the experimental groups. Therefore, it is our assumption that all GMR-GAL4 F1 generations within our experimental RNAi groups (retinin, Gbeta76c, ATPalpha, etc) express a similar amount of GAL4 protein as compared to the RNAi control flies, and thus it is unlikely that GAL4 toxicity differs among our experimental and control groups. Furthermore, we chose our RNAi controls because they share the same genetic background as our experimental UAS-lines. Although others have demonstrated GAL4 toxicity, we do not believe this is a major concern given that our GMR-GAL4>RNAi control groups display normal phototaxis behavior and lifespan compared to wildtype lines (e.g., Canton-S etc.). + +<|ref|>text<|/ref|><|det|>[[85, 518, 937, 600]]<|/det|> +- When we crossed the GMR-GAL4 to UAS-CLK-Δ1 or UAS-CLK-Δ2, we found that these flies develop to pupae but never eclose. This is likely caused by developmental toxicity from expressing dominant negative CLK. We observed a similar result with both the Trpl-GAL4 (photoreceptor driver, \\*without temperature-sensitive Gal80) and Spa-GAL4 (a cone-cell driver) when they were crossed to the UAS-CLK-Δ1/2 lines. Therefore, we combined the Trpl-GAL4 driver with the temperature-sensitive GAL80 line to make a photoreceptor-specific, temperature controlled GAL4 driver: The prCLK-Δ1 and prCLK-OE flies allowed us to assess how loss or gain of CLK function (post-developmentally) influenced photoreceptor function and degeneration (as described above). + +<|ref|>text<|/ref|><|det|>[[85, 598, 935, 680]]<|/det|> +- Given that ATPalpha is highly expressed in cone-cells in addition to photoreceptor cells, we also knocked down ATPalpha with the cone-cell specific driver Spa-GAL4. We found that these flies also have reduced phototaxis and lifespan, albeit to a lesser extent compared to GMR-GAL4>ATPalpha-RNAi (Supplemental Fig. 8a-b). These data are in support of our initial claim that forcing photoreceptor degeneration by altering ATPalpha levels is sufficient to shorten lifespan. We do not have the ability to tease out whether the difference in lifespan with ATPalpha knocked down in GMR-GAL4 vs Spa-GAL4 is due to differences in tissue expression patterns (knockdown in all eye cells vs cone-cells), GAL4 toxicity, knockdown strength, or developmental expression patterns. + +<|ref|>image<|/ref|><|det|>[[158, 690, 707, 844]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[57, 846, 925, 888]]<|/det|> +
4. As shown in Fig. 3, NCLK-1 flies display elevated immune responses and shortened lifespan and demonstrated that disrupting neuronal CLK function elevates systemic immune responses. Later the authors have demonstrated that this is also eye-driven (Fig. 3c, d). For these experiments, the authors have used fly bodies, instead of heads. Why expression was not tested in the head/eyes?
+ +<|ref|>text<|/ref|><|det|>[[85, 899, 925, 953]]<|/det|> +- We initially observed and reported that there was a significant enrichment in immune markers in the nCLK-Δ1 RNA-Seq. which was performed exclusively within heads (Fig. 4a). Additionally, when we analyzed a publicly available microarray dataset comparing gene expression in the heads of wildtype flies \((y,w)\) reared in different lighting conditions, we also observed a significant elevation of immune markers within the heads of flies reared in 12:12hr light dark as compared to constant dark conditions (Supp. Fig. 5f). Taken together, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 43, 936, 120]]<|/det|> +these results led us to question whether the photoreceptor itself could influence systemic inflammation in the fly. Given that the mammalian literature has extensively documented that retinal degeneration can strongly induce local inflammatory responses in the eye, our main objective with these experiments was to ask whether manipulating photoreceptor homeostasis in the fly could influence systemic inflammation (in the bodies); This is the main reason we decided to quantified AMP expression within bodies while only manipulating processes within the eye/neurons. We found that forcing photoreceptor degeneration (ATPalpha knockdown, Supp. Fig. 5d) promoted AMP gene expression, while reducing phototransduction (Rhodopsin null lines, Fig. 4d) reduced AMP gene expression to varying degrees. + +<|ref|>image<|/ref|><|det|>[[66, 120, 840, 300]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[60, 300, 264, 315]]<|/det|> +
*Fig. 4a and Supplemental Fig. 5f
+ +<|ref|>image<|/ref|><|det|>[[57, 316, 797, 504]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[60, 508, 268, 522]]<|/det|> +
*Supplemental Fig. 5d and Fig. 4d
+ +<|ref|>text<|/ref|><|det|>[[58, 533, 930, 561]]<|/det|> +5. Similarly, in Fig 5e, why the experiment is limited to the whole fly? Relative mRNA expression of immune genes (AttaA, DiptB, and Dro) calculated by RT-qPCR with mRNA isolated from bodies of w1118 and rhodopsin mutant flies housed in 12:12h LD. + +<|ref|>text<|/ref|><|det|>[[86, 573, 316, 586]]<|/det|> +Please see previous response to 4. + +<|ref|>text<|/ref|><|det|>[[57, 599, 933, 653]]<|/det|> +6. As I mentioned before, different drivers used for different experiments, however, the conclusion is limited to eye aging? The authors need to justify how the expression of different tissues leads to eyes aging? A clear cell-autonomous vs non-cell-autonomous justification will be required including editing Fig. 6. If neuronal damage signals propagate throughout the body to drive systemic immune responses, the authors need to find basal expression of these genes responsible for immune response in the neuronal and visual tissue/system. + +<|ref|>text<|/ref|><|det|>[[85, 669, 875, 698]]<|/det|> +As mentioned above, the inclusion of the prCLK- \(\Delta 1\) and prCLK- OE data now demonstrate a clear cell- intrinsic role for CLK in modulating photoreceptor (eye) aging. + +<|ref|>text<|/ref|><|det|>[[85, 710, 936, 737]]<|/det|> +To limit any potential confusion or overstatement of our findings, we have removed the "Systemic Inflammation" from the summary figure (now Fig. 7) and have made changes to the discussion. + +<|ref|>image<|/ref|><|det|>[[113, 736, 480, 920]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[425, 912, 476, 925]]<|/det|> +
Fig. 7
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[56, 57, 937, 111]]<|/det|> +7. Again, the authors have argued that neuronal CLK function is required for the full lifespan extension mediated by DR and indicate that photoreceptor clocks are essential for the maintenance of visual function with age and organismal survival? I think these are confusing statements and need more clarity and justification. Despite several pieces of evidence provided by authors for the neurological role, I am not sure how the outcome is limited to visual function/system? + +<|ref|>text<|/ref|><|det|>[[85, 122, 940, 183]]<|/det|> +- We thank the reviewers for their concern. We believe the addition of the new prCLK-DN1 and prCLK-OE data indicate a clear role for CLK function in photoreceptor function and degeneration with age (Fig. 3 and Supplemental Fig. 4). Furthermore, the lifespan shortening observed in prCLK-Δ1 flies (Fig. 4f) indicates that loss of CLK function only within photoreceptors (and post-developmental) is sufficient to reduce lifespan. + +<|ref|>text<|/ref|><|det|>[[60, 207, 904, 234]]<|/det|> +8. DR-protection against lifespan shortening downstream of light and/or rhodopsin-mediated signaling in a manner that requires light-adaptation, and by extension, arr1-mediated rhodopsin endocytosis. This justification needs more clarification. + +<|ref|>text<|/ref|><|det|>[[85, 235, 936, 288]]<|/det|> +- We apologize for any confusion as to our rationale for analyzing phototaxis responses and lifespan with knockdown of arr1. We have added the follow sentence within the main text to help clarify: "Arr1 mRNA is circadian in wildtype heads (Supplemental Fig. 1m) and is also a direct CLK target (CLK ChIP-Seq., Supplemental Table 1). Additionally, arr1 expression was significantly downregulated in heads of nCLK-DN1 flies compared to controls (Supplemental Fig. 7e)." \*Note, we have generated Supplemental Fig. 7c for this revision. + +<|ref|>image<|/ref|><|det|>[[58, 288, 920, 522]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[58, 523, 240, 537]]<|/det|> +
*Supplemental Fig. 1m and 7c
+ +<|ref|>text<|/ref|><|det|>[[86, 550, 927, 603]]<|/det|> +- Additionally, since we ourselves have not quantitively measured Arr1-mediated rhodopsin endocytosis in flies reared on either AL or DR we agree that our initial statement may have overstated our findings. Therefore, we decided to replace the concluding sentence that is in question with: "Together, these data suggest that modulation of rhodopsin-mediated signaling is sufficient to regulate lifespan in Drosophila." + +<|ref|>text<|/ref|><|det|>[[60, 616, 930, 644]]<|/det|> +9. Despite the noticeable difference of immune system and photoreceptors cells between, Drosophila with the mammalian visual system, the authors did not indicate the limitations of their finding. + +<|ref|>text<|/ref|><|det|>[[86, 644, 920, 697]]<|/det|> +- As mentioned above, we have listed specific limitations of the individual lines used within this study in Supplemental Data 12. Although, we have attempted to highlight potential similarities and differences between our findings and those previously published in the mammalian literature in our Supplemental Discussion 1 section, we do not believe that our utilization of Drosophila is in any way a limitation of our study and/or findings. + +<|ref|>text<|/ref|><|det|>[[60, 710, 907, 737]]<|/det|> +10. The discussion section of the main text needs a significant improvement including clarity about the above-mentioned comments. The authors have also used discussion/significance of their findings in the SI section without any clarification. + +<|ref|>text<|/ref|><|det|>[[85, 737, 904, 764]]<|/det|> +- We have re-worded portions of our main text to improve clarity. The additional discussion text was included within the supplemental section in accordance with Nature Communications guidelines and to adhere to the sizing/formatting of the manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 288, 106]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 393, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 163, 857, 216]]<|/det|> +The authors have significantly improved the manuscript. However, I believe that there is still a major problem with the conclusion that the CLK- DN effect that is reported here is related with the circadian clock, as detailed below. + +<|ref|>sub_title<|/ref|><|det|>[[116, 256, 251, 272]]<|/det|> +## p5-6 and Sup Fig 1 + +<|ref|>text<|/ref|><|det|>[[115, 273, 860, 363]]<|/det|> +The authors indicate that cycling genes experiment made in light- dark (LD) conditions are circadianly- regulated. I am afraid that there is some misunderstanding here. In LD cycles, cycling genes might be either circadianly- regulated genes or light- regulated genes. I thus do not understand why the term circadian is used here. A DD experiment would be required to show that circadian control is involved here. + +<|ref|>text<|/ref|><|det|>[[115, 364, 871, 454]]<|/det|> +This is particularly relevant for the timO mutants where no circadian transcription is known to occur, in contrast to light- regulated transcription (see Wijnen et al., PLoS Genet 2006). Thus, finding 480- 490 genes cycling in LD conditions does not mean that there are under circadian regulation. Having a circadian transcription in timO flies would be highly surprising and goes against all previous work, to my knowledge. + +<|ref|>text<|/ref|><|det|>[[115, 455, 833, 491]]<|/det|> +This is a key point that needs to be clarified since the effect of DR could well be on light- regulated transcription more than on circadianly- regulated transcription. + +<|ref|>sub_title<|/ref|><|det|>[[116, 511, 278, 527]]<|/det|> +## Figure 1 and sup fig3e + +<|ref|>text<|/ref|><|det|>[[115, 528, 870, 655]]<|/det|> +The above comment brings back the question of the CLK- DN effect. I understand that the RU486 conditional expression system that is use here and that is confirmed by the TS- gal80 system supports a non- developmental effect, and the use of the clkout mutant is also a good control for non- specific CLK- DN effects. However, it is known that CLK affects the transcription of non- circadianly controlled genes (McDonald et al., Cell 2001, Abruzzi et al., Genes Dev 2011), possibly including light- controlled genes. I would thus suggest to interpret the data differently, with DR affecting reinforcing light- regulated transcription and not circadian transcription. + +<|ref|>text<|/ref|><|det|>[[115, 656, 882, 746]]<|/det|> +In the rebuttal letter, the authors indicate that because TIM/PER repress CLK- dependent transcription, the corresponding mutants cannot be used here to confirm the circadian function of clk. I disagree with this, constitutive clk expression in the perO and timO mutants does not change the fact that the clock function is abolished. I still would like to see a phototaxis experiment with timO or perO mutants to really make the difference between a function of the CLK transcription factor and the circadian clock. + +<|ref|>text<|/ref|><|det|>[[116, 803, 393, 819]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 840, 802, 857]]<|/det|> +the authors have addressed my concerns. As such I support the publication of the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 393, 106]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 125, 867, 217]]<|/det|> +The authors did a really good job in addressing most of the concerns/questions I raised in the previous version. In addition to addressing questions, the authors have provided additional supporting data for their findings. However, a couple of important questions still need some clarification/justification with the data support. Therefore, addressing the following questions will make this study suitable for publications in the prestigious Nature Communications Journal. + +<|ref|>text<|/ref|><|det|>[[115, 236, 875, 345]]<|/det|> +1. The authors have indicated that the GMR-GAL4 driver can induce photoreceptor degeneration due to toxicity from excessive amounts of intracellular GAL4 protein. This justification is very poor. It is well established for several neurological disease models that GMR-Gal4 specific expression of mutant, not wild-type associated with ommatidia organization/degeneration. Instead of going through this intracellular toxicity theory, the authors should directly if they have received any ommatidia organization/degeneration or not? + +<|ref|>text<|/ref|><|det|>[[113, 363, 872, 580]]<|/det|> +2. The authors mentioned that when they crossed the GMR-GAL4 to UAS-CLK-delta1 or UAS-CLK-delta 2, they found that these flies develop to pupae but never eclose. How expression of UAS-CLK-delta1 or UAS-CLK-delta2 with GMR-Gal4 driver caused pupae stage lethality. It is hard to believe ocular-specific expression leads to developmental toxicity from expressing dominant-negative CLK. In my opinion, the lethality is caused because GMR-driver is not specific to ocular and is shown to express in other tissues as well. Did the authors check the expression of GMR-GAL4 in other tissues as indicated in the other tissues? https://pubmed.ncbi.nlm.nih.gov/22911584/ https://pubmed.ncbi.nlm.nih.gov/26440079/ Related to this the authors have indicated that they have similar results with both the Trpl-GAL4 (photoreceptor driver, \*without temperature-sensitive Gal80). Therefore, the authors need to explain how photoreceptor-specific expression of UAS-CLK-delta1 or UAS-CLK-delta 2 caused developmental lethality? + +<|ref|>text<|/ref|><|det|>[[115, 600, 874, 672]]<|/det|> +3. It is still hard to understand how eye-specific expression of leads to elevates systemic immune responses beyond the head as in the updated Fig.7, the authors did not explain that (including elevated AMP expression within bodies). They still need to justify the elevated level of immune response beyond ocular tissue. + +<|ref|>text<|/ref|><|det|>[[115, 692, 866, 746]]<|/det|> +4. In general, the author needs to say that some of the lethality/immune response could be due to the expression of UAS-CLK-delta1 or UAS-CLK-delta 2 expression of these dominant negative in other tissues, beyond their ocular (eye)-specific expression. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 400, 106]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 123, 872, 175]]<|/det|> +The authors have significantly improved the manuscript. However, I believe that there is still a major problem with the conclusion that the CLK- DN effect that is reported here is related with the circadian clock, as detailed below. + +<|ref|>sub_title<|/ref|><|det|>[[115, 210, 253, 225]]<|/det|> +## p5-6 and Sup Fig 1 + +<|ref|>text<|/ref|><|det|>[[115, 226, 874, 310]]<|/det|> +The authors indicate that cycling genes experiment made in light- dark (LD) conditions are circadianlyregulated. I am afraid that there is some misunderstanding here. In LD cycles, cycling genes might be either circadianly- regulated genes or light- regulated genes. I thus do not understand why the term circadian is used here. A DD experiment would be required to show that circadian control is involved here. + +<|ref|>text<|/ref|><|det|>[[115, 310, 875, 395]]<|/det|> +This is particularly relevant for the tim0 mutants where no circadian transcription is known to occur, in contrast to light- regulated transcription (see Wijnen et al., PLoS Genet 2006). Thus, finding 480- 490 genes cycling in LD conditions does not mean that there are under circadian regulation. Having a circadian transcription in tim0 flies would be highly surprising and goes against all previous work, to my knowledge. + +<|ref|>text<|/ref|><|det|>[[115, 395, 848, 429]]<|/det|> +This is a key point that needs to be clarified since the effect of DR could well be on light- regulated transcription more than on circadianly- regulated transcription. + +<|ref|>text<|/ref|><|det|>[[115, 446, 877, 530]]<|/det|> +We thank the reviewer for the comments to improve our manuscript. In our previous submission we reported that roughly 480- 490 transcripts oscillate in a circadian fashion in \(\text{tim}^{01}\) flies. We did not intend to argue, or make the distinction, that the oscillating genes we reported for the \(\text{tim}^{01}\) flies were driven by "circadian" vs "light- driven" mechanisms. Our only intention was to state the number of transcripts that displayed a circadian expression pattern on AL or DR according to our JTK_CYCLE parameters. + +<|ref|>text<|/ref|><|det|>[[115, 546, 881, 682]]<|/det|> +We appreciate the reviewer's concern that the oscillating transcripts reported for CantonS wildtype flies may be influenced by light- dark cycles, as we did not perform additional time- course microarrays in free- running conditions (DD). Our laboratory has a long history of characterizing DR- mediated lifespan benefits while housing flies in LD, and we designed our time- course microarray experiments to identify the circadian processes that are enriched on AL and DR diets in this context. It is well established that \(\text{tim}^{01}\) mutant flies are behaviorally arrhythmic in constant conditions (DD) but retain some ability to entrain to light- dark cycles due to masking effects. It is our assumption that any transcripts that display a circadian expression pattern in the \(\text{tim}^{01}\) flies housed in 12:12h LD are most likely "light- driven". + +<|ref|>text<|/ref|><|det|>[[115, 699, 880, 869]]<|/det|> +To classify which genes are circadianly- regulated in wildtype flies we subtracted the light- driven transcripts (i.e., also circadian in \(\text{tim}^{01}\) ) from the transcripts that comprise the AL and DR circadian microarrays in wildtype CantonS flies. By controlling for the potential confounding variable of light, we believe that the remaining genes (circadian in CantonS but not in \(\text{tim}^{01}\) ) are clock controlled. However, it is possible that these circadianly- regulated transcripts are also reinforced by lighting signals/cues. For instance, light- mediated intracellular signaling cascades (e.g., photoentrainment by Cry) may impinge on the circadian transcription factor CLK to influence timing (i.e., phase shifts) and/or amounts of transcriptional activation of downstream targets (i.e., amplitude). Furthermore, light- and nutrient- signals from the diet may independently or synergistically converge on the core- clock machinery to influence the transcription of clock- controlled genes/processes within photoreceptors. + +<|ref|>text<|/ref|><|det|>[[115, 886, 735, 903]]<|/det|> +We have provided the following statements to clarify these concerns within the text: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 106, 876, 208]]<|/det|> +"In LD conditions, circadian transcripts may be driven by the core-molecular clock or by rhythmic lighting cues. We performed time-course microarrays under similar conditions in arrhythmic tim \(^{01}\) mutant flies which lack circadian transcriptional rhythms, as we reasoned that the circadian transcripts identified in these mutants are primarily light-driven. Circadianly-regulated transcripts (clock-output genes) were identified as those which oscillate only in wildtype flies and not in tim \(^{01}\) mutants (Supplementary Fig. 1a)." + +<|ref|>text<|/ref|><|det|>[[115, 225, 718, 260]]<|/det|> +The following figures and datasets have been updated to reflect our new analyses: Fig. 1a- f, Supplementary Fig. 1a- b, f- g, j- k and Supplementary Data 1. + +<|ref|>sub_title<|/ref|><|det|>[[115, 294, 280, 310]]<|/det|> +## Figure 1 and sup fig3e + +<|ref|>text<|/ref|><|det|>[[115, 310, 872, 430]]<|/det|> +The above comment brings back the question of the CLK- DN effect. I understand that the RU486 conditional expression system that is use here and that is confirmed by the TS- gal80 system supports a non- developmental effect, and the use of the clkout mutant is also a good control for non- specific CLK- DN effects. However, it is known that CLK affects the transcription of non- circadianly controlled genes (McDonald et al., Cell 2001, Abruzzi et al., Genes Dev 2011), possibly including light- controlled genes. I would thus suggest to interpret the data differently, with DR reinforcing light- regulated transcription and not circadian transcription. + +<|ref|>text<|/ref|><|det|>[[115, 445, 883, 632]]<|/det|> +We agree with the reviewer on being cautious in the interpretation of our experiments and have modified the text to reflect this. In any experiment where CLK function is perturbed, there will always be the possibility that the phenotypic observations reported are due to changes in the expression of downstream circadian genes, non- circadian genes, or a combination of both gene sets. Regarding our analyses of CLK's role in mediating the beneficial effects of DR on photoreceptor physiology with age, we believe that the effects are more- likely due to changes in circadian vs non- circadian gene expression. Our initial analyses of the AL/DR circadian transcriptomes led us to identify many light and eye- related circadian transcripts. We found that the circadian phototransduction genes displayed increased expression and circadian amplitude in CantonS flies on DR but were no longer rhythmic in tim \(^{01}\) flies, suggesting that their circadian expression pattern in wildtype flies is regulated downstream of the molecular clock as opposed to light. + +<|ref|>text<|/ref|><|det|>[[115, 649, 884, 822]]<|/det|> +This argument was strengthened by our nCLK- \(\Delta 1\) RNA- Seq. experiments: We found that genes that were significantly downregulated in expression in nCLK- \(\Delta 1\) heads (DR) and were also circadian in wildtype flies displayed a significant enrichment for biological processes related to light- sensing and homeostatic processes within the eye (Supplemental Fig. 2c). Genes that were significantly downregulated in expression in nCLK- \(\Delta 1\) heads but were non- circadian in wildtype flies failed to display a significant enrichment for light- responsive pathways or eye homeostasis. Below is a table comparing the gene- ontology enrichment scores for genes that were significantly down- regulated in nCLK- \(\Delta 1\) (on DR) and are either circadian ("Circadian_Enrichment") or non- circadian ("Non- Circadian_Enrichment") in wildtype flies. Therefore, it is our interpretation that DR and CLK primarily influence eye aging via downstream regulation of circadian genes, and not non- circadian genes. + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[114, 87, 876, 666]]<|/det|> + +
TermIDTermCircadian_EnrichmentNon-
Circadian_Enrichment
GO:0009416response to light stimulus3.32E-060.7968651
GO:0009642response to light intensity1.27E-050.5084995
GO:0071482cellular response to light stimulus2.60E-050.91390436
GO:0016059deactivation of rhodopsin mediated signaling2.64E-050.71738834
GO:0022400regulation of rhodopsin mediated signaling pathway2.64E-050.71738834
GO:0007602phototransduction5.98E-050.43081234
GO:0009583detection of light stimulus8.65E-050.46534368
GO:0007603phototransduction, visible light0.0001110580.79408137
GO:0006874cellular calcium ion homeostasis0.0005615180.13304433
GO:0009584detection of visible light0.0009962150.65752068
GO:0050953sensory perception of light stimulus0.0013655510.48052537
GO:0001895retina homeostasis0.00151571
GO:0016056rhodopsin mediated signaling pathway0.00151570.64171047
GO:0002032desensitization of G protein-coupled receptor signaling pathway by arrestin0.0017040441
GO:0050962detection of light stimulus involved in sensory perception0.0021596271
GO:0007601visual perception0.0034988330.34515896
GO:0071484cellular response to light intensity0.0049724451
GO:0045494photoreceptor cell maintenance0.0090035861
GO:0016062adaptation of rhodopsin mediated signaling0.0096740641
GO:0036367light adaption0.0096740641
GO:0050908detection of light stimulus involved in visual perception0.0096740641
GO:0046154rhodopsin metabolic process0.0116433871
GO:0042052rhabdomee development0.0136231660.75601232
+ +<|ref|>text<|/ref|><|det|>[[115, 697, 857, 750]]<|/det|> +It is possible that DR reinforces CLK- mediated output by influencing light- sensing. Alternatively, light- mediated signals may influence DR's ability to regulate CLK- mediated transcriptional output. In other words, DR may promote CLK- mediated circadian transcription by reinforcing light- mediated signals. + +<|ref|>text<|/ref|><|det|>[[115, 766, 868, 816]]<|/det|> +We have updated Supplemental Data 4 has to include the gene- ontology enrichment scores for the genes that are non- circadian in wildtype flies and down- regulated in nCLK- \(\Delta 1\) RNA- Seq. (Supplemental Data 4c). We have denoted the changes in the text: + +<|ref|>text<|/ref|><|det|>[[115, 818, 875, 886]]<|/det|> +"Additionally, genes that were both circadian in wild- type heads and downregulated in nCLK- \(\Delta 1\) were highly enriched for homeostatic processes related to eye function, while downregulated genes in nCLK- \(\Delta 1\) that were non- circadian in wildtype heads displayed no such enrichment (Supplementary Fig. 2c and Supplemental Data 4)." And, in the discussion: "Given that CLK transcriptionally regulates circadian and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 847, 124]]<|/det|> +non- circadian transcripts, future studies may determine whether the time- of- day regulation of these genes by CLK is germane to promoting eye health with age." + +<|ref|>text<|/ref|><|det|>[[114, 141, 881, 243]]<|/det|> +In the rebuttal letter, the authors indicate that because TIM/PER repress CLK- dependent transcription, the corresponding mutants cannot be used here to confirm the circadian function of clk. I disagree with this, constitutive clk expression in the per0 and tim0 mutants does not change the fact that the clock function is abolished. I still would like to see a phototaxis experiment with tim0 or per0 mutants to really make the difference between a function of the CLK transcription factor and the circadian clock. + +<|ref|>text<|/ref|><|det|>[[115, 276, 867, 344]]<|/det|> +We have edited our conclusions according to the comments made by the reviewer and no longer state that circadian regulation is required for the DR- or CLK- mediated effects within our study. Thus, the additional \(per^{01} / \mathrm{tim}^{01}\) phototaxis experiments are not required to support our conclusions or interpretations. + +<|ref|>sub_title<|/ref|><|det|>[[115, 411, 400, 427]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 445, 802, 462]]<|/det|> +the authors have addressed my concerns. As such I support the publication of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 513, 400, 529]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 562, 867, 648]]<|/det|> +The authors did a really good job in addressing most of the concerns/questions I raised in the previous version. In addition to addressing questions, the authors have provided additional supporting data for their findings. However, a couple of important questions still need some clarification/justification with the data support. Therefore, addressing the following questions will make this study suitable for publications in the prestigious Nature Communications Journal. + +<|ref|>text<|/ref|><|det|>[[114, 666, 878, 767]]<|/det|> +1. The authors have indicated that the GMR-GAL4 driver can induce photoreceptor degeneration due to toxicity from excessive amounts of intracellular GAL4 protein. This justification is very poor. It is well established for several neurological disease models that GMR-Gal4 specific expression of mutant, not wild-type associated with ommatidia organization/degeneration. Instead of going through this intracellular toxicity theory, the authors should directly if they have received any ommatidia organization/degeneration or not? + +<|ref|>text<|/ref|><|det|>[[115, 768, 853, 835]]<|/det|> +We did not observe overt changes to ommatidia organization/degeneration in any of our GMR- GAL4 crosses utilized in this manuscript. Below we have crossed GMR- GAL4 with UAS- mCD8- GFP which express green fluorescent protein on the cell surface and did not observe any disorganization or degeneration of the ommatidia. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 90, 534, 252]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 286, 881, 480]]<|/det|> +2. The authors mentioned that when they crossed the GMR-GAL4 to UAS-CLK-delta1 or UAS-CLK-delta 2, they found that these flies develop to pupae but never eclipse. How expression of UAS-CLK-delta1 or UAS-CLK-delta2 with GMR-Gal4 driver caused pupae stage lethality. It is hard to believe ocular-specific expression leads to developmental toxicity from expressing dominant-negative CLK. In my opinion, the lethality is caused because GMR-driver is not specific to ocular and is shown to express in other tissues as well. Did the authors check the expression of GMR-GAL4 in other tissues as indicated in the other tissues? https://pubmed.ncbi.nlm.nih.gov/22911584/ https://pubmed.ncbi.nlm.nih.gov/26440079/ Related to this the authors have indicated that they have similar results with both the Trpl-GAL4 (photoreceptor driver, \*without temperature-sensitive Gal80). Therefore, the authors need to explain how photoreceptor-specific expression of UAS-CLK-delta1 or UAS-CLK-delta 2 caused developmental lethality? + +<|ref|>text<|/ref|><|det|>[[114, 508, 883, 679]]<|/det|> +We agree with the reviewer's comment that the observed developmental lethality in crossing the GMR- GAL4 to either UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) is surprising and may be due to mis- expression of the GAL4 in non- ocular tissues. Since others have extensively characterized the mis- expression of GMR- GAL4 in non- ocular tissues we did not feel it was necessary for us to recapitulate those studies here, especially as we were able to utilize the Trpl- GAL80- GAL4 line which allowed us to examine the effects of modulating CLK specifically in adult photoreceptors. We did however observe a similar pupae stage lethality when crossing the UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) with the SPA- GAL4 driver (a commonly used cone- cell specific driver) and the RDGA- GAL4 driver (an additional eye driver). We do note that it is possible that the developmental lethality observed with SPA or RDGA driver lines may also be caused by mis- expression in extra- ocular tissues. + +<|ref|>text<|/ref|><|det|>[[114, 680, 881, 835]]<|/det|> +We would like to clarify our previous response where we stated that the non- temperature- sensitive photoreceptor driver, Trpl- GAL4, flies were 'similar' to the GMR- GAL4 flies when crossed to UAS- CLK- \(\Delta 1\) or - CLK- \(\Delta 2\) , as this statement may have been unintentionally misleading. To be clear, we did not observe any developmental lethality when crossing Trpl- GAL4 flies with either UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) ; these flies eclosed normally. However, we found that upon eclosion, Trpl- GAL4>UAS- CLK- \(\Delta 1\) or UAS- CLK- \(\Delta 2\) flies displayed very low positive phototaxis responses, and overt disruption to their photoreceptors, measured by transverse sections of the eye (below). These observations suggest that CLK is required for proper development of photoreceptors. Furthermore, these findings were central in our reasoning for using the temperature sensitive Trpl;GAL80- GAL4 line for further analysis. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[137, 110, 870, 255]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 277, 481, 293]]<|/det|> +
Figure 1: trpl-gal4>Clk-DN1 cross-section at day 2.
+ +<|ref|>image<|/ref|><|det|>[[115, 303, 420, 486]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 551, 840, 619]]<|/det|> +3. It is still hard to understand how eye-specific expression of leads to elevates systemic immune responses beyond the head as in the updated Fig.7, the authors did not explain that (including elevated AMP expression within bodies). They still need to justify the elevated level of immune response beyond ocular tissue. + +<|ref|>text<|/ref|><|det|>[[114, 653, 875, 891]]<|/det|> +We thank the reviewer for their comments to improve our study. Our main reasoning for assessing systemic immune responses and providing those data within this manuscript were due to the fact that we observed large elevations in anti-microbial peptide (AMP) expression when manipulating CLK (nCLK- \(\Delta 1\) ) and when forcing photoreceptor degeneration (GMR- GAL4>UAS- ATPalpha- RNAi). AMP expression has been shown to result from local damage responses, but they are primarily upregulated within the fat- body. We do not fully understand the mechanisms by which the Drosophila eye and more specifically, the photoreceptors influence systemic immune responses. However, we can speculate on several potential explanations, including: 1. A retinal- blood barrier exists to keep the hemolymph separate from the ommatidia such that the extracellular space surrounding the photoreceptors can maintain a proper ion balance required for photoreceptor viability and the ion gradient required for phototransduction to occur. With age and neurodegeneration, there is leakiness of both the retinal/brain and blood/brain barrier in Drosophila. Interestingly, recent reports have indicated that the blood- brain barrier is under direct circadian control. The upregulation of the AMPs in the body, which is indicative of a systemic immune response, may indicate that photoreceptor degeneration can lead to a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 880, 208]]<|/det|> +breakdown of the retinal brain barrier and damage signals propagating throughout the hemolymph may then activate the fat body to increase the expression of AMPs. 2. An additional explanation may be that as photoreceptors degenerate they do so in a necrotic fashion vs apoptosis. Previous reports have indicated that promoting photoreceptor degeneration by over- expressing a leaky channel can drive local neuronal death in other wise healthy cells. As the photoreceptors degenerate due to age and \(\mathtt{Ca2 + }\) induced toxicity from light exposure, they may promote a feed- forward cycle of neuronal cell death and inflammation that ultimately leads to systemic inflammatory responses. + +<|ref|>text<|/ref|><|det|>[[115, 225, 870, 293]]<|/det|> +Since we have only demonstrated the correlations between photoreceptor degeneration and systemic inflammation with age and have not directly claimed that these systemic immune responses are causal for the phenotypes we described (visual function, lifespan). We have added some of these explanation in the revised submission in the discussion + +<|ref|>text<|/ref|><|det|>[[115, 310, 740, 326]]<|/det|> +We have provided the following text within the discussion to address these concerns: + +<|ref|>text<|/ref|><|det|>[[114, 327, 883, 582]]<|/det|> +"Among the more interesting and unexpecting observations of this study is that the Drosophila eye can influence systemic immune responses, as we observed elevated AMP expression in the bodies of flies overexpressing CLK- \(\Delta 1\) pan- neuronally and in flies with forced photoreceptor degeneration (ATPalpha- RNAi). It is possible that GAL4 mis- expression may promote inflammatory responses in the fly bodies, although we found a reduction in systemic inflammation in the rhodopsin- null lines indicating that this phenomenon can originate at the photoreceptor. We also found that these systemic immune responses correlate with lifespan changes (increased body AMP expression is associated with declines in longevity, and vise- versa), similar to what is reported with chronic inflammation or "inflammaging" in other models. However, we cannot conclude whether neuronal or eye- mediated increases in systemic inflammation are at all causal to aging in other tissues. Furthermore, we do not fully understand the mechanisms by which the Drosophila eye and more specifically, the photoreceptor influences systemic immune responses although we speculate that photoreceptor degeneration may disrupt the retinal- blood barrier such that damage signals from the eye may propagate through the hemolymph to activate AMP expression in distal tissues. Future studies are aimed at elucidating the mechanisms by which the eye influences systemic inflammation and its relation to aging and longevity." + +<|ref|>text<|/ref|><|det|>[[115, 616, 880, 666]]<|/det|> +4. In general, the author needs to say that some of the lethality/immune response could be due to the expression of UAS-CLK-delta1 or UAS-CLK- delta 2 expression of these dominant negative in other tissues, beyond their ocular (eye)-specific expression. + +<|ref|>text<|/ref|><|det|>[[115, 700, 880, 768]]<|/det|> +To address this potential limitation, we have provided the follow text within the manuscript: "However, as with all tissue- specific driver systems, we cannot rule of the possibility that our ELAV- GS- GAL4 driver expresses in a small population of non- neuronal cell- types, which, in theory, could contribute to the elevated systemic inflammatory responses and/or influence lifespan." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 300, 106]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 127, 393, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 163, 761, 199]]<|/det|> +The changes made in the new revised version of the manuscript addresses my concerns. I have one last request about the circadian versus non- circadian 24h oscillations: + +<|ref|>text<|/ref|><|det|>[[113, 217, 870, 346]]<|/det|> +The authors now define circadian transcripts as LD cycling transcripts that do not cycle in tim0 clockless flies and I think that it is a very reasonable estimation for a circadian control. In the modified sentence "In LD conditions, circadian transcripts may be driven by the core- molecular clock or by rhythmic lighting cues...", please do not use circadian for cycling transcripts in LD. I would suggest "In LD conditions, transcripts showing 24h oscillations..." This should be applied to the other instances of the word circadian in the text, please keep circadian when speaking about clock- dependent expression otherwise it is confusing for the reader. + +<|ref|>text<|/ref|><|det|>[[116, 400, 393, 417]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 436, 825, 472]]<|/det|> +All the previous concerns have been appropriately addressed and this should be now suitable for publication in Nature Communications. Best wishes + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 88, 299, 102]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 115, 364, 129]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 141, 697, 168]]<|/det|> +The changes made in the new revised version of the manuscript addresses my concerns. I have one last request about the circadian versus non- circadian 24h oscillations: + +<|ref|>text<|/ref|><|det|>[[115, 181, 870, 220]]<|/det|> +The authors now define circadian transcripts as LD cycling transcripts that do not cycle in tim0 clockless flies and I think that it is a very reasonable estimation for a circadian control. + +<|ref|>text<|/ref|><|det|>[[115, 217, 870, 255]]<|/det|> +In the modified sentence "In LD conditions, circadian transcripts may be driven by the core- molecular clock or by rhythmic lighting cues...", please do not use circadian for cycling transcripts in LD. I would suggest "In LD conditions, transcripts showing 24h oscillations..." + +<|ref|>text<|/ref|><|det|>[[115, 250, 870, 275]]<|/det|> +This should be applied to the other instances of the word circadian in the text, please keep circadian when speaking about clock- dependent expression otherwise it is confusing for the reader. + +<|ref|>text<|/ref|><|det|>[[115, 286, 870, 326]]<|/det|> +We thank the reviewer for their comment and have made the appropriate changes to the text: "In LD conditions, transcripts displaying 24h oscillations may be driven by the core- molecular clock ("circadian") or by rhythmic lighting cues [13]." + +<|ref|>text<|/ref|><|det|>[[115, 350, 364, 364]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 376, 839, 403]]<|/det|> +All the previous concerns have been appropriately addressed and this should be now suitable for publication in Nature Communications. Best wishes + +<|ref|>text<|/ref|><|det|>[[115, 415, 696, 429]]<|/det|> +We appreciate the reviewers' comments and suggestions throughout this review process. + +<--- Page Split ---> diff --git a/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/images_list.json b/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..96ac95ba2d817eaacb4b19e5f9de5ce6e2a1e144 --- /dev/null +++ b/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,70 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure: Steady-state concentrations for \\(x_{1}\\) , and for \\(x_{2}x_{3}\\) , obtained from 10,000 simulations of the second of the three CRNs discussed above. Simulations for the other two CRNs are qualitatively very similar. For each simulation, rate constants \\((c_{1}, \\ldots , c_{5})\\) and initial conditions \\((x_{1}(0), \\ldots , x_{5}(0))\\) are randomly selected from the interval (1,100). We gratefully acknowledge the assistance of my (RA's) graduate student, Cailan Jeynes-Smith, in the preparation of this Figure.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Fig. 1. The internal model principle (IMP) and its application to RPA-capable CRNs. The class of constant disturbances \\((I(t) = \\text{const})\\) is generally the disturbance class of most fundamental interest to the study of biological systems. (a) In order to exhibit RPA (i.e. 'adapt' to constant disturbances), the dynamical system \\(\\Sigma\\) should be decomposable, via a coordinate transformation if needed, into an 'output-driven internal model', \\(\\Sigma_{IM}\\) (generating all the constant signals corresponding to solutions of \\(\\dot{z}_2 = 0\\) ), and the remainder of the system, \\(\\Sigma_0\\) . The variable \\(z_2\\) thereby computes the integral of the output error. (b) A suitable coordinate change should be able to recast an RPA-capable system into integral feedback form, even if there is no feedback present in the network. As shown, a linear transformation is sufficient to identify an output-driven internal model for this particularly simple incoherent feedforward motif (Balancer module); \\(y = \\alpha_4 / \\alpha_3\\) (setpoint) at steady-state. (c) A model that employs feedback is frequently simpler to recast in 'integral feedback' form, with an output-driven internal model; here \\(y = \\alpha_3\\) (setpoint) at steady-state. Note that the reaction rates selected for illustrative purposes in (b) or (c) cannot be induced, under the law of mass action, by any CRN20.", + "footnote": [], + "bbox": [ + [ + 153, + 205, + 820, + 495 + ] + ], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Figure_1.jpg", + "caption": "Figure 1: Plots of the dynamics of network (0.3) with mass-action kinetics, with initial state \\(x(0)\\) and rate constants \\(c = (c_{1},c_{2},\\ldots)\\) . Each component of \\(x(0)\\) and \\(c\\) was randomly generated from the interval \\([1,10]\\) and here we show plots for three realisations of \\(x(0)\\) and \\(c\\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \\(x_{1}\\) is 1.", + "footnote": [], + "bbox": [ + [ + 153, + 93, + 780, + 374 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: Plots of the dynamics of network (0.4) with mass-action kinetics, with initial state \\(x(0)\\) and rate constants \\(c = (c_{1},c_{2},\\ldots)\\) . Each component of \\(x(0)\\) and \\(c\\) was randomly generated from the interval \\([1,10]\\) and here we show plots for three realisations of \\(x(0)\\) and \\(c\\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \\(x_{1}\\) is 1.", + "footnote": [], + "bbox": [ + [ + 157, + 92, + 780, + 373 + ] + ], + "page_idx": 41 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Figure 3: Plots of the dynamics of network (0.5) with mass-action kinetics, with initial state \\(x(0)\\) and rate constants \\(c = (c_{1},c_{2},\\ldots)\\) . Each component of \\(x(0)\\) and \\(c\\) was randomly generated from the interval \\([1,10]\\) and here we show plots for three realisations of \\(x(0)\\) and \\(c\\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \\(x_{1}\\) is 1.", + "footnote": [], + "bbox": [ + [ + 159, + 94, + 781, + 374 + ] + ], + "page_idx": 42 + } +] \ No newline at end of file diff --git a/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b176736057bf4395e36d62d48e867f0371a0d7b5 --- /dev/null +++ b/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,1331 @@ + +# nature portfolio + +Peer Review File + +Universal structures for adaptation in biochemical reaction networks + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +# Review: Universal structures for embedded integral control in biological adaptation + +Robyn P. Araujo and Lance A. Liotta + +Overview: Development of adaptation mechanisms is crucial for survival across biological scales. Understanding how such mechanisms are generated through biomolecular interactions is a fundamentally important problem? This issue has underpinnings in control theory and it is known that adaptation requires an embedded integral control, which, if identified, can offer insights into how a reaction network achieves adaptation and how robust this adaptation is. The aim of this paper is to construct an algebraic procedure to identify the hidden integral controller in adaptation- capable networks and connect these controllers to the structure of the networks. + +Recommendation: Even though the paper studies an important problem, I do not find the analysis presented in this paper to be convincing enough to warrant publication in Nature Communications. The manuscript has several shortcomings which I list below: + +## - Lack of sufficient novelty: + +- The general principles for RPA have been developed by (slightly) extending previous results by the authors for deficiency zero and deficiency one CRNs. These low-deficiency networks are related to 'balancer' and 'opposer' modules which are known to form a topological basis for all RPA networks [1]. This connection is explained with two illustrative examples and general principles are formulated by relying on the theory in [1]. Hence, given the earlier results in [1], the incremental novelty in this paper is not significant. + +- Many researchers have exploited Gröbner basis and ideal construction for obtaining steady-states in terms of parameters and in particular for studying ACR. For example, see [6, 5, 3] and references therein. It seems that the authors are unaware of these works and in order the assess the novelty of the methods in this paper, these existing works must be cited and discussed. + +- More importantly, the central analysis in this paper crucially depends on the result for deficiency one networks which is stated as Theorem 3 in the Supplement. However, this result is not new, as it follows from Theorem D.1 in the Supplement of [2] (see the proof in [2]). + +- Definition of RPA: The notion of RPA is not mathematically defined. In other words, it is not clear what disturbances are allowed and what are the biochemical parameters on which the output set-point is allowed to depend. On page 11 in the Supplement it is written that for RPA the set-point \(c\) should be a rational function of + +<--- Page Split ---> + +the biochemical rate constants. However, this would be the case for any steady- state and so what constitutes RPA is not clear. + +- Algorithm may not terminate: The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima-facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In particular, no proof is given showing that non-termination implies no RPA. Moreover, non-termination of a method is not something that can be ascertained with any certainty by running the code. Accordingly, the authors cannot claim that they have a full 'characterisation' of the RPA property. + +- Form of the RPA polynomial: The whole approach hinges on the RPA polynomial having the form + +\[\rho = g(x,y)(x - c)\] + +where \(g(x,y)\neq 0\) and \(y\) is a non- RPA capable variable which forms the kinetic pair to \(x\) . It is unclear why \(g(x,y)\) can only be a function of one additional variable, apart from the output variable. The proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f}\cap \mathbb{R}[\overline{{x}} ]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f}\cap I_{p}\) + +As an example consider the following network: + +\[\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1} + \mathbf{X}_{4}\quad \mathrm{and}\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\mathbf{X}_{5}.\] + +Furthermore assume that species \(\mathbf{X}_{2},\ldots ,\mathbf{X}_{5}\) participate is several reactions that do not involve \(\mathbf{X}_{1}\) but can be catalysed by it. In this scenario the RPA polynomial would be \(\rho = x_{2}x_{3}(\frac{c_{1}}{c_{2}} - x_{1})\) . Hence the function \(g\) depends on two non- RPA variables \(x_{2}\) and \(x_{3}\) . Please explain how this example is consistent with the form of \(g(x,y)\) stated above. + +Moreover, it is not immediately clear how existence of multiple opposer/balancer modules translates into existence of existence of corresponding RPA polynomials. This has not been explained in sufficient detail. + +- Connection to existing works: In [4] the authors consider RPA systems that are maximally robust and find simple linear-algebraic structural conditions that characterise this property in both deterministic and stochastic settings. How do the results in this paper connect to the results in [4]? + +## References + +[1] R. P. Araujo and L. A. Liotta. The topological requirements for robust perfect adaptation in networks of any size. Nature communications, 9(1):1- 12, 2018. + +[2] D. Cappelletti, A. Gupta, and M. Khammash. A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances. Journal of the Royal Society Interface, 17(171):20200437, 2020. + +<--- Page Split ---> + +[3] G. Craciun, A. Dickenstein, A. Shiu, and B. Sturmfels. Toric dynamical systems. Journal of Symbolic Computation, 44(11):1551–1565, 2009. + +[4] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. bioRxiv, 2022. + +[5] M. Pérez Millán, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027–1065, 2012. + +[6] A. Sadeghimanesh and E. Feliu. Gröbner bases of reaction networks with intermediate species. Advances in Applied Mathematics, 107:74–101, 2019. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: + +Reviewer #2: Remarks to the Author: + +Araujo and Liotta develop a set of precise criteria that a system needs to fulfil in order to perfect adaptation. + +This is remarkable and an extremely valuable contribution to the literature in three ways: (i) the search for "design principles" is taking centre stage in synthetic (but also e.g. developmental systems) biology; the first author has proven a leader in distilling precise mathematical criteria for robust perfect adaptation, and I hope that this study will inspire more work in this area, especially in considering the mathematical properties of chemical reaction networks to guarantee different types of behaviour; (ii) in Mathematical biology there are few instances where the mathematical statements can be so precise that biology will have to "obey" these statements. This is one such instance. Finally (iii) the maintenance and control of robust adaptation is of considerable and far reaching biological relevance. I like this manuscript for each of these three points a lot. + +The most interesting mathematical aspects of the work have, unfortunately but predictably been relegated to the supplementary information. The results in Figure 2, for example, are very clearly explained and easy to follow in the SI. I personally enjoyed the SI a lot, and while the discussion e.g. in lines 207- 215 is clear, it may be too terse for some readers to follow. The SI by contrast was very clear. Fig 3 does a nice job, however, to get the message of kinetic pairing across. + +I think it would help readers to understand how translatable to other phenotypes this type of analysis is, or if RPA is particular in this regard of allowing such general mathematical statements to be derived. + +## Small points: + +- much of chemical reaction network theory is obscure to most readers. I would like to see a clear and easy definition of integral control that is accessible to non-expert audiences. Deficiency is maybe another such concept and it would be good to define it on line 146. + +- The authors show that their criteria hold for all instances of RPA. I was wondering how easily in practice these mechanisms could be lost? Is it easy to identify points that disrupt RPA? + +- there is a vast literature on design principles which could be touched upon at least in passing (limit cycles, multistability, switch-like behaviour, Turing patterns), especially if there is scope for applying similar concepts in these contexts. + +<--- Page Split ---> + +## Reviewer #1 + +Overview: Development of adaptation mechanisms is crucial for survival across biological scales. Understanding how such mechanisms are generated through biomolecular interactions is a fundamentally important problem. This issue has underpinnings in control theory and it is known that adaptation requires an embedded integral control, which, if identified, can offer insights into how a reaction network achieves adaptation and how robust this adaptation is. The aim of this paper is to construct an algebraic procedure to identify the hidden integral controller in adaptation- capable networks and connect these controllers to the structure of the networks. + +Recommendation: Even though the paper studies an important problem, I do not find the analysis presented in this paper to be convincing enough to warrant publication in Nature Communications. The manuscript has several shortcomings which I list below: + +## Our response: + +We would like to sincerely thank the reviewer for his/her significant investment of time in considering our work, and would like to acknowledge that the reviewer - on the basis of the content in his/her feedback - is clearly an expert in the RPA field, which we both respect and value. The reviewer has given our work a rather harsh review, but we are very grateful to have the opportunity to defend our work, and to make additional improvements and clarifications after thoughtfully considering the reviewer's feedback. We thank the reviewer in advance for his/her generosity and willingness to re- consider our work in light of these detailed responses and clarifications. We have noted all revisions to the main manuscript, and to our SI, with red text, so that the reviewer can readily identify which parts of our article have been updated since the original submission. + +We do wish to respectfully point out at the outset that the primary aim of this work is not "to construct an algebraic procedure to identify the hidden integral controller in adaptation- capable networks" as the reviewer suggests. Rather, our primary goal is to provide a comprehensive and universal description of all possible RPA- capable chemical reaction networks (CRNs), that could ever exist - recognising (in contrast to Shinar/Feinberg, for example) that all instances of RPA, including ACR, must implement "some" form of integral control. In so doing, we wish to also propose a definitive criterion, or test, that captures the presence of the RPA property in any CRN that possesses it. The nature of this universal characterisation of RPA at the level of intermolecular interactions, as codified in the most general terms by our Theorem 1, does indeed suggest an algorithmic method for testing specific CRNs as to their RPA capacity, and for identifying their hidden integral controllers and setpoints. That this algorithmic method could terminate in polynomial time for any RPA- capable CRN, comparable to Gaussian elimination, is a consequence of the previously unrecognised relationship we identify between increases in CRN deficiency (ie. beyond a deficiency of one) and the associated modifications to + +<--- Page Split ---> + +polynomial invariants in the rowspan of the chemical reaction rates. For this reason we are able to identify, for the first time, the special 'almost linear' structure of the mathematical transformation (coordinate change) required to reveal the CRN's "RPA polynomial" – a central concept in our work - if such exists for the CRN in question. We thereby "solve" the integral control problem for all RPA-capable CRNs, in complete generality, at the microscale level of intermolecular interactions, with their associated mathematical graph structures. In so doing, we demonstrate how RPA may be accommodated by CRNs of arbitrary deficiency (not just "low-deficiency" CRNs, as the reviewer goes on to claim). Our two main outcomes are thus inextricably related: the special CRN structures that hold for all possible RPA-capable networks allow the system's reaction rates to be projected, mathematically, onto two variables via a process that does not differ substantially from Gaussian elimination – thereby revealing a computationally feasible algorithmic test for the presence of RPA. + +Importantly, our new and unexpected findings on the relationship between the deficiency of a CRN and its overarching topological structure allow us to make a new and crucial connection to our previous work on RPA at the network macroscale [1], thereby enabling us to identify, definitively, the one- to- one correspondence between the subsidiary linear control problems and key topological features of the CRN. The fact that we can connect these new results to our previous general (macroscale) topological solution to the RPA problem is, without question, extremely powerful. But it is entirely untrue that we simply impose our previous results on RPA topologies at the network macroscale onto the microscale of intermolecular interactions in a CRN, leading to a result of "incremental novelty" as the reviewer goes on to suggest. In fact, no previously published work to our knowledge has been able to identify the general relationship between deficiency and linear complex invariants in RPA- capable networks. Cappelletti et al. [2], for instance, do note that an "RPA polynomial" (as we call it here) can exist in the rowspan of a CRN for deficiencies greater than one – if the RPA polynomial in question happens to be in the rowspan of the CRN, which is not generally the case – BUT fail to identify how any added deficiency (beyond unity) allows this crucially important "RPA polynomial" to reside in the rowspan. As a consequence, even the very simplest RPA- capable CRNs whose RPA polynomial does not reside in the rowspan (e.g. the toy model discussed by those authors, that we analyse as Example 1 in our SI (Section S3.1)) simply elude the Cappelletti et al. [2] approach. No previous work as been able to characterise, in complete generality, the nonlinear coordinate changes that are needed to reveal the capacity for RPA in CRNs in an entirely universal manner. + +We are truly grateful for the reviewer's fresh set of eyes on our work, and have carefully revised our manuscript (and SI) to ensure that the novelty and scientific importance of our findings have been clearly and accurately communicated. We acknowledge, in particular, that the preamble to our Supplementary Information (i.e. the Supplementary Text prior to Section S1) could have been organised much better, with the aims and novel contributions of our work expressed much more explicitly. We acknowledge that our original submission mentioned the development of a + +<--- Page Split ---> + +definitive 'RPA test' first in this section, before describing the overarching goal of demonstrating the truly universal principles of RPA in CRNs, and the relationship of this universal description of RPA to integral control. This section has now been carefully revised to read as follows: + +The overarching goal of this work is to provide a comprehensive and universal description of all possible Chemical Reaction Network (CRN) structures that can implement the keystone biological function known as Robust Perfect Adaptation (RPA), and in so doing, to propose a definitive algebraic condition that captures presence of the RPA property in any CRN that possesses it. We also recognise here that all forms of RPA, including the special case known as Absolute Concentration Robustness (ACR), must implement some form of integral control. Our universal characterisation of RPA at the level of intermolecular interactions thereby provides an algorithmic method not only for detecting the RPA property, but also for identifying the hidden integral controllers, as well as the 'setpoints' of any RPA- exhibiting molecules. + +As we show in the pages to follow, providing such an all- encompassing description of RPA at the microscale- level of biological networks - that is, in CRNs, which account for the mathematical graph structure of intermolecular interactions - has required us to reconcile a wide range of disparate mathematical viewpoints, ranging from Chemical Reaction Network Theory (CRNT), control theory and the internal model principle, and algebraic geometry. The essential structure of our mathematical development is as follows: + +1. In Section S1 we identify a universal 'kinetic pairing' principle, which captures the essence of RPA in all CRNs that possess the property, and which is codified by our Two-Variable Kinetic Pairing Theorem (Theorem 1, Section S1.4). This theorem guarantees that, for all RPA capable CRNs, the geometric projection of the CRN's steady-state locus onto a state space defined by just two variables is captured by a distinguished algebraic invariant that we call an RPA polynomial. In this context the term 'variable' has a particular meaning, that we define carefully in Section S1.4. + +In this Section we also introduce readers to the fundamentally important notion of algebraically independent subnetworks - a simple yet powerful concept introduced by Martin Feinberg (see Appendix A.6 in [9] for a detailed overview), whose implications for the decomposition of CRNs into independent subnetworks, and ultimately topological modules, that are compatible with RPA are recognised for the first time in the present work. This key concept provides a vital ingredient which contributes to a definitive characterisation of RPA-capable CRNs of arbitrarily high deficiency, far beyond the simple deficiency-one ACR-capable CRNs covered by the Shinar- Feinberg theorem [7]. + +<--- Page Split ---> + +2. In Section S2 we briefly discuss the topological implications of Theorem 1 and, for later reference, make a preliminary connection with previous work on the topological structures that are known to hold, at the network macroscale, for all RPA-capable networks [1]. Importantly, the universal topological solution to the RPA problem [1] was developed considering only a single external input or disturbance, and did not account for the possibility of no external inputs, with alterations in total abundances of the interacting elements (as specified by the initial conditions of the system) constituting the only possible perturbation to the system. More importantly, and in stark contrast to the present work, the universal macroscale solution to the RPA problem [1] gives no concrete information as to the CRN structures (at the network microscale) that could engender RPA or satisfy its strict topological requirements. + +3. Since most RPA-capable CRNs identified in prior studies identify an RPA polynomial (as we call it here) from only linear coordinate changes (see, for example, Cappelletti et al. [2]), in Section S3 we consider the algebraic properties of CRNs that allow the RPA polynomial (as expressed in Theorem 1) to reside in the rowspan of the CRNs chemical reaction rates (i.e. given by an \(\mathbb{R}\) -linear combination of the rate equations). For this purpose, we analyse two carefully chosen CRN examples in detail, and demonstrate the existence of several subsidiary polynomial invariants in the rowspan for each case, and note the relationship of these polynomial invariants to the overarching topology of the system. We demonstrate via deficiency-preserving transformations of the respective CRN structures that these subsidiary polynomial invariants combine to yield the all-important RPA polynomial within the rowspan exactly when the invariants are stoichiometrically dependent. If the invariants are stoichiometrically independent, on the other hand, a concatenating monomial is required to reconcile the invariants, thereby introducing a necessary nonlinearity to the transformation that produces the RPA polynomial. The detailed analysis of these simple examples provides the reader with an accessible overview of the general principles that characterise RPA-capable CRN structures before we develop these principles more rigorously and in complete generality in the remaining Sections. + +4. In Section S4 we demonstrate, through an analysis of deficiency-increasing reactions within independent CRN subsets, that the coordinate change required to extract the all-important RPA polynomial from the CRN rate equations is always almost linear, in the sense that the RPA polynomial can always be decomposed into a collection of 'complex linear invariants'. From a control theory viewpoint, these observations lead to the previously unrecognised conclusion that the 'internal model' for any RPA-capable CRN can always be decomposed into a collection of linear integral controllers, in addition to reconciling the processing of biochemical information at the network microscale (i.e. via the intricate intermolecular interactions that + +<--- Page Split ---> + +comprise a CRN) with the overarching topological features at the network macroscale [1]. + +5. In Section S5, we provide the reader with extensively annotated code in the open-source software Singular (www.singular.uni-kl.de) to test the RPA capacity of a range of illustrative examples. This code can be adapted readily to the analysis of any CRN. If RPA does obtain for a particular CRN under investigation, an important consequence of the special almost-linear structure of the transformation required to identify the RPA polynomial is that the computational demands of this algorithm do not differ substantially from those of Gaussian elimination (a polynomial-time algorithm). + +We clarify the nature of our scientific advance in further detail as we address each of the reviewer's individual points in turn. + +## Lack of sufficient novelty: + +- The general principles for RPA have been developed by (slightly) extending previous results by the authors for deficiency zero and deficiency one CRNs. These low-deficiency networks are related to 'balancer' and 'opposer' modules which are known to form a topological basis for all RPA networks [1]. This connection is explained with two illustrative examples and general principles are formulated by relying on the theory in [1]. Hence, given the earlier results in [1], the incremental novelty in this paper is not significant. + +Our response: We wish to respectfully emphasize, first and foremost, that these completely general principles by which RPA is always realised at the level of intermolecular interactions in a CRN have by no means "been developed by (slightly) extending previous results (of ours) for deficiency zero and deficiency one CRNs". Our framework is certainly not limited to "low- deficiency networks", as the reviewer claims. The general principles, which we succinctly summarise for a general audience via two particularly simple illustrative examples, in order to provide as accessible an overview of the main ideas as possible at the outset, have most assuredly not been "formulated by relying on the theory in [1]". + +Our previous work [1], considers the broad macroscale topological structures that are compatible with an RPA response, and delineates the full solution space to the RPA problem from this viewpoint. This approach considered an abstract network, with a single 'input stimulus', or disturbance, delivered to a distinguished input node. The network was considered to exhibit RPA exactly when a distinguished output node, not necessarily distinct from the input node, could always return to a single, fixed value at steady- state (the 'setpoint'), independently of the magnitude of the input stimulus, and independently of the choice of parameter values. Using a topological method, where the flow of biochemical information could be partitioned into the subsets of a topology that accounted for the algebraic requirements of RPA, an exhaustive description of all possible RPA- compatible network designs, induced + +<--- Page Split ---> + +relative to the chosen input- output node pair, could be identified. This approach definitively established that all RPA- capable networks of this type must be decomposable into two types of well- defined topological structures, or 'modules' – Opposer modules and Balancer modules – and concluded that certain key 'computational nodes', corresponding to well- defined constraints on reaction kinetics, must be embedded into these modules. In particular, Balancer modules require one or more balancer nodes, exhibiting 'balancer kinetics' along with a single connector node, exhibiting 'connector kinetics'; Opposer modules, by contrast, require one or more opposer nodes, exhibiting 'opposer kinetics', organised (topologically) into structures known as 'opposing sets'. + +But these conclusions, by themselves, provide absolutely no information on how these 'reaction constraints' might be realised, in general, by the intricate interactions among collections of molecules. Nor has it been clear until now how any of the known RPA- capable (or ACR- capable) collections of chemical reactions (CRNs) encode any of the topological requirements for RPA that we had identified in [1]. Indeed, in our earlier paper [1], our illustrative examples employed simple 'invented' functional forms (disconnected from CRN structures) which encapsulated the principles of opposer kinetics, or balancer/connector kinetics, in the most straightforward way, since the focus of that earlier work was the overarching network design principles that must hold at the network macroscale. An opposer node \(P_{o}\) , regulated by some node \(R\) , for instance, could be assigned a kinetics of the form \(dP_{o} / dt = k_{1}R - k_{2}\) , which is zero- order in \(P_{o}\) . But this contrived reaction form could certainly not be induced by a CRN for a variety of mathematical reasons, including the fact that (by the so- called 'Hungarian Lemma'), all terms preceded by a negative sign must include the species that is the subject of the reaction equation – in this case, \(P_{o}\) . Indeed it has been entirely unclear, until now, how the necessary conditions for RPA could be realised in general by 'real' chemical reactions involving molecules that interact in specific and potentially intricate ways according to a mathematical graph structure (i.e. a CRN). Previous studies (e.g. Shinar and Feinberg [7], Cappelletti et al. [2], Karp et al. [8], etc.) have only provided partial answers for particular special cases. + +Of course, the antithetic integral control motif is a simple and well- known reaction structure that can serve as an 'opposer node', and can encode opposer kinetics (and thereby implement integral control) in a fairly obvious and straightforward manner via a particularly simple linear transformation. But this mechanism by no means explains the RPA (ACR) property observed in the Shinar- Feinberg deficiency- two model of the EnvZ- OmpR network, for example. In fact, until now, it has not been at all clear how the EnvZ- OmpR motif, or virtually any other known example of an ACR/RPA- capable CRN, might relate to the topological principles we identify in [1]. That the completely general description of RPA- permissive CRN graph structures, as we introduce in the present paper, should be able to map in such a clear, direct and well- defined way with our earlier universal description of RPA at the network macroscale is both remarkable and immensely satisfying. In particular, the revelation that balancer 'nodes', opposer 'nodes' and connector 'nodes' must necessarily be linear transformations of the CRN's molecular concentrations and + +<--- Page Split ---> + +that, combining these invariants nonlinearly in the very specific manner we describe here, gives rise to a completely general description of all possible RPA- capable CRNs, is entirely unexpected. A priori, there was no reason to think that there would necessarily be such a straightforward way to concretely reconcile the CRN microscale with established design principles of the network macroscale [1] on the basis of any previous work. Only in retrospect does this seem inevitable! + +In any case, no previous study has made the well- defined connections we make here between CRN deficiency, network topology (encoding the flow of biochemical information through the graph structure of a CRN) and the internal model principle, in addition to the general results pertaining to the decomposition of the requisite nonlinear map (that extracts a suitable internal model) into a collection of linear maps, governed by the fundamental algebro- geometric requirements of RPA (and hence, ACR). As a consequence, no previous study has been able to provide a definitive description of all possible RPA- capable (and, more specifically, ACR- capable) CRNs, nor a well- defined algebraic condition (and associated algorithmic test) that captures the presence of the RPA property in any CRN that possesses it. Although there have certainly been previous ad- hoc attempts (e.g. in [5]) to demonstrate ACR/RPA capacity in a specific CRN via computation of a suitable Gröbner basis, these ad- hoc attempts, of themselves, are not generalisable (as we explain in greater detail later, in response to the reviewer's more specific queries regarding prior work). Moreover, there was no reason to think that this approach would be computationally feasible in general prior to our demonstration of the universal decomposition of the underlying nonlinear coordinate change into a connected sequence of linear maps. (Again, this is what we mean when we claim that the nonlinear map is 'almost linear'). Of even greater computational concern is that fact that, prior to our proof that the RPA polynomial (as we call it here) is always obtained via geometric projection onto exactly two variables (noting that 'variable' does not necessarily mean 'species'!), prior ad- hoc attempts to compute RPA- relevant Gröbner bases have been forced to use the most computationally expensive monomial ordering (i.e. the lexicographic ordering), since it was not known at the outset which, or how many, variables had to be eliminated. These former potential computational challenges have all been robustly resolved by the present work. + +Of course, most of the RPA- capable CRNs that have been identified at the present time exhibit a special form of RPA known as Absolute Concentration Robustness (ACR). Unlike the abstract networks we consider in [1], there is no external 'input stimulus' for these networks, whose steady- states can only be altered by varying the total abundances of the various interacting molecules, as specified by the initial conditions for the reactions. For example, the Shinar- Feinberg models of the EnvZ- OmpR motif, comprising both deficiency- one and deficiency- two versions, are known to exhibit ACR in the phosphorylated OmpR moiety, yet no previous study of this motif (including the recent analysis of the deficiency- one version by Cappelletti et al. [2]), has succeeding in connecting the ACR capacity of this particular molecule to its topological balancer structure (and certainly not in a way that allows a general connection to be made to the set of all possible RPA/ACR- capable CRNs). As we show in great detail in our newly revised manuscript, a balancer structure arises + +<--- Page Split ---> + +from the fact that, for this CRN, the one unit of deficiency encodes two parallel pathways that regulate the phosphorylation of OmpR, whereas the two units of deficiency (in the deficiency- two version) encodes three such feedforward pathways that regulate the same phosphorylation cycle. Indeed, it is the deep connection we identify between deficiency and the flow of biochemical information (topology), along with the relationship to modularity of the decomposition of RPA- capable CRNs into algebraically- independent subnetworks, that feature among the major conceptual advances of the present work. In our original submission, we had devoted the entirety of sections S4.2.1 and S4.2.2 in our SI to a succinct consideration of these ideas. In our revised submission, we have extensively revised the preliminary sections of our SI, adding in significant additional discussion on the significance of deficiency (a key CRNT concept) in Section S1.2, and have added in an entire new section (Section S1.3), which explains the concept of algebraically independent subnetworks of a CRN in great detail. (This is in contrast to our original submission, in which our far briefer discussion of algebraically independent subnetworks was delayed until Section S4.2.1). In our revised SI, the crucial connections between deficiency and topology are thereby made clear and explicit from the outset. We also briefly analyse the example of the Cappelletti et al. [2] toy model from the point of view of a decomposition into algebraically- independent subnetworks, along with a careful consideration of the partitioning of deficiency and rank into these subnetworks, so that the topological discussion of this (and other) networks in later Sections, as well as the general relationship of CRN topologies to deficiency and independent subnetworks, can be more readily appreciated by the general reader. + +Importantly, ACR- capable CRNs, despite not being driven by exogenous inputs, nor perturbed by exogenous disturbances delivered to specific molecules, are still subject to the topological requirements that unify the broader class of RPA- capable CRNs which generally do involve external inputs – a deeply important result which fundamentally governs how such CRNs respond to perturbations by other (new) classes of disturbances (e.g. enzyme inhibitors and other small molecules), or new exogenous inputs/disturbances distinct from those represented in the original CRN. Since the detailed reaction structures governing complex cellular signalling networks (e.g. signal transduction networks in Metazoa) remain mostly unknown, having access to such a complete and universal description of RPA- capable CRN structures in the abstract is immensely powerful, particularly for considering new possibilities for molecular- targeted therapies, for instance, and for considering evolutionary alterations to CRNs. + +We do acknowledge that our earlier work [1] foreshadowed the principle of a topologically distributed internal model, where one internal model could 'feed into' another topologically related one. Nevertheless, no prior work has been able to reconcile the mathematical properties of dynamical systems induced by CRNs with these previously- identified principles, and our current work highlights that making the fundamental connection between macroscale (e.g. from [1]) and CRN microscale poses significant mathematical challenges. Our new study clearly delineates the full suite of new mathematical ideas required – on the relationship of subsidiary linear + +<--- Page Split ---> + +invariants (polynomials) to the algebraic elimination problem; on the relationship of stoichiometric independence (which is itself a function of the algebraic structure of the vertices of the CRN graph) to the inability of polynomial invariants to 'pass' within the rowspan; and on the requirement for 'concatenating monomials' and the relationship of these to the topological structure of the CRN (for which we identify a previously unrecognised connection with CRN deficiency, as we explain in far greater detail in our revised submission). + +We truly value the reviewer's feedback, which has helped us appreciate where our original submission failed to compellingly communicate the novel aspects of this work. We are deeply grateful for the reviewer's time and effort in re- considering our extensively revised work, and are thankful for his/her support. + +- Many researchers have exploited Gröbner basis and ideal construction for obtaining steady-states in terms of parameters and in particular for studying ACR. For example, see [6, 5, 3] and references therein. It seems that the authors are unaware of these works and in order the assess the novelty of the methods in this paper, these existing works must be cited and discussed. + +Our response: We thank the reviewer for highlighting these references, which use Gröbner bases to elucidate various aspects of CRNs and even consider ACR in one instance [5]. We value the reviewer's suggestion that the novelty of our new work could be made clearer by citing and discussing earlier work employing Gröbner bases and ideal construction in the context of chemical reaction networks. + +We certainly acknowledge that the elucidation of polynomial ideals via Gröbner basis computations is well- known to have wide- ranging applications to problems in science and engineering [10]. We do not claim that the use of Gröbner bases, in and of itself, to elucidate some property of a polynomial system is novel. + +There are actually exceedingly few published papers in the literature currently that employ Gröbner basis methods, or 'ideal construction' to study RPA/ACR specifically, other than the article by Perez Millan et al. [5]. Those authors compute a Gröbner basis in an ad- hoc manner for the deficiency- two EnvZ- OmpR motif, and use this result to demonstrate the capacity for ACR in one of the species. But the chief focus of that paper [5], and of the Craciun et al. paper [3], is not ACR, or RPA, but CRNs that exhibit toric steady- states. As our study makes clear, RPA- capable CRNs do not, in general, give toric ideals, or have toric steady- states. Although the EnvZ- OmpR motif analysed by Perez- Millan et al. [5], along with several of the illustrative examples we consider in our paper are characterised by toric ideals, it is clear that this could not possibly be a general property of RPA- capable CRNs for a number of reasons, including the fact that the pairing function \(g(x, y)\) (see our Theorem 1) can be a multi- term polynomial, and not simply a power product of species (monomial). In addition, even in cases where the RPA polynomial itself is a binomial, this condition does not guarantee that the steady- state ideal has a (standard) generating set composed entirely of binomials. A simple example of an RPA- capable CRN that is + +<--- Page Split ---> + +not generated by binomials, and is therefore not characterised by a toric ideal, is given in Figure 2 (previously Figure 1) of our main paper. (See, in particular, SI S5.2, where we compute a number of relevant Gröbner bases for this particular CRN, thereby demonstrating that the ideal corresponding to its chemical reaction rates cannot be generated by binomials). Thus, while the class of RPA- capable CRNs has a non- empty intersection with the class of toric dynamical systems, the study of toric ideals, unfortunately, cannot capture the fundamental essence of the RPA property in CRNs. + +In our extensively revised SI, we provide a detailed commentary on the computational demands of Gröbner basis- computing algorithms from a complexity standpoint (see Remark 3 following Definition 3 in Section S1.5), and on the simplifying structure afforded by RPA- capable CRNs (owing to the 'almost- linear' coordinate change that we demonstrate can always extract the 'RPA polynomial' from the CRN rate equations). At the conclusion of those explanations, we explain that + +"... the ACR- capacity of the deficiency- two EnvZ- OmpR motif was demonstrated via computation of a Gröbner basis, in an ad- hoc manner, by Perez Millan et al. [5]. But without knowing which, or how many, variables generally characterise the RPA- encoding elimination ideal, and without establishing the special 'almost linear' structure of the mathematical transformation required to identify the RPA polynomial in any RPA- capable CRN, this approach does not generalise, and cannot be applied to the systematic analysis of large and complicated CRNs (e.g. in the context of metabolism [11] for which candidate RPA- capable molecules have not already been posited from experimental evidence)." + +Note that this is not a criticism of the Perez- Millan et al. [5] paper in any way. Again, the focus of the Perez Millan et al paper is not ACR- capable networks, so there is nothing amiss with their ad- hoc approach to the particular CRN they consider, which happens to be characterised by a toric ideal (which is the focus of their paper); they do not claim to present a general method that will necessarily be valid (or computationally feasible) for any ACR- capable CRN. They simply show that the particular CRN they consider does exhibit ACR, and the particular Gröbner basis they compute confirms this. + +The Sadeghimanesh and Feliu paper [6], on the other hand, considers the computational demands of Gröbner basis algorithms for the analysis of CRNs, and proposes a transformation of CRNs containing 'intermediate species' to yield a core network from which these intermediates are absent. This approach allows a more computationally efficient monomial order to be employed in Gröbner basis computations, where only the intermediates are subject to the computationally- expensive lexicographic ordering, and with faster orderings (e.g. grevlex – graded reverse lexicographic) applied to non- intermediate species. Thus, what these authors effectively achieve is the development of a particular 'block ordering' on + +<--- Page Split ---> + +monomials, and which can potentially speed up Gröbner basis computations quite significantly in comparison with a 'complete' lexicographic monomial ordering. This approach can be employed, in principle, for any CRN containing intermediate species (as defined in their paper [6]) – not just RPA- capable CRNs. + +Our paper, by contrast, focusses squarely on RPA- capable CRNs, and aims to discover their general properties. For these CRNs, in contrast to the much broader class of CRNs considered by Sadeghimanesh and Feliu [6], the computational demands confronting any Gröbner basis computations are comparatively very light. There are two reasons for this: (1) If the CRN is indeed RPA- capable, then Theorem 1 guarantees that the RPA polynomial can be obtained via elimination of all but two variables. As a consequence (and as we point out explicitly in Section S5 where we instruct the reader on the implementation of these algorithms in Singular, using a variety of illustrative examples), we can always use a 'block ordering' on monomials, where the two chosen projection variables are ordered 'lower' than the remaining variables. Having established this, the computationally expensive lexicographic ordering is not required: both of the 'blocks' in this special elimination order can now accommodate a fast monomial ordering (e.g. grevlex, sometimes referred to as degrevlex, which uses the syntax 'dp' in Singular). But there is a second, and more important reason: (2) The transformation that reveals the RPA polynomial is 'almost linear' in the sense that only \(\mathbb{R}\) - linear combinations of the rows of the system are required to identified the 'fundamental' (subsidiary) polynomial invariants (which are subsequently combined nonlinearly via concatenating monomials). For this reason, the syzygy polynomials (S- polynomials) that are calculated as part of Buchberger's algorithm are identical to the linear row combinations that are computed during Gaussian elimination. But note that this computational 'streamlining' is linked inextricably to the special CRN structures that implement RPA, and establishing this key property is one of the highly novel contributions of our work. For more general CRNs, computing Gröbner bases may be computationally infeasible (especially if imposing a global lexicographic ordering at the outset, as one is often forced to do without any prior analytical guideposts); from this point of view, the approach offered by Sadeghimanesh and Feliu [6] is both interesting and potentially helpful. + +We also emphasize that the existence of an algorithm that can test for the RPA- capacity in a particular CRN does not, in and of itself, reveal the definitive properties of all possible RPA- capable CRNs. Our paper is not "about" Gröbner bases as such. That we can, indeed, employ Gröbner basis- computing algorithms (e.g. Buchberger's algorithm) to test for RPA capacity, in general, is a consequence of the special properties of RPA- capable CRNs that we identify for the first time in this new paper. + +- More importantly, the central analysis in this paper crucially depends on the result for deficiency one networks which is stated as Theorem 3 in the Supplement. However, this result is not new, as it follows from Theorem D.1 in the Supplement of [2] (see the proof in [2]). + +<--- Page Split ---> + +Our response: We have carefully scrutinized the proof to Theorem D.1 in the Supplement of [2], and acknowledge that the reviewer is entirely correct to note that our Theorem 3 follows directly from Theorem D.1 in [2], and that our essential mathematical argument is virtually identical to that in [2]. We have now updated our preamble to Theorem 3 (Section S4.2) to emphasize to the reader that this alternative version of Shinar- Feinberg's theorem draws on arguments developed by Cappelletti et al. [2], and provide a reference to Theorem D.1 in [2]. In the interests of a more comprehensive and scholarly exposition of the key ideas (for later use in the remaining sections of the SI), we have also taken this opportunity to add in a second version of the theorem (Theorem 4), applicable to deficiency- zero CRNs, which shows that binomials involving any pair of terminal complexes from the same terminal SCC must also reside in the rowspan of the CRN reaction equations. Following these two theorems, we also add a remark, again citing Cappelletti et al. [2] Proposition C.5, that the same mathematical arguments (as employed in Theorems 3 and 4) can readily be extended to demonstrate that binomials involving either a terminal complex and a non- terminal complex, or two terminal complexes from different SCCs, can never reside in the rowspan of a CRN. + +We sincerely thank the reviewer for his/her careful attention to this key technical detail, and for ensuring that all mathematical concepts presented in our work are correctly attributed. We feel that the presentation of the mathematical ideas in this section are now much more comprehensive and scholarly, and the additional references to the Cappelletti et al. [2] paper are immensely valuable. We would like to respectfully emphasize, however, that the novelty of our present paper lies in not so much in our Theorem 3 (or D.1 in [2]) but in demonstrating how this result on deficiency- one (and deficiency- zero) networks may be extended to RPA- capable networks of any deficiency. The remainder of the SI, following Theorems 3 and 4, is devoted to precisely this goal. (The generalisations the arbitrary deficiency are also much more clearly and thoroughly communicated in our revised manuscript, with the help of the comprehensive explanations in the earlier sections of the SI (particularly Sections S1.2 and S1.3) on how deficiency governs the flow of biochemical information within a CRN (and ultimately relates to topology), as well as the decomposition of a CRN into algebraically independent subnetworks). + +- Definition of RPA: The notion of RPA is not mathematically defined. In other words, it is not clear what disturbances are allowed and what are the biochemical parameters on which the output set-point is allowed to depend. On page 11 in the Supplement it is written that for RPA the set-point c should be a rational function of the biochemical rate constants. However, this would be the case for any steady-state and so what constitutes RPA is not clear. + +Our response: The reviewer's point that we should have given a more explicit mathematical definition of RPA is well taken. We truly appreciate such helpful advice. + +<--- Page Split ---> + +We now include the following text at the beginning of Section S1 in our Supplementary Information: + +## Definition of RPA + +In this study we consider Robust Perfect Adaptation (RPA) from the most general possible viewpoint. In particular, a CRN exhibits RPA in the concentration, \(x\) , of some molecule exactly when \(x\) maintains a constant steady- state value, \(c\) (the molecule's 'setpoint'), for all steady- states of the system. The setpoint, \(c\) , is a function of some collection of CRN parameters. Moreover, the CRN exhibits RPA (in \(x\) ) in response to any perturbation or disturbance that does not feature in the functional form of the setpoint, \(c\) . + +With this very broad definition of RPA in mind, we recognise that there are many possible types of perturbations/disturbances that could alter the steady- state of the system: + +1. One or more 'external' inputs. A disturbance of this type could arise in the form of some input molecule, \(I\) , whose concentration is given by a step function generated by an 'exosystem' \((dI / dt = 0\) , not included among the CRN reaction rates). + +2. Alterations in total expression levels (abundances) of the interacting molecules. If this is the only type of perturbation possible, then the CRN is considered a 'conservative network', corresponding to a 'closed' system (see [9], Chapter 4). In this scenario, the CRN captures the interconversion of molecules among a variety of possible forms. The dynamical system is thereby constrained to evolve within a particular stoichiometric compatibility class (an affine space parallel to the CRN's stoichiometric subspace - see Section S1.2) determined by the initial conditions. The orthogonal complement to the stoichiometric subspace determines the conservation relations for the CRN, which specify the constant expression levels of the various interacting molecules. Where a molecule can exhibit a fixed concentration across all steady-states when the CRN is subject to perturbations to these total expression levels, this type of RPA is referred to as Absolute Concentration Robustness (ACR, see Chapter 9 in [9]). + +3. A disturbance that is encoded in a CRN parameter such as a production rate, \(\mu\) , of some molecule, \(M\) , as reflected in a CRN reaction of the form \(\phi \xrightarrow{\mu} M\) . Note that CRN parameters determined by the intrinsic chemical properties of the interacting molecules (e.g. association/dissociation constants, catalytic constants, etc.) are very stable and not readily perturbed, except via mutation of the interacting molecules. + +In the pursuit of greatest generality, we make no assumptions a priori as to which type of network perturbation might affect a CRN, nor do we impose any restrictions on which (or how many) parameters determine the setpoint. Of course, if the setpoint for a putative RPA-capable molecule involves a parameter \(\mu\) that can be perturbed (see case 3. above) then it is clear that the molecule cannot exhibit RPA in response to that particular disturbance. + +<--- Page Split ---> + +We can appreciate that the reviewer might have a different perspective on RPA from us, and hope that he/she is willing to accept our viewpoint and mathematical goals. + +Regarding the reviewer's comment that "the set- point c (being) a rational function of the biochemical rate constants ... would be the case for any steady- state" – we agree completely with the reviewer on this point. All variables of the CRN would certainly achieve some steady- state that is a rational function of parameters; but not all variables would achieve the same rational function of parameters across all possible steady- states of the system. By noting that the setpoint is a rational function of parameters, we do not intend to convey that the steady- states of other variables are not rational functions of parameters. We are simply pointing out the mathematical nature of the setpoint (which can ultimately be computed automatically via the algorithm we propose) for the benefit of the general reader, to whom such properties may not be obvious. We did not intend this to be a major point. + +- Algorithm may not terminate: The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima-facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In particular, no proof is given showing that non-termination implies no RPA. Moreover, non-termination of a method is not something that can be ascertained with any certainty by running the code. Accordingly, the authors cannot claim that they have a full 'characterisation' of the RPA property. + +Our response: We thank the reviewer for this comment and for giving us the opportunity to provide greater clarity on these points in our revised manuscript. + +First, we respectfully point out that Buchberger's algorithm, which computes Gröbner bases, always terminates. This is because all ideals of a polynomial ring (or any Noetherian ring, for that matter) are finitely generated – a result of central importance in algebraic geometry, formalized by the Hilbert Basis Theorem. As a consequence, we are assured that Buchberger's algorithm will terminate in a finite number of steps. The problem, of course, is that the finite number of steps required could, and often will, be unmanageably large! The computational demands of Buchberger's algorithm are well known, and we do acknowledge in our paper (in both our original and revised submissions) that the problem of determining whether a general collection of polynomials constitutes a Gröbner basis (also known as the Gröbner basis detection (GBD) problem) is NP- Hard. The computational demands of Buchberger's algorithm are clear from an examination of the algorithm itself; the demands are even greater when a lexicographic monomial ordering is used since this necessarily implements a computationally expensive polynomial division process in comparison with other monomial orders. The complexity class of the GBD has been well known since the 1990s (due mainly to the work of Bernd Sturmfels and others), and has been widely discussed in the literature. + +<--- Page Split ---> + +We respectfully point out that our study does, in fact, make clear why RPA- capable CRNs have a special property which guarantees that Buchberger's algorithm will terminate in polynomial time if the CRN does indeed exhibit RPA. Indeed, we demonstrate that the mathematical transformation required to obtain the RPA polynomial from the reaction rate equations is almost linear in the sense that only \(\mathbb{R}\) - linear combinations of these equations are required to produce the 'subsidiary' polynomial invariants which are then 'concatenated' by monomials. And as long as only \(\mathbb{R}\) - linear combinations of the polynomials are required, the syzygy polynomials ("S- polynomials") that are computed at each step of Buchberger's algorithm are precisely the linear row combinations computed during Gaussian elimination (a polynomial- time algorithm). Indeed, for the simple CRNs considered by Cappelletti et al. [2], for instance, where the RPA polynomials of the CRNs were in the rowspan (no concatenating monomials required), then Buchberger's algorithm is, in fact, Gaussian elimination. Those authors present an efficient method to calculate which particular linear combination of the reaction rates is required to 'achieve' this RPA polynomial. But it is clear that for any CRN with an RPA polynomial in the rowspan of its reaction equations, the RPA polynomial itself can be obtained algorithmically by Gaussian elimination. In particular, if the equations are expressed in the matrix form \(\mathrm{dX / dt} = \mathrm{Ax}\) , where \(\mathbf{x}\) is the vector of monomials, and the two monomials of the candidate RPA polynomial are listed last (at the bottom of the vector), then performing Gaussian elimination on A will result in an echelon form in which the bottom non- zero row has exactly two entries (corresponding to the two coefficients of the constituent terms of the RPA polynomial). Which linear combinations are required to achieve the rows of this echelon form can be stored during the execution of Gaussian elimination (producing an LU- decomposition, for example). + +This process readily extends to the more general (nonlinear, but 'almost linear') case. The row combinations (corresponding to construction of S- polynomials) that are calculated during the execution of Buchberger's algorithm may be stored, and retrieved subsequently using the 'LIFT' command in Singular. We demonstrate this in the detailed annotations to our code in Section S5. Where only \(\mathbb{R}\) - linear combinations of the CRN equations are required to identify the RPA polynomial (as is for the cases considered by Cappelletti et al. [2]), the coefficients retrieved by LIFT will contain only 'constants' (polynomial functions of the CRN parameters). If the RPA polynomial is not in the rowspan, the row combinations retrieved by LIFT will contain (only) the concatenating monomials required to combine adjacent 'complex linear invariants' (subsidiary polynomials corresponding to topological features of the underlying flow of biochemical information in the CRN), in addition to the constants involving CRN parameters. + +In reflecting on the reviewer's feedback, we have made extensive revisions to our paper to ensure that the technicalities surrounding the computational complexity of Gröbner basis computations for RPA- capable networks are completely clear and explicit. We now make extensive clarifications on these points throughout the SI. In Remark 3 following our proof to Theorem 1, for example, we explain that + +<--- Page Split ---> + +"...With a well- defined algebraic elimination problem now at hand, with two candidate variables selected for the geometric projection, the existence of an RPA polynomial as the sole generator of the relevant elimination ideal can always be tested in principle via the computation of a suitable Gröbner basis [10]. Unfortunately, the problem of computing Gröbner bases (e.g. via Buchberger's algorithm) for general polynomial systems is well known to be NP- Hard [refs], so without any special simplifying structure to the collection of polynomials, we can have no assurance that any Gröbner basis- computing algorithm will terminate on a practical time- frame. However, we will show in the Sections to follow that RPA- capable CRNs do indeed have a special structure that allows the relevant Gröbner basis to be computed rapidly, on a time- scale comparable to Gaussian elimination. This is because the fundamental 'building blocks' of the RPA polynomial (i.e. its subsidiary polynomial invariants), always reside in the rowspan of the CRN reaction equations (see Sections S3 and S4), and the RPA polynomial can always be constructed from these by multiplying each by a 'concatenating monomial' (where necessary, depending on the stoichiometric dependence of the invariants, see Section S3), and adding the resulting polynomials. As a consequence, the most computationally- demanding component of the resulting algorithm for an RPA- capable CRN (cf. general polynomial systems) is the computation of these subsidiary polynomial invariants (also known as 'complex linear invariants' [8]) from the CRN reaction equations. Note, in particular, that where only \(\mathbb{R}\) - linear combinations of the rows of \(Y\mathcal{L}(G)\) are computed, the S- polynomials of Buchberger's algorithm are identical to the row combinations obtained during Gaussian elimination (applied to the matrix \(Y\mathcal{L}(G)\) ). Gaussian elimination is well- known to be a polynomial- time algorithm, which terminates rapidly even for relatively large numbers of variables (or complexes, in the case of CRNs). + +Later, in Section S4, before providing the detailed mathematical development of our approach for computing RPA- relevant polynomials in the rowspan of the rate equations - for low deficiency CRNs ( \(\delta = 0,1\) ) in the first instance, and then for CRNs of arbitrary deficiency ( \(\delta >1\) ) - we explain that: + +"... it is only on account of this special 'almost linear' coordinate change that the feasibility of this approach is guaranteed: as we noted in our remarks following Theorem 1, the general problem of computing Gröbner bases, for general collections of polynomials, is known to be NP- Hard. But the fact that the RPA polynomial can always be computed by combining a collection of polynomials in the rowspan of the system means that the algorithm that extracts the RPA polynomial from the CRN reaction equations does not differ substantially from Gaussian elimination. Moreover, even for an arbitrary choice of two projection variables, our statement of Theorem 1 offers opportunities for additional computational efficiency when computing a suitable Gröbner basis insofar as only one particular elimination ideal is required (i.e. that comprising the two chosen variables). Without prior knowledge of this particular property of the RPA polynomial, a full set of all elimination ideals for the system would be required, which necessitates an expensive lexicographic monomial ordering in the execution of the algorithm. With only one elimination ideal required, a more efficient block ordering may be chosen, with a comparatively + +<--- Page Split ---> + +fast (e.g. degree reverse lexicographic) ordering imposed on all but the two chosen variables." + +In addition, we provide much more extensive explanations throughout our SI of the mathematical technicalities underpinning this 'almost- linear' coordinate change that can always extract the RPA polynomial from the chemical reaction rates of an RPACapable CRN. The reviewer is quite right to be astounded by this special property of CRN- capable networks. It is truly remarkable (and entirely non- obvious) that the requisite mathematical structure of chemical reactions that are compatible with RPA should be characterised by such a simplicity as to obviate the computational 'black holes' that can exist for general polynomial systems, including CRN models that do not exhibit RPA. + +- Form of the RPA polynomial: The whole approach hinges on the RPA polynomial having the form + +\[\rho = g(x,y)(x - c)\] + +where \(g(x,y)\neq 0\) and \(y\) is a non- RPA capable variable which forms the kinetic pair to \(x\) . It is unclear why \(g(x,y)\) can only be a function of one additional variable, apart from the output variable. The proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f}\cap \mathbb{R}[\bar{x} ]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f}\cap I_{p}\) + +As an example consider the following network: + +\[\mathrm{X}_2 + \mathrm{X}_3\xrightarrow{c_1}\mathrm{X}_1 + \mathrm{X}_4\quad \mathrm{and}\quad \mathrm{X}_1 + \mathrm{X}_2 + \mathrm{X}_3\xrightarrow{c_2}\mathrm{X}_5.\] + +Furthermore assume that species \(X_{2}\ldots X_{5}\) participate in several reactions that do not involve \(X_{1}\) but can be catalysed by it. In this scenario the RPA polynomial would be \(\rho = x_{2}x_{3}\left(\frac{c_{1}}{c_{2}} - x_{1}\right)\) . Hence the function \(g\) depends on two non- RPA variables \(x_{2}\) and \(x_{3}\) . Please explain how this example is consistent with the form of \(g(x,y)\) stated above. + +Our response: Let us first respond to the reviewer's question regarding the proposed network, and its relationship to the two- variable requirement, before returning to the reviewer's concerns about our proof to Theorem 1. + +The reviewer proposes two chemical reactions, and adds that we should also 'assume that species \(X_{2}\ldots X_{5}\) participate in several reactions that do not involve \(X_{1}\) but can be catalysed by it'. Indeed, in the specific reactions proposed by the reviewer, \(X_{2}\) and \(X_{3}\) are only consumed, not produced, whereas \(X_{4}\) and \(X_{5}\) are only produced, not consumed; thus, there must be some additional reactions involving these four variables, so that \(X_{2}\) and \(X_{3}\) can be produced and \(X_{4}\) and \(X_{5}\) consumed, giving the CRN the potential to achieve a steady- state in the positive orthant. + +<--- Page Split ---> + +Let us consider several possible ways to 'close' the reaction set (i.e. add in reactions that produce \(X_{2}\) and \(X_{3}\) and consume \(X_{4}\) and \(X_{5}\) ). First, let us consider two additional closure reactions of the simplest possible form: + +\[X_{4}\stackrel {c_{3}}{\rightarrow}X_{2}\quad \mathrm{and}\quad X_{5}\stackrel {c_{4}}{\rightarrow}X_{3}.\] + +We emphasize that these are not suggested to be the 'best', or most biologically meaningful, or realistic, closure reactions, only that they constitute a simple solution that allows us to proceed in the first instance. Let \(x_{1}, x_{2}, x_{3}, x_{4}, x_{5}\) be the concentrations of the five species. In this case, the mass- action equations for this collection of four reactions contain a boundary variable, \(x_{2}x_{3}\) - a concept which we clearly and prominently define ("Definition 1") at the beginning of Section S1.5 in our SI, in the context of defining what we mean by a variable, before proceeding to invoke this terminology in our statement and proof of Theorem 1 (the two- variable kinetic pairing theorem). Indeed, the rate equations that are induced by this collection of four reactions are: + +\[f_{1} = c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3},\] \[f_{2} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}\bar{x}_{3} + c_{3}x_{4},\] \[f_{3} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}\bar{x}_{3} + c_{4}x_{5},\] \[f_{4} = c_{1}x_{2}x_{3} - c_{3}x_{4},\] \[f_{5} = c_{2}x_{1}x_{2}x_{3} - c_{4}x_{5}.\] + +In any case, it is clear from these equations (and, indeed, clear from the corresponding reactions themselves) that \(x_{2}x_{3}\) is a boundary variable for this CRN, since both \(x_{2}\) and \(x_{3}\) only appear in the monomials of these rate equations in the form of the factor \(x_{2}x_{3}\) . (In other words, neither species occurs either alone or contributes to a monomial that also contains some other species (e.g. \(x_{2}x_{4}\) or \(x_{5}x_{3}\) , say). This CRN thus comprises five species but four variables: \(\{x_{1}, x_{2}x_{3}, x_{4}, x_{5}\}\) . But in this particular CRN, the boundary variable technicality happens to be a moot point since this CRN is not capable of RPA (or ACR). This is because \(< f_{1}, f_{2}, f_{3}, f_{4}, f_{5} > \cap \mathbb{R}[x_{1}, x_{2}x_{3}] = < x_{2}x_{3} >\) . In other words, the generator of the ideal consisting of all polynomial consequences of \(f_{1}, f_{2}, f_{3}, f_{4}\) and \(f_{5}\) containing only the variables \(x_{1}\) and \(x_{2}x_{3}\) is not an RPA polynomial. Thus, for all steady- states of the system, regardless of parameter choices or initial conditions, \(x_{2}x_{3} = 0\) , and RPA is thereby not imposed on \(x_{1}\) , despite the fact that one of the reaction rates (\(f_{1}\) in this instance) is an RPA polynomial. In fact, our Theorem 1 makes this important subtlety crystal clear: as counterintuitive as it may seem, it is not enough for an RPA polynomial to be one of the reaction rates, or be otherwise contained in the ideal generated by a CRN's reaction equations. Rather, an RPA polynomial must generate the ideal \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) and this ideal must be principal (i.e. the RPA polynomial must be the sole generator of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) ) in order for the CRN to exhibit RPA. Just to emphasize, \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) constitutes the projection of the ideal \(< f_{1}, \ldots , f_{n} >\) onto two variables (again, being mindful of how we define a variable) - the putative RPA variable along with one non- RPA variable. + +<--- Page Split ---> + +Although we carefully define and explain the key concept of a boundary variable (see Definition 1 and ensuing discussion in Section S1.5), and elaborate on the concept again in Example 2 in Section S3.2, where we carefully explain that the CRN in question has nine species but eight variables due to the presence of a boundary variable (see discussion after Equation (34)), we recognise that these points must not have been sufficiently clear to the reviewer in our original submission. In our extensively revised SI, we have now provided the reader with a brief overview of the reviewer's CRN example in order to further highlight and explain the concept of a boundary variable in Section S1.5. We have also supplemented our explanations with the alternative terminology "power product" (another word for monomial) just to be absolutely sure that the concept will be absolutely clear to the general reader. We thank the reviewer for providing such a simple and clear example of a CRN that contains a boundary variable to enhance our explanations of this key concept. + +Please allow us the opportunity to expand even further on the subtleties that RPA imposes on the detailed underlying structures of CRNs via some additional examples, since the reviewer has been kind enough to offer such a fruitful and illuminating CRN example. In particular, let us now consider two other possible alternatives for closing the reaction set provided by the reviewer. The reviewer specifically suggests a scenario where the added reactions involving \(X_{2} \ldots X_{5}\) "do not involve \(X_{1}\) but can be catalysed by it". In line with this suggestion, let us suppose that either one, or possibly both, of the two additional reactions include \(X_{1}\) as both a reactant and a product, thereby endowing it with the properties of a catalysing enzyme that is neither produced nor consumed by the reaction. (We assume this is what the reviewer means by not involving \(X_{1}\) "but can be catalysed by it"? The wording is not 100% clear as to what the reviewer actually had in mind here. We apologise if we have misunderstood the reviewer's intentions.) + +Suppose, then, that the reaction associated with rate constant \(c_{3}\) is now replaced by + +\[X_{1} + X_{4}\xrightarrow{c_{3}}X_{1} + X_{2}.\] + +This altered \(c_{3}\) reaction leaves \(f_{1}, f_{3}\) and \(f_{5}\) unaffected, but \(f_{2}\) and \(f_{4}\) now become: + +\[\begin{array}{rl} & f_{2} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3} + c_{3}x_{1}x_{4},\qquad \mathrm{(Eq.6)}\\ & f_{4} = c_{1}x_{2}x_{3} - c_{3}x_{1}x_{4}, \end{array} \quad (Eq.7)\] + +We observe that \(x_{2}x_{3}\) is still a boundary variable for this altered CRN. When we project the ideal generated by \(f_{1}, f_{2}, f_{3}, f_{4}, f_{5}\) (using the updated versions of \(f_{2}\) and \(f_{4}\) ) onto \(x_{1}\) and \(x_{2}x_{3}\) , we still obtain \(< x_{2}x_{3} >\) . Thus, the CRN is again thwarted in any attempt to impose RPA on \(x_{1}\) , since \(x_{2}x_{3} = 0\) at all steady- states for this CRN (regardless of parameters or initial conditions). + +Finally, let us consider the possibility that one of the species that appears in the boundary variable (say \(X_{2}\) , for argument's sake) catalyses one of the additional closure reactions, rather than \(X_{1}\) . In this case, the reaction associated with rate constant \(c_{3}\) is replaced by + +\[X_{2} + X_{4}\xrightarrow{c_{3}}2X_{2},\] + +<--- Page Split ---> + +and \(f_{2}\) and \(f_{4}\) now become: + +\[\begin{array}{r l} & {f_{2} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3} + c_{3}x_{2}x_{4},}\\ & {f_{4} = c_{1}x_{2}x_{3} - c_{3}x_{2}x_{4}.} \end{array} \quad (Eq.8)\] + +In this case, \(x_{2}x_{3}\) is no longer a boundary variable since \(x_{2}\) now also features in the monomial \(x_{2}x_{4}\) . Thus, this CRN comprises five variables (all species): + +\(\{x_{1},x_{2},x_{3},x_{4},x_{5}\}\) . So, to test for RPA, we now attempt to project onto \(x1\) and \(x2\) . In this case, \(< f_{1},f_{2},f_{3},f_{4},f_{5} > \cap \mathbb{R}[x_{1},x_{2}]\) contains only zero (the additive identity for the ring). As expected, the ideal \(< f_{1},f_{2},f_{3},f_{4},f_{5} > \cap \mathbb{R}[x_{1},x_{3}]\) also contains only zero. Thus, the CRN remains incapable of RPA. If, instead, we attempt to compute \(< f_{1},f_{2},f_{3},f_{4},f_{5} > \cap \mathbb{R}[x_{1},x_{2},x_{3}]\) , projecting onto the three variables that appear in the apparent RPA polynomial in the \(f_{1}\) reaction rate, we find that this elimination ideal is given by \(< x_{2}x_{3}>\) . This confirms that for this CRN, either \(x_{2}\) or \(x_{3}\) (or both) is zero for all possible steady- states of the system. Therefore, this CRN fails to exhibit RPA (at \(x_{1}\) or otherwise). + +We warmly invite the reviewer to verify for himself/herself that the three versions of this particular CRN cannot, under any parametric circumstances, exhibit RPA. To assist, we have simulated the second version of the CRN discussed above for 10,000 randomised parameter sets, \(c_{i} \in (1,100)\) , and initial conditions, \(x_{i}(0) \in (1,100)\) , see Figure below. From these histograms, the significance of having one rate equation \((f_{1})\) in the form of an RPA polynomial is clear: If, for a specific random choice of parameters and initial conditions, \(x_{1}\) reaches the value \(c_{1} / c_{2}\) before \(x_{2}\) or \(x_{3}\) reaches zero, then the \(x_{1}\) - coordinate stops evolving and \(x_{1}\) does attain the 'apparent' setpoint at steady- state. But if either \(x_{2}\) or \(x_{3}\) reaches zero first (before \(x_{1}\) reaches \(c_{1} / c_{2}\) ), then \(x_{1}\) remains at whatever value it reached at the moment \(x_{2}\) or \(x_{3}\) reaches zero. Thus, the steady- state value of \(x_{1}\) is a matter of chance, dependent upon the vagaries of parameters in comparison with initial conditions. There is a bias in the steady- state value for \(x_{1}\) , with mode of the distribution at \(c_{1} / c_{2}\) , but \(x_{1}\) can achieve any value in principle at steady- state. Thus, the CRN does not exhibit RPA. + +<--- Page Split ---> +![](images/Figure_1.jpg) + +
Figure: Steady-state concentrations for \(x_{1}\) , and for \(x_{2}x_{3}\) , obtained from 10,000 simulations of the second of the three CRNs discussed above. Simulations for the other two CRNs are qualitatively very similar. For each simulation, rate constants \((c_{1}, \ldots , c_{5})\) and initial conditions \((x_{1}(0), \ldots , x_{5}(0))\) are randomly selected from the interval (1,100). We gratefully acknowledge the assistance of my (RA's) graduate student, Cailan Jeynes-Smith, in the preparation of this Figure.
+ +The fact remains that our Theorem 1 provides a definitive and universal condition that must be satisfied by any RPA- capable CRN - no exceptions, not even for CRNs that happen to have an RPA polynomial in the rowspan!! (Interesting, the authors of the Cappelletti et al. paper [2] appear to have overlooked this subtlety). We hope that the reviewer can now begin to appreciate that these remarkable and highly- restrictive conditions on the detailed graph structures of RPA- capable CRNs could never possibly have been gleaned just from our prior work in [1], or by any other prior work (including the work of Cappelletti et al [2]). All three examples we analyse above are incapable of RPA since they violate the conditions specified in our Theorem. Specifically, in each case, the intersection of the ideal generated by the reaction equations with a suitable polynomial ring in two variables (ie. one that comprises one RPA variable and one non- RPA variable, once again being mindful of what we mean by a variable), is not generated by a single polynomial that takes the form of an RPA polynomial. The fact that each CRN induces a reaction rate \((f_{1})\) that happens to be in the form of an RPA polynomial is (surprisingly, perhaps) irrelevant. + +We warmly encourage the reviewer to consider other chemical reactions to add to the pair he/she has proposed. Unlike the Cappelletti et al. [2] study (for example), our study goes far beyond simply 'testing' for the RPA capacity of particular CRN examples (and identifying integral variable(s) if the test is successful). Indeed, our article clarifies in detail (and even more explicitly and incisively now due to our extensive revisions, thanks to the reviewer's helpful feedback and suggestions) how + +<--- Page Split ---> + +the deficiency of an RPA- capable CRN relates to topological features of the CRN, and concretely delineates the role of this key algebraic invariant in controlling the formation of RPA- relevant 'complex linear invariants' in the CRN's rowspan. For this reason, we can go much further than simply proving that the three specific examples discussed above (encompassing the reviewer's suggested reactions) cannot exhibit RPA: The two reactions proposed by the reviewer cannot impose RPA on \(X_{1}\) no matter which reactions are added to the original two. This is because the two given reactions are linearly independent, and the CRN formed from these reactions has deficiency zero. Moreover, the two complexes that contribute to the apparent RPA- polynomial in the reaction rate \(f_{1}\) are not members of the same terminal SCC. It is clear from our discussion of the decomposition of CRNs into algebraically independent subnetworks – a decomposition which is closely tied to the partition of deficiency among independent subsets of reactions (see SI Section S1.3) - as well as our extensive discussions of rowspan polynomials (complex linear invariants) throughout the remainder of our supplement, that no possible addition of extra reactions can turn the original two into an RPA- conferring set. We briefly note in Section S4.4.1 (see also footnote in that section) the special case where a deficiency- zero collection of reactions can engender RPA – namely when the two relevant complexes reside in the same terminal SSC, and correspond topologically to a 'trivial' (isolated) connector node. The pair of reactions suggested by the reviewer are clearly not of this type. No previously published work – not Shinar and Feinberg [7], not Cappelletti et al. [2], nor any other published work on RPA/ACR – is sufficiently general and all- encompassing as to rigorously and definitively delineate the strict requirements for RPA in any CRN – regardless of size or deficiency. We emphasize again, in the most strenuous possible terms, that precisely none of these insights follows straightforwardly from our previous study in [1], which gives absolutely no insight whatsoever into viable chemical reaction structures that could impose RPA on any molecule consumed or produced by those chemical reactions. + +Having thoroughly addressed the reviewer's query regarding "how this example is consistent with the form of \(g(x,y)\) stated above" we now return to the reviewer's queries about our proof to Theorem 1. The reviewer states that "the proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f} \cap \mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) ." Just to clarify, what our proof to Theorem 1 actually says is that, given two variables \(x_{j}\) and \(x_{m}\) that do not exhibit RPA, in addition to a variable \(x_{i}\) that does exhibit RPA, then \(I_{f} \cap \mathbb{R}[x] = I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not contained in \(I_{f} \cap I_{p}\) (the ideal consisting of all polynomial consequences of the rate equations for the CRN that also vanish at \(x_{i} = c\) , the setpoint for \(x_{i}\) ). The reviewer is not specific as to why he/she feels that this technicality unclear, but we note first and foremost that should \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) contain a polynomial in \(x_{j}\) and \(x_{m}\) only (not also including \(x_{i}\) ), then this polynomial is ipso facto not in \(I_{p}\) (since all polynomials in \(I_{p}\) contain \(x_{i}\) by supposition). We also emphasize that the ideal \(I_{f}\) consists of all polynomials in the ring \(\mathbb{R}[x_{1}, \ldots , x_{n}]\) that vanish on the variety \(V(f_{1}, \ldots , f_{n})\) . In any case, our theorem is fundamentally concerned with which + +<--- Page Split ---> + +projections (i.e. choices for \(\bar{x}\) ) are guaranteed to be entirely contained within the ideal \(I_{f} \cap I_{p}\) . + +Our proof to Theorem 1 succinctly points out that if we project the polynomial consequences of the system \((I_{f})\) onto three variables, two of which \((x_{j}, x_{m})\) do not exhibit RPA, then there will be a generator for the associated elimination ideal involving only \(x_{j}\) and \(x_{m}\) (and not \(x_{i}\) – the RPA- capable variable). The reason for the existence of such a generator is that a system whose steady- states can be regulated by any number of independent disturbances (or input stimuli) must be able to adapt to each disturbance individually, corresponding to a single degree of freedom. Once the value of any one non- RPA variable \((x_{j}, \text{say})\) is specified (as a result of setting the magnitudes of the various possible disturbances), then the value of any other non- RPA variable (e.g. \(x_{m}\) ) is thereby also specified. The value of \(x_{i}\) , by contrast, is not determined through an alteration to any single degree of freedom (corresponding to one of the independent disturbances) since it exhibits RPA, and is independent of these disturbances. Thus, it follows that some polynomial involving the two non- RPA- variables \(x_{j}\) and \(x_{m}\) is a generator of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) . + +Now if, for the sake of argument, there were a single generator of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) containing all three variables, this would mean that the value of \(x_{m}\) could only be determined once the values of both \(x_{i}\) and \(x_{j}\) were specified. On the other hand, if the generator(s) of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) were to contain a polynomial in just \(x_{j}\) , then this would imply that the univariate polynomial either has no positive real roots, or possibly no real roots at all (both of which scenarios corresponding to the non- existence of a steady state for \(x_{j}\) ), or has at least one positive real root whose value is a rational function of the system rate constants (a scenario that corresponds to RPA in \(x_{j}\) ). All of these conditions violate the assumption that \(x_{j}\) is a non- RPA variable – a contradiction. + +Of course, Theorem 1 could not possibly be true in general if variables are simply taken to be species. We point out in the preamble to Theorem 1 that in most cases, the variables of a CRN are the species, however should a boundary variable exist, then this must be accounted for in the identification of variables for the CRN (since the component species of the boundary variable cannot be considered variables in that case). + +We hope these clarifications have been able to assure the reviewer of the correctness of this Theorem and its proof. We have now added a condensed version of our explanations above as a 'Remark' following the proof to Theorem 1 (and following Definitions 2 and 3). We also decided to remove the reference to ACR in the statement of the theorem (and hence in the proof), and instead added a comment on this point to the list of Remarks following the Theorem. (The reviewer's helpful suggestion to give a clear and explicit definition for RPA at the outset now makes it unnecessary to add in descriptions of ACR, and its relationship to the more general case of RPA, to our statement and proof of Theorem 1. We cannot thank the reviewer enough for such supportive advice). We do, of course, recognise that not + +<--- Page Split ---> + +all mathematical details of Theorem 1 could possibly be obvious, or clear, to the entire readership of a multidisciplinary journal. It is for this reason that we provide many illustrative examples throughout our SI to demonstrate how the fundamental mathematical principles encapsulated by Theorem 1 are reflected in a range of simple RPA- capable CRNs. + +Now to the reviewer's next concern: + +Moreover, it is not immediately clear how existence of multiple opposer/balancer modules translates into existence of existence of corresponding RPA polynomials. This has not been explained in sufficient detail. + +## Our response: + +We thank the reviewer for this very helpful advice that we make a clearer connection between the existence of multiple topological modules and the corresponding existence of associated RPA polynomials. + +Due to our extensive revisions, our manuscript (and especially our SI) now makes this connection very explicit, and explains the underlying technicalities in considerable detail. In particular, our extensive explanations on the decomposition of RPA- capable CRNs into algebraically- independent subnetworks underscores the fact that such independent subnetworks can be analysed separately as to their RPA- capacity (or otherwise), and that the RPA- capacity of 'multi- modular' networks corresponds to the existence of multiple independent RPA- capable subnetworks within such a decomposition. We state explicitly in Section S4.2, for example, as we begin to introduce the mathematical process by which higher deficiency ( \(\delta > 1\) ) CRNs can be accommodated within our framework, that + +"... for CRNs for which multiple independent subnetworks contribute independently to RPA, these independent subnetworks correspond to distinct modules from a topological perspective (see [1])." + +We also emphasize again in Section S4.5, where the general principles are summarised, that + +"... it is clear from the analysis in the preceding sections that a CRN can be decomposed into lower deficiency independent subnetworks corresponding to the individual modules of a multi- modular network and, in the case of Opposer modules, the controller portion of the module, which can be analysed separately." + +Our study thus makes it clear that each topological module, which directly corresponds to an algebraically independent subset of the CRN reactions, engenders its own RPA polynomial, specific to that module/subnetwork. Nevertheless, Theorem 1 guarantees that for a multi- modular CRN, choosing one RPA- capable variable (associated with any RPA- conferring module) and one non- RPA- capable variable (from any module, including one that is distinct from the one containing the RPA- capable variable), and projecting the entire system onto those two variables, + +<--- Page Split ---> + +will yield an RPA polynomial containing those two variables. Thus, Theorem 1 is valid for any choice of two variables with the property that one is RPA- capable and one is non- RPA- capable. + +We do acknowledge that in our discussion of the topological consequences of Theorem 1 in Section S3 (see for example Figure S4, and Figure 4 in the main paper), we are referring primarily to RPA in a CRN corresponding to a single module. This is mostly from the point of view of (i) highlighting the existence of an overarching mechanism by which a non- RPA capable variable ultimately imposes RPA on a variable, not necessarily directly; and (ii) distinguishing the (topological) significance of an RPA- capable variable being a regulating, or a regulated, variable. + +- Connection to existing works: In [4] the authors consider RPA systems that are maximally robust and find simple linear-algebraic structural conditions that characterise this property in both deterministic and stochastic settings. How do the results in this paper connect to the results in [4]? + +## Our response: + +We are grateful to the reviewer for introducing us to such an interesting and impressive recent article [4], of which we were hitherto unaware. + +An obvious point of difference between this article [4] and ours is that these authors also consider RPA in the stochastic setting, while our study is focused squarely on the deterministic setting in the interests of delineating the full space of RPA- capable CRNs in the greatest possible generality. Beyond this, the article by Gupta and Khammash focus on a particular type of RPA they refer to as maximal RPA, or "maxRPA", where 'the setpoint for the key output variable depends on the least number of network parameters, and is insensitive to all the others' – arguing that 'it makes strong evolutionary sense for intracellular RPA networks to attain (such a) maximal robustness'. In this connection, the authors claim to 'work with a stronger notion of robustness' and that their 'characterising conditions for RPA networks are more restrictive than the topological requirements expounded in (our previous work [1], for example)'. The study is able to identify, concretely, a number of mathematical conditions required for the existence of the maxRPA property, which includes (among other requirements) that the setpoint should be a function of (only) two biochemical parameters. In any case, the authors succeed in their goal to 'mathematically characterise and study the structure of biomolecular networks that constitute such maximal RPA (or maxRPA) systems' – a most impressive achievement – and propose a novel internal model principle (IMP) pertaining to these maxRPA networks. + +This focus on maxRPA networks alone constitutes the major distinction between [4] and our study, since our goal is to characterise all possible RPA- capable CRNs – as opposed to specific classes of RPA- capable CRNs (e.g. the maxRPA class [4], the deficiency- one Shinar- Feinberg class [7], the class containing a 'linear constrained integrator' [2], etc). As we noted earlier, this generality is important in the context of understanding, at an abstract level, the ability of RPA- capable networks to cope + +<--- Page Split ---> + +with new disturbances (i.e. those that were not present in the original CRN – e.g. the addition of small- molecule enzyme- inhibitors). This is particularly crucial for signalling networks for which the detailed structures of the underlying CRNs are unknown (in the context of signal transduction in metazoan cells, for instance). Moreover, we respectfully question the authors' point of view on the suggested evolutionary advantages of a setpoint involving only two network parameters. We contend that it is not the number of parameters defining the setpoint, but the nature of the parameters that is most significant to the functional robustness of the system, and ultimately, the survival of the cell/organism. A CRN could have a setpoint determined by a hundred parameters, but if all these parameters are 'stable' in the sense that they are determined entirely by the chemical properties of the interacting molecules (e.g. association/dissociation constants, or catalytic constants), alterable only by mutation or by factors such as temperature that vary very slowly on the timescale of adaptation, then this may still constitute an entirely useful form of RPA from a biological standpoint. By contrast, a CRN could have a setpoint determined by only two parameters (the minimum, as in the antithetic integral control motif), but if these are highly labile parameters relating to, for example, the rate of synthesis of a particular molecule, or the total expression level of a particular molecule, then this could potentially be problematic. + +Consider, for instance, the deficiency- two Shinar- Feinberg model of the EnvZ- OmpR motif. The setpoint for \(pOmpR\) due to this CRN involves eleven parameters (calculated from two independent setpoints arising from the balancer and connector contributions). But all of these parameters are either association/dissociation constants for pairs of molecules, or catalytic constants, and are thus highly stable in magnitude. By contrast, for the antithetic control mechanism, the setpoint for the sensor molecule involves just two parameters. But both of these parameters capture the rate of synthesis of an antithetic molecule which could, in principle, vary quite significantly on the timescale of adaptation (depending on the regulatory mechanisms governing the transcription and translation of the molecules in question). + +Moreover, perturbations to the setpoint that are either stable (e.g. due to a mutation in an RPA- relevant signalling protein) or vary on a timescale that is significantly longer than the timescale of adaptation, may not alter the functionality of the biological system whatsoever. One of the most widely- discussed examples of unaltered biological function in the face of a stably varying setpoint is the robustness of tumbling frequency, and precision of adaptation, in E.coli chemotaxis (see Alon et al. [12]). In that study [12], genomic alterations that affected the expression levels of various chemotaxis proteins were introduced, which stably altered the setpoint for the steady- state tumbling frequency as well as the adaptation time. But exact adaptation was still observed (albeit with an altered setpoint), and the chemotaxis response of the cells was unaffected. In this context we recognise that, for single- celled organisms, significant temperature variations could certainly alter biochemical parameters; but provided as temperatures vary slowly in comparison with adaptation (RPA), this might not affect the functionality of the organism at all. + +<--- Page Split ---> + +Moreover, aside from what type of setpoints are most evolutionarily advantageous, we respectfully point out that the RPA responses frequently observed in highly complex signalling networks, such as cancer signalling networks in human cells (on the basis of time- course data – see [13], for instance) are not necessarily attributable to maxRPA networks; there is simply no evidence to support this. In fact, it is currently entirely unclear what CRN architectures are generally responsible for RPA in complex signal transduction networks (in either normal or diseased states). + +We hope the reviewer will not object to a friendly and respectful debate on these points, in the interests of moving scientific frontiers forward. We contend that, to make sense of the highly complex signalling networks that arise in nature, it is absolutely essential to have access to completely general description of the mechanisms by which RPA could be implemented in CRNs. This is the brass- ring objective that we achieve in the present work. + +In raising all these points, we are by no means dismissing the study by Gupta and Khammash [4], which is incredibly interesting, and extremely impressive (mathematically and otherwise); we only point out that it is not completely general vis- à- vis RPA- promoting CRN structures (and makes no claims to be, since its focus is on the particular class of RPA- capable CRNs known as 'maxRPA'). It is a beautiful paper, and we are proud to include it in our reference list in the main manuscript. + +Concluding Comments to Reviewer #1: We sincerely thank the reviewer again for such a generous investment of time and painstaking effort, and for his/her many supportive and helpful suggestions for making our scientific goals, and our findings, much clearer and more explicit. We are truly grateful to have this opportunity to defend our work, and to provide an extensively revised version of our manuscript that offers a much more comprehensive exposition of all the relevant supporting technicalities, and a much more compelling presentation for a general scientific audience. + +References (for response to Reviewer 1) [1] R. P. Araujo and L. A. Liotta. The topological requirements for robust perfect adaptation in networks of any size. Nature communications, 9(1):1- 12, 2018. [2] D. Cappelletti, A. Gupta, and M. Khammash. A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances. Journal of the Royal Society Interface, 17(171):20200437, 2020. [3] G. Craciun, A. Dickenstein, A. Shiu, and B. Sturmfels. Toric dynamical systems. Journal of Symbolic Computation, 44(11):1551- 1565, 2009. [4] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. bioRxiv, 2022. [5] M. Perez Millan, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027- 1065, 2012. [6] A. Sadeghimanesh and E. Feliu. Gröbner bases of reaction networks with intermediate species. Advances in Applied Mathematics, 107:74- 101, 2019. + +<--- Page Split ---> + +[7] G. Shinar and M. Feinberg, M. Structural sources of robustness in biochemical reaction networks. Science, 327(5971): 1389- 1391, 2010. [8] R. L. Karp, et al. Complex- linear invariants of biochemical networks. Journal of theoretical biology. 311: 130- 138, 2012. [9] M. Feinberg. Foundations of chemical reaction network theory. Springer, 2019. [10] D. Cox, J. Little, and D. OShea. Ideals, varieties, and algorithms: an introduction to computational algebraic geometry and commutative algebra. Springer, 2013. [11] J.M. Eloundou- Mbehi, et al. A network property necessary for concentration robustness. Nature communications, 7(1): 1- 7, 2016. [12] U. Alon, et al. Robustness in bacterial chemotaxis. Nature, 397(6715): 168- 171, 1999. [13] A.J. VanMeter, et al. Laser capture microdissection and protein microarray analysis of human non- small cell lung cancer: differential epidermal growth factor receptor (EGPR) phosphorylation events associated with mutated EGFR compared with wild type. Molecular & Cellular Proteomics, 7(10): 1902- 1924, 2008. + +<--- Page Split ---> + +## Response to Reviewer #2 + +Araujo and Liotta develop a set of precise criteria that a system needs to fulfil in order to perfect adaptation. This is remarkable and an extremely valuable contribution to the literature in three ways: (i) the search for "design principles" is taking centre stage in synthetic (but also e.g. developmental systems) biology; the first author has proven a leader in distilling precise mathematical criteria for robust perfect adaptation, and I hope that this study will inspire more work in this area, especially in considering the mathematical properties of chemical reaction networks to guarantee different types of behaviour; (ii) in Mathematical biology there are few instances where the mathematical statements can be so precise that biology will have to "obey" these statements. This is one such instance. Finally (iii) the maintenance and control of robust adaptation is of considerable and far reaching biological relevance. I like this manuscript for each of these three points a lot. + +The most interesting mathematical aspects of the work have, unfortunately but predictably been relegated to the supplementary information. The results in Figure 2, for example, are very clearly explained and easy to follow in the SI. I personally enjoyed the SI a lot, and while the discussion e.g. in lines 207- 215 is clear, it may be too terse for some readers to follow. The SI by contrast was very clear. Fig 3 does a nice job, however, to get the message of kinetic pairing across. + +I think it would help readers to understand how translatable to other phenotypes this type of analysis is, or if RPA is particular in this regard of allowing such general mathematical statements to be derived. + +## Our response: + +We are truly indebted to this reviewer for his/her incredible generosity in considering our work in such careful detail, and for such genuinely helpful feedback and thoughtful suggestions for further improvement. We are immensely grateful to have the benefit of an 'extra set of eyes' cast over our work, to identify additional opportunities to make our exposition more compelling. We have noted all revisions to the main manuscript, and to our SI, with red text, to make it easy to identify which parts of our article have been updated since the original submission. + +Regarding the issue of relegating much of our detailed mathematical development to the Supplementary Information, it is true that the severe word limits in Nature Communications (6000 words for main text, excluding figure captions) have forced us to limit our exposition in the paper itself to an accessible overview of the major conceptual innovations of the study, with extensive references to all the technical details in our Supplementary Information. A significant additional challenge stems from the fact that solving the RPA problem in complete generality, at the level of intermolecular interactions, has required us to draw together a number of distinct mathematical languages - chemical reaction network theory (CRNT), engineering control theory, and algebraic geometry - into a unified framework. + +We greatly value the reviewer's insightful suggestion that "it would help readers to understand how translatable to other phenotypes this type of analysis is, or if RPA is + +<--- Page Split ---> + +particular in this regard of allowing such general mathematical statements to be derived." We now include following text at the conclusion of our article: The quest to uncover the fundamental 'design principles' that constrain complex signalling networks in nature to implement biologically important functions is considered to be one of the most important and far- reaching 'grand challenges' in the life sciences [1- 6]. On the basis of the present study, along with our earlier topological study at the network macroscale [7], RPA currently stands alone as a keystone biological response for which there now exists a universal explanatory framework – one that imposes strict and inviolable design criteria on arbitrarily large and complex networks, and one that now accounts for the subtleties of intricate intermolecular interactions at the network microscale. These universal RPA- permissive design principles now represent a launching- point for future explorations of more complex phenotypes - including some classes of embryonic patterning problems, for instance, where integral control is known to play a role in promoting adaptation of segmentation boundaries to variations in organism size [8,9]. The identification of universal design principles for many other complex phenotypes, such as Turing patterns [4, 10,11] and multistability/switching- responses [12,13], is likely to prove more challenging due in part to the central role of equilibrium stabilities, or instabilities, in these responses. These 'grand challenges' remain open, and we hope that our study will inspire bold new mathematical thinking in these vitally important directions. + +## Small points: + +- much of chemical reaction network theory is obscure to most readers. I would like to see a clear and easy definition of integral control that is accessible to non-expert audiences. Deficiency is maybe another such concept and it would be good to define it on line 146. + +Our response: We truly appreciate such helpful suggestions to improve the clarity of our exposition. In our newly revised manuscript, we give a thorough yet accessible explanation of the concept of integral control, and the internal model principle (IMP), via the introduction of a new Figure in our Introduction section (Fig. 1 in our revised submission) – see below. We have also carefully edited our explanations of integral control in-text to complement this new Figure, and to ensure that the concept (and its relationship to the goals of our study) are clear to the readership of a multidisciplinary journal. + +We have also vastly expanded our clarifications on the concept of deficiency, especially in our Supplementary Information where we give far greater detail on the concept where we first define it in SI Section S1.2, and particularly its relationship to the flow of biochemical information (and ultimately topology) in RPA- capable CRNs. We have also added in an entirely new section (SI Section S1.3) on the key concept of algebraically- independent subnetworks of a CRN (which we didn’t discuss until much later in the Supplement, in our original submission), and clearly outline the role of deficiency in partitioning the reactions of a CRN into such independent subsets. In the main paper, we also introduce the concept of deficiency much earlier + +<--- Page Split ---> + +than previously, and point out early that this is a key algebraic invariant which has fundamental (and previously unrecognised) consequences for the implementation of integral control by CRNs. Later in the main paper, where we give further detail on the underlying mathematical technicalities, we give a clear definition of deficiency, and give an example of how to calculate it, in Figure 5. + +![](images/Figure_1.jpg) + +
Fig. 1. The internal model principle (IMP) and its application to RPA-capable CRNs. The class of constant disturbances \((I(t) = \text{const})\) is generally the disturbance class of most fundamental interest to the study of biological systems. (a) In order to exhibit RPA (i.e. 'adapt' to constant disturbances), the dynamical system \(\Sigma\) should be decomposable, via a coordinate transformation if needed, into an 'output-driven internal model', \(\Sigma_{IM}\) (generating all the constant signals corresponding to solutions of \(\dot{z}_2 = 0\) ), and the remainder of the system, \(\Sigma_0\) . The variable \(z_2\) thereby computes the integral of the output error. (b) A suitable coordinate change should be able to recast an RPA-capable system into integral feedback form, even if there is no feedback present in the network. As shown, a linear transformation is sufficient to identify an output-driven internal model for this particularly simple incoherent feedforward motif (Balancer module); \(y = \alpha_4 / \alpha_3\) (setpoint) at steady-state. (c) A model that employs feedback is frequently simpler to recast in 'integral feedback' form, with an output-driven internal model; here \(y = \alpha_3\) (setpoint) at steady-state. Note that the reaction rates selected for illustrative purposes in (b) or (c) cannot be induced, under the law of mass action, by any CRN20.
+ +- The authors show that their criteria hold for all instances of RPA. I was wondering how easily in practice these mechanisms could be lost? Is it easy to identify points that disrupt RPA? + +Our response: With access to a universal and complete solution to the RPA problem in CRNs, we can now delineate, precisely and definitively, the circumstances under which various classes of disturbances, or network alterations, can either preserve the RPA property or cause RPA to fail. We have not commented on this matter in detail in our manuscript, as this is the subject of ongoing work. One of the most interesting classes of disturbances against RPA-capable CRNs is the addition of + +<--- Page Split ---> + +enzyme- inhibitors of various types (competitive, non- competitive, mixed, uncompetitive, etc.). Addition of one more enzyme- inhibitors to a CRN, whether highly specific to its target or not, corresponds to the addition of extra linkage class(es) to the CRN. We now know that certain inhibitor mechanisms are deficiency preserving, while others aren't, and their effects on the RPA property (depending on the relationship of their target protein(s) to the overarching structure of the CRN) are complex and counterintuitive, and in some cases very surprising. Generally, the RPA property is very difficult to perturb via molecular- targeted inhibitors, although we have been able to identify very specific and definitive conditions in which this is possible. Other classes of disturbances (such as those we itemize in our newly revised Supplementary Information, at the beginning of Section S1) are much easier to study from the point of view of altering the RPA property. In any case, it is only by having a completely general mathematical description of RPA- permissive reaction structures, that accounts for all possible RPA- capable CRNs, that we can make such definitive conclusions on the preservation or destruction of the RPA property in the abstract. This is particularly valuable in the context of particularly complex signalling networks (e.g. in cancer signal transduction) for which detailed CRN structures are unknown (and possibly will never be known). + +In any case, we are planning to publish this work (separately) very soon, and look forward to sharing this. + +- there is a vast literature on design principles which could be touched upon at least in passing (limit cycles, multistability, switch-like behaviour, Turing patterns), especially if there is scope for applying similar concepts in these contexts. + +Our response: This is such a wonderful suggestion, which we greatly value. As we noted in our first point above, we have added an extra paragraph that comments on this very issue at the conclusion to our manuscript. "The quest to uncover the fundamental 'design principles' that constrain complex signalling networks in nature to implement biologically important functions is considered to be one of the most important and far-reaching 'grand challenges' in the life sciences [1- 6] ... Etc." + +Concluding Comments to Reviewer #2: We cannot thank the Reviewer enough for such a generous investment of time and effort, for such incredibly supportive feedback, and for so many insightful suggestions for additions and clarifications to our exposition. We are truly grateful. + +References (for response to Reviewer 2) + +[1] Alon, U. An introduction to systems biology: design principles of biological circuits. (Chapman and Hall/CRC, 2006). [2] Green, S. Revisiting generality in biology: systems biology and the quest for design principles. Biology & Philosophy 30, 629- 652 (2015). + +<--- Page Split ---> + +[3] Novák, B. & Tyson, J. J. Design principles of biochemical oscillators. Nature reviews Molecular cell biology 9, 981- 991 (2008). [4] Vittadello, S. T., Leyshon, T., Schnoerr, D. & Stumpf, M. P. Turing pattern design principles and their robustness. Philosophical Transactions of the Royal Society A 379, 20200272 (2021). [5] Stumpf, M. P. Statistical and computational challenges for whole cell modelling. Current Opinion in Systems Biology 26, 58- 63 (2021). [6] Lim, W. A., Lee, C. M. & Tang, C. Design principles of regulatory networks: searching for the molecular algorithms of the cell. Molecular cell 49, 202- 212 (2013). [7] Araujo, R. P. & Liotta, L. A. The topological requirements for robust perfect adaptation in networks of any size. Nat Commun 9, 1757 (2018). https://doi.org:10.1038/s41467- 018- 04151- 6 [8] Ben- Zvi, D. & Barkai, N. Scaling of morphogen gradients by an expansion- repression integral feedback control. Proceedings of the National Academy of Sciences 107, 6924- 6929 (2010). https://doi.org:10.1073/pnas.0912734107 [9] Eldar, A. et al. Robustness of the BMP morphogen gradient in Drosophila embryonic patterning. Nature 419, 304- 308 (2002). https://doi.org:10.1038/nature01061 [10] Lander, A. Pattern, growth, and control. Cell 144, 955- 969 (2011). [11] Krause, A. L., Gaffney, E. A., Maini, P. K. & Klika, V. Introduction to 'Recent progress and open frontiers in Turing's theory of morphogenesis'. Philosophical Transactions of the Royal Society A 379, 20200280 (2021). [12] Ullner, E., Zaikin, A., Volkov, E. I. & Garcia- Ojalvo, J. Multistability and clustering in a population of synthetic genetic oscillators via phase- repulsive cell- to- cell communication. Physical review letters 99, 148103 (2007). [13] Duddu, A. S., Sahoo, S., Hati, S., Jhunjhunwala, S. & Jolly, M. K. Multi- stability in cellular differentiation enabled by a network of three mutually repressing master regulators. Journal of the Royal Society Interface 17, 20200631 (2020). + +<--- Page Split ---> + +# Review 2: Universal structures for embedded integral control in biological adaptation + +Robyn P. Araujo and Lance A. Liotta + +Overview: The aim of this paper is to provide an algebraic characterisation of the hidden integral controller and construct an algebraic procedure to identify it in adaptation- capable networks. It is shown that this procedure is intimately connected to the structure of the networks via the well- known deficiency theory for chemical reaction networks. + +Recommendation: I am grateful to the authors for revising the manuscript to address many of the points that I raised in the first review. Even though the paper has significantly improved, many of the more serious concerns remain. These concerns, which are outlined below, should be fully addressed before the paper can be reconsidered again for Nature Communications. + +1. Connection to integral control: The paper claims to uncover universal structures for embedded "integral control". However in order to successfully demonstrate this, a coordinate transformation (possibly nonlinear) needs to be constructed that gives rise to the "integrator" variable. It does not matter if this coordinate transformation is done in a single step or in multiple steps (as proposed by this paper), but its existence needs to be shown in order to identify the integral mechanism. In the Supplement the authors write + +We note that, although there should always exist some single nonlinear coordinate change that yields the RPA polynomial in principle, for any mass action system, identifying such a single coordinate change in practice may be extremely difficult in all but the very simplest RPA-capable CRNs. + +I agree that proving the existence of an integrator may be difficult, but unfortunately it is unavoidable for showing integral control. Let us look into this issue in more details. + +Suppose the dynamics is governed by a system of ODEs: + +\[\frac{dx}{dt} = f(x),\] + +where \(x\) is the \(n\) - dimensional state of the system and \(f(x) = (f_{1}(x),\ldots ,f_{n}(x))\) are the rates of evolution of all the species. In order to exhibit an integrator, we need to find a real- valued function \(H(x)\) such the dynamics of \(z(t) = H(x(t))\) is given by the ODE: + +\[\frac{dz}{dt} = \nabla H(x)\circ f(x) = p(x)(x_{i} - c):= \rho (x), \quad (0.1)\] + +<--- Page Split ---> + +where \(\nabla\) is the gradient operator, \(\circ\) is the usual dot product and \(\rho (x) = p(x)(x_{i} - c)\) is what the authors call the "RPA polynomial" for the RPA variable \(x_{i}\) . Suppose one is able to find nonlinear polynomials \(h_{1},\ldots ,h_{n}\) (as in Theorem 1 of the paper) such that + +\[h_{1}(x)f_{1}(x) + \cdot \cdot \cdot +h_{n}(x)f_{n}(x) = \rho (x).\] + +However this does not necessarily mean that a function \(H(x)\) can be constructed so that (0.1) holds. Observe that such a function \(H(x)\) would need to have the following partial derivatives + +\[\frac{\partial}{\partial x_{j}} H(x) = h_{i}(x)\qquad \mathrm{for}\qquad j = 1,\ldots ,n.\] + +Unless each \(h_{i}(x)\) is a constant (in which case \(H(x)\) is linear), it is unclear why such a function \(H(x)\) would exist. Since the approach in the paper uses nonlinear elimination steps (via concatenating monomials), the existence of \(H(x)\) cannot be ascertained. In fact if for a pair \(j,k\) we have + +\[\frac{\partial}{\partial x_{j}} h_{k}(x)\neq \frac{\partial}{\partial x_{k}} h_{j}(x)\] + +then certainly \(H(x)\) cannot be constructed with partial derivatives \(h_{1},\ldots ,h_{n}\) . This discussion shows that while existence of a RPA polynomial may be necessary for integral control, it is not sufficient and hence this property does not characterise integral controllers (a main claim of the paper). This gap between necessity and sufficiency can be bridged if the authors can show that for RPA networks one always has + +\[\frac{\partial}{\partial x_{j}} h_{k}(x) = \frac{\partial}{\partial x_{k}} h_{j}(x)\qquad \forall \qquad j,k.\] + +2. Questions about the Kinetic Pairing result: In the previous review round, I had proposed a possible RPA network and asked the authors how it satisfies the Kinetic Pairing result (Theorem 1). The network has two reactions given by + +\[\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1} + \mathbf{X}_{4}\quad \mathrm{and}\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\mathbf{X}_{5} \quad (0.2)\] + +and there may be several other reactions involving species \(\mathbf{X}_{2},\ldots ,\mathbf{X}_{5}\) that can be catalysed by \(\mathbf{X}_{1}\) but they do not change \(\mathbf{X}_{1}\) . In the rebuttal letter, the authors consider certain instances of such a network, and claim that in these networks all possible steady states lie on the boundary on the positive orthant (e.g. \(x_{2}\) or \(x_{3}\) is zero) and hence the networks are not RPA. In particular, the authors state in their rebuttal letter that: + +The two reactions proposed by the reviewer cannot impose RPA on \(\mathbf{X}_{1}\) no matter which reactions are added to the original two. This is because the two given reactions are linearly independent, and the CRN formed from these reactions has deficiency zero. Moreover, the two complexes that contribute to the apparent RPA- polynomial in the reaction rate \(f_{1}\) are not members of the same terminal SCC. It is clear from our discussion of the decomposition + +<--- Page Split ---> + +of CRNs into algebraically independent subnetworks a decomposition which is closely tied to the partition of deficiency among independent subsets of reactions (see SI Section S1.3) - as well as our extensive discussions of rows- pan polynomials (complex linear invariants) throughout the remainder of our supplement, that no possible addition of extra reactions can turn the original two into an RPA- conferring set. We briefly note in Section S4.4.1 (see also footnote in that section) the special case where a deficiency zero collection of reactions can engender RPA namely when the two relevant complexes reside in the same terminal SSC, and correspond topologically to a trivial (isolated) connector node. The pair of reactions suggested by the reviewer are clearly not of this type. + +To test the authors' claim above, I tried to come up with instances of such networks (i.e. (0.2) + some reactions) which are RPA and yet do not have this issue of steady- state not being in the positive orthant. Please explain how the Kinetic Pairing result fits these networks. + +I start with a simpler version of this network with only three species (i.e. species \(\mathbf{X}_{4}\) and \(\mathbf{X}_{5}\) are absent) where I add inflow and outflow for species \(\mathbf{X}_{2}\) and \(\mathbf{X}_{3}\) . So the overall network becomes + +\[\begin{array}{r l} & {\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1},\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\emptyset ,\quad \emptyset \xrightarrow{c_{3}}\mathbf{X}_{2},\quad \emptyset \xrightarrow{c_{4}}\mathbf{X}_{3}}\\ & {\qquad \mathbf{X}_{2}\xrightarrow{c_{5}}\emptyset \quad \mathrm{and}\quad \mathbf{X}_{3}\xrightarrow{c_{6}}\emptyset .} \end{array} \quad (0.3)\] + +This network has no boundary variables and so the variables are the same as species. It seems that this network will indeed show RPA for \(x_{1}\) with set- point \(c_{1} / c_{2}\) . In Figure 1 I plot the simulated dynamics (rescaled to have the set- point of \(x_{1}\) as 1) for three randomly chosen values of initial states and rate constants, and one can see that RPA holds. + +Next I modify this network to have the production of \(\mathbf{X}_{2}\) and \(\mathbf{X}_{3}\) catalysed by \(\mathbf{X}_{1}\) . So the new network becomes + +\[\begin{array}{r l} & {\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1},\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\emptyset ,}\\ & {\mathbf{X}_{1}\xrightarrow{c_{3}}\mathbf{X}_{1} + \mathbf{X}_{2},\quad \mathbf{X}_{1}\xrightarrow{c_{4}}\mathbf{X}_{1} + \mathbf{X}_{3},\quad \mathbf{X}_{2}\xrightarrow{c_{5}}\emptyset \quad \mathrm{and}\quad \mathbf{X}_{3}\xrightarrow{c_{6}}\emptyset .} \end{array} \quad (0.4)\] + +This network also appears to be RPA as shown by the simulations in Figure 2. + +Finally, I consider another variant of this network where we have species \(\mathbf{X}_{4}\) and \(\mathbf{X}_{5}\) that reversibly bind to each other to produce an inactive compound, and they catalyse the production of \(\mathbf{X}_{2}\) and \(\mathbf{X}_{3}\) respectively. Therefore the new network becomes + +\[\begin{array}{r l} & {\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1} + \mathbf{X}_{4},\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\mathbf{X}_{5},\quad \mathbf{X}_{4}\xrightarrow{c_{3}}\mathbf{X}_{4} + \mathbf{X}_{2},\quad \mathbf{X}_{5}\xrightarrow{c_{4}}\mathbf{X}_{5} + \mathbf{X}_{3},}\\ & {\mathbf{X}_{2}\xrightarrow{c_{5}}\emptyset ,\quad \mathbf{X}_{3}\xrightarrow{c_{6}}\emptyset ,\quad \mathbf{X}_{4} + \mathbf{X}_{5}\xrightarrow{c_{7}}\emptyset \quad \mathrm{and}\quad \emptyset \xrightarrow{c_{8}}\mathbf{X}_{4} + \mathbf{X}_{5}.} \end{array} \quad (0.5)\] + +This network also seems to be RPA, as shown in the simulations in Figure 3. + +These networks do not appear to satisfy the RPA characterisation given by this paper. Also consider Example 6.5.3 in [5] which does not seem to fit this result either. These + +<--- Page Split ---> +![](images/Figure_2.jpg) + +
Figure 1: Plots of the dynamics of network (0.3) with mass-action kinetics, with initial state \(x(0)\) and rate constants \(c = (c_{1},c_{2},\ldots)\) . Each component of \(x(0)\) and \(c\) was randomly generated from the interval \([1,10]\) and here we show plots for three realisations of \(x(0)\) and \(c\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \(x_{1}\) is 1.
+ +counter- examples cast doubt on the correctness of the Kinetic Pairing Theorem on which the entire paper rests. + +3. The set-point may not be a rational function of parameters: In many places in the main paper and the supplement, the system's set-point is said to be a rational function of biochemical parameters. While this holds for most examples, consider the following birth death network + +\[\emptyset \xrightarrow{c_{1}}\mathbf{X}_{1}\quad \mathrm{and}\quad 2\mathbf{X}_{1}\xrightarrow{c_{2}}\emptyset .\] + +The dynamics is given by + +\[\frac{d x_{1}}{d t} = c_{1} - 2c_{2}x_{1}^{2}\] + +and so the set- point + +\[c = \sqrt{\frac{c_{1}}{2c_{2}}}\] + +is not a rational function of \(c_{1}\) and \(c_{2}\) ? For more examples, see Examples 2.11 and 2.12 in [3]. Please revise as necessary. + +<--- Page Split ---> +![](images/Figure_3.jpg) + +
Figure 2: Plots of the dynamics of network (0.4) with mass-action kinetics, with initial state \(x(0)\) and rate constants \(c = (c_{1},c_{2},\ldots)\) . Each component of \(x(0)\) and \(c\) was randomly generated from the interval \([1,10]\) and here we show plots for three realisations of \(x(0)\) and \(c\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \(x_{1}\) is 1.
+ +4. Questions on the Buchberger's Algorithm: In the previous review round, I had raised the following issue regarding Buchberger's Algorithm + +The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima- facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In any case, checking for nontermination of a method is impractical. + +In response the authors state in their rebuttal letter that the termination is guaranteed because "all ideals of a polynomial ring (or any Noetherian ring, for that matter) are finitely generated a result of central importance in algebraic geometry, formalized by the Hilbert Basis Theorem". While I agree that termination is guaranteed, I must point out that the reason for my confusion and for raising this termination issue is the following excerpt from the previous version of the Supplement (submitted in round 1): + +Failure of the Buchberger (or other Grobner basis- computing) algorithm to terminate could thus be adduced as prima facie evidence that the CRN under consideration does not, in fact, have the capacity for RPA. + +It seems that in this statement that authors meant "terminate in practical time". I understand that due to the "almost linear" nature of coordinate change, this algorithm + +<--- Page Split ---> +![PLACEHOLDER_43_0] + +
Figure 3: Plots of the dynamics of network (0.5) with mass-action kinetics, with initial state \(x(0)\) and rate constants \(c = (c_{1},c_{2},\ldots)\) . Each component of \(x(0)\) and \(c\) was randomly generated from the interval \([1,10]\) and here we show plots for three realisations of \(x(0)\) and \(c\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \(x_{1}\) is 1.
+ +would work well for RPA networks. However, does the final RPA polynomial produced by the method depend on the monomial ordering or other choices made by the method? More importantly, if a network is not RPA, how many steps would the method need to confirm this non- RPA property? Such practical considerations must be discussed in the main text, and they are crucial for applying these ideas for characterising RPA in high- dimensional networks. + +5. Connection of examples to existing works: The authors start the Results section with "two simple examples that have eluded all previous systematic methods to detect RPA". Please specify which systematic methods are being referred to here. Also, in the example on Figure 2 it should be mentioned that \(\mathbf{X}_{3}\) is maxRPA and it can be checked from the characterisation result in [2]. Secondly since there is the reaction + +\[\mathbf{X}_{3} + \mathbf{X}_{2}\xrightarrow{k_{6}}\mathbf{X}_{2}\] + +which does not involve \(\mathbf{X}_{1}\) I do not understand why the term \(k_{6}X_{2}X_{3}\) does not enter the expression for + +\[\frac{d(X_{1} - X_{2})}{dt}\] + +in Figure 2C. Please check. If the term \(k_{6}X_{2}X_{3}\) is present then it cannot be eliminated with the concatenating monomial \(O_{1}\) . On the other hand, if this reaction is removed + +<--- Page Split ---> + +(i.e. this term is absent) then the overall network simply becomes a trivial RPA network where the output of one RPA network (i.e. the network comprising \(\mathbf{X}_{3} - \mathbf{O}_{1}\) ) is passed as an input to another RPA network (i.e. the antithetic network with \(\mathbf{X}_{1} - \mathbf{X}_{2}\) ). It is straightforward that connecting RPA networks in series (with catalytic reactions) would still result in a RPA network. Such examples are not appropriate for demonstrating the novel results in this paper. + +The second example in Figure 3 seems to be taken straight from [4] (see Fig. 2). This should be clearly stated when the example is being introduced in the main text and also in the caption of Figure 3. Also mention that the linear invariants shown in Fig. 3 can be deduced from the approach in [4] (this is stated in passing in the conclusion but it should be stated more prominently when the example is being discussed.) + +6. Many claims without proofs in the Supplement: The Supplement has been considerably revised, but still many arguments are unclear because proper proofs have not been provided or referenced: + +- Why should eq. (8) hold when eq. (9) holds? Can the networks always be partitioned this way? Please explain. + +- On page 21 in the Supplement it states that: + +Since a perturbation to the CRN that alters the steady state of \(x_{j}\) will also alter the steady-states of other non-RPA capable variables (eg. \(x_{m}\) ), If \(\mathbb{R}[\bar{x}]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) , and that are not contained in \(I_{f} \cap I_{p}\) . + +Why should such a perturbation always exist? + +- Also on page 21 in the Supplement it says that + +The set \(\bar{x}\) now contains two independent (uncoupled) variables in the sense that a perturbation to the CRN that alters the steady-state of one of the variables does not affect the steady-state of the other. + +Why does this hold? Please elaborate. + +- In general, in the proof of the Kinetic Pairing Theorem the authors work over the ring of polynomials over species-variables \(x_{1}, \ldots , x_{n}\) . Shouldn't the system parameters (i.e. rate constants) be included in this ring, as they would appear in the RPA polynomial? This inclusion of parameters is there in the Singular code but not in the proof. However simply adding the parameters in the ring is not sufficient as the \(n\) -th roots of the parameter would be added, as the examples mentioned in point 3 show. + +## 7. Other minor issues: + +- The definition of RPA must be shifted to the main text due to its centrality in understanding the message of the paper. + +- Why is the variable \(x_{i}\) missing in \(g(x_{j})\) in figure 4 (main text) and figure S4 (supplement)? + +<--- Page Split ---> + +- Replace "consistutes" with "constitutes" on line 72 in the main text. Please run a spell check. + +- The paper says that if a network is RPA the integrator is guaranteed to exist. For example the following on page 22 in the main text + +In principle, there should always exist some single nonlinear coordinate change to extract a single output-driven internal model (Fig. 9a) from systems rate equations, corresponding to a single integral of the systems tracking error (Fig. 9b) + +or the following on page 16 in the Supplement + +All classes of RPA, including ACR, thus require some form of integral control. + +Please explain which version of IMP can be used to verify this existence. See [1] for a recent review on IMP. + +- On page 20 the authors state that "It is striking to note that the original form of the CRN (Fig. 8a) eludes the Shinar-Feinberg theorem, even though the CRN exhibits ACR and has a deficiency of one." However does it fit the results in [4]? Please comment on this. Also explain why the authors found the method for finding linear invariants "ad hoc" (lines 568-569 on page 25). + +- On the Supplement page 15 it is stated that + +Mass-conservative CRNs therefore have no external stimuli or inputs, and can only be perturbed by altering the total abundances (or concentrations) of the constituent molecules - i.e. by altering the initial conditions. + +Why cannot the perturbation come in the form of parameter variation, e.g. of a conversion reaction (that conserves mass). + +## References + +[1] M. Bin, J. Huang, A. Isidori, L. Marconi, M. Mischiati, and E. Sontag. Internal models in control, bioengineering, and neuroscience. Annual Review of Control, Robotics, and Autonomous Systems, 5:55- 79, 2022. + +[2] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. Proceedings of the National Academy of Sciences, 119(43):e2207802119, 2022. + +[3] N. Meshkat, A. Shiu, and A. Torres. Absolute concentration robustness in networks with low- dimensional stoichiometric subspace. Vietnam Journal of Mathematics, 50(3):623- 651, 2022. + +[4] M. Pérez Millán, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027- 1065, 2012. + +<--- Page Split ---> + +[5] M. S. Pérez Millán. Métodos algebraicos para el estudio de redes bioquímicas. PhD thesis, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales, 2011. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: See attached. + +Reviewer #2: Remarks to the Author: + +The reviewers have comprehensively addressed my questions and points. This paper addresses a fundamentally important question in biology and it does so using a powerful mathematical framework that the authors have developed and fine- tuned. + +The particular appeal of this approach is that it sets a template (and I imagine that in the future we will see many more examples of this type) is that the mathematical analysis has a level of generality that means that the authors results are robust and reliable. Having solid mathematical foundations for a complex biological phenotype is still rare, but the current paper shows that the search for such theoretical underpinnings can be fruitful. + +<--- Page Split ---> + +Overview: The aim of this paper is to provide an algebraic characterisation of the hidden integral controller and construct an algebraic procedure to identify it in adaptation- capable networks. It is shown that this procedure is intimately connected to the structure of the networks via the well- known deficiency theory for chemical reaction networks. + +Recommendation: I am grateful to the authors for revising the manuscript to address many of the points that I raised in the first review. Even though the paper has significantly improved, many of the more serious concerns remain. These concerns, which are outlined below, should be fully addressed before the paper can be reconsidered again for Nature Communications. + +## Our response: + +Once again, we are truly grateful for the huge investment of time the reviewer has clearly made in considering our work in such careful detail. We have reflected thoughtfully on all the reviewer's points and respond to each in turn below. + +All changes made to our paper and Supplementary Information (SI) are noted in red text. + +1. Connection to integral control: The paper claims to uncover universal structures for embedded "integral control". However in order to successfully demonstrate this, a coordinate transformation (possibly nonlinear) needs to be constructed that gives rise to the "integrator" variable. It does not matter if this coordinate transformation is done in a single step or in multiple steps (as proposed by this paper), but its existence needs to be shown in order to identify the integral mechanism. In the Supplement the authors write + +We note that, although there should always exist some single nonlinear coordinate change that yields the RPA polynomial in principle, for any mass action system, identifying such a single coordinate change in practice may be extremely difficult in all but the very simplest RPA-capable CRNs. + +I agree that proving the existence of an integrator may be difficult, but unfortunately it is unavoidable for showing integral control. + +## Our response: + +What we show in this paper is that a particular type of nonlinear transformation is always able to decompose an RPA- capable set of CRN reactions into an organized collection (a 'topological hierarchy') of linear coordinate transformations. Each of these linear coordinate transformations corresponds to a subsidiary integral controller within the CRN. This is a fundamentally different type of integral control implementation from the 'conventional' interpretation of integral control in engineering control theory. Indeed, the nonlinear transformation we propose is not a coordinate transformation. Rather, it is a map from the system reaction rates to a function space with the same algebraic structure as the CRN reactions (i.e. that of a commutative ring), which offers a universal description of the coordinated interactions of (integral computing) internal models – obtained via linear coordinate changes - that holds for all possible RPA- capable CRNs. + +<--- Page Split ---> + +We do acknowledge that in our previous rebuttal letter (as opposed to our paper), we had referred to the mathematical transformation in several places as a coordinate change, which was not correct. We apologise for unwittingly sidetracking the discussion through such sloppy (and incorrect) wording in our previous response. We have now made absolutely certain that this incorrect terminology does not appear anywhere in our paper or in our accompanying SI. The reviewer is entirely correct to point out that the nonlinear transformation we present in this paper is not a nonlinear coordinate change. + +The conventional view of the 'internal model principle' (IMP) in engineering control theory (particularly for application to problems in systems biology and bioengineering [1,8,9]) suggests that, for robust rejection of constant disturbances, there must exist some decomposition of the system (obtained via a coordinate transformation, if needed) into two distinct subsystems: (i) an 'output- driven internal model' (of the constant disturbance), and (ii) the remainder of the system ([8,9]). This decomposition will generally require a nonlinear coordinate transformation, although many simple CRNs have been identified (as we point out in our paper and accompanying Supplementary Information) for which a linear coordinate transformation is sufficient. In particular, if the system at hand is not already in feedback form, then the internal model- identifying coordinate transformation must be able to recast the system into an integral feedback form (see references [1] and [9] below, as well as Figure 1b in our paper, for some simple examples of this requirement). If a network can indeed exhibit RPA, then according to this version of the IMP (see [8] and [9], for example, as well as Section 3 in [1]), there should always exist some (single) coordinate transformation that recasts the system into such a feedback system, with an embedded output- driven internal model – even if the system is topologically feedforward structured. This is the concept we are referring to in the excerpt from our Supplementary Information quoted by the reviewer above ('... there should always exist some single nonlinear coordinate change that yields the RPA polynomial... for any mass action system'). + +Note, incidentally, that (in contrast to the formulation we present in our paper) this conventional interpretation of the IMP ([8,9]) requires that certain properties of the disturbances be known a priori, including which model variables can be directly regulated by the disturbance, and also requires the prior identification of an 'output' for the model (which must be able to 'adapt' to, or reject, those disturbances). For an RPA- capable system, being able to identify such a nonlinear coordinate transformation, if it exists, simply confirms to us that the system can indeed exhibit robust asymptotic tracking of the output variable's 'setpoint' when subjected to the specified (constant in time) disturbances. It also identifies the specific transformed variable that actually computes the integral of the 'error' (where the error in question is the difference between the instantaneous value of the output variable and its setpoint). But if we already know (using some other analytical method, say) that RPA obtains for certain variable(s) in a specific CRN, then explicitly identifying the nonlinear coordinate change that transforms that particular system into integral feedback form does not actually provide any further useful information. The fundamental point we make in our Discussion is that there is no general way to + +<--- Page Split ---> + +propose a single nonlinear coordinate change that can reveal the fundamental mechanisms by which all RPA- capable CRNs actually implement RPA, and thereby provide a concrete characterization of the entire solution space to the RPA problem for CRNs. + +Consider, for example, Shinar and Feinberg's deficiency- two model of the EnvZ- OmpR osmoregulation network (first presented in the Supplementary Materials of [10], and considered in Figure 3 of our main paper). For this specific network, the existence of RPA (and ACR more specifically) in the molecule phospho- OmpR can be shown using a variety of methods. Shinar and Feinberg, in their Supplementary Materials [10], show through a sequence of manual algebraic substitutions that phospho- OmpR has a steady- state value that is a rational function of the CRN parameters, independent of the total abundances of the various interacting molecules. Karp et al. [6], on the other hand, demonstrate how 'complex- linear' invariants may be computed, and show that for this particular CRN, two linearly- independent such invariants may be combined to demonstrate RPA in phospho- OmpR, with the same setpoint as previously calculated by Shinar and Feinberg [10]. Now, since this CRN exhibits RPA (at phospho- OmpR), undoubtedly, there must undoubtedly exist some nonlinear coordinate transformation that could recast this system (a 'balancer' module, as we show, with a feedforward structure) into an integral feedback system with a single output- driven (i.e. phospho- OmpR- driven) internal model, where a single (transformed) variable computes the error in phospho- OmpR in comparison with its (known) setpoint. But even if we were to identify the requisite coordinate transformation, explicitly and analytically, for this particular CRN, what would this coordinate map actually tell us (vis- à- vis the RPA- capacity of the CRN) that we didn't already know? More importantly, what could this specific coordinate map possibly tell us about the space of all possible RPA- capable CRNs, or the general (universal) properties of collections of chemical reactions that can confer RPA on a subset of the interacting molecules? Absolutely nothing! The integral- feedback- recasting nonlinear coordinate transformation for an RPA- capable CRN is unique to that particular CRN. In other words, the single nonlinear coordinate transformation required to identify an internal model in the deficiency- two Shinar- Feinberg EnvZ- OmpR model discussed above, if such can be explicitly identified, will necessarily be a different nonlinear map from the one required for the Cappelletti et al. [11] toy model (Example 1 in Section S3.1 of our SI) – despite the fact that the two models are fundamentally alike: both are Balancer modules (topologically speaking) for which a single balancer invariant and a single connector invariant are obtained via linear coordinate transformations, and require a single concatenating monomial to obtain an RPA polynomial. + +By contrast, our nonlinear transformation (Eq. 6) is of a fundamentally different character. Nowhere in our paper do we claim that this nonlinear transformation is a coordinate transformation. Importantly, this nonlinear map relaxes the feedback requirement of the IMP in its conventional interpretation (as discussed above, see also Section 6.2 in [9]), and instead preserves the underlying topological structure of the network. Thus, RPA- capable CRNs of Balancer type retain their feedforward characteristics under this transformation. We maintain that referring to an + +<--- Page Split ---> + +embedded integral control is entirely justified since the nonlinear map in question is always able identify, for any RPA- capable CRN, a topologically organized collection of linear coordinate changes, each one of which identifies a subsidiary internal model which does recapitulate the dynamical structure of the disturbance (i.e. constant- in- time), and which thereby imposes RPA on some characteristic of the network, with its own setpoint. Each such linear coordinate change thereby corresponds to subsidiary control problem with its own linear integral variable. + +For the Cappelletti et al. [11] toy model, for instance, the nonlinear transformation which projects the system onto two variables (A and B - see Singular Code in SS.3 of our Supplementary Information) can be decomposed into two linear coordinate changes, corresponding to two key invariants. One of these is a 'balancer' invariant, \(k_{2}BC - k_{3}B^{2}\) , which represents the 'error' in the ratio of the two 'proportioner' molecules, \(C\) and \(B\) , in comparison with their 'setpoint': i.e. \(k_{2}B^{2}\left(\frac{C}{B} -\frac{k_{3}}{k_{2}}\right)\) . The other is a 'connector' invariant, \(k_{1}AB - k_{7}C\) , which represents the error in the ratio of the 'upregulating' contributions (in this case, \(AB\) ) to the 'downregulating' contributions (in this case, \(C\) ), for the 'connector' calculation: i.e. \(k_{1}C\left(\frac{AB}{C} -\frac{k_{7}}{k_{1}}\right)\) . Together, these two independent computations, each with a linear integral variable, and each conferring RPA on some (topologically important) feature of the CRN, confer RPA on the molecule \(A\) . The setpoint for \(A\) is a combination of the setpoints from the two contributing subsidiary (linear) problems. Of course, many CRNs will have much more complicated invariants than these, involving more than two terms per invariant, but the same fundamental principles hold. (This is the universality of the framework we present). + +The feedforward model presented by Bin et al. [1] provides a nice illustration of the distinction between the conventional interpretation of the IMP and the one we develop here, as applicable to RPA in CRNs. In Section 3 of [1] the authors review a very simple two- variable incoherent feedforward loop (IFFL) model (Eq. 25) that has been widely studied in the systems biology literature (including in [9]). The two model equations are + +\[\frac{dx}{dt} = \alpha u - \delta x,\] + +and + +\[\frac{dy}{dt} = \beta \frac{u}{x} -y y.\] + +The authors show that a nonlinear coordinate map that transforms these two equations into a partitioned form, corresponding to an integral feedback structure, is + +\[(x,y)\mapsto (z_{1},z_{2}) = \left(y,\phi (x,y)\right) = (y,\alpha y - \beta \log x),\] + +which produces, in the new coordinates \((z_{1},z_{2})\) : + +\[\frac{dz_{1}}{dt} = \beta u e^{(z_{2} - \alpha z_{1}) / \beta} - \gamma z_{1},\] + +<--- Page Split ---> + +\[\frac{dz_2}{dt} = \beta \delta -\alpha \gamma z_1.\] + +This transformed system has an output \(y = z_{1}\) , and has the desired internal model form, where \(z_{2}\) is the transformed variable that integrates the error (in \(z_{1} = y\) ). This nonlinear coordinate change nicely confirms that RPA is possible at \(y\) , and that its setpoint is \(\beta \delta /\alpha \gamma\) . But a different nonlinear transformation of the system (not a coordinate transformation) is also possible: + +\[\beta \frac{dx}{dt} -\alpha x\frac{dy}{dt} = \alpha \gamma x\left(y - \frac{\delta\beta}{\alpha\gamma}\right)\] + +Unlike the coordinate transformation considered previously, this particular transformation underscores the fact that this simple two- variable reaction system is fundamentally of the same type as both the Cappelletti et al. [11] toy model (Example 1 in our Supplementary Information S3.1) and the deficiency- two Shinar- Feinberg EnvZ- OmpR model we discussed above: a Balancer module, with two independent (linear) invariants - a balancer invariant, and a connector invariant - combined via a single concatenating monomial (in this case, \(x\) ). This transformation also reveals the setpoint, \(y = \beta \delta /\alpha \gamma\) . Of course, we do acknowledge that the rate equations above are not polynomials, the only consequence of which, in the context of our paper, is that we cannot use the powerful automated algorithms of algebraic geometry that compute Gröbner bases (which pertain to polynomials); nevertheless, rational functions are \(C^{1}\) - smooth functions on \((0, \infty)\) , and thus possess the algebraic properties of a ring as required for the application of our Theorem 1. The RPA polynomial so obtained involves two variables (one RPA- capable (i.e. \(y\) ) and one non- RPA- capable (i.e. \(x\) )) and is thus the single generator of the relevant ideal. By contrast, the nonlinear coordinate transformation discussed in [1], as noted above, is unique to this particular set of rate equations, and provides no insight into the general properties of all RPA- capable CRNs (or even its fundamental connection to the RPA- conferring properties of the Cappelletti et al. [11] or Shinar- Feinberg [10] models discussed above). Shoval et al. [9] acknowledge that the coordinate transformations that recast systems into integral feedback form 'may well be merely a mathematical construct with no biological meaning' (see Section 6.3 in [9]). + +Again, we maintain emphatically that this is a fundamentally different way of looking at integral control from the IMP as it is usually understood in engineering control theory. This approach identifies where, within the collection of reactions themselves, the computations relevant to RPA actually occur at the level of the interacting molecules of the CRN. Identifying a (single) nonlinear coordinate change that transforms the system into an integral feedback system, with a single embedded internal model, can only confirm that RPA will obtain; it does not explain how it is implemented by the original variables of the system (i.e. the molecular concentrations). + +<--- Page Split ---> + +Being able to characterize the entire space of all possible RPA- capable CRNs in such a general way has enormous practical implications because it provides a completely comprehensive and universal understanding of how to either destroy or maintain the presence of RPA – through evolution, or via experimental or clinical interventions, where new mutational events or exogenous enzyme inhibitors exert their effects at the molecular level. In particular, we can destroy the RPA property in a CRN by disrupting any one linear integral controller. By contrast, retaining the RPA property requires that all linear integral controllers already present be preserved. Cappelletti et al. [11], for instance, consider how a linear integral controller can be preserved when adding in a new (exogenous) stimulus to the network (see Theorem 5.1 in [11]); but there are many other types of perturbations that could occur in CRNs in either an evolutionary setting, or in experimental/clinical settings. Given that many of the most complex signalling networks that arise in nature, such as signal transduction networks in mammalian cancer cells, will likely never be delineated in complete intricate detail in terms of elementary chemical reactions, the robustness- conferring mechanisms that self- assemble in biology require a completely new approach, an entirely new language, for understanding the fundamental structures of life’s networks. In this paper we wish to offer just such an approach. + +Let us look into this issue in more details. Suppose the dynamics is governed by a system of ODEs: + +\[\frac{dx}{dt} = f(x),\] + +where \(x\) is the \(n\) - dimensional state of the system and \(f(x) = (f_{1}(x), \ldots , f_{n}(x))\) are the rates of evolution of all the species. In order to exhibit an integrator, we need to find a real- valued function \(H(x)\) such the dynamics of \(z(t) = H(x(t))\) is given by the ODE: + +\[\frac{dz}{dt} = \nabla H(x)\cdot f(x) = p(x)(x_{i} - c):= \rho (x), \quad (0.1)\] + +where \(\nabla\) is the gradient operator, \(\cdot\) is the usual dot product and \(\rho (x) = p(x)(x_{i} - c)\) is what the authors call the “RPA polynomial” for the RPA variable \(x_{i}\) . Suppose one is able to find nonlinear polynomials \(h_{1}, \ldots , h_{n}\) (as in Theorem 1 of the paper) such that + +\[h_{1}(x)f_{1}(x) + \dots +h_{n}(x)f_{n}(x) = \rho (x).\] + +However this does not necessarily mean that a function \(H(x)\) can be constructed so that (0.1) holds. Observe that such a function \(H(x)\) would need to have the following partial derivatives + +\[\frac{\partial}{\partial x_{j}} H(x) = h_{i}(x)\quad \mathrm{for}\quad j = 1,\dots ,n.\] + +Unless each \(h_{i}(x)\) is a constant (in which case \(H(x)\) is linear), it is unclear why such a function \(H(x)\) would exist. Since the approach in the paper uses nonlinear elimination steps + +<--- Page Split ---> + +(via concatenating monomials), the existence of \(H(x)\) cannot be ascertained. In fact if for a pair \(j, k\) we have + +\[\frac{\partial}{\partial x_j} h_k(x) \neq \frac{\partial}{\partial x_k} h_j(x)\] + +then certainly \(\mathrm{H}(x)\) cannot be constructed with partial derivatives \(h_1, \ldots , h_n\) . This discussion shows that while existence of a RPA polynomial may be necessary for integral control, it is not sufficient and hence this property does not characterise integral controllers (a main claim of the paper). This gap between necessity and sufficiency can be bridged if the authors can show that for RPA networks one always has + +\[\frac{\partial}{\partial x_j} h_k(x) = \frac{\partial}{\partial x_k} h_j(x) \forall j, k.\] + +Our response: Yes, the reviewer is entirely correct to point out that the nonlinear map we propose in this paper (Eq. 6) is not a coordinate transformation. But again, we don't actually seek a diffeomorphism \(H(x)\) of the type the reviewer describes, and we don't claim that our collection of elimination polynomials gives rise to a coordinate transformation (other than in the special case of constant elimination polynomials). We do apologise again for incorrectly referring to the nonlinear map as a nonlinear coordinate change in our previous rebuttal letter. This was sloppy (and incorrect) wording, and we have made absolutely certain that no such inaccuracies appear anywhere in our manuscript or in our SI. + +It is true that the existence of an RPA polynomial, \(\rho\) , contained in the ideal \(I_f = \{h_1 f_i + \dots + h_n f_n: h_i \in \mathbb{R}[x_1, \ldots , x_n]\}\) is a necessary but insufficient condition for RPA. As our Theorem 1 makes clear, \(\rho = g(x_i, x_j)(x_i - c)\) must generate the principal ideal in two variables, \(I_f \cap \mathbb{R}[x_i, x_j]\) , where \(x_j\) is (any) non- RPA- capable variable. This condition is both necessary and sufficient for RPA at \(x_i\) , under the assumption of stability. But nowhere do we claim that a CRN for which \(\rho (x_i, x_j)\) generates \(I_f \cap \mathbb{R}[x_i, x_j]\) contains "an" integrator. This can only be true if the elimination polynomials are constants, as the reviewer points out. If non- constant elimination polynomials are required, our framework requires there to be multiple independent (linear) integrators, connected via concatenating monomials; the nonlinearity is thereby relegated entirely to the concatenating process, not to the identification of internal models. In general, the output for one internal model will be an input for another. This collection of linear coordinate maps is always obtainable from a decomposition of the special nonlinear transformation we identify. That is the viewpoint we develop here. + +Again, we are re- interpreting the IMP from a completely different standpoint from the one considered in prior work, in which the existence of a nonlinear coordinate transformation, and an associated output- driven internal model, is normally at issue. Note that the RPA polynomial we reference in Eq. 6 (and Theorem 1 – the Two- Variable Kinetic Pairing Theorem) contains strictly two variables in contrast to \(\rho (x)\) in + +<--- Page Split ---> + +(0.1) above, which involves an unspecified number of variables. We simply do not claim that the transformation that identifies the (two-variable) RPA polynomial is associated with a single integrator. Rather, we claim that this transformation is always able to obtain \(\rho\) via a connected collection of linear integrators, each requiring a linear coordinate change, and each imposing RPA on some topologically important feature of the CRN. + +Bin et al. in [1] offer a particularly insightful comment. They state in Section 3: 'The question that the IMP asks is, If a system ... is seen experimentally to regulate against all inputs (in some class of functions, e.g. constants), then what can be said about its internal structure? Answers to this question may help guide experimentalists and modelers by ruling out putative mechanisms and suggesting a search for components responsible for adaptation'. The version of the IMP those authors go on to discuss in that paper (involving a coordinate transformation that identifies an output- driven internal model, within a feedback structure) provides one answer as to what can be said about the internal structure of RPA- capable networks. Our paper provides a different answer – one that reveals the universal properties, at the molecular level, of all RPA- capable networks. + +2. Questions about the Kinetic Pairing result: In the previous review round, I had proposed a possible RPA network and asked the authors how it satisfies the Kinetic Pairing result (Theorem 1). The network has two reactions given by + +\[X_{2} + X_{3}\xrightarrow{c_{1}}X_{1} + X_{4}\mathrm{~and~}X_{1} + X_{2} + X_{3}\xrightarrow{c_{2}}X_{5} \quad (0.2)\] + +and there may be several other reactions involving species \(X_{2},\ldots ,X_{5}\) that can be catalysed by \(X_{1}\) but they do not change \(X_{1}\) . In the rebuttal letter, the authors consider certain instances of such a network, and claim that in these networks all possible steady states lie on the boundary on the positive orthant (e.g. \(x_{2}\) or \(x_{3}\) is zero) and hence the networks are not RPA. In particular, the authors state in their rebuttal letter that: + +The two reactions proposed by the reviewer cannot impose RPA on \(X_{1}\) no matter which reactions are added to the original two. This is because the two given reactions are linearly independent, and the CRN formed from these reactions has deficiency zero. Moreover, the two complexes that contribute to the apparent RPA- polynomial in the reaction rate \(f_{i}\) are not members of the same terminal SCC. It is clear from our discussion of the decomposition of CRNs into algebraically independent subnetworks a decomposition which is closely tied to the partition of deficiency among independent subsets of reactions (see SI Section S1.3) - as well as our extensive discussions of rowspan polynomials (complex linear invariants) throughout the remainder of our supplement, that no possible addition of extra reactions can turn the original two into an RPA- conferring set. We briefly note in Section S4.4.1 (see also footnote in that section) the special case where a deficiency zero collection of reactions can engender RPA namely when the two relevant complexes reside in the same terminal SSC, and correspond topologically to a trivial (isolated) connector node. The pair of reactions suggested by the reviewer are clearly not of this type. + +<--- Page Split ---> + +To test the authors' claim above, I tried to come up with instances of such networks (i.e. (0.2) + some reactions) which are RPA and yet do not have this issue of steadystate not being in the positive orthant. Please explain how the Kinetic Pairing result fits these networks. + +Our response: Yes, in the previous round of review the reviewer provided us with the two reactions given in (0.2) above and, pointing out that such a reaction pair would produce a reaction rate \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) , asked us how this could be reconciled to the claims of our Two- Variable Kinetic Pairing Theorem since this equation has the apparent form of an RPA polynomial, yet appears to have three rather than two variables. We pointed out that it is possible to have an RPA polynomial involving three (or more) species, but only two variables, in CRNs containing a 'boundary variable'. But more importantly, we went on to show that, for the particular reaction pair proposed by the reviewer equipped with the needed 'closure' reactions (for which we provided three different examples), the projection of the ideal generated by the collection of CRN rate equations \((I_f)\) onto two variables (one RPA- capable, and one non- RPA- capable) produced the elimination ideal \(< x_2x_3>\) . Hence, none of the three CRN examples could exhibit RPA. + +Our Theorem 1 (the 'two- variable kinetic pairing theorem') states, simply, that a CRN is RPA- capable in some variable \(x_i\) exactly when the projection of the steady- state ideal, \(I_f\) , onto \(x_i\) and \(x_j\) (for any non- RPA- capable \(x_j\) ) is generated by a single polynomial of the form \(\rho = g(x_i, x_j)(x_i - c)\) . We call such polynomials 'RPA polynomials'. As we pointed out in our earlier rebuttal, it is not enough for a set of CRN equations to contain a reaction rate that has the form of an RPA polynomial (as is the case for all the reviewer's examples, both here and in the previous round of review, which all have \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) ). Rather, the elimination ideal \(I_f \cap \mathbb{R}[x_1, x_j]\) must be generated by an RPA polynomial. + +In the reviewer's new report, he/she provides three alternative collections of reactions, all of which contain the reaction \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) , and all of which do, in fact, exhibit RPA. As the reviewer rightly points out, none of these examples contain any boundary variables. According to our Theorem 1, all three of these new examples will indeed exhibit RPA since the elimination ideal \(I_f \cap \mathbb{R}[x_1, x_j]\) in each case (with \(x_j \in \{x_2, x_3\}\) for the first two CRN examples, and \(x_j \in \{x_2, x_3, x_4, x_5\}\) for the third example) is generated by a two- variable RPA polynomial. In particular, \(\rho = x_1 - c_1 / c_2\) in the first and third CRN examples (where the pairing function is zero- order in both its arguments), and \(\rho = x_1^2 (x_1 - c_1 / c_2)\) in the second CRN example (where the pairing function is zero- order in the non- RPA variable). Thus, all relevant two- variable projections for these CRNs produce an ideal generated by a single polynomial of the requisite form, hence the CRN exhibits RPA. Notice that the three- variable reaction rate for \(x_i\) is not the generator of \(I_f \cap \mathbb{R}[x_1, x_j]\) in any of these examples (although it is obviously contained in \(I_f\) ). As we explained previously, the fact that a CRN contains a reaction rate of the form \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) is, in and of itself, irrelevant vis- à- vis the RPA capacity of the CRN (and hence, the claims of our Theorem 1). What matters is + +<--- Page Split ---> + +what actually generates the ideal \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) – i.e. the projection of \(I_{f}\) onto the two variables \(x_{i}\) and \(x_{j}\) (where one of these is RPA-capable, and one is not). The three CRNs discussed in the previous round of review, as well as the three new CRNs offered by the reviewer, all contain the reaction rate \(\frac{dx_{1}}{dt} = c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3}\) . But for the previous set of three CRNs (considered in the last review round), the relevant elimination ideal is \(< x_{2}x_{3} >\) , and as a consequence, those CRNs cannot exhibit RPA in \(x_{1}\) (or anything else). For the new set of CRNs, the relevant elimination ideal is \(< x_{1} - c_{1} / c_{2} >\) for the first and third examples, and \(< x_{1}^{2}(x_{1} - c_{1} / c_{2})>\) for the second example, and as a consequence, these CRNs do exhibit RPA at \(x_{1}\) , with setpoint \(c_{1} / c_{2}\) . + +We make some additional observations for each of the three new CRNs in turn below. As the reviewer notes, we had observed in our previous rebuttal that the two specific reactions originally proposed by the reviewer together have deficiency zero, and that the addition of the necessary closure reactions will not be able to increase this deficiency. As a consequence, that CRN could not exhibit RPA. In other words, the fact that those particular CRNs were not RPA capable was not tied to the specific choices of closure reactions that we provided as illustrative examples. Of course, if one begins with a different pair of reactions (i.e. not involving \(X_{4}\) and \(X_{5}\) ), as is the case for the first two new examples the reviewer provides, or adds in more than the needed closure reactions, as is the case for the third new example, then one can certainly increase deficiency, and thereby arrive at an RPA- capable set. But in this case, the RPA- capacity is tied inextricably to the altered structure arising from the different starting pair and/or the redundant closure reactions, with the attendant increase in deficiency associated with that altered structure, and is not due solely to the mere presence of the original pair (which appear to produce an apparent 'RPA polynomial' for \(\frac{dx_{1}}{dt}\) in all cases). We explain this point in more detail in our ensuing analysis. We apologise if we unwittingly side- tracked the discussion by raising the issue of the original pair being characterized by a deficiency of zero, and that adding in the necessary 'closure' reactions to allow us to work with that original pair cannot increase deficiency. The point we were really trying to emphasize was that the mere presence of \(\frac{dx_{1}}{dt} = c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3}\) in the rowspan of the system, even for cases where \(x_{2}x_{3}\) is a boundary variable, does not, in and of itself, imply RPA. Our Theorem 1 explains why this is the case. + +Again, the fundamental issue in all six CRN examples (the three here, as well as the three from the previous round of review) is that the reaction rate for \(x_{1}\) does not actually generate the two- variable elimination ideal for these CRNs. In general, CRNs for which one of the reaction equations is an 'apparent' RPA polynomial may or may not exhibit RPA. + +I start with a simpler version of this network with only three species (i.e. species \(X_{4}\) and \(X_{5}\) are absent) where I add inflow and outflow for species \(X_{2}\) and \(X_{3}\) . So the overall network becomes + +<--- Page Split ---> + +\[X_{2} + X_{3}\xrightarrow{c_{1}}X_{1},\quad X_{1} + X_{2} + X_{3}\xrightarrow{c_{2}}\emptyset,\quad \emptyset\xrightarrow{c_{3}}X_{2},\quad \emptyset\xrightarrow{c_{4}}X_{3}\qquad (0.3)\] + +This network has no boundary variables and so the variables are the same as species. It seems that this network will indeed show RPA for \(x_{1}\) with set- point \(c_{1} / c_{2}\) . In Figure 1 I plot the simulated dynamics (rescaled to have the set- point of \(x_{1}\) as 1) for three randomly chosen values of initial states and rate constants, and one can see that RPA holds. + +Our response: Here, the reviewer starts with a different version of the initial two reactions (rather than the two given in (0.2)), so this CRN can have a deficiency of one, even with only the minimum needed closure reactions. In any case, this CRN does indeed exhibit RPA because \(< \frac{dx_{1}}{dt}, \frac{dx_{2}}{dt}, \frac{dx_{3}}{dt} > \cap \mathbb{R}[x_{1}, x_{2}] = < x_{1} - \frac{c_{1}}{c_{2}} >\) . We provide our Singular code and output below so that the reviewer can verify (see \(G[1]\) ): + +Last login: Wed Dec 14 11:35:16 on ttys000 /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit (base) araujo@SEF- PA00144783 \\~ % /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit SINGULAR / Development A Computer Algebra System for Polynomial Computations / version 4.1.2 by: W. Decker, G.- M. Greuel, G. Pfister, H. Schoenemann \ \(Feb 2019 FB Mathematik der Universitaet, D- 67653 Kaiserslautern\) > ring R = (0, c1, c2, c3, c4, c5, c6), (x3, x2, x1), lp; \(>poly f1 = c1*x2*x3 - c2*x1*x2*x3;\) \(>poly f2 = c3 - c5*x2 - c1*x2*x3 - c2*x1*x2*x3;\) \(>p o l y f3 = c4 - c6*x3 - c1*x2*x3 - c2*x1*x2*x3;\) \(>ideal I = f1,f2,f3;\) \(>ideal GI = groebner(I);\) \(>GI;\) \(GI[1] = (c2*c3*c4)*x1 + (-c1*c3*c4)\) \(GI[2] = (2*c1*c5)*x2^2 + (-2*c1*c3 + 2*c1*c4 + c5*c6)*x2 + (-c3*c6)\) \(GI[3] = (c6)*x3 + (-c5)*x2 + (c3 - c4)\) + +Whereas (0.2) includes two additional species, \(X_{4}\) and \(X_{5}\) , each assigned to a different reaction in the pair, thereby guaranteeing the linear independence of the reactions once the requisite closure reactions are added, this property is no longer present in the new reaction set. When organized correctly into its linkage classes, this CRN has six complexes, two linkage classes and a rank of three, resulting in a deficiency of one. + +![PLACEHOLDER_58_0] + + +<--- Page Split ---> + +The CRN has just two non- terminal complexes, from which it follows that there is a polynomial of the form \(a_{1}x_{2}x_{3} - a_{2}x_{1}x_{2}x_{3}\) in the rowspan of the system - a feature that was already obvious from the form of \(\frac{dx_1}{dt}\) . But note that this fact, in and of itself, does not guarantee that RPA will obtain. The three examples considered in the previous round of review also contained \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) but did not exhibit RPA. Note that the Shinar- Feinberg theorem presupposes that the system admits a positive steady- state; it does not, in and of itself, provide any method for checking that this will indeed be the case. Note also that for the cases previously considered in which \(x_{2}x_{3}\) was a boundary variable, it was possible (in principle) for the generating RPA polynomial (referenced in our Theorem 1) to take the form \(c_1x_2x_3 - c_2x_1x_2x_3\) , since this is a two- variable polynomial in that case. (But again, since \(I_f \cap \mathbb{R}[x_1, x_2x_3] = < x_2x_3>\) for those examples, the CRNs could not actually exhibit RPA.) Here, where there are no boundary variables, it is not possible for the (generating) RPA polynomial to take the form \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) since this contains three variables. An RPA polynomial contains (at most) two variables. + +The reason this particular CRN has a deficiency of one is that a linear combination of the reactions involving \(c_2, c_3, c_4\) (in the second linkage class only) produces \(X_1 \to \emptyset\) , whereas a linear combination of the reactions involving \(c_1, c_3, c_4\) (involving the first linkage class, and thus involving the new pair of complexes \(X_2 + X_3\) and \(X_1\) ) produces \(\emptyset \to X_1\) . Thus, \(X_2\) and \(X_3\) regulate both the production and the degradation of \(X_1\) . This makes the CRN a balancer module, where \(X_2\) and \(X_3\) play the role of diverter species. Note that although the reaction involving \(c_5\) could be used in place of the reaction involving \(c_3\) in the argument above, these two reactions involve the same complexes (\(\emptyset\) and \(X_1\) ), so the 'redundancy' in the reactions does not result in an increase in deficiency (nor any distinct new cycles or feedforward actions). The same holds for using the reaction involving \(c_6\) in place of the reaction involving \(c_4\) . + +Next I modify this network to have the production of \(X_2\) and \(X_3\) catalysed by \(X_1\) . So the new network becomes + +\[X_2 + X_3\xrightarrow{c_1}X_1,\quad X_1 + X_2 + X_3\xrightarrow{c_2}\emptyset ,\] \[X_1\xrightarrow{c_3}X_1 + X_2,\quad X_1\xrightarrow{c_4}X_1 + X_3,\quad X_2\xrightarrow{c_5}\emptyset \mathrm{and} X_3\xrightarrow{c_6}\emptyset .\] + +This network also appears to be RPA as shown by the simulations in Figure 2. + +Our response: Yes, this CRN does indeed exhibit RPA because \(< \frac{dx_1}{dt}, \frac{dx_2}{dt}, \frac{dx_3}{dt} > \cap \mathbb{R}[x_1, x_2] = < x_1^2 \left(x_1 - \frac{c_1}{c_2}\right)>\) . Our Singular code and output are provided below for easy verification: + +<--- Page Split ---> + +Last login: Thu Dec 15 08:32:11 on console /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit (base) araujo@SEF- PA00144783 ~ % /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit SINGULAR + +A Computer Algebra System for Polynomial Computations / Development + +by: W. Decker, G.- M. Greuel, G. Pfister, H. Schoenemann 0< + +FB Mathematik der Universitaet, D- 67653 Kaiserslautern 1 + +> ring R = (0, c1, c2, c3, c4, c5, c6), (x3, x2, x1), lp; + +> poly f1 = c1*x2*x3 - c2*x1*x2*x3; + +> poly f2 = - c1*x2*x3 - c2*x1*x2*x3 + c3*x1 - c5*x2; + +> poly f3 = - c1*x2*x3 - c2*x1*x2*x3 + c4*x1 - c6*x3; + +> ideal I = f1, f2, f3; + +> ideal GI = groebner(I); + +> GI; + +GI[1]=(c2*c3*c4)*x1^3+(- c1*c3*c4)*x1^2 + +GI[2]=(c2*c5)*x2*x1+(- c1*c5)*x2+(- c2*c3)*x1^2+(- c1*c3)*x1 + +GI[3]=(2*c1*c5)*x2^2+(- 2*c1*c3+2*c1*c4)*x2*x1+(- c5*c6)*x2+(- c3*c6)*x1 + +GI[4]=(c6)*x3+(- c5)*x2+(- c3-c4)*x1 + +> + +Once again, this particular CRN does not actually contain (0.2) but a different pair of starting reactions, so its deficiency readily exceeds zero (unlike the three CRNs we considered in the previous round of review). When correctly organized into linkage classes, this CRN has eight complexes, two linkage classes, and a rank of three, giving a deficiency of three. The reason for the two extra units of deficiency in comparison with the previous case is that the reaction \(X_{2} \rightarrow \emptyset\) is replicated using a different set of complexes via the reaction \(X_{1} \rightarrow X_{1} + X_{2}\) (accounting for the first additional unit of deficiency), while the reaction \(X_{3} \rightarrow \emptyset\) is replicated using a different set of complexes via the reaction \(X_{1} \rightarrow X_{1} + X_{3}\) (accounting for the second additional unit of deficiency). + +![PLACEHOLDER_60_0] + + +Finally, I consider another variant of this network where we have species \(X_{4}\) and \(X_{5}\) that reversibly bind to each other to produce an inactive compound, and they catalyse the production of \(X_{2}\) and \(X_{3}\) respectively. Therefore the new network becomes + +\[X_{2} + X_{3}\xrightarrow{c_{1}}X_{1} + X_{4},\quad X_{1} + X_{2} + X_{3}\xrightarrow{c_{2}}X_{5},\quad X_{4}\xrightarrow{c_{3}}X_{4} + X_{2},\quad X_{5}\xrightarrow{c_{4}}X_{5} + X_{3}\] \[X_{2}\xrightarrow{c_{5}}\emptyset ,\quad X_{3}\xrightarrow{c_{6}}\emptyset ,\quad X_{4} + X_{5}\xrightarrow{c_{7}}\emptyset \mathrm{and}\quad \emptyset \xrightarrow{c_{8}}X_{4} + X_{5}.\qquad (0.5)\] + +<--- Page Split ---> + +This network also seems to be RPA, as shown in the simulations in Figure 3. + +Our response: Yes, for the same reason as the previous two examples, this CRN does indeed exhibit RPA. This particular CRN does actually employ (0.2), and the reviewer has discovered a clever way to separate the necessary closure reactions into three distinct steps, \(X_{4} \xrightarrow{c_{3}} X_{4} + X_{2}\) , \(X_{5} \xrightarrow{c_{4}} X_{5} + X_{3}\) and \(X_{4} + X_{5} \xrightarrow{c_{7}} \emptyset\) , giving a deficiency of one, which creates the needed parallel routes for the production/degradation of \(X_{1}\) as discussed in the previous two examples. The reactions involving \(c_{5}, c_{6}\) replicate the reactions involving \(c_{3}, c_{4}\) (respectively) using different sets of complexes, thereby increasing the deficiency from one to three. The reaction involving \(c_{8}\) replicates the reaction involving \(c_{7}\) using the same set of complexes, and therefore does not contribute to any further deficiency increases. Our Singular code and output is provided below: + +Last login: Thu Dec 15 12:11:13 on ttys000 /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit (base) araujo@SEF- PA00144783 \\~ % /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit + +A Computer Algebra System for Polynomial Computations / Development + +A Computer Algebra System for Polynomial Computations / version 4.1.2 + +by: W. Decker, G.- M. Greuel, G. Pfister, H. Schoenemann \ \(Feb 2019\) + +FB Mathematik der Universitaet, D- 67653 Kaiserslautern + +> ring R = (0, c1, c2, c3, c4, c5, c6, c7, c8), (x5, x4, x3, x2, x1), lp; + +> poly f1 = c1*x2*x3 - c2*x1*x2*x3; + +> poly f2 = - c1*x2*x3 - c2*x1*x2*x3 + c3*x4 - c5*x2; + +> poly f3 = - c1*x2*x3 - c2*x1*x2*x3 + c4*x5 - c6*x3; + +> poly f4 = c1*x2*x3 - c7*x4*x5 + c8; + +> poly f5 = c2*x1*x2*x3 - c7*x4*x5 + c8; + +> ideal I = f1, f2, f3, f4, f5; + +> ideal GI = groebner(I); + +> GI; + +GI[1]=(c2*c3*c4*c8)*x1+(-c1*c3*c4*c8) + +GI[2]=(4*c1^2*c7)*x3^2*x2^2+(2*c1*c6*c7)*x3^2*x2+(2*c1*c5*c7)*x3*x2^2+(-c1*c3*c4+c5*c6*c7)*x3*x2+(-c3*c4*c8) + +GI[3]=(c3)*x4+(-2*c1)*x3*x2+(-c5)*x2 + +GI[4]=(c4)*x5+(-c3)*x4+(-c6)*x3+(c5)*x2 + +> + +This CRN has eleven complexes, four linkage classes, a rank of four, and therefore a deficiency of three. Once again, the added deficiency arises from the additional replication of the 'needed' closure reactions employing different sets of complexes. + +![PLACEHOLDER_61_0] + + +<--- Page Split ---> + +These networks do not appear to satisfy the RPA characterisation given by this paper. Also consider Example 6.5.3 in [5] which does not seem to fit this result either. These counter- examples cast doubt on the correctness of the Kinetic Pairing Theorem on which the entire paper rests. + +Our response: None of these networks constitute counter- examples. All of these networks satisfy the RPA characterization given by our paper. Our Theorem 1 (the 'Two- Variable Kinetic Pairing Theorem') correctly identifies that the three examples suggested here by the reviewer will exhibit RPA at \(x_{1}\) , since a two- variable RPA polynomial generates the principal elimination ideal \(I_{f} \cap \mathbb{R}[x_{1}, x_{j}]\) . In addition, our Theorem 1 correctly identifies that the three similar examples considered in the previous round of review cannot exhibit RPA since the generator of the relevant elimination ideal is not an RPA polynomial (despite the fact that one of the rate equations has the apparent form of an RPA polynomial). + +The reviewer mentions Example 6.5.3 in [5], which is the following: + +Example 6.5.3. Consider the following polynomials in two variables: + +\[f_{1}(\mathbf{x}) = x_{1}[(x_{1} - 1)^{2} + (x_{2} - 2)^{2}]\] \[f_{2}(\mathbf{x}) = x_{2}[(x_{1} - 1)^{2} + (x_{2} - 2)^{2}].\] + +Notice that these polynomials also have the shape: \(f_{i} = p_{i} - x_{i}q_{i}, i = 1,2\) , where all the coefficients of \(p_{i}, q_{i}\) are non negative. As we mentioned before, it is possible to find a reaction network modeled with mass- action kinetics, such that the associated system is \(dx_{1} / dt = f_{1}, dx_{2} / dt = f_{2}\) . + +It is easy to see in this example that the system shows ACR for both variables, since the only positive solution is \(x_{1} = 1, x_{2} = 2\) . However, we will ignore this obvious fact and use a procedure inspired by our previous discussion. All the computations here can be checked using any computer algebra system, such as Macaulay2 [61] and Singular [35]. + +Although this example claims that 'the system shows ACR for both variables', this system does not describe an RPA- capable (or ACR- capable) CRN since there are no parameters, and no possible 'input' or disturbance, in this model. So there's really nothing for the network to adapt to here. Thus, there is no non- RPA- capable variable; both of the variables appear to exhibit 'RPA', since the system's steady- state is a single fixed point in \(\mathbb{R}^{2}\) (and again, that's not really what RPA is). The special type of RPA known as ACR normally pertains to CRNs where there are mass conservation relationships linking the molecular concentrations, such that the 'total' concentration of a particular type/class of molecule can be varied (by altering the initial conditions of the system, for instance). In any case, in order for a CRN to adapt to any kind of disturbance, there must always be at least one non- RPA- capable variable in the CRN (otherwise how can there possibly be any kind of 'internal model', or any network components that 'offset' the disturbance?) In any case, the definition of RPA adopted in our work (as general as this is!) does not accommodate 'non- adaptive' cases like this where there's simply nothing for the network to adapt to. We must respectfully point out that the author of [5] has been a little hasty in + +<--- Page Split ---> + +describing this as an ACR- capable network simply because there is a single positive solution \(x_{1} = 1\) , \(x_{2} = 2\) . + +In addition, the author of Example 6.5.3 claims that 'it is possible to find a reaction network modeled with mass- action kinetics, such that the associated system is \(dx_{1} / dt = f_{1}\) , \(dx_{2} / dt = f_{2}\) '. The condition being referred to here \((f_{i} = p_{i} - x_{i}q_{i}\) , with all coefficients of \(p_{i}\) , \(q_{i}\) non- negative) is the so- called Hungarian Lemma, which states (roughly) that for a polynomial dynamical system to be inducible by a CRN under the mass- action assumption, any term in a rate equation preceded by a negative sign must be divisible by the subject of the rate equation. In other words, for the \(dx_{1} / dt\) equation, each term preceded by a negative sign must include \(x_{1}\) as a factor. But the Hungarian Lemma, strictly speaking, pertains to CRNs in which each chemical reaction occurs at a rate (normally noted as a kinetic parameter superposed on the associated reaction arrow), that is independent of the corresponding rates of all other reactions. Because Example 6.5.3 is not suitably parametrized in this sense, there is necessarily an ambiguity introduced in terms of which specific reactions might produce the various terms of the equations. In other words, there is not a one- to- one correspondence between reaction rates and putative CRN structure, as predicted by the Hungarian Lemma under the specified conditions. The rate \(f_{1}\) , for example, contains the term \(- 2x_{1}^{2}\) ; this could in principle arise from either \(2X_{1} \xrightarrow{2} X_{1}\) or from \(2X_{1} \xrightarrow{1} \emptyset\) . From this point of view, we should not really even accept the two given equations as a valid CRN model. In any case, on both counts (not being ACR- capable, and not being a valid CRN model), this Example simply does not constitute any sort of counterexample to the claims of our paper. + +We do very much appreciate the lengths to which the reviewer has gone in order to make absolutely certain that all our claims are \(100\%\) accurate and watertight. But we do hope the reviewer is now willing to accept the correctness of our assertions. Two variables is always the right number of variables for assessing RPA capacity, the mathematical reason for which is given in our proof to Theorem 1. For all RPA- capable CRNs, the geometric projection of their rate equations onto two variables is generated by a single polynomial of the form \(\rho = g(x_{i}, x_{j})(x_{i} - c)\) . Any CRN that does not satisfy this property cannot exhibit RPA - no exceptions, un point c'est tout. + +3. The set-point may not be a rational function of parameters: In many places in the main paper and the supplement, the system's set-point is said to be a rational function of biochemical parameters. While this holds for most examples, consider the following birth death network + +\[\emptyset \xrightarrow{c_{1}} X_{1} \quad \text{and} \quad 2X_{1} \xrightarrow{c_{1}} \emptyset .\] + +The dynamics is given by + +\[\frac{dx_{1}}{dt} = c_{1} - 2c_{2}x_{1}^{2}\] + +<--- Page Split ---> + +and so the set- point + +\[c = \sqrt{\frac{c_1}{2c_2}}\] + +is not a rational function of \(c_1\) and \(c_2\) ? For more examples, see Examples 2.11 and 2.12 in [3]. Please revise as necessary. + +Our response: We sincerely thank the reviewer once again for such a meticulous review of our work and for such careful attention to every possible technical detail. In this particular case, \(x_1^2\) is a boundary variable since \(x_1\) only appears in the CRN rate equations in the form of the monomial \(x_1^2\) . Therefore, the setpoint for this variable is \(c_1 / 2c_2\) , which is a rational function of parameters, as expected. With boundary variables accounted for in this way, we can be assured that the setpoint of any RPA- capable variable will be a rational function of parameters, since we are working with a commutative ring structure (multivariate polynomials) with coefficients taken over a field (real numbers, with all coefficients considered symbolically). We allow only addition and additive inverses (subtraction) and multiplication without inverses (i.e. no division) of the ring elements; the coefficients admit addition/subtraction as well as multiplication/division (due to the field structure). No radicals may be taken. + +But we do completely appreciate the reviewer's point, and that the boundary variable technicality might be lost on some readers (despite the fact that we do highlight the concept quite prominently). The setpoint of the species concentration may indeed be an algebraic (rather than a rational) function of parameters in these special cases. + +Examples 2.11 and 2.12 in [3] also contain a species setpoint that is an \(n\) - th root of a rational function of parameters simply because the species in question contributes to an RPA- capable boundary variable in each case. In Example 2.11 - a continuation of Example \(2.3 - x_{A}\) appears only in the form \(x_{A}^{n}\) . Likewise, in Example 2.12 - a continuation of Example \(2.8 - x_{B}\) appears only in the form \(x_{B}^{n}\) . + +We now add the following clarification of this matter to Remark 3 after the statement and proof to Theorem 1 (immediately following Definition 3, in Section S1.5 in our SI): + +<--- Page Split ---> + +3. If the setpoint, \(c\) , depends only on biochemical rate constants and not on total concentrations \((X_{k t o t})\) or production/degradation rates of any of the molecules, the system also has the capacity for ACR in the variable \(x_{i}\) . + +Moreover, although we note in the statement and proof of Theorem 1 that \(c\) is a rational function of biochemical parameters, in the special case of an RPA variable that is a boundary variable, the setpoint of the corresponding RPA species may be an algebraic, rather than a rational, function of parameters. Consider, for instance, the one- species system: \(\frac{d x}{d t} = c_{1} - 2c_{2}x^{2}\) ; here \(x\) appears only in the form of the monomial \(x^{2}\) , which is therefore a boundary variable. The 'setpoint' for the boundary variable, \(x^{2}\) , is thus \(\frac{c_{1}}{2c_{2}} - a\) rational function of parameters - while the setpoint for the species \(x\) is \(\sqrt{\frac{c_{1}}{2c_{2}}}\) . + +We now also refer to this Remark in the main paper (at the end of the paragraph immediately following Eq. 6), where it is noted that \(c\) is a rational function of parameters. + +4. Questions on the Buchberger's Algorithm: In the previous review round, I had raised the following issue regarding Buchberger's Algorithm + +The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima- facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In any case, checking for nontermination of a method is impractical. + +In response the authors state in their rebuttal letter that the termination is guaranteed because "all ideals of a polynomial ring (or any Noetherian ring, for that matter) are finitely generated - a result of central importance in algebraic geometry, formalized by the Hilbert Basis Theorem". While I agree that termination is guaranteed, I must point out that the reason for my confusion and for raising this termination issue is the following excerpt from the previous version of the Supplement (submitted in round 1): + +Failure of the Buchberger (or other Gröbner basis- computing) algorithm to terminate could thus be adduced as prima facie evidence that the CRN under consideration does not, in fact, have the capacity for RPA. + +It seems that in this statement that authors meant "terminate in practical time". I understand that due to the "almost linear" nature of coordinate change, this algorithm would work well for RPA networks. However, does the final RPA polynomial produced by the method depend on the monomial ordering or other choices made by the method? + +Our response: No, whether or not the elimination ideal referenced in our Theorem 1 is generated by an RPA polynomial is completely unrelated to the choice of monomial ordering. The form of the 'final RPA polynomial' is also unrelated to the + +<--- Page Split ---> + +choice of monomial ordering: it is the generator of a principal ideal. But it's important to bear in mind that only monomial orderings that can achieve the desired elimination are suitable for testing this property (i.e. an elimination ordering). One cannot apply some completely arbitrary monomial ordering and expect to obtain (any) elimination ideal. We do refer to the highly accessible text by Cox et al. [7] in both our main text and in our SI for the benefit of any reader who wants to understand these technicalities fully. More importantly, we provide sample code at the end of our SI, with a discussion of a particularly efficient elimination ordering (using command '\((dp(n - 2), dp(2))\) ' - see Section S5.1), should this be required for large and complicated CRNs. + +Note that the reviewer's quotation from our original submission ('Failure of the Buchberger (or other Gröbner basis- computing) algorithm to terminate could thus be adduced as prima facie evidence that the CRN under consideration does not, in fact, have the capacity for RPA.') was removed from our revised submission, and is no longer included in our SI. + +More importantly, if a network is not RPA, how many steps would the method need to confirm this non- RPA property? Such practical considerations must be discussed in the main text, and they are crucial for applying these ideas for characterising RPA in high- dimensional networks. + +Our response: Of course there is no possible way to be specific about the number of steps that would be required to confirm the inability of some general (non- RPA- capable) CRN to exhibit RPA. If the algorithm is being applied completely mindlessly to a large and complicated CRN, with a random choice of two variables, then we quite agree that if the algorithm seems to be taking an inordinately long time to terminate, then the RPA- capacity or otherwise of the CRN is entirely unclear. + +Now, the algorithm we present can be applied mindlessly, without any real understanding of the mathematical principles we discuss at length in our paper, and if the CRN under consideration is indeed RPA- capable, then such a completely mindless approach will be able to provide a confirmation of RPA capacity, along with an explicit identification of the setpoint. If the sole contribution of our paper were the development of an algorithmic test for RPA capacity, the reviewer would be quite correct to point out that this algorithm cannot easily distinguish between non- RPA- capable CRNs, and extremely large and complicated RPA- capable CRNs that could require a significant (and indeterminate) time- frame for the execution of the algorithm. But it's important to recognize that if the algorithm seems to be taking a long time to terminate, then our paper presents analytical approaches to check whether the CRN at hand has any potential for RPA capacity through a decomposition into independent subnetworks (wherever possible), and an analysis of deficiency in these subnetworks. + +As an example, consider the CRN for the mammalian enzyme 6- phosphofructo- 2- kinase/fructose- 2,6- bisphosphatase (PFK- 2/FBPase- 2), which operates bifunctionally to both activate and inactivate fructose- 2,6- bisphosphate (F2,6BP), as discussed by + +<--- Page Split ---> + +Karp et al. [6] in terms of the potential RPA- capacity of F2,6BP. As we will show, this CRN cannot exhibit RPA. The CRN (presented in [6]), organized into its linkage classes, with \(X_{1} \equiv E\) , \(X_{2} \equiv E\) - ATP, \(X_{3} \equiv F6P\) , \(X_{4} \equiv E\) - ATP- F6P, \(X_{5} \equiv F2,6BP\) , \(X_{6} \equiv E\) - F2,6BP, \(X_{7} \equiv E\) - ATP- F2,6BP, and \(X_{8} \equiv E\) - ATP- F6P- F2,6BP, is given by + +![PLACEHOLDER_67_0] + + +Interestingly, Karp et al. [6] claim that the Gröbner basis implementation in Mathematica does not terminate for this CRN, although they give no information as to how they've ordered their variables, or which monomial ordering they chose (although they almost certainly would have used a lexicographic monomial ordering since, prior to our work, it was not known that an elimination ideal involving just two variables is all that's required to test RPA capacity; the lexicographic ordering is generally an extremely computationally expensive elimination ordering since it produces a full complement of elimination ideals, in vast excess of what's actually required to solve the RPA problem). We used Singular and used an efficient block monomial ordering (to project onto two variables) that allowed the algorithm to terminate in several seconds, from which we could confirm that this particular CRN is not RPA- capable (at \(X_{5} \equiv F2,6BP\) or otherwise). We provide our Singular code below: + +<--- Page Split ---> + +way of general advice to the reader, if one allows the algorithm to run for several hours (e.g. overnight) using the most efficient implementation possible (as described above) and it still hasn't terminated after this period, then one should consider undertaking some additional analysis of the CRN (as we provide below) through (i) first decomposing into algebraically- independent subnetworks (if possible), and then (ii) considering where deficiency arises within these independent subnetworks, and whether the deficiency corresponds to the presence of parallel pathways and/or feedback cycles, as required for RPA. Consider also that one should have a reason to suspect that a CRN exhibits RPA. It is clear from the detailed principles we develop here, as well as our previous topological analysis of RPA- capable network architectures at the network macroscale [12], that RPA- capable networks are actually very 'special', with very specific structural requirements, and are therefore extremely rare in the space of all possible networks. If one has a completely arbitrary network, with no particular reason to suspect it might be able to exhibit this special type of robustness, then it almost certainly doesn't. In the specific case we analyse here, the CRN involves a bifunctional enzyme \((X_{1})\) which both upregulates and downregulates its target protein \((X_{5})\) ; a priori, this fact presents the possibility that this CRN might have the capacity for RPA (even if, in the final analysis, it actually doesn't). + +Now, recall that deficiency is a measure of the linear independence of the reactions of a CRN, relative to their distribution into the connected components (linkage classes) of a graph. In particular, the deficiency of a CRN is increased by one for every instance of a reaction being 'replicated' elsewhere in the network via a different set of complexes. Reversible reactions, for example, which duplicate a single reaction using the same pair of complexes, do not of themselves contribute to any deficiency increases. Recall also that, for an RPA- capable CRN, these replicated reactions must constitute either (i) a collection of parallel pathways, where the production/degradation (or interconversion between activation states) of the RPA- molecule must be orchestrated via different collections of reactions (involving different sets of complexes), or (ii) a cycle in the production/degradation (or interconversion between activation states) of a non- RPA- molecule (as regulated by the RPA- capable molecule), where the individual components of the cycle must be orchestrated via different collections of reactions (involving different sets of complexes). There's simply no other way for the right linear invariants to emerge! We highlight and discuss these principles repeatedly throughout the analysis of the worked examples in our SI. + +Returning now to the non- RPA- capable CRN at hand: Note that the CRN for PFK- 2/FBPhase- 2 has a deficiency of 5, comprising 14 complexes, 3 linkage classes and a rank of 6. By noting which reactions are 'replicated' (using different sets of complexes) to yield each of these 5 units of deficiency, it is straightforward to see that this CRN does not have the right structure to impose RPA on \(X_{5}\) (or any other molecule). First, we note that the eight species of the model are all intricately interconnected in the nineteen reactions of the CRN, such that no decomposition into independent subsets is possible (see discussion of this point in S1.3 of our Supplementary Information). Moreover, in assessing the linear independence of the + +<--- Page Split ---> + +require a long (and potentially indeterminate) timeframe for the algorithm to terminate. We provide a fully analysed example of a non- RPA- capable CRN, to illustrate these principles, in SI Section S4.5. + +We have also added in an entire new subsection to our SI (Section S4.5), entitled 'A note on non- RPA- capable CRNs and computational challenges', in which we summarise the commentary given above, and provide a full analysis of the PFK- 2/FBPase- 2 CRN (from Karp et al. [6]) as presented above. + +5. Connection of examples to existing works: The authors start the Results section with "two simple examples that have eluded all previous systematic methods to detect RPA". Please specify which systematic methods are being referred to here. + +Our response: We now add in a number of key references at this point in our text to highlight which systematic methods are being referred to. In particular, the Shinar- Feinberg theorem provides a systematic way to determine ACR for deficiency- one networks containing two complexes that differ in a single species, but is silent on all CRNs with deficiency greater than one (and also cannot detect ACR in deficiency- one CRNs that do not contain two complexes that differ in a single species, such as the CRN we consider in Figure 8a in our paper). Cappelletti et al. provide a systematic method for detecting RPA, and a (single linear) integral controller, but is only applicable if an RPA polynomial is contained in the rowspan of the system. Even exceedingly simple CRNs (like the one we consider as Example 1 in our S3.1 of our SI, or the even simpler version we consider in Figure 8a of the main paper) elude this method if there is no RPA polynomial in the system's rowspan. Eloundou- Mbebi et al. [13] present a necessary condition for RPA in CRNs of any deficiency, and thereby provide a systematic test that is generally able to identify some CRN species that certainly cannot exhibit RPA (which can thereby be excluded from further analysis). But this method is silent on whether any species that is not excluded by this test actually does exhibit RPA. In fact, all nine species in the deficiency- two Shinar- Feinberg EnvZ- OmpR model (considered in Figure 3 in our paper) satisfy the necessary condition proposed by Eloundou- Mbebi et al. [13], even though only one of these (pOmpR) actually does exhibit RPA. Gupta and Khammash [2] provide a universal characterization of maxRPA networks, but this approach is not applicable to any RPA- capable CRN that does not exhibit maxRPA. We discuss the universality of our approach in comparison with previous work in our Discussion section. + +Of course, there are many other approaches to the analysis of CRNs, but none of these are 'systematic' approaches to the study of RPA (or ACR) in the sense that they can be applied to any CRN (of any deficiency, whether there is an RPA in the rowspan or not), without the need for guesses, or prior insight, and provide definitive information on the capacity for RPA and on the mechanisms for implementing it. The method for identifying 'complex linear invariants' developed by Karp et al. [6] can detect RPA in the deficiency- two Shinar- Feinberg EnvZ- OmpR model, but this is not a systematic method for RPA detection since those authors had to "guess" which complexes would end up in the invariants we identify via our + +<--- Page Split ---> + +systematic approach. In fact, those authors state in Section 2.6 of their paper, referring to the above- noted example, in addition to another example they considered: 'The two examples discussed above had already been analysed by other methods, so we had an idea of which invariants to expect and which subset of complexes to consider. For a new network such information may not be available, so how can non- trivial type 1 complex- linear invariants (simply, "invariants") be found? The automatic procedure outlined in Section 2.2 can be used in principle but this becomes computationally infeasible when there are many complexes. We have found the following systematic procedure to be helpful on several examples'. The authors go on to provide some practical suggestions to the reader on computing useful 'complex linear invariants', which do not constitute a truly systematic procedure for rigorous application to general CRNs. Moreover, the 'automatic procedure outlined in Section 2.2' mentioned by these authors refers to computing a Gröbner basis for the system. But again, those authors did not account for algebro- geometric properties of RPA- capable CRNs that we identify in our paper, including the requirement for projection onto two variables only; thus, as a consequence, this systematic computation is now more widely applicable to CRNs (for the determination of RPA capacity, at least) than previously considered (where a lexicographic monomial ordering was necessary, producing a full collection of elimination ideals, since it was not previously recognized that only a specific elimination ideal is actually required to detect RPA). We emphasize again here the fact that these authors attempted to compute a Gröbner basis for a CRN involving the mammalian bifunctional enzyme PFK- 2/FBPase- 2, and found that their algorithm did not terminate; by contrast, by exploiting the use of a highly efficient elimination ordering (a consequence of our Theorem 1), we were able to compute a suitable Gröbner basis in under three minutes and thereby confirm that the CRN in question cannot exhibit RPA. + +Also, in the example on Figure 2 it should be mentioned that \(X_{3}\) is maxRPA and it can be checked from the characterisation result in [2]. Secondly since there is the reaction + +\[X_{3} + X_{2}\xrightarrow{k_{6}}X_{2}\] + +which does not involve \(X_{1}\) I do not understand why the term \(k_{6}X_{2}X_{3}\) does not enter the expression for + +\[\frac{d(X_1 - X_2)}{dt}\] + +in Figure 2C. Please check. + +Our response: We analyze the example in Figure 2 in careful detail in our Supplementary Information, where we provide a full discussion – first in Section S1.6 where we undertake a full algebro- geometric analysis to illustrate the consequences of Theorem 1 (the two- variable kinetic pairing theorem), then again in Section S4.4.2 where we show that the CRN's set of eight reactions can be partitioned into two algebraically- independent subnetworks, and describe how various polynomial invariants may be determined within these subsets using an analysis of deficiency. + +<--- Page Split ---> + +We also provide a complete Singular code for this example in Section S5.2, where we consider several different two- variable projections, and also show how the single concatenating monomial for this CRN can be computed automatically using the lift command in Singular. + +As indicated in our Singular code (SI Section S5.2), the CRN depicted in Figure 2 of our paper (and analysed from a number of different viewpoints throughout our SI) induces the following set of four reaction equations under the law of mass- action: + +\[\frac{dX_1}{dt} = k_1R - k_2X_1X_2,\] \[\frac{dX_2}{dt} = k_3 - k_2X_1X_2 + k_4X_3,\] \[\frac{dX_3}{dt} = k_5 - k_6X_2X_3 - k_7O_1X_3,\] \[\frac{dO_1}{dt} = k_7O_1X_3 - k_8O_1.\] + +From this it follows that + +\[\frac{d}{dt} (X_1 - X_2) = k_1R - k_3 - k_4X_3\] + +We are unsure on the basis of the reviewer's comment why he/she feels the term \(k_6X_2X_3\) should be present in the expression for \(d(X_1 - X_2) / dt\) . We have carefully checked this example (and all other examples in our paper) and can assure the reviewer that these reaction forms, and the expression for \(d(X_1 - X_2) / dt\) in particular, are all completely correct. + +On the matter of \(X_3\) being maxRPA, although this is certainly true, this is not quite the point of Figure 2, which is attempting to provide a representation of the general properties of all CRNs that act on Opposer Module (which could contain any number of opposer 'nodes', in principle, organized into an opposing set structure). For this simple example, a two- node opposing set is shown, where the two opposer nodes are as simple as possible (hence the distal opposer is indeed maxRPA). Since \(X_3\) and \(X_2\) regulate each other (and thereby form a feedback loop), and since \(X_2\) contributes to a different opposer node (regulated by \(R\) , upon which RPA is ultimately conferred), one cannot generally consider the reactions involving \(O_1\) and \(X_3\) in isolation before ensuring that the CRN as a whole has been correctly decomposed into algebraically independent subnetworks. We undertake this analysis carefully in Section S4.4.2. As shown, this allows us to determine the correct algebraic invariant (involving \(O_1\) and \(X_3\) ) to be 'passed' to the other opposer node (involving \(R\) ). + +If the term \(k_6X_2X_3\) is present then it cannot be eliminated with the concatenating monomial \(O_1\) . On the other hand, if this reaction is removed (i.e. this term is absent) then the overall network simply becomes a trivial RPA network where the output of one RPA network (i.e. the network comprising \(X_3 - O_1\) ) is passed as an input to another RPA network (i.e. the antithetic network with \(X_1 - X_2\) ). It is straightforward that connecting RPA networks in + +<--- Page Split ---> + +series (with catalytic reactions) would still result in a RPA network. Such examples are not appropriate for demonstrating the novel results in this paper. + +Our response: We offer several additional points of clarification regarding the reaction occurring at rate \(k_6\) , which contributes the term \(k_6 X_2 X_3\) to the rate equations, and the absolute necessity of including this reaction in order to confer RPA on the CRN (including the entire 'embedded network'). + +First, regarding the elimination of \(k_6 X_2 X_3\) , and the identity of the requisite concatenating monomial, we'd like to point out that the four mass- action equations corresponding to this CRN (noted above in our previous comment) can be analysed systematically in Singular, from which the concatenating monomial can be computed automatically. This is explained in detail, including the use of the Singular command lift (which is used to identify the concatenating monomial) in our analysis of the Singular code at the end of Section S5.2. + +Second, we cannot remove the reaction \(X_3 + X_2 \xrightarrow{k_6} X_2\) as it is necessary for RPA in the "full" (i.e. embedded) network if the molecule \(O_1\) is responsible for regulating the embedded network, as indicated in Figure 2(a,d) The reviewer points out that "if this reaction is removed ... then the overall network simply becomes a trivial RPA network where the output of one RPA network (i.e. the network comprising \(X_3 - O_1\) ) is passed as an input to another RPA network (i.e. the antithetic network with \(X_1 - X_2\) ). It is straightforward that connecting RPA networks in series (with catalytic reactions) would still result in an RPA network." This is not actually true if \(O_1\) is responsible for regulating the embedded network, as we will explain below. But if, instead, \(X_2\) is responsible for regulating the embedded network, then the reviewer is entirely correct. In this latter case, and with the reaction \(X_3 + X_2 \xrightarrow{k_6} X_2\) removed, the reactions involving \(O_1\) and \(X_3\) are completely isolated from any disturbances to the embedded network (i.e. there is no 'signal detection' in these reactions), and can therefore be considered at their steady- state \((X_3 = k_8 / k_7, O_1 = k_5 / k_8)\) . The controller mechanism thereby reduces to the well- known antithetic- integral controller structure, with \(d(X_1 - X_2) / dt = k_1 R - k_{\alpha}\) , where \(k_{\alpha} = k_3 + k_4 k_8 / k_7\) . This constitutes a single opposer node, obtained via a single linear coordinate change. Nevertheless, it is clear that much more complicated opposer mechanisms could arise, and that a single opposer node is insufficient to characterize the space of all possible Opposer modules orchestrated by CRNs. Note also that the molecule \(O_1\) has a fixed concentration \((k_5 / k_8)\) in the scenario just considered; thus, if \(O_1\) were to regulate the embedded network (rather than \(X_2\) ), then RPA would not be possible at \(R\) since the antithetic controller would no longer be able to regulate the embedded network via a feedback loop. It's important to recognize that what we are actually analyzing in Figure 2 is just the controller part of the overall network. Considered in isolation, with \(R\) (the 'sensor' molecule from the 'embedded network') as the input, the network will not actually exhibit RPA at \(R\) unless the CRN is embedded into the requisite feedback structure, as indicated in Figure 2(a,d). (We do discuss the distinction between being RPA capable and exhibiting RPA in SI Section S1.5 - see Definition 3). + +<--- Page Split ---> + +We make it clear in the main text that we consider \(X_{3}\) to be a network protein, which can therefore be affected in some way by disturbances to the embedded network. + +This is possible due to the inclusion of the reaction \(X_{3} + X_{2} \xrightarrow{k_{6}} X_{2}\) , whereby the molecule \(X_{2}\) downregulates the molecule \(X_{3}\) ; this reaction permits a controller structure in which (in contrast to the scenario considered above) \(O_{1}\) is not RPA- capable, (unlike \(X_{3}\) , which is RPA- capable either way) and is thereby able to provide the necessary 'actuation' to the embedded network. The resulting CRN architecture, corresponds to what we previously described [12] as a two- node opposing set. The architecture of an opposing set consists of a collection of interlinked feedback loops, embedded into the feedback portion of an overarching feedback loop into which the 'controlled' system is embedded. Our current paper now makes clear why the interlinking of feedback loops is required in opposing sets (which was not entirely clear from our prior topological analysis [12]): signal transfer from the 'distal' opposer to the 'proximal' opposer (see Figure S12 in our Supplementary Information) is required for the passing of invariants, using concatenating monomials as needed; signal transfer from the proximal opposer to the distal opposer is necessary to embed these interactions in a feedback loop. + +The second example in Figure 3 seems to be taken straight from [4] (see Fig. 2). This should be clearly stated when the example is being introduced in the main text and also in the caption of Figure 3. Also mention that the linear invariants shown in Fig. 3 can be deduced from the approach in [4] (this is stated in passing in the conclusion but it should be stated more prominently when the example is being discussed.) + +Our response: No, we most assuredly did not just take our example in Figure 3 straight from [4]. This example was considered by Shinar and Feinberg in the Supplementary Materials to their seminal paper in Science [10], and we refer to this fact in- text in our discussion of Figure 3. We now add in an additional reference to this fact in our caption to the Figure, to ensure that this is absolutely clear. Perez- Millan et al. [4] also discuss the fact that this example is taken from the SM of Shinar and Feinberg's paper. We are wondering if the reviewer might actually mean Karp et al. [6] here? In any case, Karp et al. [6] also take the example from the SM of Shinar and Feinberg's paper, and those authors also make it clear that the Shinar- Feinberg paper is the source of the example. This deficiency- two model of the EnvZ- OmpR motif (due to Shinar/Feinberg) has been extensively discussed in the literature (including by [4] and [6], who have also analysed this model using different theoretical viewpoints from the one we consider here). Neither of those prior viewpoints provides a clear and definitive way to connect the properties of this particular example to the properties of all possible RPA- capable CRNs, however. More generally, it has been a subject of tremendous interest to discover robust and systematic ways to handle ACR/RPA in CRNs of deficiency greater than one. + +We're not quite so sure that the two linear invariants can be deduced straightforwardly from the approach in [4]. The connector invariant actually involves three terms, not two, so cannot arise from the theory of toric ideals. Again, we + +<--- Page Split ---> + +suspect the reviewer might be referring to the approach by Karp et al. [6]. While it is certainly true that Karp et al. [6] were able to identify the linear invariants relevant to Figure 3, this was only possible once it was clear which complexes/monomials are involved in these invariants (on the basis of the solution originally obtained by Shinar and Feinberg [10] through manual substitution, and possibly also through the analysis of the CRN undertaken by [4], since both papers [4] and [6] have authors in common). But more importantly, it is entirely unclear from the invariants computed by Karp et al. [6] how this solution relates to the complete solution space of all RPA- capable CRNs! This is the fundamental idea we are attempting to communicate through these simple examples in Figures 2 and 3. And again, we stand by our claim that prior to our work, there has been no systematic way (not involving 'guesses' or Ansätze, or prior analysis via other methods) to analyse general CRNs, of arbitrary deficiency, for which an RPA polynomial is not contained in the rowspan of the system. + +6. Many claims without proofs in the Supplement: The Supplement has been considerably revised, but still many arguments are unclear because proper proofs have not been provided or referenced: + +- Why should eq. (8) hold when eq. (9) holds? Can the networks always be partitioned this way? Please explain. + +Our response: We have scrutinized our exposition in Section S1.3 of our SI, and agree with the reviewer that Eq. (8) is not guaranteed to hold when Eq. (9) holds. Unlike the rest of the material in this section, this specific detail was not actually part of Martin Feinberg's treatment in Appendix 6.A of his text. We have now removed this detail from our SI, as it does not follow from the preceding results. In many of the examples we analyse in our paper, the deficiency does partition into the same subsets obtained from a partition of CRN rank; but this might not obtain in general. We have carefully worked through our entire manuscript and SI to ensure that our discussion of deficiency is accurate throughout (and does not make use of what was formerly Eq. (8)). We do thank the reviewer once again for such a meticulous review of every technical detail in our paper. + +- On page 21 in the Supplement it states that: + +Since a perturbation to the CRN that alters the steady state of \(x_{j}\) will also alter the steady- states of other non- RPA capable variables (eg. \(x_{m}\) ), If \(\mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) , and that are not contained in \(I_{f} \cap I_{p}\) . + +Why should such a perturbation always exist? + +<--- Page Split ---> + +Our response: When we say perturbation here, we are simply referring to a disturbance that the CRN is able to 'reject', thereby exhibiting RPA in one or more variables. It's really only meaningful to talk about RPA in the context of a CRN subjected to some sort of disturbance which alters the steady- state of the system. If the CRN is not subjected to any disturbance at all, the CRN can only exhibit a 'trivial' form of RPA (since nothing in the network can ever change). + +If the reviewer is querying why there should always be at least one variable that is non- RPA- capable, then we emphasize again that this is a key component of RPA. If all variables in the network are 'fixed' at steady- state, and can never be altered by any disturbance, then the network is not able to adapt to disturbances (and there can be no 'internal model', which recapitulates the disturbance). + +Of course, special cases of CRNs could exist with only one non- RPA- capable variable, rather than two or more, in which case the statement above vacuously holds (ex falso quodlibet). In any event, the selection of variables taken for the projection consists of one non- RPA- capable variable, in addition to the putative RPA- capable variable. + +- Also on page 21 in the Supplement it says that + +The set \(\bar{x}\) now contains two independent (uncoupled) variables in the sense that a perturbation to the CRN that alters the steady- state of one of the variables does not affect the steady- state of the other. + +Why does this hold? Please elaborate. + +Our response: Here we are referring to the fact that \(\bar{x}\) now contains two variables - one RPA- capable and one non- RPA- capable. The two variables are ipso facto uncoupled since a disturbance to the system that alters the steady- state of the non- RPA- variable necessarily has no effect on the steady- state of the RPA- variable (whose setpoint is independent of the disturbance). + +- In general, in the proof of the Kinetic Pairing Theorem the authors work over the ring of polynomials over species-variables \(x_1, \ldots , x_n\). Shouldn't the system parameters (i.e. rate constants) be included in this ring, as they would appear in the RPA polynomial? This inclusion of parameters is there in the Singular code but not in the proof. However simply adding the parameters in the ring is not sufficient as the n-th roots of the parameter would be added, as the examples mentioned in point 3 show. + +Our response: In general, the ring of interest in these problems is the ring of polynomials in \(n\) variables, with real- valued coefficients - i.e. \(\mathbb{R}[x_1, \ldots , x_n]\). In this case, since we want to handle all coefficients (parameters) symbolically, we adjoin the coefficients to the ring with the algebraic structure of a fraction field. Notice in our Singular code that we declare two sets, each enclosed by round brackets (). The first of these, which declares the symbolic parameters, begins with a zero, which declares the characteristic of the field. Characteristic zero fields include the set of + +<--- Page Split ---> + +real numbers, but also the rationals (including fraction fields). This is a standard way to handle symbolic coefficients in algebro- geometric computations of this type. Since these coefficients come from a field, we can apply all field operations (including division/multiplicative inverses) to these during the execution of any algorithms. By contrast, monomials/polynomials can only be added/subtracted and multiplied (no division) since these are defined to be elements of a ring. + +Of course, if one particularly wants to define a parameter \(k\) to be a variable of the model for analytical purposes, one can certainly make this choice if desired, and consider the ring \(\mathbb{R}[x_1, \ldots , x_n, k]\) . This allows the ring to incorporate \(k\) within the power products (monomials), instead of interpreting it as a coefficient in the field over which the ring is defined. This could be useful if one particularly wanted to project the system onto \(k\) (as the non- RPA- capable variable) in the application of Theorem 1 – which might be helpful if it is difficult to posit a suitable non- RPA variable a priori (for a complicated new CRN that one suspects to be RPA- capable), and if the parameter \(k\) is a CRN property that can be used as a disturbance. But even so, it's important to recognize that there's no need to declare specific biochemical parameters to be variables of the model to check if the CRN can adapt to these as disturbances. If the CRN is RPA capable, then it can adapt to any disturbance that is not present in the identified setpoint. By contrast, if the parameter is in the setpoint, the CRN cannot adapt to perturbations to that parameter. We mention this point explicitly in our definition of RPA. + +## 7. Other minor issues: + +- The definition of RPA must be shifted to the main text due to its centrality in understanding the message of the paper. + +Our response: We have now shifted the definition of RPA to the main text. We sincerely thank the reviewer for such helpful and supportive suggestions. + +- Why is the variable \(x_i\) missing in \(g(x_i)\) in figure 4 (main text) and figure S4 (supplement)? + +Our response: We had stated in the caption to Figure 4 (main text) that 'when \(x_j\) is the diverter node of the Balancer module, \(g\) will generally be zero- order in \(x_i\) ' and in the caption to Figure S4 in our SI that 'for clarity, we depict a functional form for \(g\) that is zero order in \(x_i\) , since this is the most common form obtained in practice (i.e. provide the RPA variable \(x_i\) is not autoregulatory). The main reason for presenting the simplified form of \(g\) that usually obtains was to emphasize the topological role of \(x_j\) (relative to \(x_i\) ) in orchestrating a 'pairing' action. This simplification is really not essential, however, and our exposition of the pairing principle is unaffected if we include the general form of the pairing function, \(g(x_i, x_j)\) . In response to the reviewer's query, we have now updated this figure in both the main paper (Figure 4) and the SI (Figure S4) to feature the general form of the pairing function, \(g(x_i, x_j)\) , and have updated our captions accordingly. + +<--- Page Split ---> + +- Replace "consistutes" with "constitutes" on line 72 in the main text. Please run a spell check. + +Our response: We thank the reviewer for spotting this typo, which has now been corrected. We have run a spell check, and there are no additional typos. + +- The paper says that if a network is RPA the integrator is guaranteed to exist. For example the following on page 22 in the main text In principle, there should always exist some single nonlinear coordinate change to extract a single output-driven internal model (Fig. 9a) from systems rate equations, corresponding to a single integral of the systems tracking error (Fig. 9b) + +or the following on page 16 in the Supplement + +All classes of RPA, including ACR, thus require some form of integral control. + +Please explain which version of IMP can be used to verify this existence. See [1] for a recent review on IMP. + +Our response: Here we are referencing a long- standing idea in the systems biology literature (see, for example [8] and [9], and Section 3 of [1]) that, where RPA obtains, there 'should' exist some (generally nonlinear) coordinate change that recasts the system into integral feedback form (if necessary, if the system in question has a feedforward architecture, and is subjected to a disturbance at its 'divierter'). The integral in question should operate on the system's tracking error. Reference [8], in particular, provides a very detailed mathematical elaboration of these ideas, which hold for nonlinear systems under several technical assumptions (which are very mild in the context of CRNs). Both [1] and [8] apply these ideas to identify a nonlinear transformation that identifies an output- driven internal model for a simple CRN with a feedforward structure, through a recasting into feedback form. We reviewed this simple example in our response to the Reviewer's Point 1. Again, our paper provides a very different viewpoint, distinct from the notion that 'there should always exist some single nonlinear coordinate change to extract a single output- driven internal model ... corresponding to a single integral'. Our reason for referencing the viewpoint of prior control theoretic literature [1,8,9] is to contrast it with our new completely different viewpoint, and not to present that prior viewpoint as axiomatic. + +We now add in these three references [1,8,9] at the location noted by the reviewer, to emphasize the prior IMP viewpoint we draw upon here. + +- On page 20 the authors state that "It is striking to note that the original form of the CRN (Fig. 8a) eludes the Shinar-Feinberg theorem, even though the CRN exhibits ACR and has a deficiency of one." However does it fit the results in [4]? Please comment on this. Also explain why the authors found the method for finding linear invariants "ad hoc" (lines 568-569 on page 25). + +<--- Page Split ---> + +Our response: As noted in many of our previous responses, we suspect the reviewer is actually referring to Karp et al. [6], rather than Perez Millan et al. [4], in this comment. Certainly, once one knows which particular complexes (and hence, which monomials) one needs to include in any RPA/ACR- relevant invariants, one can certainly use the method developed Karp et al. [6] to compute those invariants. In this specific simple case, however, the invariants in question happen to be the actual rate equations \(dA / dt\) (the connector polynomial) and \(dB / dt\) (the balancer polynomial), so the method is hardly necessary. + +Regarding our description of the Karp et al. [6] method for finding linear invariants as 'ad hoc', those authors themselves acknowledge that this method relies on knowing ahead of time which complexes (monomials) are relevant. As we had noted in one of our earlier responses, the authors specifically state that the 'examples (analysed in that paper) had already been analysed by other methods, so we had an idea of which invariants to expect and which subset of complexes to consider. For a new network such information may not be available, so how can non- trivial type 1 complex- linear invariants (simply, "invariants") be found?'. The authors go on to provide some practical suggestions for the reader on computing useful 'complex linear invariants', which may be helpful in studying new CRNs but certainly do not constitute a truly systematic procedure for rigorous application to general CRNs. + +- On the Supplement page 15 it is stated that Mass-conservative CRNs therefore have no external stimuli or inputs, and can only be perturbed by altering the total abundances (or concentrations) of the constituent molecules - i.e. by altering the initial conditions. + +Why cannot the perturbation come in the form of parameter variation, e.g. of a conversion reaction (that conserves mass). + +Our response: Yes, the reviewer certainly does make an interesting point. In practice, conversion reactions are normally mediated by enzymes, so if the enzyme in question is not part of the network, we agree that the corresponding parameter (which reflects the concentration of the enzyme) could be perturbed. Almost any parameter of a CRN could be perturbed in principle. But the framework we develop here emphasizes that a CRN can adapt to perturbations to any parameter that does not appear in the RPA-variable's setpoint, regardless of whether the CRN is mass- conservative or not. + +We did not intend the statement in question to constitute a major technical point. Nevertheless, in response to the reviewer's comment, we have adjusted the wording of that statement to read: 'Mass- conservative CRNs therefore have no external stimuli or inputs, and are typically perturbed by altering the total abundances (or concentrations) of the constituent molecules - i.e. by altering the initial conditions'. We do thank the reviewer again for such meticulous attention to every possible technical detail. + +<--- Page Split ---> + +Final comments to the reviewer: We would like to sincerely thank the reviewer again for the incredible generosity he/she has shown us by scrutinizing our work in such extraordinary detail. We trust the reviewer will now be satisfied that our claims are all accurate and well- substantiated, and can now agree that our paper is ready for publication. + +## References + +[1] M. Bin, J. Huang, A. Isidori, L. Marconi, M. Mischiati, and E. Sontag. Internal models in control, bioengineering, and neuroscience. Annual Review of Control, Robotics, and Autonomous Systems, 5:55- 79, 2022. [2] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. Proceedings of the National Academy of Sciences, 119(43):e2207802119, 2022. [3] N. Meshkat, A. Shiu, and A. Torres. Absolute concentration robustness in networks with low- dimensional stoichiometric subspace. Vietnam Journal of Mathematics, 50(3):623- 651, 2022. [4] M. Perez Millan, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027- 1065, 2012. [5] M. S. Perez Millan. Metodos algebraicos para el estudio de redes bioquimicas. PhD thesis, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales, 2011. [6] R.L. Karp, M. Perez Millan, T. Dasgupta, A. Dickenstein, and J. Gunawardena. Complex- linear invariants of biochemical networks. Journal Theoretical Biology, 311:130- 138, 2012. [7] D. Cox, J. Little, and D. O'Shea. Ideals, varieties, and algorithms: an introduction to computational algebraic geometry and commutative algebra. Springer Science & Business Media, 2013. [8] E.D. Sontag. Adaptation and regulation with signal detection implies internal model. Systems & Control Letters, 50:119- 126, 2003. [9] O. Shoval, U. Alon, and E. Sontag. Symmetry Invariance for Adapting Biological Systems. SIAM Journal on Applied Dynamical Systems, 10: 857- 886, 2011. [10] G. Shinar and M. Feinberg, M. Structural sources of robustness in biochemical reaction networks. Science, 327(5971):1389- 1391, 2010. [11] D. Cappelletti, A. Gupta and M. Khammash. A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances. Journal of the Royal Society Interface, 17(171):20200437, 2020. [12] R.P. Araujo and L.A. Liotta. The topological requirements for robust perfect adaptation in networks of any size. Nature Communications, 9(1):1- 12, 2018. [13] J.M. Eloundou- Mbehi, A. Kuken, N. Omranian, S. Kleessen, J. Neigenfind, G. Basler and Z. Nikoloski. A network property necessary for concentration robustness. Nature Communications, 7(1):1- 7, 2016, + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +I went over the revised version of the paper, and while I truly appreciate the efforts of the authors in preparing the revision, I am still of the opinion that this paper is not suitable for an interdisciplinary journal like Nature Communications. The main issues I have are as follows: + +1. As the title of the paper suggests, the aim of this study is to identify embedded integral control in adapting circuits. While the paper does construct a series of subsidiary integrators within the network via linear coordinate transformations, it does not provide a global coordinate transformation that would identify a global integrator. Hence the connection with standard integral controllers, and the standard Internal Model Principle is tenuous. By algebraically showing the existence of an RPA polynomial, only regulation and tracking are established, not integral control. + +2. The proof of the Kinetic Pairing Result is hard to understand and verify for non-specialists in algebraic methods (like myself). In fact, when I showed the proof to a specialist in such methods (with the permission of the editor), that person also found the proof particularly difficult to understand. Here I am specifically referring to pages 20-21 in the Supplement. This difficulty was mentioned to the authors in the previous review report, but the authors have not addressed it by simplifying/elaborating on the proof. Therefore, after two rounds of revisions (and more than 2 months of time spent on this paper!) I still cannot ascertain the correctness of the reported results. + +3. Even if the Kinetic Pairing result is correct, the final outcome is not a clean characterization of adapting networks. The characterization is done via an algorithm whose termination can take an inordinately large time for even moderately-sized networks. In cases where the algorithm does not terminate in a reasonable time, the authors suggest using analytical approaches like decomposing the large network into several independent networks and then performing deficiency analysis. However, this type of analysis is beyond the scope of most readers who might be interested in this work. If possible, the authors should try to extend their algorithm by incorporating this analysis. + +Reviewer #2 (Remarks to the Author): + +The manuscript by Araujo and Liotta addresses both a fundamental biological problem, and a fundamental conceptual innovation. + +The biological problem is that of organisms' ability to adapt to changes in the environment or their physiological state. This is a hallmark of many signalling processes where adaptation is required to safeguard the appropriate response. This has been a longstanding problem across many biological areas. + +The conceptual advance offered by Araujo and Liotta is to derive mathematical results and conditions that guarantee adaptive behaviour. This is a tour de force and highly innovative; I like the idea of generalising integral control to dissect the design principles of adaptive behaviour a lot - there is scope for further applications of this framework. Many areas of biology will benefit from a more mathematically framework, and this work is a major contribution in this direction. Being able to prove formally aspects that biological systems have to obey to exhibit certain behaviour is exciting. In addition to the authors' earlier - outstanding in my view - work (PMID: 29717141), there is a growing body of other exciting work in this domain (see e.g. PMID: 19536158; PMID: 20223989, PMID 30194237); the present manuscript makes a substantial contribution to this important area of research. What sets the current work apart from these earlier studies are the more general biological relevance of adaptive behaviour. + +The response to the reviewers' comments now exceeds the manuscript in length and I was unable to follow some of the criticisms voiced by the other reviewer. It is clear that the ideas underlying the alternative formulation of an integral controller are highly technical but the derivations contain the appropriate level of detail and I was able (admittedly with some work and effort) to follow the arguments laid out in the manuscript and especially the now substantial supplementary material. + +<--- Page Split ---> + +I can understand that the references to additional mathematical work and proofs (e.g. in Refs 7 ad 15 in the supplementary material) does potentially add problems for a reader in reconstructing the full mathematical framework. In my view the authors negotiate the difficulties of exposing and explaining their proof in a clear and laudable manner. Developing a mathematical framework for a multidisciplinary audience is challenging but the work presented here provides important pointers how we can achieve this and find common ground between the often opposing needs of mathematical and biological audiences. + +Minor point: + +Lines 438- 442 contain in my reading one of the essential messages if this paper and I would suggest that the authors stress this and make the innovation in the paper more explicit. + +In summary, this is exactly the type of mathematical biology that I and many others want to see. + +<--- Page Split ---> + +## Reviewer #1 + +I went over the revised version of the paper, and while I truly appreciate the efforts of the authors in preparing the revision, I am still of the opinion that this paper is not suitable for an interdisciplinary journal like Nature Communications. The main issues I have are as follows: + +1. As the title of the paper suggests, the aim of this study is to identify embedded integral control in adapting circuits. While the paper does construct a series of subsidiary integrators within the network via linear coordinate transformations, it does not provide a global coordinate transformation that would identify a global integrator. Hence the connection with standard integral controllers, and the standard Internal Model Principle is tenuous. By algebraically showing the existence of an RPA polynomial, only regulation and tracking are established, not integral control. + +## Our Response: + +We sincerely thank the reviewer again for such a significant investment of his/her time in considering our work. We would like to emphasize once again, however, that there simply is no (and can be no) global coordinate transformation (and hence, no single 'global integrator') that can reveal the general properties of all possible RPA- capable CRNs. As we explained in our most recent response, one of the major points of our article is that the conventional approach to control theory, with its 'standard integral controllers' and 'standard Internal Model Principle' (as the Reviewer calls them) is wholly inadequate to capture the fundamental design principles that organize all forms of biological complexity into robustness- promoting (and ultimately, survival- promoting) structures. What we demonstrate instead is that all RPA- capable chemical reaction networks - without exception - are constructed from a topological hierarchy of building blocks ('invariants'), which independently implement the Internal Model Principle by robustly rejecting disturbances to specific network features (e.g., a ratio in the concentrations of specific molecules constituting a balancing mechanism) and which thereby work together collaboratively to implement RPA on specific molecule(s). Our analysis identifies the remarkable fact that all such RPA- promoting subsidiary invariants are obtained via linear coordinate changes, and recapitulate - locally within the topology of the network - the dynamical properties of the disturbance. By proving that all RPA- capable CRNs are decomposable into these well- defined topological hierarchies of internal models, we provide a universal description for the implementation of integral control that holds for all collections of chemical reactions that exhibit RPA (including any special case of RPA, such as absolute concentration robustness (ACR)). + +2. The proof of the Kinetic Pairing Result is hard to understand and verify for non- specialists in algebraic methods (like myself). In fact, when I showed the proof to a specialist in such methods (with the permission of the editor), that person also found + +<--- Page Split ---> + +the proof particularly difficult to understand. Here I am specifically referring to pages 20- 21 in the Supplement. This difficulty was mentioned to the authors in the previous review report, but the authors have not addressed it by simplifying/elaborating on the proof. Therefore, after two rounds of revisions (and more than 2 months of time spent on this paper!) I still cannot ascertain the correctness of the reported results. + +## Our Response: + +We thank the Reviewer for clarifying further the section of the proof they found hard to understand. This gives us the opportunity to restate, highlight, and summarize again the several additional clarifications of the proof we provided in the previous rounds of response. In fact, our extensive additional clarifications on the proof to our Theorem 1 (the Kinetic Pairing theorem) were added after the first round of review, through a series of 'Remarks' following the proof in our Supplementary Information. + +In particular, the Reviewer stated in his/her first report that "...The proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f} \cap \mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) ", and proceeded to give an example of a CRN that he/she believed to be a counterexample to our Theorem. We responded with a detailed explanation as to why 'the ideal \(I_{f} \cap \mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) ", along with a detailed analysis to demonstrate that the Reviewer's example is entirely consistent with our Theorem. The Reviewer responded in the following round by challenging us with three new CRN examples which he/she proposed were counterexamples to our Theorem. We responded by providing a careful and detailed analysis of these new examples, and demonstrating that these were entirely consistent with our Theorem - not counter- examples. In fact, we used our detailed analysis of the Reviewer's various CRNs to underscore the fact that these illustrations demonstrate how (and why) the Theorem works. + +The Reviewer also now provides new information about consulting with a 'specialist' third- party ('...when I showed the proof to a specialist in such methods ... that person also found the proof particularly difficult to understand'). Nevertheless, we respectfully point out that the Reviewer has not been very specific as to what he/she does not understand in our proof to the Kinetic Pairing Theorem beyond the initial question regarding "polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) " (which we addressed thoroughly, as noted above). It is also possible that extensive clarifications of our proof in past rounds of responses, along with our lengthy and detailed analyses of the CRN examples, might not have been shown in extenso to the Reviewer's consultant. + +3. Even if the Kinetic Pairing result is correct, the final outcome is not a clean characterization of adapting networks. The characterization is done via an algorithm whose termination can take an inordinately large time for even moderately-sized networks. In cases where the algorithm does not terminate in a reasonable time, the + +<--- Page Split ---> + +authors suggest using analytical approaches like decomposing the large network into several independent networks and then performing deficiency analysis. However, this type of analysis is beyond the scope of most readers who might be interested in this work. If possible, the authors should try to extend their algorithm by incorporating this analysis. + +## Our Response: + +We respectfully emphasize once again that within the original and revised manuscript versions we have provided detailed and rigorous mathematical arguments to support the correctness of the Kinetic Pairing result, and have additionally provided detailed analyses of all the new CRN examples suggested to us by the Reviewer to demonstrate how they reflect the essential underlying principles of this key Theorem. + +In addition, the Reviewer suggests that "the final outcome is not a clean characterization of adapting networks" and that the "characterization is done via an algorithm ...". We feel it is important to clarify for the record that the universal characterisation of adaptation- capable CRNs presented in our study is not obtained from an algorithm, but from our carefully- developed mathematical arguments that all such adapting networks are constructed from topological building blocks that are obtained by linear coordinate changes (associated with linear integral controllers). Since all RPA- capable CRNs must be constructed from these fundamental building blocks, and because the topological principles governing RPA capacity are now known in complete generality, our findings definitively characterise the full set of chemical reaction structures that can implement RPA. In other words, through identifying the fundamental building blocks of RPA in CRNs and the algebraic structures (in terms of CRN deficiency, etc.) by which these building blocks are constructed, as well as the general principles by which the building blocks are connected together into larger networks, we are able to provide a comprehensive (i.e. universal) description all possible RPA- capable CRNs at the level of intermolecular interactions. + +Now, for a specific RPA- capable CRN under consideration, we present an algorithmic test that can demonstrate the ability of a particular molecule to exhibit RPA, in addition to identifying the decomposition (of the requisite nonlinear transformation of the system) into subsidiary linear controllers, as well as the 'setpoint' of the system as a function of parameters. This is a completely separate matter from the issue of the 'universal characterisation' of RPA- capable CRNs. Although the reviewer suggests that the termination of the algorithm 'can take an inordinately large time for even moderately- sized networks', we respectfully emphasize once again that it is, in fact, only non- RPA- capable CRNs that may require an indeterminate (and potentially impractical) timeframe for the algorithm to terminate. We clearly explain the technical reasons for this fact in our paper (in both the main article, as well as in the Supplementary Information), and provide an alternative analytical approach to establish the inability of a CRN to exhibit RPA, should our 'general' algorithm take too long to terminate. We respectfully point out that this 'deficiency analysis' requires only linear algebraic techniques, and is thus + +<--- Page Split ---> + +accessible to the mainstream scientific community. We provide a fully- worked example of the application of this alternative analytical approach to a specific CRN in our Supplementary Information. + +The complete generality of our findings on RPA- capable chemical reaction networks, along with the clarity and comprehensiveness of our analysis, will now enable the scientific community to consider fundamental questions about the evolution of biochemical reaction networks at the whole- cell level, and at the level of entire organisms. As such, we believe strongly that this study will be of interest to researchers from a huge variety of different fields, including evolutionary biology, bioengineering, cancer research, developmental biology, pharmacology, whole- cell modelling, and many others. + +## Reviewer #2 + +The manuscript by Araujo and Liotta addresses both a fundamental biological problem, and a fundamental conceptual innovation. The biological problem is that of organisms' ability to adapt to changes in the environment or their physiological state. This is a hallmark of many signalling processes where adaptation is required to safeguard the appropriate response. This has been a longstanding problem across many biological areas. + +The conceptual advance offered by Araujo and Liotta is to derive mathematical results and conditions that guarantee adaptive behaviour. This is a tour de force and highly innovative; I like the idea of generalising integral control to dissect the design principles of adaptive behaviour a lot - there is scope for further applications of this framework. Many areas of biology will benefit from a more mathematically framework, and this work is a major contribution in this direction. Being able to prove formally aspects that biological systems have to obey to exhibit certain behaviour is exciting. In addition to the authors' earlier - outstanding in my view - work (PMID: 29717141), there is a growing body of other exciting work in this domain (see e.g. PMID: 19536158; PMID: 20223989, PMID 30194237); the present manuscript makes a substantial contribution to this important area of research. What sets the current work apart from these earlier studies are the more general biological relevance of adaptive behaviour. + +The response to the reviewers' comments now exceeds the manuscript in length and I was unable to follow some of the criticisms voiced by the other reviewer. It is clear that the ideas underlying the alternative formulation of an integral controller are highly technical but the derivations contain the appropriate level of detail and I was able (admittedly with some work and effort) to follow the arguments laid out in the manuscript and especially the now substantial supplementary material. I can understand that the references to additional mathematical work and proofs (e.g. in Refs 7 ad 15 in the supplementary material) does potentially add problems for a reader in reconstructing the full mathematical framework. In my view the authors negotiate the difficulties of exposing and explaining their proof in a clear and laudable manner. Developing a mathematical framework for a multidisciplinary + +<--- Page Split ---> + +audience is challenging but the work presented here provides important pointers how we can achieve this and find common ground between the often opposing needs of mathematical and biological audiences. + +Minor point: + +Lines 438- 442 contain in my reading one of the essential messages if this paper and I would suggest that the authors stress this and make the innovation in the paper more explicit. + +In summary, this is exactly the type of mathematical biology that I and many others want to see. + +## Our Response: + +We are indebted to Reviewer 2 for such an authoritative and thorough consideration of our work - both in terms of our admittedly complicated mathematical arguments and in terms of the broad conceptual contributions of our study - and for such generous suggestions to strengthen our exposition even further. We are truly grateful that the Reviewer has been willing to invest the time required to carefully review all our technical arguments to verify their mathematical soundness. + +We have taken on board the Reviewer's helpful suggestion to further emphasize the content of Lines 438- 442, in order to 'make the innovation in the paper more explicit'. (Lines 438- 442 contain the text: "Until now strategies for identifying an internal model, and an associated integral, via a nonlinear coordinate change have only been applicable to exceedingly simple CRNs. By contrast, our approach identifies a well- defined nonlinear map between reaction rates of the model variables \(f_{1}, \ldots , f_{n}\) , and a defining algebraic invariant, \(\rho\) (Eq. 6), which exists for all adaptation- capable CRNs"). With this suggestion in mind, we have now amplified the ideas contained in lines 438- 442 of the previous version and more explicitly highlighted the innovation in our paper by adding in an extensive new paragraph at the end of the Introduction section (now lines 130- 142 in this final version). We now explain + +"As we will show in the sections to follow, a mathematical transformation may always be applied to the reaction rates of any RPA- capable CRN to produce a special two- variable invariant called an 'RPA polynomial'. This distinguished algebraic invariant encodes the robust asymptotic tracking of a molecular setpoint, no matter how complex or intricate the intermolecular interactions, nor how vast the network of interacting molecules. Unlike the nonlinear coordinate transformations invoked in the 'standard' IMP, where a global coordinate transformation (unique to each RPA- capable network) is required to identify a single internal model, the nonlinear transformation we identify here has a special 'almost linear' structure (and, in special cases, exactly linear) and is decomposable into a topologically organised collection of linear integral controllers, each with its own independent internal model. In this way, we are able to identify the fundamental building blocks of all possible RPA- capable CRNs, + +<--- Page Split ---> + +thereby revealing definitive and universal structural requirements that characterize all adaptation- capable collections of interacting molecules." + +This new material now leads directly to the detailed and careful analysis of our two simple running examples (which exemplify the properties of all RPA- capable CRNs), which lead, in turn, to a careful exposition of the underlying technicalities (comprehensively supported by our detailed Supplementary Information). + +<--- Page Split ---> diff --git a/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..030151a4c1cfc8d7d6b5f5b94418b2b1b6f5cc9d --- /dev/null +++ b/peer_reviews/9992385fed83bd9914118057a4fbaa147a8938845ca9fa54b836e6884c0cbc29/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1804 @@ +<|ref|>title<|/ref|><|det|>[[61, 41, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 363, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 880, 210]]<|/det|> +Universal structures for adaptation in biochemical reaction networks + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[98, 141, 841, 196]]<|/det|> +# Review: Universal structures for embedded integral control in biological adaptation + +<|ref|>text<|/ref|><|det|>[[275, 218, 660, 240]]<|/det|> +Robyn P. Araujo and Lance A. Liotta + +<|ref|>text<|/ref|><|det|>[[85, 274, 853, 421]]<|/det|> +Overview: Development of adaptation mechanisms is crucial for survival across biological scales. Understanding how such mechanisms are generated through biomolecular interactions is a fundamentally important problem? This issue has underpinnings in control theory and it is known that adaptation requires an embedded integral control, which, if identified, can offer insights into how a reaction network achieves adaptation and how robust this adaptation is. The aim of this paper is to construct an algebraic procedure to identify the hidden integral controller in adaptation- capable networks and connect these controllers to the structure of the networks. + +<|ref|>text<|/ref|><|det|>[[85, 428, 853, 484]]<|/det|> +Recommendation: Even though the paper studies an important problem, I do not find the analysis presented in this paper to be convincing enough to warrant publication in Nature Communications. The manuscript has several shortcomings which I list below: + +<|ref|>sub_title<|/ref|><|det|>[[115, 495, 380, 513]]<|/det|> +## - Lack of sufficient novelty: + +<|ref|>text<|/ref|><|det|>[[152, 524, 853, 653]]<|/det|> +- The general principles for RPA have been developed by (slightly) extending previous results by the authors for deficiency zero and deficiency one CRNs. These low-deficiency networks are related to 'balancer' and 'opposer' modules which are known to form a topological basis for all RPA networks [1]. This connection is explained with two illustrative examples and general principles are formulated by relying on the theory in [1]. Hence, given the earlier results in [1], the incremental novelty in this paper is not significant. + +<|ref|>text<|/ref|><|det|>[[152, 658, 853, 749]]<|/det|> +- Many researchers have exploited Gröbner basis and ideal construction for obtaining steady-states in terms of parameters and in particular for studying ACR. For example, see [6, 5, 3] and references therein. It seems that the authors are unaware of these works and in order the assess the novelty of the methods in this paper, these existing works must be cited and discussed. + +<|ref|>text<|/ref|><|det|>[[152, 754, 853, 828]]<|/det|> +- More importantly, the central analysis in this paper crucially depends on the result for deficiency one networks which is stated as Theorem 3 in the Supplement. However, this result is not new, as it follows from Theorem D.1 in the Supplement of [2] (see the proof in [2]). + +<|ref|>text<|/ref|><|det|>[[115, 839, 853, 912]]<|/det|> +- Definition of RPA: The notion of RPA is not mathematically defined. In other words, it is not clear what disturbances are allowed and what are the biochemical parameters on which the output set-point is allowed to depend. On page 11 in the Supplement it is written that for RPA the set-point \(c\) should be a rational function of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[132, 91, 853, 128]]<|/det|> +the biochemical rate constants. However, this would be the case for any steady- state and so what constitutes RPA is not clear. + +<|ref|>text<|/ref|><|det|>[[114, 140, 854, 270]]<|/det|> +- Algorithm may not terminate: The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima-facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In particular, no proof is given showing that non-termination implies no RPA. Moreover, non-termination of a method is not something that can be ascertained with any certainty by running the code. Accordingly, the authors cannot claim that they have a full 'characterisation' of the RPA property. + +<|ref|>text<|/ref|><|det|>[[113, 280, 853, 317]]<|/det|> +- Form of the RPA polynomial: The whole approach hinges on the RPA polynomial having the form + +<|ref|>equation<|/ref|><|det|>[[419, 320, 567, 338]]<|/det|> +\[\rho = g(x,y)(x - c)\] + +<|ref|>text<|/ref|><|det|>[[133, 342, 854, 437]]<|/det|> +where \(g(x,y)\neq 0\) and \(y\) is a non- RPA capable variable which forms the kinetic pair to \(x\) . It is unclear why \(g(x,y)\) can only be a function of one additional variable, apart from the output variable. The proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f}\cap \mathbb{R}[\overline{{x}} ]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f}\cap I_{p}\) + +<|ref|>text<|/ref|><|det|>[[133, 459, 525, 478]]<|/det|> +As an example consider the following network: + +<|ref|>equation<|/ref|><|det|>[[267, 490, 716, 511]]<|/det|> +\[\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1} + \mathbf{X}_{4}\quad \mathrm{and}\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\mathbf{X}_{5}.\] + +<|ref|>text<|/ref|><|det|>[[132, 523, 854, 599]]<|/det|> +Furthermore assume that species \(\mathbf{X}_{2},\ldots ,\mathbf{X}_{5}\) participate is several reactions that do not involve \(\mathbf{X}_{1}\) but can be catalysed by it. In this scenario the RPA polynomial would be \(\rho = x_{2}x_{3}(\frac{c_{1}}{c_{2}} - x_{1})\) . Hence the function \(g\) depends on two non- RPA variables \(x_{2}\) and \(x_{3}\) . Please explain how this example is consistent with the form of \(g(x,y)\) stated above. + +<|ref|>text<|/ref|><|det|>[[132, 603, 853, 659]]<|/det|> +Moreover, it is not immediately clear how existence of multiple opposer/balancer modules translates into existence of existence of corresponding RPA polynomials. This has not been explained in sufficient detail. + +<|ref|>text<|/ref|><|det|>[[113, 670, 853, 744]]<|/det|> +- Connection to existing works: In [4] the authors consider RPA systems that are maximally robust and find simple linear-algebraic structural conditions that characterise this property in both deterministic and stochastic settings. How do the results in this paper connect to the results in [4]? + +<|ref|>sub_title<|/ref|><|det|>[[85, 771, 235, 793]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[85, 807, 853, 846]]<|/det|> +[1] R. P. Araujo and L. A. Liotta. The topological requirements for robust perfect adaptation in networks of any size. Nature communications, 9(1):1- 12, 2018. + +<|ref|>text<|/ref|><|det|>[[85, 857, 852, 913]]<|/det|> +[2] D. Cappelletti, A. Gupta, and M. Khammash. A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances. Journal of the Royal Society Interface, 17(171):20200437, 2020. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[84, 90, 857, 130]]<|/det|> +[3] G. Craciun, A. Dickenstein, A. Shiu, and B. Sturmfels. Toric dynamical systems. Journal of Symbolic Computation, 44(11):1551–1565, 2009. + +<|ref|>text<|/ref|><|det|>[[85, 140, 855, 179]]<|/det|> +[4] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. bioRxiv, 2022. + +<|ref|>text<|/ref|><|det|>[[85, 189, 855, 228]]<|/det|> +[5] M. Pérez Millán, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027–1065, 2012. + +<|ref|>text<|/ref|><|det|>[[85, 238, 855, 277]]<|/det|> +[6] A. Sadeghimanesh and E. Feliu. Gröbner bases of reaction networks with intermediate species. Advances in Applied Mathematics, 107:74–101, 2019. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 295, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[118, 112, 300, 140]]<|/det|> +Reviewer #1: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 195, 300, 222]]<|/det|> +Reviewer #2: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 223, 863, 250]]<|/det|> +Araujo and Liotta develop a set of precise criteria that a system needs to fulfil in order to perfect adaptation. + +<|ref|>text<|/ref|><|det|>[[118, 251, 873, 378]]<|/det|> +This is remarkable and an extremely valuable contribution to the literature in three ways: (i) the search for "design principles" is taking centre stage in synthetic (but also e.g. developmental systems) biology; the first author has proven a leader in distilling precise mathematical criteria for robust perfect adaptation, and I hope that this study will inspire more work in this area, especially in considering the mathematical properties of chemical reaction networks to guarantee different types of behaviour; (ii) in Mathematical biology there are few instances where the mathematical statements can be so precise that biology will have to "obey" these statements. This is one such instance. Finally (iii) the maintenance and control of robust adaptation is of considerable and far reaching biological relevance. I like this manuscript for each of these three points a lot. + +<|ref|>text<|/ref|><|det|>[[118, 391, 866, 462]]<|/det|> +The most interesting mathematical aspects of the work have, unfortunately but predictably been relegated to the supplementary information. The results in Figure 2, for example, are very clearly explained and easy to follow in the SI. I personally enjoyed the SI a lot, and while the discussion e.g. in lines 207- 215 is clear, it may be too terse for some readers to follow. The SI by contrast was very clear. Fig 3 does a nice job, however, to get the message of kinetic pairing across. + +<|ref|>text<|/ref|><|det|>[[118, 475, 866, 518]]<|/det|> +I think it would help readers to understand how translatable to other phenotypes this type of analysis is, or if RPA is particular in this regard of allowing such general mathematical statements to be derived. + +<|ref|>sub_title<|/ref|><|det|>[[118, 546, 219, 560]]<|/det|> +## Small points: + +<|ref|>text<|/ref|><|det|>[[118, 574, 870, 616]]<|/det|> +- much of chemical reaction network theory is obscure to most readers. I would like to see a clear and easy definition of integral control that is accessible to non-expert audiences. Deficiency is maybe another such concept and it would be good to define it on line 146. + +<|ref|>text<|/ref|><|det|>[[118, 630, 864, 659]]<|/det|> +- The authors show that their criteria hold for all instances of RPA. I was wondering how easily in practice these mechanisms could be lost? Is it easy to identify points that disrupt RPA? + +<|ref|>text<|/ref|><|det|>[[118, 672, 866, 715]]<|/det|> +- there is a vast literature on design principles which could be touched upon at least in passing (limit cycles, multistability, switch-like behaviour, Turing patterns), especially if there is scope for applying similar concepts in these contexts. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 138, 246, 154]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[150, 170, 830, 309]]<|/det|> +Overview: Development of adaptation mechanisms is crucial for survival across biological scales. Understanding how such mechanisms are generated through biomolecular interactions is a fundamentally important problem. This issue has underpinnings in control theory and it is known that adaptation requires an embedded integral control, which, if identified, can offer insights into how a reaction network achieves adaptation and how robust this adaptation is. The aim of this paper is to construct an algebraic procedure to identify the hidden integral controller in adaptation- capable networks and connect these controllers to the structure of the networks. + +<|ref|>text<|/ref|><|det|>[[151, 327, 825, 379]]<|/det|> +Recommendation: Even though the paper studies an important problem, I do not find the analysis presented in this paper to be convincing enough to warrant publication in Nature Communications. The manuscript has several shortcomings which I list below: + +<|ref|>sub_title<|/ref|><|det|>[[206, 397, 312, 412]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[206, 412, 845, 602]]<|/det|> +We would like to sincerely thank the reviewer for his/her significant investment of time in considering our work, and would like to acknowledge that the reviewer - on the basis of the content in his/her feedback - is clearly an expert in the RPA field, which we both respect and value. The reviewer has given our work a rather harsh review, but we are very grateful to have the opportunity to defend our work, and to make additional improvements and clarifications after thoughtfully considering the reviewer's feedback. We thank the reviewer in advance for his/her generosity and willingness to re- consider our work in light of these detailed responses and clarifications. We have noted all revisions to the main manuscript, and to our SI, with red text, so that the reviewer can readily identify which parts of our article have been updated since the original submission. + +<|ref|>text<|/ref|><|det|>[[205, 620, 842, 901]]<|/det|> +We do wish to respectfully point out at the outset that the primary aim of this work is not "to construct an algebraic procedure to identify the hidden integral controller in adaptation- capable networks" as the reviewer suggests. Rather, our primary goal is to provide a comprehensive and universal description of all possible RPA- capable chemical reaction networks (CRNs), that could ever exist - recognising (in contrast to Shinar/Feinberg, for example) that all instances of RPA, including ACR, must implement "some" form of integral control. In so doing, we wish to also propose a definitive criterion, or test, that captures the presence of the RPA property in any CRN that possesses it. The nature of this universal characterisation of RPA at the level of intermolecular interactions, as codified in the most general terms by our Theorem 1, does indeed suggest an algorithmic method for testing specific CRNs as to their RPA capacity, and for identifying their hidden integral controllers and setpoints. That this algorithmic method could terminate in polynomial time for any RPA- capable CRN, comparable to Gaussian elimination, is a consequence of the previously unrecognised relationship we identify between increases in CRN deficiency (ie. beyond a deficiency of one) and the associated modifications to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 848, 327]]<|/det|> +polynomial invariants in the rowspan of the chemical reaction rates. For this reason we are able to identify, for the first time, the special 'almost linear' structure of the mathematical transformation (coordinate change) required to reveal the CRN's "RPA polynomial" – a central concept in our work - if such exists for the CRN in question. We thereby "solve" the integral control problem for all RPA-capable CRNs, in complete generality, at the microscale level of intermolecular interactions, with their associated mathematical graph structures. In so doing, we demonstrate how RPA may be accommodated by CRNs of arbitrary deficiency (not just "low-deficiency" CRNs, as the reviewer goes on to claim). Our two main outcomes are thus inextricably related: the special CRN structures that hold for all possible RPA-capable networks allow the system's reaction rates to be projected, mathematically, onto two variables via a process that does not differ substantially from Gaussian elimination – thereby revealing a computationally feasible algorithmic test for the presence of RPA. + +<|ref|>text<|/ref|><|det|>[[205, 345, 848, 763]]<|/det|> +Importantly, our new and unexpected findings on the relationship between the deficiency of a CRN and its overarching topological structure allow us to make a new and crucial connection to our previous work on RPA at the network macroscale [1], thereby enabling us to identify, definitively, the one- to- one correspondence between the subsidiary linear control problems and key topological features of the CRN. The fact that we can connect these new results to our previous general (macroscale) topological solution to the RPA problem is, without question, extremely powerful. But it is entirely untrue that we simply impose our previous results on RPA topologies at the network macroscale onto the microscale of intermolecular interactions in a CRN, leading to a result of "incremental novelty" as the reviewer goes on to suggest. In fact, no previously published work to our knowledge has been able to identify the general relationship between deficiency and linear complex invariants in RPA- capable networks. Cappelletti et al. [2], for instance, do note that an "RPA polynomial" (as we call it here) can exist in the rowspan of a CRN for deficiencies greater than one – if the RPA polynomial in question happens to be in the rowspan of the CRN, which is not generally the case – BUT fail to identify how any added deficiency (beyond unity) allows this crucially important "RPA polynomial" to reside in the rowspan. As a consequence, even the very simplest RPA- capable CRNs whose RPA polynomial does not reside in the rowspan (e.g. the toy model discussed by those authors, that we analyse as Example 1 in our SI (Section S3.1)) simply elude the Cappelletti et al. [2] approach. No previous work as been able to characterise, in complete generality, the nonlinear coordinate changes that are needed to reveal the capacity for RPA in CRNs in an entirely universal manner. + +<|ref|>text<|/ref|><|det|>[[206, 780, 846, 902]]<|/det|> +We are truly grateful for the reviewer's fresh set of eyes on our work, and have carefully revised our manuscript (and SI) to ensure that the novelty and scientific importance of our findings have been clearly and accurately communicated. We acknowledge, in particular, that the preamble to our Supplementary Information (i.e. the Supplementary Text prior to Section S1) could have been organised much better, with the aims and novel contributions of our work expressed much more explicitly. We acknowledge that our original submission mentioned the development of a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[207, 84, 832, 154]]<|/det|> +definitive 'RPA test' first in this section, before describing the overarching goal of demonstrating the truly universal principles of RPA in CRNs, and the relationship of this universal description of RPA to integral control. This section has now been carefully revised to read as follows: + +<|ref|>text<|/ref|><|det|>[[206, 172, 833, 362]]<|/det|> +The overarching goal of this work is to provide a comprehensive and universal description of all possible Chemical Reaction Network (CRN) structures that can implement the keystone biological function known as Robust Perfect Adaptation (RPA), and in so doing, to propose a definitive algebraic condition that captures presence of the RPA property in any CRN that possesses it. We also recognise here that all forms of RPA, including the special case known as Absolute Concentration Robustness (ACR), must implement some form of integral control. Our universal characterisation of RPA at the level of intermolecular interactions thereby provides an algorithmic method not only for detecting the RPA property, but also for identifying the hidden integral controllers, as well as the 'setpoints' of any RPA- exhibiting molecules. + +<|ref|>text<|/ref|><|det|>[[206, 379, 848, 502]]<|/det|> +As we show in the pages to follow, providing such an all- encompassing description of RPA at the microscale- level of biological networks - that is, in CRNs, which account for the mathematical graph structure of intermolecular interactions - has required us to reconcile a wide range of disparate mathematical viewpoints, ranging from Chemical Reaction Network Theory (CRNT), control theory and the internal model principle, and algebraic geometry. The essential structure of our mathematical development is as follows: + +<|ref|>text<|/ref|><|det|>[[234, 536, 848, 676]]<|/det|> +1. In Section S1 we identify a universal 'kinetic pairing' principle, which captures the essence of RPA in all CRNs that possess the property, and which is codified by our Two-Variable Kinetic Pairing Theorem (Theorem 1, Section S1.4). This theorem guarantees that, for all RPA capable CRNs, the geometric projection of the CRN's steady-state locus onto a state space defined by just two variables is captured by a distinguished algebraic invariant that we call an RPA polynomial. In this context the term 'variable' has a particular meaning, that we define carefully in Section S1.4. + +<|ref|>text<|/ref|><|det|>[[260, 693, 844, 867]]<|/det|> +In this Section we also introduce readers to the fundamentally important notion of algebraically independent subnetworks - a simple yet powerful concept introduced by Martin Feinberg (see Appendix A.6 in [9] for a detailed overview), whose implications for the decomposition of CRNs into independent subnetworks, and ultimately topological modules, that are compatible with RPA are recognised for the first time in the present work. This key concept provides a vital ingredient which contributes to a definitive characterisation of RPA-capable CRNs of arbitrarily high deficiency, far beyond the simple deficiency-one ACR-capable CRNs covered by the Shinar- Feinberg theorem [7]. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[234, 85, 848, 310]]<|/det|> +2. In Section S2 we briefly discuss the topological implications of Theorem 1 and, for later reference, make a preliminary connection with previous work on the topological structures that are known to hold, at the network macroscale, for all RPA-capable networks [1]. Importantly, the universal topological solution to the RPA problem [1] was developed considering only a single external input or disturbance, and did not account for the possibility of no external inputs, with alterations in total abundances of the interacting elements (as specified by the initial conditions of the system) constituting the only possible perturbation to the system. More importantly, and in stark contrast to the present work, the universal macroscale solution to the RPA problem [1] gives no concrete information as to the CRN structures (at the network microscale) that could engender RPA or satisfy its strict topological requirements. + +<|ref|>text<|/ref|><|det|>[[234, 329, 841, 692]]<|/det|> +3. Since most RPA-capable CRNs identified in prior studies identify an RPA polynomial (as we call it here) from only linear coordinate changes (see, for example, Cappelletti et al. [2]), in Section S3 we consider the algebraic properties of CRNs that allow the RPA polynomial (as expressed in Theorem 1) to reside in the rowspan of the CRNs chemical reaction rates (i.e. given by an \(\mathbb{R}\) -linear combination of the rate equations). For this purpose, we analyse two carefully chosen CRN examples in detail, and demonstrate the existence of several subsidiary polynomial invariants in the rowspan for each case, and note the relationship of these polynomial invariants to the overarching topology of the system. We demonstrate via deficiency-preserving transformations of the respective CRN structures that these subsidiary polynomial invariants combine to yield the all-important RPA polynomial within the rowspan exactly when the invariants are stoichiometrically dependent. If the invariants are stoichiometrically independent, on the other hand, a concatenating monomial is required to reconcile the invariants, thereby introducing a necessary nonlinearity to the transformation that produces the RPA polynomial. The detailed analysis of these simple examples provides the reader with an accessible overview of the general principles that characterise RPA-capable CRN structures before we develop these principles more rigorously and in complete generality in the remaining Sections. + +<|ref|>text<|/ref|><|det|>[[234, 710, 836, 885]]<|/det|> +4. In Section S4 we demonstrate, through an analysis of deficiency-increasing reactions within independent CRN subsets, that the coordinate change required to extract the all-important RPA polynomial from the CRN rate equations is always almost linear, in the sense that the RPA polynomial can always be decomposed into a collection of 'complex linear invariants'. From a control theory viewpoint, these observations lead to the previously unrecognised conclusion that the 'internal model' for any RPA-capable CRN can always be decomposed into a collection of linear integral controllers, in addition to reconciling the processing of biochemical information at the network microscale (i.e. via the intricate intermolecular interactions that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[260, 85, 817, 119]]<|/det|> +comprise a CRN) with the overarching topological features at the network macroscale [1]. + +<|ref|>text<|/ref|><|det|>[[233, 137, 842, 276]]<|/det|> +5. In Section S5, we provide the reader with extensively annotated code in the open-source software Singular (www.singular.uni-kl.de) to test the RPA capacity of a range of illustrative examples. This code can be adapted readily to the analysis of any CRN. If RPA does obtain for a particular CRN under investigation, an important consequence of the special almost-linear structure of the transformation required to identify the RPA polynomial is that the computational demands of this algorithm do not differ substantially from those of Gaussian elimination (a polynomial-time algorithm). + +<|ref|>text<|/ref|><|det|>[[206, 311, 844, 345]]<|/det|> +We clarify the nature of our scientific advance in further detail as we address each of the reviewer's individual points in turn. + +<|ref|>sub_title<|/ref|><|det|>[[150, 381, 374, 397]]<|/det|> +## Lack of sufficient novelty: + +<|ref|>text<|/ref|><|det|>[[150, 399, 803, 520]]<|/det|> +- The general principles for RPA have been developed by (slightly) extending previous results by the authors for deficiency zero and deficiency one CRNs. These low-deficiency networks are related to 'balancer' and 'opposer' modules which are known to form a topological basis for all RPA networks [1]. This connection is explained with two illustrative examples and general principles are formulated by relying on the theory in [1]. Hence, given the earlier results in [1], the incremental novelty in this paper is not significant. + +<|ref|>text<|/ref|><|det|>[[205, 538, 848, 693]]<|/det|> +Our response: We wish to respectfully emphasize, first and foremost, that these completely general principles by which RPA is always realised at the level of intermolecular interactions in a CRN have by no means "been developed by (slightly) extending previous results (of ours) for deficiency zero and deficiency one CRNs". Our framework is certainly not limited to "low- deficiency networks", as the reviewer claims. The general principles, which we succinctly summarise for a general audience via two particularly simple illustrative examples, in order to provide as accessible an overview of the main ideas as possible at the outset, have most assuredly not been "formulated by relying on the theory in [1]". + +<|ref|>text<|/ref|><|det|>[[205, 711, 845, 902]]<|/det|> +Our previous work [1], considers the broad macroscale topological structures that are compatible with an RPA response, and delineates the full solution space to the RPA problem from this viewpoint. This approach considered an abstract network, with a single 'input stimulus', or disturbance, delivered to a distinguished input node. The network was considered to exhibit RPA exactly when a distinguished output node, not necessarily distinct from the input node, could always return to a single, fixed value at steady- state (the 'setpoint'), independently of the magnitude of the input stimulus, and independently of the choice of parameter values. Using a topological method, where the flow of biochemical information could be partitioned into the subsets of a topology that accounted for the algebraic requirements of RPA, an exhaustive description of all possible RPA- compatible network designs, induced + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 844, 259]]<|/det|> +relative to the chosen input- output node pair, could be identified. This approach definitively established that all RPA- capable networks of this type must be decomposable into two types of well- defined topological structures, or 'modules' – Opposer modules and Balancer modules – and concluded that certain key 'computational nodes', corresponding to well- defined constraints on reaction kinetics, must be embedded into these modules. In particular, Balancer modules require one or more balancer nodes, exhibiting 'balancer kinetics' along with a single connector node, exhibiting 'connector kinetics'; Opposer modules, by contrast, require one or more opposer nodes, exhibiting 'opposer kinetics', organised (topologically) into structures known as 'opposing sets'. + +<|ref|>text<|/ref|><|det|>[[205, 277, 845, 640]]<|/det|> +But these conclusions, by themselves, provide absolutely no information on how these 'reaction constraints' might be realised, in general, by the intricate interactions among collections of molecules. Nor has it been clear until now how any of the known RPA- capable (or ACR- capable) collections of chemical reactions (CRNs) encode any of the topological requirements for RPA that we had identified in [1]. Indeed, in our earlier paper [1], our illustrative examples employed simple 'invented' functional forms (disconnected from CRN structures) which encapsulated the principles of opposer kinetics, or balancer/connector kinetics, in the most straightforward way, since the focus of that earlier work was the overarching network design principles that must hold at the network macroscale. An opposer node \(P_{o}\) , regulated by some node \(R\) , for instance, could be assigned a kinetics of the form \(dP_{o} / dt = k_{1}R - k_{2}\) , which is zero- order in \(P_{o}\) . But this contrived reaction form could certainly not be induced by a CRN for a variety of mathematical reasons, including the fact that (by the so- called 'Hungarian Lemma'), all terms preceded by a negative sign must include the species that is the subject of the reaction equation – in this case, \(P_{o}\) . Indeed it has been entirely unclear, until now, how the necessary conditions for RPA could be realised in general by 'real' chemical reactions involving molecules that interact in specific and potentially intricate ways according to a mathematical graph structure (i.e. a CRN). Previous studies (e.g. Shinar and Feinberg [7], Cappelletti et al. [2], Karp et al. [8], etc.) have only provided partial answers for particular special cases. + +<|ref|>text<|/ref|><|det|>[[205, 659, 844, 902]]<|/det|> +Of course, the antithetic integral control motif is a simple and well- known reaction structure that can serve as an 'opposer node', and can encode opposer kinetics (and thereby implement integral control) in a fairly obvious and straightforward manner via a particularly simple linear transformation. But this mechanism by no means explains the RPA (ACR) property observed in the Shinar- Feinberg deficiency- two model of the EnvZ- OmpR network, for example. In fact, until now, it has not been at all clear how the EnvZ- OmpR motif, or virtually any other known example of an ACR/RPA- capable CRN, might relate to the topological principles we identify in [1]. That the completely general description of RPA- permissive CRN graph structures, as we introduce in the present paper, should be able to map in such a clear, direct and well- defined way with our earlier universal description of RPA at the network macroscale is both remarkable and immensely satisfying. In particular, the revelation that balancer 'nodes', opposer 'nodes' and connector 'nodes' must necessarily be linear transformations of the CRN's molecular concentrations and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 85, 841, 188]]<|/det|> +that, combining these invariants nonlinearly in the very specific manner we describe here, gives rise to a completely general description of all possible RPA- capable CRNs, is entirely unexpected. A priori, there was no reason to think that there would necessarily be such a straightforward way to concretely reconcile the CRN microscale with established design principles of the network macroscale [1] on the basis of any previous work. Only in retrospect does this seem inevitable! + +<|ref|>text<|/ref|><|det|>[[205, 207, 844, 658]]<|/det|> +In any case, no previous study has made the well- defined connections we make here between CRN deficiency, network topology (encoding the flow of biochemical information through the graph structure of a CRN) and the internal model principle, in addition to the general results pertaining to the decomposition of the requisite nonlinear map (that extracts a suitable internal model) into a collection of linear maps, governed by the fundamental algebro- geometric requirements of RPA (and hence, ACR). As a consequence, no previous study has been able to provide a definitive description of all possible RPA- capable (and, more specifically, ACR- capable) CRNs, nor a well- defined algebraic condition (and associated algorithmic test) that captures the presence of the RPA property in any CRN that possesses it. Although there have certainly been previous ad- hoc attempts (e.g. in [5]) to demonstrate ACR/RPA capacity in a specific CRN via computation of a suitable Gröbner basis, these ad- hoc attempts, of themselves, are not generalisable (as we explain in greater detail later, in response to the reviewer's more specific queries regarding prior work). Moreover, there was no reason to think that this approach would be computationally feasible in general prior to our demonstration of the universal decomposition of the underlying nonlinear coordinate change into a connected sequence of linear maps. (Again, this is what we mean when we claim that the nonlinear map is 'almost linear'). Of even greater computational concern is that fact that, prior to our proof that the RPA polynomial (as we call it here) is always obtained via geometric projection onto exactly two variables (noting that 'variable' does not necessarily mean 'species'!), prior ad- hoc attempts to compute RPA- relevant Gröbner bases have been forced to use the most computationally expensive monomial ordering (i.e. the lexicographic ordering), since it was not known at the outset which, or how many, variables had to be eliminated. These former potential computational challenges have all been robustly resolved by the present work. + +<|ref|>text<|/ref|><|det|>[[206, 676, 848, 902]]<|/det|> +Of course, most of the RPA- capable CRNs that have been identified at the present time exhibit a special form of RPA known as Absolute Concentration Robustness (ACR). Unlike the abstract networks we consider in [1], there is no external 'input stimulus' for these networks, whose steady- states can only be altered by varying the total abundances of the various interacting molecules, as specified by the initial conditions for the reactions. For example, the Shinar- Feinberg models of the EnvZ- OmpR motif, comprising both deficiency- one and deficiency- two versions, are known to exhibit ACR in the phosphorylated OmpR moiety, yet no previous study of this motif (including the recent analysis of the deficiency- one version by Cappelletti et al. [2]), has succeeding in connecting the ACR capacity of this particular molecule to its topological balancer structure (and certainly not in a way that allows a general connection to be made to the set of all possible RPA/ACR- capable CRNs). As we show in great detail in our newly revised manuscript, a balancer structure arises + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 83, 844, 504]]<|/det|> +from the fact that, for this CRN, the one unit of deficiency encodes two parallel pathways that regulate the phosphorylation of OmpR, whereas the two units of deficiency (in the deficiency- two version) encodes three such feedforward pathways that regulate the same phosphorylation cycle. Indeed, it is the deep connection we identify between deficiency and the flow of biochemical information (topology), along with the relationship to modularity of the decomposition of RPA- capable CRNs into algebraically- independent subnetworks, that feature among the major conceptual advances of the present work. In our original submission, we had devoted the entirety of sections S4.2.1 and S4.2.2 in our SI to a succinct consideration of these ideas. In our revised submission, we have extensively revised the preliminary sections of our SI, adding in significant additional discussion on the significance of deficiency (a key CRNT concept) in Section S1.2, and have added in an entire new section (Section S1.3), which explains the concept of algebraically independent subnetworks of a CRN in great detail. (This is in contrast to our original submission, in which our far briefer discussion of algebraically independent subnetworks was delayed until Section S4.2.1). In our revised SI, the crucial connections between deficiency and topology are thereby made clear and explicit from the outset. We also briefly analyse the example of the Cappelletti et al. [2] toy model from the point of view of a decomposition into algebraically- independent subnetworks, along with a careful consideration of the partitioning of deficiency and rank into these subnetworks, so that the topological discussion of this (and other) networks in later Sections, as well as the general relationship of CRN topologies to deficiency and independent subnetworks, can be more readily appreciated by the general reader. + +<|ref|>text<|/ref|><|det|>[[205, 519, 842, 745]]<|/det|> +Importantly, ACR- capable CRNs, despite not being driven by exogenous inputs, nor perturbed by exogenous disturbances delivered to specific molecules, are still subject to the topological requirements that unify the broader class of RPA- capable CRNs which generally do involve external inputs – a deeply important result which fundamentally governs how such CRNs respond to perturbations by other (new) classes of disturbances (e.g. enzyme inhibitors and other small molecules), or new exogenous inputs/disturbances distinct from those represented in the original CRN. Since the detailed reaction structures governing complex cellular signalling networks (e.g. signal transduction networks in Metazoa) remain mostly unknown, having access to such a complete and universal description of RPA- capable CRN structures in the abstract is immensely powerful, particularly for considering new possibilities for molecular- targeted therapies, for instance, and for considering evolutionary alterations to CRNs. + +<|ref|>text<|/ref|><|det|>[[205, 762, 842, 902]]<|/det|> +We do acknowledge that our earlier work [1] foreshadowed the principle of a topologically distributed internal model, where one internal model could 'feed into' another topologically related one. Nevertheless, no prior work has been able to reconcile the mathematical properties of dynamical systems induced by CRNs with these previously- identified principles, and our current work highlights that making the fundamental connection between macroscale (e.g. from [1]) and CRN microscale poses significant mathematical challenges. Our new study clearly delineates the full suite of new mathematical ideas required – on the relationship of subsidiary linear + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 844, 206]]<|/det|> +invariants (polynomials) to the algebraic elimination problem; on the relationship of stoichiometric independence (which is itself a function of the algebraic structure of the vertices of the CRN graph) to the inability of polynomial invariants to 'pass' within the rowspan; and on the requirement for 'concatenating monomials' and the relationship of these to the topological structure of the CRN (for which we identify a previously unrecognised connection with CRN deficiency, as we explain in far greater detail in our revised submission). + +<|ref|>text<|/ref|><|det|>[[205, 225, 846, 293]]<|/det|> +We truly value the reviewer's feedback, which has helped us appreciate where our original submission failed to compellingly communicate the novel aspects of this work. We are deeply grateful for the reviewer's time and effort in re- considering our extensively revised work, and are thankful for his/her support. + +<|ref|>text<|/ref|><|det|>[[150, 326, 844, 412]]<|/det|> +- Many researchers have exploited Gröbner basis and ideal construction for obtaining steady-states in terms of parameters and in particular for studying ACR. For example, see [6, 5, 3] and references therein. It seems that the authors are unaware of these works and in order the assess the novelty of the methods in this paper, these existing works must be cited and discussed. + +<|ref|>text<|/ref|><|det|>[[205, 431, 846, 516]]<|/det|> +Our response: We thank the reviewer for highlighting these references, which use Gröbner bases to elucidate various aspects of CRNs and even consider ACR in one instance [5]. We value the reviewer's suggestion that the novelty of our new work could be made clearer by citing and discussing earlier work employing Gröbner bases and ideal construction in the context of chemical reaction networks. + +<|ref|>text<|/ref|><|det|>[[205, 534, 846, 604]]<|/det|> +We certainly acknowledge that the elucidation of polynomial ideals via Gröbner basis computations is well- known to have wide- ranging applications to problems in science and engineering [10]. We do not claim that the use of Gröbner bases, in and of itself, to elucidate some property of a polynomial system is novel. + +<|ref|>text<|/ref|><|det|>[[205, 621, 846, 900]]<|/det|> +There are actually exceedingly few published papers in the literature currently that employ Gröbner basis methods, or 'ideal construction' to study RPA/ACR specifically, other than the article by Perez Millan et al. [5]. Those authors compute a Gröbner basis in an ad- hoc manner for the deficiency- two EnvZ- OmpR motif, and use this result to demonstrate the capacity for ACR in one of the species. But the chief focus of that paper [5], and of the Craciun et al. paper [3], is not ACR, or RPA, but CRNs that exhibit toric steady- states. As our study makes clear, RPA- capable CRNs do not, in general, give toric ideals, or have toric steady- states. Although the EnvZ- OmpR motif analysed by Perez- Millan et al. [5], along with several of the illustrative examples we consider in our paper are characterised by toric ideals, it is clear that this could not possibly be a general property of RPA- capable CRNs for a number of reasons, including the fact that the pairing function \(g(x, y)\) (see our Theorem 1) can be a multi- term polynomial, and not simply a power product of species (monomial). In addition, even in cases where the RPA polynomial itself is a binomial, this condition does not guarantee that the steady- state ideal has a (standard) generating set composed entirely of binomials. A simple example of an RPA- capable CRN that is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 84, 844, 223]]<|/det|> +not generated by binomials, and is therefore not characterised by a toric ideal, is given in Figure 2 (previously Figure 1) of our main paper. (See, in particular, SI S5.2, where we compute a number of relevant Gröbner bases for this particular CRN, thereby demonstrating that the ideal corresponding to its chemical reaction rates cannot be generated by binomials). Thus, while the class of RPA- capable CRNs has a non- empty intersection with the class of toric dynamical systems, the study of toric ideals, unfortunately, cannot capture the fundamental essence of the RPA property in CRNs. + +<|ref|>text<|/ref|><|det|>[[206, 241, 832, 362]]<|/det|> +In our extensively revised SI, we provide a detailed commentary on the computational demands of Gröbner basis- computing algorithms from a complexity standpoint (see Remark 3 following Definition 3 in Section S1.5), and on the simplifying structure afforded by RPA- capable CRNs (owing to the 'almost- linear' coordinate change that we demonstrate can always extract the 'RPA polynomial' from the CRN rate equations). At the conclusion of those explanations, we explain that + +<|ref|>text<|/ref|><|det|>[[260, 380, 830, 555]]<|/det|> +"... the ACR- capacity of the deficiency- two EnvZ- OmpR motif was demonstrated via computation of a Gröbner basis, in an ad- hoc manner, by Perez Millan et al. [5]. But without knowing which, or how many, variables generally characterise the RPA- encoding elimination ideal, and without establishing the special 'almost linear' structure of the mathematical transformation required to identify the RPA polynomial in any RPA- capable CRN, this approach does not generalise, and cannot be applied to the systematic analysis of large and complicated CRNs (e.g. in the context of metabolism [11] for which candidate RPA- capable molecules have not already been posited from experimental evidence)." + +<|ref|>text<|/ref|><|det|>[[206, 588, 844, 727]]<|/det|> +Note that this is not a criticism of the Perez- Millan et al. [5] paper in any way. Again, the focus of the Perez Millan et al paper is not ACR- capable networks, so there is nothing amiss with their ad- hoc approach to the particular CRN they consider, which happens to be characterised by a toric ideal (which is the focus of their paper); they do not claim to present a general method that will necessarily be valid (or computationally feasible) for any ACR- capable CRN. They simply show that the particular CRN they consider does exhibit ACR, and the particular Gröbner basis they compute confirms this. + +<|ref|>text<|/ref|><|det|>[[206, 744, 833, 902]]<|/det|> +The Sadeghimanesh and Feliu paper [6], on the other hand, considers the computational demands of Gröbner basis algorithms for the analysis of CRNs, and proposes a transformation of CRNs containing 'intermediate species' to yield a core network from which these intermediates are absent. This approach allows a more computationally efficient monomial order to be employed in Gröbner basis computations, where only the intermediates are subject to the computationally- expensive lexicographic ordering, and with faster orderings (e.g. grevlex – graded reverse lexicographic) applied to non- intermediate species. Thus, what these authors effectively achieve is the development of a particular 'block ordering' on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 84, 846, 154]]<|/det|> +monomials, and which can potentially speed up Gröbner basis computations quite significantly in comparison with a 'complete' lexicographic monomial ordering. This approach can be employed, in principle, for any CRN containing intermediate species (as defined in their paper [6]) – not just RPA- capable CRNs. + +<|ref|>text<|/ref|><|det|>[[205, 171, 845, 659]]<|/det|> +Our paper, by contrast, focusses squarely on RPA- capable CRNs, and aims to discover their general properties. For these CRNs, in contrast to the much broader class of CRNs considered by Sadeghimanesh and Feliu [6], the computational demands confronting any Gröbner basis computations are comparatively very light. There are two reasons for this: (1) If the CRN is indeed RPA- capable, then Theorem 1 guarantees that the RPA polynomial can be obtained via elimination of all but two variables. As a consequence (and as we point out explicitly in Section S5 where we instruct the reader on the implementation of these algorithms in Singular, using a variety of illustrative examples), we can always use a 'block ordering' on monomials, where the two chosen projection variables are ordered 'lower' than the remaining variables. Having established this, the computationally expensive lexicographic ordering is not required: both of the 'blocks' in this special elimination order can now accommodate a fast monomial ordering (e.g. grevlex, sometimes referred to as degrevlex, which uses the syntax 'dp' in Singular). But there is a second, and more important reason: (2) The transformation that reveals the RPA polynomial is 'almost linear' in the sense that only \(\mathbb{R}\) - linear combinations of the rows of the system are required to identified the 'fundamental' (subsidiary) polynomial invariants (which are subsequently combined nonlinearly via concatenating monomials). For this reason, the syzygy polynomials (S- polynomials) that are calculated as part of Buchberger's algorithm are identical to the linear row combinations that are computed during Gaussian elimination. But note that this computational 'streamlining' is linked inextricably to the special CRN structures that implement RPA, and establishing this key property is one of the highly novel contributions of our work. For more general CRNs, computing Gröbner bases may be computationally infeasible (especially if imposing a global lexicographic ordering at the outset, as one is often forced to do without any prior analytical guideposts); from this point of view, the approach offered by Sadeghimanesh and Feliu [6] is both interesting and potentially helpful. + +<|ref|>text<|/ref|><|det|>[[205, 675, 843, 780]]<|/det|> +We also emphasize that the existence of an algorithm that can test for the RPA- capacity in a particular CRN does not, in and of itself, reveal the definitive properties of all possible RPA- capable CRNs. Our paper is not "about" Gröbner bases as such. That we can, indeed, employ Gröbner basis- computing algorithms (e.g. Buchberger's algorithm) to test for RPA capacity, in general, is a consequence of the special properties of RPA- capable CRNs that we identify for the first time in this new paper. + +<|ref|>text<|/ref|><|det|>[[150, 830, 768, 902]]<|/det|> +- More importantly, the central analysis in this paper crucially depends on the result for deficiency one networks which is stated as Theorem 3 in the Supplement. However, this result is not new, as it follows from Theorem D.1 in the Supplement of [2] (see the proof in [2]). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[204, 100, 840, 397]]<|/det|> +Our response: We have carefully scrutinized the proof to Theorem D.1 in the Supplement of [2], and acknowledge that the reviewer is entirely correct to note that our Theorem 3 follows directly from Theorem D.1 in [2], and that our essential mathematical argument is virtually identical to that in [2]. We have now updated our preamble to Theorem 3 (Section S4.2) to emphasize to the reader that this alternative version of Shinar- Feinberg's theorem draws on arguments developed by Cappelletti et al. [2], and provide a reference to Theorem D.1 in [2]. In the interests of a more comprehensive and scholarly exposition of the key ideas (for later use in the remaining sections of the SI), we have also taken this opportunity to add in a second version of the theorem (Theorem 4), applicable to deficiency- zero CRNs, which shows that binomials involving any pair of terminal complexes from the same terminal SCC must also reside in the rowspan of the CRN reaction equations. Following these two theorems, we also add a remark, again citing Cappelletti et al. [2] Proposition C.5, that the same mathematical arguments (as employed in Theorems 3 and 4) can readily be extended to demonstrate that binomials involving either a terminal complex and a non- terminal complex, or two terminal complexes from different SCCs, can never reside in the rowspan of a CRN. + +<|ref|>text<|/ref|><|det|>[[204, 414, 844, 676]]<|/det|> +We sincerely thank the reviewer for his/her careful attention to this key technical detail, and for ensuring that all mathematical concepts presented in our work are correctly attributed. We feel that the presentation of the mathematical ideas in this section are now much more comprehensive and scholarly, and the additional references to the Cappelletti et al. [2] paper are immensely valuable. We would like to respectfully emphasize, however, that the novelty of our present paper lies in not so much in our Theorem 3 (or D.1 in [2]) but in demonstrating how this result on deficiency- one (and deficiency- zero) networks may be extended to RPA- capable networks of any deficiency. The remainder of the SI, following Theorems 3 and 4, is devoted to precisely this goal. (The generalisations the arbitrary deficiency are also much more clearly and thoroughly communicated in our revised manuscript, with the help of the comprehensive explanations in the earlier sections of the SI (particularly Sections S1.2 and S1.3) on how deficiency governs the flow of biochemical information within a CRN (and ultimately relates to topology), as well as the decomposition of a CRN into algebraically independent subnetworks). + +<|ref|>text<|/ref|><|det|>[[150, 725, 787, 830]]<|/det|> +- Definition of RPA: The notion of RPA is not mathematically defined. In other words, it is not clear what disturbances are allowed and what are the biochemical parameters on which the output set-point is allowed to depend. On page 11 in the Supplement it is written that for RPA the set-point c should be a rational function of the biochemical rate constants. However, this would be the case for any steady-state and so what constitutes RPA is not clear. + +<|ref|>text<|/ref|><|det|>[[205, 848, 797, 899]]<|/det|> +Our response: The reviewer's point that we should have given a more explicit mathematical definition of RPA is well taken. We truly appreciate such helpful advice. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 102, 742, 137]]<|/det|> +We now include the following text at the beginning of Section S1 in our Supplementary Information: + +<|ref|>sub_title<|/ref|><|det|>[[206, 155, 340, 170]]<|/det|> +## Definition of RPA + +<|ref|>text<|/ref|><|det|>[[206, 172, 838, 293]]<|/det|> +In this study we consider Robust Perfect Adaptation (RPA) from the most general possible viewpoint. In particular, a CRN exhibits RPA in the concentration, \(x\) , of some molecule exactly when \(x\) maintains a constant steady- state value, \(c\) (the molecule's 'setpoint'), for all steady- states of the system. The setpoint, \(c\) , is a function of some collection of CRN parameters. Moreover, the CRN exhibits RPA (in \(x\) ) in response to any perturbation or disturbance that does not feature in the functional form of the setpoint, \(c\) . + +<|ref|>text<|/ref|><|det|>[[206, 310, 839, 361]]<|/det|> +With this very broad definition of RPA in mind, we recognise that there are many possible types of perturbations/disturbances that could alter the steady- state of the system: + +<|ref|>text<|/ref|><|det|>[[234, 363, 839, 432]]<|/det|> +1. One or more 'external' inputs. A disturbance of this type could arise in the form of some input molecule, \(I\) , whose concentration is given by a step function generated by an 'exosystem' \((dI / dt = 0\) , not included among the CRN reaction rates). + +<|ref|>text<|/ref|><|det|>[[234, 433, 844, 675]]<|/det|> +2. Alterations in total expression levels (abundances) of the interacting molecules. If this is the only type of perturbation possible, then the CRN is considered a 'conservative network', corresponding to a 'closed' system (see [9], Chapter 4). In this scenario, the CRN captures the interconversion of molecules among a variety of possible forms. The dynamical system is thereby constrained to evolve within a particular stoichiometric compatibility class (an affine space parallel to the CRN's stoichiometric subspace - see Section S1.2) determined by the initial conditions. The orthogonal complement to the stoichiometric subspace determines the conservation relations for the CRN, which specify the constant expression levels of the various interacting molecules. Where a molecule can exhibit a fixed concentration across all steady-states when the CRN is subject to perturbations to these total expression levels, this type of RPA is referred to as Absolute Concentration Robustness (ACR, see Chapter 9 in [9]). + +<|ref|>text<|/ref|><|det|>[[234, 676, 844, 783]]<|/det|> +3. A disturbance that is encoded in a CRN parameter such as a production rate, \(\mu\) , of some molecule, \(M\) , as reflected in a CRN reaction of the form \(\phi \xrightarrow{\mu} M\) . Note that CRN parameters determined by the intrinsic chemical properties of the interacting molecules (e.g. association/dissociation constants, catalytic constants, etc.) are very stable and not readily perturbed, except via mutation of the interacting molecules. + +<|ref|>text<|/ref|><|det|>[[206, 802, 842, 906]]<|/det|> +In the pursuit of greatest generality, we make no assumptions a priori as to which type of network perturbation might affect a CRN, nor do we impose any restrictions on which (or how many) parameters determine the setpoint. Of course, if the setpoint for a putative RPA-capable molecule involves a parameter \(\mu\) that can be perturbed (see case 3. above) then it is clear that the molecule cannot exhibit RPA in response to that particular disturbance. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 101, 844, 136]]<|/det|> +We can appreciate that the reviewer might have a different perspective on RPA from us, and hope that he/she is willing to accept our viewpoint and mathematical goals. + +<|ref|>text<|/ref|><|det|>[[205, 153, 847, 345]]<|/det|> +Regarding the reviewer's comment that "the set- point c (being) a rational function of the biochemical rate constants ... would be the case for any steady- state" – we agree completely with the reviewer on this point. All variables of the CRN would certainly achieve some steady- state that is a rational function of parameters; but not all variables would achieve the same rational function of parameters across all possible steady- states of the system. By noting that the setpoint is a rational function of parameters, we do not intend to convey that the steady- states of other variables are not rational functions of parameters. We are simply pointing out the mathematical nature of the setpoint (which can ultimately be computed automatically via the algorithm we propose) for the benefit of the general reader, to whom such properties may not be obvious. We did not intend this to be a major point. + +<|ref|>text<|/ref|><|det|>[[150, 379, 800, 501]]<|/det|> +- Algorithm may not terminate: The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima-facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In particular, no proof is given showing that non-termination implies no RPA. Moreover, non-termination of a method is not something that can be ascertained with any certainty by running the code. Accordingly, the authors cannot claim that they have a full 'characterisation' of the RPA property. + +<|ref|>text<|/ref|><|det|>[[205, 519, 808, 553]]<|/det|> +Our response: We thank the reviewer for this comment and for giving us the opportunity to provide greater clarity on these points in our revised manuscript. + +<|ref|>text<|/ref|><|det|>[[205, 570, 845, 866]]<|/det|> +First, we respectfully point out that Buchberger's algorithm, which computes Gröbner bases, always terminates. This is because all ideals of a polynomial ring (or any Noetherian ring, for that matter) are finitely generated – a result of central importance in algebraic geometry, formalized by the Hilbert Basis Theorem. As a consequence, we are assured that Buchberger's algorithm will terminate in a finite number of steps. The problem, of course, is that the finite number of steps required could, and often will, be unmanageably large! The computational demands of Buchberger's algorithm are well known, and we do acknowledge in our paper (in both our original and revised submissions) that the problem of determining whether a general collection of polynomials constitutes a Gröbner basis (also known as the Gröbner basis detection (GBD) problem) is NP- Hard. The computational demands of Buchberger's algorithm are clear from an examination of the algorithm itself; the demands are even greater when a lexicographic monomial ordering is used since this necessarily implements a computationally expensive polynomial division process in comparison with other monomial orders. The complexity class of the GBD has been well known since the 1990s (due mainly to the work of Bernd Sturmfels and others), and has been widely discussed in the literature. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[204, 84, 840, 520]]<|/det|> +We respectfully point out that our study does, in fact, make clear why RPA- capable CRNs have a special property which guarantees that Buchberger's algorithm will terminate in polynomial time if the CRN does indeed exhibit RPA. Indeed, we demonstrate that the mathematical transformation required to obtain the RPA polynomial from the reaction rate equations is almost linear in the sense that only \(\mathbb{R}\) - linear combinations of these equations are required to produce the 'subsidiary' polynomial invariants which are then 'concatenated' by monomials. And as long as only \(\mathbb{R}\) - linear combinations of the polynomials are required, the syzygy polynomials ("S- polynomials") that are computed at each step of Buchberger's algorithm are precisely the linear row combinations computed during Gaussian elimination (a polynomial- time algorithm). Indeed, for the simple CRNs considered by Cappelletti et al. [2], for instance, where the RPA polynomials of the CRNs were in the rowspan (no concatenating monomials required), then Buchberger's algorithm is, in fact, Gaussian elimination. Those authors present an efficient method to calculate which particular linear combination of the reaction rates is required to 'achieve' this RPA polynomial. But it is clear that for any CRN with an RPA polynomial in the rowspan of its reaction equations, the RPA polynomial itself can be obtained algorithmically by Gaussian elimination. In particular, if the equations are expressed in the matrix form \(\mathrm{dX / dt} = \mathrm{Ax}\) , where \(\mathbf{x}\) is the vector of monomials, and the two monomials of the candidate RPA polynomial are listed last (at the bottom of the vector), then performing Gaussian elimination on A will result in an echelon form in which the bottom non- zero row has exactly two entries (corresponding to the two coefficients of the constituent terms of the RPA polynomial). Which linear combinations are required to achieve the rows of this echelon form can be stored during the execution of Gaussian elimination (producing an LU- decomposition, for example). + +<|ref|>text<|/ref|><|det|>[[205, 537, 847, 762]]<|/det|> +This process readily extends to the more general (nonlinear, but 'almost linear') case. The row combinations (corresponding to construction of S- polynomials) that are calculated during the execution of Buchberger's algorithm may be stored, and retrieved subsequently using the 'LIFT' command in Singular. We demonstrate this in the detailed annotations to our code in Section S5. Where only \(\mathbb{R}\) - linear combinations of the CRN equations are required to identify the RPA polynomial (as is for the cases considered by Cappelletti et al. [2]), the coefficients retrieved by LIFT will contain only 'constants' (polynomial functions of the CRN parameters). If the RPA polynomial is not in the rowspan, the row combinations retrieved by LIFT will contain (only) the concatenating monomials required to combine adjacent 'complex linear invariants' (subsidiary polynomials corresponding to topological features of the underlying flow of biochemical information in the CRN), in addition to the constants involving CRN parameters. + +<|ref|>text<|/ref|><|det|>[[206, 780, 846, 867]]<|/det|> +In reflecting on the reviewer's feedback, we have made extensive revisions to our paper to ensure that the technicalities surrounding the computational complexity of Gröbner basis computations for RPA- capable networks are completely clear and explicit. We now make extensive clarifications on these points throughout the SI. In Remark 3 following our proof to Theorem 1, for example, we explain that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 840, 537]]<|/det|> +"...With a well- defined algebraic elimination problem now at hand, with two candidate variables selected for the geometric projection, the existence of an RPA polynomial as the sole generator of the relevant elimination ideal can always be tested in principle via the computation of a suitable Gröbner basis [10]. Unfortunately, the problem of computing Gröbner bases (e.g. via Buchberger's algorithm) for general polynomial systems is well known to be NP- Hard [refs], so without any special simplifying structure to the collection of polynomials, we can have no assurance that any Gröbner basis- computing algorithm will terminate on a practical time- frame. However, we will show in the Sections to follow that RPA- capable CRNs do indeed have a special structure that allows the relevant Gröbner basis to be computed rapidly, on a time- scale comparable to Gaussian elimination. This is because the fundamental 'building blocks' of the RPA polynomial (i.e. its subsidiary polynomial invariants), always reside in the rowspan of the CRN reaction equations (see Sections S3 and S4), and the RPA polynomial can always be constructed from these by multiplying each by a 'concatenating monomial' (where necessary, depending on the stoichiometric dependence of the invariants, see Section S3), and adding the resulting polynomials. As a consequence, the most computationally- demanding component of the resulting algorithm for an RPA- capable CRN (cf. general polynomial systems) is the computation of these subsidiary polynomial invariants (also known as 'complex linear invariants' [8]) from the CRN reaction equations. Note, in particular, that where only \(\mathbb{R}\) - linear combinations of the rows of \(Y\mathcal{L}(G)\) are computed, the S- polynomials of Buchberger's algorithm are identical to the row combinations obtained during Gaussian elimination (applied to the matrix \(Y\mathcal{L}(G)\) ). Gaussian elimination is well- known to be a polynomial- time algorithm, which terminates rapidly even for relatively large numbers of variables (or complexes, in the case of CRNs). + +<|ref|>text<|/ref|><|det|>[[206, 555, 841, 623]]<|/det|> +Later, in Section S4, before providing the detailed mathematical development of our approach for computing RPA- relevant polynomials in the rowspan of the rate equations - for low deficiency CRNs ( \(\delta = 0,1\) ) in the first instance, and then for CRNs of arbitrary deficiency ( \(\delta >1\) ) - we explain that: + +<|ref|>text<|/ref|><|det|>[[205, 641, 848, 902]]<|/det|> +"... it is only on account of this special 'almost linear' coordinate change that the feasibility of this approach is guaranteed: as we noted in our remarks following Theorem 1, the general problem of computing Gröbner bases, for general collections of polynomials, is known to be NP- Hard. But the fact that the RPA polynomial can always be computed by combining a collection of polynomials in the rowspan of the system means that the algorithm that extracts the RPA polynomial from the CRN reaction equations does not differ substantially from Gaussian elimination. Moreover, even for an arbitrary choice of two projection variables, our statement of Theorem 1 offers opportunities for additional computational efficiency when computing a suitable Gröbner basis insofar as only one particular elimination ideal is required (i.e. that comprising the two chosen variables). Without prior knowledge of this particular property of the RPA polynomial, a full set of all elimination ideals for the system would be required, which necessitates an expensive lexicographic monomial ordering in the execution of the algorithm. With only one elimination ideal required, a more efficient block ordering may be chosen, with a comparatively + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 85, 833, 118]]<|/det|> +fast (e.g. degree reverse lexicographic) ordering imposed on all but the two chosen variables." + +<|ref|>text<|/ref|><|det|>[[205, 136, 845, 293]]<|/det|> +In addition, we provide much more extensive explanations throughout our SI of the mathematical technicalities underpinning this 'almost- linear' coordinate change that can always extract the RPA polynomial from the chemical reaction rates of an RPACapable CRN. The reviewer is quite right to be astounded by this special property of CRN- capable networks. It is truly remarkable (and entirely non- obvious) that the requisite mathematical structure of chemical reactions that are compatible with RPA should be characterised by such a simplicity as to obviate the computational 'black holes' that can exist for general polynomial systems, including CRN models that do not exhibit RPA. + +<|ref|>text<|/ref|><|det|>[[147, 328, 783, 363]]<|/det|> +- Form of the RPA polynomial: The whole approach hinges on the RPA polynomial having the form + +<|ref|>equation<|/ref|><|det|>[[429, 363, 580, 381]]<|/det|> +\[\rho = g(x,y)(x - c)\] + +<|ref|>text<|/ref|><|det|>[[147, 380, 787, 470]]<|/det|> +where \(g(x,y)\neq 0\) and \(y\) is a non- RPA capable variable which forms the kinetic pair to \(x\) . It is unclear why \(g(x,y)\) can only be a function of one additional variable, apart from the output variable. The proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f}\cap \mathbb{R}[\bar{x} ]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f}\cap I_{p}\) + +<|ref|>text<|/ref|><|det|>[[147, 487, 502, 504]]<|/det|> +As an example consider the following network: + +<|ref|>equation<|/ref|><|det|>[[316, 518, 679, 544]]<|/det|> +\[\mathrm{X}_2 + \mathrm{X}_3\xrightarrow{c_1}\mathrm{X}_1 + \mathrm{X}_4\quad \mathrm{and}\quad \mathrm{X}_1 + \mathrm{X}_2 + \mathrm{X}_3\xrightarrow{c_2}\mathrm{X}_5.\] + +<|ref|>text<|/ref|><|det|>[[147, 560, 811, 640]]<|/det|> +Furthermore assume that species \(X_{2}\ldots X_{5}\) participate in several reactions that do not involve \(X_{1}\) but can be catalysed by it. In this scenario the RPA polynomial would be \(\rho = x_{2}x_{3}\left(\frac{c_{1}}{c_{2}} - x_{1}\right)\) . Hence the function \(g\) depends on two non- RPA variables \(x_{2}\) and \(x_{3}\) . Please explain how this example is consistent with the form of \(g(x,y)\) stated above. + +<|ref|>text<|/ref|><|det|>[[205, 656, 805, 707]]<|/det|> +Our response: Let us first respond to the reviewer's question regarding the proposed network, and its relationship to the two- variable requirement, before returning to the reviewer's concerns about our proof to Theorem 1. + +<|ref|>text<|/ref|><|det|>[[205, 725, 828, 847]]<|/det|> +The reviewer proposes two chemical reactions, and adds that we should also 'assume that species \(X_{2}\ldots X_{5}\) participate in several reactions that do not involve \(X_{1}\) but can be catalysed by it'. Indeed, in the specific reactions proposed by the reviewer, \(X_{2}\) and \(X_{3}\) are only consumed, not produced, whereas \(X_{4}\) and \(X_{5}\) are only produced, not consumed; thus, there must be some additional reactions involving these four variables, so that \(X_{2}\) and \(X_{3}\) can be produced and \(X_{4}\) and \(X_{5}\) consumed, giving the CRN the potential to achieve a steady- state in the positive orthant. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 839, 136]]<|/det|> +Let us consider several possible ways to 'close' the reaction set (i.e. add in reactions that produce \(X_{2}\) and \(X_{3}\) and consume \(X_{4}\) and \(X_{5}\) ). First, let us consider two additional closure reactions of the simplest possible form: + +<|ref|>equation<|/ref|><|det|>[[396, 136, 603, 158]]<|/det|> +\[X_{4}\stackrel {c_{3}}{\rightarrow}X_{2}\quad \mathrm{and}\quad X_{5}\stackrel {c_{4}}{\rightarrow}X_{3}.\] + +<|ref|>text<|/ref|><|det|>[[205, 175, 847, 350]]<|/det|> +We emphasize that these are not suggested to be the 'best', or most biologically meaningful, or realistic, closure reactions, only that they constitute a simple solution that allows us to proceed in the first instance. Let \(x_{1}, x_{2}, x_{3}, x_{4}, x_{5}\) be the concentrations of the five species. In this case, the mass- action equations for this collection of four reactions contain a boundary variable, \(x_{2}x_{3}\) - a concept which we clearly and prominently define ("Definition 1") at the beginning of Section S1.5 in our SI, in the context of defining what we mean by a variable, before proceeding to invoke this terminology in our statement and proof of Theorem 1 (the two- variable kinetic pairing theorem). Indeed, the rate equations that are induced by this collection of four reactions are: + +<|ref|>equation<|/ref|><|det|>[[203, 366, 540, 460]]<|/det|> +\[f_{1} = c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3},\] \[f_{2} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}\bar{x}_{3} + c_{3}x_{4},\] \[f_{3} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}\bar{x}_{3} + c_{4}x_{5},\] \[f_{4} = c_{1}x_{2}x_{3} - c_{3}x_{4},\] \[f_{5} = c_{2}x_{1}x_{2}x_{3} - c_{4}x_{5}.\] + +<|ref|>text<|/ref|><|det|>[[203, 472, 845, 860]]<|/det|> +In any case, it is clear from these equations (and, indeed, clear from the corresponding reactions themselves) that \(x_{2}x_{3}\) is a boundary variable for this CRN, since both \(x_{2}\) and \(x_{3}\) only appear in the monomials of these rate equations in the form of the factor \(x_{2}x_{3}\) . (In other words, neither species occurs either alone or contributes to a monomial that also contains some other species (e.g. \(x_{2}x_{4}\) or \(x_{5}x_{3}\) , say). This CRN thus comprises five species but four variables: \(\{x_{1}, x_{2}x_{3}, x_{4}, x_{5}\}\) . But in this particular CRN, the boundary variable technicality happens to be a moot point since this CRN is not capable of RPA (or ACR). This is because \(< f_{1}, f_{2}, f_{3}, f_{4}, f_{5} > \cap \mathbb{R}[x_{1}, x_{2}x_{3}] = < x_{2}x_{3} >\) . In other words, the generator of the ideal consisting of all polynomial consequences of \(f_{1}, f_{2}, f_{3}, f_{4}\) and \(f_{5}\) containing only the variables \(x_{1}\) and \(x_{2}x_{3}\) is not an RPA polynomial. Thus, for all steady- states of the system, regardless of parameter choices or initial conditions, \(x_{2}x_{3} = 0\) , and RPA is thereby not imposed on \(x_{1}\) , despite the fact that one of the reaction rates (\(f_{1}\) in this instance) is an RPA polynomial. In fact, our Theorem 1 makes this important subtlety crystal clear: as counterintuitive as it may seem, it is not enough for an RPA polynomial to be one of the reaction rates, or be otherwise contained in the ideal generated by a CRN's reaction equations. Rather, an RPA polynomial must generate the ideal \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) and this ideal must be principal (i.e. the RPA polynomial must be the sole generator of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) ) in order for the CRN to exhibit RPA. Just to emphasize, \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) constitutes the projection of the ideal \(< f_{1}, \ldots , f_{n} >\) onto two variables (again, being mindful of how we define a variable) - the putative RPA variable along with one non- RPA variable. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 848, 310]]<|/det|> +Although we carefully define and explain the key concept of a boundary variable (see Definition 1 and ensuing discussion in Section S1.5), and elaborate on the concept again in Example 2 in Section S3.2, where we carefully explain that the CRN in question has nine species but eight variables due to the presence of a boundary variable (see discussion after Equation (34)), we recognise that these points must not have been sufficiently clear to the reviewer in our original submission. In our extensively revised SI, we have now provided the reader with a brief overview of the reviewer's CRN example in order to further highlight and explain the concept of a boundary variable in Section S1.5. We have also supplemented our explanations with the alternative terminology "power product" (another word for monomial) just to be absolutely sure that the concept will be absolutely clear to the general reader. We thank the reviewer for providing such a simple and clear example of a CRN that contains a boundary variable to enhance our explanations of this key concept. + +<|ref|>text<|/ref|><|det|>[[205, 328, 844, 555]]<|/det|> +Please allow us the opportunity to expand even further on the subtleties that RPA imposes on the detailed underlying structures of CRNs via some additional examples, since the reviewer has been kind enough to offer such a fruitful and illuminating CRN example. In particular, let us now consider two other possible alternatives for closing the reaction set provided by the reviewer. The reviewer specifically suggests a scenario where the added reactions involving \(X_{2} \ldots X_{5}\) "do not involve \(X_{1}\) but can be catalysed by it". In line with this suggestion, let us suppose that either one, or possibly both, of the two additional reactions include \(X_{1}\) as both a reactant and a product, thereby endowing it with the properties of a catalysing enzyme that is neither produced nor consumed by the reaction. (We assume this is what the reviewer means by not involving \(X_{1}\) "but can be catalysed by it"? The wording is not 100% clear as to what the reviewer actually had in mind here. We apologise if we have misunderstood the reviewer's intentions.) + +<|ref|>text<|/ref|><|det|>[[204, 572, 840, 590]]<|/det|> +Suppose, then, that the reaction associated with rate constant \(c_{3}\) is now replaced by + +<|ref|>equation<|/ref|><|det|>[[452, 590, 602, 611]]<|/det|> +\[X_{1} + X_{4}\xrightarrow{c_{3}}X_{1} + X_{2}.\] + +<|ref|>text<|/ref|><|det|>[[204, 627, 827, 647]]<|/det|> +This altered \(c_{3}\) reaction leaves \(f_{1}, f_{3}\) and \(f_{5}\) unaffected, but \(f_{2}\) and \(f_{4}\) now become: + +<|ref|>equation<|/ref|><|det|>[[204, 661, 576, 700]]<|/det|> +\[\begin{array}{rl} & f_{2} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3} + c_{3}x_{1}x_{4},\qquad \mathrm{(Eq.6)}\\ & f_{4} = c_{1}x_{2}x_{3} - c_{3}x_{1}x_{4}, \end{array} \quad (Eq.7)\] + +<|ref|>text<|/ref|><|det|>[[205, 715, 829, 802]]<|/det|> +We observe that \(x_{2}x_{3}\) is still a boundary variable for this altered CRN. When we project the ideal generated by \(f_{1}, f_{2}, f_{3}, f_{4}, f_{5}\) (using the updated versions of \(f_{2}\) and \(f_{4}\) ) onto \(x_{1}\) and \(x_{2}x_{3}\) , we still obtain \(< x_{2}x_{3} >\) . Thus, the CRN is again thwarted in any attempt to impose RPA on \(x_{1}\) , since \(x_{2}x_{3} = 0\) at all steady- states for this CRN (regardless of parameters or initial conditions). + +<|ref|>text<|/ref|><|det|>[[205, 819, 806, 888]]<|/det|> +Finally, let us consider the possibility that one of the species that appears in the boundary variable (say \(X_{2}\) , for argument's sake) catalyses one of the additional closure reactions, rather than \(X_{1}\) . In this case, the reaction associated with rate constant \(c_{3}\) is replaced by + +<|ref|>equation<|/ref|><|det|>[[464, 888, 590, 911]]<|/det|> +\[X_{2} + X_{4}\xrightarrow{c_{3}}2X_{2},\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 101, 414, 118]]<|/det|> +and \(f_{2}\) and \(f_{4}\) now become: + +<|ref|>equation<|/ref|><|det|>[[204, 135, 576, 174]]<|/det|> +\[\begin{array}{r l} & {f_{2} = -c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3} + c_{3}x_{2}x_{4},}\\ & {f_{4} = c_{1}x_{2}x_{3} - c_{3}x_{2}x_{4}.} \end{array} \quad (Eq.8)\] + +<|ref|>text<|/ref|><|det|>[[204, 188, 840, 222]]<|/det|> +In this case, \(x_{2}x_{3}\) is no longer a boundary variable since \(x_{2}\) now also features in the monomial \(x_{2}x_{4}\) . Thus, this CRN comprises five variables (all species): + +<|ref|>text<|/ref|><|det|>[[204, 222, 843, 380]]<|/det|> +\(\{x_{1},x_{2},x_{3},x_{4},x_{5}\}\) . So, to test for RPA, we now attempt to project onto \(x1\) and \(x2\) . In this case, \(< f_{1},f_{2},f_{3},f_{4},f_{5} > \cap \mathbb{R}[x_{1},x_{2}]\) contains only zero (the additive identity for the ring). As expected, the ideal \(< f_{1},f_{2},f_{3},f_{4},f_{5} > \cap \mathbb{R}[x_{1},x_{3}]\) also contains only zero. Thus, the CRN remains incapable of RPA. If, instead, we attempt to compute \(< f_{1},f_{2},f_{3},f_{4},f_{5} > \cap \mathbb{R}[x_{1},x_{2},x_{3}]\) , projecting onto the three variables that appear in the apparent RPA polynomial in the \(f_{1}\) reaction rate, we find that this elimination ideal is given by \(< x_{2}x_{3}>\) . This confirms that for this CRN, either \(x_{2}\) or \(x_{3}\) (or both) is zero for all possible steady- states of the system. Therefore, this CRN fails to exhibit RPA (at \(x_{1}\) or otherwise). + +<|ref|>text<|/ref|><|det|>[[204, 397, 845, 656]]<|/det|> +We warmly invite the reviewer to verify for himself/herself that the three versions of this particular CRN cannot, under any parametric circumstances, exhibit RPA. To assist, we have simulated the second version of the CRN discussed above for 10,000 randomised parameter sets, \(c_{i} \in (1,100)\) , and initial conditions, \(x_{i}(0) \in (1,100)\) , see Figure below. From these histograms, the significance of having one rate equation \((f_{1})\) in the form of an RPA polynomial is clear: If, for a specific random choice of parameters and initial conditions, \(x_{1}\) reaches the value \(c_{1} / c_{2}\) before \(x_{2}\) or \(x_{3}\) reaches zero, then the \(x_{1}\) - coordinate stops evolving and \(x_{1}\) does attain the 'apparent' setpoint at steady- state. But if either \(x_{2}\) or \(x_{3}\) reaches zero first (before \(x_{1}\) reaches \(c_{1} / c_{2}\) ), then \(x_{1}\) remains at whatever value it reached at the moment \(x_{2}\) or \(x_{3}\) reaches zero. Thus, the steady- state value of \(x_{1}\) is a matter of chance, dependent upon the vagaries of parameters in comparison with initial conditions. There is a bias in the steady- state value for \(x_{1}\) , with mode of the distribution at \(c_{1} / c_{2}\) , but \(x_{1}\) can achieve any value in principle at steady- state. Thus, the CRN does not exhibit RPA. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[244, 100, 750, 420]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[206, 425, 848, 504]]<|/det|> +
Figure: Steady-state concentrations for \(x_{1}\) , and for \(x_{2}x_{3}\) , obtained from 10,000 simulations of the second of the three CRNs discussed above. Simulations for the other two CRNs are qualitatively very similar. For each simulation, rate constants \((c_{1}, \ldots , c_{5})\) and initial conditions \((x_{1}(0), \ldots , x_{5}(0))\) are randomly selected from the interval (1,100). We gratefully acknowledge the assistance of my (RA's) graduate student, Cailan Jeynes-Smith, in the preparation of this Figure.
+ +<|ref|>text<|/ref|><|det|>[[205, 520, 845, 782]]<|/det|> +The fact remains that our Theorem 1 provides a definitive and universal condition that must be satisfied by any RPA- capable CRN - no exceptions, not even for CRNs that happen to have an RPA polynomial in the rowspan!! (Interesting, the authors of the Cappelletti et al. paper [2] appear to have overlooked this subtlety). We hope that the reviewer can now begin to appreciate that these remarkable and highly- restrictive conditions on the detailed graph structures of RPA- capable CRNs could never possibly have been gleaned just from our prior work in [1], or by any other prior work (including the work of Cappelletti et al [2]). All three examples we analyse above are incapable of RPA since they violate the conditions specified in our Theorem. Specifically, in each case, the intersection of the ideal generated by the reaction equations with a suitable polynomial ring in two variables (ie. one that comprises one RPA variable and one non- RPA variable, once again being mindful of what we mean by a variable), is not generated by a single polynomial that takes the form of an RPA polynomial. The fact that each CRN induces a reaction rate \((f_{1})\) that happens to be in the form of an RPA polynomial is (surprisingly, perhaps) irrelevant. + +<|ref|>text<|/ref|><|det|>[[205, 799, 837, 903]]<|/det|> +We warmly encourage the reviewer to consider other chemical reactions to add to the pair he/she has proposed. Unlike the Cappelletti et al. [2] study (for example), our study goes far beyond simply 'testing' for the RPA capacity of particular CRN examples (and identifying integral variable(s) if the test is successful). Indeed, our article clarifies in detail (and even more explicitly and incisively now due to our extensive revisions, thanks to the reviewer's helpful feedback and suggestions) how + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[204, 81, 847, 572]]<|/det|> +the deficiency of an RPA- capable CRN relates to topological features of the CRN, and concretely delineates the role of this key algebraic invariant in controlling the formation of RPA- relevant 'complex linear invariants' in the CRN's rowspan. For this reason, we can go much further than simply proving that the three specific examples discussed above (encompassing the reviewer's suggested reactions) cannot exhibit RPA: The two reactions proposed by the reviewer cannot impose RPA on \(X_{1}\) no matter which reactions are added to the original two. This is because the two given reactions are linearly independent, and the CRN formed from these reactions has deficiency zero. Moreover, the two complexes that contribute to the apparent RPA- polynomial in the reaction rate \(f_{1}\) are not members of the same terminal SCC. It is clear from our discussion of the decomposition of CRNs into algebraically independent subnetworks – a decomposition which is closely tied to the partition of deficiency among independent subsets of reactions (see SI Section S1.3) - as well as our extensive discussions of rowspan polynomials (complex linear invariants) throughout the remainder of our supplement, that no possible addition of extra reactions can turn the original two into an RPA- conferring set. We briefly note in Section S4.4.1 (see also footnote in that section) the special case where a deficiency- zero collection of reactions can engender RPA – namely when the two relevant complexes reside in the same terminal SSC, and correspond topologically to a 'trivial' (isolated) connector node. The pair of reactions suggested by the reviewer are clearly not of this type. No previously published work – not Shinar and Feinberg [7], not Cappelletti et al. [2], nor any other published work on RPA/ACR – is sufficiently general and all- encompassing as to rigorously and definitively delineate the strict requirements for RPA in any CRN – regardless of size or deficiency. We emphasize again, in the most strenuous possible terms, that precisely none of these insights follows straightforwardly from our previous study in [1], which gives absolutely no insight whatsoever into viable chemical reaction structures that could impose RPA on any molecule consumed or produced by those chemical reactions. + +<|ref|>text<|/ref|><|det|>[[204, 588, 844, 880]]<|/det|> +Having thoroughly addressed the reviewer's query regarding "how this example is consistent with the form of \(g(x,y)\) stated above" we now return to the reviewer's queries about our proof to Theorem 1. The reviewer states that "the proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f} \cap \mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) ." Just to clarify, what our proof to Theorem 1 actually says is that, given two variables \(x_{j}\) and \(x_{m}\) that do not exhibit RPA, in addition to a variable \(x_{i}\) that does exhibit RPA, then \(I_{f} \cap \mathbb{R}[x] = I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not contained in \(I_{f} \cap I_{p}\) (the ideal consisting of all polynomial consequences of the rate equations for the CRN that also vanish at \(x_{i} = c\) , the setpoint for \(x_{i}\) ). The reviewer is not specific as to why he/she feels that this technicality unclear, but we note first and foremost that should \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) contain a polynomial in \(x_{j}\) and \(x_{m}\) only (not also including \(x_{i}\) ), then this polynomial is ipso facto not in \(I_{p}\) (since all polynomials in \(I_{p}\) contain \(x_{i}\) by supposition). We also emphasize that the ideal \(I_{f}\) consists of all polynomials in the ring \(\mathbb{R}[x_{1}, \ldots , x_{n}]\) that vanish on the variety \(V(f_{1}, \ldots , f_{n})\) . In any case, our theorem is fundamentally concerned with which + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 84, 820, 120]]<|/det|> +projections (i.e. choices for \(\bar{x}\) ) are guaranteed to be entirely contained within the ideal \(I_{f} \cap I_{p}\) . + +<|ref|>text<|/ref|><|det|>[[205, 136, 844, 388]]<|/det|> +Our proof to Theorem 1 succinctly points out that if we project the polynomial consequences of the system \((I_{f})\) onto three variables, two of which \((x_{j}, x_{m})\) do not exhibit RPA, then there will be a generator for the associated elimination ideal involving only \(x_{j}\) and \(x_{m}\) (and not \(x_{i}\) – the RPA- capable variable). The reason for the existence of such a generator is that a system whose steady- states can be regulated by any number of independent disturbances (or input stimuli) must be able to adapt to each disturbance individually, corresponding to a single degree of freedom. Once the value of any one non- RPA variable \((x_{j}, \text{say})\) is specified (as a result of setting the magnitudes of the various possible disturbances), then the value of any other non- RPA variable (e.g. \(x_{m}\) ) is thereby also specified. The value of \(x_{i}\) , by contrast, is not determined through an alteration to any single degree of freedom (corresponding to one of the independent disturbances) since it exhibits RPA, and is independent of these disturbances. Thus, it follows that some polynomial involving the two non- RPA- variables \(x_{j}\) and \(x_{m}\) is a generator of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) . + +<|ref|>text<|/ref|><|det|>[[205, 404, 844, 586]]<|/det|> +Now if, for the sake of argument, there were a single generator of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) containing all three variables, this would mean that the value of \(x_{m}\) could only be determined once the values of both \(x_{i}\) and \(x_{j}\) were specified. On the other hand, if the generator(s) of \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}, x_{m}]\) were to contain a polynomial in just \(x_{j}\) , then this would imply that the univariate polynomial either has no positive real roots, or possibly no real roots at all (both of which scenarios corresponding to the non- existence of a steady state for \(x_{j}\) ), or has at least one positive real root whose value is a rational function of the system rate constants (a scenario that corresponds to RPA in \(x_{j}\) ). All of these conditions violate the assumption that \(x_{j}\) is a non- RPA variable – a contradiction. + +<|ref|>text<|/ref|><|det|>[[205, 604, 840, 708]]<|/det|> +Of course, Theorem 1 could not possibly be true in general if variables are simply taken to be species. We point out in the preamble to Theorem 1 that in most cases, the variables of a CRN are the species, however should a boundary variable exist, then this must be accounted for in the identification of variables for the CRN (since the component species of the boundary variable cannot be considered variables in that case). + +<|ref|>text<|/ref|><|det|>[[205, 726, 848, 900]]<|/det|> +We hope these clarifications have been able to assure the reviewer of the correctness of this Theorem and its proof. We have now added a condensed version of our explanations above as a 'Remark' following the proof to Theorem 1 (and following Definitions 2 and 3). We also decided to remove the reference to ACR in the statement of the theorem (and hence in the proof), and instead added a comment on this point to the list of Remarks following the Theorem. (The reviewer's helpful suggestion to give a clear and explicit definition for RPA at the outset now makes it unnecessary to add in descriptions of ACR, and its relationship to the more general case of RPA, to our statement and proof of Theorem 1. We cannot thank the reviewer enough for such supportive advice). We do, of course, recognise that not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 85, 833, 170]]<|/det|> +all mathematical details of Theorem 1 could possibly be obvious, or clear, to the entire readership of a multidisciplinary journal. It is for this reason that we provide many illustrative examples throughout our SI to demonstrate how the fundamental mathematical principles encapsulated by Theorem 1 are reflected in a range of simple RPA- capable CRNs. + +<|ref|>text<|/ref|><|det|>[[206, 189, 480, 204]]<|/det|> +Now to the reviewer's next concern: + +<|ref|>text<|/ref|><|det|>[[150, 223, 828, 275]]<|/det|> +Moreover, it is not immediately clear how existence of multiple opposer/balancer modules translates into existence of existence of corresponding RPA polynomials. This has not been explained in sufficient detail. + +<|ref|>sub_title<|/ref|><|det|>[[206, 295, 313, 309]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[206, 311, 770, 362]]<|/det|> +We thank the reviewer for this very helpful advice that we make a clearer connection between the existence of multiple topological modules and the corresponding existence of associated RPA polynomials. + +<|ref|>text<|/ref|><|det|>[[205, 380, 845, 555]]<|/det|> +Due to our extensive revisions, our manuscript (and especially our SI) now makes this connection very explicit, and explains the underlying technicalities in considerable detail. In particular, our extensive explanations on the decomposition of RPA- capable CRNs into algebraically- independent subnetworks underscores the fact that such independent subnetworks can be analysed separately as to their RPA- capacity (or otherwise), and that the RPA- capacity of 'multi- modular' networks corresponds to the existence of multiple independent RPA- capable subnetworks within such a decomposition. We state explicitly in Section S4.2, for example, as we begin to introduce the mathematical process by which higher deficiency ( \(\delta > 1\) ) CRNs can be accommodated within our framework, that + +<|ref|>text<|/ref|><|det|>[[206, 572, 836, 624]]<|/det|> +"... for CRNs for which multiple independent subnetworks contribute independently to RPA, these independent subnetworks correspond to distinct modules from a topological perspective (see [1])." + +<|ref|>text<|/ref|><|det|>[[206, 642, 762, 676]]<|/det|> +We also emphasize again in Section S4.5, where the general principles are summarised, that + +<|ref|>text<|/ref|><|det|>[[206, 694, 843, 763]]<|/det|> +"... it is clear from the analysis in the preceding sections that a CRN can be decomposed into lower deficiency independent subnetworks corresponding to the individual modules of a multi- modular network and, in the case of Opposer modules, the controller portion of the module, which can be analysed separately." + +<|ref|>text<|/ref|><|det|>[[206, 781, 843, 902]]<|/det|> +Our study thus makes it clear that each topological module, which directly corresponds to an algebraically independent subset of the CRN reactions, engenders its own RPA polynomial, specific to that module/subnetwork. Nevertheless, Theorem 1 guarantees that for a multi- modular CRN, choosing one RPA- capable variable (associated with any RPA- conferring module) and one non- RPA- capable variable (from any module, including one that is distinct from the one containing the RPA- capable variable), and projecting the entire system onto those two variables, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 85, 847, 136]]<|/det|> +will yield an RPA polynomial containing those two variables. Thus, Theorem 1 is valid for any choice of two variables with the property that one is RPA- capable and one is non- RPA- capable. + +<|ref|>text<|/ref|><|det|>[[206, 154, 840, 276]]<|/det|> +We do acknowledge that in our discussion of the topological consequences of Theorem 1 in Section S3 (see for example Figure S4, and Figure 4 in the main paper), we are referring primarily to RPA in a CRN corresponding to a single module. This is mostly from the point of view of (i) highlighting the existence of an overarching mechanism by which a non- RPA capable variable ultimately imposes RPA on a variable, not necessarily directly; and (ii) distinguishing the (topological) significance of an RPA- capable variable being a regulating, or a regulated, variable. + +<|ref|>text<|/ref|><|det|>[[150, 294, 813, 364]]<|/det|> +- Connection to existing works: In [4] the authors consider RPA systems that are maximally robust and find simple linear-algebraic structural conditions that characterise this property in both deterministic and stochastic settings. How do the results in this paper connect to the results in [4]? + +<|ref|>sub_title<|/ref|><|det|>[[206, 383, 314, 398]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[206, 399, 781, 432]]<|/det|> +We are grateful to the reviewer for introducing us to such an interesting and impressive recent article [4], of which we were hitherto unaware. + +<|ref|>text<|/ref|><|det|>[[205, 450, 847, 780]]<|/det|> +An obvious point of difference between this article [4] and ours is that these authors also consider RPA in the stochastic setting, while our study is focused squarely on the deterministic setting in the interests of delineating the full space of RPA- capable CRNs in the greatest possible generality. Beyond this, the article by Gupta and Khammash focus on a particular type of RPA they refer to as maximal RPA, or "maxRPA", where 'the setpoint for the key output variable depends on the least number of network parameters, and is insensitive to all the others' – arguing that 'it makes strong evolutionary sense for intracellular RPA networks to attain (such a) maximal robustness'. In this connection, the authors claim to 'work with a stronger notion of robustness' and that their 'characterising conditions for RPA networks are more restrictive than the topological requirements expounded in (our previous work [1], for example)'. The study is able to identify, concretely, a number of mathematical conditions required for the existence of the maxRPA property, which includes (among other requirements) that the setpoint should be a function of (only) two biochemical parameters. In any case, the authors succeed in their goal to 'mathematically characterise and study the structure of biomolecular networks that constitute such maximal RPA (or maxRPA) systems' – a most impressive achievement – and propose a novel internal model principle (IMP) pertaining to these maxRPA networks. + +<|ref|>text<|/ref|><|det|>[[206, 798, 835, 902]]<|/det|> +This focus on maxRPA networks alone constitutes the major distinction between [4] and our study, since our goal is to characterise all possible RPA- capable CRNs – as opposed to specific classes of RPA- capable CRNs (e.g. the maxRPA class [4], the deficiency- one Shinar- Feinberg class [7], the class containing a 'linear constrained integrator' [2], etc). As we noted earlier, this generality is important in the context of understanding, at an abstract level, the ability of RPA- capable networks to cope + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 84, 847, 415]]<|/det|> +with new disturbances (i.e. those that were not present in the original CRN – e.g. the addition of small- molecule enzyme- inhibitors). This is particularly crucial for signalling networks for which the detailed structures of the underlying CRNs are unknown (in the context of signal transduction in metazoan cells, for instance). Moreover, we respectfully question the authors' point of view on the suggested evolutionary advantages of a setpoint involving only two network parameters. We contend that it is not the number of parameters defining the setpoint, but the nature of the parameters that is most significant to the functional robustness of the system, and ultimately, the survival of the cell/organism. A CRN could have a setpoint determined by a hundred parameters, but if all these parameters are 'stable' in the sense that they are determined entirely by the chemical properties of the interacting molecules (e.g. association/dissociation constants, or catalytic constants), alterable only by mutation or by factors such as temperature that vary very slowly on the timescale of adaptation, then this may still constitute an entirely useful form of RPA from a biological standpoint. By contrast, a CRN could have a setpoint determined by only two parameters (the minimum, as in the antithetic integral control motif), but if these are highly labile parameters relating to, for example, the rate of synthesis of a particular molecule, or the total expression level of a particular molecule, then this could potentially be problematic. + +<|ref|>text<|/ref|><|det|>[[205, 432, 845, 623]]<|/det|> +Consider, for instance, the deficiency- two Shinar- Feinberg model of the EnvZ- OmpR motif. The setpoint for \(pOmpR\) due to this CRN involves eleven parameters (calculated from two independent setpoints arising from the balancer and connector contributions). But all of these parameters are either association/dissociation constants for pairs of molecules, or catalytic constants, and are thus highly stable in magnitude. By contrast, for the antithetic control mechanism, the setpoint for the sensor molecule involves just two parameters. But both of these parameters capture the rate of synthesis of an antithetic molecule which could, in principle, vary quite significantly on the timescale of adaptation (depending on the regulatory mechanisms governing the transcription and translation of the molecules in question). + +<|ref|>text<|/ref|><|det|>[[205, 641, 845, 884]]<|/det|> +Moreover, perturbations to the setpoint that are either stable (e.g. due to a mutation in an RPA- relevant signalling protein) or vary on a timescale that is significantly longer than the timescale of adaptation, may not alter the functionality of the biological system whatsoever. One of the most widely- discussed examples of unaltered biological function in the face of a stably varying setpoint is the robustness of tumbling frequency, and precision of adaptation, in E.coli chemotaxis (see Alon et al. [12]). In that study [12], genomic alterations that affected the expression levels of various chemotaxis proteins were introduced, which stably altered the setpoint for the steady- state tumbling frequency as well as the adaptation time. But exact adaptation was still observed (albeit with an altered setpoint), and the chemotaxis response of the cells was unaffected. In this context we recognise that, for single- celled organisms, significant temperature variations could certainly alter biochemical parameters; but provided as temperatures vary slowly in comparison with adaptation (RPA), this might not affect the functionality of the organism at all. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 84, 845, 206]]<|/det|> +Moreover, aside from what type of setpoints are most evolutionarily advantageous, we respectfully point out that the RPA responses frequently observed in highly complex signalling networks, such as cancer signalling networks in human cells (on the basis of time- course data – see [13], for instance) are not necessarily attributable to maxRPA networks; there is simply no evidence to support this. In fact, it is currently entirely unclear what CRN architectures are generally responsible for RPA in complex signal transduction networks (in either normal or diseased states). + +<|ref|>text<|/ref|><|det|>[[206, 224, 825, 327]]<|/det|> +We hope the reviewer will not object to a friendly and respectful debate on these points, in the interests of moving scientific frontiers forward. We contend that, to make sense of the highly complex signalling networks that arise in nature, it is absolutely essential to have access to completely general description of the mechanisms by which RPA could be implemented in CRNs. This is the brass- ring objective that we achieve in the present work. + +<|ref|>text<|/ref|><|det|>[[206, 345, 841, 450]]<|/det|> +In raising all these points, we are by no means dismissing the study by Gupta and Khammash [4], which is incredibly interesting, and extremely impressive (mathematically and otherwise); we only point out that it is not completely general vis- à- vis RPA- promoting CRN structures (and makes no claims to be, since its focus is on the particular class of RPA- capable CRNs known as 'maxRPA'). It is a beautiful paper, and we are proud to include it in our reference list in the main manuscript. + +<|ref|>text<|/ref|><|det|>[[206, 484, 833, 623]]<|/det|> +Concluding Comments to Reviewer #1: We sincerely thank the reviewer again for such a generous investment of time and painstaking effort, and for his/her many supportive and helpful suggestions for making our scientific goals, and our findings, much clearer and more explicit. We are truly grateful to have this opportunity to defend our work, and to provide an extensively revised version of our manuscript that offers a much more comprehensive exposition of all the relevant supporting technicalities, and a much more compelling presentation for a general scientific audience. + +<|ref|>text<|/ref|><|det|>[[150, 658, 850, 902]]<|/det|> +References (for response to Reviewer 1) [1] R. P. Araujo and L. A. Liotta. The topological requirements for robust perfect adaptation in networks of any size. Nature communications, 9(1):1- 12, 2018. [2] D. Cappelletti, A. Gupta, and M. Khammash. A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances. Journal of the Royal Society Interface, 17(171):20200437, 2020. [3] G. Craciun, A. Dickenstein, A. Shiu, and B. Sturmfels. Toric dynamical systems. Journal of Symbolic Computation, 44(11):1551- 1565, 2009. [4] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. bioRxiv, 2022. [5] M. Perez Millan, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027- 1065, 2012. [6] A. Sadeghimanesh and E. Feliu. Gröbner bases of reaction networks with intermediate species. Advances in Applied Mathematics, 107:74- 101, 2019. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 848, 327]]<|/det|> +[7] G. Shinar and M. Feinberg, M. Structural sources of robustness in biochemical reaction networks. Science, 327(5971): 1389- 1391, 2010. [8] R. L. Karp, et al. Complex- linear invariants of biochemical networks. Journal of theoretical biology. 311: 130- 138, 2012. [9] M. Feinberg. Foundations of chemical reaction network theory. Springer, 2019. [10] D. Cox, J. Little, and D. OShea. Ideals, varieties, and algorithms: an introduction to computational algebraic geometry and commutative algebra. Springer, 2013. [11] J.M. Eloundou- Mbehi, et al. A network property necessary for concentration robustness. Nature communications, 7(1): 1- 7, 2016. [12] U. Alon, et al. Robustness in bacterial chemotaxis. Nature, 397(6715): 168- 171, 1999. [13] A.J. VanMeter, et al. Laser capture microdissection and protein microarray analysis of human non- small cell lung cancer: differential epidermal growth factor receptor (EGPR) phosphorylation events associated with mutated EGFR compared with wild type. Molecular & Cellular Proteomics, 7(10): 1902- 1924, 2008. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[151, 86, 345, 102]]<|/det|> +## Response to Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[150, 119, 844, 310]]<|/det|> +Araujo and Liotta develop a set of precise criteria that a system needs to fulfil in order to perfect adaptation. This is remarkable and an extremely valuable contribution to the literature in three ways: (i) the search for "design principles" is taking centre stage in synthetic (but also e.g. developmental systems) biology; the first author has proven a leader in distilling precise mathematical criteria for robust perfect adaptation, and I hope that this study will inspire more work in this area, especially in considering the mathematical properties of chemical reaction networks to guarantee different types of behaviour; (ii) in Mathematical biology there are few instances where the mathematical statements can be so precise that biology will have to "obey" these statements. This is one such instance. Finally (iii) the maintenance and control of robust adaptation is of considerable and far reaching biological relevance. I like this manuscript for each of these three points a lot. + +<|ref|>text<|/ref|><|det|>[[150, 327, 848, 432]]<|/det|> +The most interesting mathematical aspects of the work have, unfortunately but predictably been relegated to the supplementary information. The results in Figure 2, for example, are very clearly explained and easy to follow in the SI. I personally enjoyed the SI a lot, and while the discussion e.g. in lines 207- 215 is clear, it may be too terse for some readers to follow. The SI by contrast was very clear. Fig 3 does a nice job, however, to get the message of kinetic pairing across. + +<|ref|>text<|/ref|><|det|>[[151, 450, 835, 501]]<|/det|> +I think it would help readers to understand how translatable to other phenotypes this type of analysis is, or if RPA is particular in this regard of allowing such general mathematical statements to be derived. + +<|ref|>sub_title<|/ref|><|det|>[[206, 520, 314, 535]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[206, 536, 840, 658]]<|/det|> +We are truly indebted to this reviewer for his/her incredible generosity in considering our work in such careful detail, and for such genuinely helpful feedback and thoughtful suggestions for further improvement. We are immensely grateful to have the benefit of an 'extra set of eyes' cast over our work, to identify additional opportunities to make our exposition more compelling. We have noted all revisions to the main manuscript, and to our SI, with red text, to make it easy to identify which parts of our article have been updated since the original submission. + +<|ref|>text<|/ref|><|det|>[[206, 675, 844, 850]]<|/det|> +Regarding the issue of relegating much of our detailed mathematical development to the Supplementary Information, it is true that the severe word limits in Nature Communications (6000 words for main text, excluding figure captions) have forced us to limit our exposition in the paper itself to an accessible overview of the major conceptual innovations of the study, with extensive references to all the technical details in our Supplementary Information. A significant additional challenge stems from the fact that solving the RPA problem in complete generality, at the level of intermolecular interactions, has required us to draw together a number of distinct mathematical languages - chemical reaction network theory (CRNT), engineering control theory, and algebraic geometry - into a unified framework. + +<|ref|>text<|/ref|><|det|>[[206, 867, 840, 901]]<|/det|> +We greatly value the reviewer's insightful suggestion that "it would help readers to understand how translatable to other phenotypes this type of analysis is, or if RPA is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[202, 84, 845, 450]]<|/det|> +particular in this regard of allowing such general mathematical statements to be derived." We now include following text at the conclusion of our article: The quest to uncover the fundamental 'design principles' that constrain complex signalling networks in nature to implement biologically important functions is considered to be one of the most important and far- reaching 'grand challenges' in the life sciences [1- 6]. On the basis of the present study, along with our earlier topological study at the network macroscale [7], RPA currently stands alone as a keystone biological response for which there now exists a universal explanatory framework – one that imposes strict and inviolable design criteria on arbitrarily large and complex networks, and one that now accounts for the subtleties of intricate intermolecular interactions at the network microscale. These universal RPA- permissive design principles now represent a launching- point for future explorations of more complex phenotypes - including some classes of embryonic patterning problems, for instance, where integral control is known to play a role in promoting adaptation of segmentation boundaries to variations in organism size [8,9]. The identification of universal design principles for many other complex phenotypes, such as Turing patterns [4, 10,11] and multistability/switching- responses [12,13], is likely to prove more challenging due in part to the central role of equilibrium stabilities, or instabilities, in these responses. These 'grand challenges' remain open, and we hope that our study will inspire bold new mathematical thinking in these vitally important directions. + +<|ref|>sub_title<|/ref|><|det|>[[150, 485, 248, 501]]<|/det|> +## Small points: + +<|ref|>text<|/ref|><|det|>[[151, 519, 844, 572]]<|/det|> +- much of chemical reaction network theory is obscure to most readers. I would like to see a clear and easy definition of integral control that is accessible to non-expert audiences. Deficiency is maybe another such concept and it would be good to define it on line 146. + +<|ref|>text<|/ref|><|det|>[[205, 588, 844, 728]]<|/det|> +Our response: We truly appreciate such helpful suggestions to improve the clarity of our exposition. In our newly revised manuscript, we give a thorough yet accessible explanation of the concept of integral control, and the internal model principle (IMP), via the introduction of a new Figure in our Introduction section (Fig. 1 in our revised submission) – see below. We have also carefully edited our explanations of integral control in-text to complement this new Figure, and to ensure that the concept (and its relationship to the goals of our study) are clear to the readership of a multidisciplinary journal. + +<|ref|>text<|/ref|><|det|>[[205, 745, 845, 902]]<|/det|> +We have also vastly expanded our clarifications on the concept of deficiency, especially in our Supplementary Information where we give far greater detail on the concept where we first define it in SI Section S1.2, and particularly its relationship to the flow of biochemical information (and ultimately topology) in RPA- capable CRNs. We have also added in an entirely new section (SI Section S1.3) on the key concept of algebraically- independent subnetworks of a CRN (which we didn’t discuss until much later in the Supplement, in our original submission), and clearly outline the role of deficiency in partitioning the reactions of a CRN into such independent subsets. In the main paper, we also introduce the concept of deficiency much earlier + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 85, 847, 171]]<|/det|> +than previously, and point out early that this is a key algebraic invariant which has fundamental (and previously unrecognised) consequences for the implementation of integral control by CRNs. Later in the main paper, where we give further detail on the underlying mathematical technicalities, we give a clear definition of deficiency, and give an example of how to calculate it, in Figure 5. + +<|ref|>image<|/ref|><|det|>[[153, 205, 820, 495]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[152, 511, 848, 685]]<|/det|> +
Fig. 1. The internal model principle (IMP) and its application to RPA-capable CRNs. The class of constant disturbances \((I(t) = \text{const})\) is generally the disturbance class of most fundamental interest to the study of biological systems. (a) In order to exhibit RPA (i.e. 'adapt' to constant disturbances), the dynamical system \(\Sigma\) should be decomposable, via a coordinate transformation if needed, into an 'output-driven internal model', \(\Sigma_{IM}\) (generating all the constant signals corresponding to solutions of \(\dot{z}_2 = 0\) ), and the remainder of the system, \(\Sigma_0\) . The variable \(z_2\) thereby computes the integral of the output error. (b) A suitable coordinate change should be able to recast an RPA-capable system into integral feedback form, even if there is no feedback present in the network. As shown, a linear transformation is sufficient to identify an output-driven internal model for this particularly simple incoherent feedforward motif (Balancer module); \(y = \alpha_4 / \alpha_3\) (setpoint) at steady-state. (c) A model that employs feedback is frequently simpler to recast in 'integral feedback' form, with an output-driven internal model; here \(y = \alpha_3\) (setpoint) at steady-state. Note that the reaction rates selected for illustrative purposes in (b) or (c) cannot be induced, under the law of mass action, by any CRN20.
+ +<|ref|>text<|/ref|><|det|>[[150, 737, 825, 789]]<|/det|> +- The authors show that their criteria hold for all instances of RPA. I was wondering how easily in practice these mechanisms could be lost? Is it easy to identify points that disrupt RPA? + +<|ref|>text<|/ref|><|det|>[[205, 807, 840, 912]]<|/det|> +Our response: With access to a universal and complete solution to the RPA problem in CRNs, we can now delineate, precisely and definitively, the circumstances under which various classes of disturbances, or network alterations, can either preserve the RPA property or cause RPA to fail. We have not commented on this matter in detail in our manuscript, as this is the subject of ongoing work. One of the most interesting classes of disturbances against RPA-capable CRNs is the addition of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 85, 847, 397]]<|/det|> +enzyme- inhibitors of various types (competitive, non- competitive, mixed, uncompetitive, etc.). Addition of one more enzyme- inhibitors to a CRN, whether highly specific to its target or not, corresponds to the addition of extra linkage class(es) to the CRN. We now know that certain inhibitor mechanisms are deficiency preserving, while others aren't, and their effects on the RPA property (depending on the relationship of their target protein(s) to the overarching structure of the CRN) are complex and counterintuitive, and in some cases very surprising. Generally, the RPA property is very difficult to perturb via molecular- targeted inhibitors, although we have been able to identify very specific and definitive conditions in which this is possible. Other classes of disturbances (such as those we itemize in our newly revised Supplementary Information, at the beginning of Section S1) are much easier to study from the point of view of altering the RPA property. In any case, it is only by having a completely general mathematical description of RPA- permissive reaction structures, that accounts for all possible RPA- capable CRNs, that we can make such definitive conclusions on the preservation or destruction of the RPA property in the abstract. This is particularly valuable in the context of particularly complex signalling networks (e.g. in cancer signal transduction) for which detailed CRN structures are unknown (and possibly will never be known). + +<|ref|>text<|/ref|><|det|>[[206, 415, 816, 449]]<|/det|> +In any case, we are planning to publish this work (separately) very soon, and look forward to sharing this. + +<|ref|>text<|/ref|><|det|>[[150, 482, 848, 534]]<|/det|> +- there is a vast literature on design principles which could be touched upon at least in passing (limit cycles, multistability, switch-like behaviour, Turing patterns), especially if there is scope for applying similar concepts in these contexts. + +<|ref|>text<|/ref|><|det|>[[206, 570, 843, 674]]<|/det|> +Our response: This is such a wonderful suggestion, which we greatly value. As we noted in our first point above, we have added an extra paragraph that comments on this very issue at the conclusion to our manuscript. "The quest to uncover the fundamental 'design principles' that constrain complex signalling networks in nature to implement biologically important functions is considered to be one of the most important and far-reaching 'grand challenges' in the life sciences [1- 6] ... Etc." + +<|ref|>text<|/ref|><|det|>[[206, 710, 830, 779]]<|/det|> +Concluding Comments to Reviewer #2: We cannot thank the Reviewer enough for such a generous investment of time and effort, for such incredibly supportive feedback, and for so many insightful suggestions for additions and clarifications to our exposition. We are truly grateful. + +<|ref|>text<|/ref|><|det|>[[150, 814, 454, 830]]<|/det|> +References (for response to Reviewer 2) + +<|ref|>text<|/ref|><|det|>[[150, 832, 822, 901]]<|/det|> +[1] Alon, U. An introduction to systems biology: design principles of biological circuits. (Chapman and Hall/CRC, 2006). [2] Green, S. Revisiting generality in biology: systems biology and the quest for design principles. Biology & Philosophy 30, 629- 652 (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[145, 84, 840, 560]]<|/det|> +[3] Novák, B. & Tyson, J. J. Design principles of biochemical oscillators. Nature reviews Molecular cell biology 9, 981- 991 (2008). [4] Vittadello, S. T., Leyshon, T., Schnoerr, D. & Stumpf, M. P. Turing pattern design principles and their robustness. Philosophical Transactions of the Royal Society A 379, 20200272 (2021). [5] Stumpf, M. P. Statistical and computational challenges for whole cell modelling. Current Opinion in Systems Biology 26, 58- 63 (2021). [6] Lim, W. A., Lee, C. M. & Tang, C. Design principles of regulatory networks: searching for the molecular algorithms of the cell. Molecular cell 49, 202- 212 (2013). [7] Araujo, R. P. & Liotta, L. A. The topological requirements for robust perfect adaptation in networks of any size. Nat Commun 9, 1757 (2018). https://doi.org:10.1038/s41467- 018- 04151- 6 [8] Ben- Zvi, D. & Barkai, N. Scaling of morphogen gradients by an expansion- repression integral feedback control. Proceedings of the National Academy of Sciences 107, 6924- 6929 (2010). https://doi.org:10.1073/pnas.0912734107 [9] Eldar, A. et al. Robustness of the BMP morphogen gradient in Drosophila embryonic patterning. Nature 419, 304- 308 (2002). https://doi.org:10.1038/nature01061 [10] Lander, A. Pattern, growth, and control. Cell 144, 955- 969 (2011). [11] Krause, A. L., Gaffney, E. A., Maini, P. K. & Klika, V. Introduction to 'Recent progress and open frontiers in Turing's theory of morphogenesis'. Philosophical Transactions of the Royal Society A 379, 20200280 (2021). [12] Ullner, E., Zaikin, A., Volkov, E. I. & Garcia- Ojalvo, J. Multistability and clustering in a population of synthetic genetic oscillators via phase- repulsive cell- to- cell communication. Physical review letters 99, 148103 (2007). [13] Duddu, A. S., Sahoo, S., Hati, S., Jhunjhunwala, S. & Jolly, M. K. Multi- stability in cellular differentiation enabled by a network of three mutually repressing master regulators. Journal of the Royal Society Interface 17, 20200631 (2020). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[97, 141, 842, 196]]<|/det|> +# Review 2: Universal structures for embedded integral control in biological adaptation + +<|ref|>text<|/ref|><|det|>[[275, 218, 661, 240]]<|/det|> +Robyn P. Araujo and Lance A. Liotta + +<|ref|>text<|/ref|><|det|>[[85, 275, 853, 350]]<|/det|> +Overview: The aim of this paper is to provide an algebraic characterisation of the hidden integral controller and construct an algebraic procedure to identify it in adaptation- capable networks. It is shown that this procedure is intimately connected to the structure of the networks via the well- known deficiency theory for chemical reaction networks. + +<|ref|>text<|/ref|><|det|>[[85, 356, 853, 448]]<|/det|> +Recommendation: I am grateful to the authors for revising the manuscript to address many of the points that I raised in the first review. Even though the paper has significantly improved, many of the more serious concerns remain. These concerns, which are outlined below, should be fully addressed before the paper can be reconsidered again for Nature Communications. + +<|ref|>text<|/ref|><|det|>[[110, 462, 854, 592]]<|/det|> +1. Connection to integral control: The paper claims to uncover universal structures for embedded "integral control". However in order to successfully demonstrate this, a coordinate transformation (possibly nonlinear) needs to be constructed that gives rise to the "integrator" variable. It does not matter if this coordinate transformation is done in a single step or in multiple steps (as proposed by this paper), but its existence needs to be shown in order to identify the integral mechanism. In the Supplement the authors write + +<|ref|>text<|/ref|><|det|>[[175, 603, 812, 678]]<|/det|> +We note that, although there should always exist some single nonlinear coordinate change that yields the RPA polynomial in principle, for any mass action system, identifying such a single coordinate change in practice may be extremely difficult in all but the very simplest RPA-capable CRNs. + +<|ref|>text<|/ref|><|det|>[[131, 689, 853, 727]]<|/det|> +I agree that proving the existence of an integrator may be difficult, but unfortunately it is unavoidable for showing integral control. Let us look into this issue in more details. + +<|ref|>text<|/ref|><|det|>[[133, 731, 611, 751]]<|/det|> +Suppose the dynamics is governed by a system of ODEs: + +<|ref|>equation<|/ref|><|det|>[[445, 763, 540, 797]]<|/det|> +\[\frac{dx}{dt} = f(x),\] + +<|ref|>text<|/ref|><|det|>[[133, 807, 853, 864]]<|/det|> +where \(x\) is the \(n\) - dimensional state of the system and \(f(x) = (f_{1}(x),\ldots ,f_{n}(x))\) are the rates of evolution of all the species. In order to exhibit an integrator, we need to find a real- valued function \(H(x)\) such the dynamics of \(z(t) = H(x(t))\) is given by the ODE: + +<|ref|>equation<|/ref|><|det|>[[310, 874, 851, 911]]<|/det|> +\[\frac{dz}{dt} = \nabla H(x)\circ f(x) = p(x)(x_{i} - c)\coloneqq \rho (x), \quad (0.1)\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 90, 853, 147]]<|/det|> +where \(\nabla\) is the gradient operator, \(\circ\) is the usual dot product and \(\rho (x) = p(x)(x_{i} - c)\) is what the authors call the "RPA polynomial" for the RPA variable \(x_{i}\) . Suppose one is able to find nonlinear polynomials \(h_{1},\ldots ,h_{n}\) (as in Theorem 1 of the paper) such that + +<|ref|>equation<|/ref|><|det|>[[334, 161, 650, 179]]<|/det|> +\[h_{1}(x)f_{1}(x) + \cdot \cdot \cdot +h_{n}(x)f_{n}(x) = \rho (x).\] + +<|ref|>text<|/ref|><|det|>[[133, 191, 853, 247]]<|/det|> +However this does not necessarily mean that a function \(H(x)\) can be constructed so that (0.1) holds. Observe that such a function \(H(x)\) would need to have the following partial derivatives + +<|ref|>equation<|/ref|><|det|>[[317, 258, 666, 297]]<|/det|> +\[\frac{\partial}{\partial x_{j}} H(x) = h_{i}(x)\qquad \mathrm{for}\qquad j = 1,\ldots ,n.\] + +<|ref|>text<|/ref|><|det|>[[133, 307, 853, 381]]<|/det|> +Unless each \(h_{i}(x)\) is a constant (in which case \(H(x)\) is linear), it is unclear why such a function \(H(x)\) would exist. Since the approach in the paper uses nonlinear elimination steps (via concatenating monomials), the existence of \(H(x)\) cannot be ascertained. In fact if for a pair \(j,k\) we have + +<|ref|>equation<|/ref|><|det|>[[400, 395, 585, 432]]<|/det|> +\[\frac{\partial}{\partial x_{j}} h_{k}(x)\neq \frac{\partial}{\partial x_{k}} h_{j}(x)\] + +<|ref|>text<|/ref|><|det|>[[133, 441, 853, 534]]<|/det|> +then certainly \(H(x)\) cannot be constructed with partial derivatives \(h_{1},\ldots ,h_{n}\) . This discussion shows that while existence of a RPA polynomial may be necessary for integral control, it is not sufficient and hence this property does not characterise integral controllers (a main claim of the paper). This gap between necessity and sufficiency can be bridged if the authors can show that for RPA networks one always has + +<|ref|>equation<|/ref|><|det|>[[340, 546, 644, 584]]<|/det|> +\[\frac{\partial}{\partial x_{j}} h_{k}(x) = \frac{\partial}{\partial x_{k}} h_{j}(x)\qquad \forall \qquad j,k.\] + +<|ref|>text<|/ref|><|det|>[[108, 597, 853, 654]]<|/det|> +2. Questions about the Kinetic Pairing result: In the previous review round, I had proposed a possible RPA network and asked the authors how it satisfies the Kinetic Pairing result (Theorem 1). The network has two reactions given by + +<|ref|>equation<|/ref|><|det|>[[270, 664, 850, 686]]<|/det|> +\[\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1} + \mathbf{X}_{4}\quad \mathrm{and}\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\mathbf{X}_{5} \quad (0.2)\] + +<|ref|>text<|/ref|><|det|>[[133, 699, 853, 792]]<|/det|> +and there may be several other reactions involving species \(\mathbf{X}_{2},\ldots ,\mathbf{X}_{5}\) that can be catalysed by \(\mathbf{X}_{1}\) but they do not change \(\mathbf{X}_{1}\) . In the rebuttal letter, the authors consider certain instances of such a network, and claim that in these networks all possible steady states lie on the boundary on the positive orthant (e.g. \(x_{2}\) or \(x_{3}\) is zero) and hence the networks are not RPA. In particular, the authors state in their rebuttal letter that: + +<|ref|>text<|/ref|><|det|>[[175, 802, 813, 913]]<|/det|> +The two reactions proposed by the reviewer cannot impose RPA on \(\mathbf{X}_{1}\) no matter which reactions are added to the original two. This is because the two given reactions are linearly independent, and the CRN formed from these reactions has deficiency zero. Moreover, the two complexes that contribute to the apparent RPA- polynomial in the reaction rate \(f_{1}\) are not members of the same terminal SCC. It is clear from our discussion of the decomposition + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[174, 90, 812, 293]]<|/det|> +of CRNs into algebraically independent subnetworks a decomposition which is closely tied to the partition of deficiency among independent subsets of reactions (see SI Section S1.3) - as well as our extensive discussions of rows- pan polynomials (complex linear invariants) throughout the remainder of our supplement, that no possible addition of extra reactions can turn the original two into an RPA- conferring set. We briefly note in Section S4.4.1 (see also footnote in that section) the special case where a deficiency zero collection of reactions can engender RPA namely when the two relevant complexes reside in the same terminal SSC, and correspond topologically to a trivial (isolated) connector node. The pair of reactions suggested by the reviewer are clearly not of this type. + +<|ref|>text<|/ref|><|det|>[[133, 303, 855, 378]]<|/det|> +To test the authors' claim above, I tried to come up with instances of such networks (i.e. (0.2) + some reactions) which are RPA and yet do not have this issue of steady- state not being in the positive orthant. Please explain how the Kinetic Pairing result fits these networks. + +<|ref|>text<|/ref|><|det|>[[133, 382, 854, 439]]<|/det|> +I start with a simpler version of this network with only three species (i.e. species \(\mathbf{X}_{4}\) and \(\mathbf{X}_{5}\) are absent) where I add inflow and outflow for species \(\mathbf{X}_{2}\) and \(\mathbf{X}_{3}\) . So the overall network becomes + +<|ref|>equation<|/ref|><|det|>[[219, 444, 853, 499]]<|/det|> +\[\begin{array}{r l} & {\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1},\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\emptyset ,\quad \emptyset \xrightarrow{c_{3}}\mathbf{X}_{2},\quad \emptyset \xrightarrow{c_{4}}\mathbf{X}_{3}}\\ & {\qquad \mathbf{X}_{2}\xrightarrow{c_{5}}\emptyset \quad \mathrm{and}\quad \mathbf{X}_{3}\xrightarrow{c_{6}}\emptyset .} \end{array} \quad (0.3)\] + +<|ref|>text<|/ref|><|det|>[[133, 504, 855, 596]]<|/det|> +This network has no boundary variables and so the variables are the same as species. It seems that this network will indeed show RPA for \(x_{1}\) with set- point \(c_{1} / c_{2}\) . In Figure 1 I plot the simulated dynamics (rescaled to have the set- point of \(x_{1}\) as 1) for three randomly chosen values of initial states and rate constants, and one can see that RPA holds. + +<|ref|>text<|/ref|><|det|>[[133, 600, 854, 638]]<|/det|> +Next I modify this network to have the production of \(\mathbf{X}_{2}\) and \(\mathbf{X}_{3}\) catalysed by \(\mathbf{X}_{1}\) . So the new network becomes + +<|ref|>equation<|/ref|><|det|>[[209, 645, 853, 699]]<|/det|> +\[\begin{array}{r l} & {\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1},\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\emptyset ,}\\ & {\mathbf{X}_{1}\xrightarrow{c_{3}}\mathbf{X}_{1} + \mathbf{X}_{2},\quad \mathbf{X}_{1}\xrightarrow{c_{4}}\mathbf{X}_{1} + \mathbf{X}_{3},\quad \mathbf{X}_{2}\xrightarrow{c_{5}}\emptyset \quad \mathrm{and}\quad \mathbf{X}_{3}\xrightarrow{c_{6}}\emptyset .} \end{array} \quad (0.4)\] + +<|ref|>text<|/ref|><|det|>[[133, 705, 795, 725]]<|/det|> +This network also appears to be RPA as shown by the simulations in Figure 2. + +<|ref|>text<|/ref|><|det|>[[133, 729, 855, 786]]<|/det|> +Finally, I consider another variant of this network where we have species \(\mathbf{X}_{4}\) and \(\mathbf{X}_{5}\) that reversibly bind to each other to produce an inactive compound, and they catalyse the production of \(\mathbf{X}_{2}\) and \(\mathbf{X}_{3}\) respectively. Therefore the new network becomes + +<|ref|>equation<|/ref|><|det|>[[133, 792, 874, 845]]<|/det|> +\[\begin{array}{r l} & {\mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{1}}\mathbf{X}_{1} + \mathbf{X}_{4},\quad \mathbf{X}_{1} + \mathbf{X}_{2} + \mathbf{X}_{3}\xrightarrow{c_{2}}\mathbf{X}_{5},\quad \mathbf{X}_{4}\xrightarrow{c_{3}}\mathbf{X}_{4} + \mathbf{X}_{2},\quad \mathbf{X}_{5}\xrightarrow{c_{4}}\mathbf{X}_{5} + \mathbf{X}_{3},}\\ & {\mathbf{X}_{2}\xrightarrow{c_{5}}\emptyset ,\quad \mathbf{X}_{3}\xrightarrow{c_{6}}\emptyset ,\quad \mathbf{X}_{4} + \mathbf{X}_{5}\xrightarrow{c_{7}}\emptyset \quad \mathrm{and}\quad \emptyset \xrightarrow{c_{8}}\mathbf{X}_{4} + \mathbf{X}_{5}.} \end{array} \quad (0.5)\] + +<|ref|>text<|/ref|><|det|>[[133, 852, 780, 871]]<|/det|> +This network also seems to be RPA, as shown in the simulations in Figure 3. + +<|ref|>text<|/ref|><|det|>[[133, 876, 855, 914]]<|/det|> +These networks do not appear to satisfy the RPA characterisation given by this paper. Also consider Example 6.5.3 in [5] which does not seem to fit this result either. These + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[153, 93, 780, 374]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[84, 402, 854, 495]]<|/det|> +
Figure 1: Plots of the dynamics of network (0.3) with mass-action kinetics, with initial state \(x(0)\) and rate constants \(c = (c_{1},c_{2},\ldots)\) . Each component of \(x(0)\) and \(c\) was randomly generated from the interval \([1,10]\) and here we show plots for three realisations of \(x(0)\) and \(c\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \(x_{1}\) is 1.
+ +<|ref|>text<|/ref|><|det|>[[132, 533, 852, 571]]<|/det|> +counter- examples cast doubt on the correctness of the Kinetic Pairing Theorem on which the entire paper rests. + +<|ref|>text<|/ref|><|det|>[[109, 583, 853, 658]]<|/det|> +3. The set-point may not be a rational function of parameters: In many places in the main paper and the supplement, the system's set-point is said to be a rational function of biochemical parameters. While this holds for most examples, consider the following birth death network + +<|ref|>equation<|/ref|><|det|>[[373, 670, 612, 690]]<|/det|> +\[\emptyset \xrightarrow{c_{1}}\mathbf{X}_{1}\quad \mathrm{and}\quad 2\mathbf{X}_{1}\xrightarrow{c_{2}}\emptyset .\] + +<|ref|>text<|/ref|><|det|>[[133, 704, 350, 723]]<|/det|> +The dynamics is given by + +<|ref|>equation<|/ref|><|det|>[[421, 737, 567, 771]]<|/det|> +\[\frac{d x_{1}}{d t} = c_{1} - 2c_{2}x_{1}^{2}\] + +<|ref|>text<|/ref|><|det|>[[133, 782, 303, 800]]<|/det|> +and so the set- point + +<|ref|>equation<|/ref|><|det|>[[449, 814, 537, 855]]<|/det|> +\[c = \sqrt{\frac{c_{1}}{2c_{2}}}\] + +<|ref|>text<|/ref|><|det|>[[131, 864, 853, 903]]<|/det|> +is not a rational function of \(c_{1}\) and \(c_{2}\) ? For more examples, see Examples 2.11 and 2.12 in [3]. Please revise as necessary. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[157, 92, 780, 373]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[84, 402, 854, 494]]<|/det|> +
Figure 2: Plots of the dynamics of network (0.4) with mass-action kinetics, with initial state \(x(0)\) and rate constants \(c = (c_{1},c_{2},\ldots)\) . Each component of \(x(0)\) and \(c\) was randomly generated from the interval \([1,10]\) and here we show plots for three realisations of \(x(0)\) and \(c\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \(x_{1}\) is 1.
+ +<|ref|>text<|/ref|><|det|>[[108, 533, 853, 572]]<|/det|> +4. Questions on the Buchberger's Algorithm: In the previous review round, I had raised the following issue regarding Buchberger's Algorithm + +<|ref|>text<|/ref|><|det|>[[175, 583, 810, 676]]<|/det|> +The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima- facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In any case, checking for nontermination of a method is impractical. + +<|ref|>text<|/ref|><|det|>[[133, 686, 854, 798]]<|/det|> +In response the authors state in their rebuttal letter that the termination is guaranteed because "all ideals of a polynomial ring (or any Noetherian ring, for that matter) are finitely generated a result of central importance in algebraic geometry, formalized by the Hilbert Basis Theorem". While I agree that termination is guaranteed, I must point out that the reason for my confusion and for raising this termination issue is the following excerpt from the previous version of the Supplement (submitted in round 1): + +<|ref|>text<|/ref|><|det|>[[175, 808, 812, 864]]<|/det|> +Failure of the Buchberger (or other Grobner basis- computing) algorithm to terminate could thus be adduced as prima facie evidence that the CRN under consideration does not, in fact, have the capacity for RPA. + +<|ref|>text<|/ref|><|det|>[[133, 876, 854, 914]]<|/det|> +It seems that in this statement that authors meant "terminate in practical time". I understand that due to the "almost linear" nature of coordinate change, this algorithm + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[159, 94, 781, 374]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[84, 401, 854, 495]]<|/det|> +
Figure 3: Plots of the dynamics of network (0.5) with mass-action kinetics, with initial state \(x(0)\) and rate constants \(c = (c_{1},c_{2},\ldots)\) . Each component of \(x(0)\) and \(c\) was randomly generated from the interval \([1,10]\) and here we show plots for three realisations of \(x(0)\) and \(c\) . The corresponding steady-state (unscaled) is stated and note that the plots are shown for the dynamics which is rescaled so that the steady-state value of \(x_{1}\) is 1.
+ +<|ref|>text<|/ref|><|det|>[[133, 533, 854, 644]]<|/det|> +would work well for RPA networks. However, does the final RPA polynomial produced by the method depend on the monomial ordering or other choices made by the method? More importantly, if a network is not RPA, how many steps would the method need to confirm this non- RPA property? Such practical considerations must be discussed in the main text, and they are crucial for applying these ideas for characterising RPA in high- dimensional networks. + +<|ref|>text<|/ref|><|det|>[[109, 656, 854, 750]]<|/det|> +5. Connection of examples to existing works: The authors start the Results section with "two simple examples that have eluded all previous systematic methods to detect RPA". Please specify which systematic methods are being referred to here. Also, in the example on Figure 2 it should be mentioned that \(\mathbf{X}_{3}\) is maxRPA and it can be checked from the characterisation result in [2]. Secondly since there is the reaction + +<|ref|>equation<|/ref|><|det|>[[422, 764, 564, 787]]<|/det|> +\[\mathbf{X}_{3} + \mathbf{X}_{2}\xrightarrow{k_{6}}\mathbf{X}_{2}\] + +<|ref|>text<|/ref|><|det|>[[132, 800, 853, 836]]<|/det|> +which does not involve \(\mathbf{X}_{1}\) I do not understand why the term \(k_{6}X_{2}X_{3}\) does not enter the expression for + +<|ref|>equation<|/ref|><|det|>[[442, 835, 545, 871]]<|/det|> +\[\frac{d(X_{1} - X_{2})}{dt}\] + +<|ref|>text<|/ref|><|det|>[[132, 875, 853, 912]]<|/det|> +in Figure 2C. Please check. If the term \(k_{6}X_{2}X_{3}\) is present then it cannot be eliminated with the concatenating monomial \(O_{1}\) . On the other hand, if this reaction is removed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 90, 853, 202]]<|/det|> +(i.e. this term is absent) then the overall network simply becomes a trivial RPA network where the output of one RPA network (i.e. the network comprising \(\mathbf{X}_{3} - \mathbf{O}_{1}\) ) is passed as an input to another RPA network (i.e. the antithetic network with \(\mathbf{X}_{1} - \mathbf{X}_{2}\) ). It is straightforward that connecting RPA networks in series (with catalytic reactions) would still result in a RPA network. Such examples are not appropriate for demonstrating the novel results in this paper. + +<|ref|>text<|/ref|><|det|>[[133, 206, 853, 300]]<|/det|> +The second example in Figure 3 seems to be taken straight from [4] (see Fig. 2). This should be clearly stated when the example is being introduced in the main text and also in the caption of Figure 3. Also mention that the linear invariants shown in Fig. 3 can be deduced from the approach in [4] (this is stated in passing in the conclusion but it should be stated more prominently when the example is being discussed.) + +<|ref|>text<|/ref|><|det|>[[108, 310, 853, 367]]<|/det|> +6. Many claims without proofs in the Supplement: The Supplement has been considerably revised, but still many arguments are unclear because proper proofs have not been provided or referenced: + +<|ref|>text<|/ref|><|det|>[[155, 380, 852, 419]]<|/det|> +- Why should eq. (8) hold when eq. (9) holds? Can the networks always be partitioned this way? Please explain. + +<|ref|>text<|/ref|><|det|>[[155, 422, 553, 442]]<|/det|> +- On page 21 in the Supplement it states that: + +<|ref|>text<|/ref|><|det|>[[210, 447, 818, 523]]<|/det|> +Since a perturbation to the CRN that alters the steady state of \(x_{j}\) will also alter the steady-states of other non-RPA capable variables (eg. \(x_{m}\) ), If \(\mathbb{R}[\bar{x}]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) , and that are not contained in \(I_{f} \cap I_{p}\) . + +<|ref|>text<|/ref|><|det|>[[175, 527, 565, 546]]<|/det|> +Why should such a perturbation always exist? + +<|ref|>text<|/ref|><|det|>[[155, 551, 572, 570]]<|/det|> +- Also on page 21 in the Supplement it says that + +<|ref|>text<|/ref|><|det|>[[210, 575, 818, 630]]<|/det|> +The set \(\bar{x}\) now contains two independent (uncoupled) variables in the sense that a perturbation to the CRN that alters the steady-state of one of the variables does not affect the steady-state of the other. + +<|ref|>text<|/ref|><|det|>[[175, 636, 500, 655]]<|/det|> +Why does this hold? Please elaborate. + +<|ref|>text<|/ref|><|det|>[[155, 660, 853, 789]]<|/det|> +- In general, in the proof of the Kinetic Pairing Theorem the authors work over the ring of polynomials over species-variables \(x_{1}, \ldots , x_{n}\) . Shouldn't the system parameters (i.e. rate constants) be included in this ring, as they would appear in the RPA polynomial? This inclusion of parameters is there in the Singular code but not in the proof. However simply adding the parameters in the ring is not sufficient as the \(n\) -th roots of the parameter would be added, as the examples mentioned in point 3 show. + +<|ref|>sub_title<|/ref|><|det|>[[110, 803, 323, 821]]<|/det|> +## 7. Other minor issues: + +<|ref|>text<|/ref|><|det|>[[155, 834, 853, 872]]<|/det|> +- The definition of RPA must be shifted to the main text due to its centrality in understanding the message of the paper. + +<|ref|>text<|/ref|><|det|>[[155, 876, 852, 914]]<|/det|> +- Why is the variable \(x_{i}\) missing in \(g(x_{j})\) in figure 4 (main text) and figure S4 (supplement)? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[155, 91, 853, 128]]<|/det|> +- Replace "consistutes" with "constitutes" on line 72 in the main text. Please run a spell check. + +<|ref|>text<|/ref|><|det|>[[155, 134, 852, 171]]<|/det|> +- The paper says that if a network is RPA the integrator is guaranteed to exist. For example the following on page 22 in the main text + +<|ref|>text<|/ref|><|det|>[[210, 177, 820, 251]]<|/det|> +In principle, there should always exist some single nonlinear coordinate change to extract a single output-driven internal model (Fig. 9a) from systems rate equations, corresponding to a single integral of the systems tracking error (Fig. 9b) + +<|ref|>text<|/ref|><|det|>[[174, 256, 565, 275]]<|/det|> +or the following on page 16 in the Supplement + +<|ref|>text<|/ref|><|det|>[[210, 281, 819, 316]]<|/det|> +All classes of RPA, including ACR, thus require some form of integral control. + +<|ref|>text<|/ref|><|det|>[[173, 323, 852, 360]]<|/det|> +Please explain which version of IMP can be used to verify this existence. See [1] for a recent review on IMP. + +<|ref|>text<|/ref|><|det|>[[155, 366, 853, 459]]<|/det|> +- On page 20 the authors state that "It is striking to note that the original form of the CRN (Fig. 8a) eludes the Shinar-Feinberg theorem, even though the CRN exhibits ACR and has a deficiency of one." However does it fit the results in [4]? Please comment on this. Also explain why the authors found the method for finding linear invariants "ad hoc" (lines 568-569 on page 25). + +<|ref|>text<|/ref|><|det|>[[155, 464, 549, 483]]<|/det|> +- On the Supplement page 15 it is stated that + +<|ref|>text<|/ref|><|det|>[[210, 489, 819, 543]]<|/det|> +Mass-conservative CRNs therefore have no external stimuli or inputs, and can only be perturbed by altering the total abundances (or concentrations) of the constituent molecules - i.e. by altering the initial conditions. + +<|ref|>text<|/ref|><|det|>[[172, 550, 853, 586]]<|/det|> +Why cannot the perturbation come in the form of parameter variation, e.g. of a conversion reaction (that conserves mass). + +<|ref|>sub_title<|/ref|><|det|>[[85, 613, 235, 636]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[85, 650, 856, 707]]<|/det|> +[1] M. Bin, J. Huang, A. Isidori, L. Marconi, M. Mischiati, and E. Sontag. Internal models in control, bioengineering, and neuroscience. Annual Review of Control, Robotics, and Autonomous Systems, 5:55- 79, 2022. + +<|ref|>text<|/ref|><|det|>[[85, 718, 856, 774]]<|/det|> +[2] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. Proceedings of the National Academy of Sciences, 119(43):e2207802119, 2022. + +<|ref|>text<|/ref|><|det|>[[85, 785, 854, 840]]<|/det|> +[3] N. Meshkat, A. Shiu, and A. Torres. Absolute concentration robustness in networks with low- dimensional stoichiometric subspace. Vietnam Journal of Mathematics, 50(3):623- 651, 2022. + +<|ref|>text<|/ref|><|det|>[[85, 852, 854, 890]]<|/det|> +[4] M. Pérez Millán, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027- 1065, 2012. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[85, 92, 850, 127]]<|/det|> +[5] M. S. Pérez Millán. Métodos algebraicos para el estudio de redes bioquímicas. PhD thesis, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales, 2011. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 295, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[118, 112, 300, 153]]<|/det|> +Reviewer #1: Remarks to the Author: See attached. + +<|ref|>text<|/ref|><|det|>[[118, 195, 300, 222]]<|/det|> +Reviewer #2: Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 223, 864, 265]]<|/det|> +The reviewers have comprehensively addressed my questions and points. This paper addresses a fundamentally important question in biology and it does so using a powerful mathematical framework that the authors have developed and fine- tuned. + +<|ref|>text<|/ref|><|det|>[[118, 280, 863, 350]]<|/det|> +The particular appeal of this approach is that it sets a template (and I imagine that in the future we will see many more examples of this type) is that the mathematical analysis has a level of generality that means that the authors results are robust and reliable. Having solid mathematical foundations for a complex biological phenotype is still rare, but the current paper shows that the search for such theoretical underpinnings can be fruitful. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 855, 151]]<|/det|> +Overview: The aim of this paper is to provide an algebraic characterisation of the hidden integral controller and construct an algebraic procedure to identify it in adaptation- capable networks. It is shown that this procedure is intimately connected to the structure of the networks via the well- known deficiency theory for chemical reaction networks. + +<|ref|>text<|/ref|><|det|>[[119, 166, 862, 250]]<|/det|> +Recommendation: I am grateful to the authors for revising the manuscript to address many of the points that I raised in the first review. Even though the paper has significantly improved, many of the more serious concerns remain. These concerns, which are outlined below, should be fully addressed before the paper can be reconsidered again for Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[180, 267, 299, 282]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[180, 283, 860, 334]]<|/det|> +Once again, we are truly grateful for the huge investment of time the reviewer has clearly made in considering our work in such careful detail. We have reflected thoughtfully on all the reviewer's points and respond to each in turn below. + +<|ref|>text<|/ref|><|det|>[[180, 353, 866, 386]]<|/det|> +All changes made to our paper and Supplementary Information (SI) are noted in red text. + +<|ref|>text<|/ref|><|det|>[[119, 419, 863, 519]]<|/det|> +1. Connection to integral control: The paper claims to uncover universal structures for embedded "integral control". However in order to successfully demonstrate this, a coordinate transformation (possibly nonlinear) needs to be constructed that gives rise to the "integrator" variable. It does not matter if this coordinate transformation is done in a single step or in multiple steps (as proposed by this paper), but its existence needs to be shown in order to identify the integral mechanism. In the Supplement the authors write + +<|ref|>text<|/ref|><|det|>[[119, 535, 856, 601]]<|/det|> +We note that, although there should always exist some single nonlinear coordinate change that yields the RPA polynomial in principle, for any mass action system, identifying such a single coordinate change in practice may be extremely difficult in all but the very simplest RPA-capable CRNs. + +<|ref|>text<|/ref|><|det|>[[120, 617, 839, 651]]<|/det|> +I agree that proving the existence of an integrator may be difficult, but unfortunately it is unavoidable for showing integral control. + +<|ref|>sub_title<|/ref|><|det|>[[180, 668, 300, 682]]<|/det|> +## Our response: + +<|ref|>text<|/ref|><|det|>[[179, 684, 874, 892]]<|/det|> +What we show in this paper is that a particular type of nonlinear transformation is always able to decompose an RPA- capable set of CRN reactions into an organized collection (a 'topological hierarchy') of linear coordinate transformations. Each of these linear coordinate transformations corresponds to a subsidiary integral controller within the CRN. This is a fundamentally different type of integral control implementation from the 'conventional' interpretation of integral control in engineering control theory. Indeed, the nonlinear transformation we propose is not a coordinate transformation. Rather, it is a map from the system reaction rates to a function space with the same algebraic structure as the CRN reactions (i.e. that of a commutative ring), which offers a universal description of the coordinated interactions of (integral computing) internal models – obtained via linear coordinate changes - that holds for all possible RPA- capable CRNs. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 866, 224]]<|/det|> +We do acknowledge that in our previous rebuttal letter (as opposed to our paper), we had referred to the mathematical transformation in several places as a coordinate change, which was not correct. We apologise for unwittingly sidetracking the discussion through such sloppy (and incorrect) wording in our previous response. We have now made absolutely certain that this incorrect terminology does not appear anywhere in our paper or in our accompanying SI. The reviewer is entirely correct to point out that the nonlinear transformation we present in this paper is not a nonlinear coordinate change. + +<|ref|>text<|/ref|><|det|>[[179, 241, 880, 607]]<|/det|> +The conventional view of the 'internal model principle' (IMP) in engineering control theory (particularly for application to problems in systems biology and bioengineering [1,8,9]) suggests that, for robust rejection of constant disturbances, there must exist some decomposition of the system (obtained via a coordinate transformation, if needed) into two distinct subsystems: (i) an 'output- driven internal model' (of the constant disturbance), and (ii) the remainder of the system ([8,9]). This decomposition will generally require a nonlinear coordinate transformation, although many simple CRNs have been identified (as we point out in our paper and accompanying Supplementary Information) for which a linear coordinate transformation is sufficient. In particular, if the system at hand is not already in feedback form, then the internal model- identifying coordinate transformation must be able to recast the system into an integral feedback form (see references [1] and [9] below, as well as Figure 1b in our paper, for some simple examples of this requirement). If a network can indeed exhibit RPA, then according to this version of the IMP (see [8] and [9], for example, as well as Section 3 in [1]), there should always exist some (single) coordinate transformation that recasts the system into such a feedback system, with an embedded output- driven internal model – even if the system is topologically feedforward structured. This is the concept we are referring to in the excerpt from our Supplementary Information quoted by the reviewer above ('... there should always exist some single nonlinear coordinate change that yields the RPA polynomial... for any mass action system'). + +<|ref|>text<|/ref|><|det|>[[179, 624, 875, 904]]<|/det|> +Note, incidentally, that (in contrast to the formulation we present in our paper) this conventional interpretation of the IMP ([8,9]) requires that certain properties of the disturbances be known a priori, including which model variables can be directly regulated by the disturbance, and also requires the prior identification of an 'output' for the model (which must be able to 'adapt' to, or reject, those disturbances). For an RPA- capable system, being able to identify such a nonlinear coordinate transformation, if it exists, simply confirms to us that the system can indeed exhibit robust asymptotic tracking of the output variable's 'setpoint' when subjected to the specified (constant in time) disturbances. It also identifies the specific transformed variable that actually computes the integral of the 'error' (where the error in question is the difference between the instantaneous value of the output variable and its setpoint). But if we already know (using some other analytical method, say) that RPA obtains for certain variable(s) in a specific CRN, then explicitly identifying the nonlinear coordinate change that transforms that particular system into integral feedback form does not actually provide any further useful information. The fundamental point we make in our Discussion is that there is no general way to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[180, 85, 868, 154]]<|/det|> +propose a single nonlinear coordinate change that can reveal the fundamental mechanisms by which all RPA- capable CRNs actually implement RPA, and thereby provide a concrete characterization of the entire solution space to the RPA problem for CRNs. + +<|ref|>text<|/ref|><|det|>[[178, 170, 870, 767]]<|/det|> +Consider, for example, Shinar and Feinberg's deficiency- two model of the EnvZ- OmpR osmoregulation network (first presented in the Supplementary Materials of [10], and considered in Figure 3 of our main paper). For this specific network, the existence of RPA (and ACR more specifically) in the molecule phospho- OmpR can be shown using a variety of methods. Shinar and Feinberg, in their Supplementary Materials [10], show through a sequence of manual algebraic substitutions that phospho- OmpR has a steady- state value that is a rational function of the CRN parameters, independent of the total abundances of the various interacting molecules. Karp et al. [6], on the other hand, demonstrate how 'complex- linear' invariants may be computed, and show that for this particular CRN, two linearly- independent such invariants may be combined to demonstrate RPA in phospho- OmpR, with the same setpoint as previously calculated by Shinar and Feinberg [10]. Now, since this CRN exhibits RPA (at phospho- OmpR), undoubtedly, there must undoubtedly exist some nonlinear coordinate transformation that could recast this system (a 'balancer' module, as we show, with a feedforward structure) into an integral feedback system with a single output- driven (i.e. phospho- OmpR- driven) internal model, where a single (transformed) variable computes the error in phospho- OmpR in comparison with its (known) setpoint. But even if we were to identify the requisite coordinate transformation, explicitly and analytically, for this particular CRN, what would this coordinate map actually tell us (vis- à- vis the RPA- capacity of the CRN) that we didn't already know? More importantly, what could this specific coordinate map possibly tell us about the space of all possible RPA- capable CRNs, or the general (universal) properties of collections of chemical reactions that can confer RPA on a subset of the interacting molecules? Absolutely nothing! The integral- feedback- recasting nonlinear coordinate transformation for an RPA- capable CRN is unique to that particular CRN. In other words, the single nonlinear coordinate transformation required to identify an internal model in the deficiency- two Shinar- Feinberg EnvZ- OmpR model discussed above, if such can be explicitly identified, will necessarily be a different nonlinear map from the one required for the Cappelletti et al. [11] toy model (Example 1 in Section S3.1 of our SI) – despite the fact that the two models are fundamentally alike: both are Balancer modules (topologically speaking) for which a single balancer invariant and a single connector invariant are obtained via linear coordinate transformations, and require a single concatenating monomial to obtain an RPA polynomial. + +<|ref|>text<|/ref|><|det|>[[180, 781, 875, 904]]<|/det|> +By contrast, our nonlinear transformation (Eq. 6) is of a fundamentally different character. Nowhere in our paper do we claim that this nonlinear transformation is a coordinate transformation. Importantly, this nonlinear map relaxes the feedback requirement of the IMP in its conventional interpretation (as discussed above, see also Section 6.2 in [9]), and instead preserves the underlying topological structure of the network. Thus, RPA- capable CRNs of Balancer type retain their feedforward characteristics under this transformation. We maintain that referring to an + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 84, 875, 208]]<|/det|> +embedded integral control is entirely justified since the nonlinear map in question is always able identify, for any RPA- capable CRN, a topologically organized collection of linear coordinate changes, each one of which identifies a subsidiary internal model which does recapitulate the dynamical structure of the disturbance (i.e. constant- in- time), and which thereby imposes RPA on some characteristic of the network, with its own setpoint. Each such linear coordinate change thereby corresponds to subsidiary control problem with its own linear integral variable. + +<|ref|>text<|/ref|><|det|>[[178, 224, 875, 525]]<|/det|> +For the Cappelletti et al. [11] toy model, for instance, the nonlinear transformation which projects the system onto two variables (A and B - see Singular Code in SS.3 of our Supplementary Information) can be decomposed into two linear coordinate changes, corresponding to two key invariants. One of these is a 'balancer' invariant, \(k_{2}BC - k_{3}B^{2}\) , which represents the 'error' in the ratio of the two 'proportioner' molecules, \(C\) and \(B\) , in comparison with their 'setpoint': i.e. \(k_{2}B^{2}\left(\frac{C}{B} -\frac{k_{3}}{k_{2}}\right)\) . The other is a 'connector' invariant, \(k_{1}AB - k_{7}C\) , which represents the error in the ratio of the 'upregulating' contributions (in this case, \(AB\) ) to the 'downregulating' contributions (in this case, \(C\) ), for the 'connector' calculation: i.e. \(k_{1}C\left(\frac{AB}{C} -\frac{k_{7}}{k_{1}}\right)\) . Together, these two independent computations, each with a linear integral variable, and each conferring RPA on some (topologically important) feature of the CRN, confer RPA on the molecule \(A\) . The setpoint for \(A\) is a combination of the setpoints from the two contributing subsidiary (linear) problems. Of course, many CRNs will have much more complicated invariants than these, involving more than two terms per invariant, but the same fundamental principles hold. (This is the universality of the framework we present). + +<|ref|>text<|/ref|><|det|>[[179, 540, 870, 645]]<|/det|> +The feedforward model presented by Bin et al. [1] provides a nice illustration of the distinction between the conventional interpretation of the IMP and the one we develop here, as applicable to RPA in CRNs. In Section 3 of [1] the authors review a very simple two- variable incoherent feedforward loop (IFFL) model (Eq. 25) that has been widely studied in the systems biology literature (including in [9]). The two model equations are + +<|ref|>equation<|/ref|><|det|>[[456, 660, 588, 694]]<|/det|> +\[\frac{dx}{dt} = \alpha u - \delta x,\] + +<|ref|>text<|/ref|><|det|>[[179, 696, 214, 710]]<|/det|> +and + +<|ref|>equation<|/ref|><|det|>[[456, 710, 590, 745]]<|/det|> +\[\frac{dy}{dt} = \beta \frac{u}{x} -y y.\] + +<|ref|>text<|/ref|><|det|>[[179, 761, 880, 796]]<|/det|> +The authors show that a nonlinear coordinate map that transforms these two equations into a partitioned form, corresponding to an integral feedback structure, is + +<|ref|>equation<|/ref|><|det|>[[305, 796, 752, 817]]<|/det|> +\[(x,y)\mapsto (z_{1},z_{2}) = \left(y,\phi (x,y)\right) = (y,\alpha y - \beta \log x),\] + +<|ref|>text<|/ref|><|det|>[[179, 833, 580, 850]]<|/det|> +which produces, in the new coordinates \((z_{1},z_{2})\) : + +<|ref|>equation<|/ref|><|det|>[[412, 867, 650, 901]]<|/det|> +\[\frac{dz_{1}}{dt} = \beta u e^{(z_{2} - \alpha z_{1}) / \beta} - \gamma z_{1},\] + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[415, 102, 571, 137]]<|/det|> +\[\frac{dz_2}{dt} = \beta \delta -\alpha \gamma z_1.\] + +<|ref|>text<|/ref|><|det|>[[179, 152, 879, 240]]<|/det|> +This transformed system has an output \(y = z_{1}\) , and has the desired internal model form, where \(z_{2}\) is the transformed variable that integrates the error (in \(z_{1} = y\) ). This nonlinear coordinate change nicely confirms that RPA is possible at \(y\) , and that its setpoint is \(\beta \delta /\alpha \gamma\) . But a different nonlinear transformation of the system (not a coordinate transformation) is also possible: + +<|ref|>equation<|/ref|><|det|>[[390, 255, 656, 294]]<|/det|> +\[\beta \frac{dx}{dt} -\alpha x\frac{dy}{dt} = \alpha \gamma x\left(y - \frac{\delta\beta}{\alpha\gamma}\right)\] + +<|ref|>text<|/ref|><|det|>[[177, 308, 878, 692]]<|/det|> +Unlike the coordinate transformation considered previously, this particular transformation underscores the fact that this simple two- variable reaction system is fundamentally of the same type as both the Cappelletti et al. [11] toy model (Example 1 in our Supplementary Information S3.1) and the deficiency- two Shinar- Feinberg EnvZ- OmpR model we discussed above: a Balancer module, with two independent (linear) invariants - a balancer invariant, and a connector invariant - combined via a single concatenating monomial (in this case, \(x\) ). This transformation also reveals the setpoint, \(y = \beta \delta /\alpha \gamma\) . Of course, we do acknowledge that the rate equations above are not polynomials, the only consequence of which, in the context of our paper, is that we cannot use the powerful automated algorithms of algebraic geometry that compute Gröbner bases (which pertain to polynomials); nevertheless, rational functions are \(C^{1}\) - smooth functions on \((0, \infty)\) , and thus possess the algebraic properties of a ring as required for the application of our Theorem 1. The RPA polynomial so obtained involves two variables (one RPA- capable (i.e. \(y\) ) and one non- RPA- capable (i.e. \(x\) )) and is thus the single generator of the relevant ideal. By contrast, the nonlinear coordinate transformation discussed in [1], as noted above, is unique to this particular set of rate equations, and provides no insight into the general properties of all RPA- capable CRNs (or even its fundamental connection to the RPA- conferring properties of the Cappelletti et al. [11] or Shinar- Feinberg [10] models discussed above). Shoval et al. [9] acknowledge that the coordinate transformations that recast systems into integral feedback form 'may well be merely a mathematical construct with no biological meaning' (see Section 6.3 in [9]). + +<|ref|>text<|/ref|><|det|>[[179, 709, 877, 865]]<|/det|> +Again, we maintain emphatically that this is a fundamentally different way of looking at integral control from the IMP as it is usually understood in engineering control theory. This approach identifies where, within the collection of reactions themselves, the computations relevant to RPA actually occur at the level of the interacting molecules of the CRN. Identifying a (single) nonlinear coordinate change that transforms the system into an integral feedback system, with a single embedded internal model, can only confirm that RPA will obtain; it does not explain how it is implemented by the original variables of the system (i.e. the molecular concentrations). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 878, 416]]<|/det|> +Being able to characterize the entire space of all possible RPA- capable CRNs in such a general way has enormous practical implications because it provides a completely comprehensive and universal understanding of how to either destroy or maintain the presence of RPA – through evolution, or via experimental or clinical interventions, where new mutational events or exogenous enzyme inhibitors exert their effects at the molecular level. In particular, we can destroy the RPA property in a CRN by disrupting any one linear integral controller. By contrast, retaining the RPA property requires that all linear integral controllers already present be preserved. Cappelletti et al. [11], for instance, consider how a linear integral controller can be preserved when adding in a new (exogenous) stimulus to the network (see Theorem 5.1 in [11]); but there are many other types of perturbations that could occur in CRNs in either an evolutionary setting, or in experimental/clinical settings. Given that many of the most complex signalling networks that arise in nature, such as signal transduction networks in mammalian cancer cells, will likely never be delineated in complete intricate detail in terms of elementary chemical reactions, the robustness- conferring mechanisms that self- assemble in biology require a completely new approach, an entirely new language, for understanding the fundamental structures of life’s networks. In this paper we wish to offer just such an approach. + +<|ref|>text<|/ref|><|det|>[[118, 447, 584, 482]]<|/det|> +Let us look into this issue in more details. Suppose the dynamics is governed by a system of ODEs: + +<|ref|>equation<|/ref|><|det|>[[444, 495, 544, 530]]<|/det|> +\[\frac{dx}{dt} = f(x),\] + +<|ref|>text<|/ref|><|det|>[[118, 544, 868, 597]]<|/det|> +where \(x\) is the \(n\) - dimensional state of the system and \(f(x) = (f_{1}(x), \ldots , f_{n}(x))\) are the rates of evolution of all the species. In order to exhibit an integrator, we need to find a real- valued function \(H(x)\) such the dynamics of \(z(t) = H(x(t))\) is given by the ODE: + +<|ref|>equation<|/ref|><|det|>[[234, 610, 761, 639]]<|/det|> +\[\frac{dz}{dt} = \nabla H(x)\cdot f(x) = p(x)(x_{i} - c)\coloneqq \rho (x), \quad (0.1)\] + +<|ref|>text<|/ref|><|det|>[[118, 653, 864, 706]]<|/det|> +where \(\nabla\) is the gradient operator, \(\cdot\) is the usual dot product and \(\rho (x) = p(x)(x_{i} - c)\) is what the authors call the “RPA polynomial” for the RPA variable \(x_{i}\) . Suppose one is able to find nonlinear polynomials \(h_{1}, \ldots , h_{n}\) (as in Theorem 1 of the paper) such that + +<|ref|>equation<|/ref|><|det|>[[333, 720, 663, 739]]<|/det|> +\[h_{1}(x)f_{1}(x) + \dots +h_{n}(x)f_{n}(x) = \rho (x).\] + +<|ref|>text<|/ref|><|det|>[[118, 752, 874, 804]]<|/det|> +However this does not necessarily mean that a function \(H(x)\) can be constructed so that (0.1) holds. Observe that such a function \(H(x)\) would need to have the following partial derivatives + +<|ref|>equation<|/ref|><|det|>[[337, 818, 660, 850]]<|/det|> +\[\frac{\partial}{\partial x_{j}} H(x) = h_{i}(x)\quad \mathrm{for}\quad j = 1,\dots ,n.\] + +<|ref|>text<|/ref|><|det|>[[118, 864, 865, 899]]<|/det|> +Unless each \(h_{i}(x)\) is a constant (in which case \(H(x)\) is linear), it is unclear why such a function \(H(x)\) would exist. Since the approach in the paper uses nonlinear elimination steps + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 860, 119]]<|/det|> +(via concatenating monomials), the existence of \(H(x)\) cannot be ascertained. In fact if for a pair \(j, k\) we have + +<|ref|>equation<|/ref|><|det|>[[391, 134, 592, 174]]<|/det|> +\[\frac{\partial}{\partial x_j} h_k(x) \neq \frac{\partial}{\partial x_k} h_j(x)\] + +<|ref|>text<|/ref|><|det|>[[118, 188, 872, 272]]<|/det|> +then certainly \(\mathrm{H}(x)\) cannot be constructed with partial derivatives \(h_1, \ldots , h_n\) . This discussion shows that while existence of a RPA polynomial may be necessary for integral control, it is not sufficient and hence this property does not characterise integral controllers (a main claim of the paper). This gap between necessity and sufficiency can be bridged if the authors can show that for RPA networks one always has + +<|ref|>equation<|/ref|><|det|>[[362, 286, 624, 325]]<|/det|> +\[\frac{\partial}{\partial x_j} h_k(x) = \frac{\partial}{\partial x_k} h_j(x) \forall j, k.\] + +<|ref|>text<|/ref|><|det|>[[178, 357, 868, 515]]<|/det|> +Our response: Yes, the reviewer is entirely correct to point out that the nonlinear map we propose in this paper (Eq. 6) is not a coordinate transformation. But again, we don't actually seek a diffeomorphism \(H(x)\) of the type the reviewer describes, and we don't claim that our collection of elimination polynomials gives rise to a coordinate transformation (other than in the special case of constant elimination polynomials). We do apologise again for incorrectly referring to the nonlinear map as a nonlinear coordinate change in our previous rebuttal letter. This was sloppy (and incorrect) wording, and we have made absolutely certain that no such inaccuracies appear anywhere in our manuscript or in our SI. + +<|ref|>text<|/ref|><|det|>[[178, 531, 872, 800]]<|/det|> +It is true that the existence of an RPA polynomial, \(\rho\) , contained in the ideal \(I_f = \{h_1 f_i + \dots + h_n f_n: h_i \in \mathbb{R}[x_1, \ldots , x_n]\}\) is a necessary but insufficient condition for RPA. As our Theorem 1 makes clear, \(\rho = g(x_i, x_j)(x_i - c)\) must generate the principal ideal in two variables, \(I_f \cap \mathbb{R}[x_i, x_j]\) , where \(x_j\) is (any) non- RPA- capable variable. This condition is both necessary and sufficient for RPA at \(x_i\) , under the assumption of stability. But nowhere do we claim that a CRN for which \(\rho (x_i, x_j)\) generates \(I_f \cap \mathbb{R}[x_i, x_j]\) contains "an" integrator. This can only be true if the elimination polynomials are constants, as the reviewer points out. If non- constant elimination polynomials are required, our framework requires there to be multiple independent (linear) integrators, connected via concatenating monomials; the nonlinearity is thereby relegated entirely to the concatenating process, not to the identification of internal models. In general, the output for one internal model will be an input for another. This collection of linear coordinate maps is always obtainable from a decomposition of the special nonlinear transformation we identify. That is the viewpoint we develop here. + +<|ref|>text<|/ref|><|det|>[[179, 816, 876, 904]]<|/det|> +Again, we are re- interpreting the IMP from a completely different standpoint from the one considered in prior work, in which the existence of a nonlinear coordinate transformation, and an associated output- driven internal model, is normally at issue. Note that the RPA polynomial we reference in Eq. 6 (and Theorem 1 – the Two- Variable Kinetic Pairing Theorem) contains strictly two variables in contrast to \(\rho (x)\) in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 866, 190]]<|/det|> +(0.1) above, which involves an unspecified number of variables. We simply do not claim that the transformation that identifies the (two-variable) RPA polynomial is associated with a single integrator. Rather, we claim that this transformation is always able to obtain \(\rho\) via a connected collection of linear integrators, each requiring a linear coordinate change, and each imposing RPA on some topologically important feature of the CRN. + +<|ref|>text<|/ref|><|det|>[[179, 207, 881, 399]]<|/det|> +Bin et al. in [1] offer a particularly insightful comment. They state in Section 3: 'The question that the IMP asks is, If a system ... is seen experimentally to regulate against all inputs (in some class of functions, e.g. constants), then what can be said about its internal structure? Answers to this question may help guide experimentalists and modelers by ruling out putative mechanisms and suggesting a search for components responsible for adaptation'. The version of the IMP those authors go on to discuss in that paper (involving a coordinate transformation that identifies an output- driven internal model, within a feedback structure) provides one answer as to what can be said about the internal structure of RPA- capable networks. Our paper provides a different answer – one that reveals the universal properties, at the molecular level, of all RPA- capable networks. + +<|ref|>text<|/ref|><|det|>[[118, 430, 880, 482]]<|/det|> +2. Questions about the Kinetic Pairing result: In the previous review round, I had proposed a possible RPA network and asked the authors how it satisfies the Kinetic Pairing result (Theorem 1). The network has two reactions given by + +<|ref|>equation<|/ref|><|det|>[[255, 496, 741, 522]]<|/det|> +\[X_{2} + X_{3}\xrightarrow{c_{1}}X_{1} + X_{4}\mathrm{~and~}X_{1} + X_{2} + X_{3}\xrightarrow{c_{2}}X_{5} \quad (0.2)\] + +<|ref|>text<|/ref|><|det|>[[118, 534, 880, 618]]<|/det|> +and there may be several other reactions involving species \(X_{2},\ldots ,X_{5}\) that can be catalysed by \(X_{1}\) but they do not change \(X_{1}\) . In the rebuttal letter, the authors consider certain instances of such a network, and claim that in these networks all possible steady states lie on the boundary on the positive orthant (e.g. \(x_{2}\) or \(x_{3}\) is zero) and hence the networks are not RPA. In particular, the authors state in their rebuttal letter that: + +<|ref|>text<|/ref|><|det|>[[118, 633, 877, 864]]<|/det|> +The two reactions proposed by the reviewer cannot impose RPA on \(X_{1}\) no matter which reactions are added to the original two. This is because the two given reactions are linearly independent, and the CRN formed from these reactions has deficiency zero. Moreover, the two complexes that contribute to the apparent RPA- polynomial in the reaction rate \(f_{i}\) are not members of the same terminal SCC. It is clear from our discussion of the decomposition of CRNs into algebraically independent subnetworks a decomposition which is closely tied to the partition of deficiency among independent subsets of reactions (see SI Section S1.3) - as well as our extensive discussions of rowspan polynomials (complex linear invariants) throughout the remainder of our supplement, that no possible addition of extra reactions can turn the original two into an RPA- conferring set. We briefly note in Section S4.4.1 (see also footnote in that section) the special case where a deficiency zero collection of reactions can engender RPA namely when the two relevant complexes reside in the same terminal SSC, and correspond topologically to a trivial (isolated) connector node. The pair of reactions suggested by the reviewer are clearly not of this type. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 875, 136]]<|/det|> +To test the authors' claim above, I tried to come up with instances of such networks (i.e. (0.2) + some reactions) which are RPA and yet do not have this issue of steadystate not being in the positive orthant. Please explain how the Kinetic Pairing result fits these networks. + +<|ref|>text<|/ref|><|det|>[[178, 151, 874, 386]]<|/det|> +Our response: Yes, in the previous round of review the reviewer provided us with the two reactions given in (0.2) above and, pointing out that such a reaction pair would produce a reaction rate \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) , asked us how this could be reconciled to the claims of our Two- Variable Kinetic Pairing Theorem since this equation has the apparent form of an RPA polynomial, yet appears to have three rather than two variables. We pointed out that it is possible to have an RPA polynomial involving three (or more) species, but only two variables, in CRNs containing a 'boundary variable'. But more importantly, we went on to show that, for the particular reaction pair proposed by the reviewer equipped with the needed 'closure' reactions (for which we provided three different examples), the projection of the ideal generated by the collection of CRN rate equations \((I_f)\) onto two variables (one RPA- capable, and one non- RPA- capable) produced the elimination ideal \(< x_2x_3>\) . Hence, none of the three CRN examples could exhibit RPA. + +<|ref|>text<|/ref|><|det|>[[178, 402, 875, 570]]<|/det|> +Our Theorem 1 (the 'two- variable kinetic pairing theorem') states, simply, that a CRN is RPA- capable in some variable \(x_i\) exactly when the projection of the steady- state ideal, \(I_f\) , onto \(x_i\) and \(x_j\) (for any non- RPA- capable \(x_j\) ) is generated by a single polynomial of the form \(\rho = g(x_i, x_j)(x_i - c)\) . We call such polynomials 'RPA polynomials'. As we pointed out in our earlier rebuttal, it is not enough for a set of CRN equations to contain a reaction rate that has the form of an RPA polynomial (as is the case for all the reviewer's examples, both here and in the previous round of review, which all have \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) ). Rather, the elimination ideal \(I_f \cap \mathbb{R}[x_1, x_j]\) must be generated by an RPA polynomial. + +<|ref|>text<|/ref|><|det|>[[178, 586, 876, 905]]<|/det|> +In the reviewer's new report, he/she provides three alternative collections of reactions, all of which contain the reaction \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) , and all of which do, in fact, exhibit RPA. As the reviewer rightly points out, none of these examples contain any boundary variables. According to our Theorem 1, all three of these new examples will indeed exhibit RPA since the elimination ideal \(I_f \cap \mathbb{R}[x_1, x_j]\) in each case (with \(x_j \in \{x_2, x_3\}\) for the first two CRN examples, and \(x_j \in \{x_2, x_3, x_4, x_5\}\) for the third example) is generated by a two- variable RPA polynomial. In particular, \(\rho = x_1 - c_1 / c_2\) in the first and third CRN examples (where the pairing function is zero- order in both its arguments), and \(\rho = x_1^2 (x_1 - c_1 / c_2)\) in the second CRN example (where the pairing function is zero- order in the non- RPA variable). Thus, all relevant two- variable projections for these CRNs produce an ideal generated by a single polynomial of the requisite form, hence the CRN exhibits RPA. Notice that the three- variable reaction rate for \(x_i\) is not the generator of \(I_f \cap \mathbb{R}[x_1, x_j]\) in any of these examples (although it is obviously contained in \(I_f\) ). As we explained previously, the fact that a CRN contains a reaction rate of the form \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) is, in and of itself, irrelevant vis- à- vis the RPA capacity of the CRN (and hence, the claims of our Theorem 1). What matters is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 878, 270]]<|/det|> +what actually generates the ideal \(I_{f} \cap \mathbb{R}[x_{i}, x_{j}]\) – i.e. the projection of \(I_{f}\) onto the two variables \(x_{i}\) and \(x_{j}\) (where one of these is RPA-capable, and one is not). The three CRNs discussed in the previous round of review, as well as the three new CRNs offered by the reviewer, all contain the reaction rate \(\frac{dx_{1}}{dt} = c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3}\) . But for the previous set of three CRNs (considered in the last review round), the relevant elimination ideal is \(< x_{2}x_{3} >\) , and as a consequence, those CRNs cannot exhibit RPA in \(x_{1}\) (or anything else). For the new set of CRNs, the relevant elimination ideal is \(< x_{1} - c_{1} / c_{2} >\) for the first and third examples, and \(< x_{1}^{2}(x_{1} - c_{1} / c_{2})>\) for the second example, and as a consequence, these CRNs do exhibit RPA at \(x_{1}\) , with setpoint \(c_{1} / c_{2}\) . + +<|ref|>text<|/ref|><|det|>[[178, 285, 876, 700]]<|/det|> +We make some additional observations for each of the three new CRNs in turn below. As the reviewer notes, we had observed in our previous rebuttal that the two specific reactions originally proposed by the reviewer together have deficiency zero, and that the addition of the necessary closure reactions will not be able to increase this deficiency. As a consequence, that CRN could not exhibit RPA. In other words, the fact that those particular CRNs were not RPA capable was not tied to the specific choices of closure reactions that we provided as illustrative examples. Of course, if one begins with a different pair of reactions (i.e. not involving \(X_{4}\) and \(X_{5}\) ), as is the case for the first two new examples the reviewer provides, or adds in more than the needed closure reactions, as is the case for the third new example, then one can certainly increase deficiency, and thereby arrive at an RPA- capable set. But in this case, the RPA- capacity is tied inextricably to the altered structure arising from the different starting pair and/or the redundant closure reactions, with the attendant increase in deficiency associated with that altered structure, and is not due solely to the mere presence of the original pair (which appear to produce an apparent 'RPA polynomial' for \(\frac{dx_{1}}{dt}\) in all cases). We explain this point in more detail in our ensuing analysis. We apologise if we unwittingly side- tracked the discussion by raising the issue of the original pair being characterized by a deficiency of zero, and that adding in the necessary 'closure' reactions to allow us to work with that original pair cannot increase deficiency. The point we were really trying to emphasize was that the mere presence of \(\frac{dx_{1}}{dt} = c_{1}x_{2}x_{3} - c_{2}x_{1}x_{2}x_{3}\) in the rowspan of the system, even for cases where \(x_{2}x_{3}\) is a boundary variable, does not, in and of itself, imply RPA. Our Theorem 1 explains why this is the case. + +<|ref|>text<|/ref|><|det|>[[179, 717, 880, 804]]<|/det|> +Again, the fundamental issue in all six CRN examples (the three here, as well as the three from the previous round of review) is that the reaction rate for \(x_{1}\) does not actually generate the two- variable elimination ideal for these CRNs. In general, CRNs for which one of the reaction equations is an 'apparent' RPA polynomial may or may not exhibit RPA. + +<|ref|>text<|/ref|><|det|>[[118, 837, 857, 888]]<|/det|> +I start with a simpler version of this network with only three species (i.e. species \(X_{4}\) and \(X_{5}\) are absent) where I add inflow and outflow for species \(X_{2}\) and \(X_{3}\) . So the overall network becomes + +<--- Page Split ---> +<|ref|>equation<|/ref|><|det|>[[213, 82, 785, 130]]<|/det|> +\[X_{2} + X_{3}\xrightarrow{c_{1}}X_{1},\quad X_{1} + X_{2} + X_{3}\xrightarrow{c_{2}}\emptyset,\quad \emptyset\xrightarrow{c_{3}}X_{2},\quad \emptyset\xrightarrow{c_{4}}X_{3}\qquad (0.3)\] + +<|ref|>text<|/ref|><|det|>[[118, 143, 878, 212]]<|/det|> +This network has no boundary variables and so the variables are the same as species. It seems that this network will indeed show RPA for \(x_{1}\) with set- point \(c_{1} / c_{2}\) . In Figure 1 I plot the simulated dynamics (rescaled to have the set- point of \(x_{1}\) as 1) for three randomly chosen values of initial states and rate constants, and one can see that RPA holds. + +<|ref|>text<|/ref|><|det|>[[178, 243, 858, 357]]<|/det|> +Our response: Here, the reviewer starts with a different version of the initial two reactions (rather than the two given in (0.2)), so this CRN can have a deficiency of one, even with only the minimum needed closure reactions. In any case, this CRN does indeed exhibit RPA because \(< \frac{dx_{1}}{dt}, \frac{dx_{2}}{dt}, \frac{dx_{3}}{dt} > \cap \mathbb{R}[x_{1}, x_{2}] = < x_{1} - \frac{c_{1}}{c_{2}} >\) . We provide our Singular code and output below so that the reviewer can verify (see \(G[1]\) ): + +<|ref|>text<|/ref|><|det|>[[180, 372, 890, 565]]<|/det|> +Last login: Wed Dec 14 11:35:16 on ttys000 /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit (base) araujo@SEF- PA00144783 \\~ % /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit SINGULAR / Development A Computer Algebra System for Polynomial Computations / version 4.1.2 by: W. Decker, G.- M. Greuel, G. Pfister, H. Schoenemann \ \(Feb 2019 FB Mathematik der Universitaet, D- 67653 Kaiserslautern\) > ring R = (0, c1, c2, c3, c4, c5, c6), (x3, x2, x1), lp; \(>poly f1 = c1*x2*x3 - c2*x1*x2*x3;\) \(>poly f2 = c3 - c5*x2 - c1*x2*x3 - c2*x1*x2*x3;\) \(>p o l y f3 = c4 - c6*x3 - c1*x2*x3 - c2*x1*x2*x3;\) \(>ideal I = f1,f2,f3;\) \(>ideal GI = groebner(I);\) \(>GI;\) \(GI[1] = (c2*c3*c4)*x1 + (-c1*c3*c4)\) \(GI[2] = (2*c1*c5)*x2^2 + (-2*c1*c3 + 2*c1*c4 + c5*c6)*x2 + (-c3*c6)\) \(GI[3] = (c6)*x3 + (-c5)*x2 + (c3 - c4)\) + +<|ref|>text<|/ref|><|det|>[[179, 584, 861, 689]]<|/det|> +Whereas (0.2) includes two additional species, \(X_{4}\) and \(X_{5}\) , each assigned to a different reaction in the pair, thereby guaranteeing the linear independence of the reactions once the requisite closure reactions are added, this property is no longer present in the new reaction set. When organized correctly into its linkage classes, this CRN has six complexes, two linkage classes and a rank of three, resulting in a deficiency of one. + +<|ref|>image<|/ref|><|det|>[[370, 714, 700, 861]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 875, 370]]<|/det|> +The CRN has just two non- terminal complexes, from which it follows that there is a polynomial of the form \(a_{1}x_{2}x_{3} - a_{2}x_{1}x_{2}x_{3}\) in the rowspan of the system - a feature that was already obvious from the form of \(\frac{dx_1}{dt}\) . But note that this fact, in and of itself, does not guarantee that RPA will obtain. The three examples considered in the previous round of review also contained \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) but did not exhibit RPA. Note that the Shinar- Feinberg theorem presupposes that the system admits a positive steady- state; it does not, in and of itself, provide any method for checking that this will indeed be the case. Note also that for the cases previously considered in which \(x_{2}x_{3}\) was a boundary variable, it was possible (in principle) for the generating RPA polynomial (referenced in our Theorem 1) to take the form \(c_1x_2x_3 - c_2x_1x_2x_3\) , since this is a two- variable polynomial in that case. (But again, since \(I_f \cap \mathbb{R}[x_1, x_2x_3] = < x_2x_3>\) for those examples, the CRNs could not actually exhibit RPA.) Here, where there are no boundary variables, it is not possible for the (generating) RPA polynomial to take the form \(\frac{dx_1}{dt} = c_1x_2x_3 - c_2x_1x_2x_3\) since this contains three variables. An RPA polynomial contains (at most) two variables. + +<|ref|>text<|/ref|><|det|>[[178, 384, 880, 595]]<|/det|> +The reason this particular CRN has a deficiency of one is that a linear combination of the reactions involving \(c_2, c_3, c_4\) (in the second linkage class only) produces \(X_1 \to \emptyset\) , whereas a linear combination of the reactions involving \(c_1, c_3, c_4\) (involving the first linkage class, and thus involving the new pair of complexes \(X_2 + X_3\) and \(X_1\) ) produces \(\emptyset \to X_1\) . Thus, \(X_2\) and \(X_3\) regulate both the production and the degradation of \(X_1\) . This makes the CRN a balancer module, where \(X_2\) and \(X_3\) play the role of diverter species. Note that although the reaction involving \(c_5\) could be used in place of the reaction involving \(c_3\) in the argument above, these two reactions involve the same complexes (\(\emptyset\) and \(X_1\) ), so the 'redundancy' in the reactions does not result in an increase in deficiency (nor any distinct new cycles or feedforward actions). The same holds for using the reaction involving \(c_6\) in place of the reaction involving \(c_4\) . + +<|ref|>text<|/ref|><|det|>[[118, 609, 864, 644]]<|/det|> +Next I modify this network to have the production of \(X_2\) and \(X_3\) catalysed by \(X_1\) . So the new network becomes + +<|ref|>equation<|/ref|><|det|>[[217, 656, 778, 707]]<|/det|> +\[X_2 + X_3\xrightarrow{c_1}X_1,\quad X_1 + X_2 + X_3\xrightarrow{c_2}\emptyset ,\] \[X_1\xrightarrow{c_3}X_1 + X_2,\quad X_1\xrightarrow{c_4}X_1 + X_3,\quad X_2\xrightarrow{c_5}\emptyset \mathrm{and} X_3\xrightarrow{c_6}\emptyset .\] + +<|ref|>text<|/ref|><|det|>[[118, 718, 753, 737]]<|/det|> +This network also appears to be RPA as shown by the simulations in Figure 2. + +<|ref|>text<|/ref|><|det|>[[178, 750, 875, 821]]<|/det|> +Our response: Yes, this CRN does indeed exhibit RPA because \(< \frac{dx_1}{dt}, \frac{dx_2}{dt}, \frac{dx_3}{dt} > \cap \mathbb{R}[x_1, x_2] = < x_1^2 \left(x_1 - \frac{c_1}{c_2}\right)>\) . Our Singular code and output are provided below for easy verification: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[180, 85, 904, 123]]<|/det|> +Last login: Thu Dec 15 08:32:11 on console /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit (base) araujo@SEF- PA00144783 ~ % /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit SINGULAR + +<|ref|>text<|/ref|><|det|>[[185, 123, 710, 135]]<|/det|> +A Computer Algebra System for Polynomial Computations / Development + +<|ref|>text<|/ref|><|det|>[[180, 137, 710, 149]]<|/det|> +by: W. Decker, G.- M. Greuel, G. Pfister, H. Schoenemann 0< + +<|ref|>text<|/ref|><|det|>[[180, 149, 710, 160]]<|/det|> +FB Mathematik der Universitaet, D- 67653 Kaiserslautern 1 + +<|ref|>text<|/ref|><|det|>[[180, 160, 592, 171]]<|/det|> +> ring R = (0, c1, c2, c3, c4, c5, c6), (x3, x2, x1), lp; + +<|ref|>text<|/ref|><|det|>[[180, 171, 500, 182]]<|/det|> +> poly f1 = c1*x2*x3 - c2*x1*x2*x3; + +<|ref|>text<|/ref|><|det|>[[180, 183, 556, 194]]<|/det|> +> poly f2 = - c1*x2*x3 - c2*x1*x2*x3 + c3*x1 - c5*x2; + +<|ref|>text<|/ref|><|det|>[[180, 194, 556, 205]]<|/det|> +> poly f3 = - c1*x2*x3 - c2*x1*x2*x3 + c4*x1 - c6*x3; + +<|ref|>text<|/ref|><|det|>[[180, 205, 360, 216]]<|/det|> +> ideal I = f1, f2, f3; + +<|ref|>text<|/ref|><|det|>[[180, 216, 360, 227]]<|/det|> +> ideal GI = groebner(I); + +<|ref|>text<|/ref|><|det|>[[180, 228, 220, 238]]<|/det|> +> GI; + +<|ref|>text<|/ref|><|det|>[[180, 239, 460, 249]]<|/det|> +GI[1]=(c2*c3*c4)*x1^3+(- c1*c3*c4)*x1^2 + +<|ref|>text<|/ref|><|det|>[[180, 250, 592, 260]]<|/det|> +GI[2]=(c2*c5)*x2*x1+(- c1*c5)*x2+(- c2*c3)*x1^2+(- c1*c3)*x1 + +<|ref|>text<|/ref|><|det|>[[180, 261, 670, 272]]<|/det|> +GI[3]=(2*c1*c5)*x2^2+(- 2*c1*c3+2*c1*c4)*x2*x1+(- c5*c6)*x2+(- c3*c6)*x1 + +<|ref|>text<|/ref|><|det|>[[180, 272, 420, 283]]<|/det|> +GI[4]=(c6)*x3+(- c5)*x2+(- c3-c4)*x1 + +<|ref|>text<|/ref|><|det|>[[180, 284, 201, 293]]<|/det|> +> + +<|ref|>text<|/ref|><|det|>[[178, 312, 876, 488]]<|/det|> +Once again, this particular CRN does not actually contain (0.2) but a different pair of starting reactions, so its deficiency readily exceeds zero (unlike the three CRNs we considered in the previous round of review). When correctly organized into linkage classes, this CRN has eight complexes, two linkage classes, and a rank of three, giving a deficiency of three. The reason for the two extra units of deficiency in comparison with the previous case is that the reaction \(X_{2} \rightarrow \emptyset\) is replicated using a different set of complexes via the reaction \(X_{1} \rightarrow X_{1} + X_{2}\) (accounting for the first additional unit of deficiency), while the reaction \(X_{3} \rightarrow \emptyset\) is replicated using a different set of complexes via the reaction \(X_{1} \rightarrow X_{1} + X_{3}\) (accounting for the second additional unit of deficiency). + +<|ref|>image<|/ref|><|det|>[[346, 520, 697, 700]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 777, 832, 829]]<|/det|> +Finally, I consider another variant of this network where we have species \(X_{4}\) and \(X_{5}\) that reversibly bind to each other to produce an inactive compound, and they catalyse the production of \(X_{2}\) and \(X_{3}\) respectively. Therefore the new network becomes + +<|ref|>equation<|/ref|><|det|>[[171, 840, 822, 890]]<|/det|> +\[X_{2} + X_{3}\xrightarrow{c_{1}}X_{1} + X_{4},\quad X_{1} + X_{2} + X_{3}\xrightarrow{c_{2}}X_{5},\quad X_{4}\xrightarrow{c_{3}}X_{4} + X_{2},\quad X_{5}\xrightarrow{c_{4}}X_{5} + X_{3}\] \[X_{2}\xrightarrow{c_{5}}\emptyset ,\quad X_{3}\xrightarrow{c_{6}}\emptyset ,\quad X_{4} + X_{5}\xrightarrow{c_{7}}\emptyset \mathrm{and}\quad \emptyset \xrightarrow{c_{8}}X_{4} + X_{5}.\qquad (0.5)\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[120, 83, 741, 101]]<|/det|> +This network also seems to be RPA, as shown in the simulations in Figure 3. + +<|ref|>text<|/ref|><|det|>[[178, 117, 875, 315]]<|/det|> +Our response: Yes, for the same reason as the previous two examples, this CRN does indeed exhibit RPA. This particular CRN does actually employ (0.2), and the reviewer has discovered a clever way to separate the necessary closure reactions into three distinct steps, \(X_{4} \xrightarrow{c_{3}} X_{4} + X_{2}\) , \(X_{5} \xrightarrow{c_{4}} X_{5} + X_{3}\) and \(X_{4} + X_{5} \xrightarrow{c_{7}} \emptyset\) , giving a deficiency of one, which creates the needed parallel routes for the production/degradation of \(X_{1}\) as discussed in the previous two examples. The reactions involving \(c_{5}, c_{6}\) replicate the reactions involving \(c_{3}, c_{4}\) (respectively) using different sets of complexes, thereby increasing the deficiency from one to three. The reaction involving \(c_{8}\) replicates the reaction involving \(c_{7}\) using the same set of complexes, and therefore does not contribute to any further deficiency increases. Our Singular code and output is provided below: + +<|ref|>text<|/ref|><|det|>[[180, 330, 904, 360]]<|/det|> +Last login: Thu Dec 15 12:11:13 on ttys000 /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit (base) araujo@SEF- PA00144783 \\~ % /Applications/Singular.app/Contents/MacOS/../bin/SINGULAR.sh ; exit + +<|ref|>text<|/ref|><|det|>[[180, 360, 900, 380]]<|/det|> +A Computer Algebra System for Polynomial Computations / Development + +<|ref|>text<|/ref|><|det|>[[180, 380, 750, 393]]<|/det|> +A Computer Algebra System for Polynomial Computations / version 4.1.2 + +<|ref|>text<|/ref|><|det|>[[180, 393, 707, 405]]<|/det|> +by: W. Decker, G.- M. Greuel, G. Pfister, H. Schoenemann \ \(Feb 2019\) + +<|ref|>text<|/ref|><|det|>[[180, 404, 636, 415]]<|/det|> +FB Mathematik der Universitaet, D- 67653 Kaiserslautern + +<|ref|>text<|/ref|><|det|>[[180, 415, 707, 427]]<|/det|> +> ring R = (0, c1, c2, c3, c4, c5, c6, c7, c8), (x5, x4, x3, x2, x1), lp; + +<|ref|>text<|/ref|><|det|>[[180, 427, 465, 437]]<|/det|> +> poly f1 = c1*x2*x3 - c2*x1*x2*x3; + +<|ref|>text<|/ref|><|det|>[[180, 437, 555, 448]]<|/det|> +> poly f2 = - c1*x2*x3 - c2*x1*x2*x3 + c3*x4 - c5*x2; + +<|ref|>text<|/ref|><|det|>[[180, 448, 555, 459]]<|/det|> +> poly f3 = - c1*x2*x3 - c2*x1*x2*x3 + c4*x5 - c6*x3; + +<|ref|>text<|/ref|><|det|>[[180, 459, 465, 470]]<|/det|> +> poly f4 = c1*x2*x3 - c7*x4*x5 + c8; + +<|ref|>text<|/ref|><|det|>[[180, 470, 465, 481]]<|/det|> +> poly f5 = c2*x1*x2*x3 - c7*x4*x5 + c8; + +<|ref|>text<|/ref|><|det|>[[180, 481, 400, 492]]<|/det|> +> ideal I = f1, f2, f3, f4, f5; + +<|ref|>text<|/ref|><|det|>[[180, 492, 360, 503]]<|/det|> +> ideal GI = groebner(I); + +<|ref|>text<|/ref|><|det|>[[180, 503, 214, 513]]<|/det|> +> GI; + +<|ref|>text<|/ref|><|det|>[[180, 513, 460, 524]]<|/det|> +GI[1]=(c2*c3*c4*c8)*x1+(-c1*c3*c4*c8) + +<|ref|>text<|/ref|><|det|>[[180, 524, 958, 536]]<|/det|> +GI[2]=(4*c1^2*c7)*x3^2*x2^2+(2*c1*c6*c7)*x3^2*x2+(2*c1*c5*c7)*x3*x2^2+(-c1*c3*c4+c5*c6*c7)*x3*x2+(-c3*c4*c8) + +<|ref|>text<|/ref|><|det|>[[180, 536, 460, 547]]<|/det|> +GI[3]=(c3)*x4+(-2*c1)*x3*x2+(-c5)*x2 + +<|ref|>text<|/ref|><|det|>[[180, 547, 460, 558]]<|/det|> +GI[4]=(c4)*x5+(-c3)*x4+(-c6)*x3+(c5)*x2 + +<|ref|>text<|/ref|><|det|>[[180, 558, 214, 568]]<|/det|> +> + +<|ref|>text<|/ref|><|det|>[[180, 590, 866, 642]]<|/det|> +This CRN has eleven complexes, four linkage classes, a rank of four, and therefore a deficiency of three. Once again, the added deficiency arises from the additional replication of the 'needed' closure reactions employing different sets of complexes. + +<|ref|>image<|/ref|><|det|>[[325, 660, 744, 884]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 870, 152]]<|/det|> +These networks do not appear to satisfy the RPA characterisation given by this paper. Also consider Example 6.5.3 in [5] which does not seem to fit this result either. These counter- examples cast doubt on the correctness of the Kinetic Pairing Theorem on which the entire paper rests. + +<|ref|>text<|/ref|><|det|>[[178, 167, 867, 325]]<|/det|> +Our response: None of these networks constitute counter- examples. All of these networks satisfy the RPA characterization given by our paper. Our Theorem 1 (the 'Two- Variable Kinetic Pairing Theorem') correctly identifies that the three examples suggested here by the reviewer will exhibit RPA at \(x_{1}\) , since a two- variable RPA polynomial generates the principal elimination ideal \(I_{f} \cap \mathbb{R}[x_{1}, x_{j}]\) . In addition, our Theorem 1 correctly identifies that the three similar examples considered in the previous round of review cannot exhibit RPA since the generator of the relevant elimination ideal is not an RPA polynomial (despite the fact that one of the rate equations has the apparent form of an RPA polynomial). + +<|ref|>text<|/ref|><|det|>[[180, 341, 731, 359]]<|/det|> +The reviewer mentions Example 6.5.3 in [5], which is the following: + +<|ref|>text<|/ref|><|det|>[[193, 377, 675, 393]]<|/det|> +Example 6.5.3. Consider the following polynomials in two variables: + +<|ref|>equation<|/ref|><|det|>[[393, 401, 640, 440]]<|/det|> +\[f_{1}(\mathbf{x}) = x_{1}[(x_{1} - 1)^{2} + (x_{2} - 2)^{2}]\] \[f_{2}(\mathbf{x}) = x_{2}[(x_{1} - 1)^{2} + (x_{2} - 2)^{2}].\] + +<|ref|>text<|/ref|><|det|>[[192, 466, 842, 527]]<|/det|> +Notice that these polynomials also have the shape: \(f_{i} = p_{i} - x_{i}q_{i}, i = 1,2\) , where all the coefficients of \(p_{i}, q_{i}\) are non negative. As we mentioned before, it is possible to find a reaction network modeled with mass- action kinetics, such that the associated system is \(dx_{1} / dt = f_{1}, dx_{2} / dt = f_{2}\) . + +<|ref|>text<|/ref|><|det|>[[192, 527, 842, 587]]<|/det|> +It is easy to see in this example that the system shows ACR for both variables, since the only positive solution is \(x_{1} = 1, x_{2} = 2\) . However, we will ignore this obvious fact and use a procedure inspired by our previous discussion. All the computations here can be checked using any computer algebra system, such as Macaulay2 [61] and Singular [35]. + +<|ref|>text<|/ref|><|det|>[[179, 621, 878, 902]]<|/det|> +Although this example claims that 'the system shows ACR for both variables', this system does not describe an RPA- capable (or ACR- capable) CRN since there are no parameters, and no possible 'input' or disturbance, in this model. So there's really nothing for the network to adapt to here. Thus, there is no non- RPA- capable variable; both of the variables appear to exhibit 'RPA', since the system's steady- state is a single fixed point in \(\mathbb{R}^{2}\) (and again, that's not really what RPA is). The special type of RPA known as ACR normally pertains to CRNs where there are mass conservation relationships linking the molecular concentrations, such that the 'total' concentration of a particular type/class of molecule can be varied (by altering the initial conditions of the system, for instance). In any case, in order for a CRN to adapt to any kind of disturbance, there must always be at least one non- RPA- capable variable in the CRN (otherwise how can there possibly be any kind of 'internal model', or any network components that 'offset' the disturbance?) In any case, the definition of RPA adopted in our work (as general as this is!) does not accommodate 'non- adaptive' cases like this where there's simply nothing for the network to adapt to. We must respectfully point out that the author of [5] has been a little hasty in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 84, 860, 120]]<|/det|> +describing this as an ACR- capable network simply because there is a single positive solution \(x_{1} = 1\) , \(x_{2} = 2\) . + +<|ref|>text<|/ref|><|det|>[[178, 136, 878, 510]]<|/det|> +In addition, the author of Example 6.5.3 claims that 'it is possible to find a reaction network modeled with mass- action kinetics, such that the associated system is \(dx_{1} / dt = f_{1}\) , \(dx_{2} / dt = f_{2}\) '. The condition being referred to here \((f_{i} = p_{i} - x_{i}q_{i}\) , with all coefficients of \(p_{i}\) , \(q_{i}\) non- negative) is the so- called Hungarian Lemma, which states (roughly) that for a polynomial dynamical system to be inducible by a CRN under the mass- action assumption, any term in a rate equation preceded by a negative sign must be divisible by the subject of the rate equation. In other words, for the \(dx_{1} / dt\) equation, each term preceded by a negative sign must include \(x_{1}\) as a factor. But the Hungarian Lemma, strictly speaking, pertains to CRNs in which each chemical reaction occurs at a rate (normally noted as a kinetic parameter superposed on the associated reaction arrow), that is independent of the corresponding rates of all other reactions. Because Example 6.5.3 is not suitably parametrized in this sense, there is necessarily an ambiguity introduced in terms of which specific reactions might produce the various terms of the equations. In other words, there is not a one- to- one correspondence between reaction rates and putative CRN structure, as predicted by the Hungarian Lemma under the specified conditions. The rate \(f_{1}\) , for example, contains the term \(- 2x_{1}^{2}\) ; this could in principle arise from either \(2X_{1} \xrightarrow{2} X_{1}\) or from \(2X_{1} \xrightarrow{1} \emptyset\) . From this point of view, we should not really even accept the two given equations as a valid CRN model. In any case, on both counts (not being ACR- capable, and not being a valid CRN model), this Example simply does not constitute any sort of counterexample to the claims of our paper. + +<|ref|>text<|/ref|><|det|>[[179, 526, 878, 668]]<|/det|> +We do very much appreciate the lengths to which the reviewer has gone in order to make absolutely certain that all our claims are \(100\%\) accurate and watertight. But we do hope the reviewer is now willing to accept the correctness of our assertions. Two variables is always the right number of variables for assessing RPA capacity, the mathematical reason for which is given in our proof to Theorem 1. For all RPA- capable CRNs, the geometric projection of their rate equations onto two variables is generated by a single polynomial of the form \(\rho = g(x_{i}, x_{j})(x_{i} - c)\) . Any CRN that does not satisfy this property cannot exhibit RPA - no exceptions, un point c'est tout. + +<|ref|>text<|/ref|><|det|>[[119, 700, 847, 769]]<|/det|> +3. The set-point may not be a rational function of parameters: In many places in the main paper and the supplement, the system's set-point is said to be a rational function of biochemical parameters. While this holds for most examples, consider the following birth death network + +<|ref|>equation<|/ref|><|det|>[[399, 783, 598, 807]]<|/det|> +\[\emptyset \xrightarrow{c_{1}} X_{1} \quad \text{and} \quad 2X_{1} \xrightarrow{c_{1}} \emptyset .\] + +<|ref|>text<|/ref|><|det|>[[119, 821, 330, 838]]<|/det|> +The dynamics is given by + +<|ref|>equation<|/ref|><|det|>[[415, 854, 572, 889]]<|/det|> +\[\frac{dx_{1}}{dt} = c_{1} - 2c_{2}x_{1}^{2}\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 280, 100]]<|/det|> +and so the set- point + +<|ref|>equation<|/ref|><|det|>[[451, 100, 540, 152]]<|/det|> +\[c = \sqrt{\frac{c_1}{2c_2}}\] + +<|ref|>text<|/ref|><|det|>[[118, 152, 820, 187]]<|/det|> +is not a rational function of \(c_1\) and \(c_2\) ? For more examples, see Examples 2.11 and 2.12 in [3]. Please revise as necessary. + +<|ref|>text<|/ref|><|det|>[[178, 201, 877, 411]]<|/det|> +Our response: We sincerely thank the reviewer once again for such a meticulous review of our work and for such careful attention to every possible technical detail. In this particular case, \(x_1^2\) is a boundary variable since \(x_1\) only appears in the CRN rate equations in the form of the monomial \(x_1^2\) . Therefore, the setpoint for this variable is \(c_1 / 2c_2\) , which is a rational function of parameters, as expected. With boundary variables accounted for in this way, we can be assured that the setpoint of any RPA- capable variable will be a rational function of parameters, since we are working with a commutative ring structure (multivariate polynomials) with coefficients taken over a field (real numbers, with all coefficients considered symbolically). We allow only addition and additive inverses (subtraction) and multiplication without inverses (i.e. no division) of the ring elements; the coefficients admit addition/subtraction as well as multiplication/division (due to the field structure). No radicals may be taken. + +<|ref|>text<|/ref|><|det|>[[179, 428, 870, 515]]<|/det|> +But we do completely appreciate the reviewer's point, and that the boundary variable technicality might be lost on some readers (despite the fact that we do highlight the concept quite prominently). The setpoint of the species concentration may indeed be an algebraic (rather than a rational) function of parameters in these special cases. + +<|ref|>text<|/ref|><|det|>[[179, 531, 874, 620]]<|/det|> +Examples 2.11 and 2.12 in [3] also contain a species setpoint that is an \(n\) - th root of a rational function of parameters simply because the species in question contributes to an RPA- capable boundary variable in each case. In Example 2.11 - a continuation of Example \(2.3 - x_{A}\) appears only in the form \(x_{A}^{n}\) . Likewise, in Example 2.12 - a continuation of Example \(2.8 - x_{B}\) appears only in the form \(x_{B}^{n}\) . + +<|ref|>text<|/ref|><|det|>[[179, 635, 853, 689]]<|/det|> +We now add the following clarification of this matter to Remark 3 after the statement and proof to Theorem 1 (immediately following Definition 3, in Section S1.5 in our SI): + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[186, 88, 840, 156]]<|/det|> +3. If the setpoint, \(c\) , depends only on biochemical rate constants and not on total concentrations \((X_{k t o t})\) or production/degradation rates of any of the molecules, the system also has the capacity for ACR in the variable \(x_{i}\) . + +<|ref|>text<|/ref|><|det|>[[207, 168, 841, 340]]<|/det|> +Moreover, although we note in the statement and proof of Theorem 1 that \(c\) is a rational function of biochemical parameters, in the special case of an RPA variable that is a boundary variable, the setpoint of the corresponding RPA species may be an algebraic, rather than a rational, function of parameters. Consider, for instance, the one- species system: \(\frac{d x}{d t} = c_{1} - 2c_{2}x^{2}\) ; here \(x\) appears only in the form of the monomial \(x^{2}\) , which is therefore a boundary variable. The 'setpoint' for the boundary variable, \(x^{2}\) , is thus \(\frac{c_{1}}{2c_{2}} - a\) rational function of parameters - while the setpoint for the species \(x\) is \(\sqrt{\frac{c_{1}}{2c_{2}}}\) . + +<|ref|>text<|/ref|><|det|>[[179, 366, 844, 418]]<|/det|> +We now also refer to this Remark in the main paper (at the end of the paragraph immediately following Eq. 6), where it is noted that \(c\) is a rational function of parameters. + +<|ref|>text<|/ref|><|det|>[[118, 450, 877, 486]]<|/det|> +4. Questions on the Buchberger's Algorithm: In the previous review round, I had raised the following issue regarding Buchberger's Algorithm + +<|ref|>text<|/ref|><|det|>[[118, 499, 872, 568]]<|/det|> +The Gröbner basis algorithm to find the RPA polynomial may not terminate. It is mentioned that failure to terminate for a chemical reaction network (CRN) is a prima- facie evidence that the CRN does not exhibit RPA. However this is not mathematically shown. In any case, checking for nontermination of a method is impractical. + +<|ref|>text<|/ref|><|det|>[[118, 597, 878, 700]]<|/det|> +In response the authors state in their rebuttal letter that the termination is guaranteed because "all ideals of a polynomial ring (or any Noetherian ring, for that matter) are finitely generated - a result of central importance in algebraic geometry, formalized by the Hilbert Basis Theorem". While I agree that termination is guaranteed, I must point out that the reason for my confusion and for raising this termination issue is the following excerpt from the previous version of the Supplement (submitted in round 1): + +<|ref|>text<|/ref|><|det|>[[118, 713, 870, 765]]<|/det|> +Failure of the Buchberger (or other Gröbner basis- computing) algorithm to terminate could thus be adduced as prima facie evidence that the CRN under consideration does not, in fact, have the capacity for RPA. + +<|ref|>text<|/ref|><|det|>[[118, 779, 876, 847]]<|/det|> +It seems that in this statement that authors meant "terminate in practical time". I understand that due to the "almost linear" nature of coordinate change, this algorithm would work well for RPA networks. However, does the final RPA polynomial produced by the method depend on the monomial ordering or other choices made by the method? + +<|ref|>text<|/ref|><|det|>[[178, 861, 866, 914]]<|/det|> +Our response: No, whether or not the elimination ideal referenced in our Theorem 1 is generated by an RPA polynomial is completely unrelated to the choice of monomial ordering. The form of the 'final RPA polynomial' is also unrelated to the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 878, 260]]<|/det|> +choice of monomial ordering: it is the generator of a principal ideal. But it's important to bear in mind that only monomial orderings that can achieve the desired elimination are suitable for testing this property (i.e. an elimination ordering). One cannot apply some completely arbitrary monomial ordering and expect to obtain (any) elimination ideal. We do refer to the highly accessible text by Cox et al. [7] in both our main text and in our SI for the benefit of any reader who wants to understand these technicalities fully. More importantly, we provide sample code at the end of our SI, with a discussion of a particularly efficient elimination ordering (using command '\((dp(n - 2), dp(2))\) ' - see Section S5.1), should this be required for large and complicated CRNs. + +<|ref|>text<|/ref|><|det|>[[179, 277, 877, 362]]<|/det|> +Note that the reviewer's quotation from our original submission ('Failure of the Buchberger (or other Gröbner basis- computing) algorithm to terminate could thus be adduced as prima facie evidence that the CRN under consideration does not, in fact, have the capacity for RPA.') was removed from our revised submission, and is no longer included in our SI. + +<|ref|>text<|/ref|><|det|>[[119, 393, 876, 461]]<|/det|> +More importantly, if a network is not RPA, how many steps would the method need to confirm this non- RPA property? Such practical considerations must be discussed in the main text, and they are crucial for applying these ideas for characterising RPA in high- dimensional networks. + +<|ref|>text<|/ref|><|det|>[[179, 477, 875, 581]]<|/det|> +Our response: Of course there is no possible way to be specific about the number of steps that would be required to confirm the inability of some general (non- RPA- capable) CRN to exhibit RPA. If the algorithm is being applied completely mindlessly to a large and complicated CRN, with a random choice of two variables, then we quite agree that if the algorithm seems to be taking an inordinately long time to terminate, then the RPA- capacity or otherwise of the CRN is entirely unclear. + +<|ref|>text<|/ref|><|det|>[[179, 599, 875, 842]]<|/det|> +Now, the algorithm we present can be applied mindlessly, without any real understanding of the mathematical principles we discuss at length in our paper, and if the CRN under consideration is indeed RPA- capable, then such a completely mindless approach will be able to provide a confirmation of RPA capacity, along with an explicit identification of the setpoint. If the sole contribution of our paper were the development of an algorithmic test for RPA capacity, the reviewer would be quite correct to point out that this algorithm cannot easily distinguish between non- RPA- capable CRNs, and extremely large and complicated RPA- capable CRNs that could require a significant (and indeterminate) time- frame for the execution of the algorithm. But it's important to recognize that if the algorithm seems to be taking a long time to terminate, then our paper presents analytical approaches to check whether the CRN at hand has any potential for RPA capacity through a decomposition into independent subnetworks (wherever possible), and an analysis of deficiency in these subnetworks. + +<|ref|>text<|/ref|><|det|>[[180, 860, 875, 911]]<|/det|> +As an example, consider the CRN for the mammalian enzyme 6- phosphofructo- 2- kinase/fructose- 2,6- bisphosphatase (PFK- 2/FBPase- 2), which operates bifunctionally to both activate and inactivate fructose- 2,6- bisphosphate (F2,6BP), as discussed by + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 84, 863, 156]]<|/det|> +Karp et al. [6] in terms of the potential RPA- capacity of F2,6BP. As we will show, this CRN cannot exhibit RPA. The CRN (presented in [6]), organized into its linkage classes, with \(X_{1} \equiv E\) , \(X_{2} \equiv E\) - ATP, \(X_{3} \equiv F6P\) , \(X_{4} \equiv E\) - ATP- F6P, \(X_{5} \equiv F2,6BP\) , \(X_{6} \equiv E\) - F2,6BP, \(X_{7} \equiv E\) - ATP- F2,6BP, and \(X_{8} \equiv E\) - ATP- F6P- F2,6BP, is given by + +<|ref|>image<|/ref|><|det|>[[270, 167, 785, 440]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[178, 482, 877, 707]]<|/det|> +Interestingly, Karp et al. [6] claim that the Gröbner basis implementation in Mathematica does not terminate for this CRN, although they give no information as to how they've ordered their variables, or which monomial ordering they chose (although they almost certainly would have used a lexicographic monomial ordering since, prior to our work, it was not known that an elimination ideal involving just two variables is all that's required to test RPA capacity; the lexicographic ordering is generally an extremely computationally expensive elimination ordering since it produces a full complement of elimination ideals, in vast excess of what's actually required to solve the RPA problem). We used Singular and used an efficient block monomial ordering (to project onto two variables) that allowed the algorithm to terminate in several seconds, from which we could confirm that this particular CRN is not RPA- capable (at \(X_{5} \equiv F2,6BP\) or otherwise). We provide our Singular code below: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 880, 416]]<|/det|> +way of general advice to the reader, if one allows the algorithm to run for several hours (e.g. overnight) using the most efficient implementation possible (as described above) and it still hasn't terminated after this period, then one should consider undertaking some additional analysis of the CRN (as we provide below) through (i) first decomposing into algebraically- independent subnetworks (if possible), and then (ii) considering where deficiency arises within these independent subnetworks, and whether the deficiency corresponds to the presence of parallel pathways and/or feedback cycles, as required for RPA. Consider also that one should have a reason to suspect that a CRN exhibits RPA. It is clear from the detailed principles we develop here, as well as our previous topological analysis of RPA- capable network architectures at the network macroscale [12], that RPA- capable networks are actually very 'special', with very specific structural requirements, and are therefore extremely rare in the space of all possible networks. If one has a completely arbitrary network, with no particular reason to suspect it might be able to exhibit this special type of robustness, then it almost certainly doesn't. In the specific case we analyse here, the CRN involves a bifunctional enzyme \((X_{1})\) which both upregulates and downregulates its target protein \((X_{5})\) ; a priori, this fact presents the possibility that this CRN might have the capacity for RPA (even if, in the final analysis, it actually doesn't). + +<|ref|>text<|/ref|><|det|>[[178, 433, 876, 728]]<|/det|> +Now, recall that deficiency is a measure of the linear independence of the reactions of a CRN, relative to their distribution into the connected components (linkage classes) of a graph. In particular, the deficiency of a CRN is increased by one for every instance of a reaction being 'replicated' elsewhere in the network via a different set of complexes. Reversible reactions, for example, which duplicate a single reaction using the same pair of complexes, do not of themselves contribute to any deficiency increases. Recall also that, for an RPA- capable CRN, these replicated reactions must constitute either (i) a collection of parallel pathways, where the production/degradation (or interconversion between activation states) of the RPA- molecule must be orchestrated via different collections of reactions (involving different sets of complexes), or (ii) a cycle in the production/degradation (or interconversion between activation states) of a non- RPA- molecule (as regulated by the RPA- capable molecule), where the individual components of the cycle must be orchestrated via different collections of reactions (involving different sets of complexes). There's simply no other way for the right linear invariants to emerge! We highlight and discuss these principles repeatedly throughout the analysis of the worked examples in our SI. + +<|ref|>text<|/ref|><|det|>[[179, 746, 875, 903]]<|/det|> +Returning now to the non- RPA- capable CRN at hand: Note that the CRN for PFK- 2/FBPhase- 2 has a deficiency of 5, comprising 14 complexes, 3 linkage classes and a rank of 6. By noting which reactions are 'replicated' (using different sets of complexes) to yield each of these 5 units of deficiency, it is straightforward to see that this CRN does not have the right structure to impose RPA on \(X_{5}\) (or any other molecule). First, we note that the eight species of the model are all intricately interconnected in the nineteen reactions of the CRN, such that no decomposition into independent subsets is possible (see discussion of this point in S1.3 of our Supplementary Information). Moreover, in assessing the linear independence of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[240, 85, 876, 137]]<|/det|> +require a long (and potentially indeterminate) timeframe for the algorithm to terminate. We provide a fully analysed example of a non- RPA- capable CRN, to illustrate these principles, in SI Section S4.5. + +<|ref|>text<|/ref|><|det|>[[179, 155, 866, 224]]<|/det|> +We have also added in an entire new subsection to our SI (Section S4.5), entitled 'A note on non- RPA- capable CRNs and computational challenges', in which we summarise the commentary given above, and provide a full analysis of the PFK- 2/FBPase- 2 CRN (from Karp et al. [6]) as presented above. + +<|ref|>text<|/ref|><|det|>[[120, 259, 842, 308]]<|/det|> +5. Connection of examples to existing works: The authors start the Results section with "two simple examples that have eluded all previous systematic methods to detect RPA". Please specify which systematic methods are being referred to here. + +<|ref|>text<|/ref|><|det|>[[178, 325, 878, 725]]<|/det|> +Our response: We now add in a number of key references at this point in our text to highlight which systematic methods are being referred to. In particular, the Shinar- Feinberg theorem provides a systematic way to determine ACR for deficiency- one networks containing two complexes that differ in a single species, but is silent on all CRNs with deficiency greater than one (and also cannot detect ACR in deficiency- one CRNs that do not contain two complexes that differ in a single species, such as the CRN we consider in Figure 8a in our paper). Cappelletti et al. provide a systematic method for detecting RPA, and a (single linear) integral controller, but is only applicable if an RPA polynomial is contained in the rowspan of the system. Even exceedingly simple CRNs (like the one we consider as Example 1 in our S3.1 of our SI, or the even simpler version we consider in Figure 8a of the main paper) elude this method if there is no RPA polynomial in the system's rowspan. Eloundou- Mbebi et al. [13] present a necessary condition for RPA in CRNs of any deficiency, and thereby provide a systematic test that is generally able to identify some CRN species that certainly cannot exhibit RPA (which can thereby be excluded from further analysis). But this method is silent on whether any species that is not excluded by this test actually does exhibit RPA. In fact, all nine species in the deficiency- two Shinar- Feinberg EnvZ- OmpR model (considered in Figure 3 in our paper) satisfy the necessary condition proposed by Eloundou- Mbebi et al. [13], even though only one of these (pOmpR) actually does exhibit RPA. Gupta and Khammash [2] provide a universal characterization of maxRPA networks, but this approach is not applicable to any RPA- capable CRN that does not exhibit maxRPA. We discuss the universality of our approach in comparison with previous work in our Discussion section. + +<|ref|>text<|/ref|><|det|>[[179, 742, 880, 898]]<|/det|> +Of course, there are many other approaches to the analysis of CRNs, but none of these are 'systematic' approaches to the study of RPA (or ACR) in the sense that they can be applied to any CRN (of any deficiency, whether there is an RPA in the rowspan or not), without the need for guesses, or prior insight, and provide definitive information on the capacity for RPA and on the mechanisms for implementing it. The method for identifying 'complex linear invariants' developed by Karp et al. [6] can detect RPA in the deficiency- two Shinar- Feinberg EnvZ- OmpR model, but this is not a systematic method for RPA detection since those authors had to "guess" which complexes would end up in the invariants we identify via our + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 85, 880, 556]]<|/det|> +systematic approach. In fact, those authors state in Section 2.6 of their paper, referring to the above- noted example, in addition to another example they considered: 'The two examples discussed above had already been analysed by other methods, so we had an idea of which invariants to expect and which subset of complexes to consider. For a new network such information may not be available, so how can non- trivial type 1 complex- linear invariants (simply, "invariants") be found? The automatic procedure outlined in Section 2.2 can be used in principle but this becomes computationally infeasible when there are many complexes. We have found the following systematic procedure to be helpful on several examples'. The authors go on to provide some practical suggestions to the reader on computing useful 'complex linear invariants', which do not constitute a truly systematic procedure for rigorous application to general CRNs. Moreover, the 'automatic procedure outlined in Section 2.2' mentioned by these authors refers to computing a Gröbner basis for the system. But again, those authors did not account for algebro- geometric properties of RPA- capable CRNs that we identify in our paper, including the requirement for projection onto two variables only; thus, as a consequence, this systematic computation is now more widely applicable to CRNs (for the determination of RPA capacity, at least) than previously considered (where a lexicographic monomial ordering was necessary, producing a full collection of elimination ideals, since it was not previously recognized that only a specific elimination ideal is actually required to detect RPA). We emphasize again here the fact that these authors attempted to compute a Gröbner basis for a CRN involving the mammalian bifunctional enzyme PFK- 2/FBPase- 2, and found that their algorithm did not terminate; by contrast, by exploiting the use of a highly efficient elimination ordering (a consequence of our Theorem 1), we were able to compute a suitable Gröbner basis in under three minutes and thereby confirm that the CRN in question cannot exhibit RPA. + +<|ref|>text<|/ref|><|det|>[[119, 589, 844, 624]]<|/det|> +Also, in the example on Figure 2 it should be mentioned that \(X_{3}\) is maxRPA and it can be checked from the characterisation result in [2]. Secondly since there is the reaction + +<|ref|>equation<|/ref|><|det|>[[430, 639, 558, 666]]<|/det|> +\[X_{3} + X_{2}\xrightarrow{k_{6}}X_{2}\] + +<|ref|>text<|/ref|><|det|>[[119, 664, 797, 696]]<|/det|> +which does not involve \(X_{1}\) I do not understand why the term \(k_{6}X_{2}X_{3}\) does not enter the expression for + +<|ref|>equation<|/ref|><|det|>[[444, 695, 546, 731]]<|/det|> +\[\frac{d(X_1 - X_2)}{dt}\] + +<|ref|>text<|/ref|><|det|>[[119, 745, 342, 761]]<|/det|> +in Figure 2C. Please check. + +<|ref|>text<|/ref|><|det|>[[178, 778, 880, 900]]<|/det|> +Our response: We analyze the example in Figure 2 in careful detail in our Supplementary Information, where we provide a full discussion – first in Section S1.6 where we undertake a full algebro- geometric analysis to illustrate the consequences of Theorem 1 (the two- variable kinetic pairing theorem), then again in Section S4.4.2 where we show that the CRN's set of eight reactions can be partitioned into two algebraically- independent subnetworks, and describe how various polynomial invariants may be determined within these subsets using an analysis of deficiency. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 878, 155]]<|/det|> +We also provide a complete Singular code for this example in Section S5.2, where we consider several different two- variable projections, and also show how the single concatenating monomial for this CRN can be computed automatically using the lift command in Singular. + +<|ref|>text<|/ref|><|det|>[[179, 172, 860, 225]]<|/det|> +As indicated in our Singular code (SI Section S5.2), the CRN depicted in Figure 2 of our paper (and analysed from a number of different viewpoints throughout our SI) induces the following set of four reaction equations under the law of mass- action: + +<|ref|>equation<|/ref|><|det|>[[177, 240, 435, 370]]<|/det|> +\[\frac{dX_1}{dt} = k_1R - k_2X_1X_2,\] \[\frac{dX_2}{dt} = k_3 - k_2X_1X_2 + k_4X_3,\] \[\frac{dX_3}{dt} = k_5 - k_6X_2X_3 - k_7O_1X_3,\] \[\frac{dO_1}{dt} = k_7O_1X_3 - k_8O_1.\] + +<|ref|>text<|/ref|><|det|>[[179, 392, 379, 408]]<|/det|> +From this it follows that + +<|ref|>equation<|/ref|><|det|>[[379, 406, 665, 442]]<|/det|> +\[\frac{d}{dt} (X_1 - X_2) = k_1R - k_3 - k_4X_3\] + +<|ref|>text<|/ref|><|det|>[[179, 458, 863, 546]]<|/det|> +We are unsure on the basis of the reviewer's comment why he/she feels the term \(k_6X_2X_3\) should be present in the expression for \(d(X_1 - X_2) / dt\) . We have carefully checked this example (and all other examples in our paper) and can assure the reviewer that these reaction forms, and the expression for \(d(X_1 - X_2) / dt\) in particular, are all completely correct. + +<|ref|>text<|/ref|><|det|>[[178, 562, 875, 790]]<|/det|> +On the matter of \(X_3\) being maxRPA, although this is certainly true, this is not quite the point of Figure 2, which is attempting to provide a representation of the general properties of all CRNs that act on Opposer Module (which could contain any number of opposer 'nodes', in principle, organized into an opposing set structure). For this simple example, a two- node opposing set is shown, where the two opposer nodes are as simple as possible (hence the distal opposer is indeed maxRPA). Since \(X_3\) and \(X_2\) regulate each other (and thereby form a feedback loop), and since \(X_2\) contributes to a different opposer node (regulated by \(R\) , upon which RPA is ultimately conferred), one cannot generally consider the reactions involving \(O_1\) and \(X_3\) in isolation before ensuring that the CRN as a whole has been correctly decomposed into algebraically independent subnetworks. We undertake this analysis carefully in Section S4.4.2. As shown, this allows us to determine the correct algebraic invariant (involving \(O_1\) and \(X_3\) ) to be 'passed' to the other opposer node (involving \(R\) ). + +<|ref|>text<|/ref|><|det|>[[118, 821, 860, 907]]<|/det|> +If the term \(k_6X_2X_3\) is present then it cannot be eliminated with the concatenating monomial \(O_1\) . On the other hand, if this reaction is removed (i.e. this term is absent) then the overall network simply becomes a trivial RPA network where the output of one RPA network (i.e. the network comprising \(X_3 - O_1\) ) is passed as an input to another RPA network (i.e. the antithetic network with \(X_1 - X_2\) ). It is straightforward that connecting RPA networks in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 857, 119]]<|/det|> +series (with catalytic reactions) would still result in a RPA network. Such examples are not appropriate for demonstrating the novel results in this paper. + +<|ref|>text<|/ref|><|det|>[[179, 134, 850, 204]]<|/det|> +Our response: We offer several additional points of clarification regarding the reaction occurring at rate \(k_6\) , which contributes the term \(k_6 X_2 X_3\) to the rate equations, and the absolute necessity of including this reaction in order to confer RPA on the CRN (including the entire 'embedded network'). + +<|ref|>text<|/ref|><|det|>[[179, 221, 880, 344]]<|/det|> +First, regarding the elimination of \(k_6 X_2 X_3\) , and the identity of the requisite concatenating monomial, we'd like to point out that the four mass- action equations corresponding to this CRN (noted above in our previous comment) can be analysed systematically in Singular, from which the concatenating monomial can be computed automatically. This is explained in detail, including the use of the Singular command lift (which is used to identify the concatenating monomial) in our analysis of the Singular code at the end of Section S5.2. + +<|ref|>text<|/ref|><|det|>[[179, 360, 883, 894]]<|/det|> +Second, we cannot remove the reaction \(X_3 + X_2 \xrightarrow{k_6} X_2\) as it is necessary for RPA in the "full" (i.e. embedded) network if the molecule \(O_1\) is responsible for regulating the embedded network, as indicated in Figure 2(a,d) The reviewer points out that "if this reaction is removed ... then the overall network simply becomes a trivial RPA network where the output of one RPA network (i.e. the network comprising \(X_3 - O_1\) ) is passed as an input to another RPA network (i.e. the antithetic network with \(X_1 - X_2\) ). It is straightforward that connecting RPA networks in series (with catalytic reactions) would still result in an RPA network." This is not actually true if \(O_1\) is responsible for regulating the embedded network, as we will explain below. But if, instead, \(X_2\) is responsible for regulating the embedded network, then the reviewer is entirely correct. In this latter case, and with the reaction \(X_3 + X_2 \xrightarrow{k_6} X_2\) removed, the reactions involving \(O_1\) and \(X_3\) are completely isolated from any disturbances to the embedded network (i.e. there is no 'signal detection' in these reactions), and can therefore be considered at their steady- state \((X_3 = k_8 / k_7, O_1 = k_5 / k_8)\) . The controller mechanism thereby reduces to the well- known antithetic- integral controller structure, with \(d(X_1 - X_2) / dt = k_1 R - k_{\alpha}\) , where \(k_{\alpha} = k_3 + k_4 k_8 / k_7\) . This constitutes a single opposer node, obtained via a single linear coordinate change. Nevertheless, it is clear that much more complicated opposer mechanisms could arise, and that a single opposer node is insufficient to characterize the space of all possible Opposer modules orchestrated by CRNs. Note also that the molecule \(O_1\) has a fixed concentration \((k_5 / k_8)\) in the scenario just considered; thus, if \(O_1\) were to regulate the embedded network (rather than \(X_2\) ), then RPA would not be possible at \(R\) since the antithetic controller would no longer be able to regulate the embedded network via a feedback loop. It's important to recognize that what we are actually analyzing in Figure 2 is just the controller part of the overall network. Considered in isolation, with \(R\) (the 'sensor' molecule from the 'embedded network') as the input, the network will not actually exhibit RPA at \(R\) unless the CRN is embedded into the requisite feedback structure, as indicated in Figure 2(a,d). (We do discuss the distinction between being RPA capable and exhibiting RPA in SI Section S1.5 - see Definition 3). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 877, 120]]<|/det|> +We make it clear in the main text that we consider \(X_{3}\) to be a network protein, which can therefore be affected in some way by disturbances to the embedded network. + +<|ref|>text<|/ref|><|det|>[[178, 123, 878, 389]]<|/det|> +This is possible due to the inclusion of the reaction \(X_{3} + X_{2} \xrightarrow{k_{6}} X_{2}\) , whereby the molecule \(X_{2}\) downregulates the molecule \(X_{3}\) ; this reaction permits a controller structure in which (in contrast to the scenario considered above) \(O_{1}\) is not RPA- capable, (unlike \(X_{3}\) , which is RPA- capable either way) and is thereby able to provide the necessary 'actuation' to the embedded network. The resulting CRN architecture, corresponds to what we previously described [12] as a two- node opposing set. The architecture of an opposing set consists of a collection of interlinked feedback loops, embedded into the feedback portion of an overarching feedback loop into which the 'controlled' system is embedded. Our current paper now makes clear why the interlinking of feedback loops is required in opposing sets (which was not entirely clear from our prior topological analysis [12]): signal transfer from the 'distal' opposer to the 'proximal' opposer (see Figure S12 in our Supplementary Information) is required for the passing of invariants, using concatenating monomials as needed; signal transfer from the proximal opposer to the distal opposer is necessary to embed these interactions in a feedback loop. + +<|ref|>text<|/ref|><|det|>[[119, 435, 870, 520]]<|/det|> +The second example in Figure 3 seems to be taken straight from [4] (see Fig. 2). This should be clearly stated when the example is being introduced in the main text and also in the caption of Figure 3. Also mention that the linear invariants shown in Fig. 3 can be deduced from the approach in [4] (this is stated in passing in the conclusion but it should be stated more prominently when the example is being discussed.) + +<|ref|>text<|/ref|><|det|>[[178, 535, 878, 830]]<|/det|> +Our response: No, we most assuredly did not just take our example in Figure 3 straight from [4]. This example was considered by Shinar and Feinberg in the Supplementary Materials to their seminal paper in Science [10], and we refer to this fact in- text in our discussion of Figure 3. We now add in an additional reference to this fact in our caption to the Figure, to ensure that this is absolutely clear. Perez- Millan et al. [4] also discuss the fact that this example is taken from the SM of Shinar and Feinberg's paper. We are wondering if the reviewer might actually mean Karp et al. [6] here? In any case, Karp et al. [6] also take the example from the SM of Shinar and Feinberg's paper, and those authors also make it clear that the Shinar- Feinberg paper is the source of the example. This deficiency- two model of the EnvZ- OmpR motif (due to Shinar/Feinberg) has been extensively discussed in the literature (including by [4] and [6], who have also analysed this model using different theoretical viewpoints from the one we consider here). Neither of those prior viewpoints provides a clear and definitive way to connect the properties of this particular example to the properties of all possible RPA- capable CRNs, however. More generally, it has been a subject of tremendous interest to discover robust and systematic ways to handle ACR/RPA in CRNs of deficiency greater than one. + +<|ref|>text<|/ref|><|det|>[[180, 848, 880, 900]]<|/det|> +We're not quite so sure that the two linear invariants can be deduced straightforwardly from the approach in [4]. The connector invariant actually involves three terms, not two, so cannot arise from the theory of toric ideals. Again, we + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[178, 85, 879, 328]]<|/det|> +suspect the reviewer might be referring to the approach by Karp et al. [6]. While it is certainly true that Karp et al. [6] were able to identify the linear invariants relevant to Figure 3, this was only possible once it was clear which complexes/monomials are involved in these invariants (on the basis of the solution originally obtained by Shinar and Feinberg [10] through manual substitution, and possibly also through the analysis of the CRN undertaken by [4], since both papers [4] and [6] have authors in common). But more importantly, it is entirely unclear from the invariants computed by Karp et al. [6] how this solution relates to the complete solution space of all RPA- capable CRNs! This is the fundamental idea we are attempting to communicate through these simple examples in Figures 2 and 3. And again, we stand by our claim that prior to our work, there has been no systematic way (not involving 'guesses' or Ansätze, or prior analysis via other methods) to analyse general CRNs, of arbitrary deficiency, for which an RPA polynomial is not contained in the rowspan of the system. + +<|ref|>text<|/ref|><|det|>[[119, 377, 872, 429]]<|/det|> +6. Many claims without proofs in the Supplement: The Supplement has been considerably revised, but still many arguments are unclear because proper proofs have not been provided or referenced: + +<|ref|>text<|/ref|><|det|>[[120, 444, 870, 479]]<|/det|> +- Why should eq. (8) hold when eq. (9) holds? Can the networks always be partitioned this way? Please explain. + +<|ref|>text<|/ref|><|det|>[[178, 494, 880, 686]]<|/det|> +Our response: We have scrutinized our exposition in Section S1.3 of our SI, and agree with the reviewer that Eq. (8) is not guaranteed to hold when Eq. (9) holds. Unlike the rest of the material in this section, this specific detail was not actually part of Martin Feinberg's treatment in Appendix 6.A of his text. We have now removed this detail from our SI, as it does not follow from the preceding results. In many of the examples we analyse in our paper, the deficiency does partition into the same subsets obtained from a partition of CRN rank; but this might not obtain in general. We have carefully worked through our entire manuscript and SI to ensure that our discussion of deficiency is accurate throughout (and does not make use of what was formerly Eq. (8)). We do thank the reviewer once again for such a meticulous review of every technical detail in our paper. + +<|ref|>text<|/ref|><|det|>[[149, 772, 533, 789]]<|/det|> +- On page 21 in the Supplement it states that: + +<|ref|>text<|/ref|><|det|>[[179, 805, 848, 858]]<|/det|> +Since a perturbation to the CRN that alters the steady state of \(x_{j}\) will also alter the steady- states of other non- RPA capable variables (eg. \(x_{m}\) ), If \(\mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) , and that are not contained in \(I_{f} \cap I_{p}\) . + +<|ref|>text<|/ref|><|det|>[[179, 875, 553, 892]]<|/det|> +Why should such a perturbation always exist? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 877, 190]]<|/det|> +Our response: When we say perturbation here, we are simply referring to a disturbance that the CRN is able to 'reject', thereby exhibiting RPA in one or more variables. It's really only meaningful to talk about RPA in the context of a CRN subjected to some sort of disturbance which alters the steady- state of the system. If the CRN is not subjected to any disturbance at all, the CRN can only exhibit a 'trivial' form of RPA (since nothing in the network can ever change). + +<|ref|>text<|/ref|><|det|>[[179, 208, 864, 293]]<|/det|> +If the reviewer is querying why there should always be at least one variable that is non- RPA- capable, then we emphasize again that this is a key component of RPA. If all variables in the network are 'fixed' at steady- state, and can never be altered by any disturbance, then the network is not able to adapt to disturbances (and there can be no 'internal model', which recapitulates the disturbance). + +<|ref|>text<|/ref|><|det|>[[179, 311, 872, 398]]<|/det|> +Of course, special cases of CRNs could exist with only one non- RPA- capable variable, rather than two or more, in which case the statement above vacuously holds (ex falso quodlibet). In any event, the selection of variables taken for the projection consists of one non- RPA- capable variable, in addition to the putative RPA- capable variable. + +<|ref|>text<|/ref|><|det|>[[150, 432, 558, 450]]<|/det|> +- Also on page 21 in the Supplement it says that + +<|ref|>text<|/ref|><|det|>[[179, 465, 853, 515]]<|/det|> +The set \(\bar{x}\) now contains two independent (uncoupled) variables in the sense that a perturbation to the CRN that alters the steady- state of one of the variables does not affect the steady- state of the other. + +<|ref|>text<|/ref|><|det|>[[180, 531, 486, 548]]<|/det|> +Why does this hold? Please elaborate. + +<|ref|>text<|/ref|><|det|>[[179, 564, 873, 650]]<|/det|> +Our response: Here we are referring to the fact that \(\bar{x}\) now contains two variables - one RPA- capable and one non- RPA- capable. The two variables are ipso facto uncoupled since a disturbance to the system that alters the steady- state of the non- RPA- variable necessarily has no effect on the steady- state of the RPA- variable (whose setpoint is independent of the disturbance). + +<|ref|>text<|/ref|><|det|>[[150, 668, 877, 769]]<|/det|> +- In general, in the proof of the Kinetic Pairing Theorem the authors work over the ring of polynomials over species-variables \(x_1, \ldots , x_n\). Shouldn't the system parameters (i.e. rate constants) be included in this ring, as they would appear in the RPA polynomial? This inclusion of parameters is there in the Singular code but not in the proof. However simply adding the parameters in the ring is not sufficient as the n-th roots of the parameter would be added, as the examples mentioned in point 3 show. + +<|ref|>text<|/ref|><|det|>[[179, 785, 872, 906]]<|/det|> +Our response: In general, the ring of interest in these problems is the ring of polynomials in \(n\) variables, with real- valued coefficients - i.e. \(\mathbb{R}[x_1, \ldots , x_n]\). In this case, since we want to handle all coefficients (parameters) symbolically, we adjoin the coefficients to the ring with the algebraic structure of a fraction field. Notice in our Singular code that we declare two sets, each enclosed by round brackets (). The first of these, which declares the symbolic parameters, begins with a zero, which declares the characteristic of the field. Characteristic zero fields include the set of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 873, 190]]<|/det|> +real numbers, but also the rationals (including fraction fields). This is a standard way to handle symbolic coefficients in algebro- geometric computations of this type. Since these coefficients come from a field, we can apply all field operations (including division/multiplicative inverses) to these during the execution of any algorithms. By contrast, monomials/polynomials can only be added/subtracted and multiplied (no division) since these are defined to be elements of a ring. + +<|ref|>text<|/ref|><|det|>[[179, 206, 863, 467]]<|/det|> +Of course, if one particularly wants to define a parameter \(k\) to be a variable of the model for analytical purposes, one can certainly make this choice if desired, and consider the ring \(\mathbb{R}[x_1, \ldots , x_n, k]\) . This allows the ring to incorporate \(k\) within the power products (monomials), instead of interpreting it as a coefficient in the field over which the ring is defined. This could be useful if one particularly wanted to project the system onto \(k\) (as the non- RPA- capable variable) in the application of Theorem 1 – which might be helpful if it is difficult to posit a suitable non- RPA variable a priori (for a complicated new CRN that one suspects to be RPA- capable), and if the parameter \(k\) is a CRN property that can be used as a disturbance. But even so, it's important to recognize that there's no need to declare specific biochemical parameters to be variables of the model to check if the CRN can adapt to these as disturbances. If the CRN is RPA capable, then it can adapt to any disturbance that is not present in the identified setpoint. By contrast, if the parameter is in the setpoint, the CRN cannot adapt to perturbations to that parameter. We mention this point explicitly in our definition of RPA. + +<|ref|>sub_title<|/ref|><|det|>[[120, 500, 310, 516]]<|/det|> +## 7. Other minor issues: + +<|ref|>text<|/ref|><|det|>[[149, 532, 805, 568]]<|/det|> +- The definition of RPA must be shifted to the main text due to its centrality in understanding the message of the paper. + +<|ref|>text<|/ref|><|det|>[[177, 584, 836, 619]]<|/det|> +Our response: We have now shifted the definition of RPA to the main text. We sincerely thank the reviewer for such helpful and supportive suggestions. + +<|ref|>text<|/ref|><|det|>[[149, 635, 800, 670]]<|/det|> +- Why is the variable \(x_i\) missing in \(g(x_i)\) in figure 4 (main text) and figure S4 (supplement)? + +<|ref|>text<|/ref|><|det|>[[178, 684, 880, 900]]<|/det|> +Our response: We had stated in the caption to Figure 4 (main text) that 'when \(x_j\) is the diverter node of the Balancer module, \(g\) will generally be zero- order in \(x_i\) ' and in the caption to Figure S4 in our SI that 'for clarity, we depict a functional form for \(g\) that is zero order in \(x_i\) , since this is the most common form obtained in practice (i.e. provide the RPA variable \(x_i\) is not autoregulatory). The main reason for presenting the simplified form of \(g\) that usually obtains was to emphasize the topological role of \(x_j\) (relative to \(x_i\) ) in orchestrating a 'pairing' action. This simplification is really not essential, however, and our exposition of the pairing principle is unaffected if we include the general form of the pairing function, \(g(x_i, x_j)\) . In response to the reviewer's query, we have now updated this figure in both the main paper (Figure 4) and the SI (Figure S4) to feature the general form of the pairing function, \(g(x_i, x_j)\) , and have updated our captions accordingly. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 101, 876, 136]]<|/det|> +- Replace "consistutes" with "constitutes" on line 72 in the main text. Please run a spell check. + +<|ref|>text<|/ref|><|det|>[[178, 152, 852, 187]]<|/det|> +Our response: We thank the reviewer for spotting this typo, which has now been corrected. We have run a spell check, and there are no additional typos. + +<|ref|>text<|/ref|><|det|>[[150, 219, 857, 303]]<|/det|> +- The paper says that if a network is RPA the integrator is guaranteed to exist. For example the following on page 22 in the main text In principle, there should always exist some single nonlinear coordinate change to extract a single output-driven internal model (Fig. 9a) from systems rate equations, corresponding to a single integral of the systems tracking error (Fig. 9b) + +<|ref|>text<|/ref|><|det|>[[179, 317, 559, 335]]<|/det|> +or the following on page 16 in the Supplement + +<|ref|>text<|/ref|><|det|>[[179, 350, 813, 368]]<|/det|> +All classes of RPA, including ACR, thus require some form of integral control. + +<|ref|>text<|/ref|><|det|>[[179, 382, 877, 417]]<|/det|> +Please explain which version of IMP can be used to verify this existence. See [1] for a recent review on IMP. + +<|ref|>text<|/ref|><|det|>[[178, 433, 878, 727]]<|/det|> +Our response: Here we are referencing a long- standing idea in the systems biology literature (see, for example [8] and [9], and Section 3 of [1]) that, where RPA obtains, there 'should' exist some (generally nonlinear) coordinate change that recasts the system into integral feedback form (if necessary, if the system in question has a feedforward architecture, and is subjected to a disturbance at its 'divierter'). The integral in question should operate on the system's tracking error. Reference [8], in particular, provides a very detailed mathematical elaboration of these ideas, which hold for nonlinear systems under several technical assumptions (which are very mild in the context of CRNs). Both [1] and [8] apply these ideas to identify a nonlinear transformation that identifies an output- driven internal model for a simple CRN with a feedforward structure, through a recasting into feedback form. We reviewed this simple example in our response to the Reviewer's Point 1. Again, our paper provides a very different viewpoint, distinct from the notion that 'there should always exist some single nonlinear coordinate change to extract a single output- driven internal model ... corresponding to a single integral'. Our reason for referencing the viewpoint of prior control theoretic literature [1,8,9] is to contrast it with our new completely different viewpoint, and not to present that prior viewpoint as axiomatic. + +<|ref|>text<|/ref|><|det|>[[178, 744, 870, 779]]<|/det|> +We now add in these three references [1,8,9] at the location noted by the reviewer, to emphasize the prior IMP viewpoint we draw upon here. + +<|ref|>text<|/ref|><|det|>[[150, 795, 855, 880]]<|/det|> +- On page 20 the authors state that "It is striking to note that the original form of the CRN (Fig. 8a) eludes the Shinar-Feinberg theorem, even though the CRN exhibits ACR and has a deficiency of one." However does it fit the results in [4]? Please comment on this. Also explain why the authors found the method for finding linear invariants "ad hoc" (lines 568-569 on page 25). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 85, 879, 224]]<|/det|> +Our response: As noted in many of our previous responses, we suspect the reviewer is actually referring to Karp et al. [6], rather than Perez Millan et al. [4], in this comment. Certainly, once one knows which particular complexes (and hence, which monomials) one needs to include in any RPA/ACR- relevant invariants, one can certainly use the method developed Karp et al. [6] to compute those invariants. In this specific simple case, however, the invariants in question happen to be the actual rate equations \(dA / dt\) (the connector polynomial) and \(dB / dt\) (the balancer polynomial), so the method is hardly necessary. + +<|ref|>text<|/ref|><|det|>[[179, 241, 879, 433]]<|/det|> +Regarding our description of the Karp et al. [6] method for finding linear invariants as 'ad hoc', those authors themselves acknowledge that this method relies on knowing ahead of time which complexes (monomials) are relevant. As we had noted in one of our earlier responses, the authors specifically state that the 'examples (analysed in that paper) had already been analysed by other methods, so we had an idea of which invariants to expect and which subset of complexes to consider. For a new network such information may not be available, so how can non- trivial type 1 complex- linear invariants (simply, "invariants") be found?'. The authors go on to provide some practical suggestions for the reader on computing useful 'complex linear invariants', which may be helpful in studying new CRNs but certainly do not constitute a truly systematic procedure for rigorous application to general CRNs. + +<|ref|>text<|/ref|><|det|>[[150, 451, 881, 518]]<|/det|> +- On the Supplement page 15 it is stated that Mass-conservative CRNs therefore have no external stimuli or inputs, and can only be perturbed by altering the total abundances (or concentrations) of the constituent molecules - i.e. by altering the initial conditions. + +<|ref|>text<|/ref|><|det|>[[180, 533, 817, 566]]<|/det|> +Why cannot the perturbation come in the form of parameter variation, e.g. of a conversion reaction (that conserves mass). + +<|ref|>text<|/ref|><|det|>[[180, 599, 872, 737]]<|/det|> +Our response: Yes, the reviewer certainly does make an interesting point. In practice, conversion reactions are normally mediated by enzymes, so if the enzyme in question is not part of the network, we agree that the corresponding parameter (which reflects the concentration of the enzyme) could be perturbed. Almost any parameter of a CRN could be perturbed in principle. But the framework we develop here emphasizes that a CRN can adapt to perturbations to any parameter that does not appear in the RPA-variable's setpoint, regardless of whether the CRN is mass- conservative or not. + +<|ref|>text<|/ref|><|det|>[[180, 755, 879, 875]]<|/det|> +We did not intend the statement in question to constitute a major technical point. Nevertheless, in response to the reviewer's comment, we have adjusted the wording of that statement to read: 'Mass- conservative CRNs therefore have no external stimuli or inputs, and are typically perturbed by altering the total abundances (or concentrations) of the constituent molecules - i.e. by altering the initial conditions'. We do thank the reviewer again for such meticulous attention to every possible technical detail. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[179, 102, 863, 189]]<|/det|> +Final comments to the reviewer: We would like to sincerely thank the reviewer again for the incredible generosity he/she has shown us by scrutinizing our work in such extraordinary detail. We trust the reviewer will now be satisfied that our claims are all accurate and well- substantiated, and can now agree that our paper is ready for publication. + +<|ref|>sub_title<|/ref|><|det|>[[119, 242, 216, 257]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 255, 880, 800]]<|/det|> +[1] M. Bin, J. Huang, A. Isidori, L. Marconi, M. Mischiati, and E. Sontag. Internal models in control, bioengineering, and neuroscience. Annual Review of Control, Robotics, and Autonomous Systems, 5:55- 79, 2022. [2] A. Gupta and M. Khammash. Universal structural requirements for maximal robust perfect adaptation in biomolecular networks. Proceedings of the National Academy of Sciences, 119(43):e2207802119, 2022. [3] N. Meshkat, A. Shiu, and A. Torres. Absolute concentration robustness in networks with low- dimensional stoichiometric subspace. Vietnam Journal of Mathematics, 50(3):623- 651, 2022. [4] M. Perez Millan, A. Dickenstein, A. Shiu, and C. Conradi. Chemical reaction systems with toric steady states. Bulletin of mathematical biology, 74(5):1027- 1065, 2012. [5] M. S. Perez Millan. Metodos algebraicos para el estudio de redes bioquimicas. PhD thesis, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales, 2011. [6] R.L. Karp, M. Perez Millan, T. Dasgupta, A. Dickenstein, and J. Gunawardena. Complex- linear invariants of biochemical networks. Journal Theoretical Biology, 311:130- 138, 2012. [7] D. Cox, J. Little, and D. O'Shea. Ideals, varieties, and algorithms: an introduction to computational algebraic geometry and commutative algebra. Springer Science & Business Media, 2013. [8] E.D. Sontag. Adaptation and regulation with signal detection implies internal model. Systems & Control Letters, 50:119- 126, 2003. [9] O. Shoval, U. Alon, and E. Sontag. Symmetry Invariance for Adapting Biological Systems. SIAM Journal on Applied Dynamical Systems, 10: 857- 886, 2011. [10] G. Shinar and M. Feinberg, M. Structural sources of robustness in biochemical reaction networks. Science, 327(5971):1389- 1391, 2010. [11] D. Cappelletti, A. Gupta and M. Khammash. A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances. Journal of the Royal Society Interface, 17(171):20200437, 2020. [12] R.P. Araujo and L.A. Liotta. The topological requirements for robust perfect adaptation in networks of any size. Nature Communications, 9(1):1- 12, 2018. [13] J.M. Eloundou- Mbehi, A. Kuken, N. Omranian, S. Kleessen, J. Neigenfind, G. Basler and Z. Nikoloski. A network property necessary for concentration robustness. Nature Communications, 7(1):1- 7, 2016, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 415, 97]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 111, 875, 153]]<|/det|> +I went over the revised version of the paper, and while I truly appreciate the efforts of the authors in preparing the revision, I am still of the opinion that this paper is not suitable for an interdisciplinary journal like Nature Communications. The main issues I have are as follows: + +<|ref|>text<|/ref|><|det|>[[118, 167, 875, 252]]<|/det|> +1. As the title of the paper suggests, the aim of this study is to identify embedded integral control in adapting circuits. While the paper does construct a series of subsidiary integrators within the network via linear coordinate transformations, it does not provide a global coordinate transformation that would identify a global integrator. Hence the connection with standard integral controllers, and the standard Internal Model Principle is tenuous. By algebraically showing the existence of an RPA polynomial, only regulation and tracking are established, not integral control. + +<|ref|>text<|/ref|><|det|>[[118, 265, 868, 377]]<|/det|> +2. The proof of the Kinetic Pairing Result is hard to understand and verify for non-specialists in algebraic methods (like myself). In fact, when I showed the proof to a specialist in such methods (with the permission of the editor), that person also found the proof particularly difficult to understand. Here I am specifically referring to pages 20-21 in the Supplement. This difficulty was mentioned to the authors in the previous review report, but the authors have not addressed it by simplifying/elaborating on the proof. Therefore, after two rounds of revisions (and more than 2 months of time spent on this paper!) I still cannot ascertain the correctness of the reported results. + +<|ref|>text<|/ref|><|det|>[[118, 391, 878, 490]]<|/det|> +3. Even if the Kinetic Pairing result is correct, the final outcome is not a clean characterization of adapting networks. The characterization is done via an algorithm whose termination can take an inordinately large time for even moderately-sized networks. In cases where the algorithm does not terminate in a reasonable time, the authors suggest using analytical approaches like decomposing the large network into several independent networks and then performing deficiency analysis. However, this type of analysis is beyond the scope of most readers who might be interested in this work. If possible, the authors should try to extend their algorithm by incorporating this analysis. + +<|ref|>text<|/ref|><|det|>[[119, 544, 415, 558]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 573, 833, 601]]<|/det|> +The manuscript by Araujo and Liotta addresses both a fundamental biological problem, and a fundamental conceptual innovation. + +<|ref|>text<|/ref|><|det|>[[118, 602, 875, 657]]<|/det|> +The biological problem is that of organisms' ability to adapt to changes in the environment or their physiological state. This is a hallmark of many signalling processes where adaptation is required to safeguard the appropriate response. This has been a longstanding problem across many biological areas. + +<|ref|>text<|/ref|><|det|>[[118, 671, 878, 826]]<|/det|> +The conceptual advance offered by Araujo and Liotta is to derive mathematical results and conditions that guarantee adaptive behaviour. This is a tour de force and highly innovative; I like the idea of generalising integral control to dissect the design principles of adaptive behaviour a lot - there is scope for further applications of this framework. Many areas of biology will benefit from a more mathematically framework, and this work is a major contribution in this direction. Being able to prove formally aspects that biological systems have to obey to exhibit certain behaviour is exciting. In addition to the authors' earlier - outstanding in my view - work (PMID: 29717141), there is a growing body of other exciting work in this domain (see e.g. PMID: 19536158; PMID: 20223989, PMID 30194237); the present manuscript makes a substantial contribution to this important area of research. What sets the current work apart from these earlier studies are the more general biological relevance of adaptive behaviour. + +<|ref|>text<|/ref|><|det|>[[118, 840, 872, 910]]<|/det|> +The response to the reviewers' comments now exceeds the manuscript in length and I was unable to follow some of the criticisms voiced by the other reviewer. It is clear that the ideas underlying the alternative formulation of an integral controller are highly technical but the derivations contain the appropriate level of detail and I was able (admittedly with some work and effort) to follow the arguments laid out in the manuscript and especially the now substantial supplementary material. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 875, 182]]<|/det|> +I can understand that the references to additional mathematical work and proofs (e.g. in Refs 7 ad 15 in the supplementary material) does potentially add problems for a reader in reconstructing the full mathematical framework. In my view the authors negotiate the difficulties of exposing and explaining their proof in a clear and laudable manner. Developing a mathematical framework for a multidisciplinary audience is challenging but the work presented here provides important pointers how we can achieve this and find common ground between the often opposing needs of mathematical and biological audiences. + +<|ref|>text<|/ref|><|det|>[[118, 210, 211, 223]]<|/det|> +Minor point: + +<|ref|>text<|/ref|><|det|>[[118, 224, 830, 252]]<|/det|> +Lines 438- 442 contain in my reading one of the essential messages if this paper and I would suggest that the authors stress this and make the innovation in the paper more explicit. + +<|ref|>text<|/ref|><|det|>[[115, 265, 866, 281]]<|/det|> +In summary, this is exactly the type of mathematical biology that I and many others want to see. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[152, 133, 253, 149]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[151, 165, 845, 232]]<|/det|> +I went over the revised version of the paper, and while I truly appreciate the efforts of the authors in preparing the revision, I am still of the opinion that this paper is not suitable for an interdisciplinary journal like Nature Communications. The main issues I have are as follows: + +<|ref|>text<|/ref|><|det|>[[151, 247, 842, 364]]<|/det|> +1. As the title of the paper suggests, the aim of this study is to identify embedded integral control in adapting circuits. While the paper does construct a series of subsidiary integrators within the network via linear coordinate transformations, it does not provide a global coordinate transformation that would identify a global integrator. Hence the connection with standard integral controllers, and the standard Internal Model Principle is tenuous. By algebraically showing the existence of an RPA polynomial, only regulation and tracking are established, not integral control. + +<|ref|>sub_title<|/ref|><|det|>[[206, 379, 339, 395]]<|/det|> +## Our Response: + +<|ref|>text<|/ref|><|det|>[[205, 396, 844, 806]]<|/det|> +We sincerely thank the reviewer again for such a significant investment of his/her time in considering our work. We would like to emphasize once again, however, that there simply is no (and can be no) global coordinate transformation (and hence, no single 'global integrator') that can reveal the general properties of all possible RPA- capable CRNs. As we explained in our most recent response, one of the major points of our article is that the conventional approach to control theory, with its 'standard integral controllers' and 'standard Internal Model Principle' (as the Reviewer calls them) is wholly inadequate to capture the fundamental design principles that organize all forms of biological complexity into robustness- promoting (and ultimately, survival- promoting) structures. What we demonstrate instead is that all RPA- capable chemical reaction networks - without exception - are constructed from a topological hierarchy of building blocks ('invariants'), which independently implement the Internal Model Principle by robustly rejecting disturbances to specific network features (e.g., a ratio in the concentrations of specific molecules constituting a balancing mechanism) and which thereby work together collaboratively to implement RPA on specific molecule(s). Our analysis identifies the remarkable fact that all such RPA- promoting subsidiary invariants are obtained via linear coordinate changes, and recapitulate - locally within the topology of the network - the dynamical properties of the disturbance. By proving that all RPA- capable CRNs are decomposable into these well- defined topological hierarchies of internal models, we provide a universal description for the implementation of integral control that holds for all collections of chemical reactions that exhibit RPA (including any special case of RPA, such as absolute concentration robustness (ACR)). + +<|ref|>text<|/ref|><|det|>[[150, 852, 840, 904]]<|/det|> +2. The proof of the Kinetic Pairing Result is hard to understand and verify for non- specialists in algebraic methods (like myself). In fact, when I showed the proof to a specialist in such methods (with the permission of the editor), that person also found + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 845, 168]]<|/det|> +the proof particularly difficult to understand. Here I am specifically referring to pages 20- 21 in the Supplement. This difficulty was mentioned to the authors in the previous review report, but the authors have not addressed it by simplifying/elaborating on the proof. Therefore, after two rounds of revisions (and more than 2 months of time spent on this paper!) I still cannot ascertain the correctness of the reported results. + +<|ref|>sub_title<|/ref|><|det|>[[206, 200, 338, 216]]<|/det|> +## Our Response: + +<|ref|>text<|/ref|><|det|>[[206, 216, 847, 331]]<|/det|> +We thank the Reviewer for clarifying further the section of the proof they found hard to understand. This gives us the opportunity to restate, highlight, and summarize again the several additional clarifications of the proof we provided in the previous rounds of response. In fact, our extensive additional clarifications on the proof to our Theorem 1 (the Kinetic Pairing theorem) were added after the first round of review, through a series of 'Remarks' following the proof in our Supplementary Information. + +<|ref|>text<|/ref|><|det|>[[205, 345, 842, 599]]<|/det|> +In particular, the Reviewer stated in his/her first report that "...The proof given on page 12 in the Supplement does not satisfactorily explain why the ideal \(I_{f} \cap \mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) ", and proceeded to give an example of a CRN that he/she believed to be a counterexample to our Theorem. We responded with a detailed explanation as to why 'the ideal \(I_{f} \cap \mathbb{R}[x]\) will contain polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) ", along with a detailed analysis to demonstrate that the Reviewer's example is entirely consistent with our Theorem. The Reviewer responded in the following round by challenging us with three new CRN examples which he/she proposed were counterexamples to our Theorem. We responded by providing a careful and detailed analysis of these new examples, and demonstrating that these were entirely consistent with our Theorem - not counter- examples. In fact, we used our detailed analysis of the Reviewer's various CRNs to underscore the fact that these illustrations demonstrate how (and why) the Theorem works. + +<|ref|>text<|/ref|><|det|>[[205, 614, 848, 797]]<|/det|> +The Reviewer also now provides new information about consulting with a 'specialist' third- party ('...when I showed the proof to a specialist in such methods ... that person also found the proof particularly difficult to understand'). Nevertheless, we respectfully point out that the Reviewer has not been very specific as to what he/she does not understand in our proof to the Kinetic Pairing Theorem beyond the initial question regarding "polynomials in \(x_{j}\) and \(x_{m}\) that are not in \(I_{f} \cap I_{p}\) " (which we addressed thoroughly, as noted above). It is also possible that extensive clarifications of our proof in past rounds of responses, along with our lengthy and detailed analyses of the CRN examples, might not have been shown in extenso to the Reviewer's consultant. + +<|ref|>text<|/ref|><|det|>[[150, 845, 839, 912]]<|/det|> +3. Even if the Kinetic Pairing result is correct, the final outcome is not a clean characterization of adapting networks. The characterization is done via an algorithm whose termination can take an inordinately large time for even moderately-sized networks. In cases where the algorithm does not terminate in a reasonable time, the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 848, 166]]<|/det|> +authors suggest using analytical approaches like decomposing the large network into several independent networks and then performing deficiency analysis. However, this type of analysis is beyond the scope of most readers who might be interested in this work. If possible, the authors should try to extend their algorithm by incorporating this analysis. + +<|ref|>sub_title<|/ref|><|det|>[[206, 199, 338, 214]]<|/det|> +## Our Response: + +<|ref|>text<|/ref|><|det|>[[207, 215, 826, 313]]<|/det|> +We respectfully emphasize once again that within the original and revised manuscript versions we have provided detailed and rigorous mathematical arguments to support the correctness of the Kinetic Pairing result, and have additionally provided detailed analyses of all the new CRN examples suggested to us by the Reviewer to demonstrate how they reflect the essential underlying principles of this key Theorem. + +<|ref|>text<|/ref|><|det|>[[205, 330, 848, 624]]<|/det|> +In addition, the Reviewer suggests that "the final outcome is not a clean characterization of adapting networks" and that the "characterization is done via an algorithm ...". We feel it is important to clarify for the record that the universal characterisation of adaptation- capable CRNs presented in our study is not obtained from an algorithm, but from our carefully- developed mathematical arguments that all such adapting networks are constructed from topological building blocks that are obtained by linear coordinate changes (associated with linear integral controllers). Since all RPA- capable CRNs must be constructed from these fundamental building blocks, and because the topological principles governing RPA capacity are now known in complete generality, our findings definitively characterise the full set of chemical reaction structures that can implement RPA. In other words, through identifying the fundamental building blocks of RPA in CRNs and the algebraic structures (in terms of CRN deficiency, etc.) by which these building blocks are constructed, as well as the general principles by which the building blocks are connected together into larger networks, we are able to provide a comprehensive (i.e. universal) description all possible RPA- capable CRNs at the level of intermolecular interactions. + +<|ref|>text<|/ref|><|det|>[[205, 640, 847, 904]]<|/det|> +Now, for a specific RPA- capable CRN under consideration, we present an algorithmic test that can demonstrate the ability of a particular molecule to exhibit RPA, in addition to identifying the decomposition (of the requisite nonlinear transformation of the system) into subsidiary linear controllers, as well as the 'setpoint' of the system as a function of parameters. This is a completely separate matter from the issue of the 'universal characterisation' of RPA- capable CRNs. Although the reviewer suggests that the termination of the algorithm 'can take an inordinately large time for even moderately- sized networks', we respectfully emphasize once again that it is, in fact, only non- RPA- capable CRNs that may require an indeterminate (and potentially impractical) timeframe for the algorithm to terminate. We clearly explain the technical reasons for this fact in our paper (in both the main article, as well as in the Supplementary Information), and provide an alternative analytical approach to establish the inability of a CRN to exhibit RPA, should our 'general' algorithm take too long to terminate. We respectfully point out that this 'deficiency analysis' requires only linear algebraic techniques, and is thus + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[207, 83, 847, 133]]<|/det|> +accessible to the mainstream scientific community. We provide a fully- worked example of the application of this alternative analytical approach to a specific CRN in our Supplementary Information. + +<|ref|>text<|/ref|><|det|>[[207, 149, 844, 281]]<|/det|> +The complete generality of our findings on RPA- capable chemical reaction networks, along with the clarity and comprehensiveness of our analysis, will now enable the scientific community to consider fundamental questions about the evolution of biochemical reaction networks at the whole- cell level, and at the level of entire organisms. As such, we believe strongly that this study will be of interest to researchers from a huge variety of different fields, including evolutionary biology, bioengineering, cancer research, developmental biology, pharmacology, whole- cell modelling, and many others. + +<|ref|>sub_title<|/ref|><|det|>[[151, 346, 255, 362]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[150, 378, 843, 478]]<|/det|> +The manuscript by Araujo and Liotta addresses both a fundamental biological problem, and a fundamental conceptual innovation. The biological problem is that of organisms' ability to adapt to changes in the environment or their physiological state. This is a hallmark of many signalling processes where adaptation is required to safeguard the appropriate response. This has been a longstanding problem across many biological areas. + +<|ref|>text<|/ref|><|det|>[[149, 494, 842, 707]]<|/det|> +The conceptual advance offered by Araujo and Liotta is to derive mathematical results and conditions that guarantee adaptive behaviour. This is a tour de force and highly innovative; I like the idea of generalising integral control to dissect the design principles of adaptive behaviour a lot - there is scope for further applications of this framework. Many areas of biology will benefit from a more mathematically framework, and this work is a major contribution in this direction. Being able to prove formally aspects that biological systems have to obey to exhibit certain behaviour is exciting. In addition to the authors' earlier - outstanding in my view - work (PMID: 29717141), there is a growing body of other exciting work in this domain (see e.g. PMID: 19536158; PMID: 20223989, PMID 30194237); the present manuscript makes a substantial contribution to this important area of research. What sets the current work apart from these earlier studies are the more general biological relevance of adaptive behaviour. + +<|ref|>text<|/ref|><|det|>[[149, 723, 845, 903]]<|/det|> +The response to the reviewers' comments now exceeds the manuscript in length and I was unable to follow some of the criticisms voiced by the other reviewer. It is clear that the ideas underlying the alternative formulation of an integral controller are highly technical but the derivations contain the appropriate level of detail and I was able (admittedly with some work and effort) to follow the arguments laid out in the manuscript and especially the now substantial supplementary material. I can understand that the references to additional mathematical work and proofs (e.g. in Refs 7 ad 15 in the supplementary material) does potentially add problems for a reader in reconstructing the full mathematical framework. In my view the authors negotiate the difficulties of exposing and explaining their proof in a clear and laudable manner. Developing a mathematical framework for a multidisciplinary + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 847, 133]]<|/det|> +audience is challenging but the work presented here provides important pointers how we can achieve this and find common ground between the often opposing needs of mathematical and biological audiences. + +<|ref|>text<|/ref|><|det|>[[150, 150, 247, 165]]<|/det|> +Minor point: + +<|ref|>text<|/ref|><|det|>[[150, 166, 842, 215]]<|/det|> +Lines 438- 442 contain in my reading one of the essential messages if this paper and I would suggest that the authors stress this and make the innovation in the paper more explicit. + +<|ref|>text<|/ref|><|det|>[[150, 231, 829, 264]]<|/det|> +In summary, this is exactly the type of mathematical biology that I and many others want to see. + +<|ref|>sub_title<|/ref|><|det|>[[206, 297, 339, 313]]<|/det|> +## Our Response: + +<|ref|>text<|/ref|><|det|>[[206, 313, 847, 428]]<|/det|> +We are indebted to Reviewer 2 for such an authoritative and thorough consideration of our work - both in terms of our admittedly complicated mathematical arguments and in terms of the broad conceptual contributions of our study - and for such generous suggestions to strengthen our exposition even further. We are truly grateful that the Reviewer has been willing to invest the time required to carefully review all our technical arguments to verify their mathematical soundness. + +<|ref|>text<|/ref|><|det|>[[206, 444, 846, 640]]<|/det|> +We have taken on board the Reviewer's helpful suggestion to further emphasize the content of Lines 438- 442, in order to 'make the innovation in the paper more explicit'. (Lines 438- 442 contain the text: "Until now strategies for identifying an internal model, and an associated integral, via a nonlinear coordinate change have only been applicable to exceedingly simple CRNs. By contrast, our approach identifies a well- defined nonlinear map between reaction rates of the model variables \(f_{1}, \ldots , f_{n}\) , and a defining algebraic invariant, \(\rho\) (Eq. 6), which exists for all adaptation- capable CRNs"). With this suggestion in mind, we have now amplified the ideas contained in lines 438- 442 of the previous version and more explicitly highlighted the innovation in our paper by adding in an extensive new paragraph at the end of the Introduction section (now lines 130- 142 in this final version). We now explain + +<|ref|>text<|/ref|><|det|>[[261, 657, 847, 904]]<|/det|> +"As we will show in the sections to follow, a mathematical transformation may always be applied to the reaction rates of any RPA- capable CRN to produce a special two- variable invariant called an 'RPA polynomial'. This distinguished algebraic invariant encodes the robust asymptotic tracking of a molecular setpoint, no matter how complex or intricate the intermolecular interactions, nor how vast the network of interacting molecules. Unlike the nonlinear coordinate transformations invoked in the 'standard' IMP, where a global coordinate transformation (unique to each RPA- capable network) is required to identify a single internal model, the nonlinear transformation we identify here has a special 'almost linear' structure (and, in special cases, exactly linear) and is decomposable into a topologically organised collection of linear integral controllers, each with its own independent internal model. In this way, we are able to identify the fundamental building blocks of all possible RPA- capable CRNs, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[261, 83, 831, 133]]<|/det|> +thereby revealing definitive and universal structural requirements that characterize all adaptation- capable collections of interacting molecules." + +<|ref|>text<|/ref|><|det|>[[206, 149, 847, 233]]<|/det|> +This new material now leads directly to the detailed and careful analysis of our two simple running examples (which exemplify the properties of all RPA- capable CRNs), which lead, in turn, to a careful exposition of the underlying technicalities (comprehensively supported by our detailed Supplementary Information). + +<--- Page Split ---> diff --git a/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/images_list.json b/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..b282d5428c5f33221afdb0eade4971ef77cb84d6 --- /dev/null +++ b/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: a) Training and test set sample sizes for each cancer type. b,c) Top-1 and top-2 accuracy as well as d) the confusion matrix based on cross-validation (left bars/cells) and test set (right bars/cells) predictions.", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b46ad608e0595462e70222e5136e49aeb6e97865 --- /dev/null +++ b/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,153 @@ + +# nature portfolio + +Peer Review File + +Machine learning- based tissue of origin classification for cancer of unknown primary diagnostics using genome- wide mutation features + +![](images/Figure_2.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors modified the manuscript according to my previous suggestions. + +I have only a minor concern about reference 12, which does not cover the mentioned topic (CUP TOO prediction using microRNA signatures). Please select proper references (see PMID: 22618571 PMID: 34075699). + +Reviewer #4, commented on your responses to Reviewer's #3 previous concerns (Remarks to the Author): + +This study presents a classification tool for tumor site of origin using whole- genome sequencing data using off- the- shelf machine learning algorithms. The analysis differs from existing work in the inclusion of structural variants. Some of the findings on the SV side include the chromothripsis in lipo- sarcoma, TMPRSS2_ERG for prostate cancer. Many of the SV events discussed are well known and can be detected using whole- exome and targeted panels. It is unclear what's new from this whole- genome analysis. Overall, I appreciate the amount of work presented in this study but not convinced that this study presented sufficient technical or scientific advance over existing work. + +A major technical limitation is that there is substantial imbalance in sample size in this dataset as reviewer 3 pointed out, and many cancer types and subtypes have insufficient sample sizes to conduct proper hold- out test and even cross- validation. The overall accuracy measure can be misleadingly high in cases with high imbalance of case and "control". The analysis should restrict to cancer types that have sufficient sample size. In addition, sensitivity and PPV should be reported as a more honest assessment of the classification performance. For rare cancer types a classifier should take into account of the prevalence of the disease. + +Despite the combined PCAWG and Hartwig cohort, the sample size is still far from sufficient to establish a classifier for all \(30+\) tumor types. The clinical utility is also unclear due to the limited availability of WGS in clinical setting. + +<--- Page Split ---> + +## RESPONSE TO REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors modified the manuscript according to my previous suggestions. + +I have only a minor concern about reference 12, which does not cover the mentioned topic (CUP TOO prediction using microRNA signatures). Please select proper references (see PMID: 22618571 PMID: 34075699). + +We thank the reviewer for the reference recommendations and have added these to the text. + +Reviewer #4, commented on your responses to Reviewer's #3 previous concerns (Remarks to the Author): + +This study presents a classification tool for tumor site of origin using whole- genome sequencing data using off- the- shelf machine learning algorithms. The analysis differs from existing work in the inclusion of structural variants. Some of the findings on the SV side include the chromothripsis in lipo- sarcoma, TMPRSS2_ERG for prostate cancer. Many of the SV events discussed are well known and can be detected using whole- exome and targeted panels. It is unclear what's new from this whole- genome analysis. Overall, I appreciate the amount of work presented in this study but not convinced that this study presented sufficient technical or scientific advance over existing work. + +We respectfully disagree with the view of the reviewer. While the tumor- specific biological observations underlying the classifier are indeed not novel, this is also not the scope of the paper. We here describe a novel tissue of origin classifier that can be used in a diagnostic setting. This classifier uses previously described principles, but also includes novel features. Although such features have been described in other contexts, they have never been shown to be informative in a pan- cancer tissue of origin classification approach. + +We agree that some of the SV events such as fusions are detectable with other DNA or RNA- based sequencing approaches. However, some SV events, such as LINE insertions (important for classifying gastric and urothelial cancers) or viral sequence insertions (important for classifying skin carcinoma, cervical cancer and head/neck cancer) are not detectable (or routinely detected) by whole- exome/targeted sequencing. Furthermore, the regional mutation density (RMD) features do require WGS data and we demonstrate that these are the most predictive features for tumor type classification overall. + +The strength of WGS is that only one sequencing assay is needed to extract both RMD and SV features (but also other genomic features). For example, while it is true that TMPRSS2_ERG fusions as well as AR amplifications are (potentially) detectable with whole- exome/targeted sequencing and are defining characteristics of prostate cancer, not all prostate cancers carry these events. In our cohort, 209/560 (37%, see below table) of prostate patients have neither of these events. + +<--- Page Split ---> + +Cancer type classification for these 209 patients could still be performed based on the prostate RMD profile which is highly predictive of prostate cancer (rmd.Prostate.1, see barplot below). This data is readily available with WGS, whereas with whole- exome/targeted sequencing additional assays would need to be performed to come to the same conclusion for each individual patient tested. + +
TMPRSS2_ERGAR_ampFreq
FALSEFALSE209
TRUEFALSE217
FALSETRUE70
TRUETRUE64
+ +Frequency of TMPRSS2- ERG fusions and/or AR amplifications in prostate cancer samples + +![PLACEHOLDER_4_0] + + +Excerpt from Supplementary figure 7: Feature importances for the 'Prostate' random forest within CUPLR. + +A major technical limitation is that there is substantial imbalance in sample size in this dataset as reviewer 3 pointed out, and many cancer types and subtypes have insufficient sample sizes to conduct proper hold- out test and even cross- validation. The overall accuracy measure can be misleadingly high in cases with high imbalance of case and "control". The analysis should restrict to cancer types that have sufficient sample size. In addition, sensitivity and PPV should be reported as a more honest assessment of the classification performance. For rare cancer types a classifier should take into account of the prevalence of the disease. + +Regarding accuracy and class imbalance: + +It is indeed correct that accuracy would be misleading if we would have calculated total accuracy: (number of samples correctly predicted as e.g. breast) / (number of samples across all cancer types). However, we have calculated per cancer type accuracy which is not affected by class imbalances: (number of samples correctly predicted as breast) / (total number of breast samples). However, to better illustrate the performance per tumor type, we have now added sensitivity and PPV curves for each cancer type binary classifier in CUPLR as Supplementary figure 11 to the revised manuscript. + +Regarding sample sizes: + +In our training set, 32/35 cancer types had \(> = 30\) samples, with the smallest cancer type cohort (NET_Lung) having 23 samples (see table below). We believe that this is sufficient sample size to assess CV performance. We do agree that there is insufficient sample size to properly + +<--- Page Split ---> + +calculate performance for certain cancer types on the independent test set. However, we observe that the CV and test set accuracies across cancer types are generally concordant (see Figure 2d below), suggesting that CV accuracy adequately represents test set accuracy. For these reasons, we have chosen to report both CV and test set accuracy in Figure 2d so that one can rely on CV accuracy for cancer types with low test set sample size. + +
cancer_typen_testn_train
Breast100896
Colorectal71639
Lung_NonSmallCell58530
Prostate56504
Skin_Melanoma40366
Pancreas35312
Liver34306
Gastroesophageal33295
Ovarian28256
Kidney_ClearCell24213
Lymphoid21197
Urothelial20180
CNS_Medullo15123
CNS_Glioma13118
Sarcoma_Other13118
NET_Pancreas12107
Biliary12102
HeadAndNeck_Other982
Uterus768
Thyroid661
Sarcoma_GIST760
Sarcoma_Leiomyo757
Cervix653
CNS_PiloAstro652
NET_Gastrointestinal549
Lung_SmallCell548
Sarcoma_Osteo440
Kidney_Chromophobe439
Sarcoma_Lipo438
Mesothelioma437
HeadAndNeck_SalivaryGland331
Myeloid430
Kidney_Papillary329
NET_Lung323
Skin_Carcinoma223
+ +Training and test set sample sizes for each cancer type, sorted by training sample size. + +<--- Page Split ---> +![PLACEHOLDER_6_0] + +
Figure 2: a) Training and test set sample sizes for each cancer type. b,c) Top-1 and top-2 accuracy as well as d) the confusion matrix based on cross-validation (left bars/cells) and test set (right bars/cells) predictions.
+ +<--- Page Split ---> + +Despite the combined PCAWG and Hartwig cohort, the sample size is still far from sufficient to establish a classifier for all \(30+\) tumor types. + +We acknowledge that increased sample size would of course be more ideal for classifier training for some cancer types, such as Kidney_Papillary, NET_Lung, Skin_Carcinoma, HeadAndNeck_SalivaryGland, Myeloid (which all have \(\leq 31\) training samples and \(\leq 70\%\) accuracy based on either CV or test set; Figure 2a and d). + +Low sample sizes are mainly the result of splitting cancer types into subtypes, which is often clinically relevant but ignored in many previously described classifiers. It should be noted that for many cancer types, CUPLR still predicts the correct supertype. For example, Kidney_Papillary is most often misclassified as Kidney_ClearCell, meaning that the cancer supertype (kidney) is still correctly predicted (Figure 2d). Likewise, NET_Lung is most often misclassified as other neuroendocrine tumors (NET_Gastrointestinal or NET_Pancreas). Additionally, other cancer types with relative few but slightly more training samples (<60 samples) also have frequently correct supertype (but not subtype) predictions, such as Lung_SmallCell (misclassified as Lung_NonSmallCell), or Sarcoma_Osteo/Sarcoma_Leiomyo (misclassified as other sarcomas). However, in most cases, CUPLR more often predicted the subtype correctly than incorrectly and we thus believe that CUPLR can still provide highly relevant information to support diagnosis despite low sample sizes for certain cancer (sub)types. + +From a clinical perspective, when dealing with CUPs, some indication of the potential cancer type (e.g. from CUPLR) is already better than no indication (which would often have been the original and final diagnosis). Additionally, it is important to note that CUPLR is intended to complement other clinical evidence (e.g. from histopathological stainings or patient metadata) to determine tissue of origin, rather than to come to the final decision of the tissue of origin by itself. Since CUPLR outputs explanations as to which features support a prediction, existing knowledge can be used to reject potentially bad predictions on a case by case basis. This reasoning is included in the discussion. + +The clinical utility is also unclear due to the limited availability of WGS in clinical setting. As in the response to reviewer #1, we acknowledge that WGS is not yet standard in routine diagnostics in all hospitals in all countries and therefore CUPLR is not (yet) applicable for every situation. However, we see increasingly more labs and countries, especially in Europe, developing WGS- based cancer diagnostics programs [Campbell et al 2019] and the tool described here is targeting those developments. Of note, in the Netherlands, WGS (and not panel- based sequencing) is a reimbursed diagnostic approach for CUP patients since 2021 and used by an increasing number of hospitals despite the fresh- frozen material requirement, clearly illustrating that the current real- world scenario is changing and future directions likely include WGS. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #4 (Remarks to the Author): + +There is some fundamental confusion on the definition of classification accuracy used in the study. + +The authors defined a per sample accuracy as (number of samples correctly predicted as breast) / (total number of breast samples). This is the definition of "sensitivity" or "recall", NOT "overall accuracy". + +The missing side of the equation is "precision" or "PPV" which is the fraction of actual breast cancer cases out of predicted breast cancer of origin. + +Both precisions and recalls should be reported in the main text and a direct comparison of these values to those reported in the published whole- genome TOO studies they cited in the paper (ref 6 and 7) would more convincingly show the added value of this study. + +<--- Page Split ---> + +## RESPONSE TO REVIEWER COMMENTS + +## Reviewer #4 + +There is some fundamental confusion on the definition of classification accuracy used in the study. + +The authors defined a per sample accuracy as (number of samples correctly predicted as breast) / (total number of breast samples). This is the definition of "sensitivity" or "recall", NOT "overall accuracy". + +To avoid any further confusion, we have replaced (per- class) "accuracy" with "recall" in the manuscript. In the methods (under "Performance evaluation") we have added the following text to define our performance metrics: + +Performance metrics per cancer type were defined as follows (using 'Breast' as an example): + +Recall \(=\) Fraction of Breast samples predicted as Breast Top- 2 recall \(=\) Fraction of Breast samples where the 1st or 2nd top prediction was Breast Precision \(=\) Amongst samples predicted as Breast, fraction of samples predicted as Breast + +Overall performance metrics were micro- averages of the per- cancer- type metrics and defined as follows: + +Micro- averaged recall \(=\) Accuracy \(=\) Fraction of all samples correctly predicted Micro- averaged top- 2 recall \(=\) Top- 2 accuracy \(=\) Fraction of all samples where the 1st or The missin, side of the equation is "precision" or "PPV" which is the fraction of actual breast cancer cases out of predicted breast cancer of all of the 1st or 2nd top per- cancer- type precision + +Both precisions and recalls should be reported in the main text and a direct comparison of these values to those reported in the published whole- genome TOO studies they cited in the paper (ref 6 and 7) would more convincingly show the added value of this study. + +We have included precision numbers in Figure 2 (see below) and mentioned these in the manuscript. + +<--- Page Split ---> +![PLACEHOLDER_10_0] + + +We have also included a comparison of CUPLR's precision to the classifiers in ref 6 (PCAWG neural network) and ref 7 (SVM from Salvadores et al) as Supplementary figure 10 (see below). We have mentioned in the manuscript that precision was overall similar to or better than the other classifiers, except for head and neck, myeloid, thyroid, and uterine cancers. + +<--- Page Split ---> +![PLACEHOLDER_11_0] + + +<--- Page Split ---> diff --git a/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..60720db346a26b889d81a7e33b8f436d852b06f5 --- /dev/null +++ b/peer_reviews/9996cfd0b15a9cf22945820c0b46352ef32eedaaee0dc8f65c730df41a4c7b37/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,200 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[67, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[90, 154, 914, 240]]<|/det|> +Machine learning- based tissue of origin classification for cancer of unknown primary diagnostics using genome- wide mutation features + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 839, 141]]<|/det|> +This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 314, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 113, 415, 128]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 143, 699, 158]]<|/det|> +The authors modified the manuscript according to my previous suggestions. + +<|ref|>text<|/ref|><|det|>[[119, 173, 871, 218]]<|/det|> +I have only a minor concern about reference 12, which does not cover the mentioned topic (CUP TOO prediction using microRNA signatures). Please select proper references (see PMID: 22618571 PMID: 34075699). + +<|ref|>text<|/ref|><|det|>[[118, 277, 870, 307]]<|/det|> +Reviewer #4, commented on your responses to Reviewer's #3 previous concerns (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 322, 876, 427]]<|/det|> +This study presents a classification tool for tumor site of origin using whole- genome sequencing data using off- the- shelf machine learning algorithms. The analysis differs from existing work in the inclusion of structural variants. Some of the findings on the SV side include the chromothripsis in lipo- sarcoma, TMPRSS2_ERG for prostate cancer. Many of the SV events discussed are well known and can be detected using whole- exome and targeted panels. It is unclear what's new from this whole- genome analysis. Overall, I appreciate the amount of work presented in this study but not convinced that this study presented sufficient technical or scientific advance over existing work. + +<|ref|>text<|/ref|><|det|>[[118, 441, 864, 547]]<|/det|> +A major technical limitation is that there is substantial imbalance in sample size in this dataset as reviewer 3 pointed out, and many cancer types and subtypes have insufficient sample sizes to conduct proper hold- out test and even cross- validation. The overall accuracy measure can be misleadingly high in cases with high imbalance of case and "control". The analysis should restrict to cancer types that have sufficient sample size. In addition, sensitivity and PPV should be reported as a more honest assessment of the classification performance. For rare cancer types a classifier should take into account of the prevalence of the disease. + +<|ref|>text<|/ref|><|det|>[[118, 561, 857, 606]]<|/det|> +Despite the combined PCAWG and Hartwig cohort, the sample size is still far from sufficient to establish a classifier for all \(30+\) tumor types. The clinical utility is also unclear due to the limited availability of WGS in clinical setting. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 88, 457, 106]]<|/det|> +## RESPONSE TO REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 125, 420, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 162, 718, 181]]<|/det|> +The authors modified the manuscript according to my previous suggestions. + +<|ref|>text<|/ref|><|det|>[[115, 199, 875, 253]]<|/det|> +I have only a minor concern about reference 12, which does not cover the mentioned topic (CUP TOO prediction using microRNA signatures). Please select proper references (see PMID: 22618571 PMID: 34075699). + +<|ref|>text<|/ref|><|det|>[[115, 253, 855, 272]]<|/det|> +We thank the reviewer for the reference recommendations and have added these to the text. + +<|ref|>text<|/ref|><|det|>[[115, 290, 867, 327]]<|/det|> +Reviewer #4, commented on your responses to Reviewer's #3 previous concerns (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 345, 875, 492]]<|/det|> +This study presents a classification tool for tumor site of origin using whole- genome sequencing data using off- the- shelf machine learning algorithms. The analysis differs from existing work in the inclusion of structural variants. Some of the findings on the SV side include the chromothripsis in lipo- sarcoma, TMPRSS2_ERG for prostate cancer. Many of the SV events discussed are well known and can be detected using whole- exome and targeted panels. It is unclear what's new from this whole- genome analysis. Overall, I appreciate the amount of work presented in this study but not convinced that this study presented sufficient technical or scientific advance over existing work. + +<|ref|>text<|/ref|><|det|>[[114, 492, 872, 603]]<|/det|> +We respectfully disagree with the view of the reviewer. While the tumor- specific biological observations underlying the classifier are indeed not novel, this is also not the scope of the paper. We here describe a novel tissue of origin classifier that can be used in a diagnostic setting. This classifier uses previously described principles, but also includes novel features. Although such features have been described in other contexts, they have never been shown to be informative in a pan- cancer tissue of origin classification approach. + +<|ref|>text<|/ref|><|det|>[[114, 620, 870, 750]]<|/det|> +We agree that some of the SV events such as fusions are detectable with other DNA or RNA- based sequencing approaches. However, some SV events, such as LINE insertions (important for classifying gastric and urothelial cancers) or viral sequence insertions (important for classifying skin carcinoma, cervical cancer and head/neck cancer) are not detectable (or routinely detected) by whole- exome/targeted sequencing. Furthermore, the regional mutation density (RMD) features do require WGS data and we demonstrate that these are the most predictive features for tumor type classification overall. + +<|ref|>text<|/ref|><|det|>[[114, 767, 877, 877]]<|/det|> +The strength of WGS is that only one sequencing assay is needed to extract both RMD and SV features (but also other genomic features). For example, while it is true that TMPRSS2_ERG fusions as well as AR amplifications are (potentially) detectable with whole- exome/targeted sequencing and are defining characteristics of prostate cancer, not all prostate cancers carry these events. In our cohort, 209/560 (37%, see below table) of prostate patients have neither of these events. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 870, 180]]<|/det|> +Cancer type classification for these 209 patients could still be performed based on the prostate RMD profile which is highly predictive of prostate cancer (rmd.Prostate.1, see barplot below). This data is readily available with WGS, whereas with whole- exome/targeted sequencing additional assays would need to be performed to come to the same conclusion for each individual patient tested. + +<|ref|>table<|/ref|><|det|>[[115, 200, 380, 280]]<|/det|> + +
TMPRSS2_ERGAR_ampFreq
FALSEFALSE209
TRUEFALSE217
FALSETRUE70
TRUETRUE64
+ +<|ref|>text<|/ref|><|det|>[[115, 281, 840, 300]]<|/det|> +Frequency of TMPRSS2- ERG fusions and/or AR amplifications in prostate cancer samples + +<|ref|>image<|/ref|><|det|>[[120, 305, 460, 462]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 468, 840, 504]]<|/det|> +Excerpt from Supplementary figure 7: Feature importances for the 'Prostate' random forest within CUPLR. + +<|ref|>text<|/ref|><|det|>[[114, 522, 880, 653]]<|/det|> +A major technical limitation is that there is substantial imbalance in sample size in this dataset as reviewer 3 pointed out, and many cancer types and subtypes have insufficient sample sizes to conduct proper hold- out test and even cross- validation. The overall accuracy measure can be misleadingly high in cases with high imbalance of case and "control". The analysis should restrict to cancer types that have sufficient sample size. In addition, sensitivity and PPV should be reported as a more honest assessment of the classification performance. For rare cancer types a classifier should take into account of the prevalence of the disease. + +<|ref|>text<|/ref|><|det|>[[115, 671, 450, 688]]<|/det|> +Regarding accuracy and class imbalance: + +<|ref|>text<|/ref|><|det|>[[114, 689, 880, 818]]<|/det|> +It is indeed correct that accuracy would be misleading if we would have calculated total accuracy: (number of samples correctly predicted as e.g. breast) / (number of samples across all cancer types). However, we have calculated per cancer type accuracy which is not affected by class imbalances: (number of samples correctly predicted as breast) / (total number of breast samples). However, to better illustrate the performance per tumor type, we have now added sensitivity and PPV curves for each cancer type binary classifier in CUPLR as Supplementary figure 11 to the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 836, 314, 853]]<|/det|> +Regarding sample sizes: + +<|ref|>text<|/ref|><|det|>[[115, 854, 874, 909]]<|/det|> +In our training set, 32/35 cancer types had \(> = 30\) samples, with the smallest cancer type cohort (NET_Lung) having 23 samples (see table below). We believe that this is sufficient sample size to assess CV performance. We do agree that there is insufficient sample size to properly + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 881, 179]]<|/det|> +calculate performance for certain cancer types on the independent test set. However, we observe that the CV and test set accuracies across cancer types are generally concordant (see Figure 2d below), suggesting that CV accuracy adequately represents test set accuracy. For these reasons, we have chosen to report both CV and test set accuracy in Figure 2d so that one can rely on CV accuracy for cancer types with low test set sample size. + +<|ref|>table<|/ref|><|det|>[[117, 198, 365, 660]]<|/det|> + +
cancer_typen_testn_train
Breast100896
Colorectal71639
Lung_NonSmallCell58530
Prostate56504
Skin_Melanoma40366
Pancreas35312
Liver34306
Gastroesophageal33295
Ovarian28256
Kidney_ClearCell24213
Lymphoid21197
Urothelial20180
CNS_Medullo15123
CNS_Glioma13118
Sarcoma_Other13118
NET_Pancreas12107
Biliary12102
HeadAndNeck_Other982
Uterus768
Thyroid661
Sarcoma_GIST760
Sarcoma_Leiomyo757
Cervix653
CNS_PiloAstro652
NET_Gastrointestinal549
Lung_SmallCell548
Sarcoma_Osteo440
Kidney_Chromophobe439
Sarcoma_Lipo438
Mesothelioma437
HeadAndNeck_SalivaryGland331
Myeloid430
Kidney_Papillary329
NET_Lung323
Skin_Carcinoma223
+ +<|ref|>table_footnote<|/ref|><|det|>[[117, 664, 808, 681]]<|/det|> +Training and test set sample sizes for each cancer type, sorted by training sample size. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 880, 728]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 727, 863, 782]]<|/det|> +
Figure 2: a) Training and test set sample sizes for each cancer type. b,c) Top-1 and top-2 accuracy as well as d) the confusion matrix based on cross-validation (left bars/cells) and test set (right bars/cells) predictions.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 870, 127]]<|/det|> +Despite the combined PCAWG and Hartwig cohort, the sample size is still far from sufficient to establish a classifier for all \(30+\) tumor types. + +<|ref|>text<|/ref|><|det|>[[113, 130, 870, 233]]<|/det|> +We acknowledge that increased sample size would of course be more ideal for classifier training for some cancer types, such as Kidney_Papillary, NET_Lung, Skin_Carcinoma, HeadAndNeck_SalivaryGland, Myeloid (which all have \(\leq 31\) training samples and \(\leq 70\%\) accuracy based on either CV or test set; Figure 2a and d). + +<|ref|>text<|/ref|><|det|>[[113, 254, 867, 494]]<|/det|> +Low sample sizes are mainly the result of splitting cancer types into subtypes, which is often clinically relevant but ignored in many previously described classifiers. It should be noted that for many cancer types, CUPLR still predicts the correct supertype. For example, Kidney_Papillary is most often misclassified as Kidney_ClearCell, meaning that the cancer supertype (kidney) is still correctly predicted (Figure 2d). Likewise, NET_Lung is most often misclassified as other neuroendocrine tumors (NET_Gastrointestinal or NET_Pancreas). Additionally, other cancer types with relative few but slightly more training samples (<60 samples) also have frequently correct supertype (but not subtype) predictions, such as Lung_SmallCell (misclassified as Lung_NonSmallCell), or Sarcoma_Osteo/Sarcoma_Leiomyo (misclassified as other sarcomas). However, in most cases, CUPLR more often predicted the subtype correctly than incorrectly and we thus believe that CUPLR can still provide highly relevant information to support diagnosis despite low sample sizes for certain cancer (sub)types. + +<|ref|>text<|/ref|><|det|>[[114, 510, 880, 658]]<|/det|> +From a clinical perspective, when dealing with CUPs, some indication of the potential cancer type (e.g. from CUPLR) is already better than no indication (which would often have been the original and final diagnosis). Additionally, it is important to note that CUPLR is intended to complement other clinical evidence (e.g. from histopathological stainings or patient metadata) to determine tissue of origin, rather than to come to the final decision of the tissue of origin by itself. Since CUPLR outputs explanations as to which features support a prediction, existing knowledge can be used to reject potentially bad predictions on a case by case basis. This reasoning is included in the discussion. + +<|ref|>text<|/ref|><|det|>[[114, 676, 820, 860]]<|/det|> +The clinical utility is also unclear due to the limited availability of WGS in clinical setting. As in the response to reviewer #1, we acknowledge that WGS is not yet standard in routine diagnostics in all hospitals in all countries and therefore CUPLR is not (yet) applicable for every situation. However, we see increasingly more labs and countries, especially in Europe, developing WGS- based cancer diagnostics programs [Campbell et al 2019] and the tool described here is targeting those developments. Of note, in the Netherlands, WGS (and not panel- based sequencing) is a reimbursed diagnostic approach for CUP patients since 2021 and used by an increasing number of hospitals despite the fresh- frozen material requirement, clearly illustrating that the current real- world scenario is changing and future directions likely include WGS. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 313, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 111, 415, 126]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 139, 870, 154]]<|/det|> +There is some fundamental confusion on the definition of classification accuracy used in the study. + +<|ref|>text<|/ref|><|det|>[[118, 167, 870, 210]]<|/det|> +The authors defined a per sample accuracy as (number of samples correctly predicted as breast) / (total number of breast samples). This is the definition of "sensitivity" or "recall", NOT "overall accuracy". + +<|ref|>text<|/ref|><|det|>[[118, 223, 827, 252]]<|/det|> +The missing side of the equation is "precision" or "PPV" which is the fraction of actual breast cancer cases out of predicted breast cancer of origin. + +<|ref|>text<|/ref|><|det|>[[118, 265, 874, 308]]<|/det|> +Both precisions and recalls should be reported in the main text and a direct comparison of these values to those reported in the published whole- genome TOO studies they cited in the paper (ref 6 and 7) would more convincingly show the added value of this study. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 118, 458, 137]]<|/det|> +## RESPONSE TO REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[115, 152, 218, 168]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[115, 170, 850, 205]]<|/det|> +There is some fundamental confusion on the definition of classification accuracy used in the study. + +<|ref|>text<|/ref|><|det|>[[115, 224, 861, 278]]<|/det|> +The authors defined a per sample accuracy as (number of samples correctly predicted as breast) / (total number of breast samples). This is the definition of "sensitivity" or "recall", NOT "overall accuracy". + +<|ref|>text<|/ref|><|det|>[[115, 279, 872, 333]]<|/det|> +To avoid any further confusion, we have replaced (per- class) "accuracy" with "recall" in the manuscript. In the methods (under "Performance evaluation") we have added the following text to define our performance metrics: + +<|ref|>text<|/ref|><|det|>[[115, 352, 857, 370]]<|/det|> +Performance metrics per cancer type were defined as follows (using 'Breast' as an example): + +<|ref|>text<|/ref|><|det|>[[144, 371, 883, 440]]<|/det|> +Recall \(=\) Fraction of Breast samples predicted as Breast Top- 2 recall \(=\) Fraction of Breast samples where the 1st or 2nd top prediction was Breast Precision \(=\) Amongst samples predicted as Breast, fraction of samples predicted as Breast + +<|ref|>text<|/ref|><|det|>[[115, 444, 864, 479]]<|/det|> +Overall performance metrics were micro- averages of the per- cancer- type metrics and defined as follows: + +<|ref|>text<|/ref|><|det|>[[115, 480, 877, 558]]<|/det|> +Micro- averaged recall \(=\) Accuracy \(=\) Fraction of all samples correctly predicted Micro- averaged top- 2 recall \(=\) Top- 2 accuracy \(=\) Fraction of all samples where the 1st or The missin, side of the equation is "precision" or "PPV" which is the fraction of actual breast cancer cases out of predicted breast cancer of all of the 1st or 2nd top per- cancer- type precision + +<|ref|>text<|/ref|><|det|>[[115, 567, 880, 620]]<|/det|> +Both precisions and recalls should be reported in the main text and a direct comparison of these values to those reported in the published whole- genome TOO studies they cited in the paper (ref 6 and 7) would more convincingly show the added value of this study. + +<|ref|>text<|/ref|><|det|>[[115, 639, 824, 675]]<|/det|> +We have included precision numbers in Figure 2 (see below) and mentioned these in the manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[144, 88, 850, 680]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 700, 875, 774]]<|/det|> +We have also included a comparison of CUPLR's precision to the classifiers in ref 6 (PCAWG neural network) and ref 7 (SVM from Salvadores et al) as Supplementary figure 10 (see below). We have mentioned in the manuscript that precision was overall similar to or better than the other classifiers, except for head and neck, myeloid, thyroid, and uterine cancers. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[112, 87, 884, 680]]<|/det|> + +<--- Page Split ---> diff --git a/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..edffb1aade94aa3904fc9d9f571a59696417f9cd --- /dev/null +++ b/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,814 @@ + +# A proof-of-concept study in small and large animal models for coupling liver normothermic machine perfusion with mesenchymal stromal cell bioreactors + +Corresponding Author: Dr Caterina Lonati + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) Review Report + +The authors have skillfully design a promising platform to study the effect of mesenchymal stem cells (MSC) during ex vivo perfusion of rat livers. This is a very interesting approach to overcome some issues observed in direct MSC infusion in organ- in- a- pump models, like microvasculature clogging. The main successful points are the modification of a rat liver normothermic machine perfusion (NMP) system to include a bioreactor for MSC cell therapy and the maintenance of hepatocyte viability during MSC- NMP. However, there are some concerns that need to be addressed: + +## Introduction + +Authors claim that MSC only activate their secretory potential after exposure to inflammatory stimuli. However, this is not true as demonstrated earlier (i.e. Park et al., Int J Stem Cells., 2009) but MSC secretory profile is modulated by the microenvironment (i.e. Burja et al., Curr Res Transl Med., 2020). + +## Methods + +MSC in vitro culture. Authors describe "MSCs were cultured at a concentration of \(2^{*}105\) in \(14~\mathrm{mL}\) in oMEM medium". What vessel was used to seed the cells and what is the final seeding density in this vessel? Characterization of MSC after NMP. Cells were retrieved from the bioreactor. Were the cells directly analysed (cytometry). For how long were the MSC re- cultured for the morphology tests and what were the conditions of that culture? (cell seeding density, culture time, etc.). Also, did the authors count the total number of cells retrieved from the bioreactor and compared with the original number? Exposure to perfusion fluid may have altered their metabolism and survival, acting as a licensing agent itself. + +Flow cytometry. For reproducibility purposes, please add the reference numbers of antibodies used for flow cytometry and other relevant reagent. + +Liver NMP. Perfusion took place in two phases: a warming phase and a stable normothermic phase. Was the bioreactor connected to the circuit during the entire perfusion (warming+stable phases)? Similar to the question related to shipment, rewarming time might affect MSC survival and metabolism during this time. + +The authors seeded \(20^{*}10^{*}7\) MSC in a bioreactor. Is this number constant throughout the perfusion experiment? Do MSC die and are replaced by proliferating MSC? These dead cells might be responsible for the uncontrolled release of cytokines. In addition, average rat liver weight is 4- 5 grams which results in a MSC dose of \(4^{*}10^{*}9\) MSC/kg, an extremely high dose which has a poor translation towards a clinically relevant setup. + +In addition, authors sent MSC in a bioreactor from one laboratory to another at room temperature. Culture temperature is key for MSC survival and temperatures lower to \(37^{\circ}C\) are deleterious (Pratiwi et al., Cytoherapy, 2019). Did the authors study the status of MSC after the shipment? + +## Results + +The authors describe an increase in certain metabolites such as lactate, IL- 6, IL- 1ra, among other, during liverless NMP+bioreactor. However, these are inflammatory cytokines and lactate production has been related to increased ROS production (i.e. Li et al., Signal Transduct Target Ther., 2022). Though the authors address the increase in inflammatory + +<--- Page Split ---> + +cytokines as a positive results, they should discuss the inflammatory perfusate profile and elaborate on this in the discussion section as it appears to be a setback of their NMP circuit. + +Immune cells outflow. Authors describe outflow of an increased number of immune cells when the bioreactor is connected during NMP. However, they do not show data for cell characterization in the outflow perfusate. + +EV origin. The authors hint that observed differences in EV size are related to their hepatocyte or MSC origin. This is a difficult assumption to make based only on EV size. + +pH stabilization. The authors claim that MSC in the bioreactor regulate the pH of the perfusate. However, exposure to MSC medium present in the bioreactor, which contains a buffered solution to maintain pH, might be the responsible factor of pH stabilization. + +## Reviewer #2 + +(Remarks to the Author) + +This study reports the effects of the addition of an MSC- bioreactor to the NMP circuit in an isolated rat liver model. The study mainly shows the safety and feasibility of this approach and some beneficial effects of using an MSC bioreactor approach rather than thawed MSCs. The MSC- bioreactor effects included decreased injury markers, increased bile production; increased acute phase proteins; more effective washout of blood; reduced ATP depletion; absence of succinate accumulation. + +Please address the following: + +1. You state that the 'translational value is high'. This needs justification when using a rodent model as many such models have been shown not to have reproducible effects in large animals and humans. +2. Although you acknowledge that the cold ischaemic time is very short, this is. major limitation with little clinical relevance. +3. Please discuss the potential effects of raised TNF and IL-6 in the bioreactor group. These acute phase proteins can have pro-inflammatory wells as protective effects. +4. It is difficult to make conclusions about ATP depletion when the ATP;ADSP ratio has not been measured. +5. In the discussion you state that the ATP recovery mechanism is likely due to a transfer of viable mitochondria to injured cells but you do not present any data to support such a contention. +6. In the discussion you conclude that Bioreactor-MSCs had an impact on different aspects of immune modulation and inflammation. Please justify this conclusion further. +7. There are several typographical and syntax errors. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have made a revision of their manuscript replying to the comments made by the reviewers. Additionally, the authors have included new results from a different study describing one case of successful 17- day human liver NMP perfusion with a custom setup based on commercially available equipment to promote direct translation. It is interesting the development of an strategy to increase the pool of organs for research purposes. These two studies are not correlated, as each of them uses a different setup and has different objectives. In this new context, authors should address the following: Liver NMP case. + +Some damage markers such as AST, are reduced until day 11, remaining stable until day 14. From there it rises, indicating a possible injury in liver. Authors may elaborate on the discussion section about fin tuning of the proposed setup. Images in supplementary Figure 11 have not an appropriate resolution. Authors should provide better quality images. + +Rat model + +- Authors state that after shipment, 5x104 MSC are found in the supernatant, accounting for 2.5% of the total number of MSC. If 20x107 were seeded in the bioreactor, this ratio is not correct. Please review this data. + +- There is a pronounced difference between the number of MSC seeded in the bioreactor (20x107) and the retrieved cells after perfusion (106). Although authors show no increase in CK18 during liverless perfusion, this 95% decrease in the number of cells rises a concern about the impact of shipment and perfusion conditions on MSC, including cell death, and the effects observed in the present study. Authors must explain the possible causes. + +- In line with the previous comment, authors could measure viable MSC cell numbers in the bioreactor after shipping and after the recovery time prior to NMP to identify the actual amount of MSC at the beginning of NMP, in case they die or proliferate. + +- Cell dosing is still a limitation authors should include. Extrapolation of their data indicates the need of 12 x 1010 cells for an 80 Kg person. Generating these numbers and developing/dedicating bioreactors for this purpose are holding back the translation of this setup, which should be reflected in the discussion. + +- AGP and A2M increase during perfusion, common markers for liver damage. Authors could mention how they will solve this issue. + +- Authors describe immune cell leakage from the liver based on particle size found in the perfusate outflow. However, more cell types, such as endothelial cell or MSC could, flush through the system. Moreover, identification of EV origin according to size is not correct, as all cells can secrete vesicles of different sizes. It is not possible to sustain this claim with the presented data. + +<--- Page Split ---> + +## General comments + +General commentsTranslation from preclinical work to human liver NMP should be proposed carefully. These studies are different at several levels such as perfusion fluid composition, organ preservation, oxygen carriers, equipment used (bioreactor, blood hemodialysis unit, etc.) + +Overall, the translational value of the preclinical study should be assumed carefully. Authors themselves are aware of the differences between their preclinical model and human studies in the responses to the reviewer's comments. The authors may consider mentioning that translation in the future after confirming result in large animal models could be possible. + +## Reviewer #3 + +(Remarks to the Author) + +Study A: The authors report on a single liver graft perfused using a modified commercial system. This system is very similar to the one described by Lau et al(1)., with the primary difference being the use of continuous venovenous hemodiafiltration (CVVHDF) instead of a less expensive dialysis system. The authors reported graft survival for up to 17 days. However is unclear what viability criteria were used. Only bile production and lactate levels are included. Study B reports on the addition of an MSC- bioreactor to an NMP circuit in an isolated rat model, noting decreased injury markers. However, the rat liver was perfused for only 4 hours, and no transplant was performed. + +Please address the following points: + +## Study A + +1. The authors describe a system very similar to that of Lau et al., based on a commercially available perfusion machine, the Liver Assist. Similar to the Lau et al.'s system(1), the authors' system includes a long-term oxygenator, gas mixer, and a blood purification system for dialysis. Instead of a standard dialysis system, the authors used a continuous hemodiafiltration (CVVHDF) technique. The authors claim that CVVHDF offers significant advantages over dialysis by allowing the removal of larger molecules. However, this assertion is not supported by any evidence. Both techniques have their pros and cons and mainly filter water-soluble molecules. CVVHDF provides limited clearance of protein-bound solutes. Besides clearing water-soluble toxins, dialysis and CVVHDF also eliminate nutrients and hormones. The authors should moderate their claim of longer survival because of the use of CVVHDF instead of dialysis. They should also discuss that CVVHDF requires a dedicated machine, while dialysis is more available, cheaper and easier to integrate. Furthermore, the authors should acknowledge that their model is very similar to the one already described by Lau et al. + +2. Donor graft quality is a significant determinant of long-term survival, as described by Lau et al(1). + +Eshmunimov et al. (2) and Lau et al.(1) used organs unsuitable for transplantation, these graft had usually a quite long cold ischemia time and were mainly steatotic or DCD grafts. The authors used a graft from a 56-year-old patient with unresectable colorectal metastases. While using a graft with liver tumors is an interesting model, it is not comparable to the poor-quality grafts used by Lau et al.(1) and Eshmunimov et al.(2) The graft clearly was of higher quality considering the likely short cold and warm ischemia, although data about the cold ischemia time are missing. The authors should discuss that despite previously receiving chemotherapy the quality of graft used and the minimal ischemic injury has played a major role in graft survival. + +3. Data about liver viability are very limited. No viability criteria are defined. A liver can continue to produce bile even in the presence of massive liver necrosis. Detailed data of histology at various time points is needed, The authors describe massive necrosis at the later stage of perfusion, but data are very limited. + +Data about ATP content, and oxygen consumption are also missing. Such data should be included. + +4. The title is misleading. The authors report a significant worsening of liver function on day 15, yet it is unclear why the experiment was stopped on day 17. Viability criteria should be defined, and the contribution of CVVHDF in reducing lactate levels should be discussed. + +5. Important details of the protocol used are missing. What type of Total Parenteral Nutrition (TPN) and concentration was used? Were biliary acids used? Compared to Lau et al. and Eshmunimov et al., RBCs were added during perfusion, which may suggest increased hemodialysis by the CVVHDF. This should be discussed. + +6. Was any culture of the perfusate performed? Lau et al. (3) demonstrated an increased risk of infection with prolonged duration of perfusion. This should be discussed. + +7. Only a single experiment is reported. The limitations of such a single experiment should be more extensively discussed. + +Study B: + +1. The main innovation is the modification of a rat liver normothermic machine perfusion system to incorporate a bioreactor for mesenchymal stem cell (MSC) therapy. However, I have reservations regarding the translational value of this model. Rodent models have limited reproducible effects in humans. The sole advantage of a rat model is the potential for transplanting perfused organs, yet no transplant was performed. Additionally, the ex vivo perfusion was limited to just 280 minutes, and the cold ischemia time was notably short. Considering that the authors aim to support the possibility of manipulating organs during long-term perfusion, the animal model used seems to have limited translational value. The authors should better acknowledge the limitations of their model and explain why they did not proceed with transplantation. + +<--- Page Split ---> + +2. Considering the limited number of animals per group, the authors should discuss the technical challenges of perfusing small liver grafts which may have affected the results. Also how sample size was determined is not very clear and require better justification. + +3. The model used included a very short cold ischemia time and a short duration of perfusion, only 4 hours. The only conclusion that can be made is that the ischemia reperfusion injury was reduced. A model with prolonged perfusion and large animal model is needed to demonstrate "organ manipulation". + +4. The title of the paper, "From 17-day human liver machine perfusion to a preclinical mesenchymal cell bioreactor towards a long-term ex-situ platform for organ manipulation," is quite misleading. Study A included only one long-term perfusion, and Study B comprised only short-term perfusion of just 4 hours. + +5. The authors reported the induction of factors involved in resolution/regeneration. However the authors have very limited data suggesting regeneration. Most of their results could be explained with a reduction of IR injury. Furthermore the short duration of perfusion (4 hrs) limits any conclusion. Please justify this conclusion further. + +## REFERENCES + +1) Lau, N. S. et al. Long-term ex situ normothermic perfusion of human split livers for more than 1 week. Nat. Commun. 14, (2023). +2) Eshmuninov, D. et al. An integrated perfusion machine preserves injured human livers for 1 week. Nat. Biotechnol. 38, 189-198 (2020). +3) Lau NS, Ly M, Dennis C, Toomath S, Huang JL, Huang J, Ly H, Chanda S, Marinelli T, Davis R, Liu K, McCaughan G, Crawford M, Pulitano C. Microbial Contamination During Long-term Ex Vivo Normothermic Machine Perfusion of Human Livers. Transplantation. 2024 Jan 1;108(1):198-203. + +Version 2: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have reviewed their manuscript according to suggestions and concerns made by the reviewers. Additionally, they have included some pilot results in a large animal NMP model to improve the translational impact of their work. Here are some issues that need to be addressed. + +1) According to the international society for cell and gene therapy, the correct term for MSC is now "mesenchymal stromal cells" (Viswanathan et al., Cytotherapy, 2019). Authors should update their manuscript. + +2) Although the addition to the NMP circuit might be novel, culture of MSC in hollow fiber bioreactors is already known. Additionally, commercial distribution of MSC has been offering the possibility of shipping cultured MSC in culture flasks or other formats, keeping their properties intact after transportation, which is quite similar to the logistic procedure described here. Novelty of this fact is scarce. + +3) Authors need to update figure 4 and supplemental data including all cell types susceptible to be measured in "wash-outs", (i.e. MSC, endothelial cells, etc.) Even in low numbers, MSC can still detach and flush through the system. + +4) Authors mention the section supplementary methods 1.12 which is not included in the supplementary material. + +5) Supplementary figure 12. Regardless of measured parameters used to evaluate success in NMP, visual evaluation is still key during perfusion. In the images, there is a clear difference in perfusion between both organs, with the one from the MSC group having a paler color. This unequivocally show bad perfusion of the organ. + +6) There is a discrepancy regarding the number of cells used for the pig experiments described in the results and methods section. 37x107 cells noted in the results section does not equal 37 million cells (20 ml of a 1.85x106 cells/ml suspension). Please correct accordingly. + +7) Authors have used 2x10^7 MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. Comparison of results is therefore very limited between both models. + +<--- Page Split ---> + +8) Additionally, cell density in bioreactors is extremely different: 18500 MSC per cm2 for pig bioreactor vs. 40000 MSC/cm2 in rat bioreactors. Cell density is known to alter MSC functionality, secretory profile and immunomodulatory potential. Authors should justify these differences and elaborate about possible consequences. + +9) The large animal model used by the authors lacks potential for translation. Clinical strategies used in human liver NMP trials include perfusion times ranging from 9-20+ hours. Although authors are presenting preliminary results in a large animal preclinical model coupled to an MSC bioreactor, clinical translation assumptions should be made carefully, as the author do not present sufficient data supporting their claims. + +10) Even though these are preliminary results, only \(n = 3\) animals were used for the large animal study. This small sample size needs justification and sample size calculation need to be explained. + +## Reviewer #2 + +(Remarks to the Author) + +The incorporation of an MSC- bioreactor in a normothermic machine perfusion (NMP) circuit is a novel concept although other groups are working in this area. There is a body of work demonstrating that MSCs can ameliorate ischaemia reperfusion injury and it is known that this is due to the release of EVs and paracrine factors from the stem cells and that MSCs themselves have a number of potentially adverse effects. The isolated organ preservation offered by NMP removes problems with targeting stem cells to a specific organ and bypassing the reticuloendothelial system. NMP also reduces the risk of off-target adverse effects. The addition of a bioreactor to the NMP circuit is a logical development. The authors have demonstrated the feasibility of this new approach and in the rat model evidence that the addition of a bioreactor can counter some of the changes associated with I/R injury. + +There are a number of issues that the authors should consider: + +1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. +2. The procine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model that the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. +3. The group size for the porcine experiments is small at \(n = 3\) and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& Ipha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. +4. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. + +## Version 3: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have replied to most of the reviewers comments, with a very elaborated explanation in some cases. + +Some questions still arise: + +- The authors missed one of the previous comments: Authors have used 2x10^7 MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. Comparison of results is therefore very limited between both models. + +- Regarding MSC detaching from the bioreactor. MSC do not flush through during liver-less perfusion. However, as fluid composition changes due to the liver secreted moleculas and cytokines, there is no data confirming this subject as conditions change. The authors do not provide any direct proof of the cell types leaving the NMP system. Therefore, all cells present in the NMP system should be taken into account, including MSC. + +- The authors have provided preliminary data on the technical feasibility of coupling an MSC bioreactor in a porcine NMP setup. The objective was to set a translatable setup for human use in the clinic. With this in mind, the very small population size (n=3) do not allow to obtain any conclusion and larger studies need to be carried out. + +<--- Page Split ---> + +(Remarks to the Author) + +1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. + +The authors address the use of rodent models on the basis that this is common practice and that rodent models are an important step in the evolution of new technologies. These are reasonable points but still don't answer the issue of translatability. There is not much the authors can do about this limitation. + +2. The porcine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model than the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. + +The authors have answered my concerns to some extent. The use of a porcine model provides useful feasibility evidence that the technology can be upscaled to a large animal set-up that resembles the clinical situation. + +3. The group size for the porcine experiments is small at \(n = 3\) and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& Ipha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. + +3. My comments relating to the small group size in the small group size in the porcine experiments have been acknowledged by revision of the supplementary information. In relation to the short duration of the perfusion experiments, the authors are planning experiments with more relevant prolonged perfusion. It would have strengthened the work to wait for these results. + +4. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. The authors agree that declined human livers that have been declined for transplantation will be useful in the future. + +Overall, the authors have explored a potentially important development in normothermic organ perfusion and they present a useful dataset. Nonetheless, their findings are preliminary and the further studies suggested by reviewers and planned by the authors would lend much more weight to + +<--- Page Split ---> + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS + +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +We thank the reviewers for their helpful feedback. Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<--- Page Split ---> + +## Reviewer #1 + +The authors have skillfully design a promising platform to study the effect of mesenchymal stem cells (MSC) during ex vivo perfusion of rat livers. This is a very interesting approach to overcome some issues observed in direct MSC infusion in organ- in- a- pump models, like microvasculature clogging. The main successful points are the modification of a rat liver normothermic machine perfusion (NMP) system to include a bioreactor for MSC cell therapy and the maintenance of hepatocyte viability during MSC- NMP. However, there are some concerns that need to be addressed: + +## Introduction + +1. Authors claim that MSC only activate their secretory potential after exposure to inflammatory stimuli. However, this is not true as demonstrated earlier (i.e. Park et al., Int J Stem Cells., 2009) but MSC secretory profile is modulated by the microenvironment (i.e. Burja et al., Curr Res Transl Med., 2020). + +We thank the Reviewer for stressing this concept and for providing an additional reference demonstrating the plasticity of the immunoregulation mediated by adipose tissue (AT)- MSCs, which can mount distinct responses to different inflammatory stimuli. These observations reinforce the rationale behind the design of our platform, where stem cells' secretory activity can be specifically activated by the inflammatory mediators release by each individual liver. The sentence "...MSCs secretory activity is induced only after cell exposure to an inflammatory microenvironment, ..." was re-formulated as follows: "...MSCs secretory activity is boosted after exposure to inflammatory microenvironment and different inflammatory stimuli can elicit distinct responses, ..." (lines 214- 215, page 9 of the tracked version of the revised manuscript). + +## Methods + +2. MSC in vitro culture. Authors describe "MSCs were cultured at a concentration of \(2^{*}105\) in \(14\mathrm{mL}\) in aMEM medium". What vessel was used to seed the cells and what is the final seeding density in this vessel? + +Two hundred thousand human AT- MSCs were cultured at a concentration of \(14.3^{*}10^{4}\) cells/ml in \(75\mathrm{cm}^2\) culture flasks (Sarstedt AG & Co. KG, Numbrecht, Germany), in \(14\mathrm{mL}\) of complete medium. This information was added to the Supplementary Methods 1.1.1. + +3. Characterization of MSC after NMP. Cells were retrieved from the bioreactor. Were the cells directly analysed (cytometry). For how long were the MSC re-cultured for the morphology tests and what were the conditions of that culture? (cell seeding density, culture time, etc.). Also, did the authors count the total number of cells retrieved from the bioreactor and compared with the original number? + +<--- Page Split ---> + +We thank the Reviewer for noting that relevant information was missing. The methods for cell detachment from the bioreactor and processing before flow cytometry have been added to Supplementary Methods 1.1.3. + +## 4. Exposure to perfusion fluid may have altered their metabolism and survival, acting as a licensing agent itself. + +The Reviewer's comment is pertinent. As previously demonstrated by Sierra Parraga and coworkers, the conditions required to perform the NMP procedure influence MSCs viability and function. In particular, exposure of thawed MSCs to the perfusion fluid and the suspension condition are associated with reduced cell viability, slower mitochondrial metabolism, and generation of reactive oxygen species (ROS) \(^{1,2}\) . Conversely, the authors reported no negative influences of the perfusion fluid on survival when the cells are kept under adherent conditions \(^{1}\) . + +The innovative configuration of our platform allows keeping the cells in their optimal culture environment during NMP, i.e. adherent to the bioreactor fibers. Moreover, the use of a bioreactor provides the cells with a resting period after thawing, during which they can recover from structural damage and oxidative stress induced by cryopreservation. Consistently, we did not reveal massive cell death during liverless- NMP experiments. In fact, no circulating cells, detached from the bioreactor, were detected in the perfusate samples, while the release of the apoptotic marker caspase- cleaved keratin 18 (CK18) remained stable throughout the procedure (Figure 3). + +Therefore, the particular setting of the present model offers MSCs the opportunity to recover from cryopreservation, while ensuring optimal culture conditions during NMP. These points were further clarified in the Introduction (lines 153- 155, page 7 of the tracked version of the revised manuscript) and in the Discussion (lines 373- 375, page 14 of the tracked version of the revised manuscript). + +5. Flow cytometry. For reproducibility purposes, please add the reference numbers of antibodies used for flow cytometry and other relevant reagent. + +These details have been added to Supplementary Methods 1.1.3 + +6. Liver NMP. Perfusion took place in two phases: a warming phase and a stable normothermic phase. Was the bioreactor connected to he circuit during the entire perfusion (warming+stable phases)? Similar to the question related to shipment, rewarming time might affect MSC survival and metabolism during this time. + +The bioreactor was attached to the circuit immediately before liver connection and was therefore exposed to a temperature ranging from \(24 - 26^{\circ}\mathrm{C}\) , which was increased to \(37^{\circ}\mathrm{C}\) over \(40\mathrm{min}\) . As suggested by the Reviewer, we investigated whether MSCs underwent cell death during rewarming, by assessing the release of human CK18 into the perfusate. The data show that the degree of apoptosis activation during liver- NMP is similar to that observed during liverless- NMP, indicating that the cells did not experience excessive distress during the different phases of the liver- NMP procedure. These results were added to the Supplementary Results 1.2.10 + +7. The authors seeded \(20*10*7\) MSC in a bioreactor. Is this number constant throughout the perfusion experiment? Do MSC die and are replaced by proliferating MSC? These dead cells might be responsible for the uncontrolled release of cytokines. + +As discussed at points 3 and 5 of the present document, no massive cell death was observed during the experiments. + +<--- Page Split ---> + +## 8. In addition, average rat liver weight is 4-5 grams which results in a MSC dose of \(4*10^{-9}\) MSC/kg, an extremely high dose which has a poor translation towards a clinically relevant setup. + +In our experiments, the average rat liver weight was 13- 15 g; as a result, \(1.5*10^{6}\) cells were used per gram of liver, which, as highlighted by the Reviewer, is about 1000- times higher than the dosage currently adopted in clinical trials. However, we believe that this is a strength, rather than a limitation. In fact, the application of a high dosage- cell therapy appears essential for maximizing liver cell exposure to the MSCs secretome within the short time window offered by the NMP procedure. By completely eliminating the risk of embolism, the bioreactor- based setting enables to safely increase the quantity of stem cells delivered in a single administration. Additionally, the use of a bioreactor avoids cell migration to target tissues, thus preventing possible cell de- differentiation or long- term retention. Overall, this represents a significant clinical advantage, considering that for certain patients and diseases, multiple administrations of standard- dose MSCs are needed to achieve the desired therapeutic effect \(^{3}\) . + +In support of the practical applicability of our platform, we demonstrated in a pilot study the feasibility of integrating the MSCs- bioreactor into a circuit currently used in the clinical setting (Abstract \(\mathrm{N}^{\circ}1307\) , "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, we performed NMP of porcine livers procured from cardiac death donors, using the Liver Assist® machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. + +These preliminary data, together with the growing availability of novel technologies for cell upscaling and manufacturing \(^{3,4}\) , reinforce the translational value of our advanced circuit. + +9. In addition, authors sent MSC in a bioreactor from one laboratory to another at room temperature. Culture temperature is key for MSC survival and temperatures lower to \(37^{\circ}\) C are deleterious (Pratiwi et al., Cytotherapy, 2019). Did the authors study the status of MSC after the shipment? + +Bioreactor supernatants were collected upon devices arrival to the Milan Lab and were then analyzed using an automated cell counter, gas-analysis, and ELISA. Results of this analysis are reported in the session Assessment of MSCs viability after bioreactor shipment pg 9-10 of the original version of the manuscript and in the Supplementary Table 2. + +## Results + +1. The authors describe an increase in certain metabolites such as lactate, IL-6, IL-1ra, among other, during liverless NMP+bioreactor. However, these are inflammatory cytokines and lactate production has been related to increased ROS production (i.e. Li et al., Signal Transduct Target Ther., 2022). Though the authors address the increase in inflammatory cytokines as a positive results, they should discuss the inflammatory perfustate profile and elaborate on this in the discussion section as it appears to be a setback of their NMP circuit. + +<--- Page Split ---> + +The production of lactate, along with glucose consumption, indicates that the cells were metabolically active and initiated anaerobic glycolysis during Liverless- NMP. + +With regard to the increased cytokine perfusate concentration, a mild inflammatory activation of the cells seeded in the bioreactor was expected, since both shipment and the NMP procedure itself represent stress- inducing factors. + +Accepting the Reviewer's suggestion, we investigated whether MSCs were exposed to oxidative stress, by assessing the release of 8- hydroxy- 2'- deoxyguanosine (8- OHdG) in the perfusates collected during Liverless- NMP. We found increasing concentrations of 8- OHdG over the procedure (from \(15630\pm 2211\mathrm{pg}\) at \(1\mathrm{h}\) to \(19965\pm 3532\mathrm{pg}\) at \(4\mathrm{h}\) ). However, higher amounts \((28211\pm 1489\mathrm{pg})\) were detected in the supernatant collected from the bioreactor immediately after device arrival to the Milan lab. This interesting observation indicates that MSCs experience an oxidative burst during shipment and highlight the need for a technical improvement of this stage, for example by supplementing the culture medium with antioxidants (vitamin C, glutathione). We thank the Reviewer for pointing out the need to refine these important aspects, in view of a potential translational use of our platform. + +## 2. Immune cells outflow. Authors describe outflow of an increased number of immune cells when the bioreactor is connected during NMP. H. however, they do not show data for cell characterization in the outflow perfusate. + +Accepting the Reviewer's suggestion, we performed a qualitative assessment of individual donor cell populations removed during the initial wash- out. Briefly, cell pellets obtained from wash- out samples were originally counted using the \(\mathrm{Scpeptr^{TM}}\) cell counter (Merck KGaA) equipped with \(40\mu \mathrm{m}\) sensors, according to the Coulter principle. The acquired data were further analyzed based on particle size and volume using the software \(\mathrm{Scpeptr^{TM}}2.0\) software pro (Merck KGaA) \(^{5}\) . The obtained results are presented in Figure 5, while methods are detailed in the Supplementary Information 1.1.8. Note that, since the bioreactors used in this research have membranes with pores that are \(150\mathrm{nm}\) in size, the particles found in the perfusate originate solely from the liver. + +We thank the Reviewer for his comment which lead to a significant improvement in the description of the wash- out samples. + +## 3. EV origin. The authors hint that observed differences in EV size are related to their hepatocyte or MSC origin. This is a difficult assumption to make based only on EV size. + +We agree with the Reviewer and acknowledge that the assessment of EV size alone is not entirely adequate to attribute their origin to either stem cells or the liver. + +However, due to the inherent technical difficulties in analyzing Oxyglobin- enriched samples, a more thorough evaluation of the EVs released in the perfusate was unfeasible. Based on this, the results of EVs analysis were excluded from the main findings and relocated in the Supplementary Results 1.2.4. + +## 4. pH stabilization. The authors claim that MSC in the bioreactor regulate the pH of the perfusate. However, exposure to MSC medium present in the bioreactor, which contains a buffered solution to maintain pH, might be the responsible factor of pH stabilization + +After connection to the NMP circuit, the bioreactors were filled with perfusion fluid ( \(100\mathrm{ml}\) ), while the cell medium ( \(10\mathrm{ml}\) ) was progressively removed over the NMP procedure. Perfusate pH stabilization appears therefore the consequence of an active modulation mediated by MSCs. Bioreactor- based perfusion was indeed associated with changes in \(\mathrm{pCO_2}\) as well as in various + +<--- Page Split ---> + +electrolytes which can directly influence perfusate pH, as reported in Supplementary Figure 6 - Gas analysis of perfusate samples collected during liver- NMP. + +<--- Page Split ---> + +## Reviewer #2 + +This study reports the effects of the addition of an MSC- bioreactor to the NMP circuit in an isolated rat liver model. The study mainly shows the safety and feasibility of this approach and some beneficial effects of using an MSC bioreactor approach rather than thawed MSCs. The MSC- bioreactor effects included decreased injury markers, increased bile production; increased acute phase proteins; more effective washout of blood; reduced ATP depletion; absence of succinate accumulation. Please address the following: + +1. You state that the 'translational value is high'. This needs justification when using a rodent model as many such models have been shown not to have reproducible effects in large animals and humans. + +Although we acknowledge the difficulties encountered when transferring the findings from preclinical studies to the clinical scenario, we deem that starting from a rodent model was an essential step in the development of the novel circuit for liver NMP, where the livers can be treated with a MSCs- based therapy before transplantation. In fact, establishment of such an innovative platform required the consideration and implementation of various technical aspects related to both MSCs and the NMP procedure, including cell type selection, seeding density, design of the bioreactor circuit, and oxygen supply to the liver. The use of rodent models shows several advantages compared to large animals, including a more rapid recovery of hepatic homeostasis and function, less intra- experimental group variability, and greater selection of specific laboratory reagents. Thus, small animal models emerge as the optimal choice at this early stage of the research. + +The knowledge gained with the present study was used to guide the translational application of the novel platform to porcine liver NMP (Abstract \(\mathrm{N}^{\circ}\) 1307, "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, porcine livers procured from cardiac death donors were ex situ- perfused using the Liver Assist \(^{\mathrm{\textregistered}}\) machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. This pilot study demonstrates the practical applicability of our novel configuration when the clinical devices/consumables are used. + +These observations underscore the translational value of the present proof- of- concept study in a rodent model. In response to the Reviewer's comment, we improved the clarity of the message delivered, by reformulating the original sentence as follows: "Overall, these observations support the high translational value of the present advanced NMP platform to inform the application of this innovative setup in large animal models, and, ultimately, in the clinical setting" (lines 385- 388, page 13 of the tracked version of the revised manuscript). + +## 2. Although you acknowledge that the cold ischaemic time is very short, this is. major limitation with little clinical relevance. + +As stated by the Reviewer in the previous comment, rodent models show inherent differences relative to large animals and humans. With regard to the liver anatomy, there is an increasing dependence on the hepatic artery contribution for lobular perfusion in larger mammals compared with small organisms \(^{6}\) . This affects the outcome of liver transplantation; for example, liver transplants in mice do not need a hepatic artery anastomosis to avoid biliary complications, whereas those in humans do \(^{6}\) . The anatomic peculiarities also determine qualitative differences in the pathophysiological + +<--- Page Split ---> + +responses to stress stimuli between the livers of the various species. Therefore, a direct comparison of human and experimental procedures may not be entirely adequate when time intervals are considered. + +Consistently, the present research shows that a different duration of ischemia enabled to obtain the same outcome. In fact, the IR challenge applied in this study not only induced the release of cytolysis markers, but it likewise promoted many of the detrimental biological events typically triggered by IR, including intracellular ATP depletion (Figure 6), succinate accumulation (Figure 6), and production of inflammatory mediators (Figure 7). + +Thus, although the ischemic time is shorter than that observed in the clinical setting, the experimental findings support the reliability of our model in reproducing the key pathophysiological features of liver IR injury and support its translational use as a useful starting point for future studies in porcine and human livers. + +More prolonged or extreme stimuli can be applied to our model. However, here we describe the set- up phase of NMP+bioreactor and we believe that smaller but significant injuries could lead to more informative results in this research phase. + +## 3. Please discuss the potential effects of raised TNF and IL-6 in the bioreactor group. These acute phase proteins can have pro-inflammatory as well as protective effects. + +As highlighted by the Reviewer, IL- 6 and TNF- \(\alpha\) can exert either protective or harmful effects depending on various factors, including the amount released, the duration of their expression, and the underlying liver condition. + +In the early stages of IRI, TNF- \(\alpha\) and IL- 6 are secreted as part of the pathophysiological immune response to the ischemic damage \(^{7,8}\) . Their role involves recruiting immune cells to the injured site and activating pathways related to tissue repair and removal of damaged cells \(^{9}\) . In addition, TNF- \(\alpha\) and IL- 6 are established key factors in the onset of liver cell regeneration \(^{10}\) . + +In the bioreactor- based perfusion, concomitant with increased TNF- \(\alpha\) and IL- 6 perfusate concentration, there was a rise of Adiponectin, CTGF, HGF, and, at the initial stage after reperfusion, of IL- 13 (Figure 7). Compared to the standard NMP, the treated group likewise exhibited lower perfusate concentration of different mediators related to inflammation (Figure 7). This molecular scenario can be interpreted as a coordinated adaptive response to the reperfusive injury. The observed induction of Adiponectin is particularly relevant in this regard, due to its well- known properties in the mitigation of inflammation \(^{11,12}\) . + +We thank the Reviewer for pointing out the need to improve the discussion of these results (lines 417- 435, page 15- 16 of the tracked version of the revised manuscript). + +## 4. It is difficult to make conclusions about ATP depletion when the ATP::ADSP ratio has not been measured. + +Accepting the Reviewer's suggestion, we performed additional experiments using High- performance liquid chromatography (HPLC) to investigate the concentration of ATP breakdown products in liver biopsies, according to \(^{13}\) . The results have been added to the main text (lines 296- 297, pages 11 of the tracked version of the revised manuscript), while the methods are described in Supplementary information 1.1.11 + +## 5. In the discussion you state that the ATP recovery mechanism is likely due to a transfer of viable mitochondria to injured cells but you do not present any data to support such a contention. + +Thank you for your note. We reformulated the paragraph dedicated to MSCs- induced protection of cell energy status (lines 401- 416, page 15 of the tracked version of the revised manuscript), specifying that the transfer of mitochondria from stem cells to liver tissue has been proposed as a potential + +<--- Page Split ---> + +underlying mechanism based on previous evidence \(^{14,15}\) . Further research is required to verify whether this process plays a role in the context of hepatic IRI. + +6. In the discussion you conclude that Bioreactor-MSCs had an impact on different aspects of immune modulation and inflammation. Please justify this conclusion further. These points have been further discussed in lines 417-435 of the tracked version of the revised manuscript (pages 15-16). + +7. There are several typographical and syntax errors. + +Thank you very much for highlighting these inaccuracies. After a thorough of the manuscript, all the imprecisions have been corrected. + +<--- Page Split ---> + +## References + +1. Sierra Parraga, J. M. et al. Effects of normothermic machine perfusion conditions on mesenchymal stromal cells. Front. Immunol. 10, 1–11 (2019).2. Deng, B. et al. Removal from adherent culture contributes to apoptosis in human bone marrow mesenchymal stem cells. Mol. Med. Rep. 15, 3499–3506 (2017).3. Hassan, M. N. F. Bin et al. Large-Scale Expansion of Human Mesenchymal Stem Cells. Stem Cells Int. 2020, (2020).4. Panchalingam, K. M., Jung, S., Rosenberg, L. & Behie, L. A. Bioprocessing strategies for the large-scale production of human mesenchymal stem cells: A review Mesenchymal Stem/Stromal Cells - An update. Stem Cell Res. Ther. 6, 1–10 (2015).5. Merck KGaA. Size-based Immunomonitoring using the Scepter™ 3.0 Handheld Cell Counter. Application note https://www.sigmaaldrich.com/IT/it/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/size-based-immunomonitoring-scepter-handheld-cell-counter (2023).6. Kruepunga, N., Hakvoort, T. B. M., Hikspoors, J. P. J. M., Köhler, S. E. & Lamers, W. H. Anatomy of rodent and human livers: What are the differences? Biochim. Biophys. Acta - Mol. Basis Dis. 1865, 869–878 (2019).7. Soares, R. O. S., Losada, D. M., Jordani, M. C., Évora, P. & Castro-E-Silva, O. Ischemia/reperfusion injury revisited: An overview of the latest pharmacological strategies. Int. J. Mol. Sci. 20, (2019).8. Wu, M. Y. et al. Current Mechanistic Concepts in Ischemia and Reperfusion Injury. Cell. Physiol. Biochem. 46, 1650–1667 (2018).9. Blindenbacher, A. et al. Interleukin 6 is important for survival after partial hepatectomy in mice. Hepatology 38, 674–682 (2003).10. Moris, D. et al. Mechanistic insights of rapid liver regeneration after associating liver partition and portal vein ligation for stage hepatectomy. World J. Gastroenterol. 22, 7613–7624 (2016).11. Ruan, H. & Dong, L. Q. Adiponectin signaling and function in insulin target tissues. J. Mol. Cell Biol. 8, 101–109 (2016).12. Blandin, A. et al. Extracellular vesicles are carriers of adiponectin with insulin-sensitizing and anti-inflammatory properties. Cell Rep. 42, (2023).13. Meszaros, A. T. et al. Mitochondrial respiration during normothermic liver machine perfusion predicts clinical outcome. EBioMedicine 85, (2022).14. Peruzzotti-Jametti, L. et al. Neural stem cells traffic functional mitochondria via extracellular vesicles. PLoS Biology vol. 19 (2021).15. Phinney, D. G. et al. Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs. Nat. Commun. 6, 1–15 (2015). + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS + +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +We thank the reviewers for their helpful feedback. Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<--- Page Split ---> + +## Reviewer #1 + +The authors have skillfully design a promising platform to study the effect of mesenchymal stem cells (MSC) during ex vivo perfusion of rat livers. This is a very interesting approach to overcome some issues observed in direct MSC infusion in organ- in- a- pump models, like microvasculature clogging. The main successful points are the modification of a rat liver normothermic machine perfusion (NMP) system to include a bioreactor for MSC cell therapy and the maintenance of hepatocyte viability during MSC- NMP. However, there are some concerns that need to be addressed: + +## Introduction + +1. Authors claim that MSC only activate their secretory potential after exposure to inflammatory stimuli. However, this is not true as demonstrated earlier (i.e. Park et al., Int J Stem Cells., 2009) but MSC secretory profile is modulated by the microenvironment (i.e. Burja et al., Curr Res Transl Med., 2020). + +We thank the Reviewer for stressing this concept and for providing an additional reference demonstrating the plasticity of the immunoregulation mediated by adipose tissue (AT)- MSCs, which can mount distinct responses to different inflammatory stimuli. These observations reinforce the rationale behind the design of our platform, where stem cells' secretory activity can be specifically activated by the inflammatory mediators release by each individual liver. The sentence "...MSCs secretory activity is induced only after cell exposure to an inflammatory microenvironment, ..." was re-formulated as follows: "...MSCs secretory activity is boosted after exposure to inflammatory microenvironment and different inflammatory stimuli can elicit distinct responses, ..." (lines 214- 215, page 9 of the tracked version of the revised manuscript). + +## Methods + +2. MSC in vitro culture. Authors describe "MSCs were cultured at a concentration of \(2^{*}105\) in \(14\mathrm{mL}\) in aMEM medium". What vessel was used to seed the cells and what is the final seeding density in this vessel? + +Two hundred thousand human AT- MSCs were cultured at a concentration of \(14.3^{*}10^{4}\) cells/ml in \(75\mathrm{cm}^2\) culture flasks (Sarstedt AG & Co. KG, Numbrecht, Germany), in \(14\mathrm{mL}\) of complete medium. This information was added to the Supplementary Methods 1.1.1. + +3. Characterization of MSC after NMP. Cells were retrieved from the bioreactor. Were the cells directly analysed (cytometry). For how long were the MSC re-cultured for the morphology tests and what were the conditions of that culture? (cell seeding density, culture time, etc.). Also, did the authors count the total number of cells retrieved from the bioreactor and compared with the original number? + +<--- Page Split ---> + +We thank the Reviewer for noting that relevant information was missing. The methods for cell detachment from the bioreactor and processing before flow cytometry have been added to Supplementary Methods 1.1.3. + +## 4. Exposure to perfusion fluid may have altered their metabolism and survival, acting as a licensing agent itself. + +The Reviewer's comment is pertinent. As previously demonstrated by Sierra Parraga and coworkers, the conditions required to perform the NMP procedure influence MSCs viability and function. In particular, exposure of thawed MSCs to the perfusion fluid and the suspension condition are associated with reduced cell viability, slower mitochondrial metabolism, and generation of reactive oxygen species (ROS) \(^{1,2}\) . Conversely, the authors reported no negative influences of the perfusion fluid on survival when the cells are kept under adherent conditions \(^{1}\) . + +The innovative configuration of our platform allows keeping the cells in their optimal culture environment during NMP, i.e. adherent to the bioreactor fibers. Moreover, the use of a bioreactor provides the cells with a resting period after thawing, during which they can recover from structural damage and oxidative stress induced by cryopreservation. Consistently, we did not reveal massive cell death during liverless- NMP experiments. In fact, no circulating cells, detached from the bioreactor, were detected in the perfusate samples, while the release of the apoptotic marker caspase- cleaved keratin 18 (CK18) remained stable throughout the procedure (Figure 3). + +Therefore, the particular setting of the present model offers MSCs the opportunity to recover from cryopreservation, while ensuring optimal culture conditions during NMP. These points were further clarified in the Introduction (lines 153- 155, page 7 of the tracked version of the revised manuscript) and in the Discussion (lines 373- 375, page 14 of the tracked version of the revised manuscript). + +5. Flow cytometry. For reproducibility purposes, please add the reference numbers of antibodies used for flow cytometry and other relevant reagent. + +These details have been added to Supplementary Methods 1.1.3 + +6. Liver NMP. Perfusion took place in two phases: a warming phase and a stable normothermic phase. Was the bioreactor connected to he circuit during the entire perfusion (warming+stable phases)? Similar to the question related to shipment, rewarming time might affect MSC survival and metabolism during this time. + +The bioreactor was attached to the circuit immediately before liver connection and was therefore exposed to a temperature ranging from \(24 - 26^{\circ}\mathrm{C}\) , which was increased to \(37^{\circ}\mathrm{C}\) over \(40\mathrm{min}\) . As suggested by the Reviewer, we investigated whether MSCs underwent cell death during rewarming, by assessing the release of human CK18 into the perfusate. The data show that the degree of apoptosis activation during liver- NMP is similar to that observed during liverless- NMP, indicating that the cells did not experience excessive distress during the different phases of the liver- NMP procedure. These results were added to the Supplementary Results 1.2.10 + +7. The authors seeded \(20*10*7\) MSC in a bioreactor. Is this number constant throughout the perfusion experiment? Do MSC die and are replaced by proliferating MSC? These dead cells might be responsible for the uncontrolled release of cytokines. + +As discussed at points 3 and 5 of the present document, no massive cell death was observed during the experiments. + +<--- Page Split ---> + +## 8. In addition, average rat liver weight is 4-5 grams which results in a MSC dose of \(4*10^{-9}\) MSC/kg, an extremely high dose which has a poor translation towards a clinically relevant setup. + +In our experiments, the average rat liver weight was 13- 15 g; as a result, \(1.5*10^{6}\) cells were used per gram of liver, which, as highlighted by the Reviewer, is about 1000- times higher than the dosage currently adopted in clinical trials. However, we believe that this is a strength, rather than a limitation. In fact, the application of a high dosage- cell therapy appears essential for maximizing liver cell exposure to the MSCs secretome within the short time window offered by the NMP procedure. By completely eliminating the risk of embolism, the bioreactor- based setting enables to safely increase the quantity of stem cells delivered in a single administration. Additionally, the use of a bioreactor avoids cell migration to target tissues, thus preventing possible cell de- differentiation or long- term retention. Overall, this represents a significant clinical advantage, considering that for certain patients and diseases, multiple administrations of standard- dose MSCs are needed to achieve the desired therapeutic effect \(^{3}\) . + +In support of the practical applicability of our platform, we demonstrated in a pilot study the feasibility of integrating the MSCs- bioreactor into a circuit currently used in the clinical setting (Abstract \(\mathrm{N}^{\circ}1307\) , "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, we performed NMP of porcine livers procured from cardiac death donors, using the Liver Assist® machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. + +These preliminary data, together with the growing availability of novel technologies for cell upscaling and manufacturing \(^{3,4}\) , reinforce the translational value of our advanced circuit. + +9. In addition, authors sent MSC in a bioreactor from one laboratory to another at room temperature. Culture temperature is key for MSC survival and temperatures lower to \(37^{\circ}\) C are deleterious (Pratiwi et al., Cytotherapy, 2019). Did the authors study the status of MSC after the shipment? + +Bioreactor supernatants were collected upon devices arrival to the Milan Lab and were then analyzed using an automated cell counter, gas-analysis, and ELISA. Results of this analysis are reported in the session Assessment of MSCs viability after bioreactor shipment pg 9-10 of the original version of the manuscript and in the Supplementary Table 2. + +## Results + +1. The authors describe an increase in certain metabolites such as lactate, IL-6, IL-1ra, among other, during liverless NMP+bioreactor. However, these are inflammatory cytokines and lactate production has been related to increased ROS production (i.e. Li et al., Signal Transduct Target Ther., 2022). Though the authors address the increase in inflammatory cytokines as a positive results, they should discuss the inflammatory perfustate profile and elaborate on this in the discussion section as it appears to be a setback of their NMP circuit. + +<--- Page Split ---> + +The production of lactate, along with glucose consumption, indicates that the cells were metabolically active and initiated anaerobic glycolysis during Liverless- NMP. + +With regard to the increased cytokine perfusate concentration, a mild inflammatory activation of the cells seeded in the bioreactor was expected, since both shipment and the NMP procedure itself represent stress- inducing factors. + +Accepting the Reviewer's suggestion, we investigated whether MSCs were exposed to oxidative stress, by assessing the release of 8- hydroxy- 2'- deoxyguanosine (8- OHdG) in the perfusates collected during Liverless- NMP. We found increasing concentrations of 8- OHdG over the procedure (from \(15630\pm 2211\mathrm{pg}\) at \(1\mathrm{h}\) to \(19965\pm 3532\mathrm{pg}\) at \(4\mathrm{h}\) ). However, higher amounts \((28211\pm 1489\mathrm{pg})\) were detected in the supernatant collected from the bioreactor immediately after device arrival to the Milan lab. This interesting observation indicates that MSCs experience an oxidative burst during shipment and highlight the need for a technical improvement of this stage, for example by supplementing the culture medium with antioxidants (vitamin C, glutathione). We thank the Reviewer for pointing out the need to refine these important aspects, in view of a potential translational use of our platform. + +## 2. Immune cells outflow. Authors describe outflow of an increased number of immune cells when the bioreactor is connected during NMP. H. however, they do not show data for cell characterization in the outflow perfusate. + +Accepting the Reviewer's suggestion, we performed a qualitative assessment of individual donor cell populations removed during the initial wash- out. Briefly, cell pellets obtained from wash- out samples were originally counted using the \(\mathrm{Scpeptr^{TM}}\) cell counter (Merck KGaA) equipped with \(40\mu \mathrm{m}\) sensors, according to the Coulter principle. The acquired data were further analyzed based on particle size and volume using the software \(\mathrm{Scpeptr^{TM}}2.0\) software pro (Merck KGaA) \(^5\) . The obtained results are presented in Figure 5, while methods are detailed in the Supplementary Information 1.1.8. Note that, since the bioreactors used in this research have membranes with pores that are \(150\mathrm{nm}\) in size, the particles found in the perfusate originate solely from the liver. + +We thank the Reviewer for his comment which lead to a significant improvement in the description of the wash- out samples. + +## 3. EV origin. The authors hint that observed differences in EV size are related to their hepatocyte or MSC origin. This is a difficult assumption to make based only on EV size. + +We agree with the Reviewer and acknowledge that the assessment of EV size alone is not entirely adequate to attribute their origin to either stem cells or the liver. + +However, due to the inherent technical difficulties in analyzing Oxyglobin- enriched samples, a more thorough evaluation of the EVs released in the perfusate was unfeasible. Based on this, the results of EVs analysis were excluded from the main findings and relocated in the Supplementary Results 1.2.4. + +## 4. pH stabilization. The authors claim that MSC in the bioreactor regulate the pH of the perfusate. However, exposure to MSC medium present in the bioreactor, which contains a buffered solution to maintain pH, might be the responsible factor of pH stabilization + +After connection to the NMP circuit, the bioreactors were filled with perfusion fluid ( \(100\mathrm{ml}\) ), while the cell medium ( \(10\mathrm{ml}\) ) was progressively removed over the NMP procedure. Perfusate pH stabilization appears therefore the consequence of an active modulation mediated by MSCs. Bioreactor- based perfusion was indeed associated with changes in \(\mathrm{pCO_2}\) as well as in various + +<--- Page Split ---> + +electrolytes which can directly influence perfusate pH, as reported in Supplementary Figure 6 - Gas analysis of perfusate samples collected during liver- NMP. + +<--- Page Split ---> + +## Reviewer #2 + +This study reports the effects of the addition of an MSC- bioreactor to the NMP circuit in an isolated rat liver model. The study mainly shows the safety and feasibility of this approach and some beneficial effects of using an MSC bioreactor approach rather than thawed MSCs. The MSC- bioreactor effects included decreased injury markers, increased bile production; increased acute phase proteins; more effective washout of blood; reduced ATP depletion; absence of succinate accumulation. Please address the following: + +1. You state that the 'translational value is high'. This needs justification when using a rodent model as many such models have been shown not to have reproducible effects in large animals and humans. + +Although we acknowledge the difficulties encountered when transferring the findings from preclinical studies to the clinical scenario, we deem that starting from a rodent model was an essential step in the development of the novel circuit for liver NMP, where the livers can be treated with a MSCs- based therapy before transplantation. In fact, establishment of such an innovative platform required the consideration and implementation of various technical aspects related to both MSCs and the NMP procedure, including cell type selection, seeding density, design of the bioreactor circuit, and oxygen supply to the liver. The use of rodent models shows several advantages compared to large animals, including a more rapid recovery of hepatic homeostasis and function, less intra- experimental group variability, and greater selection of specific laboratory reagents. Thus, small animal models emerge as the optimal choice at this early stage of the research. + +The knowledge gained with the present study was used to guide the translational application of the novel platform to porcine liver NMP (Abstract \(\mathrm{N}^{\circ}\) 1307, "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, porcine livers procured from cardiac death donors were ex situ- perfused using the Liver Assist \(^{\mathrm{\textregistered}}\) machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. This pilot study demonstrates the practical applicability of our novel configuration when the clinical devices/consumables are used. + +These observations underscore the translational value of the present proof- of- concept study in a rodent model. In response to the Reviewer's comment, we improved the clarity of the message delivered, by reformulating the original sentence as follows: "Overall, these observations support the high translational value of the present advanced NMP platform to inform the application of this innovative setup in large animal models, and, ultimately, in the clinical setting" (lines 385- 388, page 13 of the tracked version of the revised manuscript). + +## 2. Although you acknowledge that the cold ischaemic time is very short, this is. major limitation with little clinical relevance. + +As stated by the Reviewer in the previous comment, rodent models show inherent differences relative to large animals and humans. With regard to the liver anatomy, there is an increasing dependence on the hepatic artery contribution for lobular perfusion in larger mammals compared with small organisms \(^{6}\) . This affects the outcome of liver transplantation; for example, liver transplants in mice do not need a hepatic artery anastomosis to avoid biliary complications, whereas those in humans do \(^{6}\) . The anatomic peculiarities also determine qualitative differences in the pathophysiological + +<--- Page Split ---> + +responses to stress stimuli between the livers of the various species. Therefore, a direct comparison of human and experimental procedures may not be entirely adequate when time intervals are considered. + +Consistently, the present research shows that a different duration of ischemia enabled to obtain the same outcome. In fact, the IR challenge applied in this study not only induced the release of cytolysis markers, but it likewise promoted many of the detrimental biological events typically triggered by IR, including intracellular ATP depletion (Figure 6), succinate accumulation (Figure 6), and production of inflammatory mediators (Figure 7). + +Thus, although the ischemic time is shorter than that observed in the clinical setting, the experimental findings support the reliability of our model in reproducing the key pathophysiological features of liver IR injury and support its translational use as a useful starting point for future studies in porcine and human livers. + +More prolonged or extreme stimuli can be applied to our model. However, here we describe the set- up phase of NMP+bioreactor and we believe that smaller but significant injuries could lead to more informative results in this research phase. + +## 3. Please discuss the potential effects of raised TNF and IL-6 in the bioreactor group. These acute phase proteins can have pro-inflammatory as well as protective effects. + +As highlighted by the Reviewer, IL- 6 and TNF- \(\alpha\) can exert either protective or harmful effects depending on various factors, including the amount released, the duration of their expression, and the underlying liver condition. + +In the early stages of IRI, TNF- \(\alpha\) and IL- 6 are secreted as part of the pathophysiological immune response to the ischemic damage \(^{7,8}\) . Their role involves recruiting immune cells to the injured site and activating pathways related to tissue repair and removal of damaged cells \(^{9}\) . In addition, TNF- \(\alpha\) and IL- 6 are established key factors in the onset of liver cell regeneration \(^{10}\) . + +In the bioreactor- based perfusion, concomitant with increased TNF- \(\alpha\) and IL- 6 perfusate concentration, there was a rise of Adiponectin, CTGF, HGF, and, at the initial stage after reperfusion, of IL- 13 (Figure 7). Compared to the standard NMP, the treated group likewise exhibited lower perfusate concentration of different mediators related to inflammation (Figure 7). This molecular scenario can be interpreted as a coordinated adaptive response to the reperfusive injury. The observed induction of Adiponectin is particularly relevant in this regard, due to its well- known properties in the mitigation of inflammation \(^{11,12}\) . + +We thank the Reviewer for pointing out the need to improve the discussion of these results (lines 417- 435, page 15- 16 of the tracked version of the revised manuscript). + +## 4. It is difficult to make conclusions about ATP depletion when the ATP::ADSP ratio has not been measured. + +Accepting the Reviewer's suggestion, we performed additional experiments using High- performance liquid chromatography (HPLC) to investigate the concentration of ATP breakdown products in liver biopsies, according to \(^{13}\) . The results have been added to the main text (lines 296- 297, pages 11 of the tracked version of the revised manuscript), while the methods are described in Supplementary information 1.1.11 + +## 5. In the discussion you state that the ATP recovery mechanism is likely due to a transfer of viable mitochondria to injured cells but you do not present any data to support such a contention. + +Thank you for your note. We reformulated the paragraph dedicated to MSCs- induced protection of cell energy status (lines 401- 416, page 15 of the tracked version of the revised manuscript), specifying that the transfer of mitochondria from stem cells to liver tissue has been proposed as a potential + +<--- Page Split ---> + +underlying mechanism based on previous evidence \(^{14,15}\) . Further research is required to verify whether this process plays a role in the context of hepatic IRI. + +6. In the discussion you conclude that Bioreactor-MSCs had an impact on different aspects of immune modulation and inflammation. Please justify this conclusion further. These points have been further discussed in lines 417-435 of the tracked version of the revised manuscript (pages 15-16). + +7. There are several typographical and syntax errors. + +Thank you very much for highlighting these inaccuracies. After a thorough of the manuscript, all the imprecisions have been corrected. + +<--- Page Split ---> + +## References + +1. Sierra Parraga, J. M. et al. Effects of normothermic machine perfusion conditions on mesenchymal stromal cells. Front. Immunol. 10, 1–11 (2019).2. Deng, B. et al. Removal from adherent culture contributes to apoptosis in human bone marrow mesenchymal stem cells. Mol. Med. Rep. 15, 3499–3506 (2017).3. Hassan, M. N. F. Bin et al. Large-Scale Expansion of Human Mesenchymal Stem Cells. Stem Cells Int. 2020, (2020).4. Panchalingam, K. M., Jung, S., Rosenberg, L. & Behie, L. A. Bioprocessing strategies for the large-scale production of human mesenchymal stem cells: A review Mesenchymal Stem/Stromal Cells - An update. Stem Cell Res. Ther. 6, 1–10 (2015).5. Merck KGaA. Size-based Immunomonitoring using the Scepter™ 3.0 Handheld Cell Counter. Application note https://www.sigmaaldrich.com/IT/it/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/size-based-immunomonitoring-scepter-handheld-cell-counter (2023).6. Kruepunga, N., Hakvoort, T. B. M., Hikspoors, J. P. J. M., Köhler, S. E. & Lamers, W. H. Anatomy of rodent and human livers: What are the differences? Biochim. Biophys. Acta - Mol. Basis Dis. 1865, 869–878 (2019).7. Soares, R. O. S., Losada, D. M., Jordani, M. C., Évora, P. & Castro-E-Silva, O. Ischemia/reperfusion injury revisited: An overview of the latest pharmacological strategies. Int. J. Mol. Sci. 20, (2019).8. Wu, M. Y. et al. Current Mechanistic Concepts in Ischemia and Reperfusion Injury. Cell. Physiol. Biochem. 46, 1650–1667 (2018).9. Blindenbacher, A. et al. Interleukin 6 is important for survival after partial hepatectomy in mice. Hepatology 38, 674–682 (2003).10. Moris, D. et al. Mechanistic insights of rapid liver regeneration after associating liver partition and portal vein ligation for stage hepatectomy. World J. Gastroenterol. 22, 7613–7624 (2016).11. Ruan, H. & Dong, L. Q. Adiponectin signaling and function in insulin target tissues. J. Mol. Cell Biol. 8, 101–109 (2016).12. Blandin, A. et al. Extracellular vesicles are carriers of adiponectin with insulin-sensitizing and anti-inflammatory properties. Cell Rep. 42, (2023).13. Meszaros, A. T. et al. Mitochondrial respiration during normothermic liver machine perfusion predicts clinical outcome. EBioMedicine 85, (2022).14. Peruzzotti-Jametti, L. et al. Neural stem cells traffic functional mitochondria via extracellular vesicles. PLoS Biology vol. 19 (2021).15. Phinney, D. G. et al. Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs. Nat. Commun. 6, 1–15 (2015). + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS + +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +We thank the reviewers for their helpful feedback. Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +## Reviewer #1 + +The authors have reviewed their manuscript according to suggestions and concerns made by the reviewers. Additionally, they have included some pilot results in a large animal NMP model to improve the translational impact of their work. Here are some issues that need to be addressed. + +1) According to the international society for cell and gene therapy, the correct term for MSC is now "mesenchymal stromal cells" (Viswanathan et al., Cytotherapy, 2019). Authors should update their manuscript. + +We thank the Reviewer for this important suggestion. The manuscript has been changed accordingly. + +2) Although the addition to the NMP circuit might be novel, culture of MSC in hollow fiber bioreactors is already known. Additionally, commercial distribution of MSC has been offering the possibility of shipping cultured MSC in culture flasks or other formats, keeping their properties intact after transportation, which is quite similar to the logistic procedure described here. Novelty of this fact is scarce + +As noted by the Reviewer, the novelty of our study resides in the connection of a MSCs- bioreactor to a NMP platform. This innovative experimental setup has not been explored in previous researches, nor the core properties of MSCs in a bioreactor have been investigated after exposure to a perfusion procedure. A recent analysis performed by Fu and coworkers highlights the huge therapeutic potential of coupling MSCs- bioreactors to ex situ perfusion, but does not provide experimental clues supporting its applicability, and claim the need to perform targeted experiments aimed at addressing this point 3. + +Our research fills this knowledge gap, providing for the first time evidence showing both feasibility and efficacy of this modern MP platform. This important information is essential to proceed with the clinical implementation of this new technology. In this regard, the possibility of shipping pre- seeded bioreactors from a specialized cell facility to any Transplant Centers, could contribute to accelerating the translational process. + +3) Authors need to update figure 4 and supplemental data including all cell types susceptible to be measured in "wash-outs", (i.e. MSC, endothelial cells, etc.) Even in low numbers, MSC can still detach and flush through the system. + +<--- Page Split ---> + +Figure 4 was updated to include "endothelial cells" among cells detected within the following cell diameter range: \(9 - 18 \mu \mathrm{m}^{4}\) . In line with the Reviewer's comment, the supplementary material has been likewise revised (line 184, page 10). + +With regard to the Reviewer's suggestion to include also MSCs among the cells detached during the NMP procedure, we respectfully hold a different viewpoint and would appreciate the opportunity to offer an explanation justifying our decision. The wash- out samples drained from livers subjected to the bioreactor- based perfusion showed a higher cell count and a greater concentration of nitric oxide (NO) metabolites compared to those collected during standard NMP. The increased availability of the vasodilator NO, together with increased cell concentration, support a more effective wash- out of donor blood in livers exposed to the MSCs- derived secretome compared to controls. Moreover, as described in the previous "Response to Reviewers" (Reviewer #1, point 6), the results obtained from liverless- NMP experiments clearly indicate no MSCs detachment during the perfusion procedure (lines 152- 153, page 8 of the revised version of the manuscript). These evidence collectively suggest that the cells found in the perfusates derive solely from the liver. + +4) Authors mention the section supplementary methods 1.12 which is not included in the supplementary material. + +Authors thank the Reviewer for pointing this out. All the references to section 1.12 were removed from the main text. + +5) Supplementary figure 12. Regardless of measured parameters used to evaluate success in NMP, visual evaluation is still key during perfusion. In the images, there is a clear difference in perfusion between both organs, with the one from the MSC group having a paler color. This unequivocally show bad perfusion of the organ. + +Supplementary figure 12 does not compare livers from the control and the NMP+b-MSCs group, rather the pictures represent a random liver before and after undergoing the bioreactor- based perfusion procedure. + +As suggested by the Reviewer, the macroscopic appearance of the liver provides a first general impression of the liver during perfusion, but its clinical value is still debated. Indeed, at a recent international guideline meeting on liver viability during in- situ/ex- situ machine perfusion organized by ELITA/ESOT (Madrid, March 18- 20, 2024), a dedicated discussion was devoted to this topic. While the macroscopic appearance of the liver was considered a possible parameter in in- situ perfusion (normothermic regional perfusion, NRP), it was not included among the viability parameters in ex- situ perfusion (NMP). In fact, the macroscopic appearance of the liver during NMP was hardly related to perfusion quality and viability. During the session, a patchy and/or pale appearance of the NMP liver, rather than possible differences in the light exposure of the camera, was related to non- physiological perfusion conditions (e.g., outside the human body) and to the position of the liver during NMP, but not to the overall perfusion quality when NMP fluidodynamics and metabolism were preserved. In our study, all clinically derived parameters were met, fluidodynamics parameters were preserved throughout the perfusion time and, lastly, histology was preserved. At the above mentioned meeting, three of the authors of the present manuscript participated as "experts" and here we report a preliminary and confidential extract of the statement resulting from the meeting to further support the above statements: + +"Comment to Q11: What parameters measured during in-situ normothermic regional perfusion may be used to assess DCD liver viability? + +[...] The parameter "gross appearance of the liver" is very subjective and often based on the perception and experience of the procurement surgeon and team involved in NRP. [...] + +"Statement Q13: What parameters measured during ex situ normothermic machine perfusion may be used to assess deceased donor liver viability? + +<--- Page Split ---> + +1) Expert Panel Statement: Perfusion quality parameters, perfusate parameters (pH, lactate, transaminases, Glucose) and bile parameters (bile flow, pH, Glucose, Bicarbonate) may be used to assess deceased donor liver viability. Recommendation grade: conditional recommendation for Median level of evidence: 2 (range 3 to \(2 +\) )" + +Authors thank the reviewer for the opportunity to discuss this topic and anticipate some aspects that will be further explored in literature in the near future. + +This being said, based on the poor predictive potential of macroscopic aspects in the context of ex situ perfusion procedures, and in line with the Reviewer's comment, we would remove the panels a and b from Supplementary figure 12. + +6) There is a discrepancy regarding the number of cells used for the pig experiments described in the results and methods section. 37x107 cells noted in the results section does not equal 37 million cells (20 ml of a 1.85x106 cells/ml suspension). Please correct accordingly. We apologize for this imprecision; the total number of cells seeded in the bioreactors was \(3.7 \times 10^{7}\). Authors are very grateful to the Reviewer for his accurate revision. + +7) Authors have used \(2 \times 10^{7}\) MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. Comparison of results is therefore very limited between both models. + +8) Additionally, cell density in bioreactors is extremely different: 18500 MSC per cm2 for pig bioreactor vs. 40000 MSC/cm2 in rat bioreactors. Cell density is known to alter MSC functionality, secretory profile and immunomodulatory potential. Authors should justify these differences and elaborate about possible consequences. + +All the calculations made by the Reviewer are correct. However, we would like to clarify that the pilot study in porcine livers was conducted to investigate whether a bioreactor can be technically integrated into a clinical device and to test whether this new configuration can sustain the protocol for human liver MP. Our intention was to provide experimental evidence in support of the clinical applicability of our new setup, addressing the concerns raised in the previous revisions on this topic. Thus, in addition to the differences pointed out by the Reviewer, the porcine study involved several other changes compared to the small animal model, which were introduced to progress towards the setting adopted in the human scenario. First, porcine livers were exposed to a period of warm ischemia. Second, the NMP was performed using leukocyte-depleted autologous blood including red blood cells and the perfusate was pumped into the liver through both hepatic artery and portal vein. Moreover, portal vein target pressure was different compared to the setting adopted in the rat NMP, and the porcine circuit was equipped with two oxygenators. These, and other, adjustments were needed to test the feasibility of the bioreactor-based perfusion in a human-like setting. + +This being said, as highlighted by the Reviewer, no comparison in the MSCs effects between rat and pig livers was provided, nor were the MSCs functionality and secretory profile explored in porcine experiments, since the experimental aims of these two work packages were different. + +9) The large animal model used by the authors lacks potential for translation. Clinical strategies used in human liver NMP trials include perfusion times ranging from 9-20+ hours. Although authors are presenting preliminary results in a large animal preclinical model coupled to an MSC bioreactor, clinical translation assumptions should be made carefully, as the author do not present sufficient data supporting their claims. + +<--- Page Split ---> + +We agree with the reviewer on the potential drawbacks of our large animal model from a translational point of view. For this reason, we used pig experiments only to test the possible integration of an MSC bioreactor into a commercial perfusion device, as in other studies where pigs were used for technological assessment. In this setting, a NMP duration of \(4\mathrm{h}\) was chosen by our group. In the clinical literature, perfusion time varies widely within the same study and between studies. In fact, while most studies did not specify a per- protocol NMP duration, it usually depends on the goal of the perfusion, how it is applied (e.g., back to base or in the donor hospital approach), and other logistical issues. While preservation and viability might require a longer NMP time, reconditioning might benefit from a shorter NMP duration when used to face organ reperfusion, as in the DCDnet trial (NCT04744389) in which some of the present authors are involved. For these reasons, we decided to use a 4- hour NMP in our WP3. In addition, since our goal was to test the integration of the bioreactor into a commercial NMP device, most of the technological issues should become apparent early after the start of the NMP. Following the Reviewer's suggestion, we revised and, in some cases, reformulated, all the claims about the clinical translational of our results. As pointed out by the Reviewer, longer preservation times will be applied in future studies to verify the biological changes secondary to the connection of the MSC bioreactor to an NMP. + +10) Even though these are preliminary results, only \(n = 3\) animals were used for the large animal study. This small sample size needs justification and sample size calculation need to be explained. + +We appreciate this important note on sample size calculation in the pilot study and consistently improved the dedicated paragraph in the Supplementary material by adding the requested information (1.11.1 Sample size, page 14). + +As discussed above, the work package in large animals investigated feasibility of bioreactor integration into an existing perfusion circuit for human use. The possible outcomes were, therefore, defined as categorical, namely 1) success of execution (feasible) or 2) failure of execution (unfeasible). + +Due to lack of prior data and consequent unavailability of a formal verification of sample size, the number of pigs needed as liver donors was determined based on our experience in the set up and implementation of novel perfusion platforms for preclinical models 5- 7. + +Considering these assumptions, while adhering to the ethical principles in animal research 8,9, we elected to use 3 animals for each experimental group. + +<--- Page Split ---> + +## Reviewer #2 + +The incorporation of an MSC- bioreactor in a normothermic machine perfusion (NMP) circuit is a novel concept although other groups are working in this area. There is a body of work demonstrating that MSCs can ameliorate ischaemia reperfusion injury and it is known that this is due to the release of EVs and paracrine factors from the stem cells and that MSCs themselves have a number of potentially adverse effects. The isolated organ preservation offered by NMP removes problems with targeting stem cells to a specific organ and bypassing the reticuloendothelial system. NMP also reduces the risk of off- target adverse effects. The addition of a bioreactor to the NMP circuit is a logical development. The authors have demonstrated the feasibility of this new approach and in the rat model evidence that the addition of a bioreactor can counter some of the changes associated with I/R injury. + +There are a number of issues that the authors should consider: + +## 1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. + +We thank the Reviewer for the opportunity to further discuss the scientific background of our research, which provides a proof of concept to implement a new platform for liver NMP. + +Based on the existing literature, rodent models of ischemia/reperfusion injury (IRI) are widely utilized to investigate novel intervention strategies or gain insights into the biological mechanisms elicited by IR. Of interest, a recent systematic review explored the use of cell- based therapies to counteract IRI in transplantable organs 2. The analysis indicated that out of the 97 studies examined, 45 utilized rat models of ischemic injury, while 46 researches were conducted in mice. Therefore, although we acknowledge that clinical translation could be challenging, preclinical models still represent valuable tools for scientific investigation in this field. + +Moreover, it's important to consider that the typical pathway to develop a new medical setup involves the progression from initial testing in rodent models to subsequent studies in larger animals before advancing to human research. Since we aimed at establishing an unprecedented technology, the use of a small animal model was necessary to depict the various technical and biological aspects essential to successfully integrate the bioreactor into a NMP circuit, while demonstrating MSCs' efficacy in mitigating IRI. + +2. The procine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model than the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. + +We thank the Reviewer for the comment which allows improving the description of the research aims. As highlighted, the pilot study in porcine livers was conducted to investigate the potential of the bioreactor to be upscaled and integrated into a clinical device, while providing information supporting the ability of the new configuration to sustain the protocol for human liver MP. Our intention was to provide experimental evidence to demonstrate the technical feasibility of our new setup in a scenario resembling the clinical setting, addressing the concerns raised in the previous revisions on this topic. Therefore, as noted by the Reviewer, we did not investigate the MSCs' effects on porcine liver IRI. On the other hand, this aspect was extensively studied in rat livers, taking advantage of the expertise of our Research Team as well as on availability of a variety of bio- molecular technologies previously validated for this model 11- 17. + +<--- Page Split ---> + +3. The group size for the porcine experiments is small at \(n = 3\) and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& lpha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. + +We recognize that sample size calculation for the pilot study needed to be expanded and, as a consequence, we changed the dedicated paragraph in the Supplementary material to better justify our evaluation (1.11.1 Sample size, page 14). + +We agree with the Reviewer that the investigation of the bioreactor- based perfusion effects during prolonged procedures is an intriguing research perspective. In fact, we are currently working on the setup of extended bioreactor- based NMP, with the ultimate aim to explore the long- term consequences of MSCs. In this regard, our Group recently completed the development and optimization of a stable protocol for \(12\mathrm{h}\) - NMP in rodents 17. + +4. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. We appreciate the Reviewer's suggestion regarding the use of human livers deemed unsuitable for transplantation. This approach could indeed provide valuable insights into the efficacy of bioreactor-based NMP and, as such, it appears as a logical next research step. The scientific community could take advantage of the seminal results provided by the present study, and consider conducting targeted experiments to investigate the benefits of bioreactor-based NMP in human livers. We added a sentence in the Discussion section (lines 360-363, page 15 of the revised version of the manuscript) to highlight this concept. + +<--- Page Split ---> + +## References + +1. Shao, B. et al. Structural and Temporal Dynamics of Mesenchymal Stem Cells in Liver Diseases From 2001 to 2021: A Bibliometric Analysis. Front. Immunol. 13, 1–18 (2022). +2. Blondeel, J., Gilbo, N., De Bondt, S. & Monbaliu, D. Stem cell Derived Extracellular Vesicles to Alleviate ischemia-reperfusion Injury of Transplantable Organs. A Systematic Review. Stem Cell Rev. Reports 19, 2225–2250 (2023). +3. Fu, Y. et al. Mesenchymal Stem Cell Utilization for In Vitro Donor Liver Machine Perfusion Preservation: Current Status and Future Directions. Stem Cells Transl. Med. 12, 665–675 (2023). +4. Merck KGaA. Size-based Immunomonitoring using the Scepter™ 3.0 Handheld Cell Counter. Application note https://www.sigmaaldrich.com/IT/it/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/size-based-immunomonitoring-scepter-handheld-cell-counter (2023). +5. Bassani, G. A. et al. Ex vivo lung perfusion in the rat: Detailed procedure and videos. PLoS One 11, (2016). +6. Dondossola, D. Procurement and ex-situ perfusion of isolated slaughterhouse-derived livers as a model of donors after circulatory death. ALTEX (2019) doi:10.14573/altex.1909131. +7. Dondossola, D. et al. Human Red Blood Cells as Oxygen Carriers to Improve Ex-Situ Liver Perfusion in a Rat Model. J. Clin. Med. (2019) doi:10.3390/jcm8111918. +8. Balls, M. It’s Time to Reconsider The Principles of Humane Experimental Technique. ATLA Altern. to Lab. Anim. 48, 40–46 (2020). +9. Smith, A. J., Clutton, R. E., Lilley, E., Hansen, K. E. A. & Brattelid, T. PREPARE: guidelines for planning animal research and testing. Lab. Anim. 52, 135–141 (2018). +10. Bhattacharjee, R. N. et al. Renal protection against ischemia reperfusion injury: Hemoglobin-based oxygen carrier-201 versus blood as an oxygen carrier in ex vivo subnormothermic machine perfusion. Transplantation 104, 482–489 (2020). +11. Lonati, C. et al. Influence of ex vivo perfusion on the biomolecular profile of rat lungs. FASEB J. 32, (2018). +12. Lonati, C. et al. Mesenchymal stem cell–derived extracellular vesicles improve the molecular phenotype of isolated rat lungs during ischemia/reperfusion injury. J. Hear. Lung Transplant. (2019) doi:10.1016/j.health.2019.08.016. +13. Lonati, C. et al. NDP-MSH treatment recovers marginal lungs during ex vivo lung perfusion (EVLP). Peptides 141, (2021). +14. Catania, A. et al. The peptide NDP-MSH induces phenotype changes in the heart that resemble ischemic preconditioning. Peptides (2010) doi:10.1016/j.peptides.2009.09.030. +15. Colombo, G. et al. Treatment with α-melanocyte stimulating hormone preserves calcium regulatory proteins in rat heart allografts. Brain. Behav. Immun. 22, (2008). + +<--- Page Split ---> + +16. Lonati, C. et al. Quantitative Metabolomics of Tissue, Perfusate, and Bile from Rat Livers Subjected to Normothermic Machine Perfusion. Biomedicines 10, (2022). +17. Dondossola, D. et al. Twelve-hour normothermic liver perfusion in a rat model: characterization of the changes in the ex-situ bio-molecular phenotype and metabolism. Sci. Rep. 14, 1–13 (2024). + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS + +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +We thank the Editor for the opportunity to re- evaluate our manuscript and the Reviewers for their helpful feedback. + +Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<--- Page Split ---> + +## Reviewer #1 + +The authors have replied to most of the reviewers comments, with a very elaborated explanation in some cases. + +Thank you for recognizing our efforts to improve the clarity and the relevance of our manuscript. + +## Some questions still arise: + +1. The authors missed one of the previous comments: Authors have used \(2 \times 10^{7}\) MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. + +Comparison of results is therefore very limited between both models. + +We apologize if we did not make this point clear. The exact number is \(2.8 \times 10^{4}\) cells per gram of liver tissue. + +While we agree with the Reviewer that comparison of results is very limited between the models, this observation open up two different discussions. The first is the aim of the porcine study and the second is the normalization. + +First, we would like to emphasize that the large animal study was not conducted to compare the effects of MSCs on porcine versus rat liver. Instead, its primary goal was to test the feasibility of integrating our bioreactor into a clinical NMP platform. This crucial step must be completed before advancing with further research and required a dedicated pilot study to avoid future failures, as recommended by NC3Rs 1. + +Concerning normalization, the selection of normalization criteria and of the compounds that should be normalized is still a matter of debate in the MP field. In fact, it is either partially applied or not applied at all in MP literature, even in those experiments that use depurative strategies such as dialysis, that could deeply manipulate the concentration of some compounds 2- 5. This being said, according to the number of cells, we had the same concerns of the Reviewer. Indeed, whether the effect of the MSCs is directed to the liver or the MSCs are primed by the liver- secreted factors leads to a different normalization. In the first case, the normalization would be based on MSC/g of liver, in the other on the volume and flow of the perfusate. Since we could not get a direct answer from the literature and other experiments, we applied a normalization based on the perfusate volume and flow rate into the bioreactor, due to the inherent differences in the perfusion settings of rodent and pig model. This combined factor was comparable between the rodent and porcine models. + +We thank the Reviewer for the comment and have added the paragraph "1.12.2 Preparation of the bioreactor suitable for porcine livers", in the Supplementary information, willing to open a debate on this issue. We are, indeed, aware that the type and the selection of the normalization criteria can be criticized. + +2. Regarding MSC detaching from the bioreactor. MSC do not flush through during liver-less perfusion. However, as fluid composition changes due to the liver secreted molecules and cytokines, there is no data confirming this subject as conditions change. The authors do not provide any direct proof of the cell types leaving the NMP system. Therefore, all cells present in the NMP system should be taken into account, including MSC. + +We agree with the Reviewer that the factors secreted by the liver could have had a chemotactic effect on the MSCs. As suggested, we cannot directly prove the absence of small MSCs or MSCs fragments in the perfusion fluid during liver NMP. Therefore, Figure 4 was accordingly updated to include "MSCs" among cells detected within the following cell diameter range: \(9 - 18 \mu \mathrm{m}\) . + +<--- Page Split ---> + +This being said, we would like to point out that the bioreactor fibers are made of semi-permeable membranes with a pore diameter of around \(150~\mathrm{nm}\) , as already reported in the Supplementary information (Supplementary figure 1 and Supplementary figure 9). Given that the average size of the MSCs cultured under standard conditions is \(15 - 30~\mu \mathrm{m}^{6,7}\) , the likelihood for an intact stem cell to pass through the pores appears very low and must assume a considerable degree of cell deformability \(^{8}\) . Moreover, it should be noted that the same fibers are used in clinical plasmalifters to trap erythrocytes, which have a smaller diameter than MSCs. + +To improve the clarity on this point, we have reported the bioreactor fiber pore size even in the main text (page 17- 18, lines 449- 476 of the tracked version of the manuscript) and added a detailed bioreactor description to the Supplementary information 1.2 (page 5). + +3. The authors have provided preliminary data on the technical feasibility of coupling an MSC bioreactor in a porcine NMP setup. The objective was to set a translatable setup for human use in the clinic. With this in mind, the very small population size (n= 3) do not allow to obtain any conclusion and larger studies need to be carried out. + +By definition, pilot studies are "designed to test the feasibility of methods and procedures for later use on a large scale or to search for possible effects and associations that may be worth following up in a subsequent larger study" \(^{9}\) . Since the large animal work package was performed to investigate the use of the novel bioreactor- based configuration as a part of multistep project, it fully meets the criteria set for a pilot study. Consistently, our claim was to test the possible integration of our MSCs bioreactor in a human device, rather than providing evidence on direct clinical translatability. + +We fully agree with the reviewers and the editor that sample size is a critical issue. As highlighted and accepted by Reviewer #2 (point 4) and in accordance with NC3Rs \(^{1}\) , in our pilot study in porcine livers, the sample size was determined as detailed in the Supplementary information 1.12: + +### 1.12.1. Sample size + +This pilot study was designed to establish a novel perfusion system by combining the Liver Assist® machine to a stem cell bioreactor. Sample size was determined according to the guidance published by NC3R \(^{1}\) , considering the following possible outcomes: 1) success of execution (feasible) or 2) failure of execution (unfeasible). Based on our experience in the set up and implementation of unprecedent perfusion platforms for preclinical models \(^{10 - 12}\) , we deemed necessary using 3 animals for the NMP+bioreactor group. Therefore, work package 3 involved a total of 6 animals. + +To provide further clarification on this issue, we have added a brief description in the main text (page 20, lines 551- 558 of the tracked version of the manuscript). If the Reviewers and Editor deem it preferable to more extensively use the term "pilot study" to enhance clarity regarding the aim of the large animal model, and if it aligns with the journal's guidelines, we will incorporate this suggestion in subsequent manuscript versions. + +<--- Page Split ---> + +## Reviewer #2 + +1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. The authors address the use of rodent models on the basis that this is common practice and that rodent models are an important step in the evolution of new technologies. These are reasonable points but still don't answer the issue of translatability. There is not much the authors can do about this limitation. + +As declared in previous review rounds, we are in full agreement with the assertions made by Reviewer #2. Indeed, the low translatability rate from rodent studies to clinical applications is well documented 13, but this observation needs to be carefully interpreted to avoid simplism (e.g. futility of rodent models in biomedical research). In fact, it is established that rodent models remain an invaluable resource for investigating the biological mechanisms underlying a given phenomenon. As a consequence, the poor translatability does not preclude the use of these models in the pathway towards clinical implementation of a novel technology or treatment. + +Of note, different Societies, Associations, and Institutions relevant to preclinical research, indicated a poor methodological approach and the lack of protocol standardization among the main reasons causing the low translational rate and the failure to recapitulate many human disease symptoms 14- 17. To address this important issue, we strictly adhered to the PREPARE guidelines 14 during the approval phase of the protocol, and to the ARRIVE guidelines 18 during article preparation, as recommended by NC3Rs, Felasa, and NORECOPA. + +We have never claimed the use of rodent models as "common practice", but we believe that it is could be considered a "common science" based on international literature (see response to point 1 raised by Reviewer #2 in the previous review round) and guidelines. The disadvantages of not initiating the process from a rodent model include incomplete comprehension of a complex phenomenon and a reliance on previously published studies to develop a protocol or interpret results. In addition, it must be noted that this iter is also needed for the legislative approval of a new device/drug [https://health.ec.europa.eu/medical- devices- sector_en]. + +In the transplantation field, no study have ever demonstrated that a MSC- bioreactor can be coupled to liver NMP and that MSCs can be activated by the interaction with the liver. To address this intriguing research question, after an in- vitro phase (liverless perfusion), we employed a rat model and, upon successfully accomplishing this objective, in line with the recommendations of the Reviewers and the Editor, we explored the bioreactor integration into a commercial human device. + +The final step of our project will be the clinical applicability of our technology, which, in our idea, will deserve a separate research project (see also paragraph 2 of points 3- 4, Reviewer #3) and a separate paper. In a "translational" perspective, the present results will be the milestones needed to properly set up this future study. We do not believe that reporting a new device or drug (MSCs are considered drugs for Italian legislation) would require the inclusion of all the research steps in a single publication. + +The role of small animal model was better clarified in the Discussion (page 12, lines 279- 282 of the tracked version of the manuscript). + +2. The porcine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model than the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. + +The authors have answered my concerns to some extent. The use of a porcine model provides + +<--- Page Split ---> + +## useful feasibility evidence that the technology can be upscaled to a large animal set-up that resembles the clinical situation. + +The comments provided by the Reviewer are in complete accordance with the considerations outlined in our previous correspondence and in the various versions of the main text. As the Reviewer correctly asserted, the porcine model was employed solely for the purpose of evaluating the feasibility of upscaling the bioreactor in a commercial device. Furthermore, it is important to note that this is not merely a straightforward issue of scaling up (as outlined in points 7- 8 of the previous "Letter to the Reviewers" by Reviewer #1), but also entails adapting our bioreactor to a distinctly engineered circuit, compared to that for rat liver NMP. The integration of the bioreactor in a commercial human device was successful, with no failure of the circuit or machine and no macroscopic, as pointed out by the Reviewer #2 damage to the liver (Supplementary table 6 and Supplementary figure 12). Therefore, the point was not only addressed to "some extent", but any further elaboration on the analyses or the possible underlying mechanisms (as requested in point 3 by Reviewer #2) would exceed the scope of our large animal study. Indeed, we are fully aware of the differences in structure and biological mechanisms between human and porcine livers, and we agree with the Reviewer on this matter. Nevertheless, the underlying premise of our experimental design is that porcine livers, despite their heterogeneity, may still serve a role in device setup and technology testing \(^{19}\) . This concept is supported by a substantial body of literature, as evidenced by the fact that the Pubmed search "liver normothermic machine perfusion AND pig" provides 63 articles. A systematic review on this topic was published in 2018 in Transplantation by leading experts in the fields of liver MP and stem cells \(^{20}\) . This review identifies the porcine model as a convenient method to explore novel approaches of perfusion and to study the early events of IRI. Among the presented NMP model, we selected the Groningen approach \(^{21}\) , which was adapted to be used with the commercial device Liver Assist (XIVVO). Of note, pig livers have been used in recent years to develop novel MP techniques, which have been subsequently tested on non- viable livers \(^{3,5}\) . This ultimately led to the clinical transplantation of the liver \(^{22}\) . + +We recognize that our initial presentation may have lacked clarity; thus, we have expanded the "Study design" paragraph (page 7, lines 129- 130 of the tracked version of the manuscript) and the discussion on the rationale behind our large animal model (page 12, lines 279- 284 and page 15- 16, lines 380- 388 of the tracked version of the manuscript). + +3. The group size for the porcine experiments is small at n=3 and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& Ipha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. 4. My comments relating to the small group size in the small group size in the porcine experiments have been acknowledged by revision of the supplementary information. In relation to the short duration of the perfusion experiments, the authors are planning experiments with more relevant prolonged perfusion. It would have strengthened the work to wait for these results. + +We will address these two points together, as they are subject to similar criticisms. First of all, we would like to thank the Reviewer for accepting the sample size justification for our pilot study, provided in the previous review round. Sample size justification (pilot large animal model) and calculation (rodent model) have been performed according to the PREPARE guidelines \(^{14}\) . Making this point clear and repeatable (as requested by the ARRIVE guidelines \(^{18}\) observed by this journal) is for us of paramount importance. + +As the Reviewer correctly observed, prolonging the perfusion time in both rodent and porcine models would have offered an intriguing pathway for further investigations. A longer perfusion time would provide a time window during which organs could be not only "reconditioned", but also "repaired". + +<--- Page Split ---> + +However, as declared in the previous version of the paper and review rounds, this was not the objective of our study. Instead, the rodent model was employed to establish the bioreactor- based NMP platform, to investigate the potential of MSC utilization in liver perfusion, and their impact on early IRI, while the pig model was utilized for to test feasibility of bioreactor integration into a commercial device used in the clinical practice. + +Beside the fact that the effects of a prolonged perfusion felt outside our aims, at the time of experiment execution, no prolonged perfusion rat models were available in the literature. A \(12\mathrm{h}\) - perfusion model was reported for the first time by our group after completing the present study \(^{23}\) . It is important to note that, despite meeting all clinical criteria for viability at the end of the 12- hour perfusion, perfused livers exhibited a number of metabolic changes compared to the native liver. These changes could have influenced the interpretation of the MSC effect on prolonged liver perfusion. The same non- physiological effects were showed by Guo et al. in ischemia- free human livers, indicating that ex- situ perfusion could lead to deleterious effects \(^{24}\) that potentially concours to liver viability failure, even at the end of a prolonged perfusion time \(^{3,4}\) . As a result, while prolonging perfusion in a human/large animal model is an intriguing perspective, extended perfusion itself modifies liver biology and would have affected the understanding of MSC effects. For these reasons, MSC survival, effect, and outcome in prolonged perfusion necessary represents a second step of the present research. + +This point is discussed in the Limitations section (page 16, lines 389- 392 of the tracked version of the manuscript) and in the Conclusion section (page 17, lines 418- 419 of the tracked version of the manuscript). + +5. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. We recognize the potential of non-viable human livers as a tool to explore clinical utility of novel technologies and compounds. However, the Reviewer defined non-viable humans as the "best model", yet no supporting evidence was provided or could be identified in the literature (21 original articles or commentaries on PubMed [normothermic machine perfusion AND split OR reduced liver]: 12 of them for ex-situ clinical split liver). In addition to the low level of evidence, the use of non-viable split livers introduces two fundamental confounding factors that remain poorly understood: first, the high degree of heterogeneity among cases, and second, the presence of a resection line. + +In regard to the first well- known issue \(^{5}\) , "by definition" non- viable livers are not utilized for a number of reasons, including prolonged warm ischemia time and high steatosis grade. As reported in a recent series published in Nature Communication \(^{4}\) , despite the exceptional results achieved, this resulted in heterogeneity in fulfilling viability criteria and in unrecognized metabolic changes due to the inherent liver physiopathological conditions. This could lead to difficulties in interpreting the data if a new technology is tested. + +As for the presence of a resection line, it can introduce additional confounding factors when using split livers as an internal control. Indeed, the potential influence of the resection line on resolution and repair mechanisms has already been demonstrated in- vivo models and in humans (e.g. associated liver partition to portal vein ligation in staged hepatectomy – ALPPS \(^{25,26}\) ). + +In addition, the precise ex vivo pump flow required for the hemi liver remains to be established \(^{27}\) . All these variables would have further complicated the investigation of a MSC- bioreactor effects during NMP. + +Finally, for completeness towards Reviewers and Editors, it is important to acknowledge that the use of non- viable livers for research purposes is no longer permitted in Italy. This observation was not reported in the previous revisions because it does not represent an insurmountable limitation. Indeed, international collaborations can be sought within the scientific community (although the funds of this grant cannot be used for non- Italian collaborations). + +<--- Page Split ---> + +Despite reiterating that the ultimate objective of the present research is not the full clinical application of our MSC- bioreactor, we are pursuing these avenues. Indeed, we have recently published a paper on human liver NMP using the native liver of the recipient. + +Since this topic is of high interest in the field of MP, we discussed this point as a future development of our research (page 17, lines 454- 456 of the tracked version of the manuscript). + +We kindly request that the comment on Italian legislation not be included in the paper, as it is not crucial for the scientific community. + +<--- Page Split ---> + +## References + +<--- Page Split ---> + +ex vivo liver perfusion (NEVLP) reduces liver and bile duct in DCD liver grafts. Am. J. Transplant. 13, 3290 (2013).22. Clavien, P. A. et al. Transplantation of a human liver following 3 days of ex situ normothermic preservation. Nat. Biotechnol. 40, 1610–1616 (2022).23. Dondossola, D. et al. Twelve-hour normothermic liver perfusion in a rat model: characterization of the changes in the ex-situ bio-molecular phenotype and metabolism. Sci. Rep. 14, 1–13 (2024).24. Guo, Z. et al. Metabolomics Differences of the Donor Livers Between In Situ and Ex Situ Conditions During Ischemia-free Liver Transplantation. Transplantation Publish Ah, 139–151 (2023).25. Wang, R. et al. Pathophysiological mechanisms of ALPPS: Experimental model. Br. J. Surg. 109, 510–519 (2022).26. Kambakamba, P. et al. Early Postoperative Serum Phosphate Drop Predicts Sufficient Hypertrophy After Liver Surgery. Ann. Surg. 278, 763–771 (2023).27. Yagi, S., Hirata, M., Miyachi, Y. & Uemoto, S. Liver regeneration after hepatectomy and partial liver transplantation. Int. J. Mol. Sci. 21, 1–23 (2020). + +<--- Page Split ---> diff --git a/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f30f9b74e3ace19a1ed91cbe575b097daeff95d8 --- /dev/null +++ b/peer_reviews/99a3c92e568bf2518467b41cddef112d05cddde1c3f59c5e841c80d1d96e7e8a/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1120 @@ +<|ref|>title<|/ref|><|det|>[[73, 163, 881, 234]]<|/det|> +# A proof-of-concept study in small and large animal models for coupling liver normothermic machine perfusion with mesenchymal stromal cell bioreactors + +<|ref|>text<|/ref|><|det|>[[74, 248, 433, 265]]<|/det|> +Corresponding Author: Dr Caterina Lonati + +<|ref|>text<|/ref|><|det|>[[72, 299, 864, 313]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 352, 144, 365]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 378, 219, 391]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 404, 160, 417]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 430, 238, 456]]<|/det|> +(Remarks to the Author) Review Report + +<|ref|>text<|/ref|><|det|>[[73, 468, 909, 535]]<|/det|> +The authors have skillfully design a promising platform to study the effect of mesenchymal stem cells (MSC) during ex vivo perfusion of rat livers. This is a very interesting approach to overcome some issues observed in direct MSC infusion in organ- in- a- pump models, like microvasculature clogging. The main successful points are the modification of a rat liver normothermic machine perfusion (NMP) system to include a bioreactor for MSC cell therapy and the maintenance of hepatocyte viability during MSC- NMP. However, there are some concerns that need to be addressed: + +<|ref|>sub_title<|/ref|><|det|>[[73, 548, 156, 560]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[73, 560, 900, 600]]<|/det|> +Authors claim that MSC only activate their secretory potential after exposure to inflammatory stimuli. However, this is not true as demonstrated earlier (i.e. Park et al., Int J Stem Cells., 2009) but MSC secretory profile is modulated by the microenvironment (i.e. Burja et al., Curr Res Transl Med., 2020). + +<|ref|>sub_title<|/ref|><|det|>[[73, 613, 133, 625]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[72, 625, 905, 715]]<|/det|> +MSC in vitro culture. Authors describe "MSCs were cultured at a concentration of \(2^{*}105\) in \(14~\mathrm{mL}\) in oMEM medium". What vessel was used to seed the cells and what is the final seeding density in this vessel? Characterization of MSC after NMP. Cells were retrieved from the bioreactor. Were the cells directly analysed (cytometry). For how long were the MSC re- cultured for the morphology tests and what were the conditions of that culture? (cell seeding density, culture time, etc.). Also, did the authors count the total number of cells retrieved from the bioreactor and compared with the original number? Exposure to perfusion fluid may have altered their metabolism and survival, acting as a licensing agent itself. + +<|ref|>text<|/ref|><|det|>[[72, 715, 904, 742]]<|/det|> +Flow cytometry. For reproducibility purposes, please add the reference numbers of antibodies used for flow cytometry and other relevant reagent. + +<|ref|>text<|/ref|><|det|>[[72, 742, 904, 782]]<|/det|> +Liver NMP. Perfusion took place in two phases: a warming phase and a stable normothermic phase. Was the bioreactor connected to the circuit during the entire perfusion (warming+stable phases)? Similar to the question related to shipment, rewarming time might affect MSC survival and metabolism during this time. + +<|ref|>text<|/ref|><|det|>[[72, 782, 916, 834]]<|/det|> +The authors seeded \(20^{*}10^{*}7\) MSC in a bioreactor. Is this number constant throughout the perfusion experiment? Do MSC die and are replaced by proliferating MSC? These dead cells might be responsible for the uncontrolled release of cytokines. In addition, average rat liver weight is 4- 5 grams which results in a MSC dose of \(4^{*}10^{*}9\) MSC/kg, an extremely high dose which has a poor translation towards a clinically relevant setup. + +<|ref|>text<|/ref|><|det|>[[72, 834, 916, 873]]<|/det|> +In addition, authors sent MSC in a bioreactor from one laboratory to another at room temperature. Culture temperature is key for MSC survival and temperatures lower to \(37^{\circ}C\) are deleterious (Pratiwi et al., Cytoherapy, 2019). Did the authors study the status of MSC after the shipment? + +<|ref|>sub_title<|/ref|><|det|>[[72, 886, 128, 898]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[72, 899, 891, 939]]<|/det|> +The authors describe an increase in certain metabolites such as lactate, IL- 6, IL- 1ra, among other, during liverless NMP+bioreactor. However, these are inflammatory cytokines and lactate production has been related to increased ROS production (i.e. Li et al., Signal Transduct Target Ther., 2022). Though the authors address the increase in inflammatory + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 900, 75]]<|/det|> +cytokines as a positive results, they should discuss the inflammatory perfusate profile and elaborate on this in the discussion section as it appears to be a setback of their NMP circuit. + +<|ref|>text<|/ref|><|det|>[[72, 74, 905, 113]]<|/det|> +Immune cells outflow. Authors describe outflow of an increased number of immune cells when the bioreactor is connected during NMP. However, they do not show data for cell characterization in the outflow perfusate. + +<|ref|>text<|/ref|><|det|>[[72, 111, 905, 137]]<|/det|> +EV origin. The authors hint that observed differences in EV size are related to their hepatocyte or MSC origin. This is a difficult assumption to make based only on EV size. + +<|ref|>text<|/ref|><|det|>[[72, 135, 910, 173]]<|/det|> +pH stabilization. The authors claim that MSC in the bioreactor regulate the pH of the perfusate. However, exposure to MSC medium present in the bioreactor, which contains a buffered solution to maintain pH, might be the responsible factor of pH stabilization. + +<|ref|>sub_title<|/ref|><|det|>[[73, 191, 163, 204]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 216, 238, 230]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 230, 919, 294]]<|/det|> +This study reports the effects of the addition of an MSC- bioreactor to the NMP circuit in an isolated rat liver model. The study mainly shows the safety and feasibility of this approach and some beneficial effects of using an MSC bioreactor approach rather than thawed MSCs. The MSC- bioreactor effects included decreased injury markers, increased bile production; increased acute phase proteins; more effective washout of blood; reduced ATP depletion; absence of succinate accumulation. + +<|ref|>text<|/ref|><|det|>[[73, 308, 278, 321]]<|/det|> +Please address the following: + +<|ref|>text<|/ref|><|det|>[[70, 320, 912, 460]]<|/det|> +1. You state that the 'translational value is high'. This needs justification when using a rodent model as many such models have been shown not to have reproducible effects in large animals and humans. +2. Although you acknowledge that the cold ischaemic time is very short, this is. major limitation with little clinical relevance. +3. Please discuss the potential effects of raised TNF and IL-6 in the bioreactor group. These acute phase proteins can have pro-inflammatory wells as protective effects. +4. It is difficult to make conclusions about ATP depletion when the ATP;ADSP ratio has not been measured. +5. In the discussion you state that the ATP recovery mechanism is likely due to a transfer of viable mitochondria to injured cells but you do not present any data to support such a contention. +6. In the discussion you conclude that Bioreactor-MSCs had an impact on different aspects of immune modulation and inflammation. Please justify this conclusion further. +7. There are several typographical and syntax errors. + +<|ref|>text<|/ref|><|det|>[[73, 490, 145, 503]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 515, 218, 529]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 541, 160, 554]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 567, 238, 580]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 580, 912, 658]]<|/det|> +The authors have made a revision of their manuscript replying to the comments made by the reviewers. Additionally, the authors have included new results from a different study describing one case of successful 17- day human liver NMP perfusion with a custom setup based on commercially available equipment to promote direct translation. It is interesting the development of an strategy to increase the pool of organs for research purposes. These two studies are not correlated, as each of them uses a different setup and has different objectives. In this new context, authors should address the following: Liver NMP case. + +<|ref|>text<|/ref|><|det|>[[72, 657, 923, 697]]<|/det|> +Some damage markers such as AST, are reduced until day 11, remaining stable until day 14. From there it rises, indicating a possible injury in liver. Authors may elaborate on the discussion section about fin tuning of the proposed setup. Images in supplementary Figure 11 have not an appropriate resolution. Authors should provide better quality images. + +<|ref|>text<|/ref|><|det|>[[73, 696, 144, 707]]<|/det|> +Rat model + +<|ref|>text<|/ref|><|det|>[[72, 707, 916, 735]]<|/det|> +- Authors state that after shipment, 5x104 MSC are found in the supernatant, accounting for 2.5% of the total number of MSC. If 20x107 were seeded in the bioreactor, this ratio is not correct. Please review this data. + +<|ref|>text<|/ref|><|det|>[[72, 735, 920, 788]]<|/det|> +- There is a pronounced difference between the number of MSC seeded in the bioreactor (20x107) and the retrieved cells after perfusion (106). Although authors show no increase in CK18 during liverless perfusion, this 95% decrease in the number of cells rises a concern about the impact of shipment and perfusion conditions on MSC, including cell death, and the effects observed in the present study. Authors must explain the possible causes. + +<|ref|>text<|/ref|><|det|>[[72, 788, 900, 827]]<|/det|> +- In line with the previous comment, authors could measure viable MSC cell numbers in the bioreactor after shipping and after the recovery time prior to NMP to identify the actual amount of MSC at the beginning of NMP, in case they die or proliferate. + +<|ref|>text<|/ref|><|det|>[[72, 826, 920, 866]]<|/det|> +- Cell dosing is still a limitation authors should include. Extrapolation of their data indicates the need of 12 x 1010 cells for an 80 Kg person. Generating these numbers and developing/dedicating bioreactors for this purpose are holding back the translation of this setup, which should be reflected in the discussion. + +<|ref|>text<|/ref|><|det|>[[72, 865, 920, 892]]<|/det|> +- AGP and A2M increase during perfusion, common markers for liver damage. Authors could mention how they will solve this issue. + +<|ref|>text<|/ref|><|det|>[[72, 892, 920, 945]]<|/det|> +- Authors describe immune cell leakage from the liver based on particle size found in the perfusate outflow. However, more cell types, such as endothelial cell or MSC could, flush through the system. Moreover, identification of EV origin according to size is not correct, as all cells can secrete vesicles of different sizes. It is not possible to sustain this claim with the presented data. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[73, 48, 205, 60]]<|/det|> +## General comments + +<|ref|>text<|/ref|><|det|>[[73, 60, 902, 100]]<|/det|> +General commentsTranslation from preclinical work to human liver NMP should be proposed carefully. These studies are different at several levels such as perfusion fluid composition, organ preservation, oxygen carriers, equipment used (bioreactor, blood hemodialysis unit, etc.) + +<|ref|>text<|/ref|><|det|>[[73, 100, 902, 140]]<|/det|> +Overall, the translational value of the preclinical study should be assumed carefully. Authors themselves are aware of the differences between their preclinical model and human studies in the responses to the reviewer's comments. The authors may consider mentioning that translation in the future after confirming result in large animal models could be possible. + +<|ref|>sub_title<|/ref|><|det|>[[73, 165, 162, 178]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 191, 238, 203]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 204, 923, 284]]<|/det|> +Study A: The authors report on a single liver graft perfused using a modified commercial system. This system is very similar to the one described by Lau et al(1)., with the primary difference being the use of continuous venovenous hemodiafiltration (CVVHDF) instead of a less expensive dialysis system. The authors reported graft survival for up to 17 days. However is unclear what viability criteria were used. Only bile production and lactate levels are included. Study B reports on the addition of an MSC- bioreactor to an NMP circuit in an isolated rat model, noting decreased injury markers. However, the rat liver was perfused for only 4 hours, and no transplant was performed. + +<|ref|>text<|/ref|><|det|>[[73, 295, 322, 309]]<|/det|> +Please address the following points: + +<|ref|>sub_title<|/ref|><|det|>[[72, 321, 130, 333]]<|/det|> +## Study A + +<|ref|>text<|/ref|><|det|>[[72, 334, 923, 464]]<|/det|> +1. The authors describe a system very similar to that of Lau et al., based on a commercially available perfusion machine, the Liver Assist. Similar to the Lau et al.'s system(1), the authors' system includes a long-term oxygenator, gas mixer, and a blood purification system for dialysis. Instead of a standard dialysis system, the authors used a continuous hemodiafiltration (CVVHDF) technique. The authors claim that CVVHDF offers significant advantages over dialysis by allowing the removal of larger molecules. However, this assertion is not supported by any evidence. Both techniques have their pros and cons and mainly filter water-soluble molecules. CVVHDF provides limited clearance of protein-bound solutes. Besides clearing water-soluble toxins, dialysis and CVVHDF also eliminate nutrients and hormones. The authors should moderate their claim of longer survival because of the use of CVVHDF instead of dialysis. They should also discuss that CVVHDF requires a dedicated machine, while dialysis is more available, cheaper and easier to integrate. Furthermore, the authors should acknowledge that their model is very similar to the one already described by Lau et al. + +<|ref|>text<|/ref|><|det|>[[72, 476, 748, 490]]<|/det|> +2. Donor graft quality is a significant determinant of long-term survival, as described by Lau et al(1). + +<|ref|>text<|/ref|><|det|>[[72, 490, 915, 580]]<|/det|> +Eshmunimov et al. (2) and Lau et al.(1) used organs unsuitable for transplantation, these graft had usually a quite long cold ischemia time and were mainly steatotic or DCD grafts. The authors used a graft from a 56-year-old patient with unresectable colorectal metastases. While using a graft with liver tumors is an interesting model, it is not comparable to the poor-quality grafts used by Lau et al.(1) and Eshmunimov et al.(2) The graft clearly was of higher quality considering the likely short cold and warm ischemia, although data about the cold ischemia time are missing. The authors should discuss that despite previously receiving chemotherapy the quality of graft used and the minimal ischemic injury has played a major role in graft survival. + +<|ref|>text<|/ref|><|det|>[[72, 592, 911, 633]]<|/det|> +3. Data about liver viability are very limited. No viability criteria are defined. A liver can continue to produce bile even in the presence of massive liver necrosis. Detailed data of histology at various time points is needed, The authors describe massive necrosis at the later stage of perfusion, but data are very limited. + +<|ref|>text<|/ref|><|det|>[[72, 633, 750, 646]]<|/det|> +Data about ATP content, and oxygen consumption are also missing. Such data should be included. + +<|ref|>text<|/ref|><|det|>[[72, 658, 915, 698]]<|/det|> +4. The title is misleading. The authors report a significant worsening of liver function on day 15, yet it is unclear why the experiment was stopped on day 17. Viability criteria should be defined, and the contribution of CVVHDF in reducing lactate levels should be discussed. + +<|ref|>text<|/ref|><|det|>[[72, 710, 911, 750]]<|/det|> +5. Important details of the protocol used are missing. What type of Total Parenteral Nutrition (TPN) and concentration was used? Were biliary acids used? Compared to Lau et al. and Eshmunimov et al., RBCs were added during perfusion, which may suggest increased hemodialysis by the CVVHDF. This should be discussed. + +<|ref|>text<|/ref|><|det|>[[72, 762, 884, 789]]<|/det|> +6. Was any culture of the perfusate performed? Lau et al. (3) demonstrated an increased risk of infection with prolonged duration of perfusion. This should be discussed. + +<|ref|>text<|/ref|><|det|>[[70, 801, 905, 815]]<|/det|> +7. Only a single experiment is reported. The limitations of such a single experiment should be more extensively discussed. + +<|ref|>text<|/ref|><|det|>[[73, 827, 133, 840]]<|/det|> +Study B: + +<|ref|>text<|/ref|><|det|>[[72, 854, 911, 946]]<|/det|> +1. The main innovation is the modification of a rat liver normothermic machine perfusion system to incorporate a bioreactor for mesenchymal stem cell (MSC) therapy. However, I have reservations regarding the translational value of this model. Rodent models have limited reproducible effects in humans. The sole advantage of a rat model is the potential for transplanting perfused organs, yet no transplant was performed. Additionally, the ex vivo perfusion was limited to just 280 minutes, and the cold ischemia time was notably short. Considering that the authors aim to support the possibility of manipulating organs during long-term perfusion, the animal model used seems to have limited translational value. The authors should better acknowledge the limitations of their model and explain why they did not proceed with transplantation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 60, 900, 100]]<|/det|> +2. Considering the limited number of animals per group, the authors should discuss the technical challenges of perfusing small liver grafts which may have affected the results. Also how sample size was determined is not very clear and require better justification. + +<|ref|>text<|/ref|><|det|>[[72, 112, 896, 153]]<|/det|> +3. The model used included a very short cold ischemia time and a short duration of perfusion, only 4 hours. The only conclusion that can be made is that the ischemia reperfusion injury was reduced. A model with prolonged perfusion and large animal model is needed to demonstrate "organ manipulation". + +<|ref|>text<|/ref|><|det|>[[72, 164, 920, 205]]<|/det|> +4. The title of the paper, "From 17-day human liver machine perfusion to a preclinical mesenchymal cell bioreactor towards a long-term ex-situ platform for organ manipulation," is quite misleading. Study A included only one long-term perfusion, and Study B comprised only short-term perfusion of just 4 hours. + +<|ref|>text<|/ref|><|det|>[[72, 217, 905, 257]]<|/det|> +5. The authors reported the induction of factors involved in resolution/regeneration. However the authors have very limited data suggesting regeneration. Most of their results could be explained with a reduction of IR injury. Furthermore the short duration of perfusion (4 hrs) limits any conclusion. Please justify this conclusion further. + +<|ref|>sub_title<|/ref|><|det|>[[73, 281, 183, 295]]<|/det|> +## REFERENCES + +<|ref|>text<|/ref|><|det|>[[72, 307, 904, 398]]<|/det|> +1) Lau, N. S. et al. Long-term ex situ normothermic perfusion of human split livers for more than 1 week. Nat. Commun. 14, (2023). +2) Eshmuninov, D. et al. An integrated perfusion machine preserves injured human livers for 1 week. Nat. Biotechnol. 38, 189-198 (2020). +3) Lau NS, Ly M, Dennis C, Toomath S, Huang JL, Huang J, Ly H, Chanda S, Marinelli T, Davis R, Liu K, McCaughan G, Crawford M, Pulitano C. Microbial Contamination During Long-term Ex Vivo Normothermic Machine Perfusion of Human Livers. Transplantation. 2024 Jan 1;108(1):198-203. + +<|ref|>text<|/ref|><|det|>[[73, 476, 144, 489]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 503, 219, 516]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 528, 160, 542]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 555, 238, 567]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 567, 900, 606]]<|/det|> +The authors have reviewed their manuscript according to suggestions and concerns made by the reviewers. Additionally, they have included some pilot results in a large animal NMP model to improve the translational impact of their work. Here are some issues that need to be addressed. + +<|ref|>text<|/ref|><|det|>[[70, 618, 900, 646]]<|/det|> +1) According to the international society for cell and gene therapy, the correct term for MSC is now "mesenchymal stromal cells" (Viswanathan et al., Cytotherapy, 2019). Authors should update their manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 658, 904, 710]]<|/det|> +2) Although the addition to the NMP circuit might be novel, culture of MSC in hollow fiber bioreactors is already known. Additionally, commercial distribution of MSC has been offering the possibility of shipping cultured MSC in culture flasks or other formats, keeping their properties intact after transportation, which is quite similar to the logistic procedure described here. Novelty of this fact is scarce. + +<|ref|>text<|/ref|><|det|>[[70, 722, 920, 750]]<|/det|> +3) Authors need to update figure 4 and supplemental data including all cell types susceptible to be measured in "wash-outs", (i.e. MSC, endothelial cells, etc.) Even in low numbers, MSC can still detach and flush through the system. + +<|ref|>text<|/ref|><|det|>[[70, 762, 842, 776]]<|/det|> +4) Authors mention the section supplementary methods 1.12 which is not included in the supplementary material. + +<|ref|>text<|/ref|><|det|>[[72, 788, 917, 829]]<|/det|> +5) Supplementary figure 12. Regardless of measured parameters used to evaluate success in NMP, visual evaluation is still key during perfusion. In the images, there is a clear difference in perfusion between both organs, with the one from the MSC group having a paler color. This unequivocally show bad perfusion of the organ. + +<|ref|>text<|/ref|><|det|>[[72, 840, 911, 880]]<|/det|> +6) There is a discrepancy regarding the number of cells used for the pig experiments described in the results and methods section. 37x107 cells noted in the results section does not equal 37 million cells (20 ml of a 1.85x106 cells/ml suspension). Please correct accordingly. + +<|ref|>text<|/ref|><|det|>[[72, 892, 920, 945]]<|/det|> +7) Authors have used 2x10^7 MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. Comparison of results is therefore very limited between both models. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 60, 912, 101]]<|/det|> +8) Additionally, cell density in bioreactors is extremely different: 18500 MSC per cm2 for pig bioreactor vs. 40000 MSC/cm2 in rat bioreactors. Cell density is known to alter MSC functionality, secretory profile and immunomodulatory potential. Authors should justify these differences and elaborate about possible consequences. + +<|ref|>text<|/ref|><|det|>[[72, 112, 921, 166]]<|/det|> +9) The large animal model used by the authors lacks potential for translation. Clinical strategies used in human liver NMP trials include perfusion times ranging from 9-20+ hours. Although authors are presenting preliminary results in a large animal preclinical model coupled to an MSC bioreactor, clinical translation assumptions should be made carefully, as the author do not present sufficient data supporting their claims. + +<|ref|>text<|/ref|><|det|>[[70, 177, 904, 205]]<|/det|> +10) Even though these are preliminary results, only \(n = 3\) animals were used for the large animal study. This small sample size needs justification and sample size calculation need to be explained. + +<|ref|>sub_title<|/ref|><|det|>[[73, 230, 161, 243]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 257, 238, 270]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 270, 904, 366]]<|/det|> +The incorporation of an MSC- bioreactor in a normothermic machine perfusion (NMP) circuit is a novel concept although other groups are working in this area. There is a body of work demonstrating that MSCs can ameliorate ischaemia reperfusion injury and it is known that this is due to the release of EVs and paracrine factors from the stem cells and that MSCs themselves have a number of potentially adverse effects. The isolated organ preservation offered by NMP removes problems with targeting stem cells to a specific organ and bypassing the reticuloendothelial system. NMP also reduces the risk of off-target adverse effects. The addition of a bioreactor to the NMP circuit is a logical development. The authors have demonstrated the feasibility of this new approach and in the rat model evidence that the addition of a bioreactor can counter some of the changes associated with I/R injury. + +<|ref|>text<|/ref|><|det|>[[73, 383, 503, 397]]<|/det|> +There are a number of issues that the authors should consider: + +<|ref|>text<|/ref|><|det|>[[70, 410, 923, 570]]<|/det|> +1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. +2. The procine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model that the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. +3. The group size for the porcine experiments is small at \(n = 3\) and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& Ipha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. +4. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. + +<|ref|>sub_title<|/ref|><|det|>[[73, 594, 144, 607]]<|/det|> +## Version 3: + +<|ref|>text<|/ref|><|det|>[[73, 620, 218, 633]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 646, 160, 659]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 672, 238, 685]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 685, 835, 700]]<|/det|> +The authors have replied to most of the reviewers comments, with a very elaborated explanation in some cases. + +<|ref|>text<|/ref|><|det|>[[73, 711, 254, 724]]<|/det|> +Some questions still arise: + +<|ref|>text<|/ref|><|det|>[[72, 737, 905, 790]]<|/det|> +- The authors missed one of the previous comments: Authors have used 2x10^7 MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. Comparison of results is therefore very limited between both models. + +<|ref|>text<|/ref|><|det|>[[72, 802, 916, 855]]<|/det|> +- Regarding MSC detaching from the bioreactor. MSC do not flush through during liver-less perfusion. However, as fluid composition changes due to the liver secreted moleculas and cytokines, there is no data confirming this subject as conditions change. The authors do not provide any direct proof of the cell types leaving the NMP system. Therefore, all cells present in the NMP system should be taken into account, including MSC. + +<|ref|>text<|/ref|><|det|>[[72, 866, 910, 907]]<|/det|> +- The authors have provided preliminary data on the technical feasibility of coupling an MSC bioreactor in a porcine NMP setup. The objective was to set a translatable setup for human use in the clinic. With this in mind, the very small population size (n=3) do not allow to obtain any conclusion and larger studies need to be carried out. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 74, 238, 87]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 87, 922, 112]]<|/det|> +1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. + +<|ref|>text<|/ref|><|det|>[[72, 112, 884, 153]]<|/det|> +The authors address the use of rodent models on the basis that this is common practice and that rodent models are an important step in the evolution of new technologies. These are reasonable points but still don't answer the issue of translatability. There is not much the authors can do about this limitation. + +<|ref|>text<|/ref|><|det|>[[70, 165, 922, 220]]<|/det|> +2. The porcine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model than the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. + +<|ref|>text<|/ref|><|det|>[[70, 220, 905, 246]]<|/det|> +The authors have answered my concerns to some extent. The use of a porcine model provides useful feasibility evidence that the technology can be upscaled to a large animal set-up that resembles the clinical situation. + +<|ref|>text<|/ref|><|det|>[[72, 245, 920, 298]]<|/det|> +3. The group size for the porcine experiments is small at \(n = 3\) and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& Ipha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. + +<|ref|>text<|/ref|><|det|>[[72, 309, 923, 350]]<|/det|> +3. My comments relating to the small group size in the small group size in the porcine experiments have been acknowledged by revision of the supplementary information. In relation to the short duration of the perfusion experiments, the authors are planning experiments with more relevant prolonged perfusion. It would have strengthened the work to wait for these results. + +<|ref|>text<|/ref|><|det|>[[70, 360, 916, 400]]<|/det|> +4. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. The authors agree that declined human livers that have been declined for transplantation will be useful in the future. + +<|ref|>text<|/ref|><|det|>[[72, 411, 916, 452]]<|/det|> +Overall, the authors have explored a potentially important development in normothermic organ perfusion and they present a useful dataset. Nonetheless, their findings are preliminary and the further studies suggested by reviewers and planned by the authors would lend much more weight to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 618, 61]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[127, 83, 499, 108]]<|/det|> +## RESPONSE TO REVIEWERS + +<|ref|>text<|/ref|><|det|>[[127, 123, 500, 140]]<|/det|> +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +<|ref|>text<|/ref|><|det|>[[127, 172, 870, 224]]<|/det|> +We thank the reviewers for their helpful feedback. Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[128, 85, 272, 107]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[127, 129, 864, 261]]<|/det|> +The authors have skillfully design a promising platform to study the effect of mesenchymal stem cells (MSC) during ex vivo perfusion of rat livers. This is a very interesting approach to overcome some issues observed in direct MSC infusion in organ- in- a- pump models, like microvasculature clogging. The main successful points are the modification of a rat liver normothermic machine perfusion (NMP) system to include a bioreactor for MSC cell therapy and the maintenance of hepatocyte viability during MSC- NMP. However, there are some concerns that need to be addressed: + +<|ref|>sub_title<|/ref|><|det|>[[127, 300, 230, 316]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[155, 336, 848, 409]]<|/det|> +1. Authors claim that MSC only activate their secretory potential after exposure to inflammatory stimuli. However, this is not true as demonstrated earlier (i.e. Park et al., Int J Stem Cells., 2009) but MSC secretory profile is modulated by the microenvironment (i.e. Burja et al., Curr Res Transl Med., 2020). + +<|ref|>text<|/ref|><|det|>[[126, 411, 872, 580]]<|/det|> +We thank the Reviewer for stressing this concept and for providing an additional reference demonstrating the plasticity of the immunoregulation mediated by adipose tissue (AT)- MSCs, which can mount distinct responses to different inflammatory stimuli. These observations reinforce the rationale behind the design of our platform, where stem cells' secretory activity can be specifically activated by the inflammatory mediators release by each individual liver. The sentence "...MSCs secretory activity is induced only after cell exposure to an inflammatory microenvironment, ..." was re-formulated as follows: "...MSCs secretory activity is boosted after exposure to inflammatory microenvironment and different inflammatory stimuli can elicit distinct responses, ..." (lines 214- 215, page 9 of the tracked version of the revised manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[127, 620, 198, 636]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[128, 655, 867, 710]]<|/det|> +2. MSC in vitro culture. Authors describe "MSCs were cultured at a concentration of \(2^{*}105\) in \(14\mathrm{mL}\) in aMEM medium". What vessel was used to seed the cells and what is the final seeding density in this vessel? + +<|ref|>text<|/ref|><|det|>[[128, 712, 852, 767]]<|/det|> +Two hundred thousand human AT- MSCs were cultured at a concentration of \(14.3^{*}10^{4}\) cells/ml in \(75\mathrm{cm}^2\) culture flasks (Sarstedt AG & Co. KG, Numbrecht, Germany), in \(14\mathrm{mL}\) of complete medium. This information was added to the Supplementary Methods 1.1.1. + +<|ref|>text<|/ref|><|det|>[[155, 787, 865, 880]]<|/det|> +3. Characterization of MSC after NMP. Cells were retrieved from the bioreactor. Were the cells directly analysed (cytometry). For how long were the MSC re-cultured for the morphology tests and what were the conditions of that culture? (cell seeding density, culture time, etc.). Also, did the authors count the total number of cells retrieved from the bioreactor and compared with the original number? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[127, 82, 870, 138]]<|/det|> +We thank the Reviewer for noting that relevant information was missing. The methods for cell detachment from the bioreactor and processing before flow cytometry have been added to Supplementary Methods 1.1.3. + +<|ref|>sub_title<|/ref|><|det|>[[152, 158, 860, 194]]<|/det|> +## 4. Exposure to perfusion fluid may have altered their metabolism and survival, acting as a licensing agent itself. + +<|ref|>text<|/ref|><|det|>[[127, 196, 870, 308]]<|/det|> +The Reviewer's comment is pertinent. As previously demonstrated by Sierra Parraga and coworkers, the conditions required to perform the NMP procedure influence MSCs viability and function. In particular, exposure of thawed MSCs to the perfusion fluid and the suspension condition are associated with reduced cell viability, slower mitochondrial metabolism, and generation of reactive oxygen species (ROS) \(^{1,2}\) . Conversely, the authors reported no negative influences of the perfusion fluid on survival when the cells are kept under adherent conditions \(^{1}\) . + +<|ref|>text<|/ref|><|det|>[[127, 309, 870, 440]]<|/det|> +The innovative configuration of our platform allows keeping the cells in their optimal culture environment during NMP, i.e. adherent to the bioreactor fibers. Moreover, the use of a bioreactor provides the cells with a resting period after thawing, during which they can recover from structural damage and oxidative stress induced by cryopreservation. Consistently, we did not reveal massive cell death during liverless- NMP experiments. In fact, no circulating cells, detached from the bioreactor, were detected in the perfusate samples, while the release of the apoptotic marker caspase- cleaved keratin 18 (CK18) remained stable throughout the procedure (Figure 3). + +<|ref|>text<|/ref|><|det|>[[127, 441, 870, 515]]<|/det|> +Therefore, the particular setting of the present model offers MSCs the opportunity to recover from cryopreservation, while ensuring optimal culture conditions during NMP. These points were further clarified in the Introduction (lines 153- 155, page 7 of the tracked version of the revised manuscript) and in the Discussion (lines 373- 375, page 14 of the tracked version of the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[152, 535, 839, 571]]<|/det|> +5. Flow cytometry. For reproducibility purposes, please add the reference numbers of antibodies used for flow cytometry and other relevant reagent. + +<|ref|>text<|/ref|><|det|>[[128, 573, 600, 590]]<|/det|> +These details have been added to Supplementary Methods 1.1.3 + +<|ref|>text<|/ref|><|det|>[[154, 610, 830, 685]]<|/det|> +6. Liver NMP. Perfusion took place in two phases: a warming phase and a stable normothermic phase. Was the bioreactor connected to he circuit during the entire perfusion (warming+stable phases)? Similar to the question related to shipment, rewarming time might affect MSC survival and metabolism during this time. + +<|ref|>text<|/ref|><|det|>[[127, 686, 870, 816]]<|/det|> +The bioreactor was attached to the circuit immediately before liver connection and was therefore exposed to a temperature ranging from \(24 - 26^{\circ}\mathrm{C}\) , which was increased to \(37^{\circ}\mathrm{C}\) over \(40\mathrm{min}\) . As suggested by the Reviewer, we investigated whether MSCs underwent cell death during rewarming, by assessing the release of human CK18 into the perfusate. The data show that the degree of apoptosis activation during liver- NMP is similar to that observed during liverless- NMP, indicating that the cells did not experience excessive distress during the different phases of the liver- NMP procedure. These results were added to the Supplementary Results 1.2.10 + +<|ref|>text<|/ref|><|det|>[[154, 836, 864, 891]]<|/det|> +7. The authors seeded \(20*10*7\) MSC in a bioreactor. Is this number constant throughout the perfusion experiment? Do MSC die and are replaced by proliferating MSC? These dead cells might be responsible for the uncontrolled release of cytokines. + +<|ref|>text<|/ref|><|det|>[[127, 892, 860, 928]]<|/det|> +As discussed at points 3 and 5 of the present document, no massive cell death was observed during the experiments. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[153, 101, 815, 157]]<|/det|> +## 8. In addition, average rat liver weight is 4-5 grams which results in a MSC dose of \(4*10^{-9}\) MSC/kg, an extremely high dose which has a poor translation towards a clinically relevant setup. + +<|ref|>text<|/ref|><|det|>[[126, 158, 871, 364]]<|/det|> +In our experiments, the average rat liver weight was 13- 15 g; as a result, \(1.5*10^{6}\) cells were used per gram of liver, which, as highlighted by the Reviewer, is about 1000- times higher than the dosage currently adopted in clinical trials. However, we believe that this is a strength, rather than a limitation. In fact, the application of a high dosage- cell therapy appears essential for maximizing liver cell exposure to the MSCs secretome within the short time window offered by the NMP procedure. By completely eliminating the risk of embolism, the bioreactor- based setting enables to safely increase the quantity of stem cells delivered in a single administration. Additionally, the use of a bioreactor avoids cell migration to target tissues, thus preventing possible cell de- differentiation or long- term retention. Overall, this represents a significant clinical advantage, considering that for certain patients and diseases, multiple administrations of standard- dose MSCs are needed to achieve the desired therapeutic effect \(^{3}\) . + +<|ref|>text<|/ref|><|det|>[[126, 365, 870, 496]]<|/det|> +In support of the practical applicability of our platform, we demonstrated in a pilot study the feasibility of integrating the MSCs- bioreactor into a circuit currently used in the clinical setting (Abstract \(\mathrm{N}^{\circ}1307\) , "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, we performed NMP of porcine livers procured from cardiac death donors, using the Liver Assist® machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. + +<|ref|>text<|/ref|><|det|>[[127, 496, 870, 533]]<|/det|> +These preliminary data, together with the growing availability of novel technologies for cell upscaling and manufacturing \(^{3,4}\) , reinforce the translational value of our advanced circuit. + +<|ref|>text<|/ref|><|det|>[[153, 553, 863, 627]]<|/det|> +9. In addition, authors sent MSC in a bioreactor from one laboratory to another at room temperature. Culture temperature is key for MSC survival and temperatures lower to \(37^{\circ}\) C are deleterious (Pratiwi et al., Cytotherapy, 2019). Did the authors study the status of MSC after the shipment? + +<|ref|>text<|/ref|><|det|>[[127, 628, 870, 702]]<|/det|> +Bioreactor supernatants were collected upon devices arrival to the Milan Lab and were then analyzed using an automated cell counter, gas-analysis, and ELISA. Results of this analysis are reported in the session Assessment of MSCs viability after bioreactor shipment pg 9-10 of the original version of the manuscript and in the Supplementary Table 2. + +<|ref|>sub_title<|/ref|><|det|>[[100, 761, 159, 777]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[128, 797, 857, 928]]<|/det|> +1. The authors describe an increase in certain metabolites such as lactate, IL-6, IL-1ra, among other, during liverless NMP+bioreactor. However, these are inflammatory cytokines and lactate production has been related to increased ROS production (i.e. Li et al., Signal Transduct Target Ther., 2022). Though the authors address the increase in inflammatory cytokines as a positive results, they should discuss the inflammatory perfustate profile and elaborate on this in the discussion section as it appears to be a setback of their NMP circuit. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 82, 869, 119]]<|/det|> +The production of lactate, along with glucose consumption, indicates that the cells were metabolically active and initiated anaerobic glycolysis during Liverless- NMP. + +<|ref|>text<|/ref|><|det|>[[128, 121, 870, 175]]<|/det|> +With regard to the increased cytokine perfusate concentration, a mild inflammatory activation of the cells seeded in the bioreactor was expected, since both shipment and the NMP procedure itself represent stress- inducing factors. + +<|ref|>text<|/ref|><|det|>[[127, 177, 870, 345]]<|/det|> +Accepting the Reviewer's suggestion, we investigated whether MSCs were exposed to oxidative stress, by assessing the release of 8- hydroxy- 2'- deoxyguanosine (8- OHdG) in the perfusates collected during Liverless- NMP. We found increasing concentrations of 8- OHdG over the procedure (from \(15630\pm 2211\mathrm{pg}\) at \(1\mathrm{h}\) to \(19965\pm 3532\mathrm{pg}\) at \(4\mathrm{h}\) ). However, higher amounts \((28211\pm 1489\mathrm{pg})\) were detected in the supernatant collected from the bioreactor immediately after device arrival to the Milan lab. This interesting observation indicates that MSCs experience an oxidative burst during shipment and highlight the need for a technical improvement of this stage, for example by supplementing the culture medium with antioxidants (vitamin C, glutathione). We thank the Reviewer for pointing out the need to refine these important aspects, in view of a potential translational use of our platform. + +<|ref|>sub_title<|/ref|><|det|>[[128, 365, 857, 418]]<|/det|> +## 2. Immune cells outflow. Authors describe outflow of an increased number of immune cells when the bioreactor is connected during NMP. H. however, they do not show data for cell characterization in the outflow perfusate. + +<|ref|>text<|/ref|><|det|>[[127, 420, 870, 572]]<|/det|> +Accepting the Reviewer's suggestion, we performed a qualitative assessment of individual donor cell populations removed during the initial wash- out. Briefly, cell pellets obtained from wash- out samples were originally counted using the \(\mathrm{Scpeptr^{TM}}\) cell counter (Merck KGaA) equipped with \(40\mu \mathrm{m}\) sensors, according to the Coulter principle. The acquired data were further analyzed based on particle size and volume using the software \(\mathrm{Scpeptr^{TM}}2.0\) software pro (Merck KGaA) \(^{5}\) . The obtained results are presented in Figure 5, while methods are detailed in the Supplementary Information 1.1.8. Note that, since the bioreactors used in this research have membranes with pores that are \(150\mathrm{nm}\) in size, the particles found in the perfusate originate solely from the liver. + +<|ref|>text<|/ref|><|det|>[[128, 574, 870, 609]]<|/det|> +We thank the Reviewer for his comment which lead to a significant improvement in the description of the wash- out samples. + +<|ref|>sub_title<|/ref|><|det|>[[128, 629, 840, 666]]<|/det|> +## 3. EV origin. The authors hint that observed differences in EV size are related to their hepatocyte or MSC origin. This is a difficult assumption to make based only on EV size. + +<|ref|>text<|/ref|><|det|>[[128, 668, 870, 702]]<|/det|> +We agree with the Reviewer and acknowledge that the assessment of EV size alone is not entirely adequate to attribute their origin to either stem cells or the liver. + +<|ref|>text<|/ref|><|det|>[[128, 705, 870, 758]]<|/det|> +However, due to the inherent technical difficulties in analyzing Oxyglobin- enriched samples, a more thorough evaluation of the EVs released in the perfusate was unfeasible. Based on this, the results of EVs analysis were excluded from the main findings and relocated in the Supplementary Results 1.2.4. + +<|ref|>sub_title<|/ref|><|det|>[[128, 780, 866, 835]]<|/det|> +## 4. pH stabilization. The authors claim that MSC in the bioreactor regulate the pH of the perfusate. However, exposure to MSC medium present in the bioreactor, which contains a buffered solution to maintain pH, might be the responsible factor of pH stabilization + +<|ref|>text<|/ref|><|det|>[[128, 837, 870, 910]]<|/det|> +After connection to the NMP circuit, the bioreactors were filled with perfusion fluid ( \(100\mathrm{ml}\) ), while the cell medium ( \(10\mathrm{ml}\) ) was progressively removed over the NMP procedure. Perfusate pH stabilization appears therefore the consequence of an active modulation mediated by MSCs. Bioreactor- based perfusion was indeed associated with changes in \(\mathrm{pCO_2}\) as well as in various + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[125, 81, 870, 120]]<|/det|> +electrolytes which can directly influence perfusate pH, as reported in Supplementary Figure 6 - Gas analysis of perfusate samples collected during liver- NMP. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[128, 85, 275, 108]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[127, 129, 857, 242]]<|/det|> +This study reports the effects of the addition of an MSC- bioreactor to the NMP circuit in an isolated rat liver model. The study mainly shows the safety and feasibility of this approach and some beneficial effects of using an MSC bioreactor approach rather than thawed MSCs. The MSC- bioreactor effects included decreased injury markers, increased bile production; increased acute phase proteins; more effective washout of blood; reduced ATP depletion; absence of succinate accumulation. Please address the following: + +<|ref|>text<|/ref|><|det|>[[128, 261, 844, 316]]<|/det|> +1. You state that the 'translational value is high'. This needs justification when using a rodent model as many such models have been shown not to have reproducible effects in large animals and humans. + +<|ref|>text<|/ref|><|det|>[[127, 317, 871, 504]]<|/det|> +Although we acknowledge the difficulties encountered when transferring the findings from preclinical studies to the clinical scenario, we deem that starting from a rodent model was an essential step in the development of the novel circuit for liver NMP, where the livers can be treated with a MSCs- based therapy before transplantation. In fact, establishment of such an innovative platform required the consideration and implementation of various technical aspects related to both MSCs and the NMP procedure, including cell type selection, seeding density, design of the bioreactor circuit, and oxygen supply to the liver. The use of rodent models shows several advantages compared to large animals, including a more rapid recovery of hepatic homeostasis and function, less intra- experimental group variability, and greater selection of specific laboratory reagents. Thus, small animal models emerge as the optimal choice at this early stage of the research. + +<|ref|>text<|/ref|><|det|>[[127, 505, 870, 655]]<|/det|> +The knowledge gained with the present study was used to guide the translational application of the novel platform to porcine liver NMP (Abstract \(\mathrm{N}^{\circ}\) 1307, "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, porcine livers procured from cardiac death donors were ex situ- perfused using the Liver Assist \(^{\mathrm{\textregistered}}\) machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. This pilot study demonstrates the practical applicability of our novel configuration when the clinical devices/consumables are used. + +<|ref|>text<|/ref|><|det|>[[127, 657, 870, 768]]<|/det|> +These observations underscore the translational value of the present proof- of- concept study in a rodent model. In response to the Reviewer's comment, we improved the clarity of the message delivered, by reformulating the original sentence as follows: "Overall, these observations support the high translational value of the present advanced NMP platform to inform the application of this innovative setup in large animal models, and, ultimately, in the clinical setting" (lines 385- 388, page 13 of the tracked version of the revised manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[128, 789, 868, 824]]<|/det|> +## 2. Although you acknowledge that the cold ischaemic time is very short, this is. major limitation with little clinical relevance. + +<|ref|>text<|/ref|><|det|>[[127, 827, 870, 925]]<|/det|> +As stated by the Reviewer in the previous comment, rodent models show inherent differences relative to large animals and humans. With regard to the liver anatomy, there is an increasing dependence on the hepatic artery contribution for lobular perfusion in larger mammals compared with small organisms \(^{6}\) . This affects the outcome of liver transplantation; for example, liver transplants in mice do not need a hepatic artery anastomosis to avoid biliary complications, whereas those in humans do \(^{6}\) . The anatomic peculiarities also determine qualitative differences in the pathophysiological + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[127, 82, 870, 132]]<|/det|> +responses to stress stimuli between the livers of the various species. Therefore, a direct comparison of human and experimental procedures may not be entirely adequate when time intervals are considered. + +<|ref|>text<|/ref|><|det|>[[127, 133, 870, 215]]<|/det|> +Consistently, the present research shows that a different duration of ischemia enabled to obtain the same outcome. In fact, the IR challenge applied in this study not only induced the release of cytolysis markers, but it likewise promoted many of the detrimental biological events typically triggered by IR, including intracellular ATP depletion (Figure 6), succinate accumulation (Figure 6), and production of inflammatory mediators (Figure 7). + +<|ref|>text<|/ref|><|det|>[[127, 216, 870, 280]]<|/det|> +Thus, although the ischemic time is shorter than that observed in the clinical setting, the experimental findings support the reliability of our model in reproducing the key pathophysiological features of liver IR injury and support its translational use as a useful starting point for future studies in porcine and human livers. + +<|ref|>text<|/ref|><|det|>[[127, 280, 870, 329]]<|/det|> +More prolonged or extreme stimuli can be applied to our model. However, here we describe the set- up phase of NMP+bioreactor and we believe that smaller but significant injuries could lead to more informative results in this research phase. + +<|ref|>sub_title<|/ref|><|det|>[[127, 344, 870, 377]]<|/det|> +## 3. Please discuss the potential effects of raised TNF and IL-6 in the bioreactor group. These acute phase proteins can have pro-inflammatory as well as protective effects. + +<|ref|>text<|/ref|><|det|>[[127, 378, 870, 426]]<|/det|> +As highlighted by the Reviewer, IL- 6 and TNF- \(\alpha\) can exert either protective or harmful effects depending on various factors, including the amount released, the duration of their expression, and the underlying liver condition. + +<|ref|>text<|/ref|><|det|>[[127, 427, 870, 492]]<|/det|> +In the early stages of IRI, TNF- \(\alpha\) and IL- 6 are secreted as part of the pathophysiological immune response to the ischemic damage \(^{7,8}\) . Their role involves recruiting immune cells to the injured site and activating pathways related to tissue repair and removal of damaged cells \(^{9}\) . In addition, TNF- \(\alpha\) and IL- 6 are established key factors in the onset of liver cell regeneration \(^{10}\) . + +<|ref|>text<|/ref|><|det|>[[127, 492, 870, 606]]<|/det|> +In the bioreactor- based perfusion, concomitant with increased TNF- \(\alpha\) and IL- 6 perfusate concentration, there was a rise of Adiponectin, CTGF, HGF, and, at the initial stage after reperfusion, of IL- 13 (Figure 7). Compared to the standard NMP, the treated group likewise exhibited lower perfusate concentration of different mediators related to inflammation (Figure 7). This molecular scenario can be interpreted as a coordinated adaptive response to the reperfusive injury. The observed induction of Adiponectin is particularly relevant in this regard, due to its well- known properties in the mitigation of inflammation \(^{11,12}\) . + +<|ref|>text<|/ref|><|det|>[[127, 607, 870, 640]]<|/det|> +We thank the Reviewer for pointing out the need to improve the discussion of these results (lines 417- 435, page 15- 16 of the tracked version of the revised manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[127, 655, 870, 688]]<|/det|> +## 4. It is difficult to make conclusions about ATP depletion when the ATP::ADSP ratio has not been measured. + +<|ref|>text<|/ref|><|det|>[[127, 690, 870, 780]]<|/det|> +Accepting the Reviewer's suggestion, we performed additional experiments using High- performance liquid chromatography (HPLC) to investigate the concentration of ATP breakdown products in liver biopsies, according to \(^{13}\) . The results have been added to the main text (lines 296- 297, pages 11 of the tracked version of the revised manuscript), while the methods are described in Supplementary information 1.1.11 + +<|ref|>sub_title<|/ref|><|det|>[[127, 801, 860, 854]]<|/det|> +## 5. In the discussion you state that the ATP recovery mechanism is likely due to a transfer of viable mitochondria to injured cells but you do not present any data to support such a contention. + +<|ref|>text<|/ref|><|det|>[[127, 858, 870, 911]]<|/det|> +Thank you for your note. We reformulated the paragraph dedicated to MSCs- induced protection of cell energy status (lines 401- 416, page 15 of the tracked version of the revised manuscript), specifying that the transfer of mitochondria from stem cells to liver tissue has been proposed as a potential + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[127, 80, 870, 120]]<|/det|> +underlying mechanism based on previous evidence \(^{14,15}\) . Further research is required to verify whether this process plays a role in the context of hepatic IRI. + +<|ref|>text<|/ref|><|det|>[[125, 138, 852, 214]]<|/det|> +6. In the discussion you conclude that Bioreactor-MSCs had an impact on different aspects of immune modulation and inflammation. Please justify this conclusion further. These points have been further discussed in lines 417-435 of the tracked version of the revised manuscript (pages 15-16). + +<|ref|>text<|/ref|><|det|>[[127, 234, 556, 251]]<|/det|> +7. There are several typographical and syntax errors. + +<|ref|>text<|/ref|><|det|>[[127, 253, 844, 289]]<|/det|> +Thank you very much for highlighting these inaccuracies. After a thorough of the manuscript, all the imprecisions have been corrected. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[128, 85, 260, 106]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[123, 105, 860, 900]]<|/det|> +1. Sierra Parraga, J. M. et al. Effects of normothermic machine perfusion conditions on mesenchymal stromal cells. Front. Immunol. 10, 1–11 (2019).2. Deng, B. et al. Removal from adherent culture contributes to apoptosis in human bone marrow mesenchymal stem cells. Mol. Med. Rep. 15, 3499–3506 (2017).3. Hassan, M. N. F. Bin et al. Large-Scale Expansion of Human Mesenchymal Stem Cells. Stem Cells Int. 2020, (2020).4. Panchalingam, K. M., Jung, S., Rosenberg, L. & Behie, L. A. Bioprocessing strategies for the large-scale production of human mesenchymal stem cells: A review Mesenchymal Stem/Stromal Cells - An update. Stem Cell Res. Ther. 6, 1–10 (2015).5. Merck KGaA. Size-based Immunomonitoring using the Scepter™ 3.0 Handheld Cell Counter. Application note https://www.sigmaaldrich.com/IT/it/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/size-based-immunomonitoring-scepter-handheld-cell-counter (2023).6. Kruepunga, N., Hakvoort, T. B. M., Hikspoors, J. P. J. M., Köhler, S. E. & Lamers, W. H. Anatomy of rodent and human livers: What are the differences? Biochim. Biophys. Acta - Mol. Basis Dis. 1865, 869–878 (2019).7. Soares, R. O. S., Losada, D. M., Jordani, M. C., Évora, P. & Castro-E-Silva, O. Ischemia/reperfusion injury revisited: An overview of the latest pharmacological strategies. Int. J. Mol. Sci. 20, (2019).8. Wu, M. Y. et al. Current Mechanistic Concepts in Ischemia and Reperfusion Injury. Cell. Physiol. Biochem. 46, 1650–1667 (2018).9. Blindenbacher, A. et al. Interleukin 6 is important for survival after partial hepatectomy in mice. Hepatology 38, 674–682 (2003).10. Moris, D. et al. Mechanistic insights of rapid liver regeneration after associating liver partition and portal vein ligation for stage hepatectomy. World J. Gastroenterol. 22, 7613–7624 (2016).11. Ruan, H. & Dong, L. Q. Adiponectin signaling and function in insulin target tissues. J. Mol. Cell Biol. 8, 101–109 (2016).12. Blandin, A. et al. Extracellular vesicles are carriers of adiponectin with insulin-sensitizing and anti-inflammatory properties. Cell Rep. 42, (2023).13. Meszaros, A. T. et al. Mitochondrial respiration during normothermic liver machine perfusion predicts clinical outcome. EBioMedicine 85, (2022).14. Peruzzotti-Jametti, L. et al. Neural stem cells traffic functional mitochondria via extracellular vesicles. PLoS Biology vol. 19 (2021).15. Phinney, D. G. et al. Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs. Nat. Commun. 6, 1–15 (2015). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[127, 83, 499, 108]]<|/det|> +## RESPONSE TO REVIEWERS + +<|ref|>text<|/ref|><|det|>[[127, 123, 500, 140]]<|/det|> +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +<|ref|>text<|/ref|><|det|>[[127, 172, 870, 224]]<|/det|> +We thank the reviewers for their helpful feedback. Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[128, 85, 272, 107]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[127, 129, 864, 261]]<|/det|> +The authors have skillfully design a promising platform to study the effect of mesenchymal stem cells (MSC) during ex vivo perfusion of rat livers. This is a very interesting approach to overcome some issues observed in direct MSC infusion in organ- in- a- pump models, like microvasculature clogging. The main successful points are the modification of a rat liver normothermic machine perfusion (NMP) system to include a bioreactor for MSC cell therapy and the maintenance of hepatocyte viability during MSC- NMP. However, there are some concerns that need to be addressed: + +<|ref|>sub_title<|/ref|><|det|>[[127, 300, 230, 316]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[155, 336, 848, 409]]<|/det|> +1. Authors claim that MSC only activate their secretory potential after exposure to inflammatory stimuli. However, this is not true as demonstrated earlier (i.e. Park et al., Int J Stem Cells., 2009) but MSC secretory profile is modulated by the microenvironment (i.e. Burja et al., Curr Res Transl Med., 2020). + +<|ref|>text<|/ref|><|det|>[[126, 411, 872, 580]]<|/det|> +We thank the Reviewer for stressing this concept and for providing an additional reference demonstrating the plasticity of the immunoregulation mediated by adipose tissue (AT)- MSCs, which can mount distinct responses to different inflammatory stimuli. These observations reinforce the rationale behind the design of our platform, where stem cells' secretory activity can be specifically activated by the inflammatory mediators release by each individual liver. The sentence "...MSCs secretory activity is induced only after cell exposure to an inflammatory microenvironment, ..." was re-formulated as follows: "...MSCs secretory activity is boosted after exposure to inflammatory microenvironment and different inflammatory stimuli can elicit distinct responses, ..." (lines 214- 215, page 9 of the tracked version of the revised manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[127, 620, 198, 636]]<|/det|> +## Methods + +<|ref|>text<|/ref|><|det|>[[128, 655, 866, 710]]<|/det|> +2. MSC in vitro culture. Authors describe "MSCs were cultured at a concentration of \(2^{*}105\) in \(14\mathrm{mL}\) in aMEM medium". What vessel was used to seed the cells and what is the final seeding density in this vessel? + +<|ref|>text<|/ref|><|det|>[[128, 712, 852, 767]]<|/det|> +Two hundred thousand human AT- MSCs were cultured at a concentration of \(14.3^{*}10^{4}\) cells/ml in \(75\mathrm{cm}^2\) culture flasks (Sarstedt AG & Co. KG, Numbrecht, Germany), in \(14\mathrm{mL}\) of complete medium. This information was added to the Supplementary Methods 1.1.1. + +<|ref|>text<|/ref|><|det|>[[155, 787, 864, 880]]<|/det|> +3. Characterization of MSC after NMP. Cells were retrieved from the bioreactor. Were the cells directly analysed (cytometry). For how long were the MSC re-cultured for the morphology tests and what were the conditions of that culture? (cell seeding density, culture time, etc.). Also, did the authors count the total number of cells retrieved from the bioreactor and compared with the original number? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[127, 82, 870, 138]]<|/det|> +We thank the Reviewer for noting that relevant information was missing. The methods for cell detachment from the bioreactor and processing before flow cytometry have been added to Supplementary Methods 1.1.3. + +<|ref|>sub_title<|/ref|><|det|>[[152, 158, 860, 194]]<|/det|> +## 4. Exposure to perfusion fluid may have altered their metabolism and survival, acting as a licensing agent itself. + +<|ref|>text<|/ref|><|det|>[[127, 196, 870, 308]]<|/det|> +The Reviewer's comment is pertinent. As previously demonstrated by Sierra Parraga and coworkers, the conditions required to perform the NMP procedure influence MSCs viability and function. In particular, exposure of thawed MSCs to the perfusion fluid and the suspension condition are associated with reduced cell viability, slower mitochondrial metabolism, and generation of reactive oxygen species (ROS) \(^{1,2}\) . Conversely, the authors reported no negative influences of the perfusion fluid on survival when the cells are kept under adherent conditions \(^{1}\) . + +<|ref|>text<|/ref|><|det|>[[127, 309, 870, 440]]<|/det|> +The innovative configuration of our platform allows keeping the cells in their optimal culture environment during NMP, i.e. adherent to the bioreactor fibers. Moreover, the use of a bioreactor provides the cells with a resting period after thawing, during which they can recover from structural damage and oxidative stress induced by cryopreservation. Consistently, we did not reveal massive cell death during liverless- NMP experiments. In fact, no circulating cells, detached from the bioreactor, were detected in the perfusate samples, while the release of the apoptotic marker caspase- cleaved keratin 18 (CK18) remained stable throughout the procedure (Figure 3). + +<|ref|>text<|/ref|><|det|>[[127, 441, 870, 515]]<|/det|> +Therefore, the particular setting of the present model offers MSCs the opportunity to recover from cryopreservation, while ensuring optimal culture conditions during NMP. These points were further clarified in the Introduction (lines 153- 155, page 7 of the tracked version of the revised manuscript) and in the Discussion (lines 373- 375, page 14 of the tracked version of the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[152, 535, 839, 571]]<|/det|> +5. Flow cytometry. For reproducibility purposes, please add the reference numbers of antibodies used for flow cytometry and other relevant reagent. + +<|ref|>text<|/ref|><|det|>[[128, 573, 600, 590]]<|/det|> +These details have been added to Supplementary Methods 1.1.3 + +<|ref|>text<|/ref|><|det|>[[154, 610, 830, 685]]<|/det|> +6. Liver NMP. Perfusion took place in two phases: a warming phase and a stable normothermic phase. Was the bioreactor connected to he circuit during the entire perfusion (warming+stable phases)? Similar to the question related to shipment, rewarming time might affect MSC survival and metabolism during this time. + +<|ref|>text<|/ref|><|det|>[[127, 686, 870, 816]]<|/det|> +The bioreactor was attached to the circuit immediately before liver connection and was therefore exposed to a temperature ranging from \(24 - 26^{\circ}\mathrm{C}\) , which was increased to \(37^{\circ}\mathrm{C}\) over \(40\mathrm{min}\) . As suggested by the Reviewer, we investigated whether MSCs underwent cell death during rewarming, by assessing the release of human CK18 into the perfusate. The data show that the degree of apoptosis activation during liver- NMP is similar to that observed during liverless- NMP, indicating that the cells did not experience excessive distress during the different phases of the liver- NMP procedure. These results were added to the Supplementary Results 1.2.10 + +<|ref|>text<|/ref|><|det|>[[154, 836, 864, 891]]<|/det|> +7. The authors seeded \(20*10*7\) MSC in a bioreactor. Is this number constant throughout the perfusion experiment? Do MSC die and are replaced by proliferating MSC? These dead cells might be responsible for the uncontrolled release of cytokines. + +<|ref|>text<|/ref|><|det|>[[127, 892, 860, 928]]<|/det|> +As discussed at points 3 and 5 of the present document, no massive cell death was observed during the experiments. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[153, 101, 815, 157]]<|/det|> +## 8. In addition, average rat liver weight is 4-5 grams which results in a MSC dose of \(4*10^{-9}\) MSC/kg, an extremely high dose which has a poor translation towards a clinically relevant setup. + +<|ref|>text<|/ref|><|det|>[[126, 158, 871, 364]]<|/det|> +In our experiments, the average rat liver weight was 13- 15 g; as a result, \(1.5*10^{6}\) cells were used per gram of liver, which, as highlighted by the Reviewer, is about 1000- times higher than the dosage currently adopted in clinical trials. However, we believe that this is a strength, rather than a limitation. In fact, the application of a high dosage- cell therapy appears essential for maximizing liver cell exposure to the MSCs secretome within the short time window offered by the NMP procedure. By completely eliminating the risk of embolism, the bioreactor- based setting enables to safely increase the quantity of stem cells delivered in a single administration. Additionally, the use of a bioreactor avoids cell migration to target tissues, thus preventing possible cell de- differentiation or long- term retention. Overall, this represents a significant clinical advantage, considering that for certain patients and diseases, multiple administrations of standard- dose MSCs are needed to achieve the desired therapeutic effect \(^{3}\) . + +<|ref|>text<|/ref|><|det|>[[126, 365, 870, 496]]<|/det|> +In support of the practical applicability of our platform, we demonstrated in a pilot study the feasibility of integrating the MSCs- bioreactor into a circuit currently used in the clinical setting (Abstract \(\mathrm{N}^{\circ}1307\) , "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, we performed NMP of porcine livers procured from cardiac death donors, using the Liver Assist® machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. + +<|ref|>text<|/ref|><|det|>[[127, 496, 870, 533]]<|/det|> +These preliminary data, together with the growing availability of novel technologies for cell upscaling and manufacturing \(^{3,4}\) , reinforce the translational value of our advanced circuit. + +<|ref|>text<|/ref|><|det|>[[153, 553, 863, 627]]<|/det|> +9. In addition, authors sent MSC in a bioreactor from one laboratory to another at room temperature. Culture temperature is key for MSC survival and temperatures lower to \(37^{\circ}\) C are deleterious (Pratiwi et al., Cytotherapy, 2019). Did the authors study the status of MSC after the shipment? + +<|ref|>text<|/ref|><|det|>[[127, 628, 870, 702]]<|/det|> +Bioreactor supernatants were collected upon devices arrival to the Milan Lab and were then analyzed using an automated cell counter, gas-analysis, and ELISA. Results of this analysis are reported in the session Assessment of MSCs viability after bioreactor shipment pg 9-10 of the original version of the manuscript and in the Supplementary Table 2. + +<|ref|>sub_title<|/ref|><|det|>[[100, 761, 159, 777]]<|/det|> +## Results + +<|ref|>text<|/ref|><|det|>[[128, 797, 857, 928]]<|/det|> +1. The authors describe an increase in certain metabolites such as lactate, IL-6, IL-1ra, among other, during liverless NMP+bioreactor. However, these are inflammatory cytokines and lactate production has been related to increased ROS production (i.e. Li et al., Signal Transduct Target Ther., 2022). Though the authors address the increase in inflammatory cytokines as a positive results, they should discuss the inflammatory perfustate profile and elaborate on this in the discussion section as it appears to be a setback of their NMP circuit. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[128, 82, 869, 119]]<|/det|> +The production of lactate, along with glucose consumption, indicates that the cells were metabolically active and initiated anaerobic glycolysis during Liverless- NMP. + +<|ref|>text<|/ref|><|det|>[[128, 121, 870, 175]]<|/det|> +With regard to the increased cytokine perfusate concentration, a mild inflammatory activation of the cells seeded in the bioreactor was expected, since both shipment and the NMP procedure itself represent stress- inducing factors. + +<|ref|>text<|/ref|><|det|>[[127, 177, 870, 345]]<|/det|> +Accepting the Reviewer's suggestion, we investigated whether MSCs were exposed to oxidative stress, by assessing the release of 8- hydroxy- 2'- deoxyguanosine (8- OHdG) in the perfusates collected during Liverless- NMP. We found increasing concentrations of 8- OHdG over the procedure (from \(15630\pm 2211\mathrm{pg}\) at \(1\mathrm{h}\) to \(19965\pm 3532\mathrm{pg}\) at \(4\mathrm{h}\) ). However, higher amounts \((28211\pm 1489\mathrm{pg})\) were detected in the supernatant collected from the bioreactor immediately after device arrival to the Milan lab. This interesting observation indicates that MSCs experience an oxidative burst during shipment and highlight the need for a technical improvement of this stage, for example by supplementing the culture medium with antioxidants (vitamin C, glutathione). We thank the Reviewer for pointing out the need to refine these important aspects, in view of a potential translational use of our platform. + +<|ref|>sub_title<|/ref|><|det|>[[128, 365, 857, 418]]<|/det|> +## 2. Immune cells outflow. Authors describe outflow of an increased number of immune cells when the bioreactor is connected during NMP. H. however, they do not show data for cell characterization in the outflow perfusate. + +<|ref|>text<|/ref|><|det|>[[127, 420, 870, 572]]<|/det|> +Accepting the Reviewer's suggestion, we performed a qualitative assessment of individual donor cell populations removed during the initial wash- out. Briefly, cell pellets obtained from wash- out samples were originally counted using the \(\mathrm{Scpeptr^{TM}}\) cell counter (Merck KGaA) equipped with \(40\mu \mathrm{m}\) sensors, according to the Coulter principle. The acquired data were further analyzed based on particle size and volume using the software \(\mathrm{Scpeptr^{TM}}2.0\) software pro (Merck KGaA) \(^5\) . The obtained results are presented in Figure 5, while methods are detailed in the Supplementary Information 1.1.8. Note that, since the bioreactors used in this research have membranes with pores that are \(150\mathrm{nm}\) in size, the particles found in the perfusate originate solely from the liver. + +<|ref|>text<|/ref|><|det|>[[128, 574, 869, 609]]<|/det|> +We thank the Reviewer for his comment which lead to a significant improvement in the description of the wash- out samples. + +<|ref|>sub_title<|/ref|><|det|>[[128, 629, 840, 666]]<|/det|> +## 3. EV origin. The authors hint that observed differences in EV size are related to their hepatocyte or MSC origin. This is a difficult assumption to make based only on EV size. + +<|ref|>text<|/ref|><|det|>[[128, 668, 870, 702]]<|/det|> +We agree with the Reviewer and acknowledge that the assessment of EV size alone is not entirely adequate to attribute their origin to either stem cells or the liver. + +<|ref|>text<|/ref|><|det|>[[128, 705, 870, 758]]<|/det|> +However, due to the inherent technical difficulties in analyzing Oxyglobin- enriched samples, a more thorough evaluation of the EVs released in the perfusate was unfeasible. Based on this, the results of EVs analysis were excluded from the main findings and relocated in the Supplementary Results 1.2.4. + +<|ref|>sub_title<|/ref|><|det|>[[128, 780, 866, 835]]<|/det|> +## 4. pH stabilization. The authors claim that MSC in the bioreactor regulate the pH of the perfusate. However, exposure to MSC medium present in the bioreactor, which contains a buffered solution to maintain pH, might be the responsible factor of pH stabilization + +<|ref|>text<|/ref|><|det|>[[128, 837, 870, 910]]<|/det|> +After connection to the NMP circuit, the bioreactors were filled with perfusion fluid ( \(100\mathrm{ml}\) ), while the cell medium ( \(10\mathrm{ml}\) ) was progressively removed over the NMP procedure. Perfusate pH stabilization appears therefore the consequence of an active modulation mediated by MSCs. Bioreactor- based perfusion was indeed associated with changes in \(\mathrm{pCO_2}\) as well as in various + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[126, 81, 870, 120]]<|/det|> +electrolytes which can directly influence perfusate pH, as reported in Supplementary Figure 6 - Gas analysis of perfusate samples collected during liver- NMP. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[128, 85, 275, 108]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[127, 129, 856, 242]]<|/det|> +This study reports the effects of the addition of an MSC- bioreactor to the NMP circuit in an isolated rat liver model. The study mainly shows the safety and feasibility of this approach and some beneficial effects of using an MSC bioreactor approach rather than thawed MSCs. The MSC- bioreactor effects included decreased injury markers, increased bile production; increased acute phase proteins; more effective washout of blood; reduced ATP depletion; absence of succinate accumulation. Please address the following: + +<|ref|>text<|/ref|><|det|>[[128, 262, 844, 316]]<|/det|> +1. You state that the 'translational value is high'. This needs justification when using a rodent model as many such models have been shown not to have reproducible effects in large animals and humans. + +<|ref|>text<|/ref|><|det|>[[127, 318, 871, 504]]<|/det|> +Although we acknowledge the difficulties encountered when transferring the findings from preclinical studies to the clinical scenario, we deem that starting from a rodent model was an essential step in the development of the novel circuit for liver NMP, where the livers can be treated with a MSCs- based therapy before transplantation. In fact, establishment of such an innovative platform required the consideration and implementation of various technical aspects related to both MSCs and the NMP procedure, including cell type selection, seeding density, design of the bioreactor circuit, and oxygen supply to the liver. The use of rodent models shows several advantages compared to large animals, including a more rapid recovery of hepatic homeostasis and function, less intra- experimental group variability, and greater selection of specific laboratory reagents. Thus, small animal models emerge as the optimal choice at this early stage of the research. + +<|ref|>text<|/ref|><|det|>[[127, 506, 870, 655]]<|/det|> +The knowledge gained with the present study was used to guide the translational application of the novel platform to porcine liver NMP (Abstract \(\mathrm{N}^{\circ}\) 1307, "Set up of a DCD pig model of normothermic machine perfusion associated to a mesenchymal stromal cell coated bioreactor to improve organ preservation", presented at ESOT congress 2021, Milan). More specifically, porcine livers procured from cardiac death donors were ex situ- perfused using the Liver Assist \(^{\mathrm{\textregistered}}\) machine (XVIVO Perfusion AB, Sweden) coupled with a plasma filter (Aferetica srl, Bologna, Italy), seeded with mesenchymal stem cells. This pilot study demonstrates the practical applicability of our novel configuration when the clinical devices/consumables are used. + +<|ref|>text<|/ref|><|det|>[[127, 657, 870, 768]]<|/det|> +These observations underscore the translational value of the present proof- of- concept study in a rodent model. In response to the Reviewer's comment, we improved the clarity of the message delivered, by reformulating the original sentence as follows: "Overall, these observations support the high translational value of the present advanced NMP platform to inform the application of this innovative setup in large animal models, and, ultimately, in the clinical setting" (lines 385- 388, page 13 of the tracked version of the revised manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[128, 789, 867, 824]]<|/det|> +## 2. Although you acknowledge that the cold ischaemic time is very short, this is. major limitation with little clinical relevance. + +<|ref|>text<|/ref|><|det|>[[127, 827, 870, 925]]<|/det|> +As stated by the Reviewer in the previous comment, rodent models show inherent differences relative to large animals and humans. With regard to the liver anatomy, there is an increasing dependence on the hepatic artery contribution for lobular perfusion in larger mammals compared with small organisms \(^{6}\) . This affects the outcome of liver transplantation; for example, liver transplants in mice do not need a hepatic artery anastomosis to avoid biliary complications, whereas those in humans do \(^{6}\) . The anatomic peculiarities also determine qualitative differences in the pathophysiological + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[127, 82, 870, 132]]<|/det|> +responses to stress stimuli between the livers of the various species. Therefore, a direct comparison of human and experimental procedures may not be entirely adequate when time intervals are considered. + +<|ref|>text<|/ref|><|det|>[[127, 133, 870, 215]]<|/det|> +Consistently, the present research shows that a different duration of ischemia enabled to obtain the same outcome. In fact, the IR challenge applied in this study not only induced the release of cytolysis markers, but it likewise promoted many of the detrimental biological events typically triggered by IR, including intracellular ATP depletion (Figure 6), succinate accumulation (Figure 6), and production of inflammatory mediators (Figure 7). + +<|ref|>text<|/ref|><|det|>[[127, 216, 870, 280]]<|/det|> +Thus, although the ischemic time is shorter than that observed in the clinical setting, the experimental findings support the reliability of our model in reproducing the key pathophysiological features of liver IR injury and support its translational use as a useful starting point for future studies in porcine and human livers. + +<|ref|>text<|/ref|><|det|>[[127, 280, 870, 329]]<|/det|> +More prolonged or extreme stimuli can be applied to our model. However, here we describe the set- up phase of NMP+bioreactor and we believe that smaller but significant injuries could lead to more informative results in this research phase. + +<|ref|>sub_title<|/ref|><|det|>[[127, 344, 870, 377]]<|/det|> +## 3. Please discuss the potential effects of raised TNF and IL-6 in the bioreactor group. These acute phase proteins can have pro-inflammatory as well as protective effects. + +<|ref|>text<|/ref|><|det|>[[127, 378, 870, 426]]<|/det|> +As highlighted by the Reviewer, IL- 6 and TNF- \(\alpha\) can exert either protective or harmful effects depending on various factors, including the amount released, the duration of their expression, and the underlying liver condition. + +<|ref|>text<|/ref|><|det|>[[127, 427, 870, 492]]<|/det|> +In the early stages of IRI, TNF- \(\alpha\) and IL- 6 are secreted as part of the pathophysiological immune response to the ischemic damage \(^{7,8}\) . Their role involves recruiting immune cells to the injured site and activating pathways related to tissue repair and removal of damaged cells \(^{9}\) . In addition, TNF- \(\alpha\) and IL- 6 are established key factors in the onset of liver cell regeneration \(^{10}\) . + +<|ref|>text<|/ref|><|det|>[[127, 492, 870, 606]]<|/det|> +In the bioreactor- based perfusion, concomitant with increased TNF- \(\alpha\) and IL- 6 perfusate concentration, there was a rise of Adiponectin, CTGF, HGF, and, at the initial stage after reperfusion, of IL- 13 (Figure 7). Compared to the standard NMP, the treated group likewise exhibited lower perfusate concentration of different mediators related to inflammation (Figure 7). This molecular scenario can be interpreted as a coordinated adaptive response to the reperfusive injury. The observed induction of Adiponectin is particularly relevant in this regard, due to its well- known properties in the mitigation of inflammation \(^{11,12}\) . + +<|ref|>text<|/ref|><|det|>[[127, 607, 870, 640]]<|/det|> +We thank the Reviewer for pointing out the need to improve the discussion of these results (lines 417- 435, page 15- 16 of the tracked version of the revised manuscript). + +<|ref|>sub_title<|/ref|><|det|>[[127, 655, 870, 688]]<|/det|> +## 4. It is difficult to make conclusions about ATP depletion when the ATP::ADSP ratio has not been measured. + +<|ref|>text<|/ref|><|det|>[[127, 690, 870, 780]]<|/det|> +Accepting the Reviewer's suggestion, we performed additional experiments using High- performance liquid chromatography (HPLC) to investigate the concentration of ATP breakdown products in liver biopsies, according to \(^{13}\) . The results have been added to the main text (lines 296- 297, pages 11 of the tracked version of the revised manuscript), while the methods are described in Supplementary information 1.1.11 + +<|ref|>sub_title<|/ref|><|det|>[[127, 801, 860, 854]]<|/det|> +## 5. In the discussion you state that the ATP recovery mechanism is likely due to a transfer of viable mitochondria to injured cells but you do not present any data to support such a contention. + +<|ref|>text<|/ref|><|det|>[[127, 858, 870, 911]]<|/det|> +Thank you for your note. We reformulated the paragraph dedicated to MSCs- induced protection of cell energy status (lines 401- 416, page 15 of the tracked version of the revised manuscript), specifying that the transfer of mitochondria from stem cells to liver tissue has been proposed as a potential + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[127, 80, 870, 120]]<|/det|> +underlying mechanism based on previous evidence \(^{14,15}\) . Further research is required to verify whether this process plays a role in the context of hepatic IRI. + +<|ref|>text<|/ref|><|det|>[[125, 138, 852, 214]]<|/det|> +6. In the discussion you conclude that Bioreactor-MSCs had an impact on different aspects of immune modulation and inflammation. Please justify this conclusion further. These points have been further discussed in lines 417-435 of the tracked version of the revised manuscript (pages 15-16). + +<|ref|>text<|/ref|><|det|>[[127, 234, 556, 251]]<|/det|> +7. There are several typographical and syntax errors. + +<|ref|>text<|/ref|><|det|>[[127, 253, 844, 289]]<|/det|> +Thank you very much for highlighting these inaccuracies. After a thorough of the manuscript, all the imprecisions have been corrected. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[128, 85, 260, 106]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[123, 105, 860, 900]]<|/det|> +1. Sierra Parraga, J. M. et al. Effects of normothermic machine perfusion conditions on mesenchymal stromal cells. Front. Immunol. 10, 1–11 (2019).2. Deng, B. et al. Removal from adherent culture contributes to apoptosis in human bone marrow mesenchymal stem cells. Mol. Med. Rep. 15, 3499–3506 (2017).3. Hassan, M. N. F. Bin et al. Large-Scale Expansion of Human Mesenchymal Stem Cells. Stem Cells Int. 2020, (2020).4. Panchalingam, K. M., Jung, S., Rosenberg, L. & Behie, L. A. Bioprocessing strategies for the large-scale production of human mesenchymal stem cells: A review Mesenchymal Stem/Stromal Cells - An update. Stem Cell Res. Ther. 6, 1–10 (2015).5. Merck KGaA. Size-based Immunomonitoring using the Scepter™ 3.0 Handheld Cell Counter. Application note https://www.sigmaaldrich.com/IT/it/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/size-based-immunomonitoring-scepter-handheld-cell-counter (2023).6. Kruepunga, N., Hakvoort, T. B. M., Hikspoors, J. P. J. M., Köhler, S. E. & Lamers, W. H. Anatomy of rodent and human livers: What are the differences? Biochim. Biophys. Acta - Mol. Basis Dis. 1865, 869–878 (2019).7. Soares, R. O. S., Losada, D. M., Jordani, M. C., Évora, P. & Castro-E-Silva, O. Ischemia/reperfusion injury revisited: An overview of the latest pharmacological strategies. Int. J. Mol. Sci. 20, (2019).8. Wu, M. Y. et al. Current Mechanistic Concepts in Ischemia and Reperfusion Injury. Cell. Physiol. Biochem. 46, 1650–1667 (2018).9. Blindenbacher, A. et al. Interleukin 6 is important for survival after partial hepatectomy in mice. Hepatology 38, 674–682 (2003).10. Moris, D. et al. Mechanistic insights of rapid liver regeneration after associating liver partition and portal vein ligation for stage hepatectomy. World J. Gastroenterol. 22, 7613–7624 (2016).11. Ruan, H. & Dong, L. Q. Adiponectin signaling and function in insulin target tissues. J. Mol. Cell Biol. 8, 101–109 (2016).12. Blandin, A. et al. Extracellular vesicles are carriers of adiponectin with insulin-sensitizing and anti-inflammatory properties. Cell Rep. 42, (2023).13. Meszaros, A. T. et al. Mitochondrial respiration during normothermic liver machine perfusion predicts clinical outcome. EBioMedicine 85, (2022).14. Peruzzotti-Jametti, L. et al. Neural stem cells traffic functional mitochondria via extracellular vesicles. PLoS Biology vol. 19 (2021).15. Phinney, D. G. et al. Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs. Nat. Commun. 6, 1–15 (2015). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 100, 500, 125]]<|/det|> +## RESPONSE TO REVIEWERS + +<|ref|>text<|/ref|><|det|>[[92, 162, 501, 179]]<|/det|> +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +<|ref|>text<|/ref|><|det|>[[92, 209, 904, 265]]<|/det|> +We thank the reviewers for their helpful feedback. Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<|ref|>sub_title<|/ref|><|det|>[[93, 333, 234, 354]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[92, 370, 899, 437]]<|/det|> +The authors have reviewed their manuscript according to suggestions and concerns made by the reviewers. Additionally, they have included some pilot results in a large animal NMP model to improve the translational impact of their work. Here are some issues that need to be addressed. + +<|ref|>text<|/ref|><|det|>[[92, 469, 900, 520]]<|/det|> +1) According to the international society for cell and gene therapy, the correct term for MSC is now "mesenchymal stromal cells" (Viswanathan et al., Cytotherapy, 2019). Authors should update their manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 520, 901, 537]]<|/det|> +We thank the Reviewer for this important suggestion. The manuscript has been changed accordingly. + +<|ref|>text<|/ref|><|det|>[[92, 551, 905, 633]]<|/det|> +2) Although the addition to the NMP circuit might be novel, culture of MSC in hollow fiber bioreactors is already known. Additionally, commercial distribution of MSC has been offering the possibility of shipping cultured MSC in culture flasks or other formats, keeping their properties intact after transportation, which is quite similar to the logistic procedure described here. Novelty of this fact is scarce + +<|ref|>text<|/ref|><|det|>[[92, 634, 905, 748]]<|/det|> +As noted by the Reviewer, the novelty of our study resides in the connection of a MSCs- bioreactor to a NMP platform. This innovative experimental setup has not been explored in previous researches, nor the core properties of MSCs in a bioreactor have been investigated after exposure to a perfusion procedure. A recent analysis performed by Fu and coworkers highlights the huge therapeutic potential of coupling MSCs- bioreactors to ex situ perfusion, but does not provide experimental clues supporting its applicability, and claim the need to perform targeted experiments aimed at addressing this point 3. + +<|ref|>text<|/ref|><|det|>[[92, 748, 905, 829]]<|/det|> +Our research fills this knowledge gap, providing for the first time evidence showing both feasibility and efficacy of this modern MP platform. This important information is essential to proceed with the clinical implementation of this new technology. In this regard, the possibility of shipping pre- seeded bioreactors from a specialized cell facility to any Transplant Centers, could contribute to accelerating the translational process. + +<|ref|>text<|/ref|><|det|>[[92, 846, 889, 896]]<|/det|> +3) Authors need to update figure 4 and supplemental data including all cell types susceptible to be measured in "wash-outs", (i.e. MSC, endothelial cells, etc.) Even in low numbers, MSC can still detach and flush through the system. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 904, 133]]<|/det|> +Figure 4 was updated to include "endothelial cells" among cells detected within the following cell diameter range: \(9 - 18 \mu \mathrm{m}^{4}\) . In line with the Reviewer's comment, the supplementary material has been likewise revised (line 184, page 10). + +<|ref|>text<|/ref|><|det|>[[92, 134, 905, 316]]<|/det|> +With regard to the Reviewer's suggestion to include also MSCs among the cells detached during the NMP procedure, we respectfully hold a different viewpoint and would appreciate the opportunity to offer an explanation justifying our decision. The wash- out samples drained from livers subjected to the bioreactor- based perfusion showed a higher cell count and a greater concentration of nitric oxide (NO) metabolites compared to those collected during standard NMP. The increased availability of the vasodilator NO, together with increased cell concentration, support a more effective wash- out of donor blood in livers exposed to the MSCs- derived secretome compared to controls. Moreover, as described in the previous "Response to Reviewers" (Reviewer #1, point 6), the results obtained from liverless- NMP experiments clearly indicate no MSCs detachment during the perfusion procedure (lines 152- 153, page 8 of the revised version of the manuscript). These evidence collectively suggest that the cells found in the perfusates derive solely from the liver. + +<|ref|>text<|/ref|><|det|>[[92, 331, 904, 364]]<|/det|> +4) Authors mention the section supplementary methods 1.12 which is not included in the supplementary material. + +<|ref|>text<|/ref|><|det|>[[92, 365, 904, 396]]<|/det|> +Authors thank the Reviewer for pointing this out. All the references to section 1.12 were removed from the main text. + +<|ref|>text<|/ref|><|det|>[[92, 412, 904, 477]]<|/det|> +5) Supplementary figure 12. Regardless of measured parameters used to evaluate success in NMP, visual evaluation is still key during perfusion. In the images, there is a clear difference in perfusion between both organs, with the one from the MSC group having a paler color. This unequivocally show bad perfusion of the organ. + +<|ref|>text<|/ref|><|det|>[[92, 478, 904, 526]]<|/det|> +Supplementary figure 12 does not compare livers from the control and the NMP+b-MSCs group, rather the pictures represent a random liver before and after undergoing the bioreactor- based perfusion procedure. + +<|ref|>text<|/ref|><|det|>[[92, 527, 904, 789]]<|/det|> +As suggested by the Reviewer, the macroscopic appearance of the liver provides a first general impression of the liver during perfusion, but its clinical value is still debated. Indeed, at a recent international guideline meeting on liver viability during in- situ/ex- situ machine perfusion organized by ELITA/ESOT (Madrid, March 18- 20, 2024), a dedicated discussion was devoted to this topic. While the macroscopic appearance of the liver was considered a possible parameter in in- situ perfusion (normothermic regional perfusion, NRP), it was not included among the viability parameters in ex- situ perfusion (NMP). In fact, the macroscopic appearance of the liver during NMP was hardly related to perfusion quality and viability. During the session, a patchy and/or pale appearance of the NMP liver, rather than possible differences in the light exposure of the camera, was related to non- physiological perfusion conditions (e.g., outside the human body) and to the position of the liver during NMP, but not to the overall perfusion quality when NMP fluidodynamics and metabolism were preserved. In our study, all clinically derived parameters were met, fluidodynamics parameters were preserved throughout the perfusion time and, lastly, histology was preserved. At the above mentioned meeting, three of the authors of the present manuscript participated as "experts" and here we report a preliminary and confidential extract of the statement resulting from the meeting to further support the above statements: + +<|ref|>text<|/ref|><|det|>[[92, 805, 904, 838]]<|/det|> +"Comment to Q11: What parameters measured during in-situ normothermic regional perfusion may be used to assess DCD liver viability? + +<|ref|>text<|/ref|><|det|>[[92, 839, 904, 871]]<|/det|> +[...] The parameter "gross appearance of the liver" is very subjective and often based on the perception and experience of the procurement surgeon and team involved in NRP. [...] + +<|ref|>text<|/ref|><|det|>[[92, 888, 904, 920]]<|/det|> +"Statement Q13: What parameters measured during ex situ normothermic machine perfusion may be used to assess deceased donor liver viability? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 836, 166]]<|/det|> +1) Expert Panel Statement: Perfusion quality parameters, perfusate parameters (pH, lactate, transaminases, Glucose) and bile parameters (bile flow, pH, Glucose, Bicarbonate) may be used to assess deceased donor liver viability. Recommendation grade: conditional recommendation for Median level of evidence: 2 (range 3 to \(2 +\) )" + +<|ref|>text<|/ref|><|det|>[[92, 182, 904, 215]]<|/det|> +Authors thank the reviewer for the opportunity to discuss this topic and anticipate some aspects that will be further explored in literature in the near future. + +<|ref|>text<|/ref|><|det|>[[92, 231, 904, 280]]<|/det|> +This being said, based on the poor predictive potential of macroscopic aspects in the context of ex situ perfusion procedures, and in line with the Reviewer's comment, we would remove the panels a and b from Supplementary figure 12. + +<|ref|>text<|/ref|><|det|>[[92, 296, 904, 379]]<|/det|> +6) There is a discrepancy regarding the number of cells used for the pig experiments described in the results and methods section. 37x107 cells noted in the results section does not equal 37 million cells (20 ml of a 1.85x106 cells/ml suspension). Please correct accordingly. We apologize for this imprecision; the total number of cells seeded in the bioreactors was \(3.7 \times 10^{7}\). Authors are very grateful to the Reviewer for his accurate revision. + +<|ref|>text<|/ref|><|det|>[[92, 394, 904, 476]]<|/det|> +7) Authors have used \(2 \times 10^{7}\) MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. Comparison of results is therefore very limited between both models. + +<|ref|>text<|/ref|><|det|>[[92, 477, 904, 542]]<|/det|> +8) Additionally, cell density in bioreactors is extremely different: 18500 MSC per cm2 for pig bioreactor vs. 40000 MSC/cm2 in rat bioreactors. Cell density is known to alter MSC functionality, secretory profile and immunomodulatory potential. Authors should justify these differences and elaborate about possible consequences. + +<|ref|>text<|/ref|><|det|>[[92, 543, 904, 755]]<|/det|> +All the calculations made by the Reviewer are correct. However, we would like to clarify that the pilot study in porcine livers was conducted to investigate whether a bioreactor can be technically integrated into a clinical device and to test whether this new configuration can sustain the protocol for human liver MP. Our intention was to provide experimental evidence in support of the clinical applicability of our new setup, addressing the concerns raised in the previous revisions on this topic. Thus, in addition to the differences pointed out by the Reviewer, the porcine study involved several other changes compared to the small animal model, which were introduced to progress towards the setting adopted in the human scenario. First, porcine livers were exposed to a period of warm ischemia. Second, the NMP was performed using leukocyte-depleted autologous blood including red blood cells and the perfusate was pumped into the liver through both hepatic artery and portal vein. Moreover, portal vein target pressure was different compared to the setting adopted in the rat NMP, and the porcine circuit was equipped with two oxygenators. These, and other, adjustments were needed to test the feasibility of the bioreactor-based perfusion in a human-like setting. + +<|ref|>text<|/ref|><|det|>[[92, 756, 904, 804]]<|/det|> +This being said, as highlighted by the Reviewer, no comparison in the MSCs effects between rat and pig livers was provided, nor were the MSCs functionality and secretory profile explored in porcine experiments, since the experimental aims of these two work packages were different. + +<|ref|>text<|/ref|><|det|>[[92, 837, 891, 919]]<|/det|> +9) The large animal model used by the authors lacks potential for translation. Clinical strategies used in human liver NMP trials include perfusion times ranging from 9-20+ hours. Although authors are presenting preliminary results in a large animal preclinical model coupled to an MSC bioreactor, clinical translation assumptions should be made carefully, as the author do not present sufficient data supporting their claims. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 905, 345]]<|/det|> +We agree with the reviewer on the potential drawbacks of our large animal model from a translational point of view. For this reason, we used pig experiments only to test the possible integration of an MSC bioreactor into a commercial perfusion device, as in other studies where pigs were used for technological assessment. In this setting, a NMP duration of \(4\mathrm{h}\) was chosen by our group. In the clinical literature, perfusion time varies widely within the same study and between studies. In fact, while most studies did not specify a per- protocol NMP duration, it usually depends on the goal of the perfusion, how it is applied (e.g., back to base or in the donor hospital approach), and other logistical issues. While preservation and viability might require a longer NMP time, reconditioning might benefit from a shorter NMP duration when used to face organ reperfusion, as in the DCDnet trial (NCT04744389) in which some of the present authors are involved. For these reasons, we decided to use a 4- hour NMP in our WP3. In addition, since our goal was to test the integration of the bioreactor into a commercial NMP device, most of the technological issues should become apparent early after the start of the NMP. Following the Reviewer's suggestion, we revised and, in some cases, reformulated, all the claims about the clinical translational of our results. As pointed out by the Reviewer, longer preservation times will be applied in future studies to verify the biological changes secondary to the connection of the MSC bioreactor to an NMP. + +<|ref|>text<|/ref|><|det|>[[92, 361, 905, 411]]<|/det|> +10) Even though these are preliminary results, only \(n = 3\) animals were used for the large animal study. This small sample size needs justification and sample size calculation need to be explained. + +<|ref|>text<|/ref|><|det|>[[92, 411, 905, 460]]<|/det|> +We appreciate this important note on sample size calculation in the pilot study and consistently improved the dedicated paragraph in the Supplementary material by adding the requested information (1.11.1 Sample size, page 14). + +<|ref|>text<|/ref|><|det|>[[92, 460, 905, 526]]<|/det|> +As discussed above, the work package in large animals investigated feasibility of bioreactor integration into an existing perfusion circuit for human use. The possible outcomes were, therefore, defined as categorical, namely 1) success of execution (feasible) or 2) failure of execution (unfeasible). + +<|ref|>text<|/ref|><|det|>[[92, 526, 905, 576]]<|/det|> +Due to lack of prior data and consequent unavailability of a formal verification of sample size, the number of pigs needed as liver donors was determined based on our experience in the set up and implementation of novel perfusion platforms for preclinical models 5- 7. + +<|ref|>text<|/ref|><|det|>[[92, 576, 904, 608]]<|/det|> +Considering these assumptions, while adhering to the ethical principles in animal research 8,9, we elected to use 3 animals for each experimental group. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[94, 84, 235, 105]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[92, 121, 904, 280]]<|/det|> +The incorporation of an MSC- bioreactor in a normothermic machine perfusion (NMP) circuit is a novel concept although other groups are working in this area. There is a body of work demonstrating that MSCs can ameliorate ischaemia reperfusion injury and it is known that this is due to the release of EVs and paracrine factors from the stem cells and that MSCs themselves have a number of potentially adverse effects. The isolated organ preservation offered by NMP removes problems with targeting stem cells to a specific organ and bypassing the reticuloendothelial system. NMP also reduces the risk of off- target adverse effects. The addition of a bioreactor to the NMP circuit is a logical development. The authors have demonstrated the feasibility of this new approach and in the rat model evidence that the addition of a bioreactor can counter some of the changes associated with I/R injury. + +<|ref|>text<|/ref|><|det|>[[94, 290, 633, 307]]<|/det|> +There are a number of issues that the authors should consider: + +<|ref|>sub_title<|/ref|><|det|>[[93, 353, 888, 386]]<|/det|> +## 1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. + +<|ref|>text<|/ref|><|det|>[[93, 385, 904, 418]]<|/det|> +We thank the Reviewer for the opportunity to further discuss the scientific background of our research, which provides a proof of concept to implement a new platform for liver NMP. + +<|ref|>text<|/ref|><|det|>[[92, 418, 905, 531]]<|/det|> +Based on the existing literature, rodent models of ischemia/reperfusion injury (IRI) are widely utilized to investigate novel intervention strategies or gain insights into the biological mechanisms elicited by IR. Of interest, a recent systematic review explored the use of cell- based therapies to counteract IRI in transplantable organs 2. The analysis indicated that out of the 97 studies examined, 45 utilized rat models of ischemic injury, while 46 researches were conducted in mice. Therefore, although we acknowledge that clinical translation could be challenging, preclinical models still represent valuable tools for scientific investigation in this field. + +<|ref|>text<|/ref|><|det|>[[92, 531, 905, 630]]<|/det|> +Moreover, it's important to consider that the typical pathway to develop a new medical setup involves the progression from initial testing in rodent models to subsequent studies in larger animals before advancing to human research. Since we aimed at establishing an unprecedented technology, the use of a small animal model was necessary to depict the various technical and biological aspects essential to successfully integrate the bioreactor into a NMP circuit, while demonstrating MSCs' efficacy in mitigating IRI. + +<|ref|>text<|/ref|><|det|>[[92, 646, 900, 745]]<|/det|> +2. The procine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model than the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. + +<|ref|>text<|/ref|><|det|>[[92, 745, 905, 908]]<|/det|> +We thank the Reviewer for the comment which allows improving the description of the research aims. As highlighted, the pilot study in porcine livers was conducted to investigate the potential of the bioreactor to be upscaled and integrated into a clinical device, while providing information supporting the ability of the new configuration to sustain the protocol for human liver MP. Our intention was to provide experimental evidence to demonstrate the technical feasibility of our new setup in a scenario resembling the clinical setting, addressing the concerns raised in the previous revisions on this topic. Therefore, as noted by the Reviewer, we did not investigate the MSCs' effects on porcine liver IRI. On the other hand, this aspect was extensively studied in rat livers, taking advantage of the expertise of our Research Team as well as on availability of a variety of bio- molecular technologies previously validated for this model 11- 17. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[91, 82, 904, 164]]<|/det|> +3. The group size for the porcine experiments is small at \(n = 3\) and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& lpha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. + +<|ref|>text<|/ref|><|det|>[[92, 164, 905, 212]]<|/det|> +We recognize that sample size calculation for the pilot study needed to be expanded and, as a consequence, we changed the dedicated paragraph in the Supplementary material to better justify our evaluation (1.11.1 Sample size, page 14). + +<|ref|>text<|/ref|><|det|>[[92, 213, 905, 296]]<|/det|> +We agree with the Reviewer that the investigation of the bioreactor- based perfusion effects during prolonged procedures is an intriguing research perspective. In fact, we are currently working on the setup of extended bioreactor- based NMP, with the ultimate aim to explore the long- term consequences of MSCs. In this regard, our Group recently completed the development and optimization of a stable protocol for \(12\mathrm{h}\) - NMP in rodents 17. + +<|ref|>text<|/ref|><|det|>[[90, 312, 905, 461]]<|/det|> +4. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. We appreciate the Reviewer's suggestion regarding the use of human livers deemed unsuitable for transplantation. This approach could indeed provide valuable insights into the efficacy of bioreactor-based NMP and, as such, it appears as a logical next research step. The scientific community could take advantage of the seminal results provided by the present study, and consider conducting targeted experiments to investigate the benefits of bioreactor-based NMP in human livers. We added a sentence in the Discussion section (lines 360-363, page 15 of the revised version of the manuscript) to highlight this concept. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 84, 220, 105]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[90, 120, 907, 920]]<|/det|> +1. Shao, B. et al. Structural and Temporal Dynamics of Mesenchymal Stem Cells in Liver Diseases From 2001 to 2021: A Bibliometric Analysis. Front. Immunol. 13, 1–18 (2022). +2. Blondeel, J., Gilbo, N., De Bondt, S. & Monbaliu, D. Stem cell Derived Extracellular Vesicles to Alleviate ischemia-reperfusion Injury of Transplantable Organs. A Systematic Review. Stem Cell Rev. Reports 19, 2225–2250 (2023). +3. Fu, Y. et al. Mesenchymal Stem Cell Utilization for In Vitro Donor Liver Machine Perfusion Preservation: Current Status and Future Directions. Stem Cells Transl. Med. 12, 665–675 (2023). +4. Merck KGaA. Size-based Immunomonitoring using the Scepter™ 3.0 Handheld Cell Counter. Application note https://www.sigmaaldrich.com/IT/it/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/size-based-immunomonitoring-scepter-handheld-cell-counter (2023). +5. Bassani, G. A. et al. Ex vivo lung perfusion in the rat: Detailed procedure and videos. PLoS One 11, (2016). +6. Dondossola, D. Procurement and ex-situ perfusion of isolated slaughterhouse-derived livers as a model of donors after circulatory death. ALTEX (2019) doi:10.14573/altex.1909131. +7. Dondossola, D. et al. Human Red Blood Cells as Oxygen Carriers to Improve Ex-Situ Liver Perfusion in a Rat Model. J. Clin. Med. (2019) doi:10.3390/jcm8111918. +8. Balls, M. It’s Time to Reconsider The Principles of Humane Experimental Technique. ATLA Altern. to Lab. Anim. 48, 40–46 (2020). +9. Smith, A. J., Clutton, R. E., Lilley, E., Hansen, K. E. A. & Brattelid, T. PREPARE: guidelines for planning animal research and testing. Lab. Anim. 52, 135–141 (2018). +10. Bhattacharjee, R. N. et al. Renal protection against ischemia reperfusion injury: Hemoglobin-based oxygen carrier-201 versus blood as an oxygen carrier in ex vivo subnormothermic machine perfusion. Transplantation 104, 482–489 (2020). +11. Lonati, C. et al. Influence of ex vivo perfusion on the biomolecular profile of rat lungs. FASEB J. 32, (2018). +12. Lonati, C. et al. Mesenchymal stem cell–derived extracellular vesicles improve the molecular phenotype of isolated rat lungs during ischemia/reperfusion injury. J. Hear. Lung Transplant. (2019) doi:10.1016/j.health.2019.08.016. +13. Lonati, C. et al. NDP-MSH treatment recovers marginal lungs during ex vivo lung perfusion (EVLP). Peptides 141, (2021). +14. Catania, A. et al. The peptide NDP-MSH induces phenotype changes in the heart that resemble ischemic preconditioning. Peptides (2010) doi:10.1016/j.peptides.2009.09.030. +15. Colombo, G. et al. Treatment with α-melanocyte stimulating hormone preserves calcium regulatory proteins in rat heart allografts. Brain. Behav. Immun. 22, (2008). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 81, 904, 180]]<|/det|> +16. Lonati, C. et al. Quantitative Metabolomics of Tissue, Perfusate, and Bile from Rat Livers Subjected to Normothermic Machine Perfusion. Biomedicines 10, (2022). +17. Dondossola, D. et al. Twelve-hour normothermic liver perfusion in a rat model: characterization of the changes in the ex-situ bio-molecular phenotype and metabolism. Sci. Rep. 14, 1–13 (2024). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 83, 500, 108]]<|/det|> +## RESPONSE TO REVIEWERS + +<|ref|>text<|/ref|><|det|>[[92, 145, 500, 163]]<|/det|> +MANUSCRIPT NUMBER: NCOMMS- 23- 38868 + +<|ref|>text<|/ref|><|det|>[[92, 192, 904, 229]]<|/det|> +We thank the Editor for the opportunity to re- evaluate our manuscript and the Reviewers for their helpful feedback. + +<|ref|>text<|/ref|><|det|>[[92, 236, 904, 273]]<|/det|> +Below, we present our responses to the points raised and a description of the changes made accordingly. Reviewers' comments are typed in bold and our corresponding responses in regular text. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 85, 252, 107]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[92, 140, 816, 175]]<|/det|> +The authors have replied to most of the reviewers comments, with a very elaborated explanation in some cases. + +<|ref|>text<|/ref|><|det|>[[92, 175, 900, 192]]<|/det|> +Thank you for recognizing our efforts to improve the clarity and the relevance of our manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[93, 223, 315, 239]]<|/det|> +## Some questions still arise: + +<|ref|>text<|/ref|><|det|>[[92, 255, 900, 320]]<|/det|> +1. The authors missed one of the previous comments: Authors have used \(2 \times 10^{7}\) MSC for the rat NMP setup and average liver weight was 15 grams, resulting in a dose of 1.3 million MSC per gram of tissue. However, only 28-280 thousand cells (depending on correction made based on the previous point) per gram of liver tissue was reached in the pig experiments. + +<|ref|>text<|/ref|><|det|>[[93, 320, 686, 336]]<|/det|> +Comparison of results is therefore very limited between both models. + +<|ref|>text<|/ref|><|det|>[[92, 337, 902, 369]]<|/det|> +We apologize if we did not make this point clear. The exact number is \(2.8 \times 10^{4}\) cells per gram of liver tissue. + +<|ref|>text<|/ref|><|det|>[[92, 370, 904, 418]]<|/det|> +While we agree with the Reviewer that comparison of results is very limited between the models, this observation open up two different discussions. The first is the aim of the porcine study and the second is the normalization. + +<|ref|>text<|/ref|><|det|>[[92, 419, 904, 500]]<|/det|> +First, we would like to emphasize that the large animal study was not conducted to compare the effects of MSCs on porcine versus rat liver. Instead, its primary goal was to test the feasibility of integrating our bioreactor into a clinical NMP platform. This crucial step must be completed before advancing with further research and required a dedicated pilot study to avoid future failures, as recommended by NC3Rs 1. + +<|ref|>text<|/ref|><|det|>[[92, 501, 904, 681]]<|/det|> +Concerning normalization, the selection of normalization criteria and of the compounds that should be normalized is still a matter of debate in the MP field. In fact, it is either partially applied or not applied at all in MP literature, even in those experiments that use depurative strategies such as dialysis, that could deeply manipulate the concentration of some compounds 2- 5. This being said, according to the number of cells, we had the same concerns of the Reviewer. Indeed, whether the effect of the MSCs is directed to the liver or the MSCs are primed by the liver- secreted factors leads to a different normalization. In the first case, the normalization would be based on MSC/g of liver, in the other on the volume and flow of the perfusate. Since we could not get a direct answer from the literature and other experiments, we applied a normalization based on the perfusate volume and flow rate into the bioreactor, due to the inherent differences in the perfusion settings of rodent and pig model. This combined factor was comparable between the rodent and porcine models. + +<|ref|>text<|/ref|><|det|>[[92, 682, 904, 746]]<|/det|> +We thank the Reviewer for the comment and have added the paragraph "1.12.2 Preparation of the bioreactor suitable for porcine livers", in the Supplementary information, willing to open a debate on this issue. We are, indeed, aware that the type and the selection of the normalization criteria can be criticized. + +<|ref|>text<|/ref|><|det|>[[92, 779, 900, 860]]<|/det|> +2. Regarding MSC detaching from the bioreactor. MSC do not flush through during liver-less perfusion. However, as fluid composition changes due to the liver secreted molecules and cytokines, there is no data confirming this subject as conditions change. The authors do not provide any direct proof of the cell types leaving the NMP system. Therefore, all cells present in the NMP system should be taken into account, including MSC. + +<|ref|>text<|/ref|><|det|>[[92, 861, 904, 928]]<|/det|> +We agree with the Reviewer that the factors secreted by the liver could have had a chemotactic effect on the MSCs. As suggested, we cannot directly prove the absence of small MSCs or MSCs fragments in the perfusion fluid during liver NMP. Therefore, Figure 4 was accordingly updated to include "MSCs" among cells detected within the following cell diameter range: \(9 - 18 \mu \mathrm{m}\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 904, 197]]<|/det|> +This being said, we would like to point out that the bioreactor fibers are made of semi-permeable membranes with a pore diameter of around \(150~\mathrm{nm}\) , as already reported in the Supplementary information (Supplementary figure 1 and Supplementary figure 9). Given that the average size of the MSCs cultured under standard conditions is \(15 - 30~\mu \mathrm{m}^{6,7}\) , the likelihood for an intact stem cell to pass through the pores appears very low and must assume a considerable degree of cell deformability \(^{8}\) . Moreover, it should be noted that the same fibers are used in clinical plasmalifters to trap erythrocytes, which have a smaller diameter than MSCs. + +<|ref|>text<|/ref|><|det|>[[92, 198, 904, 247]]<|/det|> +To improve the clarity on this point, we have reported the bioreactor fiber pore size even in the main text (page 17- 18, lines 449- 476 of the tracked version of the manuscript) and added a detailed bioreactor description to the Supplementary information 1.2 (page 5). + +<|ref|>text<|/ref|><|det|>[[92, 280, 889, 345]]<|/det|> +3. The authors have provided preliminary data on the technical feasibility of coupling an MSC bioreactor in a porcine NMP setup. The objective was to set a translatable setup for human use in the clinic. With this in mind, the very small population size (n= 3) do not allow to obtain any conclusion and larger studies need to be carried out. + +<|ref|>text<|/ref|><|det|>[[92, 345, 904, 443]]<|/det|> +By definition, pilot studies are "designed to test the feasibility of methods and procedures for later use on a large scale or to search for possible effects and associations that may be worth following up in a subsequent larger study" \(^{9}\) . Since the large animal work package was performed to investigate the use of the novel bioreactor- based configuration as a part of multistep project, it fully meets the criteria set for a pilot study. Consistently, our claim was to test the possible integration of our MSCs bioreactor in a human device, rather than providing evidence on direct clinical translatability. + +<|ref|>text<|/ref|><|det|>[[92, 444, 904, 492]]<|/det|> +We fully agree with the reviewers and the editor that sample size is a critical issue. As highlighted and accepted by Reviewer #2 (point 4) and in accordance with NC3Rs \(^{1}\) , in our pilot study in porcine livers, the sample size was determined as detailed in the Supplementary information 1.12: + +<|ref|>sub_title<|/ref|><|det|>[[94, 509, 250, 525]]<|/det|> +### 1.12.1. Sample size + +<|ref|>text<|/ref|><|det|>[[92, 530, 905, 628]]<|/det|> +This pilot study was designed to establish a novel perfusion system by combining the Liver Assist® machine to a stem cell bioreactor. Sample size was determined according to the guidance published by NC3R \(^{1}\) , considering the following possible outcomes: 1) success of execution (feasible) or 2) failure of execution (unfeasible). Based on our experience in the set up and implementation of unprecedent perfusion platforms for preclinical models \(^{10 - 12}\) , we deemed necessary using 3 animals for the NMP+bioreactor group. Therefore, work package 3 involved a total of 6 animals. + +<|ref|>text<|/ref|><|det|>[[92, 646, 904, 727]]<|/det|> +To provide further clarification on this issue, we have added a brief description in the main text (page 20, lines 551- 558 of the tracked version of the manuscript). If the Reviewers and Editor deem it preferable to more extensively use the term "pilot study" to enhance clarity regarding the aim of the large animal model, and if it aligns with the journal's guidelines, we will incorporate this suggestion in subsequent manuscript versions. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 84, 253, 106]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[92, 123, 888, 222]]<|/det|> +1. The relevance of the rat model is questionable as studies using rodent models of ischaemia reperfusion injury have a very poor record of translation into clinical practice. The authors address the use of rodent models on the basis that this is common practice and that rodent models are an important step in the evolution of new technologies. These are reasonable points but still don't answer the issue of translatability. There is not much the authors can do about this limitation. + +<|ref|>text<|/ref|><|det|>[[92, 222, 905, 338]]<|/det|> +As declared in previous review rounds, we are in full agreement with the assertions made by Reviewer #2. Indeed, the low translatability rate from rodent studies to clinical applications is well documented 13, but this observation needs to be carefully interpreted to avoid simplism (e.g. futility of rodent models in biomedical research). In fact, it is established that rodent models remain an invaluable resource for investigating the biological mechanisms underlying a given phenomenon. As a consequence, the poor translatability does not preclude the use of these models in the pathway towards clinical implementation of a novel technology or treatment. + +<|ref|>text<|/ref|><|det|>[[92, 338, 904, 436]]<|/det|> +Of note, different Societies, Associations, and Institutions relevant to preclinical research, indicated a poor methodological approach and the lack of protocol standardization among the main reasons causing the low translational rate and the failure to recapitulate many human disease symptoms 14- 17. To address this important issue, we strictly adhered to the PREPARE guidelines 14 during the approval phase of the protocol, and to the ARRIVE guidelines 18 during article preparation, as recommended by NC3Rs, Felasa, and NORECOPA. + +<|ref|>text<|/ref|><|det|>[[92, 435, 904, 551]]<|/det|> +We have never claimed the use of rodent models as "common practice", but we believe that it is could be considered a "common science" based on international literature (see response to point 1 raised by Reviewer #2 in the previous review round) and guidelines. The disadvantages of not initiating the process from a rodent model include incomplete comprehension of a complex phenomenon and a reliance on previously published studies to develop a protocol or interpret results. In addition, it must be noted that this iter is also needed for the legislative approval of a new device/drug [https://health.ec.europa.eu/medical- devices- sector_en]. + +<|ref|>text<|/ref|><|det|>[[92, 550, 904, 630]]<|/det|> +In the transplantation field, no study have ever demonstrated that a MSC- bioreactor can be coupled to liver NMP and that MSCs can be activated by the interaction with the liver. To address this intriguing research question, after an in- vitro phase (liverless perfusion), we employed a rat model and, upon successfully accomplishing this objective, in line with the recommendations of the Reviewers and the Editor, we explored the bioreactor integration into a commercial human device. + +<|ref|>text<|/ref|><|det|>[[92, 630, 904, 730]]<|/det|> +The final step of our project will be the clinical applicability of our technology, which, in our idea, will deserve a separate research project (see also paragraph 2 of points 3- 4, Reviewer #3) and a separate paper. In a "translational" perspective, the present results will be the milestones needed to properly set up this future study. We do not believe that reporting a new device or drug (MSCs are considered drugs for Italian legislation) would require the inclusion of all the research steps in a single publication. + +<|ref|>text<|/ref|><|det|>[[92, 730, 903, 764]]<|/det|> +The role of small animal model was better clarified in the Discussion (page 12, lines 279- 282 of the tracked version of the manuscript). + +<|ref|>text<|/ref|><|det|>[[92, 796, 897, 895]]<|/det|> +2. The porcine model demonstrated the potential for upscaling but there was much less analysis of outcome compared to the rat component and it is not clear why. The porcine liver is a better model than the rat but still has important differences to the human liver. Porcine livers have a histological structure based on very distinct lobules whereas the basic unit of the human liver is acinar. In addition, porcine livers are more resistant to warm ischaemic injury than the human organ. + +<|ref|>text<|/ref|><|det|>[[92, 895, 895, 912]]<|/det|> +The authors have answered my concerns to some extent. The use of a porcine model provides + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 83, 872, 115]]<|/det|> +## useful feasibility evidence that the technology can be upscaled to a large animal set-up that resembles the clinical situation. + +<|ref|>text<|/ref|><|det|>[[92, 116, 904, 508]]<|/det|> +The comments provided by the Reviewer are in complete accordance with the considerations outlined in our previous correspondence and in the various versions of the main text. As the Reviewer correctly asserted, the porcine model was employed solely for the purpose of evaluating the feasibility of upscaling the bioreactor in a commercial device. Furthermore, it is important to note that this is not merely a straightforward issue of scaling up (as outlined in points 7- 8 of the previous "Letter to the Reviewers" by Reviewer #1), but also entails adapting our bioreactor to a distinctly engineered circuit, compared to that for rat liver NMP. The integration of the bioreactor in a commercial human device was successful, with no failure of the circuit or machine and no macroscopic, as pointed out by the Reviewer #2 damage to the liver (Supplementary table 6 and Supplementary figure 12). Therefore, the point was not only addressed to "some extent", but any further elaboration on the analyses or the possible underlying mechanisms (as requested in point 3 by Reviewer #2) would exceed the scope of our large animal study. Indeed, we are fully aware of the differences in structure and biological mechanisms between human and porcine livers, and we agree with the Reviewer on this matter. Nevertheless, the underlying premise of our experimental design is that porcine livers, despite their heterogeneity, may still serve a role in device setup and technology testing \(^{19}\) . This concept is supported by a substantial body of literature, as evidenced by the fact that the Pubmed search "liver normothermic machine perfusion AND pig" provides 63 articles. A systematic review on this topic was published in 2018 in Transplantation by leading experts in the fields of liver MP and stem cells \(^{20}\) . This review identifies the porcine model as a convenient method to explore novel approaches of perfusion and to study the early events of IRI. Among the presented NMP model, we selected the Groningen approach \(^{21}\) , which was adapted to be used with the commercial device Liver Assist (XIVVO). Of note, pig livers have been used in recent years to develop novel MP techniques, which have been subsequently tested on non- viable livers \(^{3,5}\) . This ultimately led to the clinical transplantation of the liver \(^{22}\) . + +<|ref|>text<|/ref|><|det|>[[92, 508, 904, 574]]<|/det|> +We recognize that our initial presentation may have lacked clarity; thus, we have expanded the "Study design" paragraph (page 7, lines 129- 130 of the tracked version of the manuscript) and the discussion on the rationale behind our large animal model (page 12, lines 279- 284 and page 15- 16, lines 380- 388 of the tracked version of the manuscript). + +<|ref|>text<|/ref|><|det|>[[92, 606, 904, 771]]<|/det|> +3. The group size for the porcine experiments is small at n=3 and the period of NMP was only 4 hours. More prolonged NMP (at least 24h and even up to several days) have been proved feasible and would have allowed more detailed study of the influence of the bioreactor on liver injury (e.g. A2M a& Ipha-1 glycoprotein increases). More prolonged perfusion would also help define whether the MSCs survive in the bioreactor for longer than 4h. 4. My comments relating to the small group size in the small group size in the porcine experiments have been acknowledged by revision of the supplementary information. In relation to the short duration of the perfusion experiments, the authors are planning experiments with more relevant prolonged perfusion. It would have strengthened the work to wait for these results. + +<|ref|>text<|/ref|><|det|>[[92, 772, 904, 870]]<|/det|> +We will address these two points together, as they are subject to similar criticisms. First of all, we would like to thank the Reviewer for accepting the sample size justification for our pilot study, provided in the previous review round. Sample size justification (pilot large animal model) and calculation (rodent model) have been performed according to the PREPARE guidelines \(^{14}\) . Making this point clear and repeatable (as requested by the ARRIVE guidelines \(^{18}\) observed by this journal) is for us of paramount importance. + +<|ref|>text<|/ref|><|det|>[[92, 871, 904, 919]]<|/det|> +As the Reviewer correctly observed, prolonging the perfusion time in both rodent and porcine models would have offered an intriguing pathway for further investigations. A longer perfusion time would provide a time window during which organs could be not only "reconditioned", but also "repaired". + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 83, 904, 166]]<|/det|> +However, as declared in the previous version of the paper and review rounds, this was not the objective of our study. Instead, the rodent model was employed to establish the bioreactor- based NMP platform, to investigate the potential of MSC utilization in liver perfusion, and their impact on early IRI, while the pig model was utilized for to test feasibility of bioreactor integration into a commercial device used in the clinical practice. + +<|ref|>text<|/ref|><|det|>[[92, 166, 904, 361]]<|/det|> +Beside the fact that the effects of a prolonged perfusion felt outside our aims, at the time of experiment execution, no prolonged perfusion rat models were available in the literature. A \(12\mathrm{h}\) - perfusion model was reported for the first time by our group after completing the present study \(^{23}\) . It is important to note that, despite meeting all clinical criteria for viability at the end of the 12- hour perfusion, perfused livers exhibited a number of metabolic changes compared to the native liver. These changes could have influenced the interpretation of the MSC effect on prolonged liver perfusion. The same non- physiological effects were showed by Guo et al. in ischemia- free human livers, indicating that ex- situ perfusion could lead to deleterious effects \(^{24}\) that potentially concours to liver viability failure, even at the end of a prolonged perfusion time \(^{3,4}\) . As a result, while prolonging perfusion in a human/large animal model is an intriguing perspective, extended perfusion itself modifies liver biology and would have affected the understanding of MSC effects. For these reasons, MSC survival, effect, and outcome in prolonged perfusion necessary represents a second step of the present research. + +<|ref|>text<|/ref|><|det|>[[93, 361, 904, 410]]<|/det|> +This point is discussed in the Limitations section (page 16, lines 389- 392 of the tracked version of the manuscript) and in the Conclusion section (page 17, lines 418- 419 of the tracked version of the manuscript). + +<|ref|>text<|/ref|><|det|>[[92, 443, 904, 590]]<|/det|> +5. The best model would be to use human livers that were declined for transplantation. These can even be split into left and right lobes to allow a comparison of intervention vs control NMP. We recognize the potential of non-viable human livers as a tool to explore clinical utility of novel technologies and compounds. However, the Reviewer defined non-viable humans as the "best model", yet no supporting evidence was provided or could be identified in the literature (21 original articles or commentaries on PubMed [normothermic machine perfusion AND split OR reduced liver]: 12 of them for ex-situ clinical split liver). In addition to the low level of evidence, the use of non-viable split livers introduces two fundamental confounding factors that remain poorly understood: first, the high degree of heterogeneity among cases, and second, the presence of a resection line. + +<|ref|>text<|/ref|><|det|>[[92, 590, 904, 688]]<|/det|> +In regard to the first well- known issue \(^{5}\) , "by definition" non- viable livers are not utilized for a number of reasons, including prolonged warm ischemia time and high steatosis grade. As reported in a recent series published in Nature Communication \(^{4}\) , despite the exceptional results achieved, this resulted in heterogeneity in fulfilling viability criteria and in unrecognized metabolic changes due to the inherent liver physiopathological conditions. This could lead to difficulties in interpreting the data if a new technology is tested. + +<|ref|>text<|/ref|><|det|>[[92, 689, 904, 755]]<|/det|> +As for the presence of a resection line, it can introduce additional confounding factors when using split livers as an internal control. Indeed, the potential influence of the resection line on resolution and repair mechanisms has already been demonstrated in- vivo models and in humans (e.g. associated liver partition to portal vein ligation in staged hepatectomy – ALPPS \(^{25,26}\) ). + +<|ref|>text<|/ref|><|det|>[[92, 755, 904, 803]]<|/det|> +In addition, the precise ex vivo pump flow required for the hemi liver remains to be established \(^{27}\) . All these variables would have further complicated the investigation of a MSC- bioreactor effects during NMP. + +<|ref|>text<|/ref|><|det|>[[92, 804, 904, 885]]<|/det|> +Finally, for completeness towards Reviewers and Editors, it is important to acknowledge that the use of non- viable livers for research purposes is no longer permitted in Italy. This observation was not reported in the previous revisions because it does not represent an insurmountable limitation. Indeed, international collaborations can be sought within the scientific community (although the funds of this grant cannot be used for non- Italian collaborations). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 83, 905, 131]]<|/det|> +Despite reiterating that the ultimate objective of the present research is not the full clinical application of our MSC- bioreactor, we are pursuing these avenues. Indeed, we have recently published a paper on human liver NMP using the native liver of the recipient. + +<|ref|>text<|/ref|><|det|>[[90, 131, 905, 164]]<|/det|> +Since this topic is of high interest in the field of MP, we discussed this point as a future development of our research (page 17, lines 454- 456 of the tracked version of the manuscript). + +<|ref|>text<|/ref|><|det|>[[90, 164, 905, 197]]<|/det|> +We kindly request that the comment on Italian legislation not be included in the paper, as it is not crucial for the scientific community. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 87, 189, 104]]<|/det|> +## References + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 81, 905, 375]]<|/det|> +ex vivo liver perfusion (NEVLP) reduces liver and bile duct in DCD liver grafts. Am. J. Transplant. 13, 3290 (2013).22. Clavien, P. A. et al. Transplantation of a human liver following 3 days of ex situ normothermic preservation. Nat. Biotechnol. 40, 1610–1616 (2022).23. Dondossola, D. et al. Twelve-hour normothermic liver perfusion in a rat model: characterization of the changes in the ex-situ bio-molecular phenotype and metabolism. Sci. Rep. 14, 1–13 (2024).24. Guo, Z. et al. Metabolomics Differences of the Donor Livers Between In Situ and Ex Situ Conditions During Ischemia-free Liver Transplantation. Transplantation Publish Ah, 139–151 (2023).25. Wang, R. et al. Pathophysiological mechanisms of ALPPS: Experimental model. Br. J. Surg. 109, 510–519 (2022).26. Kambakamba, P. et al. Early Postoperative Serum Phosphate Drop Predicts Sufficient Hypertrophy After Liver Surgery. Ann. Surg. 278, 763–771 (2023).27. Yagi, S., Hirata, M., Miyachi, Y. & Uemoto, S. Liver regeneration after hepatectomy and partial liver transplantation. Int. J. Mol. Sci. 21, 1–23 (2020). + +<--- Page Split ---> diff --git a/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/images_list.json b/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..c9463b0e9adf55158c51ab2ff5c0b59d02371dd3 --- /dev/null +++ b/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1,107 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1. Comparison of MCDs called with epic2 on macroH2A1 CUT&RUN vs. ChIP-seq data.", + "footnote": [], + "bbox": [ + [ + 125, + 593, + 860, + 814 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R2. Correlation of genome-wide enrichment of macroH2A between ChIP-seq and CUT&RUN methodologies. ChIP-seq and associated inputs were previously generated in dermal fibroblasts (\"DF\" samples), CUT&RUN was performed in serum-starved unstimulated (\"U\") and serum-stimulated (\"S\") WT CAFs, with associated IgG control.", + "footnote": [], + "bbox": [ + [ + 137, + 460, + 884, + 765 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure R3. Binned H3K27ac signal at promoters and proximity-associated enhancers of 39 inflammatory genes upregulated in sorted dKO CAFs.", + "footnote": [], + "bbox": [ + [ + 124, + 580, + 716, + 742 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure R4. H3K27ac at enhancer peaks within 50 kb of DEG promoters and control static genes with matched expression levels.", + "footnote": [], + "bbox": [ + [ + 113, + 652, + 757, + 805 + ] + ], + "page_idx": 25 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure R5. IOBR analysis of T cell signatures in TCGA SKCM primary tumors stratified by macroH2A expression levels. Signatures relevant to CD8 T cells are highlighted in bold. Green rectangles further highlight which of these signatures are significantly lower in macroH2A low tumors.", + "footnote": [], + "bbox": [ + [ + 141, + 512, + 898, + 789 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Figure R6. IOBR analysis of CIBERSORT immune cell type scores in TCGA SKCM primary tumors that have expression values of both macroH2A genes above or below the median.", + "footnote": [], + "bbox": [ + [ + 140, + 239, + 904, + 504 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Figure R7. macroH2A1 and macroH2A2 ChIP signal around the Cxcl1 locus in dermal fibroblasts.", + "footnote": [], + "bbox": [ + [ + 115, + 523, + 884, + 686 + ] + ], + "page_idx": 39 + } +] \ No newline at end of file diff --git a/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d42678a96b89acf2bb860071472b39145923e9c6 --- /dev/null +++ b/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,1031 @@ + +# natureresearch + +# Peer Review Information + +Journal: Nature Cell Biology Manuscript Title: MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin looping Corresponding author name(s): Dan Filipescu, Emily Bernstein + +## Editorial Notes: + +## Reviewer Comments & Decisions: + +# Decision Letter, initial version: + +\*Please delete the link to your author homepage if you wish to forward this email to co- authors. + +Dear Dr Bernstein, + +Your manuscript, "MacroH2A restricts melanoma progression via inhibition of inflammatory gene expression in cancer- associated fibroblasts", has now been seen by 3 referees, who are experts in histone variant biology (referee 1); CAFs (referee 2); and melanoma and immunology (referee 3). As you will see from their comments (attached below) they find this work of potential interest, but have raised substantial concerns, which in our view would need to be addressed with considerable revisions before we can consider publication in Nature Cell Biology. + +Nature Cell Biology editors discuss the referee reports in detail within the editorial team, including the chief editor, to identify key referee points that should be addressed with priority, and requests that are overruled as being beyond the scope of the current study. To guide the scope of the revisions, I have listed these points below. We are committed to providing a fair and constructive peer- review process, so please feel free to contact me if you would like to discuss any of the referee comments further. + +In particular, it would be essential to: + +A) Address the concerns related to the proposed mechanism as questioned by Reviewer 1: + +"The attempt to mechanistically explain how macroH2A ablation affects inflammatory genes falls short." + +<--- Page Split ---> + +# natureresearch + +"...but fails to explain how macroH2A actually affects gene transcription." + +"It should be clarified if the genes upregulated in CAFs are actually mediating the phenotype (tumor growth or immunosuppression). Can this be shown in vivo? If not, could a co- culture experiment help? If the signals are secreted, media transfer experiments can be helpful." + +"It should be clarified if the loss of macroH2A in tumor cells contribute to the phenotype and CAFs respond. Again, do CAFs respond to a secreted or a cell- bound signal. Is this signal the same in WT and dKO cancer cells? Do WT and dKO CAFs respond differently to WT cancer cells. Do WT CAFs respond differently to" + +B) It would be a plus if you could add data to strengthen the human relevance as suggested by Reviewer 2 and 3; + +C) All other referee concerns pertaining to strengthening existing data, providing controls, methodological details, clarifications and textual changes, as applicable should also be addressed. + +D) Finally please pay close attention to our guidelines on statistical and methodological reporting (listed below) as failure to do so may delay the reconsideration of the revised manuscript. In particular please provide: + +- a Supplementary Figure including unprocessed images of all gels/blots in the form of a multi-page pdf file. Please ensure that blots/gels are labeled and the sections presented in the figures are clearly indicated. + +- a Supplementary Table including all numerical source data in Excel format, with data for different figures provided as different sheets within a single Excel file. The file should include source data giving rise to graphical representations and statistical descriptions in the paper and for all instances where the figures present representative experiments of multiple independent repeats, the source data of all repeats should be provided. + +We would be happy to consider a revised manuscript that would satisfactorily address these points, unless a similar paper is published elsewhere, or is accepted for publication in Nature Cell Biology in the meantime. + +When revising the manuscript please: + +- ensure that it conforms to our format instructions and publication policies (see below and https://www.nature.com/nature/for-authors). + +- provide a point-by-point rebuttal to the full referee reports verbatim, as provided at the end of this letter. + +- provide the completed Reporting Summary (found here https://www.nature.com/documents/nr-reporting-summary.pdf). This is essential for reconsideration of the manuscript will be available to editors and referees in the event of peer review. For more information see http://www.nature.com/authors/policies/availability.html or contact me. + +<--- Page Split ---> + +# natureresearch + +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. + +- that control panels for gels and western blots are appropriately described as loading on sample processing controls + +- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +Nature Cell Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +This journal strongly supports public availability of data. Please place the data used in your paper into a public data repository, or alternatively, present the data as Supplementary Information. If data can only be shared on request, please explain why in your Data Availability Statement, and also in the correspondence with your editor. Please note that for some data types, deposition in a public repository is mandatory - more information on our data deposition policies and available repositories appears below. + +Please submit the revised manuscript files and the point- by- point rebuttal to the referee comments using this link: + +## [REDACTED] + +\*This url links to your confidential home page and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We would like to receive a revised submission within six months. + +We hope that you will find our referees' comments, and editorial guidance helpful. Please do not hesitate to contact me if there is anything you would like to discuss. + +Best wishes, Zhe Wang + +Zhe Wang, PhD + +<--- Page Split ---> + +# natureresearch + +Senior Editor Nature Cell Biology + +Tel: +44 (0) 207 843 4924 email: zhe.wang@nature.com + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +MacroH2A histone variants have tumor suppressive roles in many cancer types. This was pioneered by the last author's lab showing that loss of macroH2A increased the aggressiveness of melanoma cells reflected in increased metastasis in a xenograft model. In their current manuscript by Filipescu et al. they present the logical and long- awaited follow- up describing how the systemic absence of all macroH2A impinges on melanoma growth in a fully competent mouse model. Increased tumor growth in macroH2A- deficient mice is associated with a change in tumor- infiltrating immune cells and an inflammatory expression signature in bulk tissue. Specifically, results suggest a reduction in cytotoxic T cells and an increase in tumor suppressive myeloid cells. Single- cell RNA- seq indicates that differential abundances in two major cell populations that are a subpopulation of tumor cells with a stemness signature (NC- RXR) and cancer- associated fibroblast (CAF). CAFs are shown to the main source of upregulated cytokines and chemokines likely to trigger the immunophenotype. Up and downregulated genes and their enhancers are enriched in macroH2A. Upregulation is associated with increased enhancer activity. + +Strength: + +- First study assessing the impact of macroH2As on cancer in a fully immunocompetent mouse model. +- Dissection of changes in a complex cancer tissue type. Identification of cell types and populations affected by the loss of macroH2A. + +- Demonstration that macroH2A has a repressive role in inflammatory genes in CAF. + +Weakness: + +- Figures are difficult to read (overloaded, non-intuitive abbreviations, missing labels and graphical legends). + +- The attempt to mechanistically explain how macroH2A ablation affects inflammatory genes falls short. + +The strengths of the study clearly lies on the cell biology of a complex tumor and how the loss of macroH2A histone variants affects the tumor microenvironment. This is an important and interesting aspect that will warrant publication if further strengthened. As of now the study is descriptive with a very high level of quality and quantity. + +In addition, the authors provide a wealth of genomic data including from isolated primary cells that will be a valuable resource for the field. As in many studies before the genomic data indicates previously known associations but fails to explain how macroH2A actually affects gene transcription. Elucidating the exact mechanism is beyond scope of the presented study. + +MAJOR COMMENTS: + +<--- Page Split ---> + +# natureresearch + +1. It should be clarified if the genes upregulated in CAFs are actually mediating the phenotype (tumor growth or immunosuppression). Can this be shown in vivo? If not, could a co-culture experiment help? If the signals are secreted, media transfer experiments can be helpful. + +2. It should be clarified if the loss of macroH2A in tumor cells contribute to the phenotype and CAFs respond. Again, do CAFs respond to a secreted or a cell-boud signal. Is this signal the same in WT and dKO cancer cells? Do WT and dKO CAFs respond differently to WT cancer cells. Do WT CAFs respond differently to + +## OTHER GENERAL COMMENTS: + +Given our expertise in genomic studies, we provide detailed suggestions on how to improve the data presentation (see further below). I consider that no additional data is needed on this side. + +Statistical tests are missing in many figure panels. It has to be clear without reading the figure legend or the results text if differences are significant or not. \(^+\) + +Legends are missing in several panels (eg 5c and related). + +Please reduce the number of panels to the most informative ones. + +Label the panels with the cells / tissues analyzed e.g. 'sorted CAFs' in 5e. + +In my humble opinion the authors could consider a different flow of their results. The single- cell RNA- seq is most informative and could be presented earlier (maybe right after presenting the phenotype) to introduce the two main results: 1. the change in tumor- composition and 2. changes in inflammatory gene expression. All other results could then be built on this. + +The presentation of the immunophenotype is confusing and scattered. Consider compilating all data on immune cells in one coherent figure. + +It should be clarified if there is anything special to the repressed 39 inflammatory genes compared to other macroH2A- regulated genes. + +## SUGGESTIONS FOR SPECIFIC FIGURES: + +## Figures 4-5 + +The NC Rxrg cluster has a high contribution to the dKO bulk gene expression changes, comparable to the CAF Meg3 which are the focus of further analysis. I am missing a description of genes differentially expressed in melanoma, in particular NC Rxrg cells. What was the rationale for excluding this tumor cell population from further analysis? See my major comment. + +Figure 5c could perhaps be converted to a heatmap summarizing the expression differences to make it more visual and equivalent to other representations. + +Figure 5g lacks statistical testing results. + +<--- Page Split ---> + +# natureresearch + +Could the Milo cell abundance method be applied to the re- clustered immune cell data shown in Figure S4i to assess changes in composition of immune subtypes? + +Figure 6 and S6 + +In these figures the authors present results obtained in CAFs and iDFs, but it is not always labelled in a way that allows easy interpretation without resorting to the legend or main text. For example, panels c to e versus panels h to j could be more readily interpreted by indicating the cells analyzed. This applies to the Supplementary Figure 6 and also to other parts of the manuscript, I think it would improve readability and faster interpretation of the results. + +As far as I know, this is the first time a profiling of macroH2A by CUT&RUN is reported in a manuscript. The authors show a depletion from the gene bodies of highly expressed genes and some example loci, and in both cases the results are highly reminiscent of previous published results for ChIP- seq. Given the novelty of the experimental technique applied to this histone variant, I would appreciate a better generic description of the CUT&RUN results and a comparison to previously performed ChIP- seq (eg dermal fibroblast data) as benchmark, at least: the total number of enriched regions called ("MCDs"), size distribution of the identified MCDs, total \(\%\) of genome coverage by all MCDs. + +The results in Figure 6c and d show an increased H3K27Ac enrichment at enhancers and promoters of the selected 39 upregulated inflammatory genes, however the difference seems mild when compared to the genome- wide effect shown in Figure S6a and the shaded area of the profiles (as I understand, a confidence interval) are largely overlapping. Could the authors perform a statistic test on the area around the enhancer centers or TSS to show that this is statistically significant? Perhaps a Fisher exact test on the read counts? + +MacroH2A1 has a higher enrichment in the 39 inflammatory genes than on thousands of static genes. This is also true for all dKO up and down genes (Figure 6k). The current presentation is misleading. I think a more logical description would be to first show the genome- wide analysis and then present that this holds true for the subset of genes that the authors propose are linked to the phenotype. Although the authors put the spotlight on this set of genes, I think it is important to highlight that the findings regarding mH2A occupancy and H3K27Ac changes are not exclusive of these genes but general for all mH2A- sensitive genes. + +Given the importance placed on these 39 DEGs, it would be important to know how many of them are detected as upregulated in both scRNA- Seq and sorted- bulk RNA- Seq datasets. Moreover, are they also deregulated in the NC clusters or exclusively in the CAFs? + +Similarly, the analysis of H3K27Ac in Figure 6c and d could also be performed for all enhancer peaks within 50kb and the TSS of all the dKO up and dKO down genes, providing a general analysis of how the changes in H3K27Ac enrichment relate to the expression changes in the dKO CAFs. + +Which test was performed in Figure S6 L and N? + +<--- Page Split ---> + +# natureresearch + +Remarks to the Author: + +A. Summary of the key results + +MacroH2A as a key epigenetic suppressor of tumour growth and progression in melanoma. The mechanism is shown to be likely caused by alteration in immunoregulation in the tumour mediated by the production of inflammatory cytokines by cancer activated fibroblasts. This was shown by use of a murine double- KO for macroH2A (H2afy and H2afy2) and autochthonous immunocompetent model for melanoma. The results are largely based on transcriptomic (both bulk and single cell) analyses of melanoma induced in this mouse model compared to mice that do not have the double- KO for macroH2A. The role of macroH2A in the epigenetic landscape in various cell types in the tumour microenvironment is also explored + +B. Originality and significance: if not novel, please include reference + +This study uncovers several key findings in the context of melanoma: + +- Firstly, the heterogeneity of the melanoma tumour microenvironment is delineated on a cellular transcriptional level herein. This has already been done for an orthotopic transplantation model of melanoma (Davidson et al., 2020; https://pubmed.ncbi.nlm.nih.gov/32433953/). However, to my knowledge this is first time this has been performed in this autochthonous murine model of melanoma. + +- Secondly, to my knowledge this is the first study to perform single cell RNA sequencing on macroH2A deficient murine melanoma models. + +- Thirdly, a link between the function between cancer activated fibroblasts and immunoregulation in melanoma is re-enforced by this study. This hypothesis/discovery is not novel in and of itself (Papaccio et al., 2021; https://pubmed.ncbi.nlm.nih.gov/34298873/), however this study adds valuable high-resolution data, previously unexplored, that adds to this body of evidence. + +- Finally, a link between the function of macroH2A and cancer activated fibroblast behaviour is linked and underpinned as the consequential difference in melanoma progression with or without macroH2A. Namely, melanomas with cancer activated fibroblasts with dysfunctional macroH2A have increased pro-inflammatory cytokine expression by means of an altered epigenetic landscape in absence of macroH2A. The consequence of increased pro-inflammatory cytokine expression is an immunosuppressive tumour microenvironment, that promotes melanoma growth and progression. + +C. Data & methodology: validity of approach, quality of data, quality of presentation + +Validity of approach: + +- A fine approach and line of inquiry for the issue of delineating macroH2A function in the melanoma microenvironment. + +Quality of data: + +- Data is generally of high quality. + +- Concern over number of replicates in the scRNAseq data. + +Data presentation: + +- Data is generally presented well, with little issue for legibility or font size. + +D. Appropriate use of statistics and treatment of uncertainties + +The approaches used are generally appropriate and well performed. + +E. Conclusions: robustness, validity, reliability + +The final line states that "the convergence of these mechanisms would predict poor response of + +<--- Page Split ---> + +# natureresearch + +macroH2A- low tumors to immunotherapy, suggesting a possible biomarker application to stratify melanoma patients." However this is speculative and not sufficiently evidenced in this study - how does the mouse model respond to immunotherapy based upon macroH2A status, for example? + +F. Suggested improvements: experiments, data for possible revision + +As noted in E., treating dKO and WT mice by immunotherapy to observe difference in response would strengthen this conclusion. Additionally/alternatively, a human tissue microarray (TMA) demonstrating variable macroH2A protein levels and correlating this with differences in immune cell infiltration as observed in the mouse model would be of merit. + +Only two tumours per condition are profiled by scRNAseq which is insufficient given the prominence these data have in the study. At least one more replicate per condition should be included which would also permit interrogation in the differences of tumour composition. + +CIBERSORT should be used to also determine whether there is a difference in myeloid cell populations when stratifying patients based on MACROH2A1 and MACROH2A2 expression. + +When stratifying tumours by MACROH2A2 expression (Fig 2c- d) there is a significant reduction in CD8 T cell markers but no difference in the inferred prevalence of CD8 T cells from CIBERSORT. How is this accounted for? + +G. References: appropriate credit to previous work? Manuscript is well referenced. + +H. Clarity and context: lucidity of abstract/summary, appropriateness of abstract, introduction and conclusions. + +The manuscript is delightfully written and easy to follow. The abstract is an appropriate summary of the findings. The introduction is similarly concise and appropriate. The conclusions also follow and are written well. However, as noted earlier, the final sentence of the discussion is not directly supported by the evidence presented and so must be supplied as an optimistic speculation. If, however, there were direct evidence to support this claim, the manuscript would be greatly elevated from identification of biologically relevant and interesting mechanism to also that of clinical and therapeutic relevance. + +## Reviewer #3: + +Remarks to the Author: + +In this manuscript, the authors tested macroH2A knockout in a BRAFV600E;PTEN- deficient melanoma model. They found by that macroH2A accelerated tumor growth but exhibited insignificant differences in other metrics by histology. The authors then performed bulk RNA- sequencing on the KO and WT tumors and discovered upregulation of genes involved in myeloid cell recruitment and downregulation of genes involved in myeloid cell inhibition and cytotoxic T cell activation. Flow cytometry of the murine model exhibited an increase in monocytes in the dKO and a decrease in CD8 T cells. scRNA- seq revealed an enrichment of de- differentiated neural crest cells and immunosuppressive Mrc1+ macrophages in dKO tumors. The authors identify 3 CAF clusters, which upregulated the gene signature associated with the dKO bulk RNA- seq and overexpressed the myeloid chemoattractant genes upregulated in the bulk RNA- seq. The authors also see H2afy2 expression is specific to CAF cells in the scRNA- seq. Cultured CAF cells exhibited higher expression of the chemokines in the dKO with serum stimulation, suggesting CAF cell- intrinsic mechanisms of immunosuppression with macroH2A + +<--- Page Split ---> + +# natureresearch + +KO. ChIP- seq for H3K27ac showed a distinct landscape between dKO and WT CAFs but a minimal change in chromatin accessibility by ATAC- seq, and macroH2A1 CUT&RUN showed enrichment proximal to the dKO upregulated inflammatory genes. Collectively, the authors conclude that macroH2A KO relieves repression at inflammatory genes, eliciting CAF- induced promotion of an immunosuppressive tumor microenvironment. The primary finding of the paper is identification of a previously undescribed role for macroH2A in suppressing inflammatory signaling in fibroblasts, as well as evidence for macroH2A suppression of melanoma cell de- differentiation. These findings were largely convincing and are interesting contributions to the literature but require some further connection to human tumors to establish relevance to human biology. + +## Major Comments: + +- The authors' primary finding relates to the effect of macroH2A KO in the CAFs and suggest a cell-intrinsic mechanism by in vitro studies. This provides new information about the role of macroH2A in CAFs but is limited in data to support relevance in human samples. Do human melanomas with downregulated macroH2A exhibit increased infiltration of the myeloid compartment and decreased infiltration of lymphocytes (e.g., by histology)? In probing published human scRNA-seq datasets, does the stromal compartment exhibit a macroH2A-high and -low state? If so, do these states correlate with a distinct immune landscape? + +- When comparing the GSEA data from the murine model versus the human samples, several of the pathways upregulated in the murine dKO model are downregulated in the human MACROH2A1 low samples (TNFa signaling via NFKB, IL6 Jak Stat3 signaling, IFNa/g response). What would explain this signature inversion? In looking at the myeloid-related genes (as in Fig 2B) in the human datasets, do they have a similar expression pattern? Does testing a gene signature for myeloid cell activation, cytotoxic T cell activation, etc. show a parallel between the murine and human samples? + +## Minor Comments: + +- Interesting that the H2A2-low tumors exhibit a significant decrease in the cytotoxic genes (Fig 2C) but an insignificant difference in CD8 T cell abundance (Fig 2D). What explains why H2A1 would significantly decrease CD8 T cells but not H2A2? If the samples are stratified that are low in both H2A1 and H2A2, is the difference even more pronounced? + +- Is there an increase in myeloid cells by histology in the dKO? Where do these cells localize? Localization to the stroma would further support a CAF-centric effect. + +- Please include a description of the acronyms used in Fig 4A in the figure, legend, or text. + +- After filtering the cells, are there equivalent numbers of cells for the WT and dKO samples in Fig 4? Normalizing the values in Fig 4C to the total number of cells per tumor (% filtered cells of parent tumor) would correct for sampling bias. + +- CAF Tnc drive the dKO transcriptional profile most significantly, but CAF Meg3 shows the biggest change in abundance in dKO. Do the authors believe all 3 CAF subpopulations contribute to this dKO phenotype? + +- Fig S5g shows H2afy2 expression in CAFs and H2afy expression in all clusters. This is assumedly in the WT tumors but isn't specified in the figure or corresponding legend. Please show or describe the sample origin of this expression. + +- In looking at the CAF ATAC-seq for the inflammatory genes differentially expressed in the CAF RNA-seq and exhibiting differential H3K27ac, are these genes in the newly open peaks or unchanged but open in both dKO and WT? + +- Line 347 misspelled word "previously" should be "previously." + +- Since macroH2A2 was shown to be specific to CAFs, would it be expected that CUT&RUN for H2A2 would exhibit distinct enrichment localization? + +<--- Page Split ---> + +# natureresearch + +- Figure S4i isn't referenced in the text, and lines 352-353 should reference Fig 6f and 6g. + +## GUIDELINES FOR MANUSCRIPT SUBMISSION TO NATURE CELL BIOLOGY + +READABILITY OF MANUSCRIPTS - Nature Cell Biology is read by cell biologists from diverse backgrounds, many of whom are not native English speakers. 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The reviewers made favorable comments about our study, including: + +- "the strength of the study clearly lies on the cell biology of a complex tumor and how the loss of macroH2A histone variants affects the tumor microenvironment"- "the manuscript is delightfully written and easy to follow"- "these findings were largely convincing and are interesting contributions to the literature" + +The reviewers also made helpful suggestions and provided constructive critiques, which we believe have significantly improved the quality and impact of our manuscript and enhanced our mechanistic understanding of macroH2A-deficiency in melanoma, with a focus on the CAF compartment. Our substantially revised manuscript contains two heavily amended Main figures (Figs. 5 & 7 and their corresponding Supplementary figures), consisting of almost entirely new data. Here, we highlight some of the key new data: + +1. To mechanistically explain how macroH2A ablation affects inflammatory gene expression in CAFs, we performed promoter-capture Micro-C (pcMicro-C, a chromosome conformation capture technique that identifies chromatin loops with nucleosomal precision, here using promoters as the bait) to investigate the role of macroH2A in 3D chromatin architecture. Notably, this analysis has been computationally integrated with extensive transcriptomics and epigenomics data. We find the following: + +I. loss of macroH2A is associated with global changes in chromatin contacts (Fig. 7a) + +<--- Page Split ---> + +# natureresearch + +II. a significant correlation between dKO activated enhancers (gain of H3K27ac) with dKO-specific promoter-enhancer loops (Fig. 7b)III. enrichment of inflammatory genes among those that gain promoter-enhancer contacts with increased enhancer activity in the dKO setting (Fig. 7d). + +Overall, this new data suggests that macroH2A variants regulate the 3D chromatin landscape, and furthers our understanding of the regulatory elements behind those genes that drive the dKO CAF inflammatory phenotype. + +2. Second, as requested by reviewer 2, we carried out an additional single cell RNA-sequencing (scRNA-seq) experiment of BRAFV600E/PTEN-deficient melanomas for a total of three WT and three dKO mice, generating a dataset of \(\sim 24,000\) high-quality cells (Fig. 3a). While this additional replicate has not changed our overall conclusions, attesting to the robustness of our original scRNA-seq analysis, it has allowed us to call cell clusters in more detail, as well as to add statistical significance to differences in the proportions of cells (Fig. 3d). This newly analyzed data continues to demonstrate significant changes in the NC and CAF populations, as well as various immune cell types (immunosuppressive myeloid, and cytotoxic T cells) in the dKO vs. WT melanomas (Fig. 3d). This data further maintains the role of CAFs as the drivers of inflammatory mediators in the TME (Fig. 4a-c). Moreover, it has now allowed us to robustly call receptor-ligand interactions, which revealed the predominant role of CAFs in communicating to other cell types (Fig. 5a, b), and the increased communication along the CCL2, CXCL1 and IL-6 pathways from dKO CAFs to myeloid cells (Fig. 5a). + +3. To complement the scRNA-seq data, and to identify interactions between transformed melanocytes, CAFs, and the immune compartment in their native morphological context, we performed spatial transcriptomics using the 10X Visium spatial gene expression assay on WT and dKO melanomas. This approach allowed us to infer functional relationships between cell types that we identified in scRNA-seq data. As suggested by reviewers, we now present evidence of spatial colocalization between CAFs and immunosuppressive myeloid cells, and their exclusion of cytotoxic T cells from their tissue niches (Fig. 5b, c). Moreover, genetically engineered melanoma models have limited spatial transcriptomics data; thus we hereby also provide a key resource for the melanoma community. + +4. Finally, as requested by reviewers 2 and 3, we also translated our murine findings to human biology through the use of patient-derived melanoma CAFs, as well as analyzing a published pan-cancer human CAF scRNA-seq dataset. Interestingly, we find that human melanoma CAFs vary in their levels of macroH2A2, and via ELISA assays, we demonstrate that macroH2A2low CAFs secrete more CCL2, CXCL1 and IL-6 upon stimulation (Fig. 5f, g). Moreover, by analyzing scRNA-seq data from over 56,000 CAFs across 98 tumor samples, we find CCL2, CXCL1 and IL6 are positively correlated with each other, while IL6 and MACROH2A2 show a negative correlation (Fig. 5j). + +<--- Page Split ---> + +# natureresearch + +Overall, we would like to point out that our study is the first to: 1) report a cancer- associated phenotype in macroH2A- deficient animals, and 2) associate a histone variant with the non- immune tumor stroma, a compartment of increasing relevance to cancer biology. We demonstrate that CAF activation in the absence of macroH2A shapes tumor initiation and the ensuing dampened immune response by producing inflammatory cytokines that recruit pro- tumorigenic monocytes (also known as MDSCs) that can suppress T cell function. Moreover, we have utilized multiple innovative approaches, including scRNA- seq, spatial transcriptomics, and 3D chromatin structural analyses. The latter two approaches were performed during the revision process. Moreover, the use of patient- derived melanoma CAFs and mining of publicly available CAF datasets supports our findings in the human setting. + +We highlighted sections of the manuscript and figure legends referring to this new data and revised analysis by using underlined text. + +Please see our point- by- point responses to reviewers' comments below in blue: + +<--- Page Split ---> + +# natureresearch + +## Reviewer #1: + +## Remarks to the Author: + +MacroH2A histone variants have tumor suppressive roles in many cancer types. This was pioneered by the last author's lab showing that loss of macroH2A increased the aggressiveness of melanoma cells reflected in increased metastasis in a xenograft model. In their current manuscript by Filipescu et al. they present the logical and long- awaited follow- up describing how the systemic absence of all macroH2A impinges on melanoma growth in a fully competent mouse model. Increased tumor growth in macroH2A- deficient mice is associated with a change in tumor- infiltrating immune cells and an inflammatory expression signature in bulk tissue. Specifically, results suggest a reduction in cytotoxic T cells and an increase in tumor suppressive myeloid cells. Single- cell RNA- seq indicates that differential abundances in two major cell populations that are a subpopulation of tumor cells with a stemness signature (NC- RXR) and cancer- associated fibroblast (CAF). CAFs are shown to the main source of upregulated cytokines and chemokines likely to trigger the immunophenotype. Up and downregulated genes and their enhancers are enriched in macroH2A. Upregulation is associated with increased enhancer activity. + +## Strength: + +- First study assessing the impact of macroH2As on cancer in a fully immunocompetent mouse model.- Dissection of changes in a complex cancer tissue type. Identification of cell types and populations affected by the loss of macroH2A.- Demonstration that macroH2A has a repressive role in inflammatory genes in CAF. + +## Weakness: + +- Figures are difficult to read (overloaded, non-intuitive abbreviations, missing labels and graphical legends).- The attempt to mechanistically explain how macroH2A ablation affects inflammatory genes falls short. + +The strengths of the study clearly lies on the cell biology of a complex tumor and how the loss of macroH2A histone variants affects the tumor microenvironment. This is an important and interesting aspect that will warrant publication if further strengthened. As of now the study is descriptive with a very high level of quality and quantity. In addition, the authors provide a wealth of genomic data + +<--- Page Split ---> + +# natureresearch + +including from isolated primary cells that will be a valuable resource for the field. As in many studies before the genomic data indicates previously known associations but fails to explain how macroH2A actually affects gene transcription. Elucidating the exact mechanism is beyond scope of the presented study. + +We thank the reviewer for acknowledging the significance of our study and recognizing its value. While the reviewer suggests that we do not fully address the mechanism by which macroH2A deficiency affects inflammatory gene expression, they also mention that it is "beyond the scope of the present study". Nonetheless, we are pleased to provide new data implicating macroH2A in the regulation of 3D chromatin interactions, particularly at inflammatory gene loci in CAFs. Specific points are addressed below. + +## MAJOR COMMENTS: + +1. It should be clarified if the genes upregulated in CAFs are actually mediating the phenotype (tumor growth or immunosuppression). Can this be shown in vivo? If not, could a co-culture experiment help? If the signals are secreted, media transfer experiments can be helpful. + +We thank the reviewer for raising this important point. We have now edited the manuscript to ensure the clarity of our message regarding the contribution of inflammatory gene expression in CAFs to the phenotype, as well as experimental/computational steps to further validate this hypothesis. + +First, following the reviewer's suggestion of a co- culture experiment, we demonstrate that serum- stimulated dKO CAFs induce increased migration of WT monocytes compared to WT CAFs via transwell assays (Fig. 5d). Second, using our scRNA- seq dataset, which is now expanded through the addition of a third replicate per genotype, we performed ligand- receptor analysis to dissect the extent of cellular communication between CAFs and myeloid cells, and confirmed increased signaling from the former to the latter along the signaling pathways comprising the upregulated cytokines (Fig. 5a). Furthermore, by leveraging a new spatial transcriptomics dataset we generated in WT and dKO melanomas, we confirmed accumulation of Mac Mrc1 cells (myeloid cells with a predicted immunosuppressive profile) in the vicinity of CAFs, coupled to the exclusion of cytotoxic T cells (Fig. 5b, c). Taken together, these data suggest that macroH2A deficiency in CAFs is sufficient to drive increased monocyte/monocyte- derived cell accumulation in the TME. + +Finally, we have now emphasized throughout the text that CCL2, CXCL1 and IL- 6 are widely accepted as signals secreted by CAFs to attract myeloid cells and polarize them toward an immunosuppressive phenotype across several cancer types. The revised manuscript cites a review summarizing these studies: https://pubmed.ncbi.nlm.nih.gov/35331673/ + +<--- Page Split ---> + +# natureresearch + +2. It should be clarified if the loss of macroH2A in tumor cells contribute to the phenotype and CAFs respond. Again, do CAFs respond to a secreted or a cell-bound signal. Is this signal the same in WT and dKO cancer cells? Do WT and dKO CAFs respond differently to WT cancer cells. Do WT CAFs respond differently to (please note this sentence was not completed by the reviewer) + +The reviewer raises a valid point regarding communication from the tumor compartment towards CAFs. Signals from tumor cells (in our case, the NC compartment) can reprogram normal tissue mesenchymal cells into CAFs, and provide one of the pathways for CAF accumulation in the TME (reviewed in https://pubmed.ncbi.nlm.nih.gov/34670861/). While we cannot formally rule out extrinsic factors, several lines of evidence strongly suggest the inflammatory phenotype is CAF- intrinsic. + +First, while we would have been keen to perform an experiment involving stimulation of WT CAFs with conditioned medium from WT or dKO melanoma/NC cells, followed by measurement of cytokine expression in CAFs, unfortunately it is not feasible. Despite considerable efforts, we have not been able to purify NC- derived cells from our melanoma model, or establish culture conditions that select for and allow propagation of tumor cells out of the mixed primary cell culture. However, our stimulation experiments in cultured CAFs, in the absence of any active signaling from tumor cells (given their absence from these cultures), show dKO CAFs can intrinsically sustain increased inflammatory signaling (Fig. 4f, S4n) and functionally, lead to increased recruitment of WT monocytes in vitro (Fig. 5d, S5c). Second, iDF stimulation experiments (Fig. S4o, S6m- o) show that this same phenotype occurs outside of any influence of the TME, since these WT and dKO fibroblasts were derived from normal skin. Third, ligand- receptor interaction analysis shows the NC compartment actually communicates less towards CAFs in the dKO, while CAFs have a stronger strength of interaction towards NC in the dKO (Fig. S5b). + +## OTHER GENERAL COMMENTS: + +Given our expertise in genomic studies, we provide detailed suggestions on how to improve the data presentation (see further below). I consider that no additional data is needed on this side. + +Statistical tests are missing in many figure panels. It has to be clear without reading the figure legend or the results text if differences are significant or not.+ + +Details of statistical tests performed are now present in all figures, and we state in the legend when non- significant differences are not labeled. We deliberately omitted marking nonsignificant differences with "ns" when significant differences are also marked, in order to maintain figure clarity. For example, adding "ns" in panels such as Fig. 2c would render them less legible. + +<--- Page Split ---> + +# natureresearch + +Legends are missing in several panels (eg 5c and related). + +We apologize for any omissions and have modified the current version. + +Please reduce the number of panels to the most informative ones. + +We reorganized figures in the interest of clarity and moved multiple panels to the Supplement. The reviewer will now appreciate that former Figures 2 and 3 were combined and former Figures 3 and 4 have been simplified. + +Label the panels with the cells / tissues analyzed e.g. 'sorted CAFs' in 5e. + +We thank the reviewer for this suggestion. This is now the case for figures where data from multiple sources is shown. + +In my humble opinion the authors could consider a different flow of their results. The single- cell RNA- seq is most informative and could be presented earlier (maybe right after presenting the phenotype) to introduce the two main results: 1. the change in tumor- composition and 2. changes in inflammatory gene expression. All other results could then be built on this. + +We thank the reviewer for the suggestion. Accordingly, we tried to move this data forward as much as possible, especially considering the additional data added during revision. However, we believe the current flow of the paper allows the scRNA- seq data to link more readily to the aspects presented immediately after, and the data presented before provides strong evidence justifying its application, which we present in new Fig. 2 (a merge of previous Figures 2 and 3). We hope the flow of the revised manuscript showcases the scRNA- seq and continues to build out from there. + +The presentation of the immunophenotype is confusing and scattered. Consider compilating all data on immune cells in one coherent figure. + +We thank the reviewer for the suggestion. We have now simplified the immunophenotypic analysis and grouped it with the bulk tumor transcriptomic analysis into revised Fig. 2. + +It should be clarified if there is anything special to the repressed 39 inflammatory genes compared to other macroH2A- regulated genes. + +While this is somewhat open to speculation, as included in the Discussion, the promoter- capture Micro- C looping data generated during revision provides some insight into this question. By intersecting genes upregulated by macroH2A loss with the bona fide target genes of enhancers gaining H3K27ac in the dKO (determined by pcMicro- C looping data), 7 out of 20 genes were part of inflammatory signaling pathways (Fig. 7d), with significant enrichment for NF- \(\kappa\) B targets (Table 7). In addition, 17 out of these 20 genes also had a net increase in the number of loops in the dKO (Fig. 7d). Therefore, several inflammatory genes are at the + +<--- Page Split ---> + +# natureresearch + +intersection of expression, looping and enhancer activity perturbations induced by macroH2A loss. While this does not encompass all genes, it is known that IL- 6 can signal in a paracrine manner, activating its own targets, and therefore some gene expression changes might be secondary to that. + +## SUGGESTIONS FOR SPECIFIC FIGURES: + +Figures 4- 5 + +The NC Rxrg cluster has a high contribution to the dKO bulk gene expression changes, comparable to the CAF Meg3 which are the focus of further analysis. I am missing a description of genes differentially expressed in melanoma, in particular NC Rxrg cells. What was the rationale for excluding this tumor cell population from further analysis? See my major comment. + +The reviewer correctly points out that the NC Zeb2 cluster (previously annotated as Nc Rxrg but has been renamed after the additional scRNA- seq data set requested by reviewer 2) has proven difficult to analyze. The significant accumulation of NC Zeb2 cells in the dKO (Fig. 3d) and their de- differentiated nature (Fig. S3g- h) are consistent with macroH2A loss driving tumor progression, as we showed previously (Kapoor et al., 2010). However, NC Zeb2 cells displayed minimal upregulation of any Hallmark pathway in the dKO, compared to much more significant and pronounced (in terms of fold change) downregulation of pathways (Fig. S4g). Furthermore, among the downregulated pathways, some were seemingly antagonistic (G2M checkpoint/p53 vs. E2F targets; oxidative phosphorylation vs. hypoxia), which did not aid in informing what processes are being affected in this cluster. More importantly, because of a lack of specific markers suited for FACS, we were unable to isolate NC Zeb2 (or any other NC cells) from tumors, precluding any validation or molecular dissection of macroH2A's role in this cell type. + +Figure 5c could perhaps be converted to a heatmap summarizing the expression differences to make it more visual and equivalent to other representations. + +We maintained this standard representation of scRNA- seq data (now Fig. 4b), as in addition to differences between WT and dKO, the violin plot shape also displays the proportion of expressing cells and maximum expression value, showing which cluster is the main source of each highlighted cytokine/gene. This second point gets lost in heatmaps, where data is normalized as Z- scores for each gene to emphasize difference over absolute value. + +Figure 5g lacks statistical testing results. + +Statistical testing results and individual replicate values have been added to what is now Fig. 4f. + +<--- Page Split ---> + +# natureresearch + +Could the Milo cell abundance method be applied to the re- clustered immune cell data shown in Figure S4i to assess changes in composition of immune subtypes? + +We performed this analysis as suggested, and it confirmed local changes in CD8 clusters. This has been included as Fig. S3n. + +Figure 6 and S6 + +In these figures the authors present results obtained in CAFs and iDFs, but it is not always labelled in a way that allows easy interpretation without resorting to the legend or main text. For example, panels c to e versus panels h to j could be more readily interpreted by indicating the cells analyzed. This applies to the Supplementary Figure 6 and also to other parts of the manuscript, I think it would improve readability and faster interpretation of the results. + +We agree that comparing multiple cell types within the same figure can lead to confusion and have labeled these panels accordingly. + +As far as I know, this is the first time a profiling of macroH2A by CUT&RUN is reported in a manuscript. The authors show a depletion from the gene bodies of highly expressed genes and some example loci, and in both cases the results are highly reminiscent of previous published results for ChIP- seq. Given the novelty of the experimental technique applied to this histone variant, I would appreciate a better generic description of the CUT&RUN results and a comparison to previously performed ChIP- seq (eg dermal fibroblast data) as benchmark, at least: the total number of enriched regions called ("MCDs"), size distribution of the identified MCDs, total \(\%\) of genome coverage by all MCDs. + +We thank the reviewer for the suggestions and have now included the total number of MCDs (Fig. S6b legend), panels on size distribution of the identified MCDs (Fig. S6c) and total \(\%\) of + +![](images/Figure_unknown_0.jpg) + +
Figure R1. Comparison of MCDs called with epic2 on macroH2A1 CUT&RUN vs. ChIP-seq data.
+ +<--- Page Split ---> + +# natureresearch + +genome coverage by all MCDs (Fig. S6d). We observed MCDs varied greatly in size, as well as in the level of macroH2A enrichment, prompting us to stratify them into super vs. standard, using an approach adapted for enhancer analysis. While we make no claim that these categories parallel the differences between traditional and superenhancers, we observe a more pronounced link with gene/enhancer deregulation at regions highly enriched in macroH2A such as the super MCDs. + +As suggested, we attempted to compare our MCDs called on CUT&RUN data in CAFs with previously called MCDs on ChIP- seq in DFs (Sun et al., 2018). However, the two had different size distributions and patterns, which was likely due to the different methods used to call them. Therefore, we attempted to use the same methodology in the hope of obtaining a more comparable result, based on a recent publication analyzing macroH2A ChIP- seq. Corujo et al. (2022) used epic2 (Stovner and Saetrom, 2019), a peak caller tailored to broad enrichment regions, which we applied to our macroH2A1 ChIP- seq and CUT&RUN datasets. After testing multiple parameters to optimize the identification of MCDs (e.g., gap size, bin size, q- value, background), we observed that epic2 performed well for ChIP- seq, identifying large macro domains that corresponded to highly enriched regions, while it did not perform well for CUT&RUN, missing multiple large macroH2A enriched domains previously identified by the + +![](images/Figure_unknown_1.jpg) + +
Figure R2. Correlation of genome-wide enrichment of macroH2A between ChIP-seq and CUT&RUN methodologies. ChIP-seq and associated inputs were previously generated in dermal fibroblasts ("DF" samples), CUT&RUN was performed in serum-starved unstimulated ("U") and serum-stimulated ("S") WT CAFs, with associated IgG control.
+ +<--- Page Split ---> + +# natureresearch + +identification of large domains from CUT&RUN data, and were not able to perform a domain- based comparison. + +Nevertheless, we compared actual enrichment signal in the form of bigwig files, for their genome- wide correlation. Using this approach, we found a high degree of correlation \((r = 0.79)\) between macroH2A1 ChIP- seq and CUT&RUN (Fig. R2). We unfortunately do not have space in the Supplemental figures to add this data; however, we now mention our benchmarking of macroH2A CUT&RUN vs. ChIP- seq in the Methods section: "MacroH2A1 enrichment determined by CUT&RUN was benchmarked by correlation analysis with published macroH2A1 ChIP- seq in dermal fibroblasts (Sun 2018). Enrichment at the level of read pileups had a correlation coefficient of 0.79 (data not shown)." + +The results in Figure 6c and d show an increased H3K27Ac enrichment at enhancers and promoters of the selected 39 upregulated inflammatory genes, however the difference seems mild when compared to the genome- wide effect shown in Figure S6a and the shaded area of the profiles (as I understand, a confidence interval) are largely overlapping. Could the authors perform a statistic test on the area around the enhancer centers or TSS to show that this is statistically significant? Perhaps a Fisher exact test on the read counts? + +We performed a test after binning the signal upstream, on and downstream of the elements and indeed, it is not statistically significant (Fig. R3). This prompted us to examine other mechanisms of gene regulation, such as chromatin looping. We used looping data to delineate promoter- enhancer associations based on interactions in 3D, moving away from proximity- based associations (which are predictions), and have now removed the data the reviewer refers to. + +![](images/Figure_unknown_2.jpg) + +
Figure R3. Binned H3K27ac signal at promoters and proximity-associated enhancers of 39 inflammatory genes upregulated in sorted dKO CAFs.
+ +MacroH2A1 has a higher enrichment in the 39 inflammatory genes than on thousands of static genes. This is also true for all dKO up and down genes (Figure 6k). The current presentation is misleading. I think a more logical description would be to first show the genome- wide analysis and then present that + +<--- Page Split ---> + +# natureresearch + +this holds true for the subset of genes that the authors propose are linked to the phenotype. Although the authors put the spotlight on this set of genes, I think it is important to highlight that the findings regarding mRNA occupancy and H3K27Ac changes are not exclusive of these genes but general for all mRNA- sensitive genes. + +We took the reviewer's suggestion and organized Fig. 6 accordingly, emphasizing statistically significant genome- wide associations between macroH2A occupancy and gene/enhancer dysfunction. + +Given the importance placed on these 39 DEGs, it would be important to know how many of them are detected as upregulated in both scRNA- Seq and sorted- bulk RNA- Seq datasets. Moreover, are they also deregulated in the NC clusters or exclusively in the CAFs? + +We include Table R1 below to show 17 of the 39 genes derived from sorted CAFs are also significantly upregulated in CAF Meg3 of the scRNA- seq dataset, the most abundant CAF cluster that shows a 3- fold frequency increase in the dKO. Furthermore, CAF Wif1, CAF Fbln1 and CAF Lrrc15 follow in terms of most genes upregulated within that list. Among NC clusters, only NC Aqp1 displays upregulation of 2 such genes. This confirms the bulk of inflammatory gene upregulation in the dKO originates in CAFs. + +Similarly, the analysis of H3K27Ac in Figure 6c and d could also be performed for all enhancer peaks within 50kb and the TSS of all the dKO up and dKO down genes, providing a general analysis of how the changes in H3K27Ac enrichment relate to the expression changes in the dKO CAFs. + +As above, we revised our analysis to move away from proximity- based associations, which were not significant in the way suggested by the reviewer. We include the data (Fig. R4), where on average, H3K27ac at enhancers within 50 kb of TSS of all DEGs does not change in the direction of expression changes. Accordingly, we have also emphasized in the discussion that enhancer activity changes are not sufficient to explain all gene expression changes we observe. + +![](images/Figure_unknown_3.jpg) + +
Figure R4. H3K27ac at enhancer peaks within 50 kb of DEG promoters and control static genes with matched expression levels.
+ +<--- Page Split ---> + +# natureresearch + +Which test was performed in Figure S6 L and N? + +A chi- square test was performed, now presented in Fig. 6b and 6e, with appropriate description in the legend. + +<--- Page Split ---> + +**Table R1.** Upregulation status of inflammatory genes identified in sorted CAFs, across clusters defined by scRNA-seq in murine melanoma. A value of T (true) represents significant upregulation (P-adj < 0.05, log2fc > 0) of indicated gene in indicated cluster. Genes and clusters with no T values are not shown. + +
CAF Meg3CAF Wif1Mac Mrc1Mono-cyteMela- nocyteCAF Lrrc15NC Aqp1CAF Fbln1Mac Arg1BECAdven-titial
ApoeTTFFTTTTFFT
Hmgb1TFFFFFTTFFF
Ntrk2TTFFFFTFFFF
Ccl11TTFFFFFFFF
Tnfsf9TFFFFFFFFF
Thbs1TFFTFFFFTFF
CebpdTTFFFFFFFF
Tac1TFFFFFFFFF
Ccl2TTFFFFFFFF
CpFTTFFTFTFFF
Serping1TTFFFFFTFFF
Cxcl1TTFTFTFTTTF
Il6TFFFFFFFFF
Fosl2TFFFFFFFFF
KitlTFFFFFFFFF
Agtr1aFFFFFFFTFFF
CfhTTFFFFFTFFF
Dock10TTFFFFFTFFF
TslpFFTFFFFFFF
ApodFTFFFFFFFF
Il6stTFFFFFFFFF
+ +<--- Page Split ---> + +# natureresearch + +## Reviewer #2: + +## Remarks to the Author: + +### A. Summary of the key results + +MacroH2A as a key epigenetic suppressor of tumour growth and progression in melanoma. The mechanism is shown to be likely caused by alteration in immunoregulation in the tumour mediated by the production of inflammatory cytokines by cancer activated fibroblasts. This was shown by use of a murine double- KO for macroH2A (H2afy and H2afy2) and autochthonous immunocompetent model for melanoma. The results are largely based on transcriptomic (both bulk and single cell) analyses of melanoma induced in this mouse model compared to mice that do not have the double- KO for macroH2A. The role of macroH2A in the epigenetic landscape in various cell types in the tumour microenvironment is also explored + +### B. Originality and significance: if not novel, please include reference + +This study uncovers several key findings in the context of melanoma: + +- Firstly, the heterogeneity of the melanoma tumour microenvironment is delineated on a cellular transcriptional level herein. This has already been done for an orthotopic transplantation model of melanoma (Davidson et al., 2020; https://pubmed.ncbi.nlm.nih.gov/32433953/). However, to my knowledge this is first time this has been performed in this autochthonous murine model of melanoma.- Secondly, to my knowledge this is the first study to perform single cell RNA sequencing on macroH2A deficient murine melanoma models.- Thirdly, a link between the function between cancer activated fibroblasts and immunoregulation in melanoma is re-enforced by this study. This hypothesis/discovery is not novel in and of itself (Papaccio et al., 2021; https://pubmed.ncbi.nlm.nih.gov/34298873/), however this study adds valuable high-resolution data, previously unexplored, that adds to this body of evidence.- Finally, a link between the function of macroH2A and cancer activated fibroblast behaviour is linked and underpinned as the consequential difference in melanoma progression with or without macroH2A. Namely, melanomas with cancer activated fibroblasts with dysfunctional macroH2A have increased pro-inflammatory cytokine expression by means of an altered epigenetic landscape in absence of macroH2A. The consequence of increased pro-inflammatory cytokine expression is an immunosuppressive tumour microenvironment, that promotes melanoma growth and progression. + +<--- Page Split ---> + +# natureresearch + +We thank the reviewer for recognizing the value of our study and emphasizing its novel findings. We hope they will appreciate the additional insight of the macroH2A- deficient TME provided by the spatial transcriptomics, 3D chromatin conformation and human data analysis included in the revised manuscript. + +### C. Data & methodology: validity of approach, quality of data, quality of presentation + +Validity of approach: + +- A fine approach and line of inquiry for the issue of delineating macroH2A function in the melanoma microenvironment. + +Quality of data: + +- Data is generally of high quality.- Concern over number of replicates in the scRNAseq data. + +Data presentation: + +- Data is generally presented well, with little issue for legibility or font size. + +### D. Appropriate use of statistics and treatment of uncertainties + +The approaches used are generally appropriate and well performed. + +### E. Conclusions: robustness, validity, reliability + +The final line states that "the convergence of these mechanisms would predict poor response of macroH2A- low tumors to immunotherapy, suggesting a possible biomarker application to stratify melanoma patients." However this is speculative and not sufficiently evidenced in this study - how does the mouse model respond to immunotherapy based upon macroH2A status, for example? + +We thank the reviewer for bringing up this point. We reserved this statement for the discussion section, given its speculative nature, and now state the following: "We speculate that the convergence of these mechanisms would predict poor response of macroH2Alow tumors to immunotherapy, suggesting a possible biomarker application to stratify melanoma patients". + +We agree that testing response to immunotherapy may complement our data, but we believe this is beyond the scope of our study, in which we focus on the mechanistic understanding of macroH2A to inflammatory gene regulation in CAFs. While we considered performing immune checkpoint blockade, anti PD- 1 or PD- L1 monotherapy has been attempted in this melanoma model and shows minimal effects (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4097121/ + +<--- Page Split ---> + +# natureresearch + +see Fig. 5). Furthermore, these BRAFV600E/Ptennull tumors respond only partially to anti- CTLA- 4 + anti- PD- L1 combination therapy (https://www.nature.com/articles/nature14404 in Figure 4), which is not surprising given the lack of neoantigens in these tumors. Given these drawbacks, and the considerable expense of the drug regimen for a cohort of 20 mice over a period of 25 days, we did not pursue this approach. + +### F. Suggested improvements: experiments, data for possible revision + +As noted in E., treating dKO and WT mice by immunotherapy to observe difference in response would strengthen this conclusion. Additionally/alternatively, a human tissue microarray (TMA) demonstrating variable macroH2A protein levels and correlating this with differences in immune cell infiltration as observed in the mouse model would be of merit. + +We have addressed point E above. + +We have addressed point E above.We thank the reviewer for the suggestion to consider TMAs, however, unfortunately, the small cores of tissue present in these arrays do not allow one to assess all the cell types of interest in the TME. Further, the impact of macroH2A loss on the tumor immune microenvironment appears to stem primarily from the CAF population, and thus the IHC analysis would need to target this population specifically. We note that IHC does not have the necessary resolution to evaluate macroH2A levels in CAFs vs. rest of the tumor, and would require simultaneous detection of at least one CAF marker, macroH2A1/2, and normalization controls such as histone H3. However, we now include two new sources of data that confirm our observations in human CAFs. + +First, we obtained human melanoma CAF cultures from the NCI PDMR and Andrew Aplin's team at Thomas Jefferson University, who has published multiple studies using these CAFs (https://pubmed.ncbi.nlm.nih.gov/26269601/; https://pubmed.ncbi.nlm.nih.gov/30115691/). Our studies revealed an anticorrelation between endogenous macroH2A2 levels and CCL2, CXCL1, and IL- 6 cytokine production in these human CAFs (Fig. 5f, g, S5h). While this analysis did not reach statistical significance (likely due to heterogeneous source material and/or human biological variation), it indeed paralleled our observations from the mouse model. + +Second, we analyzed a published scRNA- seq dataset containing over 56,000 CAFs across 98 samples comprising multiple cancer types. By calculating pseudobulk values, we found a significant pan- cancer anticorrelation between macroH2A2 and IL- 6 expression (Fig. S5j). + +Only two tumours per condition are profiled by scRNAseq which is insufficient given the prominence these data have in the study. At least one more replicate per condition should be included which would also permit interrogation in the differences of tumour composition. + +<--- Page Split ---> + +# natureresearch + +We followed the reviewer's suggestion and added a third biological replicate per genotype. While this additional replicate has not changed our overall conclusions, attesting to the robustness of our original scRNA- seq analysis, it has allowed us to call cell clusters in more detail, as well as to add statistical significance to the differences in proportions of cells (Fig. 3d). This newly analyzed data continues to show significant changes in the NC populations, CAFs, and various immune cell types (immunosuppressive myeloid, and cytotoxic T cells) in the dKO vs. WT melanomas (Fig. 3d). This data maintained the role of CAFs as drivers of the accumulation of inflammatory mediators in the TME (Fig. 4a- c). Furthermore, it allowed us to robustly call receptor- ligand interactions, which revealed the predominant role of CAFs in communicating to other cell types (Fig. S5a, b), and the increase of communication along the CCL2, CXCL1 and IL- 6 pathways from dKO CAFs to myeloid cells (Fig. 5a). + +CIBERSORT should be used to also determine whether there is a difference in myeloid cell populations when stratifying patients based on MACROH2A1 and MACROH2A2 expression. + +We agree with the reviewer regarding the potential of CIBERSORT to interrogate accumulation of myeloid cells in macroH2Alow tumors. Therefore, we completely overhauled this analysis by implementing a recent analysis package, IOBR, which contains the CIBERSORT functionality. In contrast to our previous approach, this allowed us to use data normalized in the same manner via the robust TMM method, both for stratifying samples according to macroH2A expression, and for calculating immune population estimates. We no longer relied on CIBERSORT scores calculated by others; we compared samples in the \(1^{\text{st}}\) and \(3^{\text{rd}}\) macroH2A1 or macroH2A2 expression terciles, eliminating samples with intermediate expression levels which may have reduced the amplitude of differences observed. + +The updated CIBERSORT analysis shows M2 (pro- tumor) macrophages are significantly more abundant in macroH2A2low primary tumors and near significance in macroH2A1low tumors (Fig. 5e). Of note, some myeloid subtypes are negatively correlated with macroH2A2 in metastases (Fig. S5d), although macroH2Alow tumors appear overall depleted of immune cells and conversely display increased tumor purity (Fig. S5e), which likely affects our ability to detect relative increases of immune subtypes via CIBERSORT. We also emphasize that the TCGA SKCM metastatic samples mainly comprise lymph node lesions, where the TME is different - both through a presence of immune populations residing in the lymph node, and a lack of skin- derived CAFs - therefore it is difficult to translate findings from our mouse model to these samples. + +When stratifying tumours by MACROH2A2 expression (Fig 2c- d) there is a significant reduction in CD8 T cell markers but no difference in the inferred prevalence of CD8 T cells from CIBERSORT. How is this accounted for? + +<--- Page Split ---> + +# natureresearch + +This was a shortcoming of the approach we used previously (see above). MACROH2A2 RNA- seq counts are low and likely affected the accuracy of stratification using the previous FPKM normalization method. Our updated CIBERSORT approach now shows significant CD8 T cell depletion in macroH2A1 and 2 low tumors both in the primary and metastatic setting (Fig. 5e, S5d). + +### G. References: appropriate credit to previous work? + +Manuscript is well referenced. + +### H. Clarity and context: lucidity of abstract/summary, appropriateness of abstract, introduction and conclusions. + +The manuscript is delightfully written and easy to follow. The abstract is an appropriate summary of the findings. The introduction is similarly concise and appropriate. The conclusions also follow and are written well. However, as noted earlier, the final sentence of the discussion is not directly supported by the evidence presented and so must be supplied as an optimistic speculation. If, however, there were direct evidence to support this claim, the manuscript would be greatly elevated from identification of biologically relevant and interesting mechanism to also that of clinical and therapeutic relevance. + +We thank the reviewer for acknowledging the clarity and context of our manuscript. + +<--- Page Split ---> + +# natureresearch + +## Reviewer #3: + +## Remarks to the Author: + +In this manuscript, the authors tested macroH2A knockout in a BRAFV600E;PTEN- deficient melanoma model. They found by that macroH2A accelerated tumor growth but exhibited insignificant differences in other metrics by histology. The authors then performed bulk RNA- sequencing on the KO and WT tumors and discovered upregulation of genes involved in myeloid cell recruitment and downregulation of genes involved in myeloid cell inhibition and cytotoxic T cell activation. Flow cytometry of the murine model exhibited an increase in monocytes in the dKO and a decrease in CD8 T cells. scRNA- seq revealed an enrichment of de- differentiated neural crest cells and immunosuppressive Mrc1+ macrophages in dKO tumors. The authors identify 3 CAF clusters, which upregulated the gene signature associated with the dKO bulk RNA- seq and overexpressed the myeloid chemoattractant genes upregulated in the bulk RNA- seq. The authors also see H2afy2 expression is specific to CAF cells in the scRNA- seq. Cultured CAF cells exhibited higher expression of the chemokines in the dKO with serum stimulation, suggesting CAF cell- intrinsic mechanisms of immunosuppression with macroH2A KO. ChIP- seq for H3K27ac showed a distinct landscape between dKO and WT CAFs but a minimal change in chromatin accessibility by ATAC- seq, and macroH2A1 CUT&RUN showed enrichment proximal to the dKO upregulated inflammatory genes. Collectively, the authors conclude that macroH2A KO relieves repression at inflammatory genes, eliciting CAF- induced promotion of an immunosuppressive tumor microenvironment. The primary finding of the paper is identification of a previously undescribed role for macroH2A in suppressing inflammatory signaling in fibroblasts, as well as evidence for macroH2A suppression of melanoma cell de- differentiation. These findings were largely convincing and are interesting contributions to the literature but require some further connection to human tumors to establish relevance to human biology. + +We thank the reviewer for highlighting the interesting contributions of our study and convincing nature of our data. We agree that addressing the consequences of macroH2A deregulation in human CAFs would extend the relevance of our findings. We hope the reviewer will appreciate our efforts to translate our findings to human melanoma: 1) we investigated macroH2A biology in patient- derived melanoma CAFs and 2) we analyzed a published a pan- cancer scRNA- seq dataset containing over 56,000 CAFs across 98 samples. Please see below for further details. + +## Major Comments: + +The authors' primary finding relates to the effect of macroH2A KO in the CAFs and suggest a cell- intrinsic mechanism by in vitro studies. This provides new information about the role of macroH2A in CAFs but is limited in data to support relevance in human samples. Do human melanomas with downregulated + +<--- Page Split ---> + +# natureresearch + +macroH2A exhibit increased infiltration of the myeloid compartment and decreased infiltration of lymphocytes (e.g., by histology)? In probing published human scRNA- seq datasets, does the stromal compartment exhibit a macroH2A- high and - low state? If so, do these states correlate with a distinct immune landscape? + +We thank the reviewer for these suggestions. Our updated CIBERSORT analysis shows M2 (pro- tumor) macrophages are significantly more abundant in macroH2A2low primary tumors and near significance in macroH2A1low tumors, accompanied by significant CD8 T cell depletion in macroH2A1 and 2 low tumors (Fig. 5e). + +We agree that further confirmatory assays such as IHC in human samples would supplement our data. As the reviewer remarks, the impact of macroH2A loss on the TME appears to stem from the CAF population, therefore, this analysis should target the CAF population specifically. We note that IHC does not have the necessary resolution to evaluate macroH2A levels in CAFs vs. rest of the tumor, and would require simultaneous detection of at least one CAF marker, macroH2A1/2, and normalization controls such as histone H3. However, we now include two new sources of data that confirm our observations in human CAFs. + +We obtained melanoma CAF cultures from the NCI Patient- Derived Models Repository (note: application proposal approval was required), as well as additional cultures from Dr. Andrew Aplin who successfully used them to demonstrate the role of stromal ligands in promoting melanoma resistance to targeted therapy (https://pubmed.ncbi.nlm.nih.gov/26269601/ , https://pubmed.ncbi.nlm.nih.gov/30115691/). Our studies revealed an anticorrelation between endogenous macroH2A2 levels and CCL2, CXCL1, and IL- 6 cytokine production in these human CAFs (Fig. 5f, g, S5h). While this analysis did not reach significance, not surprising given the heterogeneous source material and possible confounding variables, it paralleled the direction of change observed in our mouse model. + +Following the reviewer's suggestion, we analyzed a large scRNA- seq dataset containing over 56,000 CAFs across 98 samples comprising multiple cancer types. We found that macroH2A2 expression is below the detection threshold of 10X Visium scRNA- seq (Fig. S5i), therefore we could not carry out correlation analysis at the single cell level. Instead, we calculated pseudobulk values for the entire CAF population of each tumor and found a subset of tumors were populated with CAFs in a macroH2A2low state. Importantly, a significant anticorrelation between macroH2A2 and IL- 6 expression emerged (Fig. S5j). + +- When comparing the GSEA data from the murine model versus the human samples, several of the pathways upregulated in the murine dKO model are downregulated in the human MACROH2A1 low samples (TNFa signaling via NFKB, IL6 Jak Stat3 signaling, IFNa/g response). What would explain this signature inversion? In looking at the myeloid-related genes (as in Fig 2B) in the human datasets, do they have a similar expression pattern? Does testing a gene signature for myeloid cell activation, cytotoxic T cell activation, etc. show a parallel between the murine and human samples? + +<--- Page Split ---> + +# natureresearch + +We believe the downregulation of inflammatory pathways in the human MACROH2A1low metastatic samples is driven by their overall paucity in immune cells and increase in tumor purity, as evidenced in our updated TME deconvolution analysis (Fig. S5e). This would lead to downregulation of any pathways defined by genes specific to immune cells. Thus, we removed this data, and instead focus on cell type abundance analysis as described below (and Fig. 5e, S5d). Furthermore, our analysis now emphasizes primary tumors, since the TCGA SKCM metastatic samples mainly comprise lymph node lesions, where the TME is different - both through a presence of immune populations residing in the lymph node, and a lack of skin- derived CAFs. + +While we were unable to find a similar expression pattern for myeloid- related genes such as CCL2, CXCL1 or IL- 6 in the TCGA SKCM dataset, as we noted above, at the bulk transcriptomic level, the depletion of total immune cells in macroH2A1low tumors might act as a confounding factor and likely affects our ability to detect relative increases of immune- associated genes. In addition, human scRNA- seq data shows CAFs in a macroH2A2low state overexpress higher levels of IL- 6, which would induce increased myeloid cell recruitment based on published studies (reviewed in: https://pubmed.ncbi.nlm.nih.gov/35331673/). + +Furthermore, we updated our TCGA data analysis (see response to following point) using a ssGSEA approach, which calculated various cell type/activation state scores relevant to CD8 T cell function. Many of these scores are significantly lower in MACROH2A1low and + +![](images/Figure_unknown_4.jpg) + +
Figure R5. IOBR analysis of T cell signatures in TCGA SKCM primary tumors stratified by macroH2A expression levels. Signatures relevant to CD8 T cells are highlighted in bold. Green rectangles further highlight which of these signatures are significantly lower in macroH2A low tumors.
+ +<--- Page Split ---> + +# natureresearch + +MACROH2A2low primary tumors (Fig. R5), as the reviewer expected. Regarding myeloid cell activation, the updated CIBERSORT analysis shows the macrophage alternative activation signature (M2 macrophages) is significantly higher in macroH2A2low primary tumors and near significance in macroH2A1low tumors (Fig. 5e), altogether showing a parallel between the murine model and human samples. + +## Minor Comments: + +- Interesting that the H2A2-low tumors exhibit a significant decrease in the cytotoxic genes (Fig 2C) but an insignificant difference in CD8 T cell abundance (Fig 2D). What explains why H2A1 would significantly decrease CD8 T cells but not H2A2? If the samples are stratified that are low in both H2A1 and H2A2, is the difference even more pronounced? + +We completely overhauled the TCGA analysis by implementing a recent analysis package, IOBR, which contains the CIBERSORT functionality. In contrast to our previous approach, this allowed us to use data normalized in the same manner via the robust TMM method, both for stratifying samples according to macroH2A expression, and for calculating immune population estimates; we no longer relied on CIBERSORT scores calculated by others; we compared samples in the \(1^{\text{st}}\) and \(3^{\text{rd}}\) macroH2A1 or macroH2A2 expression terciles, eliminating samples with intermediate expression levels which may have reduced the amplitude of differences observed. + +The discrepancy highlighted by the reviewer was a shortcoming of the approach we used previously. MACROH2A2 RNA- seq counts are low and likely affected the accuracy of stratification using the previous FPKM normalization method. Our updated CIBERSORT approach now shows significant CD8 T cell depletion in macroH2A1 and 2 low tumors both in the primary and metastatic setting (Fig. 5e, S5d). + +<--- Page Split ---> + +# natureresearch + +As suggested by the reviewer, we also compared samples with combined low levels of both macroH2A1 and macroH2A2. For this, we stratified each gene based on the median instead of terciles (otherwise, there would be too few samples in each of the possible 9 categories), and the results are similar (Fig. R6). + +![](images/Figure_unknown_5.jpg) + +
Figure R6. IOBR analysis of CIBERSORT immune cell type scores in TCGA SKCM primary tumors that have expression values of both macroH2A genes above or below the median.
+ +- Is there an increase in myeloid cells by histology in the dKO? Where do these cells localize? Localization to the stroma would further support a CAF-centric effect. + +Regarding the increase in myeloid cells, we believe that flow cytometric analysis of \(n_{WT} = 12\) and \(n_{dKO} = 15\) mice in 3 independent flow cytometry experiments is robust evidence, complemented by an orthogonal technique, scRNA-seq, where now a 3rd replicate also shows the Mac Mrc1 cluster is more abundant in the dKO. Both flow cytometry and scRNA-seq approaches sample a single cell suspension of the entire tumor and is likely more accurate/representative than histology, which would assess a single section per tumor. Furthermore, distinguishing the Mac Mrc1 cells (or cells annotated as monocytes by flow cytometry) from other myeloid cells (i.e., DCs with a different functional impact on tumor immunity) by IHC would be very challenging as it relies on co- staining for multiple markers. + +To address cell type co- localization as requested by the reviewer, we instead performed spatial transcriptomics on WT and dKO tumors at the same time point during melanoma development, and projected cell identities from the scRNA- seq dataset onto the spatial dataset. This showed a distinct peritumoral localization of both the significantly dKO enriched Mac Mrc1 cells and 3 + +<--- Page Split ---> + +# natureresearch + +out of 4 CAF clusters (Fig. 5b). Furthermore, correlation analysis of these projected cell type scores revealed a significant, positive association between Mac Mrc1 and the 3 CAF clusters at the spot level (Fig. 5c). Importantly, we also observed a significant negative association between Tc (cytotoxic T cells) and both Mac Mrc1 and the 3 CAF clusters (Meg3, Lrrc15, Fbln1), supporting our hypothesis that CAFs and the myeloid cells they attract exclude cytotoxic T cells. + +Furthermore, we demonstrate experimentally that serum- stimulated dKO CAFs induce increased migration and/or proliferation of WT monocytes compared to WT CAFs via a transwell assay (Fig. 5d, S5c). This functional readout supports our assumption that more monocyte- derived cells would be recruited to the TME niche where dKO CAFs reside. + +- Please include a description of the acronyms used in Fig 4A in the figure, legend, or text. + +We apologize for the oversight and have updated the corresponding figure legend (now Fig. 3a) to point the reader to Table 3, which describes these acronyms. + +- After filtering the cells, are there equivalent numbers of cells for the WT and dKO samples in Fig 4? Normalizing the values in Fig 4C to the total number of cells per tumor (% filtered cells of parent tumor) would correct for sampling bias. + +Values in this panel, now located in Fig. 3d, are presented as normalized to the total number of cells per tumor passing quality control filters. This is now emphasized in the figure legend. + +- CAF Tnc drive the dKO transcriptional profile most significantly, but CAF Meg3 shows the biggest change in abundance in dKO. Do the authors believe all 3 CAF subpopulations contribute to this dKO phenotype? + +The Augur analysis, performed on a dataset now including a \(3^{\text{rd}}\) replicate and updated clustering of cell populations including CAFs, now shows CAF Meg3 as the top driver of the transcriptional profile, besides its change in abundance in the dKO. However, we observe significant increase in the TNFα signaling via NF-κB pathway and immediate- early gene induction in all CAF clusters (Fig. 4c, S4e, f), as well as upregulation of individual inflammatory genes we associate with macroH2A- driven epigenetic alterations (Table R1; see above in response to reviewer 1). + +- Fig S5g shows H2afy2 expression in CAFs and H2afy expression in all clusters. This is assumedly in the WT tumors but isn't specified in the figure or corresponding legend. Please show or describe the sample origin of this expression. + +We apologize for the oversight and have updated the panel, now Fig. S6h, to state expression is shown in WT samples. + +<--- Page Split ---> + +# natureresearch + +- In looking at the CAF ATAC-seq for the inflammatory genes differentially expressed in the CAF RNA-seq and exhibiting differential H3K27ac, are these genes in the newly open peaks or unchanged but open in both dKO and WT? + +ATAC- seq changes are minimal and show minimal overlap with gene expression changes. To our knowledge, other groups have also found a lack of ATAC changes upon macroH2A depletion, but their data remains unpublished. Inflammatory genes, examples of which are shown in Fig. 7e-g and Fig. S7g-h, display open chromatin in both dKO and WT. Only Cxcl1 gains accessibility in an intragenic ATAC peak. + +- Line 347 misspelled word "previously" should be "previously." + +This mistake was corrected. + +- Since macroH2A2 was shown to be specific to CAFs, would it be expected that CUT&RUN for H2A2 would exhibit distinct enrichment localization? + +We attempted to perform macroH2A2 CUT&RUN but failed for reasons that remain unclear, but may be due to much lower abundance of this variant vs. macroH2A1 (~5-fold at RNA level). In dermal fibroblasts, which express both variants, they are distributed in a similar manner, with correlated enrichment levels (Fig. R2, R7). We therefore expect this similar distribution to be maintained in CAFs; however, we cannot rule out distinct functions for macroH2A2 in the CAF compartment. + +![](images/Figure_unknown_6.jpg) + +
Figure R7. macroH2A1 and macroH2A2 ChIP signal around the Cxcl1 locus in dermal fibroblasts.
+ +- Figure S4i isn't referenced in the text, and lines 352-353 should reference Fig 6f and 6g. We thank the reviewer for noticing, and this omission was corrected. + +<--- Page Split ---> + +# natureresearch + +Our ref: NCB- A48296A + +11th May 2023 + +Dear Dr. Bernstein, + +Thank you for submitting your revised manuscript "MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin interactions" (NCB- A48296A). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Cell Biology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)- - we can not proceed with PDFs at this stage. + +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +Thank you again for your interest in Nature Cell Biology Please do not hesitate to contact me if you have any questions. + +Sincerely, + +Zhe Wang, PhD Senior Editor Nature Cell Biology + +Tel: +44 (0) 207 843 4924 email: zhe.wang@nature.com + +Reviewer #1 (Remarks to the Author): + +Filippescu et al. present the revised version of the manuscript showing that loss of macroH2A contributes to melanoma progression by changing the tumor microenvironment. In particular, they convincingly demonstrate that cancer- associated fibroblasts are highly macroH2A- sensitive and that its loss results in the upregulation of cytokine- encoding genes and immunomodulation consisting of increased attraction of immunosuppressive monocytes and a reduction of cytotoxic T- cells. + +This is a great study which advances the fields of cancer, chromatin biology and inflammation. For the histone variant community these findings are a milestone and exemplify the importance of histone variants in inflammatory gene expression and immunomodulation. + +While I was supportive of the study from the very beginning, I had many comments and suggestions that the authors have addressed in an extensive revision. The revised version and in particular the new figures are easy to read and data and results are of high quality. I have left a few very minor + +<--- Page Split ---> + +# natureresearch + +comments that I believe the authors will be able to address without the need of another revision from my side. I am looking forward to seeing the study published. + +Minor comments: + +Figure 3c and 5b: Consider showing 'zoom ins' to illustrate the points you wish to make. Figure 4b: Add a legend showing what is blue, red, light red and light blue. Figure 5b: Add a legend showing what bullet size encodes and add a label to the color scale. Figure 7b: Consider adding a figure showing how super and standard domains were defined. Figure 7d: Consider changing the top label to 'Genes gaining loops in dKO' to clarify that this analysis is on the gene level. + +I conclude by congratulating the authors to their work and this excellent revision. + +Marcus Buschbeck with the support of David Corujo + +Reviewer #2 (Remarks to the Author): + +After going through your point by point response and evaluated the revised manuscript I think you have addressed my previous concerns sufficiently. + +Reviewer #3 (Remarks to the Author): + +In this revised manuscript, the authors have made substantial edits and added additional datasets in response to our comments, strengthening human melanoma relevance and adding additional mechanistic insight. These revisions have sufficiently addressed our concerns. The manuscript will be of benefit to the readers of Nature Cell Biology. + +# Author Rebuttal, first revision: + +## Reviewer #1 (Remarks to the Author): + +Filippescu et al. present the revised version of the manuscript showing that loss of macroH2A contributes to melanoma progression by changing the tumor microenvironment. In particular, they convincingly demonstrate that cancer- associated fibroblasts are highly macroH2A- sensitive and that its loss results in the upregulation of cytokine- encoding genes and immunomodulation consisting of increased attraction of immunosuppressive monocytes and a reduction of cytotoxic T- cells. + +This is a great study which advances the fields of cancer, chromatin biology and inflammation. For the histone variant community these findings are a milestone and exemplify the importance of histone variants in inflammatory gene expression and immunomodulation. + +While I was supportive of the study from the very beginning, I had many comments and + +<--- Page Split ---> + +# natureresearch + +suggestions that the authors have addressed in an extensive revision. The revised version and in particular the new figures are easy to read and data and results are of high quality. I have left a few very minor comments that I believe the authors will be able to address without the need of another revision from my side. I am looking forward to seeing the study published. + +We thank the Reviewer(s) for their overall enthusiasm and support of our study that demonstrates 'the importance of histone variants in inflammatory gene expression and immunomodulation'. We have addressed these final minor comments below: + +Minor comments: Figure 3c and 5b: Consider showing 'zoom ins' to illustrate the points you wish to make. + +Response: We thank the Reviewer for this very helpful suggestion and have added the requested zoomed inserts. + +Figure 4b: Add a legend showing what is blue, red, light red and light blue. + +Response: A legend was added to this panel. + +Figure 5b: Add a legend showing what bullet size encodes and add a label to the color scale. + +Response: We believe the Reviewer is referring to Figure 5c; we have added a statement to the legend explaining dot size is proportional to the r coefficient. + +Figure 7b: Consider adding a figure showing how super and standard domains were defined. + +Response: The approach used to define different macroH2A domain classes is described in detail in the Methods section and accompanied by plots illustrating the features of these domains in Supplemental Figure 6c- e. + +Figure 7d: Consider changing the top label to 'Genes gaining loops in dKO' to clarify that this analysis is on the gene level. + +Response: To clarify this point, we added the label "Classes of genes:", which applies to all categories overlapped in Figure 7d. + +<--- Page Split ---> + +# natureresearch + +I conclude by congratulating the authors to their work and this excellent revision. + +We thank the Reviewer(s) once again for their continued support of our manuscript, in- depth review, and valuable recommendations during the revision process. + +Marcus Buschbeck with the support of David Corujo + +## Reviewer #2 (Remarks to the Author): + +After going through your point by point response and evaluated the revised manuscript I think you have addressed my previous concerns sufficiently. + +Response: We thank the Reviewer for their careful review and support of our study. + +## Reviewer #3 (Remarks to the Author): + +In this revised manuscript, the authors have made substantial edits and added additional datasets in response to our comments, strengthening human melanoma relevance and adding additional mechanistic insight. These revisions have sufficiently addressed our concerns. The manuscript will be of benefit to the readers of Nature Cell Biology. + +Response: We are pleased to have strengthened the human melanoma relevance and thank the Reviewer for their support of publication in Nature Cell Biology. + +## Final Decision Letter: + +Dear Dr Bernstein, + +I am pleased to inform you that your manuscript, "MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin looping", has now been accepted for publication in Nature Cell Biology. + +Thank you for sending us the final manuscript files to be processed for print and online production, + +<--- Page Split ---> + +# natureresearch + +and for returning the manuscript checklists and other forms. 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If you have any questions please click here.\*\* + +<--- Page Split ---> diff --git a/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..4e3e2dddf43db30cbac55da944d4c90cfbdec2bf --- /dev/null +++ b/peer_reviews/9ad4e0bbdcd3168d369f12451e278c8f57f4f6e2212beab37ce1d38001cd0dbc/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,1440 @@ +<|ref|>title<|/ref|><|det|>[[549, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>title<|/ref|><|det|>[[116, 188, 571, 219]]<|/det|> +# Peer Review Information + +<|ref|>text<|/ref|><|det|>[[115, 245, 808, 313]]<|/det|> +Journal: Nature Cell Biology Manuscript Title: MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin looping Corresponding author name(s): Dan Filipescu, Emily Bernstein + +<|ref|>sub_title<|/ref|><|det|>[[116, 331, 327, 355]]<|/det|> +## Editorial Notes: + +<|ref|>sub_title<|/ref|><|det|>[[116, 392, 568, 417]]<|/det|> +## Reviewer Comments & Decisions: + +<|ref|>title<|/ref|><|det|>[[123, 452, 353, 467]]<|/det|> +# Decision Letter, initial version: + +<|ref|>text<|/ref|><|det|>[[116, 485, 830, 502]]<|/det|> +\*Please delete the link to your author homepage if you wish to forward this email to co- authors. + +<|ref|>text<|/ref|><|det|>[[116, 515, 255, 530]]<|/det|> +Dear Dr Bernstein, + +<|ref|>text<|/ref|><|det|>[[115, 545, 876, 636]]<|/det|> +Your manuscript, "MacroH2A restricts melanoma progression via inhibition of inflammatory gene expression in cancer- associated fibroblasts", has now been seen by 3 referees, who are experts in histone variant biology (referee 1); CAFs (referee 2); and melanoma and immunology (referee 3). As you will see from their comments (attached below) they find this work of potential interest, but have raised substantial concerns, which in our view would need to be addressed with considerable revisions before we can consider publication in Nature Cell Biology. + +<|ref|>text<|/ref|><|det|>[[115, 650, 875, 740]]<|/det|> +Nature Cell Biology editors discuss the referee reports in detail within the editorial team, including the chief editor, to identify key referee points that should be addressed with priority, and requests that are overruled as being beyond the scope of the current study. To guide the scope of the revisions, I have listed these points below. We are committed to providing a fair and constructive peer- review process, so please feel free to contact me if you would like to discuss any of the referee comments further. + +<|ref|>text<|/ref|><|det|>[[116, 755, 395, 770]]<|/det|> +In particular, it would be essential to: + +<|ref|>text<|/ref|><|det|>[[115, 784, 789, 800]]<|/det|> +A) Address the concerns related to the proposed mechanism as questioned by Reviewer 1: + +<|ref|>text<|/ref|><|det|>[[115, 814, 836, 844]]<|/det|> +"The attempt to mechanistically explain how macroH2A ablation affects inflammatory genes falls short." + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 141, 661, 157]]<|/det|> +"...but fails to explain how macroH2A actually affects gene transcription." + +<|ref|>text<|/ref|><|det|>[[116, 172, 872, 217]]<|/det|> +"It should be clarified if the genes upregulated in CAFs are actually mediating the phenotype (tumor growth or immunosuppression). Can this be shown in vivo? If not, could a co- culture experiment help? If the signals are secreted, media transfer experiments can be helpful." + +<|ref|>text<|/ref|><|det|>[[116, 231, 878, 291]]<|/det|> +"It should be clarified if the loss of macroH2A in tumor cells contribute to the phenotype and CAFs respond. Again, do CAFs respond to a secreted or a cell- bound signal. Is this signal the same in WT and dKO cancer cells? Do WT and dKO CAFs respond differently to WT cancer cells. Do WT CAFs respond differently to" + +<|ref|>text<|/ref|><|det|>[[115, 306, 825, 336]]<|/det|> +B) It would be a plus if you could add data to strengthen the human relevance as suggested by Reviewer 2 and 3; + +<|ref|>text<|/ref|><|det|>[[115, 351, 844, 380]]<|/det|> +C) All other referee concerns pertaining to strengthening existing data, providing controls, methodological details, clarifications and textual changes, as applicable should also be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 395, 881, 440]]<|/det|> +D) Finally please pay close attention to our guidelines on statistical and methodological reporting (listed below) as failure to do so may delay the reconsideration of the revised manuscript. In particular please provide: + +<|ref|>text<|/ref|><|det|>[[115, 455, 872, 500]]<|/det|> +- a Supplementary Figure including unprocessed images of all gels/blots in the form of a multi-page pdf file. Please ensure that blots/gels are labeled and the sections presented in the figures are clearly indicated. + +<|ref|>text<|/ref|><|det|>[[115, 515, 878, 590]]<|/det|> +- a Supplementary Table including all numerical source data in Excel format, with data for different figures provided as different sheets within a single Excel file. The file should include source data giving rise to graphical representations and statistical descriptions in the paper and for all instances where the figures present representative experiments of multiple independent repeats, the source data of all repeats should be provided. + +<|ref|>text<|/ref|><|det|>[[116, 604, 863, 649]]<|/det|> +We would be happy to consider a revised manuscript that would satisfactorily address these points, unless a similar paper is published elsewhere, or is accepted for publication in Nature Cell Biology in the meantime. + +<|ref|>text<|/ref|><|det|>[[116, 664, 396, 679]]<|/det|> +When revising the manuscript please: + +<|ref|>text<|/ref|><|det|>[[115, 694, 794, 724]]<|/det|> +- ensure that it conforms to our format instructions and publication policies (see below and https://www.nature.com/nature/for-authors). + +<|ref|>text<|/ref|><|det|>[[115, 739, 866, 768]]<|/det|> +- provide a point-by-point rebuttal to the full referee reports verbatim, as provided at the end of this letter. + +<|ref|>text<|/ref|><|det|>[[115, 784, 848, 843]]<|/det|> +- provide the completed Reporting Summary (found here https://www.nature.com/documents/nr-reporting-summary.pdf). This is essential for reconsideration of the manuscript will be available to editors and referees in the event of peer review. For more information see http://www.nature.com/authors/policies/availability.html or contact me. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 157, 841, 203]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +<|ref|>text<|/ref|><|det|>[[115, 217, 840, 255]]<|/det|> +- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. + +<|ref|>text<|/ref|><|det|>[[115, 247, 844, 290]]<|/det|> +- that control panels for gels and western blots are appropriately described as loading on sample processing controls + +<|ref|>text<|/ref|><|det|>[[115, 297, 852, 310]]<|/det|> +- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +<|ref|>text<|/ref|><|det|>[[115, 305, 857, 352]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[115, 365, 879, 472]]<|/det|> +Nature Cell Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[115, 484, 872, 575]]<|/det|> +This journal strongly supports public availability of data. Please place the data used in your paper into a public data repository, or alternatively, present the data as Supplementary Information. If data can only be shared on request, please explain why in your Data Availability Statement, and also in the correspondence with your editor. Please note that for some data types, deposition in a public repository is mandatory - more information on our data deposition policies and available repositories appears below. + +<|ref|>text<|/ref|><|det|>[[115, 589, 856, 619]]<|/det|> +Please submit the revised manuscript files and the point- by- point rebuttal to the referee comments using this link: + +<|ref|>sub_title<|/ref|><|det|>[[115, 633, 210, 648]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[115, 664, 872, 709]]<|/det|> +\*This url links to your confidential home page and associated information about manuscripts you may have submitted or be reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[115, 723, 597, 738]]<|/det|> +We would like to receive a revised submission within six months. + +<|ref|>text<|/ref|><|det|>[[115, 752, 833, 783]]<|/det|> +We hope that you will find our referees' comments, and editorial guidance helpful. Please do not hesitate to contact me if there is anything you would like to discuss. + +<|ref|>text<|/ref|><|det|>[[115, 798, 208, 828]]<|/det|> +Best wishes, Zhe Wang + +<|ref|>text<|/ref|><|det|>[[115, 843, 233, 858]]<|/det|> +Zhe Wang, PhD + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 260, 174]]<|/det|> +Senior Editor Nature Cell Biology + +<|ref|>text<|/ref|><|det|>[[115, 188, 340, 218]]<|/det|> +Tel: +44 (0) 207 843 4924 email: zhe.wang@nature.com + +<|ref|>text<|/ref|><|det|>[[116, 261, 285, 276]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 290, 220, 304]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 305, 293, 319]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[114, 320, 876, 516]]<|/det|> +MacroH2A histone variants have tumor suppressive roles in many cancer types. This was pioneered by the last author's lab showing that loss of macroH2A increased the aggressiveness of melanoma cells reflected in increased metastasis in a xenograft model. In their current manuscript by Filipescu et al. they present the logical and long- awaited follow- up describing how the systemic absence of all macroH2A impinges on melanoma growth in a fully competent mouse model. Increased tumor growth in macroH2A- deficient mice is associated with a change in tumor- infiltrating immune cells and an inflammatory expression signature in bulk tissue. Specifically, results suggest a reduction in cytotoxic T cells and an increase in tumor suppressive myeloid cells. Single- cell RNA- seq indicates that differential abundances in two major cell populations that are a subpopulation of tumor cells with a stemness signature (NC- RXR) and cancer- associated fibroblast (CAF). CAFs are shown to the main source of upregulated cytokines and chemokines likely to trigger the immunophenotype. Up and downregulated genes and their enhancers are enriched in macroH2A. Upregulation is associated with increased enhancer activity. + +<|ref|>text<|/ref|><|det|>[[115, 530, 187, 545]]<|/det|> +Strength: + +<|ref|>text<|/ref|><|det|>[[115, 545, 874, 586]]<|/det|> +- First study assessing the impact of macroH2As on cancer in a fully immunocompetent mouse model. +- Dissection of changes in a complex cancer tissue type. Identification of cell types and populations affected by the loss of macroH2A. + +<|ref|>text<|/ref|><|det|>[[115, 588, 741, 604]]<|/det|> +- Demonstration that macroH2A has a repressive role in inflammatory genes in CAF. + +<|ref|>text<|/ref|><|det|>[[115, 620, 196, 633]]<|/det|> +Weakness: + +<|ref|>text<|/ref|><|det|>[[115, 634, 852, 664]]<|/det|> +- Figures are difficult to read (overloaded, non-intuitive abbreviations, missing labels and graphical legends). + +<|ref|>text<|/ref|><|det|>[[115, 664, 841, 694]]<|/det|> +- The attempt to mechanistically explain how macroH2A ablation affects inflammatory genes falls short. + +<|ref|>text<|/ref|><|det|>[[115, 709, 865, 769]]<|/det|> +The strengths of the study clearly lies on the cell biology of a complex tumor and how the loss of macroH2A histone variants affects the tumor microenvironment. This is an important and interesting aspect that will warrant publication if further strengthened. As of now the study is descriptive with a very high level of quality and quantity. + +<|ref|>text<|/ref|><|det|>[[115, 769, 861, 829]]<|/det|> +In addition, the authors provide a wealth of genomic data including from isolated primary cells that will be a valuable resource for the field. As in many studies before the genomic data indicates previously known associations but fails to explain how macroH2A actually affects gene transcription. Elucidating the exact mechanism is beyond scope of the presented study. + +<|ref|>text<|/ref|><|det|>[[115, 843, 264, 857]]<|/det|> +MAJOR COMMENTS: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 877, 180]]<|/det|> +1. It should be clarified if the genes upregulated in CAFs are actually mediating the phenotype (tumor growth or immunosuppression). Can this be shown in vivo? If not, could a co-culture experiment help? If the signals are secreted, media transfer experiments can be helpful. + +<|ref|>text<|/ref|><|det|>[[115, 180, 879, 247]]<|/det|> +2. It should be clarified if the loss of macroH2A in tumor cells contribute to the phenotype and CAFs respond. Again, do CAFs respond to a secreted or a cell-boud signal. Is this signal the same in WT and dKO cancer cells? Do WT and dKO CAFs respond differently to WT cancer cells. Do WT CAFs respond differently to + +<|ref|>sub_title<|/ref|><|det|>[[116, 277, 340, 291]]<|/det|> +## OTHER GENERAL COMMENTS: + +<|ref|>text<|/ref|><|det|>[[115, 292, 866, 321]]<|/det|> +Given our expertise in genomic studies, we provide detailed suggestions on how to improve the data presentation (see further below). I consider that no additional data is needed on this side. + +<|ref|>text<|/ref|><|det|>[[115, 336, 875, 366]]<|/det|> +Statistical tests are missing in many figure panels. It has to be clear without reading the figure legend or the results text if differences are significant or not. \(^+\) + +<|ref|>text<|/ref|><|det|>[[115, 381, 550, 396]]<|/det|> +Legends are missing in several panels (eg 5c and related). + +<|ref|>text<|/ref|><|det|>[[115, 410, 607, 425]]<|/det|> +Please reduce the number of panels to the most informative ones. + +<|ref|>text<|/ref|><|det|>[[115, 440, 660, 455]]<|/det|> +Label the panels with the cells / tissues analyzed e.g. 'sorted CAFs' in 5e. + +<|ref|>text<|/ref|><|det|>[[115, 470, 881, 529]]<|/det|> +In my humble opinion the authors could consider a different flow of their results. The single- cell RNA- seq is most informative and could be presented earlier (maybe right after presenting the phenotype) to introduce the two main results: 1. the change in tumor- composition and 2. changes in inflammatory gene expression. All other results could then be built on this. + +<|ref|>text<|/ref|><|det|>[[115, 544, 879, 573]]<|/det|> +The presentation of the immunophenotype is confusing and scattered. Consider compilating all data on immune cells in one coherent figure. + +<|ref|>text<|/ref|><|det|>[[115, 589, 872, 619]]<|/det|> +It should be clarified if there is anything special to the repressed 39 inflammatory genes compared to other macroH2A- regulated genes. + +<|ref|>sub_title<|/ref|><|det|>[[116, 649, 415, 664]]<|/det|> +## SUGGESTIONS FOR SPECIFIC FIGURES: + +<|ref|>sub_title<|/ref|><|det|>[[115, 679, 202, 694]]<|/det|> +## Figures 4-5 + +<|ref|>text<|/ref|><|det|>[[115, 708, 880, 768]]<|/det|> +The NC Rxrg cluster has a high contribution to the dKO bulk gene expression changes, comparable to the CAF Meg3 which are the focus of further analysis. I am missing a description of genes differentially expressed in melanoma, in particular NC Rxrg cells. What was the rationale for excluding this tumor cell population from further analysis? See my major comment. + +<|ref|>text<|/ref|><|det|>[[115, 783, 880, 812]]<|/det|> +Figure 5c could perhaps be converted to a heatmap summarizing the expression differences to make it more visual and equivalent to other representations. + +<|ref|>text<|/ref|><|det|>[[115, 827, 420, 842]]<|/det|> +Figure 5g lacks statistical testing results. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 879, 174]]<|/det|> +Could the Milo cell abundance method be applied to the re- clustered immune cell data shown in Figure S4i to assess changes in composition of immune subtypes? + +<|ref|>text<|/ref|><|det|>[[116, 188, 235, 203]]<|/det|> +Figure 6 and S6 + +<|ref|>text<|/ref|><|det|>[[115, 216, 872, 292]]<|/det|> +In these figures the authors present results obtained in CAFs and iDFs, but it is not always labelled in a way that allows easy interpretation without resorting to the legend or main text. For example, panels c to e versus panels h to j could be more readily interpreted by indicating the cells analyzed. This applies to the Supplementary Figure 6 and also to other parts of the manuscript, I think it would improve readability and faster interpretation of the results. + +<|ref|>text<|/ref|><|det|>[[115, 306, 872, 426]]<|/det|> +As far as I know, this is the first time a profiling of macroH2A by CUT&RUN is reported in a manuscript. The authors show a depletion from the gene bodies of highly expressed genes and some example loci, and in both cases the results are highly reminiscent of previous published results for ChIP- seq. Given the novelty of the experimental technique applied to this histone variant, I would appreciate a better generic description of the CUT&RUN results and a comparison to previously performed ChIP- seq (eg dermal fibroblast data) as benchmark, at least: the total number of enriched regions called ("MCDs"), size distribution of the identified MCDs, total \(\%\) of genome coverage by all MCDs. + +<|ref|>text<|/ref|><|det|>[[115, 440, 881, 530]]<|/det|> +The results in Figure 6c and d show an increased H3K27Ac enrichment at enhancers and promoters of the selected 39 upregulated inflammatory genes, however the difference seems mild when compared to the genome- wide effect shown in Figure S6a and the shaded area of the profiles (as I understand, a confidence interval) are largely overlapping. Could the authors perform a statistic test on the area around the enhancer centers or TSS to show that this is statistically significant? Perhaps a Fisher exact test on the read counts? + +<|ref|>text<|/ref|><|det|>[[115, 544, 876, 650]]<|/det|> +MacroH2A1 has a higher enrichment in the 39 inflammatory genes than on thousands of static genes. This is also true for all dKO up and down genes (Figure 6k). The current presentation is misleading. I think a more logical description would be to first show the genome- wide analysis and then present that this holds true for the subset of genes that the authors propose are linked to the phenotype. Although the authors put the spotlight on this set of genes, I think it is important to highlight that the findings regarding mH2A occupancy and H3K27Ac changes are not exclusive of these genes but general for all mH2A- sensitive genes. + +<|ref|>text<|/ref|><|det|>[[115, 664, 875, 710]]<|/det|> +Given the importance placed on these 39 DEGs, it would be important to know how many of them are detected as upregulated in both scRNA- Seq and sorted- bulk RNA- Seq datasets. Moreover, are they also deregulated in the NC clusters or exclusively in the CAFs? + +<|ref|>text<|/ref|><|det|>[[115, 724, 866, 769]]<|/det|> +Similarly, the analysis of H3K27Ac in Figure 6c and d could also be performed for all enhancer peaks within 50kb and the TSS of all the dKO up and dKO down genes, providing a general analysis of how the changes in H3K27Ac enrichment relate to the expression changes in the dKO CAFs. + +<|ref|>text<|/ref|><|det|>[[115, 783, 475, 799]]<|/det|> +Which test was performed in Figure S6 L and N? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[116, 142, 291, 156]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 158, 346, 172]]<|/det|> +A. Summary of the key results + +<|ref|>text<|/ref|><|det|>[[115, 173, 877, 293]]<|/det|> +MacroH2A as a key epigenetic suppressor of tumour growth and progression in melanoma. The mechanism is shown to be likely caused by alteration in immunoregulation in the tumour mediated by the production of inflammatory cytokines by cancer activated fibroblasts. This was shown by use of a murine double- KO for macroH2A (H2afy and H2afy2) and autochthonous immunocompetent model for melanoma. The results are largely based on transcriptomic (both bulk and single cell) analyses of melanoma induced in this mouse model compared to mice that do not have the double- KO for macroH2A. The role of macroH2A in the epigenetic landscape in various cell types in the tumour microenvironment is also explored + +<|ref|>text<|/ref|><|det|>[[115, 307, 630, 322]]<|/det|> +B. Originality and significance: if not novel, please include reference + +<|ref|>text<|/ref|><|det|>[[116, 323, 633, 337]]<|/det|> +This study uncovers several key findings in the context of melanoma: + +<|ref|>text<|/ref|><|det|>[[115, 338, 850, 411]]<|/det|> +- Firstly, the heterogeneity of the melanoma tumour microenvironment is delineated on a cellular transcriptional level herein. This has already been done for an orthotopic transplantation model of melanoma (Davidson et al., 2020; https://pubmed.ncbi.nlm.nih.gov/32433953/). However, to my knowledge this is first time this has been performed in this autochthonous murine model of melanoma. + +<|ref|>text<|/ref|><|det|>[[115, 411, 803, 441]]<|/det|> +- Secondly, to my knowledge this is the first study to perform single cell RNA sequencing on macroH2A deficient murine melanoma models. + +<|ref|>text<|/ref|><|det|>[[115, 441, 861, 500]]<|/det|> +- Thirdly, a link between the function between cancer activated fibroblasts and immunoregulation in melanoma is re-enforced by this study. This hypothesis/discovery is not novel in and of itself (Papaccio et al., 2021; https://pubmed.ncbi.nlm.nih.gov/34298873/), however this study adds valuable high-resolution data, previously unexplored, that adds to this body of evidence. + +<|ref|>text<|/ref|><|det|>[[115, 500, 872, 590]]<|/det|> +- Finally, a link between the function of macroH2A and cancer activated fibroblast behaviour is linked and underpinned as the consequential difference in melanoma progression with or without macroH2A. Namely, melanomas with cancer activated fibroblasts with dysfunctional macroH2A have increased pro-inflammatory cytokine expression by means of an altered epigenetic landscape in absence of macroH2A. The consequence of increased pro-inflammatory cytokine expression is an immunosuppressive tumour microenvironment, that promotes melanoma growth and progression. + +<|ref|>text<|/ref|><|det|>[[115, 604, 742, 620]]<|/det|> +C. Data & methodology: validity of approach, quality of data, quality of presentation + +<|ref|>text<|/ref|><|det|>[[115, 634, 270, 648]]<|/det|> +Validity of approach: + +<|ref|>text<|/ref|><|det|>[[115, 650, 863, 680]]<|/det|> +- A fine approach and line of inquiry for the issue of delineating macroH2A function in the melanoma microenvironment. + +<|ref|>text<|/ref|><|det|>[[115, 681, 231, 694]]<|/det|> +Quality of data: + +<|ref|>text<|/ref|><|det|>[[115, 696, 370, 710]]<|/det|> +- Data is generally of high quality. + +<|ref|>text<|/ref|><|det|>[[115, 711, 550, 725]]<|/det|> +- Concern over number of replicates in the scRNAseq data. + +<|ref|>text<|/ref|><|det|>[[115, 727, 255, 740]]<|/det|> +Data presentation: + +<|ref|>text<|/ref|><|det|>[[115, 741, 673, 756]]<|/det|> +- Data is generally presented well, with little issue for legibility or font size. + +<|ref|>text<|/ref|><|det|>[[115, 771, 577, 785]]<|/det|> +D. Appropriate use of statistics and treatment of uncertainties + +<|ref|>text<|/ref|><|det|>[[115, 786, 620, 800]]<|/det|> +The approaches used are generally appropriate and well performed. + +<|ref|>text<|/ref|><|det|>[[115, 814, 459, 829]]<|/det|> +E. Conclusions: robustness, validity, reliability + +<|ref|>text<|/ref|><|det|>[[115, 843, 828, 858]]<|/det|> +The final line states that "the convergence of these mechanisms would predict poor response of + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 853, 188]]<|/det|> +macroH2A- low tumors to immunotherapy, suggesting a possible biomarker application to stratify melanoma patients." However this is speculative and not sufficiently evidenced in this study - how does the mouse model respond to immunotherapy based upon macroH2A status, for example? + +<|ref|>text<|/ref|><|det|>[[115, 203, 625, 218]]<|/det|> +F. Suggested improvements: experiments, data for possible revision + +<|ref|>text<|/ref|><|det|>[[115, 218, 879, 277]]<|/det|> +As noted in E., treating dKO and WT mice by immunotherapy to observe difference in response would strengthen this conclusion. Additionally/alternatively, a human tissue microarray (TMA) demonstrating variable macroH2A protein levels and correlating this with differences in immune cell infiltration as observed in the mouse model would be of merit. + +<|ref|>text<|/ref|><|det|>[[115, 277, 880, 322]]<|/det|> +Only two tumours per condition are profiled by scRNAseq which is insufficient given the prominence these data have in the study. At least one more replicate per condition should be included which would also permit interrogation in the differences of tumour composition. + +<|ref|>text<|/ref|><|det|>[[115, 321, 875, 351]]<|/det|> +CIBERSORT should be used to also determine whether there is a difference in myeloid cell populations when stratifying patients based on MACROH2A1 and MACROH2A2 expression. + +<|ref|>text<|/ref|><|det|>[[115, 351, 880, 395]]<|/det|> +When stratifying tumours by MACROH2A2 expression (Fig 2c- d) there is a significant reduction in CD8 T cell markers but no difference in the inferred prevalence of CD8 T cells from CIBERSORT. How is this accounted for? + +<|ref|>text<|/ref|><|det|>[[115, 410, 501, 440]]<|/det|> +G. References: appropriate credit to previous work? Manuscript is well referenced. + +<|ref|>text<|/ref|><|det|>[[115, 455, 850, 485]]<|/det|> +H. Clarity and context: lucidity of abstract/summary, appropriateness of abstract, introduction and conclusions. + +<|ref|>text<|/ref|><|det|>[[115, 500, 875, 604]]<|/det|> +The manuscript is delightfully written and easy to follow. The abstract is an appropriate summary of the findings. The introduction is similarly concise and appropriate. The conclusions also follow and are written well. However, as noted earlier, the final sentence of the discussion is not directly supported by the evidence presented and so must be supplied as an optimistic speculation. If, however, there were direct evidence to support this claim, the manuscript would be greatly elevated from identification of biologically relevant and interesting mechanism to also that of clinical and therapeutic relevance. + +<|ref|>sub_title<|/ref|><|det|>[[115, 650, 216, 663]]<|/det|> +## Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 665, 291, 678]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 679, 880, 857]]<|/det|> +In this manuscript, the authors tested macroH2A knockout in a BRAFV600E;PTEN- deficient melanoma model. They found by that macroH2A accelerated tumor growth but exhibited insignificant differences in other metrics by histology. The authors then performed bulk RNA- sequencing on the KO and WT tumors and discovered upregulation of genes involved in myeloid cell recruitment and downregulation of genes involved in myeloid cell inhibition and cytotoxic T cell activation. Flow cytometry of the murine model exhibited an increase in monocytes in the dKO and a decrease in CD8 T cells. scRNA- seq revealed an enrichment of de- differentiated neural crest cells and immunosuppressive Mrc1+ macrophages in dKO tumors. The authors identify 3 CAF clusters, which upregulated the gene signature associated with the dKO bulk RNA- seq and overexpressed the myeloid chemoattractant genes upregulated in the bulk RNA- seq. The authors also see H2afy2 expression is specific to CAF cells in the scRNA- seq. Cultured CAF cells exhibited higher expression of the chemokines in the dKO with serum stimulation, suggesting CAF cell- intrinsic mechanisms of immunosuppression with macroH2A + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 881, 278]]<|/det|> +KO. ChIP- seq for H3K27ac showed a distinct landscape between dKO and WT CAFs but a minimal change in chromatin accessibility by ATAC- seq, and macroH2A1 CUT&RUN showed enrichment proximal to the dKO upregulated inflammatory genes. Collectively, the authors conclude that macroH2A KO relieves repression at inflammatory genes, eliciting CAF- induced promotion of an immunosuppressive tumor microenvironment. The primary finding of the paper is identification of a previously undescribed role for macroH2A in suppressing inflammatory signaling in fibroblasts, as well as evidence for macroH2A suppression of melanoma cell de- differentiation. These findings were largely convincing and are interesting contributions to the literature but require some further connection to human tumors to establish relevance to human biology. + +<|ref|>sub_title<|/ref|><|det|>[[116, 293, 249, 307]]<|/det|> +## Major Comments: + +<|ref|>text<|/ref|><|det|>[[115, 308, 877, 412]]<|/det|> +- The authors' primary finding relates to the effect of macroH2A KO in the CAFs and suggest a cell-intrinsic mechanism by in vitro studies. This provides new information about the role of macroH2A in CAFs but is limited in data to support relevance in human samples. Do human melanomas with downregulated macroH2A exhibit increased infiltration of the myeloid compartment and decreased infiltration of lymphocytes (e.g., by histology)? In probing published human scRNA-seq datasets, does the stromal compartment exhibit a macroH2A-high and -low state? If so, do these states correlate with a distinct immune landscape? + +<|ref|>text<|/ref|><|det|>[[115, 411, 876, 501]]<|/det|> +- When comparing the GSEA data from the murine model versus the human samples, several of the pathways upregulated in the murine dKO model are downregulated in the human MACROH2A1 low samples (TNFa signaling via NFKB, IL6 Jak Stat3 signaling, IFNa/g response). What would explain this signature inversion? In looking at the myeloid-related genes (as in Fig 2B) in the human datasets, do they have a similar expression pattern? Does testing a gene signature for myeloid cell activation, cytotoxic T cell activation, etc. show a parallel between the murine and human samples? + +<|ref|>sub_title<|/ref|><|det|>[[116, 516, 248, 530]]<|/det|> +## Minor Comments: + +<|ref|>text<|/ref|><|det|>[[115, 531, 866, 599]]<|/det|> +- Interesting that the H2A2-low tumors exhibit a significant decrease in the cytotoxic genes (Fig 2C) but an insignificant difference in CD8 T cell abundance (Fig 2D). What explains why H2A1 would significantly decrease CD8 T cells but not H2A2? If the samples are stratified that are low in both H2A1 and H2A2, is the difference even more pronounced? + +<|ref|>text<|/ref|><|det|>[[115, 590, 860, 620]]<|/det|> +- Is there an increase in myeloid cells by histology in the dKO? Where do these cells localize? Localization to the stroma would further support a CAF-centric effect. + +<|ref|>text<|/ref|><|det|>[[115, 620, 790, 636]]<|/det|> +- Please include a description of the acronyms used in Fig 4A in the figure, legend, or text. + +<|ref|>text<|/ref|><|det|>[[115, 635, 870, 680]]<|/det|> +- After filtering the cells, are there equivalent numbers of cells for the WT and dKO samples in Fig 4? Normalizing the values in Fig 4C to the total number of cells per tumor (% filtered cells of parent tumor) would correct for sampling bias. + +<|ref|>text<|/ref|><|det|>[[115, 680, 866, 725]]<|/det|> +- CAF Tnc drive the dKO transcriptional profile most significantly, but CAF Meg3 shows the biggest change in abundance in dKO. Do the authors believe all 3 CAF subpopulations contribute to this dKO phenotype? + +<|ref|>text<|/ref|><|det|>[[115, 725, 870, 770]]<|/det|> +- Fig S5g shows H2afy2 expression in CAFs and H2afy expression in all clusters. This is assumedly in the WT tumors but isn't specified in the figure or corresponding legend. Please show or describe the sample origin of this expression. + +<|ref|>text<|/ref|><|det|>[[115, 770, 872, 814]]<|/det|> +- In looking at the CAF ATAC-seq for the inflammatory genes differentially expressed in the CAF RNA-seq and exhibiting differential H3K27ac, are these genes in the newly open peaks or unchanged but open in both dKO and WT? + +<|ref|>text<|/ref|><|det|>[[115, 814, 590, 829]]<|/det|> +- Line 347 misspelled word "previously" should be "previously." + +<|ref|>text<|/ref|><|det|>[[115, 829, 860, 858]]<|/det|> +- Since macroH2A2 was shown to be specific to CAFs, would it be expected that CUT&RUN for H2A2 would exhibit distinct enrichment localization? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 787, 158]]<|/det|> +- Figure S4i isn't referenced in the text, and lines 352-353 should reference Fig 6f and 6g. + +<|ref|>sub_title<|/ref|><|det|>[[115, 290, 660, 307]]<|/det|> +## GUIDELINES FOR MANUSCRIPT SUBMISSION TO NATURE CELL BIOLOGY + +<|ref|>text<|/ref|><|det|>[[115, 320, 850, 427]]<|/det|> +READABILITY OF MANUSCRIPTS - Nature Cell Biology is read by cell biologists from diverse backgrounds, many of whom are not native English speakers. Authors should aim to communicate their findings clearly, explaining technical jargon that might be unfamiliar to non- specialists, and avoiding non- standard abbreviations. Titles and abstracts should concisely communicate the main findings of the study, and the background, rationale, results and conclusions should be clearly explained in the manuscript in a manner accessible to a broad cell biology audience. Nature Cell Biology uses British spelling. + +<|ref|>text<|/ref|><|det|>[[115, 439, 808, 471]]<|/det|> +MANUSCRIPT FORMAT - please follow the guidelines listed in our Guide to Authors regarding manuscript formats at Nature Cell Biology. + +<|ref|>text<|/ref|><|det|>[[115, 500, 857, 531]]<|/det|> +TITLE - should be no more than 100 characters including spaces, without punctuation and avoiding technical terms, abbreviations, and active verbs.. + +<|ref|>text<|/ref|><|det|>[[115, 545, 425, 560]]<|/det|> +AUTHOR NAMES - should be given in full. + +<|ref|>text<|/ref|><|det|>[[115, 575, 870, 620]]<|/det|> +AUTHOR AFFILIATIONS - should be denoted with numerical superscripts (not symbols) preceding the names. Full addresses should be included, with US states in full and providing zip/post codes. The corresponding author is denoted by: "Correspondence should be addressed to [initials]." + +<|ref|>text<|/ref|><|det|>[[115, 634, 875, 725]]<|/det|> +ABSTRACT AND MAIN TEXT - please follow the guidelines that are specific to the format of your manuscript, as listed in our Guide to Authors (http://www.nature.com/ncb/pdf/ncb_gta.pdf) Briefly, Nature Cell Biology Articles, Resources and Technical Reports have 3500 words, including a 150 word abstract, and the main text is subdivided in Introduction, Results, and Discussion sections. Nature Cell Biology Letters have up to 2500 words, including a 180 word introductory paragraph (abstract), and the text is not subdivided in sections. + +<|ref|>text<|/ref|><|det|>[[115, 739, 839, 769]]<|/det|> +ACKNOWLEDGEMENTS - should be kept brief. Professional titles and affiliations are unnecessary. Grant numbers can be listed. + +<|ref|>text<|/ref|><|det|>[[115, 784, 880, 828]]<|/det|> +AUTHOR CONTRIBUTIONS - must be included after the Acknowledgements, detailing the contributions of each author to the paper (e.g. experimental work, project planning, data analysis etc.). Each author should be listed by his/her initials. + +<|ref|>text<|/ref|><|det|>[[115, 842, 849, 858]]<|/det|> +FINANCIAL AND NON- FINANCIAL COMPETING INTERESTS - the authors must include one of three + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 877, 234]]<|/det|> +declarations: (1) that they have no financial and non- financial competing interests; (2) that they have financial and non- financial competing interests; or (3) that they decline to respond, after the Author Contributions section. This statement will be published with the article, and in cases where financial and non- financial competing interests are declared, these will be itemized in a web supplement to the article. For further details please see https://www.nature.com/licenceforms/nrg/competing- interests.pdf. + +<|ref|>text<|/ref|><|det|>[[115, 245, 875, 383]]<|/det|> +REFERENCES - are limited to a total of 70 for Articles, Resources, Technical Reports; and 40 for Letters. This includes references in the main text and Methods combined. References must be numbered sequentially as they appear in the main text, tables and figure legends and Methods and must follow the precise style of Nature Cell Biology references. References only cited in the Methods should be numbered consecutively following the last reference cited in the main text. References only associated with Supplementary Information (e.g. in supplementary legends) do not count toward the total reference limit and do not need to be cited in numerical continuity with references in the main text. Only published papers can be cited, and each publication cited should be included in the numbered reference list, which should include the manuscript titles. Footnotes are not permitted. + +<|ref|>text<|/ref|><|det|>[[115, 396, 877, 442]]<|/det|> +METHODS - Nature Cell Biology publishes methods online. The methods section should be provided as a separate Word document, which will be copyedited and appended to the manuscript PDF, and incorporated within the HTML format of the paper. + +<|ref|>text<|/ref|><|det|>[[115, 455, 874, 635]]<|/det|> +Methods should be written concisely, but should contain all elements necessary to allow interpretation and replication of the results. As a guideline, Methods sections typically do not exceed 3,000 words. The Methods should be divided into subsections listing reagents and techniques. When citing previous methods, accurate references should be provided and any alterations should be noted. Information must be provided about: antibody dilutions, company names, catalogue numbers and clone numbers for monoclonal antibodies; sequences of RNAi and cDNA probes/primers or company names and catalogue numbers if reagents are commercial; cell line names, sources and information on cell line identity and authentication. Animal studies and experiments involving human subjects must be reported in detail, identifying the committees approving the protocols. For studies involving human subjects/samples, a statement must be included confirming that informed consent was obtained. Statistical analyses and information on the reproducibility of experimental results should be provided in a section titled "Statistics and Reproducibility". + +<|ref|>text<|/ref|><|det|>[[115, 649, 857, 740]]<|/det|> +All Nature Cell Biology manuscripts submitted on or after March 21 2016 must include a Data availability statement as a separate section after Methods but before references, under the heading "Data Availability". . For Springer Nature policies on data availability see http://www.nature.com/authors/policies/availability.html; for more information on this particular policy see http://www.nature.com/authors/policies/data/data- availability- statements- datacitations.pdf. The Data availability statement should include: + +<|ref|>text<|/ref|><|det|>[[115, 753, 859, 858]]<|/det|> +- Accession codes for primary datasets (generated during the study under consideration and designated as "primary accessions") and secondary datasets (published datasets reanalysed during the study under consideration, designated as "referenced accessions"). For primary accessions data should be made public to coincide with publication of the manuscript. 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For supplementary tables see below. + +<|ref|>text<|/ref|><|det|>[[115, 722, 870, 843]]<|/det|> +SUPPLEMENTARY INFORMATION - Supplementary information is material directly relevant to the conclusion of a paper, but which cannot be included in the printed version in order to keep the manuscript concise and accessible to the general reader. Supplementary information is an integral part of a Nature Cell Biology publication and should be prepared and presented with as much care as the main display item, but it must not include non- essential data or text, which may be removed at the editor's discretion. All supplementary material is fully peer- reviewed and published online as part of the HTML version of the manuscript. Supplementary Figures and Supplementary Notes are appended at the end of the main PDF of the published manuscript. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 876, 203]]<|/det|> +Supplementary items should relate to a main text figure, wherever possible, and should be mentioned sequentially in the main manuscript, designated as Supplementary Figure, Table, Video, or Note, and numbered continuously (e.g. Supplementary Figure 1, Supplementary Figure 2, Supplementary Table 1, Supplementary Table 2 etc.). + +<|ref|>text<|/ref|><|det|>[[115, 216, 877, 322]]<|/det|> +Unprocessed scans of all key data generated through electrophoretic separation techniques need to be presented in a supplementary figure that should be labelled and numbered as the final supplementary figure, and should be mentioned in every relevant figure legend. This figure does not count towards the total number of figures and is the only figure that can be displayed over multiple pages, but should be provided as a single file, in PDF or TIFF format. Data in this figure can be displayed in a relatively informal style, but size markers and the figures panels corresponding to the presented data must be indicated. + +<|ref|>text<|/ref|><|det|>[[115, 336, 870, 411]]<|/det|> +The total number of Supplementary Figures (not including the "unprocessed scans" Supplementary Figure) should not exceed the number of main display items (figures and/or tables (see our Guide to Authors and March 2012 editorial http://www.nature.com/ncb/authors/submit/index.html#suppinfo; http://www.nature.com/ncb/journal/v14/n3/index.html#ed). No restrictions apply to Supplementary Tables or Videos, but we advise authors to be selective in including supplemental data. + +<|ref|>text<|/ref|><|det|>[[115, 424, 875, 500]]<|/det|> +Each Supplementary Figure should be provided as a single page and as an individual file in one of our accepted figure formats and should be presented according to our figure guidelines (see above). Supplementary Tables should be provided as individual Excel files. Supplementary Videos should be provided as .avi or .mov files up to 50 MB in size. Supplementary Figures, Tables and Videos much be accompanied by a separate Word document including titles and legends. + +<|ref|>sub_title<|/ref|><|det|>[[115, 529, 598, 545]]<|/det|> +## GUIDELINES FOR EXPERIMENTAL AND STATISTICAL REPORTING + +<|ref|>text<|/ref|><|det|>[[115, 559, 882, 650]]<|/det|> +REPORTING REQUIREMENTS - We are trying to improve the quality of methods and statistics reporting in our papers. To that end, we are now asking authors to complete a reporting summary that collects information on experimental design and reagents. The Reporting Summary can be found here https://www.nature.com/documents/nr- reporting- summary.pdf)If you would like to reference the guidance text as you complete the template, please access these flattened versions at http://www.nature.com/authors/policies/availability.html. + +<|ref|>text<|/ref|><|det|>[[115, 664, 879, 828]]<|/det|> +STATISTICS - Wherever statistics have been derived the legend needs to provide the n number (i.e. the sample size used to derive statistics) as a precise value (not a range), and define what this value represents. Error bars need to be defined in the legends (e.g. SD, SEM) together with a measure of centre (e.g. mean, median). Box plots need to be defined in terms of minima, maxima, centre, and percentiles. Ranges are more appropriate than standard errors for small data sets. Wherever statistical significance has been derived, precise p values need to be provided and the statistical test used needs to be stated in the legend. Statistics such as error bars must not be derived from \(n< 3\) . For sample sizes of \(n< 5\) please plot the individual data points rather than providing bar graphs. Deriving statistics from technical replicate samples, rather than biological replicates is strongly discouraged. Wherever statistical significance has been derived, precise p values need to be provided and the statistical test stated in the legend. + +<|ref|>text<|/ref|><|det|>[[115, 842, 844, 858]]<|/det|> +Information on how many times each experiment was repeated independently with similar results + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 141, 857, 174]]<|/det|> +needs to be provided in the legends and/or Methods for all experiments, and in particular wherever representative experiments are shown. + +<|ref|>text<|/ref|><|det|>[[115, 186, 880, 293]]<|/det|> +We strongly recommend the presentation of source data for graphical and statistical analyses as a separate Supplementary Table, and request that source data for all independent repeats are provided when representative experiments of multiple independent repeats, or averages of two independent experiments are presented. This supplementary table should be in Excel format, with data for different figures provided as different sheets within a single Excel file. It should be labelled and numbered as one of the supplementary tables, titled "Statistics Source Data", and mentioned in all relevant figure legends. + +<|ref|>text<|/ref|><|det|>[[115, 320, 867, 353]]<|/det|> +Please don't hesitate to contact NCB@nature.com should you have queries about any of the above requirements + +<|ref|>sub_title<|/ref|><|det|>[[122, 371, 396, 388]]<|/det|> +## Author Rebuttal to Initial comments + +<|ref|>text<|/ref|><|det|>[[116, 407, 325, 423]]<|/det|> +Dear Dr. Zhe and Reviewers, + +<|ref|>text<|/ref|><|det|>[[115, 434, 850, 490]]<|/det|> +We thank the reviewers for their time and effort in reviewing our manuscript now titled "MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin interactions". The reviewers made favorable comments about our study, including: + +<|ref|>text<|/ref|><|det|>[[142, 500, 884, 579]]<|/det|> +- "the strength of the study clearly lies on the cell biology of a complex tumor and how the loss of macroH2A histone variants affects the tumor microenvironment"- "the manuscript is delightfully written and easy to follow"- "these findings were largely convincing and are interesting contributions to the literature" + +<|ref|>text<|/ref|><|det|>[[115, 587, 880, 696]]<|/det|> +The reviewers also made helpful suggestions and provided constructive critiques, which we believe have significantly improved the quality and impact of our manuscript and enhanced our mechanistic understanding of macroH2A-deficiency in melanoma, with a focus on the CAF compartment. Our substantially revised manuscript contains two heavily amended Main figures (Figs. 5 & 7 and their corresponding Supplementary figures), consisting of almost entirely new data. Here, we highlight some of the key new data: + +<|ref|>text<|/ref|><|det|>[[144, 707, 884, 821]]<|/det|> +1. To mechanistically explain how macroH2A ablation affects inflammatory gene expression in CAFs, we performed promoter-capture Micro-C (pcMicro-C, a chromosome conformation capture technique that identifies chromatin loops with nucleosomal precision, here using promoters as the bait) to investigate the role of macroH2A in 3D chromatin architecture. Notably, this analysis has been computationally integrated with extensive transcriptomics and epigenomics data. We find the following: + +<|ref|>text<|/ref|><|det|>[[192, 824, 819, 842]]<|/det|> +I. loss of macroH2A is associated with global changes in chromatin contacts (Fig. 7a) + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[184, 143, 884, 220]]<|/det|> +II. a significant correlation between dKO activated enhancers (gain of H3K27ac) with dKO-specific promoter-enhancer loops (Fig. 7b)III. enrichment of inflammatory genes among those that gain promoter-enhancer contacts with increased enhancer activity in the dKO setting (Fig. 7d). + +<|ref|>text<|/ref|><|det|>[[115, 228, 835, 283]]<|/det|> +Overall, this new data suggests that macroH2A variants regulate the 3D chromatin landscape, and furthers our understanding of the regulatory elements behind those genes that drive the dKO CAF inflammatory phenotype. + +<|ref|>text<|/ref|><|det|>[[144, 293, 884, 546]]<|/det|> +2. Second, as requested by reviewer 2, we carried out an additional single cell RNA-sequencing (scRNA-seq) experiment of BRAFV600E/PTEN-deficient melanomas for a total of three WT and three dKO mice, generating a dataset of \(\sim 24,000\) high-quality cells (Fig. 3a). While this additional replicate has not changed our overall conclusions, attesting to the robustness of our original scRNA-seq analysis, it has allowed us to call cell clusters in more detail, as well as to add statistical significance to differences in the proportions of cells (Fig. 3d). This newly analyzed data continues to demonstrate significant changes in the NC and CAF populations, as well as various immune cell types (immunosuppressive myeloid, and cytotoxic T cells) in the dKO vs. WT melanomas (Fig. 3d). This data further maintains the role of CAFs as the drivers of inflammatory mediators in the TME (Fig. 4a-c). Moreover, it has now allowed us to robustly call receptor-ligand interactions, which revealed the predominant role of CAFs in communicating to other cell types (Fig. 5a, b), and the increased communication along the CCL2, CXCL1 and IL-6 pathways from dKO CAFs to myeloid cells (Fig. 5a). + +<|ref|>text<|/ref|><|det|>[[144, 548, 884, 720]]<|/det|> +3. To complement the scRNA-seq data, and to identify interactions between transformed melanocytes, CAFs, and the immune compartment in their native morphological context, we performed spatial transcriptomics using the 10X Visium spatial gene expression assay on WT and dKO melanomas. This approach allowed us to infer functional relationships between cell types that we identified in scRNA-seq data. As suggested by reviewers, we now present evidence of spatial colocalization between CAFs and immunosuppressive myeloid cells, and their exclusion of cytotoxic T cells from their tissue niches (Fig. 5b, c). Moreover, genetically engineered melanoma models have limited spatial transcriptomics data; thus we hereby also provide a key resource for the melanoma community. + +<|ref|>text<|/ref|><|det|>[[144, 722, 884, 857]]<|/det|> +4. Finally, as requested by reviewers 2 and 3, we also translated our murine findings to human biology through the use of patient-derived melanoma CAFs, as well as analyzing a published pan-cancer human CAF scRNA-seq dataset. Interestingly, we find that human melanoma CAFs vary in their levels of macroH2A2, and via ELISA assays, we demonstrate that macroH2A2low CAFs secrete more CCL2, CXCL1 and IL-6 upon stimulation (Fig. 5f, g). Moreover, by analyzing scRNA-seq data from over 56,000 CAFs across 98 tumor samples, we find CCL2, CXCL1 and IL6 are positively correlated with each other, while IL6 and MACROH2A2 show a negative correlation (Fig. 5j). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[114, 142, 880, 308]]<|/det|> +Overall, we would like to point out that our study is the first to: 1) report a cancer- associated phenotype in macroH2A- deficient animals, and 2) associate a histone variant with the non- immune tumor stroma, a compartment of increasing relevance to cancer biology. We demonstrate that CAF activation in the absence of macroH2A shapes tumor initiation and the ensuing dampened immune response by producing inflammatory cytokines that recruit pro- tumorigenic monocytes (also known as MDSCs) that can suppress T cell function. Moreover, we have utilized multiple innovative approaches, including scRNA- seq, spatial transcriptomics, and 3D chromatin structural analyses. The latter two approaches were performed during the revision process. Moreover, the use of patient- derived melanoma CAFs and mining of publicly available CAF datasets supports our findings in the human setting. + +<|ref|>text<|/ref|><|det|>[[114, 318, 845, 354]]<|/det|> +We highlighted sections of the manuscript and figure legends referring to this new data and revised analysis by using underlined text. + +<|ref|>text<|/ref|><|det|>[[116, 365, 698, 382]]<|/det|> +Please see our point- by- point responses to reviewers' comments below in blue: + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[116, 149, 328, 178]]<|/det|> +## Reviewer #1: + +<|ref|>sub_title<|/ref|><|det|>[[115, 209, 404, 232]]<|/det|> +## Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[113, 241, 870, 480]]<|/det|> +MacroH2A histone variants have tumor suppressive roles in many cancer types. This was pioneered by the last author's lab showing that loss of macroH2A increased the aggressiveness of melanoma cells reflected in increased metastasis in a xenograft model. In their current manuscript by Filipescu et al. they present the logical and long- awaited follow- up describing how the systemic absence of all macroH2A impinges on melanoma growth in a fully competent mouse model. Increased tumor growth in macroH2A- deficient mice is associated with a change in tumor- infiltrating immune cells and an inflammatory expression signature in bulk tissue. Specifically, results suggest a reduction in cytotoxic T cells and an increase in tumor suppressive myeloid cells. Single- cell RNA- seq indicates that differential abundances in two major cell populations that are a subpopulation of tumor cells with a stemness signature (NC- RXR) and cancer- associated fibroblast (CAF). CAFs are shown to the main source of upregulated cytokines and chemokines likely to trigger the immunophenotype. Up and downregulated genes and their enhancers are enriched in macroH2A. Upregulation is associated with increased enhancer activity. + +<|ref|>sub_title<|/ref|><|det|>[[115, 505, 230, 528]]<|/det|> +## Strength: + +<|ref|>text<|/ref|><|det|>[[143, 537, 884, 636]]<|/det|> +- First study assessing the impact of macroH2As on cancer in a fully immunocompetent mouse model.- Dissection of changes in a complex cancer tissue type. Identification of cell types and populations affected by the loss of macroH2A.- Demonstration that macroH2A has a repressive role in inflammatory genes in CAF. + +<|ref|>sub_title<|/ref|><|det|>[[115, 662, 249, 684]]<|/det|> +## Weakness: + +<|ref|>text<|/ref|><|det|>[[143, 695, 884, 771]]<|/det|> +- Figures are difficult to read (overloaded, non-intuitive abbreviations, missing labels and graphical legends).- The attempt to mechanistically explain how macroH2A ablation affects inflammatory genes falls short. + +<|ref|>text<|/ref|><|det|>[[115, 780, 857, 854]]<|/det|> +The strengths of the study clearly lies on the cell biology of a complex tumor and how the loss of macroH2A histone variants affects the tumor microenvironment. This is an important and interesting aspect that will warrant publication if further strengthened. As of now the study is descriptive with a very high level of quality and quantity. In addition, the authors provide a wealth of genomic data + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 863, 216]]<|/det|> +including from isolated primary cells that will be a valuable resource for the field. As in many studies before the genomic data indicates previously known associations but fails to explain how macroH2A actually affects gene transcription. Elucidating the exact mechanism is beyond scope of the presented study. + +<|ref|>text<|/ref|><|det|>[[137, 225, 883, 336]]<|/det|> +We thank the reviewer for acknowledging the significance of our study and recognizing its value. While the reviewer suggests that we do not fully address the mechanism by which macroH2A deficiency affects inflammatory gene expression, they also mention that it is "beyond the scope of the present study". Nonetheless, we are pleased to provide new data implicating macroH2A in the regulation of 3D chromatin interactions, particularly at inflammatory gene loci in CAFs. Specific points are addressed below. + +<|ref|>sub_title<|/ref|><|det|>[[116, 361, 370, 384]]<|/det|> +## MAJOR COMMENTS: + +<|ref|>text<|/ref|><|det|>[[115, 393, 872, 448]]<|/det|> +1. It should be clarified if the genes upregulated in CAFs are actually mediating the phenotype (tumor growth or immunosuppression). Can this be shown in vivo? If not, could a co-culture experiment help? If the signals are secreted, media transfer experiments can be helpful. + +<|ref|>text<|/ref|><|det|>[[137, 458, 883, 531]]<|/det|> +We thank the reviewer for raising this important point. We have now edited the manuscript to ensure the clarity of our message regarding the contribution of inflammatory gene expression in CAFs to the phenotype, as well as experimental/computational steps to further validate this hypothesis. + +<|ref|>text<|/ref|><|det|>[[137, 538, 883, 758]]<|/det|> +First, following the reviewer's suggestion of a co- culture experiment, we demonstrate that serum- stimulated dKO CAFs induce increased migration of WT monocytes compared to WT CAFs via transwell assays (Fig. 5d). Second, using our scRNA- seq dataset, which is now expanded through the addition of a third replicate per genotype, we performed ligand- receptor analysis to dissect the extent of cellular communication between CAFs and myeloid cells, and confirmed increased signaling from the former to the latter along the signaling pathways comprising the upregulated cytokines (Fig. 5a). Furthermore, by leveraging a new spatial transcriptomics dataset we generated in WT and dKO melanomas, we confirmed accumulation of Mac Mrc1 cells (myeloid cells with a predicted immunosuppressive profile) in the vicinity of CAFs, coupled to the exclusion of cytotoxic T cells (Fig. 5b, c). Taken together, these data suggest that macroH2A deficiency in CAFs is sufficient to drive increased monocyte/monocyte- derived cell accumulation in the TME. + +<|ref|>text<|/ref|><|det|>[[138, 766, 883, 840]]<|/det|> +Finally, we have now emphasized throughout the text that CCL2, CXCL1 and IL- 6 are widely accepted as signals secreted by CAFs to attract myeloid cells and polarize them toward an immunosuppressive phenotype across several cancer types. The revised manuscript cites a review summarizing these studies: https://pubmed.ncbi.nlm.nih.gov/35331673/ + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 866, 216]]<|/det|> +2. It should be clarified if the loss of macroH2A in tumor cells contribute to the phenotype and CAFs respond. Again, do CAFs respond to a secreted or a cell-bound signal. Is this signal the same in WT and dKO cancer cells? Do WT and dKO CAFs respond differently to WT cancer cells. Do WT CAFs respond differently to (please note this sentence was not completed by the reviewer) + +<|ref|>text<|/ref|><|det|>[[138, 225, 883, 336]]<|/det|> +The reviewer raises a valid point regarding communication from the tumor compartment towards CAFs. Signals from tumor cells (in our case, the NC compartment) can reprogram normal tissue mesenchymal cells into CAFs, and provide one of the pathways for CAF accumulation in the TME (reviewed in https://pubmed.ncbi.nlm.nih.gov/34670861/). While we cannot formally rule out extrinsic factors, several lines of evidence strongly suggest the inflammatory phenotype is CAF- intrinsic. + +<|ref|>text<|/ref|><|det|>[[137, 342, 883, 600]]<|/det|> +First, while we would have been keen to perform an experiment involving stimulation of WT CAFs with conditioned medium from WT or dKO melanoma/NC cells, followed by measurement of cytokine expression in CAFs, unfortunately it is not feasible. Despite considerable efforts, we have not been able to purify NC- derived cells from our melanoma model, or establish culture conditions that select for and allow propagation of tumor cells out of the mixed primary cell culture. However, our stimulation experiments in cultured CAFs, in the absence of any active signaling from tumor cells (given their absence from these cultures), show dKO CAFs can intrinsically sustain increased inflammatory signaling (Fig. 4f, S4n) and functionally, lead to increased recruitment of WT monocytes in vitro (Fig. 5d, S5c). Second, iDF stimulation experiments (Fig. S4o, S6m- o) show that this same phenotype occurs outside of any influence of the TME, since these WT and dKO fibroblasts were derived from normal skin. Third, ligand- receptor interaction analysis shows the NC compartment actually communicates less towards CAFs in the dKO, while CAFs have a stronger strength of interaction towards NC in the dKO (Fig. S5b). + +<|ref|>sub_title<|/ref|><|det|>[[115, 626, 485, 650]]<|/det|> +## OTHER GENERAL COMMENTS: + +<|ref|>text<|/ref|><|det|>[[115, 658, 857, 694]]<|/det|> +Given our expertise in genomic studies, we provide detailed suggestions on how to improve the data presentation (see further below). I consider that no additional data is needed on this side. + +<|ref|>text<|/ref|><|det|>[[115, 713, 872, 749]]<|/det|> +Statistical tests are missing in many figure panels. It has to be clear without reading the figure legend or the results text if differences are significant or not.+ + +<|ref|>text<|/ref|><|det|>[[138, 759, 882, 850]]<|/det|> +Details of statistical tests performed are now present in all figures, and we state in the legend when non- significant differences are not labeled. We deliberately omitted marking nonsignificant differences with "ns" when significant differences are also marked, in order to maintain figure clarity. For example, adding "ns" in panels such as Fig. 2c would render them less legible. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 535, 161]]<|/det|> +Legends are missing in several panels (eg 5c and related). + +<|ref|>text<|/ref|><|det|>[[135, 171, 705, 189]]<|/det|> +We apologize for any omissions and have modified the current version. + +<|ref|>text<|/ref|><|det|>[[115, 198, 601, 215]]<|/det|> +Please reduce the number of panels to the most informative ones. + +<|ref|>text<|/ref|><|det|>[[137, 225, 882, 280]]<|/det|> +We reorganized figures in the interest of clarity and moved multiple panels to the Supplement. The reviewer will now appreciate that former Figures 2 and 3 were combined and former Figures 3 and 4 have been simplified. + +<|ref|>text<|/ref|><|det|>[[115, 289, 643, 307]]<|/det|> +Label the panels with the cells / tissues analyzed e.g. 'sorted CAFs' in 5e. + +<|ref|>text<|/ref|><|det|>[[137, 316, 883, 352]]<|/det|> +We thank the reviewer for this suggestion. This is now the case for figures where data from multiple sources is shown. + +<|ref|>text<|/ref|><|det|>[[115, 361, 875, 434]]<|/det|> +In my humble opinion the authors could consider a different flow of their results. The single- cell RNA- seq is most informative and could be presented earlier (maybe right after presenting the phenotype) to introduce the two main results: 1. the change in tumor- composition and 2. changes in inflammatory gene expression. All other results could then be built on this. + +<|ref|>text<|/ref|><|det|>[[137, 443, 883, 572]]<|/det|> +We thank the reviewer for the suggestion. Accordingly, we tried to move this data forward as much as possible, especially considering the additional data added during revision. However, we believe the current flow of the paper allows the scRNA- seq data to link more readily to the aspects presented immediately after, and the data presented before provides strong evidence justifying its application, which we present in new Fig. 2 (a merge of previous Figures 2 and 3). We hope the flow of the revised manuscript showcases the scRNA- seq and continues to build out from there. + +<|ref|>text<|/ref|><|det|>[[115, 580, 875, 616]]<|/det|> +The presentation of the immunophenotype is confusing and scattered. Consider compilating all data on immune cells in one coherent figure. + +<|ref|>text<|/ref|><|det|>[[137, 626, 882, 663]]<|/det|> +We thank the reviewer for the suggestion. We have now simplified the immunophenotypic analysis and grouped it with the bulk tumor transcriptomic analysis into revised Fig. 2. + +<|ref|>text<|/ref|><|det|>[[115, 671, 860, 707]]<|/det|> +It should be clarified if there is anything special to the repressed 39 inflammatory genes compared to other macroH2A- regulated genes. + +<|ref|>text<|/ref|><|det|>[[137, 717, 883, 846]]<|/det|> +While this is somewhat open to speculation, as included in the Discussion, the promoter- capture Micro- C looping data generated during revision provides some insight into this question. By intersecting genes upregulated by macroH2A loss with the bona fide target genes of enhancers gaining H3K27ac in the dKO (determined by pcMicro- C looping data), 7 out of 20 genes were part of inflammatory signaling pathways (Fig. 7d), with significant enrichment for NF- \(\kappa\) B targets (Table 7). In addition, 17 out of these 20 genes also had a net increase in the number of loops in the dKO (Fig. 7d). Therefore, several inflammatory genes are at the + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 142, 883, 216]]<|/det|> +intersection of expression, looping and enhancer activity perturbations induced by macroH2A loss. While this does not encompass all genes, it is known that IL- 6 can signal in a paracrine manner, activating its own targets, and therefore some gene expression changes might be secondary to that. + +<|ref|>sub_title<|/ref|><|det|>[[114, 241, 577, 266]]<|/det|> +## SUGGESTIONS FOR SPECIFIC FIGURES: + +<|ref|>text<|/ref|><|det|>[[115, 276, 199, 292]]<|/det|> +Figures 4- 5 + +<|ref|>text<|/ref|><|det|>[[115, 303, 880, 376]]<|/det|> +The NC Rxrg cluster has a high contribution to the dKO bulk gene expression changes, comparable to the CAF Meg3 which are the focus of further analysis. I am missing a description of genes differentially expressed in melanoma, in particular NC Rxrg cells. What was the rationale for excluding this tumor cell population from further analysis? See my major comment. + +<|ref|>text<|/ref|><|det|>[[137, 385, 883, 623]]<|/det|> +The reviewer correctly points out that the NC Zeb2 cluster (previously annotated as Nc Rxrg but has been renamed after the additional scRNA- seq data set requested by reviewer 2) has proven difficult to analyze. The significant accumulation of NC Zeb2 cells in the dKO (Fig. 3d) and their de- differentiated nature (Fig. S3g- h) are consistent with macroH2A loss driving tumor progression, as we showed previously (Kapoor et al., 2010). However, NC Zeb2 cells displayed minimal upregulation of any Hallmark pathway in the dKO, compared to much more significant and pronounced (in terms of fold change) downregulation of pathways (Fig. S4g). Furthermore, among the downregulated pathways, some were seemingly antagonistic (G2M checkpoint/p53 vs. E2F targets; oxidative phosphorylation vs. hypoxia), which did not aid in informing what processes are being affected in this cluster. More importantly, because of a lack of specific markers suited for FACS, we were unable to isolate NC Zeb2 (or any other NC cells) from tumors, precluding any validation or molecular dissection of macroH2A's role in this cell type. + +<|ref|>text<|/ref|><|det|>[[115, 631, 869, 668]]<|/det|> +Figure 5c could perhaps be converted to a heatmap summarizing the expression differences to make it more visual and equivalent to other representations. + +<|ref|>text<|/ref|><|det|>[[138, 677, 883, 769]]<|/det|> +We maintained this standard representation of scRNA- seq data (now Fig. 4b), as in addition to differences between WT and dKO, the violin plot shape also displays the proportion of expressing cells and maximum expression value, showing which cluster is the main source of each highlighted cytokine/gene. This second point gets lost in heatmaps, where data is normalized as Z- scores for each gene to emphasize difference over absolute value. + +<|ref|>text<|/ref|><|det|>[[115, 778, 408, 795]]<|/det|> +Figure 5g lacks statistical testing results. + +<|ref|>text<|/ref|><|det|>[[135, 805, 881, 841]]<|/det|> +Statistical testing results and individual replicate values have been added to what is now Fig. 4f. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 872, 180]]<|/det|> +Could the Milo cell abundance method be applied to the re- clustered immune cell data shown in Figure S4i to assess changes in composition of immune subtypes? + +<|ref|>text<|/ref|><|det|>[[135, 190, 881, 226]]<|/det|> +We performed this analysis as suggested, and it confirmed local changes in CD8 clusters. This has been included as Fig. S3n. + +<|ref|>text<|/ref|><|det|>[[115, 235, 231, 252]]<|/det|> +Figure 6 and S6 + +<|ref|>text<|/ref|><|det|>[[115, 262, 870, 353]]<|/det|> +In these figures the authors present results obtained in CAFs and iDFs, but it is not always labelled in a way that allows easy interpretation without resorting to the legend or main text. For example, panels c to e versus panels h to j could be more readily interpreted by indicating the cells analyzed. This applies to the Supplementary Figure 6 and also to other parts of the manuscript, I think it would improve readability and faster interpretation of the results. + +<|ref|>text<|/ref|><|det|>[[135, 363, 881, 400]]<|/det|> +We agree that comparing multiple cell types within the same figure can lead to confusion and have labeled these panels accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 407, 880, 535]]<|/det|> +As far as I know, this is the first time a profiling of macroH2A by CUT&RUN is reported in a manuscript. The authors show a depletion from the gene bodies of highly expressed genes and some example loci, and in both cases the results are highly reminiscent of previous published results for ChIP- seq. Given the novelty of the experimental technique applied to this histone variant, I would appreciate a better generic description of the CUT&RUN results and a comparison to previously performed ChIP- seq (eg dermal fibroblast data) as benchmark, at least: the total number of enriched regions called ("MCDs"), size distribution of the identified MCDs, total \(\%\) of genome coverage by all MCDs. + +<|ref|>text<|/ref|><|det|>[[135, 545, 883, 582]]<|/det|> +We thank the reviewer for the suggestions and have now included the total number of MCDs (Fig. S6b legend), panels on size distribution of the identified MCDs (Fig. S6c) and total \(\%\) of + +<|ref|>image<|/ref|><|det|>[[125, 593, 860, 814]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[140, 824, 770, 840]]<|/det|> +
Figure R1. Comparison of MCDs called with epic2 on macroH2A1 CUT&RUN vs. ChIP-seq data.
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 141, 883, 252]]<|/det|> +genome coverage by all MCDs (Fig. S6d). We observed MCDs varied greatly in size, as well as in the level of macroH2A enrichment, prompting us to stratify them into super vs. standard, using an approach adapted for enhancer analysis. While we make no claim that these categories parallel the differences between traditional and superenhancers, we observe a more pronounced link with gene/enhancer deregulation at regions highly enriched in macroH2A such as the super MCDs. + +<|ref|>text<|/ref|><|det|>[[137, 259, 884, 460]]<|/det|> +As suggested, we attempted to compare our MCDs called on CUT&RUN data in CAFs with previously called MCDs on ChIP- seq in DFs (Sun et al., 2018). However, the two had different size distributions and patterns, which was likely due to the different methods used to call them. Therefore, we attempted to use the same methodology in the hope of obtaining a more comparable result, based on a recent publication analyzing macroH2A ChIP- seq. Corujo et al. (2022) used epic2 (Stovner and Saetrom, 2019), a peak caller tailored to broad enrichment regions, which we applied to our macroH2A1 ChIP- seq and CUT&RUN datasets. After testing multiple parameters to optimize the identification of MCDs (e.g., gap size, bin size, q- value, background), we observed that epic2 performed well for ChIP- seq, identifying large macro domains that corresponded to highly enriched regions, while it did not perform well for CUT&RUN, missing multiple large macroH2A enriched domains previously identified by the + +<|ref|>image<|/ref|><|det|>[[137, 460, 884, 765]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[245, 770, 777, 838]]<|/det|> +
Figure R2. Correlation of genome-wide enrichment of macroH2A between ChIP-seq and CUT&RUN methodologies. ChIP-seq and associated inputs were previously generated in dermal fibroblasts ("DF" samples), CUT&RUN was performed in serum-starved unstimulated ("U") and serum-stimulated ("S") WT CAFs, with associated IgG control.
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[549, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 141, 881, 179]]<|/det|> +identification of large domains from CUT&RUN data, and were not able to perform a domain- based comparison. + +<|ref|>text<|/ref|><|det|>[[138, 187, 884, 334]]<|/det|> +Nevertheless, we compared actual enrichment signal in the form of bigwig files, for their genome- wide correlation. Using this approach, we found a high degree of correlation \((r = 0.79)\) between macroH2A1 ChIP- seq and CUT&RUN (Fig. R2). We unfortunately do not have space in the Supplemental figures to add this data; however, we now mention our benchmarking of macroH2A CUT&RUN vs. ChIP- seq in the Methods section: "MacroH2A1 enrichment determined by CUT&RUN was benchmarked by correlation analysis with published macroH2A1 ChIP- seq in dermal fibroblasts (Sun 2018). Enrichment at the level of read pileups had a correlation coefficient of 0.79 (data not shown)." + +<|ref|>text<|/ref|><|det|>[[115, 341, 882, 451]]<|/det|> +The results in Figure 6c and d show an increased H3K27Ac enrichment at enhancers and promoters of the selected 39 upregulated inflammatory genes, however the difference seems mild when compared to the genome- wide effect shown in Figure S6a and the shaded area of the profiles (as I understand, a confidence interval) are largely overlapping. Could the authors perform a statistic test on the area around the enhancer centers or TSS to show that this is statistically significant? Perhaps a Fisher exact test on the read counts? + +<|ref|>text<|/ref|><|det|>[[138, 460, 884, 570]]<|/det|> +We performed a test after binning the signal upstream, on and downstream of the elements and indeed, it is not statistically significant (Fig. R3). This prompted us to examine other mechanisms of gene regulation, such as chromatin looping. We used looping data to delineate promoter- enhancer associations based on interactions in 3D, moving away from proximity- based associations (which are predictions), and have now removed the data the reviewer refers to. + +<|ref|>image<|/ref|><|det|>[[124, 580, 716, 742]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[138, 750, 718, 779]]<|/det|> +
Figure R3. Binned H3K27ac signal at promoters and proximity-associated enhancers of 39 inflammatory genes upregulated in sorted dKO CAFs.
+ +<|ref|>text<|/ref|><|det|>[[115, 802, 872, 856]]<|/det|> +MacroH2A1 has a higher enrichment in the 39 inflammatory genes than on thousands of static genes. This is also true for all dKO up and down genes (Figure 6k). The current presentation is misleading. I think a more logical description would be to first show the genome- wide analysis and then present that + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 866, 216]]<|/det|> +this holds true for the subset of genes that the authors propose are linked to the phenotype. Although the authors put the spotlight on this set of genes, I think it is important to highlight that the findings regarding mRNA occupancy and H3K27Ac changes are not exclusive of these genes but general for all mRNA- sensitive genes. + +<|ref|>text<|/ref|><|det|>[[137, 225, 882, 281]]<|/det|> +We took the reviewer's suggestion and organized Fig. 6 accordingly, emphasizing statistically significant genome- wide associations between macroH2A occupancy and gene/enhancer dysfunction. + +<|ref|>text<|/ref|><|det|>[[115, 288, 875, 344]]<|/det|> +Given the importance placed on these 39 DEGs, it would be important to know how many of them are detected as upregulated in both scRNA- Seq and sorted- bulk RNA- Seq datasets. Moreover, are they also deregulated in the NC clusters or exclusively in the CAFs? + +<|ref|>text<|/ref|><|det|>[[137, 353, 883, 464]]<|/det|> +We include Table R1 below to show 17 of the 39 genes derived from sorted CAFs are also significantly upregulated in CAF Meg3 of the scRNA- seq dataset, the most abundant CAF cluster that shows a 3- fold frequency increase in the dKO. Furthermore, CAF Wif1, CAF Fbln1 and CAF Lrrc15 follow in terms of most genes upregulated within that list. Among NC clusters, only NC Aqp1 displays upregulation of 2 such genes. This confirms the bulk of inflammatory gene upregulation in the dKO originates in CAFs. + +<|ref|>text<|/ref|><|det|>[[115, 471, 875, 527]]<|/det|> +Similarly, the analysis of H3K27Ac in Figure 6c and d could also be performed for all enhancer peaks within 50kb and the TSS of all the dKO up and dKO down genes, providing a general analysis of how the changes in H3K27Ac enrichment relate to the expression changes in the dKO CAFs. + +<|ref|>text<|/ref|><|det|>[[137, 536, 883, 647]]<|/det|> +As above, we revised our analysis to move away from proximity- based associations, which were not significant in the way suggested by the reviewer. We include the data (Fig. R4), where on average, H3K27ac at enhancers within 50 kb of TSS of all DEGs does not change in the direction of expression changes. Accordingly, we have also emphasized in the discussion that enhancer activity changes are not sufficient to explain all gene expression changes we observe. + +<|ref|>image<|/ref|><|det|>[[113, 652, 757, 805]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[137, 809, 755, 837]]<|/det|> +
Figure R4. H3K27ac at enhancer peaks within 50 kb of DEG promoters and control static genes with matched expression levels.
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 143, 468, 160]]<|/det|> +Which test was performed in Figure S6 L and N? + +<|ref|>text<|/ref|><|det|>[[135, 170, 883, 207]]<|/det|> +A chi- square test was performed, now presented in Fig. 6b and 6e, with appropriate description in the legend. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[137, 142, 884, 184]]<|/det|> +**Table R1.** Upregulation status of inflammatory genes identified in sorted CAFs, across clusters defined by scRNA-seq in murine melanoma. A value of T (true) represents significant upregulation (P-adj < 0.05, log2fc > 0) of indicated gene in indicated cluster. Genes and clusters with no T values are not shown. + +<|ref|>table<|/ref|><|det|>[[114, 204, 864, 750]]<|/det|> +
CAF Meg3CAF Wif1Mac Mrc1Mono-cyteMela- nocyteCAF Lrrc15NC Aqp1CAF Fbln1Mac Arg1BECAdven-titial
ApoeTTFFTTTTFFT
Hmgb1TFFFFFTTFFF
Ntrk2TTFFFFTFFFF
Ccl11TTFFFFFFFF
Tnfsf9TFFFFFFFFF
Thbs1TFFTFFFFTFF
CebpdTTFFFFFFFF
Tac1TFFFFFFFFF
Ccl2TTFFFFFFFF
CpFTTFFTFTFFF
Serping1TTFFFFFTFFF
Cxcl1TTFTFTFTTTF
Il6TFFFFFFFFF
Fosl2TFFFFFFFFF
KitlTFFFFFFFFF
Agtr1aFFFFFFFTFFF
CfhTTFFFFFTFFF
Dock10TTFFFFFTFFF
TslpFFTFFFFFFF
ApodFTFFFFFFFF
Il6stTFFFFFFFFF
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[117, 148, 328, 178]]<|/det|> +## Reviewer #2: + +<|ref|>sub_title<|/ref|><|det|>[[116, 209, 404, 232]]<|/det|> +## Remarks to the Author: + +<|ref|>sub_title<|/ref|><|det|>[[116, 254, 404, 274]]<|/det|> +### A. Summary of the key results + +<|ref|>text<|/ref|><|det|>[[115, 282, 872, 427]]<|/det|> +MacroH2A as a key epigenetic suppressor of tumour growth and progression in melanoma. The mechanism is shown to be likely caused by alteration in immunoregulation in the tumour mediated by the production of inflammatory cytokines by cancer activated fibroblasts. This was shown by use of a murine double- KO for macroH2A (H2afy and H2afy2) and autochthonous immunocompetent model for melanoma. The results are largely based on transcriptomic (both bulk and single cell) analyses of melanoma induced in this mouse model compared to mice that do not have the double- KO for macroH2A. The role of macroH2A in the epigenetic landscape in various cell types in the tumour microenvironment is also explored + +<|ref|>sub_title<|/ref|><|det|>[[115, 446, 760, 467]]<|/det|> +### B. Originality and significance: if not novel, please include reference + +<|ref|>text<|/ref|><|det|>[[115, 474, 620, 491]]<|/det|> +This study uncovers several key findings in the context of melanoma: + +<|ref|>text<|/ref|><|det|>[[140, 502, 886, 856]]<|/det|> +- Firstly, the heterogeneity of the melanoma tumour microenvironment is delineated on a cellular transcriptional level herein. This has already been done for an orthotopic transplantation model of melanoma (Davidson et al., 2020; https://pubmed.ncbi.nlm.nih.gov/32433953/). However, to my knowledge this is first time this has been performed in this autochthonous murine model of melanoma.- Secondly, to my knowledge this is the first study to perform single cell RNA sequencing on macroH2A deficient murine melanoma models.- Thirdly, a link between the function between cancer activated fibroblasts and immunoregulation in melanoma is re-enforced by this study. This hypothesis/discovery is not novel in and of itself (Papaccio et al., 2021; https://pubmed.ncbi.nlm.nih.gov/34298873/), however this study adds valuable high-resolution data, previously unexplored, that adds to this body of evidence.- Finally, a link between the function of macroH2A and cancer activated fibroblast behaviour is linked and underpinned as the consequential difference in melanoma progression with or without macroH2A. Namely, melanomas with cancer activated fibroblasts with dysfunctional macroH2A have increased pro-inflammatory cytokine expression by means of an altered epigenetic landscape in absence of macroH2A. The consequence of increased pro-inflammatory cytokine expression is an immunosuppressive tumour microenvironment, that promotes melanoma growth and progression. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 142, 883, 216]]<|/det|> +We thank the reviewer for recognizing the value of our study and emphasizing its novel findings. We hope they will appreciate the additional insight of the macroH2A- deficient TME provided by the spatial transcriptomics, 3D chromatin conformation and human data analysis included in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[115, 235, 792, 279]]<|/det|> +### C. Data & methodology: validity of approach, quality of data, quality of presentation + +<|ref|>text<|/ref|><|det|>[[115, 286, 269, 303]]<|/det|> +Validity of approach: + +<|ref|>text<|/ref|><|det|>[[141, 315, 883, 352]]<|/det|> +- A fine approach and line of inquiry for the issue of delineating macroH2A function in the melanoma microenvironment. + +<|ref|>text<|/ref|><|det|>[[115, 362, 231, 378]]<|/det|> +Quality of data: + +<|ref|>text<|/ref|><|det|>[[144, 390, 592, 429]]<|/det|> +- Data is generally of high quality.- Concern over number of replicates in the scRNAseq data. + +<|ref|>text<|/ref|><|det|>[[115, 438, 255, 455]]<|/det|> +Data presentation: + +<|ref|>text<|/ref|><|det|>[[144, 467, 710, 486]]<|/det|> +- Data is generally presented well, with little issue for legibility or font size. + +<|ref|>sub_title<|/ref|><|det|>[[115, 505, 709, 526]]<|/det|> +### D. Appropriate use of statistics and treatment of uncertainties + +<|ref|>text<|/ref|><|det|>[[115, 532, 615, 550]]<|/det|> +The approaches used are generally appropriate and well performed. + +<|ref|>sub_title<|/ref|><|det|>[[115, 570, 551, 590]]<|/det|> +### E. Conclusions: robustness, validity, reliability + +<|ref|>text<|/ref|><|det|>[[115, 597, 880, 670]]<|/det|> +The final line states that "the convergence of these mechanisms would predict poor response of macroH2A- low tumors to immunotherapy, suggesting a possible biomarker application to stratify melanoma patients." However this is speculative and not sufficiently evidenced in this study - how does the mouse model respond to immunotherapy based upon macroH2A status, for example? + +<|ref|>text<|/ref|><|det|>[[138, 680, 884, 754]]<|/det|> +We thank the reviewer for bringing up this point. We reserved this statement for the discussion section, given its speculative nature, and now state the following: "We speculate that the convergence of these mechanisms would predict poor response of macroH2Alow tumors to immunotherapy, suggesting a possible biomarker application to stratify melanoma patients". + +<|ref|>text<|/ref|><|det|>[[138, 760, 884, 852]]<|/det|> +We agree that testing response to immunotherapy may complement our data, but we believe this is beyond the scope of our study, in which we focus on the mechanistic understanding of macroH2A to inflammatory gene regulation in CAFs. While we considered performing immune checkpoint blockade, anti PD- 1 or PD- L1 monotherapy has been attempted in this melanoma model and shows minimal effects (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4097121/ + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[137, 141, 883, 234]]<|/det|> +see Fig. 5). Furthermore, these BRAFV600E/Ptennull tumors respond only partially to anti- CTLA- 4 + anti- PD- L1 combination therapy (https://www.nature.com/articles/nature14404 in Figure 4), which is not surprising given the lack of neoantigens in these tumors. Given these drawbacks, and the considerable expense of the drug regimen for a cohort of 20 mice over a period of 25 days, we did not pursue this approach. + +<|ref|>sub_title<|/ref|><|det|>[[116, 254, 760, 275]]<|/det|> +### F. Suggested improvements: experiments, data for possible revision + +<|ref|>text<|/ref|><|det|>[[115, 281, 870, 353]]<|/det|> +As noted in E., treating dKO and WT mice by immunotherapy to observe difference in response would strengthen this conclusion. Additionally/alternatively, a human tissue microarray (TMA) demonstrating variable macroH2A protein levels and correlating this with differences in immune cell infiltration as observed in the mouse model would be of merit. + +<|ref|>text<|/ref|><|det|>[[139, 364, 420, 381]]<|/det|> +We have addressed point E above. + +<|ref|>text<|/ref|><|det|>[[137, 388, 884, 555]]<|/det|> +We have addressed point E above.We thank the reviewer for the suggestion to consider TMAs, however, unfortunately, the small cores of tissue present in these arrays do not allow one to assess all the cell types of interest in the TME. Further, the impact of macroH2A loss on the tumor immune microenvironment appears to stem primarily from the CAF population, and thus the IHC analysis would need to target this population specifically. We note that IHC does not have the necessary resolution to evaluate macroH2A levels in CAFs vs. rest of the tumor, and would require simultaneous detection of at least one CAF marker, macroH2A1/2, and normalization controls such as histone H3. However, we now include two new sources of data that confirm our observations in human CAFs. + +<|ref|>text<|/ref|><|det|>[[137, 562, 884, 708]]<|/det|> +First, we obtained human melanoma CAF cultures from the NCI PDMR and Andrew Aplin's team at Thomas Jefferson University, who has published multiple studies using these CAFs (https://pubmed.ncbi.nlm.nih.gov/26269601/; https://pubmed.ncbi.nlm.nih.gov/30115691/). Our studies revealed an anticorrelation between endogenous macroH2A2 levels and CCL2, CXCL1, and IL- 6 cytokine production in these human CAFs (Fig. 5f, g, S5h). While this analysis did not reach statistical significance (likely due to heterogeneous source material and/or human biological variation), it indeed paralleled our observations from the mouse model. + +<|ref|>text<|/ref|><|det|>[[137, 716, 883, 771]]<|/det|> +Second, we analyzed a published scRNA- seq dataset containing over 56,000 CAFs across 98 samples comprising multiple cancer types. By calculating pseudobulk values, we found a significant pan- cancer anticorrelation between macroH2A2 and IL- 6 expression (Fig. S5j). + +<|ref|>text<|/ref|><|det|>[[115, 780, 874, 834]]<|/det|> +Only two tumours per condition are profiled by scRNAseq which is insufficient given the prominence these data have in the study. At least one more replicate per condition should be included which would also permit interrogation in the differences of tumour composition. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 141, 883, 345]]<|/det|> +We followed the reviewer's suggestion and added a third biological replicate per genotype. While this additional replicate has not changed our overall conclusions, attesting to the robustness of our original scRNA- seq analysis, it has allowed us to call cell clusters in more detail, as well as to add statistical significance to the differences in proportions of cells (Fig. 3d). This newly analyzed data continues to show significant changes in the NC populations, CAFs, and various immune cell types (immunosuppressive myeloid, and cytotoxic T cells) in the dKO vs. WT melanomas (Fig. 3d). This data maintained the role of CAFs as drivers of the accumulation of inflammatory mediators in the TME (Fig. 4a- c). Furthermore, it allowed us to robustly call receptor- ligand interactions, which revealed the predominant role of CAFs in communicating to other cell types (Fig. S5a, b), and the increase of communication along the CCL2, CXCL1 and IL- 6 pathways from dKO CAFs to myeloid cells (Fig. 5a). + +<|ref|>text<|/ref|><|det|>[[115, 352, 866, 389]]<|/det|> +CIBERSORT should be used to also determine whether there is a difference in myeloid cell populations when stratifying patients based on MACROH2A1 and MACROH2A2 expression. + +<|ref|>text<|/ref|><|det|>[[138, 397, 883, 564]]<|/det|> +We agree with the reviewer regarding the potential of CIBERSORT to interrogate accumulation of myeloid cells in macroH2Alow tumors. Therefore, we completely overhauled this analysis by implementing a recent analysis package, IOBR, which contains the CIBERSORT functionality. In contrast to our previous approach, this allowed us to use data normalized in the same manner via the robust TMM method, both for stratifying samples according to macroH2A expression, and for calculating immune population estimates. We no longer relied on CIBERSORT scores calculated by others; we compared samples in the \(1^{\text{st}}\) and \(3^{\text{rd}}\) macroH2A1 or macroH2A2 expression terciles, eliminating samples with intermediate expression levels which may have reduced the amplitude of differences observed. + +<|ref|>text<|/ref|><|det|>[[138, 571, 883, 755]]<|/det|> +The updated CIBERSORT analysis shows M2 (pro- tumor) macrophages are significantly more abundant in macroH2A2low primary tumors and near significance in macroH2A1low tumors (Fig. 5e). Of note, some myeloid subtypes are negatively correlated with macroH2A2 in metastases (Fig. S5d), although macroH2Alow tumors appear overall depleted of immune cells and conversely display increased tumor purity (Fig. S5e), which likely affects our ability to detect relative increases of immune subtypes via CIBERSORT. We also emphasize that the TCGA SKCM metastatic samples mainly comprise lymph node lesions, where the TME is different - both through a presence of immune populations residing in the lymph node, and a lack of skin- derived CAFs - therefore it is difficult to translate findings from our mouse model to these samples. + +<|ref|>text<|/ref|><|det|>[[115, 763, 872, 817]]<|/det|> +When stratifying tumours by MACROH2A2 expression (Fig 2c- d) there is a significant reduction in CD8 T cell markers but no difference in the inferred prevalence of CD8 T cells from CIBERSORT. How is this accounted for? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[137, 142, 883, 234]]<|/det|> +This was a shortcoming of the approach we used previously (see above). MACROH2A2 RNA- seq counts are low and likely affected the accuracy of stratification using the previous FPKM normalization method. Our updated CIBERSORT approach now shows significant CD8 T cell depletion in macroH2A1 and 2 low tumors both in the primary and metastatic setting (Fig. 5e, S5d). + +<|ref|>sub_title<|/ref|><|det|>[[115, 253, 610, 274]]<|/det|> +### G. References: appropriate credit to previous work? + +<|ref|>text<|/ref|><|det|>[[116, 281, 339, 298]]<|/det|> +Manuscript is well referenced. + +<|ref|>sub_title<|/ref|><|det|>[[115, 309, 780, 347]]<|/det|> +### H. Clarity and context: lucidity of abstract/summary, appropriateness of abstract, introduction and conclusions. + +<|ref|>text<|/ref|><|det|>[[115, 349, 876, 459]]<|/det|> +The manuscript is delightfully written and easy to follow. The abstract is an appropriate summary of the findings. The introduction is similarly concise and appropriate. The conclusions also follow and are written well. However, as noted earlier, the final sentence of the discussion is not directly supported by the evidence presented and so must be supplied as an optimistic speculation. If, however, there were direct evidence to support this claim, the manuscript would be greatly elevated from identification of biologically relevant and interesting mechanism to also that of clinical and therapeutic relevance. + +<|ref|>text<|/ref|><|det|>[[137, 468, 797, 486]]<|/det|> +We thank the reviewer for acknowledging the clarity and context of our manuscript. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>sub_title<|/ref|><|det|>[[117, 148, 328, 178]]<|/det|> +## Reviewer #3: + +<|ref|>sub_title<|/ref|><|det|>[[116, 208, 404, 232]]<|/det|> +## Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[113, 240, 877, 625]]<|/det|> +In this manuscript, the authors tested macroH2A knockout in a BRAFV600E;PTEN- deficient melanoma model. They found by that macroH2A accelerated tumor growth but exhibited insignificant differences in other metrics by histology. The authors then performed bulk RNA- sequencing on the KO and WT tumors and discovered upregulation of genes involved in myeloid cell recruitment and downregulation of genes involved in myeloid cell inhibition and cytotoxic T cell activation. Flow cytometry of the murine model exhibited an increase in monocytes in the dKO and a decrease in CD8 T cells. scRNA- seq revealed an enrichment of de- differentiated neural crest cells and immunosuppressive Mrc1+ macrophages in dKO tumors. The authors identify 3 CAF clusters, which upregulated the gene signature associated with the dKO bulk RNA- seq and overexpressed the myeloid chemoattractant genes upregulated in the bulk RNA- seq. The authors also see H2afy2 expression is specific to CAF cells in the scRNA- seq. Cultured CAF cells exhibited higher expression of the chemokines in the dKO with serum stimulation, suggesting CAF cell- intrinsic mechanisms of immunosuppression with macroH2A KO. ChIP- seq for H3K27ac showed a distinct landscape between dKO and WT CAFs but a minimal change in chromatin accessibility by ATAC- seq, and macroH2A1 CUT&RUN showed enrichment proximal to the dKO upregulated inflammatory genes. Collectively, the authors conclude that macroH2A KO relieves repression at inflammatory genes, eliciting CAF- induced promotion of an immunosuppressive tumor microenvironment. The primary finding of the paper is identification of a previously undescribed role for macroH2A in suppressing inflammatory signaling in fibroblasts, as well as evidence for macroH2A suppression of melanoma cell de- differentiation. These findings were largely convincing and are interesting contributions to the literature but require some further connection to human tumors to establish relevance to human biology. + +<|ref|>text<|/ref|><|det|>[[137, 633, 884, 744]]<|/det|> +We thank the reviewer for highlighting the interesting contributions of our study and convincing nature of our data. We agree that addressing the consequences of macroH2A deregulation in human CAFs would extend the relevance of our findings. We hope the reviewer will appreciate our efforts to translate our findings to human melanoma: 1) we investigated macroH2A biology in patient- derived melanoma CAFs and 2) we analyzed a published a pan- cancer scRNA- seq dataset containing over 56,000 CAFs across 98 samples. Please see below for further details. + +<|ref|>sub_title<|/ref|><|det|>[[116, 770, 337, 794]]<|/det|> +## Major Comments: + +<|ref|>text<|/ref|><|det|>[[116, 802, 882, 857]]<|/det|> +The authors' primary finding relates to the effect of macroH2A KO in the CAFs and suggest a cell- intrinsic mechanism by in vitro studies. This provides new information about the role of macroH2A in CAFs but is limited in data to support relevance in human samples. Do human melanomas with downregulated + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 855, 215]]<|/det|> +macroH2A exhibit increased infiltration of the myeloid compartment and decreased infiltration of lymphocytes (e.g., by histology)? In probing published human scRNA- seq datasets, does the stromal compartment exhibit a macroH2A- high and - low state? If so, do these states correlate with a distinct immune landscape? + +<|ref|>text<|/ref|><|det|>[[138, 225, 883, 300]]<|/det|> +We thank the reviewer for these suggestions. Our updated CIBERSORT analysis shows M2 (pro- tumor) macrophages are significantly more abundant in macroH2A2low primary tumors and near significance in macroH2A1low tumors, accompanied by significant CD8 T cell depletion in macroH2A1 and 2 low tumors (Fig. 5e). + +<|ref|>text<|/ref|><|det|>[[138, 306, 883, 436]]<|/det|> +We agree that further confirmatory assays such as IHC in human samples would supplement our data. As the reviewer remarks, the impact of macroH2A loss on the TME appears to stem from the CAF population, therefore, this analysis should target the CAF population specifically. We note that IHC does not have the necessary resolution to evaluate macroH2A levels in CAFs vs. rest of the tumor, and would require simultaneous detection of at least one CAF marker, macroH2A1/2, and normalization controls such as histone H3. However, we now include two new sources of data that confirm our observations in human CAFs. + +<|ref|>text<|/ref|><|det|>[[138, 442, 884, 607]]<|/det|> +We obtained melanoma CAF cultures from the NCI Patient- Derived Models Repository (note: application proposal approval was required), as well as additional cultures from Dr. Andrew Aplin who successfully used them to demonstrate the role of stromal ligands in promoting melanoma resistance to targeted therapy (https://pubmed.ncbi.nlm.nih.gov/26269601/ , https://pubmed.ncbi.nlm.nih.gov/30115691/). Our studies revealed an anticorrelation between endogenous macroH2A2 levels and CCL2, CXCL1, and IL- 6 cytokine production in these human CAFs (Fig. 5f, g, S5h). While this analysis did not reach significance, not surprising given the heterogeneous source material and possible confounding variables, it paralleled the direction of change observed in our mouse model. + +<|ref|>text<|/ref|><|det|>[[138, 615, 884, 744]]<|/det|> +Following the reviewer's suggestion, we analyzed a large scRNA- seq dataset containing over 56,000 CAFs across 98 samples comprising multiple cancer types. We found that macroH2A2 expression is below the detection threshold of 10X Visium scRNA- seq (Fig. S5i), therefore we could not carry out correlation analysis at the single cell level. Instead, we calculated pseudobulk values for the entire CAF population of each tumor and found a subset of tumors were populated with CAFs in a macroH2A2low state. Importantly, a significant anticorrelation between macroH2A2 and IL- 6 expression emerged (Fig. S5j). + +<|ref|>text<|/ref|><|det|>[[115, 752, 848, 861]]<|/det|> +- When comparing the GSEA data from the murine model versus the human samples, several of the pathways upregulated in the murine dKO model are downregulated in the human MACROH2A1 low samples (TNFa signaling via NFKB, IL6 Jak Stat3 signaling, IFNa/g response). What would explain this signature inversion? In looking at the myeloid-related genes (as in Fig 2B) in the human datasets, do they have a similar expression pattern? Does testing a gene signature for myeloid cell activation, cytotoxic T cell activation, etc. show a parallel between the murine and human samples? + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 141, 884, 308]]<|/det|> +We believe the downregulation of inflammatory pathways in the human MACROH2A1low metastatic samples is driven by their overall paucity in immune cells and increase in tumor purity, as evidenced in our updated TME deconvolution analysis (Fig. S5e). This would lead to downregulation of any pathways defined by genes specific to immune cells. Thus, we removed this data, and instead focus on cell type abundance analysis as described below (and Fig. 5e, S5d). Furthermore, our analysis now emphasizes primary tumors, since the TCGA SKCM metastatic samples mainly comprise lymph node lesions, where the TME is different - both through a presence of immune populations residing in the lymph node, and a lack of skin- derived CAFs. + +<|ref|>text<|/ref|><|det|>[[138, 315, 884, 444]]<|/det|> +While we were unable to find a similar expression pattern for myeloid- related genes such as CCL2, CXCL1 or IL- 6 in the TCGA SKCM dataset, as we noted above, at the bulk transcriptomic level, the depletion of total immune cells in macroH2A1low tumors might act as a confounding factor and likely affects our ability to detect relative increases of immune- associated genes. In addition, human scRNA- seq data shows CAFs in a macroH2A2low state overexpress higher levels of IL- 6, which would induce increased myeloid cell recruitment based on published studies (reviewed in: https://pubmed.ncbi.nlm.nih.gov/35331673/). + +<|ref|>text<|/ref|><|det|>[[139, 450, 884, 506]]<|/det|> +Furthermore, we updated our TCGA data analysis (see response to following point) using a ssGSEA approach, which calculated various cell type/activation state scores relevant to CD8 T cell function. Many of these scores are significantly lower in MACROH2A1low and + +<|ref|>image<|/ref|><|det|>[[141, 512, 898, 789]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[160, 796, 905, 839]]<|/det|> +
Figure R5. IOBR analysis of T cell signatures in TCGA SKCM primary tumors stratified by macroH2A expression levels. Signatures relevant to CD8 T cells are highlighted in bold. Green rectangles further highlight which of these signatures are significantly lower in macroH2A low tumors.
+ +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 47, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 141, 883, 234]]<|/det|> +MACROH2A2low primary tumors (Fig. R5), as the reviewer expected. Regarding myeloid cell activation, the updated CIBERSORT analysis shows the macrophage alternative activation signature (M2 macrophages) is significantly higher in macroH2A2low primary tumors and near significance in macroH2A1low tumors (Fig. 5e), altogether showing a parallel between the murine model and human samples. + +<|ref|>sub_title<|/ref|><|det|>[[116, 261, 338, 284]]<|/det|> +## Minor Comments: + +<|ref|>text<|/ref|><|det|>[[115, 292, 875, 365]]<|/det|> +- Interesting that the H2A2-low tumors exhibit a significant decrease in the cytotoxic genes (Fig 2C) but an insignificant difference in CD8 T cell abundance (Fig 2D). What explains why H2A1 would significantly decrease CD8 T cells but not H2A2? If the samples are stratified that are low in both H2A1 and H2A2, is the difference even more pronounced? + +<|ref|>text<|/ref|><|det|>[[137, 374, 883, 522]]<|/det|> +We completely overhauled the TCGA analysis by implementing a recent analysis package, IOBR, which contains the CIBERSORT functionality. In contrast to our previous approach, this allowed us to use data normalized in the same manner via the robust TMM method, both for stratifying samples according to macroH2A expression, and for calculating immune population estimates; we no longer relied on CIBERSORT scores calculated by others; we compared samples in the \(1^{\text{st}}\) and \(3^{\text{rd}}\) macroH2A1 or macroH2A2 expression terciles, eliminating samples with intermediate expression levels which may have reduced the amplitude of differences observed. + +<|ref|>text<|/ref|><|det|>[[138, 529, 883, 622]]<|/det|> +The discrepancy highlighted by the reviewer was a shortcoming of the approach we used previously. MACROH2A2 RNA- seq counts are low and likely affected the accuracy of stratification using the previous FPKM normalization method. Our updated CIBERSORT approach now shows significant CD8 T cell depletion in macroH2A1 and 2 low tumors both in the primary and metastatic setting (Fig. 5e, S5d). + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[139, 142, 884, 216]]<|/det|> +As suggested by the reviewer, we also compared samples with combined low levels of both macroH2A1 and macroH2A2. For this, we stratified each gene based on the median instead of terciles (otherwise, there would be too few samples in each of the possible 9 categories), and the results are similar (Fig. R6). + +<|ref|>image<|/ref|><|det|>[[140, 239, 904, 504]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[159, 515, 905, 544]]<|/det|> +
Figure R6. IOBR analysis of CIBERSORT immune cell type scores in TCGA SKCM primary tumors that have expression values of both macroH2A genes above or below the median.
+ +<|ref|>text<|/ref|><|det|>[[115, 567, 795, 603]]<|/det|> +- Is there an increase in myeloid cells by histology in the dKO? Where do these cells localize? Localization to the stroma would further support a CAF-centric effect. + +<|ref|>text<|/ref|><|det|>[[138, 613, 884, 778]]<|/det|> +Regarding the increase in myeloid cells, we believe that flow cytometric analysis of \(n_{WT} = 12\) and \(n_{dKO} = 15\) mice in 3 independent flow cytometry experiments is robust evidence, complemented by an orthogonal technique, scRNA-seq, where now a 3rd replicate also shows the Mac Mrc1 cluster is more abundant in the dKO. Both flow cytometry and scRNA-seq approaches sample a single cell suspension of the entire tumor and is likely more accurate/representative than histology, which would assess a single section per tumor. Furthermore, distinguishing the Mac Mrc1 cells (or cells annotated as monocytes by flow cytometry) from other myeloid cells (i.e., DCs with a different functional impact on tumor immunity) by IHC would be very challenging as it relies on co- staining for multiple markers. + +<|ref|>text<|/ref|><|det|>[[139, 786, 884, 858]]<|/det|> +To address cell type co- localization as requested by the reviewer, we instead performed spatial transcriptomics on WT and dKO tumors at the same time point during melanoma development, and projected cell identities from the scRNA- seq dataset onto the spatial dataset. This showed a distinct peritumoral localization of both the significantly dKO enriched Mac Mrc1 cells and 3 + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[138, 142, 883, 253]]<|/det|> +out of 4 CAF clusters (Fig. 5b). Furthermore, correlation analysis of these projected cell type scores revealed a significant, positive association between Mac Mrc1 and the 3 CAF clusters at the spot level (Fig. 5c). Importantly, we also observed a significant negative association between Tc (cytotoxic T cells) and both Mac Mrc1 and the 3 CAF clusters (Meg3, Lrrc15, Fbln1), supporting our hypothesis that CAFs and the myeloid cells they attract exclude cytotoxic T cells. + +<|ref|>text<|/ref|><|det|>[[138, 260, 883, 334]]<|/det|> +Furthermore, we demonstrate experimentally that serum- stimulated dKO CAFs induce increased migration and/or proliferation of WT monocytes compared to WT CAFs via a transwell assay (Fig. 5d, S5c). This functional readout supports our assumption that more monocyte- derived cells would be recruited to the TME niche where dKO CAFs reside. + +<|ref|>text<|/ref|><|det|>[[115, 342, 772, 360]]<|/det|> +- Please include a description of the acronyms used in Fig 4A in the figure, legend, or text. + +<|ref|>text<|/ref|><|det|>[[135, 370, 881, 406]]<|/det|> +We apologize for the oversight and have updated the corresponding figure legend (now Fig. 3a) to point the reader to Table 3, which describes these acronyms. + +<|ref|>text<|/ref|><|det|>[[115, 414, 876, 468]]<|/det|> +- After filtering the cells, are there equivalent numbers of cells for the WT and dKO samples in Fig 4? Normalizing the values in Fig 4C to the total number of cells per tumor (% filtered cells of parent tumor) would correct for sampling bias. + +<|ref|>text<|/ref|><|det|>[[135, 479, 880, 516]]<|/det|> +Values in this panel, now located in Fig. 3d, are presented as normalized to the total number of cells per tumor passing quality control filters. This is now emphasized in the figure legend. + +<|ref|>text<|/ref|><|det|>[[115, 523, 852, 578]]<|/det|> +- CAF Tnc drive the dKO transcriptional profile most significantly, but CAF Meg3 shows the biggest change in abundance in dKO. Do the authors believe all 3 CAF subpopulations contribute to this dKO phenotype? + +<|ref|>text<|/ref|><|det|>[[137, 588, 883, 717]]<|/det|> +The Augur analysis, performed on a dataset now including a \(3^{\text{rd}}\) replicate and updated clustering of cell populations including CAFs, now shows CAF Meg3 as the top driver of the transcriptional profile, besides its change in abundance in the dKO. However, we observe significant increase in the TNFα signaling via NF-κB pathway and immediate- early gene induction in all CAF clusters (Fig. 4c, S4e, f), as well as upregulation of individual inflammatory genes we associate with macroH2A- driven epigenetic alterations (Table R1; see above in response to reviewer 1). + +<|ref|>text<|/ref|><|det|>[[115, 725, 878, 779]]<|/det|> +- Fig S5g shows H2afy2 expression in CAFs and H2afy expression in all clusters. This is assumedly in the WT tumors but isn't specified in the figure or corresponding legend. Please show or describe the sample origin of this expression. + +<|ref|>text<|/ref|><|det|>[[135, 789, 881, 825]]<|/det|> +We apologize for the oversight and have updated the panel, now Fig. S6h, to state expression is shown in WT samples. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 881, 197]]<|/det|> +- In looking at the CAF ATAC-seq for the inflammatory genes differentially expressed in the CAF RNA-seq and exhibiting differential H3K27ac, are these genes in the newly open peaks or unchanged but open in both dKO and WT? + +<|ref|>text<|/ref|><|det|>[[137, 207, 883, 300]]<|/det|> +ATAC- seq changes are minimal and show minimal overlap with gene expression changes. To our knowledge, other groups have also found a lack of ATAC changes upon macroH2A depletion, but their data remains unpublished. Inflammatory genes, examples of which are shown in Fig. 7e-g and Fig. S7g-h, display open chromatin in both dKO and WT. Only Cxcl1 gains accessibility in an intragenic ATAC peak. + +<|ref|>text<|/ref|><|det|>[[115, 308, 584, 325]]<|/det|> +- Line 347 misspelled word "previously" should be "previously." + +<|ref|>text<|/ref|><|det|>[[139, 335, 363, 352]]<|/det|> +This mistake was corrected. + +<|ref|>text<|/ref|><|det|>[[115, 362, 848, 398]]<|/det|> +- Since macroH2A2 was shown to be specific to CAFs, would it be expected that CUT&RUN for H2A2 would exhibit distinct enrichment localization? + +<|ref|>text<|/ref|><|det|>[[137, 406, 883, 517]]<|/det|> +We attempted to perform macroH2A2 CUT&RUN but failed for reasons that remain unclear, but may be due to much lower abundance of this variant vs. macroH2A1 (~5-fold at RNA level). In dermal fibroblasts, which express both variants, they are distributed in a similar manner, with correlated enrichment levels (Fig. R2, R7). We therefore expect this similar distribution to be maintained in CAFs; however, we cannot rule out distinct functions for macroH2A2 in the CAF compartment. + +<|ref|>image<|/ref|><|det|>[[115, 523, 884, 686]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[137, 690, 777, 707]]<|/det|> +
Figure R7. macroH2A1 and macroH2A2 ChIP signal around the Cxcl1 locus in dermal fibroblasts.
+ +<|ref|>text<|/ref|><|det|>[[115, 727, 768, 772]]<|/det|> +- Figure S4i isn't referenced in the text, and lines 352-353 should reference Fig 6f and 6g. We thank the reviewer for noticing, and this omission was corrected. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 48, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[118, 142, 290, 157]]<|/det|> +Our ref: NCB- A48296A + +<|ref|>text<|/ref|><|det|>[[117, 173, 229, 188]]<|/det|> +11th May 2023 + +<|ref|>text<|/ref|><|det|>[[116, 202, 260, 217]]<|/det|> +Dear Dr. Bernstein, + +<|ref|>text<|/ref|><|det|>[[115, 232, 879, 323]]<|/det|> +Thank you for submitting your revised manuscript "MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin interactions" (NCB- A48296A). It has now been seen by the original referees and their comments are below. The reviewers find that the paper has improved in revision, and therefore we'll be happy in principle to publish it in Nature Cell Biology, pending minor revisions to satisfy the referees' final requests and to comply with our editorial and formatting guidelines. + +<|ref|>text<|/ref|><|det|>[[115, 336, 857, 368]]<|/det|> +If the current version of your manuscript is in a PDF format, please email us a copy of the file in an editable format (Microsoft Word or LaTex)- - we can not proceed with PDFs at this stage. + +<|ref|>text<|/ref|><|det|>[[116, 380, 857, 427]]<|/det|> +We are now performing detailed checks on your paper and will send you a checklist detailing our editorial and formatting requirements in about a week. Please do not upload the final materials and make any revisions until you receive this additional information from us. + +<|ref|>text<|/ref|><|det|>[[115, 439, 854, 472]]<|/det|> +Thank you again for your interest in Nature Cell Biology Please do not hesitate to contact me if you have any questions. + +<|ref|>text<|/ref|><|det|>[[116, 486, 190, 501]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[115, 515, 260, 562]]<|/det|> +Zhe Wang, PhD Senior Editor Nature Cell Biology + +<|ref|>text<|/ref|><|det|>[[115, 575, 339, 606]]<|/det|> +Tel: +44 (0) 207 843 4924 email: zhe.wang@nature.com + +<|ref|>text<|/ref|><|det|>[[116, 634, 404, 650]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 664, 864, 740]]<|/det|> +Filippescu et al. present the revised version of the manuscript showing that loss of macroH2A contributes to melanoma progression by changing the tumor microenvironment. In particular, they convincingly demonstrate that cancer- associated fibroblasts are highly macroH2A- sensitive and that its loss results in the upregulation of cytokine- encoding genes and immunomodulation consisting of increased attraction of immunosuppressive monocytes and a reduction of cytotoxic T- cells. + +<|ref|>text<|/ref|><|det|>[[115, 753, 876, 800]]<|/det|> +This is a great study which advances the fields of cancer, chromatin biology and inflammation. For the histone variant community these findings are a milestone and exemplify the importance of histone variants in inflammatory gene expression and immunomodulation. + +<|ref|>text<|/ref|><|det|>[[115, 813, 870, 860]]<|/det|> +While I was supportive of the study from the very beginning, I had many comments and suggestions that the authors have addressed in an extensive revision. The revised version and in particular the new figures are easy to read and data and results are of high quality. I have left a few very minor + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 872, 174]]<|/det|> +comments that I believe the authors will be able to address without the need of another revision from my side. I am looking forward to seeing the study published. + +<|ref|>text<|/ref|><|det|>[[115, 188, 245, 202]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 203, 872, 293]]<|/det|> +Figure 3c and 5b: Consider showing 'zoom ins' to illustrate the points you wish to make. Figure 4b: Add a legend showing what is blue, red, light red and light blue. Figure 5b: Add a legend showing what bullet size encodes and add a label to the color scale. Figure 7b: Consider adding a figure showing how super and standard domains were defined. Figure 7d: Consider changing the top label to 'Genes gaining loops in dKO' to clarify that this analysis is on the gene level. + +<|ref|>text<|/ref|><|det|>[[115, 307, 721, 322]]<|/det|> +I conclude by congratulating the authors to their work and this excellent revision. + +<|ref|>text<|/ref|><|det|>[[115, 337, 500, 352]]<|/det|> +Marcus Buschbeck with the support of David Corujo + +<|ref|>text<|/ref|><|det|>[[115, 381, 404, 396]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 411, 852, 441]]<|/det|> +After going through your point by point response and evaluated the revised manuscript I think you have addressed my previous concerns sufficiently. + +<|ref|>text<|/ref|><|det|>[[115, 470, 404, 485]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 500, 869, 560]]<|/det|> +In this revised manuscript, the authors have made substantial edits and added additional datasets in response to our comments, strengthening human melanoma relevance and adding additional mechanistic insight. These revisions have sufficiently addressed our concerns. The manuscript will be of benefit to the readers of Nature Cell Biology. + +<|ref|>title<|/ref|><|det|>[[120, 580, 355, 595]]<|/det|> +# Author Rebuttal, first revision: + +<|ref|>sub_title<|/ref|><|det|>[[115, 614, 438, 631]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 649, 882, 751]]<|/det|> +Filippescu et al. present the revised version of the manuscript showing that loss of macroH2A contributes to melanoma progression by changing the tumor microenvironment. In particular, they convincingly demonstrate that cancer- associated fibroblasts are highly macroH2A- sensitive and that its loss results in the upregulation of cytokine- encoding genes and immunomodulation consisting of increased attraction of immunosuppressive monocytes and a reduction of cytotoxic T- cells. + +<|ref|>text<|/ref|><|det|>[[115, 770, 872, 820]]<|/det|> +This is a great study which advances the fields of cancer, chromatin biology and inflammation. For the histone variant community these findings are a milestone and exemplify the importance of histone variants in inflammatory gene expression and immunomodulation. + +<|ref|>text<|/ref|><|det|>[[115, 838, 810, 855]]<|/det|> +While I was supportive of the study from the very beginning, I had many comments and + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 50, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 879, 213]]<|/det|> +suggestions that the authors have addressed in an extensive revision. The revised version and in particular the new figures are easy to read and data and results are of high quality. I have left a few very minor comments that I believe the authors will be able to address without the need of another revision from my side. I am looking forward to seeing the study published. + +<|ref|>text<|/ref|><|det|>[[115, 248, 808, 301]]<|/det|> +We thank the Reviewer(s) for their overall enthusiasm and support of our study that demonstrates 'the importance of histone variants in inflammatory gene expression and immunomodulation'. We have addressed these final minor comments below: + +<|ref|>text<|/ref|><|det|>[[115, 319, 812, 354]]<|/det|> +Minor comments: Figure 3c and 5b: Consider showing 'zoom ins' to illustrate the points you wish to make. + +<|ref|>text<|/ref|><|det|>[[115, 362, 808, 397]]<|/det|> +Response: We thank the Reviewer for this very helpful suggestion and have added the requested zoomed inserts. + +<|ref|>text<|/ref|><|det|>[[115, 423, 706, 441]]<|/det|> +Figure 4b: Add a legend showing what is blue, red, light red and light blue. + +<|ref|>text<|/ref|><|det|>[[115, 450, 478, 468]]<|/det|> +Response: A legend was added to this panel. + +<|ref|>text<|/ref|><|det|>[[115, 521, 855, 540]]<|/det|> +Figure 5b: Add a legend showing what bullet size encodes and add a label to the color scale. + +<|ref|>text<|/ref|><|det|>[[115, 550, 879, 585]]<|/det|> +Response: We believe the Reviewer is referring to Figure 5c; we have added a statement to the legend explaining dot size is proportional to the r coefficient. + +<|ref|>text<|/ref|><|det|>[[115, 639, 854, 658]]<|/det|> +Figure 7b: Consider adding a figure showing how super and standard domains were defined. + +<|ref|>text<|/ref|><|det|>[[115, 666, 850, 719]]<|/det|> +Response: The approach used to define different macroH2A domain classes is described in detail in the Methods section and accompanied by plots illustrating the features of these domains in Supplemental Figure 6c- e. + +<|ref|>text<|/ref|><|det|>[[115, 773, 855, 807]]<|/det|> +Figure 7d: Consider changing the top label to 'Genes gaining loops in dKO' to clarify that this analysis is on the gene level. + +<|ref|>text<|/ref|><|det|>[[115, 808, 844, 843]]<|/det|> +Response: To clarify this point, we added the label "Classes of genes:", which applies to all categories overlapped in Figure 7d. + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 85]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 159, 754, 177]]<|/det|> +I conclude by congratulating the authors to their work and this excellent revision. + +<|ref|>text<|/ref|><|det|>[[115, 187, 852, 222]]<|/det|> +We thank the Reviewer(s) once again for their continued support of our manuscript, in- depth review, and valuable recommendations during the revision process. + +<|ref|>text<|/ref|><|det|>[[115, 276, 530, 294]]<|/det|> +Marcus Buschbeck with the support of David Corujo + +<|ref|>sub_title<|/ref|><|det|>[[115, 328, 438, 346]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 362, 860, 397]]<|/det|> +After going through your point by point response and evaluated the revised manuscript I think you have addressed my previous concerns sufficiently. + +<|ref|>text<|/ref|><|det|>[[115, 434, 778, 452]]<|/det|> +Response: We thank the Reviewer for their careful review and support of our study. + +<|ref|>sub_title<|/ref|><|det|>[[115, 486, 438, 504]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 520, 867, 590]]<|/det|> +In this revised manuscript, the authors have made substantial edits and added additional datasets in response to our comments, strengthening human melanoma relevance and adding additional mechanistic insight. These revisions have sufficiently addressed our concerns. The manuscript will be of benefit to the readers of Nature Cell Biology. + +<|ref|>text<|/ref|><|det|>[[115, 627, 857, 661]]<|/det|> +Response: We are pleased to have strengthened the human melanoma relevance and thank the Reviewer for their support of publication in Nature Cell Biology. + +<|ref|>sub_title<|/ref|><|det|>[[122, 710, 283, 725]]<|/det|> +## Final Decision Letter: + +<|ref|>text<|/ref|><|det|>[[115, 744, 256, 760]]<|/det|> +Dear Dr Bernstein, + +<|ref|>text<|/ref|><|det|>[[115, 774, 881, 821]]<|/det|> +I am pleased to inform you that your manuscript, "MacroH2A restricts inflammatory gene expression in melanoma cancer- associated fibroblasts by coordinating chromatin looping", has now been accepted for publication in Nature Cell Biology. + +<|ref|>text<|/ref|><|det|>[[115, 834, 852, 851]]<|/det|> +Thank you for sending us the final manuscript files to be processed for print and online production, + +<--- Page Split ---> +<|ref|>title<|/ref|><|det|>[[548, 49, 872, 87]]<|/det|> +# natureresearch + +<|ref|>text<|/ref|><|det|>[[115, 142, 860, 189]]<|/det|> +and for returning the manuscript checklists and other forms. Your manuscript will now be passed to our production team who will be in contact with you if there are any questions with the production quality of supplied figures and text. + +<|ref|>text<|/ref|><|det|>[[115, 202, 874, 264]]<|/det|> +Over the next few weeks, your paper will be copyedited to ensure that it conforms to Nature Cell Biology style. Once your paper is typeset, you will receive an email with a link to choose the appropriate publishing options for your paper and our Author Services team will be in touch regarding any additional information that may be required. + +<|ref|>text<|/ref|><|det|>[[115, 277, 866, 323]]<|/det|> +After the grant of rights is completed, you will receive a link to your electronic proof via email with a request to make any corrections within 48 hours. 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Further information can be found at www.nature.com/protocolexchange/about + +<|ref|>text<|/ref|><|det|>[[115, 470, 872, 516]]<|/det|> +You can use a single sign- on for all your accounts, view the status of all your manuscript submissions and reviews, access usage statistics for your published articles and download a record of your refereeing activity for the Nature Portfolio. + +<|ref|>text<|/ref|><|det|>[[115, 530, 531, 545]]<|/det|> +Please feel free to contact us if you have any questions. + +<|ref|>text<|/ref|><|det|>[[115, 560, 253, 575]]<|/det|> +With kind regards, + +<|ref|>text<|/ref|><|det|>[[115, 590, 260, 636]]<|/det|> +Zhe Wang, PhD Senior Editor Nature Cell Biology + +<|ref|>text<|/ref|><|det|>[[115, 650, 340, 680]]<|/det|> +Tel: +44 (0) 207 843 4924 email: zhe.wang@nature.com + +<|ref|>text<|/ref|><|det|>[[115, 723, 700, 754]]<|/det|> +Click here if you would like to recommend Nature Cell Biology to your librarian http://www.nature.com/subscriptions/recommend.html#forms + +<|ref|>text<|/ref|><|det|>[[115, 783, 857, 829]]<|/det|> +\*\* Visit the Springer Nature Editorial and Publishing website at www.springernature.com/editorial- and- publishing- jobs for more information about our career opportunities. If you have any questions please click here.\*\* + +<--- Page Split ---> diff --git a/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/images_list.json b/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd b/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..0ef6ccca49cc30373b994217fda0c22413e14de2 --- /dev/null +++ b/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/supplementary_1_Peer Review File.mmd @@ -0,0 +1,552 @@ + +# nature portfolio + +Peer Review File + +# Molecular basis for the activation of outer dynein arms in cilia + +Corresponding Author: Dr Girish Mali + +Version 0: + +Decision Letter: + +30th Oct 2024 + +Dear Dr. Mali, + +Thank you for submitting your manuscript "Molecular basis for the activation of outer dynein arms in cilia". We have now carefully evaluated the work and discussed it among the editorial team. Unfortunately, we have decided not to consider the manuscript further for publication in Nature Structural & Molecular Biology. + +We can only consider a small proportion of the manuscripts submitted to our journal and are often forced to make difficult decisions. Manuscripts are evaluated editorially for their potential interest to a broad audience, the level of novel insight obtained and whether the findings represent a significant advance relative to the published literature, among other considerations. + +In this case, we are interested in this area of research and appreciate the potential role for a Shulin- Arl3 complex in regulating Shulin and its rebinding to ODAs. We recognize that the findings will be of value to others working in this area. However, after discussion among the editorial staff, I am afraid we are not persuaded that the level of mechanistic insight and degree of conceptual advance obtained warrants publication in Nature Structural & Molecular Biology, after taking into account relevant published work [including, but not limited to, studies suggesting that DNAAF9 may bind to ARL3; other work showing that Arl3 binds to another potential ODA transport adaptor, Oda16, with Oda16 proposed to act as an effector in ciliary transport] + +Although we cannot offer to publish your manuscript, I suggest that you consider Nature Communications as a suitable venue for this work. To transfer your manuscript, please use our manuscript transfer portal. You will not have to re- supply manuscript metadata and files, unless you wish to make modifications. For more information, please see our manuscript transfer FAQ page. + +I am sorry we could not be more positive on this occasion. We thank you for the opportunity to consider this work and wish you success in seeking publication elsewhere. + +Sincerely, + +Melina Casadio, PhD Consulting Editor, Nature Structural & Molecular Biology Senior Editor, Nature Cell Biology ORCID ID: https://orcid.org/0000- 0003- 2389- 2243 + +\*\* For Springer Nature Limited general information and news for authors, see http://npg.nature.com/authors. + +Version 1: + +Decision Letter: + +4th Dec 2024 + +Dear Dr. Mali, + +<--- Page Split ---> + +Thank you for your letter concerning your manuscript "Molecular basis for the activation of outer dynein arms in cilia". We really appreciate your patience with the process and are sorry we cannot prioritize appeals over new submissions. We have now had a chance to discuss the points you raised in detail, and we have decided to send your paper out to review. Prior to peer review, please see the points below to prepare the files necessary for peer review: + +1- We want to ensure that the methods and statistics reporting in our papers are of the highest quality. To that end, we ask authors to fill out a Reporting Summary that collects information on experimental design and reagents, as well as an editorial Policy Checklist, which confirms compliance with our editorial policies, including the declaration of Competing Interests. + +These documents can be found by following the links below: + +Reporting Summary: https://www.nature.com/documents/nr-reporting-summary.pdf + +Editorial Policy Checklist: https://www.nature.com/documents/nr- editorial- policy- checklist.pdf + +Please complete the relevant forms and include them with your files for peer review. Please note that these forms are dynamic 'smart pdfs' and must, therefore, be downloaded and completed in Adobe Reader. We will then flatten them for ease of use by the reviewers. If you would like to reference the guidance text as you complete the template, please access these flattened versions at http://www.nature.com/authors/policies/availability.html. + +Note that you are not required to revise your paper to include the information provided in the reporting summary. However, all points on the policy checklist must be addressed; please include a new version of the manuscript with your completed checklist if needed. + +Once we receive these documents and review them to ensure that all requested information is provided, we will proceed to send your paper for review. If you have questions or anticipate delays, please let me know as soon as possible. + +2- Proteomics datasets should be deposited and made available to the reviewers at a minimum. Please clarify where the mass spectrometry datasets can be accessed with your resubmission. + +3- When preparing your revised manuscript including the appeal data, please note that, if any personal communications are included, you would need to forward an email permission to us stating that the persons who made these communications to you approve their inclusions in this particular manuscript. Please let me know if you have any questions. + +You can use the link below to be taken directly to the site and submit your manuscript: + +Link Redacted + +Sincerely, + +Melina + +Melina Casadio, PhD Consulting Editor, Nature Structural & Molecular Biology Senior Editor, Nature Cell Biology ORCID ID: https://orcid.org/0000- 0003- 2389- 2243 + +Version 2: + +Decision Letter: + +24th Jan 2025 + +Dear Dr Mali, + +Thank you again for submitting your manuscript "Molecular basis for the activation of outer dynein arms in cilia". I apologize for the delay in responding, which resulted from the difficulty in obtaining suitable referee reports. We now have comments (below) from the 3 reviewers who evaluated your paper. In light of those reports, we remain interested in your study and would like to see your response to the comments of the referees in the form of a revised manuscript. + +To guide the scope of the revisions, we list below a prioritized set of referee points that should be addressed in the revision, + +<--- Page Split ---> + +which we hope will be helpful to you. You will see that the reviewers found the model interesting but asked for additional evidence to support it, as well as clarifications: + +- In revision, please strengthen the mechanism of Shulin-ODA complex regulation by Arl3 (Rev#2 point #2 – please also see Rev#1 point #1 to strengthen the functional implications for DNAAF9) and the studies characterizing the binding between DNAAF9 and Arl3 (Rev#2 point #1) + +- Please address all minor points and suggestions to strengthen the current dataset including Rev#1's point #2; please address Rev#1's questions in point #3 about the various models used. + +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. 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As such, if there are any changes that should be reported, please submit an updated version of the Reporting Summary along with your revision. + +Reporting Summary: https://www.nature.com/documents/nr- reporting- summary.pdf + +Please note that the form is a dynamic 'smart pdf' and must therefore be downloaded and completed in Adobe Reader. + +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. +- that control panels for gels and western blots are appropriately described as loading on sample processing controls +- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +## EXTENDED DATA FIGURES + +When re- submitting your manuscript, please ensure that any supplementary figures and tables that are crucial to the manuscript's conclusions are converted into Extended Data figures and tables to increase visibility of these data. 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While these data can be displayed in a relatively informal style, they must refer back to the relevant figures. These data should be submitted with the last revision, prior to acceptance, but you may want to start putting it together at this point. + +SOURCE DATA: we urge authors to provide, in tabular form, the data underlying the graphical representations used in figures. This is to further increase transparency in data reporting, as detailed in this editorial (http://www.nature.com/nsmb/journal/v22/n10/full/nsmb.3110. html). Spreadsheets can be submitted in excel format. Only one (1) file per figure is permitted; thus, for multi- paneled figures, the source data for each panel should be clearly labeled in the Excel file; alternately the data can be provided as multiple, clearly labeled sheets in an Excel file. When submitting files, the title field should indicate which figure the source data pertains to. We encourage our authors to provide source data at the revision stage, so that they are part of the peer- review process. + +While we encourage the use of color in preparing figures, please note that this will incur a charge to partially defray the cost of printing. Information about color charges can be found at http://www.nature.com/nsmb/authors/submit/index.html#costs + +We require deposition of coordinates (and, in the case of crystal structures, structure factors) into the Protein Data Bank with + +<--- Page Split ---> + +the designation of immediate release upon publication (HPUB). Electron microscopy- derived density maps and coordinate data must be deposited in EMDB and released upon publication. Deposition and immediate release of NMR chemical shift assignments are highly encouraged. Deposition of deep sequencing and microarray data is mandatory, and the datasets must be released prior to or upon publication. To avoid delays in publication, dataset accession numbers must be supplied with the final accepted manuscript and appropriate release dates must be indicated at the galley proof stage. Please find the complete NRG policies on data availability at http://www.nature.com/authors/policies/availability.html. + +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +Please use the link below to submit your revised manuscript and related files: + +Link Redacted + +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +Sincerely, + +Melina Casadio, PhD Locum Chief Editor, Nature Structural & Molecular Biology ORCID ID: https://orcid.org/0000- 0003- 2389- 2243 + +Referee expertise: + +Referee #1: dynein + +Referee #2: dynein, structural biology + +Referee #3: cilia + +Reviewers' Comments: + +Reviewer #1 (Remarks to the Author): + +This is an excellent manuscript with very clearly stated hypotheses and satisfying answers to the questions posed. In brief, the authors follow up on a 2021 manuscript in which they initially described Shulin's biochemical and biological activity along with a high resolution cryo- EM structure. They speculate that DNAAF9 is a likely homolog to the T. thermophila Shulin protein, which their previous work demonstrated was an important effector of OAD's autoinhibited state. They find that DNAAF9 localizes to the developing cilia of human airway epithelial cells (but not to mature cilia), co- IPs with OAD components (eg. DNAI2), and its addition to purified OAD causes a change in conformation to a 'closed'/presumably autoinhibited state. The authors then focus on testing the hypothesis that the Ari3 GTPase releases ODA from DNAAF9 in a GTP- dependent manner. They find Ari3 from human and T. thermophila both bind to DNAAF9/Shulin. Using negative stain EM and AF2, they map the approximate contact point between Ari3 and DNAAF9 that the confirm via mutagenesis and binding assays. Finally, the authors show that a GTP- bound Ari3 indeed has the capacity to dissociate a T. thermophila Shulin- ODA complex. I strongly support publication of the manuscript providing they address a few concerns I have, which may help to improve the manuscript prior to publication. + +Major concerns: + +1) With regard to "Taken together, these findings indicate that human DNAAF9 interacts with mammalian ODAs and maintains them in a closed conformation sharing its role as an inhibitor with its Tetrahymena ortholog Shulin", I wonder why the authors didn't test DNAAF9 in a gliding assay as they did previously (Mali et al., Science 2021)? Although the negative stain EM evidence is fairly strong, I'm not sure their findings "indicate" a role for DNAAF9 in inhibiting ODAs. Such an experiment would provide much stronger evidence that DNAAF9 indeed performs an analogous role to Shulin in ODA function. It would also provide support for the "inhibitory role" proposed in this sentence from the Discussion: "...we favour a model where the critical inhibitory role played by Shulin (DNAAF9) is central to stabilising IFT-ODA interactions for efficient transport into cilia." Without such evidence, the language would need to be changed to reflect this. + +2) Although I'm okay with the model in Figure 2i being presented as is, the data to support it is a bit thin (quantitative MS data). In particular, the model for dynein-1 transport of DNAAF9, although intriguing, may need more support. Do the authors see any cargo adaptor proteins in the MS data? Although not required, this would make this argument more convincing. + +<--- Page Split ---> + +Also, have the authors tried looking for dynein- 1 complex components in their EC vs MC pull- downs? + +3) I was a little confused by the back-and-forth between model systems. I think it's great that the authors included all these data, but my head started to spin by the last figure in particular. It would help if there was more explanation as to why they performed some experiments with human components, and others with T. thermophila proteins. For example, why didn't the authors test whether human Arl3 induces dissociation of the DNAAF9-ODA complex? + +## Minor points: + +1) Although I was able to guess which was which, the AF2 models for Shulin and DNAAF9 in Fig. S1 are not labeled. Please add labels. + +2) It seems that the sequence for T. thermophila Shulin is missing from Figure S2. If not, please label accordingly. If so, I think this would be a helpful point of comparison. + +3) The data presented in the Discussion should either be moved to the Results section (and described in detail) or removed from the paper entirely (and saved for a future paper). This includes Fig. S9 and 10. + +4) The paragraphs in the Discussion describing Oda16 and potential transport adaptors (line 366-390) seemed off-topic, and was a distraction to me as a reader. I had trouble finding out how this fit into the paper. I feel the same is true for their argument that DNAAF9 is a transport adaptor for IFT. I would suggest removing this part of the discussion and accompanying data in Figure S10 (save it for another paper) and simply focus on discussing the data within the results section. + +5) "Given these emerging links between ARL3 and the biogenesis of motile cilia, we recommend that primary ciliopathy patients carrying ARL3 variants should be additionally assessed for clinical features indicative of defective motile cilia." Maybe this is born from ignorance, but wouldn't primary ciliopathy patients already be assessed for potential clinical features of defective motile cilia? + +Reviewer #2 (Remarks to the Author): + +Issa et al. set out to determine the functional consequence of the interaction between DNAAF9 and the small g protein Arl3. The authors find that DNAAF9 (and its tetrahymena homolog Shulin) preferentially bind to GTP- bound Arl3. Arl3- DNAAF9 interaction displaces DNAAF9 from outer dynein arm complex, thus resulting in dynein activation in cilia. The motivation for this work is important, as ciliary beating defects causes ciliopathies and the findings were described clearly. Pending two important points below, I recommend this work for publication. + +## Major points: + +1. The authors use mutagenesis to try to validate the predicted interface between DNAAF9 and Arl3 (they make three mutations: F51A, Y77A, and Y81A). However, these mutations should be made in the Arl3-Q70L GTP-locked background, not the WT background. The data in Figure 3A shows that WT Arl3 that can GTP cycle doesn't really bind DNAAF9 (maybe there is a little shoulder that shows complex co-elution, but the interaction is not robust enough to see Arl3 on the SDS-PAGE gel in b). The authors should test if the Arl3-F51A, Y77A, Y81A mutant in the Q70L background has reduced affinity for DNAAF9. + +2. The data in Figure 5 is very important to the authors model but is the least convincing in the paper. The following points are important to fortify this data: + +a. The data in Figure 5d must be quantified, rather than just shown qualitatively. For example, the authors could measure the intensity of the bands of ODA heavy chain: Shulin in peak complex fractions with and without inclusion of Arl3. In fact, it is actually very challenging to tell if inclusion of Arl3 really does reduce Shulin-ODA interaction because there is significantly more total protein loaded on the gel for the experiment without Arl3. + +b. The GTPase dead Arl3 mutant or the Arl3 mutant variants that don't bind (but in the GTP-locked background) would be a great negative control for this study. + +c. Finally, the authors should show the SEC traces for the experiments with and without Arl3, as well as show gels that have the exact same fractions (and where they correspond to the SEC elution profile) for each experiment. It is hard to assess the quality of this data without seeing the traces and all the same corresponding fractions. + +## Minor points: + +1. Zoom in on figure 1d would be helpful to show the DNAA9 staining on the cilia. + +2. Can the authors report the \(\%\) open and \(\%\) closed ODA conformations with and without DNAAF9 (data in figure S5) to quantify the effect of DNAAF9 on ODA structure? + +Reviewer #3 (Remarks to the Author): + +Review of NSMB- A49966B + +The manuscript by Issa et al. from the Mali lab addresses a fundamental question in ciliary biology. More specifically, how + +<--- Page Split ---> + +are the multimeric axonemal dyneins assembled and maintained in the cytoplasm in an inactive form and then activated once they enter cilia and flagella and attach to the outer doublet microtubules. In previous work the authors identified a dynein chaperone known as Shulin that maintains outer dynein arms (ODAs) in an inactive conformation in the cytoplasm and co- localizes with ODAs in regenerating Tetrahymena cilia. In the present study they ask (1) whether this inhibitory mechanism is conserved in Shulin orthologs such as the human DNAAF9, (2), whether it interacts with transport factors to target ODAs to cilia, and (3) how is Shulin/DNAAF9 released from ODAs inside cilia to allow ODA activation? + +Most significant findings: + +Other studies had shown that DNAAF9 could be pulled down with the small GTPase ARL3, which suggested that DNAAF9 might be involved in the ciliary transport of ODAs. The authors used AlphaFold 2 (AF2) analyses to compare the structures and sequences of Shulin and DNAAF9 (Figures S1, S2). These analyses identified several conserved domains with significant structural similarity that could be involved in binding to ODAs during transport. The authors test this model using human airway epithelial cells cultured at an air- liquid interface to induce differentiation of basal cells into multiciliated cells (Figure 1). Consistent with their hypothesis that Shulin and DNAAF9 share a similar function, they observed that DNAAF9 enters growing motile cilia in differentiating airway cells (Fig 1d, e). Similar results were observed using zebrafish embryos (Figure S3). + +To gain a better understanding into the mechanism by which DNAAF9/Shulin might facilitate the transport of ODAs, they used immunoprecipitation, TMT labeling, and mass spectrometry to identify interacting proteins (Figure 2, Supplemental Datafile 1). This identified more than 87 proteins found at different stages of differentiation, including ODA subunits, IFT- B subunits, ciliary tip proteins, and ARL3. The proteomics work appears to be rigorous, and the major take- home are nicely summarized in their Figure 2, but I would have liked to have seen more detailed explanation of their results in the Supplemental Datafile 1. If I understand their methods correctly, the IPs were performed using total cell lysates and not purified cilia. Thus, the model proposed in Figure 2i is an inference based on the results from total cell lysates. However, they test several key points of their model using a clever series of in vitro binding experiments. + +To test the hypothesis that ARL3 might regulate that activity of DNAAF9 and Shulin, they expressed recombinant DNAAF9 and Tetrahymena ARL3 in its GTP and GDP mimicking states using Q70L and T30N variants respectively. They found that all Arl3 variants co- eluted with DNAAF9 in high GTP (Fig. S6) but only Arl3Q70L binds DNAAF9 in the presence of GDP (Figure 3). Using this Arl3 variant as bait and lysates of Tetrahymena cells undergoing ciliary regeneration, they co- immunoprecipitated several known effectors of Arl3 and Shulin (Figure 3), suggesting that Arl3 is likely to regulate transport of ODAs through its interaction with Shulin. + +The authors extended this work by analyzing the interaction between recombinant DNAAF9 (or Shulin) in complex with ArlQ70L in vitro by negative stain electron microscopy (Figure 4, Fig. S7). Single particle averaging identified a subset of images ( \(\sim 50\%\) ) containing a DNAAF9/Shulin- Arl3 complex, with the ARL3 subunit bound to the N1 domain of DNAAF9/Shulin. Analytical chromatography confirmed that this interaction was most stable using the Arl3Q70L variant. They extended these observations using AF2 to model the interaction interface and then disrupted the interaction using specific ARL3 mutations (Figure 4e). Further modeling using AF3 suggests that ARL3 interacts with DNAAF9 in the presence of GTP but not GDP (Fig. S8). Additional in vitro studies demonstrate that ARL3 and can disrupt the interaction between purified Shulin and ODAs in the presence of GTP (Figure 5). + +## Overall Evaluation and Significance + +In summary, the authors combine sophisticated modeling, well executed proteomics, and elegant in vitro studies to test a new model of how the ARL3 GTPase might regulate the interaction between a dynein chaperone and the ODAs to maintain the ODAs in an inactive state in the cytoplasm and release and activate the ODAs upon entry into the cilia. The experimental logic is clearly described, the experiments are well executed, and the suggested mechanism of regulation for dynein activation in vivo is a novel, exciting hypothesis. Future in vivo studies will be needed to determine the precise timing and location of ODA activation, but the work presented here is an exciting step forward. I think the work will be of broad interest to people working in the field of motor activation and targeting, and I highly recommend publication. + +Version 3: + +Decision Letter: + +23rd May 2025 + +Dear Girish, + +Thank you again for alerting us to the issue with data in S3df in your manuscript "Molecular basis for the activation of outer dynein arms in cilia". + +I have now discussed this matter with our Editorial Director. + +We thank you for bringing to our attention the use of an incorrect myc construct in experiments underlying the data in S3df. Following our internal assessment and given the need to provide new data and remove present data, we regret that we are unable to proceed with the acceptance in principle of the current version of the manuscript. + +<--- Page Split ---> + +We are open to reconsidering the manuscript on the condition that revised data in full compliance with our policies are provided. 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They speculate that DNAAF9 is a likely homolog to the T. thermophila Shulin protein, which their previous work demonstrated was an important effector of OAD's autoinhibited state. They find that DNAAF9 localizes to the developing cilia of human airway epithelial cells (but not to mature cilia), co- IPs with OAD components (eg. DNAI2), and its addition to purified OAD causes a change in conformation to a 'closed'/presumably autoinhibited state. The authors then focus on testing the hypothesis that the Arl3 GTPase releases ODA from DNAAF9 in a GTP- dependent manner. They find Arl3 from human and T. thermophila both bind to DNAAF9/Shulin. Using negative stain EM and AF2, they map the approximate contact point between Arl3 and DNAAF9 that the confirm via mutagenesis and binding assays. Finally, the authors show that a GTP- bound Arl3 indeed has the capacity to dissociate a T. thermophila Shulin- ODA complex. I strongly support publication of the manuscript providing they address a few concerns I have, which may help to improve the manuscript prior to publication. + +## Major concerns: + +1) With regard to "Taken together, these findings indicate that human DNAAF9 interacts with mammalian ODAs and maintains them in a closed conformation sharing its role as an inhibitor with its Tetrahymena ortholog Shulin", I wonder why the authors didn't test DNAAF9 in a gliding assay as they did previously (Mali et al., Science 2021)? Although the negative stain EM evidence is fairly strong, I'm not sure their findings "indicate" a role for DNAAF9 in inhibiting ODAs. Such an experiment would provide much stronger evidence that DNAAF9 indeed performs an analogous role to Shulin in ODA function. It would also provide support for the "inhibitory role" proposed in this sentence from the Discussion: "...we favour a model where the critical inhibitory role played by Shulin (DNAAF9) is central to stabilising IFT-ODA interactions for efficient transport into cilia." Without such evidence, the language would need to be changed to reflect this. + +This is an important point and although we agree that functional assays such as a gliding assay would directly support DNAAF9's inhibitory role on mammalian ODAs, currently it is + +<--- Page Split ---> + +technically impossible to conduct such assays using mammalian ODA motors. Two key limitations prevent this. + +a) Obtaining functionally intact mammalian axonemal ODA motor complexes of sufficient purity and in sufficient quantities remains a major technical bottleneck in the dynein field. Hence, all displacement experiments were performed using purified Tetrahymena ODAs. +b) Methods for reconstituting axonemal dynein's using recombinant subunits obtained from heterologous expression systems (ex. insect cell-baculovirus) have not been developed. We think this is due to the still poorly understood chaperoning requirements that appear to be specific for the biosynthesis of axonemal dyneins. + +To reflect this limitation, we have changed the language by focusing the last paragraph more on Shulin and added the below sentence (lines 432- 435). + +"Although our observation that pig ODAs adopt a closed conformation in the presence of DNAAF9 could hint at its inhibitory role in mammalian ODAs (similar to Shulin in Tetrahymena ODAs), more functional assays using mammalian ODAs are needed to directly test this in the future." + +2) Although I'm okay with the model in Figure 2i being presented as is, the data to support it is a bit thin (quantitative MS data). In particular, the model for dynein-1 transport of DNAAF9, although intriguing, may need more support. Do the authors see any cargo adaptor proteins in the MS data? Although not required, this would make this argument more convincing. Also, have the authors tried looking for dynein-1 complex components in their EC vs MC pull-downs? + +We do not detect known dynein- 1 cargo adaptors in the dataset. However, we detect dynein- 1 light intermediate chain (DYNC1LI2) and intermediate chain (DYNC1I2) subunits in EC vs MC IPs with differential enrichments. These are shown in the scatter plots (Fig. 2a, b) and the dot plot (Fig. 2f). We have amended the text as below to emphasize that the connection to dynein- 1 transport needs further support (lines 223- 225). We have also added question marks in Fig. 2e and 2i to emphasize this point and updated the figure legend accordingly. + +"ODAs then reach the peri-basal body pool. Apical enrichment around the basal body could be achieved via the dynein- 1 transport machinery or another mechanism. More work is needed to address this" + +3) I was a little confused by the back-and-forth between model systems. I think it's great that the authors included all these data, but my head started to spin by the last figure in particular. It would help if there was more explanation as to why they performed some experiments with + +<--- Page Split ---> + +human components, and others with T. thermophila proteins. For example, why didn't the authors test whether human Arl3 induces dissociation of the DNAAF9- ODA complex? + +We performed cross- species interaction studies to highlight that the interaction between DNAAF9 and ARL3 is evolutionarily conserved. Technical limitations of obtaining human/mammalian ODAs restricted us to using Tetrahymena ODAs for the reconstitutions and subsequent displacement experiments. These were performed using Tetrahymena proteins. We have included the below sentence to explain this point (lines 875- 876). + +"Displacement assays were performed using ODAs purified from isolated Tetrahymena cilia and Tetrahymena Shulin due to technical limitations in purifying mammalian ODAs" + +To address the point of going back- and- forth between model systems (and also point #2 raised by reviewer #2) more thoroughly, we performed new reconstitutions under 1mM GTP or 1mM GDP conditions as detailed below: + +1. Human DNAAF9 + Human ARL3Q71L +2. Human DNAAF9 + Human ARL3T31N +3. Human DNAAF9 + Human ARL3Q71L-FYY +4. Tetrahymena Shulin + Tetrahymena Arl3Q70L +5. Tetrahymena Shulin + Tetrahymena Arl3T30N +6. Tetrahymena Shulin + Tetrahymena Arl3Q70L-FYY + +These new data are consistent with our previous finding of a cross- species interaction between human DNAAF9 and Tetrahymena Arl3. We have incorporated these new data into updated Fig. S10 and updated the text describing these data (lines 270- 272). + +## Minor points: + +1) Although I was able to guess which was which, the AF2 models for Shulin and DNAAF9 in Fig. S1 are not labeled. Please add labels. + +We have now labelled these in Fig. S1. + +2) It seems that the sequence for T. thermophila Shulin is missing from Figure S2. If not, please label accordingly. If so, I think this would be a helpful point of comparison. + +The sequence for Shulin was labelled with its UniProt ID (Q22YU3_TETTS). We have relabelled to include the name Shulin and added the names with corresponding Uniprot IDs in the figure legend. + +<--- Page Split ---> + +3) The data presented in the Discussion should either be moved to the Results section (and described in detail) or removed from the paper entirely (and saved for a future paper). This includes Fig. S9 and 10. + +We have retained the data showing the hydrocephalus phenotype as it supports a role for DNAAF9 in motile cilia functions. Text relating to this data has been incorporated into the main results section (lines 192- 200) and updated in the discussion (lines 402- 403). Fig. S6 replaces the old Fig. S9. Fig. S7 replaces the old Fig. S10 (detailed in point 4 below). The numbering of subsequent supplementary figures has been updated accordingly. + +4) The paragraphs in the Discussion describing Oda16 and potential transport adaptors (line 366-390) seemed off-topic and was a distraction to me as a reader. I had trouble finding out how this fit into the paper. I feel the same is true for their argument that DNAAF9 is a transport adaptor for IFT. I would suggest removing this part of the discussion and accompanying data in Figure S10 (save it for another paper) and simply focus on discussing the data within the results section. + +We have removed the Oda16 data and text describing potential transport adaptors from the manuscript (previous lines 366- 390). We have retained the IFT binding data as it validates the interaction with IFT74 and IFT81 detected by endogenous IP- MS. Text relating to this data has been incorporated in the main results section (lines 213- 219) and the discussion (lines 409- 413). Fig. S7 replaces the old Fig. S10. + +5) "Given these emerging links between ARL3 and the biogenesis of motile cilia, we recommend that primary ciliopathy patients carrying ARL3 variants should be additionally assessed for clinical features indicative of defective motile cilia." Maybe this is born from ignorance, but wouldn't primary ciliopathy patients already be assessed for potential clinical features of defective motile cilia? + +We have rephrased this sentence as below (lines 423- 424). + +"Further work is needed to dissect the emerging links between ARL3 and its effector proteins in the trafficking of motility- related cargoes during motile cilia formation." + +<--- Page Split ---> + +## Reviewer 2 [Referee expertise: dynein, structural biology] + +Issa et al. set out to determine the functional consequence of the interaction between DNAAF9 and the small g protein Arl3. The authors find that DNAAF9 (and its tetrahymena homolog Shulin) preferentially bind to GTP- bound Arl3. Arl3- DNAAF9 interaction displaces DNAAF9 from outer dynein arm complex, thus resulting in dynein activation in cilia. The motivation for this work is important, as ciliary beating defects causes ciliopathies and the findings were described clearly. Pending two important points below, I recommend this work for publication. + +## Major points: + +1. The authors use mutagenesis to try to validate the predicted interface between DNAAF9 and Arl3 (they make three mutations: F51A, Y77A, and Y81A). However, these mutations should be made in the Arl3-Q70L GTP-locked background, not the WT background. The data in Figure 3A shows that WT Arl3 that can GTP cycle doesn't really bind DNAAF9 (maybe there is a little shoulder that shows complex co-elution, but the interaction is not robust enough to see Arl3 on the SDS-PAGE gel in b). The authors should test if the Arl3-F51A, Y77A, Y81A mutant in the Q70L background has reduced affinity for DNAAF9. + +This is an important point. To address this, we reconstituted DNAAF9 with human ARL3Q71L or ARL3Q71L- FYY and Shulin with Tetrahymena Arl3Q70L or Arl3Q70L- FYY; (FYY = interface triple mutant on a QL GTP-locked background). These data showed that the FYY interface triple mutants on GTP-locked QL backgrounds have reduced affinities for DNAAF9 and Shulin proteins respectively compared to the QL variants alone in both species. We have included these new data in Fig. 4 (new panel e) and Fig. S10. + +2. The data in Figure 5 is very important to the authors model but is the least convincing in the paper. The following points are important to fortify this data: + +a. The data in Figure 5d must be quantified, rather than just shown qualitatively. For example, the authors could measure the intensity of the bands of ODA heavy chain: Shulin in peak complex fractions with and without inclusion of Arl3. In fact, it is actually very challenging to tell if inclusion of Arl3 really does reduce Shulin-ODA interaction because there is significantly + +<--- Page Split ---> + +more total protein loaded on the gel for the experiment without Arl3. b. The GTPase dead Arl3 mutant or the Arl3 mutant variants that don't bind (but in the GTP- locked background) would be a great negative control for this study. + +We conducted new reconstitution, and displacement experiments and quantified these data using gel densitometry. These have now been included in a new Fig. 5. The original Fig. 5 has been replaced by a new Fig. 6 which presents our overall proposed model. We have also updated the relevant methods section (lines 875- 888). Briefly, we reconstituted Tetrahymena ODAs with Shulin. The reconstituted ODA- Shulin complex was divided equally into two fractions to test the impact of Arl3 in displacing Shulin. The ODA- Shulin complex fractions were incubated with either \(\mathrm{Arl3^{Q70L}}\) (active GTP- locked variant) or \(\mathrm{Arl3^{Q70L - FYY}}\) (interface mutant on a QL background) as a negative control. Gel densitometry analyses were performed on replicate runs to calculate the Shulin:ODA heavy chain and Shulin:ODA IC2 ratios for each of the three experimental conditions. + +These new data and analyses (included in new Fig. 5) show that reduced levels of Shulin co- elute with the ODA complex in the presence of the \(\mathrm{Arl3^{Q70L}}\) variant compared to in the presence of \(\mathrm{Arl3^{Q70L - FYY}}\) mutant which has reduced affinity for Shulin. Overall, this suggests that Shulin gets displaced from ODAs by \(\mathrm{Arl3^{Q70L}}\) (i.e., active Arl3) and is sequestered in a complex with \(\mathrm{Arl3^{Q70L}}\) . + +c. Finally, the authors should show the SEC traces for the experiments with and without Arl3, as well as show gels that have the exact same fractions (and where they correspond to the SEC elution profile) for each experiment. It is hard to assess the quality of this data without seeing the traces and all the same corresponding fractions. + +Gel filtration traces for reconstitution and displacement experiments with corresponding gels are included in new Fig. 5. + +Minor points: + +1. Zoom in on figure 1d would be helpful to show the DNAA9 staining on the cilia. + +We have added zoomed panels to show the DNAA9 and DNAI2 staining in cilia in Fig.1d and updated the figure legend. + +2. Can the authors report the % open and % closed ODA conformations with and without DNAA9 (data in figure S5) to quantify the effect of DNAA9 on ODA structure? + +<--- Page Split ---> + +We have added the percentages for open and closed conformations for ODA alone and for ODA mixed with DNAAF9. Text in the legend for Fig. S5 and the relevant methods section (lines 901- 907) has been updated. + +## Reviewer 3 [Referee expertise: cilia] + +The manuscript by Issa et al. from the Mali lab addresses a fundamental question in ciliary biology. More specifically, how are the multimeric axonemal dyneins assembled and maintained in the cytoplasm in an inactive form and then activated once they enter cilia and flagella and attach to the outer doublet microtubules. In previous work the authors identified a dynein chaperone known as Shulin that maintains outer dynein arms (ODAs) in an inactive conformation in the cytoplasm and co- localizes with ODAs in regenerating Tetrahymena cilia. In the present study they ask (1) whether this inhibitory mechanism is conserved in Shulin orthologs such as the human DNAAF9, (2), whether it interacts with transport factors to target ODAs to cilia, and (3) how is Shulin/DNAAF9 released from ODAs inside cilia to allow ODA activation? + +Most significant findings: + +Other studies had shown that DNAAF9 could be pulled down with the small GTPase ARL3, which suggested that DNAAF9 might be involved in the ciliary transport of ODAs. The authors used AlphaFold 2 (AF2) analyses to compare the structures and sequences of Shulin and DNAAF9 (Figures S1, S2). These analyses identified several conserved domains with significant structural similarity that could be involved in binding to ODAs during transport. The authors test this model using human airway epithelial cells cultured at an air- liquid interface to induce differentiation of basal cells into multiciliated cells (Figure 1). Consistent with their hypothesis that Shulin and DNAAF9 share a similar function, they observed that DNAAF9 enters growing motile cilia in differentiating airway cells (Fig 1d, e). Similar results were observed using zebrafish embryos (Figure S3). + +To gain a better understanding into the mechanism by which DNAAF9/Shulin might facilitate the transport of ODAs, they used immunoprecipitation, TMT labeling, and mass spectrometry to identify interacting proteins (Figure 2, Supplemental Datafile 1). This identified more than 87 proteins found at different stages of differentiation, including ODA subunits, IFT- B subunits, ciliary tip proteins, and ARL3. The proteomics work appears to be rigorous, and the major take- homes are nicely summarized in their Figure 2, but I would have liked to have seen more + +<--- Page Split ---> + +detailed explanation of their results in the Supplemental Datafile 1. If I understand their methods correctly, the IPs were performed using total cell lysates and not purified cilia. Thus, the model proposed in Figure 2i is an inference based on the results from total cell lysates. However, they test several key points of their model using a clever series of in vitro binding experiments. + +To test the hypothesis that ARL3 might regulate that activity of DNAAF9 and Shulin, they expressed recombinant DNAAF9 and Tetrahymena ARL3 in its GTP and GDP mimicking states using Q70L and T30N variants respectively. They found that all Arl3 variants co- eluted with DNAAF9 in high GTP (Fig. S6) but only Arl3Q70L binds DNAAF9 in the presence of GDP (Figure 3). Using this Arl3 variant as bait and lysates of Tetrahymena cells undergoing ciliary regeneration, they co- immunoprecipitated several known effectors of Arl3 and Shulin (Figure 3), suggesting that Arl3 is likely to regulate transport of ODAs through its interaction with Shulin. + +The authors extended this work by analyzing the interaction between recombinant DNAAF9 (or Shulin) in complex with ArlQ70L in vitro by negative stain electron microscopy (Figure 4, Fig. S7). Single particle averaging identified a subset of images ( \(\sim 50\%\) ) containing a DNAAF9/Shulin- Arl3 complex, with the ARL3 subunit bound to the N1 domain of DNAAF9/Shulin. Analytical chromatography confirmed that this interaction was most stable using the Arl3Q70L variant. They extended these observations using AF2 to model the interaction interface and then disrupted the interaction using specific ARL3 mutations (Figure 4e). Further modeling using AF3 suggests that ARL3 interacts with DNAAF9 in the presence of GTP but not GDP (Fig. S8). Additional in vitro studies demonstrate that ARL3 and can disrupt the interaction between purified Shulin and ODAs in the presence of GTP (Figure 5). + +## Overall Evaluation and Significance + +In summary, the authors combine sophisticated modeling, well executed proteomics, and elegant in vitro studies to test a new model of how the ARL3 GTPase might regulate the interaction between a dynein chaperone and the ODAs to maintain the ODAs in an inactive state in the cytoplasm and release and activate the ODAs upon entry into the cilia. The experimental logic is clearly described, the experiments are well executed, and the suggested mechanism of regulation for dynein activation in vivo is a novel, exciting hypothesis. Future in vivo studies will be needed to determine the precise timing and location of ODA activation, but the work presented here is an exciting step forward. I think the work will be of broad interest + +<--- Page Split ---> + +to people working in the field of motor activation and targeting, and I highly recommend publication. + +We thank the reviewer for their helpful overall evaluation of our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd b/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..bb0ba894fe54730e01469d893606e58cc94ebc7c --- /dev/null +++ b/peer_reviews/9c19a0d63e6a06a8342aa6046ef7d991ce998be94a0433d98addc78ef529cde7/supplementary_1_Peer Review File/supplementary_1_Peer Review File_det.mmd @@ -0,0 +1,783 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 118]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 161, 863, 208]]<|/det|> +# Molecular basis for the activation of outer dynein arms in cilia + +<|ref|>text<|/ref|><|det|>[[73, 224, 393, 240]]<|/det|> +Corresponding Author: Dr Girish Mali + +<|ref|>text<|/ref|><|det|>[[73, 275, 145, 288]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 301, 182, 314]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[73, 327, 171, 340]]<|/det|> +30th Oct 2024 + +<|ref|>text<|/ref|><|det|>[[73, 353, 168, 366]]<|/det|> +Dear Dr. Mali, + +<|ref|>text<|/ref|><|det|>[[72, 379, 910, 419]]<|/det|> +Thank you for submitting your manuscript "Molecular basis for the activation of outer dynein arms in cilia". We have now carefully evaluated the work and discussed it among the editorial team. Unfortunately, we have decided not to consider the manuscript further for publication in Nature Structural & Molecular Biology. + +<|ref|>text<|/ref|><|det|>[[72, 430, 897, 483]]<|/det|> +We can only consider a small proportion of the manuscripts submitted to our journal and are often forced to make difficult decisions. Manuscripts are evaluated editorially for their potential interest to a broad audience, the level of novel insight obtained and whether the findings represent a significant advance relative to the published literature, among other considerations. + +<|ref|>text<|/ref|><|det|>[[72, 496, 912, 589]]<|/det|> +In this case, we are interested in this area of research and appreciate the potential role for a Shulin- Arl3 complex in regulating Shulin and its rebinding to ODAs. We recognize that the findings will be of value to others working in this area. However, after discussion among the editorial staff, I am afraid we are not persuaded that the level of mechanistic insight and degree of conceptual advance obtained warrants publication in Nature Structural & Molecular Biology, after taking into account relevant published work [including, but not limited to, studies suggesting that DNAAF9 may bind to ARL3; other work showing that Arl3 binds to another potential ODA transport adaptor, Oda16, with Oda16 proposed to act as an effector in ciliary transport] + +<|ref|>text<|/ref|><|det|>[[72, 600, 912, 665]]<|/det|> +Although we cannot offer to publish your manuscript, I suggest that you consider Nature Communications as a suitable venue for this work. To transfer your manuscript, please use our manuscript transfer portal. You will not have to re- supply manuscript metadata and files, unless you wish to make modifications. For more information, please see our manuscript transfer FAQ page. + +<|ref|>text<|/ref|><|det|>[[70, 676, 904, 704]]<|/det|> +I am sorry we could not be more positive on this occasion. We thank you for the opportunity to consider this work and wish you success in seeking publication elsewhere. + +<|ref|>text<|/ref|><|det|>[[73, 717, 142, 730]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[72, 743, 460, 795]]<|/det|> +Melina Casadio, PhD Consulting Editor, Nature Structural & Molecular Biology Senior Editor, Nature Cell Biology ORCID ID: https://orcid.org/0000- 0003- 2389- 2243 + +<|ref|>text<|/ref|><|det|>[[70, 820, 803, 835]]<|/det|> +\*\* For Springer Nature Limited general information and news for authors, see http://npg.nature.com/authors. + +<|ref|>text<|/ref|><|det|>[[73, 847, 144, 860]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 873, 182, 886]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[73, 899, 167, 911]]<|/det|> +4th Dec 2024 + +<|ref|>text<|/ref|><|det|>[[73, 925, 168, 938]]<|/det|> +Dear Dr. Mali, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 59, 920, 113]]<|/det|> +Thank you for your letter concerning your manuscript "Molecular basis for the activation of outer dynein arms in cilia". We really appreciate your patience with the process and are sorry we cannot prioritize appeals over new submissions. We have now had a chance to discuss the points you raised in detail, and we have decided to send your paper out to review. Prior to peer review, please see the points below to prepare the files necessary for peer review: + +<|ref|>text<|/ref|><|det|>[[73, 125, 923, 166]]<|/det|> +1- We want to ensure that the methods and statistics reporting in our papers are of the highest quality. To that end, we ask authors to fill out a Reporting Summary that collects information on experimental design and reagents, as well as an editorial Policy Checklist, which confirms compliance with our editorial policies, including the declaration of Competing Interests. + +<|ref|>text<|/ref|><|det|>[[73, 177, 488, 191]]<|/det|> +These documents can be found by following the links below: + +<|ref|>text<|/ref|><|det|>[[73, 204, 515, 232]]<|/det|> +Reporting Summary: https://www.nature.com/documents/nr-reporting-summary.pdf + +<|ref|>text<|/ref|><|det|>[[73, 244, 528, 271]]<|/det|> +Editorial Policy Checklist: https://www.nature.com/documents/nr- editorial- policy- checklist.pdf + +<|ref|>text<|/ref|><|det|>[[73, 282, 909, 335]]<|/det|> +Please complete the relevant forms and include them with your files for peer review. Please note that these forms are dynamic 'smart pdfs' and must, therefore, be downloaded and completed in Adobe Reader. We will then flatten them for ease of use by the reviewers. If you would like to reference the guidance text as you complete the template, please access these flattened versions at http://www.nature.com/authors/policies/availability.html. + +<|ref|>text<|/ref|><|det|>[[73, 346, 909, 386]]<|/det|> +Note that you are not required to revise your paper to include the information provided in the reporting summary. However, all points on the policy checklist must be addressed; please include a new version of the manuscript with your completed checklist if needed. + +<|ref|>text<|/ref|><|det|>[[73, 398, 910, 425]]<|/det|> +Once we receive these documents and review them to ensure that all requested information is provided, we will proceed to send your paper for review. If you have questions or anticipate delays, please let me know as soon as possible. + +<|ref|>text<|/ref|><|det|>[[70, 437, 900, 465]]<|/det|> +2- Proteomics datasets should be deposited and made available to the reviewers at a minimum. Please clarify where the mass spectrometry datasets can be accessed with your resubmission. + +<|ref|>text<|/ref|><|det|>[[73, 476, 916, 518]]<|/det|> +3- When preparing your revised manuscript including the appeal data, please note that, if any personal communications are included, you would need to forward an email permission to us stating that the persons who made these communications to you approve their inclusions in this particular manuscript. Please let me know if you have any questions. + +<|ref|>text<|/ref|><|det|>[[73, 542, 658, 555]]<|/det|> +You can use the link below to be taken directly to the site and submit your manuscript: + +<|ref|>text<|/ref|><|det|>[[73, 568, 175, 581]]<|/det|> +Link Redacted + +<|ref|>text<|/ref|><|det|>[[73, 607, 144, 620]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[73, 633, 121, 645]]<|/det|> +Melina + +<|ref|>text<|/ref|><|det|>[[73, 658, 460, 710]]<|/det|> +Melina Casadio, PhD Consulting Editor, Nature Structural & Molecular Biology Senior Editor, Nature Cell Biology ORCID ID: https://orcid.org/0000- 0003- 2389- 2243 + +<|ref|>text<|/ref|><|det|>[[73, 763, 144, 775]]<|/det|> +Version 2: + +<|ref|>text<|/ref|><|det|>[[73, 789, 181, 802]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[73, 815, 168, 828]]<|/det|> +24th Jan 2025 + +<|ref|>text<|/ref|><|det|>[[73, 841, 165, 854]]<|/det|> +Dear Dr Mali, + +<|ref|>text<|/ref|><|det|>[[73, 866, 915, 920]]<|/det|> +Thank you again for submitting your manuscript "Molecular basis for the activation of outer dynein arms in cilia". I apologize for the delay in responding, which resulted from the difficulty in obtaining suitable referee reports. We now have comments (below) from the 3 reviewers who evaluated your paper. In light of those reports, we remain interested in your study and would like to see your response to the comments of the referees in the form of a revised manuscript. + +<|ref|>text<|/ref|><|det|>[[70, 931, 914, 946]]<|/det|> +To guide the scope of the revisions, we list below a prioritized set of referee points that should be addressed in the revision, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[70, 46, 895, 75]]<|/det|> +which we hope will be helpful to you. You will see that the reviewers found the model interesting but asked for additional evidence to support it, as well as clarifications: + +<|ref|>text<|/ref|><|det|>[[72, 85, 900, 127]]<|/det|> +- In revision, please strengthen the mechanism of Shulin-ODA complex regulation by Arl3 (Rev#2 point #2 – please also see Rev#1 point #1 to strengthen the functional implications for DNAAF9) and the studies characterizing the binding between DNAAF9 and Arl3 (Rev#2 point #1) + +<|ref|>text<|/ref|><|det|>[[70, 138, 888, 166]]<|/det|> +- Please address all minor points and suggestions to strengthen the current dataset including Rev#1's point #2; please address Rev#1's questions in point #3 about the various models used. + +<|ref|>text<|/ref|><|det|>[[72, 177, 921, 245]]<|/det|> +We are committed to providing a fair and constructive peer- review process. Do not hesitate to contact us if there are specific requests from the reviewers that you believe are technically impossible or unlikely to yield a meaningful outcome. Please be sure to address/respond to all concerns of the referees in full in a point- by- point response and highlight all changes in the revised manuscript text file. If you have comments that are intended for editors only, please include those in a separate cover letter. + +<|ref|>text<|/ref|><|det|>[[72, 255, 921, 309]]<|/det|> +Our standard revision period is 3 to 6 months. If you cannot send it within this time, please let us know. We will be happy to consider your revision as long as nothing similar has been accepted for publication at NSMB or published elsewhere. Should your manuscript be substantially delayed without notifying us in advance and your article is eventually published, the received date would be that of the revised, not the original, version. + +<|ref|>text<|/ref|><|det|>[[72, 320, 916, 362]]<|/det|> +As you already know, we put great emphasis on ensuring that the methods and statistics reported in our papers are correct and accurate. As such, if there are any changes that should be reported, please submit an updated version of the Reporting Summary along with your revision. + +<|ref|>text<|/ref|><|det|>[[72, 373, 491, 401]]<|/det|> +Reporting Summary: https://www.nature.com/documents/nr- reporting- summary.pdf + +<|ref|>text<|/ref|><|det|>[[70, 411, 884, 426]]<|/det|> +Please note that the form is a dynamic 'smart pdf' and must therefore be downloaded and completed in Adobe Reader. + +<|ref|>text<|/ref|><|det|>[[72, 437, 914, 478]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +<|ref|>text<|/ref|><|det|>[[72, 490, 876, 530]]<|/det|> +- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. +- that control panels for gels and western blots are appropriately described as loading on sample processing controls +- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +<|ref|>sub_title<|/ref|><|det|>[[73, 541, 281, 555]]<|/det|> +## EXTENDED DATA FIGURES + +<|ref|>text<|/ref|><|det|>[[72, 567, 914, 635]]<|/det|> +When re- submitting your manuscript, please ensure that any supplementary figures and tables that are crucial to the manuscript's conclusions are converted into Extended Data figures and tables to increase visibility of these data. Extended Data figures and tables are online- only (present in the online PDF and full- text HTML versions of the paper), peer- reviewed display items that provide essential background to the article but are not included in the main article due to space constraints. A maximum of ten Extended Data display items (figures and tables) is permitted. + +<|ref|>text<|/ref|><|det|>[[70, 645, 916, 673]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[70, 684, 914, 712]]<|/det|> +If there are additional or modified structures presented in the final revision, please submit the corresponding PDB validation reports. + +<|ref|>text<|/ref|><|det|>[[72, 723, 920, 777]]<|/det|> +Please note that all key data shown in the main figures as cropped gels or blots should be presented in uncropped form, with molecular weight markers. These data can be aggregated into a single supplementary figure. While these data can be displayed in a relatively informal style, they must refer back to the relevant figures. These data should be submitted with the last revision, prior to acceptance, but you may want to start putting it together at this point. + +<|ref|>text<|/ref|><|det|>[[72, 788, 916, 880]]<|/det|> +SOURCE DATA: we urge authors to provide, in tabular form, the data underlying the graphical representations used in figures. This is to further increase transparency in data reporting, as detailed in this editorial (http://www.nature.com/nsmb/journal/v22/n10/full/nsmb.3110. html). Spreadsheets can be submitted in excel format. Only one (1) file per figure is permitted; thus, for multi- paneled figures, the source data for each panel should be clearly labeled in the Excel file; alternately the data can be provided as multiple, clearly labeled sheets in an Excel file. When submitting files, the title field should indicate which figure the source data pertains to. We encourage our authors to provide source data at the revision stage, so that they are part of the peer- review process. + +<|ref|>text<|/ref|><|det|>[[70, 892, 914, 920]]<|/det|> +While we encourage the use of color in preparing figures, please note that this will incur a charge to partially defray the cost of printing. Information about color charges can be found at http://www.nature.com/nsmb/authors/submit/index.html#costs + +<|ref|>text<|/ref|><|det|>[[70, 931, 916, 945]]<|/det|> +We require deposition of coordinates (and, in the case of crystal structures, structure factors) into the Protein Data Bank with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 128]]<|/det|> +the designation of immediate release upon publication (HPUB). Electron microscopy- derived density maps and coordinate data must be deposited in EMDB and released upon publication. Deposition and immediate release of NMR chemical shift assignments are highly encouraged. Deposition of deep sequencing and microarray data is mandatory, and the datasets must be released prior to or upon publication. To avoid delays in publication, dataset accession numbers must be supplied with the final accepted manuscript and appropriate release dates must be indicated at the galley proof stage. Please find the complete NRG policies on data availability at http://www.nature.com/authors/policies/availability.html. + +<|ref|>text<|/ref|><|det|>[[72, 138, 923, 230]]<|/det|> +Nature Structural & Molecular Biology is committed to improving transparency in authorship. As part of our efforts in this direction, we are now requesting that all authors identified as 'corresponding author' on published papers create and link their Open Researcher and Contributor Identifier (ORCID) with their account on the Manuscript Tracking System (MTS), prior to acceptance. This applies to primary research papers only. ORCID helps the scientific community achieve unambiguous attribution of all scholarly contributions. You can create and link your ORCID from the home page of the MTS by clicking on 'Modify my Springer Nature account'. For more information please visit please visit www.springernature.com/orcid. + +<|ref|>text<|/ref|><|det|>[[72, 241, 601, 256]]<|/det|> +Please use the link below to submit your revised manuscript and related files: + +<|ref|>text<|/ref|><|det|>[[73, 269, 175, 283]]<|/det|> +Link Redacted + +<|ref|>text<|/ref|><|det|>[[72, 295, 881, 336]]<|/det|> +Note: This URL links to your confidential home page and associated information about manuscripts you may have submitted, or that you are reviewing for us. If you wish to forward this email to co- authors, please delete the link to your homepage. + +<|ref|>text<|/ref|><|det|>[[72, 345, 780, 361]]<|/det|> +We look forward to seeing the revised manuscript and thank you for the opportunity to review your work. + +<|ref|>text<|/ref|><|det|>[[73, 372, 142, 386]]<|/det|> +Sincerely, + +<|ref|>text<|/ref|><|det|>[[72, 397, 473, 438]]<|/det|> +Melina Casadio, PhD Locum Chief Editor, Nature Structural & Molecular Biology ORCID ID: https://orcid.org/0000- 0003- 2389- 2243 + +<|ref|>text<|/ref|><|det|>[[73, 461, 201, 475]]<|/det|> +Referee expertise: + +<|ref|>text<|/ref|><|det|>[[73, 488, 206, 501]]<|/det|> +Referee #1: dynein + +<|ref|>text<|/ref|><|det|>[[73, 514, 330, 528]]<|/det|> +Referee #2: dynein, structural biology + +<|ref|>text<|/ref|><|det|>[[73, 540, 188, 554]]<|/det|> +Referee #3: cilia + +<|ref|>text<|/ref|><|det|>[[73, 565, 234, 579]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[73, 591, 332, 605]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 616, 920, 777]]<|/det|> +This is an excellent manuscript with very clearly stated hypotheses and satisfying answers to the questions posed. In brief, the authors follow up on a 2021 manuscript in which they initially described Shulin's biochemical and biological activity along with a high resolution cryo- EM structure. They speculate that DNAAF9 is a likely homolog to the T. thermophila Shulin protein, which their previous work demonstrated was an important effector of OAD's autoinhibited state. They find that DNAAF9 localizes to the developing cilia of human airway epithelial cells (but not to mature cilia), co- IPs with OAD components (eg. DNAI2), and its addition to purified OAD causes a change in conformation to a 'closed'/presumably autoinhibited state. The authors then focus on testing the hypothesis that the Ari3 GTPase releases ODA from DNAAF9 in a GTP- dependent manner. They find Ari3 from human and T. thermophila both bind to DNAAF9/Shulin. Using negative stain EM and AF2, they map the approximate contact point between Ari3 and DNAAF9 that the confirm via mutagenesis and binding assays. Finally, the authors show that a GTP- bound Ari3 indeed has the capacity to dissociate a T. thermophila Shulin- ODA complex. I strongly support publication of the manuscript providing they address a few concerns I have, which may help to improve the manuscript prior to publication. + +<|ref|>text<|/ref|><|det|>[[72, 788, 184, 801]]<|/det|> +Major concerns: + +<|ref|>text<|/ref|><|det|>[[72, 801, 917, 907]]<|/det|> +1) With regard to "Taken together, these findings indicate that human DNAAF9 interacts with mammalian ODAs and maintains them in a closed conformation sharing its role as an inhibitor with its Tetrahymena ortholog Shulin", I wonder why the authors didn't test DNAAF9 in a gliding assay as they did previously (Mali et al., Science 2021)? Although the negative stain EM evidence is fairly strong, I'm not sure their findings "indicate" a role for DNAAF9 in inhibiting ODAs. Such an experiment would provide much stronger evidence that DNAAF9 indeed performs an analogous role to Shulin in ODA function. It would also provide support for the "inhibitory role" proposed in this sentence from the Discussion: "...we favour a model where the critical inhibitory role played by Shulin (DNAAF9) is central to stabilising IFT-ODA interactions for efficient transport into cilia." Without such evidence, the language would need to be changed to reflect this. + +<|ref|>text<|/ref|><|det|>[[72, 906, 920, 946]]<|/det|> +2) Although I'm okay with the model in Figure 2i being presented as is, the data to support it is a bit thin (quantitative MS data). In particular, the model for dynein-1 transport of DNAAF9, although intriguing, may need more support. Do the authors see any cargo adaptor proteins in the MS data? Although not required, this would make this argument more convincing. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 765, 60]]<|/det|> +Also, have the authors tried looking for dynein- 1 complex components in their EC vs MC pull- downs? + +<|ref|>text<|/ref|><|det|>[[72, 60, 917, 113]]<|/det|> +3) I was a little confused by the back-and-forth between model systems. I think it's great that the authors included all these data, but my head started to spin by the last figure in particular. It would help if there was more explanation as to why they performed some experiments with human components, and others with T. thermophila proteins. For example, why didn't the authors test whether human Arl3 induces dissociation of the DNAAF9-ODA complex? + +<|ref|>sub_title<|/ref|><|det|>[[72, 127, 163, 139]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[72, 139, 884, 166]]<|/det|> +1) Although I was able to guess which was which, the AF2 models for Shulin and DNAAF9 in Fig. S1 are not labeled. Please add labels. + +<|ref|>text<|/ref|><|det|>[[72, 165, 895, 192]]<|/det|> +2) It seems that the sequence for T. thermophila Shulin is missing from Figure S2. If not, please label accordingly. If so, I think this would be a helpful point of comparison. + +<|ref|>text<|/ref|><|det|>[[72, 191, 920, 218]]<|/det|> +3) The data presented in the Discussion should either be moved to the Results section (and described in detail) or removed from the paper entirely (and saved for a future paper). This includes Fig. S9 and 10. + +<|ref|>text<|/ref|><|det|>[[72, 217, 921, 283]]<|/det|> +4) The paragraphs in the Discussion describing Oda16 and potential transport adaptors (line 366-390) seemed off-topic, and was a distraction to me as a reader. I had trouble finding out how this fit into the paper. I feel the same is true for their argument that DNAAF9 is a transport adaptor for IFT. I would suggest removing this part of the discussion and accompanying data in Figure S10 (save it for another paper) and simply focus on discussing the data within the results section. + +<|ref|>text<|/ref|><|det|>[[72, 282, 923, 335]]<|/det|> +5) "Given these emerging links between ARL3 and the biogenesis of motile cilia, we recommend that primary ciliopathy patients carrying ARL3 variants should be additionally assessed for clinical features indicative of defective motile cilia." Maybe this is born from ignorance, but wouldn't primary ciliopathy patients already be assessed for potential clinical features of defective motile cilia? + +<|ref|>text<|/ref|><|det|>[[73, 372, 332, 386]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[72, 423, 916, 490]]<|/det|> +Issa et al. set out to determine the functional consequence of the interaction between DNAAF9 and the small g protein Arl3. The authors find that DNAAF9 (and its tetrahymena homolog Shulin) preferentially bind to GTP- bound Arl3. Arl3- DNAAF9 interaction displaces DNAAF9 from outer dynein arm complex, thus resulting in dynein activation in cilia. The motivation for this work is important, as ciliary beating defects causes ciliopathies and the findings were described clearly. Pending two important points below, I recommend this work for publication. + +<|ref|>sub_title<|/ref|><|det|>[[72, 503, 162, 515]]<|/det|> +## Major points: + +<|ref|>text<|/ref|><|det|>[[72, 515, 916, 594]]<|/det|> +1. The authors use mutagenesis to try to validate the predicted interface between DNAAF9 and Arl3 (they make three mutations: F51A, Y77A, and Y81A). However, these mutations should be made in the Arl3-Q70L GTP-locked background, not the WT background. The data in Figure 3A shows that WT Arl3 that can GTP cycle doesn't really bind DNAAF9 (maybe there is a little shoulder that shows complex co-elution, but the interaction is not robust enough to see Arl3 on the SDS-PAGE gel in b). The authors should test if the Arl3-F51A, Y77A, Y81A mutant in the Q70L background has reduced affinity for DNAAF9. + +<|ref|>text<|/ref|><|det|>[[72, 594, 905, 621]]<|/det|> +2. The data in Figure 5 is very important to the authors model but is the least convincing in the paper. The following points are important to fortify this data: + +<|ref|>text<|/ref|><|det|>[[72, 620, 923, 672]]<|/det|> +a. The data in Figure 5d must be quantified, rather than just shown qualitatively. For example, the authors could measure the intensity of the bands of ODA heavy chain: Shulin in peak complex fractions with and without inclusion of Arl3. In fact, it is actually very challenging to tell if inclusion of Arl3 really does reduce Shulin-ODA interaction because there is significantly more total protein loaded on the gel for the experiment without Arl3. + +<|ref|>text<|/ref|><|det|>[[72, 672, 916, 699]]<|/det|> +b. The GTPase dead Arl3 mutant or the Arl3 mutant variants that don't bind (but in the GTP-locked background) would be a great negative control for this study. + +<|ref|>text<|/ref|><|det|>[[72, 699, 920, 737]]<|/det|> +c. Finally, the authors should show the SEC traces for the experiments with and without Arl3, as well as show gels that have the exact same fractions (and where they correspond to the SEC elution profile) for each experiment. It is hard to assess the quality of this data without seeing the traces and all the same corresponding fractions. + +<|ref|>sub_title<|/ref|><|det|>[[72, 750, 162, 762]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[72, 763, 629, 776]]<|/det|> +1. Zoom in on figure 1d would be helpful to show the DNAA9 staining on the cilia. + +<|ref|>text<|/ref|><|det|>[[72, 789, 888, 816]]<|/det|> +2. Can the authors report the \(\%\) open and \(\%\) closed ODA conformations with and without DNAAF9 (data in figure S5) to quantify the effect of DNAAF9 on ODA structure? + +<|ref|>text<|/ref|><|det|>[[73, 879, 333, 892]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[73, 905, 262, 919]]<|/det|> +Review of NSMB- A49966B + +<|ref|>text<|/ref|><|det|>[[72, 931, 901, 946]]<|/det|> +The manuscript by Issa et al. from the Mali lab addresses a fundamental question in ciliary biology. More specifically, how + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 47, 905, 127]]<|/det|> +are the multimeric axonemal dyneins assembled and maintained in the cytoplasm in an inactive form and then activated once they enter cilia and flagella and attach to the outer doublet microtubules. In previous work the authors identified a dynein chaperone known as Shulin that maintains outer dynein arms (ODAs) in an inactive conformation in the cytoplasm and co- localizes with ODAs in regenerating Tetrahymena cilia. In the present study they ask (1) whether this inhibitory mechanism is conserved in Shulin orthologs such as the human DNAAF9, (2), whether it interacts with transport factors to target ODAs to cilia, and (3) how is Shulin/DNAAF9 released from ODAs inside cilia to allow ODA activation? + +<|ref|>text<|/ref|><|det|>[[73, 139, 243, 152]]<|/det|> +Most significant findings: + +<|ref|>text<|/ref|><|det|>[[72, 164, 912, 270]]<|/det|> +Other studies had shown that DNAAF9 could be pulled down with the small GTPase ARL3, which suggested that DNAAF9 might be involved in the ciliary transport of ODAs. The authors used AlphaFold 2 (AF2) analyses to compare the structures and sequences of Shulin and DNAAF9 (Figures S1, S2). These analyses identified several conserved domains with significant structural similarity that could be involved in binding to ODAs during transport. The authors test this model using human airway epithelial cells cultured at an air- liquid interface to induce differentiation of basal cells into multiciliated cells (Figure 1). Consistent with their hypothesis that Shulin and DNAAF9 share a similar function, they observed that DNAAF9 enters growing motile cilia in differentiating airway cells (Fig 1d, e). Similar results were observed using zebrafish embryos (Figure S3). + +<|ref|>text<|/ref|><|det|>[[72, 280, 904, 386]]<|/det|> +To gain a better understanding into the mechanism by which DNAAF9/Shulin might facilitate the transport of ODAs, they used immunoprecipitation, TMT labeling, and mass spectrometry to identify interacting proteins (Figure 2, Supplemental Datafile 1). This identified more than 87 proteins found at different stages of differentiation, including ODA subunits, IFT- B subunits, ciliary tip proteins, and ARL3. The proteomics work appears to be rigorous, and the major take- home are nicely summarized in their Figure 2, but I would have liked to have seen more detailed explanation of their results in the Supplemental Datafile 1. If I understand their methods correctly, the IPs were performed using total cell lysates and not purified cilia. Thus, the model proposed in Figure 2i is an inference based on the results from total cell lysates. However, they test several key points of their model using a clever series of in vitro binding experiments. + +<|ref|>text<|/ref|><|det|>[[72, 397, 914, 476]]<|/det|> +To test the hypothesis that ARL3 might regulate that activity of DNAAF9 and Shulin, they expressed recombinant DNAAF9 and Tetrahymena ARL3 in its GTP and GDP mimicking states using Q70L and T30N variants respectively. They found that all Arl3 variants co- eluted with DNAAF9 in high GTP (Fig. S6) but only Arl3Q70L binds DNAAF9 in the presence of GDP (Figure 3). Using this Arl3 variant as bait and lysates of Tetrahymena cells undergoing ciliary regeneration, they co- immunoprecipitated several known effectors of Arl3 and Shulin (Figure 3), suggesting that Arl3 is likely to regulate transport of ODAs through its interaction with Shulin. + +<|ref|>text<|/ref|><|det|>[[72, 488, 897, 594]]<|/det|> +The authors extended this work by analyzing the interaction between recombinant DNAAF9 (or Shulin) in complex with ArlQ70L in vitro by negative stain electron microscopy (Figure 4, Fig. S7). Single particle averaging identified a subset of images ( \(\sim 50\%\) ) containing a DNAAF9/Shulin- Arl3 complex, with the ARL3 subunit bound to the N1 domain of DNAAF9/Shulin. Analytical chromatography confirmed that this interaction was most stable using the Arl3Q70L variant. They extended these observations using AF2 to model the interaction interface and then disrupted the interaction using specific ARL3 mutations (Figure 4e). Further modeling using AF3 suggests that ARL3 interacts with DNAAF9 in the presence of GTP but not GDP (Fig. S8). Additional in vitro studies demonstrate that ARL3 and can disrupt the interaction between purified Shulin and ODAs in the presence of GTP (Figure 5). + +<|ref|>sub_title<|/ref|><|det|>[[73, 606, 320, 620]]<|/det|> +## Overall Evaluation and Significance + +<|ref|>text<|/ref|><|det|>[[72, 632, 920, 722]]<|/det|> +In summary, the authors combine sophisticated modeling, well executed proteomics, and elegant in vitro studies to test a new model of how the ARL3 GTPase might regulate the interaction between a dynein chaperone and the ODAs to maintain the ODAs in an inactive state in the cytoplasm and release and activate the ODAs upon entry into the cilia. The experimental logic is clearly described, the experiments are well executed, and the suggested mechanism of regulation for dynein activation in vivo is a novel, exciting hypothesis. Future in vivo studies will be needed to determine the precise timing and location of ODA activation, but the work presented here is an exciting step forward. I think the work will be of broad interest to people working in the field of motor activation and targeting, and I highly recommend publication. + +<|ref|>text<|/ref|><|det|>[[72, 735, 144, 748]]<|/det|> +Version 3: + +<|ref|>text<|/ref|><|det|>[[72, 761, 183, 775]]<|/det|> +Decision Letter: + +<|ref|>text<|/ref|><|det|>[[72, 788, 178, 801]]<|/det|> +23rd May 2025 + +<|ref|>text<|/ref|><|det|>[[72, 814, 156, 827]]<|/det|> +Dear Girish, + +<|ref|>text<|/ref|><|det|>[[72, 840, 905, 867]]<|/det|> +Thank you again for alerting us to the issue with data in S3df in your manuscript "Molecular basis for the activation of outer dynein arms in cilia". + +<|ref|>text<|/ref|><|det|>[[72, 879, 477, 892]]<|/det|> +I have now discussed this matter with our Editorial Director. + +<|ref|>text<|/ref|><|det|>[[72, 905, 910, 945]]<|/det|> +We thank you for bringing to our attention the use of an incorrect myc construct in experiments underlying the data in S3df. Following our internal assessment and given the need to provide new data and remove present data, we regret that we are unable to proceed with the acceptance in principle of the current version of the manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 60, 879, 114]]<|/det|> +We are open to reconsidering the manuscript on the condition that revised data in full compliance with our policies are provided. Any decision to proceed with such a revised manuscript will depend on further assessment of these data editorially and might involve reinitiating the peer- review process to determine whether the level of support for the interpretation of the data and the conclusions drawn remains unaltered. + +<|ref|>text<|/ref|><|det|>[[72, 125, 871, 154]]<|/det|> +Please also pay close attention to our image integrity and imaging standards policies https://www.nature.com/nature- portfolio/editorial- policies/image- integrity + +<|ref|>text<|/ref|><|det|>[[70, 164, 910, 192]]<|/det|> +Please provide a document (e.g., cover letter) clarifying the issues detected for particular figure panels (S3df and any other) in the current set of figures (version NSMB- A49966C) and how these issues were addressed in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[70, 203, 900, 232]]<|/det|> +Please note that you will also need to re- upload with your final resubmission all source data files (source numerical data, source blots) and the reporting summary. + +<|ref|>text<|/ref|><|det|>[[73, 243, 914, 284]]<|/det|> +As you already know, we put great emphasis on ensuring that the methods and statistics reported in our papers are correct and accurate. As such, if there are any changes that should be reported, please submit an updated version of the Reporting Summary along with your revision. + +<|ref|>text<|/ref|><|det|>[[73, 295, 440, 309]]<|/det|> +Please follow the links below to download these files: + +<|ref|>text<|/ref|><|det|>[[73, 320, 496, 348]]<|/det|> +Reporting Summary: https://www.nature.com/documents/nr- reporting- summary.pdf + +<|ref|>text<|/ref|><|det|>[[70, 359, 884, 373]]<|/det|> +Please note that the form is a dynamic 'smart pdf' and must therefore be downloaded and completed in Adobe Reader. + +<|ref|>text<|/ref|><|det|>[[72, 398, 912, 439]]<|/det|> +When submitting the revised version of your manuscript, please pay close attention to our href="https://www.nature.com/nature- portfolio/editorial- policies/image- integrity">Digital Image Integrity Guidelines. and to the following points below: + +<|ref|>text<|/ref|><|det|>[[72, 450, 877, 491]]<|/det|> +- that unprocessed scans are clearly labelled and match the gels and western blots presented in figures. +- that control panels for gels and western blots are appropriately described as loading on sample processing controls +- all images in the paper are checked for duplication of panels and for splicing of gel lanes. + +<|ref|>sub_title<|/ref|><|det|>[[73, 503, 281, 517]]<|/det|> +## EXTENDED DATA FIGURES + +<|ref|>text<|/ref|><|det|>[[72, 529, 914, 595]]<|/det|> +When re- submitting your manuscript, please ensure that any supplementary figures and tables that are crucial to the manuscript's conclusions are converted into Extended Data figures and tables to increase visibility of these data. Extended Data figures and tables are online- only (present in the online PDF and full- text HTML versions of the paper), peer- reviewed display items that provide essential background to the article but are not included in the main article due to space constraints. A maximum of ten Extended Data display items (figures and tables) is permitted. + +<|ref|>text<|/ref|><|det|>[[72, 606, 916, 634]]<|/det|> +Finally, please ensure that you retain unprocessed data and metadata files after publication, ideally archiving data in perpetuity, as these may be requested during the peer review and production process or after publication if any issues arise. + +<|ref|>text<|/ref|><|det|>[[72, 645, 915, 673]]<|/det|> +If there are additional or modified structures presented in the final revision, please submit the corresponding PDB validation reports. + +<|ref|>text<|/ref|><|det|>[[72, 685, 920, 738]]<|/det|> +Please note that all key data shown in the main figures as cropped gels or blots should be presented in uncropped form, with molecular weight markers. These data can be aggregated into a single supplementary figure item. While these data can be displayed in a relatively informal style, they must refer back to the relevant figures. These data should be submitted with the final revision, as source data, prior to acceptance, but you may want to start putting it together at this point. + +<|ref|>text<|/ref|><|det|>[[72, 749, 918, 842]]<|/det|> +SOURCE DATA: we urge authors to provide, in tabular form, the data underlying the graphical representations used in figures. This is to further increase transparency in data reporting, as detailed in this editorial (http://www.nature.com/nsmb/journal/v22/n10/full/nsmb.3110. html). Spreadsheets can be submitted in excel format. Only one (1) file per figure is permitted; thus, for multi- paneled figures, the source data for each panel should be clearly labeled in the Excel file; alternately the data can be provided as multiple, clearly labeled sheets in an Excel file. When submitting files, the title field should indicate which figure the source data pertains to. We encourage our authors to provide source data at the revision stage, so that they are part of the peer- review process. + +<|ref|>text<|/ref|><|det|>[[72, 853, 920, 920]]<|/det|> +Data availability: this journal strongly supports public availability of data. All data used in accepted papers should be available via a public data repository, or alternatively, as Supplementary Information. If data can only be shared on request, please explain why in your Data Availability Statement, and also in the correspondence with your editor. Please note that for some data types, deposition in a public repository is mandatory - more information on our data deposition policies and available repositories can be found below: + +<|ref|>text<|/ref|><|det|>[[72, 920, 737, 933]]<|/det|> +https://www.nature.com/nature- research/editorial- policies/reporting- standards#availability- of- data + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 916, 128]]<|/det|> +We require deposition of coordinates (and, in the case of crystal structures, structure factors) into the Protein Data Bank with the designation of immediate release upon publication (HPUB). Electron microscopy- derived density maps and coordinate data must be deposited in EMDB and released upon publication. Deposition and immediate release of NMR chemical shift assignments are highly encouraged. Deposition of deep sequencing and microarray data is mandatory, and the datasets must be released prior to or upon publication. 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If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 126]]<|/det|> +The authors thank all three reviewers for their helpful comments. Please see our responses to the comments and a detailed description of all changes below. + +<|ref|>sub_title<|/ref|><|det|>[[118, 155, 444, 172]]<|/det|> +## Reviewer 1 [Referee expertise: dynein] + +<|ref|>text<|/ref|><|det|>[[116, 191, 882, 526]]<|/det|> +This is an excellent manuscript with very clearly stated hypotheses and satisfying answers to the questions posed. In brief, the authors follow up on a 2021 manuscript in which they initially described Shulin's biochemical and biological activity along with a high resolution cryo- EM structure. They speculate that DNAAF9 is a likely homolog to the T. thermophila Shulin protein, which their previous work demonstrated was an important effector of OAD's autoinhibited state. They find that DNAAF9 localizes to the developing cilia of human airway epithelial cells (but not to mature cilia), co- IPs with OAD components (eg. DNAI2), and its addition to purified OAD causes a change in conformation to a 'closed'/presumably autoinhibited state. The authors then focus on testing the hypothesis that the Arl3 GTPase releases ODA from DNAAF9 in a GTP- dependent manner. They find Arl3 from human and T. thermophila both bind to DNAAF9/Shulin. Using negative stain EM and AF2, they map the approximate contact point between Arl3 and DNAAF9 that the confirm via mutagenesis and binding assays. Finally, the authors show that a GTP- bound Arl3 indeed has the capacity to dissociate a T. thermophila Shulin- ODA complex. I strongly support publication of the manuscript providing they address a few concerns I have, which may help to improve the manuscript prior to publication. + +<|ref|>sub_title<|/ref|><|det|>[[118, 545, 262, 561]]<|/det|> +## Major concerns: + +<|ref|>text<|/ref|><|det|>[[116, 582, 883, 825]]<|/det|> +1) With regard to "Taken together, these findings indicate that human DNAAF9 interacts with mammalian ODAs and maintains them in a closed conformation sharing its role as an inhibitor with its Tetrahymena ortholog Shulin", I wonder why the authors didn't test DNAAF9 in a gliding assay as they did previously (Mali et al., Science 2021)? Although the negative stain EM evidence is fairly strong, I'm not sure their findings "indicate" a role for DNAAF9 in inhibiting ODAs. Such an experiment would provide much stronger evidence that DNAAF9 indeed performs an analogous role to Shulin in ODA function. It would also provide support for the "inhibitory role" proposed in this sentence from the Discussion: "...we favour a model where the critical inhibitory role played by Shulin (DNAAF9) is central to stabilising IFT-ODA interactions for efficient transport into cilia." Without such evidence, the language would need to be changed to reflect this. + +<|ref|>text<|/ref|><|det|>[[118, 845, 856, 886]]<|/det|> +This is an important point and although we agree that functional assays such as a gliding assay would directly support DNAAF9's inhibitory role on mammalian ODAs, currently it is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 835, 123]]<|/det|> +technically impossible to conduct such assays using mammalian ODA motors. Two key limitations prevent this. + +<|ref|>text<|/ref|><|det|>[[117, 128, 870, 282]]<|/det|> +a) Obtaining functionally intact mammalian axonemal ODA motor complexes of sufficient purity and in sufficient quantities remains a major technical bottleneck in the dynein field. Hence, all displacement experiments were performed using purified Tetrahymena ODAs. +b) Methods for reconstituting axonemal dynein's using recombinant subunits obtained from heterologous expression systems (ex. insect cell-baculovirus) have not been developed. We think this is due to the still poorly understood chaperoning requirements that appear to be specific for the biosynthesis of axonemal dyneins. + +<|ref|>text<|/ref|><|det|>[[118, 303, 877, 340]]<|/det|> +To reflect this limitation, we have changed the language by focusing the last paragraph more on Shulin and added the below sentence (lines 432- 435). + +<|ref|>text<|/ref|><|det|>[[118, 355, 879, 441]]<|/det|> +"Although our observation that pig ODAs adopt a closed conformation in the presence of DNAAF9 could hint at its inhibitory role in mammalian ODAs (similar to Shulin in Tetrahymena ODAs), more functional assays using mammalian ODAs are needed to directly test this in the future." + +<|ref|>text<|/ref|><|det|>[[117, 460, 883, 590]]<|/det|> +2) Although I'm okay with the model in Figure 2i being presented as is, the data to support it is a bit thin (quantitative MS data). In particular, the model for dynein-1 transport of DNAAF9, although intriguing, may need more support. Do the authors see any cargo adaptor proteins in the MS data? Although not required, this would make this argument more convincing. Also, have the authors tried looking for dynein-1 complex components in their EC vs MC pull-downs? + +<|ref|>text<|/ref|><|det|>[[117, 609, 878, 741]]<|/det|> +We do not detect known dynein- 1 cargo adaptors in the dataset. However, we detect dynein- 1 light intermediate chain (DYNC1LI2) and intermediate chain (DYNC1I2) subunits in EC vs MC IPs with differential enrichments. These are shown in the scatter plots (Fig. 2a, b) and the dot plot (Fig. 2f). We have amended the text as below to emphasize that the connection to dynein- 1 transport needs further support (lines 223- 225). We have also added question marks in Fig. 2e and 2i to emphasize this point and updated the figure legend accordingly. + +<|ref|>text<|/ref|><|det|>[[118, 760, 870, 823]]<|/det|> +"ODAs then reach the peri-basal body pool. Apical enrichment around the basal body could be achieved via the dynein- 1 transport machinery or another mechanism. More work is needed to address this" + +<|ref|>text<|/ref|><|det|>[[117, 850, 881, 913]]<|/det|> +3) I was a little confused by the back-and-forth between model systems. I think it's great that the authors included all these data, but my head started to spin by the last figure in particular. It would help if there was more explanation as to why they performed some experiments with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 880, 123]]<|/det|> +human components, and others with T. thermophila proteins. For example, why didn't the authors test whether human Arl3 induces dissociation of the DNAAF9- ODA complex? + +<|ref|>text<|/ref|><|det|>[[117, 143, 862, 252]]<|/det|> +We performed cross- species interaction studies to highlight that the interaction between DNAAF9 and ARL3 is evolutionarily conserved. Technical limitations of obtaining human/mammalian ODAs restricted us to using Tetrahymena ODAs for the reconstitutions and subsequent displacement experiments. These were performed using Tetrahymena proteins. We have included the below sentence to explain this point (lines 875- 876). + +<|ref|>text<|/ref|><|det|>[[118, 271, 870, 311]]<|/det|> +"Displacement assays were performed using ODAs purified from isolated Tetrahymena cilia and Tetrahymena Shulin due to technical limitations in purifying mammalian ODAs" + +<|ref|>text<|/ref|><|det|>[[118, 339, 870, 401]]<|/det|> +To address the point of going back- and- forth between model systems (and also point #2 raised by reviewer #2) more thoroughly, we performed new reconstitutions under 1mM GTP or 1mM GDP conditions as detailed below: + +<|ref|>text<|/ref|><|det|>[[147, 405, 571, 534]]<|/det|> +1. Human DNAAF9 + Human ARL3Q71L +2. Human DNAAF9 + Human ARL3T31N +3. Human DNAAF9 + Human ARL3Q71L-FYY +4. Tetrahymena Shulin + Tetrahymena Arl3Q70L +5. Tetrahymena Shulin + Tetrahymena Arl3T30N +6. Tetrahymena Shulin + Tetrahymena Arl3Q70L-FYY + +<|ref|>text<|/ref|><|det|>[[118, 541, 877, 603]]<|/det|> +These new data are consistent with our previous finding of a cross- species interaction between human DNAAF9 and Tetrahymena Arl3. We have incorporated these new data into updated Fig. S10 and updated the text describing these data (lines 270- 272). + +<|ref|>sub_title<|/ref|><|det|>[[118, 631, 237, 648]]<|/det|> +## Minor points: + +<|ref|>text<|/ref|><|det|>[[118, 676, 879, 716]]<|/det|> +1) Although I was able to guess which was which, the AF2 models for Shulin and DNAAF9 in Fig. S1 are not labeled. Please add labels. + +<|ref|>text<|/ref|><|det|>[[118, 736, 441, 753]]<|/det|> +We have now labelled these in Fig. S1. + +<|ref|>text<|/ref|><|det|>[[118, 773, 879, 806]]<|/det|> +2) It seems that the sequence for T. thermophila Shulin is missing from Figure S2. If not, please label accordingly. If so, I think this would be a helpful point of comparison. + +<|ref|>text<|/ref|><|det|>[[118, 818, 870, 880]]<|/det|> +The sequence for Shulin was labelled with its UniProt ID (Q22YU3_TETTS). We have relabelled to include the name Shulin and added the names with corresponding Uniprot IDs in the figure legend. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 881, 146]]<|/det|> +3) The data presented in the Discussion should either be moved to the Results section (and described in detail) or removed from the paper entirely (and saved for a future paper). This includes Fig. S9 and 10. + +<|ref|>text<|/ref|><|det|>[[117, 165, 872, 275]]<|/det|> +We have retained the data showing the hydrocephalus phenotype as it supports a role for DNAAF9 in motile cilia functions. Text relating to this data has been incorporated into the main results section (lines 192- 200) and updated in the discussion (lines 402- 403). Fig. S6 replaces the old Fig. S9. Fig. S7 replaces the old Fig. S10 (detailed in point 4 below). The numbering of subsequent supplementary figures has been updated accordingly. + +<|ref|>text<|/ref|><|det|>[[117, 300, 883, 432]]<|/det|> +4) The paragraphs in the Discussion describing Oda16 and potential transport adaptors (line 366-390) seemed off-topic and was a distraction to me as a reader. I had trouble finding out how this fit into the paper. I feel the same is true for their argument that DNAAF9 is a transport adaptor for IFT. I would suggest removing this part of the discussion and accompanying data in Figure S10 (save it for another paper) and simply focus on discussing the data within the results section. + +<|ref|>text<|/ref|><|det|>[[117, 450, 870, 560]]<|/det|> +We have removed the Oda16 data and text describing potential transport adaptors from the manuscript (previous lines 366- 390). We have retained the IFT binding data as it validates the interaction with IFT74 and IFT81 detected by endogenous IP- MS. Text relating to this data has been incorporated in the main results section (lines 213- 219) and the discussion (lines 409- 413). Fig. S7 replaces the old Fig. S10. + +<|ref|>text<|/ref|><|det|>[[117, 578, 883, 686]]<|/det|> +5) "Given these emerging links between ARL3 and the biogenesis of motile cilia, we recommend that primary ciliopathy patients carrying ARL3 variants should be additionally assessed for clinical features indicative of defective motile cilia." Maybe this is born from ignorance, but wouldn't primary ciliopathy patients already be assessed for potential clinical features of defective motile cilia? + +<|ref|>text<|/ref|><|det|>[[118, 706, 611, 723]]<|/det|> +We have rephrased this sentence as below (lines 423- 424). + +<|ref|>text<|/ref|><|det|>[[118, 744, 880, 785]]<|/det|> +"Further work is needed to dissect the emerging links between ARL3 and its effector proteins in the trafficking of motility- related cargoes during motile cilia formation." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 188, 595, 205]]<|/det|> +## Reviewer 2 [Referee expertise: dynein, structural biology] + +<|ref|>text<|/ref|><|det|>[[117, 217, 883, 350]]<|/det|> +Issa et al. set out to determine the functional consequence of the interaction between DNAAF9 and the small g protein Arl3. The authors find that DNAAF9 (and its tetrahymena homolog Shulin) preferentially bind to GTP- bound Arl3. Arl3- DNAAF9 interaction displaces DNAAF9 from outer dynein arm complex, thus resulting in dynein activation in cilia. The motivation for this work is important, as ciliary beating defects causes ciliopathies and the findings were described clearly. Pending two important points below, I recommend this work for publication. + +<|ref|>sub_title<|/ref|><|det|>[[118, 377, 236, 394]]<|/det|> +## Major points: + +<|ref|>text<|/ref|><|det|>[[117, 420, 883, 574]]<|/det|> +1. The authors use mutagenesis to try to validate the predicted interface between DNAAF9 and Arl3 (they make three mutations: F51A, Y77A, and Y81A). However, these mutations should be made in the Arl3-Q70L GTP-locked background, not the WT background. The data in Figure 3A shows that WT Arl3 that can GTP cycle doesn't really bind DNAAF9 (maybe there is a little shoulder that shows complex co-elution, but the interaction is not robust enough to see Arl3 on the SDS-PAGE gel in b). The authors should test if the Arl3-F51A, Y77A, Y81A mutant in the Q70L background has reduced affinity for DNAAF9. + +<|ref|>text<|/ref|><|det|>[[117, 599, 868, 732]]<|/det|> +This is an important point. To address this, we reconstituted DNAAF9 with human ARL3Q71L or ARL3Q71L- FYY and Shulin with Tetrahymena Arl3Q70L or Arl3Q70L- FYY; (FYY = interface triple mutant on a QL GTP-locked background). These data showed that the FYY interface triple mutants on GTP-locked QL backgrounds have reduced affinities for DNAAF9 and Shulin proteins respectively compared to the QL variants alone in both species. We have included these new data in Fig. 4 (new panel e) and Fig. S10. + +<|ref|>text<|/ref|><|det|>[[117, 758, 881, 799]]<|/det|> +2. The data in Figure 5 is very important to the authors model but is the least convincing in the paper. The following points are important to fortify this data: + +<|ref|>text<|/ref|><|det|>[[117, 825, 882, 911]]<|/det|> +a. The data in Figure 5d must be quantified, rather than just shown qualitatively. For example, the authors could measure the intensity of the bands of ODA heavy chain: Shulin in peak complex fractions with and without inclusion of Arl3. In fact, it is actually very challenging to tell if inclusion of Arl3 really does reduce Shulin-ODA interaction because there is significantly + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 880, 146]]<|/det|> +more total protein loaded on the gel for the experiment without Arl3. b. The GTPase dead Arl3 mutant or the Arl3 mutant variants that don't bind (but in the GTP- locked background) would be a great negative control for this study. + +<|ref|>text<|/ref|><|det|>[[117, 172, 877, 394]]<|/det|> +We conducted new reconstitution, and displacement experiments and quantified these data using gel densitometry. These have now been included in a new Fig. 5. The original Fig. 5 has been replaced by a new Fig. 6 which presents our overall proposed model. We have also updated the relevant methods section (lines 875- 888). Briefly, we reconstituted Tetrahymena ODAs with Shulin. The reconstituted ODA- Shulin complex was divided equally into two fractions to test the impact of Arl3 in displacing Shulin. The ODA- Shulin complex fractions were incubated with either \(\mathrm{Arl3^{Q70L}}\) (active GTP- locked variant) or \(\mathrm{Arl3^{Q70L - FYY}}\) (interface mutant on a QL background) as a negative control. Gel densitometry analyses were performed on replicate runs to calculate the Shulin:ODA heavy chain and Shulin:ODA IC2 ratios for each of the three experimental conditions. + +<|ref|>text<|/ref|><|det|>[[117, 420, 861, 529]]<|/det|> +These new data and analyses (included in new Fig. 5) show that reduced levels of Shulin co- elute with the ODA complex in the presence of the \(\mathrm{Arl3^{Q70L}}\) variant compared to in the presence of \(\mathrm{Arl3^{Q70L - FYY}}\) mutant which has reduced affinity for Shulin. Overall, this suggests that Shulin gets displaced from ODAs by \(\mathrm{Arl3^{Q70L}}\) (i.e., active Arl3) and is sequestered in a complex with \(\mathrm{Arl3^{Q70L}}\) . + +<|ref|>text<|/ref|><|det|>[[117, 555, 877, 641]]<|/det|> +c. Finally, the authors should show the SEC traces for the experiments with and without Arl3, as well as show gels that have the exact same fractions (and where they correspond to the SEC elution profile) for each experiment. It is hard to assess the quality of this data without seeing the traces and all the same corresponding fractions. + +<|ref|>text<|/ref|><|det|>[[118, 668, 873, 708]]<|/det|> +Gel filtration traces for reconstitution and displacement experiments with corresponding gels are included in new Fig. 5. + +<|ref|>text<|/ref|><|det|>[[118, 736, 225, 752]]<|/det|> +Minor points: + +<|ref|>text<|/ref|><|det|>[[118, 757, 783, 776]]<|/det|> +1. Zoom in on figure 1d would be helpful to show the DNAA9 staining on the cilia. + +<|ref|>text<|/ref|><|det|>[[118, 803, 860, 844]]<|/det|> +We have added zoomed panels to show the DNAA9 and DNAI2 staining in cilia in Fig.1d and updated the figure legend. + +<|ref|>text<|/ref|><|det|>[[118, 871, 849, 912]]<|/det|> +2. Can the authors report the % open and % closed ODA conformations with and without DNAA9 (data in figure S5) to quantify the effect of DNAA9 on ODA structure? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 105, 864, 168]]<|/det|> +We have added the percentages for open and closed conformations for ODA alone and for ODA mixed with DNAAF9. Text in the legend for Fig. S5 and the relevant methods section (lines 901- 907) has been updated. + +<|ref|>sub_title<|/ref|><|det|>[[119, 196, 421, 213]]<|/det|> +## Reviewer 3 [Referee expertise: cilia] + +<|ref|>text<|/ref|><|det|>[[117, 240, 883, 462]]<|/det|> +The manuscript by Issa et al. from the Mali lab addresses a fundamental question in ciliary biology. More specifically, how are the multimeric axonemal dyneins assembled and maintained in the cytoplasm in an inactive form and then activated once they enter cilia and flagella and attach to the outer doublet microtubules. In previous work the authors identified a dynein chaperone known as Shulin that maintains outer dynein arms (ODAs) in an inactive conformation in the cytoplasm and co- localizes with ODAs in regenerating Tetrahymena cilia. In the present study they ask (1) whether this inhibitory mechanism is conserved in Shulin orthologs such as the human DNAAF9, (2), whether it interacts with transport factors to target ODAs to cilia, and (3) how is Shulin/DNAAF9 released from ODAs inside cilia to allow ODA activation? + +<|ref|>text<|/ref|><|det|>[[119, 490, 320, 506]]<|/det|> +Most significant findings: + +<|ref|>text<|/ref|><|det|>[[117, 533, 883, 755]]<|/det|> +Other studies had shown that DNAAF9 could be pulled down with the small GTPase ARL3, which suggested that DNAAF9 might be involved in the ciliary transport of ODAs. The authors used AlphaFold 2 (AF2) analyses to compare the structures and sequences of Shulin and DNAAF9 (Figures S1, S2). These analyses identified several conserved domains with significant structural similarity that could be involved in binding to ODAs during transport. The authors test this model using human airway epithelial cells cultured at an air- liquid interface to induce differentiation of basal cells into multiciliated cells (Figure 1). Consistent with their hypothesis that Shulin and DNAAF9 share a similar function, they observed that DNAAF9 enters growing motile cilia in differentiating airway cells (Fig 1d, e). Similar results were observed using zebrafish embryos (Figure S3). + +<|ref|>text<|/ref|><|det|>[[117, 781, 883, 912]]<|/det|> +To gain a better understanding into the mechanism by which DNAAF9/Shulin might facilitate the transport of ODAs, they used immunoprecipitation, TMT labeling, and mass spectrometry to identify interacting proteins (Figure 2, Supplemental Datafile 1). This identified more than 87 proteins found at different stages of differentiation, including ODA subunits, IFT- B subunits, ciliary tip proteins, and ARL3. The proteomics work appears to be rigorous, and the major take- homes are nicely summarized in their Figure 2, but I would have liked to have seen more + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 881, 190]]<|/det|> +detailed explanation of their results in the Supplemental Datafile 1. If I understand their methods correctly, the IPs were performed using total cell lysates and not purified cilia. Thus, the model proposed in Figure 2i is an inference based on the results from total cell lysates. However, they test several key points of their model using a clever series of in vitro binding experiments. + +<|ref|>text<|/ref|><|det|>[[117, 217, 882, 394]]<|/det|> +To test the hypothesis that ARL3 might regulate that activity of DNAAF9 and Shulin, they expressed recombinant DNAAF9 and Tetrahymena ARL3 in its GTP and GDP mimicking states using Q70L and T30N variants respectively. They found that all Arl3 variants co- eluted with DNAAF9 in high GTP (Fig. S6) but only Arl3Q70L binds DNAAF9 in the presence of GDP (Figure 3). Using this Arl3 variant as bait and lysates of Tetrahymena cells undergoing ciliary regeneration, they co- immunoprecipitated several known effectors of Arl3 and Shulin (Figure 3), suggesting that Arl3 is likely to regulate transport of ODAs through its interaction with Shulin. + +<|ref|>text<|/ref|><|det|>[[117, 420, 882, 642]]<|/det|> +The authors extended this work by analyzing the interaction between recombinant DNAAF9 (or Shulin) in complex with ArlQ70L in vitro by negative stain electron microscopy (Figure 4, Fig. S7). Single particle averaging identified a subset of images ( \(\sim 50\%\) ) containing a DNAAF9/Shulin- Arl3 complex, with the ARL3 subunit bound to the N1 domain of DNAAF9/Shulin. Analytical chromatography confirmed that this interaction was most stable using the Arl3Q70L variant. They extended these observations using AF2 to model the interaction interface and then disrupted the interaction using specific ARL3 mutations (Figure 4e). Further modeling using AF3 suggests that ARL3 interacts with DNAAF9 in the presence of GTP but not GDP (Fig. S8). Additional in vitro studies demonstrate that ARL3 and can disrupt the interaction between purified Shulin and ODAs in the presence of GTP (Figure 5). + +<|ref|>sub_title<|/ref|><|det|>[[120, 668, 411, 685]]<|/det|> +## Overall Evaluation and Significance + +<|ref|>text<|/ref|><|det|>[[117, 712, 882, 890]]<|/det|> +In summary, the authors combine sophisticated modeling, well executed proteomics, and elegant in vitro studies to test a new model of how the ARL3 GTPase might regulate the interaction between a dynein chaperone and the ODAs to maintain the ODAs in an inactive state in the cytoplasm and release and activate the ODAs upon entry into the cilia. The experimental logic is clearly described, the experiments are well executed, and the suggested mechanism of regulation for dynein activation in vivo is a novel, exciting hypothesis. Future in vivo studies will be needed to determine the precise timing and location of ODA activation, but the work presented here is an exciting step forward. I think the work will be of broad interest + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 880, 123]]<|/det|> +to people working in the field of motor activation and targeting, and I highly recommend publication. + +<|ref|>text<|/ref|><|det|>[[117, 150, 733, 168]]<|/det|> +We thank the reviewer for their helpful overall evaluation of our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/images_list.json b/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/supplementary_0_Peer review.mmd b/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/supplementary_0_Peer review.mmd new file mode 100644 index 0000000000000000000000000000000000000000..dde24f65b7692444c12fbea762ded38cabc99eea --- /dev/null +++ b/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/supplementary_0_Peer review.mmd @@ -0,0 +1,66 @@ + +# nature portfolio + +Peer Review File + +# Integrated Molecular and Clinical Characterization of Pulmonary Large Cell Neuroendocrine Carcinoma + +Corresponding Author: Dr Anne Chiang + +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Communications. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have thoroughly addressed each of my concerns to the best of their ability. Given the substantial effort this study represents in advancing our understanding of LCNEC, I can only recommend this work for publication in Nature Communications. + +Reviewer #3 + +(Remarks to the Author) + +The authors have responded to all of the comments appropriately. This manuscript is well organized. I am satisfied with the revised manuscript. + +Reviewer #4 + +(Remarks to the Author) Authors have addressed the reviewers' comments satisfactorily. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## RESPONSE TO REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have thoroughly addressed each of my concerns to the best of their ability. Given the substantial effort this study represents in advancing our understanding of LCNEC, I can only recommend this work for publication in Nature Communications. + +We sincerely thank Reviewer #1 for the thoughtful feedback and generous remarks. We are especially grateful for the recognition of the effort and significance of our work. + +Reviewer #3 (Remarks to the Author): + +The authors have responded to all of the comments appropriately. This manuscript is well organized. I am satisfied with the revised manuscript. + +We thank Reviewer #3 for the careful review and for acknowledging that we appropriately addressed all comments. We are pleased that the revised manuscript was found to be well organized and satisfactory. + +Reviewer #4 (Remarks to the Author): + +Authors have addressed the reviewers' comments satisfactorily. + +We appreciate Reviewer #4's constructive feedback and are glad that our responses and revisions have addressed the comments satisfactorily. + +<--- Page Split ---> diff --git a/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/supplementary_0_Peer review_det.mmd b/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/supplementary_0_Peer review_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..21563dbfeb98e6893262a74a68d39d4576899c97 --- /dev/null +++ b/peer_reviews/a5ae5dc4bceb0be2c09846183e6eddb36ab07aec39f0eb62031429b6f3eadcb8/supplementary_0_Peer review/supplementary_0_Peer review_det.mmd @@ -0,0 +1,93 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 296, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[74, 160, 800, 210]]<|/det|> +# Integrated Molecular and Clinical Characterization of Pulmonary Large Cell Neuroendocrine Carcinoma + +<|ref|>text<|/ref|><|det|>[[74, 223, 412, 241]]<|/det|> +Corresponding Author: Dr Anne Chiang + +<|ref|>text<|/ref|><|det|>[[72, 274, 875, 302]]<|/det|> +This manuscript has been previously reviewed at another journal. This document only contains information relating to versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[72, 313, 866, 329]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 366, 145, 379]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 392, 220, 405]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 418, 161, 431]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 444, 238, 457]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 457, 921, 498]]<|/det|> +The authors have thoroughly addressed each of my concerns to the best of their ability. Given the substantial effort this study represents in advancing our understanding of LCNEC, I can only recommend this work for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[73, 510, 161, 523]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 536, 238, 549]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 549, 911, 576]]<|/det|> +The authors have responded to all of the comments appropriately. This manuscript is well organized. I am satisfied with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[73, 589, 161, 601]]<|/det|> +Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 615, 510, 641]]<|/det|> +(Remarks to the Author) Authors have addressed the reviewers' comments satisfactorily. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 100, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 113, 911, 166]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 166, 618, 180]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 149, 475, 167]]<|/det|> +## RESPONSE TO REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 181, 420, 199]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 213, 880, 263]]<|/det|> +The authors have thoroughly addressed each of my concerns to the best of their ability. Given the substantial effort this study represents in advancing our understanding of LCNEC, I can only recommend this work for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[116, 277, 847, 311]]<|/det|> +We sincerely thank Reviewer #1 for the thoughtful feedback and generous remarks. We are especially grateful for the recognition of the effort and significance of our work. + +<|ref|>text<|/ref|><|det|>[[116, 343, 420, 360]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 375, 832, 408]]<|/det|> +The authors have responded to all of the comments appropriately. This manuscript is well organized. I am satisfied with the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[116, 422, 839, 472]]<|/det|> +We thank Reviewer #3 for the careful review and for acknowledging that we appropriately addressed all comments. We are pleased that the revised manuscript was found to be well organized and satisfactory. + +<|ref|>text<|/ref|><|det|>[[116, 486, 420, 503]]<|/det|> +Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 520, 624, 537]]<|/det|> +Authors have addressed the reviewers' comments satisfactorily. + +<|ref|>text<|/ref|><|det|>[[115, 552, 825, 585]]<|/det|> +We appreciate Reviewer #4's constructive feedback and are glad that our responses and revisions have addressed the comments satisfactorily. + +<--- Page Split ---> diff --git a/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/images_list.json b/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..b67d7ebf34bfabcffebc78c2312e1fd4ecc3dca0 --- /dev/null +++ b/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/images_list.json @@ -0,0 +1,93 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure S8. Tumor growth curve of mice with B16F10 tumors treated with reduced dosing frequency of LD4172. The administration of LD4172 was modified to a reduced dosage of \\(20mg / kg\\) every other day \\((n = 8)\\) . The data are expressed as the mean \\(\\pm\\) SEM. \\* \\(p< 0.1\\) ; \\*\\* \\(p< 0.01\\) ; \\*\\*\\* \\(p< 0.001\\) ; \\*\\*\\*\\* \\(p< 0.0001\\) . ns, no statistical significance.", + "footnote": [], + "bbox": [], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure S3: Cell viability of B16F10 cells with indicated treatment (72 h, \\(n = 3\\) ).", + "footnote": [], + "bbox": [ + [ + 291, + 308, + 707, + 519 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Figure: Chemical structures and potency of new CRBN-based PROTACs.", + "footnote": [], + "bbox": [ + [ + 128, + 93, + 820, + 343 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Figure: Flow cytometric analysis of B16F10 cell killing (DiO+PI+) after cotreated with activated T cells for 24 hours.", + "footnote": [], + "bbox": [ + [ + 110, + 123, + 847, + 339 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Figure S9. LD4172 concentrations in various tissues of B16F10 tumor-bearing C57BL/6J mice at different time points following a \\(20 \\mathrm{mg / kg}\\) intraperitoneal (i.p.) administration \\((n = 4)\\) .", + "footnote": [], + "bbox": [ + [ + 192, + 103, + 812, + 346 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Figure S9. LD4172 concentrations in various tissues of B16F10 tumor-bearing C57BL/6J mice at different time points following a \\(20 \\mathrm{mg / kg}\\) intraperitoneal (i.p.) administration \\((n = 4)\\) .", + "footnote": [], + "bbox": [ + [ + 216, + 103, + 780, + 323 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Figure S7. Pharmacodynamic (PD) properties of LD4172 with intratumoral administration (i.t.). Representative immunoblots of RIPK1 expression in various tissues of C57BL/6J mice treated with LD4172 are shown. Mice with syngeneic B16F10 tumors received intratumoral injections of LD4172 (10mg/kg) twice daily for three days. Upon sacrifice, tissues were collected, and the levels of RIPK1 were quantified through Western blotting.", + "footnote": [], + "bbox": [], + "page_idx": 17 + } +] \ No newline at end of file diff --git a/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd b/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d56f2d61b87859e2b82df4dc546a01e7860f1b79 --- /dev/null +++ b/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd @@ -0,0 +1,445 @@ + +# nature portfolio + +# Peer Review File + +# Development of a RIPK1 Degrader to Enhance Antitumor Immunity + +Corresponding Author: Professor Jin Wang + +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +This manuscript by Yu et al describes the development and testing of a novel RIPK1 protac LD4172. Using a RIPK1 type II kinase inhibitor attached to a VHL ligand, the authors showed that LD4172 can effectively degrade RIPK1 in multiple human and mouse tumor cell lines in vitro, as well as in some but not all tissues in vivo. The compound also sensitized B16F10 cells to apoptosis induced by TNF in vitro. This is in line with reports in the literature that RIPK1 has a pro- death function that is dependent on its kinase, as well as a pro- survival function via its intermediate and death domain. The latter scaffold function has been suggested to be due to RIPK1's role in stabilizing pro- survival molecules such as TRAF2, and/or its role in activating NFkappaB. RIPK1 also has a pro- survival role by blocking the interaction between ZBP1 and RIPK3 to suppress RIPK3- dependent death. In vivo, LD4172 enhanced the sensitivity of B16 F10 tumors to immune checkpoint blockade by anti- PD1. The authors suggests that tumor death conferred by RIPK1 degradation is immunogenic based on HMGB1 release, calreticulin exposure, and recruitment of various inflammatory cells to the dying tumor microenvironment. Quite interestingly, RIPK1 degradation seems to be much more pronounced in the tumor tissue than in non- tumor tissues. Authors speculated that this could be due to the compound binding to albumin, which may accumulate in tumor sites. This is largely a descriptive study of the effect of administrating the RIPK1 protac in vitro and in vivo. Overall, this is a thorough study that provides proof- of- concept for targeting RIPK1 in a preclinical setting. + +1. The main deficiency is that there is not much mechanistic dissection. The prior publication from Cucolo et al (Ref #5) had suggested that in the absence of RIPK1, there is a shift from Complex I to Complex II in the TNFR1 pathway. It would be nice to show that this is also true when RIPK1 is acutely removed by the protac. + +2. While the in vitro studies showed that LD4172 sensitizes to TNFR1-induced apoptosis, it is less clear whether this is the case in vivo or whether other death receptors in the TNFRsF family may also be involved. If TNF/TNFR1 signaling is responsible for the sensitizing effect of LD4172 in vivo, then one would predict that B16 F10 cells that are knockout for TNFR1 would be resistant to the effect of LD4172 + anti-PD1. Experiment in Fig 4F can be repeated comparing WT vs TNFR1 KO B16 cells. It would be interesting to know one way or the other. + +3. While the proteomic analysis in Fig. 2J indicates a high degree of specificity, an additional control that could be included is to show that the related kinases RIPK2 and RIPK3 are not affected by LD4172. + +4. In the legend for Figure 3, the early apoptotic cells (AV+, PI-) should be in the upper left quadrant, not lower right. +5. The key to the graph in Fig S2A for the MC38 experiments appears to be incorrect. Shouldn't it be PD1 and LD4172 treatment instead of RIPK1 KO? + +## Reviewer #2 + +(Remarks to the Author) + +The authors have generated a PROTAC targeting RIPK1 for degradation and showed that it recapitulates the effect of loss of RIPK1 in tumours in vitro and in vivo. Interestingly, their RIPK1 PROTAC synergises with anti- PD1 therapy in vivo. This study is generally well designed and controlled. To my knowledge, it is the first RIPK1 PROTAC showing such good synergism in vivo. Given the lethality of RIPK1 mice, this tool can also be used to study the role of RIPK1 in vivo in adult development, infectious diseases, etc. There are a few imprecisions and clumsiness throughout the manuscript that need to be addressed. Please see specific comments. + +<--- Page Split ---> + +Specific comments: + +In Fig. 2D- E, the authors should acknowledge that RIPK1 is already re- expressed after a 4- hour washout. This could be important in terms of RIPK1- dependent responses, as we don't know what level of RIPK1 is required to fully reconstitute its function. For example, there is a small proportion of RIPK1 that goes to TNF- induced Complex I; therefore, \(10\%\) of RIPK1 (after 4- hour washout) could be enough to provide a normal TNF response. + +Line 125 'In contrast to situations where RIPK1 is kinase- dead, genetic deletion of RIPK1 has been found to trigger apoptosis both in vitro and in vivo 15.' + +Ref 15 is only about RIPK1 knock- out mice and not about RIPK1 kinase dead. Plus, ref 15 is not the only one and the first one to show that loss of RIPK1 induces apoptosis. The authors should be fair and cite all RIPK1 kinase dead and RIPK1 knock- out papers that support their statement, e.g., Kelliher Immunity 1998; Kaiser PNAS 2014; Rickard Cell 2014; Polykratis JI 2014; Berger JI 2014; Newton Science 2014. + +In Fig S2A the legend says that it's sgNC vs RIPK1 KO, while in the manuscript, the authors described it as tumours being treated with LD4172. Is it a mistake with the legend or the wrong graph? + +In Line 181 the authors wrote "Consistent with the in vitro findings, LD4172 also triggered significant cell death in the tumor (Fig. 182 5A, 2nd column). + +The 2nd column is H&E, which does not reflect of cell death but rather absence or presence of cells. Caspase- 3/7 are the cell death markers. Please correct the text accordingly. + +The authors wrote in line 184 'While apoptotic cell death was traditionally considered non- immunogenic, accumulating experimental data have revealed its potential to drive immune cell infiltration and anti- cancer immunity 16- 19. Supporting the activation of immunogenic apoptosis, we observed a significant increase in plasma HMGB1 levels (Fig. 5B) and enhanced exposure of calreticulin on the surface of B16F10 tumor cells (Fig. 5A, 5th column).' + +However, the authors don't have supporting evidence that apoptosis is the mode of cell death that is immunogenic because it is well established that loss of RIPK1 can also induce RIPK3- dependent necroptosis (Kaiser PNAS 2014; Rickard Cell 2014; Dillon cell 2014; Berger JI 2014; Newton Science 2016), which is also immunogenic. One way to determine if apoptosis or necroptosis is immunogenic is to analyse MLKL- /- and casp3/7- /- tumours treated with RIPK1 PROTAC. The authors should rewrite this part. + +The authors wrote in line 196 'In addition, combined therapy with LD4172 and anti- PD1 not only induced extensive TIL infiltration (Fig. 5D- H) but also significantly enhanced anti- PD1 positivity in immunologically cold B16F10 tumors, as demonstrated by increased infiltration of cytotoxic CD8+ T cells (CD8+IFN- \(\gamma +\) , Fig. 5A, 6th column, and 5G- H) and decreased infiltration of FOXP3+ T regulatory cells (Fig. 5A, 7th column) within the TME.' + +This is wrong: LD4172 did not increased TIL infiltration CD8+ T cells induced by anti- PD1 because there is not statistical difference between anti- PD1 treatment and anti- PD1+ LD4172 treatment in Fig 5C, G and H. Please correct this part. + +The authors wrote in line 235 'Unlike Ripk1 knockout mice, which die at 1- 3 days of age due to their widespread roles in multiple tissues and organs 25, homozygous loss- of- function RIPK1 mutations are well tolerated in humans 26. Patients with complete loss of RIPK1 protein only showed symptoms confined to the immune system, with primary immunodeficiency and/or intestinal inflammation 26.' + +And Line 240 'Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies, human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable, especially with transient intervention in well- controlled clinical settings.' + +And Line 259 'Considering the predicted safety profile of RIPK1 degradation based on human genetics' + +By stating that loss of RIPK1 is 'well tolerated in humans', 'only showed symptoms confined to the immune system', 'human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable' and 'predicted safety profile of RIPK1 degradation based on human genetics', the authors are minimising the effect of loss of RIPK1 in human to promote the use of RIPK1 PROTAC. This is extremely clumsy because Ref 26 and Li et al PNAS 2019 (doi.org/10.1073/pnas.18135821, which should be cited alongside Ref 26) showed that RIPK1 deficient patients are affected with severe immunodeficiency which can lead to the death of the patients at really young age. The authors should rephrase this part by stating that despite the severe immunodeficiency cause by permanent loss of RIPK1 in human, acute, chemical and transient depletion of RIPK1 might be tolerable in humans. Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies. + +## Reviewer #3 + +(Remarks to the Author) + +The authors reported the development of the first- in- class RIPK1 degraders that utilize the VHL E3 ligase to potently degrade RIPK1 in various cells. One of the lead compounds, LD4172, is highly specific and only degrade RIPK1 in cells with high Dmax and DC50 values in a VHL and proteasome- dependent manner. LD4172 can synergistically kill B16F10 mouse melanoma cells in combination with TNFa. Interestingly, administration of B16F10 tumor- bearing mice with LD4172 resulted in significant reduction in RIPK1 expression in the tumors but not in normal tissues. This reduction was associated with the potentiation of tumor growth inhibition when it was combined with anti- PD1 antibody. More importantly, the synergistic effect was greater with the combination of anti- PD1 antibody and LD4172 than that of anti- PD1 antibody and the + +<--- Page Split ---> + +RIPK1 inhibitor. These findings demonstrate that RIPK1 degraders may exert stronger antitumor activity than RIPK1 inhibitors by degrading RIPK1 to remove both its kinase and scaffold activity. In addition, this combination can also enhance antitumor immunity. + +Concerns: + +1. It is very interesting that only VHL-based PROTACs can effectively degrade RIPK1 but not CRBN- and MDM2-based and adamantane-tagged PROTACs. Can the authors share some insights why only VHL can degrade RIPK1? Have the authors tried to use different linker length for other PROTACs to validate the lack of degradation for RIPK1? + +2. The authors showed that LD4172 can sensitize B16F10 cells to TNFa. Since they also showed that LD4172 can synergistically suppress B16F10 tumor growth with Anti-PD1 antibody, have the authors tested whether LD4172 can sensitize B16F10 cells to cytotoxic T cells? + +3. The finding that LD4172 was more effectively in degrading RIPK1 in tumor tissues than in normal tissues is very interesting. Do the authors explore why these normal tissues exhibited less RIPK1 degradation after the treatment with LD4172? Is this related to different uptake of the compounds between tumors and normal tissues? + +4. RIPK1 KO has a profound effect in mice as they die at 1-3 days of age while patients with homozygous loss-of-function RIPK1 are alive and only exhibit some less server abnormalities such as primary immunodeficiency and/or intestinal inflammation. However, the mice treated with LD4172 did not show any side effects in mice. This may be attributable to the inability of LD4172 to effectively degrade RIPK1 in normal tissues. This finding may have important implications in developing RIPK1 targeted therapy because RIPK1 might be more toxic to normal tissues while RIPK1 PROTACs might be more selective to tumors. As such, RIPK1 PROTACs may have a better opportunity to be developed as anticancer drugs. + +5. The finding that depletion of CD8 T cells with an antibody abrogated the synergistic antitumor activity of LD4172 and anti-PD1 antibody suggests that the direct antitumor activity of RIPK1 PROTACs is less important than the induction of CD8 T cell-mediated antitumor immunity in the B16F10 tumor model. + +## Reviewer #4 + +(Remarks to the Author) + +I support publication of this work after addressing comments below. + +- What are the noteworthy results? + +This is a nice study describing the discovery and characterization of the first PROTAC-based RIPK1 degrader. The study appears to be done with excellent quality and the conclusions are well supported by the provided data. + +Key results: + +1. RIPK1 can be degraded using a suitably designed/optimized PROTAC degrader +2. RIPK1 degrader has fundamentally different pharmacology relative to RIPK1 inhibitor +3. Degradation of RIPK1 by LD4172 triggered immunogenic cell death (ICD) +4. Degradation of RIPK1 resulted in an increase in tumor-infiltrating lymphocytes and sensitized tumors to anti-PD1 therapy + +The efficacy in the mouse models is limited (this would be called progressive disease in patients) but does show the mechanism appears to be active in a murine model. + +It would be nice to see: + +1. PK data for LD4172 to enable understanding of how much drug exposure there was following the dosing regime used. +2. To show evidence of target degradation in vivo (blood and tumor tissue). +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. +- Yes demonstrates another use of small molecule degraders to achieve novel pharmacology. +- Does the work support the conclusions and claims, or is additional evidence needed? +- The work is well supported by the data provided. +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? None that I could find. +- Is the methodology sound? Does the work meet the expected standards in your field? +- Is there enough detail provided in the methods for the work to be reproduced? +- Yes experimental sections appear to be sound, nice characterization data is provided for the compounds. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +This revised manuscript by Yu et al has addressed the critiques of this reviewer. While an experiment using TNFR1 KO of the B16 F10 cells would have been preferable in the in vivo studies, the authors used anti-TNF to show that the anti-tumor effect of the LD4172 protac is TNF- dependent. A recent published study from Pascal Meier's group also showed similar findings with a different RIPK1 protac and in that study, some of the effects of a RIPK1 protac on TNFR1 signaling complexes were examined. Some of the sloppiness in the manuscript brought up by this and other reviewers were also addressed. The manuscript is now acceptable. + +<--- Page Split ---> + +Reviewer #2 + +(Remarks to the Author) The authors have adequately addressed all my comments. + +Reviewer #3 + +(Remarks to the Author) + +The revised manuscript has significantly improved with new experimental data to address all my concerns. Particularly, the data from the LD4172 tissue distribution study and RIPK1 degradation in tumors vs various normal tissues are very interesting. I agree with the authors that albumin binding and higher uptake and degradation of albumin by tumor cells may contribute to the differences between tumors and normal tissues observed. It would be interesting to explore this further in future studies. + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +1 Dear Editor and Reviewers: + +2 We have completed the revisions for our manuscript titled "Development of a First- in- Class RIPK1 Degrader to Enhance Antitumor Immunity". We sincerely appreciate the thorough and professional review of our work. As noted, there were several issues that needed to be addressed. In response to the reviewers' suggestions, we have made significant corrections to the manuscript, which are highlighted in the revised version. Our detailed responses to the reviewers' comments are provided below. + +Thank you for your continued consideration. + +Detailed responses to the reviewers' comments: + +Reviewer #1 (Remarks to the Author): with expertise in cancer immunotherapy, cell death signaling, RIPK1 + +14 + +This manuscript by Yu et al describes the development and testing of a novel RIPK1 protac LD4172. Using a RIPK1 type II kinase inhibitor attached to a VHL ligand, the authors showed that LD4172 can effectively degrade RIPK1 in multiple human and mouse tumor cell lines in vitro, as well as in some but not all tissues in vivo. The compound also sensitized B16F10 cells to apoptosis induced by TNF in vitro. This is in line with reports in the literature that RIPK1 has a pro- death function that is dependent on its kinase, as well as a pro- survival function via its intermediate and death domain. The latter scaffold function has been suggested to be due to RIPK1's role in stabilizing pro- survival molecules such as TRAF2, and/or its role in activating NFkappaB. RIPK1 also has a pro- survival role by blocking the interaction between ZBP1 and RIPK3 to suppress RIPK3- dependent death. In vivo, LD4172 enhanced the sensitivity of B16 F10 tumors to immune checkpoint blockade by anti- PD1. The authors suggests that tumor death conferred by RIPK1 degradation is immunogenic based on HMGB1 release, calreticulin exposure, and recruitment of various inflammatory cells to the dying tumor microenvironment. Quite interestingly, RIPK1 degradation seems to be much more pronounced in the tumor tissue than in non- tumor tissues. Authors speculated that this could be due to the compound binding to albumin, which may accumulate in tumor sites. This is largely a descriptive study of the effect of administrating the RIPK1 protac in vitro and in vivo. Overall, this is a thorough study that provides proof- of- concept for targeting RIPK1 in a preclinical setting. + +<--- Page Split ---> + +1. The main deficiency is that there is not much mechanistic dissection. The prior publication from Cucolo et al (Ref #5) had suggested that in the absence of RIPK1, there is a shift from Complex I to Complex II in the TNFR1 pathway. It would be nice to show that this is also true when RIPK1 is acutely removed by the protac. + +Response: Thank you for your insightful comment. You are absolutely correct in noting that RIPK1, known for its scaffold function, is recruited into complex I upon TNF- \(\alpha\) signaling. Following its ubiquitylation, the recruitment of the TAK1- TAB2/3 complex and the NEMO- IKKα- IKKβ complex is crucial for the activation of NF- \(\kappa\) B signaling. Our NF- \(\kappa\) B reporter assay results support this, showing significant NF- \(\kappa\) B activation by TNF- \(\alpha\) in B16F10 cells (Figure 3A). As expected, the RIPK1 degrader LD4172, as opposed to the RIPK1 kinase inhibitor T2I, significantly inhibited TNF- \(\alpha\) - induced NF- \(\kappa\) B activation. Furthermore, the combination of TNF- \(\alpha\) with LD4172 led to a marked induction of apoptosis in B16F10 cells (Figure 3B- D), indicating that acute deletion of RIPK1 shifts the cells from a pro- survival to a pro- death state. Interestingly, a recent study by the Meier group, published in Immunity, reported the development of a RIPK1 PROTAC degrader, R1- ICR- 5. Their findings demonstrate that RIPK1 degradation can promote the interactions of TNFR1, TRADD, TRAF2, cIAP, and HOIP, forming a RIPK1- independent complex I, with enhanced ubiquitylation leading to deregulated TNF signaling (Figure adapted from Mannion's paper). These findings underscore the potential of RIPK1 degraders as powerful chemical probes for investigating the biological roles of RIPK1 in complex I and complex II. We have incorporated these updates in lines 130- 137, 227- 237 and Figure 3A. + +## [figure redacted] + +Adapted from Mannion's paper: Acute degradation of RIPK1 deregulates TNFR1 signaling, L929 Cells were treated with DMSO or R1- ICR- 5 (overnight) before anti- GST- TUBE pull- down to isolate the ubiquitylated proteome. + +![](images/Figure_unknown_0.jpg) + + +<--- Page Split ---> + +63 Figure 3A. NF- kB activity of B16F10 cells expressing a NanoLuc reporter for NF- kB response with indicated treatments for 48 hours. + +65 Updated paragraph in the manuscript can be found as follows: + +66 Lines 130- 137: "RIPK1- deficient MEFs exhibit a severe impairment in their ability to activate NF- kB signaling, whereas kinase- dead RIPK1 knock- in mice remain viable and display normal TNFR1- mediated NF- kB signaling16- 18. Moreover, unlike the kinase- dead RIPK1 scenario, the genetic deletion of RIPK1 has been shown to trigger apoptosis both in vitro and in vivo19- 24. To evaluate NF- kB activity in B16F10 cells, we transiently transfected them with a plasmid encoding a Nanoluc reporter containing the NF- kB response element, allowing us to monitor NF- kB activity through luminescence. Upon TNF- α treatment, B16F10 cells exhibited a robust induction of NF- kB activity, which was significantly attenuated by LD4172 but not by the RIPK1 kinase inhibitor (Fig. 3A)." + +75 Lines 227- 237: "Upon TNF- α signaling, RIPK1 is recruited to complex I, where it acts as a crucial scaffold, essential for the ubiquitylation- dependent activation of NF- kB signaling. Our findings demonstrate that LD4172- induced RIPK1 degradation, unlike the action of RIPK1 kinase inhibitors, significantly impairs TNF- α- induced NF- kB activation. Furthermore, the combination of TNF- α and LD4172 markedly induces apoptosis in B16F10 cells. This suggests that acute RIPK1 deletion shifts the cellular response from a pro- survival to a pro- death state by altering the composition of complexes I and II. Interestingly, the Meier group developed a similar RIPK1 degrader18, revealing that RIPK1 degradation promotes the formation of a RIPK1- independent complex I. This complex display enhanced interactions among TNFR1, TRADD, TRAF2, cIAP, and HOIP, leading to deregulated TNF signaling through increased ubiquitylation. These findings underscore the potential of RIPK1 degraders as valuable chemical tools for in vitro studies, offering new insights into the biological roles of RIPK1 within various signaling complexes." + +29. While the in vitro studies showed that LD4172 sensitizes to TNFR1-induced apoptosis, it is less clear whether this is the case in vivo or whether other death receptors in the TNFRSF family may also be involved. If TNF/TNFR1 signaling is responsible for the sensitizing effect of LD4172 in vivo, then one would predict that B16 F10 cells that are knockout for TNFR1 would be resistant to the effect of LD4172 + anti-PD1. Experiment in Fig 4F can be repeated comparing WT vs TNFR1 KO B16 cells. It would be interesting to know one way or the other. + +Response: Thank you for highlighting this important aspect that we initially overlooked in our study of LD4172. As you suggested, the sensitizing effect of LD4172 in vivo is indeed dependent on TNF/TNFR1 signaling. Our findings demonstrate that neutralizing TNFα with anti-mouse TNFα in vivo completely abolishes the synergy between LD4172 and anti-PD1 therapy. This result is consistent with our in vitro experiments, which + +<--- Page Split ---> + +101 suggest that LD4172- induced apoptosis in B16F10 tumors involves TNF/TNFR1 102 signaling. We have addressed this in lines 238- 248, and the relevant figures have been 103 added to the supplementary data (Figure S6). + +![](images/Figure_unknown_1.jpg) + + +104 + +105 Figure S6. Anti- TNFα reversed the synergy between LD4172 and anti- PD1. C57B6/J 106 mice were subcutaneously inoculated with \(3 \times 10^{5}\) B16F10 tumor cells. After seven days 107 (tumor size \(\sim 100 \text{mm}^3\) ), mice were treated every three days with anti- PD1 (100 \(\mu \text{g}\) per 108 dose, i.p.), daily with LD4172 (20 mg/kg, i.p.), a combination of LD4172 and anti- PD1 109 (same dose as their individual doses), the combination plus anti- TNFα (200ug every 110 three days, i.p.), or their corresponding vehicle control (n=5). + +111 Updated paragraph in the manuscript can be found as follows: + +112 Lines 238- 248: "LD4172 has also demonstrated significant therapeutic efficacy in vivo 113 by inducing RIPK1 degradation within tumors and exhibiting a synergistic effect on 114 tumor growth inhibition when combined with anti- PD1 therapy. Although LD4172 plays a 115 role in inducing ICD in B16F10 tumors, the degradation of RIPK1 alone is insufficient, 116 as RIPK1 primarily acts as a brake on immunogenic pathways18. Therefore, additional 117 ligands are required to fully activate these pathways. Anti- PD1 can supply these 118 necessary ligands by promoting TNF production, thereby sensitizing cancer cells to cell 119 death in the absence of RIPK1. This synergistic relationship is further evidenced by the 120 finding that the combination of LD4172 and anti- PD1 loses its efficacy when anti- TNF- α 121 is introduced, completely abolishing their combined effect (Figure S6). Moreover, when 122 used in conjunction with anti- PD1, LD4172 reshapes the tumor immune 123 microenvironment by enhancing the infiltration of dendritic cells and IFNγ+ T cells, as 124 well as by promoting the secretion of immunostimulatory cytokines, leading to 125 substantial antitumor effects." + +126 3. While the proteomic analysis in Fig. 2J indicates a high degree of specificity, an 127 additional control that could be included is to show that the related kinases RIPK2 and 128 RIPK3 are not affected by LD4172. + +<--- Page Split ---> + +Response: This is an excellent point. Our proteomic data does not rule out the possibility that RIPK2 and RIPK3 are unaffected by LD4172. To test the selectivity of LD4172, we used the THP1 cell line, which expresses RIPK1, RIPK2, and RIPK3. After treating the cells with LD4172 at varying concentrations for 24 hours, we observed significant degradation of RIPK1 at 16nM, while RIPK2 and RIPK3 levels remained unchanged, indicating the selectivity of LD4172 for RIPK1. We have addressed this in lines 122- 124, and the relevant figures have been added to the supplementary data (Figure S2). + +![](images/Figure_unknown_2.jpg) + + +Figure S2. Western blot analysis showing the expression levels of RIPK1, RIPK2, and RIPK3 in THP1 cells following 24- hour treatment with varying concentrations of LD4172. + +Updated paragraph in the manuscript can be found as follows: + +Lines 122- 124: "Additionally, at effective LD4172 concentrations (16 nM- 10 μM) that induce RIPK1 degradation in THP1 cells, we observed no significant changes in the protein levels of related kinases, such as RIPK2 and RIPK3 (Fig. S2)." + +4. In the legend for Figure 3, the early apoptotic cells (AV+, PI-) should be in the upper left quadrant, not lower right. + +Response: Thanks for pointing this out and sorry for our carelessness, the corresponding correction is highlighted in Figure 3. + +5. The key to the graph in Fig S4A for the MC38 experiments appears to be incorrect. Shouldn't it be PD1 and LD4172 treatment instead of RIPK1 KO? + +Response: Thank you very much for catching the mistake. Figure S4A demonstrates the synergistic effect between LD4172 and Anti-PD1, and the figure legend has been corrected. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): with expertise in cancer, inflammation, RIPK1 + +The authors have generated a PROTAC targeting RIPK1 for degradation and showed that it recapitulates the effect of loss of RIPK1 in tumours in vitro and in vivo. Interestingly, their RIPK1 PROTAC synergises with anti- PD1 therapy in vivo. This study is generally well designed and controlled. To my knowledge, it is the first RIPK1 PROTAC showing such good synergism in vivo. Given the lethality of RIPK1 mice, this tool can also be used to study the role of RIPK1 in vivo in adult development, infectious diseases, etc. There are a few imprecisions and clumsiness throughout the manuscript that need to be addressed. Please see specific comments. + +Specific comments: + +In Fig. 2D- E, the authors should acknowledge that RIPK1 is already re- expressed after a 4- hour washout. This could be important in terms of RIPK1- dependent responses, as we don't know what level of RIPK1 is required to fully reconstitute its function. For example, there is a small proportion of RIPK1 that goes to TNF- induced Complex I; therefore, \(10\%\) of RIPK1 (after 4- hour washout) could be enough to provide a normal TNF response. + +Response: Thank you for raising this excellent point. As you suggested, inadequate RIPK1 degradation can indeed affect the observed phenotype. As demonstrated in Figure S8, at the late stage of treatment (more than 15 days after tumor inoculation), the synergy between anti- PD1 and a low dose of LD4172 (20 mg/kg, twice daily) is less potent compared to a high dose of LD4172 (20 mg/kg, once daily). This indicates that more thorough and persistent RIPK1 degradation can enhance the synergistic effect. Additionally, Mannion et al. have shown that intratumoral injection of a RIPK1 degrader can synergize with anti- PD1 to regress \(30\%\) of EO771 breast tumor growth (Figure adapted from Mannion et al.'s paper). This further suggests that adequate degradation of RIPK1 in the tumor is more beneficial for promoting cancer immunotherapy, and that the remaining RIPK1 in tumor might still be sufficient to execute its pro- survival functions. We have emphasized this point in both Figure 2E legend and lines 82- 84 of the main text. + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Figure S8. Tumor growth curve of mice with B16F10 tumors treated with reduced dosing frequency of LD4172. The administration of LD4172 was modified to a reduced dosage of \(20mg / kg\) every other day \((n = 8)\) . The data are expressed as the mean \(\pm\) SEM. \* \(p< 0.1\) ; \*\* \(p< 0.01\) ; \*\*\* \(p< 0.001\) ; \*\*\*\* \(p< 0.0001\) . ns, no statistical significance.
+ +## [figure redacted] + +Figure adapted from Mannion's paper: RIPK1 PROTACs enhance response to immune checkpoint blockade + +(A) Schematic depicting the treatment regimen of tumor-bearing mice. I.P., intraperitoneal injection; I.T., intratumoral injection. +(B) Tumor growth curves of tumor bearing mice treated as in (A). Thick lines represent average tumor growth. + +Updated paragraph in the manuscript can be found as follows: + +Lines 82- 84: "Four hours after the removal of LD4172, RIPK1 starts to resynthesize in both cell lines. The resynthesis half-lives are approximately 48 and 24 hours in Jurkat and B16F10 cells, respectively (Fig. 2D- E)." + +Line 125 'In contrast to situations where RIPK1 is kinase- dead, genetic deletion of RIPK1 has been found to trigger apoptosis both in vitro and in vivo 15. ' + +Ref 15 is only about RIPK1 knock- out mice and not about RIPK1 kinase dead. Plus, ref 15 is not the only one and the first one to show that loss of RIPK1 induces apoptosis. The authors should be fair and cite all RIPK1 kinase dead and RIPK1 knock- out papers that support their statement, e.g., Kelliher Immunity 1998; Kaiser PNAS 2014; Rickard Cell 2014; Polykratis JI 2014; Berger JI 2014; Newton Science 2014. + +<--- Page Split ---> + +Response: Thank you for pointing this out. The recommended papers are at the forefront of illustrating the kinase- dependent and - independent functions of RIPK1, and we have cited them in our manuscript. + +In Fig S4A the legend says that it's sgNC vs RIPK1 KO, while in the manuscript, the authors described it as tumours being treated with LD4172. Is it a mistake with the legend or the wrong graph? + +Response: Thanks for pointing this out, it is a mistake with the legend, and we have fixed it in Figure S4A legend. + +In Line 181 the authors wrote "Consistent with the in vitro findings, LD4172 also triggered significant cell death in the tumor (Fig. 182 5A, 2nd column). + +The 2nd column is H&E, which does not reflect of cell death but rather absence or presence of cells. Caspase- 3/7 are the cell death markers. Please correct the text accordingly. + +Response: Thanks for pointing this out, we should be strict about description about the figures, the corrected text is highlighted in main text, lines 194- 197. + +Updated paragraph in the manuscript can be found as follows: + +Lines 194- 197: "LD4142 treatment significantly disrupted the dense structure of B16F10 tumors, as evidenced by a marked reduction in cellular density observed in H&E staining (Fig. 5A, 2nd column). Importantly, a notable increase in cleaved caspase 3/7 levels was observed in the LD4172- treated tumors, indicating the occurrence of apoptosis (Fig. 5A, 3rd and 4th columns)." + +The authors wrote in line 184 'While apoptotic cell death was traditionally considered non- immunogenic, accumulating experimental data have revealed its potential to drive immune cell infiltration and anti- cancer immunity 16- 19. Supporting the activation of immunogenic apoptosis, we observed a significant increase in plasma HMGB1 levels (Fig. 5B) and enhanced exposure of calreticulin on the surface of B16F10 tumor cells (Fig. 5A, 5th column).' + +However, the authors don't have supporting evidence that apoptosis is the mode of cell death that is immunogenic because it is well established that loss of RIPK1 can also induce RIPK3- dependent necroptosis (Kaiser PNAS 2014; Rickard Cell 2014; Dillon cell 2014; Berger JI 2014; Newton Science 2016), which is also immunogenic. One way to determine if apoptosis or necroptosis is immunogenic is to analyse MLKL- /- and casp3/7- /- tumours treated with RIPK1 PROTAC. The authors should rewrite this part. + +<--- Page Split ---> + +Response: Thank you for highlighting this important point. In our investigation of the kinase- dependent and - independent functions of RIPK1 using LD4172 and T2I, we attempted to induce necroptosis in B16F10 cells with a combination of TNF- \(\alpha\) , SMAC mimetic (LCL161), and the pan- caspase inhibitor z- VAD- FMK. However, even after 72 hours of treatment, the B16F10 cells remained unresponsive to this necroptotic trigger (Figure S2), suggesting that RIPK3- dependent necroptosis is not active in these cells. This is consistent with reports that B16F10 hardly expresses RIPK325, which may explain their resistance to necroptosis induction. We have emphasized this point in lines 140- 144, and the relevant figures have been added to the supplementary data (Figure S3). + +![](images/Figure_unknown_4.jpg) + +
Figure S3: Cell viability of B16F10 cells with indicated treatment (72 h, \(n = 3\) ).
+ +Updated paragraph in the manuscript can be found as follows: + +Lines 140- 144: "Although B16F10 cells remained unresponsive to necroptotic triggers (TNFα + LCL161 + Z- VAD- FMK, Fig. S3), likely due to the low expression of RIPK325, the combination of TNFα and LD4172 induced significant apoptosis (Fig. 3B- D). This was evidenced by the enhanced surface exposure of phosphatidylserine (Fig. 3B) and increased levels of cleaved caspase- 3/7 and PARP (Fig. 3C- D). Notably, these apoptotic effects were reversed with Z- VAD- FMK treatment (Fig. 3B- D)." + +The authors wrote in line 196 'In addition, combined therapy with LD4172 and anti- PD1 not only induced extensive TIL infiltration (Fig. 5D- H) but also significantly enhanced anti- PD1 positivity in immunologically cold B16F10 tumors, as demonstrated by increased infiltration of cytotoxic CD8+ T cells (CD8+IFN- γ+, Fig. 5A, 6th column, and 5G- H) and decreased infiltration of FOXP3+ T regulatory cells (Fig. 5A, 7th column) within the TME.' + +<--- Page Split ---> + +271 This is wrong: LD4172 did not increased TIL infiltration CD8+ T cells induced by antiPD1 because there is not statistical difference between anti- PD1 treatment and antiPD1+ LD4172 treatment in Fig 5C, G and H. Please correct this part. + +Response: Thanks for your careful checks. As you suggested, we were mixing up the individual effects of LD4172 and anti- PD1 in this part. This has been corrected and highlighted in lines 209- 212. + +Updated paragraph in the manuscript can be found as follows: + +Lines 209- 212: "Additionally, combined therapy with LD4172 and anti- PD1 significantly enhanced anti- PD1 positivity in immunologically cold B16F10 tumors, as demonstrated by increased infiltration of cytotoxic CD8+ T cells (CD8+IFN- \(\gamma +\) , Fig. 5A, 6th column, and 5G- H) and decreased infiltration of FOXP3+ T regulatory cells (Fig. 5A, 7th column) within the TME." + +The authors wrote in line 235 'Unlike Ripk1 knockout mice, which die at 1- 3 days of age due to their widespread roles in multiple tissues and organs 25, homozygous loss- of- function RIPK1 mutations are well tolerated in humans 26. Patients with complete loss of RIPK1 protein only showed symptoms confined to the immune system, with primary immunodeficiency and/or intestinal inflammation 26.' + +And Line 240 'Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies, human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable, especially with transient intervention in well- controlled clinical settings.' + +And Line 259 'Considering the predicted safety profile of RIPK1 degradation based on human genetics' + +By stating that loss of RIPK1 is 'well tolerated in humans', 'only showed symptoms confined to the immune system', 'human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable' and 'predicted safety profile of RIPK1 degradation based on human genetics', the authors are minimising the effect of loss of RIPK1 in human to promote the use of RIPK1 PROTAC. This is extremely clumsy because Ref 26 and Li et al PNAS 2019 (doi.org/10.1073/pnas.18135821, which should be cited alongside Ref 26) showed that RIPK1 deficient patients are affected with severe immunodeficiency which can lead to the death of the patients at really young age. The authors should rephrase this part by stating that despite the severe immunodeficiency cause by permanent loss of RIPK1 in human, acute, chemical and transient depletion of RIPK1 might be tolerable in humans. Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies. + +<--- Page Split ---> + +Response: Thank you for your valuable comments. We realize that we were perhaps too forceful in emphasizing the potential safety of LD4172 and agree that a more critical and unbiased discussion is necessary. We have revised the discussion accordingly, as per your recommendation, which is reflected in lines 265- 270. + +Updated paragraph in the manuscript can be found as follows: + +Lines 265- 270: "Unlike Ripk1 knockout mice, which die within 1- 3 days of age due to the critical role of RIPK1 in multiple tissues and organs31, the phenotypes of homozygous loss- of- function RIPK1 mutations in humans are relatively less severe32. Although permanent loss of RIPK1 in patients leads to severe immunodeficiency and/or intestinal inflammation33, chemical- induced protein degradation of RIPK1, which is acute, transient, and potentially tissue- specific34, might be more tolerable in humans. However, the safety profiles of RIPK1 degraders need to be evaluated in future clinical studies." + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): with expertise in cancer therapeutics and degrader design + +The authors reported the development of the first- in- class RIPK1 degraders that utilize the VHL E3 ligase to potently degrade RIPK1 in various cells. One of the lead compounds, LD4172, is highly specific and only degrade RIPK1 in cells with high Dmax and DC50 values in a VHL and proteasome- dependent manner. LD4172 can synergistically kill B16F10 mouse melanoma cells in combination with TNFa. Interestingly, administration of B16F10 tumor- bearing mice with LD4172 resulted in significant reduction in RIPK1 expression in the tumors but not in normal tissues. This reduction was associated with the potentiation of tumor growth inhibition when it was combined with anti- PD1 antibody. More importantly, the synergistic effect was greater with the combination of anti- PD1 antibody and LD4172 than that of anti- PD1 antibody and the RIPK1 inhibitor. These findings demonstrate that RIPK1 degraders may exert stronger antitumor activity than RIPK1 inhibitors by degrading RIPK1 to remove both its kinase and scaffold activity. In addition, this combination can also enhance antitumor immunity. + +Concerns: + +1. It is very interesting that only VHL-based PROTACs can effectively degrade RIPK1 but not CRBN- and MDM2-based and adamantane-tagged PROTACs. Can the authors share some insights why only VHL can degrade RIPK1? Have the authors tried to use different linker length for other PROTACs to validate the lack of degradation for RIPK1? + +Response: Thank you for bringing up this point. In our initial exploration of E3 ligases, we synthesized two CRBN- based PROTACs with distinct PEG linkers, as detailed in our manuscript. However, subsequent analysis revealed minimal degradation activity for RIPK1 with these PROTACs. Following the manuscript submission, we further investigated this issue and synthesized additional CRBN- based PROTACs with varying carbon atom linkers, as illustrated in the following Figure. Our western blot results demonstrated that one of these newly developed CRBN- based PROTAC, T2C10CRBN, exhibited notable degradation activity for RIPK1 at 100 nM concentration when linker length reached 10 carbon atoms, albeit with a significant hook effect. However, the potency of these PROTACs was considerably weaker compared to the VHL- based PROTAC, LD4172. Currently, LD4172 remains the most potent RIPK1 degrader in our study. Moving forward, we are dedicated to optimizing CRBN- based PROTACs to enhance their potency as RIPK1 degraders. + +<--- Page Split ---> +![](images/Figure_unknown_5.jpg) + +
Figure: Chemical structures and potency of new CRBN-based PROTACs.
+ +2. The authors showed that LD4172 can sensitize B16F10 cells to TNFa. Since they also showed that LD4172 can synergistically suppress B16F10 tumor growth with Anti-PD1 antibody, have the authors tested whether LD4172 can sensitize B16F10 cells to cytotoxic T cells? + +Response: Thank you for pointing this out. To test whether LD4172 sensitizes B16F10 cells to cytotoxic T cells, we isolated CD8+ T cells using a mouse CD8a+ T cell isolation kit (Miltenyi Biotec) from C57BL/6J mice. These cells were stimulated with \(2\mu \mathrm{g / ml}\) plateletbound anti-CD3 (BioLegend, clone 145- 2C11) and \(2\mu \mathrm{g / ml}\) soluble anti-CD28 (BioLegend, clone 37.51) in RPMI 1640 medium supplemented with \(10\%\) FBS, \(1\%\) P/S, \(50\mathrm{nM}\) BME, and \(10\mathrm{ng / mL}\) IL- 2 for 2 days. Meanwhile, B16F10 cells were labeled with Vybrant™ DiO (ThermoFisher, V22886) and treated with LD4172 (1μM) and \(1\mathrm{ng / ml}\) IFNγ for 24 hours. After discarding the medium, we added the activated T cells for 24 hours at a 1:1 effector to target ratio. The T cells were then removed and killed B16F10 (DiO+PI+) cells were analyzed using LSRII. Contrary to our expectations, we observed no significant tumor killing, as demonstrated in the figure below. Potential explanations include: (1) as the activity of CD8+ T cells are also regulated by other immune cells, it is difficult to reconstitute the immune system in vitro; (2) Using antigen-specific B16F10 cells, such as B16F10- OVA, along with OT- 1 T cells might be necessary for better specificity; or (3) Although we washed away LD4172 before adding T cells to avoid its effects on T cells, our washout experiments indicate that B16F10 cells begin to resynthesize RIPK1 four hours after LD4172 removal, potentially restoring interactions that protect the tumor cells. While this isn't the focus of this manuscript, we plan to establish a B16F10- RIPK1- KO- OVA cell line to repeat this experiment in the future. + +<--- Page Split ---> +![](images/Figure_unknown_6.jpg) + +
Figure: Flow cytometric analysis of B16F10 cell killing (DiO+PI+) after cotreated with activated T cells for 24 hours.
+ +3. The finding that LD4172 was more effectively in degrading RIPK1 in tumor tissues than in normal tissues is very interesting. Do the authors explore why these normal tissues exhibited less RIPK1 degradation after the treatment with LD4172? Is this related to different uptake of the compounds between tumors and normal tissues? + +Response: Thank you for raising this excellent point. Following your recommendation, we conducted a pharmacokinetic (PK) study by administering a single dose of LD4172 (20 mg/kg) to B16F10 tumor-bearing mice and collected tissue samples at various time points. Interestingly, although LD4172 uptake in tumors was relatively low, the compound appeared to be retained within the tumor tissue. Twelve hours post- administration, the concentration of LD4172 within the tumors remained nearly unchanged (Figure S9). These findings suggest that the potent degradation of RIPK1 observed in tumors, as compared to normal tissues, may be due to the prolonged retention of LD4172 within the tumor microenvironment. We have incorporated this information in lines 279- 286, and the relevant figures have been added to the supplementary data (Figure S9). + +<--- Page Split ---> +![PLACEHOLDER_18_0] + +
Figure S9. LD4172 concentrations in various tissues of B16F10 tumor-bearing C57BL/6J mice at different time points following a \(20 \mathrm{mg / kg}\) intraperitoneal (i.p.) administration \((n = 4)\) .
+ +Updated paragraph in the manuscript can be found as follows: + +Lines 279- 286: "Albumin, which constitutes approximately \(60\%\) of total plasma protein, preferentially accumulates in tumors due to the high demand for amino acids and energy in these tissues \(^{35,36}\) . Given that \(98.6\%\) of LD4172 is bound to plasma proteins (Table 1), it is plausible that LD4172 may be "piggybacking" on albumin accumulation in tumors, thereby achieving tumor- selective RIPK1 degradation. Supporting this hypothesis, following a single \(20 \mathrm{mg / kg}\) dose of LD4172 in C57BL/6J mice bearing B16F10 tumors, LD4172 was found to persist in the tumor for an extended period compared to other tissues (Figure S9). This prolonged retention in the tumor could further mitigate potential toxicity concerns related to RIPK1 degradation in normal tissues." + +4. RIPK1 KO has a profound effect in mice as they die at 1-3 days of age while patients with homozygous loss-of-function RIPK1 are alive and only exhibit some less server abnormalities such as primary immunodeficiency and/or intestinal inflammation. However, the mice treated with LD4172 did not show any side effects in mice. This may be attributable to the inability of LD4172 to effectively degrade RIPK1 in normal tissues. This finding may have important implications in developing RIPK1 targeted therapy because RIPK1 might be more toxic to normal tissues while RIPK1 PROTACs might be more selective to tumors. As such, RIPK1 PROTACs may have a better opportunity to be developed as anticancer drugs. + +<--- Page Split ---> + +Response: Thank you for pointing this out. We agree with the reviewer that transient RIPK1 degradation induced by LD4172 may have very different pharmacology from persistent RIPK knockout in cells. In addition, the tissue selectivity of RIPK1 degradation included by LD4172 may be another intriguing feature to further develop these degraders as therapeutics. + +5. The finding that depletion of CD8 T cells with an antibody abrogated the synergistic antitumor activity of LD4172 and anti-PD1 antibody suggests that the direct antitumor activity of RIPK1 PROTACs is less important than the induction of CD8 T cell-mediated antitumor immunity in the B16F10 tumor model. + +Response: Thank you for pointing this out. In all the cancer cell lines we tested, we did not observe toxicity or inhibition of proliferation induced by LD4172 alone. However, degradation of RIPK1 rewires the cancer cell death pathways and also boost the anticancer immunity through interacting with immune cells. We view this RIPK1 degrader more like a catalyst than an executioner. + +<--- Page Split ---> + +Reviewer #4 (Remarks to the Author): with expertise in cancer therapeutics and degrader design + +I support publication of this work after addressing comments below. + +- What are the noteworthy results? + +This is a nice study describing the discovery and characterization of the first PROTAC- based RIPK1 degrader. The study appears to be done with excellent quality and the conclusions are well supported by the provided data. + +Key results: + +1. RIPK1 can be degraded using a suitably designed/optimized PROTAC degrader + +2. RIPK1 degrader has fundamentally different pharmacology relative to RIPK1 inhibitor + +3. Degradation of RIPK1 by LD4172 triggered immunogenic cell death (ICD) + +4. Degradation of RIPK1 resulted in an increase in tumor-infiltrating lymphocytes and sensitized tumors to anti-PD1 therapy + +The efficacy in the mouse models is limited (this would be called progressive disease in patients) but does show the mechanism appears to be active in a murine model. + +It would be nice to see: + +1. PK data for LD4172 to enable understanding of how much drug exposure there was following the dosing regime used. + +Response: Thank you for highlighting this important point. In the initial phase of the LD4172 PK study, we aimed to use the lowest effective dose and did not include the 20 mg/kg dosing regimen. Based on your suggestion, we repeated the PK study with a 20 mg/kg (i.p.) dose of LD4172, measuring its concentration in various tissues at different time points (Figure S8). Consistent with our previous findings, LD4172 was rapidly metabolized and cleared from the blood. However, in B16F10 tumors, LD4172 was found to persist in the tumor for an extended period compared to other tissues. This prolonged retention in the tumor could further mitigate potential toxicity concerns related to RIPK1 degradation in normal tissues. The relevant figure has been added to the supplementary data (Figure S9). + +<--- Page Split ---> +![PLACEHOLDER_21_0] + +
Figure S9. LD4172 concentrations in various tissues of B16F10 tumor-bearing C57BL/6J mice at different time points following a \(20 \mathrm{mg / kg}\) intraperitoneal (i.p.) administration \((n = 4)\) .
+ +2. To show evidence of target degradation in vivo (blood and tumor tissue). + +Response: Thank you for bringing up this crucial point, which has been a key focus in the development of LD4172. We conducted a pharmacodynamic (PD) experiment in C57BL/6J mice bearing B16F10 tumors with intraperitoneally delivery (i.p.) of indicated dosages (Figure 4B). Among the various tissues tested, we observed that potent RIPK1 degradation occurred primarily in the tumors. To further understand this, we performed a pharmacokinetic (PK) study to measure LD4172 concentrations across different tissues. Interestingly, while B16F10 tumors did not exhibit the highest uptake of LD4172, the clearance of the compound in the tumor was slower, allowing for a longer duration of RIPK1 degradation. Additionally, we explored intratumoral delivery (i.t.) of LD4172 in C57BL/6J mice, which resulted in more pronounced RIPK1 degradation compared to intraperitoneal administration (Figure S7). Moving forward, we plan to optimize LD4172 to improve its penetration and efficacy in tumor tissues. + +![PLACEHOLDER_21_1] + + +<--- Page Split ---> + +499 Figure 4B. Representative immunoblots of RIPK1 in different tissues of C57BL/6J mice treated with LD4172 (n=3- 4). + +![PLACEHOLDER_22_0] + +
Figure S7. Pharmacodynamic (PD) properties of LD4172 with intratumoral administration (i.t.). Representative immunoblots of RIPK1 expression in various tissues of C57BL/6J mice treated with LD4172 are shown. Mice with syngeneic B16F10 tumors received intratumoral injections of LD4172 (10mg/kg) twice daily for three days. Upon sacrifice, tissues were collected, and the levels of RIPK1 were quantified through Western blotting.
+ +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +Yes demonstrates another use of small molecule degraders to achieve novel pharmacology. + +- Does the work support the conclusions and claims, or is additional evidence needed? + +The work is well supported by the data provided. + +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +None that I could find. + +- Is the methodology sound? Does the work meet the expected standards in your field? + +- Is there enough detail provided in the methods for the work to be reproduced? + +Yes experimental sections appear to be sound, nice characterization data is provided for the compounds. + +<--- Page Split ---> diff --git a/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd b/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..2ee5978f9b7847e15a6fc9476a48ce7730f42418 --- /dev/null +++ b/peer_reviews/bb32931d81bea1a1b5abf4af6b7c0b93e1915dfa699fd2f5b285f793199a0bbe/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd @@ -0,0 +1,598 @@ +<|ref|>title<|/ref|><|det|>[[73, 50, 295, 78]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[75, 96, 295, 118]]<|/det|> +# Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 858, 210]]<|/det|> +# Development of a RIPK1 Degrader to Enhance Antitumor Immunity + +<|ref|>text<|/ref|><|det|>[[73, 224, 445, 241]]<|/det|> +Corresponding Author: Professor Jin Wang + +<|ref|>text<|/ref|><|det|>[[72, 275, 712, 289]]<|/det|> +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +<|ref|>text<|/ref|><|det|>[[70, 301, 864, 315]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 354, 144, 368]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 380, 219, 394]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 405, 160, 419]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 432, 238, 445]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 444, 922, 625]]<|/det|> +This manuscript by Yu et al describes the development and testing of a novel RIPK1 protac LD4172. Using a RIPK1 type II kinase inhibitor attached to a VHL ligand, the authors showed that LD4172 can effectively degrade RIPK1 in multiple human and mouse tumor cell lines in vitro, as well as in some but not all tissues in vivo. The compound also sensitized B16F10 cells to apoptosis induced by TNF in vitro. This is in line with reports in the literature that RIPK1 has a pro- death function that is dependent on its kinase, as well as a pro- survival function via its intermediate and death domain. The latter scaffold function has been suggested to be due to RIPK1's role in stabilizing pro- survival molecules such as TRAF2, and/or its role in activating NFkappaB. RIPK1 also has a pro- survival role by blocking the interaction between ZBP1 and RIPK3 to suppress RIPK3- dependent death. In vivo, LD4172 enhanced the sensitivity of B16 F10 tumors to immune checkpoint blockade by anti- PD1. The authors suggests that tumor death conferred by RIPK1 degradation is immunogenic based on HMGB1 release, calreticulin exposure, and recruitment of various inflammatory cells to the dying tumor microenvironment. Quite interestingly, RIPK1 degradation seems to be much more pronounced in the tumor tissue than in non- tumor tissues. Authors speculated that this could be due to the compound binding to albumin, which may accumulate in tumor sites. This is largely a descriptive study of the effect of administrating the RIPK1 protac in vitro and in vivo. Overall, this is a thorough study that provides proof- of- concept for targeting RIPK1 in a preclinical setting. + +<|ref|>text<|/ref|><|det|>[[72, 625, 916, 666]]<|/det|> +1. The main deficiency is that there is not much mechanistic dissection. The prior publication from Cucolo et al (Ref #5) had suggested that in the absence of RIPK1, there is a shift from Complex I to Complex II in the TNFR1 pathway. It would be nice to show that this is also true when RIPK1 is acutely removed by the protac. + +<|ref|>text<|/ref|><|det|>[[72, 666, 914, 732]]<|/det|> +2. While the in vitro studies showed that LD4172 sensitizes to TNFR1-induced apoptosis, it is less clear whether this is the case in vivo or whether other death receptors in the TNFRsF family may also be involved. If TNF/TNFR1 signaling is responsible for the sensitizing effect of LD4172 in vivo, then one would predict that B16 F10 cells that are knockout for TNFR1 would be resistant to the effect of LD4172 + anti-PD1. Experiment in Fig 4F can be repeated comparing WT vs TNFR1 KO B16 cells. It would be interesting to know one way or the other. + +<|ref|>text<|/ref|><|det|>[[70, 732, 911, 759]]<|/det|> +3. While the proteomic analysis in Fig. 2J indicates a high degree of specificity, an additional control that could be included is to show that the related kinases RIPK2 and RIPK3 are not affected by LD4172. + +<|ref|>text<|/ref|><|det|>[[72, 759, 884, 787]]<|/det|> +4. In the legend for Figure 3, the early apoptotic cells (AV+, PI-) should be in the upper left quadrant, not lower right. +5. The key to the graph in Fig S2A for the MC38 experiments appears to be incorrect. Shouldn't it be PD1 and LD4172 treatment instead of RIPK1 KO? + +<|ref|>sub_title<|/ref|><|det|>[[73, 821, 161, 834]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 848, 237, 861]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 861, 923, 938]]<|/det|> +The authors have generated a PROTAC targeting RIPK1 for degradation and showed that it recapitulates the effect of loss of RIPK1 in tumours in vitro and in vivo. Interestingly, their RIPK1 PROTAC synergises with anti- PD1 therapy in vivo. This study is generally well designed and controlled. To my knowledge, it is the first RIPK1 PROTAC showing such good synergism in vivo. Given the lethality of RIPK1 mice, this tool can also be used to study the role of RIPK1 in vivo in adult development, infectious diseases, etc. There are a few imprecisions and clumsiness throughout the manuscript that need to be addressed. Please see specific comments. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 61, 209, 73]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[73, 73, 912, 126]]<|/det|> +In Fig. 2D- E, the authors should acknowledge that RIPK1 is already re- expressed after a 4- hour washout. This could be important in terms of RIPK1- dependent responses, as we don't know what level of RIPK1 is required to fully reconstitute its function. For example, there is a small proportion of RIPK1 that goes to TNF- induced Complex I; therefore, \(10\%\) of RIPK1 (after 4- hour washout) could be enough to provide a normal TNF response. + +<|ref|>text<|/ref|><|det|>[[73, 137, 860, 164]]<|/det|> +Line 125 'In contrast to situations where RIPK1 is kinase- dead, genetic deletion of RIPK1 has been found to trigger apoptosis both in vitro and in vivo 15.' + +<|ref|>text<|/ref|><|det|>[[73, 164, 904, 216]]<|/det|> +Ref 15 is only about RIPK1 knock- out mice and not about RIPK1 kinase dead. Plus, ref 15 is not the only one and the first one to show that loss of RIPK1 induces apoptosis. The authors should be fair and cite all RIPK1 kinase dead and RIPK1 knock- out papers that support their statement, e.g., Kelliher Immunity 1998; Kaiser PNAS 2014; Rickard Cell 2014; Polykratis JI 2014; Berger JI 2014; Newton Science 2014. + +<|ref|>text<|/ref|><|det|>[[70, 228, 905, 256]]<|/det|> +In Fig S2A the legend says that it's sgNC vs RIPK1 KO, while in the manuscript, the authors described it as tumours being treated with LD4172. Is it a mistake with the legend or the wrong graph? + +<|ref|>text<|/ref|><|det|>[[70, 268, 907, 295]]<|/det|> +In Line 181 the authors wrote "Consistent with the in vitro findings, LD4172 also triggered significant cell death in the tumor (Fig. 182 5A, 2nd column). + +<|ref|>text<|/ref|><|det|>[[70, 295, 904, 322]]<|/det|> +The 2nd column is H&E, which does not reflect of cell death but rather absence or presence of cells. Caspase- 3/7 are the cell death markers. Please correct the text accordingly. + +<|ref|>text<|/ref|><|det|>[[72, 333, 909, 386]]<|/det|> +The authors wrote in line 184 'While apoptotic cell death was traditionally considered non- immunogenic, accumulating experimental data have revealed its potential to drive immune cell infiltration and anti- cancer immunity 16- 19. Supporting the activation of immunogenic apoptosis, we observed a significant increase in plasma HMGB1 levels (Fig. 5B) and enhanced exposure of calreticulin on the surface of B16F10 tumor cells (Fig. 5A, 5th column).' + +<|ref|>text<|/ref|><|det|>[[72, 386, 914, 452]]<|/det|> +However, the authors don't have supporting evidence that apoptosis is the mode of cell death that is immunogenic because it is well established that loss of RIPK1 can also induce RIPK3- dependent necroptosis (Kaiser PNAS 2014; Rickard Cell 2014; Dillon cell 2014; Berger JI 2014; Newton Science 2016), which is also immunogenic. One way to determine if apoptosis or necroptosis is immunogenic is to analyse MLKL- /- and casp3/7- /- tumours treated with RIPK1 PROTAC. The authors should rewrite this part. + +<|ref|>text<|/ref|><|det|>[[72, 463, 895, 516]]<|/det|> +The authors wrote in line 196 'In addition, combined therapy with LD4172 and anti- PD1 not only induced extensive TIL infiltration (Fig. 5D- H) but also significantly enhanced anti- PD1 positivity in immunologically cold B16F10 tumors, as demonstrated by increased infiltration of cytotoxic CD8+ T cells (CD8+IFN- \(\gamma +\) , Fig. 5A, 6th column, and 5G- H) and decreased infiltration of FOXP3+ T regulatory cells (Fig. 5A, 7th column) within the TME.' + +<|ref|>text<|/ref|><|det|>[[72, 516, 900, 543]]<|/det|> +This is wrong: LD4172 did not increased TIL infiltration CD8+ T cells induced by anti- PD1 because there is not statistical difference between anti- PD1 treatment and anti- PD1+ LD4172 treatment in Fig 5C, G and H. Please correct this part. + +<|ref|>text<|/ref|><|det|>[[72, 555, 923, 607]]<|/det|> +The authors wrote in line 235 'Unlike Ripk1 knockout mice, which die at 1- 3 days of age due to their widespread roles in multiple tissues and organs 25, homozygous loss- of- function RIPK1 mutations are well tolerated in humans 26. Patients with complete loss of RIPK1 protein only showed symptoms confined to the immune system, with primary immunodeficiency and/or intestinal inflammation 26.' + +<|ref|>text<|/ref|><|det|>[[72, 607, 920, 647]]<|/det|> +And Line 240 'Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies, human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable, especially with transient intervention in well- controlled clinical settings.' + +<|ref|>text<|/ref|><|det|>[[72, 647, 778, 661]]<|/det|> +And Line 259 'Considering the predicted safety profile of RIPK1 degradation based on human genetics' + +<|ref|>text<|/ref|><|det|>[[72, 672, 921, 789]]<|/det|> +By stating that loss of RIPK1 is 'well tolerated in humans', 'only showed symptoms confined to the immune system', 'human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable' and 'predicted safety profile of RIPK1 degradation based on human genetics', the authors are minimising the effect of loss of RIPK1 in human to promote the use of RIPK1 PROTAC. This is extremely clumsy because Ref 26 and Li et al PNAS 2019 (doi.org/10.1073/pnas.18135821, which should be cited alongside Ref 26) showed that RIPK1 deficient patients are affected with severe immunodeficiency which can lead to the death of the patients at really young age. The authors should rephrase this part by stating that despite the severe immunodeficiency cause by permanent loss of RIPK1 in human, acute, chemical and transient depletion of RIPK1 might be tolerable in humans. Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies. + +<|ref|>sub_title<|/ref|><|det|>[[73, 815, 162, 828]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 841, 238, 854]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 854, 915, 945]]<|/det|> +The authors reported the development of the first- in- class RIPK1 degraders that utilize the VHL E3 ligase to potently degrade RIPK1 in various cells. One of the lead compounds, LD4172, is highly specific and only degrade RIPK1 in cells with high Dmax and DC50 values in a VHL and proteasome- dependent manner. LD4172 can synergistically kill B16F10 mouse melanoma cells in combination with TNFa. Interestingly, administration of B16F10 tumor- bearing mice with LD4172 resulted in significant reduction in RIPK1 expression in the tumors but not in normal tissues. This reduction was associated with the potentiation of tumor growth inhibition when it was combined with anti- PD1 antibody. More importantly, the synergistic effect was greater with the combination of anti- PD1 antibody and LD4172 than that of anti- PD1 antibody and the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 88]]<|/det|> +RIPK1 inhibitor. These findings demonstrate that RIPK1 degraders may exert stronger antitumor activity than RIPK1 inhibitors by degrading RIPK1 to remove both its kinase and scaffold activity. In addition, this combination can also enhance antitumor immunity. + +<|ref|>text<|/ref|><|det|>[[72, 88, 145, 100]]<|/det|> +Concerns: + +<|ref|>text<|/ref|><|det|>[[70, 100, 920, 140]]<|/det|> +1. It is very interesting that only VHL-based PROTACs can effectively degrade RIPK1 but not CRBN- and MDM2-based and adamantane-tagged PROTACs. Can the authors share some insights why only VHL can degrade RIPK1? Have the authors tried to use different linker length for other PROTACs to validate the lack of degradation for RIPK1? + +<|ref|>text<|/ref|><|det|>[[70, 140, 870, 180]]<|/det|> +2. The authors showed that LD4172 can sensitize B16F10 cells to TNFa. Since they also showed that LD4172 can synergistically suppress B16F10 tumor growth with Anti-PD1 antibody, have the authors tested whether LD4172 can sensitize B16F10 cells to cytotoxic T cells? + +<|ref|>text<|/ref|><|det|>[[70, 180, 897, 220]]<|/det|> +3. The finding that LD4172 was more effectively in degrading RIPK1 in tumor tissues than in normal tissues is very interesting. Do the authors explore why these normal tissues exhibited less RIPK1 degradation after the treatment with LD4172? Is this related to different uptake of the compounds between tumors and normal tissues? + +<|ref|>text<|/ref|><|det|>[[70, 219, 917, 304]]<|/det|> +4. RIPK1 KO has a profound effect in mice as they die at 1-3 days of age while patients with homozygous loss-of-function RIPK1 are alive and only exhibit some less server abnormalities such as primary immunodeficiency and/or intestinal inflammation. However, the mice treated with LD4172 did not show any side effects in mice. This may be attributable to the inability of LD4172 to effectively degrade RIPK1 in normal tissues. This finding may have important implications in developing RIPK1 targeted therapy because RIPK1 might be more toxic to normal tissues while RIPK1 PROTACs might be more selective to tumors. As such, RIPK1 PROTACs may have a better opportunity to be developed as anticancer drugs. + +<|ref|>text<|/ref|><|det|>[[70, 303, 917, 330]]<|/det|> +5. The finding that depletion of CD8 T cells with an antibody abrogated the synergistic antitumor activity of LD4172 and anti-PD1 antibody suggests that the direct antitumor activity of RIPK1 PROTACs is less important than the induction of CD8 T cell-mediated antitumor immunity in the B16F10 tumor model. + +<|ref|>sub_title<|/ref|><|det|>[[72, 358, 161, 371]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[72, 385, 230, 398]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 399, 533, 412]]<|/det|> +I support publication of this work after addressing comments below. + +<|ref|>text<|/ref|><|det|>[[72, 425, 309, 438]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[70, 438, 900, 465]]<|/det|> +This is a nice study describing the discovery and characterization of the first PROTAC-based RIPK1 degrader. The study appears to be done with excellent quality and the conclusions are well supported by the provided data. + +<|ref|>text<|/ref|><|det|>[[72, 465, 150, 477]]<|/det|> +Key results: + +<|ref|>text<|/ref|><|det|>[[70, 477, 920, 530]]<|/det|> +1. RIPK1 can be degraded using a suitably designed/optimized PROTAC degrader +2. RIPK1 degrader has fundamentally different pharmacology relative to RIPK1 inhibitor +3. Degradation of RIPK1 by LD4172 triggered immunogenic cell death (ICD) +4. Degradation of RIPK1 resulted in an increase in tumor-infiltrating lymphocytes and sensitized tumors to anti-PD1 therapy + +<|ref|>text<|/ref|><|det|>[[70, 542, 870, 568]]<|/det|> +The efficacy in the mouse models is limited (this would be called progressive disease in patients) but does show the mechanism appears to be active in a murine model. + +<|ref|>text<|/ref|><|det|>[[72, 568, 230, 580]]<|/det|> +It would be nice to see: + +<|ref|>text<|/ref|><|det|>[[70, 580, 920, 740]]<|/det|> +1. PK data for LD4172 to enable understanding of how much drug exposure there was following the dosing regime used. +2. To show evidence of target degradation in vivo (blood and tumor tissue). +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. +- Yes demonstrates another use of small molecule degraders to achieve novel pharmacology. +- Does the work support the conclusions and claims, or is additional evidence needed? +- The work is well supported by the data provided. +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? None that I could find. +- Is the methodology sound? Does the work meet the expected standards in your field? +- Is there enough detail provided in the methods for the work to be reproduced? +- Yes experimental sections appear to be sound, nice characterization data is provided for the compounds. + +<|ref|>text<|/ref|><|det|>[[72, 776, 144, 789]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 803, 219, 816]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 829, 160, 842]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 856, 238, 869]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 869, 907, 946]]<|/det|> +This revised manuscript by Yu et al has addressed the critiques of this reviewer. While an experiment using TNFR1 KO of the B16 F10 cells would have been preferable in the in vivo studies, the authors used anti-TNF to show that the anti-tumor effect of the LD4172 protac is TNF- dependent. A recent published study from Pascal Meier's group also showed similar findings with a different RIPK1 protac and in that study, some of the effects of a RIPK1 protac on TNFR1 signaling complexes were examined. Some of the sloppiness in the manuscript brought up by this and other reviewers were also addressed. The manuscript is now acceptable. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[73, 60, 162, 73]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 86, 475, 113]]<|/det|> +(Remarks to the Author) The authors have adequately addressed all my comments. + +<|ref|>text<|/ref|><|det|>[[73, 125, 162, 139]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 152, 238, 165]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 165, 911, 231]]<|/det|> +The revised manuscript has significantly improved with new experimental data to address all my concerns. Particularly, the data from the LD4172 tissue distribution study and RIPK1 degradation in tumors vs various normal tissues are very interesting. I agree with the authors that albumin binding and higher uptake and degradation of albumin by tumor cells may contribute to the differences between tumors and normal tissues observed. It would be interesting to explore this further in future studies. + +<|ref|>text<|/ref|><|det|>[[72, 597, 916, 652]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[75, 650, 800, 664]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[73, 664, 911, 717]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[73, 715, 618, 729]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[75, 90, 358, 108]]<|/det|> +1 Dear Editor and Reviewers: + +<|ref|>text<|/ref|><|det|>[[70, 118, 870, 245]]<|/det|> +2 We have completed the revisions for our manuscript titled "Development of a First- in- Class RIPK1 Degrader to Enhance Antitumor Immunity". We sincerely appreciate the thorough and professional review of our work. As noted, there were several issues that needed to be addressed. In response to the reviewers' suggestions, we have made significant corrections to the manuscript, which are highlighted in the revised version. Our detailed responses to the reviewers' comments are provided below. + +<|ref|>text<|/ref|><|det|>[[115, 252, 499, 271]]<|/det|> +Thank you for your continued consideration. + +<|ref|>text<|/ref|><|det|>[[70, 310, 567, 329]]<|/det|> +Detailed responses to the reviewers' comments: + +<|ref|>text<|/ref|><|det|>[[70, 370, 841, 410]]<|/det|> +Reviewer #1 (Remarks to the Author): with expertise in cancer immunotherapy, cell death signaling, RIPK1 + +<|ref|>text<|/ref|><|det|>[[70, 423, 90, 437]]<|/det|> +14 + +<|ref|>text<|/ref|><|det|>[[70, 450, 875, 856]]<|/det|> +This manuscript by Yu et al describes the development and testing of a novel RIPK1 protac LD4172. Using a RIPK1 type II kinase inhibitor attached to a VHL ligand, the authors showed that LD4172 can effectively degrade RIPK1 in multiple human and mouse tumor cell lines in vitro, as well as in some but not all tissues in vivo. The compound also sensitized B16F10 cells to apoptosis induced by TNF in vitro. This is in line with reports in the literature that RIPK1 has a pro- death function that is dependent on its kinase, as well as a pro- survival function via its intermediate and death domain. The latter scaffold function has been suggested to be due to RIPK1's role in stabilizing pro- survival molecules such as TRAF2, and/or its role in activating NFkappaB. RIPK1 also has a pro- survival role by blocking the interaction between ZBP1 and RIPK3 to suppress RIPK3- dependent death. In vivo, LD4172 enhanced the sensitivity of B16 F10 tumors to immune checkpoint blockade by anti- PD1. The authors suggests that tumor death conferred by RIPK1 degradation is immunogenic based on HMGB1 release, calreticulin exposure, and recruitment of various inflammatory cells to the dying tumor microenvironment. Quite interestingly, RIPK1 degradation seems to be much more pronounced in the tumor tissue than in non- tumor tissues. Authors speculated that this could be due to the compound binding to albumin, which may accumulate in tumor sites. This is largely a descriptive study of the effect of administrating the RIPK1 protac in vitro and in vivo. Overall, this is a thorough study that provides proof- of- concept for targeting RIPK1 in a preclinical setting. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[111, 88, 870, 170]]<|/det|> +1. The main deficiency is that there is not much mechanistic dissection. The prior publication from Cucolo et al (Ref #5) had suggested that in the absence of RIPK1, there is a shift from Complex I to Complex II in the TNFR1 pathway. It would be nice to show that this is also true when RIPK1 is acutely removed by the protac. + +<|ref|>text<|/ref|><|det|>[[111, 178, 880, 544]]<|/det|> +Response: Thank you for your insightful comment. You are absolutely correct in noting that RIPK1, known for its scaffold function, is recruited into complex I upon TNF- \(\alpha\) signaling. Following its ubiquitylation, the recruitment of the TAK1- TAB2/3 complex and the NEMO- IKKα- IKKβ complex is crucial for the activation of NF- \(\kappa\) B signaling. Our NF- \(\kappa\) B reporter assay results support this, showing significant NF- \(\kappa\) B activation by TNF- \(\alpha\) in B16F10 cells (Figure 3A). As expected, the RIPK1 degrader LD4172, as opposed to the RIPK1 kinase inhibitor T2I, significantly inhibited TNF- \(\alpha\) - induced NF- \(\kappa\) B activation. Furthermore, the combination of TNF- \(\alpha\) with LD4172 led to a marked induction of apoptosis in B16F10 cells (Figure 3B- D), indicating that acute deletion of RIPK1 shifts the cells from a pro- survival to a pro- death state. Interestingly, a recent study by the Meier group, published in Immunity, reported the development of a RIPK1 PROTAC degrader, R1- ICR- 5. Their findings demonstrate that RIPK1 degradation can promote the interactions of TNFR1, TRADD, TRAF2, cIAP, and HOIP, forming a RIPK1- independent complex I, with enhanced ubiquitylation leading to deregulated TNF signaling (Figure adapted from Mannion's paper). These findings underscore the potential of RIPK1 degraders as powerful chemical probes for investigating the biological roles of RIPK1 in complex I and complex II. We have incorporated these updates in lines 130- 137, 227- 237 and Figure 3A. + +<|ref|>sub_title<|/ref|><|det|>[[427, 554, 568, 572]]<|/det|> +## [figure redacted] + +<|ref|>text<|/ref|><|det|>[[112, 584, 877, 644]]<|/det|> +Adapted from Mannion's paper: Acute degradation of RIPK1 deregulates TNFR1 signaling, L929 Cells were treated with DMSO or R1- ICR- 5 (overnight) before anti- GST- TUBE pull- down to isolate the ubiquitylated proteome. + +<|ref|>image<|/ref|><|det|>[[350, 662, 647, 894]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[65, 88, 840, 128]]<|/det|> +63 Figure 3A. NF- kB activity of B16F10 cells expressing a NanoLuc reporter for NF- kB response with indicated treatments for 48 hours. + +<|ref|>text<|/ref|><|det|>[[66, 139, 657, 159]]<|/det|> +65 Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[66, 168, 882, 352]]<|/det|> +66 Lines 130- 137: "RIPK1- deficient MEFs exhibit a severe impairment in their ability to activate NF- kB signaling, whereas kinase- dead RIPK1 knock- in mice remain viable and display normal TNFR1- mediated NF- kB signaling16- 18. Moreover, unlike the kinase- dead RIPK1 scenario, the genetic deletion of RIPK1 has been shown to trigger apoptosis both in vitro and in vivo19- 24. To evaluate NF- kB activity in B16F10 cells, we transiently transfected them with a plasmid encoding a Nanoluc reporter containing the NF- kB response element, allowing us to monitor NF- kB activity through luminescence. Upon TNF- α treatment, B16F10 cells exhibited a robust induction of NF- kB activity, which was significantly attenuated by LD4172 but not by the RIPK1 kinase inhibitor (Fig. 3A)." + +<|ref|>text<|/ref|><|det|>[[66, 360, 880, 644]]<|/det|> +75 Lines 227- 237: "Upon TNF- α signaling, RIPK1 is recruited to complex I, where it acts as a crucial scaffold, essential for the ubiquitylation- dependent activation of NF- kB signaling. Our findings demonstrate that LD4172- induced RIPK1 degradation, unlike the action of RIPK1 kinase inhibitors, significantly impairs TNF- α- induced NF- kB activation. Furthermore, the combination of TNF- α and LD4172 markedly induces apoptosis in B16F10 cells. This suggests that acute RIPK1 deletion shifts the cellular response from a pro- survival to a pro- death state by altering the composition of complexes I and II. Interestingly, the Meier group developed a similar RIPK1 degrader18, revealing that RIPK1 degradation promotes the formation of a RIPK1- independent complex I. This complex display enhanced interactions among TNFR1, TRADD, TRAF2, cIAP, and HOIP, leading to deregulated TNF signaling through increased ubiquitylation. These findings underscore the potential of RIPK1 degraders as valuable chemical tools for in vitro studies, offering new insights into the biological roles of RIPK1 within various signaling complexes." + +<|ref|>text<|/ref|><|det|>[[66, 653, 877, 796]]<|/det|> +29. While the in vitro studies showed that LD4172 sensitizes to TNFR1-induced apoptosis, it is less clear whether this is the case in vivo or whether other death receptors in the TNFRSF family may also be involved. If TNF/TNFR1 signaling is responsible for the sensitizing effect of LD4172 in vivo, then one would predict that B16 F10 cells that are knockout for TNFR1 would be resistant to the effect of LD4172 + anti-PD1. Experiment in Fig 4F can be repeated comparing WT vs TNFR1 KO B16 cells. It would be interesting to know one way or the other. + +<|ref|>text<|/ref|><|det|>[[66, 805, 875, 905]]<|/det|> +Response: Thank you for highlighting this important aspect that we initially overlooked in our study of LD4172. As you suggested, the sensitizing effect of LD4172 in vivo is indeed dependent on TNF/TNFR1 signaling. Our findings demonstrate that neutralizing TNFα with anti-mouse TNFα in vivo completely abolishes the synergy between LD4172 and anti-PD1 therapy. This result is consistent with our in vitro experiments, which + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[60, 88, 875, 150]]<|/det|> +101 suggest that LD4172- induced apoptosis in B16F10 tumors involves TNF/TNFR1 102 signaling. We have addressed this in lines 238- 248, and the relevant figures have been 103 added to the supplementary data (Figure S6). + +<|ref|>image<|/ref|><|det|>[[318, 169, 676, 345]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[60, 345, 90, 360]]<|/det|> +104 + +<|ref|>text<|/ref|><|det|>[[60, 366, 872, 486]]<|/det|> +105 Figure S6. Anti- TNFα reversed the synergy between LD4172 and anti- PD1. C57B6/J 106 mice were subcutaneously inoculated with \(3 \times 10^{5}\) B16F10 tumor cells. After seven days 107 (tumor size \(\sim 100 \text{mm}^3\) ), mice were treated every three days with anti- PD1 (100 \(\mu \text{g}\) per 108 dose, i.p.), daily with LD4172 (20 mg/kg, i.p.), a combination of LD4172 and anti- PD1 109 (same dose as their individual doses), the combination plus anti- TNFα (200ug every 110 three days, i.p.), or their corresponding vehicle control (n=5). + +<|ref|>text<|/ref|><|det|>[[60, 497, 657, 517]]<|/det|> +111 Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[60, 526, 877, 811]]<|/det|> +112 Lines 238- 248: "LD4172 has also demonstrated significant therapeutic efficacy in vivo 113 by inducing RIPK1 degradation within tumors and exhibiting a synergistic effect on 114 tumor growth inhibition when combined with anti- PD1 therapy. Although LD4172 plays a 115 role in inducing ICD in B16F10 tumors, the degradation of RIPK1 alone is insufficient, 116 as RIPK1 primarily acts as a brake on immunogenic pathways18. Therefore, additional 117 ligands are required to fully activate these pathways. Anti- PD1 can supply these 118 necessary ligands by promoting TNF production, thereby sensitizing cancer cells to cell 119 death in the absence of RIPK1. This synergistic relationship is further evidenced by the 120 finding that the combination of LD4172 and anti- PD1 loses its efficacy when anti- TNF- α 121 is introduced, completely abolishing their combined effect (Figure S6). Moreover, when 122 used in conjunction with anti- PD1, LD4172 reshapes the tumor immune 123 microenvironment by enhancing the infiltration of dendritic cells and IFNγ+ T cells, as 124 well as by promoting the secretion of immunostimulatory cytokines, leading to 125 substantial antitumor effects." + +<|ref|>text<|/ref|><|det|>[[60, 820, 866, 880]]<|/det|> +126 3. While the proteomic analysis in Fig. 2J indicates a high degree of specificity, an 127 additional control that could be included is to show that the related kinases RIPK2 and 128 RIPK3 are not affected by LD4172. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 874, 250]]<|/det|> +Response: This is an excellent point. Our proteomic data does not rule out the possibility that RIPK2 and RIPK3 are unaffected by LD4172. To test the selectivity of LD4172, we used the THP1 cell line, which expresses RIPK1, RIPK2, and RIPK3. After treating the cells with LD4172 at varying concentrations for 24 hours, we observed significant degradation of RIPK1 at 16nM, while RIPK2 and RIPK3 levels remained unchanged, indicating the selectivity of LD4172 for RIPK1. We have addressed this in lines 122- 124, and the relevant figures have been added to the supplementary data (Figure S2). + +<|ref|>image<|/ref|><|det|>[[380, 262, 612, 412]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[112, 423, 880, 465]]<|/det|> +Figure S2. Western blot analysis showing the expression levels of RIPK1, RIPK2, and RIPK3 in THP1 cells following 24- hour treatment with varying concentrations of LD4172. + +<|ref|>text<|/ref|><|det|>[[112, 475, 658, 496]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[112, 505, 852, 567]]<|/det|> +Lines 122- 124: "Additionally, at effective LD4172 concentrations (16 nM- 10 μM) that induce RIPK1 degradation in THP1 cells, we observed no significant changes in the protein levels of related kinases, such as RIPK2 and RIPK3 (Fig. S2)." + +<|ref|>text<|/ref|><|det|>[[112, 576, 866, 618]]<|/det|> +4. In the legend for Figure 3, the early apoptotic cells (AV+, PI-) should be in the upper left quadrant, not lower right. + +<|ref|>text<|/ref|><|det|>[[112, 627, 760, 668]]<|/det|> +Response: Thanks for pointing this out and sorry for our carelessness, the corresponding correction is highlighted in Figure 3. + +<|ref|>text<|/ref|><|det|>[[112, 677, 857, 719]]<|/det|> +5. The key to the graph in Fig S4A for the MC38 experiments appears to be incorrect. Shouldn't it be PD1 and LD4172 treatment instead of RIPK1 KO? + +<|ref|>text<|/ref|><|det|>[[112, 728, 880, 789]]<|/det|> +Response: Thank you very much for catching the mistake. Figure S4A demonstrates the synergistic effect between LD4172 and Anti-PD1, and the figure legend has been corrected. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 90, 844, 110]]<|/det|> +Reviewer #2 (Remarks to the Author): with expertise in cancer, inflammation, RIPK1 + +<|ref|>text<|/ref|><|det|>[[112, 150, 872, 310]]<|/det|> +The authors have generated a PROTAC targeting RIPK1 for degradation and showed that it recapitulates the effect of loss of RIPK1 in tumours in vitro and in vivo. Interestingly, their RIPK1 PROTAC synergises with anti- PD1 therapy in vivo. This study is generally well designed and controlled. To my knowledge, it is the first RIPK1 PROTAC showing such good synergism in vivo. Given the lethality of RIPK1 mice, this tool can also be used to study the role of RIPK1 in vivo in adult development, infectious diseases, etc. There are a few imprecisions and clumsiness throughout the manuscript that need to be addressed. Please see specific comments. + +<|ref|>text<|/ref|><|det|>[[113, 352, 288, 370]]<|/det|> +Specific comments: + +<|ref|>text<|/ref|><|det|>[[112, 381, 872, 501]]<|/det|> +In Fig. 2D- E, the authors should acknowledge that RIPK1 is already re- expressed after a 4- hour washout. This could be important in terms of RIPK1- dependent responses, as we don't know what level of RIPK1 is required to fully reconstitute its function. For example, there is a small proportion of RIPK1 that goes to TNF- induced Complex I; therefore, \(10\%\) of RIPK1 (after 4- hour washout) could be enough to provide a normal TNF response. + +<|ref|>text<|/ref|><|det|>[[112, 512, 880, 775]]<|/det|> +Response: Thank you for raising this excellent point. As you suggested, inadequate RIPK1 degradation can indeed affect the observed phenotype. As demonstrated in Figure S8, at the late stage of treatment (more than 15 days after tumor inoculation), the synergy between anti- PD1 and a low dose of LD4172 (20 mg/kg, twice daily) is less potent compared to a high dose of LD4172 (20 mg/kg, once daily). This indicates that more thorough and persistent RIPK1 degradation can enhance the synergistic effect. Additionally, Mannion et al. have shown that intratumoral injection of a RIPK1 degrader can synergize with anti- PD1 to regress \(30\%\) of EO771 breast tumor growth (Figure adapted from Mannion et al.'s paper). This further suggests that adequate degradation of RIPK1 in the tumor is more beneficial for promoting cancer immunotherapy, and that the remaining RIPK1 in tumor might still be sufficient to execute its pro- survival functions. We have emphasized this point in both Figure 2E legend and lines 82- 84 of the main text. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[340, 94, 639, 293]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 310, 880, 391]]<|/det|> +
Figure S8. Tumor growth curve of mice with B16F10 tumors treated with reduced dosing frequency of LD4172. The administration of LD4172 was modified to a reduced dosage of \(20mg / kg\) every other day \((n = 8)\) . The data are expressed as the mean \(\pm\) SEM. \* \(p< 0.1\) ; \*\* \(p< 0.01\) ; \*\*\* \(p< 0.001\) ; \*\*\*\* \(p< 0.0001\) . ns, no statistical significance.
+ +<|ref|>sub_title<|/ref|><|det|>[[428, 434, 568, 453]]<|/det|> +## [figure redacted] + +<|ref|>text<|/ref|><|det|>[[113, 495, 872, 533]]<|/det|> +Figure adapted from Mannion's paper: RIPK1 PROTACs enhance response to immune checkpoint blockade + +<|ref|>text<|/ref|><|det|>[[113, 545, 870, 625]]<|/det|> +(A) Schematic depicting the treatment regimen of tumor-bearing mice. I.P., intraperitoneal injection; I.T., intratumoral injection. +(B) Tumor growth curves of tumor bearing mice treated as in (A). Thick lines represent average tumor growth. + +<|ref|>text<|/ref|><|det|>[[115, 635, 658, 654]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[113, 665, 864, 725]]<|/det|> +Lines 82- 84: "Four hours after the removal of LD4172, RIPK1 starts to resynthesize in both cell lines. The resynthesis half-lives are approximately 48 and 24 hours in Jurkat and B16F10 cells, respectively (Fig. 2D- E)." + +<|ref|>text<|/ref|><|det|>[[113, 736, 830, 775]]<|/det|> +Line 125 'In contrast to situations where RIPK1 is kinase- dead, genetic deletion of RIPK1 has been found to trigger apoptosis both in vitro and in vivo 15. ' + +<|ref|>text<|/ref|><|det|>[[113, 786, 875, 885]]<|/det|> +Ref 15 is only about RIPK1 knock- out mice and not about RIPK1 kinase dead. Plus, ref 15 is not the only one and the first one to show that loss of RIPK1 induces apoptosis. The authors should be fair and cite all RIPK1 kinase dead and RIPK1 knock- out papers that support their statement, e.g., Kelliher Immunity 1998; Kaiser PNAS 2014; Rickard Cell 2014; Polykratis JI 2014; Berger JI 2014; Newton Science 2014. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 872, 150]]<|/det|> +Response: Thank you for pointing this out. The recommended papers are at the forefront of illustrating the kinase- dependent and - independent functions of RIPK1, and we have cited them in our manuscript. + +<|ref|>text<|/ref|><|det|>[[112, 159, 844, 220]]<|/det|> +In Fig S4A the legend says that it's sgNC vs RIPK1 KO, while in the manuscript, the authors described it as tumours being treated with LD4172. Is it a mistake with the legend or the wrong graph? + +<|ref|>text<|/ref|><|det|>[[112, 230, 844, 270]]<|/det|> +Response: Thanks for pointing this out, it is a mistake with the legend, and we have fixed it in Figure S4A legend. + +<|ref|>text<|/ref|><|det|>[[112, 310, 808, 350]]<|/det|> +In Line 181 the authors wrote "Consistent with the in vitro findings, LD4172 also triggered significant cell death in the tumor (Fig. 182 5A, 2nd column). + +<|ref|>text<|/ref|><|det|>[[112, 360, 830, 421]]<|/det|> +The 2nd column is H&E, which does not reflect of cell death but rather absence or presence of cells. Caspase- 3/7 are the cell death markers. Please correct the text accordingly. + +<|ref|>text<|/ref|><|det|>[[112, 431, 869, 472]]<|/det|> +Response: Thanks for pointing this out, we should be strict about description about the figures, the corrected text is highlighted in main text, lines 194- 197. + +<|ref|>text<|/ref|><|det|>[[112, 482, 658, 502]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[112, 511, 877, 613]]<|/det|> +Lines 194- 197: "LD4142 treatment significantly disrupted the dense structure of B16F10 tumors, as evidenced by a marked reduction in cellular density observed in H&E staining (Fig. 5A, 2nd column). Importantly, a notable increase in cleaved caspase 3/7 levels was observed in the LD4172- treated tumors, indicating the occurrence of apoptosis (Fig. 5A, 3rd and 4th columns)." + +<|ref|>text<|/ref|><|det|>[[112, 622, 867, 744]]<|/det|> +The authors wrote in line 184 'While apoptotic cell death was traditionally considered non- immunogenic, accumulating experimental data have revealed its potential to drive immune cell infiltration and anti- cancer immunity 16- 19. Supporting the activation of immunogenic apoptosis, we observed a significant increase in plasma HMGB1 levels (Fig. 5B) and enhanced exposure of calreticulin on the surface of B16F10 tumor cells (Fig. 5A, 5th column).' + +<|ref|>text<|/ref|><|det|>[[112, 754, 879, 875]]<|/det|> +However, the authors don't have supporting evidence that apoptosis is the mode of cell death that is immunogenic because it is well established that loss of RIPK1 can also induce RIPK3- dependent necroptosis (Kaiser PNAS 2014; Rickard Cell 2014; Dillon cell 2014; Berger JI 2014; Newton Science 2016), which is also immunogenic. One way to determine if apoptosis or necroptosis is immunogenic is to analyse MLKL- /- and casp3/7- /- tumours treated with RIPK1 PROTAC. The authors should rewrite this part. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 864, 290]]<|/det|> +Response: Thank you for highlighting this important point. In our investigation of the kinase- dependent and - independent functions of RIPK1 using LD4172 and T2I, we attempted to induce necroptosis in B16F10 cells with a combination of TNF- \(\alpha\) , SMAC mimetic (LCL161), and the pan- caspase inhibitor z- VAD- FMK. However, even after 72 hours of treatment, the B16F10 cells remained unresponsive to this necroptotic trigger (Figure S2), suggesting that RIPK3- dependent necroptosis is not active in these cells. This is consistent with reports that B16F10 hardly expresses RIPK325, which may explain their resistance to necroptosis induction. We have emphasized this point in lines 140- 144, and the relevant figures have been added to the supplementary data (Figure S3). + +<|ref|>image<|/ref|><|det|>[[291, 308, 707, 519]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 536, 787, 557]]<|/det|> +
Figure S3: Cell viability of B16F10 cells with indicated treatment (72 h, \(n = 3\) ).
+ +<|ref|>text<|/ref|><|det|>[[113, 567, 658, 587]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[112, 596, 864, 717]]<|/det|> +Lines 140- 144: "Although B16F10 cells remained unresponsive to necroptotic triggers (TNFα + LCL161 + Z- VAD- FMK, Fig. S3), likely due to the low expression of RIPK325, the combination of TNFα and LD4172 induced significant apoptosis (Fig. 3B- D). This was evidenced by the enhanced surface exposure of phosphatidylserine (Fig. 3B) and increased levels of cleaved caspase- 3/7 and PARP (Fig. 3C- D). Notably, these apoptotic effects were reversed with Z- VAD- FMK treatment (Fig. 3B- D)." + +<|ref|>text<|/ref|><|det|>[[112, 728, 868, 848]]<|/det|> +The authors wrote in line 196 'In addition, combined therapy with LD4172 and anti- PD1 not only induced extensive TIL infiltration (Fig. 5D- H) but also significantly enhanced anti- PD1 positivity in immunologically cold B16F10 tumors, as demonstrated by increased infiltration of cytotoxic CD8+ T cells (CD8+IFN- γ+, Fig. 5A, 6th column, and 5G- H) and decreased infiltration of FOXP3+ T regulatory cells (Fig. 5A, 7th column) within the TME.' + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[60, 88, 856, 149]]<|/det|> +271 This is wrong: LD4172 did not increased TIL infiltration CD8+ T cells induced by antiPD1 because there is not statistical difference between anti- PD1 treatment and antiPD1+ LD4172 treatment in Fig 5C, G and H. Please correct this part. + +<|ref|>text<|/ref|><|det|>[[115, 159, 857, 220]]<|/det|> +Response: Thanks for your careful checks. As you suggested, we were mixing up the individual effects of LD4172 and anti- PD1 in this part. This has been corrected and highlighted in lines 209- 212. + +<|ref|>text<|/ref|><|det|>[[115, 230, 658, 250]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[115, 260, 877, 360]]<|/det|> +Lines 209- 212: "Additionally, combined therapy with LD4172 and anti- PD1 significantly enhanced anti- PD1 positivity in immunologically cold B16F10 tumors, as demonstrated by increased infiltration of cytotoxic CD8+ T cells (CD8+IFN- \(\gamma +\) , Fig. 5A, 6th column, and 5G- H) and decreased infiltration of FOXP3+ T regulatory cells (Fig. 5A, 7th column) within the TME." + +<|ref|>text<|/ref|><|det|>[[115, 371, 877, 472]]<|/det|> +The authors wrote in line 235 'Unlike Ripk1 knockout mice, which die at 1- 3 days of age due to their widespread roles in multiple tissues and organs 25, homozygous loss- of- function RIPK1 mutations are well tolerated in humans 26. Patients with complete loss of RIPK1 protein only showed symptoms confined to the immune system, with primary immunodeficiency and/or intestinal inflammation 26.' + +<|ref|>text<|/ref|><|det|>[[115, 482, 855, 563]]<|/det|> +And Line 240 'Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies, human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable, especially with transient intervention in well- controlled clinical settings.' + +<|ref|>text<|/ref|><|det|>[[115, 573, 864, 613]]<|/det|> +And Line 259 'Considering the predicted safety profile of RIPK1 degradation based on human genetics' + +<|ref|>text<|/ref|><|det|>[[115, 623, 881, 865]]<|/det|> +By stating that loss of RIPK1 is 'well tolerated in humans', 'only showed symptoms confined to the immune system', 'human genetic data suggest that pharmacological RIPK1 degradation is potentially safe and tolerable' and 'predicted safety profile of RIPK1 degradation based on human genetics', the authors are minimising the effect of loss of RIPK1 in human to promote the use of RIPK1 PROTAC. This is extremely clumsy because Ref 26 and Li et al PNAS 2019 (doi.org/10.1073/pnas.18135821, which should be cited alongside Ref 26) showed that RIPK1 deficient patients are affected with severe immunodeficiency which can lead to the death of the patients at really young age. The authors should rephrase this part by stating that despite the severe immunodeficiency cause by permanent loss of RIPK1 in human, acute, chemical and transient depletion of RIPK1 might be tolerable in humans. Although the safety profiles of RIPK1 degraders remain to be tested in future clinical studies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[111, 88, 879, 170]]<|/det|> +Response: Thank you for your valuable comments. We realize that we were perhaps too forceful in emphasizing the potential safety of LD4172 and agree that a more critical and unbiased discussion is necessary. We have revised the discussion accordingly, as per your recommendation, which is reflected in lines 265- 270. + +<|ref|>text<|/ref|><|det|>[[115, 179, 658, 199]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[112, 209, 881, 352]]<|/det|> +Lines 265- 270: "Unlike Ripk1 knockout mice, which die within 1- 3 days of age due to the critical role of RIPK1 in multiple tissues and organs31, the phenotypes of homozygous loss- of- function RIPK1 mutations in humans are relatively less severe32. Although permanent loss of RIPK1 in patients leads to severe immunodeficiency and/or intestinal inflammation33, chemical- induced protein degradation of RIPK1, which is acute, transient, and potentially tissue- specific34, might be more tolerable in humans. However, the safety profiles of RIPK1 degraders need to be evaluated in future clinical studies." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 808, 128]]<|/det|> +Reviewer #3 (Remarks to the Author): with expertise in cancer therapeutics and degrader design + +<|ref|>text<|/ref|><|det|>[[112, 169, 875, 451]]<|/det|> +The authors reported the development of the first- in- class RIPK1 degraders that utilize the VHL E3 ligase to potently degrade RIPK1 in various cells. One of the lead compounds, LD4172, is highly specific and only degrade RIPK1 in cells with high Dmax and DC50 values in a VHL and proteasome- dependent manner. LD4172 can synergistically kill B16F10 mouse melanoma cells in combination with TNFa. Interestingly, administration of B16F10 tumor- bearing mice with LD4172 resulted in significant reduction in RIPK1 expression in the tumors but not in normal tissues. This reduction was associated with the potentiation of tumor growth inhibition when it was combined with anti- PD1 antibody. More importantly, the synergistic effect was greater with the combination of anti- PD1 antibody and LD4172 than that of anti- PD1 antibody and the RIPK1 inhibitor. These findings demonstrate that RIPK1 degraders may exert stronger antitumor activity than RIPK1 inhibitors by degrading RIPK1 to remove both its kinase and scaffold activity. In addition, this combination can also enhance antitumor immunity. + +<|ref|>text<|/ref|><|det|>[[113, 462, 208, 480]]<|/det|> +Concerns: + +<|ref|>text<|/ref|><|det|>[[112, 491, 877, 572]]<|/det|> +1. It is very interesting that only VHL-based PROTACs can effectively degrade RIPK1 but not CRBN- and MDM2-based and adamantane-tagged PROTACs. Can the authors share some insights why only VHL can degrade RIPK1? Have the authors tried to use different linker length for other PROTACs to validate the lack of degradation for RIPK1? + +<|ref|>text<|/ref|><|det|>[[111, 583, 884, 844]]<|/det|> +Response: Thank you for bringing up this point. In our initial exploration of E3 ligases, we synthesized two CRBN- based PROTACs with distinct PEG linkers, as detailed in our manuscript. However, subsequent analysis revealed minimal degradation activity for RIPK1 with these PROTACs. Following the manuscript submission, we further investigated this issue and synthesized additional CRBN- based PROTACs with varying carbon atom linkers, as illustrated in the following Figure. Our western blot results demonstrated that one of these newly developed CRBN- based PROTAC, T2C10CRBN, exhibited notable degradation activity for RIPK1 at 100 nM concentration when linker length reached 10 carbon atoms, albeit with a significant hook effect. However, the potency of these PROTACs was considerably weaker compared to the VHL- based PROTAC, LD4172. Currently, LD4172 remains the most potent RIPK1 degrader in our study. Moving forward, we are dedicated to optimizing CRBN- based PROTACs to enhance their potency as RIPK1 degraders. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[128, 93, 820, 343]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 350, 754, 370]]<|/det|> +
Figure: Chemical structures and potency of new CRBN-based PROTACs.
+ +<|ref|>text<|/ref|><|det|>[[113, 410, 870, 490]]<|/det|> +2. The authors showed that LD4172 can sensitize B16F10 cells to TNFa. Since they also showed that LD4172 can synergistically suppress B16F10 tumor growth with Anti-PD1 antibody, have the authors tested whether LD4172 can sensitize B16F10 cells to cytotoxic T cells? + +<|ref|>text<|/ref|><|det|>[[111, 501, 881, 886]]<|/det|> +Response: Thank you for pointing this out. To test whether LD4172 sensitizes B16F10 cells to cytotoxic T cells, we isolated CD8+ T cells using a mouse CD8a+ T cell isolation kit (Miltenyi Biotec) from C57BL/6J mice. These cells were stimulated with \(2\mu \mathrm{g / ml}\) plateletbound anti-CD3 (BioLegend, clone 145- 2C11) and \(2\mu \mathrm{g / ml}\) soluble anti-CD28 (BioLegend, clone 37.51) in RPMI 1640 medium supplemented with \(10\%\) FBS, \(1\%\) P/S, \(50\mathrm{nM}\) BME, and \(10\mathrm{ng / mL}\) IL- 2 for 2 days. Meanwhile, B16F10 cells were labeled with Vybrant™ DiO (ThermoFisher, V22886) and treated with LD4172 (1μM) and \(1\mathrm{ng / ml}\) IFNγ for 24 hours. After discarding the medium, we added the activated T cells for 24 hours at a 1:1 effector to target ratio. The T cells were then removed and killed B16F10 (DiO+PI+) cells were analyzed using LSRII. Contrary to our expectations, we observed no significant tumor killing, as demonstrated in the figure below. Potential explanations include: (1) as the activity of CD8+ T cells are also regulated by other immune cells, it is difficult to reconstitute the immune system in vitro; (2) Using antigen-specific B16F10 cells, such as B16F10- OVA, along with OT- 1 T cells might be necessary for better specificity; or (3) Although we washed away LD4172 before adding T cells to avoid its effects on T cells, our washout experiments indicate that B16F10 cells begin to resynthesize RIPK1 four hours after LD4172 removal, potentially restoring interactions that protect the tumor cells. While this isn't the focus of this manuscript, we plan to establish a B16F10- RIPK1- KO- OVA cell line to repeat this experiment in the future. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[110, 123, 847, 339]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[112, 369, 842, 408]]<|/det|> +
Figure: Flow cytometric analysis of B16F10 cell killing (DiO+PI+) after cotreated with activated T cells for 24 hours.
+ +<|ref|>text<|/ref|><|det|>[[112, 419, 852, 500]]<|/det|> +3. The finding that LD4172 was more effectively in degrading RIPK1 in tumor tissues than in normal tissues is very interesting. Do the authors explore why these normal tissues exhibited less RIPK1 degradation after the treatment with LD4172? Is this related to different uptake of the compounds between tumors and normal tissues? + +<|ref|>text<|/ref|><|det|>[[112, 510, 870, 732]]<|/det|> +Response: Thank you for raising this excellent point. Following your recommendation, we conducted a pharmacokinetic (PK) study by administering a single dose of LD4172 (20 mg/kg) to B16F10 tumor-bearing mice and collected tissue samples at various time points. Interestingly, although LD4172 uptake in tumors was relatively low, the compound appeared to be retained within the tumor tissue. Twelve hours post- administration, the concentration of LD4172 within the tumors remained nearly unchanged (Figure S9). These findings suggest that the potent degradation of RIPK1 observed in tumors, as compared to normal tissues, may be due to the prolonged retention of LD4172 within the tumor microenvironment. We have incorporated this information in lines 279- 286, and the relevant figures have been added to the supplementary data (Figure S9). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[192, 103, 812, 346]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 370, 808, 430]]<|/det|> +
Figure S9. LD4172 concentrations in various tissues of B16F10 tumor-bearing C57BL/6J mice at different time points following a \(20 \mathrm{mg / kg}\) intraperitoneal (i.p.) administration \((n = 4)\) .
+ +<|ref|>text<|/ref|><|det|>[[113, 441, 657, 461]]<|/det|> +Updated paragraph in the manuscript can be found as follows: + +<|ref|>text<|/ref|><|det|>[[112, 470, 880, 672]]<|/det|> +Lines 279- 286: "Albumin, which constitutes approximately \(60\%\) of total plasma protein, preferentially accumulates in tumors due to the high demand for amino acids and energy in these tissues \(^{35,36}\) . Given that \(98.6\%\) of LD4172 is bound to plasma proteins (Table 1), it is plausible that LD4172 may be "piggybacking" on albumin accumulation in tumors, thereby achieving tumor- selective RIPK1 degradation. Supporting this hypothesis, following a single \(20 \mathrm{mg / kg}\) dose of LD4172 in C57BL/6J mice bearing B16F10 tumors, LD4172 was found to persist in the tumor for an extended period compared to other tissues (Figure S9). This prolonged retention in the tumor could further mitigate potential toxicity concerns related to RIPK1 degradation in normal tissues." + +<|ref|>text<|/ref|><|det|>[[112, 714, 877, 894]]<|/det|> +4. RIPK1 KO has a profound effect in mice as they die at 1-3 days of age while patients with homozygous loss-of-function RIPK1 are alive and only exhibit some less server abnormalities such as primary immunodeficiency and/or intestinal inflammation. However, the mice treated with LD4172 did not show any side effects in mice. This may be attributable to the inability of LD4172 to effectively degrade RIPK1 in normal tissues. This finding may have important implications in developing RIPK1 targeted therapy because RIPK1 might be more toxic to normal tissues while RIPK1 PROTACs might be more selective to tumors. As such, RIPK1 PROTACs may have a better opportunity to be developed as anticancer drugs. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[111, 88, 857, 190]]<|/det|> +Response: Thank you for pointing this out. We agree with the reviewer that transient RIPK1 degradation induced by LD4172 may have very different pharmacology from persistent RIPK knockout in cells. In addition, the tissue selectivity of RIPK1 degradation included by LD4172 may be another intriguing feature to further develop these degraders as therapeutics. + +<|ref|>text<|/ref|><|det|>[[112, 199, 874, 280]]<|/det|> +5. The finding that depletion of CD8 T cells with an antibody abrogated the synergistic antitumor activity of LD4172 and anti-PD1 antibody suggests that the direct antitumor activity of RIPK1 PROTACs is less important than the induction of CD8 T cell-mediated antitumor immunity in the B16F10 tumor model. + +<|ref|>text<|/ref|><|det|>[[112, 290, 870, 392]]<|/det|> +Response: Thank you for pointing this out. In all the cancer cell lines we tested, we did not observe toxicity or inhibition of proliferation induced by LD4172 alone. However, degradation of RIPK1 rewires the cancer cell death pathways and also boost the anticancer immunity through interacting with immune cells. We view this RIPK1 degrader more like a catalyst than an executioner. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[111, 88, 808, 130]]<|/det|> +Reviewer #4 (Remarks to the Author): with expertise in cancer therapeutics and degrader design + +<|ref|>text<|/ref|><|det|>[[111, 170, 700, 190]]<|/det|> +I support publication of this work after addressing comments below. + +<|ref|>text<|/ref|><|det|>[[112, 230, 418, 249]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[112, 260, 866, 321]]<|/det|> +This is a nice study describing the discovery and characterization of the first PROTAC- based RIPK1 degrader. The study appears to be done with excellent quality and the conclusions are well supported by the provided data. + +<|ref|>text<|/ref|><|det|>[[112, 331, 220, 350]]<|/det|> +Key results: + +<|ref|>text<|/ref|><|det|>[[111, 360, 836, 381]]<|/det|> +1. RIPK1 can be degraded using a suitably designed/optimized PROTAC degrader + +<|ref|>text<|/ref|><|det|>[[111, 390, 875, 411]]<|/det|> +2. RIPK1 degrader has fundamentally different pharmacology relative to RIPK1 inhibitor + +<|ref|>text<|/ref|><|det|>[[111, 420, 777, 441]]<|/det|> +3. Degradation of RIPK1 by LD4172 triggered immunogenic cell death (ICD) + +<|ref|>text<|/ref|><|det|>[[111, 451, 857, 492]]<|/det|> +4. Degradation of RIPK1 resulted in an increase in tumor-infiltrating lymphocytes and sensitized tumors to anti-PD1 therapy + +<|ref|>text<|/ref|><|det|>[[112, 533, 875, 574]]<|/det|> +The efficacy in the mouse models is limited (this would be called progressive disease in patients) but does show the mechanism appears to be active in a murine model. + +<|ref|>text<|/ref|><|det|>[[112, 583, 320, 602]]<|/det|> +It would be nice to see: + +<|ref|>text<|/ref|><|det|>[[112, 613, 869, 654]]<|/det|> +1. PK data for LD4172 to enable understanding of how much drug exposure there was following the dosing regime used. + +<|ref|>text<|/ref|><|det|>[[111, 663, 880, 866]]<|/det|> +Response: Thank you for highlighting this important point. In the initial phase of the LD4172 PK study, we aimed to use the lowest effective dose and did not include the 20 mg/kg dosing regimen. Based on your suggestion, we repeated the PK study with a 20 mg/kg (i.p.) dose of LD4172, measuring its concentration in various tissues at different time points (Figure S8). Consistent with our previous findings, LD4172 was rapidly metabolized and cleared from the blood. However, in B16F10 tumors, LD4172 was found to persist in the tumor for an extended period compared to other tissues. This prolonged retention in the tumor could further mitigate potential toxicity concerns related to RIPK1 degradation in normal tissues. The relevant figure has been added to the supplementary data (Figure S9). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[216, 103, 780, 323]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 347, 808, 405]]<|/det|> +
Figure S9. LD4172 concentrations in various tissues of B16F10 tumor-bearing C57BL/6J mice at different time points following a \(20 \mathrm{mg / kg}\) intraperitoneal (i.p.) administration \((n = 4)\) .
+ +<|ref|>text<|/ref|><|det|>[[113, 416, 763, 437]]<|/det|> +2. To show evidence of target degradation in vivo (blood and tumor tissue). + +<|ref|>text<|/ref|><|det|>[[112, 446, 881, 688]]<|/det|> +Response: Thank you for bringing up this crucial point, which has been a key focus in the development of LD4172. We conducted a pharmacodynamic (PD) experiment in C57BL/6J mice bearing B16F10 tumors with intraperitoneally delivery (i.p.) of indicated dosages (Figure 4B). Among the various tissues tested, we observed that potent RIPK1 degradation occurred primarily in the tumors. To further understand this, we performed a pharmacokinetic (PK) study to measure LD4172 concentrations across different tissues. Interestingly, while B16F10 tumors did not exhibit the highest uptake of LD4172, the clearance of the compound in the tumor was slower, allowing for a longer duration of RIPK1 degradation. Additionally, we explored intratumoral delivery (i.t.) of LD4172 in C57BL/6J mice, which resulted in more pronounced RIPK1 degradation compared to intraperitoneal administration (Figure S7). Moving forward, we plan to optimize LD4172 to improve its penetration and efficacy in tumor tissues. + +<|ref|>image<|/ref|><|det|>[[115, 740, 861, 895]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[52, 90, 872, 130]]<|/det|> +499 Figure 4B. Representative immunoblots of RIPK1 in different tissues of C57BL/6J mice treated with LD4172 (n=3- 4). + +<|ref|>image<|/ref|><|det|>[[243, 150, 770, 355]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[55, 375, 880, 496]]<|/det|> +
Figure S7. Pharmacodynamic (PD) properties of LD4172 with intratumoral administration (i.t.). Representative immunoblots of RIPK1 expression in various tissues of C57BL/6J mice treated with LD4172 are shown. Mice with syngeneic B16F10 tumors received intratumoral injections of LD4172 (10mg/kg) twice daily for three days. Upon sacrifice, tissues were collected, and the levels of RIPK1 were quantified through Western blotting.
+ +<|ref|>text<|/ref|><|det|>[[111, 506, 875, 549]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +<|ref|>text<|/ref|><|det|>[[112, 558, 783, 599]]<|/det|> +Yes demonstrates another use of small molecule degraders to achieve novel pharmacology. + +<|ref|>text<|/ref|><|det|>[[111, 608, 870, 628]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed? + +<|ref|>text<|/ref|><|det|>[[112, 638, 538, 658]]<|/det|> +The work is well supported by the data provided. + +<|ref|>text<|/ref|><|det|>[[112, 668, 839, 708]]<|/det|> +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +<|ref|>text<|/ref|><|det|>[[112, 718, 308, 737]]<|/det|> +None that I could find. + +<|ref|>text<|/ref|><|det|>[[111, 748, 872, 769]]<|/det|> +- Is the methodology sound? Does the work meet the expected standards in your field? + +<|ref|>text<|/ref|><|det|>[[111, 778, 806, 799]]<|/det|> +- Is there enough detail provided in the methods for the work to be reproduced? + +<|ref|>text<|/ref|><|det|>[[112, 808, 884, 849]]<|/det|> +Yes experimental sections appear to be sound, nice characterization data is provided for the compounds. + +<--- Page Split ---> diff --git a/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/images_list.json b/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d9dedbe308d7a4117b1350f5232bc74692508ff7 --- /dev/null +++ b/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,149 @@ + +# nature portfolio + +Peer Review File + +An Intermetallic Molecular Nanomagnet with the Lanthanide Coordinated Only by Transition Metals + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors combine a known strategy, namely equatorial Er3+ coordination with relatively rigid ligands, with an exciting and novel approach, namely direct coordination of lanthanide ions by transition metals, and report a significant and interesting molecular nanomagnet. This work presents magnetically important, chemically novel results, which are also unusually timely after the ultra- hard molecular nanomagnet breakthrough recently reported in Science. I recommend it to be published as- is, or, at most, with minor modifications. + +I include here a few minor comments: + +- As a minor readability note, to facilitate understanding for non-experts, one could explicitly state "diamagnetic" when introducing the Re(I)-based ligand, rather than just implicitly suggesting its diamagnetic nature e.g. by confirming that the molar XT value at 260K for the complex is close to what would be expected for a single Er(III) complex. + +- To avoid confusions for synthetic chemists looking for inspiration, it also might be good to briefly clarify the similarities and differences between the current and the (extensively explored) approach of placing a diamagnetic transition metal in the proximity of the Ln ion. + +- A minor positive point to put the current results in perspective with known data: the experimental findings reported herein in terms of slow vs fast magnetic dynamics are consistent with recent data analysis showing relatively high hysteresis temperatures for equatorial Er3+ coordination with rigid ligands, compared with relatively low maxima of out-of-phase susceptibility for the same systems; in contrast, for Tb and Dy SIMs, hysteresis in the 6-10K range would correspond to higher ac maxima (at typical 1000Hz) in a 30-60K range. The relation between Ueff and tau0 in their fit is also in the statistically expected range for Er3+ SIMs (and lower values for tau0\*Ueff^2.4 than what would have been expected for Dy3+ or Tb3+ SIMs). [ https://www.researchsquare.com/article/rs-490959/v1, https://go.uv.es/rosaleny/SIMDAVIS ] I understand these coincidences with the existing dataset as an independent validation of the results. + +- While I would not recommend to do this in the current work, it would be interesting, in the future, to substantially extend the active space considered in the OpenMolcas studies to include the d orbitals of the Re(I) ions. This may give a more profound insight into what makes this system special. + +- I don't think it's really consistent to claim that the \(\sim 7\) A Er-Er separation means a sufficiently good magnetic isolation (which implicitly assumes that no magnetic moment is delocalized towards the Re ions) and at the same time justify the anomaly in Fig S5 as resulting from a ferromagnetic interaction between neighbouring molecules. + +Alejandro Gaita-Ariño + +Reviewer #2 (Remarks to the Author): + +This paper describes the synthesis and magnetic properties of an erbium complex with three [ReIcp2]- ligands, with Er- Re bonds. The work seems well done, and the compounds have been perfectly characterised. However, I believe that the work does not merit publication in Nature Commun. This is because the authors tell us that this would be a good alternative to try to improve the magnetic properties of current SMMs, whose record blocking temperature is 80 K. But this is not reflected at all in the magnetic data: the blocking temperature of this compound is less than 2 K, with a zero coercive magnetic field. Moreover, the compound is very unstable in air and, to make matters worse, it is prepared in benzene, a solvent which has been shown to be carcinogenic. I do not + +<--- Page Split ---> + +therefore see what is new about the work of Layfield et al (their reference 7) or Chilton et al (their reference 36). Accordingly, I believe that the work is not original enough to be published in Nat. Commun., and should therefore be rejected. + +Reviewer #3 (Remarks to the Author): + +This is a high quality paper in terms of data presented and the manner in which it is conveyed. The paper is well written and concise. The figures are clear. The topic is also of significant current interest. That being said, my initial thought was that because of ref. 34, the paper should be published in a more specialized journal like IC. However, upon reading ref. 34 carefully, it is clear that the authors of this study are being self- effacing. The Er- Re3 core that they are presenting might have been derived from a similar synthetic methodology used to prepare Ln- TM dinuclear cores in ref. 34, but that is where the similarities end. This molecule is distinct and displays single molecule magnetism that will motivate others to pursue this route for mimicking the core of SmCo5. In short, I think it should be accepted by Nat. Commun. + +<--- Page Split ---> + +## Reviewer #1: Alejandro Gaita-Ariño + +Thank you very much for the positive feedback on our work. We have modified our manuscript according to your comments (please see below): + +1. As a minor readability note, to facilitate understanding for non-experts, one could explicitly state "diamagnetic" when introducing the Re(I)-based ligand, rather than just implicitly suggesting its diamagnetic nature e.g. by confirming that the molar XT value at 260K for the complex is close to what would be expected for a single Er(III) complex + +We have added an explicit statement regarding the diamagnetism of the coordinated \(\mathrm{Cp_2Re}\) ligand as suggest by the reviewer. + +2. To avoid confusions for synthetic chemists looking for inspiration, it also might be good to briefly clarify the similarities and differences between the current and the (extensively explored) approach of placing a diamagnetic transition metal in the proximity of the Ln ion. + +The extensively explored approach towards bimetallic complexes combining transition metals (TM) and lanthanides (Ln) bridged by various ligands (L) is well- established and produced numerous TM- Ln compounds where the TM is in a close vicinity of the Ln ion (Yan, D., Joana, C., Lorena, R., Salvador, C., José, J.B., and Alejandro, G.- A. (2021). Data mining, dashboards and statistics: a powerful framework for the chemical design of molecular nanomagnets. Research Square. 10.21203/rs.3.rs- 490959/v1. While this approach can enhance the energy barrier for the magnetization reversal, the bridging ligands provide only weak or no electronic coupling between the two metal ions. In the approach demonstrated in our study, the direct TM- Ln bonds may lead to strong or even very strong interactions resulting in unprecedented electronic and magnetic properties. Chemically, the proposed approach is significantly more challenging as there are no universal strategies towards direct TM- Ln bonded compounds as compared to TM- Ln complexes which can be easily designed using coordination chemistry and crystal engineering methods. A few relevant sentences have been added in the introduction section together with references 44- 46: + +"Noteworthy, the concept of placing transition metal ions in the proximity of Ln- based MNMs by means of suitable bridging ligands was pursued for tens of years with several examples showing enhancement of the slow relaxation of the magnetization due to the presence of the transition metal.44, 45, 46 However, this strategy, while providing very good control of the connectivity of the target multi- metallic compound, cannot warrant strong coupling between the two metal ions due to the weak overlap of the relevant orbitals of the lanthanide and the bridging moiety. Only the direct bonding of the transition metal to the lanthanide center could result in strong electronic and magnetic interactions." + +3. A minor positive point to put the current results in perspective with known data: the experimental findings reported herein in terms of slow vs fast magnetic dynamics are consistent with recent data analysis showing relatively high hysteresis temperatures for equatorial \(\mathrm{Er3 + }\) coordination with rigid ligands, compared with relatively low maxima of out-of-phase susceptibility for the same systems; in contrast, for Tb and Dy SIMs, hysteresis in the 6-10K range would correspond to higher ac maxima (at typical \(1000\mathrm{Hz}\) ) in a 30-60K range. The relation between Ueff and tau0 in their fit is also in the statistically expected range for \(\mathrm{Er3 + }\) SIMs (and lower values for tau0\*Ueff^2.4 than what would have been expected for Dy3+ or Tb3+ SIMs). [https://www.researchsquare.com/article/rs-490959/v1, https://go.uv.es/rosaleny/SIMDAVIS] I understand these coincidences with the existing dataset as an independent validation of the results. + +<--- Page Split ---> + +Thank you for pointing it out, we've completely missed this important observation. We would like to add the following two sentences based entirely on this comment in the Results and Discussion section: + +"The relation between \(U_{\mathrm{eff}}\) and \(\tau_0\) falls perfectly in the statistically expected range for prolate Ln MNMs as analyzed by Gaita- Ariño et al. in their work covering 1405 examples of SIMs. \(^{12}\) " + +and + +"Our findings regarding the magnetic dynamics of \(\mathsf{ErRe}_3\) are consistent with the recent data analysis by Gaita- Ariño et al. \(^{12}\) The analysis shows relatively high magnetic hysteresis temperatures for prolate systems such as equatorial \(\mathsf{Er}^{\mathsf{III}}\) SIMs (coordinated by rigid ligands) accompanied by relatively low maxima of the out- of- phase magnetic susceptibility \((\chi^{\prime \prime})\) . \(\mathsf{ErRe3}\) is a perfect demonstration of this trend with the \(T_{\mathrm{hyst}}\) of \(7.2 \text{K}\) and \(U_{\mathrm{eff}} = 314 \text{K}\) ." + +We've also placed a sentence in the acknowledgments section referring to the reviewer's comment that was included in the manuscript: + +"The authors acknowledge Alejandro Gaita- Ariño for pointing out and formulating an important observation regarding the slow magnetic dynamics of the reported compound \(\mathsf{ErRe}_3\) in comparison to known Ln- SIMs." + +4. While I would not recommend to do this in the current work, it would be interesting, in the future, to substantially extend the active space considered in the OpenMolcas studies to include the d orbitals of the Re(l) ions. This may give a more profound insight into what makes this system special. + +Thank you for this suggestion. We are currently investigating other Re-Ln MNMs and we will definitely extend the active space in our calculations to include the d orbitals. + +5. I don't think it's really consistent to claim that the \(\sim 7A\) Er-Er separation means a sufficiently good magnetic isolation (which implicitly assumes that no magnetic moment is delocalized towards the Re ions) and at the same time justify the anomaly in Fig S5 as resulting from a ferromagnetic interaction between neighbouring molecules. + +By "a sufficiently good magnetic isolation" we've meant separation that is sufficient for the observation of the slow magnetic relaxation of the molecular origin. However, we agree that this statement might be confusing. The relevant fragment of the text in the subsection describing the crystal structure of \(\mathsf{ErRe}_3\) was modified: + +"This ensures magnetic isolation of the individual \([\mathrm{Er}^{\mathrm{III}}(\mathrm{Re}^{\prime}\mathrm{Cp}_2)_3]\) molecules that is sufficient for the observation of slow magnetization dynamics." + +## Reviewer #2 + +Thank you very much for your critical review. We deeply disagree with your opinion. + +However, I believe that the work does not merit publication in Nature Commun. This is because the authors tell us that this would be a good alternative to try to improve the magnetic properties of current SMMs, whose record blocking temperature is \(80 \text{K}\) . But this is not reflected at all in the magnetic data: the blocking temperature of this compound is less than \(2 \text{K}\) , with a zero coercive magnetic field. + +- Indeed, the presented \(\mathsf{ErRe}_3\) complex does not beat the DyIII metallocene SIMs. It is, however, one of the best ErIII SIMs ever reported and this fact already validates the proposed strategy of using direct TM-Ln bonds in the design of high-performance molecular nanomagnets that mimic the structure of SmCo5 and other permanent Ln-based magnets. Moreover, the recently published "ultra-hard molecular nanomagnet" (Science, 2022) also features metal- + +<--- Page Split ---> + +metal bonding as the main responsible for its record breaking magnetic properties. As pointed out by reviewer #1, the presented results are "unusually timely" in this regard. + +Moreover, the compound is very unstable in air... + +- the compound is indeed unstable in air. However, the same applies to basically all organometallic Ln-SIMs including the DyIII metallocenes (Guo et al. Science 2018, 362, 1400-1403 and Goodwin et al. Nature 2017, 548, 439-442) or the ultra-hard Dy2 nanomagnet published this year (Gould et al. Science 2022, 375, 198-202). + +...and to make matters worse, it is prepared in benzene, a solvent which has been shown to be carcinogenic. + +- Organometallic SIMs are commonly synthesized using chemicals that are toxic or carcinogenic (Gould et al. J. Am. Chem. Soc. 2019, 141, 33, 12967-12973 or Goodwin et al. Nature 2017, 548, 439-442). If handled and disposed of responsibly, the risks are minimal. Nevertheless, we've added a suitable sentence in the experimental section in order to warn the readers that benzene causes cancer in humans and should be handled with great caution: "Warning! Benzene is recognized as carcinogenic to humans and should be handled with caution using a well-ventilated hood or glovebox." + +## Reviewer #3 + +Thank you for the positive feedback on our manuscript. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +With respect to my own comments, I am satisfied with the improvements. I would add that, for the interpretation of the fits of the ac data (Orbach- only vs Orbach+ Raman vs energy level estimates via quantum chemistry calculations) the authors may benefit from considering the perspective of Gu, Wu, Phys. Rev. B (2021) 103, 014401. Gu and Wu performed a serius analysis of the detailed physical processes that may be underlying the general assumption of "Orbach+ Raman" and give insights about how this is still a simplification. + +With respect to the comments of Reviewer #2: + +- I think issues with toxicity / stability (or lack thereof) are not relevant for publication of this work in Nature Communications, since the work is fundamental science rather than an attempt to reach mass production for applied purposes. However I do think that mentioning the issue improves the manuscript. + +- I think the main criticism, while not enough to reject the work from Nature Communications, has some merits in terms of toning down the claims. The title is purely descriptive and not misleading, and the same can be said for the conclusions. However, the abstract, in its current wording, can be read as suggesting that the present work is aimed towards practical high-density data storage, or that the presented new family of compounds is about to beat the 80 K record for hysteresis. The manuscript would gain quality if the style here was toned down for realism. + +I reiterate my recommendation of acceptance, perhaps after minor corrections. + +<--- Page Split ---> + +We have modified our manuscript according to the comments of the reviewer: + +1. With respect to my own comments, I am satisfied with the improvements. I would add that, for the interpretation of the fits of the ac data (Orbach-only vs Orbach+Raman vs energy level estimates via quantum chemistry calculations) the authors may benefit from considering the perspective of Gu, Wu, Phys. Rev. B (2021) 103, 014401. Gu and Wu performed a serious analysis of the detailed physical processes that may be underlying the general assumption of "Orbach+Raman" and give insights about how this is still a simplification. + +We have added a short sentence referring to the work of Gu and Wu with a short sentence explaining the low Raman exponent observed in the magnetic behavior of our compound: + +"The observed low Raman exponent of 4.74 is most probably caused by spin-lattice coupling with optical phonons as summarized and discussed by Gu and Wu (ref. 56). + +2. I think issues with toxicity / stability (or lack thereof) are not relevant for publication of this work in Nature Communications, since the work is fundamental science rather than an attempt to reach mass production for applied purposes. However I do think that mentioning the issue improves the manuscript. + +We fully agree with this view. + +3. I think the main criticism, while not enough to reject the work from Nature Communications, has some merits in terms of toning down the claims. The title is purely descriptive and not misleading, and the same can be said for the conclusions. However, the abstract, in its current wording, can be read as suggesting that the present work is aimed towards practical high-density data storage, or that the presented new family of compounds is about to beat the 80 K record for hysteresis. The manuscript would gain quality if the style here was toned down for realism. + +We have modified the abstract by removing the sentences referring to high- density data storage and the hypothesis that the presented compound might beat the current 80 K threshold. The new abstract is included below and in the final manuscript: + +"Inspired by the hexagonal structure of the hardest intermetallic magnet SmCo5, we have synthesized a nanomagnetic molecule where the central lanthanide (Ln) \(\mathrm{Er^{III}}\) is coordinated solely by three transition metal ions (TM) in a perfectly trigonal planar fashion. This intermetallic molecule \([\mathrm{Er^{III}}(\mathrm{ReCp_2})_3]\) (ErRe) starts a family of molecular nanomagnets (MNM) with unsupported Ln- TM bonds and paves the way towards molecular intermetallics with strong direct magnetic exchange interactions - a promising route towards high- performance single- molecule magnets." + +<--- Page Split ---> diff --git a/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a1f2524ffc50d75aa010b7fcc784464b6340364c --- /dev/null +++ b/peer_reviews/bb390faf8f1c6aa8df2403350299b15f137ed314c21ce18b63fc7d2cbb390aef/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,205 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[80, 154, 918, 211]]<|/det|> +An Intermetallic Molecular Nanomagnet with the Lanthanide Coordinated Only by Transition Metals + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 82, 312, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 112, 402, 127]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 142, 874, 231]]<|/det|> +The authors combine a known strategy, namely equatorial Er3+ coordination with relatively rigid ligands, with an exciting and novel approach, namely direct coordination of lanthanide ions by transition metals, and report a significant and interesting molecular nanomagnet. This work presents magnetically important, chemically novel results, which are also unusually timely after the ultra- hard molecular nanomagnet breakthrough recently reported in Science. I recommend it to be published as- is, or, at most, with minor modifications. + +<|ref|>text<|/ref|><|det|>[[120, 245, 400, 260]]<|/det|> +I include here a few minor comments: + +<|ref|>text<|/ref|><|det|>[[119, 274, 841, 335]]<|/det|> +- As a minor readability note, to facilitate understanding for non-experts, one could explicitly state "diamagnetic" when introducing the Re(I)-based ligand, rather than just implicitly suggesting its diamagnetic nature e.g. by confirming that the molar XT value at 260K for the complex is close to what would be expected for a single Er(III) complex. + +<|ref|>text<|/ref|><|det|>[[119, 348, 871, 393]]<|/det|> +- To avoid confusions for synthetic chemists looking for inspiration, it also might be good to briefly clarify the similarities and differences between the current and the (extensively explored) approach of placing a diamagnetic transition metal in the proximity of the Ln ion. + +<|ref|>text<|/ref|><|det|>[[118, 407, 872, 555]]<|/det|> +- A minor positive point to put the current results in perspective with known data: the experimental findings reported herein in terms of slow vs fast magnetic dynamics are consistent with recent data analysis showing relatively high hysteresis temperatures for equatorial Er3+ coordination with rigid ligands, compared with relatively low maxima of out-of-phase susceptibility for the same systems; in contrast, for Tb and Dy SIMs, hysteresis in the 6-10K range would correspond to higher ac maxima (at typical 1000Hz) in a 30-60K range. The relation between Ueff and tau0 in their fit is also in the statistically expected range for Er3+ SIMs (and lower values for tau0\*Ueff^2.4 than what would have been expected for Dy3+ or Tb3+ SIMs). [ https://www.researchsquare.com/article/rs-490959/v1, https://go.uv.es/rosaleny/SIMDAVIS ] I understand these coincidences with the existing dataset as an independent validation of the results. + +<|ref|>text<|/ref|><|det|>[[119, 569, 864, 614]]<|/det|> +- While I would not recommend to do this in the current work, it would be interesting, in the future, to substantially extend the active space considered in the OpenMolcas studies to include the d orbitals of the Re(I) ions. This may give a more profound insight into what makes this system special. + +<|ref|>text<|/ref|><|det|>[[119, 628, 867, 687]]<|/det|> +- I don't think it's really consistent to claim that the \(\sim 7\) A Er-Er separation means a sufficiently good magnetic isolation (which implicitly assumes that no magnetic moment is delocalized towards the Re ions) and at the same time justify the anomaly in Fig S5 as resulting from a ferromagnetic interaction between neighbouring molecules. + +<|ref|>text<|/ref|><|det|>[[119, 702, 281, 716]]<|/det|> +Alejandro Gaita-Ariño + +<|ref|>text<|/ref|><|det|>[[120, 760, 402, 775]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 790, 867, 910]]<|/det|> +This paper describes the synthesis and magnetic properties of an erbium complex with three [ReIcp2]- ligands, with Er- Re bonds. The work seems well done, and the compounds have been perfectly characterised. However, I believe that the work does not merit publication in Nature Commun. This is because the authors tell us that this would be a good alternative to try to improve the magnetic properties of current SMMs, whose record blocking temperature is 80 K. But this is not reflected at all in the magnetic data: the blocking temperature of this compound is less than 2 K, with a zero coercive magnetic field. Moreover, the compound is very unstable in air and, to make matters worse, it is prepared in benzene, a solvent which has been shown to be carcinogenic. I do not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 840, 128]]<|/det|> +therefore see what is new about the work of Layfield et al (their reference 7) or Chilton et al (their reference 36). Accordingly, I believe that the work is not original enough to be published in Nat. Commun., and should therefore be rejected. + +<|ref|>text<|/ref|><|det|>[[120, 181, 402, 195]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 210, 875, 344]]<|/det|> +This is a high quality paper in terms of data presented and the manner in which it is conveyed. The paper is well written and concise. The figures are clear. The topic is also of significant current interest. That being said, my initial thought was that because of ref. 34, the paper should be published in a more specialized journal like IC. However, upon reading ref. 34 carefully, it is clear that the authors of this study are being self- effacing. The Er- Re3 core that they are presenting might have been derived from a similar synthetic methodology used to prepare Ln- TM dinuclear cores in ref. 34, but that is where the similarities end. This molecule is distinct and displays single molecule magnetism that will motivate others to pursue this route for mimicking the core of SmCo5. In short, I think it should be accepted by Nat. Commun. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 146, 376, 161]]<|/det|> +## Reviewer #1: Alejandro Gaita-Ariño + +<|ref|>text<|/ref|><|det|>[[115, 163, 880, 194]]<|/det|> +Thank you very much for the positive feedback on our work. We have modified our manuscript according to your comments (please see below): + +<|ref|>text<|/ref|><|det|>[[115, 209, 881, 274]]<|/det|> +1. As a minor readability note, to facilitate understanding for non-experts, one could explicitly state "diamagnetic" when introducing the Re(I)-based ligand, rather than just implicitly suggesting its diamagnetic nature e.g. by confirming that the molar XT value at 260K for the complex is close to what would be expected for a single Er(III) complex + +<|ref|>text<|/ref|><|det|>[[174, 275, 880, 305]]<|/det|> +We have added an explicit statement regarding the diamagnetism of the coordinated \(\mathrm{Cp_2Re}\) ligand as suggest by the reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 320, 881, 368]]<|/det|> +2. To avoid confusions for synthetic chemists looking for inspiration, it also might be good to briefly clarify the similarities and differences between the current and the (extensively explored) approach of placing a diamagnetic transition metal in the proximity of the Ln ion. + +<|ref|>text<|/ref|><|det|>[[175, 370, 881, 592]]<|/det|> +The extensively explored approach towards bimetallic complexes combining transition metals (TM) and lanthanides (Ln) bridged by various ligands (L) is well- established and produced numerous TM- Ln compounds where the TM is in a close vicinity of the Ln ion (Yan, D., Joana, C., Lorena, R., Salvador, C., José, J.B., and Alejandro, G.- A. (2021). Data mining, dashboards and statistics: a powerful framework for the chemical design of molecular nanomagnets. Research Square. 10.21203/rs.3.rs- 490959/v1. While this approach can enhance the energy barrier for the magnetization reversal, the bridging ligands provide only weak or no electronic coupling between the two metal ions. In the approach demonstrated in our study, the direct TM- Ln bonds may lead to strong or even very strong interactions resulting in unprecedented electronic and magnetic properties. Chemically, the proposed approach is significantly more challenging as there are no universal strategies towards direct TM- Ln bonded compounds as compared to TM- Ln complexes which can be easily designed using coordination chemistry and crystal engineering methods. A few relevant sentences have been added in the introduction section together with references 44- 46: + +<|ref|>text<|/ref|><|det|>[[176, 593, 881, 720]]<|/det|> +"Noteworthy, the concept of placing transition metal ions in the proximity of Ln- based MNMs by means of suitable bridging ligands was pursued for tens of years with several examples showing enhancement of the slow relaxation of the magnetization due to the presence of the transition metal.44, 45, 46 However, this strategy, while providing very good control of the connectivity of the target multi- metallic compound, cannot warrant strong coupling between the two metal ions due to the weak overlap of the relevant orbitals of the lanthanide and the bridging moiety. Only the direct bonding of the transition metal to the lanthanide center could result in strong electronic and magnetic interactions." + +<|ref|>text<|/ref|><|det|>[[115, 736, 882, 896]]<|/det|> +3. A minor positive point to put the current results in perspective with known data: the experimental findings reported herein in terms of slow vs fast magnetic dynamics are consistent with recent data analysis showing relatively high hysteresis temperatures for equatorial \(\mathrm{Er3 + }\) coordination with rigid ligands, compared with relatively low maxima of out-of-phase susceptibility for the same systems; in contrast, for Tb and Dy SIMs, hysteresis in the 6-10K range would correspond to higher ac maxima (at typical \(1000\mathrm{Hz}\) ) in a 30-60K range. The relation between Ueff and tau0 in their fit is also in the statistically expected range for \(\mathrm{Er3 + }\) SIMs (and lower values for tau0\*Ueff^2.4 than what would have been expected for Dy3+ or Tb3+ SIMs). [https://www.researchsquare.com/article/rs-490959/v1, https://go.uv.es/rosaleny/SIMDAVIS] I understand these coincidences with the existing dataset as an independent validation of the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[177, 82, 881, 130]]<|/det|> +Thank you for pointing it out, we've completely missed this important observation. We would like to add the following two sentences based entirely on this comment in the Results and Discussion section: + +<|ref|>text<|/ref|><|det|>[[177, 131, 880, 163]]<|/det|> +"The relation between \(U_{\mathrm{eff}}\) and \(\tau_0\) falls perfectly in the statistically expected range for prolate Ln MNMs as analyzed by Gaita- Ariño et al. in their work covering 1405 examples of SIMs. \(^{12}\) " + +<|ref|>text<|/ref|><|det|>[[177, 180, 207, 194]]<|/det|> +and + +<|ref|>text<|/ref|><|det|>[[177, 210, 881, 290]]<|/det|> +"Our findings regarding the magnetic dynamics of \(\mathsf{ErRe}_3\) are consistent with the recent data analysis by Gaita- Ariño et al. \(^{12}\) The analysis shows relatively high magnetic hysteresis temperatures for prolate systems such as equatorial \(\mathsf{Er}^{\mathsf{III}}\) SIMs (coordinated by rigid ligands) accompanied by relatively low maxima of the out- of- phase magnetic susceptibility \((\chi^{\prime \prime})\) . \(\mathsf{ErRe3}\) is a perfect demonstration of this trend with the \(T_{\mathrm{hyst}}\) of \(7.2 \text{K}\) and \(U_{\mathrm{eff}} = 314 \text{K}\) ." + +<|ref|>text<|/ref|><|det|>[[177, 306, 880, 337]]<|/det|> +We've also placed a sentence in the acknowledgments section referring to the reviewer's comment that was included in the manuscript: + +<|ref|>text<|/ref|><|det|>[[177, 338, 880, 385]]<|/det|> +"The authors acknowledge Alejandro Gaita- Ariño for pointing out and formulating an important observation regarding the slow magnetic dynamics of the reported compound \(\mathsf{ErRe}_3\) in comparison to known Ln- SIMs." + +<|ref|>text<|/ref|><|det|>[[116, 401, 881, 449]]<|/det|> +4. While I would not recommend to do this in the current work, it would be interesting, in the future, to substantially extend the active space considered in the OpenMolcas studies to include the d orbitals of the Re(l) ions. This may give a more profound insight into what makes this system special. + +<|ref|>text<|/ref|><|det|>[[174, 450, 880, 481]]<|/det|> +Thank you for this suggestion. We are currently investigating other Re-Ln MNMs and we will definitely extend the active space in our calculations to include the d orbitals. + +<|ref|>text<|/ref|><|det|>[[116, 497, 881, 560]]<|/det|> +5. I don't think it's really consistent to claim that the \(\sim 7A\) Er-Er separation means a sufficiently good magnetic isolation (which implicitly assumes that no magnetic moment is delocalized towards the Re ions) and at the same time justify the anomaly in Fig S5 as resulting from a ferromagnetic interaction between neighbouring molecules. + +<|ref|>text<|/ref|><|det|>[[176, 561, 881, 625]]<|/det|> +By "a sufficiently good magnetic isolation" we've meant separation that is sufficient for the observation of the slow magnetic relaxation of the molecular origin. However, we agree that this statement might be confusing. The relevant fragment of the text in the subsection describing the crystal structure of \(\mathsf{ErRe}_3\) was modified: + +<|ref|>text<|/ref|><|det|>[[176, 626, 880, 657]]<|/det|> +"This ensures magnetic isolation of the individual \([\mathrm{Er}^{\mathrm{III}}(\mathrm{Re}^{\prime}\mathrm{Cp}_2)_3]\) molecules that is sufficient for the observation of slow magnetization dynamics." + +<|ref|>sub_title<|/ref|><|det|>[[116, 690, 208, 703]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[116, 705, 741, 720]]<|/det|> +Thank you very much for your critical review. We deeply disagree with your opinion. + +<|ref|>text<|/ref|><|det|>[[116, 736, 881, 815]]<|/det|> +However, I believe that the work does not merit publication in Nature Commun. This is because the authors tell us that this would be a good alternative to try to improve the magnetic properties of current SMMs, whose record blocking temperature is \(80 \text{K}\) . But this is not reflected at all in the magnetic data: the blocking temperature of this compound is less than \(2 \text{K}\) , with a zero coercive magnetic field. + +<|ref|>text<|/ref|><|det|>[[146, 816, 881, 895]]<|/det|> +- Indeed, the presented \(\mathsf{ErRe}_3\) complex does not beat the DyIII metallocene SIMs. It is, however, one of the best ErIII SIMs ever reported and this fact already validates the proposed strategy of using direct TM-Ln bonds in the design of high-performance molecular nanomagnets that mimic the structure of SmCo5 and other permanent Ln-based magnets. Moreover, the recently published "ultra-hard molecular nanomagnet" (Science, 2022) also features metal- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[174, 83, 880, 115]]<|/det|> +metal bonding as the main responsible for its record breaking magnetic properties. As pointed out by reviewer #1, the presented results are "unusually timely" in this regard. + +<|ref|>text<|/ref|><|det|>[[117, 132, 475, 147]]<|/det|> +Moreover, the compound is very unstable in air... + +<|ref|>text<|/ref|><|det|>[[145, 148, 881, 211]]<|/det|> +- the compound is indeed unstable in air. However, the same applies to basically all organometallic Ln-SIMs including the DyIII metallocenes (Guo et al. Science 2018, 362, 1400-1403 and Goodwin et al. Nature 2017, 548, 439-442) or the ultra-hard Dy2 nanomagnet published this year (Gould et al. Science 2022, 375, 198-202). + +<|ref|>text<|/ref|><|det|>[[115, 228, 880, 259]]<|/det|> +...and to make matters worse, it is prepared in benzene, a solvent which has been shown to be carcinogenic. + +<|ref|>text<|/ref|><|det|>[[145, 260, 881, 360]]<|/det|> +- Organometallic SIMs are commonly synthesized using chemicals that are toxic or carcinogenic (Gould et al. J. Am. Chem. Soc. 2019, 141, 33, 12967-12973 or Goodwin et al. Nature 2017, 548, 439-442). If handled and disposed of responsibly, the risks are minimal. Nevertheless, we've added a suitable sentence in the experimental section in order to warn the readers that benzene causes cancer in humans and should be handled with great caution: "Warning! Benzene is recognized as carcinogenic to humans and should be handled with caution using a well-ventilated hood or glovebox." + +<|ref|>sub_title<|/ref|><|det|>[[116, 403, 209, 416]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[116, 418, 528, 433]]<|/det|> +Thank you for the positive feedback on our manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 82, 312, 97]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 112, 402, 127]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 142, 875, 230]]<|/det|> +With respect to my own comments, I am satisfied with the improvements. I would add that, for the interpretation of the fits of the ac data (Orbach- only vs Orbach+ Raman vs energy level estimates via quantum chemistry calculations) the authors may benefit from considering the perspective of Gu, Wu, Phys. Rev. B (2021) 103, 014401. Gu and Wu performed a serius analysis of the detailed physical processes that may be underlying the general assumption of "Orbach+ Raman" and give insights about how this is still a simplification. + +<|ref|>text<|/ref|><|det|>[[120, 245, 463, 260]]<|/det|> +With respect to the comments of Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 274, 875, 335]]<|/det|> +- I think issues with toxicity / stability (or lack thereof) are not relevant for publication of this work in Nature Communications, since the work is fundamental science rather than an attempt to reach mass production for applied purposes. However I do think that mentioning the issue improves the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 348, 876, 438]]<|/det|> +- I think the main criticism, while not enough to reject the work from Nature Communications, has some merits in terms of toning down the claims. The title is purely descriptive and not misleading, and the same can be said for the conclusions. However, the abstract, in its current wording, can be read as suggesting that the present work is aimed towards practical high-density data storage, or that the presented new family of compounds is about to beat the 80 K record for hysteresis. The manuscript would gain quality if the style here was toned down for realism. + +<|ref|>text<|/ref|><|det|>[[118, 452, 702, 468]]<|/det|> +I reiterate my recommendation of acceptance, perhaps after minor corrections. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 131, 702, 147]]<|/det|> +We have modified our manuscript according to the comments of the reviewer: + +<|ref|>text<|/ref|><|det|>[[115, 162, 882, 258]]<|/det|> +1. With respect to my own comments, I am satisfied with the improvements. I would add that, for the interpretation of the fits of the ac data (Orbach-only vs Orbach+Raman vs energy level estimates via quantum chemistry calculations) the authors may benefit from considering the perspective of Gu, Wu, Phys. Rev. B (2021) 103, 014401. Gu and Wu performed a serious analysis of the detailed physical processes that may be underlying the general assumption of "Orbach+Raman" and give insights about how this is still a simplification. + +<|ref|>text<|/ref|><|det|>[[174, 260, 882, 288]]<|/det|> +We have added a short sentence referring to the work of Gu and Wu with a short sentence explaining the low Raman exponent observed in the magnetic behavior of our compound: + +<|ref|>text<|/ref|><|det|>[[174, 289, 881, 321]]<|/det|> +"The observed low Raman exponent of 4.74 is most probably caused by spin-lattice coupling with optical phonons as summarized and discussed by Gu and Wu (ref. 56). + +<|ref|>text<|/ref|><|det|>[[115, 352, 881, 417]]<|/det|> +2. I think issues with toxicity / stability (or lack thereof) are not relevant for publication of this work in Nature Communications, since the work is fundamental science rather than an attempt to reach mass production for applied purposes. However I do think that mentioning the issue improves the manuscript. + +<|ref|>text<|/ref|><|det|>[[176, 418, 395, 433]]<|/det|> +We fully agree with this view. + +<|ref|>text<|/ref|><|det|>[[115, 464, 882, 560]]<|/det|> +3. I think the main criticism, while not enough to reject the work from Nature Communications, has some merits in terms of toning down the claims. The title is purely descriptive and not misleading, and the same can be said for the conclusions. However, the abstract, in its current wording, can be read as suggesting that the present work is aimed towards practical high-density data storage, or that the presented new family of compounds is about to beat the 80 K record for hysteresis. The manuscript would gain quality if the style here was toned down for realism. + +<|ref|>text<|/ref|><|det|>[[175, 561, 881, 608]]<|/det|> +We have modified the abstract by removing the sentences referring to high- density data storage and the hypothesis that the presented compound might beat the current 80 K threshold. The new abstract is included below and in the final manuscript: + +<|ref|>text<|/ref|><|det|>[[175, 609, 882, 720]]<|/det|> +"Inspired by the hexagonal structure of the hardest intermetallic magnet SmCo5, we have synthesized a nanomagnetic molecule where the central lanthanide (Ln) \(\mathrm{Er^{III}}\) is coordinated solely by three transition metal ions (TM) in a perfectly trigonal planar fashion. This intermetallic molecule \([\mathrm{Er^{III}}(\mathrm{ReCp_2})_3]\) (ErRe) starts a family of molecular nanomagnets (MNM) with unsupported Ln- TM bonds and paves the way towards molecular intermetallics with strong direct magnetic exchange interactions - a promising route towards high- performance single- molecule magnets." + +<--- Page Split ---> diff --git a/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./images_list.json b/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./supplementary_0_Peer Review File..mmd b/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./supplementary_0_Peer Review File..mmd new file mode 100644 index 0000000000000000000000000000000000000000..2e5eb4f6480bdb57544f35003319de79f76b9402 --- /dev/null +++ b/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./supplementary_0_Peer Review File..mmd @@ -0,0 +1,49 @@ + +# nature portfolio + +Peer Review File + +Increased lethality in influenza and SARS- CoV- 2 coinfection is prevented by influenza immunity but not SARS- CoV- 2 immunity + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: The authors have addressed my concerns. The additional experiments have strengthened the manuscript. + +Reviewer #2: + +Remarks to the Author: + +The paper by Achdout et al. studies the effect of SARS- CoV- 2/influenza superinfection in a transgenic mouse model expressing human ACE2 under the K18 promoter. The data obtained in this model is compared with that obtained in C57BL/6 mice in which ACE2 is delivery via Adenovirus infection. The study indicates that superinfection results in severe respiratory disease. This is precluded by previous immunity to flu but not SARS- CoV- 2, and this immunity is antibody dependent. + +This is a great study, well conducted and with conclusions of obvious public health relevance. I only have some minor suggestions as indicated below. Well done. + +1- In the abstract (Line 27), I think antibody- dependent is more adequate than humoral- dependent. Alternatively 'dependent on humoral immunity'. + +2- Why do the authors conclude that 'in the human population, coinfection is most likely to occur during the asymptomatic period'? This for sure does not apply for mild cases of COVID- 19 which are the vast majority. + +3- I think that throughout the paper, superinfection is more appropriate than coinfection + +4- Did the authors sequenced their SARS- CoV- 2 stocks? This is important in view of the furing cleavage deletions appearing as a consequence of passage in Vero's. This should be indicated + +5- it would be easier for the reader if the color codes of the graphs were maintained in all the figures + +<--- Page Split ---> + + +
REVIEWERS' COMMENTSAnswer
REVIEWERS' COMMENTS
Reviewer #1 (Remarks to the Author):
The authors have addressed my concerns. The
additional experiments have strengthened the
manuscript.
We wish to thank the Reviewer for his valuable
remarks. We also believe that the additions made
following his remarks strengthened the
manuscript.
REVIEWERS' COMMENTS
Reviewer #2 (Remarks to the Author):
The paper by Achdout et al. studies the effect of
SARS-CoV-2/influenza superinfection in a
transgenic mouse model expressing human ACE2
under the K18 promoter. The data obtained in
this model is compared with that obtained in
C57BL/6 mice in which ACE2 is delivery via
Adenovirus infection. The study indicates that
superinfection results in severe respiratory
disease. This is precluded by previous immunity to flu but not SARS-CoV-2, and this immunity is
antibody dependent.
This is a great study, well conducted and with
conclusions of obvious public health relevance. I only have some minor suggestions as indicated
below. Well done.
We wish to thank the Reviewer for his comments and remarks. Our replay for his suggestions
appears below.
The line numbers specified are for the track
changes version.
1- In the abstract (Line 27), I think antibody-dependent is more adequate than humoral-dependent. Alternatively 'dependent on humoral immunity'.As suggested, changed to antibody-dependent.
2- Why do the authors conclude that 'in the
human population, coinfection is most likely to
occur during the asymptomatic period'? This for sure does not apply for mild cases of COVID-19
which are the vast majority.
We are sorry for the misunderstanding. We
added clarification for the meaning of
asymptomatic period of influenza (lines 112-113).
3- I think that throughout the paper,
superinfection is more appropriate than
coinfection
We address the terms coinfection and
superinfection in lines 81-84.
("While the terms coinfection and superinfection are often used interchangeably, the use of
'coinfection' here refers to a sequential infection with 2 viruses within a very short time, with the
second infection occurring prior to the
elimination of the first virus.").
+ +<--- Page Split ---> + + +
4- Did the authors sequenced their SARS-CoV-2 stocks? This is important in view of the furing cleavage deletions appearing as a consequence of passage in Vero's. This should be indicatedYes. GISAID submission: EPI_ISL_3838266. No deletion in the furin cleavage site is noted. Data was added to the text, lines 262-264.
5- it would be easier for the reader if the color codes of the graphs were maintained in all the figuresThe color codes of the groups are maintain in all figures when possible.
+ +<--- Page Split ---> diff --git a/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./supplementary_0_Peer Review File._det.mmd b/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./supplementary_0_Peer Review File._det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d689b6734d3442e4927fac3e04eb9975e54423e1 --- /dev/null +++ b/peer_reviews/be834470d518c850b908959fca0cb3295c70157ca34ea00c672f21b5b20c41c8/supplementary_0_Peer Review File./supplementary_0_Peer Review File._det.mmd @@ -0,0 +1,62 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[107, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[107, 154, 875, 240]]<|/det|> +Increased lethality in influenza and SARS- CoV- 2 coinfection is prevented by influenza immunity but not SARS- CoV- 2 immunity + +<|ref|>image<|/ref|><|det|>[[93, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[272, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 872, 142]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 175, 286, 190]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[115, 207, 810, 270]]<|/det|> +Reviewer #1: Remarks to the Author: The authors have addressed my concerns. The additional experiments have strengthened the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 319, 216, 333]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[115, 336, 291, 350]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 350, 872, 429]]<|/det|> +The paper by Achdout et al. studies the effect of SARS- CoV- 2/influenza superinfection in a transgenic mouse model expressing human ACE2 under the K18 promoter. The data obtained in this model is compared with that obtained in C57BL/6 mice in which ACE2 is delivery via Adenovirus infection. The study indicates that superinfection results in severe respiratory disease. This is precluded by previous immunity to flu but not SARS- CoV- 2, and this immunity is antibody dependent. + +<|ref|>text<|/ref|><|det|>[[115, 444, 860, 476]]<|/det|> +This is a great study, well conducted and with conclusions of obvious public health relevance. I only have some minor suggestions as indicated below. Well done. + +<|ref|>text<|/ref|><|det|>[[115, 492, 861, 523]]<|/det|> +1- In the abstract (Line 27), I think antibody- dependent is more adequate than humoral- dependent. Alternatively 'dependent on humoral immunity'. + +<|ref|>text<|/ref|><|det|>[[115, 540, 864, 588]]<|/det|> +2- Why do the authors conclude that 'in the human population, coinfection is most likely to occur during the asymptomatic period'? This for sure does not apply for mild cases of COVID- 19 which are the vast majority. + +<|ref|>text<|/ref|><|det|>[[115, 604, 775, 620]]<|/det|> +3- I think that throughout the paper, superinfection is more appropriate than coinfection + +<|ref|>text<|/ref|><|det|>[[115, 636, 820, 668]]<|/det|> +4- Did the authors sequenced their SARS- CoV- 2 stocks? This is important in view of the furing cleavage deletions appearing as a consequence of passage in Vero's. This should be indicated + +<|ref|>text<|/ref|><|det|>[[112, 683, 866, 699]]<|/det|> +5- it would be easier for the reader if the color codes of the graphs were maintained in all the figures + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[113, 88, 883, 858]]<|/det|> + +
REVIEWERS' COMMENTSAnswer
REVIEWERS' COMMENTS
Reviewer #1 (Remarks to the Author):
The authors have addressed my concerns. The
additional experiments have strengthened the
manuscript.
We wish to thank the Reviewer for his valuable
remarks. We also believe that the additions made
following his remarks strengthened the
manuscript.
REVIEWERS' COMMENTS
Reviewer #2 (Remarks to the Author):
The paper by Achdout et al. studies the effect of
SARS-CoV-2/influenza superinfection in a
transgenic mouse model expressing human ACE2
under the K18 promoter. The data obtained in
this model is compared with that obtained in
C57BL/6 mice in which ACE2 is delivery via
Adenovirus infection. The study indicates that
superinfection results in severe respiratory
disease. This is precluded by previous immunity to flu but not SARS-CoV-2, and this immunity is
antibody dependent.
This is a great study, well conducted and with
conclusions of obvious public health relevance. I only have some minor suggestions as indicated
below. Well done.
We wish to thank the Reviewer for his comments and remarks. Our replay for his suggestions
appears below.
The line numbers specified are for the track
changes version.
1- In the abstract (Line 27), I think antibody-dependent is more adequate than humoral-dependent. Alternatively 'dependent on humoral immunity'.As suggested, changed to antibody-dependent.
2- Why do the authors conclude that 'in the
human population, coinfection is most likely to
occur during the asymptomatic period'? This for sure does not apply for mild cases of COVID-19
which are the vast majority.
We are sorry for the misunderstanding. We
added clarification for the meaning of
asymptomatic period of influenza (lines 112-113).
3- I think that throughout the paper,
superinfection is more appropriate than
coinfection
We address the terms coinfection and
superinfection in lines 81-84.
("While the terms coinfection and superinfection are often used interchangeably, the use of
'coinfection' here refers to a sequential infection with 2 viruses within a very short time, with the
second infection occurring prior to the
elimination of the first virus.").
+ +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[115, 88, 881, 210]]<|/det|> + +
4- Did the authors sequenced their SARS-CoV-2 stocks? This is important in view of the furing cleavage deletions appearing as a consequence of passage in Vero's. This should be indicatedYes. GISAID submission: EPI_ISL_3838266. No deletion in the furin cleavage site is noted. Data was added to the text, lines 262-264.
5- it would be easier for the reader if the color codes of the graphs were maintained in all the figuresThe color codes of the groups are maintain in all figures when possible.
+ +<--- Page Split ---> diff --git a/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..4c32b270ff4310fd33247ecb9910773fabe4174c --- /dev/null +++ b/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,32 @@ +[ + { + "type": "image", + "img_path": "images/Supplementary_Figure_3.jpg", + "caption": "Supplementary Figure 3. Diagram of optical path through the HRR to the LFIA line.", + "footnote": [], + "bbox": [ + [ + 135, + 85, + 744, + 330 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Figure 5. Bland-Altman plots for log transformed K18 concentration using SERS-LFIA and M65 ELISA. Study A plots for A) non-DILI, B) DILI. Study B plots for C) non-DILI, D) DILI. The yellow horizontal lines represent the upper and lower limits of agreement (with 95% CI), and the blue line represents the geometric mean - bias. DILI, drug-induced liver injury; ELISA, enzyme-linked immunosorbent assay; K18, cytokeratin 18; LFIA, lateral flow immunoassay; SERS, surface enhanced Raman scattering.", + "footnote": [], + "bbox": [ + [ + 131, + 85, + 968, + 530 + ] + ], + "page_idx": 13 + } +] \ No newline at end of file diff --git a/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..cacccedf115c73030ebb843f628966f9e08b2b2b --- /dev/null +++ b/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,273 @@ + +# nature portfolio + +Peer Review File + +# A new point-of-care diagnostic for drug-induced liver injury using surface-enhanced Raman scattering lateral flow immunoassay + +Corresponding Author: Professor James Dear + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The group from Edinburgh report on the development of a POC instrument to quantify serum Cytokeratin 18 levels from patients who had been enrolled in prior clinical trials of APAP overdose presenting to the ER. The rationale for the study and methods are well described and justified. + +1. Data analysis- Two cohorts of patients in Study A and B are reported that had biobanked serum samples tested in the initial and modified Raman LFIA devices. The authors state that the sera of 50 patients with DILI (elevated ALT) and no DILI (ALT < ULN) at presentation were randomly selected for testing. Since the readout of the device is quantitative it would be of interest in the NO DILI patients to see if the quantitative level of CK-18 in those who went on to develop DILI during the study were higher compared to the non-DILI patients who never developed DILI. Based upon Ref #9 it is reasonable to speculate that subclinical DILI may be detected prior to ALT increase with this assay and it would be interest to know if the initial non-DILI cases who did develop DILI had elevated CK18 from the get go. + +2. Abstract & Intro- In abstract, authors state that there 100,000 cases of APAP overdose in UK and in intro they state 50,000 cases. Please address and clarify. + +3. Need for further studies- In the DISCUSSION, the need to define an optimal cut off for DILI vs non-DILI in a prospective cohort with capillary blood sampling and in a real time clinical context should be further emphasized. + +4. Factors impacting CK-19 levels in health volunteers- The authors state that there was substantial intra and interindividual variability in the control and test bands of the LFIA. What factors are likely to contribute to this? Does total bilirubin levels impact performance characteristics of the test or lipid profile? + +Reviewer #2 + +(Remarks to the Author) + +Manuscript represents high quality research on rapid and accurate detection of drug- induced liver injury using Lateral Flow Immunoassay combined with handheld Raman Reader and surface- enhanced Raman scattering. Presented results on diagnostic accuracy for drug- induced liver injury with a specificity of \(94\%\) and sensitivity of \(82\%\) are well supported by satisfactory amount of clinical results for patients for this proof of concept study. + +Nevertheless, presented method of SERS- LFIA is not novel as state of the art was well described in Discussion section. However, the application of drug- induced liver injury using SERS- LFIA is novel and very relevant for the development of point of care diagnostics. + +Therefore, I suggest publication of this manuscript in Nature Communications if authors will reflect on my comments: 1. It has been mentioned in the manuscript that novel handheld Raman reader was developed (line 394). Therefore, I would expect to see the optical schema of the novel Raman reader with detailed description of all optical elements for laser beam delivery and Raman beam delivery. Please try to add supplementary Figure with detailed optical schema and detailed description of all elements and explanation of novelty of such custom spectrometer. In particular: + +a. Please describe optical parameters of novel Raman reader: spectral range, resolution, throughput from sample to detector. + +b. What laser was used: multimode or single mode? Max laser power measured just from the laser and on the sample? How + +<--- Page Split ---> + +laser attenuation was done? What was the laser manufacturer? + +c. What was the length of the laser line on the sample focal plane? Was the laser line homogeneously illuminated? Typically, Powell lens provides inhomogeneous illumination on the sample, especially on the edges of the line. Was it taken into account and post corrected by the software via line intensity normalization? + +d. What was the sample probe (microscope objective) NA, focal length, model? + +2. It is mentioned that Raman reader is Class 3R. Is it a problem to make it Class 1? Do you plan to implement Class 1 in the future? Please discuss this in the manuscript. + +3. I could not find detailed information on spectra analysis routine. Please add details on chemometric methods being used, spectral range being used, spectra postprocessing details like background correction or smoothing. It is not enough to mention that "spectra baseline corrected on Wasatch Photonics software" (line 75 in supplementary). Please describe baseline correction method and settings of the method. + +## Reviewer #3 + +(Remarks to the Author) + +A comprehensive SERS- based study on the rapid diagnosis of severe liver injury induced by a paracetamol overdose is presented. Specifically, quantitative SERS results for the biomarker cytokeratin 18 in numerous patient samples are obtained by using a lateral flow immunoassay in conjunction with a customised handheld Raman instrument. + +This study will certainly attract the attention of readers from applied and clinical chemistry since it is well performed on a statistically relevant number of real- world samples. However, other groups have already reported similar SERS- LFIA- based clinical studies on other diseases such as COVID- 19 (many studies!), scrub typhus, as well as infections caused by respiratory bacteria, e.g., Streptococcus pneumoniae, and respiratory Virus, e.g., influenza A. This is complemented by various environmental studies using the SERS- LFIA technology, e.g. DOI: 10.1021/acsann.4c03280. Even the same technical approach using a similar handheld device in combination with a line Focus has been published recently (DOI: 10.1039/D4SD00056K). + +A major claim made by the authors is the ability to quantify the concentration of the target protein by SERS- LFIA. The qualitative diagnostic capability of SERS- LFIA (non- DILI/DILI) is clearly demonstrated by their ROC curve in Fig. 3 on p. 11. Although the data in Fig. 2d on p. 8 of their manuscript compare the performance of both SERS- LFIA and ELISA as a gold standard, this statistical analysis is not sufficient. The quantification performance of the two techniques must be separately evaluated. In other words, a statistical approach is needed to clearly compare the differences between the two techniques, for example, by Passing- Bablok regression or Bland- Altman plots (see Sensors & Actuators: B. Chemical (2024) - Fig. 5d in DOI: 10.1016/j.snb.2024.136078 and also ACS Nano (2017) - Fig. 6 a&b in DOI: 10.1021/acsnano.7b01536. ) + +Overall, this submission lacks the necessary novelty for acceptance in this journal. Submission to a journal devoted on analytical or clinical chemistry or Sensors is recommended. + +## Reviewer #4 + +(Remarks to the Author) + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors appear to have addressed my concerns and comments as well as those of the other reviewers. + +Reviewer #2 + +(Remarks to the Author) + +I fully accept all modifications regarding my comments, and I accept manuscript for publication. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +We thank the reviewers for taking the time to provide us with valuable feedback that has helped us to improve our manuscript. We have addressed all the points raised and believe the paper has been substantially strengthened as a result. We hope you find these corrections satisfactory and look favourably upon our revised manuscript. We have shown all changes as follows: + +Italic - reviewers' comment Red text - response Highlighted text - excerpts from the revised Manuscript or Supporting Information. + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +The group from Edinburgh report on the development of a POC instrument to quantify serum Cytokeratin 18 levels from patients who had been enrolled in prior clinical trials of APAP overdose presenting to the ER. The rationale for the study and methods are well described and justified. + +1. Data analysis- Two cohorts of patients in Study A and B are reported that had biobanked serum samples tested in the initial and modified Raman LFIA devices. The authors state that the sera of 50 patients with DILI (elevated ALT) and no DILI (ALT < ULN) at presentation were randomly selected for testing. Since the readout of the device is quantitative it would be of interest in the NO DILI patients to see if the quantitative level of CK-18 in those who went on to develop DILI during the study were higher compared to the non-DILI patients who never developed DILI. Based upon Ref #9 it is reasonable to speculate that subclinical DILI may be detected prior to ALT increase with this assay and it would be interest to know if the initial non-DILI cases who did develop DILI had elevated CK18 from the get go. + +We thank the reviewer for highlighting this interesting point regarding the outcomes of the patients in the trial. Of the 100 non- DILI participants across study A and B, only one had a subsequent rise in ALT (study sample ALT = 8 U/L, peak ALT = 542 U/L (ULN=50)). The participant's ALT was not raised until 30 hours after the first sample (analysed in study B) was taken. In the study sample the K18 was in the non- DILI range (SERS K18 = 43.0 ng/mL - median non- DILI SERS K18 = 55.5 ng/mL, M65 ELISA = 16.0 ng/mL - median non- DILI M65 ELISA = 10.0ng/mL). This may reflect K18 having not yet increased because the study sample was taken only 4 hours after ingestion of the paracetamol overdose. + +<--- Page Split ---> + +Given that there was only one patient, we have not added these data to the main manuscript. We are happy to add this if the Editor feels that it would be beneficial for the readership. + +2. Abstract & Intro- In abstract, authors state that there 100,000 cases of APAP overdose in UK and in intro they state 50,000 cases. Please address and clarify. + +We thank the reviewer for this comment. We have rephrased this in the Introduction as follows "Paracetamol overdose (POD) is common, with around 100,000 people presenting to emergency departments following a POD and approximately 50,000 patients requiring emergency antidote treatment to prevent drug-induced liver injury (DILI), and subsequent ALF, every year in the UK alone." + +3. Need for further studies- In the DISCUSSION, the need to define an optimal cut off for DILI vs non-DILI in a prospective cohort with capillary blood sampling and in a real time clinical context should be further emphasized. + +Thank you, this is an important point. We are performing a prospective diagnostic performance evaluation in capillary blood at the time of writing (https://www.isrctn.com/ISRCTN11484200). + +We have revised the manuscript as per your suggestion. We have added the following text to the Discussion: + +"Defining an optimal cut- off value for the SERS- LFIA using capillary blood is crucial to ensure accurate detection of DILI in a real- time clinical context. This study provides an initial reference point in serum; however, capillary blood has distinct physiological characteristics that may influence biomarker concentrations and test performance. Carefully determining the cut- off value through prospective cohort analysis would help to mitigate potential variations in analyte levels, minimise misclassification errors, and maintain the tests diagnostic sensitivity and specificity when transitioning to a more convenient and patient- friendly sampling method like capillary blood." + +4. Factors impacting CK-19 levels in health volunteers- The authors state that there was substantial intra and interindividual variability in the control and test bands of the LFIA. What factors are likely to contribute to this? Does total bilirubin levels impact performance characteristics of the test or lipid profile? + +<--- Page Split ---> + +As the reviewer points out, there was intra and inter- individual variability in the control and test band measurements of the LFIA in healthy volunteers. In the SI of the manuscript, we have hypothesised that this is due to the 'serum effect'. We have expanded on this term in the SI to describe the factors that are likely to contribute to this and how we have mitigated them. + +The following text has been added to the SI: + +"Serum proteins can bind to the gold nanoparticle surface forming a protein corona with each serum sample producing its own unique corona. It is termed unique as volunteers have slightly different serum composition due to factors which influence protein production. This includes genetics, diet, health status and environmental impacts. The formation of the protein corona will impact the antibody- antigen interaction and in most cases, it reduces the non- specific binding'. It can also impact the flow of the nanoparticles through the LFIA strip as larger particles will travel slower through the strip. As different coronas are formed, the binding will be slightly different between volunteers. This is reflected in the SERS signal with higher binding corresponding to a higher SERS signal. Fortunately, this effect has been minimised by normalising the binding of the test line to the binding of the control line using the SERS spectra." + +## Reviewer #2 (Remarks to the Author): + +Manuscript represents high quality research on rapid and accurate detection of drug- induced liver injury using Lateral Flow Immunoassay combined with handheld Raman Reader and surface- enhanced Raman scattering. Presented results on diagnostic accuracy for drug- induced liver injury with a specificity of \(94\%\) and sensitivity of \(82\%\) are well supported by satisfactory amount of clinical results for patients for this proof of concept study. Nevertheless, presented method of SERS- LFIA is not novel as state of the art was well described in Discussion section. However, the application of drug- induced liver injury using SERS- LFIA is novel and very relevant for the development of point of care diagnostics. Therefore, I suggest publication of this manuscript in Nature Communications if authors will reflect on my comments: + +1. It has been mentioned in the manuscript that novel handheld Raman reader was developed (line 394). Therefore, I would expect to see the optical schema of the novel Raman reader with detailed description of all optical elements for laser beam delivery and Raman beam delivery. Please try to add supplementary Figure with detailed optical schema and detailed description of all elements and explanation of novelty of such custom spectrometer. + +<--- Page Split ---> + +We thank the reviewer for their valuable input. We have added a figure showing the optical configuration of the Raman reader into the SI and added the following text to the manuscript to explain the optical set- up and the novelty of the custom spectrometer. + +The following has been added to Results: + +"Therefore, the novelty of this HRR lies in three elements: 1) use of a highly efficient f/1.1 transmissive design with a low- cost Complementary Metal- Oxide Semiconductor (CMOS) detector for enhanced sensitivity, 2) inclusion of a Powell lens to maximize overlap between the excitation laser and LFIA strip lines, with consequent direct imaging onto the detector, and 3) use of a Class 3R laser to effectively and repeatably perform SERS measurements on a lateral flow strip, thus reducing laser exposure risk to facilitate implementation in clinical settings. A detailed optical schema of the HRR is shown in Supplementary Figure 3." + +The following has been added to the Supplementary Information: + +"Both handheld Raman readers (HRR 3A and 4A) are comprised of a 785 nm laser excitation source, spectrometer module with CMOS detector, and sampling optics to direct and image laser light into a line on the LFA strip, which also directs and filters the Raman scattered light for detection by the spectrometer. It also integrates an LFIA cassette holder accessory to house the LFIA cassette during signal acquisition, with two functions: + +1) Locating and registering of the cassette for measurement of both control and sample lines, and +2) Enclosure of the cassette to mitigate possible exposure of the user to laser light. + +The spectrometer module includes collimation and dispersion optics to spread incoming light by wavelength over a line array CMOS sensor. The diagram (Supplementary Figure 3) shows the optical path, isolated from the overall opto-electronics diagram. Light is emitted from the laser diode and passes through a Powell lens that images the Gaussian laser beam into a line of uniform intensity, which is then directed onto the sample by a dichroic long-pass mirror and focusing lens. The resulting Raman scattered light is collected by the same focusing lens, passes through the dichroic long-pass mirror and a long-pass dichroic filter to reject scattered laser light, and is directed through the slit focus assembly, a collimator assembly, and onto the diffraction grating. Light is diffracted through the grating, into the focusing lens assembly, and is directed onto the CMOS sensor for detection." + +<--- Page Split ---> +![](images/Supplementary_Figure_3.jpg) + +
Supplementary Figure 3. Diagram of optical path through the HRR to the LFIA line.
+ +a. Please describe optical parameters of novel Raman reader: spectral range, resolution, throughput from sample to detector. + +We thank the reviewer for bringing this omission to our attention. The HRR Raman readers had the following optical parameters; f/1.1 input, 600 - 1800 cm-1 range with <15 cm-1 average FWHM resolution. The throughput from sample to detector was not determined as it was based upon detection of sufficient signal. + +This information has now been included in the Instrument section. + +b. What laser was used: multimode or single mode? Max laser power measured just from the laser and on the sample? How laser attenuation was done? What was the laser manufacturer? + +A stabilised 785 nm single mode laser diode from Innovative Photonic Solutions (IPS) was used which had a maximum power output of 100 mW. However, the laser power output was limited to <5 mW before mounting within the instrument and the laser power at the sample was 3.6 mW. The laser attenuation was achieved by limiting the drive current to the laser ensuring the amount of power the spectrometer emits does not exceed the class 3R limit (<5 mW). + +We thank the reviewer for bringing this to our attention and we have included additional information in the Instrument section. + +<--- Page Split ---> + +c. What was the length of the laser line on the sample focal plane? Was the laser line homogeneously illuminated? Typically, Powell lens provides inhomogeneous illumination on the sample, especially on the edges of the line. Was it taken into account and post corrected by the software via line intensity normalization? + +The Powell lens produced a strip of illumination approximately \(3 \text{mm} \times 1 \text{mm}\) in size, the goal was to overfill the LFA sample region of interest. We did not perform studies to determine if the laser line was homogeneously illuminated as sufficiently reproducible signals were obtained across the line compared to point based measurements. Therefore, no post-correction of line intensity normalization was carried out. In the CMOS detector we vertically bin pixels to produce a single intensity reading for each horizontal row of pixels. This ensures we not only get good overlap of the LFA but mitigate for any laser power distribution effects in the long axis of the sample. + +Our focus was ensuring that we had reproducible measurements which was achieved by controlling the position of the lines using the cassette holder, which allowed the user to precisely position the LF line in front of the laser beam. This allowed repeatability of measurements between strips as well as users. + +Additional information on the Powell lens has been added to the Instrument section. + +d. What was the sample probe (microscope objective) NA, focal length, model? + +Thank you for alerting us to this omission. We used an integrated laser and probe whereby the laser line illumination and collection image are colinear with the collection optics having an NA of f/1.1. + +The complete text added to the Instrument section to address a, b, c, and d comments is as follows: + +"For each HRR, the laser was a stabilised 785 nm laser diode from Innovative Photonic Solution (IPS) rated for 100 mW, single mode. The laser output was limited within the instrument to <5 mW. Laser attenuation was achieved by limiting the drive current to the laser, ensuring the amount of power the spectrometer emits does not exceed the class 3R limit (3.6 mW at the sample). The optical parameters of the HRR were 600 - 1800 cm-1 range with a spectral resolution of <15 cm-1. A Powell lens was used to produce a stripe illumination + +<--- Page Split ---> + +approximately \(3 \text{mm} \times 1 \text{mm}\) . We used an integrated laser and probe whereby the laser line illumination and collection image are colinear with the collection optics having an NA of \(f / 1.1\) ." + +2. It is mentioned that Raman reader is Class 3R. Is it a problem to make it Class 1? Do you plan to implement Class 1 in the future? Please discuss this in the manuscript. + +Thank you for this question as it is a valuable point to highlight. The Raman reader effectively was a Class 1 device as the laser was fully enclosed within the device and sampling accessory. However, we did not carry out the certification process to confirm this so cannot definitively make this claim in the manuscript. This will be looked at in the future but was beyond the timescales of the current study. + +To address this, the following has been added to the Results section of the manuscript: "In practice, the interface between the laser and sample are fully enclosed in HRR 3A and 4A, effectively rendering the device as Class 1, as it meets the definition 'Class 1 lasers have low radiated power or are enclosed to prevent radiation from escaping'. However, as we are without certification, we have classed them both as 3R." + +3. I could not find detailed information on spectra analysis routine. Please add details on chemometric methods being used, spectral range being used, spectra postprocessing details like background correction or smoothing. It is not enough to mention that "spectra baseline corrected on Wasatch Photonics software" (line 75 in supplementary). Please describe baseline correction method and settings of the method. + +Thank you for bringing this detail to our attention. To address this, the following text has been added to the Methods section of the manuscript: + +"To determine the signal ratio between the test line and the control line, linear regression was used using the respective intensity of the two spectra at corresponding pixels. The analysis was limited to the spectral range \(750 - 1750 \text{cm}^{- 1}\) , all spectra were baseline-corrected using air PLS in second order with lambda \(= 1 \text{e}^{4}\) . No additional pre-processing was applied." + +## Reviewer #3 (Remarks to the Author): + +A comprehensive SERS- based study on the rapid diagnosis of severe liver injury induced by a paracetamol overdose is presented. Specifically, quantitative SERS results for the biomarker + +<--- Page Split ---> + +cytokeratin 18 in numerous patient samples are obtained by using a lateral flow immunoassay in conjunction with a customised handheld Raman instrument. + +This study will certainly attract the attention of readers from applied and clinical chemistry since it is well performed on a statistically relevant number of real- world samples. However, other groups have already reported similar SERS- LFIA- based clinical studies on other diseases such as COVID- 19 (many studies!), scrub typhus, as well as infections caused by respiratory bacteria, e.g., Streptococcus pneumoniae, and respiratory Virus, e.g., influenza A. This is complemented by various environmental studies using the SERS- LFIA technology, e.g. DOI: 10.1021/acsann.4c03280. Even the same technical approach using a similar handheld device in combination with a line Focus has been published recently (DOI: 10.1039/D4SD00056K). + +With respect to the Reviewer, our approach of combining a bespoke HRR, SERS measurements and LFIA platform is novel for the detection of DILI in serum. This is the first point- of- care DILI test designed to detect and quantify K18 levels, and it could lead to improved patient stratification if implemented in hospital emergency departments. Our robust study, which was performed with 200 serum samples, with matched numbers of positive and negative samples, and under clinical trial conditions is a much larger cohort tested than in previous papers. For example, the detection of scrub typhus via SERS- LFIA (DOI: 10.1021/acs.analchem.9b02363) used only 16 positive and 24 negative patient samples, a report on COVID- 19 detection via SERS- LFIA (DOI: 10.1021/acssensors.2c01808) used 49 positive and 5 negative patient samples to evaluate the clinical effectiveness and the detection of influenza A (doi.org/10.1016/j.snb.2024.136078) used 21 positive and 10 negative patient samples to validate the clinical value. The detection of chloramphenicol residue with SERS- LFIA (DOI: 10.1021/acssann.4c03280) did test a large number of environmental samples but the number of positive and negative samples were not equal (54 negatives and 148 positives). Having a large, equal number of positive and negative samples is crucial for ensuing the accuracy and reliability of the test. An imbalance in sample size can introduce bias, potentially overestimating or underestimating a tests performance. + +Furthermore, the rapid assessment which provides a result 30 minutes after sample addition has also produced a clear pathway for how SERS- LFIA paired with a portable HRR could be implemented in hospital emergency departments. This rapid analysis and portable aspects + +<--- Page Split ---> + +are often not mentioned in SERS- LFIA publications making it difficult to understand how SERS- LFIA can be translated into POC scenarios. + +Although an early version of the HRR has been published, we have emphasised the importance in the pairing of the LFIA cassettes and HRR, and we have adapted the HRR 4A to focus on increasing the reproducibility between tests by implementing inserts designed to hold the LFIA cassette in the correct position without the need for manual moving. The reader also operates as a class 3R allowing measurements to be taken safely, another vital step when moving the HRR into POC environments. Overall, we believe that these changes have allowed the test to achieve high sensitivity and specificity when diagnosing DILI in real life samples. + +A major claim made by the authors is the ability to quantify the concentration of the target protein by SERS- LFIA. The qualitative diagnostic capability of SERS- LFIA (non- DILI/DILI) is clearly demonstrated by their ROC curve in Fig. 3 on p. 11. Although the data in Fig. 2d on p. 8 of their manuscript compare the performance of both SERS- LFIA and ELISA as a gold standard, this statistical analysis is not sufficient. The quantification performance of the two techniques must be separately evaluated. In other words, a statistical approach is needed to clearly compare the differences between the two techniques, for example, by Passing- Bablok regression or Bland- Altman plots (see Sensors & Actuators: B. Chemical (2024) - Fig. 5d in DOI: 10.1016/j.snb.2024.136078 and also ACS Nano (2017) - Fig. 6 a&b in DOI: 10.1021/acsnano.7b01536. ) + +Overall, this submission lacks the necessary novelty for acceptance in this journal. Submission to a journal devoted on analytical or clinical chemistry or Sensors is recommended. + +We thank the reviewer for their detailed feedback. + +As the reviewer has suggested, we have evaluated the quantification performance of SERS- LFIA and ELISA by Bland- Altman analysis. The plots presented for the two studies for non- DILI and DILI participants (Figure 5). The analysis was performed by Elizabeth Varghese (Clinical Trials Statistician in Edinburgh Clinical Trials Unit) who has been added to the author list. The differences between the log transformed K18 measurements using SERS and ELISA have a reasonably normal distribution, but there is evidence of an association between the differences in the log transformed K18 measurements and the mean of the log transformed + +<--- Page Split ---> + +K18 measurements using SERS and ELISA so the estimates of the relative bias and limits of agreement will depend on the K18 level and the overall summaries shown here should be interpreted cautiously. + +We would like to highlight that the clinical need, and aim of our study, is to use the point- of- care test to discriminate between DILI and non- DILI cases. The assessment of agreement between SERS and ELISA was not a principal objective for the clinical study. + +The following text has been added to the Results: + +"Agreement for the quantification of K18 in the clinical samples was compared between SERS- LFIA and K18 (M65) ELISA. Bland- Altman plots are presented for study A and B in Figure 5. In both studies, the ratio between the two methods is lower for DILI than non- DILI (study A DILI = 0.5, non- DILI = 3.8 and study B DILI = 1.0 and non- DILI = 4.7). The non- DILI group also had a greater ratio between the upper and lower limits of agreement in comparison to DILI for both study A and B. The differences between the log transformed K18 measurements using SERS and ELISA have a reasonably normal distribution, but as there is evidence of an association between the difference in the log transformed K18 measurements and the mean of the log transformed K18 measurements using SERS and ELISA, the estimates of the relative bias and limits of agreement will depend on the K18 level and the overall summaries shown here should be interpreted cautiously." + +<--- Page Split ---> +![](images/Figure_5.jpg) + +
Figure 5. Bland-Altman plots for log transformed K18 concentration using SERS-LFIA and M65 ELISA. Study A plots for A) non-DILI, B) DILI. Study B plots for C) non-DILI, D) DILI. The yellow horizontal lines represent the upper and lower limits of agreement (with 95% CI), and the blue line represents the geometric mean - bias. DILI, drug-induced liver injury; ELISA, enzyme-linked immunosorbent assay; K18, cytokeratin 18; LFIA, lateral flow immunoassay; SERS, surface enhanced Raman scattering.
+ +The following text has been added to the Discussion: + +"For both studies there is good agreement between the K18 concentration obtained from the SERS-LFIA and ELISA tests for patients with DILI, with both producing high K18 concentrations. However, in non-DILI patients, the SERS-LFIA test reported higher K18 concentrations compared to the ELISA. We hypothesise that this occurred due to differences in assay protocols.34 The ELISA involves multiple wash steps designed to remove non-specific binding, resulting in consistently low K18 concentrations in non-DILI samples. In contrast, the SERS-LFIA lacks these wash steps to enable rapid testing, which may allow non-specific proteins to remain and contribute to the overall signal. An additional factor that could contribute to the elevated K18 signal in non-DILI samples is the high density of antibodies on the nanoparticle surface used in the SERS-LFIA format. As noted by Sotnikov et al., steric + +<--- Page Split ---> + +restrictions associated with densely immobilised antibodies can enhance antigen binding in the context of protein targets such as K18.35 This may account for the greater antigen- antibody interactions observed in the SERS- LFIA compared to ELISA, particularly at lower K18 concentrations. Finally, the calibration curve was created by spiking K18 protein into healthy serum which will result in overestimate of K18 concentration at the lower range due to endogenous K18 in the healthy serum. + +## Reviewer #4 (Remarks to the Author): + +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +We are grateful to the reviewer for their addition input and careful reading of our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..62807da4805e4e0fddb9616171d26d377ea1481d --- /dev/null +++ b/peer_reviews/de8dc36092ec54cd68260763df38f2a4b9fd4251755719a2c0eda3de5a40b3eb/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,378 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[75, 97, 296, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 890, 236]]<|/det|> +# A new point-of-care diagnostic for drug-induced liver injury using surface-enhanced Raman scattering lateral flow immunoassay + +<|ref|>text<|/ref|><|det|>[[73, 249, 469, 266]]<|/det|> +Corresponding Author: Professor James Dear + +<|ref|>text<|/ref|><|det|>[[70, 299, 864, 314]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 352, 144, 365]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 378, 219, 391]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 404, 160, 417]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 430, 238, 443]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 443, 922, 482]]<|/det|> +The group from Edinburgh report on the development of a POC instrument to quantify serum Cytokeratin 18 levels from patients who had been enrolled in prior clinical trials of APAP overdose presenting to the ER. The rationale for the study and methods are well described and justified. + +<|ref|>text<|/ref|><|det|>[[72, 494, 920, 589]]<|/det|> +1. Data analysis- Two cohorts of patients in Study A and B are reported that had biobanked serum samples tested in the initial and modified Raman LFIA devices. The authors state that the sera of 50 patients with DILI (elevated ALT) and no DILI (ALT < ULN) at presentation were randomly selected for testing. Since the readout of the device is quantitative it would be of interest in the NO DILI patients to see if the quantitative level of CK-18 in those who went on to develop DILI during the study were higher compared to the non-DILI patients who never developed DILI. Based upon Ref #9 it is reasonable to speculate that subclinical DILI may be detected prior to ALT increase with this assay and it would be interest to know if the initial non-DILI cases who did develop DILI had elevated CK18 from the get go. + +<|ref|>text<|/ref|><|det|>[[70, 588, 916, 614]]<|/det|> +2. Abstract & Intro- In abstract, authors state that there 100,000 cases of APAP overdose in UK and in intro they state 50,000 cases. Please address and clarify. + +<|ref|>text<|/ref|><|det|>[[70, 625, 910, 650]]<|/det|> +3. Need for further studies- In the DISCUSSION, the need to define an optimal cut off for DILI vs non-DILI in a prospective cohort with capillary blood sampling and in a real time clinical context should be further emphasized. + +<|ref|>text<|/ref|><|det|>[[72, 650, 916, 690]]<|/det|> +4. Factors impacting CK-19 levels in health volunteers- The authors state that there was substantial intra and interindividual variability in the control and test bands of the LFIA. What factors are likely to contribute to this? Does total bilirubin levels impact performance characteristics of the test or lipid profile? + +<|ref|>text<|/ref|><|det|>[[73, 703, 161, 715]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 729, 238, 742]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 742, 912, 794]]<|/det|> +Manuscript represents high quality research on rapid and accurate detection of drug- induced liver injury using Lateral Flow Immunoassay combined with handheld Raman Reader and surface- enhanced Raman scattering. Presented results on diagnostic accuracy for drug- induced liver injury with a specificity of \(94\%\) and sensitivity of \(82\%\) are well supported by satisfactory amount of clinical results for patients for this proof of concept study. + +<|ref|>text<|/ref|><|det|>[[72, 794, 897, 832]]<|/det|> +Nevertheless, presented method of SERS- LFIA is not novel as state of the art was well described in Discussion section. However, the application of drug- induced liver injury using SERS- LFIA is novel and very relevant for the development of point of care diagnostics. + +<|ref|>text<|/ref|><|det|>[[72, 833, 916, 899]]<|/det|> +Therefore, I suggest publication of this manuscript in Nature Communications if authors will reflect on my comments: 1. It has been mentioned in the manuscript that novel handheld Raman reader was developed (line 394). Therefore, I would expect to see the optical schema of the novel Raman reader with detailed description of all optical elements for laser beam delivery and Raman beam delivery. Please try to add supplementary Figure with detailed optical schema and detailed description of all elements and explanation of novelty of such custom spectrometer. In particular: + +<|ref|>text<|/ref|><|det|>[[72, 899, 866, 925]]<|/det|> +a. Please describe optical parameters of novel Raman reader: spectral range, resolution, throughput from sample to detector. + +<|ref|>text<|/ref|><|det|>[[70, 925, 916, 938]]<|/det|> +b. What laser was used: multimode or single mode? Max laser power measured just from the laser and on the sample? How + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 504, 60]]<|/det|> +laser attenuation was done? What was the laser manufacturer? + +<|ref|>text<|/ref|><|det|>[[72, 60, 920, 100]]<|/det|> +c. What was the length of the laser line on the sample focal plane? Was the laser line homogeneously illuminated? Typically, Powell lens provides inhomogeneous illumination on the sample, especially on the edges of the line. Was it taken into account and post corrected by the software via line intensity normalization? + +<|ref|>text<|/ref|><|det|>[[72, 100, 616, 112]]<|/det|> +d. What was the sample probe (microscope objective) NA, focal length, model? + +<|ref|>text<|/ref|><|det|>[[72, 112, 920, 137]]<|/det|> +2. It is mentioned that Raman reader is Class 3R. Is it a problem to make it Class 1? Do you plan to implement Class 1 in the future? Please discuss this in the manuscript. + +<|ref|>text<|/ref|><|det|>[[72, 138, 917, 190]]<|/det|> +3. I could not find detailed information on spectra analysis routine. Please add details on chemometric methods being used, spectral range being used, spectra postprocessing details like background correction or smoothing. It is not enough to mention that "spectra baseline corrected on Wasatch Photonics software" (line 75 in supplementary). Please describe baseline correction method and settings of the method. + +<|ref|>sub_title<|/ref|><|det|>[[73, 215, 162, 228]]<|/det|> +## Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 242, 238, 255]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 255, 895, 295]]<|/det|> +A comprehensive SERS- based study on the rapid diagnosis of severe liver injury induced by a paracetamol overdose is presented. Specifically, quantitative SERS results for the biomarker cytokeratin 18 in numerous patient samples are obtained by using a lateral flow immunoassay in conjunction with a customised handheld Raman instrument. + +<|ref|>text<|/ref|><|det|>[[72, 306, 916, 399]]<|/det|> +This study will certainly attract the attention of readers from applied and clinical chemistry since it is well performed on a statistically relevant number of real- world samples. However, other groups have already reported similar SERS- LFIA- based clinical studies on other diseases such as COVID- 19 (many studies!), scrub typhus, as well as infections caused by respiratory bacteria, e.g., Streptococcus pneumoniae, and respiratory Virus, e.g., influenza A. This is complemented by various environmental studies using the SERS- LFIA technology, e.g. DOI: 10.1021/acsann.4c03280. Even the same technical approach using a similar handheld device in combination with a line Focus has been published recently (DOI: 10.1039/D4SD00056K). + +<|ref|>text<|/ref|><|det|>[[72, 411, 916, 504]]<|/det|> +A major claim made by the authors is the ability to quantify the concentration of the target protein by SERS- LFIA. The qualitative diagnostic capability of SERS- LFIA (non- DILI/DILI) is clearly demonstrated by their ROC curve in Fig. 3 on p. 11. Although the data in Fig. 2d on p. 8 of their manuscript compare the performance of both SERS- LFIA and ELISA as a gold standard, this statistical analysis is not sufficient. The quantification performance of the two techniques must be separately evaluated. In other words, a statistical approach is needed to clearly compare the differences between the two techniques, for example, by Passing- Bablok regression or Bland- Altman plots (see Sensors & Actuators: B. Chemical (2024) - Fig. 5d in DOI: 10.1016/j.snb.2024.136078 and also ACS Nano (2017) - Fig. 6 a&b in DOI: 10.1021/acsnano.7b01536. ) + +<|ref|>text<|/ref|><|det|>[[72, 515, 884, 543]]<|/det|> +Overall, this submission lacks the necessary novelty for acceptance in this journal. Submission to a journal devoted on analytical or clinical chemistry or Sensors is recommended. + +<|ref|>sub_title<|/ref|><|det|>[[73, 555, 161, 568]]<|/det|> +## Reviewer #4 + +<|ref|>text<|/ref|><|det|>[[73, 581, 237, 594]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 594, 864, 633]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[73, 646, 144, 659]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 672, 219, 684]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 697, 160, 710]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 723, 240, 736]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 736, 803, 750]]<|/det|> +The authors appear to have addressed my concerns and comments as well as those of the other reviewers. + +<|ref|>text<|/ref|><|det|>[[73, 762, 162, 775]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 789, 240, 802]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 802, 718, 816]]<|/det|> +I fully accept all modifications regarding my comments, and I accept manuscript for publication. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 796, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 910, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 882, 191]]<|/det|> +We thank the reviewers for taking the time to provide us with valuable feedback that has helped us to improve our manuscript. We have addressed all the points raised and believe the paper has been substantially strengthened as a result. We hope you find these corrections satisfactory and look favourably upon our revised manuscript. We have shown all changes as follows: + +<|ref|>text<|/ref|><|det|>[[118, 217, 788, 282]]<|/det|> +Italic - reviewers' comment Red text - response Highlighted text - excerpts from the revised Manuscript or Supporting Information. + +<|ref|>sub_title<|/ref|><|det|>[[119, 309, 333, 326]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[119, 332, 450, 349]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 354, 883, 441]]<|/det|> +The group from Edinburgh report on the development of a POC instrument to quantify serum Cytokeratin 18 levels from patients who had been enrolled in prior clinical trials of APAP overdose presenting to the ER. The rationale for the study and methods are well described and justified. + +<|ref|>text<|/ref|><|det|>[[117, 468, 884, 668]]<|/det|> +1. Data analysis- Two cohorts of patients in Study A and B are reported that had biobanked serum samples tested in the initial and modified Raman LFIA devices. The authors state that the sera of 50 patients with DILI (elevated ALT) and no DILI (ALT < ULN) at presentation were randomly selected for testing. Since the readout of the device is quantitative it would be of interest in the NO DILI patients to see if the quantitative level of CK-18 in those who went on to develop DILI during the study were higher compared to the non-DILI patients who never developed DILI. Based upon Ref #9 it is reasonable to speculate that subclinical DILI may be detected prior to ALT increase with this assay and it would be interest to know if the initial non-DILI cases who did develop DILI had elevated CK18 from the get go. + +<|ref|>text<|/ref|><|det|>[[117, 694, 883, 870]]<|/det|> +We thank the reviewer for highlighting this interesting point regarding the outcomes of the patients in the trial. Of the 100 non- DILI participants across study A and B, only one had a subsequent rise in ALT (study sample ALT = 8 U/L, peak ALT = 542 U/L (ULN=50)). The participant's ALT was not raised until 30 hours after the first sample (analysed in study B) was taken. In the study sample the K18 was in the non- DILI range (SERS K18 = 43.0 ng/mL - median non- DILI SERS K18 = 55.5 ng/mL, M65 ELISA = 16.0 ng/mL - median non- DILI M65 ELISA = 10.0ng/mL). This may reflect K18 having not yet increased because the study sample was taken only 4 hours after ingestion of the paracetamol overdose. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 879, 123]]<|/det|> +Given that there was only one patient, we have not added these data to the main manuscript. We are happy to add this if the Editor feels that it would be beneficial for the readership. + +<|ref|>text<|/ref|><|det|>[[118, 175, 881, 216]]<|/det|> +2. Abstract & Intro- In abstract, authors state that there 100,000 cases of APAP overdose in UK and in intro they state 50,000 cases. Please address and clarify. + +<|ref|>text<|/ref|><|det|>[[118, 243, 881, 350]]<|/det|> +We thank the reviewer for this comment. We have rephrased this in the Introduction as follows "Paracetamol overdose (POD) is common, with around 100,000 people presenting to emergency departments following a POD and approximately 50,000 patients requiring emergency antidote treatment to prevent drug-induced liver injury (DILI), and subsequent ALF, every year in the UK alone." + +<|ref|>text<|/ref|><|det|>[[118, 377, 881, 440]]<|/det|> +3. Need for further studies- In the DISCUSSION, the need to define an optimal cut off for DILI vs non-DILI in a prospective cohort with capillary blood sampling and in a real time clinical context should be further emphasized. + +<|ref|>text<|/ref|><|det|>[[118, 468, 880, 508]]<|/det|> +Thank you, this is an important point. We are performing a prospective diagnostic performance evaluation in capillary blood at the time of writing (https://www.isrctn.com/ISRCTN11484200). + +<|ref|>text<|/ref|><|det|>[[118, 535, 880, 575]]<|/det|> +We have revised the manuscript as per your suggestion. We have added the following text to the Discussion: + +<|ref|>text<|/ref|><|det|>[[117, 581, 881, 756]]<|/det|> +"Defining an optimal cut- off value for the SERS- LFIA using capillary blood is crucial to ensure accurate detection of DILI in a real- time clinical context. This study provides an initial reference point in serum; however, capillary blood has distinct physiological characteristics that may influence biomarker concentrations and test performance. Carefully determining the cut- off value through prospective cohort analysis would help to mitigate potential variations in analyte levels, minimise misclassification errors, and maintain the tests diagnostic sensitivity and specificity when transitioning to a more convenient and patient- friendly sampling method like capillary blood." + +<|ref|>text<|/ref|><|det|>[[118, 785, 881, 870]]<|/det|> +4. Factors impacting CK-19 levels in health volunteers- The authors state that there was substantial intra and interindividual variability in the control and test bands of the LFIA. What factors are likely to contribute to this? Does total bilirubin levels impact performance characteristics of the test or lipid profile? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 881, 169]]<|/det|> +As the reviewer points out, there was intra and inter- individual variability in the control and test band measurements of the LFIA in healthy volunteers. In the SI of the manuscript, we have hypothesised that this is due to the 'serum effect'. We have expanded on this term in the SI to describe the factors that are likely to contribute to this and how we have mitigated them. + +<|ref|>text<|/ref|><|det|>[[118, 196, 481, 213]]<|/det|> +The following text has been added to the SI: + +<|ref|>text<|/ref|><|det|>[[117, 218, 882, 463]]<|/det|> +"Serum proteins can bind to the gold nanoparticle surface forming a protein corona with each serum sample producing its own unique corona. It is termed unique as volunteers have slightly different serum composition due to factors which influence protein production. This includes genetics, diet, health status and environmental impacts. The formation of the protein corona will impact the antibody- antigen interaction and in most cases, it reduces the non- specific binding'. It can also impact the flow of the nanoparticles through the LFIA strip as larger particles will travel slower through the strip. As different coronas are formed, the binding will be slightly different between volunteers. This is reflected in the SERS signal with higher binding corresponding to a higher SERS signal. Fortunately, this effect has been minimised by normalising the binding of the test line to the binding of the control line using the SERS spectra." + +<|ref|>sub_title<|/ref|><|det|>[[119, 491, 450, 508]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 513, 884, 734]]<|/det|> +Manuscript represents high quality research on rapid and accurate detection of drug- induced liver injury using Lateral Flow Immunoassay combined with handheld Raman Reader and surface- enhanced Raman scattering. Presented results on diagnostic accuracy for drug- induced liver injury with a specificity of \(94\%\) and sensitivity of \(82\%\) are well supported by satisfactory amount of clinical results for patients for this proof of concept study. Nevertheless, presented method of SERS- LFIA is not novel as state of the art was well described in Discussion section. However, the application of drug- induced liver injury using SERS- LFIA is novel and very relevant for the development of point of care diagnostics. Therefore, I suggest publication of this manuscript in Nature Communications if authors will reflect on my comments: + +<|ref|>text<|/ref|><|det|>[[118, 748, 883, 855]]<|/det|> +1. It has been mentioned in the manuscript that novel handheld Raman reader was developed (line 394). Therefore, I would expect to see the optical schema of the novel Raman reader with detailed description of all optical elements for laser beam delivery and Raman beam delivery. Please try to add supplementary Figure with detailed optical schema and detailed description of all elements and explanation of novelty of such custom spectrometer. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 880, 145]]<|/det|> +We thank the reviewer for their valuable input. We have added a figure showing the optical configuration of the Raman reader into the SI and added the following text to the manuscript to explain the optical set- up and the novelty of the custom spectrometer. + +<|ref|>text<|/ref|><|det|>[[119, 173, 460, 190]]<|/det|> +The following has been added to Results: + +<|ref|>text<|/ref|><|det|>[[117, 195, 881, 350]]<|/det|> +"Therefore, the novelty of this HRR lies in three elements: 1) use of a highly efficient f/1.1 transmissive design with a low- cost Complementary Metal- Oxide Semiconductor (CMOS) detector for enhanced sensitivity, 2) inclusion of a Powell lens to maximize overlap between the excitation laser and LFIA strip lines, with consequent direct imaging onto the detector, and 3) use of a Class 3R laser to effectively and repeatably perform SERS measurements on a lateral flow strip, thus reducing laser exposure risk to facilitate implementation in clinical settings. A detailed optical schema of the HRR is shown in Supplementary Figure 3." + +<|ref|>text<|/ref|><|det|>[[118, 376, 652, 394]]<|/det|> +The following has been added to the Supplementary Information: + +<|ref|>text<|/ref|><|det|>[[117, 399, 881, 508]]<|/det|> +"Both handheld Raman readers (HRR 3A and 4A) are comprised of a 785 nm laser excitation source, spectrometer module with CMOS detector, and sampling optics to direct and image laser light into a line on the LFA strip, which also directs and filters the Raman scattered light for detection by the spectrometer. It also integrates an LFIA cassette holder accessory to house the LFIA cassette during signal acquisition, with two functions: + +<|ref|>text<|/ref|><|det|>[[147, 534, 880, 600]]<|/det|> +1) Locating and registering of the cassette for measurement of both control and sample lines, and +2) Enclosure of the cassette to mitigate possible exposure of the user to laser light. + +<|ref|>text<|/ref|><|det|>[[117, 624, 881, 846]]<|/det|> +The spectrometer module includes collimation and dispersion optics to spread incoming light by wavelength over a line array CMOS sensor. The diagram (Supplementary Figure 3) shows the optical path, isolated from the overall opto-electronics diagram. Light is emitted from the laser diode and passes through a Powell lens that images the Gaussian laser beam into a line of uniform intensity, which is then directed onto the sample by a dichroic long-pass mirror and focusing lens. The resulting Raman scattered light is collected by the same focusing lens, passes through the dichroic long-pass mirror and a long-pass dichroic filter to reject scattered laser light, and is directed through the slit focus assembly, a collimator assembly, and onto the diffraction grating. Light is diffracted through the grating, into the focusing lens assembly, and is directed onto the CMOS sensor for detection." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[135, 85, 744, 330]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 342, 674, 358]]<|/det|> +
Supplementary Figure 3. Diagram of optical path through the HRR to the LFIA line.
+ +<|ref|>text<|/ref|><|det|>[[118, 405, 880, 447]]<|/det|> +a. Please describe optical parameters of novel Raman reader: spectral range, resolution, throughput from sample to detector. + +<|ref|>text<|/ref|><|det|>[[118, 473, 881, 561]]<|/det|> +We thank the reviewer for bringing this omission to our attention. The HRR Raman readers had the following optical parameters; f/1.1 input, 600 - 1800 cm-1 range with <15 cm-1 average FWHM resolution. The throughput from sample to detector was not determined as it was based upon detection of sufficient signal. + +<|ref|>text<|/ref|><|det|>[[119, 587, 657, 604]]<|/det|> +This information has now been included in the Instrument section. + +<|ref|>text<|/ref|><|det|>[[118, 631, 881, 673]]<|/det|> +b. What laser was used: multimode or single mode? Max laser power measured just from the laser and on the sample? How laser attenuation was done? What was the laser manufacturer? + +<|ref|>text<|/ref|><|det|>[[117, 700, 881, 835]]<|/det|> +A stabilised 785 nm single mode laser diode from Innovative Photonic Solutions (IPS) was used which had a maximum power output of 100 mW. However, the laser power output was limited to <5 mW before mounting within the instrument and the laser power at the sample was 3.6 mW. The laser attenuation was achieved by limiting the drive current to the laser ensuring the amount of power the spectrometer emits does not exceed the class 3R limit (<5 mW). + +<|ref|>text<|/ref|><|det|>[[118, 861, 880, 902]]<|/det|> +We thank the reviewer for bringing this to our attention and we have included additional information in the Instrument section. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 105, 882, 191]]<|/det|> +c. What was the length of the laser line on the sample focal plane? Was the laser line homogeneously illuminated? Typically, Powell lens provides inhomogeneous illumination on the sample, especially on the edges of the line. Was it taken into account and post corrected by the software via line intensity normalization? + +<|ref|>text<|/ref|><|det|>[[117, 217, 882, 395]]<|/det|> +The Powell lens produced a strip of illumination approximately \(3 \text{mm} \times 1 \text{mm}\) in size, the goal was to overfill the LFA sample region of interest. We did not perform studies to determine if the laser line was homogeneously illuminated as sufficiently reproducible signals were obtained across the line compared to point based measurements. Therefore, no post-correction of line intensity normalization was carried out. In the CMOS detector we vertically bin pixels to produce a single intensity reading for each horizontal row of pixels. This ensures we not only get good overlap of the LFA but mitigate for any laser power distribution effects in the long axis of the sample. + +<|ref|>text<|/ref|><|det|>[[118, 421, 881, 508]]<|/det|> +Our focus was ensuring that we had reproducible measurements which was achieved by controlling the position of the lines using the cassette holder, which allowed the user to precisely position the LF line in front of the laser beam. This allowed repeatability of measurements between strips as well as users. + +<|ref|>text<|/ref|><|det|>[[118, 533, 802, 551]]<|/det|> +Additional information on the Powell lens has been added to the Instrument section. + +<|ref|>text<|/ref|><|det|>[[118, 580, 768, 599]]<|/det|> +d. What was the sample probe (microscope objective) NA, focal length, model? + +<|ref|>text<|/ref|><|det|>[[118, 626, 880, 690]]<|/det|> +Thank you for alerting us to this omission. We used an integrated laser and probe whereby the laser line illumination and collection image are colinear with the collection optics having an NA of f/1.1. + +<|ref|>text<|/ref|><|det|>[[118, 717, 880, 757]]<|/det|> +The complete text added to the Instrument section to address a, b, c, and d comments is as follows: + +<|ref|>text<|/ref|><|det|>[[118, 762, 881, 893]]<|/det|> +"For each HRR, the laser was a stabilised 785 nm laser diode from Innovative Photonic Solution (IPS) rated for 100 mW, single mode. The laser output was limited within the instrument to <5 mW. Laser attenuation was achieved by limiting the drive current to the laser, ensuring the amount of power the spectrometer emits does not exceed the class 3R limit (3.6 mW at the sample). The optical parameters of the HRR were 600 - 1800 cm-1 range with a spectral resolution of <15 cm-1. A Powell lens was used to produce a stripe illumination + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 82, 880, 123]]<|/det|> +approximately \(3 \text{mm} \times 1 \text{mm}\) . We used an integrated laser and probe whereby the laser line illumination and collection image are colinear with the collection optics having an NA of \(f / 1.1\) ." + +<|ref|>text<|/ref|><|det|>[[118, 151, 881, 193]]<|/det|> +2. It is mentioned that Raman reader is Class 3R. Is it a problem to make it Class 1? Do you plan to implement Class 1 in the future? Please discuss this in the manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 221, 883, 330]]<|/det|> +Thank you for this question as it is a valuable point to highlight. The Raman reader effectively was a Class 1 device as the laser was fully enclosed within the device and sampling accessory. However, we did not carry out the certification process to confirm this so cannot definitively make this claim in the manuscript. This will be looked at in the future but was beyond the timescales of the current study. + +<|ref|>text<|/ref|><|det|>[[117, 357, 881, 466]]<|/det|> +To address this, the following has been added to the Results section of the manuscript: "In practice, the interface between the laser and sample are fully enclosed in HRR 3A and 4A, effectively rendering the device as Class 1, as it meets the definition 'Class 1 lasers have low radiated power or are enclosed to prevent radiation from escaping'. However, as we are without certification, we have classed them both as 3R." + +<|ref|>text<|/ref|><|det|>[[117, 494, 882, 602]]<|/det|> +3. I could not find detailed information on spectra analysis routine. Please add details on chemometric methods being used, spectral range being used, spectra postprocessing details like background correction or smoothing. It is not enough to mention that "spectra baseline corrected on Wasatch Photonics software" (line 75 in supplementary). Please describe baseline correction method and settings of the method. + +<|ref|>text<|/ref|><|det|>[[118, 631, 880, 672]]<|/det|> +Thank you for bringing this detail to our attention. To address this, the following text has been added to the Methods section of the manuscript: + +<|ref|>text<|/ref|><|det|>[[117, 700, 881, 787]]<|/det|> +"To determine the signal ratio between the test line and the control line, linear regression was used using the respective intensity of the two spectra at corresponding pixels. The analysis was limited to the spectral range \(750 - 1750 \text{cm}^{- 1}\) , all spectra were baseline-corrected using air PLS in second order with lambda \(= 1 \text{e}^{4}\) . No additional pre-processing was applied." + +<|ref|>sub_title<|/ref|><|det|>[[118, 822, 450, 840]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 854, 881, 895]]<|/det|> +A comprehensive SERS- based study on the rapid diagnosis of severe liver injury induced by a paracetamol overdose is presented. Specifically, quantitative SERS results for the biomarker + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 83, 880, 124]]<|/det|> +cytokeratin 18 in numerous patient samples are obtained by using a lateral flow immunoassay in conjunction with a customised handheld Raman instrument. + +<|ref|>text<|/ref|><|det|>[[118, 152, 883, 352]]<|/det|> +This study will certainly attract the attention of readers from applied and clinical chemistry since it is well performed on a statistically relevant number of real- world samples. However, other groups have already reported similar SERS- LFIA- based clinical studies on other diseases such as COVID- 19 (many studies!), scrub typhus, as well as infections caused by respiratory bacteria, e.g., Streptococcus pneumoniae, and respiratory Virus, e.g., influenza A. This is complemented by various environmental studies using the SERS- LFIA technology, e.g. DOI: 10.1021/acsann.4c03280. Even the same technical approach using a similar handheld device in combination with a line Focus has been published recently (DOI: 10.1039/D4SD00056K). + +<|ref|>text<|/ref|><|det|>[[116, 388, 883, 775]]<|/det|> +With respect to the Reviewer, our approach of combining a bespoke HRR, SERS measurements and LFIA platform is novel for the detection of DILI in serum. This is the first point- of- care DILI test designed to detect and quantify K18 levels, and it could lead to improved patient stratification if implemented in hospital emergency departments. Our robust study, which was performed with 200 serum samples, with matched numbers of positive and negative samples, and under clinical trial conditions is a much larger cohort tested than in previous papers. For example, the detection of scrub typhus via SERS- LFIA (DOI: 10.1021/acs.analchem.9b02363) used only 16 positive and 24 negative patient samples, a report on COVID- 19 detection via SERS- LFIA (DOI: 10.1021/acssensors.2c01808) used 49 positive and 5 negative patient samples to evaluate the clinical effectiveness and the detection of influenza A (doi.org/10.1016/j.snb.2024.136078) used 21 positive and 10 negative patient samples to validate the clinical value. The detection of chloramphenicol residue with SERS- LFIA (DOI: 10.1021/acssann.4c03280) did test a large number of environmental samples but the number of positive and negative samples were not equal (54 negatives and 148 positives). Having a large, equal number of positive and negative samples is crucial for ensuing the accuracy and reliability of the test. An imbalance in sample size can introduce bias, potentially overestimating or underestimating a tests performance. + +<|ref|>text<|/ref|><|det|>[[118, 819, 881, 883]]<|/det|> +Furthermore, the rapid assessment which provides a result 30 minutes after sample addition has also produced a clear pathway for how SERS- LFIA paired with a portable HRR could be implemented in hospital emergency departments. This rapid analysis and portable aspects + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 880, 123]]<|/det|> +are often not mentioned in SERS- LFIA publications making it difficult to understand how SERS- LFIA can be translated into POC scenarios. + +<|ref|>text<|/ref|><|det|>[[117, 171, 882, 348]]<|/det|> +Although an early version of the HRR has been published, we have emphasised the importance in the pairing of the LFIA cassettes and HRR, and we have adapted the HRR 4A to focus on increasing the reproducibility between tests by implementing inserts designed to hold the LFIA cassette in the correct position without the need for manual moving. The reader also operates as a class 3R allowing measurements to be taken safely, another vital step when moving the HRR into POC environments. Overall, we believe that these changes have allowed the test to achieve high sensitivity and specificity when diagnosing DILI in real life samples. + +<|ref|>text<|/ref|><|det|>[[117, 385, 884, 606]]<|/det|> +A major claim made by the authors is the ability to quantify the concentration of the target protein by SERS- LFIA. The qualitative diagnostic capability of SERS- LFIA (non- DILI/DILI) is clearly demonstrated by their ROC curve in Fig. 3 on p. 11. Although the data in Fig. 2d on p. 8 of their manuscript compare the performance of both SERS- LFIA and ELISA as a gold standard, this statistical analysis is not sufficient. The quantification performance of the two techniques must be separately evaluated. In other words, a statistical approach is needed to clearly compare the differences between the two techniques, for example, by Passing- Bablok regression or Bland- Altman plots (see Sensors & Actuators: B. Chemical (2024) - Fig. 5d in DOI: 10.1016/j.snb.2024.136078 and also ACS Nano (2017) - Fig. 6 a&b in DOI: 10.1021/acsnano.7b01536. ) + +<|ref|>text<|/ref|><|det|>[[118, 635, 881, 676]]<|/det|> +Overall, this submission lacks the necessary novelty for acceptance in this journal. Submission to a journal devoted on analytical or clinical chemistry or Sensors is recommended. + +<|ref|>text<|/ref|><|det|>[[118, 714, 527, 732]]<|/det|> +We thank the reviewer for their detailed feedback. + +<|ref|>text<|/ref|><|det|>[[117, 759, 882, 912]]<|/det|> +As the reviewer has suggested, we have evaluated the quantification performance of SERS- LFIA and ELISA by Bland- Altman analysis. The plots presented for the two studies for non- DILI and DILI participants (Figure 5). The analysis was performed by Elizabeth Varghese (Clinical Trials Statistician in Edinburgh Clinical Trials Unit) who has been added to the author list. The differences between the log transformed K18 measurements using SERS and ELISA have a reasonably normal distribution, but there is evidence of an association between the differences in the log transformed K18 measurements and the mean of the log transformed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 880, 146]]<|/det|> +K18 measurements using SERS and ELISA so the estimates of the relative bias and limits of agreement will depend on the K18 level and the overall summaries shown here should be interpreted cautiously. + +<|ref|>text<|/ref|><|det|>[[118, 172, 880, 236]]<|/det|> +We would like to highlight that the clinical need, and aim of our study, is to use the point- of- care test to discriminate between DILI and non- DILI cases. The assessment of agreement between SERS and ELISA was not a principal objective for the clinical study. + +<|ref|>text<|/ref|><|det|>[[118, 263, 525, 281]]<|/det|> +The following text has been added to the Results: + +<|ref|>text<|/ref|><|det|>[[115, 285, 881, 530]]<|/det|> +"Agreement for the quantification of K18 in the clinical samples was compared between SERS- LFIA and K18 (M65) ELISA. Bland- Altman plots are presented for study A and B in Figure 5. In both studies, the ratio between the two methods is lower for DILI than non- DILI (study A DILI = 0.5, non- DILI = 3.8 and study B DILI = 1.0 and non- DILI = 4.7). The non- DILI group also had a greater ratio between the upper and lower limits of agreement in comparison to DILI for both study A and B. The differences between the log transformed K18 measurements using SERS and ELISA have a reasonably normal distribution, but as there is evidence of an association between the difference in the log transformed K18 measurements and the mean of the log transformed K18 measurements using SERS and ELISA, the estimates of the relative bias and limits of agreement will depend on the K18 level and the overall summaries shown here should be interpreted cautiously." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[131, 85, 968, 530]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 535, 883, 626]]<|/det|> +
Figure 5. Bland-Altman plots for log transformed K18 concentration using SERS-LFIA and M65 ELISA. Study A plots for A) non-DILI, B) DILI. Study B plots for C) non-DILI, D) DILI. The yellow horizontal lines represent the upper and lower limits of agreement (with 95% CI), and the blue line represents the geometric mean - bias. DILI, drug-induced liver injury; ELISA, enzyme-linked immunosorbent assay; K18, cytokeratin 18; LFIA, lateral flow immunoassay; SERS, surface enhanced Raman scattering.
+ +<|ref|>text<|/ref|><|det|>[[118, 662, 554, 680]]<|/det|> +The following text has been added to the Discussion: + +<|ref|>text<|/ref|><|det|>[[116, 685, 881, 906]]<|/det|> +"For both studies there is good agreement between the K18 concentration obtained from the SERS-LFIA and ELISA tests for patients with DILI, with both producing high K18 concentrations. However, in non-DILI patients, the SERS-LFIA test reported higher K18 concentrations compared to the ELISA. We hypothesise that this occurred due to differences in assay protocols.34 The ELISA involves multiple wash steps designed to remove non-specific binding, resulting in consistently low K18 concentrations in non-DILI samples. In contrast, the SERS-LFIA lacks these wash steps to enable rapid testing, which may allow non-specific proteins to remain and contribute to the overall signal. An additional factor that could contribute to the elevated K18 signal in non-DILI samples is the high density of antibodies on the nanoparticle surface used in the SERS-LFIA format. As noted by Sotnikov et al., steric + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 82, 882, 215]]<|/det|> +restrictions associated with densely immobilised antibodies can enhance antigen binding in the context of protein targets such as K18.35 This may account for the greater antigen- antibody interactions observed in the SERS- LFIA compared to ELISA, particularly at lower K18 concentrations. Finally, the calibration curve was created by spiking K18 protein into healthy serum which will result in overestimate of K18 concentration at the lower range due to endogenous K18 in the healthy serum. + +<|ref|>sub_title<|/ref|><|det|>[[120, 241, 451, 258]]<|/det|> +## Reviewer #4 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 263, 881, 328]]<|/det|> +I co- reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co- review manuscripts. + +<|ref|>text<|/ref|><|det|>[[115, 349, 872, 368]]<|/det|> +We are grateful to the reviewer for their addition input and careful reading of our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/images_list.json b/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..71573e8dd288d11cf6a79dc87af26f907b6b231c --- /dev/null +++ b/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,280 @@ +[ + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig. 3. (b) The open-circuit voltage versus time in the moisture wetting process by a humidifier. (c) The testing results of the working cycle period of the open-circuit voltage and short-circuit current.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S5. The water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process. It can be found that the P(MEDSAH-co-AA) polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b).", + "footnote": [], + "bbox": [ + [ + 172, + 464, + 830, + 664 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_4a.jpg", + "caption": "Fig. 4a. Maximum short-circuit current density and open-circuit voltage for energy harvesters with the MEDSAH/AA ratios of 1/2, 1/3, and 1/4, at \\(28^{\\circ}\\mathrm{C}\\) .", + "footnote": [], + "bbox": [ + [ + 285, + 101, + 707, + 330 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. S22. The phase portraits of the system, showing the oscillating and chaotic behaviors. The", + "footnote": [], + "bbox": [ + [ + 188, + 456, + 809, + 860 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.", + "footnote": [], + "bbox": [ + [ + 186, + 656, + 810, + 844 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig. 3. (b) The open-circuit voltage versus time in the moisture wetting process by a humidifier. (c) The testing results of the working cycle period of the open-circuit voltage and short-circuit current.", + "footnote": [], + "bbox": [ + [ + 168, + 95, + 830, + 295 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_2e.jpg", + "caption": "Fig. 2e. COMSOL simulation results showing the surface potential oscillation of an energy harvester versus time.", + "footnote": [], + "bbox": [ + [ + 280, + 397, + 718, + 728 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S22. The phase portraits of the system, showing the oscillating and chaotic behaviors. The above six figures are projections on different concentration coordinate systems in the four-dimensional space. The projection planes are (a) \\(\\mathrm{H^{+}}\\) and \\(\\mathrm{-SO_3}\\) ; (b) \\(\\mathrm{H^{+}}\\) and \\(\\mathrm{-SO_3N^{+}}\\) ; (c) \\(\\mathrm{H^{+}}\\) and \\(\\mathrm{H_2O}\\) ; (d) \\(\\mathrm{H_2O}\\) and \\(\\mathrm{-SO_3}\\) ; (e) \\(\\mathrm{H_2O}\\) and \\(\\mathrm{-SO_3N^{+}}\\) ; (f) \\(\\mathrm{-SO_3N^{+}}\\) and \\(\\mathrm{-SO_3}\\) .", + "footnote": [], + "bbox": [ + [ + 179, + 85, + 824, + 502 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. S10. The histogram of energy generation cycle period of a prototype energy harvester: (a) energy generation period; and (b) low electrical output periods (noises).", + "footnote": [], + "bbox": [ + [ + 176, + 366, + 816, + 590 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.", + "footnote": [], + "bbox": [ + [ + 175, + 156, + 820, + 350 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig. 4 (a) Maximum short-circuit current density and open-circuit voltage for energy harvesters with the MEDSAH/AA ratios of 1/2, 1/3, and 1/4, at \\(28^{\\circ}\\mathrm{C}\\) . (c) Maximum short-circuit current density and open-circuit voltage of energy harvesters under temperatures of 12, 28, and \\(60^{\\circ}\\mathrm{C}\\) , respectively.", + "footnote": [], + "bbox": [ + [ + 160, + 207, + 840, + 390 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. S11. The measured output current density versus time of the prototype energy harvester under various humidity levels of (a) \\(59\\%\\) RH, (b) \\(80\\%\\) RH, and (c) \\(90\\%\\) RH. (d) Average maximum current density versus relative humidity.", + "footnote": [], + "bbox": [ + [ + 170, + 91, + 830, + 540 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. S5. The water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process. It can be found that the P(MEDSAH-co-AA) polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b).", + "footnote": [], + "bbox": [ + [ + 202, + 204, + 802, + 388 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.", + "footnote": [], + "bbox": [ + [ + 197, + 523, + 797, + 705 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_3.jpg", + "caption": "Fig. 3. (d) An example of replacing MEDSAH monomer with PAA to remove the \\(\\mathrm{SO}^{3 - }\\) and \\(\\mathrm{N + }\\) groups in the polymer, which stops the autonomous oscillations to result in DC electrical outputs. (e) In another example, the AA monomer is replaced with acrylamide to remove the -COOH groups and only DC outputs are observed.", + "footnote": [], + "bbox": [ + [ + 174, + 108, + 815, + 296 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. S9. The (a) close-circuit current and (b) open-circuit voltage vs. time results of a prototype device by using a copy paper instead of the P(MEDSAH-co-AA) polymer. No visible electrical outputs are identified.", + "footnote": [], + "bbox": [ + [ + 200, + 437, + 795, + 628 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. S12. The output current vs. time plot by placing a water droplet on the device.", + "footnote": [], + "bbox": [ + [ + 315, + 204, + 672, + 432 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. S19. The measured stress-strain curves of the polymer (a) before and (b) after the hydration process. The calculated Young's modulus are 30.6 MPa and 66.8 kPa before and after hydration, respectively.", + "footnote": [], + "bbox": [ + [ + 192, + 142, + 808, + 333 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_5a.jpg", + "caption": "Fig. 5a. Comparison moisture-induced electric generators based on artificial materials in the operation period and energy density. This work has the long persistence time and high energy density among moisture-based energy harvesters, and these two parameters could be further improved by using other materials based on similar self-oscillation mechanisms.", + "footnote": [], + "bbox": [ + [ + 230, + 98, + 770, + 370 + ] + ], + "page_idx": 24 + } +] \ No newline at end of file diff --git a/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6b76da5f4aba739dc9033a3b737529cbdf81a6ae --- /dev/null +++ b/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,398 @@ + +# nature portfolio + +Peer Review File + +Moisture- induced autonomous surface potential oscillations for energy harvesting + +![](images/Figure_3.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The paper reports a novel phenomenon about the moisture- induced autonomous surface potential oscillation, and introduces its potential applications in energy harvest. The experiments were carefully planned and the results are presented systematically. However, there still are some issues needed to be addressed before the consideration for publication: + +(1) Can you present the open-circuit oscillation voltage vs. time curve of one single device? It could be helpful for mechanism understanding. + +(2) In this device, the harvested energy comes from the water attraction. In Line 124-125, you mention that "The carboxylic acid (-COOH) groups generate free protons upon the exposure to moisture (r1), which increases the polarity and attracts more moistures to accelerate the ionization process". Can you provide more evidences to prove the enhanced water attraction? Will this phenomenon increase the harvested energy? Besides, if the water attraction keeps a balance with the water evaporation eventually, will this device continue generating power? + +(3) Can you mark and explain where are the 1st pool and 2nd pool in this device? In the schematic diagram of Fig. S6, it seems the 1st pool and 2nd pool are the top and bottom surfaces, respectively. But in Fig. 2, the proton transportations happen between some nearby functional groups. How the proton migration within molecules in nanoscale induces a significant output current in macroscale? Does the current generate because the difference of water concentration between the two surfaces, or the asymmetric orientation of the P(MEDSAH-co-AA) molecules? + +(4) As we know, current generation is a process of power consumption. Can you describe the energy conversion process in this device in theory? In some devices, the energy comes from chemical reactions, and the ion flow in the device transform into electron flow by electrochemical reactions, such as the research in ACS Appl. Mater. Interfaces 2020, 12, 21, 24289-24297. Since the reactions in your study is a loop, how the ion flow within the device transforms into electron flow in the external circuit? + +Reviewer #2 (Remarks to the Author): + +This manuscript reports the copolymer- based AC energy harvester that utilizes the surface potential oscillation behavior by moisture. The moisture was diffused into P(MEDSAH- co- AA) to induce the surface potential oscillation originated in- between the two polymer branches, which results in the AC electricity generation. However, the manuscript requires further clarification on its energy generation mechanism and its electrical potential oscillation to justify their arguments. Therefore, the reviewer feel that the present manuscript is not suitable for publication in Nature Communications. Significant + +<--- Page Split ---> + +improvement of the manuscript is required. + +Please address the following comments: + +1. The design of the copolymer-based AC energy harvesting device is almost same as the previous moist-driven energy harvesters (Energy Environ. Sci. 9, 912-916 (2016)). The previous devices generate both DC forms of voltage and currents by proton or ion transfer phenomena. However, the energy harvester in this work produces the AC form of current and DC form of voltage. This shows that the current generation mechanism and the voltage generation mechanism is clearly different. However, the manuscripts lack information about the mechanism, which makes the reader ambiguous about the energy generation mechanism to understand this work. The author needs to clarify the energy generation mechanism for both voltage and current more clearly compared with previous researches. + +1. Author suggested an operation mechanism with the circulation of the protons by scheme r1-r5. However, in the macroscale, no real-time potential oscillation is expected through the given mechanism, as the overall movement of protons is in a dynamic equilibrium state. Thus the real-time proton tracking analysis should be conducted (KPFM analysis has a too broad frequency of data collection). Additionally, the mechanism of the current oscillation needs to be clarified compared to the surface potential oscillation. + +2. The kinetic simulation showed in Fig. 1d shows the concentration oscillation over time due to the proton transportation by \(\mathsf{N}+\) , -SO3-, COOH groups. However, it is hard to understand the scale of the relative intensity of proton in the y-axis. Besides, the configuration of the macromolecules and the analysis method about the computational simulation need further information to evaluate the results. Lastly, the calculated proton oscillation results are periodical, but the real current measurement lacks periodicity. All of these results need further analysis and clarification. + +3. Usage of Fig.2b-e is neither appropriate nor persuasive. The authors interpreted the KPFM data as evidence of potential oscillation. However, the KPFM measurement needs 12 minutes of data accumulation (720 seconds), which is too long to sense the 57\~97 second of the current oscillation period. + +4. Authors' interpretation of alternative current is suspicious. The author stated \(2\mu \mathrm{A} / \mathrm{cm}2\) of current was generated at 2000 seconds in Fig.3c. However, it is the summation of the current in the negative direction and positive direction. In the results, the current value of \(0.9\mu \mathrm{A} / \mathrm{cm}2\) in a positive direction and the current value of \(1.1\mu \mathrm{A} / \mathrm{cm}2\) in a negative direction was generated, which has \(\sim 1\mu \mathrm{A} / \mathrm{cm}2\) of alternating current. As a consequence, although the authors emphasized the generation of alternating current, it is hard to accept the significance of the shown performances of the energy harvester. Additionally, the rectifier should be used to utilize the generated power, which seems not to coincide with the concept of paper. Rectifying alternative current implies no evident advantages of alternating current and inducing power drop. + +<--- Page Split ---> + +5. In the experimental section, there is no description of washing the synthesized polymer. It is required to add a proper washing procedure for eliminating un-reacted reactants and inhibitors. + +6. Authors only discussed the oscillation of current, but the surface potential oscillation that should be read as an alternating voltage is not discussed. In addition, The information of an un-rectified voltage profile should be added and discussed. + +7. Fig. 6a should be edited. (white-colored words are not visible.) + +Reviewer #3 (Remarks to the Author): + +In this manuscript by Long et al., the authors report a unique phenomenon of moisture- induced electrical potential oscillations on P(MEDSAH- co- AA) polymers during the diffusion of water molecules. The new phenomenon of self- excited proton concentration oscillations is found to be used to induce the surface electrical potential oscillates continuously to result in alternating current (AC) electrical outputs. Such a result is quite different from the previously reported mechanism of direct current (DC) induced electricity outputs by moistures. An energy harvester was constructed to demonstrate the continuous energy production for more than 15000 seconds with an energy density of \(16.824 \text{mJ/cm}^2\) . The results reported in this study are interesting. However, major issues on the proposed mechanism and experimental evidence still existed, which is very important to the study. Therefore, at the current stage, this manuscript can not be accept for publication in Nature Communications. However, this manuscript can be re- considered after the author addressing these issues. + +Major issues: + +1. It is noticed that the AC outputs experiments were carried out at \(100\%\) RH in this work, so how sensitive is the P(MEDSAH-co-AA) polymer to humidity? If it could work under normal humidity, for example, \(60\%\) RH, or other lower humidity environment conditions? The electrical output performance under different RH should be provided. + +2. The author described that "a specimen has been dried at \(30\%\) RH for 24 hours before a wetting process via an ultrasonic humidifier". Does this mean that the inherent water molecules absorbed by P(MEDSAH-co-AA) polymer would weaken the performance of alternating current? Can we assume that the P(MEDSAH-co-AA) polymer placed in a normal ambient humidity without drying pretreatment does not have the phenomenon of moisture-induced electrical potential oscillations? + +3. The authors used the kinetic simulation method to clarify the electrochemical oscillation process. I suggest that more experiments need to be designed to prove it, more experimental data need to be provided to support the mechanism in this work. + +<--- Page Split ---> + +4. Compared with moisture-induced autonomous surface potential oscillations for energy harvesting, we believe that water-induced autonomous surface potential oscillations for energy harvesting are more accurate according to the description of this work. How about dropping a small amount of water to the P(MEDSAH-co-AA) polymer directly to observe the performance of electricity? + +5. I noticed that the Au electrodes and wires were soldered together with tin without encapsulation as shown in Movie S2. Is there any redox reaction at the junction when being exposed to \(100\%\) RH? + +6. Comparisons of using PAA only should be provided in the manuscript. + +7. It is noted the P(MEDSAH-co-AA) polymers were used without crosslinking. Therefore, the stability of the materials or the devices should be considered. + +<--- Page Split ---> + +## List of Changes and Response to Reviewer Comments + +## Reviewer # 1 + +## General Comment + +The paper reports a novel phenomenon about the moisture- induced autonomous surface potential oscillation and introduces its potential applications in energy harvest. The experiments were carefully planned, and the results are presented systematically. However, there still are some issues needed to be addressed before the consideration for publication: + +Response: We thank the reviewer for the positive comments. We have modified the manuscript per the referee's constructive comments and suggestions. + +Comment 1: Can you present the open- circuit oscillation voltage vs. time curve of one single device? It could be helpful for mechanism understanding. + +Response: The measured open- circuit voltage versus time plot is added in Fig. 3b and the average oscillation period is 70.3 seconds, which is closed to that of the short- circuit current result at 76.7 seconds (Fig. 3c). The open- circuit voltage and short- circuit current tests were conducted independently. + +![](images/Figure_unknown_0.jpg) + +
Fig. 3. (b) The open-circuit voltage versus time in the moisture wetting process by a humidifier. (c) The testing results of the working cycle period of the open-circuit voltage and short-circuit current.
+ +<--- Page Split ---> + +Comment 2: In this device, the harvested energy comes from the water attraction. In Line 124- 125, you mention that “The carboxylic acid (- COOH) groups generate free protons upon the exposure to moisture (r1), which increases the polarity and attracts more moistures to accelerate the ionization process”. Can you provide more evidences to prove the enhanced water attraction? Will this phenomenon increase the harvested energy? Besides, if the water attraction keeps a balance with the water evaporation eventually, will this device continue generating power? + +Response: The moisture contents versus time plots during the hydration and dehydration process for polymers of different compositions are added in Figs. S5a and S5b, respectively. It is observed that polymers with high carboxylic acid group (- COOH) can absorb more moisture at a faster speed in the hydration process and maintain higher moisture concentrations in the dehydration process. This phenomenon does increase the harvested energy as depicted in Fig. 4a. However, at the equilibrium state, there will be no moisture concentration gradient and the energy harvesting process will stop. + +![](images/Figure_4a.jpg) + +
Fig. S5. The water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process. It can be found that the P(MEDSAH-co-AA) polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b).
+ +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Fig. 4a. Maximum short-circuit current density and open-circuit voltage for energy harvesters with the MEDSAH/AA ratios of 1/2, 1/3, and 1/4, at \(28^{\circ}\mathrm{C}\) .
+ +Comment 3: Can you mark and explain where are the 1st pool and 2nd pool in this device? In the schematic diagram of Fig. S6, it seems the 1st pool and 2nd pool are the top and bottom surfaces, respectively. But in Fig. 2, the proton transportations happen between some nearby functional groups. How the proton migration within molecules in nanoscale induces a significant output current in macroscale? Does the current generate because the difference of water concentration between the two surfaces, or the asymmetric orientation of the P(MEDSAH- co- AA) molecules? + +Response: The resemblance of the biological Calcium- induced \(\mathrm{Ca^{2 + }}\) release (CICR) process to the current work is utilized to help further explain the phenomenon while the one- to- one matching may not be fully established. As such, we have moved the comparisons to Supporting Explanation 3 with an illustrating Table. Specifically, the \(\mathrm{IP}_3\) in the CICR process plays a role similar to \(\mathrm{H}_2\mathrm{O}\) to start the proton concentration oscillation process. The \(1^{\mathrm{st}}\) pool in the CICR process is in analogy to the - COOH group for the positive feedback process, and the \(2^{\mathrm{nd}}\) pool in the CICR process is in analogy to and - \(\mathrm{SO}_3\) group for the negative feedback process. The self- excited oscillation is further analyzed in Supporting Explanation 2 by establishing basic equations based on chemical reactions of r1 to r5 and the conservation of matters. Afterwards, small perturbations are added to each variable and the system dynamic equations + +<--- Page Split ---> + +are derived. The stability matrix and phase portraits (Fig. S22) of the dynamic equations are then analyzed and it is found that the system has the chaotic nature and oscillates with hidden attractors. As a result, this moisture-induced autonomous surface potential oscillation phenomenon is characterized as a chaotic system with no equilibria in favor of extending the operation period. + +Comparison between this work and \(\mathbf{Ca}^{2 + }\) oscillation + +
Ca2+ oscillationThis workSimilarity
IP3H2OStart the oscillation
Ca2+H+Oscillated signal
1st pool-COOHIn positive feedback(s)
2nd pool-SO3-In negative feedback(s)
+ +![](images/Figure_2.jpg) + +
Fig. S22. The phase portraits of the system, showing the oscillating and chaotic behaviors. The
+ +<--- Page Split ---> + +above six figures are projections on different concentration coordinate systems in the four- dimensional space. The projection planes are (a) \(\mathrm{H^{+}}\) and \(\mathrm{- SO_3}\) ; (b) \(\mathrm{H^{+}}\) and \(\mathrm{- SO_3N^{+}}\) ; (c) \(\mathrm{H^{+}}\) and \(\mathrm{H_2O}\) ; (d) \(\mathrm{H_2O}\) and \(\mathrm{- SO_3}\) ; (e) \(\mathrm{H_2O}\) and \(\mathrm{- SO_3N^{+}}\) ; (f) \(\mathrm{- SO_3N^{+}}\) and \(\mathrm{- SO_3}\) . + +Comment 4: As we know, current generation is a process of power consumption. Can you describe the energy conversion process in this device in theory? In some devices, the energy comes from chemical reactions, and the ion flow in the device transform into electron flow by electrochemical reactions, such as the research in ACS Appl. Mater. Interfaces 2020, 12, 21, 24289- 24297. Since the reactions in your study is a loop, how the ion flow within the device transforms into electron flow in the external circuit? + +Response: We have added the surface proton concentration oscillation measurements by using a pH sensor. Fig. 2b shows the measured pH vs. time plot in one cycle and Fig. 2c shows the measured voltage vs. time plot of the energy harvester in one cycle. These real- time measurement results demonstrate the proton/voltage oscillation phenomenon. This behavior is believed to come from the chemical potential change as the moisture from the environment diffuses through the polymer structure. Specifically, the chemical potential of water moisture in a high humidity environment is higher than that of absorbed moisture in the polymer. As a result, the change of Gibbs free energy in the absorbed moisture is converted to electric energy in the chemical potential- based energy harvester1 instead of galvanic corrosion and water decomposition2. + +![](images/Figure_3.jpg) + +
Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.
+ +<--- Page Split ---> + +1. Zhao, F., Liang, Y., Cheng, H., Jiang, L. & Qu, L. Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. \*Energy Environ. Sci.\* 9, 912–916 (2016). +2. Feng, J. \*et al.\* High-Performance Magnesium–Carbon Nanofiber Hygroelectric Generator Based on Interface-Mediation-Enhanced Capacitive Discharging Effect. \*ACS Appl. Mater. Interfaces\* 12, 24289–24297 (2020). + +## Reviewer: #2 + +## General Comment + +This manuscript reports the copolymer- based AC energy harvester that utilizes the surface potential oscillation behavior by moisture. The moisture was diffused into P(MEDSAH- co- AA) to induce the surface potential oscillation originated in- between the two polymer branches, which results in the AC electricity generation. However, the manuscript requires further clarification on its energy generation mechanism and its electrical potential oscillation to justify their arguments. Therefore, the reviewer feel that the present manuscript is not suitable for publication in Nature Communications. Significant improvement of the manuscript is required. + +Response: We thank the reviewer for reviewing our manuscript carefully and give us helpful and detailed comments. We have modified the manuscript per the referee's constructive comments and suggestions. + +Comment 1: The design of the copolymer- based AC energy harvesting device is almost same as the previous moist- driven energy harvesters (Energy Environ. Sci. 9, 912–916 (2016)). The previous devices generate both DC forms of voltage and currents by proton or ion transfer phenomena. However, the energy harvester in this work produces the AC form of current and DC form of voltage. This shows that the current generation mechanism and the voltage generation mechanism is clearly different. However, the manuscripts lack information about the mechanism, which makes the reader ambiguous about the energy generation mechanism to understand this work. The author needs to clarify the energy generation mechanism for both voltage and current more clearly compared with previous research. + +Response: Our polymer system is very different than the one used in the previous moist- driven + +<--- Page Split ---> + +energy harvesters. In fact, both the output voltage and current generated in this work are in AC forms. In the initial submission, we used a rectifier to convert the AC voltage output to DC voltage. In this revision, we directly measured the open- circuit AC voltage versus time, as shown in Fig. 3b and the average oscillation period is 70.3 seconds, which is close to that of the short- circuit current result at 76.7 seconds (Fig. 3c). Our moisture- induced energy harvester belongs to a chemical potential energy harvester. The mechanism starts from the chemical potential of water moisture in a high humidity environment higher than that of absorbed moisture in the P(MEDSAH- co- AA) polymer. As a result, the change of Gibbs free energy in the absorbed moisture is converted to electric energy in the chemical potential- based energy harvester instead of galvanic corrosion or water decomposition. Different from the previous research, the surface potential oscillations on the P(MEDSAH- co- AA) polymer film can induce the electrostatic potential oscillations on the top electrode, which results in AC outputs as demonstrated in COMSOL simulation results in Fig. 2e and Movie S1. The electrostatic stationary simulation is implemented here to illustrate electrostatic potential outputs induced by the oscillation of the surface charges. The simulated output voltage range is between - 0.2 to 0.4 V, which is consistent with the experimental results in Fig. 3b. + +1. Zhao, F., Liang, Y., Cheng, H., Jiang, L. & Qu, L. Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. Energy Environ. Sci. 9, 912-916 (2016). + +2. Feng, J. et al. High-Performance Magnesium-Carbon Nanofiber Hygroelectric Generator Based on Interface-Mediation-Enhanced Capacitive Discharging Effect. ACS Appl. Mater. Interfaces 12, 24289-24297 (2020). + +<--- Page Split ---> +![](images/Figure_2e.jpg) + +
Fig. 3. (b) The open-circuit voltage versus time in the moisture wetting process by a humidifier. (c) The testing results of the working cycle period of the open-circuit voltage and short-circuit current.
+ +![](images/Figure_unknown_2.jpg) + +
Fig. 2e. COMSOL simulation results showing the surface potential oscillation of an energy harvester versus time.
+ +Comment 2: Author suggested an operation mechanism with the circulation of the protons by scheme r1- r5. However, in the macroscale, no real- time potential oscillation is expected through the given mechanism, as the overall movement of protons is in a dynamic equilibrium + +<--- Page Split ---> + +state. Thus the real- time proton tracking analysis should be conducted (KPFM analysis has a too broad frequency of data collection). Additionally, the mechanism of the current oscillation needs to be clarified compared to the surface potential oscillation. + +Response: We agree with the reviewer that the KPFM result is too broad frequency of data collection and has moved it to Supplementary Materials. In order to further analyze the operation mechanisms, we have added results from the analyses of stability matrix and phase portraits for better explanations (Supporting Explanation 2) by establishing basic equations based on chemical reactions of r1 to r5 and the conservation of matters. Afterwards, small perturbations are added to each variable and the system dynamic equations are derived. The stability matrix and phase portraits (Fig. S22) of the dynamic equations are then analyzed and it is found that the system has the chaotic nature and oscillates with hidden attractors. As a result, this moisture- induced autonomous surface potential oscillation phenomenon is characterized as a chaotic system with no equilibria in favor of extending the operation period. + +3. Panahi, S., Pham, V.-T., Rajagopal, K., Boubaker, O. & Jafari, S. A New Four-Dimensional Chaotic System With No Equilibrium Point. in Recent Advances in Chaotic Systems and Synchronization 63-76 (Elsevier, 2019). doi:10.1016/b978-0-12-815838-8.00004-2. + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Fig. S22. The phase portraits of the system, showing the oscillating and chaotic behaviors. The above six figures are projections on different concentration coordinate systems in the four-dimensional space. The projection planes are (a) \(\mathrm{H^{+}}\) and \(\mathrm{-SO_3}\) ; (b) \(\mathrm{H^{+}}\) and \(\mathrm{-SO_3N^{+}}\) ; (c) \(\mathrm{H^{+}}\) and \(\mathrm{H_2O}\) ; (d) \(\mathrm{H_2O}\) and \(\mathrm{-SO_3}\) ; (e) \(\mathrm{H_2O}\) and \(\mathrm{-SO_3N^{+}}\) ; (f) \(\mathrm{-SO_3N^{+}}\) and \(\mathrm{-SO_3}\) .
+ +Comment 3: The kinetic simulation showed in Fig. 1d shows the concentration oscillation over time due to the proton transportation by \(\mathrm{N + }\) , \(\mathrm{- SO_3}\) , \(\mathrm{COOH}\) groups. However, it is hard to understand the scale of the relative intensity of proton in the y- axis. Besides, the configuration of the macromolecules and the analysis method about the computational simulation need further information to evaluate the results. Lastly, the calculated proton oscillation results are periodical, but the real current measurement lacks periodicity. All of these results need further analysis and clarification. + +Response: In order to simulate the system, we use upwind explicit differential scheme to solve the partial differential equations in the kinetic simulation (Supporting Explanations 1), and + +<--- Page Split ---> + +the results have been normalized in Fig. 1c with respect to the initial proton concentration which corresponds to the relative intensity of protons. In order to further analyze the operation mechanisms, we have added results from the analyses of stability matrix and phase portraits for better explanations (See detailed responses in Comment 2). Due to the chaotic nature of the process, kinetic simulations cannot precisely predict the experimental results. Nevertheless, main experimental results are summarized as: (1) the average current and voltage oscillation periods in experiments are at 76 and 70 seconds, respectively; and (2) statistical data show a high number of the operation period around 70 seconds, while the non- operational period (noises with low level outputs) is about 150 seconds in the added figure in Fig. S10. These provide better analyses and explanations for this work. + +![](images/Figure_2.jpg) + +
Fig. S10. The histogram of energy generation cycle period of a prototype energy harvester: (a) energy generation period; and (b) low electrical output periods (noises).
+ +Comment 4: Usage of Fig.2b- e is neither appropriate nor persuasive. The authors interpreted the KPFM data as evidence of potential oscillation. However, the KPFM measurement needs 12 minutes of data accumulation (720 seconds), which is too long to sense the 57\~97 second of the current oscillation period. + +Response: We agree with the reviewer that the KPFM result is too broad frequency of data collection and has moved it to Supplementary Materials. Furthermore, we added new results by probing the pH variation on the P(MEDSAH- co- AA) polymer surface in Fig. 2b. The pH vs. time curves has similar waveform shape and period time with voltage vs. time curves of the + +<--- Page Split ---> + +energy harvester based on the P(MEDSAH- co- AA) polymer (Fig. 2c). These real- time results help illustrating the proton concentration oscillations to induce the AC outputs. + +![](images/Figure_4.jpg) + +
Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.
+ +Comment 5: Authors' interpretation of alternative current is suspicious. The author stated 2 \(\mu \mathrm{A / cm^2}\) of current was generated at 2000 seconds in Fig.3c. However, it is the summation of the current in the negative direction and positive direction. In the results, the current value of \(0.9 \mu \mathrm{A / cm^2}\) in a positive direction and the current value of \(1.1 \mu \mathrm{A / cm^2}\) in a negative direction was generated, which has \(\sim 1 \mu \mathrm{A / cm^2}\) of alternating current. As a consequence, although the authors emphasized the generation of alternating current, it is hard to accept the significance of the shown performances of the energy harvester. Additionally, the rectifier should be used to utilize the generated power, which seems not to coincide with the concept of paper. Rectifying alternative current implies no evident advantages of alternating current and inducing power drop. + +Response: The maximum current density comment from the reviewer is correct. We have changed our expression to maximum values in the revised Figs. 4a and 4c. On the other hand, the alternating current generation from other types of energy harvesters is common such as piezoelectric and triboelectric energy harvesters. For application demonstration, many other works also use rectifiers to accumulate the AC electricity in capacitors. \(^{4,5}\) + +<--- Page Split ---> + +4. Hu Y, Zhang Y, Xu C, Lin L, Snyder RL, Wang ZL. Self-powered system with wireless data transmission. Nano Lett. 11, 2572-2577 (2011). + +5. Niu S, Wang X, Yi F, Zhou YS, Wang ZL. A universal self-charging system driven by random biomechanical energy for sustainable operation of mobile electronics. Nat. Commun. 6, 8975 (2015). + +![](images/Figure_unknown_4.jpg) + +
Fig. 4 (a) Maximum short-circuit current density and open-circuit voltage for energy harvesters with the MEDSAH/AA ratios of 1/2, 1/3, and 1/4, at \(28^{\circ}\mathrm{C}\) . (c) Maximum short-circuit current density and open-circuit voltage of energy harvesters under temperatures of 12, 28, and \(60^{\circ}\mathrm{C}\) , respectively.
+ +Comment 6: In the experimental section, there is no description of washing the synthesized polymer. It is required to add a proper washing procedure for eliminating un- reacted reactants and inhibitors. + +Response: The polymer system has an ultra- high molecular weight and contains a large amount of ionic bonds and hydrogen bonds which can serve as crosslinkers. We did not use the common liquid extraction method to wash the polymer but we did clean the polymer by rinsing it with DI water and this method is added in the revised manuscript. + +Comment 7: Authors only discussed the oscillation of current, but the surface potential oscillation that should be read as an alternating voltage is not discussed. In addition, the information of an un- rectified voltage profile should be added and discussed. + +Response: The measured open- circuit voltage versus time plot is added in Fig. 3b. Please also see other detailed responses in Comment 1. + +<--- Page Split ---> + +Comment 8: Fig. 6a should be edited. (white-colored words are not visible.) + +Response: We have addressed this problem in the revised manuscript. + +## Reviewer # 3 + +## General Comment + +In this manuscript by Long et al., the authors report a unique phenomenon of moisture- induced electrical potential oscillations on P(MEDSAH- co- AA) polymers during the diffusion of water molecules. The new phenomenon of self- excited proton concentration oscillations is found to be used to induce the surface electrical potential oscillates continuously to result in alternating current (AC) electrical outputs. Such a result is quite different from the previously reported mechanism of direct current (DC) induced electricity outputs by moistures. An energy harvester was constructed to demonstrate the continuous energy production for more than 15000 seconds with an energy density of \(16.824 \mathrm{mJ / cm^2}\) . The results reported in this study are interesting. However, major issues on the proposed mechanism and experimental evidence still existed, which is very important to the study. Therefore, at the current stage, this manuscript can not be accept for publication in Nature Communications. However, this manuscript can be re- considered after the author addressing these issues. + +Response: We thank the reviewer for reviewing our manuscript carefully and give us helpful and detailed comments. We have modified the manuscript per the referee's constructive comments and suggestions. + +Comment 1: It is noticed that the AC outputs experiments were carried out at \(100\%\) RH in this work, so how sensitive is the P(MEDSAH- co- AA) polymer to humidity? If it could work under normal humidity, for example, \(60\%\) RH, or other lower humidity environment conditions? The electrical output performance under different RH should be provided. + +Response: The electrical output performances under different RH are added as shown in Fig. S11. It is found that low humidity levels will lead to low current density outputs. + +<--- Page Split ---> +![](images/Figure_unknown_5.jpg) + +
Fig. S11. The measured output current density versus time of the prototype energy harvester under various humidity levels of (a) \(59\%\) RH, (b) \(80\%\) RH, and (c) \(90\%\) RH. (d) Average maximum current density versus relative humidity.
+ +Comment 2: The author described that "a specimen has been dried at \(30\%\) RH for 24 hours before a wetting process via an ultrasonic humidifier". Does this mean that the inherent water molecules absorbed by P(MEDSAH- co- AA) polymer would weaken the performance of alternating current? Can we assume that the P(MEDSAH- co- AA) polymer placed in a normal ambient humidity without drying pretreatment does not have the phenomenon of moisture- induced electrical potential oscillations? + +Response: The initial inherent moisture will weaken the electrical outputs as this energy harvester is based on the chemical potential changes from the moisture with a potential in the high humidity environment to a low potential when the moisture is absorbed by the polymer. + +<--- Page Split ---> + +Our real- time measurement results demonstrate the proton/voltage oscillation phenomenon. This behavior is believed to come from the chemical potential change as the moisture from the environment diffuses through the polymer structure. Specifically, the chemical potential of water moisture in a high humidity environment is higher than that of absorbed moisture in the polymer. As a result, the change of Gibbs free energy in the absorbed moisture is converted to electric energy in the chemical potential- based energy harvester. The input energy is the chemical potential change of water from high humidity environment, \(\mu_{h}\) , to low humidity polymer, \(\mu_{l}\) . In this case, \(\mu_{h}\) is a constant, as the outside concentration of moisture, \(C_{0}\) , is a constant; \(\mu_{l}\) is also a constant which can be derived from the water concentration absorbed in the polymer, \(\Delta C\) . The change of Gibbs energy: + +\[\Delta G = \mu_{h} - \mu_{l}\approx RTln(\frac{C_{0}}{C_{0} - \Delta C})\] + +Without sufficient drying pretreatment, \(\Delta C\) could be small and without a high environmental humidity, \(C_{0}\) could be small. + +1. Zhao, F., Liang, Y., Cheng, H., Jiang, L. & Qu, L. Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. Energy Environ. Sci. 9, 912-916 (2016). + +Comment 3: The authors used the kinetic simulation method to clarify the electrochemical oscillation process. I suggest that more experiments need to be designed to prove it, more experimental data need to be provided to support the mechanism in this work. + +Response: We have added more theoretical analyses to clarify the electrochemical oscillation process by using the stability matrix and phase portraits for the chaotic system (Supporting Explanation 2 and Fig. S22). We have also added more experiments to clarify and support the proposed mechanism: (1) Figs. S5a and S5b are added for measured water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process to show that the polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b); (2) Figs. 2d and 2c are added for measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle and measured voltage vs. time curve in one cycle of a fabricated energy harvester with similar waveform shape and + +<--- Page Split ---> + +period time; (3) Figs. 3d and Fig. 3e are outputs of the polymers containing only one kind of functional groups with only DC outputs; and (4) Fig. S9 is added to show that the AC outputs come from the proton oscillation instead of the electrochemical reactions at the junction of gold electrodes and copper wires. + +![](images/Figure_2.jpg) + +
Fig. S5. The water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process. It can be found that the P(MEDSAH-co-AA) polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b).
+ +![](images/Figure_3.jpg) + +
Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.
+ +<--- Page Split ---> +![](images/Figure_unknown_6.jpg) + +
Fig. 3. (d) An example of replacing MEDSAH monomer with PAA to remove the \(\mathrm{SO}^{3 - }\) and \(\mathrm{N + }\) groups in the polymer, which stops the autonomous oscillations to result in DC electrical outputs. (e) In another example, the AA monomer is replaced with acrylamide to remove the -COOH groups and only DC outputs are observed.
+ +![](images/Figure_unknown_7.jpg) + +
Fig. S9. The (a) close-circuit current and (b) open-circuit voltage vs. time results of a prototype device by using a copy paper instead of the P(MEDSAH-co-AA) polymer. No visible electrical outputs are identified.
+ +Comment 4: Compared with moisture- induced autonomous surface potential oscillations for energy harvesting, we believe that water- induced autonomous surface potential oscillations for energy harvesting are more accurate according to the description of this work. How about dropping a small amount of water to the P(MEDSAH- co- AA) polymer directly to observe the performance of electricity? + +<--- Page Split ---> + +Response: We have added experimental results by placing water droplet on the device to generate electricity and the performances are close to those of energy harvesters exposed to the condition of \(100\%\) RH moisture in Fig. S12. Since moisture under different RH also generates electricity as shown in Fig. S11, we prefer using "moisture" instead of "water" for our device. + +![](images/Figure_unknown_8.jpg) + +
Fig. S12. The output current vs. time plot by placing a water droplet on the device.
+ +Comment 5: I noticed that the Au electrodes and wires were soldered together with tin without encapsulation as shown in Movie S2. Is there any redox reaction at the junction when being exposed to \(100\%\) RH? + +Response: We added one more experiment by replacing the polymer layer with a commercial copy paper and visible electrical outputs were identified as shown in Fig. S9 to illustrate no redox reaction at the junctions. + +Comment 6: Comparisons of using PAA only should be provided in the manuscript. + +Response: The comparisons of only using PAA is provided in the manuscript in Fig. 3d as this device only generates DC electricity. + +Comment 7: It is noted the P(MEDSAH- co- AA) polymers were used without crosslinking. Therefore, the stability of the materials or the devices should be considered. + +Response: Since the polymers contain dynamic bonds – hydrogen bonds and ionic bonds, their + +<--- Page Split ---> + +mechanical properties are stable before and after the hydration processes (Fig. S19). A rinsing process in DI water is used to get rid of unreacted reactants. + +![](images/Figure_5a.jpg) + +
Fig. S19. The measured stress-strain curves of the polymer (a) before and (b) after the hydration process. The calculated Young's modulus are 30.6 MPa and 66.8 kPa before and after hydration, respectively.
+ +<--- Page Split ---> + +REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors provided some useful information and added additional experiment data and explanations to support their conclusions. But there still are questions needed to be answered properly: + +(1) The measured open-circuit voltage versus time plot is added. An open-circuit voltage of \(\sim 0.4 \mathrm{~V}\) is comparable to the previously reported results. The AC voltage and current signals are interesting but not necessary for the promotion of voltage and current output. What are the advantages of AC signals compared to DC signals? + +(2) The author still did not explain how the proton migration within molecules in nanoscale induces a significant output current in macroscale, in Comment 3. In your device, the distribution of P(MEDSAH-co-AA) polymer is isotropic. To my understanding, power generation is caused by the water concentration difference between the surface and the middle. The 1st pool is the -COOH on the surface, and the 2nd pool is the -SO3- in the middle. Please clarify this. + +Reviewer #2 (Remarks to the Author): + +I recommend the publication of revised manuscript. The authors addressed well the comments in responses. + +Reviewer #3 (Remarks to the Author): + +In this revised manuscript, the authors have made proper modification according to the reviewers' comments. I believe that this manuscript in the current form can be accepted for publication in Nature Communications. + +<--- Page Split ---> + +## List of Changes and Response to Reviewer Comments + +## Reviewer # 1 + +## General Comment + +The authors provided some useful information and added additional experiment data and explanations to support their conclusions. But there still are questions needed to be answered properly: + +Response: We thank the reviewer for positive comments. We have modified the manuscript per the referee's constructive comments. + +Comment 1: The measured open- circuit voltage versus time plot is added. An open- circuit voltage of \(\sim 0.4 \mathrm{~V}\) is comparable to the previously reported results. The AC voltage and current signals are interesting but not necessary for the promotion of voltage and current output. What are the advantages of AC signals compared to DC signals? + +Response: The reviewer is correct that AC voltage and current signals are interesting but not necessary for the promotion of voltage and current outputs. The important parameter of an energy harvester is the overall energy outputs. In this regard, we have summarized the published works in the field of moisture- induced energy harvesters in Fig. 5a. Autonomous surface potential oscillations are utilized to produce alternating current (AC) or voltage outputs and enable long persistence operation time as well as good energy density from prototype devices, while longer operation time and higher energy density devices/mechanisms should be future explored. + +<--- Page Split ---> +![PLACEHOLDER_27_0] + +
Fig. 5a. Comparison moisture-induced electric generators based on artificial materials in the operation period and energy density. This work has the long persistence time and high energy density among moisture-based energy harvesters, and these two parameters could be further improved by using other materials based on similar self-oscillation mechanisms.
+ +Comment 2: The author still did not explain how the proton migration within molecules in nanoscale induces a significant output current in macroscale, in Comment 3. In your device, the distribution of P(MEDSAH- co- AA) polymer is isotropic. To my understanding, power generation is caused by the water concentration difference between the surface and the middle. The 1st pool is the - COOH on the surface, and the 2nd pool is the - SO3- in the middle. Please clarify this. + +Response: The reviewer is correct that the distribution of P(MEDSAH- co- AA) polymer is isotropic, and the energy generation stops when the moisture concentration is fully saturated inside the polymer (no concentration gradient). In general, our energy harvester is based on the chemical potential changes. It is observed that the chemical potential of moisture in a high humidity environment is larger than that in the polymer and the Gibbs free energy change from the absorbed moisture is transferred to the electrical energy. Specifically, the chemical potential of moisture from the high humidity environment, \(\mu_{h}\) , is higher than the chemical potential of moisture in the low humidity polymer, \(\mu_{l}\) . + +<--- Page Split ---> + +The change of Gibbs energy is expressed as: + +\[\Delta G = \mu_{h} - \mu_{l}\approx RTln(\frac{C_{0}}{C_{0} - \Delta C})\] + +where \(C_0\) is the moisture concentration in the high humidity environment and \(\Delta C\) is the moisture concentration absorbed by the polymer. The \(1^{\mathrm{st}}\) pool is the - COOH and the \(2^{\mathrm{nd}}\) pool is the - SO \(_3\) in the same location of the polymer. When there is moisture concentration gradient inside the polymer, it can induce the anisotropic oscillations of the local proton concentrations to result in the general surface electrical potential oscillations and AC outputs. + +## Reviewer: #2 + +## General Comment + +I recommend the publication of revised manuscript. The authors addressed well the comments in responses. + +Response: We thank the reviewer for recommending the publication of this paper. + +## Reviewer #3 + +## General Comment + +In this revised manuscript, the authors have made proper modification according to the reviewers' comments. I believe that this manuscript in the current form can be accepted for publication in Nature Communications. + +Response: We thank the reviewer for recommending the publication of this paper. + +<--- Page Split ---> diff --git a/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..6328ba41f0eb8cf434dab1077dee94c8b6510547 --- /dev/null +++ b/peer_reviews/de99a67f72d7b15c0ae56a04d1b0f5ea4d21d0d04a3fe5147ae85be2e5cb101c/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,507 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 900, 212]]<|/det|> +Moisture- induced autonomous surface potential oscillations for energy harvesting + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 350, 106]]<|/det|> +REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 129, 393, 145]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 167, 877, 243]]<|/det|> +The paper reports a novel phenomenon about the moisture- induced autonomous surface potential oscillation, and introduces its potential applications in energy harvest. The experiments were carefully planned and the results are presented systematically. However, there still are some issues needed to be addressed before the consideration for publication: + +<|ref|>text<|/ref|><|det|>[[115, 265, 864, 302]]<|/det|> +(1) Can you present the open-circuit oscillation voltage vs. time curve of one single device? It could be helpful for mechanism understanding. + +<|ref|>text<|/ref|><|det|>[[114, 322, 875, 440]]<|/det|> +(2) In this device, the harvested energy comes from the water attraction. In Line 124-125, you mention that "The carboxylic acid (-COOH) groups generate free protons upon the exposure to moisture (r1), which increases the polarity and attracts more moistures to accelerate the ionization process". Can you provide more evidences to prove the enhanced water attraction? Will this phenomenon increase the harvested energy? Besides, if the water attraction keeps a balance with the water evaporation eventually, will this device continue generating power? + +<|ref|>text<|/ref|><|det|>[[114, 459, 880, 575]]<|/det|> +(3) Can you mark and explain where are the 1st pool and 2nd pool in this device? In the schematic diagram of Fig. S6, it seems the 1st pool and 2nd pool are the top and bottom surfaces, respectively. But in Fig. 2, the proton transportations happen between some nearby functional groups. How the proton migration within molecules in nanoscale induces a significant output current in macroscale? Does the current generate because the difference of water concentration between the two surfaces, or the asymmetric orientation of the P(MEDSAH-co-AA) molecules? + +<|ref|>text<|/ref|><|det|>[[114, 596, 882, 692]]<|/det|> +(4) As we know, current generation is a process of power consumption. Can you describe the energy conversion process in this device in theory? In some devices, the energy comes from chemical reactions, and the ion flow in the device transform into electron flow by electrochemical reactions, such as the research in ACS Appl. Mater. Interfaces 2020, 12, 21, 24289-24297. Since the reactions in your study is a loop, how the ion flow within the device transforms into electron flow in the external circuit? + +<|ref|>text<|/ref|><|det|>[[116, 752, 393, 769]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 790, 878, 907]]<|/det|> +This manuscript reports the copolymer- based AC energy harvester that utilizes the surface potential oscillation behavior by moisture. The moisture was diffused into P(MEDSAH- co- AA) to induce the surface potential oscillation originated in- between the two polymer branches, which results in the AC electricity generation. However, the manuscript requires further clarification on its energy generation mechanism and its electrical potential oscillation to justify their arguments. Therefore, the reviewer feel that the present manuscript is not suitable for publication in Nature Communications. Significant + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 437, 106]]<|/det|> +improvement of the manuscript is required. + +<|ref|>text<|/ref|><|det|>[[115, 130, 411, 146]]<|/det|> +Please address the following comments: + +<|ref|>text<|/ref|><|det|>[[114, 167, 880, 323]]<|/det|> +1. The design of the copolymer-based AC energy harvesting device is almost same as the previous moist-driven energy harvesters (Energy Environ. Sci. 9, 912-916 (2016)). The previous devices generate both DC forms of voltage and currents by proton or ion transfer phenomena. However, the energy harvester in this work produces the AC form of current and DC form of voltage. This shows that the current generation mechanism and the voltage generation mechanism is clearly different. However, the manuscripts lack information about the mechanism, which makes the reader ambiguous about the energy generation mechanism to understand this work. The author needs to clarify the energy generation mechanism for both voltage and current more clearly compared with previous researches. + +<|ref|>text<|/ref|><|det|>[[114, 362, 883, 477]]<|/det|> +1. Author suggested an operation mechanism with the circulation of the protons by scheme r1-r5. However, in the macroscale, no real-time potential oscillation is expected through the given mechanism, as the overall movement of protons is in a dynamic equilibrium state. Thus the real-time proton tracking analysis should be conducted (KPFM analysis has a too broad frequency of data collection). Additionally, the mechanism of the current oscillation needs to be clarified compared to the surface potential oscillation. + +<|ref|>text<|/ref|><|det|>[[114, 498, 864, 614]]<|/det|> +2. The kinetic simulation showed in Fig. 1d shows the concentration oscillation over time due to the proton transportation by \(\mathsf{N}+\) , -SO3-, COOH groups. However, it is hard to understand the scale of the relative intensity of proton in the y-axis. Besides, the configuration of the macromolecules and the analysis method about the computational simulation need further information to evaluate the results. Lastly, the calculated proton oscillation results are periodical, but the real current measurement lacks periodicity. All of these results need further analysis and clarification. + +<|ref|>text<|/ref|><|det|>[[114, 635, 854, 710]]<|/det|> +3. Usage of Fig.2b-e is neither appropriate nor persuasive. The authors interpreted the KPFM data as evidence of potential oscillation. However, the KPFM measurement needs 12 minutes of data accumulation (720 seconds), which is too long to sense the 57\~97 second of the current oscillation period. + +<|ref|>text<|/ref|><|det|>[[113, 732, 866, 907]]<|/det|> +4. Authors' interpretation of alternative current is suspicious. The author stated \(2\mu \mathrm{A} / \mathrm{cm}2\) of current was generated at 2000 seconds in Fig.3c. However, it is the summation of the current in the negative direction and positive direction. In the results, the current value of \(0.9\mu \mathrm{A} / \mathrm{cm}2\) in a positive direction and the current value of \(1.1\mu \mathrm{A} / \mathrm{cm}2\) in a negative direction was generated, which has \(\sim 1\mu \mathrm{A} / \mathrm{cm}2\) of alternating current. As a consequence, although the authors emphasized the generation of alternating current, it is hard to accept the significance of the shown performances of the energy harvester. Additionally, the rectifier should be used to utilize the generated power, which seems not to coincide with the concept of paper. Rectifying alternative current implies no evident advantages of alternating current and inducing power drop. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 108, 875, 146]]<|/det|> +5. In the experimental section, there is no description of washing the synthesized polymer. It is required to add a proper washing procedure for eliminating un-reacted reactants and inhibitors. + +<|ref|>text<|/ref|><|det|>[[115, 167, 866, 224]]<|/det|> +6. Authors only discussed the oscillation of current, but the surface potential oscillation that should be read as an alternating voltage is not discussed. In addition, The information of an un-rectified voltage profile should be added and discussed. + +<|ref|>text<|/ref|><|det|>[[115, 245, 592, 262]]<|/det|> +7. Fig. 6a should be edited. (white-colored words are not visible.) + +<|ref|>text<|/ref|><|det|>[[115, 323, 393, 340]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 361, 880, 575]]<|/det|> +In this manuscript by Long et al., the authors report a unique phenomenon of moisture- induced electrical potential oscillations on P(MEDSAH- co- AA) polymers during the diffusion of water molecules. The new phenomenon of self- excited proton concentration oscillations is found to be used to induce the surface electrical potential oscillates continuously to result in alternating current (AC) electrical outputs. Such a result is quite different from the previously reported mechanism of direct current (DC) induced electricity outputs by moistures. An energy harvester was constructed to demonstrate the continuous energy production for more than 15000 seconds with an energy density of \(16.824 \text{mJ/cm}^2\) . The results reported in this study are interesting. However, major issues on the proposed mechanism and experimental evidence still existed, which is very important to the study. Therefore, at the current stage, this manuscript can not be accept for publication in Nature Communications. However, this manuscript can be re- considered after the author addressing these issues. + +<|ref|>text<|/ref|><|det|>[[115, 597, 213, 612]]<|/det|> +Major issues: + +<|ref|>text<|/ref|><|det|>[[115, 616, 872, 692]]<|/det|> +1. It is noticed that the AC outputs experiments were carried out at \(100\%\) RH in this work, so how sensitive is the P(MEDSAH-co-AA) polymer to humidity? If it could work under normal humidity, for example, \(60\%\) RH, or other lower humidity environment conditions? The electrical output performance under different RH should be provided. + +<|ref|>text<|/ref|><|det|>[[115, 712, 876, 808]]<|/det|> +2. The author described that "a specimen has been dried at \(30\%\) RH for 24 hours before a wetting process via an ultrasonic humidifier". Does this mean that the inherent water molecules absorbed by P(MEDSAH-co-AA) polymer would weaken the performance of alternating current? Can we assume that the P(MEDSAH-co-AA) polymer placed in a normal ambient humidity without drying pretreatment does not have the phenomenon of moisture-induced electrical potential oscillations? + +<|ref|>text<|/ref|><|det|>[[115, 829, 855, 886]]<|/det|> +3. The authors used the kinetic simulation method to clarify the electrochemical oscillation process. I suggest that more experiments need to be designed to prove it, more experimental data need to be provided to support the mechanism in this work. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 881, 166]]<|/det|> +4. Compared with moisture-induced autonomous surface potential oscillations for energy harvesting, we believe that water-induced autonomous surface potential oscillations for energy harvesting are more accurate according to the description of this work. How about dropping a small amount of water to the P(MEDSAH-co-AA) polymer directly to observe the performance of electricity? + +<|ref|>text<|/ref|><|det|>[[113, 187, 870, 224]]<|/det|> +5. I noticed that the Au electrodes and wires were soldered together with tin without encapsulation as shown in Movie S2. Is there any redox reaction at the junction when being exposed to \(100\%\) RH? + +<|ref|>text<|/ref|><|det|>[[114, 246, 642, 263]]<|/det|> +6. Comparisons of using PAA only should be provided in the manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 285, 875, 322]]<|/det|> +7. It is noted the P(MEDSAH-co-AA) polymers were used without crosslinking. Therefore, the stability of the materials or the devices should be considered. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[230, 92, 799, 116]]<|/det|> +## List of Changes and Response to Reviewer Comments + +<|ref|>sub_title<|/ref|><|det|>[[150, 145, 253, 163]]<|/det|> +## Reviewer # 1 + +<|ref|>sub_title<|/ref|><|det|>[[150, 173, 299, 191]]<|/det|> +## General Comment + +<|ref|>text<|/ref|><|det|>[[149, 199, 849, 303]]<|/det|> +The paper reports a novel phenomenon about the moisture- induced autonomous surface potential oscillation and introduces its potential applications in energy harvest. The experiments were carefully planned, and the results are presented systematically. However, there still are some issues needed to be addressed before the consideration for publication: + +<|ref|>text<|/ref|><|det|>[[150, 320, 848, 368]]<|/det|> +Response: We thank the reviewer for the positive comments. We have modified the manuscript per the referee's constructive comments and suggestions. + +<|ref|>text<|/ref|><|det|>[[150, 402, 848, 451]]<|/det|> +Comment 1: Can you present the open- circuit oscillation voltage vs. time curve of one single device? It could be helpful for mechanism understanding. + +<|ref|>text<|/ref|><|det|>[[149, 467, 849, 571]]<|/det|> +Response: The measured open- circuit voltage versus time plot is added in Fig. 3b and the average oscillation period is 70.3 seconds, which is closed to that of the short- circuit current result at 76.7 seconds (Fig. 3c). The open- circuit voltage and short- circuit current tests were conducted independently. + +<|ref|>image<|/ref|><|det|>[[168, 583, 830, 787]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 803, 848, 876]]<|/det|> +
Fig. 3. (b) The open-circuit voltage versus time in the moisture wetting process by a humidifier. (c) The testing results of the working cycle period of the open-circuit voltage and short-circuit current.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 857, 248]]<|/det|> +Comment 2: In this device, the harvested energy comes from the water attraction. In Line 124- 125, you mention that “The carboxylic acid (- COOH) groups generate free protons upon the exposure to moisture (r1), which increases the polarity and attracts more moistures to accelerate the ionization process”. Can you provide more evidences to prove the enhanced water attraction? Will this phenomenon increase the harvested energy? Besides, if the water attraction keeps a balance with the water evaporation eventually, will this device continue generating power? + +<|ref|>text<|/ref|><|det|>[[148, 264, 850, 451]]<|/det|> +Response: The moisture contents versus time plots during the hydration and dehydration process for polymers of different compositions are added in Figs. S5a and S5b, respectively. It is observed that polymers with high carboxylic acid group (- COOH) can absorb more moisture at a faster speed in the hydration process and maintain higher moisture concentrations in the dehydration process. This phenomenon does increase the harvested energy as depicted in Fig. 4a. However, at the equilibrium state, there will be no moisture concentration gradient and the energy harvesting process will stop. + +<|ref|>image<|/ref|><|det|>[[172, 464, 830, 664]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 682, 849, 784]]<|/det|> +
Fig. S5. The water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process. It can be found that the P(MEDSAH-co-AA) polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b).
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[285, 101, 707, 330]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 348, 847, 395]]<|/det|> +
Fig. 4a. Maximum short-circuit current density and open-circuit voltage for energy harvesters with the MEDSAH/AA ratios of 1/2, 1/3, and 1/4, at \(28^{\circ}\mathrm{C}\) .
+ +<|ref|>text<|/ref|><|det|>[[149, 430, 850, 616]]<|/det|> +Comment 3: Can you mark and explain where are the 1st pool and 2nd pool in this device? In the schematic diagram of Fig. S6, it seems the 1st pool and 2nd pool are the top and bottom surfaces, respectively. But in Fig. 2, the proton transportations happen between some nearby functional groups. How the proton migration within molecules in nanoscale induces a significant output current in macroscale? Does the current generate because the difference of water concentration between the two surfaces, or the asymmetric orientation of the P(MEDSAH- co- AA) molecules? + +<|ref|>text<|/ref|><|det|>[[149, 633, 850, 904]]<|/det|> +Response: The resemblance of the biological Calcium- induced \(\mathrm{Ca^{2 + }}\) release (CICR) process to the current work is utilized to help further explain the phenomenon while the one- to- one matching may not be fully established. As such, we have moved the comparisons to Supporting Explanation 3 with an illustrating Table. Specifically, the \(\mathrm{IP}_3\) in the CICR process plays a role similar to \(\mathrm{H}_2\mathrm{O}\) to start the proton concentration oscillation process. The \(1^{\mathrm{st}}\) pool in the CICR process is in analogy to the - COOH group for the positive feedback process, and the \(2^{\mathrm{nd}}\) pool in the CICR process is in analogy to and - \(\mathrm{SO}_3\) group for the negative feedback process. The self- excited oscillation is further analyzed in Supporting Explanation 2 by establishing basic equations based on chemical reactions of r1 to r5 and the conservation of matters. Afterwards, small perturbations are added to each variable and the system dynamic equations + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 90, 849, 219]]<|/det|> +are derived. The stability matrix and phase portraits (Fig. S22) of the dynamic equations are then analyzed and it is found that the system has the chaotic nature and oscillates with hidden attractors. As a result, this moisture-induced autonomous surface potential oscillation phenomenon is characterized as a chaotic system with no equilibria in favor of extending the operation period. + +<|ref|>table<|/ref|><|det|>[[149, 277, 792, 421]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[150, 256, 557, 275]]<|/det|> +Comparison between this work and \(\mathbf{Ca}^{2 + }\) oscillation + +
Ca2+ oscillationThis workSimilarity
IP3H2OStart the oscillation
Ca2+H+Oscillated signal
1st pool-COOHIn positive feedback(s)
2nd pool-SO3-In negative feedback(s)
+ +<|ref|>image<|/ref|><|det|>[[188, 456, 809, 860]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 881, 847, 900]]<|/det|> +
Fig. S22. The phase portraits of the system, showing the oscillating and chaotic behaviors. The
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 849, 164]]<|/det|> +above six figures are projections on different concentration coordinate systems in the four- dimensional space. The projection planes are (a) \(\mathrm{H^{+}}\) and \(\mathrm{- SO_3}\) ; (b) \(\mathrm{H^{+}}\) and \(\mathrm{- SO_3N^{+}}\) ; (c) \(\mathrm{H^{+}}\) and \(\mathrm{H_2O}\) ; (d) \(\mathrm{H_2O}\) and \(\mathrm{- SO_3}\) ; (e) \(\mathrm{H_2O}\) and \(\mathrm{- SO_3N^{+}}\) ; (f) \(\mathrm{- SO_3N^{+}}\) and \(\mathrm{- SO_3}\) . + +<|ref|>text<|/ref|><|det|>[[149, 199, 850, 358]]<|/det|> +Comment 4: As we know, current generation is a process of power consumption. Can you describe the energy conversion process in this device in theory? In some devices, the energy comes from chemical reactions, and the ion flow in the device transform into electron flow by electrochemical reactions, such as the research in ACS Appl. Mater. Interfaces 2020, 12, 21, 24289- 24297. Since the reactions in your study is a loop, how the ion flow within the device transforms into electron flow in the external circuit? + +<|ref|>text<|/ref|><|det|>[[148, 375, 850, 645]]<|/det|> +Response: We have added the surface proton concentration oscillation measurements by using a pH sensor. Fig. 2b shows the measured pH vs. time plot in one cycle and Fig. 2c shows the measured voltage vs. time plot of the energy harvester in one cycle. These real- time measurement results demonstrate the proton/voltage oscillation phenomenon. This behavior is believed to come from the chemical potential change as the moisture from the environment diffuses through the polymer structure. Specifically, the chemical potential of water moisture in a high humidity environment is higher than that of absorbed moisture in the polymer. As a result, the change of Gibbs free energy in the absorbed moisture is converted to electric energy in the chemical potential- based energy harvester1 instead of galvanic corrosion and water decomposition2. + +<|ref|>image<|/ref|><|det|>[[186, 656, 810, 844]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 858, 847, 904]]<|/det|> +
Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 848, 220]]<|/det|> +1. Zhao, F., Liang, Y., Cheng, H., Jiang, L. & Qu, L. Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. \*Energy Environ. Sci.\* 9, 912–916 (2016). +2. Feng, J. \*et al.\* High-Performance Magnesium–Carbon Nanofiber Hygroelectric Generator Based on Interface-Mediation-Enhanced Capacitive Discharging Effect. \*ACS Appl. Mater. Interfaces\* 12, 24289–24297 (2020). + +<|ref|>sub_title<|/ref|><|det|>[[150, 256, 256, 273]]<|/det|> +## Reviewer: #2 + +<|ref|>sub_title<|/ref|><|det|>[[150, 284, 299, 301]]<|/det|> +## General Comment + +<|ref|>text<|/ref|><|det|>[[149, 310, 852, 499]]<|/det|> +This manuscript reports the copolymer- based AC energy harvester that utilizes the surface potential oscillation behavior by moisture. The moisture was diffused into P(MEDSAH- co- AA) to induce the surface potential oscillation originated in- between the two polymer branches, which results in the AC electricity generation. However, the manuscript requires further clarification on its energy generation mechanism and its electrical potential oscillation to justify their arguments. Therefore, the reviewer feel that the present manuscript is not suitable for publication in Nature Communications. Significant improvement of the manuscript is required. + +<|ref|>text<|/ref|><|det|>[[150, 514, 848, 590]]<|/det|> +Response: We thank the reviewer for reviewing our manuscript carefully and give us helpful and detailed comments. We have modified the manuscript per the referee's constructive comments and suggestions. + +<|ref|>text<|/ref|><|det|>[[149, 624, 850, 867]]<|/det|> +Comment 1: The design of the copolymer- based AC energy harvesting device is almost same as the previous moist- driven energy harvesters (Energy Environ. Sci. 9, 912–916 (2016)). The previous devices generate both DC forms of voltage and currents by proton or ion transfer phenomena. However, the energy harvester in this work produces the AC form of current and DC form of voltage. This shows that the current generation mechanism and the voltage generation mechanism is clearly different. However, the manuscripts lack information about the mechanism, which makes the reader ambiguous about the energy generation mechanism to understand this work. The author needs to clarify the energy generation mechanism for both voltage and current more clearly compared with previous research. + +<|ref|>text<|/ref|><|det|>[[149, 885, 846, 904]]<|/det|> +Response: Our polymer system is very different than the one used in the previous moist- driven + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 87, 850, 528]]<|/det|> +energy harvesters. In fact, both the output voltage and current generated in this work are in AC forms. In the initial submission, we used a rectifier to convert the AC voltage output to DC voltage. In this revision, we directly measured the open- circuit AC voltage versus time, as shown in Fig. 3b and the average oscillation period is 70.3 seconds, which is close to that of the short- circuit current result at 76.7 seconds (Fig. 3c). Our moisture- induced energy harvester belongs to a chemical potential energy harvester. The mechanism starts from the chemical potential of water moisture in a high humidity environment higher than that of absorbed moisture in the P(MEDSAH- co- AA) polymer. As a result, the change of Gibbs free energy in the absorbed moisture is converted to electric energy in the chemical potential- based energy harvester instead of galvanic corrosion or water decomposition. Different from the previous research, the surface potential oscillations on the P(MEDSAH- co- AA) polymer film can induce the electrostatic potential oscillations on the top electrode, which results in AC outputs as demonstrated in COMSOL simulation results in Fig. 2e and Movie S1. The electrostatic stationary simulation is implemented here to illustrate electrostatic potential outputs induced by the oscillation of the surface charges. The simulated output voltage range is between - 0.2 to 0.4 V, which is consistent with the experimental results in Fig. 3b. + +<|ref|>text<|/ref|><|det|>[[149, 560, 847, 610]]<|/det|> +1. Zhao, F., Liang, Y., Cheng, H., Jiang, L. & Qu, L. Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. Energy Environ. Sci. 9, 912-916 (2016). + +<|ref|>text<|/ref|><|det|>[[149, 617, 845, 690]]<|/det|> +2. Feng, J. et al. High-Performance Magnesium-Carbon Nanofiber Hygroelectric Generator Based on Interface-Mediation-Enhanced Capacitive Discharging Effect. ACS Appl. Mater. Interfaces 12, 24289-24297 (2020). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[168, 95, 830, 295]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 311, 847, 384]]<|/det|> +
Fig. 3. (b) The open-circuit voltage versus time in the moisture wetting process by a humidifier. (c) The testing results of the working cycle period of the open-circuit voltage and short-circuit current.
+ +<|ref|>image<|/ref|><|det|>[[280, 397, 718, 728]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 746, 847, 792]]<|/det|> +
Fig. 2e. COMSOL simulation results showing the surface potential oscillation of an energy harvester versus time.
+ +<|ref|>text<|/ref|><|det|>[[149, 828, 848, 904]]<|/det|> +Comment 2: Author suggested an operation mechanism with the circulation of the protons by scheme r1- r5. However, in the macroscale, no real- time potential oscillation is expected through the given mechanism, as the overall movement of protons is in a dynamic equilibrium + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 848, 163]]<|/det|> +state. Thus the real- time proton tracking analysis should be conducted (KPFM analysis has a too broad frequency of data collection). Additionally, the mechanism of the current oscillation needs to be clarified compared to the surface potential oscillation. + +<|ref|>text<|/ref|><|det|>[[148, 181, 850, 452]]<|/det|> +Response: We agree with the reviewer that the KPFM result is too broad frequency of data collection and has moved it to Supplementary Materials. In order to further analyze the operation mechanisms, we have added results from the analyses of stability matrix and phase portraits for better explanations (Supporting Explanation 2) by establishing basic equations based on chemical reactions of r1 to r5 and the conservation of matters. Afterwards, small perturbations are added to each variable and the system dynamic equations are derived. The stability matrix and phase portraits (Fig. S22) of the dynamic equations are then analyzed and it is found that the system has the chaotic nature and oscillates with hidden attractors. As a result, this moisture- induced autonomous surface potential oscillation phenomenon is characterized as a chaotic system with no equilibria in favor of extending the operation period. + +<|ref|>text<|/ref|><|det|>[[150, 486, 848, 561]]<|/det|> +3. Panahi, S., Pham, V.-T., Rajagopal, K., Boubaker, O. & Jafari, S. A New Four-Dimensional Chaotic System With No Equilibrium Point. in Recent Advances in Chaotic Systems and Synchronization 63-76 (Elsevier, 2019). doi:10.1016/b978-0-12-815838-8.00004-2. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[179, 85, 824, 502]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 515, 850, 618]]<|/det|> +
Fig. S22. The phase portraits of the system, showing the oscillating and chaotic behaviors. The above six figures are projections on different concentration coordinate systems in the four-dimensional space. The projection planes are (a) \(\mathrm{H^{+}}\) and \(\mathrm{-SO_3}\) ; (b) \(\mathrm{H^{+}}\) and \(\mathrm{-SO_3N^{+}}\) ; (c) \(\mathrm{H^{+}}\) and \(\mathrm{H_2O}\) ; (d) \(\mathrm{H_2O}\) and \(\mathrm{-SO_3}\) ; (e) \(\mathrm{H_2O}\) and \(\mathrm{-SO_3N^{+}}\) ; (f) \(\mathrm{-SO_3N^{+}}\) and \(\mathrm{-SO_3}\) .
+ +<|ref|>text<|/ref|><|det|>[[148, 652, 850, 839]]<|/det|> +Comment 3: The kinetic simulation showed in Fig. 1d shows the concentration oscillation over time due to the proton transportation by \(\mathrm{N + }\) , \(\mathrm{- SO_3}\) , \(\mathrm{COOH}\) groups. However, it is hard to understand the scale of the relative intensity of proton in the y- axis. Besides, the configuration of the macromolecules and the analysis method about the computational simulation need further information to evaluate the results. Lastly, the calculated proton oscillation results are periodical, but the real current measurement lacks periodicity. All of these results need further analysis and clarification. + +<|ref|>text<|/ref|><|det|>[[150, 857, 848, 904]]<|/det|> +Response: In order to simulate the system, we use upwind explicit differential scheme to solve the partial differential equations in the kinetic simulation (Supporting Explanations 1), and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 88, 850, 358]]<|/det|> +the results have been normalized in Fig. 1c with respect to the initial proton concentration which corresponds to the relative intensity of protons. In order to further analyze the operation mechanisms, we have added results from the analyses of stability matrix and phase portraits for better explanations (See detailed responses in Comment 2). Due to the chaotic nature of the process, kinetic simulations cannot precisely predict the experimental results. Nevertheless, main experimental results are summarized as: (1) the average current and voltage oscillation periods in experiments are at 76 and 70 seconds, respectively; and (2) statistical data show a high number of the operation period around 70 seconds, while the non- operational period (noises with low level outputs) is about 150 seconds in the added figure in Fig. S10. These provide better analyses and explanations for this work. + +<|ref|>image<|/ref|><|det|>[[176, 366, 816, 590]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 608, 848, 655]]<|/det|> +
Fig. S10. The histogram of energy generation cycle period of a prototype energy harvester: (a) energy generation period; and (b) low electrical output periods (noises).
+ +<|ref|>text<|/ref|><|det|>[[149, 690, 849, 792]]<|/det|> +Comment 4: Usage of Fig.2b- e is neither appropriate nor persuasive. The authors interpreted the KPFM data as evidence of potential oscillation. However, the KPFM measurement needs 12 minutes of data accumulation (720 seconds), which is too long to sense the 57\~97 second of the current oscillation period. + +<|ref|>text<|/ref|><|det|>[[149, 810, 849, 914]]<|/det|> +Response: We agree with the reviewer that the KPFM result is too broad frequency of data collection and has moved it to Supplementary Materials. Furthermore, we added new results by probing the pH variation on the P(MEDSAH- co- AA) polymer surface in Fig. 2b. The pH vs. time curves has similar waveform shape and period time with voltage vs. time curves of the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 847, 135]]<|/det|> +energy harvester based on the P(MEDSAH- co- AA) polymer (Fig. 2c). These real- time results help illustrating the proton concentration oscillations to induce the AC outputs. + +<|ref|>image<|/ref|><|det|>[[175, 156, 820, 350]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 367, 847, 413]]<|/det|> +
Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.
+ +<|ref|>text<|/ref|><|det|>[[148, 448, 850, 719]]<|/det|> +Comment 5: Authors' interpretation of alternative current is suspicious. The author stated 2 \(\mu \mathrm{A / cm^2}\) of current was generated at 2000 seconds in Fig.3c. However, it is the summation of the current in the negative direction and positive direction. In the results, the current value of \(0.9 \mu \mathrm{A / cm^2}\) in a positive direction and the current value of \(1.1 \mu \mathrm{A / cm^2}\) in a negative direction was generated, which has \(\sim 1 \mu \mathrm{A / cm^2}\) of alternating current. As a consequence, although the authors emphasized the generation of alternating current, it is hard to accept the significance of the shown performances of the energy harvester. Additionally, the rectifier should be used to utilize the generated power, which seems not to coincide with the concept of paper. Rectifying alternative current implies no evident advantages of alternating current and inducing power drop. + +<|ref|>text<|/ref|><|det|>[[149, 735, 850, 866]]<|/det|> +Response: The maximum current density comment from the reviewer is correct. We have changed our expression to maximum values in the revised Figs. 4a and 4c. On the other hand, the alternating current generation from other types of energy harvesters is common such as piezoelectric and triboelectric energy harvesters. For application demonstration, many other works also use rectifiers to accumulate the AC electricity in capacitors. \(^{4,5}\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 89, 849, 135]]<|/det|> +4. Hu Y, Zhang Y, Xu C, Lin L, Snyder RL, Wang ZL. Self-powered system with wireless data transmission. Nano Lett. 11, 2572-2577 (2011). + +<|ref|>text<|/ref|><|det|>[[148, 145, 850, 191]]<|/det|> +5. Niu S, Wang X, Yi F, Zhou YS, Wang ZL. A universal self-charging system driven by random biomechanical energy for sustainable operation of mobile electronics. Nat. Commun. 6, 8975 (2015). + +<|ref|>image<|/ref|><|det|>[[160, 207, 840, 390]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 404, 849, 506]]<|/det|> +
Fig. 4 (a) Maximum short-circuit current density and open-circuit voltage for energy harvesters with the MEDSAH/AA ratios of 1/2, 1/3, and 1/4, at \(28^{\circ}\mathrm{C}\) . (c) Maximum short-circuit current density and open-circuit voltage of energy harvesters under temperatures of 12, 28, and \(60^{\circ}\mathrm{C}\) , respectively.
+ +<|ref|>text<|/ref|><|det|>[[148, 542, 849, 616]]<|/det|> +Comment 6: In the experimental section, there is no description of washing the synthesized polymer. It is required to add a proper washing procedure for eliminating un- reacted reactants and inhibitors. + +<|ref|>text<|/ref|><|det|>[[148, 635, 849, 737]]<|/det|> +Response: The polymer system has an ultra- high molecular weight and contains a large amount of ionic bonds and hydrogen bonds which can serve as crosslinkers. We did not use the common liquid extraction method to wash the polymer but we did clean the polymer by rinsing it with DI water and this method is added in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[149, 773, 849, 847]]<|/det|> +Comment 7: Authors only discussed the oscillation of current, but the surface potential oscillation that should be read as an alternating voltage is not discussed. In addition, the information of an un- rectified voltage profile should be added and discussed. + +<|ref|>text<|/ref|><|det|>[[149, 866, 847, 912]]<|/det|> +Response: The measured open- circuit voltage versus time plot is added in Fig. 3b. Please also see other detailed responses in Comment 1. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 90, 720, 108]]<|/det|> +Comment 8: Fig. 6a should be edited. (white-colored words are not visible.) + +<|ref|>text<|/ref|><|det|>[[150, 127, 669, 145]]<|/det|> +Response: We have addressed this problem in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[150, 183, 255, 200]]<|/det|> +## Reviewer # 3 + +<|ref|>sub_title<|/ref|><|det|>[[150, 210, 300, 227]]<|/det|> +## General Comment + +<|ref|>text<|/ref|><|det|>[[148, 237, 850, 562]]<|/det|> +In this manuscript by Long et al., the authors report a unique phenomenon of moisture- induced electrical potential oscillations on P(MEDSAH- co- AA) polymers during the diffusion of water molecules. The new phenomenon of self- excited proton concentration oscillations is found to be used to induce the surface electrical potential oscillates continuously to result in alternating current (AC) electrical outputs. Such a result is quite different from the previously reported mechanism of direct current (DC) induced electricity outputs by moistures. An energy harvester was constructed to demonstrate the continuous energy production for more than 15000 seconds with an energy density of \(16.824 \mathrm{mJ / cm^2}\) . The results reported in this study are interesting. However, major issues on the proposed mechanism and experimental evidence still existed, which is very important to the study. Therefore, at the current stage, this manuscript can not be accept for publication in Nature Communications. However, this manuscript can be re- considered after the author addressing these issues. + +<|ref|>text<|/ref|><|det|>[[150, 579, 848, 653]]<|/det|> +Response: We thank the reviewer for reviewing our manuscript carefully and give us helpful and detailed comments. We have modified the manuscript per the referee's constructive comments and suggestions. + +<|ref|>text<|/ref|><|det|>[[150, 662, 848, 764]]<|/det|> +Comment 1: It is noticed that the AC outputs experiments were carried out at \(100\%\) RH in this work, so how sensitive is the P(MEDSAH- co- AA) polymer to humidity? If it could work under normal humidity, for example, \(60\%\) RH, or other lower humidity environment conditions? The electrical output performance under different RH should be provided. + +<|ref|>text<|/ref|><|det|>[[150, 782, 847, 829]]<|/det|> +Response: The electrical output performances under different RH are added as shown in Fig. S11. It is found that low humidity levels will lead to low current density outputs. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[170, 91, 830, 540]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 552, 848, 627]]<|/det|> +
Fig. S11. The measured output current density versus time of the prototype energy harvester under various humidity levels of (a) \(59\%\) RH, (b) \(80\%\) RH, and (c) \(90\%\) RH. (d) Average maximum current density versus relative humidity.
+ +<|ref|>text<|/ref|><|det|>[[148, 662, 849, 820]]<|/det|> +Comment 2: The author described that "a specimen has been dried at \(30\%\) RH for 24 hours before a wetting process via an ultrasonic humidifier". Does this mean that the inherent water molecules absorbed by P(MEDSAH- co- AA) polymer would weaken the performance of alternating current? Can we assume that the P(MEDSAH- co- AA) polymer placed in a normal ambient humidity without drying pretreatment does not have the phenomenon of moisture- induced electrical potential oscillations? + +<|ref|>text<|/ref|><|det|>[[149, 838, 848, 914]]<|/det|> +Response: The initial inherent moisture will weaken the electrical outputs as this energy harvester is based on the chemical potential changes from the moisture with a potential in the high humidity environment to a low potential when the moisture is absorbed by the polymer. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 88, 850, 358]]<|/det|> +Our real- time measurement results demonstrate the proton/voltage oscillation phenomenon. This behavior is believed to come from the chemical potential change as the moisture from the environment diffuses through the polymer structure. Specifically, the chemical potential of water moisture in a high humidity environment is higher than that of absorbed moisture in the polymer. As a result, the change of Gibbs free energy in the absorbed moisture is converted to electric energy in the chemical potential- based energy harvester. The input energy is the chemical potential change of water from high humidity environment, \(\mu_{h}\) , to low humidity polymer, \(\mu_{l}\) . In this case, \(\mu_{h}\) is a constant, as the outside concentration of moisture, \(C_{0}\) , is a constant; \(\mu_{l}\) is also a constant which can be derived from the water concentration absorbed in the polymer, \(\Delta C\) . The change of Gibbs energy: + +<|ref|>equation<|/ref|><|det|>[[371, 363, 625, 399]]<|/det|> +\[\Delta G = \mu_{h} - \mu_{l}\approx RTln(\frac{C_{0}}{C_{0} - \Delta C})\] + +<|ref|>text<|/ref|><|det|>[[149, 403, 847, 451]]<|/det|> +Without sufficient drying pretreatment, \(\Delta C\) could be small and without a high environmental humidity, \(C_{0}\) could be small. + +<|ref|>text<|/ref|><|det|>[[150, 486, 847, 534]]<|/det|> +1. Zhao, F., Liang, Y., Cheng, H., Jiang, L. & Qu, L. Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. Energy Environ. Sci. 9, 912-916 (2016). + +<|ref|>text<|/ref|><|det|>[[149, 569, 848, 645]]<|/det|> +Comment 3: The authors used the kinetic simulation method to clarify the electrochemical oscillation process. I suggest that more experiments need to be designed to prove it, more experimental data need to be provided to support the mechanism in this work. + +<|ref|>text<|/ref|><|det|>[[148, 660, 850, 904]]<|/det|> +Response: We have added more theoretical analyses to clarify the electrochemical oscillation process by using the stability matrix and phase portraits for the chaotic system (Supporting Explanation 2 and Fig. S22). We have also added more experiments to clarify and support the proposed mechanism: (1) Figs. S5a and S5b are added for measured water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process to show that the polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b); (2) Figs. 2d and 2c are added for measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle and measured voltage vs. time curve in one cycle of a fabricated energy harvester with similar waveform shape and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 88, 850, 191]]<|/det|> +period time; (3) Figs. 3d and Fig. 3e are outputs of the polymers containing only one kind of functional groups with only DC outputs; and (4) Fig. S9 is added to show that the AC outputs come from the proton oscillation instead of the electrochemical reactions at the junction of gold electrodes and copper wires. + +<|ref|>image<|/ref|><|det|>[[202, 204, 802, 388]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 404, 850, 507]]<|/det|> +
Fig. S5. The water content of polymers with different compositions during: (a) the hydration and (b) the dehydration process. It can be found that the P(MEDSAH-co-AA) polymer containing more -COOH can absorb more moisture at a faster speed in (a) and maintain higher moisture concentrations in (b).
+ +<|ref|>image<|/ref|><|det|>[[197, 523, 797, 705]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 718, 848, 767]]<|/det|> +
Fig. 2 (b) The measured pH vs. time plot for the P(MEDSAH-co-AA) polymer surface in one cycle. (c) Measured voltage vs. time curve in one cycle.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[174, 108, 815, 296]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 310, 848, 413]]<|/det|> +
Fig. 3. (d) An example of replacing MEDSAH monomer with PAA to remove the \(\mathrm{SO}^{3 - }\) and \(\mathrm{N + }\) groups in the polymer, which stops the autonomous oscillations to result in DC electrical outputs. (e) In another example, the AA monomer is replaced with acrylamide to remove the -COOH groups and only DC outputs are observed.
+ +<|ref|>image<|/ref|><|det|>[[200, 437, 795, 628]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 643, 848, 719]]<|/det|> +
Fig. S9. The (a) close-circuit current and (b) open-circuit voltage vs. time results of a prototype device by using a copy paper instead of the P(MEDSAH-co-AA) polymer. No visible electrical outputs are identified.
+ +<|ref|>text<|/ref|><|det|>[[148, 754, 850, 886]]<|/det|> +Comment 4: Compared with moisture- induced autonomous surface potential oscillations for energy harvesting, we believe that water- induced autonomous surface potential oscillations for energy harvesting are more accurate according to the description of this work. How about dropping a small amount of water to the P(MEDSAH- co- AA) polymer directly to observe the performance of electricity? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 88, 849, 192]]<|/det|> +Response: We have added experimental results by placing water droplet on the device to generate electricity and the performances are close to those of energy harvesters exposed to the condition of \(100\%\) RH moisture in Fig. S12. Since moisture under different RH also generates electricity as shown in Fig. S11, we prefer using "moisture" instead of "water" for our device. + +<|ref|>image<|/ref|><|det|>[[315, 204, 672, 432]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 441, 762, 461]]<|/det|> +
Fig. S12. The output current vs. time plot by placing a water droplet on the device.
+ +<|ref|>text<|/ref|><|det|>[[149, 495, 849, 570]]<|/det|> +Comment 5: I noticed that the Au electrodes and wires were soldered together with tin without encapsulation as shown in Movie S2. Is there any redox reaction at the junction when being exposed to \(100\%\) RH? + +<|ref|>text<|/ref|><|det|>[[149, 588, 848, 662]]<|/det|> +Response: We added one more experiment by replacing the polymer layer with a commercial copy paper and visible electrical outputs were identified as shown in Fig. S9 to illustrate no redox reaction at the junctions. + +<|ref|>text<|/ref|><|det|>[[150, 699, 781, 718]]<|/det|> +Comment 6: Comparisons of using PAA only should be provided in the manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 736, 848, 782]]<|/det|> +Response: The comparisons of only using PAA is provided in the manuscript in Fig. 3d as this device only generates DC electricity. + +<|ref|>text<|/ref|><|det|>[[150, 819, 846, 866]]<|/det|> +Comment 7: It is noted the P(MEDSAH- co- AA) polymers were used without crosslinking. Therefore, the stability of the materials or the devices should be considered. + +<|ref|>text<|/ref|><|det|>[[149, 885, 848, 904]]<|/det|> +Response: Since the polymers contain dynamic bonds – hydrogen bonds and ionic bonds, their + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 90, 848, 135]]<|/det|> +mechanical properties are stable before and after the hydration processes (Fig. S19). A rinsing process in DI water is used to get rid of unreacted reactants. + +<|ref|>image<|/ref|><|det|>[[192, 142, 808, 333]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 348, 851, 423]]<|/det|> +
Fig. S19. The measured stress-strain curves of the polymer (a) before and (b) after the hydration process. The calculated Young's modulus are 30.6 MPa and 66.8 kPa before and after hydration, respectively.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 362, 106]]<|/det|> +REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 129, 393, 145]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 167, 871, 204]]<|/det|> +The authors provided some useful information and added additional experiment data and explanations to support their conclusions. But there still are questions needed to be answered properly: + +<|ref|>text<|/ref|><|det|>[[115, 225, 866, 302]]<|/det|> +(1) The measured open-circuit voltage versus time plot is added. An open-circuit voltage of \(\sim 0.4 \mathrm{~V}\) is comparable to the previously reported results. The AC voltage and current signals are interesting but not necessary for the promotion of voltage and current output. What are the advantages of AC signals compared to DC signals? + +<|ref|>text<|/ref|><|det|>[[115, 323, 877, 418]]<|/det|> +(2) The author still did not explain how the proton migration within molecules in nanoscale induces a significant output current in macroscale, in Comment 3. In your device, the distribution of P(MEDSAH-co-AA) polymer is isotropic. To my understanding, power generation is caused by the water concentration difference between the surface and the middle. The 1st pool is the -COOH on the surface, and the 2nd pool is the -SO3- in the middle. Please clarify this. + +<|ref|>text<|/ref|><|det|>[[115, 480, 393, 496]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 518, 830, 555]]<|/det|> +I recommend the publication of revised manuscript. The authors addressed well the comments in responses. + +<|ref|>text<|/ref|><|det|>[[115, 596, 393, 613]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 635, 867, 692]]<|/det|> +In this revised manuscript, the authors have made proper modification according to the reviewers' comments. I believe that this manuscript in the current form can be accepted for publication in Nature Communications. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[230, 92, 797, 115]]<|/det|> +## List of Changes and Response to Reviewer Comments + +<|ref|>sub_title<|/ref|><|det|>[[150, 145, 253, 162]]<|/det|> +## Reviewer # 1 + +<|ref|>sub_title<|/ref|><|det|>[[150, 173, 299, 190]]<|/det|> +## General Comment + +<|ref|>text<|/ref|><|det|>[[150, 199, 848, 274]]<|/det|> +The authors provided some useful information and added additional experiment data and explanations to support their conclusions. But there still are questions needed to be answered properly: + +<|ref|>text<|/ref|><|det|>[[150, 292, 847, 339]]<|/det|> +Response: We thank the reviewer for positive comments. We have modified the manuscript per the referee's constructive comments. + +<|ref|>text<|/ref|><|det|>[[149, 374, 848, 479]]<|/det|> +Comment 1: The measured open- circuit voltage versus time plot is added. An open- circuit voltage of \(\sim 0.4 \mathrm{~V}\) is comparable to the previously reported results. The AC voltage and current signals are interesting but not necessary for the promotion of voltage and current output. What are the advantages of AC signals compared to DC signals? + +<|ref|>text<|/ref|><|det|>[[148, 495, 849, 708]]<|/det|> +Response: The reviewer is correct that AC voltage and current signals are interesting but not necessary for the promotion of voltage and current outputs. The important parameter of an energy harvester is the overall energy outputs. In this regard, we have summarized the published works in the field of moisture- induced energy harvesters in Fig. 5a. Autonomous surface potential oscillations are utilized to produce alternating current (AC) or voltage outputs and enable long persistence operation time as well as good energy density from prototype devices, while longer operation time and higher energy density devices/mechanisms should be future explored. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[230, 98, 770, 370]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[148, 385, 849, 488]]<|/det|> +
Fig. 5a. Comparison moisture-induced electric generators based on artificial materials in the operation period and energy density. This work has the long persistence time and high energy density among moisture-based energy harvesters, and these two parameters could be further improved by using other materials based on similar self-oscillation mechanisms.
+ +<|ref|>text<|/ref|><|det|>[[148, 523, 850, 682]]<|/det|> +Comment 2: The author still did not explain how the proton migration within molecules in nanoscale induces a significant output current in macroscale, in Comment 3. In your device, the distribution of P(MEDSAH- co- AA) polymer is isotropic. To my understanding, power generation is caused by the water concentration difference between the surface and the middle. The 1st pool is the - COOH on the surface, and the 2nd pool is the - SO3- in the middle. Please clarify this. + +<|ref|>text<|/ref|><|det|>[[148, 699, 850, 914]]<|/det|> +Response: The reviewer is correct that the distribution of P(MEDSAH- co- AA) polymer is isotropic, and the energy generation stops when the moisture concentration is fully saturated inside the polymer (no concentration gradient). In general, our energy harvester is based on the chemical potential changes. It is observed that the chemical potential of moisture in a high humidity environment is larger than that in the polymer and the Gibbs free energy change from the absorbed moisture is transferred to the electrical energy. Specifically, the chemical potential of moisture from the high humidity environment, \(\mu_{h}\) , is higher than the chemical potential of moisture in the low humidity polymer, \(\mu_{l}\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 89, 481, 107]]<|/det|> +The change of Gibbs energy is expressed as: + +<|ref|>equation<|/ref|><|det|>[[371, 113, 625, 149]]<|/det|> +\[\Delta G = \mu_{h} - \mu_{l}\approx RTln(\frac{C_{0}}{C_{0} - \Delta C})\] + +<|ref|>text<|/ref|><|det|>[[148, 153, 849, 285]]<|/det|> +where \(C_0\) is the moisture concentration in the high humidity environment and \(\Delta C\) is the moisture concentration absorbed by the polymer. The \(1^{\mathrm{st}}\) pool is the - COOH and the \(2^{\mathrm{nd}}\) pool is the - SO \(_3\) in the same location of the polymer. When there is moisture concentration gradient inside the polymer, it can induce the anisotropic oscillations of the local proton concentrations to result in the general surface electrical potential oscillations and AC outputs. + +<|ref|>sub_title<|/ref|><|det|>[[150, 321, 256, 338]]<|/det|> +## Reviewer: #2 + +<|ref|>sub_title<|/ref|><|det|>[[150, 349, 299, 366]]<|/det|> +## General Comment + +<|ref|>text<|/ref|><|det|>[[149, 375, 847, 422]]<|/det|> +I recommend the publication of revised manuscript. The authors addressed well the comments in responses. + +<|ref|>text<|/ref|><|det|>[[149, 441, 758, 460]]<|/det|> +Response: We thank the reviewer for recommending the publication of this paper. + +<|ref|>sub_title<|/ref|><|det|>[[150, 497, 255, 513]]<|/det|> +## Reviewer #3 + +<|ref|>sub_title<|/ref|><|det|>[[150, 524, 299, 541]]<|/det|> +## General Comment + +<|ref|>text<|/ref|><|det|>[[149, 551, 848, 625]]<|/det|> +In this revised manuscript, the authors have made proper modification according to the reviewers' comments. I believe that this manuscript in the current form can be accepted for publication in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[149, 644, 759, 663]]<|/det|> +Response: We thank the reviewer for recommending the publication of this paper. + +<--- Page Split ---> diff --git a/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/images_list.json b/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..1a29340143c8ab730cd7861055cac6728727a482 --- /dev/null +++ b/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,427 @@ + +# nature portfolio + +Peer Review File + +The chromatin regulator Ankrd11 controls cardiac neural crest cell- mediated outflow tract remodeling and heart function + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Kibalnyk and colleagues study Ankrd11 in cardiac neural crest cells. They knock out the gene using the Wnt1Cre2 allele and characterize the cardiac defects caused by loss of Ankrd11. Their data show that loss of Ankrd11 in neural crest cells results in outflow tract defects (though the authors may be more precise whether the types of conotruncal defects observed in their mice are also observed in humans). Their analysis nominates at least 3 pathways which are dysregulated upon Ankrd11 deletion. Overall, the manuscript is well- written and the figures easy to follow. The immunohistochemistry is of high quality and quantification of various defects is provided. My major concern with the manuscript relate to the conceptual advance provided by the manuscript. For example, it is that it is unclear if any of the pathways shown to be dysregulated in the mutant embryos are causative of phenotype. I think experiments trying to address that point would substantially improve the impact of the manuscript. Major points for the authors to consider: + +1. The authors should provide evidence that Ankrd11 transcript, or ideally protein, is absent in neural crest cells. + +2. The authors implicate three candidate pathways, Sema3C, BMP and mTOR - on the basis of differences in expression levels observed in immunohistochemistry. The strength of these findings would be bolstered with orthogonal evidence of pathways involvement. For example - immunohistochemistry of target genes and/or qPCR/immunoblotting for relevant pathway effectors from dissected tissue. + +3. The conceptual impact of the manuscript would be significantly improved if the authors could nominate a causal pathway in development in (some) aspect of the phenotypes observed. Could the authors turn to an explant system and determine whether restoration of BMP or mTOR levels prevents aspects of the phenotype? For example, given the OFT cushion defects, are valve defects observed (as observed in patients) and if so, is there a loss of EMT? Is this mediated by BMP and/or mTOR? + +4. The Sema3C RNA-scope is difficult to visualize. The authors may consider changing the pseudocolor of the Sema3C probe and DAPI to better visualize the Sema3C signal. + +Reviewer #2 (Remarks to the Author): + +In this paper, Kibalnyk and colleagues characterize the role of the chromatin regulator gene Ankrd11 in cardiovascular development. By using a combination of \(\mu \mathrm{CT}\) and mouse genetics, the authors show that homozygous loss of Ankrd11 results in persistent truncus arteriosus, amongst other cardiac abnormalities, with \(100\%\) penetrance. They hypothesize that this phenotype is not a result of aberrant proliferation or apoptosis of cardiac neural crest cells, but that of delayed organization in the outflow tract. Finally, through immunostainings for two effector proteins, pSmad and pS6, the authors conclude that BMP and mTOR signaling pathways play a role in proper outflow tract septation. + +While the title and introduction promise to tackle the very important question of how chromatin regulators affect cardiac neural crest development, the manuscript falls short of addressing this question. Instead, the authors simply describe the phenotypes they observed in a heterozygous and homozygous mutant for Ankrd11. This mouse model appears to have been previously described by this lab in a recent 2021 paper, where they looked at craniofacial defects in Ankrd11 mutant background. The conclusions drawn by the paper, in the absence of any mechanistic insights on how Ankrd11 interacts with BMP and mTOR signaling, are a mere validation of previous studies that have shown these signaling pathways to be important for cardiovascular development. Even the analysis in + +<--- Page Split ---> + +figure 5N was previously described by Darrigrand and colleagues. It is unclear to this reviewer as to how this paper advances the field and fits within the scope of Nature Communications. I encourage the authors to work out the mechanism by which Ankrd11 is recruiting BMP and/or mTOR signaling in regulating OFT septation. + +More specific comments and issues are listed below: + +1. Lines 122-124: The authors use Fig.S1C-E as evidence for Ankrd11 expression in the cardiac neural crest. However, it seems that only a subset of cells have any RNAscope signal. Using the authors' approach of quantifying RNAscope signal in sections, I wonder what percentage of cardiac crest cells actually express Ankrd11? The scRNA-seq from the Adameyko lab would suggest that a greater proportion of cells express this gene, at least at earlier stages. Is Ankrd11 lost from the cardiac crest? If so, how does that explain the phenotypes described in the paper? Please quantify the signal and report what proportion of cells express Ankrd11. + +2. Lines 142-144: What is the number/proportion of SMA+/YFP+ cells in WT and Ankrd11ncko mutant embryos? Please quantify and report the difference, or lack thereof, in the paper. + +3. Lines 191-192: The conclusion authors draw here is confusing. Why would a greater proportion of the outflow tract be colonized by cardiac neural crest cells (supp figure 3d) if the overall number of cardiac neural crest cells is reduced (figures 3-4)? On a similar note, how would the observation of unperturbed distance of CNCC migration into the outflow tract be explained by "...a modest defect in migration rather than abnormal proliferation or apoptosis..."? + +4. What structural features were used to define proximal, medial, and distal regions of the outflow tract? Given the marginally significant differences reported in figures 3 and 4, this reviewer is concerned that the results may have a confounding variable. + +5. Lines 539-540: On that note, how were the YFP+ cells quantified? More information in the materials and methods section is warranted. Given that the mesenchymal cells in the heart tend to condense, segmenting cytoplasmic signal can result in quantification errors. + +6. If the cardiac neural crest occupation of the outflow tract seemed to recover in the mutant background, could the septation process also be delayed? How late was the phenotype characterized in sections? + +7. It is unclear why the authors chose to only quantify their phenotypes at the medial level of the outflow tract in figure 7. Also, the pSmad fluorescence intensity should be normalized to the number of YFP+ cells within the ROI and reported as a proportion similar to panel 7N to rule out potential effects due to reduced cell numbers. + +8. This reviewer would like to see the raw data that was used to perform statistical analysis to ensure that conditions for using a parametric test on a small sample size were met. The data plotted in the figures suggest unequal variance between samples, which doesn't seem to have been considered in the authors' choice of statistical test. + +Reviewer #3 (Remarks to the Author): + +In this study the authors claim that Ankrd11 is a critical regulator of heart development. Ankrd11 is a chromatin regulator related to KBG syndrome which clinical manifestation includes, macrodontia, craniofacial findings, short stature, skeletal anomalies, global developmental delay, seizures, and intellectual disability. Heart anomalies were initially described in a minor proportion (Sirmaci, A., et al. + +<--- Page Split ---> + +Am. J. Hum. Genet. 89: 289- 294, 2011), but now is found in \(\sim 44\%\) of KBG patients (Digilio MC, et al. Am J Med Genet A. 2022 Apr;188(4):1149- 1159). + +- What are the noteworthy results? + +The authors showed that ablation of Ankrd11 in the murine neural crest is related to aberrant heart development and function. This is the main result. In addition, the characterization an abnormal signaling pathways pinpoint the molecular mechanism that may be involved. + +- Will the work be of significance to the field and related fields? How does it compare to the + +established literature? If the work is not original, please provide relevant references. + +The work is original. The cardiac defects are more severe than the ones observed in KBG syndrome, but that difference may be related to gene dosage. + +- Does the work support the conclusions and claims, or is additional evidence needed + +1. One concern is that the ablation of Ankrd11 is very detrimental by itself. Ankrd11 KO animals don't survive. So, maybe the ablation of Ankrd11 is killing the cardiac neural crest cells. It seems not to be the case since YFP markers are present in the ncko embryos, but YPF expression is a reporter for wnt1 expression, and maybe ectopic expression of wnt1 is marking other cells. + +2. It is known that ablation of neural crest cells resulted in persistent truncus arteriosus, mis-patterning of the great vessels, outflow malalignments, and hypoplasia or aplasia of the pharyngeal glands. If Ankrd11ablation in the neural crest cells is not killing the cells but is affecting exclusively the cardiovascular development then hypoplasia of thymus, thyroid, and parathyroid glands, should not be present. How are the thymus, thyroid, and parathyroid glands in the ncko animals? If they are normal, this will reinforce that the effect is on cardiac development specifically. I understand that craniofacial abnormalities are also seen in these mice, but those are also seen in KBG syndrome, hence expected. + +3. Something that maybe problematic is that when you look into the information on B6.Cg-E2f1Tg(Wnt1-Cre)2Sor/J Strain #022501Common Name: B6 Wnt1-Cre2 https://www.informatics.jax.org/allele/MGI:5485027?recomRibbon=open): you find + +cardiovascular system + +pulmonary trunk hypoplasia (J:298597) + +- about \(5\%\) of mutants show a hypoplastic pulmonary trunk at E15.5 and E16.5 interrupted aortic arch, type b (J:298597) + +- about \(30\%\) of mutants exhibit interrupted aortic arch, type b at E15.5 and E16.5 abnormal conotruncal ridge morphology (J:298597) + +- the number of neural crest cells in the proximal outflow tract cushions is reduced at E11.5 double outlet right ventricle (J:298597) + +- all mutants exhibit the double outlet right ventricle at E15.5 and E16.5 + +ventricular septal defect (J:298597) + +- all mutants exhibit a ventricular septal defect at E15.5 and E16.5 + +If https://www.jax.org/strain/022501 is not the strain used, please clarify. + +4. Ankrd11 nchet embryos (Ankrd11fl/WT; Wnt1Cre2) showed normal OFT septation, how many embryos were analyzed? There are some haploinsufficiency Ankrd11 related to KBG syndrome presenting heart abnormalities (Digilio MC, et al.. Am J Med Genet A. 2022 Apr;188(4):1149-1159). It is strange that no defect is seen in heterozygous animals. + +Minor issues: + +1. Embryonic hearts at E18.5 were analyzed for anatomical anomalies: all Ankrd11ncko embryos exhibited a persistent truncus arteriosus (PTA). How many? + +2. Supplemental Figure 3: not sure that the image for the wt and the Ankrd11 ncko embryos are in the same plane, hence comparable. + +3. Figure 3 A and D seem to show a different area for the distal part (white squares). + +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +If the authors can explain the points raised, I think it is a good work. Main concern is if the phenotype + +<--- Page Split ---> + +observed (that is very well documented) is related to Ankrd11 ablation.- Is the methodology sound? Does the work meet the expected standards in your field? Yes- Is there enough detail provided in the methods for the work to be reproduced? Yes + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this manuscript, Kibalnyk and colleagues study Ankrd11 in cardiac neural crest cells. They knock out the gene using the Wnt1Cre2 allele and characterize the cardiac defects caused by loss of Ankrd11. Their data show that loss of Ankrd11 in neural crest cells results in outflow tract defects (though the authors may be more precise whether the types of conotruncal defects observed in their mice are also observed in humans). Their analysis nominates at least 3 pathways which are dysregulated upon Ankrd11 deletion. Overall, the manuscript is well- written and the figures easy to follow. The immunohistochemistry is of high quality and quantification of various defects is provided. + +We thank the reviewer for providing their constructive feedback and for highlighting the potential of our results. Below we have addressed all raised concerns. + +My major concern with the manuscript relate to the conceptual advance provided by the manuscript. For example, it is that it is unclear if any of the pathways shown to be dysregulated in the mutant embryos are causative of phenotype. I think experiments trying to address that point would substantially improve the impact of the manuscript. Major points for the authors to consider: + +1. The authors should provide evidence that Ankrd11 transcript, or ideally protein, is absent in neural crest cells. + +We thank the reviewer for this suggestion. Unfortunately, there are no good commercial antibodies raised against Ankrd11 that we have been able to validate. Some custom antibodies existed, but they are no longer available. Instead, we have addressed this concern by performing BaseScope, a single- molecule RNA fluorescent in situ hybridization technique and showed that \(\sim 80\%\) of the control (Ankrd11nchet) outflow tract (OFT) mesenchymal cells expressed Ankrd11 mRNA. In contrast, \(\sim 20\%\) of Ankrd11ncko OFT mesenchymal cells expressed Ankrd11 mRNA (new Fig. 1i- j', l). Please note that technical limitations prevented us from counterstaining against YFP to identify neural crest cells, however, the OFT mesenchyme is predominantly composed of YFP+ cells1. The residual Ankrd11 signal in Ankrd11ncko OFT mesenchyme could be due to the presence of second heart field (SHF), nonneural crest derived cells in the OFT mesenchyme1, or incomplete recombination. Notably, a Basescope assay with a negative control probe did not yield a signal (new Fig. 1k). Furthermore, in response to reviewer #2, we further stratified Ankrd11- expressing cells in the control OFT mesenchyme based on the Ankrd11 expression level (new Fig. 1m). Our results demonstrate low, mid, and high Ankrd11- expressing cells (new Fig. 1m). Overall, our BaseScope results are in line with expanded reanalysis of published neural crest single- cell RNA sequencing dataset that also demonstrates low, mid and high Ankrd11- expressing CNCCs (former Fig. S1, now updated Fig. 1a- e). + +We have reflected new data in Fig. 1 and associated text in "Materials and Methods" on pages 16- 17, 19- 20, and "Results" on page 5 + +2. The authors implicate three candidate pathways, Sema3C, BMP and mTOR - on the basis of differences in expression levels observed in immunohistochemistry. The strength of these findings would be bolstered with orthogonal evidence of pathways involvement. For example - immunohistochemistry of target genes and/or qPCR/immunoblotting for relevant pathway effectors from dissected tissue. + +<--- Page Split ---> + +Thank you for the insightful suggestion. The OFT displays distinct gene expression and signalling pathway activation in distal, medial and proximal areas 2. Therefore, we could not utilize qPCR or immunoblotting techniques from the entire OFT tissue as this does not permit a spatial analysis. We have therefore opted to use some additional immunohistochemistry analysis at E11.5 and E12.5 and have expanded our E11.5 OFT analysis to the single cell spatial transcriptomics technique MERFISH (Multiplexed Error- Robust Fluorescence in situ Hybridization) with a custom 140 target gene panel. This custom panel included genes that are known to be important for OFT development and/or that were previously shown to be expressed in the OFT during the septation process in a scRNAseq dataset 2- 12. These include factors of important signaling pathways, extracellular matrix components, chemokines, transcription and chromatin remodeling factors, and cell type markers (new Table S1). + +With regard to the BMP pathway, MERFISH analysis identified reduced expression of Bmp4, Bmpr2, and Acvr1 in E11.5 Ankrd11ncko CNCCs (new Fig. 8a- c). Furthermore, results in 2 suggest that BMP signaling at least in part controls Sema3c expression. We found downregulated Sema3c in E11.5 Ankrd11ncko CNCCs using MERFISH, which we corroborated with RNAscope (new Fig. 8a- c & S6), indicating a potential downstream effect of impaired BMP signaling. Finally, in response to reviewer #2, we have re- analyzed E11.5 IHC images of pSmad1/5/8, the intracellular effectors of Smad- dependent BMP signaling 2,13,14. New analysis shows reduced proportion of pSmad1/5/8+ CNCCs in E11.5 Ankrd11ncko medial OFT compared to Ankrd11nchet (former Fig. 7, now updated Fig. 4). Altogether, this supports and expands our original conclusion that the BMP pathway is deregulated in Ankrd11ncko CNCCs. + +pS6 remains the gold standard readout of mTOR signaling 15,16, which is what we used in our original submission. Notably, the involvement of the mTOR pathway in OFT development is a recent discovery 12. As such, there are no known direct mTOR targets for cardiac neural crest cells to date. However, Nie 2021 identified that mTOR deletion causes dysregulation of actin dynamics and Smad1/5/8 phosphorylation 12, which were both affected in Ankrd11ncko OFTs (Former Figs. 5, 7; now updated Figs. 3- 5), suggesting a potential crosstalk between mTOR and BMP signaling. + +The MERFISH assay revealed several differentially expressed genes (DEGs) in Ankrd11ncko CNCCs for various signaling pathways known to be important for OFT development, including Wnt (Fzd4, Vangl2, Fzd1), BMP (Id2, Bmp4, Smad7, Bmpr2, Acvr1), TGF- \(\beta\) (Tgf \(\beta\) 2, Smad7), Notch (Heyl, Jag1, Notch1), Hippo (Yap1), JNK (Jun), Retinoic acid (Rcra, Rarg), FGF (Fgfr2), EGFR (Erbb3), and JAK- STAT (Stat3) 2- 12 (new Fig. 8a- c and Table S2). Furthermore, it identified downregulation in neuropilin- 1 (Nrp1), a known receptor for Sema3c 4, which may amplify the effects of the dysregulation (please see above). Other chemokines and growth factors included ephrin A5 (Efna5) and transforming growth factor beta 2 (Tgf \(\beta\) 2) 17,18 (new Fig. 8a- c and Table S2). DEGs also included other transcription and chromatin remodeling factors important for OFT development such as Egr1, Hoxa3, Ets1, Gata4, Sox11, Foxc1 and Chd7 10,19,20, and cytoskeletal or extracellular matrix factors, such as Cdh11, Mmp14, Adamts1, and Adam19 21 (new Fig. 8a- c and Table S2). These results suggest that Ankrd11 ablation affects multiple signaling pathways, transcription factors and chromatin remodelers important for CNCC function and OFT morphogenesis. + +We expanded our IHC analysis to additional signalling pathways and molecules to corroborate some of the MERFISH results. We focused on phosphorylated Smad2/3, the intracellular effectors of Smad- dependent TGF- \(\beta\) signaling 22, and Cellular retinoic acid binding protein 2 (Crabp2), a protein that transports retinoic acid from the cytoplasm to the nucleus, which facilitates retinoic acid signaling 23. We observed asymmetrical pSmad2/3 and Crabp2 signal in control medial parietal (top- right) and septal (bottom- left) OFT cushions at E11.5 (new Figs. 6 and S4). In contrast, E11.5 Ankrd11ncko medial + +<--- Page Split ---> + +OFT parietal and septal cushions had similar levels of pSmad2/3 or Crabp2 (new Figs. 6 and S4). While nothing is known about the mechanism behind the pSmad2/3 and Crabp2 asymmetry within CNCCs or its downstream effects on AP septum formation, there is evidence for CNCC asymmetry. Gandhi et al \(^{24}\) observed that ablation of the right cardiac neural folds in chick, which removes CNCCs from the right side of the embryo, produced a more severe septation impairment compared to ablation of the left cardiac neural folds. + +Please note that in response to reviewer #2, we have expanded pS6, pSmad1/5/8, pSmad2/3 and actin dynamics analysis to E12.5 (updated Figs. 3- 5 and S3, new Fig. 6). Overall, our results show comparable levels of pS6, pSmad1/5/8 and pSmad2/3 in E12.5 Ankrd11ncnet and Ankrd11ncno medial OFT cushions (distal cushions were analyzed as well, but only in Ankrd11ncno samples), suggesting a delay in mTOR, BMP and TGF- \(\beta\) signalling pathways and CNCC condensation. + +Overall, we propose that several dysregulated pathways contribute to Ankrd11ncno CNCC delay in condensation and convergence at the midline to form the AP septum, including BMP, mTOR, and TGF- \(\beta\) . + +We have reflected new data in Figs. 4- 8, S3- 4 and associated text in "Materials and Methods" on pages 16- 22, "Results" on pages 8- 11 and "Discussion" on pages 12- 14. + +3. The conceptual impact of the manuscript would be significantly improved if the authors could nominate a causal pathway in development in (some) aspect of the phenotypes observed. Could the authors turn to an explant system and determine whether restoration of BMP or mTOR levels prevents aspects of the phenotype? For example, given the OFT cushion defects, are valve defects observed (as observed in patients) and if so, is there a loss of EMT? Is this mediated by BMP and/or mTOR? + +Thank you for this suggestion. Neural crest cells participate in a strict spatiotemporal control of tissue (OFT) morphogenesis. It has proven difficult to recapitulate our main findings (failure of OFT septation) in an explant culture. We have attempted a neural tube explant to measure Ankrd11ncno neural crest migration, however preliminary results did not show a migration defect (data not shown). This is corroborated by our in vivo findings, where we found small and region- specific decreases in CNCC number in the OFT. Furthermore, the explant system cannot faithfully recapitulate the morphogenesis of AP septation, which is the main affected phenotype in our manuscript. + +Moreover, the MERFISH assay shows a broad set of genes and signalling pathways to be dysregulated in Ankrd11ncno CNCCs (please see above and new Figs. 7- 8, Tables S1- 2). It is thus not feasible to name a nominal pathway as our data suggest ablation of Ankrd11 leads to perturbations in various signalling pathways, extending beyond the originally nominated BMP and mTOR signalling pathways in our original submission. Finally, due to signalling pathway cross- talk, it is difficult to choose a single nominal pathway and rescue strategy. + +Nevertheless, we have attempted pharmacological rescues in vivo, using a BMP agonist Sb4 \(^{25}\) and an mTOR agonist L- leucine \(^{26}\) administration into pregnant dams. Due to previous research showing that Ankrd11 represses the retinoic acid receptor RAR \(\alpha^{27}\) , we also used retinoic acid signaling inhibitor BMS493 \(^{28}\) . None of the experiments resulted in a rescue in Ankrd11ncno embryos (data not shown) and overall proved to be extremely difficult to interpret. This is at least in part due to the pan- effects of these drugs on all tissues, not just CNCCs. As CNCCs and surrounding tissues participate in cross- talk + +<--- Page Split ---> + +during OFT morphogenesis, the drugs affect all tissues with active signalling pathway of choice. Moreover, BMP, mTOR and/or RA signalling is vital for proper embryogenesis. Thus, interpretation of results even in control embryos would be very challenging. + +We have therefore re- focussed our efforts on MERFISH and additional IHC analysis. To our knowledge, our report is the first one to apply spatial single cell transcriptomics to OFT septation. Our dataset will be useful for the community- at- large and will provide a rich resource for data mining in control and Ankrd11- deficient embryos (please note that the datasets will be deposited into a public repository and an open visualization website prior to publication; meanwhile, we have uploaded processed and meta- data alongside source code via GitHub). Furthermore, we provide evidence for asymmetric signaling in control OFT cushions involving the TGF- \(\beta\) and retinoic acid pathways, which to our knowledge has not been described previously. + +Overall, our new and expanded results support and extend our work, suggesting that Ankrd11 controls a complex network of genes required for OFT development. + +Finally, we have also analyzed valve development and observed dysplastic valves in 3 of 5 Ankrd11ncko hearts (new Fig. S1d- i). Since these valves appear hypertrophic, this does not suggest a loss of EMT, but rather a failure of the CNCCs to remodel the valves correctly 29, echoing their failure to remodel the AP septum. Based on our OFT signaling pathway results using IHC and MERFISH (updated and/or new Figs. 4- 8), we suspect that this is caused by impairment of multiple pathways. + +We have reflected new data in Figs. S1, S3- 4, 6- 8, Tables S1- S2, and associated text in "Materials and Methods" on pages 16- 22, "Results" on pages 6, 8- 11 and "Discussion" on pages 11- 14. + +4. The Sema3C RNA-scope is difficult to visualize. The authors may consider changing the pseudocolor of the Sema3C probe and DAPI to better visualize the Sema3C signal. + +Thank you for this comment. This has been addressed in new Fig. S6 (former Fig. S4). Moreover, we have added representative Sema3c MERFISH images to this figure, which corroborate our RNA scope findings (MERFISH images in new Fig. S6A, MERFISH results in new Fig. 8). + +Reviewer #2 (Remarks to the Author): + +In this paper, Kibalnyk and colleagues characterize the role of the chromatin regulator gene Ankrd11 in cardiovascular development. By using a combination of \(\mu \mathrm{CT}\) and mouse genetics, the authors show that homozygous loss of Ankrd11 results in persistent truncus arteriosus, amongst other cardiac abnormalities, with \(100\%\) penetrance. They hypothesize that this phenotype is not a result of aberrant proliferation or apoptosis of cardiac neural crest cells, but that of delayed organization in the outflow tract. Finally, through immunostainings for two effector proteins, pSmad and pS6, the authors conclude that BMP and mTOR signaling pathways play a role in proper outflow tract septation. + +While the title and introduction promise to tackle the very important question of how chromatin regulators affect cardiac neural crest development, the manuscript falls short of addressing this question. Instead, the authors simply describe the phenotypes they observed in a heterozygous and + +<--- Page Split ---> + +homozygous mutant for Ankrd11. This mouse model appears to have been previously described by this lab in a recent 2021 paper, where they looked at craniofacial defects in Ankrd11 mutant background. The conclusions drawn by the paper, in the absence of any mechanistic insights on how Ankrd11 interacts with BMP and mTOR signaling, are a mere validation of previous studies that have shown these signaling pathways to be important for cardiovascular development. Even the analysis in figure 5N was previously described by Darrigrand and colleagues. It is unclear to this reviewer as to how this paper advances the field and fits within the scope of Nature Communications. I encourage the authors to work out the mechanism by which Ankrd11 is recruiting BMP and/or mTOR signaling in regulating OFT septation. + +Thank you for your constructive feedback and recommendation. Reviewer #1 has also recommended to "nominate a causal pathway in development in (some) aspect of the phenotypes observed". Our combined response is below: + +Neural crest cells participate in a strict spatiotemporal control of tissue (OFT) morphogenesis. We were unable to use an in vitro system to interrogate the mechanism of Ankrd11 in OFT morphogenesis because the explant system cannot faithfully recapitulate the morphogenesis of AP septation, which is the main affected phenotype in our manuscript. For example, we have attempted a neural tube explant to measure Ankrd11ncko neural crest migration, however preliminary results did not show a migration defect (data not shown). This is corroborated by our in vivo findings, where we found small and region- specific decreases in CNCC number in the OFT. We were thus unable to use explant or other in vitro systems to study the mechanism. + +However, we performed two new major sets of in vivo experiments to address the mechanism. + +First, we performed single cell spatial transcriptomics MERFISH (Multiplexed Error- Robust Fluorescence in situ Hybridization) with a custom 140 target gene panel. This custom panel included genes that are known to be important for OFT development and/or that were previously shown to be expressed in the OFT during the septation process in a scRNAseq dataset2-12. These include factors of important signaling pathways, extracellular matrix components, chemokines, transcription and chromatin remodeling factors, and cell type markers (new Table S1). This technique was chosen due to spatially controlled gene expression in distal, medial and proximal OFT areas2. Therefore, we could not utilize scRNA-seq, qPCR or immunoblotting techniques from entire OFT tissue as they do not permit a spatial analysis. + +The MERFISH assay shows a broad set of genes and signalling pathways to be dysregulated in Ankrd11ncko CNCCs (new Figs. 7- 8, Tables S1- 2). In summary, MERFISH assay revealed several differentially expressed genes (DEGs) in Ankrd11ncko CNCCs for several signaling pathways known to be important for OFT development, including Wnt (Fzd4, Vangl2, Fzd1), BMP (Id2, Bmp4, Smad7, Bmpr2, Acvr1), TGF- \(\beta\) (Tgf\(\beta\)2, Smad7), Notch (Heyl, Jag1, Notch1), Hippo (Yap1), JNK (Jun), Retinoic acid (Rxra, Rarg), FGF (Fgf\(\beta\)2), EGFR (Erbb3), and JAK- STAT (Stat3) 2-12 (new Fig. 8a- c and Table S2). We found DEGs in several growth factors and chemokines. In cluster 2, one of the most downregulated DEGs in Ankrd11ncko cells was Sema3c, which we have corroborated with single molecule FISH (RNA scope) (new Fig. S6). The class 3 Semaphorin C (Sema3C) plays a major role in CNCC migration into the OFT, their condensation in the OFT cushions, and their convergence to create the AP septum, at least in part due to its role as a chemoattractant and aggregation factor 2,30-33. Furthermore, the assay identified downregulation in neuropilin- 1 (Nrp1), a known receptor for Sema3c 4, which may amplify the effects of the dysregulation. Other factors included ephrin A5 (Efna5), which is known to guide neural crest migration, and transforming growth factor beta 2 (Tgf\(\beta\)2), which is + +<--- Page Split ---> + +important for OFT morphogenesis \(^{17,18}\) (new Fig. 8a- c and Table S2). DEGs also included other transcription and chromatin remodeling factors important for OFT development such as Egr1, Hoxa3, Ets1, Gata4, Sox11, Foxc1 and Chd7 \(^{10,19,20}\) , and cytoskeletal or extracellular matrix factors, such as Cdh11, Mmp14, Adamts1, and Adam19 \(^{21}\) (new Fig. 8a- c and Table S2). These results suggest that Ankrd11 ablation affects multiple signaling pathways, transcription factors and chromatin remodelers important for CNCC function and OFT morphogenesis, further supporting our expanded IHC results in updated or new Figs. 4- 6. + +Thus, it is unlikely that Ankrd11 controls OFT morphogenesis via BMP and/or mTOR signalling pathways only. It is more likely that Ankrd11 knockout leads to dysregulation of many signalling pathways and their cross- talk. + +In addition, and in response to this reviewer's additional concerns below, we have extended our IHC analysis to distal OFT regions at E11.5 and included medial and distal OFT analysis at E12.5. This analysis showed spatiotemporal differential dysregulation of mTOR (pS6), BMP (pSmad1/5/8), TGF- \(\beta\) (pSmad2/3) and RA (Crabp2) signaling pathways (updated and new Figs. 4- 6, S3- 4). Thus, further mechanistic interrogation of how Ankrd11 recruits BMP, mTOR or other dysregulated signaling during OFT septation will require novel spatial tools as using traditional entire OFT primary cells or explants will not yield spatially resolved specimens for appropriate interpretation of the results. Such further mechanistic work lies outside of the scope of this manuscript. + +Second, we have attempted pharmacological rescues in vivo, using a BMP agonist \(\mathrm{Sb4}^{25}\) and an mTOR agonist L- leucine \(^{26}\) . Due to previous research showing that Ankrd11 represses the retinoic acid receptor \(\mathrm{RAR}\alpha^{27}\) , we also used retinoic acid signaling inhibitor BMS493 \(^{28}\) . None of the experiments resulted in a rescue in Ankrd11 \(^{1\mathrm{nck0}}\) embryos (data not shown) and overall proved to be extremely difficult to interpret. This is at least in part due to the pan- effects of these drugs on all tissues, not just CNCCs. As CNCCs and surrounding tissues participate in cross- talk during OFT morphogenesis, the drugs affect all tissues. Moreover, BMP, mTOR and/or RA signalling is vital for proper embryogenesis. Thus, interpretation of results even in control embryos would be very challenging. Finally, our MERFISH results show a broad set of genes and signalling pathways to be dysregulated in Ankrd11 \(^{1\mathrm{nck0}}\) CNCCs (please see above and new Figs. 7- 8, Tables S1- 2). It is thus not feasible to name a nominal pathway as our data suggest ablation of Ankrd11 leads to perturbations in various signalling pathways, extending beyond the originally nominated BMP and mTOR signalling pathways in our original submission. + +We have therefore re- focussed our efforts on MERFISH and additional IHC analysis. To our knowledge, our report is the first one to apply spatial single cell transcriptomics to OFT septation. Our dataset will be useful for the community- at- large and will provide a rich resource for data mining in control and Ankrd11- deficient embryos (please note that the datasets will be deposited into a public repository and an open visualization website prior to publication; meanwhile, we have uploaded processed and meta- data alongside source code via GitHub). Furthermore, we provide evidence for asymmetric signaling in control OFT cushions involving the TGF- \(\beta\) and retinoic acid pathways, which to our knowledge has not been described previously. Finally, our new results support and expand our original conclusions, and suggest that Ankrd11 controls a complex network of genes required for OFT development. These new datasets have shown known, and more importantly, novel signalling pathways that Ankrd11 controls. In our future work, we will study an in- depth mechanism by which Ankrd11 controls these signalling pathways and gene expression. However, this is outside of the scope of the current manuscript. + +<--- Page Split ---> + +We have reflected new data in Figs. 4- 8, S3- S4, Tables S1- S2, and associated text in “Materials and Methods” on pages 16- 22, “Results” on pages 8- 11 and “Discussion” on pages 12- 14. + +More specific comments and issues are listed below: + +1. Lines 122-124: The authors use Fig.S1C-E as evidence for Ankrd11 expression in the cardiac neural crest. However, it seems that only a subset of cells have any RNAscope signal. Using the authors' approach of quantifying RNAscope signal in sections, I wonder what percentage of cardiac crest cells actually express Ankrd11? The scRNA-seq from the Adameyko lab would suggest that a greater proportion of cells express this gene, at least at earlier stages. Is Ankrd11 lost from the cardiac crest? If so, how does that explain the phenotypes described in the paper? Please quantify the signal and report what proportion of cells express Ankrd11. + +We thank the reviewer for this suggestion. We have addressed this concern by performing BaseScope, a single- molecule RNA fluorescent in situ hybridization technique and showed that \(\sim 80\%\) of the control (Ankrd11nchet) outflow tract (OFT) mesenchymal cells expressed Ankrd11 mRNA (new Fig. 1i, l). Notably, a Basescope assay with a negative control probe did not yield a signal (new Fig. 1k). Please note that technical limitations prevented us from counterstaining against YFP to identify neural crest cells, however, the OFT mesenchyme is predominantly composed of YFP+ cells1. We further stratified Ankrd11-expressing cells in the control OFT mesenchyme based on the Ankrd11 expression level (new Fig. 1m). Our results demonstrate low, mid and high Ankrd11-expressing cells (Fig. 1m). Re-analysis of published neural crest single-cell RNA sequencing dataset also demonstrates low, mid and high Ankrd11-expressing CNCCs (former Fig. S1, now updated Fig. 1a-e). Notably, in comparison to \(\sim 80\%\) of CNCCs expressing Ankrd11 in control CNCCs, scRNAseq shows that all CNCCs express Ankrd11. This could be due to different methods used (BaseScope vs scRNA-seq), samples (WT in scRNA-seq vs Ankrd11nchet in BaseScope) and/or potential inclusion of second heart field (SHF), nonneural crest derived cells in the OFT mesenchyme1, in BaseScope analysis. + +We have reflected new data in Fig. 1 and associated text in “Materials and Methods” on pages 16- 17, 20, and “Results” on page 5. + +2. Lines 142-144: What is the number/proportion of SMA+/YFP+ cells in WT and Ankrd11ncko mutant embryos? Please quantify and report the difference, or lack thereof, in the paper. + +Thank you for this suggestion. To address this concern, we have performed immunofluorescence analysis of cross sections of E18.5 outflow tract vessels and quantified SMA+/YFP+ cells out of the total SMA+ cells within the proximal (closest to the heart) and distal regions of the vessels (new Fig. S1j-p). In the proximal region, analysis of the αSMA+ (alpha-smooth muscle actin) smooth muscle layer of the E18.5 Ankrd11ncko truncal artery did not show a deficiency of CNCC-derived smooth muscle cells compared to the Ankrd11nchet aortic and pulmonary arteries (new Fig. S1j-p). Although the Ankrd11ncko distal region showed a decreased proportion of smooth muscle cells that are CNCC derived (% αSMA+/YFP+/αSMA+; new Fig. S1n), this was not due to their decreased number (#YFP+/αSMA+; new Fig. S1o), but rather due to an increase in non-CNCC derived smooth muscle cells (#YFP-/αSMA+; new Fig. S1p). + +We have reflected new data in Fig. S1 and associated text in “Materials and Methods” on page 19, and “Results” on page 6. + +<--- Page Split ---> + +3. Lines 191-192: The conclusion authors draw here is confusing. Why would a greater proportion of the outflow tract be colonized by cardiac neural crest cells (supp figure 3d) if the overall number of cardiac neural crest cells is reduced (figures 3-4)? On a similar note, how would the observation of unperturbed distance of CNCC migration into the outflow tract be explained by "...a modest defect in migration rather than abnormal proliferation or apoptosis..."? + +Thank you for highlighting this and we apologize for the confusion. Former Fig. S3 showed that there are no statistically significant differences in the distance traveled by the first invading cardiac neural crest cells into the proximal outflow tract. This differs from other genetic models of cardiac neural crest deficiency, where the cells are not able to infiltrate the most proximal regions of the OFT, indicating a more severe migration defect \(^{34}\) . This indicates that the Ankrd11 \(^{nck0}\) cardiac neural crest cells have a more subtle migration defect, where the cells were able to populate the full length of the OFT, but in smaller numbers, since proliferation or apoptosis was not affected (Fig. S2a-i; former Fig. 3). This is in line with findings from other genetic models, including Nie et al. \(^{12}\) , which showed that mTOR deletion led to reduced CNCC numbers in the OFT without changes in apoptosis or proliferation prior to E11.5, suggesting that the cell deficit was caused by a migration defect. + +Since reviewer 3 also found concerns with these results, we removed these results from the manuscript to remove confusion, as they are not critical for our conclusions. + +4. What structural features were used to define proximal, medial, and distal regions of the outflow tract? Given the marginally significant differences reported in figures 3 and 4, this reviewer is concerned that the results may have a confounding variable. + +Due to the expansion of the manuscript and the similarity in the results between E10.5 and E11.25 (Figs. 3- 4 in original submission), we have removed the E11.25 data from the manuscript to remove redundancy and confusion between E11.25 and E11.5 ages. E10.5 data are now presented in Fig. S2. + +To address this comment, we have added a detailed description defining the OFT regions to the manuscript and expanded it to include all ages analyzed (E10.5, E11.5, E12.5). + +At E10.5, the proximal OFT region has a small lumen and dispersed CNCCs, the medial region has a large lumen, dispersed CNCCs and a thickened bottom cushion, and the distal region has a large lumen, more compacted CNCCs, and a thickened bottom cushion (Fig. S2a-f). We have therefore used these features to define proximal, medial and distal regions of E10.5 OFT. To analyze anatomically matched sections of Ankrd11 \(^{nchet}\) and Ankrd11 \(^{nck0}\) OFTs at E11.5 and E12.5, the Ankrd11 \(^{nck0}\) distal region was determined to be the equivalent region to the Ankrd11 \(^{nchet}\) septated region based on the number of OFT sections it occupied, and the medial sections used for analysis were adjacent to this boundary. We used this method to avoid relying on the differing morphology between Ankrd11 \(^{nchet}\) and Ankrd11 \(^{nck0}\) OFTs and between embryonic ages. We have addressed this clarification in materials and methods on pages 19- 20. + +5. Lines 539-540: On that note, how were the YFP+ cells quantified? More information in the materials and methods section is warranted. Given that the mesenchymal cells in the heart tend to condense, segmenting cytoplasmic signal can result in quantification errors. + +Cells were identified as YFP+ when YFP+ cytoplasm overlayed with a Hoechst+ nucleus. All cells were counted manually. This clarification is added on page 20. + +<--- Page Split ---> + +6. If the cardiac neural crest occupation of the outflow tract seemed to recover in the mutant background, could the septation process also be delayed? How late was the phenotype characterized in sections? + +Thank you for the insightful comment. We extended our analysis to E12.5 Ankrd11ncko OFTs. Surprisingly, we found that the very distal edge of E12.5 Ankrd11ncko OFT showed septation (new Fig. 3l-m). However, the septation failed to progress any further, as at E18.5 we observe the persistent truncus arteriosus phenotype characteristic of OFT septation failure (Fig. 2). + +Furthermore, we have extended pS6 and pSmad1/5/8 and added pSmad2/3 signalling analysis to include E12.5 samples as well as distal OFT in both E11.5 and E12.5 samples. With regard to CNCC condensation, the Ankrd11ncko CNCCs in the cardiac cushions in the unseptated distal region at E12.5 were still visibly disorganized (updated Fig. 3p-q). For BMP and mTOR signalling, while E11.5 Ankrd11ncko showed reduced % pS6+ and % pSmad1/5/8+ medial CNCCs compared to Ankrd11nchet, their levels were similar in E12.5 medial CNCCs (updated Figs. 4- 5). For the distal region, we only analyzed Ankrd11ncko cardiac cushions as controls have formed a septum in this area. Unseptated distal region in E12.5 Ankrd11ncko OFT showed pS6 and pSmad1/5/8 signal that was elevated in comparison to the distal region in E11.5 Ankrd11ncko OFT (Fig. 4k- l, 5k- l). Finally, we included new analysis of pSmad2/3, the intracellular effectors of Smad- dependent TGF- \(\beta\) signaling22. We found asymmetric pSmad2/3 signaling in control medial parietal (top- right) and septal (bottom- left) OFT cushions at E11.5 (new Fig. 6). In contrast, E11.5 Ankrd11ncko medial OFT parietal and septal cushions had similar levels of pSmad2. However, by E12.5, Ankrd11ncko medial OFT showed asymmetric pSmad2/3 staining. (new Fig. 6). As described above, for the distal region, we only analyzed Ankrd11ncko cardiac cushions as controls have formed a septum in this area. In the distal region, at both E11.5 and E12.5, we detected comparable levels of pSmad2/3+ CNCCs between Ankrd11ncko parietal and septal cushions (new Fig. 6). Therefore, these results show that the Ankrd11ncko CNCCs display a delay in BMP and mTOR signalling and a delay in asymmetric activation of TGF- \(\beta\) signalling. Even though some signalling was recovered in E12.5 Ankrd11ncko OFT, the Ankrd11ncko AP septum failed to fully establish. This suggests that the Ankrd11ncko CNCCs missed a developmental window necessary for septation progression. + +We have reflected new data in Figs. 3- 6, S3 and associated text in "Materials and Methods" on page 19- 20, "Results" on pages 7- 10 and "Discussion" on pages 12- 14. + +7. It is unclear why the authors chose to only quantify their phenotypes at the medial level of the outflow tract in figure 7. Also, the pSmad fluorescence intensity should be normalized to the number of YFP+ cells within the ROI and reported as a proportion similar to panel 7N to rule out potential effects due to reduced cell numbers. + +Thank you for this suggestion. Since the control distal region does not have OFT cushions due to AP septum formation, we chose to compare the medial regions in both control and Ankrd11ncko cushions to have anatomically matched regions. However, we have extended our analysis to distal regions of Ankrd11ncko OFT cushions (updated Figs. 4- 5, new Figs. 6, S3- 4). + +We have also quantified pSmad1/5/8 signal by setting a signal intensity threshold and only counting marker+ cells that showed a signal above the threshold (former Fig. 7; now updated Fig. 4). This allowed us to count all YFP+ CNCC cells in the OFT mesenchyme and present the results as a + +<--- Page Split ---> + +proportion of total YFP+ cells. Our new results support our original conclusions and show reduced % of pSmad1/5/8+ CNCCs in medial E11.5 Ankrd11nck CNCCs. + +We have reflected new data in Figs. 4- 5 and associated text in “Materials and Methods” on page 19- 20, “Results” on page 7 and “Discussion” on page 12. + +8. This reviewer would like to see the raw data that was used to perform statistical analysis to ensure that conditions for using a parametric test on a small sample size were met. The data plotted in the figures suggest unequal variance between samples, which doesn't seem to have been considered in the authors' choice of statistical test. + +Thank you for expressing this concern. All IHC data were subjected to normality tests using the Anderson- Darling, D'Agostino & Pearson, and Kolmogorov- Smirnov tests (using Prism) and were found to be normal or have insufficient sample size for these tests and were thus considered normal, except for Fig. S1c, which was then tested using the Mann- Whitney test. Insufficient sample size is typical for biological data as normality tests often require \(>n = 5\) . Our data has typically included \(n = 3 - 4\) biological replicates per genotype. Statistical tests and number of biological replicates is reflected this in Materials and Methods on page 21 and in each figure legend. We have also supplied the data in Source files and details on biological replicates, statistical tests and other parameters in the accompanying reporting summary. + +Reviewer #3 (Remarks to the Author): + +In this study the authors claim that Ankrd11 is a critical regulator of heart development. Ankrd11 is a chromatin regulator related to KBG syndrome which clinical manifestation includes, macrodontia, craniofacial findings, short stature, skeletal anomalies, global developmental delay, seizures, and intellectual disability. Heart anomalies were initially described in a minor proportion (Sirmaci, A., et al. Am. J. Hum. Genet. 89: 289- 294, 2011), but now is found in \(\sim 44\%\) of KBG patients (Digilio MC, et al.. Am J Med Genet A. 2022 Apr;188(4):1149- 1159). + +- What are the noteworthy results? + +The authors showed that ablation of Ankrd11 in the murine neural crest is related to aberrant heart development and function. This is the main result. In addition, the characterization an abnormal signaling pathways pinpoint the molecular mechanism that may be involved. + +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. The work is original. The cardiac defects are more severe than the ones observed in KBG syndrome, but that difference may be related to gene dosage. + +We thank the reviewer for providing their constructive feedback and for highlighting the potential of our results. Below we have addressed all raised concerns. + +- Does the work support the conclusions and claims, or is additional evidence needed 1. One concern is that the ablation of Ankrd11 is very detrimental by itself. Ankrd11 KO animals don’t survive. So, maybe the ablation of Ankrd11 is killing the cardiac neural crest cells. It seems not to be the case since YFP markers are present in the ncko embryos, but YPF expression is a reporter for wnt1 expression, and maybe ectopic expression of wnt1 is marking other cells. + +<--- Page Split ---> + +We thank the reviewer for their feedback. The Wnt1Cre mouse model is the most widely used model for studying cardiac neural crest cells 4. At E11.5 the YFP distribution in Ankrd11nchet and Ankrd11ncko is characteristic of the neural crest lineage (new Fig. 1f-g) and consistent with other publications 35, which includes derivatives of the pharyngeal arches and regions alongside the neural tube, which will become dorsal root ganglia of the peripheral nervous system. Therefore, the YFP+ cells in our mouse models are behaving like neural crest cells. + +In the OFT, TUNEL staining of YFP+ cells showed no difference in apoptosis between control and Ankrd11ncko embryos, indicating that apoptosis, which represents major cell death in the developing OFT 36, is not a contributing factor in the neural crest dysregulation (Fig. S2a"- f", former Figs. 3- 4). + +Furthermore, our results show only minor migration defects of Ankrd11ncko CNCCs at E10.5 as well as the cells' ability to produce SMA+ smooth muscle cells (updated Fig. S2a-i, Fig. S1j- p). For SMA, we have performed immunofluorescence analysis of cross sections of E18.5 outflow tract vessels and quantified SMA+ YFP+ cells out of the total SMA+ cells within the proximal (closest to the heart) and distal regions of the vessels (new Fig. S1j- p). In the proximal region, analysis of the \(\alpha \mathrm{SMA}+\) (alpha- smooth muscle actin) smooth muscle layer of the E18.5 Ankrd11ncko truncal artery did not show a deficiency of CNCC- derived smooth muscle cells compared to the Ankrd11nchet aortic and pulmonary arteries (new Fig. S1j- p). Although the Ankrd11ncko distal region showed a decreased proportion of smooth muscle cells that are CNCC derived ( \(\% \alpha \mathrm{SMA}+\) YFP+/ \(\alpha \mathrm{SMA}+\) ; new Fig. S1n), this was not due to their decreased number (#YFP+ \(\alpha \mathrm{SMA}+\) ; new Fig. S1o), but rather due to an increase in non- CNCC derived smooth muscle cells (#YFP- \(\alpha \mathrm{SMA}+\) ; new Fig. S1p). Together, these results indicate that YFP+ cells in Ankrd11nchet and Ankrd11ncko embryos behave as cardiac neural crest cells, although Ankrd11ncko CNCCs exhibit delayed condensation and OFT septation. + +2. It is known that ablation of neural crest cells resulted in persistent truncus arteriosus, mis-patterning of the great vessels, outflow malalignments, and hypoplasia or aplasia of the pharyngeal glands. If Ankrd11ablation in the neural crest cells is not killing the cells but is affecting exclusively the cardiovascular development then hypoplasia of thymus, thyroid, and parathyroid glands, should not be present. How are the thymus, thyroid, and parathyroid glands in the ncko animals? If they are normal, this will reinforce that the effect is on cardiac development specifically. I understand that craniofacial abnormalities are also seen in these mice, but those are also seen in KBG syndrome, hence expected. + +Thank you for this great suggestion. We were successful in analyzing the sizes of the thymus at E18.5, which did not differ between control and Ankrd11ncko embryos (page 6, new Fig. S1a- c). + +3. Something that maybe problematic is that when you look into the information on B6.Cg- E2f1Tg(Wnt1-Cre)2Sor/J Strain #022501Common Name: B6 Wnt1- Cre2 https://www.informatics.jax.org/allele/MGI:5485027?recomRibbon=open): you find + +cardiovascular system pulmonary trunk hypoplasia (J:298597) • about \(5\%\) of mutants show a hypoplastic pulmonary trunk at E15.5 and E16.5 interrupted aortic arch, type b (J:298597) • about \(30\%\) of mutants exhibit interrupted aortic arch, type b at E15.5 and E16.5 abnormal conotruncal ridge morphology (J:298597) • the number of neural crest cells in the proximal outflow tract cushions is reduced at E11.5 + +<--- Page Split ---> + +double outlet right ventricle (J:298597) - all mutants exhibit the double outlet right ventricle at E15.5 and E16.5 ventricular septal defect (J:298597) - all mutants exhibit a ventricular septal defect at E15.5 and E16.5 + +If https://www.jax.org/strain/022501 is not the strain used, please clarify. + +Thank you for your comment. The phenotypes quoted above were taken from mouse models that used the Wnt1Cre2 driver to ablate other genes. Fore example, J:298597 refers to an mouse model with this allelic composition: Chd7tm2a(EUCOMM)Wtsi/Chd7tm2a(EUCOMM)Wtsi/E2f1Tg(Wnt1- cre)2Sor/E2f1+/Gt(ROSA)26Sortm4(ACTB- tdTomato,- EGFP)Luo/Gt(ROSA)26Sor+. This creates a knockout of the Chd7 allele using the Wnt1Cre2 driver. Upon publication of this manuscript, Ankrd11nck0 phenotypes described in this report will be similarly captured in the MGI database. + +4. Ankrd11 nchet embryos (Ankrd11fl/WT; Wnt1Cre2) showed normal OFT septation, how many embryos were analyzed? There are some haploinsufficiency Ankrd11 related to KBG syndrome presenting heart abnormalities (Digilio MC, et al.. Am J Med Genet A. 2022 Apr;188(4):1149-1159). It is strange that no defect is seen in heterozygous animals. + +At E18.5, we have dissected 9 Ankrd11WT/WT, 29 Ankrd11nchet, and 40 Ankrd11nck0 embryos, and we found septation defects only in Ankrd11nck0 hearts (updated page 6). While we have not observed severe cardiac defects in the Ankrd11nchet mice, it is possible that they may have subtle defects that we were not able to identify using our analysis techniques. Furthermore, multiple cell types contribute to heart development. Ankrd11nck0 mice only had Ankrd11 ablation in the neural crest. The effect of Ankrd11 on other heart cell types is still unknown. Therefore, the cardiac phenotype in KBG patients may be compounded by defects in all the heart cell types, leading to a more severe phenotype. This is reflected in Discussion, page 14. + +Minor issues: + +1. Embryonic hearts at E18.5 were analyzed for anatomical anomalies: all Ankrd11nck0 embryos exhibited a persistent truncus arteriosus (PTA). How many? + +At E18.5, we have dissected 9 Ankrd11WT/WT, 29 Ankrd11nchet, and 40 Ankrd11nck0 embryos, and we found PTA in all Ankrd11nck0 hearts. + +2. Supplemental Figure 3: not sure that the image for the wt and the Ankrd11 ncko embryos are in the same plane, hence comparable. + +Thank you for this comment. Due to expansion of the manuscript and since reviewer 2 has also expressed concerns about these images, we have removed these results and associated conclusions from the manuscript to remove confusion. + +3. Figure 3 A and D seem to show a different area for the distal part (white squares). + +Thank you for the insightful comment. For analysis, all CNCCs in the OFT mesenchymal were counted. However, due to the rarity of TUNEL+ cells, we needed to use different regions of the OFT for magnified images to show these cells. + +<--- Page Split ---> + +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +If the authors can explain the points raised, I think it is a good work. Main concern is if the phenotype observed (that is very well documented) is related to Ankrd11 ablation. + +- Is the methodology sound? Does the work meet the expected standards in your field? Yes + +- Is there enough detail provided in the methods for the work to be reproduced? Yes + +Thank you for this positive feedback. As we replied above, the phenotypes quoted above were taken from mouse models that used the Wnt1Cre2 driver to ablate other genes. For example, J:298597 refers to an mouse model with this allelic composition: + +Chd7tm2a(EUCOMM)Wtsi/Chd7tm2a(EUCOMM)Wtsi/E2f1Tg(Wnt1- cre)2Sor/E2f1+/Gt(ROSA)26Sortm4(ACTB- tdTomato,- EGFP)Luo/Gt(ROSA)26Sor+. This creates a knockout of the Chd7 allele using the Wnt1Cre2 driver. Upon publication of this manuscript, Ankrd11nck0 phenotypes described in this report will be similarly captured in the MGI database. + +## References: + +1 Jiang, X., Rowitch Dh Fau - Soriano, P., Soriano P Fau - McMahon, A. P., McMahon Ap Fau - Sucov, H. M. & Sucov, H. M. Fate of the mammalian cardiac neural crest. Development 127 (2000). 2 Darrigrand, J. F. et al. Dullard- mediated Smad1/5/8 inhibition controls mouse cardiac neural crest cells condensation and outflow tract septation. Elife 9, doi:10.7554/elife.50325 (2020). 3 Liu, X. et al. Single- Cell RNA- Seq of the Developing Cardiac Outflow Tract Reveals Convergent Development of the Vascular Smooth Muscle Cells. Cell Rep 28, 1346- 1361 e1344, doi:10.1016/j.celrep.2019.06.092 (2019). 4 Neeb, Z., Lajiness, J. D., Bolanis, E. & Conway, S. J. Cardiac outflow tract anomalies. Wiley Interdiscip Rev Dev Biol 2, 499- 530, doi:10.1002/wdev.98 (2013). 5 Zaffran, S., Robrini, N. & Bertrand, N. Retinoids and Cardiac Development. 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Regulation of Sema3c and the Interaction between Cardiac Neural Crest and Second Heart Field during Outflow Tract Development. Sci Rep 7, 6771, doi:10.1038/s41598- 017- 06964- 9 (2017).33 Delloye- Bourgeois, C. et al. Microenvironment- Driven Shift of Cohesion/Detachment Balance within Tumors Induces a Switch toward Metastasis in Neuroblastoma. Cancer Cell 32, 427- 443 e428, doi:10.1016/j.ccell.2017.09.006 (2017).34 Kaartinen, V. et al. Cardiac outflow tract defects in mice lacking ALK2 in neural crest cells. Development 131, 3481- 3490, doi:10.1242/dev.01214 (2004). + +<--- Page Split ---> + +35 Lewis, A. E., Vasudevan, H. N., O'Neill, A. K., Soriano, P. & Bush, J. O. The widely used Wnt1- Cre transgene causes developmental phenotypes by ectopic activation of Wnt signaling. Dev Biol 379, 229- 234, doi:10.1016/j.ydbio.2013.04.026 (2013). + +36 Wang, J. et al. Defective ALK5 signaling in the neural crest leads to increased postmigratory neural crest cell apoptosis and severe outflow tract defects. BMC Dev Biol 6, 51, doi:10.1186/1471- 213X- 6- 51 (2006). + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +In this revised manuscript, Kibalnyk and colleagues continue to explore the role Ankrd11 in cardiac neural crest cells. As mentioned by Reviewer 2, this is an extension of the group's work published in 2021. I appreciate the effort the authors put into the revised manuscript. The pathways identified as dysregulated in the original manuscript are supported with additional analyses/staining. However, some of their response does not really address the original comments directly. + +In figure 1J - I would have expected Ankrd11 to be preserved in non- lineage traced/neural crest- derived cells. However, I do not see any any signal for Ankrd11 in the cells outside the indicated neural crest prongs.... (especially since it is predicted to be broadly expressed by the single cell RNA seq data and external expression datasets). Additional pictures and/or changing the color of the DAPI signal (to generate more contrast between the RNA signal and DAPI) might be helpful. In addition, I appreciate the reduction in pSMAD 1/5/8+ and pS6+ cells in the mutant OFT at E11.5 relative to controls. However, the normalization by E12.5 suggests that perhaps the slight alteration in BMP signaling or mTORC which is normalized may not be relevant to the dramatic separation defect observed. + +The MERFISH identifies additional dysregulated pathways and changes in cellular populations. However, my comment originally that the work is mostly descriptive and the MERFISH does not address how Ankrd11 KO causally results in disrupted OFT septation. It is understandable (and perhaps expected) that treating pregnant dams will prove to be difficult and hence my suggestion to consider an explant model to normalize some fraction of relevant gene expression and/or proxy of neural crest behavior (and not necessarily septation). As the authors suggest, it is possible that the control datasets are useful to the community. + +Reviewer #2 (Remarks to the Author): + +In this revised manuscript, the authors have reframed the conclusions made in the original submission. The revised text describes changes observed in different signaling pathways, and hypothesizes their role in proper OFT septation. The addition of MERFISH data is extremely useful to contextualize the in vivo findings. Overall, I am satisfied by the authors' response to my original comments. + +This work will be useful for scientists studying outflow tract development. I commend the authors on their revision experiments. + +Reviewer #2 (Remarks on code availability): + +While I did not run the code, I scanned through it. The code looks okay to me, although it can benefit from more comments. + +Reviewer #3 (Remarks to the Author): + +Very interesting and informative work. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +In this revised manuscript, Kibalnyk and colleagues continue to explore the role Ankrd11 in cardiac neural crest cells. As mentioned by Reviewer 2, this is an extension of the group's work published in 2021. I appreciate the effort the authors put into the revised manuscript. The pathways identified as dysregulated in the original manuscript are supported with additional analyses/staining. However, some of their response does not really address the original comments directly. + +In figure 1J - I would have expected Ankrd11 to be preserved in non- lineage traced/neural crestederived cells. However, I do not see any any signal for Ankrd11 in the cells outside the indicated neural crest prongs.... (especially since it is predicted to be broadly expressed by the single cell RNA seq data and external expression datasets). Additional pictures and/or changing the color of the DAPI signal (to generate more contrast between the RNA signal and DAPI) might be helpful. + +Thank you for this insightful comment. We apologize for not presenting clear images from various OFT compartments. As requested, we changed the colors and separated channel images for the Ankrd11 mRNA and DAPI in order to make the Ankrd11 signal more visible (Fig. 1i- 1). We also added additional zoomed in images of the OFT myocardium (Fig. 1i"- 1") and neural tube (Fig. 1n- o), which show preserved Ankrd11 signal in the Ankrd11nckonon- neural crestederived cells. This mirrors successful recombination in CNCCs and absence of recombination in non- neural crest derived tissues like myocardium as assessed by YFP immunostaining (Figs. 3- 6). Importantly, our MERFISH results show a reduction in Sema3c, a critical regulator of CNCC condensation and OFT septation, only in CNCCs and not OFT myocardium (Fig. S6). Furthermore, we show perturbations in pSmad1/5/8, pS6, pSmad2/3 and CRABP only in E11.5 CNCCs with apparently comparable levels in OFT myocardium (Figs. 4a- h, 5a- h, 6a- h and S4a- h). Finally, human patients with ANKRD11 loss- of- function variants display heart defects in tissues that are derived from or shaped by the CNCCs, such as dysplastic valves, ventricular septal defects (VSD), aortic coarctation and patent ductus arteriosus 1. Therefore, our data converge from and are supported by several independent lines of evidence. + +We have reflected new data in Fig. 1i- o and associated text in lines 141- 145 ("Furthermore, the non- neural crest- derived OFT myocardium and neural tube tissue showed comparable Ankrd11 signal in control and Ankrd11nckon embryos (Fig. 1i"- 1", n- o).") + +In addition, I appreciate the reduction in pSMAD 1/5/8+ and pS6+ cells in the mutant OFT at E11.5 relative to controls. However, the normalization by E12.5 suggests that perhaps the slight alteration in BMP signaling or mTORC which is normalized may not be relevant to the dramatic separation defect observed. + +Thank you for the comment. Any tissue morphogenesis, including OFT morphogenesis, requires the developmental processes, such as mesenchymal condensation, to occur at precise developmental time windows 2- 6. A delay in gene expression patterns, which control developmental dynamics, has been strongly linked to pathobiological mechanisms of various developmental disorders 2- 5. While OFT condensation delay has not been studied extensively, Darrigand et al. found that activation of BMP signalling doubled pSmad1/5/8 levels in CNCCs at + +<--- Page Split ---> + +E11.5, leading to premature CNCC condensation and asymmetric OFT septation, causing pulmonary stenosis \(^{6}\) . Our findings support these results by showing that a \(50\%\) reduction in pSmad1/5/8+ cells (proxy for BMP signalling) in Ankrd11 \(^{nck0}\) OFT mesenchymal at E11.5 correlated with delayed CNCC condensation, since both the pSmad1/5/8 signal and condensation were restored at E12.5. Furthermore, Darrigrand et al. found that the BMP pathway at least in part regulated Sema3c expression, a crucial chemoattractant for CNCC condensation and OFT septation, where overactivation of BMP signaling in CNCCs caused increased Sema3C expression, contributing to an overcondensation phenotype \(^{6}\) . Notably, Sema3c was reduced in the Ankrd11 \(^{nck0}\) OFT in MERFISH and RNA scope results (Figs. S6, 8), correlating with the impaired condensation phenotype. This provides evidence that the fine- tuning of BMP signalling is important for OFT condensation, and small changes to the signal level can cause defects in the condensation and consequent septation process. Notably, there are no studies investigating how mTORC1 fine- tuning affects OFT septation. We have highlighted this in the discussion on lines 495- 508: + +"Neural crest- specific ablation of Ctdnep1, a BMP inhibitor, causes an opposing phenotype to the defects observed in the Ankrd11 \(^{nck0}\) embryos, specifically premature CNCC condensation and asymmetric AP septum formation, as well as increased pSmad1/5/8 activity \(^{6}\) . Furthermore, the BMP pathway was found to at least in part regulate Sema3c expression \(^{6}\) , a crucial factor for CNCC condensation that was downregulated in the Ankrd11 \(^{nck0}\) OFT in MERFISH and RNA scope results. Sema3C is a glycoprotein that is secreted within the OFT and pharyngeal arches, and is considered a chemoattractant guidance signal to promote CNCC migration into these structures, their condensation within the cardiac cushions and their migration to create the AP septum \(^{6 - 10}\) . Overactivation of BMP signaling in CNCCs causes increased Sema3C expression, contributing to an overcondensation phenotype \(^{6}\) . This suggests that the BMP signaling deficiency observed in Ankrd11 \(^{nck0}\) CNCCs may at least in part lead to their delayed condensation. Together, this provides evidence that the fine- tuning of BMP signalling is important for OFT condensation, and relatively small changes to the signal level can cause defects in the condensation and consequent septation process." + +The MERFISH identifies additional dysregulated pathways and changes in cellular populations. However, my comment originally that the work is mostly descriptive and the MERFISH does not address how Ankrd11 KO causally results in disrupted OFT septation. It is understandable (and perhaps expected) that treating pregnant dams will prove to be difficult and hence my suggestion to consider an explant model to normalize some fraction of relevant gene expression and/or proxy of neural crest behavior (and not necessarily septation). As the authors suggest, it is possible that the control datasets are useful to the community. + +Thank you for this suggestion. We would have also liked to perform explant studies. There are several caveats with this approach that precluded us from pursuing these experiments. First, as we have highlighted in our first response to reviewers, our in vivo results do not show differences in CNCC proliferation, apoptosis or migration, which are primary outcome measures in neural crest explants \(^{7,11}\) . Furthermore, we have performed bulk RNA- seq on entire OFT dissected from E11.25 Ankrd11 \(^{Control}\) and Ankrd11 \(^{nck0}\) embryos (data not shown), which did not show statistically significant changes in global gene expression except for three genes whose role in OFT morphogenesis is not known (Spock1, Mctp2, Shc4). This is most probably due to the presence of a large amount of non- neural crest derived cells and/or lack of spatial resolution. + +<--- Page Split ---> + +This is supported by our MERFISH results, which show e.g. a reduction in Sema3c only in CNCCs and not OFT myocardium (Fig. S6). This further supports the choice of single cell spatial transcriptomics experiments to probe the role of Ankrd11 in CNCC gene expression (Figs. 7- 8, S6). + +We thank the reviewer for highlighting the utility of our control datasets for the research community. Our work is also contributing to the field of OFT morphogenesis by chromatin regulators, like Ankrd11, and to the understanding of pathobiological mechanisms of KBG syndrome. + +## References: + +1 Digilio, M. C. et al. Congenital heart defects in molecularly confirmed KBG syndrome patients. Am J Med Genet A, doi:10.1002/ajmg.a.62632 (2021). 2 Chojnowski, J. L. et al. Multiple roles for HOXA3 in regulating thymus and parathyroid differentiation and morphogenesis in mouse. Development 141, 3697- 3708, doi:10.1242/dev.110833 (2014). 3 Gao, G. et al. Isthmin- 1 (Ism1) modulates renal branching morphogenesis and mesenchyme condensation during early kidney development. Nat Commun 14, 2378, doi:10.1038/s41467- 023- 37992- x (2023). 4 Hinton, R. J. Genes that regulate morphogenesis and growth of the temporomandibular joint: a review. Dev Dyn 243, 864- 874, doi:10.1002/dvdy.24130 (2014). 5 Kathiriya, I. S. & Srivastava, D. Left- right asymmetry and cardiac looping: implications for cardiac development and congenital heart disease. Am J Med Genet 97, 271- 279, doi:10.1002/1096- 8628(200024)97:4<271::aid- ajmg1277>3.0. co;2- o (2000). 6 Darrigrand, J. F. et al. Dullard- mediated Smad1/5/8 inhibition controls mouse cardiac neural crest cells condensation and outflow tract septation. Elife 9, doi:10.7554/eLife.50325 (2020). 7 Plein, A. et al. Neural crest- derived SEMA3C activates endothelial NRP1 for cardiac outflow tract septation. J Clin Invest 125, 2661- 2676, doi:10.1172/JCI79668 (2015). 8 Toyofuku, T. et al. Repulsive and attractive semaphorins cooperate to direct the navigation of cardiac neural crest cells. Dev Biol 321, 251- 262, doi:10.1016/j.ydbio.2008.06.028 (2008). 9 Kodo, K. et al. Regulation of Sema3c and the Interaction between Cardiac Neural Crest and Second Heart Field during Outflow Tract Development. Sci Rep 7, 6771, doi:10.1038/s41598- 017- 06964- 9 (2017). 10 Delloye- Bourgeois, C. et al. Microenvironment- Driven Shift of Cohesion/Detachment Balance within Tumors Induces a Switch toward Metastasis in Neuroblastoma. Cancer Cell 32, 427- 443 e428, doi:10.1016/j.ccell.2017.09.006 (2017). 11 He, F. & Soriano, P. A critical role for PDGFRalpha signaling in medial nasal process development. PLoS Genet 9, e1003851, doi:10.1371/journal.pgen.1003851 (2013). + +<--- Page Split ---> diff --git a/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8658f074546d5fedcec34f74f08bb2f35d9376fd --- /dev/null +++ b/peer_reviews/deaed6fedf739c81b124b7cdb01817de4f3bcb39b1989b4e8f693ba99bc65535/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,590 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[106, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[108, 155, 890, 210]]<|/det|> +The chromatin regulator Ankrd11 controls cardiac neural crest cell- mediated outflow tract remodeling and heart function + +<|ref|>image<|/ref|><|det|>[[95, 732, 262, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[271, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 88, 305, 103]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 118, 403, 133]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 147, 867, 313]]<|/det|> +In this manuscript, Kibalnyk and colleagues study Ankrd11 in cardiac neural crest cells. They knock out the gene using the Wnt1Cre2 allele and characterize the cardiac defects caused by loss of Ankrd11. Their data show that loss of Ankrd11 in neural crest cells results in outflow tract defects (though the authors may be more precise whether the types of conotruncal defects observed in their mice are also observed in humans). Their analysis nominates at least 3 pathways which are dysregulated upon Ankrd11 deletion. Overall, the manuscript is well- written and the figures easy to follow. The immunohistochemistry is of high quality and quantification of various defects is provided. My major concern with the manuscript relate to the conceptual advance provided by the manuscript. For example, it is that it is unclear if any of the pathways shown to be dysregulated in the mutant embryos are causative of phenotype. I think experiments trying to address that point would substantially improve the impact of the manuscript. Major points for the authors to consider: + +<|ref|>text<|/ref|><|det|>[[115, 327, 870, 357]]<|/det|> +1. The authors should provide evidence that Ankrd11 transcript, or ideally protein, is absent in neural crest cells. + +<|ref|>text<|/ref|><|det|>[[115, 371, 855, 447]]<|/det|> +2. The authors implicate three candidate pathways, Sema3C, BMP and mTOR - on the basis of differences in expression levels observed in immunohistochemistry. The strength of these findings would be bolstered with orthogonal evidence of pathways involvement. For example - immunohistochemistry of target genes and/or qPCR/immunoblotting for relevant pathway effectors from dissected tissue. + +<|ref|>text<|/ref|><|det|>[[115, 461, 879, 536]]<|/det|> +3. The conceptual impact of the manuscript would be significantly improved if the authors could nominate a causal pathway in development in (some) aspect of the phenotypes observed. Could the authors turn to an explant system and determine whether restoration of BMP or mTOR levels prevents aspects of the phenotype? For example, given the OFT cushion defects, are valve defects observed (as observed in patients) and if so, is there a loss of EMT? Is this mediated by BMP and/or mTOR? + +<|ref|>text<|/ref|><|det|>[[115, 550, 877, 580]]<|/det|> +4. The Sema3C RNA-scope is difficult to visualize. The authors may consider changing the pseudocolor of the Sema3C probe and DAPI to better visualize the Sema3C signal. + +<|ref|>text<|/ref|><|det|>[[116, 624, 402, 639]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 654, 880, 760]]<|/det|> +In this paper, Kibalnyk and colleagues characterize the role of the chromatin regulator gene Ankrd11 in cardiovascular development. By using a combination of \(\mu \mathrm{CT}\) and mouse genetics, the authors show that homozygous loss of Ankrd11 results in persistent truncus arteriosus, amongst other cardiac abnormalities, with \(100\%\) penetrance. They hypothesize that this phenotype is not a result of aberrant proliferation or apoptosis of cardiac neural crest cells, but that of delayed organization in the outflow tract. Finally, through immunostainings for two effector proteins, pSmad and pS6, the authors conclude that BMP and mTOR signaling pathways play a role in proper outflow tract septation. + +<|ref|>text<|/ref|><|det|>[[115, 774, 872, 895]]<|/det|> +While the title and introduction promise to tackle the very important question of how chromatin regulators affect cardiac neural crest development, the manuscript falls short of addressing this question. Instead, the authors simply describe the phenotypes they observed in a heterozygous and homozygous mutant for Ankrd11. This mouse model appears to have been previously described by this lab in a recent 2021 paper, where they looked at craniofacial defects in Ankrd11 mutant background. The conclusions drawn by the paper, in the absence of any mechanistic insights on how Ankrd11 interacts with BMP and mTOR signaling, are a mere validation of previous studies that have shown these signaling pathways to be important for cardiovascular development. Even the analysis in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 872, 150]]<|/det|> +figure 5N was previously described by Darrigrand and colleagues. It is unclear to this reviewer as to how this paper advances the field and fits within the scope of Nature Communications. I encourage the authors to work out the mechanism by which Ankrd11 is recruiting BMP and/or mTOR signaling in regulating OFT septation. + +<|ref|>text<|/ref|><|det|>[[115, 163, 504, 178]]<|/det|> +More specific comments and issues are listed below: + +<|ref|>text<|/ref|><|det|>[[115, 193, 878, 298]]<|/det|> +1. Lines 122-124: The authors use Fig.S1C-E as evidence for Ankrd11 expression in the cardiac neural crest. However, it seems that only a subset of cells have any RNAscope signal. Using the authors' approach of quantifying RNAscope signal in sections, I wonder what percentage of cardiac crest cells actually express Ankrd11? The scRNA-seq from the Adameyko lab would suggest that a greater proportion of cells express this gene, at least at earlier stages. Is Ankrd11 lost from the cardiac crest? If so, how does that explain the phenotypes described in the paper? Please quantify the signal and report what proportion of cells express Ankrd11. + +<|ref|>text<|/ref|><|det|>[[115, 312, 875, 342]]<|/det|> +2. Lines 142-144: What is the number/proportion of SMA+/YFP+ cells in WT and Ankrd11ncko mutant embryos? Please quantify and report the difference, or lack thereof, in the paper. + +<|ref|>text<|/ref|><|det|>[[115, 357, 866, 431]]<|/det|> +3. Lines 191-192: The conclusion authors draw here is confusing. Why would a greater proportion of the outflow tract be colonized by cardiac neural crest cells (supp figure 3d) if the overall number of cardiac neural crest cells is reduced (figures 3-4)? On a similar note, how would the observation of unperturbed distance of CNCC migration into the outflow tract be explained by "...a modest defect in migration rather than abnormal proliferation or apoptosis..."? + +<|ref|>text<|/ref|><|det|>[[115, 446, 850, 491]]<|/det|> +4. What structural features were used to define proximal, medial, and distal regions of the outflow tract? Given the marginally significant differences reported in figures 3 and 4, this reviewer is concerned that the results may have a confounding variable. + +<|ref|>text<|/ref|><|det|>[[115, 505, 879, 550]]<|/det|> +5. Lines 539-540: On that note, how were the YFP+ cells quantified? More information in the materials and methods section is warranted. Given that the mesenchymal cells in the heart tend to condense, segmenting cytoplasmic signal can result in quantification errors. + +<|ref|>text<|/ref|><|det|>[[115, 565, 866, 610]]<|/det|> +6. If the cardiac neural crest occupation of the outflow tract seemed to recover in the mutant background, could the septation process also be delayed? How late was the phenotype characterized in sections? + +<|ref|>text<|/ref|><|det|>[[115, 625, 866, 685]]<|/det|> +7. It is unclear why the authors chose to only quantify their phenotypes at the medial level of the outflow tract in figure 7. Also, the pSmad fluorescence intensity should be normalized to the number of YFP+ cells within the ROI and reported as a proportion similar to panel 7N to rule out potential effects due to reduced cell numbers. + +<|ref|>text<|/ref|><|det|>[[115, 700, 870, 760]]<|/det|> +8. This reviewer would like to see the raw data that was used to perform statistical analysis to ensure that conditions for using a parametric test on a small sample size were met. The data plotted in the figures suggest unequal variance between samples, which doesn't seem to have been considered in the authors' choice of statistical test. + +<|ref|>text<|/ref|><|det|>[[116, 804, 402, 819]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 834, 872, 893]]<|/det|> +In this study the authors claim that Ankrd11 is a critical regulator of heart development. Ankrd11 is a chromatin regulator related to KBG syndrome which clinical manifestation includes, macrodontia, craniofacial findings, short stature, skeletal anomalies, global developmental delay, seizures, and intellectual disability. Heart anomalies were initially described in a minor proportion (Sirmaci, A., et al. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 879, 120]]<|/det|> +Am. J. Hum. Genet. 89: 289- 294, 2011), but now is found in \(\sim 44\%\) of KBG patients (Digilio MC, et al. Am J Med Genet A. 2022 Apr;188(4):1149- 1159). + +<|ref|>text<|/ref|><|det|>[[117, 120, 377, 134]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[114, 135, 864, 178]]<|/det|> +The authors showed that ablation of Ankrd11 in the murine neural crest is related to aberrant heart development and function. This is the main result. In addition, the characterization an abnormal signaling pathways pinpoint the molecular mechanism that may be involved. + +<|ref|>text<|/ref|><|det|>[[116, 179, 800, 193]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the + +<|ref|>text<|/ref|><|det|>[[117, 193, 740, 207]]<|/det|> +established literature? If the work is not original, please provide relevant references. + +<|ref|>text<|/ref|><|det|>[[116, 208, 861, 237]]<|/det|> +The work is original. The cardiac defects are more severe than the ones observed in KBG syndrome, but that difference may be related to gene dosage. + +<|ref|>text<|/ref|><|det|>[[116, 238, 752, 252]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed + +<|ref|>text<|/ref|><|det|>[[115, 253, 877, 312]]<|/det|> +1. One concern is that the ablation of Ankrd11 is very detrimental by itself. Ankrd11 KO animals don't survive. So, maybe the ablation of Ankrd11 is killing the cardiac neural crest cells. It seems not to be the case since YFP markers are present in the ncko embryos, but YPF expression is a reporter for wnt1 expression, and maybe ectopic expression of wnt1 is marking other cells. + +<|ref|>text<|/ref|><|det|>[[115, 327, 882, 433]]<|/det|> +2. It is known that ablation of neural crest cells resulted in persistent truncus arteriosus, mis-patterning of the great vessels, outflow malalignments, and hypoplasia or aplasia of the pharyngeal glands. If Ankrd11ablation in the neural crest cells is not killing the cells but is affecting exclusively the cardiovascular development then hypoplasia of thymus, thyroid, and parathyroid glands, should not be present. How are the thymus, thyroid, and parathyroid glands in the ncko animals? If they are normal, this will reinforce that the effect is on cardiac development specifically. I understand that craniofacial abnormalities are also seen in these mice, but those are also seen in KBG syndrome, hence expected. + +<|ref|>text<|/ref|><|det|>[[115, 447, 794, 492]]<|/det|> +3. Something that maybe problematic is that when you look into the information on B6.Cg-E2f1Tg(Wnt1-Cre)2Sor/J Strain #022501Common Name: B6 Wnt1-Cre2 https://www.informatics.jax.org/allele/MGI:5485027?recomRibbon=open): you find + +<|ref|>text<|/ref|><|det|>[[115, 506, 281, 520]]<|/det|> +cardiovascular system + +<|ref|>text<|/ref|><|det|>[[115, 521, 420, 535]]<|/det|> +pulmonary trunk hypoplasia (J:298597) + +<|ref|>text<|/ref|><|det|>[[115, 536, 710, 565]]<|/det|> +- about \(5\%\) of mutants show a hypoplastic pulmonary trunk at E15.5 and E16.5 interrupted aortic arch, type b (J:298597) + +<|ref|>text<|/ref|><|det|>[[115, 566, 730, 595]]<|/det|> +- about \(30\%\) of mutants exhibit interrupted aortic arch, type b at E15.5 and E16.5 abnormal conotruncal ridge morphology (J:298597) + +<|ref|>text<|/ref|><|det|>[[115, 596, 800, 625]]<|/det|> +- the number of neural crest cells in the proximal outflow tract cushions is reduced at E11.5 double outlet right ventricle (J:298597) + +<|ref|>text<|/ref|><|det|>[[115, 626, 656, 640]]<|/det|> +- all mutants exhibit the double outlet right ventricle at E15.5 and E16.5 + +<|ref|>text<|/ref|><|det|>[[115, 641, 390, 655]]<|/det|> +ventricular septal defect (J:298597) + +<|ref|>text<|/ref|><|det|>[[115, 656, 614, 670]]<|/det|> +- all mutants exhibit a ventricular septal defect at E15.5 and E16.5 + +<|ref|>text<|/ref|><|det|>[[115, 685, 668, 700]]<|/det|> +If https://www.jax.org/strain/022501 is not the strain used, please clarify. + +<|ref|>text<|/ref|><|det|>[[115, 701, 881, 760]]<|/det|> +4. Ankrd11 nchet embryos (Ankrd11fl/WT; Wnt1Cre2) showed normal OFT septation, how many embryos were analyzed? There are some haploinsufficiency Ankrd11 related to KBG syndrome presenting heart abnormalities (Digilio MC, et al.. Am J Med Genet A. 2022 Apr;188(4):1149-1159). It is strange that no defect is seen in heterozygous animals. + +<|ref|>text<|/ref|><|det|>[[115, 761, 213, 773]]<|/det|> +Minor issues: + +<|ref|>text<|/ref|><|det|>[[115, 775, 839, 804]]<|/det|> +1. Embryonic hearts at E18.5 were analyzed for anatomical anomalies: all Ankrd11ncko embryos exhibited a persistent truncus arteriosus (PTA). How many? + +<|ref|>text<|/ref|><|det|>[[115, 805, 857, 834]]<|/det|> +2. Supplemental Figure 3: not sure that the image for the wt and the Ankrd11 ncko embryos are in the same plane, hence comparable. + +<|ref|>text<|/ref|><|det|>[[115, 835, 750, 849]]<|/det|> +3. Figure 3 A and D seem to show a different area for the distal part (white squares). + +<|ref|>text<|/ref|><|det|>[[115, 850, 800, 878]]<|/det|> +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +<|ref|>text<|/ref|><|det|>[[115, 880, 875, 894]]<|/det|> +If the authors can explain the points raised, I think it is a good work. Main concern is if the phenotype + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 800, 160]]<|/det|> +observed (that is very well documented) is related to Ankrd11 ablation.- Is the methodology sound? Does the work meet the expected standards in your field? Yes- Is there enough detail provided in the methods for the work to be reproduced? Yes + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[91, 70, 323, 88]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[91, 105, 394, 123]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[90, 140, 899, 264]]<|/det|> +In this manuscript, Kibalnyk and colleagues study Ankrd11 in cardiac neural crest cells. They knock out the gene using the Wnt1Cre2 allele and characterize the cardiac defects caused by loss of Ankrd11. Their data show that loss of Ankrd11 in neural crest cells results in outflow tract defects (though the authors may be more precise whether the types of conotruncal defects observed in their mice are also observed in humans). Their analysis nominates at least 3 pathways which are dysregulated upon Ankrd11 deletion. Overall, the manuscript is well- written and the figures easy to follow. The immunohistochemistry is of high quality and quantification of various defects is provided. + +<|ref|>text<|/ref|><|det|>[[90, 278, 884, 313]]<|/det|> +We thank the reviewer for providing their constructive feedback and for highlighting the potential of our results. Below we have addressed all raised concerns. + +<|ref|>text<|/ref|><|det|>[[90, 328, 881, 398]]<|/det|> +My major concern with the manuscript relate to the conceptual advance provided by the manuscript. For example, it is that it is unclear if any of the pathways shown to be dysregulated in the mutant embryos are causative of phenotype. I think experiments trying to address that point would substantially improve the impact of the manuscript. Major points for the authors to consider: + +<|ref|>text<|/ref|><|det|>[[90, 414, 888, 450]]<|/det|> +1. The authors should provide evidence that Ankrd11 transcript, or ideally protein, is absent in neural crest cells. + +<|ref|>text<|/ref|><|det|>[[88, 464, 904, 744]]<|/det|> +We thank the reviewer for this suggestion. Unfortunately, there are no good commercial antibodies raised against Ankrd11 that we have been able to validate. Some custom antibodies existed, but they are no longer available. Instead, we have addressed this concern by performing BaseScope, a single- molecule RNA fluorescent in situ hybridization technique and showed that \(\sim 80\%\) of the control (Ankrd11nchet) outflow tract (OFT) mesenchymal cells expressed Ankrd11 mRNA. In contrast, \(\sim 20\%\) of Ankrd11ncko OFT mesenchymal cells expressed Ankrd11 mRNA (new Fig. 1i- j', l). Please note that technical limitations prevented us from counterstaining against YFP to identify neural crest cells, however, the OFT mesenchyme is predominantly composed of YFP+ cells1. The residual Ankrd11 signal in Ankrd11ncko OFT mesenchyme could be due to the presence of second heart field (SHF), nonneural crest derived cells in the OFT mesenchyme1, or incomplete recombination. Notably, a Basescope assay with a negative control probe did not yield a signal (new Fig. 1k). Furthermore, in response to reviewer #2, we further stratified Ankrd11- expressing cells in the control OFT mesenchyme based on the Ankrd11 expression level (new Fig. 1m). Our results demonstrate low, mid, and high Ankrd11- expressing cells (new Fig. 1m). Overall, our BaseScope results are in line with expanded reanalysis of published neural crest single- cell RNA sequencing dataset that also demonstrates low, mid and high Ankrd11- expressing CNCCs (former Fig. S1, now updated Fig. 1a- e). + +<|ref|>text<|/ref|><|det|>[[90, 758, 888, 794]]<|/det|> +We have reflected new data in Fig. 1 and associated text in "Materials and Methods" on pages 16- 17, 19- 20, and "Results" on page 5 + +<|ref|>text<|/ref|><|det|>[[90, 804, 874, 890]]<|/det|> +2. The authors implicate three candidate pathways, Sema3C, BMP and mTOR - on the basis of differences in expression levels observed in immunohistochemistry. The strength of these findings would be bolstered with orthogonal evidence of pathways involvement. For example - immunohistochemistry of target genes and/or qPCR/immunoblotting for relevant pathway effectors from dissected tissue. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 70, 896, 247]]<|/det|> +Thank you for the insightful suggestion. The OFT displays distinct gene expression and signalling pathway activation in distal, medial and proximal areas 2. Therefore, we could not utilize qPCR or immunoblotting techniques from the entire OFT tissue as this does not permit a spatial analysis. We have therefore opted to use some additional immunohistochemistry analysis at E11.5 and E12.5 and have expanded our E11.5 OFT analysis to the single cell spatial transcriptomics technique MERFISH (Multiplexed Error- Robust Fluorescence in situ Hybridization) with a custom 140 target gene panel. This custom panel included genes that are known to be important for OFT development and/or that were previously shown to be expressed in the OFT during the septation process in a scRNAseq dataset 2- 12. These include factors of important signaling pathways, extracellular matrix components, chemokines, transcription and chromatin remodeling factors, and cell type markers (new Table S1). + +<|ref|>text<|/ref|><|det|>[[88, 262, 891, 437]]<|/det|> +With regard to the BMP pathway, MERFISH analysis identified reduced expression of Bmp4, Bmpr2, and Acvr1 in E11.5 Ankrd11ncko CNCCs (new Fig. 8a- c). Furthermore, results in 2 suggest that BMP signaling at least in part controls Sema3c expression. We found downregulated Sema3c in E11.5 Ankrd11ncko CNCCs using MERFISH, which we corroborated with RNAscope (new Fig. 8a- c & S6), indicating a potential downstream effect of impaired BMP signaling. Finally, in response to reviewer #2, we have re- analyzed E11.5 IHC images of pSmad1/5/8, the intracellular effectors of Smad- dependent BMP signaling 2,13,14. New analysis shows reduced proportion of pSmad1/5/8+ CNCCs in E11.5 Ankrd11ncko medial OFT compared to Ankrd11nchet (former Fig. 7, now updated Fig. 4). Altogether, this supports and expands our original conclusion that the BMP pathway is deregulated in Ankrd11ncko CNCCs. + +<|ref|>text<|/ref|><|det|>[[89, 451, 904, 558]]<|/det|> +pS6 remains the gold standard readout of mTOR signaling 15,16, which is what we used in our original submission. Notably, the involvement of the mTOR pathway in OFT development is a recent discovery 12. As such, there are no known direct mTOR targets for cardiac neural crest cells to date. However, Nie 2021 identified that mTOR deletion causes dysregulation of actin dynamics and Smad1/5/8 phosphorylation 12, which were both affected in Ankrd11ncko OFTs (Former Figs. 5, 7; now updated Figs. 3- 5), suggesting a potential crosstalk between mTOR and BMP signaling. + +<|ref|>text<|/ref|><|det|>[[88, 572, 907, 800]]<|/det|> +The MERFISH assay revealed several differentially expressed genes (DEGs) in Ankrd11ncko CNCCs for various signaling pathways known to be important for OFT development, including Wnt (Fzd4, Vangl2, Fzd1), BMP (Id2, Bmp4, Smad7, Bmpr2, Acvr1), TGF- \(\beta\) (Tgf \(\beta\) 2, Smad7), Notch (Heyl, Jag1, Notch1), Hippo (Yap1), JNK (Jun), Retinoic acid (Rcra, Rarg), FGF (Fgfr2), EGFR (Erbb3), and JAK- STAT (Stat3) 2- 12 (new Fig. 8a- c and Table S2). Furthermore, it identified downregulation in neuropilin- 1 (Nrp1), a known receptor for Sema3c 4, which may amplify the effects of the dysregulation (please see above). Other chemokines and growth factors included ephrin A5 (Efna5) and transforming growth factor beta 2 (Tgf \(\beta\) 2) 17,18 (new Fig. 8a- c and Table S2). DEGs also included other transcription and chromatin remodeling factors important for OFT development such as Egr1, Hoxa3, Ets1, Gata4, Sox11, Foxc1 and Chd7 10,19,20, and cytoskeletal or extracellular matrix factors, such as Cdh11, Mmp14, Adamts1, and Adam19 21 (new Fig. 8a- c and Table S2). These results suggest that Ankrd11 ablation affects multiple signaling pathways, transcription factors and chromatin remodelers important for CNCC function and OFT morphogenesis. + +<|ref|>text<|/ref|><|det|>[[89, 816, 904, 921]]<|/det|> +We expanded our IHC analysis to additional signalling pathways and molecules to corroborate some of the MERFISH results. We focused on phosphorylated Smad2/3, the intracellular effectors of Smad- dependent TGF- \(\beta\) signaling 22, and Cellular retinoic acid binding protein 2 (Crabp2), a protein that transports retinoic acid from the cytoplasm to the nucleus, which facilitates retinoic acid signaling 23. We observed asymmetrical pSmad2/3 and Crabp2 signal in control medial parietal (top- right) and septal (bottom- left) OFT cushions at E11.5 (new Figs. 6 and S4). In contrast, E11.5 Ankrd11ncko medial + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 70, 900, 175]]<|/det|> +OFT parietal and septal cushions had similar levels of pSmad2/3 or Crabp2 (new Figs. 6 and S4). While nothing is known about the mechanism behind the pSmad2/3 and Crabp2 asymmetry within CNCCs or its downstream effects on AP septum formation, there is evidence for CNCC asymmetry. Gandhi et al \(^{24}\) observed that ablation of the right cardiac neural folds in chick, which removes CNCCs from the right side of the embryo, produced a more severe septation impairment compared to ablation of the left cardiac neural folds. + +<|ref|>text<|/ref|><|det|>[[90, 192, 890, 280]]<|/det|> +Please note that in response to reviewer #2, we have expanded pS6, pSmad1/5/8, pSmad2/3 and actin dynamics analysis to E12.5 (updated Figs. 3- 5 and S3, new Fig. 6). Overall, our results show comparable levels of pS6, pSmad1/5/8 and pSmad2/3 in E12.5 Ankrd11ncnet and Ankrd11ncno medial OFT cushions (distal cushions were analyzed as well, but only in Ankrd11ncno samples), suggesting a delay in mTOR, BMP and TGF- \(\beta\) signalling pathways and CNCC condensation. + +<|ref|>text<|/ref|><|det|>[[90, 296, 904, 350]]<|/det|> +Overall, we propose that several dysregulated pathways contribute to Ankrd11ncno CNCC delay in condensation and convergence at the midline to form the AP septum, including BMP, mTOR, and TGF- \(\beta\) . + +<|ref|>text<|/ref|><|det|>[[90, 364, 901, 400]]<|/det|> +We have reflected new data in Figs. 4- 8, S3- 4 and associated text in "Materials and Methods" on pages 16- 22, "Results" on pages 8- 11 and "Discussion" on pages 12- 14. + +<|ref|>text<|/ref|><|det|>[[90, 442, 896, 530]]<|/det|> +3. The conceptual impact of the manuscript would be significantly improved if the authors could nominate a causal pathway in development in (some) aspect of the phenotypes observed. Could the authors turn to an explant system and determine whether restoration of BMP or mTOR levels prevents aspects of the phenotype? For example, given the OFT cushion defects, are valve defects observed (as observed in patients) and if so, is there a loss of EMT? Is this mediated by BMP and/or mTOR? + +<|ref|>text<|/ref|><|det|>[[90, 546, 891, 668]]<|/det|> +Thank you for this suggestion. Neural crest cells participate in a strict spatiotemporal control of tissue (OFT) morphogenesis. It has proven difficult to recapitulate our main findings (failure of OFT septation) in an explant culture. We have attempted a neural tube explant to measure Ankrd11ncno neural crest migration, however preliminary results did not show a migration defect (data not shown). This is corroborated by our in vivo findings, where we found small and region- specific decreases in CNCC number in the OFT. Furthermore, the explant system cannot faithfully recapitulate the morphogenesis of AP septation, which is the main affected phenotype in our manuscript. + +<|ref|>text<|/ref|><|det|>[[90, 685, 900, 790]]<|/det|> +Moreover, the MERFISH assay shows a broad set of genes and signalling pathways to be dysregulated in Ankrd11ncno CNCCs (please see above and new Figs. 7- 8, Tables S1- 2). It is thus not feasible to name a nominal pathway as our data suggest ablation of Ankrd11 leads to perturbations in various signalling pathways, extending beyond the originally nominated BMP and mTOR signalling pathways in our original submission. Finally, due to signalling pathway cross- talk, it is difficult to choose a single nominal pathway and rescue strategy. + +<|ref|>text<|/ref|><|det|>[[90, 807, 901, 912]]<|/det|> +Nevertheless, we have attempted pharmacological rescues in vivo, using a BMP agonist Sb4 \(^{25}\) and an mTOR agonist L- leucine \(^{26}\) administration into pregnant dams. Due to previous research showing that Ankrd11 represses the retinoic acid receptor RAR \(\alpha^{27}\) , we also used retinoic acid signaling inhibitor BMS493 \(^{28}\) . None of the experiments resulted in a rescue in Ankrd11ncno embryos (data not shown) and overall proved to be extremely difficult to interpret. This is at least in part due to the pan- effects of these drugs on all tissues, not just CNCCs. As CNCCs and surrounding tissues participate in cross- talk + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 70, 905, 124]]<|/det|> +during OFT morphogenesis, the drugs affect all tissues with active signalling pathway of choice. Moreover, BMP, mTOR and/or RA signalling is vital for proper embryogenesis. Thus, interpretation of results even in control embryos would be very challenging. + +<|ref|>text<|/ref|><|det|>[[90, 140, 900, 280]]<|/det|> +We have therefore re- focussed our efforts on MERFISH and additional IHC analysis. To our knowledge, our report is the first one to apply spatial single cell transcriptomics to OFT septation. Our dataset will be useful for the community- at- large and will provide a rich resource for data mining in control and Ankrd11- deficient embryos (please note that the datasets will be deposited into a public repository and an open visualization website prior to publication; meanwhile, we have uploaded processed and meta- data alongside source code via GitHub). Furthermore, we provide evidence for asymmetric signaling in control OFT cushions involving the TGF- \(\beta\) and retinoic acid pathways, which to our knowledge has not been described previously. + +<|ref|>text<|/ref|><|det|>[[90, 304, 905, 339]]<|/det|> +Overall, our new and expanded results support and extend our work, suggesting that Ankrd11 controls a complex network of genes required for OFT development. + +<|ref|>text<|/ref|><|det|>[[90, 355, 907, 444]]<|/det|> +Finally, we have also analyzed valve development and observed dysplastic valves in 3 of 5 Ankrd11ncko hearts (new Fig. S1d- i). Since these valves appear hypertrophic, this does not suggest a loss of EMT, but rather a failure of the CNCCs to remodel the valves correctly 29, echoing their failure to remodel the AP septum. Based on our OFT signaling pathway results using IHC and MERFISH (updated and/or new Figs. 4- 8), we suspect that this is caused by impairment of multiple pathways. + +<|ref|>text<|/ref|><|det|>[[90, 459, 895, 495]]<|/det|> +We have reflected new data in Figs. S1, S3- 4, 6- 8, Tables S1- S2, and associated text in "Materials and Methods" on pages 16- 22, "Results" on pages 6, 8- 11 and "Discussion" on pages 11- 14. + +<|ref|>text<|/ref|><|det|>[[90, 554, 810, 589]]<|/det|> +4. The Sema3C RNA-scope is difficult to visualize. The authors may consider changing the pseudocolor of the Sema3C probe and DAPI to better visualize the Sema3C signal. + +<|ref|>text<|/ref|><|det|>[[90, 603, 897, 656]]<|/det|> +Thank you for this comment. This has been addressed in new Fig. S6 (former Fig. S4). Moreover, we have added representative Sema3c MERFISH images to this figure, which corroborate our RNA scope findings (MERFISH images in new Fig. S6A, MERFISH results in new Fig. 8). + +<|ref|>text<|/ref|><|det|>[[90, 689, 393, 706]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[90, 723, 904, 845]]<|/det|> +In this paper, Kibalnyk and colleagues characterize the role of the chromatin regulator gene Ankrd11 in cardiovascular development. By using a combination of \(\mu \mathrm{CT}\) and mouse genetics, the authors show that homozygous loss of Ankrd11 results in persistent truncus arteriosus, amongst other cardiac abnormalities, with \(100\%\) penetrance. They hypothesize that this phenotype is not a result of aberrant proliferation or apoptosis of cardiac neural crest cells, but that of delayed organization in the outflow tract. Finally, through immunostainings for two effector proteins, pSmad and pS6, the authors conclude that BMP and mTOR signaling pathways play a role in proper outflow tract septation. + +<|ref|>text<|/ref|><|det|>[[90, 862, 865, 915]]<|/det|> +While the title and introduction promise to tackle the very important question of how chromatin regulators affect cardiac neural crest development, the manuscript falls short of addressing this question. Instead, the authors simply describe the phenotypes they observed in a heterozygous and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 71, 904, 228]]<|/det|> +homozygous mutant for Ankrd11. This mouse model appears to have been previously described by this lab in a recent 2021 paper, where they looked at craniofacial defects in Ankrd11 mutant background. The conclusions drawn by the paper, in the absence of any mechanistic insights on how Ankrd11 interacts with BMP and mTOR signaling, are a mere validation of previous studies that have shown these signaling pathways to be important for cardiovascular development. Even the analysis in figure 5N was previously described by Darrigrand and colleagues. It is unclear to this reviewer as to how this paper advances the field and fits within the scope of Nature Communications. I encourage the authors to work out the mechanism by which Ankrd11 is recruiting BMP and/or mTOR signaling in regulating OFT septation. + +<|ref|>text<|/ref|><|det|>[[90, 244, 905, 297]]<|/det|> +Thank you for your constructive feedback and recommendation. Reviewer #1 has also recommended to "nominate a causal pathway in development in (some) aspect of the phenotypes observed". Our combined response is below: + +<|ref|>text<|/ref|><|det|>[[89, 314, 907, 455]]<|/det|> +Neural crest cells participate in a strict spatiotemporal control of tissue (OFT) morphogenesis. We were unable to use an in vitro system to interrogate the mechanism of Ankrd11 in OFT morphogenesis because the explant system cannot faithfully recapitulate the morphogenesis of AP septation, which is the main affected phenotype in our manuscript. For example, we have attempted a neural tube explant to measure Ankrd11ncko neural crest migration, however preliminary results did not show a migration defect (data not shown). This is corroborated by our in vivo findings, where we found small and region- specific decreases in CNCC number in the OFT. We were thus unable to use explant or other in vitro systems to study the mechanism. + +<|ref|>text<|/ref|><|det|>[[90, 471, 830, 490]]<|/det|> +However, we performed two new major sets of in vivo experiments to address the mechanism. + +<|ref|>text<|/ref|><|det|>[[89, 505, 901, 663]]<|/det|> +First, we performed single cell spatial transcriptomics MERFISH (Multiplexed Error- Robust Fluorescence in situ Hybridization) with a custom 140 target gene panel. This custom panel included genes that are known to be important for OFT development and/or that were previously shown to be expressed in the OFT during the septation process in a scRNAseq dataset2-12. These include factors of important signaling pathways, extracellular matrix components, chemokines, transcription and chromatin remodeling factors, and cell type markers (new Table S1). This technique was chosen due to spatially controlled gene expression in distal, medial and proximal OFT areas2. Therefore, we could not utilize scRNA-seq, qPCR or immunoblotting techniques from entire OFT tissue as they do not permit a spatial analysis. + +<|ref|>text<|/ref|><|det|>[[88, 680, 905, 923]]<|/det|> +The MERFISH assay shows a broad set of genes and signalling pathways to be dysregulated in Ankrd11ncko CNCCs (new Figs. 7- 8, Tables S1- 2). In summary, MERFISH assay revealed several differentially expressed genes (DEGs) in Ankrd11ncko CNCCs for several signaling pathways known to be important for OFT development, including Wnt (Fzd4, Vangl2, Fzd1), BMP (Id2, Bmp4, Smad7, Bmpr2, Acvr1), TGF- \(\beta\) (Tgf\(\beta\)2, Smad7), Notch (Heyl, Jag1, Notch1), Hippo (Yap1), JNK (Jun), Retinoic acid (Rxra, Rarg), FGF (Fgf\(\beta\)2), EGFR (Erbb3), and JAK- STAT (Stat3) 2-12 (new Fig. 8a- c and Table S2). We found DEGs in several growth factors and chemokines. In cluster 2, one of the most downregulated DEGs in Ankrd11ncko cells was Sema3c, which we have corroborated with single molecule FISH (RNA scope) (new Fig. S6). The class 3 Semaphorin C (Sema3C) plays a major role in CNCC migration into the OFT, their condensation in the OFT cushions, and their convergence to create the AP septum, at least in part due to its role as a chemoattractant and aggregation factor 2,30-33. Furthermore, the assay identified downregulation in neuropilin- 1 (Nrp1), a known receptor for Sema3c 4, which may amplify the effects of the dysregulation. Other factors included ephrin A5 (Efna5), which is known to guide neural crest migration, and transforming growth factor beta 2 (Tgf\(\beta\)2), which is + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 70, 900, 194]]<|/det|> +important for OFT morphogenesis \(^{17,18}\) (new Fig. 8a- c and Table S2). DEGs also included other transcription and chromatin remodeling factors important for OFT development such as Egr1, Hoxa3, Ets1, Gata4, Sox11, Foxc1 and Chd7 \(^{10,19,20}\) , and cytoskeletal or extracellular matrix factors, such as Cdh11, Mmp14, Adamts1, and Adam19 \(^{21}\) (new Fig. 8a- c and Table S2). These results suggest that Ankrd11 ablation affects multiple signaling pathways, transcription factors and chromatin remodelers important for CNCC function and OFT morphogenesis, further supporting our expanded IHC results in updated or new Figs. 4- 6. + +<|ref|>text<|/ref|><|det|>[[90, 210, 857, 263]]<|/det|> +Thus, it is unlikely that Ankrd11 controls OFT morphogenesis via BMP and/or mTOR signalling pathways only. It is more likely that Ankrd11 knockout leads to dysregulation of many signalling pathways and their cross- talk. + +<|ref|>text<|/ref|><|det|>[[89, 279, 905, 420]]<|/det|> +In addition, and in response to this reviewer's additional concerns below, we have extended our IHC analysis to distal OFT regions at E11.5 and included medial and distal OFT analysis at E12.5. This analysis showed spatiotemporal differential dysregulation of mTOR (pS6), BMP (pSmad1/5/8), TGF- \(\beta\) (pSmad2/3) and RA (Crabp2) signaling pathways (updated and new Figs. 4- 6, S3- 4). Thus, further mechanistic interrogation of how Ankrd11 recruits BMP, mTOR or other dysregulated signaling during OFT septation will require novel spatial tools as using traditional entire OFT primary cells or explants will not yield spatially resolved specimens for appropriate interpretation of the results. Such further mechanistic work lies outside of the scope of this manuscript. + +<|ref|>text<|/ref|><|det|>[[88, 437, 905, 664]]<|/det|> +Second, we have attempted pharmacological rescues in vivo, using a BMP agonist \(\mathrm{Sb4}^{25}\) and an mTOR agonist L- leucine \(^{26}\) . Due to previous research showing that Ankrd11 represses the retinoic acid receptor \(\mathrm{RAR}\alpha^{27}\) , we also used retinoic acid signaling inhibitor BMS493 \(^{28}\) . None of the experiments resulted in a rescue in Ankrd11 \(^{1\mathrm{nck0}}\) embryos (data not shown) and overall proved to be extremely difficult to interpret. This is at least in part due to the pan- effects of these drugs on all tissues, not just CNCCs. As CNCCs and surrounding tissues participate in cross- talk during OFT morphogenesis, the drugs affect all tissues. Moreover, BMP, mTOR and/or RA signalling is vital for proper embryogenesis. Thus, interpretation of results even in control embryos would be very challenging. Finally, our MERFISH results show a broad set of genes and signalling pathways to be dysregulated in Ankrd11 \(^{1\mathrm{nck0}}\) CNCCs (please see above and new Figs. 7- 8, Tables S1- 2). It is thus not feasible to name a nominal pathway as our data suggest ablation of Ankrd11 leads to perturbations in various signalling pathways, extending beyond the originally nominated BMP and mTOR signalling pathways in our original submission. + +<|ref|>text<|/ref|><|det|>[[88, 680, 904, 907]]<|/det|> +We have therefore re- focussed our efforts on MERFISH and additional IHC analysis. To our knowledge, our report is the first one to apply spatial single cell transcriptomics to OFT septation. Our dataset will be useful for the community- at- large and will provide a rich resource for data mining in control and Ankrd11- deficient embryos (please note that the datasets will be deposited into a public repository and an open visualization website prior to publication; meanwhile, we have uploaded processed and meta- data alongside source code via GitHub). Furthermore, we provide evidence for asymmetric signaling in control OFT cushions involving the TGF- \(\beta\) and retinoic acid pathways, which to our knowledge has not been described previously. Finally, our new results support and expand our original conclusions, and suggest that Ankrd11 controls a complex network of genes required for OFT development. These new datasets have shown known, and more importantly, novel signalling pathways that Ankrd11 controls. In our future work, we will study an in- depth mechanism by which Ankrd11 controls these signalling pathways and gene expression. However, this is outside of the scope of the current manuscript. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 70, 875, 107]]<|/det|> +We have reflected new data in Figs. 4- 8, S3- S4, Tables S1- S2, and associated text in “Materials and Methods” on pages 16- 22, “Results” on pages 8- 11 and “Discussion” on pages 12- 14. + +<|ref|>text<|/ref|><|det|>[[90, 133, 504, 151]]<|/det|> +More specific comments and issues are listed below: + +<|ref|>text<|/ref|><|det|>[[90, 167, 904, 291]]<|/det|> +1. Lines 122-124: The authors use Fig.S1C-E as evidence for Ankrd11 expression in the cardiac neural crest. However, it seems that only a subset of cells have any RNAscope signal. Using the authors' approach of quantifying RNAscope signal in sections, I wonder what percentage of cardiac crest cells actually express Ankrd11? The scRNA-seq from the Adameyko lab would suggest that a greater proportion of cells express this gene, at least at earlier stages. Is Ankrd11 lost from the cardiac crest? If so, how does that explain the phenotypes described in the paper? Please quantify the signal and report what proportion of cells express Ankrd11. + +<|ref|>text<|/ref|><|det|>[[88, 304, 904, 550]]<|/det|> +We thank the reviewer for this suggestion. We have addressed this concern by performing BaseScope, a single- molecule RNA fluorescent in situ hybridization technique and showed that \(\sim 80\%\) of the control (Ankrd11nchet) outflow tract (OFT) mesenchymal cells expressed Ankrd11 mRNA (new Fig. 1i, l). Notably, a Basescope assay with a negative control probe did not yield a signal (new Fig. 1k). Please note that technical limitations prevented us from counterstaining against YFP to identify neural crest cells, however, the OFT mesenchyme is predominantly composed of YFP+ cells1. We further stratified Ankrd11-expressing cells in the control OFT mesenchyme based on the Ankrd11 expression level (new Fig. 1m). Our results demonstrate low, mid and high Ankrd11-expressing cells (Fig. 1m). Re-analysis of published neural crest single-cell RNA sequencing dataset also demonstrates low, mid and high Ankrd11-expressing CNCCs (former Fig. S1, now updated Fig. 1a-e). Notably, in comparison to \(\sim 80\%\) of CNCCs expressing Ankrd11 in control CNCCs, scRNAseq shows that all CNCCs express Ankrd11. This could be due to different methods used (BaseScope vs scRNA-seq), samples (WT in scRNA-seq vs Ankrd11nchet in BaseScope) and/or potential inclusion of second heart field (SHF), nonneural crest derived cells in the OFT mesenchyme1, in BaseScope analysis. + +<|ref|>text<|/ref|><|det|>[[90, 564, 888, 600]]<|/det|> +We have reflected new data in Fig. 1 and associated text in “Materials and Methods” on pages 16- 17, 20, and “Results” on page 5. + +<|ref|>text<|/ref|><|det|>[[90, 608, 855, 644]]<|/det|> +2. Lines 142-144: What is the number/proportion of SMA+/YFP+ cells in WT and Ankrd11ncko mutant embryos? Please quantify and report the difference, or lack thereof, in the paper. + +<|ref|>text<|/ref|><|det|>[[89, 658, 901, 833]]<|/det|> +Thank you for this suggestion. To address this concern, we have performed immunofluorescence analysis of cross sections of E18.5 outflow tract vessels and quantified SMA+/YFP+ cells out of the total SMA+ cells within the proximal (closest to the heart) and distal regions of the vessels (new Fig. S1j-p). In the proximal region, analysis of the αSMA+ (alpha-smooth muscle actin) smooth muscle layer of the E18.5 Ankrd11ncko truncal artery did not show a deficiency of CNCC-derived smooth muscle cells compared to the Ankrd11nchet aortic and pulmonary arteries (new Fig. S1j-p). Although the Ankrd11ncko distal region showed a decreased proportion of smooth muscle cells that are CNCC derived (% αSMA+/YFP+/αSMA+; new Fig. S1n), this was not due to their decreased number (#YFP+/αSMA+; new Fig. S1o), but rather due to an increase in non-CNCC derived smooth muscle cells (#YFP-/αSMA+; new Fig. S1p). + +<|ref|>text<|/ref|><|det|>[[90, 847, 896, 884]]<|/det|> +We have reflected new data in Fig. S1 and associated text in “Materials and Methods” on page 19, and “Results” on page 6. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 70, 894, 158]]<|/det|> +3. Lines 191-192: The conclusion authors draw here is confusing. Why would a greater proportion of the outflow tract be colonized by cardiac neural crest cells (supp figure 3d) if the overall number of cardiac neural crest cells is reduced (figures 3-4)? On a similar note, how would the observation of unperturbed distance of CNCC migration into the outflow tract be explained by "...a modest defect in migration rather than abnormal proliferation or apoptosis..."? + +<|ref|>text<|/ref|><|det|>[[89, 172, 907, 349]]<|/det|> +Thank you for highlighting this and we apologize for the confusion. Former Fig. S3 showed that there are no statistically significant differences in the distance traveled by the first invading cardiac neural crest cells into the proximal outflow tract. This differs from other genetic models of cardiac neural crest deficiency, where the cells are not able to infiltrate the most proximal regions of the OFT, indicating a more severe migration defect \(^{34}\) . This indicates that the Ankrd11 \(^{nck0}\) cardiac neural crest cells have a more subtle migration defect, where the cells were able to populate the full length of the OFT, but in smaller numbers, since proliferation or apoptosis was not affected (Fig. S2a-i; former Fig. 3). This is in line with findings from other genetic models, including Nie et al. \(^{12}\) , which showed that mTOR deletion led to reduced CNCC numbers in the OFT without changes in apoptosis or proliferation prior to E11.5, suggesting that the cell deficit was caused by a migration defect. + +<|ref|>text<|/ref|><|det|>[[90, 364, 899, 400]]<|/det|> +Since reviewer 3 also found concerns with these results, we removed these results from the manuscript to remove confusion, as they are not critical for our conclusions. + +<|ref|>text<|/ref|><|det|>[[90, 416, 863, 469]]<|/det|> +4. What structural features were used to define proximal, medial, and distal regions of the outflow tract? Given the marginally significant differences reported in figures 3 and 4, this reviewer is concerned that the results may have a confounding variable. + +<|ref|>text<|/ref|><|det|>[[90, 485, 883, 538]]<|/det|> +Due to the expansion of the manuscript and the similarity in the results between E10.5 and E11.25 (Figs. 3- 4 in original submission), we have removed the E11.25 data from the manuscript to remove redundancy and confusion between E11.25 and E11.5 ages. E10.5 data are now presented in Fig. S2. + +<|ref|>text<|/ref|><|det|>[[90, 554, 844, 590]]<|/det|> +To address this comment, we have added a detailed description defining the OFT regions to the manuscript and expanded it to include all ages analyzed (E10.5, E11.5, E12.5). + +<|ref|>text<|/ref|><|det|>[[89, 606, 905, 782]]<|/det|> +At E10.5, the proximal OFT region has a small lumen and dispersed CNCCs, the medial region has a large lumen, dispersed CNCCs and a thickened bottom cushion, and the distal region has a large lumen, more compacted CNCCs, and a thickened bottom cushion (Fig. S2a-f). We have therefore used these features to define proximal, medial and distal regions of E10.5 OFT. To analyze anatomically matched sections of Ankrd11 \(^{nchet}\) and Ankrd11 \(^{nck0}\) OFTs at E11.5 and E12.5, the Ankrd11 \(^{nck0}\) distal region was determined to be the equivalent region to the Ankrd11 \(^{nchet}\) septated region based on the number of OFT sections it occupied, and the medial sections used for analysis were adjacent to this boundary. We used this method to avoid relying on the differing morphology between Ankrd11 \(^{nchet}\) and Ankrd11 \(^{nck0}\) OFTs and between embryonic ages. We have addressed this clarification in materials and methods on pages 19- 20. + +<|ref|>text<|/ref|><|det|>[[90, 799, 904, 852]]<|/det|> +5. Lines 539-540: On that note, how were the YFP+ cells quantified? More information in the materials and methods section is warranted. Given that the mesenchymal cells in the heart tend to condense, segmenting cytoplasmic signal can result in quantification errors. + +<|ref|>text<|/ref|><|det|>[[90, 867, 870, 902]]<|/det|> +Cells were identified as YFP+ when YFP+ cytoplasm overlayed with a Hoechst+ nucleus. All cells were counted manually. This clarification is added on page 20. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 70, 899, 123]]<|/det|> +6. If the cardiac neural crest occupation of the outflow tract seemed to recover in the mutant background, could the septation process also be delayed? How late was the phenotype characterized in sections? + +<|ref|>text<|/ref|><|det|>[[90, 140, 899, 210]]<|/det|> +Thank you for the insightful comment. We extended our analysis to E12.5 Ankrd11ncko OFTs. Surprisingly, we found that the very distal edge of E12.5 Ankrd11ncko OFT showed septation (new Fig. 3l-m). However, the septation failed to progress any further, as at E18.5 we observe the persistent truncus arteriosus phenotype characteristic of OFT septation failure (Fig. 2). + +<|ref|>text<|/ref|><|det|>[[88, 227, 903, 594]]<|/det|> +Furthermore, we have extended pS6 and pSmad1/5/8 and added pSmad2/3 signalling analysis to include E12.5 samples as well as distal OFT in both E11.5 and E12.5 samples. With regard to CNCC condensation, the Ankrd11ncko CNCCs in the cardiac cushions in the unseptated distal region at E12.5 were still visibly disorganized (updated Fig. 3p-q). For BMP and mTOR signalling, while E11.5 Ankrd11ncko showed reduced % pS6+ and % pSmad1/5/8+ medial CNCCs compared to Ankrd11nchet, their levels were similar in E12.5 medial CNCCs (updated Figs. 4- 5). For the distal region, we only analyzed Ankrd11ncko cardiac cushions as controls have formed a septum in this area. Unseptated distal region in E12.5 Ankrd11ncko OFT showed pS6 and pSmad1/5/8 signal that was elevated in comparison to the distal region in E11.5 Ankrd11ncko OFT (Fig. 4k- l, 5k- l). Finally, we included new analysis of pSmad2/3, the intracellular effectors of Smad- dependent TGF- \(\beta\) signaling22. We found asymmetric pSmad2/3 signaling in control medial parietal (top- right) and septal (bottom- left) OFT cushions at E11.5 (new Fig. 6). In contrast, E11.5 Ankrd11ncko medial OFT parietal and septal cushions had similar levels of pSmad2. However, by E12.5, Ankrd11ncko medial OFT showed asymmetric pSmad2/3 staining. (new Fig. 6). As described above, for the distal region, we only analyzed Ankrd11ncko cardiac cushions as controls have formed a septum in this area. In the distal region, at both E11.5 and E12.5, we detected comparable levels of pSmad2/3+ CNCCs between Ankrd11ncko parietal and septal cushions (new Fig. 6). Therefore, these results show that the Ankrd11ncko CNCCs display a delay in BMP and mTOR signalling and a delay in asymmetric activation of TGF- \(\beta\) signalling. Even though some signalling was recovered in E12.5 Ankrd11ncko OFT, the Ankrd11ncko AP septum failed to fully establish. This suggests that the Ankrd11ncko CNCCs missed a developmental window necessary for septation progression. + +<|ref|>text<|/ref|><|det|>[[90, 607, 877, 643]]<|/det|> +We have reflected new data in Figs. 3- 6, S3 and associated text in "Materials and Methods" on page 19- 20, "Results" on pages 7- 10 and "Discussion" on pages 12- 14. + +<|ref|>text<|/ref|><|det|>[[90, 670, 905, 740]]<|/det|> +7. It is unclear why the authors chose to only quantify their phenotypes at the medial level of the outflow tract in figure 7. Also, the pSmad fluorescence intensity should be normalized to the number of YFP+ cells within the ROI and reported as a proportion similar to panel 7N to rule out potential effects due to reduced cell numbers. + +<|ref|>text<|/ref|><|det|>[[90, 754, 903, 825]]<|/det|> +Thank you for this suggestion. Since the control distal region does not have OFT cushions due to AP septum formation, we chose to compare the medial regions in both control and Ankrd11ncko cushions to have anatomically matched regions. However, we have extended our analysis to distal regions of Ankrd11ncko OFT cushions (updated Figs. 4- 5, new Figs. 6, S3- 4). + +<|ref|>text<|/ref|><|det|>[[90, 841, 879, 894]]<|/det|> +We have also quantified pSmad1/5/8 signal by setting a signal intensity threshold and only counting marker+ cells that showed a signal above the threshold (former Fig. 7; now updated Fig. 4). This allowed us to count all YFP+ CNCC cells in the OFT mesenchyme and present the results as a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 70, 888, 106]]<|/det|> +proportion of total YFP+ cells. Our new results support our original conclusions and show reduced % of pSmad1/5/8+ CNCCs in medial E11.5 Ankrd11nck CNCCs. + +<|ref|>text<|/ref|><|det|>[[90, 120, 900, 157]]<|/det|> +We have reflected new data in Figs. 4- 5 and associated text in “Materials and Methods” on page 19- 20, “Results” on page 7 and “Discussion” on page 12. + +<|ref|>text<|/ref|><|det|>[[90, 182, 892, 253]]<|/det|> +8. This reviewer would like to see the raw data that was used to perform statistical analysis to ensure that conditions for using a parametric test on a small sample size were met. The data plotted in the figures suggest unequal variance between samples, which doesn't seem to have been considered in the authors' choice of statistical test. + +<|ref|>text<|/ref|><|det|>[[89, 269, 896, 427]]<|/det|> +Thank you for expressing this concern. All IHC data were subjected to normality tests using the Anderson- Darling, D'Agostino & Pearson, and Kolmogorov- Smirnov tests (using Prism) and were found to be normal or have insufficient sample size for these tests and were thus considered normal, except for Fig. S1c, which was then tested using the Mann- Whitney test. Insufficient sample size is typical for biological data as normality tests often require \(>n = 5\) . Our data has typically included \(n = 3 - 4\) biological replicates per genotype. Statistical tests and number of biological replicates is reflected this in Materials and Methods on page 21 and in each figure legend. We have also supplied the data in Source files and details on biological replicates, statistical tests and other parameters in the accompanying reporting summary. + +<|ref|>text<|/ref|><|det|>[[90, 444, 393, 461]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[89, 478, 904, 584]]<|/det|> +In this study the authors claim that Ankrd11 is a critical regulator of heart development. Ankrd11 is a chromatin regulator related to KBG syndrome which clinical manifestation includes, macrodontia, craniofacial findings, short stature, skeletal anomalies, global developmental delay, seizures, and intellectual disability. Heart anomalies were initially described in a minor proportion (Sirmaci, A., et al. Am. J. Hum. Genet. 89: 289- 294, 2011), but now is found in \(\sim 44\%\) of KBG patients (Digilio MC, et al.. Am J Med Genet A. 2022 Apr;188(4):1149- 1159). + +<|ref|>text<|/ref|><|det|>[[90, 585, 363, 601]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[89, 601, 870, 653]]<|/det|> +The authors showed that ablation of Ankrd11 in the murine neural crest is related to aberrant heart development and function. This is the main result. In addition, the characterization an abnormal signaling pathways pinpoint the molecular mechanism that may be involved. + +<|ref|>text<|/ref|><|det|>[[90, 653, 870, 723]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. The work is original. The cardiac defects are more severe than the ones observed in KBG syndrome, but that difference may be related to gene dosage. + +<|ref|>text<|/ref|><|det|>[[90, 737, 884, 773]]<|/det|> +We thank the reviewer for providing their constructive feedback and for highlighting the potential of our results. Below we have addressed all raised concerns. + +<|ref|>text<|/ref|><|det|>[[90, 805, 902, 893]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed 1. One concern is that the ablation of Ankrd11 is very detrimental by itself. Ankrd11 KO animals don’t survive. So, maybe the ablation of Ankrd11 is killing the cardiac neural crest cells. It seems not to be the case since YFP markers are present in the ncko embryos, but YPF expression is a reporter for wnt1 expression, and maybe ectopic expression of wnt1 is marking other cells. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[89, 70, 900, 175]]<|/det|> +We thank the reviewer for their feedback. The Wnt1Cre mouse model is the most widely used model for studying cardiac neural crest cells 4. At E11.5 the YFP distribution in Ankrd11nchet and Ankrd11ncko is characteristic of the neural crest lineage (new Fig. 1f-g) and consistent with other publications 35, which includes derivatives of the pharyngeal arches and regions alongside the neural tube, which will become dorsal root ganglia of the peripheral nervous system. Therefore, the YFP+ cells in our mouse models are behaving like neural crest cells. + +<|ref|>text<|/ref|><|det|>[[90, 190, 880, 243]]<|/det|> +In the OFT, TUNEL staining of YFP+ cells showed no difference in apoptosis between control and Ankrd11ncko embryos, indicating that apoptosis, which represents major cell death in the developing OFT 36, is not a contributing factor in the neural crest dysregulation (Fig. S2a"- f", former Figs. 3- 4). + +<|ref|>text<|/ref|><|det|>[[88, 257, 909, 485]]<|/det|> +Furthermore, our results show only minor migration defects of Ankrd11ncko CNCCs at E10.5 as well as the cells' ability to produce SMA+ smooth muscle cells (updated Fig. S2a-i, Fig. S1j- p). For SMA, we have performed immunofluorescence analysis of cross sections of E18.5 outflow tract vessels and quantified SMA+ YFP+ cells out of the total SMA+ cells within the proximal (closest to the heart) and distal regions of the vessels (new Fig. S1j- p). In the proximal region, analysis of the \(\alpha \mathrm{SMA}+\) (alpha- smooth muscle actin) smooth muscle layer of the E18.5 Ankrd11ncko truncal artery did not show a deficiency of CNCC- derived smooth muscle cells compared to the Ankrd11nchet aortic and pulmonary arteries (new Fig. S1j- p). Although the Ankrd11ncko distal region showed a decreased proportion of smooth muscle cells that are CNCC derived ( \(\% \alpha \mathrm{SMA}+\) YFP+/ \(\alpha \mathrm{SMA}+\) ; new Fig. S1n), this was not due to their decreased number (#YFP+ \(\alpha \mathrm{SMA}+\) ; new Fig. S1o), but rather due to an increase in non- CNCC derived smooth muscle cells (#YFP- \(\alpha \mathrm{SMA}+\) ; new Fig. S1p). Together, these results indicate that YFP+ cells in Ankrd11nchet and Ankrd11ncko embryos behave as cardiac neural crest cells, although Ankrd11ncko CNCCs exhibit delayed condensation and OFT septation. + +<|ref|>text<|/ref|><|det|>[[89, 501, 900, 623]]<|/det|> +2. It is known that ablation of neural crest cells resulted in persistent truncus arteriosus, mis-patterning of the great vessels, outflow malalignments, and hypoplasia or aplasia of the pharyngeal glands. If Ankrd11ablation in the neural crest cells is not killing the cells but is affecting exclusively the cardiovascular development then hypoplasia of thymus, thyroid, and parathyroid glands, should not be present. How are the thymus, thyroid, and parathyroid glands in the ncko animals? If they are normal, this will reinforce that the effect is on cardiac development specifically. I understand that craniofacial abnormalities are also seen in these mice, but those are also seen in KBG syndrome, hence expected. + +<|ref|>text<|/ref|><|det|>[[90, 656, 897, 692]]<|/det|> +Thank you for this great suggestion. We were successful in analyzing the sizes of the thymus at E18.5, which did not differ between control and Ankrd11ncko embryos (page 6, new Fig. S1a- c). + +<|ref|>text<|/ref|><|det|>[[90, 724, 809, 777]]<|/det|> +3. Something that maybe problematic is that when you look into the information on B6.Cg- E2f1Tg(Wnt1-Cre)2Sor/J Strain #022501Common Name: B6 Wnt1- Cre2 https://www.informatics.jax.org/allele/MGI:5485027?recomRibbon=open): you find + +<|ref|>text<|/ref|><|det|>[[90, 794, 808, 915]]<|/det|> +cardiovascular system pulmonary trunk hypoplasia (J:298597) • about \(5\%\) of mutants show a hypoplastic pulmonary trunk at E15.5 and E16.5 interrupted aortic arch, type b (J:298597) • about \(30\%\) of mutants exhibit interrupted aortic arch, type b at E15.5 and E16.5 abnormal conotruncal ridge morphology (J:298597) • the number of neural crest cells in the proximal outflow tract cushions is reduced at E11.5 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[90, 71, 656, 141]]<|/det|> +double outlet right ventricle (J:298597) - all mutants exhibit the double outlet right ventricle at E15.5 and E16.5 ventricular septal defect (J:298597) - all mutants exhibit a ventricular septal defect at E15.5 and E16.5 + +<|ref|>text<|/ref|><|det|>[[90, 157, 664, 175]]<|/det|> +If https://www.jax.org/strain/022501 is not the strain used, please clarify. + +<|ref|>text<|/ref|><|det|>[[90, 190, 896, 296]]<|/det|> +Thank you for your comment. The phenotypes quoted above were taken from mouse models that used the Wnt1Cre2 driver to ablate other genes. Fore example, J:298597 refers to an mouse model with this allelic composition: Chd7tm2a(EUCOMM)Wtsi/Chd7tm2a(EUCOMM)Wtsi/E2f1Tg(Wnt1- cre)2Sor/E2f1+/Gt(ROSA)26Sortm4(ACTB- tdTomato,- EGFP)Luo/Gt(ROSA)26Sor+. This creates a knockout of the Chd7 allele using the Wnt1Cre2 driver. Upon publication of this manuscript, Ankrd11nck0 phenotypes described in this report will be similarly captured in the MGI database. + +<|ref|>text<|/ref|><|det|>[[90, 327, 905, 397]]<|/det|> +4. Ankrd11 nchet embryos (Ankrd11fl/WT; Wnt1Cre2) showed normal OFT septation, how many embryos were analyzed? There are some haploinsufficiency Ankrd11 related to KBG syndrome presenting heart abnormalities (Digilio MC, et al.. Am J Med Genet A. 2022 Apr;188(4):1149-1159). It is strange that no defect is seen in heterozygous animals. + +<|ref|>text<|/ref|><|det|>[[90, 410, 896, 552]]<|/det|> +At E18.5, we have dissected 9 Ankrd11WT/WT, 29 Ankrd11nchet, and 40 Ankrd11nck0 embryos, and we found septation defects only in Ankrd11nck0 hearts (updated page 6). While we have not observed severe cardiac defects in the Ankrd11nchet mice, it is possible that they may have subtle defects that we were not able to identify using our analysis techniques. Furthermore, multiple cell types contribute to heart development. Ankrd11nck0 mice only had Ankrd11 ablation in the neural crest. The effect of Ankrd11 on other heart cell types is still unknown. Therefore, the cardiac phenotype in KBG patients may be compounded by defects in all the heart cell types, leading to a more severe phenotype. This is reflected in Discussion, page 14. + +<|ref|>text<|/ref|><|det|>[[90, 586, 198, 601]]<|/det|> +Minor issues: + +<|ref|>text<|/ref|><|det|>[[90, 602, 860, 637]]<|/det|> +1. Embryonic hearts at E18.5 were analyzed for anatomical anomalies: all Ankrd11nck0 embryos exhibited a persistent truncus arteriosus (PTA). How many? + +<|ref|>text<|/ref|><|det|>[[90, 650, 880, 686]]<|/det|> +At E18.5, we have dissected 9 Ankrd11WT/WT, 29 Ankrd11nchet, and 40 Ankrd11nck0 embryos, and we found PTA in all Ankrd11nck0 hearts. + +<|ref|>text<|/ref|><|det|>[[90, 701, 890, 736]]<|/det|> +2. Supplemental Figure 3: not sure that the image for the wt and the Ankrd11 ncko embryos are in the same plane, hence comparable. + +<|ref|>text<|/ref|><|det|>[[90, 751, 907, 803]]<|/det|> +Thank you for this comment. Due to expansion of the manuscript and since reviewer 2 has also expressed concerns about these images, we have removed these results and associated conclusions from the manuscript to remove confusion. + +<|ref|>text<|/ref|><|det|>[[90, 836, 752, 854]]<|/det|> +3. Figure 3 A and D seem to show a different area for the distal part (white squares). + +<|ref|>text<|/ref|><|det|>[[90, 869, 904, 921]]<|/det|> +Thank you for the insightful comment. For analysis, all CNCCs in the OFT mesenchymal were counted. However, due to the rarity of TUNEL+ cells, we needed to use different regions of the OFT for magnified images to show these cells. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[88, 88, 900, 123]]<|/det|> +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +<|ref|>text<|/ref|><|det|>[[90, 123, 895, 159]]<|/det|> +If the authors can explain the points raised, I think it is a good work. Main concern is if the phenotype observed (that is very well documented) is related to Ankrd11 ablation. + +<|ref|>text<|/ref|><|det|>[[90, 158, 770, 193]]<|/det|> +- Is the methodology sound? Does the work meet the expected standards in your field? Yes + +<|ref|>text<|/ref|><|det|>[[90, 194, 715, 228]]<|/det|> +- Is there enough detail provided in the methods for the work to be reproduced? Yes + +<|ref|>text<|/ref|><|det|>[[90, 260, 899, 312]]<|/det|> +Thank you for this positive feedback. As we replied above, the phenotypes quoted above were taken from mouse models that used the Wnt1Cre2 driver to ablate other genes. For example, J:298597 refers to an mouse model with this allelic composition: + +<|ref|>text<|/ref|><|det|>[[90, 313, 890, 383]]<|/det|> +Chd7tm2a(EUCOMM)Wtsi/Chd7tm2a(EUCOMM)Wtsi/E2f1Tg(Wnt1- cre)2Sor/E2f1+/Gt(ROSA)26Sortm4(ACTB- tdTomato,- EGFP)Luo/Gt(ROSA)26Sor+. This creates a knockout of the Chd7 allele using the Wnt1Cre2 driver. Upon publication of this manuscript, Ankrd11nck0 phenotypes described in this report will be similarly captured in the MGI database. + +<|ref|>sub_title<|/ref|><|det|>[[90, 447, 189, 464]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[87, 480, 905, 890]]<|/det|> +1 Jiang, X., Rowitch Dh Fau - Soriano, P., Soriano P Fau - McMahon, A. P., McMahon Ap Fau - Sucov, H. M. & Sucov, H. M. Fate of the mammalian cardiac neural crest. Development 127 (2000). 2 Darrigrand, J. F. et al. Dullard- mediated Smad1/5/8 inhibition controls mouse cardiac neural crest cells condensation and outflow tract septation. Elife 9, doi:10.7554/elife.50325 (2020). 3 Liu, X. et al. Single- Cell RNA- Seq of the Developing Cardiac Outflow Tract Reveals Convergent Development of the Vascular Smooth Muscle Cells. Cell Rep 28, 1346- 1361 e1344, doi:10.1016/j.celrep.2019.06.092 (2019). 4 Neeb, Z., Lajiness, J. D., Bolanis, E. & Conway, S. J. Cardiac outflow tract anomalies. 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Neural crest delamination and migration: from epithelium- to- mesenchyme transition to collective cell migration. Dev Biol 366, 34- 54, doi:10.1016/j.ydbio.2011.12.041 (2012).22 Chen, Q. et al. Smad7 is required for the development and function of the heart. J Biol Chem 284, 292- 300, doi:10.1074/jbc.M807233200 (2009).23 Napoli, J. L. Cellular retinoid binding- proteins, CRBP, CRABP, FABP5: Effects on retinoid metabolism, function and related diseases. Pharmacol Ther 173, 19- 33, doi:10.1016/j.pharmthera.2017.01.004 (2017).24 Gandhi, S., Ezin, M. & Bronner, M. E. Reprogramming Axial Level Identity to Rescue Neural- Crest- Related Congenital Heart Defects. Dev Cell 53, 300- 315 e304, doi:10.1016/j.devcel.2020.04.005 (2020).25 Saadey, A. A. et al. Rebalancing TGFbeta1/BMP signals in exhausted T cells unlocks responsiveness to immune checkpoint blockade therapy. Nat Immunol 24, 280- 294, doi:10.1038/s41590- 022- 01384- y (2023).26 Jaako, P. et al. Dietary L- leucine improves the anemia in a mouse model for Diamond- Blackfan anemia. Blood 120, 2225- 2228, doi:10.1182/blood- 2012- 05- 431437 (2012).27 Zhang, A. et al. Identification of a novel family of ankyrin repeats containing cofactors for p160 nuclear receptor coactivators. J Biol Chem 279, 33799- 33805, doi:10.1074/jbc.M403997200 (2004).28 Comai, G. E. et al. Local retinoic acid signaling directs emergence of the extraocular muscle functional unit. PLoS Biol 18, e3000902, doi:10.1371/journal.pbio.3000902 (2020).29 Jain, R. et al. Cardiac neural crest orchestrates remodeling and functional maturation of mouse semilunar valves. J Clin Invest 121, 422- 430, doi:10.1172/JCI44244 (2011).30 Plein, A. et al. Neural crest- derived SEMA3C activates endothelial NRP1 for cardiac outflow tract septation. J Clin Invest 125, 2661- 2676, doi:10.1172/JCI79668 (2015).31 Toyofuku, T. et al. Repulsive and attractive semaphorins cooperate to direct the navigation of cardiac neural crest cells. Dev Biol 321, 251- 262, doi:10.1016/j.ydbio.2008.06.028 (2008).32 Kodo, K. et al. Regulation of Sema3c and the Interaction between Cardiac Neural Crest and Second Heart Field during Outflow Tract Development. Sci Rep 7, 6771, doi:10.1038/s41598- 017- 06964- 9 (2017).33 Delloye- Bourgeois, C. et al. Microenvironment- Driven Shift of Cohesion/Detachment Balance within Tumors Induces a Switch toward Metastasis in Neuroblastoma. Cancer Cell 32, 427- 443 e428, doi:10.1016/j.ccell.2017.09.006 (2017).34 Kaartinen, V. et al. Cardiac outflow tract defects in mice lacking ALK2 in neural crest cells. Development 131, 3481- 3490, doi:10.1242/dev.01214 (2004). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[88, 71, 901, 101]]<|/det|> +35 Lewis, A. E., Vasudevan, H. N., O'Neill, A. K., Soriano, P. & Bush, J. O. The widely used Wnt1- Cre transgene causes developmental phenotypes by ectopic activation of Wnt signaling. Dev Biol 379, 229- 234, doi:10.1016/j.ydbio.2013.04.026 (2013). + +<|ref|>text<|/ref|><|det|>[[90, 101, 901, 131]]<|/det|> +36 Wang, J. et al. Defective ALK5 signaling in the neural crest leads to increased postmigratory neural crest cell apoptosis and severe outflow tract defects. BMC Dev Biol 6, 51, doi:10.1186/1471- 213X- 6- 51 (2006). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 88, 305, 104]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 118, 403, 134]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 148, 866, 224]]<|/det|> +In this revised manuscript, Kibalnyk and colleagues continue to explore the role Ankrd11 in cardiac neural crest cells. As mentioned by Reviewer 2, this is an extension of the group's work published in 2021. I appreciate the effort the authors put into the revised manuscript. The pathways identified as dysregulated in the original manuscript are supported with additional analyses/staining. However, some of their response does not really address the original comments directly. + +<|ref|>text<|/ref|><|det|>[[115, 237, 874, 372]]<|/det|> +In figure 1J - I would have expected Ankrd11 to be preserved in non- lineage traced/neural crest- derived cells. However, I do not see any any signal for Ankrd11 in the cells outside the indicated neural crest prongs.... (especially since it is predicted to be broadly expressed by the single cell RNA seq data and external expression datasets). Additional pictures and/or changing the color of the DAPI signal (to generate more contrast between the RNA signal and DAPI) might be helpful. In addition, I appreciate the reduction in pSMAD 1/5/8+ and pS6+ cells in the mutant OFT at E11.5 relative to controls. However, the normalization by E12.5 suggests that perhaps the slight alteration in BMP signaling or mTORC which is normalized may not be relevant to the dramatic separation defect observed. + +<|ref|>text<|/ref|><|det|>[[115, 400, 864, 506]]<|/det|> +The MERFISH identifies additional dysregulated pathways and changes in cellular populations. However, my comment originally that the work is mostly descriptive and the MERFISH does not address how Ankrd11 KO causally results in disrupted OFT septation. It is understandable (and perhaps expected) that treating pregnant dams will prove to be difficult and hence my suggestion to consider an explant model to normalize some fraction of relevant gene expression and/or proxy of neural crest behavior (and not necessarily septation). As the authors suggest, it is possible that the control datasets are useful to the community. + +<|ref|>text<|/ref|><|det|>[[116, 550, 403, 565]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 579, 865, 655]]<|/det|> +In this revised manuscript, the authors have reframed the conclusions made in the original submission. The revised text describes changes observed in different signaling pathways, and hypothesizes their role in proper OFT septation. The addition of MERFISH data is extremely useful to contextualize the in vivo findings. Overall, I am satisfied by the authors' response to my original comments. + +<|ref|>text<|/ref|><|det|>[[115, 669, 866, 700]]<|/det|> +This work will be useful for scientists studying outflow tract development. I commend the authors on their revision experiments. + +<|ref|>text<|/ref|><|det|>[[116, 714, 447, 729]]<|/det|> +Reviewer #2 (Remarks on code availability): + +<|ref|>text<|/ref|><|det|>[[115, 744, 872, 774]]<|/det|> +While I did not run the code, I scanned through it. The code looks okay to me, although it can benefit from more comments. + +<|ref|>text<|/ref|><|det|>[[116, 835, 403, 850]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 865, 402, 879]]<|/det|> +Very interesting and informative work. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 419, 107]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 124, 867, 230]]<|/det|> +In this revised manuscript, Kibalnyk and colleagues continue to explore the role Ankrd11 in cardiac neural crest cells. As mentioned by Reviewer 2, this is an extension of the group's work published in 2021. I appreciate the effort the authors put into the revised manuscript. The pathways identified as dysregulated in the original manuscript are supported with additional analyses/staining. However, some of their response does not really address the original comments directly. + +<|ref|>text<|/ref|><|det|>[[115, 245, 880, 335]]<|/det|> +In figure 1J - I would have expected Ankrd11 to be preserved in non- lineage traced/neural crestederived cells. However, I do not see any any signal for Ankrd11 in the cells outside the indicated neural crest prongs.... (especially since it is predicted to be broadly expressed by the single cell RNA seq data and external expression datasets). Additional pictures and/or changing the color of the DAPI signal (to generate more contrast between the RNA signal and DAPI) might be helpful. + +<|ref|>text<|/ref|><|det|>[[113, 363, 877, 626]]<|/det|> +Thank you for this insightful comment. We apologize for not presenting clear images from various OFT compartments. As requested, we changed the colors and separated channel images for the Ankrd11 mRNA and DAPI in order to make the Ankrd11 signal more visible (Fig. 1i- 1). We also added additional zoomed in images of the OFT myocardium (Fig. 1i"- 1") and neural tube (Fig. 1n- o), which show preserved Ankrd11 signal in the Ankrd11nckonon- neural crestederived cells. This mirrors successful recombination in CNCCs and absence of recombination in non- neural crest derived tissues like myocardium as assessed by YFP immunostaining (Figs. 3- 6). Importantly, our MERFISH results show a reduction in Sema3c, a critical regulator of CNCC condensation and OFT septation, only in CNCCs and not OFT myocardium (Fig. S6). Furthermore, we show perturbations in pSmad1/5/8, pS6, pSmad2/3 and CRABP only in E11.5 CNCCs with apparently comparable levels in OFT myocardium (Figs. 4a- h, 5a- h, 6a- h and S4a- h). Finally, human patients with ANKRD11 loss- of- function variants display heart defects in tissues that are derived from or shaped by the CNCCs, such as dysplastic valves, ventricular septal defects (VSD), aortic coarctation and patent ductus arteriosus 1. Therefore, our data converge from and are supported by several independent lines of evidence. + +<|ref|>text<|/ref|><|det|>[[115, 630, 866, 685]]<|/det|> +We have reflected new data in Fig. 1i- o and associated text in lines 141- 145 ("Furthermore, the non- neural crest- derived OFT myocardium and neural tube tissue showed comparable Ankrd11 signal in control and Ankrd11nckon embryos (Fig. 1i"- 1", n- o).") + +<|ref|>text<|/ref|><|det|>[[115, 712, 875, 783]]<|/det|> +In addition, I appreciate the reduction in pSMAD 1/5/8+ and pS6+ cells in the mutant OFT at E11.5 relative to controls. However, the normalization by E12.5 suggests that perhaps the slight alteration in BMP signaling or mTORC which is normalized may not be relevant to the dramatic separation defect observed. + +<|ref|>text<|/ref|><|det|>[[115, 800, 880, 905]]<|/det|> +Thank you for the comment. Any tissue morphogenesis, including OFT morphogenesis, requires the developmental processes, such as mesenchymal condensation, to occur at precise developmental time windows 2- 6. A delay in gene expression patterns, which control developmental dynamics, has been strongly linked to pathobiological mechanisms of various developmental disorders 2- 5. While OFT condensation delay has not been studied extensively, Darrigand et al. found that activation of BMP signalling doubled pSmad1/5/8 levels in CNCCs at + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 881, 334]]<|/det|> +E11.5, leading to premature CNCC condensation and asymmetric OFT septation, causing pulmonary stenosis \(^{6}\) . Our findings support these results by showing that a \(50\%\) reduction in pSmad1/5/8+ cells (proxy for BMP signalling) in Ankrd11 \(^{nck0}\) OFT mesenchymal at E11.5 correlated with delayed CNCC condensation, since both the pSmad1/5/8 signal and condensation were restored at E12.5. Furthermore, Darrigrand et al. found that the BMP pathway at least in part regulated Sema3c expression, a crucial chemoattractant for CNCC condensation and OFT septation, where overactivation of BMP signaling in CNCCs caused increased Sema3C expression, contributing to an overcondensation phenotype \(^{6}\) . Notably, Sema3c was reduced in the Ankrd11 \(^{nck0}\) OFT in MERFISH and RNA scope results (Figs. S6, 8), correlating with the impaired condensation phenotype. This provides evidence that the fine- tuning of BMP signalling is important for OFT condensation, and small changes to the signal level can cause defects in the condensation and consequent septation process. Notably, there are no studies investigating how mTORC1 fine- tuning affects OFT septation. We have highlighted this in the discussion on lines 495- 508: + +<|ref|>text<|/ref|><|det|>[[114, 339, 879, 585]]<|/det|> +"Neural crest- specific ablation of Ctdnep1, a BMP inhibitor, causes an opposing phenotype to the defects observed in the Ankrd11 \(^{nck0}\) embryos, specifically premature CNCC condensation and asymmetric AP septum formation, as well as increased pSmad1/5/8 activity \(^{6}\) . Furthermore, the BMP pathway was found to at least in part regulate Sema3c expression \(^{6}\) , a crucial factor for CNCC condensation that was downregulated in the Ankrd11 \(^{nck0}\) OFT in MERFISH and RNA scope results. Sema3C is a glycoprotein that is secreted within the OFT and pharyngeal arches, and is considered a chemoattractant guidance signal to promote CNCC migration into these structures, their condensation within the cardiac cushions and their migration to create the AP septum \(^{6 - 10}\) . Overactivation of BMP signaling in CNCCs causes increased Sema3C expression, contributing to an overcondensation phenotype \(^{6}\) . This suggests that the BMP signaling deficiency observed in Ankrd11 \(^{nck0}\) CNCCs may at least in part lead to their delayed condensation. Together, this provides evidence that the fine- tuning of BMP signalling is important for OFT condensation, and relatively small changes to the signal level can cause defects in the condensation and consequent septation process." + +<|ref|>text<|/ref|><|det|>[[114, 600, 881, 724]]<|/det|> +The MERFISH identifies additional dysregulated pathways and changes in cellular populations. However, my comment originally that the work is mostly descriptive and the MERFISH does not address how Ankrd11 KO causally results in disrupted OFT septation. It is understandable (and perhaps expected) that treating pregnant dams will prove to be difficult and hence my suggestion to consider an explant model to normalize some fraction of relevant gene expression and/or proxy of neural crest behavior (and not necessarily septation). As the authors suggest, it is possible that the control datasets are useful to the community. + +<|ref|>text<|/ref|><|det|>[[114, 740, 881, 899]]<|/det|> +Thank you for this suggestion. We would have also liked to perform explant studies. There are several caveats with this approach that precluded us from pursuing these experiments. First, as we have highlighted in our first response to reviewers, our in vivo results do not show differences in CNCC proliferation, apoptosis or migration, which are primary outcome measures in neural crest explants \(^{7,11}\) . Furthermore, we have performed bulk RNA- seq on entire OFT dissected from E11.25 Ankrd11 \(^{Control}\) and Ankrd11 \(^{nck0}\) embryos (data not shown), which did not show statistically significant changes in global gene expression except for three genes whose role in OFT morphogenesis is not known (Spock1, Mctp2, Shc4). This is most probably due to the presence of a large amount of non- neural crest derived cells and/or lack of spatial resolution. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 835, 161]]<|/det|> +This is supported by our MERFISH results, which show e.g. a reduction in Sema3c only in CNCCs and not OFT myocardium (Fig. S6). This further supports the choice of single cell spatial transcriptomics experiments to probe the role of Ankrd11 in CNCC gene expression (Figs. 7- 8, S6). + +<|ref|>text<|/ref|><|det|>[[115, 166, 835, 237]]<|/det|> +We thank the reviewer for highlighting the utility of our control datasets for the research community. Our work is also contributing to the field of OFT morphogenesis by chromatin regulators, like Ankrd11, and to the understanding of pathobiological mechanisms of KBG syndrome. + +<|ref|>sub_title<|/ref|><|det|>[[115, 260, 209, 277]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[112, 286, 870, 797]]<|/det|> +1 Digilio, M. C. et al. Congenital heart defects in molecularly confirmed KBG syndrome patients. Am J Med Genet A, doi:10.1002/ajmg.a.62632 (2021). 2 Chojnowski, J. L. et al. Multiple roles for HOXA3 in regulating thymus and parathyroid differentiation and morphogenesis in mouse. Development 141, 3697- 3708, doi:10.1242/dev.110833 (2014). 3 Gao, G. et al. Isthmin- 1 (Ism1) modulates renal branching morphogenesis and mesenchyme condensation during early kidney development. Nat Commun 14, 2378, doi:10.1038/s41467- 023- 37992- x (2023). 4 Hinton, R. J. Genes that regulate morphogenesis and growth of the temporomandibular joint: a review. Dev Dyn 243, 864- 874, doi:10.1002/dvdy.24130 (2014). 5 Kathiriya, I. S. & Srivastava, D. Left- right asymmetry and cardiac looping: implications for cardiac development and congenital heart disease. Am J Med Genet 97, 271- 279, doi:10.1002/1096- 8628(200024)97:4<271::aid- ajmg1277>3.0. co;2- o (2000). 6 Darrigrand, J. F. et al. Dullard- mediated Smad1/5/8 inhibition controls mouse cardiac neural crest cells condensation and outflow tract septation. Elife 9, doi:10.7554/eLife.50325 (2020). 7 Plein, A. et al. Neural crest- derived SEMA3C activates endothelial NRP1 for cardiac outflow tract septation. J Clin Invest 125, 2661- 2676, doi:10.1172/JCI79668 (2015). 8 Toyofuku, T. et al. Repulsive and attractive semaphorins cooperate to direct the navigation of cardiac neural crest cells. Dev Biol 321, 251- 262, doi:10.1016/j.ydbio.2008.06.028 (2008). 9 Kodo, K. et al. Regulation of Sema3c and the Interaction between Cardiac Neural Crest and Second Heart Field during Outflow Tract Development. Sci Rep 7, 6771, doi:10.1038/s41598- 017- 06964- 9 (2017). 10 Delloye- Bourgeois, C. et al. Microenvironment- Driven Shift of Cohesion/Detachment Balance within Tumors Induces a Switch toward Metastasis in Neuroblastoma. Cancer Cell 32, 427- 443 e428, doi:10.1016/j.ccell.2017.09.006 (2017). 11 He, F. & Soriano, P. A critical role for PDGFRalpha signaling in medial nasal process development. PLoS Genet 9, e1003851, doi:10.1371/journal.pgen.1003851 (2013). + +<--- Page Split ---> diff --git a/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/images_list.json b/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7c4a70e4bc3e033e65277268ff6d54ac0ccfd2d5 --- /dev/null +++ b/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,96 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S47. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the RBM when Wuhan and G614 spikes are incubated at 1:2 and 1:3 ratios with ACE2. No significant differences in ΔHDX are observed between the two incubation ratios and for both spike trimers.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "C Peptide 963-977 - Priming for fusion of HR1", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Fig. 6 Spike priming for fusion. A) Regions manifesting increased dynamics in spikes bound to ACE2 are superimposed and colored in red on a single protomer of the structure of D614 spike with one RBD bound (PDB: 7a9514); regions with increased dynamics only in spike of alpha and omicron variants bound to ACE2 are colored in magenta. B) The magnitude of the destabilization of the core helices is represented by differential colouring (red scale) for the various spike trimers. The HR1 region (962-982) manifesting HDX bimodality is framed in grey. C) The bimodal isotopic envelopes of a model peptide spanning the HR1 region 962-982 are shown at 15 s and 1 min time points for spike (S) variants in the ACE2-bound form and for omicron spike alone, to exemplify their priming for fusion upon receptor engagement. Bimodal envelopes manifest in omicron spike also in the absence of ACE2, indicating it as pre-primed for fusion.", + "footnote": [], + "bbox": [ + [ + 117, + 418, + 875, + 580 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_28.jpg", + "caption": "Fig. 3 Effect of spike binding on ACE2 dynamics. A) Regions of ACE2 manifesting a significant decrease in HDX upon spike binding are superimposed on the structure of ACE2 ectodomain bound to RBD (PDB: 2ajf), colored in blue scale according to the magnitude of the HDX effect. The region colored in red indicates increased HDX upon binding, in dark gray regions with no coverage. B) ACE2 binding avidity. The cumulative difference in HDX (ΔHDX) between ACE2 alone and ACE2 bound to spikes and the isolated ancestral RBD for selected peptides spanning binding sites and across time points 20 s on ice, 10 min at 23 °C and 360 min at 28 °C is plotted. A plot for all time points in Supplementary Fig. 28.", + "footnote": [], + "bbox": [], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_4.jpg", + "caption": "Supplementary Fig. 4. Influence of amino acid changes on the \\(k_{ch}\\) of residues of spike variants. The ratios between the \\(kch\\) of spike variants and Wuhan spike and the \\(kch\\) of G614 spike residues is plotted from residue 1 to 628 (a) and from residue 629 to 1256 (b). Values are extracted from Supplementary Data 1. Amino acid changes are illustrated on the left of the graphs.", + "footnote": [], + "bbox": [], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S47. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the RBM when Wuhan and G614 spikes are incubated at 1:2 and 1:3 ratios with ACE2. No significant differences in ΔHDX are observed between the two incubation ratios and for both spike trimers.", + "footnote": [], + "bbox": [], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "C Peptide 963-977 - Priming for fusion of HR1", + "footnote": [], + "bbox": [], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Fig. 6 Spike priming for fusion. A) Regions manifesting increased dynamics in spikes bound to ACE2 are superimposed and colored in red on a single protomer of the structure of D614 spike with one RBD bound (PDB: 7a9514); regions with increased dynamics only in spike of alpha and omicron variants bound to ACE2 are colored in magenta. B) The magnitude of the destabilization of the core helices is represented by differential colouring (red scale) for the various spike trimers. The HR1 region (962-982) manifesting HDX bimodality is framed in grey. C) The bimodal isotopic envelopes of a model peptide spanning the HR1 region 962-982 are shown at 15 s and 1 min time points for spike (S) variants in the ACE2-bound form and for omicron spike alone, to exemplify their priming for fusion upon receptor engagement. Bimodal envelopes manifest in omicron spike also in the absence of ACE2, indicating it as pre-primed for fusion.", + "footnote": [], + "bbox": [ + [ + 117, + 418, + 877, + 580 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_28.jpg", + "caption": "Fig. 3 Effect of spike binding on ACE2 dynamics. A) Regions of ACE2 manifesting a significant decrease in HDX upon spike binding are superimposed on the structure of ACE2 ectodomain bound to RBD (PDB: 2ajf), colored in blue scale according to the magnitude of the HDX effect. The region colored in red indicates increased HDX upon binding, in dark gray regions with no coverage. B) ACE2 binding avidity. The cumulative difference in HDX (ΔHDX) between ACE2 alone and ACE2 bound to spikes and the isolated ancestral RBD for selected peptides spanning binding sites and across time points 20 s on ice, 10 min at 23 °C and 360 min at 28 °C is plotted. A plot for all time points in Supplementary Fig. 28.", + "footnote": [], + "bbox": [], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_4.jpg", + "caption": "Supplementary Fig. 4. Influence of amino acid changes on the \\(k_{ch}\\) of residues of spike variants. The ratios between the \\(kch\\) of spike variants and Wuhan spike and the \\(kch\\) of G614 spike residues is plotted from residue 1 to 628 (a) and from residue 629 to 1256 (b). Values are extracted from Supplementary Data 1. Amino acid changes are illustrated on the left of the graphs.", + "footnote": [], + "bbox": [], + "page_idx": 19 + } +] \ No newline at end of file diff --git a/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..dd8bdc7596531e54e1df1be22fc8cf784c44216b --- /dev/null +++ b/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,825 @@ + +# nature portfolio + +Peer Review File + +Structural dynamics in the evolution of SARS- CoV- 2 spike glycoprotein + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: + +https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): + +https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 + +https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 + +Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +<--- Page Split ---> + +Other issues: + +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and overreaching. This should be rephrased to indicate what the figure is showing, ie., Differences in HDX between Wuhan D614 and G614 spikes. + +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion + +conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +Reviewer #2 (Remarks to the Author): + +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +<--- Page Split ---> + +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +Reviewer #3 (Remarks to the Author): + +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +## Major concern: + +Why did the authors use a ratio of 1:2 spike: Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? Additionally, how long was the spike: ACE2 complex incubated prior to exchanges? Do the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +<--- Page Split ---> + +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +## Major point 2: + +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much + +<--- Page Split ---> + +slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit this section. + +## Minor point: + +The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +<--- Page Split ---> + +Reviewer #1 (Remarks to the Author): + +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): + +https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 + +https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 + +Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +We thank the reviewer for pointing out this discrepancy, as indeed, in the interest of saving space, we oversimplified this issue. Following the reviewer's suggestion, we have now addressed it in the lines 435- 441 and 445- 446 of the discussion session. + +## Other issues: + +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and overreaching. This should be rephrased to indicate what the figure is showing, i.e., Differences in HDX between Wuhan D614 and G614 spikes. + +<--- Page Split ---> + +We thank the reviewer for the suggestion. We have now changed the figure caption in 'Differences in structural dynamics between Wuhan (D614) spike and G614 spike' + +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +We now changed this sentence to: 'Hence, in all analyses we used a version of spike ectodomains stabilized by R682S, R685S substitutions in the polybasic cleavage sites and K986P, K987P (2P) substitutions, which combined make the spikes furin- uncleavable and unable to transition to the postfusion conformation.' (lines 143- 147) + +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +We have now removed a reference to the 'closed state' in the figure. + +Reviewer #2 (Remarks to the Author): + +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +We thank the reviewer for the suggestions. We had cited two of Ganesh Anand's papers (ref. 35 and 39), and we have now included his recent preprint (ref. 40). We have also now included the work for Wilson group on the RBD (ref. 41) and a very recent article based on mass photometry data (ref. 42). However, we could not find any HDX-MS study on spike conducted by Komives group. + +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +We thank the reviewer for this suggestion. We have now analysed with HX- Express2 another peptide spanning the RBM (peptide 495- 510) and included this extra analysis in the supplementary information (a peptide spanning the same residues is unfortunately absent in the omicron spike) (Fig. S44- 45). It is worth noting that the HX- express fitting returned very similar relative size of populations and their timedependent evolution, for every spike variant, as the peptide previously included. We have also extracted + +<--- Page Split ---> + +from DynamX the stacked spectral plots of many other peptides encompassing this region, and included them in the supplementary figures (Fig. S41). We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless the peptide signal- to- noise ratio. Here below the additional figures. + +![](images/Figure_unknown_1.jpg) + + +<--- Page Split ---> +![](images/Figure_6.jpg) + + +<--- Page Split ---> +![](images/Supplementary_Figure_28.jpg) + + +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express \(2^{2}\) (see Supplementary Figs. 42- 45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +![](images/Supplementary_Figure_4.jpg) + + +<--- Page Split ---> + +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity - BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express \(^{2}\) and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. 45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + + +<--- Page Split ---> + +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. A) Mass spectra of peptide of Wuhan, G614 and delta spikes. B) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with binomial fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +This is a very interesting input and we completely align with the reviewer's thoughts. We have added the following paragraph in the discussion (lines 410- 415): + +"The conformational plasticity of this NTD site presumably allows antibody- vulnerable configurations of conformational epitopes to remain occasionally populated, reducing, but not completely abrogating, antibody- mediated protection. At the same time, linear NTD epitopes are likely more impacted by the residue changes in spike variants rather than by a different conformational aspect of the NTD of VOCs." + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +Major concern: + +Why did the authors use a ratio of 1:2 spike: Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +This an important point and we thank the reviewer for the opportunity to clarify it. For a Spike trimer to be ACE2 binding- competent at least one of its RBDs must be erect and a mixture of its open and closed states within the trimer is well known in the literature (see e.g. https://doi.org/10.1016/j.cell.2020.02.058, https://www.nature.com/articles/s41594- 020- 0468- 7. pdf?origin=ppub, https://www.pnas.org/doi/10.1073/pnas.2022586118, and https://www.nature.com/articles/s41467- 022- 28882- 9). Spikes with all three RBDs accessible are rarely observed, at least in cryoEM. Although we cannot be sure of the precise ratios of up and down states in spikes in solution, in non- cryogenic state, the conformational dynamics between these adopted structures governs this interaction and is what our solution HDX- MS experiments can report on. In our experiments we, therefore, try to capture a situation where we can monitor this behaviour within the experimental limitations of required sample amounts and concentration – with large concentrations of the material difficult to produce. + +The 1:2 ratio was chosen after initial optimization HDX- MS experiments. We incubated Wuhan and G614 spikes at 1:2 and 1:3 ratio spike: ACE2 and found the same difference in HDX for spike peptides within the RBM at both ratios. This suggests that increased ACE2 above 1:2 was not increasing spike binding occupancy, but likely leads to an increased population of unbound ACE2 in our labelled sample. Accordingly, the HDX differences observed within ACE2 incubated at 1:2 and 1:3 ratios spike: ACE2 appeared significantly higher at ratio 1:2 than at 1:3, which supports that a higher fraction of unbound ACE2 is present in the latter case. In support of the ratio chosen, a very recent mass photometry paper (https://pubs.rsc.org/en/content/articlelanding/2022/cc/d2cc04711j) on Wuhan and omicron spikes (in the same '2P' pre- fusion stabilised version we use) reported that 1:4 spike: ACE2 shows predominantly spike bound to one ACE2, with some spike bound to 2 ACE2 but negligible amounts bound to 3 ACE2. + +Considering these observations, 1:2 ratio likely provides information on saturated spike ACE2- accessible 'up' states. As the reviewer points out, this would mean that one of the RBDs will be unbound, but it is likely to be in an ACE2- inaccessible "down" state. The experiment performed to address major concern 2 provides further evidences in support of the ratio chosen, for every spike analysed (please see below). + +<--- Page Split ---> + +In this revised version, we inserted this optimization procedure in a dedicated paragraph of the method session (Optimization of the HDX conditions – lines 546- 554) and added two figures showing these results in the supplementary information and present them below. + +![](images/Figure_6.jpg) + +
Fig. S47. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the RBM when Wuhan and G614 spikes are incubated at 1:2 and 1:3 ratios with ACE2. No significant differences in ΔHDX are observed between the two incubation ratios and for both spike trimers.
+ +![](images/Supplementary_Figure_28.jpg) + + +Supplementary Fig. 48. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the ACE2 binding site when ACE2 is incubated at 2:1 and 3:1 ratios with Wuhan spike. A minor decrease in HDX is observed at ratio 3:1. + +<--- Page Split ---> + +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? + +Bimodal spectra were not observed in apo spikes by working with freshly prepared spike samples. In the ACE2- bound state, beyond the 495- 513 region, we observed - for every spike trimer analyzed - the appearance of bimodal isotopic envelopes in the HR1 region spanning residues 962- 982, which is one of the segments becoming more dynamic during the priming for fusion of spike. In the interest of writing the manuscript for a broad readership, we did not describe the specific HDX regime of this particular segment in detail, rather summarizing the increased HDX observed in various S2 stretches as 'increased dynamics'. However, following the reviewer's inquiry, we have reconsidered our initial thoughts and have now described the HDX bimodality seen in this region of bound- spikes in the manuscript test, as presumably it also contributes to the priming mechanism (lines 355- 363). + +"Notably, peptides spanning residues 962- 982 manifested increased HDX in the form of bimodal isotopic envelopes when spikes are engaged to ACE2 (Fig. 6c and Supplementary Fig. 46). This segment encompasses the HR1 helix, which undergoes a large conformational rearrangement upon the transition to post- fusion state15, suggesting that our analysis captured the specific dynamic events leading to the HR1 reorientation, which primes spikes for fusion. The breadth of this HDX bimodality varies with \(\text{omicron} > \text{alpha} > \text{beta} > \text{G614} \approx \text{Wuhan spike}\) , with omicron spike pre- manifesting it also in the absence of ACE2 (Fig. 6c and Supplementary Fig. 46)." + +Additionally, we have modified Fig. 6c in the main text to include the isotopic envelopes of peptides 963- 977, in place of its uptake plots. We believe that the envelopes deliver a much clearer message. We also added a supplementary figure (S46) including the stacked spectral plots of peptide 963- 977 and an overlapping peptide (962- 977). + +<--- Page Split ---> +![](images/Supplementary_Figure_4.jpg) + +
C Peptide 963-977 - Priming for fusion of HR1
+ +![PLACEHOLDER_19_1] + +
Fig. 6 Spike priming for fusion. A) Regions manifesting increased dynamics in spikes bound to ACE2 are superimposed and colored in red on a single protomer of the structure of D614 spike with one RBD bound (PDB: 7a9514); regions with increased dynamics only in spike of alpha and omicron variants bound to ACE2 are colored in magenta. B) The magnitude of the destabilization of the core helices is represented by differential colouring (red scale) for the various spike trimers. The HR1 region (962-982) manifesting HDX bimodality is framed in grey. C) The bimodal isotopic envelopes of a model peptide spanning the HR1 region 962-982 are shown at 15 s and 1 min time points for spike (S) variants in the ACE2-bound form and for omicron spike alone, to exemplify their priming for fusion upon receptor engagement. Bimodal envelopes manifest in omicron spike also in the absence of ACE2, indicating it as pre-primed for fusion.
+ +<--- Page Split ---> +![PLACEHOLDER_20_0] + + +Supplementary Fig. 46. HDX bimodality in the HR1 of spikes in complex with ACE2 and omicron spike alone. Stacked spectral plots of peptides 962- 977 and 963- 977 illustrate the evolution of the bimodal isotopic envelopes over the time points studied. Particularly, time points 15 s and 1 min (23 °C) show clear separation between the low- and high- mass envelopes in every spike trimer, with the relative intensity and centroids of the two envelopes reporting on the degree of destabilization exerted by the ACE2 binding on the HR1. The isotopic envelopes in omicron spike alone manifest evident peak broadening, suggesting that the its HR1 follows a bimodal HDX behaviour even in the absence of ACE2. + +<--- Page Split ---> + +Additionally, how long was the spike:ACE2 complex incubated prior to exchanges? Do the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +Spikes- ACE2 complexes were incubated for one hour before starting the deuterium labelling (we now specified this in the method session). Given the Kds are, depending on the variant, in the order of 10 to 150 nM with kons between 0.07 and \(0.2 \text{ uM}^{- 1} \text{s}^{- 1}\) (https://doi.org/10.1038/s41467- 022- 28768- w - see supplementary info), we believe that this incubation period largely suffices for system equilibration. + +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors' coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +We thank the reviewer for highlighting this important point. We have now extracted from DynamX the stacked spectral plots of many other peptides encompassing this region and included them in the supplementary figures. We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless of the peptide signal- to- noise ratio (Fig. S41). We also analysed the bimodal isotopic distributions of another peptide (495- 510) with HX- express2 and included this extra analysis in the supplementary information (a matching peptide is unfortunately absent in the omicron variant) (Fig. S44- 45). It is worth noting that the HX- express2 fitting returned very similar relative size of populations and their time- dependent evolution, for every spike variant, compared to the peptide previously included. The result of this extra analysis could also address the reviewer's following concern about the calculated size of the populations. + +![PLACEHOLDER_21_0] + + +<--- Page Split ---> +![PLACEHOLDER_22_0] + + +<--- Page Split ---> +![PLACEHOLDER_23_0] + + +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express2 (see Supplementary Figs. 42- S45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +![PLACEHOLDER_24_0] + + +<--- Page Split ---> + +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity - BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express \(^{2}\) and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. S45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +![PLACEHOLDER_26_0] + + +<--- Page Split ---> +![PLACEHOLDER_27_0] + + +<--- Page Split ---> + +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. a) Mass spectra of peptide of Wuhan, G614 and delta spikes. b) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with bimomial fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +We thank the reviewer for considering this important aspect. We based our interpretation on the following observations and experiments. + +As the reviewer suggests, we had carefully compared the HDX of the high- mass population of the bound states and the HDX of the population (unimodal spectra) of the apo state (also shown in fig. S42 and S44). The two HDX profiles do not appear consistent. We believe that, if the ACE2 was not sufficient to saturate the binding of the monomers with accessible (erect) RBD, the high- mass population in the bound states should align on the m/z scale to the apo spike states, manifesting already, and with clear separation from the low- mass population, at 4 s or 20 s on ice, but this does not appear to be the case. We do not observe it at 4 s on ice for Wuhan and G614 bound- spikes, or at 20 s on ice for alpha, beta and omicron bound- spikes. We have now added a note on this in the figure caption of fig. S42 and S44. + +<--- Page Split ---> + +To better investigate this aspect, for this revised version, we performed an extra experiment. We performed HDX- MS on the isolated RBD of the ancestral Wuhan spike in the presence and absence of ACE2, at ratio 3:2 RBD:ACE2, which simulates our 1:2 spike trimer:ACE2 ratio used in our experiments. Given that the whole population of isolated RBD molecules are binding- competent, with such a binding stoichiometry, \(33\%\) of the RBD population remain effectively unbound in the presence of ACE2. We did not observe bimodal distributions in the RBM of the bound- RBD state, indicating that a mixture of bound and unbound monomers, with same conformational characteristics in the apo state, does not manifest with a clear envelope bimodality under the conditions studied. We now included the extracted stacked spectral plot of the bound- RBD in the supplementary figures (please, see previous figure S41). Furthermore, the preliminary data shown above and the experiment performed to address major point 2 support a scenario where spike erect RBDs are saturated in binding occupancy. + +These observations prompt us to associate the RBM bimodal HDX profiles to the spike cooperative binding mode reported in previous studies; we thus interpreted the high- mass population as an extra monomer that erects upon ACE2 binding (in a cooperative manner) and is likely able to engage with an extra ACE2 molecule, thus displaying an HDX profile that differs from the monomers in the unbound state. This gives rise to a fine- tuned equilibrium of states, characteristic for each spike variant, that we aimed at deciphering with our analysis. + +We agree with the reviewer that we should not strictly refer to this HDX behaviour as EX1 kinetics, as we associated it to the behaviour of different monomers, and not to an individual protein stretch displaying correlated exchange. We thus now refer to it as "HDX bimodality". We also modified the text (lines 306- 324) to better explain these observations and include the extra experiment performed, and we present it here below. + +"Furthermore, we observed that the HDX profiles of all peptides spanning the RBM of spike trimers (residues 495- 503) in the ACE2- bound states showed bimodal isotopic distributions, hence a high- and a low- mass population, whereas a single unimodal distribution characterized the apo states (Fig. 5 and Supplementary Figs. 41- 45). The HDX of the high- mass populations in the bound states appeared inconsistent with the HDX of the respective apo states. In contrast, the ACE2- bound state of the isolated ancestral RBD (3:2 RBD: ACE2), containing a significant fraction (33%) of unbound population, did not display bimodal isotopic distributions in the RBM (Supplementary Fig. 41), ruling out that a mixture of bound and unbound populations, with same conformational characteristics in the apo state, manifests with an HDX bimodality under the conditions studied. These data thus suggest that the RBD of bound spikes can explore two distinct and slowly interconverting populations, which exchange giving rise to two resolved isotopic distributions. We rationalize, based on the receptor binding mode reported in previous studies14,55, that the bimodal HDX profile of the bound spike states reports on cooperative opening within the spike trimer, with the less exchanged (low- mass) population accounting for open protomers with a bound RBD, whilst the more exchanged (high- mass) population likely corresponding to closed protomers transitioning to the open state and readying to engage another receptor molecule." + +We also would like to highlight that bimodal spectra were not observed in the bound states of ACE2, even though we observed these states at uncomplete binding occupancy (please, see answer to Major point 2). + +<--- Page Split ---> + +Major point 2: + +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +The reviewer is right; however, the experiments we referred to were all based on methods (biolayer interferometry) that measure only the affinity of a single monomer binding to one ACE2, as spikes are immobilised and thus their concentrations (as well as the effective concentrations of individual accessible RBDs) irrelevant for the measurement, while ACE2 monomers form a mobile phase. We have now specified this in the text (lines 269- 270). In our HDX- MS experiments, we equilibrated all complexes for one hour before labelling, which, considering the aforementioned favourable kon and Kd, should allow for equilibration to be reached. + +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit + +We thank the reviewer for highlighting this important point and below we provide further details to support our experimental design and their conclusions. + +<--- Page Split ---> + +Despite the molar excess of spike monomers, ACE2 is in excess compared to the binding- competent open monomers with available erect RBDs within spike trimers. To confirm this also in HDX- MS, we performed an additional experiment for this revised version of the manuscript. We labelled ACE2 in the presence and absence of the isolated ancestral RBD, at a 3:2 ratio RBD:ACE2, which simulates a 1:2 spike trimer:ACE2 ratio. Differently from the RBDs embedded in a spike trimer, the whole population of isolated RBD is binding- competent. In this scenario, the RBD is effectively in excess compared to ACE2, granting full ACE2 binding occupancy, and indeed, we observed that the binding effect on ACE2 manifested with much greater magnitude (cumulative \(\Delta \mathrm{HDX} = 19.15\) Da) compared to that induced by spike trimers, which show generally less cumulative \(\Delta \mathrm{HDX}\) due to the presence of a (varied) fraction of unbound ACE2 in the bound state. This experiment indicates that the ACE2 is not saturated in binding occupancy in the HDX- MS experiments performed on spike trimers (hence spike trimers are saturated or close to saturated), therefore we argue that the magnitude of HDX effects ( \(\Delta \mathrm{HDX}\) ) on the ACE2 holds useful information on the spike- ACE2 binding stoichiometry. + +It has to be noted that the \(\Delta \mathrm{HDX}\) induced by alpha, beta and delta spikes also have a contribution from the stability of the hydrogen bonding network engaged with ACE2 (related to the affinity of their individual binding- competent monomers to the receptor), which will result in a cumulative effect given by their binding stoichiometry and affinity (reported as higher than for G614 in several studies). This is presumably the reason why for alpha spike a cumulative \(\Delta \mathrm{HDX}\) slightly higher than that of the isolated RBD was observed. + +In our hands, the incomplete binding occupancy of ACE2 did not manifest with isotopic bimodal distributions in its spike binding sites, making it difficult to estimate the fraction of unbound ACE2 for the different trimers. This is one of the reasons why we refrain from proposing any stoichiometry model. + +We have now included the results of this extra experiment (see figures below) in fig. 3 of the main text and Fig S27 and S40 of supplementary information and have also rewritten this section in the main text to provide a clearer explanation of our rationale (lines 243- 255). + +"Next, by studying the HDX of the ACE2 ectodomain alone and in complex with spike trimers (1:2 spike trimer:ACE2) and the isolated ancestral RBD (3:2 RBD:ACE2), we measured the magnitude of the HDX effects ( \(\Delta \mathrm{HDX}\) ) induced by spike binding to ACE2. The whole population of the isolated RBD is binding competent, granting complete occupancy of the ACE2 binding sites, whereas only a fraction of the RBDs embedded within spikes are erect and thus able to engage the receptor. The observed \(\Delta \mathrm{HDX}\) results from a cumulative effect of binding stoichiometry (how many ACE2 molecules are bound) and the stability of the hydrogen- bonding network between spikes and ACE2 (which can be related to the spike- receptor binding affinity), enabling us to rank the spike- receptor binding avidity (i.e. the overall strength of binding arising from the affinity of an individual RBD- ACE2 interaction and the stoichiometry of each spike trimer engaging between zero and three ACE2 molecules at once)." + +For clarity, we also modified the following sentence (lines 261- 268): + +"The cumulative \(\Delta \mathrm{HDX}\) induced by different spikes varied with alpha \(> \text{beta} > \text{delta} > \text{G614} > \text{Wuhan} \approx \text{omicron (Fig. 3b and Supplementary Fig. 28). These} \Delta \text{HDX values were generally lower than that induced by the isolated RBD, indicating that a fraction of ACE2 molecules remained unbound in the spike:ACE2 states, thus suggesting that all binding- competent RBDs within the trimers were fully occupied." + +<--- Page Split ---> +![PLACEHOLDER_32_0] + +
Fig. 3 Effect of spike binding on ACE2 dynamics. A) Regions of ACE2 manifesting a significant decrease in HDX upon spike binding are superimposed on the structure of ACE2 ectodomain bound to RBD (PDB: 2ajf), colored in blue scale according to the magnitude of the HDX effect. The region colored in red indicates increased HDX upon binding, in dark gray regions with no coverage. B) ACE2 binding avidity. The cumulative difference in HDX (ΔHDX) between ACE2 alone and ACE2 bound to spikes and the isolated ancestral RBD for selected peptides spanning binding sites and across time points 20 s on ice, 10 min at 23 °C and 360 min at 28 °C is plotted. A plot for all time points in Supplementary Fig. 28.
+ +<--- Page Split ---> +![PLACEHOLDER_33_0] + + +Supplementary Fig 27. Difference plot illustrating the difference in HDX between ACE2 in complex with the isolated ancestral RBD and ACE2 alone (orange line indicates: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Peptide segments of interest are highlighted. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance and a dotted black line the 99% CI as a threshold for significance. + +![PLACEHOLDER_33_1] + + +Supplementary Fig 40. Difference plot illustrating the difference in HDX between the isolated ancestral RBD in complex with ACE2 and the isolated ancestral RBD alone (orange line: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Residues comprising a region with significant differences in HDX are indicated. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance. + +<--- Page Split ---> + +Minor point: + +Minor point:The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +We gratefully thank the reviewer for highlighting the caveat arising from the comparison of peptides harboring mutations and suggesting the paper (which we now cited). We briefly explained in the method section how they were compared but did not consider this to a sufficient degree. We explain our comparative workflow below and the additional \(\mathsf{k}_{\mathrm{ch}}\) considerations done: + +## Workflow: + +We selected for comparison only peptides with identical cleavage, i.e. same N- and C- termini. Thanks to the numerous peptides available and the high redundancy, we could, in most instances, find matching peptides. However, this became impossible in case of deletions and insertions. We normalized the uptake values of mutant peptides by the uptake of their MaxD (= fully deuterated control) and obtained absolute uptake values (in Da) referencing to G614 spike, with the following equation (now included in the method session): + +\[\Delta HDX = \left(\frac{DU\:mutant\:peptide}{DU\:MaxD\:mutant\:peptide}\times DU\:MaxD\:G614\:spike\:peptide}\right) - DU\:G614\:spike\:peptide\] + +For instance, at a given time point, peptide X of G614 spike has DU of 3 Da with a MaxD of 10 Da; its matching peptide Y in alpha spike has DU of 4 Da with MaxD of 10.3 Da; the normalized DU for alpha spike is 3.88 Da. The \(\Delta HDX\) reported in the butterfly plot is \(+0.88\) Da. This was done with the aim to insert mutant peptides in the butterfly plots, making the HDX comparison more visually intuitive and easily readable. + +## Considering kch differences: + +We acknowledge the fact that the MaxD does not entirely alleviate the caveat arising from the difference in kch between peptides harboring mutations. Before performing the experiments, we had checked the values of \(\mathsf{k}_{\mathrm{ch}}\) (according to the 2018 updated values: doi: 10.1007/s13361- 018- 2021- z) and + +<--- Page Split ---> + +noticed that the differences are minor and most likely give rise to \(\Delta \mathsf{HDX}\) below the threshold of significance when comparing peptides without a significant difference in \(k_{\mathrm{op}}\) . + +However, we now performed a more thorough analysis on the impact that the \(k_{\mathrm{ch}}\) offset has on the differences measured. We included this analysis in a supplementary table (Supplementary Data 1). We tested a null hypothesis in which every difference in HDX observed arises from a difference in \(k_{\mathrm{ch}}\) . + +In more detail: we calculated the average \(k_{\mathrm{ch}}\) for a peptide and its mutant variant - excluding the N- terminal residue (one peptide per mutation was analyzed). The average \(k_{\mathrm{ch}}\) was selected as the individual amide HDX rates are averaged when measured by MS at peptide level. We then calculated the \(\%\) of observed \(\Delta \mathsf{HDX}\) for that peptide normalized by MaxD, selecting the time point showing the highest \(\Delta \mathsf{HDX}\) , as considered the most sensitive to differences. + +In most instances, as the reviewer foresaw, the \(\% \Delta \mathsf{HDX}\) significantly surpasses the \(\% \Delta k_{\mathrm{ch}}\) , including for peptides spanning K417N (the table includes a 'note' column describing the outcome of the analysis). Therefore, while acknowledging the fact that the \(\Delta \mathsf{HDX}\) values have an offset at quantitative level, the observed \(\Delta \mathsf{HDX}\) can be considered qualitatively reliable. Only for one peptide (946- 961 of delta spike), we cannot unambiguously demonstrate that the observed \(\Delta \mathsf{HDX}\) arises from a real difference in dynamics in respective to G614 spike. Therefore, we have not based any discussion on that peptide. + +We now mentioned this in lines 184- 187 of the results and included the description of this approach in the method session (lines 612- 630), acknowledged the presence of this caveat. We also included new figures in the supplementary information (Fig. S4) where residue- level \(k_{\mathrm{ch}}\) ratios are plotted. + +"To compare peptides containing residue substitutions in spike variants (mutant peptides) with peptides of G614 spike, segments with identical N- and C- termini were selected. Their difference in deuterium incorporation ( \(\Delta \mathsf{HDX}\) ) was calculated according the equation 1 and plotted in Supplementary Figs. 9- 12: + +\[\Delta \mathsf{HDX} = \left(\frac{\mathsf{DU~mutant~peptide}}{\mathsf{DU~MaxD~mutant~peptide}}\times \mathsf{DU~MaxD~G614~spike~peptide}\right) - \mathsf{DU~G614~spike~peptide} \quad (1)\] + +To estimate the impact of the difference in chemical exchange rate constants \((k_{\mathrm{ch}})\) on the observed \(\Delta \mathsf{HDX}\) between mutant peptides and peptides of G614 spike \(^{50}\) , firstly the \(k_{\mathrm{ch}}\) of individual residues within the spike protein sequences were calculated \(^{49}\) . Successively, at peptide level, the percentage of difference in \(k_{\mathrm{ch}}\) ( \(\% \Delta k_{\mathrm{ch}}\) ) were compared to the percentage of \(\Delta \mathsf{HDX}\) normalized by the MaxD ( \(\% \Delta \mathsf{HDX}\) ) in the time point showing maximal effect, as reported in Supplementary Data 1. The identified differences in HDX between spike variants and G614 spike in segments spanning amino acid changes resulted of high- confidence, with the impact of \(k_{\mathrm{ch}}\) negligible, except for peptide 946- 961 of delta spike." + +<--- Page Split ---> +![PLACEHOLDER_36_0] + +
Supplementary Fig. 4. Influence of amino acid changes on the \(k_{ch}\) of residues of spike variants. The ratios between the \(kch\) of spike variants and Wuhan spike and the \(kch\) of G614 spike residues is plotted from residue 1 to 628 (a) and from residue 629 to 1256 (b). Values are extracted from Supplementary Data 1. Amino acid changes are illustrated on the left of the graphs.
+ +<--- Page Split ---> +![PLACEHOLDER_37_0] + + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The authors have addressed many of the questions I had, and I commend them on including much of the data that is used to inform how they interpret their bimodal spectra. Based on this data and their response, there are a few last minor points that should be addressed prior to publication. + +I agree with the authors that the isolated RBD experiment sheds a lot of light on the source of the bimodal spectra, so it likely does not stem from a lobe of the trimer simply being unbound. In line 322, the authors state "whilst the more exchanged (high- mass) population likely corresponding to a closed protomer transitioning to the open state and readying to engage another receptor molecule". This statement makes it sound like the high- mass population should be able to bind Ace2, but then why is it unable to bind another molecule of Ace2? Maybe rephrasing this line to indicate that the high- mass population is somehow perturbed, but somehow still does not engage Ace2 like the other lobes of the trimer would help minimize confusion. If prior literature has made speculations about what this third lobe could be doing, then I recommend referencing those here. + +- The attached additional spectra help confirm the reproducibility of the observed bimodals, but for several cases the two populations are so poorly resolved that deconvolution to extract data specific to each subpopulation can be ambiguous and potentially misleading. For example in figure S45 the spectra for G614 at 15 s and 1 min can likely be fit just as well with many other combinations of deuterium levels and intensities. The specific phrase: "The HDX of the high-mass population in the bound states appeared inconsistent with the HDX of the respective apo states." should be clarified so that it specifically refers to the earliest time point where no evidence was seen for a population consistent with unbound RBD. + +- In light of the attached spectra data there is one other possibility the authors should consider as a source of the observed bimodal spectra. Dissociation of ACE2 during deuterium exchange might also explain observed bimodals presented in Fig S42, S44, as unbinding of ACE2 during D2O incubation will likely start to occur in a matter of minutes. The general trend from Wuhan/G14 to Beta to Alpha showing later transitions in the EX1, appear to match the same trend in koff kinetics reported by Wrobel et al: https://www.nature.com/articles/s41467-022-28768-w#MOESM1. This source of bimodal would also be consistent with the earliest time point in the Ace2 bound form not yet showing a second (highly deuterated population) as the dissociation has yet to occur to any appreciable degree. I don't think the authors need to elaborate on this, but I think this is something the authors should at least mention as another possible confounding factor that is influencing the observed bimodal spectra in either the results or discussion. + +- The authors should also include what temperature the pre-binding with Ace2 for 1 hour was conducted at. I know this seems nitpicky but there several labs working on similar systems and temperature may drastically affect binding kinetics for anyone attempting to reproduce these studies. + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +## Other issues: + +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and over- reaching. This should be rephrased to indicate what the figure is showing, ie., Differences in HDX between Wuhan D614 and G614 spikes. + +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +## Reviewer #3 (Remarks to the Author): + +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +## Major concern: + +Why did the authors use a ratio of 1:2 spike:Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? Additionally, how long was the spike:ACE2 complex incubated prior to exchanges? Do + +<--- Page Split ---> + +the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +## Major point 2: + +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT + +<--- Page Split ---> + +and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit this section. + +Minor point: + +The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +We thank the reviewer for pointing out this discrepancy, as indeed, in the interest of saving space, we oversimplified this issue. Following the reviewer's suggestion, we have now addressed it in the lines 435- 441 and 445- 446 of the discussion session. + +Other issues: + +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and over + +<--- Page Split ---> + +reaching. This should be rephrased to indicate what the figure is showing, ie., Differences in HDX between Wuhan D614 and G614 spikes. + +We thank the reviewer for the suggestion. We have now changed the figure caption in 'Differences in structural dynamics between Wuhan (D614) spike and G614 spike' + +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +We now changed this sentence to: 'Hence, in all analyses we used a version of spike ectodomains stabilized by R682S, R685S substitutions in the polybasic cleavage sites and K986P, K987P (2P) substitutions, which combined make the spikes furin- uncleavable and unable to transition to the postfusion conformation." (lines 143- 147) + +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +We have now removed a reference to the 'closed state' in the figure. + +## Reviewer #2 (Remarks to the Author): + +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +We thank the reviewer for the suggestions. We had cited two of Ganesh Anand's papers (ref. 35 and 39), and we have now included his recent preprint (ref. 40). We have also now included the work for Wilson group on the RBD (ref. 41) and a very recent article based on mass photometry data (ref. 42). However, we could not find any HDX-MS study on spike conducted by Komives group. + +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +We thank the reviewer for this suggestion. We have now analysed with HX- Express2 another peptide spanning the RBM (peptide 495- 510) and included this extra analysis in the supplementary information + +<--- Page Split ---> + +(a peptide spanning the same residues is unfortunately absent in the omicron spike) (Fig. S44- 45). It is worth noting that the HX- express fitting returned very similar relative size of populations and their time- dependent evolution, for every spike variant, as the peptide previously included. We have also extracted from DynamX the stacked spectral plots of many other peptides encompassing this region, and included them in the supplementary figures (Fig. S41). We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless the peptide signal- to- noise ratio. Here below the additional figures. + +![PLACEHOLDER_45_0] + + +<--- Page Split ---> +![PLACEHOLDER_46_0] + + +<--- Page Split ---> +![PLACEHOLDER_47_0] + + +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express22 (see Supplementary Figs. 42- 45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +![PLACEHOLDER_48_0] + + +<--- Page Split ---> + +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity -BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express22 and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. 45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +![PLACEHOLDER_50_0] + + +<--- Page Split ---> +![PLACEHOLDER_51_0] + + +<--- Page Split ---> + +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. A) Mass spectra of peptide of Wuhan, G614 and delta spikes. B) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with bimodal fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +This is a very interesting input and we completely align with the reviewer's thoughts. We have added the following paragraph in the discussion (lines 410- 415): + +"The conformational plasticity of this NTD site presumably allows antibody- vulnerable configurations of conformational epitopes to remain occasionally populated, reducing, but not completely abrogating, antibody- mediated protection. At the same time, linear NTD epitopes are likely more impacted by the residue changes in spike variants rather than by a different conformational aspect of the NTD of VOCs." + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +## Major concern: + +Why did the authors use a ratio of 1:2 spike: Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +This an important point and we thank the reviewer for the opportunity to clarify it. For a Spike trimer to be ACE2 binding- competent at least one of its RBDs must be erect and a mixture of its open and closed states within the trimer is well known in the literature (see e.g. https://doi.org/10.1016/j.cell.2020.02.058, https://www.nature.com/articles/s41594- 020- 0468- 7. pdf?origin=ppub, https://www.pnas.org/doi/10.1073/pnas.2022586118, and https://www.nature.com/articles/s41467- 022- 28882- 9). Spikes with all three RBDs accessible are rarely observed, at least in cryoEM. Although we cannot be sure of the precise ratios of up and down states in spikes in solution, in non- cryogenic state, the conformational dynamics between these adopted structures governs this interaction and is what our solution HDX- MS experiments can report on. In our experiments we, therefore, try to capture a situation where we can monitor this behaviour within the experimental limitations of required sample amounts and concentration - with large concentrations of the material difficult to produce. + +The 1:2 ratio was chosen after initial optimization HDX- MS experiments. We incubated Wuhan and G614 spikes at 1:2 and 1:3 ratio spike: ACE2 and found the same difference in HDX for spike peptides within the RBM at both ratios. This suggests that increased ACE2 above 1:2 was not increasing spike binding occupancy, but likely leads to an increased population of unbound ACE2 in our labelled sample. Accordingly, the HDX differences observed within ACE2 incubated at 1:2 and 1:3 ratios spike: ACE2 appeared significantly higher at ratio 1:2 than at 1:3, which supports that a higher fraction of unbound ACE2 is present in the latter case. In support of the ratio chosen, a very recent mass photometry paper (https://pubs.rsc.org/en/content/articlelanding/2022/cc/d2cc04711j) on Wuhan and omicron spikes (in the same '2P' pre- fusion stabilised version we use) reported that 1:4 spike: ACE2 shows predominantly spike bound to one ACE2, with some spike bound to 2 ACE2 but negligible amounts bound to 3 ACE2. + +Considering these observations, 1:2 ratio likely provides information on saturated spike ACE2- accessible 'up' states. As the reviewer points out, this would mean that one of the RBDs will be unbound, but it is likely to be in an ACE2- inaccessible "down" state. The experiment performed to address major concern 2 provides further evidences in support of the ratio chosen, for every spike analysed (please see below). + +<--- Page Split ---> + +In this revised version, we inserted this optimization procedure in a dedicated paragraph of the method session (Optimization of the HDX conditions – lines 546- 554) and added two figures showing these results in the supplementary information and present them below. + +![PLACEHOLDER_54_0] + +
Fig. S47. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the RBM when Wuhan and G614 spikes are incubated at 1:2 and 1:3 ratios with ACE2. No significant differences in ΔHDX are observed between the two incubation ratios and for both spike trimers.
+ +![PLACEHOLDER_54_1] + + +Supplementary Fig. 48. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the ACE2 binding site when ACE2 is incubated at 2:1 and 3:1 ratios with Wuhan spike. A minor decrease in HDX is observed at ratio 3:1. + +<--- Page Split ---> + +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? + +Bimodal spectra were not observed in apo spikes by working with freshly prepared spike samples. In the ACE2- bound state, beyond the 495- 513 region, we observed - for every spike trimer analyzed - the appearance of bimodal isotopic envelopes in the HR1 region spanning residues 962- 982, which is one of the segments becoming more dynamic during the priming for fusion of spike. In the interest of writing the manuscript for a broad readership, we did not describe the specific HDX regime of this particular segment in detail, rather summarizing the increased HDX observed in various S2 stretches as 'increased dynamics'. However, following the reviewer's inquiry, we have reconsidered our initial thoughts and have now described the HDX bimodality seen in this region of bound- spikes in the manuscript test, as presumably it also contributes to the priming mechanism (lines 355- 363). + +"Notably, peptides spanning residues 962- 982 manifested increased HDX in the form of bimodal isotopic envelopes when spikes are engaged to ACE2 (Fig. 6c and Supplementary Fig. 46). This segment encompasses the HR1 helix, which undergoes a large conformational rearrangement upon the transition to post- fusion state15, suggesting that our analysis captured the specific dynamic events leading to the HR1 reorientation, which primes spikes for fusion. The breadth of this HDX bimodality varies with \(\text{omicron} > \text{alpha} > \text{beta} > \text{G614} \approx \text{Wuhan spike}\) , with omicron spike pre- manifesting it also in the absence of ACE2 (Fig. 6c and Supplementary Fig. 46)." + +Additionally, we have modified Fig. 6c in the main text to include the isotopic envelopes of peptides 963- 977, in place of its uptake plots. We believe that the envelopes deliver a much clearer message. We also added a supplementary figure (S46) including the stacked spectral plots of peptide 963- 977 and an overlapping peptide (962- 977). + +<--- Page Split ---> +![PLACEHOLDER_56_0] + +
C Peptide 963-977 - Priming for fusion of HR1
+ +![PLACEHOLDER_56_1] + +
Fig. 6 Spike priming for fusion. A) Regions manifesting increased dynamics in spikes bound to ACE2 are superimposed and colored in red on a single protomer of the structure of D614 spike with one RBD bound (PDB: 7a9514); regions with increased dynamics only in spike of alpha and omicron variants bound to ACE2 are colored in magenta. B) The magnitude of the destabilization of the core helices is represented by differential colouring (red scale) for the various spike trimers. The HR1 region (962-982) manifesting HDX bimodality is framed in grey. C) The bimodal isotopic envelopes of a model peptide spanning the HR1 region 962-982 are shown at 15 s and 1 min time points for spike (S) variants in the ACE2-bound form and for omicron spike alone, to exemplify their priming for fusion upon receptor engagement. Bimodal envelopes manifest in omicron spike also in the absence of ACE2, indicating it as pre-primed for fusion.
+ +<--- Page Split ---> +![PLACEHOLDER_57_0] + + +Supplementary Fig. 46. HDX bimodality in the HR1 of spikes in complex with ACE2 and omicron spike alone. Stacked spectral plots of peptides 962- 977 and 963- 977 illustrate the evolution of the bimodal isotopic envelopes over the time points studied. Particularly, time points 15 s and 1 min (23 °C) show clear separation between the low- and high- mass envelopes in every spike trimer, with the relative intensity and centroids of the two envelopes reporting on the degree of destabilization exerted by the ACE2 binding on the HR1. The isotopic envelopes in omicron spike alone manifest evident peak broadening, suggesting that the its HR1 follows a bimodal HDX behaviour even in the absence of ACE2. + +<--- Page Split ---> + +Additionally, how long was the spike:ACE2 complex incubated prior to exchanges? Do the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +Spikes- ACE2 complexes were incubated for one hour before starting the deuterium labelling (we now specified this in the method session). Given the Kds are, depending on the variant, in the order of 10 to 150 nM with kons between 0.07 and 0.2 uM \(^{- 1}\) s \(^{- 1}\) (https://doi.org/10.1038/s41467- 022- 28768- w - see supplementary info), we believe that this incubation period largely suffices for system equilibration. + +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors' coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +We thank the reviewer for highlighting this important point. We have now extracted from DynamX the stacked spectral plots of many other peptides encompassing this region and included them in the supplementary figures. We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless of the peptide signal- to- noise ratio (Fig. S41). We also analysed the bimodal isotopic distributions of another peptide (495- 510) with HX- express2 and included this extra analysis in the supplementary information (a matching peptide is unfortunately absent in the omicron variant) (Fig. S44- 45). It is worth noting that the HX- express2 fitting returned very similar relative size of populations and their time- dependent evolution, for every spike variant, compared to the peptide previously included. The result of this extra analysis could also address the reviewer's following concern about the calculated size of the populations. + +![PLACEHOLDER_58_0] + + +<--- Page Split ---> +![PLACEHOLDER_59_0] + + +<--- Page Split ---> +![PLACEHOLDER_60_0] + + +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express22 (see Supplementary Figs. 42- S45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +![PLACEHOLDER_61_0] + + +<--- Page Split ---> + +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity -BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express22 and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. S45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +![PLACEHOLDER_63_0] + + +<--- Page Split ---> +![PLACEHOLDER_64_0] + + +<--- Page Split ---> + +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. a) Mass spectra of peptide of Wuhan, G614 and delta spikes. b) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with binomial fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +We thank the reviewer for considering this important aspect. We based our interpretation on the following observations and experiments. + +As the reviewer suggests, we had carefully compared the HDX of the high- mass population of the bound states and the HDX of the population (unimodal spectra) of the apo state (also shown in fig. S42 and S44). The two HDX profiles do not appear consistent. We believe that, if the ACE2 was not sufficient to saturate the binding of the monomers with accessible (erect) RBD, the high- mass population in the bound states should align on the m/z scale to the apo spike states, manifesting already, and with clear separation from the low- mass population, at 4 s or 20 s on ice, but this does not appear to be the case. We do not observe it at 4 s on ice for Wuhan and G614 bound- spikes, or at 20 s on ice for alpha, beta and omicron bound- spikes. We have now added a note on this in the figure caption of fig. S42 and S44. + +<--- Page Split ---> + +To better investigate this aspect, for this revised version, we performed an extra experiment. We performed HDX- MS on the isolated RBD of the ancestral Wuhan spike in the presence and absence of ACE2, at ratio 3:2 RBD:ACE2, which simulates our 1:2 spike trimer:ACE2 ratio used in our experiments. Given that the whole population of isolated RBD molecules are binding- competent, with such a binding stoichiometry, \(33\%\) of the RBD population remain effectively unbound in the presence of ACE2. We did not observe bimodal distributions in the RBM of the bound- RBD state, indicating that a mixture of bound and unbound monomers, with same conformational characteristics in the apo state, does not manifest with a clear envelope bimodality under the conditions studied. We now included the extracted stacked spectral plot of the bound- RBD in the supplementary figures (please, see previous figure S41). Furthermore, the preliminary data shown above and the experiment performed to address major point 2 support a scenario where spike erect RBDs are saturated in binding occupancy. + +These observations prompt us to associate the RBM bimodal HDX profiles to the spike cooperative binding mode reported in previous studies; we thus interpreted the high- mass population as an extra monomer that erects upon ACE2 binding (in a cooperative manner) and is likely able to engage with an extra ACE2 molecule, thus displaying an HDX profile that differs from the monomers in the unbound state. This gives rise to a fine- tuned equilibrium of states, characteristic for each spike variant, that we aimed at deciphering with our analysis. + +We agree with the reviewer that we should not strictly refer to this HDX behaviour as EX1 kinetics, as we associated it to the behaviour of different monomers, and not to an individual protein stretch displaying correlated exchange. We thus now refer to it as "HDX bimodality". We also modified the text (lines 306- 324) to better explain these observations and include the extra experiment performed, and we present it here below. + +"Furthermore, we observed that the HDX profiles of all peptides spanning the RBM of spike trimers (residues 495- 503) in the ACE2- bound states showed bimodal isotopic distributions, hence a high- and a low- mass population, whereas a single unimodal distribution characterized the apo states (Fig. 5 and Supplementary Figs. 41- 45). The HDX of the high- mass populations in the bound states appeared inconsistent with the HDX of the respective apo states. In contrast, the ACE2- bound state of the isolated ancestral RBD (3:2 RBD: ACE2), containing a significant fraction (33%) of unbound population, did not display bimodal isotopic distributions in the RBM (Supplementary Fig. 41), ruling out that a mixture of bound and unbound populations, with same conformational characteristics in the apo state, manifests with an HDX bimodality under the conditions studied. These data thus suggest that the RBD of bound spikes can explore two distinct and slowly interconverting populations, which exchange giving rise to two resolved isotopic distributions. We rationalize, based on the receptor binding mode reported in previous studies \(^{14,55}\) , that the bimodal HDX profile of the bound spike states reports on cooperative opening within the spike trimer, with the less exchanged (low- mass) population accounting for open protomers with a bound RBD, whilst the more exchanged (high- mass) population likely corresponding to closed protomers transitioning to the open state and readying to engage another receptor molecule." + +We also would like to highlight that bimodal spectra were not observed in the bound states of ACE2, even though we observed these states at uncomplete binding occupancy (please, see answer to Major point 2). + +<--- Page Split ---> + +Major point 2: + +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +The reviewer is right; however, the experiments we referred to were all based on methods (biolayer interferometry) that measure only the affinity of a single monomer binding to one ACE2, as spikes are immobilised and thus their concentrations (as well as the effective concentrations of individual accessible RBDs) irrelevant for the measurement, while ACE2 monomers form a mobile phase. We have now specified this in the text (lines 269- 270). In our HDX- MS experiments, we equilibrated all complexes for one hour before labelling, which, considering the aforementioned favourable kon and Kd, should allow for equilibration to be reached. + +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit + +We thank the reviewer for highlighting this important point and below we provide further details to support our experimental design and their conclusions. + +<--- Page Split ---> + +Despite the molar excess of spike monomers, ACE2 is in excess compared to the binding- competent open monomers with available erect RBDs within spike trimers. To confirm this also in HDX- MS, we performed an additional experiment for this revised version of the manuscript. We labelled ACE2 in the presence and absence of the isolated ancestral RBD, at a 3:2 ratio RBD:ACE2, which simulates a 1:2 spike trimer:ACE2 ratio. Differently from the RBDs embedded in a spike trimer, the whole population of isolated RBD is binding- competent. In this scenario, the RBD is effectively in excess compared to ACE2, granting full ACE2 binding occupancy, and indeed, we observed that the binding effect on ACE2 manifested with much greater magnitude (cumulative \(\Delta \mathrm{HDX} = 19.15\) Da) compared to that induced by spike trimers, which show generally less cumulative \(\Delta \mathrm{HDX}\) due to the presence of a (varied) fraction of unbound ACE2 in the bound state. This experiment indicates that the ACE2 is not saturated in binding occupancy in the HDX- MS experiments performed on spike trimers (hence spike trimers are saturated or close to saturated), therefore we argue that the magnitude of HDX effects ( \(\Delta \mathrm{HDX}\) ) on the ACE2 holds useful information on the spike- ACE2 binding stoichiometry. + +It has to be noted that the \(\Delta \mathrm{HDX}\) induced by alpha, beta and delta spikes also have a contribution from the stability of the hydrogen bonding network engaged with ACE2 (related to the affinity of their individual binding- competent monomers to the receptor), which will result in a cumulative effect given by their binding stoichiometry and affinity (reported as higher than for G614 in several studies). This is presumably the reason why for alpha spike a cumulative \(\Delta \mathrm{HDX}\) slightly higher than that of the isolated RBD was observed. + +In our hands, the incomplete binding occupancy of ACE2 did not manifest with isotopic bimodal distributions in its spike binding sites, making it difficult to estimate the fraction of unbound ACE2 for the different trimers. This is one of the reasons why we refrain from proposing any stoichiometry model. + +We have now included the results of this extra experiment (see figures below) in fig. 3 of the main text and Fig S27 and S40 of supplementary information and have also rewritten this section in the main text to provide a clearer explanation of our rationale (lines 243- 255). + +"Next, by studying the HDX of the ACE2 ectodomain alone and in complex with spike trimers (1:2 spike trimer:ACE2) and the isolated ancestral RBD (3:2 RBD:ACE2), we measured the magnitude of the HDX effects ( \(\Delta \mathrm{HDX}\) ) induced by spike binding to ACE2. The whole population of the isolated RBD is binding competent, granting complete occupancy of the ACE2 binding sites, whereas only a fraction of the RBDs embedded within spikes are erect and thus able to engage the receptor. The observed \(\Delta \mathrm{HDX}\) results from a cumulative effect of binding stoichiometry (how many ACE2 molecules are bound) and the stability of the hydrogen- bonding network between spikes and ACE2 (which can be related to the spike- receptor binding affinity), enabling us to rank the spike- receptor binding avidity (i.e. the overall strength of binding arising from the affinity of an individual RBD- ACE2 interaction and the stoichiometry of each spike trimer engaging between zero and three ACE2 molecules at once)." + +For clarity, we also modified the following sentence (lines 261- 268): + +"The cumulative \(\Delta \mathrm{HDX}\) induced by different spikes varied with alpha \(> \text{beta} > \text{delta} > \text{G614} > \text{Wuhan} \approx \text{omicron (Fig. 3b and Supplementary Fig. 28). These} \Delta \mathrm{HDX}\) values were generally lower than that induced by the isolated RBD, indicating that a fraction of ACE2 molecules remained unbound in the spike:ACE2 states, thus suggesting that all binding- competent RBDs within the trimers were fully occupied." + +<--- Page Split ---> +![PLACEHOLDER_69_0] + +
Fig. 3 Effect of spike binding on ACE2 dynamics. A) Regions of ACE2 manifesting a significant decrease in HDX upon spike binding are superimposed on the structure of ACE2 ectodomain bound to RBD (PDB: 2ajf), colored in blue scale according to the magnitude of the HDX effect. The region colored in red indicates increased HDX upon binding, in dark gray regions with no coverage. B) ACE2 binding avidity. The cumulative difference in HDX (ΔHDX) between ACE2 alone and ACE2 bound to spikes and the isolated ancestral RBD for selected peptides spanning binding sites and across time points 20 s on ice, 10 min at 23 °C and 360 min at 28 °C is plotted. A plot for all time points in Supplementary Fig. 28.
+ +<--- Page Split ---> +![PLACEHOLDER_70_0] + + +Supplementary Fig 27. Difference plot illustrating the difference in HDX between ACE2 in complex with the isolated ancestral RBD and ACE2 alone (orange line indicates: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Peptide segments of interest are highlighted. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance and a dotted black line the 99% CI as a threshold for significance. + +![PLACEHOLDER_70_1] + + +Supplementary Fig 40. Difference plot illustrating the difference in HDX between the isolated ancestral RBD in complex with ACE2 and the isolated ancestral RBD alone (orange line: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Residues comprising a region with significant differences in HDX are indicated. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance. + +<--- Page Split ---> + +Minor point: + +Minor point:The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +We gratefully thank the reviewer for highlighting the caveat arising from the comparison of peptides harboring mutations and suggesting the paper (which we now cited). We briefly explained in the method section how they were compared but did not consider this to a sufficient degree. We explain our comparative workflow below and the additional \(\mathsf{k}_{\mathrm{ch}}\) considerations done: + +## Workflow: + +We selected for comparison only peptides with identical cleavage, i.e. same N- and C- termini. Thanks to the numerous peptides available and the high redundancy, we could, in most instances, find matching peptides. However, this became impossible in case of deletions and insertions. We normalized the uptake values of mutant peptides by the uptake of their MaxD (= fully deuterated control) and obtained absolute uptake values (in Da) referencing to G614 spike, with the following equation (now included in the method session): + +\[\Delta HDX = \left(\frac{DU\:mutant\:peptide}{DU\:MaxD\:mutant\:peptide}\times DU\:MaxD\:G614\:spike\:peptide}\right) - DU\:G614\:spike\:peptide\] + +For instance, at a given time point, peptide X of G614 spike has DU of 3 Da with a MaxD of 10 Da; its matching peptide Y in alpha spike has DU of 4 Da with MaxD of 10.3 Da; the normalized DU for alpha spike is 3.88 Da. The \(\Delta HDX\) reported in the butterfly plot is \(+0.88\) Da. This was done with the aim to insert mutant peptides in the butterfly plots, making the HDX comparison more visually intuitive and easily readable. + +## Considering kch differences: + +We acknowledge the fact that the MaxD does not entirely alleviate the caveat arising from the difference in kch between peptides harboring mutations. Before performing the experiments, we had checked the values of \(\mathsf{k}_{\mathrm{ch}}\) (according to the 2018 updated values: doi: 10.1007/s13361- 018- 2021- z) and + +<--- Page Split ---> + +noticed that the differences are minor and most likely give rise to \(\Delta \mathsf{HDX}\) below the threshold of significance when comparing peptides without a significant difference in \(k_{\mathrm{op}}\) . + +However, we now performed a more thorough analysis on the impact that the \(k_{\mathrm{ch}}\) offset has on the differences measured. We included this analysis in a supplementary table (Supplementary Data 1). We tested a null hypothesis in which every difference in HDX observed arises from a difference in \(k_{\mathrm{ch}}\) . + +In more detail: we calculated the average \(k_{\mathrm{ch}}\) for a peptide and its mutant variant - excluding the N- terminal residue (one peptide per mutation was analyzed). The average \(k_{\mathrm{ch}}\) was selected as the individual amide HDX rates are averaged when measured by MS at peptide level. We then calculated the \(\%\) of observed \(\Delta \mathsf{HDX}\) for that peptide normalized by MaxD, selecting the time point showing the highest \(\Delta \mathsf{HDX}\) , as considered the most sensitive to differences. + +In most instances, as the reviewer foresaw, the \(\% \Delta \mathsf{HDX}\) significantly surpasses the \(\% \Delta k_{\mathrm{ch}}\) , including for peptides spanning K417N (the table includes a 'note' column describing the outcome of the analysis). Therefore, while acknowledging the fact that the \(\Delta \mathsf{HDX}\) values have an offset at quantitative level, the observed \(\Delta \mathsf{HDX}\) can be considered qualitatively reliable. Only for one peptide (946- 961 of delta spike), we cannot unambiguously demonstrate that the observed \(\Delta \mathsf{HDX}\) arises from a real difference in dynamics in respective to G614 spike. Therefore, we have not based any discussion on that peptide. + +We now mentioned this in lines 184- 187 of the results and included the description of this approach in the method session (lines 612- 630), acknowledged the presence of this caveat. We also included new figures in the supplementary information (Fig. S4) where residue- level \(k_{\mathrm{ch}}\) ratios are plotted. + +"To compare peptides containing residue substitutions in spike variants (mutant peptides) with peptides of G614 spike, segments with identical N- and C- termini were selected. Their difference in deuterium incorporation ( \(\Delta \mathsf{HDX}\) ) was calculated according the equation 1 and plotted in Supplementary Figs. 9- 12: + +\[\Delta \mathsf{HDX} = \left(\frac{\mathsf{D}\mathsf{U}\mathsf{m}\mathsf{u}\mathsf{t}\mathsf{a}\mathsf{n}\mathsf{t}\mathsf{p}\mathsf{e}\mathsf{p}\mathsf{t}\mathsf{i}\mathsf{d}}{\mathsf{D}\mathsf{U}\mathsf{M}\mathsf{a}\mathsf{x}\mathsf{D}\mathsf{m}\mathsf{u}\mathsf{t}\mathsf{a}\mathsf{n}\mathsf{t}\mathsf{p}\mathsf{e}\mathsf{t}\mathsf{p}\mathsf{i}\mathsf{d}}\times \mathsf{D}\mathsf{U}\mathsf{M}\mathsf{a}\mathsf{x}\mathsf{D}\mathsf{G}\mathsf{6}14\mathsf{s}\mathsf{p}\mathsf{i}\mathsf{k}\mathsf{e}\mathsf{p}\mathsf{e}\mathsf{t}\mathsf{p}\mathsf{i}\mathsf{d}\right) - \mathsf{D}\mathsf{U}\mathsf{G}\mathsf{6}14\mathsf{s}\mathsf{p}\mathsf{i}\mathsf{k}\mathsf{e}\mathsf{p}\mathsf{e}\mathsf{t}\mathsf{p}\mathsf{i}\mathsf{d} \quad (1)\] + +To estimate the impact of the difference in chemical exchange rate constants \((k_{\mathrm{ch}})\) on the observed \(\Delta \mathsf{HDX}\) between mutant peptides and peptides of G614 spike \(^{50}\) , firstly the \(k_{\mathrm{ch}}\) of individual residues within the spike protein sequences were calculated \(^{49}\) . Successively, at peptide level, the percentage of difference in \(k_{\mathrm{ch}}\) ( \(\% \Delta k_{\mathrm{ch}}\) ) were compared to the percentage of \(\Delta \mathsf{HDX}\) normalized by the MaxD ( \(\% \Delta \mathsf{HDX}\) ) in the time point showing maximal effect, as reported in Supplementary Data 1. The identified differences in HDX between spike variants and G614 spike in segments spanning amino acid changes resulted of high- confidence, with the impact of \(k_{\mathrm{ch}}\) negligible, except for peptide 946- 961 of delta spike." + +<--- Page Split ---> +![PLACEHOLDER_73_0] + +
Supplementary Fig. 4. Influence of amino acid changes on the \(k_{ch}\) of residues of spike variants. The ratios between the \(kch\) of spike variants and Wuhan spike and the \(kch\) of G614 spike residues is plotted from residue 1 to 628 (a) and from residue 629 to 1256 (b). Values are extracted from Supplementary Data 1. Amino acid changes are illustrated on the left of the graphs.
+ +<--- Page Split ---> +![PLACEHOLDER_74_0] + + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +The authors have addressed many of the questions I had, and I commend them on including much of the data that is used to inform how they interpret their bimodal spectra. Based on this data and their response, there are a few last minor points that should be addressed prior to publication. I agree with the authors that the isolated RBD experiment sheds a lot of light on the source of the bimodal spectra, so it likely does not stem from a lobe of the trimer simply being unbound. In line 322, the authors state "whilst the more exchanged (high- mass) population likely corresponding to a closed protomer transitioning to the open state and readying to engage another receptor molecule". This statement makes it sound like the high- mass population should be able to bind Ace2, but then why is it unable to bind another molecule of Ace2? Maybe rephrasing this line to indicate that the high- mass population is somehow perturbed, but somehow still does not engage Ace2 like the other lobes of the trimer would help minimize confusion. If prior literature has made speculations about what this third lobe could be doing, then I recommend referencing those here. + +- The attached additional spectra help confirm the reproducibility of the observed bimodals, but for several cases the two populations are so poorly resolved that deconvolution to extract data specific to each subpopulation can be ambiguous and potentially misleading. For example in figure S45 the spectra for G614 at 15 s and 1 min can likely be fit just as well with many other combinations of deuterium levels and intensities. The specific phrase: "The HDX of the high-mass population in the bound states appeared inconsistent with the HDX of the respective apo states." should be clarified so that it specifically refers to the earliest time point where no evidence was seen for a population consistent with unbound RBD. + +- In light of the attached spectra data there is one other possibility the authors should consider as a source of the observed bimodal spectra. Dissociation of ACE2 during deuterium exchange might also explain observed bimodals presented in Fig S42, S44, as unbinding of ACE2 during D2O incubation will likely start to occur in a matter of minutes. The general trend from Wuhan/G14 to Beta to Alpha showing later transitions in the EX1, appear to match the same trend in koff kinetics reported by Wrobel et al: https://www.nature.com/articles/s41467-022-28768-w#MOESM1. This source of bimodal would also be consistent with the earliest time point in the Ace2 bound form not yet showing a second (highly deuterated population) as the dissociation has yet to occur to any appreciable degree. I don't think the authors need to elaborate on this, but I think this is something the authors should at least mention as another possible confounding factor that is influencing the observed bimodal spectra in either the results or discussion. + +- The authors should also include what temperature the pre-binding with Ace2 for 1 hour was conducted at. I know this seems nitpicky but there several labs working on similar systems and temperature may drastically affect binding kinetics for anyone attempting to reproduce these studies. + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +The authors have addressed many of the questions I had, and I commend them on including much of the data that is used to inform how they interpret their bimodal spectra. Based on this data and their response, there are a few last minor points that should be addressed prior to publication. I agree with the authors that the isolated RBD experiment sheds a lot of light on the source of the bimodal spectra, so it likely does not stem from a lobe of the trimer simply being unbound. In line 322, the authors state "whilst the more exchanged (high- mass) population likely corresponding to a closed protomer transitioning to the open state and readying to engage another receptor molecule". This statement makes it sound like the high- mass population should be able to bind Ace2, but then why is it unable to bind another molecule of Ace2? Maybe rephrasing this line to indicate that the high- mass population is somehow perturbed, but somehow still does not engage Ace2 like the other lobes of the trimer would help minimize confusion. If prior literature has made speculations about what this third lobe could be doing, then I recommend referencing those here. + +Thank you. We welcome the opportunity to better elaborate and agree with the reviewer: the high- mass population likely represents an unbound state, which is no longer closed but not properly open. Disordered RBD lobes characterizing such intermediate states have been described for cryo- EM datasets of SARS- CoV- 2 spikes \(^{1,2,3}\) . In cryo- EM, these exposed RBD lobes generally constitute a minor population, as also seen by our HDX- MS analysis, and have been proposed to represent transient dynamic conformations leading to a fully open, ACE2- binding- competent form. This can explain why the HDX of high- mass population, which may be associated with these disordered RBDs, does not align to the low- mass population of the bound states or to the population of the unbound states. We have now rephrased the relevant passage referencing the cryo- EM studies \(^{1,2,3}\) (lines 313- 314 and 323- 326). + +1. SARS-CoV-2 and bat RaTG13 spike glycoprotein structures inform on virus evolution and furincleavage effects. doi: 10.1038/s41594-020-0468-7 +2. Distinct conformational states of SARS-CoV-2 spike protein. doi: 10.1126/science.abd4251 +3. Structures and distributions of SARS-CoV-2 spike proteins on intact virions. doi: 10.1038/s41586-020-2665-2 + +- The attached additional spectra help confirm the reproducibility of the observed bimodals, but for several cases the two populations are so poorly resolved that deconvolution to extract data specific to each subpopulation can be ambiguous and potentially misleading. For example in figure S45 the spectra for G614 at 15 s and 1 min can likely be fit just as well with many other combinations of deuterium levels and intensities. The specific phrase: "The HDX of the high-mass population in the bound states appeared inconsistent with the HDX of the respective apo states." should be clarified so that it specifically refers to the earliest time point where no evidence was seen for a population consistent with unbound RBD. + +Following the reviewer's advices, we have clarified that no evidence of a population consistent with unbound RBM is seen at the early HDX time points (lines 316- 317). We have now clearly specified that the exact relative proportion of the low- and high- mass subpopulations cannot be derived from our data (lines 330- 332) and modified the caption of figs. 5, S42 and S44 to clarify that our data need to be regarded as trends. + +<--- Page Split ---> + +- In light of the attached spectra data there is one other possibility the authors should consider as a source of the observed bimodal spectra. Dissociation of ACE2 during deuterium exchange might also explain observed bimodals presented in Fig S42, S44, as unbinding of ACE2 during D2O incubation will likely start to occur in a matter of minutes. The general trend from Wuhan/G14 to Beta to Alpha showing later transitions in the EX1, appear to match the same trend in koff kinetics reported by Wrobel et al: https://www.nature.com/articles/s41467-022-28768-w#MOESM1. This source of bimodal would also be consistent with the earliest time point in the Ace2 bound form not yet showing a second (highly deuterated population) as the dissociation has yet to occur to any appreciable degree. I don't think the authors need to elaborate on this, but I think this is something the authors should at least mention as another possible confounding factor that is influencing the observed bimodal spectra in either the results or discussion. + +We agree with the reviewer that the koff of the complexes suggest that receptor dissociation starts occurring during the exchange reaction. The control experiment on the isolated RBD bound to ACE2, where a significant fraction of RBD remains unbound, indicates that mixture of bound and unbound RBDs does not manifest with a clear bimodality under the HDX conditions employed. In the same way, we believe it is unlikely that the spike RBDs remaining transiently unbound because of receptor dissociation could give rise to bimodality. However, following the reviewer's observation, we have adapted the text to include this alternative explanation and the evidence in support of this hypothesis (lines 313- 318). + +The whole paragraph now reads: + +"...The more exchanged (high- mass) population represents RBDs perturbed by the presence of ACE2 but likely unbound: either because ACE2 transiently dissociates from them over the course of the exchange reaction or because they assume an intermediate, not fully erect state. The former hypothesis is supported by the observation that no evidence of a population consistent with the HDX of the unbound RBMs appears in the spike bound states at the early time points. However, the ACE2- bound state of the isolated ancestral RBD (3:2 RBD: ACE2), containing a significant fraction (33%) of unbound population, does not display bimodal isotopic distributions in the RBM under the conditions studied (Supplementary Fig. 41), suggesting that a simple mixture of bound and unbound populations of RBDs, even in the context of a spike trimer, would not manifest with an HDX bimodality either. Hence, we associated the high- mass populations of the bimodal HDX profiles with RBDs in an intermediate state, between closed and fully erect, receptor- binding- competent conformations. Such populations, characterized by disordered RBDs, have been observed and described before in cryo- EM studies11,15,55. We thus rationalize, also based on the spike receptor binding mode reported in previous studies14,56, that this population reports on the trimer capability to erect additional RBDs upon ACE2 binding to the neighbouring one/- s: a sign of cooperative opening. The exact relative proportion of the low- and high- mass subpopulations cannot be derived from our data as we cannot accurately deconvolve the two isotopic distributions. Nevertheless, the apparent abundance of the high- mass population seems to correlate with the overall preference of a given spike to adopt the open conformation as described above." + +<--- Page Split ---> + +- The authors should also include what temperature the pre-binding with Ace2 for 1 hour was conducted at. I know this seems nitpicky but there several labs working on similar systems and temperature may drastically affect binding kinetics for anyone attempting to reproduce these studies. + +We have now added this information (lines 577- 579); the method session now reads: + +"Before initiating the exchange reactions, spikes and ACE2 were incubated alone or in complex at ratio 1:2 spike trimer: ACE2 for one hour at the selected labelling temperatures (i.e. on ice or in the thermomixer at 23 °C or 28 °C) and the labelling buffer was as well temperature equilibrated." + +<--- Page Split ---> diff --git a/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..8d4024be3ed895a330fab17b01f49dc1dcb72acb --- /dev/null +++ b/peer_reviews/dec3dbb867d00d61e838a7d2408a0a70f30789717fc095ec13f45c5642ccb456/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1019 @@ +<|ref|>title<|/ref|><|det|>[[61, 41, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 111, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 156, 852, 216]]<|/det|> +Structural dynamics in the evolution of SARS- CoV- 2 spike glycoprotein + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 782]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 145, 393, 161]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 202, 845, 256]]<|/det|> +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +<|ref|>text<|/ref|><|det|>[[115, 295, 857, 423]]<|/det|> +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +<|ref|>text<|/ref|><|det|>[[115, 461, 883, 570]]<|/det|> +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: + +<|ref|>text<|/ref|><|det|>[[115, 583, 650, 629]]<|/det|> +https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +<|ref|>text<|/ref|><|det|>[[115, 667, 861, 702]]<|/det|> +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): + +<|ref|>text<|/ref|><|det|>[[115, 714, 631, 731]]<|/det|> +https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 + +<|ref|>text<|/ref|><|det|>[[115, 742, 612, 759]]<|/det|> +https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 + +<|ref|>text<|/ref|><|det|>[[115, 770, 875, 898]]<|/det|> +Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 211, 134]]<|/det|> +Other issues: + +<|ref|>text<|/ref|><|det|>[[115, 174, 826, 230]]<|/det|> +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and overreaching. This should be rephrased to indicate what the figure is showing, ie., Differences in HDX between Wuhan D614 and G614 spikes. + +<|ref|>text<|/ref|><|det|>[[115, 268, 830, 305]]<|/det|> +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion + +<|ref|>text<|/ref|><|det|>[[115, 314, 794, 351]]<|/det|> +conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +<|ref|>text<|/ref|><|det|>[[115, 389, 839, 408]]<|/det|> +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +<|ref|>text<|/ref|><|det|>[[115, 504, 393, 520]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 559, 880, 652]]<|/det|> +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +<|ref|>text<|/ref|><|det|>[[115, 690, 867, 763]]<|/det|> +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +<|ref|>text<|/ref|><|det|>[[115, 801, 850, 856]]<|/det|> +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 872, 200]]<|/det|> +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +<|ref|>text<|/ref|><|det|>[[116, 266, 393, 283]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 322, 883, 469]]<|/det|> +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +<|ref|>sub_title<|/ref|><|det|>[[116, 509, 228, 525]]<|/det|> +## Major concern: + +<|ref|>text<|/ref|><|det|>[[115, 535, 876, 627]]<|/det|> +Why did the authors use a ratio of 1:2 spike: Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +<|ref|>text<|/ref|><|det|>[[115, 666, 864, 720]]<|/det|> +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? Additionally, how long was the spike: ACE2 complex incubated prior to exchanges? Do the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +<|ref|>text<|/ref|><|det|>[[114, 758, 877, 886]]<|/det|> +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 116, 872, 355]]<|/det|> +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +<|ref|>text<|/ref|><|det|>[[114, 365, 880, 494]]<|/det|> +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +<|ref|>sub_title<|/ref|><|det|>[[116, 533, 221, 549]]<|/det|> +## Major point 2: + +<|ref|>text<|/ref|><|det|>[[114, 560, 881, 761]]<|/det|> +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +<|ref|>text<|/ref|><|det|>[[114, 800, 880, 891]]<|/det|> +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 847, 125]]<|/det|> +slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +<|ref|>text<|/ref|><|det|>[[114, 163, 880, 347]]<|/det|> +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit this section. + +<|ref|>sub_title<|/ref|><|det|>[[115, 388, 208, 404]]<|/det|> +## Minor point: + +<|ref|>text<|/ref|><|det|>[[114, 414, 881, 650]]<|/det|> +The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +<|ref|>text<|/ref|><|det|>[[115, 689, 872, 724]]<|/det|> +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 393, 106]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 126, 842, 180]]<|/det|> +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +<|ref|>text<|/ref|><|det|>[[115, 200, 860, 328]]<|/det|> +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +<|ref|>text<|/ref|><|det|>[[115, 338, 884, 485]]<|/det|> +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +<|ref|>text<|/ref|><|det|>[[115, 502, 866, 536]]<|/det|> +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): + +<|ref|>text<|/ref|><|det|>[[115, 537, 632, 553]]<|/det|> +https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 + +<|ref|>text<|/ref|><|det|>[[115, 556, 610, 572]]<|/det|> +https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 + +<|ref|>text<|/ref|><|det|>[[115, 574, 875, 701]]<|/det|> +Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 713, 861, 766]]<|/det|> +We thank the reviewer for pointing out this discrepancy, as indeed, in the interest of saving space, we oversimplified this issue. Following the reviewer's suggestion, we have now addressed it in the lines 435- 441 and 445- 446 of the discussion session. + +<|ref|>sub_title<|/ref|><|det|>[[115, 807, 212, 822]]<|/det|> +## Other issues: + +<|ref|>text<|/ref|><|det|>[[115, 843, 826, 896]]<|/det|> +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and overreaching. This should be rephrased to indicate what the figure is showing, i.e., Differences in HDX between Wuhan D614 and G614 spikes. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 860, 125]]<|/det|> +We thank the reviewer for the suggestion. We have now changed the figure caption in 'Differences in structural dynamics between Wuhan (D614) spike and G614 spike' + +<|ref|>text<|/ref|><|det|>[[115, 144, 830, 216]]<|/det|> +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +<|ref|>text<|/ref|><|det|>[[115, 227, 826, 300]]<|/det|> +We now changed this sentence to: 'Hence, in all analyses we used a version of spike ectodomains stabilized by R682S, R685S substitutions in the polybasic cleavage sites and K986P, K987P (2P) substitutions, which combined make the spikes furin- uncleavable and unable to transition to the postfusion conformation.' (lines 143- 147) + +<|ref|>text<|/ref|><|det|>[[115, 319, 840, 336]]<|/det|> +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +<|ref|>text<|/ref|><|det|>[[115, 348, 620, 364]]<|/det|> +We have now removed a reference to the 'closed state' in the figure. + +<|ref|>text<|/ref|><|det|>[[115, 420, 393, 437]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 456, 880, 548]]<|/det|> +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +<|ref|>text<|/ref|><|det|>[[115, 567, 870, 639]]<|/det|> +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +<|ref|>text<|/ref|><|det|>[[115, 650, 883, 722]]<|/det|> +We thank the reviewer for the suggestions. We had cited two of Ganesh Anand's papers (ref. 35 and 39), and we have now included his recent preprint (ref. 40). We have also now included the work for Wilson group on the RBD (ref. 41) and a very recent article based on mass photometry data (ref. 42). However, we could not find any HDX-MS study on spike conducted by Komives group. + +<|ref|>text<|/ref|><|det|>[[115, 751, 852, 805]]<|/det|> +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +<|ref|>text<|/ref|><|det|>[[115, 816, 880, 907]]<|/det|> +We thank the reviewer for this suggestion. We have now analysed with HX- Express2 another peptide spanning the RBM (peptide 495- 510) and included this extra analysis in the supplementary information (a peptide spanning the same residues is unfortunately absent in the omicron spike) (Fig. S44- 45). It is worth noting that the HX- express fitting returned very similar relative size of populations and their timedependent evolution, for every spike variant, as the peptide previously included. We have also extracted + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 877, 162]]<|/det|> +from DynamX the stacked spectral plots of many other peptides encompassing this region, and included them in the supplementary figures (Fig. S41). We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless the peptide signal- to- noise ratio. Here below the additional figures. + +<|ref|>image<|/ref|><|det|>[[115, 196, 856, 805]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 753, 690]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 90, 336, 285]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[392, 117, 953, 273]]<|/det|> +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express \(2^{2}\) (see Supplementary Figs. 42- 45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 90, 844, 820]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 883, 365]]<|/det|> +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity - BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express \(^{2}\) and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. 45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 88, 777, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 88, 567, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 245]]<|/det|> +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. A) Mass spectra of peptide of Wuhan, G614 and delta spikes. B) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with binomial fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +<|ref|>text<|/ref|><|det|>[[114, 281, 883, 391]]<|/det|> +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +<|ref|>text<|/ref|><|det|>[[114, 401, 857, 437]]<|/det|> +This is a very interesting input and we completely align with the reviewer's thoughts. We have added the following paragraph in the discussion (lines 410- 415): + +<|ref|>text<|/ref|><|det|>[[115, 448, 872, 520]]<|/det|> +"The conformational plasticity of this NTD site presumably allows antibody- vulnerable configurations of conformational epitopes to remain occasionally populated, reducing, but not completely abrogating, antibody- mediated protection. At the same time, linear NTD epitopes are likely more impacted by the residue changes in spike variants rather than by a different conformational aspect of the NTD of VOCs." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 91, 393, 106]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 118, 882, 264]]<|/det|> +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +<|ref|>text<|/ref|><|det|>[[115, 285, 230, 300]]<|/det|> +Major concern: + +<|ref|>text<|/ref|><|det|>[[115, 302, 877, 392]]<|/det|> +Why did the authors use a ratio of 1:2 spike: Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +<|ref|>text<|/ref|><|det|>[[113, 402, 884, 620]]<|/det|> +This an important point and we thank the reviewer for the opportunity to clarify it. For a Spike trimer to be ACE2 binding- competent at least one of its RBDs must be erect and a mixture of its open and closed states within the trimer is well known in the literature (see e.g. https://doi.org/10.1016/j.cell.2020.02.058, https://www.nature.com/articles/s41594- 020- 0468- 7. pdf?origin=ppub, https://www.pnas.org/doi/10.1073/pnas.2022586118, and https://www.nature.com/articles/s41467- 022- 28882- 9). Spikes with all three RBDs accessible are rarely observed, at least in cryoEM. Although we cannot be sure of the precise ratios of up and down states in spikes in solution, in non- cryogenic state, the conformational dynamics between these adopted structures governs this interaction and is what our solution HDX- MS experiments can report on. In our experiments we, therefore, try to capture a situation where we can monitor this behaviour within the experimental limitations of required sample amounts and concentration – with large concentrations of the material difficult to produce. + +<|ref|>text<|/ref|><|det|>[[114, 632, 884, 813]]<|/det|> +The 1:2 ratio was chosen after initial optimization HDX- MS experiments. We incubated Wuhan and G614 spikes at 1:2 and 1:3 ratio spike: ACE2 and found the same difference in HDX for spike peptides within the RBM at both ratios. This suggests that increased ACE2 above 1:2 was not increasing spike binding occupancy, but likely leads to an increased population of unbound ACE2 in our labelled sample. Accordingly, the HDX differences observed within ACE2 incubated at 1:2 and 1:3 ratios spike: ACE2 appeared significantly higher at ratio 1:2 than at 1:3, which supports that a higher fraction of unbound ACE2 is present in the latter case. In support of the ratio chosen, a very recent mass photometry paper (https://pubs.rsc.org/en/content/articlelanding/2022/cc/d2cc04711j) on Wuhan and omicron spikes (in the same '2P' pre- fusion stabilised version we use) reported that 1:4 spike: ACE2 shows predominantly spike bound to one ACE2, with some spike bound to 2 ACE2 but negligible amounts bound to 3 ACE2. + +<|ref|>text<|/ref|><|det|>[[115, 825, 883, 896]]<|/det|> +Considering these observations, 1:2 ratio likely provides information on saturated spike ACE2- accessible 'up' states. As the reviewer points out, this would mean that one of the RBDs will be unbound, but it is likely to be in an ACE2- inaccessible "down" state. The experiment performed to address major concern 2 provides further evidences in support of the ratio chosen, for every spike analysed (please see below). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 143]]<|/det|> +In this revised version, we inserted this optimization procedure in a dedicated paragraph of the method session (Optimization of the HDX conditions – lines 546- 554) and added two figures showing these results in the supplementary information and present them below. + +<|ref|>image<|/ref|><|det|>[[124, 188, 840, 454]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 469, 884, 538]]<|/det|> +
Fig. S47. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the RBM when Wuhan and G614 spikes are incubated at 1:2 and 1:3 ratios with ACE2. No significant differences in ΔHDX are observed between the two incubation ratios and for both spike trimers.
+ +<|ref|>image<|/ref|><|det|>[[290, 585, 700, 825]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 850, 883, 904]]<|/det|> +Supplementary Fig. 48. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the ACE2 binding site when ACE2 is incubated at 2:1 and 3:1 ratios with Wuhan spike. A minor decrease in HDX is observed at ratio 3:1. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 125]]<|/det|> +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? + +<|ref|>text<|/ref|><|det|>[[114, 136, 883, 300]]<|/det|> +Bimodal spectra were not observed in apo spikes by working with freshly prepared spike samples. In the ACE2- bound state, beyond the 495- 513 region, we observed - for every spike trimer analyzed - the appearance of bimodal isotopic envelopes in the HR1 region spanning residues 962- 982, which is one of the segments becoming more dynamic during the priming for fusion of spike. In the interest of writing the manuscript for a broad readership, we did not describe the specific HDX regime of this particular segment in detail, rather summarizing the increased HDX observed in various S2 stretches as 'increased dynamics'. However, following the reviewer's inquiry, we have reconsidered our initial thoughts and have now described the HDX bimodality seen in this region of bound- spikes in the manuscript test, as presumably it also contributes to the priming mechanism (lines 355- 363). + +<|ref|>text<|/ref|><|det|>[[114, 311, 883, 440]]<|/det|> +"Notably, peptides spanning residues 962- 982 manifested increased HDX in the form of bimodal isotopic envelopes when spikes are engaged to ACE2 (Fig. 6c and Supplementary Fig. 46). This segment encompasses the HR1 helix, which undergoes a large conformational rearrangement upon the transition to post- fusion state15, suggesting that our analysis captured the specific dynamic events leading to the HR1 reorientation, which primes spikes for fusion. The breadth of this HDX bimodality varies with \(\text{omicron} > \text{alpha} > \text{beta} > \text{G614} \approx \text{Wuhan spike}\) , with omicron spike pre- manifesting it also in the absence of ACE2 (Fig. 6c and Supplementary Fig. 46)." + +<|ref|>text<|/ref|><|det|>[[114, 450, 882, 522]]<|/det|> +Additionally, we have modified Fig. 6c in the main text to include the isotopic envelopes of peptides 963- 977, in place of its uptake plots. We believe that the envelopes deliver a much clearer message. We also added a supplementary figure (S46) including the stacked spectral plots of peptide 963- 977 and an overlapping peptide (962- 977). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 90, 876, 380]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 397, 420, 411]]<|/det|> +
C Peptide 963-977 - Priming for fusion of HR1
+ +<|ref|>image<|/ref|><|det|>[[117, 418, 875, 580]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 615, 884, 799]]<|/det|> +
Fig. 6 Spike priming for fusion. A) Regions manifesting increased dynamics in spikes bound to ACE2 are superimposed and colored in red on a single protomer of the structure of D614 spike with one RBD bound (PDB: 7a9514); regions with increased dynamics only in spike of alpha and omicron variants bound to ACE2 are colored in magenta. B) The magnitude of the destabilization of the core helices is represented by differential colouring (red scale) for the various spike trimers. The HR1 region (962-982) manifesting HDX bimodality is framed in grey. C) The bimodal isotopic envelopes of a model peptide spanning the HR1 region 962-982 are shown at 15 s and 1 min time points for spike (S) variants in the ACE2-bound form and for omicron spike alone, to exemplify their priming for fusion upon receptor engagement. Bimodal envelopes manifest in omicron spike also in the absence of ACE2, indicating it as pre-primed for fusion.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 858, 490]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 500, 884, 624]]<|/det|> +Supplementary Fig. 46. HDX bimodality in the HR1 of spikes in complex with ACE2 and omicron spike alone. Stacked spectral plots of peptides 962- 977 and 963- 977 illustrate the evolution of the bimodal isotopic envelopes over the time points studied. Particularly, time points 15 s and 1 min (23 °C) show clear separation between the low- and high- mass envelopes in every spike trimer, with the relative intensity and centroids of the two envelopes reporting on the degree of destabilization exerted by the ACE2 binding on the HR1. The isotopic envelopes in omicron spike alone manifest evident peak broadening, suggesting that the its HR1 follows a bimodal HDX behaviour even in the absence of ACE2. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 126]]<|/det|> +Additionally, how long was the spike:ACE2 complex incubated prior to exchanges? Do the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +<|ref|>text<|/ref|><|det|>[[115, 137, 883, 209]]<|/det|> +Spikes- ACE2 complexes were incubated for one hour before starting the deuterium labelling (we now specified this in the method session). Given the Kds are, depending on the variant, in the order of 10 to 150 nM with kons between 0.07 and \(0.2 \text{ uM}^{- 1} \text{s}^{- 1}\) (https://doi.org/10.1038/s41467- 022- 28768- w - see supplementary info), we believe that this incubation period largely suffices for system equilibration. + +<|ref|>text<|/ref|><|det|>[[115, 238, 883, 365]]<|/det|> +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors' coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +<|ref|>text<|/ref|><|det|>[[114, 376, 883, 576]]<|/det|> +We thank the reviewer for highlighting this important point. We have now extracted from DynamX the stacked spectral plots of many other peptides encompassing this region and included them in the supplementary figures. We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless of the peptide signal- to- noise ratio (Fig. S41). We also analysed the bimodal isotopic distributions of another peptide (495- 510) with HX- express2 and included this extra analysis in the supplementary information (a matching peptide is unfortunately absent in the omicron variant) (Fig. S44- 45). It is worth noting that the HX- express2 fitting returned very similar relative size of populations and their time- dependent evolution, for every spike variant, compared to the peptide previously included. The result of this extra analysis could also address the reviewer's following concern about the calculated size of the populations. + +<|ref|>image<|/ref|><|det|>[[115, 640, 853, 840]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 90, 852, 690]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 540, 696]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 708, 883, 814]]<|/det|> +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express2 (see Supplementary Figs. 42- S45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 90, 844, 820]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 883, 365]]<|/det|> +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity - BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express \(^{2}\) and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. S45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 88, 777, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 88, 567, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 884, 245]]<|/det|> +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. a) Mass spectra of peptide of Wuhan, G614 and delta spikes. b) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with bimomial fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +<|ref|>text<|/ref|><|det|>[[114, 300, 874, 538]]<|/det|> +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +<|ref|>text<|/ref|><|det|>[[114, 539, 880, 666]]<|/det|> +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +<|ref|>text<|/ref|><|det|>[[114, 677, 880, 713]]<|/det|> +We thank the reviewer for considering this important aspect. We based our interpretation on the following observations and experiments. + +<|ref|>text<|/ref|><|det|>[[114, 723, 883, 869]]<|/det|> +As the reviewer suggests, we had carefully compared the HDX of the high- mass population of the bound states and the HDX of the population (unimodal spectra) of the apo state (also shown in fig. S42 and S44). The two HDX profiles do not appear consistent. We believe that, if the ACE2 was not sufficient to saturate the binding of the monomers with accessible (erect) RBD, the high- mass population in the bound states should align on the m/z scale to the apo spike states, manifesting already, and with clear separation from the low- mass population, at 4 s or 20 s on ice, but this does not appear to be the case. We do not observe it at 4 s on ice for Wuhan and G614 bound- spikes, or at 20 s on ice for alpha, beta and omicron bound- spikes. We have now added a note on this in the figure caption of fig. S42 and S44. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 884, 290]]<|/det|> +To better investigate this aspect, for this revised version, we performed an extra experiment. We performed HDX- MS on the isolated RBD of the ancestral Wuhan spike in the presence and absence of ACE2, at ratio 3:2 RBD:ACE2, which simulates our 1:2 spike trimer:ACE2 ratio used in our experiments. Given that the whole population of isolated RBD molecules are binding- competent, with such a binding stoichiometry, \(33\%\) of the RBD population remain effectively unbound in the presence of ACE2. We did not observe bimodal distributions in the RBM of the bound- RBD state, indicating that a mixture of bound and unbound monomers, with same conformational characteristics in the apo state, does not manifest with a clear envelope bimodality under the conditions studied. We now included the extracted stacked spectral plot of the bound- RBD in the supplementary figures (please, see previous figure S41). Furthermore, the preliminary data shown above and the experiment performed to address major point 2 support a scenario where spike erect RBDs are saturated in binding occupancy. + +<|ref|>text<|/ref|><|det|>[[114, 301, 883, 411]]<|/det|> +These observations prompt us to associate the RBM bimodal HDX profiles to the spike cooperative binding mode reported in previous studies; we thus interpreted the high- mass population as an extra monomer that erects upon ACE2 binding (in a cooperative manner) and is likely able to engage with an extra ACE2 molecule, thus displaying an HDX profile that differs from the monomers in the unbound state. This gives rise to a fine- tuned equilibrium of states, characteristic for each spike variant, that we aimed at deciphering with our analysis. + +<|ref|>text<|/ref|><|det|>[[114, 420, 883, 512]]<|/det|> +We agree with the reviewer that we should not strictly refer to this HDX behaviour as EX1 kinetics, as we associated it to the behaviour of different monomers, and not to an individual protein stretch displaying correlated exchange. We thus now refer to it as "HDX bimodality". We also modified the text (lines 306- 324) to better explain these observations and include the extra experiment performed, and we present it here below. + +<|ref|>text<|/ref|><|det|>[[114, 522, 884, 797]]<|/det|> +"Furthermore, we observed that the HDX profiles of all peptides spanning the RBM of spike trimers (residues 495- 503) in the ACE2- bound states showed bimodal isotopic distributions, hence a high- and a low- mass population, whereas a single unimodal distribution characterized the apo states (Fig. 5 and Supplementary Figs. 41- 45). The HDX of the high- mass populations in the bound states appeared inconsistent with the HDX of the respective apo states. In contrast, the ACE2- bound state of the isolated ancestral RBD (3:2 RBD: ACE2), containing a significant fraction (33%) of unbound population, did not display bimodal isotopic distributions in the RBM (Supplementary Fig. 41), ruling out that a mixture of bound and unbound populations, with same conformational characteristics in the apo state, manifests with an HDX bimodality under the conditions studied. These data thus suggest that the RBD of bound spikes can explore two distinct and slowly interconverting populations, which exchange giving rise to two resolved isotopic distributions. We rationalize, based on the receptor binding mode reported in previous studies14,55, that the bimodal HDX profile of the bound spike states reports on cooperative opening within the spike trimer, with the less exchanged (low- mass) population accounting for open protomers with a bound RBD, whilst the more exchanged (high- mass) population likely corresponding to closed protomers transitioning to the open state and readying to engage another receptor molecule." + +<|ref|>text<|/ref|><|det|>[[114, 835, 883, 889]]<|/det|> +We also would like to highlight that bimodal spectra were not observed in the bound states of ACE2, even though we observed these states at uncomplete binding occupancy (please, see answer to Major point 2). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 222, 106]]<|/det|> +Major point 2: + +<|ref|>text<|/ref|><|det|>[[113, 108, 882, 328]]<|/det|> +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +<|ref|>text<|/ref|><|det|>[[114, 345, 881, 474]]<|/det|> +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +<|ref|>text<|/ref|><|det|>[[114, 483, 880, 612]]<|/det|> +The reviewer is right; however, the experiments we referred to were all based on methods (biolayer interferometry) that measure only the affinity of a single monomer binding to one ACE2, as spikes are immobilised and thus their concentrations (as well as the effective concentrations of individual accessible RBDs) irrelevant for the measurement, while ACE2 monomers form a mobile phase. We have now specified this in the text (lines 269- 270). In our HDX- MS experiments, we equilibrated all complexes for one hour before labelling, which, considering the aforementioned favourable kon and Kd, should allow for equilibration to be reached. + +<|ref|>text<|/ref|><|det|>[[114, 640, 881, 822]]<|/det|> +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit + +<|ref|>text<|/ref|><|det|>[[114, 834, 882, 869]]<|/det|> +We thank the reviewer for highlighting this important point and below we provide further details to support our experimental design and their conclusions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 326]]<|/det|> +Despite the molar excess of spike monomers, ACE2 is in excess compared to the binding- competent open monomers with available erect RBDs within spike trimers. To confirm this also in HDX- MS, we performed an additional experiment for this revised version of the manuscript. We labelled ACE2 in the presence and absence of the isolated ancestral RBD, at a 3:2 ratio RBD:ACE2, which simulates a 1:2 spike trimer:ACE2 ratio. Differently from the RBDs embedded in a spike trimer, the whole population of isolated RBD is binding- competent. In this scenario, the RBD is effectively in excess compared to ACE2, granting full ACE2 binding occupancy, and indeed, we observed that the binding effect on ACE2 manifested with much greater magnitude (cumulative \(\Delta \mathrm{HDX} = 19.15\) Da) compared to that induced by spike trimers, which show generally less cumulative \(\Delta \mathrm{HDX}\) due to the presence of a (varied) fraction of unbound ACE2 in the bound state. This experiment indicates that the ACE2 is not saturated in binding occupancy in the HDX- MS experiments performed on spike trimers (hence spike trimers are saturated or close to saturated), therefore we argue that the magnitude of HDX effects ( \(\Delta \mathrm{HDX}\) ) on the ACE2 holds useful information on the spike- ACE2 binding stoichiometry. + +<|ref|>text<|/ref|><|det|>[[114, 337, 883, 445]]<|/det|> +It has to be noted that the \(\Delta \mathrm{HDX}\) induced by alpha, beta and delta spikes also have a contribution from the stability of the hydrogen bonding network engaged with ACE2 (related to the affinity of their individual binding- competent monomers to the receptor), which will result in a cumulative effect given by their binding stoichiometry and affinity (reported as higher than for G614 in several studies). This is presumably the reason why for alpha spike a cumulative \(\Delta \mathrm{HDX}\) slightly higher than that of the isolated RBD was observed. + +<|ref|>text<|/ref|><|det|>[[114, 457, 883, 511]]<|/det|> +In our hands, the incomplete binding occupancy of ACE2 did not manifest with isotopic bimodal distributions in its spike binding sites, making it difficult to estimate the fraction of unbound ACE2 for the different trimers. This is one of the reasons why we refrain from proposing any stoichiometry model. + +<|ref|>text<|/ref|><|det|>[[114, 521, 883, 576]]<|/det|> +We have now included the results of this extra experiment (see figures below) in fig. 3 of the main text and Fig S27 and S40 of supplementary information and have also rewritten this section in the main text to provide a clearer explanation of our rationale (lines 243- 255). + +<|ref|>text<|/ref|><|det|>[[114, 586, 883, 768]]<|/det|> +"Next, by studying the HDX of the ACE2 ectodomain alone and in complex with spike trimers (1:2 spike trimer:ACE2) and the isolated ancestral RBD (3:2 RBD:ACE2), we measured the magnitude of the HDX effects ( \(\Delta \mathrm{HDX}\) ) induced by spike binding to ACE2. The whole population of the isolated RBD is binding competent, granting complete occupancy of the ACE2 binding sites, whereas only a fraction of the RBDs embedded within spikes are erect and thus able to engage the receptor. The observed \(\Delta \mathrm{HDX}\) results from a cumulative effect of binding stoichiometry (how many ACE2 molecules are bound) and the stability of the hydrogen- bonding network between spikes and ACE2 (which can be related to the spike- receptor binding affinity), enabling us to rank the spike- receptor binding avidity (i.e. the overall strength of binding arising from the affinity of an individual RBD- ACE2 interaction and the stoichiometry of each spike trimer engaging between zero and three ACE2 molecules at once)." + +<|ref|>text<|/ref|><|det|>[[114, 807, 611, 824]]<|/det|> +For clarity, we also modified the following sentence (lines 261- 268): + +<|ref|>text<|/ref|><|det|>[[114, 835, 883, 907]]<|/det|> +"The cumulative \(\Delta \mathrm{HDX}\) induced by different spikes varied with alpha \(> \text{beta} > \text{delta} > \text{G614} > \text{Wuhan} \approx \text{omicron (Fig. 3b and Supplementary Fig. 28). These} \Delta \text{HDX values were generally lower than that induced by the isolated RBD, indicating that a fraction of ACE2 molecules remained unbound in the spike:ACE2 states, thus suggesting that all binding- competent RBDs within the trimers were fully occupied." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[131, 100, 875, 600]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 644, 884, 790]]<|/det|> +
Fig. 3 Effect of spike binding on ACE2 dynamics. A) Regions of ACE2 manifesting a significant decrease in HDX upon spike binding are superimposed on the structure of ACE2 ectodomain bound to RBD (PDB: 2ajf), colored in blue scale according to the magnitude of the HDX effect. The region colored in red indicates increased HDX upon binding, in dark gray regions with no coverage. B) ACE2 binding avidity. The cumulative difference in HDX (ΔHDX) between ACE2 alone and ACE2 bound to spikes and the isolated ancestral RBD for selected peptides spanning binding sites and across time points 20 s on ice, 10 min at 23 °C and 360 min at 28 °C is plotted. A plot for all time points in Supplementary Fig. 28.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[146, 92, 857, 395]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 411, 884, 504]]<|/det|> +Supplementary Fig 27. Difference plot illustrating the difference in HDX between ACE2 in complex with the isolated ancestral RBD and ACE2 alone (orange line indicates: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Peptide segments of interest are highlighted. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance and a dotted black line the 99% CI as a threshold for significance. + +<|ref|>image<|/ref|><|det|>[[337, 542, 661, 808]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 821, 884, 910]]<|/det|> +Supplementary Fig 40. Difference plot illustrating the difference in HDX between the isolated ancestral RBD in complex with ACE2 and the isolated ancestral RBD alone (orange line: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Residues comprising a region with significant differences in HDX are indicated. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 209, 106]]<|/det|> +Minor point: + +<|ref|>text<|/ref|><|det|>[[113, 108, 881, 346]]<|/det|> +Minor point:The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +<|ref|>text<|/ref|><|det|>[[115, 364, 872, 400]]<|/det|> +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +<|ref|>text<|/ref|><|det|>[[115, 410, 882, 483]]<|/det|> +We gratefully thank the reviewer for highlighting the caveat arising from the comparison of peptides harboring mutations and suggesting the paper (which we now cited). We briefly explained in the method section how they were compared but did not consider this to a sufficient degree. We explain our comparative workflow below and the additional \(\mathsf{k}_{\mathrm{ch}}\) considerations done: + +<|ref|>sub_title<|/ref|><|det|>[[115, 495, 193, 510]]<|/det|> +## Workflow: + +<|ref|>text<|/ref|><|det|>[[115, 522, 883, 631]]<|/det|> +We selected for comparison only peptides with identical cleavage, i.e. same N- and C- termini. Thanks to the numerous peptides available and the high redundancy, we could, in most instances, find matching peptides. However, this became impossible in case of deletions and insertions. We normalized the uptake values of mutant peptides by the uptake of their MaxD (= fully deuterated control) and obtained absolute uptake values (in Da) referencing to G614 spike, with the following equation (now included in the method session): + +<|ref|>equation<|/ref|><|det|>[[117, 640, 879, 678]]<|/det|> +\[\Delta HDX = \left(\frac{DU\:mutant\:peptide}{DU\:MaxD\:mutant\:peptide}\times DU\:MaxD\:G614\:spike\:peptide}\right) - DU\:G614\:spike\:peptide\] + +<|ref|>text<|/ref|><|det|>[[115, 688, 883, 779]]<|/det|> +For instance, at a given time point, peptide X of G614 spike has DU of 3 Da with a MaxD of 10 Da; its matching peptide Y in alpha spike has DU of 4 Da with MaxD of 10.3 Da; the normalized DU for alpha spike is 3.88 Da. The \(\Delta HDX\) reported in the butterfly plot is \(+0.88\) Da. This was done with the aim to insert mutant peptides in the butterfly plots, making the HDX comparison more visually intuitive and easily readable. + +<|ref|>sub_title<|/ref|><|det|>[[116, 819, 320, 835]]<|/det|> +## Considering kch differences: + +<|ref|>text<|/ref|><|det|>[[115, 846, 882, 900]]<|/det|> +We acknowledge the fact that the MaxD does not entirely alleviate the caveat arising from the difference in kch between peptides harboring mutations. Before performing the experiments, we had checked the values of \(\mathsf{k}_{\mathrm{ch}}\) (according to the 2018 updated values: doi: 10.1007/s13361- 018- 2021- z) and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 126]]<|/det|> +noticed that the differences are minor and most likely give rise to \(\Delta \mathsf{HDX}\) below the threshold of significance when comparing peptides without a significant difference in \(k_{\mathrm{op}}\) . + +<|ref|>text<|/ref|><|det|>[[115, 137, 882, 191]]<|/det|> +However, we now performed a more thorough analysis on the impact that the \(k_{\mathrm{ch}}\) offset has on the differences measured. We included this analysis in a supplementary table (Supplementary Data 1). We tested a null hypothesis in which every difference in HDX observed arises from a difference in \(k_{\mathrm{ch}}\) . + +<|ref|>text<|/ref|><|det|>[[115, 202, 882, 292]]<|/det|> +In more detail: we calculated the average \(k_{\mathrm{ch}}\) for a peptide and its mutant variant - excluding the N- terminal residue (one peptide per mutation was analyzed). The average \(k_{\mathrm{ch}}\) was selected as the individual amide HDX rates are averaged when measured by MS at peptide level. We then calculated the \(\%\) of observed \(\Delta \mathsf{HDX}\) for that peptide normalized by MaxD, selecting the time point showing the highest \(\Delta \mathsf{HDX}\) , as considered the most sensitive to differences. + +<|ref|>text<|/ref|><|det|>[[115, 303, 883, 412]]<|/det|> +In most instances, as the reviewer foresaw, the \(\% \Delta \mathsf{HDX}\) significantly surpasses the \(\% \Delta k_{\mathrm{ch}}\) , including for peptides spanning K417N (the table includes a 'note' column describing the outcome of the analysis). Therefore, while acknowledging the fact that the \(\Delta \mathsf{HDX}\) values have an offset at quantitative level, the observed \(\Delta \mathsf{HDX}\) can be considered qualitatively reliable. Only for one peptide (946- 961 of delta spike), we cannot unambiguously demonstrate that the observed \(\Delta \mathsf{HDX}\) arises from a real difference in dynamics in respective to G614 spike. Therefore, we have not based any discussion on that peptide. + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 505]]<|/det|> +We now mentioned this in lines 184- 187 of the results and included the description of this approach in the method session (lines 612- 630), acknowledged the presence of this caveat. We also included new figures in the supplementary information (Fig. S4) where residue- level \(k_{\mathrm{ch}}\) ratios are plotted. + +<|ref|>text<|/ref|><|det|>[[115, 544, 882, 600]]<|/det|> +"To compare peptides containing residue substitutions in spike variants (mutant peptides) with peptides of G614 spike, segments with identical N- and C- termini were selected. Their difference in deuterium incorporation ( \(\Delta \mathsf{HDX}\) ) was calculated according the equation 1 and plotted in Supplementary Figs. 9- 12: + +<|ref|>equation<|/ref|><|det|>[[115, 610, 880, 647]]<|/det|> +\[\Delta \mathsf{HDX} = \left(\frac{\mathsf{DU~mutant~peptide}}{\mathsf{DU~MaxD~mutant~peptide}}\times \mathsf{DU~MaxD~G614~spike~peptide}\right) - \mathsf{DU~G614~spike~peptide} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[115, 658, 883, 787]]<|/det|> +To estimate the impact of the difference in chemical exchange rate constants \((k_{\mathrm{ch}})\) on the observed \(\Delta \mathsf{HDX}\) between mutant peptides and peptides of G614 spike \(^{50}\) , firstly the \(k_{\mathrm{ch}}\) of individual residues within the spike protein sequences were calculated \(^{49}\) . Successively, at peptide level, the percentage of difference in \(k_{\mathrm{ch}}\) ( \(\% \Delta k_{\mathrm{ch}}\) ) were compared to the percentage of \(\Delta \mathsf{HDX}\) normalized by the MaxD ( \(\% \Delta \mathsf{HDX}\) ) in the time point showing maximal effect, as reported in Supplementary Data 1. The identified differences in HDX between spike variants and G614 spike in segments spanning amino acid changes resulted of high- confidence, with the impact of \(k_{\mathrm{ch}}\) negligible, except for peptide 946- 961 of delta spike." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 92, 600, 945]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[625, 100, 907, 287]]<|/det|> +
Supplementary Fig. 4. Influence of amino acid changes on the \(k_{ch}\) of residues of spike variants. The ratios between the \(kch\) of spike variants and Wuhan spike and the \(kch\) of G614 spike residues is plotted from residue 1 to 628 (a) and from residue 629 to 1256 (b). Values are extracted from Supplementary Data 1. Amino acid changes are illustrated on the left of the graphs.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 90, 610, 931]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 149, 393, 165]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 203, 882, 257]]<|/det|> +The authors have addressed many of the questions I had, and I commend them on including much of the data that is used to inform how they interpret their bimodal spectra. Based on this data and their response, there are a few last minor points that should be addressed prior to publication. + +<|ref|>text<|/ref|><|det|>[[114, 268, 875, 431]]<|/det|> +I agree with the authors that the isolated RBD experiment sheds a lot of light on the source of the bimodal spectra, so it likely does not stem from a lobe of the trimer simply being unbound. In line 322, the authors state "whilst the more exchanged (high- mass) population likely corresponding to a closed protomer transitioning to the open state and readying to engage another receptor molecule". This statement makes it sound like the high- mass population should be able to bind Ace2, but then why is it unable to bind another molecule of Ace2? Maybe rephrasing this line to indicate that the high- mass population is somehow perturbed, but somehow still does not engage Ace2 like the other lobes of the trimer would help minimize confusion. If prior literature has made speculations about what this third lobe could be doing, then I recommend referencing those here. + +<|ref|>text<|/ref|><|det|>[[114, 442, 881, 587]]<|/det|> +- The attached additional spectra help confirm the reproducibility of the observed bimodals, but for several cases the two populations are so poorly resolved that deconvolution to extract data specific to each subpopulation can be ambiguous and potentially misleading. For example in figure S45 the spectra for G614 at 15 s and 1 min can likely be fit just as well with many other combinations of deuterium levels and intensities. The specific phrase: "The HDX of the high-mass population in the bound states appeared inconsistent with the HDX of the respective apo states." should be clarified so that it specifically refers to the earliest time point where no evidence was seen for a population consistent with unbound RBD. + +<|ref|>text<|/ref|><|det|>[[114, 598, 881, 799]]<|/det|> +- In light of the attached spectra data there is one other possibility the authors should consider as a source of the observed bimodal spectra. Dissociation of ACE2 during deuterium exchange might also explain observed bimodals presented in Fig S42, S44, as unbinding of ACE2 during D2O incubation will likely start to occur in a matter of minutes. The general trend from Wuhan/G14 to Beta to Alpha showing later transitions in the EX1, appear to match the same trend in koff kinetics reported by Wrobel et al: https://www.nature.com/articles/s41467-022-28768-w#MOESM1. This source of bimodal would also be consistent with the earliest time point in the Ace2 bound form not yet showing a second (highly deuterated population) as the dissociation has yet to occur to any appreciable degree. I don't think the authors need to elaborate on this, but I think this is something the authors should at least mention as another possible confounding factor that is influencing the observed bimodal spectra in either the results or discussion. + +<|ref|>text<|/ref|><|det|>[[115, 839, 881, 892]]<|/det|> +- The authors should also include what temperature the pre-binding with Ace2 for 1 hour was conducted at. I know this seems nitpicky but there several labs working on similar systems and temperature may drastically affect binding kinetics for anyone attempting to reproduce these studies. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 399, 106]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 123, 845, 175]]<|/det|> +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +<|ref|>text<|/ref|><|det|>[[115, 192, 860, 310]]<|/det|> +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +<|ref|>text<|/ref|><|det|>[[115, 327, 882, 462]]<|/det|> +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +<|ref|>text<|/ref|><|det|>[[115, 480, 870, 664]]<|/det|> +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +<|ref|>sub_title<|/ref|><|det|>[[116, 683, 210, 698]]<|/det|> +## Other issues: + +<|ref|>text<|/ref|><|det|>[[116, 716, 827, 767]]<|/det|> +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and over- reaching. This should be rephrased to indicate what the figure is showing, ie., Differences in HDX between Wuhan D614 and G614 spikes. + +<|ref|>text<|/ref|><|det|>[[116, 784, 830, 852]]<|/det|> +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +<|ref|>text<|/ref|><|det|>[[113, 869, 839, 886]]<|/det|> +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 125, 399, 141]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 158, 879, 243]]<|/det|> +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +<|ref|>text<|/ref|><|det|>[[115, 260, 867, 327]]<|/det|> +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +<|ref|>text<|/ref|><|det|>[[115, 344, 850, 395]]<|/det|> +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +<|ref|>text<|/ref|><|det|>[[115, 411, 872, 514]]<|/det|> +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +<|ref|>sub_title<|/ref|><|det|>[[116, 565, 399, 580]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 598, 881, 734]]<|/det|> +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +<|ref|>sub_title<|/ref|><|det|>[[116, 752, 228, 767]]<|/det|> +## Major concern: + +<|ref|>text<|/ref|><|det|>[[115, 768, 875, 853]]<|/det|> +Why did the authors use a ratio of 1:2 spike:Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +<|ref|>text<|/ref|><|det|>[[115, 870, 863, 903]]<|/det|> +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? Additionally, how long was the spike:ACE2 complex incubated prior to exchanges? Do + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 737, 107]]<|/det|> +the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +<|ref|>text<|/ref|><|det|>[[115, 123, 876, 243]]<|/det|> +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +<|ref|>text<|/ref|><|det|>[[114, 259, 872, 480]]<|/det|> +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +<|ref|>text<|/ref|><|det|>[[115, 480, 879, 600]]<|/det|> +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +<|ref|>sub_title<|/ref|><|det|>[[115, 617, 222, 632]]<|/det|> +## Major point 2: + +<|ref|>text<|/ref|><|det|>[[115, 633, 880, 820]]<|/det|> +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +<|ref|>text<|/ref|><|det|>[[115, 836, 877, 904]]<|/det|> +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 880, 141]]<|/det|> +and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +<|ref|>text<|/ref|><|det|>[[115, 158, 880, 327]]<|/det|> +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit this section. + +<|ref|>text<|/ref|><|det|>[[115, 346, 209, 361]]<|/det|> +Minor point: + +<|ref|>text<|/ref|><|det|>[[114, 363, 880, 581]]<|/det|> +The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +<|ref|>text<|/ref|><|det|>[[115, 599, 872, 632]]<|/det|> +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 108, 400, 124]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 144, 847, 198]]<|/det|> +In the manuscript titled "Structural dynamics in the evolution of 1 SARS- CoV- 2 spike glycoprotein", Calvaresi et al. utilize HDX- MS to study the structure and dynamics of the SARS- CoV- 2 spike protein. They relate their observations to published structures of the spike. + +<|ref|>text<|/ref|><|det|>[[114, 217, 860, 346]]<|/det|> +Several of the results presented are consistent with expectations based on existing structural data and/or add to our understanding of the SARS- CoV- 2 spike structure and dynamics. These include the increase in HDX in regions of the spike where increased flexibility/mobility is expected because of the D614G mutation, the decreased HDX in the regions spanning the ACE2- RBD interface, ACE2- induced changes in the S2 subunit, and the observation of increased inner flexibility of the Omicron spike RBD that agrees with observations of differing thermostability of the Omicron RBDs (https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7). + +<|ref|>text<|/ref|><|det|>[[114, 355, 884, 500]]<|/det|> +There are other observations, however, that do not agree with structural data despite the authors' claims that they do. Notable among these is the observation, which is also a primary result/conclusion of this study that the "substitutions in omicron spike lead to predominantly closed conformations, presumably enabling it to escape antibodies". The constructs studied in this paper include the 2P mutations. Published cryo- EM structures of Omicron spikes that include the 2P mutations show a preponderance of open states. Two examples of these are: https://www.nature.com/articles/s41467- 022- 28882- 9 https://www.sciencedirect.com/science/article/pii/S2211124722001528 + +<|ref|>text<|/ref|><|det|>[[114, 519, 865, 720]]<|/det|> +The HDX results presented do agree well with structural results obtained without the 2P mutations as described in these papers (which, by the way, are not cited): https://www.cell.com/molecular- cell/fulltext/S1097- 2765(22)00266- 0 https://www.cell.com/cell- reports/fulltext/S2211- 1247(22)00798- 7 Indeed, the agreement is quite striking not only with the results related to the higher proportion of the closed conformation, but also the changes in the S2 region that pre- dispose the Omicron spikes to undergo structural changes required for fusion. Bottomline, the differences observed between 2P and non- 2P Omicron spikes, especially related to proportions of closed vs open conformations, are now well documented, and the results presented here, agree more with what was observed in non- 2P spikes, although the spikes used for the HDX- MS experiments include the 2P mutations. This is an important discrepancy that must be addressed. + +<|ref|>text<|/ref|><|det|>[[116, 730, 861, 784]]<|/det|> +We thank the reviewer for pointing out this discrepancy, as indeed, in the interest of saving space, we oversimplified this issue. Following the reviewer's suggestion, we have now addressed it in the lines 435- 441 and 445- 446 of the discussion session. + +<|ref|>text<|/ref|><|det|>[[116, 825, 212, 841]]<|/det|> +Other issues: + +<|ref|>text<|/ref|><|det|>[[113, 861, 825, 879]]<|/det|> +The title of figure 1 "Mechanism of transition from closed to open states" is misleading and over + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 825, 125]]<|/det|> +reaching. This should be rephrased to indicate what the figure is showing, ie., Differences in HDX between Wuhan D614 and G614 spikes. + +<|ref|>text<|/ref|><|det|>[[115, 136, 857, 172]]<|/det|> +We thank the reviewer for the suggestion. We have now changed the figure caption in 'Differences in structural dynamics between Wuhan (D614) spike and G614 spike' + +<|ref|>text<|/ref|><|det|>[[115, 191, 830, 263]]<|/det|> +Line 150: "Hence, in all analyses we used a stabilized version of spike ectodomains containing '2P' mutations, which make them furin- uncleavable and unable to transition to the postfusion conformation." The 2P mutations do not have the spike furin uncleavable, the RRAR to GSAS substitution in the SD2 subdomain does. + +<|ref|>text<|/ref|><|det|>[[115, 275, 825, 346]]<|/det|> +We now changed this sentence to: 'Hence, in all analyses we used a version of spike ectodomains stabilized by R682S, R685S substitutions in the polybasic cleavage sites and K986P, K987P (2P) substitutions, which combined make the spikes furin- uncleavable and unable to transition to the postfusion conformation." (lines 143- 147) + +<|ref|>text<|/ref|><|det|>[[115, 365, 839, 383]]<|/det|> +In Figure 2, panel A, "D614 vs G614 (closed state)" not clear what the "closed state" here indicates. + +<|ref|>text<|/ref|><|det|>[[115, 394, 620, 410]]<|/det|> +We have now removed a reference to the 'closed state' in the figure. + +<|ref|>sub_title<|/ref|><|det|>[[115, 467, 400, 484]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 503, 879, 595]]<|/det|> +This manuscript describes H/D Exchange of the intact COVID spike protein, comparing all major variants of concern for shifts in conformational dynamics associated with 'open/closed' and 'fusion priming'. The paper is well written, the data are well presented and the results provide some important insights about mutation- dependent dynamic shifts in the NTD, Ace2 binding and fusion- priming. The evidence unambiguously supports the conclusions. I have only a few minor suggestions: + +<|ref|>text<|/ref|><|det|>[[115, 613, 870, 686]]<|/det|> +1. The Authors could do a better job of citing previous HDX studies on COVID spike, some of which provide highly relevant foundation and corroborating evidence for the current work. In particular, the work of Ganesh Anand should be cited. Also, the Wilson and Komives groups have measured dynamics of Spike by HDX in various contexts that may be relevant. + +<|ref|>text<|/ref|><|det|>[[115, 697, 883, 769]]<|/det|> +We thank the reviewer for the suggestions. We had cited two of Ganesh Anand's papers (ref. 35 and 39), and we have now included his recent preprint (ref. 40). We have also now included the work for Wilson group on the RBD (ref. 41) and a very recent article based on mass photometry data (ref. 42). However, we could not find any HDX-MS study on spike conducted by Komives group. + +<|ref|>text<|/ref|><|det|>[[115, 799, 850, 852]]<|/det|> +2. The 'bubble plots' are an excellent way of representing EX1 kinetics. It would be interesting to see these for more than one peptide in this region, perhaps in supplemental. To have full confidence in these data, similar kinetics for overlapping or nearby peptides should be included. + +<|ref|>text<|/ref|><|det|>[[115, 863, 870, 899]]<|/det|> +We thank the reviewer for this suggestion. We have now analysed with HX- Express2 another peptide spanning the RBM (peptide 495- 510) and included this extra analysis in the supplementary information + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 881, 216]]<|/det|> +(a peptide spanning the same residues is unfortunately absent in the omicron spike) (Fig. S44- 45). It is worth noting that the HX- express fitting returned very similar relative size of populations and their time- dependent evolution, for every spike variant, as the peptide previously included. We have also extracted from DynamX the stacked spectral plots of many other peptides encompassing this region, and included them in the supplementary figures (Fig. S41). We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless the peptide signal- to- noise ratio. Here below the additional figures. + +<|ref|>image<|/ref|><|det|>[[115, 250, 856, 864]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 88, 752, 691]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 90, 336, 284]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[393, 116, 953, 273]]<|/det|> +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express22 (see Supplementary Figs. 42- 45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 90, 844, 821]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 883, 365]]<|/det|> +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity -BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express22 and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. 45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 88, 777, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 87, 565, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 245]]<|/det|> +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. A) Mass spectra of peptide of Wuhan, G614 and delta spikes. B) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with bimodal fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +<|ref|>text<|/ref|><|det|>[[114, 281, 882, 391]]<|/det|> +3. The idea of increased dynamics as a way of evading antibody binding is an interesting one. The authors may wish to reflect on how this mechanism would impact a continuous vs. discontinuous epitope in the discussion. (At first pass, my thought would be that this mode of evasion would be much more impactful on discontinuous epitopes than on continuous ones, and that it would never offer 'complete' protection, since the 'vulnerable' configuration would still occasionally be populated... Essentially, manipulation of conformer selection for antibody binding). + +<|ref|>text<|/ref|><|det|>[[114, 401, 857, 437]]<|/det|> +This is a very interesting input and we completely align with the reviewer's thoughts. We have added the following paragraph in the discussion (lines 410- 415): + +<|ref|>text<|/ref|><|det|>[[115, 448, 873, 520]]<|/det|> +"The conformational plasticity of this NTD site presumably allows antibody- vulnerable configurations of conformational epitopes to remain occasionally populated, reducing, but not completely abrogating, antibody- mediated protection. At the same time, linear NTD epitopes are likely more impacted by the residue changes in spike variants rather than by a different conformational aspect of the NTD of VOCs." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 400, 107]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 118, 881, 265]]<|/det|> +The manuscript by Calvaresi reports an extensive HDX- MS comparative analysis of various CoV2 spike proteins in the unbound or ACE2- complexed states. The data are well presented, and the study can reveal some useful insight into the solution behavior of the spike protein. I applaud the authors for using freshly purified proteins to minimize confounding effects of freeze thaw that have previously been observed. The methods and the majority of the analysis is solid, including the direct comparison of the solution behavior of all the variants. There are a few major concerns going back to the experimental design for the ACE2 bound complexes as outlined below, along with a other minor issues listed below that need to be addressed. + +<|ref|>sub_title<|/ref|><|det|>[[115, 285, 230, 300]]<|/det|> +## Major concern: + +<|ref|>text<|/ref|><|det|>[[115, 301, 877, 392]]<|/det|> +Why did the authors use a ratio of 1:2 spike: Ace2? Won't this mean that 1 of the 3 RBDs of the spike is unbound? For the most conclusive HDX studies it is really important to favor full binding of your protein of interest so that you measure the full extent of changes associated with binding. With the 1:2 ratio used here, only a maximum of \(66\%\) of the spike RBD population can be in the bound form. This may manifest as two apparent populations for regions that are most perturbed by ACE2 binding. + +<|ref|>text<|/ref|><|det|>[[113, 402, 884, 620]]<|/det|> +This an important point and we thank the reviewer for the opportunity to clarify it. For a Spike trimer to be ACE2 binding- competent at least one of its RBDs must be erect and a mixture of its open and closed states within the trimer is well known in the literature (see e.g. https://doi.org/10.1016/j.cell.2020.02.058, https://www.nature.com/articles/s41594- 020- 0468- 7. pdf?origin=ppub, https://www.pnas.org/doi/10.1073/pnas.2022586118, and https://www.nature.com/articles/s41467- 022- 28882- 9). Spikes with all three RBDs accessible are rarely observed, at least in cryoEM. Although we cannot be sure of the precise ratios of up and down states in spikes in solution, in non- cryogenic state, the conformational dynamics between these adopted structures governs this interaction and is what our solution HDX- MS experiments can report on. In our experiments we, therefore, try to capture a situation where we can monitor this behaviour within the experimental limitations of required sample amounts and concentration - with large concentrations of the material difficult to produce. + +<|ref|>text<|/ref|><|det|>[[114, 631, 884, 814]]<|/det|> +The 1:2 ratio was chosen after initial optimization HDX- MS experiments. We incubated Wuhan and G614 spikes at 1:2 and 1:3 ratio spike: ACE2 and found the same difference in HDX for spike peptides within the RBM at both ratios. This suggests that increased ACE2 above 1:2 was not increasing spike binding occupancy, but likely leads to an increased population of unbound ACE2 in our labelled sample. Accordingly, the HDX differences observed within ACE2 incubated at 1:2 and 1:3 ratios spike: ACE2 appeared significantly higher at ratio 1:2 than at 1:3, which supports that a higher fraction of unbound ACE2 is present in the latter case. In support of the ratio chosen, a very recent mass photometry paper (https://pubs.rsc.org/en/content/articlelanding/2022/cc/d2cc04711j) on Wuhan and omicron spikes (in the same '2P' pre- fusion stabilised version we use) reported that 1:4 spike: ACE2 shows predominantly spike bound to one ACE2, with some spike bound to 2 ACE2 but negligible amounts bound to 3 ACE2. + +<|ref|>text<|/ref|><|det|>[[115, 825, 883, 898]]<|/det|> +Considering these observations, 1:2 ratio likely provides information on saturated spike ACE2- accessible 'up' states. As the reviewer points out, this would mean that one of the RBDs will be unbound, but it is likely to be in an ACE2- inaccessible "down" state. The experiment performed to address major concern 2 provides further evidences in support of the ratio chosen, for every spike analysed (please see below). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 883, 143]]<|/det|> +In this revised version, we inserted this optimization procedure in a dedicated paragraph of the method session (Optimization of the HDX conditions – lines 546- 554) and added two figures showing these results in the supplementary information and present them below. + +<|ref|>image<|/ref|><|det|>[[123, 188, 840, 455]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 469, 884, 539]]<|/det|> +
Fig. S47. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the RBM when Wuhan and G614 spikes are incubated at 1:2 and 1:3 ratios with ACE2. No significant differences in ΔHDX are observed between the two incubation ratios and for both spike trimers.
+ +<|ref|>image<|/ref|><|det|>[[290, 585, 700, 825]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 850, 883, 904]]<|/det|> +Supplementary Fig. 48. Histogram illustrating the magnitude of decreased HDX (ΔHDX) manifesting in selected peptides of the ACE2 binding site when ACE2 is incubated at 2:1 and 3:1 ratios with Wuhan spike. A minor decrease in HDX is observed at ratio 3:1. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 882, 125]]<|/det|> +Were bimodal spectra observed across different regions of the spike beyond the 495- 513 region that was presented? + +<|ref|>text<|/ref|><|det|>[[114, 136, 883, 300]]<|/det|> +Bimodal spectra were not observed in apo spikes by working with freshly prepared spike samples. In the ACE2- bound state, beyond the 495- 513 region, we observed - for every spike trimer analyzed - the appearance of bimodal isotopic envelopes in the HR1 region spanning residues 962- 982, which is one of the segments becoming more dynamic during the priming for fusion of spike. In the interest of writing the manuscript for a broad readership, we did not describe the specific HDX regime of this particular segment in detail, rather summarizing the increased HDX observed in various S2 stretches as 'increased dynamics'. However, following the reviewer's inquiry, we have reconsidered our initial thoughts and have now described the HDX bimodality seen in this region of bound- spikes in the manuscript test, as presumably it also contributes to the priming mechanism (lines 355- 363). + +<|ref|>text<|/ref|><|det|>[[114, 310, 883, 440]]<|/det|> +"Notably, peptides spanning residues 962- 982 manifested increased HDX in the form of bimodal isotopic envelopes when spikes are engaged to ACE2 (Fig. 6c and Supplementary Fig. 46). This segment encompasses the HR1 helix, which undergoes a large conformational rearrangement upon the transition to post- fusion state15, suggesting that our analysis captured the specific dynamic events leading to the HR1 reorientation, which primes spikes for fusion. The breadth of this HDX bimodality varies with \(\text{omicron} > \text{alpha} > \text{beta} > \text{G614} \approx \text{Wuhan spike}\) , with omicron spike pre- manifesting it also in the absence of ACE2 (Fig. 6c and Supplementary Fig. 46)." + +<|ref|>text<|/ref|><|det|>[[114, 449, 882, 522]]<|/det|> +Additionally, we have modified Fig. 6c in the main text to include the isotopic envelopes of peptides 963- 977, in place of its uptake plots. We believe that the envelopes deliver a much clearer message. We also added a supplementary figure (S46) including the stacked spectral plots of peptide 963- 977 and an overlapping peptide (962- 977). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[119, 90, 878, 380]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 397, 419, 411]]<|/det|> +
C Peptide 963-977 - Priming for fusion of HR1
+ +<|ref|>image<|/ref|><|det|>[[117, 418, 877, 580]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 615, 884, 799]]<|/det|> +
Fig. 6 Spike priming for fusion. A) Regions manifesting increased dynamics in spikes bound to ACE2 are superimposed and colored in red on a single protomer of the structure of D614 spike with one RBD bound (PDB: 7a9514); regions with increased dynamics only in spike of alpha and omicron variants bound to ACE2 are colored in magenta. B) The magnitude of the destabilization of the core helices is represented by differential colouring (red scale) for the various spike trimers. The HR1 region (962-982) manifesting HDX bimodality is framed in grey. C) The bimodal isotopic envelopes of a model peptide spanning the HR1 region 962-982 are shown at 15 s and 1 min time points for spike (S) variants in the ACE2-bound form and for omicron spike alone, to exemplify their priming for fusion upon receptor engagement. Bimodal envelopes manifest in omicron spike also in the absence of ACE2, indicating it as pre-primed for fusion.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[113, 88, 860, 490]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[114, 501, 883, 624]]<|/det|> +Supplementary Fig. 46. HDX bimodality in the HR1 of spikes in complex with ACE2 and omicron spike alone. Stacked spectral plots of peptides 962- 977 and 963- 977 illustrate the evolution of the bimodal isotopic envelopes over the time points studied. Particularly, time points 15 s and 1 min (23 °C) show clear separation between the low- and high- mass envelopes in every spike trimer, with the relative intensity and centroids of the two envelopes reporting on the degree of destabilization exerted by the ACE2 binding on the HR1. The isotopic envelopes in omicron spike alone manifest evident peak broadening, suggesting that the its HR1 follows a bimodal HDX behaviour even in the absence of ACE2. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 126]]<|/det|> +Additionally, how long was the spike:ACE2 complex incubated prior to exchanges? Do the authors know if this time was sufficient for equilibration to the \(66\%\) bound form? + +<|ref|>text<|/ref|><|det|>[[115, 137, 883, 209]]<|/det|> +Spikes- ACE2 complexes were incubated for one hour before starting the deuterium labelling (we now specified this in the method session). Given the Kds are, depending on the variant, in the order of 10 to 150 nM with kons between 0.07 and 0.2 uM \(^{- 1}\) s \(^{- 1}\) (https://doi.org/10.1038/s41467- 022- 28768- w - see supplementary info), we believe that this incubation period largely suffices for system equilibration. + +<|ref|>text<|/ref|><|det|>[[115, 238, 883, 365]]<|/det|> +Bimodal spectra at the 495- 513 region presented look convincing. Based on the authors' coverage maps each of the mutants have several peptides that span this same region in the spike proteins. The authors need to check and make sure that the bimodal (or peak broadening) is evident in all of those overlapping peptides too. I do not think it is critical for the authors to fit and thoroughly analyze all of the overlapping peptides, as it is not a central conclusion of the paper, but at the least the authors need to validate that it is observed consistently among the overlapping peptides and make a note of this in the results. + +<|ref|>text<|/ref|><|det|>[[114, 376, 884, 576]]<|/det|> +We thank the reviewer for highlighting this important point. We have now extracted from DynamX the stacked spectral plots of many other peptides encompassing this region and included them in the supplementary figures. We included peptides of both high and moderate data quality, to demonstrate that bimodal spectra, or peak broadening, were visually distinguishable across all of them, regardless of the peptide signal- to- noise ratio (Fig. S41). We also analysed the bimodal isotopic distributions of another peptide (495- 510) with HX- express2 and included this extra analysis in the supplementary information (a matching peptide is unfortunately absent in the omicron variant) (Fig. S44- 45). It is worth noting that the HX- express2 fitting returned very similar relative size of populations and their time- dependent evolution, for every spike variant, compared to the peptide previously included. The result of this extra analysis could also address the reviewer's following concern about the calculated size of the populations. + +<|ref|>image<|/ref|><|det|>[[115, 639, 854, 840]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 855, 690]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 87, 541, 696]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 708, 884, 814]]<|/det|> +Supplementary Fig. 41 (a,b). EX1 kinetics in selected peptides spanning residues 495- 503 of spike receptor binding motif (RBM) of spike trimers and the isolated RBD in complex with ACE2. Stacked spectral plots elucidate the evolution of the bimodal isotopic envelopes across the time points studied and for different overlapping peptides in spike trimers. The bimodal isotopic envelopes of peptides 495- 510 and 495- 513 have been also analysed with HX- Express22 (see Supplementary Figs. 42- S45). The isotopic envelopes of the isolated ancestral RBD does not display bimodal features nor evident peak broadening. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 90, 844, 821]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 883, 365]]<|/det|> +Supplementary Fig. 44. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. From top to bottom: peptide YGFQPTNGVGYQPYRV (495- 510) of Wuhan spike; peptide YGFQPTNGVGYQPYRV (495- 510) of G614 spike; peptide YGFQPTNGVGYQPYRV (493- 509) of delta spike; peptide YGFQPTYGVGYQPYRV (492- 507) of alpha spike; peptide YGFQPTYGVGYQPYRV (492- 507) for beta spike. From left to right: bubble plots representing the level of deuteration and the relative intensity of the low- and high- mass envelope (binomial fit 1 and binomial fit 2, respectively) for bimodal isotopic distributions and the level of deuteration of the unimodal envelope (unimodal fit), set at 100% intensity, in the ACE2 bound state; peak width of the isotopic distribution (calculated at 20% of Baseline Peak Intensity -BPI) and number of exchangeable amides (#NHs), in the bound state; deuterium level of the low- mass envelopes (binomial 1), high- mass envelopes (binomial 2) and unimodal distributions (centroid) in ACE2- bound spike; deuterium level of spikes in apo state (unimodal distributions - centroid). Spectral analysis was conducted with HX- Express22 and graphs were automatically generated upon fitting the isotopic envelopes shown in Supplementary Fig. S45. Bimodal fit was applied to peptide spectra at time points showing clear features of bimodality and/or enhanced peak width. Note that the high- mass population does not manifest at early time points, thus does not follow the HDX of the unbound state. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 88, 777, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[117, 87, 565, 970]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 884, 245]]<|/det|> +Supplementary Fig. 45. EX1 kinetics in the receptor binding motif (RBM) of spikes in complex with ACE2. Mass spectra of the representative peptides of the RBM (listed in Supplementary Fig. 44) deconvoluted with bimodal or unimodal fittings with HX- Express 2. a) Mass spectra of peptide of Wuhan, G614 and delta spikes. b) Mass spectra of peptide of alpha, beta and omicron spikes. The horizontal orange lines indicate the distribution width at \(20\%\) BPI; the red dots mark the envelope peaks; the vertical green lines indicate the centroid mass; the dark blue lines fit the unimodal envelope distributions deconvoluted with binomial fitting; the green lines fit the low- mass envelope distributions deconvoluted with bimodal fitting; the light blue lines fit the high- mass envelope distributions deconvoluted with bimodal fitting. + +<|ref|>text<|/ref|><|det|>[[114, 300, 874, 538]]<|/det|> +While the peak broadening is evident by eye, it also looks like the separation of the two populations within the bimodal is poor. Because of this, I do not think that there is high confidence associated with the fitting to extract the exact deuterium incorporation and exact sizes for the two populations. The authors interpret the bimodal as EX1 kinetics, but the two populations could easily result from the \(66\%\) that is ACE2 bound and the remaining \(33\%\) that is unbound. There will likely also be a distribution of different stoichiometries of ACE2- spike among the different spike molecules. For example there will be some finite number of spikes with all three lobes bound to ACE2, the majority with 2 lobes bound, a small fraction of only a single lobe bound, and a really small population of completely unbound spike. These different populations can easily result in complicated bimodal mass envelopes that have nothing to do with true EX1 kinetics. One thing the authors can do is to see if the higher deuterated population appears consistent with what was observed in the unbound spike. If bimodal profiles are observed in both the spike and the ACE2 then the authors might be able to interpret what fraction of the protein was actually bound. + +<|ref|>text<|/ref|><|det|>[[114, 539, 878, 666]]<|/det|> +These issues could have been alleviated if the experiment was designed with a sufficient excess of ACE2 to ensure fully bound complexes. I appreciate that these reagents are challenging to make and the experiments are difficult to carry out, and do not expect the authors to go back and redo the experiment. Furthermore, I think the data in this section can still be insightful, but the authors need to reexamine and rewrite this portion with full acknowledgment of all the confounding factors that limit how much can be concluded. The problem of incomplete ACE2 binding may also be a confounding factor for the following section on the S2 subunit priming. + +<|ref|>text<|/ref|><|det|>[[114, 678, 880, 713]]<|/det|> +We thank the reviewer for considering this important aspect. We based our interpretation on the following observations and experiments. + +<|ref|>text<|/ref|><|det|>[[114, 725, 883, 869]]<|/det|> +As the reviewer suggests, we had carefully compared the HDX of the high- mass population of the bound states and the HDX of the population (unimodal spectra) of the apo state (also shown in fig. S42 and S44). The two HDX profiles do not appear consistent. We believe that, if the ACE2 was not sufficient to saturate the binding of the monomers with accessible (erect) RBD, the high- mass population in the bound states should align on the m/z scale to the apo spike states, manifesting already, and with clear separation from the low- mass population, at 4 s or 20 s on ice, but this does not appear to be the case. We do not observe it at 4 s on ice for Wuhan and G614 bound- spikes, or at 20 s on ice for alpha, beta and omicron bound- spikes. We have now added a note on this in the figure caption of fig. S42 and S44. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 290]]<|/det|> +To better investigate this aspect, for this revised version, we performed an extra experiment. We performed HDX- MS on the isolated RBD of the ancestral Wuhan spike in the presence and absence of ACE2, at ratio 3:2 RBD:ACE2, which simulates our 1:2 spike trimer:ACE2 ratio used in our experiments. Given that the whole population of isolated RBD molecules are binding- competent, with such a binding stoichiometry, \(33\%\) of the RBD population remain effectively unbound in the presence of ACE2. We did not observe bimodal distributions in the RBM of the bound- RBD state, indicating that a mixture of bound and unbound monomers, with same conformational characteristics in the apo state, does not manifest with a clear envelope bimodality under the conditions studied. We now included the extracted stacked spectral plot of the bound- RBD in the supplementary figures (please, see previous figure S41). Furthermore, the preliminary data shown above and the experiment performed to address major point 2 support a scenario where spike erect RBDs are saturated in binding occupancy. + +<|ref|>text<|/ref|><|det|>[[114, 301, 883, 410]]<|/det|> +These observations prompt us to associate the RBM bimodal HDX profiles to the spike cooperative binding mode reported in previous studies; we thus interpreted the high- mass population as an extra monomer that erects upon ACE2 binding (in a cooperative manner) and is likely able to engage with an extra ACE2 molecule, thus displaying an HDX profile that differs from the monomers in the unbound state. This gives rise to a fine- tuned equilibrium of states, characteristic for each spike variant, that we aimed at deciphering with our analysis. + +<|ref|>text<|/ref|><|det|>[[114, 420, 883, 511]]<|/det|> +We agree with the reviewer that we should not strictly refer to this HDX behaviour as EX1 kinetics, as we associated it to the behaviour of different monomers, and not to an individual protein stretch displaying correlated exchange. We thus now refer to it as "HDX bimodality". We also modified the text (lines 306- 324) to better explain these observations and include the extra experiment performed, and we present it here below. + +<|ref|>text<|/ref|><|det|>[[114, 522, 883, 797]]<|/det|> +"Furthermore, we observed that the HDX profiles of all peptides spanning the RBM of spike trimers (residues 495- 503) in the ACE2- bound states showed bimodal isotopic distributions, hence a high- and a low- mass population, whereas a single unimodal distribution characterized the apo states (Fig. 5 and Supplementary Figs. 41- 45). The HDX of the high- mass populations in the bound states appeared inconsistent with the HDX of the respective apo states. In contrast, the ACE2- bound state of the isolated ancestral RBD (3:2 RBD: ACE2), containing a significant fraction (33%) of unbound population, did not display bimodal isotopic distributions in the RBM (Supplementary Fig. 41), ruling out that a mixture of bound and unbound populations, with same conformational characteristics in the apo state, manifests with an HDX bimodality under the conditions studied. These data thus suggest that the RBD of bound spikes can explore two distinct and slowly interconverting populations, which exchange giving rise to two resolved isotopic distributions. We rationalize, based on the receptor binding mode reported in previous studies \(^{14,55}\) , that the bimodal HDX profile of the bound spike states reports on cooperative opening within the spike trimer, with the less exchanged (low- mass) population accounting for open protomers with a bound RBD, whilst the more exchanged (high- mass) population likely corresponding to closed protomers transitioning to the open state and readying to engage another receptor molecule." + +<|ref|>text<|/ref|><|det|>[[114, 835, 883, 890]]<|/det|> +We also would like to highlight that bimodal spectra were not observed in the bound states of ACE2, even though we observed these states at uncomplete binding occupancy (please, see answer to Major point 2). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 222, 106]]<|/det|> +Major point 2: + +<|ref|>text<|/ref|><|det|>[[113, 108, 883, 328]]<|/det|> +The authors examine HDX changes within ACE2 in complex with the various spike constructs to assess the binding affinity and avidity. This section is highly problematic. I am having trouble trying to understand the logic of why this experiment would reveal what the authors suggest. I agree that tighter binding will lead to more protection in the ACE2. Based on the methods the authors preincubated at a ratio of 1:2 spike trimer:ACE2. This ratio should correspond to a 3:2 ratio of spike monomer:ACE2, and if the interaction is of sufficient affinity then the vast majority of the ACE2 should be bound. For HDX studies you typically want an excess of the ligand with sufficient preincubation so you can be sure that you have near- full occupancy of the binding sites in the protein of interest. If not then you risk looking at a mixture of bound and unbound species that will depend on affinity and possibly incubation time. Depending on the association/dissociation kinetics this can also result in bimodal isotopic envelopes as the data might reflect a combination of free and bound populations, further complicating the analysis. + +<|ref|>text<|/ref|><|det|>[[114, 345, 881, 474]]<|/det|> +The authors suggest that since previous binding studies have indicate similar affinities between WT and G614, that a higher portion of the ACE2 is bound in the presence of G614 spikes. While this may be true, this would indicate that the complexes were not incubated long enough to reach equilibrium. At equilibrium with equal affinities there should be an identical amount of complex formed for both WT and G614 spikes. If there isn't then it might relate to the formation of the ACE2- WT complex being much slower, perhaps because more time is needed for the WT to sample open conformations capable of binding. + +<|ref|>text<|/ref|><|det|>[[114, 483, 880, 612]]<|/det|> +The reviewer is right; however, the experiments we referred to were all based on methods (biolayer interferometry) that measure only the affinity of a single monomer binding to one ACE2, as spikes are immobilised and thus their concentrations (as well as the effective concentrations of individual accessible RBDs) irrelevant for the measurement, while ACE2 monomers form a mobile phase. We have now specified this in the text (lines 269- 270). In our HDX- MS experiments, we equilibrated all complexes for one hour before labelling, which, considering the aforementioned favourable kon and Kd, should allow for equilibration to be reached. + +<|ref|>text<|/ref|><|det|>[[114, 640, 881, 822]]<|/det|> +Additionally, if the binding is incomplete then I would expect to see a bimodal isotopic profile near the binding site reflecting the population of bound and unbound ACE2. This bimodal may actually be a much more direct way to assess what portion of the ACE2 is able to bind the spike. However, in many cases the two populations in bimodal spectra are not well- resolved and quantifying the populations is difficult to determine with any confidence. Overall, this assay has a lot more variables and caveats than the authors account for, and I would be very hesitant to conclude anything from this data. I'm guessing the authors thought they could extract some additional information for the ACE2 since it's already in the dataset, but this is not a well- designed experiment for any solid conclusions. It might be a useful assay for future studies to examine kinetics of binding among the variants, but since this is not an integral part of the current paper, I advise the authors simply omit + +<|ref|>text<|/ref|><|det|>[[114, 834, 881, 869]]<|/det|> +We thank the reviewer for highlighting this important point and below we provide further details to support our experimental design and their conclusions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 326]]<|/det|> +Despite the molar excess of spike monomers, ACE2 is in excess compared to the binding- competent open monomers with available erect RBDs within spike trimers. To confirm this also in HDX- MS, we performed an additional experiment for this revised version of the manuscript. We labelled ACE2 in the presence and absence of the isolated ancestral RBD, at a 3:2 ratio RBD:ACE2, which simulates a 1:2 spike trimer:ACE2 ratio. Differently from the RBDs embedded in a spike trimer, the whole population of isolated RBD is binding- competent. In this scenario, the RBD is effectively in excess compared to ACE2, granting full ACE2 binding occupancy, and indeed, we observed that the binding effect on ACE2 manifested with much greater magnitude (cumulative \(\Delta \mathrm{HDX} = 19.15\) Da) compared to that induced by spike trimers, which show generally less cumulative \(\Delta \mathrm{HDX}\) due to the presence of a (varied) fraction of unbound ACE2 in the bound state. This experiment indicates that the ACE2 is not saturated in binding occupancy in the HDX- MS experiments performed on spike trimers (hence spike trimers are saturated or close to saturated), therefore we argue that the magnitude of HDX effects ( \(\Delta \mathrm{HDX}\) ) on the ACE2 holds useful information on the spike- ACE2 binding stoichiometry. + +<|ref|>text<|/ref|><|det|>[[114, 337, 883, 445]]<|/det|> +It has to be noted that the \(\Delta \mathrm{HDX}\) induced by alpha, beta and delta spikes also have a contribution from the stability of the hydrogen bonding network engaged with ACE2 (related to the affinity of their individual binding- competent monomers to the receptor), which will result in a cumulative effect given by their binding stoichiometry and affinity (reported as higher than for G614 in several studies). This is presumably the reason why for alpha spike a cumulative \(\Delta \mathrm{HDX}\) slightly higher than that of the isolated RBD was observed. + +<|ref|>text<|/ref|><|det|>[[114, 457, 883, 511]]<|/det|> +In our hands, the incomplete binding occupancy of ACE2 did not manifest with isotopic bimodal distributions in its spike binding sites, making it difficult to estimate the fraction of unbound ACE2 for the different trimers. This is one of the reasons why we refrain from proposing any stoichiometry model. + +<|ref|>text<|/ref|><|det|>[[114, 522, 883, 576]]<|/det|> +We have now included the results of this extra experiment (see figures below) in fig. 3 of the main text and Fig S27 and S40 of supplementary information and have also rewritten this section in the main text to provide a clearer explanation of our rationale (lines 243- 255). + +<|ref|>text<|/ref|><|det|>[[114, 587, 884, 769]]<|/det|> +"Next, by studying the HDX of the ACE2 ectodomain alone and in complex with spike trimers (1:2 spike trimer:ACE2) and the isolated ancestral RBD (3:2 RBD:ACE2), we measured the magnitude of the HDX effects ( \(\Delta \mathrm{HDX}\) ) induced by spike binding to ACE2. The whole population of the isolated RBD is binding competent, granting complete occupancy of the ACE2 binding sites, whereas only a fraction of the RBDs embedded within spikes are erect and thus able to engage the receptor. The observed \(\Delta \mathrm{HDX}\) results from a cumulative effect of binding stoichiometry (how many ACE2 molecules are bound) and the stability of the hydrogen- bonding network between spikes and ACE2 (which can be related to the spike- receptor binding affinity), enabling us to rank the spike- receptor binding avidity (i.e. the overall strength of binding arising from the affinity of an individual RBD- ACE2 interaction and the stoichiometry of each spike trimer engaging between zero and three ACE2 molecules at once)." + +<|ref|>text<|/ref|><|det|>[[114, 807, 611, 824]]<|/det|> +For clarity, we also modified the following sentence (lines 261- 268): + +<|ref|>text<|/ref|><|det|>[[114, 836, 884, 908]]<|/det|> +"The cumulative \(\Delta \mathrm{HDX}\) induced by different spikes varied with alpha \(> \text{beta} > \text{delta} > \text{G614} > \text{Wuhan} \approx \text{omicron (Fig. 3b and Supplementary Fig. 28). These} \Delta \mathrm{HDX}\) values were generally lower than that induced by the isolated RBD, indicating that a fraction of ACE2 molecules remained unbound in the spike:ACE2 states, thus suggesting that all binding- competent RBDs within the trimers were fully occupied." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[131, 101, 876, 600]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 644, 884, 789]]<|/det|> +
Fig. 3 Effect of spike binding on ACE2 dynamics. A) Regions of ACE2 manifesting a significant decrease in HDX upon spike binding are superimposed on the structure of ACE2 ectodomain bound to RBD (PDB: 2ajf), colored in blue scale according to the magnitude of the HDX effect. The region colored in red indicates increased HDX upon binding, in dark gray regions with no coverage. B) ACE2 binding avidity. The cumulative difference in HDX (ΔHDX) between ACE2 alone and ACE2 bound to spikes and the isolated ancestral RBD for selected peptides spanning binding sites and across time points 20 s on ice, 10 min at 23 °C and 360 min at 28 °C is plotted. A plot for all time points in Supplementary Fig. 28.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[147, 92, 856, 396]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 411, 884, 504]]<|/det|> +Supplementary Fig 27. Difference plot illustrating the difference in HDX between ACE2 in complex with the isolated ancestral RBD and ACE2 alone (orange line indicates: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Peptide segments of interest are highlighted. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance and a dotted black line the 99% CI as a threshold for significance. + +<|ref|>image<|/ref|><|det|>[[338, 541, 664, 808]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 821, 884, 910]]<|/det|> +Supplementary Fig 40. Difference plot illustrating the difference in HDX between the isolated ancestral RBD in complex with ACE2 and the isolated ancestral RBD alone (orange line: 20 s on ice, green line: 10 min at 23 °C, dark blue line: 360 min at 28 °C). Residues comprising a region with significant differences in HDX are indicated. The peptides are arranged according to their peptide centre residue. A dotted grey line indicates the 98% CI as a threshold for significance. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 209, 106]]<|/det|> +Minor point: + +<|ref|>text<|/ref|><|det|>[[113, 108, 880, 346]]<|/det|> +Minor point:The authors should make a note that there is a caveat when comparing peptides among spike variants where the peptide sequences are not perfectly matched. The intrinsic rates of exchange will be offset by some of the amino acid substitutions, so it is possible to observe different exchange kinetics even if there is no actual difference in the structural dynamics of that region of the protein. The authors should make a note how they handled the comparison at regions where peptide sequences were not matched. It should help that the authors had a fully deuterated control so they can compare % deuteration instead of deuterium uptake, but this won't alleviate the caveat entirely. For example, one of the largest changes seen in with beta spikes was attributed K417N, and from the coverage map it looks like all of the peptides reporting around this region span residue 417. The authors should check how much of an effect the mutation will have on the intrinsic exchange rate. In many cases it will be relatively minor and the magnitude of the observed difference in exchange will surpass any effect of the point mutation. However, in some cases, for example proline mutations, the number of amides will be affected and therefore have a larger effect. + +<|ref|>text<|/ref|><|det|>[[115, 364, 872, 400]]<|/det|> +This paper has a description of how peptides with divergent sequences can be handled for comparative HDX studies: doi: 10.1007/s13361- 016- 1365- 5 + +<|ref|>text<|/ref|><|det|>[[115, 410, 882, 484]]<|/det|> +We gratefully thank the reviewer for highlighting the caveat arising from the comparison of peptides harboring mutations and suggesting the paper (which we now cited). We briefly explained in the method section how they were compared but did not consider this to a sufficient degree. We explain our comparative workflow below and the additional \(\mathsf{k}_{\mathrm{ch}}\) considerations done: + +<|ref|>sub_title<|/ref|><|det|>[[115, 495, 193, 511]]<|/det|> +## Workflow: + +<|ref|>text<|/ref|><|det|>[[114, 522, 883, 631]]<|/det|> +We selected for comparison only peptides with identical cleavage, i.e. same N- and C- termini. Thanks to the numerous peptides available and the high redundancy, we could, in most instances, find matching peptides. However, this became impossible in case of deletions and insertions. We normalized the uptake values of mutant peptides by the uptake of their MaxD (= fully deuterated control) and obtained absolute uptake values (in Da) referencing to G614 spike, with the following equation (now included in the method session): + +<|ref|>equation<|/ref|><|det|>[[117, 640, 879, 678]]<|/det|> +\[\Delta HDX = \left(\frac{DU\:mutant\:peptide}{DU\:MaxD\:mutant\:peptide}\times DU\:MaxD\:G614\:spike\:peptide}\right) - DU\:G614\:spike\:peptide\] + +<|ref|>text<|/ref|><|det|>[[115, 688, 883, 779]]<|/det|> +For instance, at a given time point, peptide X of G614 spike has DU of 3 Da with a MaxD of 10 Da; its matching peptide Y in alpha spike has DU of 4 Da with MaxD of 10.3 Da; the normalized DU for alpha spike is 3.88 Da. The \(\Delta HDX\) reported in the butterfly plot is \(+0.88\) Da. This was done with the aim to insert mutant peptides in the butterfly plots, making the HDX comparison more visually intuitive and easily readable. + +<|ref|>sub_title<|/ref|><|det|>[[116, 818, 320, 835]]<|/det|> +## Considering kch differences: + +<|ref|>text<|/ref|><|det|>[[115, 846, 882, 900]]<|/det|> +We acknowledge the fact that the MaxD does not entirely alleviate the caveat arising from the difference in kch between peptides harboring mutations. Before performing the experiments, we had checked the values of \(\mathsf{k}_{\mathrm{ch}}\) (according to the 2018 updated values: doi: 10.1007/s13361- 018- 2021- z) and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 126]]<|/det|> +noticed that the differences are minor and most likely give rise to \(\Delta \mathsf{HDX}\) below the threshold of significance when comparing peptides without a significant difference in \(k_{\mathrm{op}}\) . + +<|ref|>text<|/ref|><|det|>[[115, 137, 882, 191]]<|/det|> +However, we now performed a more thorough analysis on the impact that the \(k_{\mathrm{ch}}\) offset has on the differences measured. We included this analysis in a supplementary table (Supplementary Data 1). We tested a null hypothesis in which every difference in HDX observed arises from a difference in \(k_{\mathrm{ch}}\) . + +<|ref|>text<|/ref|><|det|>[[115, 202, 883, 292]]<|/det|> +In more detail: we calculated the average \(k_{\mathrm{ch}}\) for a peptide and its mutant variant - excluding the N- terminal residue (one peptide per mutation was analyzed). The average \(k_{\mathrm{ch}}\) was selected as the individual amide HDX rates are averaged when measured by MS at peptide level. We then calculated the \(\%\) of observed \(\Delta \mathsf{HDX}\) for that peptide normalized by MaxD, selecting the time point showing the highest \(\Delta \mathsf{HDX}\) , as considered the most sensitive to differences. + +<|ref|>text<|/ref|><|det|>[[115, 303, 883, 412]]<|/det|> +In most instances, as the reviewer foresaw, the \(\% \Delta \mathsf{HDX}\) significantly surpasses the \(\% \Delta k_{\mathrm{ch}}\) , including for peptides spanning K417N (the table includes a 'note' column describing the outcome of the analysis). Therefore, while acknowledging the fact that the \(\Delta \mathsf{HDX}\) values have an offset at quantitative level, the observed \(\Delta \mathsf{HDX}\) can be considered qualitatively reliable. Only for one peptide (946- 961 of delta spike), we cannot unambiguously demonstrate that the observed \(\Delta \mathsf{HDX}\) arises from a real difference in dynamics in respective to G614 spike. Therefore, we have not based any discussion on that peptide. + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 505]]<|/det|> +We now mentioned this in lines 184- 187 of the results and included the description of this approach in the method session (lines 612- 630), acknowledged the presence of this caveat. We also included new figures in the supplementary information (Fig. S4) where residue- level \(k_{\mathrm{ch}}\) ratios are plotted. + +<|ref|>text<|/ref|><|det|>[[115, 544, 883, 600]]<|/det|> +"To compare peptides containing residue substitutions in spike variants (mutant peptides) with peptides of G614 spike, segments with identical N- and C- termini were selected. Their difference in deuterium incorporation ( \(\Delta \mathsf{HDX}\) ) was calculated according the equation 1 and plotted in Supplementary Figs. 9- 12: + +<|ref|>equation<|/ref|><|det|>[[115, 610, 880, 647]]<|/det|> +\[\Delta \mathsf{HDX} = \left(\frac{\mathsf{D}\mathsf{U}\mathsf{m}\mathsf{u}\mathsf{t}\mathsf{a}\mathsf{n}\mathsf{t}\mathsf{p}\mathsf{e}\mathsf{p}\mathsf{t}\mathsf{i}\mathsf{d}}{\mathsf{D}\mathsf{U}\mathsf{M}\mathsf{a}\mathsf{x}\mathsf{D}\mathsf{m}\mathsf{u}\mathsf{t}\mathsf{a}\mathsf{n}\mathsf{t}\mathsf{p}\mathsf{e}\mathsf{t}\mathsf{p}\mathsf{i}\mathsf{d}}\times \mathsf{D}\mathsf{U}\mathsf{M}\mathsf{a}\mathsf{x}\mathsf{D}\mathsf{G}\mathsf{6}14\mathsf{s}\mathsf{p}\mathsf{i}\mathsf{k}\mathsf{e}\mathsf{p}\mathsf{e}\mathsf{t}\mathsf{p}\mathsf{i}\mathsf{d}\right) - \mathsf{D}\mathsf{U}\mathsf{G}\mathsf{6}14\mathsf{s}\mathsf{p}\mathsf{i}\mathsf{k}\mathsf{e}\mathsf{p}\mathsf{e}\mathsf{t}\mathsf{p}\mathsf{i}\mathsf{d} \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[115, 658, 883, 787]]<|/det|> +To estimate the impact of the difference in chemical exchange rate constants \((k_{\mathrm{ch}})\) on the observed \(\Delta \mathsf{HDX}\) between mutant peptides and peptides of G614 spike \(^{50}\) , firstly the \(k_{\mathrm{ch}}\) of individual residues within the spike protein sequences were calculated \(^{49}\) . Successively, at peptide level, the percentage of difference in \(k_{\mathrm{ch}}\) ( \(\% \Delta k_{\mathrm{ch}}\) ) were compared to the percentage of \(\Delta \mathsf{HDX}\) normalized by the MaxD ( \(\% \Delta \mathsf{HDX}\) ) in the time point showing maximal effect, as reported in Supplementary Data 1. The identified differences in HDX between spike variants and G614 spike in segments spanning amino acid changes resulted of high- confidence, with the impact of \(k_{\mathrm{ch}}\) negligible, except for peptide 946- 961 of delta spike." + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 90, 600, 940]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[626, 99, 907, 287]]<|/det|> +
Supplementary Fig. 4. Influence of amino acid changes on the \(k_{ch}\) of residues of spike variants. The ratios between the \(kch\) of spike variants and Wuhan spike and the \(kch\) of G614 spike residues is plotted from residue 1 to 628 (a) and from residue 629 to 1256 (b). Values are extracted from Supplementary Data 1. Amino acid changes are illustrated on the left of the graphs.
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[116, 90, 610, 936]]<|/det|> + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 91, 400, 107]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 123, 880, 325]]<|/det|> +The authors have addressed many of the questions I had, and I commend them on including much of the data that is used to inform how they interpret their bimodal spectra. Based on this data and their response, there are a few last minor points that should be addressed prior to publication. I agree with the authors that the isolated RBD experiment sheds a lot of light on the source of the bimodal spectra, so it likely does not stem from a lobe of the trimer simply being unbound. In line 322, the authors state "whilst the more exchanged (high- mass) population likely corresponding to a closed protomer transitioning to the open state and readying to engage another receptor molecule". This statement makes it sound like the high- mass population should be able to bind Ace2, but then why is it unable to bind another molecule of Ace2? Maybe rephrasing this line to indicate that the high- mass population is somehow perturbed, but somehow still does not engage Ace2 like the other lobes of the trimer would help minimize confusion. If prior literature has made speculations about what this third lobe could be doing, then I recommend referencing those here. + +<|ref|>text<|/ref|><|det|>[[114, 327, 881, 461]]<|/det|> +- The attached additional spectra help confirm the reproducibility of the observed bimodals, but for several cases the two populations are so poorly resolved that deconvolution to extract data specific to each subpopulation can be ambiguous and potentially misleading. For example in figure S45 the spectra for G614 at 15 s and 1 min can likely be fit just as well with many other combinations of deuterium levels and intensities. The specific phrase: "The HDX of the high-mass population in the bound states appeared inconsistent with the HDX of the respective apo states." should be clarified so that it specifically refers to the earliest time point where no evidence was seen for a population consistent with unbound RBD. + +<|ref|>text<|/ref|><|det|>[[114, 462, 880, 648]]<|/det|> +- In light of the attached spectra data there is one other possibility the authors should consider as a source of the observed bimodal spectra. Dissociation of ACE2 during deuterium exchange might also explain observed bimodals presented in Fig S42, S44, as unbinding of ACE2 during D2O incubation will likely start to occur in a matter of minutes. The general trend from Wuhan/G14 to Beta to Alpha showing later transitions in the EX1, appear to match the same trend in koff kinetics reported by Wrobel et al: https://www.nature.com/articles/s41467-022-28768-w#MOESM1. This source of bimodal would also be consistent with the earliest time point in the Ace2 bound form not yet showing a second (highly deuterated population) as the dissociation has yet to occur to any appreciable degree. I don't think the authors need to elaborate on this, but I think this is something the authors should at least mention as another possible confounding factor that is influencing the observed bimodal spectra in either the results or discussion. + +<|ref|>text<|/ref|><|det|>[[115, 664, 880, 715]]<|/det|> +- The authors should also include what temperature the pre-binding with Ace2 for 1 hour was conducted at. I know this seems nitpicky but there several labs working on similar systems and temperature may drastically affect binding kinetics for anyone attempting to reproduce these studies. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 400, 107]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[113, 125, 881, 346]]<|/det|> +The authors have addressed many of the questions I had, and I commend them on including much of the data that is used to inform how they interpret their bimodal spectra. Based on this data and their response, there are a few last minor points that should be addressed prior to publication. I agree with the authors that the isolated RBD experiment sheds a lot of light on the source of the bimodal spectra, so it likely does not stem from a lobe of the trimer simply being unbound. In line 322, the authors state "whilst the more exchanged (high- mass) population likely corresponding to a closed protomer transitioning to the open state and readying to engage another receptor molecule". This statement makes it sound like the high- mass population should be able to bind Ace2, but then why is it unable to bind another molecule of Ace2? Maybe rephrasing this line to indicate that the high- mass population is somehow perturbed, but somehow still does not engage Ace2 like the other lobes of the trimer would help minimize confusion. If prior literature has made speculations about what this third lobe could be doing, then I recommend referencing those here. + +<|ref|>text<|/ref|><|det|>[[114, 356, 880, 520]]<|/det|> +Thank you. We welcome the opportunity to better elaborate and agree with the reviewer: the high- mass population likely represents an unbound state, which is no longer closed but not properly open. Disordered RBD lobes characterizing such intermediate states have been described for cryo- EM datasets of SARS- CoV- 2 spikes \(^{1,2,3}\) . In cryo- EM, these exposed RBD lobes generally constitute a minor population, as also seen by our HDX- MS analysis, and have been proposed to represent transient dynamic conformations leading to a fully open, ACE2- binding- competent form. This can explain why the HDX of high- mass population, which may be associated with these disordered RBDs, does not align to the low- mass population of the bound states or to the population of the unbound states. We have now rephrased the relevant passage referencing the cryo- EM studies \(^{1,2,3}\) (lines 313- 314 and 323- 326). + +<|ref|>text<|/ref|><|det|>[[143, 530, 880, 615]]<|/det|> +1. SARS-CoV-2 and bat RaTG13 spike glycoprotein structures inform on virus evolution and furincleavage effects. doi: 10.1038/s41594-020-0468-7 +2. Distinct conformational states of SARS-CoV-2 spike protein. doi: 10.1126/science.abd4251 +3. Structures and distributions of SARS-CoV-2 spike proteins on intact virions. doi: 10.1038/s41586-020-2665-2 + +<|ref|>text<|/ref|><|det|>[[114, 643, 883, 789]]<|/det|> +- The attached additional spectra help confirm the reproducibility of the observed bimodals, but for several cases the two populations are so poorly resolved that deconvolution to extract data specific to each subpopulation can be ambiguous and potentially misleading. For example in figure S45 the spectra for G614 at 15 s and 1 min can likely be fit just as well with many other combinations of deuterium levels and intensities. The specific phrase: "The HDX of the high-mass population in the bound states appeared inconsistent with the HDX of the respective apo states." should be clarified so that it specifically refers to the earliest time point where no evidence was seen for a population consistent with unbound RBD. + +<|ref|>text<|/ref|><|det|>[[114, 808, 881, 902]]<|/det|> +Following the reviewer's advices, we have clarified that no evidence of a population consistent with unbound RBM is seen at the early HDX time points (lines 316- 317). We have now clearly specified that the exact relative proportion of the low- and high- mass subpopulations cannot be derived from our data (lines 330- 332) and modified the caption of figs. 5, S42 and S44 to clarify that our data need to be regarded as trends. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 880, 290]]<|/det|> +- In light of the attached spectra data there is one other possibility the authors should consider as a source of the observed bimodal spectra. Dissociation of ACE2 during deuterium exchange might also explain observed bimodals presented in Fig S42, S44, as unbinding of ACE2 during D2O incubation will likely start to occur in a matter of minutes. The general trend from Wuhan/G14 to Beta to Alpha showing later transitions in the EX1, appear to match the same trend in koff kinetics reported by Wrobel et al: https://www.nature.com/articles/s41467-022-28768-w#MOESM1. This source of bimodal would also be consistent with the earliest time point in the Ace2 bound form not yet showing a second (highly deuterated population) as the dissociation has yet to occur to any appreciable degree. I don't think the authors need to elaborate on this, but I think this is something the authors should at least mention as another possible confounding factor that is influencing the observed bimodal spectra in either the results or discussion. + +<|ref|>text<|/ref|><|det|>[[114, 301, 866, 448]]<|/det|> +We agree with the reviewer that the koff of the complexes suggest that receptor dissociation starts occurring during the exchange reaction. The control experiment on the isolated RBD bound to ACE2, where a significant fraction of RBD remains unbound, indicates that mixture of bound and unbound RBDs does not manifest with a clear bimodality under the HDX conditions employed. In the same way, we believe it is unlikely that the spike RBDs remaining transiently unbound because of receptor dissociation could give rise to bimodality. However, following the reviewer's observation, we have adapted the text to include this alternative explanation and the evidence in support of this hypothesis (lines 313- 318). + +<|ref|>text<|/ref|><|det|>[[116, 487, 357, 503]]<|/det|> +The whole paragraph now reads: + +<|ref|>text<|/ref|><|det|>[[113, 513, 878, 844]]<|/det|> +"...The more exchanged (high- mass) population represents RBDs perturbed by the presence of ACE2 but likely unbound: either because ACE2 transiently dissociates from them over the course of the exchange reaction or because they assume an intermediate, not fully erect state. The former hypothesis is supported by the observation that no evidence of a population consistent with the HDX of the unbound RBMs appears in the spike bound states at the early time points. However, the ACE2- bound state of the isolated ancestral RBD (3:2 RBD: ACE2), containing a significant fraction (33%) of unbound population, does not display bimodal isotopic distributions in the RBM under the conditions studied (Supplementary Fig. 41), suggesting that a simple mixture of bound and unbound populations of RBDs, even in the context of a spike trimer, would not manifest with an HDX bimodality either. Hence, we associated the high- mass populations of the bimodal HDX profiles with RBDs in an intermediate state, between closed and fully erect, receptor- binding- competent conformations. Such populations, characterized by disordered RBDs, have been observed and described before in cryo- EM studies11,15,55. We thus rationalize, also based on the spike receptor binding mode reported in previous studies14,56, that this population reports on the trimer capability to erect additional RBDs upon ACE2 binding to the neighbouring one/- s: a sign of cooperative opening. The exact relative proportion of the low- and high- mass subpopulations cannot be derived from our data as we cannot accurately deconvolve the two isotopic distributions. Nevertheless, the apparent abundance of the high- mass population seems to correlate with the overall preference of a given spike to adopt the open conformation as described above." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 880, 141]]<|/det|> +- The authors should also include what temperature the pre-binding with Ace2 for 1 hour was conducted at. I know this seems nitpicky but there several labs working on similar systems and temperature may drastically affect binding kinetics for anyone attempting to reproduce these studies. + +<|ref|>text<|/ref|><|det|>[[115, 159, 738, 176]]<|/det|> +We have now added this information (lines 577- 579); the method session now reads: + +<|ref|>text<|/ref|><|det|>[[116, 195, 867, 246]]<|/det|> +"Before initiating the exchange reactions, spikes and ACE2 were incubated alone or in complex at ratio 1:2 spike trimer: ACE2 for one hour at the selected labelling temperatures (i.e. on ice or in the thermomixer at 23 °C or 28 °C) and the labelling buffer was as well temperature equilibrated." + +<--- Page Split ---> diff --git a/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/images_list.json b/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..d8d59b55a0d952e2f83260f7e95b15f9d35b2e5e --- /dev/null +++ b/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,40 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S7. Third-order intermodulation distortion (IMD3) suppression at various two-tone frequencies with notch response at \\(12\\mathrm{GHz}\\) . (a) two-tone signal at \\(8\\mathrm{GHz}\\) (b) two-tone signal at \\(9\\mathrm{GHz}\\) (c) two-tone signal at \\(10\\mathrm{GHz}\\) (d) two-tone signal at \\(16\\mathrm{GHz}\\) .", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. S8. Spurious-free dynamic range (SFDR) measurements at various two-tone frequencies with notch response at 12 GHz. (a) SFDR at 8 GHz (b) SFDR at 9 GHz (c) SFDR at 10 GHz (d) SFDR at 16 GHz. IMD3: third-order intermodulation distortion, IMD5: fifth-order intermodulation distortion.", + "footnote": [], + "bbox": [ + [ + 156, + 88, + 852, + 515 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S6. The RF gain of the RF notch filter. Plot of the maximum RF gain of the RF notch filter over the entire frequency range.", + "footnote": [], + "bbox": [ + [ + 270, + 447, + 730, + 664 + ] + ], + "page_idx": 11 + } +] \ No newline at end of file diff --git a/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..10601e8a1dd5e7ffed6780d3bae40e3eb3f50179 --- /dev/null +++ b/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,719 @@ + +# nature portfolio + +# Peer Review File + +# Ultrahigh Dynamic Range and Low Noise Figure Programmable Integrated Microwave Photonic Filter + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## Reviewers' comments: + +## Reviewer #1 (Remarks to the Author): + +This is a good work covering the essences of working principles of integrated microwave photonics. The general readers would find useful information on the concept, implementation, and performance optimization of such approaches for RF functionalities. The authors are well known experts in the field. Their previous work has built up the basis and led to a new contribution to the field reported in this work. The work reported here is sound and complete including both theory and experimental verification and results discussion. It is also clear to see the amount of effort in different forms put in this work. I recommend acceptance for publication. On the other hand, above the reported work, I would like to ask authors to add comments on their options what is the future outlook of microwave photonics? What key technology improvement must be reached for a true advancing? What would be the must- be- microwave photonics applications? + +## Reviewer #2 (Remarks to the Author): + +A programmable integrated microwave photonic (MwP) filter based on integrated SiN waveguide technology is presented. The circuit comprises a modulation transformer (MT) and a double- injected ring resonator (RR). A high rejection notch filter with high RF gain of 10 dB, low noise figure (NF) of 15 dB, and large spurious free dynamic range (SFDR) of 116 dB/Hz is first demonstrated using a low- biasing technique for the off- chip intensity modulator (IM). + +Using the same set- up, a passband RF filter transfer function can be obtained by properly reconfiguring the circuit. By replacing the external IM with a PM, a SFDR in excess of 120 dB. Hz is also reported at frequencies outside the RF notch filter, using an on- chip linearization technique previously developed by the authors. + +The scheme is conceived for combining the advantages of programmable photonic integration without sacrificing the performance of application- specific circuits. Although, I agree that the work represents a step forward in this sense, I believe that this claim is only partially supported by the results that, in my opinion, seems to provide marginal novelty and/or improvements, as discussed in the following comments. + +## MAIN COMMENTS + +The architecture is not entirely novel, as it follows from previous works from the authors (references [40] [42], [59]), the main novelty seemingly being the inclusion of the DI- MRR (previously discussed for instance in [43]) enabling for switching between the notch and bandpass RF filtering functionality (contrary to [40] where the two functions are obtained using two cascaded ring resonators). Noise figure reduction through low- biased IM is also well- known. A preliminary study of the same circuit discussed in the manuscript has recently appeared in [O. Daulay, "Programmable Integrated Microwave Photonic Filter using a Modulation Transformer and a Double- Injection Ring Resonator." 2021 European Conference on Optical Communication (ECOC). IEEE, 2021] that should be quoted in the manuscript, and in reference [45]. + +The proposed passband RF filter guarantees a moderate out- of- band rejection in the RF + +<--- Page Split ---> + +transmission response of 15 dB in a limited frequency range between 5 and 15 GHz, as reported for instance in Fig. S6(b) of the supplementary material. More importantly, the same figure shows that the filter response degrades when departing from the optimal condition of Fig. 3(e) and gets very noisy when tuned above about 10 GHz. This should be discussed in the manuscript. Wide tuning range is often regarded as a key feature of MWP filters with respect to electronics- based solutions. However, given the operation at relatively low frequencies, these results should be compared with electronics circuits performing bandpass operation with better performance in terms of rejection and tunability, and operating in the same or even higher range of frequencies. + +A couple of examples are provided below: + +Z. Yang, +D. Psychogiou and +D. Peroulis, "Design and Optimization of Tunable Silicon-Integrated Evanescent-Mode Bandpass Filters," IEEE Trans. Microwave Theory Tech., vol. 66, no. 4, pp. 1790-1803, Apr. 2018. + +J. Chang, et al., "High Performance, Continuously Tunable Microwave Filters Using MEMS Devices With Very Large, Controlled, Out-of-Plane Actuation," in Journal of Microelectromechanical Systems, vol. 27, no. 6, pp. 1135-1147, Dec. 2018, d + +Concerning the performance of the RF notch filter using IM, the authors state that "These results represent the best RF gain, noise figure, and SFDR combination for an MWP notch filter". There seems however to be marginal improvements with respect to the results previously reported from the authors in [36] and [37] (RF gain from 8 to 10, NF from 16 to 15, and the same SFDR of 116 dB. Hz) + +Positive RF gain is achieved using two EDFAs. For applications in which compactness/low- weight is a primary requirement, what would be the RF gain without optical amplification in the system? + +As shown in Fig. 3 and Fig. 4, the extended linearity operation of the notch filter requires replacing the external IM with a PM, which limits the claimed full- reconfigurability of the device. This should be commented in the text. + +## MINOR COMMENTS + +In Figure 3c, the maximum RF gain and minimum NF is achieved for the minimum considered modulator bias voltage of roughly 9 V. What happen for bias values below that first point? Do the two figures of merit degrade or are there other system performance metrics that would be affected at lower values of modulator bias? What is the half- wave voltage of the modulator? + +It seems that in order to switch between scheme "d" and "e" of Fig. S5, a dual- drive Mach- Zehnder intensity modulator should be used with additional RF 90 degree hybrid, as the MT accepts at its input a dual- sideband modulated spectrum for the case of scheme "d" and a single- sideband modulated spectrum for the case of scheme "e". Alternatively, a dual- parallel MZM modulator should be used. This should be discussed in the text + +What are the dimensions of the fabricated photonic chip? + +Few typos around the text (examples): + +On page 2: "...which leading to sideband cancellation..." should be "...which leads to sideband cancellation..." + +In the caption of Fig. S5: "at the otch frequency" should be "at the notch frequency" On page 16 of the Supplementary material "which spatially isolated one sideband", should be "which spatially isolates one sideband" + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +In this manuscript, the authors proposed a programmable integrated microwave photonic filter with ultrahigh dynamic range and low noise figure. The principle of the proposed scheme was introduced in the supplementary information, and a proof- of- concept experiment was carried out to demonstrate the capability of the proposed microwave photonic filter to improve the performance of microwave photonic links. However, there still exist many problems, and the proposed integrated microwave photonic filter lacks innovation. Based on the above consideration, I do not think the paper is suitable for publication in Nature Communication in the present form. My comments are listed below. + +1) The modulation transformer (MT) with three ring resonators topology and the double-injection ring resonator (DI-RR) have been proposed and demonstrated in [Ref. 1, Ref. 2]. In my opinion, this paper is only a combination of these two methods, so the innovation of the proposed programmable integrated microwave photonic filter is not enough to support publication in Nature Communication. + +2) In this manuscript, the units of dynamic range are not uniform. "120 dB" is used in the abstract, "120 dB.Hz" is used in the introduction, "116 dB.Hz2/3" and "116 dB.Hz2/3" are used in Fig. 3. + +3) Only the notch filter achieves the high linearity, the SFDRs of other filters are still lower than 120 dB-Hz2/3. Therefore, it is inaccurate to claim that "ultra-high dynamic range of > 120 dB.Hz" is achieved. + +4) Since the linearization is only for notch filters, not for all filters, it is misleading to directly use "ultrahigh dynamic range" in the title. Meanwhile, this paper only achieves the integration of several passive devices, so "integrated microwave photonic filter" is also inappropriate. + +5) From the supplementary information, the tuning range of the bandpass filter is obviously not as wide as the 4-20GHz stated in TABLE I. + +6) Only the normalized response is given in the manuscript, and the non-normalized response also should be given, so that the reader can understand the actual insertion loss of the microwave photonic filter. + +7) The linearization is realized by the widely-used optical sideband phase and amplitude manipulation, which is usually regarded as a narrowband approach. So, within which frequency range the SFDR can reach 120 dB-Hz2/3? The authors should provide the SDFR results at other frequencies. + +8) From the description of the experimental details, the power of the input two-tone signal is 10 dBm, but the power of fundamental and spurious at this input power is not reflected in Fig. 4(d). [Ref. 1] L.-W. Luo, S. Ibrahim, A. Nitkowski et al., "High bandwidth on-chip silicon photonic interleaver," Optics express, vol. 18, no. 22, pp. 23 079-23 087, 2010. + +[Ref. 2] R. Cohen, O. Amrani, and S. Ruschin, "Response shaping with a silicon ring resonator via double injection," Nature Photonics, vol. 12, no. 11, pp. 706-712, 2018. + +<--- Page Split ---> + +We also thank the reviewers for their valuable comments and their time spent in evaluating this work. In this response, we addressed each comment/question from the reviewers point by point. The reviewer's comments are in Black, our responses are in Blue, and revisions in the manuscript are in Red. + +## Point-to-point response: + +## Reviewer: 1 + +This is a good work covering the essences of working principles of integrated microwave photonics. The general readers would find useful information on the concept, implementation, and performance optimization of such approaches for RF functionalities. The authors are well known experts in the field. Their previous work has built up the basis and led to a new contribution to the field reported in this work. The work reported here is sound and complete including both theory and experimental verification and results discussion. It is also clear to see the amount of effort in different forms put in this work. I recommend acceptance for publication. On the other hand, above the reported work, I would like to ask authors to add comments on their options what is the future outlook of microwave photonics? What key technology improvement must be reached for a true advancing? What would be the must- be- microwave photonics applications? + +## Reply: + +We are grateful for the reviewer's recommendation of publication. In general, the outlook of microwave photonics would be having photonics – electronics co- integration in a single system- on- chip (SoC) or system- in- package (SiP). In particular, the outlook of integrated microwave photonics is having a hybrid- integrated microwave photonic systems containing of a low RIN laser with high output optical power, an ultra- linear modulator with high optical power handling and broad bandwidth, a low loss optical signal processor with mixed architecture (combination of application specific and programmable photonics), and a fast photodetector with high optical power handling and broad bandwidth. + +For the proposed architecture, an improved version of modulation transformer (MT) is desirable. The improved version needs to be able to independently tailor the amplitude and the phase of each element in modulation spectrum (optical carrier and sidebands) simultaneously. Then, a new optical circuit design with improved versatility compared to DI- + +<--- Page Split ---> + +RR is also desirable with addition of nonlinear optical element, such as stimulated Brillouin scattering (SBS) for improved signal processing resolution. + +## Reviewer: 2 + +A programmable integrated microwave photonic (MWP) filter based on integrated SiN waveguide technology is presented. The circuit comprises a modulation transformer (MT) and a double- injected ring resonator (RR). A high rejection notch filter with high RF gain of \(10 \mathrm{~dB}\) , low noise figure (NF) of \(15 \mathrm{~dB}\) , and large spurious free dynamic range (SFDR) of \(116 \mathrm{~dB / Hz}\) is first demonstrated using a low- biasing technique for the off- chip intensity modulator (IM). + +Using the same set- up, a passband RF filter transfer function can be obtained by properly reconfiguring the circuit. By replacing the external IM with a PM, a SFDR in excess of \(120 \mathrm{~dB / Hz}\) is also reported at frequencies outside the RF notch filter, using an on- chip linearization technique previously developed by the authors. + +The scheme is conceived for combining the advantages of programmable photonic integration without sacrificing the performance of application- specific circuits. Although, I agree that the work represents a step forward in this sense, I believe that this claim is only partially supported by the results that, in my opinion, seems to provide marginal novelty and/or improvements, as discussed in the following comments. + +## MAIN COMMENTS + +1) The architecture is not entirely novel, as it follows from previous works from the authors (references [40] [42], [59]), the main novelty seemingly being the inclusion of the DI-MRR (previously discussed for instance in [43]) enabling for switching between the notch and bandpass RF filtering functionality (contrary to [40] where the two functions are obtained using two cascaded ring resonators). Noise figure reduction through low-biased IM is also well-known. A preliminary study of the same circuit discussed in the manuscript has recently appeared in [O. Daulay, "Programmable Integrated Microwave Photonic Filter using a Modulation Transformer and a Double-Injection Ring Resonator." 2021 European Conference on Optical Communication (ECOC). IEEE, 2021] that should be quoted in the manuscript, and in reference [45]. + +## Reply: + +We disagree with the assessment of this reviewer. Integrated microwave photonics, much like RF electronics, relies on judicious interconnection of known, but reliable components which in turn enables prime performance or functionality that is previously unachievable. This is illustrated by the following examples, recently published in Nature Communications: + +- Silicon Brillouin waveguide: S. Gertler et al., Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon, Nat. Commun. 13(1), 2022. + +<--- Page Split ---> + +- Dual integrated lasers: S. Jia et al., Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications, Nat. Commun. 13, 1388, 2022. +- Mach-Zehnder interferometer delay lines: V. Duarte et al., Modular coherent photonic-aided payload receiver for communications satellites, Nat. Commun. 10, 1984, 2019. + +Indeed, the inclusion of the DI- RR in our work is very novel in the context of microwave photonics. The interconnection of DI- RR and the versatile modulation transformer (MT) in a low- loss integration platform such as silicon nitride (as opposed to Silicon- on- insulator in Ref [40] in the revised manuscript) can mutually unlock the performance potential and application scope, which has never been attempted before. The combination of all aspects, in this case is a must to achieve the one- of- a- kind combination of performance metrics reported in this work (i.e., programmability, tight integration, and high RF performance). + +Moreover, when compared to the previous work mentioned by this reviewer (Ref [40] in the revised manuscript), our work significantly overcomes the limitation in previous MT design, simultaneously achieving high bandwidth ( \(>40\) GHz over merely \(10\) GHz) and ultra- sharp filtering response (3.5 GHz transition band over \(7\) GHz in previous work) that allows for the demanded access to low RF frequencies. Compared to previously used two cascaded ring resonators, the inclusion of DIRR lead to previously unattainable functionalities in reduced chip area. We also show the first ever complex (phase and amplitude) characterization of DI- RR (Supplementary Information B. Importantly, there was no investigation nor optimization of RF performance in previous works (Ref [40] in the revised manuscript). In fact, our work reports the best RF performance ever reported for a reconfigurable integrated microwave photonic system. + +We agree to add the recent ECOC 2021 manuscript in the list of references (Ref [43] in the revised manuscript). + +2) The proposed passband RF filter guarantees a moderate out-of-band rejection in the RF transmission response of 15 dB in a limited frequency range between 5 and 15 GHz, as reported for instance in Fig. S6(b) of the supplementary material. More importantly, the same figure shows that the filter response degrades when departing from the optimal condition of Fig. 3(e) and gets very noisy when tuned above about 10 GHz. This should be discussed in the manuscript. + +## Reply: + +We thank the reviewer for the suggestion. We have included new measurement results of the RF bandpass filter with improved filtering extinction ratio and wideband tunability in the main text. The bandpass filter has \(>20\) dB extinction over 5- 20 GHz frequency tuning. Through improved control of the measurement parameters, we have maintained the integrity of the passband response over the entire tuning range. Moreover, we have demonstrated that it is possible to have both high link gain and low noise figure in the filter passband. The measured metrics of 1.2 dB (positive/amplified) link gain and 21.8 dB noise figure constitute 11.2 dB gain enhancement and 5.2 dB reduction of noise figure when compared to any previously demonstrated work with next best performance metrics (Ref [54] in the revised manuscript), with nearly 3 times wider tuning range and nearly 13 dB improves SFDR when compared to any reported integrated MWP BPF. Therefore, our results represent the best performance metrics ever for integrated MWP BPF and represent a significant step forward in the field. + +<--- Page Split ---> + +These results have now been included in the main text of the revised manuscript, and an excerpt of the figure has been included below. + +## Revision: + +We have updated Fig. 3(e) - 3(g) of the main text with new and significantly improved experimental data. + +![](images/Figure_unknown_1.jpg) + + +3) Wide tuning range is often regarded as a key feature of MWP filters with respect to electronics-based solutions. However, given the operation at relatively low frequencies, these results should be compared with electronics circuits performing bandpass operation with better performance in terms of rejection and tunability, and operating in the same or even higher range of frequencies. + +A couple of examples are provided below: + +Z. Yang, +D. Psychogiou and +D. Peroulis, "Design and Optimization of Tunable Silicon-Integrated Evanescent-Mode Bandpass Filters," IEEE Trans. Microwave Theory Tech., vol. 66, no. 4, pp. 1790-1803, Apr. 2018. + +J. Chang, et al., "High Performance, Continuously Tunable Microwave Filters Using MEMS Devices With Very Large, Controlled, Out-of-Plane Actuation," in Journal of Microelectromechanical Systems, vol. 27, no. 6, pp. 1135-1147, Dec. 2018, d + +## Reply: + +We thank the reviewer for the suggestion. We have included the examples cited by the reviewer for comparison in Table I. Indeed, these MEMS- based RF filters can exhibit operation at very high frequencies. The one from Chang et al. exhibits similar tuning range as our filter but with higher insertion loss (-3 dB) and does not report the noise figure. The work of Yang et al. has larger tuning range 20- 40 GHz, but also higher insertion loss (- 1.1 dB). But of course, the glaring difference with our results is that these RF filters are limited in the synthesized response, i.e., only bandpass filter. Our results embodied the real strengths of microwave photonics, where a single circuit can be programmed to exhibit various functions and responses, leading to ultra- versatile front end. The tuning range reported here is not by any means a fundamental limitation and is currently limited only by our experimental apparatus. Previously, 1- 30 GHz tunable MWP filter with similar principle of operation has been demonstrated (Ref [47] in the revised manuscript). + +<--- Page Split ---> + +## Revision: + +We have updated the Table I in the revised main text with additional comparison data. + +TABLE I. Performance Comparison of Programmable Microwave Photonic Circuits + +
YearTechnology platformType of devicesNumber of functionsType of functionsTuning range (GHz)Performance enhancement (dB)GainNoise figure (dB)SFDR (dB·Hz2/3)
2017 [10]InPLas., Mod., RR, PD1LPF0-6No-20N/A81.4
2018 [33]SOIMZI mesh20BPF, notchN/ANoN/AN/AN/A
2017 [36]Si3N4RR1Notch0-12NF:LB815.6116
2018 [48]SOIMod., RR, PD1BPF3-10No-39N/A92.4
2018 [49]SiMEMS1BPF20-40No-1.1N/AN/A
2018 [50]SiMEMS1BPF5.5-15No-3N/AN/A
2019 [51]As2S3RR, SBS1Notch0-15NF:LB-1027.196.5
2019 [52]InPLas., Mod., MMI7BPF, notch IFM, RFG8-15NoN/AN/AN/A
2020 [53]SOISBS1BPF4-10No-1756.790.3
2020 [54]Si3N4RR1BPF2-7NF:CS-1027N/A
2021 [39]Si3N4RR1Notch3-10NF:CS331100
2021 [40]SOIMod., MT, RR, PD2Notch, BPF5-25NoN/AN/AN/A
2021 [12]InP+SOILas., Mod., RR, PD2Notch, BPF3-25No-285199.7
2021 [55]Si3N4+As2S3RR, SBS1Notch2-12NoN/AN/A92.2
2021 [56]Si3N4+LiNbO3Mod., RR MT, DI-RR1Downconversion4-20No-1045105
(this work)Si3N4MT, DI-RR6Notch5-20NF:LB1015116
(this work)Si3N4MT, DI-RR1BPF5-20NF:LB1.221.8112
Notch6-18SFDR:Lin.-2635123
+ +RR: ring resonator, PD: photodetector, Mod: modulator, MMI: multi-mode interference, SBS: stimulated Brillouin scattering, MT: modulation transformer, DI-RR: double-injection ring resonator, LPF: low pass filter, BPF: bandpass filter, IFM: instantaneous frequency measurement, PS: phase shifter, NF: noise figure, LB: low biasing, CS: carrier suppression, SFDR: spurious-free dynamic range, Lin: linearization, MEMS: microelectromechanical systems. + +4) Concerning the performance of the RF notch filter using IM, the authors state that "These results represent the best RF gain, noise figure, and SFDR combination for an MWP notch filter". There seems however to be marginal improvements with respect to the results previously reported from the authors in [36] and [37] (RF gain from 8 to 10, NF from 16 to 15, and the same SFDR of 116 dB.Hz) + +## Reply: + +We stand by our claim that the reported values are the best performance combination for any MWP notch filter. The fact that we achieved these improved values with wider tuning range, and much improved programmability should be acknowledged. We should note that the reported link performance in previous work is achieved using very simple integrated photonic devices with low interconnection loss, i.e., only a ring resonator; in contrast, here we use much more complex integrated photonic circuits, but achieved comparable or even better performance. In addition, these record values for the notch filter are obtained using the same system as the one demonstrating a record performance for bandpass filter. In our experiments we used a low + +<--- Page Split ---> + +half- wave voltage modulator, with of 2.2 V. This leads to the improvements in link gain and noise figure of the filter. + +5) Positive RF gain is achieved using two EDFAs. For applications in which compactness/low-weight is a primary requirement, what would be the RF gain without optical amplification in the system? + +## Reply: + +We thank the reviewer for the question. At present, RF performance without amplification is way below our demonstrated performance. For example, non- amplified filter with gain \(= - 28 \mathrm{~dB}\) , NF \(= 51 \mathrm{~dB}\) and SFDR of \(99.7 \mathrm{~dB} \mathrm{~Hz}^{2 / 3}\) has been reported (Ref [12] in the revised manuscript) has been reported. In our case, the unamplified and unoptimized RF gain was - 56.5 dB. However, adding amplifiers to the system need not to add significant weight and footprint. Mini and micro- EDFAs technology has been used in microwave photonics systems. Moreover, recent advances in low- noise amplification using erbium- doped waveguide amplifiers in silicon nitride [1] can offer high performance integrated MWP system with low weight and footprint. + +## Reference: + +[1] Y. Liu et al., A photonic integrated circuit- based erbium- doped amplifier, Science, 376, 1309- 1313, 2022. + +## Revision: + +We have added the statement about amplification in discussion part of main text. + +At current state, the positive RF gain in both IM- based MWP filters is achieved using two external erbium- doped fiber amplifiers (EDFAs). The recent advances in low- noise amplification using erbium- doped waveguide amplifiers in silicon nitride [63] can offer high performance integrated MWP system with low weight and reduced footprint. + +As shown in Fig. 3 and Fig. 4, the extended linearity operation of the notch filter requires replacing the external IM with a PM, which limits the claimed full- reconfigurability of the device. This should be commented in the text. + +## Reply: + +We understand the point of view of the reviewer. Indeed, that the linearization technique we present here thus far works only for PM links. This is why we didn't claim the linearized performance together with the IM- based system (see Table 1, where we separate the results in two lines). What we claim is that the same circuit can carry out both the IM- based and PM- based performance enhancements, therefore highlighting the reconfigurability of the circuit. We have explained this in the revised manuscript as the following. + +<--- Page Split ---> + +## Revision: + +We have added this limitation in discussion part of main text. + +Our linearization method, on the other hand, is working for PM- based MWP filter where maximum IMD3 suppression is achieved when the optical carrier is partially suppressed (See Supplementary Information D). Due to the limitation in maximum optical amplification in our experimental setup, the measured ultra- high SFDR is still accompanied by relatively low link gain and high NF (Table 1). Achieving the gain, NF, and SFDR advantages simultaneously is feasible in the PM link when higher optical amplification and higher power handling components are used. Because current linearization method only works in PM- based MWP notch filter, a similar strategy development is desirable for low- biased IM- based MWP filters. + +## MINOR COMMENTS + +In Figure 3c, the maximum RF gain and minimum NF is achieved for the minimum considered modulator bias voltage of roughly 9 V. What happen for bias values below that first point? Do the two figures of merit degrade or are there other system performance metrics that would be affected at lower values of modulator bias? What is the half- wave voltage of the modulator? + +## Reply: + +We thank the reviewer for the question. When the bias voltage is tuned to lower voltage ( \(< 9.3\) V), the RF gain degrades and the NF increases. This transition can be seen in the updated Fig. 3(c) and (f) in the main text. The RF half- wave voltage of the IM according to the datasheet is 2.2 V at 1 GHz and 3.5 V at 20 GHz. + +## Revision: + +We have updated the measured RF performance of the notch and bandpass filter in Fig. 3(c) and 3(f) of the revised main text. + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + + +It seems that in order to switch between scheme “d” and “e” of Fig. S5, a dual- drive Mach- Zehnder intensity modulator should be used with additional RF 90- degree hybrid, as the MT accepts at its input a dual- sideband modulated spectrum for the case of scheme “d” and a single- sideband modulated spectrum for the case of scheme “e”. Alternatively, a dual- parallel MZM modulator should be used. This should be discussed in the text + +## Reply: + +We thank the reviewer for the positive assessment of our work. The switch between scheme “d” and “e” of Fig. S5 can be happened using an external bandpass filter to completely cancel one sideband in an IM spectrum. The authors added new setup used to switch between scheme “d” and “e” of Fig. S5. + +## Revision: + +We updated with additional setup used to switch between scheme “d” and “e” of Fig. S5 and the description of extended experiment in Supplementary Information C. + +<--- Page Split ---> +![PLACEHOLDER_12_0] + + +What are the dimensions of the fabricated photonic chip? + +## Reply: + +We thank the reviewer for the question. The fabricated photonic chip containing of multiple circuit with dimension of \(8 \times 16 \mathrm{~mm}\) with the proposed circuit occupy area with dimension of \(3.2 \times 6.8 \mathrm{~mm}\) . + +<--- Page Split ---> + +Few typos around the text (examples): + +On page 2: "...which leading to sideband cancellation..." should be "...which leads to sideband cancellation..." In the caption of Fig. S5: "at the oth frequency" should be "at the notch frequency" On page 16 of the Supplementary material "which spatially isolated one sideband", should be "which spatially isolates one sideband" + +## Reply: + +We thank the reviewer for the input of our work. We have corrected these errors in our revised manuscript. + +## Revision: + +We exemplify the intensity modulation- to- phase modulation (IM- PM) conversion by inverting the phase of one sideband by \(\pi\) , which leads to sideband cancellation with 62 dB extinction in direct photodetection (Fig. 2b). + +Cancellation notch filter. MT is used to create asymmetric dual- sideband modulation conversion while DI- RR shows 5 dB- deep notch response. Destructive interference at the notch frequency amplifies the RF notch filter response to 58 dB. + +An IM signal is sent to pass through a spectral de- interleaver in the MT, which spatially isolates one sideband in the spectrum from another sideband and optical carrier. + +## Reviewer: 3 + +In this manuscript, the authors proposed a programmable integrated microwave photonic filter with ultrahigh dynamic range and low noise figure. The principle of the proposed scheme was introduced in the supplementary information, and a proof- of- concept experiment was carried out to demonstrate the capability of the proposed microwave photonic filter to improve the performance of microwave photonic links. However, there still exist many problems, and the proposed integrated microwave photonic filter lacks innovation. Based on the above consideration, I do not think the paper is suitable for publication in Nature Communication in the present form. My comments are listed below. + +1) The modulation transformer (MT) with three ring resonators topology and the double-injection ring resonator (DI-RR) have been proposed and demonstrated in [Ref. 1, Ref. 2]. In my opinion, this paper is only a combination of these two methods, so the innovation of the proposed programmable integrated microwave photonic filter is not enough to support publication in Nature Communication. + +<--- Page Split ---> + +## Reply: + +We disagree with the assessment of this reviewer. Integrated microwave photonics, much like RF electronics, relies on judicious interconnection of known, but reliable components which in turn enables prime performance or functionality that is previously unachievable. This is illustrated by the following examples, recently published in Nature Communications: + +- Silicon Brillouin waveguide: S. Gertler et al., Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon, Nat. Commun. 13(1), 2022. +- Dual integrated lasers: S. Jia et al., Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications, Nat. Commun. 13, 1388, 2022. +- Mach-Zehnder interferometer delay lines: V. Duarte et al., Modular coherent photonic-aided payload receiver for communications satellites, Nat. Commun. 10, 1984, 2019. + +The [Ref. 1] only discussed about an optical circuit called spectral de- interleaver. Such circuit is only a partial component in a modulation transformer (MT) with additional two channels containing of a tunable attenuator, a phase shifter, a delay line, and a combiner at the output of these two channels. The MT is properly explained in supplementary material. The combination of a spectral de- interleaver and a DIRR is NOT equal to the combination of a MT and a DI- RR proposed in this article. + +The inclusion of the DI- RR in our work is very novel in the context of microwave photonics. The interconnection of DI- RR and the versatile modulation transformer (MT) in a low- loss integration platform such as silicon nitride (as opposed to Silicon- on- insulator in Ref [40] in the revised manuscript) has never been attempted before. The combination of all aspects, in this case is a must to achieve the one- of- a- kind combination of performance metrics reported in this work (i.e., programmability, tight integration, and high RF performance). + +2) In this manuscript, the units of dynamic range are not uniform. "120 dB" is used in the abstract, "120 dB.Hz" is used in the introduction, "116 dB.Hz2/3" and "116 dB.Hz2/3" are used in Fig. 3. + +## Reply: + +We thank the reviewer for the critical feedback. We have used uniform expression of dB.Hz2/3 throughout our manuscript. + +3) Only the notch filter achieves the high linearity, the SFDRs of other filters are still lower than 120 dB.Hz2/3. Therefore, it is inaccurate to claim that "ultra-high dynamic range of > 120 dB.Hz" is achieved. + +## Reply: + +We aim to clarify that the SFDR of \(112 - 116 \mathrm{dB.Hz}^{2 / 3}\) achieved for RF bandpass and RF notch filters in this work is still very high when compared to previous results. The only RF notch filter with SFDR of \(>100 \mathrm{dB.Hz}^{2 / 3}\) was reported in Ref [36] in the revised manuscript, which is a work led by the senior author of our paper. This comparison rings even more true when + +<--- Page Split ---> + +considering RF bandpass filter, with the highest previously reported SFDR of nearly 13 dB lower than our results (99.7 dB. \(\mathrm{Hz}^{2 / 3}\) ) in Ref [12] in the revised manuscript. The ultra- high dynamic range of \(>120 \mathrm{dB}.\mathrm{Hz}^{2 / 3}\) shown in this article is a proof concept of on- chip linearization and simultaneous RF notch filter using a single photonic chip. + +To avoid confusion, we have revised the abstract and introduction as + +## Abstract + +Here, we report, for the first time, a multi- functional photonic integrated circuit that enables programmable filtering functions with record- high performance. We demonstrate a switchable filter function with record- low noise figure and a RF notch filter with ultra- high dynamic range. + + + +## Introduction + +In this work, we demonstrate a programmable integrated MWP circuit with a unique combination of a versatile MT device and a DI- RR, realized in a low- loss silicon nitride platform. With this circuit, we show for the first time, an array of RF filters in three different scenarios simultaneously with record- low noise figure for RF notch and RF bandpass filter, achieved using low- biasing technique [36, 37] in an intensity modulator (IM)- based system, and ultra- high dynamic range for RF notch filter, achieved using on- chip linearization in a phase modulator (PM)- based system. + + + +4) Since the linearization is only for notch filters, not for all filters, it is misleading to directly use "ultrahigh dynamic range" in the title. Meanwhile, this paper only achieves the integration of several passive devices, so "integrated microwave photonic filter" is also inappropriate. + +## Reply: + +We believe that all the dynamic range values reported throughout this paper, using both the IM and PM- based enhancement fall in the category of high dynamic range. To put it in the context, these values are more than an order of magnitude higher than previously reported (except for Ref [36] in the revised manuscript, which was a work led by the senior author of this paper). The linearized link indeed shows ultra- high dynamic range with SFDR of \(123 \mathrm{dB}.\mathrm{Hz}^{4 / 5}\) . + +Regarding the terminology integrated microwave photonic filter, we never claimed that the device is fully integrated, where the lasers, modulators, detectors, and signal processor are either hybrid/heterogeneously integrated. Nevertheless, we believe, our system is still an integrated microwave photonic system by definition, see for example integrated microwave photonic papers (Ref [6] and Ref [7] in the revised manuscript). Indeed, that it is important to achieve high performance in all integrated system. But in reality, the performance of such systems is much poorer when compared to our results (see Ref [10] and Ref [12] in the revised manuscript as examples). The highest gain, noise figure and SFDR are \(39 \mathrm{dB}\) , \(36 \mathrm{dB}\) , and \(16 \mathrm{dB}\) lower, respectively, than our reported results here. So, our work here serves as evidence that + +<--- Page Split ---> + +a partially integrated MWP system can achieve high performance and address a unique area/metric that has never been demonstrated before, and therefore constitute a significant leap in the field. + +5) From the supplementary information, the tuning range of the bandpass filter is obviously not as wide as the \(4 - 20GHz\) stated in TABLE I. + +## Reply: + +We thank the reviewer for the critical feedbacks to the tuning range of the bandpass filter. We added new experiment results covering the tuning range of the bandpass filter and updated the Table I in main text. + +## Revision: + +We have updated the measured performance of the bandpass filter in Fig. 3(e)- (g) and Table I of the revised main text. + +![PLACEHOLDER_16_0] + + +<--- Page Split ---> + + +TABLE I. Performance Comparison of Programmable Microwave Photonic Circuits + +
YearTechnology platformType of devicesNumber of functionsType of functionsTuning range (GHz)Performance enhancementGain (dB)Noise figure (dB)SFDR (dB·Hz2/3)
2017 [10]InPLas., Mod., RR, PD1LPF0-6No-20N/A81.4
2018 [33]SOIMZI mesh20BPF, notchN/ANoN/AN/AN/A
2017 [36]Si3N4RR1Notch0-12NF:LB815.6116
2018 [48]SOIMod., RR, PD1BPF3-10No-39N/A92.4
2018 [49]SiMEMS1BPF20-40No-1.1N/AN/A
2018 [50]SiMEMS1BPF5.5-15No-3N/AN/A
2019 [51]As2S3RR, SBS1Notch0-15NF:LB-1027.196.5
2019 [52]InPLas., Mod., MMI7BPF, notch8-15NoN/AN/AN/A
2020 [53]SOISBS1IFM, RFG
2020 [54]Si3N4RR1BPF4-10No-1756.790.3
2021 [39]Si3N4RR1BPF2-7NF:CS-1027N/A
2021 [40]SOIMod., MT, RR, PD2Notch, BPF3-10NF:CS331100
2021 [12]InP+SOILas., Mod., RR, PD2Notch, BPF5-25NoN/AN/AN/A
2021 [55]Si3N4+As2S3RR, SBS1Notch3-25No-285199.7
2021 [56]Si3N4+LiNbO3 (this work)Mod., RR MT, DI-RR1Downconversion2-12NoN/AN/A92.2
6Notch4-20No-1045105
1BPF5-20NF:LB1015116
1Notch6-18SFDR.Lin.1.221.8112
1Notch6-18SFDR.Lin.-2635123
+ +RR: ring resonator, PD: photodetector, Mod: modulator, MMI: multi-mode interference, SBS: stimulated Brillouin scattering, MT: modulation transformer, DI-RR: double-injection ring resonator, LPF: low pass filter, BPF: bandpass filter, IFM: instantaneous frequency measurement, PS: phase shifter, NF: noise figure, LB: low biasing, CS: carrier suppression, SFDR: spurious-free dynamic range, Lin: linearization, MEMS: microelectromechanical systems. + +6) Only the normalized response is given in the manuscript, and the non-normalized response also should be given, so that the reader can understand the actual insertion loss of the microwave photonic filter. + +## Reply: + +We thank the reviewer for the critical feedbacks to the manuscript. We added the non- normalized RF response of both RF notch and RF bandpass filter in Fig.3(b) and 3(e) of the main text. + +7) The linearization is realized by the widely used optical sideband phase and amplitude manipulation, which is usually regarded as a narrowband approach. So, within which frequency range the SFDR can reach \(120 \mathrm{dB} \cdot \mathrm{Hz}2 / 3\) ? The authors should provide the SFDR results at other frequencies. + +## Reply: + +We thank the reviewer for the critical feedbacks to the manuscript. We have added extensive experiment results of SFDR after linearization at other frequencies in Supplementary Information F. The ultra-high SFDR \(>120 \mathrm{dB} \cdot \mathrm{Hz}^{2 / 3}\) is maintained at 8, 9, 10, and 16 GHz, showing the broadband nature of our results. + +<--- Page Split ---> + +## Revision: + +We have updated the measured SFDR post linearization at different frequencies in supplementary information F. + +To further characterize the performance of our proposed linearized RF notch filter, we extended our measurements of IMD3 suppression and SFDR when the two- tone test frequency and the notch filter frequency was tuned separately. We first fixed the notch frequency at \(12\mathrm{GHz}\) and performed two tone measurements at \(8\mathrm{GHz}\) , \(9\mathrm{GHz}\) , \(10\mathrm{GHz}\) , and \(16\mathrm{GHz}\) . The results of the IMD3 suppression are shown in Fig. S7. It is clear that the IMD3 terms are greatly suppressed for more than \(28\mathrm{dB}\) in all of these two- tone frequencies. + +The results of the SFDR at different frequencies are shown in Fig. S8. In all the cases, SFDR of more than \(122\mathrm{dB} \cdot \mathrm{Hz}^{2 / 3}\) are observed with improvements around \(20\mathrm{dB}\) compared with nonlinearized states. + +![PLACEHOLDER_18_0] + +
Fig. S7. Third-order intermodulation distortion (IMD3) suppression at various two-tone frequencies with notch response at \(12\mathrm{GHz}\) . (a) two-tone signal at \(8\mathrm{GHz}\) (b) two-tone signal at \(9\mathrm{GHz}\) (c) two-tone signal at \(10\mathrm{GHz}\) (d) two-tone signal at \(16\mathrm{GHz}\) .
+ +<--- Page Split ---> +![PLACEHOLDER_19_0] + +
Fig. S8. Spurious-free dynamic range (SFDR) measurements at various two-tone frequencies with notch response at 12 GHz. (a) SFDR at 8 GHz (b) SFDR at 9 GHz (c) SFDR at 10 GHz (d) SFDR at 16 GHz. IMD3: third-order intermodulation distortion, IMD5: fifth-order intermodulation distortion.
+ +8) From the description of the experimental details, the power of the input two-tone signal is 10 dBm, but the power of fundamental and spurious at this input power is not reflected in Fig. 4(d). + +## Reply: + +We thank the reviewer for the feedback about two-tone signal. The input RF power of two-tone signal to the PM is 8 dBm. We updated the number in main text. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +## Reviewer #1 (Remarks to the Author): + +My comments have been addressed. I recommend acceptance for publication. + +## Reviewer #2 (Remarks to the Author): + +The authors did good efforts in replying to my comments. As a personal opinion, I believe that the performance of the bandpass functionality for the proposed reconfigurable microwave photonics (MWP) filter is below that of state- of- the- art electronics components. A fair comparison with the MEMS- based devices discussed in refs. [49] and [50] of the revised manuscript should account that the RF loss of 1 and 3 dB, respectively, are obtained in fully passive devices, whereas two power- consuming erbium- doped fiber amplifiers are required for positive RF gain in the proposed MWP approach. At the same time, the MEMS- based filters typically can provide larger rejection, faster roll- off and improved passband flatness (which are parameters that are not considered in TABLE I). The claimed advantage of reconfigurability can be handled in electronics- domain with digitally controlled filter banks and switches, although I agree that this is not an optimal solution. There is also still a concern about the moderate improvement in terms of RF gain and noise figure (NF) (of 2 and 1 dB, respectively) compared with authors' previous works (see refs [36] and [37]) since, as stated by the authors in the answer to comment 4, the improvement seems to be partially ascribed to the use of an external modulator with lower half- wave voltage. + +However, in view of the improved quality of the manuscript with new and more accurate measurement results, and in recognizing the advancement in the field brought by the proposed approach in terms of programmable functionality, the paper can be considered for publication in Nature Communications. Below my new comments: + +1) In the answer to Comment 3, the authors state that MWP filter tuning in the 1-30 GHz range has been achieved in a previous circuit with similar operation principle. However, the MWP filter discussed in the quoted reference [47] of the revised manuscript is based on stimulated Brillouin scattering (SBS) effect, for which the highest operating frequency is not limited by the free-spectral range (FSR) of microring-resonator (MRRs)-based filtering elements, as in the proposed approach. On the other hand, as discussed in the supplementary material of the original manuscript, the lowest operating frequency of this scheme is 5 GHz, due to the leakage at low modulation frequencies between the two output ports of the spectral de-interleaver in the modulation transformer (MT). This makes the operating frequency range 15 GHz (5-20 GHz, as reported in Table I), and the two statements on page 3 of the revised manuscript claiming that the filter is tunable over 20 GHz should be corrected accordingly. + +2) At which frequency is measured the RF gain of the MWP notch filter in Fig. 3c? How does the maximum RF gain scale over the 5-20 GHz filter operating range? + +3) In answering my comment about the half-wave voltage of the intensity modulator, the authors indicated the nominal values of 2.2 V and 3.5 V at 1 GHz and 20 GHz, respectively, but missed to include this information in the revised manuscript. Please, add the details of the half-wave voltage for the employed modulator within the main text. + +4) Few typos around: (Abstract): We demonstrate a switchable filter functions... (Page 5) Similar record-high SFDR also observed in different frequencies (see Supplementary Information F). (Methods Section) Because typical top cladding thickness cannot achieved only by LPCVD TEOS... (Methods Section) A thicker layers can be achieved... + +<--- Page Split ---> + +## Reviewer #3 (Remarks to the Author): + +I appreciate the authors taking the effort in answering the questions raised by both the reviewers i n previous report. They provided new information to highlight the advantages of their work, which makes it more solid. However, the answers still cannot convince me to recommend this manuscript for publication in Nature Communications: + +1) Although the authors give more words to explain their innovation, but it still cannot change the fact that the entire chip is very simple, and the ideas of modulation transformation and noise figure reduction, linearity improvement are reported before. I read the References the authors used to reply the first question from Reviewer 2, from my opinion, the chips reported in these References, e.g., the SBS waveguide, laser chip and the satellite payload chip, are novel in terms of the chip itself or its application systems, which clearly shows the levels of the chip and the system demonstration. However, I still cannot see such distinguished novelty from this paper. +2) The comparison with the electrical filters is not reasonable. Although NF and SFDR are not measured in Ref. [49] and Ref. [50], I believe they have better performances than the photonic filter, since they do not involve EO & OE conversions and active amplification. The advantages of the proposed filter are the relatively higher gain and reconfigurability. However, the gain is realized by two EDFAs which will sacrifice the analog performance. For the reconfigurability, I cannot clearly see (or find from the manuscript) the necessity of such a filter. Therefore, the significance of the work and the impact on the researchers in both MWP and microwave communities are not clear. + +3) From the Method, the power of the input two-tone RF signal is 8 dBm. According to Fig. 4(c), the power of the fundamental components are nearly -30 dBm, which cannot agree with the -26 dB claimed in Table I and the results shown in Fig. 4d. Please check it. + +4) Although SFDRs at different frequencies are measured, it would be more convincing to directly input a wideband RF signal (for example, a QAM signal) to demonstrate its high dynamic range after filtering. + +<--- Page Split ---> + +## Ultrahigh Dynamic Range and Low Noise Figure Programmable Integrated Microwave Photonic Filter: \(2^{\mathrm{nd}}\) Response to Reviewers' comments + +NCOMMS- 22- 10585 + +We thank the reviewers for their valuable comments and their time spent in evaluating this work. In this response, we addressed each comment/question from the reviewers point by point. The reviewer's comments are in Black, our responses are in Blue, and revisions in the manuscript are in Red + +## Point-to-point response: + +## Reviewer: 1 + +My comments have been addressed. I recommend acceptance for publication. + +## Reply: + +We thank the reviewer for the positive assessment of our paper. + +## Reviewer: 2 + +The authors did good efforts in replying to my comments. As a personal opinion, I believe that the performance of the bandpass functionality for the proposed reconfigurable microwave photonics (MWP) filter is below that of state- of- the- art electronics components. A fair comparison with the MEMS- based devices discussed in refs. [49] and [50] of the revised manuscript should account that the RF loss of 1 and 3 dB, respectively, are obtained in fully passive devices, whereas two power- consuming erbium- doped fiber amplifiers are required for positive RF gain in the proposed MWP approach. At the same time, the MEMS- based filters typically can provide larger rejection, faster roll- off and improved passband flatness (which are parameters that are not considered in TABLE I). The claimed advantage of reconfigurability can be handled in electronics- domain with digitally controlled filter banks and switches, although I agree that this is not an optimal solution. There is also still a concern about the moderate improvement in terms of RF gain and noise figure (NF) (of 2 and 1 dB, respectively) compared with authors' previous works (see refs [36] and [37]) since, as stated by the authors in the answer to comment 4, the improvement seems to be partially ascribed to the use of an external modulator with lower half- wave voltage. + +However, in view of the improved quality of the manuscript with new and more accurate measurement results, and in recognizing the advancement in the field brought by the proposed approach in terms of programmable functionality, the paper can be considered for publication in Nature Communications. + +## Reply: + +We thank the reviewer for the positive recommendation and the highly valuable perspectives given for our paper. + +<--- Page Split ---> + +We agree with the reviewer on the fact that the MEMS- based filter can exhibit a lower noise figure (determined by the passive circuit insertion loss) while the MWP filters can be considered 'active', because the system requires lasers, electro- optic modulators, optical amplifiers, and photodetectors that actively consumes power. These optical components usually contribute to more noise, higher losses, and thus higher noise figure to the system. However, there are number of reports about active bandpass filter that show comparable performance with our work because of the usage of active- RC [1], active capacitance [2] or active inductor [3- 5] in the circuit. + +Despite the \(>10\mathrm{dB}\) noise figures of reported MWP filters, it is fundamentally feasible to achieve single- digit dB level with lower- RIN lasers, high- efficiency modulators and photodetectors, and low- loss photonic interconnects. Thus, reducing the noise figure of MWP filters will be realized based on the advances and innovation of these optical components, which has been continuously driven by the need for high- performance devices not only for optical communications but also for optical signal processing and computing. + +## References: + +[1] B. Wu et al., A 40 nm CMOS Derivative- Free IF Active- RC BPF With Programmable Bandwidth and Center Frequency Achieving Over 30 dBm IIP3, IEEE Journal of Solid- State Circuits, 50(8), 1772- 1784, 2015. + +[2] D. Colaiuda et al., A Second Order 1.8- 1.9 GHz Tunable Active Band- Pass Filter with Improved Noise Performance, Electronics, 11(2781), 1- 10, 2022. + +[3] Z. Gao et al., A Fully Integrated CMOS Active Bandpass Filter for Multiband RF Front- Ends, IEEE Transactions on Circuits and Systems II: Express Briefs, 55(8), 718- 722, 2008. + +[4] V. Kumar et al., A 2.5 GHz Low Power, High- Q, Reliable Design of Active Bandpass Filter, IEEE Transactions on Device and Materials Reliability, 17(1), 229- 244, 2017. + +[5] R. Mehra et al., Reliable and Q- Enhanced Floating Active Inductors and Their Application in RF Bandpass Filter, IEEE Access, 6, 48181- 48194, 2018. + +Below my new comments: + +1) In the answer to Comment 3, the authors state that MWP filter tuning in the 1-30 GHz range has been achieved in a previous circuit with similar operation principle. However, the MWP filter discussed in the quoted reference [47] of the revised manuscript is based on stimulated Brillouin scattering (SBS) effect, for which the highest operating frequency is not limited by the free-spectral range (FSR) of microring-resonator (MRRs)-based filtering elements, as in the proposed approach. On the other hand, as discussed in the supplementary material of the original manuscript, the lowest operating frequency of this scheme is 5 GHz, due to the leakage at low modulation frequencies between the two output ports of the spectral de-interleaver in + +<--- Page Split ---> + +the modulation transformer (MT). This makes the operating frequency range 15 GHz (5- 20 GHz, as reported in Table I), and the two statements on page 3 of the revised manuscript claiming that the filter is tunable over 20 GHz should be corrected accordingly. + +## Reply: + +We agree with the comments of the reviewer and have corrected the statement in page 3 to 15 GHz. + +## Revision: + +The RF notch filter central frequency can be tuned from 5 to 20 GHz (Fig. 3b) with maximum RF gain of more than 0 dB over the frequency range (see Supplementary Information D). + +RF bandpass filter with 20 dB rejection, with up to 15 GHz tuning range (from 5 GHz to 20 GHz) (Fig. 3e), limited by the roll-off and the dispersion of the spectral de- interleaver, notably at the transition band (see Supplementary Information A). This tuning range can be feasibly increased using improved design of (de)- interleaver with faster roll- off and a larger FSR. + +2) At which frequency is measured the RF gain of the MWP notch filter in Fig. 3c? How does the maximum RF gain scale over the 5-20 GHz filter operating range? + +## Reply: + +The RF gain of MWP notch filter in Fig. 3c is measured at frequency of 1 GHz. The RF link gain stays above 0 dB over the entire frequency range of 5- 20 GHz. Below we list the RF gain at various frequencies: + +
Freq. (GHz)RF gain (dB)Freq. (GHz)RF gain (dB)Freq.
(GHz)
RF gain (dB)Freq.
(GHz)
Freq.
(dB)
54.2392.60132.71171.61
64.01102.39142.05181.19
73.62112.16152.60191.14
82.87122.72162.11201.71
+ +## Revision: + +We have added the list and graph of the maximum RF gain of MWP notch filter over the tuning range (5- 20 GHz) in the Supplementary Information D as follows, + +<--- Page Split ---> + +## Main text: + +The RF notch filter central frequency can be tuned from 5 to \(20\mathrm{GHz}\) (Fig. 3b) with maximum RF gain of more than \(0\mathrm{dB}\) over the frequency range (see Supplementary Information D). + +## Supplementary Information: + +The maximum RF gain of the RF notch filter stays above \(0\mathrm{dB}\) over the entire frequency range of \(5 - 20\mathrm{GHz}\) . Fig. S6 shows the RF gain at various frequencies. + +TABLE S1. The maximum RF Gain of the RF notch filter over the entire frequency range + +
Freq. (GHz)RF Gain (dB)Freq. (GHz)RF Gain (dB)Freq.RF Gain (GHz)Freq.RF Gain (dB)
54.2392.60132.71171.61
64.01102.39142.05181.19
73.62112.16152.60191.14
82.87122.72162.11201.71
+ +![PLACEHOLDER_25_0] + +
Fig. S6. The RF gain of the RF notch filter. Plot of the maximum RF gain of the RF notch filter over the entire frequency range.
+ +3) In answering my comment about the half-wave voltage of the intensity modulator, the authors indicated the nominal values of \(2.2\mathrm{V}\) and \(3.5\mathrm{V}\) at \(1\mathrm{GHz}\) and \(20\mathrm{GHz}\) , respectively, but missed to include this information in the revised manuscript. Please, add the details of the half-wave voltage for the employed modulator within the main text. + +# Reply: + +<--- Page Split ---> + +We have added the modulator half- wave voltage information in the revised manuscript. + +## Revision: + +(Thorlabs, LNLVL- IM- Z 40 GHz, \(V_{\pi ,RF}\) of 2.2 V at 1 GHz and 3.5 V at 20 GHz) + +4) Few typos around: + +(Abstract): We demonstrate a switchable filter functions ... + +(Page 5) Similar record- high SFDR also observed in different frequencies (see Supplementary Information F). + +(Methods Section) Because typical top cladding thickness cannot achieved only by LPCVD TEOS... + +(Methods Section) A thicker layers can be achieved... + +## Reply: + +We thank the reviewer for careful reading of our manuscript, we have revised the manuscript accordingly. + +## Revision: + +(Abstract) We demonstrate reconfigurable filter functions... + +(Page 5) Similar record- high SFDR also can be observed in different frequencies. + +(Methods Section) Because typical top cladding thickness cannot be achieved only by LPCVD TEOS... + +(Methods Section) Thicker layers can be achieved... + +## Reviewer: 3 + +I appreciate the authors taking the effort in answering the questions raised by both the review ers in previous report. They provided new information to highlight the advantages of their wor k, which makes it more solid. However, the answers still cannot convince me to recommend this manuscript for publication in Nature Communications: + +<--- Page Split ---> + +## Reply: + +We thank the reviewer for appreciating our work and efforts. In what follows, we will try to address the raised concerns and add suggested clarifications. + +1) Although the authors give more words to explain their innovation, but it still cannot change the fact that the entire chip is very simple, and the ideas of modulation transformation and noise figure reduction, linearity improvement are reported before. I read the References the authors used to reply the first question from Reviewer 2, from my opinion, the chips reported in these References, e.g., the SBS waveguide, laser chip and the satellite payload chip, are novel in terms of the chip itself or its application systems, which clearly shows the levels of the chip and the system demonstration. However, I still cannot see such distinguished novelty from this paper. + +## Reply: + +We respectfully disagree that the simplicity of the circuit should be interpreted as lack of novelty in our work. On contrary, we believe that we have demonstrated that such high performance and programmability is indeed accessible through relatively simple chip topology which is previously unachievable. + +We agree that individually, modulation transformation, noise figure reduction, and linearization have been achieved. This is precisely the key breakthrough in our work, that we simultaneously achieve these features in our relatively simple photonic chip that has never been demonstrated before. This function and performance novelty is equally important as the device innovation or novel applications. In our work, the novelty lies in how these concepts and devices are used to unlock previously unachievable system performance. + +2) The comparison with the electrical filters is not reasonable. Although NF and SFDR are not measured in Ref. [49] and Ref. [50], I believe they have better performances than the photonic filter, since they do not involve EO & OE conversions and active amplification. + +## Reply: + +We respectfully disagree with this comment. First, we cannot make a fair comparison of the NF and SFDR of previous works, as they are not reported. Assuming that they have better performance would be speculative. + +Recently, there are number of investigations about active RF bandpass filter with active- RC [1], active capacitance [2] or active inductor [3- 5], that is built in CMOS technology. Nevertheless, the reported noise figure and dynamic range in these studies are comparable with our work (Table I). + +This comparable result shows the uniqueness of programmable MWP circuit in our work. With simpler chip topology, our work can compete in term of performance, but with better wide tuning range, continuous tunability, and less hardware numbers that cannot be achieved easily by its electronic counterparts. + +References: + +<--- Page Split ---> + +[1] B. Wu et al., A 40 nm CMOS Derivative-Free IF Active-RC BPF With Programmable Bandwidth and Center Frequency Achieving Over 30 dBm IIP3, IEEE Journal of Solid-State Circuits, 50(8), 1772- 1784, 2015. + +[2] D. Colaiuda et al., A Second Order 1.8- 1.9 GHz Tunable Active Band- Pass Filter with Improved Noise Performance, Electronics, 11(2781), 1- 10, 2022. + +[3] Z. Gao et al., A Fully Integrated CMOS Active Bandpass Filter for Multiband RF Front- Ends, IEEE Transactions on Circuits and Systems II: Express Briefs, 55(8), 718- 722, 2008. + +[4] V. Kumar et al., A 2.5 GHz Low Power, High- Q, Reliable Design of Active Bandpass Filter, IEEE Transactions on Device and Materials Reliability, 17(1), 229- 244, 2017. + +[5] R. Mehra et al., Reliable and Q- Enhanced Floating Active Inductors and Their Application in RF Bandpass Filter, IEEE Access, 6, 48181- 48194, 2018. + +The advantages of the proposed filter are the relatively higher gain and reconfigurability. However, the gain is realized by two EDFAs which will sacrifice the analog performance. + +## Reply: + +We respectfully disagree with this comment. At this point, all MWP system is active and requires sufficient laser power and EDFA to compensate the optical losses in the system. The combination of EDFA with low- biasing Mach- Zehnder modulator (MZM) has been reported, can be used to improve the performance of the analog photonic system [1] which is the opposite of the reviewer comment. In fact, the positive result of having combination of EDFA and low- biasing MZM in the system is in- line with our work, as we reported the highest ever analog performance using our system. + +Finally, the need for external EDFAs can be feasibly eliminated using high- power erbium- doped waveguide amplifiers (EDWA) in the silicon nitride ( \(Si_{3}N_{4}\) ) photonic integrated circuits, which is recently demonstrated by one of the co- authors of this work [2]. It can be reasonably foreseen in the future that applying the on- chip Erbium amplifier to the MWP chip will overcome the current necessities of the off- chip EDFAs, and at the same time it can enable demanded link gain and noise figure. + +## Reference: + +[1] V.J. Urick et al., Analysis of an Analog Fiber- Optic Link Employing a Low- Biased Mach Zehnder Modulator Followed by an Erbium- Doped Fiber Amplifier, IEEE Journal of Lightwave Technology, 27(12), 2013- 2019, 2009. + +<--- Page Split ---> + +[2] Y. Liu et al., A photonic integrated circuit-based erbium-doped amplifier, Science, 376, 1309- 1313, 2022. + +For the reconfigurability, I cannot clearly see (or find from the manuscript) the necessity of such a filter. Therefore, the significance of the work and the impact on the researchers in both MWP and microwave communities are not clear. + +## Reply: + +Naturally, reconfigurable bandpass- bandstop filters are important for modern microwave and wireless systems with spectrally cognitive operation [1,2] and in modern multi- mode transceivers adaptable for several operation bands [3,4]. It is desirable to eliminate the need for large- volume switchable filter banks which are not unlimitedly scalable due to the limits in space, weight and power consumption. These filters can dynamically select RF signals of interest and mitigate frequency- agile interferers [5- 7]. This need for reconfigurable filters has been clearly mentioned in the following supplementary references and has been motivating the progress of the topic of MWP. Additionally, the reconfigurable filter in our work can be achieved in integrated form factor as opposite with the usage of discrete components in references which gives our work the upper hand in term of the size and weight. + +Recently, U.S. Defense Advance Research Project Agency (DARPA) announced a project called COFFEE or COmpact Front- end Filters at the EIEment- level to address the challenges hampering the use of wideband Active Electronically Scanned Array (AESA) in congested RF environments [8]. With this project, DARPA seeks to create new class of integrable, high- frequency filters with low loss, high- power handling, and seamless uniformity for superior electromagnetic spectrum operations in the modern era with one area of priority: heightened multifunctionality and granular optimization in AESAs [8]. The COFFEE project aims to develop integrable filters that operate over a wide range of frequencies, small enough to fit behind the element of phased array, and on the analog front- end to make the array in AESA more robust and resistant to interference before digital processing on the back- end [9]. + +## References: + +[1] E.J. Naglich et al., A Tunable Bandpass- to- Bandstop Reconfigurable Filter with Independent Bandwidths and Tunable Response Shape, IEEE Transactions on Microwave Theory and Techniques, 58(12), 3770- 3779, 2010. + +[2] T. Yang et al., Bandpass- to- Bandstop Reconfigurable Tunable Filters with Frequency and Bandwidth Controls, IEEE Transactions on Microwave Theory and Techniques, 65(7), 2288- 2297, 2017. + +[3] J. Lee et al., New Bandstop Filter Circuit Topology and Its Application to Design of a Bandstop- to- Bandpass Switchable Filter, IEEE Transactions on Microwave Theory and Techniques, 61(3), 1114- 1123, 2013. + +<--- Page Split ---> + +[4] Y- H. Cho et al., Two- and Four- Pole Tunable 0.7- 1.1- GHz Bandpass- to- Bandstop Filters with Bandwidth Control, IEEE Transactions on Microwave Theory and Techniques, 62(3), 457- 463, 2014. + +[5] Y- C. Chiou et al., A Tunable Three- Pole 1.5- 2.2- GHz Bandpass Filter with Bandwidth and Transmission Zero Control, IEEE Transactions on Microwave Theory and Techniques, 59(11), 2872- 2878, 2011. + +[6] E.J. Naglich et al., Switchless Tunable Bandstop- to- All- Pass Reconfigurable Filter, IEEE Transactions on Microwave Theory and Techniques, 60(5), 1258- 1265, 2012. + +[7] M. Fan et al., Compact Bandpass- to- Bandstop Reconfigurable Filter with Wide Tuning Range, IEEE Transactions on Microwave Theory and Techniques, 29(3), 198- 200, 2019. + +[8] Defense Advance Research Project Agency. (2022), COFFEE Program Jump- Starts Integrable Filtering for Wideband Superiority, https://www.darpa.mil/news- events/2022- 06- 01, Last accessed on 2022 Sept. + +[9] Defense Advance Research Project Agency. (2021), Filtering Out Interference for Next- Generation Wideband Arrays, https://www.darpa.mil/news- events/2021- 06- 10, Last accessed on 2022 Sept. + +## Revision: + +We have clarified in the main text about the necessity of reconfigurable filter for modern RF applications as the following: + +## Introduction + +As radio frequency (RF) and microwave systems are moving forward into cognitive operation, novel reconfigurable filter will become a key component to enable the full potential of these systems performance [1- 3]. This filter can intelligently operate to differentiate RF signal of interest from the interferers [4- 6]. There is a need of developing reconfigurable filter for modern RF systems to address the challenges impeding the use of active electronically scanned array (AESA) that operate at wide range of frequencies in dense RF environment [7]. The filter is aimed to make the array in AESA more resistant to interference before signal processing [8]. Integrated microwave photonic (MWP) can offer significant advantages to realize advanced concepts of reconfigurable filter for multi- band, all spectrum communications [9] and broadband programmable front- ends [10], which are important for modern RF communications (i.e. cognitive radio). To play a key role in modern RF applications, integrated MWP circuits need to simultaneously show advanced programmability and exceptional performance in terms of low losses, low noise figure, and high dynamic range in a reduced footprint [11- 15]. In recent pasts, a number of programmable integrated MWP filters have widely been demonstrated [16- 20]. Typically, these filters were achieved in application specific circuits, and the measured RF metrics were only sparsely reported. The values of the RF gain, noise figure (NF), and spurious + +<--- Page Split ---> + +free dynamic range (SFDR) in these circuits are usually far- off from the requirements for practical RF systems. + + + +The capability of the proposed reconfigurable filter is expected to improve the system performance across S- band through Ku- band (i.e. 2 GHz to 18 GHz) frequency range and play a key role for the realization of practical programmable integrated MWP circuit that can operate in congested RF environment. + +3) From the Method, the power of the input two-tone RF signal is 8 dBm. According to Fig. 4(c), the power of the fundamental components are nearly -30 dBm, which cannot agree with the -26 dB claimed in Table I and the results shown in Fig. 4d. Please check it. + +## Reply: + +We thank the reviewer for the feedback about the two- tone signal. In the method section, the 8 dBm RF power is the output RF power from the signal generator. However, when we combine the RF signal from two signal generators, the RF combiner and the RF cable will introduce an 8.5 dB insertion loss, so the power sent to the phase modulator (the real input RF power) is around - 0.5 dBm. The power of the fundamental components in Fig. 4(c) is - 26.65 dBm. The difference between the output fundamental power and the real input RF power matches the link gain of the system, which is - 26 dB. + +We have updated the RF input power as - 0.5 dBm in the method section. + +For the SFDR measurements, we increased the input RF signal to observe the growing trends of the IMD3 and the fundamental terms after linearization. Then, we compare them with the changes of the IMD3 and the fundamental terms in the non- linearized system. The input RF power in Fig. 4(d) is the power sent to the phase modulator (PM). Here, we have already subtracted the insertion loss of the RF combiner and the RF cable. + +## Revision: + +For the IMD3 suppression experiment, the two- tone RF signal with power of - 0.5 dBm, centered at 9 GHz with a space of 10 MHz from signal generators (Wiltron 69147A and Rohde- Schwarz SMP02) is used to drive the PM. + +4) Although SFDRs at different frequencies are measured, it would be more convincing to directly input a wideband RF signal (for example, a QAM signal) to demonstrate its high dynamic range after filtering. + +<--- Page Split ---> + +## Reply: + +Reply:The presented SFDR is obtained from the standard measurement methods widely used in analog electronics RF/microwave [1- 5] and analog microwave photonics [6- 10], therefore, the measurement technique itself is reliable. We acknowledge the suggestion of the reviewer for wideband RF signal input. However, at this moment we do not have access to the experimental equipment capable of generating QAM signals and to measure their quality/error rate. + +## References: + +[1] C. Garcia- Alberdi et al., Tunable Class AB CMOS \(G_{m} - C\) Filter Based on Quasi- Floating Gate Techniques, IEEE Transactions on Circuits and Systems I: Regular Papers, 60(5), 1300- 1309, 2013. + +[2] M. De Matteis et al., A 33 MHz 70 dB- SNR Super- Source- Follower- Based Low- Pass Analog Filter, IEEE Journal of Solid- State Circuits, 50(7), 1516- 1524, 2015. + +[3] J.S. Mincey et al., Low- Power \(G_{m} - C\) Filter Employing Current- reuse Differential Difference Amplifiers, IEEE Transactions on Circuits and Systems II: Express Briefs, 64(6), 635- 639, 2017. + +[4] Y. Xu et al., A 77- dB- DR 0.65- mW 20- MHz \(5^{\mathrm{th}}\) - order Coupled Source Followers Based Low- Pass Filter, IEEE Journal of Solid- State Circuits, 55(10), 2810- 2818, 2020. + +[5] M. De Matteis et al., 64 dB Dynamic- Range 810 \(\mu W\) 90 MHz Fully- Differential Flipped- Source- Follower Analog Filter in 28nm- CMOS, IEEE Transactions on Circuits and Systems II: Express Briefs, 68(9), 3068- 3072, 2021. + +[6] G. Liu et al., Integrated Microwave Photonic Spectral Shaping for Linearization and Spurious- Free Dynamic Range Enhancement, IEEE Journal of Lightwave Technology, 39(24), 7551- 7562, 2021. + +[7] O. Daulay et al., Microwave Photonic Notch Filter with Integrated Phase- to- Intensity Modulation Transformation and Optical Carrier Suppression, Optics Letters, 46(3), 488- 491, 2021. + +[8] H. Shun Wen et al., Ultrahigh Spectral Resolution Single Passband Microwave Photonic Filter, Optics Express, 29(18), 28725- 28740, 2021. + +[9] R. Zheng et al., Microwave Photonic Link with Improved Dynamic Range for Long- Haul Multi- Octave Applications, IEEE Journal of Lightwave Technology, 39(24), 7915- 7924, 2021. + +[10] Y. Liu et al., Tunable and Reconfigurable Microwave Photonic Bandpass Filter Based on Cascaded Silicon Microring Resonators, IEEE Journal of Lightwave Technology, 40(14), 4655- 4662, 2022. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +## Reviewer #2 (Remarks to the Author): + +My comments have been reasonably addressed by the authors. The manuscript can be considered for publication. + +<--- Page Split ---> diff --git a/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..d5a5cf1ef354a120d876f8c9238b298f0eb3c623 --- /dev/null +++ b/peer_reviews/dec983238865e559cbef993ae0e1c8376ef45ee0bb21c7395848ff206eafec25/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,989 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 507, 90]]<|/det|> +# nature portfolio + +<|ref|>title<|/ref|><|det|>[[70, 110, 360, 140]]<|/det|> +# Peer Review File + +<|ref|>title<|/ref|><|det|>[[72, 154, 930, 211]]<|/det|> +# Ultrahigh Dynamic Range and Low Noise Figure Programmable Integrated Microwave Photonic Filter + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 783]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[120, 113, 376, 131]]<|/det|> +## Reviewers' comments: + +<|ref|>sub_title<|/ref|><|det|>[[120, 167, 448, 182]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 196, 877, 336]]<|/det|> +This is a good work covering the essences of working principles of integrated microwave photonics. The general readers would find useful information on the concept, implementation, and performance optimization of such approaches for RF functionalities. The authors are well known experts in the field. Their previous work has built up the basis and led to a new contribution to the field reported in this work. The work reported here is sound and complete including both theory and experimental verification and results discussion. It is also clear to see the amount of effort in different forms put in this work. I recommend acceptance for publication. On the other hand, above the reported work, I would like to ask authors to add comments on their options what is the future outlook of microwave photonics? What key technology improvement must be reached for a true advancing? What would be the must- be- microwave photonics applications? + +<|ref|>sub_title<|/ref|><|det|>[[120, 457, 448, 472]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 485, 860, 556]]<|/det|> +A programmable integrated microwave photonic (MwP) filter based on integrated SiN waveguide technology is presented. The circuit comprises a modulation transformer (MT) and a double- injected ring resonator (RR). A high rejection notch filter with high RF gain of 10 dB, low noise figure (NF) of 15 dB, and large spurious free dynamic range (SFDR) of 116 dB/Hz is first demonstrated using a low- biasing technique for the off- chip intensity modulator (IM). + +<|ref|>text<|/ref|><|det|>[[118, 569, 870, 625]]<|/det|> +Using the same set- up, a passband RF filter transfer function can be obtained by properly reconfiguring the circuit. By replacing the external IM with a PM, a SFDR in excess of 120 dB. Hz is also reported at frequencies outside the RF notch filter, using an on- chip linearization technique previously developed by the authors. + +<|ref|>text<|/ref|><|det|>[[118, 639, 872, 710]]<|/det|> +The scheme is conceived for combining the advantages of programmable photonic integration without sacrificing the performance of application- specific circuits. Although, I agree that the work represents a step forward in this sense, I believe that this claim is only partially supported by the results that, in my opinion, seems to provide marginal novelty and/or improvements, as discussed in the following comments. + +<|ref|>sub_title<|/ref|><|det|>[[118, 724, 254, 738]]<|/det|> +## MAIN COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 752, 872, 878]]<|/det|> +The architecture is not entirely novel, as it follows from previous works from the authors (references [40] [42], [59]), the main novelty seemingly being the inclusion of the DI- MRR (previously discussed for instance in [43]) enabling for switching between the notch and bandpass RF filtering functionality (contrary to [40] where the two functions are obtained using two cascaded ring resonators). Noise figure reduction through low- biased IM is also well- known. A preliminary study of the same circuit discussed in the manuscript has recently appeared in [O. Daulay, "Programmable Integrated Microwave Photonic Filter using a Modulation Transformer and a Double- Injection Ring Resonator." 2021 European Conference on Optical Communication (ECOC). IEEE, 2021] that should be quoted in the manuscript, and in reference [45]. + +<|ref|>text<|/ref|><|det|>[[118, 892, 789, 906]]<|/det|> +The proposed passband RF filter guarantees a moderate out- of- band rejection in the RF + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 870, 198]]<|/det|> +transmission response of 15 dB in a limited frequency range between 5 and 15 GHz, as reported for instance in Fig. S6(b) of the supplementary material. More importantly, the same figure shows that the filter response degrades when departing from the optimal condition of Fig. 3(e) and gets very noisy when tuned above about 10 GHz. This should be discussed in the manuscript. Wide tuning range is often regarded as a key feature of MWP filters with respect to electronics- based solutions. However, given the operation at relatively low frequencies, these results should be compared with electronics circuits performing bandpass operation with better performance in terms of rejection and tunability, and operating in the same or even higher range of frequencies. + +<|ref|>text<|/ref|><|det|>[[120, 211, 438, 225]]<|/det|> +A couple of examples are provided below: + +<|ref|>text<|/ref|><|det|>[[118, 238, 876, 281]]<|/det|> +Z. Yang, +D. Psychogiou and +D. Peroulis, "Design and Optimization of Tunable Silicon-Integrated Evanescent-Mode Bandpass Filters," IEEE Trans. Microwave Theory Tech., vol. 66, no. 4, pp. 1790-1803, Apr. 2018. + +<|ref|>text<|/ref|><|det|>[[118, 293, 865, 337]]<|/det|> +J. Chang, et al., "High Performance, Continuously Tunable Microwave Filters Using MEMS Devices With Very Large, Controlled, Out-of-Plane Actuation," in Journal of Microelectromechanical Systems, vol. 27, no. 6, pp. 1135-1147, Dec. 2018, d + +<|ref|>text<|/ref|><|det|>[[118, 350, 868, 421]]<|/det|> +Concerning the performance of the RF notch filter using IM, the authors state that "These results represent the best RF gain, noise figure, and SFDR combination for an MWP notch filter". There seems however to be marginal improvements with respect to the results previously reported from the authors in [36] and [37] (RF gain from 8 to 10, NF from 16 to 15, and the same SFDR of 116 dB. Hz) + +<|ref|>text<|/ref|><|det|>[[118, 433, 872, 462]]<|/det|> +Positive RF gain is achieved using two EDFAs. For applications in which compactness/low- weight is a primary requirement, what would be the RF gain without optical amplification in the system? + +<|ref|>text<|/ref|><|det|>[[118, 475, 875, 518]]<|/det|> +As shown in Fig. 3 and Fig. 4, the extended linearity operation of the notch filter requires replacing the external IM with a PM, which limits the claimed full- reconfigurability of the device. This should be commented in the text. + +<|ref|>sub_title<|/ref|><|det|>[[118, 532, 266, 546]]<|/det|> +## MINOR COMMENTS + +<|ref|>text<|/ref|><|det|>[[118, 560, 877, 616]]<|/det|> +In Figure 3c, the maximum RF gain and minimum NF is achieved for the minimum considered modulator bias voltage of roughly 9 V. What happen for bias values below that first point? Do the two figures of merit degrade or are there other system performance metrics that would be affected at lower values of modulator bias? What is the half- wave voltage of the modulator? + +<|ref|>text<|/ref|><|det|>[[118, 630, 866, 700]]<|/det|> +It seems that in order to switch between scheme "d" and "e" of Fig. S5, a dual- drive Mach- Zehnder intensity modulator should be used with additional RF 90 degree hybrid, as the MT accepts at its input a dual- sideband modulated spectrum for the case of scheme "d" and a single- sideband modulated spectrum for the case of scheme "e". Alternatively, a dual- parallel MZM modulator should be used. This should be discussed in the text + +<|ref|>text<|/ref|><|det|>[[118, 714, 556, 728]]<|/det|> +What are the dimensions of the fabricated photonic chip? + +<|ref|>text<|/ref|><|det|>[[118, 742, 418, 756]]<|/det|> +Few typos around the text (examples): + +<|ref|>text<|/ref|><|det|>[[118, 757, 830, 785]]<|/det|> +On page 2: "...which leading to sideband cancellation..." should be "...which leads to sideband cancellation..." + +<|ref|>text<|/ref|><|det|>[[118, 786, 833, 825]]<|/det|> +In the caption of Fig. S5: "at the otch frequency" should be "at the notch frequency" On page 16 of the Supplementary material "which spatially isolated one sideband", should be "which spatially isolates one sideband" + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 135, 448, 150]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 163, 874, 275]]<|/det|> +In this manuscript, the authors proposed a programmable integrated microwave photonic filter with ultrahigh dynamic range and low noise figure. The principle of the proposed scheme was introduced in the supplementary information, and a proof- of- concept experiment was carried out to demonstrate the capability of the proposed microwave photonic filter to improve the performance of microwave photonic links. However, there still exist many problems, and the proposed integrated microwave photonic filter lacks innovation. Based on the above consideration, I do not think the paper is suitable for publication in Nature Communication in the present form. My comments are listed below. + +<|ref|>text<|/ref|><|det|>[[117, 275, 870, 345]]<|/det|> +1) The modulation transformer (MT) with three ring resonators topology and the double-injection ring resonator (DI-RR) have been proposed and demonstrated in [Ref. 1, Ref. 2]. In my opinion, this paper is only a combination of these two methods, so the innovation of the proposed programmable integrated microwave photonic filter is not enough to support publication in Nature Communication. + +<|ref|>text<|/ref|><|det|>[[117, 345, 870, 387]]<|/det|> +2) In this manuscript, the units of dynamic range are not uniform. "120 dB" is used in the abstract, "120 dB.Hz" is used in the introduction, "116 dB.Hz2/3" and "116 dB.Hz2/3" are used in Fig. 3. + +<|ref|>text<|/ref|><|det|>[[117, 387, 870, 429]]<|/det|> +3) Only the notch filter achieves the high linearity, the SFDRs of other filters are still lower than 120 dB-Hz2/3. Therefore, it is inaccurate to claim that "ultra-high dynamic range of > 120 dB.Hz" is achieved. + +<|ref|>text<|/ref|><|det|>[[117, 429, 870, 471]]<|/det|> +4) Since the linearization is only for notch filters, not for all filters, it is misleading to directly use "ultrahigh dynamic range" in the title. Meanwhile, this paper only achieves the integration of several passive devices, so "integrated microwave photonic filter" is also inappropriate. + +<|ref|>text<|/ref|><|det|>[[117, 471, 874, 499]]<|/det|> +5) From the supplementary information, the tuning range of the bandpass filter is obviously not as wide as the 4-20GHz stated in TABLE I. + +<|ref|>text<|/ref|><|det|>[[117, 500, 874, 541]]<|/det|> +6) Only the normalized response is given in the manuscript, and the non-normalized response also should be given, so that the reader can understand the actual insertion loss of the microwave photonic filter. + +<|ref|>text<|/ref|><|det|>[[117, 541, 852, 598]]<|/det|> +7) The linearization is realized by the widely-used optical sideband phase and amplitude manipulation, which is usually regarded as a narrowband approach. So, within which frequency range the SFDR can reach 120 dB-Hz2/3? The authors should provide the SDFR results at other frequencies. + +<|ref|>text<|/ref|><|det|>[[117, 599, 861, 655]]<|/det|> +8) From the description of the experimental details, the power of the input two-tone signal is 10 dBm, but the power of fundamental and spurious at this input power is not reflected in Fig. 4(d). [Ref. 1] L.-W. Luo, S. Ibrahim, A. Nitkowski et al., "High bandwidth on-chip silicon photonic interleaver," Optics express, vol. 18, no. 22, pp. 23 079-23 087, 2010. + +<|ref|>text<|/ref|><|det|>[[117, 655, 866, 683]]<|/det|> +[Ref. 2] R. Cohen, O. Amrani, and S. Ruschin, "Response shaping with a silicon ring resonator via double injection," Nature Photonics, vol. 12, no. 11, pp. 706-712, 2018. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 93, 884, 168]]<|/det|> +We also thank the reviewers for their valuable comments and their time spent in evaluating this work. In this response, we addressed each comment/question from the reviewers point by point. The reviewer's comments are in Black, our responses are in Blue, and revisions in the manuscript are in Red. + +<|ref|>sub_title<|/ref|><|det|>[[114, 189, 322, 205]]<|/det|> +## Point-to-point response: + +<|ref|>sub_title<|/ref|><|det|>[[113, 235, 217, 251]]<|/det|> +## Reviewer: 1 + +<|ref|>text<|/ref|><|det|>[[112, 262, 885, 470]]<|/det|> +This is a good work covering the essences of working principles of integrated microwave photonics. The general readers would find useful information on the concept, implementation, and performance optimization of such approaches for RF functionalities. The authors are well known experts in the field. Their previous work has built up the basis and led to a new contribution to the field reported in this work. The work reported here is sound and complete including both theory and experimental verification and results discussion. It is also clear to see the amount of effort in different forms put in this work. I recommend acceptance for publication. On the other hand, above the reported work, I would like to ask authors to add comments on their options what is the future outlook of microwave photonics? What key technology improvement must be reached for a true advancing? What would be the must- be- microwave photonics applications? + +<|ref|>sub_title<|/ref|><|det|>[[113, 491, 171, 506]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[112, 508, 885, 641]]<|/det|> +We are grateful for the reviewer's recommendation of publication. In general, the outlook of microwave photonics would be having photonics – electronics co- integration in a single system- on- chip (SoC) or system- in- package (SiP). In particular, the outlook of integrated microwave photonics is having a hybrid- integrated microwave photonic systems containing of a low RIN laser with high output optical power, an ultra- linear modulator with high optical power handling and broad bandwidth, a low loss optical signal processor with mixed architecture (combination of application specific and programmable photonics), and a fast photodetector with high optical power handling and broad bandwidth. + +<|ref|>text<|/ref|><|det|>[[113, 654, 884, 721]]<|/det|> +For the proposed architecture, an improved version of modulation transformer (MT) is desirable. The improved version needs to be able to independently tailor the amplitude and the phase of each element in modulation spectrum (optical carrier and sidebands) simultaneously. Then, a new optical circuit design with improved versatility compared to DI- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 83, 884, 117]]<|/det|> +RR is also desirable with addition of nonlinear optical element, such as stimulated Brillouin scattering (SBS) for improved signal processing resolution. + +<|ref|>sub_title<|/ref|><|det|>[[113, 150, 219, 166]]<|/det|> +## Reviewer: 2 + +<|ref|>text<|/ref|><|det|>[[113, 177, 885, 270]]<|/det|> +A programmable integrated microwave photonic (MWP) filter based on integrated SiN waveguide technology is presented. The circuit comprises a modulation transformer (MT) and a double- injected ring resonator (RR). A high rejection notch filter with high RF gain of \(10 \mathrm{~dB}\) , low noise figure (NF) of \(15 \mathrm{~dB}\) , and large spurious free dynamic range (SFDR) of \(116 \mathrm{~dB / Hz}\) is first demonstrated using a low- biasing technique for the off- chip intensity modulator (IM). + +<|ref|>text<|/ref|><|det|>[[113, 290, 885, 364]]<|/det|> +Using the same set- up, a passband RF filter transfer function can be obtained by properly reconfiguring the circuit. By replacing the external IM with a PM, a SFDR in excess of \(120 \mathrm{~dB / Hz}\) is also reported at frequencies outside the RF notch filter, using an on- chip linearization technique previously developed by the authors. + +<|ref|>text<|/ref|><|det|>[[113, 384, 885, 476]]<|/det|> +The scheme is conceived for combining the advantages of programmable photonic integration without sacrificing the performance of application- specific circuits. Although, I agree that the work represents a step forward in this sense, I believe that this claim is only partially supported by the results that, in my opinion, seems to provide marginal novelty and/or improvements, as discussed in the following comments. + +<|ref|>sub_title<|/ref|><|det|>[[113, 497, 288, 513]]<|/det|> +## MAIN COMMENTS + +<|ref|>text<|/ref|><|det|>[[112, 535, 885, 722]]<|/det|> +1) The architecture is not entirely novel, as it follows from previous works from the authors (references [40] [42], [59]), the main novelty seemingly being the inclusion of the DI-MRR (previously discussed for instance in [43]) enabling for switching between the notch and bandpass RF filtering functionality (contrary to [40] where the two functions are obtained using two cascaded ring resonators). Noise figure reduction through low-biased IM is also well-known. A preliminary study of the same circuit discussed in the manuscript has recently appeared in [O. Daulay, "Programmable Integrated Microwave Photonic Filter using a Modulation Transformer and a Double-Injection Ring Resonator." 2021 European Conference on Optical Communication (ECOC). IEEE, 2021] that should be quoted in the manuscript, and in reference [45]. + +<|ref|>sub_title<|/ref|><|det|>[[113, 744, 172, 759]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[113, 761, 885, 828]]<|/det|> +We disagree with the assessment of this reviewer. Integrated microwave photonics, much like RF electronics, relies on judicious interconnection of known, but reliable components which in turn enables prime performance or functionality that is previously unachievable. This is illustrated by the following examples, recently published in Nature Communications: + +<|ref|>text<|/ref|><|det|>[[140, 842, 884, 875]]<|/det|> +- Silicon Brillouin waveguide: S. Gertler et al., Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon, Nat. Commun. 13(1), 2022. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[140, 82, 885, 168]]<|/det|> +- Dual integrated lasers: S. Jia et al., Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications, Nat. Commun. 13, 1388, 2022. +- Mach-Zehnder interferometer delay lines: V. Duarte et al., Modular coherent photonic-aided payload receiver for communications satellites, Nat. Commun. 10, 1984, 2019. + +<|ref|>text<|/ref|><|det|>[[111, 179, 885, 295]]<|/det|> +Indeed, the inclusion of the DI- RR in our work is very novel in the context of microwave photonics. The interconnection of DI- RR and the versatile modulation transformer (MT) in a low- loss integration platform such as silicon nitride (as opposed to Silicon- on- insulator in Ref [40] in the revised manuscript) can mutually unlock the performance potential and application scope, which has never been attempted before. The combination of all aspects, in this case is a must to achieve the one- of- a- kind combination of performance metrics reported in this work (i.e., programmability, tight integration, and high RF performance). + +<|ref|>text<|/ref|><|det|>[[111, 308, 885, 490]]<|/det|> +Moreover, when compared to the previous work mentioned by this reviewer (Ref [40] in the revised manuscript), our work significantly overcomes the limitation in previous MT design, simultaneously achieving high bandwidth ( \(>40\) GHz over merely \(10\) GHz) and ultra- sharp filtering response (3.5 GHz transition band over \(7\) GHz in previous work) that allows for the demanded access to low RF frequencies. Compared to previously used two cascaded ring resonators, the inclusion of DIRR lead to previously unattainable functionalities in reduced chip area. We also show the first ever complex (phase and amplitude) characterization of DI- RR (Supplementary Information B. Importantly, there was no investigation nor optimization of RF performance in previous works (Ref [40] in the revised manuscript). In fact, our work reports the best RF performance ever reported for a reconfigurable integrated microwave photonic system. + +<|ref|>text<|/ref|><|det|>[[111, 502, 885, 536]]<|/det|> +We agree to add the recent ECOC 2021 manuscript in the list of references (Ref [43] in the revised manuscript). + +<|ref|>text<|/ref|><|det|>[[111, 567, 886, 660]]<|/det|> +2) The proposed passband RF filter guarantees a moderate out-of-band rejection in the RF transmission response of 15 dB in a limited frequency range between 5 and 15 GHz, as reported for instance in Fig. S6(b) of the supplementary material. More importantly, the same figure shows that the filter response degrades when departing from the optimal condition of Fig. 3(e) and gets very noisy when tuned above about 10 GHz. This should be discussed in the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[112, 682, 168, 698]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[111, 711, 885, 909]]<|/det|> +We thank the reviewer for the suggestion. We have included new measurement results of the RF bandpass filter with improved filtering extinction ratio and wideband tunability in the main text. The bandpass filter has \(>20\) dB extinction over 5- 20 GHz frequency tuning. Through improved control of the measurement parameters, we have maintained the integrity of the passband response over the entire tuning range. Moreover, we have demonstrated that it is possible to have both high link gain and low noise figure in the filter passband. The measured metrics of 1.2 dB (positive/amplified) link gain and 21.8 dB noise figure constitute 11.2 dB gain enhancement and 5.2 dB reduction of noise figure when compared to any previously demonstrated work with next best performance metrics (Ref [54] in the revised manuscript), with nearly 3 times wider tuning range and nearly 13 dB improves SFDR when compared to any reported integrated MWP BPF. Therefore, our results represent the best performance metrics ever for integrated MWP BPF and represent a significant step forward in the field. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 83, 825, 116]]<|/det|> +These results have now been included in the main text of the revised manuscript, and an excerpt of the figure has been included below. + +<|ref|>sub_title<|/ref|><|det|>[[112, 131, 196, 146]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[112, 149, 819, 183]]<|/det|> +We have updated Fig. 3(e) - 3(g) of the main text with new and significantly improved experimental data. + +<|ref|>image<|/ref|><|det|>[[122, 196, 875, 355]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[111, 387, 888, 480]]<|/det|> +3) Wide tuning range is often regarded as a key feature of MWP filters with respect to electronics-based solutions. However, given the operation at relatively low frequencies, these results should be compared with electronics circuits performing bandpass operation with better performance in terms of rejection and tunability, and operating in the same or even higher range of frequencies. + +<|ref|>text<|/ref|><|det|>[[112, 501, 455, 518]]<|/det|> +A couple of examples are provided below: + +<|ref|>text<|/ref|><|det|>[[111, 538, 886, 592]]<|/det|> +Z. Yang, +D. Psychogiou and +D. Peroulis, "Design and Optimization of Tunable Silicon-Integrated Evanescent-Mode Bandpass Filters," IEEE Trans. Microwave Theory Tech., vol. 66, no. 4, pp. 1790-1803, Apr. 2018. + +<|ref|>text<|/ref|><|det|>[[111, 612, 888, 667]]<|/det|> +J. Chang, et al., "High Performance, Continuously Tunable Microwave Filters Using MEMS Devices With Very Large, Controlled, Out-of-Plane Actuation," in Journal of Microelectromechanical Systems, vol. 27, no. 6, pp. 1135-1147, Dec. 2018, d + +<|ref|>sub_title<|/ref|><|det|>[[112, 690, 171, 705]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[111, 707, 888, 887]]<|/det|> +We thank the reviewer for the suggestion. We have included the examples cited by the reviewer for comparison in Table I. Indeed, these MEMS- based RF filters can exhibit operation at very high frequencies. The one from Chang et al. exhibits similar tuning range as our filter but with higher insertion loss (-3 dB) and does not report the noise figure. The work of Yang et al. has larger tuning range 20- 40 GHz, but also higher insertion loss (- 1.1 dB). But of course, the glaring difference with our results is that these RF filters are limited in the synthesized response, i.e., only bandpass filter. Our results embodied the real strengths of microwave photonics, where a single circuit can be programmed to exhibit various functions and responses, leading to ultra- versatile front end. The tuning range reported here is not by any means a fundamental limitation and is currently limited only by our experimental apparatus. Previously, 1- 30 GHz tunable MWP filter with similar principle of operation has been demonstrated (Ref [47] in the revised manuscript). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[112, 85, 195, 99]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[112, 101, 809, 118]]<|/det|> +We have updated the Table I in the revised main text with additional comparison data. + +<|ref|>table<|/ref|><|det|>[[127, 177, 870, 525]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[238, 157, 728, 170]]<|/det|> +TABLE I. Performance Comparison of Programmable Microwave Photonic Circuits + +
YearTechnology platformType of devicesNumber of functionsType of functionsTuning range (GHz)Performance enhancement (dB)GainNoise figure (dB)SFDR (dB·Hz2/3)
2017 [10]InPLas., Mod., RR, PD1LPF0-6No-20N/A81.4
2018 [33]SOIMZI mesh20BPF, notchN/ANoN/AN/AN/A
2017 [36]Si3N4RR1Notch0-12NF:LB815.6116
2018 [48]SOIMod., RR, PD1BPF3-10No-39N/A92.4
2018 [49]SiMEMS1BPF20-40No-1.1N/AN/A
2018 [50]SiMEMS1BPF5.5-15No-3N/AN/A
2019 [51]As2S3RR, SBS1Notch0-15NF:LB-1027.196.5
2019 [52]InPLas., Mod., MMI7BPF, notch IFM, RFG8-15NoN/AN/AN/A
2020 [53]SOISBS1BPF4-10No-1756.790.3
2020 [54]Si3N4RR1BPF2-7NF:CS-1027N/A
2021 [39]Si3N4RR1Notch3-10NF:CS331100
2021 [40]SOIMod., MT, RR, PD2Notch, BPF5-25NoN/AN/AN/A
2021 [12]InP+SOILas., Mod., RR, PD2Notch, BPF3-25No-285199.7
2021 [55]Si3N4+As2S3RR, SBS1Notch2-12NoN/AN/A92.2
2021 [56]Si3N4+LiNbO3Mod., RR MT, DI-RR1Downconversion4-20No-1045105
(this work)Si3N4MT, DI-RR6Notch5-20NF:LB1015116
(this work)Si3N4MT, DI-RR1BPF5-20NF:LB1.221.8112
Notch6-18SFDR:Lin.-2635123
+ +<|ref|>table_footnote<|/ref|><|det|>[[127, 526, 850, 572]]<|/det|> +RR: ring resonator, PD: photodetector, Mod: modulator, MMI: multi-mode interference, SBS: stimulated Brillouin scattering, MT: modulation transformer, DI-RR: double-injection ring resonator, LPF: low pass filter, BPF: bandpass filter, IFM: instantaneous frequency measurement, PS: phase shifter, NF: noise figure, LB: low biasing, CS: carrier suppression, SFDR: spurious-free dynamic range, Lin: linearization, MEMS: microelectromechanical systems. + +<|ref|>text<|/ref|><|det|>[[111, 610, 887, 702]]<|/det|> +4) Concerning the performance of the RF notch filter using IM, the authors state that "These results represent the best RF gain, noise figure, and SFDR combination for an MWP notch filter". There seems however to be marginal improvements with respect to the results previously reported from the authors in [36] and [37] (RF gain from 8 to 10, NF from 16 to 15, and the same SFDR of 116 dB.Hz) + +<|ref|>sub_title<|/ref|><|det|>[[111, 723, 169, 740]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[111, 756, 887, 888]]<|/det|> +We stand by our claim that the reported values are the best performance combination for any MWP notch filter. The fact that we achieved these improved values with wider tuning range, and much improved programmability should be acknowledged. We should note that the reported link performance in previous work is achieved using very simple integrated photonic devices with low interconnection loss, i.e., only a ring resonator; in contrast, here we use much more complex integrated photonic circuits, but achieved comparable or even better performance. In addition, these record values for the notch filter are obtained using the same system as the one demonstrating a record performance for bandpass filter. In our experiments we used a low + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 83, 886, 117]]<|/det|> +half- wave voltage modulator, with of 2.2 V. This leads to the improvements in link gain and noise figure of the filter. + +<|ref|>text<|/ref|><|det|>[[118, 130, 886, 184]]<|/det|> +5) Positive RF gain is achieved using two EDFAs. For applications in which compactness/low-weight is a primary requirement, what would be the RF gain without optical amplification in the system? + +<|ref|>sub_title<|/ref|><|det|>[[118, 214, 175, 229]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[117, 231, 887, 380]]<|/det|> +We thank the reviewer for the question. At present, RF performance without amplification is way below our demonstrated performance. For example, non- amplified filter with gain \(= - 28 \mathrm{~dB}\) , NF \(= 51 \mathrm{~dB}\) and SFDR of \(99.7 \mathrm{~dB} \mathrm{~Hz}^{2 / 3}\) has been reported (Ref [12] in the revised manuscript) has been reported. In our case, the unamplified and unoptimized RF gain was - 56.5 dB. However, adding amplifiers to the system need not to add significant weight and footprint. Mini and micro- EDFAs technology has been used in microwave photonics systems. Moreover, recent advances in low- noise amplification using erbium- doped waveguide amplifiers in silicon nitride [1] can offer high performance integrated MWP system with low weight and footprint. + +<|ref|>sub_title<|/ref|><|det|>[[118, 401, 205, 416]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[118, 419, 866, 453]]<|/det|> +[1] Y. Liu et al., A photonic integrated circuit- based erbium- doped amplifier, Science, 376, 1309- 1313, 2022. + +<|ref|>sub_title<|/ref|><|det|>[[118, 475, 200, 491]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[118, 494, 771, 511]]<|/det|> +We have added the statement about amplification in discussion part of main text. + +<|ref|>text<|/ref|><|det|>[[118, 531, 886, 602]]<|/det|> +At current state, the positive RF gain in both IM- based MWP filters is achieved using two external erbium- doped fiber amplifiers (EDFAs). The recent advances in low- noise amplification using erbium- doped waveguide amplifiers in silicon nitride [63] can offer high performance integrated MWP system with low weight and reduced footprint. + +<|ref|>text<|/ref|><|det|>[[118, 630, 886, 685]]<|/det|> +As shown in Fig. 3 and Fig. 4, the extended linearity operation of the notch filter requires replacing the external IM with a PM, which limits the claimed full- reconfigurability of the device. This should be commented in the text. + +<|ref|>sub_title<|/ref|><|det|>[[118, 707, 175, 722]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[118, 725, 886, 836]]<|/det|> +We understand the point of view of the reviewer. Indeed, that the linearization technique we present here thus far works only for PM links. This is why we didn't claim the linearized performance together with the IM- based system (see Table 1, where we separate the results in two lines). What we claim is that the same circuit can carry out both the IM- based and PM- based performance enhancements, therefore highlighting the reconfigurability of the circuit. We have explained this in the revised manuscript as the following. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[112, 123, 195, 138]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[113, 140, 609, 157]]<|/det|> +We have added this limitation in discussion part of main text. + +<|ref|>text<|/ref|><|det|>[[112, 178, 881, 319]]<|/det|> +Our linearization method, on the other hand, is working for PM- based MWP filter where maximum IMD3 suppression is achieved when the optical carrier is partially suppressed (See Supplementary Information D). Due to the limitation in maximum optical amplification in our experimental setup, the measured ultra- high SFDR is still accompanied by relatively low link gain and high NF (Table 1). Achieving the gain, NF, and SFDR advantages simultaneously is feasible in the PM link when higher optical amplification and higher power handling components are used. Because current linearization method only works in PM- based MWP notch filter, a similar strategy development is desirable for low- biased IM- based MWP filters. + +<|ref|>sub_title<|/ref|><|det|>[[112, 380, 292, 396]]<|/det|> +## MINOR COMMENTS + +<|ref|>text<|/ref|><|det|>[[112, 416, 881, 492]]<|/det|> +In Figure 3c, the maximum RF gain and minimum NF is achieved for the minimum considered modulator bias voltage of roughly 9 V. What happen for bias values below that first point? Do the two figures of merit degrade or are there other system performance metrics that would be affected at lower values of modulator bias? What is the half- wave voltage of the modulator? + +<|ref|>sub_title<|/ref|><|det|>[[112, 513, 170, 529]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[112, 531, 880, 604]]<|/det|> +We thank the reviewer for the question. When the bias voltage is tuned to lower voltage ( \(< 9.3\) V), the RF gain degrades and the NF increases. This transition can be seen in the updated Fig. 3(c) and (f) in the main text. The RF half- wave voltage of the IM according to the datasheet is 2.2 V at 1 GHz and 3.5 V at 20 GHz. + +<|ref|>sub_title<|/ref|><|det|>[[112, 626, 195, 642]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[112, 644, 864, 680]]<|/det|> +We have updated the measured RF performance of the notch and bandpass filter in Fig. 3(c) and 3(f) of the revised main text. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[135, 92, 860, 500]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[111, 560, 888, 654]]<|/det|> +It seems that in order to switch between scheme “d” and “e” of Fig. S5, a dual- drive Mach- Zehnder intensity modulator should be used with additional RF 90- degree hybrid, as the MT accepts at its input a dual- sideband modulated spectrum for the case of scheme “d” and a single- sideband modulated spectrum for the case of scheme “e”. Alternatively, a dual- parallel MZM modulator should be used. This should be discussed in the text + +<|ref|>sub_title<|/ref|><|det|>[[112, 676, 171, 692]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[112, 693, 887, 766]]<|/det|> +We thank the reviewer for the positive assessment of our work. The switch between scheme “d” and “e” of Fig. S5 can be happened using an external bandpass filter to completely cancel one sideband in an IM spectrum. The authors added new setup used to switch between scheme “d” and “e” of Fig. S5. + +<|ref|>sub_title<|/ref|><|det|>[[112, 788, 196, 803]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[112, 805, 872, 841]]<|/det|> +We updated with additional setup used to switch between scheme “d” and “e” of Fig. S5 and the description of extended experiment in Supplementary Information C. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[123, 88, 880, 760]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[113, 781, 578, 799]]<|/det|> +What are the dimensions of the fabricated photonic chip? + +<|ref|>sub_title<|/ref|><|det|>[[113, 820, 171, 835]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[113, 838, 872, 891]]<|/det|> +We thank the reviewer for the question. The fabricated photonic chip containing of multiple circuit with dimension of \(8 \times 16 \mathrm{~mm}\) with the proposed circuit occupy area with dimension of \(3.2 \times 6.8 \mathrm{~mm}\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 84, 422, 100]]<|/det|> +Few typos around the text (examples): + +<|ref|>text<|/ref|><|det|>[[110, 120, 878, 213]]<|/det|> +On page 2: "...which leading to sideband cancellation..." should be "...which leads to sideband cancellation..." In the caption of Fig. S5: "at the oth frequency" should be "at the notch frequency" On page 16 of the Supplementary material "which spatially isolated one sideband", should be "which spatially isolates one sideband" + +<|ref|>sub_title<|/ref|><|det|>[[111, 235, 170, 250]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[111, 253, 870, 289]]<|/det|> +We thank the reviewer for the input of our work. We have corrected these errors in our revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[111, 310, 195, 326]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[111, 328, 885, 378]]<|/det|> +We exemplify the intensity modulation- to- phase modulation (IM- PM) conversion by inverting the phase of one sideband by \(\pi\) , which leads to sideband cancellation with 62 dB extinction in direct photodetection (Fig. 2b). + +<|ref|>text<|/ref|><|det|>[[111, 386, 885, 437]]<|/det|> +Cancellation notch filter. MT is used to create asymmetric dual- sideband modulation conversion while DI- RR shows 5 dB- deep notch response. Destructive interference at the notch frequency amplifies the RF notch filter response to 58 dB. + +<|ref|>text<|/ref|><|det|>[[110, 445, 885, 480]]<|/det|> +An IM signal is sent to pass through a spectral de- interleaver in the MT, which spatially isolates one sideband in the spectrum from another sideband and optical carrier. + +<|ref|>sub_title<|/ref|><|det|>[[111, 525, 216, 542]]<|/det|> +## Reviewer: 3 + +<|ref|>text<|/ref|><|det|>[[110, 552, 887, 704]]<|/det|> +In this manuscript, the authors proposed a programmable integrated microwave photonic filter with ultrahigh dynamic range and low noise figure. The principle of the proposed scheme was introduced in the supplementary information, and a proof- of- concept experiment was carried out to demonstrate the capability of the proposed microwave photonic filter to improve the performance of microwave photonic links. However, there still exist many problems, and the proposed integrated microwave photonic filter lacks innovation. Based on the above consideration, I do not think the paper is suitable for publication in Nature Communication in the present form. My comments are listed below. + +<|ref|>text<|/ref|><|det|>[[110, 722, 886, 816]]<|/det|> +1) The modulation transformer (MT) with three ring resonators topology and the double-injection ring resonator (DI-RR) have been proposed and demonstrated in [Ref. 1, Ref. 2]. In my opinion, this paper is only a combination of these two methods, so the innovation of the proposed programmable integrated microwave photonic filter is not enough to support publication in Nature Communication. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[113, 84, 170, 100]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[113, 120, 881, 188]]<|/det|> +We disagree with the assessment of this reviewer. Integrated microwave photonics, much like RF electronics, relies on judicious interconnection of known, but reliable components which in turn enables prime performance or functionality that is previously unachievable. This is illustrated by the following examples, recently published in Nature Communications: + +<|ref|>text<|/ref|><|det|>[[140, 200, 881, 317]]<|/det|> +- Silicon Brillouin waveguide: S. Gertler et al., Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon, Nat. Commun. 13(1), 2022. +- Dual integrated lasers: S. Jia et al., Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications, Nat. Commun. 13, 1388, 2022. +- Mach-Zehnder interferometer delay lines: V. Duarte et al., Modular coherent photonic-aided payload receiver for communications satellites, Nat. Commun. 10, 1984, 2019. + +<|ref|>text<|/ref|><|det|>[[112, 329, 881, 428]]<|/det|> +The [Ref. 1] only discussed about an optical circuit called spectral de- interleaver. Such circuit is only a partial component in a modulation transformer (MT) with additional two channels containing of a tunable attenuator, a phase shifter, a delay line, and a combiner at the output of these two channels. The MT is properly explained in supplementary material. The combination of a spectral de- interleaver and a DIRR is NOT equal to the combination of a MT and a DI- RR proposed in this article. + +<|ref|>text<|/ref|><|det|>[[112, 441, 881, 543]]<|/det|> +The inclusion of the DI- RR in our work is very novel in the context of microwave photonics. The interconnection of DI- RR and the versatile modulation transformer (MT) in a low- loss integration platform such as silicon nitride (as opposed to Silicon- on- insulator in Ref [40] in the revised manuscript) has never been attempted before. The combination of all aspects, in this case is a must to achieve the one- of- a- kind combination of performance metrics reported in this work (i.e., programmability, tight integration, and high RF performance). + +<|ref|>text<|/ref|><|det|>[[112, 591, 880, 648]]<|/det|> +2) In this manuscript, the units of dynamic range are not uniform. "120 dB" is used in the abstract, "120 dB.Hz" is used in the introduction, "116 dB.Hz2/3" and "116 dB.Hz2/3" are used in Fig. 3. + +<|ref|>sub_title<|/ref|><|det|>[[112, 669, 171, 685]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[112, 687, 870, 723]]<|/det|> +We thank the reviewer for the critical feedback. We have used uniform expression of dB.Hz2/3 throughout our manuscript. + +<|ref|>text<|/ref|><|det|>[[112, 742, 881, 797]]<|/det|> +3) Only the notch filter achieves the high linearity, the SFDRs of other filters are still lower than 120 dB.Hz2/3. Therefore, it is inaccurate to claim that "ultra-high dynamic range of > 120 dB.Hz" is achieved. + +<|ref|>sub_title<|/ref|><|det|>[[112, 820, 171, 835]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[112, 837, 881, 910]]<|/det|> +We aim to clarify that the SFDR of \(112 - 116 \mathrm{dB.Hz}^{2 / 3}\) achieved for RF bandpass and RF notch filters in this work is still very high when compared to previous results. The only RF notch filter with SFDR of \(>100 \mathrm{dB.Hz}^{2 / 3}\) was reported in Ref [36] in the revised manuscript, which is a work led by the senior author of our paper. This comparison rings even more true when + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 84, 886, 157]]<|/det|> +considering RF bandpass filter, with the highest previously reported SFDR of nearly 13 dB lower than our results (99.7 dB. \(\mathrm{Hz}^{2 / 3}\) ) in Ref [12] in the revised manuscript. The ultra- high dynamic range of \(>120 \mathrm{dB}.\mathrm{Hz}^{2 / 3}\) shown in this article is a proof concept of on- chip linearization and simultaneous RF notch filter using a single photonic chip. + +<|ref|>text<|/ref|><|det|>[[112, 177, 668, 194]]<|/det|> +To avoid confusion, we have revised the abstract and introduction as + +<|ref|>sub_title<|/ref|><|det|>[[112, 217, 183, 231]]<|/det|> +## Abstract + +<|ref|>text<|/ref|><|det|>[[112, 255, 876, 306]]<|/det|> +Here, we report, for the first time, a multi- functional photonic integrated circuit that enables programmable filtering functions with record- high performance. We demonstrate a switchable filter function with record- low noise figure and a RF notch filter with ultra- high dynamic range. + +<|ref|>text<|/ref|><|det|>[[112, 321, 140, 333]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[112, 354, 214, 369]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[111, 392, 886, 512]]<|/det|> +In this work, we demonstrate a programmable integrated MWP circuit with a unique combination of a versatile MT device and a DI- RR, realized in a low- loss silicon nitride platform. With this circuit, we show for the first time, an array of RF filters in three different scenarios simultaneously with record- low noise figure for RF notch and RF bandpass filter, achieved using low- biasing technique [36, 37] in an intensity modulator (IM)- based system, and ultra- high dynamic range for RF notch filter, achieved using on- chip linearization in a phase modulator (PM)- based system. + +<|ref|>text<|/ref|><|det|>[[112, 530, 140, 541]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[112, 562, 887, 616]]<|/det|> +4) Since the linearization is only for notch filters, not for all filters, it is misleading to directly use "ultrahigh dynamic range" in the title. Meanwhile, this paper only achieves the integration of several passive devices, so "integrated microwave photonic filter" is also inappropriate. + +<|ref|>sub_title<|/ref|><|det|>[[112, 639, 170, 654]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[112, 656, 886, 737]]<|/det|> +We believe that all the dynamic range values reported throughout this paper, using both the IM and PM- based enhancement fall in the category of high dynamic range. To put it in the context, these values are more than an order of magnitude higher than previously reported (except for Ref [36] in the revised manuscript, which was a work led by the senior author of this paper). The linearized link indeed shows ultra- high dynamic range with SFDR of \(123 \mathrm{dB}.\mathrm{Hz}^{4 / 5}\) . + +<|ref|>text<|/ref|><|det|>[[111, 752, 886, 900]]<|/det|> +Regarding the terminology integrated microwave photonic filter, we never claimed that the device is fully integrated, where the lasers, modulators, detectors, and signal processor are either hybrid/heterogeneously integrated. Nevertheless, we believe, our system is still an integrated microwave photonic system by definition, see for example integrated microwave photonic papers (Ref [6] and Ref [7] in the revised manuscript). Indeed, that it is important to achieve high performance in all integrated system. But in reality, the performance of such systems is much poorer when compared to our results (see Ref [10] and Ref [12] in the revised manuscript as examples). The highest gain, noise figure and SFDR are \(39 \mathrm{dB}\) , \(36 \mathrm{dB}\) , and \(16 \mathrm{dB}\) lower, respectively, than our reported results here. So, our work here serves as evidence that + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[111, 83, 880, 133]]<|/det|> +a partially integrated MWP system can achieve high performance and address a unique area/metric that has never been demonstrated before, and therefore constitute a significant leap in the field. + +<|ref|>text<|/ref|><|det|>[[110, 177, 857, 211]]<|/det|> +5) From the supplementary information, the tuning range of the bandpass filter is obviously not as wide as the \(4 - 20GHz\) stated in TABLE I. + +<|ref|>sub_title<|/ref|><|det|>[[111, 225, 171, 241]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[111, 243, 875, 293]]<|/det|> +We thank the reviewer for the critical feedbacks to the tuning range of the bandpass filter. We added new experiment results covering the tuning range of the bandpass filter and updated the Table I in main text. + +<|ref|>sub_title<|/ref|><|det|>[[111, 308, 195, 324]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[110, 336, 872, 370]]<|/det|> +We have updated the measured performance of the bandpass filter in Fig. 3(e)- (g) and Table I of the revised main text. + +<|ref|>image<|/ref|><|det|>[[130, 392, 860, 799]]<|/det|> + +<--- Page Split ---> +<|ref|>table<|/ref|><|det|>[[128, 111, 870, 460]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[238, 91, 728, 104]]<|/det|> +TABLE I. Performance Comparison of Programmable Microwave Photonic Circuits + +
YearTechnology platformType of devicesNumber of functionsType of functionsTuning range (GHz)Performance enhancementGain (dB)Noise figure (dB)SFDR (dB·Hz2/3)
2017 [10]InPLas., Mod., RR, PD1LPF0-6No-20N/A81.4
2018 [33]SOIMZI mesh20BPF, notchN/ANoN/AN/AN/A
2017 [36]Si3N4RR1Notch0-12NF:LB815.6116
2018 [48]SOIMod., RR, PD1BPF3-10No-39N/A92.4
2018 [49]SiMEMS1BPF20-40No-1.1N/AN/A
2018 [50]SiMEMS1BPF5.5-15No-3N/AN/A
2019 [51]As2S3RR, SBS1Notch0-15NF:LB-1027.196.5
2019 [52]InPLas., Mod., MMI7BPF, notch8-15NoN/AN/AN/A
2020 [53]SOISBS1IFM, RFG
2020 [54]Si3N4RR1BPF4-10No-1756.790.3
2021 [39]Si3N4RR1BPF2-7NF:CS-1027N/A
2021 [40]SOIMod., MT, RR, PD2Notch, BPF3-10NF:CS331100
2021 [12]InP+SOILas., Mod., RR, PD2Notch, BPF5-25NoN/AN/AN/A
2021 [55]Si3N4+As2S3RR, SBS1Notch3-25No-285199.7
2021 [56]Si3N4+LiNbO3 (this work)Mod., RR MT, DI-RR1Downconversion2-12NoN/AN/A92.2
6Notch4-20No-1045105
1BPF5-20NF:LB1015116
1Notch6-18SFDR.Lin.1.221.8112
1Notch6-18SFDR.Lin.-2635123
+ +<|ref|>table_footnote<|/ref|><|det|>[[130, 460, 850, 506]]<|/det|> +RR: ring resonator, PD: photodetector, Mod: modulator, MMI: multi-mode interference, SBS: stimulated Brillouin scattering, MT: modulation transformer, DI-RR: double-injection ring resonator, LPF: low pass filter, BPF: bandpass filter, IFM: instantaneous frequency measurement, PS: phase shifter, NF: noise figure, LB: low biasing, CS: carrier suppression, SFDR: spurious-free dynamic range, Lin: linearization, MEMS: microelectromechanical systems. + +<|ref|>text<|/ref|><|det|>[[115, 527, 884, 577]]<|/det|> +6) Only the normalized response is given in the manuscript, and the non-normalized response also should be given, so that the reader can understand the actual insertion loss of the microwave photonic filter. + +<|ref|>sub_title<|/ref|><|det|>[[115, 592, 175, 607]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 609, 884, 666]]<|/det|> +We thank the reviewer for the critical feedbacks to the manuscript. We added the non- normalized RF response of both RF notch and RF bandpass filter in Fig.3(b) and 3(e) of the main text. + +<|ref|>text<|/ref|><|det|>[[115, 684, 884, 758]]<|/det|> +7) The linearization is realized by the widely used optical sideband phase and amplitude manipulation, which is usually regarded as a narrowband approach. So, within which frequency range the SFDR can reach \(120 \mathrm{dB} \cdot \mathrm{Hz}2 / 3\) ? The authors should provide the SFDR results at other frequencies. + +<|ref|>sub_title<|/ref|><|det|>[[115, 780, 175, 795]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 797, 884, 870]]<|/det|> +We thank the reviewer for the critical feedbacks to the manuscript. We have added extensive experiment results of SFDR after linearization at other frequencies in Supplementary Information F. The ultra-high SFDR \(>120 \mathrm{dB} \cdot \mathrm{Hz}^{2 / 3}\) is maintained at 8, 9, 10, and 16 GHz, showing the broadband nature of our results. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[112, 85, 195, 100]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[112, 103, 866, 139]]<|/det|> +We have updated the measured SFDR post linearization at different frequencies in supplementary information F. + +<|ref|>text<|/ref|><|det|>[[111, 158, 887, 265]]<|/det|> +To further characterize the performance of our proposed linearized RF notch filter, we extended our measurements of IMD3 suppression and SFDR when the two- tone test frequency and the notch filter frequency was tuned separately. We first fixed the notch frequency at \(12\mathrm{GHz}\) and performed two tone measurements at \(8\mathrm{GHz}\) , \(9\mathrm{GHz}\) , \(10\mathrm{GHz}\) , and \(16\mathrm{GHz}\) . The results of the IMD3 suppression are shown in Fig. S7. It is clear that the IMD3 terms are greatly suppressed for more than \(28\mathrm{dB}\) in all of these two- tone frequencies. + +<|ref|>text<|/ref|><|det|>[[111, 273, 887, 327]]<|/det|> +The results of the SFDR at different frequencies are shown in Fig. S8. In all the cases, SFDR of more than \(122\mathrm{dB} \cdot \mathrm{Hz}^{2 / 3}\) are observed with improvements around \(20\mathrm{dB}\) compared with nonlinearized states. + +<|ref|>image<|/ref|><|det|>[[156, 340, 833, 767]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[110, 795, 886, 846]]<|/det|> +
Fig. S7. Third-order intermodulation distortion (IMD3) suppression at various two-tone frequencies with notch response at \(12\mathrm{GHz}\) . (a) two-tone signal at \(8\mathrm{GHz}\) (b) two-tone signal at \(9\mathrm{GHz}\) (c) two-tone signal at \(10\mathrm{GHz}\) (d) two-tone signal at \(16\mathrm{GHz}\) .
+ +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[156, 88, 852, 515]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[110, 547, 881, 618]]<|/det|> +
Fig. S8. Spurious-free dynamic range (SFDR) measurements at various two-tone frequencies with notch response at 12 GHz. (a) SFDR at 8 GHz (b) SFDR at 9 GHz (c) SFDR at 10 GHz (d) SFDR at 16 GHz. IMD3: third-order intermodulation distortion, IMD5: fifth-order intermodulation distortion.
+ +<|ref|>text<|/ref|><|det|>[[110, 645, 881, 682]]<|/det|> +8) From the description of the experimental details, the power of the input two-tone signal is 10 dBm, but the power of fundamental and spurious at this input power is not reflected in Fig. 4(d). + +<|ref|>sub_title<|/ref|><|det|>[[111, 704, 170, 720]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[110, 722, 878, 758]]<|/det|> +We thank the reviewer for the feedback about two-tone signal. The input RF power of two-tone signal to the PM is 8 dBm. We updated the number in main text. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 85, 357, 101]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[120, 125, 448, 139]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[120, 153, 714, 167]]<|/det|> +My comments have been addressed. I recommend acceptance for publication. + +<|ref|>sub_title<|/ref|><|det|>[[120, 217, 448, 231]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 245, 872, 444]]<|/det|> +The authors did good efforts in replying to my comments. As a personal opinion, I believe that the performance of the bandpass functionality for the proposed reconfigurable microwave photonics (MWP) filter is below that of state- of- the- art electronics components. A fair comparison with the MEMS- based devices discussed in refs. [49] and [50] of the revised manuscript should account that the RF loss of 1 and 3 dB, respectively, are obtained in fully passive devices, whereas two power- consuming erbium- doped fiber amplifiers are required for positive RF gain in the proposed MWP approach. At the same time, the MEMS- based filters typically can provide larger rejection, faster roll- off and improved passband flatness (which are parameters that are not considered in TABLE I). The claimed advantage of reconfigurability can be handled in electronics- domain with digitally controlled filter banks and switches, although I agree that this is not an optimal solution. There is also still a concern about the moderate improvement in terms of RF gain and noise figure (NF) (of 2 and 1 dB, respectively) compared with authors' previous works (see refs [36] and [37]) since, as stated by the authors in the answer to comment 4, the improvement seems to be partially ascribed to the use of an external modulator with lower half- wave voltage. + +<|ref|>text<|/ref|><|det|>[[119, 457, 856, 512]]<|/det|> +However, in view of the improved quality of the manuscript with new and more accurate measurement results, and in recognizing the advancement in the field brought by the proposed approach in terms of programmable functionality, the paper can be considered for publication in Nature Communications. Below my new comments: + +<|ref|>text<|/ref|><|det|>[[118, 526, 875, 681]]<|/det|> +1) In the answer to Comment 3, the authors state that MWP filter tuning in the 1-30 GHz range has been achieved in a previous circuit with similar operation principle. However, the MWP filter discussed in the quoted reference [47] of the revised manuscript is based on stimulated Brillouin scattering (SBS) effect, for which the highest operating frequency is not limited by the free-spectral range (FSR) of microring-resonator (MRRs)-based filtering elements, as in the proposed approach. On the other hand, as discussed in the supplementary material of the original manuscript, the lowest operating frequency of this scheme is 5 GHz, due to the leakage at low modulation frequencies between the two output ports of the spectral de-interleaver in the modulation transformer (MT). This makes the operating frequency range 15 GHz (5-20 GHz, as reported in Table I), and the two statements on page 3 of the revised manuscript claiming that the filter is tunable over 20 GHz should be corrected accordingly. + +<|ref|>text<|/ref|><|det|>[[118, 694, 850, 723]]<|/det|> +2) At which frequency is measured the RF gain of the MWP notch filter in Fig. 3c? How does the maximum RF gain scale over the 5-20 GHz filter operating range? + +<|ref|>text<|/ref|><|det|>[[118, 736, 872, 792]]<|/det|> +3) In answering my comment about the half-wave voltage of the intensity modulator, the authors indicated the nominal values of 2.2 V and 3.5 V at 1 GHz and 20 GHz, respectively, but missed to include this information in the revised manuscript. Please, add the details of the half-wave voltage for the employed modulator within the main text. + +<|ref|>text<|/ref|><|det|>[[118, 806, 860, 890]]<|/det|> +4) Few typos around: (Abstract): We demonstrate a switchable filter functions... (Page 5) Similar record-high SFDR also observed in different frequencies (see Supplementary Information F). (Methods Section) Because typical top cladding thickness cannot achieved only by LPCVD TEOS... (Methods Section) A thicker layers can be achieved... + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 448, 97]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 111, 878, 167]]<|/det|> +I appreciate the authors taking the effort in answering the questions raised by both the reviewers i n previous report. They provided new information to highlight the advantages of their work, which makes it more solid. However, the answers still cannot convince me to recommend this manuscript for publication in Nature Communications: + +<|ref|>text<|/ref|><|det|>[[117, 168, 870, 375]]<|/det|> +1) Although the authors give more words to explain their innovation, but it still cannot change the fact that the entire chip is very simple, and the ideas of modulation transformation and noise figure reduction, linearity improvement are reported before. I read the References the authors used to reply the first question from Reviewer 2, from my opinion, the chips reported in these References, e.g., the SBS waveguide, laser chip and the satellite payload chip, are novel in terms of the chip itself or its application systems, which clearly shows the levels of the chip and the system demonstration. However, I still cannot see such distinguished novelty from this paper. +2) The comparison with the electrical filters is not reasonable. Although NF and SFDR are not measured in Ref. [49] and Ref. [50], I believe they have better performances than the photonic filter, since they do not involve EO & OE conversions and active amplification. The advantages of the proposed filter are the relatively higher gain and reconfigurability. However, the gain is realized by two EDFAs which will sacrifice the analog performance. For the reconfigurability, I cannot clearly see (or find from the manuscript) the necessity of such a filter. Therefore, the significance of the work and the impact on the researchers in both MWP and microwave communities are not clear. + +<|ref|>text<|/ref|><|det|>[[117, 376, 860, 416]]<|/det|> +3) From the Method, the power of the input two-tone RF signal is 8 dBm. According to Fig. 4(c), the power of the fundamental components are nearly -30 dBm, which cannot agree with the -26 dB claimed in Table I and the results shown in Fig. 4d. Please check it. + +<|ref|>text<|/ref|><|det|>[[118, 417, 864, 458]]<|/det|> +4) Although SFDRs at different frequencies are measured, it would be more convincing to directly input a wideband RF signal (for example, a QAM signal) to demonstrate its high dynamic range after filtering. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 83, 872, 118]]<|/det|> +## Ultrahigh Dynamic Range and Low Noise Figure Programmable Integrated Microwave Photonic Filter: \(2^{\mathrm{nd}}\) Response to Reviewers' comments + +<|ref|>text<|/ref|><|det|>[[116, 127, 293, 143]]<|/det|> +NCOMMS- 22- 10585 + +<|ref|>text<|/ref|><|det|>[[116, 154, 884, 229]]<|/det|> +We thank the reviewers for their valuable comments and their time spent in evaluating this work. In this response, we addressed each comment/question from the reviewers point by point. The reviewer's comments are in Black, our responses are in Blue, and revisions in the manuscript are in Red + +<|ref|>sub_title<|/ref|><|det|>[[116, 250, 325, 266]]<|/det|> +## Point-to-point response: + +<|ref|>sub_title<|/ref|><|det|>[[116, 269, 220, 285]]<|/det|> +## Reviewer: 1 + +<|ref|>text<|/ref|><|det|>[[116, 296, 743, 313]]<|/det|> +My comments have been addressed. I recommend acceptance for publication. + +<|ref|>sub_title<|/ref|><|det|>[[116, 335, 176, 351]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[116, 353, 630, 369]]<|/det|> +We thank the reviewer for the positive assessment of our paper. + +<|ref|>sub_title<|/ref|><|det|>[[116, 390, 221, 406]]<|/det|> +## Reviewer: 2 + +<|ref|>text<|/ref|><|det|>[[114, 417, 884, 700]]<|/det|> +The authors did good efforts in replying to my comments. As a personal opinion, I believe that the performance of the bandpass functionality for the proposed reconfigurable microwave photonics (MWP) filter is below that of state- of- the- art electronics components. A fair comparison with the MEMS- based devices discussed in refs. [49] and [50] of the revised manuscript should account that the RF loss of 1 and 3 dB, respectively, are obtained in fully passive devices, whereas two power- consuming erbium- doped fiber amplifiers are required for positive RF gain in the proposed MWP approach. At the same time, the MEMS- based filters typically can provide larger rejection, faster roll- off and improved passband flatness (which are parameters that are not considered in TABLE I). The claimed advantage of reconfigurability can be handled in electronics- domain with digitally controlled filter banks and switches, although I agree that this is not an optimal solution. There is also still a concern about the moderate improvement in terms of RF gain and noise figure (NF) (of 2 and 1 dB, respectively) compared with authors' previous works (see refs [36] and [37]) since, as stated by the authors in the answer to comment 4, the improvement seems to be partially ascribed to the use of an external modulator with lower half- wave voltage. + +<|ref|>text<|/ref|><|det|>[[116, 720, 882, 792]]<|/det|> +However, in view of the improved quality of the manuscript with new and more accurate measurement results, and in recognizing the advancement in the field brought by the proposed approach in terms of programmable functionality, the paper can be considered for publication in Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[116, 815, 175, 831]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[116, 833, 880, 869]]<|/det|> +We thank the reviewer for the positive recommendation and the highly valuable perspectives given for our paper. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 882, 232]]<|/det|> +We agree with the reviewer on the fact that the MEMS- based filter can exhibit a lower noise figure (determined by the passive circuit insertion loss) while the MWP filters can be considered 'active', because the system requires lasers, electro- optic modulators, optical amplifiers, and photodetectors that actively consumes power. These optical components usually contribute to more noise, higher losses, and thus higher noise figure to the system. However, there are number of reports about active bandpass filter that show comparable performance with our work because of the usage of active- RC [1], active capacitance [2] or active inductor [3- 5] in the circuit. + +<|ref|>text<|/ref|><|det|>[[115, 251, 882, 365]]<|/det|> +Despite the \(>10\mathrm{dB}\) noise figures of reported MWP filters, it is fundamentally feasible to achieve single- digit dB level with lower- RIN lasers, high- efficiency modulators and photodetectors, and low- loss photonic interconnects. Thus, reducing the noise figure of MWP filters will be realized based on the advances and innovation of these optical components, which has been continuously driven by the need for high- performance devices not only for optical communications but also for optical signal processing and computing. + +<|ref|>sub_title<|/ref|><|det|>[[116, 384, 212, 400]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[115, 420, 881, 476]]<|/det|> +[1] B. Wu et al., A 40 nm CMOS Derivative- Free IF Active- RC BPF With Programmable Bandwidth and Center Frequency Achieving Over 30 dBm IIP3, IEEE Journal of Solid- State Circuits, 50(8), 1772- 1784, 2015. + +<|ref|>text<|/ref|><|det|>[[115, 496, 881, 533]]<|/det|> +[2] D. Colaiuda et al., A Second Order 1.8- 1.9 GHz Tunable Active Band- Pass Filter with Improved Noise Performance, Electronics, 11(2781), 1- 10, 2022. + +<|ref|>text<|/ref|><|det|>[[115, 552, 881, 590]]<|/det|> +[3] Z. Gao et al., A Fully Integrated CMOS Active Bandpass Filter for Multiband RF Front- Ends, IEEE Transactions on Circuits and Systems II: Express Briefs, 55(8), 718- 722, 2008. + +<|ref|>text<|/ref|><|det|>[[115, 609, 881, 646]]<|/det|> +[4] V. Kumar et al., A 2.5 GHz Low Power, High- Q, Reliable Design of Active Bandpass Filter, IEEE Transactions on Device and Materials Reliability, 17(1), 229- 244, 2017. + +<|ref|>text<|/ref|><|det|>[[115, 666, 881, 702]]<|/det|> +[5] R. Mehra et al., Reliable and Q- Enhanced Floating Active Inductors and Their Application in RF Bandpass Filter, IEEE Access, 6, 48181- 48194, 2018. + +<|ref|>text<|/ref|><|det|>[[121, 723, 330, 739]]<|/det|> +Below my new comments: + +<|ref|>text<|/ref|><|det|>[[115, 759, 882, 910]]<|/det|> +1) In the answer to Comment 3, the authors state that MWP filter tuning in the 1-30 GHz range has been achieved in a previous circuit with similar operation principle. However, the MWP filter discussed in the quoted reference [47] of the revised manuscript is based on stimulated Brillouin scattering (SBS) effect, for which the highest operating frequency is not limited by the free-spectral range (FSR) of microring-resonator (MRRs)-based filtering elements, as in the proposed approach. On the other hand, as discussed in the supplementary material of the original manuscript, the lowest operating frequency of this scheme is 5 GHz, due to the leakage at low modulation frequencies between the two output ports of the spectral de-interleaver in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 881, 137]]<|/det|> +the modulation transformer (MT). This makes the operating frequency range 15 GHz (5- 20 GHz, as reported in Table I), and the two statements on page 3 of the revised manuscript claiming that the filter is tunable over 20 GHz should be corrected accordingly. + +<|ref|>sub_title<|/ref|><|det|>[[115, 159, 176, 174]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 177, 880, 210]]<|/det|> +We agree with the comments of the reviewer and have corrected the statement in page 3 to 15 GHz. + +<|ref|>sub_title<|/ref|><|det|>[[115, 225, 199, 242]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[115, 254, 880, 289]]<|/det|> +The RF notch filter central frequency can be tuned from 5 to 20 GHz (Fig. 3b) with maximum RF gain of more than 0 dB over the frequency range (see Supplementary Information D). + +<|ref|>text<|/ref|><|det|>[[115, 301, 881, 369]]<|/det|> +RF bandpass filter with 20 dB rejection, with up to 15 GHz tuning range (from 5 GHz to 20 GHz) (Fig. 3e), limited by the roll-off and the dispersion of the spectral de- interleaver, notably at the transition band (see Supplementary Information A). This tuning range can be feasibly increased using improved design of (de)- interleaver with faster roll- off and a larger FSR. + +<|ref|>text<|/ref|><|det|>[[115, 400, 880, 436]]<|/det|> +2) At which frequency is measured the RF gain of the MWP notch filter in Fig. 3c? How does the maximum RF gain scale over the 5-20 GHz filter operating range? + +<|ref|>sub_title<|/ref|><|det|>[[115, 457, 176, 474]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 486, 880, 537]]<|/det|> +The RF gain of MWP notch filter in Fig. 3c is measured at frequency of 1 GHz. The RF link gain stays above 0 dB over the entire frequency range of 5- 20 GHz. Below we list the RF gain at various frequencies: + +<|ref|>table<|/ref|><|det|>[[115, 549, 880, 727]]<|/det|> + +
Freq. (GHz)RF gain (dB)Freq. (GHz)RF gain (dB)Freq.
(GHz)
RF gain (dB)Freq.
(GHz)
Freq.
(dB)
54.2392.60132.71171.61
64.01102.39142.05181.19
73.62112.16152.60191.14
82.87122.72162.11201.71
+ +<|ref|>sub_title<|/ref|><|det|>[[115, 817, 199, 833]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[115, 845, 880, 881]]<|/det|> +We have added the list and graph of the maximum RF gain of MWP notch filter over the tuning range (5- 20 GHz) in the Supplementary Information D as follows, + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 84, 208, 100]]<|/det|> +## Main text: + +<|ref|>text<|/ref|><|det|>[[115, 120, 881, 158]]<|/det|> +The RF notch filter central frequency can be tuned from 5 to \(20\mathrm{GHz}\) (Fig. 3b) with maximum RF gain of more than \(0\mathrm{dB}\) over the frequency range (see Supplementary Information D). + +<|ref|>sub_title<|/ref|><|det|>[[115, 196, 367, 213]]<|/det|> +## Supplementary Information: + +<|ref|>text<|/ref|><|det|>[[115, 232, 881, 269]]<|/det|> +The maximum RF gain of the RF notch filter stays above \(0\mathrm{dB}\) over the entire frequency range of \(5 - 20\mathrm{GHz}\) . Fig. S6 shows the RF gain at various frequencies. + +<|ref|>table<|/ref|><|det|>[[243, 309, 760, 411]]<|/det|> +<|ref|>table_caption<|/ref|><|det|>[[182, 286, 803, 302]]<|/det|> +TABLE S1. The maximum RF Gain of the RF notch filter over the entire frequency range + +
Freq. (GHz)RF Gain (dB)Freq. (GHz)RF Gain (dB)Freq.RF Gain (GHz)Freq.RF Gain (dB)
54.2392.60132.71171.61
64.01102.39142.05181.19
73.62112.16152.60191.14
82.87122.72162.11201.71
+ +<|ref|>image<|/ref|><|det|>[[270, 447, 730, 664]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 684, 881, 718]]<|/det|> +
Fig. S6. The RF gain of the RF notch filter. Plot of the maximum RF gain of the RF notch filter over the entire frequency range.
+ +<|ref|>text<|/ref|><|det|>[[115, 804, 883, 879]]<|/det|> +3) In answering my comment about the half-wave voltage of the intensity modulator, the authors indicated the nominal values of \(2.2\mathrm{V}\) and \(3.5\mathrm{V}\) at \(1\mathrm{GHz}\) and \(20\mathrm{GHz}\) , respectively, but missed to include this information in the revised manuscript. Please, add the details of the half-wave voltage for the employed modulator within the main text. + +<|ref|>title<|/ref|><|det|>[[115, 898, 175, 914]]<|/det|> +# Reply: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 82, 822, 100]]<|/det|> +We have added the modulator half- wave voltage information in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 115, 199, 131]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[115, 151, 773, 170]]<|/det|> +(Thorlabs, LNLVL- IM- Z 40 GHz, \(V_{\pi ,RF}\) of 2.2 V at 1 GHz and 3.5 V at 20 GHz) + +<|ref|>text<|/ref|><|det|>[[116, 201, 292, 218]]<|/det|> +4) Few typos around: + +<|ref|>text<|/ref|><|det|>[[115, 238, 593, 256]]<|/det|> +(Abstract): We demonstrate a switchable filter functions ... + +<|ref|>text<|/ref|><|det|>[[115, 276, 881, 312]]<|/det|> +(Page 5) Similar record- high SFDR also observed in different frequencies (see Supplementary Information F). + +<|ref|>text<|/ref|><|det|>[[115, 332, 881, 368]]<|/det|> +(Methods Section) Because typical top cladding thickness cannot achieved only by LPCVD TEOS... + +<|ref|>text<|/ref|><|det|>[[115, 388, 550, 406]]<|/det|> +(Methods Section) A thicker layers can be achieved... + +<|ref|>sub_title<|/ref|><|det|>[[115, 427, 176, 444]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 446, 881, 480]]<|/det|> +We thank the reviewer for careful reading of our manuscript, we have revised the manuscript accordingly. + +<|ref|>sub_title<|/ref|><|det|>[[115, 494, 199, 510]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[115, 530, 601, 548]]<|/det|> +(Abstract) We demonstrate reconfigurable filter functions... + +<|ref|>text<|/ref|><|det|>[[115, 560, 777, 578]]<|/det|> +(Page 5) Similar record- high SFDR also can be observed in different frequencies. + +<|ref|>text<|/ref|><|det|>[[115, 590, 881, 625]]<|/det|> +(Methods Section) Because typical top cladding thickness cannot be achieved only by LPCVD TEOS... + +<|ref|>text<|/ref|><|det|>[[115, 638, 540, 656]]<|/det|> +(Methods Section) Thicker layers can be achieved... + +<|ref|>sub_title<|/ref|><|det|>[[115, 792, 222, 809]]<|/det|> +## Reviewer: 3 + +<|ref|>text<|/ref|><|det|>[[115, 820, 881, 894]]<|/det|> +I appreciate the authors taking the effort in answering the questions raised by both the review ers in previous report. They provided new information to highlight the advantages of their wor k, which makes it more solid. However, the answers still cannot convince me to recommend this manuscript for publication in Nature Communications: + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 83, 175, 99]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 101, 881, 137]]<|/det|> +We thank the reviewer for appreciating our work and efforts. In what follows, we will try to address the raised concerns and add suggested clarifications. + +<|ref|>text<|/ref|><|det|>[[115, 156, 884, 289]]<|/det|> +1) Although the authors give more words to explain their innovation, but it still cannot change the fact that the entire chip is very simple, and the ideas of modulation transformation and noise figure reduction, linearity improvement are reported before. I read the References the authors used to reply the first question from Reviewer 2, from my opinion, the chips reported in these References, e.g., the SBS waveguide, laser chip and the satellite payload chip, are novel in terms of the chip itself or its application systems, which clearly shows the levels of the chip and the system demonstration. However, I still cannot see such distinguished novelty from this paper. + +<|ref|>sub_title<|/ref|><|det|>[[115, 310, 175, 325]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 328, 881, 401]]<|/det|> +We respectfully disagree that the simplicity of the circuit should be interpreted as lack of novelty in our work. On contrary, we believe that we have demonstrated that such high performance and programmability is indeed accessible through relatively simple chip topology which is previously unachievable. + +<|ref|>text<|/ref|><|det|>[[115, 420, 881, 533]]<|/det|> +We agree that individually, modulation transformation, noise figure reduction, and linearization have been achieved. This is precisely the key breakthrough in our work, that we simultaneously achieve these features in our relatively simple photonic chip that has never been demonstrated before. This function and performance novelty is equally important as the device innovation or novel applications. In our work, the novelty lies in how these concepts and devices are used to unlock previously unachievable system performance. + +<|ref|>text<|/ref|><|det|>[[115, 552, 881, 608]]<|/det|> +2) The comparison with the electrical filters is not reasonable. Although NF and SFDR are not measured in Ref. [49] and Ref. [50], I believe they have better performances than the photonic filter, since they do not involve EO & OE conversions and active amplification. + +<|ref|>sub_title<|/ref|><|det|>[[115, 629, 175, 645]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 647, 881, 702]]<|/det|> +We respectfully disagree with this comment. First, we cannot make a fair comparison of the NF and SFDR of previous works, as they are not reported. Assuming that they have better performance would be speculative. + +<|ref|>text<|/ref|><|det|>[[115, 722, 881, 789]]<|/det|> +Recently, there are number of investigations about active RF bandpass filter with active- RC [1], active capacitance [2] or active inductor [3- 5], that is built in CMOS technology. Nevertheless, the reported noise figure and dynamic range in these studies are comparable with our work (Table I). + +<|ref|>text<|/ref|><|det|>[[115, 789, 881, 855]]<|/det|> +This comparable result shows the uniqueness of programmable MWP circuit in our work. With simpler chip topology, our work can compete in term of performance, but with better wide tuning range, continuous tunability, and less hardware numbers that cannot be achieved easily by its electronic counterparts. + +<|ref|>text<|/ref|><|det|>[[115, 872, 212, 887]]<|/det|> +References: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 881, 138]]<|/det|> +[1] B. Wu et al., A 40 nm CMOS Derivative-Free IF Active-RC BPF With Programmable Bandwidth and Center Frequency Achieving Over 30 dBm IIP3, IEEE Journal of Solid-State Circuits, 50(8), 1772- 1784, 2015. + +<|ref|>text<|/ref|><|det|>[[115, 156, 881, 194]]<|/det|> +[2] D. Colaiuda et al., A Second Order 1.8- 1.9 GHz Tunable Active Band- Pass Filter with Improved Noise Performance, Electronics, 11(2781), 1- 10, 2022. + +<|ref|>text<|/ref|><|det|>[[115, 214, 881, 251]]<|/det|> +[3] Z. Gao et al., A Fully Integrated CMOS Active Bandpass Filter for Multiband RF Front- Ends, IEEE Transactions on Circuits and Systems II: Express Briefs, 55(8), 718- 722, 2008. + +<|ref|>text<|/ref|><|det|>[[115, 270, 881, 308]]<|/det|> +[4] V. Kumar et al., A 2.5 GHz Low Power, High- Q, Reliable Design of Active Bandpass Filter, IEEE Transactions on Device and Materials Reliability, 17(1), 229- 244, 2017. + +<|ref|>text<|/ref|><|det|>[[115, 326, 881, 364]]<|/det|> +[5] R. Mehra et al., Reliable and Q- Enhanced Floating Active Inductors and Their Application in RF Bandpass Filter, IEEE Access, 6, 48181- 48194, 2018. + +<|ref|>text<|/ref|><|det|>[[115, 383, 880, 421]]<|/det|> +The advantages of the proposed filter are the relatively higher gain and reconfigurability. However, the gain is realized by two EDFAs which will sacrifice the analog performance. + +<|ref|>sub_title<|/ref|><|det|>[[115, 441, 175, 457]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 458, 882, 590]]<|/det|> +We respectfully disagree with this comment. At this point, all MWP system is active and requires sufficient laser power and EDFA to compensate the optical losses in the system. The combination of EDFA with low- biasing Mach- Zehnder modulator (MZM) has been reported, can be used to improve the performance of the analog photonic system [1] which is the opposite of the reviewer comment. In fact, the positive result of having combination of EDFA and low- biasing MZM in the system is in- line with our work, as we reported the highest ever analog performance using our system. + +<|ref|>text<|/ref|><|det|>[[115, 608, 882, 722]]<|/det|> +Finally, the need for external EDFAs can be feasibly eliminated using high- power erbium- doped waveguide amplifiers (EDWA) in the silicon nitride ( \(Si_{3}N_{4}\) ) photonic integrated circuits, which is recently demonstrated by one of the co- authors of this work [2]. It can be reasonably foreseen in the future that applying the on- chip Erbium amplifier to the MWP chip will overcome the current necessities of the off- chip EDFAs, and at the same time it can enable demanded link gain and noise figure. + +<|ref|>sub_title<|/ref|><|det|>[[115, 780, 204, 796]]<|/det|> +## Reference: + +<|ref|>text<|/ref|><|det|>[[115, 817, 882, 873]]<|/det|> +[1] V.J. Urick et al., Analysis of an Analog Fiber- Optic Link Employing a Low- Biased Mach Zehnder Modulator Followed by an Erbium- Doped Fiber Amplifier, IEEE Journal of Lightwave Technology, 27(12), 2013- 2019, 2009. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 880, 118]]<|/det|> +[2] Y. Liu et al., A photonic integrated circuit-based erbium-doped amplifier, Science, 376, 1309- 1313, 2022. + +<|ref|>text<|/ref|><|det|>[[115, 139, 882, 193]]<|/det|> +For the reconfigurability, I cannot clearly see (or find from the manuscript) the necessity of such a filter. Therefore, the significance of the work and the impact on the researchers in both MWP and microwave communities are not clear. + +<|ref|>sub_title<|/ref|><|det|>[[115, 217, 175, 232]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 234, 882, 420]]<|/det|> +Naturally, reconfigurable bandpass- bandstop filters are important for modern microwave and wireless systems with spectrally cognitive operation [1,2] and in modern multi- mode transceivers adaptable for several operation bands [3,4]. It is desirable to eliminate the need for large- volume switchable filter banks which are not unlimitedly scalable due to the limits in space, weight and power consumption. These filters can dynamically select RF signals of interest and mitigate frequency- agile interferers [5- 7]. This need for reconfigurable filters has been clearly mentioned in the following supplementary references and has been motivating the progress of the topic of MWP. Additionally, the reconfigurable filter in our work can be achieved in integrated form factor as opposite with the usage of discrete components in references which gives our work the upper hand in term of the size and weight. + +<|ref|>text<|/ref|><|det|>[[115, 440, 882, 627]]<|/det|> +Recently, U.S. Defense Advance Research Project Agency (DARPA) announced a project called COFFEE or COmpact Front- end Filters at the EIEment- level to address the challenges hampering the use of wideband Active Electronically Scanned Array (AESA) in congested RF environments [8]. With this project, DARPA seeks to create new class of integrable, high- frequency filters with low loss, high- power handling, and seamless uniformity for superior electromagnetic spectrum operations in the modern era with one area of priority: heightened multifunctionality and granular optimization in AESAs [8]. The COFFEE project aims to develop integrable filters that operate over a wide range of frequencies, small enough to fit behind the element of phased array, and on the analog front- end to make the array in AESA more robust and resistant to interference before digital processing on the back- end [9]. + +<|ref|>sub_title<|/ref|><|det|>[[115, 649, 212, 664]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[115, 685, 881, 740]]<|/det|> +[1] E.J. Naglich et al., A Tunable Bandpass- to- Bandstop Reconfigurable Filter with Independent Bandwidths and Tunable Response Shape, IEEE Transactions on Microwave Theory and Techniques, 58(12), 3770- 3779, 2010. + +<|ref|>text<|/ref|><|det|>[[115, 760, 881, 814]]<|/det|> +[2] T. Yang et al., Bandpass- to- Bandstop Reconfigurable Tunable Filters with Frequency and Bandwidth Controls, IEEE Transactions on Microwave Theory and Techniques, 65(7), 2288- 2297, 2017. + +<|ref|>text<|/ref|><|det|>[[115, 836, 881, 890]]<|/det|> +[3] J. Lee et al., New Bandstop Filter Circuit Topology and Its Application to Design of a Bandstop- to- Bandpass Switchable Filter, IEEE Transactions on Microwave Theory and Techniques, 61(3), 1114- 1123, 2013. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 881, 138]]<|/det|> +[4] Y- H. Cho et al., Two- and Four- Pole Tunable 0.7- 1.1- GHz Bandpass- to- Bandstop Filters with Bandwidth Control, IEEE Transactions on Microwave Theory and Techniques, 62(3), 457- 463, 2014. + +<|ref|>text<|/ref|><|det|>[[115, 156, 881, 213]]<|/det|> +[5] Y- C. Chiou et al., A Tunable Three- Pole 1.5- 2.2- GHz Bandpass Filter with Bandwidth and Transmission Zero Control, IEEE Transactions on Microwave Theory and Techniques, 59(11), 2872- 2878, 2011. + +<|ref|>text<|/ref|><|det|>[[115, 232, 881, 270]]<|/det|> +[6] E.J. Naglich et al., Switchless Tunable Bandstop- to- All- Pass Reconfigurable Filter, IEEE Transactions on Microwave Theory and Techniques, 60(5), 1258- 1265, 2012. + +<|ref|>text<|/ref|><|det|>[[115, 289, 881, 326]]<|/det|> +[7] M. Fan et al., Compact Bandpass- to- Bandstop Reconfigurable Filter with Wide Tuning Range, IEEE Transactions on Microwave Theory and Techniques, 29(3), 198- 200, 2019. + +<|ref|>text<|/ref|><|det|>[[115, 345, 881, 401]]<|/det|> +[8] Defense Advance Research Project Agency. (2022), COFFEE Program Jump- Starts Integrable Filtering for Wideband Superiority, https://www.darpa.mil/news- events/2022- 06- 01, Last accessed on 2022 Sept. + +<|ref|>text<|/ref|><|det|>[[115, 420, 881, 476]]<|/det|> +[9] Defense Advance Research Project Agency. (2021), Filtering Out Interference for Next- Generation Wideband Arrays, https://www.darpa.mil/news- events/2021- 06- 10, Last accessed on 2022 Sept. + +<|ref|>sub_title<|/ref|><|det|>[[115, 497, 199, 514]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[115, 533, 881, 570]]<|/det|> +We have clarified in the main text about the necessity of reconfigurable filter for modern RF applications as the following: + +<|ref|>sub_title<|/ref|><|det|>[[115, 591, 228, 608]]<|/det|> +## Introduction + +<|ref|>text<|/ref|><|det|>[[115, 627, 881, 912]]<|/det|> +As radio frequency (RF) and microwave systems are moving forward into cognitive operation, novel reconfigurable filter will become a key component to enable the full potential of these systems performance [1- 3]. This filter can intelligently operate to differentiate RF signal of interest from the interferers [4- 6]. There is a need of developing reconfigurable filter for modern RF systems to address the challenges impeding the use of active electronically scanned array (AESA) that operate at wide range of frequencies in dense RF environment [7]. The filter is aimed to make the array in AESA more resistant to interference before signal processing [8]. Integrated microwave photonic (MWP) can offer significant advantages to realize advanced concepts of reconfigurable filter for multi- band, all spectrum communications [9] and broadband programmable front- ends [10], which are important for modern RF communications (i.e. cognitive radio). To play a key role in modern RF applications, integrated MWP circuits need to simultaneously show advanced programmability and exceptional performance in terms of low losses, low noise figure, and high dynamic range in a reduced footprint [11- 15]. In recent pasts, a number of programmable integrated MWP filters have widely been demonstrated [16- 20]. Typically, these filters were achieved in application specific circuits, and the measured RF metrics were only sparsely reported. The values of the RF gain, noise figure (NF), and spurious + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 81, 880, 117]]<|/det|> +free dynamic range (SFDR) in these circuits are usually far- off from the requirements for practical RF systems. + +<|ref|>text<|/ref|><|det|>[[117, 133, 137, 144]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[116, 165, 881, 236]]<|/det|> +The capability of the proposed reconfigurable filter is expected to improve the system performance across S- band through Ku- band (i.e. 2 GHz to 18 GHz) frequency range and play a key role for the realization of practical programmable integrated MWP circuit that can operate in congested RF environment. + +<|ref|>text<|/ref|><|det|>[[116, 263, 881, 319]]<|/det|> +3) From the Method, the power of the input two-tone RF signal is 8 dBm. According to Fig. 4(c), the power of the fundamental components are nearly -30 dBm, which cannot agree with the -26 dB claimed in Table I and the results shown in Fig. 4d. Please check it. + +<|ref|>sub_title<|/ref|><|det|>[[116, 341, 175, 357]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 358, 881, 482]]<|/det|> +We thank the reviewer for the feedback about the two- tone signal. In the method section, the 8 dBm RF power is the output RF power from the signal generator. However, when we combine the RF signal from two signal generators, the RF combiner and the RF cable will introduce an 8.5 dB insertion loss, so the power sent to the phase modulator (the real input RF power) is around - 0.5 dBm. The power of the fundamental components in Fig. 4(c) is - 26.65 dBm. The difference between the output fundamental power and the real input RF power matches the link gain of the system, which is - 26 dB. + +<|ref|>text<|/ref|><|det|>[[116, 517, 704, 535]]<|/det|> +We have updated the RF input power as - 0.5 dBm in the method section. + +<|ref|>text<|/ref|><|det|>[[115, 572, 881, 660]]<|/det|> +For the SFDR measurements, we increased the input RF signal to observe the growing trends of the IMD3 and the fundamental terms after linearization. Then, we compare them with the changes of the IMD3 and the fundamental terms in the non- linearized system. The input RF power in Fig. 4(d) is the power sent to the phase modulator (PM). Here, we have already subtracted the insertion loss of the RF combiner and the RF cable. + +<|ref|>sub_title<|/ref|><|det|>[[116, 748, 198, 763]]<|/det|> +## Revision: + +<|ref|>text<|/ref|><|det|>[[116, 783, 880, 838]]<|/det|> +For the IMD3 suppression experiment, the two- tone RF signal with power of - 0.5 dBm, centered at 9 GHz with a space of 10 MHz from signal generators (Wiltron 69147A and Rohde- Schwarz SMP02) is used to drive the PM. + +<|ref|>text<|/ref|><|det|>[[115, 858, 881, 913]]<|/det|> +4) Although SFDRs at different frequencies are measured, it would be more convincing to directly input a wideband RF signal (for example, a QAM signal) to demonstrate its high dynamic range after filtering. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 123, 175, 138]]<|/det|> +## Reply: + +<|ref|>text<|/ref|><|det|>[[115, 140, 881, 222]]<|/det|> +Reply:The presented SFDR is obtained from the standard measurement methods widely used in analog electronics RF/microwave [1- 5] and analog microwave photonics [6- 10], therefore, the measurement technique itself is reliable. We acknowledge the suggestion of the reviewer for wideband RF signal input. However, at this moment we do not have access to the experimental equipment capable of generating QAM signals and to measure their quality/error rate. + +<|ref|>sub_title<|/ref|><|det|>[[115, 238, 212, 253]]<|/det|> +## References: + +<|ref|>text<|/ref|><|det|>[[115, 270, 881, 320]]<|/det|> +[1] C. Garcia- Alberdi et al., Tunable Class AB CMOS \(G_{m} - C\) Filter Based on Quasi- Floating Gate Techniques, IEEE Transactions on Circuits and Systems I: Regular Papers, 60(5), 1300- 1309, 2013. + +<|ref|>text<|/ref|><|det|>[[115, 335, 881, 370]]<|/det|> +[2] M. De Matteis et al., A 33 MHz 70 dB- SNR Super- Source- Follower- Based Low- Pass Analog Filter, IEEE Journal of Solid- State Circuits, 50(7), 1516- 1524, 2015. + +<|ref|>text<|/ref|><|det|>[[115, 385, 881, 436]]<|/det|> +[3] J.S. Mincey et al., Low- Power \(G_{m} - C\) Filter Employing Current- reuse Differential Difference Amplifiers, IEEE Transactions on Circuits and Systems II: Express Briefs, 64(6), 635- 639, 2017. + +<|ref|>text<|/ref|><|det|>[[115, 450, 881, 485]]<|/det|> +[4] Y. Xu et al., A 77- dB- DR 0.65- mW 20- MHz \(5^{\mathrm{th}}\) - order Coupled Source Followers Based Low- Pass Filter, IEEE Journal of Solid- State Circuits, 55(10), 2810- 2818, 2020. + +<|ref|>text<|/ref|><|det|>[[115, 500, 881, 550]]<|/det|> +[5] M. De Matteis et al., 64 dB Dynamic- Range 810 \(\mu W\) 90 MHz Fully- Differential Flipped- Source- Follower Analog Filter in 28nm- CMOS, IEEE Transactions on Circuits and Systems II: Express Briefs, 68(9), 3068- 3072, 2021. + +<|ref|>text<|/ref|><|det|>[[115, 565, 881, 615]]<|/det|> +[6] G. Liu et al., Integrated Microwave Photonic Spectral Shaping for Linearization and Spurious- Free Dynamic Range Enhancement, IEEE Journal of Lightwave Technology, 39(24), 7551- 7562, 2021. + +<|ref|>text<|/ref|><|det|>[[115, 631, 881, 681]]<|/det|> +[7] O. Daulay et al., Microwave Photonic Notch Filter with Integrated Phase- to- Intensity Modulation Transformation and Optical Carrier Suppression, Optics Letters, 46(3), 488- 491, 2021. + +<|ref|>text<|/ref|><|det|>[[115, 697, 881, 730]]<|/det|> +[8] H. Shun Wen et al., Ultrahigh Spectral Resolution Single Passband Microwave Photonic Filter, Optics Express, 29(18), 28725- 28740, 2021. + +<|ref|>text<|/ref|><|det|>[[115, 746, 881, 795]]<|/det|> +[9] R. Zheng et al., Microwave Photonic Link with Improved Dynamic Range for Long- Haul Multi- Octave Applications, IEEE Journal of Lightwave Technology, 39(24), 7915- 7924, 2021. + +<|ref|>text<|/ref|><|det|>[[115, 812, 881, 861]]<|/det|> +[10] Y. Liu et al., Tunable and Reconfigurable Microwave Photonic Bandpass Filter Based on Cascaded Silicon Microring Resonators, IEEE Journal of Lightwave Technology, 40(14), 4655- 4662, 2022. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 376, 101]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>sub_title<|/ref|><|det|>[[118, 138, 448, 153]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 166, 870, 195]]<|/det|> +My comments have been reasonably addressed by the authors. The manuscript can be considered for publication. + +<--- Page Split ---> diff --git a/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/images_list.json b/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd b/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..76a9f6ba1c359ef2985a2fc3fe5af5179f5c7a3a --- /dev/null +++ b/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/supplementary_0_Peer Review file.mmd @@ -0,0 +1,236 @@ + +# Phylotranscriptomics reveals the phylogeny of Asparagales and the evolution of allium flavor biosynthesis + +Corresponding Author: Professor Ling- Yun Chen Chen + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +Wang et al. performed a series of evolutional genomic analysis to establish a robust phylogenetic framework for Asparagales and explored the biogeography of Asparagales. They also reported gene expansion, increased expression, and particularly amino acid mutations of genes involved in allium flavor formation driving the evolution of Allium- specific compounds. Obviously, their findings deepen our understanding of phylotranscriptomic relationships of Asparagales and the genetic mechanism of functional Allium- specific bioactive compounds formation. However, I still have some major concerns that need to be addressed by the authors: + +Major concerns: + +1. How did the authors detect the compounds to distinguish Alliin and isoalliin, because there was no significant difference in retention time of isoalliin and alliin (Fig 3b), but the differences between Allium fistulosum, Allium cepa, Allium macrostemon, Allium taishanense, Allium prostratum, Allium neriniflorum and Allium stativum, Allium tuberosum, Allium micodictyon were observed (Fig 3a). Please provide more information about how the authors did the experiment and tell the difference from the two bioactive derivatives. + +2. Please make clear what criteria are used to delimit the areas in the biogeographical section. + +3. Is the geographical distribution of all species used to calculate their origin based on the sampling location or the ancestral location? If it is based on the ancestral location, the species source information should be indicated and included in Supplement. + +4. In this article, the authors propose a potential dispersal route for each species within the family. Are all the families monophyletic? If not, how could the authors explain the migration route for each species. Please specify it clearly. Minor concern: + +Line 89- 90. This sentence expression is inappropriate. Actually, prior study have reported on transcription evidence that suggested allinase genes were also expanded in Chinese chive (Allium tuberosum) (Liu et al. 2021). Therefore, the statement "It remains unclear whether these two genes have widely expanded across Allium species or exclusively in the three Allium species." is not correct. Please reference the added article below and make revise it. + +Ref : Liu, N., J. Tong, M. Hu, Y. Ji, B. Wang, H. Liang, M. Liu, and Z. Wu. 2021. 'Transcriptome landscapes of multiple tissues highlight the genes involved in the flavor metabolic pathway in Chinese chive (Allium tuberosum)', Genomics, 113: 2145- 57. + +## Reviewer #2 + +(Remarks to the Author) + +1. The authors utilized multiple data from 464 species of Asparagales to investigate the evolutionary patterns of genes associated with allium flavor formation. They reconstructed phylogenetic relationships and analyzed the relationships among families. They also identified gene expansions in eight related metabolic pathways, and pinpointed specific mutation sites exclusive to allium metabolite synthesis. These findings offer valuable insights into the molecular mechanisms underlying the synthesis of compounds of allium flavor. I have some suggestions for improvement and strongly recommend the publication of this paper. + +2. The authors examined gene expression related to the CSO pathway, and there were differences in CSO gene expression in leaves and bulbs (Fig. 4d), but the authors did not mention or explain this in their article. + +3. ILS or hybridization should be detected using multiple methods, such as MSCquartets analysis. + +<--- Page Split ---> + +4. Does WGD lead to an increase in onion-like genes in onion species? + +5. We understand that the production of each plant metabolite is essential, whether to aid the plant in resisting unfavorable abiotic environments or to defend against natural enemies. The authors explain that the duplication of two genes, allinase and LFS gene, in Allium spp. is linked to a significant surge in insect numbers 10 million years ago, and they inquire whether similar phenomena have been observed in other plants with different metabolites? + +6. mutations at the four identified sites (Q388 in allinase and F84, F104, and W155 in LFS) may impact protein substrate recognition, consequently influencing metabolite production. Whether it can be verified by gene editing technology? If it can be verified, choosing one or two sites to verify the effects. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +The authors have conducted additional experiments and made responding revisions. They have answered major concerns and I am satisfied with their efforts and explanations and have no further comments. + +Reviewer #2 + +(Remarks to the Author) + +I apologize for not being able to return the review comments in a timely manner. Upon re- examining the article, it is evident that the author has made conscientious and meticulous revisions, addressing the questions I raised. I recommend that this article be published! + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## Reviewer #1 (Remarks to the Author): + +Wang et al. performed a series of evolutional genomic analysis to establish a robust phylogenetic framework for Asparagales and explored the biogeography of Asparagales. They also reported gene expansion, increased expression, and particularly amino acid mutations of genes involved in allium flavor formation driving the evolution of Allium- specific compounds. Obviously, their findings deepen our understanding of phylotranscriptomic relationships of Asparagales and the genetic mechanism of functional Allium- specific bioactive compounds formation. However, I still have some major concerns that need to be addressed by the authors: + +Reply: Thanks for your suggestions, we have addressed all the concerns you came up with. + +Major concerns: + +1, How did the authors detect the compounds to distinguish Alliin and isoalliin, because there was no significant difference in retention time of isoalliin and alliin (Fig 3b), but the differences between Allium fistulosum, Allium cepa, Allium macrostemon, Allium taishanense, Allium prostratum, Allium neriniflorum and Allium stativum, Allium tuberosum, Allium micodictoyn were observed (Fig 3a). Please provide more information about how the authors did the experiment and tell the difference from the two bioactive derivatives. + +Reply: According to your comment, we reviewed the last version of Fig. 3b. Yes, it is hard to distinguish isoalliin and alliin using their retention time in that figure. This is probably due to the inappropriate UPLC condition previously employed. Following your suggestion, we have repeated the experiments to identify compounds with the UPLC conditions from Liao et al. \(^{1}\) , which enable the differentiation of alliin and isoalliin. For example, in the previous manuscript, mobile phase A consisted of deionized water with \(0.2\%\) formic acid (v/v), and mobile phase B was a mixture of acetonitrile with \(0.2\%\) formic acid (v/v). In this revision, both phases contain \(0.5\%\) formic acid (v/v). These methodological changes are detailed in the Supplementary Text (lines 222- 227). + +We updated Fig. 3 and described the results about distinguishing isoalliin and alliin in the Results and discussion section (lines 479- 482): "Isoalliin was identified at a retention time of approximately 5.1 min, while alliin was detected at approximately 5.3 min. Additionally, alliin presented a secondary ion fragment with an \(m / z\) value of approximately 137.0140, a feature not observed for isoalliin". The chromatograms for the other six metabolites are shown in Supplementary Fig. 10 and 11. + +2. Please make clear what criteria are used to delimit the areas in the biogeographical section. Reply: Following your suggestion, we have detailed our criteria in the Methods section (lines 459-466): "Eight geographical areas were designated: Europe (A), Africa (B), mainland Asia (C), South Asian islands (D), Australia and Papua New Guinea (E), North America (F), South America (G), and Pacific (H), similar to a study on Orchidaceae \(^{28}\) . We have distinguished Europe and mainland Asia as separate regions, reflecting their significant geological separation during the period (100-40 Ma) when the Asparagales families originated. This approach aligns with methodologies adopted in other biogeographic studies, including those on Dryopteris \(^{63}\) ." + +<--- Page Split ---> + +3. Is the geographical distribution of all species used to calculate their origin based on the sampling location or the ancestral location? If it is based on the ancestral location, the species source information should be indicated and included in Supplemental. + +Reply: In our biogeographic analysis, we employed a grafted phylogeny consisting of 303 Asparagales taxa, following a method in Antonelli et al.2. The natural distribution areas for these taxa were sourced from the Plants of the World Online (POWO, https://powo.science.kew.org/; retrieved 12 October 2023). + +Thanks to your comments, we realized that our initial description of biogeographic methods was unclear. To improve this, we have now included a description of our methods in the Results and discussion section (lines 449- 457): "For biogeographic inference, a grafted phylogeny consisting of 303 Asparagales taxa was used. For the construction of the grafted phylogeny, we used the inter- family relationships depicted in the Asparagales species tree (Fig. 1a) as a backbone. To enhance the representation of the Orchidaceae, seven genera and 53 subtribes were incorporated into this backbone. Additionally, generic relationships for other families, such as Amaryllidaceae, Asparagaceae, and Asphodelaceae, were determined from our ITS trees and previous studies and manually integrated into the backbone (Supplementary Tables 4 and 5). The natural distribution of each taxon was accessed from the POWO (retrieved 12 October 2023)." + +We also included a comprehensive description of our methods in the Supplementary Text (lines 161- 174): "A grafted phylogeny consisting of 303 Asparagales taxa was used for the biogeographic analysis (See Supplementary Fig. 8). For the construction of the grafted phylogeny, the inter- family relationships in the Asparagales species tree (Fig. 1a) were used as a backbone. Orchidaceae has more than 26,000 species and ca. 705 genera (the Plants of the World Online (http://www.plantsoftheworldonline.org/), which is too hard to sample all the species or genera. To represent Orchidaceae, seven genera and 53 subtribes within Orchidaceae with relationships compiled from Fig. 5 in Zhang et al.29 were added to the backbone. Each of the family Amaryllidaceae, Asparagaceae, Asphodelaceae, and Iridaceae has more than 40 genera (World Flora Online: http://www.worldfloraonline.org). To represent the genera within these families, we first constructed ML trees using ITS sequences obtained from GenBank for the four families separately. Then, we added the genera that only existed in these ML trees to the reported phylogenies of the four families (Supplementary Table 4). Then, we added the modified phylogenies of the four families to the backbone. Generic relationships for other families were obtained from previous studies (Supplementary Table 4)." + +4. In this article, the authors propose a potential dispersal route for each species within the family. Are all the families monophyletic? If not, how could the authors explain the migration route for each species. Please specify it clearly. + +Reply: In response to your suggestion, we revisited our phylogenetic analyses and consulted recent studies3- 9. Our finding confirms that all families within Asparagales and genera we proposed biogeography, except Agave, exhibit monophyly. Specifically, Agave is paraphyletic; Manfreda, Polianthes, and Prochnyanthes are embedded within Agave9. However, according to the POWO, these genera are treated as synonyms of Agave. Since the classification of most families and genera listed on POWO has been reviewed based on available literature and herbarium consultations, it has a certain degree of reliability. Therefore, the biogeographic + +<--- Page Split ---> + +analysis conducted here adopts the classification from POWO, ensuring that these taxa are monophyletic. + +According to your comment, we described the monophyly of these families and genera in the Results and discussion section (lines 457- 459): "According to our phylogenetic analyses and the classification of POWO, all the 14 families and genera for which we proposed possible dispersal routes are monophyletic (Fig. 1a)". + +Minor concern: + +Line 89- 90. This sentence expression is inappropriate. Actually, prior study have reported on transcription evidence that suggested alliinase genes were also expanded in Chinese chive (Allium tuberosum) (Liu et al. 2021). Therefore, the statement "It remains unclear whether these two genes have widely expanded across Allium species or exclusively in the three Allium species." is not correct. Please reference the added article below and make revise it. Ref: Liu, N., J. Tong, M. Hu, Y. Ji, B. Wang, H. Liang, M. Liu, and Z. Wu. 2021. "Transcriptome landscapes of multiple tissues highlight the genes involved in the flavor metabolic pathway in Chinese chive (Allium tuberosum)", Genomics, 113: 2145- 57. + +Reply: Thanks for your suggestion. Accordingly, we have updated our manuscript to include the sentence (lines 87- 89) "Transcriptome analysis revealed that the alliinase, ATP- sulfurylase (ATPS), and O- acetylserine (thiol) lyase (OASTL) expanded in Chinese chive (A. tuberosum) \(^{21}\) ", citing Liu et al. \(^{10}\) as the source. Moreover, we have revised the sentence from "It remains unclear whether these two genes have widely expanded across Allium species or exclusively in the three Allium species" to a more concise one as "It remains unclear whether these genes have widely expanded across Allium species." (lines 90- 91). + +## Reviewer #2 (Remarks to the Author): + +1. The authors utilized multiple data from 464 species of Asparagales to investigate the evolutionary patterns of genes associated with allium flavor formation. They reconstructed phylogenetic relationships and analyzed the relationships among families. They also identified gene expansions in eight related metabolic pathways, and pinpointed specific mutation sites exclusive to allium metabolite synthesis. These findings offer valuable insights into the molecular mechanisms underlying the synthesis of compounds of allium flavor. I have some suggestions for improvement and strongly recommend the publication of this paper. + +Reply: Thanks for your positive evaluation of our work. We have addressed all the suggestions except the last one, for which we hope our explanations make sense. + +2. The authors examined gene expression related to the CSO pathway, and there were differences in CSO gene expression in leaves and bulbs (Fig. 4d), but the authors did not mention or explain this in their article. + +Reply: The reviewer brought up a very good point. Accordingly, we assessed the mean expression levels of the 13 genes in the CSOs pathway across nine Allium species and compared their expression in leaf versus bulb tissues. These results are described and discussed in the Results and discussion section (lines 333- 343): "A comparison across nine Allium species revealed that, except AHAS and BCAT, 11 of the 13 genes exhibited higher expression levels in the bulb than in the leaf (Supplementary Fig. 18). A previous study reported that garlic bulbs + +<--- Page Split ---> + +contain a higher concentration of alliin compared to leaves54. Our findings revealed that the FMO gene, which involves the last step of alliin synthesis, exhibits a higher expression in the bulb than in the leaf, aligning with the results of Yang et al.54 and Yoshimoto et al.55. However, compared to our results, the FMO exhibited an opposite expression pattern in two studies17, 56. This inconsistency could be explained by the factor that the expression of genes in CSOs biosynthesis varied during growth55. Further research is needed to explore the relationship among developing stages, organs, and CSOs biosynthesis." + +These findings are illustrated in supplementary Fig. 18 (below). + +![PLACEHOLDER_5_0] + + +3. ILS or hybridization should be detected using multiple methods, such as MSCquarts analysis. Reply: In the previous version of this manuscript, we conducted PhyloNet analyses on 18 clades within Asparagales. We described the results of PhyloNet in the Results and discussion section (lines 168–169 and 174–176: “The relationship within these ten clades, which have reticulation, should be better explained by phylogenetic networks…The relationship within these eight clades could be better represented by “true” bifurcating trees.” The results are also shown in Supplementary Fig. 6. + +Following your suggestion, we added MSCquarts analyses for these 18 clades. Both PhyloNet and MSCquarts obtained similar results. These findings are detailed in the Results and discussion section (lines 177–191): “Results of the MSCquarts analyses generally aligned with that of PhyloNet, yielding similar conclusions for 17 of the 18 clades examined. For instance, PhyloNet suggested that the ancestor of the clade comprising Asteliaceae, Hypoxidaceae, and Lanariaceae inherited 33% of its genome from an extinct or unsampled taxon, possibly a sister group to Boryaceae, implying a historical hybridization event (Fig. 1c). Meanwhile, MSCquarts revealed that 8.4% of gene trees (indicated by red triangles) in the Asparagales clade rejected the 'tree & star' model, with numerous points deviating significantly from the vertices to the centroid (Supplementary Fig. 6), also indicating non-tree-like relationships (hybridization and introgression). The only discrepancy between the two methods was observed in the clade Orchidaceae- 8 (Supplementary Fig. 6). While PhyloNet detected no reticulation signals within this clade, 11.1% of gene trees in the MSCquarts analysis rejected the 'tree & star' model, and approximately 15 points were positioned centrally, suggesting ILS or introgression. This inconsistency, while challenging to discern, is often expected in the detection of ancient ILS or introgression events30, 35.” + +The methodology for the MSCquarts analysis was described in the Methods section (lines 439–441): “Moreover, we used the function quarterTreeTestInd in the MSCquarts v.2.031 with the ‘T3 model’ to evaluate the level of ILS within the 18 clades.” + +<--- Page Split ---> + +4. Does WGD lead to an increase in onion-like genes in onion species? + +Reply: Based on your suggestion, we further analyzed the WGD events within Amaryllidaceae using two tree-based methods, Tree2GD and the script map_dups_mrca.py. Subsequently, we examined whether the 13 genes in the CSOs biosynthesis pathway were included in the AABB gene clusters that supported WGD. Along with analyses using DupGen_finder, we found that the expansion of genes in the CSOs biosynthesis pathway arose from WGD, dispersed, proximal, and tandem duplications. + +The methods for detecting WGD were described in the Supplementary Text (lines 252- 266): "Moreover, we checked whether the duplication of these genes was led by whole genome duplication (WGD) events. WGD events within Amaryllidaceae were investigated using Tree2GD v.1.0.3743 and the script map_dups_mrca.py44. These two methods calculate the number and proportion of duplicated gene clusters for each node within the Amaryllidaceae phylogeny. Nine species within Amaryllidaceae were used in Tree2GD. A duplicated gene cluster in a clade, which retains two subclades, indicates a signal of WGD event (AABB duplication)45. For map_dups_mrca.py, gene trees of homologs inferred from 501 samples were mapped to the Asparagales species tree, and the proportion of duplicated genes was counted. We employed a criterion to propose a WGD event, requiring \(\geq 200\) AABB gene clusters (inferred from Tree2GD) and \(\geq 20\%\) of duplicated gene clusters inferred from map_dups_mrca.py for a given clade. Under this criterion, we identified a WGD event at the MRCA of Allium, consistent with Hao et al.36. 1,029 AABB gene clusters were found to support the WGD at the MRCA of Allium. Subsequently, we checked whether the 13 genes in the CSOs biosynthesis pathway were included in these 1,029 gene clusters by comparing if there were identical sequence names between gene clusters and trees of the 13 genes". + +The results were described in the Results and discussion section (lines 289- 297): "Whole genome duplication (WGD) analyses using Tree2GD40 and the methods of Yang et al.41 (map_dups_mrca.py) supported a WGD event that occurred at the MRCA of Allium (Supplementary Table 10). Four (OASTL, BCAT, allinase, and LFS) of the eight expanded genes are indeed included within the 1,029 AABB gene clusters that supported the WGD at the MRCA of Allium (Supplementary Text). Analyses using DupGen_finder42 indicated that the 13 genes derived from dispersed, proximal, tandem duplications with two OASTL copies in A. sativum derived from WGD (Fig. 4c; Supplementary Table 11)." + +5. We understand that the production of each plant metabolite is essential, whether to aid the plant in resisting unfavorable abiotic environments or to defend against natural enemies. The authors explain that the duplication of two genes, allinase and LFS gene, in Allium spp. is linked to a significant surge in insect numbers 10 million years ago, and they inquire whether similar phenomena have been observed in other plants with different metabolites? + +Reply: According to your suggestion, we explored research on the evolution of metabolites and their corresponding genes across various studies. We reviewed the literature on diverse metabolites, including terpenoids13, phenolic compounds like salicylic acid (SA)14, flavonoids15, benzylisoquinoline alkaloid16, tropane alkaloid17, nicotine18, anthocyanin19, carotenoid20, phenylpropanoid21, phenylpropanoids and flavonoids22, ubiquinone23, steroids24, isoprenoids25, + +<--- Page Split ---> + +and tannins26. Additionally, we investigated studies on plant- insect interactions27- 32 and host- plant interactions33. + +Our literature review indicated varied timescales for the evolution of gene families to these plant metabolites. For instance, the morphine pathway appears to have evolved less than 18 \(\mathrm{M a}^{34}\) , while caffeine syntheses emerged from tandem gene duplications around \(1.4 \mathrm{M a}^{35}\) . Plant 5'- diphosphate glycosyltransferases (UGTs), crucial for glycosylation of triterpenoids, had undergone multiple duplications from 104 to \(10 \mathrm{M a}^{36}\) . However, there was no common pattern regarding the timescale of gene family evolution related to plant metabolites. + +According to your suggestion, we added some extrapolation in the Results and discussion section (lines 310- 320): "To investigate whether there is a gene with a timescale of duplication similar to allinase and LFS, we explored research on the evolution of metabolites and their corresponding genes across various studies, such as those on steroids49 and benzylisoquinoline alkaloid50. However, there was no common pattern regarding the timescale of gene family evolution related to plant metabolites. This variability could be explained by the different environments in which plants live and the diverse ecological functions of plant metabolites, such as attracting pollinators and resisting biotic and abiotic environmental stressors51. Furthermore, no similar timescale phenomena were observed for genes associated with plant metabolite resistance to insects; however, such a phenomenon was noted for rye Pm3- and wheat Pm8- like genes, which related to pathogen resistance52. + +6. mutations at the four identified sites (Q388 in allinase and F84, F104, and W155 in LFS) may impact protein substrate recognition, consequently influencing metabolite production. Whether it can be verified by gene editing technology? If it can be verified, choosing one or two sites to verify the effects. + +Reply: Thank you very much for your valuable suggestion. It would be very interesting to make clear whether the four identified sites impact protein substrate recognition, which could further hint at the synthesis of allinase. Nevertheless, in this revision, we did not pursue functional verification of identified sites through gene editing technology. Our decision is primarily influenced by our team's specialization in evolutionary biology, coupled with limited experience in functional experimental methods. Additionally, the preparation of necessary materials and technologies for transgenic experiments in Allium species presents significant challenges and requires extensive time. Moreover, initiating collaboration with another laboratory at this advanced stage of the review process would necessitate including additional key authors, which could complicate the submission timeline. Given the focus and context of this study, where the site mutations in allinase represent a relatively minor aspect of our findings, we felt it prudent to focus our resources more efficiently. + +Nonetheless, we recognize the importance of these sites and are encouraged that two of the four identified sites (F84 and F104 in LFS) have obtained support from previous research. Specifically, Arakawa et al.37 conducted site- directed mutagenesis, protein expression, and activity assays on onion LFS (AcLFS), and their findings corroborate our predictions: mutations at F104 markedly reduced AcLFS activity, and the side chain of F84, adjacent to E88 (a validated active site), acts as an indicative residue for the binding state of AcLFS. These findings lend credibility to our bioinformatics predictions and provide a basis for future experimental validation. + +<--- Page Split ---> + +Thanks to your suggestion, we acknowledged that our previous description of these findings was unclear. Therefore, we have now detailed the aforementioned experiment on site- directed mutagenesis of the previous study37 in the Results and discussion section (lines 367–371): “Previous research utilizing site- directed mutagenesis, protein expression, and activity assays found that mutagenesis at F104 comparatively reduced the activity of \(A c L F S^{58}\) . The side chain of F84, adjacent to E88 - a validated active site - serves as an indicative residue for the binding state of \(A c L F S^{58}\) . In addition, we have acknowledged the need for further verification of the functions of these sites as a limitation of our study, which is discussed in the lines 382–383: “The functions of these four sites require further verification through wet lab experiments.” + +## References cited in the blue-colored text of this file + +1. Liao, N. et al. Chromosome-level genome assembly of bunching onion illuminates genome evolution and flavor formation in Allium crops. Nat. Commun. 13, 6690 (2022). +2. Antonelli, A. et al. Toward a self-updating platform for estimating rates of speciation and migration, ages, and relationships of taxa. Syst. Biol. 66, 152–166 (2017). +3. Xie, D. F. et al. Insights into phylogeny, age and evolution of Allium (Amaryllidaceae) based on the whole plastome sequences. Ann. Bot. 125, 1039–1055 (2020). +4. Zhang, G. et al. Comprehensive phylogenetic analyses of Orchidaceae using nuclear genes and evolutionary insights into epiphytsim. J. Integr. Plant Biol. 65, 1204–1225 (2023). +5. Cole, T. C. H. Asparagaceae Phylogeny Poster (2023). Retrieved from https://www.researchgate.net/publication/366618976_ASPARAGACEAE_Phylogeny_Poster r_AspPP +6. Devey, D. S. et al. Systematics of Xanthorrhoeaceae sensu lato, with an emphasis on Bulbine. Aliso 22, 345–351 (2006). +7. Namgung, J., Do, H. D. K., Kim, C., Choi, H. J. & Kim, J. H. Complete chloroplast genomes shed light on phylogenetic relationships, divergence time, and biogeography of Allioideae (Amaryllidaceae). Sci. Rep. 11, 3262 (2021). +8. Zuntini, A. R. et al. Phylogenomics and the rise of the angiosperms. Nature 629, 843–850 (2024). +9. Jiménez-Barron, O. et al. Phylogeny, diversification rate, and divergence time of Agave sensu lato (Asparagaceae), a group of recent origin in the process of diversification. Front. Plant Sci. 11, 536135 (2020). +10. Liu, N. et al. Transcriptome landscapes of multiple tissues highlight the genes involved in the flavor metabolic pathway in Chinese chive (Allium tuberosum). Genomics 113, 2145–2157 (2021). +11. Sousa, V. & Hey, J. Understanding the origin of species with genome-scale data: Modelling gene flow. Nat. Rev. Genet. 14, 404–414 (2013). +12. Wen, D., Yu, Y., Zhu, J. & Nakhleh, L. Inferring phylogenetic networks using PhyloNet. Syst. Biol. 67, 735–740 (2018). +13. Jia, Q. D. et al. Origin and early evolution of the plant terpene synthase family. Proc. Natl. Acad. Sci. U.S.A. 119, e2100361119 (2022). +14. Jia, X. et al. The origin and evolution of salicylic acid signaling and biosynthesis in plants. Mol. Plant 16, 245–259 (2023). + +<--- Page Split ---> + +15. Jia, Y. et al. Evolutionary dynamic analyses on monocot flavonoid 3'-hydroxylase gene family reveal evidence of plant-environment interaction. BMC Plant Biol. 19, 347 (2019). + +16. Xu, Z. et al. The genome of Corydalis reveals the evolution of benzylisoquinoline alkaloid biosynthesis in Ranunculales. Plant J. 111, 217-230 (2022). + +17. Zhang, F. et al. Revealing evolution of tropane alkaloid biosynthesis by analyzing two genomes in the Solanaceae family. Nat. Commun. 14, 1446 (2023). + +18. Xu, S. et al. Wild tobacco genomes reveal the evolution of nicotine biosynthesis. Proc. Natl. Acad. Sci. U.S.A. 114, 6133-6138 (2017). + +19. Song, X. et al. Chromosome-level pepino genome provides insights into genome evolution and anthocyanin biosynthesis in Solanaceae. Plant J. 110, 1128-1143 (2022). + +20. Sandmann, G. Diversity and origin of carotenoid biosynthesis: its history of coevolution towards plant photosynthesis. New Phytol. 232, 479-493 (2021). + +21. Pratyusha, D. S. & Sarada, D. V. L. MYB transcription factors-master regulators of phenylpropanoid biosynthesis and diverse developmental and stress responses. Plant Cell Rep. 41, 2245-2260 (2022). + +22. Zhu, S. et al. Chromosome-level reference genome of Tetrastigma hemisleyanum (Vitaceae) provides insights into genomic evolution and the biosynthesis of phenylpropanoids and flavonoids. Plant J. 114, 805-823 (2023). + +23. Block, A. et al. The origin and biosynthesis of the benzenoid moiety of ubiquinone (coenzyme Q) in Arabidopsis. Plant Cell 26, 1938-1948 (2014). + +24. Christ, B. et al. Repeated evolution of cytochrome P450-mediated spiroketal steroid biosynthesis in plants. Nat. Commun. 10, 3206 (2019). + +25. de Luna-Valdez, L. et al. Reassessing the evolution of the 1-deoxy-D-xylulose 5-phosphate synthase family suggests a possible novel function for the DXS class 3 proteins. Plant Sci. 310, 110960 (2021). + +26. Wang, L. et al. The chromosome-scale reference genome of Rubus chingii Hu provides insight into the biosynthetic pathway of hydrolyzable tannins. Plant J. 107, 1466-1477 (2021). + +27. Chen, H. et al. Molecular mechanisms of tannin accumulation in Rhus galls and genes involved in plant-insect interactions. Sci. Rep. 8, 9841 (2018). + +28. Erb, M. & Reymond, P. Molecular interactions between plants and insect herbivores. Annu. Rev. Plant. Biol. 70, 527-557 (2019). + +29. Percy, D. M., Page, R. D. & Cronk, Q. C. Plant-insect interactions: double-dating associated insect and plant lineages reveals asynchronous radiations. Syst. Biol. 53, 120-127 (2004). + +30. Shen, Z. Q. & Ni, L. Y. The research of plant-insect interactions over the last two decades. Appl. Ecol. Env. Res. 22, 3087-3098 (2024). + +31. Barker, H. L. et al. Linking plant genes to insect communities: identifying the genetic bases of plant traits and community composition. Mol. Ecol. 28, 4404-4421 (2019). + +32. Luo, S. X. et al. The largest early-diverging angiosperm family is mostly pollinated by ovipositing insects and so are most surviving lineages of early angiosperms. P. Roy. Soc. B-Biol. Sci. 285, 20172365 (2018). + +33. Boulain, H. et al. Fast evolution and lineage-specific gene family expansions of aphid salivary effectors driven by interactions with host-plants. Genome Biol. Evol. 10, 1554-1572 (2018). + +<--- Page Split ---> + +34. Li, Y., Winzer, T., He, Z., and Graham, I. A. Over 100 million years of enzyme evolution underpinning the production of morphine in the Papaveraceae family of flowering plants. Plant Commun. 1, 100029 (2020).35. Xu, Z. et al. Tandem gene duplications drive divergent evolution of caffeine and crocin biosynthetic pathways in plants. BMC Biol. 18, 63 (2020).36. Krishnamurthy, P., Tsukamoto, C. & Ishimoto, M. Reconstruction of the evolutionary histories of UGT gene superfamily in Legumes clarifies the functional divergence of duplicates in specialized metabolism. Int. J. Mol. Sci. 21, 1855 (2020).37. Arakawa, T. et al. Dissecting the stereocontrolled conversion of short-lived sulfenic acid by lachrymatory factor synthase. ACS Catal. 10, 9–19 (2020). + +<--- Page Split ---> diff --git a/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd b/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..08eb1d7b86143862995cbfbd131af4b7f89a94c4 --- /dev/null +++ b/peer_reviews/deffadbb7826afdf2ab8ad33c642df1e1e47832002716b5ccbc5b5c2417b4676/supplementary_0_Peer Review file/supplementary_0_Peer Review file_det.mmd @@ -0,0 +1,323 @@ +<|ref|>title<|/ref|><|det|>[[73, 161, 902, 210]]<|/det|> +# Phylotranscriptomics reveals the phylogeny of Asparagales and the evolution of allium flavor biosynthesis + +<|ref|>text<|/ref|><|det|>[[73, 224, 544, 240]]<|/det|> +Corresponding Author: Professor Ling- Yun Chen Chen + +<|ref|>text<|/ref|><|det|>[[72, 274, 865, 288]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[73, 327, 144, 340]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 354, 220, 367]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 380, 160, 393]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 405, 238, 418]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 419, 921, 496]]<|/det|> +Wang et al. performed a series of evolutional genomic analysis to establish a robust phylogenetic framework for Asparagales and explored the biogeography of Asparagales. They also reported gene expansion, increased expression, and particularly amino acid mutations of genes involved in allium flavor formation driving the evolution of Allium- specific compounds. Obviously, their findings deepen our understanding of phylotranscriptomic relationships of Asparagales and the genetic mechanism of functional Allium- specific bioactive compounds formation. However, I still have some major concerns that need to be addressed by the authors: + +<|ref|>text<|/ref|><|det|>[[73, 497, 187, 509]]<|/det|> +Major concerns: + +<|ref|>text<|/ref|><|det|>[[72, 510, 911, 575]]<|/det|> +1. How did the authors detect the compounds to distinguish Alliin and isoalliin, because there was no significant difference in retention time of isoalliin and alliin (Fig 3b), but the differences between Allium fistulosum, Allium cepa, Allium macrostemon, Allium taishanense, Allium prostratum, Allium neriniflorum and Allium stativum, Allium tuberosum, Allium micodictyon were observed (Fig 3a). Please provide more information about how the authors did the experiment and tell the difference from the two bioactive derivatives. + +<|ref|>text<|/ref|><|det|>[[72, 575, 714, 588]]<|/det|> +2. Please make clear what criteria are used to delimit the areas in the biogeographical section. + +<|ref|>text<|/ref|><|det|>[[72, 589, 916, 627]]<|/det|> +3. Is the geographical distribution of all species used to calculate their origin based on the sampling location or the ancestral location? If it is based on the ancestral location, the species source information should be indicated and included in Supplement. + +<|ref|>text<|/ref|><|det|>[[72, 627, 870, 666]]<|/det|> +4. In this article, the authors propose a potential dispersal route for each species within the family. Are all the families monophyletic? If not, how could the authors explain the migration route for each species. Please specify it clearly. Minor concern: + +<|ref|>text<|/ref|><|det|>[[72, 666, 905, 720]]<|/det|> +Line 89- 90. This sentence expression is inappropriate. Actually, prior study have reported on transcription evidence that suggested allinase genes were also expanded in Chinese chive (Allium tuberosum) (Liu et al. 2021). Therefore, the statement "It remains unclear whether these two genes have widely expanded across Allium species or exclusively in the three Allium species." is not correct. Please reference the added article below and make revise it. + +<|ref|>text<|/ref|><|det|>[[72, 720, 911, 759]]<|/det|> +Ref : Liu, N., J. Tong, M. Hu, Y. Ji, B. Wang, H. Liang, M. Liu, and Z. Wu. 2021. 'Transcriptome landscapes of multiple tissues highlight the genes involved in the flavor metabolic pathway in Chinese chive (Allium tuberosum)', Genomics, 113: 2145- 57. + +<|ref|>sub_title<|/ref|><|det|>[[73, 784, 161, 796]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 810, 237, 822]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 823, 920, 900]]<|/det|> +1. The authors utilized multiple data from 464 species of Asparagales to investigate the evolutionary patterns of genes associated with allium flavor formation. They reconstructed phylogenetic relationships and analyzed the relationships among families. They also identified gene expansions in eight related metabolic pathways, and pinpointed specific mutation sites exclusive to allium metabolite synthesis. These findings offer valuable insights into the molecular mechanisms underlying the synthesis of compounds of allium flavor. I have some suggestions for improvement and strongly recommend the publication of this paper. + +<|ref|>text<|/ref|><|det|>[[70, 900, 916, 927]]<|/det|> +2. The authors examined gene expression related to the CSO pathway, and there were differences in CSO gene expression in leaves and bulbs (Fig. 4d), but the authors did not mention or explain this in their article. + +<|ref|>text<|/ref|><|det|>[[70, 927, 737, 940]]<|/det|> +3. ILS or hybridization should be detected using multiple methods, such as MSCquartets analysis. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 47, 560, 61]]<|/det|> +4. Does WGD lead to an increase in onion-like genes in onion species? + +<|ref|>text<|/ref|><|det|>[[72, 60, 917, 115]]<|/det|> +5. We understand that the production of each plant metabolite is essential, whether to aid the plant in resisting unfavorable abiotic environments or to defend against natural enemies. The authors explain that the duplication of two genes, allinase and LFS gene, in Allium spp. is linked to a significant surge in insect numbers 10 million years ago, and they inquire whether similar phenomena have been observed in other plants with different metabolites? + +<|ref|>text<|/ref|><|det|>[[72, 114, 920, 155]]<|/det|> +6. mutations at the four identified sites (Q388 in allinase and F84, F104, and W155 in LFS) may impact protein substrate recognition, consequently influencing metabolite production. Whether it can be verified by gene editing technology? If it can be verified, choosing one or two sites to verify the effects. + +<|ref|>text<|/ref|><|det|>[[73, 167, 145, 180]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[73, 192, 218, 205]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 217, 160, 230]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 243, 238, 255]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 255, 911, 283]]<|/det|> +The authors have conducted additional experiments and made responding revisions. They have answered major concerns and I am satisfied with their efforts and explanations and have no further comments. + +<|ref|>text<|/ref|><|det|>[[73, 295, 161, 308]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 321, 238, 334]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[72, 334, 911, 374]]<|/det|> +I apologize for not being able to return the review comments in a timely manner. Upon re- examining the article, it is evident that the author has made conscientious and meticulous revisions, addressing the questions I raised. I recommend that this article be published! + +<|ref|>text<|/ref|><|det|>[[72, 728, 916, 780]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 780, 796, 794]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 794, 911, 846]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 845, 618, 859]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[86, 90, 382, 106]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 108, 850, 236]]<|/det|> +Wang et al. performed a series of evolutional genomic analysis to establish a robust phylogenetic framework for Asparagales and explored the biogeography of Asparagales. They also reported gene expansion, increased expression, and particularly amino acid mutations of genes involved in allium flavor formation driving the evolution of Allium- specific compounds. Obviously, their findings deepen our understanding of phylotranscriptomic relationships of Asparagales and the genetic mechanism of functional Allium- specific bioactive compounds formation. However, I still have some major concerns that need to be addressed by the authors: + +<|ref|>text<|/ref|><|det|>[[144, 236, 802, 253]]<|/det|> +Reply: Thanks for your suggestions, we have addressed all the concerns you came up with. + +<|ref|>text<|/ref|><|det|>[[144, 274, 263, 290]]<|/det|> +Major concerns: + +<|ref|>text<|/ref|><|det|>[[144, 291, 850, 401]]<|/det|> +1, How did the authors detect the compounds to distinguish Alliin and isoalliin, because there was no significant difference in retention time of isoalliin and alliin (Fig 3b), but the differences between Allium fistulosum, Allium cepa, Allium macrostemon, Allium taishanense, Allium prostratum, Allium neriniflorum and Allium stativum, Allium tuberosum, Allium micodictoyn were observed (Fig 3a). Please provide more information about how the authors did the experiment and tell the difference from the two bioactive derivatives. + +<|ref|>text<|/ref|><|det|>[[144, 402, 846, 565]]<|/det|> +Reply: According to your comment, we reviewed the last version of Fig. 3b. Yes, it is hard to distinguish isoalliin and alliin using their retention time in that figure. This is probably due to the inappropriate UPLC condition previously employed. Following your suggestion, we have repeated the experiments to identify compounds with the UPLC conditions from Liao et al. \(^{1}\) , which enable the differentiation of alliin and isoalliin. For example, in the previous manuscript, mobile phase A consisted of deionized water with \(0.2\%\) formic acid (v/v), and mobile phase B was a mixture of acetonitrile with \(0.2\%\) formic acid (v/v). In this revision, both phases contain \(0.5\%\) formic acid (v/v). These methodological changes are detailed in the Supplementary Text (lines 222- 227). + +<|ref|>text<|/ref|><|det|>[[144, 566, 850, 675]]<|/det|> +We updated Fig. 3 and described the results about distinguishing isoalliin and alliin in the Results and discussion section (lines 479- 482): "Isoalliin was identified at a retention time of approximately 5.1 min, while alliin was detected at approximately 5.3 min. Additionally, alliin presented a secondary ion fragment with an \(m / z\) value of approximately 137.0140, a feature not observed for isoalliin". The chromatograms for the other six metabolites are shown in Supplementary Fig. 10 and 11. + +<|ref|>text<|/ref|><|det|>[[144, 694, 850, 841]]<|/det|> +2. Please make clear what criteria are used to delimit the areas in the biogeographical section. Reply: Following your suggestion, we have detailed our criteria in the Methods section (lines 459-466): "Eight geographical areas were designated: Europe (A), Africa (B), mainland Asia (C), South Asian islands (D), Australia and Papua New Guinea (E), North America (F), South America (G), and Pacific (H), similar to a study on Orchidaceae \(^{28}\) . We have distinguished Europe and mainland Asia as separate regions, reflecting their significant geological separation during the period (100-40 Ma) when the Asparagales families originated. This approach aligns with methodologies adopted in other biogeographic studies, including those on Dryopteris \(^{63}\) ." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 88, 822, 143]]<|/det|> +3. Is the geographical distribution of all species used to calculate their origin based on the sampling location or the ancestral location? If it is based on the ancestral location, the species source information should be indicated and included in Supplemental. + +<|ref|>text<|/ref|><|det|>[[144, 145, 844, 216]]<|/det|> +Reply: In our biogeographic analysis, we employed a grafted phylogeny consisting of 303 Asparagales taxa, following a method in Antonelli et al.2. The natural distribution areas for these taxa were sourced from the Plants of the World Online (POWO, https://powo.science.kew.org/; retrieved 12 October 2023). + +<|ref|>text<|/ref|><|det|>[[144, 218, 848, 416]]<|/det|> +Thanks to your comments, we realized that our initial description of biogeographic methods was unclear. To improve this, we have now included a description of our methods in the Results and discussion section (lines 449- 457): "For biogeographic inference, a grafted phylogeny consisting of 303 Asparagales taxa was used. For the construction of the grafted phylogeny, we used the inter- family relationships depicted in the Asparagales species tree (Fig. 1a) as a backbone. To enhance the representation of the Orchidaceae, seven genera and 53 subtribes were incorporated into this backbone. Additionally, generic relationships for other families, such as Amaryllidaceae, Asparagaceae, and Asphodelaceae, were determined from our ITS trees and previous studies and manually integrated into the backbone (Supplementary Tables 4 and 5). The natural distribution of each taxon was accessed from the POWO (retrieved 12 October 2023)." + +<|ref|>text<|/ref|><|det|>[[144, 419, 850, 693]]<|/det|> +We also included a comprehensive description of our methods in the Supplementary Text (lines 161- 174): "A grafted phylogeny consisting of 303 Asparagales taxa was used for the biogeographic analysis (See Supplementary Fig. 8). For the construction of the grafted phylogeny, the inter- family relationships in the Asparagales species tree (Fig. 1a) were used as a backbone. Orchidaceae has more than 26,000 species and ca. 705 genera (the Plants of the World Online (http://www.plantsoftheworldonline.org/), which is too hard to sample all the species or genera. To represent Orchidaceae, seven genera and 53 subtribes within Orchidaceae with relationships compiled from Fig. 5 in Zhang et al.29 were added to the backbone. Each of the family Amaryllidaceae, Asparagaceae, Asphodelaceae, and Iridaceae has more than 40 genera (World Flora Online: http://www.worldfloraonline.org). To represent the genera within these families, we first constructed ML trees using ITS sequences obtained from GenBank for the four families separately. Then, we added the genera that only existed in these ML trees to the reported phylogenies of the four families (Supplementary Table 4). Then, we added the modified phylogenies of the four families to the backbone. Generic relationships for other families were obtained from previous studies (Supplementary Table 4)." + +<|ref|>text<|/ref|><|det|>[[144, 713, 845, 767]]<|/det|> +4. In this article, the authors propose a potential dispersal route for each species within the family. Are all the families monophyletic? If not, how could the authors explain the migration route for each species. Please specify it clearly. + +<|ref|>text<|/ref|><|det|>[[144, 769, 837, 895]]<|/det|> +Reply: In response to your suggestion, we revisited our phylogenetic analyses and consulted recent studies3- 9. Our finding confirms that all families within Asparagales and genera we proposed biogeography, except Agave, exhibit monophyly. Specifically, Agave is paraphyletic; Manfreda, Polianthes, and Prochnyanthes are embedded within Agave9. However, according to the POWO, these genera are treated as synonyms of Agave. Since the classification of most families and genera listed on POWO has been reviewed based on available literature and herbarium consultations, it has a certain degree of reliability. Therefore, the biogeographic + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 799, 125]]<|/det|> +analysis conducted here adopts the classification from POWO, ensuring that these taxa are monophyletic. + +<|ref|>text<|/ref|><|det|>[[144, 126, 850, 200]]<|/det|> +According to your comment, we described the monophyly of these families and genera in the Results and discussion section (lines 457- 459): "According to our phylogenetic analyses and the classification of POWO, all the 14 families and genera for which we proposed possible dispersal routes are monophyletic (Fig. 1a)". + +<|ref|>text<|/ref|><|det|>[[144, 220, 257, 235]]<|/det|> +Minor concern: + +<|ref|>text<|/ref|><|det|>[[143, 237, 844, 384]]<|/det|> +Line 89- 90. This sentence expression is inappropriate. Actually, prior study have reported on transcription evidence that suggested alliinase genes were also expanded in Chinese chive (Allium tuberosum) (Liu et al. 2021). Therefore, the statement "It remains unclear whether these two genes have widely expanded across Allium species or exclusively in the three Allium species." is not correct. Please reference the added article below and make revise it. Ref: Liu, N., J. Tong, M. Hu, Y. Ji, B. Wang, H. Liang, M. Liu, and Z. Wu. 2021. "Transcriptome landscapes of multiple tissues highlight the genes involved in the flavor metabolic pathway in Chinese chive (Allium tuberosum)", Genomics, 113: 2145- 57. + +<|ref|>text<|/ref|><|det|>[[143, 386, 845, 514]]<|/det|> +Reply: Thanks for your suggestion. Accordingly, we have updated our manuscript to include the sentence (lines 87- 89) "Transcriptome analysis revealed that the alliinase, ATP- sulfurylase (ATPS), and O- acetylserine (thiol) lyase (OASTL) expanded in Chinese chive (A. tuberosum) \(^{21}\) ", citing Liu et al. \(^{10}\) as the source. Moreover, we have revised the sentence from "It remains unclear whether these two genes have widely expanded across Allium species or exclusively in the three Allium species" to a more concise one as "It remains unclear whether these genes have widely expanded across Allium species." (lines 90- 91). + +<|ref|>sub_title<|/ref|><|det|>[[86, 532, 382, 549]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[144, 551, 852, 679]]<|/det|> +1. The authors utilized multiple data from 464 species of Asparagales to investigate the evolutionary patterns of genes associated with allium flavor formation. They reconstructed phylogenetic relationships and analyzed the relationships among families. They also identified gene expansions in eight related metabolic pathways, and pinpointed specific mutation sites exclusive to allium metabolite synthesis. These findings offer valuable insights into the molecular mechanisms underlying the synthesis of compounds of allium flavor. I have some suggestions for improvement and strongly recommend the publication of this paper. + +<|ref|>text<|/ref|><|det|>[[144, 680, 835, 715]]<|/det|> +Reply: Thanks for your positive evaluation of our work. We have addressed all the suggestions except the last one, for which we hope our explanations make sense. + +<|ref|>text<|/ref|><|det|>[[144, 734, 843, 787]]<|/det|> +2. The authors examined gene expression related to the CSO pathway, and there were differences in CSO gene expression in leaves and bulbs (Fig. 4d), but the authors did not mention or explain this in their article. + +<|ref|>text<|/ref|><|det|>[[144, 790, 842, 899]]<|/det|> +Reply: The reviewer brought up a very good point. Accordingly, we assessed the mean expression levels of the 13 genes in the CSOs pathway across nine Allium species and compared their expression in leaf versus bulb tissues. These results are described and discussed in the Results and discussion section (lines 333- 343): "A comparison across nine Allium species revealed that, except AHAS and BCAT, 11 of the 13 genes exhibited higher expression levels in the bulb than in the leaf (Supplementary Fig. 18). A previous study reported that garlic bulbs + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 88, 848, 217]]<|/det|> +contain a higher concentration of alliin compared to leaves54. Our findings revealed that the FMO gene, which involves the last step of alliin synthesis, exhibits a higher expression in the bulb than in the leaf, aligning with the results of Yang et al.54 and Yoshimoto et al.55. However, compared to our results, the FMO exhibited an opposite expression pattern in two studies17, 56. This inconsistency could be explained by the factor that the expression of genes in CSOs biosynthesis varied during growth55. Further research is needed to explore the relationship among developing stages, organs, and CSOs biosynthesis." + +<|ref|>text<|/ref|><|det|>[[144, 245, 604, 262]]<|/det|> +These findings are illustrated in supplementary Fig. 18 (below). + +<|ref|>image<|/ref|><|det|>[[144, 264, 678, 399]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[144, 420, 850, 550]]<|/det|> +3. ILS or hybridization should be detected using multiple methods, such as MSCquarts analysis. Reply: In the previous version of this manuscript, we conducted PhyloNet analyses on 18 clades within Asparagales. We described the results of PhyloNet in the Results and discussion section (lines 168–169 and 174–176: “The relationship within these ten clades, which have reticulation, should be better explained by phylogenetic networks…The relationship within these eight clades could be better represented by “true” bifurcating trees.” The results are also shown in Supplementary Fig. 6. + +<|ref|>text<|/ref|><|det|>[[144, 550, 852, 842]]<|/det|> +Following your suggestion, we added MSCquarts analyses for these 18 clades. Both PhyloNet and MSCquarts obtained similar results. These findings are detailed in the Results and discussion section (lines 177–191): “Results of the MSCquarts analyses generally aligned with that of PhyloNet, yielding similar conclusions for 17 of the 18 clades examined. For instance, PhyloNet suggested that the ancestor of the clade comprising Asteliaceae, Hypoxidaceae, and Lanariaceae inherited 33% of its genome from an extinct or unsampled taxon, possibly a sister group to Boryaceae, implying a historical hybridization event (Fig. 1c). Meanwhile, MSCquarts revealed that 8.4% of gene trees (indicated by red triangles) in the Asparagales clade rejected the 'tree & star' model, with numerous points deviating significantly from the vertices to the centroid (Supplementary Fig. 6), also indicating non-tree-like relationships (hybridization and introgression). The only discrepancy between the two methods was observed in the clade Orchidaceae- 8 (Supplementary Fig. 6). While PhyloNet detected no reticulation signals within this clade, 11.1% of gene trees in the MSCquarts analysis rejected the 'tree & star' model, and approximately 15 points were positioned centrally, suggesting ILS or introgression. This inconsistency, while challenging to discern, is often expected in the detection of ancient ILS or introgression events30, 35.” + +<|ref|>text<|/ref|><|det|>[[144, 843, 846, 897]]<|/det|> +The methodology for the MSCquarts analysis was described in the Methods section (lines 439–441): “Moreover, we used the function quarterTreeTestInd in the MSCquarts v.2.031 with the ‘T3 model’ to evaluate the level of ILS within the 18 clades.” + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 107, 658, 125]]<|/det|> +4. Does WGD lead to an increase in onion-like genes in onion species? + +<|ref|>text<|/ref|><|det|>[[144, 125, 850, 234]]<|/det|> +Reply: Based on your suggestion, we further analyzed the WGD events within Amaryllidaceae using two tree-based methods, Tree2GD and the script map_dups_mrca.py. Subsequently, we examined whether the 13 genes in the CSOs biosynthesis pathway were included in the AABB gene clusters that supported WGD. Along with analyses using DupGen_finder, we found that the expansion of genes in the CSOs biosynthesis pathway arose from WGD, dispersed, proximal, and tandem duplications. + +<|ref|>text<|/ref|><|det|>[[143, 235, 852, 530]]<|/det|> +The methods for detecting WGD were described in the Supplementary Text (lines 252- 266): "Moreover, we checked whether the duplication of these genes was led by whole genome duplication (WGD) events. WGD events within Amaryllidaceae were investigated using Tree2GD v.1.0.3743 and the script map_dups_mrca.py44. These two methods calculate the number and proportion of duplicated gene clusters for each node within the Amaryllidaceae phylogeny. Nine species within Amaryllidaceae were used in Tree2GD. A duplicated gene cluster in a clade, which retains two subclades, indicates a signal of WGD event (AABB duplication)45. For map_dups_mrca.py, gene trees of homologs inferred from 501 samples were mapped to the Asparagales species tree, and the proportion of duplicated genes was counted. We employed a criterion to propose a WGD event, requiring \(\geq 200\) AABB gene clusters (inferred from Tree2GD) and \(\geq 20\%\) of duplicated gene clusters inferred from map_dups_mrca.py for a given clade. Under this criterion, we identified a WGD event at the MRCA of Allium, consistent with Hao et al.36. 1,029 AABB gene clusters were found to support the WGD at the MRCA of Allium. Subsequently, we checked whether the 13 genes in the CSOs biosynthesis pathway were included in these 1,029 gene clusters by comparing if there were identical sequence names between gene clusters and trees of the 13 genes". + +<|ref|>text<|/ref|><|det|>[[144, 530, 850, 677]]<|/det|> +The results were described in the Results and discussion section (lines 289- 297): "Whole genome duplication (WGD) analyses using Tree2GD40 and the methods of Yang et al.41 (map_dups_mrca.py) supported a WGD event that occurred at the MRCA of Allium (Supplementary Table 10). Four (OASTL, BCAT, allinase, and LFS) of the eight expanded genes are indeed included within the 1,029 AABB gene clusters that supported the WGD at the MRCA of Allium (Supplementary Text). Analyses using DupGen_finder42 indicated that the 13 genes derived from dispersed, proximal, tandem duplications with two OASTL copies in A. sativum derived from WGD (Fig. 4c; Supplementary Table 11)." + +<|ref|>text<|/ref|><|det|>[[144, 694, 848, 787]]<|/det|> +5. We understand that the production of each plant metabolite is essential, whether to aid the plant in resisting unfavorable abiotic environments or to defend against natural enemies. The authors explain that the duplication of two genes, allinase and LFS gene, in Allium spp. is linked to a significant surge in insect numbers 10 million years ago, and they inquire whether similar phenomena have been observed in other plants with different metabolites? + +<|ref|>text<|/ref|><|det|>[[144, 787, 839, 877]]<|/det|> +Reply: According to your suggestion, we explored research on the evolution of metabolites and their corresponding genes across various studies. We reviewed the literature on diverse metabolites, including terpenoids13, phenolic compounds like salicylic acid (SA)14, flavonoids15, benzylisoquinoline alkaloid16, tropane alkaloid17, nicotine18, anthocyanin19, carotenoid20, phenylpropanoid21, phenylpropanoids and flavonoids22, ubiquinone23, steroids24, isoprenoids25, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 88, 850, 125]]<|/det|> +and tannins26. Additionally, we investigated studies on plant- insect interactions27- 32 and host- plant interactions33. + +<|ref|>text<|/ref|><|det|>[[144, 125, 850, 235]]<|/det|> +Our literature review indicated varied timescales for the evolution of gene families to these plant metabolites. For instance, the morphine pathway appears to have evolved less than 18 \(\mathrm{M a}^{34}\) , while caffeine syntheses emerged from tandem gene duplications around \(1.4 \mathrm{M a}^{35}\) . Plant 5'- diphosphate glycosyltransferases (UGTs), crucial for glycosylation of triterpenoids, had undergone multiple duplications from 104 to \(10 \mathrm{M a}^{36}\) . However, there was no common pattern regarding the timescale of gene family evolution related to plant metabolites. + +<|ref|>text<|/ref|><|det|>[[144, 236, 853, 437]]<|/det|> +According to your suggestion, we added some extrapolation in the Results and discussion section (lines 310- 320): "To investigate whether there is a gene with a timescale of duplication similar to allinase and LFS, we explored research on the evolution of metabolites and their corresponding genes across various studies, such as those on steroids49 and benzylisoquinoline alkaloid50. However, there was no common pattern regarding the timescale of gene family evolution related to plant metabolites. This variability could be explained by the different environments in which plants live and the diverse ecological functions of plant metabolites, such as attracting pollinators and resisting biotic and abiotic environmental stressors51. Furthermore, no similar timescale phenomena were observed for genes associated with plant metabolite resistance to insects; however, such a phenomenon was noted for rye Pm3- and wheat Pm8- like genes, which related to pathogen resistance52. + +<|ref|>text<|/ref|><|det|>[[144, 455, 847, 528]]<|/det|> +6. mutations at the four identified sites (Q388 in allinase and F84, F104, and W155 in LFS) may impact protein substrate recognition, consequently influencing metabolite production. Whether it can be verified by gene editing technology? If it can be verified, choosing one or two sites to verify the effects. + +<|ref|>text<|/ref|><|det|>[[144, 529, 845, 750]]<|/det|> +Reply: Thank you very much for your valuable suggestion. It would be very interesting to make clear whether the four identified sites impact protein substrate recognition, which could further hint at the synthesis of allinase. Nevertheless, in this revision, we did not pursue functional verification of identified sites through gene editing technology. Our decision is primarily influenced by our team's specialization in evolutionary biology, coupled with limited experience in functional experimental methods. Additionally, the preparation of necessary materials and technologies for transgenic experiments in Allium species presents significant challenges and requires extensive time. Moreover, initiating collaboration with another laboratory at this advanced stage of the review process would necessitate including additional key authors, which could complicate the submission timeline. Given the focus and context of this study, where the site mutations in allinase represent a relatively minor aspect of our findings, we felt it prudent to focus our resources more efficiently. + +<|ref|>text<|/ref|><|det|>[[144, 750, 852, 896]]<|/det|> +Nonetheless, we recognize the importance of these sites and are encouraged that two of the four identified sites (F84 and F104 in LFS) have obtained support from previous research. Specifically, Arakawa et al.37 conducted site- directed mutagenesis, protein expression, and activity assays on onion LFS (AcLFS), and their findings corroborate our predictions: mutations at F104 markedly reduced AcLFS activity, and the side chain of F84, adjacent to E88 (a validated active site), acts as an indicative residue for the binding state of AcLFS. These findings lend credibility to our bioinformatics predictions and provide a basis for future experimental validation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[143, 90, 850, 253]]<|/det|> +Thanks to your suggestion, we acknowledged that our previous description of these findings was unclear. Therefore, we have now detailed the aforementioned experiment on site- directed mutagenesis of the previous study37 in the Results and discussion section (lines 367–371): “Previous research utilizing site- directed mutagenesis, protein expression, and activity assays found that mutagenesis at F104 comparatively reduced the activity of \(A c L F S^{58}\) . The side chain of F84, adjacent to E88 - a validated active site - serves as an indicative residue for the binding state of \(A c L F S^{58}\) . In addition, we have acknowledged the need for further verification of the functions of these sites as a limitation of our study, which is discussed in the lines 382–383: “The functions of these four sites require further verification through wet lab experiments.” + +<|ref|>sub_title<|/ref|><|det|>[[144, 273, 535, 290]]<|/det|> +## References cited in the blue-colored text of this file + +<|ref|>text<|/ref|><|det|>[[143, 291, 850, 880]]<|/det|> +1. Liao, N. et al. Chromosome-level genome assembly of bunching onion illuminates genome evolution and flavor formation in Allium crops. Nat. Commun. 13, 6690 (2022). +2. Antonelli, A. et al. Toward a self-updating platform for estimating rates of speciation and migration, ages, and relationships of taxa. Syst. Biol. 66, 152–166 (2017). +3. Xie, D. F. et al. Insights into phylogeny, age and evolution of Allium (Amaryllidaceae) based on the whole plastome sequences. Ann. Bot. 125, 1039–1055 (2020). +4. Zhang, G. et al. Comprehensive phylogenetic analyses of Orchidaceae using nuclear genes and evolutionary insights into epiphytsim. J. Integr. Plant Biol. 65, 1204–1225 (2023). +5. Cole, T. C. H. Asparagaceae Phylogeny Poster (2023). Retrieved from https://www.researchgate.net/publication/366618976_ASPARAGACEAE_Phylogeny_Poster r_AspPP +6. Devey, D. S. et al. Systematics of Xanthorrhoeaceae sensu lato, with an emphasis on Bulbine. Aliso 22, 345–351 (2006). +7. Namgung, J., Do, H. D. K., Kim, C., Choi, H. J. & Kim, J. H. Complete chloroplast genomes shed light on phylogenetic relationships, divergence time, and biogeography of Allioideae (Amaryllidaceae). Sci. Rep. 11, 3262 (2021). +8. Zuntini, A. R. et al. Phylogenomics and the rise of the angiosperms. Nature 629, 843–850 (2024). +9. Jiménez-Barron, O. et al. Phylogeny, diversification rate, and divergence time of Agave sensu lato (Asparagaceae), a group of recent origin in the process of diversification. Front. Plant Sci. 11, 536135 (2020). +10. Liu, N. et al. Transcriptome landscapes of multiple tissues highlight the genes involved in the flavor metabolic pathway in Chinese chive (Allium tuberosum). Genomics 113, 2145–2157 (2021). +11. Sousa, V. & Hey, J. Understanding the origin of species with genome-scale data: Modelling gene flow. Nat. Rev. Genet. 14, 404–414 (2013). +12. Wen, D., Yu, Y., Zhu, J. & Nakhleh, L. Inferring phylogenetic networks using PhyloNet. Syst. Biol. 67, 735–740 (2018). +13. Jia, Q. D. et al. Origin and early evolution of the plant terpene synthase family. Proc. Natl. Acad. Sci. U.S.A. 119, e2100361119 (2022). +14. Jia, X. et al. The origin and evolution of salicylic acid signaling and biosynthesis in plants. Mol. Plant 16, 245–259 (2023). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[140, 90, 840, 125]]<|/det|> +15. Jia, Y. et al. Evolutionary dynamic analyses on monocot flavonoid 3'-hydroxylase gene family reveal evidence of plant-environment interaction. BMC Plant Biol. 19, 347 (2019). + +<|ref|>text<|/ref|><|det|>[[144, 124, 833, 161]]<|/det|> +16. Xu, Z. et al. The genome of Corydalis reveals the evolution of benzylisoquinoline alkaloid biosynthesis in Ranunculales. Plant J. 111, 217-230 (2022). + +<|ref|>text<|/ref|><|det|>[[144, 163, 803, 199]]<|/det|> +17. Zhang, F. et al. Revealing evolution of tropane alkaloid biosynthesis by analyzing two genomes in the Solanaceae family. Nat. Commun. 14, 1446 (2023). + +<|ref|>text<|/ref|><|det|>[[144, 200, 844, 235]]<|/det|> +18. Xu, S. et al. Wild tobacco genomes reveal the evolution of nicotine biosynthesis. Proc. Natl. Acad. Sci. U.S.A. 114, 6133-6138 (2017). + +<|ref|>text<|/ref|><|det|>[[144, 236, 836, 272]]<|/det|> +19. Song, X. et al. Chromosome-level pepino genome provides insights into genome evolution and anthocyanin biosynthesis in Solanaceae. Plant J. 110, 1128-1143 (2022). + +<|ref|>text<|/ref|><|det|>[[144, 273, 819, 309]]<|/det|> +20. Sandmann, G. Diversity and origin of carotenoid biosynthesis: its history of coevolution towards plant photosynthesis. New Phytol. 232, 479-493 (2021). + +<|ref|>text<|/ref|><|det|>[[144, 310, 828, 363]]<|/det|> +21. Pratyusha, D. S. & Sarada, D. V. L. MYB transcription factors-master regulators of phenylpropanoid biosynthesis and diverse developmental and stress responses. Plant Cell Rep. 41, 2245-2260 (2022). + +<|ref|>text<|/ref|><|det|>[[144, 365, 841, 418]]<|/det|> +22. Zhu, S. et al. Chromosome-level reference genome of Tetrastigma hemisleyanum (Vitaceae) provides insights into genomic evolution and the biosynthesis of phenylpropanoids and flavonoids. Plant J. 114, 805-823 (2023). + +<|ref|>text<|/ref|><|det|>[[144, 420, 780, 455]]<|/det|> +23. Block, A. et al. The origin and biosynthesis of the benzenoid moiety of ubiquinone (coenzyme Q) in Arabidopsis. Plant Cell 26, 1938-1948 (2014). + +<|ref|>text<|/ref|><|det|>[[144, 456, 787, 491]]<|/det|> +24. Christ, B. et al. Repeated evolution of cytochrome P450-mediated spiroketal steroid biosynthesis in plants. Nat. Commun. 10, 3206 (2019). + +<|ref|>text<|/ref|><|det|>[[144, 492, 840, 546]]<|/det|> +25. de Luna-Valdez, L. et al. Reassessing the evolution of the 1-deoxy-D-xylulose 5-phosphate synthase family suggests a possible novel function for the DXS class 3 proteins. Plant Sci. 310, 110960 (2021). + +<|ref|>text<|/ref|><|det|>[[144, 548, 810, 601]]<|/det|> +26. Wang, L. et al. The chromosome-scale reference genome of Rubus chingii Hu provides insight into the biosynthetic pathway of hydrolyzable tannins. Plant J. 107, 1466-1477 (2021). + +<|ref|>text<|/ref|><|det|>[[144, 603, 803, 639]]<|/det|> +27. Chen, H. et al. Molecular mechanisms of tannin accumulation in Rhus galls and genes involved in plant-insect interactions. Sci. Rep. 8, 9841 (2018). + +<|ref|>text<|/ref|><|det|>[[144, 640, 840, 675]]<|/det|> +28. Erb, M. & Reymond, P. Molecular interactions between plants and insect herbivores. Annu. Rev. Plant. Biol. 70, 527-557 (2019). + +<|ref|>text<|/ref|><|det|>[[144, 677, 844, 712]]<|/det|> +29. Percy, D. M., Page, R. D. & Cronk, Q. C. Plant-insect interactions: double-dating associated insect and plant lineages reveals asynchronous radiations. Syst. Biol. 53, 120-127 (2004). + +<|ref|>text<|/ref|><|det|>[[144, 714, 835, 749]]<|/det|> +30. Shen, Z. Q. & Ni, L. Y. The research of plant-insect interactions over the last two decades. Appl. Ecol. Env. Res. 22, 3087-3098 (2024). + +<|ref|>text<|/ref|><|det|>[[144, 750, 840, 786]]<|/det|> +31. Barker, H. L. et al. Linking plant genes to insect communities: identifying the genetic bases of plant traits and community composition. Mol. Ecol. 28, 4404-4421 (2019). + +<|ref|>text<|/ref|><|det|>[[144, 787, 844, 840]]<|/det|> +32. Luo, S. X. et al. The largest early-diverging angiosperm family is mostly pollinated by ovipositing insects and so are most surviving lineages of early angiosperms. P. Roy. Soc. B-Biol. Sci. 285, 20172365 (2018). + +<|ref|>text<|/ref|><|det|>[[144, 842, 850, 896]]<|/det|> +33. Boulain, H. et al. Fast evolution and lineage-specific gene family expansions of aphid salivary effectors driven by interactions with host-plants. Genome Biol. Evol. 10, 1554-1572 (2018). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[142, 88, 830, 273]]<|/det|> +34. Li, Y., Winzer, T., He, Z., and Graham, I. A. Over 100 million years of enzyme evolution underpinning the production of morphine in the Papaveraceae family of flowering plants. Plant Commun. 1, 100029 (2020).35. Xu, Z. et al. Tandem gene duplications drive divergent evolution of caffeine and crocin biosynthetic pathways in plants. BMC Biol. 18, 63 (2020).36. Krishnamurthy, P., Tsukamoto, C. & Ishimoto, M. Reconstruction of the evolutionary histories of UGT gene superfamily in Legumes clarifies the functional divergence of duplicates in specialized metabolism. Int. J. Mol. Sci. 21, 1855 (2020).37. Arakawa, T. et al. Dissecting the stereocontrolled conversion of short-lived sulfenic acid by lachrymatory factor synthase. ACS Catal. 10, 9–19 (2020). + +<--- Page Split ---> diff --git a/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..f79bcd373eeb734d81e2b25cdde3610b619b7353 --- /dev/null +++ b/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,170 @@ +[ + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current 1 pA, dwell time 10 \\(\\mu \\mathrm{s}\\) , spacing 1 nm. The change width experiments are conducted with rectangular pattern of scan spots with constant length 20 \\(\\mu \\mathrm{m}\\) and different width, while keeping the beam current beam current 1 pA, dwell time 2 \\(\\mu \\mathrm{s}\\) , spacing 1 nm constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths58,59, the deep blue line is the calculation result employing average slip length58.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "“Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \\(1 \\mathrm{pA}\\) , dwell time \\(10 \\mu \\mathrm{s}\\) , spacing \\(1 \\mathrm{nm}\\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \\(20 \\mu \\mathrm{m}\\) and different width, while keeping the beam current beam current \\(1 \\mathrm{pA}\\) , dwell time \\(2 \\mu \\mathrm{s}\\) , spacing \\(1 \\mathrm{nm}\\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths \\(^{58,59}\\) , the deep blue line is the calculation result employing the average slip length \\(^{58,}\\) .”", + "footnote": [], + "bbox": [ + [ + 262, + 432, + 728, + 714 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure. 4: (c) In-situ chemical reaction chip. The left part is the schematics of the chip. Crosshair channels connect four droplets which are used to inject reagent water solutions. \\(0.1\\mu \\mathrm{L}\\) of \\(0.1\\mathrm{M}\\mathrm{NaSCN}\\) , \\(0.1\\mathrm{mM}\\mathrm{Co}^{2 + }\\) , \\(0.1\\mathrm{mM}\\mathrm{Fe}^{3 + }\\) and \\(0.1\\mathrm{mM}\\mathrm{Cu}^{2 + }\\) are injected clockwise into four droplets (top, right, bottom, left). The inset on the top-left compares the size of microchip with fingertip, with red circle shows the four droplets. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for \\(48\\mathrm{h}\\) after the injection, the color of complexes is more obvious with water removed from the system.", + "footnote": [], + "bbox": [], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4 (d) The schematics of a three-electrode electrochemistry experiment. A droplet of IL with IBFW liquid film pattern printed onto the working electrode is the solvent for analytes.", + "footnote": [], + "bbox": [], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: Working principle of IBFW nano-printing. (a-c) Schematic of the IBFW working principle. (a) When HFIB irradiates the CTL, the positive surface charging induces the primary anion emission. (b) When HFIB ceases to scan, surface charging dissipates and the emitted anions induce the secondary cation emission. (c) The emitted ions from previous stages form an ultra-thin precursor film, and the consequent disjoining pressure propels and stabilizes liquid film. (d) The mechanical balance between the surface charge density induced electrostatic force and surface tension of IL-vacuum interface. The distance between HFIB scans spot and contact line is \\(d\\) ; the surface charging uniformly distributes over a region with length scale, \\(l_0\\) ; the surface-charge-exert electrostatic force and distorts the IL-vacuum interface, balanced by the surface tension \\(\\gamma\\) . (e) Experimental HFIB dosage density to induce IL flow (ions per square of nm) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. (f) IBFW induced liquid film lengths ( \\(\\mu \\mathrm{m}\\) ) on substrates with different conductivities. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. (g) Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removement. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. The shaded regions (red) represent the surface injection region with positive charges. (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at", + "footnote": [], + "bbox": [], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R1: HIM images of IL droplets on \\(100\\mathrm{nm}\\mathrm{SiO_2}\\) and the optical image of the same droplets and film", + "footnote": [], + "bbox": [ + [ + 147, + 253, + 855, + 486 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_1e.jpg", + "caption": "Fig. 1e: The HIM image of IL pattern (brighter part) on PECVD \\(\\mathrm{SiO_2}\\) (the black back ground, the reabsorption of SEs is so strong that the \\(\\mathrm{SiO_2}\\) substrate can barely be observed) is quoted from main text to compare with Fig. R1.", + "footnote": [], + "bbox": [ + [ + 217, + 546, + 777, + 769 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: Working principle of IBFW nano-printing. (a-c) Schematic of the IBFW working principle. (a) When HFIB irradiates the CTL, the positive surface charging induces the primary anion emission. (b) When HFIB ceases to scan, surface charging dissipates and the emitted anions induce the secondary cation emission. (c) The emitted ions from previous stages form an ultra-thin precursor film, and the consequent disjoining pressure propels and stabilizes liquid film. (d) The mechanical balance between the surface charge density induced electrostatic force and the surface tension of IL-vacuum interface. The distance between HFIB scans spot and contact line is \\(d\\) ; the surface charging uniformly distributes over a region with length scale, \\(l_0\\) ; the surface-charge-exert electrostatic force and distorts the IL-vacuum interface, balanced by the surface \\(\\gamma\\) ; \\(\\alpha\\) is the angle between substrate the connection line of SCD center and ion emission center; \\(r^*\\) is the ion emission critical radius, and is also the vertical distance between ion emission center and substrate. (e) Experimental HFIB dosage density to induce IL flow (ions per square of nm) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. (f) IBFW induced liquid film lengths ( \\(\\mu \\mathrm{m}\\) ) on substrates with different conductivities. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. (g) Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removement. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. The shaded regions (red)", + "footnote": [], + "bbox": [ + [ + 168, + 87, + 838, + 490 + ] + ], + "page_idx": 19 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2 (e) Experimental HFIB dosage density to induce IL flow (ions/nm²) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b.", + "footnote": [], + "bbox": [ + [ + 270, + 395, + 737, + 667 + ] + ], + "page_idx": 21 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "“Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \\(1\\mathrm{pA}\\) , dwell time \\(10\\mu \\mathrm{s}\\) , spacing \\(1\\mathrm{nm}\\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \\(20\\mu \\mathrm{m}\\) and different width, while keeping the beam current beam current \\(1\\mathrm{pA}\\) , dwell time \\(2\\mu \\mathrm{s}\\) , spacing \\(1\\mathrm{nm}\\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths \\(^{58,59}\\) , the deep blue line is the calculation result employing the average slip length \\(^{58}\\) .”", + "footnote": [], + "bbox": [ + [ + 245, + 100, + 741, + 404 + ] + ], + "page_idx": 22 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "(Page 23-24, Main text)", + "footnote": [], + "bbox": [ + [ + 120, + 653, + 860, + 802 + ] + ], + "page_idx": 24 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig. 4 (a,b) Proof-of-concept gas sensing prototype. (a) the IBFW liquid nanofilm connected two droplets of IL settled on two Au electrodes for electrochemistry data collection. (b) Results of IBFW liquid nano-circuit in gas sensing and compared with a micro meter droplet settled between and connects two identical Au electrodes. The inset shows the schematic of a room-humidity sensor based on IBFW fabricated nanofilm. The drainage-source currents of both microdroplet and nanofilm are illustrated and the linear fitting results are depicted as dash lines. The voltage exerted between two electrodes is 1 V. The background color map represents the relative humidity of test chamber ranges from 40% to 70%.", + "footnote": [], + "bbox": [ + [ + 180, + 533, + 825, + 707 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure. 4: (c) In-situ chemical reaction chip. The left part is the schematics of the chip. Crosshair channels connect four droplets which are used to inject reagent water solutions. \\(0.1 \\mu \\mathrm{L}\\) of \\(0.1 \\mathrm{M} \\mathrm{NaSCN}\\) , \\(0.1 \\mathrm{mM} \\mathrm{Co}^{2 + }\\) , \\(0.1 \\mathrm{mM} \\mathrm{Fe}^{3 + }\\) and \\(0.1 \\mathrm{mM} \\mathrm{Cu}^{2 + }\\) are injected clockwise into four droplets (top, right, bottom, left). The inset on the top-left compares the size of microchip with fingertip, with red circle shows the four droplets. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for \\(48 \\mathrm{h}\\) after the injection, the color of complexes is more obvious with water removed from the system.", + "footnote": [], + "bbox": [], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Figure 4 (d) The schematics of a three-electrode electrochemistry experiment. A droplet of IL with IBFW liquid film pattern printed onto the working electrode is the solvent for analytes.", + "footnote": [], + "bbox": [], + "page_idx": 32 + } +] \ No newline at end of file diff --git a/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..75936cc796357c3df39d543f87787600117dbbed --- /dev/null +++ b/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,956 @@ + +# nature portfolio + +Peer Review File + +Rewritable printing of ionic liquid nanofilm utilizing focused ion beam induced film wetting + +![](images/Figure_2.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The present paper develops a promising technique using ion beam induced film wetting (IBFW) for the nanoscale patterning of ionic liquids film without any surface fabrications or special electric circuits. The newly- developed technique has nanoscale resolution and can be used for the open surface nanofluidics fabrication and rewritable nano print. Both the resolution and fabrication efficiency have been improved by several orders of magnitude compared to the existing technique, such as optofluidic and thermal gradient technique. Further, the authors performed systematic study on the working mechanism, the modeling and performance evaluation of the IBFM based technique, which is helpful for the fabrication parameters setup and performance improvement in the future engineering application. The present work is exciting and I suggest its publication. Furthermore, the following comments should be addressed to improve the work. + +1. The key of the present work is to overcome the pinning of contact line by the electrostatic forces, which are generated by the focused ion beam. Although the authors studied the IBFW induced liquid film lengths on substrates with different conductivities, however, the effects of wetting status or surface energy of different substrates on the performances should be discussed. + +2. The present work reported that the flow velocity decreases with the film length, and give a model of these two parameters. Based on the analysis, what is the fabrication limit of film length for the present technique? The authors should give necessary discussion. + +3. Based on the analysis of working mechanism of the present work, the electrostatic force is important for the film generation. However, the surface charge on the substrate will also generate electric double layer (EDL) in the IL. At the same time, the thickness of film is only tens of nanometer, the EDLs on the solid-liquid interface and liquid-gas interface will overlap and generate obvious electrokinetic effect when the IF flows. What is the possible effect of EDL on the flow velocity and film generation? + +4. Based on the previous MD simulation, the molecular slip happens on even smooth surface. Did the authors measure the slip on their sample pairs using MD? Because the precursor film is assumed to be \(0.6 \text{nm}\), the molecular slip can generate significant effect on the IL motion. This may explain the the discrepancy of flow velocity between the experiments and theory. + +5. What are effects of temperature gradient and evaporation on the present technique? + +Reviewer #2 (Remarks to the Author): + +Referee report on the manuscript NCOMMS- 23- 30881 "Rewritable nano print of ionic liquids utilizing focused ion beam induced film wetting" by Gu et al. + +<--- Page Split ---> + +This manuscript describes experiments demonstrating a novel way to print ionic liquids on insulating substrates using a He- ion beam writing. To my knowledge results are novel, there importance to the field of controlling liquid flows are hard for me to judge. The explanation of the working principle has several apparent deficiencies. + +There are several remarks I would like to make: + +- The relevance for applications was not entirely clear to me. Several references were cited in the beginning, listing a broad range of applications for "programmable control of fluid motion". But as I understood, the present technique works for ionic liquids only. Thus, I was left wondering what the applications are specific to ionic liquids. That needs to be explained much better. + +- The fabrication has to be performed in an ultra-high vacuum environment. It was not very clearly stated or studied, what happens to the samples after they are taken out of the HIM and exposed to air, tilting of the chip (gravity pulling in another direction), static charges, mechanical contact or other environmental variables. Common sense picture of liquids gives the impression that the "circuit" is not very stable. If it is, data needs to be provided to convince the reader otherwise. + +- Some data was provided with different substrates. What about varying the surface treatment, or cleaning? How sensitive is the success of the writing to the cleanliness of the substrate? You say you anneal the substrates at \(320 \text{C}\) in hydrogen flow. Is that to remove organic contaminants? What if you skip the annealing step? Or use oxygen plasma cleaning instead? + +- How do you know that the ions of the ionic liquid stay intact (are not broken down) under the He ion irradiation? Typically, organic compounds (such as resists for example) can be strongly modified (bonds broken etc) with high energy ion beams. + +- What sets the "minimal line width" scale of \(100 \text{nm}\) ? Shouldn't it in principle be much narrower, as the He ion beam interaction volume at the surface is very small (Fig S7) (hence its high imaging resolution < nm). + +- Related to that, I do not understand the suggested mechanism. In Fig. 2A the local surface charges, induced by the beam current, are located directly under the IL droplet. Yet, in the unnumbered Figure in Note S3 (Electric field driven ion emission calculation), the surface charge is located some distance away from the IL reservoir. Something doesn't match. + +<--- Page Split ---> + +- Eq. (1) cites for example Ref. 46, where some of the terms were introduced. However, in that paper, surface charge density Q was specifically described as "areal hole density" i.e. describing a positive charge, whereas you seem to assume a negative charge. How can you apply the same equations to these two opposing cases? Why would in your case the negative charge be dominant, (which the authors in Ref 46 assume can be neutralized more easily)? + +- In addition, you should describe already in the main text what each term in Eq (1) describes, and define every variable of the equations of the main text (including Eq (2)). + +- Shouldn't the electrons of the flood gun be somehow part of the modelling of Eq. (1)? + +To understand Eq (2), the figure from Supplementary Note 3 is required in the main text. + +How did you measure the experimental surface charge density of Fig. 2 D? Could you experimentally determine the sign of the charge? If you used Eq (1), how is that an "experimental" result? + +- "The qualitative consistency ... verifies the mechanism we propose." Big statement, considering that you refer to Fig. 2E where the agreement is NOT good. (i.e. modelling doesn't predict at all differences between different insulating substrates) + +"The relationship between flow velocity and film length can also be measured experimentally". I don't understand how you can measure the flow velocity in your experimental setting. + +AFM measurements "The liquid-vacuum interface..." Is the AFM measurement done in vacuum instead of air? + +"The current in nanofilm linearly depends on the humidity". What is the mechanism?? Anyways, it seems the current is not only a function of humidity as it depends directly on time as well based on Fig. S18. How could you disentangle the effect of time from the effect of humidity in a real sensor as some voltage bias history dependence seems to exist (referring to Fig. S18F) + +Fig. 3F use real current units instead of dimensionless and tell what the bias voltage used was. BTW Fig. S18 C has wrong units (A vs nA). Fig. S18G has no caption, what is it? + +<--- Page Split ---> + +In conclusion, major revisions are required, in my opinion. + +The impact is also not clear, so at the moment I cannot recommend publication in Nat Comm. + +Reviewer #3 (Remarks to the Author): + +The authors developed a new method to perform rewritable surface printing of ionic liquids. The method relies on the disjoining pressure to induce surface films of nanometer thickness, and utilizes helium ion beams to initiate the flow of liquids and pattern creation. The manuscript comprehensively characterizes and explains the underlying mechanism of this printing process. However, as an application- driven work, the prospect of practical real- world applications is a bit weak. Although the authors demonstrated a sensing device application (Fig. 3F), it only utilizes the nanoscale thickness of the ionic liquid film, and the surface patterning is not very relevant. Specific concerns include: + +1. This method utilizes ionic liquids, and seems hard to extend to other liquid systems due to the high-vacuum requirements of the helium ion microscope. Ionic liquid as of now are still quite expensive, limiting the range of applications. Are there ways to improve or revise the method so that other liquid or even solid structures can also be printed? + +2. The surface-wetting driven printing process is limited to patterns that are continuously connected. For printing applications, most of the time disconnected patterns are needed. Are there ways to create such disconnected patterns (in the nano/micron scale)? + +If either or both of the above concerns can be successfully addressed, I suggest that this manuscript may be reconsidered. Otherwise, it may be more suitable to a more specialized journal. + +<--- Page Split ---> + +## Responses to Reviewer #1: + +The present paper develops a promising technique using ion beam induced film wetting (IBFW) for the nanoscale patterning of ionic liquids film without any surface fabrications or special electric circuits. The newly- developed technique has nanoscale resolution and can be used for the open surface nanofluidics fabrication and rewritable nano print. Both the resolution and fabrication efficiency have been improved by several orders of magnitude compared to the existing technique, such as optofluidic and thermal gradient technique. Further, the authors performed systematic study on the working mechanism, the modeling and performance evaluation of the IBFM based technique, which is helpful for the fabrication parameters setup and performance improvement in the future engineering application. The present work is exciting and I suggest its publication. Furthermore, the following comments should be addressed to improve the work. + +Response: We thank the reviewer for the positive comments on our manuscript. + +Comment #1: The key of the present work is to overcome the pinning of contact line by the electrostatic forces, which are generated by the focused ion beam. Although the authors studied the IBFW induced liquid film lengths on substrates with different conductivities, however, the effects of wetting status or surface energy of different substrates on the performances should be discussed. + +Response: We thank the reviewer for the inspiring suggestion. We have tested the wetting status of several liquid- solid combinations and include them in the Supplementary Table 4, but interestingly we find the relation between wetting status and Ion Beam induced Film Wetting (IBFW) effect is quite ambiguous, indicating that the electrostatic forces of IBFW is not quite relevant with the wetting status, which is possible since the IBFW electrostatic forces are much greater than the wetting van der Waals forces at the contact line. No significant differences were observed between same liquids on different insulating substrates (TOX/PECVD \(\mathrm{SiO_2}\) , 15 nm metal on \(\mathrm{SiO_2}\) ). While different liquids with different viscosities showed quite different performances on the same \(\mathrm{SiO_2}\) substrate. + +On the other hand, the liquid viscosity has significant influence, as included in Supplementary Fig. 11. The viscosity raises flow friction which works as a counterpart of the electrostatic driving forces. ILs with lower viscosity can be easily induced to flow on all 3 substrates and form liquid film with hundred \(\mu \mathrm{m}\) length, such as [EMIM][DCA] and [EMIM][NTf2]. The results in Supplementary Fig. 11 only shows the film length fabricated by one time scan of a \(50\mu m\times 1\mu m\) pattern. For [EMIM]BF4, the viscosity increases slightly and can only be induced to flow for several \(\mu \mathrm{m}\) , and difficult to form desired patterns. When the viscosity increases dramatically, for example [BMIM]PF6, helium focused ion beam (HFIB) cannot induce liquid flow on any solid surfaces. + +"Not only the solid substrates, the ILs employed also influence the IBFW performances. Four kinds of ILs are tested on \(\mathrm{SiO_2}\) substrate with the results shown in Supplementary Fig. 11. The results show that liquid viscosity has significant influence on IBFW liquid film, by raising the + +<--- Page Split ---> + +flow friction which works as a counterpart of the electrostatic driven forces. The relation between wetting status and IBFW effect, however, is ambiguous, indicating that the electrostatic forces of IBFW is not quite relevant with the wetting status. It is probably due to the fact that the IBFW electrostatic forces are much greater than the wetting van der Waals forces at the contact line." + +(Page 6- 7, Main text) + +## Supplementary Table 3. + +Parameters of 4 RTILs employed (20 °C) + +
NameMW (g/mol)Surface Tension (mN/m)Density (g/cm³)Viscosity (cP)
[EMIM][DCA]177.2147.31.1121
[EMIM]BF4197.97491.29445
[BMIM]PF6284.18381.37284.18
[EMIM][NTf2]391.31361.5332
+ +## Supplementary Table 4. + +Wetting status of different RTILs on three solid surfaces (contact angle in degree, 20 °C) + +
NamePECVD
SiO2
TOX
SiO2
10 nm Au
on SiO2
[EMIM][DCA]71.04 ± 6.440.1 ± 3.847.0 ± 4.5
[EMIM]BF458.9 ± 3.435.7 ± 4.855.1 ± 4.1
[BMIM]PF682.6 ± 6.362.9 ± 2.168.2 ± 8.9
[EMIM][NTf2]59.2 ± 5.736.2 ± 3.937.8 ± 4.1
+ +(Page S41- 42, Supplementary) + +![](images/Figure_2.jpg) + + +Supplementary Figure 11: the IBFW results of different ILs and the relationship with Oh number. + +(a) Film lengths of different liquids on \(\mathrm{SiO_2}\) substrate can be induced with a same pattern. Scan parameters are 1 pA, 2.5 nm spacing, 3 \(\mu \mathrm{s}\) dwell time, \(50 \times 1\mu m\) pattern. (b) The flow + +<--- Page Split ---> + +velocity of different ILs. (c) The relationship between Ohnsorge number \(Oh = \frac{\mu}{\sqrt{\rho} dy}\) and flow velocity, the fluid data can be found in Supplementary Table 3. + +(Page S28, Supplementary) + +Comment #2: The present work reported that the flow velocity decreases with the film length, and give a model of these two parameters. Based on the analysis, what is the fabrication limit of film length for the present technique? The authors should give necessary discussion. + +Response: We thank the reviewer for this important suggestion. The flow speed of IBFW film decreases with the film length, but as far as we know the flow speed does not decrease to exact zero. Therefore, the fabrication limit of film length for IBFW depends on the user's endurance for the fabrication speed of liquid film. Base on the liquid film length- speed relation curve (Fig. 2h), the film length upper limit can be determined to fulfill specific requirements for fabrication efficiency. For example, the longest film we fabricated reaches \(800 \mu \mathrm{m}\) to \(900 \mu \mathrm{m}\) , with the film velocity decreases to \(10^{- 2} \mu \mathrm{m / s}\) (the in- situ chemical reaction chip in Fig. 4c and Supplementary Fig. 20). We included an explanation in the main text as an instruction for IBFW fabrication. The optical figure of in- situ reaction chip in Supplementary Fig. 20d is a good example of IBFW liquid channel with upper limit length. + +"The inset of Fig. 1e presents an example of minimal line width, \(100 \mathrm{nm}\) , IBFW can achieve. By assembly of separate scan patterns sequentially, the IBFW technique can also fabricate liquid film channel up to hundreds \(\mu \mathrm{m}\) in length." + +(Page 4, Main text) + +"The consistency between the calculation and experiments suggests that disjoining pressure can explain the propagation of IBFW film. The discrepancy at extreme long film length may be due to the HFIB irradiation history. The fabrication of film with hundreds \(\mu \mathrm{m}\) length usually takes hours of HFIB irradiation. The accumulated positive charges lead to a higher surface potential and a boundary slip length that exceeds the upper limit in literature, which give rise to an unexpected higher film speed. Base on the film length- speed relationship curve (Fig. 2h), the fabrication limit of film length for IBFW technique can be determined to fulfill specific requirements for fabrication efficiency. For example, the longest film we fabricated reaches \(800 \mu \mathrm{m}\) to \(900 \mu \mathrm{m}\) , with the film velocity decreases to \(10^{- 2} \mu \mathrm{m / s}\) (the in- situ chemical reaction chip in Fig. 4c and Supplementary Fig. 20)." + +(Page 8, Main text) + +<--- Page Split ---> +![](images/Figure_4.jpg) + + +## Supplementary Figure 20: Time series of in-situ chemical reaction chip. + +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non-direct physical contact for solution injections. (f) The reaction chip one month after injection (one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. (Page S37, Supplementary) + +(Page S37, Supplementary) + +Comment #3: Based on the analysis of working mechanism of the present work, the electrostatic force is important for the film generation. However, the surface charge on the substrate will also generate electric double layer (EDL) in the IL. At the same time, the thickness of film is only tens of nanometer, the EDLs on the solid- liquid interface and liquid- gas interface will overlap and generate obvious electrokinetic effect when the IF flows. What is the possible effect of EDL on the flow velocity and film generation? + +Response: We thank the reviewer for this very important comment. The EDL in IL and the + +<--- Page Split ---> + +electrokinetic phenomena exert significant influence on the hydrodynamics behavior of ionic liquids, and a positive surface charge would enhance the flow velocity of ionic liquids with similar cation/anion sizes ([EMIM][NTf₂], [EMIM][DCA] in our experiments) by increasing the boundary slip length. The EDL determines the structure of the IL- solid interface, and adjusts to different surface potential (main text Ref. [58- 60]). The consequent boundary slip length can vary from several nm to over 16 nm. A larger surface potential creates an absorbed ion lubrication layer which can further reduce the IL- solid interface friction, in our case this may further enhance the flow velocity. The IL- vacuum interface influence on the structure of IL- solid is negligible due to its involatile nature, we neglect its influence on the hydrodynamics. Apart from surface potential, the surface roughness may also enhance the slip length. The slip length data from literature (main text Ref. [58, 59]) of imidazolium IL- \(\mathrm{SiO_2}\) interface is adopted to modify our flow model. Since slip length can be easily tuned by surface potential, we employ the lower (2 nm) and upper (16 nm) limits of slip length (Ref. [59]) to give an estimation on the possible range of flow speed in Fig. 2h, and the average value 10 nm (Ref. [58]) is shown by the deep blue line. The modified flow model can better explain the high velocity range observed in IBFW experiments. + +The EDL effect on the ion emission from liquid- vacuum interface may be not important. The MD simulation results indicate that the characteristic electric field ( \(10^{9} \mathrm{~V / m}\) for separate ion emission, \(10^{10 - 11} \mathrm{~V / m}\) for ion clusters emission) that lead to significant ion emission agrees with literature results (Ref. [56]) where the ion emission directly from an IL- vacuum interface far from the solid surface. + +"We next verify that the disjoining pressure propels and stabilizes the nanofilm. The propagation speed of IBFW liquid film decreases monotonically with the increase of film length: + +\[U\sim \frac{h^{2} + 3b h}{3\mu}\cdot \frac{\Pi(h_{m i n}) - \gamma\kappa}{L}. \quad (4)\] + +Where \(U\) is the average flow speed, \(h\) is equilibrium film thickness, \(b\) is the slip length of IL- \(\mathrm{SiO_2}\) interface \(^{58 - 60}\) , \(\mu\) is IL viscosity, \(\Pi (h_{min})\) is disjoining pressure at minimum film thickness \(h_{min}\) , \(L\) is film length, \(\gamma\) is IL surface tension, and \(\kappa\) is curvature of IL- vacuum interface at the conjunction of film and reservoir (Supplementary Table. 2, Supplementary Note 4, Supplementary Fig. 13). We depict the calculation results in Fig. 2h. Since the boundary slip length of IL- \(\mathrm{SiO_2}\) interface depends on the combined surface conditions and ranges from 2 nm to over 16 nm, we employ the lower (2 nm) and upper (16 nm) limits of slip length to give an estimation on the possible range of flow speed in Fig. 2h as the blue shaded region, and the results of average value \(10 \mathrm{nm}^{58}\) is shown by the deep blue line." + +(Page 7, Main text) + +"We adopt the average slip length data \(b \approx 10 \mathrm{~nm}\) of ionic- liquid- \(\mathrm{SiO_2}\) interface from literature \(^{1,2}\) , and zero lateral shear stress is taken at the liquid vacuum interface. According to the literatures, the boundary slip length of IL- solid interface depends on the specific conditions \(^{3}\) , such as, the liquid solid combination, the surface roughness, the surface potential. In most cases, the slip length increases with the roughness. The boundary slip length at different surface potential has been reported to vary due to the structure of EDL adjust to different surface + +<--- Page Split ---> + +potential, ILs with higher conductivity can be influenced more easily3. A larger surface potential has been reported to have an absorbed ion lubrication layer which can further reduce the IL- solid interface friction4, in our case this may further enhance the flow velocity. For a better understanding of the hydrodynamics behavior of IBFW flow, both AFM measurements and MD simulation can be conducted." + +## Modeling of flow velocity + +The simplified 2- dimensional form of Navier- Stokes equation (4.1) is adopted and together with the zero- shear- stress condition (4.2) and the boundary slip condition (4.3) give rise to the flow velocity as a function of vertical coordination \(z\) (4.4). + +\[\begin{array}{l}\mu \frac{d^2u}{dz^2} = \frac{dp}{dx}\\ \displaystyle \frac{du}{dz}\big|_{z = h} = 0,\\ \displaystyle u(0) = b\cdot \frac{du}{dz}\big|_{z = 0},\\ \displaystyle u(z) = \frac{1}{2\mu}\frac{dp}{dx} z^2 -\frac{h}{\mu}\frac{dp}{dx} z - \frac{bh}{\mu}\frac{dp}{dx}. \end{array} \quad (4.4)\] + +The flow rate can be calculated as + +\[Q = d\cdot \int_{0}^{h}u(z)dz\sim -\frac{d\cdot h^{2}(h + 3b)}{3\mu}\frac{dp}{dx}. \quad (4.5)\] + +With the average flow speed is expressed as + +\[u_{ave} = \frac{Q}{S}\sim -\frac{h^{2} + 3bh}{3\mu}\frac{dp}{dx}. \quad (4.6)\] + +According to the IBFW hypothesis and the MD results, the precursor film ahead of the propagation bulk film has a thickness comparable with the size of the ion pairs of the IL, in our case the [EMIM][DCA] pair namely. An appropriate estimation for \(h_{min}\) is taken as \(6\times\) \(10^{- 10} m\) , and the excess disjoining pressure of the precursor film serves as the driving force with the interface curvature induced capillary pressure serving as the resisting force, which gives a rough estimation for the pressure gradient \((\Pi (h)\ll \Pi (h_{min})\) and is omitted) + +\[\frac{dp}{dx}\sim \frac{\Delta p}{\Delta x} = \frac{\Pi(h_{min}) - \gamma\kappa}{L} = \frac{\left[-\left(\frac{A_{SI} - A_{II}l'}{6\pi h_{min}^3} - s_p\exp \left(\frac{d_{min} - h_{min}}{l}\right) - 8c_{IL}\cdot h_{min}^7\right) - \gamma\kappa}{L}\right]}{L} \quad (4.7)\] + +Where \(s_{p}\) is the polar component of the spreading coefficient, \(d_{min}\) is the atomic cut- off distance, \(l\) is the correlation length, \(c_{IL}\) is the strength Born repulsion. The result from Note S5 is employed. + +A rudimental estimation for the average flow speed i.e. the mesoscopic propagation speed of IBFW liquid film can be expressed as a function of the length of the flow pattern, the flow speed decreases monotonically with the increase of flow length: + +\[U\sim u_{ave} = \frac{h^2 + 3bh}{3\mu}\cdot \frac{\Pi(h_{min}) - \gamma\kappa}{L}. \quad (4.8)\] + +(Page S10- 11, Supplementary) + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current 1 pA, dwell time 10 \(\mu \mathrm{s}\) , spacing 1 nm. The change width experiments are conducted with rectangular pattern of scan spots with constant length 20 \(\mu \mathrm{m}\) and different width, while keeping the beam current beam current 1 pA, dwell time 2 \(\mu \mathrm{s}\) , spacing 1 nm constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths58,59, the deep blue line is the calculation result employing average slip length58.
+ +(Page 22, Main text) + +Comment #4: Based on the previous MD simulation, the molecular slip happens on even smooth surface. Did the authors measure the slip on their sample pairs using MD? Because the precursor film is assumed to be 0.6 nm, the molecular slip can generate significant effect on the IL motion. This may explain the the discrepancy of flow velocity between the experiments and theory. + +Response: We sincerely thank the reviewer for this important insight. We have accordingly modified the flow model to slip boundary, and adopted the experimental slip length range from literatures (Ref. [58- 60]). The boundary slip lengths of ILs are typically around several to tens of nanometers as reported in literatures (Ref. [58, 59]). The exact value of slip length depends strongly on the combined surface conditions including: surface roughness, surface potential and specific surface treatments. For our film system with thickness down to nanometer scale, the slip length greatly improves the calculated flow velocity at constant driving force, and agrees with our experiment results better (main text Fig. 2h). The formation of the 0.6 nm precursor film is related to the significant ion emission processes in current model, and we did not include it into the flow modeling. The discrepancy at long film length in Fig. 2h may be + +<--- Page Split ---> + +due to the HFIB irradiation history. The fabrication of film with hundreds of \(\mu \mathrm{m}\) length usually takes hours of HFIB irradiation, and the accumulated positive charges lead to a higher surface potential and a boundary slip length that exceeds the upper limit in literature, which give rise to an unexpected higher film speed. + +We also added an illustration of the two different flow velocity measurement methods adopted in our IBFW experiment according to other Reviewer's comments, with more data measured. Which can be found in main text and Fig.2h. To help illustrate our velocity measurement, we added Supplementary Fig. 14. The modification of the liquid flow model has been quoted in our response to Comment #3 and will not be quoted repeatedly. + +"We next verify that the disjoining pressure propels and stabilizes the nanofilm. The propagation speed of IBFW liquid film decreases monotonically with the increase of film length: + +\[U\sim \frac{h^2 + 3bh}{3\mu}\cdot \frac{\Pi(h_{min}) - \gamma\kappa}{L}. \quad (4)\] + +Where \(U\) is the average flow speed, \(h\) is equilibrium film thickness, \(b\) is the slip length of \(\mathrm{IL - }\) \(\mathrm{SiO_2}\) interface \(^{58,59}\) , \(\mu\) is IL viscosity, \(\Pi (h_{min})\) is disjoining pressure at minimum film thickness \(h_{min}\) , \(L\) is film length, \(\gamma\) is IL surface tension, and \(\kappa\) is curvature of IL- vacuum interface at the conjunction of film and reservoir (Supplementary Table. 2, Supplementary Note 4, Supplementary Fig. 13). We depict the calculation results in Fig. 2h. Since the boundary slip length of \(\mathrm{IL - SiO_2}\) interface depends on the surface potential and ranges from \(2\mathrm{nm}\) to over \(16\mathrm{nm}^{59}\) , we employ the lower ( \(2\mathrm{nm}\) ) and upper ( \(16\mathrm{nm}\) ) limits of slip length to give an estimation on the possible range of flow speed in Fig. 2h as the blue shaded region, and the calculation result of average value \(10\mathrm{nm}^{58}\) is shown by the deep blue line. + +The relationship between flow velocity and film length can also be measured experimentally. As shown in Supplementary Fig. 4, the HFIB scans the designed pattern row by row, so the beam speed vertical to the CTL can be calculated as: + +\[v_{beam} = \frac{s_{vertical}}{N_{row}\tau + V_{refresh}}, \quad (5)\] + +Where, \(s_{vertical}\) is the vertical scan spacing, \(N_{row}\) is the number of scan spots in one row, \(\tau\) is the dwell time that HFIB stay at a single spot, \(V_{refresh}\) is a small time ( \(10\mu \mathrm{s}\) ) that NPVE takes to reset the HFIB for next row of scan. If the vertical speed of HFIB exceeds the film velocity, the distance between the scan spot and the liquid film CTL would increases until the scan spot is too far ahead of the film which would cease to flow. The critical interaction distance with given beam parameters can be determined experimentally (Supplementary Fig. 14a). Due to the pronounced impact of dose density on the flow velocity of liquid film (Supplementary Fig. 14b), the flow velocity measurements are conducted under the same dose density by keeping the beam current \(I = 1\) \(pA\) , scan spot spacing \(s = 1\) \(nm\) and dwell time \(\tau = 2\mu \mathrm{s}\) constant and only alter the width of the rectangle pattern. The pattern width controls the \(N_{row}\) and consequently alters the beam vertical speed. By scanning rectangle patterns with same length but different widths outwards from the reservoir CTL, the vertical speed of beam can be changed at constant HFIB dose density. The IBFW film length decreases with the beam speed + +<--- Page Split ---> + +increasing (Supplementary Fig. 14c), and consequently the average flow velocity of films with different length can be measured. The change width measurement results are shown in Fig. 2h by the hollow orange stars. The results of film speed at extremely long film lengths are acquired by first fabricating a long liquid film ( \(300 \mu m \times 10 \mu m\) , \(600 \mu m \times 10 \mu m\) , and \(900 \mu m \times 10 \mu m\) respectively) from the reservoir, then the change width measurements are conducted at the front of the long film. Since the fabrication of extreme long film can be time consuming, these data are only measured once. The other experiments are repeated for at least ten times with the average value and standard error shown in Fig. 2h. + +The shortage of the change- width method is that the NPVE scan pattern assembling limits the maximum velocity the beam can move vertically. To overcome such limitation, we adopt single spot scan method. In which, a line pattern made up by a series of scan spots is used. The scan speed is altered by changing the vertical refresh time between each scan spot, while keeping beam current \(1 \mathrm{pA}\) , dwell time \(10 \mu \mathrm{s}\) and spacing \(1 \mathrm{nm}\) all constant. The dwell time is elongated to compensate the dose density reduction, since the scan area is influenced by neighboring scan spots in a rectangular pattern. All single spot measurements are repeated at least five times. The results of single spot scan are represented by the orange stars in Fig. 2h." + +(Page 7- 8, Main text) + +![](images/Figure_2.jpg) + +
“Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \(1 \mathrm{pA}\) , dwell time \(10 \mu \mathrm{s}\) , spacing \(1 \mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20 \mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1 \mathrm{pA}\) , dwell time \(2 \mu \mathrm{s}\) , spacing \(1 \mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths \(^{58,59}\) , the deep blue line is the calculation result employing the average slip length \(^{58,}\) .”
+ +(Page 24, Main text) + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + + +## "Supplementary Figure 14: Flow speed measurement experiments. + +(a) The single spot scan style in HIM, which scans one-dimensionally along the pattern direction, is applied to analyze the interaction spatial range of a single irradiation spot quantitatively. The critical maximum spacing between neighbor scan spots to induce liquid flow, \(\mathbf{s}_{\mathrm{c}}\) , represents the upper limit for the interaction spatial range of the beam spot. When scan spot spacing exceed \(\mathbf{s}_{\mathrm{c}}\) , HFIB fails to induce continuous flow however large the dose is. The injection dose density, D, is regulated by changing beam current, I, at constant dwell time 100 \(\mu \mathrm{s}\) , or changing dwell time, \(\tau\) , at constant beam current 0.7 pA. The relationship between sc and D of each beam spot is plotted. (b) Maximal flow velocity as a function of the beam current I for a 20 \(\mu \mathrm{m}\) length rectangle pattern. The scan speed is changed by the pattern width. The flow speed increases with increasing beam current at same dwell time, 5 \(\mu \mathrm{s}\) , and spacing, 1 nm. (c) An example of the change width method for the measurements of flow velocity at different film length." + +(Page S31, Supplementary) + +Comment #5: What are effects of temperature gradient and evaporation on the present technique? + +Comment #5: What are effects of temperature gradient and evaporation on the present technique?Response: We thank the reviewer for the inspiring question. Temperature gradients can alter the flow of IL by Marangoni effect or evaporation- absorption effect. In our cases, the temperature gradient and evaporation induced by the HFIB are insignificant. We investigated the heating effect and the Marangoni effect of He ion beam on IL liquid by employing SRIM software as described in Supplementary Note 1. We find out the temperature difference induced by HFIB is less than 1 K, and the consequent surface tension gradient is not enough to induce liquid flow. Besides, the kinetic energy difference induced by this heating is \(k_{b}\Delta T < 1K \cdot k_{b} = 8.62 \times 10^{-5}eV\) . While the solvation energy of ion pairs in [EMIM][DCA] ionic liquid is 11.62 eV, which is the energy barrier for a single ion to overcome to evaporate from the liquid phase. Consequently, the temperature effect on the evaporation of ions from reservoir is negligible. Also, the ILs are known for their negligible vapor pressure (0.157 Pa at 499 K, the value at room temperature is negligible). Consequently, we believe the effect of temperature and evaporation are irrelevant. + +Nevertheless, temperature is always an important parameter for a liquid film system, and the reviewer's question inspires us to use external heating to explore intensive thermal influence. + +<--- Page Split ---> + +The viscosity of ILs can be lowered by temperature increasing, which may improve the IBFW fabrication efficiency and help this technique be more efficient and practical. We thank the reviewer and we will settle the external heating tests in near future. + +"We also exclude the potential roles played by HFIB induced surface morphological or chemical modification effects and heating effect induced Marangoni flow in Supplementary Note 1, Supplementary Fig. 16, and Supplementary Fig. 17. More details of MD can be found in Supplementary Note 6. Since the temperature increasing effect is less than 1 K based on our calculation. The thermal energy difference, \(k_{b}\Delta T < 1K \cdot k_{b} = 8.62 \times 10^{- 5}eV\) , induced by HFIB is far less than the energy barrier for ions to overcome to evaporate from the liquid phase. Therefore, the evaporation effect may also be insignificant in current experiments." + +(Page 8, Main text) + +<--- Page Split ---> + +## Responses to Reviewer #2 + +This manuscript describes experiments demonstrating a novel way to print ionic liquids on insulating substrates using a He- ion beam writing. To my knowledge results are novel, there importance to the field of controlling liquid flows are hard for me to judge. The explanation of the working principle has several apparent deficiencies. + +There are several remarks I would like to make: + +We thank the reviewer for the comments. + +Comment #1: - The relevance for applications was not entirely clear to me. Several references were cited in the beginning, listing a broad range of applications for "programmable control of fluid motion". But as I understood, the present technique works for ionic liquids only. Thus, I was left wondering what the applications are specific to ionic liquids. That needs to be explained much better. + +Response: We thank the reviewer for the very important suggestion. Accordingly, we have analyzed two specific application fields and carried out demos. First, this Ion Beam induced Film Wetting (IBFW) technology can be useful for the miniaturization of chemical reaction chips. The ionic liquids (ILs) film pattern can serve as the micro flow channel for the aqueous or organic solutions of analytes injected into the IL droplet reservoir since ILs are good solvent for water and organic solutions. With the reagents dissolve and diffuse into the film channel, in- situ chemical reaction can be conducted. Second, IBFW technology can be combined with electrochemistry to transform patterned liquid film into solid materials. The ILs known for wide potential window, low toxicity and thermal stability, can be used as solutions for electrochemical experiments. With patterned liquid film printed to electrode surface, solid materials can be deposited with designed patterns through electrochemical procedures, which is important for nano- circuit manufacture. Adjustments have been made to our manuscript and are listed here. + +1. We modified the introduction to introduce potential application fields suitable for ionic liquids. + +2. We added a new section 'Applications of IBFW' for further demonstration. We used IBFW to fabricate liquid channels as a guidance for aqueous solutions of reagent which were later injected into the IL droplets for the in-situ colorimetric reactions of SCN with various metal ions. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte solutions. + +3. We conducted electrochemical experiments to reveal that IBFW is also capable of transforming liquid film pattern into desired solid materials. Electrochemistry analytes are dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]). The solution droplet was settled on ultra-thin metal film (15 nm) deposited on SiO2 wafer, and film patterns were printed by IBFW. The following electrochemical deposition transforms the liquid pattern into solid materials. Since the stopping range of 30 kV Helium ions exceeds 290 nm, a 15 nm metal film exerts no significant influence on the surface charge injection of HFIB, and consequently the IBFW + +<--- Page Split ---> + +can be conducted on very thin metal film. Monte Carlo simulation results were added to explain the penetrating capability of He ions (Supplementary Fig. 9b). We also discussed the potential influence of electrowetting on the IBFW film, and drew the conclusion that the voltage we adopted won't overcome the contact angel hysteresis and the IBFW films were not influenced by the deposition voltage. + +For now, we only tested Ag nano- particles and AgTCNQ (7,7,8,8- tetracyanoquinodimethane) complex, but more electrochemistry tests can be undertaken to test the capability of solid deposition of both organic and inorganic materials. + +"Based on the IBFW inducing mode, we develop a nano- printing technique of ILs, with film thickness down to \(20 \sim 30 \mathrm{~nm}\) , minimal line width about \(100 \mathrm{~nm}\) and corner radius down to \(20 \mathrm{~nm}\) , and compare its performances with the reported methods. Besides, ILs are also known for their unique properties such as wide electrochemical potential window, high ionic conductivity, low toxicity and thermostability. These features make ILs increasingly important as electrolytes for lithium battery \(^{40,41}\) and electrodepositions of various materials ranging from metal nanoparticles \(^{42,43}\) , metal organic complexes \(^{44}\) to conducting polymer films \(^{45}\) . We further demonstrate the IBFW as a versatile tool for various application fields including gas sensing circuit, in- situ chemical reaction chip, and electrochemical deposition of solid materials with desired patterns. The simplicity and versatility of IBFW technique suggests prospect in a range of liquid manipulation applications. By combining with electrochemical procedures, such technique can not only produce patterned liquid film but also solid materials which reveals possibility in nano- transistors fabrication \(^{46}\) , energy devices \(^{40}\) and immunosensor circuit printing \(^{47}\) . We expect this technique can open a new avenue for applications in nano- printing and nano- circuit manufacturing." + +(Page 2- 3, Main text) + +## "Applications of IBFW + +As discussed previously, IL film pattern prepared by IBFW technology manifests three distinguishable features. First, the ultralow film thickness down to \(30 \mathrm{~nm}\) indicates a high surface- volume ratio which is a key role in improving the gas sensing circuit sensitivity. Second, the capability of fabricating liquid film with desired pattern in a programmable and rewritable manner, which is important for in- situ chemical reaction and microfluidics chips. Third, the ILs are widely used in electrochemistry and reveal the possibility of transforming liquid film pattern into various solid materials ranges from organic to inorganic compounds." + +(Page 9, Main text) + +"To demonstrate the potential of IBFW for microfluidics chip fabrication, we design an in- situ chemical reaction micro- chip. In Fig. 4c, the schematics shows a crosshair shaped micro fluid channel connects four separated droplets in four directions. Four square expansion windows are made on each part of the channel for the convenience of observation. The top- left inset shows the chip with four droplets on finger- tip. After the IBFW fabrications, \(0.1 \mu \mathrm{L}\) of sodium thiocyanate solution (NaSCN \(0.1 \mathrm{M}\) in deionized water) is injected into the top droplet, and serves as the colorimetric reagent for the detection of and in- situ reaction with different metal ions. After the injection of NaSCN, \(0.1 \mu \mathrm{L}\) of \(0.1 \mathrm{mM} \mathrm{Fe}^{3 + }\) solution, \(0.1 \mathrm{mM} \mathrm{Cu}^{2 + }\) solution and + +<--- Page Split ---> + +\(0.1\mathrm{mM}\mathrm{Co}^{2 + }\) are injected into the bottom, left and right droplets respectively. The microchip is rested in atmosphere for \(20\mathrm{min}\) for the metal ions fully diffuse into the channels and react with \(\mathrm{SCN}^{- }\) within different square windows with the ion names printed previously. Then the sample is transferred into vacuum chamber for \(48\mathrm{h}\) to diminish the water content in the solution system, which will alter the hydration status of the metal ion complexes and improve the colorimetric visibility. The red complex \(\mathrm{Fe(SCN)_3}\) deposits in the bottom window. The gray deposition in the left window is complex \(\mathrm{Cu(SCN)_2}\) . And the blue deposition in the right window is complex \(\mathrm{Co(SCN)_2}\) . As shown in Fig. 4c, the \(\mathrm{SCN}^{- }\) participates into 3 different reactions within several hundreds of micrometers flow channel. The time series pictures are shown in Supplementary Fig. 20, and the liquid film patterns remain unchanged during the experiments which last for over one month. The IBFW fluid channel exhibits great stabilities against vacuum/air transferring, the injection of solutions into droplet reservoir, and gravity. Such behavior demonstrates the robustness of the IBFW liquid film. More importantly, all reagents are dissolved in deionized water then injected into the IL droplets and diffuse into the IL flow channel. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte dissolved in water, ethanol and various molecular liquids due to the amphiphilicity of ILs. Such results greatly broaden the potential application fields for IBFW." + +(Page 10, Main text) + +![](images/Figure_1e.jpg) + +
Figure. 4: (c) In-situ chemical reaction chip. The left part is the schematics of the chip. Crosshair channels connect four droplets which are used to inject reagent water solutions. \(0.1\mu \mathrm{L}\) of \(0.1\mathrm{M}\mathrm{NaSCN}\) , \(0.1\mathrm{mM}\mathrm{Co}^{2 + }\) , \(0.1\mathrm{mM}\mathrm{Fe}^{3 + }\) and \(0.1\mathrm{mM}\mathrm{Cu}^{2 + }\) are injected clockwise into four droplets (top, right, bottom, left). The inset on the top-left compares the size of microchip with fingertip, with red circle shows the four droplets. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for \(48\mathrm{h}\) after the injection, the color of complexes is more obvious with water removed from the system.
+ +(Page 27- 28, Main text) + +<--- Page Split ---> +![](images/Figure_2.jpg) + + +## Supplementary Figure 20: Time series images of in-situ chemical reaction chip. + +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48 h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non-direct physical contact for solution injections. (f) The reaction chip one month after injection (one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. (Page S37, Supplementary) + +(Page S37, Supplementary) + +"Due to their unique properties, ILs have been proved to be an important category of solvent and electrolytes. Here we demonstrate that, by further combining with electrochemical procedure, the IBFW also manifests the capability of transforming liquid film pattern into various solid materials. Fig. 4d shows the schematics of a three- electrode electrochemistry experiment. A droplet of 1- ethyl- 3- methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) serves as the solvent of possible analytes, which are Silver bis (trifluoromethylsulfonyl)imide (Ag[NTf₂]) or a mixture of Ag⁺ and 7,7,8,8- tetracyanoquinodimethane (TCNQ) in our experiments. The liquid film pattern is fabricated by the IBFW technology onto the thin gold electrode and would be subsequently transformed into + +<--- Page Split ---> + +nanoparticles. A \(10 \mathrm{nm}\) Au and \(5 \mathrm{nm}\) Ti film deposited onto \(\mathrm{SiO}_2\) serves as the working electrode and is connected to the workstation by a Pt probe. As revealed by the MC simulation results (Supplementary Fig. 9 b), the He ions with vertical stopping- range exceeds \(290 \mathrm{nm}\) can easily penetrate the \(15 \mathrm{nm}\) metal film and deposit positive charges into the \(300 \mathrm{nm}\) \(\mathrm{SiO}_2\) layer underneath. Therefore, the IBFW can be achieved on an ultra- thin metal film deposited on insulating substrate, and is not contradict with the conclusion that pure conducting substrates lead to the failure of IBFW shown in Fig. 2f. The counter electrode is a Pt probe emerged in IL, and a silver- plated probe serves as a pseudo reference electrode. + +In Fig. 4e, we present an example of solid particles deposited from IBFW liquid film. The upper part shows silver nanoparticles with designed pattern (a \(20 \mu \mathrm{m} \times 3 \mu \mathrm{m}\) channel and PKU letters) potentiostatically deposited at - 0.2 V (vs. Ag) for 180 s onto the gold electrode surface. And the lower part shows blue AgTCNQ particles on gold surface make up a \(50 \mu \mathrm{m} \times 10 \mu \mathrm{m}\) rectangular pattern deposited at - 0.1 V (vs. Ag). Noteworthily, the electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees63. When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al.64, a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards, which is also observed in our experiments. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film. + +Four cycles of cyclic voltammogram (CV) of \(10 \mathrm{mM} \mathrm{Ag}^+\) in IL is shown in Fig. 4f. The reduction peak of \(\mathrm{Ag}^+\) takes place at - 0.29 V (vs. Ag) with the peak current decreases as the scan cycles increases. We believe that the micro litter droplet with limited analyte dissolved lead to such results. The \(\mathrm{Ag}^+\) concentration decreases quickly after each cycle of CV scan, and the electron transfer is slower for the oxidation of \(\mathrm{Ag}\) metal. In Fig. 4g, we test the CV curves of five scan cycles of IL droplet with \(6 \mathrm{mM} \mathrm{Ag}^+\) and \(5 \mathrm{mM} \mathrm{TCNQ}\) . Two reduction peaks can be distinguished, one at 0.095 V (vs. Ag), and the other at - 0.21 V (vs. Ag). The first peak corresponds to the reduction of \(\mathrm{Ag}^+\) to \(\mathrm{Ag}^0\) (metal)44, and the second peak is related to the formation of \(\mathrm{AgTCNQ}\) complex (solid). Finally, we conceptually validate that IBFW technology is capable of transferring liquid film pattern into various solid materials and reveal the possibilities can be produced by combining IBFW with electrochemical procedures. The three- electrode experiment configuration, example of open- circuit- potential V- t curve and potentiostatic deposit I- t curve are shown in Supplementary Fig. 21. ” + +(Page 10- 11, Main text) + +“As summarized in Fig. 4h, the IBFW technology manifests several intriguing features that can be harnessed for a variety of application fields. The IBFW technique can fabricate patterned ILs film with \(30 \mathrm{nm}\) thickness, \(100 \mathrm{nm}\) spatial resolution and over hundreds of \(\mu \mathrm{m}\) film length on insulating substrates (or coated with conducting metal films with \(10^1 \mathrm{nm}\) thickness). The surface- volume ratio endowed by the nanometer scale thickness can largely enhance the sensitivity of the IBFW film, and can be utilized in gas sensing circuit. The good solubility and biocompatibility of ILs make them suitable for the dissolve of various analytes. + +<--- Page Split ---> + +The IBFW film also exhibits robustness against air environment exposure, gravity, and physical contact to droplet reservoir. Such features reveal that the IBFW film can act as stable flow channel for the analyte solutions injected to the reservoir, and can largely simplify the fabrication procedures of micro/nanofluidic chips. Last but not least, IBFW liquid film with wide potential window can be combined with electrochemical procedures and the patterned liquid film can be transformed into different solid particles. Such results demonstrate the IBFW as a versatile tool for both nanofluidics and liquid/solid materials printing." + +(Page 11, Main text) + +![](images/Figure_2.jpg) + +
Figure 4 (d) The schematics of a three-electrode electrochemistry experiment. A droplet of IL with IBFW liquid film pattern printed onto the working electrode is the solvent for analytes.
+ +<--- Page Split ---> + +10 nm Au and 5 nm Ti deposited to \(300\mathrm{nm}\) TOX \(\mathrm{SiO_2}\) serves as the working electrode, Pt probe and silver- plated probe stuck into the droplet are the counter and pseudo- reference electrodes respectively. (e) An example of the patterned solid particles deposited on Au electrode surface. The upper part shows Ag particles make up a \(20\mu m\times 3\mu m\) rectangular film with PKU letters pattern which are deposited to Au surface at - 0.2 V (vs. Ag). The lower part shows blue AgTCNQ particles make up a \(50\mu m\times 10\mu m\) pattern which are deposited to Au surface at - 0.1 V (vs. Ag). Both are potentiostatically deposited for 180 s. (f) Four cycles of cyclic voltammogram of \(10\mathrm{mMAg^{+}([EMIM][NTf_2])}\) solution. The reduction peak at - 0.295 V (vs. Ag) can be seen, with peak current decreases with cycles. After four cycles, the reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal becomes less obvious. (g) Five cycles of cyclic voltammogram of \(6\mathrm{mM}\) \(\mathrm{Ag^{+}}\) and \(5\mathrm{mM}\) TCNQ ([EMIM][NTf2]) solution. The first reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal at 0.095 V (vs. Ag) can be seen. The \(+300\mathrm{mV}\) shift of Ag reduction peak at present of TCNQ is consistent with literature44. The reduction peak current of Ag reduces quickly and become hard to distinguish as cycle increases. (h) A summary schematic to show the distinct features of IBFW technique, and the potential application fields that are suitable for IBFW. + +(Page 27- 28, Main text) + +![](images/Figure_2.jpg) + + +Supplementary Figure 21: The electrodeposition experiments of AgTCNQ. + +(a) The three-electrode configuration adopted in current work. (b) The green line is the V-t curve of AgTCNQ open circuit potential measurement, which serves as a reference for the subsequent experiments. The purple line is the deposition current vs. time curve of AgTCNQ deposition at constant potential, -0.1 V (vs. Ag). + +(Page S38, Supplementary) + +<--- Page Split ---> + +Comment #2: The fabrication has to be performed in an ultra- high vacuum environment. It was not very clearly stated or studied, what happens to the samples after they are taken out of the HIM and exposed to air, tilting of the chip (gravity pulling in another direction), static charges, mechanical contact or other environmental variables. Common sense picture of liquids gives the impression that the "circuit" is not very stable. If it is, data needs to be provided to convince the reader otherwise. + +## Response: + +We thank the reviewer for the inspiring suggestions. + +IBFW films are stable to the exposure to air environment or transferring between vacuum/air conditions. The in- situ reaction chip presented in Supplementary Fig. 20 proves that the IBFW liquid film is quite stable after exposure to atmosphere, and the transfer between vacuum chamber and air environment repeatedly. The negligible vapor pressure of ionic liquids accounts for its vacuum/air environment stability. The evaporation of ionic liquids at ambient condition is indiscernible and do not suffer from coffee ring effect. The contact line of ionic liquid is pinned by solid substrate and the sample patterns are barely changed for one month in Supplementary Fig. 20. + +IBFW films are stable to gravity. We employed a customized sample holder which can adjust the tilting angle from 0 to \(180^{\circ}\) . The in- situ reaction chip was mounted to the holder with tilting angle settled at \(120^{\circ}\) (inset of Supplementary Fig. 20f), and the reaction chip with IBFW patterns was stored in the sample box for one week. The optical images (Supplementary Fig. 20) show that the IBFW film pattern was barely changed through the experiments. The micronano meter size of liquid film can explain this stability. For liquid film down to nm thickness and micrometer length, the surface tension, disjoining pressure far exceeds the gravity, so turning the chip upside down or tilting dose not influence the film pattern. + +IBFW films are relatively stable at mild static charge conditions. In the electrochemistry measurement, solid patterns were deposited from the liquid film at a relative low bias voltage \((- 0.1 \sim - 0.2 \mathrm{~V})\) see Fig. 4e. Such a result indicates that the IBFW film exhibits relative stability to static charge. The electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees (Ref. [63]). When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al. (Ref. [64]), a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards. Such phenomenon is also observed in our cyclic voltammogram (CV) experiments, where the entire contact line was moved and the IBFW film patterns were destroyed. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film. + +IBFW film cannot remain the same after a direct physical contact of daily subjects, but direct contact to the droplet reservoir does not change the liquid film. In the in- situ reaction chip experiments and the electrochemical experiments, the droplet connected to the liquid film is penetrated by micropump for solution injection or electrode probes. The liquid film remains + +<--- Page Split ---> + +intact through the experiments, and remains barely changed for days. As can be seen from the comparison of microchip optical images and HIM images before and after the injection and reaction (Supplementary Fig. 20). + +IBFW film is vulnerable to a direct exposure to dust or other contaminations. Since the size of the liquid film is small, too much dusts absorbed to the chip surface or the liquid will damage the liquid film. Short time exposure to the atmosphere condition is acceptable. The IBFW samples are stored in a vacuum chamber and are only took out for experiments. + +"As shown in Fig. 4c, the SCN- participates into 3 different reactions within several hundreds of micrometers flow channel. The time series pictures are shown in Supplementary Fig. 20, and the liquid film patterns remain unchanged during the experiments which last for over one month. The IBFW fluid channel exhibits great stabilities against vacuum/air transferring, the injection of solutions into droplet reservoir, and gravity. Such behavior demonstrates the robustness of the IBFW liquid film. More importantly, all reagents are dissolved in deionized water then injected into the IL droplets and diffuse into the IL flow channel. These experiments demonstrate that IBFW liquid film pattern can act as a stable flow channel for later injection of analytes dissolved in water, ethanol, and various molecular liquids due to the amphiphilicity of ILs." + +(Page 10, Main text) + +![](images/Figure_unknown_1.jpg) + + +## Supplementary Figure 20: Time series images of in-situ chemical reaction chip. + +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48 h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes + +<--- Page Split ---> + +become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non- direct physical contact for solution injections. (f) The reaction chip one month after injection (with one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. + +(Page S37, Supplementary) + +"We delineate a system free energy ratio scenario for a liquid film system with unit length/ width and thickness vary from \(1\mathrm{nm}\) to \(4\mathrm{mm}\) in Fig. 3e, and the film thickness and corner radius are compared with published results \(^{16,18,23,24}\) . System free energy composes of the volumetric term (gravity, electrostatic, etc.), the surface tension term, and the disjoining pressure term. The surface tension remains fixed magnitude of \(10^{1} \mathrm{mN} / \mathrm{m}\) , and its contribution to the system is almost constant with the thickness variation. When system size exceeds capillary length, \(\lambda_{\text{capillary}}\) , the volumetric term contributes most of the system free energy. For any system with characteristic length below capillary length, however, the influence of volumetric term (gravity etc.) can be neglected. At millimeter to micrometer range, the surface tension dominates, and the majority of traditional microfluidics methods belong to such region, with the spatial resolution difficult to approach nanoscale." + +(Page 9, Main text) + +"In Fig. 4e, we present an example of solid particles deposited from IBFW liquid film. The upper part shows silver nanoparticles with designed pattern (a \(20 \mu \mathrm{m} \times 3 \mu \mathrm{m}\) channel and PKU letters) potentiostatically deposited at - 0.2 V (vs. Ag) for 180 s onto the gold electrode surface. And the lower part shows blue AgTCNQ particles on gold surface make up a \(50 \mu \mathrm{m} \times 10 \mu \mathrm{m}\) rectangular pattern deposited at - 0.1 V (vs. Ag). Noteworthily, the electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees \(^{63}\) . When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al. \(^{64}\) , a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards, which is also observed in our experiments. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film." + +(Page 11, Main text) + +Comment #3: Some data was provided with different substrates. What about varying the surface treatment, or cleaning? How sensitive is the success of the writing to the cleanliness of the substrate? You say you anneal the substrates at \(320 \mathrm{C}\) in hydrogen flow. Is that to remove organic contaminants? What if you skip the annealing step? Or use oxygen plasma cleaning + +<--- Page Split ---> + +instead? + +## Response: + +Response:We thank the reviewer for the questions. Vary the surface treatment or cleaning procedures does not influence the IBFW experiments as long as the surface cleanliness is guaranteed. The cleanliness of the substrate is crucial for the IBFW experiment. The liquid film is about \(30 \mathrm{nm}\) thick, so any dust or pollutants can easily influence the liquid film. Besides, the Helium ion microscope (HIM) is sensitive to organic pollutants. Therefore, the solid substrate and liquid have to be cleaned thoroughly before transferred into the HIM chamber, to eliminate potential volatile pollutants. The annealing progress is to remove possible organic contaminants under this consideration. Skipping the annealing or other cleaning process may do harm to the instrument, so we did not attempt to do so. We tested with a SUNJUNE oxygen plasma cleaner and achieved the same cleanliness we need and included it into the Methods section. + +## "IBFW experiment + +The fabrication details of the experiments used \(\mathrm{SiO_2}\) wafers are described below. An amorphous \(\mathrm{SiO_2}\) layer with a thickness of approximately \(3\mu \mathrm{m}\) is deposited by plasma- enhanced chemical vapor deposition (PECVD) on a \(500\mu \mathrm{m}\) thickness quartz substrate surface. Prior to the experiment, chips are cleaned with acetone, ethanol, and ultrapure water sequentially with ultrasonication. To remove any surface organic pollutants, the wafers are annealed in a tubing furnace at \(320^{\circ}\mathrm{C}\) with a mixture gas flow of hydrogen and argon for at least 3 hours, a SUNJUNE oxygen plasma cleaner can also fulfill the purpose." + +(Page 11, Main text) + +Comment #4: How do you know that the ions of the ionic liquid stay intact (are not broken down) under the He ion irradiation? Typically, organic compounds (such as resists for example) can be strongly modified (bonds broken etc) with high energy ion beams. + +## Response: + +We thank the reviewer for the important comments. Both ions (EMIM \(^+\) and DCA \(^+\) ) employed are reported to show good radiolytic stability. The imidazolium cations have shown good radiolytic stability due to the aromatic ring can adsorb and relax the radiation energy. The dosage of helium focused ion beam (HFIB) in our IBFW experiments is much smaller than the damage dosage reported in literature \(^{1,2}\) (main text Ref. [79, 80]). The radiolytic stability of imidazolium based ionic liquids under \(\mathrm{He}^{2 + }\) radiation was tested \(^{1}\) . Decompose products \(\mathrm{H}_2\) were measured by NMR with irradiation dose ranges from 2 to \(400 \mathrm{kGy}\) , and no trace of reaction \((< 1\%)\) was detected for \(2 \mathrm{kGy}\) irradiation. The irradiation dosage of Helium ion is \(0.25 \mathrm{Gy}\) during a typical IBFW experiment. For a \(10 \mu \mathrm{m} \times 1 \mu \mathrm{m}\) film pattern with scanned area \(A\) fabricated from a \(1 \mu \mathrm{L}\) IL droplet with \(1 \mathrm{pA}\) beam current \(I\) , \(1 \mu \mathrm{s}\) dwell time \(\tau\) , \(1 \mathrm{nm}\) scan spacing \(s\) , and \(30 \mathrm{kV}\) accelerate voltage \(U\) , the dosage can be calculated as: + +\[D = \frac{I n c i d e n t E n e r g y}{M a s s o f I L} = \frac{U\cdot I\cdot\tau\frac{A}{s^2}}{V\cdot\rho} = \frac{30\times 10^3V\times\frac{10^{-12}C / s}{1.602\times 10^{-19}C / e}\times\frac{10\times 1\mu m^2}{1\times 1n m^2}}{0.001cm^3\times 1.11g / cm^3} = 0.25\frac{J}{kg} = 0.25 G y.\] + +<--- Page Split ---> + +The [EMIM+] adopted in IBFW has a shorter alkyl chain attached to the aromatic ring, so the radiolytic stability of [EMIM+] should be better than the [BMIM+] tested in literature. Therefore, we believe that the cations of imidazolium are intact. + +Anions structures also influence the radiolytic stability. The [DCA+] is the most radiolytic stable anions among all anions2. The stability of a free radical decreases when the hybridization of the carbon goes from sp3 to sp2 to sp. Thus, it is hard to induce cleavage of the C≡N bond of [DCA+] to form ·C=N. + +Besides, the electrochemical results of the Ag(NTF2) and TCNQ were consistent with literatures (main text Ref. [43, 44]), we believe they are not infected by the HFIB irradiation. In summary, the radiolysis effect on our sample can be negligible. + +We plan to conduct a XPS or Raman experiment to verify our idea, but the instrument is not available at the time, we shall conduct it as soon as possible. + +1. Allen, D. et al. An investigation of the radiochemical stability of ionic liquids. Green Chem. 4, 152-158 (2002). + +2. Xue, Z., Qin, L., Jiang, J., Mu, T. & Gao, G. Thermal, electrochemical and radiolytic stabilities of ionic liquids. Phys. Chem. Chem. Phys. 20, 8382-8402 (2018). + +## "Supplementary Note 7: Influence of radiolysis effect in IBFW + +The ILs and the electrochemistry analytes in the main text remain intact through the IBFW experiments. The conclusion is based on the following discussion. + +The imidazolium cations have shown good radiolytic stability. The dosage of HIB in our IBFW experiments is much smaller than the damage dosage reported in literature30,31. The radiolytic stability of imidazolium based ionic liquids under \(\mathrm{He}^{2 + }\) radiation were tested1. Decompose products \(\mathrm{H}_{2}\) were measured by NMR with irradiation dose ranges from 2 to \(400\mathrm{kGy}\) , and no trace of reaction (<1%) was detected for \(2\mathrm{kGy}\) irradiation. The irradiation dosage of Helium ion is 0.25 Gy during a typical IBFW experiment. For a \(10\mu \mathrm{m}\times 1\mu \mathrm{m}\) film pattern with scanned area \(A\) fabricated from a \(1\mu \mathrm{L}\) IL droplet with \(1\mathrm{pA}\) beam current \(I\) , \(1\mu \mathrm{s}\) dwell time \(\tau\) , \(1\mathrm{nm}\) scan spacing \(s\) , and \(30\mathrm{kV}\) accelerate voltage \(U\) , the dosage can be calculated as: + +\[D = \frac{I n c i d e n t E n e r g y}{M a s s o f I L} = \frac{U\cdot I\cdot\frac{A}{s^{2}}}{V\cdot\rho} = \frac{30\times 10^{3}V\times\frac{10^{-12}C / s}{1.602\times 10^{-19}C / e}\times\frac{10\times 1\mu m^{2}}{1\times 1n m^{2}}}{0.001c m^{3}\times 1.11g / c m^{3}} = 0.25\frac{J}{k g} = 0.25 G y.\] + +The [EMIM+] adopted in IBFW has a shorter alkyl chain attached to the aromatic ring, so the radiolytic stability of [EMIM+] should be better than the [BMIM+] tested in literature. Therefore, we believe that the cations of imidazolium are intact. + +Anions structures also influence the radiolytic stability. The [DCA+] is the most radiolytic stable anions among all anions31. The stability of a free radical decreases when the hybridization of the carbon goes from sp3 to sp2 to sp. Thus, it is hard to induce cleavage of the C≡N bond of [DCA+] to form ·C=N. + +Besides, the electrochemical results of the Ag(NTF2) and TCNQ were consistent with literatures (main text Ref. [43, 44]), we believe they are not infected by the HFIB irradiation. In summary, the radiolysis effect on our sample can be negligible." + +(Page S16, Supplementary) + +Comment #5: What sets the "minimal line width" scale of 100 nm? Shouldn't it in principle + +<--- Page Split ---> + +be much narrower, as the He ion beam interaction volume at the surface is very small (Fig S7) (hence its high imaging resolution \(< \mathrm{nm}\) ). + +## Response: + +We thank the reviewer for the important comment. The \(100\mathrm{nm}\) resolution of liquid film is determined by the surface charge injected by the helium focused ion beam (HFIB). The beam spot of HFIB is \(0.5\mathrm{nm}\) , but the He ions interact with the sample atoms and would be diffracted while traveling through the solid materials. Our Monte Carlo simulation results (Supplementary Fig. 9) and Ohya et. al's results (main text Ref. [48]) revealed the Helium ions irradiating \(\mathrm{SiO_2}\) (we also tested \(15\mathrm{nm}\) metal on \(300\mathrm{nm}\mathrm{SiO_2}\) for electrochemistry experiments) substrates have lateral projection length ranges from \(90\mathrm{nm}\) to \(110\mathrm{nm}\) , therefore the positive charges distribute around \(200\mathrm{nm}\) in lateral direction for single injection spot of He ions. The \(100\mathrm{nm}\) range is probably the center region of surface charging that is strong enough to induce ion emission and form liquid film. Consequently, the resolution of IBFW liquid film is \(100\mathrm{nm}\) for the amorphous \(\mathrm{SiO_2}\) substrate in our experiments. Since electron beams can be diffracted more easily than HFIB, the surface charging region induced by electron beam is much larger. As a result, \(5\mathrm{kV}\) electron beam fails to achieve the programmable control of the liquid film. We conducted experiment employing scanning electron microscope (SEM) for comparison. We added an explanation to liquid film resolution and a comparison of the liquid inducing results of HFIB and electron beam in the main text and Supplementary Fig. 8. + +"When HFIB irradiates at or near the CTL of droplet, the Helium ions generate special charges distribution48 in the \(\mathrm{SiO_2}\) substrate, the positive surface charges induce the primary ion emission from the IL reservoir (Fig.2a). HFIB exhibits two distinguishable features compared with electron beam and other ion beams48. Firstly, the divergence of HFIB interacting with solid samples is much smaller than electron beam due to its larger mass49, which lead to a more localized surface charging area and consequently a programmable control over liquid flow (Supplementary Fig. 8). Secondly, HFIB tends to penetrate sample and induce less damaging compared with Gallium beams48. The penetration depth exerts significant influence on IBFW's application potential in electrochemistry field. For example, \(30\mathrm{keV}\) He beams with hundreds nm stopping range can easily penetrate a \(10\mathrm{nm}\) Au and \(5\mathrm{nm}\) Ti electrode deposited on \(\mathrm{SiO_2}\) wafer and induce patterned liquid flow without devastating effect to Au surface (Supplementary Fig. 9), while \(30\mathrm{keV}\) Ga with stopping range less than \(20\mathrm{nm}^{48}\) is hard to penetrate metal films and can easily cause damage to the electrode." + +(Page 4, Main text) + +"Monte Carlo simulation results48 reveal that the lateral projection length of \(30\mathrm{kV}\) He ions irradiated on \(\mathrm{SiO_2}\) (also \(\mathrm{SiO_2}\) with \(10\mathrm{nm}\) Au and \(5\mathrm{nm}\) Ti layers) ranges from \(90\mathrm{nm}\) to \(110\mathrm{nm}\) (Supplementary Fig. 9a,b). The consequent positive charges (ions, holes) distribute over \(10^{2}\mathrm{nm}\) in lateral direction and determine the ion emission and IBFW spatial resolution." + +(Page 4, Main text) + +<--- Page Split ---> +![](images/Figure_4.jpg) + + +Supplementary Figure 8: SEM images of liquid film induced by ion and electron beams. + +(a) 30 keV helium focused ion beam induced liquid film on a SiO2 substrate; (b) 5 keV electron beam induced liquid flow on the identical substrate. The liquid can also be induced to flow from the reservoir, but the flow pattern is out of control. The much more diffractive nature of the electron beam-sample interaction, and the consequent wider surface charges lateral distribution give rise to such results. + +(Page S24, Supplementary) + +<--- Page Split ---> +![](images/Figure_4.jpg) + + +Supplementary Figure 9: The HFIB irradiation interaction with liquid and substrates under experimental conditions. (a) Monte Carlo simulation results of 3000 He ion irradiating a ionic liquid film of 30 nm thickness above silica substrate, the accelerate voltage is 30 keV to reproduce the experimental conditions. The right part is the magnification of He ions' near liquid trajectory lines and spatial distribution. (b) the MC simulation results of He ions with 30 KV irradiate 10 nm Au, 5 nm Ti and 300 nm SiO2. Similar to the results in the previous case, the HFIB can easily penetrate the first 15 nm layers of metal and deposit positive ions into the insulating SiO2 substrate. Such results indicate that IBFW can also be done on insulating substrates with thin film of metal deposited on the surface. The vertical stopping range of He ions exceed 290 nm on both substrates. The lateral projection distances of He ions in both cases range from 90 nm to 110 nm in separated repeated simulations, which agree with the IBFW film resolution 100 nm. (c) the XPS spectra of the same substrate before (black) and after (red) + +<--- Page Split ---> + +the irradiation of HFIB under experimental conditions with insets show the ESEM results of pristine and irradiated area of solid surface. + +(Page S25- 26, Supplementary) + +Comment #6: Related to that, I do not understand the suggested mechanism. In Fig. 2A the local surface charges, induced by the beam current, are located directly under the IL droplet. Yet, in the unnumbered Figure in Note S3 (Electric field driven ion emission calculation), the surface charge is located some distance away from the IL reservoir. Something doesn't match. + +## Response: + +We thank the reviewer for the comment. The two figures illustrate different situations and lead to this mismatch. The IBFW effect can be achieved by set the start scan position right at or near the contact line. As long as the surface charges injected by HFIB is strong enough to induce ion emission and form precursor film, liquid film can be induced. Fig. 2a shows the typical condition in standard IBFW experiments, where HFIB scans right at the contact line to achieve the best patterning performances. The unnumbered figure has been moved to the main text according to Comment #10 and labeled as Fig. 2d. When the start scan position is a bit away from the contact line, the surface charge injected by HFIB is still enough to induce liquid film, but the HFIB dosage required increases with this distance. Fig. 2d illustrates the mechanical balance between the surface tension and the electrostatic force exerted by surface charges located at a distance away from the IL- vacuum interface. + +We have reconstructed the Working principal section, and a more detailed response can be found in the latter response to comments 7- 10. + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Figure 2: Working principle of IBFW nano-printing. (a-c) Schematic of the IBFW working principle. (a) When HFIB irradiates the CTL, the positive surface charging induces the primary anion emission. (b) When HFIB ceases to scan, surface charging dissipates and the emitted anions induce the secondary cation emission. (c) The emitted ions from previous stages form an ultra-thin precursor film, and the consequent disjoining pressure propels and stabilizes liquid film. (d) The mechanical balance between the surface charge density induced electrostatic force and surface tension of IL-vacuum interface. The distance between HFIB scans spot and contact line is \(d\) ; the surface charging uniformly distributes over a region with length scale, \(l_0\) ; the surface-charge-exert electrostatic force and distorts the IL-vacuum interface, balanced by the surface tension \(\gamma\) . (e) Experimental HFIB dosage density to induce IL flow (ions per square of nm) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. (f) IBFW induced liquid film lengths ( \(\mu \mathrm{m}\) ) on substrates with different conductivities. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. (g) Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removement. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. The shaded regions (red) represent the surface injection region with positive charges. (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at
+ +<--- Page Split ---> + +constant beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20\mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1\mathrm{pA}\) , dwell time \(2\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit. The discrepancy at extreme long film length may be due to the HFIB irradiation history. The fabrication of film with hundreds \(\mu \mathrm{m}\) length usually takes hours of HFIB irradiation. The accumulated positive charges lead to a higher surface potential and a boundary slip length that exceeds the upper limit in literature, which give rise to an unexpected higher film speed. + +(Page 22, Main text) + +Comment #7: Eq. (1) cites for example Ref. 46, where some of the terms were introduced. However, in that paper, surface charge density \(Q\) was specifically described as "areal hole density" i.e. describing a positive charge, whereas you seem to assume a negative charge. How can you apply the same equations to these two opposing cases? Why would in your case the negative charge be dominant, (which the authors in Ref 46 assume can be neutralized more easily)? + +Comment #8: - In addition, you should describe already in the main text what each term in Eq (1) describes, and define every variable of the equations of the main text (including Eq (2)). Comment #9: - Shouldn't the electrons of the flood gun be somehow part of the modelling of Eq. (1)? + +Comment #10: To understand Eq (2), the figure from Supplementary Note 3 is required in the main text. + +## Responses to: + +## Comment #7 + +We thank the reviewer for these very important suggestions and questions that inspire us to have a thorough reconsideration of the ion emission model. After carefully reconsideration and further experiments, we believe that the positive charges injected by HFIB induce the primary ion emission, and the equation 1 cited from Ref. [46] is still employed to explain the positive surface charge density. Several reasons change our mind: + +1. The charge carrier lifetime in amorphous \(\mathrm{SiO_2}\) is of \(10\mathrm{ns}\) magnitude (main text Ref. [50, 51]), which means the electrons only survive for \(10\mathrm{ns}\) before recombination with holes and ions. This makes the reabsorb secondary electrons impossible to accumulate and induce ion emission. +2. The secondary electrons (SEs) are reabsorbed by positive surface charge and gather near the surface when the \(\mathrm{SiO_2}\) layer thickness reaches \(300\mathrm{nm}\) . When silicon dioxide thickness is down to \(100\mathrm{nm}\) , no significant SE reabsorption takes place (main text Ref. [48]). This is consistent with our observation of Si wafer with \(100\mathrm{nm}\) thermal oxidized (TOX) \(\mathrm{SiO_2}\) layer (Fig. R1a). The HIM images come from a SE detector with positive bias voltage to + +<--- Page Split ---> + +collect the SEs excited by HFIB. Therefore, if reabsorption of SE takes place, the HIM image of the \(\mathrm{SiO_2}\) would be black. In Fig. R1(a) the \(\mathrm{SiO_2}\) substrate is brighter than IL droplet which is contrary to the results observed on the \(300\mathrm{nm}\) or pure \(\mathrm{SiO_2}\) substrate employed in the manuscript (as shown in main text Fig. 1e). The results confirm that SE reabsorption does not happen on \(100\mathrm{nm}\mathrm{SiO_2}\) substrate. As shown in Fig. R1, we successfully conducted IBFW experiments to induce IL film from liquid reservoir on \(100\mathrm{nm}\mathrm{SiO_2}\) layer oxidized on Si wafer. Since no SE reabsorption happens on this substrate, we believe that not the negative charges but the positive charges account for the ion emission process involved in IBFW. + +![PLACEHOLDER_34_0] + +
Fig. R1: HIM images of IL droplets on \(100\mathrm{nm}\mathrm{SiO_2}\) and the optical image of the same droplets and film
+ +![PLACEHOLDER_34_1] + +
Fig. 1e: The HIM image of IL pattern (brighter part) on PECVD \(\mathrm{SiO_2}\) (the black back ground, the reabsorption of SEs is so strong that the \(\mathrm{SiO_2}\) substrate can barely be observed) is quoted from main text to compare with Fig. R1.
+ +3. According to main text Ref. [48], the electron beam also induces positive surface charges in \(\mathrm{SiO_2}\) . This is due to the Secondary Electron Yield (which means the average number of SEs excited by one incident electron) of electron beam is larger than one, so with one electron injected to the sample more than one electrons are excited out from the sample. + +<--- Page Split ---> + +Therefore, the overall charging effect of electron beam is positive. The electron beam can also induce the flow of ionic liquids (Supplementary Fig. 8), but the film pattern induced by electron beam is out of control. The diffractive nature of electron lead to a much wider surface charge lateral distribution may give rise to such results. + +Based on these results, we have reconstructed the working principal section in our manuscript. The positive surface charges injected by HIM induce the primary ion emission and the IBFW phenomenon. We have also reconducted the MD simulation, using only positive charges injected and removed from the substrate to induce an identical film of ions and the movement of the droplet mass center. The equation we adopted from literature (old [46], now Ref. [54]) that modeling the positive charge of silica by HFIB irradiation is still adopted in our manuscript. + +Comment #8 - In addition, you should describe already in the main text what each term in Eq (1) describes, and define every variable of the equations of the main text (including Eq (2)). We expanded the working principal section so that every term of the equations in main text have been explained. + +Comment #9- Shouldn't the electrons of the flood gun be somehow part of the modelling of Eq. (1)? + +There are two reasons we did not include the flood gun current into calculation: + +1. The flood gun can only work after the HFIB finishes an entire row (or entire frame) of scan spots and is always turned off during the HFIB irradiation, with a small beam current 0.5 pA. The NPVE scan spots array usually composes \(1024 \times 1024\) scan spots, so the injection dosage of HFIB exceeds the flood gun at least three to six orders of magnitude. +2. The ion emission model considers HFIB scans a single spot or a very small area near the contact line to induce ion emission, the flood gun most likely is not working under such conditions. + +Comment #10: To understand Eq (2), the figure from Supplementary Note 3 is required in the main text. + +We have added the figure to the main text, and labeled as Fig. 2d. + +## "Working Principles of IBFW + +When HFIB irradiates at or near the CTL of droplet, the Helium ions generate special charges distribution48 in the \(\mathrm{SiO}_2\) substrate, the positive surface charges induce the primary ion emission from the IL reservoir (Fig.2a). HFIB exhibits two distinguishable features compared with electron beam and other ion beams48. Firstly, the divergence of HFIB interacting with solid samples is much smaller than electron beam due to its larger mass49, which lead to a more localized surface charging area and consequently a programmable control over liquid flow (Supplementary Fig. 8). Secondly, HFIB tends to penetrate sample and induce less damaging compared with Gallium beams48. The penetration depth exerts significant influence on IBFW's application potential in electrochemistry field. For example, \(30 \mathrm{keV}\) He beams with hundreds nm stopping range can easily penetrate a \(10 \mathrm{nm}\) Au electrode deposited on \(\mathrm{SiO}_2\) wafer and induce patterned liquid flow without devastating effect to Au surface (Supplementary Fig. 9), while \(30 \mathrm{keV}\) Ga with stopping range less than \(20 \mathrm{nm}\)48 is hard to penetrate metal films and can + +<--- Page Split ---> + +easily cause damage to the electrode. During the HFIB irradiation, He ions interact with solid atoms and excite holes- electrons in the sample, then the He ions lose kinetic energy and rest within the stopping range. Since the excited electrons in amorphous \(\mathrm{SiO_2}\) only survive \(10\mathrm{ns}\) or less before the recombination takes place \(^{50,51}\) , the positive charges dominate the surface charging and account for the primary anion emission. Monte Carlo simulation results \(^{48}\) reveal that the lateral projection length of \(30\mathrm{kV}\) He ions irradiated on \(\mathrm{SiO_2}\) (also \(\mathrm{SiO_2}\) with \(10\mathrm{nm}\) Au and \(5\mathrm{nm}\) Ti layers) ranges from \(90\mathrm{nm}\) to \(110\mathrm{nm}\) (Supplementary Fig. 9a,b). The consequent positive charges (ions, holes) distribute over \(10^{2}\mathrm{nm}\) in lateral direction and determine the ion emission and IBFW spatial resolution. + +When the HFIB ceases to irradiate, the surface charges dissipate due to the drainage current and the electron- hole recombination (Fig. 2b) then the emitted anions induce the secondary cation emission. Both ions meet ahead of the CTL and form an ultra- thin precursor film with thickness comparable to ion size at the irradiated area. As a matter of fact, when the electric field of surface charge is strong enough, not only separate ions but clusters or even tiny droplets contain both ions are emitted \(^{52}\) to scanned area and make up the precursor films. In both cases, the ultralow thickness of precursor film gives rise to the high disjoining pressure \((10^{5 - 6}\mathrm{Pa})\) that irrigates and thickens the precursor film until be balanced by the capillary force \((10^{2 - 3}\mathrm{Pa})\) and a continuous liquid film is formed (Fig. 2c). + +The surface charging process of dielectric materials ( \(\mathrm{SiO_2}\) for example) under the irradiation of focus ion beams ( \(\mathrm{Ga}^+\) or \(\mathrm{He}^+\) ) was thoroughly discussed in literatures \(^{53 - 55}\) , and the charging accumulation and dissipation is manipulated by the following factors: (1) generation of electron- hole pairs in the solid by incident ions; (2) neutralization of the incident ions by the excited free electrons; (3) sputtering of the surface atoms; (4) charging due to the secondary ion- electron emission; (5) leakage of mobile electron- hole pairs to the silicon substrate; (6) induced shallow traps by the incident ions and a consequent preferred trapping relative to the deep traps. The surface charge density (SCD) of \(\mathrm{SiO_2}\) at HFIB irradiation \(^{54}\) can be expressed as a function of time (Supplementary Note 2): + +\[\frac{dQ(t)}{dt} = P(1 + \gamma_{e})\cdot I(t) - k\frac{Q(t)}{\epsilon_{r}\epsilon_{0}} -\frac{7}{4} Y I(t)\cdot \Omega_{0}\frac{Q(t)}{R_{p}} -\int_{0}^{t}J(t)dt \quad (1)\] + +(1) + +The RHS composes of 4 terms. The first is the ion incident term which represents the electron- hole pairs accumulation induced by the ion incident and secondary emission, where \(P\) is the probability factor accounts for the electron- hole recombination, \(\gamma_{e}\) is the secondary electron emission yield of \(\mathrm{SiO_2}\) , and \(I(t)\) is the beam current density of HFIB. The second term is the leakage current term, where \(k\) is the conductivity of the substrate, \(\epsilon_{r}\) is the substrate relative permittivity, and \(\epsilon_{0}\) is the vacuum permittivity constant. The third term is the sputtering yield induced charge reduction, where \(Y\) is the sputtering yield acquired from SRIM simulation, \(\Omega_{0}\) is the atomic volume which can be estimated by the average density of \(\mathrm{SiO_2}\) , \(R_{p}\) is the ions stopping range from SRIM. The last term accounts for the accumulation of emitted counterions, where \(J(t)\) is the ion emission rate at current SCD, which is often described as a kinetic process in which ions evaporate from liquid- vacuum interface. The emission current density reads \(^{56}\) : + +\[j_{e} = \frac{k_{B}T}{h}\sigma \exp \left(-\frac{\Delta G - G(E_{k}^{n})}{k_{B}T}\right), \quad (2)\] + +<--- Page Split ---> + +where \(j_{e}\) is the current emitted per unit IL- vacuum surface area, \(k_{B}\) is Boltzmann's constant, \(T\) is the liquid temperature, \(h\) is Planck's constant, \(\sigma\) is the local net charge density at the liquid- vacuum interface, \(\Delta G\) is the Gibbs free energy barrier for an ion to be emitted, \(E_{n}^{\nu}\) is the local vacuum electric field normal to the interface. \(G(E_{n}^{\nu})\) is the reduction of solvation energy barrier due to the external electric field, assumed to take the form \(G(E_{n}^{\nu}) = \sqrt{\frac{q^{3}E_{n}^{\nu}}{4\pi\epsilon_{0}}\frac{\epsilon_{r} - 1}{\epsilon_{r} + 1}}\) by the Schottky hump, where \(\mathbf{q}\) is the ion's charge. The solvation energy of emitted ion can be estimated by the Born model as \(\Delta G = \left(\frac{27}{4}\pi\right)^{1 / 3}\frac{\gamma^{1 / 3}}{(4\pi\epsilon_{0})^{2 / 3}}\frac{q^{4 / 3}(1 - \epsilon_{r})^{2 / 3}}{(4\pi\epsilon_{0})^{2 / 3}}\) , where \(\gamma\) is the liquid vacuum surface tension. Adopting the mechanical model proposed in the following paragraph, the electric field of SCD, \(E_{n}^{\nu}\) , can help to calculate the ion emission rate and the SCD. + +A schematic diagram is shown in Fig. 2d to model the mechanical balance between IL surface tension and the electrostatic force exerted by the surface charge. The IL- vacuum surface is distorted by the electric field and forms a bumping meniscus. When the meniscus is distorted to be hemispherical, the vertical component of surface tension reaches maximum. Once the surface charge continues to increase, a significant ion emission would take place during which both ions, clusters and tiny droplets may emit from the interface \(^{52,56,57}\) . The distance between the scan spot (center of surface charge) and the contact line ranges from \(10^{0}\) to \(10^{2}\) nm, as long as the surface charge is strong enough to induce ion emission. The critical SCD that can induce significant ion emission depends on the distance between the scan spot and the reservoir CTL (more detailed deduction can be found in Supplementary Note 3): + +\[Q_{surf} \cong \frac{(d + r^{*})^{2} + l_{0}(d + r^{*})}{k_{0}cos^{3}\alpha} E^{*}\] + +(3) + +Where \(d\) is the distance between the scan spot and the CTL; \(r^{*} = \frac{q^{6}\gamma}{4\pi^{2}\epsilon_{0}^{3}(\Delta G)^{4}} \sim 10^{-8}m\) is the characteristic ion emission radius derived in literature \(^{52}\) ; \(l_{0}\) is the surface charging area length scale, which represents the lateral distribution of positive surface charges \(^{48}\) ; \(k_{0}\) is the Coulomb constant; \(\alpha\) is the ion emission angle as depicted in Fig. 2d; and \(E^{*} \sim 10^{9 - 11}V / m\) is the characteristic electric field \(^{56}\) for significant ion emission. At given separation distance \(d\) , the critical SCD can be calculated by equation 3. By invoking equations 1 and 2, the dosage of HFIB required for the critical SCD can be calculated." + +(Page 4- 6, Main text) + +<--- Page Split ---> +![PLACEHOLDER_38_0] + +
Figure 2: Working principle of IBFW nano-printing. (a-c) Schematic of the IBFW working principle. (a) When HFIB irradiates the CTL, the positive surface charging induces the primary anion emission. (b) When HFIB ceases to scan, surface charging dissipates and the emitted anions induce the secondary cation emission. (c) The emitted ions from previous stages form an ultra-thin precursor film, and the consequent disjoining pressure propels and stabilizes liquid film. (d) The mechanical balance between the surface charge density induced electrostatic force and the surface tension of IL-vacuum interface. The distance between HFIB scans spot and contact line is \(d\) ; the surface charging uniformly distributes over a region with length scale, \(l_0\) ; the surface-charge-exert electrostatic force and distorts the IL-vacuum interface, balanced by the surface \(\gamma\) ; \(\alpha\) is the angle between substrate the connection line of SCD center and ion emission center; \(r^*\) is the ion emission critical radius, and is also the vertical distance between ion emission center and substrate. (e) Experimental HFIB dosage density to induce IL flow (ions per square of nm) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. (f) IBFW induced liquid film lengths ( \(\mu \mathrm{m}\) ) on substrates with different conductivities. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. (g) Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removement. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. The shaded regions (red)
+ +<--- Page Split ---> + +represent the surface injection region with positive charges. (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20\mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1\mathrm{pA}\) , dwell time \(2\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit. + +(Page 22- 23, Main text) + +"The influence of substrate conductivity over ion emission and IBFW film inducing is clear. There are two reasons we did not include the flood gun current into calculation: + +1. The flood gun can only work after the HFIB finishes an entire row (or entire frame) of scan spots. The NPVE scan spots array usually composes \(1024 \times 1024\) scan spots, so the injection dosage of HFIB exceeds the flood gun three to six orders of magnitude. + +2. The ion emission model considers HFIB scans a single spot or a very small area near the contact lien to induce ion emission, the flood gun most likely is not working under such conditions." + +(Page S7, Supplementary) + +Comment #11: How did you measure the experimental surface charge density of Fig. 2 D? Could you experimentally determine the sign of the charge? If you used Eq (1), how is that an "experimental" result? + +Response: We thank the reviewer for the questions and comments. The experimental surface charge density (SCD) in Fig. 2d was the critical HFIB injection dose density that takes to induce consecutive liquid film from the reservoir. We corrected this mistake, and recalculated the critical HFIB dose density to induce significant ion emission to compare with our experimental result. The experiments were conducted with beam current \(1\mathrm{pA}\) and scan spacing \(1\mathrm{nm}\) , and the dwell time was used to adjust the irradiation dose density which can be directly calculated: \(D_{\text{experiment}} = I \cdot \tau \cdot s^{- 2}\) . Where \(I\) is beam current, \(\tau\) is dwell time and \(s\) is scan spacing. To compare with the experimental dose density, we employ equation 3, \(Q_{\text{surf}} \cong \frac{(d + r^*)^2 + l_0(d + r^*)}{k_0 \cos^3 \alpha} E^*\) , to calculate the critical surface charge density at different distance \(d\) + +between scan spot and contact line. Invoking equation 1, \(\frac{dQ(t)}{dt} = P(1 + \gamma_e) \cdot I(t) - \sigma \frac{Q(t)}{\epsilon_r \epsilon_0} - \frac{7}{4} Y I(t) \cdot \Omega_0 \frac{Q(t)}{R_p} - \int_0^t J(t)dt\) , we can calculate the dwell time and the dose density it takes to reach the critical surface charge densities at given distance \(d\) . We corrected the words and terms we used in the main text and changed Fig. 2f to compare the calculated dose density with the experiment dose density. + +The measurement of sign of charge within the HIM chamber with the Helium ion source powering on is risky. We demonstrated experimentally in Figure R1 that the reabsorbed SE is not the driving force of IBFW, and positive charges of dielectric materials at the irradiation of Helium ion beam is well accepted. Therefore, we did not conduct further experiment to test the + +<--- Page Split ---> + +sign of charge. + +"At given separation distance \(d\) , the critical SCD can be calculated by equation 3. By invoking equations 1 and 2, the dosage of HFIB required for the critical SCD can be acquired. + +The relationship between critical HFIB dose density to induce IBFW, and the distance between starting scan spot and droplet CTL, \(d\) , is calculated employing equations 1 to 3 with the results depicted in Fig. 2e by blue line. The beam current employed in calculation is \(1\mathrm{pA}\) , scan spacing is \(1\mathrm{nm}\) , and the dwell time determines the calculated dose density. Here, we assume that the critical dose density that takes to induce significant ion emission coincides with the dose to achieve IBFW. The experiments are conducted to measure the critical HFIB dose density with \(1\mathrm{pA}\) beam current and \(1\mathrm{nm}\) spacing to induce continuous liquid film from reservoir with the results shown in Fig. 2e by orange rhombuses. The calculation results agree with the experimental critical dose density qualitatively, and confirm our hypothesis that the surface charging induced ion emission accounts for the IBFW." + +(Page 6, Main text) + +![PLACEHOLDER_40_0] + +
Figure 2 (e) Experimental HFIB dosage density to induce IL flow (ions/nm²) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b.
+ +(Page 22, Main text) + +Comment #12: "The qualitative consistency ... verifies the mechanism we propose." Big statement, considering that you refer to Fig. 2E where the agreement is NOT good. (i.e. modelling doesn't predict at all differences between different insulating substrates) + +Response: We thank the reviewer for the comments. The 'qualitative consistency' just means + +<--- Page Split ---> + +that our crude model can distinguish insulating, semi conductive and conducting substrates. The ion emission model we proposed fails to explain the differences between different insulating substrates due to other factors that have not been considered in our model. For example, the solid surface roughness elements distort the contact line and the IL- vacuum interface. The distorted interface with different curvature can influence the ion emission energy barrier (main text Ref. [68]). Therefore, we discovered in experiments that at some positions of CTL, film can be easily produced, while some other positions of the same droplet cannot. This is one of the possible reasons that lead to the different behavior of different insulating material substrates. We changed the words we used in the main text, and explained the shortage of our model in the Supplementary Note 3. Currently, our simplified models cannot distinguish different insulating materials, where some factors may have not included. + +"The orange rectangles represent the lengths of liquid film that can be induced on different substrates under identical HFIB treatment. IL film cannot be induced on pure conducting samples such as Au and Cu, liquid extends slightly on semiconductor (Si), whereas liquid film propagates a long distance on insulated substrates e.g., quartz and mica. Employing equations 1- 3, we can calculate the numbers of emitted ions during a single spot scan of HFIB (Supplementary Note 2, Supplementary Fig. 10), and is depicted in Fig. 2f as blue circles. As can be seen, the ion emission model we propose herein can qualitatively explain the different effects of IBFW on conducting, semi- conducting and insulating substrates. Yet the IBFW effect is also influenced by other substrate situations (roughness, for example), and the differences between various insulated substrates are failed to be captured by the simplified 2D model." + +(Page 6, Main text) + +"The solvation energy of emitted ion can be estimated by the Born model as \(\Delta G = \left(\frac{27}{4}\pi\right)^{1 / 3}\gamma^{1 / 3}q^{4 / 3}\frac{(1 - \epsilon_r)^{2 / 3}}{(4\pi\epsilon_0)^{2 / 3}}\) , where \(\gamma\) is the liquid - vacuum surface tension. Noteworthily, the ion emission energy barrier can be altered significantly by the local curvature of the IL- vacuum surface \(^{25}\) , but we consider a simple 2- dimensional model in current work and exclude this factor. Such influence should be considered to explain the different performances of IBFW at the CTL of the same liquid reservoir in the future." + +(Page S9- 10, Supplementary) + +Comment #13: "The relationship between flow velocity and film length can also be measured experimentally". I don't understand how you can measure the flow velocity in your experimental setting. + +Response: We thank the reviewer for the important comments. Two methods were adopted to measure the flow velocity, and are illustrated here: + +The HFIB scans the designed pattern row by row, so the beam speed vertical to the CTL can be calculated as: + +\[v_{beam} = \frac{s_{vertical}}{N_{row}\tau + V_{refresh}}, \quad (5)\] + +Where, \(s_{vertical}\) is the vertical scan spacing, \(N_{row}\) is the number of scan spots in one row, \(\tau\) + +<--- Page Split ---> + +is the dwell time that HFIB stay at a single spot, \(V_{refresh}\) is a small time (10 \(\mu \mathrm{s}\) ) that software takes to reset the HFIB ready for the next row of scan. If the vertical speed of HFIB exceeds the film velocity, the distance between the scan spot and the liquid film CTL would increases until the scan spot is too far ahead of the film and the liquid would cease to flow. The critical interaction distance with given beam parameters can be determined experimentally (Supplementary Fig. 14a). Due to the pronounced impact of dose density on the flow velocity of liquid film (Supplementary Fig. 14b), the flow velocity measurements are conducted under the same dose density by keeping the beam current \(I = 1\) \(pA\) , scan spot spacing \(s = 1\) \(nm\) and dwell time \(\tau = 2\) \(\mu \mathrm{s}\) constant and only alter the width of the rectangle pattern. The pattern width controls the \(N_{row}\) and consequently alters the beam vertical speed. By scanning rectangle patterns with same length but different widths outwards from the reservoir CTL, the vertical speed of beam can be changed at constant HFIB dose density. The IBFW film length decreases with the beam speed increasing (Supplementary Fig. 14c), and consequently the average flow velocity of films with different length can be measured. The change width measurement results are shown in Fig. 2b by the hollow orange stars. The results of film speed at extremely long film length are acquired by first fabricating a long liquid film (300 \(\mu \mathrm{m} \times 10 \mu \mathrm{m}\) , 600 \(\mu \mathrm{m} \times 10 \mu \mathrm{m}\) , and 900 \(\mu \mathrm{m} \times 10 \mu \mathrm{m}\) respectively) from the reservoir, then the change width measurements are conducted at the front of the long film. Since the fabrication of extreme long film can be time consuming, these data are only measured once. The other experiments are repeated for at least ten times with the average value and standard error shown in Fig. 2h. + +The shortage of the change- width method is that the NPVE scan pattern assembling limits the maximum velocity the beam can move vertically. To overcome such limitation, we adopt single spot scan method. In which, a line pattern made up by a series of scan spots is used. The scan speed is altered by changing the vertical refresh time between each scan spot, while keeping beam current 1 pA, dwell time 10 \(\mu \mathrm{s}\) and spacing 1 nm all constant. The dwell time is elongated to compensate the dose density reduction, since the scan area is influenced by neighboring scan spots in a rectangular pattern. All single spot measurements are repeated at least five times. The results of single spot scan are represented by the orange stars in Fig. 2h. + +Apart from velocity measurement explanation, the flow model is modified by the introduction of boundary slip length of IL- \(\mathrm{SiO_2}\) interface according to other Reviewer's comment. Since the slip length vary from 2 nm to over 16 nm determined by the combined surface conditions (Ref. [58- 60]), the possible flow velocity range is calculated employing the lower and upper limit of IL slip length as shown by the blue region in Fig. 2h. + +"We next verify that the disjoining pressure propels and stabilizes the nanofilm. The propagation speed of IBFW liquid film decreases monotonically with the increase of film length: + +\[U\sim \frac{h^2 + 3bh}{3\mu}\cdot \frac{\Pi(h_{min}) - \gamma\kappa}{L} \quad (4)\] + +Where \(U\) is the average flow speed, \(h\) is equilibrium film thickness, \(b\) is the slip length of IL- \(\mathrm{SiO_2}\) interface \(^{58 - 60}\) , \(\mu\) is IL viscosity, \(\Pi (h_{min})\) is disjoining pressure at minimum film thickness \(h_{min}\) , \(L\) is film length, \(\gamma\) is IL surface tension, and \(\kappa\) is curvature of IL- vacuum interface at the + +<--- Page Split ---> + +conjunction of film and reservoir (Supplementary Table. 2, Supplementary Note 4, Supplementary Fig. 13). We depict the calculation results in Fig. 2h. Since the boundary slip length of IL- \(\mathrm{SiO_2}\) interface depends on the combined surface conditions and ranges from \(2\mathrm{nm}\) to over \(16\mathrm{nm}\) , we employ the lower \((2\mathrm{nm})\) and upper \((16\mathrm{nm})\) limits of slip length to give an estimation on the possible range of flow speed in Fig. 2h as the blue shaded region, and the results of average value \(10\mathrm{nm}^{58}\) is shown by the deep blue line. + +The relationship between flow velocity and film length can also be measured experimentally. As shown in Supplementary Fig. 4, the HFIB scans the designed pattern row by row, so the beam speed vertical to the CTL can be calculated as: + +\[V_{beam} = \frac{S_{vertical}}{N_{row}\tau + V_{refresh}}, \quad (5)\] + +Where, \(S_{vertical}\) is the vertical scan spacing, \(N_{row}\) is the number of scan spots in one row, \(\tau\) is the dwell time that HFIB stay at a single spot, \(V_{refresh}\) is a small time \((10\mu \mathrm{s})\) that NPVE takes to reset the HFIB for next row of scan. If the vertical speed of HFIB exceeds the film velocity, the distance between the scan spot and the liquid film CTL would increases until the scan spot is too far ahead of the film and the liquid would cease to flow. The critical interaction distance with given beam parameters can be determined experimentally (Supplementary Fig. 14a). Due to the pronounced impact of dose density on the flow velocity of liquid film (Supplementary Fig. 14b), the flow velocity measurements are conducted under the same dose density by keeping the beam current \(I = 1\mathrm{pA}\) , scan spot spacing \(s = 1\mathrm{nm}\) and dwell time \(\tau = 2\mu \mathrm{s}\) constant and only alter the width of the rectangle pattern. The pattern width controls the \(N_{row}\) and consequently alters the beam vertical speed. By scanning rectangle patterns with same length but different widths outwards from the reservoir CTL, the vertical speed of beam can be changed at constant HFIB dose density. The IBFW film length decreases with the beam speed increasing (Supplementary Fig. 14c), and consequently the average flow velocity of films with different length can be measured. The change width measurement results are shown in Fig. 2h by the hollow orange stars. The results of film speed at extremely long film lengths are acquired by first fabricating a long liquid film \((300\mu m\times 10\mu m\) , \(600\mu m\times 10\mu m\) , and \(900\mu m\times 10\mu m\) respectively) from the reservoir, then the change width measurements are conducted at the front of the long film. Since the fabrication of extreme long film can be time consuming, these data are only measured once. The other experiments are repeated for at least ten times with the average value and standard error shown in Fig. 2h. + +The shortage of the change- width method is that the NPVE scan pattern assembling limits the maximum velocity the beam can move vertically. To overcome such limitation, we adopt single spot scan method. In which, a line pattern made up by a series of scan spots is used. The scan speed is altered by changing the vertical refresh time between each scan spot, while keeping beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) and spacing \(1\mathrm{nm}\) all constant. The dwell time is elongated to compensate the dose density reduction, since the scan area is influenced by neighboring scan spots in a rectangular pattern. All single spot measurements are repeated at least five times. The results of single spot scan are represented by the orange stars in Fig. 2h. The consistency between the calculation and experiments suggests that disjoining pressure can explain the propagation of IBFW film." + +(Page 7- 8, Main text) + +<--- Page Split ---> +![PLACEHOLDER_44_0] + +
“Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20\mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1\mathrm{pA}\) , dwell time \(2\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths \(^{58,59}\) , the deep blue line is the calculation result employing the average slip length \(^{58}\) .”
+ +![PLACEHOLDER_44_1] + +
(Page 23-24, Main text)
+ +# “Supplementary Figure 14: Flow speed measurement experiments. + +(a) The single-spot scan style in HIM, which scans one-dimensionally along the pattern direction, is applied to analyze the interaction spatial range of a single irradiation spot quantitatively. The critical maximum spacing between neighbor scan spots to induce liquid + +<--- Page Split ---> + +flow, \(\mathbf{s}_{\mathrm{c}}\) , represents the upper limit for the interaction spatial range of the beam spot. When scan spot spacing exceed \(\mathbf{s}_{\mathrm{c}}\) , HFIB fails to induce continuous flow however large the dose is. The injection dose density, D, is regulated by changing beam current, I, at constant dwell time 100 \(\mu \mathrm{s}\) , or changing dwell time, \(\tau\) , at constant beam current 0.7 pA. The relationship between \(\mathbf{s}_{\mathrm{c}}\) and D of each beam spot is plotted. (b) Maximal flow velocity as a function of the beam current I for a \(20\mu \mathrm{m}\) length liquid film. The scan speed is changed by the pattern width. The flow speed increases with increasing beam current at same dwell time 1 \(\mu \mathrm{s}\) . (c) An example of the change width method for the measurements of flow velocity at different film length." + +(Page S31, Supplementary) + +Comment #14: AFM measurements "The liquid- vacuum interface ..." Is the AFM measurement done in vacuum instead of air? + +Response: We thank the reviewer for the question. The AFM measurements were conducted all in atmosphere condition. We have corrected the mistake in the main text. + +"We employ atomic force microscope (AFM) to manifest the nanoscale flow control of IBFW. Fig. 3a shows the front \(7\mu \mathrm{m}\) of a \(28\mu \mathrm{m}\times 1\mu \mathrm{m}\) IL film with thickness around \(30\mathrm{- }40\mathrm{nm}\) (an average of \(35.4\pm 1.7\mathrm{nm}\) ). The film thickness remains unchanged along the flow path (Fig. 3A). The film width is \(1\mu \mathrm{m}\) , coincides with designed pattern. The liquid- air interface is much smoother than solid substrate (RMS roughness \(7.9\pm 5.7\mathrm{nm}\) ). The minimal line width of IBFW film reaches \(106nm\) (Supplementary Fig. 15), and is limited by the surface charges spatial distribution which was reported around \(10^{2}nm^{15}\) . If the surface charges can be trapped within a narrower spatial range, the ideal line width limitation may be comparable with film thickness." + +(Page 8, Main text) + +Comment #15: "The current in nanofilm linearly depends on the humidity". What is the mechanism?? Anyways, it seems the current is not only a function of humidity as it depends directly on time as well based on Fig. S18. How could you disentangle the effect of time from the effect of humidity in a real sensor as some voltage bias history dependence seems to exist (referring to Fig. S18F) + +Response: We thank the reviewer for the important questions. We believe the reaction- diffusion competition differences and the higher adsorption rate endowed by higher surface- volume ratio of nanocircuit leads to the differences in the humidity response curve we measured. For the droplet circuit, the long distance for the water molecules to diffuse to the electrode restricts the reaction rate, therefore, the change of current with humidity is not obvious. Nevertheless, the thin liquid film circuit with much shorter diffusion distance largely accelerate the diffusion process, which is the rate- determining step of current experiment. Moreover, the larger surface- volume ratio benefits the adsorption of the vapor molecules and further improve + +<--- Page Split ---> + +the reaction current. We have expanded the paragraph in main text to further illustrate the mechanism. + +The time dependent current measured in Supplementary Fig. S18 is due to the gathering of counterions to the electrodes to form an electric double layer (EDL) when the voltage is switched on. If the voltage has been switched on for a long time, the EDL at the electrodes- IL interface comes into a thermodynamics equilibrium would electrostatically block the electrode voltage, and no measurable current can be detected. Employing a sensing circuit that has reached equilibrium (with bias voltage turned on for a long time, 1h is more than adequate) will disentangle the time effect. + +The bias history dependence comes from repeatedly switched on and off the voltage, which is another mistake we made during the caption of Supplementary Fig. 18. When bias voltage switched on, counterions gathering to form an EDL and give rise to a current jump. As the EDL developing, the electrode voltage is gradually being blocked and the current decay to near zero until reaches equilibrium. When voltage switched off, the EDL will gradually disappear and return to the initial condition. If the rest time is long enough, the history dependence would disappear. But the rest time in our experiment was too short, and the EDL has not reached equilibrium before the bias voltage is exerted again. When the bias voltage turned on again, the real voltage feels by the IL is actually smaller than the bias voltage we exert since part of the old EDL still absorbed at the electrode surface, which leads to a history dependence in Supplementary Fig. 18f. + +"In Fig. 4a, b and Supplementary Fig. 19, we present a room- humidity- sensing circuit utilizing IBFW technique. The water molecules are adsorbed by the IL then diffuse to and react at the electrode surfaces, generating a reaction current \(I_{\mathrm{ds}}\) . The source- drain currents of a IBFW nanofilm circuit and a micrometer- size droplet circuit are measured within the same chamber with the relative humidity ranging from \(40\%\) to \(70\%\) . The current in nanofilm linearly depends on the humidity, while no significant change can be observed for the micrometer droplet. The competition between the adsorption at liquid- air interface and the diffusion within liquid circuit can explain such differences. For the droplet circuit, the long distance for the water molecules to diffuse to the electrode surface restricts the reaction rate, therefore, the change of current with humidity is not obvious. Nevertheless, the thin liquid film circuit with much shorter diffusion distance and relaxation time largely accelerates the diffusion process, which is the rate- determining step of the current experiment. Moreover, the much higher surface- volume ratio benefits the adsorption of the vapor molecules and further improves the reaction current sensitivity. Both the sensitivity and response speed are greatly enhanced due to the size effect endowed by IBFW nano film. The simple device presented here can manifest the feasibility of the IBFW circuit in sensing circuit manufacturing." + +(Page 9, Main text) + +Comment #16: Fig. 3F use real current units instead of dimensionless and tell what the bias voltage used was. BTW Fig. S18 C has wrong units (A vs nA). Fig. S18G has no caption, what is it? + +Response: We thank the reviewer for the suggestions. We corrected the units to dimensionless + +<--- Page Split ---> + +in Fig. 4b, and the voltage exerted between the two Au electrodes was 1 V. We have corrected the wrong units used in Supplementary Fig. 19 a and b (used to be labeled as Fig. S18). The captions for the previous version of Supplementary Fig. S18 f and g were ambiguous and wrong. Fig. S18 f was the Drain current I-t curve with the source drain voltage, 10 V, switched on and off periodically (turned on 480s, then off 20s) for four times. Fig. S18 g was the Drain current I-t curve with constant source-drain voltage 10 V. Supplementary Fig. 19 has been reconstructed. + +We think part of the old version was irrelevant to illustrate the difference between nano circuit and micro droplet. In current version, Supplementary Fig. 19c is the drain current I-t curve of a droplet circuit and a nano- film circuit in atmosphere and in vacuum chamber at constant source- drain voltage 10 V. Both the droplet circuit and nanofilm circuit have a higher current in atmosphere than in vacuum chamber, this is due to the water molecules adsorbed by the droplet and the film that react at the electrode surface and create a reaction current. The result in vacuum chamber is more intriguing. The adsorption- reaction current has been disentangled, and the current we measured is solely contributed by the formation of electric double layer. As shown by the yellow curve, the EDL formation current curve of nanofilm circuit quickly decreases to be indiscernible, which indicate that the EDL in nanofilm circuit established quickly and reaches an equilibrium. On the contrary, the EDL formation current of droplet circuit decrease much slower, and keep on decreasing at the end of the 300 s measurement, which indicate that the equilibrium is hard to attain in a droplet circuit. Such differences explain that nano film circuit with a much shorter relaxation time is more suitable for gas sensing purpose. Supplementary Fig. 19d is an HIM image of the nanocircuit fabricated. + +![PLACEHOLDER_47_0] + +
Fig. 4 (a,b) Proof-of-concept gas sensing prototype. (a) the IBFW liquid nanofilm connected two droplets of IL settled on two Au electrodes for electrochemistry data collection. (b) Results of IBFW liquid nano-circuit in gas sensing and compared with a micro meter droplet settled between and connects two identical Au electrodes. The inset shows the schematic of a room-humidity sensor based on IBFW fabricated nanofilm. The drainage-source currents of both microdroplet and nanofilm are illustrated and the linear fitting results are depicted as dash lines. The voltage exerted between two electrodes is 1 V. The background color map represents the relative humidity of test chamber ranges from 40% to 70%.
+ +(Page 26- 27, Main text) + +<--- Page Split ---> +![PLACEHOLDER_48_0] + + +Supplementary Figure 19: Volt- Ampere characteristics analysis of IL nano film circuit. (a) Drain current between Au electrodes vs. time, the black line represents an identical measurement with no liquid film connect the electrodes; (b) linear sweep volt- ampere curve of liquid film circuit; (c) The transient current curves of IL film circuit and droplet circuit in high vacuum and in atmospheric environment as a function of time, the source- drain voltage is 10 V. Both the droplet circuit and nanofilm circuit have a higher current in atmosphere than in vacuum chamber, this is due to the water molecules adsorbed by the droplet and the film that react at the electrode surface and create a reaction current. The result in vacuum chamber is more intriguing. The adsorption- reaction current has been disentangled, and the current we measured is solely contributed by the formation of electric double layer. As shown by the yellow curve, the EDL formation current curve of nanofilm circuit quickly decreases to be indiscernible, which indicate that the EDL in nanofilm circuit established quickly and reaches an equilibrium. On the contrary, the EDL formation current of droplet circuit decrease much slower, and keep on decreasing at the end of the 300 s measurement, which indicate that the equilibrium is hard to attain in a droplet circuit. Such differences explain that nano film circuit with a much shorter relaxation time is more suitable for gas sensing purpose. (d) The HIM image of the liquid nano circuit employed in this experiment. + +(Page S36, Supplementary) + +<--- Page Split ---> + +## Responses to Reviewer #3: + +The authors developed a new method to perform rewritable surface printing of ionic liquids. The method relies on the disjoining pressure to induce surface films of nanometer thickness, and utilizes helium ion beams to initiate the flow of liquids and pattern creation. The manuscript comprehensively characterizes and explains the underlying mechanism of this printing process. However, as an application- driven work, the prospect of practical real- world applications is a bit weak. Although the authors demonstrated a sensing device application (Fig. 3F), it only utilizes the nanoscale thickness of the ionic liquid film, and the surface patterning is not very relevant. Specific concerns include: + +Response: We thank the reviewer for the positive comments on our manuscript. + +Comment #1: This method utilizes ionic liquids, and seems hard to extend to other liquid systems due to the high- vacuum requirements of the helium ion microscope. Ionic liquid as of now are still quite expensive, limiting the range of applications. Are there ways to improve or revise the method so that other liquid or even solid structures can also be printed? + +Response: We thank the reviewer for these inspiring suggestions. The liquid working media can be expanded by injection of aqueous or organic solution into the liquid reservoir of the IBFW liquid film. The film pattern can act as a stable flow channel for the solutions injected, we fabricated the in- situ chemical reaction chip to serve as a proof- of- concept prototype. Moreover, the electric field induced Taylor cone and ion emission are ubiquitous for many liquids including water. If an appropriate capsule can be fabricated with windows transparent to ion beams, we believe many other liquids can be employed in IBFW experiments. + +The IBFW liquid film pattern can be electrochemical deposited to be solid particles with designed patterns. We added the 'Applications of IBFW' in the main text to discuss in details. The ILs is more expensive than water or ethanol, but many types of them are still cheap enough for research. The [EMIM][DCA] we used in our experiments were purchased at a price of 24 CNY \(\sim 3\) USD for \(20\mathrm{g}\) . + +We listed the modifications we made to our manuscript that can answer the reviewer's questions. + +1. We modified the introduction to introduce potential application fields suitable for ionic liquids. +2. We added a new section 'Applications of IBFW' for further demonstration. We used IBFW to fabricate liquid channels as a guidance for aqueous solutions of reagent which were later injected into the IL droplets for the in-situ colorimetric reactions of SCN- with various metal ions. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte solutions. +3. We conducted electrochemical experiments to reveal that IBFW is also capable of transforming liquid film pattern into desired solid materials. Electrochemistry analytes are dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]). The solution droplet was settled on ultra-thin metal film (15 nm) + +<--- Page Split ---> + +deposited on \(\mathrm{SiO_2}\) wafer, and film patterns were printed by IBFW. The following electrochemical deposition transforms the liquid patter into solid materials. Since the stopping range of \(30\mathrm{kV}\) Helium ions exceeds \(290\mathrm{nm}\) , a \(15\mathrm{nm}\) metal film exerts no significant influence on the surface charge injection of HFIB, and consequently the IBFW can be conducted on very thin metal film. Monte Carlo simulation results were added to explain the penetrating capability of He ions (Supplementary Fig. 9b). We also discussed the potential influence of electrowetting on the IBFW film, and drew the conclusion that the voltage we adopted won't overcome the contact angel hysteresis and the IBFW films were not influenced by the deposition voltage. + +For now, we only tested Ag nano- particles and AgTCNQ (7,7,8,8- tetracyanoquinodimethane) complex, but more electrochemistry tests can be undertaken to test the capability of solid deposition of both organic and inorganic materials. + +"Based on the IBFW inducing mode, we develop a nano- printing technique of ILs, with film thickness down to \(20 \sim 30 \mathrm{nm}\) , minimal line width about \(100 \mathrm{nm}\) and corner radius down to \(20 \mathrm{nm}\) , and compare its performances with the reported methods. Besides, ILs are also known for their unique properties such as wide electrochemical potential window, high ionic conductivity, low toxicity and thermostability. These features make ILs increasingly important as electrolytes for lithium battery \(^{40,41}\) and electrodepositions of various materials ranging from metal nanoparticles \(^{42,43}\) , metal organic complexes \(^{44}\) to conducting polymer films \(^{45}\) . We further demonstrate the IBFW as a versatile tool for various application fields including gas sensing circuit, in- situ chemical reaction chip, and electrochemical deposition of solid materials with desired patterns. The simplicity and versatility of IBFW technique suggests prospect in a range of liquid manipulation applications. By combining with electrochemical procedures, such technique can not only produce patterned liquid film but also solid materials which reveals possibility in nano- transistors fabrication \(^{46}\) , energy devices \(^{40}\) and immunosensor circuit printing \(^{47}\) . We expect this technique can open a new avenue for applications in nano- printing and nano- circuit manufacturing." + +(Page 2- 3, Main text) + +## "Applications of IBFW + +As discussed previously, IL film pattern prepared by IBFW technology manifests three distinguishable features. First, the ultralow film thickness down to \(30 \mathrm{nm}\) indicates a high surface- volume ratio which is a key role in improving the gas sensing circuit sensitivity. Second, the capability of fabricating liquid film with desired pattern in a programmable and rewritable manner, which is important for in- situ chemical reaction and microfluidics chips. Third, the ILs are widely used in electrochemistry and reveal the possibility of transforming liquid film pattern into various solid materials ranges from organic to inorganic compounds." + +(Page 9, Main text) + +"To demonstrate the potential of IBFW for microfluidics chip fabrication, we design an in- situ chemical reaction micro- chip. In Fig. 4c, the schematics shows a crosshair shaped micro fluid channel connects four separated droplets in four directions. Four square expansion windows are made on each part of the channel for the convenience of observation. The top- left inset + +<--- Page Split ---> + +shows the chip with four droplets on finger- tip. After the IBFW fabrications, \(0.1 \mu \mathrm{L}\) of sodium thiocyanate solution (NaSCN \(0.1 \mathrm{M}\) in deionized water) is injected into the top droplet, and serves as the colorimetric reagent for the detection of and in- situ reaction with different metal ions. After the injection of NaSCN, \(0.1 \mu \mathrm{L}\) of \(0.1 \mathrm{mM} \mathrm{Fe}^{3 + }\) solution, \(0.1 \mathrm{mM} \mathrm{Cu}^{2 + }\) solution and \(0.1 \mathrm{mM} \mathrm{Co}^{2 + }\) are injected into the bottom, left and right droplets respectively. The microchip is rested in atmosphere for 20 min for the metal ions fully diffuse into the channels and react with SCN- within different square windows with the ion names printed previously. Then the sample is transferred into vacuum chamber for \(48 \mathrm{h}\) to diminish the water content in the solution system, which will alter the hydration status of the metal ion complexes and improve the colorimetric visibility. The red complex \(\mathrm{Fe(SCN)_3}\) deposits in the bottom window. The gray deposition in the left window is complex \(\mathrm{Cu(SCN)_2}\) . And the blue deposition in the right window is complex \(\mathrm{Co(SCN)_2}\) . As shown in Fig. 4c, the SCN- participates into 3 different reactions within several hundreds of micrometers flow channel. The time series pictures are shown in Supplementary Fig. 20, and the liquid film patterns remain unchanged during the experiments which last for over one month. The IBFW fluid channel exhibits great stabilities against vacuum/air transferring, the injection of solutions into droplet reservoir, and gravity. Such behavior demonstrates the robustness of the IBFW liquid film. More importantly, all reagents are dissolved in deionized water then injected into the IL droplets and diffuse into the IL flow channel. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte dissolved in water, ethanol and various molecular liquids due to the amphiphilicity of ILs. Such results greatly broaden the potential application fields for IBFW." + +(Page 10, Main text) + +![PLACEHOLDER_51_0] + +
Figure. 4: (c) In-situ chemical reaction chip. The left part is the schematics of the chip. Crosshair channels connect four droplets which are used to inject reagent water solutions. \(0.1 \mu \mathrm{L}\) of \(0.1 \mathrm{M} \mathrm{NaSCN}\) , \(0.1 \mathrm{mM} \mathrm{Co}^{2 + }\) , \(0.1 \mathrm{mM} \mathrm{Fe}^{3 + }\) and \(0.1 \mathrm{mM} \mathrm{Cu}^{2 + }\) are injected clockwise into four droplets (top, right, bottom, left). The inset on the top-left compares the size of microchip with fingertip, with red circle shows the four droplets. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for \(48 \mathrm{h}\) after the injection, the color of complexes is more obvious with water removed from the system.
+ +(Page 27- 28, Main text) + +<--- Page Split ---> +![PLACEHOLDER_52_0] + + +## Supplementary Figure 20: Time series images of in-situ chemical reaction chip. + +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48 h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non-direct physical contact for solution injections. (f) The reaction chip one month after injection (one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. (Page S37, Supplementary) + +(Page S37, Supplementary) + +"Due to their unique properties, ILs have been proved to be an important category of solvent and electrolytes. Here we demonstrate that, by further combining with electrochemical procedure, the IBFW also manifests the capability of transforming liquid film pattern into various solid materials. Fig. 4d shows the schematics of a three-electrode electrochemistry experiment. A droplet of 1- ethyl- 3- methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) serves as the solvent of possible analytes, which are Silver bis (trifluoromethylsulfonyl)imide (Ag[NTf₂]) or a mixture of Ag⁺ and 7,7,8,8- tetracyanoquinodimethane (TCNQ) in our experiments. The liquid film pattern is fabricated by the IBFW technology onto the thin gold electrode and would be subsequently transformed into + +<--- Page Split ---> + +nanoparticles. A \(10 \mathrm{nm}\) Au and \(5 \mathrm{nm}\) Ti film deposited onto \(\mathrm{SiO}_2\) serves as the working electrode and is connected to the workstation by a Pt probe. As revealed by the MC simulation results (Supplementary Fig. 9 b), the He ions with vertical stopping- range exceeds \(290 \mathrm{nm}\) can easily penetrate the \(15 \mathrm{nm}\) metal film and deposit positive charges into the \(300 \mathrm{nm}\) \(\mathrm{SiO}_2\) layer underneath. Therefore, the IBFW can be achieved on an ultra- thin metal film deposited on insulating substrate, and is not contradict with the conclusion that pure conducting substrates lead to the failure of IBFW shown in Fig. 2f. The counter electrode is a Pt probe emerged in IL, and a silver- plated probe serves as a pseudo reference electrode. + +In Fig. 4e, we present an example of solid particles deposited from IBFW liquid film. The upper part shows silver nanoparticles with designed pattern (a \(20 \mu m \times 3 \mu m\) channel and PKU letters) potentiostatically deposited at - 0.2 V (vs. Ag) for \(180 \mathrm{s}\) onto the gold electrode surface. And the lower part shows blue AgTCNQ particles on gold surface make up a \(50 \mu m \times 10 \mu m\) rectangular pattern deposited at - 0.1 V (vs. Ag). Noteworthily, the electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees63. When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al.64, a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards, which is also observed in our experiments. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film. + +Four cycles of cyclic voltammogram (CV) of \(10 \mathrm{mM} \mathrm{Ag}^+\) in IL is shown in Fig. 4f. The reduction peak of \(\mathrm{Ag}^+\) takes place at - 0.29 V (vs. Ag) with the peak current decreases as the scan cycles increases. We believe that the micro litter droplet with limited analyte dissolved lead to such results. The \(\mathrm{Ag}^+\) concentration decreases quickly after each cycle of CV scan, and the electron transfer is slower for the oxidation of \(\mathrm{Ag}\) metal. In Fig. 4g, we test the CV curves of five scan cycles of IL droplet with \(6 \mathrm{mM} \mathrm{Ag}^+\) and \(5 \mathrm{mM} \mathrm{TCNQ}\) . Two reduction peaks can be distinguished, one at \(0.095 \mathrm{V}\) (vs. Ag), and the other at - 0.21 V (vs. Ag). The first peak corresponds to the reduction of \(\mathrm{Ag}^+\) to \(\mathrm{Ag}^0\) (metal)44, and the second peak is related to the formation of AgTCNQ complex (solid). Finally, we conceptually validate that IBFW technology is capable of transferring liquid film pattern into various solid materials and reveal the possibilities can be produced by combining IBFW with electrochemical procedures. The three- electrode experiment configuration, example of open- circuit- potential V- t curve and potentiostatic deposit I- t curve are shown in Supplementary Fig. 21. ” + +(Page 10- 11, Main text) + +“As summarized in Fig. 4h, the IBFW technology manifests several intriguing features that can be harnessed for a variety of application fields. The IBFW technique can fabricate patterned ILs film with \(30 \mathrm{nm}\) thickness, \(100 \mathrm{nm}\) spatial resolution and over hundreds of \(\mu \mathrm{m}\) film length on insulating substrates (or coated with conducting metal films with \(10^1 \mathrm{nm}\) thickness). The surface- volume ratio endowed by the nanometer scale thickness can largely enhance the sensitivity of the IBFW film, and can be utilized in gas sensing circuit. The good solubility and biocompatibility of ILs make them suitable for the dissolve of various analytes. + +<--- Page Split ---> + +The IBFW film also exhibits robustness against air environment exposure, gravity, and physical contact to droplet reservoir. Such features reveal that the IBFW film can act as stable flow channel for the analyte solutions injected to the reservoir, and can largely simplify the fabrication procedures of micro/nanofluidic chips. Last but not least, IBFW liquid film with wide potential window can be combined with electrochemical procedures and the patterned liquid film can be transformed into different solid particles. Such results demonstrate the IBFW as a versatile tool for both nanofluidics and liquid/solid materials printing." + +(Page 11, Main text) + +![PLACEHOLDER_54_0] + +
Figure 4 (d) The schematics of a three-electrode electrochemistry experiment. A droplet of IL with IBFW liquid film pattern printed onto the working electrode is the solvent for analytes.
+ +<--- Page Split ---> + +10 nm Au and \(5\mathrm{nm}\) Ti deposited to \(300\mathrm{nm}\) TOX \(\mathrm{SiO_2}\) serves as the working electrode, Pt probe and silver- plated probe stuck into the droplet are the counter and pseudo- reference electrodes respectively. (e) An example of the patterned solid particles deposited on Au electrode surface. The upper part shows Ag particles make up a \(20\mu m\times 3\mu m\) rectangular film with PKU letters pattern which are deposited to Au surface at \(- 0.2\mathrm{V}\) (vs. Ag). The lower part shows blue AgTCNQ particles make up a \(50\mu m\times 10\mu m\) pattern which are deposited to Au surface at \(- 0.1\mathrm{V}\) (vs. Ag). Both are potentiostatically deposited for \(180\mathrm{s}\) . (f) Four cycles of cyclic voltammogram of \(10\mathrm{mMAg^{+}([EMIM][NTf_2])}\) solution. The reduction peak at \(- 0.295\mathrm{V}\) (vs. Ag) can be seen, with peak current decreases with cycles. After four cycles, the reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal becomes less obvious. (g) Five cycles of cyclic voltammogram of \(6\mathrm{mM}\) \(\mathrm{Ag^{+}}\) and \(5\mathrm{mM}\) TCNQ ([EMIM][NTf2]) solution. The first reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal at \(0.095\mathrm{V}\) (vs. Ag) can be seen. The \(+300\mathrm{mV}\) shift of Ag reduction peak at present of TCNQ is consistent with literature44. The reduction peak current of Ag reduces quickly and become hard to distinguish as cycle increases. (h) A summary schematic to show the distinct features of IBFW technique, and the potential application fields that are suitable for IBFW. + +(Page 27- 28, Main text) + +![PLACEHOLDER_55_0] + + +Supplementary Figure 21: The electrodeposition experiments of AgTCNQ. + +(a) The three-electrode configuration adopted in current work. (b) The green line is the V-t curve of AgTCNQ open circuit potential measurement, which serves as a reference for the subsequent experiments. The purple line is the deposition current vs. time curve of AgTCNQ deposition at constant potential, -0.1 V (vs. Ag). + +(Page S38, Supplementary) + +Comment #2: The surface- wetting driven printing process is limited to patterns that are + +<--- Page Split ---> + +continuously connected. For printing applications, most of the time disconnected patterns are needed. Are there ways to create such disconnected patterns (in the nano/micron scale)? + +Response: We thank the reviewer for the important suggestions. By employing the more common feature of HFIB, which is to decompose and etch the sample, discontinuous liquid film patterns can also be printed. After the printing of a continuous liquid film, we use the NPVE software to scan a small region repeatedly to etch the unwanted part of the pattern to get a discontinuous pattern. + +"Apart from continuous pattern, discontinuous liquid pattern can be fabricated by the introduction of damaging mode of HFIB. As shown in Supplementary Fig. 7, a PKU pattern is separated from the flow channel that connect to the droplet reservoir." + +(Page 4, Main text) + +![PLACEHOLDER_56_0] + + +Supplementary Figure 7: Discontinuous pattern achieved by employing damaging mode of HFIB. + +After the PKU letters pattern has been induced from a continuous liquid film channel, the conjunction parts between the film channel and the letters pattern are etched by HIM (by setting the scan dose density to \(10^{4}\) ions/nm \(^2\) , the liquid film is etched). + +(Page S23, Supplementary) + +Comment: If either or both of the above concerns can be successfully addressed, I suggest that this manuscript may be reconsidered. Otherwise, it may be more suitable to a more specialized journal. + +Response: In our resubmitted version of manuscript, we have attempted to address the + +<--- Page Split ---> + +concerns about the application versatility of IBFW through two experiments that can broaden the liquid working media of IBFW and can transfer liquid pattern into solid materials. Discontinuous pattern can also be printed by combining the liquid inducing mode with damaging mode of the helium focused ion beam. + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have addressed my comments to satisfaction. I recommend publication. + +Reviewer #2 (Remarks to the Author): + +The authors have seriously considered all my previous comments and, in particular, improved the manuscript significantly based on them. In particular my main concern of lack of application potential was addressed with additional experiments and a new section in the manuscript. + +I can recommend publication now. + +Reviewer #3 (Remarks to the Author): + +The authors have successfully addressed all of my previous concerns. I suggest publication as is. + +<--- Page Split ---> + +## Responses to Reviewer #1: + +The authors have addressed my comments to satisfaction. I recommend publication. + +Response: We thank the reviewer for the comments that have significantly improved our manuscript. + +<--- Page Split ---> + +## Responses to Reviewer #2: + +The authors have seriously considered all my previous comments and, in particular, improved the manuscript significantly based on them. In particular my main concern of lack of application potential was addressed with additional experiments and a new section in the manuscript. + +I can recommend publication now. + +Response: We thank the reviewer for the comments that have significantly improved our manuscript. + +<--- Page Split ---> + +## Responses to Reviewer #3: + +The authors have successfully addressed all of my previous concerns. I suggest publication as is. + +Response: We thank the reviewer for the comments that have significantly improved our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..69a7b97277dc43c4ccd3ca81bab533c7e4de4a93 --- /dev/null +++ b/peer_reviews/df0a2ec3781bb1b5c29bb25640fc7debb4274748e08b88354518f72e3785a518/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1266 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 888, 211]]<|/det|> +Rewritable printing of ionic liquid nanofilm utilizing focused ion beam induced film wetting + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 98, 287, 112]]<|/det|> +REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 148, 392, 164]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[114, 203, 879, 385]]<|/det|> +The present paper develops a promising technique using ion beam induced film wetting (IBFW) for the nanoscale patterning of ionic liquids film without any surface fabrications or special electric circuits. The newly- developed technique has nanoscale resolution and can be used for the open surface nanofluidics fabrication and rewritable nano print. Both the resolution and fabrication efficiency have been improved by several orders of magnitude compared to the existing technique, such as optofluidic and thermal gradient technique. Further, the authors performed systematic study on the working mechanism, the modeling and performance evaluation of the IBFM based technique, which is helpful for the fabrication parameters setup and performance improvement in the future engineering application. The present work is exciting and I suggest its publication. Furthermore, the following comments should be addressed to improve the work. + +<|ref|>text<|/ref|><|det|>[[115, 396, 874, 468]]<|/det|> +1. The key of the present work is to overcome the pinning of contact line by the electrostatic forces, which are generated by the focused ion beam. Although the authors studied the IBFW induced liquid film lengths on substrates with different conductivities, however, the effects of wetting status or surface energy of different substrates on the performances should be discussed. + +<|ref|>text<|/ref|><|det|>[[115, 479, 869, 533]]<|/det|> +2. The present work reported that the flow velocity decreases with the film length, and give a model of these two parameters. Based on the analysis, what is the fabrication limit of film length for the present technique? The authors should give necessary discussion. + +<|ref|>text<|/ref|><|det|>[[115, 544, 870, 635]]<|/det|> +3. Based on the analysis of working mechanism of the present work, the electrostatic force is important for the film generation. However, the surface charge on the substrate will also generate electric double layer (EDL) in the IL. At the same time, the thickness of film is only tens of nanometer, the EDLs on the solid-liquid interface and liquid-gas interface will overlap and generate obvious electrokinetic effect when the IF flows. What is the possible effect of EDL on the flow velocity and film generation? + +<|ref|>text<|/ref|><|det|>[[115, 646, 865, 718]]<|/det|> +4. Based on the previous MD simulation, the molecular slip happens on even smooth surface. Did the authors measure the slip on their sample pairs using MD? Because the precursor film is assumed to be \(0.6 \text{nm}\), the molecular slip can generate significant effect on the IL motion. This may explain the the discrepancy of flow velocity between the experiments and theory. + +<|ref|>text<|/ref|><|det|>[[115, 729, 755, 746]]<|/det|> +5. What are effects of temperature gradient and evaporation on the present technique? + +<|ref|>text<|/ref|><|det|>[[115, 787, 392, 803]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 842, 856, 877]]<|/det|> +Referee report on the manuscript NCOMMS- 23- 30881 "Rewritable nano print of ionic liquids utilizing focused ion beam induced film wetting" by Gu et al. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 162]]<|/det|> +This manuscript describes experiments demonstrating a novel way to print ionic liquids on insulating substrates using a He- ion beam writing. To my knowledge results are novel, there importance to the field of controlling liquid flows are hard for me to judge. The explanation of the working principle has several apparent deficiencies. + +<|ref|>text<|/ref|><|det|>[[115, 174, 461, 190]]<|/det|> +There are several remarks I would like to make: + +<|ref|>text<|/ref|><|det|>[[115, 229, 840, 302]]<|/det|> +- The relevance for applications was not entirely clear to me. Several references were cited in the beginning, listing a broad range of applications for "programmable control of fluid motion". But as I understood, the present technique works for ionic liquids only. Thus, I was left wondering what the applications are specific to ionic liquids. That needs to be explained much better. + +<|ref|>text<|/ref|><|det|>[[115, 341, 882, 432]]<|/det|> +- The fabrication has to be performed in an ultra-high vacuum environment. It was not very clearly stated or studied, what happens to the samples after they are taken out of the HIM and exposed to air, tilting of the chip (gravity pulling in another direction), static charges, mechanical contact or other environmental variables. Common sense picture of liquids gives the impression that the "circuit" is not very stable. If it is, data needs to be provided to convince the reader otherwise. + +<|ref|>text<|/ref|><|det|>[[115, 471, 857, 544]]<|/det|> +- Some data was provided with different substrates. What about varying the surface treatment, or cleaning? How sensitive is the success of the writing to the cleanliness of the substrate? You say you anneal the substrates at \(320 \text{C}\) in hydrogen flow. Is that to remove organic contaminants? What if you skip the annealing step? Or use oxygen plasma cleaning instead? + +<|ref|>text<|/ref|><|det|>[[115, 583, 866, 637]]<|/det|> +- How do you know that the ions of the ionic liquid stay intact (are not broken down) under the He ion irradiation? Typically, organic compounds (such as resists for example) can be strongly modified (bonds broken etc) with high energy ion beams. + +<|ref|>text<|/ref|><|det|>[[115, 676, 872, 730]]<|/det|> +- What sets the "minimal line width" scale of \(100 \text{nm}\) ? Shouldn't it in principle be much narrower, as the He ion beam interaction volume at the surface is very small (Fig S7) (hence its high imaging resolution < nm). + +<|ref|>text<|/ref|><|det|>[[115, 770, 876, 842]]<|/det|> +- Related to that, I do not understand the suggested mechanism. In Fig. 2A the local surface charges, induced by the beam current, are located directly under the IL droplet. Yet, in the unnumbered Figure in Note S3 (Electric field driven ion emission calculation), the surface charge is located some distance away from the IL reservoir. Something doesn't match. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 180]]<|/det|> +- Eq. (1) cites for example Ref. 46, where some of the terms were introduced. However, in that paper, surface charge density Q was specifically described as "areal hole density" i.e. describing a positive charge, whereas you seem to assume a negative charge. How can you apply the same equations to these two opposing cases? Why would in your case the negative charge be dominant, (which the authors in Ref 46 assume can be neutralized more easily)? + +<|ref|>text<|/ref|><|det|>[[114, 219, 875, 256]]<|/det|> +- In addition, you should describe already in the main text what each term in Eq (1) describes, and define every variable of the equations of the main text (including Eq (2)). + +<|ref|>text<|/ref|><|det|>[[114, 294, 752, 312]]<|/det|> +- Shouldn't the electrons of the flood gun be somehow part of the modelling of Eq. (1)? + +<|ref|>text<|/ref|><|det|>[[114, 350, 758, 368]]<|/det|> +To understand Eq (2), the figure from Supplementary Note 3 is required in the main text. + +<|ref|>text<|/ref|><|det|>[[114, 407, 855, 444]]<|/det|> +How did you measure the experimental surface charge density of Fig. 2 D? Could you experimentally determine the sign of the charge? If you used Eq (1), how is that an "experimental" result? + +<|ref|>text<|/ref|><|det|>[[114, 482, 880, 537]]<|/det|> +- "The qualitative consistency ... verifies the mechanism we propose." Big statement, considering that you refer to Fig. 2E where the agreement is NOT good. (i.e. modelling doesn't predict at all differences between different insulating substrates) + +<|ref|>text<|/ref|><|det|>[[114, 576, 861, 612]]<|/det|> +"The relationship between flow velocity and film length can also be measured experimentally". I don't understand how you can measure the flow velocity in your experimental setting. + +<|ref|>text<|/ref|><|det|>[[114, 651, 867, 686]]<|/det|> +AFM measurements "The liquid-vacuum interface..." Is the AFM measurement done in vacuum instead of air? + +<|ref|>text<|/ref|><|det|>[[114, 727, 868, 800]]<|/det|> +"The current in nanofilm linearly depends on the humidity". What is the mechanism?? Anyways, it seems the current is not only a function of humidity as it depends directly on time as well based on Fig. S18. How could you disentangle the effect of time from the effect of humidity in a real sensor as some voltage bias history dependence seems to exist (referring to Fig. S18F) + +<|ref|>text<|/ref|><|det|>[[113, 838, 868, 873]]<|/det|> +Fig. 3F use real current units instead of dimensionless and tell what the bias voltage used was. BTW Fig. S18 C has wrong units (A vs nA). Fig. S18G has no caption, what is it? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 91, 540, 107]]<|/det|> +In conclusion, major revisions are required, in my opinion. + +<|ref|>text<|/ref|><|det|>[[115, 119, 797, 136]]<|/det|> +The impact is also not clear, so at the moment I cannot recommend publication in Nat Comm. + +<|ref|>text<|/ref|><|det|>[[115, 204, 392, 220]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 259, 863, 388]]<|/det|> +The authors developed a new method to perform rewritable surface printing of ionic liquids. The method relies on the disjoining pressure to induce surface films of nanometer thickness, and utilizes helium ion beams to initiate the flow of liquids and pattern creation. The manuscript comprehensively characterizes and explains the underlying mechanism of this printing process. However, as an application- driven work, the prospect of practical real- world applications is a bit weak. Although the authors demonstrated a sensing device application (Fig. 3F), it only utilizes the nanoscale thickness of the ionic liquid film, and the surface patterning is not very relevant. Specific concerns include: + +<|ref|>text<|/ref|><|det|>[[115, 398, 879, 470]]<|/det|> +1. This method utilizes ionic liquids, and seems hard to extend to other liquid systems due to the high-vacuum requirements of the helium ion microscope. Ionic liquid as of now are still quite expensive, limiting the range of applications. Are there ways to improve or revise the method so that other liquid or even solid structures can also be printed? + +<|ref|>text<|/ref|><|det|>[[115, 481, 878, 535]]<|/det|> +2. The surface-wetting driven printing process is limited to patterns that are continuously connected. For printing applications, most of the time disconnected patterns are needed. Are there ways to create such disconnected patterns (in the nano/micron scale)? + +<|ref|>text<|/ref|><|det|>[[115, 545, 878, 581]]<|/det|> +If either or both of the above concerns can be successfully addressed, I suggest that this manuscript may be reconsidered. Otherwise, it may be more suitable to a more specialized journal. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[384, 86, 612, 102]]<|/det|> +## Responses to Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[115, 121, 881, 325]]<|/det|> +The present paper develops a promising technique using ion beam induced film wetting (IBFW) for the nanoscale patterning of ionic liquids film without any surface fabrications or special electric circuits. The newly- developed technique has nanoscale resolution and can be used for the open surface nanofluidics fabrication and rewritable nano print. Both the resolution and fabrication efficiency have been improved by several orders of magnitude compared to the existing technique, such as optofluidic and thermal gradient technique. Further, the authors performed systematic study on the working mechanism, the modeling and performance evaluation of the IBFM based technique, which is helpful for the fabrication parameters setup and performance improvement in the future engineering application. The present work is exciting and I suggest its publication. Furthermore, the following comments should be addressed to improve the work. + +<|ref|>text<|/ref|><|det|>[[118, 344, 764, 362]]<|/det|> +Response: We thank the reviewer for the positive comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 381, 880, 472]]<|/det|> +Comment #1: The key of the present work is to overcome the pinning of contact line by the electrostatic forces, which are generated by the focused ion beam. Although the authors studied the IBFW induced liquid film lengths on substrates with different conductivities, however, the effects of wetting status or surface energy of different substrates on the performances should be discussed. + +<|ref|>text<|/ref|><|det|>[[117, 492, 880, 656]]<|/det|> +Response: We thank the reviewer for the inspiring suggestion. We have tested the wetting status of several liquid- solid combinations and include them in the Supplementary Table 4, but interestingly we find the relation between wetting status and Ion Beam induced Film Wetting (IBFW) effect is quite ambiguous, indicating that the electrostatic forces of IBFW is not quite relevant with the wetting status, which is possible since the IBFW electrostatic forces are much greater than the wetting van der Waals forces at the contact line. No significant differences were observed between same liquids on different insulating substrates (TOX/PECVD \(\mathrm{SiO_2}\) , 15 nm metal on \(\mathrm{SiO_2}\) ). While different liquids with different viscosities showed quite different performances on the same \(\mathrm{SiO_2}\) substrate. + +<|ref|>text<|/ref|><|det|>[[117, 658, 880, 825]]<|/det|> +On the other hand, the liquid viscosity has significant influence, as included in Supplementary Fig. 11. The viscosity raises flow friction which works as a counterpart of the electrostatic driving forces. ILs with lower viscosity can be easily induced to flow on all 3 substrates and form liquid film with hundred \(\mu \mathrm{m}\) length, such as [EMIM][DCA] and [EMIM][NTf2]. The results in Supplementary Fig. 11 only shows the film length fabricated by one time scan of a \(50\mu m\times 1\mu m\) pattern. For [EMIM]BF4, the viscosity increases slightly and can only be induced to flow for several \(\mu \mathrm{m}\) , and difficult to form desired patterns. When the viscosity increases dramatically, for example [BMIM]PF6, helium focused ion beam (HFIB) cannot induce liquid flow on any solid surfaces. + +<|ref|>text<|/ref|><|det|>[[118, 844, 880, 899]]<|/det|> +"Not only the solid substrates, the ILs employed also influence the IBFW performances. Four kinds of ILs are tested on \(\mathrm{SiO_2}\) substrate with the results shown in Supplementary Fig. 11. The results show that liquid viscosity has significant influence on IBFW liquid film, by raising the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 85, 880, 177]]<|/det|> +flow friction which works as a counterpart of the electrostatic driven forces. The relation between wetting status and IBFW effect, however, is ambiguous, indicating that the electrostatic forces of IBFW is not quite relevant with the wetting status. It is probably due to the fact that the IBFW electrostatic forces are much greater than the wetting van der Waals forces at the contact line." + +<|ref|>text<|/ref|><|det|>[[694, 179, 878, 196]]<|/det|> +(Page 6- 7, Main text) + +<|ref|>sub_title<|/ref|><|det|>[[117, 212, 328, 229]]<|/det|> +## Supplementary Table 3. + +<|ref|>text<|/ref|><|det|>[[117, 233, 476, 251]]<|/det|> +Parameters of 4 RTILs employed (20 °C) + +<|ref|>table<|/ref|><|det|>[[145, 268, 850, 406]]<|/det|> + +
NameMW (g/mol)Surface Tension (mN/m)Density (g/cm³)Viscosity (cP)
[EMIM][DCA]177.2147.31.1121
[EMIM]BF4197.97491.29445
[BMIM]PF6284.18381.37284.18
[EMIM][NTf2]391.31361.5332
+ +<|ref|>sub_title<|/ref|><|det|>[[117, 444, 328, 460]]<|/det|> +## Supplementary Table 4. + +<|ref|>text<|/ref|><|det|>[[117, 462, 848, 497]]<|/det|> +Wetting status of different RTILs on three solid surfaces (contact angle in degree, 20 °C) + +<|ref|>table<|/ref|><|det|>[[203, 515, 792, 635]]<|/det|> + +
NamePECVD
SiO2
TOX
SiO2
10 nm Au
on SiO2
[EMIM][DCA]71.04 ± 6.440.1 ± 3.847.0 ± 4.5
[EMIM]BF458.9 ± 3.435.7 ± 4.855.1 ± 4.1
[BMIM]PF682.6 ± 6.362.9 ± 2.168.2 ± 8.9
[EMIM][NTf2]59.2 ± 5.736.2 ± 3.937.8 ± 4.1
+ +<|ref|>text<|/ref|><|det|>[[603, 636, 878, 653]]<|/det|> +(Page S41- 42, Supplementary) + +<|ref|>image<|/ref|><|det|>[[118, 677, 880, 817]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[117, 821, 880, 855]]<|/det|> +Supplementary Figure 11: the IBFW results of different ILs and the relationship with Oh number. + +<|ref|>text<|/ref|><|det|>[[117, 857, 880, 894]]<|/det|> +(a) Film lengths of different liquids on \(\mathrm{SiO_2}\) substrate can be induced with a same pattern. Scan parameters are 1 pA, 2.5 nm spacing, 3 \(\mu \mathrm{s}\) dwell time, \(50 \times 1\mu m\) pattern. (b) The flow + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 88, 880, 140]]<|/det|> +velocity of different ILs. (c) The relationship between Ohnsorge number \(Oh = \frac{\mu}{\sqrt{\rho} dy}\) and flow velocity, the fluid data can be found in Supplementary Table 3. + +<|ref|>text<|/ref|><|det|>[[631, 159, 878, 177]]<|/det|> +(Page S28, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 196, 810, 268]]<|/det|> +Comment #2: The present work reported that the flow velocity decreases with the film length, and give a model of these two parameters. Based on the analysis, what is the fabrication limit of film length for the present technique? The authors should give necessary discussion. + +<|ref|>text<|/ref|><|det|>[[117, 288, 881, 473]]<|/det|> +Response: We thank the reviewer for this important suggestion. The flow speed of IBFW film decreases with the film length, but as far as we know the flow speed does not decrease to exact zero. Therefore, the fabrication limit of film length for IBFW depends on the user's endurance for the fabrication speed of liquid film. Base on the liquid film length- speed relation curve (Fig. 2h), the film length upper limit can be determined to fulfill specific requirements for fabrication efficiency. For example, the longest film we fabricated reaches \(800 \mu \mathrm{m}\) to \(900 \mu \mathrm{m}\) , with the film velocity decreases to \(10^{- 2} \mu \mathrm{m / s}\) (the in- situ chemical reaction chip in Fig. 4c and Supplementary Fig. 20). We included an explanation in the main text as an instruction for IBFW fabrication. The optical figure of in- situ reaction chip in Supplementary Fig. 20d is a good example of IBFW liquid channel with upper limit length. + +<|ref|>text<|/ref|><|det|>[[118, 492, 879, 547]]<|/det|> +"The inset of Fig. 1e presents an example of minimal line width, \(100 \mathrm{nm}\) , IBFW can achieve. By assembly of separate scan patterns sequentially, the IBFW technique can also fabricate liquid film channel up to hundreds \(\mu \mathrm{m}\) in length." + +<|ref|>text<|/ref|><|det|>[[712, 549, 878, 565]]<|/det|> +(Page 4, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 586, 880, 770]]<|/det|> +"The consistency between the calculation and experiments suggests that disjoining pressure can explain the propagation of IBFW film. The discrepancy at extreme long film length may be due to the HFIB irradiation history. The fabrication of film with hundreds \(\mu \mathrm{m}\) length usually takes hours of HFIB irradiation. The accumulated positive charges lead to a higher surface potential and a boundary slip length that exceeds the upper limit in literature, which give rise to an unexpected higher film speed. Base on the film length- speed relationship curve (Fig. 2h), the fabrication limit of film length for IBFW technique can be determined to fulfill specific requirements for fabrication efficiency. For example, the longest film we fabricated reaches \(800 \mu \mathrm{m}\) to \(900 \mu \mathrm{m}\) , with the film velocity decreases to \(10^{- 2} \mu \mathrm{m / s}\) (the in- situ chemical reaction chip in Fig. 4c and Supplementary Fig. 20)." + +<|ref|>text<|/ref|><|det|>[[712, 772, 878, 788]]<|/det|> +(Page 8, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[122, 87, 880, 396]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[118, 413, 735, 432]]<|/det|> +## Supplementary Figure 20: Time series of in-situ chemical reaction chip. + +<|ref|>text<|/ref|><|det|>[[117, 435, 880, 697]]<|/det|> +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non-direct physical contact for solution injections. (f) The reaction chip one month after injection (one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. (Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[631, 697, 877, 714]]<|/det|> +(Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 750, 880, 861]]<|/det|> +Comment #3: Based on the analysis of working mechanism of the present work, the electrostatic force is important for the film generation. However, the surface charge on the substrate will also generate electric double layer (EDL) in the IL. At the same time, the thickness of film is only tens of nanometer, the EDLs on the solid- liquid interface and liquid- gas interface will overlap and generate obvious electrokinetic effect when the IF flows. What is the possible effect of EDL on the flow velocity and film generation? + +<|ref|>text<|/ref|><|det|>[[118, 880, 877, 899]]<|/det|> +Response: We thank the reviewer for this very important comment. The EDL in IL and the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 881, 380]]<|/det|> +electrokinetic phenomena exert significant influence on the hydrodynamics behavior of ionic liquids, and a positive surface charge would enhance the flow velocity of ionic liquids with similar cation/anion sizes ([EMIM][NTf₂], [EMIM][DCA] in our experiments) by increasing the boundary slip length. The EDL determines the structure of the IL- solid interface, and adjusts to different surface potential (main text Ref. [58- 60]). The consequent boundary slip length can vary from several nm to over 16 nm. A larger surface potential creates an absorbed ion lubrication layer which can further reduce the IL- solid interface friction, in our case this may further enhance the flow velocity. The IL- vacuum interface influence on the structure of IL- solid is negligible due to its involatile nature, we neglect its influence on the hydrodynamics. Apart from surface potential, the surface roughness may also enhance the slip length. The slip length data from literature (main text Ref. [58, 59]) of imidazolium IL- \(\mathrm{SiO_2}\) interface is adopted to modify our flow model. Since slip length can be easily tuned by surface potential, we employ the lower (2 nm) and upper (16 nm) limits of slip length (Ref. [59]) to give an estimation on the possible range of flow speed in Fig. 2h, and the average value 10 nm (Ref. [58]) is shown by the deep blue line. The modified flow model can better explain the high velocity range observed in IBFW experiments. + +<|ref|>text<|/ref|><|det|>[[118, 381, 880, 473]]<|/det|> +The EDL effect on the ion emission from liquid- vacuum interface may be not important. The MD simulation results indicate that the characteristic electric field ( \(10^{9} \mathrm{~V / m}\) for separate ion emission, \(10^{10 - 11} \mathrm{~V / m}\) for ion clusters emission) that lead to significant ion emission agrees with literature results (Ref. [56]) where the ion emission directly from an IL- vacuum interface far from the solid surface. + +<|ref|>text<|/ref|><|det|>[[118, 492, 880, 547]]<|/det|> +"We next verify that the disjoining pressure propels and stabilizes the nanofilm. The propagation speed of IBFW liquid film decreases monotonically with the increase of film length: + +<|ref|>equation<|/ref|><|det|>[[117, 548, 876, 583]]<|/det|> +\[U\sim \frac{h^{2} + 3b h}{3\mu}\cdot \frac{\Pi(h_{m i n}) - \gamma\kappa}{L}. \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[117, 586, 880, 750]]<|/det|> +Where \(U\) is the average flow speed, \(h\) is equilibrium film thickness, \(b\) is the slip length of IL- \(\mathrm{SiO_2}\) interface \(^{58 - 60}\) , \(\mu\) is IL viscosity, \(\Pi (h_{min})\) is disjoining pressure at minimum film thickness \(h_{min}\) , \(L\) is film length, \(\gamma\) is IL surface tension, and \(\kappa\) is curvature of IL- vacuum interface at the conjunction of film and reservoir (Supplementary Table. 2, Supplementary Note 4, Supplementary Fig. 13). We depict the calculation results in Fig. 2h. Since the boundary slip length of IL- \(\mathrm{SiO_2}\) interface depends on the combined surface conditions and ranges from 2 nm to over 16 nm, we employ the lower (2 nm) and upper (16 nm) limits of slip length to give an estimation on the possible range of flow speed in Fig. 2h as the blue shaded region, and the results of average value \(10 \mathrm{nm}^{58}\) is shown by the deep blue line." + +<|ref|>text<|/ref|><|det|>[[712, 753, 878, 770]]<|/det|> +(Page 7, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 789, 884, 899]]<|/det|> +"We adopt the average slip length data \(b \approx 10 \mathrm{~nm}\) of ionic- liquid- \(\mathrm{SiO_2}\) interface from literature \(^{1,2}\) , and zero lateral shear stress is taken at the liquid vacuum interface. According to the literatures, the boundary slip length of IL- solid interface depends on the specific conditions \(^{3}\) , such as, the liquid solid combination, the surface roughness, the surface potential. In most cases, the slip length increases with the roughness. The boundary slip length at different surface potential has been reported to vary due to the structure of EDL adjust to different surface + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 83, 880, 177]]<|/det|> +potential, ILs with higher conductivity can be influenced more easily3. A larger surface potential has been reported to have an absorbed ion lubrication layer which can further reduce the IL- solid interface friction4, in our case this may further enhance the flow velocity. For a better understanding of the hydrodynamics behavior of IBFW flow, both AFM measurements and MD simulation can be conducted." + +<|ref|>sub_title<|/ref|><|det|>[[118, 196, 361, 215]]<|/det|> +## Modeling of flow velocity + +<|ref|>text<|/ref|><|det|>[[117, 223, 880, 280]]<|/det|> +The simplified 2- dimensional form of Navier- Stokes equation (4.1) is adopted and together with the zero- shear- stress condition (4.2) and the boundary slip condition (4.3) give rise to the flow velocity as a function of vertical coordination \(z\) (4.4). + +<|ref|>equation<|/ref|><|det|>[[150, 282, 857, 425]]<|/det|> +\[\begin{array}{l}\mu \frac{d^2u}{dz^2} = \frac{dp}{dx}\\ \displaystyle \frac{du}{dz}\big|_{z = h} = 0,\\ \displaystyle u(0) = b\cdot \frac{du}{dz}\big|_{z = 0},\\ \displaystyle u(z) = \frac{1}{2\mu}\frac{dp}{dx} z^2 -\frac{h}{\mu}\frac{dp}{dx} z - \frac{bh}{\mu}\frac{dp}{dx}. \end{array} \quad (4.4)\] + +<|ref|>text<|/ref|><|det|>[[118, 428, 396, 445]]<|/det|> +The flow rate can be calculated as + +<|ref|>equation<|/ref|><|det|>[[152, 447, 857, 481]]<|/det|> +\[Q = d\cdot \int_{0}^{h}u(z)dz\sim -\frac{d\cdot h^{2}(h + 3b)}{3\mu}\frac{dp}{dx}. \quad (4.5)\] + +<|ref|>text<|/ref|><|det|>[[118, 484, 476, 501]]<|/det|> +With the average flow speed is expressed as + +<|ref|>equation<|/ref|><|det|>[[152, 502, 857, 536]]<|/det|> +\[u_{ave} = \frac{Q}{S}\sim -\frac{h^{2} + 3bh}{3\mu}\frac{dp}{dx}. \quad (4.6)\] + +<|ref|>text<|/ref|><|det|>[[117, 537, 880, 650]]<|/det|> +According to the IBFW hypothesis and the MD results, the precursor film ahead of the propagation bulk film has a thickness comparable with the size of the ion pairs of the IL, in our case the [EMIM][DCA] pair namely. An appropriate estimation for \(h_{min}\) is taken as \(6\times\) \(10^{- 10} m\) , and the excess disjoining pressure of the precursor film serves as the driving force with the interface curvature induced capillary pressure serving as the resisting force, which gives a rough estimation for the pressure gradient \((\Pi (h)\ll \Pi (h_{min})\) and is omitted) + +<|ref|>equation<|/ref|><|det|>[[115, 653, 820, 703]]<|/det|> +\[\frac{dp}{dx}\sim \frac{\Delta p}{\Delta x} = \frac{\Pi(h_{min}) - \gamma\kappa}{L} = \frac{\left[-\left(\frac{A_{SI} - A_{II}l'}{6\pi h_{min}^3} - s_p\exp \left(\frac{d_{min} - h_{min}}{l}\right) - 8c_{IL}\cdot h_{min}^7\right) - \gamma\kappa}{L}\right]}{L} \quad (4.7)\] + +<|ref|>text<|/ref|><|det|>[[117, 706, 880, 761]]<|/det|> +Where \(s_{p}\) is the polar component of the spreading coefficient, \(d_{min}\) is the atomic cut- off distance, \(l\) is the correlation length, \(c_{IL}\) is the strength Born repulsion. The result from Note S5 is employed. + +<|ref|>text<|/ref|><|det|>[[117, 762, 879, 817]]<|/det|> +A rudimental estimation for the average flow speed i.e. the mesoscopic propagation speed of IBFW liquid film can be expressed as a function of the length of the flow pattern, the flow speed decreases monotonically with the increase of flow length: + +<|ref|>equation<|/ref|><|det|>[[115, 820, 840, 853]]<|/det|> +\[U\sim u_{ave} = \frac{h^2 + 3bh}{3\mu}\cdot \frac{\Pi(h_{min}) - \gamma\kappa}{L}. \quad (4.8)\] + +<|ref|>text<|/ref|><|det|>[[616, 856, 879, 874]]<|/det|> +(Page S10- 11, Supplementary) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[262, 92, 728, 373]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 381, 881, 530]]<|/det|> +
Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current 1 pA, dwell time 10 \(\mu \mathrm{s}\) , spacing 1 nm. The change width experiments are conducted with rectangular pattern of scan spots with constant length 20 \(\mu \mathrm{m}\) and different width, while keeping the beam current beam current 1 pA, dwell time 2 \(\mu \mathrm{s}\) , spacing 1 nm constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths58,59, the deep blue line is the calculation result employing average slip length58.
+ +<|ref|>text<|/ref|><|det|>[[700, 549, 878, 565]]<|/det|> +(Page 22, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 621, 880, 714]]<|/det|> +Comment #4: Based on the previous MD simulation, the molecular slip happens on even smooth surface. Did the authors measure the slip on their sample pairs using MD? Because the precursor film is assumed to be 0.6 nm, the molecular slip can generate significant effect on the IL motion. This may explain the the discrepancy of flow velocity between the experiments and theory. + +<|ref|>text<|/ref|><|det|>[[117, 715, 881, 900]]<|/det|> +Response: We sincerely thank the reviewer for this important insight. We have accordingly modified the flow model to slip boundary, and adopted the experimental slip length range from literatures (Ref. [58- 60]). The boundary slip lengths of ILs are typically around several to tens of nanometers as reported in literatures (Ref. [58, 59]). The exact value of slip length depends strongly on the combined surface conditions including: surface roughness, surface potential and specific surface treatments. For our film system with thickness down to nanometer scale, the slip length greatly improves the calculated flow velocity at constant driving force, and agrees with our experiment results better (main text Fig. 2h). The formation of the 0.6 nm precursor film is related to the significant ion emission processes in current model, and we did not include it into the flow modeling. The discrepancy at long film length in Fig. 2h may be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 159]]<|/det|> +due to the HFIB irradiation history. The fabrication of film with hundreds of \(\mu \mathrm{m}\) length usually takes hours of HFIB irradiation, and the accumulated positive charges lead to a higher surface potential and a boundary slip length that exceeds the upper limit in literature, which give rise to an unexpected higher film speed. + +<|ref|>text<|/ref|><|det|>[[118, 159, 880, 252]]<|/det|> +We also added an illustration of the two different flow velocity measurement methods adopted in our IBFW experiment according to other Reviewer's comments, with more data measured. Which can be found in main text and Fig.2h. To help illustrate our velocity measurement, we added Supplementary Fig. 14. The modification of the liquid flow model has been quoted in our response to Comment #3 and will not be quoted repeatedly. + +<|ref|>text<|/ref|><|det|>[[118, 277, 880, 333]]<|/det|> +"We next verify that the disjoining pressure propels and stabilizes the nanofilm. The propagation speed of IBFW liquid film decreases monotonically with the increase of film length: + +<|ref|>equation<|/ref|><|det|>[[117, 341, 877, 374]]<|/det|> +\[U\sim \frac{h^2 + 3bh}{3\mu}\cdot \frac{\Pi(h_{min}) - \gamma\kappa}{L}. \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[117, 383, 880, 550]]<|/det|> +Where \(U\) is the average flow speed, \(h\) is equilibrium film thickness, \(b\) is the slip length of \(\mathrm{IL - }\) \(\mathrm{SiO_2}\) interface \(^{58,59}\) , \(\mu\) is IL viscosity, \(\Pi (h_{min})\) is disjoining pressure at minimum film thickness \(h_{min}\) , \(L\) is film length, \(\gamma\) is IL surface tension, and \(\kappa\) is curvature of IL- vacuum interface at the conjunction of film and reservoir (Supplementary Table. 2, Supplementary Note 4, Supplementary Fig. 13). We depict the calculation results in Fig. 2h. Since the boundary slip length of \(\mathrm{IL - SiO_2}\) interface depends on the surface potential and ranges from \(2\mathrm{nm}\) to over \(16\mathrm{nm}^{59}\) , we employ the lower ( \(2\mathrm{nm}\) ) and upper ( \(16\mathrm{nm}\) ) limits of slip length to give an estimation on the possible range of flow speed in Fig. 2h as the blue shaded region, and the calculation result of average value \(10\mathrm{nm}^{58}\) is shown by the deep blue line. + +<|ref|>text<|/ref|><|det|>[[118, 557, 879, 612]]<|/det|> +The relationship between flow velocity and film length can also be measured experimentally. As shown in Supplementary Fig. 4, the HFIB scans the designed pattern row by row, so the beam speed vertical to the CTL can be calculated as: + +<|ref|>equation<|/ref|><|det|>[[116, 621, 666, 652]]<|/det|> +\[v_{beam} = \frac{s_{vertical}}{N_{row}\tau + V_{refresh}}, \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[117, 664, 880, 904]]<|/det|> +Where, \(s_{vertical}\) is the vertical scan spacing, \(N_{row}\) is the number of scan spots in one row, \(\tau\) is the dwell time that HFIB stay at a single spot, \(V_{refresh}\) is a small time ( \(10\mu \mathrm{s}\) ) that NPVE takes to reset the HFIB for next row of scan. If the vertical speed of HFIB exceeds the film velocity, the distance between the scan spot and the liquid film CTL would increases until the scan spot is too far ahead of the film which would cease to flow. The critical interaction distance with given beam parameters can be determined experimentally (Supplementary Fig. 14a). Due to the pronounced impact of dose density on the flow velocity of liquid film (Supplementary Fig. 14b), the flow velocity measurements are conducted under the same dose density by keeping the beam current \(I = 1\) \(pA\) , scan spot spacing \(s = 1\) \(nm\) and dwell time \(\tau = 2\mu \mathrm{s}\) constant and only alter the width of the rectangle pattern. The pattern width controls the \(N_{row}\) and consequently alters the beam vertical speed. By scanning rectangle patterns with same length but different widths outwards from the reservoir CTL, the vertical speed of beam can be changed at constant HFIB dose density. The IBFW film length decreases with the beam speed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 233]]<|/det|> +increasing (Supplementary Fig. 14c), and consequently the average flow velocity of films with different length can be measured. The change width measurement results are shown in Fig. 2h by the hollow orange stars. The results of film speed at extremely long film lengths are acquired by first fabricating a long liquid film ( \(300 \mu m \times 10 \mu m\) , \(600 \mu m \times 10 \mu m\) , and \(900 \mu m \times 10 \mu m\) respectively) from the reservoir, then the change width measurements are conducted at the front of the long film. Since the fabrication of extreme long film can be time consuming, these data are only measured once. The other experiments are repeated for at least ten times with the average value and standard error shown in Fig. 2h. + +<|ref|>text<|/ref|><|det|>[[117, 240, 880, 389]]<|/det|> +The shortage of the change- width method is that the NPVE scan pattern assembling limits the maximum velocity the beam can move vertically. To overcome such limitation, we adopt single spot scan method. In which, a line pattern made up by a series of scan spots is used. The scan speed is altered by changing the vertical refresh time between each scan spot, while keeping beam current \(1 \mathrm{pA}\) , dwell time \(10 \mu \mathrm{s}\) and spacing \(1 \mathrm{nm}\) all constant. The dwell time is elongated to compensate the dose density reduction, since the scan area is influenced by neighboring scan spots in a rectangular pattern. All single spot measurements are repeated at least five times. The results of single spot scan are represented by the orange stars in Fig. 2h." + +<|ref|>text<|/ref|><|det|>[[695, 391, 878, 408]]<|/det|> +(Page 7- 8, Main text) + +<|ref|>image<|/ref|><|det|>[[262, 432, 728, 714]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 722, 880, 870]]<|/det|> +
“Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \(1 \mathrm{pA}\) , dwell time \(10 \mu \mathrm{s}\) , spacing \(1 \mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20 \mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1 \mathrm{pA}\) , dwell time \(2 \mu \mathrm{s}\) , spacing \(1 \mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths \(^{58,59}\) , the deep blue line is the calculation result employing the average slip length \(^{58,}\) .”
+ +<|ref|>text<|/ref|><|det|>[[701, 889, 878, 906]]<|/det|> +(Page 24, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[130, 113, 886, 266]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[118, 272, 694, 290]]<|/det|> +## "Supplementary Figure 14: Flow speed measurement experiments. + +<|ref|>text<|/ref|><|det|>[[115, 290, 881, 512]]<|/det|> +(a) The single spot scan style in HIM, which scans one-dimensionally along the pattern direction, is applied to analyze the interaction spatial range of a single irradiation spot quantitatively. The critical maximum spacing between neighbor scan spots to induce liquid flow, \(\mathbf{s}_{\mathrm{c}}\) , represents the upper limit for the interaction spatial range of the beam spot. When scan spot spacing exceed \(\mathbf{s}_{\mathrm{c}}\) , HFIB fails to induce continuous flow however large the dose is. The injection dose density, D, is regulated by changing beam current, I, at constant dwell time 100 \(\mu \mathrm{s}\) , or changing dwell time, \(\tau\) , at constant beam current 0.7 pA. The relationship between sc and D of each beam spot is plotted. (b) Maximal flow velocity as a function of the beam current I for a 20 \(\mu \mathrm{m}\) length rectangle pattern. The scan speed is changed by the pattern width. The flow speed increases with increasing beam current at same dwell time, 5 \(\mu \mathrm{s}\) , and spacing, 1 nm. (c) An example of the change width method for the measurements of flow velocity at different film length." + +<|ref|>text<|/ref|><|det|>[[642, 512, 878, 529]]<|/det|> +(Page S31, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 585, 878, 621]]<|/det|> +Comment #5: What are effects of temperature gradient and evaporation on the present technique? + +<|ref|>text<|/ref|><|det|>[[117, 622, 880, 860]]<|/det|> +Comment #5: What are effects of temperature gradient and evaporation on the present technique?Response: We thank the reviewer for the inspiring question. Temperature gradients can alter the flow of IL by Marangoni effect or evaporation- absorption effect. In our cases, the temperature gradient and evaporation induced by the HFIB are insignificant. We investigated the heating effect and the Marangoni effect of He ion beam on IL liquid by employing SRIM software as described in Supplementary Note 1. We find out the temperature difference induced by HFIB is less than 1 K, and the consequent surface tension gradient is not enough to induce liquid flow. Besides, the kinetic energy difference induced by this heating is \(k_{b}\Delta T < 1K \cdot k_{b} = 8.62 \times 10^{-5}eV\) . While the solvation energy of ion pairs in [EMIM][DCA] ionic liquid is 11.62 eV, which is the energy barrier for a single ion to overcome to evaporate from the liquid phase. Consequently, the temperature effect on the evaporation of ions from reservoir is negligible. Also, the ILs are known for their negligible vapor pressure (0.157 Pa at 499 K, the value at room temperature is negligible). Consequently, we believe the effect of temperature and evaporation are irrelevant. + +<|ref|>text<|/ref|><|det|>[[118, 862, 880, 898]]<|/det|> +Nevertheless, temperature is always an important parameter for a liquid film system, and the reviewer's question inspires us to use external heating to explore intensive thermal influence. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 879, 140]]<|/det|> +The viscosity of ILs can be lowered by temperature increasing, which may improve the IBFW fabrication efficiency and help this technique be more efficient and practical. We thank the reviewer and we will settle the external heating tests in near future. + +<|ref|>text<|/ref|><|det|>[[118, 158, 880, 288]]<|/det|> +"We also exclude the potential roles played by HFIB induced surface morphological or chemical modification effects and heating effect induced Marangoni flow in Supplementary Note 1, Supplementary Fig. 16, and Supplementary Fig. 17. More details of MD can be found in Supplementary Note 6. Since the temperature increasing effect is less than 1 K based on our calculation. The thermal energy difference, \(k_{b}\Delta T < 1K \cdot k_{b} = 8.62 \times 10^{- 5}eV\) , induced by HFIB is far less than the energy barrier for ions to overcome to evaporate from the liquid phase. Therefore, the evaporation effect may also be insignificant in current experiments." + +<|ref|>text<|/ref|><|det|>[[712, 290, 878, 307]]<|/det|> +(Page 8, Main text) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[387, 85, 610, 102]]<|/det|> +## Responses to Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[118, 121, 883, 195]]<|/det|> +This manuscript describes experiments demonstrating a novel way to print ionic liquids on insulating substrates using a He- ion beam writing. To my knowledge results are novel, there importance to the field of controlling liquid flows are hard for me to judge. The explanation of the working principle has several apparent deficiencies. + +<|ref|>text<|/ref|><|det|>[[120, 196, 505, 213]]<|/det|> +There are several remarks I would like to make: + +<|ref|>text<|/ref|><|det|>[[120, 234, 452, 251]]<|/det|> +We thank the reviewer for the comments. + +<|ref|>text<|/ref|><|det|>[[118, 270, 880, 362]]<|/det|> +Comment #1: - The relevance for applications was not entirely clear to me. Several references were cited in the beginning, listing a broad range of applications for "programmable control of fluid motion". But as I understood, the present technique works for ionic liquids only. Thus, I was left wondering what the applications are specific to ionic liquids. That needs to be explained much better. + +<|ref|>text<|/ref|><|det|>[[117, 381, 880, 620]]<|/det|> +Response: We thank the reviewer for the very important suggestion. Accordingly, we have analyzed two specific application fields and carried out demos. First, this Ion Beam induced Film Wetting (IBFW) technology can be useful for the miniaturization of chemical reaction chips. The ionic liquids (ILs) film pattern can serve as the micro flow channel for the aqueous or organic solutions of analytes injected into the IL droplet reservoir since ILs are good solvent for water and organic solutions. With the reagents dissolve and diffuse into the film channel, in- situ chemical reaction can be conducted. Second, IBFW technology can be combined with electrochemistry to transform patterned liquid film into solid materials. The ILs known for wide potential window, low toxicity and thermal stability, can be used as solutions for electrochemical experiments. With patterned liquid film printed to electrode surface, solid materials can be deposited with designed patterns through electrochemical procedures, which is important for nano- circuit manufacture. Adjustments have been made to our manuscript and are listed here. + +<|ref|>text<|/ref|><|det|>[[117, 621, 880, 656]]<|/det|> +1. We modified the introduction to introduce potential application fields suitable for ionic liquids. + +<|ref|>text<|/ref|><|det|>[[117, 657, 880, 750]]<|/det|> +2. We added a new section 'Applications of IBFW' for further demonstration. We used IBFW to fabricate liquid channels as a guidance for aqueous solutions of reagent which were later injected into the IL droplets for the in-situ colorimetric reactions of SCN with various metal ions. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte solutions. + +<|ref|>text<|/ref|><|det|>[[118, 751, 880, 899]]<|/det|> +3. We conducted electrochemical experiments to reveal that IBFW is also capable of transforming liquid film pattern into desired solid materials. Electrochemistry analytes are dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]). The solution droplet was settled on ultra-thin metal film (15 nm) deposited on SiO2 wafer, and film patterns were printed by IBFW. The following electrochemical deposition transforms the liquid pattern into solid materials. Since the stopping range of 30 kV Helium ions exceeds 290 nm, a 15 nm metal film exerts no significant influence on the surface charge injection of HFIB, and consequently the IBFW + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 880, 177]]<|/det|> +can be conducted on very thin metal film. Monte Carlo simulation results were added to explain the penetrating capability of He ions (Supplementary Fig. 9b). We also discussed the potential influence of electrowetting on the IBFW film, and drew the conclusion that the voltage we adopted won't overcome the contact angel hysteresis and the IBFW films were not influenced by the deposition voltage. + +<|ref|>text<|/ref|><|det|>[[148, 178, 880, 233]]<|/det|> +For now, we only tested Ag nano- particles and AgTCNQ (7,7,8,8- tetracyanoquinodimethane) complex, but more electrochemistry tests can be undertaken to test the capability of solid deposition of both organic and inorganic materials. + +<|ref|>text<|/ref|><|det|>[[117, 252, 881, 529]]<|/det|> +"Based on the IBFW inducing mode, we develop a nano- printing technique of ILs, with film thickness down to \(20 \sim 30 \mathrm{~nm}\) , minimal line width about \(100 \mathrm{~nm}\) and corner radius down to \(20 \mathrm{~nm}\) , and compare its performances with the reported methods. Besides, ILs are also known for their unique properties such as wide electrochemical potential window, high ionic conductivity, low toxicity and thermostability. These features make ILs increasingly important as electrolytes for lithium battery \(^{40,41}\) and electrodepositions of various materials ranging from metal nanoparticles \(^{42,43}\) , metal organic complexes \(^{44}\) to conducting polymer films \(^{45}\) . We further demonstrate the IBFW as a versatile tool for various application fields including gas sensing circuit, in- situ chemical reaction chip, and electrochemical deposition of solid materials with desired patterns. The simplicity and versatility of IBFW technique suggests prospect in a range of liquid manipulation applications. By combining with electrochemical procedures, such technique can not only produce patterned liquid film but also solid materials which reveals possibility in nano- transistors fabrication \(^{46}\) , energy devices \(^{40}\) and immunosensor circuit printing \(^{47}\) . We expect this technique can open a new avenue for applications in nano- printing and nano- circuit manufacturing." + +<|ref|>text<|/ref|><|det|>[[696, 530, 878, 547]]<|/det|> +(Page 2- 3, Main text) + +<|ref|>sub_title<|/ref|><|det|>[[119, 567, 320, 584]]<|/det|> +## "Applications of IBFW + +<|ref|>text<|/ref|><|det|>[[118, 586, 882, 714]]<|/det|> +As discussed previously, IL film pattern prepared by IBFW technology manifests three distinguishable features. First, the ultralow film thickness down to \(30 \mathrm{~nm}\) indicates a high surface- volume ratio which is a key role in improving the gas sensing circuit sensitivity. Second, the capability of fabricating liquid film with desired pattern in a programmable and rewritable manner, which is important for in- situ chemical reaction and microfluidics chips. Third, the ILs are widely used in electrochemistry and reveal the possibility of transforming liquid film pattern into various solid materials ranges from organic to inorganic compounds." + +<|ref|>text<|/ref|><|det|>[[712, 715, 878, 732]]<|/det|> +(Page 9, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 751, 881, 899]]<|/det|> +"To demonstrate the potential of IBFW for microfluidics chip fabrication, we design an in- situ chemical reaction micro- chip. In Fig. 4c, the schematics shows a crosshair shaped micro fluid channel connects four separated droplets in four directions. Four square expansion windows are made on each part of the channel for the convenience of observation. The top- left inset shows the chip with four droplets on finger- tip. After the IBFW fabrications, \(0.1 \mu \mathrm{L}\) of sodium thiocyanate solution (NaSCN \(0.1 \mathrm{M}\) in deionized water) is injected into the top droplet, and serves as the colorimetric reagent for the detection of and in- situ reaction with different metal ions. After the injection of NaSCN, \(0.1 \mu \mathrm{L}\) of \(0.1 \mathrm{mM} \mathrm{Fe}^{3 + }\) solution, \(0.1 \mathrm{mM} \mathrm{Cu}^{2 + }\) solution and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 83, 882, 417]]<|/det|> +\(0.1\mathrm{mM}\mathrm{Co}^{2 + }\) are injected into the bottom, left and right droplets respectively. The microchip is rested in atmosphere for \(20\mathrm{min}\) for the metal ions fully diffuse into the channels and react with \(\mathrm{SCN}^{- }\) within different square windows with the ion names printed previously. Then the sample is transferred into vacuum chamber for \(48\mathrm{h}\) to diminish the water content in the solution system, which will alter the hydration status of the metal ion complexes and improve the colorimetric visibility. The red complex \(\mathrm{Fe(SCN)_3}\) deposits in the bottom window. The gray deposition in the left window is complex \(\mathrm{Cu(SCN)_2}\) . And the blue deposition in the right window is complex \(\mathrm{Co(SCN)_2}\) . As shown in Fig. 4c, the \(\mathrm{SCN}^{- }\) participates into 3 different reactions within several hundreds of micrometers flow channel. The time series pictures are shown in Supplementary Fig. 20, and the liquid film patterns remain unchanged during the experiments which last for over one month. The IBFW fluid channel exhibits great stabilities against vacuum/air transferring, the injection of solutions into droplet reservoir, and gravity. Such behavior demonstrates the robustness of the IBFW liquid film. More importantly, all reagents are dissolved in deionized water then injected into the IL droplets and diffuse into the IL flow channel. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte dissolved in water, ethanol and various molecular liquids due to the amphiphilicity of ILs. Such results greatly broaden the potential application fields for IBFW." + +<|ref|>text<|/ref|><|det|>[[701, 418, 878, 435]]<|/det|> +(Page 10, Main text) + +<|ref|>image<|/ref|><|det|>[[150, 460, 857, 654]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 659, 881, 788]]<|/det|> +
Figure. 4: (c) In-situ chemical reaction chip. The left part is the schematics of the chip. Crosshair channels connect four droplets which are used to inject reagent water solutions. \(0.1\mu \mathrm{L}\) of \(0.1\mathrm{M}\mathrm{NaSCN}\) , \(0.1\mathrm{mM}\mathrm{Co}^{2 + }\) , \(0.1\mathrm{mM}\mathrm{Fe}^{3 + }\) and \(0.1\mathrm{mM}\mathrm{Cu}^{2 + }\) are injected clockwise into four droplets (top, right, bottom, left). The inset on the top-left compares the size of microchip with fingertip, with red circle shows the four droplets. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for \(48\mathrm{h}\) after the injection, the color of complexes is more obvious with water removed from the system.
+ +<|ref|>text<|/ref|><|det|>[[675, 789, 878, 806]]<|/det|> +(Page 27- 28, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[130, 90, 870, 393]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[118, 413, 800, 432]]<|/det|> +## Supplementary Figure 20: Time series images of in-situ chemical reaction chip. + +<|ref|>text<|/ref|><|det|>[[117, 435, 880, 696]]<|/det|> +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48 h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non-direct physical contact for solution injections. (f) The reaction chip one month after injection (one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. (Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[642, 697, 878, 714]]<|/det|> +(Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 732, 880, 899]]<|/det|> +"Due to their unique properties, ILs have been proved to be an important category of solvent and electrolytes. Here we demonstrate that, by further combining with electrochemical procedure, the IBFW also manifests the capability of transforming liquid film pattern into various solid materials. Fig. 4d shows the schematics of a three- electrode electrochemistry experiment. A droplet of 1- ethyl- 3- methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) serves as the solvent of possible analytes, which are Silver bis (trifluoromethylsulfonyl)imide (Ag[NTf₂]) or a mixture of Ag⁺ and 7,7,8,8- tetracyanoquinodimethane (TCNQ) in our experiments. The liquid film pattern is fabricated by the IBFW technology onto the thin gold electrode and would be subsequently transformed into + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 233]]<|/det|> +nanoparticles. A \(10 \mathrm{nm}\) Au and \(5 \mathrm{nm}\) Ti film deposited onto \(\mathrm{SiO}_2\) serves as the working electrode and is connected to the workstation by a Pt probe. As revealed by the MC simulation results (Supplementary Fig. 9 b), the He ions with vertical stopping- range exceeds \(290 \mathrm{nm}\) can easily penetrate the \(15 \mathrm{nm}\) metal film and deposit positive charges into the \(300 \mathrm{nm}\) \(\mathrm{SiO}_2\) layer underneath. Therefore, the IBFW can be achieved on an ultra- thin metal film deposited on insulating substrate, and is not contradict with the conclusion that pure conducting substrates lead to the failure of IBFW shown in Fig. 2f. The counter electrode is a Pt probe emerged in IL, and a silver- plated probe serves as a pseudo reference electrode. + +<|ref|>text<|/ref|><|det|>[[118, 234, 881, 491]]<|/det|> +In Fig. 4e, we present an example of solid particles deposited from IBFW liquid film. The upper part shows silver nanoparticles with designed pattern (a \(20 \mu \mathrm{m} \times 3 \mu \mathrm{m}\) channel and PKU letters) potentiostatically deposited at - 0.2 V (vs. Ag) for 180 s onto the gold electrode surface. And the lower part shows blue AgTCNQ particles on gold surface make up a \(50 \mu \mathrm{m} \times 10 \mu \mathrm{m}\) rectangular pattern deposited at - 0.1 V (vs. Ag). Noteworthily, the electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees63. When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al.64, a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards, which is also observed in our experiments. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film. + +<|ref|>text<|/ref|><|det|>[[118, 492, 881, 733]]<|/det|> +Four cycles of cyclic voltammogram (CV) of \(10 \mathrm{mM} \mathrm{Ag}^+\) in IL is shown in Fig. 4f. The reduction peak of \(\mathrm{Ag}^+\) takes place at - 0.29 V (vs. Ag) with the peak current decreases as the scan cycles increases. We believe that the micro litter droplet with limited analyte dissolved lead to such results. The \(\mathrm{Ag}^+\) concentration decreases quickly after each cycle of CV scan, and the electron transfer is slower for the oxidation of \(\mathrm{Ag}\) metal. In Fig. 4g, we test the CV curves of five scan cycles of IL droplet with \(6 \mathrm{mM} \mathrm{Ag}^+\) and \(5 \mathrm{mM} \mathrm{TCNQ}\) . Two reduction peaks can be distinguished, one at 0.095 V (vs. Ag), and the other at - 0.21 V (vs. Ag). The first peak corresponds to the reduction of \(\mathrm{Ag}^+\) to \(\mathrm{Ag}^0\) (metal)44, and the second peak is related to the formation of \(\mathrm{AgTCNQ}\) complex (solid). Finally, we conceptually validate that IBFW technology is capable of transferring liquid film pattern into various solid materials and reveal the possibilities can be produced by combining IBFW with electrochemical procedures. The three- electrode experiment configuration, example of open- circuit- potential V- t curve and potentiostatic deposit I- t curve are shown in Supplementary Fig. 21. ” + +<|ref|>text<|/ref|><|det|>[[677, 734, 878, 751]]<|/det|> +(Page 10- 11, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 778, 880, 905]]<|/det|> +“As summarized in Fig. 4h, the IBFW technology manifests several intriguing features that can be harnessed for a variety of application fields. The IBFW technique can fabricate patterned ILs film with \(30 \mathrm{nm}\) thickness, \(100 \mathrm{nm}\) spatial resolution and over hundreds of \(\mu \mathrm{m}\) film length on insulating substrates (or coated with conducting metal films with \(10^1 \mathrm{nm}\) thickness). The surface- volume ratio endowed by the nanometer scale thickness can largely enhance the sensitivity of the IBFW film, and can be utilized in gas sensing circuit. The good solubility and biocompatibility of ILs make them suitable for the dissolve of various analytes. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 215]]<|/det|> +The IBFW film also exhibits robustness against air environment exposure, gravity, and physical contact to droplet reservoir. Such features reveal that the IBFW film can act as stable flow channel for the analyte solutions injected to the reservoir, and can largely simplify the fabrication procedures of micro/nanofluidic chips. Last but not least, IBFW liquid film with wide potential window can be combined with electrochemical procedures and the patterned liquid film can be transformed into different solid particles. Such results demonstrate the IBFW as a versatile tool for both nanofluidics and liquid/solid materials printing." + +<|ref|>text<|/ref|><|det|>[[701, 222, 878, 240]]<|/det|> +(Page 11, Main text) + +<|ref|>image<|/ref|><|det|>[[198, 265, 792, 872]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 877, 880, 913]]<|/det|> +
Figure 4 (d) The schematics of a three-electrode electrochemistry experiment. A droplet of IL with IBFW liquid film pattern printed onto the working electrode is the solvent for analytes.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 362]]<|/det|> +10 nm Au and 5 nm Ti deposited to \(300\mathrm{nm}\) TOX \(\mathrm{SiO_2}\) serves as the working electrode, Pt probe and silver- plated probe stuck into the droplet are the counter and pseudo- reference electrodes respectively. (e) An example of the patterned solid particles deposited on Au electrode surface. The upper part shows Ag particles make up a \(20\mu m\times 3\mu m\) rectangular film with PKU letters pattern which are deposited to Au surface at - 0.2 V (vs. Ag). The lower part shows blue AgTCNQ particles make up a \(50\mu m\times 10\mu m\) pattern which are deposited to Au surface at - 0.1 V (vs. Ag). Both are potentiostatically deposited for 180 s. (f) Four cycles of cyclic voltammogram of \(10\mathrm{mMAg^{+}([EMIM][NTf_2])}\) solution. The reduction peak at - 0.295 V (vs. Ag) can be seen, with peak current decreases with cycles. After four cycles, the reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal becomes less obvious. (g) Five cycles of cyclic voltammogram of \(6\mathrm{mM}\) \(\mathrm{Ag^{+}}\) and \(5\mathrm{mM}\) TCNQ ([EMIM][NTf2]) solution. The first reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal at 0.095 V (vs. Ag) can be seen. The \(+300\mathrm{mV}\) shift of Ag reduction peak at present of TCNQ is consistent with literature44. The reduction peak current of Ag reduces quickly and become hard to distinguish as cycle increases. (h) A summary schematic to show the distinct features of IBFW technique, and the potential application fields that are suitable for IBFW. + +<|ref|>text<|/ref|><|det|>[[675, 364, 878, 380]]<|/det|> +(Page 27- 28, Main text) + +<|ref|>image<|/ref|><|det|>[[123, 444, 880, 664]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[117, 678, 760, 696]]<|/det|> +Supplementary Figure 21: The electrodeposition experiments of AgTCNQ. + +<|ref|>text<|/ref|><|det|>[[117, 697, 880, 769]]<|/det|> +(a) The three-electrode configuration adopted in current work. (b) The green line is the V-t curve of AgTCNQ open circuit potential measurement, which serves as a reference for the subsequent experiments. The purple line is the deposition current vs. time curve of AgTCNQ deposition at constant potential, -0.1 V (vs. Ag). + +<|ref|>text<|/ref|><|det|>[[642, 771, 878, 788]]<|/det|> +(Page S38, Supplementary) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 103, 881, 214]]<|/det|> +Comment #2: The fabrication has to be performed in an ultra- high vacuum environment. It was not very clearly stated or studied, what happens to the samples after they are taken out of the HIM and exposed to air, tilting of the chip (gravity pulling in another direction), static charges, mechanical contact or other environmental variables. Common sense picture of liquids gives the impression that the "circuit" is not very stable. If it is, data needs to be provided to convince the reader otherwise. + +<|ref|>sub_title<|/ref|><|det|>[[118, 235, 208, 251]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[118, 253, 540, 270]]<|/det|> +We thank the reviewer for the inspiring suggestions. + +<|ref|>text<|/ref|><|det|>[[118, 271, 880, 418]]<|/det|> +IBFW films are stable to the exposure to air environment or transferring between vacuum/air conditions. The in- situ reaction chip presented in Supplementary Fig. 20 proves that the IBFW liquid film is quite stable after exposure to atmosphere, and the transfer between vacuum chamber and air environment repeatedly. The negligible vapor pressure of ionic liquids accounts for its vacuum/air environment stability. The evaporation of ionic liquids at ambient condition is indiscernible and do not suffer from coffee ring effect. The contact line of ionic liquid is pinned by solid substrate and the sample patterns are barely changed for one month in Supplementary Fig. 20. + +<|ref|>text<|/ref|><|det|>[[118, 418, 880, 567]]<|/det|> +IBFW films are stable to gravity. We employed a customized sample holder which can adjust the tilting angle from 0 to \(180^{\circ}\) . The in- situ reaction chip was mounted to the holder with tilting angle settled at \(120^{\circ}\) (inset of Supplementary Fig. 20f), and the reaction chip with IBFW patterns was stored in the sample box for one week. The optical images (Supplementary Fig. 20) show that the IBFW film pattern was barely changed through the experiments. The micronano meter size of liquid film can explain this stability. For liquid film down to nm thickness and micrometer length, the surface tension, disjoining pressure far exceeds the gravity, so turning the chip upside down or tilting dose not influence the film pattern. + +<|ref|>text<|/ref|><|det|>[[117, 567, 880, 825]]<|/det|> +IBFW films are relatively stable at mild static charge conditions. In the electrochemistry measurement, solid patterns were deposited from the liquid film at a relative low bias voltage \((- 0.1 \sim - 0.2 \mathrm{~V})\) see Fig. 4e. Such a result indicates that the IBFW film exhibits relative stability to static charge. The electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees (Ref. [63]). When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al. (Ref. [64]), a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards. Such phenomenon is also observed in our cyclic voltammogram (CV) experiments, where the entire contact line was moved and the IBFW film patterns were destroyed. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film. + +<|ref|>text<|/ref|><|det|>[[118, 826, 880, 899]]<|/det|> +IBFW film cannot remain the same after a direct physical contact of daily subjects, but direct contact to the droplet reservoir does not change the liquid film. In the in- situ reaction chip experiments and the electrochemical experiments, the droplet connected to the liquid film is penetrated by micropump for solution injection or electrode probes. The liquid film remains + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 140]]<|/det|> +intact through the experiments, and remains barely changed for days. As can be seen from the comparison of microchip optical images and HIM images before and after the injection and reaction (Supplementary Fig. 20). + +<|ref|>text<|/ref|><|det|>[[118, 141, 880, 214]]<|/det|> +IBFW film is vulnerable to a direct exposure to dust or other contaminations. Since the size of the liquid film is small, too much dusts absorbed to the chip surface or the liquid will damage the liquid film. Short time exposure to the atmosphere condition is acceptable. The IBFW samples are stored in a vacuum chamber and are only took out for experiments. + +<|ref|>text<|/ref|><|det|>[[117, 233, 880, 418]]<|/det|> +"As shown in Fig. 4c, the SCN- participates into 3 different reactions within several hundreds of micrometers flow channel. The time series pictures are shown in Supplementary Fig. 20, and the liquid film patterns remain unchanged during the experiments which last for over one month. The IBFW fluid channel exhibits great stabilities against vacuum/air transferring, the injection of solutions into droplet reservoir, and gravity. Such behavior demonstrates the robustness of the IBFW liquid film. More importantly, all reagents are dissolved in deionized water then injected into the IL droplets and diffuse into the IL flow channel. These experiments demonstrate that IBFW liquid film pattern can act as a stable flow channel for later injection of analytes dissolved in water, ethanol, and various molecular liquids due to the amphiphilicity of ILs." + +<|ref|>text<|/ref|><|det|>[[701, 419, 878, 436]]<|/det|> +(Page 10, Main text) + +<|ref|>image<|/ref|><|det|>[[130, 457, 870, 760]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[118, 780, 800, 799]]<|/det|> +## Supplementary Figure 20: Time series images of in-situ chemical reaction chip. + +<|ref|>text<|/ref|><|det|>[[118, 802, 880, 912]]<|/det|> +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48 h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 234]]<|/det|> +become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non- direct physical contact for solution injections. (f) The reaction chip one month after injection (with one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. + +<|ref|>text<|/ref|><|det|>[[642, 235, 878, 252]]<|/det|> +(Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[117, 270, 880, 473]]<|/det|> +"We delineate a system free energy ratio scenario for a liquid film system with unit length/ width and thickness vary from \(1\mathrm{nm}\) to \(4\mathrm{mm}\) in Fig. 3e, and the film thickness and corner radius are compared with published results \(^{16,18,23,24}\) . System free energy composes of the volumetric term (gravity, electrostatic, etc.), the surface tension term, and the disjoining pressure term. The surface tension remains fixed magnitude of \(10^{1} \mathrm{mN} / \mathrm{m}\) , and its contribution to the system is almost constant with the thickness variation. When system size exceeds capillary length, \(\lambda_{\text{capillary}}\) , the volumetric term contributes most of the system free energy. For any system with characteristic length below capillary length, however, the influence of volumetric term (gravity etc.) can be neglected. At millimeter to micrometer range, the surface tension dominates, and the majority of traditional microfluidics methods belong to such region, with the spatial resolution difficult to approach nanoscale." + +<|ref|>text<|/ref|><|det|>[[712, 475, 878, 491]]<|/det|> +(Page 9, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 510, 880, 770]]<|/det|> +"In Fig. 4e, we present an example of solid particles deposited from IBFW liquid film. The upper part shows silver nanoparticles with designed pattern (a \(20 \mu \mathrm{m} \times 3 \mu \mathrm{m}\) channel and PKU letters) potentiostatically deposited at - 0.2 V (vs. Ag) for 180 s onto the gold electrode surface. And the lower part shows blue AgTCNQ particles on gold surface make up a \(50 \mu \mathrm{m} \times 10 \mu \mathrm{m}\) rectangular pattern deposited at - 0.1 V (vs. Ag). Noteworthily, the electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees \(^{63}\) . When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al. \(^{64}\) , a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards, which is also observed in our experiments. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film." + +<|ref|>text<|/ref|><|det|>[[702, 772, 878, 788]]<|/det|> +(Page 11, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 825, 880, 899]]<|/det|> +Comment #3: Some data was provided with different substrates. What about varying the surface treatment, or cleaning? How sensitive is the success of the writing to the cleanliness of the substrate? You say you anneal the substrates at \(320 \mathrm{C}\) in hydrogen flow. Is that to remove organic contaminants? What if you skip the annealing step? Or use oxygen plasma cleaning + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 86, 190, 100]]<|/det|> +instead? + +<|ref|>sub_title<|/ref|><|det|>[[118, 123, 207, 138]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 140, 880, 325]]<|/det|> +Response:We thank the reviewer for the questions. Vary the surface treatment or cleaning procedures does not influence the IBFW experiments as long as the surface cleanliness is guaranteed. The cleanliness of the substrate is crucial for the IBFW experiment. The liquid film is about \(30 \mathrm{nm}\) thick, so any dust or pollutants can easily influence the liquid film. Besides, the Helium ion microscope (HIM) is sensitive to organic pollutants. Therefore, the solid substrate and liquid have to be cleaned thoroughly before transferred into the HIM chamber, to eliminate potential volatile pollutants. The annealing progress is to remove possible organic contaminants under this consideration. Skipping the annealing or other cleaning process may do harm to the instrument, so we did not attempt to do so. We tested with a SUNJUNE oxygen plasma cleaner and achieved the same cleanliness we need and included it into the Methods section. + +<|ref|>sub_title<|/ref|><|det|>[[118, 345, 287, 361]]<|/det|> +## "IBFW experiment + +<|ref|>text<|/ref|><|det|>[[117, 363, 880, 492]]<|/det|> +The fabrication details of the experiments used \(\mathrm{SiO_2}\) wafers are described below. An amorphous \(\mathrm{SiO_2}\) layer with a thickness of approximately \(3\mu \mathrm{m}\) is deposited by plasma- enhanced chemical vapor deposition (PECVD) on a \(500\mu \mathrm{m}\) thickness quartz substrate surface. Prior to the experiment, chips are cleaned with acetone, ethanol, and ultrapure water sequentially with ultrasonication. To remove any surface organic pollutants, the wafers are annealed in a tubing furnace at \(320^{\circ}\mathrm{C}\) with a mixture gas flow of hydrogen and argon for at least 3 hours, a SUNJUNE oxygen plasma cleaner can also fulfill the purpose." + +<|ref|>text<|/ref|><|det|>[[703, 492, 878, 509]]<|/det|> +(Page 11, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 546, 884, 603]]<|/det|> +Comment #4: How do you know that the ions of the ionic liquid stay intact (are not broken down) under the He ion irradiation? Typically, organic compounds (such as resists for example) can be strongly modified (bonds broken etc) with high energy ion beams. + +<|ref|>sub_title<|/ref|><|det|>[[118, 623, 207, 639]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 641, 881, 844]]<|/det|> +We thank the reviewer for the important comments. Both ions (EMIM \(^+\) and DCA \(^+\) ) employed are reported to show good radiolytic stability. The imidazolium cations have shown good radiolytic stability due to the aromatic ring can adsorb and relax the radiation energy. The dosage of helium focused ion beam (HFIB) in our IBFW experiments is much smaller than the damage dosage reported in literature \(^{1,2}\) (main text Ref. [79, 80]). The radiolytic stability of imidazolium based ionic liquids under \(\mathrm{He}^{2 + }\) radiation was tested \(^{1}\) . Decompose products \(\mathrm{H}_2\) were measured by NMR with irradiation dose ranges from 2 to \(400 \mathrm{kGy}\) , and no trace of reaction \((< 1\%)\) was detected for \(2 \mathrm{kGy}\) irradiation. The irradiation dosage of Helium ion is \(0.25 \mathrm{Gy}\) during a typical IBFW experiment. For a \(10 \mu \mathrm{m} \times 1 \mu \mathrm{m}\) film pattern with scanned area \(A\) fabricated from a \(1 \mu \mathrm{L}\) IL droplet with \(1 \mathrm{pA}\) beam current \(I\) , \(1 \mu \mathrm{s}\) dwell time \(\tau\) , \(1 \mathrm{nm}\) scan spacing \(s\) , and \(30 \mathrm{kV}\) accelerate voltage \(U\) , the dosage can be calculated as: + +<|ref|>equation<|/ref|><|det|>[[116, 852, 805, 893]]<|/det|> +\[D = \frac{I n c i d e n t E n e r g y}{M a s s o f I L} = \frac{U\cdot I\cdot\tau\frac{A}{s^2}}{V\cdot\rho} = \frac{30\times 10^3V\times\frac{10^{-12}C / s}{1.602\times 10^{-19}C / e}\times\frac{10\times 1\mu m^2}{1\times 1n m^2}}{0.001cm^3\times 1.11g / cm^3} = 0.25\frac{J}{kg} = 0.25 G y.\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 140]]<|/det|> +The [EMIM+] adopted in IBFW has a shorter alkyl chain attached to the aromatic ring, so the radiolytic stability of [EMIM+] should be better than the [BMIM+] tested in literature. Therefore, we believe that the cations of imidazolium are intact. + +<|ref|>text<|/ref|><|det|>[[118, 141, 880, 214]]<|/det|> +Anions structures also influence the radiolytic stability. The [DCA+] is the most radiolytic stable anions among all anions2. The stability of a free radical decreases when the hybridization of the carbon goes from sp3 to sp2 to sp. Thus, it is hard to induce cleavage of the C≡N bond of [DCA+] to form ·C=N. + +<|ref|>text<|/ref|><|det|>[[118, 215, 880, 270]]<|/det|> +Besides, the electrochemical results of the Ag(NTF2) and TCNQ were consistent with literatures (main text Ref. [43, 44]), we believe they are not infected by the HFIB irradiation. In summary, the radiolysis effect on our sample can be negligible. + +<|ref|>text<|/ref|><|det|>[[118, 270, 880, 306]]<|/det|> +We plan to conduct a XPS or Raman experiment to verify our idea, but the instrument is not available at the time, we shall conduct it as soon as possible. + +<|ref|>text<|/ref|><|det|>[[118, 307, 877, 343]]<|/det|> +1. Allen, D. et al. An investigation of the radiochemical stability of ionic liquids. Green Chem. 4, 152-158 (2002). + +<|ref|>text<|/ref|><|det|>[[118, 344, 880, 380]]<|/det|> +2. Xue, Z., Qin, L., Jiang, J., Mu, T. & Gao, G. Thermal, electrochemical and radiolytic stabilities of ionic liquids. Phys. Chem. Chem. Phys. 20, 8382-8402 (2018). + +<|ref|>sub_title<|/ref|><|det|>[[118, 400, 656, 418]]<|/det|> +## "Supplementary Note 7: Influence of radiolysis effect in IBFW + +<|ref|>text<|/ref|><|det|>[[118, 419, 880, 455]]<|/det|> +The ILs and the electrochemistry analytes in the main text remain intact through the IBFW experiments. The conclusion is based on the following discussion. + +<|ref|>text<|/ref|><|det|>[[118, 455, 880, 604]]<|/det|> +The imidazolium cations have shown good radiolytic stability. The dosage of HIB in our IBFW experiments is much smaller than the damage dosage reported in literature30,31. The radiolytic stability of imidazolium based ionic liquids under \(\mathrm{He}^{2 + }\) radiation were tested1. Decompose products \(\mathrm{H}_{2}\) were measured by NMR with irradiation dose ranges from 2 to \(400\mathrm{kGy}\) , and no trace of reaction (<1%) was detected for \(2\mathrm{kGy}\) irradiation. The irradiation dosage of Helium ion is 0.25 Gy during a typical IBFW experiment. For a \(10\mu \mathrm{m}\times 1\mu \mathrm{m}\) film pattern with scanned area \(A\) fabricated from a \(1\mu \mathrm{L}\) IL droplet with \(1\mathrm{pA}\) beam current \(I\) , \(1\mu \mathrm{s}\) dwell time \(\tau\) , \(1\mathrm{nm}\) scan spacing \(s\) , and \(30\mathrm{kV}\) accelerate voltage \(U\) , the dosage can be calculated as: + +<|ref|>equation<|/ref|><|det|>[[117, 610, 805, 655]]<|/det|> +\[D = \frac{I n c i d e n t E n e r g y}{M a s s o f I L} = \frac{U\cdot I\cdot\frac{A}{s^{2}}}{V\cdot\rho} = \frac{30\times 10^{3}V\times\frac{10^{-12}C / s}{1.602\times 10^{-19}C / e}\times\frac{10\times 1\mu m^{2}}{1\times 1n m^{2}}}{0.001c m^{3}\times 1.11g / c m^{3}} = 0.25\frac{J}{k g} = 0.25 G y.\] + +<|ref|>text<|/ref|><|det|>[[118, 659, 880, 714]]<|/det|> +The [EMIM+] adopted in IBFW has a shorter alkyl chain attached to the aromatic ring, so the radiolytic stability of [EMIM+] should be better than the [BMIM+] tested in literature. Therefore, we believe that the cations of imidazolium are intact. + +<|ref|>text<|/ref|><|det|>[[118, 715, 880, 788]]<|/det|> +Anions structures also influence the radiolytic stability. The [DCA+] is the most radiolytic stable anions among all anions31. The stability of a free radical decreases when the hybridization of the carbon goes from sp3 to sp2 to sp. Thus, it is hard to induce cleavage of the C≡N bond of [DCA+] to form ·C=N. + +<|ref|>text<|/ref|><|det|>[[118, 789, 880, 844]]<|/det|> +Besides, the electrochemical results of the Ag(NTF2) and TCNQ were consistent with literatures (main text Ref. [43, 44]), we believe they are not infected by the HFIB irradiation. In summary, the radiolysis effect on our sample can be negligible." + +<|ref|>text<|/ref|><|det|>[[642, 846, 879, 863]]<|/det|> +(Page S16, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 881, 880, 899]]<|/det|> +Comment #5: What sets the "minimal line width" scale of 100 nm? Shouldn't it in principle + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 878, 120]]<|/det|> +be much narrower, as the He ion beam interaction volume at the surface is very small (Fig S7) (hence its high imaging resolution \(< \mathrm{nm}\) ). + +<|ref|>sub_title<|/ref|><|det|>[[118, 142, 207, 157]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 159, 880, 455]]<|/det|> +We thank the reviewer for the important comment. The \(100\mathrm{nm}\) resolution of liquid film is determined by the surface charge injected by the helium focused ion beam (HFIB). The beam spot of HFIB is \(0.5\mathrm{nm}\) , but the He ions interact with the sample atoms and would be diffracted while traveling through the solid materials. Our Monte Carlo simulation results (Supplementary Fig. 9) and Ohya et. al's results (main text Ref. [48]) revealed the Helium ions irradiating \(\mathrm{SiO_2}\) (we also tested \(15\mathrm{nm}\) metal on \(300\mathrm{nm}\mathrm{SiO_2}\) for electrochemistry experiments) substrates have lateral projection length ranges from \(90\mathrm{nm}\) to \(110\mathrm{nm}\) , therefore the positive charges distribute around \(200\mathrm{nm}\) in lateral direction for single injection spot of He ions. The \(100\mathrm{nm}\) range is probably the center region of surface charging that is strong enough to induce ion emission and form liquid film. Consequently, the resolution of IBFW liquid film is \(100\mathrm{nm}\) for the amorphous \(\mathrm{SiO_2}\) substrate in our experiments. Since electron beams can be diffracted more easily than HFIB, the surface charging region induced by electron beam is much larger. As a result, \(5\mathrm{kV}\) electron beam fails to achieve the programmable control of the liquid film. We conducted experiment employing scanning electron microscope (SEM) for comparison. We added an explanation to liquid film resolution and a comparison of the liquid inducing results of HFIB and electron beam in the main text and Supplementary Fig. 8. + +<|ref|>text<|/ref|><|det|>[[117, 473, 880, 714]]<|/det|> +"When HFIB irradiates at or near the CTL of droplet, the Helium ions generate special charges distribution48 in the \(\mathrm{SiO_2}\) substrate, the positive surface charges induce the primary ion emission from the IL reservoir (Fig.2a). HFIB exhibits two distinguishable features compared with electron beam and other ion beams48. Firstly, the divergence of HFIB interacting with solid samples is much smaller than electron beam due to its larger mass49, which lead to a more localized surface charging area and consequently a programmable control over liquid flow (Supplementary Fig. 8). Secondly, HFIB tends to penetrate sample and induce less damaging compared with Gallium beams48. The penetration depth exerts significant influence on IBFW's application potential in electrochemistry field. For example, \(30\mathrm{keV}\) He beams with hundreds nm stopping range can easily penetrate a \(10\mathrm{nm}\) Au and \(5\mathrm{nm}\) Ti electrode deposited on \(\mathrm{SiO_2}\) wafer and induce patterned liquid flow without devastating effect to Au surface (Supplementary Fig. 9), while \(30\mathrm{keV}\) Ga with stopping range less than \(20\mathrm{nm}^{48}\) is hard to penetrate metal films and can easily cause damage to the electrode." + +<|ref|>text<|/ref|><|det|>[[712, 715, 878, 731]]<|/det|> +(Page 4, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 733, 880, 807]]<|/det|> +"Monte Carlo simulation results48 reveal that the lateral projection length of \(30\mathrm{kV}\) He ions irradiated on \(\mathrm{SiO_2}\) (also \(\mathrm{SiO_2}\) with \(10\mathrm{nm}\) Au and \(5\mathrm{nm}\) Ti layers) ranges from \(90\mathrm{nm}\) to \(110\mathrm{nm}\) (Supplementary Fig. 9a,b). The consequent positive charges (ions, holes) distribute over \(10^{2}\mathrm{nm}\) in lateral direction and determine the ion emission and IBFW spatial resolution." + +<|ref|>text<|/ref|><|det|>[[712, 808, 878, 824]]<|/det|> +(Page 4, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[175, 90, 821, 260]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 284, 875, 303]]<|/det|> +Supplementary Figure 8: SEM images of liquid film induced by ion and electron beams. + +<|ref|>text<|/ref|><|det|>[[118, 306, 880, 398]]<|/det|> +(a) 30 keV helium focused ion beam induced liquid film on a SiO2 substrate; (b) 5 keV electron beam induced liquid flow on the identical substrate. The liquid can also be induced to flow from the reservoir, but the flow pattern is out of control. The much more diffractive nature of the electron beam-sample interaction, and the consequent wider surface charges lateral distribution give rise to such results. + +<|ref|>text<|/ref|><|det|>[[642, 399, 878, 417]]<|/det|> +(Page S24, Supplementary) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 90, 848, 670]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 677, 881, 899]]<|/det|> +Supplementary Figure 9: The HFIB irradiation interaction with liquid and substrates under experimental conditions. (a) Monte Carlo simulation results of 3000 He ion irradiating a ionic liquid film of 30 nm thickness above silica substrate, the accelerate voltage is 30 keV to reproduce the experimental conditions. The right part is the magnification of He ions' near liquid trajectory lines and spatial distribution. (b) the MC simulation results of He ions with 30 KV irradiate 10 nm Au, 5 nm Ti and 300 nm SiO2. Similar to the results in the previous case, the HFIB can easily penetrate the first 15 nm layers of metal and deposit positive ions into the insulating SiO2 substrate. Such results indicate that IBFW can also be done on insulating substrates with thin film of metal deposited on the surface. The vertical stopping range of He ions exceed 290 nm on both substrates. The lateral projection distances of He ions in both cases range from 90 nm to 110 nm in separated repeated simulations, which agree with the IBFW film resolution 100 nm. (c) the XPS spectra of the same substrate before (black) and after (red) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 120]]<|/det|> +the irradiation of HFIB under experimental conditions with insets show the ESEM results of pristine and irradiated area of solid surface. + +<|ref|>text<|/ref|><|det|>[[616, 122, 878, 140]]<|/det|> +(Page S25- 26, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 177, 880, 251]]<|/det|> +Comment #6: Related to that, I do not understand the suggested mechanism. In Fig. 2A the local surface charges, induced by the beam current, are located directly under the IL droplet. Yet, in the unnumbered Figure in Note S3 (Electric field driven ion emission calculation), the surface charge is located some distance away from the IL reservoir. Something doesn't match. + +<|ref|>sub_title<|/ref|><|det|>[[118, 272, 207, 288]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[117, 289, 880, 492]]<|/det|> +We thank the reviewer for the comment. The two figures illustrate different situations and lead to this mismatch. The IBFW effect can be achieved by set the start scan position right at or near the contact line. As long as the surface charges injected by HFIB is strong enough to induce ion emission and form precursor film, liquid film can be induced. Fig. 2a shows the typical condition in standard IBFW experiments, where HFIB scans right at the contact line to achieve the best patterning performances. The unnumbered figure has been moved to the main text according to Comment #10 and labeled as Fig. 2d. When the start scan position is a bit away from the contact line, the surface charge injected by HFIB is still enough to induce liquid film, but the HFIB dosage required increases with this distance. Fig. 2d illustrates the mechanical balance between the surface tension and the electrostatic force exerted by surface charges located at a distance away from the IL- vacuum interface. + +<|ref|>text<|/ref|><|det|>[[118, 511, 880, 547]]<|/det|> +We have reconstructed the Working principal section, and a more detailed response can be found in the latter response to comments 7- 10. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[168, 88, 838, 490]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 506, 881, 914]]<|/det|> +
Figure 2: Working principle of IBFW nano-printing. (a-c) Schematic of the IBFW working principle. (a) When HFIB irradiates the CTL, the positive surface charging induces the primary anion emission. (b) When HFIB ceases to scan, surface charging dissipates and the emitted anions induce the secondary cation emission. (c) The emitted ions from previous stages form an ultra-thin precursor film, and the consequent disjoining pressure propels and stabilizes liquid film. (d) The mechanical balance between the surface charge density induced electrostatic force and surface tension of IL-vacuum interface. The distance between HFIB scans spot and contact line is \(d\) ; the surface charging uniformly distributes over a region with length scale, \(l_0\) ; the surface-charge-exert electrostatic force and distorts the IL-vacuum interface, balanced by the surface tension \(\gamma\) . (e) Experimental HFIB dosage density to induce IL flow (ions per square of nm) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. (f) IBFW induced liquid film lengths ( \(\mu \mathrm{m}\) ) on substrates with different conductivities. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. (g) Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removement. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. The shaded regions (red) represent the surface injection region with positive charges. (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 251]]<|/det|> +constant beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20\mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1\mathrm{pA}\) , dwell time \(2\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit. The discrepancy at extreme long film length may be due to the HFIB irradiation history. The fabrication of film with hundreds \(\mu \mathrm{m}\) length usually takes hours of HFIB irradiation. The accumulated positive charges lead to a higher surface potential and a boundary slip length that exceeds the upper limit in literature, which give rise to an unexpected higher film speed. + +<|ref|>text<|/ref|><|det|>[[701, 285, 878, 302]]<|/det|> +(Page 22, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 321, 880, 432]]<|/det|> +Comment #7: Eq. (1) cites for example Ref. 46, where some of the terms were introduced. However, in that paper, surface charge density \(Q\) was specifically described as "areal hole density" i.e. describing a positive charge, whereas you seem to assume a negative charge. How can you apply the same equations to these two opposing cases? Why would in your case the negative charge be dominant, (which the authors in Ref 46 assume can be neutralized more easily)? + +<|ref|>text<|/ref|><|det|>[[117, 450, 881, 525]]<|/det|> +Comment #8: - In addition, you should describe already in the main text what each term in Eq (1) describes, and define every variable of the equations of the main text (including Eq (2)). Comment #9: - Shouldn't the electrons of the flood gun be somehow part of the modelling of Eq. (1)? + +<|ref|>text<|/ref|><|det|>[[117, 544, 880, 579]]<|/det|> +Comment #10: To understand Eq (2), the figure from Supplementary Note 3 is required in the main text. + +<|ref|>sub_title<|/ref|><|det|>[[118, 619, 237, 634]]<|/det|> +## Responses to: + +<|ref|>sub_title<|/ref|><|det|>[[118, 637, 235, 652]]<|/det|> +## Comment #7 + +<|ref|>text<|/ref|><|det|>[[117, 655, 880, 746]]<|/det|> +We thank the reviewer for these very important suggestions and questions that inspire us to have a thorough reconsideration of the ion emission model. After carefully reconsideration and further experiments, we believe that the positive charges injected by HFIB induce the primary ion emission, and the equation 1 cited from Ref. [46] is still employed to explain the positive surface charge density. Several reasons change our mind: + +<|ref|>text<|/ref|><|det|>[[117, 747, 880, 911]]<|/det|> +1. The charge carrier lifetime in amorphous \(\mathrm{SiO_2}\) is of \(10\mathrm{ns}\) magnitude (main text Ref. [50, 51]), which means the electrons only survive for \(10\mathrm{ns}\) before recombination with holes and ions. This makes the reabsorb secondary electrons impossible to accumulate and induce ion emission. +2. The secondary electrons (SEs) are reabsorbed by positive surface charge and gather near the surface when the \(\mathrm{SiO_2}\) layer thickness reaches \(300\mathrm{nm}\) . When silicon dioxide thickness is down to \(100\mathrm{nm}\) , no significant SE reabsorption takes place (main text Ref. [48]). This is consistent with our observation of Si wafer with \(100\mathrm{nm}\) thermal oxidized (TOX) \(\mathrm{SiO_2}\) layer (Fig. R1a). The HIM images come from a SE detector with positive bias voltage to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 881, 250]]<|/det|> +collect the SEs excited by HFIB. Therefore, if reabsorption of SE takes place, the HIM image of the \(\mathrm{SiO_2}\) would be black. In Fig. R1(a) the \(\mathrm{SiO_2}\) substrate is brighter than IL droplet which is contrary to the results observed on the \(300\mathrm{nm}\) or pure \(\mathrm{SiO_2}\) substrate employed in the manuscript (as shown in main text Fig. 1e). The results confirm that SE reabsorption does not happen on \(100\mathrm{nm}\mathrm{SiO_2}\) substrate. As shown in Fig. R1, we successfully conducted IBFW experiments to induce IL film from liquid reservoir on \(100\mathrm{nm}\mathrm{SiO_2}\) layer oxidized on Si wafer. Since no SE reabsorption happens on this substrate, we believe that not the negative charges but the positive charges account for the ion emission process involved in IBFW. + +<|ref|>image<|/ref|><|det|>[[147, 253, 855, 486]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 492, 878, 528]]<|/det|> +
Fig. R1: HIM images of IL droplets on \(100\mathrm{nm}\mathrm{SiO_2}\) and the optical image of the same droplets and film
+ +<|ref|>image<|/ref|><|det|>[[217, 546, 777, 769]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[116, 770, 880, 825]]<|/det|> +
Fig. 1e: The HIM image of IL pattern (brighter part) on PECVD \(\mathrm{SiO_2}\) (the black back ground, the reabsorption of SEs is so strong that the \(\mathrm{SiO_2}\) substrate can barely be observed) is quoted from main text to compare with Fig. R1.
+ +<|ref|>text<|/ref|><|det|>[[118, 826, 881, 899]]<|/det|> +3. According to main text Ref. [48], the electron beam also induces positive surface charges in \(\mathrm{SiO_2}\) . This is due to the Secondary Electron Yield (which means the average number of SEs excited by one incident electron) of electron beam is larger than one, so with one electron injected to the sample more than one electrons are excited out from the sample. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 880, 158]]<|/det|> +Therefore, the overall charging effect of electron beam is positive. The electron beam can also induce the flow of ionic liquids (Supplementary Fig. 8), but the film pattern induced by electron beam is out of control. The diffractive nature of electron lead to a much wider surface charge lateral distribution may give rise to such results. + +<|ref|>text<|/ref|><|det|>[[118, 159, 881, 270]]<|/det|> +Based on these results, we have reconstructed the working principal section in our manuscript. The positive surface charges injected by HIM induce the primary ion emission and the IBFW phenomenon. We have also reconducted the MD simulation, using only positive charges injected and removed from the substrate to induce an identical film of ions and the movement of the droplet mass center. The equation we adopted from literature (old [46], now Ref. [54]) that modeling the positive charge of silica by HFIB irradiation is still adopted in our manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 289, 880, 362]]<|/det|> +Comment #8 - In addition, you should describe already in the main text what each term in Eq (1) describes, and define every variable of the equations of the main text (including Eq (2)). We expanded the working principal section so that every term of the equations in main text have been explained. + +<|ref|>text<|/ref|><|det|>[[118, 380, 880, 418]]<|/det|> +Comment #9- Shouldn't the electrons of the flood gun be somehow part of the modelling of Eq. (1)? + +<|ref|>text<|/ref|><|det|>[[120, 419, 762, 437]]<|/det|> +There are two reasons we did not include the flood gun current into calculation: + +<|ref|>text<|/ref|><|det|>[[118, 437, 881, 567]]<|/det|> +1. The flood gun can only work after the HFIB finishes an entire row (or entire frame) of scan spots and is always turned off during the HFIB irradiation, with a small beam current 0.5 pA. The NPVE scan spots array usually composes \(1024 \times 1024\) scan spots, so the injection dosage of HFIB exceeds the flood gun at least three to six orders of magnitude. +2. The ion emission model considers HFIB scans a single spot or a very small area near the contact line to induce ion emission, the flood gun most likely is not working under such conditions. + +<|ref|>text<|/ref|><|det|>[[118, 568, 880, 603]]<|/det|> +Comment #10: To understand Eq (2), the figure from Supplementary Note 3 is required in the main text. + +<|ref|>text<|/ref|><|det|>[[118, 605, 648, 622]]<|/det|> +We have added the figure to the main text, and labeled as Fig. 2d. + +<|ref|>sub_title<|/ref|><|det|>[[180, 666, 440, 684]]<|/det|> +## "Working Principles of IBFW + +<|ref|>text<|/ref|><|det|>[[118, 692, 880, 912]]<|/det|> +When HFIB irradiates at or near the CTL of droplet, the Helium ions generate special charges distribution48 in the \(\mathrm{SiO}_2\) substrate, the positive surface charges induce the primary ion emission from the IL reservoir (Fig.2a). HFIB exhibits two distinguishable features compared with electron beam and other ion beams48. Firstly, the divergence of HFIB interacting with solid samples is much smaller than electron beam due to its larger mass49, which lead to a more localized surface charging area and consequently a programmable control over liquid flow (Supplementary Fig. 8). Secondly, HFIB tends to penetrate sample and induce less damaging compared with Gallium beams48. The penetration depth exerts significant influence on IBFW's application potential in electrochemistry field. For example, \(30 \mathrm{keV}\) He beams with hundreds nm stopping range can easily penetrate a \(10 \mathrm{nm}\) Au electrode deposited on \(\mathrm{SiO}_2\) wafer and induce patterned liquid flow without devastating effect to Au surface (Supplementary Fig. 9), while \(30 \mathrm{keV}\) Ga with stopping range less than \(20 \mathrm{nm}\)48 is hard to penetrate metal films and can + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 251]]<|/det|> +easily cause damage to the electrode. During the HFIB irradiation, He ions interact with solid atoms and excite holes- electrons in the sample, then the He ions lose kinetic energy and rest within the stopping range. Since the excited electrons in amorphous \(\mathrm{SiO_2}\) only survive \(10\mathrm{ns}\) or less before the recombination takes place \(^{50,51}\) , the positive charges dominate the surface charging and account for the primary anion emission. Monte Carlo simulation results \(^{48}\) reveal that the lateral projection length of \(30\mathrm{kV}\) He ions irradiated on \(\mathrm{SiO_2}\) (also \(\mathrm{SiO_2}\) with \(10\mathrm{nm}\) Au and \(5\mathrm{nm}\) Ti layers) ranges from \(90\mathrm{nm}\) to \(110\mathrm{nm}\) (Supplementary Fig. 9a,b). The consequent positive charges (ions, holes) distribute over \(10^{2}\mathrm{nm}\) in lateral direction and determine the ion emission and IBFW spatial resolution. + +<|ref|>text<|/ref|><|det|>[[117, 259, 880, 424]]<|/det|> +When the HFIB ceases to irradiate, the surface charges dissipate due to the drainage current and the electron- hole recombination (Fig. 2b) then the emitted anions induce the secondary cation emission. Both ions meet ahead of the CTL and form an ultra- thin precursor film with thickness comparable to ion size at the irradiated area. As a matter of fact, when the electric field of surface charge is strong enough, not only separate ions but clusters or even tiny droplets contain both ions are emitted \(^{52}\) to scanned area and make up the precursor films. In both cases, the ultralow thickness of precursor film gives rise to the high disjoining pressure \((10^{5 - 6}\mathrm{Pa})\) that irrigates and thickens the precursor film until be balanced by the capillary force \((10^{2 - 3}\mathrm{Pa})\) and a continuous liquid film is formed (Fig. 2c). + +<|ref|>text<|/ref|><|det|>[[117, 425, 880, 592]]<|/det|> +The surface charging process of dielectric materials ( \(\mathrm{SiO_2}\) for example) under the irradiation of focus ion beams ( \(\mathrm{Ga}^+\) or \(\mathrm{He}^+\) ) was thoroughly discussed in literatures \(^{53 - 55}\) , and the charging accumulation and dissipation is manipulated by the following factors: (1) generation of electron- hole pairs in the solid by incident ions; (2) neutralization of the incident ions by the excited free electrons; (3) sputtering of the surface atoms; (4) charging due to the secondary ion- electron emission; (5) leakage of mobile electron- hole pairs to the silicon substrate; (6) induced shallow traps by the incident ions and a consequent preferred trapping relative to the deep traps. The surface charge density (SCD) of \(\mathrm{SiO_2}\) at HFIB irradiation \(^{54}\) can be expressed as a function of time (Supplementary Note 2): + +<|ref|>equation<|/ref|><|det|>[[152, 593, 877, 625]]<|/det|> +\[\frac{dQ(t)}{dt} = P(1 + \gamma_{e})\cdot I(t) - k\frac{Q(t)}{\epsilon_{r}\epsilon_{0}} -\frac{7}{4} Y I(t)\cdot \Omega_{0}\frac{Q(t)}{R_{p}} -\int_{0}^{t}J(t)dt \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[118, 630, 145, 644]]<|/det|> +(1) + +<|ref|>text<|/ref|><|det|>[[117, 647, 880, 867]]<|/det|> +The RHS composes of 4 terms. The first is the ion incident term which represents the electron- hole pairs accumulation induced by the ion incident and secondary emission, where \(P\) is the probability factor accounts for the electron- hole recombination, \(\gamma_{e}\) is the secondary electron emission yield of \(\mathrm{SiO_2}\) , and \(I(t)\) is the beam current density of HFIB. The second term is the leakage current term, where \(k\) is the conductivity of the substrate, \(\epsilon_{r}\) is the substrate relative permittivity, and \(\epsilon_{0}\) is the vacuum permittivity constant. The third term is the sputtering yield induced charge reduction, where \(Y\) is the sputtering yield acquired from SRIM simulation, \(\Omega_{0}\) is the atomic volume which can be estimated by the average density of \(\mathrm{SiO_2}\) , \(R_{p}\) is the ions stopping range from SRIM. The last term accounts for the accumulation of emitted counterions, where \(J(t)\) is the ion emission rate at current SCD, which is often described as a kinetic process in which ions evaporate from liquid- vacuum interface. The emission current density reads \(^{56}\) : + +<|ref|>equation<|/ref|><|det|>[[115, 870, 671, 902]]<|/det|> +\[j_{e} = \frac{k_{B}T}{h}\sigma \exp \left(-\frac{\Delta G - G(E_{k}^{n})}{k_{B}T}\right), \quad (2)\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 83, 883, 288]]<|/det|> +where \(j_{e}\) is the current emitted per unit IL- vacuum surface area, \(k_{B}\) is Boltzmann's constant, \(T\) is the liquid temperature, \(h\) is Planck's constant, \(\sigma\) is the local net charge density at the liquid- vacuum interface, \(\Delta G\) is the Gibbs free energy barrier for an ion to be emitted, \(E_{n}^{\nu}\) is the local vacuum electric field normal to the interface. \(G(E_{n}^{\nu})\) is the reduction of solvation energy barrier due to the external electric field, assumed to take the form \(G(E_{n}^{\nu}) = \sqrt{\frac{q^{3}E_{n}^{\nu}}{4\pi\epsilon_{0}}\frac{\epsilon_{r} - 1}{\epsilon_{r} + 1}}\) by the Schottky hump, where \(\mathbf{q}\) is the ion's charge. The solvation energy of emitted ion can be estimated by the Born model as \(\Delta G = \left(\frac{27}{4}\pi\right)^{1 / 3}\frac{\gamma^{1 / 3}}{(4\pi\epsilon_{0})^{2 / 3}}\frac{q^{4 / 3}(1 - \epsilon_{r})^{2 / 3}}{(4\pi\epsilon_{0})^{2 / 3}}\) , where \(\gamma\) is the liquid vacuum surface tension. Adopting the mechanical model proposed in the following paragraph, the electric field of SCD, \(E_{n}^{\nu}\) , can help to calculate the ion emission rate and the SCD. + +<|ref|>text<|/ref|><|det|>[[116, 287, 881, 473]]<|/det|> +A schematic diagram is shown in Fig. 2d to model the mechanical balance between IL surface tension and the electrostatic force exerted by the surface charge. The IL- vacuum surface is distorted by the electric field and forms a bumping meniscus. When the meniscus is distorted to be hemispherical, the vertical component of surface tension reaches maximum. Once the surface charge continues to increase, a significant ion emission would take place during which both ions, clusters and tiny droplets may emit from the interface \(^{52,56,57}\) . The distance between the scan spot (center of surface charge) and the contact line ranges from \(10^{0}\) to \(10^{2}\) nm, as long as the surface charge is strong enough to induce ion emission. The critical SCD that can induce significant ion emission depends on the distance between the scan spot and the reservoir CTL (more detailed deduction can be found in Supplementary Note 3): + +<|ref|>equation<|/ref|><|det|>[[116, 475, 380, 510]]<|/det|> +\[Q_{surf} \cong \frac{(d + r^{*})^{2} + l_{0}(d + r^{*})}{k_{0}cos^{3}\alpha} E^{*}\] + +<|ref|>text<|/ref|><|det|>[[117, 512, 145, 528]]<|/det|> +(3) + +<|ref|>text<|/ref|><|det|>[[116, 531, 881, 678]]<|/det|> +Where \(d\) is the distance between the scan spot and the CTL; \(r^{*} = \frac{q^{6}\gamma}{4\pi^{2}\epsilon_{0}^{3}(\Delta G)^{4}} \sim 10^{-8}m\) is the characteristic ion emission radius derived in literature \(^{52}\) ; \(l_{0}\) is the surface charging area length scale, which represents the lateral distribution of positive surface charges \(^{48}\) ; \(k_{0}\) is the Coulomb constant; \(\alpha\) is the ion emission angle as depicted in Fig. 2d; and \(E^{*} \sim 10^{9 - 11}V / m\) is the characteristic electric field \(^{56}\) for significant ion emission. At given separation distance \(d\) , the critical SCD can be calculated by equation 3. By invoking equations 1 and 2, the dosage of HFIB required for the critical SCD can be calculated." + +<|ref|>text<|/ref|><|det|>[[695, 678, 878, 696]]<|/det|> +(Page 4- 6, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[168, 87, 838, 490]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 506, 881, 914]]<|/det|> +
Figure 2: Working principle of IBFW nano-printing. (a-c) Schematic of the IBFW working principle. (a) When HFIB irradiates the CTL, the positive surface charging induces the primary anion emission. (b) When HFIB ceases to scan, surface charging dissipates and the emitted anions induce the secondary cation emission. (c) The emitted ions from previous stages form an ultra-thin precursor film, and the consequent disjoining pressure propels and stabilizes liquid film. (d) The mechanical balance between the surface charge density induced electrostatic force and the surface tension of IL-vacuum interface. The distance between HFIB scans spot and contact line is \(d\) ; the surface charging uniformly distributes over a region with length scale, \(l_0\) ; the surface-charge-exert electrostatic force and distorts the IL-vacuum interface, balanced by the surface \(\gamma\) ; \(\alpha\) is the angle between substrate the connection line of SCD center and ion emission center; \(r^*\) is the ion emission critical radius, and is also the vertical distance between ion emission center and substrate. (e) Experimental HFIB dosage density to induce IL flow (ions per square of nm) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. (f) IBFW induced liquid film lengths ( \(\mu \mathrm{m}\) ) on substrates with different conductivities. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. (g) Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removement. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. The shaded regions (red)
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 881, 214]]<|/det|> +represent the surface injection region with positive charges. (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20\mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1\mathrm{pA}\) , dwell time \(2\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit. + +<|ref|>text<|/ref|><|det|>[[675, 215, 878, 232]]<|/det|> +(Page 22- 23, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 251, 866, 288]]<|/det|> +"The influence of substrate conductivity over ion emission and IBFW film inducing is clear. There are two reasons we did not include the flood gun current into calculation: + +<|ref|>text<|/ref|><|det|>[[117, 289, 880, 363]]<|/det|> +1. The flood gun can only work after the HFIB finishes an entire row (or entire frame) of scan spots. The NPVE scan spots array usually composes \(1024 \times 1024\) scan spots, so the injection dosage of HFIB exceeds the flood gun three to six orders of magnitude. + +<|ref|>text<|/ref|><|det|>[[117, 344, 880, 399]]<|/det|> +2. The ion emission model considers HFIB scans a single spot or a very small area near the contact lien to induce ion emission, the flood gun most likely is not working under such conditions." + +<|ref|>text<|/ref|><|det|>[[652, 400, 878, 418]]<|/det|> +(Page S7, Supplementary) + +<|ref|>text<|/ref|><|det|>[[117, 455, 880, 510]]<|/det|> +Comment #11: How did you measure the experimental surface charge density of Fig. 2 D? Could you experimentally determine the sign of the charge? If you used Eq (1), how is that an "experimental" result? + +<|ref|>text<|/ref|><|det|>[[117, 511, 881, 640]]<|/det|> +Response: We thank the reviewer for the questions and comments. The experimental surface charge density (SCD) in Fig. 2d was the critical HFIB injection dose density that takes to induce consecutive liquid film from the reservoir. We corrected this mistake, and recalculated the critical HFIB dose density to induce significant ion emission to compare with our experimental result. The experiments were conducted with beam current \(1\mathrm{pA}\) and scan spacing \(1\mathrm{nm}\) , and the dwell time was used to adjust the irradiation dose density which can be directly calculated: \(D_{\text{experiment}} = I \cdot \tau \cdot s^{- 2}\) . Where \(I\) is beam current, \(\tau\) is dwell time and \(s\) is scan spacing. To compare with the experimental dose density, we employ equation 3, \(Q_{\text{surf}} \cong \frac{(d + r^*)^2 + l_0(d + r^*)}{k_0 \cos^3 \alpha} E^*\) , to calculate the critical surface charge density at different distance \(d\) + +<|ref|>text<|/ref|><|det|>[[117, 641, 880, 825]]<|/det|> +between scan spot and contact line. Invoking equation 1, \(\frac{dQ(t)}{dt} = P(1 + \gamma_e) \cdot I(t) - \sigma \frac{Q(t)}{\epsilon_r \epsilon_0} - \frac{7}{4} Y I(t) \cdot \Omega_0 \frac{Q(t)}{R_p} - \int_0^t J(t)dt\) , we can calculate the dwell time and the dose density it takes to reach the critical surface charge densities at given distance \(d\) . We corrected the words and terms we used in the main text and changed Fig. 2f to compare the calculated dose density with the experiment dose density. + +<|ref|>text<|/ref|><|det|>[[117, 825, 880, 899]]<|/det|> +The measurement of sign of charge within the HIM chamber with the Helium ion source powering on is risky. We demonstrated experimentally in Figure R1 that the reabsorbed SE is not the driving force of IBFW, and positive charges of dielectric materials at the irradiation of Helium ion beam is well accepted. Therefore, we did not conduct further experiment to test the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 86, 238, 102]]<|/det|> +sign of charge. + +<|ref|>text<|/ref|><|det|>[[118, 121, 880, 159]]<|/det|> +"At given separation distance \(d\) , the critical SCD can be calculated by equation 3. By invoking equations 1 and 2, the dosage of HFIB required for the critical SCD can be acquired. + +<|ref|>text<|/ref|><|det|>[[117, 159, 881, 344]]<|/det|> +The relationship between critical HFIB dose density to induce IBFW, and the distance between starting scan spot and droplet CTL, \(d\) , is calculated employing equations 1 to 3 with the results depicted in Fig. 2e by blue line. The beam current employed in calculation is \(1\mathrm{pA}\) , scan spacing is \(1\mathrm{nm}\) , and the dwell time determines the calculated dose density. Here, we assume that the critical dose density that takes to induce significant ion emission coincides with the dose to achieve IBFW. The experiments are conducted to measure the critical HFIB dose density with \(1\mathrm{pA}\) beam current and \(1\mathrm{nm}\) spacing to induce continuous liquid film from reservoir with the results shown in Fig. 2e by orange rhombuses. The calculation results agree with the experimental critical dose density qualitatively, and confirm our hypothesis that the surface charging induced ion emission accounts for the IBFW." + +<|ref|>text<|/ref|><|det|>[[706, 345, 879, 362]]<|/det|> +(Page 6, Main text) + +<|ref|>image<|/ref|><|det|>[[270, 395, 737, 667]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 677, 880, 752]]<|/det|> +
Figure 2 (e) Experimental HFIB dosage density to induce IL flow (ions/nm²) and calculation results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the CTL, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b.
+ +<|ref|>text<|/ref|><|det|>[[701, 752, 878, 769]]<|/det|> +(Page 22, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 807, 879, 863]]<|/det|> +Comment #12: "The qualitative consistency ... verifies the mechanism we propose." Big statement, considering that you refer to Fig. 2E where the agreement is NOT good. (i.e. modelling doesn't predict at all differences between different insulating substrates) + +<|ref|>text<|/ref|><|det|>[[118, 881, 878, 900]]<|/det|> +Response: We thank the reviewer for the comments. The 'qualitative consistency' just means + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 288]]<|/det|> +that our crude model can distinguish insulating, semi conductive and conducting substrates. The ion emission model we proposed fails to explain the differences between different insulating substrates due to other factors that have not been considered in our model. For example, the solid surface roughness elements distort the contact line and the IL- vacuum interface. The distorted interface with different curvature can influence the ion emission energy barrier (main text Ref. [68]). Therefore, we discovered in experiments that at some positions of CTL, film can be easily produced, while some other positions of the same droplet cannot. This is one of the possible reasons that lead to the different behavior of different insulating material substrates. We changed the words we used in the main text, and explained the shortage of our model in the Supplementary Note 3. Currently, our simplified models cannot distinguish different insulating materials, where some factors may have not included. + +<|ref|>text<|/ref|><|det|>[[117, 307, 880, 491]]<|/det|> +"The orange rectangles represent the lengths of liquid film that can be induced on different substrates under identical HFIB treatment. IL film cannot be induced on pure conducting samples such as Au and Cu, liquid extends slightly on semiconductor (Si), whereas liquid film propagates a long distance on insulated substrates e.g., quartz and mica. Employing equations 1- 3, we can calculate the numbers of emitted ions during a single spot scan of HFIB (Supplementary Note 2, Supplementary Fig. 10), and is depicted in Fig. 2f as blue circles. As can be seen, the ion emission model we propose herein can qualitatively explain the different effects of IBFW on conducting, semi- conducting and insulating substrates. Yet the IBFW effect is also influenced by other substrate situations (roughness, for example), and the differences between various insulated substrates are failed to be captured by the simplified 2D model." + +<|ref|>text<|/ref|><|det|>[[712, 492, 878, 509]]<|/det|> +(Page 6, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 528, 880, 660]]<|/det|> +"The solvation energy of emitted ion can be estimated by the Born model as \(\Delta G = \left(\frac{27}{4}\pi\right)^{1 / 3}\gamma^{1 / 3}q^{4 / 3}\frac{(1 - \epsilon_r)^{2 / 3}}{(4\pi\epsilon_0)^{2 / 3}}\) , where \(\gamma\) is the liquid - vacuum surface tension. Noteworthily, the ion emission energy barrier can be altered significantly by the local curvature of the IL- vacuum surface \(^{25}\) , but we consider a simple 2- dimensional model in current work and exclude this factor. Such influence should be considered to explain the different performances of IBFW at the CTL of the same liquid reservoir in the future." + +<|ref|>text<|/ref|><|det|>[[625, 660, 878, 678]]<|/det|> +(Page S9- 10, Supplementary) + +<|ref|>text<|/ref|><|det|>[[117, 696, 880, 752]]<|/det|> +Comment #13: "The relationship between flow velocity and film length can also be measured experimentally". I don't understand how you can measure the flow velocity in your experimental setting. + +<|ref|>text<|/ref|><|det|>[[117, 770, 880, 806]]<|/det|> +Response: We thank the reviewer for the important comments. Two methods were adopted to measure the flow velocity, and are illustrated here: + +<|ref|>text<|/ref|><|det|>[[117, 807, 880, 842]]<|/det|> +The HFIB scans the designed pattern row by row, so the beam speed vertical to the CTL can be calculated as: + +<|ref|>equation<|/ref|><|det|>[[117, 846, 668, 875]]<|/det|> +\[v_{beam} = \frac{s_{vertical}}{N_{row}\tau + V_{refresh}}, \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[117, 880, 880, 900]]<|/det|> +Where, \(s_{vertical}\) is the vertical scan spacing, \(N_{row}\) is the number of scan spots in one row, \(\tau\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 82, 880, 473]]<|/det|> +is the dwell time that HFIB stay at a single spot, \(V_{refresh}\) is a small time (10 \(\mu \mathrm{s}\) ) that software takes to reset the HFIB ready for the next row of scan. If the vertical speed of HFIB exceeds the film velocity, the distance between the scan spot and the liquid film CTL would increases until the scan spot is too far ahead of the film and the liquid would cease to flow. The critical interaction distance with given beam parameters can be determined experimentally (Supplementary Fig. 14a). Due to the pronounced impact of dose density on the flow velocity of liquid film (Supplementary Fig. 14b), the flow velocity measurements are conducted under the same dose density by keeping the beam current \(I = 1\) \(pA\) , scan spot spacing \(s = 1\) \(nm\) and dwell time \(\tau = 2\) \(\mu \mathrm{s}\) constant and only alter the width of the rectangle pattern. The pattern width controls the \(N_{row}\) and consequently alters the beam vertical speed. By scanning rectangle patterns with same length but different widths outwards from the reservoir CTL, the vertical speed of beam can be changed at constant HFIB dose density. The IBFW film length decreases with the beam speed increasing (Supplementary Fig. 14c), and consequently the average flow velocity of films with different length can be measured. The change width measurement results are shown in Fig. 2b by the hollow orange stars. The results of film speed at extremely long film length are acquired by first fabricating a long liquid film (300 \(\mu \mathrm{m} \times 10 \mu \mathrm{m}\) , 600 \(\mu \mathrm{m} \times 10 \mu \mathrm{m}\) , and 900 \(\mu \mathrm{m} \times 10 \mu \mathrm{m}\) respectively) from the reservoir, then the change width measurements are conducted at the front of the long film. Since the fabrication of extreme long film can be time consuming, these data are only measured once. The other experiments are repeated for at least ten times with the average value and standard error shown in Fig. 2h. + +<|ref|>text<|/ref|><|det|>[[117, 473, 880, 621]]<|/det|> +The shortage of the change- width method is that the NPVE scan pattern assembling limits the maximum velocity the beam can move vertically. To overcome such limitation, we adopt single spot scan method. In which, a line pattern made up by a series of scan spots is used. The scan speed is altered by changing the vertical refresh time between each scan spot, while keeping beam current 1 pA, dwell time 10 \(\mu \mathrm{s}\) and spacing 1 nm all constant. The dwell time is elongated to compensate the dose density reduction, since the scan area is influenced by neighboring scan spots in a rectangular pattern. All single spot measurements are repeated at least five times. The results of single spot scan are represented by the orange stars in Fig. 2h. + +<|ref|>text<|/ref|><|det|>[[117, 621, 880, 715]]<|/det|> +Apart from velocity measurement explanation, the flow model is modified by the introduction of boundary slip length of IL- \(\mathrm{SiO_2}\) interface according to other Reviewer's comment. Since the slip length vary from 2 nm to over 16 nm determined by the combined surface conditions (Ref. [58- 60]), the possible flow velocity range is calculated employing the lower and upper limit of IL slip length as shown by the blue region in Fig. 2h. + +<|ref|>text<|/ref|><|det|>[[117, 750, 879, 806]]<|/det|> +"We next verify that the disjoining pressure propels and stabilizes the nanofilm. The propagation speed of IBFW liquid film decreases monotonically with the increase of film length: + +<|ref|>equation<|/ref|><|det|>[[117, 807, 876, 840]]<|/det|> +\[U\sim \frac{h^2 + 3bh}{3\mu}\cdot \frac{\Pi(h_{min}) - \gamma\kappa}{L} \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[117, 844, 879, 900]]<|/det|> +Where \(U\) is the average flow speed, \(h\) is equilibrium film thickness, \(b\) is the slip length of IL- \(\mathrm{SiO_2}\) interface \(^{58 - 60}\) , \(\mu\) is IL viscosity, \(\Pi (h_{min})\) is disjoining pressure at minimum film thickness \(h_{min}\) , \(L\) is film length, \(\gamma\) is IL surface tension, and \(\kappa\) is curvature of IL- vacuum interface at the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 196]]<|/det|> +conjunction of film and reservoir (Supplementary Table. 2, Supplementary Note 4, Supplementary Fig. 13). We depict the calculation results in Fig. 2h. Since the boundary slip length of IL- \(\mathrm{SiO_2}\) interface depends on the combined surface conditions and ranges from \(2\mathrm{nm}\) to over \(16\mathrm{nm}\) , we employ the lower \((2\mathrm{nm})\) and upper \((16\mathrm{nm})\) limits of slip length to give an estimation on the possible range of flow speed in Fig. 2h as the blue shaded region, and the results of average value \(10\mathrm{nm}^{58}\) is shown by the deep blue line. + +<|ref|>text<|/ref|><|det|>[[118, 196, 879, 251]]<|/det|> +The relationship between flow velocity and film length can also be measured experimentally. As shown in Supplementary Fig. 4, the HFIB scans the designed pattern row by row, so the beam speed vertical to the CTL can be calculated as: + +<|ref|>equation<|/ref|><|det|>[[118, 253, 668, 285]]<|/det|> +\[V_{beam} = \frac{S_{vertical}}{N_{row}\tau + V_{refresh}}, \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[117, 288, 880, 676]]<|/det|> +Where, \(S_{vertical}\) is the vertical scan spacing, \(N_{row}\) is the number of scan spots in one row, \(\tau\) is the dwell time that HFIB stay at a single spot, \(V_{refresh}\) is a small time \((10\mu \mathrm{s})\) that NPVE takes to reset the HFIB for next row of scan. If the vertical speed of HFIB exceeds the film velocity, the distance between the scan spot and the liquid film CTL would increases until the scan spot is too far ahead of the film and the liquid would cease to flow. The critical interaction distance with given beam parameters can be determined experimentally (Supplementary Fig. 14a). Due to the pronounced impact of dose density on the flow velocity of liquid film (Supplementary Fig. 14b), the flow velocity measurements are conducted under the same dose density by keeping the beam current \(I = 1\mathrm{pA}\) , scan spot spacing \(s = 1\mathrm{nm}\) and dwell time \(\tau = 2\mu \mathrm{s}\) constant and only alter the width of the rectangle pattern. The pattern width controls the \(N_{row}\) and consequently alters the beam vertical speed. By scanning rectangle patterns with same length but different widths outwards from the reservoir CTL, the vertical speed of beam can be changed at constant HFIB dose density. The IBFW film length decreases with the beam speed increasing (Supplementary Fig. 14c), and consequently the average flow velocity of films with different length can be measured. The change width measurement results are shown in Fig. 2h by the hollow orange stars. The results of film speed at extremely long film lengths are acquired by first fabricating a long liquid film \((300\mu m\times 10\mu m\) , \(600\mu m\times 10\mu m\) , and \(900\mu m\times 10\mu m\) respectively) from the reservoir, then the change width measurements are conducted at the front of the long film. Since the fabrication of extreme long film can be time consuming, these data are only measured once. The other experiments are repeated for at least ten times with the average value and standard error shown in Fig. 2h. + +<|ref|>text<|/ref|><|det|>[[117, 677, 880, 861]]<|/det|> +The shortage of the change- width method is that the NPVE scan pattern assembling limits the maximum velocity the beam can move vertically. To overcome such limitation, we adopt single spot scan method. In which, a line pattern made up by a series of scan spots is used. The scan speed is altered by changing the vertical refresh time between each scan spot, while keeping beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) and spacing \(1\mathrm{nm}\) all constant. The dwell time is elongated to compensate the dose density reduction, since the scan area is influenced by neighboring scan spots in a rectangular pattern. All single spot measurements are repeated at least five times. The results of single spot scan are represented by the orange stars in Fig. 2h. The consistency between the calculation and experiments suggests that disjoining pressure can explain the propagation of IBFW film." + +<|ref|>text<|/ref|><|det|>[[696, 864, 878, 880]]<|/det|> +(Page 7- 8, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[245, 100, 741, 404]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 417, 881, 567]]<|/det|> +
“Figure 2: (h) IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current \(1\mathrm{pA}\) , dwell time \(10\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) . The change width experiments are conducted with rectangular pattern of scan spots with constant length \(20\mu \mathrm{m}\) and different width, while keeping the beam current beam current \(1\mathrm{pA}\) , dwell time \(2\mu \mathrm{s}\) , spacing \(1\mathrm{nm}\) constant to keep the dose density unchanged. The blue shaded region is the range between the calculate velocity lower and upper limit due to the range of slip lengths \(^{58,59}\) , the deep blue line is the calculation result employing the average slip length \(^{58}\) .”
+ +<|ref|>image<|/ref|><|det|>[[120, 653, 860, 802]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[675, 587, 878, 604]]<|/det|> +
(Page 23-24, Main text)
+ +<|ref|>title<|/ref|><|det|>[[118, 822, 694, 841]]<|/det|> +# “Supplementary Figure 14: Flow speed measurement experiments. + +<|ref|>text<|/ref|><|det|>[[118, 844, 880, 899]]<|/det|> +(a) The single-spot scan style in HIM, which scans one-dimensionally along the pattern direction, is applied to analyze the interaction spatial range of a single irradiation spot quantitatively. The critical maximum spacing between neighbor scan spots to induce liquid + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 232]]<|/det|> +flow, \(\mathbf{s}_{\mathrm{c}}\) , represents the upper limit for the interaction spatial range of the beam spot. When scan spot spacing exceed \(\mathbf{s}_{\mathrm{c}}\) , HFIB fails to induce continuous flow however large the dose is. The injection dose density, D, is regulated by changing beam current, I, at constant dwell time 100 \(\mu \mathrm{s}\) , or changing dwell time, \(\tau\) , at constant beam current 0.7 pA. The relationship between \(\mathbf{s}_{\mathrm{c}}\) and D of each beam spot is plotted. (b) Maximal flow velocity as a function of the beam current I for a \(20\mu \mathrm{m}\) length liquid film. The scan speed is changed by the pattern width. The flow speed increases with increasing beam current at same dwell time 1 \(\mu \mathrm{s}\) . (c) An example of the change width method for the measurements of flow velocity at different film length." + +<|ref|>text<|/ref|><|det|>[[641, 234, 878, 251]]<|/det|> +(Page S31, Supplementary) + +<|ref|>text<|/ref|><|det|>[[117, 306, 880, 343]]<|/det|> +Comment #14: AFM measurements "The liquid- vacuum interface ..." Is the AFM measurement done in vacuum instead of air? + +<|ref|>text<|/ref|><|det|>[[118, 362, 880, 398]]<|/det|> +Response: We thank the reviewer for the question. The AFM measurements were conducted all in atmosphere condition. We have corrected the mistake in the main text. + +<|ref|>text<|/ref|><|det|>[[117, 424, 880, 590]]<|/det|> +"We employ atomic force microscope (AFM) to manifest the nanoscale flow control of IBFW. Fig. 3a shows the front \(7\mu \mathrm{m}\) of a \(28\mu \mathrm{m}\times 1\mu \mathrm{m}\) IL film with thickness around \(30\mathrm{- }40\mathrm{nm}\) (an average of \(35.4\pm 1.7\mathrm{nm}\) ). The film thickness remains unchanged along the flow path (Fig. 3A). The film width is \(1\mu \mathrm{m}\) , coincides with designed pattern. The liquid- air interface is much smoother than solid substrate (RMS roughness \(7.9\pm 5.7\mathrm{nm}\) ). The minimal line width of IBFW film reaches \(106nm\) (Supplementary Fig. 15), and is limited by the surface charges spatial distribution which was reported around \(10^{2}nm^{15}\) . If the surface charges can be trapped within a narrower spatial range, the ideal line width limitation may be comparable with film thickness." + +<|ref|>text<|/ref|><|det|>[[712, 592, 878, 609]]<|/det|> +(Page 8, Main text) + +<|ref|>text<|/ref|><|det|>[[117, 646, 880, 740]]<|/det|> +Comment #15: "The current in nanofilm linearly depends on the humidity". What is the mechanism?? Anyways, it seems the current is not only a function of humidity as it depends directly on time as well based on Fig. S18. How could you disentangle the effect of time from the effect of humidity in a real sensor as some voltage bias history dependence seems to exist (referring to Fig. S18F) + +<|ref|>text<|/ref|><|det|>[[117, 758, 881, 905]]<|/det|> +Response: We thank the reviewer for the important questions. We believe the reaction- diffusion competition differences and the higher adsorption rate endowed by higher surface- volume ratio of nanocircuit leads to the differences in the humidity response curve we measured. For the droplet circuit, the long distance for the water molecules to diffuse to the electrode restricts the reaction rate, therefore, the change of current with humidity is not obvious. Nevertheless, the thin liquid film circuit with much shorter diffusion distance largely accelerate the diffusion process, which is the rate- determining step of current experiment. Moreover, the larger surface- volume ratio benefits the adsorption of the vapor molecules and further improve + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 880, 120]]<|/det|> +the reaction current. We have expanded the paragraph in main text to further illustrate the mechanism. + +<|ref|>text<|/ref|><|det|>[[118, 122, 881, 251]]<|/det|> +The time dependent current measured in Supplementary Fig. S18 is due to the gathering of counterions to the electrodes to form an electric double layer (EDL) when the voltage is switched on. If the voltage has been switched on for a long time, the EDL at the electrodes- IL interface comes into a thermodynamics equilibrium would electrostatically block the electrode voltage, and no measurable current can be detected. Employing a sensing circuit that has reached equilibrium (with bias voltage turned on for a long time, 1h is more than adequate) will disentangle the time effect. + +<|ref|>text<|/ref|><|det|>[[118, 252, 881, 455]]<|/det|> +The bias history dependence comes from repeatedly switched on and off the voltage, which is another mistake we made during the caption of Supplementary Fig. 18. When bias voltage switched on, counterions gathering to form an EDL and give rise to a current jump. As the EDL developing, the electrode voltage is gradually being blocked and the current decay to near zero until reaches equilibrium. When voltage switched off, the EDL will gradually disappear and return to the initial condition. If the rest time is long enough, the history dependence would disappear. But the rest time in our experiment was too short, and the EDL has not reached equilibrium before the bias voltage is exerted again. When the bias voltage turned on again, the real voltage feels by the IL is actually smaller than the bias voltage we exert since part of the old EDL still absorbed at the electrode surface, which leads to a history dependence in Supplementary Fig. 18f. + +<|ref|>text<|/ref|><|det|>[[118, 473, 881, 770]]<|/det|> +"In Fig. 4a, b and Supplementary Fig. 19, we present a room- humidity- sensing circuit utilizing IBFW technique. The water molecules are adsorbed by the IL then diffuse to and react at the electrode surfaces, generating a reaction current \(I_{\mathrm{ds}}\) . The source- drain currents of a IBFW nanofilm circuit and a micrometer- size droplet circuit are measured within the same chamber with the relative humidity ranging from \(40\%\) to \(70\%\) . The current in nanofilm linearly depends on the humidity, while no significant change can be observed for the micrometer droplet. The competition between the adsorption at liquid- air interface and the diffusion within liquid circuit can explain such differences. For the droplet circuit, the long distance for the water molecules to diffuse to the electrode surface restricts the reaction rate, therefore, the change of current with humidity is not obvious. Nevertheless, the thin liquid film circuit with much shorter diffusion distance and relaxation time largely accelerates the diffusion process, which is the rate- determining step of the current experiment. Moreover, the much higher surface- volume ratio benefits the adsorption of the vapor molecules and further improves the reaction current sensitivity. Both the sensitivity and response speed are greatly enhanced due to the size effect endowed by IBFW nano film. The simple device presented here can manifest the feasibility of the IBFW circuit in sensing circuit manufacturing." + +<|ref|>text<|/ref|><|det|>[[712, 772, 878, 789]]<|/det|> +(Page 9, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 807, 880, 861]]<|/det|> +Comment #16: Fig. 3F use real current units instead of dimensionless and tell what the bias voltage used was. BTW Fig. S18 C has wrong units (A vs nA). Fig. S18G has no caption, what is it? + +<|ref|>text<|/ref|><|det|>[[118, 881, 878, 899]]<|/det|> +Response: We thank the reviewer for the suggestions. We corrected the units to dimensionless + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 881, 213]]<|/det|> +in Fig. 4b, and the voltage exerted between the two Au electrodes was 1 V. We have corrected the wrong units used in Supplementary Fig. 19 a and b (used to be labeled as Fig. S18). The captions for the previous version of Supplementary Fig. S18 f and g were ambiguous and wrong. Fig. S18 f was the Drain current I-t curve with the source drain voltage, 10 V, switched on and off periodically (turned on 480s, then off 20s) for four times. Fig. S18 g was the Drain current I-t curve with constant source-drain voltage 10 V. Supplementary Fig. 19 has been reconstructed. + +<|ref|>text<|/ref|><|det|>[[117, 215, 881, 492]]<|/det|> +We think part of the old version was irrelevant to illustrate the difference between nano circuit and micro droplet. In current version, Supplementary Fig. 19c is the drain current I-t curve of a droplet circuit and a nano- film circuit in atmosphere and in vacuum chamber at constant source- drain voltage 10 V. Both the droplet circuit and nanofilm circuit have a higher current in atmosphere than in vacuum chamber, this is due to the water molecules adsorbed by the droplet and the film that react at the electrode surface and create a reaction current. The result in vacuum chamber is more intriguing. The adsorption- reaction current has been disentangled, and the current we measured is solely contributed by the formation of electric double layer. As shown by the yellow curve, the EDL formation current curve of nanofilm circuit quickly decreases to be indiscernible, which indicate that the EDL in nanofilm circuit established quickly and reaches an equilibrium. On the contrary, the EDL formation current of droplet circuit decrease much slower, and keep on decreasing at the end of the 300 s measurement, which indicate that the equilibrium is hard to attain in a droplet circuit. Such differences explain that nano film circuit with a much shorter relaxation time is more suitable for gas sensing purpose. Supplementary Fig. 19d is an HIM image of the nanocircuit fabricated. + +<|ref|>image<|/ref|><|det|>[[180, 533, 825, 707]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 714, 881, 861]]<|/det|> +
Fig. 4 (a,b) Proof-of-concept gas sensing prototype. (a) the IBFW liquid nanofilm connected two droplets of IL settled on two Au electrodes for electrochemistry data collection. (b) Results of IBFW liquid nano-circuit in gas sensing and compared with a micro meter droplet settled between and connects two identical Au electrodes. The inset shows the schematic of a room-humidity sensor based on IBFW fabricated nanofilm. The drainage-source currents of both microdroplet and nanofilm are illustrated and the linear fitting results are depicted as dash lines. The voltage exerted between two electrodes is 1 V. The background color map represents the relative humidity of test chamber ranges from 40% to 70%.
+ +<|ref|>text<|/ref|><|det|>[[675, 864, 878, 880]]<|/det|> +(Page 26- 27, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[171, 110, 800, 495]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[115, 510, 881, 826]]<|/det|> +Supplementary Figure 19: Volt- Ampere characteristics analysis of IL nano film circuit. (a) Drain current between Au electrodes vs. time, the black line represents an identical measurement with no liquid film connect the electrodes; (b) linear sweep volt- ampere curve of liquid film circuit; (c) The transient current curves of IL film circuit and droplet circuit in high vacuum and in atmospheric environment as a function of time, the source- drain voltage is 10 V. Both the droplet circuit and nanofilm circuit have a higher current in atmosphere than in vacuum chamber, this is due to the water molecules adsorbed by the droplet and the film that react at the electrode surface and create a reaction current. The result in vacuum chamber is more intriguing. The adsorption- reaction current has been disentangled, and the current we measured is solely contributed by the formation of electric double layer. As shown by the yellow curve, the EDL formation current curve of nanofilm circuit quickly decreases to be indiscernible, which indicate that the EDL in nanofilm circuit established quickly and reaches an equilibrium. On the contrary, the EDL formation current of droplet circuit decrease much slower, and keep on decreasing at the end of the 300 s measurement, which indicate that the equilibrium is hard to attain in a droplet circuit. Such differences explain that nano film circuit with a much shorter relaxation time is more suitable for gas sensing purpose. (d) The HIM image of the liquid nano circuit employed in this experiment. + +<|ref|>text<|/ref|><|det|>[[631, 826, 878, 844]]<|/det|> +(Page S36, Supplementary) + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[384, 85, 612, 102]]<|/det|> +## Responses to Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[117, 121, 881, 270]]<|/det|> +The authors developed a new method to perform rewritable surface printing of ionic liquids. The method relies on the disjoining pressure to induce surface films of nanometer thickness, and utilizes helium ion beams to initiate the flow of liquids and pattern creation. The manuscript comprehensively characterizes and explains the underlying mechanism of this printing process. However, as an application- driven work, the prospect of practical real- world applications is a bit weak. Although the authors demonstrated a sensing device application (Fig. 3F), it only utilizes the nanoscale thickness of the ionic liquid film, and the surface patterning is not very relevant. Specific concerns include: + +<|ref|>text<|/ref|><|det|>[[118, 289, 765, 307]]<|/det|> +Response: We thank the reviewer for the positive comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 326, 881, 399]]<|/det|> +Comment #1: This method utilizes ionic liquids, and seems hard to extend to other liquid systems due to the high- vacuum requirements of the helium ion microscope. Ionic liquid as of now are still quite expensive, limiting the range of applications. Are there ways to improve or revise the method so that other liquid or even solid structures can also be printed? + +<|ref|>text<|/ref|><|det|>[[118, 418, 880, 547]]<|/det|> +Response: We thank the reviewer for these inspiring suggestions. The liquid working media can be expanded by injection of aqueous or organic solution into the liquid reservoir of the IBFW liquid film. The film pattern can act as a stable flow channel for the solutions injected, we fabricated the in- situ chemical reaction chip to serve as a proof- of- concept prototype. Moreover, the electric field induced Taylor cone and ion emission are ubiquitous for many liquids including water. If an appropriate capsule can be fabricated with windows transparent to ion beams, we believe many other liquids can be employed in IBFW experiments. + +<|ref|>text<|/ref|><|det|>[[118, 548, 880, 640]]<|/det|> +The IBFW liquid film pattern can be electrochemical deposited to be solid particles with designed patterns. We added the 'Applications of IBFW' in the main text to discuss in details. The ILs is more expensive than water or ethanol, but many types of them are still cheap enough for research. The [EMIM][DCA] we used in our experiments were purchased at a price of 24 CNY \(\sim 3\) USD for \(20\mathrm{g}\) . + +<|ref|>text<|/ref|><|det|>[[118, 641, 880, 677]]<|/det|> +We listed the modifications we made to our manuscript that can answer the reviewer's questions. + +<|ref|>text<|/ref|><|det|>[[118, 697, 880, 890]]<|/det|> +1. We modified the introduction to introduce potential application fields suitable for ionic liquids. +2. We added a new section 'Applications of IBFW' for further demonstration. We used IBFW to fabricate liquid channels as a guidance for aqueous solutions of reagent which were later injected into the IL droplets for the in-situ colorimetric reactions of SCN- with various metal ions. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte solutions. +3. We conducted electrochemical experiments to reveal that IBFW is also capable of transforming liquid film pattern into desired solid materials. Electrochemistry analytes are dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]). The solution droplet was settled on ultra-thin metal film (15 nm) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 880, 251]]<|/det|> +deposited on \(\mathrm{SiO_2}\) wafer, and film patterns were printed by IBFW. The following electrochemical deposition transforms the liquid patter into solid materials. Since the stopping range of \(30\mathrm{kV}\) Helium ions exceeds \(290\mathrm{nm}\) , a \(15\mathrm{nm}\) metal film exerts no significant influence on the surface charge injection of HFIB, and consequently the IBFW can be conducted on very thin metal film. Monte Carlo simulation results were added to explain the penetrating capability of He ions (Supplementary Fig. 9b). We also discussed the potential influence of electrowetting on the IBFW film, and drew the conclusion that the voltage we adopted won't overcome the contact angel hysteresis and the IBFW films were not influenced by the deposition voltage. + +<|ref|>text<|/ref|><|det|>[[149, 252, 879, 306]]<|/det|> +For now, we only tested Ag nano- particles and AgTCNQ (7,7,8,8- tetracyanoquinodimethane) complex, but more electrochemistry tests can be undertaken to test the capability of solid deposition of both organic and inorganic materials. + +<|ref|>text<|/ref|><|det|>[[117, 325, 880, 603]]<|/det|> +"Based on the IBFW inducing mode, we develop a nano- printing technique of ILs, with film thickness down to \(20 \sim 30 \mathrm{nm}\) , minimal line width about \(100 \mathrm{nm}\) and corner radius down to \(20 \mathrm{nm}\) , and compare its performances with the reported methods. Besides, ILs are also known for their unique properties such as wide electrochemical potential window, high ionic conductivity, low toxicity and thermostability. These features make ILs increasingly important as electrolytes for lithium battery \(^{40,41}\) and electrodepositions of various materials ranging from metal nanoparticles \(^{42,43}\) , metal organic complexes \(^{44}\) to conducting polymer films \(^{45}\) . We further demonstrate the IBFW as a versatile tool for various application fields including gas sensing circuit, in- situ chemical reaction chip, and electrochemical deposition of solid materials with desired patterns. The simplicity and versatility of IBFW technique suggests prospect in a range of liquid manipulation applications. By combining with electrochemical procedures, such technique can not only produce patterned liquid film but also solid materials which reveals possibility in nano- transistors fabrication \(^{46}\) , energy devices \(^{40}\) and immunosensor circuit printing \(^{47}\) . We expect this technique can open a new avenue for applications in nano- printing and nano- circuit manufacturing." + +<|ref|>text<|/ref|><|det|>[[696, 604, 878, 621]]<|/det|> +(Page 2- 3, Main text) + +<|ref|>sub_title<|/ref|><|det|>[[119, 642, 320, 658]]<|/det|> +## "Applications of IBFW + +<|ref|>text<|/ref|><|det|>[[118, 659, 881, 787]]<|/det|> +As discussed previously, IL film pattern prepared by IBFW technology manifests three distinguishable features. First, the ultralow film thickness down to \(30 \mathrm{nm}\) indicates a high surface- volume ratio which is a key role in improving the gas sensing circuit sensitivity. Second, the capability of fabricating liquid film with desired pattern in a programmable and rewritable manner, which is important for in- situ chemical reaction and microfluidics chips. Third, the ILs are widely used in electrochemistry and reveal the possibility of transforming liquid film pattern into various solid materials ranges from organic to inorganic compounds." + +<|ref|>text<|/ref|><|det|>[[712, 789, 878, 805]]<|/det|> +(Page 9, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 825, 880, 899]]<|/det|> +"To demonstrate the potential of IBFW for microfluidics chip fabrication, we design an in- situ chemical reaction micro- chip. In Fig. 4c, the schematics shows a crosshair shaped micro fluid channel connects four separated droplets in four directions. Four square expansion windows are made on each part of the channel for the convenience of observation. The top- left inset + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 84, 881, 492]]<|/det|> +shows the chip with four droplets on finger- tip. After the IBFW fabrications, \(0.1 \mu \mathrm{L}\) of sodium thiocyanate solution (NaSCN \(0.1 \mathrm{M}\) in deionized water) is injected into the top droplet, and serves as the colorimetric reagent for the detection of and in- situ reaction with different metal ions. After the injection of NaSCN, \(0.1 \mu \mathrm{L}\) of \(0.1 \mathrm{mM} \mathrm{Fe}^{3 + }\) solution, \(0.1 \mathrm{mM} \mathrm{Cu}^{2 + }\) solution and \(0.1 \mathrm{mM} \mathrm{Co}^{2 + }\) are injected into the bottom, left and right droplets respectively. The microchip is rested in atmosphere for 20 min for the metal ions fully diffuse into the channels and react with SCN- within different square windows with the ion names printed previously. Then the sample is transferred into vacuum chamber for \(48 \mathrm{h}\) to diminish the water content in the solution system, which will alter the hydration status of the metal ion complexes and improve the colorimetric visibility. The red complex \(\mathrm{Fe(SCN)_3}\) deposits in the bottom window. The gray deposition in the left window is complex \(\mathrm{Cu(SCN)_2}\) . And the blue deposition in the right window is complex \(\mathrm{Co(SCN)_2}\) . As shown in Fig. 4c, the SCN- participates into 3 different reactions within several hundreds of micrometers flow channel. The time series pictures are shown in Supplementary Fig. 20, and the liquid film patterns remain unchanged during the experiments which last for over one month. The IBFW fluid channel exhibits great stabilities against vacuum/air transferring, the injection of solutions into droplet reservoir, and gravity. Such behavior demonstrates the robustness of the IBFW liquid film. More importantly, all reagents are dissolved in deionized water then injected into the IL droplets and diffuse into the IL flow channel. This experiment demonstrates that IBFW liquid film pattern can act as a stable flow channel for later injection of analyte dissolved in water, ethanol and various molecular liquids due to the amphiphilicity of ILs. Such results greatly broaden the potential application fields for IBFW." + +<|ref|>text<|/ref|><|det|>[[701, 493, 878, 510]]<|/det|> +(Page 10, Main text) + +<|ref|>image<|/ref|><|det|>[[152, 536, 855, 730]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 732, 880, 861]]<|/det|> +
Figure. 4: (c) In-situ chemical reaction chip. The left part is the schematics of the chip. Crosshair channels connect four droplets which are used to inject reagent water solutions. \(0.1 \mu \mathrm{L}\) of \(0.1 \mathrm{M} \mathrm{NaSCN}\) , \(0.1 \mathrm{mM} \mathrm{Co}^{2 + }\) , \(0.1 \mathrm{mM} \mathrm{Fe}^{3 + }\) and \(0.1 \mathrm{mM} \mathrm{Cu}^{2 + }\) are injected clockwise into four droplets (top, right, bottom, left). The inset on the top-left compares the size of microchip with fingertip, with red circle shows the four droplets. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for \(48 \mathrm{h}\) after the injection, the color of complexes is more obvious with water removed from the system.
+ +<|ref|>text<|/ref|><|det|>[[675, 863, 878, 880]]<|/det|> +(Page 27- 28, Main text) + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[130, 90, 870, 393]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[118, 413, 799, 432]]<|/det|> +## Supplementary Figure 20: Time series images of in-situ chemical reaction chip. + +<|ref|>text<|/ref|><|det|>[[117, 435, 880, 695]]<|/det|> +(a) HIM image of channels right after the IBFW fabrication. (b) The fluid channel first transferred to the optical microscope; the colorless transparent fluid channel is a bit hard to be distinguished from the transparent silica substrate. (c) After the injection of all solutions and reacts in atmosphere for 5 min. (d) The whole picture of the reaction chip before transferred to vacuum chamber. (e) 48 h after metal ions injection and storing in vacuum. After stored in vacuum chamber, the water has been eliminated, and the color of the different complexes become obvious. The sample goes through several times of transferring between vacuum chamber and air environment and the injection of analyte solutions into droplet reservoirs, while the liquid film pattern remains barely changed through the experiments. Such results demonstrate the stability of IBFW liquid film channel to the exposure of air environment and to non-direct physical contact for solution injections. (f) The reaction chip one month after injection (one week for gravity stability test). The chip is mounted on a customized sample holder which can adjust the tilting angle from \(0 - 180^{\circ}\) to test the IBFW film stability against gravity. The inset shows the mounted sample with tilting angle \(120^{\circ}\) and is stored for one week. (Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[642, 697, 878, 714]]<|/det|> +(Page S37, Supplementary) + +<|ref|>text<|/ref|><|det|>[[117, 732, 880, 899]]<|/det|> +"Due to their unique properties, ILs have been proved to be an important category of solvent and electrolytes. Here we demonstrate that, by further combining with electrochemical procedure, the IBFW also manifests the capability of transforming liquid film pattern into various solid materials. Fig. 4d shows the schematics of a three-electrode electrochemistry experiment. A droplet of 1- ethyl- 3- methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) serves as the solvent of possible analytes, which are Silver bis (trifluoromethylsulfonyl)imide (Ag[NTf₂]) or a mixture of Ag⁺ and 7,7,8,8- tetracyanoquinodimethane (TCNQ) in our experiments. The liquid film pattern is fabricated by the IBFW technology onto the thin gold electrode and would be subsequently transformed into + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 232]]<|/det|> +nanoparticles. A \(10 \mathrm{nm}\) Au and \(5 \mathrm{nm}\) Ti film deposited onto \(\mathrm{SiO}_2\) serves as the working electrode and is connected to the workstation by a Pt probe. As revealed by the MC simulation results (Supplementary Fig. 9 b), the He ions with vertical stopping- range exceeds \(290 \mathrm{nm}\) can easily penetrate the \(15 \mathrm{nm}\) metal film and deposit positive charges into the \(300 \mathrm{nm}\) \(\mathrm{SiO}_2\) layer underneath. Therefore, the IBFW can be achieved on an ultra- thin metal film deposited on insulating substrate, and is not contradict with the conclusion that pure conducting substrates lead to the failure of IBFW shown in Fig. 2f. The counter electrode is a Pt probe emerged in IL, and a silver- plated probe serves as a pseudo reference electrode. + +<|ref|>text<|/ref|><|det|>[[118, 233, 880, 490]]<|/det|> +In Fig. 4e, we present an example of solid particles deposited from IBFW liquid film. The upper part shows silver nanoparticles with designed pattern (a \(20 \mu m \times 3 \mu m\) channel and PKU letters) potentiostatically deposited at - 0.2 V (vs. Ag) for \(180 \mathrm{s}\) onto the gold electrode surface. And the lower part shows blue AgTCNQ particles on gold surface make up a \(50 \mu m \times 10 \mu m\) rectangular pattern deposited at - 0.1 V (vs. Ag). Noteworthily, the electrowetting phenomenon is ubiquitous in IL- electrode systems with contact angle hysteresis ranges from several to tens of degrees63. When the voltage applied between the IL and electrode surface is large enough to overcome contact angle hysteresis, the contact line of the IL droplet will be shifted and the IBFW patterns will be jeopardized. According to Liu et.al.64, a negative bias voltage exceeds - 1 V would induce significant contact angle decreases for [EMIM][NTf2] on gold with contact line spreading forwards, which is also observed in our experiments. A negative voltage smaller than - 0.5 V, on the contrary, does not influence the contact angle obviously. Therefore, the deposition voltages adopted in current work does not influence the contact line position or the IBFW liquid film. + +<|ref|>text<|/ref|><|det|>[[118, 492, 880, 732]]<|/det|> +Four cycles of cyclic voltammogram (CV) of \(10 \mathrm{mM} \mathrm{Ag}^+\) in IL is shown in Fig. 4f. The reduction peak of \(\mathrm{Ag}^+\) takes place at - 0.29 V (vs. Ag) with the peak current decreases as the scan cycles increases. We believe that the micro litter droplet with limited analyte dissolved lead to such results. The \(\mathrm{Ag}^+\) concentration decreases quickly after each cycle of CV scan, and the electron transfer is slower for the oxidation of \(\mathrm{Ag}\) metal. In Fig. 4g, we test the CV curves of five scan cycles of IL droplet with \(6 \mathrm{mM} \mathrm{Ag}^+\) and \(5 \mathrm{mM} \mathrm{TCNQ}\) . Two reduction peaks can be distinguished, one at \(0.095 \mathrm{V}\) (vs. Ag), and the other at - 0.21 V (vs. Ag). The first peak corresponds to the reduction of \(\mathrm{Ag}^+\) to \(\mathrm{Ag}^0\) (metal)44, and the second peak is related to the formation of AgTCNQ complex (solid). Finally, we conceptually validate that IBFW technology is capable of transferring liquid film pattern into various solid materials and reveal the possibilities can be produced by combining IBFW with electrochemical procedures. The three- electrode experiment configuration, example of open- circuit- potential V- t curve and potentiostatic deposit I- t curve are shown in Supplementary Fig. 21. ” + +<|ref|>text<|/ref|><|det|>[[677, 733, 878, 750]]<|/det|> +(Page 10- 11, Main text) + +<|ref|>text<|/ref|><|det|>[[118, 777, 880, 905]]<|/det|> +“As summarized in Fig. 4h, the IBFW technology manifests several intriguing features that can be harnessed for a variety of application fields. The IBFW technique can fabricate patterned ILs film with \(30 \mathrm{nm}\) thickness, \(100 \mathrm{nm}\) spatial resolution and over hundreds of \(\mu \mathrm{m}\) film length on insulating substrates (or coated with conducting metal films with \(10^1 \mathrm{nm}\) thickness). The surface- volume ratio endowed by the nanometer scale thickness can largely enhance the sensitivity of the IBFW film, and can be utilized in gas sensing circuit. The good solubility and biocompatibility of ILs make them suitable for the dissolve of various analytes. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 880, 215]]<|/det|> +The IBFW film also exhibits robustness against air environment exposure, gravity, and physical contact to droplet reservoir. Such features reveal that the IBFW film can act as stable flow channel for the analyte solutions injected to the reservoir, and can largely simplify the fabrication procedures of micro/nanofluidic chips. Last but not least, IBFW liquid film with wide potential window can be combined with electrochemical procedures and the patterned liquid film can be transformed into different solid particles. Such results demonstrate the IBFW as a versatile tool for both nanofluidics and liquid/solid materials printing." + +<|ref|>text<|/ref|><|det|>[[701, 222, 878, 240]]<|/det|> +(Page 11, Main text) + +<|ref|>image<|/ref|><|det|>[[198, 265, 792, 873]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[117, 877, 880, 914]]<|/det|> +
Figure 4 (d) The schematics of a three-electrode electrochemistry experiment. A droplet of IL with IBFW liquid film pattern printed onto the working electrode is the solvent for analytes.
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 881, 362]]<|/det|> +10 nm Au and \(5\mathrm{nm}\) Ti deposited to \(300\mathrm{nm}\) TOX \(\mathrm{SiO_2}\) serves as the working electrode, Pt probe and silver- plated probe stuck into the droplet are the counter and pseudo- reference electrodes respectively. (e) An example of the patterned solid particles deposited on Au electrode surface. The upper part shows Ag particles make up a \(20\mu m\times 3\mu m\) rectangular film with PKU letters pattern which are deposited to Au surface at \(- 0.2\mathrm{V}\) (vs. Ag). The lower part shows blue AgTCNQ particles make up a \(50\mu m\times 10\mu m\) pattern which are deposited to Au surface at \(- 0.1\mathrm{V}\) (vs. Ag). Both are potentiostatically deposited for \(180\mathrm{s}\) . (f) Four cycles of cyclic voltammogram of \(10\mathrm{mMAg^{+}([EMIM][NTf_2])}\) solution. The reduction peak at \(- 0.295\mathrm{V}\) (vs. Ag) can be seen, with peak current decreases with cycles. After four cycles, the reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal becomes less obvious. (g) Five cycles of cyclic voltammogram of \(6\mathrm{mM}\) \(\mathrm{Ag^{+}}\) and \(5\mathrm{mM}\) TCNQ ([EMIM][NTf2]) solution. The first reduction peak of \(\mathrm{Ag^{+}}\) to Ag metal at \(0.095\mathrm{V}\) (vs. Ag) can be seen. The \(+300\mathrm{mV}\) shift of Ag reduction peak at present of TCNQ is consistent with literature44. The reduction peak current of Ag reduces quickly and become hard to distinguish as cycle increases. (h) A summary schematic to show the distinct features of IBFW technique, and the potential application fields that are suitable for IBFW. + +<|ref|>text<|/ref|><|det|>[[675, 364, 879, 381]]<|/det|> +(Page 27- 28, Main text) + +<|ref|>image<|/ref|><|det|>[[123, 444, 881, 664]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[117, 678, 761, 696]]<|/det|> +Supplementary Figure 21: The electrodeposition experiments of AgTCNQ. + +<|ref|>text<|/ref|><|det|>[[118, 697, 880, 769]]<|/det|> +(a) The three-electrode configuration adopted in current work. (b) The green line is the V-t curve of AgTCNQ open circuit potential measurement, which serves as a reference for the subsequent experiments. The purple line is the deposition current vs. time curve of AgTCNQ deposition at constant potential, -0.1 V (vs. Ag). + +<|ref|>text<|/ref|><|det|>[[642, 771, 879, 788]]<|/det|> +(Page S38, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 881, 880, 899]]<|/det|> +Comment #2: The surface- wetting driven printing process is limited to patterns that are + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 85, 880, 121]]<|/det|> +continuously connected. For printing applications, most of the time disconnected patterns are needed. Are there ways to create such disconnected patterns (in the nano/micron scale)? + +<|ref|>text<|/ref|><|det|>[[118, 140, 880, 232]]<|/det|> +Response: We thank the reviewer for the important suggestions. By employing the more common feature of HFIB, which is to decompose and etch the sample, discontinuous liquid film patterns can also be printed. After the printing of a continuous liquid film, we use the NPVE software to scan a small region repeatedly to etch the unwanted part of the pattern to get a discontinuous pattern. + +<|ref|>text<|/ref|><|det|>[[118, 251, 880, 306]]<|/det|> +"Apart from continuous pattern, discontinuous liquid pattern can be fabricated by the introduction of damaging mode of HFIB. As shown in Supplementary Fig. 7, a PKU pattern is separated from the flow channel that connect to the droplet reservoir." + +<|ref|>text<|/ref|><|det|>[[712, 308, 878, 325]]<|/det|> +(Page 4, Main text) + +<|ref|>image<|/ref|><|det|>[[272, 375, 723, 670]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[118, 688, 876, 723]]<|/det|> +Supplementary Figure 7: Discontinuous pattern achieved by employing damaging mode of HFIB. + +<|ref|>text<|/ref|><|det|>[[118, 729, 880, 783]]<|/det|> +After the PKU letters pattern has been induced from a continuous liquid film channel, the conjunction parts between the film channel and the letters pattern are etched by HIM (by setting the scan dose density to \(10^{4}\) ions/nm \(^2\) , the liquid film is etched). + +<|ref|>text<|/ref|><|det|>[[642, 785, 878, 802]]<|/det|> +(Page S23, Supplementary) + +<|ref|>text<|/ref|><|det|>[[118, 821, 880, 875]]<|/det|> +Comment: If either or both of the above concerns can be successfully addressed, I suggest that this manuscript may be reconsidered. Otherwise, it may be more suitable to a more specialized journal. + +<|ref|>text<|/ref|><|det|>[[115, 895, 880, 913]]<|/det|> +Response: In our resubmitted version of manuscript, we have attempted to address the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 159]]<|/det|> +concerns about the application versatility of IBFW through two experiments that can broaden the liquid working media of IBFW and can transfer liquid pattern into solid materials. Discontinuous pattern can also be printed by combining the liquid inducing mode with damaging mode of the helium focused ion beam. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 300, 106]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[115, 146, 393, 163]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 175, 730, 192]]<|/det|> +The authors have addressed my comments to satisfaction. I recommend publication. + +<|ref|>text<|/ref|><|det|>[[115, 231, 393, 248]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 260, 857, 313]]<|/det|> +The authors have seriously considered all my previous comments and, in particular, improved the manuscript significantly based on them. In particular my main concern of lack of application potential was addressed with additional experiments and a new section in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 324, 368, 341]]<|/det|> +I can recommend publication now. + +<|ref|>text<|/ref|><|det|>[[115, 380, 393, 397]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[112, 409, 810, 427]]<|/det|> +The authors have successfully addressed all of my previous concerns. I suggest publication as is. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[383, 86, 612, 103]]<|/det|> +## Responses to Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[118, 123, 795, 140]]<|/det|> +The authors have addressed my comments to satisfaction. I recommend publication. + +<|ref|>text<|/ref|><|det|>[[118, 159, 880, 195]]<|/det|> +Response: We thank the reviewer for the comments that have significantly improved our manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[383, 104, 612, 121]]<|/det|> +## Responses to Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 140, 881, 212]]<|/det|> +The authors have seriously considered all my previous comments and, in particular, improved the manuscript significantly based on them. In particular my main concern of lack of application potential was addressed with additional experiments and a new section in the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 216, 397, 232]]<|/det|> +I can recommend publication now. + +<|ref|>text<|/ref|><|det|>[[118, 252, 880, 288]]<|/det|> +Response: We thank the reviewer for the comments that have significantly improved our manuscript. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[383, 104, 612, 121]]<|/det|> +## Responses to Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[118, 140, 879, 175]]<|/det|> +The authors have successfully addressed all of my previous concerns. I suggest publication as is. + +<|ref|>text<|/ref|><|det|>[[118, 196, 880, 232]]<|/det|> +Response: We thank the reviewer for the comments that have significantly improved our manuscript. + +<--- Page Split ---> diff --git a/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..93f693c11e41c97fe23984707edcdad2e7099e6d --- /dev/null +++ b/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,175 @@ +[ + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Fig. 4. Sound pressure field visualization. a Visualization of the real part of the sound pressure field inside the cavity. The red color indicates a pressure maximum and the blue color a minimum, respectively. b Absolute value of the measured pressure field. c Superposition of the four most dominant modes (modes with the highest FFT coefficients). d Superposition of the next four modes with high coefficients. e Simulation results. The colored scales display the absolute values of the pressure in Pa, with the pressure being normalized to the incident pressure field.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Fig. 5. Experimental verification of symmetry-reduced BICs. a Schematic of a resonant cavity similar to that shown in Fig. S 1. The \\(z\\) -axis is perpendicular to the \\(xy\\) -plane. The length \\(L_{y}\\) is set to \\(160\\mathrm{mm}\\) and the diameter \\(d\\) of the pipe to \\(40\\mathrm{mm}\\) . We halve the cavity at the axis of symmetry (highlighted in red) based on the principle of mirror sources and thus obtain a cavity length of \\(L_{x} = 85\\mathrm{mm}\\) , which corresponds to half the length of the configuration with \\(L_{x} = 170\\mathrm{mm}\\) . b Further reduction of the configuration in a using the principle of mirror sources once again. c Fully reduced configuration. d Manufactured samples for configurations b ( \\(L_{x} = 85\\mathrm{mm}\\) ) and c ( \\(L_{x} = 85\\mathrm{mm}\\) for the top sample and \\(L_{x} = 77\\mathrm{mm}\\) for the bottom sample). e Absorption coefficient \\(\\alpha\\) in the frequency range \\(1900 - 2250\\mathrm{Hz}\\) . The blue line represents the result of the numerical simulation of the BIC configuration of c with \\(L_{x} = 77\\mathrm{mm}\\) . The orange dotted line, the yellow dash-dotted line and the purple dashed line represent the numerical results of \\(L_{x} = 85\\mathrm{mm}\\) for the configurations a,b, and c, respectively. f Absorption coefficient \\(\\alpha\\) in the frequency range \\(1900 - 2250\\mathrm{Hz}\\) . The blue and the yellow lines represent the results of the numerical simulation of the BIC configuration of c with \\(L_{x} = 85\\mathrm{mm}\\) and \\(L_{x} = 77\\mathrm{mm}\\) , respectively. The orange and the purple dashed lines represent the measurement results of configuration c with \\(L_{x} = 85\\mathrm{mm}\\) and \\(L_{x} = 77\\mathrm{mm}\\) . g The computed and measured absorption coefficients for configuration b are represented by the blue and orange dashed lines, respectively. h Sound pressure field of the BIC mode inside the cavity with \\(L_{x} = 170\\mathrm{mm}\\) . i Sound pressure field of the BIC mode inside the fully reduced cavity with \\(L_{x} = 85\\mathrm{mm}\\) for configuration c, framed by the black lines and extrapolated to the rectangular cavity. j Measured absolute sound pressure inside the fully reduced cavity with \\(L_{x} = 67\\mathrm{mm}\\) excited at \\(2315\\mathrm{Hz}\\) . The color scale represents the absolute pressure in Pa.", + "footnote": [], + "bbox": [ + [ + 90, + 67, + 900, + 497 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_1a.jpg", + "caption": "Fig. S 11. Simulated pressure mappings. a Maximum absolute sound pressure inside the rectangular cavity shown in Fig. 1a. The cavity length is varied from \\(L_{x} = 145 - 185\\mathrm{mm}\\) in \\(1\\mathrm{mm}\\) and \\(1\\mathrm{Hz}\\) steps in the frequency range \\(1900 - 2250\\mathrm{Hz}\\) . b Maximum absolute sound pressure inside the reduced cavity presented in Fig. 5a with cavity length \\(L_{x} = 67.5 - 92.5\\mathrm{mm}\\) in the same frequency range. c Maximum absolute sound pressure inside the further reduced cavity (Fig. 5b). The white crosses indicate the maxima.", + "footnote": [], + "bbox": [ + [ + 118, + 183, + 900, + 555 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_1a.jpg", + "caption": "Fig. S 12. Visualized pressure fields of the full cavity. a - f Absolute sound pressure inside the rectangular cavity shown in Fig. 1a. with \\(L_{x} = 170 \\mathrm{mm}\\) excited at 2070 Hz, 2075 Hz, 2077 Hz, 2079 Hz, 2081 Hz, and 2094 Hz, respectively. All color scales represent the absolute pressure in Pa.", + "footnote": [], + "bbox": [ + [ + 95, + 68, + 900, + 760 + ] + ], + "page_idx": 8 + }, + { + "type": "image", + "img_path": "images/Figure_5c.jpg", + "caption": "Fig. S 13. Simulated pressure mappings. a,b Maximum absolute sound pressure and absorption inside the cavity shown in Fig. 5c. The cavity length is varied from \\(L_{x} = 67.5 - 92.5\\mathrm{mm}\\) in \\(1\\mathrm{mm}\\) and \\(1\\mathrm{Hz}\\) steps in the frequency range 1900 - 2400 Hz. c,d Maximum absolute sound pressure and absorption at finer resolution. The cavity length is varied from \\(L_{x} = 66 - 68\\mathrm{mm}\\) in \\(0.1\\mathrm{mm}\\) and \\(0.1\\mathrm{Hz}\\) steps in the frequency range 2290 - 2330 Hz. The white crosses indicate the maxima.", + "footnote": [], + "bbox": [ + [ + 92, + 173, + 898, + 550 + ] + ], + "page_idx": 9 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. S 14. LDV samples. Printed samples of the fully reduced cavity with high-transmission glass mounted as side panels.", + "footnote": [], + "bbox": [ + [ + 303, + 65, + 692, + 280 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_5c.jpg", + "caption": "Fig. S 15. Visualized pressure fields of the fully reduced cavity. a - c Absolute sound pressure inside the fully reduced cavity shown in Fig. 5c with \\(L_{x} = 64\\mathrm{mm}\\) excited at \\(2335\\mathrm{Hz}\\) , \\(2345\\mathrm{Hz}\\) , and \\(2353\\mathrm{Hz}\\) . g - i Absolute sound pressure inside the fully reduced cavity with \\(L_{x} = 70\\mathrm{mm}\\) excited at \\(2267\\mathrm{Hz}\\) , \\(2272\\mathrm{Hz}\\) , and \\(2277\\mathrm{Hz}\\) . All color scales represent the absolute pressure in Pa.", + "footnote": [], + "bbox": [ + [ + 90, + 68, + 900, + 644 + ] + ], + "page_idx": 11 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. S 7. Transmission spectra with and without losses. a Transmission coefficient in the 1900 - 2250 Hz frequency range. The solid blue and dashed yellow lines represent the results of \\(L_{x} = 165\\mathrm{mm}\\) with and without thermo-viscous losses, respectively. The results of \\(L_{x} = 170\\mathrm{mm}\\) are shown by the red and purple lines. b Transmission loss of \\(L_{x} = 165\\mathrm{mm}\\) and \\(L_{x} = 170\\mathrm{mm}\\) with and without losses. The coloring of the lines is identical to Fig. S 7a.", + "footnote": [], + "bbox": [ + [ + 95, + 277, + 868, + 499 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_1a.jpg", + "caption": "Fig. S 8. Pressure mapping (without losses). Maximum absolute sound pressure inside the rectangular cavity shown in Fig. 1a. The cavity length is varied from \\(L_{x} = 157 - 163 \\mathrm{mm}\\) in \\(0.1 \\mathrm{Hz}\\) steps in the frequency range \\(2135 - 2160 \\mathrm{Hz}\\) .", + "footnote": [], + "bbox": [ + [ + 286, + 65, + 716, + 267 + ] + ], + "page_idx": 13 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. S 5. Complex eigenfrequencies for varying \\(L_{x}\\) . a The spectrum of propagating waves dominated by the pipe is marked by the region colored blue. Cavity resonances are highlighted by the region colored red. BIC 1 and BIC 2 are marked by the red crosses. b Evolution over \\(L_{x}\\) of the interacting modes that form BIC 1 & 2.", + "footnote": [], + "bbox": [ + [ + 95, + 468, + 867, + 692 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. S 1. Schematic drawing of a coupled two-dimensional waveguide-resonator system.", + "footnote": [], + "bbox": [ + [ + 352, + 63, + 660, + 253 + ] + ], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. S 2. Eigenfield profile. Decomposition of Friedrich-Wintgen BIC into eigenmodes \\(M_{31}\\) and \\(M_{13}\\) .", + "footnote": [], + "bbox": [ + [ + 98, + 631, + 911, + 738 + ] + ], + "page_idx": 19 + } +] \ No newline at end of file diff --git a/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..f2fd5388109c33747b0543390b1622d27ea44ad4 --- /dev/null +++ b/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,411 @@ + +# nature portfolio + +Peer Review File + +Realistic prediction and engineering of high- Q modes to implement stable Fano resonances in acoustic devices + +![](images/Figure_4.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +The authors theoretically investigated and experimentally demonstrated the existence of FW- BICs by measuring the transmission spectrum. By scanning the size ratio of rectangular resonators, BIC is converted into QBIC, which is usually manifested by the Fano resonance in the transmission spectrum. Besides the transmission spectrum, the authors image the pressure field distribution of QBICs based on FW- BICs by using laser Doppler vibrometry, proving the direct evidence of the existence of FW- BICs. Although this work presents some interesting results, some concerns must be addressed + +(1) The biggest selling point lies in directly imaging the QBICs based on FW-BIC. In Fig.4, indeed, the measured pressure distribution of QBICs matches very well with the simulated one. Due to the thermal-viscous loss, the pressure field enhancement is not as high as the simulated one if the lossless system is considered. Therefore, to further push the applications of QBICs, real intensities instead of normalized intensities of the pressure field of QBICs shall be presented because the maximum pressure field plays a central role in governing acoustic-matter interactions, such as acoustic emissions. Therefore, I may suggest authors provide more data with the real intensities of the pressure field at different size ratios to demonstrate that the pressure field enhancement reaches the maximum when the size ratio is close to the critical value forming FW-BICs. With real information on pressure intensity, it may provide useful guidance for designing acoustic sources. + +(2) In Fig.2c-d, a good agreement can be found between measurement and simulation. It is well known that in real systems, there are thermo-viscous losses that may influence the transmission significantly. Do authors consider the thermo-viscous losses in the simulation to match the experiments? If yes, they need to provide more details on how thermo-viscous losses affect the simulated transmission. + +(3) Since the authors show the pressure imaging of FW-BICs in Fig.4, I may suggest the authors also do the same thing on the BICs formed in structures of Fig.5d. By doing this, the authors may know which structure gives the best pressure confinement of QBICs. + +(4) In Fig.2c, Fig.4e-f, Fig.4h-i, what does it mean for y-axis, T[-], R[-], alpha[-]? Usually, the unit is included in the bracket. + +Reviewer #2: + +Remarks to the Author: + +The authors demonstrate theoretically and experimentally the existence of Friedrich- Wintgen (FW) type bound in continuum states (BICs) in an open acoustic cavity. The BIC is revealed in the transmission coefficient under the shape of a Fano resonance (quasi- BIC) whose linewidth vanishes when approaching the geometrical parameters of the cavity satisfying the BIC condition. They show the best conditions to observe the QBIC in presence of thermoviscous losses. Moreover, by using a laser Doppler vibrometry (LDV) technique, they are able to reveal for the first time the map of the pressure field associated with the BIC inside the cavity. Finally, they present the design of new type high- quality BIC relying on reduced symmetry and avoiding the excitation of unwanted resonances in the cavity. The agreement between theory and experiment is very accurate throughout the manuscript. + +The paper is generally well presented and contains some interesting and new results. It is timely because of the continuing interest in BICs and their applications based on the high sensitivity of the resulting Fano resonances to the environment. However, the cavity designed in this paper and the associated BICs and their analysis have some similarities with those presented in recent papers. The main novelty of this manuscript is the observation of the BIC pressure field inside the cavity by using LDV. This is an interesting proposal that deserves to be published. But from the point of view of physical originality or attraction for a broad audience, the paper would probably not reach the level required for acceptance in Nature Communications. Perhaps, another of the Nature journals would be more appropriate. + +<--- Page Split ---> + +A few minor remarks are mentioned for the attention of the authors. + +- A short explanation about FW BIC can be useful, as well as on the physical principle of LDV. +- In page 5, the sentence "a reduction of a factor of \(k = 3.41\) between the inlet and the outlet sound pressure amplitudes was noticed" needs a better explanation. + +- In Figure S3, one cannot clearly see the evolution of Lx on the curves, so some precision would be helpful. + +- In section S5, Figures S6 are referred to as Fig. 6 (Fig. 6(a), 6(b) and 6(c)). In Fig. S6, two panels are labeled b instead of b and c. Please correct + +Reviewer #3: + +Remarks to the Author: + +The authors demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by numerical simulations and experiments, and indirectly measure the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry. The specific questions are as follows: + +vibrometry. The specific questions are as follows: + +(1) The models in this article are very similar to previous works (such as Phys. Rev. Applied 18, 054021), the innovative of the work should be further explained, and there is no detailed theory analysis in this article. + +(2) As far as I know, it is not the first time to indirectly measure the acoustic pressure in air by the laser Doppler vibrometry. On the other hand, for the model size in this article, it is possible to directly measure the pressure field by such as \(1 / 4''\) microphone. + +(3) Could authors explain further the black dotted line in the Fig.1(b)(c)? How do authors calculate them through the coupled mode theory? + +(4) Does the technique involved in this article using laser Doppler vibrometry require the structural size of the sample? When it comes to practicality, does this technique work on smaller structures? + +<--- Page Split ---> + +## Response to the Reviewers + +Journal: + +Nature Communications + +Manuscript No.: + +NCOMMS- 22- 48526A- Z + +Title: + +Realistic prediction and engineering of high- Q modes to implement stable Fano resonances in acoustic devices + +## Authors: + +Felix Kronowetter, Marcus Maeder, Yan Kei Chiang, Lujun Huang, Johannes Schmid, Sebastian Oberst, David A. Powell, and Steffen Marburg + +## General Remarks + +Dear Reviewers: + +We would like to express our appreciation for the efforts made by the reviewers to improve our paper. The comments are very constructive and helpful in improving the quality and presentation of the paper. We have done a substantial amount of work to incorporate the suggestions and address the concerns raised by the reviewers. In response to reviewer #1's request, we have performed extensive numerical simulations and put considerable effort into fabricating new samples and performing additional experiments. In response to the requests of reviewers #2 and #3, we have added more data and more detailed explanations to the manuscript to highlight the novelty, innovation, and scientific impact of our work. We have added a complete theoretical model in response to reviewer #3. We have incorporated the suggestions and addressed the concerns raised by the reviewers. Red- colored text indicates changes made to the manuscript, while blue- colored text highlights the authors' responses. + +<--- Page Split ---> + +## Specific Response to Reviewer #1: + +The authors theoretically investigated and experimentally demonstrated the existence of FW- BICs by measuring the transmission spectrum. By scanning the size ratio of rectangular resonators, BIC is converted into QBIC, which is usually manifested by the Fano resonance in the transmission spectrum. Besides the transmission spectrum, the authors image the pressure field distribution of QBICs based on FW- BICs by using laser Doppler vibrometry, proving the direct evidence of the existence of FW- BICs. Although this work presents some interesting results, some concerns must be addressed. + +Thank you for your feedback and helpful comments. We have tried to incorporate all of them to a satisfactory level. + +1. The biggest selling point lies in directly imaging the QBICs based on FW-BIC. In Fig. 4, indeed, the measured pressure distribution of QBICs matches very well with the simulated one. Due to the thermal-viscous loss, the pressure field enhancement is not as high as the simulated one if the lossless system is considered. Therefore, to further push the applications of QBICs, real intensities instead of normalized intensities of the pressure field of QBICs shall be presented because the maximum pressure field plays a central role in governing acoustic-matter interactions, such as acoustic emissions. Therefore, I may suggest authors provide more data with the real intensities of the pressure field at different size ratios to demonstrate that the pressure field enhancement reaches the maximum when the size ratio is close to the critical value forming FW-BICs. With real information on pressure intensity, it may provide useful guidance for designing acoustic sources. + +We have changed Fig. 4 and the corresponding text to show the actual pressure values. We use absolute pressure from here on to be independent of the phase (section: Results, Fig. 4, pages: 6 and 7): + +The visualized sound pressure field of the QBIC within the experimental set- up is presented in Fig. 4a. In addition, we show a mapping of the absolute values of the pure measurement data in Fig. 4b for better comparison with the numerical data displayed in Fig. 4e. We observe that the measurement is in good agreement with the numerical prediction. As expected, the pressure maxima are located at both the edges and the center of the cavity. Minor inaccuracies within the numerical prediction are due to real losses and uncertainties within the experiments, i.e. imprecise alignment of the parts or imperfect plane wave excitation. We note only a slight pressure fluctuation in the center, just below the marked node in Fig. 4a. The position of the LDV for this measurement point is normal incidence to the glass. This results in a lower signal- to- noise ratio, which leads to higher measurement errors. We obtain a stable image of the QBIC that is in good agreement with the simulated sound pressure field. Thus, we present the visual evidence of a QBIC. + +In addition, we have added plots of the maximum pressure inside the cavity versus cavity length and frequency for all configurations presented in the manuscript to see where the real maximum field enhancement occurs. We have also measured the cavity with \(L_{x} = 170 \mathrm{mm}\) excited at several frequencies to observe the evolution of the modal field and to determine the frequency with the highest pressure enhancement. We have also provided additional data with different size ratios of the fully reduced cavity, shown in Fig. 5c, to demonstrate the parameter configuration where the pressure field enhancement reaches its maximum. We have chosen this configuration to experimentally determine where the maximum pressure enhancement occurs. The results for the configuration with the highest pressure enhancement are presented in the manuscript as they provide seminal insights for the design of QBICs (section: Results, Pressure Enhancement, Fig. 5, pages: 6 - 8): + +<--- Page Split ---> +![](images/Figure_5.jpg) + +
Fig. 4. Sound pressure field visualization. a Visualization of the real part of the sound pressure field inside the cavity. The red color indicates a pressure maximum and the blue color a minimum, respectively. b Absolute value of the measured pressure field. c Superposition of the four most dominant modes (modes with the highest FFT coefficients). d Superposition of the next four modes with high coefficients. e Simulation results. The colored scales display the absolute values of the pressure in Pa, with the pressure being normalized to the incident pressure field.
+ +Figs. 5a to 5c show three schematics of the previously studied resonant cavities reduced in size by applying the principle of mirror sources. We cut the geometry in half at a particular axis of symmetry (marked by the red lines in the schematics mentioned above). The axis of symmetry has to be chosen with care since the BIC mode needs to be sustained and all anti- symmetric modes with respect to this axis need to be suppressed. Fig. 5c depicts the schematic of the fully reduced geometry. We manufacture three additional samples for impedance tube measurements, shown in Fig. 5d. Fig. 5e shows the numerically obtained absorption coefficients of the configurations in Figs. 5a to 5c with \(L_{x} = 85 \mathrm{mm}\) and also of the BIC configuration in Fig. 5c determined at \(L_{x} = 77 \mathrm{mm}\) . The more we reduce the geometry, the more unwanted modes are removed. Accordingly, we observe a clear peak in the absorption spectrum. We perform impedance tube measurements to validate our observations. The measured absorption coefficients are presented in Fig. 5f for the fully reduced configuration, see Fig. 5c, and in Fig. 5g for the configuration shown in Fig. 5b. The measurement results agree with our prediction. We observe the collapse of the Fano resonance (yellow and dashed purple lines in Fig 5f), the sharp peak of the Fano resonance with no further absorption in the spectrum shown (blue and dashed red lines), and thus prove the existence of a Friedrich- Wintgen BIC based on the concept of fully reduced symmetry without exciting unwanted modes. Fig. 5h shows the unexcited QBIC mode for a rectangular cavity with \(L_{x} = 170 \mathrm{mm}\) . The sound pressure field of the fully reduced geometry framed by the black lines is depicted in Fig. 5i. For comparison, we extrapolate the reduced sound pressure field onto the rectangular cavity. We infer from comparing Fig. 5h + +<--- Page Split ---> +![](images/Figure_1a.jpg) + +
Fig. 5. Experimental verification of symmetry-reduced BICs. a Schematic of a resonant cavity similar to that shown in Fig. S 1. The \(z\) -axis is perpendicular to the \(xy\) -plane. The length \(L_{y}\) is set to \(160\mathrm{mm}\) and the diameter \(d\) of the pipe to \(40\mathrm{mm}\) . We halve the cavity at the axis of symmetry (highlighted in red) based on the principle of mirror sources and thus obtain a cavity length of \(L_{x} = 85\mathrm{mm}\) , which corresponds to half the length of the configuration with \(L_{x} = 170\mathrm{mm}\) . b Further reduction of the configuration in a using the principle of mirror sources once again. c Fully reduced configuration. d Manufactured samples for configurations b ( \(L_{x} = 85\mathrm{mm}\) ) and c ( \(L_{x} = 85\mathrm{mm}\) for the top sample and \(L_{x} = 77\mathrm{mm}\) for the bottom sample). e Absorption coefficient \(\alpha\) in the frequency range \(1900 - 2250\mathrm{Hz}\) . The blue line represents the result of the numerical simulation of the BIC configuration of c with \(L_{x} = 77\mathrm{mm}\) . The orange dotted line, the yellow dash-dotted line and the purple dashed line represent the numerical results of \(L_{x} = 85\mathrm{mm}\) for the configurations a,b, and c, respectively. f Absorption coefficient \(\alpha\) in the frequency range \(1900 - 2250\mathrm{Hz}\) . The blue and the yellow lines represent the results of the numerical simulation of the BIC configuration of c with \(L_{x} = 85\mathrm{mm}\) and \(L_{x} = 77\mathrm{mm}\) , respectively. The orange and the purple dashed lines represent the measurement results of configuration c with \(L_{x} = 85\mathrm{mm}\) and \(L_{x} = 77\mathrm{mm}\) . g The computed and measured absorption coefficients for configuration b are represented by the blue and orange dashed lines, respectively. h Sound pressure field of the BIC mode inside the cavity with \(L_{x} = 170\mathrm{mm}\) . i Sound pressure field of the BIC mode inside the fully reduced cavity with \(L_{x} = 85\mathrm{mm}\) for configuration c, framed by the black lines and extrapolated to the rectangular cavity. j Measured absolute sound pressure inside the fully reduced cavity with \(L_{x} = 67\mathrm{mm}\) excited at \(2315\mathrm{Hz}\) . The color scale represents the absolute pressure in Pa.
+ +to Fig. 5i that identical sound pressure distributions are obtained. Finally, we manage to preserve the BIC mode although the geometry is reduced significantly and thus present a new type of fully reduced high- Q mode without exciting unwanted modes. + +<--- Page Split ---> + +Pressure enhancement. Impedance tube studies allow us to extract values for reflection spectra and absorption, but not for cavity pressure enhancement. The missing cavity pressure information is provided by the LDV. The numerical and experimental procedure to determine the maximum pressure is presented in detail in Supplementary Information Section 6. Fig. 5j shows the measured absolute pressure field inside the fully reduced cavity with \(L_{x} = 67\mathrm{mm}\) excited at \(2315\mathrm{Hz}\) . This configuration leads to the maximum pressure enhancement possible for this structure with a measured peak value of \(36.74\mathrm{Pa}\) . We additionally measure the sound pressure fields of the fully reduced cavity with \(L_{x} = 64\mathrm{mm}\) and \(L_{x} = 70\mathrm{mm}\) to prove the existence of a pressure peak. The measurements show peak pressures of \(26.08\mathrm{Pa}\) and \(32.26\mathrm{Pa}\) , respectively. To demonstrate the magnitude of the pressure enhancement, we measure the pressure field inside the full cavity with \(L_{x} = 170\mathrm{mm}\) for several frequencies. The maximum pressure is \(12.61\mathrm{Pa}\) . Thus, the fully reduced cavity leads to the highest pressure enhancement of the investigated Friedrich- Wintgen BIC by a factor of about three compared to the full cavity. + +Finally, we extract the sound pressure field of a QBIC mode. The sound pressure field inside the cavity gives us accurate information about the influence of losses and hence the stability and confinement of the mode. We also show that LDV measurements are a powerful tool for predicting the maximum pressure enhancement of high- Q modes, can resolve even small deviations from numerical predictions, and thus provide seminal guidance for the application of QBICs. Thus, we present the realistic sound pressure field of a stable high- Q mode, enabling further analysis and its application to acoustic devices. + +<--- Page Split ---> + +All other results are shown in Supplementary Information Section S 6: + +## Pressure enhancement + +The configuration with the highest pressure field enhancement is determined by parameter studies. Therefore, we vary the cavity lengths of the configurations depicted in Fig. 1a, Fig. 5a and Fig. 5b. The corresponding plots are shown in Fig. S 11. + +![](images/Figure_1a.jpg) + +
Fig. S 11. Simulated pressure mappings. a Maximum absolute sound pressure inside the rectangular cavity shown in Fig. 1a. The cavity length is varied from \(L_{x} = 145 - 185\mathrm{mm}\) in \(1\mathrm{mm}\) and \(1\mathrm{Hz}\) steps in the frequency range \(1900 - 2250\mathrm{Hz}\) . b Maximum absolute sound pressure inside the reduced cavity presented in Fig. 5a with cavity length \(L_{x} = 67.5 - 92.5\mathrm{mm}\) in the same frequency range. c Maximum absolute sound pressure inside the further reduced cavity (Fig. 5b). The white crosses indicate the maxima.
+ +Pressure enhancement can be observed in certain regions around the BIC configurations. We can also see that the maximum pressure enhancement does not occur directly adjacent to the BIC as it would without losses, i.e., see Fig. S 8. Thermo- viscous losses shift the maximum enhancement away from the BIC configuration. The pressure peaks are \(5.50\mathrm{Pa}\) , \(9.54\mathrm{Pa}\) , and \(12.89\mathrm{Pa}\) . It can be said that the more the geometry is reduced and thus the antisymmetric modes are suppressed, the higher the pressure enhancement. The visualized pressure fields for the full cavity are shown in Fig. S 12. + +<--- Page Split ---> +![](images/Figure_5c.jpg) + +
Fig. S 12. Visualized pressure fields of the full cavity. a - f Absolute sound pressure inside the rectangular cavity shown in Fig. 1a. with \(L_{x} = 170 \mathrm{mm}\) excited at 2070 Hz, 2075 Hz, 2077 Hz, 2079 Hz, 2081 Hz, and 2094 Hz, respectively. All color scales represent the absolute pressure in Pa.
+ +The corresponding maximum pressure values in Figs. S 12a to 12f are 12.04 Pa, 12.61 Pa, 12.44 Pa, 12.02 Pa, 11.32 Pa, and 8.59 Pa, respectively. Therefore, we can say that the maximum pressure enhancement occurs at 2075 Hz. The evolution of the modal field is also demonstrated. The dark blue line + +<--- Page Split ---> + +representing the pressure nodes extends in the \(y\) - direction, the more the configuration deviates from the BIC configuration. + +We numerically determine the configuration with the highest pressure gain by plotting the maximum absolute sound pressure inside the cavity as the cavity length is varied in the 1900 - 2400 Hz frequency range and excited by a plane wave of 1 Pa. This is shown in Fig. S 13 for the fully reduced cavity presented in Fig. 5c. + +![](images/Figure_unknown_0.jpg) + +
Fig. S 13. Simulated pressure mappings. a,b Maximum absolute sound pressure and absorption inside the cavity shown in Fig. 5c. The cavity length is varied from \(L_{x} = 67.5 - 92.5\mathrm{mm}\) in \(1\mathrm{mm}\) and \(1\mathrm{Hz}\) steps in the frequency range 1900 - 2400 Hz. c,d Maximum absolute sound pressure and absorption at finer resolution. The cavity length is varied from \(L_{x} = 66 - 68\mathrm{mm}\) in \(0.1\mathrm{mm}\) and \(0.1\mathrm{Hz}\) steps in the frequency range 2290 - 2330 Hz. The white crosses indicate the maxima.
+ +The BIC is visible as the dark blue dot in the center of the red lines in Figs. S 13a to 13b. Pressure enhancement can be observed in certain regions around the BIC configurations. The smaller the cavity length, the higher the frequency of the enhancement and vice versa. It can be seen that the maximum pressure enhancement and absorption occurs at a cavity length of \(L_{x} = 67\mathrm{mm}\) . We fabricate three additional samples of the fully reduced cavity ( \(L_{x} = 64\) , 67, and \(70\mathrm{mm}\) ) to experimentally validate our numerical predictions, see Fig. S 14. + +<--- Page Split ---> +![](images/Figure_5c.jpg) + +
Fig. S 14. LDV samples. Printed samples of the fully reduced cavity with high-transmission glass mounted as side panels.
+ +We then measure the sound pressure field inside the cavity for several frequencies to determine the configuration (frequency and cavity length) where the maximum absolute sound pressure is found. The visualized pressure fields for the fully reduced cavity with \(L_{x} = 64\mathrm{mm}\) , \(L_{x} = 67\mathrm{mm}\) , and \(L_{x} = 70\mathrm{mm}\) are shown in Fig. S 15. + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Fig. S 15. Visualized pressure fields of the fully reduced cavity. a - c Absolute sound pressure inside the fully reduced cavity shown in Fig. 5c with \(L_{x} = 64\mathrm{mm}\) excited at \(2335\mathrm{Hz}\) , \(2345\mathrm{Hz}\) , and \(2353\mathrm{Hz}\) . g - i Absolute sound pressure inside the fully reduced cavity with \(L_{x} = 70\mathrm{mm}\) excited at \(2267\mathrm{Hz}\) , \(2272\mathrm{Hz}\) , and \(2277\mathrm{Hz}\) . All color scales represent the absolute pressure in Pa.
+ +The data are not normalized to the incident pressure field, but the actual pressure values are shown. The corresponding maximum pressure values in Figs. S 15a to 15i are \(25.61\mathrm{Pa}\) , \(26.07\mathrm{Pa}\) , \(24.80\mathrm{Pa}\) , \(36.11\mathrm{Pa}\) , \(36.74\mathrm{Pa}\) , \(33.98\mathrm{Pa}\) , \(31.83\mathrm{Pa}\) , \(32.26\mathrm{Pa}\) , and \(28.12\mathrm{Pa}\) , respectively. Therefore, we can say that the maximum pressure enhancement for the cavity with \(L_{x} = 64\mathrm{mm}\) occurs at \(2345\mathrm{Hz}\) and for the cavity with \(L_{x} = 70\mathrm{mm}\) at \(2272\mathrm{Hz}\) . The maximum pressure enhancement occurs at \(L_{x} = 67\mathrm{mm}\) at \(2315\mathrm{Hz}\) and reaches \(36.74\mathrm{Pa}\) . This is similar to the results shown in Fig. S 13c. + +We compare this maximum pressure value to the sound pressure fields of the fully reduced cavity with \(L_{x} = 64\mathrm{mm}\) and \(L_{x} = 70\mathrm{mm}\) to prove the existence of a pressure peak. The measurements show peak pressures of \(26.07\mathrm{and}32.26\mathrm{Pa}\) , respectively. To demonstrate the magnitude of the pressure enhancement, we also compare it to the pressure field inside the full cavity with \(L_{x} = 170\mathrm{mm}\) for several frequencies. + +<--- Page Split ---> + +The maximum pressure of the full cavity is 12.61 Pa. Thus, the fully reduced cavity leads to the highest pressure enhancement of the investigated Friedrich- Wintgen BIC by a factor of about three. + +2. In Fig.2c-d, a good agreement can be found between measurement and simulation. It is well known that in real systems, there are thermo-viscous losses that may influence the transmission significantly. Do authors consider the thermo-viscous losses in the simulation to match the experiments? If yes, they need to provide more details on how thermo-viscous losses affect the simulated transmission. + +We have included thermo-viscous losses in our simulations. To address the effect of losses on the transmission and reflection spectra, we have added a more detailed explanation in section S 4 in the Supplementary Information (section: S 4, pages: 7 and 8): + +The effect of thermo- viscous losses on the Fano peaks in the transmission spectra is shown in Fig. S 7. + +![](images/Figure_1a.jpg) + +
Fig. S 7. Transmission spectra with and without losses. a Transmission coefficient in the 1900 - 2250 Hz frequency range. The solid blue and dashed yellow lines represent the results of \(L_{x} = 165\mathrm{mm}\) with and without thermo-viscous losses, respectively. The results of \(L_{x} = 170\mathrm{mm}\) are shown by the red and purple lines. b Transmission loss of \(L_{x} = 165\mathrm{mm}\) and \(L_{x} = 170\mathrm{mm}\) with and without losses. The coloring of the lines is identical to Fig. S 7a.
+ +Thermo- viscous losses significantly reduce the transmission coefficient due to increased absorption. Nevertheless, the transmission goes to zero at the frequency of the QBIC, see Fig. S 7a. The maxima of the Fano peaks in the TL also decrease including the losses. We observe a reduction from \(\approx 42\mathrm{dB}\) to \(\approx 17\mathrm{dB}\) \((L_{x} = 165\mathrm{mm})\) and from \(\approx 43\mathrm{dB}\) to \(\approx 24\mathrm{dB}\) \((L_{x} = 170\mathrm{mm})\) . The losses have a more significant effect on the amplitude of the Fano peak of the TL the closer we are to the BIC configuration. In addition, due to thermo- viscous losses, the Fano peaks are shifted to lower frequencies by about \(2\mathrm{Hz}\) . To illustrate the effect of losses on pressure field enhancement, the maximum absolute sound pressure is plotted against cavity length and frequency in Fig. S 8. + +<--- Page Split ---> +![](images/Figure_unknown_2.jpg) + +
Fig. S 8. Pressure mapping (without losses). Maximum absolute sound pressure inside the rectangular cavity shown in Fig. 1a. The cavity length is varied from \(L_{x} = 157 - 163 \mathrm{mm}\) in \(0.1 \mathrm{Hz}\) steps in the frequency range \(2135 - 2160 \mathrm{Hz}\) .
+ +We observe amplified sound pressure up to \(160 \mathrm{dB}\) when excited at \(1 \mathrm{Pa}\) and narrow Fano peaks near the BIC. Figs. S 6 to S 8 illustrate the importance of considering thermo- viscous losses in our simulations. + +3. Since the authors show the pressure imaging of FW-BICs in Fig.4, I may suggest the authors also do the same thing on the BICs formed in structures of Fig.5d. By doing this, the authors may know which structure gives the best pressure confinement of QBICs. + +We have manufactured three additional configurations of the fully reduced cavity, shown in Fig. 5c, and have visualized the pressure fields. We have chosen this configuration to experimentally determine where the maximum pressure enhancement occurs. The results of the configuration with the highest pressure enhancement are presented in the manuscript as they provide seminal insights for the design of QBICs, while the results for the other configurations appear in Supporting Information S 6. See the answer to your first point for more details. + +4. In Fig.2c, Fig.4e-f, Fig.4h-i, what does it mean for y-axis, T[-], R[-], alpha[-]? Usually, the unit is included in the bracket. + +We have used [-] to indicate, that the corresponding quantities are dimensionless, but have removed them for a better understanding. + +<--- Page Split ---> + +## Specific Response to Reviewer #2: + +The authors demonstrate theoretically and experimentally the existence of Friedrich- Wintgen (FW) type bound in continuum states (BICs) in an open acoustic cavity. The BIC is revealed in the transmission coefficient under the shape of a Fano resonance (quasi- BIC) whose linewidth vanishes when approaching the geometrical parameters of the cavity satisfying the BIC condition. They show the best conditions to observe the QBIC in presence of thermoviscous losses. Moreover, by using a laser Doppler vibrometry (LDV) technique, they are able to reveal for the first time the map of the pressure field associated with the BIC inside the cavity. Finally, they present the design of new type high- quality BIC relying on reduced symmetry and avoiding the excitation of unwanted resonances in the cavity. The agreement between theory and experiment is very accurate throughout the manuscript. + +The paper is generally well presented and contains some interesting and new results. It is timely because of the continuing interest in BICs and their applications based on the high sensitivity of the resulting Fano resonances to the environment. However, the cavity designed in this paper and the associated BICs and their analysis have some similarities with those presented in recent papers. The main novelty of this manuscript is the observation of the BIC pressure field inside the cavity by using LDV. This is an interesting proposal that deserves to be published. But from the point of view of physical originality or attraction for a broad audience, the paper would probably not reach the level required for acceptance in Nature Communications. Perhaps, another of the Nature journals would be more appropriate. + +To emphasize the novelty, innovation, and scientific impact of our work, we have modified the abstract (section: Abstract, page: 1): + +Bound states in the continuum (BICs) coupling into the propagating spectrum lead to the formation of quasi- BICs (QBICs) with high quality (Q) factor. These high- Q modes typically manifest as Fano resonances in the transmission or reflection spectrum. Fano resonances are highly sensitive, and even a small change in geometric or environmental variables results in a significant change in the transmission spectrum. This presents a challenge in predicting stable Fano peaks for realistic applications. In addition, we do not yet have any information on whether or not a large field enhancement occurs when thermo- viscous losses are taken into account in real acoustic devices. In this work, we demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by theory and experiment. In agreement with theoretical predictions, the appearance of the BIC is characterized by the vanishing line width of the Fano resonance in the measured transmission spectrum. We map the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry, which is the first reported visualization of an acoustic BIC. Mapping the pressure field of the BIC is a new technique for extracting real sound pressure values of high- Q modes. From the pressure values, we accurately infer the confinement of the BIC and thus its transmission or reflection properties. Furthermore, based on our results, we design a new type of symmetry- reduced BIC and analyze its absorption spectrum. Laser Doppler vibrometer (LDV) measurements provide the missing field enhancement data. We achieve a field enhancement by a factor of about three compared to the original cavity. The main findings are that LDV measurements are a powerful tool for predicting the maximum pressure enhancement of high- Q modes, and thus a new technique for obtaining the missing field enhancement data. The presented results facilitate the future applications of BICs in acoustics as high- intensity sound sources, filters, and sensors. + +We have added a more detailed explanation of the innovation and of the importance of our findings (section: Introduction, page: 2): + +We further present the first direct visualization of a Friedrich- Wintgen BIC using laser Doppler vibrometry as a pressure field mapping technique. We use laser Doppler vibrometry measurements to obtain a complete mapping of the sound pressure field to better understand BIC formation in the presence of realistic losses. The reflection and transmission spectra are obtained using microphones, but do not provide information about the exact pressure enhancement inside the cavity. The pressure distribution inside the cavity is needed to develop high- performance acoustic devices based on BICs, such as acoustic sources and sound lasers. Because BICs are extremely sensitive, any perturbation of the high- Q mode, energy extraction, or backscattering from microphones will degrade the BIC, so we use this technique to avoid any perturbation of the pressure field. By mapping the sound pressure field of the BIC, we have direct access to the actual pressure values and thus to the critical information of when and where the pressure magnitude reaches a maximum. The interaction between the localized thermo- viscous losses and the concentrated high intensity fields of the BIC is the key to deter + +<--- Page Split ---> + +mining the achievable Q- factor and pressure field enhancement. We facilitate the accurate analysis of high- Q modes in the presence of realistic losses, determine the configuration with maximum pressure enhancement, and enable the future application of high- Q Fano resonances to acoustic devices. + +A few minor remarks are mentioned for the attention of the authors. + +1. A short explanation about FW BIC can be useful, as well as on the physical principle of LDV. + +We have added an explanation of the formation mechanism (section: S 1, pages: 1 - 3). For a detailed response, please see Specific Response to Reviewer #3, 1. ). We have also added a short description of the analytical solution to predict the eigenfield profile of the Friedrich- Wintgen BIC (section: Methods, page: 9): + +Analytical Model. The eigenfield profile of the Friedrich- Wintgen BIC can be predicted from the following equation + +\[\psi_{B I C}(x,y)\approx \cos \theta \psi_{31}(x,y) + \sin \theta \psi_{13}(x,y)\] + +where + +\[\cos \theta = \frac{A}{\sqrt{A^{2} + B^{2}}},\quad \sin \theta = \frac{B}{\sqrt{A^{2} + B^{2}}},\] + +\[A =\] \[-\sqrt{\frac{L_{y}}{2\pi^{2}L_{x}}}\left[\sin \left(\frac{\pi(L_{y} + 1)}{L_{y}}\right) - \sin \left(\frac{\pi(L_{y} - 1)}{L_{y}}\right)\right],\] \[B = \sqrt{\frac{2}{L_{x}L_{y}}}.\] + +See Supplementary Information Section 1 for a complete theoretical analysis. + +We have added an explanation of the physical principle of the LDV (section: Results, Visualization of QBIC, page: 4): + +To conduct the refracto- vibrometry, a laser Doppler scanning vibrometer PSV- 500 from Polytec \(^{1}\) is used to measure the changes of the refractive index of the fluid, which is proportional to the acoustic pressure variation within the cavity [43- 46]: + +\[v(\omega) = \omega \frac{1}{\gamma p_{0}}\frac{n_{0} - 1}{n_{0}}\int_{L}p(l,\omega)\mathrm{d}l \quad (1)\] + +where \(\omega\) is the angular frequency, \(v\) is the LDV velocity, \(p\) is the sound pressure, \(n_{0}\) is the refractive index of air at standard atmospheric pressure, \(p_{0}\) is the static atmospheric pressure, and \(\gamma\) is the specific heat capacity ratio of air. The basic principle of the LDV is based on the well- known Doppler shift. The pressure waves inside the cavity slightly shift the phase of the emitted monochromatic laser light. The superimposition of the reflected and emitted laser light produces a speckle pattern on the photodetector, which allows the measurement of the corresponding frequency of the pressure waves and the change in the refractive index. The latter is proportional to the sound pressure inside the cavity. This makes it possible to visualize the corresponding pressure distribution. + +We have also added a more detailed explanation of the visualization and its limits (section: Methods, pages: 9 and 10): + +Visualization. We use refracto- vibrometry to visualize the sound pressure field inside the cavity. A laser Doppler scanning vibrometer PSV- 500 from Polytec is used to measure the changes in the refraction index of the fluid, which is proportional to the acoustic pressure variation within the cavity. Overall, 225 measurement points were sequentially recorded with a sampling frequency of \(50\mathrm{kHz}\) for a duration + +<--- Page Split ---> + +of \(2\mathrm{ms}\) , while the measurements were triggered by the sinusoidal sound generator. To ensure an optimal signal- to- noise ratio, a highly reflective sheet was placed against the rigid surface behind the sample to improve diffuse light reflection. Note that usually a LDV is used for surface normal vibration measurements of structures but captures the pressure wave- induced variation in the refraction index when measured against a rigid surface. In the case of a low- vibration surface, the velocity measurement from the LDV is dominated by the dynamic phase, caused by the sound pressure fluctuations, and the changed refractive index of the acoustic medium, along the traveling path of the light. To ensure the required rigidity, a single point LDV (Polytec PDV- 100) measured the surface vibration of the rigid surface from the opposite direction. The surface velocities were found to be orders of magnitude smaller than the signal of the scanning PSV500, confirming that the acoustic pressure dominates the measured results. As the LDV works up to frequencies of \(1\mathrm{MHz}\) , the frequency range is not a limiting factor for pressure field mapping. The size of the structure can be much smaller than those presented in this article and is only limited by the focal point of the laser \((25\mu \mathrm{m})\) . We use such large structures here because we need to measure the transmission/reflection spectra using an impedance tube with a diameter of \(40\mathrm{mm}\) . Since the Helmholtz equation is linearly scalable, our results can be transferred to different frequency ranges. + +2. In page 5, the sentence "a reduction of a factor of \(\mathrm{k} = 3.41\) between the inlet and the outlet sound pressure amplitudes was noticed" needs a better explanation. + +We have removed that part and have introduced new results regarding the pressure amplification inside the cavity. The new results also show the importance of our findings. Please see Specific Response to Reviewer #1, 1. ). + +3. In Figure S3, one cannot clearly see the evolution of Lx on the curves, so some precision would be helpful. + +We have added an explanation of the evolution of \(L_{x}\) (section: S 3, Fig. S 5, page: 6): + +![](images/Figure_unknown_3.jpg) + +
Fig. S 5. Complex eigenfrequencies for varying \(L_{x}\) . a The spectrum of propagating waves dominated by the pipe is marked by the region colored blue. Cavity resonances are highlighted by the region colored red. BIC 1 and BIC 2 are marked by the red crosses. b Evolution over \(L_{x}\) of the interacting modes that form BIC 1 & 2.
+ +4. In section S5, Figures S6 are referred to as Fig. 6 (Fig. 6(a), 6(b) and 6(c)). In Fig. S6, two panels are labeled b instead of b and c. Please correct + +We have changed the labels. + +<--- Page Split ---> + +## Specific Response to Reviewer #3: + +The authors demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by numerical simulations and experiments, and indirectly measure the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry. The specific questions are as follows: + +1. The models in this article are very similar to previous works (such as Phys. Rev. Applied 18, 054021), the innovative of the work should be further explained, and there is no detailed theory analysis in this article. + +To emphasize the novelty, innovation, and scientific impact of our work, we have modified the abstract (section: Abstract, page: 1): + +Bound states in the continuum (BICs) coupling into the propagating spectrum lead to the formation of quasi- BICs (QBICs) with high quality (Q) factor. These high- Q modes typically manifest as Fano resonances in the transmission or reflection spectrum. Fano resonances are highly sensitive, and even a small change in geometric or environmental variables results in a significant change in the transmission spectrum. This presents a challenge in predicting stable Fano peaks for realistic applications. In addition, we do not yet have any information on whether or not a large field enhancement occurs when thermo- viscous losses are taken into account in real acoustic devices. In this work, we demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by theory and experiment. In agreement with theoretical predictions, the appearance of the BIC is characterized by the vanishing line width of the Fano resonance in the measured transmission spectrum. We map the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry, which is the first reported visualization of an acoustic BIC. Mapping the pressure field of the BIC is a new technique for extracting real sound pressure values of high- Q modes. From the pressure values, we accurately infer the confinement of the BIC and thus its transmission or reflection properties. Furthermore, based on our results, we design a new type of symmetry- reduced BIC and analyze its absorption spectrum. Laser Doppler vibrometer (LDV) measurements provide the missing field enhancement data. We achieve a field enhancement by a factor of about three compared to the original cavity. The main findings are that LDV measurements are a powerful tool for predicting the maximum pressure enhancement of high- Q modes, and thus a new technique for obtaining the missing field enhancement data. The presented results facilitate the future applications of BICs in acoustics as high- intensity sound sources, filters, and sensors. + +We have added a more detailed explanation of the innovation and of the importance of our findings (section: Introduction, page: 2): + +We have added a more detailed explanation of the innovation and of the importance of our findings (section: Introduction, page: 2):We further present the first direct visualization of a Friedrich- Wintgen BIC using laser Doppler vibrometry as a pressure field mapping technique. We use laser Doppler vibrometry measurements to obtain a complete mapping of the sound pressure field to better understand BIC formation in the presence of realistic losses. The reflection and transmission spectra are obtained using microphones, but do not provide information about the exact pressure enhancement inside the cavity. The pressure distribution inside the cavity is needed to develop high- performance acoustic devices based on BICs, such as acoustic sources and sound lasers. Because BICs are extremely sensitive, any perturbation of the high- Q mode, energy extraction, or backscattering from microphones will degrade the BIC, so we use this technique to avoid any perturbation of the pressure field. By mapping the sound pressure field of the BIC, we have direct access to the actual pressure values and thus to the critical information of when and where the pressure magnitude reaches a maximum. The interaction between the localized thermo- viscous losses and the concentrated high intensity fields of the BIC is the key to determining the achievable Q- factor and pressure field enhancement. We facilitate the accurate analysis of high- Q modes in the presence of realistic losses, determine the configuration with maximum pressure enhancement, and enable the future application of high- Q Fano resonances to acoustic devices. + +We have added an explanation of the formation mechanism (section: S 1, pages: 1 - 3): + +## Coupled mode theory + +We use coupled mode theory [1,2,3] to predict the location of the BIC. For simplicity, we consider a reduced two- dimensional coupled rectangular waveguide- resonator system shown in Fig. S 1. + +<--- Page Split ---> +![](images/Figure_unknown_4.jpg) + +
Fig. S 1. Schematic drawing of a coupled two-dimensional waveguide-resonator system.
+ +To make the conclusion as general as possible, we set the width of the waveguide \(d = 1\) (unitless), and the width and height of the resonator are \(L_{x}\) and \(L_{y}\) , respectively. Also, the center of the resonator is set as the origin, and the left and right waveguides are attached along the \(x\) - axis. Thus, the waveguide spans from \(y = - 1 / 2\) to \(y = +1 / 2\) . The first step is to compute the eigenfrequencies and eigenmodes of a closed resonator. They eigenfrequencies can be solved analytically with Neumann boundary conditions as follows + +\[\frac{\nu_{m,n}^{2}}{\omega_{0}^{2}} = \left(\frac{(m - 1)}{L_{x}}\right)^{2} + \left(\frac{(n - 1)}{L_{y}}\right)^{2},\quad n,m = 1,2,3,\ldots \quad (2)\] + +where \(\nu_{m,n}\) is the resonant frequency and \(\omega_{0} = \pi c / d\) , \(c\) is the speed of sound in air. We obtain the corresponding modes \(\psi\) by + +\[\psi_{m,n} = \sqrt{\frac{(2 - \delta_{m}^{1})(2 - \delta_{n}^{1})}{L_{x}L_{y}}}\cos \left(\frac{\pi(m - 1)(2x + L_{x})}{2L_{x}}\right)\cos \left(\frac{\pi(n - 1)(2y + L_{y})}{2L_{y}}\right) \quad (3)\] + +with \(\delta_{n}^{1}\) and \(\delta_{m}^{1}\) being the Kronecker delta. The propagating wave numbers in the waveguide are given by + +\[\frac{\nu^{2}}{\omega_{0}^{2}} = \frac{(k_{p}^{2}}{\pi^{2}} +(p - 1)^{2} \quad (4)\] + +with \(k_{p}\) being the wavenumber of the \(p\) th channel of the waveguide. We obtain the corresponding modes \(\phi\) by + +\[\phi_{p} = \sqrt{(2 - \delta_{p}^{1})}\cos \left(\frac{\pi(p - 1)(2y + 1)}{2}\right)e^{ik_{p}x}. \quad (5)\] + +Then the coupling matrix elements between eigenmodes of closed resonator and \(p\) th propagation channels of the left/right waveguide can be obtained by + +\[W_{m,n;p} = \int_{-\frac{1}{2}}^{\frac{1}{2}}\psi_{m,n}(x = -\frac{L_{x}}{2},y)\phi_{p}(x = -\frac{L_{x}}{2},y)dy. \quad (6)\] + +After obtaining the coupling matrix, we compute the complex eigenvalues of the effective Hamiltonian [4,5,6,7], where the real parts correspond to the resonance frequencies and the imaginary parts to the half resonance linewidth. Thus, the search for BICs amounts to finding the zero imaginary part of the eigenvalues. In general, the eigenfunction of any BIC can be decomposed as + +\[\phi_{BIC} = \sum_{m,n}a_{m,n}\psi_{m,n}(x,y). \quad (7)\] + +Since the BIC is perfectly decoupled from the continuum, its eigenfunction must be given by + +\[\int_{-\frac{1}{2}}^{\frac{1}{2}}\phi_{BIC}(x = -\frac{L_{x}}{2},y)dy = 0. \quad (8)\] + +<--- Page Split ---> + +When two resonant states approach each other as a function of a certain continuous parameter, interference causes an avoided crossing of the two states in their energy positions. At the same time, one of the resonance line widths vanishes exactly at a certain value of the parameter and the other one is boosted to maximum. This is known as Friedrich- Wintgen BIC [8]. Typically, a pair of eigenmodes \(M_{mn}\) and \(M_{m + 2,n - 2}\) (or \(M_{mn}\) and \(M_{m - 2,n + 2}\) ) is often used to construct Friedrich- Wintgen BICs. The essence of finding Friedrich- Wintgen BICs is to find two degenerate resonances in a closed resonator with a certain size ratio. + +In the present work, we consider the Friedrich- Wintgen BIC in a rectangular resonator embedded in the first channel \(p = 1\) , provided that other channels are closed for \(\nu < 1\) . There are numerous degeneracies in a closed rectangular resonator + +\[\frac{m^{2}}{L_{x}^{2}} +\frac{n^{2}}{L_{y}^{2}} = \frac{m^{\prime 2}}{L_{x}^{2}} +\frac{n^{\prime 2}}{L_{y}^{2}}. \quad (9)\] + +The lowest case corresponds to \(m,n = 1,3\) and \(m^{\prime},n^{\prime} = 3,1\) for a square resonator \(L_{x} = L_{y}\) + +After the introduction of the left and right waveguides, these two modes \(M_{13}\) and \(M_{31}\) are strongly coupled to each other, giving rise to an increase in the destructive interference at a given size ratio. Thus, the resonance frequencies of two modes experience avoided crossing. At the same time, one of the imaginary parts is suppressed to zero while the other is boosted to maximum. Therefore, the formation of such a BIC can be mainly attributed to the destructive interference of modes \(M_{13}\) and \(M_{31}\) in a closed resonator. We can approximate the eigenfunction of this Friedrich- Wintgen BIC as a superposition of the two eigenmodes of the closed resonator, and its coefficients \(A\) and \(B\) can be rigorously calculated by + +\[\psi_{BIC}(x,y)\approx A\psi_{31}(x,y) + B\psi_{13}(x,y). \quad (10)\] + +Substituting Eq. (10) in Eq. (8) gives us + +\[A = -W_{1,3;p = 1} = -\frac{1}{2\pi}\sqrt{\frac{2L_{y}}{L_{x}}}\left[\sin \left(\frac{\pi(L_{y} + 1)}{L_{y}}\right) - \sin \left(\frac{\pi(L_{y} - 1)}{L_{y}}\right)\right], \quad (11)\] + +\[B = W_{3,1;p = 1} = \sqrt{\frac{2}{L_{x}L_{y}}}. \quad (12)\] + +We can rewrite Eq. (10) as + +\[\psi_{BIC}(x,y)\approx \cos \theta \psi_{31}(x,y) + \sin \theta \psi_{13}(x,y), \quad (13)\] + +\[\cos \theta = \frac{A}{\sqrt{A^{2} + B^{2}}},\quad \sin \theta = \frac{B}{\sqrt{A^{2} + B^{2}}} \quad (14)\] + +Excellent agreement is found between the eigenfield profile predicted from Eqs.(8- 9) and the numerically calculated eigenfield profile of Friedrich- Wintgen BIC, see Fig. S 2. + +![PLACEHOLDER_20_0] + +
Fig. S 2. Eigenfield profile. Decomposition of Friedrich-Wintgen BIC into eigenmodes \(M_{31}\) and \(M_{13}\) .
+ +2. As far as I know, it is not the first time to indirectly measure the acoustic pressure in air by the laser Doppler vibrometry. On the other hand, for the model size in this article, it is possible to directly measure the pressure field by such as \(1 / 4\) microphone. + +We have incorporated the answer to this question into the answer to your first question. Microphones would not work properly because we are perturbing the high- Q mode, and any energy extraction or backscattering will degrade the QBIC. + +<--- Page Split ---> + +3. Could authors explain further the black dotted line in the Fig.1(b)(c)? How do authors calculate them through the coupled mode theory? + +Please see the answer to your first comment for a complete theory analysis. + +4. Does the technique involved in this article using laser Doppler vibrometry require the structural size of the sample? When it comes to practicality, does this technique work on smaller structures? + +We have added an explanation of the physical principle of the LDV (section: Results, Visualization of QBIC, page: 4): + +To conduct the refracto- vibrometry, a laser Doppler scanning vibrometer PSV- 500 from Polytec \(^{1}\) is used to measure the changes of the refractive index of the fluid, which is proportional to the acoustic pressure variation within the cavity [43- 46]: + +\[v(\omega) = \omega \frac{1}{\gamma p_{0}} \frac{n_{0} - 1}{n_{0}} \int_{L} p(l, \omega) \mathrm{d}l \quad (15)\] + +where \(\omega\) is the angular frequency, \(v\) is the LDV velocity, \(p\) is the sound pressure, \(n_{0}\) is the refractive index of air at standard atmospheric pressure, \(p_{0}\) is the static atmospheric pressure, and \(\gamma\) is the specific heat capacity ratio of air. The basic principle of the LDV is based on the well- known Doppler shift. The pressure waves inside the cavity slightly shift the phase of the emitted monochromatic laser light. The superimposition of the reflected and emitted laser light produces a speckle pattern on the photodetector, which allows the measurement of the corresponding frequency of the pressure waves and the change in the refractive index. The latter is proportional to the sound pressure inside the cavity. This makes it possible to visualize the corresponding pressure distribution. + +We have also added a more detailed explanation of the visualization and its limits (section: Methods, pages: 9 and 10): + +Visualization. We use refracto- vibrometry to visualize the sound pressure field inside the cavity. A laser Doppler scanning vibrometer PSV- 500 from Polytec is used to measure the changes in the refraction index of the fluid, which is proportional to the acoustic pressure variation within the cavity. Overall, 225 measurement points were sequentially recorded with a sampling frequency of \(50\mathrm{kHz}\) for a duration of \(2\mathrm{ms}\) , while the measurements were triggered by the sinusoidal sound generator. To ensure an optimal signal- to- noise ratio, a highly reflective sheet was placed against the rigid surface behind the sample to improve diffuse light reflection. Note that usually a LDV is used for surface normal vibration measurements of structures but captures the pressure wave- induced variation in the refraction index when measured against a rigid surface. In the case of a low- vibration surface, the velocity measurement from the LDV is dominated by the dynamic phase, caused by the sound pressure fluctuations, and the changed refractive index of the acoustic medium, along the traveling path of the light. To ensure the required rigidity, a single point LDV (Polytec PDV- 100) measured the surface vibration of the rigid surface from the opposite direction. The surface velocities were found to be orders of magnitude smaller than the signal of the scanning PSV500, confirming that the acoustic pressure dominates the measured results. As the LDV works up to frequencies of \(1\mathrm{MHz}\) , the frequency range is not a limiting factor for pressure field mapping. The size of the structure can be much smaller than those presented in this article and is only limited by the focal point of the laser ( \(25\mu \mathrm{m}\) ). We use such large structures here because we need to measure the transmission/reflection spectra using an impedance tube with a diameter of \(40\mathrm{mm}\) . Since the Helmholtz equation is linearly scalable, our results can be transferred to different frequency ranges. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +After a thorough examination of the authors' response, I have found that the current version exhibits higher quality. Consequently, I recommend accepting it in its current form. + +Reviewer #2: + +Remarks to the Author: + +The authors have carefully taken account of the comments and added several improvements to the manuscript. So, I would recommend the acceptance of the paper for publication + +Reviewer #3: + +Remarks to the Author: + +The authors have revised the paper as required. + +<--- Page Split ---> diff --git a/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..e641dcee4de8b8f893e42ef10e339c9cc0cc64a0 --- /dev/null +++ b/peer_reviews/df2635e404542ed48d980fc9d2fbf5f1448ec436b3e8498304871a351db78c64/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,554 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 110, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 154, 836, 211]]<|/det|> +Realistic prediction and engineering of high- Q modes to implement stable Fano resonances in acoustic devices + +<|ref|>image<|/ref|><|det|>[[57, 732, 240, 781]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 785]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 85, 293, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 112, 223, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 140, 875, 237]]<|/det|> +The authors theoretically investigated and experimentally demonstrated the existence of FW- BICs by measuring the transmission spectrum. By scanning the size ratio of rectangular resonators, BIC is converted into QBIC, which is usually manifested by the Fano resonance in the transmission spectrum. Besides the transmission spectrum, the authors image the pressure field distribution of QBICs based on FW- BICs by using laser Doppler vibrometry, proving the direct evidence of the existence of FW- BICs. Although this work presents some interesting results, some concerns must be addressed + +<|ref|>text<|/ref|><|det|>[[118, 238, 878, 378]]<|/det|> +(1) The biggest selling point lies in directly imaging the QBICs based on FW-BIC. In Fig.4, indeed, the measured pressure distribution of QBICs matches very well with the simulated one. Due to the thermal-viscous loss, the pressure field enhancement is not as high as the simulated one if the lossless system is considered. Therefore, to further push the applications of QBICs, real intensities instead of normalized intensities of the pressure field of QBICs shall be presented because the maximum pressure field plays a central role in governing acoustic-matter interactions, such as acoustic emissions. Therefore, I may suggest authors provide more data with the real intensities of the pressure field at different size ratios to demonstrate that the pressure field enhancement reaches the maximum when the size ratio is close to the critical value forming FW-BICs. With real information on pressure intensity, it may provide useful guidance for designing acoustic sources. + +<|ref|>text<|/ref|><|det|>[[118, 392, 863, 462]]<|/det|> +(2) In Fig.2c-d, a good agreement can be found between measurement and simulation. It is well known that in real systems, there are thermo-viscous losses that may influence the transmission significantly. Do authors consider the thermo-viscous losses in the simulation to match the experiments? If yes, they need to provide more details on how thermo-viscous losses affect the simulated transmission. + +<|ref|>text<|/ref|><|det|>[[118, 476, 867, 518]]<|/det|> +(3) Since the authors show the pressure imaging of FW-BICs in Fig.4, I may suggest the authors also do the same thing on the BICs formed in structures of Fig.5d. By doing this, the authors may know which structure gives the best pressure confinement of QBICs. + +<|ref|>text<|/ref|><|det|>[[118, 532, 850, 560]]<|/det|> +(4) In Fig.2c, Fig.4e-f, Fig.4h-i, what does it mean for y-axis, T[-], R[-], alpha[-]? Usually, the unit is included in the bracket. + +<|ref|>text<|/ref|><|det|>[[118, 603, 223, 615]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 617, 300, 630]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 630, 877, 771]]<|/det|> +The authors demonstrate theoretically and experimentally the existence of Friedrich- Wintgen (FW) type bound in continuum states (BICs) in an open acoustic cavity. The BIC is revealed in the transmission coefficient under the shape of a Fano resonance (quasi- BIC) whose linewidth vanishes when approaching the geometrical parameters of the cavity satisfying the BIC condition. They show the best conditions to observe the QBIC in presence of thermoviscous losses. Moreover, by using a laser Doppler vibrometry (LDV) technique, they are able to reveal for the first time the map of the pressure field associated with the BIC inside the cavity. Finally, they present the design of new type high- quality BIC relying on reduced symmetry and avoiding the excitation of unwanted resonances in the cavity. The agreement between theory and experiment is very accurate throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 785, 872, 911]]<|/det|> +The paper is generally well presented and contains some interesting and new results. It is timely because of the continuing interest in BICs and their applications based on the high sensitivity of the resulting Fano resonances to the environment. However, the cavity designed in this paper and the associated BICs and their analysis have some similarities with those presented in recent papers. The main novelty of this manuscript is the observation of the BIC pressure field inside the cavity by using LDV. This is an interesting proposal that deserves to be published. But from the point of view of physical originality or attraction for a broad audience, the paper would probably not reach the level required for acceptance in Nature Communications. Perhaps, another of the Nature journals would be more appropriate. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 98, 642, 112]]<|/det|> +A few minor remarks are mentioned for the attention of the authors. + +<|ref|>text<|/ref|><|det|>[[118, 112, 850, 140]]<|/det|> +- A short explanation about FW BIC can be useful, as well as on the physical principle of LDV. +- In page 5, the sentence "a reduction of a factor of \(k = 3.41\) between the inlet and the outlet sound pressure amplitudes was noticed" needs a better explanation. + +<|ref|>text<|/ref|><|det|>[[118, 141, 860, 168]]<|/det|> +- In Figure S3, one cannot clearly see the evolution of Lx on the curves, so some precision would be helpful. + +<|ref|>text<|/ref|><|det|>[[118, 180, 835, 208]]<|/det|> +- In section S5, Figures S6 are referred to as Fig. 6 (Fig. 6(a), 6(b) and 6(c)). In Fig. S6, two panels are labeled b instead of b and c. Please correct + +<|ref|>text<|/ref|><|det|>[[118, 252, 222, 264]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[118, 267, 300, 279]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 280, 855, 320]]<|/det|> +The authors demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by numerical simulations and experiments, and indirectly measure the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry. The specific questions are as follows: + +<|ref|>text<|/ref|><|det|>[[118, 312, 500, 325]]<|/det|> +vibrometry. The specific questions are as follows: + +<|ref|>text<|/ref|><|det|>[[118, 335, 860, 376]]<|/det|> +(1) The models in this article are very similar to previous works (such as Phys. Rev. Applied 18, 054021), the innovative of the work should be further explained, and there is no detailed theory analysis in this article. + +<|ref|>text<|/ref|><|det|>[[118, 377, 875, 418]]<|/det|> +(2) As far as I know, it is not the first time to indirectly measure the acoustic pressure in air by the laser Doppler vibrometry. On the other hand, for the model size in this article, it is possible to directly measure the pressure field by such as \(1 / 4''\) microphone. + +<|ref|>text<|/ref|><|det|>[[118, 418, 875, 445]]<|/det|> +(3) Could authors explain further the black dotted line in the Fig.1(b)(c)? How do authors calculate them through the coupled mode theory? + +<|ref|>text<|/ref|><|det|>[[118, 446, 875, 474]]<|/det|> +(4) Does the technique involved in this article using laser Doppler vibrometry require the structural size of the sample? When it comes to practicality, does this technique work on smaller structures? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 62, 415, 81]]<|/det|> +## Response to the Reviewers + +<|ref|>text<|/ref|><|det|>[[93, 92, 163, 106]]<|/det|> +Journal: + +<|ref|>text<|/ref|><|det|>[[93, 120, 273, 135]]<|/det|> +Nature Communications + +<|ref|>text<|/ref|><|det|>[[93, 149, 232, 163]]<|/det|> +Manuscript No.: + +<|ref|>text<|/ref|><|det|>[[93, 177, 270, 191]]<|/det|> +NCOMMS- 22- 48526A- Z + +<|ref|>text<|/ref|><|det|>[[93, 205, 140, 219]]<|/det|> +Title: + +<|ref|>text<|/ref|><|det|>[[92, 233, 904, 262]]<|/det|> +Realistic prediction and engineering of high- Q modes to implement stable Fano resonances in acoustic devices + +<|ref|>sub_title<|/ref|><|det|>[[93, 277, 168, 291]]<|/det|> +## Authors: + +<|ref|>text<|/ref|><|det|>[[92, 304, 904, 334]]<|/det|> +Felix Kronowetter, Marcus Maeder, Yan Kei Chiang, Lujun Huang, Johannes Schmid, Sebastian Oberst, David A. Powell, and Steffen Marburg + +<|ref|>sub_title<|/ref|><|det|>[[93, 364, 266, 380]]<|/det|> +## General Remarks + +<|ref|>text<|/ref|><|det|>[[93, 389, 212, 402]]<|/det|> +Dear Reviewers: + +<|ref|>text<|/ref|><|det|>[[92, 416, 905, 558]]<|/det|> +We would like to express our appreciation for the efforts made by the reviewers to improve our paper. The comments are very constructive and helpful in improving the quality and presentation of the paper. We have done a substantial amount of work to incorporate the suggestions and address the concerns raised by the reviewers. In response to reviewer #1's request, we have performed extensive numerical simulations and put considerable effort into fabricating new samples and performing additional experiments. In response to the requests of reviewers #2 and #3, we have added more data and more detailed explanations to the manuscript to highlight the novelty, innovation, and scientific impact of our work. We have added a complete theoretical model in response to reviewer #3. We have incorporated the suggestions and addressed the concerns raised by the reviewers. Red- colored text indicates changes made to the manuscript, while blue- colored text highlights the authors' responses. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 65, 439, 82]]<|/det|> +## Specific Response to Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[92, 88, 905, 175]]<|/det|> +The authors theoretically investigated and experimentally demonstrated the existence of FW- BICs by measuring the transmission spectrum. By scanning the size ratio of rectangular resonators, BIC is converted into QBIC, which is usually manifested by the Fano resonance in the transmission spectrum. Besides the transmission spectrum, the authors image the pressure field distribution of QBICs based on FW- BICs by using laser Doppler vibrometry, proving the direct evidence of the existence of FW- BICs. Although this work presents some interesting results, some concerns must be addressed. + +<|ref|>text<|/ref|><|det|>[[92, 187, 904, 216]]<|/det|> +Thank you for your feedback and helpful comments. We have tried to incorporate all of them to a satisfactory level. + +<|ref|>text<|/ref|><|det|>[[113, 225, 905, 368]]<|/det|> +1. The biggest selling point lies in directly imaging the QBICs based on FW-BIC. In Fig. 4, indeed, the measured pressure distribution of QBICs matches very well with the simulated one. Due to the thermal-viscous loss, the pressure field enhancement is not as high as the simulated one if the lossless system is considered. Therefore, to further push the applications of QBICs, real intensities instead of normalized intensities of the pressure field of QBICs shall be presented because the maximum pressure field plays a central role in governing acoustic-matter interactions, such as acoustic emissions. Therefore, I may suggest authors provide more data with the real intensities of the pressure field at different size ratios to demonstrate that the pressure field enhancement reaches the maximum when the size ratio is close to the critical value forming FW-BICs. With real information on pressure intensity, it may provide useful guidance for designing acoustic sources. + +<|ref|>text<|/ref|><|det|>[[133, 380, 904, 410]]<|/det|> +We have changed Fig. 4 and the corresponding text to show the actual pressure values. We use absolute pressure from here on to be independent of the phase (section: Results, Fig. 4, pages: 6 and 7): + +<|ref|>text<|/ref|><|det|>[[133, 428, 905, 585]]<|/det|> +The visualized sound pressure field of the QBIC within the experimental set- up is presented in Fig. 4a. In addition, we show a mapping of the absolute values of the pure measurement data in Fig. 4b for better comparison with the numerical data displayed in Fig. 4e. We observe that the measurement is in good agreement with the numerical prediction. As expected, the pressure maxima are located at both the edges and the center of the cavity. Minor inaccuracies within the numerical prediction are due to real losses and uncertainties within the experiments, i.e. imprecise alignment of the parts or imperfect plane wave excitation. We note only a slight pressure fluctuation in the center, just below the marked node in Fig. 4a. The position of the LDV for this measurement point is normal incidence to the glass. This results in a lower signal- to- noise ratio, which leads to higher measurement errors. We obtain a stable image of the QBIC that is in good agreement with the simulated sound pressure field. Thus, we present the visual evidence of a QBIC. + +<|ref|>text<|/ref|><|det|>[[133, 589, 905, 732]]<|/det|> +In addition, we have added plots of the maximum pressure inside the cavity versus cavity length and frequency for all configurations presented in the manuscript to see where the real maximum field enhancement occurs. We have also measured the cavity with \(L_{x} = 170 \mathrm{mm}\) excited at several frequencies to observe the evolution of the modal field and to determine the frequency with the highest pressure enhancement. We have also provided additional data with different size ratios of the fully reduced cavity, shown in Fig. 5c, to demonstrate the parameter configuration where the pressure field enhancement reaches its maximum. We have chosen this configuration to experimentally determine where the maximum pressure enhancement occurs. The results for the configuration with the highest pressure enhancement are presented in the manuscript as they provide seminal insights for the design of QBICs (section: Results, Pressure Enhancement, Fig. 5, pages: 6 - 8): + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[90, 70, 900, 488]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 502, 905, 590]]<|/det|> +
Fig. 4. Sound pressure field visualization. a Visualization of the real part of the sound pressure field inside the cavity. The red color indicates a pressure maximum and the blue color a minimum, respectively. b Absolute value of the measured pressure field. c Superposition of the four most dominant modes (modes with the highest FFT coefficients). d Superposition of the next four modes with high coefficients. e Simulation results. The colored scales display the absolute values of the pressure in Pa, with the pressure being normalized to the incident pressure field.
+ +<|ref|>text<|/ref|><|det|>[[133, 612, 905, 870]]<|/det|> +Figs. 5a to 5c show three schematics of the previously studied resonant cavities reduced in size by applying the principle of mirror sources. We cut the geometry in half at a particular axis of symmetry (marked by the red lines in the schematics mentioned above). The axis of symmetry has to be chosen with care since the BIC mode needs to be sustained and all anti- symmetric modes with respect to this axis need to be suppressed. Fig. 5c depicts the schematic of the fully reduced geometry. We manufacture three additional samples for impedance tube measurements, shown in Fig. 5d. Fig. 5e shows the numerically obtained absorption coefficients of the configurations in Figs. 5a to 5c with \(L_{x} = 85 \mathrm{mm}\) and also of the BIC configuration in Fig. 5c determined at \(L_{x} = 77 \mathrm{mm}\) . The more we reduce the geometry, the more unwanted modes are removed. Accordingly, we observe a clear peak in the absorption spectrum. We perform impedance tube measurements to validate our observations. The measured absorption coefficients are presented in Fig. 5f for the fully reduced configuration, see Fig. 5c, and in Fig. 5g for the configuration shown in Fig. 5b. The measurement results agree with our prediction. We observe the collapse of the Fano resonance (yellow and dashed purple lines in Fig 5f), the sharp peak of the Fano resonance with no further absorption in the spectrum shown (blue and dashed red lines), and thus prove the existence of a Friedrich- Wintgen BIC based on the concept of fully reduced symmetry without exciting unwanted modes. Fig. 5h shows the unexcited QBIC mode for a rectangular cavity with \(L_{x} = 170 \mathrm{mm}\) . The sound pressure field of the fully reduced geometry framed by the black lines is depicted in Fig. 5i. For comparison, we extrapolate the reduced sound pressure field onto the rectangular cavity. We infer from comparing Fig. 5h + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[90, 67, 900, 497]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 537, 905, 809]]<|/det|> +
Fig. 5. Experimental verification of symmetry-reduced BICs. a Schematic of a resonant cavity similar to that shown in Fig. S 1. The \(z\) -axis is perpendicular to the \(xy\) -plane. The length \(L_{y}\) is set to \(160\mathrm{mm}\) and the diameter \(d\) of the pipe to \(40\mathrm{mm}\) . We halve the cavity at the axis of symmetry (highlighted in red) based on the principle of mirror sources and thus obtain a cavity length of \(L_{x} = 85\mathrm{mm}\) , which corresponds to half the length of the configuration with \(L_{x} = 170\mathrm{mm}\) . b Further reduction of the configuration in a using the principle of mirror sources once again. c Fully reduced configuration. d Manufactured samples for configurations b ( \(L_{x} = 85\mathrm{mm}\) ) and c ( \(L_{x} = 85\mathrm{mm}\) for the top sample and \(L_{x} = 77\mathrm{mm}\) for the bottom sample). e Absorption coefficient \(\alpha\) in the frequency range \(1900 - 2250\mathrm{Hz}\) . The blue line represents the result of the numerical simulation of the BIC configuration of c with \(L_{x} = 77\mathrm{mm}\) . The orange dotted line, the yellow dash-dotted line and the purple dashed line represent the numerical results of \(L_{x} = 85\mathrm{mm}\) for the configurations a,b, and c, respectively. f Absorption coefficient \(\alpha\) in the frequency range \(1900 - 2250\mathrm{Hz}\) . The blue and the yellow lines represent the results of the numerical simulation of the BIC configuration of c with \(L_{x} = 85\mathrm{mm}\) and \(L_{x} = 77\mathrm{mm}\) , respectively. The orange and the purple dashed lines represent the measurement results of configuration c with \(L_{x} = 85\mathrm{mm}\) and \(L_{x} = 77\mathrm{mm}\) . g The computed and measured absorption coefficients for configuration b are represented by the blue and orange dashed lines, respectively. h Sound pressure field of the BIC mode inside the cavity with \(L_{x} = 170\mathrm{mm}\) . i Sound pressure field of the BIC mode inside the fully reduced cavity with \(L_{x} = 85\mathrm{mm}\) for configuration c, framed by the black lines and extrapolated to the rectangular cavity. j Measured absolute sound pressure inside the fully reduced cavity with \(L_{x} = 67\mathrm{mm}\) excited at \(2315\mathrm{Hz}\) . The color scale represents the absolute pressure in Pa.
+ +<|ref|>text<|/ref|><|det|>[[133, 833, 904, 877]]<|/det|> +to Fig. 5i that identical sound pressure distributions are obtained. Finally, we manage to preserve the BIC mode although the geometry is reduced significantly and thus present a new type of fully reduced high- Q mode without exciting unwanted modes. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 79, 905, 250]]<|/det|> +Pressure enhancement. Impedance tube studies allow us to extract values for reflection spectra and absorption, but not for cavity pressure enhancement. The missing cavity pressure information is provided by the LDV. The numerical and experimental procedure to determine the maximum pressure is presented in detail in Supplementary Information Section 6. Fig. 5j shows the measured absolute pressure field inside the fully reduced cavity with \(L_{x} = 67\mathrm{mm}\) excited at \(2315\mathrm{Hz}\) . This configuration leads to the maximum pressure enhancement possible for this structure with a measured peak value of \(36.74\mathrm{Pa}\) . We additionally measure the sound pressure fields of the fully reduced cavity with \(L_{x} = 64\mathrm{mm}\) and \(L_{x} = 70\mathrm{mm}\) to prove the existence of a pressure peak. The measurements show peak pressures of \(26.08\mathrm{Pa}\) and \(32.26\mathrm{Pa}\) , respectively. To demonstrate the magnitude of the pressure enhancement, we measure the pressure field inside the full cavity with \(L_{x} = 170\mathrm{mm}\) for several frequencies. The maximum pressure is \(12.61\mathrm{Pa}\) . Thus, the fully reduced cavity leads to the highest pressure enhancement of the investigated Friedrich- Wintgen BIC by a factor of about three compared to the full cavity. + +<|ref|>text<|/ref|><|det|>[[133, 253, 905, 341]]<|/det|> +Finally, we extract the sound pressure field of a QBIC mode. The sound pressure field inside the cavity gives us accurate information about the influence of losses and hence the stability and confinement of the mode. We also show that LDV measurements are a powerful tool for predicting the maximum pressure enhancement of high- Q modes, can resolve even small deviations from numerical predictions, and thus provide seminal guidance for the application of QBICs. Thus, we present the realistic sound pressure field of a stable high- Q mode, enabling further analysis and its application to acoustic devices. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[135, 66, 653, 81]]<|/det|> +All other results are shown in Supplementary Information Section S 6: + +<|ref|>sub_title<|/ref|><|det|>[[135, 95, 325, 109]]<|/det|> +## Pressure enhancement + +<|ref|>text<|/ref|><|det|>[[134, 123, 905, 168]]<|/det|> +The configuration with the highest pressure field enhancement is determined by parameter studies. Therefore, we vary the cavity lengths of the configurations depicted in Fig. 1a, Fig. 5a and Fig. 5b. The corresponding plots are shown in Fig. S 11. + +<|ref|>image<|/ref|><|det|>[[118, 183, 900, 555]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 570, 905, 644]]<|/det|> +
Fig. S 11. Simulated pressure mappings. a Maximum absolute sound pressure inside the rectangular cavity shown in Fig. 1a. The cavity length is varied from \(L_{x} = 145 - 185\mathrm{mm}\) in \(1\mathrm{mm}\) and \(1\mathrm{Hz}\) steps in the frequency range \(1900 - 2250\mathrm{Hz}\) . b Maximum absolute sound pressure inside the reduced cavity presented in Fig. 5a with cavity length \(L_{x} = 67.5 - 92.5\mathrm{mm}\) in the same frequency range. c Maximum absolute sound pressure inside the further reduced cavity (Fig. 5b). The white crosses indicate the maxima.
+ +<|ref|>text<|/ref|><|det|>[[134, 662, 905, 750]]<|/det|> +Pressure enhancement can be observed in certain regions around the BIC configurations. We can also see that the maximum pressure enhancement does not occur directly adjacent to the BIC as it would without losses, i.e., see Fig. S 8. Thermo- viscous losses shift the maximum enhancement away from the BIC configuration. The pressure peaks are \(5.50\mathrm{Pa}\) , \(9.54\mathrm{Pa}\) , and \(12.89\mathrm{Pa}\) . It can be said that the more the geometry is reduced and thus the antisymmetric modes are suppressed, the higher the pressure enhancement. The visualized pressure fields for the full cavity are shown in Fig. S 12. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[95, 68, 900, 760]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 772, 905, 817]]<|/det|> +
Fig. S 12. Visualized pressure fields of the full cavity. a - f Absolute sound pressure inside the rectangular cavity shown in Fig. 1a. with \(L_{x} = 170 \mathrm{mm}\) excited at 2070 Hz, 2075 Hz, 2077 Hz, 2079 Hz, 2081 Hz, and 2094 Hz, respectively. All color scales represent the absolute pressure in Pa.
+ +<|ref|>text<|/ref|><|det|>[[134, 839, 905, 882]]<|/det|> +The corresponding maximum pressure values in Figs. S 12a to 12f are 12.04 Pa, 12.61 Pa, 12.44 Pa, 12.02 Pa, 11.32 Pa, and 8.59 Pa, respectively. Therefore, we can say that the maximum pressure enhancement occurs at 2075 Hz. The evolution of the modal field is also demonstrated. The dark blue line + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 66, 904, 95]]<|/det|> +representing the pressure nodes extends in the \(y\) - direction, the more the configuration deviates from the BIC configuration. + +<|ref|>text<|/ref|><|det|>[[133, 99, 905, 158]]<|/det|> +We numerically determine the configuration with the highest pressure gain by plotting the maximum absolute sound pressure inside the cavity as the cavity length is varied in the 1900 - 2400 Hz frequency range and excited by a plane wave of 1 Pa. This is shown in Fig. S 13 for the fully reduced cavity presented in Fig. 5c. + +<|ref|>image<|/ref|><|det|>[[92, 173, 898, 550]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 564, 905, 637]]<|/det|> +
Fig. S 13. Simulated pressure mappings. a,b Maximum absolute sound pressure and absorption inside the cavity shown in Fig. 5c. The cavity length is varied from \(L_{x} = 67.5 - 92.5\mathrm{mm}\) in \(1\mathrm{mm}\) and \(1\mathrm{Hz}\) steps in the frequency range 1900 - 2400 Hz. c,d Maximum absolute sound pressure and absorption at finer resolution. The cavity length is varied from \(L_{x} = 66 - 68\mathrm{mm}\) in \(0.1\mathrm{mm}\) and \(0.1\mathrm{Hz}\) steps in the frequency range 2290 - 2330 Hz. The white crosses indicate the maxima.
+ +<|ref|>text<|/ref|><|det|>[[134, 651, 905, 738]]<|/det|> +The BIC is visible as the dark blue dot in the center of the red lines in Figs. S 13a to 13b. Pressure enhancement can be observed in certain regions around the BIC configurations. The smaller the cavity length, the higher the frequency of the enhancement and vice versa. It can be seen that the maximum pressure enhancement and absorption occurs at a cavity length of \(L_{x} = 67\mathrm{mm}\) . We fabricate three additional samples of the fully reduced cavity ( \(L_{x} = 64\) , 67, and \(70\mathrm{mm}\) ) to experimentally validate our numerical predictions, see Fig. S 14. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[303, 65, 692, 280]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[90, 290, 904, 321]]<|/det|> +
Fig. S 14. LDV samples. Printed samples of the fully reduced cavity with high-transmission glass mounted as side panels.
+ +<|ref|>text<|/ref|><|det|>[[134, 342, 905, 400]]<|/det|> +We then measure the sound pressure field inside the cavity for several frequencies to determine the configuration (frequency and cavity length) where the maximum absolute sound pressure is found. The visualized pressure fields for the fully reduced cavity with \(L_{x} = 64\mathrm{mm}\) , \(L_{x} = 67\mathrm{mm}\) , and \(L_{x} = 70\mathrm{mm}\) are shown in Fig. S 15. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[90, 68, 900, 644]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[92, 653, 905, 712]]<|/det|> +
Fig. S 15. Visualized pressure fields of the fully reduced cavity. a - c Absolute sound pressure inside the fully reduced cavity shown in Fig. 5c with \(L_{x} = 64\mathrm{mm}\) excited at \(2335\mathrm{Hz}\) , \(2345\mathrm{Hz}\) , and \(2353\mathrm{Hz}\) . g - i Absolute sound pressure inside the fully reduced cavity with \(L_{x} = 70\mathrm{mm}\) excited at \(2267\mathrm{Hz}\) , \(2272\mathrm{Hz}\) , and \(2277\mathrm{Hz}\) . All color scales represent the absolute pressure in Pa.
+ +<|ref|>text<|/ref|><|det|>[[134, 733, 905, 820]]<|/det|> +The data are not normalized to the incident pressure field, but the actual pressure values are shown. The corresponding maximum pressure values in Figs. S 15a to 15i are \(25.61\mathrm{Pa}\) , \(26.07\mathrm{Pa}\) , \(24.80\mathrm{Pa}\) , \(36.11\mathrm{Pa}\) , \(36.74\mathrm{Pa}\) , \(33.98\mathrm{Pa}\) , \(31.83\mathrm{Pa}\) , \(32.26\mathrm{Pa}\) , and \(28.12\mathrm{Pa}\) , respectively. Therefore, we can say that the maximum pressure enhancement for the cavity with \(L_{x} = 64\mathrm{mm}\) occurs at \(2345\mathrm{Hz}\) and for the cavity with \(L_{x} = 70\mathrm{mm}\) at \(2272\mathrm{Hz}\) . The maximum pressure enhancement occurs at \(L_{x} = 67\mathrm{mm}\) at \(2315\mathrm{Hz}\) and reaches \(36.74\mathrm{Pa}\) . This is similar to the results shown in Fig. S 13c. + +<|ref|>text<|/ref|><|det|>[[134, 824, 905, 881]]<|/det|> +We compare this maximum pressure value to the sound pressure fields of the fully reduced cavity with \(L_{x} = 64\mathrm{mm}\) and \(L_{x} = 70\mathrm{mm}\) to prove the existence of a pressure peak. The measurements show peak pressures of \(26.07\mathrm{and}32.26\mathrm{Pa}\) , respectively. To demonstrate the magnitude of the pressure enhancement, we also compare it to the pressure field inside the full cavity with \(L_{x} = 170\mathrm{mm}\) for several frequencies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[130, 66, 904, 96]]<|/det|> +The maximum pressure of the full cavity is 12.61 Pa. Thus, the fully reduced cavity leads to the highest pressure enhancement of the investigated Friedrich- Wintgen BIC by a factor of about three. + +<|ref|>text<|/ref|><|det|>[[113, 104, 905, 162]]<|/det|> +2. In Fig.2c-d, a good agreement can be found between measurement and simulation. It is well known that in real systems, there are thermo-viscous losses that may influence the transmission significantly. Do authors consider the thermo-viscous losses in the simulation to match the experiments? If yes, they need to provide more details on how thermo-viscous losses affect the simulated transmission. + +<|ref|>text<|/ref|><|det|>[[133, 175, 904, 219]]<|/det|> +We have included thermo-viscous losses in our simulations. To address the effect of losses on the transmission and reflection spectra, we have added a more detailed explanation in section S 4 in the Supplementary Information (section: S 4, pages: 7 and 8): + +<|ref|>text<|/ref|><|det|>[[130, 232, 904, 261]]<|/det|> +The effect of thermo- viscous losses on the Fano peaks in the transmission spectra is shown in Fig. S 7. + +<|ref|>image<|/ref|><|det|>[[95, 277, 868, 499]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[92, 514, 905, 587]]<|/det|> +
Fig. S 7. Transmission spectra with and without losses. a Transmission coefficient in the 1900 - 2250 Hz frequency range. The solid blue and dashed yellow lines represent the results of \(L_{x} = 165\mathrm{mm}\) with and without thermo-viscous losses, respectively. The results of \(L_{x} = 170\mathrm{mm}\) are shown by the red and purple lines. b Transmission loss of \(L_{x} = 165\mathrm{mm}\) and \(L_{x} = 170\mathrm{mm}\) with and without losses. The coloring of the lines is identical to Fig. S 7a.
+ +<|ref|>text<|/ref|><|det|>[[133, 608, 905, 725]]<|/det|> +Thermo- viscous losses significantly reduce the transmission coefficient due to increased absorption. Nevertheless, the transmission goes to zero at the frequency of the QBIC, see Fig. S 7a. The maxima of the Fano peaks in the TL also decrease including the losses. We observe a reduction from \(\approx 42\mathrm{dB}\) to \(\approx 17\mathrm{dB}\) \((L_{x} = 165\mathrm{mm})\) and from \(\approx 43\mathrm{dB}\) to \(\approx 24\mathrm{dB}\) \((L_{x} = 170\mathrm{mm})\) . The losses have a more significant effect on the amplitude of the Fano peak of the TL the closer we are to the BIC configuration. In addition, due to thermo- viscous losses, the Fano peaks are shifted to lower frequencies by about \(2\mathrm{Hz}\) . To illustrate the effect of losses on pressure field enhancement, the maximum absolute sound pressure is plotted against cavity length and frequency in Fig. S 8. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[286, 65, 716, 267]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 280, 905, 323]]<|/det|> +
Fig. S 8. Pressure mapping (without losses). Maximum absolute sound pressure inside the rectangular cavity shown in Fig. 1a. The cavity length is varied from \(L_{x} = 157 - 163 \mathrm{mm}\) in \(0.1 \mathrm{Hz}\) steps in the frequency range \(2135 - 2160 \mathrm{Hz}\) .
+ +<|ref|>text<|/ref|><|det|>[[130, 346, 904, 375]]<|/det|> +We observe amplified sound pressure up to \(160 \mathrm{dB}\) when excited at \(1 \mathrm{Pa}\) and narrow Fano peaks near the BIC. Figs. S 6 to S 8 illustrate the importance of considering thermo- viscous losses in our simulations. + +<|ref|>text<|/ref|><|det|>[[113, 383, 905, 427]]<|/det|> +3. Since the authors show the pressure imaging of FW-BICs in Fig.4, I may suggest the authors also do the same thing on the BICs formed in structures of Fig.5d. By doing this, the authors may know which structure gives the best pressure confinement of QBICs. + +<|ref|>text<|/ref|><|det|>[[132, 440, 905, 526]]<|/det|> +We have manufactured three additional configurations of the fully reduced cavity, shown in Fig. 5c, and have visualized the pressure fields. We have chosen this configuration to experimentally determine where the maximum pressure enhancement occurs. The results of the configuration with the highest pressure enhancement are presented in the manuscript as they provide seminal insights for the design of QBICs, while the results for the other configurations appear in Supporting Information S 6. See the answer to your first point for more details. + +<|ref|>text<|/ref|><|det|>[[112, 535, 904, 564]]<|/det|> +4. In Fig.2c, Fig.4e-f, Fig.4h-i, what does it mean for y-axis, T[-], R[-], alpha[-]? Usually, the unit is included in the bracket. + +<|ref|>text<|/ref|><|det|>[[130, 577, 904, 606]]<|/det|> +We have used [-] to indicate, that the corresponding quantities are dimensionless, but have removed them for a better understanding. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[93, 64, 439, 81]]<|/det|> +## Specific Response to Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[92, 88, 905, 203]]<|/det|> +The authors demonstrate theoretically and experimentally the existence of Friedrich- Wintgen (FW) type bound in continuum states (BICs) in an open acoustic cavity. The BIC is revealed in the transmission coefficient under the shape of a Fano resonance (quasi- BIC) whose linewidth vanishes when approaching the geometrical parameters of the cavity satisfying the BIC condition. They show the best conditions to observe the QBIC in presence of thermoviscous losses. Moreover, by using a laser Doppler vibrometry (LDV) technique, they are able to reveal for the first time the map of the pressure field associated with the BIC inside the cavity. Finally, they present the design of new type high- quality BIC relying on reduced symmetry and avoiding the excitation of unwanted resonances in the cavity. The agreement between theory and experiment is very accurate throughout the manuscript. + +<|ref|>text<|/ref|><|det|>[[92, 216, 905, 331]]<|/det|> +The paper is generally well presented and contains some interesting and new results. It is timely because of the continuing interest in BICs and their applications based on the high sensitivity of the resulting Fano resonances to the environment. However, the cavity designed in this paper and the associated BICs and their analysis have some similarities with those presented in recent papers. The main novelty of this manuscript is the observation of the BIC pressure field inside the cavity by using LDV. This is an interesting proposal that deserves to be published. But from the point of view of physical originality or attraction for a broad audience, the paper would probably not reach the level required for acceptance in Nature Communications. Perhaps, another of the Nature journals would be more appropriate. + +<|ref|>text<|/ref|><|det|>[[92, 343, 904, 373]]<|/det|> +To emphasize the novelty, innovation, and scientific impact of our work, we have modified the abstract (section: Abstract, page: 1): + +<|ref|>text<|/ref|><|det|>[[92, 385, 905, 658]]<|/det|> +Bound states in the continuum (BICs) coupling into the propagating spectrum lead to the formation of quasi- BICs (QBICs) with high quality (Q) factor. These high- Q modes typically manifest as Fano resonances in the transmission or reflection spectrum. Fano resonances are highly sensitive, and even a small change in geometric or environmental variables results in a significant change in the transmission spectrum. This presents a challenge in predicting stable Fano peaks for realistic applications. In addition, we do not yet have any information on whether or not a large field enhancement occurs when thermo- viscous losses are taken into account in real acoustic devices. In this work, we demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by theory and experiment. In agreement with theoretical predictions, the appearance of the BIC is characterized by the vanishing line width of the Fano resonance in the measured transmission spectrum. We map the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry, which is the first reported visualization of an acoustic BIC. Mapping the pressure field of the BIC is a new technique for extracting real sound pressure values of high- Q modes. From the pressure values, we accurately infer the confinement of the BIC and thus its transmission or reflection properties. Furthermore, based on our results, we design a new type of symmetry- reduced BIC and analyze its absorption spectrum. Laser Doppler vibrometer (LDV) measurements provide the missing field enhancement data. We achieve a field enhancement by a factor of about three compared to the original cavity. The main findings are that LDV measurements are a powerful tool for predicting the maximum pressure enhancement of high- Q modes, and thus a new technique for obtaining the missing field enhancement data. The presented results facilitate the future applications of BICs in acoustics as high- intensity sound sources, filters, and sensors. + +<|ref|>text<|/ref|><|det|>[[92, 670, 904, 700]]<|/det|> +We have added a more detailed explanation of the innovation and of the importance of our findings (section: Introduction, page: 2): + +<|ref|>text<|/ref|><|det|>[[92, 713, 905, 870]]<|/det|> +We further present the first direct visualization of a Friedrich- Wintgen BIC using laser Doppler vibrometry as a pressure field mapping technique. We use laser Doppler vibrometry measurements to obtain a complete mapping of the sound pressure field to better understand BIC formation in the presence of realistic losses. The reflection and transmission spectra are obtained using microphones, but do not provide information about the exact pressure enhancement inside the cavity. The pressure distribution inside the cavity is needed to develop high- performance acoustic devices based on BICs, such as acoustic sources and sound lasers. Because BICs are extremely sensitive, any perturbation of the high- Q mode, energy extraction, or backscattering from microphones will degrade the BIC, so we use this technique to avoid any perturbation of the pressure field. By mapping the sound pressure field of the BIC, we have direct access to the actual pressure values and thus to the critical information of when and where the pressure magnitude reaches a maximum. The interaction between the localized thermo- viscous losses and the concentrated high intensity fields of the BIC is the key to deter + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[92, 65, 905, 110]]<|/det|> +mining the achievable Q- factor and pressure field enhancement. We facilitate the accurate analysis of high- Q modes in the presence of realistic losses, determine the configuration with maximum pressure enhancement, and enable the future application of high- Q Fano resonances to acoustic devices. + +<|ref|>text<|/ref|><|det|>[[92, 122, 598, 138]]<|/det|> +A few minor remarks are mentioned for the attention of the authors. + +<|ref|>text<|/ref|><|det|>[[110, 159, 830, 176]]<|/det|> +1. A short explanation about FW BIC can be useful, as well as on the physical principle of LDV. + +<|ref|>text<|/ref|><|det|>[[132, 187, 905, 247]]<|/det|> +We have added an explanation of the formation mechanism (section: S 1, pages: 1 - 3). For a detailed response, please see Specific Response to Reviewer #3, 1. ). We have also added a short description of the analytical solution to predict the eigenfield profile of the Friedrich- Wintgen BIC (section: Methods, page: 9): + +<|ref|>text<|/ref|><|det|>[[131, 259, 904, 289]]<|/det|> +Analytical Model. The eigenfield profile of the Friedrich- Wintgen BIC can be predicted from the following equation + +<|ref|>equation<|/ref|><|det|>[[360, 288, 678, 303]]<|/det|> +\[\psi_{B I C}(x,y)\approx \cos \theta \psi_{31}(x,y) + \sin \theta \psi_{13}(x,y)\] + +<|ref|>text<|/ref|><|det|>[[133, 310, 180, 323]]<|/det|> +where + +<|ref|>equation<|/ref|><|det|>[[360, 320, 678, 352]]<|/det|> +\[\cos \theta = \frac{A}{\sqrt{A^{2} + B^{2}}},\quad \sin \theta = \frac{B}{\sqrt{A^{2} + B^{2}}},\] + +<|ref|>equation<|/ref|><|det|>[[323, 365, 713, 464]]<|/det|> +\[A =\] \[-\sqrt{\frac{L_{y}}{2\pi^{2}L_{x}}}\left[\sin \left(\frac{\pi(L_{y} + 1)}{L_{y}}\right) - \sin \left(\frac{\pi(L_{y} - 1)}{L_{y}}\right)\right],\] \[B = \sqrt{\frac{2}{L_{x}L_{y}}}.\] + +<|ref|>text<|/ref|><|det|>[[133, 471, 700, 487]]<|/det|> +See Supplementary Information Section 1 for a complete theoretical analysis. + +<|ref|>text<|/ref|><|det|>[[133, 499, 904, 530]]<|/det|> +We have added an explanation of the physical principle of the LDV (section: Results, Visualization of QBIC, page: 4): + +<|ref|>text<|/ref|><|det|>[[133, 540, 905, 586]]<|/det|> +To conduct the refracto- vibrometry, a laser Doppler scanning vibrometer PSV- 500 from Polytec \(^{1}\) is used to measure the changes of the refractive index of the fluid, which is proportional to the acoustic pressure variation within the cavity [43- 46]: + +<|ref|>equation<|/ref|><|det|>[[401, 593, 903, 625]]<|/det|> +\[v(\omega) = \omega \frac{1}{\gamma p_{0}}\frac{n_{0} - 1}{n_{0}}\int_{L}p(l,\omega)\mathrm{d}l \quad (1)\] + +<|ref|>text<|/ref|><|det|>[[133, 631, 905, 748]]<|/det|> +where \(\omega\) is the angular frequency, \(v\) is the LDV velocity, \(p\) is the sound pressure, \(n_{0}\) is the refractive index of air at standard atmospheric pressure, \(p_{0}\) is the static atmospheric pressure, and \(\gamma\) is the specific heat capacity ratio of air. The basic principle of the LDV is based on the well- known Doppler shift. The pressure waves inside the cavity slightly shift the phase of the emitted monochromatic laser light. The superimposition of the reflected and emitted laser light produces a speckle pattern on the photodetector, which allows the measurement of the corresponding frequency of the pressure waves and the change in the refractive index. The latter is proportional to the sound pressure inside the cavity. This makes it possible to visualize the corresponding pressure distribution. + +<|ref|>text<|/ref|><|det|>[[133, 761, 904, 791]]<|/det|> +We have also added a more detailed explanation of the visualization and its limits (section: Methods, pages: 9 and 10): + +<|ref|>text<|/ref|><|det|>[[133, 803, 905, 861]]<|/det|> +Visualization. We use refracto- vibrometry to visualize the sound pressure field inside the cavity. A laser Doppler scanning vibrometer PSV- 500 from Polytec is used to measure the changes in the refraction index of the fluid, which is proportional to the acoustic pressure variation within the cavity. Overall, 225 measurement points were sequentially recorded with a sampling frequency of \(50\mathrm{kHz}\) for a duration + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 66, 905, 281]]<|/det|> +of \(2\mathrm{ms}\) , while the measurements were triggered by the sinusoidal sound generator. To ensure an optimal signal- to- noise ratio, a highly reflective sheet was placed against the rigid surface behind the sample to improve diffuse light reflection. Note that usually a LDV is used for surface normal vibration measurements of structures but captures the pressure wave- induced variation in the refraction index when measured against a rigid surface. In the case of a low- vibration surface, the velocity measurement from the LDV is dominated by the dynamic phase, caused by the sound pressure fluctuations, and the changed refractive index of the acoustic medium, along the traveling path of the light. To ensure the required rigidity, a single point LDV (Polytec PDV- 100) measured the surface vibration of the rigid surface from the opposite direction. The surface velocities were found to be orders of magnitude smaller than the signal of the scanning PSV500, confirming that the acoustic pressure dominates the measured results. As the LDV works up to frequencies of \(1\mathrm{MHz}\) , the frequency range is not a limiting factor for pressure field mapping. The size of the structure can be much smaller than those presented in this article and is only limited by the focal point of the laser \((25\mu \mathrm{m})\) . We use such large structures here because we need to measure the transmission/reflection spectra using an impedance tube with a diameter of \(40\mathrm{mm}\) . Since the Helmholtz equation is linearly scalable, our results can be transferred to different frequency ranges. + +<|ref|>text<|/ref|><|det|>[[113, 289, 904, 319]]<|/det|> +2. In page 5, the sentence "a reduction of a factor of \(\mathrm{k} = 3.41\) between the inlet and the outlet sound pressure amplitudes was noticed" needs a better explanation. + +<|ref|>text<|/ref|><|det|>[[133, 331, 904, 375]]<|/det|> +We have removed that part and have introduced new results regarding the pressure amplification inside the cavity. The new results also show the importance of our findings. Please see Specific Response to Reviewer #1, 1. ). + +<|ref|>text<|/ref|><|det|>[[110, 383, 904, 399]]<|/det|> +3. In Figure S3, one cannot clearly see the evolution of Lx on the curves, so some precision would be helpful. + +<|ref|>text<|/ref|><|det|>[[133, 411, 770, 427]]<|/det|> +We have added an explanation of the evolution of \(L_{x}\) (section: S 3, Fig. S 5, page: 6): + +<|ref|>image<|/ref|><|det|>[[95, 468, 867, 692]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[91, 708, 905, 766]]<|/det|> +
Fig. S 5. Complex eigenfrequencies for varying \(L_{x}\) . a The spectrum of propagating waves dominated by the pipe is marked by the region colored blue. Cavity resonances are highlighted by the region colored red. BIC 1 and BIC 2 are marked by the red crosses. b Evolution over \(L_{x}\) of the interacting modes that form BIC 1 & 2.
+ +<|ref|>text<|/ref|><|det|>[[110, 790, 904, 819]]<|/det|> +4. In section S5, Figures S6 are referred to as Fig. 6 (Fig. 6(a), 6(b) and 6(c)). In Fig. S6, two panels are labeled b instead of b and c. Please correct + +<|ref|>text<|/ref|><|det|>[[134, 831, 343, 846]]<|/det|> +We have changed the labels. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[92, 65, 439, 82]]<|/det|> +## Specific Response to Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[92, 88, 905, 132]]<|/det|> +The authors demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by numerical simulations and experiments, and indirectly measure the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry. The specific questions are as follows: + +<|ref|>text<|/ref|><|det|>[[113, 140, 905, 184]]<|/det|> +1. The models in this article are very similar to previous works (such as Phys. Rev. Applied 18, 054021), the innovative of the work should be further explained, and there is no detailed theory analysis in this article. + +<|ref|>text<|/ref|><|det|>[[131, 196, 904, 226]]<|/det|> +To emphasize the novelty, innovation, and scientific impact of our work, we have modified the abstract (section: Abstract, page: 1): + +<|ref|>text<|/ref|><|det|>[[133, 239, 905, 525]]<|/det|> +Bound states in the continuum (BICs) coupling into the propagating spectrum lead to the formation of quasi- BICs (QBICs) with high quality (Q) factor. These high- Q modes typically manifest as Fano resonances in the transmission or reflection spectrum. Fano resonances are highly sensitive, and even a small change in geometric or environmental variables results in a significant change in the transmission spectrum. This presents a challenge in predicting stable Fano peaks for realistic applications. In addition, we do not yet have any information on whether or not a large field enhancement occurs when thermo- viscous losses are taken into account in real acoustic devices. In this work, we demonstrate the existence of a Friedrich- Wintgen BIC in an open acoustic cavity by theory and experiment. In agreement with theoretical predictions, the appearance of the BIC is characterized by the vanishing line width of the Fano resonance in the measured transmission spectrum. We map the pressure field of the transparent open cavity hosting a Friedrich- Wintgen BIC using laser Doppler vibrometry, which is the first reported visualization of an acoustic BIC. Mapping the pressure field of the BIC is a new technique for extracting real sound pressure values of high- Q modes. From the pressure values, we accurately infer the confinement of the BIC and thus its transmission or reflection properties. Furthermore, based on our results, we design a new type of symmetry- reduced BIC and analyze its absorption spectrum. Laser Doppler vibrometer (LDV) measurements provide the missing field enhancement data. We achieve a field enhancement by a factor of about three compared to the original cavity. The main findings are that LDV measurements are a powerful tool for predicting the maximum pressure enhancement of high- Q modes, and thus a new technique for obtaining the missing field enhancement data. The presented results facilitate the future applications of BICs in acoustics as high- intensity sound sources, filters, and sensors. + +<|ref|>text<|/ref|><|det|>[[133, 538, 904, 567]]<|/det|> +We have added a more detailed explanation of the innovation and of the importance of our findings (section: Introduction, page: 2): + +<|ref|>text<|/ref|><|det|>[[133, 580, 905, 794]]<|/det|> +We have added a more detailed explanation of the innovation and of the importance of our findings (section: Introduction, page: 2):We further present the first direct visualization of a Friedrich- Wintgen BIC using laser Doppler vibrometry as a pressure field mapping technique. We use laser Doppler vibrometry measurements to obtain a complete mapping of the sound pressure field to better understand BIC formation in the presence of realistic losses. The reflection and transmission spectra are obtained using microphones, but do not provide information about the exact pressure enhancement inside the cavity. The pressure distribution inside the cavity is needed to develop high- performance acoustic devices based on BICs, such as acoustic sources and sound lasers. Because BICs are extremely sensitive, any perturbation of the high- Q mode, energy extraction, or backscattering from microphones will degrade the BIC, so we use this technique to avoid any perturbation of the pressure field. By mapping the sound pressure field of the BIC, we have direct access to the actual pressure values and thus to the critical information of when and where the pressure magnitude reaches a maximum. The interaction between the localized thermo- viscous losses and the concentrated high intensity fields of the BIC is the key to determining the achievable Q- factor and pressure field enhancement. We facilitate the accurate analysis of high- Q modes in the presence of realistic losses, determine the configuration with maximum pressure enhancement, and enable the future application of high- Q Fano resonances to acoustic devices. + +<|ref|>text<|/ref|><|det|>[[133, 807, 777, 822]]<|/det|> +We have added an explanation of the formation mechanism (section: S 1, pages: 1 - 3): + +<|ref|>sub_title<|/ref|><|det|>[[134, 836, 320, 850]]<|/det|> +## Coupled mode theory + +<|ref|>text<|/ref|><|det|>[[133, 850, 904, 879]]<|/det|> +We use coupled mode theory [1,2,3] to predict the location of the BIC. For simplicity, we consider a reduced two- dimensional coupled rectangular waveguide- resonator system shown in Fig. S 1. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[352, 63, 660, 253]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[125, 265, 866, 283]]<|/det|> +
Fig. S 1. Schematic drawing of a coupled two-dimensional waveguide-resonator system.
+ +<|ref|>text<|/ref|><|det|>[[133, 301, 905, 388]]<|/det|> +To make the conclusion as general as possible, we set the width of the waveguide \(d = 1\) (unitless), and the width and height of the resonator are \(L_{x}\) and \(L_{y}\) , respectively. Also, the center of the resonator is set as the origin, and the left and right waveguides are attached along the \(x\) - axis. Thus, the waveguide spans from \(y = - 1 / 2\) to \(y = +1 / 2\) . The first step is to compute the eigenfrequencies and eigenmodes of a closed resonator. They eigenfrequencies can be solved analytically with Neumann boundary conditions as follows + +<|ref|>equation<|/ref|><|det|>[[303, 384, 902, 424]]<|/det|> +\[\frac{\nu_{m,n}^{2}}{\omega_{0}^{2}} = \left(\frac{(m - 1)}{L_{x}}\right)^{2} + \left(\frac{(n - 1)}{L_{y}}\right)^{2},\quad n,m = 1,2,3,\ldots \quad (2)\] + +<|ref|>text<|/ref|><|det|>[[133, 427, 904, 458]]<|/det|> +where \(\nu_{m,n}\) is the resonant frequency and \(\omega_{0} = \pi c / d\) , \(c\) is the speed of sound in air. We obtain the corresponding modes \(\psi\) by + +<|ref|>equation<|/ref|><|det|>[[225, 464, 902, 504]]<|/det|> +\[\psi_{m,n} = \sqrt{\frac{(2 - \delta_{m}^{1})(2 - \delta_{n}^{1})}{L_{x}L_{y}}}\cos \left(\frac{\pi(m - 1)(2x + L_{x})}{2L_{x}}\right)\cos \left(\frac{\pi(n - 1)(2y + L_{y})}{2L_{y}}\right) \quad (3)\] + +<|ref|>text<|/ref|><|det|>[[133, 511, 904, 528]]<|/det|> +with \(\delta_{n}^{1}\) and \(\delta_{m}^{1}\) being the Kronecker delta. The propagating wave numbers in the waveguide are given by + +<|ref|>equation<|/ref|><|det|>[[442, 533, 902, 567]]<|/det|> +\[\frac{\nu^{2}}{\omega_{0}^{2}} = \frac{(k_{p}^{2}}{\pi^{2}} +(p - 1)^{2} \quad (4)\] + +<|ref|>text<|/ref|><|det|>[[133, 572, 904, 602]]<|/det|> +with \(k_{p}\) being the wavenumber of the \(p\) th channel of the waveguide. We obtain the corresponding modes \(\phi\) by + +<|ref|>equation<|/ref|><|det|>[[352, 601, 902, 636]]<|/det|> +\[\phi_{p} = \sqrt{(2 - \delta_{p}^{1})}\cos \left(\frac{\pi(p - 1)(2y + 1)}{2}\right)e^{ik_{p}x}. \quad (5)\] + +<|ref|>text<|/ref|><|det|>[[133, 641, 904, 671]]<|/det|> +Then the coupling matrix elements between eigenmodes of closed resonator and \(p\) th propagation channels of the left/right waveguide can be obtained by + +<|ref|>equation<|/ref|><|det|>[[327, 677, 902, 716]]<|/det|> +\[W_{m,n;p} = \int_{-\frac{1}{2}}^{\frac{1}{2}}\psi_{m,n}(x = -\frac{L_{x}}{2},y)\phi_{p}(x = -\frac{L_{x}}{2},y)dy. \quad (6)\] + +<|ref|>text<|/ref|><|det|>[[133, 723, 905, 781]]<|/det|> +After obtaining the coupling matrix, we compute the complex eigenvalues of the effective Hamiltonian [4,5,6,7], where the real parts correspond to the resonance frequencies and the imaginary parts to the half resonance linewidth. Thus, the search for BICs amounts to finding the zero imaginary part of the eigenvalues. In general, the eigenfunction of any BIC can be decomposed as + +<|ref|>equation<|/ref|><|det|>[[416, 787, 902, 819]]<|/det|> +\[\phi_{BIC} = \sum_{m,n}a_{m,n}\psi_{m,n}(x,y). \quad (7)\] + +<|ref|>text<|/ref|><|det|>[[133, 825, 816, 841]]<|/det|> +Since the BIC is perfectly decoupled from the continuum, its eigenfunction must be given by + +<|ref|>equation<|/ref|><|det|>[[404, 846, 902, 885]]<|/det|> +\[\int_{-\frac{1}{2}}^{\frac{1}{2}}\phi_{BIC}(x = -\frac{L_{x}}{2},y)dy = 0. \quad (8)\] + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 65, 905, 166]]<|/det|> +When two resonant states approach each other as a function of a certain continuous parameter, interference causes an avoided crossing of the two states in their energy positions. At the same time, one of the resonance line widths vanishes exactly at a certain value of the parameter and the other one is boosted to maximum. This is known as Friedrich- Wintgen BIC [8]. Typically, a pair of eigenmodes \(M_{mn}\) and \(M_{m + 2,n - 2}\) (or \(M_{mn}\) and \(M_{m - 2,n + 2}\) ) is often used to construct Friedrich- Wintgen BICs. The essence of finding Friedrich- Wintgen BICs is to find two degenerate resonances in a closed resonator with a certain size ratio. + +<|ref|>text<|/ref|><|det|>[[133, 170, 905, 212]]<|/det|> +In the present work, we consider the Friedrich- Wintgen BIC in a rectangular resonator embedded in the first channel \(p = 1\) , provided that other channels are closed for \(\nu < 1\) . There are numerous degeneracies in a closed rectangular resonator + +<|ref|>equation<|/ref|><|det|>[[430, 208, 903, 245]]<|/det|> +\[\frac{m^{2}}{L_{x}^{2}} +\frac{n^{2}}{L_{y}^{2}} = \frac{m^{\prime 2}}{L_{x}^{2}} +\frac{n^{\prime 2}}{L_{y}^{2}}. \quad (9)\] + +<|ref|>text<|/ref|><|det|>[[135, 248, 812, 264]]<|/det|> +The lowest case corresponds to \(m,n = 1,3\) and \(m^{\prime},n^{\prime} = 3,1\) for a square resonator \(L_{x} = L_{y}\) + +<|ref|>text<|/ref|><|det|>[[133, 266, 905, 368]]<|/det|> +After the introduction of the left and right waveguides, these two modes \(M_{13}\) and \(M_{31}\) are strongly coupled to each other, giving rise to an increase in the destructive interference at a given size ratio. Thus, the resonance frequencies of two modes experience avoided crossing. At the same time, one of the imaginary parts is suppressed to zero while the other is boosted to maximum. Therefore, the formation of such a BIC can be mainly attributed to the destructive interference of modes \(M_{13}\) and \(M_{31}\) in a closed resonator. We can approximate the eigenfunction of this Friedrich- Wintgen BIC as a superposition of the two eigenmodes of the closed resonator, and its coefficients \(A\) and \(B\) can be rigorously calculated by + +<|ref|>equation<|/ref|><|det|>[[377, 376, 902, 393]]<|/det|> +\[\psi_{BIC}(x,y)\approx A\psi_{31}(x,y) + B\psi_{13}(x,y). \quad (10)\] + +<|ref|>text<|/ref|><|det|>[[133, 400, 433, 415]]<|/det|> +Substituting Eq. (10) in Eq. (8) gives us + +<|ref|>equation<|/ref|><|det|>[[260, 422, 902, 464]]<|/det|> +\[A = -W_{1,3;p = 1} = -\frac{1}{2\pi}\sqrt{\frac{2L_{y}}{L_{x}}}\left[\sin \left(\frac{\pi(L_{y} + 1)}{L_{y}}\right) - \sin \left(\frac{\pi(L_{y} - 1)}{L_{y}}\right)\right], \quad (11)\] + +<|ref|>equation<|/ref|><|det|>[[425, 470, 902, 507]]<|/det|> +\[B = W_{3,1;p = 1} = \sqrt{\frac{2}{L_{x}L_{y}}}. \quad (12)\] + +<|ref|>text<|/ref|><|det|>[[133, 512, 335, 527]]<|/det|> +We can rewrite Eq. (10) as + +<|ref|>equation<|/ref|><|det|>[[358, 534, 902, 550]]<|/det|> +\[\psi_{BIC}(x,y)\approx \cos \theta \psi_{31}(x,y) + \sin \theta \psi_{13}(x,y), \quad (13)\] + +<|ref|>equation<|/ref|><|det|>[[362, 556, 902, 590]]<|/det|> +\[\cos \theta = \frac{A}{\sqrt{A^{2} + B^{2}}},\quad \sin \theta = \frac{B}{\sqrt{A^{2} + B^{2}}} \quad (14)\] + +<|ref|>text<|/ref|><|det|>[[131, 592, 904, 622]]<|/det|> +Excellent agreement is found between the eigenfield profile predicted from Eqs.(8- 9) and the numerically calculated eigenfield profile of Friedrich- Wintgen BIC, see Fig. S 2. + +<|ref|>image<|/ref|><|det|>[[98, 631, 911, 738]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[110, 744, 884, 761]]<|/det|> +
Fig. S 2. Eigenfield profile. Decomposition of Friedrich-Wintgen BIC into eigenmodes \(M_{31}\) and \(M_{13}\) .
+ +<|ref|>text<|/ref|><|det|>[[111, 781, 904, 825]]<|/det|> +2. As far as I know, it is not the first time to indirectly measure the acoustic pressure in air by the laser Doppler vibrometry. On the other hand, for the model size in this article, it is possible to directly measure the pressure field by such as \(1 / 4\) microphone. + +<|ref|>text<|/ref|><|det|>[[133, 838, 904, 881]]<|/det|> +We have incorporated the answer to this question into the answer to your first question. Microphones would not work properly because we are perturbing the high- Q mode, and any energy extraction or backscattering will degrade the QBIC. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 65, 904, 96]]<|/det|> +3. Could authors explain further the black dotted line in the Fig.1(b)(c)? How do authors calculate them through the coupled mode theory? + +<|ref|>text<|/ref|><|det|>[[133, 108, 688, 123]]<|/det|> +Please see the answer to your first comment for a complete theory analysis. + +<|ref|>text<|/ref|><|det|>[[113, 132, 904, 162]]<|/det|> +4. Does the technique involved in this article using laser Doppler vibrometry require the structural size of the sample? When it comes to practicality, does this technique work on smaller structures? + +<|ref|>text<|/ref|><|det|>[[132, 175, 904, 205]]<|/det|> +We have added an explanation of the physical principle of the LDV (section: Results, Visualization of QBIC, page: 4): + +<|ref|>text<|/ref|><|det|>[[133, 217, 904, 260]]<|/det|> +To conduct the refracto- vibrometry, a laser Doppler scanning vibrometer PSV- 500 from Polytec \(^{1}\) is used to measure the changes of the refractive index of the fluid, which is proportional to the acoustic pressure variation within the cavity [43- 46]: + +<|ref|>equation<|/ref|><|det|>[[401, 269, 902, 302]]<|/det|> +\[v(\omega) = \omega \frac{1}{\gamma p_{0}} \frac{n_{0} - 1}{n_{0}} \int_{L} p(l, \omega) \mathrm{d}l \quad (15)\] + +<|ref|>text<|/ref|><|det|>[[133, 310, 904, 425]]<|/det|> +where \(\omega\) is the angular frequency, \(v\) is the LDV velocity, \(p\) is the sound pressure, \(n_{0}\) is the refractive index of air at standard atmospheric pressure, \(p_{0}\) is the static atmospheric pressure, and \(\gamma\) is the specific heat capacity ratio of air. The basic principle of the LDV is based on the well- known Doppler shift. The pressure waves inside the cavity slightly shift the phase of the emitted monochromatic laser light. The superimposition of the reflected and emitted laser light produces a speckle pattern on the photodetector, which allows the measurement of the corresponding frequency of the pressure waves and the change in the refractive index. The latter is proportional to the sound pressure inside the cavity. This makes it possible to visualize the corresponding pressure distribution. + +<|ref|>text<|/ref|><|det|>[[133, 437, 904, 467]]<|/det|> +We have also added a more detailed explanation of the visualization and its limits (section: Methods, pages: 9 and 10): + +<|ref|>text<|/ref|><|det|>[[133, 480, 904, 750]]<|/det|> +Visualization. We use refracto- vibrometry to visualize the sound pressure field inside the cavity. A laser Doppler scanning vibrometer PSV- 500 from Polytec is used to measure the changes in the refraction index of the fluid, which is proportional to the acoustic pressure variation within the cavity. Overall, 225 measurement points were sequentially recorded with a sampling frequency of \(50\mathrm{kHz}\) for a duration of \(2\mathrm{ms}\) , while the measurements were triggered by the sinusoidal sound generator. To ensure an optimal signal- to- noise ratio, a highly reflective sheet was placed against the rigid surface behind the sample to improve diffuse light reflection. Note that usually a LDV is used for surface normal vibration measurements of structures but captures the pressure wave- induced variation in the refraction index when measured against a rigid surface. In the case of a low- vibration surface, the velocity measurement from the LDV is dominated by the dynamic phase, caused by the sound pressure fluctuations, and the changed refractive index of the acoustic medium, along the traveling path of the light. To ensure the required rigidity, a single point LDV (Polytec PDV- 100) measured the surface vibration of the rigid surface from the opposite direction. The surface velocities were found to be orders of magnitude smaller than the signal of the scanning PSV500, confirming that the acoustic pressure dominates the measured results. As the LDV works up to frequencies of \(1\mathrm{MHz}\) , the frequency range is not a limiting factor for pressure field mapping. The size of the structure can be much smaller than those presented in this article and is only limited by the focal point of the laser ( \(25\mu \mathrm{m}\) ). We use such large structures here because we need to measure the transmission/reflection spectra using an impedance tube with a diameter of \(40\mathrm{mm}\) . Since the Helmholtz equation is linearly scalable, our results can be transferred to different frequency ranges. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 294, 98]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[119, 113, 225, 125]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[119, 127, 300, 140]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 140, 831, 169]]<|/det|> +After a thorough examination of the authors' response, I have found that the current version exhibits higher quality. Consequently, I recommend accepting it in its current form. + +<|ref|>text<|/ref|><|det|>[[119, 210, 225, 222]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[119, 225, 300, 237]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 238, 850, 266]]<|/det|> +The authors have carefully taken account of the comments and added several improvements to the manuscript. So, I would recommend the acceptance of the paper for publication + +<|ref|>text<|/ref|><|det|>[[119, 308, 225, 320]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[119, 323, 300, 335]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[119, 337, 488, 350]]<|/det|> +The authors have revised the paper as required. + +<--- Page Split ---> diff --git a/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..3914c697ccd66117429ec00055db93c27b46112b --- /dev/null +++ b/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,430 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Fig. R2. Effect of hydrogel thickness on actuation performance. (A) Bending angle over time for varying hydrogel thicknesses at \\(41^{\\circ}C\\) . (B) Measured static force changes at \\(41^{\\circ}C\\) across different hydrogel thicknesses. (C) Resistive response of a thermal sensor (ERT-J0ET102H) across a temperature range of \\(22^{\\circ}C\\) to \\(60^{\\circ}C\\) for different hydrogel thicknesses.", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Fig. R3. Actuation behavior of bilayer soft robots under ambient conditions. (A) Measured volume shrinkage of PNIPAM hydrogel during a heating process with temperature changing from \\(25^{\\circ}C\\) to \\(60^{\\circ}C\\) . (B) The resultant bending angle \\(\\theta\\) of a soft robotic arm as a function of the input electric power. (C) Measured static force changes of the soft robotic finger under different temperatures induced by different electrical powers.", + "footnote": [], + "bbox": [ + [ + 118, + 140, + 880, + 302 + ] + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_2.jpg", + "caption": "Fig. R4. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \\(36^{\\circ}C\\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this", + "footnote": [], + "bbox": [ + [ + 118, + 567, + 880, + 829 + ] + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_3.jpg", + "caption": "Fig. R5. Soft robotic gripper for monitoring bladder volume. (A) Exploded view of the soft robotic finger including actuator, sensor and stimulator components. (B) Detailed schematic illustration for the soft robotic finger, highlighting the direct tissue contact by the stimulation electrode (indicated with a red dashed line). Here the hydrogel actuators are intentionally positioned on the device's arms, marked by the blue lines, ensuring that they do not hinder the electrodes' direct engagement with the tissue, facilitating efficient electrical stimulation.", + "footnote": [], + "bbox": [ + [ + 130, + 536, + 870, + 737 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_4.jpg", + "caption": "Fig. R6. A robotic gripper for bladder control. Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \\(\\sim 100 \\text{mL}\\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly.", + "footnote": [], + "bbox": [ + [ + 215, + 88, + 780, + 416 + ] + ], + "page_idx": 10 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_5.jpg", + "caption": "Fig. R7. shape conformability of soft robotic devices with biological tissues/organs. (A) Measured static force changes of the soft robotic finger under different temperatures. (B) Adhesion strength of a PNIPAM-co-PAAm hydrogel with an LCST of 36 °C across different temperatures.", + "footnote": [], + "bbox": [ + [ + 131, + 540, + 870, + 768 + ] + ], + "page_idx": 12 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_6.jpg", + "caption": "Fig. R8. in vivo validation of a soft robotic gripper for epicardial sensing and pacing. (A) Image of a soft robotic thera-gripper grasping on the epicardial surface of a living mouse heart. Scale bar, \\(5 \\text{mm}\\) . (B) Temperature measurements from the thera-gripper during its deployment onto the mouse heart. (C) The surface ECG trace during electrical stimulation using a pair of Au pacing electrodes. (D) Representative measurements of local cardiac contractions using a soft robotic thera-gripper wrapping onto a living mouse heart.", + "footnote": [], + "bbox": [ + [ + 230, + 179, + 768, + 525 + ] + ], + "page_idx": 14 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_7.jpg", + "caption": "Fig. R9. Mechanical properties of PNIPAM hydrogel. (A&B) Optical image showing conformal attachment of the soft sensory robot onto human skin (A) and porcine tissue (B) with high mechanical compliance. (C)Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness 4mm, width 10mm, initial length 15mm), highlighting an elastic modulus (E) of \\(\\sim 1.2\\) kPa. This value is within the range of soft tissues, which typically exhibit an E from a few kPa to hundreds of kPa, ensuring the hydrogel's compatibility with biological tissues and reducing risks associated with mechanical mismatches.", + "footnote": [], + "bbox": [ + [ + 184, + 90, + 808, + 368 + ] + ], + "page_idx": 15 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_8.jpg", + "caption": "Fig. R10. Soft robots designed integrated sensing and actuation capabilities. (A) Schematic diagram of the responsive robotic gripper with control circuitry. (B) Functional block diagram of the algorithmic and hardware design of the adaptive control loop.", + "footnote": [], + "bbox": [ + [ + 216, + 345, + 790, + 716 + ] + ], + "page_idx": 16 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_9.jpg", + "caption": "Fig. R11. Soft robots designed integrated sensing and actuation capabilities. (A) Infrared and optical images of the responsive robotic grippers at different stages of controlled actuation. (B&C) Time synchronized current (B) and temperature plot (C) capturing the controlled actuation changes after a sudden change in ambient temperature.", + "footnote": [], + "bbox": [ + [ + 160, + 272, + 839, + 602 + ] + ], + "page_idx": 20 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_10.jpg", + "caption": "Fig. R12. Illustration of soft robotic implants exhibiting significant modularity and adaptability. (A-D) A starfish-inspired device featuring twelve arms. (E-H) A hand-structured soft robotic device that can be compactly housed in and released from a catheter. (I-L) A twisted soft robotic device designed for storage and deployment through a 14-Gauge Tuohy needle. Scale bars, 1 cm.", + "footnote": [], + "bbox": [ + [ + 130, + 95, + 870, + 430 + ] + ], + "page_idx": 26 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_11.jpg", + "caption": "Fig. R13. Mechanical behavior of soft robotic device. (A) Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness \\(4\\mathrm{mm}\\) , width \\(10\\mathrm{mm}\\) , initial length \\(15\\mathrm{mm}\\) ). (B&C) Optical image showing conformal attachment of the soft sensory robot onto human skin (B) and porcine tissue (C) with high mechanical compliance. (D) Measured static force changes of the soft robotic finger under different temperatures. Scale bars, \\(5\\mathrm{mm}\\) .", + "footnote": [], + "bbox": [ + [ + 125, + 95, + 872, + 298 + ] + ], + "page_idx": 27 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_12.jpg", + "caption": "Fig. R14. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \\(36^{\\circ}\\mathrm{C}\\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this threshold. All tests were conducted after overnight incubation simulating physiological conditions at \\(34^{\\circ}\\mathrm{C}\\) , \\(37^{\\circ}\\mathrm{C}\\) , and \\(40^{\\circ}\\mathrm{C}\\) . Scale bars, \\(5\\mathrm{mm}\\) .", + "footnote": [], + "bbox": [ + [ + 130, + 548, + 869, + 805 + ] + ], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_13.jpg", + "caption": "Fig. R15. FEA simulation results of a bilayer soft robotic device mimicking a chiral seedpod. (A-F) Stress distribution across the device during the shape-shifting process, facilitated by strategic stripe patterns on the 3D bilayer robot. This visualization highlights the material property mismatches including mechanical and thermal responsiveness that drive the device's complex morphological transformations.", + "footnote": [], + "bbox": [ + [ + 147, + 90, + 857, + 293 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_14.jpg", + "caption": "Fig. R16. The thermal responsiveness of PNIPAM hydrogel. (A) The volumetric shrinkage of PNIPAM hydrogel during the heating cycle across a temperature range of \\(25^{\\circ}C\\) to \\(60^{\\circ}C\\) . (B) The hydrogel's volumetric recovery during the cooling cycle, as temperatures revert to \\(25^{\\circ}C\\) , showcasing its reversible thermal behavior and resilience.", + "footnote": [], + "bbox": [ + [ + 120, + 92, + 846, + 321 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_15.jpg", + "caption": "Fig. R17. Fabrication of functional nanocomposite based on in situ solution integration method. (A) Top: Schematic illustration of patterning AgNWs network with a laser; Bottom: SEM image of as-synthesized AgNWs. (B) Top: Schematic illustration of spin coating PI solution and forming AgNW/PI nanocomposite; Bottom: SEM image of AgNW/PI nanocomposite with full PI infiltration, demonstrating a thorough infiltration of PI within the AgNW network, resulting in a cohesive nanocomposite structure.", + "footnote": [], + "bbox": [ + [ + 171, + 158, + 820, + 395 + ] + ], + "page_idx": 34 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_16.jpg", + "caption": "Fig. R18. SEM characterization of functional nanocomposite based on in situ solution integration method. (A) Top surface SEM view of the AgNW/PI nanocomposite. (B&C) Cross-sectional SEM images of AgNW/PI nanocomposite, revealing the complete penetration of PI throughout the AgNW matrix with the absence of voids.", + "footnote": [], + "bbox": [ + [ + 117, + 631, + 875, + 787 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_17.jpg", + "caption": "Fig. R19. Infrared thermograph of an AgNW/PI-based heater undergoing bending and twisting motions.", + "footnote": [], + "bbox": [ + [ + 250, + 518, + 750, + 747 + ] + ], + "page_idx": 38 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_18.jpg", + "caption": "Fig. R20. (A) Surface temperature of the AgNW/PI-based heater as a function of the input electric power. Notably, the AgNW/PI nanocomposite heater can function under relatively low input electric power. (B) The resultant bending angle of a soft robotic arm as a function of the input electric power.", + "footnote": [], + "bbox": [ + [ + 144, + 485, + 857, + 735 + ] + ], + "page_idx": 40 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_19.jpg", + "caption": "Fig. R21. (A) Static cycling test of the RGO/PI-based thermal sensor. Here, the left y-axis represents the change in resistance, while the right y-axis corresponds to the associated temperature changes. (B) Representative test of the 3D buckling strain sensor in real-time monitoring of volumetric change of the artificial bladder during cyclic movements of filling and emptying. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the associated volume changes. (C) Representative measurement of fluidic pressure of the artificial artery system using the soft robotic cuff. Here, the left y-axis is the change in resistance,", + "footnote": [], + "bbox": [ + [ + 115, + 455, + 880, + 767 + ] + ], + "page_idx": 41 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_20.jpg", + "caption": "Fig. R22. (A) Temperature measurement on the MXene/PI thermal sensor and a commercial thermal resistor (ERT-J0ET102H). (B) Temperature measurement on the RGO/PI thermal sensor and the commercial thermal resistor. (C) Resistive response at various temperatures ranging from", + "footnote": [], + "bbox": [ + [ + 133, + 657, + 866, + 816 + ] + ], + "page_idx": 42 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_21.jpg", + "caption": "Fig. R23. The effect of separation distance, horizontal offset and orientation angle on the performance of WPT system. (A) FEA results showing the variations in the coupling coefficient of the WPT coils under different separation distances. (B) Experimental evaluations of power transmission at resonance frequency (16 MHz) under different separation distances", + "footnote": [], + "bbox": [ + [ + 171, + 154, + 825, + 359 + ] + ], + "page_idx": 46 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_22.jpg", + "caption": "Fig. R24. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \\(36^{\\circ}C\\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this threshold. All tests were conducted after overnight incubation simulating physiological conditions at \\(34^{\\circ}C\\) , \\(37^{\\circ}C\\) , and \\(40^{\\circ}C\\) . Scale bars, \\(5mm\\) .", + "footnote": [], + "bbox": [ + [ + 128, + 281, + 872, + 540 + ] + ], + "page_idx": 50 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_23.jpg", + "caption": "Fig. R25. A robotic gripper for bladder control. Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \\(\\sim 100 \\text{mL}\\) , electrical stimulation amplitude of \\(3 \\text{V}\\) . Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly.", + "footnote": [], + "bbox": [ + [ + 214, + 88, + 780, + 416 + ] + ], + "page_idx": 56 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_24.jpg", + "caption": "Fig. R26. (A) schematic illustration of the soft robotic thera-gripper consisting of two temperature sensors made of thermal resistors. (B) Temperature measurements from the thera-gripper's dual-channel sensors during its deployment onto the mouse heart, demonstrating the device's capability to monitor thermal variations in real-time.", + "footnote": [], + "bbox": [ + [ + 140, + 88, + 847, + 320 + ] + ], + "page_idx": 57 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_25.jpg", + "caption": "Fig. R27. (A) Flexible pacing electrodes implantation. (B) The surface ECG trace during electrical stimulation using a pair of Au pacing electrodes. (C&D) Representative voltage traces of the cardiac electrical activity during E-stim with various parameters. (C) 500 mV voltage with 1 ms width at 6.5 Hz. (D) 500 mV voltage with 5 s width at 0.1 Hz.", + "footnote": [], + "bbox": [ + [ + 216, + 92, + 783, + 491 + ] + ], + "page_idx": 60 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_26.jpg", + "caption": "Fig. R28. (A&B) Representative measurements of local cardiac contractions before (A) and after myocardial infarction (B) using a soft robotic thera-gripper wrapping onto a living mouse heart.", + "footnote": [], + "bbox": [ + [ + 120, + 470, + 880, + 680 + ] + ], + "page_idx": 66 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_27.jpg", + "caption": "Fig. R29. In vitro setup for artificial artery model.", + "footnote": [], + "bbox": [ + [ + 113, + 385, + 888, + 635 + ] + ], + "page_idx": 67 + }, + { + "type": "image", + "img_path": "images/Figure_30.jpg", + "caption": "Fig. 30. Overview of device performance after two-week implantation. (A) Visualization of the device accurately positioned on the mouse heart, indicating its stability post two-week implantation. (B&C) Voltage response traces from the pacing electrodes embedded in the implanted device, demonstrating its operational integrity over the two-week period. Here, (B) shows a sine wave configuration at a frequency of \\(1 \\mathrm{~Hz}\\) and amplitude of \\(1 \\mathrm{~V}\\) , while (C) depicts pulse modulation with a height of \\(500 \\mathrm{mV}\\) , pulse with of \\(0.01 \\mathrm{~s}\\) , and a maximum repeating rate of \\(1 \\mathrm{~Hz}\\) . (D) Comparative analysis of the resistive response from the thermal sensor before and after the two-week implantation period, illustrating the device's consistent performance and sensor integrity over time.", + "footnote": [], + "bbox": [ + [ + 170, + 87, + 828, + 488 + ] + ], + "page_idx": 68 + } +] \ No newline at end of file diff --git a/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..12a4f5946fd0322e7b8ac37729851e6601f776b1 --- /dev/null +++ b/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,1533 @@ + +# nature portfolio + +Peer Review File + +Skin- inspired, sensory robots for electronic implants + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons + +license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The article entitled "Skin- inspired, sensory robots for electronic implants" by Zhang et al. introduces an approach for soft robots that can sense multiple parameters and provide on- demand motions. Although the proposed concept would be useful for the development of associated technologies, there are many questionable issues and experimental shortcomings that should be addressed before further progress. + +The authors need to check the overall figures again. The order of the figures in the manuscript is a total mess. Also, there is so much information about SI that it is very difficult to understand the main text or what the author is trying to say. All unnecessary SI should be discarded, and only the content that is directly related to the key points should be mentioned. + +Please understand that the comments have been randomly organized rather than in the order of the manuscript. + +1. The authors demonstrated the adhesion performance of the bio-adhesive layer using the bending image in Figure 3B, but this referee can't find any quantified data set of the adhesion force, did the authors studied how strong it is under various conditions? (e.g. dry, wet environments, etc) + +2. While the thickness of other layers was specified, the actuation hydrogel's thickness was missing (it seems to be considerably thick). Increase of the thickness might enhance actuation performance but could potentially affect sensing and stimulation properties. + +2- 1) What is the optimal thickness of the actuation layer for achieving reliable shape- morphing? 2-2) How does the thickness of the actuation layer affect sensing and stimulation performance? + +3. In Figure 3N, bending configurations appear to be different and uncontrollable although three arms had the same composition. Can the authors explain why? And, it seems those arms are not reversible since the off-arms don't seem to return to the original state + +4. In Figure 4A, there might be stability issues with the PAAM hydrogel as a pressure sensor. Considering the implant environment, swelling of the hydrogel might hinder pressure measurement due to instability in weight loss and capacitance changes. Any proposed solutions to address this concern would be necessary. + +5. The authors discussed the adhesion and actuation force of the hydrogel in Fig. S46, Supplementary Note S8. However, it seems to be considered in a dry environment. Given the nature of hydrogels, there might be swelling and degradation issues when operating in a wet environment. + +6. In Figures 5 and S47, the hydrogel was designed to face biological tissue (please correct me if not). In this case, some of physical sensors (e.g., strain and pressure gauges) would be fine, but how to figure out operation of other sensors/stimulators that need direct contacts to tissues? For example, the authors mentioned here electrical stimulation for the bladder, but is it possible to stimulate the bladder through the adhesive layer and PAAM hydrogel? That would be not. Can the authors explain how to achieve such functional operations? + +7. In Figure 5g, it is unclear what the author intended to demonstrate through the programming. Can the authors provide significance of the programming for the control of the bladder. (It is quite strange that E-stim ON when the bladder is void, and E-stim OFF after expansion/contraction cycle... Shouldn't it turn on when the volume reaches maximum?). + +8. In Figs. 6 and S52A, it appears difficult or impossible for the electronic components at the end of each arm to form a strong coupling to living tissues, particularly to tissues whose volume changes over time, such as the bladder. How did the authors control or attach the robotic arms? + +<--- Page Split ---> + +9. Page 3, line 86 It is not 'overactive', but 'underactive' bladder. + +10. In fig. 2c, is there a motivation for using such diverse materials for different components? This referee can't find outstanding characteristics of those materials for sensing components. + +11. In figs. 2f and 2g, the authors claimed that soft robots can form conformal contacts to tissues, but did the authors study or compare mechanical modulus between devices and tissues? + +12. In fig. S12B, such layered structures are likely to interfere with each other's signals. is there any reason to measure both parameters at the same time? Or, even if simultaneous measurements are made, does each sensor operate independently? + +13. there's no description for Figs. 3H&3I + +14. We usually do not include information about SI figures in main figure captions. For example, in fig.3, there is information about fig. S18 and 25, but these should be removed. + +15. please do double check all the figures including SI, whose order is a total mess + +Reviewer #2 (Remarks to the Author): + +Lin Zhang et al. developed various types of soft robots, utilizing an electronic skin (e- skin) made of materials like silver nanowires, reduced graphene oxide, MXene, and conductive polymers integrated into a polymer matrix. This e- skin is designed to mimic skin receptors, enabling the perception of various stimuli. The robots, inspired by natural forms like starfish, chiral seedpod, and others, are equipped with features for bending, twisting, and expanding, and include an artificial muscle for dynamic movement. This study also integrated wireless modules to control and communicate without tethering. Demonstrated in various medical scenarios, these devices showed capabilities such as blood pressure sensing and adapting to organ surfaces for diagnostic and therapeutic functions, exemplifying their potential as multifunctional, minimally invasive medical tools. + +However, the devices used materials commonly used in practical applications, with the exception of an in situ solution- based fabrication approach, showing no significant material novelty. This article is also lack of either long- term feasibility or detailed information about the mechanism of each sensor like the relationships between pH, pressure and resistance. + +Despite such some disadvantages, the positive aspect lies in its multifunctional ability to be implanted in real scenarios, possibly leading to successful demonstrations for various organ shapes. In specific, massive integration of multifunctional soft robots entailing high- performance functional nanomaterials and actuating modules is highly impressive. Additionally, this article demonstrates a high level of systemic completeness, considering real clinical situations. Therefore, the reviewer believes that with some modifications addressing specific comments included in the following, this paper has the potential to be accepted in Nature Communications. + +## \*Major comments + +1. In the introduction part, some references (Nature Materials volume 15, pages937-950 (2016), Nature Nanotechnology volume 9, pages397-404 (2014), and Nature Electronics volume 6, pages779-789 (2023)) regarding stable tissue-interfacing performance of wearable/implantable devices should be cited to justify the authors' research purpose. + +2. The reviewer believes that sensory-motor integration is valuable when the robot can control motors in response to signals received from sensors. However, it seems that controlling the motors and performing sensor functions operate independently. In that case, can this robot still be + +<--- Page Split ---> + +considered as the presence of responsiveness as mentioned in the introduction? + +3. It seems good that the robot is designed differently for each target organ. The reviewer is curious about the variation in curvature among different organs. For instance, in the case of organs like the heart and bladder, squeezing too much might make it challenging to grasp effectively. How was this consideration taken into account in the design? + +4. Why does the parallel strips configuration result in twisting? Is there any reference for this, or was it an original concept? + +5. On page 6, if the transfer method is well-designed, it could potentially enable multi-modal implementation. Is there a particular advantage in this solution-based approach over transfer methods? + +6. On Page 7, Figure 2H, the volume of the PNIPAM hydrogel in Figure 2H is shown to dramatically decrease between approximately \(35^{\circ}C\) and \(45^{\circ}C\) . Given that the normal human body temperature is around \(36 - 37^{\circ}C\) , even if actuation is induced by an electrothermal method, maintaining its shape seems crucial for attaching it to various organs within the body. To substantiate this point, it would be necessary for the authors to demonstrate volume changes starting from a range lower than \(35^{\circ}C\) . + +7. It was confirmed that the composite was implemented through XPS analysis. Is there a concern that this might result in lower performance compared to a full composite? + +8. After nanomaterials are created through the laser pattern, the inherent properties of the material make handling difficult. How was the surrounding material removed or treated? + +9. In Figs 3C, D, please indicate in the caption whether SEM images represent the surface or cross-section. Additionally, to determine the presence of voids, it may be necessary to examine cross-sectional TEM images. + +10. In Fig 3E, it is understood that accurately observing the exact temperature by performing twisting and bending may be challenging with an infrared camera. However, even considering this, it seems that the temperature distribution is not uniform. + +11. In Fig 3F, G, the temperature converges over time, but what is the reason for the continuous change in bending force? Additionally, once bent, how long does the bending force persist? + +12. In addition to comment 9, is it necessary to keep the heater on continuously to maintain actual bending when attaching it to an organ? + +13. The dual-axis graphs presented in this figure (Figure 3I, Figure 5F, K, N etc.) are difficult to intuitively comprehend. It is unclear whether the changes on the left axis correspond to the results on the right axis or if they were determined through variations in resistance, pressure, or pH values. Therefore, it seems necessary for the authors to modify the graphs for better intuitive understanding and provide explanations regarding the extent of numerical changes made. + +14. Using heat as a stimulus might potentially cause damage to the tissue. However, considering the hydrogel is thick enough, it may prevent such damage. How efficiently does heat transfer throughout the entire hydrogel, and is the heat dissipation effective enough to be considered safe? + +15. While applying temperature, can the thermal sensor accurately measure the temperature from the tissue? + +16. What is the reason for the difference in the transfer method in S12(b) compared to the dual printing method in S16? + +17. On Page 11, the author mentioned that "The electrothermal stimulus along with distributed sensing capabilities enables programmed actuation not only on demand but also regulated simultaneously by the sensing feedback". How was actuation implemented based on sensing feedback? + +18. On Page 14, Figure S31, in Figure S31B, it is evident that there is a tendency for the coupling coefficient to decrease as the separation distance increases. However, in Figure S31D, there is a trend showing an increase in output power relative to input power as the distance increases. This observation appears to be theoretically inconsistent. If this graph is accurate, the authors need to provide additional explanations for these results. + +19. On Page 16, in order for the sensory robots developed by the authors to conformally adhere to tissues or organs, they require not only curvilinear surfaces but also effective adhesion. While this article mentions the adhesiveness of PNIPAM, a recently published paper indicates that PNIPAM shows tissue adhesion at low temperatures (around \(25^{\circ}C\) ), but loses almost all adhesive strength when it transitions to a gel form near \(40^{\circ}C\) (Nature Biotechnology 2023, 41, 652-662). To showcase the tissue adhesion capability of the authors' device, it becomes imperative to gauge the adhesive strength of the hydrogel by varying temperatures. This would confirm that there are no issues with adhesion even after attaching it to an organ. + +<--- Page Split ---> + +20. In Figs 5, 6, the use of Au electrodes for electrical stimulation in electrotherapy seems somewhat divergent from the other sensing materials of this paper (Fig. S52B). + +21. In Fig 5G, the electrical stimulation off voltage is not 0.0 V. Is there a specific reason for this? To help readers to understand, it appears that the authors should provide additional explanations regarding the correlation between electrical stimulation and volume changes. Specifically, a clear clarification is needed on whether the specific electrical stimulation is causing an actual increase in volume or if it is transmitting signals to patients having urinary dysfunction. + +22. As the authors mentioned in the context, PNIPAM hydrogel has reversibly contract and relax property upon electrothermal trigger. If that's the case, is there no risk of delamination if the device is not well-adhered to the tissue when the internal body temperature decreases? + +Additionally, wouldn't there be a possibility that continuous electrothermal stimulation, applied to prevent deformation of the device after it is attached to the tissue, could have adverse effects on the tissue? + +23. On Page 24, Figure 6F, what is the indication T1 and T2 in Figure 6F account for? The authors need to explain these in the caption. + +24. In Fig 6G, it is challenging to consider it as functioning like a pacemaker, as pacing does not seem to lead to actual cardiac capture. + +25. In Figs 6 M, N, it was mentioned that changes were observed in S2 and S4. However, it seems that only changes in frequency are visible along the x-axis. Shouldn't the focus be on the resistance changes along the y-axis, which may represent actual strain changes? + +26. The paper lacks details on the system used to generate water flow simulating blood flow in the vascular system, including names of the equipment and the setting of flow rate. Information on the properties and thickness of the rubber used is also insufficient. + +27. This work validated through H&E staining data that a single-day stimulation has a minimal impact on the tissue. However, it remains unclear what effects may occur with continued stimulation over longer period. + +28. The 2-week histological analysis of cardiac tissue with a hydrogel-based thera-gripper, as presented in the study, raises questions. It would be insightful to know the condition of the device after this period - whether the device remained in an operable state and the device remained properly attached as intended while withstanding repeated pulsations. + +\*Minor comments + +1. Caption in figure S11 (a) : AgNW/PI -> AgNW/PDMS +2. Page 21, the third line from the bottom spelling error : PINPAM -> PNIPAM +3. Figure S51D, indication spelling error : Basi -> Basic +4. There should be a space before the units in the text and figures. + +<--- Page Split ---> + +## Responses to comments of Referee #1 + +Comments from Referee #1: + +Summary Comment: The article entitled "Skin- inspired, sensory robots for electronic implants" by Zhang et al. introduces an approach for soft robots that can sense multiple parameters and provide on- demand motions. Although the proposed concept would be useful for the development of associated technologies, there are many questionable issues and experimental shortcomings that should be addressed before further progress. The authors need to check the overall figures again. The order of the figures in the manuscript is a total mess. Also, there is so much information about SI that it is very difficult to understand the main text or what the author is trying to say. All unnecessary SI should be discarded, and only the content that is directly related to the key points should be mentioned. + +Our response: We thank the reviewer for these positive comments and for these helpful suggestions for revision. We carefully addressed the issues, as listed below, and revised our manuscript accordingly. + +Modification to the manuscript: We have modified both the manuscript and supporting information based on the reviewer's concerns and suggestions. + +Comment 1: The authors demonstrated the adhesion performance of the bio- adhesive layer using the bending image in Figure 3B, but this referee can't find any quantified data set of the adhesion force, did the authors studied how strong it is under various conditions? (e.g. dry, wet environments, etc). + +Our response: We appreciate the reviewer's comment regarding the lack of quantified data on the adhesion performance of the bio- adhesive layer. We have conducted \(180^{\circ}\) peeling tests under both dry and moist environments at physiological temperature \(\sim 37^{\circ}C\) . + +![](images/Figure_unknown_1.jpg) + + +<--- Page Split ---> + +Fig. R1. Interfacial adhesion characterization via peeling tests. (A) Adhesive force- displacement curves and (B) calculated interfacial energy from the \(180^{\circ}\) peeling test of the biodegradable layer interacting with hydrogel. The adhesion force is higher under a moist condition, mimicking the human body environment, favorable for potential implantable biomedical device applications. + +Fig. R1 presents that the bio- adhesive layer maintains robust adhesion in both dry and wet conditions. Notably, the adhesion force shows an enhancement in a moist condition that simulates the internal human body environment. This enhancement is likely due to the hydrophilic nature of the hydrogel and adhesive, which forms additional hydrogen bonds in the presence of moisture. Such behavior is advantageous for implantable devices that must maintain reliable adhesion in the moist internal conditions of the human body. We have clarified these points in the revised manuscript and supporting information, providing a clearer view of the bio- adhesive layer's performance. + +## Modification to the manuscript: + +(1) On page 26, in the revised supporting information, we added Fig. R1 as Fig. S15. + +(2) On page 9, in the revised manuscript, we added, "Importantly, the bio-adhesive layer exhibits robust adhesion under both dry and wet conditions, as displayed in Fig. S16. This feature ensures the reliability of implantable devices in the dynamic and moist human body environment." + +(3) On page 28, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +Comment 2: While the thickness of other layers was specified, the actuation hydrogel's thickness was missing (it seems to be considerably thick). Increase of the thickness might enhance actuation performance but could potentially affect sensing and stimulation properties. + +2- 1) What is the optimal thickness of the actuation layer for achieving reliable shape- morphing? + +2- 2) How does the thickness of the actuation layer affect sensing and stimulation performance? + +Our response: We thank the reviewer's comment regarding the thickness of the actuation hydrogel layer and its potential impact on the device's performance. We have conducted a series of experiments to investigate the effects of the actuation layer's thickness on both actuation performance and its interplay with sensing and stimulation functionalities. + +2- 1) Optimal thickness for shape- morphing: + +Our investigation reveals that thicker hydrogel layers exhibit more pronounced shape morphing at a given activation temperature, but with a slower response rate due to + +<--- Page Split ---> + +increased mass, as shown in Fig. R2A. Correspondingly, these thicker layers generate greater forces, enhancing actuation performance. However, this comes at the cost of increased overall device volume, which may not be ideal for minimally invasive applications where compactness is crucial. Our approach can tailor the hydrogel layer's thickness based on specific application requirements, highlighting our fabrication method's versatility. + +![](images/Figure_unknown_2.jpg) + +
Fig. R2. Effect of hydrogel thickness on actuation performance. (A) Bending angle over time for varying hydrogel thicknesses at \(41^{\circ}C\) . (B) Measured static force changes at \(41^{\circ}C\) across different hydrogel thicknesses. (C) Resistive response of a thermal sensor (ERT-J0ET102H) across a temperature range of \(22^{\circ}C\) to \(60^{\circ}C\) for different hydrogel thicknesses.
+ +2- 2) Clarification on sensing and stimulation performance: + +In our design, the sensors are embedded in a distinct sensing layer and this design strategy ensures that modifications to the thickness of the hydrogel actuation layer are primarily focused on optimizing actuation performance without affecting the sensitivity or functionality of the sensing and stimulation elements. To experimentally validate this design principle, we conducted a series of experiments focusing on the performance of temperature sensors embedded within hydrogel layers of varying thicknesses. These results indicate no significant difference in sensor performance across different hydrogel thicknesses, further supporting our design strategy. + +## Modification to the manuscript: + +(1) On page 31, in the revised supporting information, we added Fig. R2 as Fig. S20. + +(2) On pages 10-11, in the revised manuscript, we added, "Moreover, our study demonstrates that the thickness of the hydrogel layer determines the actuation performance of the device. As depicted in Fig. S20A, thicker hydrogel layers induce more pronounced shape morphing at a set activation temperature, while a slower response due to their increased mass. The thicker layers are also capable of generating higher actuation force, thereby enhancing the actuation capability of the device (Fig. S20B). However, the increased device volume may limit its applicability in minimally invasive implantable devices, where compactness is a key factor. In the device configuration, embedded sensors are strategically positioned within a single, thin e-skin layer, thus minimizing the required thickness of the hydrogel layer for efficient actuation and allowing + +<--- Page Split ---> + +the integrated system to be relative compact (Fig. S20C). Our fabrication technique accommodates customization of the hydrogel layer thickness to optimize device performance for specific applications, demonstrating the method's flexibility and adaptability to various biomedical needs. The utilization of a RGO/PI- nanocomposite temperature sensor enables to precisely identify the real- time information of temperature during muscle motion." + +Comment 3: In Figure 3N, bending configurations appear to be different and uncontrollable although three arms had the same composition. Can the authors explain why? And, it seems those arms are not reversible since the off- arms don't seem to return to the original state. + +Our response: We appreciate the reviewer's comment regarding the bending configurations in Fig. 3N. Despite the uniform material composition of the three arms, slight variations in environmental conditions during the actuation process such as minor differences in temperature and hydrogel thickness contributed to the non- uniform bending behavior. In addition to the factors already mentioned, the design embedded thermal heaters could also influence the bending behavior of each arm. The embedded heater on e- skin generates temperature control and causes the hydrogel's expansion and contraction. Consequently, the slight differences in the positioning and embedding depth of these heaters can cause variability in bending configurations. We have explained this phenomenon in the revised manuscript. + +Regarding reversibility, we would like to provide further clarification. Our experiments (Fig. S5B, and Fig. S7- S9) indicate that the recovery phase indeed requires a longer duration than the actuation process. This phenomenon is common in many smart materials. As shown in Fig. 3N, the observed variation in recovery rates of the arms back to their original shapes is directly related to the sequence and timing of their activation. Importantly, given sufficient time for recovery, our experiments have consistently shown that the arms can return to their original state (Fig. S7- S9). + +## Modification to the manuscript: + +On page 11, in the revised manuscript, we added, "Here, the observed variability in bending configuration can be attributed to differences in the positioning and depth of the functional modules within the e- skin layer." + +Comment 4: In Figure 4A, there might be stability issues with the PAAM hydrogel as a pressure sensor. Considering the implant environment, swelling of the hydrogel might hinder pressure measurement due to instability in weight loss and capacitance changes. Any proposed solutions to address this concern would be necessary. + +Our response: We appreciate the reviewer's comment on the stability challenges with the use of PAAM hydrogel as a pressure sensor within an implant environment. To address concerns about hydrogel swelling affecting pressure measurement stability, we propose two strategic solutions. First, we suggest the integration of a protective + +<--- Page Split ---> + +encapsulation layer around the hydrogel to mitigate the effects of swelling and environmental fluctuations. This encapsulation layer would be designed to be permeable enough to allow for pressure transmission while minimizing direct hydrogel exposure to body fluids that could cause excessive swelling. Secondly, optimizing the hydrogel synthesis recipe (e.g., increasing crosslinker density) to reduce its sensitivity to swelling without compromising its pressure- sensing capabilities. These measures are capable of enhancing the stability and reliability of the hydrogel as a pressure sensor within the implantable environment. We have discussed the possible solutions regarding the future implantable application in the revised manuscript. + +## Modification to the manuscript: + +On page 29, in the revised manuscript, we added, "Here, to mitigate potential stability issues regarding hydrogel swelling and its impact on pressure sensing, we propose two mitigation solutions. Firstly, we incorporate a protective encapsulation layer around the hydrogel. This layer is engineered to be permeable enough to facilitate pressure transmission while simultaneously shielding the hydrogel from direct exposure to body fluids that may induce excessive swelling. Secondly, we refine the hydrogel's composition by increasing the crosslinker concentration to diminish swelling sensitivity without impairing the hydrogel's ability to sense pressure. By applying these strategies will enhance the stability of the hydrogel as a pressure sensor for implantable applications." + +Comment 5: The authors discussed the adhesion and actuation force of the hydrogel in Fig. S46, Supplementary Note S8. However, it seems to be considered in a dry environment. Given the nature of hydrogels, there might be swelling and degradation issues when operating in a wet environment. + +Our response: We appreciate the reviewer's comment on the potential swelling of the hydrogel in our device, especially when exposed to a wet environment. The primary objective of our characterization was to understand the baseline mechanical properties and actuation capabilities of hydrogel. Hydrogels, by their nature, are highly responsive to environmental conditions, particularly moisture. However, PNIPAM hydrogel exhibits a thermal- responsive property. Once the external temperature exceeds its LCST, the hydrophobic interaction of the isopropyl group dominates, leading to a conformational transition from coil to globule. This process causes the water inside to be squeezed out, resulting in the volumetric shrinkage of the system (Fig. R3A). The temperature- induced molecular structural change significantly impacts the hydrogel's shape morphing and actuation force (Fig. R3B&C), far more than minor humidity variations typical of human body environments. Therefore, this rationale underpins our decision to not specifically investigate the hydrogel's actuation behavior in wet environments. Our investigations are thus aligned with understanding how temperature variations, rather than moisture changes, influence the actuation capabilities essential for the intended applications of our device. + +<--- Page Split ---> +![](images/Figure_unknown_3.jpg) + +
Fig. R3. Actuation behavior of bilayer soft robots under ambient conditions. (A) Measured volume shrinkage of PNIPAM hydrogel during a heating process with temperature changing from \(25^{\circ}C\) to \(60^{\circ}C\) . (B) The resultant bending angle \(\theta\) of a soft robotic arm as a function of the input electric power. (C) Measured static force changes of the soft robotic finger under different temperatures induced by different electrical powers.
+ +In response to the reviewer's note on adhesion and actuation force evaluations potentially occurring in dry conditions, we wish to clarify that our bioadhesive behavior assessments were conducted under simulated physiological conditions. All samples were incubated overnight to ensure a representative in vivo environment is achieved, maintaining the integrity of tissue/organ surfaces for accurate assessment (Fig. R4). This approach ensures a thorough evaluation of the hydrogels' performance, including their reaction to swelling and degradation, under conditions that closely emulate their intended operational environment. + +![](images/Figure_unknown_4.jpg) + +
Fig. R4. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \(36^{\circ}C\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this
+ +<--- Page Split ---> + +threshold. All tests were conducted after overnight incubation simulating physiological conditions at \(34^{\circ}\mathrm{C}\) , \(37^{\circ}\mathrm{C}\) , and \(40^{\circ}\mathrm{C}\) . Scale bars, 5 mm. + +## Modification to the manuscript: + +(1) On pages 5-6, in the revised manuscript, we modified, "The PNIPAM hydrogel can undergo a dramatic volumetric reduction of about \(90\%\) as the temperature shifts from 25 \(^\circ \mathrm{C}\) to \(60^\circ \mathrm{C}\) . Notably, this significant and rapid deswelling behavior is initiated only when temperature is beyond its LCST (32 \(^\circ \mathrm{C} \sim 34^\circ \mathrm{C}\) ), enabling excellent actuation capabilities within biological environments (Fig. S3A&B, and Fig. 2H)." + +(2) On page 29, in the revised supporting information (Fig. S19's caption), we added, "Here, all characterizations were conducted under ambient conditions because of the unique temperature-responsive nature of the PNIPAM hydrogel. Its actuation force and shape morphing capabilities are predominantly influenced by temperature-induced molecular structural changes, rather than slight humidity changes typical in human body environments. This characteristic underlines the hydrogel's efficacy in translating thermal stimuli into mechanical actions, essential for the intended biomedical applications." + +(3) On page 52, in the revised supporting information, we added Fig. R4 as Fig. S40. + +(4) On page 21, in the revised manuscript, we added, "We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature-responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +(5) On page 28, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +## Reference + +Y. Jiang, A.A. Trotsyuk, S. Niu, D. Henn, K. Chen, C.C. Shih, M.R. Larson, A.M. Mermin-Bunnell, S. Mittal, J.C. Lai, A. Saberi, E. Beard, S. Jing, D. Zhong, S.R. Steele, K. Sun, T. Jain, E. Zhao, C.R. Neimeth, W.G. Viana, J. Tang, D. Sivaraj, J. Padmanabhan, M. Rodrigues, D.P. Perrault, A. Chattopadhyay, Z.N. Maan, M.C. Leeolou, C.A. Bonham, S.H. Kwon, H.C. Kussie, K.S. Fischer, G. Gurusankar, K. Liang, K. Zhang, R. Nag, M.P. Snyder, M. Januszyk, G.C. Gurtner, Z. Bao, Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +<--- Page Split ---> + +Comment 6: In Figures 5 and S47, the hydrogel was designed to face biological tissue (please correct me if not). In this case, some of physical sensors (e.g., strain and pressure gauges) would be fine, but how to figure out operation of other sensors/stimulators that need direct contacts to tissues? For example, the authors mentioned here electrical stimulation for the bladder, but is it possible to stimulate the bladder through the adhesive layer and PAAM hydrogel? That would be not. Can the authors explain how to achieve such functional operations? + +Our response: We thank the reviewer's comment regarding the configuration of soft robotic gripper for bladder control. Here, regarding the concerns about the operation of stimulators that require direct tissue contact, we would like to clarify the design of our stimulator module. + +This stimulator module utilizes gold (Au) electrodes that are specially designed to establish direct contact with bladder tissue, as shown in Fig. R5. This direct contact is critical for the effective delivery of therapeutic interventions, such as electrical stimulation for bladder control. Moreover, even in instances where minor gaps might exist at the interface, body fluids naturally act as a conductive bridge, ensuring efficient electrical stimulation. + +The hydrogel component of our device is applied primarily to the device's arms for actuation purposes, which is intentionally designed not to interfere with the stimulator module's direct tissue contact (Fig. R5B). We have clarified this point in revised supporting information, aiming to offer clearer insights into the device's design and its capability for direct tissue engagement through the simulator module. + +![](images/Figure_unknown_5.jpg) + +
Fig. R5. Soft robotic gripper for monitoring bladder volume. (A) Exploded view of the soft robotic finger including actuator, sensor and stimulator components. (B) Detailed schematic illustration for the soft robotic finger, highlighting the direct tissue contact by the stimulation electrode (indicated with a red dashed line). Here the hydrogel actuators are intentionally positioned on the device's arms, marked by the blue lines, ensuring that they do not hinder the electrodes' direct engagement with the tissue, facilitating efficient electrical stimulation.
+ +## Modification to the manuscript: + +(1) On page 44, in the revised supporting information, we added Fig. R5B as Fig. S33B. + +<--- Page Split ---> + +(2) On page 44, in the revised supporting information, we modified the Fig. S33A&B's captions, "(A) Schematic illustration showing exploded layout of the soft robotic gripper that incorporates actuator, sensor and stimulator components. The actuation component includes a passive layer made of an Au/PI bilayer with heat functionality, and an active layer of PNIPAM hydrogel. The sensing component includes an elastic poly(acrylamide) (\~PAAm) hydrogel film and a serpentine Au/PI resistor to form a buckled strain sensor. The stimulator component is two pairs of pacing electrodes, employing Au for its exceptional electrical conductivity, biocompatibility, and stability in biological settings. (B) Detailed schematic illustration for the soft robotic finger, highlighting the direct tissue contact by the stimulation electrode (indicated with a red dashed line). Here the hydrogel actuators are intentionally positioned on the device's arms, marked by the blue lines, ensuring that they do not hinder the electrodes' direct engagement with the tissue, facilitating efficient electrical stimulation." + +Comment 7: In Figure 5g, it is unclear what the author intended to demonstrate through the programming. Can the authors provide significance of the programming for the control of the bladder. (It is quite strange that E- stim ON when the bladder is void, and E- stim OFF after expansion/contraction cycle... Shouldn't it turn on when the volume reaches maximum?). + +Our response: We thank the reviewer's comment regarding the programming strategy depicted in Fig. 5G, particularly concerning the application of electrical stimulation (E- stim) in bladder control. Our soft robotic device integrates bladder volume sensing with E- stim to offer a targeted treatment modality for underactive bladder. This strategy aligns with recent advances in bioengineering and medical devices, aiming to offer more personalized treatments for patients with urinary disorders. + +Indeed, our programming logic operates as the reviewer has anticipated: The E- stim is activated when the bladder volume surpasses a predefined threshold, set here at 100 mL, targeting the bladder muscles to facilitate urination. Once the bladder empties to below the threshold, indicating successful voiding, the system automatically deactivates the E- stim. Here, a slight delay in turning off was observed which could partially be attributed to the response time for the microcontroller unit (MCU) system to pick up the sensory change and update the output value. This programming cycle ensures that stimulation is provided only, when necessary, closely mimicking the natural urination process and enhancing patient comfort and device efficiency. + +It appears that the reviewer's confusion may be due to the unclear labeling in Fig. 5G. To ensure better clarity, we have revised the labels as shown in Fig. R6 and enhanced the explanation in the manuscript. + +<--- Page Split ---> +![](images/Figure_unknown_6.jpg) + +
Fig. R6. A robotic gripper for bladder control. Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly.
+ +## Modification to the manuscript: + +(1) On page 20, in the revised manuscript, we added Fig. R6 as Fig. 5G. + +(2) On page 21, in the revised manuscript, we modified the figure caption of Fig. 5G, "Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly." + +(3) On page 18, in the revised manuscript, we added, "When the balloon's volume reaches a predetermined threshold, set here at 100 mL, the control system initiates electrical stimulation. Following successful voiding to below the threshold, the system automatically deactivates the stimulation. While electrical stimulation has shown promising results in enhancing bladder control in various studies and clinical trials, its efficacy can differ across individuals. The effectiveness of electrical stimulation for bladder voiding and its required voltage levels requires further investigation beyond the scope of our current study. However, our prototype showcases the potential of integrating + +<--- Page Split ---> + +sensing and actuation mechanisms to facilitate timely and adaptive interventions for bladder dysfunction." + +## References + +Grill, W. M. Electrical stimulation for control of bladder function. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 2009 2369- 2370 (2009) doi:10.1109/IEMBS.2009.5335001. + +Coolen, R. L., Groen, J. & Blok, B. F. M. Electrical stimulation in the treatment of bladder dysfunction: Technology update. Med. Devices Evid. Res. 12, 337- 345 (2019). + +Comment 8: In Figs. 6 and S52A, it appears difficult or impossible for the electronic components at the end of each arm to form a strong coupling to living tissues, particularly to tissues whose volume changes over time, such as the bladder. How did the authors control or attach the robotic arms? + +Our response: We thank the reviewer's comment regarding the integration of electronic components at the end of each robotic arm with living tissues, especially those that undergo volume changes such as bladder. + +Our design employs a multilayer fabrication approach, incorporating a layer of PNIPAM hydrogel. The inherent thermos- responsive property of PNIPAM hydrogel enables our device to dynamically adapt to the body's natural thermal environment. This shape adaptability ensures that our soft robotic devices maintain a stable and effective interface with living tissues, seamlessly accommodating volumetric changes without compromising contract or functionality (Fig. R7A). + +![](images/Figure_unknown_7.jpg) + +
Fig. R7. shape conformability of soft robotic devices with biological tissues/organs. (A) Measured static force changes of the soft robotic finger under different temperatures. (B) Adhesion strength of a PNIPAM-co-PAAm hydrogel with an LCST of 36 °C across different temperatures.
+ +In addition, the inherent adhesiveness of the hydrogel layer significantly enhances the device's ability to securely couple with tissue surfaces. Upon deformation and subsequent + +<--- Page Split ---> + +contact with tissue, this adhesiveness strengthens the coupling between the device and the tissue, ensuring a strong attachment even as the tissue undergoes volumetric changes, thereby preserving the functional integrity of the device's functional modules (Fig. R7B). + +![](images/Figure_unknown_8.jpg) + +
Fig. R8. in vivo validation of a soft robotic gripper for epicardial sensing and pacing. (A) Image of a soft robotic thera-gripper grasping on the epicardial surface of a living mouse heart. Scale bar, \(5 \text{mm}\) . (B) Temperature measurements from the thera-gripper during its deployment onto the mouse heart. (C) The surface ECG trace during electrical stimulation using a pair of Au pacing electrodes. (D) Representative measurements of local cardiac contractions using a soft robotic thera-gripper wrapping onto a living mouse heart.
+ +Furthermore, as demonstrated in Fig. R8, our device has successfully detected key physiological parameters, including heart rate, contractile ability, and temperature variations, and effectively provided electrical stimulation. These findings not only showcase the device's operational capabilities but also confirm the effective coupling contact between the device and the living tissues/organs. + +## Modification to the manuscript: + +(1) On page 10, in the revised manuscript, we modified, "Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar + +<--- Page Split ---> + +hydrogel- based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +(2) On page 52, in the revised supporting information, we added Fig. R7B as Fig. S40B. + +(3) On pages 21-22, in the revised manuscript, we added, "Additionally, our device offers versatile adaptability for diverse application scenarios through customizable dimensions, sensor positioning, and geometric layouts, ensuring it aligns with the unique morphologies and functional demands of targeted tissues/organs. This flexibility is essential for enabling minimally invasive deployment. As illustrated in Fig. S38&S39, Table S2, and Supplementary Note S6, the design's adaptability enhances soft robotic technologies for effective integration in a broad spectrum of biomedical applications. We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature-responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +(4) On page 28, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +## Reference + +Y. Jiang, +A.A. Trotsyuk, +S. Niu, +D. Henn, +K. Chen, +C.C. Shih, +M.R. Larson, +A.M. Mermin-Bunnell, +S. Mittal, +J.C. Lai, +A. Saberi, +E. Beard, +S. Jing, +D. Zhong, +S.R. Steele, +K. Sun, +T. Jain, +E. Zhao, +C.R. Neimeth, +W.G. Viana, +J. Tang, +D. Sivaraj, +J. Padmanabhan, +M. Rodrigues, +D.P. Perrault, +A. Chattopadhyay, +Z.N. Maan, +M.C. Leeolou, +C.A. Bonham, +S.H. Kwon, +H.C. Kussie, +K.S. Fischer, +G. Gurusankar, +K. Liang, +K. Zhang, +R. Nag, +M.P. Snyder, +M. Januszyk, +G.C. Gurtner, +Z. Bao, Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +Comment 9: Page 3, line 86 It is not 'overactive', but 'underactive' bladder. + +Our response: We appreciate the reviewer's comment. + +## Modification to the manuscript: + +On page 3, in the revised manuscript, we have corrected "overactive" to "underactive". + +Comment 10: In fig. 2c, is there a motivation for using such diverse materials for different components? This referee can't find outstanding characteristics of those materials for sensing components. + +<--- Page Split ---> + +Our response: We appreciate the reviewer's comment regarding the selection of diverse materials for different components as depicted in Fig. 2C and the aims behind their use in sensing components of our soft robots. + +The motivation for utilizing a variety of materials in our device lies in mimicking the hierarchical structures and functionalities of biological systems, such as skin and muscle. Here, we highlight the integration of multi- electronic modules and thermally actuated hydrogels within a single platform. This integration enables our soft robotic devices to not only perform receptor- like sensing functions for detecting various stimuli but also exhibit muscle- like contractions for generating physically adaptive motion, thereby endowing the soft robotic devices with the capabilities to autonomously navigate complex environments. + +The selection of materials for the flexible composite layer is driven by the need to fabricate a multi- modal electronic skin (e- skin) that incorporates distinct sensors (e.g., strain, pressure, pH, and temperature sensors) and stimulators (thermal and electrical). Each chosen material contributes both individual properties and a synergistic effect to enhance the overall functionality of the system. For instance, AgNWs provide excellent conductivity and flexibility, making them ideal for wearable sensors. Graphene stands out for its high surface area, electrical conductivity, and mechanical strength, enhancing sensitivity and selectivity in biosensing applications. Meanwhile, MXene offers high conductivity and hydrophilicity, making it an advantageous choice for biosensor interfaces. \(^{1 - 4}\) Through such strategic material integration, we ensure our soft robotic devices can be well equipped to sensitively and accurately perceive and interact their surroundings. + +Moreover, the diversity of materials showcases the versatility of our solution- based method, enabling the integration of a wide range of advanced functional materials. Such versatility surpasses the capabilities of 3D printing or other traditional fabrication methods \(^{5 - 7}\) , allowing us to engineer devices via fine- tuning each component's properties to specific functional needs, and optimizing the performance and utility of our soft robotic systems. + +## Modification to the manuscript: + +On pages 6- 7, in the revised manuscript, we modified, "Furthermore, compared with a make- and- transfer method, our in situ solution- based fabrication approach enables the seamless integration of sensors into the e- skin matrix in a single step, enhancing mechanical and electrical performance by reducing interfacial resistances and improving mechanical conformity, thereby significantly improving sensitivity and responsiveness. This approach also offers a versatile platform that can be constructed using a broad range of functional nanomaterials hybridized with a polymeric matrix to form a multi- modal sensing system. By selecting materials that offer unique functional attributes, from AgNWs known for their conductivity and flexibility to graphene and MXene for their high surface area, electrical conductivity, and hydrophilicity, this system can emulate the skin with complex somatosensory system, where various mechanoreceptors and thermoreceptors distributed in the epidermal and dermal layers enable the spatiotemporal recognition of the magnitude and location of touch and temperature stimuli." + +<--- Page Split ---> + +## References + +ReferencesBasarir, F., Madani, Z. & Vapaavuori, J. Recent Advances in Silver Nanowire Based Flexible Capacitive Pressure Sensors: From Structure, Fabrication to Emerging Applications. Adv. Mater. Interfaces 9, (2022).Chauhan, N., Maekawa, T. & Kumar, D. N. S. Graphene based biosensors - Accelerating medical diagnostics to new- dimensions. J. Mater. Res. 32, 2860- 2882 (2017).Amara, U., Hussain, I., Ahmad, M., Mahmood, K. & Zhang, K. 2D MXene- Based Biosensing: A Review. Small 19, 1- 38 (2023).Driscoll, N. et al. MXene- infused bioelectronic interfaces for multiscale electrophysiology and stimulation. Sci. Transl. Med. 13, eabf8629 (2021).Liu, H. et al. 3D Printed Flexible Strain Sensors: From Printing to Devices and Signals. Adv. Mater. 33, 2004782 (2021).Zhu, Z., Park, H. S. & McAlpine, M. C. 3D printed deformable sensors. Sci. Adv. 6, eaba5575 (2023).Reeder, J. et al. Mechanically Adaptive Organic Transistors for Implantable Electronics. Adv. Mater. 26, 4967- 4973 (2014). + +Comment 11: In figs. 2f and 2g, the authors claimed that soft robots can form conformal contacts to tissues, but did the authors study or compare mechanical modulus between devices and tissues? + +Our response: We thank the reviewer's comment concerning the mechanical compatibility of our soft robotic devices with biological tissues, as shown in Fig. R9A (Fig. 2F) and Fig. R9B (Fig. 2G). We employ a multilayer design mimicking the relation between human skin and skeletal muscle to integrate the e- skin layer with an artificial muscle layer composed of PNIPAM- based hydrogel. This hydrogel layer, designed for direct tissue interface, is critical in our device's architecture. + +In choosing materials for our device, especially those designed for implantable biomedical applications, our priorities are biocompatibility and the mechanical softness, essential for effective tissue integration. Hydrogels, exhibiting the above- mentioned properties, are ideally suitable for our application in implantable devices. Compared to other smart materials such as shape memory polymers and alloys, which exhibit the elastic moduli (E) in the order of several megapascals (MPa) \(^8\) , hydrogels have an elastic modulus ranging from 1- 100 kPa. This range is notably similar to that of soft tissues, which typically exhibit E from a few kPa to hundreds of kPa \(^9\) . Specially, the PNIPAM hydrogel in our research exhibited an E \(\sim 1.2\) kPa, as shown in Fig. R9C. This mechanical similarity facilitates a more seamless integration with surrounding tissues and minimizes the potential damage from mechanical mismatch \(^{10}\) . + +<--- Page Split ---> +![](images/Figure_unknown_9.jpg) + +
Fig. R9. Mechanical properties of PNIPAM hydrogel. (A&B) Optical image showing conformal attachment of the soft sensory robot onto human skin (A) and porcine tissue (B) with high mechanical compliance. (C)Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness 4mm, width 10mm, initial length 15mm), highlighting an elastic modulus (E) of \(\sim 1.2\) kPa. This value is within the range of soft tissues, which typically exhibit an E from a few kPa to hundreds of kPa, ensuring the hydrogel's compatibility with biological tissues and reducing risks associated with mechanical mismatches.
+ +## Modification to the manuscript: + +(1) On page 13, in the revised supporting information, we added Fig. R9C as Fig. S3C. (C)Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness 4 mm, width 10 mm, initial length 15 mm), highlighting an elastic modulus (E) of approximately 1.2 kPa. This value is within the range of soft tissues, which typically exhibit an E from a few kPa to hundreds of kPa, ensuring the hydrogel's compatibility with biological tissues and reducing risks associated with mechanical mismatches. + +(2) On page 6, in the revised manuscript, we modified, "The as-fabricated soft robot can form a highly conformal interface with diverse biological surfaces, indicating its inherent mechanical softness and high biocompatibility. This adaptability minimizes potential risks related to mechanical incompatibility, facilitating its smooth integration with targeted tissues/organs (Fig. 2F&G, and Fig. S3C)." + +(3) On page 28, in the revised manuscript, we added, "Mechanical tests were conducted on rectangular-shape specimens with the dimensions of 10 mm in width, 2 mm in thickness, and 16 mm in length) using the Instron machine (Mark-10 ESM303)." + +## References + +Czerner, M., Fellay, L. S., Suárez, M. P., Frontini, P. M. & Fasce, L. A. Determination of Elastic Modulus of Gelatin Gels by Indentation Experiments. Procedia Mater. Sci. 8, 287- 296 (2015). + +<--- Page Split ---> + +Xie, C., Wang, X., He, H., Ding, Y. & Lu, X. Mussel- Inspired Hydrogels for Self- Adhesive Bioelectronics. Adv. Funct. Mater. 30, 1909954 (2020). + +Comment 12: In fig. S12B, such layered structures are likely to interfere with each other's signals. Is there any reason to measure both parameters at the same time? Or, even if simultaneous measurements are made, does each sensor operate independently? + +Our response: We thank the reviewer's comment regarding the potential for signal interference in the layered structures as shown in Fig. S12B (Fig. S11B in the updated supporting information). + +As shown in Fig. S11B, we employed a dual- transfer printing method to fabricate the functional modules located in different layers. This strategy allows for the integration of a minimal amount of polyimide with functional materials to form composite functional modules. This not only preserves the functional integrity of the materials within each module but also leverages the remaining polyimide to serve as a dual purpose. Beyond its inclusion in the composite, polyimide acts as an insulating barrier between adjacent modules. This barrier is crucial for our device's functionality, as it prevents electrical and chemical signal interference between modules, thereby ensuring that each functional module operates independently and as intended. + +The primary purpose of measuring multiple parameters simultaneously is to showcase the multifunctional capabilities of our solution- based approach, which closely mimicking the complex functionality of natural model (e.g., human skin), enabling the device to perform concurrent sensing operations. By demonstrating the device's ability to interact comprehensively with its environment, we not only highlight its potential for various applications but also validate our fabrication method's versatility in fabricating multifunctional e- skin. This strategy surpasses conventional fabrication methods like 3D printing, offering new possibilities for advancements in robotics, wearable technologies, and biomedical devices. + +Moreover, each functional module operates independently even during simultaneous measurements. As aforementioned, the integration of a polyimide layer between modules, serves as an effective barrier against any potential signal interference, ensuring that despite the simultaneous operation of multiple sensors, each module retains its individual functionality and delivers accurate, independent measurements. + +## Modification to the manuscript: + +On page 7, in the revised manuscript, we modified, "Fig. 2M displays a more complicated integration paradigm with multi- layer stacking, where different electronic components (e.g., PEDOT:PSS/PI- based conductive electrodes and RGO/PI temperature sensors) can be distributed in different layers of the e- skin to achieve simultaneous functional versatility and compactness. This assembly technique ensures the e- skin remarkable thinness and flexibility, enhancing its effective performance and seamless integration in implantable applications (Fig. S11B). The X- ray photoelectron spectroscopy (XPS) characterization on the e- skin layers reveals the precise nanoscale integration of active + +<--- Page Split ---> + +materials within a polymer matrix, as detailed in Fig. S12- S14 and Supplementary Note S1. It showcases the optimal distribution and intermolecular bonding of the composite components, effectively addressing the common challenge of uneven dispersion of nanomaterials, which usually undermines the performance of conventional composites. Our approach minimizes the polymer amount required to integrate nanomaterials into composite functional modules and utilizes excess polymer as an insulating layer to separate modules, preventing interference between their electrical and chemical signals, thereby ensuring that each functional module operates independently and effectively. This approach harmoniously combines the distinct properties of each constituent, achieving a balance between structural integrity and functional versatility. This advanced level of integration would be of great value for soft robots that seek to achieve multifunctionality and local sensing capabilities approaching skin." + +Comment 13: there's no description for Figs. 3H&3I. + +Our response: We thank the reviewer's comment regarding Fig. 3H&3I. We have added detailed descriptions for both figures. + +## Modification to the manuscript: + +On page 11, in the revised manuscript, we added, "Fig. 3H illustrates the resistive change in a relatively linear relation with temperature for the RGO/PI thermal sensor. The temperature coefficient of the resistance (TCR) of the RGO/PI thermal sensor is \(>0.5\% /^{\circ}\mathrm{C}\) , featuring its high thermal sensitivity. On the other hand, the RGO/PI- based thermal sensor exhibits a stable performance after 1000 bending cycles, and even after immersing in PBS solution. Fig. 3I and Fig. S21F show performance of the thermal sensor in response to cycles of temperature rise and drop, indicating good sensing stability." + +Comment 14: We usually do not include information about SI figures in main figure captions. For example, in fig.3, there is information about fig. S18 and 25, but these should be removed. + +Our response: We thank the reviewer's comment. We have removed these SI figures from the main figure captions based on reviewer's advice. + +## Modification to the manuscript: + +We have updated figure captions in the revised manuscript. + +Comment 15: Please do double check all the figures including SI, whose order is a total mess. + +Our response: We appreciate the reviewer's comment to help us significantly enhance the clarity and coherence of our manuscript. We have conducted a thorough review and reorganization of all figures and supplementary information to ensure a logical flow and clear presentation throughout our submissions. + +<--- Page Split ---> + +Modification to the manuscript: We have reorganized and updated all supplementary figures for clarity. + +<--- Page Split ---> + +## Responses to comments of Referee #2 + +Comments from Referee #2: + +Summary Comment: Lin Zhang et al. developed various types of soft robots, utilizing an electronic skin (e- skin) made of materials like silver nanowires, reduced graphene oxide, MXene, and conductive polymers integrated into a polymer matrix. This e- skin is designed to mimic skin receptors, enabling the perception of various stimuli. The robots, inspired by natural forms like starfish, chiral seedpod, and others, are equipped with features for bending, twisting, and expanding, and include an artificial muscle for dynamic movement. This study also integrated wireless modules to control and communicate without tethering. Demonstrated in various medical scenarios, these devices showed capabilities such as blood pressure sensing and adapting to organ surfaces for diagnostic and therapeutic functions, exemplifying their potential as multifunctional, minimally invasive medical tools. However, the devices used materials commonly used in practical applications, with the exception of an in situ solution- based fabrication approach, showing no significant material novelty. This article also lacks either long- term feasibility or detailed information about the mechanism of each sensor like the relationships between pH, pressure and resistance. Despite such some disadvantages, the positive aspect lies in its multifunctional ability to be implanted in real scenarios, possibly leading to successful demonstrations for various organ shapes. In specific, massive integration of multifunctional soft robots entailing high- performance functional nanomaterials and actuating modules is highly impressive. Additionally, this article demonstrates a high level of systemic completeness, considering real clinical situations. Therefore, the reviewer believes that with some modifications addressing specific comments included in the following, this paper has the potential to be accepted in Nature Communications. + +Our response: We thank the reviewer for these positive comments and for these helpful suggestions for revision. We carefully addressed the issues, as listed below, and revised our manuscript accordingly. + +Modification to the manuscript: We have revised both the manuscript and supporting information based on the reviewer's concerns and suggestions. + +Comment 1: In the introduction part, some references (Nature Materials volume 15, pages937- 950 (2016), Nature Nanotechnology volume 9, pages397- 404 (2014), and Nature Electronics volume 6, pages779- 789 (2023)) regarding stable tissue- interfacing performance of wearable/implantable devices should be cited to justify the authors' research purpose. + +Our response: We thank the reviewer's suggestion. We have carefully integrated the recommended references into the introduction section. + +Modification to the manuscript: + +<--- Page Split ---> + +On page 2, in the revised manuscript, we have cited all suggested references. + +## References + +D. Son, +J. Lee, +S. Qiao, +R. Ghaffari, +J. Kim, +J.E. Lee, +C. Song, +S.J. Kim, +D.J. Lee, +S.W. Jun, +S. Yang, +M. Park, +J. Shin, +K. Do, +M. Lee, +K. Kang, +C.S. Hwang, +N. Lu, +T. Hyeon, +D.H. Kim, Multifunctional wearable devices for diagnosis and therapy of movement disorders, Nat. Nanotechnol. 9 (2014) 397-404. https://doi.org/10.1038/nnano.2014.38. + +A. Chortos, +J. Liu, +Z. Bao, Pursuing prosthetic electronic skin, Nat. Mater. 15 (2016) 937-950. https://doi.org/10.1038/nmat4671. + +H. Choi, +Y. Kim, +S. Kim, +H. Jung, +S. Lee, +K. Kim, +H.S. Han, +J.Y. Kim, +M. Shin, +D. Son, Adhesive bioelectronics for sutureless epicardial interfacing, Nat. Electron. 6 (2023) 779-789. https://doi.org/10.1038/s41928-023-01023-w. + +Comment 2: The reviewer believes that sensory- motor integration is valuable when the robot can control motors in response to signals received from sensors. However, it seems that controlling the motors and performing sensor functions operate independently. In that case, can this robot still be considered as the presence of responsiveness as mentioned in the introduction? + +Our response: We thank the reviewer's question regarding sensory- motor integration within our soft robotic system. Our design can be engineered to offer dual- mode functionality, adapting to a broad spectrum of operational requirements, enhancing the system's versatility and application range. + +We have demonstrated that the integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration highlighted by the reviewer. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. R10A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. R10B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective + +<--- Page Split ---> + +factor and is added to the current output value to generate a new output value. The on-chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. R11 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off. + +![](images/Figure_unknown_10.jpg) + +
Fig. R10. Soft robots designed integrated sensing and actuation capabilities. (A) Schematic diagram of the responsive robotic gripper with control circuitry. (B) Functional block diagram of the algorithmic and hardware design of the adaptive control loop.
+ +Moreover, our robotic system also supports operation in an open- loop configuration, where actuation is not directly governed by immediate sensory inputs but can be pre- programmed or controlled externally. This flexibility is particularly beneficial for scenarios where actions need to be acquired based on predefined conditions rather than dynamic sensory input, offering stability in a controlled environment. An example of this functionality is our bladder control system, designed to maintain a consistent grip post + +<--- Page Split ---> + +implantation. However, we have also integrated a closed- loop mechanism between the stimulator and sensor modules for this application. Electrical stimulation is activated when the bladder reaches its maximum volume threshold, targeting the bladder muscles to facilitate urination. Upon complete voiding of the bladder, the integrated sensors detect the reduction in bladder volume, which subsequently triggers the deactivation of the electrical stimulation. This programming cycle ensures that stimulation is provided only, when necessary, closely mimicking the natural urination process and enhancing patient comfort and device efficiency (Fig. 5A- 5G, Fig. S34- S35). + +![](images/Figure_unknown_11.jpg) + +
Fig. R11. Soft robots designed integrated sensing and actuation capabilities. (A) Infrared and optical images of the responsive robotic grippers at different stages of controlled actuation. (B&C) Time synchronized current (B) and temperature plot (C) capturing the controlled actuation changes after a sudden change in ambient temperature.
+ +Our robotic system is engineered to support both responsive closed- loop feedback and stable open- loop operation for sensor- actuator integration. This not only meets the initial responsiveness criteria but also significantly expands its utility across diverse fields, ranging from precise medical interventions to versatile robotic applications. + +## Modification to the manuscript: + +(1) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. +(2) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. +(3) On page 5, in the revised supporting information, we added," + +<--- Page Split ---> + +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +(4) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a + +<--- Page Split ---> + +microcontroller- driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real- time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +(5) On page 29, in the revised manuscript, we added, " + +## The sensory-motor integration within the soft robotic system + +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +## References + +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +Comment 3: It seems good that the robot is designed differently for each target organ. The reviewer is curious about the variation in curvature among different organs. For instance, in the case of organs like the heart and bladder, squeezing too much might make it challenging to grasp effectively. How was this consideration taken into account in the design? + +Our response: We thank the reviewer's question regarding how our soft robotic systems accommodate the anatomical diversity and curvature of different target organs. Our design process incorporated multiple factors to ensure that our device can achieve shape adaptability, effective data acquisition, and potential therapeutic interventions across various applications. + +<--- Page Split ---> +![](images/Figure_unknown_12.jpg) + +
Fig. R12. Illustration of soft robotic implants exhibiting significant modularity and adaptability. (A-D) A starfish-inspired device featuring twelve arms. (E-H) A hand-structured soft robotic device that can be compactly housed in and released from a catheter. (I-L) A twisted soft robotic device designed for storage and deployment through a 14-Gauge Tuohy needle. Scale bars, 1 cm.
+ +As mentioned by the reviewer, our device is highly customizable. We design specific configurations of the device to align the morphology of different organs, considering their shape (e.g., tubular, spherical), size, and the intended functionalities. The customization extends to the device's dimensions, the selection and distribution of sensors, as well as their geometrical arrangement, as illustrated in Fig. R12, ensuring that our device can conform naturally to different organs and tissues. + +Beyond their thermo- responsive property, we have selected PNIPAM hydrogel as a key material due to their mechanical properties, which closely resemble those of body tissues/organs. Unlike other smart materials such as shape memory polymers and alloys, which possess elastic moduli (E) on the order of several megapascals (MPa) \(^{8}\) , hydrogels feature an elastic modulus within the 1- 100 kPa range. This range closely aligns with the E of soft tissues, typically spanning from a few kPa to hundreds of kPa \(^{9}\) . The PNIPAM hydrogel in our research exhibited an E \(\sim 1.2\) kPa, as shown in Fig. R13A. Such mechanical similarity facilitates a more seamless integration with surrounding tissues, substantially minimizing the potential damage from mechanical mismatch \(^{10}\) . + +<--- Page Split ---> +![](images/Figure_unknown_13.jpg) + +
Fig. R13. Mechanical behavior of soft robotic device. (A) Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness \(4\mathrm{mm}\) , width \(10\mathrm{mm}\) , initial length \(15\mathrm{mm}\) ). (B&C) Optical image showing conformal attachment of the soft sensory robot onto human skin (B) and porcine tissue (C) with high mechanical compliance. (D) Measured static force changes of the soft robotic finger under different temperatures. Scale bars, \(5\mathrm{mm}\) .
+ +This compatibility ensures that our devices can naturally conform to the contours of organs and tissues, as demonstrated in Fig. R13B&C. Furthermore, the intrinsic flexibility and low stiffness of hydrogels prevent an excessive force on the organ or tissue (Fig. R13D). Additionally, we found that the hydrogel's intrinsic adhesiveness, further enhancing the device's integration with biological tissues, ensuring that the device can maintain effective grip and functionality without exerting damaging pressure on the organ, addressing concerns related to squeezing or over- compression (Fig. R14). + +![](images/Figure_unknown_14.jpg) + +
Fig. R14. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \(36^{\circ}\mathrm{C}\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this threshold. All tests were conducted after overnight incubation simulating physiological conditions at \(34^{\circ}\mathrm{C}\) , \(37^{\circ}\mathrm{C}\) , and \(40^{\circ}\mathrm{C}\) . Scale bars, \(5\mathrm{mm}\) .
+ +<--- Page Split ---> + +In summary, our design strategy emphasizes customization, careful material selection, and empirical validation to address the complexities of interacting with various organs. In this way, we ensure that our soft robotic system is not only versatile and adaptable but also safe and effective for a wide range of biomedical applications. + +## Modification to the manuscript: + +(1) On page 21, in the revised manuscript, we added, "Additionally, our device offers versatile adaptability for diverse application scenarios through customizable dimensions, sensor positioning, and geometric layouts, ensuring it aligns with the unique morphologies and functional demands of targeted tissues/organs. This flexibility is essential for enabling minimally invasive deployment. As illustrated in Fig. S38&S39, Table S2, and Supplementary Note S6, the design's adaptability enhances soft robotic technologies for effective integration in a broad spectrum of biomedical applications." + +(2) On page 13, in the revised supporting information, we added Fig. R13A as Fig. S3C. + +(3) On page 6, in the revised manuscript, we modified, "The as-fabricated soft robot can form a highly conformal interface with diverse biological surfaces, indicating its inherent mechanical softness and high biocompatibility. This adaptability minimizes potential risks related to mechanical incompatibility, facilitating its smooth integration with targeted tissues/organs (Fig. 2F&G, and Fig. S3C)." + +(4) On page 10, in the revised manuscript, we modified, "We further evaluated the mechanical force generated by the soft robotic finger which incorporates a PNIPAM hydrogel layer roughly 1 mm thick, under various input powers. Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar hydrogel-based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +(5) On page 52, in the revised supporting information, we added Fig. R14 as Fig. S40. + +(6) On pages 21-22, in the revised manuscript, we added, "We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +<--- Page Split ---> + +(7) On page 29, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of \(13 \mathrm{mm / min}\) . + +Mechanical tests were conducted on rectangular-shape specimens with the dimensions of \(10 \mathrm{mm}\) in width, \(2 \mathrm{mm}\) in thickness, and \(16 \mathrm{mm}\) in length) using the Instron machine (Mark- 10 ESM303)." + +## Reference + +Y. Jiang, +A.A. Trotsyuk, +S. Niu, +D. Henn, +K. Chen, +C.C. Shih, +M.R. Larson, +A.M. Mermin-Bunnell, +S. Mittal, +J.C. Lai, +A. Saberi, +E. Beard, +S. Jing, +D. Zhong, +S.R. Steele, +K. Sun, +T. Jain, +E. Zhao, +C.R. Neimeth, +W.G. Viana, +J. Tang, +D. Sivaraj, +J. Padmanabhan, +M. Rodrigues, +D.P. Perrault, +A. Chattopadhyay, +Z.N. Maan, +M.C. Leeolou, +C.A. Bonham, +S.H. Kwon, +H.C. Kussie, +K.S. Fischer, +G. Gurusankar, +K. Liang, +K. Zhang, +R. Nag, +M.P. Snyder, +M. Januszyk, +G.C. Gurtner, +Z. Bao, +Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +Comment 4: Why does the parallel strips configuration result in twisting? Is there any reference for this, or was it an original concept? + +Our response: We thank the reviewer's question regarding the underlying mechanism by which the "parallel strips" configuration results in a twisting motion in our device. This phenomenon arises from the differential expansion and contraction of materials when subjected to stimuli, such as temperature changes. + +Initially, PNIPAM hydrogel is a thermo- responsive material whose volume and shape significantly change with temperature variations. Above its LCST, PNIPAM undergoes a shrinking process, leading to a reduction in the hydrogel's volume. Conversely, polyimide (PI) is a high- performance polymer known for its thermal stability, exhibiting minimal expansion or contraction upon heating, especially compared to the significant changes observed in PNIPAM hydrogel. + +When these inclined PI strips are bonded to the PNIPAM hydrogel, a hybrid bilayer structure is constructed (Fig. S8A). Upon heating, the differential thermal shrinkage of PNIPAM and the relative stability of the PI layer induce uneven expansion or contraction across the structure. Especially, as the PNIPAM hydrogel shrinks with heat, the connected PI strips generate a tilting torque, causing the entire structure to twist. This design leverages the disparate thermal response characteristics of the materials combined with a strategic structural arrangement to achieve unique mechanical behavior. The experimental results correspond very well with simulation results (Fig. R15). + +While the application of this principle has been explored in various studies11,12, our implementation within a soft robotic system, especially for implantable devices, represents a sophisticated adaption aimed at achieving specific functional objectives. We have achieved an integration of structural design with sensors, representing a more advanced extension of this concept. + +<--- Page Split ---> +![](images/Figure_unknown_15.jpg) + +
Fig. R15. FEA simulation results of a bilayer soft robotic device mimicking a chiral seedpod. (A-F) Stress distribution across the device during the shape-shifting process, facilitated by strategic stripe patterns on the 3D bilayer robot. This visualization highlights the material property mismatches including mechanical and thermal responsiveness that drive the device's complex morphological transformations.
+ +We have incorporated a more detailed discussion on the design mechanism behind the parallel strips' configuration, ensuring a comprehensive understanding of the concept and its application within our work. + +## Modification to the manuscript: + +(1) On page 18, in the revised supporting information, we added Fig. R15 as Fig. S8C. + +(2) On page 18, in the revised supporting information (Fig. S8B's caption), we added "The PNIPAM hydrogel contracts while PI maintains relative stability upon heating. The contraction of the PNIPAM hydrogel activates a tilting torque through the bonded PI strips, resulting in asymmetric deformation throughout the device." + +(3) On page 6, in the revised manuscript, we added, "Upon thermal stimulation, the PNIPAM hydrogel contracts while the PI maintains stability, generating a differential contraction across the structure. The differential thermal response induces a tilting torque, leading to local saddle-like curvature and twisting motion of the integrated robotic systems (Fig. 2J, Fig. S8B and Supplementary Movie S3)." + +## References + +Shian, S., Bertoldi, K. & Clarke, D. R. Dielectric Elastomer Based 'grippers' for Soft Robotics. Adv. Mater. 27, 6814- 6819 (2015). Shojaeifard, M., Niroumandi, S. & Baghani, M. Programming shape- shifting of flat bilayers composed of tough hydrogels under transient swelling. Acta Mech. 233, 213- 232 (2022). + +Comment 5: On page 6, if the transfer method is well- designed, it could potentially enable multi- modal implementation. Is there a particular advantage in this solution- based approach over transfer methods? + +<--- Page Split ---> + +Our response: We thank the reviewer's question regarding the specific advantages of our in- situ solution- based fabrication approach over traditional make- transfer methods, especially concerning the integration of sensors into the e- skin layer for achieving multimodal functionality. Our method is designed to facilitate seamless and monolithic structuring of functional materials with a passive polymer- based skin, thereby transforming the e- skin into a highly versatile platform. Unlike make- and- transfer methods that may introduce interface issues or compromise material compatibility, our solution- based process facilitates the uniform integration of a wide array of functional nanomaterials within a polymeric matrix. This capability is crucial for constructing e- skin that emulates the complexity of the human skin's somatosensory system. + +(1) Our solution-based method allows for the direct integration of sensors and the e-skin matrix in a single step, ensuring a seamless interface between different components. This monolithic integration is essential for reproducing the integrated somatosensory functions of natural skin, thereby significantly enhancing the e-skin's sensitivity and responsiveness. + +(2) The flexibility to incorporate a broad range of functional nanomaterials into the polymeric matrix without the constraints of transfer compatibility of thermal/mechanical sensitivity, broadens the scope of achievable functionalities. This versatility enables the e-skin to more closely mimic the multi-modal sensory capabilities of natural skin. + +(3) The direct integration of sensors within the e-skin matrix, as facilitated by our solution-based approach, results in improved mechanical and electrical performance. This improvement is due to the elimination of interfacial resistances and better mechanical conformity, which are critical for sensitive and accurate sensory detection. + +Our approach offers an effective and versatile method for developing e-skin systems capable of sophisticated multi-modal sensory functions. We have further clarified these advantages in the revised manuscript and supplementary information to provide a clearer understanding of our methods and their benefits over traditional make-and-transfer methods. + +## Modification to the manuscript: + +On pages 6- 7, in the revised manuscript, we modified, "Furthermore, compared with a make-and-transfer method, our in situ solution-based fabrication approach enables the seamless integration of sensors into the e-skin matrix in a single step, enhancing mechanical and electrical performance by reducing interfacial resistances and improving mechanical conformity, thereby significantly improving sensitivity and responsiveness. This approach also offers a versatile platform that can be constructed using a broad range of functional nanomaterials hybridized with a polymeric matrix to form a multi-modal sensing system. By selecting materials that offer unique functional attributes, from AgNWs known for their conductivity and flexibility to graphene and MXene for their high surface area, electrical conductivity, and hydrophilicity, this system can emulate the skin with complex somatosensory system, where various mechanoreceptors and thermoreceptors distributed in the epidermal and dermal layers enable the spatiotemporal recognition of the magnitude and location of touch and temperature stimuli." + +<--- Page Split ---> + +## References + +ReferencesBasarir, F., Madani, Z. & Vapaavuori, J. Recent Advances in Silver Nanowire Based Flexible Capacitive Pressure Sensors: From Structure, Fabrication to Emerging Applications. Adv. Mater. Interfaces 9, (2022).Chauhan, N., Maekawa, T. & Kumar, D. N. S. Graphene based biosensors - Accelerating medical diagnostics to new- dimensions. J. Mater. Res. 32, 2860- 2882 (2017).Amara, U., Hussain, I., Ahmad, M., Mahmood, K. & Zhang, K. 2D MXene- Based Biosensing: A Review. Small 19, 1- 38 (2023).Driscoll, N. et al. MXene- infused bioelectronic interfaces for multiscale electrophysiology and stimulation. Sci. Transl. Med. 13, eabf8629 (2021).Liu, H. et al. 3D Printed Flexible Strain Sensors: From Printing to Devices and Signals. Adv. Mater. 33, 2004782 (2021).Zhu, Z., Park, H. S. & McAlpine, M. C. 3D printed deformable sensors. Sci. Adv. 6, eaba5575 (2023).Reeder, J. et al. Mechanically Adaptive Organic Transistors for Implantable Electronics. Adv. Mater. 26, 4967- 4973 (2014). + +Comment 6: On Page 7, Figure 2H, the volume of the PNIPAM hydrogel in Figure 2H is shown to dramatically decrease between approximately \(35^{\circ}C\) and \(45^{\circ}C\) . Given that the normal human body temperature is around \(36 - 37^{\circ}C\) , even if actuation is induced by an electrothermal method, maintaining its shape seems crucial for attaching it to various organs within the body. To substantiate this point, it would be necessary for the authors to demonstrate volume changes starting from a range lower than \(35^{\circ}C\) . + +Our response: We appreciate the reviewer's comment regarding the temperature- dependent volume changes of PNIPAM hydrogel. As reviewer's suggested, we have included data on volume changes of PNIPAM hydrogel starting from temperatures lower than \(35^{\circ}C\) , extending through the normal human body temperature range to beyond its LCST. + +As shown in Fig. R16, the expanded data clearly demonstrate PNIPAM hydrogel's inherent characteristic of water retention and swelling at temperatures below its LCST, which approximately \(32^{\circ}C\) to \(34^{\circ}C\) for pure PNIPAM. Beyond this threshold, a significant and rapid deswelling process occurs due to expulsion of water, resulting in a dramatic volume reduction. This thermos- responsive deswelling behavior is the basis for the actuation mechanism used in our device designs. + +We have updated the manuscript to better reflect the PNIPAM hydrogel's behavior across relevant physiological temperature ranges. It suggests the hydrogel's applicability and adaptability in developing implantable biomedical devices, capable of dynamically interacting with the human body's thermal environment. + +<--- Page Split ---> +![](images/Figure_unknown_16.jpg) + +
Fig. R16. The thermal responsiveness of PNIPAM hydrogel. (A) The volumetric shrinkage of PNIPAM hydrogel during the heating cycle across a temperature range of \(25^{\circ}C\) to \(60^{\circ}C\) . (B) The hydrogel's volumetric recovery during the cooling cycle, as temperatures revert to \(25^{\circ}C\) , showcasing its reversible thermal behavior and resilience.
+ +## Modification to the manuscript: + +(1) On page 8, in the revised manuscript, we added Fig. R16A as Fig. 2H. +(2) On page 13, in the revised supporting information, we added Fig. R16B as Fig. S3B. +(3) On pages 5-6, in the revised manuscript, we modified, "The PNIPAM hydrogel can undergo a dramatic volumetric reduction of about \(90\%\) as the temperature shifts from 25 \(^\circ C\) to \(60^\circ C\) . Notably, this significant and rapid deswelling behavior is initiated only when temperature is beyond its lower critical solution temperature (LCST \(32^\circ C \sim 34^\circ C\) ), enabling versatile actuation capabilities within biological environments (Fig. S3A&B, and Fig. 2H). + +Comment 7: It was confirmed that the composite was implemented through XPS analysis. Is there a concern that this might result in lower performance compared to a full composite? + +Our response: We appreciate the reviewer's comment regarding the performance of our composite materials, particularly considering its implementation and characterization through XPS analysis. We wish to clarify that our work indeed successfully constructed a full composite tailored specifically for electronic skin (e- skin) applications. Unlike traditional bulk composites, our composite has a thin profile to meet the specific requirements of e- skin functionalities, where excessive thickness would compromise practicality and performance. + +Our fabrication process involves an initial step of drop- casting followed by laser patterning, which forms a thin and porous network of the functional materials (Fig. R17A). This method contributes to fabricating precise and suitable fine features required for high- performance e- skin. The subsequent step involves spin casting a polymer solution over + +<--- Page Split ---> + +this preformed structure. This process ensures the polymer solution thoroughly permeates the functional material layer, resulting in the formation of a full composite (Fig. R17B). + +![](images/Figure_unknown_17.jpg) + +
Fig. R17. Fabrication of functional nanocomposite based on in situ solution integration method. (A) Top: Schematic illustration of patterning AgNWs network with a laser; Bottom: SEM image of as-synthesized AgNWs. (B) Top: Schematic illustration of spin coating PI solution and forming AgNW/PI nanocomposite; Bottom: SEM image of AgNW/PI nanocomposite with full PI infiltration, demonstrating a thorough infiltration of PI within the AgNW network, resulting in a cohesive nanocomposite structure.
+ +The choice of XPS for surface composition and chemical state analysis (Fig. S13- S15), supplemented by SEM for morphology insights (Fig. 2C and Fig. 2D, Fig. S17A- C, Fig. S21A- C), FTIR for chemical bond identification (Fig. S17D and Fig. S21D), and XRD for crystalline structure information (Fig. S17E and Fig. S21E), commonly validates the composite's integrity and the efficacy of the fabrication process (Supplementary Note S1- S2). + +Our design and fabrication strategies align with the requirement for developing high- performance e- skin layer. By prioritizing a thin profile, we ensure that our composite not only meets the mechanical flexibility and electrical performance demands to e- skin applications but also remains lightweight and conformable to various surfaces. This approach facilitates a seamless integration of functional materials into a polymer matrix, forming a uniform and cohesive composite. Such a composition is critical for the optimal functionality of e- skin, enabling it to closely mimic the sensitivity and versatility of nature skin while ensuring durability and reliability in various operational situations. + +In the revised manuscript and supporting information, we have further explained the fabrication process and its advantages, enhancing understanding of our in situ solution- based method and its contribution to advancing e- skin technology. + +## Modification to the manuscript: + +<--- Page Split ---> + +On page 7, in the revised manuscript, we modified, "The X- ray photoelectron spectroscopy (XPS) characterization on the e- skin layers reveals the precise nanoscale integration of active materials within a polymer matrix, as detailed in Fig. S12- S14 and Supplementary Note S1. It showcases the optimal distribution and intermolecular bonding of the composite components, effectively addressing the common challenge of uneven dispersion of nanomaterials, which usually undermines the performance of conventional composites. Our approach minimizes the polymer amount required to integrate nanomaterials into composite functional modules and utilizes excess polymer as an insulating layer to separate modules, preventing interference between their electrical and chemical signals, thereby ensuring that each functional module operates independently and effectively. This simple approach combines the distinct properties of each constituent, achieving a balance between structural integrity and functional versatility [56- 60]. This advanced level of integration would be of great value for soft robots that seek to achieve multifunctionality and local sensing capabilities approaching skin." + +Comment 8: After nanomaterials are created through the laser pattern, the inherent properties of the material make handling difficult. How was the surrounding material removed or treated? + +Our response: We appreciate the reviewer's concern regarding the post- treatment process surrounding unwanted nanomaterials following laser patterning. Our approach to addressing this challenge hinges on the precise control of laser parameters during the patterning process, which effectively eliminates the need for extensive post- patterning removal steps. + +Regarding the laser patterning, the underlying mechanism relies on the laser's thermal effect, which induces localized heating upon interaction material. This heating is intense and concentrated within a precise area, corresponding to the laser's focal point. We precisely adjust the laser settings to ensure complete elimination of the nanomaterials outside the desired pattern through hatching process. This laser ablation process, characterized by its high resolution of several tens of micrometers, allows for the selective removal of unwanted nanomaterials while leaving the desired pattern intact. The accuracy and efficiency of this method significantly reduces the presence of residual materials that could potentially interfere with subsequent processing steps. Notably, any residual materials left post- hatching are minimal and do not compromise the structural integrity or functionality of the as- formed composite. By employing this laser patterning technique, we ensure the precise and clean deposition of nanomaterials in alignment with our designs, which is crucial for the operational effectiveness of the device. + +We have included the detailed laser patterning parameters applicable for various nanomaterials in the revised manuscript and supporting information, aiming to provide clear insights and facilitate a better understanding for researchers engaging in similar future endeavors. + +## Modification to the manuscript: + +<--- Page Split ---> + +(1) On page 28, in the revised manuscript, we added, "The thermal effects of laser patterning ensure minimal residual materials remain, as localized heating effectively eliminates any leftovers, facilitating seamless progression to subsequent processing steps." + +(2) On page 28, in the revised manuscript, we added, "Here, laser hatching parameters for patterning nanomaterials are set: for AgNW/PEDOT:PSS/RGO, an infrared laser power of 12% (50 W) with a hatching speed of 5000 mm/s and frequency of 40 kHz; for Au/MXene, the settings are adjusted to an infrared laser power of 10% (50 W), a hatching speed of 1000 mm/s, and frequency of 40 kHz, ensuring precision in the material's functional structuring." + +Comment 9: In Figs 3C, D, please indicate in the caption whether SEM images represent the surface or cross-section. Additionally, to determine the presence of voids, it may be necessary to examine cross-sectional TEM images. + +Our response: We thank the reviewer's comments. We have updated the captions of Fig. 3C and Fig. 3D to clearly indicate that these SEM images represent the surface of our samples. + +To further address concerns regarding void detection within the composite, we conducted cross- section SEM analysis to examine the presence of voids within the composite. Our findings from the SEM images, as shown in Fig. R18B&C, provide a comprehensive understanding of the composite structure, including the void distribution. The SEM images are fully capable of capturing the necessary information regarding voids presence, thus obviating the need for supplementary TEM studies for this purpose. + +We have included cross- sectional SEM images in our revised supporting information. These images offer an in- depth view of the composite integrity, allowing us to verify the absence of voids within the material structure, demonstrating the composite's uniformity that is essential for e- skin application requiring high sensitivity and reliability. + +![](images/Figure_unknown_18.jpg) + +
Fig. R18. SEM characterization of functional nanocomposite based on in situ solution integration method. (A) Top surface SEM view of the AgNW/PI nanocomposite. (B&C) Cross-sectional SEM images of AgNW/PI nanocomposite, revealing the complete penetration of PI throughout the AgNW matrix with the absence of voids.
+ +Modification to the manuscript: + +<--- Page Split ---> + +(1) On page 13, in the revised manuscript, we modified the figure caption of Fig. 3C&D, "(C&D) SEM images of the surface of nanocomposite films used in constructing sensory robots." + +(2) On page 27, in the revised supporting information, we added Fig. R18B&C as Fig. S17D&F, respectively. + +(3) On page 27, in the revised supporting information, we modified Fig. S17B&C. + +(4) On page 32, in the revised supporting information, we modified Fig. S21B&C. + +(3) On pages 9-10, in the revised manuscript, we modified, "The scanning electron microscope (SEM) images, including both top and side views as shown in Fig. 3C&D, Fig. S17A-F, and Fig. S21A-C, present that the curing process fully buries all the nanomaterials inside the PI matrix, resulting in a uniform composite free from observable voids." + +Comment 10: In Fig 3E, it is understood that accurately observing the exact temperature by performing twisting and bending may be challenging with an infrared camera. However, even considering this, it seems that the temperature distribution is not uniform. + +Our response: We thank the reviewer's comment regarding the observed non- uniform temperature distribution in Fig. 3E, captured using an infrared camera. As reviewer said, it is challenging to accurately capture temperature variations during dynamic movements such as twisting and bending due to the limitations of thermal imaging technology. + +![](images/Figure_unknown_19.jpg) + +
Fig. R19. Infrared thermograph of an AgNW/PI-based heater undergoing bending and twisting motions.
+ +Upon detailed analysis, we identified that the primary cause for the observed nonuniformity was related to the positioning of the sample during imaging. It appears that the sample was not maintained in a perfectly flat orientation nor consistently aligned at a uniform distance from the infrared camera. Such positioning discrepancies can significantly affect the accuracy of temperature measurements, leading to the appearance + +<--- Page Split ---> + +of non- uniform temperature distributions due to the angular and distance- related variations inherent in infrared thermography. + +To ensure more accurate temperature measurement, we have refined our experimental setup. We made efforts to ensure that the sample is evenly positioned on a flat surface, minimizing any potential distortions or variations due to uneven distances between different parts of the sample and the camera. The updated figures have been included in the revised manuscript. + +## Modification to the manuscript: + +On page 12, in the revised manuscript, we added Fig. R19 as Fig. 3E. + +Comment 11: In Fig 3F, G, the temperature converges over time, but what is the reason for the continuous change in bending force? Additionally, once bent, how long does the bending force persist? + +Our response: We thank the reviewer's question about the dynamics of temperature stabilization and the resultant bending state as shown in Fig. R20A (Fig. 3F) and Fig. R20B (Fig. 3G). Fig. R20A (Fig. 3F) presents the surface temperature of the AgNW/PI heater, showing its rapid thermal response and ability to quickly reach and stabilize at the set temperature due to the heater's efficient heat generation capabilities. This rapid thermal stabilization allows for efficient energy transfer and thermal equilibrium. + +![](images/Figure_unknown_20.jpg) + +
Fig. R20. (A) Surface temperature of the AgNW/PI-based heater as a function of the input electric power. Notably, the AgNW/PI nanocomposite heater can function under relatively low input electric power. (B) The resultant bending angle of a soft robotic arm as a function of the input electric power.
+ +Conversely, Fig. R20B (Fig. 3G) shows the actuator's deformation over time. The transmission of heat from the heater to the entire sample requires a certain duration to propagate through the material. This apparent discrepancy in response times between the graphs arises from the difference in thermal propagation and the actuator's + +<--- Page Split ---> + +mechanical response. While Fig. R20A (Fig. 3F) illustrates the heater's immediate temperature stabilization, Fig. R20B (Fig. 3G) reveals a more gradual progression in the actuator's deformation. + +Furthermore, it is important to note that Fig. R20B (Fig. 3G) shows the deformation state of the actuator within a defined timeframe. Our empirical observations indicate that, upon reaching a thermally stable state, the actuator achieves its maximum deformation. This maximum bending is not transient, instead it is maintained as long as the thermal conditions remain unchanged. This ensures that once activated to a certain threshold, it retains its deformed state indefinitely under steady thermal environments. + +To enhance clarity and provide a comprehensive understanding of these phenomena, we have updated Fig. R20B (Fig. 3G) in the revised manuscript to include a plateau segment, demonstrating the actuator's deformation state over an extended period. This clearly illustrates the actuator's capability to maintain its maximum bending force upon achieving thermal equilibrium, offering a clearer depiction of its long- term stability and performance. + +## Modification to the manuscript: + +(1) On page 13, in the revised manuscript, we added Fig. R20B as Fig. 3G. + +(2) On page 10, in the revised manuscript, we added, "Fig. 3G also indicates that the actuator reaches its peak deformation upon achieving thermal equilibrium, and importantly, this maximum bend is maintained as long as there are no changes in thermal conditions." + +Comment 12: In addition to comment 9, is it necessary to keep the heater on continuously to maintain actual bending when attaching it to an organ? + +Our response: We appreciate the reviewer's comment regarding the necessity of continuous heating to maintain the actuator's bending state when interfaced with biological tissues/organs. For PNIPAM hydrogel, with LCST between 32- 34°C, the normal human body temperature is sufficient to trigger the desired deformation. The initial heating is primarily employed to accelerate the actuation process. Once actuation is achieved, continuous heating using the electrical heater becomes unnecessary. This feature ensures that our device can efficiently adapt and function within the physiological temperature range without the need for sustained thermal input. + +Furthermore, we can design the device with a thermal feedback mechanism that automatically adjusts the heating, thereby preventing potential overheating and ensuring a rapid yet safe actuation (Fig. R10&11). This built- in feature, combined with hydrogel's responsiveness to body temperature, enables our developing device not only to be effective but also safe for extended biomedical utilization. We have highlighted this point in the revised manuscript. + +## Modification to the manuscript: + +(1) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to + +<--- Page Split ---> + +achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +(2) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. +(3) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. +(4) On page 5, in the revised supporting information, we added," + +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was + +<--- Page Split ---> + +overheated, during which the current output drops again to reach the static phase at which the current levels off." + +(5) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +(6) On page 29, in the revised manuscript, we added, " + +## The sensory-motor integration within the soft robotic system + +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +## References + +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +Comment 13: The dual- axis graphs presented in this figure (Figure 3l, Figure 5F, K, N etc.) are difficult to intuitively comprehend. It is unclear whether the changes on the left axis correspond to the results on the right axis or if they were determined through variations in resistance, pressure, or pH values. Therefore, it seems necessary for the authors to modify the graphs for better intuitive understanding and provide explanations regarding the extent of numerical changes made. + +<--- Page Split ---> + +Our response: We appreciate the reviewer's comment on the clarity of dual- axis graphs in our figures (Fig. 3I, Fig. 5F, Fig. 5K and Fig. 5N). These graphs are intended to showcase the correlation between sensor responses (left axis) and the varying external conditions (right axis) they measure, such as temperature, volume, pressure, or pH values. + +For instance, Fig. R21A (Fig. 3I) presents the static cycling test of the RGO/PI- based thermal sensor, which operates on resistance changes. In this scenario, as we vary the environmental temperature over time, the resistance changes (indicated on the left y- axis) correspond directly to different temperature values (shown on the right y- axis). Similarly, for Fig. R21B (Fig. 5F), Fig. R21C (Fig. 5K) and Fig. R21D (Fig. 5N), where resistance- based sensors capture real- time changes in resistance as a direct response to external variations in volume, pressure, or pH. + +We have refined these figures to more clearly illustrate the correlation between resistance changes and the physical parameters under observation, thereby clarifying the direct linkage between sensor outputs and variations in environmental stimuli (Fig. R21). Moreover, we have incorporated detailed explanations on the numerical changes and their significance into the manuscript to provide comprehensive insights into the sensor's operational mechanisms. + +![](images/Figure_unknown_21.jpg) + +
Fig. R21. (A) Static cycling test of the RGO/PI-based thermal sensor. Here, the left y-axis represents the change in resistance, while the right y-axis corresponds to the associated temperature changes. (B) Representative test of the 3D buckling strain sensor in real-time monitoring of volumetric change of the artificial bladder during cyclic movements of filling and emptying. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the associated volume changes. (C) Representative measurement of fluidic pressure of the artificial artery system using the soft robotic cuff. Here, the left y-axis is the change in resistance,
+ +<--- Page Split ---> + +while the right y- axis corresponds to the pressure changes. (D) Electrical response of PEDOT:PSS/PVA hydrogel to pH change ranging from 3 to 7 over time. Here, the left y- axis is the change in resistance, while the right y- axis corresponds to the pH value changes. + +## Modification to the manuscript: + +(1) On page 13, in the revised manuscript, we added Fig. R21A as Fig. 3l. + +(2) On page 14, in the revised manuscript, we modified the caption of Fig. 3l. "(I) Static cycling test of the RGO/PI-based thermal sensor. Here, the left y-axis represents the change in resistance, while the right y-axis corresponds to the associated temperature changes." + +(3) On page 20, in the revised manuscript, we added Fig. R21B-D as Fig. 5F, Fig. 5K, and Fig. 5N, respectively. + +(4) On page 21, in the revised manuscript, we modified the caption of Fig. 5F. "(F) Representative test of the 3D buckling strain sensor in real-time monitoring of volumetric change of the artificial bladder during cyclic movements of filling and emptying. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the associated volume changes." + +(5) On page 21, in the revised manuscript, we modified the caption of Fig. 5K. "(K) Representative measurement of fluidic pressure of the artificial artery system using the soft robotic cuff. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the pressure changes." + +(6) On page 21, in the revised manuscript, we modified the caption of Fig. 5N. "(N) Electrical response of PEDOT:PSS/PVA hydrogel to pH change ranging from 3 to 7 over time. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the pH value changes." + +Comment 14: Using heat as a stimulus might potentially cause damage to the tissue. However, considering the hydrogel is thick enough, it may prevent such damage. How efficiently does heat transfer throughout the entire hydrogel, and is the heat dissipation effective enough to be considered safe? + +Our response: We appreciate the reviewer's concern about the use of heat as stimulus and its potential to cause tissue damage. As previously discussed in response to Comment 12, our device does not necessitate continuous heating. We employ initial heating to accelerate the actuation process, eliminating the need for continuous thermal input once the desired actuation is achieved. This strategy ensures that the device's adaptability and safe operation is within the physiological temperature range. + +To further address safety concerns, we can design the device with an integrated thermal feedback mechanism that meticulously regulates the heating, thereby preventing any risk of overheating (Fig. R10&11). Moreover, our design considerations ensure that heat transfer through the hydrogel is efficiently managed, maintaining operational temperatures well below the \(43^{\circ}C\) threshold known to prevent thermal tissue damage13,14. + +<--- Page Split ---> + +Our in vitro and in vivo studies also confirm the device's safety. In vitro exposure of fibroblast- like cells (3T3- J- 2) to \(39^{\circ}C\) for 48 hours demonstrated maintained cellular health and viability (Fig. 6E&F). In vivo experiments involving the device's application around a mouse's heart, facilitated by wireless power transfer at \(0.1W\) to achieve \(40^{\circ}C\) thermal stimulation, revealed no detectable damage or inflammation in critical organs (Fig. 4I and Fig. S45). + +We have updated the manuscript to highlight these aspects, providing a better understanding of the thermal dynamics and safety profiles of our hydrogel- based systems. + +## Modification to the manuscript: + +(1) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +(2) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. + +(3) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. + +(4) On page 5, in the revised supporting information, we added," + +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error + +<--- Page Split ---> + +value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on-chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +(5) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +(6) On page 29, in the revised manuscript, we added, " + +## The sensory-motor integration within the soft robotic system + +The robotic gripper and the external circuitry were connected in series with an NI DMM amperemeter set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +## References + +<--- Page Split ---> + +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +Comment 15: While applying temperature, can the thermal sensor accurately measure the temperature from the tissue? + +Our response: We appreciate the reviewer's concern regarding the precision of our thermal sensors in capturing tissue temperatures during application. To validate our sensor's performance, we conducted comparative tests against commercial thermal resistors (ERT- J0ET102H), demonstrating a high level of correlation and match in the readings, as shown in Fig. R22A (Fig. 3K) and Fig. R22B (Fig. S21G). + +As illustrated in Fig. R22C (Fig. 3H), we extensively characterized the thermal sensor's responsiveness across a wide temperature range, from \(23^{\circ}C\) to \(92^{\circ}C\) , which spans the spectrum of internal body temperature. This evaluation also included scenarios where the sensor was immersed in a phosphate- buffered saline (PBS) solution, closely simulating in vivo environmental conditions. The sensor exhibited exceptional stability and reliability even in this simulated physiological environment. + +Furthermore, we employed in situ solution- based methods to fabricate the functional modules located in different layers. This strategy allows for the integration of a minimal amount of polyimide with functional materials to form composite functional modules. This not only preserves the functional integrity of the materials within each module but also leverages the remaining polyimide to serve as a dual purpose. Beyond its inclusion in the composite, polyimide acts as an insulating barrier between adjacent modules. This barrier is crucial for our device's functionality, as it prevents electrical and chemical signal interference between modules, thereby ensuring that each functional module operates independently and as intended. + +![](images/Figure_unknown_22.jpg) + +
Fig. R22. (A) Temperature measurement on the MXene/PI thermal sensor and a commercial thermal resistor (ERT-J0ET102H). (B) Temperature measurement on the RGO/PI thermal sensor and the commercial thermal resistor. (C) Resistive response at various temperatures ranging from
+ +<--- Page Split ---> + +\(23^{\circ}C\) to \(92^{\circ}C\) , for the RGO/PI- based thermal sensor undergoing bending and twisting motions, and immersed in a solution of PBS. + +These findings solidify the capability of our thermal sensor for precise monitoring of tissue temperatures. The updated manuscript further emphasizes the sensor's applicability and stability, highlighting its potential in medical applications. + +## Modification to the manuscript: + +(1) On page 7, in the revised manuscript, we modified, "Fig. 2M displays a more complicated integration paradigm with multi-layer stacking, where different electronic components (e.g., PEDOT:PSS/PI-based conductive electrodes and RGO/PI temperature sensors) can be distributed in different layers of the e-skin to achieve simultaneous functional versatility and compactness. This assembly technique ensures the e-skin remarkable thinness and flexibility, enhancing its effective performance for implantable applications (Fig. S11B). The X-ray photoelectron spectroscopy (XPS) characterization on the e-skin layers reveals the precise nanoscale integration of active materials within a polymer matrix, as detailed in Fig. S12-S14 and Supplementary Note S1. It showcases the optimal distribution and intermolecular bonding of the composite components, effectively addressing the common challenge of uneven dispersion of nanomaterials, which usually undermines the performance of conventional composites. Our approach minimizes the polymer amount required to integrate nanomaterials into composite functional modules and utilizes excess polymer as an insulating layer to separate modules, preventing interference between their electrical and chemical signals, thereby ensuring that each functional module operates independently and effectively. This simple approach combines the distinct properties of each constituent, achieving a balance between structural integrity and functional versatility. This advanced level of integration would be of great value for soft robots that seek to achieve multifunctionality and local sensing capabilities approaching skin." + +(2) On page 11, in the revised manuscript, we added, "Fig. 3H illustrates the resistive change in a relatively linear relation with temperature for the RGO/PI thermal sensor. The temperature coefficient of the resistance (TCR) of the RGO/PI thermal sensor is > 0.5%/°C, featuring its high thermal sensitivity. On the other hand, the RGO/PI-based thermal sensor exhibits a stable performance after 1000 bending cycles, and even after immersing in PBS solution. Fig. 3I and Fig. S21F show performance of the thermal sensor in response to cycles of temperature rise and drop, indicating good sensing stability. In addition, Fig. S21G shows consistent measurements of RGO/PI nanocomposite sensing performance in comparison with a commercial thermal resistor (ERT-J0ET102H), indicating excellent sensing accuracy." + +Comment 16: What is the reason for the difference in the transfer method in S12(b) compared to the dual printing method in S16? + +Our response: We appreciate the reviewer's concern about the methods utilized in our fabrication process, specifically the transfer method illustrated in Fig. S12B (Fig. S11B + +<--- Page Split ---> + +in the updated supporting information), and the dual printing method detailed in Fig. S16 (Fig. S15 in the updated supporting information). The essential differentiation between these methods lies not in their fundamental principles but in their application and the resulting properties of the e- skin layer. The choice of method is tailored to the specific requirements of the application, ensuring that the e- skin fabricated is not only functionally effective but also optimally designed for its intended use. + +The transfer method, as shown in Fig. S12B (Fig. S11B in the updated supporting information), allows for the fabrication of an e- skin that is notably thinner and possesses enhanced flexibility. This is especially beneficial for implantable applications where e- skin needs to conform closely to the complex contour of tissues/organs, ensuring optimal functionality and integration. Conversely, the dual printing method offers advantages in producing e- skin with multiple layers, allowing for the incorporation of multiple functionalities within a single e- skin platform. + +Both methods demonstrate the versatility and adaptability of our solution- based fabrication strategy, highlighting its superiority over traditional fabrication techniques, such as 3D printing. These two methods indicate the operational ease and the broad applicability of our method in creating e- skins that can be tailored to meet the diverse requirements of both implantable devices and wearable sensors, thereby broadening the scope of potential applications in the field of soft robotics and biomedical devices. + +In the revised manuscript, we have clarified these two methods, further emphasizing our approach's flexibility in accommodating the needs of advanced e- skin systems. + +## Modification to the manuscript: + +(1) On page 7, in the revised manuscript, we modified, "Fig. 2M displays a more complicated integration paradigm with multi-layer stacking, where different electronic components (e.g., PEDOT:PSS/PI-based conductive electrodes and RGO/PI temperature sensors) can be distributed in different layers of the e-skin to achieve simultaneous functional versatility and compactness. This assembly technique ensures the e-skin remarkable thinness and flexibility, enhancing its effective performance for implantable applications (Fig. S11B)." + +(2) On page 9, in the revised manuscript, we modified, "Fig. S15A shows layer-by-layer stacking as a simple and effective approach for fabricating the e-skin. This approach stands out for its capability to fabricate multi-layered e-skin integrating diverse functionalities within an unified e-skin framework, offering a sophisticated level of device customization." + +Comment 17: On Page 11, the author mentioned that "The electrothermal stimulus along with distributed sensing capabilities enables programmed actuation not only on demand but also regulated simultaneously by the sensing feedback". How was actuation implemented based on sensing feedback? + +<--- Page Split ---> + +Our response: We thank the reviewer's question regarding the implementation of actuation based on sensing feedback. Our system design integrates a network of distributed sensors within e- skin, enabling the detection of various environmental stimuli. Upon detecting a change in external environment, these sensors convert environmental changes into electrical signals relayed to a control unit. + +We have demonstrated that the integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration highlighted by the reviewer. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. R10A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. R10B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. R11 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off. + +To clarify this feedback mechanism, we have included comprehensive details in the revised manuscript and supporting information, providing examples of how this feedback mechanism is implemented within our soft robotic system. + +<--- Page Split ---> + +## Modification to the manuscript: + +(1) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. +(2) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. +(3) On page 5, in the revised supporting information, we added," + +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<--- Page Split ---> + +(4) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +(5) On page 29, in the revised manuscript, we added, " + +## The sensory-motor integration within the soft robotic system + +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +## References + +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +Comment 18: On Page 14, Figure S31, in Figure S31B, it is evident that there is a tendency for the coupling coefficient to decrease as the separation distance increases. However, in Figure S31D, there is a trend showing an increase in output power relative to input power as the distance increases. This observation appears to be theoretically inconsistent. If this graph is accurate, the authors need to provide additional explanations for these results. + +Our response: We thank the reviewer's comment regarding the discrepancy in the coupling efficiency and output power trends with increasing separation distance, as + +<--- Page Split ---> + +shown in Fig. R23A (Fig. S31B) and Fig. R23B (Fig. S31D). After thorough review, we found a labeling error in Fig. S31D that mispresented the trend of output power relative to input power as the distance increases. + +![](images/Figure_unknown_23.jpg) + +
Fig. R23. The effect of separation distance, horizontal offset and orientation angle on the performance of WPT system. (A) FEA results showing the variations in the coupling coefficient of the WPT coils under different separation distances. (B) Experimental evaluations of power transmission at resonance frequency (16 MHz) under different separation distances
+ +We have corrected this error to accurately illustrate the anticipated decrease in output efficiency with an increase in separation distance, thus realigning our results with theoretical expectations and ensuring consistency across our data presentation. + +## Modification to the manuscript: + +On page 42, in the revised supporting information, we revised Fig. S31D. + +Comment 19: On Page 16, in order for the sensory robots developed by the authors to conformally adhere to tissues or organs, they require not only curvilinear surfaces but also effective adhesion. While this article mentions the adhesiveness of PNIPAM, a recently published paper indicates that PNIPAM shows tissue adhesion at low temperatures (around \(25^{\circ}\mathrm{C}\) ) but loses almost all adhesive strength when it transitions to a gel form near \(40^{\circ}\mathrm{C}\) (Nature Biotechnology 2023, 41, 652- 662). To showcase the tissue adhesion capability of the authors' device, it becomes imperative to gauge the adhesive strength of the hydrogel by varying temperatures. This would confirm that there are no issues with adhesion even after attaching it to an organ. + +Our response: We thank the reviewer's comment regarding the adhesive properties of PNIPAM hydrogels, particularly in light of recent literature indicating significant changes in adhesive strength at varying temperatures15. It is crucial to distinguish the type of adhesion we refer to within the scope of our device's application from the strong adhesive forces comparable to those of glues, as discussed in the mentioned Nature Biotechnology paper15. + +Our device relies on the shape adaptability induced by the thermal response of PNIPAM hydrogels rather than on adhesive forces for effective tissue interfacing where the former + +<--- Page Split ---> + +self- assembles into a conformal shape to reduce dependence on strong adhesion force and mitigate interfacial stress, thus increasing biocompatibility. The concern regarding adhesion arises in the context of ensuring that the implanted device maintains its position and functionality without being compromised by potential reswelling effects post- actuation, especially at the temperatures around the body's physiological range. + +Our approach capitalizes on the unique temperature- responsive deformation properties of PNIPAM hydrogels to maintain device efficacy, emphasizing a synergistic integration of shape adaptability and minimal adhesion to secure tissue engagement. our updated manuscript and supporting information now more clearly illustrate this perspective. + +![](images/Figure_unknown_24.jpg) + +
Fig. R24. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \(36^{\circ}C\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this threshold. All tests were conducted after overnight incubation simulating physiological conditions at \(34^{\circ}C\) , \(37^{\circ}C\) , and \(40^{\circ}C\) . Scale bars, \(5mm\) .
+ +Additionally, as the reviewer's suggested, we conducted additional characterizations of the adhesive force exhibited by a PNIPAM- co- PAAm hydrogel with an LCST of \(36^{\circ}C\) across a range of temperatures, providing a better understanding of the hydrogel's physical properties and aiming to contribute valuable insights to the development of hydrogels for biomedical applications in designing effective implantable devices. + +## Modification to the manuscript: + +(1) On page 10, in the revised manuscript, we modified, "We further evaluated the mechanical force generated by the soft robotic finger which incorporates a PNIPAM hydrogel layer roughly 1 mm thick, under various input powers. Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar + +<--- Page Split ---> + +hydrogel- based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +(2) On page 52, in the revised supporting information, we added Fig. R24 as Fig. S40. + +(3) On pages 21-22, in the revised manuscript, we added, "We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature-responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +(6) On page 29, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +## Reference + +Y. Jiang, +A.A. Trotsyuk, +S. Niu, +D. Henn, +K. Chen, +C.C. Shih, +M.R. Larson, +A.M. Mermin-Bunnell, +S. Mittal, +J.C. Lai, +A. Saberi, +E. Beard, +S. Jing, +D. Zhong, +S.R. Steele, +K. Sun, +T. Jain, +E. Zhao, +C.R. Neimeth, +W.G. Viana, +J. Tang, +D. Sivaraj, +J. Padmanabhan, +M. Rodrigues, +D.P. Perrault, +A. Chattopadhyay, +Z.N. Maan, +M.C. Leeolou, +C.A. Bonham, +S.H. Kwon, +H.C. Kussie, +K.S. Fischer, +G. Gurusankar, +K. Liang, +K. Zhang, +R. Nag, +M.P. Snyder, +M. Januszyk, +G.C. Gurtner, +Z. Bao, Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +Comment 20: In Figs 5, 6, the use of Au electrodes for electrical stimulation in electrotherapy seems somewhat divergent from the other sensing materials of this paper (Fig. S52B). + +Our response: We thank the reviewer's concern regarding the use of Au electrodes for electrical stimulation in electrotherapy, as depicted in Fig. 5 and Fig. 6. The incorporation of Au electrodes within our device exemplifies our design to functional diversity and integration. The choice of Au, known for its superior electrical conductivity, biocompatibility, and stability within biological environments. These attributes render them ideally suited for delivering reliable and precise electrical stimulation, which is a critical function in therapeutic applications. + +Our study explores a variety of materials with notable sensing and actuation capabilities. The selection of Au electrodes for demonstration emphasizes the system's modular design. This showcases our device's ability to seamlessly integrate various functional materials, enhancing its applicability across a wide range of therapeutic and monitoring scenarios. This adaptability allows for the customization of materials in alignment with + +<--- Page Split ---> + +distinct application requirements, thereby providing a versatile platform that can be tailored to a broad spectrum of biomedical applications. + +## Modification to the manuscript: + +(1) On page 44, in the revised supporting information (Fig. S33A's caption), we added, "The stimulator component is two pairs of pacing electrodes, employing Au for its exceptional electrical conductivity, biocompatibility, and stability in biological settings." + +(2) On page 53, in the revised supporting information (Fig. S41's caption), we added, "The use of Au ensures superior electrical conductivity, biocompatibility, and stability within biological environments, guaranteeing reliable and precise electrical stimulation essential for effective therapeutic interventions." + +Comment 21: In Fig 5G, the electrical stimulation off voltage is not 0.0 V. Is there a specific reason for this? To help readers to understand, it appears that the authors should provide additional explanations regarding the correlation between electrical stimulation and volume changes. Specifically, a clear clarification is needed on whether the specific electrical stimulation is causing an actual increase in volume or if it is transmitting signals to patients having urinary dysfunction. + +Our response: We thank the reviewer's questions regarding the electrical stimulation off voltage in Fig. 5G and the need for additional explanations about the correlation between electrical stimulation and volume changes. We have come into realization that in the previous experiment, the voltage electrical stimulation voltage was measured without a MOSFET power buffer. The high internal resistance of the microcontroller GPIO pins has resulted in fluctuations in the voltage measured at shut-off state. Through the application of a MOSFET power buffer, we have successfully decreased the amount of current drawn at the GPIO pin and decreased the internal resistance of the electrical stimulation output, and thereby corrects the small offset observed at shut-off state (Fig. R25). + +<--- Page Split ---> +![](images/Figure_unknown_25.jpg) + +
Fig. R25. A robotic gripper for bladder control. Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of \(3 \text{V}\) . Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly.
+ +Electrical stimulation therapy has been used in various forms to manage bladder dysfunction, including sacral nerve stimulation (SNS), posterior tibial nerve stimulation (PTNS), and direct stimulation of the bladder or surrounding tissues16,17. Our device utilizes direct stimulation on the bladder muscle to facilitate bladder contraction and assist in urination, addressing conditions where bladder muscle control is involuntary and the sensory feedback to the central nervous system is disrupted. + +Our developed soft robotic gripper provides both real- time bladder volume assessment and voiding treatment in a wireless closed- loop control manner. It features a flexible hydrogel- based actuator for conformal wrapping around the bladder, an integrated strain sensor for continuous bladder volume detection, an electrical stimulator for on- demand electrotherapy, and a control module for programmed operation (Fig. 5A- G, Fig. S33- 35). Electrical stimulation (E- stim) is activated when the bladder reaches its maximum volume threshold, targeting the bladder muscles to facilitate urination. Upon complete voiding of the bladder, the integrated sensors detect the reduction in bladder volume, which subsequently triggers the deactivation of the E- stim. This programming cycle ensures that stimulation is provided only, when necessary, closely mimicking the natural urination process and enhancing patient comfort and device efficiency. + +<--- Page Split ---> + +In several studies and clinical trials, electrical stimulation has shown positive effects on bladder control functions for some patients. However, the effectiveness of this treatment may vary among individuals and requires evaluation and supervision by healthcare professionals based on the patient's specific condition. The effectiveness of electrical stimulation for bladder voiding and its required voltage levels requires further investigation beyond the scope of our current study. However, our system demonstrates the feasibility of integrating sensing and actuation components to facilitate timely and responsive treatments for bladder dysfunction. + +In the revised manuscript, we have clarified these points and provided additional explanations regarding the operational principles of our device, its potential applications in bladder dysfunction treatment. Our goal is to contribute to the broader understanding and development of integrative solutions for managing urinary disorders, emphasizing the significance of continuous monitoring and responsive treatment mechanisms in the field of soft robotics and biomedical engineering. + +## Modification to the manuscript: + +(1) On page 20, in the revised manuscript, we added Fig. R5 as Fig. 5G. + +(2) On page 21, in the revised manuscript, we modified the figure caption of Fig. 5G, "Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly." + +(3) On page 18, in the revised manuscript, we added, "When the balloon's volume reaches a predetermined threshold, set here at 100 mL, the control system initiates electrical stimulation. Following successful voiding to below the threshold, the system automatically deactivates the stimulation. While electrical stimulation has shown promising results in enhancing bladder control in various studies and clinical trials, its efficacy can differ across individuals. The effectiveness of electrical stimulation for bladder voiding and its required voltage levels requires further investigation beyond the scope of our current study. However, our prototype showcases the potential of integrating sensing and actuation mechanisms to facilitate timely and adaptive interventions for bladder dysfunction." + +## References + +Grill, W. M. Electrical stimulation for control of bladder function. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 2009 2369- 2370 (2009) doi:10.1109/IEMBS.2009.5335001. + +Coolen, R. L., Groen, J. & Blok, B. F. M. Electrical stimulation in the treatment of bladder dysfunction: Technology update. Med. Devices Evid. Res. 12, 337- 345 (2019). + +<--- Page Split ---> + +Comment 22: As the authors mentioned in the context, PNIPAM hydrogel has reversibly contract and relax property upon electrothermal trigger. If that's the case, is there no risk of delamination if the device is not well- adhered to the tissue when the internal body temperature decreases? Additionally, wouldn't there be a possibility that continuous electrothermal stimulation, applied to prevent deformation of the device after it is attached to the tissue, could have adverse effects on the tissue? + +Our response: We appreciate the reviewer's concerns regarding the potential for delamination and the impact of continuous electrothermal stimulation with the use of PNIPAM hydrogel in our device. The inherent reversible contraction and relaxation properties of PNIPAM hydrogel, activated by electrothermal triggers, are indeed central to our device's operational design. + +In our study, we utilize a bilayer structure for our soft robotic designs, where bending motion is primarily driven by the anisotropic response to the temperature change. As shown in Fig. S2B, our bilayer system mainly consists of two layers: an electronic skin (e- skin) layer and a thermal- responsive PNIPAM hydrogel artificial muscle layer. The PNIPAM undergoes volume and phase transitions in response to temperature changes. Conversely, the e- skin layer serves as a static, non- responsive layer that does not undergo deformation, thereby providing a constraint to the expansive or contractive movements of the PNIPAM layer. Upon surpassing PNIPAM's lower critical solution temperature (LCST), typically within the range of 32- 34 °C, a threshold easily reached by body natural temperature (~37 °C), the device exhibits a bending motion towards the hydrogel layer, achieving a sustained shape deformation under these conditions.18- 20 This dynamic is facilitated by the distinct material properties of both layers, allowing for significant shape transformation while maintaining the device's overall flexibility. Therefore, the device design ensures tissue integration through the mechanical architecture that promotes conformal contact with tissues for sensing, communication, or control systems. + +We can incorporate an integrated thermal feedback system that precisely regulates the device's heating to further address concerns of delamination, especially in scenarios where body temperature significantly diverges from the LCST (32- 34 °C). Fig. R10A shows our adaptively controlled robotic gripper, engineered to autonomously maintain the required actuation temperature under varying environmental conditions. The system is configured to activate the heater to preserve the actuation temperature whenever external temperatures fall below the LCST. Fig. R11 details the synchronization of current and temperature during thermal adjustments, highlighting our device's capability to rapidly respond to temperature variations and maintain stability thereafter. + +Regarding the concern of continuous electrothermal stimulation, we can carefully control the duration and intensity of the stimulation to remain within safe limits. We have conducted both in vivo and in vitro evaluations to confirm the device's safety. In vitro analysis involving fibroblast- like cells (3T3- J- 2) subjected to a 39°C environment for 48 hours showed no compromise in cell health or viability (Fig. 6E- F). Similarly, in vivo + +<--- Page Split ---> + +application involving thermal stimulation around the mice's heart revealed no significant tissue damage or inflammatory response (Fig. S45). While our studies have primarily explored the effect of a few hours of continuous heating, both theoretical and empirical evidence suggest that as long as the temperature is maintained below the critical threshold of \(43^{\circ}C\) based on previous studies \(^{13,14}\) , a risk of thermal damage to tissues can be effectively avoided. As aforementioned, the integration of a thermal feedback mechanism further ensures precise heating control, thereby preventing any risk of overheating or insufficient heating (Fig. R10&11). + +In the revised manuscript, we have provided an enhanced clarification on the operational principles of our device, emphasizing its safety and reliability profile. We hope to offer a clearer understanding of the mechanisms underlying our device's functionality, and the applicability in biomedical application through engineering solutions. + +## Modification to the manuscript: + +(1) On page 10, in the revised manuscript, we modified, "We further evaluated the mechanical force generated by the soft robotic finger which incorporates a PNIPAM hydrogel layer roughly 1 mm thick, under various input powers. Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar hydrogel-based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +(2) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +(3) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. + +(4) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. + +(5) On page 5, in the revised supporting information, we added," + +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's + +<--- Page Split ---> + +responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +(6) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to + +<--- Page Split ---> + +provide precise thermal management, enhancing both efficacy and safety in its applications." + +(7) On page 29, in the revised manuscript, we added, " + +## The sensory-motor integration within the soft robotic system + +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +## References + +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +Comment 23: On Page 24, Figure 6F, what is the indication T1 and T2 in Figure 6F account for? The authors need to explain these in the captions. + +Our response: We thank the reviewer's questions regarding the indications of T1 and T2 in Fig. 6F (Fig. 6G in the updated manuscript). T1 and T2 represent two distinct channels, each linked to a thermal sensor positioned on separate arms of our cardiac gripper, as illustrated in Fig. 6A and Fig. S41A&B. These sensors are designed to simultaneously capture the heart's temperature, facilitating a detailed assessment of temperature fluctuation across different segments of the organ. The multi- channel design exemplifies our device's capability for precise and localized temperature monitoring that is essential for a range of biomedical applications. + +<--- Page Split ---> +![](images/Figure_unknown_26.jpg) + +
Fig. R26. (A) schematic illustration of the soft robotic thera-gripper consisting of two temperature sensors made of thermal resistors. (B) Temperature measurements from the thera-gripper's dual-channel sensors during its deployment onto the mouse heart, demonstrating the device's capability to monitor thermal variations in real-time.
+ +## Modification to the manuscript: + +(1) On page 24, in the revised manuscript, we added Fig. R26B as Fig. 6G. + +(2) On page 25, in the revised manuscript (Fig. 6G's caption), we modified, "Temperature measurements from the thera-gripper's dual-channel sensors during its deployment onto the mouse heart, demonstrating the device's capability to monitor thermal variations in real-time." + +Comment 24: In Fig 6G, it is challenging to consider it as functioning like a pacemaker, as pacing does not seem to lead to actual cardiac capture. + +Our response: We thank the reviewer's concern regarding the pacing functionality described for our cardiac gripper. We agree that our gripper's electrical stimulation electrodes do not function in the traditional sense of a pacemaker. As correctly pointed out, our device introduces a general concept of an electrical stimulator module (Fig. R27A), designed to cater to a broader spectrum of potential therapeutic applications that can benefit from electrical stimulation (E-stim) (e.g., enhancing myocardial contractility), beyond the specific function of pacing \(^{21,22}\) . Our in vivo studies have demonstrated that the gripper's ability to successfully deliver various E-stim patterns (Fig. R27B-D), showing its potential in therapeutic settings. + +To address this point and clarify our intention, we have revised the descriptions within our manuscript and adjusted the annotations in the figures (Fig. R27B) accordingly. This modification aims to explore the versatility of our soft robotic gripper in delivering targeted electrical stimulation for various therapeutic scenarios. + +<--- Page Split ---> +![](images/Figure_unknown_27.jpg) + +
Fig. R27. (A) Flexible pacing electrodes implantation. (B) The surface ECG trace during electrical stimulation using a pair of Au pacing electrodes. (C&D) Representative voltage traces of the cardiac electrical activity during E-stim with various parameters. (C) 500 mV voltage with 1 ms width at 6.5 Hz. (D) 500 mV voltage with 5 s width at 0.1 Hz.
+ +## Modification to the manuscript: + +(1) On page 24, in the revised manuscript, we added Fig. R27B as Fig. 6H. + +(2) On pages 22-23, in the revised manuscript, we modified, ". The e-skin layer consists of microelectrodes for capturing electrical activity of the heart, which serves as essential guidance in operating electrical stimulation (Fig. S47). Fig. S48&S49 showcase the simultaneous sensing and stimulation capabilities on a beating heart with an in vivo mouse model, demonstrating its capability in a broad spectrum of potential therapeutic applications." + +(3) In both the revised manuscript and supporting information. We have replaced "pacing" with "electrical stimulating" to describe the functionality of our device more accurately. + +## References + +Monteiro, L. M., Vasques- Nóvoa, F., Ferreira, L., Pinto- Do- ó, P. & Nascimento, D. S. Restoring heart function and electrical integrity: Closing the circuit. npj Regen. Med. 2, 1- 13 (2017).Cao, H., Kang, B. J., Lee, C. A., Shung, K. K. & Hsiai, T. K. Electrical and Mechanical Strategies to Enable Cardiac Repair and Regeneration. IEEE Rev. Biomed. Eng. 8, 114- 124 (2015). + +<--- Page Split ---> + +Comment 25: In Figs 6 M, N, it was mentioned that changes were observed in S2 and S4. However, it seems that only changes in frequency are visible along the x- axis. Shouldn't the focus be on the resistance changes along the y- axis, which may represent actual strain changes? + +Our response: We appreciate the reviewer's concern regarding the data presented in Fig. 6M and Fig. 6N. These figures are intended to illustrate the contractility patterns of the heart's chambers under both normal and myocardial infarction (MI) conditions, as detected by our strategically positioned strain sensors on the epicardial surfaces (Fig. 6A and Fig. S41A&B). The output from these sensors, closely related to the strain they experience, provides the mechanical behaviors of specific heart chambers. + +Notably, the sensor S4, located on the left ventricle (LV), exhibits the largest amplitude of strain changes. This indicates the LV's exceptional myocardium strength, aligning with the physiological role of the LV in bearing the greatest burdens in circulating blood throughout the body's systemic circulation. Additionally, Fig. 6I offers a visual representation of the infarction area two weeks post- MI surgery, complementing the quantitative data provided by strain sensors. The decreased strain changes detected by sensors S2 (RV) and S4(LV) illustrate the impact of MI, characterized by a loss of contractile myocardium, a decrease in the force of myocardial contractility, and an altered heart rate. + +![](images/Figure_30.jpg) + +
Fig. R28. (A&B) Representative measurements of local cardiac contractions before (A) and after myocardial infarction (B) using a soft robotic thera-gripper wrapping onto a living mouse heart.
+ +We have revised the figures to feature the resistance changes more prominently along the y- axis, ensuring a balanced emphasis on both the strain measurements and the associated frequency changes, offering a comprehensive view of our device's capability to monitor and diagnose cardiac conditions through advanced sensor integration, and demonstrating the potential of custom- engineered solutions in cardiac health. + +## Modification to the manuscript: + +On page 24, in the revised manuscript, we updated Fig. R28A&B as Fig. 6M&N, respectively. + +<--- Page Split ---> + +Comment 26: The paper lacks details on the system used to generate water flow simulating blood flow in the vascular system, including names of the equipment and the setting of flow rate. Information on the properties and thickness of the rubber used is also insufficient. + +Our response: We appreciate the reviewer's concern regarding the details on our experimental setup for simulating blood flow in our study. As shown in Fig. R29, to mimic the arterial environment, we employed a silicone tube (Transparent Silicone Tube 4mm ID x 5mm OD, wall thickness \(\sim 0.5mm\) ) with large stretchability and flexibility as an arterial artery. The pulsatile water flow (30\~260 ml/min) is generated with two flow rate controllable pumps. Pump 1 maintains a constant flow rate to establish a baseline pressure, while Pump 2, connected to a solenoid valve, is regulated by a relay. This valve opens and closes periodically, replicating the pulsatile pressure of blood flow. The relay is further controlled with a pre- programmed microcontroller. All the parts for the setup were purchased from local vendors. + +![PLACEHOLDER_69_0] + +
Fig. R29. In vitro setup for artificial artery model.
+ +We have included the detailed information regarding the experiment setup in the revised manuscript and supporting information. + +## Modification to the manuscript: + +(1) On page 47, in the revised supporting information, we added Fig. R29 as Fig. 36B. + +(2) On page 31, in the revised manuscript, we added, "Measurement of biomimetic blood pressure: As shown in Fig. S36B, to mimic the arterial environment, we employed a silicone tube (Transparent Silicone Tube 4mm ID x 5mm OD, wall thickness \(\sim 0.5mm\) ) with large stretchability and flexibility as an arterial artery. The pulsatile water flow (30\~260 ml/min) is generated with two flow rate controllable pumps. Pump 1 maintains a constant flow rate to establish a baseline pressure, while Pump 2, connected to a solenoid valve, is regulated by a relay. This valve opens and closes periodically, replicating the + +<--- Page Split ---> + +pulsatile pressure of blood flow. The relay is further controlled with a pre- programmed microcontroller. All the parts for the setup were purchased from local vendors." + +Comment 27: This work validated through H&E staining data that a single- day stimulation has a minimal impact on the tissue. However, it remains unclear what effects may occur with continued stimulation over longer period. + +Our response: We appreciate the reviewer's concern regarding the long- term effects of continuous thermal stimulation. As previously discussed in Comments 12, 14, and 22, our device is engineered to operate around the body's natural temperature, significantly reducing the reliance on constant thermal input. Moreover, we can design the device with an advanced thermal feedback mechanism that precisely regulates temperature, thus mitigating risks associated with overheating or insufficient heating (Fig. R10&11). + +Furthermore, the existing literature supports that controlled thermal stimulation within safe limits typically does not lead to adverse effects even thermal input over extended periods. \(^{13,14}\) We have further explained the immediate scope of our current research phase. We focus on establishing a solid foundation for the device's safety and functionality before extending our investigation into long- term usage scenarios. + +## Modification to the manuscript: + +(1) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +(2) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. + +(3) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. + +(4) On page 5, in the revised supporting information, we added," + +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and + +<--- Page Split ---> + +predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +(5) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +(6) On page 29, in the revised manuscript, we added, " + +The sensory-motor integration within the soft robotic system + +<--- Page Split ---> + +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +## References + +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +Comment 28: The 2- week histological analysis of cardiac tissue with a hydrogel- based thera- gripper, as presented in the study, raises questions. It would be insightful to know the condition of the device after this period - whether the device remained in an operable state and the device remained properly attached as intended while withstanding repeated pulsations. + +Our response: We appreciate the reviewer's concern regarding the long- term stability and functionality of the hydrogel- based gripper after a 2- week period. After this time, we carefully examined the device and found it to be intact and effectively attached to the cardiac tissue as intended, as shown in Fig. R30A. + +We also conducted further evaluation focused on the device's performance post- implantation. As shown in Fig. R30B- D, the pacing electrodes and thermal sensor maintained exemplary performance, indicating their capability to deliver electrical stimulation and accurately sense temperature changes after two weeks. These results suggest that our hydrogel- based thera- gripper not only maintains its structural and functional integrity over an extended period but also holds promise for long- term applications in cardiac therapy and monitoring. + +We have updated our manuscript and supporting information to include these insights and highlight the device's robustness and reliability for potential long- term use. + +<--- Page Split ---> +![PLACEHOLDER_73_0] + +
Fig. 30. Overview of device performance after two-week implantation. (A) Visualization of the device accurately positioned on the mouse heart, indicating its stability post two-week implantation. (B&C) Voltage response traces from the pacing electrodes embedded in the implanted device, demonstrating its operational integrity over the two-week period. Here, (B) shows a sine wave configuration at a frequency of \(1 \mathrm{~Hz}\) and amplitude of \(1 \mathrm{~V}\) , while (C) depicts pulse modulation with a height of \(500 \mathrm{mV}\) , pulse with of \(0.01 \mathrm{~s}\) , and a maximum repeating rate of \(1 \mathrm{~Hz}\) . (D) Comparative analysis of the resistive response from the thermal sensor before and after the two-week implantation period, illustrating the device's consistent performance and sensor integrity over time.
+ +## Modification to the manuscript: + +(1) On page 64, in the revised supporting information, we added Fig. R30 as Fig. S52. + +(2) On page 24, in the revised manuscript, we added, "Our post-implantation evaluation revealed that the hydrogel-based thera-gripper remained intact and securely attached to cardiac tissue as intended, demonstrating its durability and effectiveness over time (Fig. S52A). Notably, the E-stim electrodes and thermal sensor maintained optimal performance, effectively delivering electrical stimulation (Fig. S52B&C) and precisely sensing temperature fluctuations (Fig. S52D) even after a two-week period. These results support its feasibility for long-term therapeutic and diagnostic applications." + +Comment 29: Caption in figure S11 (a) : AgNW/PI -> AgNW/PDMS + +<--- Page Split ---> + +Our response: We thank the reviewer's attention to detail and have corrected the caption in Fig. S11(a) (Fig. S10A in the updated supporting information) from AgNW/PI to AgNW/PDMS as suggested. + +## Modification to the manuscript: + +On page 20, in the revised manuscript, we have corrected "AgNW/PI" to "AgNW/PDMS". + +Comment 30: Page 21, the third line from the bottom spelling error : PINPAM -> PNIPAM + +Our response: We thank the reviewer's attention to detail and have corrected the spelling error. + +## Modification to the manuscript: + +On page 22, in the revised manuscript, we have corrected "PINPAM" to "PNIPAM". + +Comment 31: Figure S51D, indication spelling error : Basi -> Basic + +Our response: We thank the reviewer's attention to detail and have corrected the spelling error. + +## Modification to the manuscript: + +On page 48, in the revised manuscript, we have corrected "Basi" to "Basic". + +Comment 32: There should be a space before the units in the text and figures. + +Our response: We thank the reviewer's attention to detail. + +Modification to the manuscript: We have checked and revised all units in the updated manuscript and supporting information. + +## References + +1. Basarir, F., Madani, Z. & Vapaavuori, J. Recent Advances in Silver Nanowire Based Flexible Capacitive Pressure Sensors: From Structure, Fabrication to Emerging Applications. Adv. Mater. Interfaces 9, (2022). +2. Chauhan, N., Maekawa, T. & Kumar, D. N. S. Graphene based biosensors - Accelerating medical diagnostics to new-dimensions. J. Mater. Res. 32, 2860–2882 (2017). +3. Amara, U., Hussain, I., Ahmad, M., Mahmood, K. & Zhang, K. 2D MXene-Based Biosensing: A Review. Small 19, 1–38 (2023). +4. Driscoll, N. et al. MXene-infused bioelectronic interfaces for multiscale electrophysiology and stimulation. Sci. Transl. Med. 13, eabf8629 (2021). +5. Liu, H. et al. 3D Printed Flexible Strain Sensors: From Printing to Devices and Signals. Adv. Mater. 33, 2004782 (2021). +6. Zhu, Z., Park, H. S. & McAlpine, M. C. 3D printed deformable sensors. Sci. Adv. 6, eaba5575 (2023). + +<--- Page Split ---> + +7. Reeder, J. et al. Mechanically Adaptive Organic Transistors for Implantable Electronics. Adv. Mater. 26, 4967-4973 (2014).8. Xu, J. & Song, J. Thermal Responsive Shape Memory Polymers for Biomedical Applications. in (ed. Fazel-Rezai, R.) Ch. 6 (IntechOpen, 2011). doi:10.5772/19256.9. Czerner, M., Fellay, L. S., Suárez, M. P., Frontini, P. M. & Fasce, L. A. Determination of Elastic Modulus of Gelatin Gels by Indentation Experiments. Procedia Mater. Sci. 8, 287-296 (2015).10. Xie, C., Wang, X., He, H., Ding, Y. & Lu, X. Mussel-Inspired Hydrogels for Self-Adhesive Bioelectronics. Adv. Funct. Mater. 30, 1909954 (2020).11. Shian, S., Bertoldi, K. & Clarke, D. R. Dielectric Elastomer Based 'grippers' for Soft Robotics. Adv. Mater. 27, 6814-6819 (2015).12. Shojaefard, M., Niroumandi, S. & Baghani, M. Programming shape-shifting of flat bilayers composed of tough hydrogels under transient swelling. Acta Mech. 233, 213-232 (2022).13. Dewhirst, M. W., Viglianti, B. L., Lora-Michiels, M., Hoopes, P. J. & Hanson, M. THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS. Proc. SPIE--the Int. Soc. Opt. Eng. 4954, 37 (2003).14. van Rhoon, G. C. et al. CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels? Eur. Radiol. 23, 2215-2227 (2013).15. Jiang, Y. et al. Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing. Nat. Biotechnol. 41, 652-662 (2023).16. Grill, W. M. Electrical stimulation for control of bladder function. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 2009 2369-2370 (2009) doi:10.1109/IEMBS.2009.5335001.17. Coolen, R. L., Groen, J. & Blok, B. F. M. Electrical stimulation in the treatment of bladder dysfunction: Technology update. Med. Devices Evid. Res. 12, 337-345 (2019).18. Lanzalaco, S., Mingot, J., Torras, J., Alemán, C. & Armelin, E. Recent Advances in Poly(N-isopropylacrylamide) Hydrogels and Derivatives as Promising Materials for Biomedical and Engineering Emerging Applications. Adv. Eng. Mater. 25, 2201303 (2023).19. Liu, J., Jiang, L., He, S., Zhang, J. & Shao, W. Recent progress in PNIPAM-based multi-responsive actuators: A mini-review. Chem. Eng. J. 433, 133496 (2022).20. Ansari, M. J. et al. Poly(N-isopropylacrylamide)-Based Hydrogels for Biomedical Applications: A Review of the State-of-the-Art. Gels (Basel, Switzerland) 8, (2022).21. Monteiro, L. M., Vasques-Nóvoa, F., Ferreira, L., Pinto-Do-ó, P. & Nascimento, D. + +<--- Page Split ---> + +S. Restoring heart function and electrical integrity: Closing the circuit. npj Regen. Med. 2, 1–13 (2017). + +22. Cao, H., Kang, B. J., Lee, C. A., Shung, K. K. & Hsiai, T. K. Electrical and Mechanical Strategies to Enable Cardiac Repair and Regeneration. IEEE Rev. Biomed. Eng. 8, 114–124 (2015). + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +I believe that the revisions address the points that were raised in the original review. The paper is now suitable to be accepted in nature communications. + +Reviewer #2 (Remarks to the Author): + +I thank the authors for fully and thoroughly revising the manuscript. I believe their manuscript has improved significantly, and I have no further comments. + +<--- Page Split ---> + +## Responses to comments of Referee #1 + +Summary Comment: I believe that the revisions address the points that were raised in the original review. The paper is now suitable to be accepted in nature communications. + +Our response: We thank the reviewer for the positive comment. + +## Responses to comments of Referee #2 + +Summary Comment: I thank the authors for fully and thoroughly revising the manuscript. I believe their manuscript has improved significantly, and I have no further comments. + +Our response: We thank the reviewer for the positive comment. + +<--- Page Split ---> + +## Description of Additional Supplementary Files + +File name: Supplementary movie 1Description: Soft robot with a nature- inspired starfish design + +File name: Supplementary movie 2Description: Shape transformation of soft robots with various configurations + +File name: Supplementary movie 3Description: Soft robot with a helical structure biomimicking a chiral seedpod + +File name: Supplementary movie 4Description: The shape transformation of a soft robotic pill + +File name: Supplementary movie 5Description: A three- arm soft robotic gripper via sequentially programming input power + +File name: Supplementary movie 6Description: A four- arm soft robotic gripper via simultaneously programming input power + +<--- Page Split ---> diff --git a/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..39e4df800b93651db07d8eaa95dd4316b56dbc2a --- /dev/null +++ b/peer_reviews/df2aff5889e0a59a97203b46345a7092f93973c5fc2114431f41a8cde3a46862/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,2011 @@ +<|ref|>title<|/ref|><|det|>[[60, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 112, 348, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[77, 183, 812, 242]]<|/det|> +Skin- inspired, sensory robots for electronic implants + +<|ref|>image<|/ref|><|det|>[[57, 731, 238, 783]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 731, 915, 800]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons + +<|ref|>text<|/ref|><|det|>[[55, 800, 925, 927]]<|/det|> +license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 313, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 111, 414, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 139, 875, 210]]<|/det|> +The article entitled "Skin- inspired, sensory robots for electronic implants" by Zhang et al. introduces an approach for soft robots that can sense multiple parameters and provide on- demand motions. Although the proposed concept would be useful for the development of associated technologies, there are many questionable issues and experimental shortcomings that should be addressed before further progress. + +<|ref|>text<|/ref|><|det|>[[119, 223, 875, 280]]<|/det|> +The authors need to check the overall figures again. The order of the figures in the manuscript is a total mess. Also, there is so much information about SI that it is very difficult to understand the main text or what the author is trying to say. All unnecessary SI should be discarded, and only the content that is directly related to the key points should be mentioned. + +<|ref|>text<|/ref|><|det|>[[119, 293, 860, 322]]<|/det|> +Please understand that the comments have been randomly organized rather than in the order of the manuscript. + +<|ref|>text<|/ref|><|det|>[[119, 335, 839, 392]]<|/det|> +1. The authors demonstrated the adhesion performance of the bio-adhesive layer using the bending image in Figure 3B, but this referee can't find any quantified data set of the adhesion force, did the authors studied how strong it is under various conditions? (e.g. dry, wet environments, etc) + +<|ref|>text<|/ref|><|det|>[[119, 405, 876, 448]]<|/det|> +2. While the thickness of other layers was specified, the actuation hydrogel's thickness was missing (it seems to be considerably thick). Increase of the thickness might enhance actuation performance but could potentially affect sensing and stimulation properties. + +<|ref|>text<|/ref|><|det|>[[119, 462, 857, 491]]<|/det|> +2- 1) What is the optimal thickness of the actuation layer for achieving reliable shape- morphing? 2-2) How does the thickness of the actuation layer affect sensing and stimulation performance? + +<|ref|>text<|/ref|><|det|>[[119, 504, 864, 547]]<|/det|> +3. In Figure 3N, bending configurations appear to be different and uncontrollable although three arms had the same composition. Can the authors explain why? And, it seems those arms are not reversible since the off-arms don't seem to return to the original state + +<|ref|>text<|/ref|><|det|>[[119, 560, 870, 617]]<|/det|> +4. In Figure 4A, there might be stability issues with the PAAM hydrogel as a pressure sensor. Considering the implant environment, swelling of the hydrogel might hinder pressure measurement due to instability in weight loss and capacitance changes. Any proposed solutions to address this concern would be necessary. + +<|ref|>text<|/ref|><|det|>[[119, 630, 833, 686]]<|/det|> +5. The authors discussed the adhesion and actuation force of the hydrogel in Fig. S46, Supplementary Note S8. However, it seems to be considered in a dry environment. Given the nature of hydrogels, there might be swelling and degradation issues when operating in a wet environment. + +<|ref|>text<|/ref|><|det|>[[118, 700, 866, 785]]<|/det|> +6. In Figures 5 and S47, the hydrogel was designed to face biological tissue (please correct me if not). In this case, some of physical sensors (e.g., strain and pressure gauges) would be fine, but how to figure out operation of other sensors/stimulators that need direct contacts to tissues? For example, the authors mentioned here electrical stimulation for the bladder, but is it possible to stimulate the bladder through the adhesive layer and PAAM hydrogel? That would be not. Can the authors explain how to achieve such functional operations? + +<|ref|>text<|/ref|><|det|>[[118, 798, 870, 855]]<|/det|> +7. In Figure 5g, it is unclear what the author intended to demonstrate through the programming. Can the authors provide significance of the programming for the control of the bladder. (It is quite strange that E-stim ON when the bladder is void, and E-stim OFF after expansion/contraction cycle... Shouldn't it turn on when the volume reaches maximum?). + +<|ref|>text<|/ref|><|det|>[[118, 868, 863, 911]]<|/det|> +8. In Figs. 6 and S52A, it appears difficult or impossible for the electronic components at the end of each arm to form a strong coupling to living tissues, particularly to tissues whose volume changes over time, such as the bladder. How did the authors control or attach the robotic arms? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 99, 472, 125]]<|/det|> +9. Page 3, line 86 It is not 'overactive', but 'underactive' bladder. + +<|ref|>text<|/ref|><|det|>[[118, 139, 874, 168]]<|/det|> +10. In fig. 2c, is there a motivation for using such diverse materials for different components? This referee can't find outstanding characteristics of those materials for sensing components. + +<|ref|>text<|/ref|><|det|>[[118, 181, 874, 210]]<|/det|> +11. In figs. 2f and 2g, the authors claimed that soft robots can form conformal contacts to tissues, but did the authors study or compare mechanical modulus between devices and tissues? + +<|ref|>text<|/ref|><|det|>[[118, 224, 878, 266]]<|/det|> +12. In fig. S12B, such layered structures are likely to interfere with each other's signals. is there any reason to measure both parameters at the same time? Or, even if simultaneous measurements are made, does each sensor operate independently? + +<|ref|>text<|/ref|><|det|>[[120, 280, 435, 294]]<|/det|> +13. there's no description for Figs. 3H&3I + +<|ref|>text<|/ref|><|det|>[[118, 308, 875, 336]]<|/det|> +14. We usually do not include information about SI figures in main figure captions. For example, in fig.3, there is information about fig. S18 and 25, but these should be removed. + +<|ref|>text<|/ref|><|det|>[[120, 350, 754, 364]]<|/det|> +15. please do double check all the figures including SI, whose order is a total mess + +<|ref|>text<|/ref|><|det|>[[120, 433, 414, 447]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 461, 880, 602]]<|/det|> +Lin Zhang et al. developed various types of soft robots, utilizing an electronic skin (e- skin) made of materials like silver nanowires, reduced graphene oxide, MXene, and conductive polymers integrated into a polymer matrix. This e- skin is designed to mimic skin receptors, enabling the perception of various stimuli. The robots, inspired by natural forms like starfish, chiral seedpod, and others, are equipped with features for bending, twisting, and expanding, and include an artificial muscle for dynamic movement. This study also integrated wireless modules to control and communicate without tethering. Demonstrated in various medical scenarios, these devices showed capabilities such as blood pressure sensing and adapting to organ surfaces for diagnostic and therapeutic functions, exemplifying their potential as multifunctional, minimally invasive medical tools. + +<|ref|>text<|/ref|><|det|>[[118, 616, 878, 672]]<|/det|> +However, the devices used materials commonly used in practical applications, with the exception of an in situ solution- based fabrication approach, showing no significant material novelty. This article is also lack of either long- term feasibility or detailed information about the mechanism of each sensor like the relationships between pH, pressure and resistance. + +<|ref|>text<|/ref|><|det|>[[118, 686, 874, 785]]<|/det|> +Despite such some disadvantages, the positive aspect lies in its multifunctional ability to be implanted in real scenarios, possibly leading to successful demonstrations for various organ shapes. In specific, massive integration of multifunctional soft robots entailing high- performance functional nanomaterials and actuating modules is highly impressive. Additionally, this article demonstrates a high level of systemic completeness, considering real clinical situations. Therefore, the reviewer believes that with some modifications addressing specific comments included in the following, this paper has the potential to be accepted in Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[119, 800, 258, 813]]<|/det|> +## \*Major comments + +<|ref|>text<|/ref|><|det|>[[118, 814, 875, 870]]<|/det|> +1. In the introduction part, some references (Nature Materials volume 15, pages937-950 (2016), Nature Nanotechnology volume 9, pages397-404 (2014), and Nature Electronics volume 6, pages779-789 (2023)) regarding stable tissue-interfacing performance of wearable/implantable devices should be cited to justify the authors' research purpose. + +<|ref|>text<|/ref|><|det|>[[118, 870, 876, 910]]<|/det|> +2. The reviewer believes that sensory-motor integration is valuable when the robot can control motors in response to signals received from sensors. However, it seems that controlling the motors and performing sensor functions operate independently. In that case, can this robot still be + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 730, 98]]<|/det|> +considered as the presence of responsiveness as mentioned in the introduction? + +<|ref|>text<|/ref|><|det|>[[118, 99, 830, 153]]<|/det|> +3. It seems good that the robot is designed differently for each target organ. The reviewer is curious about the variation in curvature among different organs. For instance, in the case of organs like the heart and bladder, squeezing too much might make it challenging to grasp effectively. How was this consideration taken into account in the design? + +<|ref|>text<|/ref|><|det|>[[118, 154, 860, 182]]<|/det|> +4. Why does the parallel strips configuration result in twisting? Is there any reference for this, or was it an original concept? + +<|ref|>text<|/ref|><|det|>[[118, 183, 835, 223]]<|/det|> +5. On page 6, if the transfer method is well-designed, it could potentially enable multi-modal implementation. Is there a particular advantage in this solution-based approach over transfer methods? + +<|ref|>text<|/ref|><|det|>[[118, 223, 875, 308]]<|/det|> +6. On Page 7, Figure 2H, the volume of the PNIPAM hydrogel in Figure 2H is shown to dramatically decrease between approximately \(35^{\circ}C\) and \(45^{\circ}C\) . Given that the normal human body temperature is around \(36 - 37^{\circ}C\) , even if actuation is induced by an electrothermal method, maintaining its shape seems crucial for attaching it to various organs within the body. To substantiate this point, it would be necessary for the authors to demonstrate volume changes starting from a range lower than \(35^{\circ}C\) . + +<|ref|>text<|/ref|><|det|>[[118, 309, 870, 337]]<|/det|> +7. It was confirmed that the composite was implemented through XPS analysis. Is there a concern that this might result in lower performance compared to a full composite? + +<|ref|>text<|/ref|><|det|>[[118, 337, 820, 365]]<|/det|> +8. After nanomaterials are created through the laser pattern, the inherent properties of the material make handling difficult. How was the surrounding material removed or treated? + +<|ref|>text<|/ref|><|det|>[[118, 365, 852, 406]]<|/det|> +9. In Figs 3C, D, please indicate in the caption whether SEM images represent the surface or cross-section. Additionally, to determine the presence of voids, it may be necessary to examine cross-sectional TEM images. + +<|ref|>text<|/ref|><|det|>[[118, 407, 872, 448]]<|/det|> +10. In Fig 3E, it is understood that accurately observing the exact temperature by performing twisting and bending may be challenging with an infrared camera. However, even considering this, it seems that the temperature distribution is not uniform. + +<|ref|>text<|/ref|><|det|>[[118, 448, 872, 476]]<|/det|> +11. In Fig 3F, G, the temperature converges over time, but what is the reason for the continuous change in bending force? Additionally, once bent, how long does the bending force persist? + +<|ref|>text<|/ref|><|det|>[[118, 476, 875, 503]]<|/det|> +12. In addition to comment 9, is it necessary to keep the heater on continuously to maintain actual bending when attaching it to an organ? + +<|ref|>text<|/ref|><|det|>[[118, 504, 876, 572]]<|/det|> +13. The dual-axis graphs presented in this figure (Figure 3I, Figure 5F, K, N etc.) are difficult to intuitively comprehend. It is unclear whether the changes on the left axis correspond to the results on the right axis or if they were determined through variations in resistance, pressure, or pH values. Therefore, it seems necessary for the authors to modify the graphs for better intuitive understanding and provide explanations regarding the extent of numerical changes made. + +<|ref|>text<|/ref|><|det|>[[118, 573, 875, 614]]<|/det|> +14. Using heat as a stimulus might potentially cause damage to the tissue. However, considering the hydrogel is thick enough, it may prevent such damage. How efficiently does heat transfer throughout the entire hydrogel, and is the heat dissipation effective enough to be considered safe? + +<|ref|>text<|/ref|><|det|>[[118, 614, 875, 641]]<|/det|> +15. While applying temperature, can the thermal sensor accurately measure the temperature from the tissue? + +<|ref|>text<|/ref|><|det|>[[118, 643, 856, 671]]<|/det|> +16. What is the reason for the difference in the transfer method in S12(b) compared to the dual printing method in S16? + +<|ref|>text<|/ref|><|det|>[[118, 672, 848, 727]]<|/det|> +17. On Page 11, the author mentioned that "The electrothermal stimulus along with distributed sensing capabilities enables programmed actuation not only on demand but also regulated simultaneously by the sensing feedback". How was actuation implemented based on sensing feedback? + +<|ref|>text<|/ref|><|det|>[[118, 728, 868, 799]]<|/det|> +18. On Page 14, Figure S31, in Figure S31B, it is evident that there is a tendency for the coupling coefficient to decrease as the separation distance increases. However, in Figure S31D, there is a trend showing an increase in output power relative to input power as the distance increases. This observation appears to be theoretically inconsistent. If this graph is accurate, the authors need to provide additional explanations for these results. + +<|ref|>text<|/ref|><|det|>[[118, 800, 875, 911]]<|/det|> +19. On Page 16, in order for the sensory robots developed by the authors to conformally adhere to tissues or organs, they require not only curvilinear surfaces but also effective adhesion. While this article mentions the adhesiveness of PNIPAM, a recently published paper indicates that PNIPAM shows tissue adhesion at low temperatures (around \(25^{\circ}C\) ), but loses almost all adhesive strength when it transitions to a gel form near \(40^{\circ}C\) (Nature Biotechnology 2023, 41, 652-662). To showcase the tissue adhesion capability of the authors' device, it becomes imperative to gauge the adhesive strength of the hydrogel by varying temperatures. This would confirm that there are no issues with adhesion even after attaching it to an organ. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[117, 84, 810, 112]]<|/det|> +20. In Figs 5, 6, the use of Au electrodes for electrical stimulation in electrotherapy seems somewhat divergent from the other sensing materials of this paper (Fig. S52B). + +<|ref|>text<|/ref|><|det|>[[117, 112, 873, 183]]<|/det|> +21. In Fig 5G, the electrical stimulation off voltage is not 0.0 V. Is there a specific reason for this? To help readers to understand, it appears that the authors should provide additional explanations regarding the correlation between electrical stimulation and volume changes. Specifically, a clear clarification is needed on whether the specific electrical stimulation is causing an actual increase in volume or if it is transmitting signals to patients having urinary dysfunction. + +<|ref|>text<|/ref|><|det|>[[117, 183, 864, 225]]<|/det|> +22. As the authors mentioned in the context, PNIPAM hydrogel has reversibly contract and relax property upon electrothermal trigger. If that's the case, is there no risk of delamination if the device is not well-adhered to the tissue when the internal body temperature decreases? + +<|ref|>text<|/ref|><|det|>[[117, 225, 864, 266]]<|/det|> +Additionally, wouldn't there be a possibility that continuous electrothermal stimulation, applied to prevent deformation of the device after it is attached to the tissue, could have adverse effects on the tissue? + +<|ref|>text<|/ref|><|det|>[[117, 266, 864, 294]]<|/det|> +23. On Page 24, Figure 6F, what is the indication T1 and T2 in Figure 6F account for? The authors need to explain these in the caption. + +<|ref|>text<|/ref|><|det|>[[117, 294, 860, 322]]<|/det|> +24. In Fig 6G, it is challenging to consider it as functioning like a pacemaker, as pacing does not seem to lead to actual cardiac capture. + +<|ref|>text<|/ref|><|det|>[[117, 322, 872, 364]]<|/det|> +25. In Figs 6 M, N, it was mentioned that changes were observed in S2 and S4. However, it seems that only changes in frequency are visible along the x-axis. Shouldn't the focus be on the resistance changes along the y-axis, which may represent actual strain changes? + +<|ref|>text<|/ref|><|det|>[[117, 364, 872, 405]]<|/det|> +26. The paper lacks details on the system used to generate water flow simulating blood flow in the vascular system, including names of the equipment and the setting of flow rate. Information on the properties and thickness of the rubber used is also insufficient. + +<|ref|>text<|/ref|><|det|>[[117, 405, 843, 447]]<|/det|> +27. This work validated through H&E staining data that a single-day stimulation has a minimal impact on the tissue. However, it remains unclear what effects may occur with continued stimulation over longer period. + +<|ref|>text<|/ref|><|det|>[[117, 447, 870, 504]]<|/det|> +28. The 2-week histological analysis of cardiac tissue with a hydrogel-based thera-gripper, as presented in the study, raises questions. It would be insightful to know the condition of the device after this period - whether the device remained in an operable state and the device remained properly attached as intended while withstanding repeated pulsations. + +<|ref|>text<|/ref|><|det|>[[118, 519, 257, 532]]<|/det|> +\*Minor comments + +<|ref|>text<|/ref|><|det|>[[118, 533, 712, 592]]<|/det|> +1. Caption in figure S11 (a) : AgNW/PI -> AgNW/PDMS +2. Page 21, the third line from the bottom spelling error : PINPAM -> PNIPAM +3. Figure S51D, indication spelling error : Basi -> Basic +4. There should be a space before the units in the text and figures. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[316, 116, 678, 136]]<|/det|> +## Responses to comments of Referee #1 + +<|ref|>text<|/ref|><|det|>[[116, 165, 365, 184]]<|/det|> +Comments from Referee #1: + +<|ref|>text<|/ref|><|det|>[[114, 200, 883, 377]]<|/det|> +Summary Comment: The article entitled "Skin- inspired, sensory robots for electronic implants" by Zhang et al. introduces an approach for soft robots that can sense multiple parameters and provide on- demand motions. Although the proposed concept would be useful for the development of associated technologies, there are many questionable issues and experimental shortcomings that should be addressed before further progress. The authors need to check the overall figures again. The order of the figures in the manuscript is a total mess. Also, there is so much information about SI that it is very difficult to understand the main text or what the author is trying to say. All unnecessary SI should be discarded, and only the content that is directly related to the key points should be mentioned. + +<|ref|>text<|/ref|><|det|>[[115, 382, 882, 440]]<|/det|> +Our response: We thank the reviewer for these positive comments and for these helpful suggestions for revision. We carefully addressed the issues, as listed below, and revised our manuscript accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 448, 882, 487]]<|/det|> +Modification to the manuscript: We have modified both the manuscript and supporting information based on the reviewer's concerns and suggestions. + +<|ref|>text<|/ref|><|det|>[[115, 500, 882, 578]]<|/det|> +Comment 1: The authors demonstrated the adhesion performance of the bio- adhesive layer using the bending image in Figure 3B, but this referee can't find any quantified data set of the adhesion force, did the authors studied how strong it is under various conditions? (e.g. dry, wet environments, etc). + +<|ref|>text<|/ref|><|det|>[[115, 584, 882, 642]]<|/det|> +Our response: We appreciate the reviewer's comment regarding the lack of quantified data on the adhesion performance of the bio- adhesive layer. We have conducted \(180^{\circ}\) peeling tests under both dry and moist environments at physiological temperature \(\sim 37^{\circ}C\) . + +<|ref|>image<|/ref|><|det|>[[171, 657, 792, 880]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 177]]<|/det|> +Fig. R1. Interfacial adhesion characterization via peeling tests. (A) Adhesive force- displacement curves and (B) calculated interfacial energy from the \(180^{\circ}\) peeling test of the biodegradable layer interacting with hydrogel. The adhesion force is higher under a moist condition, mimicking the human body environment, favorable for potential implantable biomedical device applications. + +<|ref|>text<|/ref|><|det|>[[114, 190, 884, 341]]<|/det|> +Fig. R1 presents that the bio- adhesive layer maintains robust adhesion in both dry and wet conditions. Notably, the adhesion force shows an enhancement in a moist condition that simulates the internal human body environment. This enhancement is likely due to the hydrophilic nature of the hydrogel and adhesive, which forms additional hydrogen bonds in the presence of moisture. Such behavior is advantageous for implantable devices that must maintain reliable adhesion in the moist internal conditions of the human body. We have clarified these points in the revised manuscript and supporting information, providing a clearer view of the bio- adhesive layer's performance. + +<|ref|>sub_title<|/ref|><|det|>[[116, 348, 410, 367]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 374, 856, 395]]<|/det|> +(1) On page 26, in the revised supporting information, we added Fig. R1 as Fig. S15. + +<|ref|>text<|/ref|><|det|>[[114, 401, 883, 481]]<|/det|> +(2) On page 9, in the revised manuscript, we added, "Importantly, the bio-adhesive layer exhibits robust adhesion under both dry and wet conditions, as displayed in Fig. S16. This feature ensures the reliability of implantable devices in the dynamic and moist human body environment." + +<|ref|>text<|/ref|><|det|>[[114, 490, 883, 550]]<|/det|> +(3) On page 28, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +<|ref|>text<|/ref|><|det|>[[114, 565, 883, 642]]<|/det|> +Comment 2: While the thickness of other layers was specified, the actuation hydrogel's thickness was missing (it seems to be considerably thick). Increase of the thickness might enhance actuation performance but could potentially affect sensing and stimulation properties. + +<|ref|>text<|/ref|><|det|>[[113, 643, 881, 680]]<|/det|> +2- 1) What is the optimal thickness of the actuation layer for achieving reliable shape- morphing? + +<|ref|>text<|/ref|><|det|>[[113, 680, 881, 717]]<|/det|> +2- 2) How does the thickness of the actuation layer affect sensing and stimulation performance? + +<|ref|>text<|/ref|><|det|>[[114, 725, 883, 818]]<|/det|> +Our response: We thank the reviewer's comment regarding the thickness of the actuation hydrogel layer and its potential impact on the device's performance. We have conducted a series of experiments to investigate the effects of the actuation layer's thickness on both actuation performance and its interplay with sensing and stimulation functionalities. + +<|ref|>text<|/ref|><|det|>[[114, 826, 494, 845]]<|/det|> +2- 1) Optimal thickness for shape- morphing: + +<|ref|>text<|/ref|><|det|>[[114, 852, 883, 890]]<|/det|> +Our investigation reveals that thicker hydrogel layers exhibit more pronounced shape morphing at a given activation temperature, but with a slower response rate due to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 202]]<|/det|> +increased mass, as shown in Fig. R2A. Correspondingly, these thicker layers generate greater forces, enhancing actuation performance. However, this comes at the cost of increased overall device volume, which may not be ideal for minimally invasive applications where compactness is crucial. Our approach can tailor the hydrogel layer's thickness based on specific application requirements, highlighting our fabrication method's versatility. + +<|ref|>image<|/ref|><|det|>[[135, 216, 872, 375]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 392, 883, 462]]<|/det|> +
Fig. R2. Effect of hydrogel thickness on actuation performance. (A) Bending angle over time for varying hydrogel thicknesses at \(41^{\circ}C\) . (B) Measured static force changes at \(41^{\circ}C\) across different hydrogel thicknesses. (C) Resistive response of a thermal sensor (ERT-J0ET102H) across a temperature range of \(22^{\circ}C\) to \(60^{\circ}C\) for different hydrogel thicknesses.
+ +<|ref|>text<|/ref|><|det|>[[115, 476, 618, 495]]<|/det|> +2- 2) Clarification on sensing and stimulation performance: + +<|ref|>text<|/ref|><|det|>[[114, 503, 883, 655]]<|/det|> +In our design, the sensors are embedded in a distinct sensing layer and this design strategy ensures that modifications to the thickness of the hydrogel actuation layer are primarily focused on optimizing actuation performance without affecting the sensitivity or functionality of the sensing and stimulation elements. To experimentally validate this design principle, we conducted a series of experiments focusing on the performance of temperature sensors embedded within hydrogel layers of varying thicknesses. These results indicate no significant difference in sensor performance across different hydrogel thicknesses, further supporting our design strategy. + +<|ref|>sub_title<|/ref|><|det|>[[115, 662, 409, 680]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 687, 855, 707]]<|/det|> +(1) On page 31, in the revised supporting information, we added Fig. R2 as Fig. S20. + +<|ref|>text<|/ref|><|det|>[[114, 713, 883, 902]]<|/det|> +(2) On pages 10-11, in the revised manuscript, we added, "Moreover, our study demonstrates that the thickness of the hydrogel layer determines the actuation performance of the device. As depicted in Fig. S20A, thicker hydrogel layers induce more pronounced shape morphing at a set activation temperature, while a slower response due to their increased mass. The thicker layers are also capable of generating higher actuation force, thereby enhancing the actuation capability of the device (Fig. S20B). However, the increased device volume may limit its applicability in minimally invasive implantable devices, where compactness is a key factor. In the device configuration, embedded sensors are strategically positioned within a single, thin e-skin layer, thus minimizing the required thickness of the hydrogel layer for efficient actuation and allowing + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 202]]<|/det|> +the integrated system to be relative compact (Fig. S20C). Our fabrication technique accommodates customization of the hydrogel layer thickness to optimize device performance for specific applications, demonstrating the method's flexibility and adaptability to various biomedical needs. The utilization of a RGO/PI- nanocomposite temperature sensor enables to precisely identify the real- time information of temperature during muscle motion." + +<|ref|>text<|/ref|><|det|>[[115, 216, 882, 293]]<|/det|> +Comment 3: In Figure 3N, bending configurations appear to be different and uncontrollable although three arms had the same composition. Can the authors explain why? And, it seems those arms are not reversible since the off- arms don't seem to return to the original state. + +<|ref|>text<|/ref|><|det|>[[115, 299, 882, 489]]<|/det|> +Our response: We appreciate the reviewer's comment regarding the bending configurations in Fig. 3N. Despite the uniform material composition of the three arms, slight variations in environmental conditions during the actuation process such as minor differences in temperature and hydrogel thickness contributed to the non- uniform bending behavior. In addition to the factors already mentioned, the design embedded thermal heaters could also influence the bending behavior of each arm. The embedded heater on e- skin generates temperature control and causes the hydrogel's expansion and contraction. Consequently, the slight differences in the positioning and embedding depth of these heaters can cause variability in bending configurations. We have explained this phenomenon in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 495, 884, 628]]<|/det|> +Regarding reversibility, we would like to provide further clarification. Our experiments (Fig. S5B, and Fig. S7- S9) indicate that the recovery phase indeed requires a longer duration than the actuation process. This phenomenon is common in many smart materials. As shown in Fig. 3N, the observed variation in recovery rates of the arms back to their original shapes is directly related to the sequence and timing of their activation. Importantly, given sufficient time for recovery, our experiments have consistently shown that the arms can return to their original state (Fig. S7- S9). + +<|ref|>sub_title<|/ref|><|det|>[[116, 635, 410, 654]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 660, 882, 718]]<|/det|> +On page 11, in the revised manuscript, we added, "Here, the observed variability in bending configuration can be attributed to differences in the positioning and depth of the functional modules within the e- skin layer." + +<|ref|>text<|/ref|><|det|>[[115, 732, 882, 809]]<|/det|> +Comment 4: In Figure 4A, there might be stability issues with the PAAM hydrogel as a pressure sensor. Considering the implant environment, swelling of the hydrogel might hinder pressure measurement due to instability in weight loss and capacitance changes. Any proposed solutions to address this concern would be necessary. + +<|ref|>text<|/ref|><|det|>[[115, 815, 882, 891]]<|/det|> +Our response: We appreciate the reviewer's comment on the stability challenges with the use of PAAM hydrogel as a pressure sensor within an implant environment. To address concerns about hydrogel swelling affecting pressure measurement stability, we propose two strategic solutions. First, we suggest the integration of a protective + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 259]]<|/det|> +encapsulation layer around the hydrogel to mitigate the effects of swelling and environmental fluctuations. This encapsulation layer would be designed to be permeable enough to allow for pressure transmission while minimizing direct hydrogel exposure to body fluids that could cause excessive swelling. Secondly, optimizing the hydrogel synthesis recipe (e.g., increasing crosslinker density) to reduce its sensitivity to swelling without compromising its pressure- sensing capabilities. These measures are capable of enhancing the stability and reliability of the hydrogel as a pressure sensor within the implantable environment. We have discussed the possible solutions regarding the future implantable application in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 267, 409, 285]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 292, 883, 460]]<|/det|> +On page 29, in the revised manuscript, we added, "Here, to mitigate potential stability issues regarding hydrogel swelling and its impact on pressure sensing, we propose two mitigation solutions. Firstly, we incorporate a protective encapsulation layer around the hydrogel. This layer is engineered to be permeable enough to facilitate pressure transmission while simultaneously shielding the hydrogel from direct exposure to body fluids that may induce excessive swelling. Secondly, we refine the hydrogel's composition by increasing the crosslinker concentration to diminish swelling sensitivity without impairing the hydrogel's ability to sense pressure. By applying these strategies will enhance the stability of the hydrogel as a pressure sensor for implantable applications." + +<|ref|>text<|/ref|><|det|>[[114, 475, 882, 551]]<|/det|> +Comment 5: The authors discussed the adhesion and actuation force of the hydrogel in Fig. S46, Supplementary Note S8. However, it seems to be considered in a dry environment. Given the nature of hydrogels, there might be swelling and degradation issues when operating in a wet environment. + +<|ref|>text<|/ref|><|det|>[[114, 558, 883, 860]]<|/det|> +Our response: We appreciate the reviewer's comment on the potential swelling of the hydrogel in our device, especially when exposed to a wet environment. The primary objective of our characterization was to understand the baseline mechanical properties and actuation capabilities of hydrogel. Hydrogels, by their nature, are highly responsive to environmental conditions, particularly moisture. However, PNIPAM hydrogel exhibits a thermal- responsive property. Once the external temperature exceeds its LCST, the hydrophobic interaction of the isopropyl group dominates, leading to a conformational transition from coil to globule. This process causes the water inside to be squeezed out, resulting in the volumetric shrinkage of the system (Fig. R3A). The temperature- induced molecular structural change significantly impacts the hydrogel's shape morphing and actuation force (Fig. R3B&C), far more than minor humidity variations typical of human body environments. Therefore, this rationale underpins our decision to not specifically investigate the hydrogel's actuation behavior in wet environments. Our investigations are thus aligned with understanding how temperature variations, rather than moisture changes, influence the actuation capabilities essential for the intended applications of our device. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[118, 140, 880, 302]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 313, 883, 400]]<|/det|> +
Fig. R3. Actuation behavior of bilayer soft robots under ambient conditions. (A) Measured volume shrinkage of PNIPAM hydrogel during a heating process with temperature changing from \(25^{\circ}C\) to \(60^{\circ}C\) . (B) The resultant bending angle \(\theta\) of a soft robotic arm as a function of the input electric power. (C) Measured static force changes of the soft robotic finger under different temperatures induced by different electrical powers.
+ +<|ref|>text<|/ref|><|det|>[[114, 407, 883, 558]]<|/det|> +In response to the reviewer's note on adhesion and actuation force evaluations potentially occurring in dry conditions, we wish to clarify that our bioadhesive behavior assessments were conducted under simulated physiological conditions. All samples were incubated overnight to ensure a representative in vivo environment is achieved, maintaining the integrity of tissue/organ surfaces for accurate assessment (Fig. R4). This approach ensures a thorough evaluation of the hydrogels' performance, including their reaction to swelling and degradation, under conditions that closely emulate their intended operational environment. + +<|ref|>image<|/ref|><|det|>[[118, 567, 880, 829]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 838, 883, 890]]<|/det|> +
Fig. R4. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \(36^{\circ}C\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 124]]<|/det|> +threshold. All tests were conducted after overnight incubation simulating physiological conditions at \(34^{\circ}\mathrm{C}\) , \(37^{\circ}\mathrm{C}\) , and \(40^{\circ}\mathrm{C}\) . Scale bars, 5 mm. + +<|ref|>sub_title<|/ref|><|det|>[[116, 157, 409, 176]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 183, 882, 278]]<|/det|> +(1) On pages 5-6, in the revised manuscript, we modified, "The PNIPAM hydrogel can undergo a dramatic volumetric reduction of about \(90\%\) as the temperature shifts from 25 \(^\circ \mathrm{C}\) to \(60^\circ \mathrm{C}\) . Notably, this significant and rapid deswelling behavior is initiated only when temperature is beyond its LCST (32 \(^\circ \mathrm{C} \sim 34^\circ \mathrm{C}\) ), enabling excellent actuation capabilities within biological environments (Fig. S3A&B, and Fig. 2H)." + +<|ref|>text<|/ref|><|det|>[[115, 285, 882, 416]]<|/det|> +(2) On page 29, in the revised supporting information (Fig. S19's caption), we added, "Here, all characterizations were conducted under ambient conditions because of the unique temperature-responsive nature of the PNIPAM hydrogel. Its actuation force and shape morphing capabilities are predominantly influenced by temperature-induced molecular structural changes, rather than slight humidity changes typical in human body environments. This characteristic underlines the hydrogel's efficacy in translating thermal stimuli into mechanical actions, essential for the intended biomedical applications." + +<|ref|>text<|/ref|><|det|>[[115, 423, 856, 444]]<|/det|> +(3) On page 52, in the revised supporting information, we added Fig. R4 as Fig. S40. + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 639]]<|/det|> +(4) On page 21, in the revised manuscript, we added, "We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature-responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +<|ref|>text<|/ref|><|det|>[[115, 646, 882, 702]]<|/det|> +(5) On page 28, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +<|ref|>sub_title<|/ref|><|det|>[[115, 710, 208, 727]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[115, 735, 882, 875]]<|/det|> +Y. Jiang, A.A. Trotsyuk, S. Niu, D. Henn, K. Chen, C.C. Shih, M.R. Larson, A.M. Mermin-Bunnell, S. Mittal, J.C. Lai, A. Saberi, E. Beard, S. Jing, D. Zhong, S.R. Steele, K. Sun, T. Jain, E. Zhao, C.R. Neimeth, W.G. Viana, J. Tang, D. Sivaraj, J. Padmanabhan, M. Rodrigues, D.P. Perrault, A. Chattopadhyay, Z.N. Maan, M.C. Leeolou, C.A. Bonham, S.H. Kwon, H.C. Kussie, K.S. Fischer, G. Gurusankar, K. Liang, K. Zhang, R. Nag, M.P. Snyder, M. Januszyk, G.C. Gurtner, Z. Bao, Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 220]]<|/det|> +Comment 6: In Figures 5 and S47, the hydrogel was designed to face biological tissue (please correct me if not). In this case, some of physical sensors (e.g., strain and pressure gauges) would be fine, but how to figure out operation of other sensors/stimulators that need direct contacts to tissues? For example, the authors mentioned here electrical stimulation for the bladder, but is it possible to stimulate the bladder through the adhesive layer and PAAM hydrogel? That would be not. Can the authors explain how to achieve such functional operations? + +<|ref|>text<|/ref|><|det|>[[114, 228, 883, 303]]<|/det|> +Our response: We thank the reviewer's comment regarding the configuration of soft robotic gripper for bladder control. Here, regarding the concerns about the operation of stimulators that require direct tissue contact, we would like to clarify the design of our stimulator module. + +<|ref|>text<|/ref|><|det|>[[114, 310, 883, 423]]<|/det|> +This stimulator module utilizes gold (Au) electrodes that are specially designed to establish direct contact with bladder tissue, as shown in Fig. R5. This direct contact is critical for the effective delivery of therapeutic interventions, such as electrical stimulation for bladder control. Moreover, even in instances where minor gaps might exist at the interface, body fluids naturally act as a conductive bridge, ensuring efficient electrical stimulation. + +<|ref|>text<|/ref|><|det|>[[114, 430, 883, 525]]<|/det|> +The hydrogel component of our device is applied primarily to the device's arms for actuation purposes, which is intentionally designed not to interfere with the stimulator module's direct tissue contact (Fig. R5B). We have clarified this point in revised supporting information, aiming to offer clearer insights into the device's design and its capability for direct tissue engagement through the simulator module. + +<|ref|>image<|/ref|><|det|>[[130, 536, 870, 737]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 751, 883, 856]]<|/det|> +
Fig. R5. Soft robotic gripper for monitoring bladder volume. (A) Exploded view of the soft robotic finger including actuator, sensor and stimulator components. (B) Detailed schematic illustration for the soft robotic finger, highlighting the direct tissue contact by the stimulation electrode (indicated with a red dashed line). Here the hydrogel actuators are intentionally positioned on the device's arms, marked by the blue lines, ensuring that they do not hinder the electrodes' direct engagement with the tissue, facilitating efficient electrical stimulation.
+ +<|ref|>sub_title<|/ref|><|det|>[[116, 864, 409, 882]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[113, 889, 880, 909]]<|/det|> +(1) On page 44, in the revised supporting information, we added Fig. R5B as Fig. S33B. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 334]]<|/det|> +(2) On page 44, in the revised supporting information, we modified the Fig. S33A&B's captions, "(A) Schematic illustration showing exploded layout of the soft robotic gripper that incorporates actuator, sensor and stimulator components. The actuation component includes a passive layer made of an Au/PI bilayer with heat functionality, and an active layer of PNIPAM hydrogel. The sensing component includes an elastic poly(acrylamide) (\~PAAm) hydrogel film and a serpentine Au/PI resistor to form a buckled strain sensor. The stimulator component is two pairs of pacing electrodes, employing Au for its exceptional electrical conductivity, biocompatibility, and stability in biological settings. (B) Detailed schematic illustration for the soft robotic finger, highlighting the direct tissue contact by the stimulation electrode (indicated with a red dashed line). Here the hydrogel actuators are intentionally positioned on the device's arms, marked by the blue lines, ensuring that they do not hinder the electrodes' direct engagement with the tissue, facilitating efficient electrical stimulation." + +<|ref|>text<|/ref|><|det|>[[114, 348, 883, 444]]<|/det|> +Comment 7: In Figure 5g, it is unclear what the author intended to demonstrate through the programming. Can the authors provide significance of the programming for the control of the bladder. (It is quite strange that E- stim ON when the bladder is void, and E- stim OFF after expansion/contraction cycle... Shouldn't it turn on when the volume reaches maximum?). + +<|ref|>text<|/ref|><|det|>[[114, 450, 883, 563]]<|/det|> +Our response: We thank the reviewer's comment regarding the programming strategy depicted in Fig. 5G, particularly concerning the application of electrical stimulation (E- stim) in bladder control. Our soft robotic device integrates bladder volume sensing with E- stim to offer a targeted treatment modality for underactive bladder. This strategy aligns with recent advances in bioengineering and medical devices, aiming to offer more personalized treatments for patients with urinary disorders. + +<|ref|>text<|/ref|><|det|>[[114, 570, 883, 739]]<|/det|> +Indeed, our programming logic operates as the reviewer has anticipated: The E- stim is activated when the bladder volume surpasses a predefined threshold, set here at 100 mL, targeting the bladder muscles to facilitate urination. Once the bladder empties to below the threshold, indicating successful voiding, the system automatically deactivates the E- stim. Here, a slight delay in turning off was observed which could partially be attributed to the response time for the microcontroller unit (MCU) system to pick up the sensory change and update the output value. This programming cycle ensures that stimulation is provided only, when necessary, closely mimicking the natural urination process and enhancing patient comfort and device efficiency. + +<|ref|>text<|/ref|><|det|>[[115, 746, 883, 802]]<|/det|> +It appears that the reviewer's confusion may be due to the unclear labeling in Fig. 5G. To ensure better clarity, we have revised the labels as shown in Fig. R6 and enhanced the explanation in the manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[215, 88, 780, 416]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 425, 884, 531]]<|/det|> +
Fig. R6. A robotic gripper for bladder control. Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly.
+ +<|ref|>sub_title<|/ref|><|det|>[[116, 537, 410, 555]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[116, 563, 747, 583]]<|/det|> +(1) On page 20, in the revised manuscript, we added Fig. R6 as Fig. 5G. + +<|ref|>text<|/ref|><|det|>[[114, 588, 883, 722]]<|/det|> +(2) On page 21, in the revised manuscript, we modified the figure caption of Fig. 5G, "Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly." + +<|ref|>text<|/ref|><|det|>[[114, 728, 883, 879]]<|/det|> +(3) On page 18, in the revised manuscript, we added, "When the balloon's volume reaches a predetermined threshold, set here at 100 mL, the control system initiates electrical stimulation. Following successful voiding to below the threshold, the system automatically deactivates the stimulation. While electrical stimulation has shown promising results in enhancing bladder control in various studies and clinical trials, its efficacy can differ across individuals. The effectiveness of electrical stimulation for bladder voiding and its required voltage levels requires further investigation beyond the scope of our current study. However, our prototype showcases the potential of integrating + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 127]]<|/det|> +sensing and actuation mechanisms to facilitate timely and adaptive interventions for bladder dysfunction." + +<|ref|>sub_title<|/ref|><|det|>[[115, 135, 218, 152]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 160, 882, 210]]<|/det|> +Grill, W. M. Electrical stimulation for control of bladder function. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 2009 2369- 2370 (2009) doi:10.1109/IEMBS.2009.5335001. + +<|ref|>text<|/ref|><|det|>[[115, 216, 882, 251]]<|/det|> +Coolen, R. L., Groen, J. & Blok, B. F. M. Electrical stimulation in the treatment of bladder dysfunction: Technology update. Med. Devices Evid. Res. 12, 337- 345 (2019). + +<|ref|>text<|/ref|><|det|>[[115, 263, 882, 339]]<|/det|> +Comment 8: In Figs. 6 and S52A, it appears difficult or impossible for the electronic components at the end of each arm to form a strong coupling to living tissues, particularly to tissues whose volume changes over time, such as the bladder. How did the authors control or attach the robotic arms? + +<|ref|>text<|/ref|><|det|>[[115, 346, 882, 403]]<|/det|> +Our response: We thank the reviewer's comment regarding the integration of electronic components at the end of each robotic arm with living tissues, especially those that undergo volume changes such as bladder. + +<|ref|>text<|/ref|><|det|>[[115, 409, 882, 524]]<|/det|> +Our design employs a multilayer fabrication approach, incorporating a layer of PNIPAM hydrogel. The inherent thermos- responsive property of PNIPAM hydrogel enables our device to dynamically adapt to the body's natural thermal environment. This shape adaptability ensures that our soft robotic devices maintain a stable and effective interface with living tissues, seamlessly accommodating volumetric changes without compromising contract or functionality (Fig. R7A). + +<|ref|>image<|/ref|><|det|>[[131, 540, 870, 768]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 776, 882, 845]]<|/det|> +
Fig. R7. shape conformability of soft robotic devices with biological tissues/organs. (A) Measured static force changes of the soft robotic finger under different temperatures. (B) Adhesion strength of a PNIPAM-co-PAAm hydrogel with an LCST of 36 °C across different temperatures.
+ +<|ref|>text<|/ref|><|det|>[[115, 853, 882, 890]]<|/det|> +In addition, the inherent adhesiveness of the hydrogel layer significantly enhances the device's ability to securely couple with tissue surfaces. Upon deformation and subsequent + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 165]]<|/det|> +contact with tissue, this adhesiveness strengthens the coupling between the device and the tissue, ensuring a strong attachment even as the tissue undergoes volumetric changes, thereby preserving the functional integrity of the device's functional modules (Fig. R7B). + +<|ref|>image<|/ref|><|det|>[[230, 179, 768, 525]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 538, 883, 643]]<|/det|> +
Fig. R8. in vivo validation of a soft robotic gripper for epicardial sensing and pacing. (A) Image of a soft robotic thera-gripper grasping on the epicardial surface of a living mouse heart. Scale bar, \(5 \text{mm}\) . (B) Temperature measurements from the thera-gripper during its deployment onto the mouse heart. (C) The surface ECG trace during electrical stimulation using a pair of Au pacing electrodes. (D) Representative measurements of local cardiac contractions using a soft robotic thera-gripper wrapping onto a living mouse heart.
+ +<|ref|>text<|/ref|><|det|>[[114, 650, 883, 744]]<|/det|> +Furthermore, as demonstrated in Fig. R8, our device has successfully detected key physiological parameters, including heart rate, contractile ability, and temperature variations, and effectively provided electrical stimulation. These findings not only showcase the device's operational capabilities but also confirm the effective coupling contact between the device and the living tissues/organs. + +<|ref|>sub_title<|/ref|><|det|>[[116, 752, 409, 770]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 777, 883, 871]]<|/det|> +(1) On page 10, in the revised manuscript, we modified, "Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 127]]<|/det|> +hydrogel- based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +<|ref|>text<|/ref|><|det|>[[115, 133, 881, 154]]<|/det|> +(2) On page 52, in the revised supporting information, we added Fig. R7B as Fig. S40B. + +<|ref|>text<|/ref|><|det|>[[114, 160, 883, 461]]<|/det|> +(3) On pages 21-22, in the revised manuscript, we added, "Additionally, our device offers versatile adaptability for diverse application scenarios through customizable dimensions, sensor positioning, and geometric layouts, ensuring it aligns with the unique morphologies and functional demands of targeted tissues/organs. This flexibility is essential for enabling minimally invasive deployment. As illustrated in Fig. S38&S39, Table S2, and Supplementary Note S6, the design's adaptability enhances soft robotic technologies for effective integration in a broad spectrum of biomedical applications. We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature-responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +<|ref|>text<|/ref|><|det|>[[115, 469, 882, 525]]<|/det|> +(4) On page 28, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +<|ref|>sub_title<|/ref|><|det|>[[115, 534, 208, 551]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[114, 558, 883, 699]]<|/det|> +Y. Jiang, +A.A. Trotsyuk, +S. Niu, +D. Henn, +K. Chen, +C.C. Shih, +M.R. Larson, +A.M. Mermin-Bunnell, +S. Mittal, +J.C. Lai, +A. Saberi, +E. Beard, +S. Jing, +D. Zhong, +S.R. Steele, +K. Sun, +T. Jain, +E. Zhao, +C.R. Neimeth, +W.G. Viana, +J. Tang, +D. Sivaraj, +J. Padmanabhan, +M. Rodrigues, +D.P. Perrault, +A. Chattopadhyay, +Z.N. Maan, +M.C. Leeolou, +C.A. Bonham, +S.H. Kwon, +H.C. Kussie, +K.S. Fischer, +G. Gurusankar, +K. Liang, +K. Zhang, +R. Nag, +M.P. Snyder, +M. Januszyk, +G.C. Gurtner, +Z. Bao, Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +<|ref|>text<|/ref|><|det|>[[115, 712, 768, 732]]<|/det|> +Comment 9: Page 3, line 86 It is not 'overactive', but 'underactive' bladder. + +<|ref|>text<|/ref|><|det|>[[115, 739, 600, 758]]<|/det|> +Our response: We appreciate the reviewer's comment. + +<|ref|>sub_title<|/ref|><|det|>[[116, 766, 410, 784]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 791, 863, 810]]<|/det|> +On page 3, in the revised manuscript, we have corrected "overactive" to "underactive". + +<|ref|>text<|/ref|><|det|>[[115, 825, 882, 881]]<|/det|> +Comment 10: In fig. 2c, is there a motivation for using such diverse materials for different components? This referee can't find outstanding characteristics of those materials for sensing components. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 145]]<|/det|> +Our response: We appreciate the reviewer's comment regarding the selection of diverse materials for different components as depicted in Fig. 2C and the aims behind their use in sensing components of our soft robots. + +<|ref|>text<|/ref|><|det|>[[115, 153, 883, 285]]<|/det|> +The motivation for utilizing a variety of materials in our device lies in mimicking the hierarchical structures and functionalities of biological systems, such as skin and muscle. Here, we highlight the integration of multi- electronic modules and thermally actuated hydrogels within a single platform. This integration enables our soft robotic devices to not only perform receptor- like sensing functions for detecting various stimuli but also exhibit muscle- like contractions for generating physically adaptive motion, thereby endowing the soft robotic devices with the capabilities to autonomously navigate complex environments. + +<|ref|>text<|/ref|><|det|>[[114, 292, 883, 500]]<|/det|> +The selection of materials for the flexible composite layer is driven by the need to fabricate a multi- modal electronic skin (e- skin) that incorporates distinct sensors (e.g., strain, pressure, pH, and temperature sensors) and stimulators (thermal and electrical). Each chosen material contributes both individual properties and a synergistic effect to enhance the overall functionality of the system. For instance, AgNWs provide excellent conductivity and flexibility, making them ideal for wearable sensors. Graphene stands out for its high surface area, electrical conductivity, and mechanical strength, enhancing sensitivity and selectivity in biosensing applications. Meanwhile, MXene offers high conductivity and hydrophilicity, making it an advantageous choice for biosensor interfaces. \(^{1 - 4}\) Through such strategic material integration, we ensure our soft robotic devices can be well equipped to sensitively and accurately perceive and interact their surroundings. + +<|ref|>text<|/ref|><|det|>[[115, 506, 883, 619]]<|/det|> +Moreover, the diversity of materials showcases the versatility of our solution- based method, enabling the integration of a wide range of advanced functional materials. Such versatility surpasses the capabilities of 3D printing or other traditional fabrication methods \(^{5 - 7}\) , allowing us to engineer devices via fine- tuning each component's properties to specific functional needs, and optimizing the performance and utility of our soft robotic systems. + +<|ref|>sub_title<|/ref|><|det|>[[116, 628, 409, 646]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 653, 883, 898]]<|/det|> +On pages 6- 7, in the revised manuscript, we modified, "Furthermore, compared with a make- and- transfer method, our in situ solution- based fabrication approach enables the seamless integration of sensors into the e- skin matrix in a single step, enhancing mechanical and electrical performance by reducing interfacial resistances and improving mechanical conformity, thereby significantly improving sensitivity and responsiveness. This approach also offers a versatile platform that can be constructed using a broad range of functional nanomaterials hybridized with a polymeric matrix to form a multi- modal sensing system. By selecting materials that offer unique functional attributes, from AgNWs known for their conductivity and flexibility to graphene and MXene for their high surface area, electrical conductivity, and hydrophilicity, this system can emulate the skin with complex somatosensory system, where various mechanoreceptors and thermoreceptors distributed in the epidermal and dermal layers enable the spatiotemporal recognition of the magnitude and location of touch and temperature stimuli." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 89, 218, 106]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[112, 114, 886, 374]]<|/det|> +ReferencesBasarir, F., Madani, Z. & Vapaavuori, J. Recent Advances in Silver Nanowire Based Flexible Capacitive Pressure Sensors: From Structure, Fabrication to Emerging Applications. Adv. Mater. Interfaces 9, (2022).Chauhan, N., Maekawa, T. & Kumar, D. N. S. Graphene based biosensors - Accelerating medical diagnostics to new- dimensions. J. Mater. Res. 32, 2860- 2882 (2017).Amara, U., Hussain, I., Ahmad, M., Mahmood, K. & Zhang, K. 2D MXene- Based Biosensing: A Review. Small 19, 1- 38 (2023).Driscoll, N. et al. MXene- infused bioelectronic interfaces for multiscale electrophysiology and stimulation. Sci. Transl. Med. 13, eabf8629 (2021).Liu, H. et al. 3D Printed Flexible Strain Sensors: From Printing to Devices and Signals. Adv. Mater. 33, 2004782 (2021).Zhu, Z., Park, H. S. & McAlpine, M. C. 3D printed deformable sensors. Sci. Adv. 6, eaba5575 (2023).Reeder, J. et al. Mechanically Adaptive Organic Transistors for Implantable Electronics. Adv. Mater. 26, 4967- 4973 (2014). + +<|ref|>text<|/ref|><|det|>[[115, 388, 882, 444]]<|/det|> +Comment 11: In figs. 2f and 2g, the authors claimed that soft robots can form conformal contacts to tissues, but did the authors study or compare mechanical modulus between devices and tissues? + +<|ref|>text<|/ref|><|det|>[[115, 452, 882, 565]]<|/det|> +Our response: We thank the reviewer's comment concerning the mechanical compatibility of our soft robotic devices with biological tissues, as shown in Fig. R9A (Fig. 2F) and Fig. R9B (Fig. 2G). We employ a multilayer design mimicking the relation between human skin and skeletal muscle to integrate the e- skin layer with an artificial muscle layer composed of PNIPAM- based hydrogel. This hydrogel layer, designed for direct tissue interface, is critical in our device's architecture. + +<|ref|>text<|/ref|><|det|>[[114, 572, 883, 780]]<|/det|> +In choosing materials for our device, especially those designed for implantable biomedical applications, our priorities are biocompatibility and the mechanical softness, essential for effective tissue integration. Hydrogels, exhibiting the above- mentioned properties, are ideally suitable for our application in implantable devices. Compared to other smart materials such as shape memory polymers and alloys, which exhibit the elastic moduli (E) in the order of several megapascals (MPa) \(^8\) , hydrogels have an elastic modulus ranging from 1- 100 kPa. This range is notably similar to that of soft tissues, which typically exhibit E from a few kPa to hundreds of kPa \(^9\) . Specially, the PNIPAM hydrogel in our research exhibited an E \(\sim 1.2\) kPa, as shown in Fig. R9C. This mechanical similarity facilitates a more seamless integration with surrounding tissues and minimizes the potential damage from mechanical mismatch \(^{10}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[184, 90, 808, 368]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 382, 883, 504]]<|/det|> +
Fig. R9. Mechanical properties of PNIPAM hydrogel. (A&B) Optical image showing conformal attachment of the soft sensory robot onto human skin (A) and porcine tissue (B) with high mechanical compliance. (C)Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness 4mm, width 10mm, initial length 15mm), highlighting an elastic modulus (E) of \(\sim 1.2\) kPa. This value is within the range of soft tissues, which typically exhibit an E from a few kPa to hundreds of kPa, ensuring the hydrogel's compatibility with biological tissues and reducing risks associated with mechanical mismatches.
+ +<|ref|>sub_title<|/ref|><|det|>[[116, 512, 409, 530]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 537, 883, 650]]<|/det|> +(1) On page 13, in the revised supporting information, we added Fig. R9C as Fig. S3C. (C)Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness 4 mm, width 10 mm, initial length 15 mm), highlighting an elastic modulus (E) of approximately 1.2 kPa. This value is within the range of soft tissues, which typically exhibit an E from a few kPa to hundreds of kPa, ensuring the hydrogel's compatibility with biological tissues and reducing risks associated with mechanical mismatches. + +<|ref|>text<|/ref|><|det|>[[114, 656, 883, 752]]<|/det|> +(2) On page 6, in the revised manuscript, we modified, "The as-fabricated soft robot can form a highly conformal interface with diverse biological surfaces, indicating its inherent mechanical softness and high biocompatibility. This adaptability minimizes potential risks related to mechanical incompatibility, facilitating its smooth integration with targeted tissues/organs (Fig. 2F&G, and Fig. S3C)." + +<|ref|>text<|/ref|><|det|>[[115, 758, 882, 815]]<|/det|> +(3) On page 28, in the revised manuscript, we added, "Mechanical tests were conducted on rectangular-shape specimens with the dimensions of 10 mm in width, 2 mm in thickness, and 16 mm in length) using the Instron machine (Mark-10 ESM303)." + +<|ref|>sub_title<|/ref|><|det|>[[115, 822, 218, 840]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 848, 883, 884]]<|/det|> +Czerner, M., Fellay, L. S., Suárez, M. P., Frontini, P. M. & Fasce, L. A. Determination of Elastic Modulus of Gelatin Gels by Indentation Experiments. Procedia Mater. Sci. 8, 287- 296 (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 125]]<|/det|> +Xie, C., Wang, X., He, H., Ding, Y. & Lu, X. Mussel- Inspired Hydrogels for Self- Adhesive Bioelectronics. Adv. Funct. Mater. 30, 1909954 (2020). + +<|ref|>text<|/ref|><|det|>[[115, 138, 882, 194]]<|/det|> +Comment 12: In fig. S12B, such layered structures are likely to interfere with each other's signals. Is there any reason to measure both parameters at the same time? Or, even if simultaneous measurements are made, does each sensor operate independently? + +<|ref|>text<|/ref|><|det|>[[115, 202, 882, 258]]<|/det|> +Our response: We thank the reviewer's comment regarding the potential for signal interference in the layered structures as shown in Fig. S12B (Fig. S11B in the updated supporting information). + +<|ref|>text<|/ref|><|det|>[[115, 265, 882, 435]]<|/det|> +As shown in Fig. S11B, we employed a dual- transfer printing method to fabricate the functional modules located in different layers. This strategy allows for the integration of a minimal amount of polyimide with functional materials to form composite functional modules. This not only preserves the functional integrity of the materials within each module but also leverages the remaining polyimide to serve as a dual purpose. Beyond its inclusion in the composite, polyimide acts as an insulating barrier between adjacent modules. This barrier is crucial for our device's functionality, as it prevents electrical and chemical signal interference between modules, thereby ensuring that each functional module operates independently and as intended. + +<|ref|>text<|/ref|><|det|>[[115, 443, 882, 611]]<|/det|> +The primary purpose of measuring multiple parameters simultaneously is to showcase the multifunctional capabilities of our solution- based approach, which closely mimicking the complex functionality of natural model (e.g., human skin), enabling the device to perform concurrent sensing operations. By demonstrating the device's ability to interact comprehensively with its environment, we not only highlight its potential for various applications but also validate our fabrication method's versatility in fabricating multifunctional e- skin. This strategy surpasses conventional fabrication methods like 3D printing, offering new possibilities for advancements in robotics, wearable technologies, and biomedical devices. + +<|ref|>text<|/ref|><|det|>[[115, 619, 884, 712]]<|/det|> +Moreover, each functional module operates independently even during simultaneous measurements. As aforementioned, the integration of a polyimide layer between modules, serves as an effective barrier against any potential signal interference, ensuring that despite the simultaneous operation of multiple sensors, each module retains its individual functionality and delivers accurate, independent measurements. + +<|ref|>sub_title<|/ref|><|det|>[[116, 721, 409, 739]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 747, 882, 898]]<|/det|> +On page 7, in the revised manuscript, we modified, "Fig. 2M displays a more complicated integration paradigm with multi- layer stacking, where different electronic components (e.g., PEDOT:PSS/PI- based conductive electrodes and RGO/PI temperature sensors) can be distributed in different layers of the e- skin to achieve simultaneous functional versatility and compactness. This assembly technique ensures the e- skin remarkable thinness and flexibility, enhancing its effective performance and seamless integration in implantable applications (Fig. S11B). The X- ray photoelectron spectroscopy (XPS) characterization on the e- skin layers reveals the precise nanoscale integration of active + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 315]]<|/det|> +materials within a polymer matrix, as detailed in Fig. S12- S14 and Supplementary Note S1. It showcases the optimal distribution and intermolecular bonding of the composite components, effectively addressing the common challenge of uneven dispersion of nanomaterials, which usually undermines the performance of conventional composites. Our approach minimizes the polymer amount required to integrate nanomaterials into composite functional modules and utilizes excess polymer as an insulating layer to separate modules, preventing interference between their electrical and chemical signals, thereby ensuring that each functional module operates independently and effectively. This approach harmoniously combines the distinct properties of each constituent, achieving a balance between structural integrity and functional versatility. This advanced level of integration would be of great value for soft robots that seek to achieve multifunctionality and local sensing capabilities approaching skin." + +<|ref|>text<|/ref|><|det|>[[115, 330, 574, 349]]<|/det|> +Comment 13: there's no description for Figs. 3H&3I. + +<|ref|>text<|/ref|><|det|>[[115, 355, 883, 394]]<|/det|> +Our response: We thank the reviewer's comment regarding Fig. 3H&3I. We have added detailed descriptions for both figures. + +<|ref|>sub_title<|/ref|><|det|>[[115, 401, 409, 420]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 427, 883, 560]]<|/det|> +On page 11, in the revised manuscript, we added, "Fig. 3H illustrates the resistive change in a relatively linear relation with temperature for the RGO/PI thermal sensor. The temperature coefficient of the resistance (TCR) of the RGO/PI thermal sensor is \(>0.5\% /^{\circ}\mathrm{C}\) , featuring its high thermal sensitivity. On the other hand, the RGO/PI- based thermal sensor exhibits a stable performance after 1000 bending cycles, and even after immersing in PBS solution. Fig. 3I and Fig. S21F show performance of the thermal sensor in response to cycles of temperature rise and drop, indicating good sensing stability." + +<|ref|>text<|/ref|><|det|>[[115, 574, 882, 630]]<|/det|> +Comment 14: We usually do not include information about SI figures in main figure captions. For example, in fig.3, there is information about fig. S18 and 25, but these should be removed. + +<|ref|>text<|/ref|><|det|>[[115, 638, 882, 676]]<|/det|> +Our response: We thank the reviewer's comment. We have removed these SI figures from the main figure captions based on reviewer's advice. + +<|ref|>sub_title<|/ref|><|det|>[[115, 683, 409, 701]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 709, 631, 728]]<|/det|> +We have updated figure captions in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 743, 882, 781]]<|/det|> +Comment 15: Please do double check all the figures including SI, whose order is a total mess. + +<|ref|>text<|/ref|><|det|>[[115, 789, 882, 863]]<|/det|> +Our response: We appreciate the reviewer's comment to help us significantly enhance the clarity and coherence of our manuscript. We have conducted a thorough review and reorganization of all figures and supplementary information to ensure a logical flow and clear presentation throughout our submissions. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 89, 883, 128]]<|/det|> +Modification to the manuscript: We have reorganized and updated all supplementary figures for clarity. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[316, 89, 680, 108]]<|/det|> +## Responses to comments of Referee #2 + +<|ref|>text<|/ref|><|det|>[[116, 138, 365, 156]]<|/det|> +Comments from Referee #2: + +<|ref|>text<|/ref|><|det|>[[113, 171, 883, 586]]<|/det|> +Summary Comment: Lin Zhang et al. developed various types of soft robots, utilizing an electronic skin (e- skin) made of materials like silver nanowires, reduced graphene oxide, MXene, and conductive polymers integrated into a polymer matrix. This e- skin is designed to mimic skin receptors, enabling the perception of various stimuli. The robots, inspired by natural forms like starfish, chiral seedpod, and others, are equipped with features for bending, twisting, and expanding, and include an artificial muscle for dynamic movement. This study also integrated wireless modules to control and communicate without tethering. Demonstrated in various medical scenarios, these devices showed capabilities such as blood pressure sensing and adapting to organ surfaces for diagnostic and therapeutic functions, exemplifying their potential as multifunctional, minimally invasive medical tools. However, the devices used materials commonly used in practical applications, with the exception of an in situ solution- based fabrication approach, showing no significant material novelty. This article also lacks either long- term feasibility or detailed information about the mechanism of each sensor like the relationships between pH, pressure and resistance. Despite such some disadvantages, the positive aspect lies in its multifunctional ability to be implanted in real scenarios, possibly leading to successful demonstrations for various organ shapes. In specific, massive integration of multifunctional soft robots entailing high- performance functional nanomaterials and actuating modules is highly impressive. Additionally, this article demonstrates a high level of systemic completeness, considering real clinical situations. Therefore, the reviewer believes that with some modifications addressing specific comments included in the following, this paper has the potential to be accepted in Nature Communications. + +<|ref|>text<|/ref|><|det|>[[115, 592, 882, 651]]<|/det|> +Our response: We thank the reviewer for these positive comments and for these helpful suggestions for revision. We carefully addressed the issues, as listed below, and revised our manuscript accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 663, 882, 701]]<|/det|> +Modification to the manuscript: We have revised both the manuscript and supporting information based on the reviewer's concerns and suggestions. + +<|ref|>text<|/ref|><|det|>[[115, 716, 882, 811]]<|/det|> +Comment 1: In the introduction part, some references (Nature Materials volume 15, pages937- 950 (2016), Nature Nanotechnology volume 9, pages397- 404 (2014), and Nature Electronics volume 6, pages779- 789 (2023)) regarding stable tissue- interfacing performance of wearable/implantable devices should be cited to justify the authors' research purpose. + +<|ref|>text<|/ref|><|det|>[[115, 818, 882, 856]]<|/det|> +Our response: We thank the reviewer's suggestion. We have carefully integrated the recommended references into the introduction section. + +<|ref|>text<|/ref|><|det|>[[115, 867, 410, 885]]<|/det|> +Modification to the manuscript: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 791, 108]]<|/det|> +On page 2, in the revised manuscript, we have cited all suggested references. + +<|ref|>sub_title<|/ref|><|det|>[[115, 116, 218, 133]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 141, 883, 211]]<|/det|> +D. Son, +J. Lee, +S. Qiao, +R. Ghaffari, +J. Kim, +J.E. Lee, +C. Song, +S.J. Kim, +D.J. Lee, +S.W. Jun, +S. Yang, +M. Park, +J. Shin, +K. Do, +M. Lee, +K. Kang, +C.S. Hwang, +N. Lu, +T. Hyeon, +D.H. Kim, Multifunctional wearable devices for diagnosis and therapy of movement disorders, Nat. Nanotechnol. 9 (2014) 397-404. https://doi.org/10.1038/nnano.2014.38. + +<|ref|>text<|/ref|><|det|>[[115, 217, 881, 253]]<|/det|> +A. Chortos, +J. Liu, +Z. Bao, Pursuing prosthetic electronic skin, Nat. Mater. 15 (2016) 937-950. https://doi.org/10.1038/nmat4671. + +<|ref|>text<|/ref|><|det|>[[115, 259, 882, 312]]<|/det|> +H. Choi, +Y. Kim, +S. Kim, +H. Jung, +S. Lee, +K. Kim, +H.S. Han, +J.Y. Kim, +M. Shin, +D. Son, Adhesive bioelectronics for sutureless epicardial interfacing, Nat. Electron. 6 (2023) 779-789. https://doi.org/10.1038/s41928-023-01023-w. + +<|ref|>text<|/ref|><|det|>[[115, 327, 882, 420]]<|/det|> +Comment 2: The reviewer believes that sensory- motor integration is valuable when the robot can control motors in response to signals received from sensors. However, it seems that controlling the motors and performing sensor functions operate independently. In that case, can this robot still be considered as the presence of responsiveness as mentioned in the introduction? + +<|ref|>text<|/ref|><|det|>[[115, 428, 882, 504]]<|/det|> +Our response: We thank the reviewer's question regarding sensory- motor integration within our soft robotic system. Our design can be engineered to offer dual- mode functionality, adapting to a broad spectrum of operational requirements, enhancing the system's versatility and application range. + +<|ref|>text<|/ref|><|det|>[[115, 511, 882, 642]]<|/det|> +We have demonstrated that the integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration highlighted by the reviewer. + +<|ref|>text<|/ref|><|det|>[[115, 650, 882, 895]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. R10A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. R10B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 333]]<|/det|> +factor and is added to the current output value to generate a new output value. The on-chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. R11 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off. + +<|ref|>image<|/ref|><|det|>[[216, 345, 790, 716]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 730, 883, 784]]<|/det|> +
Fig. R10. Soft robots designed integrated sensing and actuation capabilities. (A) Schematic diagram of the responsive robotic gripper with control circuitry. (B) Functional block diagram of the algorithmic and hardware design of the adaptive control loop.
+ +<|ref|>text<|/ref|><|det|>[[114, 790, 882, 903]]<|/det|> +Moreover, our robotic system also supports operation in an open- loop configuration, where actuation is not directly governed by immediate sensory inputs but can be pre- programmed or controlled externally. This flexibility is particularly beneficial for scenarios where actions need to be acquired based on predefined conditions rather than dynamic sensory input, offering stability in a controlled environment. An example of this functionality is our bladder control system, designed to maintain a consistent grip post + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 240]]<|/det|> +implantation. However, we have also integrated a closed- loop mechanism between the stimulator and sensor modules for this application. Electrical stimulation is activated when the bladder reaches its maximum volume threshold, targeting the bladder muscles to facilitate urination. Upon complete voiding of the bladder, the integrated sensors detect the reduction in bladder volume, which subsequently triggers the deactivation of the electrical stimulation. This programming cycle ensures that stimulation is provided only, when necessary, closely mimicking the natural urination process and enhancing patient comfort and device efficiency (Fig. 5A- 5G, Fig. S34- S35). + +<|ref|>image<|/ref|><|det|>[[160, 272, 839, 602]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 611, 884, 682]]<|/det|> +
Fig. R11. Soft robots designed integrated sensing and actuation capabilities. (A) Infrared and optical images of the responsive robotic grippers at different stages of controlled actuation. (B&C) Time synchronized current (B) and temperature plot (C) capturing the controlled actuation changes after a sudden change in ambient temperature.
+ +<|ref|>text<|/ref|><|det|>[[114, 688, 883, 764]]<|/det|> +Our robotic system is engineered to support both responsive closed- loop feedback and stable open- loop operation for sensor- actuator integration. This not only meets the initial responsiveness criteria but also significantly expands its utility across diverse fields, ranging from precise medical interventions to versatile robotic applications. + +<|ref|>sub_title<|/ref|><|det|>[[115, 771, 410, 790]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 796, 866, 868]]<|/det|> +(1) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. +(2) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. +(3) On page 5, in the revised supporting information, we added," + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 89, 881, 127]]<|/det|> +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 134, 882, 266]]<|/det|> +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +<|ref|>text<|/ref|><|det|>[[114, 272, 882, 761]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<|ref|>text<|/ref|><|det|>[[115, 770, 882, 901]]<|/det|> +(4) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 258]]<|/det|> +microcontroller- driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real- time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +<|ref|>text<|/ref|><|det|>[[116, 265, 592, 284]]<|/det|> +(5) On page 29, in the revised manuscript, we added, " + +<|ref|>sub_title<|/ref|><|det|>[[116, 292, 685, 311]]<|/det|> +## The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 318, 883, 450]]<|/det|> +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +<|ref|>sub_title<|/ref|><|det|>[[115, 458, 218, 475]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 483, 883, 536]]<|/det|> +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +<|ref|>text<|/ref|><|det|>[[115, 542, 882, 595]]<|/det|> +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +<|ref|>text<|/ref|><|det|>[[115, 610, 882, 702]]<|/det|> +Comment 3: It seems good that the robot is designed differently for each target organ. The reviewer is curious about the variation in curvature among different organs. For instance, in the case of organs like the heart and bladder, squeezing too much might make it challenging to grasp effectively. How was this consideration taken into account in the design? + +<|ref|>text<|/ref|><|det|>[[115, 710, 882, 805]]<|/det|> +Our response: We thank the reviewer's question regarding how our soft robotic systems accommodate the anatomical diversity and curvature of different target organs. Our design process incorporated multiple factors to ensure that our device can achieve shape adaptability, effective data acquisition, and potential therapeutic interventions across various applications. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[130, 95, 870, 430]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 441, 883, 528]]<|/det|> +
Fig. R12. Illustration of soft robotic implants exhibiting significant modularity and adaptability. (A-D) A starfish-inspired device featuring twelve arms. (E-H) A hand-structured soft robotic device that can be compactly housed in and released from a catheter. (I-L) A twisted soft robotic device designed for storage and deployment through a 14-Gauge Tuohy needle. Scale bars, 1 cm.
+ +<|ref|>text<|/ref|><|det|>[[114, 534, 883, 648]]<|/det|> +As mentioned by the reviewer, our device is highly customizable. We design specific configurations of the device to align the morphology of different organs, considering their shape (e.g., tubular, spherical), size, and the intended functionalities. The customization extends to the device's dimensions, the selection and distribution of sensors, as well as their geometrical arrangement, as illustrated in Fig. R12, ensuring that our device can conform naturally to different organs and tissues. + +<|ref|>text<|/ref|><|det|>[[114, 655, 883, 824]]<|/det|> +Beyond their thermo- responsive property, we have selected PNIPAM hydrogel as a key material due to their mechanical properties, which closely resemble those of body tissues/organs. Unlike other smart materials such as shape memory polymers and alloys, which possess elastic moduli (E) on the order of several megapascals (MPa) \(^{8}\) , hydrogels feature an elastic modulus within the 1- 100 kPa range. This range closely aligns with the E of soft tissues, typically spanning from a few kPa to hundreds of kPa \(^{9}\) . The PNIPAM hydrogel in our research exhibited an E \(\sim 1.2\) kPa, as shown in Fig. R13A. Such mechanical similarity facilitates a more seamless integration with surrounding tissues, substantially minimizing the potential damage from mechanical mismatch \(^{10}\) . + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[125, 95, 872, 298]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 311, 883, 399]]<|/det|> +
Fig. R13. Mechanical behavior of soft robotic device. (A) Tensile stress curve of PNIPAM hydrogel (Dimensions: thickness \(4\mathrm{mm}\) , width \(10\mathrm{mm}\) , initial length \(15\mathrm{mm}\) ). (B&C) Optical image showing conformal attachment of the soft sensory robot onto human skin (B) and porcine tissue (C) with high mechanical compliance. (D) Measured static force changes of the soft robotic finger under different temperatures. Scale bars, \(5\mathrm{mm}\) .
+ +<|ref|>text<|/ref|><|det|>[[114, 405, 883, 538]]<|/det|> +This compatibility ensures that our devices can naturally conform to the contours of organs and tissues, as demonstrated in Fig. R13B&C. Furthermore, the intrinsic flexibility and low stiffness of hydrogels prevent an excessive force on the organ or tissue (Fig. R13D). Additionally, we found that the hydrogel's intrinsic adhesiveness, further enhancing the device's integration with biological tissues, ensuring that the device can maintain effective grip and functionality without exerting damaging pressure on the organ, addressing concerns related to squeezing or over- compression (Fig. R14). + +<|ref|>image<|/ref|><|det|>[[130, 548, 869, 805]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 815, 883, 902]]<|/det|> +
Fig. R14. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \(36^{\circ}\mathrm{C}\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this threshold. All tests were conducted after overnight incubation simulating physiological conditions at \(34^{\circ}\mathrm{C}\) , \(37^{\circ}\mathrm{C}\) , and \(40^{\circ}\mathrm{C}\) . Scale bars, \(5\mathrm{mm}\) .
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 165]]<|/det|> +In summary, our design strategy emphasizes customization, careful material selection, and empirical validation to address the complexities of interacting with various organs. In this way, we ensure that our soft robotic system is not only versatile and adaptable but also safe and effective for a wide range of biomedical applications. + +<|ref|>sub_title<|/ref|><|det|>[[116, 173, 409, 191]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 198, 883, 330]]<|/det|> +(1) On page 21, in the revised manuscript, we added, "Additionally, our device offers versatile adaptability for diverse application scenarios through customizable dimensions, sensor positioning, and geometric layouts, ensuring it aligns with the unique morphologies and functional demands of targeted tissues/organs. This flexibility is essential for enabling minimally invasive deployment. As illustrated in Fig. S38&S39, Table S2, and Supplementary Note S6, the design's adaptability enhances soft robotic technologies for effective integration in a broad spectrum of biomedical applications." + +<|ref|>text<|/ref|><|det|>[[115, 337, 880, 357]]<|/det|> +(2) On page 13, in the revised supporting information, we added Fig. R13A as Fig. S3C. + +<|ref|>text<|/ref|><|det|>[[115, 363, 883, 459]]<|/det|> +(3) On page 6, in the revised manuscript, we modified, "The as-fabricated soft robot can form a highly conformal interface with diverse biological surfaces, indicating its inherent mechanical softness and high biocompatibility. This adaptability minimizes potential risks related to mechanical incompatibility, facilitating its smooth integration with targeted tissues/organs (Fig. 2F&G, and Fig. S3C)." + +<|ref|>text<|/ref|><|det|>[[114, 465, 883, 635]]<|/det|> +(4) On page 10, in the revised manuscript, we modified, "We further evaluated the mechanical force generated by the soft robotic finger which incorporates a PNIPAM hydrogel layer roughly 1 mm thick, under various input powers. Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar hydrogel-based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +<|ref|>text<|/ref|><|det|>[[115, 642, 866, 662]]<|/det|> +(5) On page 52, in the revised supporting information, we added Fig. R14 as Fig. S40. + +<|ref|>text<|/ref|><|det|>[[114, 668, 883, 856]]<|/det|> +(6) On pages 21-22, in the revised manuscript, we added, "We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 147]]<|/det|> +(7) On page 29, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of \(13 \mathrm{mm / min}\) . + +<|ref|>text<|/ref|><|det|>[[115, 149, 882, 208]]<|/det|> +Mechanical tests were conducted on rectangular-shape specimens with the dimensions of \(10 \mathrm{mm}\) in width, \(2 \mathrm{mm}\) in thickness, and \(16 \mathrm{mm}\) in length) using the Instron machine (Mark- 10 ESM303)." + +<|ref|>sub_title<|/ref|><|det|>[[115, 219, 208, 235]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[114, 237, 883, 377]]<|/det|> +Y. Jiang, +A.A. Trotsyuk, +S. Niu, +D. Henn, +K. Chen, +C.C. Shih, +M.R. Larson, +A.M. Mermin-Bunnell, +S. Mittal, +J.C. Lai, +A. Saberi, +E. Beard, +S. Jing, +D. Zhong, +S.R. Steele, +K. Sun, +T. Jain, +E. Zhao, +C.R. Neimeth, +W.G. Viana, +J. Tang, +D. Sivaraj, +J. Padmanabhan, +M. Rodrigues, +D.P. Perrault, +A. Chattopadhyay, +Z.N. Maan, +M.C. Leeolou, +C.A. Bonham, +S.H. Kwon, +H.C. Kussie, +K.S. Fischer, +G. Gurusankar, +K. Liang, +K. Zhang, +R. Nag, +M.P. Snyder, +M. Januszyk, +G.C. Gurtner, +Z. Bao, +Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +<|ref|>text<|/ref|><|det|>[[115, 391, 883, 428]]<|/det|> +Comment 4: Why does the parallel strips configuration result in twisting? Is there any reference for this, or was it an original concept? + +<|ref|>text<|/ref|><|det|>[[115, 436, 882, 510]]<|/det|> +Our response: We thank the reviewer's question regarding the underlying mechanism by which the "parallel strips" configuration results in a twisting motion in our device. This phenomenon arises from the differential expansion and contraction of materials when subjected to stimuli, such as temperature changes. + +<|ref|>text<|/ref|><|det|>[[115, 517, 882, 631]]<|/det|> +Initially, PNIPAM hydrogel is a thermo- responsive material whose volume and shape significantly change with temperature variations. Above its LCST, PNIPAM undergoes a shrinking process, leading to a reduction in the hydrogel's volume. Conversely, polyimide (PI) is a high- performance polymer known for its thermal stability, exhibiting minimal expansion or contraction upon heating, especially compared to the significant changes observed in PNIPAM hydrogel. + +<|ref|>text<|/ref|><|det|>[[115, 638, 882, 790]]<|/det|> +When these inclined PI strips are bonded to the PNIPAM hydrogel, a hybrid bilayer structure is constructed (Fig. S8A). Upon heating, the differential thermal shrinkage of PNIPAM and the relative stability of the PI layer induce uneven expansion or contraction across the structure. Especially, as the PNIPAM hydrogel shrinks with heat, the connected PI strips generate a tilting torque, causing the entire structure to twist. This design leverages the disparate thermal response characteristics of the materials combined with a strategic structural arrangement to achieve unique mechanical behavior. The experimental results correspond very well with simulation results (Fig. R15). + +<|ref|>text<|/ref|><|det|>[[115, 796, 882, 890]]<|/det|> +While the application of this principle has been explored in various studies11,12, our implementation within a soft robotic system, especially for implantable devices, represents a sophisticated adaption aimed at achieving specific functional objectives. We have achieved an integration of structural design with sensors, representing a more advanced extension of this concept. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[147, 90, 857, 293]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 308, 883, 394]]<|/det|> +
Fig. R15. FEA simulation results of a bilayer soft robotic device mimicking a chiral seedpod. (A-F) Stress distribution across the device during the shape-shifting process, facilitated by strategic stripe patterns on the 3D bilayer robot. This visualization highlights the material property mismatches including mechanical and thermal responsiveness that drive the device's complex morphological transformations.
+ +<|ref|>text<|/ref|><|det|>[[115, 400, 882, 457]]<|/det|> +We have incorporated a more detailed discussion on the design mechanism behind the parallel strips' configuration, ensuring a comprehensive understanding of the concept and its application within our work. + +<|ref|>sub_title<|/ref|><|det|>[[115, 465, 409, 483]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[112, 491, 880, 512]]<|/det|> +(1) On page 18, in the revised supporting information, we added Fig. R15 as Fig. S8C. + +<|ref|>text<|/ref|><|det|>[[115, 517, 882, 593]]<|/det|> +(2) On page 18, in the revised supporting information (Fig. S8B's caption), we added "The PNIPAM hydrogel contracts while PI maintains relative stability upon heating. The contraction of the PNIPAM hydrogel activates a tilting torque through the bonded PI strips, resulting in asymmetric deformation throughout the device." + +<|ref|>text<|/ref|><|det|>[[115, 600, 882, 694]]<|/det|> +(3) On page 6, in the revised manuscript, we added, "Upon thermal stimulation, the PNIPAM hydrogel contracts while the PI maintains stability, generating a differential contraction across the structure. The differential thermal response induces a tilting torque, leading to local saddle-like curvature and twisting motion of the integrated robotic systems (Fig. 2J, Fig. S8B and Supplementary Movie S3)." + +<|ref|>sub_title<|/ref|><|det|>[[115, 702, 218, 719]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[112, 727, 881, 800]]<|/det|> +Shian, S., Bertoldi, K. & Clarke, D. R. Dielectric Elastomer Based 'grippers' for Soft Robotics. Adv. Mater. 27, 6814- 6819 (2015). Shojaeifard, M., Niroumandi, S. & Baghani, M. Programming shape- shifting of flat bilayers composed of tough hydrogels under transient swelling. Acta Mech. 233, 213- 232 (2022). + +<|ref|>text<|/ref|><|det|>[[115, 813, 882, 870]]<|/det|> +Comment 5: On page 6, if the transfer method is well- designed, it could potentially enable multi- modal implementation. Is there a particular advantage in this solution- based approach over transfer methods? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 277]]<|/det|> +Our response: We thank the reviewer's question regarding the specific advantages of our in- situ solution- based fabrication approach over traditional make- transfer methods, especially concerning the integration of sensors into the e- skin layer for achieving multimodal functionality. Our method is designed to facilitate seamless and monolithic structuring of functional materials with a passive polymer- based skin, thereby transforming the e- skin into a highly versatile platform. Unlike make- and- transfer methods that may introduce interface issues or compromise material compatibility, our solution- based process facilitates the uniform integration of a wide array of functional nanomaterials within a polymeric matrix. This capability is crucial for constructing e- skin that emulates the complexity of the human skin's somatosensory system. + +<|ref|>text<|/ref|><|det|>[[114, 284, 884, 360]]<|/det|> +(1) Our solution-based method allows for the direct integration of sensors and the e-skin matrix in a single step, ensuring a seamless interface between different components. This monolithic integration is essential for reproducing the integrated somatosensory functions of natural skin, thereby significantly enhancing the e-skin's sensitivity and responsiveness. + +<|ref|>text<|/ref|><|det|>[[114, 367, 883, 442]]<|/det|> +(2) The flexibility to incorporate a broad range of functional nanomaterials into the polymeric matrix without the constraints of transfer compatibility of thermal/mechanical sensitivity, broadens the scope of achievable functionalities. This versatility enables the e-skin to more closely mimic the multi-modal sensory capabilities of natural skin. + +<|ref|>text<|/ref|><|det|>[[114, 449, 883, 525]]<|/det|> +(3) The direct integration of sensors within the e-skin matrix, as facilitated by our solution-based approach, results in improved mechanical and electrical performance. This improvement is due to the elimination of interfacial resistances and better mechanical conformity, which are critical for sensitive and accurate sensory detection. + +<|ref|>text<|/ref|><|det|>[[114, 532, 883, 626]]<|/det|> +Our approach offers an effective and versatile method for developing e-skin systems capable of sophisticated multi-modal sensory functions. We have further clarified these advantages in the revised manuscript and supplementary information to provide a clearer understanding of our methods and their benefits over traditional make-and-transfer methods. + +<|ref|>sub_title<|/ref|><|det|>[[115, 635, 409, 653]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 660, 883, 905]]<|/det|> +On pages 6- 7, in the revised manuscript, we modified, "Furthermore, compared with a make-and-transfer method, our in situ solution-based fabrication approach enables the seamless integration of sensors into the e-skin matrix in a single step, enhancing mechanical and electrical performance by reducing interfacial resistances and improving mechanical conformity, thereby significantly improving sensitivity and responsiveness. This approach also offers a versatile platform that can be constructed using a broad range of functional nanomaterials hybridized with a polymeric matrix to form a multi-modal sensing system. By selecting materials that offer unique functional attributes, from AgNWs known for their conductivity and flexibility to graphene and MXene for their high surface area, electrical conductivity, and hydrophilicity, this system can emulate the skin with complex somatosensory system, where various mechanoreceptors and thermoreceptors distributed in the epidermal and dermal layers enable the spatiotemporal recognition of the magnitude and location of touch and temperature stimuli." + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 218, 107]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[112, 114, 886, 375]]<|/det|> +ReferencesBasarir, F., Madani, Z. & Vapaavuori, J. Recent Advances in Silver Nanowire Based Flexible Capacitive Pressure Sensors: From Structure, Fabrication to Emerging Applications. Adv. Mater. Interfaces 9, (2022).Chauhan, N., Maekawa, T. & Kumar, D. N. S. Graphene based biosensors - Accelerating medical diagnostics to new- dimensions. J. Mater. Res. 32, 2860- 2882 (2017).Amara, U., Hussain, I., Ahmad, M., Mahmood, K. & Zhang, K. 2D MXene- Based Biosensing: A Review. Small 19, 1- 38 (2023).Driscoll, N. et al. MXene- infused bioelectronic interfaces for multiscale electrophysiology and stimulation. Sci. Transl. Med. 13, eabf8629 (2021).Liu, H. et al. 3D Printed Flexible Strain Sensors: From Printing to Devices and Signals. Adv. Mater. 33, 2004782 (2021).Zhu, Z., Park, H. S. & McAlpine, M. C. 3D printed deformable sensors. Sci. Adv. 6, eaba5575 (2023).Reeder, J. et al. Mechanically Adaptive Organic Transistors for Implantable Electronics. Adv. Mater. 26, 4967- 4973 (2014). + +<|ref|>text<|/ref|><|det|>[[115, 388, 882, 501]]<|/det|> +Comment 6: On Page 7, Figure 2H, the volume of the PNIPAM hydrogel in Figure 2H is shown to dramatically decrease between approximately \(35^{\circ}C\) and \(45^{\circ}C\) . Given that the normal human body temperature is around \(36 - 37^{\circ}C\) , even if actuation is induced by an electrothermal method, maintaining its shape seems crucial for attaching it to various organs within the body. To substantiate this point, it would be necessary for the authors to demonstrate volume changes starting from a range lower than \(35^{\circ}C\) . + +<|ref|>text<|/ref|><|det|>[[115, 508, 882, 602]]<|/det|> +Our response: We appreciate the reviewer's comment regarding the temperature- dependent volume changes of PNIPAM hydrogel. As reviewer's suggested, we have included data on volume changes of PNIPAM hydrogel starting from temperatures lower than \(35^{\circ}C\) , extending through the normal human body temperature range to beyond its LCST. + +<|ref|>text<|/ref|><|det|>[[115, 610, 882, 723]]<|/det|> +As shown in Fig. R16, the expanded data clearly demonstrate PNIPAM hydrogel's inherent characteristic of water retention and swelling at temperatures below its LCST, which approximately \(32^{\circ}C\) to \(34^{\circ}C\) for pure PNIPAM. Beyond this threshold, a significant and rapid deswelling process occurs due to expulsion of water, resulting in a dramatic volume reduction. This thermos- responsive deswelling behavior is the basis for the actuation mechanism used in our device designs. + +<|ref|>text<|/ref|><|det|>[[115, 730, 882, 805]]<|/det|> +We have updated the manuscript to better reflect the PNIPAM hydrogel's behavior across relevant physiological temperature ranges. It suggests the hydrogel's applicability and adaptability in developing implantable biomedical devices, capable of dynamically interacting with the human body's thermal environment. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 92, 846, 321]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 330, 884, 400]]<|/det|> +
Fig. R16. The thermal responsiveness of PNIPAM hydrogel. (A) The volumetric shrinkage of PNIPAM hydrogel during the heating cycle across a temperature range of \(25^{\circ}C\) to \(60^{\circ}C\) . (B) The hydrogel's volumetric recovery during the cooling cycle, as temperatures revert to \(25^{\circ}C\) , showcasing its reversible thermal behavior and resilience.
+ +<|ref|>sub_title<|/ref|><|det|>[[115, 414, 410, 433]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[112, 440, 884, 608]]<|/det|> +(1) On page 8, in the revised manuscript, we added Fig. R16A as Fig. 2H. +(2) On page 13, in the revised supporting information, we added Fig. R16B as Fig. S3B. +(3) On pages 5-6, in the revised manuscript, we modified, "The PNIPAM hydrogel can undergo a dramatic volumetric reduction of about \(90\%\) as the temperature shifts from 25 \(^\circ C\) to \(60^\circ C\) . Notably, this significant and rapid deswelling behavior is initiated only when temperature is beyond its lower critical solution temperature (LCST \(32^\circ C \sim 34^\circ C\) ), enabling versatile actuation capabilities within biological environments (Fig. S3A&B, and Fig. 2H). + +<|ref|>text<|/ref|><|det|>[[115, 624, 884, 680]]<|/det|> +Comment 7: It was confirmed that the composite was implemented through XPS analysis. Is there a concern that this might result in lower performance compared to a full composite? + +<|ref|>text<|/ref|><|det|>[[115, 687, 883, 820]]<|/det|> +Our response: We appreciate the reviewer's comment regarding the performance of our composite materials, particularly considering its implementation and characterization through XPS analysis. We wish to clarify that our work indeed successfully constructed a full composite tailored specifically for electronic skin (e- skin) applications. Unlike traditional bulk composites, our composite has a thin profile to meet the specific requirements of e- skin functionalities, where excessive thickness would compromise practicality and performance. + +<|ref|>text<|/ref|><|det|>[[115, 827, 884, 901]]<|/det|> +Our fabrication process involves an initial step of drop- casting followed by laser patterning, which forms a thin and porous network of the functional materials (Fig. R17A). This method contributes to fabricating precise and suitable fine features required for high- performance e- skin. The subsequent step involves spin casting a polymer solution over + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 883, 145]]<|/det|> +this preformed structure. This process ensures the polymer solution thoroughly permeates the functional material layer, resulting in the formation of a full composite (Fig. R17B). + +<|ref|>image<|/ref|><|det|>[[171, 158, 820, 395]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 402, 883, 506]]<|/det|> +
Fig. R17. Fabrication of functional nanocomposite based on in situ solution integration method. (A) Top: Schematic illustration of patterning AgNWs network with a laser; Bottom: SEM image of as-synthesized AgNWs. (B) Top: Schematic illustration of spin coating PI solution and forming AgNW/PI nanocomposite; Bottom: SEM image of AgNW/PI nanocomposite with full PI infiltration, demonstrating a thorough infiltration of PI within the AgNW network, resulting in a cohesive nanocomposite structure.
+ +<|ref|>text<|/ref|><|det|>[[114, 513, 883, 626]]<|/det|> +The choice of XPS for surface composition and chemical state analysis (Fig. S13- S15), supplemented by SEM for morphology insights (Fig. 2C and Fig. 2D, Fig. S17A- C, Fig. S21A- C), FTIR for chemical bond identification (Fig. S17D and Fig. S21D), and XRD for crystalline structure information (Fig. S17E and Fig. S21E), commonly validates the composite's integrity and the efficacy of the fabrication process (Supplementary Note S1- S2). + +<|ref|>text<|/ref|><|det|>[[114, 633, 883, 784]]<|/det|> +Our design and fabrication strategies align with the requirement for developing high- performance e- skin layer. By prioritizing a thin profile, we ensure that our composite not only meets the mechanical flexibility and electrical performance demands to e- skin applications but also remains lightweight and conformable to various surfaces. This approach facilitates a seamless integration of functional materials into a polymer matrix, forming a uniform and cohesive composite. Such a composition is critical for the optimal functionality of e- skin, enabling it to closely mimic the sensitivity and versatility of nature skin while ensuring durability and reliability in various operational situations. + +<|ref|>text<|/ref|><|det|>[[115, 791, 882, 847]]<|/det|> +In the revised manuscript and supporting information, we have further explained the fabrication process and its advantages, enhancing understanding of our in situ solution- based method and its contribution to advancing e- skin technology. + +<|ref|>sub_title<|/ref|><|det|>[[115, 855, 410, 873]]<|/det|> +## Modification to the manuscript: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 370]]<|/det|> +On page 7, in the revised manuscript, we modified, "The X- ray photoelectron spectroscopy (XPS) characterization on the e- skin layers reveals the precise nanoscale integration of active materials within a polymer matrix, as detailed in Fig. S12- S14 and Supplementary Note S1. It showcases the optimal distribution and intermolecular bonding of the composite components, effectively addressing the common challenge of uneven dispersion of nanomaterials, which usually undermines the performance of conventional composites. Our approach minimizes the polymer amount required to integrate nanomaterials into composite functional modules and utilizes excess polymer as an insulating layer to separate modules, preventing interference between their electrical and chemical signals, thereby ensuring that each functional module operates independently and effectively. This simple approach combines the distinct properties of each constituent, achieving a balance between structural integrity and functional versatility [56- 60]. This advanced level of integration would be of great value for soft robots that seek to achieve multifunctionality and local sensing capabilities approaching skin." + +<|ref|>text<|/ref|><|det|>[[115, 386, 882, 442]]<|/det|> +Comment 8: After nanomaterials are created through the laser pattern, the inherent properties of the material make handling difficult. How was the surrounding material removed or treated? + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 544]]<|/det|> +Our response: We appreciate the reviewer's concern regarding the post- treatment process surrounding unwanted nanomaterials following laser patterning. Our approach to addressing this challenge hinges on the precise control of laser parameters during the patterning process, which effectively eliminates the need for extensive post- patterning removal steps. + +<|ref|>text<|/ref|><|det|>[[114, 551, 883, 795]]<|/det|> +Regarding the laser patterning, the underlying mechanism relies on the laser's thermal effect, which induces localized heating upon interaction material. This heating is intense and concentrated within a precise area, corresponding to the laser's focal point. We precisely adjust the laser settings to ensure complete elimination of the nanomaterials outside the desired pattern through hatching process. This laser ablation process, characterized by its high resolution of several tens of micrometers, allows for the selective removal of unwanted nanomaterials while leaving the desired pattern intact. The accuracy and efficiency of this method significantly reduces the presence of residual materials that could potentially interfere with subsequent processing steps. Notably, any residual materials left post- hatching are minimal and do not compromise the structural integrity or functionality of the as- formed composite. By employing this laser patterning technique, we ensure the precise and clean deposition of nanomaterials in alignment with our designs, which is crucial for the operational effectiveness of the device. + +<|ref|>text<|/ref|><|det|>[[115, 803, 882, 877]]<|/det|> +We have included the detailed laser patterning parameters applicable for various nanomaterials in the revised manuscript and supporting information, aiming to provide clear insights and facilitate a better understanding for researchers engaging in similar future endeavors. + +<|ref|>sub_title<|/ref|><|det|>[[116, 886, 410, 904]]<|/det|> +## Modification to the manuscript: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 164]]<|/det|> +(1) On page 28, in the revised manuscript, we added, "The thermal effects of laser patterning ensure minimal residual materials remain, as localized heating effectively eliminates any leftovers, facilitating seamless progression to subsequent processing steps." + +<|ref|>text<|/ref|><|det|>[[114, 172, 883, 284]]<|/det|> +(2) On page 28, in the revised manuscript, we added, "Here, laser hatching parameters for patterning nanomaterials are set: for AgNW/PEDOT:PSS/RGO, an infrared laser power of 12% (50 W) with a hatching speed of 5000 mm/s and frequency of 40 kHz; for Au/MXene, the settings are adjusted to an infrared laser power of 10% (50 W), a hatching speed of 1000 mm/s, and frequency of 40 kHz, ensuring precision in the material's functional structuring." + +<|ref|>text<|/ref|><|det|>[[114, 298, 883, 355]]<|/det|> +Comment 9: In Figs 3C, D, please indicate in the caption whether SEM images represent the surface or cross-section. Additionally, to determine the presence of voids, it may be necessary to examine cross-sectional TEM images. + +<|ref|>text<|/ref|><|det|>[[114, 362, 883, 419]]<|/det|> +Our response: We thank the reviewer's comments. We have updated the captions of Fig. 3C and Fig. 3D to clearly indicate that these SEM images represent the surface of our samples. + +<|ref|>text<|/ref|><|det|>[[114, 426, 883, 540]]<|/det|> +To further address concerns regarding void detection within the composite, we conducted cross- section SEM analysis to examine the presence of voids within the composite. Our findings from the SEM images, as shown in Fig. R18B&C, provide a comprehensive understanding of the composite structure, including the void distribution. The SEM images are fully capable of capturing the necessary information regarding voids presence, thus obviating the need for supplementary TEM studies for this purpose. + +<|ref|>text<|/ref|><|det|>[[114, 547, 883, 622]]<|/det|> +We have included cross- sectional SEM images in our revised supporting information. These images offer an in- depth view of the composite integrity, allowing us to verify the absence of voids within the material structure, demonstrating the composite's uniformity that is essential for e- skin application requiring high sensitivity and reliability. + +<|ref|>image<|/ref|><|det|>[[117, 631, 875, 787]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 802, 883, 871]]<|/det|> +
Fig. R18. SEM characterization of functional nanocomposite based on in situ solution integration method. (A) Top surface SEM view of the AgNW/PI nanocomposite. (B&C) Cross-sectional SEM images of AgNW/PI nanocomposite, revealing the complete penetration of PI throughout the AgNW matrix with the absence of voids.
+ +<|ref|>text<|/ref|><|det|>[[115, 879, 410, 897]]<|/det|> +Modification to the manuscript: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 884, 145]]<|/det|> +(1) On page 13, in the revised manuscript, we modified the figure caption of Fig. 3C&D, "(C&D) SEM images of the surface of nanocomposite films used in constructing sensory robots." + +<|ref|>text<|/ref|><|det|>[[113, 152, 884, 191]]<|/det|> +(2) On page 27, in the revised supporting information, we added Fig. R18B&C as Fig. S17D&F, respectively. + +<|ref|>text<|/ref|><|det|>[[113, 197, 820, 218]]<|/det|> +(3) On page 27, in the revised supporting information, we modified Fig. S17B&C. + +<|ref|>text<|/ref|><|det|>[[113, 224, 820, 244]]<|/det|> +(4) On page 32, in the revised supporting information, we modified Fig. S21B&C. + +<|ref|>text<|/ref|><|det|>[[113, 250, 883, 344]]<|/det|> +(3) On pages 9-10, in the revised manuscript, we modified, "The scanning electron microscope (SEM) images, including both top and side views as shown in Fig. 3C&D, Fig. S17A-F, and Fig. S21A-C, present that the curing process fully buries all the nanomaterials inside the PI matrix, resulting in a uniform composite free from observable voids." + +<|ref|>text<|/ref|><|det|>[[113, 360, 888, 416]]<|/det|> +Comment 10: In Fig 3E, it is understood that accurately observing the exact temperature by performing twisting and bending may be challenging with an infrared camera. However, even considering this, it seems that the temperature distribution is not uniform. + +<|ref|>text<|/ref|><|det|>[[113, 423, 883, 499]]<|/det|> +Our response: We thank the reviewer's comment regarding the observed non- uniform temperature distribution in Fig. 3E, captured using an infrared camera. As reviewer said, it is challenging to accurately capture temperature variations during dynamic movements such as twisting and bending due to the limitations of thermal imaging technology. + +<|ref|>image<|/ref|><|det|>[[250, 518, 750, 747]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 765, 883, 801]]<|/det|> +
Fig. R19. Infrared thermograph of an AgNW/PI-based heater undergoing bending and twisting motions.
+ +<|ref|>text<|/ref|><|det|>[[114, 808, 883, 901]]<|/det|> +Upon detailed analysis, we identified that the primary cause for the observed nonuniformity was related to the positioning of the sample during imaging. It appears that the sample was not maintained in a perfectly flat orientation nor consistently aligned at a uniform distance from the infrared camera. Such positioning discrepancies can significantly affect the accuracy of temperature measurements, leading to the appearance + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 127]]<|/det|> +of non- uniform temperature distributions due to the angular and distance- related variations inherent in infrared thermography. + +<|ref|>text<|/ref|><|det|>[[115, 134, 882, 229]]<|/det|> +To ensure more accurate temperature measurement, we have refined our experimental setup. We made efforts to ensure that the sample is evenly positioned on a flat surface, minimizing any potential distortions or variations due to uneven distances between different parts of the sample and the camera. The updated figures have been included in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 236, 410, 255]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 262, 726, 282]]<|/det|> +On page 12, in the revised manuscript, we added Fig. R19 as Fig. 3E. + +<|ref|>text<|/ref|><|det|>[[115, 295, 882, 353]]<|/det|> +Comment 11: In Fig 3F, G, the temperature converges over time, but what is the reason for the continuous change in bending force? Additionally, once bent, how long does the bending force persist? + +<|ref|>text<|/ref|><|det|>[[115, 360, 882, 473]]<|/det|> +Our response: We thank the reviewer's question about the dynamics of temperature stabilization and the resultant bending state as shown in Fig. R20A (Fig. 3F) and Fig. R20B (Fig. 3G). Fig. R20A (Fig. 3F) presents the surface temperature of the AgNW/PI heater, showing its rapid thermal response and ability to quickly reach and stabilize at the set temperature due to the heater's efficient heat generation capabilities. This rapid thermal stabilization allows for efficient energy transfer and thermal equilibrium. + +<|ref|>image<|/ref|><|det|>[[144, 485, 857, 735]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 752, 882, 821]]<|/det|> +
Fig. R20. (A) Surface temperature of the AgNW/PI-based heater as a function of the input electric power. Notably, the AgNW/PI nanocomposite heater can function under relatively low input electric power. (B) The resultant bending angle of a soft robotic arm as a function of the input electric power.
+ +<|ref|>text<|/ref|><|det|>[[115, 829, 882, 904]]<|/det|> +Conversely, Fig. R20B (Fig. 3G) shows the actuator's deformation over time. The transmission of heat from the heater to the entire sample requires a certain duration to propagate through the material. This apparent discrepancy in response times between the graphs arises from the difference in thermal propagation and the actuator's + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 145]]<|/det|> +mechanical response. While Fig. R20A (Fig. 3F) illustrates the heater's immediate temperature stabilization, Fig. R20B (Fig. 3G) reveals a more gradual progression in the actuator's deformation. + +<|ref|>text<|/ref|><|det|>[[115, 153, 882, 266]]<|/det|> +Furthermore, it is important to note that Fig. R20B (Fig. 3G) shows the deformation state of the actuator within a defined timeframe. Our empirical observations indicate that, upon reaching a thermally stable state, the actuator achieves its maximum deformation. This maximum bending is not transient, instead it is maintained as long as the thermal conditions remain unchanged. This ensures that once activated to a certain threshold, it retains its deformed state indefinitely under steady thermal environments. + +<|ref|>text<|/ref|><|det|>[[115, 273, 884, 368]]<|/det|> +To enhance clarity and provide a comprehensive understanding of these phenomena, we have updated Fig. R20B (Fig. 3G) in the revised manuscript to include a plateau segment, demonstrating the actuator's deformation state over an extended period. This clearly illustrates the actuator's capability to maintain its maximum bending force upon achieving thermal equilibrium, offering a clearer depiction of its long- term stability and performance. + +<|ref|>sub_title<|/ref|><|det|>[[116, 375, 409, 393]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 400, 772, 420]]<|/det|> +(1) On page 13, in the revised manuscript, we added Fig. R20B as Fig. 3G. + +<|ref|>text<|/ref|><|det|>[[115, 427, 882, 502]]<|/det|> +(2) On page 10, in the revised manuscript, we added, "Fig. 3G also indicates that the actuator reaches its peak deformation upon achieving thermal equilibrium, and importantly, this maximum bend is maintained as long as there are no changes in thermal conditions." + +<|ref|>text<|/ref|><|det|>[[115, 518, 882, 556]]<|/det|> +Comment 12: In addition to comment 9, is it necessary to keep the heater on continuously to maintain actual bending when attaching it to an organ? + +<|ref|>text<|/ref|><|det|>[[115, 563, 882, 714]]<|/det|> +Our response: We appreciate the reviewer's comment regarding the necessity of continuous heating to maintain the actuator's bending state when interfaced with biological tissues/organs. For PNIPAM hydrogel, with LCST between 32- 34°C, the normal human body temperature is sufficient to trigger the desired deformation. The initial heating is primarily employed to accelerate the actuation process. Once actuation is achieved, continuous heating using the electrical heater becomes unnecessary. This feature ensures that our device can efficiently adapt and function within the physiological temperature range without the need for sustained thermal input. + +<|ref|>text<|/ref|><|det|>[[115, 721, 882, 833]]<|/det|> +Furthermore, we can design the device with a thermal feedback mechanism that automatically adjusts the heating, thereby preventing potential overheating and ensuring a rapid yet safe actuation (Fig. R10&11). This built- in feature, combined with hydrogel's responsiveness to body temperature, enables our developing device not only to be effective but also safe for extended biomedical utilization. We have highlighted this point in the revised manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[116, 841, 409, 859]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 867, 882, 904]]<|/det|> +(1) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 166]]<|/det|> +achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +<|ref|>text<|/ref|><|det|>[[115, 171, 870, 245]]<|/det|> +(2) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. +(3) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. +(4) On page 5, in the revised supporting information, we added," + +<|ref|>sub_title<|/ref|><|det|>[[115, 250, 883, 289]]<|/det|> +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 294, 883, 428]]<|/det|> +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +<|ref|>text<|/ref|><|det|>[[113, 433, 883, 888]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 126]]<|/det|> +overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<|ref|>text<|/ref|><|det|>[[114, 133, 883, 435]]<|/det|> +(5) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +<|ref|>text<|/ref|><|det|>[[115, 443, 591, 461]]<|/det|> +(6) On page 29, in the revised manuscript, we added, " + +<|ref|>sub_title<|/ref|><|det|>[[115, 469, 685, 488]]<|/det|> +## The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 495, 883, 626]]<|/det|> +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +<|ref|>sub_title<|/ref|><|det|>[[115, 634, 217, 651]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 659, 883, 712]]<|/det|> +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +<|ref|>text<|/ref|><|det|>[[115, 719, 882, 771]]<|/det|> +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +<|ref|>text<|/ref|><|det|>[[115, 786, 883, 899]]<|/det|> +Comment 13: The dual- axis graphs presented in this figure (Figure 3l, Figure 5F, K, N etc.) are difficult to intuitively comprehend. It is unclear whether the changes on the left axis correspond to the results on the right axis or if they were determined through variations in resistance, pressure, or pH values. Therefore, it seems necessary for the authors to modify the graphs for better intuitive understanding and provide explanations regarding the extent of numerical changes made. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 183]]<|/det|> +Our response: We appreciate the reviewer's comment on the clarity of dual- axis graphs in our figures (Fig. 3I, Fig. 5F, Fig. 5K and Fig. 5N). These graphs are intended to showcase the correlation between sensor responses (left axis) and the varying external conditions (right axis) they measure, such as temperature, volume, pressure, or pH values. + +<|ref|>text<|/ref|><|det|>[[114, 189, 883, 323]]<|/det|> +For instance, Fig. R21A (Fig. 3I) presents the static cycling test of the RGO/PI- based thermal sensor, which operates on resistance changes. In this scenario, as we vary the environmental temperature over time, the resistance changes (indicated on the left y- axis) correspond directly to different temperature values (shown on the right y- axis). Similarly, for Fig. R21B (Fig. 5F), Fig. R21C (Fig. 5K) and Fig. R21D (Fig. 5N), where resistance- based sensors capture real- time changes in resistance as a direct response to external variations in volume, pressure, or pH. + +<|ref|>text<|/ref|><|det|>[[114, 329, 883, 444]]<|/det|> +We have refined these figures to more clearly illustrate the correlation between resistance changes and the physical parameters under observation, thereby clarifying the direct linkage between sensor outputs and variations in environmental stimuli (Fig. R21). Moreover, we have incorporated detailed explanations on the numerical changes and their significance into the manuscript to provide comprehensive insights into the sensor's operational mechanisms. + +<|ref|>image<|/ref|><|det|>[[115, 455, 880, 767]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 773, 883, 895]]<|/det|> +
Fig. R21. (A) Static cycling test of the RGO/PI-based thermal sensor. Here, the left y-axis represents the change in resistance, while the right y-axis corresponds to the associated temperature changes. (B) Representative test of the 3D buckling strain sensor in real-time monitoring of volumetric change of the artificial bladder during cyclic movements of filling and emptying. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the associated volume changes. (C) Representative measurement of fluidic pressure of the artificial artery system using the soft robotic cuff. Here, the left y-axis is the change in resistance,
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 142]]<|/det|> +while the right y- axis corresponds to the pressure changes. (D) Electrical response of PEDOT:PSS/PVA hydrogel to pH change ranging from 3 to 7 over time. Here, the left y- axis is the change in resistance, while the right y- axis corresponds to the pH value changes. + +<|ref|>sub_title<|/ref|><|det|>[[115, 148, 410, 167]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 174, 761, 194]]<|/det|> +(1) On page 13, in the revised manuscript, we added Fig. R21A as Fig. 3l. + +<|ref|>text<|/ref|><|det|>[[115, 200, 883, 275]]<|/det|> +(2) On page 14, in the revised manuscript, we modified the caption of Fig. 3l. "(I) Static cycling test of the RGO/PI-based thermal sensor. Here, the left y-axis represents the change in resistance, while the right y-axis corresponds to the associated temperature changes." + +<|ref|>text<|/ref|><|det|>[[115, 283, 883, 321]]<|/det|> +(3) On page 20, in the revised manuscript, we added Fig. R21B-D as Fig. 5F, Fig. 5K, and Fig. 5N, respectively. + +<|ref|>text<|/ref|><|det|>[[115, 328, 883, 421]]<|/det|> +(4) On page 21, in the revised manuscript, we modified the caption of Fig. 5F. "(F) Representative test of the 3D buckling strain sensor in real-time monitoring of volumetric change of the artificial bladder during cyclic movements of filling and emptying. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the associated volume changes." + +<|ref|>text<|/ref|><|det|>[[115, 429, 883, 504]]<|/det|> +(5) On page 21, in the revised manuscript, we modified the caption of Fig. 5K. "(K) Representative measurement of fluidic pressure of the artificial artery system using the soft robotic cuff. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the pressure changes." + +<|ref|>text<|/ref|><|det|>[[115, 512, 883, 586]]<|/det|> +(6) On page 21, in the revised manuscript, we modified the caption of Fig. 5N. "(N) Electrical response of PEDOT:PSS/PVA hydrogel to pH change ranging from 3 to 7 over time. Here, the left y-axis is the change in resistance, while the right y-axis corresponds to the pH value changes." + +<|ref|>text<|/ref|><|det|>[[115, 602, 882, 677]]<|/det|> +Comment 14: Using heat as a stimulus might potentially cause damage to the tissue. However, considering the hydrogel is thick enough, it may prevent such damage. How efficiently does heat transfer throughout the entire hydrogel, and is the heat dissipation effective enough to be considered safe? + +<|ref|>text<|/ref|><|det|>[[115, 686, 883, 799]]<|/det|> +Our response: We appreciate the reviewer's concern about the use of heat as stimulus and its potential to cause tissue damage. As previously discussed in response to Comment 12, our device does not necessitate continuous heating. We employ initial heating to accelerate the actuation process, eliminating the need for continuous thermal input once the desired actuation is achieved. This strategy ensures that the device's adaptability and safe operation is within the physiological temperature range. + +<|ref|>text<|/ref|><|det|>[[115, 807, 883, 899]]<|/det|> +To further address safety concerns, we can design the device with an integrated thermal feedback mechanism that meticulously regulates the heating, thereby preventing any risk of overheating (Fig. R10&11). Moreover, our design considerations ensure that heat transfer through the hydrogel is efficiently managed, maintaining operational temperatures well below the \(43^{\circ}C\) threshold known to prevent thermal tissue damage13,14. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 884, 202]]<|/det|> +Our in vitro and in vivo studies also confirm the device's safety. In vitro exposure of fibroblast- like cells (3T3- J- 2) to \(39^{\circ}C\) for 48 hours demonstrated maintained cellular health and viability (Fig. 6E&F). In vivo experiments involving the device's application around a mouse's heart, facilitated by wireless power transfer at \(0.1W\) to achieve \(40^{\circ}C\) thermal stimulation, revealed no detectable damage or inflammation in critical organs (Fig. 4I and Fig. S45). + +<|ref|>text<|/ref|><|det|>[[115, 210, 884, 248]]<|/det|> +We have updated the manuscript to highlight these aspects, providing a better understanding of the thermal dynamics and safety profiles of our hydrogel- based systems. + +<|ref|>sub_title<|/ref|><|det|>[[115, 255, 409, 274]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 281, 883, 394]]<|/det|> +(1) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +<|ref|>text<|/ref|><|det|>[[115, 400, 866, 421]]<|/det|> +(2) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. + +<|ref|>text<|/ref|><|det|>[[115, 427, 866, 447]]<|/det|> +(3) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. + +<|ref|>text<|/ref|><|det|>[[115, 454, 673, 473]]<|/det|> +(4) On page 5, in the revised supporting information, we added," + +<|ref|>sub_title<|/ref|><|det|>[[115, 480, 882, 518]]<|/det|> +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[114, 525, 883, 658]]<|/det|> +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +<|ref|>text<|/ref|><|det|>[[114, 665, 883, 890]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 352]]<|/det|> +value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on-chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<|ref|>text<|/ref|><|det|>[[114, 359, 883, 659]]<|/det|> +(5) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +<|ref|>text<|/ref|><|det|>[[116, 667, 590, 686]]<|/det|> +(6) On page 29, in the revised manuscript, we added, " + +<|ref|>sub_title<|/ref|><|det|>[[116, 694, 685, 714]]<|/det|> +## The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 720, 883, 852]]<|/det|> +The robotic gripper and the external circuitry were connected in series with an NI DMM amperemeter set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +<|ref|>sub_title<|/ref|><|det|>[[116, 860, 217, 877]]<|/det|> +## References + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 142]]<|/det|> +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +<|ref|>text<|/ref|><|det|>[[115, 148, 881, 201]]<|/det|> +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +<|ref|>text<|/ref|><|det|>[[115, 216, 875, 253]]<|/det|> +Comment 15: While applying temperature, can the thermal sensor accurately measure the temperature from the tissue? + +<|ref|>text<|/ref|><|det|>[[115, 260, 882, 355]]<|/det|> +Our response: We appreciate the reviewer's concern regarding the precision of our thermal sensors in capturing tissue temperatures during application. To validate our sensor's performance, we conducted comparative tests against commercial thermal resistors (ERT- J0ET102H), demonstrating a high level of correlation and match in the readings, as shown in Fig. R22A (Fig. 3K) and Fig. R22B (Fig. S21G). + +<|ref|>text<|/ref|><|det|>[[115, 361, 882, 475]]<|/det|> +As illustrated in Fig. R22C (Fig. 3H), we extensively characterized the thermal sensor's responsiveness across a wide temperature range, from \(23^{\circ}C\) to \(92^{\circ}C\) , which spans the spectrum of internal body temperature. This evaluation also included scenarios where the sensor was immersed in a phosphate- buffered saline (PBS) solution, closely simulating in vivo environmental conditions. The sensor exhibited exceptional stability and reliability even in this simulated physiological environment. + +<|ref|>text<|/ref|><|det|>[[115, 482, 882, 650]]<|/det|> +Furthermore, we employed in situ solution- based methods to fabricate the functional modules located in different layers. This strategy allows for the integration of a minimal amount of polyimide with functional materials to form composite functional modules. This not only preserves the functional integrity of the materials within each module but also leverages the remaining polyimide to serve as a dual purpose. Beyond its inclusion in the composite, polyimide acts as an insulating barrier between adjacent modules. This barrier is crucial for our device's functionality, as it prevents electrical and chemical signal interference between modules, thereby ensuring that each functional module operates independently and as intended. + +<|ref|>image<|/ref|><|det|>[[133, 657, 866, 816]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 824, 882, 875]]<|/det|> +
Fig. R22. (A) Temperature measurement on the MXene/PI thermal sensor and a commercial thermal resistor (ERT-J0ET102H). (B) Temperature measurement on the RGO/PI thermal sensor and the commercial thermal resistor. (C) Resistive response at various temperatures ranging from
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 881, 125]]<|/det|> +\(23^{\circ}C\) to \(92^{\circ}C\) , for the RGO/PI- based thermal sensor undergoing bending and twisting motions, and immersed in a solution of PBS. + +<|ref|>text<|/ref|><|det|>[[115, 131, 882, 188]]<|/det|> +These findings solidify the capability of our thermal sensor for precise monitoring of tissue temperatures. The updated manuscript further emphasizes the sensor's applicability and stability, highlighting its potential in medical applications. + +<|ref|>sub_title<|/ref|><|det|>[[116, 195, 409, 213]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[113, 222, 883, 598]]<|/det|> +(1) On page 7, in the revised manuscript, we modified, "Fig. 2M displays a more complicated integration paradigm with multi-layer stacking, where different electronic components (e.g., PEDOT:PSS/PI-based conductive electrodes and RGO/PI temperature sensors) can be distributed in different layers of the e-skin to achieve simultaneous functional versatility and compactness. This assembly technique ensures the e-skin remarkable thinness and flexibility, enhancing its effective performance for implantable applications (Fig. S11B). The X-ray photoelectron spectroscopy (XPS) characterization on the e-skin layers reveals the precise nanoscale integration of active materials within a polymer matrix, as detailed in Fig. S12-S14 and Supplementary Note S1. It showcases the optimal distribution and intermolecular bonding of the composite components, effectively addressing the common challenge of uneven dispersion of nanomaterials, which usually undermines the performance of conventional composites. Our approach minimizes the polymer amount required to integrate nanomaterials into composite functional modules and utilizes excess polymer as an insulating layer to separate modules, preventing interference between their electrical and chemical signals, thereby ensuring that each functional module operates independently and effectively. This simple approach combines the distinct properties of each constituent, achieving a balance between structural integrity and functional versatility. This advanced level of integration would be of great value for soft robots that seek to achieve multifunctionality and local sensing capabilities approaching skin." + +<|ref|>text<|/ref|><|det|>[[114, 604, 883, 793]]<|/det|> +(2) On page 11, in the revised manuscript, we added, "Fig. 3H illustrates the resistive change in a relatively linear relation with temperature for the RGO/PI thermal sensor. The temperature coefficient of the resistance (TCR) of the RGO/PI thermal sensor is > 0.5%/°C, featuring its high thermal sensitivity. On the other hand, the RGO/PI-based thermal sensor exhibits a stable performance after 1000 bending cycles, and even after immersing in PBS solution. Fig. 3I and Fig. S21F show performance of the thermal sensor in response to cycles of temperature rise and drop, indicating good sensing stability. In addition, Fig. S21G shows consistent measurements of RGO/PI nanocomposite sensing performance in comparison with a commercial thermal resistor (ERT-J0ET102H), indicating excellent sensing accuracy." + +<|ref|>text<|/ref|><|det|>[[115, 808, 881, 845]]<|/det|> +Comment 16: What is the reason for the difference in the transfer method in S12(b) compared to the dual printing method in S16? + +<|ref|>text<|/ref|><|det|>[[115, 853, 883, 890]]<|/det|> +Our response: We appreciate the reviewer's concern about the methods utilized in our fabrication process, specifically the transfer method illustrated in Fig. S12B (Fig. S11B + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 202]]<|/det|> +in the updated supporting information), and the dual printing method detailed in Fig. S16 (Fig. S15 in the updated supporting information). The essential differentiation between these methods lies not in their fundamental principles but in their application and the resulting properties of the e- skin layer. The choice of method is tailored to the specific requirements of the application, ensuring that the e- skin fabricated is not only functionally effective but also optimally designed for its intended use. + +<|ref|>text<|/ref|><|det|>[[115, 208, 883, 341]]<|/det|> +The transfer method, as shown in Fig. S12B (Fig. S11B in the updated supporting information), allows for the fabrication of an e- skin that is notably thinner and possesses enhanced flexibility. This is especially beneficial for implantable applications where e- skin needs to conform closely to the complex contour of tissues/organs, ensuring optimal functionality and integration. Conversely, the dual printing method offers advantages in producing e- skin with multiple layers, allowing for the incorporation of multiple functionalities within a single e- skin platform. + +<|ref|>text<|/ref|><|det|>[[115, 348, 883, 461]]<|/det|> +Both methods demonstrate the versatility and adaptability of our solution- based fabrication strategy, highlighting its superiority over traditional fabrication techniques, such as 3D printing. These two methods indicate the operational ease and the broad applicability of our method in creating e- skins that can be tailored to meet the diverse requirements of both implantable devices and wearable sensors, thereby broadening the scope of potential applications in the field of soft robotics and biomedical devices. + +<|ref|>text<|/ref|><|det|>[[115, 469, 883, 506]]<|/det|> +In the revised manuscript, we have clarified these two methods, further emphasizing our approach's flexibility in accommodating the needs of advanced e- skin systems. + +<|ref|>sub_title<|/ref|><|det|>[[116, 514, 409, 533]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 540, 883, 672]]<|/det|> +(1) On page 7, in the revised manuscript, we modified, "Fig. 2M displays a more complicated integration paradigm with multi-layer stacking, where different electronic components (e.g., PEDOT:PSS/PI-based conductive electrodes and RGO/PI temperature sensors) can be distributed in different layers of the e-skin to achieve simultaneous functional versatility and compactness. This assembly technique ensures the e-skin remarkable thinness and flexibility, enhancing its effective performance for implantable applications (Fig. S11B)." + +<|ref|>text<|/ref|><|det|>[[115, 679, 883, 773]]<|/det|> +(2) On page 9, in the revised manuscript, we modified, "Fig. S15A shows layer-by-layer stacking as a simple and effective approach for fabricating the e-skin. This approach stands out for its capability to fabricate multi-layered e-skin integrating diverse functionalities within an unified e-skin framework, offering a sophisticated level of device customization." + +<|ref|>text<|/ref|><|det|>[[115, 789, 882, 863]]<|/det|> +Comment 17: On Page 11, the author mentioned that "The electrothermal stimulus along with distributed sensing capabilities enables programmed actuation not only on demand but also regulated simultaneously by the sensing feedback". How was actuation implemented based on sensing feedback? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 184]]<|/det|> +Our response: We thank the reviewer's question regarding the implementation of actuation based on sensing feedback. Our system design integrates a network of distributed sensors within e- skin, enabling the detection of various environmental stimuli. Upon detecting a change in external environment, these sensors convert environmental changes into electrical signals relayed to a control unit. + +<|ref|>text<|/ref|><|det|>[[115, 190, 883, 323]]<|/det|> +We have demonstrated that the integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration highlighted by the reviewer. + +<|ref|>text<|/ref|><|det|>[[114, 328, 883, 819]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. R10A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. R10B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. R11 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off. + +<|ref|>text<|/ref|><|det|>[[115, 825, 882, 881]]<|/det|> +To clarify this feedback mechanism, we have included comprehensive details in the revised manuscript and supporting information, providing examples of how this feedback mechanism is implemented within our soft robotic system. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 410, 108]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 122, 867, 194]]<|/det|> +(1) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. +(2) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. +(3) On page 5, in the revised supporting information, we added," + +<|ref|>sub_title<|/ref|><|det|>[[115, 201, 881, 238]]<|/det|> +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 245, 883, 379]]<|/det|> +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +<|ref|>text<|/ref|><|det|>[[113, 384, 883, 875]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 390]]<|/det|> +(4) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +<|ref|>text<|/ref|><|det|>[[115, 397, 591, 416]]<|/det|> +(5) On page 29, in the revised manuscript, we added, " + +<|ref|>sub_title<|/ref|><|det|>[[116, 423, 685, 443]]<|/det|> +## The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 449, 883, 581]]<|/det|> +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +<|ref|>sub_title<|/ref|><|det|>[[116, 589, 217, 606]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 614, 883, 666]]<|/det|> +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +<|ref|>text<|/ref|><|det|>[[115, 674, 882, 726]]<|/det|> +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +<|ref|>text<|/ref|><|det|>[[115, 741, 882, 852]]<|/det|> +Comment 18: On Page 14, Figure S31, in Figure S31B, it is evident that there is a tendency for the coupling coefficient to decrease as the separation distance increases. However, in Figure S31D, there is a trend showing an increase in output power relative to input power as the distance increases. This observation appears to be theoretically inconsistent. If this graph is accurate, the authors need to provide additional explanations for these results. + +<|ref|>text<|/ref|><|det|>[[115, 861, 882, 898]]<|/det|> +Our response: We thank the reviewer's comment regarding the discrepancy in the coupling efficiency and output power trends with increasing separation distance, as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 146]]<|/det|> +shown in Fig. R23A (Fig. S31B) and Fig. R23B (Fig. S31D). After thorough review, we found a labeling error in Fig. S31D that mispresented the trend of output power relative to input power as the distance increases. + +<|ref|>image<|/ref|><|det|>[[171, 154, 825, 359]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 366, 883, 437]]<|/det|> +
Fig. R23. The effect of separation distance, horizontal offset and orientation angle on the performance of WPT system. (A) FEA results showing the variations in the coupling coefficient of the WPT coils under different separation distances. (B) Experimental evaluations of power transmission at resonance frequency (16 MHz) under different separation distances
+ +<|ref|>text<|/ref|><|det|>[[115, 443, 883, 500]]<|/det|> +We have corrected this error to accurately illustrate the anticipated decrease in output efficiency with an increase in separation distance, thus realigning our results with theoretical expectations and ensuring consistency across our data presentation. + +<|ref|>sub_title<|/ref|><|det|>[[115, 508, 410, 526]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 532, 750, 552]]<|/det|> +On page 42, in the revised supporting information, we revised Fig. S31D. + +<|ref|>text<|/ref|><|det|>[[114, 566, 883, 736]]<|/det|> +Comment 19: On Page 16, in order for the sensory robots developed by the authors to conformally adhere to tissues or organs, they require not only curvilinear surfaces but also effective adhesion. While this article mentions the adhesiveness of PNIPAM, a recently published paper indicates that PNIPAM shows tissue adhesion at low temperatures (around \(25^{\circ}\mathrm{C}\) ) but loses almost all adhesive strength when it transitions to a gel form near \(40^{\circ}\mathrm{C}\) (Nature Biotechnology 2023, 41, 652- 662). To showcase the tissue adhesion capability of the authors' device, it becomes imperative to gauge the adhesive strength of the hydrogel by varying temperatures. This would confirm that there are no issues with adhesion even after attaching it to an organ. + +<|ref|>text<|/ref|><|det|>[[114, 743, 883, 857]]<|/det|> +Our response: We thank the reviewer's comment regarding the adhesive properties of PNIPAM hydrogels, particularly in light of recent literature indicating significant changes in adhesive strength at varying temperatures15. It is crucial to distinguish the type of adhesion we refer to within the scope of our device's application from the strong adhesive forces comparable to those of glues, as discussed in the mentioned Nature Biotechnology paper15. + +<|ref|>text<|/ref|><|det|>[[115, 864, 883, 902]]<|/det|> +Our device relies on the shape adaptability induced by the thermal response of PNIPAM hydrogels rather than on adhesive forces for effective tissue interfacing where the former + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 886, 185]]<|/det|> +self- assembles into a conformal shape to reduce dependence on strong adhesion force and mitigate interfacial stress, thus increasing biocompatibility. The concern regarding adhesion arises in the context of ensuring that the implanted device maintains its position and functionality without being compromised by potential reswelling effects post- actuation, especially at the temperatures around the body's physiological range. + +<|ref|>text<|/ref|><|det|>[[114, 190, 884, 267]]<|/det|> +Our approach capitalizes on the unique temperature- responsive deformation properties of PNIPAM hydrogels to maintain device efficacy, emphasizing a synergistic integration of shape adaptability and minimal adhesion to secure tissue engagement. our updated manuscript and supporting information now more clearly illustrate this perspective. + +<|ref|>image<|/ref|><|det|>[[128, 281, 872, 540]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 554, 884, 643]]<|/det|> +
Fig. R24. Demonstration of hydrogel adhesion to biological tissues. (A&B) Adhesion behavior of a PNIPAM-co-PAAm hydrogel with an LCST of \(36^{\circ}C\) across different temperatures. Below the LCST, the hydrogel exhibits robust adhesion below its LCST, which gradually loses above this threshold. All tests were conducted after overnight incubation simulating physiological conditions at \(34^{\circ}C\) , \(37^{\circ}C\) , and \(40^{\circ}C\) . Scale bars, \(5mm\) .
+ +<|ref|>text<|/ref|><|det|>[[114, 650, 883, 744]]<|/det|> +Additionally, as the reviewer's suggested, we conducted additional characterizations of the adhesive force exhibited by a PNIPAM- co- PAAm hydrogel with an LCST of \(36^{\circ}C\) across a range of temperatures, providing a better understanding of the hydrogel's physical properties and aiming to contribute valuable insights to the development of hydrogels for biomedical applications in designing effective implantable devices. + +<|ref|>sub_title<|/ref|><|det|>[[115, 751, 410, 770]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 777, 883, 909]]<|/det|> +(1) On page 10, in the revised manuscript, we modified, "We further evaluated the mechanical force generated by the soft robotic finger which incorporates a PNIPAM hydrogel layer roughly 1 mm thick, under various input powers. Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 127]]<|/det|> +hydrogel- based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +<|ref|>text<|/ref|><|det|>[[115, 133, 870, 155]]<|/det|> +(2) On page 52, in the revised supporting information, we added Fig. R24 as Fig. S40. + +<|ref|>text<|/ref|><|det|>[[115, 160, 882, 349]]<|/det|> +(3) On pages 21-22, in the revised manuscript, we added, "We also explored the bioadhesive behavior of our device on targeted tissues/organs. We observed that hydrogel's inherent adhesiveness is significantly related to its water content and temperature. As shown in Fig. S40, there is a decline in adhesive strength as temperatures approach the hydrogel's LCST. While this inherent adhesive capability contributes to the initial secure placement of the device, it's noteworthy that solely relying on this property might not guarantee a durable bond, especially as the hydrogel experiences dehydration. However, this temperature-responsive adhesiveness can play a complementary role in enhancing the device's grasp by counterbalancing any potential decrease in force due to hydrogel reswelling." + +<|ref|>text<|/ref|><|det|>[[115, 355, 882, 415]]<|/det|> +(6) On page 29, in the revised manuscript, we added, "Adhesion force was tested by the standard \(180^{\circ}\) peel test with the Instron machine (Mark-10 ESM303). All tests were conducted with a constant peeling speed of 13 mm/min." + +<|ref|>sub_title<|/ref|><|det|>[[115, 424, 208, 441]]<|/det|> +## Reference + +<|ref|>text<|/ref|><|det|>[[115, 450, 882, 589]]<|/det|> +Y. Jiang, +A.A. Trotsyuk, +S. Niu, +D. Henn, +K. Chen, +C.C. Shih, +M.R. Larson, +A.M. Mermin-Bunnell, +S. Mittal, +J.C. Lai, +A. Saberi, +E. Beard, +S. Jing, +D. Zhong, +S.R. Steele, +K. Sun, +T. Jain, +E. Zhao, +C.R. Neimeth, +W.G. Viana, +J. Tang, +D. Sivaraj, +J. Padmanabhan, +M. Rodrigues, +D.P. Perrault, +A. Chattopadhyay, +Z.N. Maan, +M.C. Leeolou, +C.A. Bonham, +S.H. Kwon, +H.C. Kussie, +K.S. Fischer, +G. Gurusankar, +K. Liang, +K. Zhang, +R. Nag, +M.P. Snyder, +M. Januszyk, +G.C. Gurtner, +Z. Bao, Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing, Nat. Biotechnol. 41 (2023) 652-662. https://doi.org/10.1038/s41587-022-01528-3. + +<|ref|>text<|/ref|><|det|>[[115, 603, 882, 660]]<|/det|> +Comment 20: In Figs 5, 6, the use of Au electrodes for electrical stimulation in electrotherapy seems somewhat divergent from the other sensing materials of this paper (Fig. S52B). + +<|ref|>text<|/ref|><|det|>[[115, 667, 882, 799]]<|/det|> +Our response: We thank the reviewer's concern regarding the use of Au electrodes for electrical stimulation in electrotherapy, as depicted in Fig. 5 and Fig. 6. The incorporation of Au electrodes within our device exemplifies our design to functional diversity and integration. The choice of Au, known for its superior electrical conductivity, biocompatibility, and stability within biological environments. These attributes render them ideally suited for delivering reliable and precise electrical stimulation, which is a critical function in therapeutic applications. + +<|ref|>text<|/ref|><|det|>[[115, 806, 882, 900]]<|/det|> +Our study explores a variety of materials with notable sensing and actuation capabilities. The selection of Au electrodes for demonstration emphasizes the system's modular design. This showcases our device's ability to seamlessly integrate various functional materials, enhancing its applicability across a wide range of therapeutic and monitoring scenarios. This adaptability allows for the customization of materials in alignment with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 127]]<|/det|> +distinct application requirements, thereby providing a versatile platform that can be tailored to a broad spectrum of biomedical applications. + +<|ref|>sub_title<|/ref|><|det|>[[115, 135, 410, 153]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 161, 882, 216]]<|/det|> +(1) On page 44, in the revised supporting information (Fig. S33A's caption), we added, "The stimulator component is two pairs of pacing electrodes, employing Au for its exceptional electrical conductivity, biocompatibility, and stability in biological settings." + +<|ref|>text<|/ref|><|det|>[[115, 224, 882, 299]]<|/det|> +(2) On page 53, in the revised supporting information (Fig. S41's caption), we added, "The use of Au ensures superior electrical conductivity, biocompatibility, and stability within biological environments, guaranteeing reliable and precise electrical stimulation essential for effective therapeutic interventions." + +<|ref|>text<|/ref|><|det|>[[115, 314, 882, 427]]<|/det|> +Comment 21: In Fig 5G, the electrical stimulation off voltage is not 0.0 V. Is there a specific reason for this? To help readers to understand, it appears that the authors should provide additional explanations regarding the correlation between electrical stimulation and volume changes. Specifically, a clear clarification is needed on whether the specific electrical stimulation is causing an actual increase in volume or if it is transmitting signals to patients having urinary dysfunction. + +<|ref|>text<|/ref|><|det|>[[115, 434, 882, 604]]<|/det|> +Our response: We thank the reviewer's questions regarding the electrical stimulation off voltage in Fig. 5G and the need for additional explanations about the correlation between electrical stimulation and volume changes. We have come into realization that in the previous experiment, the voltage electrical stimulation voltage was measured without a MOSFET power buffer. The high internal resistance of the microcontroller GPIO pins has resulted in fluctuations in the voltage measured at shut-off state. Through the application of a MOSFET power buffer, we have successfully decreased the amount of current drawn at the GPIO pin and decreased the internal resistance of the electrical stimulation output, and thereby corrects the small offset observed at shut-off state (Fig. R25). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[214, 88, 780, 416]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 424, 883, 530]]<|/det|> +
Fig. R25. A robotic gripper for bladder control. Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of \(3 \text{V}\) . Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly.
+ +<|ref|>text<|/ref|><|det|>[[114, 536, 883, 650]]<|/det|> +Electrical stimulation therapy has been used in various forms to manage bladder dysfunction, including sacral nerve stimulation (SNS), posterior tibial nerve stimulation (PTNS), and direct stimulation of the bladder or surrounding tissues16,17. Our device utilizes direct stimulation on the bladder muscle to facilitate bladder contraction and assist in urination, addressing conditions where bladder muscle control is involuntary and the sensory feedback to the central nervous system is disrupted. + +<|ref|>text<|/ref|><|det|>[[114, 656, 883, 862]]<|/det|> +Our developed soft robotic gripper provides both real- time bladder volume assessment and voiding treatment in a wireless closed- loop control manner. It features a flexible hydrogel- based actuator for conformal wrapping around the bladder, an integrated strain sensor for continuous bladder volume detection, an electrical stimulator for on- demand electrotherapy, and a control module for programmed operation (Fig. 5A- G, Fig. S33- 35). Electrical stimulation (E- stim) is activated when the bladder reaches its maximum volume threshold, targeting the bladder muscles to facilitate urination. Upon complete voiding of the bladder, the integrated sensors detect the reduction in bladder volume, which subsequently triggers the deactivation of the E- stim. This programming cycle ensures that stimulation is provided only, when necessary, closely mimicking the natural urination process and enhancing patient comfort and device efficiency. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 240]]<|/det|> +In several studies and clinical trials, electrical stimulation has shown positive effects on bladder control functions for some patients. However, the effectiveness of this treatment may vary among individuals and requires evaluation and supervision by healthcare professionals based on the patient's specific condition. The effectiveness of electrical stimulation for bladder voiding and its required voltage levels requires further investigation beyond the scope of our current study. However, our system demonstrates the feasibility of integrating sensing and actuation components to facilitate timely and responsive treatments for bladder dysfunction. + +<|ref|>text<|/ref|><|det|>[[114, 247, 883, 360]]<|/det|> +In the revised manuscript, we have clarified these points and provided additional explanations regarding the operational principles of our device, its potential applications in bladder dysfunction treatment. Our goal is to contribute to the broader understanding and development of integrative solutions for managing urinary disorders, emphasizing the significance of continuous monitoring and responsive treatment mechanisms in the field of soft robotics and biomedical engineering. + +<|ref|>sub_title<|/ref|><|det|>[[116, 367, 409, 385]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[113, 393, 747, 412]]<|/det|> +(1) On page 20, in the revised manuscript, we added Fig. R5 as Fig. 5G. + +<|ref|>text<|/ref|><|det|>[[114, 419, 883, 552]]<|/det|> +(2) On page 21, in the revised manuscript, we modified the figure caption of Fig. 5G, "Programmed electrical stimulation (top) and measured volume of an artificial bladder based on a balloon (middle and bottom). The experimental demonstration is conducted using the following parameters: volume threshold of \(\sim 100 \text{mL}\) , electrical stimulation amplitude of 3 V. Here, a slight delay in the deactivation process could be partially attributed to the response time of microcontroller unit (MCU) system in detecting changes from the sensors and updating the output accordingly." + +<|ref|>text<|/ref|><|det|>[[114, 558, 883, 758]]<|/det|> +(3) On page 18, in the revised manuscript, we added, "When the balloon's volume reaches a predetermined threshold, set here at 100 mL, the control system initiates electrical stimulation. Following successful voiding to below the threshold, the system automatically deactivates the stimulation. While electrical stimulation has shown promising results in enhancing bladder control in various studies and clinical trials, its efficacy can differ across individuals. The effectiveness of electrical stimulation for bladder voiding and its required voltage levels requires further investigation beyond the scope of our current study. However, our prototype showcases the potential of integrating sensing and actuation mechanisms to facilitate timely and adaptive interventions for bladder dysfunction." + +<|ref|>sub_title<|/ref|><|det|>[[115, 768, 218, 785]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[114, 795, 883, 845]]<|/det|> +Grill, W. M. Electrical stimulation for control of bladder function. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 2009 2369- 2370 (2009) doi:10.1109/IEMBS.2009.5335001. + +<|ref|>text<|/ref|><|det|>[[112, 851, 880, 885]]<|/det|> +Coolen, R. L., Groen, J. & Blok, B. F. M. Electrical stimulation in the treatment of bladder dysfunction: Technology update. Med. Devices Evid. Res. 12, 337- 345 (2019). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 202]]<|/det|> +Comment 22: As the authors mentioned in the context, PNIPAM hydrogel has reversibly contract and relax property upon electrothermal trigger. If that's the case, is there no risk of delamination if the device is not well- adhered to the tissue when the internal body temperature decreases? Additionally, wouldn't there be a possibility that continuous electrothermal stimulation, applied to prevent deformation of the device after it is attached to the tissue, could have adverse effects on the tissue? + +<|ref|>text<|/ref|><|det|>[[115, 210, 882, 304]]<|/det|> +Our response: We appreciate the reviewer's concerns regarding the potential for delamination and the impact of continuous electrothermal stimulation with the use of PNIPAM hydrogel in our device. The inherent reversible contraction and relaxation properties of PNIPAM hydrogel, activated by electrothermal triggers, are indeed central to our device's operational design. + +<|ref|>text<|/ref|><|det|>[[114, 311, 882, 612]]<|/det|> +In our study, we utilize a bilayer structure for our soft robotic designs, where bending motion is primarily driven by the anisotropic response to the temperature change. As shown in Fig. S2B, our bilayer system mainly consists of two layers: an electronic skin (e- skin) layer and a thermal- responsive PNIPAM hydrogel artificial muscle layer. The PNIPAM undergoes volume and phase transitions in response to temperature changes. Conversely, the e- skin layer serves as a static, non- responsive layer that does not undergo deformation, thereby providing a constraint to the expansive or contractive movements of the PNIPAM layer. Upon surpassing PNIPAM's lower critical solution temperature (LCST), typically within the range of 32- 34 °C, a threshold easily reached by body natural temperature (~37 °C), the device exhibits a bending motion towards the hydrogel layer, achieving a sustained shape deformation under these conditions.18- 20 This dynamic is facilitated by the distinct material properties of both layers, allowing for significant shape transformation while maintaining the device's overall flexibility. Therefore, the device design ensures tissue integration through the mechanical architecture that promotes conformal contact with tissues for sensing, communication, or control systems. + +<|ref|>text<|/ref|><|det|>[[115, 619, 882, 788]]<|/det|> +We can incorporate an integrated thermal feedback system that precisely regulates the device's heating to further address concerns of delamination, especially in scenarios where body temperature significantly diverges from the LCST (32- 34 °C). Fig. R10A shows our adaptively controlled robotic gripper, engineered to autonomously maintain the required actuation temperature under varying environmental conditions. The system is configured to activate the heater to preserve the actuation temperature whenever external temperatures fall below the LCST. Fig. R11 details the synchronization of current and temperature during thermal adjustments, highlighting our device's capability to rapidly respond to temperature variations and maintain stability thereafter. + +<|ref|>text<|/ref|><|det|>[[115, 796, 882, 889]]<|/det|> +Regarding the concern of continuous electrothermal stimulation, we can carefully control the duration and intensity of the stimulation to remain within safe limits. We have conducted both in vivo and in vitro evaluations to confirm the device's safety. In vitro analysis involving fibroblast- like cells (3T3- J- 2) subjected to a 39°C environment for 48 hours showed no compromise in cell health or viability (Fig. 6E- F). Similarly, in vivo + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 88, 883, 240]]<|/det|> +application involving thermal stimulation around the mice's heart revealed no significant tissue damage or inflammatory response (Fig. S45). While our studies have primarily explored the effect of a few hours of continuous heating, both theoretical and empirical evidence suggest that as long as the temperature is maintained below the critical threshold of \(43^{\circ}C\) based on previous studies \(^{13,14}\) , a risk of thermal damage to tissues can be effectively avoided. As aforementioned, the integration of a thermal feedback mechanism further ensures precise heating control, thereby preventing any risk of overheating or insufficient heating (Fig. R10&11). + +<|ref|>text<|/ref|><|det|>[[115, 247, 883, 322]]<|/det|> +In the revised manuscript, we have provided an enhanced clarification on the operational principles of our device, emphasizing its safety and reliability profile. We hope to offer a clearer understanding of the mechanisms underlying our device's functionality, and the applicability in biomedical application through engineering solutions. + +<|ref|>sub_title<|/ref|><|det|>[[116, 330, 409, 349]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 356, 883, 526]]<|/det|> +(1) On page 10, in the revised manuscript, we modified, "We further evaluated the mechanical force generated by the soft robotic finger which incorporates a PNIPAM hydrogel layer roughly 1 mm thick, under various input powers. Fig. S19B shows that the static force exhibits a noticeable increase with rising temperature. At a temperature of 40 °C, the force reaches a maximum of 32 mN. Additionally, it is observed that the generated force remains consistent throughout 40 cycles of alternating power on and off (0.35 W), indicating the robust reversibility of the soft robot (Fig. S19C). When compared to similar hydrogel-based soft actuators, our design consistently achieves a relatively high output force, as shown in Table S1." + +<|ref|>text<|/ref|><|det|>[[114, 533, 883, 647]]<|/det|> +(2) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +<|ref|>text<|/ref|><|det|>[[114, 653, 865, 674]]<|/det|> +(3) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. + +<|ref|>text<|/ref|><|det|>[[114, 680, 866, 700]]<|/det|> +(4) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. + +<|ref|>text<|/ref|><|det|>[[114, 707, 672, 725]]<|/det|> +(5) On page 5, in the revised supporting information, we added," + +<|ref|>sub_title<|/ref|><|det|>[[114, 732, 883, 770]]<|/det|> +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[114, 778, 883, 870]]<|/det|> +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 881, 127]]<|/det|> +responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +<|ref|>text<|/ref|><|det|>[[114, 130, 882, 623]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<|ref|>text<|/ref|><|det|>[[115, 630, 882, 894]]<|/det|> +(6) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 127]]<|/det|> +provide precise thermal management, enhancing both efficacy and safety in its applications." + +<|ref|>text<|/ref|><|det|>[[115, 134, 590, 153]]<|/det|> +(7) On page 29, in the revised manuscript, we added, " + +<|ref|>sub_title<|/ref|><|det|>[[115, 161, 685, 180]]<|/det|> +## The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 187, 883, 319]]<|/det|> +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +<|ref|>sub_title<|/ref|><|det|>[[115, 326, 217, 344]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 351, 883, 405]]<|/det|> +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +<|ref|>text<|/ref|><|det|>[[115, 411, 882, 465]]<|/det|> +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +<|ref|>text<|/ref|><|det|>[[115, 479, 882, 516]]<|/det|> +Comment 23: On Page 24, Figure 6F, what is the indication T1 and T2 in Figure 6F account for? The authors need to explain these in the captions. + +<|ref|>text<|/ref|><|det|>[[114, 523, 883, 673]]<|/det|> +Our response: We thank the reviewer's questions regarding the indications of T1 and T2 in Fig. 6F (Fig. 6G in the updated manuscript). T1 and T2 represent two distinct channels, each linked to a thermal sensor positioned on separate arms of our cardiac gripper, as illustrated in Fig. 6A and Fig. S41A&B. These sensors are designed to simultaneously capture the heart's temperature, facilitating a detailed assessment of temperature fluctuation across different segments of the organ. The multi- channel design exemplifies our device's capability for precise and localized temperature monitoring that is essential for a range of biomedical applications. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[140, 88, 847, 320]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 332, 883, 403]]<|/det|> +
Fig. R26. (A) schematic illustration of the soft robotic thera-gripper consisting of two temperature sensors made of thermal resistors. (B) Temperature measurements from the thera-gripper's dual-channel sensors during its deployment onto the mouse heart, demonstrating the device's capability to monitor thermal variations in real-time.
+ +<|ref|>sub_title<|/ref|><|det|>[[115, 410, 410, 428]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 435, 772, 455]]<|/det|> +(1) On page 24, in the revised manuscript, we added Fig. R26B as Fig. 6G. + +<|ref|>text<|/ref|><|det|>[[114, 461, 883, 536]]<|/det|> +(2) On page 25, in the revised manuscript (Fig. 6G's caption), we modified, "Temperature measurements from the thera-gripper's dual-channel sensors during its deployment onto the mouse heart, demonstrating the device's capability to monitor thermal variations in real-time." + +<|ref|>text<|/ref|><|det|>[[114, 551, 883, 589]]<|/det|> +Comment 24: In Fig 6G, it is challenging to consider it as functioning like a pacemaker, as pacing does not seem to lead to actual cardiac capture. + +<|ref|>text<|/ref|><|det|>[[114, 596, 883, 766]]<|/det|> +Our response: We thank the reviewer's concern regarding the pacing functionality described for our cardiac gripper. We agree that our gripper's electrical stimulation electrodes do not function in the traditional sense of a pacemaker. As correctly pointed out, our device introduces a general concept of an electrical stimulator module (Fig. R27A), designed to cater to a broader spectrum of potential therapeutic applications that can benefit from electrical stimulation (E-stim) (e.g., enhancing myocardial contractility), beyond the specific function of pacing \(^{21,22}\) . Our in vivo studies have demonstrated that the gripper's ability to successfully deliver various E-stim patterns (Fig. R27B-D), showing its potential in therapeutic settings. + +<|ref|>text<|/ref|><|det|>[[115, 774, 883, 848]]<|/det|> +To address this point and clarify our intention, we have revised the descriptions within our manuscript and adjusted the annotations in the figures (Fig. R27B) accordingly. This modification aims to explore the versatility of our soft robotic gripper in delivering targeted electrical stimulation for various therapeutic scenarios. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[216, 92, 783, 491]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 500, 883, 570]]<|/det|> +
Fig. R27. (A) Flexible pacing electrodes implantation. (B) The surface ECG trace during electrical stimulation using a pair of Au pacing electrodes. (C&D) Representative voltage traces of the cardiac electrical activity during E-stim with various parameters. (C) 500 mV voltage with 1 ms width at 6.5 Hz. (D) 500 mV voltage with 5 s width at 0.1 Hz.
+ +<|ref|>sub_title<|/ref|><|det|>[[116, 578, 410, 596]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[114, 603, 772, 624]]<|/det|> +(1) On page 24, in the revised manuscript, we added Fig. R27B as Fig. 6H. + +<|ref|>text<|/ref|><|det|>[[114, 629, 883, 743]]<|/det|> +(2) On pages 22-23, in the revised manuscript, we modified, ". The e-skin layer consists of microelectrodes for capturing electrical activity of the heart, which serves as essential guidance in operating electrical stimulation (Fig. S47). Fig. S48&S49 showcase the simultaneous sensing and stimulation capabilities on a beating heart with an in vivo mouse model, demonstrating its capability in a broad spectrum of potential therapeutic applications." + +<|ref|>text<|/ref|><|det|>[[114, 750, 883, 788]]<|/det|> +(3) In both the revised manuscript and supporting information. We have replaced "pacing" with "electrical stimulating" to describe the functionality of our device more accurately. + +<|ref|>sub_title<|/ref|><|det|>[[115, 796, 218, 814]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[111, 821, 884, 901]]<|/det|> +Monteiro, L. M., Vasques- Nóvoa, F., Ferreira, L., Pinto- Do- ó, P. & Nascimento, D. S. Restoring heart function and electrical integrity: Closing the circuit. npj Regen. Med. 2, 1- 13 (2017).Cao, H., Kang, B. J., Lee, C. A., Shung, K. K. & Hsiai, T. K. Electrical and Mechanical Strategies to Enable Cardiac Repair and Regeneration. IEEE Rev. Biomed. Eng. 8, 114- 124 (2015). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 164]]<|/det|> +Comment 25: In Figs 6 M, N, it was mentioned that changes were observed in S2 and S4. However, it seems that only changes in frequency are visible along the x- axis. Shouldn't the focus be on the resistance changes along the y- axis, which may represent actual strain changes? + +<|ref|>text<|/ref|><|det|>[[115, 172, 882, 285]]<|/det|> +Our response: We appreciate the reviewer's concern regarding the data presented in Fig. 6M and Fig. 6N. These figures are intended to illustrate the contractility patterns of the heart's chambers under both normal and myocardial infarction (MI) conditions, as detected by our strategically positioned strain sensors on the epicardial surfaces (Fig. 6A and Fig. S41A&B). The output from these sensors, closely related to the strain they experience, provides the mechanical behaviors of specific heart chambers. + +<|ref|>text<|/ref|><|det|>[[115, 291, 882, 460]]<|/det|> +Notably, the sensor S4, located on the left ventricle (LV), exhibits the largest amplitude of strain changes. This indicates the LV's exceptional myocardium strength, aligning with the physiological role of the LV in bearing the greatest burdens in circulating blood throughout the body's systemic circulation. Additionally, Fig. 6I offers a visual representation of the infarction area two weeks post- MI surgery, complementing the quantitative data provided by strain sensors. The decreased strain changes detected by sensors S2 (RV) and S4(LV) illustrate the impact of MI, characterized by a loss of contractile myocardium, a decrease in the force of myocardial contractility, and an altered heart rate. + +<|ref|>image<|/ref|><|det|>[[120, 470, 880, 680]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 686, 882, 722]]<|/det|> +
Fig. R28. (A&B) Representative measurements of local cardiac contractions before (A) and after myocardial infarction (B) using a soft robotic thera-gripper wrapping onto a living mouse heart.
+ +<|ref|>text<|/ref|><|det|>[[115, 729, 882, 823]]<|/det|> +We have revised the figures to feature the resistance changes more prominently along the y- axis, ensuring a balanced emphasis on both the strain measurements and the associated frequency changes, offering a comprehensive view of our device's capability to monitor and diagnose cardiac conditions through advanced sensor integration, and demonstrating the potential of custom- engineered solutions in cardiac health. + +<|ref|>sub_title<|/ref|><|det|>[[116, 831, 410, 849]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 856, 882, 893]]<|/det|> +On page 24, in the revised manuscript, we updated Fig. R28A&B as Fig. 6M&N, respectively. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 882, 164]]<|/det|> +Comment 26: The paper lacks details on the system used to generate water flow simulating blood flow in the vascular system, including names of the equipment and the setting of flow rate. Information on the properties and thickness of the rubber used is also insufficient. + +<|ref|>text<|/ref|><|det|>[[114, 172, 883, 359]]<|/det|> +Our response: We appreciate the reviewer's concern regarding the details on our experimental setup for simulating blood flow in our study. As shown in Fig. R29, to mimic the arterial environment, we employed a silicone tube (Transparent Silicone Tube 4mm ID x 5mm OD, wall thickness \(\sim 0.5mm\) ) with large stretchability and flexibility as an arterial artery. The pulsatile water flow (30\~260 ml/min) is generated with two flow rate controllable pumps. Pump 1 maintains a constant flow rate to establish a baseline pressure, while Pump 2, connected to a solenoid valve, is regulated by a relay. This valve opens and closes periodically, replicating the pulsatile pressure of blood flow. The relay is further controlled with a pre- programmed microcontroller. All the parts for the setup were purchased from local vendors. + +<|ref|>image<|/ref|><|det|>[[113, 385, 888, 635]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 650, 530, 668]]<|/det|> +
Fig. R29. In vitro setup for artificial artery model.
+ +<|ref|>text<|/ref|><|det|>[[115, 675, 883, 712]]<|/det|> +We have included the detailed information regarding the experiment setup in the revised manuscript and supporting information. + +<|ref|>sub_title<|/ref|><|det|>[[115, 720, 410, 738]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 745, 870, 765]]<|/det|> +(1) On page 47, in the revised supporting information, we added Fig. R29 as Fig. 36B. + +<|ref|>text<|/ref|><|det|>[[114, 771, 883, 904]]<|/det|> +(2) On page 31, in the revised manuscript, we added, "Measurement of biomimetic blood pressure: As shown in Fig. S36B, to mimic the arterial environment, we employed a silicone tube (Transparent Silicone Tube 4mm ID x 5mm OD, wall thickness \(\sim 0.5mm\) ) with large stretchability and flexibility as an arterial artery. The pulsatile water flow (30\~260 ml/min) is generated with two flow rate controllable pumps. Pump 1 maintains a constant flow rate to establish a baseline pressure, while Pump 2, connected to a solenoid valve, is regulated by a relay. This valve opens and closes periodically, replicating the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 127]]<|/det|> +pulsatile pressure of blood flow. The relay is further controlled with a pre- programmed microcontroller. All the parts for the setup were purchased from local vendors." + +<|ref|>text<|/ref|><|det|>[[115, 141, 882, 199]]<|/det|> +Comment 27: This work validated through H&E staining data that a single- day stimulation has a minimal impact on the tissue. However, it remains unclear what effects may occur with continued stimulation over longer period. + +<|ref|>text<|/ref|><|det|>[[115, 206, 883, 319]]<|/det|> +Our response: We appreciate the reviewer's concern regarding the long- term effects of continuous thermal stimulation. As previously discussed in Comments 12, 14, and 22, our device is engineered to operate around the body's natural temperature, significantly reducing the reliance on constant thermal input. Moreover, we can design the device with an advanced thermal feedback mechanism that precisely regulates temperature, thus mitigating risks associated with overheating or insufficient heating (Fig. R10&11). + +<|ref|>text<|/ref|><|det|>[[115, 325, 883, 420]]<|/det|> +Furthermore, the existing literature supports that controlled thermal stimulation within safe limits typically does not lead to adverse effects even thermal input over extended periods. \(^{13,14}\) We have further explained the immediate scope of our current research phase. We focus on establishing a solid foundation for the device's safety and functionality before extending our investigation into long- term usage scenarios. + +<|ref|>sub_title<|/ref|><|det|>[[116, 428, 410, 446]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 453, 883, 567]]<|/det|> +(1) On page 22, in the revised manuscript, we added, "The design employed PNIPAM hydrogel with a LCST 34 °C that is closely aligned with natural body temperature to achieve necessary shape deformation. The initial heating serves primarily to accelerate the actuation, but after achieving the desired state, continuous electrical heating becomes unnecessary. This feature allows the device to effectively adapt and function within the physiological temperature range without the need for ongoing thermal input." + +<|ref|>text<|/ref|><|det|>[[115, 573, 866, 594]]<|/det|> +(2) On page 36, in the revised supporting information, we added Fig. R10 as Fig. S25. + +<|ref|>text<|/ref|><|det|>[[115, 600, 866, 620]]<|/det|> +(3) On page 37, in the revised supporting information, we added Fig. R11 as Fig. S26. + +<|ref|>text<|/ref|><|det|>[[115, 627, 673, 646]]<|/det|> +(4) On page 5, in the revised supporting information, we added," + +<|ref|>sub_title<|/ref|><|det|>[[115, 653, 882, 691]]<|/det|> +## Supplementary Note S3: The sensory-motor integration within the soft robotic system + +<|ref|>text<|/ref|><|det|>[[115, 698, 883, 830]]<|/det|> +The integrated design that leverages on the synergistic interplay between sensors and soft robotic actuators enables volatile adaptivity and responsiveness of the robotic implant in ever- changing conditions. This design allows sensory inputs to directly influence actuator outputs in real- time, creating a feedback loop that allows for automatic adjustment based on environmental stimuli. This feature underscores our system's responsiveness and adaptability, allowing with the principles of sensor- actuator integration. + +<|ref|>text<|/ref|><|det|>[[115, 837, 882, 894]]<|/det|> +As an example, we present an adaptively controlled responsive robotic gripper that maintains optimal actuation temperatures responsive to external temperature changes. The responsive self- adaptation in different thermal environments ensures optimal and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 883, 522]]<|/det|> +predictable heating patterns regardless of conditions, as well as increasing patient safety and preventing potential burn hazard caused by overheating. Fig. S25A shows an integrative system that provides temperature sensory readout and, through feedback- controlled power delivery, allows actuation responsive to external thermal environment. Fig. S25B demonstrates the working principles of controlling hardware and software. The resistive temperature sensor was connected in series with a reference resistor. The voltage drops over the sensor is read and converted by the on- chip ADC and is processed by the microcontroller to convert to a temperature value. Upon receipt of the temperature value, the control algorithm compares it with the target temperature to produce an error value. The error value is multiplied with a predefined coefficient to produce a corrective factor and is added to the current output value to generate a new output value. The on- chip pulse- width modulation (PWM) module converts the output value to a PWM voltage signal, which is then amplified by the on- board power MOSFET, forming a controller current source to produce a current through the heater. When the external temperature changes, a large corrective factor is produced to allow rapid adaptations. When the target temperature was reached, a constant current is produced to maintain the optimal temperature. Fig. S26 showed the time- synchronized current and temperature plot during different responsive phases after a sudden change in temperature. During the underheating phase, a rapid increase in output current was generated by the controlled current source in response to the sudden change in temperature. When the target temperature was first reached, the current output remains constant until the actuator was overheated, during which the current output drops again to reach the static phase at which the current levels off." + +<|ref|>text<|/ref|><|det|>[[114, 528, 883, 829]]<|/det|> +(5) On page 12, in the revised manuscript, we added, "Furthermore, our soft robotic system exemplifies advanced sensory-motor integration, leveraging the synergistic relationship between embedded sensors and actuators to achieve dynamic adaptivity and responsiveness to environmental changes. A prime example is a temperature-sensitive control system, as shown in Fig. S25A, which utilizes real-time sensory feedback to dynamically adjust heating in response to environmental temperature changes. The operational principle, as detailed in Fig. S25B and Supplementary Note S3, involves a microcontroller-driven algorithm that interprets temperature input collected by a resistive temperature sensor, and modulates the electric heater's current accordingly, enabling rapid adaptations to achieve and maintain a preset temperature. Fig. S26 presents a soft robotic finger's real-time response to temperature variations, ensuring stable shape adaptation through this regulatory mechanism. Moreover, this intelligent control significantly improves safety by preventing the risk of overheating, thereby ensuring the system's safe operation in various thermal conditions, highlighting our device's ability to provide precise thermal management, enhancing both efficacy and safety in its applications." + +<|ref|>text<|/ref|><|det|>[[115, 836, 592, 855]]<|/det|> +(6) On page 29, in the revised manuscript, we added, " + +<|ref|>text<|/ref|><|det|>[[115, 863, 685, 882]]<|/det|> +The sensory-motor integration within the soft robotic system + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 220]]<|/det|> +The robotic gripper and the external circuitry were connected in series with an NI DMM amperometer set for DC current measurement. The device was cooled to \(22^{\circ}C\) in ambient temperature before the system was started up to capture its response to a sudden decrease in ambient temperature. The temperature readouts recorded by the device's integrated sensor were logged via a microcontroller unit (MCU) and cross- referenced with data from FLIR thermal camera. Both the current and temperature data were analyzed using custom Python script designed specifically for this purpose." + +<|ref|>sub_title<|/ref|><|det|>[[115, 228, 217, 245]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 253, 883, 307]]<|/det|> +G.C. van Rhoon, T. Samaras, P.S. Yarmolenko, M.W. Dewhirst, E. Neufeld, N. Kuster, CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?, Eur. Radiol. 23 (2013) 2215- 2227. https://doi.org/10.1007/s00330- 013- 2825- y. + +<|ref|>text<|/ref|><|det|>[[115, 313, 882, 366]]<|/det|> +M.W. Dewhirst, B.L. Viglianti, M. Lora- Michiels, P.J. Hoopes, M. Hanson, THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS., Proc. SPIE- - the Int. Soc. Opt. Eng. 4954 (2003) 37. https://doi.org/10.1117/12.476637. + +<|ref|>text<|/ref|><|det|>[[115, 379, 882, 474]]<|/det|> +Comment 28: The 2- week histological analysis of cardiac tissue with a hydrogel- based thera- gripper, as presented in the study, raises questions. It would be insightful to know the condition of the device after this period - whether the device remained in an operable state and the device remained properly attached as intended while withstanding repeated pulsations. + +<|ref|>text<|/ref|><|det|>[[115, 482, 882, 556]]<|/det|> +Our response: We appreciate the reviewer's concern regarding the long- term stability and functionality of the hydrogel- based gripper after a 2- week period. After this time, we carefully examined the device and found it to be intact and effectively attached to the cardiac tissue as intended, as shown in Fig. R30A. + +<|ref|>text<|/ref|><|det|>[[115, 563, 882, 696]]<|/det|> +We also conducted further evaluation focused on the device's performance post- implantation. As shown in Fig. R30B- D, the pacing electrodes and thermal sensor maintained exemplary performance, indicating their capability to deliver electrical stimulation and accurately sense temperature changes after two weeks. These results suggest that our hydrogel- based thera- gripper not only maintains its structural and functional integrity over an extended period but also holds promise for long- term applications in cardiac therapy and monitoring. + +<|ref|>text<|/ref|><|det|>[[115, 704, 882, 741]]<|/det|> +We have updated our manuscript and supporting information to include these insights and highlight the device's robustness and reliability for potential long- term use. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[170, 87, 828, 488]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 519, 883, 675]]<|/det|> +
Fig. 30. Overview of device performance after two-week implantation. (A) Visualization of the device accurately positioned on the mouse heart, indicating its stability post two-week implantation. (B&C) Voltage response traces from the pacing electrodes embedded in the implanted device, demonstrating its operational integrity over the two-week period. Here, (B) shows a sine wave configuration at a frequency of \(1 \mathrm{~Hz}\) and amplitude of \(1 \mathrm{~V}\) , while (C) depicts pulse modulation with a height of \(500 \mathrm{mV}\) , pulse with of \(0.01 \mathrm{~s}\) , and a maximum repeating rate of \(1 \mathrm{~Hz}\) . (D) Comparative analysis of the resistive response from the thermal sensor before and after the two-week implantation period, illustrating the device's consistent performance and sensor integrity over time.
+ +<|ref|>sub_title<|/ref|><|det|>[[115, 682, 409, 700]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 708, 866, 728]]<|/det|> +(1) On page 64, in the revised supporting information, we added Fig. R30 as Fig. S52. + +<|ref|>text<|/ref|><|det|>[[114, 734, 883, 866]]<|/det|> +(2) On page 24, in the revised manuscript, we added, "Our post-implantation evaluation revealed that the hydrogel-based thera-gripper remained intact and securely attached to cardiac tissue as intended, demonstrating its durability and effectiveness over time (Fig. S52A). Notably, the E-stim electrodes and thermal sensor maintained optimal performance, effectively delivering electrical stimulation (Fig. S52B&C) and precisely sensing temperature fluctuations (Fig. S52D) even after a two-week period. These results support its feasibility for long-term therapeutic and diagnostic applications." + +<|ref|>text<|/ref|><|det|>[[115, 881, 704, 901]]<|/det|> +Comment 29: Caption in figure S11 (a) : AgNW/PI -> AgNW/PDMS + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 883, 145]]<|/det|> +Our response: We thank the reviewer's attention to detail and have corrected the caption in Fig. S11(a) (Fig. S10A in the updated supporting information) from AgNW/PI to AgNW/PDMS as suggested. + +<|ref|>sub_title<|/ref|><|det|>[[115, 153, 410, 171]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 180, 883, 199]]<|/det|> +On page 20, in the revised manuscript, we have corrected "AgNW/PI" to "AgNW/PDMS". + +<|ref|>text<|/ref|><|det|>[[115, 213, 883, 232]]<|/det|> +Comment 30: Page 21, the third line from the bottom spelling error : PINPAM -> PNIPAM + +<|ref|>text<|/ref|><|det|>[[115, 240, 883, 277]]<|/det|> +Our response: We thank the reviewer's attention to detail and have corrected the spelling error. + +<|ref|>sub_title<|/ref|><|det|>[[115, 285, 410, 303]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 310, 833, 329]]<|/det|> +On page 22, in the revised manuscript, we have corrected "PINPAM" to "PNIPAM". + +<|ref|>text<|/ref|><|det|>[[115, 344, 702, 363]]<|/det|> +Comment 31: Figure S51D, indication spelling error : Basi -> Basic + +<|ref|>text<|/ref|><|det|>[[115, 371, 883, 408]]<|/det|> +Our response: We thank the reviewer's attention to detail and have corrected the spelling error. + +<|ref|>sub_title<|/ref|><|det|>[[115, 416, 410, 435]]<|/det|> +## Modification to the manuscript: + +<|ref|>text<|/ref|><|det|>[[115, 443, 770, 461]]<|/det|> +On page 48, in the revised manuscript, we have corrected "Basi" to "Basic". + +<|ref|>text<|/ref|><|det|>[[115, 476, 806, 496]]<|/det|> +Comment 32: There should be a space before the units in the text and figures. + +<|ref|>text<|/ref|><|det|>[[115, 504, 625, 522]]<|/det|> +Our response: We thank the reviewer's attention to detail. + +<|ref|>text<|/ref|><|det|>[[115, 530, 883, 567]]<|/det|> +Modification to the manuscript: We have checked and revised all units in the updated manuscript and supporting information. + +<|ref|>sub_title<|/ref|><|det|>[[115, 583, 218, 600]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[112, 608, 866, 893]]<|/det|> +1. Basarir, F., Madani, Z. & Vapaavuori, J. Recent Advances in Silver Nanowire Based Flexible Capacitive Pressure Sensors: From Structure, Fabrication to Emerging Applications. Adv. Mater. Interfaces 9, (2022). +2. Chauhan, N., Maekawa, T. & Kumar, D. N. S. Graphene based biosensors - Accelerating medical diagnostics to new-dimensions. J. Mater. Res. 32, 2860–2882 (2017). +3. Amara, U., Hussain, I., Ahmad, M., Mahmood, K. & Zhang, K. 2D MXene-Based Biosensing: A Review. Small 19, 1–38 (2023). +4. Driscoll, N. et al. MXene-infused bioelectronic interfaces for multiscale electrophysiology and stimulation. Sci. Transl. Med. 13, eabf8629 (2021). +5. Liu, H. et al. 3D Printed Flexible Strain Sensors: From Printing to Devices and Signals. Adv. Mater. 33, 2004782 (2021). +6. Zhu, Z., Park, H. S. & McAlpine, M. C. 3D printed deformable sensors. Sci. Adv. 6, eaba5575 (2023). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[110, 88, 884, 900]]<|/det|> +7. Reeder, J. et al. Mechanically Adaptive Organic Transistors for Implantable Electronics. Adv. Mater. 26, 4967-4973 (2014).8. Xu, J. & Song, J. Thermal Responsive Shape Memory Polymers for Biomedical Applications. in (ed. Fazel-Rezai, R.) Ch. 6 (IntechOpen, 2011). doi:10.5772/19256.9. Czerner, M., Fellay, L. S., Suárez, M. P., Frontini, P. M. & Fasce, L. A. Determination of Elastic Modulus of Gelatin Gels by Indentation Experiments. Procedia Mater. Sci. 8, 287-296 (2015).10. Xie, C., Wang, X., He, H., Ding, Y. & Lu, X. Mussel-Inspired Hydrogels for Self-Adhesive Bioelectronics. Adv. Funct. Mater. 30, 1909954 (2020).11. Shian, S., Bertoldi, K. & Clarke, D. R. Dielectric Elastomer Based 'grippers' for Soft Robotics. Adv. Mater. 27, 6814-6819 (2015).12. Shojaefard, M., Niroumandi, S. & Baghani, M. Programming shape-shifting of flat bilayers composed of tough hydrogels under transient swelling. Acta Mech. 233, 213-232 (2022).13. Dewhirst, M. W., Viglianti, B. L., Lora-Michiels, M., Hoopes, P. J. & Hanson, M. THERMAL DOSE REQUIREMENT FOR TISSUE EFFECT: EXPERIMENTAL AND CLINICAL FINDINGS. Proc. SPIE--the Int. Soc. Opt. Eng. 4954, 37 (2003).14. van Rhoon, G. C. et al. CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels? Eur. Radiol. 23, 2215-2227 (2013).15. Jiang, Y. et al. Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing. Nat. Biotechnol. 41, 652-662 (2023).16. Grill, W. M. Electrical stimulation for control of bladder function. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 2009 2369-2370 (2009) doi:10.1109/IEMBS.2009.5335001.17. Coolen, R. L., Groen, J. & Blok, B. F. M. Electrical stimulation in the treatment of bladder dysfunction: Technology update. Med. Devices Evid. Res. 12, 337-345 (2019).18. Lanzalaco, S., Mingot, J., Torras, J., Alemán, C. & Armelin, E. Recent Advances in Poly(N-isopropylacrylamide) Hydrogels and Derivatives as Promising Materials for Biomedical and Engineering Emerging Applications. Adv. Eng. Mater. 25, 2201303 (2023).19. Liu, J., Jiang, L., He, S., Zhang, J. & Shao, W. Recent progress in PNIPAM-based multi-responsive actuators: A mini-review. Chem. Eng. J. 433, 133496 (2022).20. Ansari, M. J. et al. Poly(N-isopropylacrylamide)-Based Hydrogels for Biomedical Applications: A Review of the State-of-the-Art. Gels (Basel, Switzerland) 8, (2022).21. Monteiro, L. M., Vasques-Nóvoa, F., Ferreira, L., Pinto-Do-ó, P. & Nascimento, D. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[163, 88, 868, 125]]<|/det|> +S. Restoring heart function and electrical integrity: Closing the circuit. npj Regen. Med. 2, 1–13 (2017). + +<|ref|>text<|/ref|><|det|>[[115, 130, 852, 186]]<|/det|> +22. Cao, H., Kang, B. J., Lee, C. A., Shung, K. K. & Hsiai, T. K. Electrical and Mechanical Strategies to Enable Cardiac Repair and Regeneration. IEEE Rev. Biomed. Eng. 8, 114–124 (2015). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 330, 98]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 111, 415, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 139, 870, 167]]<|/det|> +I believe that the revisions address the points that were raised in the original review. The paper is now suitable to be accepted in nature communications. + +<|ref|>text<|/ref|><|det|>[[119, 196, 415, 210]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 223, 875, 252]]<|/det|> +I thank the authors for fully and thoroughly revising the manuscript. I believe their manuscript has improved significantly, and I have no further comments. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[313, 103, 676, 123]]<|/det|> +## Responses to comments of Referee #1 + +<|ref|>text<|/ref|><|det|>[[113, 180, 881, 218]]<|/det|> +Summary Comment: I believe that the revisions address the points that were raised in the original review. The paper is now suitable to be accepted in nature communications. + +<|ref|>text<|/ref|><|det|>[[113, 233, 680, 252]]<|/det|> +Our response: We thank the reviewer for the positive comment. + +<|ref|>sub_title<|/ref|><|det|>[[315, 400, 680, 420]]<|/det|> +## Responses to comments of Referee #2 + +<|ref|>text<|/ref|><|det|>[[113, 480, 881, 518]]<|/det|> +Summary Comment: I thank the authors for fully and thoroughly revising the manuscript. I believe their manuscript has improved significantly, and I have no further comments. + +<|ref|>text<|/ref|><|det|>[[113, 533, 680, 552]]<|/det|> +Our response: We thank the reviewer for the positive comment. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[118, 85, 505, 102]]<|/det|> +## Description of Additional Supplementary Files + +<|ref|>text<|/ref|><|det|>[[118, 137, 618, 171]]<|/det|> +File name: Supplementary movie 1Description: Soft robot with a nature- inspired starfish design + +<|ref|>text<|/ref|><|det|>[[118, 190, 748, 223]]<|/det|> +File name: Supplementary movie 2Description: Shape transformation of soft robots with various configurations + +<|ref|>text<|/ref|><|det|>[[118, 242, 752, 275]]<|/det|> +File name: Supplementary movie 3Description: Soft robot with a helical structure biomimicking a chiral seedpod + +<|ref|>text<|/ref|><|det|>[[118, 294, 600, 327]]<|/det|> +File name: Supplementary movie 4Description: The shape transformation of a soft robotic pill + +<|ref|>text<|/ref|><|det|>[[118, 346, 737, 397]]<|/det|> +File name: Supplementary movie 5Description: A three- arm soft robotic gripper via sequentially programming input power + +<|ref|>text<|/ref|><|det|>[[118, 416, 750, 467]]<|/det|> +File name: Supplementary movie 6Description: A four- arm soft robotic gripper via simultaneously programming input power + +<--- Page Split ---> diff --git a/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..e3832e6d9d8d5a05a87bd68dd04aeda20dbc5f87 --- /dev/null +++ b/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,176 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figures", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Response figure 2: Sx1a-mEos2 sptPALM data from Wallis et. al. 3 clustered and temporally quantified by SEMORE.", + "footnote": [], + "bbox": [ + [ + 149, + 280, + 848, + 660 + ] + ], + "page_idx": 27 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Response Figure 4 Evaluation of SEMORE on temporarily resolved live-cell PALM data of ryanodine receptors (RyRs).", + "footnote": [], + "bbox": [ + [ + 150, + 81, + 844, + 365 + ] + ], + "page_idx": 28 + }, + { + "type": "image", + "img_path": "images/Figure_4.jpg", + "caption": "Response Figure 4: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies.", + "footnote": [], + "bbox": [ + [ + 150, + 85, + 840, + 425 + ] + ], + "page_idx": 29 + }, + { + "type": "image", + "img_path": "images/Figure_5.jpg", + "caption": "Response figure 5: SEMORE classification performance for small, sparse clusters of diverse morphologies.", + "footnote": [], + "bbox": [ + [ + 150, + 80, + 840, + 677 + ] + ], + "page_idx": 30 + }, + { + "type": "image", + "img_path": "images/Figure_6.jpg", + "caption": "Response Figure 6: Deconvolution of temporal refinement on real and simulated data.", + "footnote": [], + "bbox": [ + [ + 150, + 95, + 833, + 592 + ] + ], + "page_idx": 31 + }, + { + "type": "image", + "img_path": "images/Figure_8.jpg", + "caption": "Response Figure 8: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters.", + "footnote": [], + "bbox": [], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_9.jpg", + "caption": "Response Figure 9: Benchmarking SEMORE on for heterogeneous, non-uniform noise.", + "footnote": [], + "bbox": [ + [ + 146, + 82, + 847, + 472 + ] + ], + "page_idx": 34 + }, + { + "type": "image", + "img_path": "images/Figure_10.jpg", + "caption": "Response Figure 10: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes.", + "footnote": [], + "bbox": [ + [ + 152, + 98, + 848, + 345 + ] + ], + "page_idx": 35 + }, + { + "type": "image", + "img_path": "images/Figure_11.jpg", + "caption": "Response Figure 11: Demonstration SEMORE clustering of morphology shrinkage", + "footnote": [], + "bbox": [ + [ + 152, + 608, + 848, + 789 + ] + ], + "page_idx": 36 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Supplementary Fig. x: SEMORE's Morphological Fingerprint captures gradual transitions in morphology. Thirty aggregates of each morphology class (fibril-like: fib, isotropic: iso, sterically-hindered/random: rand) of equal size were simulated resulting in ninety distinct structures which are placed sequentially in random order whilst ensuring no consecutive types. Between each of the ninety structures (89 transitions) 100 positions are constructed from interpolation (see methods). Thus, a total of 8900 intermediates gradually changing morphology between the three structures were evaluated using the fingerprinting module of SEMORE. All resulting transitions are connected", + "footnote": [], + "bbox": [ + [ + 105, + 378, + 866, + 800 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_17.jpg", + "caption": "Supplementary Fig. 17 (UPDATED): dSTORM data from Nieves et. al1 clustered and quantified by SEMORE a Raw detections from SMLM data of fibroblast growth receptor 1 (FGFR1) on a MCF7 cell presented by Nieves et al.1 b Initial clustering by SEMORE's clustering module using the inherent data-driven model choice of HDBSCAN (Min_cluster_size = 15 and Min_sample = 5). Each localization is colored by its SEMORE annotation, with black representing noise and all other colors representing captured clusters. c The final clustering by SEMORE after refinement and smart density filtering (see Methods). Localizations are colored corresponding to the final SEMORE prediction. Red box depicts the same zoom-in as seen in Nieves et al inside which they report 2 unique clustering indices similar to the initial clustering seen in b. SEMORE's additiona refinement split one of these into four distinct clustered indexes, thus resulting in five clusters. Keeping these settings constant through the 15 datasets from Nieves et al. d Histogram of cluster area estimation. SEMORE identifies mean cluster area of \\(0.004 \\pm 0.003 \\mu m^2\\) and median of \\(0.003 \\mu m^2\\). SEMORE provides more fine-grained area calculation than convex hull (see supplementary figure 20) and may split larger clusters to smaller during rounds of refinement. e Distribution of points contained in the proposed clusters with a mean of \\(52 \\pm 108\\) and a median of 29. SEMORE and Nieves et al. obtain qualitative similar results and have 88% agreement in assigning points as noise showing the general agreement as methods", + "footnote": [], + "bbox": [ + [ + 108, + 73, + 870, + 478 + ] + ], + "page_idx": 37 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_3.jpg", + "caption": "Supplementary Fig 3: Benchmarking SEMORE on for heterogeneous, non-uniform noise.", + "footnote": [], + "bbox": [], + "page_idx": 43 + } +] \ No newline at end of file diff --git a/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..18061506d0a0cc10eb2ca085a9c5d02c6e995944 --- /dev/null +++ b/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,1038 @@ + +# nature portfolio + +Peer Review File + +SEMORE: SEGmentation and MORphological fingErprinting by machine learning automates super- resolution data analysis + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +## Reviewers' comments: + +## Reviewer #1 (Remarks to the Author) + +Bender et al., present a machine learning based clustering and classification algorithm, SEMORE, for the segmentation of diverse cluster morphologies from heterogenous SMLM data. Being able to identify and segment clusters in heterogenous data is a key problem in SMLM, so the algorithm is a well- placed idea for addressing this. The algorithm is initially demonstrated on simulated data, consisting of 3 biologically relevant clustering scenarios; symmetric clusters, asymmetric clusters (non- equal growth) and fibre- like structures. The algorithm is then demonstrated on real experimental SMLM data, namely insulin aggregation and nuclear pore complex data. In the case of the insulin aggregation, with challenges in segmentation were overcome using temporal information. The paper addresses two important problems with clustering of SMLM data in general; the need for user inputs to define the segmentation, and post- analysis classification of segmented clusters to understand biological phenomena of protein distributions and assembly. + +The manuscript is well presented and easy to follow. Furthermore, the SEMORE software is easy to find with clear installation instructions. However, I found it slightly challenging to get running in a new environment (admittedly I have a basic working knowledge of python, but see below comment). Additionally, the data from the publication was all provided, and easy to look through, which should be highly commended. There are a couple of conceptual and practical points, however, that I think need addressing, which would strengthen the manuscript. + +I would recommend publication of the manuscript if the comments below can be addressed. + +Major comments: + +- The clusters within the simulated data seem to be very large in scale, some on the order of 10 microns. This is likely to be an uncommon scenario in biological SMLM data, especially when it comes to clustering of that data. I would recommend some simulations on the scale of the NPC data, i.e., several clusters sub-micron with diverse morphology. A recent paper cited in the manuscript proposed several different clustering scenarios at this scale (Nieves et al., NatMeth, 20, pages 259-267, 2023) where two different cluster types are present within the region. This would be really nice to see clusters of similar density (in that paper it was approximately 10-20 per 3x3 micron2), but analysed in a similar fashion here, i.e., analysis of the whole 40x40 micron region. This would be quite powerful if whole fields of view could be analysed quickly, without the need for subdivision of the data (see later point on performance). + +- It would be interesting to know a little more about the limits of SEMORE, as in biological SMLM data there may be several different classes of cluster, which may have stronger similarities, within the same ROI. For example, if a protein is present as a monomer and can assembles into higher order oligomers, it might be expected there are some low-level oligomers (4 proteins clustered proteins at sub-diffraction, e.g., tetramers) in the data at time of fixation. Would these small clusters be distinguishable from the noise class? Some examples of how SEMORE deals with this low-level oligomerisation (low-density clusters) would strengthen the manuscript. + +- Following on from this point, one thing lacking from the manuscript is any comment on a common problem for arguably the two most common SMLM techniques (PALM, and dSTORM - used here); multiple blinking of the fluorophore. Normally, this introduces artefactual clustering into the SMLM data, and several approaches now exist for correcting this (e.g., Jensen et al., NatMeth, 19, pages 594-602, 2022, and Bohrer et al., NatMeth, 18, pages 669-677, 2021). Thus, is relation to biological data, some structures that may appear clustered, and then segmented in uncorrected data, will not be so after correction, shifting the observed distributions of the classes. Would the authors recommend such corrections before use of SEMORE for accurate fingerprinting? Also, some sense of how the lack of blink correction could impact classification would be beneficial. This could be done by comparing a ground truth of the molecule positions and a version where the data has added blinking. + +Minor comments: + +- All figures showing SMLM data or plots of clusters etc. need a scale bar or some axes. It was hard to appreciate, until using the code, how different the length scale of the clusters between simulations and experimental data were (some several microns, whilst NPC data is much smaller scale) + +<--- Page Split ---> + +- I ran the SEMORE installation as directed on the GitHub, generating a new environment. I found quickly that I was missing the dependencies needed to run the scripts (e.g., opencv in the dependency file should be opencv-python, I assume this is why this file may not have worked for me). Further, other more basic packages are of course not there in a new environment, e.g., pandas, numpy, etc., and require the user to add them. I would recommend the authors give a full and correct dependencies file, as this troubleshooting would be beyond many of the potential users with limited coding experience. + +## Reviewer #2 (Remarks to the Author) + +Bender et al. present SEMORE, SEGmentation and MORphological fingErprinting, as a semiautomatic machine learning framework for the analysis of super- resolution data to extract and quantify protein structures. By implementing a multi- layered density- based clustering module and a morphology fingerprinting module for quantification, they demonstrated SEMORE on simulations and experimental super- resolution data, including insulin aggregates and nuclear pore complexes. Developing automatic clustering analysis without a priori knowledge and tracking the temporal evolution of morphology changes of protein clustering from single- molecule localization microscopy image data is certainly a good direction for the development of super- resolution microscopy field. However, in my view, their demonstrations are limited to the analysis of the growth of immobile clusters under well- controlled noise conditions, which could be quite different from general biological behaviors. This raises concerns about the limited applicability of this method. Additionally, although the authors insist that their method represents the first time- aware framework for 4D super- resolution data, they mainly focus on presenting the classification results for protein cluster growth, without showing identified cluster images at each time point. Therefore, it is hard to judge whether their method can effectively capture the temporal changes of protein clusters. To claim that their method is genuinely powerful for automatic clustering analysis and tracking the temporal evolution of protein clusters, they should also show the time- resolved clustering data. + +Furthermore, I cannot see the significant novelty of this method; they mainly used the reported clustering method (DBSCAN) for cluster identification. Although it appears that they additionally conducted temporal refinement after the DBSCAN analysis, this additional step seems to be mainly for dissecting clusters over time, rather than advancing the clustering analysis method. The new development of their method seems to be a morphology fingerprinting module that uses multiple feature vectors for quantification. However, the performance of this method for real experimental time- resolved super- resolution image data was demonstrated only for the relatively new imaging method REPLOM, which is not a general type of data. To demonstrate the general performance of this method, the authors should present more general time- resolved single- molecule localization microscopy data, rather than static dSTORM data. Although the authors applied their method to NPC data, it appears to be just static data, and the categorization of the clusters is not biologically meaningful (individual, overlapped, noise). For these reasons, I believe the authors' claims are not well supported, which unfortunately does not warrant publication in Nature Communications in the current form of the manuscript. + +1. As suggested above, the main problem with the current manuscript is the lack of time-resolved analyzed data. They only showed the classification results from simulation data for isotropic, random, and fibril growth. However, the time-resolved cluster morphological change data (at each time point) should also be presented to assess whether their method correctly identified each growth pattern. Additionally, I would like to see the time-scaled morphological changes of insulin aggregates and nuclear pore complexes from experimental data to evaluate whether their method performs well even with real data under heterogeneous noise conditions. + +2. The demonstrated data seems to only focus on the growth of clustering. However, changes in protein clusters in the real world could involve not only cluster growth but also significant morphological changes (e.g., spherical to tubular), shrinkage, movement, and scattering (depolymerization). For wider applicability of this method, the authors should include related data as well. + +<--- Page Split ---> + +3. Their demonstration is mostly based on simulation data, where the noise appears to be well controlled and homogeneous. Although they tested this method under different noise density conditions, it seems that the density they used is uniformly distributed across the entire field of view and throughout the entire time domain, which could differ from real conditions. Additionally, the intensity of noise could be heterogeneous. Because such heterogeneity of noise could affect the identification and classification of protein clusters, they should test the method with various types of noise. + +4. The authors claim that the use of a machine learning-based method is an important aspect of this study. However, the machine learning method employed in this paper appears to be limited to unsupervised point clustering, rather than classification or other methods. Moreover, these unsupervised point clustering methods used here do not seem to differ significantly in terms of methodology from the existing method, DBSCAN. I believe the authors have not sufficiently explained why the method they used can be considered a machine learning approach and what sets it apart as a novel contribution compared to existing methods. + +5. In the Fingerprinting module, it is mentioned that over 40 features were utilized to analyze the properties of each cluster using various methods. However, it appears that a comprehensive assessment of the strengths and weaknesses of these methods was not conducted. It is unclear why the given methods are expected to yield good features for cluster classification. Additionally, it would be beneficial to determine if all the provided methods are necessary based on the analysis results. For instance, Supplementary Figure 8 suggests that it might be possible to identify a better method instead of using all the feature vectors obtained from each feature. There is a possibility that some of them could even interfere with the analysis process, so it would be insightful to see further results in this regard. + +6. In general, the methodology is not thoroughly explained. For instance, even if the method applied in the existing DBSCAN is used as is, it would be helpful if the methodology were described in more detail. Additionally, the methodology for the classification of each point, which occurs after the fingerprinting module and embedding with UMAP, is not elaborated very well. Since the fingerprinting module appears to be the only distinctive novelty of this method, as mentioned above, it should be described in detail to provide a clearer understanding. + +## Reviewer #3 (Remarks to the Author) + +The manuscript entitled "SEMORE: SEGmentation and MORphological fingErprinting by machine learning automates super-resolution data analysis" by Hatzakis et al introduces SEMORE, a semi-automatic machine learning framework for universal, system and input-dependent, analysis of super-resolution data. The manuscript is well written and informative. However, this manuscript can be improved by addressing the following issues: + +1. The authors have developed a new analytical tool SEMORE to extract and quantify underlying structures limiting single-molecule localization microscopy (SMLM). How this newly developed tool SEMORE is better suited with SMLM than some of the previous employed tools such as SMAP (modular super-resolution microscopy analysis) + +2. The authors should explain how SEMORE deals with commonly occurring supervised and unsupervised machine learning problems. + +3. The authors should also highlight the role of SEMORE in advancement of machine learning-based approaches. + +4. Since vibrational and spherical aberrations prove to be greater hindrance at high resolution. Moreover, live samples are more adversely affected by super-resolution imaging because of high excitation intensity or extended exposure times. Does the SEMORE tool take these concerns into consideration? + +<--- Page Split ---> + +## Reviewers response + +Reviewer 1 2 + +General response 2 Comment 1.1 2 Comment 1.2 4 Comment 1.3 5 Minor comments: 6 + +Reviewer 2 6 + +General response 7 Comment 2.1 9 Comment 2.2 12 Comment 2.3 14 Comment 2.4 14 Comment 2.5 17 Comment 2.6 18 + +Reviewer 3 19 + +General response 19 Comment 3.1 20 Comment 3.2 20 Comment 3.3 22 Comment 3.4 23 + +Figures 25 + +Response Figure 1: dSTORM data from Nieves et. al. 1 clustered and quantified by SEMORE 25 + +Response figure 2: Sx1a- mEos2 sptPALM data from Wallis et. al. 3 clustered and temporally quantified by SEMORE. 26 + +Response Figure 4 Evaluation of SEMORE on temporarily resolved live- cell PALM data of ryanodine receptors (RyRs). 27 + +Response Figure 4: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies. 28 + +Response figure 5: SEMORE classification performance for small, sparse clusters of diverse morphologies. 29 + +Response Figure 6: Deconvolution of temporal refinement on real and simulated data. 31 + +Response Figure 7: Visual representation of SEMORE's ability to capture morphological growth in time 32 + +Response Figure 8: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters. 33 + +Response Figure 9: Benchmarking SEMORE on for heterogeneous, non- uniform noise. 34 + +Response Figure 10: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes. 35 + +Response Figure 11: Demonstration SEMORE clustering of morphology shrinkage 35 + +<--- Page Split ---> + +## Reviewer 1 + +Bender et al., present a machine learning based clustering and classification algorithm, SEMORE, for the segmentation of diverse cluster morphologies from heterogenous SMLM data. Being able to identify and segment clusters in heterogenous data is a key problem in SMLM, so the algorithm is a well- placed idea for addressing this. The algorithm is initially demonstrated on simulated data, consisting of 3 biologically relevant clustering scenarios; symmetric clusters, asymmetric clusters (non- equal growth) and fibre- like structures. The algorithm is then demonstrated on real experimental SMLM data, namely insulin aggregation and nuclear pore complex data. In the case of the insulin aggregation, with challenges in segmentation were overcome using temporal information. The paper addresses two important problems with clustering of SMLM data in general; the need for user inputs to define the segmentation, and post- analysis classification of segmented clusters to understand biological phenomena of protein distributions and assembly. + +The manuscript is well presented and easy to follow. Furthermore, the SEMORE software is easy to find with clear installation instructions. However, I found it slightly challenging to get running in a new environment (admittedly I have a basic working knowledge of python, but see below comment). Additionally, the data from the publication was all provided, and easy to look through, which should be highly commended. There are a couple of conceptual and practical points, however, that I think need addressing, which would strengthen the manuscript. + +I would recommend publication of the manuscript if the comments below can be addressed. + +## General response + +We are grateful for the favorable and critical comments, for acknowledging the manuscript easy to follow and for recommending publication after the comments are addressed. Fully and in detail addressing the "conceptual and practical" comments helped us further improve the manuscript and the quality and user- friendliness of our open- source implementation on Github. Figures created following your and other reviewers comments have been pasted below for your convenience. + +## Comment 1.1 + +- The clusters within the simulated data seem to be very large in scale, some on the order of 10 microns. This is likely to be an uncommon scenario in biological SMLM data, especially when it comes to clustering of that data. I would recommend some simulations on the scale of the NPC data, i.e., several clusters sub-micron with diverse morphology. A recent paper cited in the manuscript proposed several different clustering scenarios at this scale (Nieves et al., NatMeth, 20, pages 259–267, 2023) where two different cluster types are present within the region. This would be really nice to see clusters of similar density (in that paper it was approximately 10-20 per 3x3 micron2), but analysed in a similar fashion here, i.e., analysis of the whole 40x40 micron region. This would be quite powerful if whole fields of view could be analysed quickly, without the need for subdivision of the data (see later point on performance). + +<--- Page Split ---> + +## Response 1.1 + +The reviewer correctly points out that large aggregates are generally depicted in the manuscripts. We stress here that SEMORE clustering module is scale- invariant and solely relies on localisations. This is due to our choice of 3D axis standardization. Working with standardized dimensions enables SEMORE to work across experimental configurations and dimensionalities. This allows SEMORE to operate independently of the imaging dimension and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area. The comment still raises a very valuable point on the generalization and performance of SEMORE and to demonstrate this and fully answer the comment of the reviewer we performed two studies: + +1) Simulated diverse, nanometer dimension structures, and quantified SEMORE performance on their segmentation and classification for data with 8, 15 and 25 localisations in an area that corresponds to \(\sim 1\mu m\) . As can be seen in Supplementary Fig. 8 (Response figure 5) in the revised version, SEMORE reached an accuracy of \(>90\%\) in extracting clusters with 8 or more localisations with the morphology fingerprinting completely separating true clusters from noise. + +2) Simulated protein assemblies of just 4 detections and evaluated SEMORE's performance on such a small cluster representing the minimal representation of a tetramer. SEMORE achieves accuracies of up to \(70 - 90\%\) in segmenting these tiny structures depending on the noise levels while the morphological fingerprinting module captures these noisy detections allowing for potential post-processing and accuracy increase, Supplementary Fig. 7 (Response figure 4). + +3) Evaluated the number of points needed for SEMORE to accurately detect the initiation points of spatially overlapping clusters. The high accuracy of SEMORE to capture initiation points can be quantified and visualized using simulated data showing is just \(\sim 13\) frames off on average across 3 types of spatially overlapping morphologies. Furthermore, qualitative assessment using experimental data of temporally resolved insulin aggregation supports the reliability of SEMORE, Supplementary Fig. \(5 + 6\) , response figure \(6 + 7\) . + +In essence, \(\sim 10\) detections is enough for SEMORE to obtain high segmentation and classification accuracy which is well below the common number of detections in most SMLM experiments. We analyze dSTORM data of Nieves et al. NatMeth, 20, pages 259- 267, 2023 \(^{1}\) obtaining similar densities and cluster sizes but in fact analyzing the entire field of view at once see new SI fig 17 (response figure 1). We further use the approach from Nieves et al., NatMeth, 20, pages 259- 267 to simulate structures with blinking, see comment 1.3. + +## Changes in the manuscript 1.1 + +To fully address the comment of the reviewer in the revised version of the manuscript we have added a new section within "Accurate extraction of individual assemblies across diverse biologically inspired growth types.": + +"To further evaluate the performance of SEMORE on segmentation and analysis of dynamic SMLM data we performed a series of stress tests on simulated data. We firstly evaluated SEMORE's ability to track morphological changes in time using simulated data of 3 types of spatially overlapping protein clustering morphologies with temporal information included. Snapshots of SEMORE's clustering in time provide visual confirmation of SEMORE's ability to track morphological changes in time (see Supplementary Fig. 5 for snapshots of simulated and Supplementary Fig. 6 for experimental data). Further quantification of SEMORE's + +<--- Page Split ---> + +ability to accurately track and segment spatially overlapping protein assemblies in time reveals growth onset times across 3 morphological classes are predicted with an average offset of just \(\sim 13\) frames (Supplementary Fig. 6). Subsequently, we test the clustering module on simulated, sparse structures containing as little as 4, 8, 15 and 25 point detections akin to data of protein oligomerization (see Supplementary Fig. 7 & 8). SEMORE analyzes the entire field of view at once and extracts structures down to 4 detections while maintaining \(>90\%\) accuracy at biologically relevant noise to signal ratios. The morphological fingerprinting module can further refine the false positive detections from noise with as little as 4 detections, achieve full separation from noise at 8 detections and classify morphological classes in true structures at 15 detections (see Supplementary Fig. 8 & 9). Lastly we evaluated its performance to degenerate structures that shrink in time, akin to protein depolymerisation. SEMORE accurately segments 3 anisotropically degenerative morphologies showcasing it can be used to analyze dynamic shrinkage or depolymerisation of protein clusters (see Supplementary Fig. 10). In essence SEMORE only requires \(< 10\) detections to accurately segment and classify heterogeneous structures with dynamic morphologies further demonstrating its operational utility and potential for 4D SMLM." + +Elaborated in results on the scale invariance: + +" The clustering module of SEMORE consists of multiple steps that self- parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools." In addition, to address the comment we have added 5 new SI figures, namely Response figures: 1,4,5, 6, and 7. + +## Comment 1.2 + +- It would be interesting to know a little more about the limits of SEMORE, as in biological SMLM data there may be several different classes of cluster, which may have stronger similarities, within the same ROI. For example, if a protein is present as a monomer and can assembles into higher order oligomers, it might be expected there are some low-level oligomers (4 proteins clustered proteins at sub-diffraction, e.g., tetramers) in the data at time of fixation. Would these small clusters be distinguishable from the noise class? Some examples of how SEMORE deals with this low-level oligomerisation (low-density clusters) would strengthen the manuscript. + +## Response 1.2 + +This is indeed a valid comment and we thank the reviewer(s) for allowing us to address this in detail. As we detailed in response to your comment 1.1 in the revised manuscript SI fig 7 (response figure 4) we detail how SEMORE performs for low-level oligomers at sub- diffraction limit. The data demonstrate that SEMORE captures early stages of protein cluster initiation, even at diverse noise conditions. We also demonstrated how it dissects heterogeneous morphologies. + +## Changes in the manuscript 1.2 + +Please see changes as per comment 1.1 as we grouped our response and changes to this comment. In short, a new section on SEMORE's performance on small sparse clusters showcases the potential use of SEMORE on tetramers or early stages of clustering. + +<--- Page Split ---> + +## Comment 1.3 + +Comment 1.3- Following on from this point, one thing lacking from the manuscript is any comment on a common problem for arguably the two most common SMLM techniques (PALM, and dSTORM - used here); multiple blinking of the fluorophore. Normally, this introduces artefactual clustering into the SMLM data, and several approaches now exist for correcting this (e.g., Jensen et al., NatMeth, 19, pages 594- 602, 2022, and Bohrer et al., NatMeth, 18, pages 669- 677, 2021). Thus, is relation to biological data, some structures that may appear clustered, and then segmented in uncorrected data, will not be so after correction, shifting the observed distributions of the classes. Would the authors recommend such corrections before use of SEMORE for accurate fingerprinting? Also, some sense of how the lack of blink correction could impact classification would be beneficial. This could be done by comparing a ground truth of the molecule positions and a version where the data has added blinking. + +## Response 1.3 + +Response 1.3This comment on blinking is indeed very valuable. To answer and quantify SEMORE on data with and without blinking we rely on the approach Nieves et al., NatMeth, 20, pages 259- 267. SI figure (Supplementary Fig. 9, response Fig. 10) shows SEMORE's performance on data with and without simulated blinking. The results show SEMORE achieves extraction accuracies above \(90\%\) and produces morphological fingerprints that reliably differentiates morphological classes from just 15 detections regardless of blinking. While we would recommend end- users to correct for blinking prior to using SEMORE, SEMORE performs well regardless of blinking and simply requires a small number of detections as seen in the response and in response \(1.1 + 1.2\) . + +## Changes in the manuscript 1.3 + +The revised manuscript now includes a SI figure (Supplementary Fig. 9, response Fig. 10) showing performance with blinking and a discussion on blinking and our recommendation. We highlight the small effect of blinking on morphological fingerprinting in the section: + +## "Morphological fingerprinting captures defining features separating heterogeneous assemblies." : + +"Blinking is a common challenge in SMLM, especially for PALM and dSTORM, and may lead to artificial clustering and misinterpretation of protein assembly morphology. We map the effect of blinking on the morphological fingerprinting module using data with and without simulated blinking (see Methods). SEMORE remains largely unaffected by blinking achieving segmentation accuracies above \(90\%\) and reliably differentiates morphological classes from just 15 detections regardless of blinking (see supplementary Fig. 9). In addition to blinking, protein assemblies can exhibit biological behavior involving significant morphological changes (e.g., spherical to tubular), or as discussed in the evaluation of the clustering module above, depolymerization. To this end, we evaluated SEMORE's ability to track the temporal evolution of morphology between diverse morphologies, i.e. from fibril-like to spherical to asymmetric. SEMORE clearly tracks morphologies in time and transitions while outputting the most distinguishing features of each morphology offering important mechanistic insights (supplementary Fig. 15)." + +In addition, we include in the discussion our recommendation for blinking or other aberration: + +"SEMORE is currently optimized for laterally stable assemblies, albeit the temporal refinement does handle lateral movement below the agnostic, data- derived search range defined per assembly basis (see Methods). Future versions are planned to include our diffusional analysis framework for motion aware clustering analysis. Blinking has insignificant effect on SEMORE analysis, however we recommend common aberrations such as + +<--- Page Split ---> + +blinking and vibrational or spherical aberrations to be corrected prior to use of SEMORE to avoid any potential misinterpretation of the data." + +## Minor comments: + +- All figures showing SMLM data or plots of clusters etc. need a scale bar or some axes. It was hard to appreciate, until using the code, how different the length scale of the clusters between simulations and experimental data were (some several microns, whilst NPC data is much smaller scale) + +Thank you for noticing the missing element. We note that as we highlighted in response to comment 1.1 SEMORE is purposefully designed to be dimension independent therefore the simulated data are without a scale bar. We do, based on your comment 1.1 elaborate on the scale-invariance in the main text. Furthermore figures with experimental data have been rectified in the revised version to include a scale bar as seen in main figure 4 making the size difference between insulin aggregates and NPC easier to appreciate. + +- I ran the SEMORE installation as directed on the GitHub, generating a new environment. I found quickly that I was missing the dependencies needed to run the scripts (e.g., opencv in the dependency file should be opencv-python, I assume this is why this file may not have worked for me). Further, other more basic packages are of course not there in a new environment, e.g., pandas, numpy, etc., and require the user to add them. I would recommend the authors give a full and correct dependencies file, as this troubleshooting would be beyond many of the potential users with limited coding experience. We have now provided the packages as a dependency.yml to be installed with: + +git clone https://github.com/hatzakislab/SEMORE cd SEMORE conda env create - f dependency.yml conda activate SEMORE + +and extended the documentation on the GitHub page. We appreciate the test of the github structure which now should be in order but we also include contact information and are happy to assist future users. + +## Additional minor changes + +minor spelling and phrasing mistakes were rectified. minor addition to account for the fact that we have 5 experimental data sets instead of 2 in the original submission, as well 6 additional ground truth simulated data sets. addition of a few extra refs to account for reviews comments. + +## Reviewer 2 + +Bender et al. present SEMORE, SEGmentation and MORphological fingErprinting, as a semi- automatic machine learning framework for the analysis of super- resolution data to extract and quantify protein structures. By implementing a multi- layered density- based clustering module and a morphology fingerprinting module for quantification, they demonstrated SEMORE on simulations and experimental super- resolution data, including + +<--- Page Split ---> + +insulin aggregates and nuclear pore complexes. Developing automatic clustering analysis without a priori knowledge and tracking the temporal evolution of morphology changes of protein clustering from single- molecule localization microscopy image data is certainly a good direction for the development of super- resolution microscopy field. However, in my view, their demonstrations are limited to the analysis of the growth of immobile clusters under well- controlled noise conditions, which could be quite different from general biological behaviors. This raises concerns about the limited applicability of this method. Additionally, although the authors insist that their method represents the first time- aware framework for 4D super- resolution data, they mainly focus on presenting the classification results for protein cluster growth, without showing identified cluster images at each time point. Therefore, it is hard to judge whether their method can effectively capture the temporal changes of protein clusters. To claim that their method is genuinely powerful for automatic clustering analysis and tracking the temporal evolution of protein clusters, they should also show the time- resolved clustering data. + +Furthermore, I cannot see the significant novelty of this method; they mainly used the reported clustering method (DBSCAN) for cluster identification. Although it appears that they additionally conducted temporal refinement after the DBSCAN analysis, this additional step seems to be mainly for dissecting clusters over time, rather than advancing the clustering analysis method. The new development of their method seems to be a morphology fingerprinting module that uses multiple feature vectors for quantification. However, the performance of this method for real experimental time- resolved super- resolution image data was demonstrated only for the relatively new imaging method REPLOM, which is not a general type of data. To demonstrate the general performance of this method, the authors should present more general time- resolved single- molecule localization microscopy data, rather than static dSTORM data. Although the authors applied their method to NPC data, it appears to be just static data, and the categorization of the clusters is not biologically meaningful (individual, overlapped, noise). For these reasons, I believe the authors' claims are not well supported, which unfortunately does not warrant publication in Nature Communications in the current form of the manuscript. + +## General response + +We thank the reviewer for critically reading the manuscript, acknowledging that the approach we are using is certainly a good direction for the further development of the super- resolution microscopy field and providing valuable feedback. We have addressed all your comments explicitly, and in full detail by: + +a) Demonstrating SEMORE's performance on two additional experimental time-resolved super-resolution data based on sptPALM and live-cell PALM. Results show in both cases that SEMORE successfully clusters detections, captures temporal morphology changes, quantification of clusters by fingerprinting offering potential new insights. SEMORE is validated by comparison to results of the original work on these data sets; Wallis et al \(^{3}\) and Hou et al \(^{4}\) .b) Demonstrated SEMORE on additional experimental dSTORM data containing consecutive frames. Results show SEMORE obtaining comparable results in + +<--- Page Split ---> + +clustering as Nieves et al1 while temporal refinement and smart density filter to enable the additional pruning of false positives. + +c) Performing additional multiple noise variation: Simulating additional heterogeneous noise conditions with varying densities and displaying the capacity of SEMORE to accurately segment and classify them. Thus, the revised version now contains 2 independent experimental data sources with biological noise along with simulations containing homogeneous and heterogeneous noise. New noise types was also supported by additional experimental data as per a and b + +d) Displaying snapshots of SEMORE's segmentation at multiple time points during the assembly process for experimental data and simulated data. Followed by an evaluation of the number of detections needed to accurately detect the initiation point of protein assemblies. + +e) Displaying SEMORE's ability to accurately capture morphological variations as they evolve in time. Followed by an evaluation of the number of detections required to classify morphological classes. + +f) Detailing how SEMORE significantly advances the field: Explained in detail the multiple components incorporated in SEMORE prior and on top of DBSCAN, making DBSCAN a small part of one of the two modules of SEMORE. Compared SEMORE to the state of the art (DBSCAN) and detailed how the clustering module (segmentation) along with the fingerprinting module (quantification and classification) of SEMORE can propel the field of super-resolution. We stress here that we already had in the original submission a comparison of SEMORE to DBSCAN clearly demonstrating the superiority of SEMORE along with the increased accuracy following our developed smart noise filter. + +However, we respectfully disagree that REPLOM "... is not a general type of data" REPLOM represents one of SMLM approaches enabling temporally resolved observation of protein aggregation. While indeed the implementation is novel and different to more common approaches the actual data type is very similar, if not identical. REPLOM is based on TIRF microscopy to observe isolated PSFs to accurately fit subpixel localizations in essence outputting a set of xy and t, coordinates. + +The wealth of extra analysis and additional data, which fully and further support our claims, helped us improve the technical quality of the manuscript, benchmark it against state of art, and elaborate on the novelty and applicability of the method to extract mechanistic insights across a spectrum of diverse systems. + +We do hope the following point- by- point response and revised manuscript rectify all comments and convince the reviewer to join the other 2 reviewers in accepting the manuscript for publication. Figures created following your and other reviewers comments have been pasted below for your convenience. + +<--- Page Split ---> + +## Comment 2.1 + +Comment 2.11. As suggested above, the main problem with the current manuscript is the lack of time- resolved analyzed data. They only showed the classification results from simulation data for isotropic, random, and fibril growth. However, the time- resolved cluster morphological change data (at each time point) should also be presented to assess whether their method correctly identified each growth pattern. Additionally, I would like to see the time- scaled morphological changes of insulin aggregates and nuclear pore complexes from experimental data to evaluate whether their method performs well even with real data under heterogeneous noise conditions. + +## Response 2.1 + +This is a great set of questions and we thank you for giving us the chance to fully and in detail address them. In the revised version we now provide: + +a) 3 additional experimental data of 1) dynamic dSTORM 2) sptPALM and 3) live-cell PALM data sets and multiple additional simulations producing 11 additional SI figures. In all cases SEMORE precisely analyses and classifies the dynamic data sets showcasing it can be used as a universal tool (Supplementary Fig. 17 & 18 & 19, response figures 1 & 2 & 3). + +b) Snapshots of the experimental data of temporally resolved insulin aggregation displaying the temporarily resolved morphology readouts and the classification at different time points of the clustering by SEMORE and display SEMORE's prediction of the cluster initiation points (Supplementary Fig. 6, response Fig. 5). We stress that while in the original submission we displayed only one of the frames of the temporally resolved simulations or experimental data sets, the temporal refinement was existing and a key element of SEMORE and therefore underlie all figures. We thank the reviewer for noticing the insufficient explanation + +c) Additional simulation of temporarily resolved clustering data containing 3 types of growth morphologies. This type of simulation was already included in the original submission but not adequately discussed in the context of morphology detection early in the clustering process and in time. The data in the revised Supplementary Fig. 5, (response Fig. 7) show how SEMORE captures the temporal evolution of the 3 morphologies in time. + +d) Simulated dynamic morphology variation of a cluster in time by having a cluster sequentially express diverse morphologies, Supplementary Fig. 15, (response Fig. 8). The protein cluster is shown to drastically change morphology from fibril-like structures to asymmetric structures and also to spherical structures, each structure consisting of 200 data points. The temporal morphology changes were analyzed by the fingerprinting module of SEMORE and the extracted features embedded in the 2-component map resulted in a clear separation of the diverse morphologies. Thus, the new Supplementary Fig. 15, (response Fig. 8) shows how SEMORE accurately captures diverse morphologies in time. To further demonstrate the potential of SEMORE we subjected the fingerprints to a MinMax normalization and plotted them in a heatmap. As expected the morphological fingerprint not only accurately classifies the diverse temporally separated morphological growths, but outputs the geometric features that drive this classification offering further mechanistic insights. In addition, + +<--- Page Split ---> + +response \(1.1 + 1.2\) shows only 15 detections are needed for this accurate classification of morphology. + +e) Single frame of the entire clustering process for 3 diverse morphologies occurring in parallel and in a single field of view Supplementary Fig. 6, (response Fig. 6). SEMORE predicts the growth onset times with an average offset of just \(\sim 13\) frames thus accurately predicting the clustering initiation point for all three morphology classes despite them being highly heterogeneous and spatially overlapping. Panel d in new SI Supplementary Fig. 6, (response Fig. 6) displays the time from growth start to SEMORE initiation prediction highlighting that not only SEMORE predicts cluster morphology but also the initiation point accurately. + +The reviewer also asked for time- scaled morphological changes of nuclear pore complexes, albeit such data may have been produced we do not know of its existence and have not been able to locate it. The NPC data serves to demonstrate the use of SEMORE on static data and in an independent experimental setting. We addressed the comment on the classification of time- resolved morphological variations on experimental and simulated data by the a- c) above. + +To address the comment of the reviewer on the heterogeneous noise we provide new simulation on diverse noise conditions. In the original manuscript SI fig. 2, (still SI fig 2) we had a noise stress test by varying the noise- to- event ratio by more than an order of magnitude (45 fold). We now extended the stress test to apply, and account for, nonuniformly distributed noise. We simulated an additional 5- 25 noise seeds each containing 20- 50 points and also applied Gaussian distributed shifts to all initial noise points further reducing the uniformity (See new Supplementary Fig. 3, (response Fig. 9)). We are happy to report that the classification accuracy of SEMORE remains practically unaffected and more than \(85\%\) for all biological relevant noise levels. + +The response to 1.1 and 1.2 further emphasizes the ability of SEMORE to capture small sparse structures which extends to show how SEMORE performs in early stages of oligomerization. + +## Changes in the manuscript 2.1 + +To fully address the comment of the reviewer we: + +1. Introduced 7 new Supplementary figures that fully and detail address the comment of the reviewer but also include comments of the other two reviewers. +2. Added three new SI figures (SI fig. \(17 + 18 + 19\) , response figures \(1 + 2 + 3\) ) showcasing SEMORE on additional experimental data along with comments in the revised version of the manuscript: + +"we further demonstrated SEMORE's ability to utilize the temporal dimension in experimental data using three additional published data sets: Firstly, dSTORM data of fibroblast growth receptor 1 1, where SEMORE utilizes the data's reported frames for temporal refinement together with smart density filtering to accurately extract protein clusters, prune false positive detections and provide cluster size estimation (Supplementary Fig. 17). Secondly, super-resolved dynamic data syntaxin 1a spatial clustering by sptPALM 3, where SEMORE accurately captures clusters, their morphological evolution in time (Supplementary Fig. 18). Thirdly, super-resolved live-cell PALM data of ryanodine receptors (RyRs) 4. SEMORE accurately captures RyR clusters with a granularity infeasible by current methods such as DBSCAN alone (Supplementary Fig. 19). The fact that SEMORE operates across dynamic experimental + +<--- Page Split ---> + +SMLM data outputting clusters and their properties in agreement with published analysis, further highlights its potential as a robust universal tool for 4D cellular biology. " + +3. Inserted and elaborated the section "Precise extraction and quantification of experimental super-resolution data." in the main text describing SEMORE's ability to perform accurate extraction of protein assemblies in time for experimental data: "Studies of aggregating insulin using the super-resolution approach REPLOM, offering real-time recordings of the aggregation growth, revealed insulin aggregates by two distinct pathways: an isotropic pathway, generating radially grown spherical structures and an anisotropic pathway, generating more elongated asymmetric structures consistent with the presence of multiple nucleation sites. When the raw \(x, y, t\) coordinates of insulin aggregation events were fed to SEMORE, the clustering module automatically extracted 139 individual insulin aggregate structures (Fig. 4a) despite them displaying large heterogeneity in their morphology. The identified structures are largely spatially overlapping, an element that would challenge their proper separation by manual inspection or current tools. However, the implementation of the temporal element of SEMORE capturing time-dependent morphological evolution allowed their rapid and precise spatial separation, thus mitigating potential morphology misinterpretation (Fig. 4a and Sup Fig 5). Snapshots of the successful capture of insulin aggregation during its growth combined with the insulin aggregation initiation time point identification by SEMORE are displayed in supplementary fig. 6." + +In addition, to further probe SEMORE's ability to utilize the temporal dimension in experimental data SEMORE was evaluated on three additional data sets: Firstly, using dSTORM data of fibroblast growth receptor \(1^{1}\) SEMORE utilizes the data's reported frames for temporal refinement together with smart density filtering to accurately extract protein clusters, prune false positive detections and provide cluster size estimation (Supplementary Fig. 17). Secondly, utilizing super- resolved dynamic data syntaxin 1a spatial clustering by sptPALM \(^{3}\) SEMORE accurately captures clusters, their morphological evolution in time and provides potential for new insights on clusters by morphological fingerprinting (Supplementary Fig. 18). Thirdly, super- resolved live- cell PALM data of ryanodine receptors (RyRs) \(^{4}\) SEMORE accurately captures RyR clusters with a granularity infeasible by current methods such as DBSCAN alone. Lastly, SEMORE operates across dynamic experimental SMLM further highlighting its potential as a robust universal tool for 4D cellular biology. + +4. Inserted a section in the main text in "Accurate extraction of individual assemblies across diverse biologically inspired growth types." describing SEMORE's ability to perform accurate extraction of protein assemblies in time for simulated data consisting of spatially overlapping structures across 3 morphology classes: "To further evaluate the performance of SEMORE on segmentation and analysis of dynamic SMLM data we performed a series of stress tests on simulated data. We firstly evaluated SEMORE's ability to track morphological changes in time using simulated data of 3 types of spatially overlapping protein clustering morphologies with temporal information included. Snapshots of SEMORE's clustering in time provide visual confirmation of SEMORE's ability to track morphological changes in time (see Supplementary Fig. 5 for snapshots of simulated and Supplementary Fig. 6 for experimental data). Further quantification of SEMORE's ability to accurately track and segment spatially overlapping protein assemblies in time reveals growth onset times across 3 morphological classes are predicted with an average offset of just \(\sim 13\) frames (Supplementary Fig. 6)." + +5. Inserted a section in the main text within "Morphological fingerprinting captures defining features separating heterogeneous assemblies." describing SEMORE's ability to extract time-resolved morphology information for both simulated and experimental data: "In addition to blinking, protein assemblies can exhibit biological behavior involving significant morphological changes (e.g., spherical to tubular), or as discussed in the evaluation of the clustering module above, depolymerization. To this end, we evaluated SEMORE's ability to track + +<--- Page Split ---> + +the temporal evolution of morphology between diverse morphologies, i.e. from fibril- like to spherical to asymmetric. SEMORE clearly tracks morphologies in time and transitions while outputting the most distinguishing features of each morphology offering important mechanistic insights (supplementary Fig 15)." + +6. Inserted a section in the main text "Accurate extraction of individual assemblies across diverse biologically inspired growth types." on SEMORE's ability to extract protein assemblies consisting of few detections to evaluate SEMORE's ability to capture small assemblies and early stages of assemblies. "Subsequently, we test the clustering module on simulated, sparse structures containing as little as 4, 8, 15 and 25 point detections akin to data of protein oligomerization (see Supplementary Fig. 7 & 8). SEMORE analyzes the entire field of view at once and extracts structures down to 4 detections while maintaining \(>90\%\) accuracy at biologically relevant noise to signal ratios. The morphological fingerprinting module can further refine the false positive detections from noise with as little as 4 detections, achieve full separation from noise at 8 detections and classify morphological classes in true structures at 15 detections (see Supplementary Fig. 8 & 9)." + +7. We modified an existing section "Accurate extraction of individual assemblies across diverse biologically inspired growth types." discussing noise to the following "The median classification accuracy of SEMORE remained above 85% for a range of noise density levels and was practically independent of noise being homogeneous or heterogeneous (see Methods, Supplementary Fig. 2 + 3)." + +8. We modified an existing section "Precise extraction and quantification of experimental super-resolution data." discussing noise to the following + +"The summary of these results on a diverse set of experimental systems demonstrates the ability of SEMORE to generalize to completely different sets of biological systems, imaging and experimental conditions, noise types, and molecular scales without any a priori knowledge of their structure." + +9. Added in SI fig. 3 of the original submission now SI fig. 4 that data represents a single frame of a temporal simulation. + +10. Highlighted in main figures 1+3+4 in revised submission when shown data represent a single frame of a temporally resolved experiment. + +Main fig. 1 added: "... temporally resolved insulin aggregation imaged using the REPLOM \(^5\) approach on a TIRF microscope..." + +Main fig. 3 added: "Three classes of time-resolved aggregations were simulated to capture a broad aspect of biological systems (see Methods)" + +Main fig. 4 added: "Top: Final frame of accumulated super-resolution localizations from temporally resolved insulin aggregation" + +11. In Methods we have elaborated and extended the relevant sections to include these new performance evaluations. + +## Comment 2.2 + +The demonstrated data seems to only focus on the growth of clustering. However, changes in protein clusters in the real world could involve not only cluster growth but also significant morphological changes (e.g., spherical to tubular), shrinkage, movement, and scattering (depolymerization). For wider applicability of this method, the authors should include related data as well. + +## Response 2.2 + +We indeed fully agree with the reviewer that time- dependent morphological variations are an important element to study. As a matter of fact capturing temporal morphological variations + +<--- Page Split ---> + +are inherent in SEMORE and underlie accurate extracting spatially overlapping structures as highlighted in response 2.1. However, we agree this could not be fully appreciated in the original manuscript. + +We thank the reviewer for allowing us to rectify this, expanding the showcasing of SEMORE's capabilities. + +- For answering SEMORE's performance of dynamic morphological changes please see answer to this reviewer comment 2.1c, and Supplementary Fig. 15, (response Fig. 8).- Regarding the reviewer comment on lateral movement: SEMORE considers as input the set of XY(z), and t, coordinates that common SMLM software outputs. As such currently, SEMORE does not include the tracking of large lateral movement beyond what can be captured by temporal refinement, i.e. large lateral shifts (larger than the cluster dependent radius calculated per cluster, see Methods) between frames would currently be recognized as a new cluster. This is now explained in the discussion of the revised version.- Protein depolymerisation and cluster shrinkage is indeed an important element underlying biological processes and we are thankful to the reviewer for bringing this up. To evaluate how SEMORE accounts for shrinkage and depolymerisation of protein clusters we reversed the simulation of growth of diverse morphologies. In the revised Supplementary Fig. 10, (response Fig. 11) we display a simulated data set of depolymerisation as well as the clustering of these shrinking structures as they are predicted by SEMORE. The accurate clustering further supports the strength of SEMORE to also be capable of clustering shrinking protein clusters. + +## Changes in the manuscript 2.2 + +Following the reviewers comment we have strengthen the manuscript with the following: + +1) Protein depolymerisation and shrinkage: In the section "Accurate extraction of individual assemblies across diverse biologically inspired growth types." discussing the dynamic nature of SEMORE we added: "Lastly we evaluated its performance on degenerative structures that shrink in time, akin to protein de-polymerisation. SEMORE accurately segments 3 anisotropically degenerative morphologies showcasing it can be used to analyze dynamic shrinkage or depolymerisation of protein clusters (see Supplementary Fig. 10).". +2) Lateral displacement: We added in the discussion "SEMORE is currently optimized for laterally stable assemblies, albeit the temporal refinement does handle lateral movement below the agnostic, data-derived search range defined per assembly basis (see Methods). Future versions are planned to include our diffusional analysis framework for motion aware clustering analysis. Blinking has insignificant effect on SEMORE analysis, however we recommend common aberrations such as blinking and vibrational or spherical aberrations to be corrected prior to use of SEMORE to avoid any potential misinterpretation of the data." +3) Added a new Supplementary Fig. 10, (response Fig. 11) displaying how SEMORE accurate clusters protein assemblies undergoing depolymerisation for 3 diverse structures. +4) As reported in changes in the manuscript for comment 2.1 we have added in the revised version a section on SEMORE's ability to capture temporal variations in morphology. + +<--- Page Split ---> + +## Comment 2.3 + +Comment 2.3Their demonstration is mostly based on simulation data, where the noise appears to be well-controlled and homogeneous. Although they tested this method under different noise density conditions, it seems that the density they used is uniformly distributed across the entire field of view and throughout the entire time domain, which could differ from real conditions. Additionally, the intensity of noise could be heterogeneous. Because such heterogeneity of noise could affect the identification and classification of protein clusters, they should test the method with various types of noise. + +## Response 2.3 + +Response 2.3The reviewer is correct and we are thankful for bringing this to our attention. As we outlined in the response to their comment 2.1 we have now extended the stress test to apply, and account for, noise that is non- uniformly distributed in space. We simulated an additional 5- 25 noise seeds each containing 20- 50 points and also applied Gaussian distributed shifts to all initial noise points further reducing their uniformity (See new SI fig. 3, response fig. 9). We are happy to report that the classification accuracy of SEMORE remains practically unaffected and more than \(85\%\) for all biological relevant noise levels. We have also analyzed 3 additional experimental sets and we are happily reporting SEMORE accurately handles real experimental data sets with diverse and heterogeneous noise levels (see detailed answer to comment 2.1) + +## Changes in the manuscript 2.3 + +Changes in the manuscript 2.31) In the main text in the section discussing the noise simulation we added: "The median classification accuracy of SEMORE remained above \(85\%\) for a range of noise density levels and was practically independent of noise being homogeneous or heterogeneous (see Methods, Supplementary Fig. 2 + 3).". In support we added a new supplementary figure 3 displaying the benchmarking for non-uniform noise addition.2) Added analysis and results for experimental data see detailed answer to comment 2.1. + +## Comment 2.4 + +Comment 2.4The authors claim that the use of a machine learning- based method is an important aspect of this study. However, the machine learning method employed in this paper appears to be limited to unsupervised point clustering, rather than classification or other methods. Moreover, these unsupervised point clustering methods used here do not seem to differ significantly in terms of methodology from the existing method, DBSCAN. I believe the authors have not sufficiently explained why the method they used can be considered a machine learning approach and what sets it apart as a novel contribution compared to existing methods + +## Response 2.4 + +Response 2.4We respectfully, but firmly, disagree with the reviewer that the method does not differ from a DBSCAN. In fact, DBSCAN is only a small part of the multimodal part of SEMORE and we indeed had compared the operational performance of SEMORE to DBSCAN in SI fig. 3 of the original submission (now SI fig. 4). Indeed, SEMORE achieved a \(89\%\) median accuracy as compared to \(70\%\) for DBSCAN alone on simulated data, convincingly demonstrating the + +<--- Page Split ---> + +superior performance of our multimodal pipeline. For experimental data SEMORE is key to accurate analysis as DBSCAN alone can not provide the granularity required to dissect small clusters of ryanodine receptors (See new SI fig. 19, response fig. 3). An additional key example is extracting biologically correct structures and features from insulin aggregation which could otherwise lead to misinterpretation (see main figure 1 for comparison of before and after temporal refinement or SI fig. 3 of the original manuscript (now SI fig. 4). Combined these data showcase the entirety of the SEMORE clustering pipeline is required to extract spatially overlapping structures, provide granularity, filter out noisy detections as clusters that may in the case of no assemblies in the field of view produce nonsensical structures. + +Several key features sets SEMORE beyond DBSCAN and current state of that art :: + +a) Automatic, data-driven model selection between HDBSCAN and DBSCAN based on the density of localisations computed using the field of view. +b) Semi-supervised hyperparameter choices based on experimental data. +c) Topological failsafe for the case of no initial aggregation securing the clustering module does not form nonsensical clusters as DBSCAN alone might if only presented with noise, thus enhancing the clustering detection sensitivity. +d) Smart noise filtering filtering false positive detections in conjunction with our clustering greatly improves the quality of the clustering module's output. +e) Temporal refinement enables clustering of spatially overlapping structures, the dissection of initiation point of each cluster in time and following of morphology changes over time all of which are currently infeasible by DBSCAN or other available methods alone. +f) Morphological fingerprinting for quantification and ranking of interpretable geometric and kinetic descriptors, that to the best of our knowledge is introduced here by us for protein clustering, based on our earlier work on diffusional fingerprinting. + +This combination extends above and beyond any current methods and allows SEMORE to yield automatic segmentation, classification and quantitative insights on arbitrarily complicated data sets across experimental conditions of protein clustering by SMLM and the temporal evolution of morphology without a priori knowledge. + +We respectfully emphasize that a machine learning pipeline based solely on unsupervised learning is still a machine learning approach and an approach that can generalize to problems outside the training distribution. Indeed, unsupervised machine learning methodologies are routinely used in recent interdisciplinary publications6, 7, 8. Moreover, we are slightly puzzled by the comment that no classification or other machine learning approaches are present in the original manuscript: We use a) an additional DBSCAN in the UMAP embedded space (unsupervised) to classify structures in original main fig. 3 and original SI fig. 4- 6 (now SI figs. 11- 13), b) a boosted decision tree (supervised) in SI fig. 6 (now new SI fig. 13) to highlight the potential use of morphological fingerprints in a downstream model, c) a Linear Discriminant analysis (supervised) in feature importance + +<--- Page Split ---> + +ranking SI. fig. 8 (now SI fig. 16). To emphasize these important elements in the revised manuscript we elaborate on the use of the unsupervised output in supervised settings. + +## Changes in the manuscript 2.4 + +To fully address the comment of the reviewer we added a complete description of the elements that set SEMORE above and beyond the current state of the art. In the revised version, we have added: + +1) an extension to the explanation of SEMORE's clustering module in the results: "The clustering module of SEMORE consists of multiple steps that self-parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools. The pipeline initially inspects high-density areas in a standardized Euclidean 3D space, using a hyperparameter space pre-defined for this region, and provides an appropriate model choice based on a data-driven decision. The chosen density-based scanning model, either HDBSCAN or DBSCAN, extracts high-density regions of biomolecules (clusters or aggregates) from low-density regions (noise) (Fig. 1b). The initial clustering contains an added topological fail safe to prevent detection of nonsensical structures (see Methods). If a temporal dimension is available, the high-density regions are treated through our temporal refinement (Fig. 1c). Segmentation in time and temporal refinement is strictly required to dissect spatially overlapping structures within high-density areas. The clustered output is further refined by subjecting all identified assemblies to a smart density filter to eliminate falsely predicted assemblies that do not meet an agnostic, data-derived density criteria (Supplementary Fig. 1). The result is a robust clustering model outcompeting current methods and building towards the first general-purpose approach for dynamic SMLM (see Methods and Supplementary fig. 4)." + +2) The methods section of the revised manuscript have been elaborated to further highlight the key contributions of the SEMORE clustering pipeline mentioned in a-f of the response. + +3) We highlight the gain of SEMORE in accurate segmentation of spatially overlapping structures as compared to current methods on experimental data in section "Precise extraction and quantification of experimental super-resolution data.": "When the raw x, y, t coordinates of insulin aggregation events were fed to SEMORE, the clustering module automatically extracted 139 individual insulin aggregate structures (Fig. 4a) despite them displaying large heterogeneity in their morphology. The identified structures are largely spatially overlapping, an element that would challenge their proper separation by manual inspection or current tools. However, the implementation of the temporal element of SEMORE capturing time-dependent morphological evolution allowed their rapid and precise spatial separation, thus mitigating potential morphology misinterpretation (Fig. 4a and Sup Fig 5). + +4) Elaborate on the use of the unsupervised output of SEMORE in a supervised setting within "Morphological fingerprinting captures defining features separating + +heterogeneous assemblies.": "We evaluated how morphological fingerprinting can dissect the diverse types of otherwise similar morphologies by three approaches. Firstly, utilizing a second UMAP embedding and DBSCAN of the circularity feature subset offered additional investigation of the fibril cluster in the embedded fingerprint space (see fig. 3b). This resulted in two spatially separated clusters corresponding to branching and non-branching fibrils which independently can be achieved by boosted decision tree classification using all fingerprint features directly (see Supplementary Fig. 13). Secondly, by investigating the isotropic and anisotropic clusters which revealed more continuous spaces given their more smooth growth behaviors as compared to branching of fibrils, yet with clear spatial separation of fingerprint features (see Supplementary Fig. 14). Lastly, SEMORE was able to correctly classify the identity of diverse morphologies in high-density regions reaching an F1 score of >98% (See Supplementary Fig. 11). Although, morphological fingerprints represent unsupervised output these results demonstrates the versatility in supervised classification to extend beyond distinguishing between fundamentally different morphology families, i.e., fibrils vs isotropic, to also capture heterogeneity within the same morphology family i.e., branching fibrils vs non-branching fibrils. We find the morphological + +<--- Page Split ---> + +fingerprinting needs just 8 detections to fully separate true detections from noisy and 15 detections to further classify the morphology class of the true detections (Supplementary Fig. 7 & 8). Such expressive power is required to provide mechanistic insights for most biological assemblies as they often follow one assembly mechanism but still exhibit heterogeneity in their final morphologies and the mapping of which is currently an analytical challenge9. + +## Comment 2.5 + +In the Fingerprinting module, it is mentioned that over 40 features were utilized to analyze the properties of each cluster using various methods. However, it appears that a comprehensive assessment of the strengths and weaknesses of these methods was not conducted. It is unclear why the given methods are expected to yield good features for cluster classification. Additionally, it would be beneficial to determine if all the provided methods are necessary based on the analysis results. For instance, Supplementary Figure 8 suggests that it might be possible to identify a better method instead of using all the feature vectors obtained from each feature. There is a possibility that some of them could even interfere with the analysis process, so it would be insightful to see further results in this regard. + +## Response 2.5 + +The reviewer asks for the basis of the selection of the \(40+\) descriptive features and whether all features are needed, an assessment of their performance and whether their number can interfere with the analysis. + +The central scope and strength of SEMORE is the maximization of applicability and the agnostic classification across diverse systems. Based on these criteria we created an extensive set of features that relied on a combination of geometric elements designed to best capture as diverse as possible morphologies and experimental systems. Therefore the number and identity of features should not be predetermined based on the classification of one specific structure type, but should be as wide as possible so as to ensure the reliability of the agnostic classification. Similarly the strength and weakness of these features can not be predetermined, as they are system dependent and will indeed vary from dataset to dataset. + +We fully agree therefore with the reviewer that often only a fraction of the \(40+\) features can be sufficient to classify each of a given cluster morphology. We had provided this in original SI fig. 8 (now SI fig. 16) and extensively studied in the manuscript both on simulated and experimental data as per original main fig. 3+4 and original SI figures 2- 8 and \(11 + 12\) . To provide further evidence we now include additional simulated and experimental data as per new SI fig. \(17 + 18 + 19\) that shows the importance values of the most dominant features in all classifications of the original manuscript and clearly displays that some features are more important in each case. Each panel displays 18 of the features with the more dominant effect as the rest had minimal or no contribution to the classification, in agreement with what the reviewer asks. This figure stresses that each morphology requires a distinct and different set of descriptive features to be accurately classified. For example, for insulin classification, longest shortest distance (L_s_D), number of bridges in longest possible one- way route through graph (L_I_step), average number of neighbors in graph (mean K) are the dominant features while for Nuclear Pore Complexes longest shortest path in graph (L_s_path), ratio of longest distances in graph (L_I_ratio) and effectiveness of the longest shortest distance + +<--- Page Split ---> + +(L_s_effectiveness) are now the most dominant ones. This is further highlighted in the new SI fig 15 (response figure 7) towards capturing temporal evolution of morphology that clearly displays classification of diverse morphologies relies on different features sets. + +We also agree that some of the features can have overlapping interpretations. This overlap does not affect the overall accuracy of the method as only the effects that contribute to the classification are taken into account, however, they can collectively contribute to a detailed description of the clustering at hand. + +We also agree that the features can always be improved and as better features are employed in the future, our implementation of morphological fingerprinting may be further extended even by users to create a feature library. + +We are puzzled by the comment on the assessment of the descriptor importance as this is exactly displayed in SI fig. 8. Acknowledging that these may not be clear we have explained it in detail here and in the main text. + +## Changes in the manuscript 2.5 + +We agree with the reviewer on the importance of these comments surrounding features and features importance thus merits further clarification so we have highlighted the following elements in the main text revised version. + +1) In the Results discussing the descriptive feature selection we added "The number and identity of features are constructed as diverse as possible so as to agnostically capture a diverse set of protein clustering morphologies and maximize applicability across biological systems without a priori knowledge." + +2) In the same section: "Note that some of the features can have overlapping interpretations. This overlap does not affect the overall method accuracy as only features that enhance the classification are taken into account, however, they can collectively contribute to a detailed description of the system at hand. If better features are identified in the future, they can be conveniently implemented into SEMORE further extending its potential." + +3) Elaborated on the point of the possibility to extend the fingerprinting module: "We envision SEMORE's application across diverse systems, the continuous extension of the fingerprinting module and the generation of libraries of protein assembly morphologies. Libraries of morphological features could aid mapping of assembly characteristics to their identity and function for advancement of biological understanding, statistical approaches and be the basis for novel supervised learning purposes (Supplementary Fig. 13)." + +4) In the Discussion discussing the descriptive feature selection we added: "Using a broad set of features maximizes applicability across biological systems and feature ranking can reveal the features of greatest importance providing key mechanistic insights into the given system" + +## Comment 2.6 + +In general, the methodology is not thoroughly explained. For instance, even if the method applied in the existing DBSCAN is used as is, it would be helpful if the methodology were described in more detail. Additionally, the methodology for the classification of each point, which occurs after the fingerprinting module and embedding with UMAP, is not elaborated very well. Since the fingerprinting module appears to be the only distinctive novelty of this method, as mentioned above, it should be described in detail to provide a clearer understanding. + +<--- Page Split ---> + +## Response 2.6 + +Response 2.6We appreciate the help to improve the readability of the methods section and for enabling us to improve the description of the element that sets us apart from the current state of the art. As outlined in our response to comment 2.4 we have in the revised version elaborated on the clustering module of SEMORE and its contribution to the field. The classification of fingerprints into specific morphology classes occurs by an additional DBSCAN on the 2- component UMAP embedded space (Main fig. 3 and original SI fig. 6c, now SI fig. 13c) or by a boosted decision tree (original SI fig. 6d+ e, now SI fig. 13fd+ e). + +## Changes in the manuscript 2.6 + +Changes in the manuscript 2.61) For the elaboration of the clustering module kindly see the changes of response 2.4. In addition2) We have elaborated the methods section in the revised manuscript.3) We have highlighted the use of DBSCAN and boosted decision trees in classification from morphological fingerprints: "This resulted in two spatially separated clusters corresponding to branching and non- branching fibrils which independently can be achieved by boosted decision tree classification using all fingerprint features directly (see Supplementary Fig. 13). Secondly, by investigating the isotropic and anisotropic clusters which revealed more continuous spaces given their more smooth growth behaviors as compared to branching of fibrils, yet with clear spatial separation of fingerprint features (see Supplementary Fig. 14). Lastly, SEMORE was able to correctly classify the identity of diverse morphologies in high-density regions reaching an F1 score of \(>98\%\) (See Supplementary Fig. 11). Although, morphological fingerprints represent unsupervised output these results demonstrates the versatility in supervised classification to extend beyond distinguishing between fundamentally different morphology families, i.e., fibrils vs isotropic, to also capture heterogeneity within the same morphology family i.e., branching fibrils vs non- branching fibrils." + +## Additional minor changes + +minor spelling and phrasing mistakes were rectified. minor addition to account for the fact that we have 5 experimental data sets instead of 2 in the original submission, as well 6 additional ground truth simulated data sets. addition of a few extra refs to account for reviews comments. + +## Reviewer 3 + +Reviewer 3The manuscript entitled "SEMORE: SEgmentation and MORphological fingErprinting by machine learning automates super- resolution data analysis" by Hatzakis et al introduces SEMORE, a semi- automatic machine learning framework for universal, system and input- dependent, analysis of super- resolution data. The manuscript is well written and informative. However, this manuscript can be improved by addressing the following issues: + +## General response + +General responseWe thank the reviewer for critically reading the manuscript, acknowledging it is "informative" and "well written" and for proposing elements to further improve it. Fully and in detail addressing all of them helped us further improve the quality of the manuscript. Figures created following your and other reviewers comments have been pasted below for your convenience. + +<--- Page Split ---> + +## Comment 3.1 + +Comment 3.1The authors have developed a new analytical tool SEMORE to extract and quantify underlying structures limiting single- molecule localization microscopy (SMLM). How this newly developed tool SEMORE is better suited with SMLM than some of the previously employed tools such as SMAP (modular super- resolution microscopy analysis). + +## Response 3.1 + +Response 3.1We are grateful for noticing the incomplete comparison of our method with the current state of the art. Super- resolution Microscopy Analysis Platforms for SMLM data (SMAP) is a platform carrying multiple tools for SMLM users to make SMLM more accessible. This modular analysis platform contains tools for localization, post- processing, rendering and clustering (specifically DBSCAN see below). The multiple steps involved in SEMORE's clustering module, i.e. the data- driven decision of clustering approach, smart noise filtering, temporal refinement and morphology fingerprinting do not have directly comparable approaches implemented in SMAP. SMAP does have a DBSCAN implemented, which we do provide a comparison to (original SI fig 3 now SI fig. 4). In addition, SMAP does not include a module comparable to SEMORE's morphological fingerprinting for the quantification of morphology. The methodological advances of SEMORE should be viewed as a possible addition to the multiple plugins already contained within SMAP. The potential of SEMORE to be added to SMAP or to work downstream of analysis performed in SMAP is now mentioned in the revised version of the manuscript to make future users aware of the synergy. + +## Changes in the manuscript 3.1 + +We thank the reviewer for enabling us to clarify the synergy between SEMORE and upstream analysis in SMAP. This has now been added to the revised version of the manuscript in the discussion, see + +"In all cases, relevant structures are precisely extracted and featurized providing strong support for SEMORE as a universal, input- independent model as a convenient toolbox for the SMLM community to use in conjunction with or to be incorporated into SMAP." + +For comparison of SEMORE to DBSCAN we refer to the original SI figure 3 (now SI fig. 4), where we show SEMORE achieves a \(89\%\) median accuracy as compared to \(70\%\) for DBSCAN alone. + +## Comment 3.2 + +The authors should explain how SEMORE deals with commonly occurring supervised and unsupervised machine learning problems. + +## Response 3.2 + +This is indeed an important element of our work, and we are grateful for allowing us to elaborate further. Below we have detailed the challenges of both supervised and unsupervised tools and how SEMORE addresses them. + +Commonly occurring challenges in unsupervised machine learning may include: + +1) Absence of direct accuracy evaluation because the data comes without any labels, classical performance evaluations such as accuracy is not possible. + +<--- Page Split ---> + +2) The output of an unsupervised model may require human inspection to decipher how the model is performing. + +Commonly occurring problems in supervised machine learning : + +A) Collection of labels for data is often a tedious and resource-strenuous process that requires extensive a priori expertise and is potentially subjected to unconscious biases. +B) Supervised models are trained for a specific task and often require retraining when presented with a system outside the training distribution. +C) Overfitting on data presents a large challenge to supervised approaches resulting in overly optimistic expectations on model generalization. Mitigation requires reliable validation and test schemes that are independent of the training distribution are not always feasible and require more manual labels to be curated. + +SEMORE was specifically chosen to be an unsupervised approach so as to enable a universal approach for SMLM across experimental conditions and biological systems without the need for a priori knowledge or expensive label generation. We tackle the uncertainty surrounding the output of an unsupervised machine learning pipeline by extensive evaluations on simulated data with known labels and by probing performance at various perturbations. In addition, we evaluated its performance on 5 (2 in the original manuscript and now added 3 additional in new supplementary fig. 17- 19) completely diverse experimental data acquired by different groups using diverse imaging and experimental conditions, on different biological systems and with varying noise. In all cases SEMORE's output is in agreement with the published outputs supporting it can surpass commonly occurring supervised and unsupervised machine learning problems. + +## Changes in the manuscript 3.2 + +To fully address the comments we discussed extensively in the revised version the a) actual challenge of supervised vs unsupervised analysis b) how we mitigated them. They are discussed in 3 areas of the manuscript + +a) Elaboration on common challenges in unsupervised and supervised learning see section: Introduction: + +"Supervised algorithms are highly accurate when large amounts of annotated data are available albeit annotations require extensive manual labor and expert knowledge and the resulting model is often suitable for one specific data set or task. This imposes some challenges in exploring unmapped biological systems with no a priori knowledge and potentially limits their use as a general tool \(^{10 - 12}\) . Unsupervised approaches such as OPTICS \(^{13}\) and DBSCAN \(^{14}\) can overcome some of these limitations for coordinate-based input data. Their performance however is often limited by a one-size-fits-all approach. This often results in laborious human intervention in model tuning, restricting their adaptation to heterogeneity in localization densities and assembly sizes in varying experimental data \(^{15,16}\) ." + +b) To address how we mitigate the common challenges, see section Introduction: + +"We show that SEMORE provides the unbiased unsupervised clustering, and morphological cluster variation in time, without a priori knowledge and for diverse simulated and experimental data sets: heterogeneous growth pathways of insulin aggregates, the dimensions of individual nuclear pore complexes, size of individual clusters of fibroblast growth receptors 1, temporal evolution of syntaxin 1a clusters and dynamic clustering of ryanodine receptors (RyR). The implementation of temporal dependence in morphological variations is a promising platform to handle static or dynamic superresolution data and enables in-depth temporal-dependence analysis and segmentation of complex structures." + +c) we highlight the use of supervised learning on the unsupervised output from SEMORE, see section: Morphological fingerprinting captures defining features separating heterogeneous assemblies: "We evaluated how morphological fingerprinting can + +<--- Page Split ---> + +dissect the diverse types of otherwise similar morphologies by three approaches. Firstly, utilizing a second UMAP embedding and DBSCAN of the circularity feature subset offered additional investigation of the fibril cluster in the embedded fingerprint space (see fig. 3b). This resulted in two spatially separated clusters corresponding to branching and non- branching fibrils which independently can be achieved by boosted decision tree classification using all fingerprint features directly (see Supplementary Fig. 13). Secondly, by investigating the isotropic and anisotropic clusters which revealed more continuous spaces given their more smooth growth behaviors as compared to branching of fibrils, yet with clear spatial separation of fingerprint features (see Supplementary Fig. 14). Lastly, SEMORE was able to correctly classify the identity of diverse morphologies in high- density regions reaching an F1 score of \(>98\%\) (See Supplementary Fig. 11). Although, morphological fingerprints represent unsupervised output these results demonstrates the versatility in supervised classification to extend beyond distinguishing between fundamentally different morphology families, i.e., fibrils vs isotropic, to also capture heterogeneity within the same morphology family i.e., branching fibrils vs non- branching fibrils." + +## Comment 3.3 + +Comment 3.3The authors should also highlight the role of SEMORE in the advancement of machine learning- based approaches. + +## Response 3.3 + +Response 3.3We value the comment of highlighting how SEMORE advances machine learning based approaches and how further elaboration can strengthen the manuscript. We highlight how a coordinate- based approach to the structural analysis coupled with the temporal refinement, the density- based modeling choice and data- based noise filtering enhances the machine learning pipeline. In addition, we emphasize how featurization of underlying structures directly from raw data can be used to build new machine learning frameworks by future users. + +Several key features sets SEMORE beyond DBSCAN and current state of that art : + +g) Automatic, data-driven model selection between HDBSCAN and DBSCAN based on the density of localisations computed using the field of view. +h) Semi-supervised hyperparameter choices based on experimental data. +i) Topological failsafe for the case of no initial aggregation securing the clustering module does not form nonsensical clusters as DBSCAN alone might if only presented with noise, thus enhancing the clustering detection sensitivity. +j) Smart noise filtering filtering false positive detections in conjunction with our clustering greatly improves the quality of the clustering module's output. +k) Temporal refinement enables clustering of spatially overlapping structures, the dissection of initiation point of each cluster in time and following of morphology changes over time all of which are currently infeasible by DBSCAN or other available methods alone. +l) Morphological fingerprinting for quantification and ranking of interpretable geometric and kinetic descriptors, that to the best of our knowledge is introduced here by us for protein clustering, based on our earlier work on diffusional fingerprinting. + +<--- Page Split ---> + +## Changes in the manuscript 3.3 + +The revised manuscript now includes further detail on how SEMORE contributes to the field of machine learning based approaches. + +Firstly, how the clustering module of SEMORE extends beyond current state of the art see 2nd paragraph of Results : + +"The clustering module of SEMORE consists of multiple steps that self- parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools. The pipeline initially inspects high- density areas in a standardized Euclidean 3D space, using a hyperparameter space pre- defined for this region, and provides an appropriate model choice based on a data- driven decision. The chosen density- based scanning model, either HDBSCAN or DBSCAN, extracts high- density regions of biomolecules (clusters or aggregates) from low- density regions (noise) (Fig. 1b). The initial clustering contains an added topological fail safe to prevent detection of nonsensical structures (see Methods). If a temporal dimension is available, the high- density regions are treated through our temporal refinement (Fig. 1c). Segmentation in time and temporal refinement is strictly required to dissect spatially overlapping structures within high- density areas. The clustered output is further refined by subjecting all identified assemblies to a smart density filter to eliminate falsely predicted assemblies that do not meet an agnostic, data- derived density criteria (Supplementary Fig. 1). The result is a robust clustering model outcompeting current methods and building towards the first general- purpose approach for dynamic SMLM (see Methods and Supplementary fig. 4)." + +Secondly, in Discussion we elaborate further on the contribution of morphological fingerprinting module to advance ML approaches: + +"We envision SEMORE's application across diverse systems, the continuous extension of the fingerprinting module and the generation of libraries of protein assembly morphologies. Libraries of morphological features could aid mapping of assembly characteristics to their identity and function for advancement of biological understanding, statistical approaches and be the basis for novel supervised learning purposes (Supplementary Fig. 13)." + +See also response to comment 3.2 where we highlight the use of supervised learning on the unsupervised output from SEMORE allowing new downstream models to be developed by the community working on the experimental data- derived morphological fingerprints as features + +## Comment 3.4 + +Since vibrational and spherical aberrations prove to be a greater hindrance at high resolution. Moreover, live samples are more adversely affected by super- resolution imaging because of high excitation intensity or extended exposure times. Does the SEMORE tool take these concerns into consideration? + +## Response 3.4 + +Vibrational and spherical aberrations present large challenges to high resolution imaging especially in live samples, therefore they are important to comment on and we thank the reviewer for bringing this point. Removing such aberrations is often reliant on post- processing. Currently, SEMORE is downstream of any such post- processing steps, as well as the actual detection step as a pipeline working directly on existing localizations to accurately extract underlying structures and provide extensive quantitative features. We acknowledge this was not explicitly discussed in the main text so we have rectified it + +<--- Page Split ---> + +## Changes in the manuscript 3.4 + +We now discuss the consequences and the recommended approach of correction before SEMORE or to use SEMORE as an easy approach to extract morphological information quickly before correction. see Discussion: + +"SEMORE is currently optimized for laterally stable assemblies, albeit the temporal refinement does handle lateral movement below the agnostic, data- derived search range defined per assembly basis (see Methods). Future versions are planned to include our diffusional analysis framework for motion aware clustering analysis. Blinking has insignificant effect on SEMORE analysis, however we recommend common aberrations such as blinking and vibrational or spherical aberrations to be corrected prior to use of SEMORE to avoid any potential misinterpretation of the data." + +## Additional minor changes + +minor spelling and phrasing mistakes were rectified. minor addition to account for the fact that we have 5 experimental data sets instead of 2 in the original submission, as well 6 additional ground truth simulated data sets. addition of a few extra refs to account for reviews comments. + +![](images/Figure_2.jpg) + +
Figures
+ +Response Figure 1: dSTORM data from Nieves et. al. 1 clustered and quantified by SEMORE + +Supplementary Figure 17: Evaluation of SEMORE clustering on dSTORM data acquired over several consecutive frames 1 a Raw detections from SMLM data of fibroblast growth receptor 1 (FGFR1) on a MCF7 cell presented by Nieves et al. 1 b Initial clustering by SEMORE's clustering module using the data- driven model choice of HDBSCAN with Min_cluster_size = 15 and Min_sample = 5. Each localization is colored by its SEMORE annotation, with black representing noise and all other colors representing captured clusters. c The + +<--- Page Split ---> + +final clustering by SEMORE after temporal refinement and smart density filtering (see Methods). Localizations' colour corresponds to the final SEMORE prediction, with black localizations representing predicted clustered supressed by the smart density filter. Clearly depicting complete extraction of heterogeneous protein clusters while minimizing the inclusion of false positive structures demonstrates the power of temporal refinement, smart filtering and cluster specific re- evaluation. d Distribution of detections inside each cluster with each dot representing an identified cluster showing an average of 28 detections and a median of 18 detections. e Distribution of area spanned by the detections inside each predicted clusters resulting shows a mean \(2232nm^2\) and median of \(1829nm^2\) . The Relatively small areas compared to the mean of \(17000nm^2\) reported in nieves et al. 1 showing the difference in a tight area estimation we define in the morphological fingerprinting (see SI fig. 17) versus a more crude convex hull used in Nieves et al 1. F Density of each cluster for further depth in analysis and heterogeneous nature of protein clusters showing with a mean density of \(0.0179N/nm^2\) and a median of 0.009 \(N/nm^2\) . + +![](images/Figure_4.jpg) + +
Response figure 2: Sx1a-mEos2 sptPALM data from Wallis et. al. 3 clustered and temporally quantified by SEMORE.
+ +Supplementary Figure 18: Evaluation of SEMORE on temporarily resolved Sx1a-mEos2 sptPALM data 3. a, Raw localizations of all detections of Sx1a-mEos2 colored in grey for noise detections and other colors for individual clustered detections captured by SEMORE (HDBSCAN; min_cluster_size: 10, min_samples: 10, cluster_selection_epsilon: 0.04) for the entire field of view (sptPALM traces above length 20) showing near identical results to Wallis et al 3. Red box indicates a region of interest. b, Snapshots in time plotting all detections prior to the indicated acquisition time from the region of interest in a showing SEMORE captures the time-resolved appearance and growth of clusters. Last snapshot contains a red box highlighting an additional region of interest. c, 3D (xyt) plot of the region of interest presented in b showing the temporal morphological changes of clustered detections. Red box indicates a hotspot region in space with repeated clustering of detections in time. d, Shows the temporal evolution of cluster size for the region of interest in c showing SEMORE's successful capture of the repeated clustering of detections also discussed in Wallis et al 3. + +<--- Page Split ---> +![](images/Figure_4.jpg) + +
Response Figure 4 Evaluation of SEMORE on temporarily resolved live-cell PALM data of ryanodine receptors (RyRs).
+ +Supplementary Figure 19: Evaluation of SEMORE on temporarily resolved live-cell PALM data of ryanodine receptors (RyRs) 4. a, Raw localizations of all detections of RyRs from live-cell PALM from Hou et al4 colored in grey. Scale bar 2 microns. b, Initial clustering of data by DBSCAN showing clusters colored by cluster identity. c, left panel: Final clustering by the full clustering module of SEMORE utilizing the smart density filtering and temporal refinement with individual clusters colored by identity (DBSCAN; dbmin_samples: 10, SEMORE: final_min_points: 10, rough_min_points: 10, investigate_min_sample: 10). Hyperparameters of SEMORE chosen to capture the relatively small clusters formed by RyRs. Results show how SEMORE obtains granularity otherwise infeasible by DBSCAN alone. Right panel: Final clusters from SEMORE colored by the "longest shortest distance" feature from the morphological fingerprinting module with clusters exceeding a threshold of 400nm colored in red showing how SEMORE can capture RyR cluster morphology and separate noisy detections. Utilizing the tight packing assumption for RyRs 4 identified RyR clusters consist on average of 18 RyR with a median of 14 in line with results from Hou et al 4 with slightly larger estimates as we do not filter by intensity. + +<--- Page Split ---> +![](images/Figure_5.jpg) + +
Response Figure 4: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies.
+ +## Supplementary Fig. 7: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies. + +a) Simulated experiment containing both fibril (orange) and elliptical (blue) morphology class containing 4 points each. Three noise ratios were simulated 1, 2 and 3 (ratio 2 in figure) with 10 simulations per noise levels each with 30 true assemblies. b) Assembly extraction by SEMORE's clustering module. SEMORE's hyperparameters were kept across conditions for comparable results and evaluation of automated analysis. c) Accuracy evaluation performed on an aggregate-wise level (see methods) grouped into each noise level. SEMORE achieves accuracies of 90% +/- 23% (noise ratio 1), 84% +/- 30% (noise ratio 2) and 77% +/- 37% (noise ratio 3) showcasing the fidelity of the pipeline even at assembly sizes of four detections with three times as many noisy detections. Throughout all 3 noise ratios the median accuracy is 100% indicating that the found assemblies usually contain all the points of the assembly. d) The morphological fingerprints extracted for all structures visualized by an out-of-box 2-component UMAP. Right panel shows wrongly classified structures clustered, notably the noise (black) contained in the lower left corner. Each plotted assembly is represented by its noise to signal level (circle: 1, square: 2, triangle: 3) each noise to signal ratio contains 4, 9 and 38 false positives, respectively, compared to >270 true positives. Presence of false positives is due to true assemblies having densities near identical to noise impeding the smart density filter from accurately excluding the noise density. Left panel shows colour coding each assembly by density revealing true assemblies and false positives can be separated by a single feature from morphological fingerprinting. Proving morphological fingerprinting can aid a non-perfect segmentation, allowing for further correction or focus-based re-segmentation. + +<--- Page Split ---> +![](images/Figure_6.jpg) + +
Response figure 5: SEMORE classification performance for small, sparse clusters of diverse morphologies.
+ +Supplementary Fig. 8: SEMORE classification performance for small, sparse clusters of diverse morphologies. + +a) Simulated data containing temporally resolved fibril and static ellipse shape aggregates (coloured orange and blue respectively) containing 8, 15 and 25 points respectively. Each simulated data set contains 30 aggregates equally divided between the two morphology classes, additionally, noise (coloured black) ratios of 1 and 2 (noise ratio 2 depicted in the figure). 10 experiments were simulated for each condition and each noise ratio accumulating to 1800 aggregates over 60 experiments. b) Predictions made by SEMORE clustering module, with coloured aggregate being True positives (TP) and black being false positives (FP). SEMORE's clustering module is able to handle the combination of sparse static and temporally resolved assemblies contained within the same experiments. c) SEMORE's segmentation performance quantification. Through the SEMORE clustering module an aggregate-wise mean accuracy (see methods) (noise ratio 1 & 2 reported as [1] / [2] ) of; 85% / 80% +/- 24% / 31% and a median accuracy of 91%/ 89% for 8 points assemblies, mean 80%/ 81% +/- 31%/ 30% with median 94%/ 94% for 15 point assemblies and a mean 83% / 76% +/- 27%/ 35% and a median of 95%/ 93% for 25 point + +<--- Page Split ---> + +assemblies. as seen in d) the two- component UMAP of morphological fingerprints reveal all false positive assemblies (noise detections) are perfectly separated. Using this separation as correction accuracies improve: mean \(87\% /86\% + / - 21\% /21\%\) median \(91\% /89\%\) for 8 points, \(83\% /89\% + / - 27\% /20\%\) median \(94\% /94\%\) for 15 points and mean \(84\% /82\% + / - 26\% /27\%\) median \(96\% /93\%\) for 25 points. Performance is improved proportional to noise- ratio as the higher noise levels induce more false positives which in turn are corrected by morphological fingerprinting. d) Two- component UMAP embedding of the corresponding fingerprints with the different noise- ratio combined within point types (N = 611, 611, 586 for 8, 15, 25 points respectively). + +<--- Page Split ---> +![](images/Figure_8.jpg) + +
Response Figure 6: Deconvolution of temporal refinement on real and simulated data.
+ +Supplementary Fig. 6: Deconvolution of temporal refinement on real and simulated data. a) Snapshots of SEMORE's clustering module output at various frames during temporal refinement of found insulin aggregates (also depicted in Fig. 1C.) in MinMax transformed space (see Methods). Data displayed in 9 windows equally spaced throughout the 381 frame period, each initially found core point of all dissected aggregates is depicted with a red dot symbolizing the initiation of an aggregate. b) The cluster growth is directly visualized in non-transformed space revealing cluster growth in time of a) in a 3D plot after the application of the smart-density filtering (see methods). The cone-like shape of the aggregates in the positive time direction demonstrates SEMORE's ability to capture the growth behaviour of assemblies in experimental data. Each depicted cluster has its predicted initiation point marked with projected lines at the bottom of the plot to highlight the vast difference in the onset times of clusters as revealed by SEMORE. c) Simulated data (from SI fig. 3) 400 frames after initiation. Data displays that SEMORE can find assembly cores, even with high-size heterogeneity including assemblies as small as 94 points up to 7777 points while also correctly dissecting overlapping assemblies. d) The corresponding frame of the predicted initiation was used to estimate the offset in time, from growth start to SEMORE prediction, here plotting \(\sim 99\%\) of the distribution. The mean offset of 13 frames, reflects that SEMORE can accurately classify cluster initiation while showcasing the strength of SEMORE in capturing temporal assembly dynamics. + +<--- Page Split ---> +![](images/Figure_9.jpg) + + +Response Figure 7: Visual representation of SEMORE's ability to capture morphological growth in time Supplementary Fig. 5: Visual representation of SEMORE's ability to capture morphological growth in time. + +(a, b, c) depicts the inherent process of temporal segmentation of assemblies within the clustering module of SEMORE during temporal refinement shown as 9 windows across three morphological classes. a) 3 simulated fibrils that spatially overlap during growth are accurately segmented. b) 3 simulated isotropic assemblies growing very close to each other accurately extracted and separated by SEMORE. c) Simulated growth of 3 sterically- hindered assemblies captured by SEMORE. a, b, c showcases the versatility of the general clustering module of SEMORE in capturing temporal evolution of protein assemblies, while general segmentation performance can be seen in main fig 2. The second row (d, e, f), shows the structures in 3D with the time being the 3rd axis to visualize assembly growth and morphology evolution. A direct depiction of the predicted assembly initiation point is shown as projected lines to the bottom of the plots revealing SEMORE's ability to keep account of various growth onset times. This is shown for Fibril (d), Isotropic (e) and sterically hindered growth (f) assemblies. + +<--- Page Split ---> +![](images/Figure_10.jpg) + +
Response Figure 8: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters.
+ +Supplementary Fig. 15: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters. + +a) Simulated dynamic morphology variation of protein assembly by sequentially exhibiting structures with diverse morphologies. All temporal states consist of 200 points colour-coded by morphology type. Lines projected at the bottom represent a new morphology initiation (coloured by morphology type). For each temporal state, the SEMORE morphological fingerprinting module was used to extract features for probing the morphology changes across temporal states. b) The morphological fingerprints were embedded by an out-of-the-box 2-component UMAP resulting in a clear separation of the morphology class across time (with time linked by grey lines). Systems with more or less gradual change of morphology would result in a more or less regressive separation. c) MinMax transformed fingerprints plotted into a heatmap with each column representing a temporal state and white lines indicating drastic morphology type changes. Each row represents a morphological feature, in the same order as seen in Supporting Table 1. The heatmap rows showcase the morphological fingerprinting module's ability to capture the mechanistic of temporal states and map the overall features changes involved in major changes in morphology. + +<--- Page Split ---> +![](images/Figure_11.jpg) + +
Response Figure 9: Benchmarking SEMORE on for heterogeneous, non-uniform noise.
+ +## Supplementary Fig 3: Benchmarking SEMORE on for heterogeneous, non-uniform noise. + +a) Simulated data used in S1 fig. 2, but now exhibiting a heterogeneous noise profile. Heterogeneous noise is generated by introducing 5-25 "noise seeds" each containing 20-50 points have been added to each simulation, additionally, individual Gaussian distributed shifts have been applied to all initial noise points. b) we see SEMORE clustering classification performance as out-of-the-box. c) Evaluating SEMORE clustering performance versus increasing noise ratio (blue area representing biologically relevant noise-levels estimated from real data and with vertical blue line representing insulin experiments). At biologically relevant noise levels or high noise levels accuracies of SEMORE is observed to be above \(\sim 90\%\) from noise ratio \(\sim 0.2\) and onwards with up to \(93\%\) at 0.7 noise ratio reflecting SEMORE's ability to separate non-uniform noise also observed in robust treating of experimental insulin data (see main fig. 4). The unrealistic conditions with extremely low noise ratios or no noise at all are associated with lower accuracies as the smart-density noise filter expects noise and removes true positives if no noise is present, which is easily countered by turning it off. + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Response Figure 10: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes.
+ +Supplementary Fig. 9: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes. + +Each row in a) and b) are grouped and depict a certain simulated structure size (4, 8, 15 and 25 data points, respectively). a) Left side shows detections from representative fibril structures as "Ground truth" (orange) prior to blinking and the right side depicts the corresponding structures obtained after blinking (dark red). These post- blinking structures do not include the ground truth points (orange). For each row, 600 ground truth structures were simulated along their corresponding blinking counterpart and as performed in SI fig. 8 two types of morphologies were simulated in equal amounts, namely fibril- like and spherical. b) The morphological fingerprints of each structure are visualized by a 2- component UMAP with colour- coded by morphology type. The ground truth structures (no blinking) shown on the left side of b) and post- blinking structures on the right side. The results show distortion in separability induced by blinking is positively correlated with the number of detections with a given structure as expected as blinking will dominate the morphology of small structures. + +From 15 detections in a structure and above blinking has little to no effect on the morphological fingerprinting module of SEMORE. + +![](images/Supplementary_Figure_17.jpg) + +
Response Figure 11: Demonstration SEMORE clustering of morphology shrinkage
+ +Supplementary Fig. 10: Demonstration SEMORE clustering of morphology shrinkage + +a) Demonstration of 3 simulated isotropic structures that while proving a challenge due to spatial overlapping also undergo shrinking (colour-coded by identity). b) Results show SEMORE accurately identifies spatially overlapping clusters reducing in size at all frames in the simulation allowing the tracking of individual shrinkage in + +<--- Page Split ---> + +time. As shrinkage is the direct opposite of growth, SEMORE's clustering module is directly applicable as is after a simple preliminary step of flipping the temporal axis of the simulation or experiment. + +## Bibliography + +1. Nieves, D. J. et al. A framework for evaluating the performance of SMLM cluster analysis algorithms. Nat. Methods 20, 259-267 (2023). +2. Lelek, M. et al. Single-molecule localization microscopy. Nat. Rev. Methods Primers 1, (2021). +3. Wallis, T. P. et al. Super-resolved trajectory-derived nanoclustering analysis using spatiotemporal indexing. Nat. Commun. 14, 3353 (2023). +4. Hou, Y. et al. Live-cell photoactivated localization microscopy correlates nanoscale ryanodine receptor configuration to calcium sparks in cardiomyocytes. Nat. Cardiovasc. Res. 2, 251-267 (2023). +5. Zhang, M. et al. Direct observation of heterogeneous formation of amyloid spherulites in real-time by super-resolution microscopy. Commun. Biol. 5, 850 (2022). +6. Liu, C. C. et al. Robust phenotyping of highly multiplexed tissue imaging data using pixel-level clustering. Nat. Commun. 14, 4618 (2023). +7. Fleming, S. J. et al. Unsupervised removal of systematic background noise from droplet-based single-cell experiments using CellBender. Nat. Methods (2023) doi:10.1038/s41592-023-01943-7. +8. Raad, J. D. et al. Unsupervised abnormality detection in neonatal MRI brain scans using deep learning. Sci. Rep. 13, 11489 (2023). +9. Andersen, C. B. et al. Branching in amyloid fibril growth. Biophys. J. 96, 1529-1536 (2009). +10. Xu, C. & Jackson, S. A. Machine learning and complex biological data. Genome Biol. 20, 76 (2019). +11. Thiyagalingam, J., Shankar, M., Fox, G. & Hey, T. Scientific machine learning benchmarks. Nat. Rev. Phys. (2022) doi:10.1038/s42254-022-00441-7. +12. Benning, N. A. et al. Dimensional Reduction for Single-Molecule Imaging of DNA and Nucleosome Condensation by Polyamines, HP1α and Ki-67. J. Phys. Chem. B 127, 1922-1931 (2023). +13. Ankerst, M., Breunig, M. M., Kriegel, H.-P. & Sander, J. OPTICS. SIGMOD Rec. 28, 49-60 (1999). +14. A density-based algorithm for discovering clusters in large spatial databases with noise | Proceedings of the Second International Conference on Knowledge Discovery and Data Mining. https://dl.acm.org/doi/10.5555/3001460.3001507. +15. Khater, I. M., Nabi, I. R. & Hamarneh, G. A Review of Super-Resolution Single-Molecule Localization Microscopy Cluster Analysis and Quantification Methods. Patterns (N Y) 1, 100038 (2020). +16. Bzdok, D., Altman, N. & Krzywinski, M. Statistics versus machine learning. Nat. Methods 15, 233-234 (2018). + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +I would like to thank the authors for their very thorough and in- depth response to my comments. The extra benchmarking and highlighting the scale invariance has significantly improved the manuscript and will be a very useful tool for SMLM cluster analysis and classification. + +I fully recommend the revised manuscript for publication. + +Reviewer #2 (Remarks to the Author): + +The authors addressed many of my review comments regarding simulation with heterogeneous noise and added the new data analysis results, including time- resolved images. However, unfortunately, some of the newly added data and explanations are not satisfactory enough to resolve my concerns based on the following reasons. Therefore, I strongly request that the authors carefully examine their data and analysis. + +1. To address my comments on the presentation of time-resolved image data, the authors added a simulation of dynamic morphology variation of protein assembly in Supplementary Figure 15. However, this simulated data contains only drastic changes between three clearly classifiable different morphologies without transitional states. In contrast, in the real world, we can expect gradual morphological changes in proteins through intermediate states. Therefore, I'm not yet sure whether their method can detect and track such more realistic gradual changes in proteins from the experimental SMLM image data. + +2. The authors compared the SEMORE result with previously reported results and asserted that SEMORE provided comparable results with the previous reports. For example, they insisted comparable results with Nieves et al (Supp Fig 17) and Wallis et al (Supp Fig 18). However, I cannot find the related supporting quantitative comparison data, making it difficult to judge whether SEMORE really provides comparable and reasonable results with the reported results. Additionally, the authors insisted that SEMORE could minimize the inclusion of false positive structures compared to HDBSCAN (in Supp Fig 17 experimental data), but I'm uncertain whether the filtered localizations are indeed false positive structures or positive structures that should not be filtered because there is no related data shown. To make a reasonable comparison of their results with others, quantitative comparisons should be provided. + +3. In many figures, particularly in supplementary figures, scale bar information or axis units are missing. Consequently, it is challenging for me to judge whether the clustering or filtering is biologically relevant in their image data. Additionally, in supplementary Figure 17 d-f, it appears that the x-axis is meaningless, so a scatter plot for density vs. N or Area would be more reasonable. + +4. Although the authors performed additional simulations with various noise variations, I don't understand some of the data. For example, Supplementary Figure 3 shows an increasing accuracy with an increasing ratio of heterogeneous, non-uniform noise, which is contrary to the general expectation. This could be because the data in Supplementary Figure 3c were obtained from just one-time simulation for each noise ratio (there is no error bar in this data), which could not demonstrate the general trend very well. While the authors claimed that the smart-density noise filter is designed to expect noise and remove true positives, such a case could lead to incorrect filtration for real images with low noise as well. Since different SMLM microscopes and different biological samples can produce various noise levels, I believe that if such an effect exists in their analysis method, it should be resolved. + +5. Regarding the responses for my fourth comments (2.4), I do understand that unsupervised learning is also a significant component of machine learning. My previous comments might be somewhat unclear in conveying my intended message. During the SEMORE clustering process, + +<--- Page Split ---> + +there are several steps involved in clustering meaningful points. The methods you have suggested in this paper to enhance clustering primarily focus on filtering out points and implementing temporal refinements. My point of concern is related to what happens once the filtered and refined points are available. I am uncertain about the contributions of this work to the "machine- learning- based clustering algorithm" at this stage. Even if the filtering and temporal refinements can potentially aid subsequent machine- learning- based clustering algorithms, they are difficult to be considered as a machine- learning algorithm by themselves. Therefore, I am curious if you have made any contributions to the "machine- learning- based clustering algorithm itself" apart from hyperparameter tuning in existing methods like DBSCAN. Examples of such contributions might include modifications to the loss function, alterations to the architecture, improved training techniques, and so on. + +<--- Page Split ---> + +Review response 2nd + +Review response 2nd 1 + +Reviewer 1 1 + +Comment: 1 + +General response 1 + +Reviewer 2 2 + +Comment: 2 + +General response 2 + +Comment 2.1: 2 + +Response 2.1: 2 + +Changes in manuscript 2.1: 4 + +Comment 2.2: 4 + +Response 2.2: 6 + +Changes in manuscript 2.2: 8 + +Comment 2.3: 8 + +Response 2.3: 8 + +Changes in manuscript 2.3: 9 + +Comment 2.4: 11 + +Response 2.4: 11 + +Changes in manuscript 2.4: 13 + +Comment 2.5: 13 + +Response 2.5: 14 + +<--- Page Split ---> + +## Reviewer 1 + +## Comment: + +I would like to thank the authors for their very thorough and in- depth response to my comments. The extra benchmarking and highlighting the scale invariance has significantly improved the manuscript and will be a a very useful tool for SMLM cluster analysis and classification. + +I fully recommend the revised manuscript for publication. + +## General response + +We thank the reviewer for valuable feedback that strengthened the paper and for accepting this for publication + +## Reviewer 2 + +## Comment: + +The authors addressed many of my review comments regarding simulation with heterogeneous noise and added the new data analysis results, including time- resolved images. However, unfortunately, some of the newly added data and explanations are not satisfactory enough to resolve my concerns based on the following reasons. Therefore, I strongly request that the authors carefully examine their data and analysis. + +## General response + +We are sorry to see that newly added biological and simulated data as well as analysis are not satisfactory. We have below fully and in detail addressed the new comments. + +## Comment 2.1: + +1. To address my comments on the presentation of time-resolved image data, the authors added a simulation of dynamic morphology variation of protein assembly in Supplementary Figure 15. However, this simulated data contains only drastic changes between three clearly classifiable different morphologies without transitional states. In contrast, in the real world, we can expect gradual morphological changes in proteins through intermediate states. Therefore, I'm not yet sure whether their method can detect and track such more realistic gradual changes in proteins from the experimental SMLM image data. + +## Response 2.1: + +We value the reviewer's feedback towards creating the best and most convincing display of SEMORE's capabilities. We agree that Supplementary figure 15 currently shows a protein assembly undergoing more drastic changes. We displayed this, along with other supplementary figures, as the simplest case to show SEMORE captures changes in morphology over time. + +<--- Page Split ---> + +To execute directly on this revised feedback, we evaluated below SEMORes capacity to characterize 8900 intermediate structures of gradual dynamic morphology variation in supplementary figure 26. The figure displays 90 structures from the three distinct morphologies sequentially, yet no two similar classes in a row, along with 100 interpolated structures as intermediates forming the transition between each of the 90, thus totalling 8900 structures. SEMORE accurately captures intermediate morphology classes and tracks their gradual dynamic morphology putting intermediate structures on a gradient between the distinct groups of where the transition is happening. Given these structures exist in a continuous space SEMORE allows users to decide on decision boundaries for each of the structures. + +We wish to stress that a central element of SEMORE is that it inherently performs temporal segmentation, thus capturing gradual changes. As detailed in the original submission SEMORE will segment and quantify each frame individually in a given data set, thus each identified cluster will have a temporal segmentation capturing its changes in time. Please also notice that aggregation growth is an inherently gradual change in morphology. We had displayed in main figure 1, 2, and 3, as well as, Supplementary figure 4, 5, and 6) of the original submission SEMORE's capacity to capture growth. + +![](images/Supplementary_Figure_3.jpg) + +
Supplementary Fig. x: SEMORE's Morphological Fingerprint captures gradual transitions in morphology. Thirty aggregates of each morphology class (fibril-like: fib, isotropic: iso, sterically-hindered/random: rand) of equal size were simulated resulting in ninety distinct structures which are placed sequentially in random order whilst ensuring no consecutive types. Between each of the ninety structures (89 transitions) 100 positions are constructed from interpolation (see methods). Thus, a total of 8900 intermediates gradually changing morphology between the three structures were evaluated using the fingerprinting module of SEMORE. All resulting transitions are connected
+ +<--- Page Split ---> + +in time, meaning the final structure of the (i) transition is the starting structure of \((i + 1)\) transition, thus creating a single dynamic structure of gradual transitions. a- c Shows representative transitions from fibril to isotropic, from fibril to random, and from random to isotropic, respectively. The lines drawn between points in a- c represent the 100 different positions expressed throughout the interpolation from the initial structure to the target structure. The color gradient of the box around each panel in a- c is the RGB representation of the percentage of morphology transition between the three distinct morphology classes. This color map is also used in d. (d) To visualize the general data manifold of the morphological fingerprints across the 8900 structures, the high dimensional morphological feature set was dimensionality reduced through a UMAP (n_components : 2, n_neighbors: 400, min_distance: 0.5). Similar to supplementary fig. 15 the embedding shows capture of distinct morphology classes and now also the continuous gradual change between the distinct morphology classes, as each structure morphs into the next. Thus, highlighting SEMORE's strength in capturing gradual morphological evolution. \(97.9\%\) of data are grouped in the continuous flow between the three distinct morphologies \((x = 7.5, y = 6)\) . The small group around the \((x = - 5, y = 0)\) area contains 186 points representing \(2.1\%\) of the data, although outliers still show a continuous flow between morphology classes. From this visual inspection, it is clear that the fingerprints capture both drastic and gradual changes in structure. + +## Changes in manuscript 2.1: + +To fully address the comment of the referee we have: + +a) added a new supplementary figure 26 detailing the dynamic morphology variation and how SEMORE track this + +b) added a paragraph in the section "Morphological fingerprinting captures defining features separating heterogeneous assemblies." + +"A central element of SEMORE is that it inherently performs temporal segmentation thus offering the potential to capture gradual morphological changes in super resolution data. To evaluate SEMORE's performance we simulated dynamic morphology variation between three major morphologies (fibril-like, isotropic, and sterically-hindered) (Supplementary Figs. 15 and 26). We simulated thirty structures of each morphology class (totalling 90), placed these sequentially in random order whilst ensuring no identical morphology consecutively. Between each of the ninety structures 100 positions are constructed by interpolation (see Methods) resulting in 8900 intermediate structures. UMAP representation in Supplementary Fig 26 shows SEMORE accurately captures distinct morphology classes and reliably tracks their gradual dynamic morphology change by placing intermediate structures on a gradient between the distinct morphology classes of where the transition is happening. Note, the UMAP is simply a visualization tool to show structure of the high dimensional data manifold of the 8900 morphological fingerprints, it is not a requirement for usage and may vary for specific cases. As these structures exist in a continuous space SEMORE allows future users to identify dynamic morphological variations and decide on system-specific decision boundaries for each of the structures." + +## Comment 2.2: + +2. The authors compared the SEMORE result with previously reported results and asserted that SEMORE provided comparable results with the previous reports. For example, they insisted comparable results with Nieves et al (Supp Fig 17) and Wallis et al (Supp Fig 18). However, I cannot find the related supporting quantitative comparison data, making it difficult to judge whether SEMORE really provides comparable and reasonable results with the reported results. Additionally, the authors insisted that SEMORE could minimize the inclusion of false positive structures compared to HDBSCAN (in Supp Fig 17 experimental data), but I'm uncertain whether the filtered localizations are indeed false positive structures or positive structures that should not be filtered because there is no related data shown. To make a reasonable comparison of their results with others, quantitative comparisons should be provided. + +## Response 2.2: + +We thank the reviewer for allowing us to clarify and improve the presentation of the additional experimental data we use to showcase the operational utility of SEMORE. The quantification of + +<--- Page Split ---> + +SEMORE performance is extensively validated on simulated data where there is undoubtedly ground truth (supplementary figs 4, 11, 13, etc.). Comparison of performance on experimental data however requires ground truth which is only attained by field specific expert knowledge. While we had already some quantification, as we detail below, we felt that directly and outloud comparing SEMORE with existing methods dealing with experimental data where there is no strictly defined ground truth might be misinterpreted as criticism to our esteemed colleagues and future collaborators. Therefore, we had kept it minimal in the original manuscript especially as methods and research goals are different. To fully address the comment of the reviewer we now provide below the requested additional quantitative comparison. + +## SI figure 17. + +Supplementary figure 17 included reported area per cluster as Nieves et al and we had even chosen the same plotting style for easier comparison. We had also emphasized that the two approaches calculate area differently, i.e., convex hull counting white space (Nieves et al) vs Delaney triangulation and edge pruning to avoid redundant white space (ours). The comparison of the two methods was already displayed in Supplementary figure 20. + +To further strengthen the quantitative comparison, we provide: + +a) a comparison of Nieves et al and SEMORE that show an \(88\%\) agreement in categorizing detections as noise, showing that SEMORE and Nieves et al have agreement in which detections are noise and which are signal. +b) a raw count of the number of protein assemblies identified by SEMORE across the 15 experiments provided in Nieves et al and compared to the declared results in Nieves et al. We report that SEMORE identifies \(82\%\) of clusters found by Nieves et al (130 out of 158 assemblies) thus supporting SEMORE obtains comparable results, while also providing morphological fingerprints of each assembly. + +Importantly, Nieves et al use a DBSCAN with parameters (eps = 65, minPts = 32) chosen based on highest spatial similarity to one of 10 simulated data scenarios, such settings disfavor smaller clusters thus have inherent tendency to make larger clusters. SEMORE self- parameterized based on the experimental data itself and it includes a round of refinement allowing the capture of smaller clusters and splitting of large into distinct smaller clusters (as seen in main figure 1 and the updated supplementary figure 17). SEMORE captures 9.4 new small clusters per movie that is classified as noise by Nieves et al. SEMORE can easily report the same clusters by turning off the additional refinement and only using the DBSCAN. We stress that experimental data have no ground truth and they are reliant on field expertise, so we would refrain from elaborating in the main text on why SEMORE is better and rather state that the results are similar. Lastly we point out that the comparison of DBSCAN and SEMORE on simulated, and thus ground truth data, is shown in supplementary figure 4 where SEMORE also exhibited clear superiority in detecting clusters and excluding false positives. + +<--- Page Split ---> +![PLACEHOLDER_46_0] + +
Supplementary Fig. 17 (UPDATED): dSTORM data from Nieves et. al1 clustered and quantified by SEMORE a Raw detections from SMLM data of fibroblast growth receptor 1 (FGFR1) on a MCF7 cell presented by Nieves et al.1 b Initial clustering by SEMORE's clustering module using the inherent data-driven model choice of HDBSCAN (Min_cluster_size = 15 and Min_sample = 5). Each localization is colored by its SEMORE annotation, with black representing noise and all other colors representing captured clusters. c The final clustering by SEMORE after refinement and smart density filtering (see Methods). Localizations are colored corresponding to the final SEMORE prediction. Red box depicts the same zoom-in as seen in Nieves et al inside which they report 2 unique clustering indices similar to the initial clustering seen in b. SEMORE's additiona refinement split one of these into four distinct clustered indexes, thus resulting in five clusters. Keeping these settings constant through the 15 datasets from Nieves et al. d Histogram of cluster area estimation. SEMORE identifies mean cluster area of \(0.004 \pm 0.003 \mu m^2\) and median of \(0.003 \mu m^2\). SEMORE provides more fine-grained area calculation than convex hull (see supplementary figure 20) and may split larger clusters to smaller during rounds of refinement. e Distribution of points contained in the proposed clusters with a mean of \(52 \pm 108\) and a median of 29. SEMORE and Nieves et al. obtain qualitative similar results and have 88% agreement in assigning points as noise showing the general agreement as methods
+ +To answer the second comment of the reviewer on minimizing false positives in supplementary figure 17. We assume the reviewer means to compare to Nieves although they use DBSCAN ( "the authors insisted that SEMORE could minimize the inclusion of false positive structures compared to HDBSCAN (in Supp Fig 17 experimental data)"). + +- As attend above, Nieves et al and SEMORE have 88% agreement in categorizing detections as noise- Nieves et al color true and false positives, thus visual inspection of SEMORE's prediction and the declared true and false positives from Nieves et al provide a very clear qualitative estimate of the correspondence. We stress again that since these are experimental data it is hard to strictly define ground truth. We have updated the figure to show the exact + +<--- Page Split ---> + +same field of view as Nieves et al (figure 5 in Nieves et al) to facilitate an easier visual comparison and provided \(88\%\) agreement in categorizing detections as noise showing that the reported results are concordant. + +## SI figure 18. + +Supplementary figure 18 included a direct comparison of the specific example from Wallis et al showing a cluster being captured three times across time and SEMORE capturing the exact same as seen in SI figure 18c- d. + +To provide a further quantification we counted the number of clusters reported in a crop- out from Wallis et al and compared to the raw cluster count identified by SEMORE. Wallis et al have 104 clusters while SEMORE has 107 (See the figure below). We stress that SEMORE not only segments clusters but inherently tracks and links clusters in time for tracking morphology over time. Therefore, we manually counted the areas of interest identified by Wallis et al and by SEMORE in a single frame. + +![PLACEHOLDER_47_0] + + +## SI figure 19 + +Lastly, we are pleased that the results in SI figure 19 were satisfactory and without comments as this example also highlights the ability to generalize across experimental conditions as visually and quantitatively validated to results of Hou et al. To be consistent we also provide a direct comparison demonstrating once more SEMORE is on par with existing toolboxes. + +## Changes in manuscript 2.2: + +To fully address the comment of the reviewer we a) Updated and modified figure text of SI figure 17. + +<--- Page Split ---> + +b) Added the number of identified clusters to supplementary figure 18. "Last snapshot shows the N=107 for the total identified clusters in this snapshot and contains a red box highlighting an additional region of interest."c) Added in supplementary figure 19 en extra sentences for the quantitative comparison "Utilizing the tight packing assumption for RyRs \(^3\) identified RyR clusters SEMORE reports on average of 18 RyR with a median of 14 RyR in line with the 9 RyR reported by Hou et al \(^3\) importantly achieving so without any intensity thresholding."d) Added in section "Precise extraction and quantification of experimental super-resolution data." "While in experimental data sets it is hard to strictly define ground truth SEMORE outputs qualitatively outputs identical predictions with current states of the art." + +## Comment 2.3: + +3. In many figures, particularly in supplementary figures, scale bar information or axis units are missing. Consequently, it is challenging for me to judge whether the clustering or filtering is biologically relevant in their image data. Additionally, in supplementary Figure 17 d-f, it appears that the x-axis is meaningless, so a scatter plot for density vs. N or Area would be more reasonable. + +## Response 2.3: + +We agree with the reviewer's suggestion towards remaking supplementary Figure 17 d-f to be more easily readable. We were following the plotting template of Nieves et al for a more direct and easier comparison (see answer to reviewer comment 2.2) but following the reviewer's suggestion that the x-axis is meaningless we move away from Nieves et al plotting approach and now display histograms in the revised supplementary fig. 17. + +The reviewer also commented: "scale bar information or axis units are missing. Consequently, it is challenging for me to judge whether the clustering or filtering is biologically relevant in their image data." + +We fully agree that the scale bar is instrumental for judging dimensions of the morphologies. + +In the initial response to reviewer 1 we had already explained that SEMORE is purposefully designed to be dimension- independent, therefore the simulated data are without a scale bar, to which they responded: "The extra benchmarking and highlighting the scale invariance has significantly improved the manuscript and will be a very useful tool for SMLM cluster analysis and classification. I fully recommend the revised manuscript for publication." + +Please see the full question and response at the end of this section in blue colour fonts. + +However, we realize that snapshots from the data in main figure 4 seen in supplementary figures 24 and 25 did not contain error bars and only the full scale figure 4 did. We have now rectified this and we thank the reviewer for noticing this. + +As we detail below the scale invariance of SEMORE is due to our choice of 3D axis standardization. Working with standardized dimensions enables SEMORE to work across experimental configurations and dimensionalities. This allows SEMORE to operate independently of the imaging dimension and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area. + +<--- Page Split ---> + +Therefore, the simulated data is of arbitrary units, and we did not include a scale bar, however we have now included scale bars with "a.u" for units based on the reviewer's comment. + +We emphasize that SEMORE proves its dimension independence by accurate segmentation across the 5 diverse biological systems spanning from nanometer to micrometer and further by extensive quantification on simulated data at different scales. This should also help the reviewer to "judge whether the clustering or filtering is biologically relevant in their image data". The simulated data included in the manuscript supports the experimental data and serves as ground truth quantifying the output of SEMORE. + +## Changes in manuscript 2.3: + +1) Acknowledging the scale invariance may not be clear to the audience we have added an extra short section in results section that already discusses the scale invariance: "This allows SEMORE to operate independently of the imaging and cluster dimensions and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area." + +2) We have added the histograms in Supplementary figure 17 + +3) We have added scale bars on a.u in the simulated data in Supplementary figures 1, 2, 13, 20, 21 and scale bars at the experimental snipsets displayed in Supplementary figures 24, 25. + +4) We further refer to the comment and response of the first round of review (in blue below): + +5) We add in the discussion the key result that SEMORE agnostically segments across five experimental data sets spanning nanometers to micrometers by modifying an existing sentence." Effectively, SEMORE operates across five experimental data sets with spatial dimensions spanning 3 orders of magnitude from nanometer \(^{58}\) to micrometers \(^{19}\) and temporal dimensions spanning from milliseconds \(^{60}\) to second \(^{19}\) . This fact provides strong support for SEMORE as a universal, input-independent model for the SMLM community to use in conjunction with, or to be incorporated into SMAP, or as a convenient standalone toolbox" + +## Comment 1.1 (reviewer 1, first round) + +The clusters within the simulated data seem to be very large in scale, some on the order of 10 microns. This is likely to be an uncommon scenario in biological SMLM data, especially when it comes to clustering of that data. I would recommend some simulations on the scale of the NPC data, i.e., several clusters sub- micron with diverse morphology. A recent paper cited in the manuscript proposed several different clustering scenarios at this scale (Nieves et al., NatMeth, 20, pages 259- 267, 2023) where two different cluster types are present within the region. This would be really nice to see clusters of similar density (in that paper it was approximately 10- 20 per 3x3 micron2), but analysed in a similar fashion here, i.e., analysis of the whole 40x40 micron region. This would be quite powerful if whole fields of view could be analysed quickly, without the need for subdivision of the data (see later point on performance). + +## Response 1.1 + +<--- Page Split ---> + +The reviewer correctly points out that large aggregates are generally depicted in the manuscripts. We stress here that SEMORE clustering module is scale- invariant and solely relies on localisations. This is due to our choice of 3D axis standardization. Working with standardized dimensions enables SEMORE to work across experimental configurations and dimensionalities. This allows SEMORE to operate independently of the imaging dimension and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area. + +The comment still raises a very valuable point on the generalization and performance of SEMORE and to demonstrate this and fully answer the comment of the reviewer we performed two studies: + +1) Simulated diverse, nanometer dimension structures, and quantified SEMORE performance on their segmentation and classification for data with 8, 15 and 25 localisations in an area that corresponds to \(\sim 1\mathrm{um}\) . As can be seen in Supplementary Fig. 8 (Response figure 5) in the revised version, SEMORE reached an accuracy of \(>90\%\) in extracting clusters with 8 or more localisations with the morphology fingerprinting completely separating true clusters from noise. + +2) Simulated protein assemblies of just 4 detections and evaluated SEMORE's performance on such a small cluster representing the minimal representation of a tetramer. SEMORE achieves accuracies of up to \(70 - 90\%\) in segmenting these tiny structures depending on the noise levels while the morphological fingerprinting module captures these noisy detections allowing for potential post-processing and accuracy increase, Supplementary Fig. 7 (Response figure 4). + +3) Evaluated the number of points needed for SEMORE to accurately detect the initiation points of spatially overlapping clusters. The high accuracy of SEMORE to capture initiation points can be quantified and visualized using simulated data showing is just \(\sim 13\) frames off on average across 3 types of spatially overlapping morphologies. Furthermore, qualitative assessment using experimental data of temporally resolved insulin aggregation supports the reliability of SEMORE, Supplementary Fig. 5+6, response figure 6+7). + +In essence, \(\sim 10\) detections is enough for SEMORE to obtain high segmentation and classification accuracy which is well below the common number of detections in most SMLM experiments. We analyze dSTORM data of Nieves et al. NatMeth, 20, pages 259- 267, 2023 1 obtaining similar densities and cluster sizes but in fact analyzing the entire field of view at once see new SI fig 17 (response figure 1). We further use the approach from Nieves et al., NatMeth, 20, pages 259- 267 to simulate structures with blinking, see comment 1.3. + +## Changes in the manuscript 1.1 + +To fully address the comment of the reviewer in the revised version of the manuscript we have added a new section within "Accurate extraction of individual assemblies across diverse biologically inspired growth types.": + +"To further evaluate the performance of SEMORE on segmentation and analysis of dynamic SMLM data we performed a series of stress tests on simulated data. We firstly evaluated SEMORE's ability to track morphological changes in time using simulated data of 3 types of spatially overlapping protein clustering morphologies with temporal information included. Snapshots of SEMORE's clustering in time provide visual confirmation of SEMORE's ability to track morphological changes in time (see Supplementary Fig. 5 for snapshots of simulated and Supplementary Fig. 6 for experimental data). Further quantification of SEMORE's ability to accurately track and segment spatially overlapping protein assemblies in time reveals growth onset times across 3 morphological classes are predicted with an average offset of just \(\sim 13\) frames (Supplementary Fig. 6). Subsequently, we test the clustering module on + +<--- Page Split ---> + +simulated, sparse structures containing as little as 4, 8, 15 and 25 point detections akin to data of protein oligomerization (see Supplementary Fig. 7 & 8). SEMORE analyzes the entire field of view at once and extracts structures down to 4 detections while maintaining \(>90\%\) accuracy at biologically relevant noise to signal ratios. The morphological fingerprinting module can further refine the false positive detections from noise with as little as 4 detections, achieve full separation from noise at 8 detections and classify morphological classes in true structures at 15 detections (see Supplementary Fig. 8 & 9). Lastly we evaluated its performance to degenerative structures that shrink in time, akin to protein de- polymerisation. SEMORE accurately segments 3 anisotropically degenerative morphologies showcasing it can be used to analyze dynamic shrinkage or depolymerisation of protein clusters (see Supplementary Fig. 10). In essence SEMORE only requires \(< 10\) detections to accurately segment and classify heterogeneous structures with dynamic morphologies further demonstrating its operational utility and potential for 4D SMLM.". + +Elaborated in results on the scale invariance: + +" The clustering module of SEMORE consists of multiple steps that self- parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools." In addition, to address the comment we have added 5 new SI figures, namely Response figures: 1,4,5, 6, and 7. + +## Comment 2.4: + +4. Although the authors performed additional simulations with various noise variations, I don't understand some of the data. For example, Supplementary Figure 3 shows an increasing accuracy with an increasing ratio of heterogeneous, non-uniform noise, which is contrary to the general expectation. This could be because the data in Supplementary Figure 3c were obtained from just one-time simulation for each noise ratio (there is no error bar in this data), which could not demonstrate the general trend very well. While the authors claimed that the smart-density noise filter is designed to expect noise and remove true positives, such a case could lead to incorrect filtration for real images with low noise as well. Since different SMLM microscopes and different biological samples can produce various noise levels, I believe that if such an effect exists in their analysis method, it should be resolved. + +## Response 2.4: + +We appreciate the feedback for the missing clarity in Supplementary Fig. 3 and for allowing us to rectify this. The current supplementary fig. 3 relies on the data displayed in Supplementary fig 2, which, as stated in the figure legend, is a summary across 5 separate simulations each containing 13 protein assemblies. In addition, we do display in both Supplementary figures 2 and 3 an error- metric across the 5 simulations by showing the variance of accuracy, i.e. the squared standard deviation (orange line at \(\sim 12\%\) ). We thank the reviewer for pointing out that this was not clear enough and we have now further clarified this in the figure legend. + +The reviewer also commented on an upward trend in accuracy. We agree that the first 2 of 16 points display an upwards trend until the accuracy curve flat lines from point 3 to 16. These 2 points are associated with both the largest variation in accuracy and the lowest accuracy. In addition, these points represent experimental conditions with extremely low noise or no noise at all, unlikely for any single molecule localisation experiment. We had commented already on this in the figure legend stating that "at unrealistically low noise levels the smart density filter expects noise and removes true positives if no noise is present, and that this can be easily turned off." + +<--- Page Split ---> + +We emphasize that the smart noise filter only lowers accuracy for the case of no noise or noise being 10 times less than signal. The filter is easily turned off for users operating with systems that do not produce any noise or next to no noise, albeit we are unaware of such technological development. A realistic noise level is displayed by the blue shaded area. While we were aware of the above, we kept the filter on for transparency into SEMORE's output. + +To address the reviewer comment and alleviate any confusion we ran SEMORE without the noise filter (see new panel in Supplementary fig 3). As expected, not utilizing smart density filtering results at better accuracy at unrealistically low noise levels, but accuracy declines at, and above, realistic noise levels. Importantly and directly addressing the reviewer's concern SEMORE's segmentation accuracy at the extremely low or no noise levels joined the high accuracy displayed at the more realistic noise cases. + +![PLACEHOLDER_52_0] + +
Supplementary Fig 3: Benchmarking SEMORE on for heterogeneous, non-uniform noise.
+ +a) Simulated data as described and used in SI fig. 2, that includes 5 separate simulations with 13 protein assemblies each, but now exhibiting a heterogeneous noise profile. Heterogeneous noise is generated by introducing 5-25 "noise seeds" each containing 20-50 points have been added to each simulation, additionally, individual Gaussian distributed shifts have been applied to all initial noise points. b) we see SEMORE clustering classification performance as out-of-the-box. c) Evaluating SEMORE clustering performance versus increasing noise ratio (blue area representing biologically relevant noise-levels estimated from real data and with vertical blue line representing insulin experiments). At biologically relevant noise levels or high noise levels accuracies of SEMORE is observed to be above \(\sim 90\%\) with variance accuracy of \(\sim 12\%\) from noise ratio \(\sim 0.2\) and onwards with up to \(93\%\) at 0.7 noise ratio reflecting SEMORE's ability to separate non-uniform noise also observed in robust treating of experimental insulin data (see main fig. 4). The unrealistic conditions with extremely low noise ratios or no noise at all are associated with lower accuracies as the smart-density noise filter expects noise and removes true positives if no noise is present, which is easily countered by turning it off.d) SEMORE's clustering performance on the same data set without the smart noise filter (blue area representing biologically relevant noise-levels estimated from real data and with vertical blue line representing insulin experiments). SEMORE accuracy is above \(\sim 90\%\) from conditions with no noise up to around noise ratios of \(\sim 1\) + +<--- Page Split ---> + +Turning off the noise filter results in better performance at extremely and unrealistically low or no noise ratios (zero noise to noise- to- signal ratio of 0.1), but the performance strongly declines starting from around biologically relevant noise levels. For users operating with little or no noise in their experimental system the results indicate the smart filter should be turned off while users operating with realistic noise are recommended to utilize the full SEMORE pipeline. + +## Changes in manuscript 2.4: + +1. We highlight in the text that users should evaluate performance on their given system without the noise filter and turn smart density filtering off, only at unrealistically low noise levels, adding in the 2nd paragraph of section "Accurate extraction of individual assemblies across diverse biologically inspired growth types." + +While at unrealistically low noise ratios i.e ten times lower than signal, smart density filter can result in removal of true positives, we recommend using the full SEMORE pipeline for data with noise (Supplementary Fig. 3)". + +2. Added a new panel in supplementary fig 3 showing SEMORE's performance without the noise filter. + +3. We emphasize in the figure text of SI figure 3 that it is based on 5 simulated data sets with 13 protein assemblies each. + +## Comment 2.5: + +5. Regarding the responses for my fourth comment (2.4), I do understand that unsupervised learning is also a significant component of machine learning. My previous comments might be somewhat unclear in conveying my intended message. During the SEMORE clustering process, there are several steps involved in clustering meaningful points. The methods you have suggested in this paper to enhance clustering primarily focus on filtering out points and implementing temporal refinements. My point of concern is related to what happens once the filtered and refined points are available. I am uncertain about the contributions of this work to the "machine-learning-based clustering algorithm" at this stage. Even if the filtering and temporal refinements can potentially aid subsequent machine-learning-based clustering algorithms, they are difficult to be considered as a machine-learning algorithm by themselves. Therefore, I am curious if you have made any contributions to the "machine-learning-based clustering algorithm itself" apart from hyperparameter tuning in existing methods like DBSCAN. Examples of such contributions might include modifications to the loss function, alterations to the architecture, improved training techniques, and so on. + +## Response 2.5: + +Thank you for allowing us to elaborate further on this. We would like to emphasize two key points: Firstly, the reviewer states that "What happens once the filtered and refined points are available" It is important to note that without the developed modalities of SEMORE, (Automatic, data- driven model selection, semi- supervised hyperparameter choices based on experimental data, topological failsafe, Smart noise filtering and temporal refinement,) the correct clustering and segmentation of experimental data and tracking its morphology in time is not easily available, see main figure 1b vs 1d or SI figure 4. Effectively the SEMORE pipeline, building on existing models, contributes to the field by providing a universal automated and self- parameterized pipeline efficiently resolving a major obstacle that challenges the widespread implementation of SMLM, that of analysis and segmentation of the data. + +<--- Page Split ---> + +The reviewer also comments "Even if the filtering and temporal refinements can potentially aid subsequent machine- learning- based clustering algorithms...they are difficult to be considered as a machine- learning algorithm by themselves." We stress here that the refinement and filtering do not all happen prior to DBSCAN or HDBSCAN but rather as rounds of refinement in the pipeline. These rounds are both before and after the initial clustering by current methods, although mostly after. We are thus confused as to how such a scenario should be imagined, but if users somehow already have their refined and filtered points available, we contribute with the morphological fingerprinting module for further quantification. + +The reviewer continues: "... Therefore, I am curious if you have made any contributions to the "machine- learning- based clustering algorithm itself" apart from hyperparameter tuning in existing methods like DBSCAN...". We wish to highlight a few papers in interdisciplinary journals2- 5 that present methods built on existing foundational tools repurposed to work for specific fields. Whether contributions are contributions to the "machine- learning- based clustering algorithm itself" appears more semantic of nature rather than objective. For instance, Chen et al4 and Walker et al3 both enriched an existing machine learning tool, also DBSCAN, with approaches such as filtering, Otsu's algorithm, constructing graphs etc. to obtain results otherwise not readily unobtainable. Likewise, we enrich an existing tool that could not function properly for super- resolution data, extract the results of the manuscript, and do so across diverse experimental conditions and biological systems. Importantly, our method automates the agnostic analysis of super- resolution data across experimental conditions and biological systems as clearly demonstrated by the application to 5 diverse experimental datasets. + +We could further argue that the original DBSCAN/(HDBSCAN) optimizes some objective function \(\mathsf{f}(\mathbf{x})\) but we optimize \(\mathsf{g}(\mathsf{f}(\mathbf{x}))\) where \(\mathsf{g}\) is our contributions working both prior and after the output of DBSCAN. In fact, unsupervised machine learning clustering in general groups points based on characteristics by optimizing some objective function. Our contribution effectively changes these characteristics, the pipeline and thus the outcome of the ML model. This can be seen as either changing the training approach or changing the architecture/pipeline. + +We are in fact carefully phrase our contribution as a new approach to analyze super- resolution data that enables analysis across experiments and systems, something that was easily accessible before (see also main figure 2 and Supplementary figures 4, and 19 for DBSCAN and SEMORE on simulated experimental data). " SEMORE, a semi- automatic machine learning framework for universal, system and input- dependent, analysis of super- resolution data" + +## Bibliography + +1. Nieves, D. J. et al. A framework for evaluating the performance of SMLM cluster analysis algorithms. Nat. Methods 20, 259-267 (2023). + +2. Yu, W., He, B. & Tan, K. Identifying topologically associating domains and subdomains by Gaussian Mixture model And Proportion test. Nat. Commun. 8, 535 (2017). + +3. Walker, B. L. & Nie, Q. NeST: nested hierarchical structure identification in spatial transcriptomic data. Nat. Commun. 14, 6554 (2023). + +<--- Page Split ---> + +4. Chan, H. et al. Machine learning coarse grained models for water. Nat. Commun. 10, 379 (2019). + +5. Mulhall, E. M. et al. Direct observation of the conformational states of PIEZO1. Nature 620, 1117-1125 (2023). + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #2 (Remarks to the Author): + +The authors addressed all the concerns I had regarding the previous version of the manuscript. I appreciate that the authors went the extra mile to address the various concerns. + +<--- Page Split ---> diff --git a/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..a2c4f017ce94da00910c531a4348d9314aaaca0f --- /dev/null +++ b/peer_reviews/df3de3d8c7d91f0d203417db0fe2f15c4684035139c8fd4c4d617971c9c6ca76/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1407 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 508, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 162, 912, 220]]<|/det|> +SEMORE: SEGmentation and MORphological fingErprinting by machine learning automates super- resolution data analysis + +<|ref|>image<|/ref|><|det|>[[56, 732, 240, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 914, 800]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 312, 97]]<|/det|> +## Reviewers' comments: + +<|ref|>sub_title<|/ref|><|det|>[[119, 125, 443, 140]]<|/det|> +## Reviewer #1 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[118, 153, 876, 308]]<|/det|> +Bender et al., present a machine learning based clustering and classification algorithm, SEMORE, for the segmentation of diverse cluster morphologies from heterogenous SMLM data. Being able to identify and segment clusters in heterogenous data is a key problem in SMLM, so the algorithm is a well- placed idea for addressing this. The algorithm is initially demonstrated on simulated data, consisting of 3 biologically relevant clustering scenarios; symmetric clusters, asymmetric clusters (non- equal growth) and fibre- like structures. The algorithm is then demonstrated on real experimental SMLM data, namely insulin aggregation and nuclear pore complex data. In the case of the insulin aggregation, with challenges in segmentation were overcome using temporal information. The paper addresses two important problems with clustering of SMLM data in general; the need for user inputs to define the segmentation, and post- analysis classification of segmented clusters to understand biological phenomena of protein distributions and assembly. + +<|ref|>text<|/ref|><|det|>[[118, 308, 875, 393]]<|/det|> +The manuscript is well presented and easy to follow. Furthermore, the SEMORE software is easy to find with clear installation instructions. However, I found it slightly challenging to get running in a new environment (admittedly I have a basic working knowledge of python, but see below comment). Additionally, the data from the publication was all provided, and easy to look through, which should be highly commended. There are a couple of conceptual and practical points, however, that I think need addressing, which would strengthen the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 405, 819, 420]]<|/det|> +I would recommend publication of the manuscript if the comments below can be addressed. + +<|ref|>text<|/ref|><|det|>[[118, 434, 252, 447]]<|/det|> +Major comments: + +<|ref|>text<|/ref|><|det|>[[117, 448, 876, 589]]<|/det|> +- The clusters within the simulated data seem to be very large in scale, some on the order of 10 microns. This is likely to be an uncommon scenario in biological SMLM data, especially when it comes to clustering of that data. I would recommend some simulations on the scale of the NPC data, i.e., several clusters sub-micron with diverse morphology. A recent paper cited in the manuscript proposed several different clustering scenarios at this scale (Nieves et al., NatMeth, 20, pages 259-267, 2023) where two different cluster types are present within the region. This would be really nice to see clusters of similar density (in that paper it was approximately 10-20 per 3x3 micron2), but analysed in a similar fashion here, i.e., analysis of the whole 40x40 micron region. This would be quite powerful if whole fields of view could be analysed quickly, without the need for subdivision of the data (see later point on performance). + +<|ref|>text<|/ref|><|det|>[[117, 589, 872, 686]]<|/det|> +- It would be interesting to know a little more about the limits of SEMORE, as in biological SMLM data there may be several different classes of cluster, which may have stronger similarities, within the same ROI. For example, if a protein is present as a monomer and can assembles into higher order oligomers, it might be expected there are some low-level oligomers (4 proteins clustered proteins at sub-diffraction, e.g., tetramers) in the data at time of fixation. Would these small clusters be distinguishable from the noise class? Some examples of how SEMORE deals with this low-level oligomerisation (low-density clusters) would strengthen the manuscript. + +<|ref|>text<|/ref|><|det|>[[117, 686, 878, 841]]<|/det|> +- Following on from this point, one thing lacking from the manuscript is any comment on a common problem for arguably the two most common SMLM techniques (PALM, and dSTORM - used here); multiple blinking of the fluorophore. Normally, this introduces artefactual clustering into the SMLM data, and several approaches now exist for correcting this (e.g., Jensen et al., NatMeth, 19, pages 594-602, 2022, and Bohrer et al., NatMeth, 18, pages 669-677, 2021). Thus, is relation to biological data, some structures that may appear clustered, and then segmented in uncorrected data, will not be so after correction, shifting the observed distributions of the classes. Would the authors recommend such corrections before use of SEMORE for accurate fingerprinting? Also, some sense of how the lack of blink correction could impact classification would be beneficial. This could be done by comparing a ground truth of the molecule positions and a version where the data has added blinking. + +<|ref|>text<|/ref|><|det|>[[118, 841, 252, 854]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[118, 855, 860, 910]]<|/det|> +- All figures showing SMLM data or plots of clusters etc. need a scale bar or some axes. It was hard to appreciate, until using the code, how different the length scale of the clusters between simulations and experimental data were (some several microns, whilst NPC data is much smaller scale) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 877, 183]]<|/det|> +- I ran the SEMORE installation as directed on the GitHub, generating a new environment. I found quickly that I was missing the dependencies needed to run the scripts (e.g., opencv in the dependency file should be opencv-python, I assume this is why this file may not have worked for me). Further, other more basic packages are of course not there in a new environment, e.g., pandas, numpy, etc., and require the user to add them. I would recommend the authors give a full and correct dependencies file, as this troubleshooting would be beyond many of the potential users with limited coding experience. + +<|ref|>sub_title<|/ref|><|det|>[[120, 231, 442, 246]]<|/det|> +## Reviewer #2 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[117, 260, 877, 510]]<|/det|> +Bender et al. present SEMORE, SEGmentation and MORphological fingErprinting, as a semiautomatic machine learning framework for the analysis of super- resolution data to extract and quantify protein structures. By implementing a multi- layered density- based clustering module and a morphology fingerprinting module for quantification, they demonstrated SEMORE on simulations and experimental super- resolution data, including insulin aggregates and nuclear pore complexes. Developing automatic clustering analysis without a priori knowledge and tracking the temporal evolution of morphology changes of protein clustering from single- molecule localization microscopy image data is certainly a good direction for the development of super- resolution microscopy field. However, in my view, their demonstrations are limited to the analysis of the growth of immobile clusters under well- controlled noise conditions, which could be quite different from general biological behaviors. This raises concerns about the limited applicability of this method. Additionally, although the authors insist that their method represents the first time- aware framework for 4D super- resolution data, they mainly focus on presenting the classification results for protein cluster growth, without showing identified cluster images at each time point. Therefore, it is hard to judge whether their method can effectively capture the temporal changes of protein clusters. To claim that their method is genuinely powerful for automatic clustering analysis and tracking the temporal evolution of protein clusters, they should also show the time- resolved clustering data. + +<|ref|>text<|/ref|><|det|>[[117, 512, 876, 710]]<|/det|> +Furthermore, I cannot see the significant novelty of this method; they mainly used the reported clustering method (DBSCAN) for cluster identification. Although it appears that they additionally conducted temporal refinement after the DBSCAN analysis, this additional step seems to be mainly for dissecting clusters over time, rather than advancing the clustering analysis method. The new development of their method seems to be a morphology fingerprinting module that uses multiple feature vectors for quantification. However, the performance of this method for real experimental time- resolved super- resolution image data was demonstrated only for the relatively new imaging method REPLOM, which is not a general type of data. To demonstrate the general performance of this method, the authors should present more general time- resolved single- molecule localization microscopy data, rather than static dSTORM data. Although the authors applied their method to NPC data, it appears to be just static data, and the categorization of the clusters is not biologically meaningful (individual, overlapped, noise). For these reasons, I believe the authors' claims are not well supported, which unfortunately does not warrant publication in Nature Communications in the current form of the manuscript. + +<|ref|>text<|/ref|><|det|>[[118, 710, 872, 809]]<|/det|> +1. As suggested above, the main problem with the current manuscript is the lack of time-resolved analyzed data. They only showed the classification results from simulation data for isotropic, random, and fibril growth. However, the time-resolved cluster morphological change data (at each time point) should also be presented to assess whether their method correctly identified each growth pattern. Additionally, I would like to see the time-scaled morphological changes of insulin aggregates and nuclear pore complexes from experimental data to evaluate whether their method performs well even with real data under heterogeneous noise conditions. + +<|ref|>text<|/ref|><|det|>[[118, 822, 867, 891]]<|/det|> +2. The demonstrated data seems to only focus on the growth of clustering. However, changes in protein clusters in the real world could involve not only cluster growth but also significant morphological changes (e.g., spherical to tubular), shrinkage, movement, and scattering (depolymerization). For wider applicability of this method, the authors should include related data as well. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 864, 182]]<|/det|> +3. Their demonstration is mostly based on simulation data, where the noise appears to be well controlled and homogeneous. Although they tested this method under different noise density conditions, it seems that the density they used is uniformly distributed across the entire field of view and throughout the entire time domain, which could differ from real conditions. Additionally, the intensity of noise could be heterogeneous. Because such heterogeneity of noise could affect the identification and classification of protein clusters, they should test the method with various types of noise. + +<|ref|>text<|/ref|><|det|>[[118, 196, 870, 294]]<|/det|> +4. The authors claim that the use of a machine learning-based method is an important aspect of this study. However, the machine learning method employed in this paper appears to be limited to unsupervised point clustering, rather than classification or other methods. Moreover, these unsupervised point clustering methods used here do not seem to differ significantly in terms of methodology from the existing method, DBSCAN. I believe the authors have not sufficiently explained why the method they used can be considered a machine learning approach and what sets it apart as a novel contribution compared to existing methods. + +<|ref|>text<|/ref|><|det|>[[118, 308, 878, 434]]<|/det|> +5. In the Fingerprinting module, it is mentioned that over 40 features were utilized to analyze the properties of each cluster using various methods. However, it appears that a comprehensive assessment of the strengths and weaknesses of these methods was not conducted. It is unclear why the given methods are expected to yield good features for cluster classification. Additionally, it would be beneficial to determine if all the provided methods are necessary based on the analysis results. For instance, Supplementary Figure 8 suggests that it might be possible to identify a better method instead of using all the feature vectors obtained from each feature. There is a possibility that some of them could even interfere with the analysis process, so it would be insightful to see further results in this regard. + +<|ref|>text<|/ref|><|det|>[[118, 448, 877, 533]]<|/det|> +6. In general, the methodology is not thoroughly explained. For instance, even if the method applied in the existing DBSCAN is used as is, it would be helpful if the methodology were described in more detail. Additionally, the methodology for the classification of each point, which occurs after the fingerprinting module and embedding with UMAP, is not elaborated very well. Since the fingerprinting module appears to be the only distinctive novelty of this method, as mentioned above, it should be described in detail to provide a clearer understanding. + +<|ref|>sub_title<|/ref|><|det|>[[120, 574, 442, 588]]<|/det|> +## Reviewer #3 (Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[118, 602, 874, 673]]<|/det|> +The manuscript entitled "SEMORE: SEGmentation and MORphological fingErprinting by machine learning automates super-resolution data analysis" by Hatzakis et al introduces SEMORE, a semi-automatic machine learning framework for universal, system and input-dependent, analysis of super-resolution data. The manuscript is well written and informative. However, this manuscript can be improved by addressing the following issues: + +<|ref|>text<|/ref|><|det|>[[118, 686, 870, 742]]<|/det|> +1. The authors have developed a new analytical tool SEMORE to extract and quantify underlying structures limiting single-molecule localization microscopy (SMLM). How this newly developed tool SEMORE is better suited with SMLM than some of the previous employed tools such as SMAP (modular super-resolution microscopy analysis) + +<|ref|>text<|/ref|><|det|>[[118, 756, 815, 785]]<|/det|> +2. The authors should explain how SEMORE deals with commonly occurring supervised and unsupervised machine learning problems. + +<|ref|>text<|/ref|><|det|>[[118, 799, 835, 826]]<|/det|> +3. The authors should also highlight the role of SEMORE in advancement of machine learning-based approaches. + +<|ref|>text<|/ref|><|det|>[[118, 841, 858, 897]]<|/det|> +4. Since vibrational and spherical aberrations prove to be greater hindrance at high resolution. Moreover, live samples are more adversely affected by super-resolution imaging because of high excitation intensity or extended exposure times. Does the SEMORE tool take these concerns into consideration? + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 87, 450, 112]]<|/det|> +## Reviewers response + +<|ref|>text<|/ref|><|det|>[[148, 135, 852, 152]]<|/det|> +Reviewer 1 2 + +<|ref|>text<|/ref|><|det|>[[150, 155, 852, 250]]<|/det|> +General response 2 Comment 1.1 2 Comment 1.2 4 Comment 1.3 5 Minor comments: 6 + +<|ref|>text<|/ref|><|det|>[[150, 252, 850, 270]]<|/det|> +Reviewer 2 6 + +<|ref|>text<|/ref|><|det|>[[150, 270, 852, 395]]<|/det|> +General response 7 Comment 2.1 9 Comment 2.2 12 Comment 2.3 14 Comment 2.4 14 Comment 2.5 17 Comment 2.6 18 + +<|ref|>text<|/ref|><|det|>[[150, 397, 850, 415]]<|/det|> +Reviewer 3 19 + +<|ref|>text<|/ref|><|det|>[[150, 415, 850, 505]]<|/det|> +General response 19 Comment 3.1 20 Comment 3.2 20 Comment 3.3 22 Comment 3.4 23 + +<|ref|>text<|/ref|><|det|>[[150, 508, 850, 525]]<|/det|> +Figures 25 + +<|ref|>text<|/ref|><|det|>[[200, 525, 850, 558]]<|/det|> +Response Figure 1: dSTORM data from Nieves et. al. 1 clustered and quantified by SEMORE 25 + +<|ref|>text<|/ref|><|det|>[[201, 559, 850, 591]]<|/det|> +Response figure 2: Sx1a- mEos2 sptPALM data from Wallis et. al. 3 clustered and temporally quantified by SEMORE. 26 + +<|ref|>text<|/ref|><|det|>[[201, 593, 850, 625]]<|/det|> +Response Figure 4 Evaluation of SEMORE on temporarily resolved live- cell PALM data of ryanodine receptors (RyRs). 27 + +<|ref|>text<|/ref|><|det|>[[201, 626, 850, 658]]<|/det|> +Response Figure 4: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies. 28 + +<|ref|>text<|/ref|><|det|>[[201, 660, 850, 692]]<|/det|> +Response figure 5: SEMORE classification performance for small, sparse clusters of diverse morphologies. 29 + +<|ref|>text<|/ref|><|det|>[[201, 693, 850, 725]]<|/det|> +Response Figure 6: Deconvolution of temporal refinement on real and simulated data. 31 + +<|ref|>text<|/ref|><|det|>[[201, 727, 850, 759]]<|/det|> +Response Figure 7: Visual representation of SEMORE's ability to capture morphological growth in time 32 + +<|ref|>text<|/ref|><|det|>[[201, 760, 850, 793]]<|/det|> +Response Figure 8: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters. 33 + +<|ref|>text<|/ref|><|det|>[[201, 794, 850, 825]]<|/det|> +Response Figure 9: Benchmarking SEMORE on for heterogeneous, non- uniform noise. 34 + +<|ref|>text<|/ref|><|det|>[[201, 827, 850, 859]]<|/det|> +Response Figure 10: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes. 35 + +<|ref|>text<|/ref|><|det|>[[201, 860, 850, 877]]<|/det|> +Response Figure 11: Demonstration SEMORE clustering of morphology shrinkage 35 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 85, 262, 103]]<|/det|> +## Reviewer 1 + +<|ref|>text<|/ref|><|det|>[[149, 112, 846, 320]]<|/det|> +Bender et al., present a machine learning based clustering and classification algorithm, SEMORE, for the segmentation of diverse cluster morphologies from heterogenous SMLM data. Being able to identify and segment clusters in heterogenous data is a key problem in SMLM, so the algorithm is a well- placed idea for addressing this. The algorithm is initially demonstrated on simulated data, consisting of 3 biologically relevant clustering scenarios; symmetric clusters, asymmetric clusters (non- equal growth) and fibre- like structures. The algorithm is then demonstrated on real experimental SMLM data, namely insulin aggregation and nuclear pore complex data. In the case of the insulin aggregation, with challenges in segmentation were overcome using temporal information. The paper addresses two important problems with clustering of SMLM data in general; the need for user inputs to define the segmentation, and post- analysis classification of segmented clusters to understand biological phenomena of protein distributions and assembly. + +<|ref|>text<|/ref|><|det|>[[150, 320, 840, 440]]<|/det|> +The manuscript is well presented and easy to follow. Furthermore, the SEMORE software is easy to find with clear installation instructions. However, I found it slightly challenging to get running in a new environment (admittedly I have a basic working knowledge of python, but see below comment). Additionally, the data from the publication was all provided, and easy to look through, which should be highly commended. There are a couple of conceptual and practical points, however, that I think need addressing, which would strengthen the manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 457, 835, 474]]<|/det|> +I would recommend publication of the manuscript if the comments below can be addressed. + +<|ref|>sub_title<|/ref|><|det|>[[151, 512, 334, 532]]<|/det|> +## General response + +<|ref|>text<|/ref|><|det|>[[150, 538, 839, 641]]<|/det|> +We are grateful for the favorable and critical comments, for acknowledging the manuscript easy to follow and for recommending publication after the comments are addressed. Fully and in detail addressing the "conceptual and practical" comments helped us further improve the manuscript and the quality and user- friendliness of our open- source implementation on Github. Figures created following your and other reviewers comments have been pasted below for your convenience. + +<|ref|>sub_title<|/ref|><|det|>[[151, 661, 285, 680]]<|/det|> +## Comment 1.1 + +<|ref|>text<|/ref|><|det|>[[150, 687, 840, 877]]<|/det|> +- The clusters within the simulated data seem to be very large in scale, some on the order of 10 microns. This is likely to be an uncommon scenario in biological SMLM data, especially when it comes to clustering of that data. I would recommend some simulations on the scale of the NPC data, i.e., several clusters sub-micron with diverse morphology. A recent paper cited in the manuscript proposed several different clustering scenarios at this scale (Nieves et al., NatMeth, 20, pages 259–267, 2023) where two different cluster types are present within the region. This would be really nice to see clusters of similar density (in that paper it was approximately 10-20 per 3x3 micron2), but analysed in a similar fashion here, i.e., analysis of the whole 40x40 micron region. This would be quite powerful if whole fields of view could be analysed quickly, without the need for subdivision of the data (see later point on performance). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[151, 85, 283, 103]]<|/det|> +## Response 1.1 + +<|ref|>text<|/ref|><|det|>[[150, 122, 850, 293]]<|/det|> +The reviewer correctly points out that large aggregates are generally depicted in the manuscripts. We stress here that SEMORE clustering module is scale- invariant and solely relies on localisations. This is due to our choice of 3D axis standardization. Working with standardized dimensions enables SEMORE to work across experimental configurations and dimensionalities. This allows SEMORE to operate independently of the imaging dimension and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area. The comment still raises a very valuable point on the generalization and performance of SEMORE and to demonstrate this and fully answer the comment of the reviewer we performed two studies: + +<|ref|>text<|/ref|><|det|>[[177, 295, 840, 396]]<|/det|> +1) Simulated diverse, nanometer dimension structures, and quantified SEMORE performance on their segmentation and classification for data with 8, 15 and 25 localisations in an area that corresponds to \(\sim 1\mu m\) . As can be seen in Supplementary Fig. 8 (Response figure 5) in the revised version, SEMORE reached an accuracy of \(>90\%\) in extracting clusters with 8 or more localisations with the morphology fingerprinting completely separating true clusters from noise. + +<|ref|>text<|/ref|><|det|>[[177, 397, 825, 501]]<|/det|> +2) Simulated protein assemblies of just 4 detections and evaluated SEMORE's performance on such a small cluster representing the minimal representation of a tetramer. SEMORE achieves accuracies of up to \(70 - 90\%\) in segmenting these tiny structures depending on the noise levels while the morphological fingerprinting module captures these noisy detections allowing for potential post-processing and accuracy increase, Supplementary Fig. 7 (Response figure 4). + +<|ref|>text<|/ref|><|det|>[[177, 502, 825, 621]]<|/det|> +3) Evaluated the number of points needed for SEMORE to accurately detect the initiation points of spatially overlapping clusters. The high accuracy of SEMORE to capture initiation points can be quantified and visualized using simulated data showing is just \(\sim 13\) frames off on average across 3 types of spatially overlapping morphologies. Furthermore, qualitative assessment using experimental data of temporally resolved insulin aggregation supports the reliability of SEMORE, Supplementary Fig. \(5 + 6\) , response figure \(6 + 7\) . + +<|ref|>text<|/ref|><|det|>[[150, 623, 844, 726]]<|/det|> +In essence, \(\sim 10\) detections is enough for SEMORE to obtain high segmentation and classification accuracy which is well below the common number of detections in most SMLM experiments. We analyze dSTORM data of Nieves et al. NatMeth, 20, pages 259- 267, 2023 \(^{1}\) obtaining similar densities and cluster sizes but in fact analyzing the entire field of view at once see new SI fig 17 (response figure 1). We further use the approach from Nieves et al., NatMeth, 20, pages 259- 267 to simulate structures with blinking, see comment 1.3. + +<|ref|>sub_title<|/ref|><|det|>[[151, 745, 443, 764]]<|/det|> +## Changes in the manuscript 1.1 + +<|ref|>text<|/ref|><|det|>[[150, 766, 845, 817]]<|/det|> +To fully address the comment of the reviewer in the revised version of the manuscript we have added a new section within "Accurate extraction of individual assemblies across diverse biologically inspired growth types.": + +<|ref|>text<|/ref|><|det|>[[150, 818, 828, 906]]<|/det|> +"To further evaluate the performance of SEMORE on segmentation and analysis of dynamic SMLM data we performed a series of stress tests on simulated data. We firstly evaluated SEMORE's ability to track morphological changes in time using simulated data of 3 types of spatially overlapping protein clustering morphologies with temporal information included. Snapshots of SEMORE's clustering in time provide visual confirmation of SEMORE's ability to track morphological changes in time (see Supplementary Fig. 5 for snapshots of simulated and Supplementary Fig. 6 for experimental data). Further quantification of SEMORE's + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 82, 848, 270]]<|/det|> +ability to accurately track and segment spatially overlapping protein assemblies in time reveals growth onset times across 3 morphological classes are predicted with an average offset of just \(\sim 13\) frames (Supplementary Fig. 6). Subsequently, we test the clustering module on simulated, sparse structures containing as little as 4, 8, 15 and 25 point detections akin to data of protein oligomerization (see Supplementary Fig. 7 & 8). SEMORE analyzes the entire field of view at once and extracts structures down to 4 detections while maintaining \(>90\%\) accuracy at biologically relevant noise to signal ratios. The morphological fingerprinting module can further refine the false positive detections from noise with as little as 4 detections, achieve full separation from noise at 8 detections and classify morphological classes in true structures at 15 detections (see Supplementary Fig. 8 & 9). Lastly we evaluated its performance to degenerate structures that shrink in time, akin to protein depolymerisation. SEMORE accurately segments 3 anisotropically degenerative morphologies showcasing it can be used to analyze dynamic shrinkage or depolymerisation of protein clusters (see Supplementary Fig. 10). In essence SEMORE only requires \(< 10\) detections to accurately segment and classify heterogeneous structures with dynamic morphologies further demonstrating its operational utility and potential for 4D SMLM." + +<|ref|>text<|/ref|><|det|>[[150, 288, 495, 304]]<|/det|> +Elaborated in results on the scale invariance: + +<|ref|>text<|/ref|><|det|>[[150, 307, 850, 402]]<|/det|> +" The clustering module of SEMORE consists of multiple steps that self- parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools." In addition, to address the comment we have added 5 new SI figures, namely Response figures: 1,4,5, 6, and 7. + +<|ref|>sub_title<|/ref|><|det|>[[151, 439, 288, 459]]<|/det|> +## Comment 1.2 + +<|ref|>text<|/ref|><|det|>[[150, 465, 844, 602]]<|/det|> +- It would be interesting to know a little more about the limits of SEMORE, as in biological SMLM data there may be several different classes of cluster, which may have stronger similarities, within the same ROI. For example, if a protein is present as a monomer and can assembles into higher order oligomers, it might be expected there are some low-level oligomers (4 proteins clustered proteins at sub-diffraction, e.g., tetramers) in the data at time of fixation. Would these small clusters be distinguishable from the noise class? Some examples of how SEMORE deals with this low-level oligomerisation (low-density clusters) would strengthen the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[151, 620, 286, 639]]<|/det|> +## Response 1.2 + +<|ref|>text<|/ref|><|det|>[[150, 642, 843, 746]]<|/det|> +This is indeed a valid comment and we thank the reviewer(s) for allowing us to address this in detail. As we detailed in response to your comment 1.1 in the revised manuscript SI fig 7 (response figure 4) we detail how SEMORE performs for low-level oligomers at sub- diffraction limit. The data demonstrate that SEMORE captures early stages of protein cluster initiation, even at diverse noise conditions. We also demonstrated how it dissects heterogeneous morphologies. + +<|ref|>sub_title<|/ref|><|det|>[[151, 764, 445, 783]]<|/det|> +## Changes in the manuscript 1.2 + +<|ref|>text<|/ref|><|det|>[[151, 785, 831, 836]]<|/det|> +Please see changes as per comment 1.1 as we grouped our response and changes to this comment. In short, a new section on SEMORE's performance on small sparse clusters showcases the potential use of SEMORE on tetramers or early stages of clustering. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[151, 85, 288, 103]]<|/det|> +## Comment 1.3 + +<|ref|>text<|/ref|><|det|>[[150, 110, 841, 317]]<|/det|> +Comment 1.3- Following on from this point, one thing lacking from the manuscript is any comment on a common problem for arguably the two most common SMLM techniques (PALM, and dSTORM - used here); multiple blinking of the fluorophore. Normally, this introduces artefactual clustering into the SMLM data, and several approaches now exist for correcting this (e.g., Jensen et al., NatMeth, 19, pages 594- 602, 2022, and Bohrer et al., NatMeth, 18, pages 669- 677, 2021). Thus, is relation to biological data, some structures that may appear clustered, and then segmented in uncorrected data, will not be so after correction, shifting the observed distributions of the classes. Would the authors recommend such corrections before use of SEMORE for accurate fingerprinting? Also, some sense of how the lack of blink correction could impact classification would be beneficial. This could be done by comparing a ground truth of the molecule positions and a version where the data has added blinking. + +<|ref|>sub_title<|/ref|><|det|>[[151, 336, 286, 355]]<|/det|> +## Response 1.3 + +<|ref|>text<|/ref|><|det|>[[150, 358, 845, 512]]<|/det|> +Response 1.3This comment on blinking is indeed very valuable. To answer and quantify SEMORE on data with and without blinking we rely on the approach Nieves et al., NatMeth, 20, pages 259- 267. SI figure (Supplementary Fig. 9, response Fig. 10) shows SEMORE's performance on data with and without simulated blinking. The results show SEMORE achieves extraction accuracies above \(90\%\) and produces morphological fingerprints that reliably differentiates morphological classes from just 15 detections regardless of blinking. While we would recommend end- users to correct for blinking prior to using SEMORE, SEMORE performs well regardless of blinking and simply requires a small number of detections as seen in the response and in response \(1.1 + 1.2\) . + +<|ref|>sub_title<|/ref|><|det|>[[151, 530, 465, 550]]<|/det|> +## Changes in the manuscript 1.3 + +<|ref|>text<|/ref|><|det|>[[150, 551, 842, 618]]<|/det|> +The revised manuscript now includes a SI figure (Supplementary Fig. 9, response Fig. 10) showing performance with blinking and a discussion on blinking and our recommendation. We highlight the small effect of blinking on morphological fingerprinting in the section: + +<|ref|>sub_title<|/ref|><|det|>[[150, 600, 822, 635]]<|/det|> +## "Morphological fingerprinting captures defining features separating heterogeneous assemblies." : + +<|ref|>text<|/ref|><|det|>[[150, 637, 835, 797]]<|/det|> +"Blinking is a common challenge in SMLM, especially for PALM and dSTORM, and may lead to artificial clustering and misinterpretation of protein assembly morphology. We map the effect of blinking on the morphological fingerprinting module using data with and without simulated blinking (see Methods). SEMORE remains largely unaffected by blinking achieving segmentation accuracies above \(90\%\) and reliably differentiates morphological classes from just 15 detections regardless of blinking (see supplementary Fig. 9). In addition to blinking, protein assemblies can exhibit biological behavior involving significant morphological changes (e.g., spherical to tubular), or as discussed in the evaluation of the clustering module above, depolymerization. To this end, we evaluated SEMORE's ability to track the temporal evolution of morphology between diverse morphologies, i.e. from fibril-like to spherical to asymmetric. SEMORE clearly tracks morphologies in time and transitions while outputting the most distinguishing features of each morphology offering important mechanistic insights (supplementary Fig. 15)." + +<|ref|>text<|/ref|><|det|>[[150, 811, 789, 827]]<|/det|> +In addition, we include in the discussion our recommendation for blinking or other aberration: + +<|ref|>text<|/ref|><|det|>[[150, 843, 828, 901]]<|/det|> +"SEMORE is currently optimized for laterally stable assemblies, albeit the temporal refinement does handle lateral movement below the agnostic, data- derived search range defined per assembly basis (see Methods). Future versions are planned to include our diffusional analysis framework for motion aware clustering analysis. Blinking has insignificant effect on SEMORE analysis, however we recommend common aberrations such as + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 827, 112]]<|/det|> +blinking and vibrational or spherical aberrations to be corrected prior to use of SEMORE to avoid any potential misinterpretation of the data." + +<|ref|>sub_title<|/ref|><|det|>[[150, 134, 316, 152]]<|/det|> +## Minor comments: + +<|ref|>text<|/ref|><|det|>[[150, 160, 842, 228]]<|/det|> +- All figures showing SMLM data or plots of clusters etc. need a scale bar or some axes. It was hard to appreciate, until using the code, how different the length scale of the clusters between simulations and experimental data were (some several microns, whilst NPC data is much smaller scale) + +<|ref|>text<|/ref|><|det|>[[150, 229, 843, 331]]<|/det|> +Thank you for noticing the missing element. We note that as we highlighted in response to comment 1.1 SEMORE is purposefully designed to be dimension independent therefore the simulated data are without a scale bar. We do, based on your comment 1.1 elaborate on the scale-invariance in the main text. Furthermore figures with experimental data have been rectified in the revised version to include a scale bar as seen in main figure 4 making the size difference between insulin aggregates and NPC easier to appreciate. + +<|ref|>text<|/ref|><|det|>[[149, 349, 841, 500]]<|/det|> +- I ran the SEMORE installation as directed on the GitHub, generating a new environment. I found quickly that I was missing the dependencies needed to run the scripts (e.g., opencv in the dependency file should be opencv-python, I assume this is why this file may not have worked for me). Further, other more basic packages are of course not there in a new environment, e.g., pandas, numpy, etc., and require the user to add them. I would recommend the authors give a full and correct dependencies file, as this troubleshooting would be beyond many of the potential users with limited coding experience. We have now provided the packages as a dependency.yml to be installed with: + +<|ref|>text<|/ref|><|det|>[[150, 504, 521, 585]]<|/det|> +git clone https://github.com/hatzakislab/SEMORE cd SEMORE conda env create - f dependency.yml conda activate SEMORE + +<|ref|>text<|/ref|><|det|>[[150, 592, 828, 642]]<|/det|> +and extended the documentation on the GitHub page. We appreciate the test of the github structure which now should be in order but we also include contact information and are happy to assist future users. + +<|ref|>sub_title<|/ref|><|det|>[[150, 660, 360, 676]]<|/det|> +## Additional minor changes + +<|ref|>text<|/ref|><|det|>[[150, 678, 828, 745]]<|/det|> +minor spelling and phrasing mistakes were rectified. minor addition to account for the fact that we have 5 experimental data sets instead of 2 in the original submission, as well 6 additional ground truth simulated data sets. addition of a few extra refs to account for reviews comments. + +<|ref|>sub_title<|/ref|><|det|>[[150, 789, 260, 807]]<|/det|> +## Reviewer 2 + +<|ref|>text<|/ref|><|det|>[[150, 816, 823, 901]]<|/det|> +Bender et al. present SEMORE, SEGmentation and MORphological fingErprinting, as a semi- automatic machine learning framework for the analysis of super- resolution data to extract and quantify protein structures. By implementing a multi- layered density- based clustering module and a morphology fingerprinting module for quantification, they demonstrated SEMORE on simulations and experimental super- resolution data, including + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 82, 833, 325]]<|/det|> +insulin aggregates and nuclear pore complexes. Developing automatic clustering analysis without a priori knowledge and tracking the temporal evolution of morphology changes of protein clustering from single- molecule localization microscopy image data is certainly a good direction for the development of super- resolution microscopy field. However, in my view, their demonstrations are limited to the analysis of the growth of immobile clusters under well- controlled noise conditions, which could be quite different from general biological behaviors. This raises concerns about the limited applicability of this method. Additionally, although the authors insist that their method represents the first time- aware framework for 4D super- resolution data, they mainly focus on presenting the classification results for protein cluster growth, without showing identified cluster images at each time point. Therefore, it is hard to judge whether their method can effectively capture the temporal changes of protein clusters. To claim that their method is genuinely powerful for automatic clustering analysis and tracking the temporal evolution of protein clusters, they should also show the time- resolved clustering data. + +<|ref|>text<|/ref|><|det|>[[149, 325, 847, 584]]<|/det|> +Furthermore, I cannot see the significant novelty of this method; they mainly used the reported clustering method (DBSCAN) for cluster identification. Although it appears that they additionally conducted temporal refinement after the DBSCAN analysis, this additional step seems to be mainly for dissecting clusters over time, rather than advancing the clustering analysis method. The new development of their method seems to be a morphology fingerprinting module that uses multiple feature vectors for quantification. However, the performance of this method for real experimental time- resolved super- resolution image data was demonstrated only for the relatively new imaging method REPLOM, which is not a general type of data. To demonstrate the general performance of this method, the authors should present more general time- resolved single- molecule localization microscopy data, rather than static dSTORM data. Although the authors applied their method to NPC data, it appears to be just static data, and the categorization of the clusters is not biologically meaningful (individual, overlapped, noise). For these reasons, I believe the authors' claims are not well supported, which unfortunately does not warrant publication in Nature Communications in the current form of the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[151, 604, 324, 622]]<|/det|> +## General response + +<|ref|>text<|/ref|><|det|>[[150, 629, 847, 698]]<|/det|> +We thank the reviewer for critically reading the manuscript, acknowledging that the approach we are using is certainly a good direction for the further development of the super- resolution microscopy field and providing valuable feedback. We have addressed all your comments explicitly, and in full detail by: + +<|ref|>text<|/ref|><|det|>[[176, 699, 848, 870]]<|/det|> +a) Demonstrating SEMORE's performance on two additional experimental time-resolved super-resolution data based on sptPALM and live-cell PALM. Results show in both cases that SEMORE successfully clusters detections, captures temporal morphology changes, quantification of clusters by fingerprinting offering potential new insights. SEMORE is validated by comparison to results of the original work on these data sets; Wallis et al \(^{3}\) and Hou et al \(^{4}\) .b) Demonstrated SEMORE on additional experimental dSTORM data containing consecutive frames. Results show SEMORE obtaining comparable results in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[201, 82, 794, 122]]<|/det|> +clustering as Nieves et al1 while temporal refinement and smart density filter to enable the additional pruning of false positives. + +<|ref|>text<|/ref|><|det|>[[177, 127, 835, 256]]<|/det|> +c) Performing additional multiple noise variation: Simulating additional heterogeneous noise conditions with varying densities and displaying the capacity of SEMORE to accurately segment and classify them. Thus, the revised version now contains 2 independent experimental data sources with biological noise along with simulations containing homogeneous and heterogeneous noise. New noise types was also supported by additional experimental data as per a and b + +<|ref|>text<|/ref|><|det|>[[177, 262, 844, 346]]<|/det|> +d) Displaying snapshots of SEMORE's segmentation at multiple time points during the assembly process for experimental data and simulated data. Followed by an evaluation of the number of detections needed to accurately detect the initiation point of protein assemblies. + +<|ref|>text<|/ref|><|det|>[[177, 352, 837, 414]]<|/det|> +e) Displaying SEMORE's ability to accurately capture morphological variations as they evolve in time. Followed by an evaluation of the number of detections required to classify morphological classes. + +<|ref|>text<|/ref|><|det|>[[177, 419, 843, 617]]<|/det|> +f) Detailing how SEMORE significantly advances the field: Explained in detail the multiple components incorporated in SEMORE prior and on top of DBSCAN, making DBSCAN a small part of one of the two modules of SEMORE. Compared SEMORE to the state of the art (DBSCAN) and detailed how the clustering module (segmentation) along with the fingerprinting module (quantification and classification) of SEMORE can propel the field of super-resolution. We stress here that we already had in the original submission a comparison of SEMORE to DBSCAN clearly demonstrating the superiority of SEMORE along with the increased accuracy following our developed smart noise filter. + +<|ref|>text<|/ref|><|det|>[[150, 622, 844, 727]]<|/det|> +However, we respectfully disagree that REPLOM "... is not a general type of data" REPLOM represents one of SMLM approaches enabling temporally resolved observation of protein aggregation. While indeed the implementation is novel and different to more common approaches the actual data type is very similar, if not identical. REPLOM is based on TIRF microscopy to observe isolated PSFs to accurately fit subpixel localizations in essence outputting a set of xy and t, coordinates. + +<|ref|>text<|/ref|><|det|>[[150, 744, 849, 808]]<|/det|> +The wealth of extra analysis and additional data, which fully and further support our claims, helped us improve the technical quality of the manuscript, benchmark it against state of art, and elaborate on the novelty and applicability of the method to extract mechanistic insights across a spectrum of diverse systems. + +<|ref|>text<|/ref|><|det|>[[150, 809, 849, 880]]<|/det|> +We do hope the following point- by- point response and revised manuscript rectify all comments and convince the reviewer to join the other 2 reviewers in accepting the manuscript for publication. Figures created following your and other reviewers comments have been pasted below for your convenience. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 84, 277, 101]]<|/det|> +## Comment 2.1 + +<|ref|>text<|/ref|><|det|>[[150, 108, 847, 247]]<|/det|> +Comment 2.11. As suggested above, the main problem with the current manuscript is the lack of time- resolved analyzed data. They only showed the classification results from simulation data for isotropic, random, and fibril growth. However, the time- resolved cluster morphological change data (at each time point) should also be presented to assess whether their method correctly identified each growth pattern. Additionally, I would like to see the time- scaled morphological changes of insulin aggregates and nuclear pore complexes from experimental data to evaluate whether their method performs well even with real data under heterogeneous noise conditions. + +<|ref|>sub_title<|/ref|><|det|>[[150, 265, 284, 284]]<|/det|> +## Response 2.1 + +<|ref|>text<|/ref|><|det|>[[150, 286, 808, 319]]<|/det|> +This is a great set of questions and we thank you for giving us the chance to fully and in detail address them. In the revised version we now provide: + +<|ref|>text<|/ref|><|det|>[[175, 336, 825, 425]]<|/det|> +a) 3 additional experimental data of 1) dynamic dSTORM 2) sptPALM and 3) live-cell PALM data sets and multiple additional simulations producing 11 additional SI figures. In all cases SEMORE precisely analyses and classifies the dynamic data sets showcasing it can be used as a universal tool (Supplementary Fig. 17 & 18 & 19, response figures 1 & 2 & 3). + +<|ref|>text<|/ref|><|det|>[[175, 425, 847, 560]]<|/det|> +b) Snapshots of the experimental data of temporally resolved insulin aggregation displaying the temporarily resolved morphology readouts and the classification at different time points of the clustering by SEMORE and display SEMORE's prediction of the cluster initiation points (Supplementary Fig. 6, response Fig. 5). We stress that while in the original submission we displayed only one of the frames of the temporally resolved simulations or experimental data sets, the temporal refinement was existing and a key element of SEMORE and therefore underlie all figures. We thank the reviewer for noticing the insufficient explanation + +<|ref|>text<|/ref|><|det|>[[175, 562, 835, 664]]<|/det|> +c) Additional simulation of temporarily resolved clustering data containing 3 types of growth morphologies. This type of simulation was already included in the original submission but not adequately discussed in the context of morphology detection early in the clustering process and in time. The data in the revised Supplementary Fig. 5, (response Fig. 7) show how SEMORE captures the temporal evolution of the 3 morphologies in time. + +<|ref|>text<|/ref|><|det|>[[175, 666, 847, 890]]<|/det|> +d) Simulated dynamic morphology variation of a cluster in time by having a cluster sequentially express diverse morphologies, Supplementary Fig. 15, (response Fig. 8). The protein cluster is shown to drastically change morphology from fibril-like structures to asymmetric structures and also to spherical structures, each structure consisting of 200 data points. The temporal morphology changes were analyzed by the fingerprinting module of SEMORE and the extracted features embedded in the 2-component map resulted in a clear separation of the diverse morphologies. Thus, the new Supplementary Fig. 15, (response Fig. 8) shows how SEMORE accurately captures diverse morphologies in time. To further demonstrate the potential of SEMORE we subjected the fingerprints to a MinMax normalization and plotted them in a heatmap. As expected the morphological fingerprint not only accurately classifies the diverse temporally separated morphological growths, but outputs the geometric features that drive this classification offering further mechanistic insights. In addition, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[202, 83, 748, 117]]<|/det|> +response \(1.1 + 1.2\) shows only 15 detections are needed for this accurate classification of morphology. + +<|ref|>text<|/ref|><|det|>[[177, 118, 844, 256]]<|/det|> +e) Single frame of the entire clustering process for 3 diverse morphologies occurring in parallel and in a single field of view Supplementary Fig. 6, (response Fig. 6). SEMORE predicts the growth onset times with an average offset of just \(\sim 13\) frames thus accurately predicting the clustering initiation point for all three morphology classes despite them being highly heterogeneous and spatially overlapping. Panel d in new SI Supplementary Fig. 6, (response Fig. 6) displays the time from growth start to SEMORE initiation prediction highlighting that not only SEMORE predicts cluster morphology but also the initiation point accurately. + +<|ref|>text<|/ref|><|det|>[[150, 256, 840, 360]]<|/det|> +The reviewer also asked for time- scaled morphological changes of nuclear pore complexes, albeit such data may have been produced we do not know of its existence and have not been able to locate it. The NPC data serves to demonstrate the use of SEMORE on static data and in an independent experimental setting. We addressed the comment on the classification of time- resolved morphological variations on experimental and simulated data by the a- c) above. + +<|ref|>text<|/ref|><|det|>[[150, 377, 843, 531]]<|/det|> +To address the comment of the reviewer on the heterogeneous noise we provide new simulation on diverse noise conditions. In the original manuscript SI fig. 2, (still SI fig 2) we had a noise stress test by varying the noise- to- event ratio by more than an order of magnitude (45 fold). We now extended the stress test to apply, and account for, nonuniformly distributed noise. We simulated an additional 5- 25 noise seeds each containing 20- 50 points and also applied Gaussian distributed shifts to all initial noise points further reducing the uniformity (See new Supplementary Fig. 3, (response Fig. 9)). We are happy to report that the classification accuracy of SEMORE remains practically unaffected and more than \(85\%\) for all biological relevant noise levels. + +<|ref|>text<|/ref|><|det|>[[151, 549, 811, 600]]<|/det|> +The response to 1.1 and 1.2 further emphasizes the ability of SEMORE to capture small sparse structures which extends to show how SEMORE performs in early stages of oligomerization. + +<|ref|>sub_title<|/ref|><|det|>[[151, 636, 444, 655]]<|/det|> +## Changes in the manuscript 2.1 + +<|ref|>text<|/ref|><|det|>[[151, 658, 521, 674]]<|/det|> +To fully address the comment of the reviewer we: + +<|ref|>text<|/ref|><|det|>[[176, 675, 845, 740]]<|/det|> +1. Introduced 7 new Supplementary figures that fully and detail address the comment of the reviewer but also include comments of the other two reviewers. +2. Added three new SI figures (SI fig. \(17 + 18 + 19\) , response figures \(1 + 2 + 3\) ) showcasing SEMORE on additional experimental data along with comments in the revised version of the manuscript: + +<|ref|>text<|/ref|><|det|>[[203, 741, 845, 890]]<|/det|> +"we further demonstrated SEMORE's ability to utilize the temporal dimension in experimental data using three additional published data sets: Firstly, dSTORM data of fibroblast growth receptor 1 1, where SEMORE utilizes the data's reported frames for temporal refinement together with smart density filtering to accurately extract protein clusters, prune false positive detections and provide cluster size estimation (Supplementary Fig. 17). Secondly, super-resolved dynamic data syntaxin 1a spatial clustering by sptPALM 3, where SEMORE accurately captures clusters, their morphological evolution in time (Supplementary Fig. 18). Thirdly, super-resolved live-cell PALM data of ryanodine receptors (RyRs) 4. SEMORE accurately captures RyR clusters with a granularity infeasible by current methods such as DBSCAN alone (Supplementary Fig. 19). The fact that SEMORE operates across dynamic experimental + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[204, 83, 797, 113]]<|/det|> +SMLM data outputting clusters and their properties in agreement with published analysis, further highlights its potential as a robust universal tool for 4D cellular biology. " + +<|ref|>text<|/ref|><|det|>[[178, 115, 848, 357]]<|/det|> +3. Inserted and elaborated the section "Precise extraction and quantification of experimental super-resolution data." in the main text describing SEMORE's ability to perform accurate extraction of protein assemblies in time for experimental data: "Studies of aggregating insulin using the super-resolution approach REPLOM, offering real-time recordings of the aggregation growth, revealed insulin aggregates by two distinct pathways: an isotropic pathway, generating radially grown spherical structures and an anisotropic pathway, generating more elongated asymmetric structures consistent with the presence of multiple nucleation sites. When the raw \(x, y, t\) coordinates of insulin aggregation events were fed to SEMORE, the clustering module automatically extracted 139 individual insulin aggregate structures (Fig. 4a) despite them displaying large heterogeneity in their morphology. The identified structures are largely spatially overlapping, an element that would challenge their proper separation by manual inspection or current tools. However, the implementation of the temporal element of SEMORE capturing time-dependent morphological evolution allowed their rapid and precise spatial separation, thus mitigating potential morphology misinterpretation (Fig. 4a and Sup Fig 5). Snapshots of the successful capture of insulin aggregation during its growth combined with the insulin aggregation initiation time point identification by SEMORE are displayed in supplementary fig. 6." + +<|ref|>text<|/ref|><|det|>[[150, 374, 850, 580]]<|/det|> +In addition, to further probe SEMORE's ability to utilize the temporal dimension in experimental data SEMORE was evaluated on three additional data sets: Firstly, using dSTORM data of fibroblast growth receptor \(1^{1}\) SEMORE utilizes the data's reported frames for temporal refinement together with smart density filtering to accurately extract protein clusters, prune false positive detections and provide cluster size estimation (Supplementary Fig. 17). Secondly, utilizing super- resolved dynamic data syntaxin 1a spatial clustering by sptPALM \(^{3}\) SEMORE accurately captures clusters, their morphological evolution in time and provides potential for new insights on clusters by morphological fingerprinting (Supplementary Fig. 18). Thirdly, super- resolved live- cell PALM data of ryanodine receptors (RyRs) \(^{4}\) SEMORE accurately captures RyR clusters with a granularity infeasible by current methods such as DBSCAN alone. Lastly, SEMORE operates across dynamic experimental SMLM further highlighting its potential as a robust universal tool for 4D cellular biology. + +<|ref|>text<|/ref|><|det|>[[177, 615, 850, 812]]<|/det|> +4. Inserted a section in the main text in "Accurate extraction of individual assemblies across diverse biologically inspired growth types." describing SEMORE's ability to perform accurate extraction of protein assemblies in time for simulated data consisting of spatially overlapping structures across 3 morphology classes: "To further evaluate the performance of SEMORE on segmentation and analysis of dynamic SMLM data we performed a series of stress tests on simulated data. We firstly evaluated SEMORE's ability to track morphological changes in time using simulated data of 3 types of spatially overlapping protein clustering morphologies with temporal information included. Snapshots of SEMORE's clustering in time provide visual confirmation of SEMORE's ability to track morphological changes in time (see Supplementary Fig. 5 for snapshots of simulated and Supplementary Fig. 6 for experimental data). Further quantification of SEMORE's ability to accurately track and segment spatially overlapping protein assemblies in time reveals growth onset times across 3 morphological classes are predicted with an average offset of just \(\sim 13\) frames (Supplementary Fig. 6)." + +<|ref|>text<|/ref|><|det|>[[178, 814, 845, 911]]<|/det|> +5. Inserted a section in the main text within "Morphological fingerprinting captures defining features separating heterogeneous assemblies." describing SEMORE's ability to extract time-resolved morphology information for both simulated and experimental data: "In addition to blinking, protein assemblies can exhibit biological behavior involving significant morphological changes (e.g., spherical to tubular), or as discussed in the evaluation of the clustering module above, depolymerization. To this end, we evaluated SEMORE's ability to track + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[206, 82, 833, 141]]<|/det|> +the temporal evolution of morphology between diverse morphologies, i.e. from fibril- like to spherical to asymmetric. SEMORE clearly tracks morphologies in time and transitions while outputting the most distinguishing features of each morphology offering important mechanistic insights (supplementary Fig 15)." + +<|ref|>text<|/ref|><|det|>[[177, 157, 840, 330]]<|/det|> +6. Inserted a section in the main text "Accurate extraction of individual assemblies across diverse biologically inspired growth types." on SEMORE's ability to extract protein assemblies consisting of few detections to evaluate SEMORE's ability to capture small assemblies and early stages of assemblies. "Subsequently, we test the clustering module on simulated, sparse structures containing as little as 4, 8, 15 and 25 point detections akin to data of protein oligomerization (see Supplementary Fig. 7 & 8). SEMORE analyzes the entire field of view at once and extracts structures down to 4 detections while maintaining \(>90\%\) accuracy at biologically relevant noise to signal ratios. The morphological fingerprinting module can further refine the false positive detections from noise with as little as 4 detections, achieve full separation from noise at 8 detections and classify morphological classes in true structures at 15 detections (see Supplementary Fig. 8 & 9)." + +<|ref|>text<|/ref|><|det|>[[177, 332, 840, 415]]<|/det|> +7. We modified an existing section "Accurate extraction of individual assemblies across diverse biologically inspired growth types." discussing noise to the following "The median classification accuracy of SEMORE remained above 85% for a range of noise density levels and was practically independent of noise being homogeneous or heterogeneous (see Methods, Supplementary Fig. 2 + 3)." + +<|ref|>text<|/ref|><|det|>[[177, 416, 843, 450]]<|/det|> +8. We modified an existing section "Precise extraction and quantification of experimental super-resolution data." discussing noise to the following + +<|ref|>text<|/ref|><|det|>[[204, 452, 820, 497]]<|/det|> +"The summary of these results on a diverse set of experimental systems demonstrates the ability of SEMORE to generalize to completely different sets of biological systems, imaging and experimental conditions, noise types, and molecular scales without any a priori knowledge of their structure." + +<|ref|>text<|/ref|><|det|>[[177, 498, 800, 531]]<|/det|> +9. Added in SI fig. 3 of the original submission now SI fig. 4 that data represents a single frame of a temporal simulation. + +<|ref|>text<|/ref|><|det|>[[179, 532, 840, 567]]<|/det|> +10. Highlighted in main figures 1+3+4 in revised submission when shown data represent a single frame of a temporally resolved experiment. + +<|ref|>text<|/ref|><|det|>[[204, 567, 801, 602]]<|/det|> +Main fig. 1 added: "... temporally resolved insulin aggregation imaged using the REPLOM \(^5\) approach on a TIRF microscope..." + +<|ref|>text<|/ref|><|det|>[[204, 603, 825, 637]]<|/det|> +Main fig. 3 added: "Three classes of time-resolved aggregations were simulated to capture a broad aspect of biological systems (see Methods)" + +<|ref|>text<|/ref|><|det|>[[204, 637, 820, 671]]<|/det|> +Main fig. 4 added: "Top: Final frame of accumulated super-resolution localizations from temporally resolved insulin aggregation" + +<|ref|>text<|/ref|><|det|>[[180, 671, 835, 705]]<|/det|> +11. In Methods we have elaborated and extended the relevant sections to include these new performance evaluations. + +<|ref|>sub_title<|/ref|><|det|>[[150, 725, 288, 744]]<|/det|> +## Comment 2.2 + +<|ref|>text<|/ref|><|det|>[[150, 750, 850, 837]]<|/det|> +The demonstrated data seems to only focus on the growth of clustering. However, changes in protein clusters in the real world could involve not only cluster growth but also significant morphological changes (e.g., spherical to tubular), shrinkage, movement, and scattering (depolymerization). For wider applicability of this method, the authors should include related data as well. + +<|ref|>sub_title<|/ref|><|det|>[[150, 855, 286, 874]]<|/det|> +## Response 2.2 + +<|ref|>text<|/ref|><|det|>[[150, 877, 844, 911]]<|/det|> +We indeed fully agree with the reviewer that time- dependent morphological variations are an important element to study. As a matter of fact capturing temporal morphological variations + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 844, 135]]<|/det|> +are inherent in SEMORE and underlie accurate extracting spatially overlapping structures as highlighted in response 2.1. However, we agree this could not be fully appreciated in the original manuscript. + +<|ref|>text<|/ref|><|det|>[[150, 136, 763, 169]]<|/det|> +We thank the reviewer for allowing us to rectify this, expanding the showcasing of SEMORE's capabilities. + +<|ref|>text<|/ref|><|det|>[[177, 170, 845, 481]]<|/det|> +- For answering SEMORE's performance of dynamic morphological changes please see answer to this reviewer comment 2.1c, and Supplementary Fig. 15, (response Fig. 8).- Regarding the reviewer comment on lateral movement: SEMORE considers as input the set of XY(z), and t, coordinates that common SMLM software outputs. As such currently, SEMORE does not include the tracking of large lateral movement beyond what can be captured by temporal refinement, i.e. large lateral shifts (larger than the cluster dependent radius calculated per cluster, see Methods) between frames would currently be recognized as a new cluster. This is now explained in the discussion of the revised version.- Protein depolymerisation and cluster shrinkage is indeed an important element underlying biological processes and we are thankful to the reviewer for bringing this up. To evaluate how SEMORE accounts for shrinkage and depolymerisation of protein clusters we reversed the simulation of growth of diverse morphologies. In the revised Supplementary Fig. 10, (response Fig. 11) we display a simulated data set of depolymerisation as well as the clustering of these shrinking structures as they are predicted by SEMORE. The accurate clustering further supports the strength of SEMORE to also be capable of clustering shrinking protein clusters. + +<|ref|>sub_title<|/ref|><|det|>[[151, 499, 445, 518]]<|/det|> +## Changes in the manuscript 2.2 + +<|ref|>text<|/ref|><|det|>[[152, 520, 808, 537]]<|/det|> +Following the reviewers comment we have strengthen the manuscript with the following: + +<|ref|>text<|/ref|><|det|>[[175, 537, 836, 833]]<|/det|> +1) Protein depolymerisation and shrinkage: In the section "Accurate extraction of individual assemblies across diverse biologically inspired growth types." discussing the dynamic nature of SEMORE we added: "Lastly we evaluated its performance on degenerative structures that shrink in time, akin to protein de-polymerisation. SEMORE accurately segments 3 anisotropically degenerative morphologies showcasing it can be used to analyze dynamic shrinkage or depolymerisation of protein clusters (see Supplementary Fig. 10).". +2) Lateral displacement: We added in the discussion "SEMORE is currently optimized for laterally stable assemblies, albeit the temporal refinement does handle lateral movement below the agnostic, data-derived search range defined per assembly basis (see Methods). Future versions are planned to include our diffusional analysis framework for motion aware clustering analysis. Blinking has insignificant effect on SEMORE analysis, however we recommend common aberrations such as blinking and vibrational or spherical aberrations to be corrected prior to use of SEMORE to avoid any potential misinterpretation of the data." +3) Added a new Supplementary Fig. 10, (response Fig. 11) displaying how SEMORE accurate clusters protein assemblies undergoing depolymerisation for 3 diverse structures. +4) As reported in changes in the manuscript for comment 2.1 we have added in the revised version a section on SEMORE's ability to capture temporal variations in morphology. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 85, 281, 103]]<|/det|> +## Comment 2.3 + +<|ref|>text<|/ref|><|det|>[[149, 110, 845, 232]]<|/det|> +Comment 2.3Their demonstration is mostly based on simulation data, where the noise appears to be well-controlled and homogeneous. Although they tested this method under different noise density conditions, it seems that the density they used is uniformly distributed across the entire field of view and throughout the entire time domain, which could differ from real conditions. Additionally, the intensity of noise could be heterogeneous. Because such heterogeneity of noise could affect the identification and classification of protein clusters, they should test the method with various types of noise. + +<|ref|>sub_title<|/ref|><|det|>[[150, 250, 285, 268]]<|/det|> +## Response 2.3 + +<|ref|>text<|/ref|><|det|>[[149, 271, 845, 443]]<|/det|> +Response 2.3The reviewer is correct and we are thankful for bringing this to our attention. As we outlined in the response to their comment 2.1 we have now extended the stress test to apply, and account for, noise that is non- uniformly distributed in space. We simulated an additional 5- 25 noise seeds each containing 20- 50 points and also applied Gaussian distributed shifts to all initial noise points further reducing their uniformity (See new SI fig. 3, response fig. 9). We are happy to report that the classification accuracy of SEMORE remains practically unaffected and more than \(85\%\) for all biological relevant noise levels. We have also analyzed 3 additional experimental sets and we are happily reporting SEMORE accurately handles real experimental data sets with diverse and heterogeneous noise levels (see detailed answer to comment 2.1) + +<|ref|>sub_title<|/ref|><|det|>[[151, 462, 445, 481]]<|/det|> +## Changes in the manuscript 2.3 + +<|ref|>text<|/ref|><|det|>[[178, 483, 832, 603]]<|/det|> +Changes in the manuscript 2.31) In the main text in the section discussing the noise simulation we added: "The median classification accuracy of SEMORE remained above \(85\%\) for a range of noise density levels and was practically independent of noise being homogeneous or heterogeneous (see Methods, Supplementary Fig. 2 + 3).". In support we added a new supplementary figure 3 displaying the benchmarking for non-uniform noise addition.2) Added analysis and results for experimental data see detailed answer to comment 2.1. + +<|ref|>sub_title<|/ref|><|det|>[[150, 622, 281, 640]]<|/det|> +## Comment 2.4 + +<|ref|>text<|/ref|><|det|>[[149, 648, 833, 785]]<|/det|> +Comment 2.4The authors claim that the use of a machine learning- based method is an important aspect of this study. However, the machine learning method employed in this paper appears to be limited to unsupervised point clustering, rather than classification or other methods. Moreover, these unsupervised point clustering methods used here do not seem to differ significantly in terms of methodology from the existing method, DBSCAN. I believe the authors have not sufficiently explained why the method they used can be considered a machine learning approach and what sets it apart as a novel contribution compared to existing methods + +<|ref|>sub_title<|/ref|><|det|>[[150, 804, 285, 822]]<|/det|> +## Response 2.4 + +<|ref|>text<|/ref|><|det|>[[150, 825, 842, 911]]<|/det|> +Response 2.4We respectfully, but firmly, disagree with the reviewer that the method does not differ from a DBSCAN. In fact, DBSCAN is only a small part of the multimodal part of SEMORE and we indeed had compared the operational performance of SEMORE to DBSCAN in SI fig. 3 of the original submission (now SI fig. 4). Indeed, SEMORE achieved a \(89\%\) median accuracy as compared to \(70\%\) for DBSCAN alone on simulated data, convincingly demonstrating the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 82, 849, 239]]<|/det|> +superior performance of our multimodal pipeline. For experimental data SEMORE is key to accurate analysis as DBSCAN alone can not provide the granularity required to dissect small clusters of ryanodine receptors (See new SI fig. 19, response fig. 3). An additional key example is extracting biologically correct structures and features from insulin aggregation which could otherwise lead to misinterpretation (see main figure 1 for comparison of before and after temporal refinement or SI fig. 3 of the original manuscript (now SI fig. 4). Combined these data showcase the entirety of the SEMORE clustering pipeline is required to extract spatially overlapping structures, provide granularity, filter out noisy detections as clusters that may in the case of no assemblies in the field of view produce nonsensical structures. + +<|ref|>text<|/ref|><|det|>[[150, 255, 780, 273]]<|/det|> +Several key features sets SEMORE beyond DBSCAN and current state of that art :: + +<|ref|>text<|/ref|><|det|>[[175, 272, 844, 607]]<|/det|> +a) Automatic, data-driven model selection between HDBSCAN and DBSCAN based on the density of localisations computed using the field of view. +b) Semi-supervised hyperparameter choices based on experimental data. +c) Topological failsafe for the case of no initial aggregation securing the clustering module does not form nonsensical clusters as DBSCAN alone might if only presented with noise, thus enhancing the clustering detection sensitivity. +d) Smart noise filtering filtering false positive detections in conjunction with our clustering greatly improves the quality of the clustering module's output. +e) Temporal refinement enables clustering of spatially overlapping structures, the dissection of initiation point of each cluster in time and following of morphology changes over time all of which are currently infeasible by DBSCAN or other available methods alone. +f) Morphological fingerprinting for quantification and ranking of interpretable geometric and kinetic descriptors, that to the best of our knowledge is introduced here by us for protein clustering, based on our earlier work on diffusional fingerprinting. + +<|ref|>text<|/ref|><|det|>[[150, 627, 844, 697]]<|/det|> +This combination extends above and beyond any current methods and allows SEMORE to yield automatic segmentation, classification and quantitative insights on arbitrarily complicated data sets across experimental conditions of protein clustering by SMLM and the temporal evolution of morphology without a priori knowledge. + +<|ref|>text<|/ref|><|det|>[[149, 714, 840, 888]]<|/det|> +We respectfully emphasize that a machine learning pipeline based solely on unsupervised learning is still a machine learning approach and an approach that can generalize to problems outside the training distribution. Indeed, unsupervised machine learning methodologies are routinely used in recent interdisciplinary publications6, 7, 8. Moreover, we are slightly puzzled by the comment that no classification or other machine learning approaches are present in the original manuscript: We use a) an additional DBSCAN in the UMAP embedded space (unsupervised) to classify structures in original main fig. 3 and original SI fig. 4- 6 (now SI figs. 11- 13), b) a boosted decision tree (supervised) in SI fig. 6 (now new SI fig. 13) to highlight the potential use of morphological fingerprints in a downstream model, c) a Linear Discriminant analysis (supervised) in feature importance + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 84, 810, 117]]<|/det|> +ranking SI. fig. 8 (now SI fig. 16). To emphasize these important elements in the revised manuscript we elaborate on the use of the unsupervised output in supervised settings. + +<|ref|>sub_title<|/ref|><|det|>[[151, 137, 445, 155]]<|/det|> +## Changes in the manuscript 2.4 + +<|ref|>text<|/ref|><|det|>[[150, 158, 815, 207]]<|/det|> +To fully address the comment of the reviewer we added a complete description of the elements that set SEMORE above and beyond the current state of the art. In the revised version, we have added: + +<|ref|>text<|/ref|><|det|>[[178, 209, 847, 468]]<|/det|> +1) an extension to the explanation of SEMORE's clustering module in the results: "The clustering module of SEMORE consists of multiple steps that self-parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools. The pipeline initially inspects high-density areas in a standardized Euclidean 3D space, using a hyperparameter space pre-defined for this region, and provides an appropriate model choice based on a data-driven decision. The chosen density-based scanning model, either HDBSCAN or DBSCAN, extracts high-density regions of biomolecules (clusters or aggregates) from low-density regions (noise) (Fig. 1b). The initial clustering contains an added topological fail safe to prevent detection of nonsensical structures (see Methods). If a temporal dimension is available, the high-density regions are treated through our temporal refinement (Fig. 1c). Segmentation in time and temporal refinement is strictly required to dissect spatially overlapping structures within high-density areas. The clustered output is further refined by subjecting all identified assemblies to a smart density filter to eliminate falsely predicted assemblies that do not meet an agnostic, data-derived density criteria (Supplementary Fig. 1). The result is a robust clustering model outcompeting current methods and building towards the first general-purpose approach for dynamic SMLM (see Methods and Supplementary fig. 4)." + +<|ref|>text<|/ref|><|det|>[[177, 470, 844, 520]]<|/det|> +2) The methods section of the revised manuscript have been elaborated to further highlight the key contributions of the SEMORE clustering pipeline mentioned in a-f of the response. + +<|ref|>text<|/ref|><|det|>[[177, 521, 845, 675]]<|/det|> +3) We highlight the gain of SEMORE in accurate segmentation of spatially overlapping structures as compared to current methods on experimental data in section "Precise extraction and quantification of experimental super-resolution data.": "When the raw x, y, t coordinates of insulin aggregation events were fed to SEMORE, the clustering module automatically extracted 139 individual insulin aggregate structures (Fig. 4a) despite them displaying large heterogeneity in their morphology. The identified structures are largely spatially overlapping, an element that would challenge their proper separation by manual inspection or current tools. However, the implementation of the temporal element of SEMORE capturing time-dependent morphological evolution allowed their rapid and precise spatial separation, thus mitigating potential morphology misinterpretation (Fig. 4a and Sup Fig 5). + +<|ref|>text<|/ref|><|det|>[[177, 676, 841, 710]]<|/det|> +4) Elaborate on the use of the unsupervised output of SEMORE in a supervised setting within "Morphological fingerprinting captures defining features separating + +<|ref|>text<|/ref|><|det|>[[201, 712, 845, 911]]<|/det|> +heterogeneous assemblies.": "We evaluated how morphological fingerprinting can dissect the diverse types of otherwise similar morphologies by three approaches. Firstly, utilizing a second UMAP embedding and DBSCAN of the circularity feature subset offered additional investigation of the fibril cluster in the embedded fingerprint space (see fig. 3b). This resulted in two spatially separated clusters corresponding to branching and non-branching fibrils which independently can be achieved by boosted decision tree classification using all fingerprint features directly (see Supplementary Fig. 13). Secondly, by investigating the isotropic and anisotropic clusters which revealed more continuous spaces given their more smooth growth behaviors as compared to branching of fibrils, yet with clear spatial separation of fingerprint features (see Supplementary Fig. 14). Lastly, SEMORE was able to correctly classify the identity of diverse morphologies in high-density regions reaching an F1 score of >98% (See Supplementary Fig. 11). Although, morphological fingerprints represent unsupervised output these results demonstrates the versatility in supervised classification to extend beyond distinguishing between fundamentally different morphology families, i.e., fibrils vs isotropic, to also capture heterogeneity within the same morphology family i.e., branching fibrils vs non-branching fibrils. We find the morphological + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[205, 82, 845, 156]]<|/det|> +fingerprinting needs just 8 detections to fully separate true detections from noisy and 15 detections to further classify the morphology class of the true detections (Supplementary Fig. 7 & 8). Such expressive power is required to provide mechanistic insights for most biological assemblies as they often follow one assembly mechanism but still exhibit heterogeneity in their final morphologies and the mapping of which is currently an analytical challenge9. + +<|ref|>sub_title<|/ref|><|det|>[[151, 194, 281, 212]]<|/det|> +## Comment 2.5 + +<|ref|>text<|/ref|><|det|>[[150, 220, 844, 393]]<|/det|> +In the Fingerprinting module, it is mentioned that over 40 features were utilized to analyze the properties of each cluster using various methods. However, it appears that a comprehensive assessment of the strengths and weaknesses of these methods was not conducted. It is unclear why the given methods are expected to yield good features for cluster classification. Additionally, it would be beneficial to determine if all the provided methods are necessary based on the analysis results. For instance, Supplementary Figure 8 suggests that it might be possible to identify a better method instead of using all the feature vectors obtained from each feature. There is a possibility that some of them could even interfere with the analysis process, so it would be insightful to see further results in this regard. + +<|ref|>sub_title<|/ref|><|det|>[[151, 411, 285, 429]]<|/det|> +## Response 2.5 + +<|ref|>text<|/ref|><|det|>[[150, 432, 837, 483]]<|/det|> +The reviewer asks for the basis of the selection of the \(40+\) descriptive features and whether all features are needed, an assessment of their performance and whether their number can interfere with the analysis. + +<|ref|>text<|/ref|><|det|>[[150, 484, 838, 639]]<|/det|> +The central scope and strength of SEMORE is the maximization of applicability and the agnostic classification across diverse systems. Based on these criteria we created an extensive set of features that relied on a combination of geometric elements designed to best capture as diverse as possible morphologies and experimental systems. Therefore the number and identity of features should not be predetermined based on the classification of one specific structure type, but should be as wide as possible so as to ensure the reliability of the agnostic classification. Similarly the strength and weakness of these features can not be predetermined, as they are system dependent and will indeed vary from dataset to dataset. + +<|ref|>text<|/ref|><|det|>[[149, 640, 848, 899]]<|/det|> +We fully agree therefore with the reviewer that often only a fraction of the \(40+\) features can be sufficient to classify each of a given cluster morphology. We had provided this in original SI fig. 8 (now SI fig. 16) and extensively studied in the manuscript both on simulated and experimental data as per original main fig. 3+4 and original SI figures 2- 8 and \(11 + 12\) . To provide further evidence we now include additional simulated and experimental data as per new SI fig. \(17 + 18 + 19\) that shows the importance values of the most dominant features in all classifications of the original manuscript and clearly displays that some features are more important in each case. Each panel displays 18 of the features with the more dominant effect as the rest had minimal or no contribution to the classification, in agreement with what the reviewer asks. This figure stresses that each morphology requires a distinct and different set of descriptive features to be accurately classified. For example, for insulin classification, longest shortest distance (L_s_D), number of bridges in longest possible one- way route through graph (L_I_step), average number of neighbors in graph (mean K) are the dominant features while for Nuclear Pore Complexes longest shortest path in graph (L_s_path), ratio of longest distances in graph (L_I_ratio) and effectiveness of the longest shortest distance + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 842, 135]]<|/det|> +(L_s_effectiveness) are now the most dominant ones. This is further highlighted in the new SI fig 15 (response figure 7) towards capturing temporal evolution of morphology that clearly displays classification of diverse morphologies relies on different features sets. + +<|ref|>text<|/ref|><|det|>[[150, 152, 835, 220]]<|/det|> +We also agree that some of the features can have overlapping interpretations. This overlap does not affect the overall accuracy of the method as only the effects that contribute to the classification are taken into account, however, they can collectively contribute to a detailed description of the clustering at hand. + +<|ref|>text<|/ref|><|det|>[[150, 222, 825, 273]]<|/det|> +We also agree that the features can always be improved and as better features are employed in the future, our implementation of morphological fingerprinting may be further extended even by users to create a feature library. + +<|ref|>text<|/ref|><|det|>[[150, 274, 840, 325]]<|/det|> +We are puzzled by the comment on the assessment of the descriptor importance as this is exactly displayed in SI fig. 8. Acknowledging that these may not be clear we have explained it in detail here and in the main text. + +<|ref|>sub_title<|/ref|><|det|>[[150, 361, 446, 380]]<|/det|> +## Changes in the manuscript 2.5 + +<|ref|>text<|/ref|><|det|>[[150, 382, 847, 433]]<|/det|> +We agree with the reviewer on the importance of these comments surrounding features and features importance thus merits further clarification so we have highlighted the following elements in the main text revised version. + +<|ref|>text<|/ref|><|det|>[[175, 435, 848, 500]]<|/det|> +1) In the Results discussing the descriptive feature selection we added "The number and identity of features are constructed as diverse as possible so as to agnostically capture a diverse set of protein clustering morphologies and maximize applicability across biological systems without a priori knowledge." + +<|ref|>text<|/ref|><|det|>[[175, 499, 848, 573]]<|/det|> +2) In the same section: "Note that some of the features can have overlapping interpretations. This overlap does not affect the overall method accuracy as only features that enhance the classification are taken into account, however, they can collectively contribute to a detailed description of the system at hand. If better features are identified in the future, they can be conveniently implemented into SEMORE further extending its potential." + +<|ref|>text<|/ref|><|det|>[[175, 574, 848, 664]]<|/det|> +3) Elaborated on the point of the possibility to extend the fingerprinting module: "We envision SEMORE's application across diverse systems, the continuous extension of the fingerprinting module and the generation of libraries of protein assembly morphologies. Libraries of morphological features could aid mapping of assembly characteristics to their identity and function for advancement of biological understanding, statistical approaches and be the basis for novel supervised learning purposes (Supplementary Fig. 13)." + +<|ref|>text<|/ref|><|det|>[[175, 665, 852, 710]]<|/det|> +4) In the Discussion discussing the descriptive feature selection we added: "Using a broad set of features maximizes applicability across biological systems and feature ranking can reveal the features of greatest importance providing key mechanistic insights into the given system" + +<|ref|>sub_title<|/ref|><|det|>[[150, 746, 288, 765]]<|/det|> +## Comment 2.6 + +<|ref|>text<|/ref|><|det|>[[149, 771, 825, 896]]<|/det|> +In general, the methodology is not thoroughly explained. For instance, even if the method applied in the existing DBSCAN is used as is, it would be helpful if the methodology were described in more detail. Additionally, the methodology for the classification of each point, which occurs after the fingerprinting module and embedding with UMAP, is not elaborated very well. Since the fingerprinting module appears to be the only distinctive novelty of this method, as mentioned above, it should be described in detail to provide a clearer understanding. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 85, 286, 103]]<|/det|> +## Response 2.6 + +<|ref|>text<|/ref|><|det|>[[150, 105, 844, 226]]<|/det|> +Response 2.6We appreciate the help to improve the readability of the methods section and for enabling us to improve the description of the element that sets us apart from the current state of the art. As outlined in our response to comment 2.4 we have in the revised version elaborated on the clustering module of SEMORE and its contribution to the field. The classification of fingerprints into specific morphology classes occurs by an additional DBSCAN on the 2- component UMAP embedded space (Main fig. 3 and original SI fig. 6c, now SI fig. 13c) or by a boosted decision tree (original SI fig. 6d+ e, now SI fig. 13fd+ e). + +<|ref|>sub_title<|/ref|><|det|>[[150, 245, 445, 264]]<|/det|> +## Changes in the manuscript 2.6 + +<|ref|>text<|/ref|><|det|>[[175, 266, 841, 500]]<|/det|> +Changes in the manuscript 2.61) For the elaboration of the clustering module kindly see the changes of response 2.4. In addition2) We have elaborated the methods section in the revised manuscript.3) We have highlighted the use of DBSCAN and boosted decision trees in classification from morphological fingerprints: "This resulted in two spatially separated clusters corresponding to branching and non- branching fibrils which independently can be achieved by boosted decision tree classification using all fingerprint features directly (see Supplementary Fig. 13). Secondly, by investigating the isotropic and anisotropic clusters which revealed more continuous spaces given their more smooth growth behaviors as compared to branching of fibrils, yet with clear spatial separation of fingerprint features (see Supplementary Fig. 14). Lastly, SEMORE was able to correctly classify the identity of diverse morphologies in high-density regions reaching an F1 score of \(>98\%\) (See Supplementary Fig. 11). Although, morphological fingerprints represent unsupervised output these results demonstrates the versatility in supervised classification to extend beyond distinguishing between fundamentally different morphology families, i.e., fibrils vs isotropic, to also capture heterogeneity within the same morphology family i.e., branching fibrils vs non- branching fibrils." + +<|ref|>sub_title<|/ref|><|det|>[[150, 531, 361, 547]]<|/det|> +## Additional minor changes + +<|ref|>text<|/ref|><|det|>[[150, 549, 829, 617]]<|/det|> +minor spelling and phrasing mistakes were rectified. minor addition to account for the fact that we have 5 experimental data sets instead of 2 in the original submission, as well 6 additional ground truth simulated data sets. addition of a few extra refs to account for reviews comments. + +<|ref|>sub_title<|/ref|><|det|>[[150, 660, 265, 678]]<|/det|> +## Reviewer 3 + +<|ref|>text<|/ref|><|det|>[[150, 687, 840, 773]]<|/det|> +Reviewer 3The manuscript entitled "SEMORE: SEgmentation and MORphological fingErprinting by machine learning automates super- resolution data analysis" by Hatzakis et al introduces SEMORE, a semi- automatic machine learning framework for universal, system and input- dependent, analysis of super- resolution data. The manuscript is well written and informative. However, this manuscript can be improved by addressing the following issues: + +<|ref|>sub_title<|/ref|><|det|>[[150, 794, 334, 812]]<|/det|> +## General response + +<|ref|>text<|/ref|><|det|>[[150, 819, 837, 905]]<|/det|> +General responseWe thank the reviewer for critically reading the manuscript, acknowledging it is "informative" and "well written" and for proposing elements to further improve it. Fully and in detail addressing all of them helped us further improve the quality of the manuscript. Figures created following your and other reviewers comments have been pasted below for your convenience. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 85, 285, 103]]<|/det|> +## Comment 3.1 + +<|ref|>text<|/ref|><|det|>[[150, 110, 808, 179]]<|/det|> +Comment 3.1The authors have developed a new analytical tool SEMORE to extract and quantify underlying structures limiting single- molecule localization microscopy (SMLM). How this newly developed tool SEMORE is better suited with SMLM than some of the previously employed tools such as SMAP (modular super- resolution microscopy analysis). + +<|ref|>sub_title<|/ref|><|det|>[[150, 203, 283, 220]]<|/det|> +## Response 3.1 + +<|ref|>text<|/ref|><|det|>[[149, 223, 849, 465]]<|/det|> +Response 3.1We are grateful for noticing the incomplete comparison of our method with the current state of the art. Super- resolution Microscopy Analysis Platforms for SMLM data (SMAP) is a platform carrying multiple tools for SMLM users to make SMLM more accessible. This modular analysis platform contains tools for localization, post- processing, rendering and clustering (specifically DBSCAN see below). The multiple steps involved in SEMORE's clustering module, i.e. the data- driven decision of clustering approach, smart noise filtering, temporal refinement and morphology fingerprinting do not have directly comparable approaches implemented in SMAP. SMAP does have a DBSCAN implemented, which we do provide a comparison to (original SI fig 3 now SI fig. 4). In addition, SMAP does not include a module comparable to SEMORE's morphological fingerprinting for the quantification of morphology. The methodological advances of SEMORE should be viewed as a possible addition to the multiple plugins already contained within SMAP. The potential of SEMORE to be added to SMAP or to work downstream of analysis performed in SMAP is now mentioned in the revised version of the manuscript to make future users aware of the synergy. + +<|ref|>sub_title<|/ref|><|det|>[[150, 483, 444, 502]]<|/det|> +## Changes in the manuscript 3.1 + +<|ref|>text<|/ref|><|det|>[[150, 505, 777, 555]]<|/det|> +We thank the reviewer for enabling us to clarify the synergy between SEMORE and upstream analysis in SMAP. This has now been added to the revised version of the manuscript in the discussion, see + +<|ref|>text<|/ref|><|det|>[[149, 558, 847, 603]]<|/det|> +"In all cases, relevant structures are precisely extracted and featurized providing strong support for SEMORE as a universal, input- independent model as a convenient toolbox for the SMLM community to use in conjunction with or to be incorporated into SMAP." + +<|ref|>text<|/ref|><|det|>[[150, 605, 830, 655]]<|/det|> +For comparison of SEMORE to DBSCAN we refer to the original SI figure 3 (now SI fig. 4), where we show SEMORE achieves a \(89\%\) median accuracy as compared to \(70\%\) for DBSCAN alone. + +<|ref|>sub_title<|/ref|><|det|>[[150, 676, 288, 694]]<|/det|> +## Comment 3.2 + +<|ref|>text<|/ref|><|det|>[[150, 702, 825, 736]]<|/det|> +The authors should explain how SEMORE deals with commonly occurring supervised and unsupervised machine learning problems. + +<|ref|>sub_title<|/ref|><|det|>[[150, 755, 285, 773]]<|/det|> +## Response 3.2 + +<|ref|>text<|/ref|><|det|>[[150, 776, 797, 825]]<|/det|> +This is indeed an important element of our work, and we are grateful for allowing us to elaborate further. Below we have detailed the challenges of both supervised and unsupervised tools and how SEMORE addresses them. + +<|ref|>text<|/ref|><|det|>[[150, 828, 760, 844]]<|/det|> +Commonly occurring challenges in unsupervised machine learning may include: + +<|ref|>text<|/ref|><|det|>[[175, 845, 830, 878]]<|/det|> +1) Absence of direct accuracy evaluation because the data comes without any labels, classical performance evaluations such as accuracy is not possible. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[175, 83, 812, 116]]<|/det|> +2) The output of an unsupervised model may require human inspection to decipher how the model is performing. + +<|ref|>text<|/ref|><|det|>[[150, 119, 642, 135]]<|/det|> +Commonly occurring problems in supervised machine learning : + +<|ref|>text<|/ref|><|det|>[[175, 136, 833, 290]]<|/det|> +A) Collection of labels for data is often a tedious and resource-strenuous process that requires extensive a priori expertise and is potentially subjected to unconscious biases. +B) Supervised models are trained for a specific task and often require retraining when presented with a system outside the training distribution. +C) Overfitting on data presents a large challenge to supervised approaches resulting in overly optimistic expectations on model generalization. Mitigation requires reliable validation and test schemes that are independent of the training distribution are not always feasible and require more manual labels to be curated. + +<|ref|>text<|/ref|><|det|>[[149, 291, 847, 480]]<|/det|> +SEMORE was specifically chosen to be an unsupervised approach so as to enable a universal approach for SMLM across experimental conditions and biological systems without the need for a priori knowledge or expensive label generation. We tackle the uncertainty surrounding the output of an unsupervised machine learning pipeline by extensive evaluations on simulated data with known labels and by probing performance at various perturbations. In addition, we evaluated its performance on 5 (2 in the original manuscript and now added 3 additional in new supplementary fig. 17- 19) completely diverse experimental data acquired by different groups using diverse imaging and experimental conditions, on different biological systems and with varying noise. In all cases SEMORE's output is in agreement with the published outputs supporting it can surpass commonly occurring supervised and unsupervised machine learning problems. + +<|ref|>sub_title<|/ref|><|det|>[[150, 499, 446, 518]]<|/det|> +## Changes in the manuscript 3.2 + +<|ref|>text<|/ref|><|det|>[[150, 520, 840, 570]]<|/det|> +To fully address the comments we discussed extensively in the revised version the a) actual challenge of supervised vs unsupervised analysis b) how we mitigated them. They are discussed in 3 areas of the manuscript + +<|ref|>text<|/ref|><|det|>[[175, 572, 812, 604]]<|/det|> +a) Elaboration on common challenges in unsupervised and supervised learning see section: Introduction: + +<|ref|>text<|/ref|><|det|>[[203, 607, 840, 720]]<|/det|> +"Supervised algorithms are highly accurate when large amounts of annotated data are available albeit annotations require extensive manual labor and expert knowledge and the resulting model is often suitable for one specific data set or task. This imposes some challenges in exploring unmapped biological systems with no a priori knowledge and potentially limits their use as a general tool \(^{10 - 12}\) . Unsupervised approaches such as OPTICS \(^{13}\) and DBSCAN \(^{14}\) can overcome some of these limitations for coordinate-based input data. Their performance however is often limited by a one-size-fits-all approach. This often results in laborious human intervention in model tuning, restricting their adaptation to heterogeneity in localization densities and assembly sizes in varying experimental data \(^{15,16}\) ." + +<|ref|>text<|/ref|><|det|>[[175, 722, 808, 738]]<|/det|> +b) To address how we mitigate the common challenges, see section Introduction: + +<|ref|>text<|/ref|><|det|>[[203, 741, 844, 855]]<|/det|> +"We show that SEMORE provides the unbiased unsupervised clustering, and morphological cluster variation in time, without a priori knowledge and for diverse simulated and experimental data sets: heterogeneous growth pathways of insulin aggregates, the dimensions of individual nuclear pore complexes, size of individual clusters of fibroblast growth receptors 1, temporal evolution of syntaxin 1a clusters and dynamic clustering of ryanodine receptors (RyR). The implementation of temporal dependence in morphological variations is a promising platform to handle static or dynamic superresolution data and enables in-depth temporal-dependence analysis and segmentation of complex structures." + +<|ref|>text<|/ref|><|det|>[[176, 858, 844, 910]]<|/det|> +c) we highlight the use of supervised learning on the unsupervised output from SEMORE, see section: Morphological fingerprinting captures defining features separating heterogeneous assemblies: "We evaluated how morphological fingerprinting can + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[204, 82, 845, 281]]<|/det|> +dissect the diverse types of otherwise similar morphologies by three approaches. Firstly, utilizing a second UMAP embedding and DBSCAN of the circularity feature subset offered additional investigation of the fibril cluster in the embedded fingerprint space (see fig. 3b). This resulted in two spatially separated clusters corresponding to branching and non- branching fibrils which independently can be achieved by boosted decision tree classification using all fingerprint features directly (see Supplementary Fig. 13). Secondly, by investigating the isotropic and anisotropic clusters which revealed more continuous spaces given their more smooth growth behaviors as compared to branching of fibrils, yet with clear spatial separation of fingerprint features (see Supplementary Fig. 14). Lastly, SEMORE was able to correctly classify the identity of diverse morphologies in high- density regions reaching an F1 score of \(>98\%\) (See Supplementary Fig. 11). Although, morphological fingerprints represent unsupervised output these results demonstrates the versatility in supervised classification to extend beyond distinguishing between fundamentally different morphology families, i.e., fibrils vs isotropic, to also capture heterogeneity within the same morphology family i.e., branching fibrils vs non- branching fibrils." + +<|ref|>sub_title<|/ref|><|det|>[[150, 319, 288, 338]]<|/det|> +## Comment 3.3 + +<|ref|>text<|/ref|><|det|>[[150, 344, 800, 379]]<|/det|> +Comment 3.3The authors should also highlight the role of SEMORE in the advancement of machine learning- based approaches. + +<|ref|>sub_title<|/ref|><|det|>[[150, 402, 286, 420]]<|/det|> +## Response 3.3 + +<|ref|>text<|/ref|><|det|>[[149, 423, 839, 544]]<|/det|> +Response 3.3We value the comment of highlighting how SEMORE advances machine learning based approaches and how further elaboration can strengthen the manuscript. We highlight how a coordinate- based approach to the structural analysis coupled with the temporal refinement, the density- based modeling choice and data- based noise filtering enhances the machine learning pipeline. In addition, we emphasize how featurization of underlying structures directly from raw data can be used to build new machine learning frameworks by future users. + +<|ref|>text<|/ref|><|det|>[[150, 561, 780, 578]]<|/det|> +Several key features sets SEMORE beyond DBSCAN and current state of that art : + +<|ref|>text<|/ref|><|det|>[[175, 579, 841, 911]]<|/det|> +g) Automatic, data-driven model selection between HDBSCAN and DBSCAN based on the density of localisations computed using the field of view. +h) Semi-supervised hyperparameter choices based on experimental data. +i) Topological failsafe for the case of no initial aggregation securing the clustering module does not form nonsensical clusters as DBSCAN alone might if only presented with noise, thus enhancing the clustering detection sensitivity. +j) Smart noise filtering filtering false positive detections in conjunction with our clustering greatly improves the quality of the clustering module's output. +k) Temporal refinement enables clustering of spatially overlapping structures, the dissection of initiation point of each cluster in time and following of morphology changes over time all of which are currently infeasible by DBSCAN or other available methods alone. +l) Morphological fingerprinting for quantification and ranking of interpretable geometric and kinetic descriptors, that to the best of our knowledge is introduced here by us for protein clustering, based on our earlier work on diffusional fingerprinting. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[151, 101, 445, 120]]<|/det|> +## Changes in the manuscript 3.3 + +<|ref|>text<|/ref|><|det|>[[150, 123, 839, 156]]<|/det|> +The revised manuscript now includes further detail on how SEMORE contributes to the field of machine learning based approaches. + +<|ref|>text<|/ref|><|det|>[[150, 157, 830, 191]]<|/det|> +Firstly, how the clustering module of SEMORE extends beyond current state of the art see 2nd paragraph of Results : + +<|ref|>text<|/ref|><|det|>[[150, 194, 847, 410]]<|/det|> +"The clustering module of SEMORE consists of multiple steps that self- parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools. The pipeline initially inspects high- density areas in a standardized Euclidean 3D space, using a hyperparameter space pre- defined for this region, and provides an appropriate model choice based on a data- driven decision. The chosen density- based scanning model, either HDBSCAN or DBSCAN, extracts high- density regions of biomolecules (clusters or aggregates) from low- density regions (noise) (Fig. 1b). The initial clustering contains an added topological fail safe to prevent detection of nonsensical structures (see Methods). If a temporal dimension is available, the high- density regions are treated through our temporal refinement (Fig. 1c). Segmentation in time and temporal refinement is strictly required to dissect spatially overlapping structures within high- density areas. The clustered output is further refined by subjecting all identified assemblies to a smart density filter to eliminate falsely predicted assemblies that do not meet an agnostic, data- derived density criteria (Supplementary Fig. 1). The result is a robust clustering model outcompeting current methods and building towards the first general- purpose approach for dynamic SMLM (see Methods and Supplementary fig. 4)." + +<|ref|>text<|/ref|><|det|>[[150, 410, 770, 444]]<|/det|> +Secondly, in Discussion we elaborate further on the contribution of morphological fingerprinting module to advance ML approaches: + +<|ref|>text<|/ref|><|det|>[[150, 446, 833, 520]]<|/det|> +"We envision SEMORE's application across diverse systems, the continuous extension of the fingerprinting module and the generation of libraries of protein assembly morphologies. Libraries of morphological features could aid mapping of assembly characteristics to their identity and function for advancement of biological understanding, statistical approaches and be the basis for novel supervised learning purposes (Supplementary Fig. 13)." + +<|ref|>text<|/ref|><|det|>[[150, 519, 847, 586]]<|/det|> +See also response to comment 3.2 where we highlight the use of supervised learning on the unsupervised output from SEMORE allowing new downstream models to be developed by the community working on the experimental data- derived morphological fingerprints as features + +<|ref|>sub_title<|/ref|><|det|>[[150, 624, 288, 643]]<|/det|> +## Comment 3.4 + +<|ref|>text<|/ref|><|det|>[[150, 650, 839, 718]]<|/det|> +Since vibrational and spherical aberrations prove to be a greater hindrance at high resolution. Moreover, live samples are more adversely affected by super- resolution imaging because of high excitation intensity or extended exposure times. Does the SEMORE tool take these concerns into consideration? + +<|ref|>sub_title<|/ref|><|det|>[[150, 738, 285, 757]]<|/det|> +## Response 3.4 + +<|ref|>text<|/ref|><|det|>[[150, 759, 833, 878]]<|/det|> +Vibrational and spherical aberrations present large challenges to high resolution imaging especially in live samples, therefore they are important to comment on and we thank the reviewer for bringing this point. Removing such aberrations is often reliant on post- processing. Currently, SEMORE is downstream of any such post- processing steps, as well as the actual detection step as a pipeline working directly on existing localizations to accurately extract underlying structures and provide extensive quantitative features. We acknowledge this was not explicitly discussed in the main text so we have rectified it + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[152, 85, 445, 103]]<|/det|> +## Changes in the manuscript 3.4 + +<|ref|>text<|/ref|><|det|>[[150, 106, 818, 155]]<|/det|> +We now discuss the consequences and the recommended approach of correction before SEMORE or to use SEMORE as an easy approach to extract morphological information quickly before correction. see Discussion: + +<|ref|>text<|/ref|><|det|>[[150, 158, 828, 247]]<|/det|> +"SEMORE is currently optimized for laterally stable assemblies, albeit the temporal refinement does handle lateral movement below the agnostic, data- derived search range defined per assembly basis (see Methods). Future versions are planned to include our diffusional analysis framework for motion aware clustering analysis. Blinking has insignificant effect on SEMORE analysis, however we recommend common aberrations such as blinking and vibrational or spherical aberrations to be corrected prior to use of SEMORE to avoid any potential misinterpretation of the data." + +<|ref|>sub_title<|/ref|><|det|>[[151, 283, 360, 299]]<|/det|> +## Additional minor changes + +<|ref|>text<|/ref|><|det|>[[150, 300, 828, 368]]<|/det|> +minor spelling and phrasing mistakes were rectified. minor addition to account for the fact that we have 5 experimental data sets instead of 2 in the original submission, as well 6 additional ground truth simulated data sets. addition of a few extra refs to account for reviews comments. + +<|ref|>image<|/ref|><|det|>[[150, 430, 830, 783]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 397, 255, 421]]<|/det|> +
Figures
+ +<|ref|>text<|/ref|><|det|>[[150, 820, 728, 835]]<|/det|> +Response Figure 1: dSTORM data from Nieves et. al. 1 clustered and quantified by SEMORE + +<|ref|>text<|/ref|><|det|>[[150, 839, 842, 911]]<|/det|> +Supplementary Figure 17: Evaluation of SEMORE clustering on dSTORM data acquired over several consecutive frames 1 a Raw detections from SMLM data of fibroblast growth receptor 1 (FGFR1) on a MCF7 cell presented by Nieves et al. 1 b Initial clustering by SEMORE's clustering module using the data- driven model choice of HDBSCAN with Min_cluster_size = 15 and Min_sample = 5. Each localization is colored by its SEMORE annotation, with black representing noise and all other colors representing captured clusters. c The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 82, 842, 255]]<|/det|> +final clustering by SEMORE after temporal refinement and smart density filtering (see Methods). Localizations' colour corresponds to the final SEMORE prediction, with black localizations representing predicted clustered supressed by the smart density filter. Clearly depicting complete extraction of heterogeneous protein clusters while minimizing the inclusion of false positive structures demonstrates the power of temporal refinement, smart filtering and cluster specific re- evaluation. d Distribution of detections inside each cluster with each dot representing an identified cluster showing an average of 28 detections and a median of 18 detections. e Distribution of area spanned by the detections inside each predicted clusters resulting shows a mean \(2232nm^2\) and median of \(1829nm^2\) . The Relatively small areas compared to the mean of \(17000nm^2\) reported in nieves et al. 1 showing the difference in a tight area estimation we define in the morphological fingerprinting (see SI fig. 17) versus a more crude convex hull used in Nieves et al 1. F Density of each cluster for further depth in analysis and heterogeneous nature of protein clusters showing with a mean density of \(0.0179N/nm^2\) and a median of 0.009 \(N/nm^2\) . + +<|ref|>image<|/ref|><|det|>[[149, 280, 848, 660]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 681, 800, 708]]<|/det|> +
Response figure 2: Sx1a-mEos2 sptPALM data from Wallis et. al. 3 clustered and temporally quantified by SEMORE.
+ +<|ref|>text<|/ref|><|det|>[[149, 713, 848, 870]]<|/det|> +Supplementary Figure 18: Evaluation of SEMORE on temporarily resolved Sx1a-mEos2 sptPALM data 3. a, Raw localizations of all detections of Sx1a-mEos2 colored in grey for noise detections and other colors for individual clustered detections captured by SEMORE (HDBSCAN; min_cluster_size: 10, min_samples: 10, cluster_selection_epsilon: 0.04) for the entire field of view (sptPALM traces above length 20) showing near identical results to Wallis et al 3. Red box indicates a region of interest. b, Snapshots in time plotting all detections prior to the indicated acquisition time from the region of interest in a showing SEMORE captures the time-resolved appearance and growth of clusters. Last snapshot contains a red box highlighting an additional region of interest. c, 3D (xyt) plot of the region of interest presented in b showing the temporal morphological changes of clustered detections. Red box indicates a hotspot region in space with repeated clustering of detections in time. d, Shows the temporal evolution of cluster size for the region of interest in c showing SEMORE's successful capture of the repeated clustering of detections also discussed in Wallis et al 3. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 81, 844, 365]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 384, 830, 413]]<|/det|> +
Response Figure 4 Evaluation of SEMORE on temporarily resolved live-cell PALM data of ryanodine receptors (RyRs).
+ +<|ref|>text<|/ref|><|det|>[[150, 416, 840, 602]]<|/det|> +Supplementary Figure 19: Evaluation of SEMORE on temporarily resolved live-cell PALM data of ryanodine receptors (RyRs) 4. a, Raw localizations of all detections of RyRs from live-cell PALM from Hou et al4 colored in grey. Scale bar 2 microns. b, Initial clustering of data by DBSCAN showing clusters colored by cluster identity. c, left panel: Final clustering by the full clustering module of SEMORE utilizing the smart density filtering and temporal refinement with individual clusters colored by identity (DBSCAN; dbmin_samples: 10, SEMORE: final_min_points: 10, rough_min_points: 10, investigate_min_sample: 10). Hyperparameters of SEMORE chosen to capture the relatively small clusters formed by RyRs. Results show how SEMORE obtains granularity otherwise infeasible by DBSCAN alone. Right panel: Final clusters from SEMORE colored by the "longest shortest distance" feature from the morphological fingerprinting module with clusters exceeding a threshold of 400nm colored in red showing how SEMORE can capture RyR cluster morphology and separate noisy detections. Utilizing the tight packing assumption for RyRs 4 identified RyR clusters consist on average of 18 RyR with a median of 14 in line with results from Hou et al 4 with slightly larger estimates as we do not filter by intensity. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 85, 840, 425]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 446, 818, 473]]<|/det|> +
Response Figure 4: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies.
+ +<|ref|>sub_title<|/ref|><|det|>[[150, 478, 817, 506]]<|/det|> +## Supplementary Fig. 7: Evaluation of SEMORE' segmentation and structural information extraction on simulated small tetramer assemblies. + +<|ref|>text<|/ref|><|det|>[[149, 505, 844, 746]]<|/det|> +a) Simulated experiment containing both fibril (orange) and elliptical (blue) morphology class containing 4 points each. Three noise ratios were simulated 1, 2 and 3 (ratio 2 in figure) with 10 simulations per noise levels each with 30 true assemblies. b) Assembly extraction by SEMORE's clustering module. SEMORE's hyperparameters were kept across conditions for comparable results and evaluation of automated analysis. c) Accuracy evaluation performed on an aggregate-wise level (see methods) grouped into each noise level. SEMORE achieves accuracies of 90% +/- 23% (noise ratio 1), 84% +/- 30% (noise ratio 2) and 77% +/- 37% (noise ratio 3) showcasing the fidelity of the pipeline even at assembly sizes of four detections with three times as many noisy detections. Throughout all 3 noise ratios the median accuracy is 100% indicating that the found assemblies usually contain all the points of the assembly. d) The morphological fingerprints extracted for all structures visualized by an out-of-box 2-component UMAP. Right panel shows wrongly classified structures clustered, notably the noise (black) contained in the lower left corner. Each plotted assembly is represented by its noise to signal level (circle: 1, square: 2, triangle: 3) each noise to signal ratio contains 4, 9 and 38 false positives, respectively, compared to >270 true positives. Presence of false positives is due to true assemblies having densities near identical to noise impeding the smart density filter from accurately excluding the noise density. Left panel shows colour coding each assembly by density revealing true assemblies and false positives can be separated by a single feature from morphological fingerprinting. Proving morphological fingerprinting can aid a non-perfect segmentation, allowing for further correction or focus-based re-segmentation. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 80, 840, 677]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 690, 760, 720]]<|/det|> +
Response figure 5: SEMORE classification performance for small, sparse clusters of diverse morphologies.
+ +<|ref|>text<|/ref|><|det|>[[150, 724, 780, 753]]<|/det|> +Supplementary Fig. 8: SEMORE classification performance for small, sparse clusters of diverse morphologies. + +<|ref|>text<|/ref|><|det|>[[150, 753, 845, 909]]<|/det|> +a) Simulated data containing temporally resolved fibril and static ellipse shape aggregates (coloured orange and blue respectively) containing 8, 15 and 25 points respectively. Each simulated data set contains 30 aggregates equally divided between the two morphology classes, additionally, noise (coloured black) ratios of 1 and 2 (noise ratio 2 depicted in the figure). 10 experiments were simulated for each condition and each noise ratio accumulating to 1800 aggregates over 60 experiments. b) Predictions made by SEMORE clustering module, with coloured aggregate being True positives (TP) and black being false positives (FP). SEMORE's clustering module is able to handle the combination of sparse static and temporally resolved assemblies contained within the same experiments. c) SEMORE's segmentation performance quantification. Through the SEMORE clustering module an aggregate-wise mean accuracy (see methods) (noise ratio 1 & 2 reported as [1] / [2] ) of; 85% / 80% +/- 24% / 31% and a median accuracy of 91%/ 89% for 8 points assemblies, mean 80%/ 81% +/- 31%/ 30% with median 94%/ 94% for 15 point assemblies and a mean 83% / 76% +/- 27%/ 35% and a median of 95%/ 93% for 25 point + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 83, 844, 184]]<|/det|> +assemblies. as seen in d) the two- component UMAP of morphological fingerprints reveal all false positive assemblies (noise detections) are perfectly separated. Using this separation as correction accuracies improve: mean \(87\% /86\% + / - 21\% /21\%\) median \(91\% /89\%\) for 8 points, \(83\% /89\% + / - 27\% /20\%\) median \(94\% /94\%\) for 15 points and mean \(84\% /82\% + / - 26\% /27\%\) median \(96\% /93\%\) for 25 points. Performance is improved proportional to noise- ratio as the higher noise levels induce more false positives which in turn are corrected by morphological fingerprinting. d) Two- component UMAP embedding of the corresponding fingerprints with the different noise- ratio combined within point types (N = 611, 611, 586 for 8, 15, 25 points respectively). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[150, 95, 833, 592]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 611, 716, 625]]<|/det|> +
Response Figure 6: Deconvolution of temporal refinement on real and simulated data.
+ +<|ref|>text<|/ref|><|det|>[[150, 629, 833, 856]]<|/det|> +Supplementary Fig. 6: Deconvolution of temporal refinement on real and simulated data. a) Snapshots of SEMORE's clustering module output at various frames during temporal refinement of found insulin aggregates (also depicted in Fig. 1C.) in MinMax transformed space (see Methods). Data displayed in 9 windows equally spaced throughout the 381 frame period, each initially found core point of all dissected aggregates is depicted with a red dot symbolizing the initiation of an aggregate. b) The cluster growth is directly visualized in non-transformed space revealing cluster growth in time of a) in a 3D plot after the application of the smart-density filtering (see methods). The cone-like shape of the aggregates in the positive time direction demonstrates SEMORE's ability to capture the growth behaviour of assemblies in experimental data. Each depicted cluster has its predicted initiation point marked with projected lines at the bottom of the plot to highlight the vast difference in the onset times of clusters as revealed by SEMORE. c) Simulated data (from SI fig. 3) 400 frames after initiation. Data displays that SEMORE can find assembly cores, even with high-size heterogeneity including assemblies as small as 94 points up to 7777 points while also correctly dissecting overlapping assemblies. d) The corresponding frame of the predicted initiation was used to estimate the offset in time, from growth start to SEMORE prediction, here plotting \(\sim 99\%\) of the distribution. The mean offset of 13 frames, reflects that SEMORE can accurately classify cluster initiation while showcasing the strength of SEMORE in capturing temporal assembly dynamics. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[155, 80, 844, 404]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[150, 454, 832, 504]]<|/det|> +Response Figure 7: Visual representation of SEMORE's ability to capture morphological growth in time Supplementary Fig. 5: Visual representation of SEMORE's ability to capture morphological growth in time. + +<|ref|>text<|/ref|><|det|>[[150, 504, 845, 644]]<|/det|> +(a, b, c) depicts the inherent process of temporal segmentation of assemblies within the clustering module of SEMORE during temporal refinement shown as 9 windows across three morphological classes. a) 3 simulated fibrils that spatially overlap during growth are accurately segmented. b) 3 simulated isotropic assemblies growing very close to each other accurately extracted and separated by SEMORE. c) Simulated growth of 3 sterically- hindered assemblies captured by SEMORE. a, b, c showcases the versatility of the general clustering module of SEMORE in capturing temporal evolution of protein assemblies, while general segmentation performance can be seen in main fig 2. The second row (d, e, f), shows the structures in 3D with the time being the 3rd axis to visualize assembly growth and morphology evolution. A direct depiction of the predicted assembly initiation point is shown as projected lines to the bottom of the plots revealing SEMORE's ability to keep account of various growth onset times. This is shown for Fibril (d), Isotropic (e) and sterically hindered growth (f) assemblies. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[160, 92, 847, 570]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[149, 590, 835, 618]]<|/det|> +
Response Figure 8: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters.
+ +<|ref|>text<|/ref|><|det|>[[149, 622, 840, 651]]<|/det|> +Supplementary Fig. 15: Depiction of recurrent SEMORE fingerprinting for dynamic morphology variation of protein clusters. + +<|ref|>text<|/ref|><|det|>[[149, 652, 845, 821]]<|/det|> +a) Simulated dynamic morphology variation of protein assembly by sequentially exhibiting structures with diverse morphologies. All temporal states consist of 200 points colour-coded by morphology type. Lines projected at the bottom represent a new morphology initiation (coloured by morphology type). For each temporal state, the SEMORE morphological fingerprinting module was used to extract features for probing the morphology changes across temporal states. b) The morphological fingerprints were embedded by an out-of-the-box 2-component UMAP resulting in a clear separation of the morphology class across time (with time linked by grey lines). Systems with more or less gradual change of morphology would result in a more or less regressive separation. c) MinMax transformed fingerprints plotted into a heatmap with each column representing a temporal state and white lines indicating drastic morphology type changes. Each row represents a morphological feature, in the same order as seen in Supporting Table 1. The heatmap rows showcase the morphological fingerprinting module's ability to capture the mechanistic of temporal states and map the overall features changes involved in major changes in morphology. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[146, 82, 847, 472]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 504, 686, 518]]<|/det|> +
Response Figure 9: Benchmarking SEMORE on for heterogeneous, non-uniform noise.
+ +<|ref|>sub_title<|/ref|><|det|>[[150, 523, 736, 537]]<|/det|> +## Supplementary Fig 3: Benchmarking SEMORE on for heterogeneous, non-uniform noise. + +<|ref|>text<|/ref|><|det|>[[149, 538, 845, 692]]<|/det|> +a) Simulated data used in S1 fig. 2, but now exhibiting a heterogeneous noise profile. Heterogeneous noise is generated by introducing 5-25 "noise seeds" each containing 20-50 points have been added to each simulation, additionally, individual Gaussian distributed shifts have been applied to all initial noise points. b) we see SEMORE clustering classification performance as out-of-the-box. c) Evaluating SEMORE clustering performance versus increasing noise ratio (blue area representing biologically relevant noise-levels estimated from real data and with vertical blue line representing insulin experiments). At biologically relevant noise levels or high noise levels accuracies of SEMORE is observed to be above \(\sim 90\%\) from noise ratio \(\sim 0.2\) and onwards with up to \(93\%\) at 0.7 noise ratio reflecting SEMORE's ability to separate non-uniform noise also observed in robust treating of experimental insulin data (see main fig. 4). The unrealistic conditions with extremely low noise ratios or no noise at all are associated with lower accuracies as the smart-density noise filter expects noise and removes true positives if no noise is present, which is easily countered by turning it off. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[152, 98, 848, 345]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 364, 833, 393]]<|/det|> +
Response Figure 10: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes.
+ +<|ref|>text<|/ref|><|det|>[[150, 396, 840, 425]]<|/det|> +Supplementary Fig. 9: Effect of blinking on SEMORE's morphological fingerprinting and characterization of morphological classes. + +<|ref|>text<|/ref|><|det|>[[149, 425, 848, 572]]<|/det|> +Each row in a) and b) are grouped and depict a certain simulated structure size (4, 8, 15 and 25 data points, respectively). a) Left side shows detections from representative fibril structures as "Ground truth" (orange) prior to blinking and the right side depicts the corresponding structures obtained after blinking (dark red). These post- blinking structures do not include the ground truth points (orange). For each row, 600 ground truth structures were simulated along their corresponding blinking counterpart and as performed in SI fig. 8 two types of morphologies were simulated in equal amounts, namely fibril- like and spherical. b) The morphological fingerprints of each structure are visualized by a 2- component UMAP with colour- coded by morphology type. The ground truth structures (no blinking) shown on the left side of b) and post- blinking structures on the right side. The results show distortion in separability induced by blinking is positively correlated with the number of detections with a given structure as expected as blinking will dominate the morphology of small structures. + +<|ref|>text<|/ref|><|det|>[[150, 570, 819, 597]]<|/det|> +From 15 detections in a structure and above blinking has little to no effect on the morphological fingerprinting module of SEMORE. + +<|ref|>image<|/ref|><|det|>[[152, 608, 848, 789]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[150, 835, 695, 850]]<|/det|> +
Response Figure 11: Demonstration SEMORE clustering of morphology shrinkage
+ +<|ref|>text<|/ref|><|det|>[[150, 854, 707, 868]]<|/det|> +Supplementary Fig. 10: Demonstration SEMORE clustering of morphology shrinkage + +<|ref|>text<|/ref|><|det|>[[150, 868, 847, 911]]<|/det|> +a) Demonstration of 3 simulated isotropic structures that while proving a challenge due to spatial overlapping also undergo shrinking (colour-coded by identity). b) Results show SEMORE accurately identifies spatially overlapping clusters reducing in size at all frames in the simulation allowing the tracking of individual shrinkage in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 82, 840, 112]]<|/det|> +time. As shrinkage is the direct opposite of growth, SEMORE's clustering module is directly applicable as is after a simple preliminary step of flipping the temporal axis of the simulation or experiment. + +<|ref|>sub_title<|/ref|><|det|>[[150, 160, 230, 175]]<|/det|> +## Bibliography + +<|ref|>text<|/ref|><|det|>[[145, 180, 841, 890]]<|/det|> +1. Nieves, D. J. et al. A framework for evaluating the performance of SMLM cluster analysis algorithms. Nat. Methods 20, 259-267 (2023). +2. Lelek, M. et al. Single-molecule localization microscopy. Nat. Rev. Methods Primers 1, (2021). +3. Wallis, T. P. et al. Super-resolved trajectory-derived nanoclustering analysis using spatiotemporal indexing. Nat. Commun. 14, 3353 (2023). +4. Hou, Y. et al. Live-cell photoactivated localization microscopy correlates nanoscale ryanodine receptor configuration to calcium sparks in cardiomyocytes. Nat. Cardiovasc. Res. 2, 251-267 (2023). +5. Zhang, M. et al. Direct observation of heterogeneous formation of amyloid spherulites in real-time by super-resolution microscopy. Commun. Biol. 5, 850 (2022). +6. Liu, C. C. et al. Robust phenotyping of highly multiplexed tissue imaging data using pixel-level clustering. Nat. Commun. 14, 4618 (2023). +7. Fleming, S. J. et al. Unsupervised removal of systematic background noise from droplet-based single-cell experiments using CellBender. Nat. Methods (2023) doi:10.1038/s41592-023-01943-7. +8. Raad, J. D. et al. Unsupervised abnormality detection in neonatal MRI brain scans using deep learning. Sci. Rep. 13, 11489 (2023). +9. Andersen, C. B. et al. Branching in amyloid fibril growth. Biophys. J. 96, 1529-1536 (2009). +10. Xu, C. & Jackson, S. A. Machine learning and complex biological data. Genome Biol. 20, 76 (2019). +11. Thiyagalingam, J., Shankar, M., Fox, G. & Hey, T. Scientific machine learning benchmarks. Nat. Rev. Phys. (2022) doi:10.1038/s42254-022-00441-7. +12. Benning, N. A. et al. Dimensional Reduction for Single-Molecule Imaging of DNA and Nucleosome Condensation by Polyamines, HP1α and Ki-67. J. Phys. Chem. B 127, 1922-1931 (2023). +13. Ankerst, M., Breunig, M. M., Kriegel, H.-P. & Sander, J. OPTICS. SIGMOD Rec. 28, 49-60 (1999). +14. A density-based algorithm for discovering clusters in large spatial databases with noise | Proceedings of the Second International Conference on Knowledge Discovery and Data Mining. https://dl.acm.org/doi/10.5555/3001460.3001507. +15. Khater, I. M., Nabi, I. R. & Hamarneh, G. A Review of Super-Resolution Single-Molecule Localization Microscopy Cluster Analysis and Quantification Methods. Patterns (N Y) 1, 100038 (2020). +16. Bzdok, D., Altman, N. & Krzywinski, M. Statistics versus machine learning. Nat. Methods 15, 233-234 (2018). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 83, 313, 98]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 111, 414, 126]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 139, 864, 182]]<|/det|> +I would like to thank the authors for their very thorough and in- depth response to my comments. The extra benchmarking and highlighting the scale invariance has significantly improved the manuscript and will be a very useful tool for SMLM cluster analysis and classification. + +<|ref|>text<|/ref|><|det|>[[119, 195, 558, 209]]<|/det|> +I fully recommend the revised manuscript for publication. + +<|ref|>text<|/ref|><|det|>[[119, 251, 414, 265]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[119, 279, 877, 350]]<|/det|> +The authors addressed many of my review comments regarding simulation with heterogeneous noise and added the new data analysis results, including time- resolved images. However, unfortunately, some of the newly added data and explanations are not satisfactory enough to resolve my concerns based on the following reasons. Therefore, I strongly request that the authors carefully examine their data and analysis. + +<|ref|>text<|/ref|><|det|>[[118, 363, 879, 462]]<|/det|> +1. To address my comments on the presentation of time-resolved image data, the authors added a simulation of dynamic morphology variation of protein assembly in Supplementary Figure 15. However, this simulated data contains only drastic changes between three clearly classifiable different morphologies without transitional states. In contrast, in the real world, we can expect gradual morphological changes in proteins through intermediate states. Therefore, I'm not yet sure whether their method can detect and track such more realistic gradual changes in proteins from the experimental SMLM image data. + +<|ref|>text<|/ref|><|det|>[[118, 475, 864, 616]]<|/det|> +2. The authors compared the SEMORE result with previously reported results and asserted that SEMORE provided comparable results with the previous reports. For example, they insisted comparable results with Nieves et al (Supp Fig 17) and Wallis et al (Supp Fig 18). However, I cannot find the related supporting quantitative comparison data, making it difficult to judge whether SEMORE really provides comparable and reasonable results with the reported results. Additionally, the authors insisted that SEMORE could minimize the inclusion of false positive structures compared to HDBSCAN (in Supp Fig 17 experimental data), but I'm uncertain whether the filtered localizations are indeed false positive structures or positive structures that should not be filtered because there is no related data shown. To make a reasonable comparison of their results with others, quantitative comparisons should be provided. + +<|ref|>text<|/ref|><|det|>[[118, 629, 857, 700]]<|/det|> +3. In many figures, particularly in supplementary figures, scale bar information or axis units are missing. Consequently, it is challenging for me to judge whether the clustering or filtering is biologically relevant in their image data. Additionally, in supplementary Figure 17 d-f, it appears that the x-axis is meaningless, so a scatter plot for density vs. N or Area would be more reasonable. + +<|ref|>text<|/ref|><|det|>[[118, 713, 870, 854]]<|/det|> +4. Although the authors performed additional simulations with various noise variations, I don't understand some of the data. For example, Supplementary Figure 3 shows an increasing accuracy with an increasing ratio of heterogeneous, non-uniform noise, which is contrary to the general expectation. This could be because the data in Supplementary Figure 3c were obtained from just one-time simulation for each noise ratio (there is no error bar in this data), which could not demonstrate the general trend very well. While the authors claimed that the smart-density noise filter is designed to expect noise and remove true positives, such a case could lead to incorrect filtration for real images with low noise as well. Since different SMLM microscopes and different biological samples can produce various noise levels, I believe that if such an effect exists in their analysis method, it should be resolved. + +<|ref|>text<|/ref|><|det|>[[118, 867, 842, 910]]<|/det|> +5. Regarding the responses for my fourth comments (2.4), I do understand that unsupervised learning is also a significant component of machine learning. My previous comments might be somewhat unclear in conveying my intended message. During the SEMORE clustering process, + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 875, 238]]<|/det|> +there are several steps involved in clustering meaningful points. The methods you have suggested in this paper to enhance clustering primarily focus on filtering out points and implementing temporal refinements. My point of concern is related to what happens once the filtered and refined points are available. I am uncertain about the contributions of this work to the "machine- learning- based clustering algorithm" at this stage. Even if the filtering and temporal refinements can potentially aid subsequent machine- learning- based clustering algorithms, they are difficult to be considered as a machine- learning algorithm by themselves. Therefore, I am curious if you have made any contributions to the "machine- learning- based clustering algorithm itself" apart from hyperparameter tuning in existing methods like DBSCAN. Examples of such contributions might include modifications to the loss function, alterations to the architecture, improved training techniques, and so on. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[107, 100, 350, 120]]<|/det|> +Review response 2nd + +<|ref|>text<|/ref|><|det|>[[107, 129, 888, 145]]<|/det|> +Review response 2nd 1 + +<|ref|>text<|/ref|><|det|>[[107, 148, 888, 163]]<|/det|> +Reviewer 1 1 + +<|ref|>text<|/ref|><|det|>[[167, 167, 888, 181]]<|/det|> +Comment: 1 + +<|ref|>text<|/ref|><|det|>[[167, 186, 888, 200]]<|/det|> +General response 1 + +<|ref|>text<|/ref|><|det|>[[107, 204, 888, 219]]<|/det|> +Reviewer 2 2 + +<|ref|>text<|/ref|><|det|>[[167, 223, 888, 237]]<|/det|> +Comment: 2 + +<|ref|>text<|/ref|><|det|>[[167, 242, 888, 256]]<|/det|> +General response 2 + +<|ref|>text<|/ref|><|det|>[[167, 260, 888, 275]]<|/det|> +Comment 2.1: 2 + +<|ref|>text<|/ref|><|det|>[[167, 279, 888, 294]]<|/det|> +Response 2.1: 2 + +<|ref|>text<|/ref|><|det|>[[167, 298, 888, 313]]<|/det|> +Changes in manuscript 2.1: 4 + +<|ref|>text<|/ref|><|det|>[[167, 317, 888, 331]]<|/det|> +Comment 2.2: 4 + +<|ref|>text<|/ref|><|det|>[[167, 336, 888, 350]]<|/det|> +Response 2.2: 6 + +<|ref|>text<|/ref|><|det|>[[167, 354, 888, 369]]<|/det|> +Changes in manuscript 2.2: 8 + +<|ref|>text<|/ref|><|det|>[[167, 373, 888, 388]]<|/det|> +Comment 2.3: 8 + +<|ref|>text<|/ref|><|det|>[[167, 392, 888, 407]]<|/det|> +Response 2.3: 8 + +<|ref|>text<|/ref|><|det|>[[167, 411, 888, 426]]<|/det|> +Changes in manuscript 2.3: 9 + +<|ref|>text<|/ref|><|det|>[[167, 430, 888, 444]]<|/det|> +Comment 2.4: 11 + +<|ref|>text<|/ref|><|det|>[[167, 448, 888, 463]]<|/det|> +Response 2.4: 11 + +<|ref|>text<|/ref|><|det|>[[167, 467, 888, 481]]<|/det|> +Changes in manuscript 2.4: 13 + +<|ref|>text<|/ref|><|det|>[[167, 485, 888, 500]]<|/det|> +Comment 2.5: 13 + +<|ref|>text<|/ref|><|det|>[[167, 504, 888, 518]]<|/det|> +Response 2.5: 14 + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[108, 76, 230, 95]]<|/det|> +## Reviewer 1 + +<|ref|>sub_title<|/ref|><|det|>[[108, 117, 217, 135]]<|/det|> +## Comment: + +<|ref|>text<|/ref|><|det|>[[108, 142, 886, 194]]<|/det|> +I would like to thank the authors for their very thorough and in- depth response to my comments. The extra benchmarking and highlighting the scale invariance has significantly improved the manuscript and will be a a very useful tool for SMLM cluster analysis and classification. + +<|ref|>text<|/ref|><|det|>[[108, 211, 570, 228]]<|/det|> +I fully recommend the revised manuscript for publication. + +<|ref|>sub_title<|/ref|><|det|>[[108, 249, 308, 269]]<|/det|> +## General response + +<|ref|>text<|/ref|><|det|>[[107, 275, 886, 310]]<|/det|> +We thank the reviewer for valuable feedback that strengthened the paper and for accepting this for publication + +<|ref|>sub_title<|/ref|><|det|>[[108, 334, 232, 354]]<|/det|> +## Reviewer 2 + +<|ref|>sub_title<|/ref|><|det|>[[108, 375, 217, 394]]<|/det|> +## Comment: + +<|ref|>text<|/ref|><|det|>[[108, 401, 886, 488]]<|/det|> +The authors addressed many of my review comments regarding simulation with heterogeneous noise and added the new data analysis results, including time- resolved images. However, unfortunately, some of the newly added data and explanations are not satisfactory enough to resolve my concerns based on the following reasons. Therefore, I strongly request that the authors carefully examine their data and analysis. + +<|ref|>sub_title<|/ref|><|det|>[[108, 524, 308, 544]]<|/det|> +## General response + +<|ref|>text<|/ref|><|det|>[[108, 550, 886, 584]]<|/det|> +We are sorry to see that newly added biological and simulated data as well as analysis are not satisfactory. We have below fully and in detail addressed the new comments. + +<|ref|>sub_title<|/ref|><|det|>[[108, 604, 257, 623]]<|/det|> +## Comment 2.1: + +<|ref|>text<|/ref|><|det|>[[108, 630, 886, 752]]<|/det|> +1. To address my comments on the presentation of time-resolved image data, the authors added a simulation of dynamic morphology variation of protein assembly in Supplementary Figure 15. However, this simulated data contains only drastic changes between three clearly classifiable different morphologies without transitional states. In contrast, in the real world, we can expect gradual morphological changes in proteins through intermediate states. Therefore, I'm not yet sure whether their method can detect and track such more realistic gradual changes in proteins from the experimental SMLM image data. + +<|ref|>sub_title<|/ref|><|det|>[[108, 772, 260, 791]]<|/det|> +## Response 2.1: + +<|ref|>text<|/ref|><|det|>[[108, 797, 886, 866]]<|/det|> +We value the reviewer's feedback towards creating the best and most convincing display of SEMORE's capabilities. We agree that Supplementary figure 15 currently shows a protein assembly undergoing more drastic changes. We displayed this, along with other supplementary figures, as the simplest case to show SEMORE captures changes in morphology over time. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 75, 886, 230]]<|/det|> +To execute directly on this revised feedback, we evaluated below SEMORes capacity to characterize 8900 intermediate structures of gradual dynamic morphology variation in supplementary figure 26. The figure displays 90 structures from the three distinct morphologies sequentially, yet no two similar classes in a row, along with 100 interpolated structures as intermediates forming the transition between each of the 90, thus totalling 8900 structures. SEMORE accurately captures intermediate morphology classes and tracks their gradual dynamic morphology putting intermediate structures on a gradient between the distinct groups of where the transition is happening. Given these structures exist in a continuous space SEMORE allows users to decide on decision boundaries for each of the structures. + +<|ref|>text<|/ref|><|det|>[[106, 238, 886, 358]]<|/det|> +We wish to stress that a central element of SEMORE is that it inherently performs temporal segmentation, thus capturing gradual changes. As detailed in the original submission SEMORE will segment and quantify each frame individually in a given data set, thus each identified cluster will have a temporal segmentation capturing its changes in time. Please also notice that aggregation growth is an inherently gradual change in morphology. We had displayed in main figure 1, 2, and 3, as well as, Supplementary figure 4, 5, and 6) of the original submission SEMORE's capacity to capture growth. + +<|ref|>image<|/ref|><|det|>[[105, 378, 866, 800]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[105, 804, 886, 890]]<|/det|> +
Supplementary Fig. x: SEMORE's Morphological Fingerprint captures gradual transitions in morphology. Thirty aggregates of each morphology class (fibril-like: fib, isotropic: iso, sterically-hindered/random: rand) of equal size were simulated resulting in ninety distinct structures which are placed sequentially in random order whilst ensuring no consecutive types. Between each of the ninety structures (89 transitions) 100 positions are constructed from interpolation (see methods). Thus, a total of 8900 intermediates gradually changing morphology between the three structures were evaluated using the fingerprinting module of SEMORE. All resulting transitions are connected
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 75, 887, 274]]<|/det|> +in time, meaning the final structure of the (i) transition is the starting structure of \((i + 1)\) transition, thus creating a single dynamic structure of gradual transitions. a- c Shows representative transitions from fibril to isotropic, from fibril to random, and from random to isotropic, respectively. The lines drawn between points in a- c represent the 100 different positions expressed throughout the interpolation from the initial structure to the target structure. The color gradient of the box around each panel in a- c is the RGB representation of the percentage of morphology transition between the three distinct morphology classes. This color map is also used in d. (d) To visualize the general data manifold of the morphological fingerprints across the 8900 structures, the high dimensional morphological feature set was dimensionality reduced through a UMAP (n_components : 2, n_neighbors: 400, min_distance: 0.5). Similar to supplementary fig. 15 the embedding shows capture of distinct morphology classes and now also the continuous gradual change between the distinct morphology classes, as each structure morphs into the next. Thus, highlighting SEMORE's strength in capturing gradual morphological evolution. \(97.9\%\) of data are grouped in the continuous flow between the three distinct morphologies \((x = 7.5, y = 6)\) . The small group around the \((x = - 5, y = 0)\) area contains 186 points representing \(2.1\%\) of the data, although outliers still show a continuous flow between morphology classes. From this visual inspection, it is clear that the fingerprints capture both drastic and gradual changes in structure. + +<|ref|>sub_title<|/ref|><|det|>[[108, 293, 395, 312]]<|/det|> +## Changes in manuscript 2.1: + +<|ref|>text<|/ref|><|det|>[[108, 318, 466, 332]]<|/det|> +To fully address the comment of the referee we have: + +<|ref|>text<|/ref|><|det|>[[106, 339, 867, 354]]<|/det|> +a) added a new supplementary figure 26 detailing the dynamic morphology variation and how SEMORE track this + +<|ref|>text<|/ref|><|det|>[[106, 361, 886, 392]]<|/det|> +b) added a paragraph in the section "Morphological fingerprinting captures defining features separating heterogeneous assemblies." + +<|ref|>text<|/ref|><|det|>[[106, 399, 887, 583]]<|/det|> +"A central element of SEMORE is that it inherently performs temporal segmentation thus offering the potential to capture gradual morphological changes in super resolution data. To evaluate SEMORE's performance we simulated dynamic morphology variation between three major morphologies (fibril-like, isotropic, and sterically-hindered) (Supplementary Figs. 15 and 26). We simulated thirty structures of each morphology class (totalling 90), placed these sequentially in random order whilst ensuring no identical morphology consecutively. Between each of the ninety structures 100 positions are constructed by interpolation (see Methods) resulting in 8900 intermediate structures. UMAP representation in Supplementary Fig 26 shows SEMORE accurately captures distinct morphology classes and reliably tracks their gradual dynamic morphology change by placing intermediate structures on a gradient between the distinct morphology classes of where the transition is happening. Note, the UMAP is simply a visualization tool to show structure of the high dimensional data manifold of the 8900 morphological fingerprints, it is not a requirement for usage and may vary for specific cases. As these structures exist in a continuous space SEMORE allows future users to identify dynamic morphological variations and decide on system-specific decision boundaries for each of the structures." + +<|ref|>sub_title<|/ref|><|det|>[[108, 604, 256, 621]]<|/det|> +## Comment 2.2: + +<|ref|>text<|/ref|><|det|>[[106, 629, 887, 802]]<|/det|> +2. The authors compared the SEMORE result with previously reported results and asserted that SEMORE provided comparable results with the previous reports. For example, they insisted comparable results with Nieves et al (Supp Fig 17) and Wallis et al (Supp Fig 18). However, I cannot find the related supporting quantitative comparison data, making it difficult to judge whether SEMORE really provides comparable and reasonable results with the reported results. Additionally, the authors insisted that SEMORE could minimize the inclusion of false positive structures compared to HDBSCAN (in Supp Fig 17 experimental data), but I'm uncertain whether the filtered localizations are indeed false positive structures or positive structures that should not be filtered because there is no related data shown. To make a reasonable comparison of their results with others, quantitative comparisons should be provided. + +<|ref|>sub_title<|/ref|><|det|>[[108, 822, 260, 841]]<|/det|> +## Response 2.2: + +<|ref|>text<|/ref|><|det|>[[106, 848, 887, 880]]<|/det|> +We thank the reviewer for allowing us to clarify and improve the presentation of the additional experimental data we use to showcase the operational utility of SEMORE. The quantification of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 74, 886, 230]]<|/det|> +SEMORE performance is extensively validated on simulated data where there is undoubtedly ground truth (supplementary figs 4, 11, 13, etc.). Comparison of performance on experimental data however requires ground truth which is only attained by field specific expert knowledge. While we had already some quantification, as we detail below, we felt that directly and outloud comparing SEMORE with existing methods dealing with experimental data where there is no strictly defined ground truth might be misinterpreted as criticism to our esteemed colleagues and future collaborators. Therefore, we had kept it minimal in the original manuscript especially as methods and research goals are different. To fully address the comment of the reviewer we now provide below the requested additional quantitative comparison. + +<|ref|>sub_title<|/ref|><|det|>[[106, 248, 213, 264]]<|/det|> +## SI figure 17. + +<|ref|>text<|/ref|><|det|>[[137, 281, 886, 385]]<|/det|> +Supplementary figure 17 included reported area per cluster as Nieves et al and we had even chosen the same plotting style for easier comparison. We had also emphasized that the two approaches calculate area differently, i.e., convex hull counting white space (Nieves et al) vs Delaney triangulation and edge pruning to avoid redundant white space (ours). The comparison of the two methods was already displayed in Supplementary figure 20. + +<|ref|>text<|/ref|><|det|>[[106, 393, 618, 410]]<|/det|> +To further strengthen the quantitative comparison, we provide: + +<|ref|>text<|/ref|><|det|>[[135, 417, 886, 562]]<|/det|> +a) a comparison of Nieves et al and SEMORE that show an \(88\%\) agreement in categorizing detections as noise, showing that SEMORE and Nieves et al have agreement in which detections are noise and which are signal. +b) a raw count of the number of protein assemblies identified by SEMORE across the 15 experiments provided in Nieves et al and compared to the declared results in Nieves et al. We report that SEMORE identifies \(82\%\) of clusters found by Nieves et al (130 out of 158 assemblies) thus supporting SEMORE obtains comparable results, while also providing morphological fingerprints of each assembly. + +<|ref|>text<|/ref|><|det|>[[106, 569, 886, 794]]<|/det|> +Importantly, Nieves et al use a DBSCAN with parameters (eps = 65, minPts = 32) chosen based on highest spatial similarity to one of 10 simulated data scenarios, such settings disfavor smaller clusters thus have inherent tendency to make larger clusters. SEMORE self- parameterized based on the experimental data itself and it includes a round of refinement allowing the capture of smaller clusters and splitting of large into distinct smaller clusters (as seen in main figure 1 and the updated supplementary figure 17). SEMORE captures 9.4 new small clusters per movie that is classified as noise by Nieves et al. SEMORE can easily report the same clusters by turning off the additional refinement and only using the DBSCAN. We stress that experimental data have no ground truth and they are reliant on field expertise, so we would refrain from elaborating in the main text on why SEMORE is better and rather state that the results are similar. Lastly we point out that the comparison of DBSCAN and SEMORE on simulated, and thus ground truth data, is shown in supplementary figure 4 where SEMORE also exhibited clear superiority in detecting clusters and excluding false positives. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[108, 73, 870, 478]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[105, 480, 887, 682]]<|/det|> +
Supplementary Fig. 17 (UPDATED): dSTORM data from Nieves et. al1 clustered and quantified by SEMORE a Raw detections from SMLM data of fibroblast growth receptor 1 (FGFR1) on a MCF7 cell presented by Nieves et al.1 b Initial clustering by SEMORE's clustering module using the inherent data-driven model choice of HDBSCAN (Min_cluster_size = 15 and Min_sample = 5). Each localization is colored by its SEMORE annotation, with black representing noise and all other colors representing captured clusters. c The final clustering by SEMORE after refinement and smart density filtering (see Methods). Localizations are colored corresponding to the final SEMORE prediction. Red box depicts the same zoom-in as seen in Nieves et al inside which they report 2 unique clustering indices similar to the initial clustering seen in b. SEMORE's additiona refinement split one of these into four distinct clustered indexes, thus resulting in five clusters. Keeping these settings constant through the 15 datasets from Nieves et al. d Histogram of cluster area estimation. SEMORE identifies mean cluster area of \(0.004 \pm 0.003 \mu m^2\) and median of \(0.003 \mu m^2\). SEMORE provides more fine-grained area calculation than convex hull (see supplementary figure 20) and may split larger clusters to smaller during rounds of refinement. e Distribution of points contained in the proposed clusters with a mean of \(52 \pm 108\) and a median of 29. SEMORE and Nieves et al. obtain qualitative similar results and have 88% agreement in assigning points as noise showing the general agreement as methods
+ +<|ref|>text<|/ref|><|det|>[[107, 699, 886, 766]]<|/det|> +To answer the second comment of the reviewer on minimizing false positives in supplementary figure 17. We assume the reviewer means to compare to Nieves although they use DBSCAN ( "the authors insisted that SEMORE could minimize the inclusion of false positive structures compared to HDBSCAN (in Supp Fig 17 experimental data)"). + +<|ref|>text<|/ref|><|det|>[[135, 774, 887, 884]]<|/det|> +- As attend above, Nieves et al and SEMORE have 88% agreement in categorizing detections as noise- Nieves et al color true and false positives, thus visual inspection of SEMORE's prediction and the declared true and false positives from Nieves et al provide a very clear qualitative estimate of the correspondence. We stress again that since these are experimental data it is hard to strictly define ground truth. We have updated the figure to show the exact + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[166, 75, 886, 126]]<|/det|> +same field of view as Nieves et al (figure 5 in Nieves et al) to facilitate an easier visual comparison and provided \(88\%\) agreement in categorizing detections as noise showing that the reported results are concordant. + +<|ref|>sub_title<|/ref|><|det|>[[106, 152, 213, 167]]<|/det|> +## SI figure 18. + +<|ref|>text<|/ref|><|det|>[[106, 168, 886, 219]]<|/det|> +Supplementary figure 18 included a direct comparison of the specific example from Wallis et al showing a cluster being captured three times across time and SEMORE capturing the exact same as seen in SI figure 18c- d. + +<|ref|>text<|/ref|><|det|>[[106, 228, 886, 331]]<|/det|> +To provide a further quantification we counted the number of clusters reported in a crop- out from Wallis et al and compared to the raw cluster count identified by SEMORE. Wallis et al have 104 clusters while SEMORE has 107 (See the figure below). We stress that SEMORE not only segments clusters but inherently tracks and links clusters in time for tracking morphology over time. Therefore, we manually counted the areas of interest identified by Wallis et al and by SEMORE in a single frame. + +<|ref|>image<|/ref|><|det|>[[168, 356, 559, 660]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[106, 668, 210, 684]]<|/det|> +## SI figure 19 + +<|ref|>text<|/ref|><|det|>[[106, 685, 886, 753]]<|/det|> +Lastly, we are pleased that the results in SI figure 19 were satisfactory and without comments as this example also highlights the ability to generalize across experimental conditions as visually and quantitatively validated to results of Hou et al. To be consistent we also provide a direct comparison demonstrating once more SEMORE is on par with existing toolboxes. + +<|ref|>sub_title<|/ref|><|det|>[[108, 774, 395, 794]]<|/det|> +## Changes in manuscript 2.2: + +<|ref|>text<|/ref|><|det|>[[106, 800, 560, 834]]<|/det|> +To fully address the comment of the reviewer we a) Updated and modified figure text of SI figure 17. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[133, 74, 888, 265]]<|/det|> +b) Added the number of identified clusters to supplementary figure 18. "Last snapshot shows the N=107 for the total identified clusters in this snapshot and contains a red box highlighting an additional region of interest."c) Added in supplementary figure 19 en extra sentences for the quantitative comparison "Utilizing the tight packing assumption for RyRs \(^3\) identified RyR clusters SEMORE reports on average of 18 RyR with a median of 14 RyR in line with the 9 RyR reported by Hou et al \(^3\) importantly achieving so without any intensity thresholding."d) Added in section "Precise extraction and quantification of experimental super-resolution data." "While in experimental data sets it is hard to strictly define ground truth SEMORE outputs qualitatively outputs identical predictions with current states of the art." + +<|ref|>sub_title<|/ref|><|det|>[[108, 282, 256, 301]]<|/det|> +## Comment 2.3: + +<|ref|>text<|/ref|><|det|>[[108, 308, 886, 394]]<|/det|> +3. In many figures, particularly in supplementary figures, scale bar information or axis units are missing. Consequently, it is challenging for me to judge whether the clustering or filtering is biologically relevant in their image data. Additionally, in supplementary Figure 17 d-f, it appears that the x-axis is meaningless, so a scatter plot for density vs. N or Area would be more reasonable. + +<|ref|>sub_title<|/ref|><|det|>[[108, 414, 260, 433]]<|/det|> +## Response 2.3: + +<|ref|>text<|/ref|><|det|>[[108, 439, 886, 527]]<|/det|> +We agree with the reviewer's suggestion towards remaking supplementary Figure 17 d-f to be more easily readable. We were following the plotting template of Nieves et al for a more direct and easier comparison (see answer to reviewer comment 2.2) but following the reviewer's suggestion that the x-axis is meaningless we move away from Nieves et al plotting approach and now display histograms in the revised supplementary fig. 17. + +<|ref|>text<|/ref|><|det|>[[108, 533, 886, 585]]<|/det|> +The reviewer also commented: "scale bar information or axis units are missing. Consequently, it is challenging for me to judge whether the clustering or filtering is biologically relevant in their image data." + +<|ref|>text<|/ref|><|det|>[[108, 592, 860, 609]]<|/det|> +We fully agree that the scale bar is instrumental for judging dimensions of the morphologies. + +<|ref|>text<|/ref|><|det|>[[108, 616, 886, 694]]<|/det|> +In the initial response to reviewer 1 we had already explained that SEMORE is purposefully designed to be dimension- independent, therefore the simulated data are without a scale bar, to which they responded: "The extra benchmarking and highlighting the scale invariance has significantly improved the manuscript and will be a very useful tool for SMLM cluster analysis and classification. I fully recommend the revised manuscript for publication." + +<|ref|>text<|/ref|><|det|>[[108, 700, 821, 717]]<|/det|> +Please see the full question and response at the end of this section in blue colour fonts. + +<|ref|>text<|/ref|><|det|>[[108, 721, 886, 772]]<|/det|> +However, we realize that snapshots from the data in main figure 4 seen in supplementary figures 24 and 25 did not contain error bars and only the full scale figure 4 did. We have now rectified this and we thank the reviewer for noticing this. + +<|ref|>text<|/ref|><|det|>[[108, 779, 886, 866]]<|/det|> +As we detail below the scale invariance of SEMORE is due to our choice of 3D axis standardization. Working with standardized dimensions enables SEMORE to work across experimental configurations and dimensionalities. This allows SEMORE to operate independently of the imaging dimension and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 75, 886, 108]]<|/det|> +Therefore, the simulated data is of arbitrary units, and we did not include a scale bar, however we have now included scale bars with "a.u" for units based on the reviewer's comment. + +<|ref|>text<|/ref|><|det|>[[106, 116, 886, 220]]<|/det|> +We emphasize that SEMORE proves its dimension independence by accurate segmentation across the 5 diverse biological systems spanning from nanometer to micrometer and further by extensive quantification on simulated data at different scales. This should also help the reviewer to "judge whether the clustering or filtering is biologically relevant in their image data". The simulated data included in the manuscript supports the experimental data and serves as ground truth quantifying the output of SEMORE. + +<|ref|>sub_title<|/ref|><|det|>[[108, 240, 395, 259]]<|/det|> +## Changes in manuscript 2.3: + +<|ref|>text<|/ref|><|det|>[[137, 266, 887, 333]]<|/det|> +1) Acknowledging the scale invariance may not be clear to the audience we have added an extra short section in results section that already discusses the scale invariance: "This allows SEMORE to operate independently of the imaging and cluster dimensions and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area." + +<|ref|>text<|/ref|><|det|>[[135, 360, 652, 377]]<|/det|> +2) We have added the histograms in Supplementary figure 17 + +<|ref|>text<|/ref|><|det|>[[135, 384, 886, 436]]<|/det|> +3) We have added scale bars on a.u in the simulated data in Supplementary figures 1, 2, 13, 20, 21 and scale bars at the experimental snipsets displayed in Supplementary figures 24, 25. + +<|ref|>text<|/ref|><|det|>[[134, 443, 884, 461]]<|/det|> +4) We further refer to the comment and response of the first round of review (in blue below): + +<|ref|>text<|/ref|><|det|>[[135, 467, 887, 605]]<|/det|> +5) We add in the discussion the key result that SEMORE agnostically segments across five experimental data sets spanning nanometers to micrometers by modifying an existing sentence." Effectively, SEMORE operates across five experimental data sets with spatial dimensions spanning 3 orders of magnitude from nanometer \(^{58}\) to micrometers \(^{19}\) and temporal dimensions spanning from milliseconds \(^{60}\) to second \(^{19}\) . This fact provides strong support for SEMORE as a universal, input-independent model for the SMLM community to use in conjunction with, or to be incorporated into SMAP, or as a convenient standalone toolbox" + +<|ref|>sub_title<|/ref|><|det|>[[106, 631, 497, 650]]<|/det|> +## Comment 1.1 (reviewer 1, first round) + +<|ref|>text<|/ref|><|det|>[[106, 653, 887, 824]]<|/det|> +The clusters within the simulated data seem to be very large in scale, some on the order of 10 microns. This is likely to be an uncommon scenario in biological SMLM data, especially when it comes to clustering of that data. I would recommend some simulations on the scale of the NPC data, i.e., several clusters sub- micron with diverse morphology. A recent paper cited in the manuscript proposed several different clustering scenarios at this scale (Nieves et al., NatMeth, 20, pages 259- 267, 2023) where two different cluster types are present within the region. This would be really nice to see clusters of similar density (in that paper it was approximately 10- 20 per 3x3 micron2), but analysed in a similar fashion here, i.e., analysis of the whole 40x40 micron region. This would be quite powerful if whole fields of view could be analysed quickly, without the need for subdivision of the data (see later point on performance). + +<|ref|>sub_title<|/ref|><|det|>[[108, 842, 250, 861]]<|/det|> +## Response 1.1 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 75, 887, 210]]<|/det|> +The reviewer correctly points out that large aggregates are generally depicted in the manuscripts. We stress here that SEMORE clustering module is scale- invariant and solely relies on localisations. This is due to our choice of 3D axis standardization. Working with standardized dimensions enables SEMORE to work across experimental configurations and dimensionalities. This allows SEMORE to operate independently of the imaging dimension and achieve high classification accuracies solely based on the number of localizations contained within the protein assembly given the spanning area. + +<|ref|>text<|/ref|><|det|>[[106, 197, 887, 250]]<|/det|> +The comment still raises a very valuable point on the generalization and performance of SEMORE and to demonstrate this and fully answer the comment of the reviewer we performed two studies: + +<|ref|>text<|/ref|><|det|>[[137, 248, 887, 360]]<|/det|> +1) Simulated diverse, nanometer dimension structures, and quantified SEMORE performance on their segmentation and classification for data with 8, 15 and 25 localisations in an area that corresponds to \(\sim 1\mathrm{um}\) . As can be seen in Supplementary Fig. 8 (Response figure 5) in the revised version, SEMORE reached an accuracy of \(>90\%\) in extracting clusters with 8 or more localisations with the morphology fingerprinting completely separating true clusters from noise. + +<|ref|>text<|/ref|><|det|>[[137, 351, 887, 456]]<|/det|> +2) Simulated protein assemblies of just 4 detections and evaluated SEMORE's performance on such a small cluster representing the minimal representation of a tetramer. SEMORE achieves accuracies of up to \(70 - 90\%\) in segmenting these tiny structures depending on the noise levels while the morphological fingerprinting module captures these noisy detections allowing for potential post-processing and accuracy increase, Supplementary Fig. 7 (Response figure 4). + +<|ref|>text<|/ref|><|det|>[[137, 455, 887, 576]]<|/det|> +3) Evaluated the number of points needed for SEMORE to accurately detect the initiation points of spatially overlapping clusters. The high accuracy of SEMORE to capture initiation points can be quantified and visualized using simulated data showing is just \(\sim 13\) frames off on average across 3 types of spatially overlapping morphologies. Furthermore, qualitative assessment using experimental data of temporally resolved insulin aggregation supports the reliability of SEMORE, Supplementary Fig. 5+6, response figure 6+7). + +<|ref|>text<|/ref|><|det|>[[106, 575, 887, 680]]<|/det|> +In essence, \(\sim 10\) detections is enough for SEMORE to obtain high segmentation and classification accuracy which is well below the common number of detections in most SMLM experiments. We analyze dSTORM data of Nieves et al. NatMeth, 20, pages 259- 267, 2023 1 obtaining similar densities and cluster sizes but in fact analyzing the entire field of view at once see new SI fig 17 (response figure 1). We further use the approach from Nieves et al., NatMeth, 20, pages 259- 267 to simulate structures with blinking, see comment 1.3. + +<|ref|>sub_title<|/ref|><|det|>[[108, 698, 426, 717]]<|/det|> +## Changes in the manuscript 1.1 + +<|ref|>text<|/ref|><|det|>[[106, 718, 887, 770]]<|/det|> +To fully address the comment of the reviewer in the revised version of the manuscript we have added a new section within "Accurate extraction of individual assemblies across diverse biologically inspired growth types.": + +<|ref|>text<|/ref|><|det|>[[106, 771, 887, 888]]<|/det|> +"To further evaluate the performance of SEMORE on segmentation and analysis of dynamic SMLM data we performed a series of stress tests on simulated data. We firstly evaluated SEMORE's ability to track morphological changes in time using simulated data of 3 types of spatially overlapping protein clustering morphologies with temporal information included. Snapshots of SEMORE's clustering in time provide visual confirmation of SEMORE's ability to track morphological changes in time (see Supplementary Fig. 5 for snapshots of simulated and Supplementary Fig. 6 for experimental data). Further quantification of SEMORE's ability to accurately track and segment spatially overlapping protein assemblies in time reveals growth onset times across 3 morphological classes are predicted with an average offset of just \(\sim 13\) frames (Supplementary Fig. 6). Subsequently, we test the clustering module on + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 75, 888, 234]]<|/det|> +simulated, sparse structures containing as little as 4, 8, 15 and 25 point detections akin to data of protein oligomerization (see Supplementary Fig. 7 & 8). SEMORE analyzes the entire field of view at once and extracts structures down to 4 detections while maintaining \(>90\%\) accuracy at biologically relevant noise to signal ratios. The morphological fingerprinting module can further refine the false positive detections from noise with as little as 4 detections, achieve full separation from noise at 8 detections and classify morphological classes in true structures at 15 detections (see Supplementary Fig. 8 & 9). Lastly we evaluated its performance to degenerative structures that shrink in time, akin to protein de- polymerisation. SEMORE accurately segments 3 anisotropically degenerative morphologies showcasing it can be used to analyze dynamic shrinkage or depolymerisation of protein clusters (see Supplementary Fig. 10). In essence SEMORE only requires \(< 10\) detections to accurately segment and classify heterogeneous structures with dynamic morphologies further demonstrating its operational utility and potential for 4D SMLM.". + +<|ref|>text<|/ref|><|det|>[[108, 252, 485, 268]]<|/det|> +Elaborated in results on the scale invariance: + +<|ref|>text<|/ref|><|det|>[[106, 270, 888, 366]]<|/det|> +" The clustering module of SEMORE consists of multiple steps that self- parameterize based on the input data and are scale invariant due to the inherent 3D axis standardization (see Methods). This is designed to account for the inherently heterogeneous nature of biological assembly systems, in size, scale, spatial overlap, density, and morphology as well as the variability across experimental configurations that challenges current analytical tools." In addition, to address the comment we have added 5 new SI figures, namely Response figures: 1,4,5, 6, and 7. + +<|ref|>sub_title<|/ref|><|det|>[[108, 385, 257, 404]]<|/det|> +## Comment 2.4: + +<|ref|>text<|/ref|><|det|>[[106, 410, 888, 583]]<|/det|> +4. Although the authors performed additional simulations with various noise variations, I don't understand some of the data. For example, Supplementary Figure 3 shows an increasing accuracy with an increasing ratio of heterogeneous, non-uniform noise, which is contrary to the general expectation. This could be because the data in Supplementary Figure 3c were obtained from just one-time simulation for each noise ratio (there is no error bar in this data), which could not demonstrate the general trend very well. While the authors claimed that the smart-density noise filter is designed to expect noise and remove true positives, such a case could lead to incorrect filtration for real images with low noise as well. Since different SMLM microscopes and different biological samples can produce various noise levels, I believe that if such an effect exists in their analysis method, it should be resolved. + +<|ref|>sub_title<|/ref|><|det|>[[108, 604, 260, 622]]<|/det|> +## Response 2.4: + +<|ref|>text<|/ref|><|det|>[[106, 629, 887, 750]]<|/det|> +We appreciate the feedback for the missing clarity in Supplementary Fig. 3 and for allowing us to rectify this. The current supplementary fig. 3 relies on the data displayed in Supplementary fig 2, which, as stated in the figure legend, is a summary across 5 separate simulations each containing 13 protein assemblies. In addition, we do display in both Supplementary figures 2 and 3 an error- metric across the 5 simulations by showing the variance of accuracy, i.e. the squared standard deviation (orange line at \(\sim 12\%\) ). We thank the reviewer for pointing out that this was not clear enough and we have now further clarified this in the figure legend. + +<|ref|>text<|/ref|><|det|>[[106, 757, 887, 877]]<|/det|> +The reviewer also commented on an upward trend in accuracy. We agree that the first 2 of 16 points display an upwards trend until the accuracy curve flat lines from point 3 to 16. These 2 points are associated with both the largest variation in accuracy and the lowest accuracy. In addition, these points represent experimental conditions with extremely low noise or no noise at all, unlikely for any single molecule localisation experiment. We had commented already on this in the figure legend stating that "at unrealistically low noise levels the smart density filter expects noise and removes true positives if no noise is present, and that this can be easily turned off." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 75, 887, 161]]<|/det|> +We emphasize that the smart noise filter only lowers accuracy for the case of no noise or noise being 10 times less than signal. The filter is easily turned off for users operating with systems that do not produce any noise or next to no noise, albeit we are unaware of such technological development. A realistic noise level is displayed by the blue shaded area. While we were aware of the above, we kept the filter on for transparency into SEMORE's output. + +<|ref|>text<|/ref|><|det|>[[106, 168, 887, 272]]<|/det|> +To address the reviewer comment and alleviate any confusion we ran SEMORE without the noise filter (see new panel in Supplementary fig 3). As expected, not utilizing smart density filtering results at better accuracy at unrealistically low noise levels, but accuracy declines at, and above, realistic noise levels. Importantly and directly addressing the reviewer's concern SEMORE's segmentation accuracy at the extremely low or no noise levels joined the high accuracy displayed at the more realistic noise cases. + +<|ref|>image<|/ref|><|det|>[[105, 295, 835, 666]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[106, 670, 747, 685]]<|/det|> +
Supplementary Fig 3: Benchmarking SEMORE on for heterogeneous, non-uniform noise.
+ +<|ref|>text<|/ref|><|det|>[[105, 685, 887, 881]]<|/det|> +a) Simulated data as described and used in SI fig. 2, that includes 5 separate simulations with 13 protein assemblies each, but now exhibiting a heterogeneous noise profile. Heterogeneous noise is generated by introducing 5-25 "noise seeds" each containing 20-50 points have been added to each simulation, additionally, individual Gaussian distributed shifts have been applied to all initial noise points. b) we see SEMORE clustering classification performance as out-of-the-box. c) Evaluating SEMORE clustering performance versus increasing noise ratio (blue area representing biologically relevant noise-levels estimated from real data and with vertical blue line representing insulin experiments). At biologically relevant noise levels or high noise levels accuracies of SEMORE is observed to be above \(\sim 90\%\) with variance accuracy of \(\sim 12\%\) from noise ratio \(\sim 0.2\) and onwards with up to \(93\%\) at 0.7 noise ratio reflecting SEMORE's ability to separate non-uniform noise also observed in robust treating of experimental insulin data (see main fig. 4). The unrealistic conditions with extremely low noise ratios or no noise at all are associated with lower accuracies as the smart-density noise filter expects noise and removes true positives if no noise is present, which is easily countered by turning it off.d) SEMORE's clustering performance on the same data set without the smart noise filter (blue area representing biologically relevant noise-levels estimated from real data and with vertical blue line representing insulin experiments). SEMORE accuracy is above \(\sim 90\%\) from conditions with no noise up to around noise ratios of \(\sim 1\) + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[107, 74, 886, 133]]<|/det|> +Turning off the noise filter results in better performance at extremely and unrealistically low or no noise ratios (zero noise to noise- to- signal ratio of 0.1), but the performance strongly declines starting from around biologically relevant noise levels. For users operating with little or no noise in their experimental system the results indicate the smart filter should be turned off while users operating with realistic noise are recommended to utilize the full SEMORE pipeline. + +<|ref|>sub_title<|/ref|><|det|>[[108, 152, 395, 171]]<|/det|> +## Changes in manuscript 2.4: + +<|ref|>text<|/ref|><|det|>[[107, 173, 886, 243]]<|/det|> +1. We highlight in the text that users should evaluate performance on their given system without the noise filter and turn smart density filtering off, only at unrealistically low noise levels, adding in the 2nd paragraph of section "Accurate extraction of individual assemblies across diverse biologically inspired growth types." + +<|ref|>text<|/ref|><|det|>[[107, 249, 886, 302]]<|/det|> +While at unrealistically low noise ratios i.e ten times lower than signal, smart density filter can result in removal of true positives, we recommend using the full SEMORE pipeline for data with noise (Supplementary Fig. 3)". + +<|ref|>text<|/ref|><|det|>[[105, 308, 886, 342]]<|/det|> +2. Added a new panel in supplementary fig 3 showing SEMORE's performance without the noise filter. + +<|ref|>text<|/ref|><|det|>[[105, 349, 886, 384]]<|/det|> +3. We emphasize in the figure text of SI figure 3 that it is based on 5 simulated data sets with 13 protein assemblies each. + +<|ref|>sub_title<|/ref|><|det|>[[107, 404, 256, 422]]<|/det|> +## Comment 2.5: + +<|ref|>text<|/ref|><|det|>[[106, 429, 886, 671]]<|/det|> +5. Regarding the responses for my fourth comment (2.4), I do understand that unsupervised learning is also a significant component of machine learning. My previous comments might be somewhat unclear in conveying my intended message. During the SEMORE clustering process, there are several steps involved in clustering meaningful points. The methods you have suggested in this paper to enhance clustering primarily focus on filtering out points and implementing temporal refinements. My point of concern is related to what happens once the filtered and refined points are available. I am uncertain about the contributions of this work to the "machine-learning-based clustering algorithm" at this stage. Even if the filtering and temporal refinements can potentially aid subsequent machine-learning-based clustering algorithms, they are difficult to be considered as a machine-learning algorithm by themselves. Therefore, I am curious if you have made any contributions to the "machine-learning-based clustering algorithm itself" apart from hyperparameter tuning in existing methods like DBSCAN. Examples of such contributions might include modifications to the loss function, alterations to the architecture, improved training techniques, and so on. + +<|ref|>sub_title<|/ref|><|det|>[[107, 692, 260, 710]]<|/det|> +## Response 2.5: + +<|ref|>text<|/ref|><|det|>[[106, 716, 886, 890]]<|/det|> +Thank you for allowing us to elaborate further on this. We would like to emphasize two key points: Firstly, the reviewer states that "What happens once the filtered and refined points are available" It is important to note that without the developed modalities of SEMORE, (Automatic, data- driven model selection, semi- supervised hyperparameter choices based on experimental data, topological failsafe, Smart noise filtering and temporal refinement,) the correct clustering and segmentation of experimental data and tracking its morphology in time is not easily available, see main figure 1b vs 1d or SI figure 4. Effectively the SEMORE pipeline, building on existing models, contributes to the field by providing a universal automated and self- parameterized pipeline efficiently resolving a major obstacle that challenges the widespread implementation of SMLM, that of analysis and segmentation of the data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[106, 92, 888, 230]]<|/det|> +The reviewer also comments "Even if the filtering and temporal refinements can potentially aid subsequent machine- learning- based clustering algorithms...they are difficult to be considered as a machine- learning algorithm by themselves." We stress here that the refinement and filtering do not all happen prior to DBSCAN or HDBSCAN but rather as rounds of refinement in the pipeline. These rounds are both before and after the initial clustering by current methods, although mostly after. We are thus confused as to how such a scenario should be imagined, but if users somehow already have their refined and filtered points available, we contribute with the morphological fingerprinting module for further quantification. + +<|ref|>text<|/ref|><|det|>[[106, 238, 888, 462]]<|/det|> +The reviewer continues: "... Therefore, I am curious if you have made any contributions to the "machine- learning- based clustering algorithm itself" apart from hyperparameter tuning in existing methods like DBSCAN...". We wish to highlight a few papers in interdisciplinary journals2- 5 that present methods built on existing foundational tools repurposed to work for specific fields. Whether contributions are contributions to the "machine- learning- based clustering algorithm itself" appears more semantic of nature rather than objective. For instance, Chen et al4 and Walker et al3 both enriched an existing machine learning tool, also DBSCAN, with approaches such as filtering, Otsu's algorithm, constructing graphs etc. to obtain results otherwise not readily unobtainable. Likewise, we enrich an existing tool that could not function properly for super- resolution data, extract the results of the manuscript, and do so across diverse experimental conditions and biological systems. Importantly, our method automates the agnostic analysis of super- resolution data across experimental conditions and biological systems as clearly demonstrated by the application to 5 diverse experimental datasets. + +<|ref|>text<|/ref|><|det|>[[106, 469, 887, 573]]<|/det|> +We could further argue that the original DBSCAN/(HDBSCAN) optimizes some objective function \(\mathsf{f}(\mathbf{x})\) but we optimize \(\mathsf{g}(\mathsf{f}(\mathbf{x}))\) where \(\mathsf{g}\) is our contributions working both prior and after the output of DBSCAN. In fact, unsupervised machine learning clustering in general groups points based on characteristics by optimizing some objective function. Our contribution effectively changes these characteristics, the pipeline and thus the outcome of the ML model. This can be seen as either changing the training approach or changing the architecture/pipeline. + +<|ref|>text<|/ref|><|det|>[[106, 580, 887, 666]]<|/det|> +We are in fact carefully phrase our contribution as a new approach to analyze super- resolution data that enables analysis across experiments and systems, something that was easily accessible before (see also main figure 2 and Supplementary figures 4, and 19 for DBSCAN and SEMORE on simulated experimental data). " SEMORE, a semi- automatic machine learning framework for universal, system and input- dependent, analysis of super- resolution data" + +<|ref|>sub_title<|/ref|><|det|>[[107, 691, 210, 707]]<|/det|> +## Bibliography + +<|ref|>text<|/ref|><|det|>[[106, 718, 887, 763]]<|/det|> +1. Nieves, D. J. et al. A framework for evaluating the performance of SMLM cluster analysis algorithms. Nat. Methods 20, 259-267 (2023). + +<|ref|>text<|/ref|><|det|>[[106, 778, 887, 825]]<|/det|> +2. Yu, W., He, B. & Tan, K. Identifying topologically associating domains and subdomains by Gaussian Mixture model And Proportion test. Nat. Commun. 8, 535 (2017). + +<|ref|>text<|/ref|><|det|>[[106, 839, 887, 886]]<|/det|> +3. Walker, B. L. & Nie, Q. NeST: nested hierarchical structure identification in spatial transcriptomic data. Nat. Commun. 14, 6554 (2023). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[105, 74, 888, 121]]<|/det|> +4. Chan, H. et al. Machine learning coarse grained models for water. Nat. Commun. 10, 379 (2019). + +<|ref|>text<|/ref|><|det|>[[105, 133, 887, 183]]<|/det|> +5. Mulhall, E. M. et al. Direct observation of the conformational states of PIEZO1. Nature 620, 1117-1125 (2023). + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 330, 98]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 112, 415, 126]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 140, 860, 169]]<|/det|> +The authors addressed all the concerns I had regarding the previous version of the manuscript. I appreciate that the authors went the extra mile to address the various concerns. + +<--- Page Split ---> diff --git a/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0637a088a01e8ddab3bf3fa98dbe804cbde1a0dc --- /dev/null +++ b/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1 @@ +[] \ No newline at end of file diff --git a/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..4eaf23ea4498617dc4a6617e2b7e0c9b618634a2 --- /dev/null +++ b/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,311 @@ + +# natureportfolio + +Peer Review File + +Longitudinal viral shedding and antibody response characteristics of men with acute infection of monkeypox virus: a prospective cohort study + +![PLACEHOLDER_0_0] + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +Reviewer #1:Remarks to the Author:Very comprehensive article on the dynamics of antibodies and the virus both with multi- site samples on the patient and in the environment. the patient data on the multisite are not original and correspond to data already published but with more samples. What is interesting is to compare the environment and especially the type of antibodies present in a strategy for improving our vaccination policies. + +Reviewer #2: + +Remarks to the Author: + +- What are the noteworthy results? + +Yang and colleagues describe thoroughly the viral load kinetics over the first three weeks of monkeypox virus (MPXV) infection in various parts of the body by PCR- detection of MPXV DNA. They also measure MPXV DNA levels in environmental fomites swabs and describe the dynamics of IgG antibodies against different surface proteins of MPXV. + +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +The work is of significance to the mpox field, although not being the first work describing these three items. Previous works had measure MPXV DNA levels in distinct body parts, in environmental fomites and describe de dynamics of antibody responses, several of which have not been referenced in the manuscript (Mpox immune responses: Colavita et al, Journal of Medical Virology 2023; Hubert et al Cell Host Microbe 2023; Cohn et al, Lancet Infect Dis 2023; Moraes- Cardoso et al, Lancet Microbe in press / Lancet preprint.; Mpox fomites: Morgan et al, Emerg Infect Dis 2022). + +Despite not being novel, the sound methodology of systematic collection of samples makes the work valuable for the field. + +- Does the work support the conclusions and claims, or is additional evidence needed? + +Overall, the conclusions and claims expressed by the authors are supported by the data. The authors claim that their data has "profound implications for the diagnosis, treatment, prevention of transmission and development of vaccines for Mpox", which I disagree given the previous knowledge on this field. The lack of viral isolation assays prevents from really translating their findings on MPXV DNA levels into actual risk of virus transmission. + +- Are there any flaws in the data analysis, interpretation and conclusions? - Do these prohibit publication or require revision? + +I am concerned about the following analysis/interpretations, which should be revised for its publication: + +- Key characteristics of the population where this study is conducted are missing, which prevents the appropriate interpretation of the study. The authors should specify whether patients were hospitalized because of the severity of the disease or based on isolation procedures. The immune status of participants, particularly HIV-positive individuals should be specified. 5 patients received smallpox vaccination but it is not clear whether this vaccines where administered during childhood or as part of the 2022 outbreak response, please specify. + +- The authors found a higher prevalence of rectitis among HIV-positive individuals. To my knowledge, this is the first study to find this association and, given the small sample size, the authors should discuss whether this finding is truly reflecting an increased risk of rectitis among this population. In the same line, the authors observed an increased rectal viral load in HIV positive individuals. I strongly suggest that the authors conduct a sensitivity analysis comparing rectal viral loads between individuals with and without HIV, and with and without rectitis, to rule out whether the higher rectal viral load in + +<--- Page Split ---> + +HIV positive individuals is only reflecting the higher percentage of patients with rectitis in this subgroup. + +- Samples from distinct body regions are collected differently and processed differently to measure MPXV DNA. Hence, viral loads between certain samples cannot be compared and this should be clearly specified in the manuscript. In the methods section it is not clear how each sample was collected and processed. For example, the volumes of saliva, urine or plasma used; or if swabs were placed in viral transport media, which total volume of media was present in each tube, and which volume was used for DNA extraction. Viral loads measured in urine and plasma are not fully reported and they should be included. + +The authors compare the positivity rates and viral loads from skin lesions, rectal swabs, saliva and oropharyngeal swabs. Only if the authors collected saliva with a swab, results from these samples can be presented together. If not, I would separate the results of these samples so that the reader is not misled to compare the results of one and other. + +- As previously mentioned, the authors have not included relevant references describing Mpox immune responses. The authors should discuss the differential findings between their study and the published literature in terms of antibody responses and neutralization. + +- Is the methodology sound? Does the work meet the expected standards in your field? + +The methodology is sound except for the lack of viral isolation assays. It would also be highly valuable that the authors transformed the Ct values in viral copies so that their results were more comparable with the literature. The reason for discussing results above/below a Ct value of 30 should be specified + +- Suner and colleagues defined a threshold for culture positivity of 6-5 log10 copies per mL or higher (approximately a Ct value of 26). + +- Is there enough detail provided in the methods for the work to be reproduced? As previously stated, the methods section lacks information on the procedures for sample collection and processing. + +Additional comments: + +- Line 244. This sentence refers to patients' positivity in each body sample at baseline or at any timepoint? Please clarify. + +- Line 282 - Results paragraph on environmental fomites. I suggest the authors present these results ordering the locations from higher positivity rates to lower positivity rates. + +- Figure 1. Specificity whether the statistical analysis compares viral loads or positivity rates. According to the figure, it should compare viral loads, and the Figure title should state "Comparative positive rates and viral loads..." + +- Figure 1A. I suggest removing this pannel, since pannels B-D where data is separated by d.p.o. are more informative. In these pannels, I would use the same scale for all y-axes so that they are comparable. + +- The authors could potentially explore the correlations between severity and IgG responses, as done by Moraes-Cardoso and colleagues. + +Reviewer #3: + +Remarks to the Author: + +This study predominantly describes the dynamics of viral loads and viral shedding of MPXV infection within a hospital setting. IgG responses to key MPXV antigens are also explored by ELISA (endpoint titres) and FRNT. Structuring the results into HIV status is central as this is an important at- risk group to consider for MPXV infection and transmission currently. + +The interpretations of results are clear and sufficiently justified with the following conclusions standing out as most significant: + +- Correlation of patient anti-A29 and anti-H3 IgG titres to neutralisation titres. Information on the + +<--- Page Split ---> + +contribution of antibodies to particular targets will be crucial for establishing correlates of protection and the next generation of MPXV vaccines. + +- Differences in ct values between patient sampling sites over time. This will be important for diagnostic decisions.- The detailed notes on clinical presentation will aid in accurate diagnosis.- Of additional note is the comprehensive examination of environmental fomites in a clinical setting. Valuable information for limiting transmission. However, assessing the viability of these samples would have strengthened these results significantly. + +The methodology is sound, of a good standard and sufficiently detailed for reproduction. The use of endpoint titres to compare IgG responses is appropriate in the absence of a standard. The two main limitations of the study are also sufficiently highlighted. + +Please find my questions and comments below: + +- Line 66 (Introduction): Worth expanding on which genetic changes may be responsible.- Line 168 (Methods: Enzyme-linked immunosorbent assays (ELISAs)): The use of a HRP-conjugated goat anti-human IgM antibody is mentioned in the methods to detect patient IgM to various MPXV antigens. However, the results are not shown or discussed. Suggest either removing this from the methods or presenting the results. The dynamics of IgM responses to these antigens and differences to IgG will be of interest. Their omission does not detract from the conclusions of the study.- Line 215 (Results: Baseline characteristics of the cohort): This sentence may need rewording to clarify – though Table S1 does this well.- Line 215 (Results: Baseline characteristics of the cohort): It would be of interest to hear if there were any differences in those vaccinated individuals with regards to viral loads/shedding and serologically. Were these patients vaccinated in response to the current outbreak or previously?- Line 230 (Results: Baseline characteristics of the cohort): Is this the same lineage as circulating in other cities in China? + +Overall, this is a detailed and well- reasoned study which contributes to the field and will be of importance for addressing the current outbreak. + +<--- Page Split ---> + +## Reviewers' Comments: + +## Reviewer #1 (Remarks to the Author): + +Very comprehensive article on the dynamics of antibodies and the virus both with multi- site samples on the patient and in the environment. the patient data on the multisite are not original and correspond to data already published but with more samples. What is interesting is to compare the environment and especially the type of antibodies present in a strategy for improving our vaccination policies. + +Answer: Thanks for your time and positive rating about the quality of this work. + +## Reviewer #2 (Remarks to the Author): + +- What are the noteworthy results? + +Yang and colleagues describe thoroughly the viral load kinetics over the first three weeks of monkeypox virus (MPXV) infection in various parts of the body by PCR- detection of MPXV DNA. They also measure MPXV DNA levels in environmental fomites swabs and describe the dynamics of IgG antibodies against different surface proteins of MPXV. + +Answer: Thanks for your time and comments on our manuscript. + +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +The work is of significance to the mpox field, although not being the first work describing these three items. Previous works had measure MPXV DNA levels in distinct body parts, in environmental fomites and describe the dynamics of antibody responses, several of which have not been referenced in the manuscript (Mpox immune responses: Colavita et al, Journal of Medical Virology 2023; Hubert et al Cell Host Microbe 2023; Cohn et al, Lancet Infect Dis 2023; Moraes- Cardoso et al, Lancet Microbe in press / Lancet preprint.; Mpox fomites: Morgan et al, Emerg Infect Dis 2022). Despite not being novel, the sound methodology of systematic collection of samples makes the work valuable for the field. + +Answer: Thanks for your time and positive rating about the quality of this work. We have searched related articles and added some references including those you mentioned in our revised manuscript, and we have added some description and discussion based on the added references (lines 359- 367 and lines 438- 446). + +<--- Page Split ---> + +- Does the work support the conclusions and claims, or is additional evidence needed? Overall, the conclusions and claims expressed by the authors are supported by the data. The authors claim that their data has "profound implications for the diagnosis, treatment, prevention of transmission and development of vaccines for Mpox", which I disagree given the previous knowledge on this field. The lack of viral isolation assays prevents from really translating their findings on MPXV DNA levels into actual risk of virus transmission. + +Answer: Thanks for the insightful comments and suggestions. We have changed the description into "With the ongoing outbreak of Mpox worldwide, these data could provide useful information for the diagnosis, treatment, prevention of transmission and development of vaccines for Mpox". + +- Are there any flaws in the data analysis, interpretation and conclusions? - Do these prohibit publication or require revision? + +I am concerned about the following analysis/interpretations, which should be revised for its publication: + +- Key characteristics of the population where this study is conducted are missing, which prevents the appropriate interpretation of the study. The authors should specify whether patients were hospitalized because of the severity of the disease or based on isolation procedures. The immune status of participants, particularly HIV-positive individuals should be specified. 5 patients received smallpox vaccination but it is not clear whether this vaccines where administered during childhood or as part of the 2022 outbreak response, please specify. + +Answer: Thanks for the insightful comments and suggestions. All the enrolled patients came to visit the doctor actively with clinical symptoms, and most patients (76/77) with skin lesions. Mpox is novel and full of unknown for most Chinese, therefore the laboratory-confirmed patients were advised and got hospitalized voluntarily for both isolation and treatment (lines 124- 128). Meanwhile, we have added the description on the immune status of enrolled patients (lines 223- 225), and clarified the time- points of vaccination of the 5 patients (lines 220- 222). + +- The authors found a higher prevalence of rectitis among HIV-positive individuals. To my knowledge, this is the first study to find this association and, given the small + +<--- Page Split ---> + +sample size, the authors should discuss whether this finding is truly reflecting an increased risk of rectitis among this population. In the same line, the authors observed an increased rectal viral load in HIV positive individuals. I strongly suggest that the authors conduct a sensitivity analysis comparing rectal viral loads between individuals with and without HIV, and with and without rectitis, to rule out whether the higher rectal viral load in HIV positive individuals is only reflecting the higher percentage of patients with rectitis in this subgroup. + +Answer: Thanks for the insightful comments and suggestions. We have transformed the Ct values into viral copies based on the generated standard curve, and we have compared the peak rectal viral loads and viral dynamics between individuals with and without rectitis following your suggestion (Figure S4). Despite of the small sample size, we still found that Mpox patients with rectitis showed significantly higher peak viral load (Figure S4A) and much higher viral loads during disease progression (Figure S4B). These results indeed suggested a possibly significant impact of rectitis on the viral dynamics of rectum in the Mpox patients, which merits further investigation based on a large cohort. Based on the results, we have also added related discussion in the revised manuscript (lines 397- 406 and lines 476- 478). + +- Samples from distinct body regions are collected differently and processed differently to measure MPXV DNA. Hence, viral loads between certain samples cannot be compared and this should be clearly specified in the manuscript. In the methods section it is not clear how each sample was collected and processed. For example, the volumes of saliva, urine or plasma used; or if swabs were placed in viral transport media, which total volume of media was present in each tube, and which volume was used for DNA extraction. Viral loads measured in urine and plasma are not fully reported and they should be included. + +Answer: Thanks for the insightful comments and suggestions. We have added the detailed description on the collection and procession of the samples (lines 142- 146 and lines 149- 152). Actually, serial swabs from oropharynx, skin lesions, rectum and environmental fomits, and samples of saliva (about 0.3- 0.5 ml), urine (3- 5 ml) and plasma (2- 3 ml) were collected. Then, all the swabs and saliva samples were dissolved with about 2 mL of viral transport medium, and 200 μl samples were subjected for the extraction of the nucleic acid. + +<--- Page Split ---> + +The authors compare the positivity rates and viral loads from skin lesions, rectal swabs, saliva and oropharyngeal swabs. Only if the authors collected saliva with a swab, results from these samples can be presented together. If not, I would separate the results of these samples so that the reader is not misled to compare the results of one and other. + +Answer: Thanks for the insightful comments and suggestions. The saliva samples were collected with a total volume of about \(0.3 - 0.5\mathrm{ml}\) , and then dissolved with about \(2\mathrm{mL}\) of viral transport medium like the swabs. Indeed, there is a difference of \(0.2 - 0.5\mathrm{ml}\) between the total sample volumes of saliva and swabs, while very little influence on the positivity rates and viral loads. Therefore, we speculate that they were comparable. + +- As previously mentioned, the authors have not included relevant references describing Mpox immune responses. The authors should discuss the differential findings between their study and the published literature in terms of antibody responses and neutralization. + +Answer: Thanks for the insightful comments and suggestions. We have added the references and the related discussion following your suggestions (lines 359- 367 and lines 438- 446). + +- Is the methodology sound? Does the work meet the expected standards in your field? The methodology is sound except for the lack of viral isolation assays. It would also be highly valuable that the authors transformed the Ct values in viral copies so that their results were more comparable with the literature. The reason for discussing results above/below a Ct value of 30 should be specified - Suner and colleagues defined a threshold for culture positivity of 6·5 log10 copies per mL or higher (approximately a Ct value of 26). + +Answer: Thanks for the insightful comments and suggestions. We have generated the standard curve using the ten- fold serially diluted standard plasmid and transformed the Ct values into viral copies. We have carefully searched about the correlation between Ct values/viral loads and viral isolation. Several studies and a meta review have investigated the Ct values/viral loads of clinical samples and viral isolation (Lancet Infect Dis. 2023 Apr;23(4):445- 453.; J Hosp Infect. 2023 May:135:139- 144.; J Clin Virol. 2023 Apr:161:105421.; Emerg Infect Dis. 2023 Jul;29(7):1465- 1469.; + +<--- Page Split ---> + +Euro Surveill. 2022 Sep;27(35):2200636.; Euro Surveill. 2022 Sep;27(36):2200675.; J Travel Med. 2023 Sep 5;30(5):taad111.), and found that when the Ct values is above 35 (equivalent to be 4.77 \(\log_{10}\) copies per mL in our study). Therefore, we defined a threshold of 4.77 \(\log_{10}\) copies per mL to discuss the transmission risk via different sites of Mpox patients (lines 382- 397). As to the environmental fomits, previous studies have successfully recovered viable MPXV from environmental fomit swabs with lowest viral load of 6.59 \(\log_{10}\) copies per mL \((3.9 \times 10^{6}\) copies per mL) (J Hosp Infect. 2023 Jul:137:86- 88.; MMWR Morb Mortal Wkly Rep. 2022 Aug 26;71(34):1092- 1094.), so we defined a threshold of 6.59 \(\log_{10}\) copies per mL to discuss the transmission risk via direct contact with these fomits (lines 309- 313 and lines 414- 420). + +As previously stated, the methods section lacks information on the procedures for sample collection and processing. + +Answer: Thanks for the insightful comments and suggestions. We have added the detailed description on the procedures for sample collection and processing in the methods section following your suggestion (lines 142- 146 and lines 149- 152). + +Additional comments: + +- Line 244. This sentence refers to patients' positivity in each body sample at baseline or at any timepoint? Please clarify. + +Answer: Thanks for the insightful comments and suggestions. This sentence refers to patients' positivity in each body sample at any time- point. For better understanding, we have added "during the follow- up" at the end of the sentence (line 257). + +- Line 282 - Results paragraph on environmental fomites. I suggest the authors present these results ordering the locations from higher positivity rates to lower positivity rates. + +Answer: Thanks for the insightful comments and suggestions. We have changed the description following your suggestion (lines 294- 303). + +- Figure 1. Specificity whether the statistical analysis compares viral loads or positivity rates. According to the figure, it should compare viral loads, and the Figure title + +<--- Page Split ---> + +should state "Comparative positive rates and viral loads..." + +Answer: Thanks for the insightful comments and suggestions. Actually, the positive rates for different sample types are also shown in the figure above the violin plot. + +- Figure 1A. I suggest removing this pannel, since pannels B-D where data is separated by d.p.o. are more informative. In these pannels, I would use the same scale for all y-axes so that they are comparable. + +Answer: Thanks for the insightful comments and suggestions. We have unified the scale for all the y-axes following your suggestion, while we have kept the pannel of Figure 1A. Actually, Figure 1A could show the readers an overview of the comparative positive rates of multiple sites from the Mpox patients. + +- The authors could potentially explore the correlations between severity and IgG responses, as done by Moraes-Cardoso and colleagues. + +Answer: Thanks for the insightful comments and suggestions. The analysis on the correlations between severity and IgG responses is useful and informative. However, we are sorry that we did not record the disease severity related index of Mpox, such as the severity score used by Moraes-Cardoso and colleagues. In the future study, we will record the related indexes for the analyses following your suggestion. + +## Reviewer #3 (Remarks to the Author): + +This study predominantly describes the dynamics of viral loads and viral shedding of MPXV infection within a hospital setting. IgG responses to key MPXV antigens are also explored by ELISA (endpoint titres) and FRNT. Structuring the results into HIV status is central as this is an important at- risk group to consider for MPXV infection and transmission currently. + +Answer: Thanks for your time and positive rating about the quality of this work. + +The interpretations of results are clear and sufficiently justified with the following conclusions standing out as most significant: + +- Correlation of patient anti-A29 and anti-H3 IgG titres to neutralisation titres. Information on the contribution of antibodies to particular targets will be crucial for establishing correlates of protection and the next generation of MPXV vaccines. + +<--- Page Split ---> + +- Differences in ct values between patient sampling sites over time. This will be important for diagnostic decisions. + +- The detailed notes on clinical presentation will aid in accurate diagnosis. + +- Of additional note is the comprehensive examination of environmental fomites in a clinical setting. Valuable information for limiting transmission. However, assessing the viability of these samples would have strengthened these results significantly. + +Answer: Thanks for your time and positive rating about the quality of this work, and thanks for the insightful comments and suggestions. We strongly agreed with you that assessing the viability of these samples would have strengthened these results significantly. Actually, we have intended to do so at the beginning. However, in terms of bio- safety, most of the samples we received were inactivated, so we could not carry out the viral isolation. Indeed, this is a limitation of our study, and we have described it in the discussion section (lines 472- 478). + +The methodology is sound, of a good standard and sufficiently detailed for reproduction. The use of endpoint titres to compare IgG responses is appropriate in the absence of a standard. The two main limitations of the study are also sufficiently highlighted. + +Answer: Thanks for your time and comments on our work. + +Please find my questions and comments below: + +- Line 66 (Introduction): Worth expanding on which genetic changes may be responsible. + +Answer: Thanks for the insightful comments and suggestions, and we have added the description following your suggestion (lines 64- 66). + +- Line 168 (Methods: Enzyme-linked immunosorbent assays (ELISAs)): The use of a HRP-conjugated goat anti-human IgM antibody is mentioned in the methods to detect patient IgM to various MPXV antigens. However, the results are not shown or discussed. Suggest either removing this from the methods or presenting the results. The dynamics of IgM responses to these antigens and differences to IgG will be of interest. Their omission does not detract from the conclusions of the study. + +Answer: Thanks for the insightful comments and suggestions. We are sorry for the carelessness that we have mistakenly mentioned the IgM, and we have removed it. + +<--- Page Split ---> + +- Line 215 (Results: Baseline characteristics of the cohort): This sentence may need rewording to clarify – though Table S1 does this well. + +Answer: Thanks for the insightful comments and suggestions. We have revised this sentence for better understanding (lines 220- 225). + +- Line 215 (Results: Baseline characteristics of the cohort): It would be of interest to hear if there were any differences in those vaccinated individuals with regards to viral loads/shedding and serologically. Were these patients vaccinated in response to the current outbreak or previously? + +Answer: Thanks for the insightful comments and suggestions, and we strongly agree with you the mentioned analyses are valuable. Currently, the number of vaccinated individuals in our study is too small (N=5), so we speculate that it is hard to get a conclusive conclusion at this time. Therefore, we will do the analyses in the future based on a larger cohort. + +- Line 230 (Results: Baseline characteristics of the cohort): Is this the same lineage as circulating in other cities in China? + +Answer: Thanks for the insightful comments and suggestions. Indeed, the circulating lineage of MPXV in China is C.1, and we have added the description (lines 238- 240). + +Overall, this is a detailed and well- reasoned study which contributes to the field and will be of importance for addressing the current outbreak. + +Answer: Thanks for your time and positive rating about the quality of this work. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #2: + +Remarks to the Author: + +In my opinion, the manuscript has increased its clarity and its messages are more powerfully delivered, thank you for incorporating most of the suggested changes. + +I would still suggest to conduct the comparison of rectal viral loads between patients with HIV and rectitis, with HIV without rectitis, without HIV with rectitis and without HIV without rectitis. This way you will rule out which factors (HIV, rectitis or both) are really mediating an increase in rectal viral loads. + +Regarding the figures and tables, I would also suggest some minor changes to facilitate its understanding by readers: + +- Table S1 should be main, Table 1 could be supplementary. In fact, data on Table 1 might be easier to read as a supplementary figure. + +- In figure 1, I would write the competitive rates below the x axis titles, and also include the rate itself. Example: in graph A, below oropharynx write 49% (70/143) + +Congratulations on your work. + +Reviewer #3: + +Remarks to the Author: + +Thank you very much for your rebuttals, all issues have been addressed appropriately. Please find one additional suggestion below: + +Line 174 (ELISAs) - please remove mention of the use of goat anti- human IgM antibody if not presenting the data. + +<--- Page Split ---> + +## Reviewers' Comments: + +Reviewer #2 (Remarks to the Author): + +1. In my opinion, the manuscript has increased its clarity and its messages are more powerfully delivered, thank you for incorporating most of the suggested changes. I would still suggest to conduct the comparison of rectal viral loads between patients with HIV and rectitis, with HIV without rectitis, without HIV with rectitis and without HIV without rectitis. This way you will rule out which factors (HIV, rectitis or both) are really mediating an increase in rectal viral loads. + +Response: Thanks for your time and positive rating about the quality of this work. Following your suggestion, we have conduct the comparison of rectal viral loads between between patients with and without HIV among the participants without rectitis (Figure S4C and S4D), and between patients with and without rectitis among the participants with HIV (Figure S4E and S4F), and confirmed that both HIV and rectitis are factors associated with the increase in rectal viral loads. + +2. Regarding the figures and tables, I would also suggest some minor changes to facilitate its understanding by readers: + +- Table S1 should be main, Table 1 could be supplementary. In fact, data on Table 1 might be easier to read as a supplementary figure. + +- In figure 1, I would write the competitive rates below the x axis titles, and also include the rate itself. Example: in graph A, below oropharynx write 49% (70/143) + +Congratulations on your work. + +Response: Thanks for the insightful comments and suggestions. We strongly agree with you viewpoints about the figure 1 and the tables. We have changed the Table S1 into Table 1 following your suggestion, and added the comparative positives rates below the x axis titles as suggested. Thanks again for your time and the suggestions which greatly improve our work. + +3. Reviewer #3 (Remarks to the Author): + +Thank you very much for your rebuttals, all issues have been addressed appropriately. Please find one additional suggestion below: + +Line 174 (ELISAs) - please remove mention of the use of goat anti- human IgM antibody if not presenting the data. + +<--- Page Split ---> + +Response: Thanks for you time and the insightful comments on our manuscript. We are sorry for the mistake, and we have deleted it in the revised manuscript. Thanks again for your time and the suggestions which greatly improve our work. + +<--- Page Split ---> diff --git a/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..4db399031cc02f234b56b8652f6617facd87f367 --- /dev/null +++ b/peer_reviews/df4e0bacde73b8351789695eb92bfcd521da740dc86e42704fdcc9b325ef002e/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,434 @@ +<|ref|>title<|/ref|><|det|>[[100, 40, 507, 90]]<|/det|> +# natureportfolio + +<|ref|>text<|/ref|><|det|>[[105, 110, 373, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[106, 155, 832, 241]]<|/det|> +Longitudinal viral shedding and antibody response characteristics of men with acute infection of monkeypox virus: a prospective cohort study + +<|ref|>image<|/ref|><|det|>[[94, 732, 262, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[272, 732, 880, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 285, 103]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[116, 120, 216, 133]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[116, 135, 291, 148]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 149, 868, 223]]<|/det|> +Reviewer #1:Remarks to the Author:Very comprehensive article on the dynamics of antibodies and the virus both with multi- site samples on the patient and in the environment. the patient data on the multisite are not original and correspond to data already published but with more samples. What is interesting is to compare the environment and especially the type of antibodies present in a strategy for improving our vaccination policies. + +<|ref|>text<|/ref|><|det|>[[116, 268, 216, 281]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[116, 284, 291, 297]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 299, 377, 312]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[116, 313, 864, 373]]<|/det|> +Yang and colleagues describe thoroughly the viral load kinetics over the first three weeks of monkeypox virus (MPXV) infection in various parts of the body by PCR- detection of MPXV DNA. They also measure MPXV DNA levels in environmental fomites swabs and describe the dynamics of IgG antibodies against different surface proteins of MPXV. + +<|ref|>text<|/ref|><|det|>[[116, 387, 797, 416]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +<|ref|>text<|/ref|><|det|>[[116, 416, 870, 520]]<|/det|> +The work is of significance to the mpox field, although not being the first work describing these three items. Previous works had measure MPXV DNA levels in distinct body parts, in environmental fomites and describe de dynamics of antibody responses, several of which have not been referenced in the manuscript (Mpox immune responses: Colavita et al, Journal of Medical Virology 2023; Hubert et al Cell Host Microbe 2023; Cohn et al, Lancet Infect Dis 2023; Moraes- Cardoso et al, Lancet Microbe in press / Lancet preprint.; Mpox fomites: Morgan et al, Emerg Infect Dis 2022). + +<|ref|>text<|/ref|><|det|>[[116, 510, 866, 536]]<|/det|> +Despite not being novel, the sound methodology of systematic collection of samples makes the work valuable for the field. + +<|ref|>text<|/ref|><|det|>[[116, 551, 759, 566]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed? + +<|ref|>text<|/ref|><|det|>[[116, 567, 867, 640]]<|/det|> +Overall, the conclusions and claims expressed by the authors are supported by the data. The authors claim that their data has "profound implications for the diagnosis, treatment, prevention of transmission and development of vaccines for Mpox", which I disagree given the previous knowledge on this field. The lack of viral isolation assays prevents from really translating their findings on MPXV DNA levels into actual risk of virus transmission. + +<|ref|>text<|/ref|><|det|>[[116, 655, 810, 685]]<|/det|> +- Are there any flaws in the data analysis, interpretation and conclusions? - Do these prohibit publication or require revision? + +<|ref|>text<|/ref|><|det|>[[116, 686, 797, 714]]<|/det|> +I am concerned about the following analysis/interpretations, which should be revised for its publication: + +<|ref|>text<|/ref|><|det|>[[116, 715, 876, 804]]<|/det|> +- Key characteristics of the population where this study is conducted are missing, which prevents the appropriate interpretation of the study. The authors should specify whether patients were hospitalized because of the severity of the disease or based on isolation procedures. The immune status of participants, particularly HIV-positive individuals should be specified. 5 patients received smallpox vaccination but it is not clear whether this vaccines where administered during childhood or as part of the 2022 outbreak response, please specify. + +<|ref|>text<|/ref|><|det|>[[116, 805, 881, 895]]<|/det|> +- The authors found a higher prevalence of rectitis among HIV-positive individuals. To my knowledge, this is the first study to find this association and, given the small sample size, the authors should discuss whether this finding is truly reflecting an increased risk of rectitis among this population. In the same line, the authors observed an increased rectal viral load in HIV positive individuals. I strongly suggest that the authors conduct a sensitivity analysis comparing rectal viral loads between individuals with and without HIV, and with and without rectitis, to rule out whether the higher rectal viral load in + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 812, 120]]<|/det|> +HIV positive individuals is only reflecting the higher percentage of patients with rectitis in this subgroup. + +<|ref|>text<|/ref|><|det|>[[115, 120, 881, 222]]<|/det|> +- Samples from distinct body regions are collected differently and processed differently to measure MPXV DNA. Hence, viral loads between certain samples cannot be compared and this should be clearly specified in the manuscript. In the methods section it is not clear how each sample was collected and processed. For example, the volumes of saliva, urine or plasma used; or if swabs were placed in viral transport media, which total volume of media was present in each tube, and which volume was used for DNA extraction. Viral loads measured in urine and plasma are not fully reported and they should be included. + +<|ref|>text<|/ref|><|det|>[[115, 223, 878, 283]]<|/det|> +The authors compare the positivity rates and viral loads from skin lesions, rectal swabs, saliva and oropharyngeal swabs. Only if the authors collected saliva with a swab, results from these samples can be presented together. If not, I would separate the results of these samples so that the reader is not misled to compare the results of one and other. + +<|ref|>text<|/ref|><|det|>[[115, 283, 880, 328]]<|/det|> +- As previously mentioned, the authors have not included relevant references describing Mpox immune responses. The authors should discuss the differential findings between their study and the published literature in terms of antibody responses and neutralization. + +<|ref|>text<|/ref|><|det|>[[115, 342, 765, 357]]<|/det|> +- Is the methodology sound? Does the work meet the expected standards in your field? + +<|ref|>text<|/ref|><|det|>[[115, 358, 876, 402]]<|/det|> +The methodology is sound except for the lack of viral isolation assays. It would also be highly valuable that the authors transformed the Ct values in viral copies so that their results were more comparable with the literature. The reason for discussing results above/below a Ct value of 30 should be specified + +<|ref|>text<|/ref|><|det|>[[115, 402, 870, 432]]<|/det|> +- Suner and colleagues defined a threshold for culture positivity of 6-5 log10 copies per mL or higher (approximately a Ct value of 26). + +<|ref|>text<|/ref|><|det|>[[115, 447, 865, 492]]<|/det|> +- Is there enough detail provided in the methods for the work to be reproduced? As previously stated, the methods section lacks information on the procedures for sample collection and processing. + +<|ref|>text<|/ref|><|det|>[[115, 507, 278, 520]]<|/det|> +Additional comments: + +<|ref|>text<|/ref|><|det|>[[115, 522, 830, 551]]<|/det|> +- Line 244. This sentence refers to patients' positivity in each body sample at baseline or at any timepoint? Please clarify. + +<|ref|>text<|/ref|><|det|>[[115, 552, 870, 581]]<|/det|> +- Line 282 - Results paragraph on environmental fomites. I suggest the authors present these results ordering the locations from higher positivity rates to lower positivity rates. + +<|ref|>text<|/ref|><|det|>[[115, 582, 872, 626]]<|/det|> +- Figure 1. Specificity whether the statistical analysis compares viral loads or positivity rates. According to the figure, it should compare viral loads, and the Figure title should state "Comparative positive rates and viral loads..." + +<|ref|>text<|/ref|><|det|>[[115, 627, 870, 671]]<|/det|> +- Figure 1A. I suggest removing this pannel, since pannels B-D where data is separated by d.p.o. are more informative. In these pannels, I would use the same scale for all y-axes so that they are comparable. + +<|ref|>text<|/ref|><|det|>[[115, 671, 870, 701]]<|/det|> +- The authors could potentially explore the correlations between severity and IgG responses, as done by Moraes-Cardoso and colleagues. + +<|ref|>text<|/ref|><|det|>[[115, 747, 216, 760]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[115, 761, 291, 775]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[115, 776, 875, 835]]<|/det|> +This study predominantly describes the dynamics of viral loads and viral shedding of MPXV infection within a hospital setting. IgG responses to key MPXV antigens are also explored by ELISA (endpoint titres) and FRNT. Structuring the results into HIV status is central as this is an important at- risk group to consider for MPXV infection and transmission currently. + +<|ref|>text<|/ref|><|det|>[[115, 849, 875, 879]]<|/det|> +The interpretations of results are clear and sufficiently justified with the following conclusions standing out as most significant: + +<|ref|>text<|/ref|><|det|>[[115, 880, 844, 895]]<|/det|> +- Correlation of patient anti-A29 and anti-H3 IgG titres to neutralisation titres. Information on the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 861, 120]]<|/det|> +contribution of antibodies to particular targets will be crucial for establishing correlates of protection and the next generation of MPXV vaccines. + +<|ref|>text<|/ref|><|det|>[[115, 120, 861, 210]]<|/det|> +- Differences in ct values between patient sampling sites over time. This will be important for diagnostic decisions.- The detailed notes on clinical presentation will aid in accurate diagnosis.- Of additional note is the comprehensive examination of environmental fomites in a clinical setting. Valuable information for limiting transmission. However, assessing the viability of these samples would have strengthened these results significantly. + +<|ref|>text<|/ref|><|det|>[[115, 223, 861, 269]]<|/det|> +The methodology is sound, of a good standard and sufficiently detailed for reproduction. The use of endpoint titres to compare IgG responses is appropriate in the absence of a standard. The two main limitations of the study are also sufficiently highlighted. + +<|ref|>text<|/ref|><|det|>[[115, 283, 470, 298]]<|/det|> +Please find my questions and comments below: + +<|ref|>text<|/ref|><|det|>[[115, 299, 865, 490]]<|/det|> +- Line 66 (Introduction): Worth expanding on which genetic changes may be responsible.- Line 168 (Methods: Enzyme-linked immunosorbent assays (ELISAs)): The use of a HRP-conjugated goat anti-human IgM antibody is mentioned in the methods to detect patient IgM to various MPXV antigens. However, the results are not shown or discussed. Suggest either removing this from the methods or presenting the results. The dynamics of IgM responses to these antigens and differences to IgG will be of interest. Their omission does not detract from the conclusions of the study.- Line 215 (Results: Baseline characteristics of the cohort): This sentence may need rewording to clarify – though Table S1 does this well.- Line 215 (Results: Baseline characteristics of the cohort): It would be of interest to hear if there were any differences in those vaccinated individuals with regards to viral loads/shedding and serologically. Were these patients vaccinated in response to the current outbreak or previously?- Line 230 (Results: Baseline characteristics of the cohort): Is this the same lineage as circulating in other cities in China? + +<|ref|>text<|/ref|><|det|>[[115, 504, 815, 535]]<|/det|> +Overall, this is a detailed and well- reasoned study which contributes to the field and will be of importance for addressing the current outbreak. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 85, 350, 101]]<|/det|> +## Reviewers' Comments: + +<|ref|>sub_title<|/ref|><|det|>[[149, 109, 481, 126]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 133, 852, 250]]<|/det|> +Very comprehensive article on the dynamics of antibodies and the virus both with multi- site samples on the patient and in the environment. the patient data on the multisite are not original and correspond to data already published but with more samples. What is interesting is to compare the environment and especially the type of antibodies present in a strategy for improving our vaccination policies. + +<|ref|>text<|/ref|><|det|>[[149, 256, 802, 274]]<|/det|> +Answer: Thanks for your time and positive rating about the quality of this work. + +<|ref|>sub_title<|/ref|><|det|>[[149, 305, 481, 322]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[150, 330, 430, 346]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[148, 354, 852, 472]]<|/det|> +Yang and colleagues describe thoroughly the viral load kinetics over the first three weeks of monkeypox virus (MPXV) infection in various parts of the body by PCR- detection of MPXV DNA. They also measure MPXV DNA levels in environmental fomites swabs and describe the dynamics of IgG antibodies against different surface proteins of MPXV. + +<|ref|>text<|/ref|><|det|>[[149, 479, 678, 496]]<|/det|> +Answer: Thanks for your time and comments on our manuscript. + +<|ref|>text<|/ref|><|det|>[[148, 526, 850, 593]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +<|ref|>text<|/ref|><|det|>[[148, 600, 852, 814]]<|/det|> +The work is of significance to the mpox field, although not being the first work describing these three items. Previous works had measure MPXV DNA levels in distinct body parts, in environmental fomites and describe the dynamics of antibody responses, several of which have not been referenced in the manuscript (Mpox immune responses: Colavita et al, Journal of Medical Virology 2023; Hubert et al Cell Host Microbe 2023; Cohn et al, Lancet Infect Dis 2023; Moraes- Cardoso et al, Lancet Microbe in press / Lancet preprint.; Mpox fomites: Morgan et al, Emerg Infect Dis 2022). Despite not being novel, the sound methodology of systematic collection of samples makes the work valuable for the field. + +<|ref|>text<|/ref|><|det|>[[148, 821, 852, 913]]<|/det|> +Answer: Thanks for your time and positive rating about the quality of this work. We have searched related articles and added some references including those you mentioned in our revised manuscript, and we have added some description and discussion based on the added references (lines 359- 367 and lines 438- 446). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 107, 852, 273]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed? Overall, the conclusions and claims expressed by the authors are supported by the data. The authors claim that their data has "profound implications for the diagnosis, treatment, prevention of transmission and development of vaccines for Mpox", which I disagree given the previous knowledge on this field. The lack of viral isolation assays prevents from really translating their findings on MPXV DNA levels into actual risk of virus transmission. + +<|ref|>text<|/ref|><|det|>[[147, 280, 852, 372]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have changed the description into "With the ongoing outbreak of Mpox worldwide, these data could provide useful information for the diagnosis, treatment, prevention of transmission and development of vaccines for Mpox". + +<|ref|>text<|/ref|><|det|>[[147, 402, 850, 445]]<|/det|> +- Are there any flaws in the data analysis, interpretation and conclusions? - Do these prohibit publication or require revision? + +<|ref|>text<|/ref|><|det|>[[147, 451, 850, 494]]<|/det|> +I am concerned about the following analysis/interpretations, which should be revised for its publication: + +<|ref|>text<|/ref|><|det|>[[147, 500, 852, 666]]<|/det|> +- Key characteristics of the population where this study is conducted are missing, which prevents the appropriate interpretation of the study. The authors should specify whether patients were hospitalized because of the severity of the disease or based on isolation procedures. The immune status of participants, particularly HIV-positive individuals should be specified. 5 patients received smallpox vaccination but it is not clear whether this vaccines where administered during childhood or as part of the 2022 outbreak response, please specify. + +<|ref|>text<|/ref|><|det|>[[147, 673, 852, 839]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. All the enrolled patients came to visit the doctor actively with clinical symptoms, and most patients (76/77) with skin lesions. Mpox is novel and full of unknown for most Chinese, therefore the laboratory-confirmed patients were advised and got hospitalized voluntarily for both isolation and treatment (lines 124- 128). Meanwhile, we have added the description on the immune status of enrolled patients (lines 223- 225), and clarified the time- points of vaccination of the 5 patients (lines 220- 222). + +<|ref|>text<|/ref|><|det|>[[147, 869, 850, 912]]<|/det|> +- The authors found a higher prevalence of rectitis among HIV-positive individuals. To my knowledge, this is the first study to find this association and, given the small + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 83, 852, 250]]<|/det|> +sample size, the authors should discuss whether this finding is truly reflecting an increased risk of rectitis among this population. In the same line, the authors observed an increased rectal viral load in HIV positive individuals. I strongly suggest that the authors conduct a sensitivity analysis comparing rectal viral loads between individuals with and without HIV, and with and without rectitis, to rule out whether the higher rectal viral load in HIV positive individuals is only reflecting the higher percentage of patients with rectitis in this subgroup. + +<|ref|>text<|/ref|><|det|>[[147, 256, 852, 496]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have transformed the Ct values into viral copies based on the generated standard curve, and we have compared the peak rectal viral loads and viral dynamics between individuals with and without rectitis following your suggestion (Figure S4). Despite of the small sample size, we still found that Mpox patients with rectitis showed significantly higher peak viral load (Figure S4A) and much higher viral loads during disease progression (Figure S4B). These results indeed suggested a possibly significant impact of rectitis on the viral dynamics of rectum in the Mpox patients, which merits further investigation based on a large cohort. Based on the results, we have also added related discussion in the revised manuscript (lines 397- 406 and lines 476- 478). + +<|ref|>text<|/ref|><|det|>[[147, 525, 852, 715]]<|/det|> +- Samples from distinct body regions are collected differently and processed differently to measure MPXV DNA. Hence, viral loads between certain samples cannot be compared and this should be clearly specified in the manuscript. In the methods section it is not clear how each sample was collected and processed. For example, the volumes of saliva, urine or plasma used; or if swabs were placed in viral transport media, which total volume of media was present in each tube, and which volume was used for DNA extraction. Viral loads measured in urine and plasma are not fully reported and they should be included. + +<|ref|>text<|/ref|><|det|>[[147, 722, 852, 888]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have added the detailed description on the collection and procession of the samples (lines 142- 146 and lines 149- 152). Actually, serial swabs from oropharynx, skin lesions, rectum and environmental fomits, and samples of saliva (about 0.3- 0.5 ml), urine (3- 5 ml) and plasma (2- 3 ml) were collected. Then, all the swabs and saliva samples were dissolved with about 2 mL of viral transport medium, and 200 μl samples were subjected for the extraction of the nucleic acid. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 83, 852, 200]]<|/det|> +The authors compare the positivity rates and viral loads from skin lesions, rectal swabs, saliva and oropharyngeal swabs. Only if the authors collected saliva with a swab, results from these samples can be presented together. If not, I would separate the results of these samples so that the reader is not misled to compare the results of one and other. + +<|ref|>text<|/ref|><|det|>[[147, 207, 852, 348]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. The saliva samples were collected with a total volume of about \(0.3 - 0.5\mathrm{ml}\) , and then dissolved with about \(2\mathrm{mL}\) of viral transport medium like the swabs. Indeed, there is a difference of \(0.2 - 0.5\mathrm{ml}\) between the total sample volumes of saliva and swabs, while very little influence on the positivity rates and viral loads. Therefore, we speculate that they were comparable. + +<|ref|>text<|/ref|><|det|>[[147, 378, 851, 471]]<|/det|> +- As previously mentioned, the authors have not included relevant references describing Mpox immune responses. The authors should discuss the differential findings between their study and the published literature in terms of antibody responses and neutralization. + +<|ref|>text<|/ref|><|det|>[[147, 477, 851, 545]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have added the references and the related discussion following your suggestions (lines 359- 367 and lines 438- 446). + +<|ref|>text<|/ref|><|det|>[[147, 574, 852, 741]]<|/det|> +- Is the methodology sound? Does the work meet the expected standards in your field? The methodology is sound except for the lack of viral isolation assays. It would also be highly valuable that the authors transformed the Ct values in viral copies so that their results were more comparable with the literature. The reason for discussing results above/below a Ct value of 30 should be specified - Suner and colleagues defined a threshold for culture positivity of 6·5 log10 copies per mL or higher (approximately a Ct value of 26). + +<|ref|>text<|/ref|><|det|>[[147, 747, 852, 914]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have generated the standard curve using the ten- fold serially diluted standard plasmid and transformed the Ct values into viral copies. We have carefully searched about the correlation between Ct values/viral loads and viral isolation. Several studies and a meta review have investigated the Ct values/viral loads of clinical samples and viral isolation (Lancet Infect Dis. 2023 Apr;23(4):445- 453.; J Hosp Infect. 2023 May:135:139- 144.; J Clin Virol. 2023 Apr:161:105421.; Emerg Infect Dis. 2023 Jul;29(7):1465- 1469.; + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 82, 852, 348]]<|/det|> +Euro Surveill. 2022 Sep;27(35):2200636.; Euro Surveill. 2022 Sep;27(36):2200675.; J Travel Med. 2023 Sep 5;30(5):taad111.), and found that when the Ct values is above 35 (equivalent to be 4.77 \(\log_{10}\) copies per mL in our study). Therefore, we defined a threshold of 4.77 \(\log_{10}\) copies per mL to discuss the transmission risk via different sites of Mpox patients (lines 382- 397). As to the environmental fomits, previous studies have successfully recovered viable MPXV from environmental fomit swabs with lowest viral load of 6.59 \(\log_{10}\) copies per mL \((3.9 \times 10^{6}\) copies per mL) (J Hosp Infect. 2023 Jul:137:86- 88.; MMWR Morb Mortal Wkly Rep. 2022 Aug 26;71(34):1092- 1094.), so we defined a threshold of 6.59 \(\log_{10}\) copies per mL to discuss the transmission risk via direct contact with these fomits (lines 309- 313 and lines 414- 420). + +<|ref|>text<|/ref|><|det|>[[148, 378, 850, 446]]<|/det|> +As previously stated, the methods section lacks information on the procedures for sample collection and processing. + +<|ref|>text<|/ref|><|det|>[[148, 452, 850, 520]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have added the detailed description on the procedures for sample collection and processing in the methods section following your suggestion (lines 142- 146 and lines 149- 152). + +<|ref|>text<|/ref|><|det|>[[149, 551, 330, 567]]<|/det|> +Additional comments: + +<|ref|>text<|/ref|><|det|>[[148, 574, 850, 617]]<|/det|> +- Line 244. This sentence refers to patients' positivity in each body sample at baseline or at any timepoint? Please clarify. + +<|ref|>text<|/ref|><|det|>[[148, 623, 850, 691]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. This sentence refers to patients' positivity in each body sample at any time- point. For better understanding, we have added "during the follow- up" at the end of the sentence (line 257). + +<|ref|>text<|/ref|><|det|>[[148, 722, 850, 788]]<|/det|> +- Line 282 - Results paragraph on environmental fomites. I suggest the authors present these results ordering the locations from higher positivity rates to lower positivity rates. + +<|ref|>text<|/ref|><|det|>[[148, 796, 850, 838]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have changed the description following your suggestion (lines 294- 303). + +<|ref|>text<|/ref|><|det|>[[148, 870, 850, 912]]<|/det|> +- Figure 1. Specificity whether the statistical analysis compares viral loads or positivity rates. According to the figure, it should compare viral loads, and the Figure title + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 630, 101]]<|/det|> +should state "Comparative positive rates and viral loads..." + +<|ref|>text<|/ref|><|det|>[[148, 109, 850, 151]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. Actually, the positive rates for different sample types are also shown in the figure above the violin plot. + +<|ref|>text<|/ref|><|det|>[[148, 182, 850, 250]]<|/det|> +- Figure 1A. I suggest removing this pannel, since pannels B-D where data is separated by d.p.o. are more informative. In these pannels, I would use the same scale for all y-axes so that they are comparable. + +<|ref|>text<|/ref|><|det|>[[148, 256, 852, 348]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have unified the scale for all the y-axes following your suggestion, while we have kept the pannel of Figure 1A. Actually, Figure 1A could show the readers an overview of the comparative positive rates of multiple sites from the Mpox patients. + +<|ref|>text<|/ref|><|det|>[[148, 378, 850, 421]]<|/det|> +- The authors could potentially explore the correlations between severity and IgG responses, as done by Moraes-Cardoso and colleagues. + +<|ref|>text<|/ref|><|det|>[[148, 427, 852, 545]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. The analysis on the correlations between severity and IgG responses is useful and informative. However, we are sorry that we did not record the disease severity related index of Mpox, such as the severity score used by Moraes-Cardoso and colleagues. In the future study, we will record the related indexes for the analyses following your suggestion. + +<|ref|>sub_title<|/ref|><|det|>[[148, 600, 481, 618]]<|/det|> +## Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 624, 852, 740]]<|/det|> +This study predominantly describes the dynamics of viral loads and viral shedding of MPXV infection within a hospital setting. IgG responses to key MPXV antigens are also explored by ELISA (endpoint titres) and FRNT. Structuring the results into HIV status is central as this is an important at- risk group to consider for MPXV infection and transmission currently. + +<|ref|>text<|/ref|><|det|>[[148, 747, 802, 765]]<|/det|> +Answer: Thanks for your time and positive rating about the quality of this work. + +<|ref|>text<|/ref|><|det|>[[148, 796, 850, 838]]<|/det|> +The interpretations of results are clear and sufficiently justified with the following conclusions standing out as most significant: + +<|ref|>text<|/ref|><|det|>[[148, 845, 850, 912]]<|/det|> +- Correlation of patient anti-A29 and anti-H3 IgG titres to neutralisation titres. Information on the contribution of antibodies to particular targets will be crucial for establishing correlates of protection and the next generation of MPXV vaccines. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 851, 125]]<|/det|> +- Differences in ct values between patient sampling sites over time. This will be important for diagnostic decisions. + +<|ref|>text<|/ref|><|det|>[[147, 132, 750, 150]]<|/det|> +- The detailed notes on clinical presentation will aid in accurate diagnosis. + +<|ref|>text<|/ref|><|det|>[[147, 157, 851, 225]]<|/det|> +- Of additional note is the comprehensive examination of environmental fomites in a clinical setting. Valuable information for limiting transmission. However, assessing the viability of these samples would have strengthened these results significantly. + +<|ref|>text<|/ref|><|det|>[[147, 231, 852, 398]]<|/det|> +Answer: Thanks for your time and positive rating about the quality of this work, and thanks for the insightful comments and suggestions. We strongly agreed with you that assessing the viability of these samples would have strengthened these results significantly. Actually, we have intended to do so at the beginning. However, in terms of bio- safety, most of the samples we received were inactivated, so we could not carry out the viral isolation. Indeed, this is a limitation of our study, and we have described it in the discussion section (lines 472- 478). + +<|ref|>text<|/ref|><|det|>[[147, 427, 851, 519]]<|/det|> +The methodology is sound, of a good standard and sufficiently detailed for reproduction. The use of endpoint titres to compare IgG responses is appropriate in the absence of a standard. The two main limitations of the study are also sufficiently highlighted. + +<|ref|>text<|/ref|><|det|>[[148, 526, 630, 544]]<|/det|> +Answer: Thanks for your time and comments on our work. + +<|ref|>text<|/ref|><|det|>[[148, 574, 534, 592]]<|/det|> +Please find my questions and comments below: + +<|ref|>text<|/ref|><|det|>[[148, 599, 851, 641]]<|/det|> +- Line 66 (Introduction): Worth expanding on which genetic changes may be responsible. + +<|ref|>text<|/ref|><|det|>[[148, 648, 851, 691]]<|/det|> +Answer: Thanks for the insightful comments and suggestions, and we have added the description following your suggestion (lines 64- 66). + +<|ref|>text<|/ref|><|det|>[[147, 721, 852, 863]]<|/det|> +- Line 168 (Methods: Enzyme-linked immunosorbent assays (ELISAs)): The use of a HRP-conjugated goat anti-human IgM antibody is mentioned in the methods to detect patient IgM to various MPXV antigens. However, the results are not shown or discussed. Suggest either removing this from the methods or presenting the results. The dynamics of IgM responses to these antigens and differences to IgG will be of interest. Their omission does not detract from the conclusions of the study. + +<|ref|>text<|/ref|><|det|>[[148, 870, 851, 912]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We are sorry for the carelessness that we have mistakenly mentioned the IgM, and we have removed it. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 107, 850, 151]]<|/det|> +- Line 215 (Results: Baseline characteristics of the cohort): This sentence may need rewording to clarify – though Table S1 does this well. + +<|ref|>text<|/ref|><|det|>[[148, 157, 850, 201]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. We have revised this sentence for better understanding (lines 220- 225). + +<|ref|>text<|/ref|><|det|>[[147, 230, 851, 323]]<|/det|> +- Line 215 (Results: Baseline characteristics of the cohort): It would be of interest to hear if there were any differences in those vaccinated individuals with regards to viral loads/shedding and serologically. Were these patients vaccinated in response to the current outbreak or previously? + +<|ref|>text<|/ref|><|det|>[[147, 328, 852, 447]]<|/det|> +Answer: Thanks for the insightful comments and suggestions, and we strongly agree with you the mentioned analyses are valuable. Currently, the number of vaccinated individuals in our study is too small (N=5), so we speculate that it is hard to get a conclusive conclusion at this time. Therefore, we will do the analyses in the future based on a larger cohort. + +<|ref|>text<|/ref|><|det|>[[147, 476, 850, 520]]<|/det|> +- Line 230 (Results: Baseline characteristics of the cohort): Is this the same lineage as circulating in other cities in China? + +<|ref|>text<|/ref|><|det|>[[147, 525, 850, 569]]<|/det|> +Answer: Thanks for the insightful comments and suggestions. Indeed, the circulating lineage of MPXV in China is C.1, and we have added the description (lines 238- 240). + +<|ref|>text<|/ref|><|det|>[[147, 598, 850, 642]]<|/det|> +Overall, this is a detailed and well- reasoned study which contributes to the field and will be of importance for addressing the current outbreak. + +<|ref|>text<|/ref|><|det|>[[147, 648, 802, 668]]<|/det|> +Answer: Thanks for your time and positive rating about the quality of this work. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[116, 90, 285, 104]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[116, 119, 216, 133]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[116, 135, 291, 148]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[116, 149, 808, 180]]<|/det|> +In my opinion, the manuscript has increased its clarity and its messages are more powerfully delivered, thank you for incorporating most of the suggested changes. + +<|ref|>text<|/ref|><|det|>[[116, 194, 864, 254]]<|/det|> +I would still suggest to conduct the comparison of rectal viral loads between patients with HIV and rectitis, with HIV without rectitis, without HIV with rectitis and without HIV without rectitis. This way you will rule out which factors (HIV, rectitis or both) are really mediating an increase in rectal viral loads. + +<|ref|>text<|/ref|><|det|>[[116, 268, 790, 298]]<|/det|> +Regarding the figures and tables, I would also suggest some minor changes to facilitate its understanding by readers: + +<|ref|>text<|/ref|><|det|>[[113, 299, 875, 330]]<|/det|> +- Table S1 should be main, Table 1 could be supplementary. In fact, data on Table 1 might be easier to read as a supplementary figure. + +<|ref|>text<|/ref|><|det|>[[113, 330, 856, 360]]<|/det|> +- In figure 1, I would write the competitive rates below the x axis titles, and also include the rate itself. Example: in graph A, below oropharynx write 49% (70/143) + +<|ref|>text<|/ref|><|det|>[[116, 374, 340, 388]]<|/det|> +Congratulations on your work. + +<|ref|>text<|/ref|><|det|>[[116, 433, 216, 446]]<|/det|> +Reviewer #3: + +<|ref|>text<|/ref|><|det|>[[116, 448, 291, 461]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[113, 463, 875, 493]]<|/det|> +Thank you very much for your rebuttals, all issues have been addressed appropriately. Please find one additional suggestion below: + +<|ref|>text<|/ref|><|det|>[[113, 507, 816, 538]]<|/det|> +Line 174 (ELISAs) - please remove mention of the use of goat anti- human IgM antibody if not presenting the data. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 84, 350, 101]]<|/det|> +## Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[148, 108, 462, 126]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 133, 852, 273]]<|/det|> +1. In my opinion, the manuscript has increased its clarity and its messages are more powerfully delivered, thank you for incorporating most of the suggested changes. I would still suggest to conduct the comparison of rectal viral loads between patients with HIV and rectitis, with HIV without rectitis, without HIV with rectitis and without HIV without rectitis. This way you will rule out which factors (HIV, rectitis or both) are really mediating an increase in rectal viral loads. + +<|ref|>text<|/ref|><|det|>[[147, 280, 852, 421]]<|/det|> +Response: Thanks for your time and positive rating about the quality of this work. Following your suggestion, we have conduct the comparison of rectal viral loads between between patients with and without HIV among the participants without rectitis (Figure S4C and S4D), and between patients with and without rectitis among the participants with HIV (Figure S4E and S4F), and confirmed that both HIV and rectitis are factors associated with the increase in rectal viral loads. + +<|ref|>text<|/ref|><|det|>[[147, 451, 850, 494]]<|/det|> +2. Regarding the figures and tables, I would also suggest some minor changes to facilitate its understanding by readers: + +<|ref|>text<|/ref|><|det|>[[147, 500, 850, 544]]<|/det|> +- Table S1 should be main, Table 1 could be supplementary. In fact, data on Table 1 might be easier to read as a supplementary figure. + +<|ref|>text<|/ref|><|det|>[[147, 550, 850, 593]]<|/det|> +- In figure 1, I would write the competitive rates below the x axis titles, and also include the rate itself. Example: in graph A, below oropharynx write 49% (70/143) + +<|ref|>text<|/ref|><|det|>[[148, 600, 398, 617]]<|/det|> +Congratulations on your work. + +<|ref|>text<|/ref|><|det|>[[147, 624, 852, 740]]<|/det|> +Response: Thanks for the insightful comments and suggestions. We strongly agree with you viewpoints about the figure 1 and the tables. We have changed the Table S1 into Table 1 following your suggestion, and added the comparative positives rates below the x axis titles as suggested. Thanks again for your time and the suggestions which greatly improve our work. + +<|ref|>text<|/ref|><|det|>[[148, 796, 488, 813]]<|/det|> +3. Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[147, 820, 848, 863]]<|/det|> +Thank you very much for your rebuttals, all issues have been addressed appropriately. Please find one additional suggestion below: + +<|ref|>text<|/ref|><|det|>[[147, 870, 850, 912]]<|/det|> +Line 174 (ELISAs) - please remove mention of the use of goat anti- human IgM antibody if not presenting the data. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 83, 851, 151]]<|/det|> +Response: Thanks for you time and the insightful comments on our manuscript. We are sorry for the mistake, and we have deleted it in the revised manuscript. Thanks again for your time and the suggestions which greatly improve our work. + +<--- Page Split ---> diff --git a/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/images_list.json b/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..9fd19051570b23a0c2ae6afa8f4c195929a3c104 --- /dev/null +++ b/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/images_list.json @@ -0,0 +1,93 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1. Precipitation differences (mm \\(\\mathrm{d}^{-1}\\) ) highlighting the contributions of tropical cyclones and extreme precipitation events during 2019–2023: (a) Precipitation anomalies directly associated with tropical cyclones during 2019–2023. (b) Difference between the 2019–2023 mean precipitation and the long-term average (LTA, 2001–2023). (c) Difference between the 2019–2023 mean precipitation excluding tropical cyclones and the LTA, isolating non-cyclone contributions. (d) Difference between the 2019–2023 mean precipitation excluding both tropical cyclones and extreme precipitation events of 2020 and 2022 and the LTA, highlighting background precipitation patterns (see Methods for separation of precipitation contributions from tropical cyclones and extreme events).", + "footnote": [], + "bbox": [ + [ + 128, + 87, + 870, + 543 + ] + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: Examples of SSS anomalies left after TC passages in the Arabian Sea in 2019 (left panels) and corresponding accumulated rain (right panels). Data and plots are available at https://www.maxss.org/.", + "footnote": [], + "bbox": [], + "page_idx": 17 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_3.jpg", + "caption": "Figure R1. Stratification control. To quantify the relative contributions of temperature and salinity to stratification, the density ratio, \\(R_{\\rho}\\) (Ruddick, B. 1983. A practical indicator of the stability of the water column to double diffusive activity. Deep-Sea Res., 304, 1105-1107, https://doi.org/10.1016/0198-0149(83)90063-8) is calculated from potential temperature and salinity observations in the (a) northern and (b) southern regions of the Arabian Sea (refer to Supplementary Figure 3 for location) from 2014 to 2023. The density ratio is defined as: \\(R_{\\rho} =\\) \\(- \\frac{N_{\\theta}^{2}}{N_{s}^{2}}\\) where the total stratification \\((N^{2})\\) is expressed as: \\(N^{2} = - \\frac{g}{\\rho_{0}}\\frac{\\partial\\rho_{\\theta}}{\\partial z} = N_{\\theta}^{2} + N_{s}^{2}\\) with temperature stratification \\((N_{\\theta}^{2})\\) and salinity stratification \\((N_{s}^{2})\\) is defined as: \\(N_{\\theta}^{2} =\\)", + "footnote": [], + "bbox": [ + [ + 122, + 87, + 900, + 377 + ] + ], + "page_idx": 18 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_4.jpg", + "caption": "Supplementary Figure 4. Argo temperature observations in the Arabian Sea. Along-track Argo float temperature ( \\(^\\circ \\mathrm{C}\\) ) observations for three regions representing (a) northern, (b) central, and (c) southern Arabian Sea (refer to Supplementary Figure 3 for location) from 2014 to 2023. The \\(25^{\\circ}\\mathrm{C}\\) contour is overlaid in all panels. Profiles with the presence of a barrier layer is marked with white boxes. Barrier layer thickness (BLT, m) is calculated as the difference between the isothermal layer depth (ILD) and the mixed layer depth (MLD), where MLD is defined as the depth corresponding to a density change associated with a \\(0.2^{\\circ}\\mathrm{C}\\) temperature difference from the surface, and ILD defines as the depth where the temperature decreases by \\(0.2^{\\circ}\\mathrm{C}\\) from the surface. Profiles with \\(\\mathrm{BLT} \\geq 5 \\mathrm{~m}\\) are marked with white boxes. Cyclone occurrences are marked in each panel: circles indicate very severe to super cyclones, and diamonds indicate cyclones to severe cyclones. Cyclones penetrating north of \\(15^{\\circ}\\mathrm{N}\\) are marked in red.", + "footnote": [], + "bbox": [ + [ + 112, + 85, + 886, + 396 + ] + ], + "page_idx": 23 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R1. Differences between the control (CNTL) and PPE2019-23 experiments (CNTL - PPE2019-23) for the 5-year period spanning 2019–2023 in (a) surface heat flux (W m-2) and (b) sea surface temperature (°C).", + "footnote": [], + "bbox": [ + [ + 120, + 85, + 881, + 310 + ] + ], + "page_idx": 32 + }, + { + "type": "image", + "img_path": "images/Supplementary_Figure_5.jpg", + "caption": "Supplementary Figure 5. Temperature anomalies ( \\(^\\circ \\mathrm{C}\\) ) averaged in the upper \\(50\\mathrm{m}\\) from the monthly EN4 dataset. Anomalies are calculated relative to the 2000–2023 period by subtracting the long-term monthly climatology.", + "footnote": [], + "bbox": [ + [ + 114, + 320, + 886, + 461 + ] + ], + "page_idx": 33 + }, + { + "type": "image", + "img_path": "images/Figure_2.jpg", + "caption": "Figure 2: Examples of SSS anomalies left after TC passages in the Arabian Sea in 2019 (left panels) and corresponding accumulated rain (right panels). Data and plots are available at https://www.maxss.org/.", + "footnote": [], + "bbox": [], + "page_idx": 35 + } +] \ No newline at end of file diff --git a/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd b/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd new file mode 100644 index 0000000000000000000000000000000000000000..b37b72880ddfd201ce31dae55323ac74e834a6cd --- /dev/null +++ b/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file.mmd @@ -0,0 +1,841 @@ + +# nature portfolio + +Peer Review File + +# Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Precipitation Events + +Corresponding Author: Dr Prasad Thoppil + +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +Attachments originally included by the reviewers as part of their assessment can be found at the end of this file. + +Version 0: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) + +- What are the noteworthy results? + +I had great pleasure in reading the manuscript entitled "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation". The manuscript investigates the impact of freshening happened in northern Arabian Sea due to anomalous number of Tropical Cyclones (TCs) happened during 2019 - 2023 by contrasting them with the freshening due to Tcs during 2014- 2018 period. The author used, in situ Argo float measurements, satellite datasets and model simulations to examine the contrasts in freshening and resulting changes in Arabian Sea High salinity water mass formation during the two periods selected for the study. + +Important results: + +- For the first time there is an attempt to show the impact of TC induces precipitation on the upper ocean water-mass formation and salt-budget of the northern Arabian Sea- The authors use both observations and model simulations and demonstrate that both agree in demonstrating the impact of TC induced precipitation.- This study encourages to investigate future trends TC trends in northern Arabian sea and the possible impact on water-mass formation which has widespread impact on ecological balance of the region. + +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +This work is certainly novel and can give potential insights about the impact of TC associated rainfall on water-mass formation which has widespread influence on ecology, fisheries and productivity in the region. + +- Does the work support the conclusions and claims, or is additional evidence needed? + +The present analysis shown by the author supports the conclusions and claims to a good extend. However, it will be interesting if the author can clarify below questions which can improve the confidence on this work further. + +Arabian sea is a basin under the influence of Indian monsoon and there is strong seasonality for rainfall in this region. So naturally there is existence of freshening and evaporation cycle in this region. It will be interesting to understand if the differences in amplitude of freshening due to Tcs during 2019- 2023 is statistically significant with the historical amplitude of freshening due to the impact of monsoonal rainfall. + +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +<--- Page Split ---> + +The data analysis approach is sound in general, however, author may clarify below aspects. The author show differences in mean potential energy anomaly during 2024- 2018 and 2019- 2023. Is this difference in mean statistically significant? Can this be verified with a statistical significance test? + +- Is the methodology sound? Does the work meet the expected standards in your field? + +Authors use best possible datasets and model simulations to prove their arguments. And it meets the standards. The minor issues are pointed out under other relevant headings. + +- Is there enough detail provided in the methods for the work to be reproduced? + +Author use two quantities in the manuscript potential energy anomaly and ASHSW volume. Are there references for these quantities? Please specify. + +The datasets used in the study is available from public domain, however author may be asked to make the model simulations available if the results need to be reproduced using model simulations as shown in the manuscript + +Minor comments: + +1) On page 4 towards the end (it may differ as I checked word document) Although no cyclones occurred in 2022, the extremely high rainfall during July – August, which caused severe flooding and displaced over 30 million people in Pakistan, helped maintain one of the largest salinity anomalies during 2019 – 23 ever recorded (Figure 3). + +Here a reference may be added, if author wanted to state it is largest salinity anomalies "ever" recorded. Else they may modify saying largest salinity anomalies during the study period. + +2) On page 7 line two, author says "We estimated Potential Energy Anomaly" which may be re-written as I estimated as it is a single author paper or the contributor may be acknowledged if there is one. + +Reviewer #2 + +(Remarks to the Author) My review is detailed in the attached pdf documents below + +[Editorial Note: This attachment is displayed in the final 12 pages of this file] + +Reviewer #3 + +(Remarks to the Author) + +The manuscript "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation" was reviewed. The paper seems to address an interesting and important issue in these less studied and important ocean basin. It also appears to entail a substantial effort. Hence it can deserve being published. However, some comments listed below may improve it: + +1- The text is well written, but repetitions of some text parts may be reduced (changed) as they are noticeable and can be a bit tedious to the readers? As: "cyclone- induced", "formation of ASHSW" or "ASHSW formation", "salinity freshening". If it can be helped? + +2- Moving Figs to be more harmonious with text may be useful? + +3- The present work only presents salinity and precipitation records and distributions, and no records of surface heat (especially temperature records from observations or model) and momentum (currents?) fluxes are mentioned (even from the work of the others?) as they are important in understanding the issue being addressed here? + +4- No cyclone precipitation in 2022 but systemic (synoptic, as large size cyclone or depression) precipitation is substantial, but the cyclone- induced precipitation is often emphasized? Systemic precipitation have also contributed in other years and cyclone- induced ones are also short lived! Shifting pattern of precipitation northwards on the whole may be more important? Therefore, the paper title may be changed? + +ITCZ in summer, appear to have shifted more (it usually change longitudinal position much more in Indian ocean than in other equatorial regions during the year, hence monsoonal systems) northwards in recent years in the Indian Ocean region that may be due to recent fast climate change, this could have increased the overall precipitation in the Arabian sea? [ Mamalakis, A., Randerson, J.T., Yu, J.Y. et al. Zonally contrasting shifts of the tropical rain belt in response to climate change. Nat. Clim. Chang. 11, 143- 151 (2021).] + +5- In Fig 3 they may present temperature records along with shown salinity anomaly, and temperature profile in Fig.2, to + +<--- Page Split ---> + +show better the density stratification which is claimed to have been "substantially weakened"? What is the cooling effects of cloudiness during precipitation? Temperature records may show this. Although in Fig. 4 potential density shows a decrease, along with the shallowing mixed layer depth. (E.g. paper by Shee et al. Recent changes in the upper oceanic water masses over the Indian Ocean using Argo data, Sci. Rep. 2023, 13, 20252, also show some temperature records that may be worth looking at?). So presentation of temperature profiles and series changes may be recommended. + +6- As the northern Indian Ocean is experiencing the intrusions of high salinity and temperature at depth of about 100 to 500 m from the Persian Gulf and Red Sea outflows (depending on season) while being refreshed by the surface water (especially the Persian Gulf, which is also refreshed by the surface water of Arabian Sea), have these semi- enclosed seas any influence on the ASHSW? It may be worth commenting on this, in discussion? + +7- Arabian Sea oxygen- depleted waters and hence, fish kill has increased recently, can ASHSW changes influence this; this may be interesting to just point out? Oxygenation of the Oman Sea and northern Indian Ocean waters by these outflows (4) has been shown to be important, although they are at deeper depths (e.g. Font, E., Swart, S., Bruss, G., Sheehan, P. M. F., Heywood, K. J., & Queste, B. Y. (2024). "Ventilation of the Arabian Sea oxygen minimum zone by Persian Gulf water". Journal of Geophysical Research – Oceans, 129(5), [e2023JC020668]). + +8- Fig. 1 show cyclone track shifted northwards, is this due to recent climate change? Not clearly reasoned? Precipitation seems to have increased more over the eastern coast of the Arabian Sea (more summer ITCZ shift, 4, ?). + +9- Should \(\Sigma \Delta \mathrm{P}\) be \(^+\) and \(\Sigma \Delta \mathrm{S}\) be - in Fig. 3(c)? Can these be decadal Oscillation? + +10- In salinity budget equation, Fv and Fh are probably vertical and horizontal fluxes due other forcing (may be turbulence or eddy fluxes)? They better to be introduced clearly. + +Best of luck for the author. + +Version 1: + +Reviewer comments: + +Reviewer #1 + +(Remarks to the Author) The author has addressed the concerns raised by me and I suggest the manuscript may be published. + +Reviewer #3 + +(Remarks to the Author) + +The author has made a major effort in improving the paper following our comments on its early version. Hence I recommend the paper for publication. + +<--- Page Split ---> + +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +- What are the noteworthy results? + +I had great pleasure in reading the manuscript entitled "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation". The manuscript investigates the impact of freshening happened in northern Arabian Sea due to anomalous number of Tropical Cyclones (TCs) happened during 2019 - 2023 by contrasting them with the freshening due to Tcs during 2014- 2018 period. The author used, in situ Argo float measurements, satellite datasets and model simulations to examine the contrasts in freshening and resulting changes in Arabian Sea High salinity water mass formation during the two periods selected for the study. + +Important results: + +- For the first time there is an attempt to show the impact of TC induces precipitation on the upper ocean water-mass formation and salt-budget of the northern Arabian Sea +- The authors use both observations and model simulations and demonstrate that both agree in demonstrating the impact of TC induced precipitation. +- This study encourages to investigate future trends TC trends in northern Arabian sea and the possible impact on water-mass formation which has widespread impact on ecological balance of the region. + +We sincerely thank the reviewer for their thoughtful comments and constructive suggestions, which have greatly enhanced the quality of the manuscript and strengthened the scientific arguments presented. We have carefully addressed the majority of the reviewer's comments and made the necessary modifications to the manuscript. Below, we provide a detailed point- by- point response, with the reviewer's comments in black and our responses highlighted in blue. We hope that these revisions adequately address the reviewer's concerns. + +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +This work is certainly novel and can give potential insights about the impact of TC associated rainfall on water-mass formation which has widespread influence on ecology, fisheries and productivity in the region. + +- Does the work support the conclusions and claims, or is additional evidence needed? + +The present analysis shown by the author supports the conclusions and claims to a good extend. However, It will be interesting if the author can clarify below questions which can improve the confidence on this work further. + +<--- Page Split ---> + +Arabian sea is a basin under the influence of Indian monsoon and there is strong seasonality for rainfall in this region. So naturally there is existence of freshening and evaporation cycle in this region. It will be interesting to understand if the differences in amplitude of freshening due to Tcs during 2019- 2023 is statistically significant with the historical amplitude of freshening due to the impact of monsoonal rainfall. + +The reviewer raises an excellent point regarding the potential influence of seasonal and interannual variability on precipitation, particularly from the Indian Monsoon and other climate drivers such as the Indian Ocean Dipole (IOD) and Monsoon Intra- Seasonal Oscillations (MISO). Indeed, the precipitation anomaly shown in Figure 2b (after removing the monthly climatology) reveals substantial anomalies even during non- cyclone periods, indicating interannual variability in monsoonal rainfall. + +To address the reviewer's concerns, we have expanded the analysis in the revised manuscript as follows: + +1. Separation of Precipitation Sources: We distinguished precipitation contributions from tropical cyclones and other extreme precipitation events using IMERG observations, as shown in the updated Figure 2c. + +2. Additional Model Experiments: We performed three additional model experiments designed to quantify the separate and combined impacts of tropical cyclones and extreme precipitation events (notably in 2020 and 2022) on salinity freshening during the 2019–2023 period (new Figure 9). + +These results indicate that the majority of the observed salinity freshening during 2019–2023 can be attributed to the combined effects of tropical cyclones and the extreme precipitation events in 2020 and 2022. The contribution from broader monsoonal rainfall variability or other interannual climate modes appears minimal in comparison, further emphasizing the dominant role of these extreme events in driving the observed salinity freshening. + +While the above approach differs slightly from the reviewer's suggestion, it effectively addresses the underlying concern. To further clarify, the differences in precipitation due to tropical cyclones during 2019–2023 can be derived from IMERG observations (Figure R1a). By subtracting the long- term mean (2001–2023) from the 2019–2023 mean, we obtain the precipitation anomaly for this period (Figure R1b). By excluding the contributions from tropical cyclones (Figure R1c) and the combined cyclones and extreme precipitation events of 2020 and 2022 (Figure R1d) from the 2919–2023 mean, further illustrate the influence of monsoon rainfall, which is small. The methodology used to separate precipitation from cyclones and extreme events is included in Methods. Since this analysis has already been incorporated into the revised manuscript (Figure 2c), we have opted to include this additional breakdown in Supplementary Figures 1 and 2. + +<--- Page Split ---> +![](images/Figure_unknown_0.jpg) + +
Figure R1. Precipitation differences (mm \(\mathrm{d}^{-1}\) ) highlighting the contributions of tropical cyclones and extreme precipitation events during 2019–2023: (a) Precipitation anomalies directly associated with tropical cyclones during 2019–2023. (b) Difference between the 2019–2023 mean precipitation and the long-term average (LTA, 2001–2023). (c) Difference between the 2019–2023 mean precipitation excluding tropical cyclones and the LTA, isolating non-cyclone contributions. (d) Difference between the 2019–2023 mean precipitation excluding both tropical cyclones and extreme precipitation events of 2020 and 2022 and the LTA, highlighting background precipitation patterns (see Methods for separation of precipitation contributions from tropical cyclones and extreme events).
+ +• Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +The data analysis approach is sound in general, however, author may clarify below aspects. The author show differences in mean potential energy anomaly during 2024- 2018 and 2019- 2023. Is this difference in mean statistically significant? Can this be verified with a statistical significance test? + +<--- Page Split ---> + +Thank you for the insightful suggestion. In response, we have conducted statistical significance testing on the differences in means and have included error bars in Figure 4 to reflect the associated uncertainty. The results indicate that the differences in means are statistically significant at the \(95\%\) confidence interval \((p = 0.05)\) . + +- Is the methodology sound? Does the work meet the expected standards in your field? + +Authors use best possible datasets and model simulations to prove their arguments. And it meets the standards. The minor issues are pointed out under other relevant headings. + +- Is there enough detail provided in the methods for the work to be reproduced? + +Author use two quantities in the manuscript potential energy anomaly and ASHSW volume. Are there references for these quantities? Please specify. + +Thank you for the suggestion. The reference for potential energy anomaly has cited in the main text (23), as well as in Methods section, alongside the additional reference (43). Furthermore, the use of ASHSW volume in the Arabian Sea, as previously used by (8), has also been incorporated into the Methods section. + +The datasets used in the study is available from public domain, however author may be asked to make the model simulations available if the results need to be reproduced using model simulations as shown in the manuscript + +Yes, the model simulation experiments will be made available to interested researchers. + +Minor comments: + +1) On page 4 towards the end (it may differ as I checked word document) Although no cyclones occurred in 2022, the extremely high rainfall during July – August, which caused severe flooding and displaced over 30 million people in Pakistan, helped maintain one of the largest salinity anomalies during 2019 – 23 ever recorded (Figure 3). + +Here a reference may be added, if author wanted to state it is largest salinity anomalies “ever” recorded. Else they may modify saying largest salinity anomalies during the study period. + +Thank you for pointing this out. We have revised the sentence to: “Although no cyclones occurred in 2022, the extremely high rainfall during July–August, causing severe flooding and displacing over 30 million people in Pakistan \(^{17}\) , contributed to sustaining salinity freshening through 2023”. + +2) On page 7 line two, author says “We estimated Potential Energy Anomaly” which may be re + +<--- Page Split ---> + +written as I estimated as it is a single author paper or the contributor may be acknowledged if there is one. + +As suggested by the reviewer, the sentence is re- written. Thank you. + +<--- Page Split ---> + +## Reviewer #2 + +## Summary: + +In this MS, the author first analyzes the impact of Tropical Cyclones (TCs)- induced precipitation on upper ocean salinity in the North Arabian Sea (AS) over 2014- 2023 using satellite rain and in situ Argo profile data. The author reports an increased number of TC in 2019- 2023, concomitant with an increase in total precipitation and an overall decrease of upper ocean salinity in the East AS with respect to the 2014- 2018 period, with a maximum freshening observed in the North East AS region. He then analyzes the temporal evolution of the vertical salinity structure using in situ profile data, revealing sustained freshening in the Northern Arabian Sea where the Arabian Sea High Salinity Waters (ASHsW) form. The upper ocean freshening reduces the potential surface density, augmenting the vertical stratification and in fine, disrupt the convective sinking process of ASHSW. Finally, using model perturbation experiment and model- based salinity budget estimates, the author attempts to isolate the impact of TC- induced rain on salinity freshening and conclude that the recent SSS freshening is caused by the increased number of TCs from 2019 onward. + +We sincerely thank the reviewer for their thoughtful comments and constructive suggestions, which have greatly enhanced the quality of the manuscript and strengthened the scientific arguments presented. We have carefully addressed the majority of the reviewer's comments and made the necessary modifications to the manuscript. Below, we provide a detailed point- by- point response (reviewer comments in black and our responses highlighted in blue). We hope that these revisions adequately address the reviewer's concerns. + +While the revised manuscript with track changes is included, the major revisions addressing the reviewers' concerns are outline below under subsections: + +Prolonged Salinity Freshening: Observations: Detailed revisions can be found in paragraphs 2- 5, where we have separated precipitation contributions from cyclones and other extreme events. Isolating Precipitation Sources Driving ASHSW Freshening: Results from model experiments incorporating those precipitation sources contributing to the freshening of ASHSW are provided in paragraphs 1- 4. + +## Major Comments and recommendations + +The topic is of strong scientific interest, in particular for the tropical cyclone forecast, salinity remote sensing, and, ocean modeler communities. While the SST, CHLA, and SSH response to TC passage have been extensively studied, TC- induced SSS changes and their large- scale impacts on other climate processes are much less known: this work definitively participate to these community efforts. In general, the MS reads well, is interesting and the results are in general plausible. However, I have several major concerns. + +First, in the part of the MS devoted to observations analyses, the author had not at all isolated the TC- induced precipitation and associated SSS changes from other sources of + +<--- Page Split ---> + +atmospheric and oceanic variability, which weaken strongly the strength of his statements, which are often more 'suggestions' than a clear demonstration of causality between the three reported interannual anomalies seen in the observation: 1) 'increased number of TC', 2) 'increased total Precipitation', and 3) 'decreased overall upper ocean Salinity'. For me, the author has not demonstrated convincing evidences from his analyses that the reported large- scale upper ocean salinity and precipitation anomalies (shown in Figure 1 & Figure 2 in the MS), as well as their consequences on the stability of the water column (Figure 4) is dominantly due to the passage of some rare but intense tropical cyclones rainfall and associated SSS freshening. I will show below in the detailed comments section of my review several examples in 2019 where there was little precipitation accumulated during the passage of some strong TCs in this region as well as small associated SSS changes in their wake, as reported from satellite observations. The interannual SSS & P changes observed by the author could therefore be due to other processes (see details in Behara et al, 2019) such as the increased precipitation during the recent Monsoon, or e.g., due to increased runoff from the river waters out of the Gulf of Khambhat estuaries, or from elsewhere in the coasts (e.g Pakistan floods in 2022 as mentioned by the author at the end of his MS), or even more likely by large scale climate variability impact on rain and SSS (e.g., Indian Ocean Dipole, Monsoon IntraSeasonal Oscillation (MISO),...) and not necessarily because of changes in Tropical Cyclone activity per se in between 2019- 2023 and 2014- 2018. For example, Li et al (2022) found that the variance of MISO has an increasing trend from 1982 to 2017 over the northeastern Arabian Sea (AS), accompanied by increasing intraseasonal rainfall. How does this impact the precipitation excess shown in Figure 1c? The enhancement in rainfall in this case is mainly nourished by the increasing moisture supply, with a major contribution from the upward moisture advection by the intraseasonal vertical wind velocity. Since the author did not isolate the precipitation signal from TC- only with respect to total rain, and also did not isolate the salinity response to TC passage, most of his statements remain poorly evidenced, while this can be now easily estimated from the observation dataset already gathered by the author: + +1) From IMERG and Ibtracs datasets, the author could estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds or within a radius of 500 km) around the TC center tracks. + +2) Then further estimate the time series of the cumulated contribution of tropical cyclone only induced rainfall to the total precipitation over the 3 AS subregions selected by the author. Then he could compare the relative contribution of TCs separately for both period 2014-2018 and 2019-2023. + +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach has been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser (2010), Jiang et al (2011). For example, a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non- tropical cyclone (TC) days and on TC days based on IMERG data (2000- 2020). + +<--- Page Split ---> + +Thank you very much for your constructive comments and suggestions, which have greatly improved the quality of the manuscript. We particularly appreciate the extensive and detailed overview of related studies and the insightful recommendations that have strengthened the scientific arguments presented in the paper. We are especially grateful for the time and effort you dedicated to providing relevant data analyses and examples that further support this study. While the review was thorough and comprehensive, which we highly value, our responses focus primarily on addressing the key concerns raised and clarifying how they have been incorporated into the revised manuscript. + +To address the reviewers' primary concern regarding the separation of cyclone- induced precipitation from the total precipitation, we have followed the reviewer's recommendations and the methodology described by Camberlin et al. (2024). Specifically, we separated cyclone- induced precipitation from the total precipitation, and the cumulative precipitation anomalies excluding cyclone- induced rainfall during the 2019- 2023 period are now presented in Figure 2c (previous Figure 3c). + +Furthermore, we extended this analysis to distinguish extreme precipitation events, which significantly contributed to the salinity freshening observed in 2022. Using the 95th percentile threshold, we identified and isolated extreme precipitation events. Our analysis revealed that both 2022 and 2020 experienced extreme precipitation events, although the 2020 event coincided with two tropical cyclones. The combined cumulative precipitation anomalies, excluding both cyclone- induced rainfall and extreme precipitation events, are also depicted in Figure 2c. + +We also acknowledge that the increasing trend in extreme precipitation events over the Arabian Sea may be linked to large- scale climate variability, including the IOD and MISO. Notably, MISO- related rainfall has substantially intensified over the northeastern Arabian Sea in the past three decades, driven by enhanced Arabian Sea warming (Li et al. 2022). This aspect has been incorporated in the "Discussion section". + +We have repositioned Figure 3 and the associated discussion earlier in the manuscript, following Figure 1. This restructuring enables for a clearer definition of precipitation anomaly sources and provides a more logical framework for explaining ASHSW freshening in subsequent sections, focusing on the role of precipitation events. The previous Figure 3 has now been numbered as Figure 2. + +Although dividing the precipitation analysis into three subregions of the Arabian Sea seems logical, it may not effectively explain ASHSW freshening, as ASHSW changes are not purely local but also influenced by its subsequent spreading. Therefore, we focus on the eastern Arabian Sea as a whole for the observational analysis. However, in the modeling experiments, we separately analyze the northern Arabian Sea, where ASHSW forms, and the eastern Arabian Sea, where the most significant freshening has occurred. + +Lastly, the reviewer correctly highlights that local changes in sea surface salinity (SSS) during cyclones can be assessed by comparing pre- and post- storm SSS, as shown in the reviewer's Figure 2. However, while this approach effectively captures the immediate salinity response to a cyclone, it does not reflect the delayed and cumulative effects on ASHSW formation and spreading. ASHSW formation is primarily driven by excess evaporation over precipitation, and the recent increase in freshwater input from tropical cyclones and extreme precipitation events + +<--- Page Split ---> + +has altered this balance, leading to stronger stratification in the northern Arabian Sea. Since this region typically experiences net evaporative cooling throughout the year, the northward shift of tropical cyclones and increased extreme precipitation have contributed additional freshwater, further preconditioning the area for sustained ASHSW freshening. Our study focuses on this evolving freshwater imbalance and its influence on ASHSW formation, which cannot be fully captured by short- term SSS comparisons alone. + +Similarly, to best isolate the TC- induced surface freshening from other sources of SSS variability (e.g., Moonsoon rain, horizontal advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi- mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021). The author could then evaluate the cumulated TC- induced SSS changes in each season over 2014- 2023 and see how much it contributed to the overall SSS decrease observed in that region since 2019. + +Thank you again for this excellent point and the detailed explanation. While our approach differs from the method proposed by the reviewer, we have addressed the concern using model experiments. Below, we explain how we addressed the issue and clarify why the reviewer's suggested method may not be fully suitable for this study. + +To isolate the impact of precipitation from tropical cyclones and extreme precipitation events (2020 and 2022) on salinity freshening during the 2019- 2023 period, we conducted three additional model experiments by selectively excluding: (1) cyclone- induced precipitation, (2) extreme precipitation events in 2020 and 2022, and (3) the combined effects of both. We then compared these experiments against a control simulation that included all precipitation forcings. These experiments confirmed that the combined influence of cyclone- induced precipitation and the two extreme precipitation events accounted for a significant portion of the salinity freshening observed during the 2019- 2023 period. + +We agree that satellite- derived sea surface salinity (SSS) can be useful for estimating localized, short- term salinity changes induced by tropical cyclones, as demonstrated in several studies, including the example provided by the reviewer. However, satellite SSS is less suitable for the objectives of this study due to the following reasons: + +- Our focus is on the long-term impact of precipitation on the formation and seasonal spreading of the Arabian Sea High Salinity Water (ASHSW), which occupies the upper 100 m of the water column.- While SSS changes during a cyclone can be inferred by comparing pre- and post-storm SSS (as illustrated in the reviewer's Figure 2), it does not capture the delayed and prolonged effects on ASHSW formation and spreading. For instance, freshwater input from the extreme + +<--- Page Split ---> + +precipitation event in June 2019 could weaken the formation of ASHSW the following winter (November 2019- February 2020), with its influence observed later in the summer monsoon season (August- October 2020) as the ASHSW spreads southward.- The vertical salinity sections provided in the manuscript (at three locations) reveal the vertical structure and extent of ASHSW, which cannot be inferred from satellite SSS alone. For this reason, the satellite SSS provides limited additional insight compared to the Argo profile observations already presented in Figure 3. + +On the other hand, the model experiments presented in the manuscript were specifically designed to quantify the impact of precipitation on ASHSW formation and subsequent spreading. These controlled simulations allow us to isolate processes that cannot be fully captured using observations alone. + +Second, in the second part of the MS devoted to model analyses, here again the author has not directly isolated the impact of interannual variability of the TC- induced precipitation and associated SSS changes from other sources of interannual atmospheric and oceanic variability. While I agree with the author that by inverting atmospheric forcing of years 2018 and 2019 the model can reproduce the SSS freshening observation: it does only show that the interannual variability in P predominantly modulate the SSS signal: the author however did not show directly that the TC- induced rain only is responsible for that interannual signal: some other sources of precipitation variability over 2018- 2019 could be responsible for it. Once the TC- induced rain will be isolated from the total precipitation time series as I suggested previously, the author could then easily re- run his model perturbation experiments by only removing TC days in the atmospheric forcing time series: this would directly show what the author want to prove rather than by using lengthy and sometimes confusing indirect approaches. + +Thank you again for the insightful suggestions. The additional model experiments, with and without cyclone- induced precipitation, presented in Figures 9d and 9e, effectively illustrate the impact of tropical cyclones on salinity freshening. Specifically, in the northern Arabian Sea, the control experiment shows a fresher salinity by approximately 0.2 psu during November - December 2019 (Figure 9e) compared to the experiment where cyclone- induced precipitation was excluded for the same period. + +The primary objective of this case study, focusing on the 2018- 2019 period, is to demonstrate two key processes: + +1. How precipitation from post-monsoon tropical cyclones during the September-December period influences the formation of ASHSW north of \(\sim 15^{\circ}\mathrm{N}\) (the ASHSW formation region). +2. The subsequent southward spreading of ASHSW along the eastern Arabian Sea during the following late summer (September-October 2020). + +The current model setup allows us to compare the resulting salinity patterns to those from the reference control run. While the observed salinity differences in these experiments are attributed + +<--- Page Split ---> + +to variations in precipitation during the 2018–2019 period, as the reviewer correctly pointed out, we acknowledge that precipitation during September–December in the northern Arabian Sea is generally minimal in a typical period. Thus, the precipitation pattern observed during September–December 2018 can be considered representative of typical conditions. In contrast, the precipitation from five tropical cyclones during September–October 2019 significantly contributed to the weakening of ASHSW formation and its subsequent spreading along the eastern Arabian Sea. + +In addition, many time in the MS, the author used very strong statements (particularly on the impacts of TC- precipitation on SSS anomalies) without full proof of them: please rephrase those sentences to only state what is shown by your results. + +In the revised manuscript, we have made efforts to avoid strong statements of certainty. While the initial part of the discussion primarily focuses on observations, the interpretation of these results remains largely qualitative. As the processes governing ASHSW anomalies become clearer in the latter sections, particularly with the additional analysis of model results quantifying these processes, the language has been adjusted to reflect this progression more accurately. + +Therefore, despite most of the results shown by the author are plausible, I recommend that the MS undergo major revision before being considered for publication so that the author actually and properly separate the TC impacts from other sources of variability in both the Precipitation and SSS signals and in the observation and model analyses, separately: this shall in fine directly demonstrate the authors indirect statements. + +Details are given below. + +## Detailed Comments: + +L38 “evaporation- precipitation”- What about river runoff and their impacts on the northeast Arabian Sea (AS) upper salinity, in particular from the Indus and the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Khambhat estuaries? As shown in Rao et al (2009) and reproduced here below (panel d), rivers have non negligible impacts on the SSS in the North eastern AS, particularly in winter months. + +<--- Page Split ---> + +Figure1: Monthly climatological salinity for (a) July, (b) October, (c) December and (d) ARGO observations averaged for 17- 20N during 2004. From Rao et al (2009) + +Thank you for highlighting this relevant study. We agree with its findings. However, the river runoff in the northeastern Arabian Sea has a negligible impact on the formation and seasonal spreading of ASHSW, as the low- salinity water associated with river discharge remains largely confined to shallow regions along the west coast of India. While it is plausible that an increased frequency of cyclones and extreme precipitation events could lead to enhanced river runoff and contribute to surface salinity freshening in these coastal regions, the model experiments presented in our study explicitly exclude such contributions, further supporting the critical role of precipitation forcing. Although the influence of river runoff is an important topic worth further investigation, it falls beyond the scope of the present study. A brief description of river runoff treatment in the model has been added to the Methods section for clarity. + +L107- 108: this sentence is a very strong statement that definitively need more support than what is shown and discussed around Fig1 at this stage in the MS. Please re- phrase to be more accurate and keep to the point of what your data really show. It is not because Fig1 panels reveal a concomitant increase in 1) the number of TCs in the North- eastern part of the AS, 2) as well as in overall Precipitation in the eastern AS and 3) a decrease in SSS in the NE AS that this is clearly an evident proof that "the cyclone- induced precipitation have impact on the convective formation of the Arabian Sea High Salinity Waters ". This is a very strong shortcoming. As I will show further, TC in the Arabian sea are not systematically associated with heavy rain and SSS drops are not systematically observed in their trail. Deeper observation analyses are required to conclude. + +<--- Page Split ---> + +Indeed, the increase of precipitation shown in Fig1c could be due to other atmospheric sources of interannual variability (e.g., Indian Ocean Dipole, Moonsoon) than merely the change in Tropical Cyclone activity in between 2019- 2023 and 2014- 2018. What about a potentially increase in monsoon season accumulated rain in the most recent years ? + +Similarly, the SSS deacrease in the AS, while I agree is most intense where most new TCs tracks where located in 2019- 2023 is also a region of significant runoff from the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Cambay estuaries. Could the reported interannual variability in SSS in this region be also related to increased river runoff in 2019- 2023 ? and if yes, how much does it contribute to the observed SSS decrease with respect to the impact of local rain increases ? + +To resolve these uncertainties, I suggest the author shall re- analyse the datasets as follows: + +3) From IMERG and Ibtracs datasets, estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds) around the TC center track. + +4) Then further estimate the average cumulated spatial contribution of all tropical cyclone rainfall to total precipitation over the AS region, separately for both period 2014-2018 and 2019-2023. + +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach have been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser(2010), Jiang et al (2011). For example a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non-tropical cyclone (TC) days and TC days based on IMERG data (2000-2020). Such an approach could be easily applied by the author. + +5) Similarly, to best isolate the TC-induced surface freshening from other sources of SSS variability (Moonsoon rain, advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi-mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021) + +In fact, databases including TC- induced Precipitation & SSS changes for each individual TC globally over 2010- 2020 were already developed in the frame of the ESA Marine Atmosphere eXtreme Satellite Synergy (MAXSS) project (see https://www.maxss.org/) and could be used by the author to better demonstrate his statements. This dataset is publicly available (doi:10.12770/cc0577e4-55d6-4aa9-a938-b4965be121ab, Reul et al., 2023), and provides, for each storm tracks from IBTracs during the period 2010- 2020, three types of storm- related + +<--- Page Split ---> + +parameters: (1) the pre- storm upper ocean conditions (e.g., SST, SSS, upper ocean vertical density stratification strength, etc..), (2) the atmospheric forcing during the storm passage (maximum wind, accumulated rain and evaporation, wind power index, etc..) during the storm, as well as (3) the oceanic wakes left after the storm for an ensemble of key variables (SST, SSS, sea level height, ocean color parameters). I show here below few examples of estimated SSS anomalies (derived from the ESA CCI SSS products) left after TC passages in the AS as well as the corresponding accumulated precipitation (derived from merged satellite TRMM products) during their lifetime over the AS in 2019 and which is available in the MAXSS database. As evidenced from satellite data, TC passage in the AS in 2019 are not systematically associated with strong local SSS decreases and heavy precipitation: see e.g. examples of the extremely severe cyclonic storm MAHA in 2019 with small amount of accumulated precipitation associated with negligible SSS changes in the North Eastern AS, or the other case of the super cyclonic storm KYARR with locally very high accumulated rain at \(20^{\circ}\mathrm{N}\) but no significant associated SSS changes observed from satellites. Significant SSS drops were nevertheless observed after the passage of the very severe cyclonic storm VAYU in a region with significant accumulated rain. Therefore, given the high variability of the SSS response to TC passages in this region, and although Sun et al., (2021) have shown (see their Figure 16 top pannel) that on average TC do induce SSS drops in the AS, it remains unclear what the overall contributions of the TC- induced rain and associated freshening are on the 2014-2018 versus 2019-2023 interannual variability reported in Fig 1.c and Fig.1d. + +![](images/Figure_2.jpg) + + +<--- Page Split ---> +![](images/Supplementary_Figure_3.jpg) + +
Figure 2: Examples of SSS anomalies left after TC passages in the Arabian Sea in 2019 (left panels) and corresponding accumulated rain (right panels). Data and plots are available at https://www.maxss.org/.
+ +Thank you for your time and effort in providing such extensive comments and a detailed explanation of methods along with several relevant references. The reviewer has raised a number of important points and provided valuable suggestions for strengthening the manuscript. Since many of these comments align closely with previous feedback, albeit in a more detailed manner, we would like to focus our responses on the primary concerns most relevant to the core scope of our study: demonstrating that precipitation from tropical cyclones and extreme precipitation events has been a significant driver of salinity freshening in the eastern Arabian Sea during the 2019- 2023 period. + +We greatly appreciate the reviewer's independent analyses as part of this review and agree with the conclusions drawn from those efforts. However, as noted in previous responses, certain limitations exist regarding the types of data and approaches that can be applied within the scope of this study. For example, while the above mentioned analysis tool is useful for estimating local changes in sea surface salinity (SSS) or SST in the wake of TCs compared to pre- storm conditions, it does not directly capture the impact of precipitation on ASHSW formation and its subsequent spreading. + +<--- Page Split ---> + +To address the reviewer's primary concern regarding the separation of cyclone- induced precipitation from total precipitation, we have now followed the reviewer's recommendations and the methodology described by Camberlin et al. (2024). Specifically, we separated cyclone- induced precipitation from total precipitation, and the cumulative precipitation anomalies excluding cyclone- related rainfall during the 2019–2023 period are now presented in Figure 2c. + +Additionally, we extended this analysis to better differentiate extreme precipitation events, which significantly contributed to the observed salinity freshening, particularly in 2022. By applying a 95th percentile threshold, we identified and isolated extreme precipitation events. Our analysis revealed that both 2022 and 2020 experienced extreme precipitation events, although the 2020 events coincided with two tropical cyclones. The combined cumulative precipitation anomalies, excluding both cyclone- induced rainfall and extreme precipitation events, are now depicted in Figure 2c for clarity. + +To further quantify the individual and combined impacts of precipitation from tropical cyclones and extreme precipitation events (2020 and 2022) on ASHSW freshening during the 2019–2023 period, we conducted three additional model experiments where we selectively excluded: (1) cyclone- induced precipitation, (2) extreme precipitation events in 2020 and 2022, and (3) the combined effects of both. These were compared against a control simulation that included all precipitation forcings. The results confirmed that the combined influence of cyclone- induced precipitation and extreme precipitation events accounted for a substantial portion of the salinity freshening observed during the study period. + +Line 111- 113: I agree that the addition of freshwater reduces surface density but it has not been demonstrated at this stage of the MS that it disrupts the sinking process and weaken the formation of the ASHSW. Please re- phrase to only state what is shown by your results. + +As suggested by the reviewer, this statement has been moved up in the manuscript. + +Figure 2: the symbols representing the occurrences of TC are not visible enough on the figures. I would add panels illustrating the temporal evolution of the total accumulated rain and of the TC- induced rain in the three regions. In the legend, you precise that “2 extremely severe cyclones in late October to Early November triggered the largest freshening in the AS”. Please clarify and provide the references for the name (identifier) of these 2 storms and show the SSS freshening associated to them or do not mention something you did not demonstrated. According to Fig2a in the MS, the freshening after September- December 2020, or 2021, seems the two largest freshenings over the period. Satellite SSS data for the example of TC MAHA shown above and which occurred in early November 2019 do not reveal large surface freshening! + +Thank you for pointing this out. While the cyclone symbols in Figure 3c are less visible against the blue background, the same symbols used in the other two panels can be referenced for consistency. + +The salinity observations presented in Figure 3 aim to demonstrate the overall freshening observed across the northern, central, and southern Arabian Sea. To further clarify the drivers of + +<--- Page Split ---> + +this freshening, the separate contributions of cumulative precipitation anomalies, as shown in Figure 2c, provide additional insights into the sources of salinity changes resulting from 2019 tropical cyclones. Additionally, new Figure 9 quantify the impact of cyclone- induced precipitation on ASHSW freshening in 2019. Please note that we have repositioned Figure 3 and the associated discussion earlier in the manuscript, following Figure 1. + +We did not intend to suggest that the salinity freshening observed was the largest on record. Rather, our intention was to emphasize that the tropical cyclones in 2019 initiated a salinity freshening event, which persisted through 2023. We have modified the sentence in the revised manuscript for greater clarity. + +Figure 3: it is not fully clear how SSS and P anomalies were evaluated. In the method section it is said (Line 476 and 498- 499) that 'salinity and P anomalies are calculated from 2000- 2023 period'. Do you mean that you evaluated the mean seasonal cycle over 2000- 2023 and then removed it to the S and P times series or did you remove the overall local mean evaluated over the complete 2000- 2023 period independently of the season? Please precise, it is very important to understand if the mean seasonal cycle was removed or not. Please also provide y- axis labels in Fig 3a (SSSA) and b (Precipitation anomaly). Correct the typo for "IMERGE", it shall reads" IMERG." + +Thank you very much for the feedback. As per the reviewer's comments, we have clarified the methodology used to calculate the salinity and precipitation anomalies in the revised text. Specifically, we computed a monthly mean climatology (January to December) over the period 2000- 2023 and subtracted it from the salinity (average over upper \(0 - 50\mathrm{m}\) , not SSS) and precipitation time series. This approach effectively removes the long- term monthly cycle associated with monsoon precipitation. This has been clarified in the revised manuscript. + +Since Figures 2a and 2b are time- latitude plots, labelling the y- axis with the variable name could introduce confusion. Therefore, we have chosen to omit them for clarity. As suggested, we have also corrected the typo 'IMERGE' to 'IMERG' Thank you for pointing this error. + +Figure 3c: I would suggest to add the TC- induced rain accumulated precipitation time series as well, this would avoid lack of clarity on the relative contributions of TC versus other sources of atmospheric rain on the observed anomalies. + +This is an excellent suggestion by the reviewer. By separating the rainfall contributions from tropical cyclones (TCs) and other extreme precipitation events, particularly those in 2020 and 2022, we were able to quantify their relative contributions to the total rainfall more effectively. This analysis provided additional clarity on the individual impacts of TCs versus other sources of rainfall on salinity variability. + +Furthermore, the additional model experiments presented in the revised Figure 9 now isolate the rainfall from each source (TCs and extreme precipitation events) and clearly delineate their respective impacts on ASHSW freshening. + +<--- Page Split ---> + +As suggested by the reviewer, the relative contributions of rainfall from TCs and extreme events to the total rainfall have also been added in Figure 2c. It is evident from this analysis that rainfall from these events accounted for a significant portion of the excess rainfall observed during the 2019- 2023 period. The corresponding model experiments, which incorporated these rainfall sources, effectively explain the ASHSW freshening during this period, further confirming the initial results presented in the manuscript. + +We acknowledge that the extreme precipitation event in 2020 was not identified in the earlier version of the manuscript, as it coincided with two cyclones. By applying the \(95^{\text{th}}\) percentile method, we have systematically identified and separated their contributions from the total in the revised analysis. + +L129: except in 2021, it does not appear clearly that SSS freshening systematically lag behind P anomalies when comparing Fig3a and Fig3b. For example in J- S 2022, the freshening are concomitant with high rain. Please re- formulate accordingly. + +As the reviewer points out a clear lag cannot be inferred from Figures 2a and 2b, therefore the sentence is removed. We intend to suggest that the rate of salinity freshening lags behind the precipitation during the 2019- 2023 period. + +L130: here again, the author sentence "The addition of cyclone- induced freshwater increases buoyancy and strengthens stratification, which in turns weakens the depth of winter convective mixing" has not been yet demonstrated at this stage of the MS and shall be removed if not fully proofed + +To address the reviewer's concern, the sentence has been revised for clarity. The updated sentence now reads: "The addition of freshwater increases buoyancy and strengthens stratification, which in turn reduces the depth of winter convective mixing." + +L134: Fig S2 show the evolution of the MLD averaged over the box \(60^{\circ} - 70^{\circ}\mathrm{E}\) , \(15^{\circ} - 25^{\circ}\mathrm{N}\) and not separately for the 3 boxes shown in Fig3. It is rather confusing then to compare MLD & S evolution in different boxes. Please correct. + +The discussion related to Supplementary Figure 2 has been moved to Figure 4b for improved clarity. Given the limited number of observations in the EN4 dataset, a larger box average was used to better represent the mixed layer depth (MLD) in the ASHSW formation region. Figure 4b shows the MLD from the Argo observations, while Supplementary Figure 2 with the larger box in the northern Arabian Sea broadly capturing the convective formation region of ASHSW. + +L135: "While cyclone- induced precipitation weakens the convective formation of ASHSW in the north during winter,...": here again this statement have NOT been demonstrated at this stage in the MS; please remove/correct unless you show a real demonstration + +To address the reviewer's concern, the sentence has been revised for clarity. The updated sentence now reads: "While precipitation weakens the convective formation of ASHSW in the northern Arabian Sea during winter, ..." + +<--- Page Split ---> + +L148: "...salinity maximum at \(80 \mathrm{~m}\) ." Please precise that is seen in 'Figure 2f' + +Clarified as suggested, the subsurface salinity maximum in Figure 3f occurs at \(75 \mathrm{~m}\) . + +L148: "This vertical salinity stratification promotes vertical mixing (heavier over lighter water) and plays an important role in maintaining SST in the southeastern Arabian Sea". Ok, but why not showing the Brunt- Väisälä frequency to illustrate the respective contribution of S and T to vertical stratification in the 3 regions, following Maes, C., and O'Kane (2014): + +\[N2(T,S) = -g / \rho \partial \rho /\partial z\approx (g\alpha \partial T\partial z + g\beta \partial S\partial z) = N T2(T,S) + N S2(T,S)\] + +Where \(\rho\) is density, T temperature; S salinity, \(\alpha\) is the thermal expansion coefficient, \(\beta\) is the haline contraction coefficient; g is acceleration of gravity and z is vertical. This would help the reader to understand the role of freshwater on the vertical density stratification. + +Thank you again for the detailed description. Salinity stratification has been identified as a significant process regulating SST in the southeastern Arabian Sea, with implications for cyclone formation and the onset of the Indian Summer Monsoon, as documented in multiple studies, including Reference (20). In our study, we suggest that recent salinity freshening in the eastern Arabian Sea could further exacerbate SST warming. + +The primary focus of this paper is to investigate how freshwater input in the northern Arabian Sea, the formation region of ASHSW, influences stratification and the convective formation of ASHSW. To address this, we have already presented stratification for the northern region using Argo observations in Figure 4c. + +However, for clarification, we computed separate contributions of temperature and salinity to the stratification following the methodology suggested by the reviewer and they are shown in Figure R1 for (a) north and (b) southern regions of the Arabian Sea. + +<--- Page Split ---> +![](images/Supplementary_Figure_4.jpg) + +
Figure R1. Stratification control. To quantify the relative contributions of temperature and salinity to stratification, the density ratio, \(R_{\rho}\) (Ruddick, B. 1983. A practical indicator of the stability of the water column to double diffusive activity. Deep-Sea Res., 304, 1105-1107, https://doi.org/10.1016/0198-0149(83)90063-8) is calculated from potential temperature and salinity observations in the (a) northern and (b) southern regions of the Arabian Sea (refer to Supplementary Figure 3 for location) from 2014 to 2023. The density ratio is defined as: \(R_{\rho} =\) \(- \frac{N_{\theta}^{2}}{N_{s}^{2}}\) where the total stratification \((N^{2})\) is expressed as: \(N^{2} = - \frac{g}{\rho_{0}}\frac{\partial\rho_{\theta}}{\partial z} = N_{\theta}^{2} + N_{s}^{2}\) with temperature stratification \((N_{\theta}^{2})\) and salinity stratification \((N_{s}^{2})\) is defined as: \(N_{\theta}^{2} =\)
+ +\(g\alpha \frac{\partial\theta}{\partial z},N_{s}^{2} = - g\beta \frac{\partial s}{\partial z}\) Here, \(g\) is the gravitational acceleration, \(\alpha\) is the thermal expansion coefficient of seawater, and \(\beta\) is the saline contraction coefficient of seawater. For \(R_{\rho}\geq 1\) , ocean stratified by temperature, \(R_{\rho}\leq - 1\) , ocean stratified by salinity, and \(- 1< R_{\rho}< 1\) , ocean stratified by both temperature and salinity. For clarity, regions where \(R_{\rho}\leq 1\) (i.e., salinity stratification is significant or dominant) are shaded in the plots. Although the water column is predominantly stratified by temperature (white regions), salinity contribution becomes particularly important during winter in the northern Arabian Sea. This salinity influence is in the upper \(100\mathrm{m}\) due to ASHSW and below \(150\mathrm{m}\) due to the intrusion of Persian Gulf Water. In the southern Arabian Sea, salinity stratification arises from the relatively low- salinity water from the Bay of Bengal and the advection of ASHSW from the northern Arabian Sea. The closer \(R_{\rho}\) is to - 1, the stronger the opposing influence of salinity on stratification compared to temperature. + +<--- Page Split ---> + +L168- 170: Why does the extreme precipitation during the summer monsoon of 2017 in the northeastern Arabian Sea reported in reference 7 do not appear in the anomalies of Figure 3b ? + +The extreme precipitation event during 2017 was highly localized around \(67^{\circ}\mathrm{E}\) , \(22^{\circ}\mathrm{N}\) . We presume that the use of a larger area average ( \(60^{\circ} - 75^{\circ}\mathrm{E}\) ) may have weakened the amplitude of this event. However, despite its weaker signal, the event is still evident in Figure 2b as a positive precipitation anomaly north of \(20^{\circ}\mathrm{N}\) . In contrast, the extreme precipitation events identified in 2020 and 2022 show pronounced precipitation anomalies (Figures 2b and 2c). + +L192 and Figure 4: \(1\%\) change in density and \(10\mathrm{m}\) shoaling of the MLD are small changes. Can you provide error bars on the Fig4 curves given the rather small number of Argo float profiles you used to estimate these time series (4 as described in the Method section) ? Would be nice to split the contributions of S & T to the PEA following the above split for N2. + +As suggested by the reviewer, error bars have been included in Figure 4. The differences in the mean between the two periods are statistically significant at the \(95\%\) confidence level \((p = 0.05)\) . We also acknowledge that the mean difference in MLD is specific to the winter period (December- February) and the difference between the two periods is \(\sim 20\mathrm{m}\) (not \(10\mathrm{m}\) as previously noted). + +Regarding the partitioning of PEA into relative contributions from temperature and salinity, we are not aware of a standard methodology for directly separating these effects. However, we included separate contributions of stratification from temperature and salinity in Figure R1. + +L205- 206: "...coinciding with recent freshening events associated with extreme cyclones": this has not been fully proven and is a gain a fast conclusion. I agree that the stronger PEA over 20219- 2023 is coinciding with more cyclones over that period, but has discussed before, these are not necessarily and systematically associated with freshening events: so it is not a proof of causality The 2019- 23 anomalies of PEA around the mean do not systematically coincide with TC occurrences. For example, end 2020, 2021 and 2023 the last TCs of the season coincide with a locally decreasing PEA. + +To address the reviewer's concern, we have modified the sentence to refer to "extreme precipitation events" instead of "cyclone- induced precipitation," reflecting the separation of these events as discussed in Figure 2c. + +L209. Unclear meaning. What do you mean by "similarity"? Can you provide the correlation coefficient between both quantities? + +Thank you for pointing this out. The sentence has been omitted in the revised text. Our original intent was to highlight the common trend between the weakening of stratification (indicated by larger PEA) and the depth of winter convective mixing. + +L217- 219. You state "In 2018, despite the occurrence of three cyclones, none induced freshening north of \(15^{\circ}\mathrm{N}\) , where ASHSW formation takes place. However, in 2019, four out of five cyclones penetrated north of \(15^{\circ}\mathrm{N}\) , resulting in the largest salinity anomalies." It would be more + +<--- Page Split ---> + +correct to say that the increase number of TC in 2019 is “coincident” with the largest salinity anomalies: at this step in the MS, you have not clearly proven that the large SSS drop observed is dominantly due to TC- induced freshening’s. + +With the additional analyses that separate the tropical cyclone rainfall contribution from the total rainfall, along with the supporting model experiments, we believe it is now evident that TC activity was responsible for the largest salinity anomaly observed in 2019. Would it not be appropriate to make qualitative inferences, particularly when those inferences are later validated and supported by quantitative results presented in the manuscript? + +L220: by the “contrasting salinity patterns observed in the Argo data between the 2018 – 19 and 2019 – 20 periods”:, do you mean the step decrease in the average SSS after mid 2019 as observed in Fig S4, top panel? please precise. + +This section has been revised for clarity as suggested. The sentence now specifically refers to the sharp decrease in salinity observed after mid- 2019, in contrast to the higher salinity levels during the 2018–2019 period. + +Figure 5: would be nice to add in the time series panel the one of the TC- induced accumulated rain and of the total rain. While indicative, the symbols showing when TC occurred and their increased number is not a direct proof of their impacts on the reported decreased volume of high SSS waters. + +Following the reviewer's instructions, TC- induced rainfall has been separated from the total rainfall in Figure 2c and reiterated in Figure 5e. The influence of precipitation on ASHSW volume can be both immediate and delayed, as precipitation affects ASHSW formation locally but may have a delayed impact in the following summer due to southward advection. The perturbation experiments PPE2019- 20 and PPE2018- 19 further isolate the specific role of precipitation in modulating ASHSW volume. + +Line 240- 241. You stated: “The volume of high salinity water revealed a notable decline following each cyclone- induced precipitation event (Figure 5e)”. This is not true in 2021 where the first cyclone coincides with an increase in the high salinity water volume, nor for the second of the year, which was followed by a relatively stable high salinity volume (Figure 5e). Please correct accordingly. + +Thank you for the suggestion. This has been corrected accordingly. The statement referred specifically to the 2019 period. While it is true that the volume of ASHSW shows a slight increase following the first storm in June 2021, it subsequently decreases during the winter of 2021–2022, with further reduction by February 2022, influenced by the second storm in September 2021. A reduction in ASHSW volume is expected during the formation period of ASHSW and not immediately following a storm in summer. The impact of rainfall in summer 2021 on the reduction in ASHSW volume becomes evident in the following winter. + +Line 312- 313: “With the exception of 2022, the agreement between cyclone induced precipitation and the intensification of salinity freshening is clear.” …and of 2021”. You have not + +<--- Page Split ---> + +provided any measure of the "cyclone- induced precipitation" with respect total precipitation, so this is a fast conclusion. Please rephrase. + +By separating the rainfall contributions from tropical cyclones (TCs) and other extreme precipitation events, specifically those occurring in 2020 and 2022, we are able to quantify the relative contributions of each to the total rainfall. This analysis provided additional clarity on the roles of TCs versus other rainfall sources in the observed precipitation patterns. Furthermore, the additional model experiments presented in the newly added Figure 9, which isolate rainfall from each source (TCs and extreme precipitation events), clearly delineate their respective impacts on ASHSW freshening. + +L323- 325: "Thus this experiments provide additional confirmation....are largely attributable to freshwater input from tropical cyclone". No, they provide additional confirmation that the change in Precipitation forcing occurring after 2019 is responsible for the decreasing SSS and subsequent weakening of the convective process. Unless, you extract the relative contribution of TCs to total P, you can not state that firmly. + +To address the reviewer's concerns, we provided additional analyses and model experiments. By separating the rainfall contributions from tropical cyclones (TCs) and other extreme precipitation events—specifically those occurring in 2020 and 2022—we are able to quantify the relative contributions of each to the total rainfall. This analysis provided greater clarity on the roles of TCs versus other sources of rainfall. Furthermore, the additional model experiments presented in the newly added Figure 9, which isolate rainfall from each source (TCs and extreme precipitation events), clearly delineate their respective impacts on ASHSW freshening. + +The relative contributions of rainfall from TCs and extreme precipitation events to the total rainfall have been added to Figure 2c, as suggested by the reviewer. It is evident that rainfall from these events accounted for a significant portion of the excess rainfall observed during the 2019- 2023 period. The model experiments further confirm that these events played a key role in the observed ASHSW freshening during this time, supporting the conclusions drawn earlier in the manuscript. + +The intent of this experiment is to capture the salinity differences between the periods 2014- 2018 and 2019- 2023. The choice of 2018 as a reference year was based on the fact that precipitation anomalies during 2018 are broadly representative of typical conditions observed between 2014 and 2018 (Figure 4). Additionally, the tropical cyclone activity in 2018 reflects typical cyclone tracks commonly observed during this period. + +L330- 331: can you provide an estimate of the river runoff impacts (see previous comments) + +While rainfall from tropical cyclones (TCs) and extreme precipitation events could potentially increase river runoff, particularly as some TCs made landfall along the west coast of India, likely contributing to elevated runoff, the model simulations presented in this study do not account for such effects. The simulations utilized a monthly climatology derived from data prior to 1990, which excludes the impact of river runoff associated with the recent increase in TC activity. + +<--- Page Split ---> + +Therefore, the salinity freshening depicted in the model results reflects precipitation- driven effects alone, without contributions from river runoff linked to TCs and extreme events. Although the influence of river runoff is an important topic worth further investigation, it falls beyond the scope of the present study. A brief description of river runoff treatment has been added to the Methods section for clarity. + +L349- 350: it is not true each year: in 2021, the salinity tendency difference do not exceed 0.1 10- 3 psu.d- 1. Please correct + +Corrected as suggested by the reviewer. As noted, the salinity tendency term in 2021 is approximately 0.05. The revised sentence now reads: "Each year, the salinity tendency term exhibits significant decreases, with values ranging from approximately 0.05 to \(0.15 \times 10^{- 3}\) psu d- 1." + +L352- 353. In line 336, you claim that due to decrease S with depth in the AS, vertical mixing consistently brings lighter water from below into the mixed layer, so it is confusing to read here that the vertical mixing tends to increase salinity. Please clarify. Is it the difference of vertical mixing between the control and perturbation experiment which is responsible for the increase S (blue curve in Fig 8c)? + +Thank you for pointing this out. This point has been clarified in the revised text. The vertical mixing generally reduces salinity, as shown in Figures 8a and 8b. Figure 8c presents the difference in vertical mixing between the control and perturbation experiments. In this case, the reduction in salinity due to vertical mixing in the control experiment is smaller than in the perturbation experiment, resulting in a net increase in salinity in the difference plot. + +L357- 358: in 2021, the pre- and post monsoon TC do appear to have extended the duration of freshwater input but not their amplitude. + +The reviewer is correct. The sentence was intended to convey the role of tropical cyclones in prolonging the freshwater input. This has been clarified in the revised text for accuracy. + +L361- 368: since the beginning of the MS, you keep claiming that TCs are responsible for the increased P and surface freshening but you explain here that in 2022, there were no TCs and that low pressure system can contribute significantly to the observed freshening. This is very confusing and lead the reader to believe that potentially, other low- pressure systems than TCs can be responsible for the observed freshwater fluxes in other years of 2019- 23. Please clarify by extracting the actual TC- contribution to rainfall. + +Thank you for bringing this up. It is fair to say that the potential contribution of the 2022 event to salinity freshening was mentioned earlier in the manuscript before reaching the conclusions presented here. Moreover, the significant influence of the 2022 extreme rainfall event on ASHSW freshening became increasingly evident in the salt- budget analyses. This extreme event has also been well documented in a series of recent studies. + +<--- Page Split ---> + +Although the primary focus of the paper is the dominant influence of rainfall from tropical cyclones in the region north of \(15^{\circ}\mathrm{N}\) , the role of prolonged extreme rainfall events is equally important. Our analysis demonstrated that the extreme events in 2020 and 2022 played a crucial role in sustaining ASHSW freshening. Since such events are rare but appear to be increasing in frequency in recent years, they are distinct from typical Indian summer monsoon rainfall anomalies and instead result from prolonged large- scale organized weather systems like monsoonal depressions. Therefore, they can be characterized as extreme precipitation events similar in magnitude to rainfall from named tropical cyclones. + +In the revised manuscript, we have clearly separated the precipitation from tropical cyclones and extreme precipitation events using both observations and model experiments designed to quantify the contribution of each source to salinity freshening. To improve clarity, we now explicitly distinguish these precipitation sources early in the paper (Figure 2c) so that the results presented in the remainder of the manuscript can be interpreted accordingly. This distinction is summarized in paragraph 2, lines xx- yy. + +## References + +Behara, A., Vinayachandran, P. N., & Shankar, D. (2019). Influence of rainfall over eastern Arabian Sea on its salinity. Journal of Geophysical Research: Oceans, 124, 5003- 5020. https://doi.org/10.1029/2019JC014999 + +Boutin, J., N. Reul, J. Koehler, A. Martin, R. Catany, S. Guimbard, F. Rouffi, et al.. Satellite- Based Sea Surface Salinity Designed for Ocean and Climate Studies. Journal of Geophysical Research. 2021. https://doi.org/10.1029/2021JC017676 + +Chaudhuri, D., Sengupta, D., D'Asaro, E., Venkatesan, R., & Ravichandran, M. (2019). Response of the salinity- stratified Bay of Bengal to cyclone Phailin. Journal of Physical Oceanography, 49, 1121- 1140. https://doi.org/10.1175/JPO- D- 18- 0051.1 + +Camberlin, P., Assowe Dabar, O., Pohl, B., Mohamed Waberi, M., Hoarau, K., & Planchon, O. (2024). Contribution of western Arabian Sea tropical cyclones to rainfall in the Horn of Africa and southern Arabian Peninsula. Journal of Geophysical Research: Atmospheres, 129, e2024JD041109. https://doi.org/10.1029/2024JD041109 + +Chen, F. and Y. Fu, (2015) Contribution of tropical cyclone rainfall at categories to total precipitation over the Western North Pacific from 1998 to 2007, Sci. China Earth Sci. 58: 2015. doi:10.1007/s11430- 015- 5103- 9. + +Grodsky, S. A., Reul, N., Lagerloef, G., Reverdin, G., Carton, J. A., Chapron, B., et al. (2012). Haline hurricane wake in the Amazon/Orinoco plume: AQUARIUS/SACD and SMOS observations. Geophysical Research Letters, 39, L20603. https://doi.org/10.1029/2012GL053335 + +Jiang, H. and E.J. Zipser, (2010) Contribution of Tropical Cyclones to the Global Precipitation from Eight Seasons of TRMM Data: Regional, Seasonal, and Interannual Variations. Journal of Climate 23:6, 1526- 1543. + +<--- Page Split ---> + +Jiang, H., C. Liu, and E. D. Zipser (2011), A TRMM- based tropical cyclones cloud and precipitation feature database, J. Appl. Meteorol. Climatol., 50, 1255- 1274. + +Li, B., Zhou, L., Qin, J., & Murtugudde, R. (2022). Increase in intraseasonal rainfall driven by the Arabian Sea warming in recent decades. Geophysical Research Letters, 49, e2022GL100536. https://doi.org/10.1029/2022GL100536 + +Lonfat, M., F. D. Marks, and S. S. Chen, (2004) Precipitation distribution in tropical cyclones using the Tropical Rainfall Measuring Mission (TRMM) microwave imager: A global perspective. Mon. Wea. Rev., 132, 1645- 1660, doi:10.1175/1520- 0493(2004)132,1645:PDITCU.2.0. CO;2. + +Maes, C., and T. J. O'Kane (2014), Seasonal variations of the upper ocean salinity stratification in the Tropics, J. Geophys. Res. Oceans, 119, 1706- 1722, doi:10.1002/2013JC009366. + +Melnichenko. O., 2021. Multi- mission L4 Optimally Interpoated Sea Surface Salinity. Ver.1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY- MM- DD] at https://doi.org/10.5067/SMP10- 4U7CS + +Neethu, C. (2018). Insights into the haline variability induced by cyclone Vardah in the Bay of Bengal using SMAP salinity observations. Remote Sensing Letters, 9(12), 1205- 1213. https://doi.org/10.1080/2150704X.2018.1519271 + +Rao, A. D., M. Joshi, and M. Ravichandran (2009), Observed low- salinity plume off Gulf of Khambhat, India, during post- monsoon period, Geophys. Res. Lett., 36, L03605, doi:10.1029/2008GL036091. + +Reul, N., Quilfen, Y., Chapron, B., Fournier, S., Kudryavtsev, V., & Sabia, R. (2014). Multisensor observations of the Amazon- Orinoco river plume interactions with hurricanes. Journal of Geophysical Research: Oceans, 119, 8271- 8295. https://doi.org/10.1002/2014JC010107 + +Reul Nicolas, Chapron Bertrand, Grodsky Semyon A., Guimbard Sebastien, Kudryavtsev Vladimir, Foltz Gregory R., Balaguru Karthik (2021). Satellite observations of the sea surface salinity response to tropical cyclones. Geophysical Research Letters, 48(1), e2020GL091478 (10p). + +Reul N, Ifremer / LOPS. 2023. Atlas of Tropical Cyclone Induced Wakes (2010- 2020) (v1.0) for ESA Marine Atmosphere eXtreme Satellite Synergy project (MAXSS). Ver. 1.0. Ifremer, Plouzane, France. Dataset accessed [2024- 10- 11]. + +Sun, J.; Vecchi, G.; Soden, B. Sea Surface Salinity Response to Tropical Cyclones Based on Satellite Observations. Remote Sens. 2021, 13, 420. https://doi.org/10.3390/rs13030420 + +Yue, X., Zhang, B., Liu, G., Li, X., Zhang, H., & He, Y. (2018). Upper ocean response to typhoon Kalmaegi and Sarika in the South China sea from Multiple- satellite observations and numerical simulations. Remote Sensing, 10, 348. https://doi.org/10.3390/rs10020348 + +<--- Page Split ---> + +The relevant references have been included in the revised manuscript to support the points discussed. + +<--- Page Split ---> + +Reviewer #3 (Remarks to the Author): + +The manuscript "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation" was reviewed. The paper seems to address an interesting and important issue in these less studied and important ocean basin. It also appears to entail a substantial effort. Hence it can deserve being published. However, some comments listed below may improve it: + +We sincerely thank the reviewer for their thoughtful comments and constructive suggestions, which have greatly enhanced the quality of the manuscript and strengthened the scientific arguments presented. We have carefully addressed the majority of the reviewer's comments and made the necessary modifications to the manuscript. Below, we provide a point- by- point response (reviewer comments in black and our responses highlighted in blue). We hope that these revisions adequately address the reviewer's concerns. + +1- The text is well written, but repetitions of some text parts may be reduced (changed) as they are noticeable and can be a bit tedious to the readers? As: "cyclone- induced", "formation of ASHSW" or "ASHSW formation", "salinity freshening". If it can be helped? 2- Moving Figs to be more harmonious with text may be useful?! + +Thank you for the suggestion. In the revised manuscript, we have minimized repetitive text and ensured consistent terminology throughout the paper. Additionally, we have reorganized the figures to align more closely with the corresponding discussions, as recommended. + +3- The present work only presents salinity and precipitation records and distributions, and no records of surface heat (especially temperature records from observations or model) and momentum (currents?) fluxes are mentioned (even from the work of the others?) as they are important in understanding the issue being addressed here? + +We thank the reviewer for highlighting this important aspect of the study, which was not fully clarified in the initial manuscript. Temperature was excluded in the earlier version because its impact was deemed minimal in the context of our findings. The increasing salinity stratification could indeed restrict vertical mixing by generating barrier layers and potentially raise sea surface temperature (SST) in the northern Arabian Sea. The time- series of temperature observations from Argo floats (Supplementary Figure 4) show no significant differences between the 2014–2018 and 2019–2023 periods. There is, however, a slight indication of warmer winter mixed layer temperatures during the latter period (Supplementary Figure 4a), which could be linked to enhanced salinity stratification from freshwater input. We also added model temperature, which shows good agreement with Argo data, yielding high correlations of 0.84 and 0.91 (Supplementary Figure 8). + +<--- Page Split ---> +![](images/Figure_unknown_1.jpg) + +
Supplementary Figure 4. Argo temperature observations in the Arabian Sea. Along-track Argo float temperature ( \(^\circ \mathrm{C}\) ) observations for three regions representing (a) northern, (b) central, and (c) southern Arabian Sea (refer to Supplementary Figure 3 for location) from 2014 to 2023. The \(25^{\circ}\mathrm{C}\) contour is overlaid in all panels. Profiles with the presence of a barrier layer is marked with white boxes. Barrier layer thickness (BLT, m) is calculated as the difference between the isothermal layer depth (ILD) and the mixed layer depth (MLD), where MLD is defined as the depth corresponding to a density change associated with a \(0.2^{\circ}\mathrm{C}\) temperature difference from the surface, and ILD defines as the depth where the temperature decreases by \(0.2^{\circ}\mathrm{C}\) from the surface. Profiles with \(\mathrm{BLT} \geq 5 \mathrm{~m}\) are marked with white boxes. Cyclone occurrences are marked in each panel: circles indicate very severe to super cyclones, and diamonds indicate cyclones to severe cyclones. Cyclones penetrating north of \(15^{\circ}\mathrm{N}\) are marked in red.
+ +To further investigate the impact of freshwater input on SST, we compared the control (CNTL) and \(\mathrm{PPE}_{2019 - 23}\) model simulations (Figure R1). The differences in surface heat flux (W \(\mathrm{m}^{- 2}\) , Figure R1a) and SST ( \(^\circ \mathrm{C}\) , Figure R1b) between these simulations are negligibly small. A region of net heat gain ( \(\sim 8 \mathrm{~W} \mathrm{m}^{- 2}\) ) is evident along the west coast of India in the control simulation, but the SST exhibited a slight cooling ( \(\sim 0.1^{\circ}\mathrm{C}\) ), suggesting the atmosphere tends to warm the ocean through heat input. Due to the negligible magnitude of heat flux, it has not been included in the manuscript. + +<--- Page Split ---> +![](images/Supplementary_Figure_5.jpg) + +
Figure R1. Differences between the control (CNTL) and PPE2019-23 experiments (CNTL - PPE2019-23) for the 5-year period spanning 2019–2023 in (a) surface heat flux (W m-2) and (b) sea surface temperature (°C).
+ +While we do not present direct ocean current data, their influence on salinity freshening is captured in the salinity budget analysis (Figure 8). Horizontal and vertical advection terms quantify the salinity changes induced by ocean currents, which remain small in the northern Arabian Sea during winter. For a more comprehensive analysis of heat fluxes and advective processes, we reference Thoppil et al. (2022), Prasad and Ikeda (2002b) for detailed examination of these mechanisms. + +4- No cyclone precipitation in 2022 but systemic (synoptic, as large size cyclone or depression) precipitation is substantial!, but the cyclone- induced precipitation is often emphasized? Systemic precipitation have also contributed in other years and cyclone- induced ones are also short lived! Shifting pattern of precipitation northwards on the whole may be more important? Therefore, the paper title may be changed? + +We greatly appreciate the reviewer's insightful suggestion. As noted, large- scale organized weather systems like monsoonal depressions can produce substantial precipitation comparable to that of a significant tropical cyclone. Despite not being associated with a named cyclone, the precipitation from these systems had a comparable effect on salinity freshening (Figure 8). While the extreme precipitation event in 2022 was widely documented, we identified a similar event in 2020, although it coexisted with two tropical cyclones. + +In the revised manuscript, we have: + +1. Separated precipitation contributions from tropical cyclones and extreme precipitation events using IMERG observations (Figure 2c). + +<--- Page Split ---> + +2. Conducted three additional model experiments to quantify the individual and combined effects of tropical cyclones and extreme precipitation events (2020 and 2022) on salinity freshening during 2019–2023 (new Figure 9). + +These extreme precipitation events share a key characteristic: they all occurred in the northern Arabian Sea, where ASHSW forms and where extreme freshwater input events have become increasingly frequent in recent years. This trend coincides with a northward shift in tropical cyclone activity, further intensifying freshwater input and salinity freshening. Additionally, the increasing number of extreme post-monsoon tropical cyclones, which are projected to rise with ongoing climate warming, suggests a clear northward shift in their occurrence (Murakami et al., 2017). + +Since the primary focus of this study is the freshening of ASHSW driven by freshwater input, and no prior studies have indicated a systematic northward shift in precipitation patterns over the Arabian Sea, emphasizing this aspect in the title may be difficult to justify. However, to better reflect the range of precipitation sources analyzed in this study, we have revised the title to: "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Precipitation Events." The use of "extreme precipitation events" accounts for both tropical cyclone- induced rainfall and large- scale organized weather systems contributing to the observed salinity freshening. + +ITCZ in summer, appear to have shifted more (it usually change longitudinal position much more in Indian ocean than in other equatorial regions during the year, hence monsoonal systems) northwards in recent years in the Indian Ocean region that may be due to recent fast climate change, this could have increased the overall precipitation in the Arabian sea? [Mamalakis, A., Randerson, J.T., Yu, J.Y. et al. Zonally contrasting shifts of the tropical rain belt in response to climate change. Nat. Clim. Chang. 11, 143–151 (2021).] + +Thank you for directing us to this insightful study. While the results indeed project a northward shift of the ITCZ and associated precipitation over the Arabian Sea based on climate model simulations for the period 2075–2100, directly linking this projection to the recent increase in precipitation without a detailed analysis using contemporary data remains challenging. The timescales and uncertainties involved necessitate further investigation using recent observations to establish a clearer connection between observed precipitation patterns and projected long- term trends. In the revised manuscript, we have acknowledged this study as a possible future scenario that could influence the salinity budget in the Indian Ocean (Discussion, paragraph 5), while emphasizing the need for further research using recent data to draw more definitive conclusions. + +5- In Fig 3 they may present temperature records along with shown salinity anomaly, and temperature profile in Fig.2, to show better the density stratification which is claimed to have been “substantially weakened”? What is the cooling effects of cloudiness during precipitation? Temperature records may show this. Although in Fig. 4 potential density shows a decrease, along with the shallowing mixed layer depth. (E.g. paper by Shee et al. Recent changes in the upper oceanic water masses over the Indian Ocean using Argo data, Sci. Rep. 2023, 13, 20252, also + +<--- Page Split ---> + +show some temperature records that may be worth looking at?). So presentation of temperature profiles and series changes may be recommended. + +Thank you very much for the suggested recommendation. Unlike salinity, temperature anomalies (Supplementary Figure 5) do not exhibit a distinct cooling/warming pattern during 2019- 2023 period compared to 2014- 2018. They indicate an overall warming trend consistent with the findings of Shee et al. (2023). However, their analysis, focused on the upper \(700\mathrm{m}\) and excluding data after 2019, limits direct comparison with our results. Notably, there are indications of warming in the northern Arabian Sea in 2020, 2021, and 2022, potentially linked to salinity- driven stratification, which may have restricted vertical mixing. + +Related revisions can be found under subsection: Prolonged salinity freshening: Observations, paragraphs, 9 and 11, Figure 4b and supplementary Figures 4, 5 and 8. + +![](images/Figure_2.jpg) + +
Supplementary Figure 5. Temperature anomalies ( \(^\circ \mathrm{C}\) ) averaged in the upper \(50\mathrm{m}\) from the monthly EN4 dataset. Anomalies are calculated relative to the 2000–2023 period by subtracting the long-term monthly climatology.
+ +During tropical cyclone periods, latent heat flux predominantly contributes to surface cooling, though reductions in solar radiation due to cloud cover also modulate surface heat flux to a lesser extent. + +As recommended by the reviewer, we have included Argo temperature profiles in Supplementary Figure 4 for clarity, which show similar slightly warmer winter temperature during 2019–2023, likely driven by strong salinity stratification. + +6- As the northern Indian Ocean is experiencing the intrusions of high salinity and temperature at depth of about 100 to \(500\mathrm{m}\) from the Persian Gulf and Red Sea outflows (depending on season) while being refreshed by the surface water (especially the Persian Gulf, which is also refreshed by the surface water of Arabian Sea), have these semi- enclosed seas any influence on the ASHSW? It may be worth commenting on this, in discussion? + +This is an excellent suggestion by the reviewer to clarify the influence of different water masses on ASHSW. We have added a brief note in the discussion to address this point (see Discussion, paragraph 3). As noted, ASHSW is confined to the upper \(100\mathrm{m}\) , while Persian Gulf Water occurs below \(150\mathrm{m}\) , with its core around \(200\mathrm{m}\) depth, and Red Sea Water is typically found below \(500\mathrm{m}\) , spreading eastward. Therefore, these deeper water masses do not interact with ASHSW. The + +<--- Page Split ---> + +model experiments, which consistently represent these water masses, further support this distinction. + +7- Arabian Sea oxygen- depleted waters and hence, fish kill has increased recently, can ASHSW changes influence this; this may be interesting to just point out? Oxygenation of the Oman Sea and northern Indian Ocean waters by these outflows (4) has been shown to be important, although they are at deeper depths (e.g. Font, E., Swart, S., Bruss, G., Sheehan, P. M. F., Heywood, K. J., & Queste, B. Y. (2024). "Ventilation of the Arabian Sea oxygen minimum zone by Persian Gulf water". Journal of Geophysical Research – Oceans, 129(5), [e2023JC020668]). + +Thank you for pointing out this interesting recent study on the role of Persian Gulf Water in the Arabian Sea Oxygen Minimum Zone (OMZ). It is highly unlikely that ASHSW contributes to the OMZ, which occurs below \(150\mathrm{m}\) , as ASHSW is primarily confined to the upper \(100\mathrm{m}\) of the water column. We are unaware of any evidence linking ASHSW to the OMZ in the Arabian Sea. However, the weakening of winter convective mixing can directly affect primary productivity in the northern Arabian Sea, which may indirectly impact fish populations dependent on phytoplankton. This point has been incorporated into the Discussion (paragraph 4). + +8- Fig. 1 show cyclone track shifted northwards, is this due to recent climate change? Not clearly reasoned? Precipitation seems to have increased more over the eastern coast of the Arabian Sea (more summer ITCZ shift, 4, ?). + +The reviewer raises an important and relevant point. The observed northward shift in cyclone tracks is consistent with projections under changing climate scenarios. Notably, the recent increase in the frequency of post- monsoon cyclones and their northward migration closely aligns with projected changes in extreme cyclone activity, as shown by Murakami et al. (2017, see their Figure 2, referenced below). This connection was briefly discussed in the earlier version of the manuscript. + +Beyond precipitation from cyclones and synoptic- scale systems, Figure 2b also shows an overall increasing trend in precipitation in the eastern Arabian Sea. This rise could be linked to other atmospheric modes of interannual variability, such as the Indian Ocean Dipole (IOD), Monsoon Intra- Seasonal Oscillation (MISO), and monsoon depressions. However, since these processes were not the primary focus of this study, they were only briefly mentioned in the revised manuscript for context. + +<--- Page Split ---> + +Figure 2 of Murakami, H., Vecchi, G.A. & Underwood, S. Increasing frequency of extremely severe cyclonic storms over the Arabian Sea. \*Nature Clim Change\* 7, 885–889 (2017). https://doi.org/10.1038/s41558-017-0008-6 + +9- Should \(\Sigma \Delta \mathrm{P}\) be \(+\) and \(\Sigma \Delta \mathrm{S}\) be - in Fig. 3(c)? Can these be decadal Oscillation? + +Figure 2c (previous Figure 3c) presents the cumulative anomalies of salinity and precipitation depicted in Figures 2a and 2b. During the 2014–2018 period, salinity anomalies remain positive, resulting in a progressively increasing positive cumulative sum, while precipitation anomalies become increasingly negative. In contrast, the 2019–2023 period shows a reversal in the sign of both salinity and precipitation anomalies, leading to a corresponding shift in their cumulative trends. + +Determining whether the observed trend is part of a longer- term decadal oscillation would require further analysis using a longer data record. However, the study by Shee et al. (2021), based on 17 years (2003–2019) of Argo data, suggests the presence of decadal oscillations in the + +<--- Page Split ---> + +upper 700 m of the northern Arabian Sea, although the study did not explore the underlying processes driving these variations in detail. + +10- In salinity budget equation, Fv and Fh are probably vertical and horizontal fluxes due other forcing (may be turbulence or eddy fluxes)? They better to be introduced clearly. + +Thank you for the valuable suggestion. As recommended, the details of these terms have been included in the revised manuscript (see Methods) for clarity and completeness. + +Best of luck for the author. + +Thank you! + +<--- Page Split ---> + +Review of the MS entitled "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation" by P.G. Thoppil submitted to Nature Communications. + +## Summary: + +In this MS, the author first analyzes the impact of Tropical Cyclones (TCs)- induced precipitation on upper ocean salinity in the North Arabian Sea (AS) over 2014- 2023 using satellite rain and in situ Argo profile data. The author reports an increased number of TC in 2019- 2023, concomitant with an increase in total precipitation and an overall decrease of upper ocean salinity in the East AS with respect to the 2014- 2018 period, with a maximum freshening observed in the North East AS region. He then analyzes the temporal evolution of the vertical salinity structure using in situ profile data, revealing sustained freshening in the Northern Arabian Sea where the Arabian Sea High Salinity Waters (ASHsW) form. The upper ocean freshening reduces the potential surface density, augmenting the vertical stratification and in fine, disrupt the convective sinking process of ASHSW. Finally, using model perturbation experiment and model- based salinity budget estimates, the author attempts to isolate the impact of TC- induced rain on salinity freshening and conclude that the recent SSS freshening is caused by the increased number of TCs from 2019 onward. + +## Major Comments and recommendations + +The topic is of strong scientific interest, in particular for the tropical cyclone forecast, salinity remote sensing, and, ocean modeler communities. While the SST, CHLA, and SSH response to TC passage have been extensively studied, TC- induced SSS changes and their large- scale impacts on other climate processes are much less known: this work definitively participate to these community efforts. In general, the MS reads well, is interesting and the results are in general plausible. However, I have several major concerns. + +First, in the part of the MS devoted to observations analyses, the author had not at all isolated the TC- induced precipitation and associated SSS changes from other sources of atmospheric and oceanic variability, which weaken strongly the strength of his statements, which are often more 'suggestions' than a clear demonstration of causality between the three reported interannual anomalies seen in the observation: 1) 'increased number of TC', 2) 'increased total Precipitation', and 3) 'decreased overall upper ocean Salinity'. For me, the author has not demonstrated convincing evidences from his analyses that the reported large- scale upper ocean salinity and precipitation anomalies (shown in Figure 1 & Figure 2 in the MS), as well as their consequences on the stability of the water column (Figure 4) is dominantly due to the passage of some rare but intense tropical cyclones rainfall and associated SSS freshening. I will show below in the detailed comments section of my review several examples in 2019 where there was little precipitation accumulated during the passage of some strong TCs in this region as well as small associated SSS changes in their wake, as reported from satellite observations. The + +<--- Page Split ---> + +interannual SSS & P changes observed by the author could therefore be due to other processes (see details in Behara et al, 2019) such as the increased precipitation during the recent Monsoon, or e.g., due to increased runoff from the river waters out of the Gulf of Khambhat estuaries, or from elsewhere in the coasts (e.g Pakistan floods in 2022 as mentioned by the author at the end of his MS), or even more likely by large scale climate variability impact on rain and SSS (e.g., Indian Ocean Dipole, Monsoon IntraSeasonal Oscillation (MISO),...) and not necessarily because of changes in Tropical Cyclone activity per se in between 2019- 2023 and 2014- 2018. For example, Li et al (2022) found that the variance of MISO has an increasing trend from 1982 to 2017 over the northeastern Arabian Sea (AS), accompanied by increasing intraseasonal rainfall. How does this impact the precipitation excess shown in Figure 1c? The enhancement in rainfall in this case is mainly nourished by the increasing moisture supply, with a major contribution from the upward moisture advection by the intraseasonal vertical wind velocity. Since the author did not isolate the precipitation signal from TC- only with respect to total rain, and also did not isolate the salinity response to TC passage, most of his statements remain poorly evidenced, while this can be now easily estimated from the observation dataset already gathered by the author: + +1) From IMERG and Ibtracs datasets, the author could estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds or within a radius of 500 km) around the TC center tracks. +2) Then further estimate the time series of the cumulated contribution of tropical cyclone only induced rainfall to the total precipitation over the 3 AS subregions selected by the author. Then he could compare the relative contribution of TCs separately for both period 2014-2018 and 2019-2023. + +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach has been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser (2010), Jiang et al (2011). For example, a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non- tropical cyclone (TC) days and on TC days based on IMERG data (2000- 2020). + +Similarly, to best isolate the TC- induced surface freshening from other sources of SSS variability (e.g., Monsoon rain, horizontal advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now + +<--- Page Split ---> + +exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi- mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021). The author could then evaluate the cumulated TC- induced SSS changes in each season over 2014- 2023 and see how much it contributed to the overall SSS decrease observed in that region since 2019. + +Second, in the second part of the MS devoted to model analyses, here again the author has not directly isolated the impact of interannual variability of the TC- induced precipitation and associated SSS changes from other sources of interannual atmospheric and oceanic variability. While I agree with the author that by inverting atmospheric forcing of years 2018 and 2019 the model can reproduce the SSS freshening observation: it does only show that the interannual variability in P predominantly modulate the SSS signal: the author however did not show directly that the TC- induced rain only is responsible for that interannual signal: some other sources of precipitation variability over 2018- 2019 could be responsible for it. Once the TC- induced rain will be isolated from the total precipitation time series as I suggested previously, the author could then easily re- run his model perturbation experiments by only removing TC days in the atmospheric forcing time series: this would directly show what the author want to prove rather than by using lengthy and sometimes confusing indirect approaches. + +In addition, many time in the MS, the author used very strong statements (particularly on the impacts of TC- precipitation on SSS anomalies) without full proof of them: please re- phrase those sentences to only state what is shown by your results. + +Therefore, despite most of the results shown by the author are plausible, I recommend that the MS undergo major revision before being considered for publication so that the author actually and properly separate the TC impacts from other sources of variability in both the Precipitation and SSS signals and in the observation and model analyses, separately: this shall in fine directly demonstrate the authors indirect statements. + +Details are given below. + +## Detailed Comments: + +L38 "evaporation- precipitation"- What about river runoff and their impacts on the northeast Arabian Sea (AS) upper salinity, in particular from the Indus and the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Khambhat estuaries? As shown in Rao et al (2009) and reproduced here below (panel d), rivers have non negligible impacts on the SSS in the North eastern AS, particularly in winter months. + +<--- Page Split ---> + +L107- 108: this sentence is a very strong statement that definitively need more support than what is shown and discussed around Fig1 at this stage in the MS. Please re- phrase to be more accurate and keep to the point of what your data really show. It is not because Fig1 panels reveal a concomitant increase in 1) the number of TCs in the North- eastern part of the AS, 2) as well as in overall Precipitation in the eastern AS and 3) a decrease in SSS in the NE AS that this is clearly an evident proof that “the cyclone- induced precipitation have impact on the convective formation of the Arabian Sea High Salinity Waters “. This is a very strong shortcoming. As I will show further, TC in the Arabian sea are not systematically associated with heavy rain and SSS drops are not systematically observed in their trail. Deeper observation analyses are required to conclude. + +Indeed, the increase of precipitation shown in Fig1c could be due to other atmospheric sources of interannual variability (e.g., Indian Ocean Dipole, Moonsoon) than merely the change in Tropical Cyclone activity in between 2019- 2023 and 2014- 2018. What about a potentially increase in monsoon season accumulated rain in the most recent years ? + +Similarly, the SSS deacrease in the AS, while I agree is most intense where most new TCs tracks where located in 2019- 2023 is also a region of significant runoff from the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Cambay estuaries. Could the reported interannual variability in SSS in this region be also related to increased river runoff in 2019- 2023 ? and if yes, how much does it contribute to the observed SSS decrease with respect to the impact of local rain increases ? + +To resolve these uncertainties, I suggest the author shall re- analyse the datasets as follows: + +<--- Page Split ---> + +3) From IMERG and Ibtracs datasets, estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds) around the TC center track. +4) Then further estimate the average cumulated spatial contribution of all tropical cyclone rainfall to total precipitation over the AS region, separately for both period 2014-2018 and 2019-2023. + +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach have been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser(2010), Jiang et al (2011). For example a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non- tropical cyclone (TC) days and TC days based on IMERG data (2000- 2020). Such an approach could be easily applied by the author. + +5) Similarly, to best isolate the TC-induced surface freshening from other sources of SSS variability (Moonsoon rain, advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi-mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021) + +In fact, databases including TC- induced Precipitation & SSS changes for each individual TC globally over 2010- 2020 were already developed in the frame of the ESA Marine Atmosphere eXtreme Satellite Synergy (MAXSS) project (see https://www.maxss.org/) and could be used by the author to better demonstrate his statements. This dataset is publicly available (doi:10.12770/cc0577e4-55d6-4aa9-a938-b4965be121ab, Reul et al., 2023), and provides, for each storm tracks from IBTrACS during the period 2010- 2020, three types of storm- related parameters: (1) the pre- storm upper ocean conditions (e.g., SST, SSS, upper ocean vertical density stratification strength, etc.), (2) the atmospheric forcing during the storm passage (maximum wind, accumulated rain and evaporation, wind power index, etc.) during the storm, as well as (3) the oceanic wakes left after the storm for an ensemble of key variables (SST, SSS, sea level height, ocean color parameters). I show here below few examples of estimated SSS anomalies (derived from the ESA CCI SSS products) left after TC passages in the AS as well as the corresponding accumulated precipitation (derived from merged satellite TRMM products) during their lifetime over the AS in 2019 and which is available in the + +<--- Page Split ---> + +MAXSS database. As evidenced from satellite data, TC passage in the AS in 2019 are not systematically associated with strong local SSS decreases and heavy precipitation: see e.g. examples of the extremely severe cyclonic storm MAHA in 2019 with small amount of accumulated precipitation associated with negligible SSS changes in the North Eastern AS, or the other case of the super cyclonic storm KYARR with locally very high accumulated rain at \(20^{\circ}\mathrm{N}\) but no significant associated SSS changes observed from satellites. Significant SSS drops were nevertheless observed after the passage of the very severe cyclonic storm VAYU in a region with significant accumulated rain. Therefore, given the high variability of the SSS response to TC passages in this region, and although Sun et al., (2021) have shown (see their Figure 16 top pannel) that on average TC do induce SSS drops in the AS, it remains unclear what the overall contributions of the TC- induced rain and associated freshening are on the 2014- 2018 versus 2019- 2023 interannual variability reported in Fig 1.c and Fig.1d. + +![PLACEHOLDER_44_0] + + +<--- Page Split ---> +![PLACEHOLDER_45_0] + +
Figure 2: Examples of SSS anomalies left after TC passages in the Arabian Sea in 2019 (left panels) and corresponding accumulated rain (right panels). Data and plots are available at https://www.maxss.org/.
+ +Line 111- 113: I agree that the addition of freshwater reduces surface density but it has not been demonstrated at this stage of the MS that it disrupts the sinking process and weaken the formation of the ASHSW. Please re- phrase to only state what is shown by your results. + +Figure 2: the symbols representing the occurrences of TC are not visible enough on the figures. I would add panels illustrating the temporal evolution of the total accumulated rain and of the TC- induced rain in the three regions. In the legend, you precise that "2 extremely severe cyclones in late October to Early November triggered the largest freshening in the AS". Please clarify and provide the references for the name (identifier) of these 2 storms and show the SSS freshening associated to them or do not mention something you did not demonstrated. According to Fig2a in the MS, the freshening after September- December 2020, or 2021, seems the two largest freshenings over the period. Satellite SSS data for the example of TC MAHA shown above and which occurred in early November 2019 do not reveal large surface freshening! + +Figure 3: it is not fully clear how SSS and P anomalies were evaluated. In the method section it is said (Line 476 and 498- 499) that 'salinity and P anomalies are calculated from 2000- 2023 period'. Do you mean that you evaluated the mean seasonal cycle over 2000- 2023 and then removed it to the S and P times series or did you remove the overall local mean evaluated over the complete 2000- 2023 period independently of the season ? Please precise, it is very important to understand if the mean seasonal cycle was removed or not. Please + +<--- Page Split ---> + +also provide y- axis labels in Fig 3a (SSSA) and b (Precipitation anomaly). Correct the typo for "IMERGE", it shall reads" IMERG." + +Figure 3c: I would suggest to add the TC- induced rain accumulated precipitation time series as well, this would avoid lack of clarity on the relative contributions of TC versus other sources of atmospheric rain on the observed anomalies. + +L129: except in 2021, it does not appear clearly that SSS freshening systematically lag behind P anomalies when comparing Fig3a and Fig3b. For example in J- S 2022, the freshening are concomitant with high rain. Please re- formulate accordingly. + +L130: here again, the author sentence "The addition of cyclone- induced freshwater increases buoyancy and strengthens stratification, which in turns weakens the depth of winter convective mixing" has not been yet demonstrated at this stage of the MS and shall be removed if not fully proofed + +L134: Fig S2 show the evolution of the MLD averaged over the box \(60^{\circ} - 70^{\circ}\mathrm{E}\) , \(15^{\circ} - 25^{\circ}\mathrm{N}\) and not separately for the 3 boxes shown in Fig3. It is rather confusing then to compare MLD & S evolution in different boxes. Please correct. + +L135: "While cyclone- induced precipitation weakens the convective formation of ASHSW in the north during winter,...": here again this statement have NOT been demonstrated at this stage in the MS; please remove/correct unless you show a real demonstration + +L148: "...salinity maximum at \(80\mathrm{m}\) ." Please precise that is seen in 'Figure 2f + +L148: "...salinity maximum at \(80\mathrm{m}\) ." Please precise that is seen in 'Figure 2fL148: "This vertical salinity stratification promotes vertical mixing (heavier over lighter water) and plays an important role in maintaining SST in the southeastern Arabian Sea". Ok, but why not showing the Brunt- Vaisala frequency to illustrate the respective contribution of S and T to vertical stratification in the 3 regions, following Maes, C., and O'Kane (2014): + +\[N^{2}(T,S) = -\frac{g}{\rho}\frac{\partial\rho}{\partial z}\approx \left(g\alpha \frac{\partial T}{\partial z} +g\beta \frac{\partial S}{\partial z}\right) = N_{T}^{2}(T,S) + N_{S}^{2}(T,S)\] + +Where \(\rho\) is density, T temperature; S salinity, \(\alpha\) is the thermal expansion coefficient, \(\beta\) is the haline contraction coefficient; g is acceleration of gravity and z is vertical. This would help the reader to understand the role of freshwater on the vertical density stratification. + +L168- 170: Why does the extreme precipitation during the summer monsoon of 2017 in the northeastern Arabian Sea reported in reference 7 do not appear in the anomalies of Figure 3b ? + +<--- Page Split ---> + +L192 and Figure 4: \(1\%\) change in density and 10m shoaling of the MLD are small changes. Can you provide error bars on the Fig4 curves given the rather small number of Argo float profiles you used to estimate these time series (4 as described in the Method section) ? Would be nice to split the contributions of S & T to the PEA following the above split for N2. + +L205- 206: "...coinciding with recent freshening events associated with extreme cyclones': this has not been fully proven and is a gain a fast conclusion. I agree that the stronger PEA over 20219- 2023 is coinciding with more cyclones over that period, but has discussed before, these are not necessarily and systematically associated with freshening events: so it is not a proof of causality The 2019- 23 anomalies of PEA around the mean do not systematically coincide with TC occurrences. For example, end 2020, 2021 and 2023 the last TCs of the season coincide with a locally decreasing PEA. + +L209. Unclear meaning. What do you mean by "similarity"? Can you provide the correlation coefficient between both quantities? + +L217- 219. You state "In 2018, despite the occurrence of three cyclones, none induced freshening north of \(15^{\circ}\mathrm{N}\) , where ASHSW formation takes place. However, in 2019, four out of five cyclones penetrated north of \(15^{\circ}\mathrm{N}\) , resulting in the largest salinity anomalies." It would be more correct to say that the increase number of TC in 2019 is "coincident" with the largest salinity anomalies: at this step in the MS, you have not clearly proven that the large SSS drop observed is dominantly due to TC- induced freshening's. + +L220: by the "contrasting salinity patterns observed in the Argo data between the 2018 - 19 and 2019 - 20 periods":, do you mean the step decrease in the average SSS after mid 2019 as observed in Fig S4, top panel ? please precise. + +Figure 5: would be nice to add in the time series panel the one of the TC- induced accumulated rain and of the total rain. While indicative, the symbols showing when TC occurred and their increased number is not a direct proof of their impacts on the reported decreased volume of high SSS waters. + +Line 240- 241. You stated: "The volume of high salinity water revealed a notable decline following each cyclone- induced precipitation event (Figure 5e)". This is not true in 2021 where the first cyclone coincides with an increase in the high salinity water volume, nor for the second of the year, which was followed by a relatively stable high salinity volume (Figure 5e). Please correct accordingly. + +Line 312- 313: "With the exception of 2022, the agreement between cyclone- induced precipitation and the intensification of salinity freshening is clear." ...and + +<--- Page Split ---> + +of 2021". You have not provided any measure of the "cyclone- induced precipitation" with respect total precipitation, so this is a fast conclusion. Please re- phrase. + +L323- 325: "Thus this experiments provide additional confirmation.....are largely attributable to freshwater input from tropical cyclone". No, they provide additional confirmation that the change in Precipitation forcing occurring after 2019 is responsible for the decreasing SSS and subsequent weakening of the convective process. Unless, you extract the relative contribution of TCs to total P, you can not state that firmly. + +L330- 331: can you provide an estimate of the river runoff impacts (see previous comments) + +L349- 350: it is not true each year: in 2021, the salinity tendency difference do not exceed \(0.1 \times 10^{- 3}\) psu.d- 1. Please correct + +L352- 353. In line 336, you claim that due to decrease S with depth in the AS, vertical mixing consistently brings lighter water from below into the mixed layer, so it is confusing to read here that the vertical mixing tends to increase salinity. Please clarify. Is it the difference of vertical mixing between the control and perturbation experiment which is responsible for the increase S (blue curve in Fig 8c)? + +L357- 358: in 2021, the pre- and post monsoon TC do appear to have extended the duration of freshwater input but not their amplitude. + +L361- 368: since the beginning of the MS, you keep claiming that TCs are responsible for the increased P and surface freshening but you explain here that in 2022, there were no TCs and that low pressure system can contribute significantly to the observed freshening. This is very confusing and lead the reader to believe that potentially, other low- pressure systems than TCs can be responsible for the observed freshwater fluxes in other years of 2019- 23. Please clarify by extracting the actual TC- contribution to rainfall. + +## References + +Behara, A., Vinayachandran, P. N., & Shankar, D. (2019). Influence of rainfall over eastern Arabian Sea on its salinity. Journal of Geophysical Research: Oceans, 124, 5003- 5020. https://doi.org/10.1029/2019JC014999Boutin, J., N. Reul, J. Koehler, A. Martin, R. Catany, S. Guimbard, F. Rouffi, et al.. Satellite- Based Sea Surface Salinity Designed for Ocean and Climate Studies. Journal of Geophysical Research. 2021. https://doi.org/10.1029/2021JC017676 + +<--- Page Split ---> + +Chaudhuri, D., Sengupta, D., D'Asaro, E., Venkatesan, R., & Ravichandran, M. (2019). Response of the salinity- stratified Bay of Bengal to cyclone Phailin. Journal of Physical Oceanography, 49, 1121- 1140. https://doi.org/10.1175/JPO- D- 18- 0051.1 + +Camberlin, P., Assowe Dabar, O., Pohl, B., Mohamed Waberi, M., Hoarau, K., & Planchon, O. (2024). Contribution of western Arabian Sea tropical cyclones to rainfall in the Horn of Africa and southern Arabian Peninsula. Journal of Geophysical Research: Atmospheres, 129, e2024JD041109. https://doi.org/10.1029/2024JD041109 + +Chen, F. and Y. Fu, (2015) Contribution of tropical cyclone rainfall at categories to total precipitation over the Western North Pacific from 1998 to 2007, Sci. China Earth Sci. 58: 2015. doi:10.1007/s11430- 015- 5103- 9. + +Grodsky, S. A., Reul, N., Lagerloef, G., Reverdin, G., Carton, J. A., Chapron, B., et al. (2012). Haline hurricane wake in the Amazon/Orinoco plume: AQUARIUS/SACD and SMOS observations. Geophysical Research Letters, 39, L20603. https://doi.org/10.1029/2012GL053335 + +Jiang, H. and E.J. Zipser, (2010) Contribution of Tropical Cyclones to the Global Precipitation from Eight Seasons of TRMM Data: Regional, Seasonal, and Interannual Variations. Journal of Climate 23:6, 1526- 1543. + +Jiang, H., C. Liu, and E. D. Zipser (2011), A TRMM- based tropical cyclones cloud and precipitation feature database, J. Appl. Meteorol. Climatol., 50, 1255- 1274. + +Li, B., Zhou, L., Qin, J., & Murtugudde, R. (2022). Increase in intraseasonal rainfall driven by the Arabian Sea warming in recent decades. Geophysical Research Letters, 49, e2022GL100536. https://doi.org/10.1029/2022GL100536 + +Lonfat, M., F. D. Marks, and S. S. Chen, (2004) Precipitation distribution in tropical cyclones using the Tropical Rainfall Measuring Mission (TRMM) microwave imager: A global perspective. Mon. Wea. Rev., 132, 1645- 1660, doi:10.1175/1520- 0493(2004)132,1645:PDITCU.2.0. CO;2. + +Maes, C., and T. J. O'Kane (2014), Seasonal variations of the upper ocean salinity stratification in the Tropics, J. Geophys. Res. Oceans, 119, 1706- 1722, doi:10.1002/2013JC009366. + +Melnichenko. O., 2021. Multi- mission L4 Optimally Interpoated Sea Surface Salinity. Ver. 1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY- MM- DD] at https://doi.org/10.5067/SMP10- 4U7CS + +<--- Page Split ---> + +Neethu, C. (2018). Insights into the haline variability induced by cyclone Vardah in the Bay of Bengal using SMAP salinity observations. Remote Sensing Letters, 9(12), 1205- 1213. https://doi.org/10.1080/2150704X.2018.1519271Rao, A. D., M. Joshi, and M. Ravichandran (2009), Observed low- salinity plume off Gulf of Khambhat, India, during post- monsoon period, Geophys. Res. Lett., 36, L03605, doi:10.1029/2008GL036091. Reul, N., Quilfen, Y., Chapron, B., Fournier, S., Kudryavtsev, V., & Sabia, R. (2014). Multisensor observations of the Amazon- Orinoco river plume interactions with hurricanes. Journal of Geophysical Research: Oceans, 119, 8271- 8295. https://doi.org/10.1002/2014JC010107Reul Nicolas, Chapron Bertrand, Grodsky Semyon A., Guimbard Sebastien, Kudryavtsev Vladimir, Foltz Gregory R., Balaguru Karthik (2021). Satellite observations of the sea surface salinity response to tropical cyclones. Geophysical Research Letters, 48(1), e2020GL091478 (10p.).Reul N, Ifremer / LOPS. 2023. Atlas of Tropical Cyclone Induced Wakes (2010- 2020) (v1.0) for ESA Marine Atmosphere eXtreme Satellite Synergy project (MAXSS). Ver. 1.0. Ifremer, Plouzane, France. Dataset accessed [2024- 10- 11].Sun, J.; Vecchi, G.; Soden, B. Sea Surface Salinity Response to Tropical Cyclones Based on Satellite Observations. Remote Sens. 2021, 13, 420. https://doi.org/10.3390/rs13030420Yue, X., Zhang, B., Liu, G., Li, X., Zhang, H., & He, Y. (2018). Upper ocean response to typhoon Kalmaegi and Sarika in the South China sea from Multiple- satellite observations and numerical simulations. Remote Sensing, 10, 348. https://doi.org/10.3390/rs10020348 + +<--- Page Split ---> diff --git a/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd b/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..5a3604967951bc032a5b9fdacaaaab96072be155 --- /dev/null +++ b/peer_reviews/df639515a6e24ff02e1926f7fe0abd6ebd77392fd14698ef627e29d172fbd4d3/supplementary_0_Transparent Peer Review file/supplementary_0_Transparent Peer Review file_det.mmd @@ -0,0 +1,1147 @@ +<|ref|>title<|/ref|><|det|>[[72, 53, 295, 80]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[74, 96, 297, 119]]<|/det|> +Peer Review File + +<|ref|>title<|/ref|><|det|>[[73, 161, 860, 210]]<|/det|> +# Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Precipitation Events + +<|ref|>text<|/ref|><|det|>[[73, 224, 432, 240]]<|/det|> +Corresponding Author: Dr Prasad Thoppil + +<|ref|>text<|/ref|><|det|>[[72, 274, 712, 289]]<|/det|> +Parts of this Peer Review File have been redacted as indicated to remove third- party material. + +<|ref|>text<|/ref|><|det|>[[72, 301, 866, 316]]<|/det|> +This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. + +<|ref|>text<|/ref|><|det|>[[72, 327, 890, 342]]<|/det|> +Attachments originally included by the reviewers as part of their assessment can be found at the end of this file. + +<|ref|>text<|/ref|><|det|>[[73, 380, 144, 393]]<|/det|> +Version 0: + +<|ref|>text<|/ref|><|det|>[[73, 405, 219, 419]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[73, 431, 160, 445]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[73, 458, 238, 471]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 472, 308, 484]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[72, 484, 919, 563]]<|/det|> +I had great pleasure in reading the manuscript entitled "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation". The manuscript investigates the impact of freshening happened in northern Arabian Sea due to anomalous number of Tropical Cyclones (TCs) happened during 2019 - 2023 by contrasting them with the freshening due to Tcs during 2014- 2018 period. The author used, in situ Argo float measurements, satellite datasets and model simulations to examine the contrasts in freshening and resulting changes in Arabian Sea High salinity water mass formation during the two periods selected for the study. + +<|ref|>text<|/ref|><|det|>[[73, 576, 192, 589]]<|/det|> +Important results: + +<|ref|>text<|/ref|><|det|>[[72, 600, 916, 678]]<|/det|> +- For the first time there is an attempt to show the impact of TC induces precipitation on the upper ocean water-mass formation and salt-budget of the northern Arabian Sea- The authors use both observations and model simulations and demonstrate that both agree in demonstrating the impact of TC induced precipitation.- This study encourages to investigate future trends TC trends in northern Arabian sea and the possible impact on water-mass formation which has widespread impact on ecological balance of the region. + +<|ref|>text<|/ref|><|det|>[[72, 703, 921, 731]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +<|ref|>text<|/ref|><|det|>[[72, 743, 866, 770]]<|/det|> +This work is certainly novel and can give potential insights about the impact of TC associated rainfall on water-mass formation which has widespread influence on ecology, fisheries and productivity in the region. + +<|ref|>text<|/ref|><|det|>[[73, 782, 668, 796]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed? + +<|ref|>text<|/ref|><|det|>[[72, 808, 866, 835]]<|/det|> +The present analysis shown by the author supports the conclusions and claims to a good extend. However, it will be interesting if the author can clarify below questions which can improve the confidence on this work further. + +<|ref|>text<|/ref|><|det|>[[72, 847, 914, 900]]<|/det|> +Arabian sea is a basin under the influence of Indian monsoon and there is strong seasonality for rainfall in this region. So naturally there is existence of freshening and evaporation cycle in this region. It will be interesting to understand if the differences in amplitude of freshening due to Tcs during 2019- 2023 is statistically significant with the historical amplitude of freshening due to the impact of monsoonal rainfall. + +<|ref|>text<|/ref|><|det|>[[70, 911, 911, 926]]<|/det|> +- Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 88]]<|/det|> +The data analysis approach is sound in general, however, author may clarify below aspects. The author show differences in mean potential energy anomaly during 2024- 2018 and 2019- 2023. Is this difference in mean statistically significant? Can this be verified with a statistical significance test? + +<|ref|>text<|/ref|><|det|>[[73, 100, 666, 114]]<|/det|> +- Is the methodology sound? Does the work meet the expected standards in your field? + +<|ref|>text<|/ref|><|det|>[[72, 126, 702, 153]]<|/det|> +Authors use best possible datasets and model simulations to prove their arguments. And it meets the standards. The minor issues are pointed out under other relevant headings. + +<|ref|>text<|/ref|><|det|>[[73, 165, 613, 180]]<|/det|> +- Is there enough detail provided in the methods for the work to be reproduced? + +<|ref|>text<|/ref|><|det|>[[70, 191, 904, 218]]<|/det|> +Author use two quantities in the manuscript potential energy anomaly and ASHSW volume. Are there references for these quantities? Please specify. + +<|ref|>text<|/ref|><|det|>[[72, 230, 845, 257]]<|/det|> +The datasets used in the study is available from public domain, however author may be asked to make the model simulations available if the results need to be reproduced using model simulations as shown in the manuscript + +<|ref|>text<|/ref|><|det|>[[73, 269, 192, 282]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[72, 295, 923, 335]]<|/det|> +1) On page 4 towards the end (it may differ as I checked word document) Although no cyclones occurred in 2022, the extremely high rainfall during July – August, which caused severe flooding and displaced over 30 million people in Pakistan, helped maintain one of the largest salinity anomalies during 2019 – 23 ever recorded (Figure 3). + +<|ref|>text<|/ref|><|det|>[[72, 346, 884, 374]]<|/det|> +Here a reference may be added, if author wanted to state it is largest salinity anomalies "ever" recorded. Else they may modify saying largest salinity anomalies during the study period. + +<|ref|>text<|/ref|><|det|>[[70, 385, 916, 413]]<|/det|> +2) On page 7 line two, author says "We estimated Potential Energy Anomaly" which may be re-written as I estimated as it is a single author paper or the contributor may be acknowledged if there is one. + +<|ref|>text<|/ref|><|det|>[[73, 437, 162, 450]]<|/det|> +Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[73, 464, 473, 491]]<|/det|> +(Remarks to the Author) My review is detailed in the attached pdf documents below + +<|ref|>text<|/ref|><|det|>[[73, 502, 592, 516]]<|/det|> +[Editorial Note: This attachment is displayed in the final 12 pages of this file] + +<|ref|>text<|/ref|><|det|>[[73, 555, 162, 568]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[73, 581, 237, 595]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[73, 606, 907, 660]]<|/det|> +The manuscript "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation" was reviewed. The paper seems to address an interesting and important issue in these less studied and important ocean basin. It also appears to entail a substantial effort. Hence it can deserve being published. However, some comments listed below may improve it: + +<|ref|>text<|/ref|><|det|>[[72, 672, 920, 712]]<|/det|> +1- The text is well written, but repetitions of some text parts may be reduced (changed) as they are noticeable and can be a bit tedious to the readers? As: "cyclone- induced", "formation of ASHSW" or "ASHSW formation", "salinity freshening". If it can be helped? + +<|ref|>text<|/ref|><|det|>[[72, 711, 510, 724]]<|/det|> +2- Moving Figs to be more harmonious with text may be useful? + +<|ref|>text<|/ref|><|det|>[[72, 737, 923, 776]]<|/det|> +3- The present work only presents salinity and precipitation records and distributions, and no records of surface heat (especially temperature records from observations or model) and momentum (currents?) fluxes are mentioned (even from the work of the others?) as they are important in understanding the issue being addressed here? + +<|ref|>text<|/ref|><|det|>[[72, 788, 919, 841]]<|/det|> +4- No cyclone precipitation in 2022 but systemic (synoptic, as large size cyclone or depression) precipitation is substantial, but the cyclone- induced precipitation is often emphasized? Systemic precipitation have also contributed in other years and cyclone- induced ones are also short lived! Shifting pattern of precipitation northwards on the whole may be more important? Therefore, the paper title may be changed? + +<|ref|>text<|/ref|><|det|>[[72, 853, 912, 920]]<|/det|> +ITCZ in summer, appear to have shifted more (it usually change longitudinal position much more in Indian ocean than in other equatorial regions during the year, hence monsoonal systems) northwards in recent years in the Indian Ocean region that may be due to recent fast climate change, this could have increased the overall precipitation in the Arabian sea? [ Mamalakis, A., Randerson, J.T., Yu, J.Y. et al. Zonally contrasting shifts of the tropical rain belt in response to climate change. Nat. Clim. Chang. 11, 143- 151 (2021).] + +<|ref|>text<|/ref|><|det|>[[70, 931, 888, 946]]<|/det|> +5- In Fig 3 they may present temperature records along with shown salinity anomaly, and temperature profile in Fig.2, to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 46, 920, 114]]<|/det|> +show better the density stratification which is claimed to have been "substantially weakened"? What is the cooling effects of cloudiness during precipitation? Temperature records may show this. Although in Fig. 4 potential density shows a decrease, along with the shallowing mixed layer depth. (E.g. paper by Shee et al. Recent changes in the upper oceanic water masses over the Indian Ocean using Argo data, Sci. Rep. 2023, 13, 20252, also show some temperature records that may be worth looking at?). So presentation of temperature profiles and series changes may be recommended. + +<|ref|>text<|/ref|><|det|>[[72, 125, 914, 179]]<|/det|> +6- As the northern Indian Ocean is experiencing the intrusions of high salinity and temperature at depth of about 100 to 500 m from the Persian Gulf and Red Sea outflows (depending on season) while being refreshed by the surface water (especially the Persian Gulf, which is also refreshed by the surface water of Arabian Sea), have these semi- enclosed seas any influence on the ASHSW? It may be worth commenting on this, in discussion? + +<|ref|>text<|/ref|><|det|>[[72, 190, 915, 256]]<|/det|> +7- Arabian Sea oxygen- depleted waters and hence, fish kill has increased recently, can ASHSW changes influence this; this may be interesting to just point out? Oxygenation of the Oman Sea and northern Indian Ocean waters by these outflows (4) has been shown to be important, although they are at deeper depths (e.g. Font, E., Swart, S., Bruss, G., Sheehan, P. M. F., Heywood, K. J., & Queste, B. Y. (2024). "Ventilation of the Arabian Sea oxygen minimum zone by Persian Gulf water". Journal of Geophysical Research – Oceans, 129(5), [e2023JC020668]). + +<|ref|>text<|/ref|><|det|>[[70, 268, 900, 296]]<|/det|> +8- Fig. 1 show cyclone track shifted northwards, is this due to recent climate change? Not clearly reasoned? Precipitation seems to have increased more over the eastern coast of the Arabian Sea (more summer ITCZ shift, 4, ?). + +<|ref|>text<|/ref|><|det|>[[72, 307, 639, 321]]<|/det|> +9- Should \(\Sigma \Delta \mathrm{P}\) be \(^+\) and \(\Sigma \Delta \mathrm{S}\) be - in Fig. 3(c)? Can these be decadal Oscillation? + +<|ref|>text<|/ref|><|det|>[[70, 333, 920, 361]]<|/det|> +10- In salinity budget equation, Fv and Fh are probably vertical and horizontal fluxes due other forcing (may be turbulence or eddy fluxes)? They better to be introduced clearly. + +<|ref|>text<|/ref|><|det|>[[72, 372, 251, 386]]<|/det|> +Best of luck for the author. + +<|ref|>text<|/ref|><|det|>[[72, 411, 144, 424]]<|/det|> +Version 1: + +<|ref|>text<|/ref|><|det|>[[72, 437, 220, 450]]<|/det|> +Reviewer comments: + +<|ref|>text<|/ref|><|det|>[[72, 463, 160, 476]]<|/det|> +Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[72, 489, 780, 517]]<|/det|> +(Remarks to the Author) The author has addressed the concerns raised by me and I suggest the manuscript may be published. + +<|ref|>text<|/ref|><|det|>[[72, 528, 161, 541]]<|/det|> +Reviewer #3 + +<|ref|>text<|/ref|><|det|>[[72, 555, 240, 567]]<|/det|> +(Remarks to the Author) + +<|ref|>text<|/ref|><|det|>[[70, 567, 916, 594]]<|/det|> +The author has made a major effort in improving the paper following our comments on its early version. Hence I recommend the paper for publication. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[72, 45, 916, 99]]<|/det|> +Open Access This Peer Review File is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. + +<|ref|>text<|/ref|><|det|>[[72, 99, 797, 113]]<|/det|> +In cases where reviewers are anonymous, credit should be given to 'Anonymous Referee' and the source. + +<|ref|>text<|/ref|><|det|>[[72, 112, 911, 165]]<|/det|> +The images or other third party material in this Peer Review File are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. + +<|ref|>text<|/ref|><|det|>[[72, 165, 618, 179]]<|/det|> +To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[116, 90, 348, 108]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[116, 125, 417, 143]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[116, 160, 388, 177]]<|/det|> +- What are the noteworthy results? + +<|ref|>text<|/ref|><|det|>[[115, 178, 870, 318]]<|/det|> +I had great pleasure in reading the manuscript entitled "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation". The manuscript investigates the impact of freshening happened in northern Arabian Sea due to anomalous number of Tropical Cyclones (TCs) happened during 2019 - 2023 by contrasting them with the freshening due to Tcs during 2014- 2018 period. The author used, in situ Argo float measurements, satellite datasets and model simulations to examine the contrasts in freshening and resulting changes in Arabian Sea High salinity water mass formation during the two periods selected for the study. + +<|ref|>text<|/ref|><|det|>[[116, 335, 255, 352]]<|/det|> +Important results: + +<|ref|>text<|/ref|><|det|>[[115, 369, 870, 494]]<|/det|> +- For the first time there is an attempt to show the impact of TC induces precipitation on the upper ocean water-mass formation and salt-budget of the northern Arabian Sea +- The authors use both observations and model simulations and demonstrate that both agree in demonstrating the impact of TC induced precipitation. +- This study encourages to investigate future trends TC trends in northern Arabian sea and the possible impact on water-mass formation which has widespread impact on ecological balance of the region. + +<|ref|>text<|/ref|><|det|>[[115, 522, 881, 629]]<|/det|> +We sincerely thank the reviewer for their thoughtful comments and constructive suggestions, which have greatly enhanced the quality of the manuscript and strengthened the scientific arguments presented. We have carefully addressed the majority of the reviewer's comments and made the necessary modifications to the manuscript. Below, we provide a detailed point- by- point response, with the reviewer's comments in black and our responses highlighted in blue. We hope that these revisions adequately address the reviewer's concerns. + +<|ref|>text<|/ref|><|det|>[[115, 677, 843, 713]]<|/det|> +- Will the work be of significance to the field and related fields? How does it compare to the established literature? If the work is not original, please provide relevant references. + +<|ref|>text<|/ref|><|det|>[[115, 729, 855, 783]]<|/det|> +This work is certainly novel and can give potential insights about the impact of TC associated rainfall on water-mass formation which has widespread influence on ecology, fisheries and productivity in the region. + +<|ref|>text<|/ref|><|det|>[[115, 799, 793, 818]]<|/det|> +- Does the work support the conclusions and claims, or is additional evidence needed? + +<|ref|>text<|/ref|><|det|>[[115, 834, 867, 887]]<|/det|> +The present analysis shown by the author supports the conclusions and claims to a good extend. However, It will be interesting if the author can clarify below questions which can improve the confidence on this work further. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 882, 177]]<|/det|> +Arabian sea is a basin under the influence of Indian monsoon and there is strong seasonality for rainfall in this region. So naturally there is existence of freshening and evaporation cycle in this region. It will be interesting to understand if the differences in amplitude of freshening due to Tcs during 2019- 2023 is statistically significant with the historical amplitude of freshening due to the impact of monsoonal rainfall. + +<|ref|>text<|/ref|><|det|>[[115, 210, 869, 315]]<|/det|> +The reviewer raises an excellent point regarding the potential influence of seasonal and interannual variability on precipitation, particularly from the Indian Monsoon and other climate drivers such as the Indian Ocean Dipole (IOD) and Monsoon Intra- Seasonal Oscillations (MISO). Indeed, the precipitation anomaly shown in Figure 2b (after removing the monthly climatology) reveals substantial anomalies even during non- cyclone periods, indicating interannual variability in monsoonal rainfall. + +<|ref|>text<|/ref|><|det|>[[115, 330, 870, 364]]<|/det|> +To address the reviewer's concerns, we have expanded the analysis in the revised manuscript as follows: + +<|ref|>text<|/ref|><|det|>[[144, 379, 876, 430]]<|/det|> +1. Separation of Precipitation Sources: We distinguished precipitation contributions from tropical cyclones and other extreme precipitation events using IMERG observations, as shown in the updated Figure 2c. + +<|ref|>text<|/ref|><|det|>[[144, 445, 878, 515]]<|/det|> +2. Additional Model Experiments: We performed three additional model experiments designed to quantify the separate and combined impacts of tropical cyclones and extreme precipitation events (notably in 2020 and 2022) on salinity freshening during the 2019–2023 period (new Figure 9). + +<|ref|>text<|/ref|><|det|>[[115, 530, 880, 618]]<|/det|> +These results indicate that the majority of the observed salinity freshening during 2019–2023 can be attributed to the combined effects of tropical cyclones and the extreme precipitation events in 2020 and 2022. The contribution from broader monsoonal rainfall variability or other interannual climate modes appears minimal in comparison, further emphasizing the dominant role of these extreme events in driving the observed salinity freshening. + +<|ref|>text<|/ref|><|det|>[[115, 633, 879, 826]]<|/det|> +While the above approach differs slightly from the reviewer's suggestion, it effectively addresses the underlying concern. To further clarify, the differences in precipitation due to tropical cyclones during 2019–2023 can be derived from IMERG observations (Figure R1a). By subtracting the long- term mean (2001–2023) from the 2019–2023 mean, we obtain the precipitation anomaly for this period (Figure R1b). By excluding the contributions from tropical cyclones (Figure R1c) and the combined cyclones and extreme precipitation events of 2020 and 2022 (Figure R1d) from the 2919–2023 mean, further illustrate the influence of monsoon rainfall, which is small. The methodology used to separate precipitation from cyclones and extreme events is included in Methods. Since this analysis has already been incorporated into the revised manuscript (Figure 2c), we have opted to include this additional breakdown in Supplementary Figures 1 and 2. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[128, 87, 870, 543]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 553, 877, 711]]<|/det|> +
Figure R1. Precipitation differences (mm \(\mathrm{d}^{-1}\) ) highlighting the contributions of tropical cyclones and extreme precipitation events during 2019–2023: (a) Precipitation anomalies directly associated with tropical cyclones during 2019–2023. (b) Difference between the 2019–2023 mean precipitation and the long-term average (LTA, 2001–2023). (c) Difference between the 2019–2023 mean precipitation excluding tropical cyclones and the LTA, isolating non-cyclone contributions. (d) Difference between the 2019–2023 mean precipitation excluding both tropical cyclones and extreme precipitation events of 2020 and 2022 and the LTA, highlighting background precipitation patterns (see Methods for separation of precipitation contributions from tropical cyclones and extreme events).
+ +<|ref|>text<|/ref|><|det|>[[115, 742, 835, 779]]<|/det|> +• Are there any flaws in the data analysis, interpretation and conclusions? Do these prohibit publication or require revision? + +<|ref|>text<|/ref|><|det|>[[115, 795, 849, 865]]<|/det|> +The data analysis approach is sound in general, however, author may clarify below aspects. The author show differences in mean potential energy anomaly during 2024- 2018 and 2019- 2023. Is this difference in mean statistically significant? Can this be verified with a statistical significance test? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 866, 160]]<|/det|> +Thank you for the insightful suggestion. In response, we have conducted statistical significance testing on the differences in means and have included error bars in Figure 4 to reflect the associated uncertainty. The results indicate that the differences in means are statistically significant at the \(95\%\) confidence interval \((p = 0.05)\) . + +<|ref|>text<|/ref|><|det|>[[115, 176, 797, 195]]<|/det|> +- Is the methodology sound? Does the work meet the expected standards in your field? + +<|ref|>text<|/ref|><|det|>[[115, 212, 835, 247]]<|/det|> +Authors use best possible datasets and model simulations to prove their arguments. And it meets the standards. The minor issues are pointed out under other relevant headings. + +<|ref|>text<|/ref|><|det|>[[115, 263, 741, 281]]<|/det|> +- Is there enough detail provided in the methods for the work to be reproduced? + +<|ref|>text<|/ref|><|det|>[[115, 299, 872, 334]]<|/det|> +Author use two quantities in the manuscript potential energy anomaly and ASHSW volume. Are there references for these quantities? Please specify. + +<|ref|>text<|/ref|><|det|>[[115, 365, 877, 435]]<|/det|> +Thank you for the suggestion. The reference for potential energy anomaly has cited in the main text (23), as well as in Methods section, alongside the additional reference (43). Furthermore, the use of ASHSW volume in the Arabian Sea, as previously used by (8), has also been incorporated into the Methods section. + +<|ref|>text<|/ref|><|det|>[[115, 450, 872, 504]]<|/det|> +The datasets used in the study is available from public domain, however author may be asked to make the model simulations available if the results need to be reproduced using model simulations as shown in the manuscript + +<|ref|>text<|/ref|><|det|>[[115, 534, 802, 553]]<|/det|> +Yes, the model simulation experiments will be made available to interested researchers. + +<|ref|>text<|/ref|><|det|>[[115, 586, 256, 602]]<|/det|> +Minor comments: + +<|ref|>text<|/ref|><|det|>[[115, 620, 880, 691]]<|/det|> +1) On page 4 towards the end (it may differ as I checked word document) Although no cyclones occurred in 2022, the extremely high rainfall during July – August, which caused severe flooding and displaced over 30 million people in Pakistan, helped maintain one of the largest salinity anomalies during 2019 – 23 ever recorded (Figure 3). + +<|ref|>text<|/ref|><|det|>[[115, 707, 856, 743]]<|/det|> +Here a reference may be added, if author wanted to state it is largest salinity anomalies “ever” recorded. Else they may modify saying largest salinity anomalies during the study period. + +<|ref|>text<|/ref|><|det|>[[115, 775, 860, 845]]<|/det|> +Thank you for pointing this out. We have revised the sentence to: “Although no cyclones occurred in 2022, the extremely high rainfall during July–August, causing severe flooding and displacing over 30 million people in Pakistan \(^{17}\) , contributed to sustaining salinity freshening through 2023”. + +<|ref|>text<|/ref|><|det|>[[111, 876, 872, 896]]<|/det|> +2) On page 7 line two, author says “We estimated Potential Energy Anomaly” which may be re + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 852, 125]]<|/det|> +written as I estimated as it is a single author paper or the contributor may be acknowledged if there is one. + +<|ref|>text<|/ref|><|det|>[[114, 140, 652, 158]]<|/det|> +As suggested by the reviewer, the sentence is re- written. Thank you. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[115, 90, 220, 108]]<|/det|> +## Reviewer #2 + +<|ref|>sub_title<|/ref|><|det|>[[115, 121, 206, 139]]<|/det|> +## Summary: + +<|ref|>text<|/ref|><|det|>[[114, 150, 881, 377]]<|/det|> +In this MS, the author first analyzes the impact of Tropical Cyclones (TCs)- induced precipitation on upper ocean salinity in the North Arabian Sea (AS) over 2014- 2023 using satellite rain and in situ Argo profile data. The author reports an increased number of TC in 2019- 2023, concomitant with an increase in total precipitation and an overall decrease of upper ocean salinity in the East AS with respect to the 2014- 2018 period, with a maximum freshening observed in the North East AS region. He then analyzes the temporal evolution of the vertical salinity structure using in situ profile data, revealing sustained freshening in the Northern Arabian Sea where the Arabian Sea High Salinity Waters (ASHsW) form. The upper ocean freshening reduces the potential surface density, augmenting the vertical stratification and in fine, disrupt the convective sinking process of ASHSW. Finally, using model perturbation experiment and model- based salinity budget estimates, the author attempts to isolate the impact of TC- induced rain on salinity freshening and conclude that the recent SSS freshening is caused by the increased number of TCs from 2019 onward. + +<|ref|>text<|/ref|><|det|>[[115, 388, 881, 494]]<|/det|> +We sincerely thank the reviewer for their thoughtful comments and constructive suggestions, which have greatly enhanced the quality of the manuscript and strengthened the scientific arguments presented. We have carefully addressed the majority of the reviewer's comments and made the necessary modifications to the manuscript. Below, we provide a detailed point- by- point response (reviewer comments in black and our responses highlighted in blue). We hope that these revisions adequately address the reviewer's concerns. + +<|ref|>text<|/ref|><|det|>[[115, 506, 870, 545]]<|/det|> +While the revised manuscript with track changes is included, the major revisions addressing the reviewers' concerns are outline below under subsections: + +<|ref|>text<|/ref|><|det|>[[144, 560, 866, 679]]<|/det|> +Prolonged Salinity Freshening: Observations: Detailed revisions can be found in paragraphs 2- 5, where we have separated precipitation contributions from cyclones and other extreme events. Isolating Precipitation Sources Driving ASHSW Freshening: Results from model experiments incorporating those precipitation sources contributing to the freshening of ASHSW are provided in paragraphs 1- 4. + +<|ref|>sub_title<|/ref|><|det|>[[115, 723, 456, 742]]<|/det|> +## Major Comments and recommendations + +<|ref|>text<|/ref|><|det|>[[115, 753, 865, 860]]<|/det|> +The topic is of strong scientific interest, in particular for the tropical cyclone forecast, salinity remote sensing, and, ocean modeler communities. While the SST, CHLA, and SSH response to TC passage have been extensively studied, TC- induced SSS changes and their large- scale impacts on other climate processes are much less known: this work definitively participate to these community efforts. In general, the MS reads well, is interesting and the results are in general plausible. However, I have several major concerns. + +<|ref|>text<|/ref|><|det|>[[115, 871, 850, 907]]<|/det|> +First, in the part of the MS devoted to observations analyses, the author had not at all isolated the TC- induced precipitation and associated SSS changes from other sources of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 88, 880, 562]]<|/det|> +atmospheric and oceanic variability, which weaken strongly the strength of his statements, which are often more 'suggestions' than a clear demonstration of causality between the three reported interannual anomalies seen in the observation: 1) 'increased number of TC', 2) 'increased total Precipitation', and 3) 'decreased overall upper ocean Salinity'. For me, the author has not demonstrated convincing evidences from his analyses that the reported large- scale upper ocean salinity and precipitation anomalies (shown in Figure 1 & Figure 2 in the MS), as well as their consequences on the stability of the water column (Figure 4) is dominantly due to the passage of some rare but intense tropical cyclones rainfall and associated SSS freshening. I will show below in the detailed comments section of my review several examples in 2019 where there was little precipitation accumulated during the passage of some strong TCs in this region as well as small associated SSS changes in their wake, as reported from satellite observations. The interannual SSS & P changes observed by the author could therefore be due to other processes (see details in Behara et al, 2019) such as the increased precipitation during the recent Monsoon, or e.g., due to increased runoff from the river waters out of the Gulf of Khambhat estuaries, or from elsewhere in the coasts (e.g Pakistan floods in 2022 as mentioned by the author at the end of his MS), or even more likely by large scale climate variability impact on rain and SSS (e.g., Indian Ocean Dipole, Monsoon IntraSeasonal Oscillation (MISO),...) and not necessarily because of changes in Tropical Cyclone activity per se in between 2019- 2023 and 2014- 2018. For example, Li et al (2022) found that the variance of MISO has an increasing trend from 1982 to 2017 over the northeastern Arabian Sea (AS), accompanied by increasing intraseasonal rainfall. How does this impact the precipitation excess shown in Figure 1c? The enhancement in rainfall in this case is mainly nourished by the increasing moisture supply, with a major contribution from the upward moisture advection by the intraseasonal vertical wind velocity. Since the author did not isolate the precipitation signal from TC- only with respect to total rain, and also did not isolate the salinity response to TC passage, most of his statements remain poorly evidenced, while this can be now easily estimated from the observation dataset already gathered by the author: + +<|ref|>text<|/ref|><|det|>[[173, 572, 861, 625]]<|/det|> +1) From IMERG and Ibtracs datasets, the author could estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds or within a radius of 500 km) around the TC center tracks. + +<|ref|>text<|/ref|><|det|>[[173, 636, 876, 706]]<|/det|> +2) Then further estimate the time series of the cumulated contribution of tropical cyclone only induced rainfall to the total precipitation over the 3 AS subregions selected by the author. Then he could compare the relative contribution of TCs separately for both period 2014-2018 and 2019-2023. + +<|ref|>text<|/ref|><|det|>[[114, 719, 877, 860]]<|/det|> +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach has been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser (2010), Jiang et al (2011). For example, a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non- tropical cyclone (TC) days and on TC days based on IMERG data (2000- 2020). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 878, 230]]<|/det|> +Thank you very much for your constructive comments and suggestions, which have greatly improved the quality of the manuscript. We particularly appreciate the extensive and detailed overview of related studies and the insightful recommendations that have strengthened the scientific arguments presented in the paper. We are especially grateful for the time and effort you dedicated to providing relevant data analyses and examples that further support this study. While the review was thorough and comprehensive, which we highly value, our responses focus primarily on addressing the key concerns raised and clarifying how they have been incorporated into the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[114, 241, 876, 347]]<|/det|> +To address the reviewers' primary concern regarding the separation of cyclone- induced precipitation from the total precipitation, we have followed the reviewer's recommendations and the methodology described by Camberlin et al. (2024). Specifically, we separated cyclone- induced precipitation from the total precipitation, and the cumulative precipitation anomalies excluding cyclone- induced rainfall during the 2019- 2023 period are now presented in Figure 2c (previous Figure 3c). + +<|ref|>text<|/ref|><|det|>[[114, 358, 880, 464]]<|/det|> +Furthermore, we extended this analysis to distinguish extreme precipitation events, which significantly contributed to the salinity freshening observed in 2022. Using the 95th percentile threshold, we identified and isolated extreme precipitation events. Our analysis revealed that both 2022 and 2020 experienced extreme precipitation events, although the 2020 event coincided with two tropical cyclones. The combined cumulative precipitation anomalies, excluding both cyclone- induced rainfall and extreme precipitation events, are also depicted in Figure 2c. + +<|ref|>text<|/ref|><|det|>[[114, 475, 870, 563]]<|/det|> +We also acknowledge that the increasing trend in extreme precipitation events over the Arabian Sea may be linked to large- scale climate variability, including the IOD and MISO. Notably, MISO- related rainfall has substantially intensified over the northeastern Arabian Sea in the past three decades, driven by enhanced Arabian Sea warming (Li et al. 2022). This aspect has been incorporated in the "Discussion section". + +<|ref|>text<|/ref|><|det|>[[114, 575, 875, 664]]<|/det|> +We have repositioned Figure 3 and the associated discussion earlier in the manuscript, following Figure 1. This restructuring enables for a clearer definition of precipitation anomaly sources and provides a more logical framework for explaining ASHSW freshening in subsequent sections, focusing on the role of precipitation events. The previous Figure 3 has now been numbered as Figure 2. + +<|ref|>text<|/ref|><|det|>[[114, 675, 879, 780]]<|/det|> +Although dividing the precipitation analysis into three subregions of the Arabian Sea seems logical, it may not effectively explain ASHSW freshening, as ASHSW changes are not purely local but also influenced by its subsequent spreading. Therefore, we focus on the eastern Arabian Sea as a whole for the observational analysis. However, in the modeling experiments, we separately analyze the northern Arabian Sea, where ASHSW forms, and the eastern Arabian Sea, where the most significant freshening has occurred. + +<|ref|>text<|/ref|><|det|>[[114, 792, 874, 899]]<|/det|> +Lastly, the reviewer correctly highlights that local changes in sea surface salinity (SSS) during cyclones can be assessed by comparing pre- and post- storm SSS, as shown in the reviewer's Figure 2. However, while this approach effectively captures the immediate salinity response to a cyclone, it does not reflect the delayed and cumulative effects on ASHSW formation and spreading. ASHSW formation is primarily driven by excess evaporation over precipitation, and the recent increase in freshwater input from tropical cyclones and extreme precipitation events + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 89, 868, 195]]<|/det|> +has altered this balance, leading to stronger stratification in the northern Arabian Sea. Since this region typically experiences net evaporative cooling throughout the year, the northward shift of tropical cyclones and increased extreme precipitation have contributed additional freshwater, further preconditioning the area for sustained ASHSW freshening. Our study focuses on this evolving freshwater imbalance and its influence on ASHSW formation, which cannot be fully captured by short- term SSS comparisons alone. + +<|ref|>text<|/ref|><|det|>[[114, 236, 878, 429]]<|/det|> +Similarly, to best isolate the TC- induced surface freshening from other sources of SSS variability (e.g., Moonsoon rain, horizontal advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi- mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021). The author could then evaluate the cumulated TC- induced SSS changes in each season over 2014- 2023 and see how much it contributed to the overall SSS decrease observed in that region since 2019. + +<|ref|>text<|/ref|><|det|>[[115, 470, 877, 541]]<|/det|> +Thank you again for this excellent point and the detailed explanation. While our approach differs from the method proposed by the reviewer, we have addressed the concern using model experiments. Below, we explain how we addressed the issue and clarify why the reviewer's suggested method may not be fully suitable for this study. + +<|ref|>text<|/ref|><|det|>[[114, 553, 875, 693]]<|/det|> +To isolate the impact of precipitation from tropical cyclones and extreme precipitation events (2020 and 2022) on salinity freshening during the 2019- 2023 period, we conducted three additional model experiments by selectively excluding: (1) cyclone- induced precipitation, (2) extreme precipitation events in 2020 and 2022, and (3) the combined effects of both. We then compared these experiments against a control simulation that included all precipitation forcings. These experiments confirmed that the combined influence of cyclone- induced precipitation and the two extreme precipitation events accounted for a significant portion of the salinity freshening observed during the 2019- 2023 period. + +<|ref|>text<|/ref|><|det|>[[115, 705, 865, 775]]<|/det|> +We agree that satellite- derived sea surface salinity (SSS) can be useful for estimating localized, short- term salinity changes induced by tropical cyclones, as demonstrated in several studies, including the example provided by the reviewer. However, satellite SSS is less suitable for the objectives of this study due to the following reasons: + +<|ref|>text<|/ref|><|det|>[[114, 789, 875, 895]]<|/det|> +- Our focus is on the long-term impact of precipitation on the formation and seasonal spreading of the Arabian Sea High Salinity Water (ASHSW), which occupies the upper 100 m of the water column.- While SSS changes during a cyclone can be inferred by comparing pre- and post-storm SSS (as illustrated in the reviewer's Figure 2), it does not capture the delayed and prolonged effects on ASHSW formation and spreading. For instance, freshwater input from the extreme + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 88, 883, 220]]<|/det|> +precipitation event in June 2019 could weaken the formation of ASHSW the following winter (November 2019- February 2020), with its influence observed later in the summer monsoon season (August- October 2020) as the ASHSW spreads southward.- The vertical salinity sections provided in the manuscript (at three locations) reveal the vertical structure and extent of ASHSW, which cannot be inferred from satellite SSS alone. For this reason, the satellite SSS provides limited additional insight compared to the Argo profile observations already presented in Figure 3. + +<|ref|>text<|/ref|><|det|>[[115, 226, 881, 296]]<|/det|> +On the other hand, the model experiments presented in the manuscript were specifically designed to quantify the impact of precipitation on ASHSW formation and subsequent spreading. These controlled simulations allow us to isolate processes that cannot be fully captured using observations alone. + +<|ref|>text<|/ref|><|det|>[[114, 337, 879, 549]]<|/det|> +Second, in the second part of the MS devoted to model analyses, here again the author has not directly isolated the impact of interannual variability of the TC- induced precipitation and associated SSS changes from other sources of interannual atmospheric and oceanic variability. While I agree with the author that by inverting atmospheric forcing of years 2018 and 2019 the model can reproduce the SSS freshening observation: it does only show that the interannual variability in P predominantly modulate the SSS signal: the author however did not show directly that the TC- induced rain only is responsible for that interannual signal: some other sources of precipitation variability over 2018- 2019 could be responsible for it. Once the TC- induced rain will be isolated from the total precipitation time series as I suggested previously, the author could then easily re- run his model perturbation experiments by only removing TC days in the atmospheric forcing time series: this would directly show what the author want to prove rather than by using lengthy and sometimes confusing indirect approaches. + +<|ref|>text<|/ref|><|det|>[[114, 589, 868, 695]]<|/det|> +Thank you again for the insightful suggestions. The additional model experiments, with and without cyclone- induced precipitation, presented in Figures 9d and 9e, effectively illustrate the impact of tropical cyclones on salinity freshening. Specifically, in the northern Arabian Sea, the control experiment shows a fresher salinity by approximately 0.2 psu during November - December 2019 (Figure 9e) compared to the experiment where cyclone- induced precipitation was excluded for the same period. + +<|ref|>text<|/ref|><|det|>[[115, 706, 857, 742]]<|/det|> +The primary objective of this case study, focusing on the 2018- 2019 period, is to demonstrate two key processes: + +<|ref|>text<|/ref|><|det|>[[144, 753, 880, 857]]<|/det|> +1. How precipitation from post-monsoon tropical cyclones during the September-December period influences the formation of ASHSW north of \(\sim 15^{\circ}\mathrm{N}\) (the ASHSW formation region). +2. The subsequent southward spreading of ASHSW along the eastern Arabian Sea during the following late summer (September-October 2020). + +<|ref|>text<|/ref|><|det|>[[115, 867, 872, 903]]<|/det|> +The current model setup allows us to compare the resulting salinity patterns to those from the reference control run. While the observed salinity differences in these experiments are attributed + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 872, 213]]<|/det|> +to variations in precipitation during the 2018–2019 period, as the reviewer correctly pointed out, we acknowledge that precipitation during September–December in the northern Arabian Sea is generally minimal in a typical period. Thus, the precipitation pattern observed during September–December 2018 can be considered representative of typical conditions. In contrast, the precipitation from five tropical cyclones during September–October 2019 significantly contributed to the weakening of ASHSW formation and its subsequent spreading along the eastern Arabian Sea. + +<|ref|>text<|/ref|><|det|>[[114, 255, 875, 308]]<|/det|> +In addition, many time in the MS, the author used very strong statements (particularly on the impacts of TC- precipitation on SSS anomalies) without full proof of them: please rephrase those sentences to only state what is shown by your results. + +<|ref|>text<|/ref|><|det|>[[114, 320, 880, 408]]<|/det|> +In the revised manuscript, we have made efforts to avoid strong statements of certainty. While the initial part of the discussion primarily focuses on observations, the interpretation of these results remains largely qualitative. As the processes governing ASHSW anomalies become clearer in the latter sections, particularly with the additional analysis of model results quantifying these processes, the language has been adjusted to reflect this progression more accurately. + +<|ref|>text<|/ref|><|det|>[[114, 448, 879, 537]]<|/det|> +Therefore, despite most of the results shown by the author are plausible, I recommend that the MS undergo major revision before being considered for publication so that the author actually and properly separate the TC impacts from other sources of variability in both the Precipitation and SSS signals and in the observation and model analyses, separately: this shall in fine directly demonstrate the authors indirect statements. + +<|ref|>text<|/ref|><|det|>[[115, 550, 305, 566]]<|/det|> +Details are given below. + +<|ref|>sub_title<|/ref|><|det|>[[115, 579, 287, 596]]<|/det|> +## Detailed Comments: + +<|ref|>text<|/ref|><|det|>[[115, 608, 881, 696]]<|/det|> +L38 “evaporation- precipitation”- What about river runoff and their impacts on the northeast Arabian Sea (AS) upper salinity, in particular from the Indus and the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Khambhat estuaries? As shown in Rao et al (2009) and reproduced here below (panel d), rivers have non negligible impacts on the SSS in the North eastern AS, particularly in winter months. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 444, 866, 478]]<|/det|> +Figure1: Monthly climatological salinity for (a) July, (b) October, (c) December and (d) ARGO observations averaged for 17- 20N during 2004. From Rao et al (2009) + +<|ref|>text<|/ref|><|det|>[[115, 517, 884, 691]]<|/det|> +Thank you for highlighting this relevant study. We agree with its findings. However, the river runoff in the northeastern Arabian Sea has a negligible impact on the formation and seasonal spreading of ASHSW, as the low- salinity water associated with river discharge remains largely confined to shallow regions along the west coast of India. While it is plausible that an increased frequency of cyclones and extreme precipitation events could lead to enhanced river runoff and contribute to surface salinity freshening in these coastal regions, the model experiments presented in our study explicitly exclude such contributions, further supporting the critical role of precipitation forcing. Although the influence of river runoff is an important topic worth further investigation, it falls beyond the scope of the present study. A brief description of river runoff treatment in the model has been added to the Methods section for clarity. + +<|ref|>text<|/ref|><|det|>[[115, 720, 882, 896]]<|/det|> +L107- 108: this sentence is a very strong statement that definitively need more support than what is shown and discussed around Fig1 at this stage in the MS. Please re- phrase to be more accurate and keep to the point of what your data really show. It is not because Fig1 panels reveal a concomitant increase in 1) the number of TCs in the North- eastern part of the AS, 2) as well as in overall Precipitation in the eastern AS and 3) a decrease in SSS in the NE AS that this is clearly an evident proof that "the cyclone- induced precipitation have impact on the convective formation of the Arabian Sea High Salinity Waters ". This is a very strong shortcoming. As I will show further, TC in the Arabian sea are not systematically associated with heavy rain and SSS drops are not systematically observed in their trail. Deeper observation analyses are required to conclude. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 883, 160]]<|/det|> +Indeed, the increase of precipitation shown in Fig1c could be due to other atmospheric sources of interannual variability (e.g., Indian Ocean Dipole, Moonsoon) than merely the change in Tropical Cyclone activity in between 2019- 2023 and 2014- 2018. What about a potentially increase in monsoon season accumulated rain in the most recent years ? + +<|ref|>text<|/ref|><|det|>[[115, 172, 877, 277]]<|/det|> +Similarly, the SSS deacrease in the AS, while I agree is most intense where most new TCs tracks where located in 2019- 2023 is also a region of significant runoff from the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Cambay estuaries. Could the reported interannual variability in SSS in this region be also related to increased river runoff in 2019- 2023 ? and if yes, how much does it contribute to the observed SSS decrease with respect to the impact of local rain increases ? + +<|ref|>text<|/ref|><|det|>[[115, 289, 826, 308]]<|/det|> +To resolve these uncertainties, I suggest the author shall re- analyse the datasets as follows: + +<|ref|>text<|/ref|><|det|>[[172, 319, 884, 372]]<|/det|> +3) From IMERG and Ibtracs datasets, estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds) around the TC center track. + +<|ref|>text<|/ref|><|det|>[[173, 384, 881, 436]]<|/det|> +4) Then further estimate the average cumulated spatial contribution of all tropical cyclone rainfall to total precipitation over the AS region, separately for both period 2014-2018 and 2019-2023. + +<|ref|>text<|/ref|><|det|>[[114, 448, 878, 605]]<|/det|> +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach have been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser(2010), Jiang et al (2011). For example a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non-tropical cyclone (TC) days and TC days based on IMERG data (2000-2020). Such an approach could be easily applied by the author. + +<|ref|>text<|/ref|><|det|>[[172, 617, 880, 774]]<|/det|> +5) Similarly, to best isolate the TC-induced surface freshening from other sources of SSS variability (Moonsoon rain, advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi-mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021) + +<|ref|>text<|/ref|><|det|>[[114, 786, 874, 892]]<|/det|> +In fact, databases including TC- induced Precipitation & SSS changes for each individual TC globally over 2010- 2020 were already developed in the frame of the ESA Marine Atmosphere eXtreme Satellite Synergy (MAXSS) project (see https://www.maxss.org/) and could be used by the author to better demonstrate his statements. This dataset is publicly available (doi:10.12770/cc0577e4-55d6-4aa9-a938-b4965be121ab, Reul et al., 2023), and provides, for each storm tracks from IBTracs during the period 2010- 2020, three types of storm- related + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 90, 881, 440]]<|/det|> +parameters: (1) the pre- storm upper ocean conditions (e.g., SST, SSS, upper ocean vertical density stratification strength, etc..), (2) the atmospheric forcing during the storm passage (maximum wind, accumulated rain and evaporation, wind power index, etc..) during the storm, as well as (3) the oceanic wakes left after the storm for an ensemble of key variables (SST, SSS, sea level height, ocean color parameters). I show here below few examples of estimated SSS anomalies (derived from the ESA CCI SSS products) left after TC passages in the AS as well as the corresponding accumulated precipitation (derived from merged satellite TRMM products) during their lifetime over the AS in 2019 and which is available in the MAXSS database. As evidenced from satellite data, TC passage in the AS in 2019 are not systematically associated with strong local SSS decreases and heavy precipitation: see e.g. examples of the extremely severe cyclonic storm MAHA in 2019 with small amount of accumulated precipitation associated with negligible SSS changes in the North Eastern AS, or the other case of the super cyclonic storm KYARR with locally very high accumulated rain at \(20^{\circ}\mathrm{N}\) but no significant associated SSS changes observed from satellites. Significant SSS drops were nevertheless observed after the passage of the very severe cyclonic storm VAYU in a region with significant accumulated rain. Therefore, given the high variability of the SSS response to TC passages in this region, and although Sun et al., (2021) have shown (see their Figure 16 top pannel) that on average TC do induce SSS drops in the AS, it remains unclear what the overall contributions of the TC- induced rain and associated freshening are on the 2014-2018 versus 2019-2023 interannual variability reported in Fig 1.c and Fig.1d. + +<|ref|>image<|/ref|><|det|>[[115, 448, 883, 872]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[115, 88, 881, 496]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[114, 524, 842, 578]]<|/det|> +
Figure 2: Examples of SSS anomalies left after TC passages in the Arabian Sea in 2019 (left panels) and corresponding accumulated rain (right panels). Data and plots are available at https://www.maxss.org/.
+ +<|ref|>text<|/ref|><|det|>[[114, 618, 879, 760]]<|/det|> +Thank you for your time and effort in providing such extensive comments and a detailed explanation of methods along with several relevant references. The reviewer has raised a number of important points and provided valuable suggestions for strengthening the manuscript. Since many of these comments align closely with previous feedback, albeit in a more detailed manner, we would like to focus our responses on the primary concerns most relevant to the core scope of our study: demonstrating that precipitation from tropical cyclones and extreme precipitation events has been a significant driver of salinity freshening in the eastern Arabian Sea during the 2019- 2023 period. + +<|ref|>text<|/ref|><|det|>[[114, 776, 875, 901]]<|/det|> +We greatly appreciate the reviewer's independent analyses as part of this review and agree with the conclusions drawn from those efforts. However, as noted in previous responses, certain limitations exist regarding the types of data and approaches that can be applied within the scope of this study. For example, while the above mentioned analysis tool is useful for estimating local changes in sea surface salinity (SSS) or SST in the wake of TCs compared to pre- storm conditions, it does not directly capture the impact of precipitation on ASHSW formation and its subsequent spreading. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 107, 866, 196]]<|/det|> +To address the reviewer's primary concern regarding the separation of cyclone- induced precipitation from total precipitation, we have now followed the reviewer's recommendations and the methodology described by Camberlin et al. (2024). Specifically, we separated cyclone- induced precipitation from total precipitation, and the cumulative precipitation anomalies excluding cyclone- related rainfall during the 2019–2023 period are now presented in Figure 2c. + +<|ref|>text<|/ref|><|det|>[[115, 211, 879, 335]]<|/det|> +Additionally, we extended this analysis to better differentiate extreme precipitation events, which significantly contributed to the observed salinity freshening, particularly in 2022. By applying a 95th percentile threshold, we identified and isolated extreme precipitation events. Our analysis revealed that both 2022 and 2020 experienced extreme precipitation events, although the 2020 events coincided with two tropical cyclones. The combined cumulative precipitation anomalies, excluding both cyclone- induced rainfall and extreme precipitation events, are now depicted in Figure 2c for clarity. + +<|ref|>text<|/ref|><|det|>[[115, 350, 870, 492]]<|/det|> +To further quantify the individual and combined impacts of precipitation from tropical cyclones and extreme precipitation events (2020 and 2022) on ASHSW freshening during the 2019–2023 period, we conducted three additional model experiments where we selectively excluded: (1) cyclone- induced precipitation, (2) extreme precipitation events in 2020 and 2022, and (3) the combined effects of both. These were compared against a control simulation that included all precipitation forcings. The results confirmed that the combined influence of cyclone- induced precipitation and extreme precipitation events accounted for a substantial portion of the salinity freshening observed during the study period. + +<|ref|>text<|/ref|><|det|>[[115, 533, 866, 586]]<|/det|> +Line 111- 113: I agree that the addition of freshwater reduces surface density but it has not been demonstrated at this stage of the MS that it disrupts the sinking process and weaken the formation of the ASHSW. Please re- phrase to only state what is shown by your results. + +<|ref|>text<|/ref|><|det|>[[115, 598, 765, 617]]<|/det|> +As suggested by the reviewer, this statement has been moved up in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 628, 880, 787]]<|/det|> +Figure 2: the symbols representing the occurrences of TC are not visible enough on the figures. I would add panels illustrating the temporal evolution of the total accumulated rain and of the TC- induced rain in the three regions. In the legend, you precise that “2 extremely severe cyclones in late October to Early November triggered the largest freshening in the AS”. Please clarify and provide the references for the name (identifier) of these 2 storms and show the SSS freshening associated to them or do not mention something you did not demonstrated. According to Fig2a in the MS, the freshening after September- December 2020, or 2021, seems the two largest freshenings over the period. Satellite SSS data for the example of TC MAHA shown above and which occurred in early November 2019 do not reveal large surface freshening! + +<|ref|>text<|/ref|><|det|>[[115, 802, 868, 856]]<|/det|> +Thank you for pointing this out. While the cyclone symbols in Figure 3c are less visible against the blue background, the same symbols used in the other two panels can be referenced for consistency. + +<|ref|>text<|/ref|><|det|>[[115, 872, 874, 908]]<|/det|> +The salinity observations presented in Figure 3 aim to demonstrate the overall freshening observed across the northern, central, and southern Arabian Sea. To further clarify the drivers of + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 875, 178]]<|/det|> +this freshening, the separate contributions of cumulative precipitation anomalies, as shown in Figure 2c, provide additional insights into the sources of salinity changes resulting from 2019 tropical cyclones. Additionally, new Figure 9 quantify the impact of cyclone- induced precipitation on ASHSW freshening in 2019. Please note that we have repositioned Figure 3 and the associated discussion earlier in the manuscript, following Figure 1. + +<|ref|>text<|/ref|><|det|>[[115, 195, 860, 265]]<|/det|> +We did not intend to suggest that the salinity freshening observed was the largest on record. Rather, our intention was to emphasize that the tropical cyclones in 2019 initiated a salinity freshening event, which persisted through 2023. We have modified the sentence in the revised manuscript for greater clarity. + +<|ref|>text<|/ref|><|det|>[[114, 294, 880, 435]]<|/det|> +Figure 3: it is not fully clear how SSS and P anomalies were evaluated. In the method section it is said (Line 476 and 498- 499) that 'salinity and P anomalies are calculated from 2000- 2023 period'. Do you mean that you evaluated the mean seasonal cycle over 2000- 2023 and then removed it to the S and P times series or did you remove the overall local mean evaluated over the complete 2000- 2023 period independently of the season? Please precise, it is very important to understand if the mean seasonal cycle was removed or not. Please also provide y- axis labels in Fig 3a (SSSA) and b (Precipitation anomaly). Correct the typo for "IMERGE", it shall reads" IMERG." + +<|ref|>text<|/ref|><|det|>[[115, 447, 865, 551]]<|/det|> +Thank you very much for the feedback. As per the reviewer's comments, we have clarified the methodology used to calculate the salinity and precipitation anomalies in the revised text. Specifically, we computed a monthly mean climatology (January to December) over the period 2000- 2023 and subtracted it from the salinity (average over upper \(0 - 50\mathrm{m}\) , not SSS) and precipitation time series. This approach effectively removes the long- term monthly cycle associated with monsoon precipitation. This has been clarified in the revised manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 568, 875, 620]]<|/det|> +Since Figures 2a and 2b are time- latitude plots, labelling the y- axis with the variable name could introduce confusion. Therefore, we have chosen to omit them for clarity. As suggested, we have also corrected the typo 'IMERGE' to 'IMERG' Thank you for pointing this error. + +<|ref|>text<|/ref|><|det|>[[115, 662, 870, 715]]<|/det|> +Figure 3c: I would suggest to add the TC- induced rain accumulated precipitation time series as well, this would avoid lack of clarity on the relative contributions of TC versus other sources of atmospheric rain on the observed anomalies. + +<|ref|>text<|/ref|><|det|>[[115, 728, 881, 815]]<|/det|> +This is an excellent suggestion by the reviewer. By separating the rainfall contributions from tropical cyclones (TCs) and other extreme precipitation events, particularly those in 2020 and 2022, we were able to quantify their relative contributions to the total rainfall more effectively. This analysis provided additional clarity on the individual impacts of TCs versus other sources of rainfall on salinity variability. + +<|ref|>text<|/ref|><|det|>[[115, 833, 872, 885]]<|/det|> +Furthermore, the additional model experiments presented in the revised Figure 9 now isolate the rainfall from each source (TCs and extreme precipitation events) and clearly delineate their respective impacts on ASHSW freshening. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 877, 195]]<|/det|> +As suggested by the reviewer, the relative contributions of rainfall from TCs and extreme events to the total rainfall have also been added in Figure 2c. It is evident from this analysis that rainfall from these events accounted for a significant portion of the excess rainfall observed during the 2019- 2023 period. The corresponding model experiments, which incorporated these rainfall sources, effectively explain the ASHSW freshening during this period, further confirming the initial results presented in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 212, 872, 281]]<|/det|> +We acknowledge that the extreme precipitation event in 2020 was not identified in the earlier version of the manuscript, as it coincided with two cyclones. By applying the \(95^{\text{th}}\) percentile method, we have systematically identified and separated their contributions from the total in the revised analysis. + +<|ref|>text<|/ref|><|det|>[[115, 311, 872, 364]]<|/det|> +L129: except in 2021, it does not appear clearly that SSS freshening systematically lag behind P anomalies when comparing Fig3a and Fig3b. For example in J- S 2022, the freshening are concomitant with high rain. Please re- formulate accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 376, 857, 429]]<|/det|> +As the reviewer points out a clear lag cannot be inferred from Figures 2a and 2b, therefore the sentence is removed. We intend to suggest that the rate of salinity freshening lags behind the precipitation during the 2019- 2023 period. + +<|ref|>text<|/ref|><|det|>[[115, 441, 866, 511]]<|/det|> +L130: here again, the author sentence "The addition of cyclone- induced freshwater increases buoyancy and strengthens stratification, which in turns weakens the depth of winter convective mixing" has not been yet demonstrated at this stage of the MS and shall be removed if not fully proofed + +<|ref|>text<|/ref|><|det|>[[115, 523, 815, 576]]<|/det|> +To address the reviewer's concern, the sentence has been revised for clarity. The updated sentence now reads: "The addition of freshwater increases buoyancy and strengthens stratification, which in turn reduces the depth of winter convective mixing." + +<|ref|>text<|/ref|><|det|>[[115, 605, 861, 658]]<|/det|> +L134: Fig S2 show the evolution of the MLD averaged over the box \(60^{\circ} - 70^{\circ}\mathrm{E}\) , \(15^{\circ} - 25^{\circ}\mathrm{N}\) and not separately for the 3 boxes shown in Fig3. It is rather confusing then to compare MLD & S evolution in different boxes. Please correct. + +<|ref|>text<|/ref|><|det|>[[115, 671, 881, 758]]<|/det|> +The discussion related to Supplementary Figure 2 has been moved to Figure 4b for improved clarity. Given the limited number of observations in the EN4 dataset, a larger box average was used to better represent the mixed layer depth (MLD) in the ASHSW formation region. Figure 4b shows the MLD from the Argo observations, while Supplementary Figure 2 with the larger box in the northern Arabian Sea broadly capturing the convective formation region of ASHSW. + +<|ref|>text<|/ref|><|det|>[[115, 788, 880, 840]]<|/det|> +L135: "While cyclone- induced precipitation weakens the convective formation of ASHSW in the north during winter,...": here again this statement have NOT been demonstrated at this stage in the MS; please remove/correct unless you show a real demonstration + +<|ref|>text<|/ref|><|det|>[[115, 853, 857, 905]]<|/det|> +To address the reviewer's concern, the sentence has been revised for clarity. The updated sentence now reads: "While precipitation weakens the convective formation of ASHSW in the northern Arabian Sea during winter, ..." + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 118, 725, 139]]<|/det|> +L148: "...salinity maximum at \(80 \mathrm{~m}\) ." Please precise that is seen in 'Figure 2f' + +<|ref|>text<|/ref|><|det|>[[115, 149, 781, 170]]<|/det|> +Clarified as suggested, the subsurface salinity maximum in Figure 3f occurs at \(75 \mathrm{~m}\) . + +<|ref|>text<|/ref|><|det|>[[115, 179, 866, 252]]<|/det|> +L148: "This vertical salinity stratification promotes vertical mixing (heavier over lighter water) and plays an important role in maintaining SST in the southeastern Arabian Sea". Ok, but why not showing the Brunt- Väisälä frequency to illustrate the respective contribution of S and T to vertical stratification in the 3 regions, following Maes, C., and O'Kane (2014): + +<|ref|>equation<|/ref|><|det|>[[115, 261, 682, 283]]<|/det|> +\[N2(T,S) = -g / \rho \partial \rho /\partial z\approx (g\alpha \partial T\partial z + g\beta \partial S\partial z) = N T2(T,S) + N S2(T,S)\] + +<|ref|>text<|/ref|><|det|>[[115, 292, 863, 347]]<|/det|> +Where \(\rho\) is density, T temperature; S salinity, \(\alpha\) is the thermal expansion coefficient, \(\beta\) is the haline contraction coefficient; g is acceleration of gravity and z is vertical. This would help the reader to understand the role of freshwater on the vertical density stratification. + +<|ref|>text<|/ref|><|det|>[[115, 356, 878, 446]]<|/det|> +Thank you again for the detailed description. Salinity stratification has been identified as a significant process regulating SST in the southeastern Arabian Sea, with implications for cyclone formation and the onset of the Indian Summer Monsoon, as documented in multiple studies, including Reference (20). In our study, we suggest that recent salinity freshening in the eastern Arabian Sea could further exacerbate SST warming. + +<|ref|>text<|/ref|><|det|>[[115, 461, 864, 533]]<|/det|> +The primary focus of this paper is to investigate how freshwater input in the northern Arabian Sea, the formation region of ASHSW, influences stratification and the convective formation of ASHSW. To address this, we have already presented stratification for the northern region using Argo observations in Figure 4c. + +<|ref|>text<|/ref|><|det|>[[115, 548, 880, 602]]<|/det|> +However, for clarification, we computed separate contributions of temperature and salinity to the stratification following the methodology suggested by the reviewer and they are shown in Figure R1 for (a) north and (b) southern regions of the Arabian Sea. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[122, 87, 900, 377]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[123, 389, 899, 560]]<|/det|> +
Figure R1. Stratification control. To quantify the relative contributions of temperature and salinity to stratification, the density ratio, \(R_{\rho}\) (Ruddick, B. 1983. A practical indicator of the stability of the water column to double diffusive activity. Deep-Sea Res., 304, 1105-1107, https://doi.org/10.1016/0198-0149(83)90063-8) is calculated from potential temperature and salinity observations in the (a) northern and (b) southern regions of the Arabian Sea (refer to Supplementary Figure 3 for location) from 2014 to 2023. The density ratio is defined as: \(R_{\rho} =\) \(- \frac{N_{\theta}^{2}}{N_{s}^{2}}\) where the total stratification \((N^{2})\) is expressed as: \(N^{2} = - \frac{g}{\rho_{0}}\frac{\partial\rho_{\theta}}{\partial z} = N_{\theta}^{2} + N_{s}^{2}\) with temperature stratification \((N_{\theta}^{2})\) and salinity stratification \((N_{s}^{2})\) is defined as: \(N_{\theta}^{2} =\)
+ +<|ref|>text<|/ref|><|det|>[[123, 558, 899, 763]]<|/det|> +\(g\alpha \frac{\partial\theta}{\partial z},N_{s}^{2} = - g\beta \frac{\partial s}{\partial z}\) Here, \(g\) is the gravitational acceleration, \(\alpha\) is the thermal expansion coefficient of seawater, and \(\beta\) is the saline contraction coefficient of seawater. For \(R_{\rho}\geq 1\) , ocean stratified by temperature, \(R_{\rho}\leq - 1\) , ocean stratified by salinity, and \(- 1< R_{\rho}< 1\) , ocean stratified by both temperature and salinity. For clarity, regions where \(R_{\rho}\leq 1\) (i.e., salinity stratification is significant or dominant) are shaded in the plots. Although the water column is predominantly stratified by temperature (white regions), salinity contribution becomes particularly important during winter in the northern Arabian Sea. This salinity influence is in the upper \(100\mathrm{m}\) due to ASHSW and below \(150\mathrm{m}\) due to the intrusion of Persian Gulf Water. In the southern Arabian Sea, salinity stratification arises from the relatively low- salinity water from the Bay of Bengal and the advection of ASHSW from the northern Arabian Sea. The closer \(R_{\rho}\) is to - 1, the stronger the opposing influence of salinity on stratification compared to temperature. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 860, 125]]<|/det|> +L168- 170: Why does the extreme precipitation during the summer monsoon of 2017 in the northeastern Arabian Sea reported in reference 7 do not appear in the anomalies of Figure 3b ? + +<|ref|>text<|/ref|><|det|>[[115, 137, 875, 225]]<|/det|> +The extreme precipitation event during 2017 was highly localized around \(67^{\circ}\mathrm{E}\) , \(22^{\circ}\mathrm{N}\) . We presume that the use of a larger area average ( \(60^{\circ} - 75^{\circ}\mathrm{E}\) ) may have weakened the amplitude of this event. However, despite its weaker signal, the event is still evident in Figure 2b as a positive precipitation anomaly north of \(20^{\circ}\mathrm{N}\) . In contrast, the extreme precipitation events identified in 2020 and 2022 show pronounced precipitation anomalies (Figures 2b and 2c). + +<|ref|>text<|/ref|><|det|>[[115, 254, 871, 325]]<|/det|> +L192 and Figure 4: \(1\%\) change in density and \(10\mathrm{m}\) shoaling of the MLD are small changes. Can you provide error bars on the Fig4 curves given the rather small number of Argo float profiles you used to estimate these time series (4 as described in the Method section) ? Would be nice to split the contributions of S & T to the PEA following the above split for N2. + +<|ref|>text<|/ref|><|det|>[[115, 336, 867, 425]]<|/det|> +As suggested by the reviewer, error bars have been included in Figure 4. The differences in the mean between the two periods are statistically significant at the \(95\%\) confidence level \((p = 0.05)\) . We also acknowledge that the mean difference in MLD is specific to the winter period (December- February) and the difference between the two periods is \(\sim 20\mathrm{m}\) (not \(10\mathrm{m}\) as previously noted). + +<|ref|>text<|/ref|><|det|>[[115, 440, 864, 494]]<|/det|> +Regarding the partitioning of PEA into relative contributions from temperature and salinity, we are not aware of a standard methodology for directly separating these effects. However, we included separate contributions of stratification from temperature and salinity in Figure R1. + +<|ref|>text<|/ref|><|det|>[[115, 535, 875, 659]]<|/det|> +L205- 206: "...coinciding with recent freshening events associated with extreme cyclones": this has not been fully proven and is a gain a fast conclusion. I agree that the stronger PEA over 20219- 2023 is coinciding with more cyclones over that period, but has discussed before, these are not necessarily and systematically associated with freshening events: so it is not a proof of causality The 2019- 23 anomalies of PEA around the mean do not systematically coincide with TC occurrences. For example, end 2020, 2021 and 2023 the last TCs of the season coincide with a locally decreasing PEA. + +<|ref|>text<|/ref|><|det|>[[115, 671, 880, 724]]<|/det|> +To address the reviewer's concern, we have modified the sentence to refer to "extreme precipitation events" instead of "cyclone- induced precipitation," reflecting the separation of these events as discussed in Figure 2c. + +<|ref|>text<|/ref|><|det|>[[115, 736, 848, 771]]<|/det|> +L209. Unclear meaning. What do you mean by "similarity"? Can you provide the correlation coefficient between both quantities? + +<|ref|>text<|/ref|><|det|>[[115, 783, 865, 835]]<|/det|> +Thank you for pointing this out. The sentence has been omitted in the revised text. Our original intent was to highlight the common trend between the weakening of stratification (indicated by larger PEA) and the depth of winter convective mixing. + +<|ref|>text<|/ref|><|det|>[[115, 848, 875, 901]]<|/det|> +L217- 219. You state "In 2018, despite the occurrence of three cyclones, none induced freshening north of \(15^{\circ}\mathrm{N}\) , where ASHSW formation takes place. However, in 2019, four out of five cyclones penetrated north of \(15^{\circ}\mathrm{N}\) , resulting in the largest salinity anomalies." It would be more + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 881, 143]]<|/det|> +correct to say that the increase number of TC in 2019 is “coincident” with the largest salinity anomalies: at this step in the MS, you have not clearly proven that the large SSS drop observed is dominantly due to TC- induced freshening’s. + +<|ref|>text<|/ref|><|det|>[[115, 154, 877, 243]]<|/det|> +With the additional analyses that separate the tropical cyclone rainfall contribution from the total rainfall, along with the supporting model experiments, we believe it is now evident that TC activity was responsible for the largest salinity anomaly observed in 2019. Would it not be appropriate to make qualitative inferences, particularly when those inferences are later validated and supported by quantitative results presented in the manuscript? + +<|ref|>text<|/ref|><|det|>[[115, 272, 872, 325]]<|/det|> +L220: by the “contrasting salinity patterns observed in the Argo data between the 2018 – 19 and 2019 – 20 periods”:, do you mean the step decrease in the average SSS after mid 2019 as observed in Fig S4, top panel? please precise. + +<|ref|>text<|/ref|><|det|>[[115, 337, 878, 389]]<|/det|> +This section has been revised for clarity as suggested. The sentence now specifically refers to the sharp decrease in salinity observed after mid- 2019, in contrast to the higher salinity levels during the 2018–2019 period. + +<|ref|>text<|/ref|><|det|>[[115, 401, 875, 472]]<|/det|> +Figure 5: would be nice to add in the time series panel the one of the TC- induced accumulated rain and of the total rain. While indicative, the symbols showing when TC occurred and their increased number is not a direct proof of their impacts on the reported decreased volume of high SSS waters. + +<|ref|>text<|/ref|><|det|>[[115, 484, 860, 589]]<|/det|> +Following the reviewer's instructions, TC- induced rainfall has been separated from the total rainfall in Figure 2c and reiterated in Figure 5e. The influence of precipitation on ASHSW volume can be both immediate and delayed, as precipitation affects ASHSW formation locally but may have a delayed impact in the following summer due to southward advection. The perturbation experiments PPE2019- 20 and PPE2018- 19 further isolate the specific role of precipitation in modulating ASHSW volume. + +<|ref|>text<|/ref|><|det|>[[115, 617, 872, 705]]<|/det|> +Line 240- 241. You stated: “The volume of high salinity water revealed a notable decline following each cyclone- induced precipitation event (Figure 5e)”. This is not true in 2021 where the first cyclone coincides with an increase in the high salinity water volume, nor for the second of the year, which was followed by a relatively stable high salinity volume (Figure 5e). Please correct accordingly. + +<|ref|>text<|/ref|><|det|>[[115, 717, 857, 840]]<|/det|> +Thank you for the suggestion. This has been corrected accordingly. The statement referred specifically to the 2019 period. While it is true that the volume of ASHSW shows a slight increase following the first storm in June 2021, it subsequently decreases during the winter of 2021–2022, with further reduction by February 2022, influenced by the second storm in September 2021. A reduction in ASHSW volume is expected during the formation period of ASHSW and not immediately following a storm in summer. The impact of rainfall in summer 2021 on the reduction in ASHSW volume becomes evident in the following winter. + +<|ref|>text<|/ref|><|det|>[[115, 870, 880, 905]]<|/det|> +Line 312- 313: “With the exception of 2022, the agreement between cyclone induced precipitation and the intensification of salinity freshening is clear.” …and of 2021”. You have not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 870, 126]]<|/det|> +provided any measure of the "cyclone- induced precipitation" with respect total precipitation, so this is a fast conclusion. Please rephrase. + +<|ref|>text<|/ref|><|det|>[[115, 136, 877, 261]]<|/det|> +By separating the rainfall contributions from tropical cyclones (TCs) and other extreme precipitation events, specifically those occurring in 2020 and 2022, we are able to quantify the relative contributions of each to the total rainfall. This analysis provided additional clarity on the roles of TCs versus other rainfall sources in the observed precipitation patterns. Furthermore, the additional model experiments presented in the newly added Figure 9, which isolate rainfall from each source (TCs and extreme precipitation events), clearly delineate their respective impacts on ASHSW freshening. + +<|ref|>text<|/ref|><|det|>[[115, 300, 875, 390]]<|/det|> +L323- 325: "Thus this experiments provide additional confirmation....are largely attributable to freshwater input from tropical cyclone". No, they provide additional confirmation that the change in Precipitation forcing occurring after 2019 is responsible for the decreasing SSS and subsequent weakening of the convective process. Unless, you extract the relative contribution of TCs to total P, you can not state that firmly. + +<|ref|>text<|/ref|><|det|>[[115, 400, 880, 525]]<|/det|> +To address the reviewer's concerns, we provided additional analyses and model experiments. By separating the rainfall contributions from tropical cyclones (TCs) and other extreme precipitation events—specifically those occurring in 2020 and 2022—we are able to quantify the relative contributions of each to the total rainfall. This analysis provided greater clarity on the roles of TCs versus other sources of rainfall. Furthermore, the additional model experiments presented in the newly added Figure 9, which isolate rainfall from each source (TCs and extreme precipitation events), clearly delineate their respective impacts on ASHSW freshening. + +<|ref|>text<|/ref|><|det|>[[115, 540, 877, 647]]<|/det|> +The relative contributions of rainfall from TCs and extreme precipitation events to the total rainfall have been added to Figure 2c, as suggested by the reviewer. It is evident that rainfall from these events accounted for a significant portion of the excess rainfall observed during the 2019- 2023 period. The model experiments further confirm that these events played a key role in the observed ASHSW freshening during this time, supporting the conclusions drawn earlier in the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 662, 852, 752]]<|/det|> +The intent of this experiment is to capture the salinity differences between the periods 2014- 2018 and 2019- 2023. The choice of 2018 as a reference year was based on the fact that precipitation anomalies during 2018 are broadly representative of typical conditions observed between 2014 and 2018 (Figure 4). Additionally, the tropical cyclone activity in 2018 reflects typical cyclone tracks commonly observed during this period. + +<|ref|>text<|/ref|><|det|>[[115, 780, 839, 799]]<|/det|> +L330- 331: can you provide an estimate of the river runoff impacts (see previous comments) + +<|ref|>text<|/ref|><|det|>[[115, 810, 878, 899]]<|/det|> +While rainfall from tropical cyclones (TCs) and extreme precipitation events could potentially increase river runoff, particularly as some TCs made landfall along the west coast of India, likely contributing to elevated runoff, the model simulations presented in this study do not account for such effects. The simulations utilized a monthly climatology derived from data prior to 1990, which excludes the impact of river runoff associated with the recent increase in TC activity. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 857, 177]]<|/det|> +Therefore, the salinity freshening depicted in the model results reflects precipitation- driven effects alone, without contributions from river runoff linked to TCs and extreme events. Although the influence of river runoff is an important topic worth further investigation, it falls beyond the scope of the present study. A brief description of river runoff treatment has been added to the Methods section for clarity. + +<|ref|>text<|/ref|><|det|>[[115, 207, 877, 242]]<|/det|> +L349- 350: it is not true each year: in 2021, the salinity tendency difference do not exceed 0.1 10- 3 psu.d- 1. Please correct + +<|ref|>text<|/ref|><|det|>[[115, 255, 858, 323]]<|/det|> +Corrected as suggested by the reviewer. As noted, the salinity tendency term in 2021 is approximately 0.05. The revised sentence now reads: "Each year, the salinity tendency term exhibits significant decreases, with values ranging from approximately 0.05 to \(0.15 \times 10^{- 3}\) psu d- 1." + +<|ref|>text<|/ref|><|det|>[[115, 354, 868, 442]]<|/det|> +L352- 353. In line 336, you claim that due to decrease S with depth in the AS, vertical mixing consistently brings lighter water from below into the mixed layer, so it is confusing to read here that the vertical mixing tends to increase salinity. Please clarify. Is it the difference of vertical mixing between the control and perturbation experiment which is responsible for the increase S (blue curve in Fig 8c)? + +<|ref|>text<|/ref|><|det|>[[115, 454, 868, 542]]<|/det|> +Thank you for pointing this out. This point has been clarified in the revised text. The vertical mixing generally reduces salinity, as shown in Figures 8a and 8b. Figure 8c presents the difference in vertical mixing between the control and perturbation experiments. In this case, the reduction in salinity due to vertical mixing in the control experiment is smaller than in the perturbation experiment, resulting in a net increase in salinity in the difference plot. + +<|ref|>text<|/ref|><|det|>[[115, 571, 856, 606]]<|/det|> +L357- 358: in 2021, the pre- and post monsoon TC do appear to have extended the duration of freshwater input but not their amplitude. + +<|ref|>text<|/ref|><|det|>[[115, 619, 848, 654]]<|/det|> +The reviewer is correct. The sentence was intended to convey the role of tropical cyclones in prolonging the freshwater input. This has been clarified in the revised text for accuracy. + +<|ref|>text<|/ref|><|det|>[[115, 684, 879, 789]]<|/det|> +L361- 368: since the beginning of the MS, you keep claiming that TCs are responsible for the increased P and surface freshening but you explain here that in 2022, there were no TCs and that low pressure system can contribute significantly to the observed freshening. This is very confusing and lead the reader to believe that potentially, other low- pressure systems than TCs can be responsible for the observed freshwater fluxes in other years of 2019- 23. Please clarify by extracting the actual TC- contribution to rainfall. + +<|ref|>text<|/ref|><|det|>[[115, 801, 880, 888]]<|/det|> +Thank you for bringing this up. It is fair to say that the potential contribution of the 2022 event to salinity freshening was mentioned earlier in the manuscript before reaching the conclusions presented here. Moreover, the significant influence of the 2022 extreme rainfall event on ASHSW freshening became increasingly evident in the salt- budget analyses. This extreme event has also been well documented in a series of recent studies. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 89, 870, 230]]<|/det|> +Although the primary focus of the paper is the dominant influence of rainfall from tropical cyclones in the region north of \(15^{\circ}\mathrm{N}\) , the role of prolonged extreme rainfall events is equally important. Our analysis demonstrated that the extreme events in 2020 and 2022 played a crucial role in sustaining ASHSW freshening. Since such events are rare but appear to be increasing in frequency in recent years, they are distinct from typical Indian summer monsoon rainfall anomalies and instead result from prolonged large- scale organized weather systems like monsoonal depressions. Therefore, they can be characterized as extreme precipitation events similar in magnitude to rainfall from named tropical cyclones. + +<|ref|>text<|/ref|><|det|>[[115, 246, 876, 352]]<|/det|> +In the revised manuscript, we have clearly separated the precipitation from tropical cyclones and extreme precipitation events using both observations and model experiments designed to quantify the contribution of each source to salinity freshening. To improve clarity, we now explicitly distinguish these precipitation sources early in the paper (Figure 2c) so that the results presented in the remainder of the manuscript can be interpreted accordingly. This distinction is summarized in paragraph 2, lines xx- yy. + +<|ref|>sub_title<|/ref|><|det|>[[115, 394, 208, 411]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[115, 423, 833, 476]]<|/det|> +Behara, A., Vinayachandran, P. N., & Shankar, D. (2019). Influence of rainfall over eastern Arabian Sea on its salinity. Journal of Geophysical Research: Oceans, 124, 5003- 5020. https://doi.org/10.1029/2019JC014999 + +<|ref|>text<|/ref|><|det|>[[115, 487, 848, 540]]<|/det|> +Boutin, J., N. Reul, J. Koehler, A. Martin, R. Catany, S. Guimbard, F. Rouffi, et al.. Satellite- Based Sea Surface Salinity Designed for Ocean and Climate Studies. Journal of Geophysical Research. 2021. https://doi.org/10.1029/2021JC017676 + +<|ref|>text<|/ref|><|det|>[[115, 552, 880, 605]]<|/det|> +Chaudhuri, D., Sengupta, D., D'Asaro, E., Venkatesan, R., & Ravichandran, M. (2019). Response of the salinity- stratified Bay of Bengal to cyclone Phailin. Journal of Physical Oceanography, 49, 1121- 1140. https://doi.org/10.1175/JPO- D- 18- 0051.1 + +<|ref|>text<|/ref|><|det|>[[115, 618, 861, 688]]<|/det|> +Camberlin, P., Assowe Dabar, O., Pohl, B., Mohamed Waberi, M., Hoarau, K., & Planchon, O. (2024). Contribution of western Arabian Sea tropical cyclones to rainfall in the Horn of Africa and southern Arabian Peninsula. Journal of Geophysical Research: Atmospheres, 129, e2024JD041109. https://doi.org/10.1029/2024JD041109 + +<|ref|>text<|/ref|><|det|>[[115, 700, 867, 752]]<|/det|> +Chen, F. and Y. Fu, (2015) Contribution of tropical cyclone rainfall at categories to total precipitation over the Western North Pacific from 1998 to 2007, Sci. China Earth Sci. 58: 2015. doi:10.1007/s11430- 015- 5103- 9. + +<|ref|>text<|/ref|><|det|>[[115, 764, 877, 817]]<|/det|> +Grodsky, S. A., Reul, N., Lagerloef, G., Reverdin, G., Carton, J. A., Chapron, B., et al. (2012). Haline hurricane wake in the Amazon/Orinoco plume: AQUARIUS/SACD and SMOS observations. Geophysical Research Letters, 39, L20603. https://doi.org/10.1029/2012GL053335 + +<|ref|>text<|/ref|><|det|>[[115, 829, 870, 881]]<|/det|> +Jiang, H. and E.J. Zipser, (2010) Contribution of Tropical Cyclones to the Global Precipitation from Eight Seasons of TRMM Data: Regional, Seasonal, and Interannual Variations. Journal of Climate 23:6, 1526- 1543. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 88, 803, 125]]<|/det|> +Jiang, H., C. Liu, and E. D. Zipser (2011), A TRMM- based tropical cyclones cloud and precipitation feature database, J. Appl. Meteorol. Climatol., 50, 1255- 1274. + +<|ref|>text<|/ref|><|det|>[[114, 135, 875, 189]]<|/det|> +Li, B., Zhou, L., Qin, J., & Murtugudde, R. (2022). Increase in intraseasonal rainfall driven by the Arabian Sea warming in recent decades. Geophysical Research Letters, 49, e2022GL100536. https://doi.org/10.1029/2022GL100536 + +<|ref|>text<|/ref|><|det|>[[114, 200, 855, 271]]<|/det|> +Lonfat, M., F. D. Marks, and S. S. Chen, (2004) Precipitation distribution in tropical cyclones using the Tropical Rainfall Measuring Mission (TRMM) microwave imager: A global perspective. Mon. Wea. Rev., 132, 1645- 1660, doi:10.1175/1520- 0493(2004)132,1645:PDITCU.2.0. CO;2. + +<|ref|>text<|/ref|><|det|>[[114, 283, 864, 320]]<|/det|> +Maes, C., and T. J. O'Kane (2014), Seasonal variations of the upper ocean salinity stratification in the Tropics, J. Geophys. Res. Oceans, 119, 1706- 1722, doi:10.1002/2013JC009366. + +<|ref|>text<|/ref|><|det|>[[114, 330, 860, 383]]<|/det|> +Melnichenko. O., 2021. Multi- mission L4 Optimally Interpoated Sea Surface Salinity. Ver.1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY- MM- DD] at https://doi.org/10.5067/SMP10- 4U7CS + +<|ref|>text<|/ref|><|det|>[[114, 395, 861, 449]]<|/det|> +Neethu, C. (2018). Insights into the haline variability induced by cyclone Vardah in the Bay of Bengal using SMAP salinity observations. Remote Sensing Letters, 9(12), 1205- 1213. https://doi.org/10.1080/2150704X.2018.1519271 + +<|ref|>text<|/ref|><|det|>[[114, 460, 846, 513]]<|/det|> +Rao, A. D., M. Joshi, and M. Ravichandran (2009), Observed low- salinity plume off Gulf of Khambhat, India, during post- monsoon period, Geophys. Res. Lett., 36, L03605, doi:10.1029/2008GL036091. + +<|ref|>text<|/ref|><|det|>[[114, 525, 830, 595]]<|/det|> +Reul, N., Quilfen, Y., Chapron, B., Fournier, S., Kudryavtsev, V., & Sabia, R. (2014). Multisensor observations of the Amazon- Orinoco river plume interactions with hurricanes. Journal of Geophysical Research: Oceans, 119, 8271- 8295. https://doi.org/10.1002/2014JC010107 + +<|ref|>text<|/ref|><|det|>[[114, 607, 857, 679]]<|/det|> +Reul Nicolas, Chapron Bertrand, Grodsky Semyon A., Guimbard Sebastien, Kudryavtsev Vladimir, Foltz Gregory R., Balaguru Karthik (2021). Satellite observations of the sea surface salinity response to tropical cyclones. Geophysical Research Letters, 48(1), e2020GL091478 (10p). + +<|ref|>text<|/ref|><|det|>[[114, 689, 872, 743]]<|/det|> +Reul N, Ifremer / LOPS. 2023. Atlas of Tropical Cyclone Induced Wakes (2010- 2020) (v1.0) for ESA Marine Atmosphere eXtreme Satellite Synergy project (MAXSS). Ver. 1.0. Ifremer, Plouzane, France. Dataset accessed [2024- 10- 11]. + +<|ref|>text<|/ref|><|det|>[[114, 755, 840, 790]]<|/det|> +Sun, J.; Vecchi, G.; Soden, B. Sea Surface Salinity Response to Tropical Cyclones Based on Satellite Observations. Remote Sens. 2021, 13, 420. https://doi.org/10.3390/rs13030420 + +<|ref|>text<|/ref|><|det|>[[114, 802, 855, 856]]<|/det|> +Yue, X., Zhang, B., Liu, G., Li, X., Zhang, H., & He, Y. (2018). Upper ocean response to typhoon Kalmaegi and Sarika in the South China sea from Multiple- satellite observations and numerical simulations. Remote Sensing, 10, 348. https://doi.org/10.3390/rs10020348 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[114, 90, 827, 128]]<|/det|> +The relevant references have been included in the revised manuscript to support the points discussed. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 417, 107]]<|/det|> +Reviewer #3 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 124, 870, 213]]<|/det|> +The manuscript "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation" was reviewed. The paper seems to address an interesting and important issue in these less studied and important ocean basin. It also appears to entail a substantial effort. Hence it can deserve being published. However, some comments listed below may improve it: + +<|ref|>text<|/ref|><|det|>[[115, 243, 881, 350]]<|/det|> +We sincerely thank the reviewer for their thoughtful comments and constructive suggestions, which have greatly enhanced the quality of the manuscript and strengthened the scientific arguments presented. We have carefully addressed the majority of the reviewer's comments and made the necessary modifications to the manuscript. Below, we provide a point- by- point response (reviewer comments in black and our responses highlighted in blue). We hope that these revisions adequately address the reviewer's concerns. + +<|ref|>text<|/ref|><|det|>[[115, 380, 861, 454]]<|/det|> +1- The text is well written, but repetitions of some text parts may be reduced (changed) as they are noticeable and can be a bit tedious to the readers? As: "cyclone- induced", "formation of ASHSW" or "ASHSW formation", "salinity freshening". If it can be helped? 2- Moving Figs to be more harmonious with text may be useful?! + +<|ref|>text<|/ref|><|det|>[[115, 483, 866, 536]]<|/det|> +Thank you for the suggestion. In the revised manuscript, we have minimized repetitive text and ensured consistent terminology throughout the paper. Additionally, we have reorganized the figures to align more closely with the corresponding discussions, as recommended. + +<|ref|>text<|/ref|><|det|>[[115, 567, 847, 638]]<|/det|> +3- The present work only presents salinity and precipitation records and distributions, and no records of surface heat (especially temperature records from observations or model) and momentum (currents?) fluxes are mentioned (even from the work of the others?) as they are important in understanding the issue being addressed here? + +<|ref|>text<|/ref|><|det|>[[115, 670, 880, 860]]<|/det|> +We thank the reviewer for highlighting this important aspect of the study, which was not fully clarified in the initial manuscript. Temperature was excluded in the earlier version because its impact was deemed minimal in the context of our findings. The increasing salinity stratification could indeed restrict vertical mixing by generating barrier layers and potentially raise sea surface temperature (SST) in the northern Arabian Sea. The time- series of temperature observations from Argo floats (Supplementary Figure 4) show no significant differences between the 2014–2018 and 2019–2023 periods. There is, however, a slight indication of warmer winter mixed layer temperatures during the latter period (Supplementary Figure 4a), which could be linked to enhanced salinity stratification from freshwater input. We also added model temperature, which shows good agreement with Argo data, yielding high correlations of 0.84 and 0.91 (Supplementary Figure 8). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[112, 85, 886, 396]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[113, 406, 881, 599]]<|/det|> +
Supplementary Figure 4. Argo temperature observations in the Arabian Sea. Along-track Argo float temperature ( \(^\circ \mathrm{C}\) ) observations for three regions representing (a) northern, (b) central, and (c) southern Arabian Sea (refer to Supplementary Figure 3 for location) from 2014 to 2023. The \(25^{\circ}\mathrm{C}\) contour is overlaid in all panels. Profiles with the presence of a barrier layer is marked with white boxes. Barrier layer thickness (BLT, m) is calculated as the difference between the isothermal layer depth (ILD) and the mixed layer depth (MLD), where MLD is defined as the depth corresponding to a density change associated with a \(0.2^{\circ}\mathrm{C}\) temperature difference from the surface, and ILD defines as the depth where the temperature decreases by \(0.2^{\circ}\mathrm{C}\) from the surface. Profiles with \(\mathrm{BLT} \geq 5 \mathrm{~m}\) are marked with white boxes. Cyclone occurrences are marked in each panel: circles indicate very severe to super cyclones, and diamonds indicate cyclones to severe cyclones. Cyclones penetrating north of \(15^{\circ}\mathrm{N}\) are marked in red.
+ +<|ref|>text<|/ref|><|det|>[[114, 611, 877, 735]]<|/det|> +To further investigate the impact of freshwater input on SST, we compared the control (CNTL) and \(\mathrm{PPE}_{2019 - 23}\) model simulations (Figure R1). The differences in surface heat flux (W \(\mathrm{m}^{- 2}\) , Figure R1a) and SST ( \(^\circ \mathrm{C}\) , Figure R1b) between these simulations are negligibly small. A region of net heat gain ( \(\sim 8 \mathrm{~W} \mathrm{m}^{- 2}\) ) is evident along the west coast of India in the control simulation, but the SST exhibited a slight cooling ( \(\sim 0.1^{\circ}\mathrm{C}\) ), suggesting the atmosphere tends to warm the ocean through heat input. Due to the negligible magnitude of heat flux, it has not been included in the manuscript. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[120, 85, 881, 310]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[120, 320, 880, 374]]<|/det|> +
Figure R1. Differences between the control (CNTL) and PPE2019-23 experiments (CNTL - PPE2019-23) for the 5-year period spanning 2019–2023 in (a) surface heat flux (W m-2) and (b) sea surface temperature (°C).
+ +<|ref|>text<|/ref|><|det|>[[114, 408, 878, 516]]<|/det|> +While we do not present direct ocean current data, their influence on salinity freshening is captured in the salinity budget analysis (Figure 8). Horizontal and vertical advection terms quantify the salinity changes induced by ocean currents, which remain small in the northern Arabian Sea during winter. For a more comprehensive analysis of heat fluxes and advective processes, we reference Thoppil et al. (2022), Prasad and Ikeda (2002b) for detailed examination of these mechanisms. + +<|ref|>text<|/ref|><|det|>[[114, 545, 879, 635]]<|/det|> +4- No cyclone precipitation in 2022 but systemic (synoptic, as large size cyclone or depression) precipitation is substantial!, but the cyclone- induced precipitation is often emphasized? Systemic precipitation have also contributed in other years and cyclone- induced ones are also short lived! Shifting pattern of precipitation northwards on the whole may be more important? Therefore, the paper title may be changed? + +<|ref|>text<|/ref|><|det|>[[114, 666, 880, 772]]<|/det|> +We greatly appreciate the reviewer's insightful suggestion. As noted, large- scale organized weather systems like monsoonal depressions can produce substantial precipitation comparable to that of a significant tropical cyclone. Despite not being associated with a named cyclone, the precipitation from these systems had a comparable effect on salinity freshening (Figure 8). While the extreme precipitation event in 2022 was widely documented, we identified a similar event in 2020, although it coexisted with two tropical cyclones. + +<|ref|>text<|/ref|><|det|>[[115, 786, 395, 803]]<|/det|> +In the revised manuscript, we have: + +<|ref|>text<|/ref|><|det|>[[144, 818, 853, 854]]<|/det|> +1. Separated precipitation contributions from tropical cyclones and extreme precipitation events using IMERG observations (Figure 2c). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[144, 90, 870, 143]]<|/det|> +2. Conducted three additional model experiments to quantify the individual and combined effects of tropical cyclones and extreme precipitation events (2020 and 2022) on salinity freshening during 2019–2023 (new Figure 9). + +<|ref|>text<|/ref|><|det|>[[115, 157, 870, 280]]<|/det|> +These extreme precipitation events share a key characteristic: they all occurred in the northern Arabian Sea, where ASHSW forms and where extreme freshwater input events have become increasingly frequent in recent years. This trend coincides with a northward shift in tropical cyclone activity, further intensifying freshwater input and salinity freshening. Additionally, the increasing number of extreme post-monsoon tropical cyclones, which are projected to rise with ongoing climate warming, suggests a clear northward shift in their occurrence (Murakami et al., 2017). + +<|ref|>text<|/ref|><|det|>[[114, 293, 879, 435]]<|/det|> +Since the primary focus of this study is the freshening of ASHSW driven by freshwater input, and no prior studies have indicated a systematic northward shift in precipitation patterns over the Arabian Sea, emphasizing this aspect in the title may be difficult to justify. However, to better reflect the range of precipitation sources analyzed in this study, we have revised the title to: "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Precipitation Events." The use of "extreme precipitation events" accounts for both tropical cyclone- induced rainfall and large- scale organized weather systems contributing to the observed salinity freshening. + +<|ref|>text<|/ref|><|det|>[[114, 448, 881, 554]]<|/det|> +ITCZ in summer, appear to have shifted more (it usually change longitudinal position much more in Indian ocean than in other equatorial regions during the year, hence monsoonal systems) northwards in recent years in the Indian Ocean region that may be due to recent fast climate change, this could have increased the overall precipitation in the Arabian sea? [Mamalakis, A., Randerson, J.T., Yu, J.Y. et al. Zonally contrasting shifts of the tropical rain belt in response to climate change. Nat. Clim. Chang. 11, 143–151 (2021).] + +<|ref|>text<|/ref|><|det|>[[114, 585, 880, 743]]<|/det|> +Thank you for directing us to this insightful study. While the results indeed project a northward shift of the ITCZ and associated precipitation over the Arabian Sea based on climate model simulations for the period 2075–2100, directly linking this projection to the recent increase in precipitation without a detailed analysis using contemporary data remains challenging. The timescales and uncertainties involved necessitate further investigation using recent observations to establish a clearer connection between observed precipitation patterns and projected long- term trends. In the revised manuscript, we have acknowledged this study as a possible future scenario that could influence the salinity budget in the Indian Ocean (Discussion, paragraph 5), while emphasizing the need for further research using recent data to draw more definitive conclusions. + +<|ref|>text<|/ref|><|det|>[[114, 775, 880, 880]]<|/det|> +5- In Fig 3 they may present temperature records along with shown salinity anomaly, and temperature profile in Fig.2, to show better the density stratification which is claimed to have been “substantially weakened”? What is the cooling effects of cloudiness during precipitation? Temperature records may show this. Although in Fig. 4 potential density shows a decrease, along with the shallowing mixed layer depth. (E.g. paper by Shee et al. Recent changes in the upper oceanic water masses over the Indian Ocean using Argo data, Sci. Rep. 2023, 13, 20252, also + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 864, 125]]<|/det|> +show some temperature records that may be worth looking at?). So presentation of temperature profiles and series changes may be recommended. + +<|ref|>text<|/ref|><|det|>[[115, 140, 875, 262]]<|/det|> +Thank you very much for the suggested recommendation. Unlike salinity, temperature anomalies (Supplementary Figure 5) do not exhibit a distinct cooling/warming pattern during 2019- 2023 period compared to 2014- 2018. They indicate an overall warming trend consistent with the findings of Shee et al. (2023). However, their analysis, focused on the upper \(700\mathrm{m}\) and excluding data after 2019, limits direct comparison with our results. Notably, there are indications of warming in the northern Arabian Sea in 2020, 2021, and 2022, potentially linked to salinity- driven stratification, which may have restricted vertical mixing. + +<|ref|>text<|/ref|><|det|>[[115, 277, 857, 312]]<|/det|> +Related revisions can be found under subsection: Prolonged salinity freshening: Observations, paragraphs, 9 and 11, Figure 4b and supplementary Figures 4, 5 and 8. + +<|ref|>image<|/ref|><|det|>[[114, 320, 886, 461]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[115, 473, 870, 526]]<|/det|> +
Supplementary Figure 5. Temperature anomalies ( \(^\circ \mathrm{C}\) ) averaged in the upper \(50\mathrm{m}\) from the monthly EN4 dataset. Anomalies are calculated relative to the 2000–2023 period by subtracting the long-term monthly climatology.
+ +<|ref|>text<|/ref|><|det|>[[115, 541, 880, 592]]<|/det|> +During tropical cyclone periods, latent heat flux predominantly contributes to surface cooling, though reductions in solar radiation due to cloud cover also modulate surface heat flux to a lesser extent. + +<|ref|>text<|/ref|><|det|>[[115, 607, 880, 660]]<|/det|> +As recommended by the reviewer, we have included Argo temperature profiles in Supplementary Figure 4 for clarity, which show similar slightly warmer winter temperature during 2019–2023, likely driven by strong salinity stratification. + +<|ref|>text<|/ref|><|det|>[[115, 692, 880, 779]]<|/det|> +6- As the northern Indian Ocean is experiencing the intrusions of high salinity and temperature at depth of about 100 to \(500\mathrm{m}\) from the Persian Gulf and Red Sea outflows (depending on season) while being refreshed by the surface water (especially the Persian Gulf, which is also refreshed by the surface water of Arabian Sea), have these semi- enclosed seas any influence on the ASHSW? It may be worth commenting on this, in discussion? + +<|ref|>text<|/ref|><|det|>[[115, 797, 880, 884]]<|/det|> +This is an excellent suggestion by the reviewer to clarify the influence of different water masses on ASHSW. We have added a brief note in the discussion to address this point (see Discussion, paragraph 3). As noted, ASHSW is confined to the upper \(100\mathrm{m}\) , while Persian Gulf Water occurs below \(150\mathrm{m}\) , with its core around \(200\mathrm{m}\) depth, and Red Sea Water is typically found below \(500\mathrm{m}\) , spreading eastward. Therefore, these deeper water masses do not interact with ASHSW. The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 815, 125]]<|/det|> +model experiments, which consistently represent these water masses, further support this distinction. + +<|ref|>text<|/ref|><|det|>[[115, 140, 872, 247]]<|/det|> +7- Arabian Sea oxygen- depleted waters and hence, fish kill has increased recently, can ASHSW changes influence this; this may be interesting to just point out? Oxygenation of the Oman Sea and northern Indian Ocean waters by these outflows (4) has been shown to be important, although they are at deeper depths (e.g. Font, E., Swart, S., Bruss, G., Sheehan, P. M. F., Heywood, K. J., & Queste, B. Y. (2024). "Ventilation of the Arabian Sea oxygen minimum zone by Persian Gulf water". Journal of Geophysical Research – Oceans, 129(5), [e2023JC020668]). + +<|ref|>text<|/ref|><|det|>[[115, 277, 881, 399]]<|/det|> +Thank you for pointing out this interesting recent study on the role of Persian Gulf Water in the Arabian Sea Oxygen Minimum Zone (OMZ). It is highly unlikely that ASHSW contributes to the OMZ, which occurs below \(150\mathrm{m}\) , as ASHSW is primarily confined to the upper \(100\mathrm{m}\) of the water column. We are unaware of any evidence linking ASHSW to the OMZ in the Arabian Sea. However, the weakening of winter convective mixing can directly affect primary productivity in the northern Arabian Sea, which may indirectly impact fish populations dependent on phytoplankton. This point has been incorporated into the Discussion (paragraph 4). + +<|ref|>text<|/ref|><|det|>[[115, 413, 878, 466]]<|/det|> +8- Fig. 1 show cyclone track shifted northwards, is this due to recent climate change? Not clearly reasoned? Precipitation seems to have increased more over the eastern coast of the Arabian Sea (more summer ITCZ shift, 4, ?). + +<|ref|>text<|/ref|><|det|>[[115, 498, 878, 602]]<|/det|> +The reviewer raises an important and relevant point. The observed northward shift in cyclone tracks is consistent with projections under changing climate scenarios. Notably, the recent increase in the frequency of post- monsoon cyclones and their northward migration closely aligns with projected changes in extreme cyclone activity, as shown by Murakami et al. (2017, see their Figure 2, referenced below). This connection was briefly discussed in the earlier version of the manuscript. + +<|ref|>text<|/ref|><|det|>[[115, 617, 875, 723]]<|/det|> +Beyond precipitation from cyclones and synoptic- scale systems, Figure 2b also shows an overall increasing trend in precipitation in the eastern Arabian Sea. This rise could be linked to other atmospheric modes of interannual variability, such as the Indian Ocean Dipole (IOD), Monsoon Intra- Seasonal Oscillation (MISO), and monsoon depressions. However, since these processes were not the primary focus of this study, they were only briefly mentioned in the revised manuscript for context. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 591, 848, 646]]<|/det|> +Figure 2 of Murakami, H., Vecchi, G.A. & Underwood, S. Increasing frequency of extremely severe cyclonic storms over the Arabian Sea. \*Nature Clim Change\* 7, 885–889 (2017). https://doi.org/10.1038/s41558-017-0008-6 + +<|ref|>text<|/ref|><|det|>[[113, 677, 760, 697]]<|/det|> +9- Should \(\Sigma \Delta \mathrm{P}\) be \(+\) and \(\Sigma \Delta \mathrm{S}\) be - in Fig. 3(c)? Can these be decadal Oscillation? + +<|ref|>text<|/ref|><|det|>[[114, 712, 875, 818]]<|/det|> +Figure 2c (previous Figure 3c) presents the cumulative anomalies of salinity and precipitation depicted in Figures 2a and 2b. During the 2014–2018 period, salinity anomalies remain positive, resulting in a progressively increasing positive cumulative sum, while precipitation anomalies become increasingly negative. In contrast, the 2019–2023 period shows a reversal in the sign of both salinity and precipitation anomalies, leading to a corresponding shift in their cumulative trends. + +<|ref|>text<|/ref|><|det|>[[114, 833, 875, 886]]<|/det|> +Determining whether the observed trend is part of a longer- term decadal oscillation would require further analysis using a longer data record. However, the study by Shee et al. (2021), based on 17 years (2003–2019) of Argo data, suggests the presence of decadal oscillations in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[115, 90, 839, 126]]<|/det|> +upper 700 m of the northern Arabian Sea, although the study did not explore the underlying processes driving these variations in detail. + +<|ref|>text<|/ref|><|det|>[[115, 140, 864, 176]]<|/det|> +10- In salinity budget equation, Fv and Fh are probably vertical and horizontal fluxes due other forcing (may be turbulence or eddy fluxes)? They better to be introduced clearly. + +<|ref|>text<|/ref|><|det|>[[115, 207, 856, 243]]<|/det|> +Thank you for the valuable suggestion. As recommended, the details of these terms have been included in the revised manuscript (see Methods) for clarity and completeness. + +<|ref|>text<|/ref|><|det|>[[115, 274, 327, 292]]<|/det|> +Best of luck for the author. + +<|ref|>text<|/ref|><|det|>[[115, 325, 207, 342]]<|/det|> +Thank you! + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 87, 870, 143]]<|/det|> +Review of the MS entitled "Sustained Freshening of Arabian Sea High Salinity Water Induced by Extreme Tropical Cyclone Precipitation" by P.G. Thoppil submitted to Nature Communications. + +<|ref|>sub_title<|/ref|><|det|>[[113, 154, 220, 172]]<|/det|> +## Summary: + +<|ref|>text<|/ref|><|det|>[[112, 181, 884, 442]]<|/det|> +In this MS, the author first analyzes the impact of Tropical Cyclones (TCs)- induced precipitation on upper ocean salinity in the North Arabian Sea (AS) over 2014- 2023 using satellite rain and in situ Argo profile data. The author reports an increased number of TC in 2019- 2023, concomitant with an increase in total precipitation and an overall decrease of upper ocean salinity in the East AS with respect to the 2014- 2018 period, with a maximum freshening observed in the North East AS region. He then analyzes the temporal evolution of the vertical salinity structure using in situ profile data, revealing sustained freshening in the Northern Arabian Sea where the Arabian Sea High Salinity Waters (ASHsW) form. The upper ocean freshening reduces the potential surface density, augmenting the vertical stratification and in fine, disrupt the convective sinking process of ASHSW. Finally, using model perturbation experiment and model- based salinity budget estimates, the author attempts to isolate the impact of TC- induced rain on salinity freshening and conclude that the recent SSS freshening is caused by the increased number of TCs from 2019 onward. + +<|ref|>sub_title<|/ref|><|det|>[[113, 453, 523, 472]]<|/det|> +## Major Comments and recommendations + +<|ref|>text<|/ref|><|det|>[[112, 480, 884, 611]]<|/det|> +The topic is of strong scientific interest, in particular for the tropical cyclone forecast, salinity remote sensing, and, ocean modeler communities. While the SST, CHLA, and SSH response to TC passage have been extensively studied, TC- induced SSS changes and their large- scale impacts on other climate processes are much less known: this work definitively participate to these community efforts. In general, the MS reads well, is interesting and the results are in general plausible. However, I have several major concerns. + +<|ref|>text<|/ref|><|det|>[[112, 620, 884, 900]]<|/det|> +First, in the part of the MS devoted to observations analyses, the author had not at all isolated the TC- induced precipitation and associated SSS changes from other sources of atmospheric and oceanic variability, which weaken strongly the strength of his statements, which are often more 'suggestions' than a clear demonstration of causality between the three reported interannual anomalies seen in the observation: 1) 'increased number of TC', 2) 'increased total Precipitation', and 3) 'decreased overall upper ocean Salinity'. For me, the author has not demonstrated convincing evidences from his analyses that the reported large- scale upper ocean salinity and precipitation anomalies (shown in Figure 1 & Figure 2 in the MS), as well as their consequences on the stability of the water column (Figure 4) is dominantly due to the passage of some rare but intense tropical cyclones rainfall and associated SSS freshening. I will show below in the detailed comments section of my review several examples in 2019 where there was little precipitation accumulated during the passage of some strong TCs in this region as well as small associated SSS changes in their wake, as reported from satellite observations. The + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 85, 884, 404]]<|/det|> +interannual SSS & P changes observed by the author could therefore be due to other processes (see details in Behara et al, 2019) such as the increased precipitation during the recent Monsoon, or e.g., due to increased runoff from the river waters out of the Gulf of Khambhat estuaries, or from elsewhere in the coasts (e.g Pakistan floods in 2022 as mentioned by the author at the end of his MS), or even more likely by large scale climate variability impact on rain and SSS (e.g., Indian Ocean Dipole, Monsoon IntraSeasonal Oscillation (MISO),...) and not necessarily because of changes in Tropical Cyclone activity per se in between 2019- 2023 and 2014- 2018. For example, Li et al (2022) found that the variance of MISO has an increasing trend from 1982 to 2017 over the northeastern Arabian Sea (AS), accompanied by increasing intraseasonal rainfall. How does this impact the precipitation excess shown in Figure 1c? The enhancement in rainfall in this case is mainly nourished by the increasing moisture supply, with a major contribution from the upward moisture advection by the intraseasonal vertical wind velocity. Since the author did not isolate the precipitation signal from TC- only with respect to total rain, and also did not isolate the salinity response to TC passage, most of his statements remain poorly evidenced, while this can be now easily estimated from the observation dataset already gathered by the author: + +<|ref|>text<|/ref|><|det|>[[141, 412, 884, 562]]<|/det|> +1) From IMERG and Ibtracs datasets, the author could estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds or within a radius of 500 km) around the TC center tracks. +2) Then further estimate the time series of the cumulated contribution of tropical cyclone only induced rainfall to the total precipitation over the 3 AS subregions selected by the author. Then he could compare the relative contribution of TCs separately for both period 2014-2018 and 2019-2023. + +<|ref|>text<|/ref|><|det|>[[112, 572, 884, 758]]<|/det|> +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach has been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser (2010), Jiang et al (2011). For example, a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non- tropical cyclone (TC) days and on TC days based on IMERG data (2000- 2020). + +<|ref|>text<|/ref|><|det|>[[112, 767, 884, 900]]<|/det|> +Similarly, to best isolate the TC- induced surface freshening from other sources of SSS variability (e.g., Monsoon rain, horizontal advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 87, 884, 181]]<|/det|> +exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi- mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021). The author could then evaluate the cumulated TC- induced SSS changes in each season over 2014- 2023 and see how much it contributed to the overall SSS decrease observed in that region since 2019. + +<|ref|>text<|/ref|><|det|>[[112, 189, 884, 432]]<|/det|> +Second, in the second part of the MS devoted to model analyses, here again the author has not directly isolated the impact of interannual variability of the TC- induced precipitation and associated SSS changes from other sources of interannual atmospheric and oceanic variability. While I agree with the author that by inverting atmospheric forcing of years 2018 and 2019 the model can reproduce the SSS freshening observation: it does only show that the interannual variability in P predominantly modulate the SSS signal: the author however did not show directly that the TC- induced rain only is responsible for that interannual signal: some other sources of precipitation variability over 2018- 2019 could be responsible for it. Once the TC- induced rain will be isolated from the total precipitation time series as I suggested previously, the author could then easily re- run his model perturbation experiments by only removing TC days in the atmospheric forcing time series: this would directly show what the author want to prove rather than by using lengthy and sometimes confusing indirect approaches. + +<|ref|>text<|/ref|><|det|>[[113, 441, 883, 498]]<|/det|> +In addition, many time in the MS, the author used very strong statements (particularly on the impacts of TC- precipitation on SSS anomalies) without full proof of them: please re- phrase those sentences to only state what is shown by your results. + +<|ref|>text<|/ref|><|det|>[[112, 507, 884, 620]]<|/det|> +Therefore, despite most of the results shown by the author are plausible, I recommend that the MS undergo major revision before being considered for publication so that the author actually and properly separate the TC impacts from other sources of variability in both the Precipitation and SSS signals and in the observation and model analyses, separately: this shall in fine directly demonstrate the authors indirect statements. + +<|ref|>text<|/ref|><|det|>[[114, 630, 320, 648]]<|/det|> +Details are given below. + +<|ref|>sub_title<|/ref|><|det|>[[114, 658, 320, 677]]<|/det|> +## Detailed Comments: + +<|ref|>text<|/ref|><|det|>[[113, 686, 884, 780]]<|/det|> +L38 "evaporation- precipitation"- What about river runoff and their impacts on the northeast Arabian Sea (AS) upper salinity, in particular from the Indus and the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Khambhat estuaries? As shown in Rao et al (2009) and reproduced here below (panel d), rivers have non negligible impacts on the SSS in the North eastern AS, particularly in winter months. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[113, 410, 884, 605]]<|/det|> +L107- 108: this sentence is a very strong statement that definitively need more support than what is shown and discussed around Fig1 at this stage in the MS. Please re- phrase to be more accurate and keep to the point of what your data really show. It is not because Fig1 panels reveal a concomitant increase in 1) the number of TCs in the North- eastern part of the AS, 2) as well as in overall Precipitation in the eastern AS and 3) a decrease in SSS in the NE AS that this is clearly an evident proof that “the cyclone- induced precipitation have impact on the convective formation of the Arabian Sea High Salinity Waters “. This is a very strong shortcoming. As I will show further, TC in the Arabian sea are not systematically associated with heavy rain and SSS drops are not systematically observed in their trail. Deeper observation analyses are required to conclude. + +<|ref|>text<|/ref|><|det|>[[113, 615, 884, 690]]<|/det|> +Indeed, the increase of precipitation shown in Fig1c could be due to other atmospheric sources of interannual variability (e.g., Indian Ocean Dipole, Moonsoon) than merely the change in Tropical Cyclone activity in between 2019- 2023 and 2014- 2018. What about a potentially increase in monsoon season accumulated rain in the most recent years ? + +<|ref|>text<|/ref|><|det|>[[113, 690, 884, 802]]<|/det|> +Similarly, the SSS deacrease in the AS, while I agree is most intense where most new TCs tracks where located in 2019- 2023 is also a region of significant runoff from the Narmada, Sabamati, Mahi and Tapi rivers in the Gulf of Cambay estuaries. Could the reported interannual variability in SSS in this region be also related to increased river runoff in 2019- 2023 ? and if yes, how much does it contribute to the observed SSS decrease with respect to the impact of local rain increases ? + +<|ref|>text<|/ref|><|det|>[[113, 812, 833, 849]]<|/det|> +To resolve these uncertainties, I suggest the author shall re- analyse the datasets as follows: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[140, 87, 863, 200]]<|/det|> +3) From IMERG and Ibtracs datasets, estimate the rain accumulated during the passage of each storm over 2014-2023 in a spatial domain (e.g. within the wind radius of 34knot winds) around the TC center track. +4) Then further estimate the average cumulated spatial contribution of all tropical cyclone rainfall to total precipitation over the AS region, separately for both period 2014-2018 and 2019-2023. + +<|ref|>text<|/ref|><|det|>[[112, 217, 884, 404]]<|/det|> +The respective contribution of TC- induced precipitation to total rain and their interannual anomalies could then be much better estimated and would strongly re- enforce the author' statements. Such approach have been used frequently in the past literature based on satellite rain products and could be applied following for example the approaches proposed in Lonfat et al (2004), Chen and Fu (2015), Jiang and Zipser(2010), Jiang et al (2011). For example a recent study by Camberlin et al. (2024) evaluated the contribution of the Western Arabian Sea Tropical Cyclones to Rainfall in the Horn of Africa and Southern Arabian Peninsula by estimating rainfall on non- tropical cyclone (TC) days and TC days based on IMERG data (2000- 2020). Such an approach could be easily applied by the author. + +<|ref|>text<|/ref|><|det|>[[142, 421, 880, 607]]<|/det|> +5) Similarly, to best isolate the TC-induced surface freshening from other sources of SSS variability (Moonsoon rain, advection, river runoff impacts), the SSS change induced by each TC can now be evaluated systematically with confidence using satellite SSS data back to 2010 following the approaches presented in numerous papers in the literature (see for examples Chaudhuri et al., 2019; Grodsky et al., 2012; Neethu, 2018; Reul et al., 2014; Yue et al., 2018, Reul et al. 2021 and Sun et al., 2021). Merged SMOS, Aquarius and SMAP high quality Level 4 satellite SSS products now exist to perform such analyses (e.g., ESA Climate Change Initiative SSS products, Boutin et al. 2021 or the Multi-mission L4 Optimally Interpoated Sea Surface Salinity, Melnichenko, 2021) + +<|ref|>text<|/ref|><|det|>[[112, 616, 884, 896]]<|/det|> +In fact, databases including TC- induced Precipitation & SSS changes for each individual TC globally over 2010- 2020 were already developed in the frame of the ESA Marine Atmosphere eXtreme Satellite Synergy (MAXSS) project (see https://www.maxss.org/) and could be used by the author to better demonstrate his statements. This dataset is publicly available (doi:10.12770/cc0577e4-55d6-4aa9-a938-b4965be121ab, Reul et al., 2023), and provides, for each storm tracks from IBTrACS during the period 2010- 2020, three types of storm- related parameters: (1) the pre- storm upper ocean conditions (e.g., SST, SSS, upper ocean vertical density stratification strength, etc.), (2) the atmospheric forcing during the storm passage (maximum wind, accumulated rain and evaporation, wind power index, etc.) during the storm, as well as (3) the oceanic wakes left after the storm for an ensemble of key variables (SST, SSS, sea level height, ocean color parameters). I show here below few examples of estimated SSS anomalies (derived from the ESA CCI SSS products) left after TC passages in the AS as well as the corresponding accumulated precipitation (derived from merged satellite TRMM products) during their lifetime over the AS in 2019 and which is available in the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[112, 87, 884, 330]]<|/det|> +MAXSS database. As evidenced from satellite data, TC passage in the AS in 2019 are not systematically associated with strong local SSS decreases and heavy precipitation: see e.g. examples of the extremely severe cyclonic storm MAHA in 2019 with small amount of accumulated precipitation associated with negligible SSS changes in the North Eastern AS, or the other case of the super cyclonic storm KYARR with locally very high accumulated rain at \(20^{\circ}\mathrm{N}\) but no significant associated SSS changes observed from satellites. Significant SSS drops were nevertheless observed after the passage of the very severe cyclonic storm VAYU in a region with significant accumulated rain. Therefore, given the high variability of the SSS response to TC passages in this region, and although Sun et al., (2021) have shown (see their Figure 16 top pannel) that on average TC do induce SSS drops in the AS, it remains unclear what the overall contributions of the TC- induced rain and associated freshening are on the 2014- 2018 versus 2019- 2023 interannual variability reported in Fig 1.c and Fig.1d. + +<|ref|>image<|/ref|><|det|>[[170, 355, 852, 890]]<|/det|> + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[170, 85, 830, 320]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[171, 335, 866, 393]]<|/det|> +
Figure 2: Examples of SSS anomalies left after TC passages in the Arabian Sea in 2019 (left panels) and corresponding accumulated rain (right panels). Data and plots are available at https://www.maxss.org/.
+ +<|ref|>text<|/ref|><|det|>[[171, 427, 874, 503]]<|/det|> +Line 111- 113: I agree that the addition of freshwater reduces surface density but it has not been demonstrated at this stage of the MS that it disrupts the sinking process and weaken the formation of the ASHSW. Please re- phrase to only state what is shown by your results. + +<|ref|>text<|/ref|><|det|>[[171, 520, 872, 727]]<|/det|> +Figure 2: the symbols representing the occurrences of TC are not visible enough on the figures. I would add panels illustrating the temporal evolution of the total accumulated rain and of the TC- induced rain in the three regions. In the legend, you precise that "2 extremely severe cyclones in late October to Early November triggered the largest freshening in the AS". Please clarify and provide the references for the name (identifier) of these 2 storms and show the SSS freshening associated to them or do not mention something you did not demonstrated. According to Fig2a in the MS, the freshening after September- December 2020, or 2021, seems the two largest freshenings over the period. Satellite SSS data for the example of TC MAHA shown above and which occurred in early November 2019 do not reveal large surface freshening! + +<|ref|>text<|/ref|><|det|>[[171, 743, 858, 874]]<|/det|> +Figure 3: it is not fully clear how SSS and P anomalies were evaluated. In the method section it is said (Line 476 and 498- 499) that 'salinity and P anomalies are calculated from 2000- 2023 period'. Do you mean that you evaluated the mean seasonal cycle over 2000- 2023 and then removed it to the S and P times series or did you remove the overall local mean evaluated over the complete 2000- 2023 period independently of the season ? Please precise, it is very important to understand if the mean seasonal cycle was removed or not. Please + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[171, 85, 875, 125]]<|/det|> +also provide y- axis labels in Fig 3a (SSSA) and b (Precipitation anomaly). Correct the typo for "IMERGE", it shall reads" IMERG." + +<|ref|>text<|/ref|><|det|>[[171, 142, 878, 200]]<|/det|> +Figure 3c: I would suggest to add the TC- induced rain accumulated precipitation time series as well, this would avoid lack of clarity on the relative contributions of TC versus other sources of atmospheric rain on the observed anomalies. + +<|ref|>text<|/ref|><|det|>[[171, 217, 881, 292]]<|/det|> +L129: except in 2021, it does not appear clearly that SSS freshening systematically lag behind P anomalies when comparing Fig3a and Fig3b. For example in J- S 2022, the freshening are concomitant with high rain. Please re- formulate accordingly. + +<|ref|>text<|/ref|><|det|>[[171, 309, 882, 384]]<|/det|> +L130: here again, the author sentence "The addition of cyclone- induced freshwater increases buoyancy and strengthens stratification, which in turns weakens the depth of winter convective mixing" has not been yet demonstrated at this stage of the MS and shall be removed if not fully proofed + +<|ref|>text<|/ref|><|det|>[[171, 400, 881, 457]]<|/det|> +L134: Fig S2 show the evolution of the MLD averaged over the box \(60^{\circ} - 70^{\circ}\mathrm{E}\) , \(15^{\circ} - 25^{\circ}\mathrm{N}\) and not separately for the 3 boxes shown in Fig3. It is rather confusing then to compare MLD & S evolution in different boxes. Please correct. + +<|ref|>text<|/ref|><|det|>[[171, 474, 881, 550]]<|/det|> +L135: "While cyclone- induced precipitation weakens the convective formation of ASHSW in the north during winter,...": here again this statement have NOT been demonstrated at this stage in the MS; please remove/correct unless you show a real demonstration + +<|ref|>text<|/ref|><|det|>[[171, 567, 830, 587]]<|/det|> +L148: "...salinity maximum at \(80\mathrm{m}\) ." Please precise that is seen in 'Figure 2f + +<|ref|>text<|/ref|><|det|>[[171, 604, 880, 699]]<|/det|> +L148: "...salinity maximum at \(80\mathrm{m}\) ." Please precise that is seen in 'Figure 2fL148: "This vertical salinity stratification promotes vertical mixing (heavier over lighter water) and plays an important role in maintaining SST in the southeastern Arabian Sea". Ok, but why not showing the Brunt- Vaisala frequency to illustrate the respective contribution of S and T to vertical stratification in the 3 regions, following Maes, C., and O'Kane (2014): + +<|ref|>equation<|/ref|><|det|>[[269, 714, 784, 755]]<|/det|> +\[N^{2}(T,S) = -\frac{g}{\rho}\frac{\partial\rho}{\partial z}\approx \left(g\alpha \frac{\partial T}{\partial z} +g\beta \frac{\partial S}{\partial z}\right) = N_{T}^{2}(T,S) + N_{S}^{2}(T,S)\] + +<|ref|>text<|/ref|><|det|>[[171, 755, 882, 831]]<|/det|> +Where \(\rho\) is density, T temperature; S salinity, \(\alpha\) is the thermal expansion coefficient, \(\beta\) is the haline contraction coefficient; g is acceleration of gravity and z is vertical. This would help the reader to understand the role of freshwater on the vertical density stratification. + +<|ref|>text<|/ref|><|det|>[[171, 849, 875, 906]]<|/det|> +L168- 170: Why does the extreme precipitation during the summer monsoon of 2017 in the northeastern Arabian Sea reported in reference 7 do not appear in the anomalies of Figure 3b ? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 105, 876, 199]]<|/det|> +L192 and Figure 4: \(1\%\) change in density and 10m shoaling of the MLD are small changes. Can you provide error bars on the Fig4 curves given the rather small number of Argo float profiles you used to estimate these time series (4 as described in the Method section) ? Would be nice to split the contributions of S & T to the PEA following the above split for N2. + +<|ref|>text<|/ref|><|det|>[[172, 217, 884, 366]]<|/det|> +L205- 206: "...coinciding with recent freshening events associated with extreme cyclones': this has not been fully proven and is a gain a fast conclusion. I agree that the stronger PEA over 20219- 2023 is coinciding with more cyclones over that period, but has discussed before, these are not necessarily and systematically associated with freshening events: so it is not a proof of causality The 2019- 23 anomalies of PEA around the mean do not systematically coincide with TC occurrences. For example, end 2020, 2021 and 2023 the last TCs of the season coincide with a locally decreasing PEA. + +<|ref|>text<|/ref|><|det|>[[172, 384, 884, 421]]<|/det|> +L209. Unclear meaning. What do you mean by "similarity"? Can you provide the correlation coefficient between both quantities? + +<|ref|>text<|/ref|><|det|>[[172, 439, 884, 565]]<|/det|> +L217- 219. You state "In 2018, despite the occurrence of three cyclones, none induced freshening north of \(15^{\circ}\mathrm{N}\) , where ASHSW formation takes place. However, in 2019, four out of five cyclones penetrated north of \(15^{\circ}\mathrm{N}\) , resulting in the largest salinity anomalies." It would be more correct to say that the increase number of TC in 2019 is "coincident" with the largest salinity anomalies: at this step in the MS, you have not clearly proven that the large SSS drop observed is dominantly due to TC- induced freshening's. + +<|ref|>text<|/ref|><|det|>[[172, 583, 884, 638]]<|/det|> +L220: by the "contrasting salinity patterns observed in the Argo data between the 2018 - 19 and 2019 - 20 periods":, do you mean the step decrease in the average SSS after mid 2019 as observed in Fig S4, top panel ? please precise. + +<|ref|>text<|/ref|><|det|>[[172, 656, 884, 730]]<|/det|> +Figure 5: would be nice to add in the time series panel the one of the TC- induced accumulated rain and of the total rain. While indicative, the symbols showing when TC occurred and their increased number is not a direct proof of their impacts on the reported decreased volume of high SSS waters. + +<|ref|>text<|/ref|><|det|>[[172, 748, 884, 841]]<|/det|> +Line 240- 241. You stated: "The volume of high salinity water revealed a notable decline following each cyclone- induced precipitation event (Figure 5e)". This is not true in 2021 where the first cyclone coincides with an increase in the high salinity water volume, nor for the second of the year, which was followed by a relatively stable high salinity volume (Figure 5e). Please correct accordingly. + +<|ref|>text<|/ref|><|det|>[[172, 860, 884, 897]]<|/det|> +Line 312- 313: "With the exception of 2022, the agreement between cyclone- induced precipitation and the intensification of salinity freshening is clear." ...and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[172, 87, 883, 143]]<|/det|> +of 2021". You have not provided any measure of the "cyclone- induced precipitation" with respect total precipitation, so this is a fast conclusion. Please re- phrase. + +<|ref|>text<|/ref|><|det|>[[172, 161, 883, 273]]<|/det|> +L323- 325: "Thus this experiments provide additional confirmation.....are largely attributable to freshwater input from tropical cyclone". No, they provide additional confirmation that the change in Precipitation forcing occurring after 2019 is responsible for the decreasing SSS and subsequent weakening of the convective process. Unless, you extract the relative contribution of TCs to total P, you can not state that firmly. + +<|ref|>text<|/ref|><|det|>[[172, 291, 883, 328]]<|/det|> +L330- 331: can you provide an estimate of the river runoff impacts (see previous comments) + +<|ref|>text<|/ref|><|det|>[[172, 347, 883, 384]]<|/det|> +L349- 350: it is not true each year: in 2021, the salinity tendency difference do not exceed \(0.1 \times 10^{- 3}\) psu.d- 1. Please correct + +<|ref|>text<|/ref|><|det|>[[172, 402, 883, 513]]<|/det|> +L352- 353. In line 336, you claim that due to decrease S with depth in the AS, vertical mixing consistently brings lighter water from below into the mixed layer, so it is confusing to read here that the vertical mixing tends to increase salinity. Please clarify. Is it the difference of vertical mixing between the control and perturbation experiment which is responsible for the increase S (blue curve in Fig 8c)? + +<|ref|>text<|/ref|><|det|>[[172, 532, 883, 570]]<|/det|> +L357- 358: in 2021, the pre- and post monsoon TC do appear to have extended the duration of freshwater input but not their amplitude. + +<|ref|>text<|/ref|><|det|>[[172, 588, 883, 718]]<|/det|> +L361- 368: since the beginning of the MS, you keep claiming that TCs are responsible for the increased P and surface freshening but you explain here that in 2022, there were no TCs and that low pressure system can contribute significantly to the observed freshening. This is very confusing and lead the reader to believe that potentially, other low- pressure systems than TCs can be responsible for the observed freshwater fluxes in other years of 2019- 23. Please clarify by extracting the actual TC- contribution to rainfall. + +<|ref|>sub_title<|/ref|><|det|>[[113, 737, 226, 755]]<|/det|> +## References + +<|ref|>text<|/ref|><|det|>[[111, 784, 883, 910]]<|/det|> +Behara, A., Vinayachandran, P. N., & Shankar, D. (2019). Influence of rainfall over eastern Arabian Sea on its salinity. Journal of Geophysical Research: Oceans, 124, 5003- 5020. https://doi.org/10.1029/2019JC014999Boutin, J., N. Reul, J. Koehler, A. Martin, R. Catany, S. Guimbard, F. Rouffi, et al.. Satellite- Based Sea Surface Salinity Designed for Ocean and Climate Studies. Journal of Geophysical Research. 2021. https://doi.org/10.1029/2021JC017676 + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[111, 87, 886, 168]]<|/det|> +Chaudhuri, D., Sengupta, D., D'Asaro, E., Venkatesan, R., & Ravichandran, M. (2019). Response of the salinity- stratified Bay of Bengal to cyclone Phailin. Journal of Physical Oceanography, 49, 1121- 1140. https://doi.org/10.1175/JPO- D- 18- 0051.1 + +<|ref|>text<|/ref|><|det|>[[111, 179, 886, 260]]<|/det|> +Camberlin, P., Assowe Dabar, O., Pohl, B., Mohamed Waberi, M., Hoarau, K., & Planchon, O. (2024). Contribution of western Arabian Sea tropical cyclones to rainfall in the Horn of Africa and southern Arabian Peninsula. Journal of Geophysical Research: Atmospheres, 129, e2024JD041109. https://doi.org/10.1029/2024JD041109 + +<|ref|>text<|/ref|><|det|>[[111, 271, 886, 332]]<|/det|> +Chen, F. and Y. Fu, (2015) Contribution of tropical cyclone rainfall at categories to total precipitation over the Western North Pacific from 1998 to 2007, Sci. China Earth Sci. 58: 2015. doi:10.1007/s11430- 015- 5103- 9. + +<|ref|>text<|/ref|><|det|>[[111, 343, 885, 423]]<|/det|> +Grodsky, S. A., Reul, N., Lagerloef, G., Reverdin, G., Carton, J. A., Chapron, B., et al. (2012). Haline hurricane wake in the Amazon/Orinoco plume: AQUARIUS/SACD and SMOS observations. Geophysical Research Letters, 39, L20603. https://doi.org/10.1029/2012GL053335 + +<|ref|>text<|/ref|><|det|>[[111, 433, 885, 494]]<|/det|> +Jiang, H. and E.J. Zipser, (2010) Contribution of Tropical Cyclones to the Global Precipitation from Eight Seasons of TRMM Data: Regional, Seasonal, and Interannual Variations. Journal of Climate 23:6, 1526- 1543. + +<|ref|>text<|/ref|><|det|>[[111, 505, 886, 546]]<|/det|> +Jiang, H., C. Liu, and E. D. Zipser (2011), A TRMM- based tropical cyclones cloud and precipitation feature database, J. Appl. Meteorol. Climatol., 50, 1255- 1274. + +<|ref|>text<|/ref|><|det|>[[111, 557, 885, 618]]<|/det|> +Li, B., Zhou, L., Qin, J., & Murtugudde, R. (2022). Increase in intraseasonal rainfall driven by the Arabian Sea warming in recent decades. Geophysical Research Letters, 49, e2022GL100536. https://doi.org/10.1029/2022GL100536 + +<|ref|>text<|/ref|><|det|>[[111, 629, 885, 710]]<|/det|> +Lonfat, M., F. D. Marks, and S. S. Chen, (2004) Precipitation distribution in tropical cyclones using the Tropical Rainfall Measuring Mission (TRMM) microwave imager: A global perspective. Mon. Wea. Rev., 132, 1645- 1660, doi:10.1175/1520- 0493(2004)132,1645:PDITCU.2.0. CO;2. + +<|ref|>text<|/ref|><|det|>[[111, 722, 885, 782]]<|/det|> +Maes, C., and T. J. O'Kane (2014), Seasonal variations of the upper ocean salinity stratification in the Tropics, J. Geophys. Res. Oceans, 119, 1706- 1722, doi:10.1002/2013JC009366. + +<|ref|>text<|/ref|><|det|>[[111, 794, 885, 854]]<|/det|> +Melnichenko. O., 2021. Multi- mission L4 Optimally Interpoated Sea Surface Salinity. Ver. 1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY- MM- DD] at https://doi.org/10.5067/SMP10- 4U7CS + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[110, 85, 886, 606]]<|/det|> +Neethu, C. (2018). Insights into the haline variability induced by cyclone Vardah in the Bay of Bengal using SMAP salinity observations. Remote Sensing Letters, 9(12), 1205- 1213. https://doi.org/10.1080/2150704X.2018.1519271Rao, A. D., M. Joshi, and M. Ravichandran (2009), Observed low- salinity plume off Gulf of Khambhat, India, during post- monsoon period, Geophys. Res. Lett., 36, L03605, doi:10.1029/2008GL036091. Reul, N., Quilfen, Y., Chapron, B., Fournier, S., Kudryavtsev, V., & Sabia, R. (2014). Multisensor observations of the Amazon- Orinoco river plume interactions with hurricanes. Journal of Geophysical Research: Oceans, 119, 8271- 8295. https://doi.org/10.1002/2014JC010107Reul Nicolas, Chapron Bertrand, Grodsky Semyon A., Guimbard Sebastien, Kudryavtsev Vladimir, Foltz Gregory R., Balaguru Karthik (2021). Satellite observations of the sea surface salinity response to tropical cyclones. Geophysical Research Letters, 48(1), e2020GL091478 (10p.).Reul N, Ifremer / LOPS. 2023. Atlas of Tropical Cyclone Induced Wakes (2010- 2020) (v1.0) for ESA Marine Atmosphere eXtreme Satellite Synergy project (MAXSS). Ver. 1.0. Ifremer, Plouzane, France. Dataset accessed [2024- 10- 11].Sun, J.; Vecchi, G.; Soden, B. Sea Surface Salinity Response to Tropical Cyclones Based on Satellite Observations. Remote Sens. 2021, 13, 420. https://doi.org/10.3390/rs13030420Yue, X., Zhang, B., Liu, G., Li, X., Zhang, H., & He, Y. (2018). Upper ocean response to typhoon Kalmaegi and Sarika in the South China sea from Multiple- satellite observations and numerical simulations. Remote Sensing, 10, 348. https://doi.org/10.3390/rs10020348 + +<--- Page Split ---> diff --git a/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..69a96bf6be50dbc4f80e4713a1cf0c2cf173d9ee --- /dev/null +++ b/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,25 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "Figure R1. Characterizations of single-layer CrOCl. (a) Angle-dependent tunneling currents under different external fields. The external field is rotated along an in-plane axis to the \\(c\\) - axis. \\(\\theta\\) is the angle between the external field and the in-plane axis. (b) Tunneling current", + "footnote": [], + "bbox": [], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/Figure_unknown_1.jpg", + "caption": "Figure R2. Magnetoelectric coupling in a single-layer CrOCl tunneling device (device 2). (a) \\(I - B\\) curve of the CrOCl tunneling device at \\(2 \\mathrm{K}\\) with the external field along with the \\(a\\) - axis. The pink curve shows the differential current \\(\\delta I = I(B_{\\mathrm{down}}) - I(B_{\\mathrm{up}})\\) . The critical field where \\(\\delta I\\) reaches a maximum is annotated by the black arrow. (b, c) Tunneling current (b) after alternating electric and magnetic excitations. The corresponding magnetic and electric fields versus time are plotted in (c). The device was parallel-connected with a \\(10 \\mathrm{M}\\Omega\\) protection resistor.", + "footnote": [], + "bbox": [ + [ + 147, + 359, + 852, + 502 + ] + ], + "page_idx": 4 + } +] \ No newline at end of file diff --git a/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..c36610884f732bab7c9fa8657fe572b27b14c89c --- /dev/null +++ b/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,101 @@ + +# nature portfolio + +Peer Review File + +Multi- state Data Storage in a Two- dimensional Stripy Antiferromagnet Implemented by Magnetoelectric Effect + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. Mentions of prior referee reports have been redacted. + +Reviewers' Comments: + +Reviewer #1: + +Remarks to the Author: + +First of all, I would like to thank the authors for their careful and extensive answers to my questions (also questions from the other two reviewers). Overall, the manuscript presents an interesting magnetoelectric (ME) coupling in 2D CrOCl, where electric field can be used to control the magnetic order. Therefore, I support the publication of the paper. + +Regarding some details of the reply, however, I would like to give some replies to the authors and perhaps also give some suggestions about how to improve the manuscript. I don't think the authors have presented direct evidence for the antiferroelectric (AFE) order. Only the two fold lattice distortion has been previously observed by neutron and XRD. But the two fold lattice distortion is only a prerequisite for the AFE order. The AFE order itself, remains to be directly confirmed. On the other hand, I don't think the AFE order is crucial for the key experimental observations, which is the ME coupling, i.e., electric field can directly control the magnetism in 2D CrOCl. I understand that, in the current understanding, the authors need the AFE order to explain the mechanism for the ME coupling: the authors believe that E- field couples to the AFE order, which in turn couples to the magnetism. However, to me, that is only an interpretation not a direct observation. Therefore, I suggest them to tone down their claim of the AFE order. They can focus on presenting their observations of how E and B fields control the magnetic order. Then they can suggest that the observed ME coupling is due to the existence of an AFE order. Overall, the authors should think more carefully what are their direct observations, what are their interpretations, etc, and adjust their presentations accordingly. This can help them to highlight their pure experimental data observations, which I believe is already interesting and striking enough and deserves to be published in a prestigious journal. + +Reviewer #2: + +Remarks to the Author: + +Authors have revised the manuscript where the arguments are now much better supported by additional experimental and theoretical evidences. The magnetoelectric effects are clearly presented, and a demonstration of the multi- state data storage implemented by the ME effect is unique and hence guarantees the novelty of this work. Authors emphasized that the single layer SrOCl also host essentially the same phenomena, which could be also important. By the way, the explanation about the sample characterization is missing. How do authors confirm the single layer thickness? Furthermore, a comparison with thicker SrOCl will be also important. Are the magnetic and electric states maintained the same for the single layer SrOCl? And, would the explanation about the observed phenomena remain the same? I believe that the manuscript will be acceptable after adding the discussion about the single layer SrOCl. + +<--- Page Split ---> + +## Responses to Reviewer #1 + +Comment: First of all, I would like to thank the authors for their careful and extensive answers to my questions (also questions from the other two reviewers). Overall, the manuscript presents an interesting magnetoelectric (ME) coupling in 2D CrOCl, where electric field can be used to control the magnetic order. Therefore, I support the publication of the paper. + +Response: We thank the reviewer for her/his careful reading and positive evaluations and are glad that the reviewer supports the publication of our paper. According to the reviewer's suggestions, we have revised our manuscript and provided the response in the following. + +Comment: Regarding some details of the reply, however, I would like to give some replies to the authors and perhaps also give some suggestions about how to improve the manuscript. I don't think the authors have presented direct evidence for the antiferroelectric (AFE) order. Only the two fold lattice distortion has been previously observed by neutron and XRD. But the two fold lattice distortion is only a prerequisite for the AFE order. The AFE order itself, remains to be directly confirmed. On the other hand, I don't think the AFE order is crucial for the key experimental observations, which is the ME coupling, i.e., electric field can directly control the magnetism in 2D CrOCl. I understand that, in the current understanding, the authors need the AFE order to explain the mechanism for the ME coupling: the authors believe that E- field couples to the AFE order, which in turn couples to the magnetism. However, to me, that is only an interpretation not a direct observation. Therefore, I suggest them to tone down their claim of the AFE order. They can focus on presenting their observations of how E and B fields control the magnetic order. Then they can suggest that the observed ME coupling is due to the existence of an AFE order. Overall, the authors should think more carefully what are their direct observations, what are their interpretations, etc, and adjust their presentations accordingly. This can help them to highlight their pure experimental data observations, which I believe is already interesting and striking enough and deserves to be published in a prestigious journal. + +Response: We sincerely appreciate the reviewer's suggestion, which is really helpful + +<--- Page Split ---> + +for the rigor of our paper. As the reviewer has pointed out, the observation of the twofold lattice distortion doesn’t guarantee that the external field can generate a net polarization by tilting the antiferroelectric dipoles. Our central experimental observation is that the structural phase transition makes an additional contribution to the dielectric constant, which gives rise to tunable resistance states coupled to the magnetic phase transition. The phenomenological picture that the external electric field adjust the resistance states by tilting the antiferroelectric dipoles, while seemingly the most plausible explanation, remains to be directly confirmed by future high-resolution structural characterizations. Meanwhile, other analogous mechanisms such as the enhancement of the electron orbital polarization in the structural distorted phase may also lead to the additional net polarization and account for the magnetoelectric coupling effect. In the revised manuscript, we have weakened the demonstration of the tunability of AFE dipoles and discuss the possible explanations mainly based on purely experimental observations. We hope the revised manuscript will be satisfactory for publication. + +<--- Page Split ---> + +## Responses to Reviewer #2 + +Comments: Authors have revised the manuscript where the arguments are now much better supported by additional experimental and theoretical evidences. The magnetoelectric effects are clearly presented, and a demonstration of the multi- state data storage implemented by the ME effect is unique and hence guarantees the novelty of this work. Authors emphasized that the single layer SrOCl also host essentially the same phenomena, which could be also important. By the way, the explanation about the sample characterization is missing. How do authors confirm the single layer thickness? Furthermore, a comparison with thicker SrOCl will be also important. Are the magnetic and electric states maintained the same for the single layer SrOCl? And, would the explanation about the observed phenomena remain the same? I believe that the manuscript will be acceptable after adding the discussion about the single layer SrOCl. + +Response: We thank the reviewer for her/his careful reading and positive evaluations. According to the reviewer's concerns about single- layer CrOCl, we provide the experimental data and discussions in the following. + +![](images/Figure_unknown_1.jpg) + +
Figure R1. Characterizations of single-layer CrOCl. (a) Angle-dependent tunneling currents under different external fields. The external field is rotated along an in-plane axis to the \(c\) - axis. \(\theta\) is the angle between the external field and the in-plane axis. (b) Tunneling current
+ +<--- Page Split ---> + +versus the external field along the \(c\) - axis. The transition fields of CrOCl are labelled by the black arrows, where \(H_{1}\) and \(H_{2}\) mark the beginning and the end of the spin- flop transition and \(H_{3}\) marks the transition to the \(\uparrow \uparrow \uparrow \downarrow\) phase. The inset shows the atomic force microscope height image of the exfoliated single- layer CrOCl. The black scale bar is \(1\mu \mathrm{m}\) . (c) The tunneling current on the dependence of the in- plane field direction at different external fields. (d) Tunneling current versus in- plane field as the field points towards different in- plane directions. The transition field gradually increases as the external field deviates from the \(a\) - axis. All the data were obtained in the single- layer tunneling device (device 2 in the manuscript) with a bias voltage of \(-0.018\mathrm{V}\) . + +We identified the exfoliated single- layer CrOCl by atomic force microscopy. An atomic force microscopy height image of a single- layer CrOCl flake which was used to construct the tunneling device (device 2 in the manuscript) is shown in the inset of Fig. R1b. The thickness of the flake is \(\sim 0.7\mathrm{nm}\) , in accordance with the DFT calculations \(^{1,2}\) of the layer distance and the previous report \(^{3}\) . In order to confirm that the magnetic ground state of CrOCl persists down to the monolayer, we performed a series of tunneling current measurements similar to the multi- layer devices. The measured data of device 2 (the same single- layer device as in the manuscript) is presented in Fig. R1. As shown in Fig. R1a, when the external field was rotated from an in- plane axis to the \(c\) - axis, the tunneling current shows a \(180^{\circ}\) periodic symmetry. The magnetic phase transitions occur at the lowest field when the external field points to the \(c\) - axis, evidencing that the easy axis of single- layer CrOCl is still out- of- plane. The \(I - B\) curve under the out- of- plane field is shown in Fig. R1b, where the spin- flop transition and the transition to the \(\uparrow \uparrow \uparrow \downarrow\) phase can be clearly resolved. The transition fields are labelled as \(H_{1}\) , \(H_{2}\) and \(H_{3}\) , which mark the beginning, the end of the spin- flop transition and the transition to the \(\uparrow \uparrow \uparrow \downarrow\) phase, respectively. The values of the transition fields are also close to our previous results of the multi- layer tunneling devices \(^{4}\) . + +The response of the tunneling current to the in- plane field was also measured, presented in Fig. R1c and d. When the external field is rotated in the \(ab\) - plane of the sample, the tunneling current shows an exactly \(180^{\circ}\) periodic symmetry (Fig. R1c). + +<--- Page Split ---> + +This evidences the persistence of the \(C_2\) in- plane symmetry of single- layer CrOCl, characteristic of the one- dimensional stripy magnetic order. When the field points to the \(a\) - axis, the transition to the \(a - \uparrow \uparrow \uparrow \downarrow \downarrow\) phase occurs at \(\sim 5.5 \mathrm{T}\) and when the field direction rotates toward the \(b\) - axis, the transition field gradually increases and finally vanishes in our measurable field range. In summary, all the transition behaviors of the single- layer CrOCl are consistent with the reported multi- layer samples4. Our DFT calculations of the magnetic ground state and the resulted atomic distortions are also performed both in bulk and single- layer CrOCl and obtained the same results (shown in Fig. S1 in the Supplementary Information). Consequently, we conclude that the magnetic order, as well as the spin- induced electric transition, maintains the same for single- layer CrOCl. + +![PLACEHOLDER_6_0] + +
Figure R2. Magnetoelectric coupling in a single-layer CrOCl tunneling device (device 2). (a) \(I - B\) curve of the CrOCl tunneling device at \(2 \mathrm{K}\) with the external field along with the \(a\) - axis. The pink curve shows the differential current \(\delta I = I(B_{\mathrm{down}}) - I(B_{\mathrm{up}})\) . The critical field where \(\delta I\) reaches a maximum is annotated by the black arrow. (b, c) Tunneling current (b) after alternating electric and magnetic excitations. The corresponding magnetic and electric fields versus time are plotted in (c). The device was parallel-connected with a \(10 \mathrm{M}\Omega\) protection resistor.
+ +The manipulation of the electric states in single- layer CrOCl is presented in Fig. R2. Similar to the multi- layer device reported in the manuscript, we obtained the maximum hysteresis at \(B_0 = 5.72 \mathrm{T}\) by subtracting the current of the \(B\) - up curve from that of the \(B\) - down curve. Likewise, by alternately applying the magnetic and electric excitations, we can repeatedly realize the manipulation of the resistance state between two values, \(225.5 \mathrm{k}\Omega\) and \(227.5 \mathrm{k}\Omega\) . As a result, the same operation principles, as well as the microscopic mechanisms, apply to single- layer CrOCl. The only distinction is that in the single- layer device, the difference between the highest and lowest resistance states is lower, so it is difficult to realize multi- level resistance in a single device. This is probably caused by two reasons. Firstly, the tunneling + +<--- Page Split ---> + +barrier of the single- layer CrOCl is much thinner, naturally resulting in lower magnetoresistance. Secondly, the electric dipoles in a monolayer can only host in- plane interactions with each other in the absence of neighboring layers, which may produce less metastable states during the phase transition. Nevertheless, the underlying physical picture remains the same. The characterizations of the single- layer CrOCl device, together with the discussion on the magnetoelectric coupling effect, have now been added to the revised Supplementary Information, and the manuscript has been revised correspondingly. + +<--- Page Split ---> + +Reviewers' Comments: + +Reviewer #1: Remarks to the Author: I wish to thank the authors for their answers. All my questions are addressed. I support publication. + +Reviewer #2: Remarks to the Author: Authors replied my comments satisfactorily, and revised the manuscript accordingly. I now recommend the publication of this nice work in Nature Communications. + +<--- Page Split ---> + +## Responses to Reviewers + +Reviewer #1: "I wish to thank the authors for their answers. All my questions are addressed. I support publication." + +Reviewer #2: "Authors replied my comments satisfactorily, and revised the manuscript accordingly. I now recommend the publication of this nice work in Nature Communications." + +Responses: We are glad that all reviewers are satisfied with the revision and agree to publish our work in Nature Communications. We would like to sincerely thank the reviewers, as our manuscript has been improved a lot thanks to the constructive comments from them. All their concerns are crucial for improving the quality and scientific rigor of our work. + +<--- Page Split ---> diff --git a/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..7bcd2898e6be3cd513427f04a17c752cc177844c --- /dev/null +++ b/peer_reviews/df738d4229ceb6412dcb4fd7f9d79f0113f20a36b46704dba697f058765fa750/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,125 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[70, 111, 362, 140]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[70, 155, 857, 212]]<|/det|> +Multi- state Data Storage in a Two- dimensional Stripy Antiferromagnet Implemented by Magnetoelectric Effect + +<|ref|>image<|/ref|><|det|>[[57, 732, 239, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 911, 784]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 880, 151]]<|/det|> +Editorial Note: This manuscript has been previously reviewed at another journal that is not operating a transparent peer review scheme. This document only contains reviewer comments and rebuttal letters for versions considered at Nature Communications. Mentions of prior referee reports have been redacted. + +<|ref|>text<|/ref|><|det|>[[119, 189, 295, 202]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[118, 217, 219, 230]]<|/det|> +Reviewer #1: + +<|ref|>text<|/ref|><|det|>[[118, 231, 300, 244]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[118, 245, 866, 301]]<|/det|> +First of all, I would like to thank the authors for their careful and extensive answers to my questions (also questions from the other two reviewers). Overall, the manuscript presents an interesting magnetoelectric (ME) coupling in 2D CrOCl, where electric field can be used to control the magnetic order. Therefore, I support the publication of the paper. + +<|ref|>text<|/ref|><|det|>[[116, 314, 878, 555]]<|/det|> +Regarding some details of the reply, however, I would like to give some replies to the authors and perhaps also give some suggestions about how to improve the manuscript. I don't think the authors have presented direct evidence for the antiferroelectric (AFE) order. Only the two fold lattice distortion has been previously observed by neutron and XRD. But the two fold lattice distortion is only a prerequisite for the AFE order. The AFE order itself, remains to be directly confirmed. On the other hand, I don't think the AFE order is crucial for the key experimental observations, which is the ME coupling, i.e., electric field can directly control the magnetism in 2D CrOCl. I understand that, in the current understanding, the authors need the AFE order to explain the mechanism for the ME coupling: the authors believe that E- field couples to the AFE order, which in turn couples to the magnetism. However, to me, that is only an interpretation not a direct observation. Therefore, I suggest them to tone down their claim of the AFE order. They can focus on presenting their observations of how E and B fields control the magnetic order. Then they can suggest that the observed ME coupling is due to the existence of an AFE order. Overall, the authors should think more carefully what are their direct observations, what are their interpretations, etc, and adjust their presentations accordingly. This can help them to highlight their pure experimental data observations, which I believe is already interesting and striking enough and deserves to be published in a prestigious journal. + +<|ref|>text<|/ref|><|det|>[[118, 596, 222, 608]]<|/det|> +Reviewer #2: + +<|ref|>text<|/ref|><|det|>[[118, 610, 300, 622]]<|/det|> +Remarks to the Author: + +<|ref|>text<|/ref|><|det|>[[117, 623, 872, 764]]<|/det|> +Authors have revised the manuscript where the arguments are now much better supported by additional experimental and theoretical evidences. The magnetoelectric effects are clearly presented, and a demonstration of the multi- state data storage implemented by the ME effect is unique and hence guarantees the novelty of this work. Authors emphasized that the single layer SrOCl also host essentially the same phenomena, which could be also important. By the way, the explanation about the sample characterization is missing. How do authors confirm the single layer thickness? Furthermore, a comparison with thicker SrOCl will be also important. Are the magnetic and electric states maintained the same for the single layer SrOCl? And, would the explanation about the observed phenomena remain the same? I believe that the manuscript will be acceptable after adding the discussion about the single layer SrOCl. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 84, 370, 101]]<|/det|> +## Responses to Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[147, 114, 844, 234]]<|/det|> +Comment: First of all, I would like to thank the authors for their careful and extensive answers to my questions (also questions from the other two reviewers). Overall, the manuscript presents an interesting magnetoelectric (ME) coupling in 2D CrOCl, where electric field can be used to control the magnetic order. Therefore, I support the publication of the paper. + +<|ref|>text<|/ref|><|det|>[[147, 245, 842, 338]]<|/det|> +Response: We thank the reviewer for her/his careful reading and positive evaluations and are glad that the reviewer supports the publication of our paper. According to the reviewer's suggestions, we have revised our manuscript and provided the response in the following. + +<|ref|>text<|/ref|><|det|>[[145, 380, 847, 870]]<|/det|> +Comment: Regarding some details of the reply, however, I would like to give some replies to the authors and perhaps also give some suggestions about how to improve the manuscript. I don't think the authors have presented direct evidence for the antiferroelectric (AFE) order. Only the two fold lattice distortion has been previously observed by neutron and XRD. But the two fold lattice distortion is only a prerequisite for the AFE order. The AFE order itself, remains to be directly confirmed. On the other hand, I don't think the AFE order is crucial for the key experimental observations, which is the ME coupling, i.e., electric field can directly control the magnetism in 2D CrOCl. I understand that, in the current understanding, the authors need the AFE order to explain the mechanism for the ME coupling: the authors believe that E- field couples to the AFE order, which in turn couples to the magnetism. However, to me, that is only an interpretation not a direct observation. Therefore, I suggest them to tone down their claim of the AFE order. They can focus on presenting their observations of how E and B fields control the magnetic order. Then they can suggest that the observed ME coupling is due to the existence of an AFE order. Overall, the authors should think more carefully what are their direct observations, what are their interpretations, etc, and adjust their presentations accordingly. This can help them to highlight their pure experimental data observations, which I believe is already interesting and striking enough and deserves to be published in a prestigious journal. + +<|ref|>text<|/ref|><|det|>[[145, 881, 837, 900]]<|/det|> +Response: We sincerely appreciate the reviewer's suggestion, which is really helpful + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 83, 844, 448]]<|/det|> +for the rigor of our paper. As the reviewer has pointed out, the observation of the twofold lattice distortion doesn’t guarantee that the external field can generate a net polarization by tilting the antiferroelectric dipoles. Our central experimental observation is that the structural phase transition makes an additional contribution to the dielectric constant, which gives rise to tunable resistance states coupled to the magnetic phase transition. The phenomenological picture that the external electric field adjust the resistance states by tilting the antiferroelectric dipoles, while seemingly the most plausible explanation, remains to be directly confirmed by future high-resolution structural characterizations. Meanwhile, other analogous mechanisms such as the enhancement of the electron orbital polarization in the structural distorted phase may also lead to the additional net polarization and account for the magnetoelectric coupling effect. In the revised manuscript, we have weakened the demonstration of the tunability of AFE dipoles and discuss the possible explanations mainly based on purely experimental observations. We hope the revised manuscript will be satisfactory for publication. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 84, 372, 101]]<|/det|> +## Responses to Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[147, 114, 844, 405]]<|/det|> +Comments: Authors have revised the manuscript where the arguments are now much better supported by additional experimental and theoretical evidences. The magnetoelectric effects are clearly presented, and a demonstration of the multi- state data storage implemented by the ME effect is unique and hence guarantees the novelty of this work. Authors emphasized that the single layer SrOCl also host essentially the same phenomena, which could be also important. By the way, the explanation about the sample characterization is missing. How do authors confirm the single layer thickness? Furthermore, a comparison with thicker SrOCl will be also important. Are the magnetic and electric states maintained the same for the single layer SrOCl? And, would the explanation about the observed phenomena remain the same? I believe that the manuscript will be acceptable after adding the discussion about the single layer SrOCl. + +<|ref|>text<|/ref|><|det|>[[147, 416, 844, 485]]<|/det|> +Response: We thank the reviewer for her/his careful reading and positive evaluations. According to the reviewer's concerns about single- layer CrOCl, we provide the experimental data and discussions in the following. + +<|ref|>image<|/ref|><|det|>[[186, 497, 812, 850]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 866, 831, 914]]<|/det|> +
Figure R1. Characterizations of single-layer CrOCl. (a) Angle-dependent tunneling currents under different external fields. The external field is rotated along an in-plane axis to the \(c\) - axis. \(\theta\) is the angle between the external field and the in-plane axis. (b) Tunneling current
+ +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 83, 848, 222]]<|/det|> +versus the external field along the \(c\) - axis. The transition fields of CrOCl are labelled by the black arrows, where \(H_{1}\) and \(H_{2}\) mark the beginning and the end of the spin- flop transition and \(H_{3}\) marks the transition to the \(\uparrow \uparrow \uparrow \downarrow\) phase. The inset shows the atomic force microscope height image of the exfoliated single- layer CrOCl. The black scale bar is \(1\mu \mathrm{m}\) . (c) The tunneling current on the dependence of the in- plane field direction at different external fields. (d) Tunneling current versus in- plane field as the field points towards different in- plane directions. The transition field gradually increases as the external field deviates from the \(a\) - axis. All the data were obtained in the single- layer tunneling device (device 2 in the manuscript) with a bias voltage of \(-0.018\mathrm{V}\) . + +<|ref|>text<|/ref|><|det|>[[147, 248, 844, 688]]<|/det|> +We identified the exfoliated single- layer CrOCl by atomic force microscopy. An atomic force microscopy height image of a single- layer CrOCl flake which was used to construct the tunneling device (device 2 in the manuscript) is shown in the inset of Fig. R1b. The thickness of the flake is \(\sim 0.7\mathrm{nm}\) , in accordance with the DFT calculations \(^{1,2}\) of the layer distance and the previous report \(^{3}\) . In order to confirm that the magnetic ground state of CrOCl persists down to the monolayer, we performed a series of tunneling current measurements similar to the multi- layer devices. The measured data of device 2 (the same single- layer device as in the manuscript) is presented in Fig. R1. As shown in Fig. R1a, when the external field was rotated from an in- plane axis to the \(c\) - axis, the tunneling current shows a \(180^{\circ}\) periodic symmetry. The magnetic phase transitions occur at the lowest field when the external field points to the \(c\) - axis, evidencing that the easy axis of single- layer CrOCl is still out- of- plane. The \(I - B\) curve under the out- of- plane field is shown in Fig. R1b, where the spin- flop transition and the transition to the \(\uparrow \uparrow \uparrow \downarrow\) phase can be clearly resolved. The transition fields are labelled as \(H_{1}\) , \(H_{2}\) and \(H_{3}\) , which mark the beginning, the end of the spin- flop transition and the transition to the \(\uparrow \uparrow \uparrow \downarrow\) phase, respectively. The values of the transition fields are also close to our previous results of the multi- layer tunneling devices \(^{4}\) . + +<|ref|>text<|/ref|><|det|>[[148, 700, 831, 769]]<|/det|> +The response of the tunneling current to the in- plane field was also measured, presented in Fig. R1c and d. When the external field is rotated in the \(ab\) - plane of the sample, the tunneling current shows an exactly \(180^{\circ}\) periodic symmetry (Fig. R1c). + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 82, 847, 348]]<|/det|> +This evidences the persistence of the \(C_2\) in- plane symmetry of single- layer CrOCl, characteristic of the one- dimensional stripy magnetic order. When the field points to the \(a\) - axis, the transition to the \(a - \uparrow \uparrow \uparrow \downarrow \downarrow\) phase occurs at \(\sim 5.5 \mathrm{T}\) and when the field direction rotates toward the \(b\) - axis, the transition field gradually increases and finally vanishes in our measurable field range. In summary, all the transition behaviors of the single- layer CrOCl are consistent with the reported multi- layer samples4. Our DFT calculations of the magnetic ground state and the resulted atomic distortions are also performed both in bulk and single- layer CrOCl and obtained the same results (shown in Fig. S1 in the Supplementary Information). Consequently, we conclude that the magnetic order, as well as the spin- induced electric transition, maintains the same for single- layer CrOCl. + +<|ref|>image<|/ref|><|det|>[[147, 359, 852, 502]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[147, 518, 846, 630]]<|/det|> +
Figure R2. Magnetoelectric coupling in a single-layer CrOCl tunneling device (device 2). (a) \(I - B\) curve of the CrOCl tunneling device at \(2 \mathrm{K}\) with the external field along with the \(a\) - axis. The pink curve shows the differential current \(\delta I = I(B_{\mathrm{down}}) - I(B_{\mathrm{up}})\) . The critical field where \(\delta I\) reaches a maximum is annotated by the black arrow. (b, c) Tunneling current (b) after alternating electric and magnetic excitations. The corresponding magnetic and electric fields versus time are plotted in (c). The device was parallel-connected with a \(10 \mathrm{M}\Omega\) protection resistor.
+ +<|ref|>text<|/ref|><|det|>[[147, 655, 840, 898]]<|/det|> +The manipulation of the electric states in single- layer CrOCl is presented in Fig. R2. Similar to the multi- layer device reported in the manuscript, we obtained the maximum hysteresis at \(B_0 = 5.72 \mathrm{T}\) by subtracting the current of the \(B\) - up curve from that of the \(B\) - down curve. Likewise, by alternately applying the magnetic and electric excitations, we can repeatedly realize the manipulation of the resistance state between two values, \(225.5 \mathrm{k}\Omega\) and \(227.5 \mathrm{k}\Omega\) . As a result, the same operation principles, as well as the microscopic mechanisms, apply to single- layer CrOCl. The only distinction is that in the single- layer device, the difference between the highest and lowest resistance states is lower, so it is difficult to realize multi- level resistance in a single device. This is probably caused by two reasons. Firstly, the tunneling + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 82, 821, 275]]<|/det|> +barrier of the single- layer CrOCl is much thinner, naturally resulting in lower magnetoresistance. Secondly, the electric dipoles in a monolayer can only host in- plane interactions with each other in the absence of neighboring layers, which may produce less metastable states during the phase transition. Nevertheless, the underlying physical picture remains the same. The characterizations of the single- layer CrOCl device, together with the discussion on the magnetoelectric coupling effect, have now been added to the revised Supplementary Information, and the manuscript has been revised correspondingly. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 294, 97]]<|/det|> +Reviewers' Comments: + +<|ref|>text<|/ref|><|det|>[[118, 112, 792, 169]]<|/det|> +Reviewer #1: Remarks to the Author: I wish to thank the authors for their answers. All my questions are addressed. I support publication. + +<|ref|>text<|/ref|><|det|>[[118, 209, 810, 265]]<|/det|> +Reviewer #2: Remarks to the Author: Authors replied my comments satisfactorily, and revised the manuscript accordingly. I now recommend the publication of this nice work in Nature Communications. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[388, 86, 609, 105]]<|/det|> +## Responses to Reviewers + +<|ref|>text<|/ref|><|det|>[[178, 129, 820, 168]]<|/det|> +Reviewer #1: "I wish to thank the authors for their answers. All my questions are addressed. I support publication." + +<|ref|>text<|/ref|><|det|>[[178, 192, 823, 231]]<|/det|> +Reviewer #2: "Authors replied my comments satisfactorily, and revised the manuscript accordingly. I now recommend the publication of this nice work in Nature Communications." + +<|ref|>text<|/ref|><|det|>[[178, 256, 824, 339]]<|/det|> +Responses: We are glad that all reviewers are satisfied with the revision and agree to publish our work in Nature Communications. We would like to sincerely thank the reviewers, as our manuscript has been improved a lot thanks to the constructive comments from them. All their concerns are crucial for improving the quality and scientific rigor of our work. + +<--- Page Split ---> diff --git a/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/images_list.json b/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/images_list.json new file mode 100644 index 0000000000000000000000000000000000000000..dd0dc38d9738ab3ac41b9540abc2d13e83baf35d --- /dev/null +++ b/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/images_list.json @@ -0,0 +1,10 @@ +[ + { + "type": "image", + "img_path": "images/Figure_unknown_0.jpg", + "caption": "G", + "footnote": [], + "bbox": [], + "page_idx": 0 + } +] \ No newline at end of file diff --git a/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd b/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9a81d3266c25afad16f231099a5ccb6496241956 --- /dev/null +++ b/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/supplementary_0_Peer Review File.mmd @@ -0,0 +1,1006 @@ + +# nature portfolio + +Peer Review File + +CLK2 mediates IkBα- independent early termination of NF- kB activation by inducing cytoplasmic redistribution and degradation + +![](images/Figure_unknown_0.jpg) + + +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> + +Editorial Note: Parts of this Peer Review File have been redacted as indicated to remove third- party material where no permission to publish could be obtained. + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +The major finding of this manuscript is the identification of the NF- kB p65 subunit as a target of CLK2. Phosphorylation of p65 at Ser- 180 leads to nuclear export and degradation. This finding uncovers a new substrate for CLK2, a kinase previously found to modify splicing factors. Most importantly this manuscript discovers a new mechanism for negative feedback of p65- driven gene expression that is proposed to be independent of the well- known p65- dependent production of the IkBalpha inhibitor. The authors use complimentary approaches to demonstrate that loss of CLK2, CLK2 kinase function, or p65 Ser- 180 phosphorylation leads to a gain of interferon and inflammatory responses that have functional impacts on virus control and inflammatory pathologies, in cell culture and in mouse models. The parsing of main figure and supplementary figures is appropriate. That being said, there a few holes in their data that should be addressed to bolster CLK2 as the direct p65 kinase that functions prior to and independently of IkBa. + +## Major issues: + +1. They indicate that CLK2 is an early terminator of NF-kB signaling via p65 on Ser180 and independent of IkBa- but there are some discrepancies with this interpretation. +a. Most assays are at 6, 12, or 24 hrs post-stim, well-after IkBa is typically transcriptionally induced by p65. Is there clear data showing two waves of inhibition? Does IkBa ever function in the absence of CLK2 or does CLK2 dominate? +b. Does the phosphorylation change of p65 in response to CLK2 impact the ability of p65 to be bound by IkBa? If p65 is no longer recognized by IkBa in the absence of CLK2 modifications then that could lead to an accumulation of p65 in the nucleus and increased transcriptional activity. p65 S180A is a mutant that can't be phosphorylated downstream of CLK2 and has a prolonged residence in the nucleus (Fig 6), but how is the role of IkBa excluded? Do any of the phosphorylation site mutants impact targeting by IkBa? + +2. Is CLK2 the sole kinase and what activates it? + +a. They identify multiple phosphorylation sites but there is never an in vitro analysis with purified CLK2 protein. As it stands now- CLK2 is certainly an upstream kinase- but given IP is performed in HEK293T - CLK2 might be acting via another kinase? Does the CLK2 inhibitor TG003 block phosphorylation of Ser 180 on p65 or any other site? + +b. In Fig 6D, the SeV infected CLK2-/- have lower levels of phospho Ser180 p65 overall, but it is not eliminated. What kinase drives this remaining phosphorylation? What does the asterisk/upper band indicate in the western blots? + +c. This CLK2-mediated inhibition is only observed upon stimulation- so what is activating CLK2? + +3. There is a an overinterpretation that PML-associated p65 is more transcriptionally active. The PML colocalization and phase separation data is not well developed, being performed in the context of overexpression- it raises more questions than answers. Consider removing. + +4. A major flaw in the publication is the poor quality of writing. Professional editing is essential. There were numerous grammatical errors and improper word choices (e.g. 'we wonder CLK2 may be a pregnant target to treat inflammation-associated diseases and virus infection') that make it nearly impossible for the reader to work through. This did detract from my understanding of some of their summaries and interpretations. + +## Minor issues: + +1. Fig 2B. The PCR genotyping data for WT vs KO mice seems swapped. +2. Supp Fig 3 and Fig 5. have an odd arrangement of figures where the letters are not in alphabetical order. +3. The font kerning for the sequence alignment of Fig 5B is off. A monospace font is needed. +4. Fig 6 Figure legend states data are presented as SEM- but that type of data is not in the figure. +5. Information on the strain and source of SeV, VSV, and HSV virus stocks is lacking. + +<--- Page Split ---> + +Reviewer #2 (Remarks to the Author): + +The manuscript entitled "CLK2- mediated IkappaBalpha- independent early- termination of NF- kappaB activation by phosphorylating nuclear- p65 for cytoplasmic redistribution and degradation" by Shang- Ze Li and colleagues describes the identification of a novel regulatory phosphorylation site (ser180) of the NF- kappaB sub- unit p65/RelA, target of the CLK2 kinase. CLK2 phosphorylation of p65 at ser180 by cytokine treatment or viral infection leads to increased p65 accumulation in the cytoplasm, and p65 proteasome- mediated degradation. Using knock- in phosphomimetic aspartic acid substitution of ser180 a decreased p65 activity is revealed compared to wt protein, following different stimuli, and also increased viral replication. On the contrary, substitution of ser180 with alanine, determining the inability of p65 to be phosphorylated by CLK2 at this residue, results in a "super- active" protein, capable of conferring resistance to viral infection in the knock- in cellular system. Moreover, CLK2 genetic ablation or its chemical inhibition promoted chronic inflammation in a mouse psoriasis model. Authors discussed CLK- 2 mediated p65 phosphorylation at ser180 as an early NF- kappaB shutdown pathway, alternative to the canonical feed- back regulatory mechanism represented by the NF- kappaB- mediated synthesis of IkappaB- alpha occurring later after stimulation. The CLK- 2 mediated phosphorylation of p65 and the subsequent inhibition of the activity of this transcription factor, represent important and novel findings, adding another important piece of information about how NF- kappaB, one of the most studied transcription factor, works. That being said, the manuscript, despite a large number of data gathered, lacks key experiments, and is misleading regarding some data interpretation. Moreover, an extensive revision for English language and grammar is required. + +Moreover, an extensive revision for English language and grammar is required. + +## Specific comments: + +## 1-Introduction section. + +Introduction section is lacking the description of other important phosphorylation sites identified on p65 (by the way, naming this transcription factor as RelA is more appropriate). Among these, ser276, known to enhance NF- kappaB transcriptional activity, or ser468, negatively regulating NF- kappaB mediated transcription (for a review see "Posttranslational modifications of NF- kB: another layer of regulation for NF- kB signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017), the latter highly relevant in the context of this manuscript and used in fig. 6D and E panels. Moreover, the paper by Saccani S. et al. "Degradation of Promoter- bound p65/RelA Is Essential for the Prompt Termination of the Nuclear Factor B Response" (J. Exp. Med. Volume 200, Number 1, July 5, 2004 107- 113. doi: 10.1084/jem.20040196) must be acknowledged, due to fact that it describes p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. In the same paper, if proteasome activity is blocked after an activating stimulus, NF- kappaB is not rapidly removed from target genes despite IkappaB synthesis, resulting in sustained transcription. Such paper describes a very similar mechanism of NF- kappaB "shutdown" and cannot be ignored. Finally, Lys 310 acetylation, required for full RelA transcriptional activity, should not be described without acknowledging the fact that it happens subsequently to the prior phosphorylation of RelA at ser276 and ser536 (Chen LF, et al. "NF- kappaB RelA phosphorylation regulates RelA acetylation". Mol Cell Biol. 2005 Sep;25(18):7966- 75. doi: 10.1128/MCB.25.18.7966- 7975.2005). What does "CLK2" stand for? Full name (Cdc2- like kinase 2) must be present, at least the first time CLK2 is described in the introduction section. + +## 2- Fig.1 + +In the description of panel D, authors explain that they have used an ISRE reporter responding to SeV infection, to assess the impact of CLK2 on IRF- 3, to rule out IRF- 3 as a CLK2 target in IFN- beta promoter repression. However, authors did not provide evidence in the material and methods section about what specific ISRE sequence they have used in the reporter construct (indeed some commercially available ISRE reporter constructs also respond to IFN- I- induced ISGF3). In order for the authors to state that in fig. 1D they are dealing with IRF- 3 mediated stimulation, they have to use the transfection of a plasmid constitutively expressing an active form of IRF- 3, like IRF- 3 5D (Lin R. et al. Essential Role of Interferon Regulatory Factor 3 in Direct Activation of RANTES Chemokine Transcription. Mol Cell Biol. 1999 Feb; 19(2): 959- 966. doi: 10.1128/mcb.19.2.959), as a control, comparing the fold of activation obtained to those reached with SeV infection. + +<--- Page Split ---> + +In Fig.1H error bars should be present in the graphs accounting for the three separate experiments, while the right western blot panel (showing TNF- alpha time course) should not present a GAPDH blot with such a poor separation between each band, clearly the result of excessive protein loading and/or overexposure. + +## 3- Supplementary Fig.1. + +Looking at panel 1D, it seems that CLK2 expression is actually negatively affected in p65 knock- out cells compared to wt cells, therefore the authors' conclusion, that CLK2 is not that much regulated at the level of transcription, is questionable; authors should provide a statistical analysis comparing each experimental time points of wt vs knock- out cells. Moreover, authors should also perform the same experiment using TNF- alpha as a stimulus with a proper related time course of treatment, to match with the experiments shown in fig. 1H. + +## 4- Fig.2. + +Panel B is not described in details and it is not clear, based on figure labelling, what does shown bands represent. + +In panel E, particularly the right part involving MLFs, there is evidence for an increased accumulation of NFkappa in the CLK2 - /- cells even in control untreated cells. This accumulation of NFkappa matches with k310 acetylation and ser536 phosphorylation of p65, suggesting that, at least in these primary cells, CLK2 may represent a basal checkpoint acting to avoid a constitutive activation of p65 even in the absence of activating stimuli (e.g. LPS, TNF- alpha, IL- 1 beta, or viral infection). It seems that in these cells there is also an increased accumulation of p65 compared to wt cells. Authors need to comment on all these data. + +## 5- Supplementary Fig.2. + +Panel A is supposed to be positioned in the upper left part of the figure. + +In the lower right part of panel F, (like for Fig.2 panel E, right part) there is evidence for an increased accumulation of NFkappa in the CLK2 - /- cells even in control untreated cells. Even in this experiment, there is evidence for increased k310 acetylation and ser536 phosphorylation of p65 in control cells and increased accumulation of p65 compared to wt cells (the panel showing Ac- p65 Lys310 for the TNF- alpha time course must be repeated because bands are not clearly visible). + +## 5-Fig.3 + +It is not clear what is the difference between Fig3C and supplementary Fig. 3E. + +At line 169 of the result section related to Fig.3 ("CLK2 deficiency enhances virus- induced IFN- beta production and antiviral response") the word "plague" is actually "plague", and need to be substituted throughout the manuscript. + +## 6- Supplementary Fig.3 + +Panel A is supposed to be positioned in the upper left part of the figure. + +The rationale for the use of HSV- 1 compared to VSV in in vivo and in vitro experiments should be explained, together with the different results obtained. + +It is not clear what kind of supplemental information is provided with supplementary Fig.3E, that is not present in Fig.3C. + +## 7-Fig.4 + +The conclusion, related to panel A, that "CLK2 inhibits virus- triggered NF- kappaB signaling at the p65 level" (lines 197- 198 of the corresponding result paragraph) is correct, but does not rule out the possibility that there are also other upstream players in the signal transduction pathways affected by CLK2. + +In panel B equal amount of Flag- CLK2 should be present in the lysate. + +In panel C authors should also use a CLK2 inhibitor to conclude that CLK2 exerts its function with p65 depending on CLK2 kinase activity. This is because the lack of p65 binding to CLK2 K192R dead kinase, may also depend upon CLK2 conformational change due to the K to R mutation. Again, in panel C and F authors should comment about the faster migration of Flag- CLK2 dead kinase in the IP/WB experiment, compared to wt. This difference cannot be justified by K192R amino acid substitution. + +In panel D, the western blotting experiment should also be repeated with an appropriate TNFalpha time course. + +<--- Page Split ---> + +In panel E, the graph should also report the luciferase fold of inductions relative to each uninfected control, to account for the basal activity of each kinase (wt and mutant) on the promoter compared to the SeV infection or TNF- alpha treatment. + +In the western blot of panel F it is not clear why there is more p65 in the presence of wt CLK2 compared to CLK2 absence or the presence of the dead kinase. Authors should comment on this. In I and G panels, figures should be presented also showing cells with visible light, without fluorescence. + +In panel H a quantification of the detected p65 bands should be presented. + +## 8-Supplementary Fig.4 + +In panel A figures should be presented also showing cells with visible light, without fluorescence. In panel B, western blot should be repeated with a lower amount of loaded proteins (in GAPDH blot bands cannot be discriminated). Moreover, appropriate TNF- alpha time course should also be presented. + +## 9-Fig.5 + +Panel distribution is confusing (what panel does the lower right graphic belongs to? Is it panel F? If this is the case, are those cells infected with SeV? + +In panel C, figures should be presented also showing cells with visible light, without fluorescence. What is really missing, in this in depth phosphorylation site analysis involving p65, is that no attempt at all was made to identify a consensus amino acidic sequence on p65, target of the CLK2 kinase. + +This is an important shortcoming of the manuscript and must be addressed in both, the result and the discussion paragraph. + +## 10-Supplementary Fig.5 + +In panel D, figures should be presented also showing cells with visible light, without fluorescence. + +## 11-Fig.6 + +Experiments shown in Panels D and E are very important for a crucial aspect of CLK2 mediated phosphorylation of p65, and that is p65 degradation and relocation of the protein from the nucleus to the cytoplasm. While MG132 experiments provide striking qualitative data demonstrating a role for phosphorylated ser180 in protein degradation, authors must calculate p65 wt, p65 K180A and p65 K180D half- life by performing a time course of cycloheximide (CHX) treatment, thus straightening their findings with solid quantitative data. + +Moreover, as shown in CLK2 - /- cells a strong constitutive acetylation of p65 at K310 is detected, despite SeV infection or TNF- alpha treatment compared to its absence in wt cells and also an increased ser536 phosphorylation, known to precede K310 acetylation, compared to lower levels in wt cells. + +This basal activation status of p65 in the absence of CLK2 and of any stimuli, suggest a different data interpretation (see comments below). + +In the results paragraph describing Fig.6 and supplementary Fig.6, an important set of experiments is missing. Indeed no p65 DNA binding analysis was performed. Is p65 capable of binding kappaB sites when phosphorylated at ser 180 or when this residue is mutated to either aspartic acid or alanine? Particularly, is p65 capable of binding DNA kappaB sites in CLK2 knockout cells, in the absence of activation stimuli, considering that, in this case, it is highly acetylated at K310, but at the same time it is supposed to be still bound to IkappaB- alpha? These are important questions that need to be answered by performing new experiments, also considering the work by Saccani S. et al. (doi: 10.1084/jem.20040196), showing p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. + +At line 335 of the results paragraph " Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", ser- 468 phosphorylation is described as an activation hallmark of p65, but in fact is mostly associated with a state of repression of p65 transcriptional activity ( for a review see "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017). Therefore, detection of ser 468 in panels D and E should be discussed accordingly. + +<--- Page Split ---> + +Quantification is needed for the western blot results shown in panel C. + +Quantification is needed for the western blot results shown in panel C.The following sentences " So far, these studies showed that phosphorylation of p65 at Ser- 180 serves as a key switch in terminating active p65 through degradation and nuclear export. All of these experiments indicated that CLK2 acts as a brake in the early stage of NF- kappaB transcriptional activation, and it cooperates with IkappaB- alpha, which functions as a brake in the later stage, to limit the transcriptional process in the whole time of NF- kappaB signaling activation" present starting line 342 of the results paragraph " Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", should be reserved to the Discussion section. Moreover, these conclusions are only partially covering the large amount of data gathered, that also point to the CLK2 mediated phosphorylation of p65 at ser 180 as a homeostatic suppression of p65 activity before the signaling cascades of activating stimuli begin. + +## 12- Supplementary Fig.6 + +In panel B it is not clear what n.s. (non specific) refers to. Is it compared to wt p65 or S180A mutant? It is important because it seems that there is an increased mRNA expression for the S180A mutant compared to wt or the S180D mutant. + +In panel E it is not clear how this experiment was performed. Treatment of cells with MG132 results in the inhibition of p65 nuclear translocation and p65 mediated gene activation, due to the fact that IkappaB- alpha degradation is prevented (Lee, D.H. and Goldberg, A.L. 1998 "Proteasome inhibitors: valuable new tools for cell biologists". Trends Cell Biol. 8, 397- 403 doi: 10.1016/s0962- 8924(98)01346- 4. ). In this panel, though, authors show the nuclear accumulation of p65 S180D following TNF- alpha treatment in the presence of MG132. Authors should provide a plausible explanation for this considering that in this case IkappaB- alpha cannot be degraded. Moreover, IkappaB- alpha expression should be present in this western blot panel. + +13- The following sentence "These data suggest that CLK2 represents a potential therapeutic target for inflammatory diseases", starting at line 374 of the results paragraph "CLK2 inhibitor TG003 exhibits power in vitro and in vivo", seems not formally correct. On the contrary, data suggest that any pathway inhibitor of CLK2 may represent a potential therapeutic target for inflammatory diseases, because CLK2 actually acts inhibiting prolonged inflammation. + +## 14-Discussion + +Discussion should provide a better data interpretation, also including discussion of results from new experiments related to p65 DNA binding. + +Marco Sgarbanti PhD + +<--- Page Split ---> + +Point- by- point response to reviewers' comments + +Point- by- point response to reviewers' commentsWe would like to thank the reviewers for their comments and insightful suggestions, which have greatly helped us to revise the manuscript and improve our study. Based on the reviewers' comments, we have performed additional experiments and clarified certain statements/experimental procedures in the revised manuscript. Following is our point- by- point response to the reviewers' comments. + +## Reviewer #1 + +The major finding of this manuscript is the identification of the NF- kB p65 subunit as a target of CLK2. Phosphorylation of p65 at Ser- 180 leads to nuclear export and degradation. This finding uncovers a new substrate for CLK2, a kinase previously found to modify splicing factors. Most importantly this manuscript discovers a new mechanism for negative feedback of p65- driven gene expression that is proposed to be independent of the well- known p65- dependent production of the IkBa/pha inhibitor. The authors use complimentary approaches to demonstrate that loss of CLK2, CLK2 kinase function, or p65 Ser- 180 phosphorylation leads to a gain of interferon and inflammatory responses that have functional impacts on virus control and inflammatory pathologies, in cell culture and in mouse models. The parsing of main figure and supplementary figures is appropriate. That being said, there a few holes in their data that should be addressed to bolster CLK2 as the direct p65 kinase that functions prior to and independently of IkBa. + +Major issues: + +1. They indicate that CLK2 is an early terminator of NF-kB signaling via p65 on Ser180 and independent of IkBa- but there are some discrepancies with this interpretation. +a. Most assays are at 6, 12, or 24 hrs post-stim, well-after IkBa is typically transcriptionally induced by p65. Is there clear data showing two waves of inhibition? Does IkBa ever function in the absence of CLK2 or does CLK2 dominate? + +## Response: + +We actually performed the TNF- \(\alpha\) stimulation assays at 0.25, 0.5, 1, 3, and 6 hours, containing both the early and later stages of NF- \(\kappa \mathrm{B}\) activation (Fig. 5g). The results showed that \(\mathrm{p65^{S180A}}\) , which cannot be phosphorylated by CLK2, has higher transcriptional activity than \(\mathrm{p65^{WT}}\) . Additionally, we did not observe two waves of inhibition. Our opinion is that the inhibition of nuclear p65 by CLK2 is persistent, and this event starts its progression once p65 shuttles into the nucleus. In other words, the occurrence of the event we defined occurs at the early stage of active NF- \(\kappa \mathrm{B}\) , and the inhibition by resynthesis of \(\mathrm{1kBa}\) coexists with the inhibition by CLK2. Therefore, It does not have two waves of the inhibition. + +Many results exhibit that \(\mathrm{1kBa}\) still function in Clk2 knockout primary cells or CLK2 knockout cell lines, such as Fig. 2e, Supplementary Fig. 2f and Fig. 6f. + +For the question "does CLK2 dominate \(\mathrm{1kBa?}\) ", our opinion is that the role of CLK2 is to regulate p65 transcriptional activity at the post- translational modification (PTM) level. The reproduction of \(\mathrm{1kBa}\) is a downstream event of p65 phosphorylation by CLK2, similar to other PTM regulations, such as acetylation. Thus, CLK2 dominates the resynthesis of \(\mathrm{1kBa}\) but it does not dominate the function of \(\mathrm{1kBa}\) . + +<--- Page Split ---> + +b. Does the phosphorylation change of p65 in response to CLK2 impact the ability of p65 to be bound by IkBa? If p65 is no longer recognized by IkBa in the absence of CLK2 modifications then that could lead to an accumulation of p65 in the nucleus and increased transcriptional activity. p65 S180A is a mutant that can't be phosphorylated downstream of CLK2 and has a prolonged residence in the nucleus (Fig 6), but how is the role of IkBa excluded? Do any of the phosphorylation site mutants impact targeting by IkBa? + +## Response: + +We thank the reviewer for his/her insightful comments. We performed the exogenous coimmunoprecipitation assay to detect IkBa binding with p65WT or p65S180D (Supplementary Fig. 6h), and the result showed that p65S180D has a higher affinity for IkBa. This indicates that phosphorylation at Ser180 increase the ability of p65 to be bound by IkBa. + +In the absence of CLK2, p65 showed less affinity for IkBa, but it was still recognized by IkBa (Supplementary Fig. 6i). On the other hand, p65S180A/KI cells were also used to confirm this result. The data showed that p65S180A/KI decrease the interaction with IkBa (Fig. 6d), which is consistent with the result in CLK2- \(l\) - cells. Taken together, these data suggest that CLK2 deficiency or p65 mutant that cannot be phosphorylated at Ser180 decrease the interaction between p65 and IkBa. + +The results (Fig. 5g, 6b, and 6d) showed that p65S180A has less affinity for IkBa and shows more nuclear localization and more powerful transcriptional activity. We did not exclude the role of IkBa and it still participates in the regulation of NF- \(\kappa\) B signaling as a classic inhibitor. + +Both of the experiments in p65S180A/KI or p65S180D/KI cells have suggested us that phosphorylation of p65 at Ser180 did impact targeting by IkBa (Fig. 6d and Supplementary Fig. 6h). + +![PLACEHOLDER_7_0] + + +2. Is CLK2 the sole kinase and what activates it? a. They identify multiple phosphorylation sites but there is never an in vitro analysis with purified CLK2 protein. As it stands now- CLK2 is certainly an upstream kinase- but given IP is performed in HEK293T - CLK2 might be acting via another kinase? + +<--- Page Split ---> + +Does the CLK2 inhibitor TG003 block phosphorylation of Ser 180 on p65 or any other site? + +## Response: + +What a great advice promotes the quality of the manuscript. We followed your advice and performed in vitro assays, including pull- down assay and kinase assay. Unfortunately, purification full- length CLK2 and \(\mathrm{CLK2^{K192R}}\) active proteins through eukaryotic expression presents significant challenges for us. Therefore, we used the Flag- CLK2 and Flag- CLK2K192R via eukaryotic expression, and His- p65 via prokaryotic expression. The pulldown assay showed that p65 only binds to CLK2, but not \(\mathrm{CLK2^{K192R}}\) (Fig. 4f). Meanwhile, the in vitro kinase assay exhibited that CLK2 can expend more ATP with p65 (Fig. 4g). + +![PLACEHOLDER_8_0] + + +The question raised by the reviewer is quite interesting and important for us to understand the mechanism in depth. Western blot analysis was performed with and without TG003, and the results showed that TG003 can block the phosphorylation of Ser- 180 and promote the phosphorylation of Ser- 536 and the acetylation of Lys- 310 (Supplementary Fig. 6l). + +![PLACEHOLDER_8_1] + + +Therefore, we believe the phosphorylation of p65 at Ser180 acting via CLK2 but not another kinase. + +b. In Fig 6D, the SeV infected CLK2-/- have lower levels of phospho Ser180 p65 overall, but it is not eliminated. What kinase drives this remaining phosphorylation? What does the asterisk/upper band indicate in the western blots? + +## Response: + +The phosphorylation antibody was produced by Abclonal company. We consulted this question and according to the explanation of the technical support of the company, the phosphorylation of Ser- 180 in the \(\mathrm{CLK2^{- / - }}\) group can still be detected mainly due to + +<--- Page Split ---> + +the purity of the antibody. The quality may not be perfect, and a small amount of total- p65 may also be detected. In summary, these unspecific bands do not affect the conclusion reflecting the detection of dynamic changes in the phosphorylation of Ser- 180. + +The asterisk/upper band indicate the unspecific band that can be detected by the antibody and the explanation was added in the relative figure legends. + +c. This CLK2-mediated inhibition is only observed upon stimulation- so what is activating CLK2? + +## Response: + +The question deserves attention and we did perform experiments to try to figure out what activates CLK2. The CLK2 is regulated obviously upon stimulation. Mass spectrometry and Co- IP experiments showed that CLK2 interacts with PLK1 exposed with the stimuli, suggesting that PLK1 may regulate CLK2 during infection. However, subsequent experiments cannot fully prove that CLK2 is a substrate of PLK1 or the relationship between PLK1 and CLK2 during infection. In the manuscript, we did not show the figures, but we mentioned in the discussion section that the activity of CLK2 is likely regulated during infection, possibly at the protein or kinase activity level. + +3. There is a an overinterpretation that PML-associated p65 is more transcriptionally active. The PML colocalization and phase separation data is not well developed, being performed in the context of overexpression- it raises more questions than answers. Consider removing. + +## Response: + +Thanks for your advice. The phase separation data truly raised more questions and we had removed it. However, the aggregation of p65S180A and its co- localization with PML actually occurred and really interesting, we have decided to exhibit this phenomenon in the supplementary data. + +4. A major flaw in the publication is the poor quality of writing. Professional editing is essential. There were numerous grammatical errors and improper word choices (e.g. 'we wonder CLK2 may be a pregnant target to treat inflammation-associated diseases and virus infection') that make it nearly impossible for the reader to work through. This did detract from my understanding of some of their summaries and interpretations. + +## Response: + +We have revised the grammar throughout the manuscript and ask a few professors nearby to help us revise the manuscript. After the revision, the updated manuscript is now ready for exhibited. + +Minor issues: + +<--- Page Split ---> + +1. Fig 2B. The PCR genotyping data for WT vs KO mice seems swapped. + +## Response: + +Thanks for this reminding. We did swap the WT vs KO mice PCR genotyping data and revised it in Fig. 2b. + +2. Supp Fig 3 and Fig 5. have an odd arrangement of figures where the letters are not in alphabetical order. + +## Response: + +Sorry for confusing the reviewer and now Supplementary Fig. 3 and Fig. 5 have been rearranged. + +3. The font kerning for the sequence alignment of Fig 5B is off. A monospace font is needed. + +## Response: + +Thanks for your suggestion. The monospace font has been adjusted. + +4. Fig 6 Figure legend states data are presented as SEM- but that type of data is not in the figure. + +## Response: + +Thanks. The legend of Fig. 6 has been revised. + +5. Information on the strain and source of SeV, VSV, and HSV virus stocks is lacking. + +## Response: + +SeV, VSV and VSV expressing GFP (VSV- GFP) were gifts from Hongbing Shu and Bo Zhong, which they have widely used in their studies and published a series of articles (Lei C. Q et al. Glycogen synthase kinase 3beta regulates IRF3 transcription factor- mediated antiviral response via activation of the kinase TBK1. Immunity. 878- 89 (2010). doi: 10.1016/j.immuni.2010.11.021; Lian H, Zang R, Wei J, et al. The Zinc- Finger Protein ZCCHC3 Binds RNA and Facilitates Viral RNA Sensing and Activation of the RIG- I- like Receptors. Immunity. 2018;49(3):438- 448. e5. doi: 10.1016/j.immuni. 2018.08.014; Liuyu, T., Yu, K., Ye, L. et al. Induction of OTUD4 by viral infection promotes antiviral responses through deubiquitinating and stabilizing MAVS. Cell Res 29, 67- 79 (2019). doi.org/10.1038/s41422- 018- 0107- 6). The information was presented in the methods section. + +## Reviewer #2 + +The manuscript entitled "CLK2- mediated IkappaBalpha- independent early- termination of NF- kappaB activation by phosphorylating nuclear- p65 for cytoplasmic redistribution and degradation" by Shang- Ze Li and colleagues describes the + +<--- Page Split ---> + +identification of a novel regulatory phosphorylation site (ser180) of the NF- kappaB sub- unit p65/RelA, target of the CLK2 kinase. CLK2 phosphorylation of p65 at ser180 by cytokine treatment or viral infection leads to increased p65 accumulation in the cytoplasm, and p65 proteasome- mediated degradation. Using knock- in phosphomimetic aspartic acid substitution of ser180 a decreased p65 activity is revealed compared to wt protein, following different stimuli, and also increased viral replication. + +On the contrary, substitution of ser180 with alanine, determining the inability of p65 to be phosphorylated by CLK2 at this residue, results in a "super- active" protein, capable of conferring resistance to viral infection in the knock- in cellular system. Moreover, CLK2 genetic ablation or its chemical inhibition promoted chronic inflammation in a mouse psoriasis model. + +Authors discussed CLK- 2 mediated p65 phosphorylation at ser180 as an early NF- kappaB shutdown pathway, alternative to the canonical feed- back regulatory mechanism represented by the NF- kappaB- mediated synthesis of IKappaB- alpha occurring later after stimulation. + +The CLK- 2 mediated phosphorylation of p65 and the subsequent inhibition of the activity of this transcription factor, represent important and novel findings, adding another important piece of information about how NF- kappaB, one of the most studied transcription factor, works. + +That being said, the manuscript, despite a large number of data gathered, lacks key experiments, and is misleading regarding some data interpretation. + +Moreover, an extensive revision for English language and grammar is required. + +## Response: + +The extensive revision for English language and grammar has been done. We have revised the grammar throughout the manuscript and ask a few professors nearby to help us revise the manuscript. After the revision, the updated manuscript is now ready for exhibited. + +## Specific comments: + +1- Introduction section. + +Introduction section is lacking the description of other important phosphorylation sites identified on p65 (by the way, naming this transcription factor as RelA is more appropriate). Among these, ser276, known to enhance NF- kappaB transcriptional activity, or ser468, negatively regulating NF- kappaB mediated transcription (for a review see "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017), the latter highly relevant in the context of this manuscript and used in fig. 6D and E panels. Moreover, the paper by Saccani S. et al. "Degradation of Promoter- bound p65/RelA Is Essential for the Prompt Termination of the Nuclear Factor B Response" (J. Exp. Med. Volume 200, Number 1, July 5, 2004 107- 113. doi: 10.1084/jem.20040196) must be acknowledged, due to fact + +<--- Page Split ---> + +that it describes p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. In the same paper, if proteasome activity is blocked after an activating stimulus, NF- kappaB is not rapidly removed from target genes despite IkappaB synthesis, resulting in sustained transcription. Such paper describes a very similar mechanism of NF- kappaB "shutdown" and cannot be ignored. Finally, Lys 310 acetylation, required for full RelA transcriptional activity, should not be described without acknowledging the fact that it happens subsequently to the prior phosphorylation of RelA at ser276 and ser536 (Chen LF, et al. "NF- kappaB RelA phosphorylation regulates RelA acetylation". Mol Cell Biol. 2005 Sep;25(18):7966- 75. doi: 10.1128/MCB.25.18.7966- 7975.2005). + +What does "CLK2" stand for? Full name (Cdc2- like kinase 2) must be present, at least the first time CLK2 is described in the introduction section. + +## Response: + +Regarding the name of p65, we believe your advice is valuable. The name as RelA is more official and we have updated it to RelA/p65 in the title and abstract sections. However, in consideration of the wildspread use of p65, we did not revise it in other sections. + +Thank the reviewer for pointing these out for us to refine the writing of Introduction. The description of other important phosphorylation sites identified on p65 has been presented in the Introduction section. Among them, we have cited papers that focus on Ser276 and have also got acknowledge of the paper by Saccani S. et al. Additionally, we have updated the description of Lys310 acetylation followed the reviewer's advice. Meanwhile, a few more papers were cited in the introduction section (such as "Sgarbanti M, et al. IRF- 1 is required for full NF- kappaB transcriptional activity at the human immunodeficiency virus type 1 long terminal repeat enhancer. J Virol. 2008;82(7):3632- 3641. doi:10.1128/JVI.00599- 07"; "Acchioni C, Remoli AL, Marsili G, et al. Alternate NF- \(\kappa \mathrm{B}\) - Independent Signaling Reactivation of Latent HIV- 1 Provirus. J Virol. 2019;93(18): e00495- 19. Published 2019 Aug 28. doi:10.1128/JVI.00495- 19"). Here is the revised sentence "Over the last decades, significant progress has been made in understanding the nuclear import process and transcriptional activation modification of p65, such as phosphorylation of Ser- 536 and Ser- 276 is essential for the transactivation, phosphorylation of Ser- 468 may negatively regulates NF- \(\kappa \mathrm{B}\) mediated transcription and acetylation of Lys- 310 is required for full transcriptional activity of p65 subsequently to the prior phosphorylation of p65 at Ser- 276 and Ser- 536". + +The full name of CLK2 has been revised in the sentence of introduction section "In this study, we present an IkBα- independent nuclear NF- \(\kappa \mathrm{B}\) termination model at the transcriptional level through inhibitory phosphorylation by CDC like kinase 2 (CLK2)." + +## 2- Fig.1 + +In the description of panel D, authors explain that they have used an ISRE reporter responding to SeV infection, to assess the impact of CLK2 on IRF- 3, to rule out IRF- 3 as a CLK2 target in IFN- beta promoter repression. However, authors did not provide + +<--- Page Split ---> + +evidence in the material and methods section about what specific ISRE sequence they have used in the reporter construct (indeed some commercially available ISRE reporter constructs also respond to IFN- I- induced ISGF3). In order for the authors to state that in fig. 1D they are dealing with IRF- 3 mediated stimulation, they have to use the transfection of a plasmid constitutively expressing an active form of IRF- 3, like IRF- 3 5D (Lin R. et al. Essential Role of Interferon Regulatory Factor 3 in Direct Activation of RANTES Chemokine Transcription. Mol Cell Biol. 1999 Feb; 19(2): 959- 966. doi: 10.1128/mcb.19.2.959), as a control, comparing the fold of activation obtained to those reached with SeV infection. + +## Response: + +Thanks for this professional reminder. The IFN- \(\beta\) and ISRE luciferase reporter plasmids and SeV, VSV and VSV expressing GFP (VSV- GFP) were gifts from Hongbing Shu and Bo Zhong (Wuhan University, Hubei, China), which is added in the methods section. + +These luciferase reporter plasmids and virus were widely used in a lot of relatively and importantly published paper and the ISRE- Luc plasmid was tested by IRF- 3 5D previously (Lei C. Q et al. Glycogen synthase kinase 3beta regulates IRF3 transcription factor- mediated antiviral response via activation of the kinase TBK1. Immunity. 878- 89 (2010). doi: 10.1016/j.immuni.2010.11.021). Here is the specific sequence of ISRE "5'- AGGGAAAGTGAACT- 3" and the information was presented in the methods section. + +In Fig.1H error bars should be present in the graphs accounting for the three separate experiments, while the right western blot panel (showing TNF- alpha time course) should not present a GAPDH blot with such a poor separation between each band, clearly the result of excessive protein loading and/or overexposure. + +## Response: + +We do agree with the reviewer and have substituted the line charts with the data of three separate experiments (Fig. 1h). + +![PLACEHOLDER_13_0] + + +## 3-Supplementary Fig.1. + +Looking at panel 1D, it seems that CLK2 expression is actually negatively affected in p65 knock- out cells compared to wt cells, therefore the authors' conclusion, that CLK2 is not that much regulated at the level of transcription, is questionable; authors should provide a statistical analysis comparing each experimental time points of wt vs knock- out cells. Moreover, authors should also perform the same experiment using + +<--- Page Split ---> + +TNF- alpha as a stimulus with a proper related time course of treatment, to match with the experiments shown in fig. 1H. + +## Response: + +With the experiment exposed with TNF- \(\alpha\) and repeated experiment with SeV, we observed that p65 deficiency had a slight effect on the transcription of CLK2. However, compared to the transcription of other classic and specific genes induced by virus or cytokine- induced transcription, we still believe that the change in CLK2 mRNA is not obviously. (Supplementary Fig. 1d) + +![PLACEHOLDER_14_0] + + +4- Fig.2. + +Panel B is not described in details and it is not clear, based on figure labelling, what does shown bands represent. + +In panel E, particularly the right part involving MLFs, there is evidence for an increased accumulation of Nfkbia in the CLK2 - /- cells even in control untreated cells. This accumulation of Nfkbia matches with k310 acetylation and ser536 phosphorylation of p65, suggesting that, at least in these primary cells, CLK2 may represent a basal checkpoint acting to avoid a constitutive activation of p65 even in the absence of activating stimuli (e.g. LPS, TNF- alpha, IL- 1 beta, or viral infection). It seems that in these cells there is also an increased accumulation of p65 compared to wt cells. Authors need to comment on all these data. + +## Response: + +We are sorry for not providing clear descriptions of the experiments. The band of WT represents the products that can only be amplified in \(\mathrm{CLK2^{WT}}\) genome, and the band of KO represents the products that can only be amplified in the \(\mathrm{CLK2^{KO}}\) genome. Additionally, the description of panel B has been revised in the figure legend. + +Thanks for the insightful comment and comprehension of the reviewer and we deeply agree with it. In consideration of the dynamic balance in cell physiology, CLK2 deficiency may cause the slightly activation of NF- \(\kappa\) B signaling in the rest time and result in the increased accumulation of Nfkbia. The new description has been presented + +<--- Page Split ---> + +in the result and discussion section "Interestingly, there was an increased accumulation of Nfkbia in Clk2- cells, which is consistent with the increase in Lys- 310 acetylation and Ser- 536 phosphorylation of p65. It indicates that CLK2 may be a basal checkpoint to limit constitutional activation of NF- \(\kappa\) B signaling, even in the absence of activating stimuli.", "Taken together, all the results obtained from primary cells or cell lines indicated that the phosphorylation of p65 by CLK2 may be identified as a basal checkpoint, preventing a continuous activation of p65 and thus inhibiting the activation of NF- \(\kappa\) B." and "Furthermore, the CLK2 mediated phosphorylation of p65 at Ser- 180 serves as a homeostatic suppression of p65 activity before the activation of the signaling cascade". + +## 5- Supplementary Fig. 2. + +Panel A is supposed to be positioned in the upper left part of the figure. In the lower right part of panel F, (like for Fig.2 panel E, right part) there is evidence for an increased accumulation of Nfkbia in the CLK2- /- cells even in control untreated cells. Even in this experiment, there is evidence for increased k310 acetylation and ser536 phosphorylation of p65 in control cells and increased accumulation of p65 compared to wt cells (the panel showing Ac- p65 Lys310 for the TNF- alpha time course must be repeated because bands are not clearly visible). + +## Response: + +Following the reviewer's suggestion, we have rearranged Supplementary Fig. 2. + +Thank the reviewer for pointing this out for us. The detection of Ac- p65 (Lys310) have been repeated with the same protein sample and the bands have been renewed (Supplementary Fig. 2f). + +![PLACEHOLDER_15_0] + + +5- Fig.3 It is not clear what is the difference between Fig3C and supplementary Fig. 3E. At line 169 of the result section related to Fig.3 ("CLK2 deficiency enhances virus + +<--- Page Split ---> + +induced IFN- beta production and antiviral response") the word "plague" is actually "plague", and need to be substituted throughout the manuscript. + +## Response: + +We are sorry for confusing the reviewer. We performed assays in 3 different types of primary cells, including bone marrow- derived macrophages (BMDMs), mice lung fibroblasts (MLFs) and bone marrow- derived dendritic cells (BMDCs). The data of BMDMs and MLFs were exhibited in Fig. 3 and the data of BMDCs was showed in Supplementary Fig. 3. + +Thank the reviewer for point this out for us. We have corrected the plague to plaque throughout the manuscript. + +## 6- Supplementary Fig. 3 + +Panel A is supposed to be positioned in the upper left part of the figure. The rationale for the use of HSV- 1 compared to VSV in in vivo and in vitro experiments should be explained, together with the different results obtained. It is not clear what kind of supplemental information is provided with supplementary Fig.3E, that is not present in Fig.3C. + +## Response: + +Following the reviewer's suggestion, The Supplementary Fig. 3 has been rearranged. + +Vesicular stomatitis virus (VSV) is an RNA virus and herpes simplex virus type 1 (HSV- 1) is an DNA virus. Both of them can activate NF- \(\kappa\) B signaling but correspond to different receptor. All the stimulus we used were designed to verify that CLK2 is a broad- spectrum inhibitor of activated NF- \(\kappa\) B signaling. The explanation was presented in the sentence "To investigate the physiological role of Clk2 in viral infection in vivo, Clk2- deficient mice and their wild- type littermates were injected with Vesicular Stomatitis Virus (VSV) or Herpes Simplex Virus Type 1 (HSV- 1) via the tail vein and intraperitoneally". + +We have confirmed the results through BMDMs and MLFs cells and these data are convincing. The experiments in BMDCs were mainly performed as a support of these known results, so the fluorescence microscopy of BMDCs was not detected. Considering it is supplementary data, we did not show it in the figure, but we still have strong evidence to proof the conclusion. + +## 7-Fig.4 + +The conclusion, related to panel A, that "CLK2 inhibits virus- triggered NF- kappaB signaling at the p65 level" (lines 197- 198 of the corresponding result paragraph) is correct, but does not rule out the possibility that there are also other upstream players in the signal transduction pathways affected by CLK2. + +## Response: + +Thanks for the stringent description for this conclusion. It does not rule out the possibility that there are other upstream players in the signal transduction pathways + +<--- Page Split ---> + +affected by CLK2. Therefore, we detected the location of CLK2 (Supplementary Fig. 4a). Combined with the luciferase and nuclear location results, we draw the conclusion that CLK2 function with nuclear p65 to regulate the activation of the NF- \(\kappa\) B signaling. + +In panel B equal amount of Flag- CLK2 should be present in the lysate. In panel C authors should also use a CLK2 inhibitor to conclude that CLK2 exerts its function with p65 depending on CLK2 kinase activity. This is because the lack of p65 binding to CLK2 K192R dead kinase, may also depend upon CLK2 conformational change due to the K to R mutation. + +## Response: + +Thanks for your rigorous manner, the expression of Flag- CLK2 did have discrepancy and it may be caused by plasmid transfection. However, this discrepancy did not affect our conclusion and we did not replace it. + +We have followed the reviewer's advice. The assay was performed and the result showed that the interaction between p65 and CLK2 is impaired in the presence of the CLK2 inhibitor- TG003 (Fig. 4d). + +![PLACEHOLDER_17_0] + + +By the way, The \(\mathrm{CLK2^{K192R}}\) was wildly used in many other researches (Naylor, O et al. "The cellular localization of the murine serine/arginine-rich protein kinase CLK2 is regulated by serine 141 autophosphorylation." The Journal of biological chemistry vol. 273,51 (1998): 34341- 8. doi:10.1074/jbc.273.51.34341; Rodgers, Joseph T et al. "Cdc2- like kinase 2 is an insulin- regulated suppressor of hepatic gluconeogenesis." Cell metabolism vol. 11,1 (2010): 23- 34. doi:10.1016/j.cmet.2009.11.006). And the strategy of frequently replacing Lysine (Lys) in kinase activity mutations was normally used in many other researches (Hanafusa H, Kedashiro S, Tezuka M, et al. PLK1- dependent activation of LRRK1 regulates spindle orientation by phosphorylating CDK5RAP2. Nat Cell Biol. 2015;17(8):1024- 1035. doi:10.1038/ncb3204; Zhao P, Wong KI, Sun X, et al. TBK1 at the Crossroads of Inflammation and Energy Homeostasis in Adipose Tissue. Cell. 2018;172(4):731- 743. e12. doi:10.1016/j.cell.2018.01.007). So we choose the \(\mathrm{CLK2^{K192R}}\) to investigate the function of kinase activity. + +<--- Page Split ---> + +Again, in panel C and F authors should comment about the faster migration of Flag- CLK2 dead kinase in the IP/WB experiment, compared to wt. This difference cannot be justified by K192R amino acid substitution. + +## Response: + +It may be caused by the site mutation and result in the change of PTM, such as autophosphorylation. The migration of bands can be observed normally in many other kinase dead mutation. Not only in our research, but also many others research (Zhao P, Wong KI, Sun X, et al. TBK1 at the Crossroads of Inflammation and Energy Homeostasis in Adipose Tissue. Cell. 2018;172(4):731- 743. e12. doi:10.1016/j.cell.2018.01.007; Li SZ, Shu QP, Song Y, et al. Phosphorylation of MAVS/VISA by Nemo- like kinase (NLK) for degradation regulates the antiviral innate immune response. Nat Commun. 2019;10(1):3233. Published 2019 Jul 19. doi:10.1038/s41467- 019- 11258- x). + +In panel D, the western blotting experiment should also be repeated with an appropriate TNF- alpha time course. + +## Response: + +Following the reviewer's suggestion, the experiment has been repeated exposed with TNF- \(\alpha\) , and the result showed that p65 has more affinity to CLK2 under stimulation. + +![PLACEHOLDER_18_0] + + +In panel E, the graph should also report the luciferase fold of inductions relative to each uninfected control, to account for the basal activity of each kinase (wt and mutant) on the promoter compared to the SeV infection or TNF- alpha treatment. In the western blot of panel F it is not clear why there is more p65 in the presence of wt CLK2 compared to CLK2 absence or the presence of the dead kinase. Authors should comment on this. + +## Response: + +Sorry for confusing the reviewer. About panel E (updated as Supplementary Fig. 4b), the uninfected control group was been showed which was painted green. + +The difference in panel F (rearranged as Supplementary Fig. 4c) as most likely caused by transfection or western blot system error. It was ignored and actually made some misunderstandings. However, it was not a quantitative experiment and did not affect us drawing the conclusion. We have repeated the experiment multiple times and in other + +<--- Page Split ---> + +cases, it is not observed the same increased expression. Two additional repetitions are shown below. We have also rerun the same protein sample and substituted the improper graph. Finally, thanks for careful observation and reminding. + +![PLACEHOLDER_19_0] + + +In I and G panels, figures should be presented also showing cells with visible light, without fluorescence. + +## Response: + +We could understand what your concern. Usually, visible light is not showed in the figure, so we did not shoot the cells with visible (Tanaka, T., Grusby, M. & Kaisho, T. PDLIM2- mediated termination of transcription factor NF- \(\kappa\) B activation by intranuclear sequestration and degradation of the p65 subunit. Nat Immunol 8, 584- 591 (2007). https://doi.org/10.1038/ni1464; Wang, S., Lin, Y., Yuan, X. et al. REV- ERBα integrates colon clock with experimental colitis through regulation of NF- \(\kappa\) B/NLRP3 axis. Nat Commun 9, 4246 (2018). https://doi.org/10.1038/s41467- 018- 06568- 5). Instead, DAPI was used to reflect the number and condition of cells as a merged graph, and we did detect it. It is shown below, but in order to clearly show the change of p65, we did not include it in the manuscript. + +![PLACEHOLDER_19_1] + + +In panel H a quantification of the detected p65 bands should be presented. Response: + +<--- Page Split ---> + +Following the reviewer's suggestion, we have presented the line chart and updated it in Fig. 4i. + +![PLACEHOLDER_20_0] + + +8- Supplementary Fig.4 + +In panel A figures should be presented also showing cells with visible light, without fluorescence. + +## Response: + +Thanks. It is a similar question to 7- Fig. 4h and 4j, and about the question, it had been explained. + +In panel B, western blot should be repeated with a lower amount of loaded proteins (in GAPDH blot bands cannot be discriminated). Moreover, appropriate TNF- alpha time course should also be presented. + +## Response: + +We agree with the reviewer that western blot need to be revised and the updated graphs (Supplementary Fig. 4d). The results showed that CLK2 deficiency does not affect p65 stability under the stimulation. + +![PLACEHOLDER_20_1] + + +9- Fig.5 Panel distribution is confusing (what panel does the lower right graphic belongs to? Is it panel F? If this is the case, are those cells infected with SeV? + +## Response: + +We feel so sorry for confusing the reviewer and the graph has been rearranged. + +<--- Page Split ---> + +The lower right graphic belongs to panel F, and those cells were same sample that treated with SeV. Now it has been rearranged as Fig. 5e. + +In panel C, figures should be presented also showing cells with visible light, without fluorescence. + +## Response: + +It is a similar question to 7- Fig. 4h and 4j, and about the question, we have been explained previously. + +What is really missing, in this in depth phosphorylation site analysis involving p65, is that no attempt at all was made to identify a consensus amino acidic sequence on p65, target of the CLK2 kinase. + +This is an important shortcoming of the manuscript and must be addressed in both, the result and the discussion paragraph. + +## Response: + +Thanks for giving the valuable suggestions. We really appreciate it and have attempted to determine if there is a consensus amino acid sequence that is targeted by CLK2. Unfortunately, the only confirmed phosphorylated site of the substrate targeted by CLK2 is PTP1B, and there has not enough data to figure out the specific motif. Finally, we have updated it in the discussion section "Following the conserved sites analysis of p65 180 and 316 residues across species Fruit fly to Human, we tried to identify the consensus amino acid sequence on p65 targeted by CLK2. The PROMALS3D online tool was used for this investigation and yielded no significant result. Given that Ser- 50 of PTP1B is the sole site that has been determined targeted by CLK2, and no additional substrates can be concurrently analysed, the determination of this target remains challenging. However, further investigation holds promise for its eventual elucidation.". + +## 10-Supplementary Fig.5 + +In panel D, figures should be presented also showing cells with visible light, without fluorescence. + +## Response: + +It is a similar question to 7- Fig. 4h and 4j, and about the question, we have been explained previously. + +## 11- Fig.6 + +Experiments shown in Panels D and E are very important for a crucial aspect of CLK2 mediated phosphorylation of p65, and that is p65 degradation and relocation of the protein from the nucleus to the cytoplasm. While MG132 experiments provide striking qualitative data demonstrating a role for phosphorylated ser180 in protein + +<--- Page Split ---> + +degradation, authors must calculate p65 wt, p65 K180A and p65 K180D half-life by performing a time course of cycloheximide (CHX) treatment, thus straightening their findings with solid quantitative data. + +## Response: + +Following the reviewer's suggestion, we performed CHX assays and the results showed that p65S180A/KI is more stable than p65WT. Additionally, p65S180D/KI has a much shorter half- life compared to p65WT (Supplementary Fig. 6g). We also update the result section "Moreover, the nuclear p65S180D had showed higher ubiquitination level than wild- type p65 (Supplementary Fig. 6f), and the cycloheximide (CHX) treatment assay also exhibited that p65S180D has a shorter half- life than p65WT (Supplementary Fig. 6g)." + +![PLACEHOLDER_22_0] + +
G
+ +Moreover, as shown in CLK2 - /- cells a strong constitutive acetylation of p65 at K310 is detected, despite SeV infection or TNF- alpha treatment compared to its absence in wt cells and also an increased ser536 phosphorylation, known to precede K310 acetylation, compared to lower levels in wt cells. + +This basal activation status of p65 in the absence of CLK2 and of any stimuli, suggest a different data interpretation (see comments below). + +In the results paragraph describing Fig.6 and supplementary Fig.6, an important set of experiments is missing. Indeed no p65 DNA binding analysis was performed. Is p65 capable of binding kappaB sites when phosphorylated at ser 180 or when this residue is mutated to either aspartic acid or alanine? Particularly, is p65 capable of binding DNA kappaB sites in CLK2 knock- out cells, in the absence of activation stimuli, considering that, in this case, it is highly acetylated at K310, but at the same time it is supposed to be still bound to IkappaB- alpha? These are important questions that need to be answered by performing new experiments, also considering the work by Saccani S. et al. (doi: 10.1084/jem.20040196), showing p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. + +## Response: + +It is really a good question and we have followed the reviewer to perform the DNA- binding analysis with the knock- in cells. The result of ChIP- qPCR showed that p65S180A/KI has more affinity for \(\kappa \mathrm{B}\) sites than p65WT under SeV stimulation, while p65S180D/KI showed almost no binding with DNA (Fig. 6e). + +<--- Page Split ---> +![PLACEHOLDER_23_0] + + +It is similar to the result of \(\mathrm{p65}^{S180A / KI}\) , in the absence of CLK2, wild- type p65 shows more powerful DNA- binding ability (Supplementary Fig. 6j). And the manuscript has been updated as "As known, interaction with \(\mathrm{IkB\alpha}\) is usually relevant to the DNA- binding activity, so we next sought for if \(\mathrm{p65}^{S180D / KI}\) affects p65 binding with DNA. ChIP- qPCR assays showed that \(\mathrm{p65}^{S180D / KI}\) has nearly lost the ability of DNA- binding, on the contrary, \(\mathrm{p65}^{S180A / KI}\) exhibits the enhanced DNA- binding activity (Fig. 6e). In addition, p65 in CLK2- \(t\) cells also showed increase capability of DNA- binding (Supplementary Fig. 6j)." + +![PLACEHOLDER_23_1] + + +And the question about why p65 supposed to be bound with \(\mathrm{IkB\alpha}\) has high level of Lys310 acetylation, we need to say that is not contradictory. According to the paper "Acetylation of RelA at discrete sites regulates distinct nuclear functions of NF- \(\kappa \mathrm{B}\) " (doi.org/10.1093/emboj/cdf660), acetylation at K221 enhances the DNA binding of NF- \(\kappa \mathrm{B}\) and, together with acetylation at K218, impairs its association with \(\mathrm{IkB\alpha}\) . Acetylation of K310 is required for full transcriptional activity of NF- \(\kappa \mathrm{B}\) , but does not affect DNA binding or \(\mathrm{IkB\alpha}\) assembly. And every molecule has its dynamic balance, not all of the p65 binds with \(\mathrm{IkB\alpha}\) , it just takes up a portion of it. For another example, p65/p50 dimer binding with \(\mathrm{IkB\alpha}\) dynamically shuttles between the nucleus and cytoplasm and basic transcription mediated by p65 is continuously proceeding, even in the rest time without stimulus, which maintains the dynamic balance of cell physiology (Huang TT, et al. A nuclear export signal in the N- terminal regulatory domain of IkappaBalpha controls cytoplasmic localization of inactive NF- kappaB/IkappaBalpha complexes. Proc Natl Acad Sci U S A. 2000;97(3):1014- 1019. doi:10.1073/pnas.97.3.1014; Johnson C, Van Antwerp D, Hope TJ. An N- terminal nuclear export signal is required for the nucleocytoplasmic shuttling of IkappaBalpha. EMBO J. 1999;18(23):6682- 6693. doi:10.1093/emboj/18.23.6682). And \(\mathrm{IkB\alpha}\) keeps + +<--- Page Split ---> + +degradation and resynthesis in the rest time. Taken together, we can conclude that deficiency of CLK2 may result in accumulation of acetylation of a portion of p65. It enhanced the basic transcriptional activity of p65 and it is not related to binding with \(\mathrm{1kBa}\) . + +Considering the good work by Saccani S. et al. (doi: 10.1084/jem.20040196), we can observe that the mutant p65 did not eliminate the polyubiquitination (Fig. 2c) and the mRNA of TNF- \(\alpha\) was not up- regulated by TNF- \(\alpha\) in \(\mathrm{1kBa}^{- }\) cells treated with \(\beta\) lactone (Fig. 3b). It suggests that degradation of promoter- bound p65 takes up a portion of p65 degradation, and there still have other mechanism. It is not contradictory. + +At line 335 of the results paragraph "Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", ser- 468 phosphorylation is described as an activation hallmark of p65, but in fact is mostly associated with a state of repression of p65 transcriptional activity (for a review see "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017). Therefore, detection of ser 468 in panels D and E should be discussed accordingly. Quantification is needed for the western blot results shown in panel C. + +## Response: + +Thanks for figure out our mistakes and it has been revised throughout the paragraph. And about the result of increased Ser- 468 phosphorylation in CLK2- \(\mathrm{1}\) cells, here is the discussion. Ser- 468 phosphorylation is an activation hallmark of p65 and the phosphorylation occurs in the nucleus (DOI 10.1074/jbc.M508045200) which links to the negatively regulation of p65 by degradation through proteasome (doi: 10.1038/embor.2009.10; doi: 10.1101/gad.1748409). According to the result in the paper (https://doi.org/10.1096/fj.05- 3736fje), we can also find that Ser468 just has a slight effect in transactivation and does not alter the p65 translocation. Moreover, the review "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" also said "Surprisingly, phosphorylation of S468 by \(\mathrm{1K}\kappa \mathrm{e}\) in T cells enhances the transcriptional activation of NF- \(\kappa \mathrm{B}\) in response to T cell co- stimulation (DOI 10.1074/jbc.M508045200). These different outcomes suggest that phosphorylation of S468 regulates the transcriptional activity of NF- \(\kappa \mathrm{B}\) in a context- dependent manner, but the mechanism underlying this requires further investigation". Actually, in normal experiments we usually cannot find a significant change in p65 protein levels under the stimulation. Previous research has not clearly clarified the role of Ser- 468 phosphorylation, but it is a consensus that Ser- 468 phosphorylation reflects the activation of p65. Combined with our results, it is obvious that CLK2 plays a key role in supervising the posttranslational modifications of p65. The nuclear accumulation of p65 caused by CLK2 deficiency may result in the accumulation of phosphorylated p65 at Ser- 468. The result was revised as "The Ser- 536 phosphorylation and Lys- 310 acetylation is required for p65 full transcriptional activity, and Ser- 468 phosphorylation mainly negatively regulates the transcriptional activity and also can be treated as a hallmark of activation of p65". + +<--- Page Split ---> + +The quantification of panel C has been shown in Fig. 6. + +![PLACEHOLDER_25_0] + + +The following sentences "So far, these studies showed that phosphorylation of p65 at Ser- 180 serves as a key switch in terminating active p65 through degradation and nuclear export. All of these experiments indicated that CLK2 acts as a brake in the early stage of NF- kappaB transcriptional activation, and it cooperates with IkappaB- alpha, which functions as a brake in the later stage, to limit the transcriptional process in the whole time of NF- kappaB signaling activation" present starting line 342 of the results paragraph " Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", should be reserved to the Discussion section. Moreover, these conclusions are only partially covering the large amount of data gathered, that also point to the CLK2 mediated phosphorylation of p65 at ser 180 as a homeostatic suppression of p65 activity before the signaling cascades of activating stimuli begin. + +## Response: + +As suggested, the mentioned sentence was moved to the Discussion section. + +Also, we agree the statement that "Furthermore, the CLK2 mediated phosphorylation of p65 at Ser- 180 serves as a homeostatic suppression of p65 activity before the activation of the signaling cascade" and put it in the Discussion section following above sentence. + +## 12- Supplementary Fig.6 + +In panel B it is not clear what n.s. (non specific) refers to. Is it compared to wt p65 or S180A mutant? It is important because it seems that there is an increased mRNA expression for the S180A mutant compared to wt or the S180D mutant. + +## Response: + +Sorry for confusing the reviewer, the n.s. of p65S180D/KI is compared to the p65WT. And there is no significant difference between p65 and p65S180A/KI through statistical analysis. + +In panel E it is not clear how this experiment was performed. Treatment of cells with MG132 results in the inhibition of p65 nuclear translocation and p65 mediated gene activation, due to the fact that IkappaB- alpha degradation is prevented (Lee, D.H. and + +<--- Page Split ---> + +Goldberg, A.L. 1998 “Proteasome inhibitors: valuable new tools for cell biologists”. Trends Cell Biol. 8, 397–403 doi: 10.1016/s0962-8924(98)01346-4. ). In this panel, though, authors show the nuclear accumulation of p65 S180D following TNF-alpha treatment in the presence of MG132. Authors should provide a plausible explanation for this considering that in this case IkappaB-alpha cannot be degraded. Moreover, IkappaB-alpha expression should be present in this western blot panel. + +## Response: + +The p65/p50 dimer binding with IkBa dynamically shuttles between the nucleus and cytoplasm. And basic transcription, mediated by p65, continuously proceeds even during rest period without stimulation. This maintains the dynamic balance of cell physiology. The experiment was used p65S180D/K1 HEK293T cells treated with TNF- \(\alpha\) with or without MG132 and then fractionated the cytoplasm and nucleus to detect p65. + +Regarding the inhibition of IkBa, we have a statement previously that even during the rest period, physiological progression continuously proceeds at a relatively low level. Not all of the p65 binds with IkBa, and a portion of p65 can shuttle from the cytoplasm to the nucleus to maintain the dynamic balance. When exposed with MG132, the result indicated that p65S180D is largely accumulated in the nucleus. Meanwhile, the cytoplasmic IkBa, may be similar to the free resynthesized IkBa, shuttles from the cytoplasm to the nucleus. The updated Supplementary Fig. 6e is presented below. + +![PLACEHOLDER_26_0] + + +13- The following sentence “These data suggest that CLK2 represents a potential therapeutic target for inflammatory diseases”, starting at line 374 of the results paragraph “CLK2 inhibitor TG003 exhibits power in vitro and in vivo”, seems not formally correct. On the contrary, data suggest that any pathway inhibitor of CLK2 may represent a potential therapeutic target for inflammatory diseases, because CLK2 actually acts inhibiting prolonged inflammation. + +## Response: + +We agree with the reviewer and this sentence has been revised as following “These data suggest that CLK2 represents a potential therapeutic target for inflammatory diseases and TG003 may be developed as a cure of virus- infection.” + +<--- Page Split ---> + +## 14-Discussion + +Discussion should provide a better data interpretation, also including discussion of results from new experiments related to p65 DNA binding. + +## Response: + +Discussion related to p65 DNA- binding has been added in the result and discussion section "As known, interaction with \(\mathrm{1kBa}\) is usually relevant to the DNA- binding activity, so we next sought for if \(\mathrm{p65^{S180D / KI}}\) affects p65 binding with DNA. ChIP- qPCR assays showed that \(\mathrm{p65^{S180D / KI}}\) has nearly lost the ability of DNA- binding, on the contrary, \(\mathrm{p65^{S180A / KI}}\) exhibits the enhanced DNA- binding activity (Fig. 6e). In addition, p65 in \(\mathrm{CLK2^{- / - }}\) cells also showed increase capability of DNA- binding (Supplementary Fig. 6j). In summary, phosphorylation of p65 by CLK2 at Ser- 180 decreases the DNA- binding activity of p65 and enhance its interaction with CRM1 and \(\mathrm{1kBa}\) , resulting in the export of p65 from the nucleus." and "Additionally, the \(\mathrm{p65^{S180A}}\) and p65 in \(\mathrm{CLK2^{- / - }}\) cells showed less affinity for CRM1 and \(\mathrm{1kBa}\) and a stronger DNA- binding activity, further demonstrating how Ser- 180 phosphorylation affects the transcription.". + +<--- Page Split ---> + +## REVIEWER COMMENTS + +Reviewer #1 (Remarks to the Author): + +## Summary + +The authors have provided a thorough rebuttal. They note numerous figure modifications with the addition of new data and removal and rearrangement of previous data, and text clarifications that have substantially improved the manuscript. The authors have defined a role for CLK2 in the impairment of NF- kB activation and inflammation that impacts virus replication, and further improvements were made to Figs 1- 3 in response to Reviewer 2. However, I am not satisfied with the mechanistic underpinnings of the impact of CLK2 on RelA/p65. Without confirmation that CLK2 directly phosphorylates RelA/p65 and that this inhibition is truly independent of IkBa, the novelty of this publication is substantially reduced. The data provided does not strongly lock down these two claims. + +## Major concerns + +1. Weak evidence that RelA/p65 Ser180 is a direct substrate of CLK2. + +- For IP interactions and phos-tag and ADP glo kinase assays in Fig 4 and Supp Fig4: It would be ideal to perform with purified proteins. As it stands now this interaction could be part of a complex and not direct. They describe Fig 4f as an in vitro pulldown that I suppose is linked to the 'protein purification and pull-down' in Methods. This describes a purified His-p65 with FLAG- enriched lysates of transfected 293T cells. Is there a Coomassie stained gel to demonstrate the purity of the FLAG enriched lysate used for the FLAG pull-down? + +- The authors respond in the rebuttal that the CLK2K192R mutant is widely used in the field. Can they verify that the CLK2 K192R mutant is kinase dead in this system using canonical substrates? It is also notable that CLK2 undergoes autophosphorylation on Ser141, mutation changes its subnuclear localization (PMID 9852100). Does the K192R prevent this autophosphorylation? One potential explanation is that the autophosphorylated form of CLK2 is required to interact with p65 (whether due to TG003 or the K192R mutant), but does not reflect the requirement for its kinase activity. + +- TG003 is not specific for CLK2, this drug also inhibits other CLKs. This is important since CLK1,2,4 each regulate other substrates including splicing factors (PMID 33846420). They need to demonstrate that this is not impacting other CLKs or that other CLK2 substrates aren't playing a role. Why not show that the impact of TG003 is only observed in CLK2+, but not CLK2-/- cells. + +- The guidelines and other publications that use the ADP-glo kinase assay report activity based on the change in luminescence with concentration of the protein/inhibitors present. Here, they apply it as a single timepoint/readout luminescent reading- they do not report kinase activity differences in CLK compared to the CLK2 K192R mutant over a range of protein/substrate concentrations. Given that CLK2 K192R is expressed at lower levels than CLK2 in Fig 4C- this decrease in luminescence might just represent a decrease in CLK2 mutant expression levels. They don't show assay results for FLAG-CLK2K192R in the absence of His-p65. What is the source of the samples examined (lysates or purified components)? The input proteins need to be shown to verify equal inputs. Minimally, a purified CLK2 kinase enzyme system is commercially available (Promega) and could be used with their purified p65 to verify p65 is a substrate for CLK2. + +- The rationale for pursuing S180 but not S316 does not seem logical since the alignments show similar patterns of conservation across species for both (Fig 5B). + +- The analysis of the p65 S180 mutant clearly shows that S180A is more active than S180D, but the stronger experiment is to show that both retain this profile with or without CLK2 expression, unlike WT p65 (Fig 5E). + +- There was a notable difference in the expression level of HA-S180D in Fig 5 due to a decrease in stability; that is the simple explanation for loss of NF-kB activation in Fig 4 functional assays. Why + +<--- Page Split ---> + +aren't these assays shown in the presence and absence of CLK2 to demonstrate that only the WT p65 half- life/instability (Supp Fig 6G) is different between CLK2+ and CLK2- /- cells (S180A and S180D would not show any dependence on CLK2 correct, correct)? + +- I remain in doubt about the findings using the Ser-180 p-p65 antibody (Fig 6F). The phospho-specific Ser-180 antibody that they had produced shows a non-specific band and evidently cross reacts with total p65, As controls, did they profile WT p65, S180A and S180D mutants to show this only recognizes the WT p65. Did they test p65-/- cells? + +- Also there is inconsistency between the CLK2+/+ vs -/- cells in Fig6D at basal (Ohrs) conditions. The p-p65 Ser180 is the same at 0 hr in the SeV blot on left but higher in CLK2+/+ cells compared to CLK2-/- cells at 0 hrs in the right TNFa blot. + +2. I am still not convinced that CLK2 function is independent of IkBa. + +"Interestingly, there was an increased accumulation of Nfkbia in Clk2-/- cells, which is consistent with the increase in Lys-310 acetylation and Ser-536 phosphorylation of p65. It indicates that CLK2 may be a basal checkpoint to limit constitutional activation of NF-κB signaling, even in the absence of activating stimuli." + +- I remain unclear what they mean by 'early stage termination.' It seems that the impact of CLK2 on p65 and NFkbia is most apparent in the context of induction than basal conditions. IkBa is expressed and plays a role in basal and induced conditions over a 6 hr timecourse. + +- They state on lines 81-82 that 'we report an IkBa-independent nuclear NF-kB termination model at the transcriptional level through inhibitory phosphorylation by CLK2' Given that they have greater interactions of p65 with IkBa in the presence of CLK2 (without or with TNF) in Supp Fig 6I, doesn't this again indicate that IkBa can be playing a role in CLK2's inhibition of p65? Can they demonstrate that CLK2 suppresses p65 even in the absence of IkBa? + +- I don't understand their statement that IkBa functions in CLK2 KO cells- the data they cite just shows NFkbia is resynthesized by western. Do they introduce IkBa into CLK2-/- cells and show it is still inhibitory? + +- They find that S180D (which does not activate NF-kb and has a higher turnover) has a higher affinity for Nfkbia/IkBa (Supp Fig 6H), but S180A and WT in CLK2-/- cells has a decreased interaction with CRM1 and Ikba (Fig 6C &6D). This data demonstrates that the phosphorylation on S180 induced by CLK2 leads to a higher affinity for Ikba that would export and lock p65 out of nucleus; in turn this lead to the loss of NF-kB post-translational modifications and functions in the nucleus. Therefore, the impact of CLK2 on p65 Ser180 phosphorylation may be upstream of IkBa interactions, but ultimately is determined by IkBa export. It is not independent of Ikba- just not dependent on newly synthesized IkBa in late stage termination. This does not fit with their conclusions and title. + +- Lines 368-370 described showing p65 S180A and WT interactions with CRM1 and IkBa in CLK2-/- cells. Fig 6D only shows 293T cells and Fig.6i only shows WT p65 in both CLK2+/+ and CLK2-/- cells. + +Minor comments. + +1. Professional editing is required even with revisions. Numerous issues remain and some are newly introduced. 'plague' is still used where 'plague' is appropriate. +2. The IFA figures with brightfield added have become very small (Fig3, 5). The IFA for the paired flow cytometry data could be moved to supplemental or the other bar graphs in the figures could be shortened to make space. +3. I previously noted that the font kerning for the sequence alignment of Fig 5B is off and that a monospace font is needed. The authors claim to have adjusted this- but the text is still not aligned properly. +4. There is a lack of discussion regarding its canonical substrates such as splicing factors vs this + +<--- Page Split ---> + +noncanonical functions of CLK2 to target p65. How does SeV, TNFa or other stimulations that activated CLK2 tie into its impacts on splicing? When CLK2 is activated by infection to target p65, what is the impact on canonical substrates? + +5. Typo in Supp Fig 4c legend line 1057: they state 'The upper shifted band represents phosphorylated CLK2 protein.' This is actually p65, correct? +6. With regard to Fig 6D legend, they state that "The asterisk/upper band indicate the unspecific band that can be detected by the antibody and the explanation was added in the relative figure legends." This has not been corrected. + +Reviewer #2 (Remarks to the Author): + +Authors fixed all relevant issue raised, by performing new experiments as requested, and by modifying the manuscript, as suggested. I also encourage authors to make a further effort to improve manuscript written English (at pag 5 line 55, "rheumatoid arthritis", instead of "rheumatic arthritis"; at pag.6 line 89 "CLK2-deficient mice were observed to have higher levels", instead of "CLK2-deficient mice produce were observed to have higher levels"; at pag 22 line 444 "The transcription factor p65 is critical for cytokine-induced production of inflammation genes", instead of "The transcription factors p65 is critically for cytokine-induced production of inflammation genes"; at page 24 line 499 "use of site-specific phosphorylation antibody", instead of "use of site-specific phosphorylation antibody", and so on). + +Moreover, at pag. 21 line 440, I suggest to rephrase the sentence "... and TG003 may be developed as a cure of virus- infection" as "...and CLK2 inhibition may be exploited as a cure of virus- infection", due to the fact that TG003 inhibitor may not be suitable for further chemical optimization, to serve as an effective and safe antiviral. + +Marco Sgarbanti + +<--- Page Split ---> + +## Point-by-point response to reviewers' comments + +We are extremely thankful for the reviewers' constructive feedback and valuable suggestions, which have greatly contributed to the enhancement of our manuscript and study. In response to the reviewers' comments, we have conducted additional experiments and made necessary clarifications to certain statements and experimental procedures in the revised manuscript. Here is our point- by- point response to the reviewers' comments. + +## Reviewer #1 (Remarks to the Author): + +## Summary + +The authors have provided a thorough rebuttal. They note numerous figure modifications with the addition of new data and removal and rearrangement of previous data, and text clarifications that have substantially improved the manuscript. The authors have defined a role for CLK2 in the impairment of NF- kB activation and inflammation that impacts virus replication, and further improvements were made to Figs 1- 3 in response to Reviewer 2. However, I am not satisfied with the mechanistic underpinnings of the impact of CLK2 on RelA/p65. Without confirmation that CLK2 directly phosphorylates RelA/p65 and that this inhibition is truly independent of IkBa, the novelty of this publication is substantially reduced. The data provided does not strongly lock down these two claims. + +## Major concerns + +## 1. Weak evidence that RelA/p65 Ser180 is a direct substrate of CLK2. + +- For IP interactions and phos-tag and ADP glo kinase assays in Fig 4 and Supp Fig4: It would be ideal to perform with purified proteins. As it stands now this interaction could be part of a complex and not direct. They describe Fig 4f as an in vitro pulldown that I suppose is linked to the'protein purification and pull-down'in Methods. This describes a purified His-p65 with FLAG-enriched lysates of transfected 293T cells. Is there a Coomassie stained gel to demonstrate the purity of the FLAG enriched lysate used for the FLAG pull-down? + +## Response: + +It is really a valuable advice and we also agree that it would be ideal to use purified proteins. It may be complex and not show the interaction directly. We successfully purified His- p65 in prokaryotic cells, but were unable to purify full- length CLK2 and CLK2K192R in prokaryotic cells. Instead, we chose to enrich them in transfected HEK293T cells. And the method is linked to the "protein purification and pull- down" in Methods section. Additionally, we actually ran a Coomassie stained gel, but it was inadvertently not provided. Here is the new version of Fig. 4f which is presented below. + +<--- Page Split ---> +![PLACEHOLDER_32_0] + + +- The authors respond in the rebuttal that the CLK2K192R mutant is widely used in the field. Can they verify that the CLK2 K192R mutant is kinase dead in this system using canonical substrates? It is also notable that CLK2 undergoes autophosphorylation on Ser141, mutation changes its subnuclear localization (PMID 9852100). Does the K192R prevent this autophosphorylation? One potential explanation is that the autophosphorylated form of CLK2 is required to interact with p65 (whether due to TG003 or the K192R mutant), but does not reflect the requirement for its kinase activity. + +## Response: + +We apologize for not using canonical substrates to directly verify the kinase- dead status of the CLK2K192R mutant. However, we refer to the pivotal study by Joseph T. Rodgers et al. (DOI: 10.1016/j.cmet.2009.11.006), which demonstrated that CLK2K192R lacks the ability to phosphorylate PGC- 1α in a \(\gamma^{32}\mathrm{P}\) - ATP reaction, as illustrated in Supplementary Fig. 2D (presented below). This evidence firmly supports our assertion that the CLK2K192R mutant is kinase- dead. + +As the reviewer said "It is also notable that CLK2 undergoes autophosphorylation on Ser141, mutation changes its subnuclear localization (PMID 9852100). Does the K192R prevent this autophosphorylation". Addressing the reviewer's insightful query, we highlight findings from the same study by Rodgers et al., showing \(\gamma^{32}\mathrm{P}\) - ATP consumption when CLK2K192R was co- incubated with CLK2WT (Supplementary Fig. 2E and was presented below). This suggests that while CLK2K192R cannot autophosphorylate, it can be phosphorylated by CLK2WT. Furthermore, the localization pattern of CLK2K192R, closely mirroring that of the CLK2S142A mutant (DOI: 10.1074/jbc.273.51.34341), reinforces our conclusion regarding the kinase- dead status of CLK2K192R and its inability to undergo autophosphorylation. + +In our manuscript, the CLK2K192R mutant was primarily utilized as a negative control, analogous to the use of TG003 as suggested by the reviewer. Moreover, the autophosphorylated form of CLK2 itself indicates the necessity of its kinase activity. We believe that regardless of the form of CLK2 - be it K192R, S142A, or treated with + +<--- Page Split ---> + +TG003 - the K192R mutation indeed leads to the inactivation of CLK2 kinase activity, making our findings valid. + +# [REDACTED] + +Rodgers JT, Haas W, Gygi SP, Puigserver P. Cdc2- like kinase 2 is an insulin- regulated suppressor of hepatic gluconeogenesis. Cell Metab. 2010;11(1):23- 34. doi:10.1016/j.cmet.2009.11.006 + +- TG003 is not specific for CLK2, this drug also inhibits other CLKs. This is important since CLK1,2,4 each regulate other substrates including splicing factors (PMID 33846420). They need to demonstrate that this is not impacting other CLKs or that other CLK2 substrates aren't playing a role. Why not show that the impact of TG003 is only observed in CLK2+, but not CLK2-/- cells. + +## Response: + +We are grateful for your insightful comments regarding the specificity of TG003. We acknowledge that TG003 is known to inhibit several members of the CLK family, including CLK1, CLK2, and CLK4. Recognizing the critical need to demonstrate the specificity of TG003's effects in the context of our study, we have undertaken additional experiments. + +To unequivocally address the concerns raised, CLK2- /- cells. Our results, now included as Supplementary Fig. 6m, show that TG003's presence or absence did not + +<--- Page Split ---> + +influence the acetylation or phosphorylation levels of p65 in CLK2-/- cells. This outcome strongly suggests that the impact of TG003 on p65 activation is specifically mediated through inhibition of CLK2, rather than other CLK family members. + +![PLACEHOLDER_34_0] + + +- The guidelines and other publications that use the ADP-glo kinase assay report activity based on the change in luminescence with concentration of the protein/inhibitors present. Here, they apply it as a single timepoint/readout luminescent reading-they do not report kinase activity differences in CLK compared to the CLK2 K192R mutant over a range of protein/substrate concentrations. Given that CLK2 K192R is expressed at lower levels than CLK2 in Fig 4C- this decrease in luminescence might just represent a decrease in CLK2 mutant expression levels. They don't show assay results for FLAG-CLK2K192R in the absence of His-p65. What is the source of the samples examined (lysates or purified components)? The input proteins need to be shown to verify equal inputs. Minimally, a purified CLK2 kinase enzyme system is commercially available (Promega) and could be used with their purified p65 to verify p65 is a substrate for CLK2. + +## Response: + +We are grateful for your valuable advice. Taking into account previous research and the suggestion of the technical adviser from Promega, we have decided on the specific concentration of CLK2 for the kinase assay. + +It is so sorry for confusing you about the expression of CLK2 and CLK2K192R, they were utilized with the same concentration which were examined by BCA Protein Quantification Kit. We deeply regret that we are unable to detect the sample for CLK2K192R without His-p65 and did not show the examination of samples additionally. + +To directly address your concerns, we procured the commercially available CLK2 kinase enzyme system from Promega. Given the unavailability of a commercial source for CLK2K192R, we utilized the provided CLK2 enzyme and combined it with our own purified His-p65 for the kinase assay. The results clearly demonstrated a dose- dependent relationship between ATP consumption and the amount of His-p65 (0ng, 100 ng, 500 ng, 1000 ng, 2000 ng) with a constant 20 ng of CLK2 protein. These adjustments and additional experiments significantly bolster our confidence in the reported findings, establishing p65 as a substrate for CLK2. We believe these efforts adequately address your concerns and enhance the overall validity and robustness of our study. + +<--- Page Split ---> +![PLACEHOLDER_35_0] + + +-The rationale for pursuing S180 but not S316 does not seem logical since the alignments show similar patterns of conservation across species for both (Fig 5B). + +## Response: + +The question raised is a significant one, and as the statement in result section "The NF- \(\kappa \mathrm{B}\) luciferase reporter assay showed that \(\mathrm{p65^{S180D}}\) , but not \(\mathrm{p65^{S316D}}\) , completely blocked the wild- type p65- induced NF- \(\kappa \mathrm{B}\) luciferase reporter activation, suggesting that phosphorylation of p65 serine 180 is necessary for NF- \(\kappa \mathrm{B}\) deactivation (Supplementary Fig. 5d)". Our research focuses on inhibiting NF- \(\kappa \mathrm{B}\) activation in innate immunity and inflammation, and serine 180 has shown to play a crucial role in this process. As a result, we highlight the importance of serine 180 in the deactivation of NF- \(\kappa \mathrm{B}\) signaling and chose to investigate the function of serine 180 in NF- \(\kappa \mathrm{B}\) signaling activation, while excluding serine 316. + +Although Ser316 is also a potential phosphorylation site by CLK2, our experiments suggest that \(\mathrm{p65^{S316D}}\) does not affect NF- \(\kappa \mathrm{B}\) signaling transactivation in response to viral and cytokine stimulation. This finding directs our focus towards Ser180 due to its significant impact on NF- \(\kappa \mathrm{B}\) signaling. Nonetheless, we acknowledge that Ser316 may play a role in other physiological or regulatory mechanisms. Recognizing this potential, we aim to investigate the function and implications of S316 phosphorylation in future studies, thus expanding our understanding of NF- \(\kappa \mathrm{B}\) signaling regulation and its broader physiological significance. + +-The analysis of the p65 S180 mutant clearly shows that S180A is more active than S180D, but the stronger experiment is to show that both retain this profile with or without CLK2 expression, unlike WT p65 (Fig 5E). + +## Response: + +Your concern is very important, and we have previously observed that S180A maintains its profile with or without CLK2. We conducted a similar experiment by overexpressing CLK2, and the results of the Luciferase assay showed that CLK2 overexpression does not affect the activation of NF- \(\kappa \mathrm{B}\) by \(\mathrm{p65^{S180A}}\) , contrasting with the significant inhibition observed in the case of wild- type p65. Regarding the S180D mutant, which represents a phosphorylation- mimicking, deactivated form of p65, we chose not to include it in this assay. The decision was based on its intrinsic deactivated + +<--- Page Split ---> + +state, which we anticipated would not provide additional insights into the impact of CLK2 overexpression on NF- \(\kappa \mathrm{B}\) activation. The results are available and presented below, but are not included in the manuscript. + +![PLACEHOLDER_36_0] + + +- There was a notable difference in the expression level of HA-S180D in Fig 5 due to a decrease in stability; that is the simple explanation for loss of NF-kB activation in Fig 4 functional assays. Why aren't these assays shown in the presence and absence of CLK2 to demonstrate that only the WT p65 half-life/instability (Supp Fig 6G) is different between CLK2+ and CLK2-/- cells (S180A and S180D would not show any dependence on CLK2 correct, correct)? + +## Response: + +Thanks for your valuable suggestion. As what another reviewer said, "While MG132 experiments provide striking qualitative data demonstrating a role for phosphorylated ser180 in protein degradation, authors must calculate p65 wt, p65 S180A and p65 S180D half-life by performing a time course of cycloheximide (CHX) treatment, thus straightening their findings with solid quantitative data". We had performed the experiment in HEK293T, HEK293T- p65S180A/KI, and HEK293T- p65S180D/KI cell lines then to further verify the stability of p65S180A and p65S180D following the reviewer #2's advice. + +What you concerned are both reasonable and crucial. In accordance with your advice, we have performed the CHX assay in HEK293T- CLK2- /- cells and the findings have been incorporated into Supplementary Fig. 6g. The results indicate that p65WT in CLK2- /- cells exhibits slightly greater stability than p65WT in HEK293T cells, resembling the result of p65S180A/KI closely. On the other hand, the consistently phosphorylated mutant p65S180D/KI demonstrates notably inferior stability. + +This data indicates that both p65WT in CLK2- /- cells and p65S180A/KI exhibit comparable half- lives, suggesting that their stability is not influenced by CLK2- mediated phosphorylation. Accordingly, we infer that mutations at the Ser- 180 site, namely S180A and S180D, exhibit no dependency on CLK2 for their stability or degradation profiles. + +<--- Page Split ---> +![PLACEHOLDER_37_0] + + +To reflect these insights, the result section has been revised as "and a cycloheximide (CHX) assay also revealed that p65S180D had a significantly shorter half- life than p65WT. On the contrary, p65S180A, which is similar to p65WT in CLK2-/- cells, showed a bit increased stability (Supplementary Fig. 6g)". + +-I remain in doubt about the findings using the Ser- 180 p- p65 antibody (Fig 6F). The phospho- specific Ser- 180 antibody that they had produced shows a non- specific band and evidently cross reacts with total p65, As controls, did they profile WT p65, S180A and S180D mutants to show this only recognizes the WT p65. Did they test p65- /- cells? Response: + +We appreciate your concerns regarding the specificity of our phospho- specific Ser- 180 p65 antibody. Although we did not profile S180A and S180D mutants with this antibody, we conducted specificity tests using p65- /- cells as a critical control. Supplementary Fig. 6k (which was presented below) demonstrates that the level of phos- p65 (Ser180) showed dynamic changes during SeV or TNF- \(\alpha\) infection. Importantly, in p65- /- cells, where no p65 protein should be present, only a very weak band was observed. We interpret this minimal signal as non- specific binding, which is common in immunoblotting but does not detract from the overall specificity of the antibody towards its intended target under the conditions tested. + +This control experiment supports the specificity of our phospho- Ser- 180 p65 antibody, as significant reactivity is observed in the context of infections where Ser180 phosphorylation is expected to occur, while minimal background is detected in the absence of the p65 protein. We believe these findings adequately address the concern about antibody specificity and affirm the reliability of our results involving the detection of phospho- Ser180 p65. + +![PLACEHOLDER_37_1] + + +<--- Page Split ---> + +- Also there is inconsistency between the CLK2+/+ vs-/- cells in Fig6D at basal (Ohrs) conditions. The p-p65 Ser180 is the same at Ohr in the SeV blot on left but higher in CLK2+/+ cells compared to CLK2-/- cells at O hrs in the right TNFa blot. + +## Response: + +We are grateful for your keen observation and it is exactly what you describe. We also feel confused. After reviewing multiple instances of repetitions, we believe that the p- p65 Ser180 level in CLK2+/+ cells should be higher than in CLK2-/- cells at 0 hrs (The results of repetitions were presented below). This discrepancy may have been caused by a system error in a single experiment. Similar to the identification of the antibody in p65-/- cells shown in the figure below, we can find that the blot at 0 hrs in HEK293T cells and blot in p65-/- cells have a similar level of p- p65 Ser180. In conclusion, the specificity of p- p65 Ser180 has been confirmed, and the discrepancy may simply be an error that does not affect the conclusion we have reached. + +![PLACEHOLDER_38_0] + + +## 2. I am still not convinced that CLK2 function is independent of IkBa. + +"Interestingly, there was an increased accumulation of Nfkbia in Clk2-/- cells, which is consistent with the increase in Lys- 310 acetylation and Ser- 536 phosphorylation of p65. It indicates that CLK2 may be a basal checkpoint to limit constitutional activation of NF- KB signaling, even in the absence of activating stimuli." - I remain unclear what they mean by 'early stage termination.' It seems that the impact of CLK2 on p65 and NFkbia is most apparent in the context of induction than basal conditions. IkBa is expressed and plays a role in basal and induced conditions over a 6 hr timecourse. + +## Response: + +We apologize for any confusion caused by our previous explanation and we appreciate the opportunity to further clarify the role of CLK2 in the regulation of NF- \(\kappa \mathrm{B}\) signaling and its independence from IkBa- mediated termination. + +<--- Page Split ---> + +Our focus is on the termination of transcriptional activation of p65. One well- known model involves \(\mathrm{IkBa}\) interacting with p65 in the cytoplasm, known as \(\mathrm{IkBa}\) - dependent termination. However, research has shown that p65 can still be retained in the cytoplasm even in the absence of \(\mathrm{IkBa}\) (doi: 10.1128/MCB.16.5.2341), suggesting the existence of other termination mechanisms independent of \(\mathrm{IkBa}\) . Our study reveals that CLK2 phosphorylates p65, regulating its post- translational modifications and reducing its DNA- binding activity and stability, ultimately leading to the termination of its transcriptional activation. Our proposed model is distinct from the \(\mathrm{IkBa}\) - dependent termination model, and thus we refer to it as \(\mathrm{IkBa}\) - independent termination. + +According to the detailed explanation of the classic \(\mathrm{IkBa}\) - dependent termination model, \(\mathrm{IkBa}\) primarily inhibits p65 during basal conditions and in the later stage of activation. In basal conditions, \(\mathrm{IkBa}\) binds to p65 in the cytoplasm, preventing its nuclear translocation. Once the NF- \(\kappa \mathrm{B}\) signaling is activated, \(\mathrm{IkBa}\) is mostly degraded, allowing p65 shuttles into the nucleus. Meanwhile, as one of the downstream genes of p65, \(\mathrm{IkBa}\) is resynthesized, mediated by p65 in the later stage, and binds with nuclear- p65 to bring it back to the cytoplasm (DOI: 10.1016/j.cell.2008.01.020). The defect of this model is that in the early stage of activation, there is no inhibitor to suppress or terminate the transcriptional activation of p65 when \(\mathrm{IkBa}\) has been mostly degraded but not yet been resynthesized. Therefore, the "early stage" here represents the period in which p65 shuttles into the nucleus and starts the progression of transcription in the absence of \(\mathrm{IkBa}\) . However, CLK2 can inhibit the activation of NF- \(\kappa \mathrm{B}\) signaling once p65 shuttles into the nucleus, and the inhibition lasts until the termination of NF- \(\kappa \mathrm{B}\) signaling. The novel termination mechanism by CLK2 includes the early stage of activation and is not dependent on \(\mathrm{IkBa}\) . Finally, this is referred to as " \(\mathrm{IkBa}\) - independent early stage termination". + +The change of p65 and Nfkbia is indeed more apparent in the context of induction than basal conditions. During activation, p65 is subject to much post- translational modifications, while Nfkbia undergoes mostly degradation and then re- synthesis. + +About the statement " \(\mathrm{IkBa}\) is expressed and plays a role in basal and induced conditions over a 6 hr time course". Actually, the Nfkbia we mentioned here is not being investigated for its function in basal and induced conditions. Instead, the expression level of Nfkbia serves as an indicator of the transcriptional activity mediated by p65, which is known to induce Nfkbia expression. It is noteworthy that the expression of Nfkbia in \(\mathrm{Clk2}^{- / - }\) cells is more than that in \(\mathrm{Clk2}^{+ / + }\) cells, even under basal conditions (Fig. 2e and Supplementary Fig. 2f). The result indicates us that p65 displays heightened transcriptional activity in the absence of CLK2, no matter in basal or induced conditions. + +- They state on lines 81-82 that 'we report an lkBa-independent nuclear NF-kB termination model at the transcriptional level through inhibitory phosphorylation by CLK2'Given that they have greater interactions of p65 with lkBa in the presence of CLK2 (without or with TNF) in Supp Fig 61, doesn't this again indicate that lkBa can + +<--- Page Split ---> + +be playing a role in CLK2's inhibition of p65? Can they demonstrate that CLK2 suppresses p65 even in the absence of lkBa? + +## Response: + +What a great question. As we answered previously, phosphorylation of p65 by CLK2 has been shown to inhibit the transcriptional activation of p65, and it was reflected by the post- translational modification levels of p65. This inhibition by CLK2 is independent of \(\mathrm{lkBa}\) . Meanwhile, the interaction between \(\mathrm{lkBa}\) and nuclear- p65 is regulated by the acetylation of p65. According to the work by Lin- feng Chen (DOI: 10.1093/emboj/cdf660), we can understand that acetylation of p65 at K221 and K218 can enhance the DNA binding of NF- \(\kappa \mathrm{B}\) and impair its association with \(\mathrm{lkBa}\) . + +However, it is important to differentiate between the effect of CLK2 on p65 activity and the role of \(\mathrm{lkBa}\) . In our manuscript, we found that CLK2 inhibits several post- translational modifications of p65, which may also impair the acetylation levels of p65 at K221 and K218. Therefore, it makes sense that p65 has greater interactions with \(\mathrm{lkBa}\) in the presence of CLK2. Moreover, phosphorylation by CLK2 and interaction with \(\mathrm{lkBa}\) are two separate events, with a precedence relationship in time. The increased interaction between \(\mathrm{lkBa}\) and p65 is one of the results caused by phosphorylation by CLK2. In a word, the inhibition of p65 by CLK2 is not affected by the absence or presence of \(\mathrm{lkBa}\) , so it does not indicate that \(\mathrm{lkBa}\) plays a role in CLK2's inhibition of p65. + +During the activation of NF- \(\kappa \mathrm{B}\) signaling, \(\mathrm{lkBa}\) is mostly degraded and re- . synthesized. We can observe that active- p65 (phosphorylated and acetylated p65) can still be inhibited even when \(\mathrm{lkBa}\) is mostly degraded in the presence of CLK2 (the 30 min time- course of LPS treatment in MLFs in Fig. 2e, and the 10 min time- course of TNF- \(\alpha\) or IL- 1β treatment in MLFs in Supplementary Fig. 2f). Therefore, we can demonstrate that CLK2 can still suppress p65 in the absence of \(\mathrm{lkBa}\) + +-I don't understand their statement that lkBa functions in CLK2 KO cells- the data they cite just shows NFkbia is resynthesized by western. Do they introduce lkBa into CLK2/- cells and show it is still inhibitory? + +## Response: + +Thank you for the opportunity to clarify this aspect of our study. It's important to understand that \(\mathrm{lkBa}\) functions as both an inhibitor of NF- \(\kappa \mathrm{B}\) p65 and as a gene whose expression is induced by NF- \(\kappa \mathrm{B}\) activation. The results indicate that p65 displays enhanced transcriptional activity in the absence of Clk2, which result in the increased production of Nfkbia. Actually, the expression level of Nfkbia was observed as a downstream expressed protein in this context. + +Regarding the question "Do they introduce \(\mathrm{lkBa}\) into CLK2- cells and show it is still inhibitory", we need to explain that \(\mathrm{lkBa}\) inhibits p65 by interacting with it, and this interaction is dependent on the acetylation level of p65 which is directly regulated by acetylases and deacetylases, such as p300/CBP or HDAC3 (doi: 10.1093/emboj/cdf660). In the absence of CLK2, we can still observe that p65 has + +<--- Page Split ---> + +affinity to \(\mathrm{1kBa}\) , and still can interact with it. In general, \(\mathrm{1kBa}\) still exhibits its inhibitory function, although it is weakened in CLK2- cells. + +- They find that S180D (which does not activate NF-kb and has a higher turnover) has a higher affinity for Nfkbia/lkBa (Supp Fig 6H), but S180A and WT in CLK2-/- cells has a decreased interaction with CRM1 and lkba (Fig 6C &6D). This data demonstrates that the phosphorylation on S180 induced by CLK2 leads to a higher affinity for lkba that would export and lock p65 out of nucleus; in turn this lead to the loss of NF-kB post-translational modifications and functions in the nucleus. Therefore, the impact of CLK2 on p65 Ser180 phosphorylation may be upstream of lkba interactions, but ultimately is determined by lkba export. It is not independent of lkba-just not dependent on newly synthesized lkba in late stage termination. This does not fit with their conclusions and title. + +## Response: + +We apologize for our previous explanation being unclear. As we mentioned before, \(\mathrm{1kBa}\) serves as a method for nuclear exportation, but p65 can also translocate to the cytoplasm independently of \(\mathrm{1kBa}\) (doi: 10.1128/MCB.16.5.2341). In our manuscript, the result shows that \(\mathrm{1kBa}\) can be used up in p65S180D/K1 cells (Supplementary Fig. 6e). Meanwhile, we observed that p65 can still shuttle from the nucleus to the cytoplasm in 1- 3 hrs in p65S180D/K1 cells (Fig. 6b). Combine the results, they suggest that p65 can still be exported from the nucleus in absence of \(\mathrm{1kBa}\) . In summary, our conclusions reflect the broader understanding that CLK2 influences NF- \(\mathrm{kB}\) signaling through mechanisms that can both involve and bypass \(\mathrm{1kBa}\) . This nuanced view acknowledges the complexity of NF- \(\mathrm{kB}\) regulation, where multiple layers of control determine the nuclear- cytoplasmic dynamics of p65, including but not limited to its interactions with \(\mathrm{1kBa}\) . + +-Lines 368- 370 described showing p65 S180A and WT interactions with CRM1 and lkBa in CLK2-/- cells. Fig 6D only shows 293T cells and Fig.6i only shows WT p65 in both CLK2+/+ and CLK2-/- cells. + +## Response: + +We feel so sorry for confusing the reviewer. Fig. 6d displays the interaction between p65 and \(\mathrm{1kBa}\) or CRM1 in p65WT and p65S180A/K1 cells (which is on right part of Fig. 6d). Supplementary Fig. 6 shows the interaction between p65 and \(\mathrm{1kBa}\) and CRM1 in CLK2+/+ and CLK2-/- cells (both results are presented below). Therefore, the statement "Moreover, the p65S180A and p65WT in CLK2-/- cells presented decreased interaction with CRM1 and \(\mathrm{1kBa}\) (Fig. 6d and Supplementary Fig. 6i)" accurately reflects the findings. + +<--- Page Split ---> +![PLACEHOLDER_42_0] + + +## Minor comments. + +Professional editing is required even with revisions. Numerous issues remain and some are newly introduced. 'plague' is still used where 'plague' is appropriate. + +## Response: + +We appreciate the reviewer's attention to detail and their advice on the necessity of professional editing to improve the manuscript's language quality. We have taken this feedback seriously and enlisted the services of SPRINGERNATURE Author Services (SNAS) to ensure the manuscript meets the highest standards of English language, grammar, punctuation, and phrasing. We have attached the editing certificate from SNAS as proof of this professional review and editing + +## [REDACTED] + +We sincerely apologize for that we did not revised all the "plague" throughout the manuscript. Following your feedback, we have conducted a thorough review of the manuscript to correct this and any similar errors. We can now confirm that all instances have been corrected to "plague". + +The IFA figures with brightfield added have become very small (Fig3, 5). The IFA for the paired flow cytometry data could be moved to supplemental or the other bar graphs in the figures could be shortened to make space. + +<--- Page Split ---> + +## Response: + +We greatly appreciate your suggestion regarding the size of the IFA figures in Fig. 3 and 5. We recognize the importance of clearly presenting our results for effective communication of our findings. In response to your feedback, we have taken steps to enlarge the IFA figures in both Fig. 3 and 5, ensuring that the details are visible and the results can be easily interpreted. + +These adjusted figures are now included in the revised manuscript. This modification aims to enhance the overall clarity and impact of our visual data presentation. Thank you for helping us improve the quality of our figures and, by extension, our manuscript. + +![PLACEHOLDER_43_0] + + +I previously noted that the font kerning for the sequence alignment of Fig SB is off and that a monospace font is needed. The authors claim to have adjusted this- but the text is still not aligned properly. + +## Response: + +So sorry for not revising the Fig. 5b correctly, we need to apologize for it. Due to the Arial font cannot be set as monospace, we have tired many different methods and it seems like not be better. To rectify this, we have now utilized the Courier New font, which supports monospace formatting, ensuring that the text is aligned properly across the sequence. This adjustment has been applied to Fig. 5b, and we are confident that it now meets the necessary standards for clear and accurate presentation. + +<--- Page Split ---> + +Human VRDPSGRPLRPLPVLSHPIFDNRAPNTAEL Rat VRDPSGRPLRPLTVPLSHIPIFDNRAPNTAEL Mouse VRDPAGRPLLTVPLSHIPIFDNRAPNTAEL Zebrafish ITLSSGDLFPLEPVVSQPIVDNRAPNTAEL Fruitfly SEQKGRFTSPLPVVSEPIFDKAMSDLVI + +Human KRKRTYETFKISIMKKSPSFSPGTPDRPPPRR Rat KRKRTYETFKISIMKKSFPNGTPEPRPPPRR Mouse KRKRTYETFKISIMKKSFPNGTPEPRPPPRR Zebrafish KRKRTEGMLHNLKLSIIITGSSMSAERRPF Fruitfly RRKROKTGGDPMHLLLQQQQKQQLQNDHQD + +There is a lack of discussion regarding its canonical substrates such as splicing factors vs this noncanonical functions of CLK2 to target p65. How does SeV, TNFa or other stimulations that activated CLK2 tie into its impacts on splicing? When CLK2 is activated by infection to target p65, what is the impact on canonical substrates? + +## Response: + +Thanks for your reminding and we also think it is essential. The discussion has been updated and presented below. + +"On the other hand, CLK2 can be regulated significantly by SeV, TNF- \(\alpha\) or other stimulations. Activated CLK2 is usually considered to facilitate RNA alternative splicing processes involving SRSF1 and RBFOX2. When CLK2 is activated by infection to target p65, it may also promote the activation of SRSF1, which has been found that overexpression can inhibit the production of pro-inflammatory cytokines (doi: 10.1172/JCI127949). However, the promotion of RBFOX2, which can be regulated by CLK2, is considered to be positively associated with inflammation (doi: 10.1038/s42255-022-00681-y). In summary, these findings underscore the complex regulatory role of CLK2 in the inflammatory response, potentially exhibiting dual effects in different inflammatory diseases or virus infection". + +Typo in Supp Fig 4c legend line 1057: they state'The upper shifted band represents phosphorylated CLK2 protein.'This is actually p65, correct? + +## Response: + +Sorry for making that mistake and the figure legend has been revised as "The upper shifted band represents the phosphorylated p65 protein". + +With regard to Fig 6D legend, they state that "The asterisk/upper band indicate the unspecific band that can be detected by the antibody and the explanation was added in the relative figure legends." This has not been corrected. + +## Response: + +We feel so sorry that the statement of asterisk/upper band have not been corrected throughout the figure legends. Now, the statement "The upper band marked with asterisk indicates the unspecific band." have been added in the figure legends of Fig. 6f, 6g and Supplementary Fig. 6k. + +<--- Page Split ---> + +## Reviewer #2 (Remarks to the Author): + +Authors fixed all relevant issue raised, by performing new experiments as requested, and by modifying the manuscript, as suggested. I also encourage authors to make a further effort to improve manuscript written English (at pag 5 line 55, "rheumatoid arthritis", instead of "rheumatic arthritis"; at pag.6 line 89 "CLK2- deficient mice were observed to have higher levels", instead of "CLK2- deficient mice produce were observed to have higher levels"; at pag 22 line 444 "The transcription factor p65 is critical for cytokine- induced production of inflammation genes", instead of "The transcription factors p65 is critically for cytokine- induced production of inflammation genes"; at page 24 line 499" use of site- specific phosphorylation antibody", instead of "use of site- specific phosphorylation antibody", and so on). + +## Response: + +We are grateful for Reviewer #2's constructive feedback and the specific suggestions to enhance the manuscript's written English. In response, we have taken decisive action to address these concerns. The manuscript has undergone professional editing by SPRINGERNATURE Author Services (SNAS) to ensure accuracy in English language, grammar, punctuation, and phrasing. This comprehensive review aimed to correct the issues highlighted by the reviewer, including those mentioned and others throughout the document. + +We have attached the editing certificate from SNAS as evidence of this professional language editing service. This step underscores our commitment to presenting our findings clearly and professionally, and we believe it significantly improves the manuscript's overall quality. + +## [REDACTED] + +In addition, we appreciate the specific examples provided for language improvement and have made the following revisions to address these points: + +The "rheumatoid arthritis" is instead of "rheumatic arthritis". The "CLK2- deficient mice were observed to have higher levels" has been revised as "Clk2- + +<--- Page Split ---> + +deficient mice had increased serum levels of inflammatory cytokines after viral infection and showed increased resistance to virus- induced death". The "The transcription factors p65 is critically for cytokine- induced production of inflammation genes" has been modified as "The transcription factor p65 is critical for cytokine- induced production of inflammatory genes". "the use of site- specific phosphorylated antibodies" is instead of "use of site- specific phosphorylation antibody". + +Moreover, at pag. 21 line 440, I suggest to rephrase the sentence"...and TG003 may be developed as a cure of virus- infection" as"...and CLK2 inhibition may be exploited as a cure of virus- infection", due to the fact that TG003 inhibitor may not be suitable for further chemical optimization, to serve as an effective and safe antiviral. + +## Response: + +We agree with the reviewer that TG003 used here may not be suitable. Under the modification of SNAS, the sentence has been modified as "...indicating that CLK2 may be a therapeutic target for inflammatory diseases and that inhibiting CLK2 may be a strategy to cure viral infection". + +<--- Page Split ---> + +## REVIEWERS' COMMENTS + +Reviewer #1 (Remarks to the Author): + +The authors have adequately addressed my concerns and the concerns of reviewer 2 in the second revision. + +<--- Page Split ---> diff --git a/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd b/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd new file mode 100644 index 0000000000000000000000000000000000000000..9c9e8994ddda697dcd0ea812464cb34c498b571f --- /dev/null +++ b/peer_reviews/df7e829bb4ac10a7b5ccd37f38e402cdc43402390238719128d5bb78db0b7e36/supplementary_0_Peer Review File/supplementary_0_Peer Review File_det.mmd @@ -0,0 +1,1348 @@ +<|ref|>title<|/ref|><|det|>[[61, 40, 506, 90]]<|/det|> +# nature portfolio + +<|ref|>text<|/ref|><|det|>[[68, 110, 361, 139]]<|/det|> +Peer Review File + +<|ref|>text<|/ref|><|det|>[[66, 161, 922, 216]]<|/det|> +CLK2 mediates IkBα- independent early termination of NF- kB activation by inducing cytoplasmic redistribution and degradation + +<|ref|>image<|/ref|><|det|>[[56, 732, 239, 780]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[250, 732, 912, 800]]<|/det|> +Open Access This file is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. In the cases where the authors are anonymous, such as is the case for the reports of anonymous peer reviewers, author attribution should be to 'Anonymous Referee' followed by a clear attribution to the source work. The images or other third party material in this file are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 51, 812, 81]]<|/det|> +Editorial Note: Parts of this Peer Review File have been redacted as indicated to remove third- party material where no permission to publish could be obtained. + +<|ref|>sub_title<|/ref|><|det|>[[119, 125, 295, 140]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 153, 414, 168]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 182, 874, 338]]<|/det|> +The major finding of this manuscript is the identification of the NF- kB p65 subunit as a target of CLK2. Phosphorylation of p65 at Ser- 180 leads to nuclear export and degradation. This finding uncovers a new substrate for CLK2, a kinase previously found to modify splicing factors. Most importantly this manuscript discovers a new mechanism for negative feedback of p65- driven gene expression that is proposed to be independent of the well- known p65- dependent production of the IkBalpha inhibitor. The authors use complimentary approaches to demonstrate that loss of CLK2, CLK2 kinase function, or p65 Ser- 180 phosphorylation leads to a gain of interferon and inflammatory responses that have functional impacts on virus control and inflammatory pathologies, in cell culture and in mouse models. The parsing of main figure and supplementary figures is appropriate. That being said, there a few holes in their data that should be addressed to bolster CLK2 as the direct p65 kinase that functions prior to and independently of IkBa. + +<|ref|>sub_title<|/ref|><|det|>[[119, 352, 220, 365]]<|/det|> +## Major issues: + +<|ref|>text<|/ref|><|det|>[[118, 365, 870, 520]]<|/det|> +1. They indicate that CLK2 is an early terminator of NF-kB signaling via p65 on Ser180 and independent of IkBa- but there are some discrepancies with this interpretation. +a. Most assays are at 6, 12, or 24 hrs post-stim, well-after IkBa is typically transcriptionally induced by p65. Is there clear data showing two waves of inhibition? Does IkBa ever function in the absence of CLK2 or does CLK2 dominate? +b. Does the phosphorylation change of p65 in response to CLK2 impact the ability of p65 to be bound by IkBa? If p65 is no longer recognized by IkBa in the absence of CLK2 modifications then that could lead to an accumulation of p65 in the nucleus and increased transcriptional activity. p65 S180A is a mutant that can't be phosphorylated downstream of CLK2 and has a prolonged residence in the nucleus (Fig 6), but how is the role of IkBa excluded? Do any of the phosphorylation site mutants impact targeting by IkBa? + +<|ref|>text<|/ref|><|det|>[[118, 533, 490, 547]]<|/det|> +2. Is CLK2 the sole kinase and what activates it? + +<|ref|>text<|/ref|><|det|>[[118, 547, 875, 613]]<|/det|> +a. They identify multiple phosphorylation sites but there is never an in vitro analysis with purified CLK2 protein. As it stands now- CLK2 is certainly an upstream kinase- but given IP is performed in HEK293T - CLK2 might be acting via another kinase? Does the CLK2 inhibitor TG003 block phosphorylation of Ser 180 on p65 or any other site? + +<|ref|>text<|/ref|><|det|>[[118, 603, 870, 647]]<|/det|> +b. In Fig 6D, the SeV infected CLK2-/- have lower levels of phospho Ser180 p65 overall, but it is not eliminated. What kinase drives this remaining phosphorylation? What does the asterisk/upper band indicate in the western blots? + +<|ref|>text<|/ref|><|det|>[[118, 647, 856, 662]]<|/det|> +c. This CLK2-mediated inhibition is only observed upon stimulation- so what is activating CLK2? + +<|ref|>text<|/ref|><|det|>[[118, 674, 878, 716]]<|/det|> +3. There is a an overinterpretation that PML-associated p65 is more transcriptionally active. The PML colocalization and phase separation data is not well developed, being performed in the context of overexpression- it raises more questions than answers. Consider removing. + +<|ref|>text<|/ref|><|det|>[[118, 729, 870, 800]]<|/det|> +4. A major flaw in the publication is the poor quality of writing. Professional editing is essential. There were numerous grammatical errors and improper word choices (e.g. 'we wonder CLK2 may be a pregnant target to treat inflammation-associated diseases and virus infection') that make it nearly impossible for the reader to work through. This did detract from my understanding of some of their summaries and interpretations. + +<|ref|>sub_title<|/ref|><|det|>[[118, 814, 220, 827]]<|/det|> +## Minor issues: + +<|ref|>text<|/ref|><|det|>[[118, 828, 870, 912]]<|/det|> +1. Fig 2B. The PCR genotyping data for WT vs KO mice seems swapped. +2. Supp Fig 3 and Fig 5. have an odd arrangement of figures where the letters are not in alphabetical order. +3. The font kerning for the sequence alignment of Fig 5B is off. A monospace font is needed. +4. Fig 6 Figure legend states data are presented as SEM- but that type of data is not in the figure. +5. Information on the strain and source of SeV, VSV, and HSV virus stocks is lacking. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 84, 415, 98]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[117, 111, 876, 404]]<|/det|> +The manuscript entitled "CLK2- mediated IkappaBalpha- independent early- termination of NF- kappaB activation by phosphorylating nuclear- p65 for cytoplasmic redistribution and degradation" by Shang- Ze Li and colleagues describes the identification of a novel regulatory phosphorylation site (ser180) of the NF- kappaB sub- unit p65/RelA, target of the CLK2 kinase. CLK2 phosphorylation of p65 at ser180 by cytokine treatment or viral infection leads to increased p65 accumulation in the cytoplasm, and p65 proteasome- mediated degradation. Using knock- in phosphomimetic aspartic acid substitution of ser180 a decreased p65 activity is revealed compared to wt protein, following different stimuli, and also increased viral replication. On the contrary, substitution of ser180 with alanine, determining the inability of p65 to be phosphorylated by CLK2 at this residue, results in a "super- active" protein, capable of conferring resistance to viral infection in the knock- in cellular system. Moreover, CLK2 genetic ablation or its chemical inhibition promoted chronic inflammation in a mouse psoriasis model. Authors discussed CLK- 2 mediated p65 phosphorylation at ser180 as an early NF- kappaB shutdown pathway, alternative to the canonical feed- back regulatory mechanism represented by the NF- kappaB- mediated synthesis of IkappaB- alpha occurring later after stimulation. The CLK- 2 mediated phosphorylation of p65 and the subsequent inhibition of the activity of this transcription factor, represent important and novel findings, adding another important piece of information about how NF- kappaB, one of the most studied transcription factor, works. That being said, the manuscript, despite a large number of data gathered, lacks key experiments, and is misleading regarding some data interpretation. Moreover, an extensive revision for English language and grammar is required. + +<|ref|>text<|/ref|><|det|>[[120, 394, 720, 408]]<|/det|> +Moreover, an extensive revision for English language and grammar is required. + +<|ref|>sub_title<|/ref|><|det|>[[119, 422, 267, 436]]<|/det|> +## Specific comments: + +<|ref|>sub_title<|/ref|><|det|>[[120, 450, 293, 463]]<|/det|> +## 1-Introduction section. + +<|ref|>text<|/ref|><|det|>[[117, 464, 875, 744]]<|/det|> +Introduction section is lacking the description of other important phosphorylation sites identified on p65 (by the way, naming this transcription factor as RelA is more appropriate). Among these, ser276, known to enhance NF- kappaB transcriptional activity, or ser468, negatively regulating NF- kappaB mediated transcription (for a review see "Posttranslational modifications of NF- kB: another layer of regulation for NF- kB signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017), the latter highly relevant in the context of this manuscript and used in fig. 6D and E panels. Moreover, the paper by Saccani S. et al. "Degradation of Promoter- bound p65/RelA Is Essential for the Prompt Termination of the Nuclear Factor B Response" (J. Exp. Med. Volume 200, Number 1, July 5, 2004 107- 113. doi: 10.1084/jem.20040196) must be acknowledged, due to fact that it describes p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. In the same paper, if proteasome activity is blocked after an activating stimulus, NF- kappaB is not rapidly removed from target genes despite IkappaB synthesis, resulting in sustained transcription. Such paper describes a very similar mechanism of NF- kappaB "shutdown" and cannot be ignored. Finally, Lys 310 acetylation, required for full RelA transcriptional activity, should not be described without acknowledging the fact that it happens subsequently to the prior phosphorylation of RelA at ser276 and ser536 (Chen LF, et al. "NF- kappaB RelA phosphorylation regulates RelA acetylation". Mol Cell Biol. 2005 Sep;25(18):7966- 75. doi: 10.1128/MCB.25.18.7966- 7975.2005). What does "CLK2" stand for? Full name (Cdc2- like kinase 2) must be present, at least the first time CLK2 is described in the introduction section. + +<|ref|>sub_title<|/ref|><|det|>[[119, 757, 179, 770]]<|/det|> +## 2- Fig.1 + +<|ref|>text<|/ref|><|det|>[[118, 770, 875, 911]]<|/det|> +In the description of panel D, authors explain that they have used an ISRE reporter responding to SeV infection, to assess the impact of CLK2 on IRF- 3, to rule out IRF- 3 as a CLK2 target in IFN- beta promoter repression. However, authors did not provide evidence in the material and methods section about what specific ISRE sequence they have used in the reporter construct (indeed some commercially available ISRE reporter constructs also respond to IFN- I- induced ISGF3). In order for the authors to state that in fig. 1D they are dealing with IRF- 3 mediated stimulation, they have to use the transfection of a plasmid constitutively expressing an active form of IRF- 3, like IRF- 3 5D (Lin R. et al. Essential Role of Interferon Regulatory Factor 3 in Direct Activation of RANTES Chemokine Transcription. Mol Cell Biol. 1999 Feb; 19(2): 959- 966. doi: 10.1128/mcb.19.2.959), as a control, comparing the fold of activation obtained to those reached with SeV infection. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 826, 141]]<|/det|> +In Fig.1H error bars should be present in the graphs accounting for the three separate experiments, while the right western blot panel (showing TNF- alpha time course) should not present a GAPDH blot with such a poor separation between each band, clearly the result of excessive protein loading and/or overexposure. + +<|ref|>sub_title<|/ref|><|det|>[[118, 155, 303, 168]]<|/det|> +## 3- Supplementary Fig.1. + +<|ref|>text<|/ref|><|det|>[[118, 169, 874, 252]]<|/det|> +Looking at panel 1D, it seems that CLK2 expression is actually negatively affected in p65 knock- out cells compared to wt cells, therefore the authors' conclusion, that CLK2 is not that much regulated at the level of transcription, is questionable; authors should provide a statistical analysis comparing each experimental time points of wt vs knock- out cells. Moreover, authors should also perform the same experiment using TNF- alpha as a stimulus with a proper related time course of treatment, to match with the experiments shown in fig. 1H. + +<|ref|>sub_title<|/ref|><|det|>[[118, 267, 184, 279]]<|/det|> +## 4- Fig.2. + +<|ref|>text<|/ref|><|det|>[[118, 280, 853, 307]]<|/det|> +Panel B is not described in details and it is not clear, based on figure labelling, what does shown bands represent. + +<|ref|>text<|/ref|><|det|>[[118, 308, 875, 406]]<|/det|> +In panel E, particularly the right part involving MLFs, there is evidence for an increased accumulation of NFkappa in the CLK2 - /- cells even in control untreated cells. This accumulation of NFkappa matches with k310 acetylation and ser536 phosphorylation of p65, suggesting that, at least in these primary cells, CLK2 may represent a basal checkpoint acting to avoid a constitutive activation of p65 even in the absence of activating stimuli (e.g. LPS, TNF- alpha, IL- 1 beta, or viral infection). It seems that in these cells there is also an increased accumulation of p65 compared to wt cells. Authors need to comment on all these data. + +<|ref|>sub_title<|/ref|><|det|>[[118, 421, 309, 434]]<|/det|> +## 5- Supplementary Fig.2. + +<|ref|>text<|/ref|><|det|>[[118, 435, 665, 448]]<|/det|> +Panel A is supposed to be positioned in the upper left part of the figure. + +<|ref|>text<|/ref|><|det|>[[118, 449, 875, 519]]<|/det|> +In the lower right part of panel F, (like for Fig.2 panel E, right part) there is evidence for an increased accumulation of NFkappa in the CLK2 - /- cells even in control untreated cells. Even in this experiment, there is evidence for increased k310 acetylation and ser536 phosphorylation of p65 in control cells and increased accumulation of p65 compared to wt cells (the panel showing Ac- p65 Lys310 for the TNF- alpha time course must be repeated because bands are not clearly visible). + +<|ref|>sub_title<|/ref|><|det|>[[118, 534, 175, 546]]<|/det|> +## 5-Fig.3 + +<|ref|>text<|/ref|><|det|>[[118, 547, 723, 560]]<|/det|> +It is not clear what is the difference between Fig3C and supplementary Fig. 3E. + +<|ref|>text<|/ref|><|det|>[[118, 561, 875, 602]]<|/det|> +At line 169 of the result section related to Fig.3 ("CLK2 deficiency enhances virus- induced IFN- beta production and antiviral response") the word "plague" is actually "plague", and need to be substituted throughout the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[118, 617, 305, 630]]<|/det|> +## 6- Supplementary Fig.3 + +<|ref|>text<|/ref|><|det|>[[118, 631, 664, 644]]<|/det|> +Panel A is supposed to be positioned in the upper left part of the figure. + +<|ref|>text<|/ref|><|det|>[[118, 645, 866, 671]]<|/det|> +The rationale for the use of HSV- 1 compared to VSV in in vivo and in vitro experiments should be explained, together with the different results obtained. + +<|ref|>text<|/ref|><|det|>[[118, 672, 875, 699]]<|/det|> +It is not clear what kind of supplemental information is provided with supplementary Fig.3E, that is not present in Fig.3C. + +<|ref|>sub_title<|/ref|><|det|>[[118, 715, 175, 727]]<|/det|> +## 7-Fig.4 + +<|ref|>text<|/ref|><|det|>[[118, 729, 863, 784]]<|/det|> +The conclusion, related to panel A, that "CLK2 inhibits virus- triggered NF- kappaB signaling at the p65 level" (lines 197- 198 of the corresponding result paragraph) is correct, but does not rule out the possibility that there are also other upstream players in the signal transduction pathways affected by CLK2. + +<|ref|>text<|/ref|><|det|>[[118, 785, 656, 799]]<|/det|> +In panel B equal amount of Flag- CLK2 should be present in the lysate. + +<|ref|>text<|/ref|><|det|>[[118, 800, 863, 880]]<|/det|> +In panel C authors should also use a CLK2 inhibitor to conclude that CLK2 exerts its function with p65 depending on CLK2 kinase activity. This is because the lack of p65 binding to CLK2 K192R dead kinase, may also depend upon CLK2 conformational change due to the K to R mutation. Again, in panel C and F authors should comment about the faster migration of Flag- CLK2 dead kinase in the IP/WB experiment, compared to wt. This difference cannot be justified by K192R amino acid substitution. + +<|ref|>text<|/ref|><|det|>[[118, 882, 839, 909]]<|/det|> +In panel D, the western blotting experiment should also be repeated with an appropriate TNFalpha time course. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 83, 876, 124]]<|/det|> +In panel E, the graph should also report the luciferase fold of inductions relative to each uninfected control, to account for the basal activity of each kinase (wt and mutant) on the promoter compared to the SeV infection or TNF- alpha treatment. + +<|ref|>text<|/ref|><|det|>[[118, 125, 863, 181]]<|/det|> +In the western blot of panel F it is not clear why there is more p65 in the presence of wt CLK2 compared to CLK2 absence or the presence of the dead kinase. Authors should comment on this. In I and G panels, figures should be presented also showing cells with visible light, without fluorescence. + +<|ref|>text<|/ref|><|det|>[[118, 195, 691, 209]]<|/det|> +In panel H a quantification of the detected p65 bands should be presented. + +<|ref|>sub_title<|/ref|><|det|>[[118, 224, 295, 237]]<|/det|> +## 8-Supplementary Fig.4 + +<|ref|>text<|/ref|><|det|>[[118, 238, 878, 294]]<|/det|> +In panel A figures should be presented also showing cells with visible light, without fluorescence. In panel B, western blot should be repeated with a lower amount of loaded proteins (in GAPDH blot bands cannot be discriminated). Moreover, appropriate TNF- alpha time course should also be presented. + +<|ref|>sub_title<|/ref|><|det|>[[118, 309, 175, 321]]<|/det|> +## 9-Fig.5 + +<|ref|>text<|/ref|><|det|>[[118, 322, 876, 350]]<|/det|> +Panel distribution is confusing (what panel does the lower right graphic belongs to? Is it panel F? If this is the case, are those cells infected with SeV? + +<|ref|>text<|/ref|><|det|>[[118, 350, 873, 405]]<|/det|> +In panel C, figures should be presented also showing cells with visible light, without fluorescence. What is really missing, in this in depth phosphorylation site analysis involving p65, is that no attempt at all was made to identify a consensus amino acidic sequence on p65, target of the CLK2 kinase. + +<|ref|>text<|/ref|><|det|>[[118, 405, 872, 434]]<|/det|> +This is an important shortcoming of the manuscript and must be addressed in both, the result and the discussion paragraph. + +<|ref|>sub_title<|/ref|><|det|>[[118, 449, 304, 462]]<|/det|> +## 10-Supplementary Fig.5 + +<|ref|>text<|/ref|><|det|>[[118, 463, 864, 476]]<|/det|> +In panel D, figures should be presented also showing cells with visible light, without fluorescence. + +<|ref|>sub_title<|/ref|><|det|>[[118, 492, 191, 504]]<|/det|> +## 11-Fig.6 + +<|ref|>text<|/ref|><|det|>[[118, 505, 875, 589]]<|/det|> +Experiments shown in Panels D and E are very important for a crucial aspect of CLK2 mediated phosphorylation of p65, and that is p65 degradation and relocation of the protein from the nucleus to the cytoplasm. While MG132 experiments provide striking qualitative data demonstrating a role for phosphorylated ser180 in protein degradation, authors must calculate p65 wt, p65 K180A and p65 K180D half- life by performing a time course of cycloheximide (CHX) treatment, thus straightening their findings with solid quantitative data. + +<|ref|>text<|/ref|><|det|>[[118, 589, 876, 644]]<|/det|> +Moreover, as shown in CLK2 - /- cells a strong constitutive acetylation of p65 at K310 is detected, despite SeV infection or TNF- alpha treatment compared to its absence in wt cells and also an increased ser536 phosphorylation, known to precede K310 acetylation, compared to lower levels in wt cells. + +<|ref|>text<|/ref|><|det|>[[118, 645, 860, 673]]<|/det|> +This basal activation status of p65 in the absence of CLK2 and of any stimuli, suggest a different data interpretation (see comments below). + +<|ref|>text<|/ref|><|det|>[[118, 687, 868, 812]]<|/det|> +In the results paragraph describing Fig.6 and supplementary Fig.6, an important set of experiments is missing. Indeed no p65 DNA binding analysis was performed. Is p65 capable of binding kappaB sites when phosphorylated at ser 180 or when this residue is mutated to either aspartic acid or alanine? Particularly, is p65 capable of binding DNA kappaB sites in CLK2 knockout cells, in the absence of activation stimuli, considering that, in this case, it is highly acetylated at K310, but at the same time it is supposed to be still bound to IkappaB- alpha? These are important questions that need to be answered by performing new experiments, also considering the work by Saccani S. et al. (doi: 10.1084/jem.20040196), showing p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. + +<|ref|>text<|/ref|><|det|>[[118, 812, 875, 897]]<|/det|> +At line 335 of the results paragraph " Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", ser- 468 phosphorylation is described as an activation hallmark of p65, but in fact is mostly associated with a state of repression of p65 transcriptional activity ( for a review see "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017). Therefore, detection of ser 468 in panels D and E should be discussed accordingly. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 84, 656, 98]]<|/det|> +Quantification is needed for the western blot results shown in panel C. + +<|ref|>text<|/ref|><|det|>[[118, 98, 878, 239]]<|/det|> +Quantification is needed for the western blot results shown in panel C.The following sentences " So far, these studies showed that phosphorylation of p65 at Ser- 180 serves as a key switch in terminating active p65 through degradation and nuclear export. All of these experiments indicated that CLK2 acts as a brake in the early stage of NF- kappaB transcriptional activation, and it cooperates with IkappaB- alpha, which functions as a brake in the later stage, to limit the transcriptional process in the whole time of NF- kappaB signaling activation" present starting line 342 of the results paragraph " Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", should be reserved to the Discussion section. Moreover, these conclusions are only partially covering the large amount of data gathered, that also point to the CLK2 mediated phosphorylation of p65 at ser 180 as a homeostatic suppression of p65 activity before the signaling cascades of activating stimuli begin. + +<|ref|>sub_title<|/ref|><|det|>[[120, 253, 310, 266]]<|/det|> +## 12- Supplementary Fig.6 + +<|ref|>text<|/ref|><|det|>[[118, 266, 840, 308]]<|/det|> +In panel B it is not clear what n.s. (non specific) refers to. Is it compared to wt p65 or S180A mutant? It is important because it seems that there is an increased mRNA expression for the S180A mutant compared to wt or the S180D mutant. + +<|ref|>text<|/ref|><|det|>[[118, 308, 875, 420]]<|/det|> +In panel E it is not clear how this experiment was performed. Treatment of cells with MG132 results in the inhibition of p65 nuclear translocation and p65 mediated gene activation, due to the fact that IkappaB- alpha degradation is prevented (Lee, D.H. and Goldberg, A.L. 1998 "Proteasome inhibitors: valuable new tools for cell biologists". Trends Cell Biol. 8, 397- 403 doi: 10.1016/s0962- 8924(98)01346- 4. ). In this panel, though, authors show the nuclear accumulation of p65 S180D following TNF- alpha treatment in the presence of MG132. Authors should provide a plausible explanation for this considering that in this case IkappaB- alpha cannot be degraded. Moreover, IkappaB- alpha expression should be present in this western blot panel. + +<|ref|>text<|/ref|><|det|>[[119, 433, 875, 504]]<|/det|> +13- The following sentence "These data suggest that CLK2 represents a potential therapeutic target for inflammatory diseases", starting at line 374 of the results paragraph "CLK2 inhibitor TG003 exhibits power in vitro and in vivo", seems not formally correct. On the contrary, data suggest that any pathway inhibitor of CLK2 may represent a potential therapeutic target for inflammatory diseases, because CLK2 actually acts inhibiting prolonged inflammation. + +<|ref|>sub_title<|/ref|><|det|>[[120, 519, 226, 531]]<|/det|> +## 14-Discussion + +<|ref|>text<|/ref|><|det|>[[120, 532, 846, 560]]<|/det|> +Discussion should provide a better data interpretation, also including discussion of results from new experiments related to p65 DNA binding. + +<|ref|>text<|/ref|><|det|>[[120, 589, 280, 602]]<|/det|> +Marco Sgarbanti PhD + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 86, 542, 102]]<|/det|> +Point- by- point response to reviewers' comments + +<|ref|>text<|/ref|><|det|>[[148, 104, 849, 196]]<|/det|> +Point- by- point response to reviewers' commentsWe would like to thank the reviewers for their comments and insightful suggestions, which have greatly helped us to revise the manuscript and improve our study. Based on the reviewers' comments, we have performed additional experiments and clarified certain statements/experimental procedures in the revised manuscript. Following is our point- by- point response to the reviewers' comments. + +<|ref|>sub_title<|/ref|><|det|>[[148, 217, 255, 232]]<|/det|> +## Reviewer #1 + +<|ref|>text<|/ref|><|det|>[[147, 234, 850, 473]]<|/det|> +The major finding of this manuscript is the identification of the NF- kB p65 subunit as a target of CLK2. Phosphorylation of p65 at Ser- 180 leads to nuclear export and degradation. This finding uncovers a new substrate for CLK2, a kinase previously found to modify splicing factors. Most importantly this manuscript discovers a new mechanism for negative feedback of p65- driven gene expression that is proposed to be independent of the well- known p65- dependent production of the IkBa/pha inhibitor. The authors use complimentary approaches to demonstrate that loss of CLK2, CLK2 kinase function, or p65 Ser- 180 phosphorylation leads to a gain of interferon and inflammatory responses that have functional impacts on virus control and inflammatory pathologies, in cell culture and in mouse models. The parsing of main figure and supplementary figures is appropriate. That being said, there a few holes in their data that should be addressed to bolster CLK2 as the direct p65 kinase that functions prior to and independently of IkBa. + +<|ref|>text<|/ref|><|det|>[[148, 475, 260, 491]]<|/det|> +Major issues: + +<|ref|>text<|/ref|><|det|>[[147, 493, 850, 585]]<|/det|> +1. They indicate that CLK2 is an early terminator of NF-kB signaling via p65 on Ser180 and independent of IkBa- but there are some discrepancies with this interpretation. +a. Most assays are at 6, 12, or 24 hrs post-stim, well-after IkBa is typically transcriptionally induced by p65. Is there clear data showing two waves of inhibition? Does IkBa ever function in the absence of CLK2 or does CLK2 dominate? + +<|ref|>sub_title<|/ref|><|det|>[[148, 588, 237, 603]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 605, 850, 768]]<|/det|> +We actually performed the TNF- \(\alpha\) stimulation assays at 0.25, 0.5, 1, 3, and 6 hours, containing both the early and later stages of NF- \(\kappa \mathrm{B}\) activation (Fig. 5g). The results showed that \(\mathrm{p65^{S180A}}\) , which cannot be phosphorylated by CLK2, has higher transcriptional activity than \(\mathrm{p65^{WT}}\) . Additionally, we did not observe two waves of inhibition. Our opinion is that the inhibition of nuclear p65 by CLK2 is persistent, and this event starts its progression once p65 shuttles into the nucleus. In other words, the occurrence of the event we defined occurs at the early stage of active NF- \(\kappa \mathrm{B}\) , and the inhibition by resynthesis of \(\mathrm{1kBa}\) coexists with the inhibition by CLK2. Therefore, It does not have two waves of the inhibition. + +<|ref|>text<|/ref|><|det|>[[148, 770, 849, 806]]<|/det|> +Many results exhibit that \(\mathrm{1kBa}\) still function in Clk2 knockout primary cells or CLK2 knockout cell lines, such as Fig. 2e, Supplementary Fig. 2f and Fig. 6f. + +<|ref|>text<|/ref|><|det|>[[148, 807, 850, 899]]<|/det|> +For the question "does CLK2 dominate \(\mathrm{1kBa?}\) ", our opinion is that the role of CLK2 is to regulate p65 transcriptional activity at the post- translational modification (PTM) level. The reproduction of \(\mathrm{1kBa}\) is a downstream event of p65 phosphorylation by CLK2, similar to other PTM regulations, such as acetylation. Thus, CLK2 dominates the resynthesis of \(\mathrm{1kBa}\) but it does not dominate the function of \(\mathrm{1kBa}\) . + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 122, 852, 250]]<|/det|> +b. Does the phosphorylation change of p65 in response to CLK2 impact the ability of p65 to be bound by IkBa? If p65 is no longer recognized by IkBa in the absence of CLK2 modifications then that could lead to an accumulation of p65 in the nucleus and increased transcriptional activity. p65 S180A is a mutant that can't be phosphorylated downstream of CLK2 and has a prolonged residence in the nucleus (Fig 6), but how is the role of IkBa excluded? Do any of the phosphorylation site mutants impact targeting by IkBa? + +<|ref|>sub_title<|/ref|><|det|>[[148, 253, 238, 268]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 270, 850, 362]]<|/det|> +We thank the reviewer for his/her insightful comments. We performed the exogenous coimmunoprecipitation assay to detect IkBa binding with p65WT or p65S180D (Supplementary Fig. 6h), and the result showed that p65S180D has a higher affinity for IkBa. This indicates that phosphorylation at Ser180 increase the ability of p65 to be bound by IkBa. + +<|ref|>text<|/ref|><|det|>[[147, 362, 850, 473]]<|/det|> +In the absence of CLK2, p65 showed less affinity for IkBa, but it was still recognized by IkBa (Supplementary Fig. 6i). On the other hand, p65S180A/KI cells were also used to confirm this result. The data showed that p65S180A/KI decrease the interaction with IkBa (Fig. 6d), which is consistent with the result in CLK2- \(l\) - cells. Taken together, these data suggest that CLK2 deficiency or p65 mutant that cannot be phosphorylated at Ser180 decrease the interaction between p65 and IkBa. + +<|ref|>text<|/ref|><|det|>[[147, 473, 850, 547]]<|/det|> +The results (Fig. 5g, 6b, and 6d) showed that p65S180A has less affinity for IkBa and shows more nuclear localization and more powerful transcriptional activity. We did not exclude the role of IkBa and it still participates in the regulation of NF- \(\kappa\) B signaling as a classic inhibitor. + +<|ref|>text<|/ref|><|det|>[[147, 547, 850, 603]]<|/det|> +Both of the experiments in p65S180A/KI or p65S180D/KI cells have suggested us that phosphorylation of p65 at Ser180 did impact targeting by IkBa (Fig. 6d and Supplementary Fig. 6h). + +<|ref|>image<|/ref|><|det|>[[147, 623, 852, 770]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 825, 850, 899]]<|/det|> +2. Is CLK2 the sole kinase and what activates it? a. They identify multiple phosphorylation sites but there is never an in vitro analysis with purified CLK2 protein. As it stands now- CLK2 is certainly an upstream kinase- but given IP is performed in HEK293T - CLK2 might be acting via another kinase? + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 848, 120]]<|/det|> +Does the CLK2 inhibitor TG003 block phosphorylation of Ser 180 on p65 or any other site? + +<|ref|>sub_title<|/ref|><|det|>[[148, 124, 238, 139]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 141, 850, 287]]<|/det|> +What a great advice promotes the quality of the manuscript. We followed your advice and performed in vitro assays, including pull- down assay and kinase assay. Unfortunately, purification full- length CLK2 and \(\mathrm{CLK2^{K192R}}\) active proteins through eukaryotic expression presents significant challenges for us. Therefore, we used the Flag- CLK2 and Flag- CLK2K192R via eukaryotic expression, and His- p65 via prokaryotic expression. The pulldown assay showed that p65 only binds to CLK2, but not \(\mathrm{CLK2^{K192R}}\) (Fig. 4f). Meanwhile, the in vitro kinase assay exhibited that CLK2 can expend more ATP with p65 (Fig. 4g). + +<|ref|>image<|/ref|><|det|>[[313, 291, 727, 446]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 455, 851, 548]]<|/det|> +The question raised by the reviewer is quite interesting and important for us to understand the mechanism in depth. Western blot analysis was performed with and without TG003, and the results showed that TG003 can block the phosphorylation of Ser- 180 and promote the phosphorylation of Ser- 536 and the acetylation of Lys- 310 (Supplementary Fig. 6l). + +<|ref|>image<|/ref|><|det|>[[150, 553, 857, 692]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 693, 850, 728]]<|/det|> +Therefore, we believe the phosphorylation of p65 at Ser180 acting via CLK2 but not another kinase. + +<|ref|>text<|/ref|><|det|>[[148, 765, 848, 820]]<|/det|> +b. In Fig 6D, the SeV infected CLK2-/- have lower levels of phospho Ser180 p65 overall, but it is not eliminated. What kinase drives this remaining phosphorylation? What does the asterisk/upper band indicate in the western blots? + +<|ref|>sub_title<|/ref|><|det|>[[148, 823, 238, 838]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 841, 850, 895]]<|/det|> +The phosphorylation antibody was produced by Abclonal company. We consulted this question and according to the explanation of the technical support of the company, the phosphorylation of Ser- 180 in the \(\mathrm{CLK2^{- / - }}\) group can still be detected mainly due to + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 849, 157]]<|/det|> +the purity of the antibody. The quality may not be perfect, and a small amount of total- p65 may also be detected. In summary, these unspecific bands do not affect the conclusion reflecting the detection of dynamic changes in the phosphorylation of Ser- 180. + +<|ref|>text<|/ref|><|det|>[[148, 160, 848, 196]]<|/det|> +The asterisk/upper band indicate the unspecific band that can be detected by the antibody and the explanation was added in the relative figure legends. + +<|ref|>text<|/ref|><|det|>[[148, 233, 848, 269]]<|/det|> +c. This CLK2-mediated inhibition is only observed upon stimulation- so what is activating CLK2? + +<|ref|>sub_title<|/ref|><|det|>[[148, 272, 238, 288]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 289, 850, 436]]<|/det|> +The question deserves attention and we did perform experiments to try to figure out what activates CLK2. The CLK2 is regulated obviously upon stimulation. Mass spectrometry and Co- IP experiments showed that CLK2 interacts with PLK1 exposed with the stimuli, suggesting that PLK1 may regulate CLK2 during infection. However, subsequent experiments cannot fully prove that CLK2 is a substrate of PLK1 or the relationship between PLK1 and CLK2 during infection. In the manuscript, we did not show the figures, but we mentioned in the discussion section that the activity of CLK2 is likely regulated during infection, possibly at the protein or kinase activity level. + +<|ref|>text<|/ref|><|det|>[[148, 473, 850, 547]]<|/det|> +3. There is a an overinterpretation that PML-associated p65 is more transcriptionally active. The PML colocalization and phase separation data is not well developed, being performed in the context of overexpression- it raises more questions than answers. Consider removing. + +<|ref|>sub_title<|/ref|><|det|>[[148, 550, 238, 565]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 567, 850, 640]]<|/det|> +Thanks for your advice. The phase separation data truly raised more questions and we had removed it. However, the aggregation of p65S180A and its co- localization with PML actually occurred and really interesting, we have decided to exhibit this phenomenon in the supplementary data. + +<|ref|>text<|/ref|><|det|>[[148, 678, 850, 769]]<|/det|> +4. A major flaw in the publication is the poor quality of writing. Professional editing is essential. There were numerous grammatical errors and improper word choices (e.g. 'we wonder CLK2 may be a pregnant target to treat inflammation-associated diseases and virus infection') that make it nearly impossible for the reader to work through. This did detract from my understanding of some of their summaries and interpretations. + +<|ref|>sub_title<|/ref|><|det|>[[148, 772, 238, 787]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 789, 850, 842]]<|/det|> +We have revised the grammar throughout the manuscript and ask a few professors nearby to help us revise the manuscript. After the revision, the updated manuscript is now ready for exhibited. + +<|ref|>text<|/ref|><|det|>[[148, 882, 258, 897]]<|/det|> +Minor issues: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 740, 103]]<|/det|> +1. Fig 2B. The PCR genotyping data for WT vs KO mice seems swapped. + +<|ref|>sub_title<|/ref|><|det|>[[149, 106, 238, 121]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 123, 848, 158]]<|/det|> +Thanks for this reminding. We did swap the WT vs KO mice PCR genotyping data and revised it in Fig. 2b. + +<|ref|>text<|/ref|><|det|>[[148, 196, 848, 231]]<|/det|> +2. Supp Fig 3 and Fig 5. have an odd arrangement of figures where the letters are not in alphabetical order. + +<|ref|>sub_title<|/ref|><|det|>[[149, 235, 238, 250]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 252, 848, 288]]<|/det|> +Sorry for confusing the reviewer and now Supplementary Fig. 3 and Fig. 5 have been rearranged. + +<|ref|>text<|/ref|><|det|>[[148, 325, 848, 360]]<|/det|> +3. The font kerning for the sequence alignment of Fig 5B is off. A monospace font is needed. + +<|ref|>sub_title<|/ref|><|det|>[[149, 364, 238, 380]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 382, 737, 399]]<|/det|> +Thanks for your suggestion. The monospace font has been adjusted. + +<|ref|>text<|/ref|><|det|>[[148, 436, 848, 472]]<|/det|> +4. Fig 6 Figure legend states data are presented as SEM- but that type of data is not in the figure. + +<|ref|>sub_title<|/ref|><|det|>[[149, 475, 238, 491]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[188, 493, 566, 510]]<|/det|> +Thanks. The legend of Fig. 6 has been revised. + +<|ref|>text<|/ref|><|det|>[[148, 547, 838, 565]]<|/det|> +5. Information on the strain and source of SeV, VSV, and HSV virus stocks is lacking. + +<|ref|>sub_title<|/ref|><|det|>[[149, 568, 238, 583]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 585, 850, 787]]<|/det|> +SeV, VSV and VSV expressing GFP (VSV- GFP) were gifts from Hongbing Shu and Bo Zhong, which they have widely used in their studies and published a series of articles (Lei C. Q et al. Glycogen synthase kinase 3beta regulates IRF3 transcription factor- mediated antiviral response via activation of the kinase TBK1. Immunity. 878- 89 (2010). doi: 10.1016/j.immuni.2010.11.021; Lian H, Zang R, Wei J, et al. The Zinc- Finger Protein ZCCHC3 Binds RNA and Facilitates Viral RNA Sensing and Activation of the RIG- I- like Receptors. Immunity. 2018;49(3):438- 448. e5. doi: 10.1016/j.immuni. 2018.08.014; Liuyu, T., Yu, K., Ye, L. et al. Induction of OTUD4 by viral infection promotes antiviral responses through deubiquitinating and stabilizing MAVS. Cell Res 29, 67- 79 (2019). doi.org/10.1038/s41422- 018- 0107- 6). The information was presented in the methods section. + +<|ref|>sub_title<|/ref|><|det|>[[149, 827, 256, 843]]<|/det|> +## Reviewer #2 + +<|ref|>text<|/ref|><|det|>[[149, 845, 848, 899]]<|/det|> +The manuscript entitled "CLK2- mediated IkappaBalpha- independent early- termination of NF- kappaB activation by phosphorylating nuclear- p65 for cytoplasmic redistribution and degradation" by Shang- Ze Li and colleagues describes the + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 213]]<|/det|> +identification of a novel regulatory phosphorylation site (ser180) of the NF- kappaB sub- unit p65/RelA, target of the CLK2 kinase. CLK2 phosphorylation of p65 at ser180 by cytokine treatment or viral infection leads to increased p65 accumulation in the cytoplasm, and p65 proteasome- mediated degradation. Using knock- in phosphomimetic aspartic acid substitution of ser180 a decreased p65 activity is revealed compared to wt protein, following different stimuli, and also increased viral replication. + +<|ref|>text<|/ref|><|det|>[[147, 215, 850, 305]]<|/det|> +On the contrary, substitution of ser180 with alanine, determining the inability of p65 to be phosphorylated by CLK2 at this residue, results in a "super- active" protein, capable of conferring resistance to viral infection in the knock- in cellular system. Moreover, CLK2 genetic ablation or its chemical inhibition promoted chronic inflammation in a mouse psoriasis model. + +<|ref|>text<|/ref|><|det|>[[147, 308, 849, 379]]<|/det|> +Authors discussed CLK- 2 mediated p65 phosphorylation at ser180 as an early NF- kappaB shutdown pathway, alternative to the canonical feed- back regulatory mechanism represented by the NF- kappaB- mediated synthesis of IKappaB- alpha occurring later after stimulation. + +<|ref|>text<|/ref|><|det|>[[147, 381, 849, 454]]<|/det|> +The CLK- 2 mediated phosphorylation of p65 and the subsequent inhibition of the activity of this transcription factor, represent important and novel findings, adding another important piece of information about how NF- kappaB, one of the most studied transcription factor, works. + +<|ref|>text<|/ref|><|det|>[[147, 456, 849, 492]]<|/det|> +That being said, the manuscript, despite a large number of data gathered, lacks key experiments, and is misleading regarding some data interpretation. + +<|ref|>text<|/ref|><|det|>[[147, 494, 790, 510]]<|/det|> +Moreover, an extensive revision for English language and grammar is required. + +<|ref|>sub_title<|/ref|><|det|>[[148, 513, 237, 528]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 530, 849, 601]]<|/det|> +The extensive revision for English language and grammar has been done. We have revised the grammar throughout the manuscript and ask a few professors nearby to help us revise the manuscript. After the revision, the updated manuscript is now ready for exhibited. + +<|ref|>sub_title<|/ref|><|det|>[[148, 640, 305, 657]]<|/det|> +## Specific comments: + +<|ref|>text<|/ref|><|det|>[[150, 678, 333, 694]]<|/det|> +1- Introduction section. + +<|ref|>text<|/ref|><|det|>[[147, 696, 850, 899]]<|/det|> +Introduction section is lacking the description of other important phosphorylation sites identified on p65 (by the way, naming this transcription factor as RelA is more appropriate). Among these, ser276, known to enhance NF- kappaB transcriptional activity, or ser468, negatively regulating NF- kappaB mediated transcription (for a review see "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017), the latter highly relevant in the context of this manuscript and used in fig. 6D and E panels. Moreover, the paper by Saccani S. et al. "Degradation of Promoter- bound p65/RelA Is Essential for the Prompt Termination of the Nuclear Factor B Response" (J. Exp. Med. Volume 200, Number 1, July 5, 2004 107- 113. doi: 10.1084/jem.20040196) must be acknowledged, due to fact + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 270]]<|/det|> +that it describes p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. In the same paper, if proteasome activity is blocked after an activating stimulus, NF- kappaB is not rapidly removed from target genes despite IkappaB synthesis, resulting in sustained transcription. Such paper describes a very similar mechanism of NF- kappaB "shutdown" and cannot be ignored. Finally, Lys 310 acetylation, required for full RelA transcriptional activity, should not be described without acknowledging the fact that it happens subsequently to the prior phosphorylation of RelA at ser276 and ser536 (Chen LF, et al. "NF- kappaB RelA phosphorylation regulates RelA acetylation". Mol Cell Biol. 2005 Sep;25(18):7966- 75. doi: 10.1128/MCB.25.18.7966- 7975.2005). + +<|ref|>text<|/ref|><|det|>[[148, 270, 848, 306]]<|/det|> +What does "CLK2" stand for? Full name (Cdc2- like kinase 2) must be present, at least the first time CLK2 is described in the introduction section. + +<|ref|>sub_title<|/ref|><|det|>[[148, 309, 238, 324]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 326, 850, 399]]<|/det|> +Regarding the name of p65, we believe your advice is valuable. The name as RelA is more official and we have updated it to RelA/p65 in the title and abstract sections. However, in consideration of the wildspread use of p65, we did not revise it in other sections. + +<|ref|>text<|/ref|><|det|>[[147, 401, 850, 732]]<|/det|> +Thank the reviewer for pointing these out for us to refine the writing of Introduction. The description of other important phosphorylation sites identified on p65 has been presented in the Introduction section. Among them, we have cited papers that focus on Ser276 and have also got acknowledge of the paper by Saccani S. et al. Additionally, we have updated the description of Lys310 acetylation followed the reviewer's advice. Meanwhile, a few more papers were cited in the introduction section (such as "Sgarbanti M, et al. IRF- 1 is required for full NF- kappaB transcriptional activity at the human immunodeficiency virus type 1 long terminal repeat enhancer. J Virol. 2008;82(7):3632- 3641. doi:10.1128/JVI.00599- 07"; "Acchioni C, Remoli AL, Marsili G, et al. Alternate NF- \(\kappa \mathrm{B}\) - Independent Signaling Reactivation of Latent HIV- 1 Provirus. J Virol. 2019;93(18): e00495- 19. Published 2019 Aug 28. doi:10.1128/JVI.00495- 19"). Here is the revised sentence "Over the last decades, significant progress has been made in understanding the nuclear import process and transcriptional activation modification of p65, such as phosphorylation of Ser- 536 and Ser- 276 is essential for the transactivation, phosphorylation of Ser- 468 may negatively regulates NF- \(\kappa \mathrm{B}\) mediated transcription and acetylation of Lys- 310 is required for full transcriptional activity of p65 subsequently to the prior phosphorylation of p65 at Ser- 276 and Ser- 536". + +<|ref|>text<|/ref|><|det|>[[148, 733, 857, 788]]<|/det|> +The full name of CLK2 has been revised in the sentence of introduction section "In this study, we present an IkBα- independent nuclear NF- \(\kappa \mathrm{B}\) termination model at the transcriptional level through inhibitory phosphorylation by CDC like kinase 2 (CLK2)." + +<|ref|>sub_title<|/ref|><|det|>[[148, 826, 216, 842]]<|/det|> +## 2- Fig.1 + +<|ref|>text<|/ref|><|det|>[[148, 844, 846, 899]]<|/det|> +In the description of panel D, authors explain that they have used an ISRE reporter responding to SeV infection, to assess the impact of CLK2 on IRF- 3, to rule out IRF- 3 as a CLK2 target in IFN- beta promoter repression. However, authors did not provide + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 848, 251]]<|/det|> +evidence in the material and methods section about what specific ISRE sequence they have used in the reporter construct (indeed some commercially available ISRE reporter constructs also respond to IFN- I- induced ISGF3). In order for the authors to state that in fig. 1D they are dealing with IRF- 3 mediated stimulation, they have to use the transfection of a plasmid constitutively expressing an active form of IRF- 3, like IRF- 3 5D (Lin R. et al. Essential Role of Interferon Regulatory Factor 3 in Direct Activation of RANTES Chemokine Transcription. Mol Cell Biol. 1999 Feb; 19(2): 959- 966. doi: 10.1128/mcb.19.2.959), as a control, comparing the fold of activation obtained to those reached with SeV infection. + +<|ref|>sub_title<|/ref|><|det|>[[148, 254, 238, 269]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 271, 849, 343]]<|/det|> +Thanks for this professional reminder. The IFN- \(\beta\) and ISRE luciferase reporter plasmids and SeV, VSV and VSV expressing GFP (VSV- GFP) were gifts from Hongbing Shu and Bo Zhong (Wuhan University, Hubei, China), which is added in the methods section. + +<|ref|>text<|/ref|><|det|>[[147, 345, 850, 473]]<|/det|> +These luciferase reporter plasmids and virus were widely used in a lot of relatively and importantly published paper and the ISRE- Luc plasmid was tested by IRF- 3 5D previously (Lei C. Q et al. Glycogen synthase kinase 3beta regulates IRF3 transcription factor- mediated antiviral response via activation of the kinase TBK1. Immunity. 878- 89 (2010). doi: 10.1016/j.immuni.2010.11.021). Here is the specific sequence of ISRE "5'- AGGGAAAGTGAACT- 3" and the information was presented in the methods section. + +<|ref|>text<|/ref|><|det|>[[148, 510, 850, 584]]<|/det|> +In Fig.1H error bars should be present in the graphs accounting for the three separate experiments, while the right western blot panel (showing TNF- alpha time course) should not present a GAPDH blot with such a poor separation between each band, clearly the result of excessive protein loading and/or overexposure. + +<|ref|>sub_title<|/ref|><|det|>[[148, 587, 238, 602]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 604, 848, 640]]<|/det|> +We do agree with the reviewer and have substituted the line charts with the data of three separate experiments (Fig. 1h). + +<|ref|>image<|/ref|><|det|>[[147, 640, 850, 732]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[149, 771, 346, 788]]<|/det|> +## 3-Supplementary Fig.1. + +<|ref|>text<|/ref|><|det|>[[147, 789, 849, 881]]<|/det|> +Looking at panel 1D, it seems that CLK2 expression is actually negatively affected in p65 knock- out cells compared to wt cells, therefore the authors' conclusion, that CLK2 is not that much regulated at the level of transcription, is questionable; authors should provide a statistical analysis comparing each experimental time points of wt vs knock- out cells. Moreover, authors should also perform the same experiment using + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 810, 120]]<|/det|> +TNF- alpha as a stimulus with a proper related time course of treatment, to match with the experiments shown in fig. 1H. + +<|ref|>sub_title<|/ref|><|det|>[[149, 124, 238, 139]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 141, 850, 232]]<|/det|> +With the experiment exposed with TNF- \(\alpha\) and repeated experiment with SeV, we observed that p65 deficiency had a slight effect on the transcription of CLK2. However, compared to the transcription of other classic and specific genes induced by virus or cytokine- induced transcription, we still believe that the change in CLK2 mRNA is not obviously. (Supplementary Fig. 1d) + +<|ref|>image<|/ref|><|det|>[[228, 252, 777, 490]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 530, 220, 546]]<|/det|> +4- Fig.2. + +<|ref|>text<|/ref|><|det|>[[148, 548, 839, 583]]<|/det|> +Panel B is not described in details and it is not clear, based on figure labelling, what does shown bands represent. + +<|ref|>text<|/ref|><|det|>[[147, 585, 833, 732]]<|/det|> +In panel E, particularly the right part involving MLFs, there is evidence for an increased accumulation of Nfkbia in the CLK2 - /- cells even in control untreated cells. This accumulation of Nfkbia matches with k310 acetylation and ser536 phosphorylation of p65, suggesting that, at least in these primary cells, CLK2 may represent a basal checkpoint acting to avoid a constitutive activation of p65 even in the absence of activating stimuli (e.g. LPS, TNF- alpha, IL- 1 beta, or viral infection). It seems that in these cells there is also an increased accumulation of p65 compared to wt cells. Authors need to comment on all these data. + +<|ref|>sub_title<|/ref|><|det|>[[148, 735, 238, 750]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 752, 850, 824]]<|/det|> +We are sorry for not providing clear descriptions of the experiments. The band of WT represents the products that can only be amplified in \(\mathrm{CLK2^{WT}}\) genome, and the band of KO represents the products that can only be amplified in the \(\mathrm{CLK2^{KO}}\) genome. Additionally, the description of panel B has been revised in the figure legend. + +<|ref|>text<|/ref|><|det|>[[148, 826, 849, 898]]<|/det|> +Thanks for the insightful comment and comprehension of the reviewer and we deeply agree with it. In consideration of the dynamic balance in cell physiology, CLK2 deficiency may cause the slightly activation of NF- \(\kappa\) B signaling in the rest time and result in the increased accumulation of Nfkbia. The new description has been presented + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 270]]<|/det|> +in the result and discussion section "Interestingly, there was an increased accumulation of Nfkbia in Clk2- cells, which is consistent with the increase in Lys- 310 acetylation and Ser- 536 phosphorylation of p65. It indicates that CLK2 may be a basal checkpoint to limit constitutional activation of NF- \(\kappa\) B signaling, even in the absence of activating stimuli.", "Taken together, all the results obtained from primary cells or cell lines indicated that the phosphorylation of p65 by CLK2 may be identified as a basal checkpoint, preventing a continuous activation of p65 and thus inhibiting the activation of NF- \(\kappa\) B." and "Furthermore, the CLK2 mediated phosphorylation of p65 at Ser- 180 serves as a homeostatic suppression of p65 activity before the activation of the signaling cascade". + +<|ref|>sub_title<|/ref|><|det|>[[149, 308, 350, 325]]<|/det|> +## 5- Supplementary Fig. 2. + +<|ref|>text<|/ref|><|det|>[[147, 326, 850, 455]]<|/det|> +Panel A is supposed to be positioned in the upper left part of the figure. In the lower right part of panel F, (like for Fig.2 panel E, right part) there is evidence for an increased accumulation of Nfkbia in the CLK2- /- cells even in control untreated cells. Even in this experiment, there is evidence for increased k310 acetylation and ser536 phosphorylation of p65 in control cells and increased accumulation of p65 compared to wt cells (the panel showing Ac- p65 Lys310 for the TNF- alpha time course must be repeated because bands are not clearly visible). + +<|ref|>sub_title<|/ref|><|det|>[[148, 458, 238, 473]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[186, 475, 837, 492]]<|/det|> +Following the reviewer's suggestion, we have rearranged Supplementary Fig. 2. + +<|ref|>text<|/ref|><|det|>[[148, 494, 850, 548]]<|/det|> +Thank the reviewer for pointing this out for us. The detection of Ac- p65 (Lys310) have been repeated with the same protein sample and the bands have been renewed (Supplementary Fig. 2f). + +<|ref|>image<|/ref|><|det|>[[184, 550, 800, 789]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 826, 825, 881]]<|/det|> +5- Fig.3 It is not clear what is the difference between Fig3C and supplementary Fig. 3E. At line 169 of the result section related to Fig.3 ("CLK2 deficiency enhances virus + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[150, 85, 840, 120]]<|/det|> +induced IFN- beta production and antiviral response") the word "plague" is actually "plague", and need to be substituted throughout the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 124, 238, 139]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 141, 850, 232]]<|/det|> +We are sorry for confusing the reviewer. We performed assays in 3 different types of primary cells, including bone marrow- derived macrophages (BMDMs), mice lung fibroblasts (MLFs) and bone marrow- derived dendritic cells (BMDCs). The data of BMDMs and MLFs were exhibited in Fig. 3 and the data of BMDCs was showed in Supplementary Fig. 3. + +<|ref|>text<|/ref|><|det|>[[149, 234, 848, 269]]<|/det|> +Thank the reviewer for point this out for us. We have corrected the plague to plaque throughout the manuscript. + +<|ref|>sub_title<|/ref|><|det|>[[149, 308, 346, 323]]<|/det|> +## 6- Supplementary Fig. 3 + +<|ref|>text<|/ref|><|det|>[[149, 326, 850, 419]]<|/det|> +Panel A is supposed to be positioned in the upper left part of the figure. The rationale for the use of HSV- 1 compared to VSV in in vivo and in vitro experiments should be explained, together with the different results obtained. It is not clear what kind of supplemental information is provided with supplementary Fig.3E, that is not present in Fig.3C. + +<|ref|>sub_title<|/ref|><|det|>[[149, 421, 238, 436]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 439, 848, 473]]<|/det|> +Following the reviewer's suggestion, The Supplementary Fig. 3 has been rearranged. + +<|ref|>text<|/ref|><|det|>[[148, 475, 850, 620]]<|/det|> +Vesicular stomatitis virus (VSV) is an RNA virus and herpes simplex virus type 1 (HSV- 1) is an DNA virus. Both of them can activate NF- \(\kappa\) B signaling but correspond to different receptor. All the stimulus we used were designed to verify that CLK2 is a broad- spectrum inhibitor of activated NF- \(\kappa\) B signaling. The explanation was presented in the sentence "To investigate the physiological role of Clk2 in viral infection in vivo, Clk2- deficient mice and their wild- type littermates were injected with Vesicular Stomatitis Virus (VSV) or Herpes Simplex Virus Type 1 (HSV- 1) via the tail vein and intraperitoneally". + +<|ref|>text<|/ref|><|det|>[[148, 622, 850, 713]]<|/det|> +We have confirmed the results through BMDMs and MLFs cells and these data are convincing. The experiments in BMDCs were mainly performed as a support of these known results, so the fluorescence microscopy of BMDCs was not detected. Considering it is supplementary data, we did not show it in the figure, but we still have strong evidence to proof the conclusion. + +<|ref|>sub_title<|/ref|><|det|>[[149, 752, 211, 768]]<|/det|> +## 7-Fig.4 + +<|ref|>text<|/ref|><|det|>[[148, 770, 829, 842]]<|/det|> +The conclusion, related to panel A, that "CLK2 inhibits virus- triggered NF- kappaB signaling at the p65 level" (lines 197- 198 of the corresponding result paragraph) is correct, but does not rule out the possibility that there are also other upstream players in the signal transduction pathways affected by CLK2. + +<|ref|>sub_title<|/ref|><|det|>[[148, 846, 238, 861]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 864, 848, 899]]<|/det|> +Thanks for the stringent description for this conclusion. It does not rule out the possibility that there are other upstream players in the signal transduction pathways + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 849, 140]]<|/det|> +affected by CLK2. Therefore, we detected the location of CLK2 (Supplementary Fig. 4a). Combined with the luciferase and nuclear location results, we draw the conclusion that CLK2 function with nuclear p65 to regulate the activation of the NF- \(\kappa\) B signaling. + +<|ref|>text<|/ref|><|det|>[[147, 177, 846, 270]]<|/det|> +In panel B equal amount of Flag- CLK2 should be present in the lysate. In panel C authors should also use a CLK2 inhibitor to conclude that CLK2 exerts its function with p65 depending on CLK2 kinase activity. This is because the lack of p65 binding to CLK2 K192R dead kinase, may also depend upon CLK2 conformational change due to the K to R mutation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 273, 238, 288]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 290, 849, 344]]<|/det|> +Thanks for your rigorous manner, the expression of Flag- CLK2 did have discrepancy and it may be caused by plasmid transfection. However, this discrepancy did not affect our conclusion and we did not replace it. + +<|ref|>text<|/ref|><|det|>[[148, 345, 849, 400]]<|/det|> +We have followed the reviewer's advice. The assay was performed and the result showed that the interaction between p65 and CLK2 is impaired in the presence of the CLK2 inhibitor- TG003 (Fig. 4d). + +<|ref|>image<|/ref|><|det|>[[432, 408, 614, 555]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 565, 850, 825]]<|/det|> +By the way, The \(\mathrm{CLK2^{K192R}}\) was wildly used in many other researches (Naylor, O et al. "The cellular localization of the murine serine/arginine-rich protein kinase CLK2 is regulated by serine 141 autophosphorylation." The Journal of biological chemistry vol. 273,51 (1998): 34341- 8. doi:10.1074/jbc.273.51.34341; Rodgers, Joseph T et al. "Cdc2- like kinase 2 is an insulin- regulated suppressor of hepatic gluconeogenesis." Cell metabolism vol. 11,1 (2010): 23- 34. doi:10.1016/j.cmet.2009.11.006). And the strategy of frequently replacing Lysine (Lys) in kinase activity mutations was normally used in many other researches (Hanafusa H, Kedashiro S, Tezuka M, et al. PLK1- dependent activation of LRRK1 regulates spindle orientation by phosphorylating CDK5RAP2. Nat Cell Biol. 2015;17(8):1024- 1035. doi:10.1038/ncb3204; Zhao P, Wong KI, Sun X, et al. TBK1 at the Crossroads of Inflammation and Energy Homeostasis in Adipose Tissue. Cell. 2018;172(4):731- 743. e12. doi:10.1016/j.cell.2018.01.007). So we choose the \(\mathrm{CLK2^{K192R}}\) to investigate the function of kinase activity. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 835, 140]]<|/det|> +Again, in panel C and F authors should comment about the faster migration of Flag- CLK2 dead kinase in the IP/WB experiment, compared to wt. This difference cannot be justified by K192R amino acid substitution. + +<|ref|>sub_title<|/ref|><|det|>[[148, 143, 238, 158]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 160, 851, 325]]<|/det|> +It may be caused by the site mutation and result in the change of PTM, such as autophosphorylation. The migration of bands can be observed normally in many other kinase dead mutation. Not only in our research, but also many others research (Zhao P, Wong KI, Sun X, et al. TBK1 at the Crossroads of Inflammation and Energy Homeostasis in Adipose Tissue. Cell. 2018;172(4):731- 743. e12. doi:10.1016/j.cell.2018.01.007; Li SZ, Shu QP, Song Y, et al. Phosphorylation of MAVS/VISA by Nemo- like kinase (NLK) for degradation regulates the antiviral innate immune response. Nat Commun. 2019;10(1):3233. Published 2019 Jul 19. doi:10.1038/s41467- 019- 11258- x). + +<|ref|>text<|/ref|><|det|>[[148, 362, 764, 398]]<|/det|> +In panel D, the western blotting experiment should also be repeated with an appropriate TNF- alpha time course. + +<|ref|>sub_title<|/ref|><|det|>[[148, 401, 238, 416]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 419, 848, 454]]<|/det|> +Following the reviewer's suggestion, the experiment has been repeated exposed with TNF- \(\alpha\) , and the result showed that p65 has more affinity to CLK2 under stimulation. + +<|ref|>image<|/ref|><|det|>[[336, 457, 660, 624]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 658, 837, 768]]<|/det|> +In panel E, the graph should also report the luciferase fold of inductions relative to each uninfected control, to account for the basal activity of each kinase (wt and mutant) on the promoter compared to the SeV infection or TNF- alpha treatment. In the western blot of panel F it is not clear why there is more p65 in the presence of wt CLK2 compared to CLK2 absence or the presence of the dead kinase. Authors should comment on this. + +<|ref|>sub_title<|/ref|><|det|>[[148, 772, 238, 787]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 789, 848, 825]]<|/det|> +Sorry for confusing the reviewer. About panel E (updated as Supplementary Fig. 4b), the uninfected control group was been showed which was painted green. + +<|ref|>text<|/ref|><|det|>[[148, 826, 850, 899]]<|/det|> +The difference in panel F (rearranged as Supplementary Fig. 4c) as most likely caused by transfection or western blot system error. It was ignored and actually made some misunderstandings. However, it was not a quantitative experiment and did not affect us drawing the conclusion. We have repeated the experiment multiple times and in other + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 140]]<|/det|> +cases, it is not observed the same increased expression. Two additional repetitions are shown below. We have also rerun the same protein sample and substituted the improper graph. Finally, thanks for careful observation and reminding. + +<|ref|>image<|/ref|><|det|>[[259, 145, 730, 308]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 344, 848, 380]]<|/det|> +In I and G panels, figures should be presented also showing cells with visible light, without fluorescence. + +<|ref|>sub_title<|/ref|><|det|>[[148, 383, 238, 399]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 401, 850, 585]]<|/det|> +We could understand what your concern. Usually, visible light is not showed in the figure, so we did not shoot the cells with visible (Tanaka, T., Grusby, M. & Kaisho, T. PDLIM2- mediated termination of transcription factor NF- \(\kappa\) B activation by intranuclear sequestration and degradation of the p65 subunit. Nat Immunol 8, 584- 591 (2007). https://doi.org/10.1038/ni1464; Wang, S., Lin, Y., Yuan, X. et al. REV- ERBα integrates colon clock with experimental colitis through regulation of NF- \(\kappa\) B/NLRP3 axis. Nat Commun 9, 4246 (2018). https://doi.org/10.1038/s41467- 018- 06568- 5). Instead, DAPI was used to reflect the number and condition of cells as a merged graph, and we did detect it. It is shown below, but in order to clearly show the change of p65, we did not include it in the manuscript. + +<|ref|>image<|/ref|><|det|>[[203, 589, 790, 824]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 862, 752, 900]]<|/det|> +In panel H a quantification of the detected p65 bands should be presented. Response: + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 849, 120]]<|/det|> +Following the reviewer's suggestion, we have presented the line chart and updated it in Fig. 4i. + +<|ref|>image<|/ref|><|det|>[[315, 130, 675, 360]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 400, 338, 416]]<|/det|> +8- Supplementary Fig.4 + +<|ref|>text<|/ref|><|det|>[[147, 419, 848, 454]]<|/det|> +In panel A figures should be presented also showing cells with visible light, without fluorescence. + +<|ref|>sub_title<|/ref|><|det|>[[148, 458, 238, 473]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 475, 848, 510]]<|/det|> +Thanks. It is a similar question to 7- Fig. 4h and 4j, and about the question, it had been explained. + +<|ref|>text<|/ref|><|det|>[[147, 548, 849, 602]]<|/det|> +In panel B, western blot should be repeated with a lower amount of loaded proteins (in GAPDH blot bands cannot be discriminated). Moreover, appropriate TNF- alpha time course should also be presented. + +<|ref|>sub_title<|/ref|><|det|>[[148, 605, 238, 620]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 622, 849, 676]]<|/det|> +We agree with the reviewer that western blot need to be revised and the updated graphs (Supplementary Fig. 4d). The results showed that CLK2 deficiency does not affect p65 stability under the stimulation. + +<|ref|>image<|/ref|><|det|>[[222, 682, 777, 765]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 808, 833, 862]]<|/det|> +9- Fig.5 Panel distribution is confusing (what panel does the lower right graphic belongs to? Is it panel F? If this is the case, are those cells infected with SeV? + +<|ref|>sub_title<|/ref|><|det|>[[148, 865, 238, 880]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[186, 882, 848, 899]]<|/det|> +We feel so sorry for confusing the reviewer and the graph has been rearranged. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 849, 120]]<|/det|> +The lower right graphic belongs to panel F, and those cells were same sample that treated with SeV. Now it has been rearranged as Fig. 5e. + +<|ref|>text<|/ref|><|det|>[[147, 159, 833, 195]]<|/det|> +In panel C, figures should be presented also showing cells with visible light, without fluorescence. + +<|ref|>sub_title<|/ref|><|det|>[[148, 199, 238, 214]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 216, 848, 251]]<|/det|> +It is a similar question to 7- Fig. 4h and 4j, and about the question, we have been explained previously. + +<|ref|>text<|/ref|><|det|>[[148, 289, 848, 343]]<|/det|> +What is really missing, in this in depth phosphorylation site analysis involving p65, is that no attempt at all was made to identify a consensus amino acidic sequence on p65, target of the CLK2 kinase. + +<|ref|>text<|/ref|><|det|>[[148, 346, 820, 380]]<|/det|> +This is an important shortcoming of the manuscript and must be addressed in both, the result and the discussion paragraph. + +<|ref|>sub_title<|/ref|><|det|>[[148, 383, 238, 398]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 401, 850, 620]]<|/det|> +Thanks for giving the valuable suggestions. We really appreciate it and have attempted to determine if there is a consensus amino acid sequence that is targeted by CLK2. Unfortunately, the only confirmed phosphorylated site of the substrate targeted by CLK2 is PTP1B, and there has not enough data to figure out the specific motif. Finally, we have updated it in the discussion section "Following the conserved sites analysis of p65 180 and 316 residues across species Fruit fly to Human, we tried to identify the consensus amino acid sequence on p65 targeted by CLK2. The PROMALS3D online tool was used for this investigation and yielded no significant result. Given that Ser- 50 of PTP1B is the sole site that has been determined targeted by CLK2, and no additional substrates can be concurrently analysed, the determination of this target remains challenging. However, further investigation holds promise for its eventual elucidation.". + +<|ref|>sub_title<|/ref|><|det|>[[150, 659, 346, 676]]<|/det|> +## 10-Supplementary Fig.5 + +<|ref|>text<|/ref|><|det|>[[147, 679, 848, 713]]<|/det|> +In panel D, figures should be presented also showing cells with visible light, without fluorescence. + +<|ref|>sub_title<|/ref|><|det|>[[148, 717, 238, 732]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 734, 848, 769]]<|/det|> +It is a similar question to 7- Fig. 4h and 4j, and about the question, we have been explained previously. + +<|ref|>sub_title<|/ref|><|det|>[[150, 809, 227, 824]]<|/det|> +## 11- Fig.6 + +<|ref|>text<|/ref|><|det|>[[148, 827, 830, 900]]<|/det|> +Experiments shown in Panels D and E are very important for a crucial aspect of CLK2 mediated phosphorylation of p65, and that is p65 degradation and relocation of the protein from the nucleus to the cytoplasm. While MG132 experiments provide striking qualitative data demonstrating a role for phosphorylated ser180 in protein + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 838, 140]]<|/det|> +degradation, authors must calculate p65 wt, p65 K180A and p65 K180D half-life by performing a time course of cycloheximide (CHX) treatment, thus straightening their findings with solid quantitative data. + +<|ref|>sub_title<|/ref|><|det|>[[148, 143, 238, 158]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 160, 850, 270]]<|/det|> +Following the reviewer's suggestion, we performed CHX assays and the results showed that p65S180A/KI is more stable than p65WT. Additionally, p65S180D/KI has a much shorter half- life compared to p65WT (Supplementary Fig. 6g). We also update the result section "Moreover, the nuclear p65S180D had showed higher ubiquitination level than wild- type p65 (Supplementary Fig. 6f), and the cycloheximide (CHX) treatment assay also exhibited that p65S180D has a shorter half- life than p65WT (Supplementary Fig. 6g)." + +<|ref|>image<|/ref|><|det|>[[258, 310, 744, 470]]<|/det|> +<|ref|>image_caption<|/ref|><|det|>[[259, 277, 277, 292]]<|/det|> +
G
+ +<|ref|>text<|/ref|><|det|>[[147, 511, 850, 585]]<|/det|> +Moreover, as shown in CLK2 - /- cells a strong constitutive acetylation of p65 at K310 is detected, despite SeV infection or TNF- alpha treatment compared to its absence in wt cells and also an increased ser536 phosphorylation, known to precede K310 acetylation, compared to lower levels in wt cells. + +<|ref|>text<|/ref|><|det|>[[147, 586, 850, 622]]<|/det|> +This basal activation status of p65 in the absence of CLK2 and of any stimuli, suggest a different data interpretation (see comments below). + +<|ref|>text<|/ref|><|det|>[[147, 623, 850, 806]]<|/det|> +In the results paragraph describing Fig.6 and supplementary Fig.6, an important set of experiments is missing. Indeed no p65 DNA binding analysis was performed. Is p65 capable of binding kappaB sites when phosphorylated at ser 180 or when this residue is mutated to either aspartic acid or alanine? Particularly, is p65 capable of binding DNA kappaB sites in CLK2 knock- out cells, in the absence of activation stimuli, considering that, in this case, it is highly acetylated at K310, but at the same time it is supposed to be still bound to IkappaB- alpha? These are important questions that need to be answered by performing new experiments, also considering the work by Saccani S. et al. (doi: 10.1084/jem.20040196), showing p65/RelA degradation in the nucleus after activation, and in a DNA binding- dependent manner. + +<|ref|>sub_title<|/ref|><|det|>[[148, 809, 238, 824]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 826, 840, 899]]<|/det|> +It is really a good question and we have followed the reviewer to perform the DNA- binding analysis with the knock- in cells. The result of ChIP- qPCR showed that p65S180A/KI has more affinity for \(\kappa \mathrm{B}\) sites than p65WT under SeV stimulation, while p65S180D/KI showed almost no binding with DNA (Fig. 6e). + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[422, 93, 628, 247]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 250, 839, 400]]<|/det|> +It is similar to the result of \(\mathrm{p65}^{S180A / KI}\) , in the absence of CLK2, wild- type p65 shows more powerful DNA- binding ability (Supplementary Fig. 6j). And the manuscript has been updated as "As known, interaction with \(\mathrm{IkB\alpha}\) is usually relevant to the DNA- binding activity, so we next sought for if \(\mathrm{p65}^{S180D / KI}\) affects p65 binding with DNA. ChIP- qPCR assays showed that \(\mathrm{p65}^{S180D / KI}\) has nearly lost the ability of DNA- binding, on the contrary, \(\mathrm{p65}^{S180A / KI}\) exhibits the enhanced DNA- binding activity (Fig. 6e). In addition, p65 in CLK2- \(t\) cells also showed increase capability of DNA- binding (Supplementary Fig. 6j)." + +<|ref|>image<|/ref|><|det|>[[380, 408, 610, 575]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 585, 850, 901]]<|/det|> +And the question about why p65 supposed to be bound with \(\mathrm{IkB\alpha}\) has high level of Lys310 acetylation, we need to say that is not contradictory. According to the paper "Acetylation of RelA at discrete sites regulates distinct nuclear functions of NF- \(\kappa \mathrm{B}\) " (doi.org/10.1093/emboj/cdf660), acetylation at K221 enhances the DNA binding of NF- \(\kappa \mathrm{B}\) and, together with acetylation at K218, impairs its association with \(\mathrm{IkB\alpha}\) . Acetylation of K310 is required for full transcriptional activity of NF- \(\kappa \mathrm{B}\) , but does not affect DNA binding or \(\mathrm{IkB\alpha}\) assembly. And every molecule has its dynamic balance, not all of the p65 binds with \(\mathrm{IkB\alpha}\) , it just takes up a portion of it. For another example, p65/p50 dimer binding with \(\mathrm{IkB\alpha}\) dynamically shuttles between the nucleus and cytoplasm and basic transcription mediated by p65 is continuously proceeding, even in the rest time without stimulus, which maintains the dynamic balance of cell physiology (Huang TT, et al. A nuclear export signal in the N- terminal regulatory domain of IkappaBalpha controls cytoplasmic localization of inactive NF- kappaB/IkappaBalpha complexes. Proc Natl Acad Sci U S A. 2000;97(3):1014- 1019. doi:10.1073/pnas.97.3.1014; Johnson C, Van Antwerp D, Hope TJ. An N- terminal nuclear export signal is required for the nucleocytoplasmic shuttling of IkappaBalpha. EMBO J. 1999;18(23):6682- 6693. doi:10.1093/emboj/18.23.6682). And \(\mathrm{IkB\alpha}\) keeps + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 157]]<|/det|> +degradation and resynthesis in the rest time. Taken together, we can conclude that deficiency of CLK2 may result in accumulation of acetylation of a portion of p65. It enhanced the basic transcriptional activity of p65 and it is not related to binding with \(\mathrm{1kBa}\) . + +<|ref|>text<|/ref|><|det|>[[148, 159, 850, 251]]<|/det|> +Considering the good work by Saccani S. et al. (doi: 10.1084/jem.20040196), we can observe that the mutant p65 did not eliminate the polyubiquitination (Fig. 2c) and the mRNA of TNF- \(\alpha\) was not up- regulated by TNF- \(\alpha\) in \(\mathrm{1kBa}^{- }\) cells treated with \(\beta\) lactone (Fig. 3b). It suggests that degradation of promoter- bound p65 takes up a portion of p65 degradation, and there still have other mechanism. It is not contradictory. + +<|ref|>text<|/ref|><|det|>[[147, 288, 835, 437]]<|/det|> +At line 335 of the results paragraph "Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", ser- 468 phosphorylation is described as an activation hallmark of p65, but in fact is mostly associated with a state of repression of p65 transcriptional activity (for a review see "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" by Huang B. et al Cell Signal. 2010 September; 22(9): 1282- 1290. doi:10.1016/j.cellsig.2010.03.017). Therefore, detection of ser 468 in panels D and E should be discussed accordingly. Quantification is needed for the western blot results shown in panel C. + +<|ref|>sub_title<|/ref|><|det|>[[148, 439, 238, 455]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 456, 850, 899]]<|/det|> +Thanks for figure out our mistakes and it has been revised throughout the paragraph. And about the result of increased Ser- 468 phosphorylation in CLK2- \(\mathrm{1}\) cells, here is the discussion. Ser- 468 phosphorylation is an activation hallmark of p65 and the phosphorylation occurs in the nucleus (DOI 10.1074/jbc.M508045200) which links to the negatively regulation of p65 by degradation through proteasome (doi: 10.1038/embor.2009.10; doi: 10.1101/gad.1748409). According to the result in the paper (https://doi.org/10.1096/fj.05- 3736fje), we can also find that Ser468 just has a slight effect in transactivation and does not alter the p65 translocation. Moreover, the review "Posttranslational modifications of NF- \(\kappa \mathrm{B}\) : another layer of regulation for NF- \(\kappa \mathrm{B}\) signaling pathway" also said "Surprisingly, phosphorylation of S468 by \(\mathrm{1K}\kappa \mathrm{e}\) in T cells enhances the transcriptional activation of NF- \(\kappa \mathrm{B}\) in response to T cell co- stimulation (DOI 10.1074/jbc.M508045200). These different outcomes suggest that phosphorylation of S468 regulates the transcriptional activity of NF- \(\kappa \mathrm{B}\) in a context- dependent manner, but the mechanism underlying this requires further investigation". Actually, in normal experiments we usually cannot find a significant change in p65 protein levels under the stimulation. Previous research has not clearly clarified the role of Ser- 468 phosphorylation, but it is a consensus that Ser- 468 phosphorylation reflects the activation of p65. Combined with our results, it is obvious that CLK2 plays a key role in supervising the posttranslational modifications of p65. The nuclear accumulation of p65 caused by CLK2 deficiency may result in the accumulation of phosphorylated p65 at Ser- 468. The result was revised as "The Ser- 536 phosphorylation and Lys- 310 acetylation is required for p65 full transcriptional activity, and Ser- 468 phosphorylation mainly negatively regulates the transcriptional activity and also can be treated as a hallmark of activation of p65". + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[188, 85, 640, 102]]<|/det|> +The quantification of panel C has been shown in Fig. 6. + +<|ref|>image<|/ref|><|det|>[[323, 110, 675, 264]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 306, 851, 512]]<|/det|> +The following sentences "So far, these studies showed that phosphorylation of p65 at Ser- 180 serves as a key switch in terminating active p65 through degradation and nuclear export. All of these experiments indicated that CLK2 acts as a brake in the early stage of NF- kappaB transcriptional activation, and it cooperates with IkappaB- alpha, which functions as a brake in the later stage, to limit the transcriptional process in the whole time of NF- kappaB signaling activation" present starting line 342 of the results paragraph " Ser- 180 phosphorylation of p65 results in its degradation and nuclear export", should be reserved to the Discussion section. Moreover, these conclusions are only partially covering the large amount of data gathered, that also point to the CLK2 mediated phosphorylation of p65 at ser 180 as a homeostatic suppression of p65 activity before the signaling cascades of activating stimuli begin. + +<|ref|>sub_title<|/ref|><|det|>[[149, 514, 237, 529]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[156, 530, 775, 548]]<|/det|> +As suggested, the mentioned sentence was moved to the Discussion section. + +<|ref|>text<|/ref|><|det|>[[149, 549, 850, 621]]<|/det|> +Also, we agree the statement that "Furthermore, the CLK2 mediated phosphorylation of p65 at Ser- 180 serves as a homeostatic suppression of p65 activity before the activation of the signaling cascade" and put it in the Discussion section following above sentence. + +<|ref|>sub_title<|/ref|><|det|>[[150, 660, 352, 676]]<|/det|> +## 12- Supplementary Fig.6 + +<|ref|>text<|/ref|><|det|>[[149, 678, 843, 732]]<|/det|> +In panel B it is not clear what n.s. (non specific) refers to. Is it compared to wt p65 or S180A mutant? It is important because it seems that there is an increased mRNA expression for the S180A mutant compared to wt or the S180D mutant. + +<|ref|>sub_title<|/ref|><|det|>[[149, 736, 237, 750]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 751, 849, 806]]<|/det|> +Sorry for confusing the reviewer, the n.s. of p65S180D/KI is compared to the p65WT. And there is no significant difference between p65 and p65S180A/KI through statistical analysis. + +<|ref|>text<|/ref|><|det|>[[149, 844, 850, 900]]<|/det|> +In panel E it is not clear how this experiment was performed. Treatment of cells with MG132 results in the inhibition of p65 nuclear translocation and p65 mediated gene activation, due to the fact that IkappaB- alpha degradation is prevented (Lee, D.H. and + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 84, 850, 196]]<|/det|> +Goldberg, A.L. 1998 “Proteasome inhibitors: valuable new tools for cell biologists”. Trends Cell Biol. 8, 397–403 doi: 10.1016/s0962-8924(98)01346-4. ). In this panel, though, authors show the nuclear accumulation of p65 S180D following TNF-alpha treatment in the presence of MG132. Authors should provide a plausible explanation for this considering that in this case IkappaB-alpha cannot be degraded. Moreover, IkappaB-alpha expression should be present in this western blot panel. + +<|ref|>sub_title<|/ref|><|det|>[[148, 198, 238, 213]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 215, 850, 306]]<|/det|> +The p65/p50 dimer binding with IkBa dynamically shuttles between the nucleus and cytoplasm. And basic transcription, mediated by p65, continuously proceeds even during rest period without stimulation. This maintains the dynamic balance of cell physiology. The experiment was used p65S180D/K1 HEK293T cells treated with TNF- \(\alpha\) with or without MG132 and then fractionated the cytoplasm and nucleus to detect p65. + +<|ref|>text<|/ref|><|det|>[[147, 307, 850, 437]]<|/det|> +Regarding the inhibition of IkBa, we have a statement previously that even during the rest period, physiological progression continuously proceeds at a relatively low level. Not all of the p65 binds with IkBa, and a portion of p65 can shuttle from the cytoplasm to the nucleus to maintain the dynamic balance. When exposed with MG132, the result indicated that p65S180D is largely accumulated in the nucleus. Meanwhile, the cytoplasmic IkBa, may be similar to the free resynthesized IkBa, shuttles from the cytoplasm to the nucleus. The updated Supplementary Fig. 6e is presented below. + +<|ref|>image<|/ref|><|det|>[[270, 440, 732, 600]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 640, 828, 752]]<|/det|> +13- The following sentence “These data suggest that CLK2 represents a potential therapeutic target for inflammatory diseases”, starting at line 374 of the results paragraph “CLK2 inhibitor TG003 exhibits power in vitro and in vivo”, seems not formally correct. On the contrary, data suggest that any pathway inhibitor of CLK2 may represent a potential therapeutic target for inflammatory diseases, because CLK2 actually acts inhibiting prolonged inflammation. + +<|ref|>sub_title<|/ref|><|det|>[[148, 754, 238, 769]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 772, 849, 825]]<|/det|> +We agree with the reviewer and this sentence has been revised as following “These data suggest that CLK2 represents a potential therapeutic target for inflammatory diseases and TG003 may be developed as a cure of virus- infection.” + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[150, 86, 266, 101]]<|/det|> +## 14-Discussion + +<|ref|>text<|/ref|><|det|>[[150, 104, 827, 140]]<|/det|> +Discussion should provide a better data interpretation, also including discussion of results from new experiments related to p65 DNA binding. + +<|ref|>sub_title<|/ref|><|det|>[[149, 143, 237, 158]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 160, 850, 381]]<|/det|> +Discussion related to p65 DNA- binding has been added in the result and discussion section "As known, interaction with \(\mathrm{1kBa}\) is usually relevant to the DNA- binding activity, so we next sought for if \(\mathrm{p65^{S180D / KI}}\) affects p65 binding with DNA. ChIP- qPCR assays showed that \(\mathrm{p65^{S180D / KI}}\) has nearly lost the ability of DNA- binding, on the contrary, \(\mathrm{p65^{S180A / KI}}\) exhibits the enhanced DNA- binding activity (Fig. 6e). In addition, p65 in \(\mathrm{CLK2^{- / - }}\) cells also showed increase capability of DNA- binding (Supplementary Fig. 6j). In summary, phosphorylation of p65 by CLK2 at Ser- 180 decreases the DNA- binding activity of p65 and enhance its interaction with CRM1 and \(\mathrm{1kBa}\) , resulting in the export of p65 from the nucleus." and "Additionally, the \(\mathrm{p65^{S180A}}\) and p65 in \(\mathrm{CLK2^{- / - }}\) cells showed less affinity for CRM1 and \(\mathrm{1kBa}\) and a stronger DNA- binding activity, further demonstrating how Ser- 180 phosphorylation affects the transcription.". + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 75, 295, 88]]<|/det|> +## REVIEWER COMMENTS + +<|ref|>text<|/ref|><|det|>[[120, 102, 414, 116]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[119, 131, 194, 144]]<|/det|> +## Summary + +<|ref|>text<|/ref|><|det|>[[119, 158, 874, 284]]<|/det|> +The authors have provided a thorough rebuttal. They note numerous figure modifications with the addition of new data and removal and rearrangement of previous data, and text clarifications that have substantially improved the manuscript. The authors have defined a role for CLK2 in the impairment of NF- kB activation and inflammation that impacts virus replication, and further improvements were made to Figs 1- 3 in response to Reviewer 2. However, I am not satisfied with the mechanistic underpinnings of the impact of CLK2 on RelA/p65. Without confirmation that CLK2 directly phosphorylates RelA/p65 and that this inhibition is truly independent of IkBa, the novelty of this publication is substantially reduced. The data provided does not strongly lock down these two claims. + +<|ref|>sub_title<|/ref|><|det|>[[119, 299, 235, 312]]<|/det|> +## Major concerns + +<|ref|>text<|/ref|><|det|>[[120, 326, 649, 340]]<|/det|> +1. Weak evidence that RelA/p65 Ser180 is a direct substrate of CLK2. + +<|ref|>text<|/ref|><|det|>[[119, 354, 876, 439]]<|/det|> +- For IP interactions and phos-tag and ADP glo kinase assays in Fig 4 and Supp Fig4: It would be ideal to perform with purified proteins. As it stands now this interaction could be part of a complex and not direct. They describe Fig 4f as an in vitro pulldown that I suppose is linked to the 'protein purification and pull-down' in Methods. This describes a purified His-p65 with FLAG- enriched lysates of transfected 293T cells. Is there a Coomassie stained gel to demonstrate the purity of the FLAG enriched lysate used for the FLAG pull-down? + +<|ref|>text<|/ref|><|det|>[[118, 452, 869, 551]]<|/det|> +- The authors respond in the rebuttal that the CLK2K192R mutant is widely used in the field. Can they verify that the CLK2 K192R mutant is kinase dead in this system using canonical substrates? It is also notable that CLK2 undergoes autophosphorylation on Ser141, mutation changes its subnuclear localization (PMID 9852100). Does the K192R prevent this autophosphorylation? One potential explanation is that the autophosphorylated form of CLK2 is required to interact with p65 (whether due to TG003 or the K192R mutant), but does not reflect the requirement for its kinase activity. + +<|ref|>text<|/ref|><|det|>[[118, 564, 872, 621]]<|/det|> +- TG003 is not specific for CLK2, this drug also inhibits other CLKs. This is important since CLK1,2,4 each regulate other substrates including splicing factors (PMID 33846420). They need to demonstrate that this is not impacting other CLKs or that other CLK2 substrates aren't playing a role. Why not show that the impact of TG003 is only observed in CLK2+, but not CLK2-/- cells. + +<|ref|>text<|/ref|><|det|>[[118, 634, 872, 775]]<|/det|> +- The guidelines and other publications that use the ADP-glo kinase assay report activity based on the change in luminescence with concentration of the protein/inhibitors present. Here, they apply it as a single timepoint/readout luminescent reading- they do not report kinase activity differences in CLK compared to the CLK2 K192R mutant over a range of protein/substrate concentrations. Given that CLK2 K192R is expressed at lower levels than CLK2 in Fig 4C- this decrease in luminescence might just represent a decrease in CLK2 mutant expression levels. They don't show assay results for FLAG-CLK2K192R in the absence of His-p65. What is the source of the samples examined (lysates or purified components)? The input proteins need to be shown to verify equal inputs. Minimally, a purified CLK2 kinase enzyme system is commercially available (Promega) and could be used with their purified p65 to verify p65 is a substrate for CLK2. + +<|ref|>text<|/ref|><|det|>[[118, 789, 850, 817]]<|/det|> +- The rationale for pursuing S180 but not S316 does not seem logical since the alignments show similar patterns of conservation across species for both (Fig 5B). + +<|ref|>text<|/ref|><|det|>[[118, 831, 857, 873]]<|/det|> +- The analysis of the p65 S180 mutant clearly shows that S180A is more active than S180D, but the stronger experiment is to show that both retain this profile with or without CLK2 expression, unlike WT p65 (Fig 5E). + +<|ref|>text<|/ref|><|det|>[[118, 886, 870, 915]]<|/det|> +- There was a notable difference in the expression level of HA-S180D in Fig 5 due to a decrease in stability; that is the simple explanation for loss of NF-kB activation in Fig 4 functional assays. Why + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[119, 74, 864, 116]]<|/det|> +aren't these assays shown in the presence and absence of CLK2 to demonstrate that only the WT p65 half- life/instability (Supp Fig 6G) is different between CLK2+ and CLK2- /- cells (S180A and S180D would not show any dependence on CLK2 correct, correct)? + +<|ref|>text<|/ref|><|det|>[[119, 130, 877, 186]]<|/det|> +- I remain in doubt about the findings using the Ser-180 p-p65 antibody (Fig 6F). The phospho-specific Ser-180 antibody that they had produced shows a non-specific band and evidently cross reacts with total p65, As controls, did they profile WT p65, S180A and S180D mutants to show this only recognizes the WT p65. Did they test p65-/- cells? + +<|ref|>text<|/ref|><|det|>[[119, 200, 878, 242]]<|/det|> +- Also there is inconsistency between the CLK2+/+ vs -/- cells in Fig6D at basal (Ohrs) conditions. The p-p65 Ser180 is the same at 0 hr in the SeV blot on left but higher in CLK2+/+ cells compared to CLK2-/- cells at 0 hrs in the right TNFa blot. + +<|ref|>text<|/ref|><|det|>[[119, 270, 645, 284]]<|/det|> +2. I am still not convinced that CLK2 function is independent of IkBa. + +<|ref|>text<|/ref|><|det|>[[119, 298, 861, 354]]<|/det|> +"Interestingly, there was an increased accumulation of Nfkbia in Clk2-/- cells, which is consistent with the increase in Lys-310 acetylation and Ser-536 phosphorylation of p65. It indicates that CLK2 may be a basal checkpoint to limit constitutional activation of NF-κB signaling, even in the absence of activating stimuli." + +<|ref|>text<|/ref|><|det|>[[119, 368, 860, 410]]<|/det|> +- I remain unclear what they mean by 'early stage termination.' It seems that the impact of CLK2 on p65 and NFkbia is most apparent in the context of induction than basal conditions. IkBa is expressed and plays a role in basal and induced conditions over a 6 hr timecourse. + +<|ref|>text<|/ref|><|det|>[[119, 424, 874, 495]]<|/det|> +- They state on lines 81-82 that 'we report an IkBa-independent nuclear NF-kB termination model at the transcriptional level through inhibitory phosphorylation by CLK2' Given that they have greater interactions of p65 with IkBa in the presence of CLK2 (without or with TNF) in Supp Fig 6I, doesn't this again indicate that IkBa can be playing a role in CLK2's inhibition of p65? Can they demonstrate that CLK2 suppresses p65 even in the absence of IkBa? + +<|ref|>text<|/ref|><|det|>[[119, 509, 877, 550]]<|/det|> +- I don't understand their statement that IkBa functions in CLK2 KO cells- the data they cite just shows NFkbia is resynthesized by western. Do they introduce IkBa into CLK2-/- cells and show it is still inhibitory? + +<|ref|>text<|/ref|><|det|>[[118, 564, 872, 691]]<|/det|> +- They find that S180D (which does not activate NF-kb and has a higher turnover) has a higher affinity for Nfkbia/IkBa (Supp Fig 6H), but S180A and WT in CLK2-/- cells has a decreased interaction with CRM1 and Ikba (Fig 6C &6D). This data demonstrates that the phosphorylation on S180 induced by CLK2 leads to a higher affinity for Ikba that would export and lock p65 out of nucleus; in turn this lead to the loss of NF-kB post-translational modifications and functions in the nucleus. Therefore, the impact of CLK2 on p65 Ser180 phosphorylation may be upstream of IkBa interactions, but ultimately is determined by IkBa export. It is not independent of Ikba- just not dependent on newly synthesized IkBa in late stage termination. This does not fit with their conclusions and title. + +<|ref|>text<|/ref|><|det|>[[118, 705, 870, 747]]<|/det|> +- Lines 368-370 described showing p65 S180A and WT interactions with CRM1 and IkBa in CLK2-/- cells. Fig 6D only shows 293T cells and Fig.6i only shows WT p65 in both CLK2+/+ and CLK2-/- cells. + +<|ref|>text<|/ref|><|det|>[[119, 761, 250, 774]]<|/det|> +Minor comments. + +<|ref|>text<|/ref|><|det|>[[118, 789, 870, 911]]<|/det|> +1. Professional editing is required even with revisions. Numerous issues remain and some are newly introduced. 'plague' is still used where 'plague' is appropriate. +2. The IFA figures with brightfield added have become very small (Fig3, 5). The IFA for the paired flow cytometry data could be moved to supplemental or the other bar graphs in the figures could be shortened to make space. +3. I previously noted that the font kerning for the sequence alignment of Fig 5B is off and that a monospace font is needed. The authors claim to have adjusted this- but the text is still not aligned properly. +4. There is a lack of discussion regarding its canonical substrates such as splicing factors vs this + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[118, 74, 866, 116]]<|/det|> +noncanonical functions of CLK2 to target p65. How does SeV, TNFa or other stimulations that activated CLK2 tie into its impacts on splicing? When CLK2 is activated by infection to target p65, what is the impact on canonical substrates? + +<|ref|>text<|/ref|><|det|>[[118, 116, 860, 188]]<|/det|> +5. Typo in Supp Fig 4c legend line 1057: they state 'The upper shifted band represents phosphorylated CLK2 protein.' This is actually p65, correct? +6. With regard to Fig 6D legend, they state that "The asterisk/upper band indicate the unspecific band that can be detected by the antibody and the explanation was added in the relative figure legends." This has not been corrected. + +<|ref|>text<|/ref|><|det|>[[120, 241, 414, 256]]<|/det|> +Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[118, 269, 877, 397]]<|/det|> +Authors fixed all relevant issue raised, by performing new experiments as requested, and by modifying the manuscript, as suggested. I also encourage authors to make a further effort to improve manuscript written English (at pag 5 line 55, "rheumatoid arthritis", instead of "rheumatic arthritis"; at pag.6 line 89 "CLK2-deficient mice were observed to have higher levels", instead of "CLK2-deficient mice produce were observed to have higher levels"; at pag 22 line 444 "The transcription factor p65 is critical for cytokine-induced production of inflammation genes", instead of "The transcription factors p65 is critically for cytokine-induced production of inflammation genes"; at page 24 line 499 "use of site-specific phosphorylation antibody", instead of "use of site-specific phosphorylation antibody", and so on). + +<|ref|>text<|/ref|><|det|>[[119, 396, 848, 453]]<|/det|> +Moreover, at pag. 21 line 440, I suggest to rephrase the sentence "... and TG003 may be developed as a cure of virus- infection" as "...and CLK2 inhibition may be exploited as a cure of virus- infection", due to the fact that TG003 inhibitor may not be suitable for further chemical optimization, to serve as an effective and safe antiviral. + +<|ref|>text<|/ref|><|det|>[[119, 468, 244, 481]]<|/det|> +Marco Sgarbanti + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 86, 562, 103]]<|/det|> +## Point-by-point response to reviewers' comments + +<|ref|>text<|/ref|><|det|>[[149, 105, 844, 214]]<|/det|> +We are extremely thankful for the reviewers' constructive feedback and valuable suggestions, which have greatly contributed to the enhancement of our manuscript and study. In response to the reviewers' comments, we have conducted additional experiments and made necessary clarifications to certain statements and experimental procedures in the revised manuscript. Here is our point- by- point response to the reviewers' comments. + +<|ref|>sub_title<|/ref|><|det|>[[149, 234, 481, 251]]<|/det|> +## Reviewer #1 (Remarks to the Author): + +<|ref|>sub_title<|/ref|><|det|>[[149, 254, 237, 269]]<|/det|> +## Summary + +<|ref|>text<|/ref|><|det|>[[148, 271, 852, 455]]<|/det|> +The authors have provided a thorough rebuttal. They note numerous figure modifications with the addition of new data and removal and rearrangement of previous data, and text clarifications that have substantially improved the manuscript. The authors have defined a role for CLK2 in the impairment of NF- kB activation and inflammation that impacts virus replication, and further improvements were made to Figs 1- 3 in response to Reviewer 2. However, I am not satisfied with the mechanistic underpinnings of the impact of CLK2 on RelA/p65. Without confirmation that CLK2 directly phosphorylates RelA/p65 and that this inhibition is truly independent of IkBa, the novelty of this publication is substantially reduced. The data provided does not strongly lock down these two claims. + +<|ref|>sub_title<|/ref|><|det|>[[149, 457, 283, 472]]<|/det|> +## Major concerns + +<|ref|>sub_title<|/ref|><|det|>[[149, 475, 733, 492]]<|/det|> +## 1. Weak evidence that RelA/p65 Ser180 is a direct substrate of CLK2. + +<|ref|>text<|/ref|><|det|>[[148, 494, 851, 621]]<|/det|> +- For IP interactions and phos-tag and ADP glo kinase assays in Fig 4 and Supp Fig4: It would be ideal to perform with purified proteins. As it stands now this interaction could be part of a complex and not direct. They describe Fig 4f as an in vitro pulldown that I suppose is linked to the'protein purification and pull-down'in Methods. This describes a purified His-p65 with FLAG-enriched lysates of transfected 293T cells. Is there a Coomassie stained gel to demonstrate the purity of the FLAG enriched lysate used for the FLAG pull-down? + +<|ref|>sub_title<|/ref|><|det|>[[149, 624, 238, 639]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 641, 851, 770]]<|/det|> +It is really a valuable advice and we also agree that it would be ideal to use purified proteins. It may be complex and not show the interaction directly. We successfully purified His- p65 in prokaryotic cells, but were unable to purify full- length CLK2 and CLK2K192R in prokaryotic cells. Instead, we chose to enrich them in transfected HEK293T cells. And the method is linked to the "protein purification and pull- down" in Methods section. Additionally, we actually ran a Coomassie stained gel, but it was inadvertently not provided. Here is the new version of Fig. 4f which is presented below. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[230, 87, 768, 324]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 362, 850, 494]]<|/det|> +- The authors respond in the rebuttal that the CLK2K192R mutant is widely used in the field. Can they verify that the CLK2 K192R mutant is kinase dead in this system using canonical substrates? It is also notable that CLK2 undergoes autophosphorylation on Ser141, mutation changes its subnuclear localization (PMID 9852100). Does the K192R prevent this autophosphorylation? One potential explanation is that the autophosphorylated form of CLK2 is required to interact with p65 (whether due to TG003 or the K192R mutant), but does not reflect the requirement for its kinase activity. + +<|ref|>sub_title<|/ref|><|det|>[[148, 495, 238, 510]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 512, 850, 620]]<|/det|> +We apologize for not using canonical substrates to directly verify the kinase- dead status of the CLK2K192R mutant. However, we refer to the pivotal study by Joseph T. Rodgers et al. (DOI: 10.1016/j.cmet.2009.11.006), which demonstrated that CLK2K192R lacks the ability to phosphorylate PGC- 1α in a \(\gamma^{32}\mathrm{P}\) - ATP reaction, as illustrated in Supplementary Fig. 2D (presented below). This evidence firmly supports our assertion that the CLK2K192R mutant is kinase- dead. + +<|ref|>text<|/ref|><|det|>[[148, 622, 850, 805]]<|/det|> +As the reviewer said "It is also notable that CLK2 undergoes autophosphorylation on Ser141, mutation changes its subnuclear localization (PMID 9852100). Does the K192R prevent this autophosphorylation". Addressing the reviewer's insightful query, we highlight findings from the same study by Rodgers et al., showing \(\gamma^{32}\mathrm{P}\) - ATP consumption when CLK2K192R was co- incubated with CLK2WT (Supplementary Fig. 2E and was presented below). This suggests that while CLK2K192R cannot autophosphorylate, it can be phosphorylated by CLK2WT. Furthermore, the localization pattern of CLK2K192R, closely mirroring that of the CLK2S142A mutant (DOI: 10.1074/jbc.273.51.34341), reinforces our conclusion regarding the kinase- dead status of CLK2K192R and its inability to undergo autophosphorylation. + +<|ref|>text<|/ref|><|det|>[[149, 807, 850, 880]]<|/det|> +In our manuscript, the CLK2K192R mutant was primarily utilized as a negative control, analogous to the use of TG003 as suggested by the reviewer. Moreover, the autophosphorylated form of CLK2 itself indicates the necessity of its kinase activity. We believe that regardless of the form of CLK2 - be it K192R, S142A, or treated with + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[147, 85, 850, 121]]<|/det|> +TG003 - the K192R mutation indeed leads to the inactivation of CLK2 kinase activity, making our findings valid. + +<|ref|>title<|/ref|><|det|>[[432, 323, 564, 340]]<|/det|> +# [REDACTED] + +<|ref|>text<|/ref|><|det|>[[147, 585, 850, 612]]<|/det|> +Rodgers JT, Haas W, Gygi SP, Puigserver P. Cdc2- like kinase 2 is an insulin- regulated suppressor of hepatic gluconeogenesis. Cell Metab. 2010;11(1):23- 34. doi:10.1016/j.cmet.2009.11.006 + +<|ref|>text<|/ref|><|det|>[[148, 668, 850, 760]]<|/det|> +- TG003 is not specific for CLK2, this drug also inhibits other CLKs. This is important since CLK1,2,4 each regulate other substrates including splicing factors (PMID 33846420). They need to demonstrate that this is not impacting other CLKs or that other CLK2 substrates aren't playing a role. Why not show that the impact of TG003 is only observed in CLK2+, but not CLK2-/- cells. + +<|ref|>sub_title<|/ref|><|det|>[[148, 762, 238, 777]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 780, 850, 870]]<|/det|> +We are grateful for your insightful comments regarding the specificity of TG003. We acknowledge that TG003 is known to inhibit several members of the CLK family, including CLK1, CLK2, and CLK4. Recognizing the critical need to demonstrate the specificity of TG003's effects in the context of our study, we have undertaken additional experiments. + +<|ref|>text<|/ref|><|det|>[[148, 872, 850, 908]]<|/det|> +To unequivocally address the concerns raised, CLK2- /- cells. Our results, now included as Supplementary Fig. 6m, show that TG003's presence or absence did not + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 140]]<|/det|> +influence the acetylation or phosphorylation levels of p65 in CLK2-/- cells. This outcome strongly suggests that the impact of TG003 on p65 activation is specifically mediated through inhibition of CLK2, rather than other CLK family members. + +<|ref|>image<|/ref|><|det|>[[147, 157, 850, 271]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 307, 852, 529]]<|/det|> +- The guidelines and other publications that use the ADP-glo kinase assay report activity based on the change in luminescence with concentration of the protein/inhibitors present. Here, they apply it as a single timepoint/readout luminescent reading-they do not report kinase activity differences in CLK compared to the CLK2 K192R mutant over a range of protein/substrate concentrations. Given that CLK2 K192R is expressed at lower levels than CLK2 in Fig 4C- this decrease in luminescence might just represent a decrease in CLK2 mutant expression levels. They don't show assay results for FLAG-CLK2K192R in the absence of His-p65. What is the source of the samples examined (lysates or purified components)? The input proteins need to be shown to verify equal inputs. Minimally, a purified CLK2 kinase enzyme system is commercially available (Promega) and could be used with their purified p65 to verify p65 is a substrate for CLK2. + +<|ref|>sub_title<|/ref|><|det|>[[148, 531, 238, 546]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 549, 850, 603]]<|/det|> +We are grateful for your valuable advice. Taking into account previous research and the suggestion of the technical adviser from Promega, we have decided on the specific concentration of CLK2 for the kinase assay. + +<|ref|>text<|/ref|><|det|>[[148, 604, 850, 678]]<|/det|> +It is so sorry for confusing you about the expression of CLK2 and CLK2K192R, they were utilized with the same concentration which were examined by BCA Protein Quantification Kit. We deeply regret that we are unable to detect the sample for CLK2K192R without His-p65 and did not show the examination of samples additionally. + +<|ref|>text<|/ref|><|det|>[[148, 679, 850, 862]]<|/det|> +To directly address your concerns, we procured the commercially available CLK2 kinase enzyme system from Promega. Given the unavailability of a commercial source for CLK2K192R, we utilized the provided CLK2 enzyme and combined it with our own purified His-p65 for the kinase assay. The results clearly demonstrated a dose- dependent relationship between ATP consumption and the amount of His-p65 (0ng, 100 ng, 500 ng, 1000 ng, 2000 ng) with a constant 20 ng of CLK2 protein. These adjustments and additional experiments significantly bolster our confidence in the reported findings, establishing p65 as a substrate for CLK2. We believe these efforts adequately address your concerns and enhance the overall validity and robustness of our study. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[371, 90, 622, 228]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[149, 288, 850, 325]]<|/det|> +-The rationale for pursuing S180 but not S316 does not seem logical since the alignments show similar patterns of conservation across species for both (Fig 5B). + +<|ref|>sub_title<|/ref|><|det|>[[149, 327, 238, 342]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 344, 850, 510]]<|/det|> +The question raised is a significant one, and as the statement in result section "The NF- \(\kappa \mathrm{B}\) luciferase reporter assay showed that \(\mathrm{p65^{S180D}}\) , but not \(\mathrm{p65^{S316D}}\) , completely blocked the wild- type p65- induced NF- \(\kappa \mathrm{B}\) luciferase reporter activation, suggesting that phosphorylation of p65 serine 180 is necessary for NF- \(\kappa \mathrm{B}\) deactivation (Supplementary Fig. 5d)". Our research focuses on inhibiting NF- \(\kappa \mathrm{B}\) activation in innate immunity and inflammation, and serine 180 has shown to play a crucial role in this process. As a result, we highlight the importance of serine 180 in the deactivation of NF- \(\kappa \mathrm{B}\) signaling and chose to investigate the function of serine 180 in NF- \(\kappa \mathrm{B}\) signaling activation, while excluding serine 316. + +<|ref|>text<|/ref|><|det|>[[148, 511, 850, 658]]<|/det|> +Although Ser316 is also a potential phosphorylation site by CLK2, our experiments suggest that \(\mathrm{p65^{S316D}}\) does not affect NF- \(\kappa \mathrm{B}\) signaling transactivation in response to viral and cytokine stimulation. This finding directs our focus towards Ser180 due to its significant impact on NF- \(\kappa \mathrm{B}\) signaling. Nonetheless, we acknowledge that Ser316 may play a role in other physiological or regulatory mechanisms. Recognizing this potential, we aim to investigate the function and implications of S316 phosphorylation in future studies, thus expanding our understanding of NF- \(\kappa \mathrm{B}\) signaling regulation and its broader physiological significance. + +<|ref|>text<|/ref|><|det|>[[149, 696, 849, 751]]<|/det|> +-The analysis of the p65 S180 mutant clearly shows that S180A is more active than S180D, but the stronger experiment is to show that both retain this profile with or without CLK2 expression, unlike WT p65 (Fig 5E). + +<|ref|>sub_title<|/ref|><|det|>[[149, 754, 238, 769]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 771, 850, 899]]<|/det|> +Your concern is very important, and we have previously observed that S180A maintains its profile with or without CLK2. We conducted a similar experiment by overexpressing CLK2, and the results of the Luciferase assay showed that CLK2 overexpression does not affect the activation of NF- \(\kappa \mathrm{B}\) by \(\mathrm{p65^{S180A}}\) , contrasting with the significant inhibition observed in the case of wild- type p65. Regarding the S180D mutant, which represents a phosphorylation- mimicking, deactivated form of p65, we chose not to include it in this assay. The decision was based on its intrinsic deactivated + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 851, 140]]<|/det|> +state, which we anticipated would not provide additional insights into the impact of CLK2 overexpression on NF- \(\kappa \mathrm{B}\) activation. The results are available and presented below, but are not included in the manuscript. + +<|ref|>image<|/ref|><|det|>[[364, 156, 631, 290]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 344, 852, 454]]<|/det|> +- There was a notable difference in the expression level of HA-S180D in Fig 5 due to a decrease in stability; that is the simple explanation for loss of NF-kB activation in Fig 4 functional assays. Why aren't these assays shown in the presence and absence of CLK2 to demonstrate that only the WT p65 half-life/instability (Supp Fig 6G) is different between CLK2+ and CLK2-/- cells (S180A and S180D would not show any dependence on CLK2 correct, correct)? + +<|ref|>sub_title<|/ref|><|det|>[[148, 457, 238, 472]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 475, 851, 620]]<|/det|> +Thanks for your valuable suggestion. As what another reviewer said, "While MG132 experiments provide striking qualitative data demonstrating a role for phosphorylated ser180 in protein degradation, authors must calculate p65 wt, p65 S180A and p65 S180D half-life by performing a time course of cycloheximide (CHX) treatment, thus straightening their findings with solid quantitative data". We had performed the experiment in HEK293T, HEK293T- p65S180A/KI, and HEK293T- p65S180D/KI cell lines then to further verify the stability of p65S180A and p65S180D following the reviewer #2's advice. + +<|ref|>text<|/ref|><|det|>[[147, 622, 850, 731]]<|/det|> +What you concerned are both reasonable and crucial. In accordance with your advice, we have performed the CHX assay in HEK293T- CLK2- /- cells and the findings have been incorporated into Supplementary Fig. 6g. The results indicate that p65WT in CLK2- /- cells exhibits slightly greater stability than p65WT in HEK293T cells, resembling the result of p65S180A/KI closely. On the other hand, the consistently phosphorylated mutant p65S180D/KI demonstrates notably inferior stability. + +<|ref|>text<|/ref|><|det|>[[148, 732, 850, 824]]<|/det|> +This data indicates that both p65WT in CLK2- /- cells and p65S180A/KI exhibit comparable half- lives, suggesting that their stability is not influenced by CLK2- mediated phosphorylation. Accordingly, we infer that mutations at the Ser- 180 site, namely S180A and S180D, exhibit no dependency on CLK2 for their stability or degradation profiles. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[264, 85, 736, 284]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[147, 308, 850, 381]]<|/det|> +To reflect these insights, the result section has been revised as "and a cycloheximide (CHX) assay also revealed that p65S180D had a significantly shorter half- life than p65WT. On the contrary, p65S180A, which is similar to p65WT in CLK2-/- cells, showed a bit increased stability (Supplementary Fig. 6g)". + +<|ref|>text<|/ref|><|det|>[[147, 417, 851, 511]]<|/det|> +-I remain in doubt about the findings using the Ser- 180 p- p65 antibody (Fig 6F). The phospho- specific Ser- 180 antibody that they had produced shows a non- specific band and evidently cross reacts with total p65, As controls, did they profile WT p65, S180A and S180D mutants to show this only recognizes the WT p65. Did they test p65- /- cells? Response: + +<|ref|>text<|/ref|><|det|>[[147, 512, 851, 677]]<|/det|> +We appreciate your concerns regarding the specificity of our phospho- specific Ser- 180 p65 antibody. Although we did not profile S180A and S180D mutants with this antibody, we conducted specificity tests using p65- /- cells as a critical control. Supplementary Fig. 6k (which was presented below) demonstrates that the level of phos- p65 (Ser180) showed dynamic changes during SeV or TNF- \(\alpha\) infection. Importantly, in p65- /- cells, where no p65 protein should be present, only a very weak band was observed. We interpret this minimal signal as non- specific binding, which is common in immunoblotting but does not detract from the overall specificity of the antibody towards its intended target under the conditions tested. + +<|ref|>text<|/ref|><|det|>[[147, 679, 830, 789]]<|/det|> +This control experiment supports the specificity of our phospho- Ser- 180 p65 antibody, as significant reactivity is observed in the context of infections where Ser180 phosphorylation is expected to occur, while minimal background is detected in the absence of the p65 protein. We believe these findings adequately address the concern about antibody specificity and affirm the reliability of our results involving the detection of phospho- Ser180 p65. + +<|ref|>image<|/ref|><|det|>[[198, 792, 797, 896]]<|/det|> + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 122, 850, 178]]<|/det|> +- Also there is inconsistency between the CLK2+/+ vs-/- cells in Fig6D at basal (Ohrs) conditions. The p-p65 Ser180 is the same at Ohr in the SeV blot on left but higher in CLK2+/+ cells compared to CLK2-/- cells at O hrs in the right TNFa blot. + +<|ref|>sub_title<|/ref|><|det|>[[148, 180, 238, 195]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 198, 851, 362]]<|/det|> +We are grateful for your keen observation and it is exactly what you describe. We also feel confused. After reviewing multiple instances of repetitions, we believe that the p- p65 Ser180 level in CLK2+/+ cells should be higher than in CLK2-/- cells at 0 hrs (The results of repetitions were presented below). This discrepancy may have been caused by a system error in a single experiment. Similar to the identification of the antibody in p65-/- cells shown in the figure below, we can find that the blot at 0 hrs in HEK293T cells and blot in p65-/- cells have a similar level of p- p65 Ser180. In conclusion, the specificity of p- p65 Ser180 has been confirmed, and the discrepancy may simply be an error that does not affect the conclusion we have reached. + +<|ref|>image<|/ref|><|det|>[[225, 366, 770, 583]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[148, 640, 740, 658]]<|/det|> +## 2. I am still not convinced that CLK2 function is independent of IkBa. + +<|ref|>text<|/ref|><|det|>[[147, 660, 853, 808]]<|/det|> +"Interestingly, there was an increased accumulation of Nfkbia in Clk2-/- cells, which is consistent with the increase in Lys- 310 acetylation and Ser- 536 phosphorylation of p65. It indicates that CLK2 may be a basal checkpoint to limit constitutional activation of NF- KB signaling, even in the absence of activating stimuli." - I remain unclear what they mean by 'early stage termination.' It seems that the impact of CLK2 on p65 and NFkbia is most apparent in the context of induction than basal conditions. IkBa is expressed and plays a role in basal and induced conditions over a 6 hr timecourse. + +<|ref|>sub_title<|/ref|><|det|>[[148, 810, 238, 825]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 827, 849, 881]]<|/det|> +We apologize for any confusion caused by our previous explanation and we appreciate the opportunity to further clarify the role of CLK2 in the regulation of NF- \(\kappa \mathrm{B}\) signaling and its independence from IkBa- mediated termination. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 850, 250]]<|/det|> +Our focus is on the termination of transcriptional activation of p65. One well- known model involves \(\mathrm{IkBa}\) interacting with p65 in the cytoplasm, known as \(\mathrm{IkBa}\) - dependent termination. However, research has shown that p65 can still be retained in the cytoplasm even in the absence of \(\mathrm{IkBa}\) (doi: 10.1128/MCB.16.5.2341), suggesting the existence of other termination mechanisms independent of \(\mathrm{IkBa}\) . Our study reveals that CLK2 phosphorylates p65, regulating its post- translational modifications and reducing its DNA- binding activity and stability, ultimately leading to the termination of its transcriptional activation. Our proposed model is distinct from the \(\mathrm{IkBa}\) - dependent termination model, and thus we refer to it as \(\mathrm{IkBa}\) - independent termination. + +<|ref|>text<|/ref|><|det|>[[148, 252, 851, 546]]<|/det|> +According to the detailed explanation of the classic \(\mathrm{IkBa}\) - dependent termination model, \(\mathrm{IkBa}\) primarily inhibits p65 during basal conditions and in the later stage of activation. In basal conditions, \(\mathrm{IkBa}\) binds to p65 in the cytoplasm, preventing its nuclear translocation. Once the NF- \(\kappa \mathrm{B}\) signaling is activated, \(\mathrm{IkBa}\) is mostly degraded, allowing p65 shuttles into the nucleus. Meanwhile, as one of the downstream genes of p65, \(\mathrm{IkBa}\) is resynthesized, mediated by p65 in the later stage, and binds with nuclear- p65 to bring it back to the cytoplasm (DOI: 10.1016/j.cell.2008.01.020). The defect of this model is that in the early stage of activation, there is no inhibitor to suppress or terminate the transcriptional activation of p65 when \(\mathrm{IkBa}\) has been mostly degraded but not yet been resynthesized. Therefore, the "early stage" here represents the period in which p65 shuttles into the nucleus and starts the progression of transcription in the absence of \(\mathrm{IkBa}\) . However, CLK2 can inhibit the activation of NF- \(\kappa \mathrm{B}\) signaling once p65 shuttles into the nucleus, and the inhibition lasts until the termination of NF- \(\kappa \mathrm{B}\) signaling. The novel termination mechanism by CLK2 includes the early stage of activation and is not dependent on \(\mathrm{IkBa}\) . Finally, this is referred to as " \(\mathrm{IkBa}\) - independent early stage termination". + +<|ref|>text<|/ref|><|det|>[[149, 548, 850, 602]]<|/det|> +The change of p65 and Nfkbia is indeed more apparent in the context of induction than basal conditions. During activation, p65 is subject to much post- translational modifications, while Nfkbia undergoes mostly degradation and then re- synthesis. + +<|ref|>text<|/ref|><|det|>[[148, 604, 850, 769]]<|/det|> +About the statement " \(\mathrm{IkBa}\) is expressed and plays a role in basal and induced conditions over a 6 hr time course". Actually, the Nfkbia we mentioned here is not being investigated for its function in basal and induced conditions. Instead, the expression level of Nfkbia serves as an indicator of the transcriptional activity mediated by p65, which is known to induce Nfkbia expression. It is noteworthy that the expression of Nfkbia in \(\mathrm{Clk2}^{- / - }\) cells is more than that in \(\mathrm{Clk2}^{+ / + }\) cells, even under basal conditions (Fig. 2e and Supplementary Fig. 2f). The result indicates us that p65 displays heightened transcriptional activity in the absence of CLK2, no matter in basal or induced conditions. + +<|ref|>text<|/ref|><|det|>[[149, 808, 851, 881]]<|/det|> +- They state on lines 81-82 that 'we report an lkBa-independent nuclear NF-kB termination model at the transcriptional level through inhibitory phosphorylation by CLK2'Given that they have greater interactions of p65 with lkBa in the presence of CLK2 (without or with TNF) in Supp Fig 61, doesn't this again indicate that lkBa can + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[149, 85, 848, 121]]<|/det|> +be playing a role in CLK2's inhibition of p65? Can they demonstrate that CLK2 suppresses p65 even in the absence of lkBa? + +<|ref|>sub_title<|/ref|><|det|>[[149, 124, 238, 139]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 141, 850, 269]]<|/det|> +What a great question. As we answered previously, phosphorylation of p65 by CLK2 has been shown to inhibit the transcriptional activation of p65, and it was reflected by the post- translational modification levels of p65. This inhibition by CLK2 is independent of \(\mathrm{lkBa}\) . Meanwhile, the interaction between \(\mathrm{lkBa}\) and nuclear- p65 is regulated by the acetylation of p65. According to the work by Lin- feng Chen (DOI: 10.1093/emboj/cdf660), we can understand that acetylation of p65 at K221 and K218 can enhance the DNA binding of NF- \(\kappa \mathrm{B}\) and impair its association with \(\mathrm{lkBa}\) . + +<|ref|>text<|/ref|><|det|>[[148, 270, 851, 455]]<|/det|> +However, it is important to differentiate between the effect of CLK2 on p65 activity and the role of \(\mathrm{lkBa}\) . In our manuscript, we found that CLK2 inhibits several post- translational modifications of p65, which may also impair the acetylation levels of p65 at K221 and K218. Therefore, it makes sense that p65 has greater interactions with \(\mathrm{lkBa}\) in the presence of CLK2. Moreover, phosphorylation by CLK2 and interaction with \(\mathrm{lkBa}\) are two separate events, with a precedence relationship in time. The increased interaction between \(\mathrm{lkBa}\) and p65 is one of the results caused by phosphorylation by CLK2. In a word, the inhibition of p65 by CLK2 is not affected by the absence or presence of \(\mathrm{lkBa}\) , so it does not indicate that \(\mathrm{lkBa}\) plays a role in CLK2's inhibition of p65. + +<|ref|>text<|/ref|><|det|>[[149, 456, 851, 565]]<|/det|> +During the activation of NF- \(\kappa \mathrm{B}\) signaling, \(\mathrm{lkBa}\) is mostly degraded and re- . synthesized. We can observe that active- p65 (phosphorylated and acetylated p65) can still be inhibited even when \(\mathrm{lkBa}\) is mostly degraded in the presence of CLK2 (the 30 min time- course of LPS treatment in MLFs in Fig. 2e, and the 10 min time- course of TNF- \(\alpha\) or IL- 1β treatment in MLFs in Supplementary Fig. 2f). Therefore, we can demonstrate that CLK2 can still suppress p65 in the absence of \(\mathrm{lkBa}\) + +<|ref|>text<|/ref|><|det|>[[149, 603, 849, 657]]<|/det|> +-I don't understand their statement that lkBa functions in CLK2 KO cells- the data they cite just shows NFkbia is resynthesized by western. Do they introduce lkBa into CLK2/- cells and show it is still inhibitory? + +<|ref|>sub_title<|/ref|><|det|>[[149, 660, 238, 676]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 679, 850, 787]]<|/det|> +Thank you for the opportunity to clarify this aspect of our study. It's important to understand that \(\mathrm{lkBa}\) functions as both an inhibitor of NF- \(\kappa \mathrm{B}\) p65 and as a gene whose expression is induced by NF- \(\kappa \mathrm{B}\) activation. The results indicate that p65 displays enhanced transcriptional activity in the absence of Clk2, which result in the increased production of Nfkbia. Actually, the expression level of Nfkbia was observed as a downstream expressed protein in this context. + +<|ref|>text<|/ref|><|det|>[[149, 789, 850, 880]]<|/det|> +Regarding the question "Do they introduce \(\mathrm{lkBa}\) into CLK2- cells and show it is still inhibitory", we need to explain that \(\mathrm{lkBa}\) inhibits p65 by interacting with it, and this interaction is dependent on the acetylation level of p65 which is directly regulated by acetylases and deacetylases, such as p300/CBP or HDAC3 (doi: 10.1093/emboj/cdf660). In the absence of CLK2, we can still observe that p65 has + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 85, 848, 121]]<|/det|> +affinity to \(\mathrm{1kBa}\) , and still can interact with it. In general, \(\mathrm{1kBa}\) still exhibits its inhibitory function, although it is weakened in CLK2- cells. + +<|ref|>text<|/ref|><|det|>[[147, 159, 850, 344]]<|/det|> +- They find that S180D (which does not activate NF-kb and has a higher turnover) has a higher affinity for Nfkbia/lkBa (Supp Fig 6H), but S180A and WT in CLK2-/- cells has a decreased interaction with CRM1 and lkba (Fig 6C &6D). This data demonstrates that the phosphorylation on S180 induced by CLK2 leads to a higher affinity for lkba that would export and lock p65 out of nucleus; in turn this lead to the loss of NF-kB post-translational modifications and functions in the nucleus. Therefore, the impact of CLK2 on p65 Ser180 phosphorylation may be upstream of lkba interactions, but ultimately is determined by lkba export. It is not independent of lkba-just not dependent on newly synthesized lkba in late stage termination. This does not fit with their conclusions and title. + +<|ref|>sub_title<|/ref|><|det|>[[148, 347, 238, 362]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[147, 364, 852, 584]]<|/det|> +We apologize for our previous explanation being unclear. As we mentioned before, \(\mathrm{1kBa}\) serves as a method for nuclear exportation, but p65 can also translocate to the cytoplasm independently of \(\mathrm{1kBa}\) (doi: 10.1128/MCB.16.5.2341). In our manuscript, the result shows that \(\mathrm{1kBa}\) can be used up in p65S180D/K1 cells (Supplementary Fig. 6e). Meanwhile, we observed that p65 can still shuttle from the nucleus to the cytoplasm in 1- 3 hrs in p65S180D/K1 cells (Fig. 6b). Combine the results, they suggest that p65 can still be exported from the nucleus in absence of \(\mathrm{1kBa}\) . In summary, our conclusions reflect the broader understanding that CLK2 influences NF- \(\mathrm{kB}\) signaling through mechanisms that can both involve and bypass \(\mathrm{1kBa}\) . This nuanced view acknowledges the complexity of NF- \(\mathrm{kB}\) regulation, where multiple layers of control determine the nuclear- cytoplasmic dynamics of p65, including but not limited to its interactions with \(\mathrm{1kBa}\) . + +<|ref|>text<|/ref|><|det|>[[148, 621, 850, 676]]<|/det|> +-Lines 368- 370 described showing p65 S180A and WT interactions with CRM1 and lkBa in CLK2-/- cells. Fig 6D only shows 293T cells and Fig.6i only shows WT p65 in both CLK2+/+ and CLK2-/- cells. + +<|ref|>sub_title<|/ref|><|det|>[[148, 680, 238, 695]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 825]]<|/det|> +We feel so sorry for confusing the reviewer. Fig. 6d displays the interaction between p65 and \(\mathrm{1kBa}\) or CRM1 in p65WT and p65S180A/K1 cells (which is on right part of Fig. 6d). Supplementary Fig. 6 shows the interaction between p65 and \(\mathrm{1kBa}\) and CRM1 in CLK2+/+ and CLK2-/- cells (both results are presented below). Therefore, the statement "Moreover, the p65S180A and p65WT in CLK2-/- cells presented decreased interaction with CRM1 and \(\mathrm{1kBa}\) (Fig. 6d and Supplementary Fig. 6i)" accurately reflects the findings. + +<--- Page Split ---> +<|ref|>image<|/ref|><|det|>[[200, 84, 798, 252]]<|/det|> + +<|ref|>sub_title<|/ref|><|det|>[[149, 309, 296, 324]]<|/det|> +## Minor comments. + +<|ref|>text<|/ref|><|det|>[[149, 327, 849, 363]]<|/det|> +Professional editing is required even with revisions. Numerous issues remain and some are newly introduced. 'plague' is still used where 'plague' is appropriate. + +<|ref|>sub_title<|/ref|><|det|>[[149, 365, 238, 380]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 383, 850, 493]]<|/det|> +We appreciate the reviewer's attention to detail and their advice on the necessity of professional editing to improve the manuscript's language quality. We have taken this feedback seriously and enlisted the services of SPRINGERNATURE Author Services (SNAS) to ensure the manuscript meets the highest standards of English language, grammar, punctuation, and phrasing. We have attached the editing certificate from SNAS as proof of this professional review and editing + +<|ref|>sub_title<|/ref|><|det|>[[432, 590, 564, 607]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[148, 752, 850, 826]]<|/det|> +We sincerely apologize for that we did not revised all the "plague" throughout the manuscript. Following your feedback, we have conducted a thorough review of the manuscript to correct this and any similar errors. We can now confirm that all instances have been corrected to "plague". + +<|ref|>text<|/ref|><|det|>[[149, 845, 849, 900]]<|/det|> +The IFA figures with brightfield added have become very small (Fig3, 5). The IFA for the paired flow cytometry data could be moved to supplemental or the other bar graphs in the figures could be shortened to make space. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[148, 86, 238, 101]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 104, 850, 196]]<|/det|> +We greatly appreciate your suggestion regarding the size of the IFA figures in Fig. 3 and 5. We recognize the importance of clearly presenting our results for effective communication of our findings. In response to your feedback, we have taken steps to enlarge the IFA figures in both Fig. 3 and 5, ensuring that the details are visible and the results can be easily interpreted. + +<|ref|>text<|/ref|><|det|>[[148, 197, 850, 270]]<|/det|> +These adjusted figures are now included in the revised manuscript. This modification aims to enhance the overall clarity and impact of our visual data presentation. Thank you for helping us improve the quality of our figures and, by extension, our manuscript. + +<|ref|>image<|/ref|><|det|>[[150, 273, 848, 580]]<|/det|> + +<|ref|>text<|/ref|><|det|>[[148, 621, 850, 678]]<|/det|> +I previously noted that the font kerning for the sequence alignment of Fig SB is off and that a monospace font is needed. The authors claim to have adjusted this- but the text is still not aligned properly. + +<|ref|>sub_title<|/ref|><|det|>[[148, 680, 238, 696]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 697, 850, 807]]<|/det|> +So sorry for not revising the Fig. 5b correctly, we need to apologize for it. Due to the Arial font cannot be set as monospace, we have tired many different methods and it seems like not be better. To rectify this, we have now utilized the Courier New font, which supports monospace formatting, ensuring that the text is aligned properly across the sequence. This adjustment has been applied to Fig. 5b, and we are confident that it now meets the necessary standards for clear and accurate presentation. + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[357, 88, 639, 202]]<|/det|> +Human VRDPSGRPLRPLPVLSHPIFDNRAPNTAEL Rat VRDPSGRPLRPLTVPLSHIPIFDNRAPNTAEL Mouse VRDPAGRPLLTVPLSHIPIFDNRAPNTAEL Zebrafish ITLSSGDLFPLEPVVSQPIVDNRAPNTAEL Fruitfly SEQKGRFTSPLPVVSEPIFDKAMSDLVI + +<|ref|>text<|/ref|><|det|>[[357, 155, 639, 206]]<|/det|> +Human KRKRTYETFKISIMKKSPSFSPGTPDRPPPRR Rat KRKRTYETFKISIMKKSFPNGTPEPRPPPRR Mouse KRKRTYETFKISIMKKSFPNGTPEPRPPPRR Zebrafish KRKRTEGMLHNLKLSIIITGSSMSAERRPF Fruitfly RRKROKTGGDPMHLLLQQQQKQQLQNDHQD + +<|ref|>text<|/ref|><|det|>[[149, 250, 850, 326]]<|/det|> +There is a lack of discussion regarding its canonical substrates such as splicing factors vs this noncanonical functions of CLK2 to target p65. How does SeV, TNFa or other stimulations that activated CLK2 tie into its impacts on splicing? When CLK2 is activated by infection to target p65, what is the impact on canonical substrates? + +<|ref|>sub_title<|/ref|><|det|>[[149, 327, 238, 342]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 344, 849, 380]]<|/det|> +Thanks for your reminding and we also think it is essential. The discussion has been updated and presented below. + +<|ref|>text<|/ref|><|det|>[[148, 381, 850, 565]]<|/det|> +"On the other hand, CLK2 can be regulated significantly by SeV, TNF- \(\alpha\) or other stimulations. Activated CLK2 is usually considered to facilitate RNA alternative splicing processes involving SRSF1 and RBFOX2. When CLK2 is activated by infection to target p65, it may also promote the activation of SRSF1, which has been found that overexpression can inhibit the production of pro-inflammatory cytokines (doi: 10.1172/JCI127949). However, the promotion of RBFOX2, which can be regulated by CLK2, is considered to be positively associated with inflammation (doi: 10.1038/s42255-022-00681-y). In summary, these findings underscore the complex regulatory role of CLK2 in the inflammatory response, potentially exhibiting dual effects in different inflammatory diseases or virus infection". + +<|ref|>text<|/ref|><|det|>[[149, 602, 848, 639]]<|/det|> +Typo in Supp Fig 4c legend line 1057: they state'The upper shifted band represents phosphorylated CLK2 protein.'This is actually p65, correct? + +<|ref|>sub_title<|/ref|><|det|>[[149, 641, 238, 656]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 659, 848, 695]]<|/det|> +Sorry for making that mistake and the figure legend has been revised as "The upper shifted band represents the phosphorylated p65 protein". + +<|ref|>text<|/ref|><|det|>[[149, 732, 850, 788]]<|/det|> +With regard to Fig 6D legend, they state that "The asterisk/upper band indicate the unspecific band that can be detected by the antibody and the explanation was added in the relative figure legends." This has not been corrected. + +<|ref|>sub_title<|/ref|><|det|>[[149, 790, 238, 805]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[149, 807, 850, 881]]<|/det|> +We feel so sorry that the statement of asterisk/upper band have not been corrected throughout the figure legends. Now, the statement "The upper band marked with asterisk indicates the unspecific band." have been added in the figure legends of Fig. 6f, 6g and Supplementary Fig. 6k. + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[149, 103, 479, 120]]<|/det|> +## Reviewer #2 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[148, 122, 852, 325]]<|/det|> +Authors fixed all relevant issue raised, by performing new experiments as requested, and by modifying the manuscript, as suggested. I also encourage authors to make a further effort to improve manuscript written English (at pag 5 line 55, "rheumatoid arthritis", instead of "rheumatic arthritis"; at pag.6 line 89 "CLK2- deficient mice were observed to have higher levels", instead of "CLK2- deficient mice produce were observed to have higher levels"; at pag 22 line 444 "The transcription factor p65 is critical for cytokine- induced production of inflammation genes", instead of "The transcription factors p65 is critically for cytokine- induced production of inflammation genes"; at page 24 line 499" use of site- specific phosphorylation antibody", instead of "use of site- specific phosphorylation antibody", and so on). + +<|ref|>sub_title<|/ref|><|det|>[[148, 328, 238, 343]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 345, 850, 472]]<|/det|> +We are grateful for Reviewer #2's constructive feedback and the specific suggestions to enhance the manuscript's written English. In response, we have taken decisive action to address these concerns. The manuscript has undergone professional editing by SPRINGERNATURE Author Services (SNAS) to ensure accuracy in English language, grammar, punctuation, and phrasing. This comprehensive review aimed to correct the issues highlighted by the reviewer, including those mentioned and others throughout the document. + +<|ref|>text<|/ref|><|det|>[[148, 474, 850, 547]]<|/det|> +We have attached the editing certificate from SNAS as evidence of this professional language editing service. This step underscores our commitment to presenting our findings clearly and professionally, and we believe it significantly improves the manuscript's overall quality. + +<|ref|>sub_title<|/ref|><|det|>[[434, 671, 565, 688]]<|/det|> +## [REDACTED] + +<|ref|>text<|/ref|><|det|>[[148, 826, 850, 861]]<|/det|> +In addition, we appreciate the specific examples provided for language improvement and have made the following revisions to address these points: + +<|ref|>text<|/ref|><|det|>[[148, 863, 850, 898]]<|/det|> +The "rheumatoid arthritis" is instead of "rheumatic arthritis". The "CLK2- deficient mice were observed to have higher levels" has been revised as "Clk2- + +<--- Page Split ---> +<|ref|>text<|/ref|><|det|>[[148, 84, 850, 214]]<|/det|> +deficient mice had increased serum levels of inflammatory cytokines after viral infection and showed increased resistance to virus- induced death". The "The transcription factors p65 is critically for cytokine- induced production of inflammation genes" has been modified as "The transcription factor p65 is critical for cytokine- induced production of inflammatory genes". "the use of site- specific phosphorylated antibodies" is instead of "use of site- specific phosphorylation antibody". + +<|ref|>text<|/ref|><|det|>[[148, 251, 850, 343]]<|/det|> +Moreover, at pag. 21 line 440, I suggest to rephrase the sentence"...and TG003 may be developed as a cure of virus- infection" as"...and CLK2 inhibition may be exploited as a cure of virus- infection", due to the fact that TG003 inhibitor may not be suitable for further chemical optimization, to serve as an effective and safe antiviral. + +<|ref|>sub_title<|/ref|><|det|>[[148, 346, 238, 362]]<|/det|> +## Response: + +<|ref|>text<|/ref|><|det|>[[148, 364, 850, 437]]<|/det|> +We agree with the reviewer that TG003 used here may not be suitable. Under the modification of SNAS, the sentence has been modified as "...indicating that CLK2 may be a therapeutic target for inflammatory diseases and that inhibiting CLK2 may be a strategy to cure viral infection". + +<--- Page Split ---> +<|ref|>sub_title<|/ref|><|det|>[[119, 84, 310, 98]]<|/det|> +## REVIEWERS' COMMENTS + +<|ref|>text<|/ref|><|det|>[[119, 112, 415, 127]]<|/det|> +Reviewer #1 (Remarks to the Author): + +<|ref|>text<|/ref|><|det|>[[115, 140, 875, 169]]<|/det|> +The authors have adequately addressed my concerns and the concerns of reviewer 2 in the second revision. + +<--- Page Split ---> diff --git a/preprint/preprint__788c0f71544970e95288215ff1a6d06a45b8b92529d074e993bf06184284e261/preprint__788c0f71544970e95288215ff1a6d06a45b8b92529d074e993bf06184284e261_layouts.pdf b/preprint/preprint__788c0f71544970e95288215ff1a6d06a45b8b92529d074e993bf06184284e261/preprint__788c0f71544970e95288215ff1a6d06a45b8b92529d074e993bf06184284e261_layouts.pdf new file mode 100644 index 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